microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 155-157 (2008) properties of polyamide 6 fibres modified by silicate nanoparticles i. vass , m. krištofič, j. ryba slovak university of technology, faculty of chemical and food technology, institute of polymer materials department of fibres and textile chemistry, radlinského 9, 812 37 bratislava, slovak republic e-mail: iveta.vassova@stuba.sk the first part of contribution is focused to the synthesis of ternary copolyamides containing layered silicate (i.e. bentonite 11958 or cloisite 15a). concentrates were prepared from the basic comonomer, ε-caprolactam and minor polar comonomers, nylon salt an 2 from adipic acid and 1-(2-aminoethyl)piperazine and nylon salt adeta from adipic acid and diethylenetriamine in the total amount of 10.7 and 21.4 wt.%. amount of layered silicates in the concentrates is always the same, 5 wt.%. reaction scheme of synthesis of copolyamide (ch2)5 nh co n n ch2 ch2 nh o n nh+ n hooc(ch2)4coo. +nh3(ch2)2nh(ch2)2nh2 + o hooc(ch2)4coo. + h [hn(ch2)2nh(ch2)2nhco(ch2)4co]n coo(ch2)4co [nh(ch2)5co]m oh + (2n-1) h2o nh3 ch2 ch2 the second part of contribution deals with the preparation of polyamide 6 (pa 6) fibres non-modified and modified by concentrates and determination of some properties (i.e. mechanical, sorptive, barrier and thermal properties) of modified fibres, too. keywords: polyamide 6, layered silicate, concentrates, properties introduction polyamide fibres have many useful properties, but some of them such as electrostatic and sorptive ones do not meet the requirements of customers. chemical and physical modifications are the basic methods for an improvement of these properties. chemical modification is application of comonomers at the preparation of copolyamides. addition of concentrates, i.e. copolyamides containing layered silicate into pa 6 is a physical modification of pa 6. introduction of the new comonomer, with some polar atoms or groups into the backbone of poly-εcaprolactam is the possibility to prepare copolyamides which can be used as modifiers for pa 6 as well. many polyamides and polyamide fibres containing the derivatives of piperazine or piperidine are characterized by higher sorption of water vapour than pa 6 [1-3]. binary copolyamides based on ε-caprolactam and a nylon salt of adipic acid and 1-(2-aminoethyl)piperazine or 1,4-bis-(3-aminopropyl)piperazine are crystalline copolymers with good compatibility with pa 6 [4]. pa 6 fibres modified with binary copolyamides have better electrostatic and sorptive properties [5]. concentrates such as binary or ternary copolyamides based on poly-ε-caprolactam containing polar comonomers from adipic acid + 1-(2-aminoethyl)piperazine (an 2), adipic acid + diethylenetriamine (adeta) and organoclay would be effective modifiers for pa 6. materials polyamide 6, pa 6, nylstar slovakia, slovak republic, ηrel = 2.642 in hcooh, ηrel = 1.68 in h2so4, 96%, 25 °c, at the concentration c = 0.5 g of polymer / 100 ml solution, tm = 227 °c ε-caprolactam, cl, nylstar slovakia, slovak republic nylon salt an 2, an2, sut, department of fibres and textile chemistry, slovak republic, it is prepared from adipic acid, a + 1-(2-aminoethyl)piperazine, n 2 nylon salt adeta, adeta, sut, department of fibres and textile chemistry, slovak republic, it is prepared from adipic acid, a + diethylenetriamine, deta layered silicate – organophilic montmorillonite, mmt: bentonite 11958, ben, aldrich, usa, it contains sodium and quartery ammonium ions between layers 156 cloisite 15a, clo, gonzales, usa, it is mmt modified with quartery ammonium salt, i.e. ditallowdimethylammonium salt of bentonite preparation of modifiers concentrates of ε-caprolactam, nylon salts an 2 and adeta and layered silicate were prepared by the poly (addition-condensation) reaction proceeding in melt in the n2 atmosphere. the powdered cl, an 2, adeta mixture with mmt was heated in the glass apparatus. during the first 10 minutes the temperature was raised so that the nylon salts melted and homogenized in the cl. later the polyreaction started – reaction water evaporated and condensed and the viscosity of the melt increased with time to the temperature of 270-280 °c at the end of the reaction time. the concentrates were poured into the cylindrical form onto the metallic plate and cut into granules. concentrates were designed by the symbols a, b and c according to different concentration of the nylon salts. their composition and main characteristics are: a – 73.6% kl + 10.7% adeta + 10.7% an 2 + 5.0% mmt b – 84.3% kl + 10.7% an 2 + 5.0% mmt c – 73.6% kl + 10.7% adeta + 10.7% an 2 + 5.0% clo 15a preparation of modified pa 6 fibres modifiers were extracted in hot water to remove lowmolecular compounds and dried. the blends of pa 6 containing 5, 10 and 20 wt.% of concentrate a, b and c were prepared in a single-screw ribbon extruder at the temperature of zones t1 = t2 = = t3 = 250 °c. the spinning of blends was performed on the experimental equipment at the temperature of zones t1 = 260 °c, t2-4 = 255 °c and t5 = 260 °c with lubricant. after spinning the fibres were drawn at the temperature 110 °c to the drawing ratio λ = 3 and 3.5. methods used for the evaluation of the fibres properties the mechanical properties, i.e. tensile strength of pa 6 fibres were measured by instron 3343. the hydrophilicity of fibres was evaluated gravimetrically at the temperature t8 = 21.7 °c and at the 65% relative humidity. the barrier properties, i.e. ultraviolet protection factor of fibres (λ = 3) were measured by spectrophotometer with deuterium lamp, libra s12. the thermal properties of these fibres (λ = 3) were measured by perkin-elmer dsc 7 equipment. the conditions of measurement were: heating 50 °c → 250 °c cooling 250 °c → 50 °c with heating and cooling rate 10 °c/min in n2 atmosphere. results and discussion amount of low molecular compounds of concentrates (table 1) are at the same level as for pa 6. relative viscosity and melting temperature of concentrates (table 1) decrease with amount of comonomers, but these are lower than in the case of pa 6. tensile strength of fibres (table 2) increases with drawing ratio, but it decreases with the amount of concentrates in fibres. modified fibres have smaller tenacity than pa 6 fibre. fibres modified by concentrate c have the best tensile strength in comparison with other modified fibres, particularly when the amount of concentrate in fibres is lower, i.e. 5 and 10 wt.% and at the drawing ratio 3.5. values of water vapour sorption (table 2) increases with amount of concentrates in fibres and it decreases in dependence on higher drawing ratio due to higher orientation in fibres. fibres modified by concentrates a and c have better sorptive properties than fibres modified by concentrate b, because they contain higher amount of polar, hydrophilic comonomers, which improve hydrophility of fibres, because they are able to fix molecules of water vapour. if upf value is higher, then less ultraviolet radiation is transmitted through material. upf of modified fibres (table 2) depends on type of used layered silicate (bentonite or cloisite 15a). upf is better in the case of fibres modified by concentrate c, which contains cloisite 15a. melting temperatures of modified pa 6 fibres (table 3) are lower in comparison with non-modified pa 6 fibre, but their crystallization temperatures (table 3) are similar. melting entalphies and enthalphies of crystallization of modified pa 6 fibres (table 3), mainly with lower amount of concentrates a, b and c, i.e. 5 and 10 wt.% are higher or practically the same as for non-modified pa 6 fibre. table 1: time of synthesis, t, amount of low molecular compounds, lmc, relative viscosity, ηrel and melting temperature, tm of pa 6 and concentrates conc t [min] lmc [wt.%] ηrel tm [°c] pa 6 ≈600 ≈12 1.68 227 a 340 10.1 1.42 187 b 360 9.6 1.48 198 c 360 15.1 1.39 189 157 table 2: tensile strength, σ, water vapour sorption, s and ultraviolet protection factor, upf of pa 6 fibres non-modified and modified with concentrates fibres σ [cn.dtex-1] s [%] upf λ 3 3,5 3 3,5 3 pa 6 4.04 4.38 4.96 4.87 10.5 5% a 3.46 4.15 5.18 5.15 10.5 10% a 3.45 3.87 5.39 5.21 8.5 20% a 2.81 3.38 5.84 5.44 9.9 5% b 3.71 4.32 5.13 4.84 10.9 10% b 3.39 4.24 5.17 5.13 9.4 20% b 3.23 3.77 5.42 5.19 9.6 5% c 3.64 4.49 5.34 5.06 10.9 10% c 3.39 4.43 5.51 5.23 12.4 20% c 2.98 3.93 5.82 5.54 11.7 table 3: thermal properties, i.e. melting and crystallization temperatures and entalphies of pa 6 fibres non-modified and modified with concentrates, λ = 3 heating cooling fibres tm1 [°c] σδhm1 [j/g] tc1 [°c] -δhc1 [j/g] pa 6 221 79.8 188 72.1 5% a 216 81.4 188 76.0 10% a 218 75.9 187 70.4 20% a 220 69.3 186 64.9 5% b 218 77.9 188 73.7 10% b 218 77.4 188 75.5 20% b 218 76.8 187 71.1 5% c 217 82.4 189 76.6 10% c 219 78.4 189 71.4 20% c 219 71.1 187 67.0 conclusions concentrates reduce a little bit the tensile strength of modified pa 6 fibres in comparison with non-modified ones because of lower orientation in these fibres. concentrates improve sorptive properties of modified pa 6 fibres due to their higher hydrophilicity. upf depends on the type of layered silicate used for modification of fibres, from which cloisite 15a proves to be more effective. melting temperatures of modified pa 6 fibres are lower in comparison with non-modified ones because of lower melting temperature of concentrates, but their crystallization temperatures are the same or similar. lower amount of concentrates in pa 6 fibres do not have a significant effect on thermal properties. acknowledgement support of the vega 1/4456/07 (grant fchpt 920) is appreciated. references 1. krištofič, m. et al.: modification of pa 6 fibers with alkaline copolyamides, chemical papers, vol. 54, no. 1 (2000), p. 53-58 2. jap. pat. 72 32755 3. kornmann, x.: synthesis and characterisation of thermoset-clay nanocomposites, division of polymer engineering, luleå university of technology, s – 971 87 luleå, sweden 4. zanetti et al.: macromol mater eng 1 (2000), p. 9 5. mark, f. et al.: concise encyclopedia of polymer science and engeenering, new york, chickester, brisbane, toronto, singapore, 1990 microsoft word contents.doc hungarian journal of industrial chemistry veszprém vol. 34. pp. 51-54 (2006) magnetic field analysis on electromagnetic water treatment device v. kozic1, j. krope2, l. c. lipus 3 and i. ticar4 1zdraviliško naselje 14, 9252 radenci, slovenia 2faculty of chemistry and chemical technology, 3faculty of mechanical engineering, 4faculty of electrical engineering and computer science, university of maribor, smetanova 17, 2000 maribor, slovenia a short review of magnetic water treatment devices is given. analysis of electromagnetic industrial units named em i – iv is presented. the distribution of magnetic flux density of the models was measured and analyzed by the computer program electromagnetic field analysis tools. results for em iv show that an improvement can be achieved by replacing a metallic tooth, used for placing the washer ring, with nonmagnetic material. keywords: magnetic water treatment, scale prevention, magnetism introduction scale deposits by natural waters often lead to numerous technical and economical problems in industrial plants and domestic equipment by blocking the water flow in pipes or limiting heat transfer in heat exchangers. traditional chemical methods for scale control are effective but significantly change the solution composition and are expensive. therefore, an interest for physical methods is rising. one of these methods is magnetic water treatment (mwt), where water flows through a magnetic field. in the literature, there is a number of reports about mwt being effective [1-4]. when the device is properly designed, hard scale is prevented by forming sludge or alternatively, linings with low mechanical strength, which can be easily removed. the mechanism how magnetic fields affect the crystallization of calcium carbonate, is still the matter of research. it is the most possible that treatment leads to the formation of calcium carbonate particles in the bulk of the scaling water, which cannot precipitate on the walls of distribution pipes and other equipment [5]. commercial mwt devices are available in various configurations from numerous manufacturers, some using electromagnets and others using single or arrays of permanent magnets with different orientations of the magnetic field [6]. the most effective arrangements are those with perpendicular or radial magnetic fields (fig. 1). furthermore, magnetic fields can be alternating (fig. 1/a, b) or homogeneous (fig. 1/c). alternating fields seem to be more effective [5,7]. some mwt units are electromagnets using electrical input with alternating current or direct current voltage. many interesting results of laboratory research were found when samples were exposed to static magnetic field [4,8], but better results are expected when water flows through the magnetic field [9,10]. for practical use, there is a general recommendation that water flows through the magnetic field with the velocity from 0.1 to 2 m/s and the magnetic flux density is more than 0.05 t. fig.1: some basic types of magnetic fields: (a) perpendicular (parallel arrangement of magnets) (b) radial (magnetic kernel in ferromagnetic tube) (c) homogeneous (horse-shoe magnets) in this article we describe electromagnetic units named em (shown in fig. 2 with basic data given in table 1). they have alternating current electrical input and are designed for different water flow rates (i-iv). 52 the housing is iron-casting electroplating with nickel. the inner plate is from steel. the electromagnetic winding is a solenoid with rectified alternating currents, which produce pulsating magnetic field. water enters in the center on the top of the device, overflows the inner plate in radial directions, passes the rubber ring down into the lower zone, flows to the center of the inner plate and leaves out of the device. bb1 a fig.2: electromagnetic device, model em (1 – housing, 2 – rubber ring, 3 – solenoid, 4 – inner plate) table 1: basic data for em electromagnetic devices dimensions (mm) type flow rate (l/min) power (w) a b b1 connection em i 10 – 25 40 168 54 40 no 20 (3/4) em ii 15 – 40 55 168 54 40 no 26 (1) em iii 25 – 60 75 220 76 51 no 32 (r 5/4) em iv 150 400 110 320 100 52 no 65 (r 2 1/2) measurements of the magnetic field in the device em i electromagnetic measurements and characteristic results of the model em i were made in the laboratories at faculty of electrical engineering and computer science and faculty of mechanical engineering, university of maribor. 0 10 20 30 40 50 60 70 0 10 20 30 40 50 radius, r (mm) m ag ne tic fl ux d en si ty , b (m t) solenoid in the air solenoid in the housing fig.3: magnetic flux density of solenoid (a) in the air and (b) of the same solenoid in the housing with inner plate in em i device. radial distributions of the magnetic flux density b(r) are presented in fig. 3. the magnetic flux density was measured for solenoid (a) in the air and (b) with inner plate and housing together. because the value of b should be higher than 0.05 t for good efficiency of a magnetic device, em i model has good values of b from radius r1 = 30 mm to r2 = 45 mm. relative effective area ( ) ( )221 2 2 2 1 2 2 /1/ rrrrr −=− πππ is 56% of whole area of the inner plate. figure 4 shows the measurements for magnetization curve (magnetic flux density, b (t), versus magnetic field intensity, h (a/m)) of housing and inner plate for em i model. 0,00 0,25 0,50 0,75 1,00 1,25 1,50 1,75 2,00 0 2000 4000 6000 8000 10000 12000 14000 magnetic field intensity, h (a/m) m ag ne tic fl ux d en si ty , b (t ) inner plate housing fig.4: magnetization curve of housing (grade 350) and inner plate (fe360b) for em i device. conditions of v and b for effective operating of mwt devices were checked. from measurement result of em i device (fig. 1), it can be seen that the zone of efficient magnetic field (b > 50 mt) is from r1 = 30 mm to r2 = 45 mm. water flux is for radial flow expressed with the relationship: qv = 2·π·h·v (1) 53 parameters are: r = radial distance on the inner plate h = thickness of the gap = 1 cm v = water flow velocity velocity v decreases with increasing of r, being the lowest at the edge of the inner plate. for fulfillment of the condition v > 0.1 m/s in whole area of the inner plate, the water flux should be 17 l/min (calculated by eq.1 for v = 0.1 m/s at the edge of the plate). numerical calculations of the magnetic field in the device em i the distribution of magnetic flux density was also analyzed numerically. the computer program electromagnetic field analysis tools (elefant2d, elefant3d) was used. it is developed by igte, tu graz with the purpose for solving two(2d) and three dimensional (3d) problems in electromagnetic fields by the finite element method. the program enables us to determine the distribution and the magnitude of static and time depending electromagnetic fields. it comprises: 2d and 3d input graphical processors for description of a device geometry, boundary conditions, materials and sources, the main program with different mathematical numerical calculation possibilities (scalar or vector potentials) and the postprocessor for numerical and 2d or 3d graphical presentation of device’s parameters. figure 5 presents 3d mesh for em model. fig.5: 3d – mesh of em model the numerical calculation was made for dimensions of the model em iv in 2d-axisisymmetric mesh. figure 6 presents the magnetic flux density distribution. it is obvious that ''a magnetic bridge'' occurs due to the metallic tooth used for placing the rubber ring. the magnetic field very weakly penetrates into the zone of water flow and the inner plate. for constructing an improved model, a good solution was replacing the metallic tooth with a nonmagnetic ring. results are presented in fig. 7. distribution of the magnetic flux density is now favorable. magnetic field in water zone is stronger and perpendicular to the water flow direction. both facts are important for the effectiveness of the device. the comparison of the magnetic flux density curve between the manufacturer’s and the improved model is presented in fig. 8. fig.6: the distribution of the magnetic flux density, bz, in the manufacturer’s model em fig.7: the distribution of the magnetic flux density, bz, in the improved model em fig.8: distribution of magnetic flux density for em model and for the improved model. results of the numerical analysis of the improved model em iv (fig. 8) show that the zone of efficient magnetic field (b > 50 mt) is from r1 = 60 mm to r2 = 105 mm at the edge of the inner plate. relative effective area is 67%. 54 conclusion we analyzed em magnetic devices, which have been used in industry for many years and show good results in scale prevention. laboratory measurements and numerical calculations with elefant computer program of magnetic field distribution in these devices are in good agreement. it was found that the metallic tooth considerably reduces the magnetic flux density in the water zone. therefore, we made a computer simulation with nonmagnetic material, which gave much better distribution of the magnetic field. references 1. donaldson j. d., grimes s.: lifting the scales from our pipes; new scient., 1988, 117, 43-46. 2. wang y., babchin a. j., cherneyi l. t., chow r. s., sawatzky r. p.: rapid onset of calcium carbonate crystallization under the influence of a magnetic field; water research, 1997,vol.31, no.2, 346-350. 3. parsons s. a., wang b. l., judd s. j., stephenson t.: magnetic treatment of calcium carbonate scale – effect of ph control; water research, 1997, vol.31, no.2, 339-342. 4. coey j. m. d., cass s.: magnetic water treatment; journal of magnetism and magnetic materials, 2000, 209, 71-74. 5. gabrielli c., lauhari r., maurin g., keddam m.: magnetic water treatment for scale prevention; water research, 2001, vol.35, no.13, 3249-3259. 6. gruber c. e., carda d. d.: performance analysis of permanent magnet type water treatment devices; wsa research report, water quality association, 1981. 7. oshitani j., uehara r., higashitani k.: magnetic effects on electrolyte solutions in pulse and alternating fields; journal of colloid and interface science, 1999, 209, 374-379. 8. higashitani k., kage a., katamura s., imai k., hatade s.: effects of magnetic field on the formation caco3 particles; journal of colloid and interface science, 1993, 156, 90-95. 9. busch k. w., busch m. a.: laboratory studies on magnetic water treatment and their relationship to a possible mechanism for scale reduction; desalination, 1997, 109, 131-148. 10. lipus l. c., krope j., crepinsek l.: dispersion destabilization in magnetic water treatment; journal of colloid and interface science, 2001, 235, 60-66. 11. kozic v., lipus l.c.: magnetic water treatment for less tenacious scale. journal of chemical information and computer science, 2003, vol. 43, no. 6, 1815-1819. microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 23-26 (2008) production of short chain fructooligosaccharides zs. csanádi , cs. sisak university of pannonia, research institute of chemical and process engineering h-8200, egyetem u. 10., veszprém, hungary e-mail: csanadi@mukki.richem.hu pectinex ultra sp-l, a commercial enzyme preparation with fructosyl-transferase activity and ability to produce short chain fructooligosaccharides, was immobilized onto anionic ionexchange resin by a combined method. during the work this solid-phase biocatalyst was used for the production of fructooligosaccharides from saccharose, where glucose was formed as inhibiting by-product. in the experiments the optimal biocatalyst/matrix ratio and the optimal immobilization conditions: concentration of cross-linking agent, immobilization time and optimal operational conditions: temperature and ph were determined. moreover an integrated reactor system was constructed for simultaneous fructooligosaccharides production synthesis and glucose elimination to enhance the product yield. keywords: fructosyl-transferase, glucose-oxidase introduction recently maintaining physical health and well-being has become more and more important worldwide, which requires careful nutrition including wholesome food products and food additives. the so-called functional foods contain useful components that have beneficial effects on health conditions [1]. typical representatives of functional foods are the fructooligosaccharides (fos). their significance have risen recently in human and animal nutrition, primarily because of their advantageous effects on the intestinal bacterial population and general health conditions in the body [2]. fos are not decomposed in the small intestine by the digestive enzymes so reach the colon where they are fermented by the microbial flora (e.g. bifidobacteria sp., lactobacillus sp.) to lactate and short chain fatty acids, like acetate, propionate, butyrate. consequently, fos stimulate the growth and vitality of these microbes and prevent spreading of the harmful pathogens. in addition, they have low sweetness intensity, their caloric value is low, approximately 8–9 kj g-1 and cause no caries. so they can be applied as alternative sweeteners and a part of diet [3, 4]. short chain fos are mainly composed of 1-kestose (gf2), nystose (gf3) and fructosyl-nystose (gf4), in which two, three and four fructose units are bound to one unit of glucose, respectively. they can be found in plants and vegetables, including onion, asparagus, rice, sugar beet, wheat, etc. but generally in low concentration. the industrial scale recovery from these plants is not economical since their low concentration, for this reason, fos are produced commercially via biosynthetic as well as hydrolytic methods using fructosyl-transferase (ftf) enzyme. the raw material of this reaction is sucrose and the product mixture contains unconverted sucrose besides gf2, gf3 and gf4 and glucose as a by-product [5]. the latter component is a strong competitive inhibitor of the synthesis [6]. elimination of the formed by-product component can result an increase in the product yield. for this purpose several methods can be applied: e.g. membrane separation [7-9], chromatographic separation, or enzymatic method like elimination by glucose oxidase. the partial hydrolysis of inulin is also used practically for fructooligosaccharide production. inulin recovered from jerusalem artichoke (helianthus tuberosus) and chicory (cichorium intybus) species is used currently as substrate of endoinulinases (ec 3.2.1.7) by the industry to produce gf2-gf4 fos [10]. the immobilization of the biocatalysts offers a lot of practical advantages, e.g. easy separation of enzyme and product, the opportunity to realize a continuous process, the enhancement of volumetric productivity of the reactor, etc [11]. therefore the objects of our work were as follows: to develop an immobilization procedure of a commercial enzyme solution having significant ftf activity, to examine and establish the optimal immobilization conditions, to test the operational possibilities during shake flask experiments, to study the production of fos with the immobilized biocatalyst in lab scale and to investigate the operation of an integrated system developed for simultaneous byproduct elimination. in this paper part of the results of our work are summarized. 24 materials and methods a commercial grade complex enzyme preparation originated the production of short chain fructooligosaccharides, originated from aspergillus aculeatus – pectinex ultra sp-l (novozymes, denmark) – containing fructosyl-transferase activity beside other enzyme activities (pectinase, cellulose, β-galactosidase) [12]. for the glucose elimination glucose oxidase (god) enzyme (fluka) with 215 u cm-3 and catalase (sigma) with 830 u cm-3 activities were used. short chain fructooligosaccharides as 1-kestose, nystose and fructosyl-nystose were obtained from wako pure chemical industries (japan) ltd. all other reagents were reagent grade. for the immobilization of biocatalysts an anionic ion exchange resin, amberlite ira 900 cl (rohm and haas, germany) was applied. it is a styrene-divinylbenzene copolymer matrix, with 650–720 μm mean particle diameter, 40–75 nm pore diameter and 25 m2 g-1 specific surface area. in the reaction catalyzed by ftf, the same molar quantity of glucose is formed as the total moles of the different fos molecules produced. that is why the activity of the enzyme was determined measuring glucose formed in the reaction. one unit of ftf activity was defined as the quantity of enzyme that liberated one μmol of glucose per minute [5]. the catalytic activity of pectinex ultra sp-l was determined on the basis of hang & woodams [12]. the applied reaction conditions were 2 m initial sucrose concentration, at 55 °c, ph 5.6 and 2 h incubation time. it has been found that pectinex ultra sp-l has 10.9 u cm-3 fructosyl-transferase activity. the catalytic activity of god-catalase enzyme product was determined regarding to the god activity of the biocatalyst. one unit of god activity was defined as the amount of enzyme that transformed 1 μmol of glucose per minute [1]. the glucose concentration was determined with odianisidine method [13] in the case of ftf-activity determination. when glucose oxidase activity was measured we used the o-toluidine method [14]. fructooligosaccharides were analysed by hplc under the following conditions: merck-hitachi l-6000a hplc apparatus, ri-71 refractive index detector, aminex hpx-42a column of 300×7.8 mm, 25 °c, distilled water eluent, 0.2 cm3 min-1 flow rate. results during our work a solid-phase biocatalyst (15.6 u g-1) for the production of fructooligosaccharides was developed. the exact method and process were presented earlier [15]. for the elimination of glucose a co-immobilized fine chemical grade glucose oxidase-catalase solid-phase biocatalyst was manufactured. hydrogen peroxide formed in the reaction is an inhibitor for the enzyme, so it should be removed from the reaction mixture. in our system catalase was applied for the decomposition of h2o2. the god activity of the prepared biocatalyst was 40.4 u g-1 and the catalase activity was 39.5 u g-1. an immobilization procedure was elaborated for these biocatalysts onto an anionic ion exchange resin, amberlite ira 900 cl, using a combination of adsorption and cross-linking by glutaraldehyde treatment. the immobilization parameters and operational conditions have been optimized for the biocatalysts (table 1). table 1: optimal immobilization conditions and operational parameters pectinex ultra sp-l godcatalase immobilization parameters cross-linking time (h) 15 60 concentration of glutaraldehyde (%) 0.25 0.5 operational parameters temperature (°c) 53 30 ph 5.6 5.1 in our studies shaken flask experiments were carried out for the production of fructooligosaccharides with soluble and immobilized pectinex ultra sp-l also. in the first case 3 cm3 soluble pectinex ultra sp-l was added to 30 cm3 sucrose solution (2 m, ph=5.6, 0.05 m acetate buffer). the reaction was conducted at 45°c and 150 rpm. results are summarized in fig. 1. 0 100 200 300 400 500 600 700 0 2 4 6 8 10 time (h) co nc en tra tio n (m g cm -3 ) gf4 gf3 gf2 gf g figure 1: production of fructooligosaccharides with soluble pectinex ultra sp-l during the applied 8 h reaction time equilibrium of the reaction was reached and ~54 % product yield was achieved. product yield was calculated as the amount of the formed fructooligosaccharides related to the amount of the initial substrate. in the second case 6 g immobilized pectinex ultra sp-l was added to 80 cm3 sucrose solution (2 m, ph = 5.6, 0.05 m acetate buffer). the reaction was conducted at 53 °c and 150 rpm. results are summarized in fig. 2. in this experiment the reached product yield was ~60 % under the applied conditions. 25 0 100 200 300 400 500 600 700 0 5 10 15 20 25 30 35 time (h) co nc en tra tio n (m g cm -3 ) fructosyl-nystose nystose kestose sucrose glucose figure 2: production of fructooligosaccharides with immobilized pectinex ultra sp-l based on the results of the shaken flask experiments an integrated reactor system was constructed for the integrated fructooligosaccharides production and glucose elimination. the scheme of it is shown in fig. 3. the reactor unit for fructooligosacharides production was tempered to 53 °c, the other was operated at 25 °c. in this system two reactor units were connected. one of them (i.) was filled with 10 g immobilized pectinex ultra sp-l, the other (ii.) was filled with 5 g coimmobilized glucose oxidase-catalase, and 130-130 cm3 sucrose solution (2 m, ph = 5.6, 0.05 m acetate buffer) was added. the substrate solutions were changed between the two reactor units in every second hour, so the reaction was followed in 10 cycles. we measured the remaining/formed glucose concentrations after each cycles (table 2). figure 3: the scheme of the integrated reactor system for the production of fructooligosaccharides table 2: glucose concentrations after several cycles in the integrated reactor system i. ii. reactor 1 reactor 2 reactor 1 reactor 2 cycles glucose concentration (mg cm-3) glucose concentration (mg cm-3) 1 20.33 19.23 2 22.41 0.14 23.62 0.54 5 24.32 1.89 22.61 2.12 10 35.33 2.33 41.74 3.66 as it can be seen from the data of the table in the first cycle the capacity of reactor 2 was high enough to eliminate glucose completely, but later (in the further cycles) some glucose appeared in the reactor, though its concentration was quite low. after the examined cycles the amount of the formed short chain fructooligosaccharides (table 3) was determined and – as it can be seen from the table – more than 74 % product yield was achieved. table 3: product composition and yield in integrated system i. ii. gf (mg cm-3) 67.00 75.23 gf2 (mg cm-3) 245.36 237.98 gf3 (mg cm-3) 181.23 169.47 gf4 (mg cm-3) 82.58 75.36 yield (%) 74.44 70.59 summary the production possibilities of fos were examined in shaken flask experiments with immobilized ftf and ~60 % product yield was reached. glucose was found as a strong inhibitor therefore an integrated reactor system was constructed for the simultaneous enzymatic production of short chain fos and elimination of glucose by-product by a coimmobilized glucose oxidase-catalase enzyme pair in order to reduce its inhibition. in this system ~74 % product yield was achieved. it can be seen that higher product yield could be reached by application of by-product elimination. acknowledgement the financial support of the hungarian national office for research and technology via the research and technology innovation fund (contract no omfb 01675/2002) is gratefully acknowledged. 26 references 1. blandino, a., macias, m., cantero, d.: process biochemistry 36, 601-606 (2001) 2. bornet, f. r. j., brouns, f., tashiro, y., duvillier, v.: digestive and liver disease 34, 5111-5120 (2002) 3. losada, m. a., olleros, t.: nutrition research 22, 71-84 (2002) 4. fooks, l., fuller, r., gibson, g. r.: international dairy journal 9, 53-61 (1999) 5. yun, j. w.: enzyme and microbial technology 19, 107-117 (1996) 6. sheu, d. c., lio, p. j., chen, s. t., lin, c. t., duan, k. j.: biotechnology letters 23, 1499-1503 (2001) 7. bélafi-bakó, k., gubicza, l.: biocatalysts and membranes, in integration of membrane processes into bioconversions, ed. by bélafi-bakó, k. et al., kluwer academic, london, 2000 pp. 131-140 8. mulder, m.: bacis principles of membrane technology, kluwer, dordrecht, 1996 9. bélafi-bakó, k.: simultaneous application of enzymes and membranes in the food industry, in food engineering research trends, ed. by columbus, f., nova science publishers, new york, 2007 10. kaur, n., gupta, a. k.: journal of biosciences 27, 703-714 (2002) 11. rosevear, a.: journal of chemical technology and biotechnology 34, 127-150 (1984) 12. hang, y. d., woodams, e. e.: lebensmittel wissenschaft und technologie 29, 578-580 (1996) 13. sigma:http://www.sigmaaldrich.com/sigma/bulleti n/gago20bul.pdf 14. cooper, g. r., mcdaniel, v.: clinical chemistry 6, 159-170 (1970) 15. sisak, c., csanadi, z., ronay, e., szajani, b.: enzyme and microbial technology 39, 1002-1007 (2006) microsoft word contents.doc hungarian journal of industry and chemistry veszprém vol. 40(1) pp. 57–64 (2012) computer aided modelling of hybrid mini van i. lakatos1 , v. nagy2, p. kőrös3, t. orbán4 1széchenyi istván university, department of automotive and railway engineering, 1 egyetem tér, 9026 győr, hungary e-mail: lakatos@sze.hu 2széchenyi istván university, research center of vehicle industry, 1 egyetem tér, 9026 győr, hungary 3széchenyi istván university, department of mechatronics and machine design, 1 egyetem tér, 9026 győr, hungary 4széchenyi istván university, department of automotive and railway engineering, 1 egyetem tér, 9026 győr, hungary the main advantage of hybrid vehicles and their electric drive systems that they reduce local pollutant emissions – especially in urban usage. the vehicle called e-van-09 was developed at széchenyi istván university which serves understanding and optimization potential of operational processes. keywords: avl cruise, model, validation, roller bench measurements, road tests introduction the e-van-09 vehicle is based on a 2007 vintage ford transit with mwb chassis. the diesel engine drives the front wheels, while the rear wheels are driven by two electric motors connected in series. the two drives are not in operation at the same time, so the vehicle is purely electric or diesel powered. this kind of propulsion system enables researchers to examine advantages and disadvantages of the different drives separately. electric drive system and all vehicle control components (power electronics for e-motors, battery management system, etc.) were developed at the széchenyi istván university. the synchronous machine is also an academic development, not available on the market. besides the drive system, the on-board communication system was supplemented, and it had to be connected to the original system to add more functionality. a speciality of the conversion is that the van was originally built with hydraulic power steering which had to be replaced by a electro-hydraulic part due to the electric mode. a completely new data bus had to be constructed connecting to the existing can-bus network to control the units of electric drive system (ford data bus, power steering, e-motor bus). the schematic structure of the vehicle parts is shown in figure 1. modelling tool a number of companies are engaged in developing vehicle dynamics simulation software, which are capable of modelling electric vehicles. these software packages are complex systems and can be nested, so the results can be used for their development directly. in addition to simulation results, these software give the possibility for establishment of hil (hardware in the loop) sub-systems that is ready for testing given components (prototype device or new process management) under controlled conditions. during the development, the so-called v model implementation steps are used. the model operates on the same vertical level. it may get to design and modification state again after implementation. in this way, the system can continue to improve until the final version is ready (figure 2). 58 figure 1: block diagram of e-van-09 figure 2: the development method proposed by avl 59 all vehicle simulation software were ranked in 2009 by a uk-based engineering company called ricardo. the common feature of these software packages is that they work together with other general-purpose simulation programs in their unique modular design (40% software are based on matlab/simulink and 90% are able to generate simulink functions). table 1: vehicle simulation software developers (s – matlab / simulinktm based; m – modelica based) (source: ricardo) avl cruise power train simulation software is used at our university which is ranked fourth overall in the ricardo report1. the ranking is based on the level of detail, mathematical background, data management, and user-friendly operation of the simulation modelling software. cruise developed by graz-based avl, austrian company is used by auto-makers like ford, gm, and volvo. besides simulation technology, avl is also involved in the development of power-trains and building test systems meeting the needs of the automotive industry. avl cruise software the simulation model is modular, which guarantees fast and flexible modelling. the modules are connected through physical properties and data links. this modelling method is advantageous, because some of the processes can be parallelized and every sub-calculation can be optimized. the modelling software enables us to reverse the direction of the simulation. in that way, velocity, acceleration values, and losses can be calculated backwards from the wheels to the motor. this process is fast, but gives inaccurate results because the electric motor can operate in a work point which is not realistic within the given time period. instead of that solution, the model chain is the reverse: the kinetic energy generated by the drive unit is reduced through mechanical connections (taking losses into account). this is the natural model of the physical system. for example, if an undersized engine or electric motor is given for the model, then the vehicle will not be able to reach or keep prescribed speed profile. 60 table 2: simulation software evaluation summary table made by ricardo (source: ricardo) the following calculation is valid for the simulation model: 1. between the modules of the vehicle model – where connection is interpreted between two modules – the following non-linear differential equation is applied: . (1) 2. this ordinary differential equation is converted into the following integral equation: (2) 3. the trapezoidal rule discretization leads to the following equation: . (3) 4. this non-linear system of equations is solved by the software in each cycle. the software performs the prior interpolation of parameters (efficiency, torque, losses, fields, etc.). the program is using local bilinear interpolation. building up the drive-train model of e-van cad drawings of drive-train were used in the modelling process and the technical documentation. during validation, the unknown parameters were determined by characteristic values (from technical literature) and measurements, which were performed. since the two drive modes (electric and diesel) are available separately, during the development of the model, we had to stick to the principle, which says the diesel engine does not operate together with the electric motors and vice versa. fortunately, the software provides the opportunity to handle drives separately as subsystems. this modelling method is practical because major physical parameters of the vehicles examined are the same, while the power-train may vary widely. just think of the same model in different passenger cars with different internal combustion engines. modularity of cruise model the two subsystems created in the modular structure of cruise is shown below: 61 figure 3: diesel drive mode system of e-van-09 set up in avl cruise colour codes of diesel drive modules: white: components existing in both subsystems (power-train subsystem) grey: components of diesel driven system (brake modules for different methods of control subsystems) light grey: main parameters of the vehicle and „cockpit” symbolizing the driver. the model of electric drive mode is the following: figure 4: the model of electric drive system of e-van-09 set up in avl cruise software the model of electric drive system of e-van-09 is set up in avl cruise software. colour codes of electric drive modules: white: components existing in both subsystems (power-train subsystem) grey: electric motors, energy source (high voltage battery cell pack), control units dark grey: inverter module light grey: main parameters of the vehicle and „cockpit” symbolizing the driver. 62 the accuracy of simulation depends on the determination of the critical parameters of two main components. the energy storage system (in this case the lithium-ion battery cell pack) is the subsystem which defines the usability of electric vehicles. the main obstacle to the spread of electric vehicles is the low energy density and efficiency of batteries – besides high price of technology. despite energy storage difficulties, the balance tips for systems with electrical equipment of high efficiency (internal combustion engines with 20–30% efficiency value compared to nearly 90% efficiency at electric machines in almost every work point). during setting up the model, we conducted battery tests2. not only capacity but also internal resistance has to be defined, because energy charging and discharging bring losses. this resistance value is only mω per cell, but for a full battery pack it can reach decimal or integer value. internal resistance indicators show significant advantage at lithium-ion batteries compared to nickelmetal hydride batteries. the battery internal resistance test values were higher than it was shown on the data sheets. on the other side larger capacities were measured. figure 5: thundersky 40 ah battery internal resistance measurement results made with current off method figure 6: thundersky 40 ah battery output voltage at 0,5 c discharge main characteristics of the battery cell pack: 128 pcs thundersky wb-lyp40aha battery cells in series (8 pcs battery blocks) nominal voltage: 3,2 v continuous load: 3 c (120 a) pulse load: 20 c (800 a) capacity: 40 ah operating temperature range: -40°c – 80°c pmsm module performance and efficiency data of the electric motor were provided by motorsolve software, which has given around 200 work points. figure 7: motorsolve simulation table 3: parameters of vehicle vehicle: gas tank volume (m3) 0.08 pressure difference engine/environment (mbar) 0 temperature difference engine/environment (k) 0 distance from hitch to front axle 4549 wheel base 3504 net weight 2690 gross weight 2925 frontal area (m2) 4.458 drag coefficient 0.42 tire inflation pressure front axle 4.3 tire inflation pressure rear axle 4.5 single ratio transmission (front axle): transmission ratio 4.23 inertia moment in / out 0.009/0.016 efficiency 0.97 single ratio transmission (rear axle): transmission ratio 4.27 inertia moment in / out 0.009/0.016 efficiency 0.97 differential (front axle): torque split factor 1 63 inertia moment in / out 0.02/0.02/0.02 differential (rear axle): torque split factor 1 inertia moment in / out 0.02/0.02/0.02 brake (front): brake piston surface (mm2) 3619 friction coefficient (0-1) 0.27 specific brake factor (disc = 1) 1 effective friction radius 150 efficiency 0.99 inertia moment 0.136 brake (rear): brake piston surface (mm2) 1810 friction coefficient (0–1) 0.27 specific brake factor (disc = 1) 1 effective friction radius 140 efficiency 0.99 inertia moment 0.072 wheel (front): inertia moment 1.137 friction coefficient of tire 0.95 wheel load correction coefficient 0.02 static rolling radius 330 dynamic rolling radius 350 wheel (rear): inertia moment 1.137 friction coefficient of tire 0.95 wheel load correction coefficient 0.02 static rolling radius 330 dynamic rolling radius 350 table 4: centre of gravity calculation cog (center of gravity) wheelbase [mm] 3504 front axle load [n] (fa) 15210 rear axle load [n] 13380 wheel radius [mm] 306 lifting height [mm] (hem) 324 front axle load after lifting [n] (fb) 15550 cog distance to front axle [mm] 1639.857293 cog distance to rear axle [mm] 1864.142707 cog height [mm] 229.2646558 cog distance to ground [mm] 535.2646558 net weight [n] 28590 front axle load (%) 0.532004197 rear axle load (%) 0.467995803 figure 8: centre of gravity of the vehicle validation tests the validation of the model we set up in avl cruise software required measurements performed on road tests and roller bench tests. the road tests were focusing on the examination of vehicle’s driving dynamics in order to achieve validation properties. road tests each operation data was logged during the road test on highway and city traffic performed through on-board can system with special data logger equipment. roller bench measurements the following measurement cycles were performed on the roller test bench: definition of drive-line inertia (reduced to roller bench axis) examination of steady (stationary) operating conditions. this cycle is normally used for consumption and emission measurement tests. acceleration engine-power measurement cycle. determination of maximum engine power is carried out with this cycle. during the roller bench measurements the following parameters were recorded: vehicle speed traction power performance (power) all traffic took place in can network. the most important parameters are: battery voltage electric motor voltage electric motor current throttle angle power output of electric drive-train was tested on roller bench by 25–40 km/h speed. motor reverse speed limit is set to 40 km/h, so it was not exceeded. the tests were carried out on the two engines connected mechanically in series. further validation procedures are planned to be done in a way that only one electric motor will be examined, which has power 64 traction. from this measurement, clarification of required parameters validation is expected. figure 9: performance losses measurement with free running test figure 10: full load power characteristic curve of e-van-09 performance-speed characteristic curve shows that electric motor’s maximum power is 40 kw. this power was measured at 27 km/h speed. at lower speeds power output was reduced. as figure 11 shows, more than 5 kn traction force is registered at this speed. the slope of the curve shows if speed is increasing traction force is drastically decreasing. this means that the vehicle would lose velocity on rising road sections – when operating under real life circumstances. unfortunately, these conditions also have safety risks. figure 11: full load traction power characteristic curve of e-van-09 figure 12: characteristic curves of cruise model and real drives summary the model construction and validation of e-van-09 is an important part of the project within the target of electric vehicle development. the models are used to facilitate the development process and highlight its trends or directions. validation process has not been finished yet (figure 12), but the measurements and parameters have already been identified, which ensure that the result and the process can be successfully carried out. acknowledgements „támop-4.2.2.a-11/1/konv-2012-0012: basic research for the development of hybrid and electric vehicles – the project is supported by the hungarian government and co-financed by the european social fund” references 1. j. fulem: icct evaluation of vehicle simulation tools summary report (2009) 2. h-g. schweiger, o. obeidi, o. komesker, a. raschke, m. schiemann, c. zehner, m. gehnen, m. keller, p. birke: comparison of several methods for determining the internal resistance of lithium ion cells (2010) microsoft word b_32_r.doc hungarian journal of industrial chemistry veszprém vol. 38(2). pp. 215-218 (2010) high-tech boat j. lénárt robert bosch department of mechatronics, university of miskolc, miskolc-egyetemváros, hungary e-mail: lenart.jozsef@uni-miskolc.hu as an apropos of a program held in leuven, belgium, has been suggested to build a watercraft that can be controlled from the riverbank. the show was a big belgian program, the celebration of the canonization of father damien. father damien was a roman catholic priest at the 19th century. he won recognition for his ministry to people with leprosy (also known as hansen's disease), who had been placed under a government-sanctioned medical quarantine on the island of molokai in the kingdom of hawaii. keywords: boat, embedded control, remote control, gps, linux, multithreaded control objectives, motivation as an apropos of a program held in leuven, belgium, has been suggested to build a watercraft that can be controlled from the riverbank, suitable to carry some spectacular decoration and has high-tech features like cameras, displays, etc. the wishlist was: the boat should be reliably controlled on a river, able to carry a 2*1 m sized decoration, controlled from a computer (or laptop, pda) from the riverbank through wireless. the controller interface (software) should display the picture of the boats onboard camera and switchable electric units (lights, leds, motors,etc) can be switched from the controller interface. the show was a big belgian program, the celebration of the canonization of father damien. father damien was a roman catholic priest at the 19th century. he won recognition for his ministry to people with leprosy (also known as hansen's disease), who had been placed under a government-sanctioned medical quarantine on the island of molokai in the kingdom of hawaii. the decorations of the 25 small boats shows moments of his life from tremelo through leuven to molokai. the location of the river show is the dijle river from leuven to tremelo (the birth town of father damien). remote controlling the boats down the river requires sophisticated control system. designing the structure and the electronics the first step was to design a reliable driving scheme. to achieve good manoeuvrability on river requires two independent motors. the rear mounted motor gives the throttle and break power, the crosswise mounted motor in the front of the boat gives the steering by switching he motor to rotate cw or ccw. we choose the yamaha m-12 electric boat motor because it has enough power to move the boat and operates from 12v dc supply that can be a high capacity battery, and easy to switch with relays. on full throttle these motors consumes 30a current, so we need large batteries and energy-efficient control method to reach two to three hours of operation. fig. 1 shows the 3d boat model i made. on the model i placed the two 100 ah batteries to test the weight balance of the body. figure 1: 3d model of the boat 216 figure 2: arrangement of the motors under the boat the design criteria of the electronic system was as follows: the controller should be absolutely reliable, it is unadmittable to leave the boat without control, to switch the high power of the motors requires robust, high power electronics, modular design, in case of failure needs the ability to change or repair only the failed module, easy to improve and more stable. each component does only one function and does that perfectly. the first step was the development of the switching electronics. this pcb is responsible for switching the motors (throttle with three speeds, break, steering) and the decoration’s lights, which are 24 pieces of 12 v dc output. a conventional pc or laptop has only few controllable output, so we need a suitable pcb for this role. after extensive research i’ve found the solution: the pca9555n ic made by philips semiconductor. this clever circuit communicates over i2c bus and has 16 i/o general purpose pins. each pin can be configured to act as input or output independently. the boatcontroller pcb has 32 outputs (2*4 for the motors and 24 for the decoration), so can be implemented with 2 pieces of pca9555n. because of the outputs of the ic are connected with devices outside the boat (the “outer world”), it is crucial to provide sufficient protection for the sensitive circuit against overvoltage and transients. this protection consists of an optocoupler and a small relay on each ouptut pin. this means full galvanical detachment between the low current, low voltage circuit and the high current, high voltage (12 v dc) devices. the leds on the decoration are switched by those small relays, but the motors are attached through additional large, 40 amp relays. fig. 3 shows the first version of this pcb. however the switch circuit is only a small piece of the whole system. the project needs an onboard computer that serves the user interface by a java servlet and a controller computer able to communicate with buch of devices, an audio amplifier, wireless network appliances, camera for the remote control function, dc/ac inverter to power the displays. fig. 4 shows the plan of the whole on-board system. figure 3: first version of the switch circuit the next step is the selection of the onboard computer. to do this, let’s summarize it’s tasks: serves the user interface (java servlet), handles the camera over usb or wlan, plays videos, presentations, shows the cameras picture on the displays mounted on the front and back of the boat. the controller computers tasks: control the switching electronics according to the commands given by the user interface, handling the gps receiver, determining the coordinates and speed of the boat. based on those task lists, the chosen device for the role of the onboard computer is the zotac ionitx-a-e miniitx, intel atom n330 dualcore cpu based mainboard with integrated video, audio and network (wireless and wired) interface. this satisfy the our needs and the power consumption on full load is under 40 w. the controller computer also has to be energy efficient and has to be able to communicate over rs-232, i2c and ethernet. for this role the verdex pro xl6p embedded com (computer on module, shown on fig. 5) made by the gumstix co. (california, usa) is an adequate choice. this is a small device (only 80*20mm) with lower than 2w power consumption, 600 mhz marvell pxa270 cpu, 128 mb of ram and runs linux operatng system. the verdex pro xl6p has usb, i2c, spi, gpio and ethernet interfaces. 217 figure 4: system plan figure 5: gumstix verdex pro xl6p com figure 6: software components and hierarchy on the boatcontroller 218 software development, implementation my primary task was the development of the software that runs on the controller computer hence i will explain this work hereafter. the scope of this software is to control the boat, handle the gps module, collect the informations (coordinates, speed) and switch the motors and the decorations lights according to the commands given by the user interface. i’ve decided to design a multithreaded software in which the functions are running in separate threads independently. in this way the separate functions will not block each other e.g. if the gps interpreter function can’t get any correct data other functions can work nevertheless they don’t have to wait for it. the separate threads are joined in the shared memory. this stores the informations from the ui and the gps module respectively. the most important part is the one that communicates with the switching board. this piece of software is responsible for setting the outputs according to the information stored int he shared memory. if this function fails the boat gets uncontrollable. the data link between the control computer and the switching board is i2c with 400 khz clock speed. the i2c is a simple communication protocol, consists of three wires: data (sda), clock (scl) and ground (gnd). each data packet contains a 7 bit i2c address, 1 r/w bit and 16 output status bits. the ‘set/get’ type commands from the user interface comes over ethernet. the process1 interprets this commands, in case of a ‘get’ command it returns the desired data from the shared memory. in case of a ‘set’ command writes the given data to the appropriate cell of the shared memory. the process3 sends commands to the switching circuit over i2c based on the changed shared memory cells. the function of the process2 is to handle the gps receiver connected to the serial port, interpret the datas and put them to the shared memory. testing, observations the first tests of the boat were made on a lake, there the functions and the control systems reliability were examined under unperturbed conditions. on this first tests we encountered with some strange behaviours. at the moments when the relays switched and the motors started the control circuit locked up in 3 cases from 10. we have determined that the heavy voltage drop and transients affects the communication on the i2c bus that freezes hence the boat gets out of control. after correcting this problem the system worked reliable and robust under tough circumstances on rivers and waits to accomplish the demonstration. << /ascii85encodepages false 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word contents.doc hungarian journal of industrial chemistry veszprém vol. 34. pp. 21-26 (2006) separation of organic compounds by gradient simulated moving bed chromatography m. nagy 1, , t. szánya 2, z. molnár 2, g. turza 2, g. gál 2, l. hanák 2, j. argyelán 2, a. aranyi 1, k. temesvári 1 and z. horváth 1 1gedeon richter ltd., h-1475 budapest 10. po box 27. hungary; e-mail: nagymm@richter.hu 2university of pannon, department of chemical engineering pob 158, veszprém, h-8201, hungary a promising solution for the separation of organic compounds in pharmaceutical industry is the gradient simulated moving bed chromatography (smb). the above mentioned process can be used for the production of high purity materials (isomers, optical isomers, biomolecules). we assumed isotherm, isochor equilibrium adsorption (competitive multicomponent langmuir-adsorption equilibrium) in the mathematical model and neglected the effects of axial dispersion. in our present work we extended the mathematical model with solvent adsorption-desorption processes (acetone-dichloromethane eluent, steroid compounds, silicagel). the mathematical model was solved by finite differences numerical mathematical method using pc. the gradient smb separations were carried out with a laboratory scale four column equipment in open loop system at 1:1:2:0 column configuration. the smb equipment (l=25 cm, i.d.=1 cm) was planned and constructed for separation of a steroid mixture using ymc s-50 silica gel as adsorbent (specific surface=798.63 m2 g-1). the effect of switching time change (5.5 min, 9 min, 11.5 min, 22.5 min) on component separation was examined. during our measurements the amount of acetone in dichloromethane was 55 % v/v in the fresh eluent and pure dichloromethane in the feed. the process variables of the gradient smb (product purity, yield, productivity, specific solvent consumption) are very favourable. our conclusion is that the measured and the calculated data agree well and we have produced more than 99.9 %m/m purity and 90 % yield , productivity 1300-3000 g steroid kg-1 adsorbent day at 0.1-0.3 m3 fresh eluent kg-1 steroid eluent consumption. keywords: preparative liquid chromatography, simulated moving bed chromatography, solvent gradient smb introduction the smb process was developed in the early 1960s by brougthon and gerhold [1] and has been used for many years in the petrochemical and sugar industries for large scale separation [2]. recently, the separation of enantiomers due to the demand for high purity products has become necessary [3]. the smb (fig. 2.) is a continuous unit operated in cyclic mode which reproduces the performance of the equivalent true moving bed (tmb) unit (fig. 1.). the smb is divided into four sections, each constituted of a counter current adsorption column which plays a specific role in the separation. let us consider a feed mixture consisting of more retained species (a) and a less retained one (b) dissolved in the eluent. the separation is obtained in the two central sections, where b is carried by the mobile phase to the raffinate outlet. the fresh eluent is fed to the bottom of the section i, so as to desorb a and regenerate the adsorbent solid, before it is recycled to section iv. on the other hand b is retained in section iv and the pure eluent is recycled to section i. in practice the movement of the solid is not feasible and the tmb is replaced by the smb configuration where the adsorption beds are fixed and the counter-current solid-liquid movement is simulated by periodical switching the inlet and outlet ports of the unit [4]. i. feed (a+b) extract (a) raffinate (b) iv. iii. ii. a ds or be nt r ec ir cu la tio n l iq ui d re ci rc ul at io n s (e-f+r) d=s+rec rec fresh eluent fig. 1.: true moving bed (tmb) adsorber – i, ii, iii, iv – zones; s – desorbent (solvent, eluent); rec – recirculated eluent; e – extract stream with the better adsorbed component a; f – feed stream with the components a and b; r – raffinate (liquid outlet) stream with the less adsorbed component b 22 i ii iii iv d=s+rec e (a) f (a+b) r (b) liquid phase adsorbent phase fig. 2.: simulated moving bed (smb) adsorber – i, ii, iii, iv – zones, respectively hplc columns use of gradient elution is recommended, if conditions must be changed during separation. the applied gradient can be the pressure, temperature or solution composition. according to the literature of solution composition changing gradient smb, where the solution composition is chosen, four scientific „schools” exist; the mpi magdeburg inst. dyn. komplex techn. system in germany [5,6,7], the kluyer laboratory for biotechnology at delft university of technology in the netherlands [8,9,10]. eth zürich, inst. verfahrenstechnik in switzerland [4, 11] and there are significant scientific results in france [12], too. we calculated the initial parameters with the method of morbidelli et al. [13]. after the authors in a two component system can be determined a the mii-miii area from the geometric data of the smb equipment, the volumetric velocities, the parameters of langmuir-type isotherms and the concentrations of the mixture to be separated. the actual operating conditions determine a point on the mii-miii diagram. the variable operating conditions are: fresh eluent, recirculated eluent, feed, extract and raffinate flow rates, switching time. mathematical models and joined computer programmes published in our earlier papers [14,15] have been developed and applied for the calculation of smb. experiments all necessary additional information for this project, like the adsorption equilibrium data, the number of theoretical plates (ntp) and height of equivalent theoretical plate (hetp), the frontal adsorption elution measurement was published earlier [16]. parameters of smb-lc measurements we applied an 1-1-2-0 column configuration in the smb system. this way the steroid b has “bigger space” along the length of the columns. in this case we did not use the raffinate pump, we adjusted the flow rate in segment iii so that the steroid b appeared in the lrout flow in the open-looped smb system. the function of segment i is the regeneration of the adsorbent and the production of the steroid a in the extract. as fresh eluent in the segment i we used 1.2:1 (v/v) acetone dichloromethane (gradient). the function of segment ii is the separation of steroid a and b and the extraction of the steroid a in this segment. the function of segment iii is to separate steroid a and b and to produce steroid b in the lrout flow. we fed the mixture of steroid a and b into the third segment, the steroids were soluted in pure dichloromethane because this improved the solution of the steroids and helped us to use gradient smb. each of the columns in the four-column smb equipment were previously equilibrated with pure dichloromethane at 293 k, we wanted to separate the dichloromethane mixture of 42 g dm-3 steroid b and 18 g dm-3 steroid a. the fresh eluent 1.2:1 v/v acetone-dichloromethane volumetric ratio was 4.25 cm3min-1. the feed flow rate of the steroid sample was 0.8 cm3 min-1. steroid a was extracted with 2.2 cm3 min-1 parameter, so the lrout flow was 2.85 cm3min-1 and the switching time was 22.5 min. process parameters were determined by morbidelli method (fig. 3. and table 1). fig. 3.: the measurement points placed in the morbidelli triangle at different switching times when we decreased the switching time to 11.25 min, we doubled the original flow rates. when we used 5.5 min for switching time, we doubled once again the flow rates. in case of 9 min as switching time, we used computer simulation to optimize the work point to get as close to the points of morbidelli triangle as it was possible (f= 1.8 cm3min-1, d= 14.4 cm3min-1, e=7.8 cm3min-1, lrout= 8.4 cm3min-1). 23 table 1: input data of the software smb-krom-n number of components k = 3 column inner diameter id.=1 cm column length l=25 cm number of columns n=4 free volume coefficient eps= 0.8018 cm3 liquid free volume cm-3 column bulk density roh= 0.4045 g silica gel cm-3 column langmuir constants (same as on page ) feed concentration liquid cmacetonemg -3f acetone 0=c liquid cmcomponentbmg -3f b 42=c liquid cmcomponentamg -3f a 18=c flow rates * optimized by simulation liquidcomponentaorbmgs a s b 30 −== cmcc simulation smb 8/41 smb 8/42 smb 8/46* smb 8/44 switching time(min) 22.5 11.25 9 5.5 f (cm3 min-1) 0.8 1.6 1.8 3.2 d (cm3 min-1) 4.25 8.5 14.4 17.0 e (cm3 min-1) 2.2 4.4 7.8 8.8 r (cm3 min-1) 0 0 0 0 fresh eluent liquid cmacetonemg. -3f acetone 6435=c number of theoretical plates ntp=200 / 25 cm column calculation time 585 min simulation data of 1:1:2:0 column configuration smb simulation was done by smb-krom-n software. the input data are summarized in table iii. the software takes into account the solvent adsorptiondesorption phenomena, too. fig. 4 shows the profile of a and b component along the length of columns and fig. 5 shows the acetone gradient along the length of columns, at quasistationary state in case of rg smb8/46 simulation. 0 5 10 15 20 25 30 35 40 45 0 200 400 600 800 ntp c a , b c om po ne nt (g d m -3 ) b component a component fig. 4.: profile of a and b components at quasistationary state 24 fig. 5.: profile of acetone at quasi-stationary state fig. 6 and 7 shows the acetone concentration change in the raffinate and extract outlet versus simulation time in case of rg smb8/46 simulation. 200 250 300 350 400 450 711 720 729 simulation time (min) c on ce nt ra tio n a ce to ne (g d m -3 ) acetone raffinate fig. 6.: acetone concentration versus two period of simulation time in the raffinate outlet 428 429 430 431 432 433 434 435 436 437 711 720 729 simulation time (min) c on ce nt ra tio n a ce to ne (g d m -3 ) acetone extract fig. 7.: acetone concentration versus two period of simulation time in the extract outlet results measurement results of 1:1:2:0 column configuration smb compared to simulation on the fig. 8, 9, 10 and 11 those measurements are marked with grey colour where the desired results can be seen, with white colours the measurements which are out of our requirements. 0 20 40 60 80 100 prep hpl gsmb8/ (22.50 gsmb8/ (11.25 gsmb8/ (5.50 gsmb8/ (9.00 pu rit y "b "( % / raffinate > 99.9 % m/m b η b > 90 % raffinate < 99.9 % m/m b η b < 90 % fig. 8.: comparing the purity of steroid b in different measurements 0 10 20 30 40 50 60 70 80 90 100 prep. hplc gsmb8/41 (22.50 min) gsmb8/42 (11.25 min) gsmb8/44 (5.50 min) gsmb8/46 (9.00 min) yi el d "b "( % ) raffinate > 99.9 % m/m b ηb > 90 % raffinate < 99.9 % m/m b or ηb < 90 % fig. 9.: comparing the yield of steroid b in different measurements 0.0 0.5 1.0 1.5 2.0 2.5 3.0 prep. hplc gsmb8/41 (22.50 min) gsmb8/42 (11.25 min) gsmb8/44 (5.50 min) gsmb8/46 (9.00 min) p b (m g b /g si lic a ge l m in ) raffinate > 99.9 % m/m b ηb > 90 % raffinate < 99.9 % m/m b or ηb < 90 % fig. 10.: comparing the productivity of steroid b in different measurements 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 prep. hplc gsmb8/41 (22.50 min) gsmb8/42 (11.25 min) gsmb8/44 (5.50 min) gsmb8/46 (9.00 min) sf b (d m 3 e lu en t g -1 b ) raffinate > 99.9 % m/m b ηb > 90 % raffinate < 99.9 % m/m b or ηb < 90 % fig. 11.: comparing the eluent consumption of steroid b in different measurements 25 the result of the experiments shows that the decrease of the switching time highly improves the productivity, especially at the optimized 9 min switching time experiment. in this case the eluent consumption is also properly low. to describe numerically the above gsmb 8/41 and gsmb 8/46 the productivity was increased from 0.95 mg steroid b g-1 adsorbent min-1 to 2.64 mg steroid b g-1 adsorbent min-1. the eluent consumption was changed from 0.12 cm3 eluent mg-1 steroid b to 0.18 cm3 eluent mg-1 steroid b. we achieved the best favourable result in the rg1040-gsmb 8/46 measurement at 9 min switching time. in this case the calculated values of measurement were compared to data given in table 2. we note that the lrout 1, 2 are given by halving the lrout liquid stream for 0-4,5 min and 4,5-9 min fractions. table 2: results of the rg 1040 gsmb 8/46 measurement compared to result of the simulation measurement simulation purity of raffinate (lrout) lrout1 96.96 %m/m b lrout2 > 99.9 %m/m b lrout 1 +lrout 2 > 99.9 %m/m b purity of extract (e) 88.89 %m/m a 93.5 %m/m a yield lrout1 6.46 %b lrout2 92.6 %b extract 68.1 %a lrout 1 +lrout 2 > 99.99 % 98.3 % productivity lrout 2 2.14 mingelsilicag bmg extract 0.54 mingelsilicag amg lrout 1 +lrout 2 2.16 mingelsilicag bmg extract 0.69 mingelsilicag amg eluent consumption lrout 2 0.134 bmg eluentfreshcm3 extract 0.403 amg eluentfreshcm3 lrout 1 +lrout 2 0.197 bmg eluentfreshcm3 extract 0.61 amg eluentfreshcm3 discussion our conclusion on the basis of laboratory gradient, 1:1:2:0 column configuration, open loop smb measurements is that varying the switching time of smb process results big changes in productivity. in our case we get the highest productivity at 9 min switching time. we significantly increased the operation results according to the preparative hplc measurement (table 3). table 3: results of the rg 1040 gsmb 8/46 measurement compared to preparative hplc measurement preparative hplc rg1040 smb8/46 measurement (9 min) purity of raffinate (lrout 2) >99.9 % m/m b >99.9 % m/m b yield (lrout 2) ~ 95 % b >92.6 % b productivity (lrout 2) 0.303 mingelsilicag bmg 2.14 mingelsilicag bmg eluent consumption (lrout 2) 0.354 bmg eluentfreshcm3 0.134 bmg eluentfreshcm3 26 we achieved 700% productivity increase and 50 % eluent consumption decrease beside more than 99.9 % m/m b purity and 90 % b yield. it could be seen, that the developed smb process was outstandingly economic, the value of the productivity was successfully increased to 3.082 kg b/ kg silica gel within a day, at 0.134 m3 fresh eluent/kg b steroid eluent consumption. symbols cacetone concentration of acetone, g dm-3 cb concentration of steroid b, g dm-3 ca concentration of steroid a, g dm-3 k number of components k’ capacity factor id column inner diameter, cm l column length, cm f flow rate of feed, cm3 min-1 d flow rate of fresh eluent, cm3 min-1 e flow rate of extract, cm3 min-1 r flow rate of raffinate, cm3 min-1 lrout outlet liquid at 1:1:2:0 column configuration at r=0 t switching time, min ε free volume coefficient, cm3 liquid free volume cm-3 column roh bulk density, g silica gel cm-3column ntp number of theoretical plates n number of columns references 1. broughton d. b., gerhold c. g. (1961) us pat. 2 985589 2. ruthven d. m., ching c. b., (1989) chem. eng. sci. 44 (5), 1011-1038 3. jupke a., epping a., schmidt-traub h., (2002) j. chromatogr. a, 944 93-117 4. giovanni o., mazzotti m., morbidelli m., denet f., hauck w., nicoud r., (2001) j. chromatogr. a, 919 1-12 5. antos d., seidel-morgenstern a., (2002) j. chromatogr., 944 77-91 6. antos d., seidel-morgenstern a., (2001) chem. eng. sci., 56 6667-6682 7. ziomek g., kaspereit m., jezowski j., seidelmorgenstern a., antos d., (2005) j. chromatogr a, 1070 111-124 8. jensen t., reijns t., billiet h., wielen l., (2000) j. chromatogr a, 873 149-162 9. houwing j., billiet h., wielen l., (2002) j. chromatogr a, 944 189-201 10. houwing j., hateren s., billiet h., wielen l., (2002) j. chromatogr a, 952 85-98 11. abel s., mazzotti m., morbidelli m. (2002), j. chromatogr a, 944 23-29 12. hauck w., ludemann-hombourger o., nicoud r. m., di giovanni o., mazzotti m., morbidelli m., prep 2001 14th international symposium exhibit & workshop on preparative/process chromatography, washington, dc. usa 13. migliorini c., mazzotti m., morbidelli m., (1998) j chromatogr. a, 827:2 161-173 14. szánya t., argyelán j., kováts s., hanák l., (2001) j chromatogr. a, 908 265-272 15. nagy m., molnár z., hanák l., argyelán j., szánya t., ravasz b., aranyi a., temesvári k., (2004) chromatographia, 60 s 181-187. 16. nagy m., molnár z., hanák l., argyelán j., szánya t., ravasz b., turza g., aranyi a., temesvári k., (2004) hungarian journal of industrial chemistry, 32 13-21 microsoft word szolcs_eloszo.doc hungarian journal of industrial chemistry veszprém vol. 32. pp. 65-71 (2004) separation by ion exchange and adsorption parametric pumping v. cycle efficiency for batch, thermal ion exchange parametric pumping l. hanák, t. szánya and p. szolcsányi department of chemical process engineering, university of veszprém, veszprém, hungary the theoretically best attainable separation can easily be determined in the function of the theoretical cycle number. in the reality, due to the non-equilibrium ion exchange, the mixing phenomena and the “run out” of characteristics, the performance of the actual process, especially in the production of high purity materials, a cycle efficiency value can be ordered to the parametric pumping processes. the authors investigated the relationships between the more important process and operation parameters and the cycle efficiency in aqueous media and in the presence of varion-ksm ion exchange resin, ca2+, k+ cations and cl– anions. introduction production of high purity materials accounts for the major production cost in fine chemical industries. there has been a growing demand for economical and energy-efficient separation processes. the increasing interest in this area is also reflected in the numerous research articles published in the field of ion exchange and adsorption separations [1-5]. among these processes parametric pumping is a technique which has been studied extensively [6-8]. the most important property of this process is the fact that it is a reagent-free separation process in which no regeneration chemicals are needed which may pollute the environment, and in which no regenerant can contaminate either product. emphasis is placed on the following areas: • development of adsorbents and ion exchange materials [3-4, 9-10]. • investigation of possible thermodynamic parameters [11-13]. • an improved theoretical understanding of the process [14-15]. • development of new process configurations [16-17]. • development of highly efficient processes [18]. in this paper experimental data were compared with the best attainable separation achieved by the application of theoretical cycles. cycle efficiency (ηi) was defined as the ratio of the theoretical and actual cycle numbers. it presents an interesting possibility in the evaluation of experimental results, especially in the production of high purity ionic compounds. experimental part an aqueous solution of calcium and potassium cations in the presence of chloride anion on a highly acidic cation exchanger (varion-ksm, nitrochemical works of balatonfűzfő, hungary) was selected as a model system. 66 the ion exchange isotherms were determined by simple batch equilibration of a known mass of resin with a given volume of solution of known concentration and ionic composition over 36 hours at temperatures 288k and 333k. the solution was then separated from the resin and the concentration of calcium and potassium in solution were measured. the ion exchanger phase concentration was calculated by mass balance. a preliminary summary of these data have been reported elsewhere [19]. the experimentally determined ion exchange isotherms and the ion exchange selectivity coefficient ( ca kt ) as a function of resin phase composition (yca) are shown in figs. 1-3. 0 20 40 60 80 0 0.2 0.4 0.6 0.8 1yca++ tc a+ + / k + 288k 333k ca++-k+ -cl varion ksm co= 0.10 equ/dm3 0 20 40 60 80 0 0.2 0.4 0.6 0.8 1yca++ tc a+ + / k + 288k 333k ca++-k+ -cl varion ksm co= 0.10 equ/dm3 figure 1. ion exchange equilibrium of ca2+ -k+ cations at temperatures of 288k and 333k, with a total cation content of 0.10 equ/dm3 knowledge of ion exchange isotherms at two temperatures is required numerically for the mathematical modelling of the process. in our case, the ion exchange selectivity coefficient ( ca kt ) as a function of resin phase composition (yca) was used for the definition of ion exchange equilibrium. the equilibrium data were fitted to a third degree polynome of the following form: dycybyat ca 2 ca 3 ca ca k +++= (1) a least square optimization of the equilibrium data gave the constants of eq.(1). these functions and constants were used in all calculations (table 1.). table 1. constants of the ion exchange selectivity coefficient at two temperatures c0=0.10equ/dm3 c0=0.50equ/dm3 c0=1.0equ/dm3 288k 333k 288k 333k 288k 333k a -38.17 26.55 -0.727 -14.9 5.485 5.99 b 99.12 7.25 12 33.28 -8.063 -8.748 c -100.4 -100.2 -22.89 -38.9 0.596 -0.936 d 40.65 70.03 12.15 21.2 2.186 4.02 the parametric pumping experiments were carried out in a laboratory scale, automatic apparatus, described in detail in the previous paper [20]. different size glass columns with jacket and reservoirs are included in the system for direct heat transfer experiments. 0 0.2 0.4 0.6 0.8 1 0 0.2 0.4 0.6 0.8 1xca++ y c a+ + 288k 333k ca++-k+ -cl varion ksm co= 0.50 equ/dm3 0 5 10 15 20 25 0 0.2 0.4 0.6 0.8 1yca++ tc a+ + / k + 288k 333k ca++-k+ -cl varion ksm co= 0.5 equ/dm3 figure 2. ion exchange equilibrium of ca2+ -k+ cations at temperatures of 288k and 333k, with a total cation content of 0.50 equ/dm3 the effect of the following more important operation and process parameters were investigated: • liquid flow rate (vo, from 0. 1 to 2. 3 m/s) • transfer of ion fraction during a half cycle(α’, from 0.026 to 1.0 (dimensionless)) • initial ion composition (xca,0, from 0.2 to 0.8) • length of ion exchanger column (l, from 0.5 to 1.5m) • total solution concentration (c0, from 0.1 to 1.0 equ/dm3). 67 0 0.2 0.4 0.6 0.8 1 0 0.2 0.4 0.6 0.8 1xca++ y c a+ + 288k 333k ca++-k+ -cl varion ksm co= 1.0 equ/dm3 0 1 2 3 4 5 0 0.2 0.4 0.6 0.8 1yca++ tc a+ + / k + 288k 333k ca++-k+ -cl varion ksm co= 1.0 equ/dm3 figure 3. ion exchange equilibrium of ca2+ -k+ cations at temperatures of 288k and 333k, with a total cation content of 1.0 equ/dm3 the following variables and operational conditions were fixed: • the temperatures (288k and 333k) in cold and hot half cycles • particle size of ion exchanger, dp = 0,5-0,7 mm • initial condition of the experiments, the ion exchanger column was always brought into equilibrium at the lower temperature (288k) with the solution to be separated • location of the cold reservoir and the hot reservoir, in our case, the hot reservoir was always connected to the upper part of the column • length of thermostating time is 15 minutes in case of a column diameter of 28 mm and, 8 minutes in case of a 10 mm column diameter • dead-volume of the equipment. according to the temperature dependence of the ion exchange equilibrium, the concentration of calcium ions decreased in the cooled reservoir (288k). in the other case the concentration of potassium ions decreased in the heated reservoir (333k). the total cationic concentration of the solution in the mentioned reservoirs was constant. a part of the experimental results and data was published in the previous paper [20]. table 2-4 summarizes the investigated parameters and results for selected experiments at three solution concentrations. publication of about 1000 determined reservoir concentration from 45 measuring series is not possible here, only the hot and cold reservoir concentrations of the 20th cycle are given. the comparison of the calculated and experimental results using relationships presented previously for a given parametric pumping operation, the theoretically best attainable separation can easily be determined in the function of the cycle number. knowing this, it presents an interesting possibility in the evaluation of experimental results as it is shown below. among the experimental data, the reservoir concentrations of the 20th cycle were taken as basic data. (the sensitivity of the used zeiss-aas1 atomic absorption spectrophotometer was table 2. conditions and results for selected batch experiments at 0.10equ/dm3 solution concentration, l=1.0m, db=28mm no. xca,0 ∆v,dm3 b,dm3/h c20 ,mequ/dm3 nt ηi p20 ,m/m% α' vo,mm/s ca2+ ca2+ ca2+ k+ k+ k+ k+ ca2+ 1 0.20 0.4 1.0 0.038 9.8 0.49 99.981 0.026 0.45 6.07 6.6 0.33 88.555 2 0.20 0.8 1.0 0.034 10.4 0.52 99.983 0.052 0.46 2.05 8.6 0.43 95.982 3 0.20 2 1.0 0.026 11.6 0.58 99.987 0.13 0.45 1.12 9.8 0.49 97.785 4 0.20 4 1.0 0.022 12.2 0.61 99.989 0.26 0.43 7.76 6.2 0.31 85.598 5 0.20 6 1 0.019 12.6 0.63 99.990 0.39 0.45 22.7 4.4 0.22 62.999 6 0.20 8 1 0.018 12.8 0.64 99.991 0.52 0.44 45.1 2.6 0.15 37.836 7 0.50 0.4 1.0 0.1 10.4 0.5 99.971 0.026 0.44 0.025 13.6 0.68 99.950 8 0.50 0.8 1 0.052 10.6 0.53 99.974 0.052 0.45 0.02 13.8 0.69 99.960 9 0.50 2 1 0.045 11.1 0.55 99.977 0.13 0.45 0.015 14.4 0.72 99.970 10 0.50 4 1 0.033 11.4 0.57 99.983 0.26 0.47 1.28 7.2 0.36 97.472 11 0.50 6 1 0.88 6.4 0.32 99.558 0.39 0.45 5.95 5 0.25 88.768 12 0.50 8 1 8.55 3.6 0.18 95.534 0.52 0.45 13.8 3 0.15 75.747 13 0.80 0.8 1 0.68 9 0.45 99.659 0.052 0.46 0.0033 14.4 0.72 99.993 14 0.80 2 1 13.4 5.4 0.27 92.819 0.13 0.45 0.0025 15.4 0.77 99.995 15 0.80 4 1 38 3.2 0.16 76.543 0.26 0.45 0.002 15.8 0.79 99.996 16 0.80 6 1 50.2 2.4 0.12 66.489 0.39 0.44 0.27 7.2 0.36 99.461 17 0.80 8 1 58 1.8 0.09 59.155 0.52 0.45 1.86 3.8 0.19 96.348 68 inadequate for the accurate determination of the low concentration of given component, after the 20th cycle). using the calculated data, the theoretical cycle number of the former reservoir concentrations was determined, and the cycle efficiency (ηi) was defined as the ratio of the theoretical and actual cycle numbers. it is shown in the function of process parameters for ca2+–k+ ion pairs, in the presence of cl– anions, and in the case of varion ksm cation exchanger resin. table 3. conditions and results for selected batch experiments at 0.50equ/dm3 solution concentration, l=1.53m, db=28mm, ∆v=800cm3, α’=0.17 no. xca,0 b,dm3/h c20 ,mequ/dm3 nt hi p20 ,m/m% vo,mm/s ca2+ ca2+ ca2+ k+ k+ k+ k+ ca2+ 1 0.20 0.2 0.014 15.6 0.78 99.999 0.09 0.92 9.2 0.46 99.908 2 0.20 0.4 0.018 15 0.75 99.998 0.18 0.88 9.4 0.47 99.912 3 0.20 0.7 0.02 14.8 0.74 99.998 0.32 14.9 5.6 0.28 98.487 4 0.20 1.1 0.025 14.4 0.72 99.997 0.51 20.7 4.2 0.21 97.886 5 0.20 1.6 0.032 13.2 0.66 99.997 0.71 23.2 3.6 0.18 97.625 6 0.20 2.8 0.74 7.6 0.38 99.926 1.24 25.1 3.2 0.16 97.425 7 0.50 0.4 0.11 13.6 0.68 99.989 0.18 0.07 12.2 0.61 99.993 8 0.50 0.7 0.24 12.2 0.61 99.976 0.31 0.11 11.2 0.56 99.989 9 0.50 1.1 0.56 8.6 0.43 99.944 0.50 0.83 8.2 0.41 99.917 10 0.50 1.6 0.76 6.4 0.32 99.924 0.71 2.1 7.6 0.38 99.790 11 0.50 2.8 0.9 4.8 0.24 99.910 1.24 6.8 4.8 0.24 99.315 12 0.80 0.4 4.2 9.6 0.48 99.578 0.18 0.004 16.6 0.83 99.999 13 0.80 0.7 14.9 8 0.4 98.487 0.31 0.005 16.2 0.81 99.999 14 0.80 1.1 38.7 5.4 0.27 95.974 0.48 0.01 15.5 0.77 99.999 15 0.80 1.6 44.2 4.8 0.24 95.376 0.71 0.025 13 0.65 99.997 16 0.8 2.8 51.5 4.2 0.21 94.570 1.22 0.23 8.2 0.41 99.977 in figure 4 is shown the effect of flow rate, in case of 0.5 equ/dm3 solution concentrations, if various initial ion compositions are used. the cycle efficiency was increasing with the decrease of flow rate but, the measure of growth and the values of cycle efficiencies varied widely. if the initial ion composition is low, then cycle efficiency generally increases for a given ion and the effect of flow rate is small. in figure 5 are shown the values of cycle efficiency as a function of the relative ion amount (α’) correspond to a half cycle, in case if various initial ion compositions and 0.1 equ/dm3 solution concentration. the curves reach maxima, indicating the lack of equilibrium. the place of the maxima shows the amount of relative ions (α’), which should be the load for the best separation. the role of the initial ion composition is clear: the maximum place of the given component is shifted to the larger loads, proportionally to the decrease of the initial ion composition. table 4. conditions and results for selected batch experiments at 1.0equ/dm3 solution concentration, l=1.50m, db=10mm, b=0.087dm3/h, v0=0.31mm/s no. xca,0 ∆v,dm3 c20 ,mequ/dm3 nt η i p20 ,m/m% α ' ca2+ ca2+ ca2+ k+ k+ k+ k+ ca2+ 1 0.20 0.1 0.035 16.1 0.80 99.998 0.17 6.01 10.6 0.53 99.699 2 0.20 0.1 0.01 18 0.9 99.999 0.34 10 9.6 0.48 99.497 3 0.20 0.2 0.01 18 0.9 99.999 0.68 426 3.4 0.17 72.935 4 0.20 0.3 0.01 18 0.9 99.999 1 552 2.4 0.12 61.878 5 0.50 0.1 0.65 13.8 0.7 99.967 0.17 3.96 9.4 0.47 99.802 6 0.50 0.1 0.13 16.4 0.82 99.993 0.34 0.17 15.6 0.78 99.991 7 0.50 0.2 0.18 15.8 0.79 99.991 0.68 0.08 16 0.8 99.996 8 0.50 0.3 76.80 5 0.25 96.007 1 131.00 3.2 0.16 92.991 9 0.80 0.1 2.72 13.2 0.66 99.864 0.17 0.65 11.6 0.58 99.967 10 0.80 0.1 1.12 15 0.75 99.944 0.34 0.01 17.2 0.86 99.999 11 0.80 0.2 354 3.6 0.18 78.493 0.68 0.006 18.2 0.91 99.999 12 0.80 0.3 500.3 2.4 0.12 66.640 1 0.61 11.8 0.59 99.969 in figure 6 are shown the effects of the above discussed components in case of 1 equ/dm3 solution concentration. the results are the same as above, besides the considerably greater loads. in figure 7 the effects of the total concentration of solutions are presented in the function of relative ion amounts, flown through during a half cycle. with the increase of solutions total concentration, markedly increases the cycle efficiency belonging to the maxima of the curves on one hand, while on the other hand the maximum cycle efficiencies appear always at higher loads of relative ion amounts. the equilibria related to ca2+–k+ ion pairs depends strongly on the total concentration of solutions (fig. 1-3.). increasing the concentration, the selectivity values decrease and the isotherms of the so called sigmoid shape form. figure 7 proves that the decrease of selectivity values improves the load of the column. due to the sigmoid type isotherm, at the concentration of 1 equ/dm3, the shape and the 69 0 0.2 0.4 0.6 0.8 1 0 0.2 0.4 0.6 0.8 1 1.2 1.4 vo, mm/s η c a+ + xca++,o=0.80 xca++,o=0.50 xca++,o=0.20 co=0.50 equ/dm3, l=1.0 m, db=28 mm, α'=0.17 0 0.2 0.4 0.6 0.8 1 0 0.2 0.4 0.6 0.8 1 1.2 1.4 vo, mm/s ηk + xca++,o=0.80 xca++,o=0.50 xca++,o=0.20 figure 4. the changes of cycle efficiencies in the function of the flow rate 0 0.2 0.4 0.6 0.8 1 0 0.1 0.2 0.3 0.4 0.5 0.6α' η c a+ + xca++,o=0.80 xca++,o=0.50 xca++,o=0.20 co=0.10 equ/dm3, l=1.0 m, db=28mm, vo=0.45 mm/s 0 0.2 0.4 0.6 0.8 1 0 0.1 0.2 0.3 0.4 0.5 0.6α' η k + xca++,o=0.80 xca++,o=0.50 xca++,o=0.20 figure 5. the changes of cycle efficiencies with α’ at different initial ion composition and at 0.1 equ/dm3 solution concentration 0 0.2 0.4 0.6 0.8 1 0 0.2 0.4 0.6 0.8 1 1.2α' η c a+ + xca++,o=0.80 xca++,o=0.50 xca++,0=0.20 co=1.0 equ/dm3 vo=0.31 mm/s l=1.5 m, db=10 mm 0 0.2 0.4 0.6 0.8 1 0 0.2 0.4 0.6 0.8 1 1.2 α' η κ + xca++,o=0.80 xca++,o=0.50 xca++,o=0.20 figure 6. the changes of cycle efficiencies with α’ at different initial ion composition at 1 equ/dm3 solution concentration 0 0.2 0.4 0.6 0.8 1 0 0.2 0.4 0.6 0.8 1 1.2 α' η c a+ + co=0.10 equ/dm3 co=0.50 equ/dm3 co=1.0 equ/dm3 vo=0.31 mm/s, l=1.5 m, db=10 mm, xca++,o =0.80 0 0.2 0.4 0.6 0.8 1 0 0.2 0.4 0.6 0.8 1 1.2 α' η k + co=0.10 equ/dm3 co=0.50 equ/dm3 co=1.0 equ/dm3 figure 7. the changes of cycle efficiencies with different solution concentration 70 0 0.2 0.4 0.6 0.8 1 0.5 1 1.5 l, m η c a+ + xca++,o=0.80 xca++,o=0.50 xca++,o=0.20 co=0.50 equ/dm3, vo=0.18 mm/s, db=28 mm, α'=0.13 0 0.2 0.4 0.6 0.8 1 0.5 1 1.5 l, m η k + xca++,o=0.80 xca++,o=0.50 xca++,o=0.20 figure 8. the changes of cycle efficiency with the length of ion exchange column position of cycle efficiency curves of ca2+ and k+ are very similar, this is very advantageous, because the column can be operated with optimum load regarding both the ions. at last, in figure 8 are shown the change of cycle efficiencies as a function of column height, in case of 0.5 equ/dm3 initial concentration and different initial ion composition. the cycle efficiencies increase in different extent with the column height. in given circumstances, the number of equilibrium units formed in the column is proportional with the length of the ion exchanger charge, filled in the column. this basically determines the level of the component separation. summary the results of these calculations were used in the evaluation of results determined in the experiments with ca2+–k+ ion pair, the idea of cycle efficiency was defined. this is the ratio of the theoretical and practical cycle numbers belonging to a given reservoir concentration. with the help of the cycle efficiency, diagrams were constructed to elucidate the effect of some operation parameters on the component separation. with the selection of appropriate parameters and starting concentration in favourable composition range, the cycle efficiencies remain high, and the products purity reach the 99.99 or 99.999 m/m% values. symbols v0 superficial velocity of liquid phase xj ion ratio of component “j” in the liquid phase xj,0 initial ion ratio of component “j” in the liquid phase yj ion ratio of component “j” in resin phase c0 total cationic concentration of liquid phase c20,j reservoir concentration of component “j” after the 20th cycle l the length of ion exchange column nt theoretical cycle number p20,j product purity of component “j” after the 20th cycle i jt ion exchange selectivity coefficient of ion “i”, related to ion “j” ∆v volume flow through in half cycle α’ dimensionless ion proportion, the ratio of cation amount flowing through during half cycle and ion exchange capacity of the column ηi cycle efficiency related to component “i” 71 references 1. humphrey j.: chem. eng. prog.,1995, 91(10), 31-41 2. keller g.: chem. eng. prog.,1995, 91(10), 56-67 3. sheng p. z. and costa c. a. v.: ind. eng. chem.res.,1998, 37(12), 4808-4815 4. diaz m., rendueles m., fernandez a. and suarez c.: sep. sci. techn.,1998, 33(7), 1025-1042 5. agrawal a. and burns m. a.: aiche j.,1996, 42(1), 131-146 6. diez s, leitao a., ferreira l. m. and rodrigues a. e.:sep. purif. techn., 1998, 13, 25-35 7. simon g., hanák l., grevillot g., szánya t. and marton g.: j. chrom. b, 1995, 664, 17-31 8. simon g., hanák l., grevillot g., szánya t. and marton g.: chem. eng. sci., 997, 52, 467-480 9. ivanov v. a., timofeevskaja v. d., garlina o. t. and gorshkov v. i.: microporous and mesoporous materials, 2003, 65, 257-265 10. ivanov v. a., timofeevskaja v. d. and gorshkov v. i.: react. polym., 1992, 17(1), 101-107 11. ahmed z. m.: react. polym., 1987, 5(3), 227235 12. kiefer r. and höll w. h.: react. funct. polym., 2000, 45, 197-210 13. ferreira l. m. and rodrigues a. e.: adsorption, 1995, 1(3), 233-252 14. grevillot g., bailly m. and tondeur d.: int. chem. eng., 1982, 22, 440-455 15. ferreira l. m. and rodrigues a. e.: adsorption, 1995, 1(3), 213-231 16. nikolaev n. p., muraviev d. n. and muhammed m.: sep. sci. techn., 1997, 32(1-4), 849-866 17. sheng p. z. and costa c. a. v.: sep. sci. techn., 1997, 12(1), 81-95 18. wankat p. c.: large-scale adsorption and chromatography, crc press, boca raton, 1986 19. hanák l., szánya t. and szolcsányi p.: hung. j. ind. chem., 1988,16, 253-260. 20. szánya t., hanák l., mohilla r. and szolcsányi p.: hung. j. ind. chem., 1988, 16, 261-271. microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 37(2) pp. 165-167 (2009) new results on the field of “white biotechnology” a. nemeth , g. nagy, b. sevella budapest university of technology and econpomics, department of applied biotechnology and food science h–1111 budapest műegyetem rkp. 3., hungary e-mail: naron@f-labor.mkt.bme.hu “white biotechnology” term is used to describe the production of chemical compounds by enzymatic or microbial (biotechnological) methods. our research group focuses on the field of glycerol utilization and lactic acid production, and in this work we present a new kinetic model based on our laboratory lactic acid experiments, and used for planning continuous fermentation with high productivity. keywords: lactic acid, kinetic model, continuous fermentation introduction “white biotechnology” was defined by karl-erich jaeger [1] as an expression describing the biotechnological production of compounds with the help of enzymes and/or microorganisms. the work in our research group has been focusing on this field since many years, and the main topics became glycerol and lactic acid platforms. in this report we present the results of our developments on the field of fermentative lactic acid production. lactic acid (la) is a chiral carbon acid, known since more than a century, and used over several decades mostly for food industry. recently its application field was significantly expanded (pharmaceutical and polymer industry) as well as its production volume, thus it came again into the focus of researches. although it can be produced chemically as well as biologically, in the former case racemic mixture is formed, in the latter case – depending on the producer strain – optically pure (lor d-lactic acid) arises. most probably this is the reason, why it is mainly biologically produced via microbial fermentation. the fermentation ability of microorganism admit of biological production of lactic acid on glucose (glu) substrate resulting in either lactic acid alone as product (homofermentatives, using embden-meyerhof-parnas metabolic route) or lactic acid together with further products such as acetic acid, ethanol, co2 (heterofermentatives, pentose-phosphate route). there are also some strains producing solely lactic acid on glycose, or together with by-products on c5 sugars. they are usually called as facultative homofermentatives. while from the point of view of white biotechnology certainly homofermentatives are of most important, for the food industry heterofermentatives are also in the focus of interest. the reason is that in the former case the goal is to convert as much substrate into product as much is possible, while in the latter case, the given ratio of the various fermentation products serves as aroma and flavour compounds. the efficiency of lactic acid fermentation is usually given with volumetric productivity (g lactic acid/l broth/hour). in this term the published data are in a very wide range (1.5–35 g·l-1·h-1) [2] depending on the applied strain, fermentation technique, and media. however, the known industrial processes with batch operation resultin a productivity range of 2.5–3 g·l-1·h-1. we already presented [3-4] that our homofermentative microorganism belonging to lactobacilli genus makes a competitive lactic acid production possible. in this report we present a kinetic model built up on the basis of several batch lactic acid fermentations. this model was applied in simulation studies to plan continuous fermentation resulting in higher volumetric productivity. material and methods lactobacillus mkt878 was chosed on the basis of an earlier screening program run at our laboratory [3] and was deposited at national collection of agricultural and industrial microorganism with reference number ncaim-b02375. batch fermentation were carried out on the media optimized for this strains previously as follows: 120 g·l-1 glucose, 30 g·l-1 cornstep-liquor (hungrana, roquette), 6 g·l-1 yeast extract (ye), 0.5 g·l-1 mgso4·7h2o, 0.3 g·l-1 feso4·7h2o, 0.01 g·l-1 mnso4. fermentations were carried out in biostat q bench top fermenter (bbraun) at ph = 5.8 (controlling with 20% naoh and 25% h2so4), 37 °c and 700 rpm stirring 166 rate. 3 agar slants served as inoculums after suspension of cells in sterile water. the process was followed due sampling, and od600 was measured after 20x dilution to determine cell density (dry weight (g·l-1) = 0.5·od600). the filtered (through 0,2 μm pore size filter)) supernatant of the sample was analysed with waters breeze hplc system (0,5 ml·min-1 5 mm h2so4 as eluant on biorad aminex hpx87h column at 65 °c with ri detection at 40 °c) for glucose and lactic acid. since the rather rare sampling there were not enough measured data for kinetic evaluation, further dry weight, glucose and lactic acid data was calculated on the basis of base consumption (of ph control) which is proportional to the cell and product formation, and these data series were used for fitting the kinetic equations with berkeley madonna 8. software. for the calculation of dry weight, glucose and lactic acid the following factors were applied: odcalculated = 1.26·base consumption, dwcalculated = 0.5·odcalculated lacalculated=0.52·base consumption, glucalculated = glu0-(dwcalculated-lacalculated)·1.2 results in fig. 1 a tipical batch fermentation is shown with the measured and calculated data points, the latter was enabling the kinetic studies. 0 20 40 60 80 100 120 0 20 40 60 [g*l-1] fermentation time [h] 090219 la measured la calculated glucose measured glucose calculated od measured dw calculated base consumption figure 1: batch la fermetnation as basis of our fermentation model the monod equation was applied (eq. 1) completed with the product formation model of luedeking-piret (eq. 2). while the monod-model can calculate the changes in biomass concentration, l-p model is able to predict the changes in product concentration. the substrate consumption was calculated with the overall yield (yx/s) from the growth rate (eq. 3). the applied initial conditions were as follows: s0 = 105.3 g·l-1, x0 = 0.67 g·l-1 and p0 = 3.3 g·l-1. sk sx dt dx s + ⋅=⋅= max, μμμ (1) xbxa dt dp ⋅+⋅⋅= μ (2) dt dx ydt ds sx ⋅−= / 1 (3) it can be seen on fig. 1 biomass reaches its maximum (plateau) much earlier than the product concentration. the 1-3. equation system is not able to handle this situation, since through the overall yield the biomass is connected directly to the substrate. thus, when the culture reaches its plateau, the substrate has already zero value, although according to the measurements, there is a continuing product formation from substrate. to solve this problem, the model had to be reconstructed as follows: the growth-independent part of the product formation had to be converted into maintenance term (eq. 4) which appeared also in the substrate equation (eq. 5) xmxa dt dp ⋅+⋅⋅= μ (4) xm dt dx ydt ds sx ⋅−⋅−= / 1 (5) the value of the specific maintenance coefficient (‘m’) was determined from the slope of the substrate consumption, after the biomass reached its plateau. in the case of the presented fermentation (fig. 1) m = 0.222 h-1 was obtained. finally 3 variables had to be fitted to 3 data series, meanwhile 3 parameter had to be determined (yield, ks, μmax) for the flexibility of the model the duration of the lagphase and the time point of cell growth stop had to be determined either by experiments or simulations. the measured and simulated data of the presented (fig. 1) batch fermentation can be seen on fig. 2. 0 20 40 60 80 100 120 0 10 20 30 40 50 60 c on ce nt ra tio ns [ g* l1 ] fermentation time [h] calculated and simulated values 090219 s(model) gluc(calculated) p(model) la(calculated) x(model) dw(calculated) r2 average=0.998 figure 2: fitting model to calculated dataseries model fitting resulted in an adequate model with the following parameters: μmax = 0.134 h-1, ks = 0.268 g·l-1, yx/s = 0.143 g·g-1, tlag = 0.132 h, tstop = 20.22 h, a = yp/yx/s = 4.18. 167 although, the fitting results showed excellent agreement with the experimental data further fermentation was used for model verification (fig. 3). 0 20 40 60 80 100 120 140 0 20 40 60 80 100 co nc en tr at io ns [ g* l1 ] fermentation time [h] measured and simulated values 081030 s(model) gluc(measured) p(model) la(measured) x(model) dw(measured) r2 average=0.89 figure 3: model verification with further fementation, tlag = 26,5 h, tstop = 46 h since the correlation in this case was also appropriate after setting up the individual parameters (i.e. tlag and tstop), we used this model to predict the behaviour of a continuous system. figure 4: modelling continuous operation (1) cell growth stop (tstop) (2) feed start with sf = 80 g·l-1 substrate concentration the aim of our simulation was to reach high volumetric productivity beside high (industrially preparable, cost effective) product concentration. according to simulation results (fig. 4) beside d = 0.1 h-1 dilution rate 51.6 g·l la concentration can be reached, which resulted in jp = 5.2 g·l·h-1 volumetric productivity, that is nearly two fold of the original batch process’s value. since the presented product concentration is really high, before using the model in further simulation studies we want to try experimentally to verify the continuous operation. summary during the development of a fermentation technology of the more and more promisable and platform forming lactic acid we build up a kinetic model, which is able to describe the two steps of the fermentation: 1. cell growth, and 2. product formation as a “byproduct” of energy production of cells for maintenance. this model predict results beeing very closely to the measured data, thus we used it for examining the continuous operation of la fermentations. references 1. jaeger k. e.: current opinion in biotechnology, 15:269–271, (2004). 2. rojan p. j., k. madhavan nampoothiri, ashok pandey: applied microbiology and biotechnology, 74, 524–534 (2007), mini review. 3. hetényi k., németh á., sevella b.: fifth croatian professional and scientific conference on biotechnology with international participation 2007, stubicke toplice. 4. hetényi k., németh á., sevella b.: 35. műszaki kémiai napok 2007, veszprém, 164–167. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 131-136 (2008) separation of the enantiomers of p-chiral cyclic phosphorus compounds v. ujj1 , t. szuhánszki1, j. schindler2, m. czugler3, e. fogassy1, gy. keglevich1 1budapest university of technology and economic, department of organic chemistry and technology h-1521 budapest, hungary e-mail: vujj@mail.bme.hu 2budapest university of technology and economics, research group of the hungarian academy of sciences at the department of organic chemistry and technology, h-1521 budapest, hungary 3hungarian academy of sciences, chemical research center, institute of structural chemistry h-1525 budapest, hungary the antipodes of 1-aryl-, 1-alkyland 1-alkoxy-3-methyl-3-phospholene 1-oxides 1a-h were separated in good yields and in high enantiomeric excesses (up to >99% ee) by resolution via formation of diastereomeric complexes with (–)-(4r,5r)-4,5-bis(diphenylhydroxymethyl)-2,2-dimethyldioxolane (–)-2 (taddol) or (–)-(2r,3r)-α,α,α’,α’-tetraphenyl1,4-dioxaspiro[4.5]decan-2,3-dimethanol (–)-3. the resolution process of 1 with (–)-3 was further examined in various mixture of solvents. stereostructure of the supramolecular formations and absolute configuration of the resulting 3-phospholene oxides (–)-1a, (+)-1e, (+)-1f were elucidated by single crystal x-ray crystallography.1-4 the method extended to the resolution of the 1-phenyl-3-methyl-3-phospholene 1-sulfide2 4, 6-diethylamino-dibenzo[c.e][5,6]oxaphosphorine 6-oxide 5, 1-[(1’r,2’s,5’r)-(–)-menthyl]-3-methyl-3-phospholene 1-oxide 6 and 3and 5-methyl-1-phenyl-4-chloro-1,2-dihydrophosphinine 1-oxide 7, suggesting that our novel procedure may be of general value. keywords: p-chiral, resolution, diastereomeric complex, phospholene oxide, introduction phosphine oxides form an important class of phosphorus compounds, since they are precursors of the corresponding phosphines which, in turn, may serve as ligands in transition metal complexes that can be applied in several highly efficient homogenous catalytic processes.5,6 resolution and asymmetric synthesis are the primary sources of p-chiral compounds. despite the large number of enantioselective syntheses elaborated for the preparation of a single enantiomer to achieve industrial and scientific goals, resolution has not lost its significance.7 there are several methods for chiral separation, based on induced crystallization,8 resolution by diastereomeric salt formation,9 diastereomeric complex formation,10 separation by crystallization,9 distillation,11 supercritical fluid extraction12 and membrane separation,13 resolution with mixtures of resolving agents,14 by formation of covalent diastereomers9 and kinetic resolution.15 the methods described in the literature on the resolution of p(iii) and p(v) phosphorus compounds are based on the formation of separable covalent diastereomers, diastereomeric salts, diastereomeric transition metal complexes and molecular complexes, as well as chemical and enzymatic kinetic resolution.5 direct acid-base resolutions of a carboxylic acid derivative of a phosphine sulfide,16 with (+)or (–)-1-phenylethylamine are known. the resolution of phosphonium salts can be accomplished by combining the racemate with the silver salt of a chiral acid.17 enantiomeric separation of p=o derivatives via inclusion complex formation with host compounds such as 2,2'-dihydroxy-1,1'binaphthalene18 was reported previously. although these methods proved to be useful in some special cases, they did not turn out to be general. several chiral transition metal complexes, such as pd, pt, ni and fe complexes were found to be useful in the separation of racemic phosphines.19 although, the resolution via transition metal complexes was found to be reasonably general and efficient, the cost of these reagents limited its usefulness. an efficient and simple resolution process of 1-substituted-3-methyl-3-phospholene 1-oxides 1a-h has been developed. our resolution method suggested seems to be of general value for enantiomer separation of p-heterocycles. these p-chiral compounds can be ligands in transition metal complexes. 132 experimental resolution of 1-phenyl-3-methyl-3-phospholene 1-oxide 1a with taddol (–)-2 in a mixture of ethyl acetate and hexane. representative procedure. to 0.48 g (2.49 mmol) of racemic 1-phenyl-3-methylphosphol-3-ene 1-oxide 1a and 0.58 g (1.245 mmol) of taddol (–)-2 in 1 ml of hot ethyl acetate was added 5 ml of hexane. after the addition, colourless crystals of the complex started to appear immediately. after standing at room temperature for 2 hours without stirring, the crystals were separated by filtration to give 0.59 g (72%) of complex ((–)-1a·(–)-2); enantiomeric purity determined by hplc (daicel chem. ind., chiralpack ad), 71% ee. the complex was further purified by two recrystallizations at room temperature from ethyl acetate–hexane (1 ml/5 ml) to afford complex (–)-1a·(–)-2 in 54% yield with 87% ee and in 43% yield with 97% ee, respectively. column chromatography (silica gel, chloroform) of the complex regenerated 96 mg (40%) of the enantiomerically pure (–)-(s)-1-phenyl-3methyl-3-phospholene 1-oxide (–)-1a; enantiomeric purity, 97% ee, [α]d 25 = –37.0 (c 1, chcl3).2 results and discussion resolution of racemic 3-phospholene 1-oxides 1 five-membered p-heterocycles, such as 1-substituted-3phospholene 1-oxides 1 are of synthetic importance, as they can be used as starting materials in the preparation of a variety of five-, six-, seven-, and eight-membered p-heterocycles including bridged derivatives. we assumed that the 1-substituted-3-methyl-3-phospholene 1-oxides 1, which have neither acidic nor basic functional groups, could be resolved via molecular complex formation.1 therefore racemic phospholene oxide 1a was attempted to be resolved via diastereomeric complex formation by adding half equivalent of tartaric acid, o,o’-dibenzoyltartaric acid, taddol20 2 or its derivative20 3, ephedrine, 2,2'-dihydroxy-1,1'-binaphthalene, menthol, phenylalanin, prolin and ascorbic acid. we found that only taddol 2 and its derivative 3 could form co-crystalls with the phospholene oxides 1a-h. the use of other chiral auxiliaries did not afford crystallizing distereomers. enantiomerically pure 1-substituted-3-methyl-3phospholene oxides 1a-h were prepared by molecular complex formation with chiral host (–)-2 or (–)-3 fig 1 and table 1. to a solution of racemic phospholene 1-oxide 1a-h and half equivalent of (–)-taddol 2 or its analogue (–)-3 in hot ethyl acetate was added hexane where upon a 1·(–)-2 or a 1·(–)-3 crystalline complex precipitated. complexes 1a-d·(–)-2 and 1a-d·(–)-3 were analyzed by chiral hplc (chiralpack ad), while species 1e-h· (–)-2 and 1e-h·(–)-3 by chiral gc (betadectm, after decomp.). the enantiomeric purities of 1a-h obtained were 10-96% ee table 1. recrystallization of these complexes from a mixture of ethyl acetate–hexane significantly improved the enantiomeric excesses of the complexes 1·(–)-2 and 1·(–)-3, up to >99% ee in most cases table 1. after flash column chromatography, 3-phospholene 1-oxides 1a-h were recovered quantitatively without the loss of chirality. in most cases, the 1:1 complexes of 1·(–)-2 or 1·(–)-3 were formed. in the instance of 1-propyl-3-phospholene oxide 1f and resolving agent (–)-3, a 1:2 complex of (+)-1f·(–)-3 was obtained as shown by the 1h nmr spectrum. for this, the resolution of 1f was achieved with the use of 1 equivalent of (–)-3. interestingly, in all cases but two, the resolving agents (–)-2 and (–)-3 preferred the complex formation with the same enantiomer of the given 3-phospholene oxides 1a-e, h. in case of 1f and 1g, (–)-2 and (–)-3 formed complexes with opposite antipodes. the separation of the covalent diastereomers of 1-[(1’r,2’s,5’r)-(–)-menthyl]-3-methyl-3-phospholene 1-oxide 6 has not been investigated. using resolving agent (–)-3 to the separation of covalent diastereomer was successful (90% de in 45% yield). to clarify the absolute configuration of (–)-1a, (+)-1e and (+)-1f, the supramolecular formations (–)-1a·(–)-2 acetone, (+)-1e·(–)-3 and (+)-1f·(–)-2 were subjected to single crystal x-ray analysis. the absolute configuration of the p atom in (–)-1a, (+)-1e and (+)-1f was found to be s,1 r2 and r,2 respectively.1-4 r = me r = me (2), (3) oo hooh ph phph php yo + 0.5 rac-1 (r,r)-2 or (r,r)-3 etoac/hexane oo hooh ph phph ph p yo p yo (r,r)-2·1 or (r,r)-3·1 1 + r r r r • ph 2-meph 4-meph 1-naph et pr eto 2-pro (1a) (1b) (1c) (1d) (1e) (1f) (1g) (1h) y = figure 1: resolution of 3-phospholene 1-oxides 1 with taddol derivatives (–)-2 and (–)-3 133 table 1: resolution of 1-aryl-, 1-alkyland 1-alkoxy-3-methyl-3-phospholene 1-oxides 1a-h with chiral host 2 and 3.2 complex forming agents 1.(–)-2 1.(–)-3 subst. eea (%) yield (%) sb [α]d c eea (%) yield (%) sb [α]d c 1a 97 (71) [s]d 44 0.43 >99 (53) [s] 29 0.29 – 37.0 1b 57 (31) [s] 49 0.28 >99 (48) [s]e 41 0.41 – 28.6 1c 69 (29) [s] 42 0.29 >99 (11) [s]e 30 0.30 – 39.1 1d 70 (25) 42 0.29 >99 (27) 55 0.55 – 40.9 1e 24 (10) [r] 36 0.09 58 (23) [r]d 45 0.26 + 8.7 1f 95 (68) [r]d 35 0.33 + 13.4 89 (29)f [s] 30 0.27 1g 44 (20) [s] 25 0.11 95 (58) [r]e 50 0.48 – 10.6 1h >99 (89) [r] 5 0.05 >99 (96) [r]e 37 0.37 – 15.6 athe enantiomeric purities were determined by chiral hplc (chiralpack ad) or chiral gc (betadectm) after two recrystallizations (and after crystallization). bresolving capability, also known as the fogassy parameter (s = yield*enantiomeric purity). cspecific rotation of the regenerated enantiomer (c 1, chcl3). dabsolute configuration was determined by x-ray analyses. eabsolute configuration was determined by cd spectroscopy. fone equivalent of 3 was used. single crystal x-ray analysis of (–)-1a·(–)-2 and (+)-1e·(–)-3 final structure models are shown in figs 2 and 3 with the basic h-bridges indicated.1,2 the resulting crystal structure models are well ordered and contain in all cases, with 1:1 stoichiometry, the associated forms of the resolving agents with either one of the phospholene target guest molecules as in 1a·2 and 1e·3. the crystal structure of (–)-1a·(–)-2 contains an acetone molecule, so, in this case, a ternary complex (–)-1a·(–)-2·acetone is formed fig. 2. thus acetone acts not only as a cosolvent but is also essential in sustaining a closely packed crystal made up of semi-rigid molecules (–)-1a and (–)-2.1 the resolving machinery is affected by the interplay of the anchoring and identical primary o–h···o hydrogen bridges to the guest p=o functions, as well as by a series of weaker c–h···o interactions. such weak stabilizing c–h···o interactions can be formed between the oxygen atom of one of the hydroxy groups of taddol (–)-2 and the c4 atom of the p-heterocycle, and the oxygen atom of one of the hydroxy groups of taddol (–)-2 and the c4’ carbon of the phenyl ring in the crystal structure of (–)-1a·(–)-2·acetone.3 other weak interactions, such as the one between the oxygen atom of the p=o function and the c2 carbon of the p-heterocycle, and another one between the oxygen atom of one of the hydroxy groups of taddol derivative (–)-3 and the suitable hydrogen atom of the p-species stabilise the crystal structure of (+)-1e·(–)-3 fig. 3. figure 2: x-ray structure of the 1:1:1 coordinatoclathrate inclusion of 1-phenyl-3-methyl-3-phospholene 1-oxide (–)-1a with taddol (–)-2 and acetone with the basic h-bridge interactions indicated by blue lines for (–)-1a·(–)-2·acetone.1 figure 3: x-ray structure of the 1:1 inclusion of 1-ethyl-3-methyl-3-phospholene 1-oxide (+)-1e with taddol derivative (–)-3 with the basic h-bridge interactions indicated by blue lines for (+)-1e·(–)-3.2 134 solvent dependence of the resolution although, the resolution of phospholene oxides 1 with (–)-2 and (–)-3 were accomplished in ethyl acetatehexane mixture, the single crystals could only be obtained from acetone-pentane mixture. the presence of acetone influences the formation of the crystal structures of the complexes. in the case of the complex (–)-1a·with (–)-2, the acetone was incorporated to the crystal structure and a ternary complex was grown. into the crystal structure of (+)1e·(–)-3 and (+)-1f·(–)-2 acetone was not incorporated. in the course of growing a single crystal of (–)-1b-d with (–)-3, the acetone displaces the phospholene oxides from the crystals completly, because acetone may be a more suitable h acceptor for the h bridges than the phospholene oxides. the presence of acetone effected significantly the structures of the single crystals, suggesting that the acetone could effect the efficiency of the resolution as well. the results of the resolution of phospholene oxides 1a-h with (–)-3 from a mixture of acetone-hexane is summarized in table 2. it can be seen that the efficiency of the resolutions was improved in all cases. table 2: resolution of 1-aryl-, 1-alkyland 1-alkoxy-3methyl-3-phospholene 1-oxides 1 with chiral host (–)-3 in acetone-hexane complex forming agents 1.(–)-3 subst. enantiomeric puritya (% ee) sb abs. config. 1a 97 0.81 [s] 1b 88 0.42 [s] 1c 27 0.25 [s] 1d 71 0.23 1e 55 0.42 [s] 1f 38 0.34 [s] 1g 93 0.67 [r] 1h >99 0.56 [r] athe enantiomeric purities were determined by chiral hplc (chiralpack ad) or chiral gc (betadectm) after crystallization. bresolving capability, also known as the fogassy parameter (s=yield*enantiomeric purity). in the next part of the work, resolution processes of 1a with (–)-3 were further tested in various other solvents or solvent mixtures, but no crystals were obtained. therefore, the resolution process of 1a was further examined in ethyl acetate-hexane mixture adding another solvent as an additive (2 eq., based on the racemate of 1a). the results are summarized in table 3. sakai and co-workers examined the effect of the solvent(s) on the resolution process via diastereomeric salt formation. they observed that the efficiency of the resolution via diastereomeric salt formation was dependent on the dielectric constant (ε) of the solvents used. they called this phenomenon dielectrically controlled resolution process (dcr).21,22 we found that the resolution of (–)-1a·with (–)-3 via diastereomeric complex formation took place with a good efficiency only when the additive used had a dielectric constant (ε) of lower than 40 fig. 4. table 3: resolution of 1-phenyl-3-methyl-3-phospholene 1-oxides 1a with chiral host (–)-3 in ethyl acetate-hexane in the presence of additive (–)-1a.(–)-3 additive 2 eq. dielectrically constant (ε) enantiomeric puritya (% ee) sb acetone 20.7 86 0.60 dmso 46.7 25 0.32 dmf 36.7 71 0.63 acetonitrile 37.5 63 0.49 acetic acid 6.2 75 0.47 water 78.5 12 0.11 mek 18.5 74 0.52 mibk 13.1 73 0.55 ethanol 24.6 78 0.57 athe enantiomeric purities were determined by chiral hplc (chiralpack ad) after crystallization. bresolving capability, also known as the fogassy parameter (s=yield*enantiomeric purity). figure 4: dependence of the resolution on the dielectric constant of the additive dutch resolution the efficiency of a resolution can be improved in the presence of a chiral or achiral, structurally similar derivative of the substrate or the resolving agent (e.g. dutch resolution).23,24 we found that the result of the resolution of 1-phenyl-3-methyl-3-phospholene oxide (1a) with chiral host (–)-3 was improved in the presence of impurities. the resolution of pure 1a with (–)-3 led to the corresponding complex (–)-1a·(–)-3 of 53% diastereomeric excess in 87% yield. we obtained the best results when we used crude 1a. in this case the diastereomeric excess of the complex (–)-1a·(–)-3 formed was 79% de in 71% yield. it was also interesting that the resolution 1-phenyl-3methyl-3-phospholene oxide 1a with 0.25 equiv. of (–)-2 and 0.25 equiv. of (–)-3 proved to be more efficient than with either 0.5 equiv. of (–)-2 or with 0.5 equiv. of (–)-3. diastereomeric excesses of the complexes (–)-1a· 135 (–)-2·(–)-3, (–)-1a·(–)-2 and (–)-1a·(–)-3, were 77%, 71% and 53%, respectively. the (–)-1a·(–)-2·(–)-3 complex contained 40% of (–)-2 and 60% of (–)-3 based on 1h nmr. the experiments for the separation of the enantiomers of 1-phenyl-3-methyl-3-phospholene sulfide 4 with (–)-3 were puzzling at first. the resolution of the pure racemic compound 4 with (–)-3 was not too efficient (24% de). when substrate 4 contained 4% of 1-phenyl3-methyl-2-phospholene sulfide, the enantiomeric purity of the complex (+)-4 [(–)-3]2 was quite similar (20% de). the efficiency of the resolution was, however, improved significantly by using the crude product of the synthesis of 4. in this case, the diastereomeric excess of the complex (+)-4 [(–)-3]2 formed was 65% after crystallization and >99% after recrystallization ([α]d 20= –65.2 (c 1, chcl3)). the 1h nmr spectrum suggested a 1:2 stochiometry of (+)-4 and (–)-3. the 1-phenyl-3-methyl-3-phospholene sulfide was regenerated by column chromatography ([α]d 20= +7.8 (c 1, chcl3)).2 resolution of other p-heterocycles our resolution method was tested on other p-heterocycles to prove that our novel procedure may be of general value for the resolution of p-chiral cyclic compounds. the resolution of 6-diethylamino-dibenzo[c.e][5,6]oxaphosphorine 6-oxide 5 with (–)-3 was not efficient (51% de). in the course of preparation of 3and 5-methyl-4chloro-1-phenyl-1,2-dihydrophosphinine 1-oxide 7, two double-bondisomers were obtained25 that could not be separated. therefore an 1:3 mixture of dihydrophosphinine oxides 7 was resolved with (–)-3. the ratio of the double-bondisomers remained the same after crystallization and recrystallization of the diastereomers. after the resolution, dihydrophosphinine-oxides 7a and 7b with (–)-3, the diastereomers were obtained with 90% ee and in 33% yield. p s ph me o p o net2 p o o me p o ph cl 4 5 6 7 r2r1 r1 r2 h me (a) me h (b) conclusion an efficient and simple resolution process of 1-substituted3-methyl-3-phospholene 1-oxides 1a-h was developed. in our resolution method of 1a-h were resolved with half equivalent of (–)-2 or (–)-3. we found that the efficiency of the resolution is highly dependent on the solvents or the additives. the method suggested seems to be of general value for enantiomer separation of pheterocycles. acknowledgement authors are grateful for the financial support from the hungarian scientific research fund (otka, grants nos. t075236, t067679). mc acknowledges the national science and technology office for an x-ray diffractometer purchase grant (mu-00338/2003). the authors are grateful to dr. tibor novák for the fruitful discussions. references 1. novák t., schindler j., ujj v., czugler m., fogassy e., keglevich gy.: tetrahedron: asymmetry 17 (2006) 2599-2602 2. novák t., ujj v., schindler j., czugler m.; kubinyi m., mayer zs. a., fogassy e., keglevich gy.: tetrahedron: asymmetry 18 (2007) 2965-2972 3. novák t., schindler j., ujj v., czugler m., fogassy e., keglevich gy.: phosphorus, sulfur, silicon 183 (2008) 543-546 4. fogassy e., keglevich gy., novak t., schindler j., ujj v.: hun. pat. (2007) p0700278 5. pietrusiewicz k. m., zabłocka m.: chem. rev. 93 (1994) 1375-1411 6. noyori r.: asymmetric catalysis in organic synthesis, john wiley & sons, new york (1994) 7. fogassy e., nógrádi m., palovics e., schindler j.: synthesis 10 (2005) 1555-1568 8. elekes f., kovári z., mravik a., böcskei zs., fogassy e.: tetrahedron: asymmetry 9 (1998) 2895-2900 9. fogassy e., nógrádi m., kozma d., egri g., pálovics e., kiss v.: org. biomol. chem. 4 (2006) 3011-3030 10. faigl f., kozma d.: in fundamentals and methods; toda f., ed.; kluwer academic: dordrecht, 2004. chapter 9 11. ács m., mravik a., fogassy e., böcskei z.: chirality 6 (1994) 314 12. simándi b., keszei s., fogassy e., sawinsky j.: j. org. chem. 62 (1997) 4390 13. hadik p., szabó l. p., nagy e.: desalination 148 (2002) 193. 14. vries t., wynberg h., van echten e., koek j., ten hoeve w., kellog r. m., broxterman q. b., minnaard a., kaptein b., van der sluis s., hulsfhof l. a., kooistra j.: angew. chem. int. ed. 17 (1998) 2349-2354 15. kelemen-horváth i., nemestóthy n., bélafibakó k., gubicza l.: chem. pap. 56 (2002) 52-56 16. davies w. c., mann f. g. j.: chem. soc. (1944) 276-283 136 17. kumli k. f., mcewen w. e., vander werf c. a.: j. am. chem. soc. 81 (1959) 248-249 18. toda f., mori k., stein z., goldberg i.: j. org. chem. 53 (1988) 308-312 19. otsuka s., nakamura a., kano t., tani k.: j. am. chem. soc. 93 (1971) 4301-4303 20. seebach d., beck a. k., heckel a.: angew. chem. int. ed., 40 (2001) 92-138 21. sakai k., sakurai r., hirayama n.: tetrahedron: asymmetry 17 (2006) 1812-1816 22. sakai k., sakurai r., yuzawa a., hirayama n.: tetrahedron: asymmetry 14 (2003) 3713-3718 23. kaptein b., elsberg h., grimbergen r. f. p., broxterman q. b., hulsfhof l. a., pouwer k. l., vries t.: tetrahedron: asymmetry 11 (2000) 1343-1351 24. schindler j., egressy m., bálint j., hell z., fogassy e.: chirality 17 (2005) 565-569 25. keglevich gy., androsits b., tőke l.: j. org. chem. 53 (1988) 4106 microsoft word b_05_r.doc hungarian journal of industrial chemistry veszprém vol. 38(2). pp. 95-98 (2010) relationship between input channel excitation time and profinet io refresh time i. ferenczi department of transportation science and infotechnology, university college of nyíregyháza nyíregyháza, sóstói út 31/b, hungary e-mail: ferenczi@inform.hu profinet io is the communication concept for implementing modular, distributed applications such as profibus dp, based on the industrial ethernet. distributed io and field devices are integrated into the ethernet communication by means of profinet io. the user data from the field device are transmitted cyclically in a real-time channel to the process image of an automation system. in this paper, i will present what relationship exists between bus refresh time and input channel excitation time in several specific situations. keywords: profinet io, cycle time, real-time, refresh time, plc, io device, io channel, delay time, communication introduction profinet io permits direct interfacing of distributed field devices on the ethernet. all devices used are connected in a uniform network structure, and therefore offer uniform communication throughout the entire production plant. the system consists of three main elements: 1. io-controller; it has control over a distributed process of one or more field devices. it receives process data and alarms and processes them in a user program. in automation installations, an io-controller is normally a programmable logic controller (plc). 2. io-device; a profinet io-device (max. 128 device) is a field device connected in a decentralized way belonging to the process. it periodically transmits process data to the io-controller, and the iocontroller transmits control data to the filed devices (fig. 1). 3. io-supervisor; might be an engineering station (pc or laptop) in an installation, which has temporary access to the field devices or controller during the commissioning process. io controller io device 1 io device 2 io device n ethernet io supervisor plc with user programm pc or laptop field devices figure 1: elements of profinet io with profinet io, the master-slave principle known from profibus dp has been converted into a providerconsumer modell. so far communication is concerned, all profinet devices have equal privileges on the ethernet. however, a type of privilige is assigned to each device during configuration, and this defines the type and manner of communication according to the provider-consumer modell [3]. profinet communication in a real-time communication based on tcp/ip protocol, real-time (rt class1,2) packets and isochronous realtime (irt or rt class3) packets of controls requiring synchronization, which follow strictly real-time procedures, are also present beside non-real time (nrt) packets. [1]. the rt packets are supplied with priority to prevent a collision, and the irt switch always provides an open line to the irt packets [2]. context management (cm) an io-device delivers input data from the automated process to the io-controller, and receives output data from controller in order to control the process (providerconsumer). an io-supervisor can also communicate simmultaneusly with an io-device. in order to permit data exchange to occur with all devices, an application and communication relation is necessary to exist. the task of context management is to manage the application and communication relations. 96 to establish a communication channel between provider and consumer is necessary to create a virtual logical channel for each channel of devices. this is the application relation (ar). the io-controller establishes an ar with each io-device. establishment is carried out instantly during system startup. several communication relations (cr) can be established within an ar (fig. 2). the following types of cr exist: ● record data cr for acyclic transmission of records, e.g. for configuration, parameterization, etc, ● io data cr for cyclic transmission of i/o data, ● alarm cr, for acyclic transmission of events. figure 2: communication relations the last two communicate through a real-time, and the first through a traditional ethernet channel. in this paper i deal only with the i/o data cr. the io data cr operation principle the task of the io data cr is to transmit i/o data between io-controller and io-devices, according to the provider-consumer concept. the following parameters are transmitted during the establishment: ● a list of i/o data objects to be transmitted as well as their structure, ● the parameters of the send interval (send clock time, scaling, phase etc), ● the transfer frequency. the number of io data crs to be established is defined in the device configuration, depending of the number of devices installed. two opposite io data crs are always established, thus permitting bidirectional data exchange between io-controller and io-device. the data are sent cyclically from the provider to the consumer according to configured transfer frequency. in the relation, explicit acknowledgements of transmitted data frames do not take place but the consumer generate an error when the data frame listed does not arrive during a three i/o bus cycle. the data frame contains a cycle counter element, which is incremented, when the data does not arrive during a bus cycle time [3]. the io data cr features 1. the send clock time is the interval at which cyclic data are sent within an io data cr. it is defined device-specifically as an integral multiple of the basic time unit of 31.25 μs. this time is usually defined during configuration by the user. send clock time = send clock factor · 31,25 μs the send clock factor is between 1 and 128. a value of 32 corresponds to a send clock time of 1 ms that for a basic rate can be considered in a not synchronized rt communication (fig. 3). figure 3: send clock time for rt data in fig. 3 rt is a cyclical, rta is an acyclical realtime, and nrt is a non-real-time data. 2. send interval (refresh time); since high-performance transmission of all data is usually not required, the communication transmission frequency may differ from the io device. however, the slowest station must not determine the complete data throughput. for this session, low performance data are transmitted with scaling based on the send clock time: send interval = send clock time · 2n where: 2n – scaling; n – scaling ratio. so, the refresh time is transmitted periodically that defines the send cycle. in this interval, the io-devices receive data from the controller, and transmit simultaneously the process data to the controller. this duplex communication is exemplified in fig. 4. figure 4: real-time cyclical data transmission each item of i/o data contain two attributes, the iops (io provider status) and iocs (io consumer status), which permit the io-controller and io-device to evaluate the quality of the transmitted value. 97 determining some critical time values in this paper i analyzed some critical situation when the input signal excites the input channel of io-device. the length of the time sequence between the starting moment of the channel excitation and the moment at which the reaction in the addressed output channel occurs can be very often decisive. furthermore, it can also be of interest how frequently the incoming signals take place, by which obvious reactions are still observable. what is the minimal excitation time period that can still be identified by the input? in order to answer these questions, the factors determining reaction time in the profinet system should be identified: user program cycle time (ct) input channel delay time (id) profinet io refresh time set (ut) it is clearly visible that out of the three factors only the refresh time can be modified under the criteria of real-time systems. the other two determinants are not possible to be decreased considerably. it is also equally relevant when the input excitation occurs relative to the cycle time and the refresh time. in effect, the reaction time has a lower and upper boundary value. the lowest boundary value (srt) denotes the, theoretically speaking, best possible situation where the response occurs within one cycle. srt = ct + id (1) in other words, the input excitation is initiated just in time to reach the end of the refresh interval and the update of the process image input (pii). similarly, the response reaches the end of the refresh interval during the update of the process image output (pio). the worst possible is the situation (lrt) in which the signal coming from the input of the io device just misses the current refresh time and also the moment at which the process image input of the cycle gets updated after the next refresh time. thus it will only be loaded and executed during the next cycle. the response then just misses the refresh interval during the update of the process image output of the next cycle; as a result, it will be only forwarded once the next cycle starts [5]. lrt = 2·ct + id + 4·ut (2) note: the situation described above can occur if the length of the refresh time sequence is nearly identical to the cycle time. if the refresh time is much longer than the cycle time, the response comes during the two refresh intervals even in the worst possible case. profinet io test system the profinet io system takes the form of a star topology: a 100 mb full duplex ethernet network with a scalance x005 switch. a s7-300 cpu315f-pn plc with a 16-16 digital i/o module constitutes the controller. the io device is an et-200s with an im151-3 pn io device controller. it has 4 modules for the input and output respectively, with 2 digital channels each. a notebook has been used as an io-supervisor. beside that, an s7300 cpu314-2dp plc is also part of the network, which connects to the network via a cp343-1 lean interface. the latter does not take part in the measurement; it simply assumes a separate application task (fig. 5). plc+cp343 ethernet interface ip: 192.168.1.1 io-supervisor s7-300 cpu314c-2dp s7-300 cpu315f-2pn et 200s im151-3pn io-device ip: 192.168.1.3 scalance x005 network switch io-controller ip: 192.168.1.2 pc cpu 314 cpu 315 cp 343 tcp/ip ethernet connection 100 mb full duplex profinet rt connection over ethernet segment length: 1m+3m ip: 192.168.1.10 figure 5: structure of test system measuring with an universal counter for the purpose of input excitation an impulse generator was used, which provided for 0.5 –1 khz 24 v impulses with 1–50% duty cycles. the edge coming to the input and appearing on the output will be joined together after the differentiation. the input and output is visualized with a dual channel oscilloscope, and the resulted signal was applied to the input of the universal counter (fig. 6). the advantage of this method is that a measurement of even 10 μs accuracy can be conducted. as a disadvantage, a supplementary circuit and a counter device are necessary. impuls generator differentiator and adder circuit countor oscilloscop profinet io in out figure 6: measuring circuits minimal excitation time at real-time communication system beside the definition of the reaction time we have to know the frequency of input signal applicable, respectively the signal span, mainly a minimal excitation time of input channel. this chapter is concerned with the finding the minimal excitation time that is still able to cause the input reaction. 98 this is largely determined by two factors: the input channel delay time and the refresh time. let us denote the sum of these as tin. we can state that: tin > ut + id (3) in other words, the channel excitation time should be longer than the sum of the refresh time and the channel delay time. that is, in case of a 16 ms refresh time and a 3 ms delay time, this value has to be higher than 19 ms. the impulses with 0.5 hz/1% duty cycle used during the test had a time duration of 20 ms [4]. thus ut up to a value of 16 ms was to function with safety. however, according to (3) at a 36 ms refresh time, the duty cycle has to be increased to 2%. the following table shows the maximum frequency of the square wave signal in the given refresh time if the channel delay time is 3 ms or 0.5 ms. table 1: results of the measurements tin [ms] fin [ms] ut [ms] id = 3 ms id = 0.5 ms id = 3 ms id = 0.5 ms 1 4 1.5 125 330 2 5 2.5 100 200 4 7 4.5 71 110 8 11 8.5 45 58 16 19 16.5 26 30 32 35 32.5 14 15 64 67 64.5 7 7 also, it follows from the table what refresh time and channel delay time is needed to be set in order for the system to function safely. for instance, if a 50 hz square wave signal has to be used on the input, then a refresh time of at least 8 ms with 0.5 ms delay time will be needed. however, if a channel delay time of only 3 ms can be used, it follows that the refresh time has to be set to 4 ms. figure 7: bad input channel excitation in the previous figure a case is shown, in which the excitation time takes a smaller value than that in (3). this can yet lead to an error because it may occur that the input signal can not cause a reaction (fig. 7). in the case shown, the output channel reaction time (tr) has no significance. besides it always take a value between srt and lrt but it does not depend on the input excitation time [4]. in the most critical case observed, in which the refresh time was 1 ms and the delay time was 0.5 ms (tin = 1.5 ms), it followed that the input channels still react to a 330 hz square wave signal. the measurements verified this assumption. errors were not encountered even after multiple tests of longer durations. further, the reaction times did not change considerably. it is not to say that the input won’t react above 330 hz but that cases may very well occur where input impulses remain without responses when an input excitation takes place in between two refresh times. conclusion from the results of the measurements described, practical conclusions can be drawn with respect to how the profinet io system should be configured according to critical time limits of real-time processes. in the case of non-synchronized processes, it is imperative to know what differences occur between given limits, with other words, what are the value extremes between which the criteria of a real-time system are met entirely. during the measurements that ethernet communication took place without disturbance. the log file of the io controller did not register a single collision or bad frame, albeit only a minimal profinet io configuration (controller, io device and io supervisor) were part of the network. references 1. r. pigan, m. metter: automating with profinet (2006) 2. profinet real-time communication by siemens ag (2007) 3. i. ferenczi: profinet real-time kommunikációs stratégiák (gép, 2009. dec.) 4. i. ferenczi: válaszidők vizsgálata egy profinet io rendszernél (factory automation 2010, proceedings, 105–111) 5. siemens simatic cpu 31x: specification manual, 06/2008, a5e00105475-08 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 /colorconversionstrategy /cmyk /dothumbnails false /embedallfonts true /embedopentype false /parseiccprofilesincomments true /embedjoboptions true /dscreportinglevel 0 /emitdscwarnings false /endpage -1 /imagememory 1048576 /lockdistillerparams false /maxsubsetpct 100 /optimize true /opm 1 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word contents.doc hungarian journal of industrial chemistry veszprém vol. 34. pp. 35-39 (2006) optimization problems of fermentor aeration-agitation system l. kozma1, l. nyeste2 and a. szentirmai3 1chartered engineer, former leader of the technical division of biogal pharmaceuticals, postal address: őrség u. 17., h-1112 budapest, hungary, e-mail: multiplan@axelero.hu 2professor of department of biochemical engineering, budapest university of technology, szt. gellért tér 4., h-1521 budapest, hungary 3professor of microbiology and biotechnology, university of debrecen, haraszt u. 21., h-4010 debrecen, hungary after four decades of almost exclusive application of rushton turbines a number of types of impellers were developed for the fermentation industry in the last 20 years which were proven to be more efficient despite their lower power requirements. the efficiency of an impeller is affected strongly by the degree of their hydromechanical properties corresponding with the specific characteristics and requirements of a certain fermentation process. evaluation in case of non-newtonian broths cannot be carried out with proper accuracy, and their optimization becomes difficult. an increase in yield even by a few percent can be of great importance in large-scale fermentation vessels. consequently, the optimization of agitation system is a very important factor but it is only partially provided by scale-up using pilot plant data and similarity criteria. this is the reason why we need newer methods for optimization of aerationagitation systems for large-scale fermentation vessels by agitators equipped with changeable flow modifying parts. keywords: power number, non-newtonian broth, rushton turbine, shear power, scale-up, flooding advantages and disadvantages of newer agitation systems the disadvantages of flat-blade rushton turbines – less axial circulation capability and large power requirement applied in penicillin fermentation for many years due to their excellent dispersion capability became more and more obvious with the increase in size of fermentation vessels. due to these disadvantages newer types of impellers and complex agitation systems were developed. turbines the efficiency of rushton turbines (fig. 1) was increased by the application of impellers with parabolic profile instead of flat-blades in scaba 6srgt system (fig. 2). their power number has decreased from 5,56,0 to 3,2. the number of higher energy peaks around the impeller endangering more sensitive microorganisms decreased and by increasing impeller’s diameter larger volumes could be blended with the same power requirements. the impellers’ sensitivity to “flooding” phenomenon and increased viscosity had decreased, but still they had lower circulation capability. in the event of applying more impellers compart-mentalization (inadequately blended areas) may occur. that is why in newer agitation systems these are used only at the lowest, dispersion level. (a. baker et al. 1) closed turbines have better circulation capability but these are rarely applied due to their little dispersion capability. propeller agitators propeller agitators have excellent axial circulation properties but weak dispersion capability. due to their little power number of 0,5-1,1 their diameter could be larger with the same power requirement and this facilitates full blending of viscous broths and filamentous microorganisms. first ekato has developed propeller type impellers with pitched blades called mig and intermig (fig. 3). recently streamlined propeller agitators with twisted surface have been applied at the upper levels of complex agitation systems. impellers with larger diameter ratios of 1:0,5-1:0,6 narrower blades such as lightnin 310 are applied for blending of lower viscosity broths. impellers with less diameter and diameter ratio of 1:0,45 and broader blades which have power number of 1,0-1,1 such as lightnin a 315 and prochem maxflo (fig. 4 and fig. 5) are applied for blending of higher viscosity broths. according to a.w. nienow propeller agitators provide better blending efficiency for both the lower and higher viscosity broths and better mass and heat transfer than rushton turbines. other advantages of these agitators are their power number and indulgence with sensitive microorganisms (a.e. nienow 2.) vacuum agitators vacuum agitators has low power requirement, good dispersion capability but lesser circulation properties. these types can be used for blending less air volumes. 36 they are used only in certain technological processes such as in flotation devices and in yeast production. newer complex agitation sysems merely the last few decades the researchers and manufacturers have realized that the efficiency if agitation systems can be increased by development of complex systems including more agitators of different types and properties which satisfy better the requirements of the particular levels. despite many published paper literature dealt not so much with the problems of agitation of large-scale fermentation vessels. perhaps on the symposium in firenze in 1993 data on the mass transfer problems due to differences between the levels of large-scale fermentation vessels were published for the first time. these differences are stemming partially from the position of levels and partially from their different functions i.e. could be local or functional differences. local differences are mainly caused by the pressure differences due to 8-12 m height of fermentors and this may affect bubble size and the density of foaming broths, etc. functional differences are because the function of the lowest agitator is efficiently disperse air input, the function of the middle agitator(s) is the best intensity circulation of the broth-air mixture and the function of the upper agitator is recirculation of the foaming broths on the surface with less further foam formation possible. in the nineties the increase in differences due to larger and larger-scale fermentation vessels had led to the development of complex agitation systems considering the differences between levels. 6srgt modified turbine agitator with good dispersion capability is generally used on the lowest level, and high efficiency propeller agitators e.g. lightnin, prochem are applied on the highest level. (k. myers, 3.) these complex systems have better energy dissipation, dispersion and circulation capabilities, they are more efficient and more sensitive to flooding than the older systems built from components of the same type and size. optimization problems of agitation systems sizing and development of large-scale agitation systems is still based mainly on data from and experiences with pilot plant fermentors, and relations developed through the theory of similarity and dimension analysis. lately industrial measurements have been used more and more often. the application of the results of experimental measurements during scale-up is limited very much by the significant differences in the hydrodynamic fields and flow patterns of large-scale fermentors mainly due to the following reasons: a) because of the nearness of the baffles and impellers the large velocity gradient between the flowing layers in the experimental device results in large shear velocity and shear power, while in large-scale devices the much less velocity gradient due to larger sizes results less values. b) unlike in the large-scale vessels no free turbulence facilitating mass transfer is evolved because of the less reynolds number value due to the less size of the experimental device. c) flow of high viscosity broths can slow down so much in the large-scale vessels that inadequately mixed areas are formed even when newer agitation systems are applied. no secondary dispersion can occur along the baffles which may mask the deficiencies of the impeller type itself in pilot plant fermentors. d) due to the high pressure of large-scale fermentation vessels bubble size affecting oxygen transfer is decreased, solubility of gases, the density of liquidgas mixture and coalescence of bubbles are increased. e) in large-scale vessels the agitation time and crosssectional air flow velocity are increased with the same specific air volume and v/v input. kipke’s example can be cited for demonstration of the increase in agitation time, namely if a given agitation time can be produced in a laboratory fermentor of 5 liters with p/v = 1 kw/m3 power/unit volume, in a large-scale fermentation vessel of 50 m3 the same agitation time can only be achieved with 5000 kw power! the differences in magnitude show the problems of scale-up and the limitations of the application of experimental results. the scales are changed considerably during scale-up even during entirely proportioned geometric scale-up. for example, if the size of a model is increased only by tenfold, its surface increases hundred-fold but its volume increases thousand-fold. that is why even the name of similarity criteria is false since their application provides merely partial similarity. due to the unequal change in size and value ratios, physical, geometric, kinetic and dynamic similarity criteria cannot be selected simultaneously. due to the lack of a generally valid procedure many scale-up processes had been developed. the most often is to rely on power requirement per volume (p/v), volumetric oxygen transfer coefficient (kla), gas-holdup and shear stress (viscosity/velocity gradient). the variation of chosen considerations may lead to great differences. that is why many researchers’ opinion is that results do not comply with the technical and economical requirements of biotechnology and can only be informative data for developers of sizing procedures. according to m. charles: “in practice, scale-up strategies tend to be »mixed bags« engendering art enpricism, conventional wisdom and (frequently) wishful thinking” (4). for the optimization of fermentation process i.e. for the achievement of largest possible yields even distribution of the dissolved oxygen (do), medium and ingredients added during fermentation and optimum 37 mass transfer conditions should be provided besides application of high productivity microorganisms and adequate mediums. adequate oxygen level can be achieved by both proper air volume input and its best possible dispersion i.e. the least oxygen bubbles and their most even distribution. to achieve this, adequate agitation power, air volume and an agitation system is necessary which is suitable for effective dispersion of air, for creation of intensive circulation and for even distribution of bubbles. the level of dissolved oxygen (do) can be measured during fermentation and can be adjusted by the regulation of power input and/or air volume – if there are adequate quantities. considering the sometimes high values e.g. in case of penicillin fermentation the efficiency of the process is a significant factor and it is affected by the structure of the agitation system besides the power input and adequate air volume. the problem is that however, we can calculate – at least approximately the diameter and power requirement of the agitators and the air volume by the available procedures and relations, these data provide very little information on optimum design similarly to the added nutrients oxygen transfer occurs on the interfaces of air bubbles and medium particles and through the walls of microorganisms’ cells. according to the double layer theory thinning of the laminar layers on the interfaces by creating turbulent liquid flow and shear stress due to this turbulence is necessary for the acceleration of mass transfer. it is well known that vortexes are arisen during real liquid flow due to their viscosity and because of the collision of these vortexes turbulence proportional to the velocity of flow occurs. shear stresses proportional to the velocity of flow occur between turbulent liquid layers which have important role in oxygen (do) and mass transfer: these stresses thin the laminar layers of transferring interfaces, micromix the components of broths, disperse oil particles and air bubbles facilitating and accelerating mass transfer processes, disintegrate clots and in some cases cause morphological changes in the structure of microorganisms as in the case of penicillin fermentation. the magnitude of hydrodynamic forces created by agitation can be seen from the fact that according to the calculations of van’t riet and smith the centrifugal acceleration behind the vortexes created by impellers can be seven-hundredfold of the gravity (5). shear powers may, however, damage microorganisms which are especially sensitive, contribute to the creation of stable liquefied foams which generally decrease oxygen transfer, and aeration of carbon-dioxide and other gases partially on direct way and partially due to antifoaming oils. microorganisms on the interface of vortexes can be disrupted while those in the centre of the vortex may abrade each other. consequently the intensity of agitation should remain within a narrow range for keeping damaging effect at a minimum level while maintaining maximum advantages and this is the purpose of optimization. the characteristics of fermentation processes may vary due to the differences in viscosity, foaming properties, density, etc. a typical feature is that while foaming generally decreases the oxygen transfer, in certain cases the increased persistence of bubble may raise the rate of oxygen transfer in liquefied foams, and antifoaming agents may decrease it. some microorganisms such as oxytetracycline producers do not need agitation, and their fermentation can be made in slim vessels without agitator which are much cheaper. air inflated into the broths dispersed, distributed and circulated in the medium of the fermentor by the agitation system proportionally to power input. due to this procedure the volume of the medium is increasing and oxygen will be dissolved in the medium depending on the intensity of agitation, characteristics of medium and surface gas velocity vs. the degree of oxygen transfer is depending on the viscosity of the medium the characteristics of air, medium and microorganism system, and coalescing properties of air bubbles. the entrapment of air and this way oxygen fusion can decrease greatly due to increased viscosity and bubble coalescence (van’t riet, smith 5., and buchholz et al. 6.) besides the mentioned air entrapment broths volume can also be increased by the often very intensive foam formation depending on broths characteristics. stable so called liquefied foams are formed on more viscous mediums such as in penicillin fermentation. contrary to the air entrapment mentioned above this foam formation is detrimental since it limits oxygen transfer partially directly and partially through antifoaming agents, however rarely the opposite situation may occur. consequently maintaining the air input and power within a narrow range based on continuous instrumental measurement of fermentation parameters is an important requirement for dissolving oxygen and nutrients and also their transfer to microorganisms with adequate rate. considering economical importance of mass transfer problems arising from increasing size of fermentor vessels more efficient complex agitation systems were developed with lower power requirement, better dispersion and including far better circulation levels. in their paper published in 1987 b.c. buckland et al. had revealed that application of lightnin and prochem propeller agitators providing better “top to bottom” blending of viscous broths is cost effective due to saving power input and/or by the application of these agitators the production can be increased because of the higher cell concentration due to better agitation (buckland et al. 7). papers on complex agitation systems have been published more often since the beginning of 1990s (chemineer, 8). during their developmental activities manufacturers besides the relations for calculation of main sizes and powers could mainly rely on experimental results which, however, provided merely informative results due to the above reasons. it should also be noticed that uniformization, development of systems which can be distributed widely and production of their own types and licensed products are the main interests of manufacturers. all these factors eventually lead to 38 negligence of specific requirements of fermentations. exerting themselves to protect their trade secrets, factories generally provide very little possibilities for carrying out profound studies fermentation process by the professionals of manufacturers. according to the above characteristics and requirements of fermentation processes may differ very much. it follows from the above written that besides applied technologies and materials the success of fermentation processes also depends upon whether the agitation system used during fermentation is adequate for the specific requirements of fermentation. consequently the characteristics, dispersion and circulation capabilities of agitation levels should be adjusted to the features and requirements of the fermentation which may, conversely, vary because of the differences between the experimental and industrial levels. in case of viscous liquids experimental levels do not provide data and indications of adequate accuracy for the adjustment. although the analysis of experimental data has been improved very much since v. charles through the application of computers, lesser changes may also be of significance due to the large volume of industrial fermentors and these changes cannot be designed with adequate accuracy. it follows from the above that there is no adequate procedure available for actual optimization of industrial agitation systems and for establishment how much an agitation system can be considered optimal for a certain fermentation procedure. the efficiency of an agitation system is depending on its structure and considering fermentation it is depending on how the agitation system’s levels use power input for dispersion and circulation and how adequate this is for the requirements of a given fermentation process. a solution for this problem may be if manufacturers provide special separated parts for the particular levels of the agitation system which could be fixed on the system by screw this was changing the characteristics of agitation. it would not be especially difficult to solve since power input is proportionally changed with the fifth degree of the diameter of the agitator and the characteristic of flows can be modified within a wide range merely with changing the shape and angle of blades of the impeller. the application of this idea requires some change in viewpoint according to the following: 1. it cannot be expected that a manufacturer will provide an “optimal” agitation system, but it is expected to provide an agitation system of which perfusion properties can be modified within a wide range with auxiliary parts. it would be, of course, the obligation of the manufacturer to provide detailed user manuals and information sheet for the expectable effects of these auxiliary parts and provide professional assistance for testing on demand. 2. the obligation of the user would be the actual optimization of the agitation system according to provided directives and thorough analysis of the effects of the auxiliary parts. inclusion of factory professionals in the selection of the most efficient system may solve the problems of scale-up sometime mentioned as dream by m. charles (4) and may assist the establishment really optimal agitation systems. biogal pharmaceuticals established for the production of antibiotics together with research centers has endeavored to develop its devices since the beginning. according to the knowledge learned in the international symposium in prague in 1964 where both european and us professionals attended, biogal pharmaceutical was the first pharmaceutical company applying two-turns driver engine which increased power utilization by 3040%. at the beginning of 1970s the company changed the systems with rushton agitators which had asymmetric structure, and 20% better power on the lowest level. this was due to the cognition of the fact that in the applied asymmetric systems the efficiency of the lower agitators compared to the upper ones was considerably decreased by the function of dispersion. since the beginning of seventies the company had started to apply a complex system including propeller agitators and rushton turbines and with this method narrow otc fermentors without agitators could successfully be adapted for penicillin fermentation. based on these experiences also considering the construction of biogal’s newer complex agitation systems it can be concluded that there are more possibilities for the increase of efficiency and optimization of agitation systems through the application of modifiable impellers recommended above. conclusions conditions of optimization of the aeration-agitation systems of large-scale fermentors in case of viscous broths: 1. providing flow modifying parts for the agitations system for variation of dispersion and circulation capabilities and adjustment for the requirements of a specific fermentation process. 2. evaluation of the results of variation by fermentation professionals and choosing optimum variation. considering these on a long term basis may lead to gain profound knowledge about specific requirements of fermentation processes and industrial optimization may become unnecessary in the future. nonation do dissolves oxygen p/v power/volume kla volumetric oxygen transfer coefficient vs gas velocity 39 references 1. bakker a., smith j. m., meyers k. j., chemineer, po box 1123, daytona, oh45401, reprinted from chemical engineering 2. nienow a. w.: 9th biotech symposium, crystal city, usa, 1992 pp. 196-196 3. meyers k., reeder m., bakker a., rigden m.: agitating for success, the chemical engineering 4. charles m.: trends in biotechnology, vol 3., no.6 180 5. van’t riet k., smith j. m., chemical eng. sci. 1975, 30. 1083 6. buchholz h., buchholz r., niebenschutz h., schügerl k.: eur. j. appl. microb. and biotechn. 6. 1978, 115. 7. buckland et al. bioengineering vol. 31. 70. 737742. i. 1988 8. chemineer, inc. reprinted for chemical engineer crammer road, west meadows, daby, de 21 6xt, england microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 1-4 (2008) ozonation of biologically refractory pollutants b. almasiová1 , j. derco2, a. kassai2 1slovak university of technology, faculty of chemical and food technology, institute of chemical and environmental engineering, radlinského 9, 812 37 bratislava 1, slovak republic e-mail: beata.almasiova@stuba.sk 2water research institute, nábrežie l. svobodu 5, 812 49 bratislava, slovak republic advanced oxidation processes (aops) are an effective emerging technology for removal and enhancement of biodegradability of biologically resistant and toxic pollutants of wastewater. one of these aops is ozonation carried out at higher ph values. ozone is a powerful oxidizing agent available for the treatment of industrial wastewaters. the ozonation reactions are accomplished into two pathways: direct ozone oxidation and indirect free hydroxyl radical oxidation. the industrialization of human society has grown also the risk of environmental problems caused by a diversity of anthropogenic chemicals and substances in wastewater from industry. wide group of these substances are able to enter into the organism and interrupt with their endocrine systems. they are resistant and bioactive, thus they are able to pass conventional treatment systems, wide-spread with surface and underground water and enter into organisms. we have studied removal of 2-mercaptobenzothiazole (mbt) contained in synthetic wastewater. this xenobiotic compound is used mainly in the manufacture of rubber additive chemicals but also has other uses, notably as a corrosion inhibitor in cooling water and in antifreeze for automobiles. it is known as a widespread, toxic and poorly biodegradable pollutant. biological treatment of the wastewaters of rubber chemicals production often seems to be problematic, most probably due to presence of mbt. in fact, mbt is used due to its fungicidal properties, or its antimicrobial effects. data concerning the biodegradation of mbt are inconclusive. some authors have suggested it is recalcitrant to biodegradation. mbt was not metabolised by microorganisms, which were non adapted to activated sludge to this pollutant. the feasibility of utilisation of ozonation process for reduction of concentration of mbt was investigated in laboratory scale equipment. the system was operated in batch mode. synthetic wastewater with mbt was added into ozonation reactor at the beginning of trials. continuous flow of oxygen 30 l h-1 was applied for generation of ozone. ozonation trials were carried out at different performance of ozone generator in the range from 30 to 90% of the power maximum. initial concentration of mbt in synthetic wastewater was about 50 mg l-1. significant decrease of mbt content was observed after four minutes of ozonation. correspondent efficiency values for cod and toc removal were 55 and 16%. higher removal rates were achieved in the sample with lower initial content of mbt. the highest removal rate values were observed during the first 10 minutes of the process for both cod as well as toc content. the first order reaction kinetics follows for cod removal. positive influence of power of ozone generator on cod removal resulted from the work. keywords: bubble ozonation column, degradation, 2-mercaptobenzothiazole, ozone, ozonation introduction the industrialization of human society has grown also the risk of environmental problems caused by a diversity of anthropogenic chemicals and substances in wastewater from industry. wide group of these substances are able to enter into the organism and interrupt with their endocrine systems. they are resistant and bioactive, thus they are able to pass conventional treatment systems, wide-spread with surface and underground water and enter into organisms. benzothiazoles and their derivatives are manufacture worldwide for a wide variety of applications. they are used, among other things, as slimicides in the paper and pulp industry, as fungicides, as herbicides or as antialgal agents. the main use is as vulcanization accelerators in rubber production, catalyzing the formation of sulfide linkages between unsaturated elastomeric polymers in order to obtain a flexible and elastic cross linked material [1]. 2-mercaptobenzothiazole (mbt) is the member of the benzothiazole group of heterocyclic aromatic compounds. it is a pale yellow, crystalline substance with an unpleasant odor and a bitter taste, with molecular weight 167.25 g mol-1 and specific density 1.42-1.52. it is easily soluble in ethyl acetone, acetone, dilute solution of sodium hydroxide and sodium carbonate and soluble in ethyl alcohol. it is not easily soluble in benzene. mbt can occur in two tautomeric forms. this xenobiotic compound is used mainly in the manufacture of rubber additive chemicals but also has other uses, notably as a corrosion inhibitor in cooling water and in antifreeze for automobiles. it is known as a widespread, toxic and poorly biodegradable pollutant. biological 2 treatment of the wastewaters of rubber chemicals production often seems to be problematic, most probably due to presence of mbt. in fact, mbt is used for its fungicidal properties, or its antimicrobial effects. data concerning of the biodegradation of mbt are inconclusive. some authors have suggested it is recalcitrant to biodegradation [2]. epidemiological investigations indicate that workers occupationally exposed to mbt have an increased risk of death from bladder cancer. genotoxicity investigations in bacterial and mammalian test systems provide some evidence indicating that mbt has the potential to induce mutations and chromosomal aberrations. toxicity studies in rats and mice chronically exposed to mbt identified increases in various tumors. mbt interfered with the nitrification processes and exhibited biocidal effects. mbt inhibit the degradation of easily degradable organics. mbt was not metabolised by microorganisms, which were non adapted to activated sludge to this pollutant. decrease of respiration activity of non adapted activated sludge was observed with the increase of mbt concentration. utilisation of ozone as possible process for mbt removal from wastewater was studied. advanced oxidation processes (aops) are an effective emerging technology for removal and enhancement of biodegradability of biologically resistant and toxic pollutants of wastewater. one of these aops is ozonation carried out at higher ph values. ozone (o3) is a powerful oxidizing agent available for the treatment of industrial wastewaters. o3 is an unstable gas produced by electric discharge in a gas phase (air or pure oxygen). it is strong disinfectant with high oxidation power, potentially toxic and explosive, requiring on-site generation and caution for use. the ozonation reactions are accomplished into two pathways: direct ozone oxidation and indirect free hydroxyl radical oxidation. the direct ozone oxidation reaction is highly selective but relatively slow by selectively attacking the unsaturated electron-rich bonds contained in specific functional groups, e.g., aromatics, olefins and amines. in comparison, the indirect reaction has a relatively low selectivity but a quick reaction rate by hydroxyl radicals, which are generated by decomposition of ozone molecule. the hydroxyl radicals can oxidize regular organic substrates, micro-organisms and nh3-nitrogen; the oxidation reaction lead to the formation of different but stronger radicals usually represented by the r symbol. the r radical can further react with ozone molecules to generate more hydroxyl radicals for further oxidation. however, the formation of free radicals from ozone is affected by either the solution ph or the presence of some scavenger chemicals in the water to be treated [3]. experiments and results degradation of mbt with ozone has been studied. the experiments were performed in bubble ozonation column. the ozonation equipment consists of two glass columns, 0.04 m diameter and 1.70 m height. the first column was filled with synthetic wastewater with mbt, the other one was filled with solution of potassium iodide. the role of the second column was to destroy residual ozone in the outlet of the first ozonation column. the effective volume of both columns was 1.0 litre. schematic diagram of experimental bubble ozonation apparatus is shown in fig. 1. the system was operated in batch mode. synthetic wastewater with mbt was added into ozonation reactor at the beginning of trials. continuous flow of oxygen 30 l h-1 was applied for generation of ozone. the lifetech ozone generator with the maximum ozone production 5 g h-1 and lifetech ozone uv detector were used. ozonation trials were carried out at different performance of ozone generator in the range from 30 to 90% of the power maximum. the content of mbt in sampling was measured by high performance liquid chromatography with reverse osmosis (rp-hplc). concentration of cod (chemical oxygen demand) was measured by semi micro method and toc (total organic carbon) by analyser schimadzu tocvcph/cpn [4]. figure 1: schematic diagram of experimental column apparatus 1 – ozonation column, 2 – destruction of residual o3, 3 – oxygen cylinder, 4 – ozone generator, 5 – mixture of o2 and o3, 6 – distribution of o3, 7 – sampling, 8 – residual gas outlet, 9 – moisture catcher, 10 – glass fibre filter, 11 – uv detector of o3 ozonation trials were carried out with synthetic wastewater containing mbt in lab-scale ozonation apparatus. initial concentration of mbt in synthetic water was about 50 mg l-1. fien et al. [5] shown, that mbt and its breakdown products had a high affinity towards ozone as indicated by the rates for partial oxidation and mineralization. benzothiazole (bt) was identified as the first ozonation product, reaching up to 60 mol% of the original mbt concentration, followed by low concentration of 2(3-h) benzothiazolone. fig. 2a illustrates the influence of ozonation on variation of 3 concentration cod, toc and mbt at the ozone generator power 90%. the specific ozone supply was in this case 0.97 go3 gcod -1. according to results shown at the table 1 the highest cod removal was observed during the first 10 minutes of ozonation. cod removal rate 5.9 mg l-1 min-1 was achieved at 90% of maximum ozone generator power. the initial ratio of cod/mbt was 2.2 (exp1, 2). comparing with the initial cod value the 66% conversion of cod was achieved after 10 min of ozonation (exp 2) and 98% was achieved after 1 h (exp1). the first order reaction kinetics follows for cod removal. good coincidence in cod and toc removal follows from the fig. 2a. table 1: concentration of cod, toc and mbt at w = 90% and qo2 = 30 l h-1, t = 60 min (exp1) t cod toc mbt [min] [mg l-1] [mg l-1] [mg l-1] 0 95.97 24.8 44.6 5 42.59 18.8 0.1 10 13.47 14.0 0.1 15 11.05 12.9 0.008 20 8.62 12.5 0.008 60 1.34 11.5 0.008 table 2: concentration of cod, toc and mbt at w = 90% and qo2 = 30 l h-1, t = 10 min (exp2) t cod toc mbt [min] [mg l-1] [mg l-1] [mg l-1] 0 89 20.2 40.7 2 55 18.9 1.71 4 40 16.9 0.086 6 30 14.3 0.008 8 30 12.1 0.008 10 30 10.8 0.008 table 3: concentration of cod, toc and mbt at w = 70% and qo2 = 30 l h-1, t = 50 min (exp3) t cod toc mbt [min] [mg l-1] [mg l-1] [mg l-1] 0 168 56.3 54.1 5 53.4 2.34 10 116 48.2 0.089 15 42.1 0.0189 20 33 36.7 0.008 30 29.6 0.008 50 23 25.5 0.008 the efficiency of removal of toc was 46% after 10 minutes (exp2) and 54% after 1 hour (exp1) of ozonation. removal (99%) of mbt from the sample was achieved by ozonation after 5 minutes (exp 1, 2). the presence of bt was identified. the amount of bt measured after 60 minutes of ozonation corresponded to 5% of initial mbt concentration in the synthetic wastewater. fig. 2b (table 3) shows the results of ozonation process carried out at 70% of power of ozone generator and the oxygen flow 30 l h-1. the specific ozone supply was 0.59 go3 gcod -1. the initial ratio of cod/mbt was 3.1. the efficiency of removal of cod and toc were 86% and 54% after 50 minutes (exp3) of ozonation. 95.7% of mbt was removed after 5 minutes of ozonation. the process efficiency was considerably influenced by duration of ozonation. the content of mbt in synthetic wastewater containing this pollutant decreased closely to zero after first 4 minutes of ozonation performed at 90% of the maximum power of ozone generator. similar decrease of mbt was achieved after 10 minutes of ozonation carried out at the 70% of the maximum power of ozone generator. ozonation of mbt w = 90%, qo 2 = 30 l.h-1 0 20 40 60 80 100 120 0 10 20 30 40 50 60 70 t [min] c o d , m b t [m g. l-1 ] 0 5 10 15 20 25 30 t o c [m g. l-1 ] chsk, exp 1 chsk, exp 2 mbt, exp 1 mbt, exp 2 toc, exp 1 toc, exp 2 ozonation of mbt w = 70%, qo 2 = 30 l.h-1 0 40 80 120 160 200 0 10 20 30 40 50 60 t [min] c o d , m b t [m g. l-1 ] 0 20 40 60 t o c [m g. l-1 ] cod, exp 3 mbt, exp 3 toc, exp 3 figure 2: cod, toc and mbt as a function of ozonation time at oxygen flow rate 30 l h-1 a) w = 90% b.) w = 70% 4 conclusion feasibility of ozone utilisation for mbt removal from wastewater was studied. significant decrease of mbt content was observed after four minutes of ozonation carried out at 90% of maximum ozone generator power. corresponded efficiency values for cod and toc removal were 55 and 16% respectively. the highest removal rate values were observed during the first 10 minutes of the process for both cod as well as toc content. related specific ozone supply was 0.97 go3 gcod -1. cod removal follows the first order reaction kinetics. the removal rate 5.2 mg l-1 min-1 was observed at ozonation trial carried out at 70% of maximum ozone generator power was maintained. positive influence of power of ozone generator on cod removal results from the work. the removal rate 5.9 mg l-1 min-1 was achieved at the 90% of maximum ozone generator power. in conclusion, mbt is readily transformed by ozonation. acknowledgements the authors wish to thank for the financial support from vega grant 1/0866/08. references 1. de wever h., verachtert h.: water research vol. 31, no. 11, (1997) 2673-2684 2. chudoba j., tuček f., zeis k.: acta hydrochim hydrobiol. (5), (1977) 495-498 3. chiang y. p., liang y. y., chang ch. n., chao a. c.: chemosphere 65, (2006) 2395-2400 4. horáková m.: všcht praha (2006) 335 5. fiehn o., wegener g., jochimsen j., jekel m.: water research 32 (4), (1998) 1075-1084 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 /colorconversionstrategy /cmyk /dothumbnails false /embedallfonts true /embedopentype false /parseiccprofilesincomments true /embedjoboptions true /dscreportinglevel 0 /emitdscwarnings false /endpage -1 /imagememory 1048576 /lockdistillerparams 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word b_20_r.doc hungarian journal of industrial chemistry veszprém vol. 38(2). pp. 155-158 (2010) analysis of global and local environmental impacts of bus transport by lca methodologies b. simon1,2 , l. tamaska2, n. kováts1 1department of environmental engineering and chemical technologies university of pannonia, egyetem u. 10., hungary e-mail: simonbalint@gmail.com 2kmprojekt ltd., endrődi s. u. 42/c, hungary the mobility of the globalized world is supported by internal-combustion engines, which generally use fossil fuels. city people have to move daily from place a to b. for that reason cities have public transport systems, including local bus as an important element. as the bulk of the population is concentrated in the city, the atmospherical emissions of local buses have a considerable impact on human health. this study analyses these impacts using the methodology of lca and the database of the artemis project. the whole study includes the emissions models of pre-euro and euro 1-5 buses, cng, biodiesel and hydrogen buses, and the fuel production. furtermore seven scenarios for modeling traffic situations are included, too. for the impact assessment three cml2001 indicators are used. global warming potential (gwp) is for assessing the global impacts, carbon footprint; human toxicity potencial (htp) and photochemical ozone creation potential (pocp) are used for the estimation of impacts in urban environments. keywords: public transport, local bus, life cycle assessment, global warming potential, human toxicity potential, photochemical ozone creation potential introduction transportation of modern ages involves many types of vehicles, from bicycles to trains. the present study analyses the environmental impact of bus types used in hungarian cities, including the annual impact of the number and type of buses used in budapest. the number of cars in the year of 2006 was approx. 650 000 on the streets of budapest [1], simultaneously, the bkv (budapest public transport co.) had 1400 buses according to data of 2007. average daily 1.5 million passengers are transported by these buses, amounting to 42.3 % of the total daily passengers [2]. euro 0 and euro 1 motors form the biggest part of these buses (see table 2). 60% of the travels are managed by public transport and the rest by cars whose number is about one magnitude higher [3]. the fact that the fleet of buses is rather old, they have high environmental load and environmental emissions make it clear that modernizing of public transport and the bus fleet is a very important work. primary aim of this present study is to estimate environmental impacts of air emissions caused by bus transport and to serve as an important basis for a decision-making process being necessary for achieving changes. for such purpose, life cycle assessment (lca) was selected as the most appropriate methodology. several studies have been already published for estimating emissions and environmental impact, which results have been incorporated in this present study [4, 5, 6, 7, 8]. materials and methods the goal, and scope of the study should be determined by assessing the environmental impacts of public transport. in this case this is bus transportation and the production of the fuel. the study was carried out according to the iso 14044 standard [9]. the analysis provides information about the environmental impact of the different usage of different fuel types. the analysis takes the values of table 1 and 2 into account, which are derived from the artemis project database [6, 7]. the databases of fuel production and of the emissions of alternative motor driving have been gathered from international publications and doctoral theses [10-29]. table 1: emissions and fuel consumption of the bus types e5 e4 e3 hc 0.078 0.076 1.356 g/km fuel cons. 641.429 622.964 637.381 g/km co 0.652 0.645 6.934 g/km nox 9.459 13.717 27.644 g/km pmm 0.016 0.015 0.042 g/km co2 2020.504 1962.339 2007.748 g/km methane 0.001 0.001 0.027 g/km nmhc 0.076 0.075 1.328 g/km 156 table 2: emissions and fuel consumption of the bus types e2 e1 80ties hc 1.571 2.403 7.047 g/km fuel cons. 605.975 664.391 843.085 g/km co 6.939 7.092 16.703 g/km nox 22.898 21.031 31.743 g/km pmm 0.044 0.115 0.278 g/km co2 1908.823 2092.833 2655.721 g/km methane 0.031 0.048 0.141 g/km nmhc 1.539 2.355 6.906 g/km a scenario analysis is included in the study. these scenarios are modelling a yearly traffic situation (in km) according to table 3, first using the old buses and than they are displaced by the emission models of the seven buses of the alternative drives. table 3: the “present” scenario in vehicle kilometer (vkm) per year and number of pieces of buses vkm/y pieces e0 27 998 055 460 e1 34 826 840 577 e2 13 189 275 248 e3 11 120 090 151 total 87 134 260 1436 the indicators the results of emission models are investigated by the global warming potential (gwp), human toxicity potential (htp), and photochemical ozone creation potential (pocp) of cml 2001. these are impact oriented indicators, that is, the impact of emissions is given with a mass equivalent value of a reference compound. gwp puts the emphasis on the role played in the climate change, and represents the environmental impact in kg co2 equivalent. this indicator can be used during the estimation of the carbon foot print. its value equals to the impact posed by the same amount of co2. as its name indicates, it makes a global impact, and caused by emission to the air, which have life-time from some decades to several thousands of years. htp characterizes materials with human toxic potential. the impacts of such materials are normalized to dichloro-biphenyl equivalent (kg dcb equiv). it will be used as a local impact, caused by heavy metals, pm10, halide, dioxins emissions. as such, recipients are mainly those who live nearby to emitting facilities. for example, htp of a waste incinerator has negligible impact on those who live app. 100–200 kms from the facility. popc helps to determine the impact of materials, which have a big role in the formation of tropospheric ozone, wherewith help in the development of summer smog. the unit is the kg ethane equivalent. the head materials with pocp impact are the hydrocarbons (gas) and nox. [30] accordingly, due to the magnitude of the impact, in case of public transport mainly htp and pocp are emphasized, whilst considering the total emission, the gwp is a good component to characterizing of the whole system. results we show first the impacts of 1 vehicle kilometer, so differences between the bus types and fuel types addressed can be made clear. fig. 1 shows that by all bus types, except the hydrogen fuelled buses, the emissions of urban traffic cause the biggest global warming potential. the gwps of the use of diesel motors are on the same level, the highest co2 equivalent emission is posed by the buses from the 80’es. however, the average impact is around app. 2 kg co2equivalent. the gwp of fuel production changes in proportion to the fuel consumption. in case of biodiesel an app. 3 kg co2 equivalent minus appears, because the system boundaries cover the co2 assimilation of plants, too. naturally, this does not mean that biodiesel is the best choice, because the gwp does not provide information about the other environmental impacts, such as land use or eutrophication. figure 1: gwp of 1 vehicle kilometer the value of htp is mainly derived from fuel production, which is especially remarkable in case of the hydrogen. the high electricity demand of the hydrogen production makes these values so high. because the production of the electricity is the impact holder, the htp is not formed like a point source of pollution, but is dispersed between the power plants of hungary, similarly to the other environmental impacts. the black column shows the important htp impacts (inside the city). this decreases with the increase of euro norm, but is rather high in the case of biodiesel, as opposed to gwp, the htp of cng and diesel hybrid are similar. such impact of public transport is the lowest when hydrogen is used. hydrogen-shovel buses provide the highest environmental performance in this category, with the immission of max. 0.003 kg ethylene equivalent. 157 figure 2: htp of 1 vehicle kilometer favouring smog formation is a capacity being characteristic of old buses; the biodiesel and cng have better performance than the newer euro norm buses. though the pocp of diesel’s whole lice cycle is worse than that of the biodiesel and cng, the emissions of use are lower (for of urban traffic).the possibility of smog formation is the lowest in case of the hydrogen buses (see fig. 3). figure 3: pocp of 1 vehicle kilometer the scenarios different bus types and different fuel types have given different impact values, and it is not possible to determine the best bus or fuel type from environmental aspect. the next scenarios will simulate a real situation, where the composition of the bus fleet and the value of travelled kilometres are given in table 3. this is the “present” scenario. by the other scenarios the bus fleet of the “present” scenario will be displaced with the alternative bus types, like biodiesel, hybrid diesel, cng, or hydrogen bus (taking travelled kilometres as reference). the emission of ghg in case of fossil fuel buses comes mostly from the combustion of fuel. this is 20 000 ton co2-equivalent emission in the “present” scenario. this is decreased in case of the euro 5 and in case of the cng and hybrid is less than 20 000 and 10 000 tons, respectively. in the case of hydrogen buses the ghg emission amounts to almost 100% due to the hydrogen production, that causes, except the “fuel cell hydrogen” (h-fc), higher impact as the “present” scenario. the co2 assimilation ability of plants has a “negative impact” on the biodiesel production, whereby the overall ghg emission of biodiesel is negative, as such, this process rather captures than emits co2. figure 4: gwp of the scenarios the advantage of biodiesel considering gwp disappears when htp is discussed. cng has the best overall performance although this impact of the previous two bus types comes almost exclusively from the urban area. on the other hand, the hydrogen buses have higher impact, but this arises from the fuel production and accordingly these bus types have the smaller impact on the citizens. the euro 5 has the smaller impact in urban are, following the hydrogen buses. figure 5: htp of the scenarios all of the alternative buses perform better than the “present” scenario considering smog development. the euro 5 and h-fc have the smaller pocp in the urban area; these are followed by hydrogen ice and the other fossil fuel user bus types. figure 6: pocp of the scenarios 158 conclusion the environmental impacts of older buses are higher than those of the alternatives. however, this tendency does not apply to hydrogen buses, because hydrogen production poses significant environmental impact, and/or high energy consumption. the gwp of old buses is between 2–3 kg co2 equivalent per vehicle kilometres, the same impact of alternatives is less than 2 kg co2 equvalent. considering those impacts which are important in urban environments, the euro 4-5 have better environmental performance than the alternatives. it can be concluded, that in the traffic situation (scenarios) the biodiesel, diesel hybrid, the cng and the h-fc have the best gwp values. considering local impacts (important impacts in urban area, like htp and pocp) the euro 5 has better performance, but if the fuel production is also taken into account, the euro 5 occupies only the 4th and 6th positions out of the seven scenarios. as such, the euro 5 norm buses are highly capable for the urban public transport. with the improving of the environmental profile of the hydrogen production (e.g. use of renewable energy, find the high performance hydrogen storage), it can be the best adaptable bus type for the mass transport in densely populated areas, due to their almost negligible emission and environmental impact. references 1. k. mogyorósi et al.: a közép-magyarországi régió társadalmi atlasza, 2006, 40–41. 2. zs. balogh: budapesti közlekedési zártkörűen működő részvénytársaság 2007 éves jelentés. (2007) 3. e. beliczay, a. lukács: ajánlások budapestért. (2006) 4. m. chester, a. horvath: environmental lifecycle assessment of passenger transportation: a detailed methodology for energy, greenhouse gas and criteria pollutant inventories of automobiles, buses, light rail, heavy rail and air v.2. (2008) 5. m. keller, m. lebküchner et al.: diesel, gas-, oder trolleybus? (2006) 6. m. rexeis, s. hausberger et al.: assessment and reliability of transport emission models and inventory systems, heavy duty vehicle emissions; final report. (2005) 7. m. rexeis, s. hausberger et al.: heavy duty vehicle emissions (artemis). (2005) 8. m. wang: greet life-cycle analysis model development. (2008) 9. int. stand. org.: iso 14040:2006 environmental management – life cycle assessment – requirements and guidelines. (2006) 10. r. ahluwalia, x. wang et al.: fuel economy of hydrogen fuel cell vehicles, journal of power sources, 130, 2004, 192–201. 11. j. a. barclay: advances in cryogenic engineering/ cryofuels now and in the future, p. kittel (ed.), plenum press, 1995. 12. e. booth, j. booth et al.: economic evaluation of biodiesel production from oilseed rape grown in north and east scotland. (2005) 13. compair: cng refuelling solutions. (2009) 14. http://www.e-traction.com/fuel_cell.htm (2009, september). 15. fiba canning inc: gas transportation vehicles (broshure). (2005) 16. fiba canning inc.: gas transportation vehicles (broshure). (2005) 17. hennlich ipartech.: professzionális elektromos diesel üzemanyag-szivattyúk (www.hennlich.hu). (2009) 18. ikp stuttgart & pe-europe: gabi software, manual. (2003) 19. jp sauer & sohn: sauer compressors for gas compression. (2009) 20. http://www.global-hydrogen-bus-platform.com/# (2009, september) 21. man nutzfahrzeuge ag.: ecology and economy – the hybrid city bus. (2009) 22. http://www.nrel.gov/lci/ (2009, september) 23. m. pehnt: ganzheitliche bilanzierung von brennstoffzellen in der energieund verkehrstechnik. institut für technische thermodynamik deutsches zentrum für luftund raumfahrt; institut für energiewirtschaft und rationelle energieverwendung. (2002) 24. w. peschka: advances in cryogenic engineering/ hydrogen cryofuel in internal combustion engines, p. kittel (ed.), plenum press, 1993. 25. e. rebhan: energie handbuch, gewinnung, wandlung und nutzung von energie, springer berlin-heidelberg, 2002. 26. j. sheehan, v. camobreco et al.: life cycle inventory of biodiesel and petroleum diesel for use in an urban bus. (1998) 27. http://www.agraroldal.hu/repce-5_cikk.html (2009, september) 28. p. l. spath, m. k. mann: life cycle assessment of hydrogen production via natural gas steam reforming. (2001) 29. umweltbundesamt & ökoinstitut: processorientierte basisdaten für umweltmanagement-isntrumente. (2009) 30. m. goedkoop, a. m. siebel: lca methodology and practice. (2005) 31. b. j. guinée, m. gorrée et al.: life cycle assessment, an operational guide to the iso standards. 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 149-153 (2008) determination of safety operating regimes based on the analysis of characteristic equation of state-space model t. varga , g. horváth, j. abonyi university of pannonia, department of process engineering, h-8200 veszprém egyetem street 10., hungary e-mail: vargat@fmt.uni-pannon.hu determining safe regions of operation is important at the design, control and optimization of process systems. process alarms and safety systems should be designed based on such knowledge. in classical control systems these regions are represented as independent constraints on process variables. in case of a highly exothermic reaction takes place in any kind of reactor there is a high risk to develop reactor runaway if the produced heat can’t be removed. reactor runaway phenomena is a serious problem in many chemical industrial processes, hence the most of reactions are exothermic. reactor runaway means a sudden and considerable change in process variables such as reactor temperature. to detect and forecast the development of runaway a model based criteria is introduced in this manuscript. the criteria is based on indirect ljapunov’s stability analysis of a process model. the aim of this work is to compare methods for calculation of eigenvalues. eigenvalues of the jacobian matrix were calculated with a numerical method and there were also computed analytically. stability of two-phases fed-batch reactor with highly exothermic reactions are analyzed with the investigated stability analysis methods. analytical solution is more sensitive and of course it is more accurate than the numerical one still the algorithm based on the analytical solution is a lot more faster. keywords: operating regime, process model, simulation fed-batch reactor, stability analysis. introduction safe and at the same time optimal operation is always a key issue in the wide spectrum of chemical engineering problems. e.g. the design of optimal feeding trajectory of a fed-batch reactor where a highly exothermic reaction takes place. so to apply any kind of optimization methods some constraints on operating variables must be determined, i.e. the safe operating regimes must be characterized. in this paper the first step of this problem solution is investigated. it is introuced, how the safe operating regimes can be extracted from a process model. the most important phenomena from the safety of operation was investigated closely. it is called reactor runaway. it has contributed to industrial chemical accidents, most notably the 1984 explosion of a union carbide plant in bhopal, india that produced methyl isocyanate. thermal runaway is also a concern in hydrocracking, an oil refinery processes. reactor runaway means a sudden and considerable change in process variables. it is a serious problem in many chemical industrial technologies, like oxidation processes and polymerization technologies [1-3]. e.g. in case of a highly exothermic reaction thermal runaway occurs when reaction rate increases due to an increase in temperature. it causes a further increase in temperature and it further increases the reaction rate. the temperature increasing will be stoped only if all reactants are depleted and reaction rate is getting zero. detection of runaway has two main important aspects. on one hand runaway forecast has a safety aspect, since it is important for avoiding the damage of constructional material of reactor or in the worst case the reactor explosion. on the other hand it has a technology aspect, since the forecast of the runaway can be used for avoiding the development of hot spots in catalytic bed, which speeds up the ageing of catalyst [4; 5]. the avoid of runaway can be important in decreasing of the produced amount of byproducts, e.g. in synthesis of 2-octanone from 2-octanol [1; 6; 7]. a control system which is able to modify operating conditions of reactor in appropriate time decreases the costs and increases the safety of operation. the first step to develop such control system is the development of a reliable runaway criterion. most of runaway criteria found in literature can be classified as dataor model-based criteria [8-10]. to apply data-based criterion it is necessary to have some measured data. it means the use of a data-based criterion has some restrictions on the forecasting. other problem with data-based methods is found in measurement conditions, e.g. measurement noise can result in false forecast. model-based criteria require parameter sensitivity and/or stability analysis, so for the application of these kinds of criteria it is necessary to have exact process model with correct model parameters. in the design process of a reactor in which a reversible reaction takes place the first step must be the calculation of equilibrium temperature. reactor temperature can’t cross this line. after everything is 150 known about the equilibrium the calculation of optimal temperature profile or trajectory can be performed. it can be generated easily with differentiating of the rate of reaction with respect to reactor temperature. hence the most of reactions in chemical industry are exothermic the generated heat must be removed to keep the operation in stable and controllable operating regime. in our earlier studies ljapunov’s stability analysis method proved to be appropriate to detect reactor runaway [11; 12]. the applied stability analysis method based on the analysis of eigenvalues [13]. the aim of this article is the investigation of the relability of numerically calculated eigenvalues. to check the applicability of the choosen calculation method the results are compared with the analytically calculated eigenvalues. next to relability the calculation time is the second important property of the proposed tool since it can be a part of an operator support system (oss) [14-15]. after a short introduction about the analyzed chemical engineering problem and the possible detection technics the investigated case study is presented, than results obtained by applying the developed programs are compared and finally some conclusions are stated and some possible future steps are described. stability analysis in advanced model based techniques reactor runaway is detected through the stability analysis of the process model, e.g. by ljapunov’s indirect method [16]. the state space model of the process: ( ) ,xf d xd = τ where: x – state variable; τ – independent variable (e.g. time). generation of the jacobian-matrix of first principles model is the first step in application of ljapunov’s indirect method to investigate stability: ( ) , x xfj 0x ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ∂ ∂ = where j – jacobian matrix; x0 – investigated work point. it is followed by the examination of eigenvalues of the jacobian-matrix. ,0ij =λ− where λ – eigenvalues; i – unit matrix. in case all of eigenvalues are negative than the model is stable but if one of eigenvalues is over zero than model is unstable at the investigated operating point of reactor. to calculate the eigenvalues of the jacobian the determinant method can be applied. in case there are m correlations and n state variables the size of jacobian matrix is nxm. to apply determinant method it is necessary that the number of correlations is equal with the number of state variables so the jacobian matrix must be a square matrix. eigenvalues can be calculated from the following characteristic polinomial: ( ) , jj jj ijdet mmm1m m1111 λ− λ− =λ− k mom l ljapunov’s stability analysis is suitable in detection of the development of runaway and the algorithm based on this stability analysis can separate the cases whether the runaway occurs in the reactor or not [11; 12]. however, it is quite difficult to implement this criterion in an industrial environment. furthermore, it is applicable to detect when the runaway has been occurred, which is interesting from the analysis of historical process data point of view, but it is not usable for on-line process monitoring and control, where the operator is interested in the region of the safe operation and the last time instant when the runaway can be avoided by the control system. for the predictive analysis of the process not only a detailed (accurate) process model is needed, but also a process simulator that is able to estimate the trajectories of the process variables in case of normal and abnormal operations. this simulator should be also able to model the dynamical behavior control system, including its safety elements. this knowledge is extremely important since these elements of the control system define and sometimes ”widen” the region of safe operation. the most common method for calculating eigenvalues of a small jacobian matrix is the calculation of roots of characteristic polynomial. it can be performed with applying numerical root-finding algorithms or in case the order of characteristic polynomial is not higher than four the roots can be calculated analytically. next to root-finding the second common method is the power method or vector iteration method. in this paper the accuracy, reliabilty and the speed of the developed algorithms based on numerical and analytical root-finding are analyzed and compared in stability analysis of a complex system. case study to illustrate the applicability of numerically calculated ljapunov’s indirect stability analysis a well-stirred fedbatch reactor with jacket cooling was investigated, where 2-octanone is produced from 2-octanol in a highly exothermic oxidation reaction. 151 reactor model the main product, 2-octanone is produced in a twophases reaction system in a fed-batch reactor from 2octanol. the 2-octanol is continuously fed into the organic phase, which does not exist before the start of the feeding. hence, the organic phase is the dispersed and the aqueous nitric acid phase where all the reaction steps take place is the continuous phase. two phases are connected by the mass and heat transfer phenomena. based on castellan et al.’s work [17] which shows that the oxidation processes in room temperature mostly take place according to ionic mechanism, woezik and westerterp [6] determined a reaction scheme describing the way of oxidation of 2-octanol to 2-octanone in nitric acid, which is proved to be feasible. in the first step of this reaction mechanism the nitrosonium ion forms. this reaction has a very long induction time, which can be shortened by adding a small amount of an initiator like nano2 to generate the necessary nitrous acid faster. the nitrosonium ion forms only in the aqueous phase. it is followed by the oxidation of 2-octanol forming 2octanone and the further oxidation producing different carboxylic acids. this process can be considered as an advanced benchmark problem in the field of process engineering. in [1] the control of this process is analyzed. in [6] the safety issues related to the operation is discussed. a report how the simulator of this process can be used in process engineering education can be read in [7]. from the viewpoint of our paper it is the most relevant work where the hazard and operability analysis (hazop) of this process is developed and also based on the application of process simulator. mathematical model of the system was worked out by woezik and westerterp [6]. the introduced mechanistic model is based on a simplified form of the above introduced mechanism to predict the dynamic behavior of the reactor. the simplified reaction mechanism: xbp b2pba ⇒+ +⇒+ where a is 2-octanol, b is nitrosonium ion, p is 2octanone and x represents all the byproducts. in the next part just a brief introduction will be given about this model; a well detailed description can be found in [9-10]. the structure of the dynamic model can be found in fig. 1. in the interconnection of organic and aqueous phases are considered only the mass transfer process and the temperature of the mixed phases are the same. the reactor insight and the jacket are coupled by only the heat transfer through the reactor wall. the main and the side reaction takes place in aqueous phase so at first 2octanol have to get through there from the feeded organic phase. to intensificate the process a well-stirred reactor can be applied with as huge heat transfer area as it can be built in because of the highly exothermic reactions. reactor reactor insight jacket aqueous phase a p b x a p x mass transport reaction(s) heat transport liquid phase w organic phase n figure 1: structure of woezik and westerterp’s reactor model based on the assumed reaction mechanism the overal reaction rates are calculated with the following correlations: ( ) ( ) ,cck1r cck1r aq b org p2,eff org 2 aq b org a1,eff org 1 ⋅⋅⋅ε−= ⋅⋅⋅ε−= where εorg – void fraction of the organic phase in the reactor; keff,– effective reaction rate constant, since in both equations the concentration of reagents are considered in different phases; corg – concentration of component indexed in subscript in organic phase; caq – concentration of component indexed in subscript in aqueuos phase. the effective reaction rate constants are depend on the temperature of the reactor insight and the acidity of the aqueous phase which is based on the concentration of solved nitric acid: ,ekk 0,0hr ,eff,a hm tr e 0 ,eff,eff ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ⋅− ⋅ − −− − − ⋅= where k0 eff,– effective reaction rate constant; ea,eff,– activation energy; r – ideal gas constant; tr – temperature of reactor insight; h0 – hammett-acidity function. to describe the component mass trajectories during the operation the following component mass balances which are ordinary differential equations must be solved. the a component is continously feeding into the reactor during the first part of the operation so volume of reaction medium is increasing too: ( ) ,rvcb dt cvd 1 rin a in,r org a r ⋅−⋅= ⋅ where vr – volume of reaction medium; br,in – flow rate of reagent feed; ca in – concentration of a component in feed. 152 because only the a component is being fed into the reactor during the operation the term which is considered this is missing from the other component mass balances: ( ) ( )21 r aq b r rrv dt cvd −⋅= ⋅ ( ) ( )21 r org p r rrv dt cvd −⋅= ⋅ ( ) 2 r org x r rv dt cvd ⋅= ⋅ ( ) ( ) ,rrv dt cvd 21 r aq n r +⋅−= ⋅ where cn aq – concentration of n component (nitric acid) in aqueous phase. to simulate the effect of producing heat from reactions and the jacket cooling on the temperature of the reactor a heat balance must be solved: ( ) ,qqqq hc 1 dt dt rarcin,r rr r −−+⋅= where hcr – heat capacity of reaction medium; qr – heat produced by reactions; qr,in – heat produced by the feeding; qrc – heat flux from the reactor insight to the jacket; qra – heat flux from the reactor insight to ambient. finally to calculate the modifications in jacket temperature: ( ) ,qq hc 1 dt dt rcin,c c c +⋅= where tc – temperature of jacket; hcc – heat capacity of cooling medium; qc,in – heat produced by the feeding of jacket. 0 2 4 6 8 10 12 14 16 18 0 1 2 3 t [h] n a [kmol] n p [kmol] n x [kmol] n b [kmol] 0 2 4 6 8 10 12 14 16 18 16 17 18 19 t [h] n n [kmol] 0 2 4 6 8 10 12 14 16 18 260 270 280 t [h] tr [k] tc [k] 0 2 4 6 8 10 12 14 16 18 0 1 2 3 t [h] n a [kmol] n p [kmol] n x [kmol] n b [kmol] 0 2 4 6 8 10 12 14 16 18 16 18 20 t [h] n n [kmol] 0 2 4 6 8 10 12 14 16 18 260 270 280 t [h] tr [k] tc [k] a) normal reactor operation – analytically b) normal reactor operation – numerically 0 2 4 6 8 10 12 14 16 18 0 1 2 3 t [h] n a [kmol] n p [kmol] n x [kmol] n b [kmol] 0 2 4 6 8 10 12 14 16 18 14 16 18 t [h] n n [kmol] 0 2 4 6 8 10 12 14 16 18 300 350 400 t [h] tr [k] tc [k] 0 2 4 6 8 10 12 14 16 18 0 1 2 3 t [h] n a [kmol] n p [kmol] n x [kmol] n b [kmol] 0 2 4 6 8 10 12 14 16 18 14 16 18 20 t [h] n n [kmol] 0 2 4 6 8 10 12 14 16 18 300 350 400 t [h] tr [k] tc [k] c) reactor runaway occurs – analytically d) reactor runaway occurs – numerically figure 2: calculated trajectories of state variables 153 results and discussions the model was solved in matlab with a numerical solver based on runge-kutta method. to illustrate the complex dynamical behavior of process the following two experiments are performed. trajectories of statevariables in fig. 2a-b show the normal operation of the reactor when 2-octanone is the main product and the total quantity of byproducts is low. a small, only 3 k change in the inlet temperature of the jacket results the development of reactor runaway (see in fig. 2c-d). in this case byproducts are mainly generated during the operation while the conversion of 2-octanol is significantly decreased at the end of the operation. in fig. 2 grey areas represent the instability regimes of the process. these areas are determined by using ljapunov’s indirect stability analysis. it can be seen that in a small time interval the reactor becomes instable still in normal reactor operation (fig. 2a) applying analytic calculations. this is not thermal instability, which is a synonym of reactor runaway, but it can be originated from the autocatalytic reaction scheme. the main difference between analytically and numerically calculated eigenvalues is that while in the analytically calculation all the eigenvalues are arranged from the jacobian-matrix of the developed process model, in the numerically calculation only the jacobianmatrix is generated and eigenvalues are determined by using the solver of matlab. in fig. 2 on the left hand side can be found the result of analytical analysis while the numerical is shown on the right hand side. comparing results seen in fig. 2 it can be seen that the sensitivity of the analytical calculation is more higher than the numerical technic. it means that runaway detection based on stability analysis and calculating the eigenvalues of jacobian matrix detects the development of runaway sooner than using a numerical solver to calculate eigenvalues. other very important thing that the algorithm based on analytical solution is three times faster than the other algorithm. this difference in calculation times makes the analytical technic more applicable in on-line monitoring system or in an oss. conclusions and future work process operators usually have only temperature measurements to follow the operation and to check and keep the safe way of operation. therefore a tool based on process models and stability analysis can be very useful in checking the appropriate operation and helping their work. the paper investigates that numerical analysis of characteristic equation of a dynamic process model how reliable in detection of reactor runaway. analytical solution is not just more accurate but much more faster than the other numerical one. therefore the message of this work is that with a bit more use of mathematic a lot more reliable and applicable tool can be developed to forecast or simply to detect the development of reactor runaway. further research will focus on how the extracted knowledge can be transformed into a set of constrains on the process variables and how these constrains can be applied in batch-to-batch and in feeding trajectory optimization. acknowledgements the authors would like to acknowledge the financial support of the cooperative research centre (vikkk, project 2004-iii/2), the hungarian research found (otka 49534), the bolyai janos fellowship of the hungarian academy science, and the öveges fellowship. references 1. woezik b. a. a., westerterp k. r.: chemical engineering and processing 41 (2001) 59-77 2. albert j., luft g.: chemical engineering and processing 37 (1998) 55-59 3. kao c. s., hu k. h.: journal of loss prevention in the process industries 15 (2002) 213-222 4. henda r., machac a., nilsson b.: chemical engineering journal 143 (2008) 195-200 5. véchot l., bigot j. p., testa d., kazmierczak m., vicot p.: journal of loss prevention of process industries 21 (2008) 359-366 6. woezik b. a. a., westerterp k. r.: chemical engineering and processing 39 (2001) 521-537 7. eizenberg s., shacham m., brauner n.: journal of loss prevention in the process industries 19 (2006) 754-761 8. barkelew c. h.: chemical engineering progress symposium series 25 (1959) 37-46 9. adler j., enig j. w.: combustion and flame 8 (1964) 97-103 10. lacey a. a.: international journal of engineering science, 21 (1983) 501-515 11. varga t., abonyi j., szeifert f.: acta agraria kaposvariensis 10 (2006) 121-133 12. varga t., szeifert f., abonyi j.: acta agraria kaposvariensis 11 (2007) 175-186 13. sastry s.: nonlinear systems: analysis stability and control, springer (1999) 14. varde p. v., sankar s., verma a. k.: reliability engineering and system safety 60 (1998) 53-69 15. góes a. g. a, alvarenga m. a. b., melo p. f. f.: reliability engineering and system safety 87 (2005) 149-161 16. lyapunov a. m.: international journal of control 55 (1992) 531-773 17. castellan a., bart j. c. j., cavallaro s.: catalysis today 9 (1991) 255-283 microsoft word szolcs_eloszo.doc compounds a (l/g) b (l/g) a 5.859 0.029676 b 13.3 0.050386 hungarian journal of industrial chemistry veszprém vol. 32. pp. 5-12 (2004) separation of a two-component steroid mixture by simulated moving bed chromatography k. temesvári1, a. aranyi1, s. balogh2, gy. bánkuti2 and b. csukás2 1gedeon richter ltd., budapest 10. p.o.b. 27. h-1475 hungary 2university of kaposvár, guba s. u. 40., h-7400 kaposvár, hungary e-mail: k.temesvari@richter.hu, csukas@mail.atk.u-kaposvar.hu a method, combining laboratory scale equilibrium and elution experiments, simplified model based heuristic rules, as well as sophisticated dynamic simulation, was applied to design the separation of a two-component steroid crude mixture in a given laboratory-scale simulated moving bed unit. the adsorption equilibrium isotherms of the pure components were determined by frontal analysis method. langmuir isotherm model was fitted to the measured isotherm data. with the knowledge of these a priori data, elution chromatograms of the pure components were measured for the identification of the hydrodynamic and kinetic parameters in the smb columns. the process simulation was made by the new method, based on the direct computer mapping of the generic, bi-layered net model. the first estimations of the smb parameters were derived by means of the morbidelli’s triangle theory. starting from a feasible solution, stepwise improvement of the smb process was carried out by the detailed dynamic simulation, according to a strategy, based on the role of the design parameters. simultaneously, laboratory-scale smb experiments were carried out. good agreement of the measured and calculated data was found. in the next step, the dynamic simulation has been applied for the improvement of the smb separation (production rate, solvent consumption, recovery). in comparison with simple elution chromatographic separation method, considerable improvement of specific capacity parameters was obtained. keywords: simulated moving bed, direct computer mapping, generic bi-layered net model, dynamic simulation, process design introduction in our recently published papers [1-2] a methodology, combining laboratory scale equilibrium and elution experiments, simplified model based and heuristic rules, as well as sophisticated dynamic simulation was introduced to design the separation of a two-component steroid crude mixture in a given laboratory-scale simulated moving bed unit. the adsorption equilibrium isotherms of the pure components were determined by frontal analysis method. [3-6] langmuir isotherm model was fitted to the measured isotherm data (see table 1). with the knowledge of langmuir constants, elution chromatograms of the pure components were measured for the identification of the hydrodynamic and kinetic parameters in the smb columns. the elution experiments were carried out table 1: parameters of langmuir adsorption isotherms of component a and b in one of the columns of the smb unit. two elution experiments were carried out for each compound. one of them was used for the identification and the other for the validation of the obtained parameters. for the identification we combined the dynamic simulator with a genetic algorithm [7] that changed the parameters to be identified within the prescribed 6 ranges, and evaluated the simulation with the integrated (summarized) quadratic difference of the calculated and the measured values. finally, the suggested solution was refined by a few manually evaluated simulation trials. the fixed hydrodynamic and kinetic parameters of the models were the following: number of compartments (n) = 200; mixing coefficient (w) = 0; kinetic constant for both components (k) = 0.2 1/s these hydrodynamic and kinetic parameters were used for all smb simulations. [1-2] the process simulation was made by the new method, based on the direct computer mapping of the generic, bi-layered net model. [8-10] table 2: parameters of the laboratory scale smb experiments process parameters smb-1 smb-2 smb-3 smb-4 smb-5 smb-7 smb-8 smb-9 smb-10 smb-11 column connection 2-2-2-2 2-2-2-2 2-2-2-2 2-2-2-2 2-2-2-2 2-6-6-2 2-6-6-2 3-4-7-2 3-4-7-2 3-5-8-0 feed (ml/s) 0.025 0.025 0.0125 0.025 0.025 0.05 0.05 0.05 0.05 0.05 conc. b (mg/ml) 1 1 6 9 9 9 9 9 9 12 conc. a (mg/ml) 4 4 24 36 36 36 36 36 36 48 eluent (ml/s) 0.1253 0.1217 0.1317 0.1567 0.1767 0.3633 0.37 0.2534 0.28 0.39 extract (ml/s) 0.1083 0.1083 0.1183 0.1484 0.1683 0.3233 0.35 0.2148 0.255 0.255 raffinate (ml/s) 0.042 0.0384 0.0259 0.0333 0.0334 0.09 0.07 0.0886 0.075 0.185 column switching time step (s) 1350 1350 1200 600 750 360 360 360 360 360 liquid recycle (ml/s) 0.0367 0.0367 0.037 0.06 0.055 0.11 0.11 0.11 0.11 to find a feasible parameter set for the first smb experiments, the morbidelli’s triangle theory [11-14] was applied and a few simulation experiments were made. the input/output interface of the generic bi-layered net model based dynamic simulator is described in an excel workbook, where, with the knowledge of the filled input data, a macro generates the nonlinear morbidelli diagram, and shows the point characterizing the proposed design to be tried. starting from a feasible solution, stepwise improvement of the smb process was carried out by the detailed dynamic simulation, according to a strategy, based on the role of the design parameters. simultaneously, some laboratory-scale smb experiments were carried out. good agreement of the measured and calculated data was found. it was shown, that the applied simulation model is suitable for prediction of smb processes. consequently in the following work, based on extensive computer simulations, we tried to improve the specific capacity parameters of the smb separation (higher production rate and recovery and less solvent consumption), while we allowed a limited amount of the less retained compound (a) in the extract. experimental chemicals the problem under investigation was the separation of a two-component non-isomer steroid crude mixture, produced by gedeon richter ltd. the goal was to produce pure raffinate (maximum 0.3% strongly retained compound is allowed) and optionally slightly contaminated extract (maximum 5% weakly retained compound is allowed) products. for the isotherm measurements and elution experiments the pure compounds with a purity of > 99% m/m were used. the pure compounds were produced by preparative elution chromatography. for the smb investigations model mixtures of pure compounds were prepared with a composition, similar to the real crude mixture. the less retained compound is steroid a with k’=3.082, while the more retained one is steroid b with k’=8.046, (α=2.61). ymc gel silica 6 nm s-50 µm was used as stationary phase, it was purchased from ymc, europe gmbh (schermbeck/weselerwald, germany). 7 the mobile phase was methylene-chlorideacetone 50:50% v/v. solvents were purchased from merck kgaa (darmstadt, germany). simulated moving bed experiments a laboratory-scale smb unit (knauer csep 9116) was used for the smb experiments. the number of columns in the four zones was changed between 8 and 16, respectively. in case of eightcolumn configuration two columns were in each zone. when sixteen columns were applied, different column configurations were used (2-6-6-2, 3-4-7-2). in one case a special open loop three-zone configuration was also examined (3-5-8-0 column configuration). the columns were packed by drypacking method, using vibration (column dimension was i.d.=10 mm l=250 mm). the uniformity of columns was tested by elution experiments, injecting pure a compounds on the columns and eluting it with the eluent. the parameters of the laboratory scale smb experiments are summarized in table 2. analytical method for measurement of smb samples the samples of smb experiments were examined by analytical hplc which consisted of a gradient pump (spectrasystem p2000), a controller (spectrasystem sn4000), a light scattering detector (polymer laboratories pl-els 2100), a thermostat (jet-stream plus) and an injection valve (rheodyne, 20 µl loop). the system was operated by windows nt/chromquest software. a normal phase hplc system was applied for measurements. the column was merck, lichrospher si 60, particle size 5 µm, i.d.=4mm l=250mm the eluent was acetone-methylene-chloridemethanol 40:50:10% v/v. the injected sample volume was 20 µl, the volumetric flow rate of eluent was 1 ml/min. the experiments were carried out at 25°c column temperature. the nebulization and evaporation temperature was 32°c and the volumetric flow rate of the nebulizer gas was 0.8 slm nitrogen. process design of simulated moving bed separation of the given compounds the simulated moving bed (smb) process is the up-to-date solution for the continuous, counter current preparative chromatography. the principle of the technique has been described in numerous publications [15-16]. the essence of the process is that instead of the impossible continuous transportation of the particulate solid phase, the packed columns are changed stepwise, cyclically. this cyclic change is solved either by switching of valves or by the real rotation of the columns, connected to special distributing valves (as it is shown in fig. 1). figure 1: the main parameters of the smb unit in the smb the strong (more retained, b) and weak (less retained, a) components of the feed (f) of concentration cf,b and cf,a are separated into two outlet flows. in the extract (e, ce,b, ce,a) the better adsorbing strong, while in the raffinate (r, cr,b, cr,a) the less adsorbing weak components are enriched, respectively. the process parameters to be controlled are the liquid recycle (l), the recycle of the packing (p), the flow rate of the fresh solvent (d) and the ratio e/(e+r) of the outlet flows. the process is characterized by the very slow transient of the fluctuating concentrations, converging toward the (optionally multiple and sometimes impossible) steady state. the simulation needs the solution of systems of nonlinear, coupled ipdae (integer partial differencial algebraic equations) under cyclically changing initial and boundary conditions. the conventional smb unit consists of four zones, containing a number of columns that can be changed. in our last paper [1] three eight-column configuration smb experiments were described. (2 columns were in each section of the smb unit.) it was shown that the applied simulation model is 1 2 3 4 5 6 7 8 e , b e , ae , c , c f , b f , af , c , c r , b r , ar , c , c e lu en t l iq u id rec y c le c yc lic c o lu m n sw itch 1 2 3 4 5 6 7 8 e , b e , ae , c , c f , b f , af , c , c r , b r , ar , c , c e lu en t l iq u id rec y c le c yc lic c o lu m n sw itch d l p1 2 3 4 5 6 7 8 e , b e , ae , c , c f , b f , af , c , c r , b r , ar , c , c e lu en t l iq u id rec y c le c yc lic c o lu m n sw itch 1 2 3 4 5 6 7 8 e , b e , ae , c , c f , b f , af , c , c r , b r , ar , c , c e lu en t l iq u id rec y c le c yc lic c o lu m n sw itch d l p 8 suitable for prediction of smb processes. consequently in the following work, based on computer simulations, we tried to improve the specific capacity parameters of the smb separation (higher production rate and recovery and less solvent consumption) while we allowed a limited amount of the less retained compound (a) in the extract. in fig. 2 the eight-column (2-2-2-2) configuration experiments are compared with preparative elution chromatographic separation of the respective compounds. it can be seen, that applying only eight columns in the smb unit, considerable improvement of specific capacity parameters was obtained. it is worth mentioning that in case of eight columns (2-2-2-2 connection) the impurity level of the extract was a little bit higher than five percent, but there was no option to change the number of columns in the zones, freely. the other feasible 1-3-3-1 connection would not be appropriate for safe separation, because in the first and fourth zones two columns are required for cleaning the recycling streams. the next step was to increase the number of columns in the smb unit from eight columns to sixteen. the improvement of the specific capacity parameters and purity of both products were examined. it was apparent from computer simulations, that increasing the number of columns from 2-2-22 connection to 4-4-4-4 connection, i.e. the proportional scaling-up of the respective streams, did not improve the specific capacity parameters and the purity of products, either. consequently, we examined the effect of the different column configurations of the four-zone smb on the more effective separation of compounds. accordingly in the next smb experiment (smb-7) the column connection was 2-6-6-2. the feed flow rate was doubled, compared to the eight column configuration (2-2-2-2 connection) system. the recycling streams were proportionally increased. the eluent flow rate proportionally increased, but for the appropriate extract quality, the eluent excess was distributed among the two outlets. carrying out an smb experiment with the above described experimental conditions, the more retained compound b appeared in the raffinate after sixteen cycles (see figs. 3a-3d and table 3). 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 prep. hplc smb-1 smb-2 smb-3 smb-4 smb-5 pr od . r at e p a (m g/ gm in ) 0 0,2 0,4 0,6 0,8 1 1,2 1,4 1,6 prep. hplc smb-1 smb-2 smb-3 smb-4 smb-5sp ec . s ol v. c on s. (m l/m g a ) 80 85 90 95 100 prep. hplc smb-1 smb-2 smb-3 smb-4 smb-5 r ec ov er y % 90 92 94 96 98 100 prep. hplc smb-1 smb-2 smb-3 smb-4 smb-5 pu rit y % figure 2: comparison of the eight-column smb experiments with the simple preparative elution data fig. 3d shows the long term simulation results in a logarithmic scale. it can be seen, that the contamination of the raffinate is the result of a very slow transient process which could be avoided by deep investigation of long term simulation data. contamination of the raffinate can be prevented by using more fresh eluent and higher extract/raffinate ratio. in the smb-8 experiment only the amount of fresh eluent and the extract/raffinate ratio were increased, compared to experiment smb-7. (see table 2.) in this way we were able to produce pure raffinate and only slightly contaminated extract, but the specific solvent consumption was a little bit higher, than in case of the best eight-column (smb-5) experiment. (see table 3.) 9 0 0,2 0,4 0,6 0,8 1 1,2 1,4 0 20000 40000 60000 80000 100000 120000 140000 160000 180000 200000 time (sec) c on ce nt ra tio n (g /l) calculated a calculated b measured a measured b 0 5 10 15 20 25 0 20000 40000 60000 80000 100000 120000 140000 160000 180000 200000 time (sec) c on ce nt ra tio n (g /l) calculated a calculated b measured a measured b table 3: specific capacity parameters of smb experiments smb experiments feed a:b (g/l) production rate pa [mg/(g min)] specific solvent consumption (ml/mg a) recovery (%) purity (%) isocratic, 8 columns, 4 zones, column connection: 2-2-2-2 smb-5 36:9 0.7891 0.2429 98.62 100 isocratic, 16 columns, 4 zones smb-7 2-6-6-2 36:9 0.8114 0.2376 100 97.46 smb-8 2-6-6-2 36:9 0.7920 0.2471 99.31 100 smb-10 3-4-7-2 36:9 0.8065 0.1907 99.25 100 gradient, 16 columns, 3 zones smb-11 3-5-8 48:12 1.0175 0.2015 99.86 100 therefore in the following the main goal was to decrease the specific solvent consumption by changing the column distribution in the four zones of the smb unit. based on computer simulations, this objective can be reached by changing the column connection for 3-4-7-2, while leaving the recycle and feed streams unchanged. (see table 2.) this asymmetrical column connection can be explained by the actual separation task, because the separation of the less retained compound a (which is present in a much higher amount than compound b) and the more retained compound b occured in the third and second zones. the first zone had an important role too, in which there were three columns, because the desorption of the more retained compound b accomplished here. as it can be seen from figs. 4a-4c and from table 3, using the above described experimental conditions the specific solvent consumption could be decreased. finally, we tried also a three-zone (open-loop) smb configuration, where there was no liquid recycle at all. in this case the steroid mixture was solved in pure methylene-chloride. in this way the solubility of the compounds could be considerable increased, that is why the specific capacity parameters of the smb 11 separation could be improved further (see figs 5a-5c and table 3). figure 3: measured and simulated data of the experiment smb-7 3a) average concentration of the raffinate figure 3: measured and simulated data of the experiment smb-7 3b) average concentration of the extract 10 0 5 10 15 20 25 0 2 4 6 8 10 12 14 16 columns c on ce nt ra tio n (g /l) a b 0 5 10 15 20 25 0 50000 100000 150000 200000 250000 time (sec) c on ce nt ra tio n (g /l) calculated a calculated b measured a measured b 0 0 ,2 0 ,4 0 ,6 0 ,8 1 1 ,2 1 ,4 1 ,6 1 ,8 2 0 50000 100000 150000 200000 250000 tim e (sec) co nc en tra tio n (g /l) calcula ted a calcula ted b m easured a m easured b 0 5 10 15 20 25 30 0 2 4 6 8 10 12 14 16 columns c on ce nt ra tio n (g /l) a b 0 2 4 6 8 10 12 14 16 18 20 0 20000 40000 60000 80000 100000 120000 140000 time (sec) c on ce nt ra tio n (g /l) calculated a calculated b measured a measured b 0 0,5 1 1,5 2 2,5 3 0 20000 40000 60000 80000 100000 120000 140000 time (sec) c on ce nt ra tio n (g /l) calculated a calculated b measured a measured b 0 5 10 15 20 25 30 35 40 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 columns c on ce nt ra tio n (g /l) a b -10 -8 -6 -4 -2 0 0 50000 100000 150000 200000 time (sec) lg (c b g /l) b in raffinate figure 3: measured and simulated data of the experiment smb-7 3c) average concentration profiles in the liquid phase figure 3: measured and simulated data of the experiment smb-7 3d) illustration of the slow transient in logarithmic scale figure 4: measured and simulated data of the experiment smb-10 4a) average concentration of the raffinate figure 4: measured and simulated dataof the experiment smb-10 4b) average concentration of the extract figure 4: measured and simulated data of the experiment smb-10 4c) average concentration profiles in the liquid phase x figure 5. measured and simulated data of the experiment smb-11 5b) average concentration of the extract figure 5. measured and simulated data of the experiment smb-11 5b) average concentration of the extract figure 5. measured and simulated data of the experiment smb-11 5c) average concentration profiles in the liquid phase 11 conclusions 1. the application of the generic bi-layered net based direct computer mapping makes possible to develop an appropriate tool for the detailed dynamic simulation of the simulated moving bed process. the measured and calculated results agree with each other. 2. we have elaborated a methodology, combining – experimental determination of the langmuir isotherms for the individual components, – use of the competitive langmuir equation for the calculation of the driving force in the kinetic model, – simulation based identification of the kinetic and hydrodynamic parameters from elution chromatograms, – application of the morbidelli’s triangle theory to find feasible initial solutions, and – simulation based improvement and optimization of the smb process. the method has been proved to be applicable for the solution of the detailed process design of the smb separation. 3. based on the new design methodology, involving the generic bi-layered net model we solved an actual, industrial separation problem successfully. the specific capacity parameters of the smb separation (production rate, specific solvent consumption, recovery) considerably improved compared to simple preparative elution chromatographic separation of the given compounds. symbols a less retained compound b more retained compound ai, bi langmuir parameters n number of cell w mixing coefficient k kinetic constant k’ capacity factor slm standard litre per minute (gas flow rate) i.d. internal diameter v/v volumetric ratio m/m mass ratio f feed c concentration of the compounds r raffinate e extract l liquid recycle d fresh solvent p “recycle of the packing”, column switching time greek letter α selectivity indices i identifier of the components a less retained compound b more retained compound f feed r raffinate e extract references 1. temesvári k., aranyi a., csukás b. and balogh s.: chromatographia, 2004, (60), s189-s199 2. temesvári k., aranyi a., bánkuti gy., csukás b. and balogh s.: acta agraria kaposvariensis, 2004, (in press) 3. jacobson j., frenz j. and horváth cs.: j of chromatography, 1984, 316, 53-68 4. jacobson j. m., frenz j. h. and horváth cs.: ind. eng. chem. res., 1987, 26, 43-50 5. guiochon g., golshan shirazi s. and katti a. m.: fundamentals of preparative and nonlinear chromatography, academic press, london, pp. 49-135, 1994 6. gritti f., gotmar g., stanley j. b. and guiochon g.: j. of chromatography a, 2003, 988, 85-203 7. csukás b., and balogh s.: computers in industry, 1998, 36, 181-197 8. csukás b.: simulation by direct mapping of the structural models onto executable programs. aiche annual meeteng, 1998, paper #239/9 12 9. csukás b. and bánkuti gy.: direct computer mapping of process models. in: grossmann i.e. and mcdonald c. (eds): foundations of computer assisted process operations, a view to the future integration of r&d, manufacturing and the global supply chain, aiche informs, 2003, 577-581 10. csukás b. and bánkuti gy.: generic bilayered net model of conservational and informational processes. in: dagli, buczak, ghosh, embrechts and ersoy (eds) smart engineering system design: neural networks, fuzzy logic, evolutionary programming, data mining and complex systems, asme press, 2003, 769-774 11. juza m., mazzotti m. and morbidelli m.: tibtech, 2000, 18, 108-118 12. mazzotti m., storti g. and morbidelli m.: j. chromatogr a, 1997, 769, 3-24 13. gentilini a., migliorini c., mazzotti m. and morbidelli m.: j. chromatogr a, 1998, 805, 37-44 14. migliorini c., mazzotti m. and morbidelli m.: j. chromatogr a, 1998, 827, 161-173 15. nicoud r-m. and bailly m.: choice and optimization of operating mode in industrial chromatography. proceedings of “prep 92”, nancy (france), 6-8 april, isbn 2-90526718-6. 205-220, 1992 16. blehaut j. and nicoud r-m.: analusis magazine, 1998, 26 (7), 60-70 microsoft word b_59_herseczki_r.doc hungarian journal of industrial chemistry veszprém vol. 39(2) pp. 183-187 (2011) enhanced use of renewable resources: transesterification of glycerol, the byproduct of biodiesel production z. herseczki , g. marton, t. varga university of pannonia, institute of chemical and process engineering, 8200 veszprém egyetem u. 10., hungary e-mail: hzsanett@almos.uni-pannon.hu methyl esters of fatty acids (also known as biodiesel) made from transesterification of vegetable oils and animal fats with methanol, have shown a lot of promise as alternative diesel fuels. glycerol is the inevitable byproduct of transesterification process for which new uses need to be found. while there are existing markets for glycerol, a significant increase in availability of glycerol, resulting from the expanded use of vegetable oils and animal fats, would destabilize glycerol market. in this study synthesis of glycerol carbonate from glycerol and dimethyl carbonate was investigated. glycerol carbonate is a key multifunctional compound employed as solvent, additive, monomer and chemical intermediate. resulting glycerol carbonate was obtained in almost quantitative yield. according to measured data a well-elaborated mathematical model of the reactor was used for experiments can be adequate to assign parameters of kinetic equations of the assumed reaction mechanism. component mass balances were built into the reactor model and order of reactions was fixed. keywords: biodiesel, glycerol, glycerol carbonate introduction crude glycerol is a considerable by-product of biodiesel production. approximately 10% of the converted feedstock is released as crude glycerol. this product fraction comprises several impurities, e.g. residues of vegetable oil and esters, salts, different alkaline catalysts and water. however, the process is far from being environmentally friendly as the final mixture needs to be separated, neutralised and thoroughly washed, generating a great amount of waste in terms of salt residues. the catalyst cannot also be recycled. these several additional steps inevitably put the total overall biodiesel production costs up, reducing at the same time the quality of the glycerol obtained as by-product [1]. the lowest price that crude glycerol could fall to is equivalent to its energy content, i.e. incineration is the lowest value utilisation pathway. pure glycerol (pharma or kosher quality) is a high price commodity, because of the energy-intensive step that is required during the processing. hence it is viable only at a certain economic scale. typically, smes operate small scale biodiesel production plants and don’t purify small quantities of crude glycerol for economical reasons. glycerol holds the potential of being an extremely versatile building block within the biorefinery. although many uses have been developed for glycerol, most product markets are currently small and fragmented. however, development of a biodiesel market could have a huge impact on the availability and use of glycerol. since glycerol is a key coproduct of biodiesel manufacture, increasing use of biodiesel will lead to much greater glycerol availability and lower cost. at lower projected costs, there is a tremendous potential to develop a variety of new processes and product lines from glycerol, taking advantage of its unique structure and properties. as a renewable and cheap raw chemical, conversion processes of glycerol to useful materials have received increasing attentions, and recently several examples have been reported: acid-induced dehydration of glycerol to acrolein in supercritical water [2], glycerol oxidation to dihydroxyacetone and glyceric acid using carbonsupported gold catalysts [3], and 1,3-propanediol production by metabolic engineering approach [4]. glycerol carbonate is a stable and colorless liquid that offers useful applications as a novel component of gas separation membranes, a surfactant component, a new solvent for several types of materials or a nonvolatile solvent in the paint industry, a component in coatings, and a component of detergents and. also glycerol carbonate can be utilized as a source of new polymeric materials [5]. glycerol carbonate can be obtained according to various methods, using epoxy compounds as well as glycerol as raw materials. it was reported that glycerol carbonate can be formed in the reaction of epichlorohydrin with khco3 carried out at 80 °c in the presence of 18-crown ether [6]. nevertheless, more attractive methods are those utilizing glycerol as a renewable and cheap raw material. taking into consideration that biofuels for diesel engines are being introduced on the market in increasing amounts, 184 a large amount of glycerol will be available as a sideproduct of the vegetable oils methanolysis. a typical method of obtaining carbonate derivatives of glycerol is its transesterification with ethylene carbonate or dialkyl carbonate. in the reaction with ethylene carbonate carried out at 125 °c in the presence of sodium bicarbonate the product was formed in a yield of 81% [7]. recently, in the patent literature, a glycerol carbonate synthesis was reported in which urea was used as reaction partner of glycerol to give the product with a good selectivity (92%) [8]. promising methods of glycerol carbonate preparation comprise the reaction of glycerol with co2 or carbon monoxide and oxygen in the presence of cu(i) catalysts [9]. the reaction of glycerol with carbon dioxide was carried out in a scco2 medium in the presence of zeolite and ethylene carbonate as a co-source of carbonate groups [10]. nevertheless, according to all the above mentioned methods glycerol carbonate should be purified by distillation under reduced pressure at a relatively high temperature (125–150 °c). in our approach, the glycerol carbonate synthesis was carried out under mild conditions without any solvent, using glycerol and dimethyl carbonate as environmentally benign and renewable reagents. due to the almost quantitative reaction yield there is no need for product purification by distillation at high temperature and recovery of unreacted glycerol. materials and methods dimethyl carbonate, glycerol, glycerol carbonate and k2co3 were purchased from sigma-aldrich and used without further purification. apparatus and procedure as first step reactions were carried out in a 500 ml glass flask equipped with a mechanic stirrer, thermometer and liebig cooler. glycerol (92 g, 1 mol) and dimethyl carbonate (270 g, 3 mol) were mixed in the flask. when reactor temperature reached 60 °c, k2co3 (4.14 g, 0.03 mol) was added to the mixture as catalyst. dimethyl carbonate (dmc) was used in a molar excess (3:1) and methanol was removed continuously to shift the reaction equilibrium towards the product. methanol forms a minimum boiling azeotrop with dmc (table 1), so when methanol is removed, dmc leaves the flask, as well. table 1: composition of methanol-dmc azeotrope boiling point (c°) molecular weight binary azeotrope (70% methanol + 30% dmc) 63.2 methanol 64.6 32.04 dmc 89.8 90.01 reaction was carried out at 71–76 °c in presence of k2co3 as a catalyst for 5 h, and then unreacted dimethyl carbonate was distilled off at 40 °c under reduced pressure (4–6 kpa). reaction progress was monitored by collecting samples of reaction mixture. as next step reaction was carried out in a mettler toledo labmax automatic lab reactor (fig. 1). the transparent, double-walled glass reactor allows automatic performance of chemical syntheses in the temperature range -50 to 220 °c (tr). the pressure range varies from vacuum to ambient pressure. the working volume of the glass reactor is 0.6 liter. figure 1: mettler toledo labmax automatic lab reactor analysis samples of reaction products were analysed with a merck lachrom hplc equipped with an ultrahydrogel column (i.d. = 7.8 mm, l = 300 mm) and a merck lachrom ri detector. water was used as eluent. retention time of the components in minutes: glycerol – 10.97; unknown component – 12.58; glycerol carbonate – 16.31 and dmc – 19.27. result and discussion we have developed a convenient method for synthesis of glycerol carbonate from glycerol and dimethyl carbonate (fig. 2) using k2co3 as catalyst. resulting glycerol carbonate was obtained in almost quantitative yield. o o o oh oh oh oh o o oh o oh oo o + meoh meoh a b c d figure 2: synthesis of glycerol carbonate between two types of hydroxyl group in glycerol, two primary alcohols are presumably more reactive than 185 a secondary hydroxyl group. therefore, intermediate c might be formed at the first step, and subsequently formation of product d occurs through intramolecular conversion. this mechanism is supported by analytical spectrums. on the analytical spectrums it can be seen that there is an unknown peak at retention time 12.5812.59, which is probably intermediate c. samples were collected from reaction mixtures at 1, 3, 5, 7, 10, 30, 60, 120, 180, 240 and 300 minutes. unfortunately the first three samples were not representative because during this period there are two phases in the flask (glycerol and dimethyl carbonate) and solubilization starts when mixture contains enough amount of glycerol carbonate. fig. 3 contains composition of samples. 0 10 20 30 40 50 60 70 80 90 100 0 50 100 150 200 250 time (min) c on ce nt ra tio n (w t% ) glycerol glycerol carbonate dmc figure 3: influence of time on reaction of glycerol and dimethyl carbonate reactor model when a reactor is designed the first step is to investigate the possible reactions take place in reactor, all the micro and macro processes (e.g. stirring) and operating conditions which have some influence on them. reactors are planned and used to make value added compounds, so the most important task to know how the cheap raw materials can be converted into a value added product. the conversion pathway can be demonstrated by reaction mechanism. unfortunately, reaction mechanism does not contain all necessary information which is needed to design a reactor because it gathers steps of conversion but does not give any information about the reaction rate. to run a reactor under optimal operation conditions or to find the optimal operating range it is inevitable to know the rate of individual reaction steps. many kind of correlation can be applied to describe the rate of a reaction with different number of unknown parameters. to calculate reaction rates the arrhenius equation (eq. 3) was used with two unknown parameters (pre-exponential factor and activation energy). the produced heat during the reactions is called reaction heat, which is over 0 if the reaction is endothermic while it is below zero if the reaction is exothermic. every reaction has reaction heat which differs from 0. hence, to characterize a reaction, next to the earlier mentioned two parameters, the reaction heat must be determined too. it can be performed with some calorimetric measures. determination of unknown parameters can be achieved by using well-carried out experiments to collect accurate analytical data, but nowadays different kind of modeling techniques can be applied to reduce the number of necessary experiments. according to measured data a well-elaborated mathematical model of the reactor was used for experiments can be adequate to assign parameters of kinetic equations of the assumed reaction mechanism. structure of the elaborated model of reactor is shown in fig. 4. ecba k k +⇔+ 1 2 , (1) edc k k +⇔ 3 4 , (2) where: a – gycerol b – dimethyl-carbonate c – intermediate d –gycerol-carbonate e – methanol ( ) { }4321 0 ;;;i treexpkk r i,a,ii = ⋅−⋅= , (3) as eq. 1-2. show both of the reactions in the assumed reaction mechanism are equilibrium reactions so next to the unknown parameters in kinetic equations it is necessary to have a correlation between the inside temperature of reactor and the equilibrium content. arrhenius-type temperature dependent was used to calculate the reaction equilibrium. to investigate the effect of the producing methanol on the performance of synthesis the methanol is considered in back reactions, so both of back reactions are second order. the first reaction (eq. 1) is second order since in the first step the glycerol and dimethyl-carbonate must be formed the intermediate which is decomposed into glycerol-carbonate and methanol. on this level of work based on the introduced reaction mechanism component mass balances were built into the reactor model and order of reactions was fixed. a heat transport couples the inside and the jacket of the reactor as it can be seen in fig. 4 and the heat conductivity phenomena in the reactor wall was not consider in this model. silica oil is circulated in the jacket through a thermostat to keep the temperature of the jacket at desired value so only the heat balance of the reactor inside was built into the model. at the next level in the model hierarchy there is the level of phases. since the reactions equilibrium is modified with the evaporation of products it is necessary to calculate the content of gas phase. the temperature of the liquid and gas phase is equal so only the mass transport couples these phases. at the bottom of the model structure can be found the level of components. the reactions are considered at this level. as it can be seen in fig. 4 the reactions takes place only in the liquid phase since the catalyst doesn’t evaporate. 186 figure 4: the structure of the reactor model to check the assumed reaction mechanism the component balances in the liquid phase were completed with component sources based on equations 1-2. the identification of missing model parameters was performed by comparing the analytically determined masses of components and the measured temperature trajectory of reactor inside with the calculated ones using the model. identification of model parameters some of the missing model parameters can be determined from the literature (e.g. all the necessary properties of components) but there is no information about parameters of kinetic and equilibrium expressions so parameter identification was performed based on the comparison of measured and calculated trajectories of state-variables. the square sum of the difference was calculated in every sample time. to find the global minima of this multi variable optimization problem an evolutionary algorithm (ea), the covariant matrix adaptation evolutionary strategy (cma-es) was applied. the ea is an optimization method which based on the natural selection and survival of the fittest as it works in the real world. eas consistently perform well approximating solutions to all types of problems because they do not make any assumption about the underlying fitness landscape, hence it makes eas applicable from different fields of engineering to social sciences [11]. learning the covariance matrix in the cma-es can improve the performance on ill-conditioned and/or nonseparable problems by orders of magnitude. the cmaes overcomes typical problems that are often associated with eas, e.g. the poor performance on badly scaled and/or highly non-separable objective functions [12, 13]. another application of cma-es in an engineering problem can be found in [14]. the result of the identification of missing model parameters is summarized in table 2 while measured and calculated trajectories can be compared in fig. 5. only seven samples were taken and analyzed. in the identification process the measured value of state variables were linearly interpolated between nearby samples to help searching algorithm with increasing the number of learning samples. table 2: identified reactor model parameters k01 [m-3·mol·s-1] k02 [s-1] ea1 [j·mol-1] ea2 [j·mol-1] 16.08 664.8 4.40e4 2.12e4 ak1 [ ] bk1 [ ] ak2 [ ] bk2 [ ] 5.122 1.00e4 3.328 5.75e4 ∆hreac,1 [j·mol-1] ∆hreac,2 [j·mol-1] αrj [w·m-2] cv [kg·s-1·bar-1] -4.97e4 -6.43e4 6.057e3 0.2546 as it can be seen in fig. 5 there are some differences between the measured and calculated trajectories after much of reagents transformed. to improve the accuracy of the worked out model more experiments with varying jacket temperature trajectory need to be performed in the reactor but results are promising. 0 1000 2000 3000 4000 5000 6000 7000 0 20 40 60 80 100 time [s] m a [g ] 0 1000 2000 3000 4000 5000 6000 7000 160 180 200 220 240 260 280 time [s] m b [g ] 0 1000 2000 3000 4000 5000 6000 7000 0 50 100 150 time [s] m d [g ] 0 1000 2000 3000 4000 5000 6000 7000 280 300 320 340 360 time [s] t r [k ] figure 5: calculated(thin) and the measured(thick) trajectories of state-variables summary synthesis of glycerol and dimethyl carbonate was investigated. a convenient method has been developed for synthesis of glycerol carbonate from glycerol and dimethyl carbonate using k2co3 as catalyst. resulting glycerol carbonate was obtained in almost quantitative yield. created reaction mechanism was supported by analytical spectrums. a well detailed dynamic model of the reactor where the experiments were performed has been worked out. the developed mathematical model of reactor can be applied to unfold reaction steps of other synthesis, but before a final conclusion can be drawn more experiments need to be done. due to the reactor model other synthesis can be performed and analyzed in the reactor system in future. 187 references 1. m. verziu, b. cojocaru, j. hu, r. richards, c. ciuculescu, p. filip, v. i. parvulescu: sunflower and rapeseed oil transesterification to biodiesel over different nanocrystalline mgo catalysts, green chem., 10, (2008), 373–381 2. l. ott, m. bicker, h. vogel: catalytic dehydration of glycerol in suband supercritical water: a new chemical process for acrolein production, green chem., 8, (2006), 214–220 3. s. demirel, k. lehnert, m. lucas, p. claus: use of renewables for the production of chemicals: glycerol oxidation over carbon supported gold catalysts, appl. catal. b-environ., 70, (2007), 637–643 4. m. gonzalez-pajuleo, i. meynial-salles, f. mendes, j. c. andrade, i. vasconcelos, p. soucaille: metabolic engineering of clostridium acetobutylicum for the industrial production of 1,3propanediol from glycerol, metab. eng., 7(5-6), (2005), 329–336 5. s. c. kim, y. h. kim, h. lee, d. y. yoon, b. k. song: lipase-catalyzed synthesis of glycerol carbonate from renewable glycerol and dimethyl carbonate through transesterification, journal of molecular catalysis b: enzymatic, 49, (2007), 75–78 6. g. rokicki, w. kuran: cyclic carbonates obtained by reactions of alkali metal carbonates with epihalohydrins, bull. chem. soc. jpn., 57(6), 1984, 1662–1666 7. j. b. bell, v. a. currier, j. d. malkemus: method for preparing glycerin carbonate, us pat. 2 915 529 (1959) 8. m. okutsu, t. kitsuki: process for the preparation of glycerol carbonate, us pat. 6 495 703 (2002) 9. j. h. teles, n. rieber, w. harder: preparation of glyceryl carbonate, us pat. 5 359 094 (1994) 10. c. vieville, j. w. yoo, s. pelet, z. mouloungui: synthesis of glycerol carbonate by direct carbonatation of glycerol in supercritical co2 in the presence of zeolites and ion exchange resins, catal. lett., 56(4), (1998), 245–247 11. a. e. eiben, j. e. smith: introduction to evoultionary computing (2nd printing), springer, (2007) 12. n. hansen: invariance, self-adaptation and correlated mutations in evolution strategies, in proceedings of the 6th international conference on parallel problem solving from nature, (2000), pp. 355–364 13. n. hansen: references to cma-es applications, www.bionik.tu-berlin.de/ user/niko/cmaapplications.pdf, (2005) 14. t. varga, f. szeifert, j. abonyi: evolutionary strategy for feeding trajectory optimization of fedbatch reactors, acta polytechnica hungarica, 4(4), (2007), 121–131 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word szolcs_eloszo.doc hungarian journal of industrial chemistry veszprém vol. 32. pp. 23-31 (2004) investigation of reverse phase smb-chromatographic bioseparations of amino acid aqueous solutions z. molnár1, m. nagy1, a. aranyi2, l. hanák1, t. szánya1 and j. argyelán1 1university of veszprém, department of chemical engineering, h-8201 veszprém, p.o.box 158, hungary; fax number: +36 88 421 905 e-mail: hmolnar78@freemail.hu 2gedeon richter pharmaceutical works, h-1475 budapest, p.o.box. 27, hungary the authors investigated amino acid aqueous solutions as model system for the purpose of studying reverse phase chromatographic bioseparation. desalting of dl-β-phenylalanine was studied on a small-laboratory scale simulated moving bed (smb) preparative liquid chromatograph (number of columns=6, column length=125mm, column i.d.=13mm). diaion hp20 polymeric adsorbent resin was used for the reverse phase chromatography. the feed (sample) of the smb equipment is 3.5g dl-β-phenylalanine/dm3 and 58.5g sodium-chloride/dm3 aqueous solution. with the three zones opened loop smb with 2-2-2 column configuration can amino acid product be achieved with less than 50ppm nacl in crystal form after evaporation. later a large laboratory scale (number of columns=4, column length=500mm, column id=50mm) automatized smb equipment was constructed. the applied model system for bioseparation contains glycine (1.5g/dm3), l-phenylalanine (3.3g/dm3) in water and sepabeads sp825 adsorbent. both l-phenylalanine and glycine were produced in more than 99.9% m/m purity and 99% yield at productivity 3.7-9.5mg/(g adsorbent h) in case of three zones open loop 2-1-1 column configuration. the smb experiments were simulated with the help of equilibrium cascade model. the measured and calculated data agreed well. keywords: simulated moving bed (smb), column liquid chromatography, polymeric adsorbent resin, amino acid aqueous solution introduction it is typical in biotechnology and pharmaceutical industry that water phase mixture for processing contains end-product or active ingredient in small concentration beside the contaminant or polluting components. simulated moving bed (smb) preparative chromatography can be advantageous among the end-product recovery methods for continuous processing of high purity products, or products being difficult to isolate. basically the smb chromatograph works similarly to the true moving bed (hereafter abbreviated as tmb). the tmb works in the following way by figure 1a: in a column the mobile phase moves upwards through the adsorbent that moves downwards simultaneously. the column is fitted with a feed inlet in the middle of the side-wall, a raffinate outlet on the upper part and an extract outlet on the lower part. choosing the appropriate adsorbent moving velocity value and suitable eluent, feed, extract and raffinate flow rates, a stationary state can be obtained in the column with constant concentration profiles. the more binding component occurs in the lower (i-ii) part of the column and the less binding one is located on the upper part (iii-iv) of the column. this way two pure components can be obtained simultaneously in the extract and in the raffinate. the chromatographic quality of tmb is difficult to realize technically, therefore an smb was employed in the preparative chromatography. smb liquid chromatograph (hereafterabbreviated smb-lc) (fig. 1b) is a multi-column system with two inputs and outputs (products), in 24 which liquid phase moves in counter-current of adsorbent phase. the counter-current stream is not real, but simulated, since the packed chromatographic stationary phase moves periodically after each switching time. the shorter the switching time and the more the number of columns are in the smb-lc, the better it converges to the tmb-lc. the smb technique is basically a two product preparative chromatographic operation. it is suitable for mixtures to be separated having two components or can be produced two product fractions. in case of continuous system the two input streams are the fresh eluent and feed, the two outputs are the extract and raffinate. above all in basic case regenerated eluent of re-circulating stream is added to the fresh eluent. similarly to the tmb the lower part (i-ii) of the column is rich in the more binding component and at the upper part (iii-iv) of the column contains the less binding component. the inlet and the outlet fluid flow streams divide the column system into four zones (fig.1.) i ii iii iv eluens f e r a rec d+d rec d rec d cm iv iii d+d rec f r e i ii d rec a; b; figure 1. the scheme of a) true moving bed (tmb) and b) simulated moving bed (smb). true moving bed (tmb) adsorber: i, ii, iii, iv – zones; d – desorbent (solvent, eluent); d rec – recirculated eluent; a rec – adsorbent recirculation; e – extract stream with the better adsorbed component a; f – feed stream with the components a and b; r – raffinate stream with the less adsorbed component b. simulated moving bed (smb) liquid chromatograph – i, ii, iii, iv – zones, respectively hplc columns; cm – direction of simulated moving of hplc columns. the inlet liquid stream of the first zone is the mixture of the fresh and recirculated eluent. the first column of the first zone has to be regenerated till the end of each switching time period to protect carrying strongly adsorbed components by adsorbent phase. the inlet liquid stream of the second zone is the mobile phase from the first zone minus the flow stream of the extract. this flow stream must be determined so that the less binding component could leave the first column of the second zone till the end of the switching period avoiding to get into the extract. the inlet liquid stream of the third zone is the mobile phase from the second zone plus the feed stream to be separated. the function of this zone is holding the more binding component in the adsorbent phase, since the less binding component is taken away as a raffinate at the end of the zone. four-zone smb is favourable when retarding the less binding component – regenerating the solvent. the regenerated solvent can be recycled and added to the fresh eluent. in case of recycled solvent the system is called closed loop smb. this version is more favourable compared to the open loop system from economic and environmental point of view. three-zone smb is preferred in systems with high selectivity factor, when the less binding component has low capacity factor flowing nearly together with the mobile phase [1,2]. according to the above facts the operational parameters of the process are the switching time, the flow rates of the mobile phase in each zones determined by the external flow rates (fresh and recycled eluent, extract, feed, raffinate). summing up the possibilities for amino acid preparative separation the following chromatographic methods were applied in practice: ion-exchange column liquid chromatography, ionexchange parametric pumping, size-exclusion chromatography, reverse phase adsorption chromatography. in case of reverse phase adsorption chromatography for separation of amino acids solved in water: the styrene-divynilbenzene copolymers with non-polar surface and the polymethacrylate resins with weakly polar surface can be used in the presence of electrolytes or polar solvent. in such systems the adsorption equilibrium depends on the temperature, the solvent strength, the ph [3,4] and on the electrolyte concentration of aqueous solution [2]. the design of industrial scale smb-lc process requires numerous preliminary experiments. at the selection of the packing we can reduce the number of the possible alternatives if we consider the chemical character of the adsorbents. the most frequently used technique is the determination of adsorption selectivity with an analytical hplc instrument with a given adsorbent by injection method. the adsorbent is giving the best selectivity to be examined further on within small-scale or large-scale laboratory circumstances. we examined the model samples by frontal adsorption-desorption 25 method on the small scale lab size column packed with polymer adsorbent. the advantage of this method is that frontal adsorption and desorption processes of the smb-lc can be investigated. after determining the equilibrium data of the selected systems and the column packing characteristics the initial operating parameters of the smb can be calculated. the initial operating parameters for a three zone open loop smb was calculated by the method of morbidelli et al. [5]. the first zone regeneration is appropriate when: )l(1 lt a d mk ia ε ε − − =< (1) the less binding component must be removed from the second zone till the end of the switching time. the function of the third zone is the retarding of the better-adsorbed component, namely this component must not break through the third zone: aiib k )l(1 lt a ed m<k < − −− = ε ε (2) aiiib k )l(1 lt a f+ed m<k < − − − = ε ε (3) in a two component-system a mii-miii area can be determined from the geometric data of the smb equipment, the equilibrium parameters of langmuir-type isotherms and the concentrations of the mixture to be separated. the given operating conditions determined a point in the mii-miii diagram. this point must be placed in the morbidelli-area (or morbidellitriangle), then both products stream purity are theoretically 100%. when the optimal chromatographic packing is selected, the following operating variable can have influence on the smblc operation: fresh eluent, recirculated eluent, feed, extract and raffinate flow rates, column switching time. during calculation the influence of a given parameter can be investigated while the others must be considered as constants. better productivity, product purity, yield, eluent consumption can be achieved by optimizing operating conditions by computer. the morbidelli-area changes with the change of the following parameters during the planning: geometrics of smb equipment, temperature and exchange of adsorbent, composition of fresh eluent and feed. during the planning of a preparative chromatography it must be considered, that the models of linear chromatography described is not appropriate the system. many research schools are dealing with the mathematical modeling of the nonlinear chromatography [6,7]. experiments the examined model systems during research are the aqueous solution of dl-β-phenylalanine and sodium-chloride, and the aqueous solution of glycine and dl-β-phenylalanine. select reversed phase packing in case of l-phenylalanine and glycine amino acids separation in water the next reversed phase non-polar polymer adsorbents were studied by frontal adsorption-desorption methods: diaion hp20, sepabeads sp825. for desalting dl-βphenylalanine diaion hp2mg, amberlite xad7 polymethacrylate, amberlite xad1180, diaion hp20 styrene-divynilbenzene copolymer resins were investigated. parameters of research: measurement went on glass column in which resin bed length was 122 mm, i.d. 13 mm. l-phenylalanine concentration 0.005 mol l-phenylalanine/dm3 aqueous solution, glycine concentration 0.0025 mol glycine/dm3 aqueous solution, volumetric stream 2.9 ml/min. lphenylalanine was detected on-line by gilson116 uv-spectrophotometer at 271 nm wavelength. glycine and phenylalanine analyses went on afterwards, samples fractionally taken in each 4 ml by oe914 amino acid analyzer. while desalting 0.02 mol/dm3 dl-β-phenylalanine aqueous solution and 1mol sodium-chloride/dm3 aqueous solution, the next detection was used during adsorbent selection. the phenylalanine was detected on-line uv at 271nm, nacl by conductivity meter with flowing through cuvette. ion exchanged water was used for all experiments as desorbents. measurement of packing properties frontal adsorption–desorption method for adsorbent selection gave the best packing filled by slurry technique into smb-lc column. after packing, the number of theoretical plate (ntp) was measured in function of volume stream for l=500mm i.d.=50mm preparative smb-column in 30-180 cm3/min range using na2so4 detecting compound. in case of l=125mm id=13mm small 26 laboratory smb column ntp and column porosity (ε) were determined in 3.0-22 cm3/min range by injection method with 0.25 mol na2so4/dm3 water solution at 20°c. the answer function of the injection was detected by a radelkis ok102/1 conductivity meter with flow-through cuvette. this date is necessary for modeling, too. measurement of bulk density: resin being packed in a column was quantitatively removed and placed in max 5 mm thin layer on a plate in known mass and dried at 85-90°c till constant mass, then re-measured. measurement of equilibrium isotherms multi-step frontal adsorption method was used in a glass column (l=122 mm, id=13 mm) packed with diaion hp20 respectively sepabeads sp825 at 20°c in 0.002 mol/dm3…0.02 mol/dm3 aqueous solution concentration range with 0.002, 0.005, 0.01, 0.015, and 0.02 mol amino acid /dm3 water solutions, cc. 2 cm3/min volumetric stream. the 60°c isotherm measurement went on jacketed glass column equipped with plunger with 147 mm packing length and id 12 mm similarly to the measurement at 20°c. l-phenylalanine was detected at 271 nm, glycine at 230 nm by uvspectrophotometer. the equilibrium isotherms of dl-β-phenylalanine were measured in ionexchanged water, further in 0.25 and 1 mol nacl / dm3 aqueous solutions. equilibrium data were used for planning processing parameters and mathematical models. description of production-scale smb-lc and small-laboratory smb-lc equipments there are geometric and other parameters of the 4column production scale smb-lc equipment being constructed by the central workshop of university of veszprém: column number is four and made of stainless steel. useful column length: 500 mm, id 50 mm. special hole-channel system and 50 µm stainless steel fritts assure liquid distribution and collection on the full cross-section. columns are supplied with stainless steel thermostable jacket. joining pipes are 1/8’’ made of stainless steel. for switching time controlling of input and output sites 4 pieces of 4-way 5 set and 4 pieces of 2 way 3 set cocks were built in. above all, there are 2 pieces of 2 ways 3 set deairation cocks built in for removing air from pump outputs. the two input streams are assured by membrane pumps in 0-250 ml/min region; output streams are forwarded by two plunger type pumps. pumps are placed on separate scaffolds. the third output point, where regenerated solvent is taken away in the four-zone running, is open to the atmosphere without recirculation. there are the working parameters of the 4-column smb-lc: a four-zone 1-1-1-1-column configuration and a 3-zone 1-1-20, 2-1-1-0 and 1-2-1-0 column configuration. the listed working methods have been built in the program of the plc controlled automation. the six-column, three-zone small-laboratory smb-lc was built of six glass columns of equal geometry, with packing length of 127 mm and with inner diameter of 13 mm, a six-position low pressure multifunction valve, a time actuator and teflon pipes. the upper part of the valve is fixed through which the inlet of the sample and the eluent is carried out. the lower part is the rotating one which revolves along with the columns by a column position in every given time interval (fig. 2.) figure 2. photography of a) production scale smb and b) small-lab smb equipment. parameters of smb-lc measurements the l-phenylalanine – glycine – water separation was carried out on the production scale smb equipment (aa03, aa06). the initial experiment at 20°c, later on at 60°c was improved with the help of the equilibrium cascade model. the desalinization process of dl-β-phenylalanine was carried out on the small-lab scale smb (smb 3, 4, 5) unit. we varied the flow streams of eluent, feed, raffinate, extract and the switching time (table i.) a) b) 27 table i. operating conditions of desalting of phenylalanine with the small-laboratory scale six-column smb (smb3, smb4, smb5), and of phenylalanine-glycine separation with the preparative four-column smb (aa03, aa06). column configuration temperature t d e f r phe nacl (min) (cm3/min) (cm3/min) (cm3/min) (cm3/min) column configuration temperature t d e f lrout phe nacl (min) (cm3/min) (cm3/min) (cm3/min) (cm3/min) aa06 3.3 1.5 2:1:1:0 43.5 78.8 cf (g/dm3) 20.3 60.6 60°c 30 237.4 202.1 aa03 3.3 1.5 2:1:1:0 20°c 45 241.9 201.6 1.21 5.11 prep. smb 0.83 3.93 smb5 3.5 58.5 2:2:2 20°c 12.5 6.95 3.06 20°c 15 5.55 2.45smb4 3.5 58.5 2:2:2 1.23 0.33 1.962:2:2 20°c 26 2.86 cf (g/dm3) smb3 3.5 58.5 small lab smb smb product stream analysis production scale smb unit – phenylalanine – glycine separation: both extract and raffinate were collected in separate reservoir by switching times. after shaking it, sample was taken out of the reservoirs and analyzed by aminochromii oe914 amino acid analyzer. over the average sample, part sample was taken in the last switching time by a given periodicity to examine concentration transient within cycle [quasi-stationary state]. half a minute sample was taken in every 7 minutes at the 20°c measurement, at 60°c first in the second minute, then by 5 minutes. summarizing the amino acid analysis: glycine and l-phenylalanine were separated on high efficiency durrum dc-4a cation exchange column at constant ph and ion strength. components leaving the column were mixed with ninhydrine reagent and reacted in capillary pipe reactor at 80 °c for ca. 10 min, the forming colorful products were detected by spectrophotometer at 570 nm. after proper dilution the samples were injected by automatic injector from the 30 µl loop (extract was not diluted, raffinate and feed in 5 times dilution). used eluent ph is 4.25, ion strength is 0.2, volume stream is 20 ml/hour. ninhydrine volume stream is 10 ml/hour. amino acid content of the sample is proportional to the area beneath the chromatographic peak. amino acid mixture was used as calibrating standard with 0.0005 mol/l amino acid concentration. the analysis time was ca. 25 min/sample. small-lab smb unit – phenylalanine desalting: both in extract and raffinate stream on-line uv detection of amino acid at 271 nm wavelength. salt detection: on-line by conductivity meter with flowing-through cuvette. results packing selection frontal measurements were evaluated by the next capacity relation: nacl naclaminoacid' v vv k − = (4) dead volume (vnacl) was defined by 1 mol nacl/dm3 water injection (vnacl). the following capacity factors were given at 20°c for the selected resins: hp20 for desalinization: dl-phenylalanine k’=4.20 sp825 for glycine-phenylalanine separation: lphenylalanine k’=12.99; glycine k’=0.73 (table ii.) 28 table ii. capacity factors of the investigated resins. nacl phe nacl phe xad7 123.00 3.00 13.80 29.30 1.12 58.40 3.00 13.80 23.40 0.70 58.40 3.00 13.80 23.80 0.72 hp2mg 58.50 2.70 12.10 33.20 1.74 58.50 3.22 12.10 21.00 0.74 xad1180 58.50 2.70 14.00 62.90 3.49 58.50 3.22 14.00 56.00 3.00 hp20 58.50 2.70 12.50 75.30 5.02 58.50 3.22 12.50 65.00 4.20 gly phe gly phe hp20 1.50 3.30 14.85 62.70 0.19 4.03 sp825 1.50 3.30 16.50 133.65 0.73 12.99 adsorbent for glyphe separation sample composition [g dm-3] volume/breaktrough curve inflection point [cm3] capacity factor k' gly phe capacity factor k' adsorbent for phe desalinization sample composition [g dm-3] volume/breaktrough curve inflection point [cm3] equilibrium measurement l-phenylalanine and glycine adsorption on sp825 resin can be written by langmuir equilibrium isotherms. the amino acid isotherms at 20°c (fig. 3.a): gly gly gly 0.9291c1 0.5344c q + = and phe phe phe 0.1621c1 34.01cq + = (5) at 60°c: gly gly gly 0.9535c1 0.353c q + = and phe phe phe 0.671c1 23.47cq + = (6) the unit of liquid phase concentrations (cphe, cgly) is mg amino acid/cm3 solution, the solid phase concentrations (qphe, qgly) are in mg amino acid/ g dry resin. rising temperature solid phase amino acid quantity decreases. 0 10 20 30 40 50 60 70 80 0 0,5 1 1,5 2 2,5 3 3,5 4 c [mg amino acid/ml solution] q [m g am in o ac id /g d ry a ds or be nt ] 0 0,5 1 1,5 2 2,5 3 3,5 4 4,5 5 phe t=20°c phe t=60°c gly t=20°c gly t=60°c sepabeads (a) 0 0,05 0,1 0,15 0,2 0,25 0,3 0,35 0 0,005 0,01 0,015 0,02 0,025 c phenylalanine [mol/dm3] q ph en yl al an in e [m ol /d m 3 ] diaion hp20 (b) figure 3. a) adsorption isotherms of glycine and of lphenylalanine in aqueous solution at temperature 20°c and 60°c on sp825 resin. c: liquid phase amino acid concentration in mg amino acid/ cm3 liquid, q: solid phase amino acid concentration in mg amino acid/ g dry adsorbent. b) isotherms of dl-β-phenylalanine on hp20 resin. langmuir parameters depends on the nacl concentration of the liquid phase: in water (marker *): a=20.86, b=33.5; in 0.25 m nacl solution (marker +): a=22.37, b=32.1; in 1 m nacl solution (marker x): a=26.94, b= 32.8. the dimension of langmuir-b parameter: cm3 mmol-1. langmuir-a is dimensionless. the investigated adsorption of the dl-βphenylalanine in aqueous phase and in salt solution on hp20 adsorbent can be characterized also by langmuir isotherms (fig. 3.b). increase of the concentration of the salt solution means the dl-βphenylalanine concentration increase in the resin phase. taking into consideration the dependence of the “a” parameter of the langmuir equation on the salt concentration it can be written as: phe phephenacl phe 32.8c1 20.86cc6.08cq + + = (7) the concentration units are in mmol amino acid/ ml solution (cnacl, cphe), respectively in mmol amino acid/ ml packing total volume (qphe). 29 packing characteristics smb-lc columns were characterized by na2so4 – water solution injection at different volumetric streams. the production-scale smb-columns i.d.=50mm l=500mm were packed with 0.3 mm particle diameter sp825 resin by water slurry technique. each column was filled with 265.0 g sp825 adsorbent air dried till constant mass value. for example the ntp of the column no.2. can be determined with the following equation: 1.20350.0043u 50ntp + = (8) unit of “u” : cm3/min mobile phase flow rate. the ntp is defined with this equation for 500 mm packing length. overall porosity of columns were determined by salt-solution injection and ε=0.59 value was received for all the four columns. the bulk density value is 0.27 g dry resin/cm3 column volume. the ntp of the small-lab scale smb packed with 16.0 g hp20 resin per column can be determined: 0.02910.00225v 125ntp 0 + = (9) unit of „v0” : mm/min mobile phase velocity. overall porosity: ε=0.71 . results of smb-lc measurements results of measurement at 20°c on 2-1-1-0 column configuration of the production-scale fourcolumns smb unit: more than 99.9% m/m amino acid purity in extract for l-phenylalanine and in raffinate for glycine. the yields are over 99% for both amino acids. productivity depending on the feed, volumetric velocity and concentration is relatively low. l-phenylalanine productivity is 3.76 mg/g sp825/h, glycine productivity is 1.72 mg/g sp825/h (aa03 measurement). in case of measurement at 60°c (aa06 measurement) on 2-1-1-0 column configuration the feed volumetric velocity was increased from 25 to 45 ml/min, so productivity was increased 1.8 times and less diluted product output was given. values of purity are over 99.9% m/m and the yields over 99% m/m. desalting dl-β-phenylalanine (smb 3, 4, 5 measurements): productivity for phenylalanine was 0.67-2.3 mg/g hp20/h, yield 89-96% and amino acid purity 98.5% m/m (table iii.) discussion planning of smb-lc processing parameters the task of the first zone in the 4 zone recirculation smb-lc is the regeneration of adsorbent, namely the washing down and desorption of the better binding component, till the end of switching time. the second and third zones are the separation zones. the less binding component must be removed from the second zone till the end of the switching time. the function of the third zone is the retarding of the better binding component on the stationary phase. in the fourth zone a portion of the eluent is recovered purely, so here the less adsorbing component is to be adsorbed, retained. because of the very weak glycine respectively nacl adsorption in this water phase system, very low recirculation is possible – not much more than empty volume liquid quantity calculated from column total porosity. thus, the fourth zone was neglected and the work was continued in the open three-zone smb-lc system. 0 5 10 15 20 25 0 5 10 15 20 25 mii m ii i morbidelli triangle t=20°c aa03 measurement t=20°c morbidelli triangle t=60°c aa06 measurement t=60°c (a) 0 5 10 15 20 0 5 10 15 20 mii m iii kphe mii=miii smb3 smb4 smb5 (b) figure 4.the measurements points placed in the morbidelli triangle: a) phenylalanine-glycine separation at temperature 20°c (aa03) and 60°c (aa06) b) desalting of phenylalanine (smb 3, 4, 5). 30 table iii. operation parameters of the smb separations. smb3 smb4 smb5 phenylalanine glycine phenylalanine glycine phenylalanine glycine aa03, t=20°c 3.760 1.724 >99.9 >99.9 >99.9 >99.9 aa06, t=60°c 8.130 3.697 >99.9 >99.9 >99.9 >99.9 small lab smb preparative smb phenylalanine 95.58 93 89.072.302 phenylalanine 98.34 98.5 98.21 productivity [mg/gh] purity [%] yield [%] productivity [mg/gh] purity [%] yield [%] phenylalanine 0.667 1.645 beside the prescribed purity and yield in industrial production the productivity must be the highest, the solvent use the less and adsorbent utility is the best. the initial operating conditions were planned with the help of morbidelli’s equilibrium method (fig. 4.). the first parameters can be improved, while increasing the feed value or concentration. an obvious possibility is the increase of all flow rates (eluent, feed, extract, raffinate) proportionally and decrease the switching time. we used this method for desalting of dl-β-phenylalanine on the small-lab smb. there are kinetic limits of the flow rate increase (fig. 5.). other possibility is to improve the regeneration of the first zone for example by increasing temperature. with this method less fresh eluent is necessary, thus we can increase the feed flow rate and so the productivity improves. by the phenylalanine–glycine separation lower selectivity was measured at higher temperature. the initial steep of adsorption equilibrium isotherm decreased, therefore l-phenylalanine desorption went on easier. thus the switching time could be reduced from 45 min to 30 min, so feed stream was increased from 20.3 ml/min to max. 43.5 ml/min. conclusions we planned initial parameters with the help of morbidelli’s equilibrium method for smb separation in water of phenylalanine-glycine, respectively phenylalanine–sodium-chloride model systems on polymer adsorbents. we investigated two ways to improve the productivity. the increase of all flow streams and the decrease of period time in the desalting of dl-β-phenylalanine is limited by adsorption and desorption kinetics of the amino acid: the productivity was increased 3 times, but the yield decreased from 95.6% to 89% (smb 3, 4, 5 measurements). 0 2 4 6 8 10 12 14 0 12.5 25 37.5 50 62.5 75 87.5 measurement time [min] u v , c on du ct iv ity si gn al [m v ] (a) 0 5 10 15 20 25 0 12.5 25 37.5 50 62.5 75 87.5 measurement time [min] u v , c on du ct iv ity si gn al [m v ] (b) figure 5. measured concentration commensurable signals by smb5 experiment in a) raffinate and b) extract. markers: signal of phenylalanine (+) and signal of nacl (*). the phenylalanine–glycine smb-lc system temperature was risen from 20°c to 60°c (aa03, aa06 measurements), thus productivity was increased 1.8 times. rising temperature gives solution only for an optimal value because application of ventiles, cocks, fittings, etc. is limited by temperature. 31 symbols d – flow rate of eluent (cm3/min) e – flow rate of extract (cm3/min) f – flow rate of feed to be separated (cm3/min) t – period time or column switching time (min) a – cross-section of the smb-column (cm2) l – column length (cm) ε – overall porosity mi, mii, miii, miv – morbidelli’s parameters ka, kb – equilibrium distribution coefficient k’ – capacity factor vaminoacid, vnacl – inflection point of the breakthrough curve (cm3) qphe – phenylalanine concentration in stationary phase (mg/g) cphe – phenylalanine concentration in mobile phase (mg/cm3) cnacl – nacl concentration in mobile phase (mg/cm3) references 1. hashimoto k., yamada m. and shirai y.: j. of chem. eng. (1987), vol. 20 no. 4, 405-409 2. molnar z., nagy m., hanak l., szanya t. and argyelan j.: j. chromatogr. (2004), vol. 60, 75-80 3. grzegorczyk d. s. and carta g.: chem. eng. sci., 51 (1996) 807 4. grzegorczyk d. s. and carta g.: chem. eng. sci., 51 (1996) 819 5. migliorini c., mazzotti m. and morbidelli m.: j. chromatogr. a, 827 (1998) 161 6. guiochon g.: j. chrom. a. 965 (2002) 129161 7. heuer c., küstens e., plattner t. and seidel-morgenstern a.: j. chromatogr. a, 827 (1998) 175 8. szanya t., argyelan j., kovats s. and hanak l.: j. chromatogr. a, 908 (2001) 265 microsoft word content.doc hungarian journal of industrial chemistry veszprém vol. 40 (2) pp. 83–86 (2012) study on analysis of antibiotic compounds from enthomopathogenic bacteria by ft-ir d. vozik1, j. madarász2, z. csanádi1 , a. fodor3,4, k. dublecz4, k. bélafi-bakó1 1university of pannonia, faculty of engineering, research institute on bioengineering, membrane technology and energetics, 10 egyetem str., 8200 veszprém, hungary 2university of pannonia, faculty of engineering, department of organic chemistry, 10 egyetem str., 8200 veszprém, hungary 3university of pannonia, georgikon faculty, institute of plant protection, 16 deák f. str., 8360 keszthely, hungary 4university of pannonia, georgikon faculty, department of animal sciences, cepo group, 16 deák f. str., 8360 keszthely, hungary e-mail: csanadi@almos.uni-pannon.hu entomopathogenic bacteria produce antibiotic molecules effective against plant, animal and human plant pathogenic bacteria. they produce broad-spectrum antibiotics, which can be applied in several different fields where suppression of microbes is needed. these antibiotic molecules have different chemical structure such as peptides. analysis and identification of these molecules provide useful ways in the research and development of drugs and agrochemicals. keywords: entomopathogenic bacteria, antimicrobial activity, peptides, analysis introduction insect pathogenic or entomopathogenic nematodes (epn) and their symbiotic entomopathogenic bacteria (epb) can be used as microbial control agents against agricultural insect pests [1]. these nematodes of heterorhabditis and steinernema species are symbiotically associated with the members of the bacteria family enterobacteriaceae as photorhabdus and xenorhabdus species, respectively [2–3]. the epb have several special functions in this symbiotic relationship. one of them is the production ability of broad-spectrum antibiotics, which keep monoxenic conditions in insect cadavers in soil [4]. antibacterial resistance is increasing worldwide. the compounds produced by epn symbiotic bacteria have showed a wide range of bioactivities of medicinal and agricultural interest, such as antibiotic, antimycotic and insecticidal effects [5]. these antimicrobial peptides have been successfully applied in pharmaceutics, plant disease control and many other fields [6]. antimicrobial peptides have many beneficial characteristics, such as broad-spectrum antibiotic activity, thermal stability, and low molecular weight, and most significantly, compared with most antibiotics, they are not easy to lead to the development of resistance in the target [7]. these compounds were reported as showing in vitro activity against gram-positive bacteria, including for example the multi-drug resistant strain of staphylococcus aureus. they have diverse chemical structures including peptides as well [5]. analytical study of these molecules can be achieved in different ways. edman degradation, developed by pehr edman [8], is a method of sequencing amino acids in a peptide. in this method, the amino-terminal residue is labeled and cleaved from the peptide without disrupting the peptide bonds between other amino acid residues. a major drawback to this technique is that the peptides being sequenced in this manner cannot have more than 50 to 60 residues (and in practice, under 30). the peptide length is limited due to the cyclical derivatization not always going to completion. the infrared spectrum of a protein provides a wealth of information on structure and environment of the protein backbone and the amino acid side chains [9]. this makes infrared spectroscopy an extremely useful tool for the investigation of protein structure. the absorption of a side chain in a protein may deviate significantly from their absorption in solution or in crystal. the special environment provided by a protein is able to modulate the electron density and the polarity of bonds, thus changing the vibrational frequency and the absorption coefficient. therefore, the band positions given in reviews should be regarded only as guidelines for interpretation of spectra [10]. in this study, we aimed the isolation and analysis of some peptide-type antibiotic compounds from two epb strains. 84 material and methods antibacterial peptide-producing entomopathogenic bacteria were xenorhabdus budapestensis (ema) and xenorhabdus szentirmaii (emc). they were cultured in luria broth (lb and lba) liquid and solid media as previously described [11]. cell-free culture media (cfcm) were prepared as follows: aliquots of the stock culture were added separately into 900 ml sterile medium. the flasks were incubated in a shaker at 200 rpm and 30ºc for 24 h and centrifuged at 13 000 rpm (10 000 g for 30’). after centrifugation the supernatant was filtrated through express plus filter (0.22 µm) (merck millipore). purification of antimicrobial compounds: 1000 ml of cfcm was mixed with activated amberlite xad polymeric adsorbent in a 1:20 ratio and incubated for 24 h. the resin-cfcm mixture was filtered through millipore express plus filter of 0.22 µm pore-size and washed subsequently with 200 ml of distilled water, 200-200 ml of 25 v/v%, 50 v/v% and 80 v/v% methanol (meoh), removing all inactive compounds by this way. after this the resin was washed with 200 ml cc. meoh:hcl (99:1) and 200 ml i-propanol (iproh) to eluate biologically active compounds. these samples were evaporated by vacuum distillation and resulted samples with meoh and iproh, respectively. for the analysis of the purified antimicrobial compounds a thermo nicolet avatar ft-ir-330 ftir apparatus was used to determine ft-ir spectra and a hitachi u-2910 uv-vis spectrophotometer was used to form the uv spectra. solid samples were prepared for the ir: some quantity of samples were ground with purified kbr and this mixtures were pressed in a mechanical press to form a transparent pellet through which the beam of the spectrometer can pass. resolution: 2.000 cm-1, scans: 16. results and discussion the most precise method for the protein and peptide identification after their separation by high-performance liquid chromatography (hplc) is mass spectrometry [12]. however, this method is quite expensive. absorbance at low wavelength (<220 nm) detects peptide bonds and amino acid residues with detection limits between nanomoles and picomoles. peptides having aromatic residues (phenylalanine (phe), tyrosine (tyr), and trypthophan (trp)) can be detected at 254 or/and 280 nm. for this reason we made a uv spectra of the purified antibiotic activity compounds. results of these measurements are shown in table 1. table 1: uv absorbance (nm) of the antibiotic compounds ema emc iproh meoh iproh meoh 201 203 200 202 213 218 217 ir spectra were made with the above described method. results of these measurements are shown in figures 1–4. figure 1: antibiotic compounds purified with iproh from ema figure 2: antibiotic compounds purified with meoh from ema in the case of amino acids only two side chain moieties absorb in spectral regions that are free from overlapping absorption by other groups and thus allow the spectroscopists an unambiguous assignment without further experiments. these are the sh group of cysteine (2550–2600 cm-1) and the carbonyl group of protonated carboxyl groups (1710–1790 cm-1). these groups were obtained in none of the ir spectra. figure 3: antibiotic compounds purified with iproh form emc 85 all other side chain absorption overlap with the absorption of other side chains or of the polypeptide backbone and further experiments are needed to assign an absorption band to a specific side chain moiety. figure 4: antibiotic compounds purified with meoh from emc the ν(c=o) vibration of glutamine side chains near 1680 cm-1 is a relative strong infrared absorber, the bands are sensitive to h-bonding and the band position is lower the stronger the h-bond is (table 2, 3). the ν(c=o) vibration of the deprotonated carboxylate group of the glutamate shows two strong bands near 1400 and 1570 cm-1 for symmetric and antisymmetric stretching vibration, respectively (tab. 2, 3). the ν(cn) vibration of histidine is a useful band near 1100 cm-1 (tab. 2, 3). tyrosine is a relatively strong infrared absorber due to its polar character. the most intense bands originate from ν(cc), the ν(c-o) and the δ(coh) mode near 1517, at 1235–1270 and at 1169–1260 cm-1 (tab. 2, 3). table 2: the ir spectra of ema antibiotic compounds with different eluents band position in cm-1 assignment iproh meoh 1659 1654 glutamine (ν(co) in proteins 1659–1696 cm-1) 1634 1638 histidine (ν(c=c) in proteins 1617 cm-1) 1605 tyrosine (ν(cc) ring in proteins 1615 cm-1) 1548 1556 glutamine (νas(coo-) in proteins 1553–1575 cm-1) 1520 tyrosine (ν(cc) ring, δ(ch) in proteins 1516–1518 cm-1) 1446 lysine (δ(ch2) in proteins 1445 cm-1) 1409 1405 glutamine (νs(coo-) in proteins 1397–1424 cm-1) 1246 1234 tyrosine (δ(coh) in proteins 1228–1250 cm-1) 1108 1082 histidine (ν(cn), δ(ch) in proteins 1094–1114 cm-1) while the δas(ch3), the δ(ch2) and the δs(ch3) vibration near 1465, 1450 and 1375 cm-1 are relatively good group frequencies, the δ(ch) and γ(ch2) vibrations are often coupled to other modes (tab. 2, 3). the only tryptophan bands with considerable infrared intensity seem to be those at 1334 and 1455 cm-1 (tab. 2, 3). table 3: the ir spectra of emc antibiotic compounds with different eluents band position in cm-1 assignment iproh meoh 1653 glutamine (ν(co) in proteins 1659–1696 cm-1) 1640 histidine (ν(c=c) in proteins 1617 cm-1) 1548 1542 glutamine (νas(coo-) in proteins 1553–1575 cm-1) 1446 1452 tryptophane (ν(chb)a, ν(ccb)a, ν(cn) in proteins 1455 cm-1) / lysine (δ(ch2) in proteins 1445 cm-1) 1403 1406 glutamine (νs(coo-) in proteins 1397–1424 cm-1 1336 tryptophane (ν(ccp)a, ν(cn) in proteins 1334 cm-1)/ lysine (γ(ch2), γ(ch2) in proteins 1345 cm-1 1246 1245 tyrosine (δ(coh) in proteins 1228–1250 cm-1 1201 tryptophane (ν(cc) 1203 cm-1 1152 proline (γ(ch2), 1168 cm-1 1085 1084 histidine (ν(cn), δ(ch) in proteins 1094–1114 cm-1) “b” and “p” indicate vibrations of the benzene or pyrole moieties, respectively. acknowledgement this work was partly supported by cepo, the austrianhungarian cooperation project for poultry excellence centre, working within the frame of erfa between 2007–2013 and támop-4.2.2/b-10/1-2010-0025. references 1. g. c. smart: entomopathogenic nematodes for the biological control of insects, journal of nematology, 27 (1995), pp. 529–534 2. g. m. thomas, g. o. poinar: xenorhabdus gen. nov., a genus of entornopathogenic, nematophilic bacteria of the family enterobacteriaceae, international journal of systematic bacteriology, 29 (1979), pp. 352–360 86 3. n. e. boemare, r. j. akhurst, r. g. mourant: dna relatedness between xenorhabdus spp. (enterobacteriaceae), symbiotic bacteria of entomopathogenic nematodes, and a proposal to transfer xenorhabdus luminescens to a new genus, photorhabdus gen. nov.. international journal of systematic bacteriology, 43 (1993), pp. 249–255 4. r. j. akhurst: antibiotic activity of xenorhabdus species, bacteria symbiotically associated with insect pathogenic nematodes of the families heterorhabditidae and steinernematidae, journal of general microbiology, 128 (1982), pp. 3061–3065 5. j. m. webster, g. chen, k. hu, j. li: bacterial metabolites, in: entomopathogenic nematology, cabi publishing, usa (2002), pp. 99–115 6. y. j. gordon, e. g. romanowski, a. m. mcdermott: a review of antimicrobial peptides and their therapeutic potential as anti-infective drugs, current eye research, 30 (2005), pp. 505–515 7. y. xiao, f. meng, d. qiu, x. yang: two novel antimicrobial peptides purified from the symbiotic bacteria xenorhabdus budapestensis nmc-10, peptides, 35 (2012), pp. 253–260 8. p. edman, e. högfeldt, l. g. sillén, p. o. kinell: method for determination of the amino acid sequence in peptides, acta chemica scandinavica, 4 (1950), pp. 283–293 9. a. barth: the infrared absorption of amino acid side chains, progress in biophysics & molecular biology, 74 (2000), pp. 141–173 10. b. hernandez-ledesma, l. amigo, m. ramos, i. recio: application of high-performance liquid chromatography-tandem mass spectrometry to the identification of biologically active peptides produced by milk fermentation and simulated gastrointestinal digestion, journal of chromatography a., 1049 (2004), pp. 107–114 11. e. m. motitu: evaluating antibacterial potential of entomopathogenic bacterium strains on agriculturally important plant pathogenic bacteria. master thesis, university of pannonia, georgikon faculty, institute of plant protection, keszthely, hungary (2011) 12. t. herraiz: sample preparation and reversed phase-high performance liquid chromatography analysis of food-derived peptides, analytica chimica acta, 352 (1997), pp. 119–139 editorial editorial preface the editorial board of hjic dedicates this issue to the national scientific students’ associations (tudományos diákkör, in hungarian, abbreviated as tdk) that is a real hungaricum with a 62 years old tradition. this association includes all the universities and colleges of hungary, where scientific research of any kind is being conducted. the members of the association are the faculty members, scientific advisors, and their b.sc. or m.sc. students. participation in the work of tdk is completely voluntary. students spend some of their free time with a faculty mentor, choose a research topic, learn the basics of the field, do the measurements or the calculations under the supervision of the chosen teacher/researcher in addition to their regular academic duties. at the end, they write a dissertation based on their results. these dissertations are peer reviewed and then presented at yearly institutional tdkconferences, where the students receive suggestions from a panel of scientists and professors, receive a score for their written documents and oral presentations. based on these scores, they may win legitimacy to present their results at the national tdk-conference. tdk is a remarkable organization in hungary that was kept alive by people who do their work from pure enthusiasm for the love of their profession. it is not an exaggeration to say that the tdk-students form the elite of all the university students. they are the ones who proceed to m.sc. level, become phd students, and, at the end, ideally become colleagues of their former faculty advisors. during their work as part of tdk, students learn systematic problem-solving, formulating good questions, critical thinking, composing their thoughts into concise, wellformulated sentences, preparing meaningful figures, elaborating the literature of the field, and presenting their result in front of a scientific panel and an audience. even those students who do not continue their life in the academia tend to remember their time spend on tdk activities as useful and memorable. often, the skills acquired while being involved in a tdk project are not part of the regular education at a given university. tdk gives them something extra. this issue contains selected articles from students and their supervisors about their results presented at the tdk conferences during 2013-2014. with this issue, the editorial board wishes to honour the effort of all tdk students and their advisors for keeping this unique tradition alive with their devoted work. dezső boda and tibor dulai university of pannonia, veszprém, hungary guest editors microsoft word contents.doc hungarian journal of industry and chemistry veszprém vol. 40(1) pp. 45–52 (2012) production of gas oil components from waste fats p. baladincz1 , a. ludányi1, l. leveles2, j. hancsók1 1university of pannonia, department of mol hydrocarbon and coal processing 10 egyetem str., 8200 veszprém, hungary e-mail: baladinczp@almos.uni-pannon.hu 2mol nyrt., danube refinery, ds development, 2 olajmunkás str., 2440 százhalombatta, hungary the modern-minded man has discovered that it is necessary to substitute a part of the fossil-derived energy sources with renewable energy sources to cover the energy demand of mobility, which sustains and accelerates the human society and economy. nowadays, the transportation sector tries to achieve this through the development and utilisation of bio-derived motor fuels. in terms of diesel-engines the biodiesel has been utilized in great volumes already, which is made from triglycerides via esterification (fatty-acid-methyl-ester, fame). the fame or biodiesel, due to its molecular structure, has some unfavourable properties. therefore, it was necessary to develop a new generation of bio-derived motor fuel for diesel-engines. the most promising product of these efforts is the bio gas oil, which is a mixture of nand i-paraffins and obtained via hydroconversion of triglycerides. these compounds are the best components of conventional gas oils, too. nowadays, mainly different vegetable oils are used as triglyceride source, but for the hydroconversion any feedstock with high triglyceride content can be used (e.g. brown greases of sewage works, used cooking oils, animal fats, etc.). the waste feedstocks can be especially beneficial. hence, during the experimental work, our aim was to investigate the possibilities of the production of bio gas oil and bio gas oil containing gas oils on waste fat basis via the hydroconversion of waste rancid lard itself and as a 50% mixture with gas oils. we applied a como/al2o3 catalyst in sulphide and in nonsulphide state for our experiments. we studied the effects of the process parameters (temperature: 300–380°c, pressure: 40–80 bar, lhsv: 1.0–2.0 h-1, h2/feedstock ratio: 600 nm3/m3) on the quality and yield of the products. the obtained main product fraction at the process parameters (360–380°c, 60–80 bar, lhsv: 1.0 h-1, h2/feedstock rate: 600 nm3/m3) found to be favourable by us which were met the valid diesel gas oil standard en 590:2009 + a1:2010 without additivation, except for its cold flow properties. keywords: lard, hydrogenation, renewable, diesel gas oil, animal fat introduction the modern society and economy are increasingly dependent on mobility. mobility of people and products is usually realized using vehicles. their number is growing with each day and almost every one of them (>95%) operates with fossil derived fuels. at the same time, the limited amount and the unequal distribution of the available oil reserves is a source of international tensions, because most countries rely on import. besides, there are more and more vehicles, which means more and more intense environmental pollution. for this reason, in the whole world, research has been started for the development and utilization of cleaner and more available energy sources. among these alternative fuels, there are the renewable, agricultural-derived fuels from biomass and amongst them the bio-derived motor fuels (agro-motor fuels), which are the primary bio-derived motor fuels of the present and the near future. because of environmental considerations and its intense rely on import energy sources, the european union treats the research of agriculture derived, renewable energy sources with great attention and urges their utilization in greater volumes [1–4], besides attending to the agricultural production, too. in this context, the union literally declared the necessity of the production of bio motor fuels and their extensive utilization [1] and allows the blending of biocomponents (in the case of diesel gas oil this means maximum 7v/v biodiesel) to conventional fuels. in addition, the union treats the effort to expand the feedstock supplies of bio motor fuels with great importance too [2]. the actual objective of the european union is to raise the average share of the renewable energy sources to 20% until 2020. the average content of renewable fuels, particularly, must be raised to 10% in all automotive fuels in the european market until 2020 [1–4]. however, it has been proposed recently that the share of the motor fuels derived from feedstocks that can also be used in food processing could be maximum 5%. before the worldwide economic crisis, the tendency of the automotive fuel market in the european union (figure 1) showed a probable increase in the demand [5] for diesel fuels and this tendency will restore despite the feasible spread of hybrid vehicles. therefore, the research and development of the agriculture derived bio motor fuels are coming to the front. 46 figure 1: the tendency of the fuel market of the eu (before the economic crisis) the research and development of the agriculturederived bio motor fuels, therefore, is extremely important. bio-derived motor fuels of diesel-engines the primordial fuel of the diesel-engine was a vegetable oil (peanut oil), thus for the sake of satisfying the continuously increasing gas oil demand, vegetable oils and their different percentage mixtures with gas oil are attempted to be utilized [6]. the main components of the vegetable oils (and animal fats, etc.) are the triglycerides, which are esters of a polyvalent alcohol, the glycerine, and natural fatty acids (the carbon number of the chain is always paired and they contain unsaturated bonds in a different measure) with different carbon numbers (figure 2). c h 2 ch 2 ch 3c h 2 c h c h 94c ch 2 ch 2 ch 3c h 2 c h ch 76c c h 2 c h 2 c h 3ch 2 ch c h 85c o oc h 2 c h o oc h 2 o o figure 2: typical triglyceride molecule however, the differences between the physical and application properties of these compounds are not suitable to simply replace the conventional gas oils. therefore, it is necessary to convert them with different conversion pathways. these conversion pathways can be: thermal and catalytic pathway. in practice, the more important is the latter one. biodiesel nowadays, the agriculture derived bio motor fuel and bio blending component that are produced and utilized in the greatest volume is the fame (fatty-acid-methylester) or biodiesel. this is made by the catalytic esterification of vegetable oils and other fats [7–10]. however the technologies producing biodiesel and the product itself also have numerous disadvantages. cch2 ch2 ch2 ch2 ch2 ch2 ch2 ch ch ch2 ch ch ch2 ch2 ch2 ch2 ch3 o o ch3 figure 3: typical fame chemical structure and the reactive sites in the molecule the disadvantages are caused by the chemical structure, which can be seen in figure 3 [10, 15, 21]: high unsaturated content (causing bad thermal, oxidation, and thus storage stability), high water content (corrosion problems) sensitivity to hydrolysis (poor storage stability), methanol content (toxic), reactive oh-group (corrosion of coloured metals), low energy content that results in greater fuel consumption (~ 10–15%), unfavourable cold properties (cold-start and pulverizing, cfpp). high production costs compared to the applicational value, limited feedstock supplies, etc. bio gas oil the most suitable for the utilization in diesel engines and the most valuable compounds of the fossil derived gas oils are the normaland iso-paraffins with high cetane number and with good cold flow properties. therefore, intense research has started to produce products with a similar chemical structure on triglyceride base, which do not have the disadvantages of the already utilised biodiesel because of their different (more stable) chemical structure and thus they can be blended to conventional fuels with no limitations [11–24]. one of the alternatives to produce such a product rich in iso-paraffins on triglyceride base is the catalytic hydrogenation (fig. 1) and if necessary, their isomerisation [25–27]. figure 4: the reaction pathway of the bio gas oil production (r1, r2, r3: carbon chains with c11-c23 carbon number) 47 through the reaction pathway, in the first step the hydrogenating of the unsaturated bonds of the triglycerides takes place, then deoxygenating reaction occurs by three different pathways: decarboxylation, decarbonylation, and hydrodeoxygenation (reduction, hdo). as the next possible step in the process, isomerisation reactions can occur, of which measure depends on the applied catalyst and process parameters. cracking reactions may occur in the course of the whole process [11–24]. the product of the reaction is the so called bio gas oil, which is a mixture of nand i-paraffins in the gas oil boiling point range, made with specific catalytic hydrogenating process of raw materials with high triglyceride content (vegetable oils, animal fats, used frying oils, brown greases of sewage works etc.) [11, 13, 15, 21]. to produce bio gas oil and products containing it, there are different technological methods (figure 5). figure 5: possible technological solutions to produce bio gas oil it is possible to pre-treat the triglyceride containing feedstock in a pre-treater reactor and then hydrodeoxygenate it, in other words, convert it in a second hdo reactor as a stand-alone unit. the obtained product in this technology is rich in normal-paraffins, has very high cetane number (90–105), but besides it, the product needs to be isomerised after the separation to improve its poor cold flow properties (18–26°c) [14, 20–21, 25, 27]. the bio gas oil obtained with such a technology can be blended to deeply desulphurized gas oil stream and thus gas oil with bio component content can be made. beyond that, through blending the pre-treated triglyceride containing feedstock to a straight run gas oil stream and process this feedstock mixture in an existing (or slightly modified) desulphurization plant, bio-component containing gas oil can be obtained (fig. 2) [15–19, 24]. as we mentioned before, a wide range of publications deal with the examination of the conversion of triglycerides per se, or the so called co-processing. however, these articles deal mostly with the hydroconversion of vegetable oils (sunflower oil and rapeseed oil mostly). the bio gas oil – as we already mentioned – can be produced from animal fats and any kind of fats and oils beside vegetable oils, too. this is important, because the increasing degree of the cultivation of oilseeds takes the land from the cultivation of food and fodder, and thus it can have an influence on the food prices. however, as a by-product or waste of the food industry and the agricultural sector, streams rich in triglycerides (rendered fats from slaughterhouse by-products and animal carcasses) forms, which can be applied for the production of bio gas oil, and thus they do not affect the food prices. in this paper, we investigate the hydroconversion of rancid lard, which can adumbrate the possibility of the application of such animal derived feedstocks. experimental during the experimental work our aim was to investigate the possibilities of bio gas oil and bio gas oil containing gas oils on waste fat basis via the hydroconversion of waste rancid lard in itself and as a 50% mixture with gas oils. we investigated the application of a como/al2o3 catalyst in sulphide and in non-sulphide state. in the course of the experiments, we studied the effects of the process parameters on the quality and yield of the products and in addition the utilisation possibilities of the main product. experimental equipment the experiments were carried out in experimental equipment (tubular reactor of 100 cm3 active volume capacity) in continuous mode [15, 17, 19, 21]. 48 figure 6: experimental equipment (legend: 1, 6, 11, 13, 14, 18, 20, 22, 26, 30, 34, 36, 37, 38: throttle valves; 2, 8, 31, 39: controlling valves; 3, 7, 9, 15: manometers; 4: deoxygenizer; 5: gasdrier; 10, 28: gasfilter; 12: gasflow measurer; 16, 23: non-return valve; 17: holding burette; 19: feeder burette; 21: pump; 24: preheater; 25: reactor; 27, 29: chillers; 28: separator; 33: pressure register; 35: pressure controller; 40: gas-meter) applied feedstocks and catalyst as the base stock of the heterogeneous catalytic hydrogenating experiments we used lard (fatty acid composition is in table 1) of hungarian origin and a deep desulphurized gas oil stream (properties in table 2) – derived by mol plc. – obtained from russian crude. as feedstock we used pure lard, pure gas oil, and their mixtures of 50%. table 1: the typical fatty acid composition of the applied lard feedstock fatty acid lard c14:0 1.19 c16:0 21.35 c16:1 2.04 c18:0 11.54 c18:1 45.40 c18:2 12.50 c18:3 0.78 c20:1 1.06 c22:2 0.67 *cx:y, where x: carbon number of the fatty acid, y: number of the unsaturated bonds in the fatty acids. table 2: the heteroatom and aromatic content of the feedstocks properties gas oil lard boiling point range, °c 197.8–383.2 sulphur content, mg/kg 5 20 nitrogen content, mg/kg <1 61 aromatic content, % 22.5 polyaromatic content, % 2.4 0.0 we investigated the application of a como/al2o3 catalyst in sulphide and in non-sulphide state in the course of the experiments. in the first case, the catalyst had been sulphided “in-situ”, and the sulphur content of the feedstock was adjusted to 1000 mg/kg with the use of a sulphur containing chemical (dimethyl-disulphide, which is easily degradable in the investigated process conditions) to preserve the sulphide state of the catalyst. process parameters the process parameters were based on previous experimental results, considering both the physical and chemical properties of the feedstock. the series of the experiments were carried out at the following process parameters: temperature: 300–380°c, pressure: 40–80 bar, lhsv: 1.0–2.0 h-1, h2/feedstock ratio: 600 nm3/m3. analytical methods the properties of the feedstock and the products were specified according to the specifications of the valid en 590:2009 + a1:2010 diesel fuel standard, and with standardised calculation methods. the obtained liquid organic product’s composition was identified by high temperature gas chromatography [15, 25]. obtaining the main product fraction the fractionating of the product mixture was carried out as it can be seen in figure 7. in the course of the experiments, the product mixture was separated into gaseous and liquid phases in the separator unit of the 49 experimental equipment. after separating the water from the obtained liquid product mixture, we separated the light, c5-c9 hydrocarbon products by distillation up to 180°c from the organic liquid phase. the fraction above the boiling point of 180°c was separated to gas oil boiling point range main product (c10-c22 hydrocarbons up to the boiling point of 360°c) and to residual fraction by vacuum-distillation. figure 7: the method of the product fractionating all product yields are based on the amount of the feedstock. results and discussion the gaseous phase, besides hydrogen, contained carbonoxides formed during the deoxygenation, propane originating from the triglyceride molecule, hydrogen sulphide and ammonia formed in the course of heteroatom removal, and a very small amount of lighter hydrocarbons (c4-) originating from the hydrocracking reactions. with increasing the temperature, the yield of the gaseous product slightly increased because the cracking reactions came to the front and the deoxygenation, desulphurisation, and aromatic saturation reactions took place increasingly. the yield of the main product fractions increased with increasing temperature (figure 8–12) in the case of both sulphide and non-sulphide state catalyst, which refer to the increasing conversion of the feedstock triglyceride content. 0 10 20 30 40 50 60 70 80 90 280 300 320 340 360 380 400 y ie ld o f t he m ai n pr od uc t f ra ct io n, % hőmérséklet, °c 50% lard, 40 bar 50% lard, 60 bar 50% lard, 80 bar 100% lard, 40 bar 100% lard, 60 bar 100% lard, 80 bar figure 8: yield of the main product fraction as a function of temperature and pressure (catalyst: non-sulphided como/al2o3; lhsv = 1.0 h-1; h2/feedstock ratio: 600 nm3/m3) 20 30 40 50 60 70 80 90 280 300 320 340 360 380 400 y ie ld o f t he m ai n pr od uc t f ra ct io n, % temperature, °c 50% lard, 40 bar 50% lard, 60 bar 50% lard, 80 bar 100% lard, 40 bar 100% lard, 60 bar 100% lard, 80 bar figure 9: yield of the main product fraction as a function of temperature and pressure (catalyst: sulphided como/al2o3; lhsv = 1.0 h-1; h2/feedstock ratio: 600 nm3/m3) as a function of the pressure (fig. 8, 9) – in the investigated parameter range – there were no clear trends; in the case of sulphided catalyst and pure lard feedstock, the higher pressure (80 bar) seemed to be favourable, but in the case of mixture feedstock, the lower pressure seemed to be favourable; in the case of non-sulphided catalyst and pure lard feedstock, the lower pressure (40 bar) seemed to be favourable, but in the case of mixture feedstock, the pressure of 60 bar seemed to be favourable. 0 10 20 30 40 50 60 70 80 90 280 300 320 340 360 380 400 y ie ld o f t he m ai n pr od uc t f ra ct io n, % hőmérséklet, °c 50% lard, lhsv = 1.0 1/h 50% lard, lhsv = 1.5 1/h 50% lard, lhsv = 2.0 1/h 100% lard, lhsv = 1.0 1/h 100% lard, lhsv = 1.5 1/h 100% lard, lhsv = 2.0 1/h figure 10: yield of the main product fraction as a function of temperature and lhsv (catalyst: non-sulphided como/al2o3;p = 80 bar; h2/feedstock ratio: 600 nm3/m3) 0 10 20 30 40 50 60 70 80 90 280 300 320 340 360 380 400 y ie ld o f t he m m ai n pr od uc t f ra ct io n, % hőmérséklet, °c 50% lard, lhsv = 1.0 1/h 100% lard, lhsv = 1.0 1/h 50% lard, lhsv = 1.5 1/h 100% lard, lhsv = 1.5 1/h 50% lard, lhsv = 2.0 1/h 100% lard, lhsv = 2.0 1/h figure 11: yield of the main product fraction as a function of temperature and lhsv (catalyst: non-sulphided como/al2o3;p = 80 bar; h2/feedstock ratio: 600 nm3/m3) 50 decreasing the liquid hourly space velocity favoured the triglyceride conversion to paraffins in the case of both feedstock and the state of the catalyst, so the yield of the main product fraction increased with decreasing the liquid hourly space velocity (fig. 10, 11). this was caused by the higher retention time of the reactants on the active sites. based on the yields of the main product fractions in the cases of both states of the catalyst (fig. 12), we determined that in the case of the sulphide state catalyst, the yield of the main product fraction was higher, but not even in this case was the conversion of the triglycerides full, because the yield of the residual fraction was still significant (figure 13). 0 10 20 30 40 50 60 70 80 90 280 300 320 340 360 380 400 y ie ld o f t he m ai n pr od uc t fr ac tio n, % temperature, °c 100% lard, sulphided como/al2o3 100% lard, non-sulphided como/al2o3 50% lard, sulphided como/al2o3 50% lard, non-sulphided como/al2o3 figure 12: yield of the main product fractions as a function of the temperature in the case of different feedstock and states of the catalyst (p: 80 bar; lhsv: 1.0 h-1; h2/feedstock ratio 600 nm3/m3) the decreasing of the yield of the residual fraction (fig. 13) with increasing the temperature also provides information about the increasing conversion of the triglyceride content of the feedstock, but at the strictest process parameters, the yield of the residual fraction was still significant. 0 10 20 30 40 50 60 70 80 280 300 320 340 360 380 400 y ie ld o f t he r es id ua l f ra ct io n, % temperature, °c 100% lard, sulphided como/al2o3 100% lard, non-sulphided como/al2o3 50% lard, sulphided como/al2o3 50% lard, non-sulphided como/al2o3 figure 13: yield of the residual fractions as a function of the temperature in the case of different feedstocks and states of catalyst (p: 80 bar; lhsv: 1.0 h-1; h2/feedstock ratio 600 nm3/m3) figure 14 provides information about how the different deoxygenating reactions (mechanisms) take place and about the relationship between them. in the course of the deoxygenation of the natural – and so containing fatty acids with conjugated carbon numbers in their carbon chains – triglycerides, during the hydrodeoxygenation (hdo) reaction pathway paraffins with the same carbon numbers as the fatty acids form next to water. in the course of decarboxylationdecarbonylation (dco) reaction pathways, paraffins with one less carbon numbers as the fatty acids form next to carbon oxides. the hdo/dco ratio of the hydroconversion pathways, which is favourable for the yield of the main product fraction, was higher in the case of non-sulphided catalyst than in the case of the sulphided catalyst. 0 2 4 6 8 10 12 14 16 18 20 0,5 1,0 1,5 2,0 2,5 3,0 280 300 320 340 360 380 400 h d o /d c o r at io o n no nsu lp hi de d ca ta ly t h d o /d c o r at io n on s ul ph id ed c at al ys t temperature, °c sulphided como/al2o3 non-sulphided como/al2o3 figure 14: the change in the ratio of the different routes of oxygen removal as a function of the temperature (p: 80 bar; lhsv: 1.0 h-1; h2/feedstock ratio: 600 nm3/m3) the isoparaffin content of the main product fractions (high isoparaffin content is favourable for the good cold flow properties) was the highest in the case of the nonsulphided state como/al2o3 catalyst (figure 15), because of the high isomerisation activity of the non-sulphided como bimetallic system [25]. 0,00 0,05 0,10 0,15 0,20 0,25 280 300 320 340 360 380 400 r at io o f i -p ar af fin /n -p ar af fin temperature, °c sulphided como/al2o3 non-sulphided como/al2o3 figure 15: the change in the isoand normal-paraffin content of the products as a function of the temperature (p: 80 bar; lhsv: 1.0 h-1; h2/feedstock ratio: 600 nm3/m3) conclusion in this paper we shortly presented the necessity of the research and development of the bio-derived motorfuels, the already known bio-derived fuels of dieselengines, and the bio gas oil or bio gas oil containing gas oil producing technologies, respectively. during the experimental work, our aim was to investigate the 51 possibilities of bio gas oil and bio gas oil containing gas oils on waste fat basis via the hydroconversion of waste rancid lard in itself and as a 50% mixture with gas oils on a como/al2o3 catalyst in sulphide and in nonsulphide state. the experimental results adumbrate the industrial application of different animal derived (waste) fats, with which the feedstock supplies can be expanded, for the production of bio derived motor fuel components to expand the feedstock supplies. the properties of the feedstock and the products were specified according to the specifications of the valid en 590:2009 + a1:2010 diesel fuel standard, and with standardised calculation methods. in the case of mixture feedstock and sulphide state como/al2o3 catalyst, the yield of the main product fraction (81%) was higher than in the case of nonsulphided state como/al2o3 catalyst (72%) at the strictest process parameters. however, in both forms (i.e. sulphided and non-sulphided) of the applied catalyst, the yield of the unconverted residual fraction (boiling point >360°c) was significant. the cause of this was that the oxygen content of the lard is high, about 11%. besides this, it contains compounds (n-compounds) that strongly adsorb to the catalytically active sites, and thus decrease the possibilities of the deoxygenating reactions to take place. the hdo/dco ratio of the hydroconversion pathways which is favourable for the yield of the main product fraction was higher in the case of non-sulphided catalyst than in the case of the sulphided catalyst. the iso-paraffin content of the main product fractions (high iso-paraffin content is favourable for the good cold flow properties) was the highest in the case of non-sulphided state como/al2o3 catalyst, because of the high isomerisation activity of the non-sulphided como bimetallic system. the properties of the main product fractions obtained at these process parameter combinations meet the valid diesel gas oil standard en 590:2009 + a1:2010, except for their cold flow properties (cfpp). however, these products could be excellent diesel gas oil blending components because of their very low sulphur and nitrogen content, and decreased aromatic content, and because their high cetane number is ensured by the n-paraffins forming during the triglyceride conversion. the cold flow properties of the products can be improved by catalytic hydroisomerisation of the n-paraffins then with additives. thus, a high quality bio-motor fuel or bio-derived blending component containing diesel motor fuel can be obtained which meets the valid diesel gas oil standard. briefly, we determined that considering the yield of the main product fraction the sulphided state como/al2o3 catalyst is more preferable for the hydroconversion of lard. in the case of non-sulphided state catalyst, the main product fraction contained a higher amount of i-paraffins, which are beneficial from the point of view of cold flow properties. the experiments were carried out on a “once flow” reactor system. therefore, it may be a possibility for increasing the conversion to separate the residual fraction from the product and recycle it to the reactor. to corroborate, further experiments and tests should be carried out. acknowledgement this work was supported by the european union and co-financed by the european social fund in the frame of the támop-4.2.1/b-09/1/konv-2010-0003 and támop-4.2.2/b-10/1-2010-0025 projects. references 1. directive 2003/30/ec of the european parliament and of the council, official journal of the european union (2003) 31(13) pp. 188–192 2. commission of the european communities, com (2006) 848, 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catalysis in liquid phase, applied catalysis a: general, volume 192, issue 1, 4 february 2000, pp. 9–22 27. j. hancsók, s. kovács, gy. pölczmann, t. kasza: investigation the effect of oxygenic compounds on the isomerization of bioparaffins over pt/sapo-11, topics in catalysis (2011) 54, pp. 1094–1101 hungarian journal of industrial chemistry veszprém vol. 33(1-2). pp. 97–104 (2005) model predictive control of continuous crystallizers n. moldoványi1 and b.g. lakatos2 1honeywell process solutions, h-1139 budapest petneházy u. 2-4 hungary, 2department of process engineering, university of veszprém, h-8201 veszprém, p.o. box 158, hungary the problem of model predictive control of continuous isothermal crystallizers, using a detailed moment equation model is analysed. the mean size of the crystalline product and the variance of crystal size are the controlled variables, while the manipulated variables are the input concentration of the solute and the flow-rate. the controllability and observability, as well as the coupling between the inputs and the outputs are analyzed by simulation using the linearised model. the crystallizer has proved to be a nonlinear multi-input multi-output system with strong coupling between the state variables. it is shown that the mean crystal size and the variance of can be controlled nearly separately by the residence time and the inlet solute concentration, respectively. by seeding, the controllability of the crystallizer increases significantly. the linear model predictive controller synthesized using the moment equation model appears to be an efficient controller for continuous crystallizers. keywords: model predictive control; continuous isothermal crystallizer, computer simulation introduction model predictive control (mpc) refers to a class of computer control algorithms that utilize an explicit process model to predict the future response of the plant. at each control interval an mpc algorithm attempts to optimize future plant behaviour by computing a sequence of future manipulated variable adjustments. the first input in the optimal sequence is then sent into the plant, and the entire calculation is repeated at subsequent control intervals [1]. originally developed to meet the specialized control needs of power plants and petroleum refineries, mpc technology can now be found in a wide variety of application areas including chemicals (honeywell has mpc at polypropylene units at tvk, hungary), food processing (honeywell is right now working on a dairy product unit at the uk), automotive and aerospace applications. the presented work is an opening to an another new application, the mpc control of continuous crystallizers. crystallization is a widely used cleaning, separation and grain producing technique in the chemical industry, particularly at the pharmaceutical works. from the point of view of controlling a crystallizer the main quality criteria are the properties of the produced crystals, first of all the size-distribution and the mean size. crystallization is a multi-variable system, with multi input and multi output (mimo) often with strong coupling. thus a good, up-to-date control is possible using a model-based mimo control system. there are only few examples in the literature for this [2-5]. since one can do nothing to change the size distribution of the crystals in the system once crystals have grown beyond a stable nucleus size. therefore a predictive type of control would be better than the corrective type. one of the main problems is that for a proper model-based control of the sizedistribution, because of the mentioned properties of the population balance equation, high-order control is required, which means serious difficulties. but the crystallizers are dissipative systems [6], so that a crystallizer as a dynamical system possesses finite dimensional global attractors [7] that create an adequate basis for the synthesis and usage of good quality, low-order model-based control systems. at the same time it means that for the synthesis of the model-based control system of crystallizers the moment equation model, generated from population balance equation governing the crystal size distribution can be used. chui and cristofides [8] applied this property to design a nonlinear siso controller. in this paper a model-based mimo control system of a continuous isothermal crystallizer is presented. for the synthesis of the control system a multi-variable statespace model is composed. linear controllability and observability analysis is presented, and the coupling of the inputs and the outputs are analysed. the efficiency of the developed model predictive controller is demonstrated by simulation. 98 concept of mpc in model predictive control, the control action is provided after solving – on-line at each sampling instant – an optimization problem, and the first element in the optimized control sequence is applied to the process (receding horizon control). the “moving horizon” concept of mpc is a key feature that distinguishes it from classical controllers, where a pre-computed control law is employed. the major factor of the success of predictive control is its applicability to problems where analytic control law is difficult, or even impossible to obtain. the methodology of all the controllers belonging to the mpc family is characterized by the following strategy, represented in fig.1 (y is the output, w is the setpoint and u is the input): futurepast control horizon prediction horizon u(.) w(.) y(.) k k+1k-1k-2 k+2 fig 1. mpc horizons prediction horizon (hp) represents the number of samples taken from the future over which mpc computes the predicted process variable profile and minimizes the predicted error. the control signals change only inside the control horizon, hc remaining constant afterwards 1,...,),1()( −=−+=+ pcc hhjhkujku (1) the basic steps: 1. as it is shown, in the mpc future outputs for a determined prediction horizon hp are predicted at each instant k using a prediction model. these predicted outputs phjkjky ,...1),(ˆ =+ (means the value at the instant k+j, calculated at instant k) depend on the known values up to instant k (past inputs and outputs) and the future control signals 1,...0),( −=+ phjkjku , which are those to be sent to the system and to be calculated. 2. the set of control signals is calculated by optimizing a cost function in order to keep the process as close as possible to the reference trajectory . this criterion usually takes the form of a quadratic function of the errors between the predicted output signal and the reference trajectory. the control effort is included in the objective function in most of the cases. an explicit solution can be obtained if the criterion is quadratic, the model is linear and there are no constraints, otherwise an iterative optimization method has to be used. phjjkw ,...1),( =+ 3. the control signal )( kku is sent to the process whilst the next control signals calculated are rejected, because at the next sampling instant y(k+1) is already known and step 1 is repeated with this new value and all the sequences are brought up to date. thus the )11( ++ kku is calculated (which in principle will be different to the )1( kku + because of the new information available) using a receding horizon concept. in order to implement this strategy, the basic structure shown is fig.2 is used. a model is used to predict the future plant outputs, based on past and current values and on the proposed optimal future control actions. these actions are calculated by the optimizer taking into account the cost function (where the future tracking error is considered) as well as the constraints. optimizer model past inputs and outputs future inputs cost function constraints future errors predicted outputs reference trajectory + fig.2: basic structure of mpc the process model plays, in consequence, a decisive role in the controller. the chosen model must be capable of capturing the process dynamics so as to precisely predict the future outputs as well as being simple to implement and to understand. as mpc is not a unique technique but a set of different methodologies, there are many types of models used in various formulations. honeywell uses mostly black-box models at the refineries, getting them by stepping the plant. the new tendency is using chemical engineering, so called “greybox” models. the presented case study clearly fills this requirement. the optimizer is another fundamental part of the strategy as it provides the control actions. if the cost function is quadratic, its minimum can be obtained as an explicit function (linear) of past inputs and outputs and the future reference trajectory. in the presence of inequality constraints the solution has to be obtained by more computationally taxing algorithms. the size of optimization problems depends on the number of variables and on the prediction horizon used and usually turn out to be relatively modest optimization problems which do not require sophisticated computer codes to be solved. however the amount of time needed for the constrained and robust cases can be various orders of magnitude higher than that needed for the unconstrained case and 99 the bandwidth of the process to which constrained mpc can be applied is considerably reduced. for a continuous-time model (the cost function is discrete), the mpc problem can be represented as [ ,)(),(min )( kukyj ku ψ= ] (2) [ ] thttttutxftx p∆+≤≤= *,*)(*),(*)(ˆ (3) (3) [ ] thttthtthtutu pcc ∆+≤≤∆−+∆−+= *)1(,)1(*)( [ ],)(),(),(0 kukykxφ= (5) )(0 kdu≥ (6) )(0 kdy≥ (7) where ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ + + ≡ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ + + ≡ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ −+ + ≡ )( )1( )( )( , )( )1( )( )(, )1( )1( )( )( khkx kkx kkx kx khky kky kky ky khku kku kku ku p pc m mm . here, )( kku is the input calculated from information available at time k, )(ku )( kky is the output calculated from information available at time k, hc is the control horizon and hp is the prediction horizon, while x denotes the state variable. constraint (3) corresponds to satisfaction of the continuous-time model equations over the prediction horizon, while (4) enforces the requirement that all inputs beyond the control horizon are held constant. algebraic equation (5) represents constraints for the model, and for the sake of completeness eqs (6) and (7) correspond to the constraints on the input and output variables, respectively. )(ky the process model is assumed to have the following discrete-time representation, (8) [ ),(),()1( kukxfkx =+ ] ] (9) [ ,)()( kxhky = where x is the n-dimensional vector of state variables, u is the m-dimensional vector of manipulated input variables, and y is the p-dimensional vector of controlled output variables. such a model can be obtained by discretizing a continuous-time, state-space model or by deriving a state-space realization of a discrete-time, inputoutput model. it is important to note that time delays can be handled by augmenting the state vector such that the resulting state-space model has no delays. the optimization problem for the prototypical mpc formulation is [9]: [ ] [ ,)(),(),( )(min 1 0 )1(),...1(),( ∑ − = −++ +∆++ ++= p c h j pkhkukkukku kjkukjkukjkyl khkyj φ ] (10) where )1()()( kjkukjkukjku −+−+=+∆ , φ and l are (possibly) (non)linear functions of their arguments. the optimization problem is solved to the constraints discussed below. the functions φ and l can be chosen to satisfy a wide variety of objectives, including minimization of overall process cost. however, economic optimization may be performed by a higher-level system which determines appropriate setpoints for the mpc controller. in this case it is meaningful to consider quadratic functions of the following form: [ ] [ ] [ ] [ ] ),j(k)j(k )()ju(k)()ju(k )()jy(k)()jy(k kusku kukrkuk kykqkykl t s t s s t s +∆+∆+ −+−++ −+−+= (11) [ ] [ ])()h(k)()h(k pp kykyqkyky s t s −+−+=φ (12) where and are steady-state targets for u and y, respectively, and q, r, s are positive definite weighting matrices. the principal controller tuning parameters are hc, hp, q, r, s and the sampling period ∆t. )(kus )(kys the prediction outputs are obtained from the model (8-9). successive iterations of the model equations yield [ ] [ ][ ] [ ] [ ] [ ][ ] [ ] [ ],)1(),...1(),(),()( ,)1(),(),( ,)1(,)(),( ,)1(),1()2( ,)(),( ,)(),()1()1( 2 1 1 1 kjkukkukkukxgkjky kkukkukxg kkukkukkxfg kkukkxgkky kkukxg kkukkxfhkkxhkky j −++=+ +≡ +≡ ++=+ ≡ =+=+ m (13) where )()( kxkkx = is a vector of current state variables. if the control horizon (hc) is less than the prediction horizon (hp), the output predictions are generated by setting inputs beyond the control horizon equal to the last computed value: .,)1()( pcc hjhkhkukjku ≤≤−+=+ note that the prediction )( kjky + depends on the current stable variables, as well as on the calculated input sequence. therefore, mpc requires measurements or estimates of the state variables. solution of the mpc problems yields the input sequence { })1(),...,1(),( khkukkukku c −++ only the first input vector in the sequence is actually implemented: )()( kkuku = . then the prediction horizon is moved forward one time step, and the problem is resolved using new process measurements. this receding horizon formulation yields improved closed-loop performance in the presence of unmeasured disturbances and modelling errors. 100 case study: continuous crystallizer moment equation model the mathematical model of a continuous msmpr crystallizer consists of the population balance equation for crystals, of the balance equations for sol-vent and crystallizing substance, and of the equations describing the variation of the equilibrium saturation concentration. in the present analysis, the crystallizer is assumed to be isothermal, thus the equilibrium saturation concentration c* is constant during the course of the process. it is assumed that the following conditions are satisfied: (1) the volumetric feed and withdrawal rates of the crystallizer are constant and equal, thus the working volume is constant during the course of the operation; (2) the crystals can be characterized by a linear dimension l; (3) all new crystals are formed at a nominal size ln≅0 so that we assume ln=0; (4) crystal breakage and agglomeration are negligible; (5) no growth rate fluctuations occur; (6) the overall linear growth rate of crystals g is size-dependent and has the form of the power law expression of supersaturation ; (14) ( alcckg g g +−= 1*)( ) (7) the primary nucleation rate bp is described by the volmer model ⎟⎟ ⎟ ⎟ ⎟ ⎠ ⎞ ⎜⎜ ⎜ ⎜ ⎜ ⎝ ⎛ ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ −= * ln exp 2 c c kkb e pp ε (15) the secondary nucleation rate bs is described by the power law relation (16) jb bb cckb 3*)( µ−= where µ3 is the third of the ordinary moments of the population density function n, which are defined as (17) ...3,2,1,0,),( 0 == ∫ ∞ mdltlnlm mµ with these assumptions the population balance equation governing the crystal size dynamics becomes: [ ] [ 0,0 ),(),(),(*),,(),( >> −=⎟ ⎠ ⎞ ⎜ ⎝ ⎛ + lt tlntlnq l tlnclcg t tlnv in∂ ∂ ∂ ∂ ] (18) subject to the following initial and boundary conditions: (19) 0),()0,( 0 ≥= llnln 0,*),,(),(*),,(lim 0 ≥== → tbpccbtlnclcg l νν (20) (21) 0,0),(lim ≥= ∞→ ttln l here, n(l,t)dl expresses the number of crystals having sizes in the range l to l+dl at time t in a unit volume of suspension. the mass balance of the crystallizing substance has the form [ ] [ cin c cqqc dt cdv ρεε ρεε )1()1( −+−= −+ ] (22) with the initial condition (23) 0)0( cc = where the voidage of suspension ε is related to n and l by (24) ∫ ∞ −=−= 0 3 3 ),(11 dltlnlkk vv µε finally, the mass balance of the solvent is written in the form ( ) svsvin sv cqqc dt cdv ε ε −= (25) with the initial condition . (26) 0)0( svsv cc = therefore, the state at time t≥0 of the continuous isothermal msmpr crystallizer is given by the triple [c(t),csv(t),n(t)], and its dynamics is described by the distributed parameter model formed by the mixed set of partial and ordinary differential eqs (18), (22) and (25), subject to the initial and boundary conditions (19-21) (23) and (26). the evolution in time of this system occurs in the state space r2×n that is the descartes product of the vector space r2 of concentrations and of the function space n of the population density functions. consideration of dynamical problems of crystallizers in this product space, however, seems to be quite complex and not constructive. in the present study, we concentrate on a reduced case, considering the problem in a finite dimensional state space model based on the moments of the population density function instead of the distributed parameter system (18)-(21). since the overall crystal growth rate (14) is a linear function of size l, the population balance eq. (18) can be converted into an infinite set of recursive ordinary differential equations for the moments of population density function: ( ) bpvbq dt dv in ,,00 0 =+−= νµµ µ ν (27) ( ) )(*)( 1min mm g gm m accvmkq dt dv µµµµ µ +−+−= − m=1,2,3 (28) which can be closed by eq.(22), describing the mass balance of the crystallizing substance, at the equation for the third order moment. then eq.(22) takes the form )(*))((31)( 32 µµρ εε acccvkkccq dt dcv g cgvin +−−−−= (29) while eq.(12) can be rewritten as )(*)(31)( 32 µµ εε accvckkccq dt dcv g svgvsvsvin sv +−−−= (30) 101 where csv stands for the concentration of solvent. here, because of the selective withdrawal, the voidage in the crystallizer and that in the outlet stream are not equal. therefore, the first four moment equations from the system (27-28) with eqs (29-30) provide a closed moment equations model of the crystallizer. dimensionless equations. scaling we introduce the following set of dimensionless variables svincsvinsvcsvincin cmmmt csycsyccsy ccsymsxts ==−= −==== ,*),( *),(,3,2,1,0,, µξ into eqs (27)-(30), where st, sc and sm, m=0,1,2,3, are scale factors defined as *}max{ 1: cc s in c − = , , ( g intgv ccskks 333 0 *}max{6: −= − ) ( ) g intgv ccskks 222 1 *}max{6: −= − ( )gintgv ccskks *}max{3: 1 2 −= − vks =:3 and max{cin} denotes the maximal value of inlet concentration, as well as the set of dimensionless parameters q vsts tt ==:τ , ( 1*}max{*)(: −−−= ccc inρα ) ( )gintg ccask *}max{: 1 −= −β ( ) g intgvpap ccskkkd 343 *}max{6: −= − ( ) bg intg j vbab ccskkkd +−− −= 3431 *}max{6: *}max{ **: cc ccs in c − ==γ then the dimensionless governing equations take the form: bpxx d dx in ,,000 =θ+ − = ν τξ ν (31) 3,2,1),( 1 min =++ − = − mxmxyxx d dx mm gmm β τξ (32) ( ) 3 32 3 1 )3()( 1 x xxyy x yy d dy g in − +− − − − = βα τξ (33) ( ) 3 32 3 1 )3( 1 x xxyy x yy d dy g svsvsvinsv − + + − − = β τξ (34) subject to the initial conditions 000 )0(,)0(,3,2,1,0,)0( svsvmm yyyymxx ==== where ( ) ⎟ ⎟ ⎟ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎜ ⎜ ⎜ ⎝ ⎛ ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ + −−= γ γ θ y kxd e app 2 3 ln exp1 (36) and jb abb xyd 3=θ . (37) it follows from physical reasoning that the physically admissible solutions to eqs (31-34) should satisfy the constraints 110,0 ,0,0,0 minmax33 3 1 022 3 2 01100 <−=<≤≤≤ ≤≤≤≤≤≤ εxxxax xaxxxyy m mmin (38) where x0m denotes the maximal value of the zero order moment, while ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ − = ρ ε *1 min cv vsv (39) where vsv is the volume of solvent in the crystallizer. the parameters, which in the case of primary and secondary nucleation form the vectors of real numbers pp=(τ,α,g,β,dap,ke,γ) and pb=(τ,α,g,β,dab,b,j), respectively, are also bounded: 0,0,0,0 0,0,,0,0,0 min ≥≥≥≥ ≥≥≥≥≥≥ γ ββατ jbk ddg e abap (40) as a consequence, the state of crystallizer (31)-(34) is represented by the vector of variables (x0,x1,x2,x3,y, ysv), and its time evolution occurs in the feasible region of solutions (38) of the six-dimensional state space r6. the behaviour of crystallizer in the neighbourhood of a stationary state may be deduced by examining the eigenvalues of the jacobian matrix of eqs (36-38) at this state which becomes ( ) ( ) ( ) ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ − + − − − − − − − − − − − − − − − − − − − − − )1( 1 )1( )( 1 3 1 00 0 1 )(3 1 )( 00 01300 00120 0001 0001 3 3 333 55 33 33 22 11 1514 s s ss svssvin s g ssvs s g ssvs s s g ss s g ss s insg s g s s insg s g s s insg s g s ss x x xy yyg x yy x yy j x yy x yy y xxgyy y xxgyy y xxgyy jj τ β αβα ττ β ττ β ττ β τ νν (41) where in the case of primary nucleation ( )s sin ps x xx j 3 00 14 1− − = τ and ( ) ( ) ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ + + − = γ γ γτ s s inse ps yy xxkj 3 00 15 ln 2 (42) ( )[ ] ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ − −−− +− − = )( )(1 1 1 3 55 ss sssin s s yy ygyyy x j ατ α τ while for secondary nucleation s s ss x x jj 3 0 14 = and s s ss y sj 0 15 = x (43) in order to formulate the state-space model, we define ( ) ( )6543213210 ,,,,,,,,,, uuuuuuwyxxxx ininininin ==u (44) where τττ ω ==== v qtq vsssvqsw . (45) now: 102 bpxxw d dx in ,,000 =θ+ ω − = ν ξ ν (46) )( 1 min mm gmm xmxyxxw d dx β ωξ ++ − = − m=1,2,3 (47) ( ) 3 32 3 1 )3()( 1 x xxyy x yyw d dy g in − +− − −ω − = βα ξ (48) ( ) 3 32 3 1 )3( 1 x xxyy x yyw d dy g svsvsvinsv − + − −ω − = β ξ (49) subject to the initial conditions 000 )0(,)0(,3,2,1,0,)0( svsvmm yyyymxx ==== (50) i.e. bpxuu d dx ,,01 6 0 =θ+ ω − = ν ξ ν (51) )( 16 mm gmmm xmxyxuu d dx β ωξ ++ − = − , m=1,2,3 (52) ( ) 3 32 3 5 6 1 )3()( 1 x xxyy x yuu d dy g − +− − −ω − = βα ξ (53) ( ) 3 32 3 5 6 1 )3( 1 )( x xxyy x yuyu d dy g svsvsvinsv − + − −ω − = β ξ (54) where ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −=⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −= ρ ρ ρ ρ 5usysy csv in csvsvin (55) to summarize as a control engineering problem: vector of state-variables is x=(x0,x1,x2,x3,,y,ysv), its changes represented by a nonlinear state space model (51)-(55); the input vector of is u=(x0in,x1in,x2in,x3in,yin,w) and the output is defined as y=x. analysis of the model stability and bifurcation in linear dynamics, one seeks the fundamental solutions from which one can build all other solutions. in nonlinear dynamics, the main questions are: what is the qualitative behaviour of the system? which and how many non-wandering sets (i.e. a fixed point, a limit cycle, a quasi-periodic or chaotic orbit) occur? which of them are stable? how does the number of nonwandering sets change while changing a parameter of the system (called control parameter)? the appearance and disappearance of a non-wandering set is called a bifurcation. change of stability and bifurcation always coincide. the number of attractors in a nonlinear dynamical system can change when a system parameter is changed. this change is called bifurcation. it is accompanied by a change of the stability of an attractor. in a bifurcation point, at least one eigenvalue (λ) of the jacobian matrix gets a zero real part. there are three generic types of socalled co-dimension-one bifurcations (the term codimension counts the number of control parameters for which fine tuning is necessary to get such a bifurcation). back to the crystallizer, changing the value of ke, the parameter of primary nucleation rate and observing the supersaturation, hopf bifurcation occurs as it shown in fig.3. 0,45 0,4 ymin ymax 0,35 0,3 fig. 3: bifurcation diagram ke-ys of the crystallizer for further studies of controlling the crystallizer an operating point has been chosen from the region of stable steady states exhibiting only damped oscillations, that is at ke=0.01. controllability and observability there are two basic problems we need to consider. the first one is the coupling between the input and the state: can any state be controlled by the input? this is a controllability problem. another is the relationship between the state and the output: can all the information about the state be observed from the output? this is an observability problem. for the controllability and observability test a linearized model (at the operating point) of the nonlinear system was used. xcy buaxx t= +=& (56) where the state transition matrix (a) is the jacobi matrix of the system, the input matrix (b) can also be derived from the model and the output matrix (ct) is a diagonal matrix. for a mimo system the necessary and sufficient conditions for the system to have completely controllability is nrank =⎥⎦ ⎤ ⎢⎣ ⎡ − babaabb 1n2 l (57) for the general system the necessary and sufficient condition of a linear system for complete observability is nrank t nttt =⎥⎦ ⎤ ⎢⎣ ⎡ − cacacac 12 )()( l (58) the results of the calculation is that the linearized system is completely controllable and observable at a certain operating point. 0 0,0 0,1 0,15 0,2 0,25 bifurcation point ys damped oscillations 0,001 0,01 0,1 limit-cycle oscillations 1ke 103 relative –gain array )1()1( ))(ˆ)(())(ˆ)(( ),,,,( 1 21 2 1 −+−++ +−++−+ = ∑ ∑ = = jkjk jkjkjkjk hhhj c p p h j t t h hj cpp ∆ur∆u ywqyw qr (61) the relative-gain array provides exactly a methodology, whereby we select pairs of input and output variables in order to minimize the amount of iteration among the resulting loops. it was first proposed by bristol and today is a very popular tool for the selection of control loops. where denotes the predicted process outputs, and are the minimum and the maximum prediction horizons, is the control horizon, q and r are positive definite weighting matrices. )(ˆ jk +y 1ph 2ph ch in our crystallization system the control variables can be the mean size of crystals, the variance of the crystal size (σ2) and the productivity, i.e. the total volume of the crystals: 33 2 0 1 0 2 2 0 1 1 ,, x x x x x x x =⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −== υυυ (59) the manipulated variables are the input concentration of the solute and the flow-rate: . (60) wuyu in ==== 6251 , ϑϑ an optimization algorithm will be applied to compute a sequence of future control signals that minimizes the cost function. for unconstrained control based on linear process model(s) and quadratic cost function the control sequence can be analytically calculated. after tuning the , the and 3=ch 11 =ph 52 =ph . by seeding, the controllability of the crystallizer increase, the overshoots and the oscillation are smaller. the results of the controlling study have shown that the linear mpc is an adaptable and feasible controller as it illustrated by fig.4. here, the first two rows are the outputs (solid lines) with the corresponding setpoints (dashed lines), while the third and fourth rows present the time variations of the inputs of the crystallizer. note that since the volume of the crystal suspension was kept constant the mean residence time was varied by changing the volumetric feed. for the crystallizer we have two outputs and two inputs, there are three possible pairs of control variables, so three different relative-gain arrays can be formed and computed (the value 0 and 1 are rounded.): ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ ∆ ∆ ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ − − =⎥ ⎦ ⎤ ⎢ ⎣ ⎡ ∆ ∆ 2 1 2 1 21.12821.127 21.12721.128 ϑ ϑ υ υ , ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ ∆ ∆ ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ =⎥ ⎦ ⎤ ⎢ ⎣ ⎡ ∆ ∆ 2 1 3 1 10 01 ϑ ϑ υ υ ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ ∆ ∆ ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ =⎥ ⎦ ⎤ ⎢ ⎣ ⎡ ∆ ∆ 2 1 3 2 10 01 ϑ ϑ υ υ the results show that controlling the mean size and the variance together would be very difficult. however, by putting crystal grains to the input (seeding), the control of the variance also becomes possible. the new different relative-gain array: fig.4. performance of the mpc of the continuous isothermal msmpr crystallizer ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ ∆ ∆ ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ − − =⎥ ⎦ ⎤ ⎢ ⎣ ⎡ ∆ ∆ 2 1 2 1 24.124.0 24.024.1 ϑ ϑ υ υ in this case, the mean-size and the variance can be nearly separately controlled. for the further experiments these two outputs will be selected. the system is very sensible to the quality and the quantity of the seeding. it is assumed to be fixed to a suitable operating point. results of simulations the cost function is chosen to satisfy a wide variety of objectives, including minimization of overall process costs. however, economic optimization may be performed by a higher-level system which determinates the appropriate setpoints for the controller. in this case cost function is formulated reflecting the reference tracking error and the control action. the general expression of such an objective function is 104 next steps references 1. qin s. j. and badgwell t.a control engineering practice, 2003, 11, 733-764 the presented model is going to be developed in unisim, the simulation software of honeywell, to make possible to connect it to the profit controller. the mpc of honeywell. the final step is to control a real continuous crystallizer at a plant. 2. myerson a.s. et al. proc. 10th symposium. industrial crystallization. academia, praha, 1987 3. jager, j., et al. powder technology, 1992, 69, 11 4. miller, s.m. and rawlings, j.b., aiche journal, 1994, 40, 1312 conclusions 5. rohani, s. et al. computers and chemical engineering, 1999, 23, 279. 6. lakatos, b.g. and sapundzhiev, ts.j., bulgarian chemical communications, 1997, 29, 28 the moment equation model of a continuous isothermal msmpr crystallizer was presented and the model was analyzed. better control of the variance of the crystal size was possible by introducing some seeding into the crystallizer. by seeding, the controllability of the crystallizer increase, the overshoots and the oscillation are smaller. the results of the controlling study have shown that the linear mpc is an adaptable and feasible controller for continuous crystallizers. 7. temam, r., infinite-dimensional dynamical systems in mechanics and physics. springer-verlag, new york, 1988 8. chiu, t. and christofides, p.d., aiche journal, 1999, 45, 1279 9. meadows, e.s. and rawlings, j.b, model predictive control, englewoods cliffs. nj: prenticehall, 1997 nonlinear process control, chapter 5. (233-310). microsoft word 2012_dr_bodor_endre_hjic.doc hungarian journal of industrial chemistry veszprém vol. 39(3) pp. 419-425 (2011) asymmetric lactic acid esterification with biocatalysts in ionic liquid g. németh , k. bélafi-bakó, n. nemestóthy, l. gubicza university of pannonia, research institute on bioengineering, membrane technology and energetics veszprém, egyetem u. 10. h-8200, hungary e-mail: nemethg@almos.uni-pannon.hu biodegradability and environmentally friendly technologies recently came into prominence; this is the reason why we assayed to develop a new “green” technology for l-lactic-acid (lla) production. racemic lactic acid (rla) mixture produced by chemical industry is difficult to handle. the product of esterification with low carbon chain alcohols has higher volatility than lactic acid (la) itself, therefore it can be more effectively separated. our reactions were carried out with biocatalysts (enzymes) — some of them prefer reactions with l-enantiomer — result in enantioselective esterification. after lla ester production the hydrolysis leads to separated lla, which is the starting material of a biodegradable plastic. our aim was to achieve enantioselectivity in phosphonium-type ionic liquid solvents by the optimization of several parameters, such as temperature, substrate molar ratio, amount of il, water content. reasonable results were achieved with three types (candida antarctica, candida rugosa, amano ps-im) of lipases. the use of enzymes and ionic liquids can make the technology “greener”, where an ingredient of a biodegradable plastic can be produced. the toxic heavy metals or hazardous acids can be replaced by biocatalyst (enzymes). these intermediates are re-usable, and they work at lower temperature, than conventional catalysts, thus the operational costs can be reduced. ionic liquids — compared with conventional organic solvents — have insignificant vapour pressure, they are non-flammable and re-usable after a purification process, furthermore they can be tailor made for a certain application. it is not negligible that the structure affects the environmental features like biodegradability or toxicity. the high lactic acid dissolving capacity is the reason why phosphonium-type ionic liquids were used. there are research teams, apply them for lactic acid extraction from fermentation broth. keywords: lactic acid, enzyme, ionic liquid, enantioselectivity, esterification introduction according to sustainable development environment needs to be protected beyond industrial production. this is the reason why non pollutant, biodegradable materials spread widely nowadays. polylactides (pla) and some of their derivatives are thermoplastic, biodegradable and biocompatible polymers with mechanical properties similar to the plastics which are commonly used, like polystyrene or polyethylene terephtalate. that is the reason why they were extensively studied in the last 20 years [1]. economic studies show that pla is an economically feasible material to use as a packaging polymer [2, 3]. second generation pla application could be seen mainly in the area of fresh products where pla is being used as a food packaging polymer for short shelf life products, such as fruit and vegetables [4]. currently, pla is used in compostable yard bags to encourage recycling and composting efforts. in addition, new applications such as fibres [5-8], textiles, foamed articles and paper coatings [4] can be pursued. lactic acid (2-hydroxypropionic acid) is the simplest hydroxyl-carbonyl acid. it has an asymmetric carbon atom and exists in two optically active configurations; the l(-) and d(+) isomers. the chemical synthesis route can be used to produce large scale quantities of rla [9]. the l(-) and d(+) isomers can be produced in bacterial systems. mammalian systems produce only the l(-) isomer which is easily assimilated. the majority of lactic acid is made by bacterial fermentation of carbohydrates. the fermentation processes can be classified according to the type of bacteria used [3]. poly(l-lactic acid) (plla) can be degraded by natural environments. the crystallinity of plla depends on the optical purity of the l-lactate units in the polymer, hence the higher the optical purity of the l-lactate units, the higher is its crystallinity. the production of highly crystalline plla requires the optical purity of l-lactic acid (lla). optical pure lla can be produced by a particular microorganism in a selected medium [10]. lee [11] observed that the biodegradable polymer produced from lla does not have proper mechanical properties; it is hard and breakable. polymerized dla has the same disadvantages. since there is no industrial technology for producing dla, németh and co-workers [12] started to develop a fermentation technology. lactobacillus coryniformis bacterium was applied for 420 the production of dla. the experiments led to high yield at low glucose content, but the bacteria are need to be developed further. synthesis of plla with a wide range of molecular weight using toxic inorganic catalysts or inducers has been reported [13]. the use of enzyme biocatalysts is advantageous in catalysis because they proceed in mild reaction conditions without metal or toxic organic contaminations [14]. matsumura et al. [15] observed first the bulk polymerization of lla with low plla yields using lipase from burkholderia cepacia. recently, some authors have claimed that it is possible to synthesize plla in bulk [16] and in ionic liquids using the readily available immobilized lipase b from candida antarctica (calb) in its commercial form novozym 435 [17, 18, 19]. although, there are some studies about using enzymes for asymmetric reactions, for example enantioselective esterification of (±)-menthol [20], hydrolysis of (d,l)-phenylglycine methyl ester [21], esterification of racemic ibuprofen [22] and 2-substitued-propanoic acid [23], ohara et al. was the only ones who [10, 24] investigated the optical resolution of lactic acid using enzymes. in the latest report [25] the optical resolution of butyl land d-lactate (bulla, budla) using an immobilized lipase was investigated. bulla and budla mixtures were used in the presence of novozym 435 lipase. at 80 °c the oligomerization of budla was induced enantioselectively, whereas bulla was not involved in the reaction. ionic liquids, which are liquids at ambient or far below ambient temperature, have been extensively used in the past decades as potential green alternatives for toxic, hazardous, flammable and highly volatile organic solvents. indeed, their many attractive physicochemical properties, including negligible vapour pressure, excellent chemical and thermal stability and high ionic conductivity make ils great candidates for replacing volatile organic compounds [26]. biodegradability depends on the ions of the il, the ligands and bonds in the cation and the selected anion [27]. all these interesting combinations of properties open the road to a wide range of applications, including organic and inorganic synthesis, catalysis, separation and enzymatic reactions. studies on enzymatic reactions in ils over the last 10 years have revealed not only that ils are environmentally friendly alternatives but that enzymes in these solvents exhibit excellent substrate, regioand enantioselectivity [26]. compared to polar organic solvents ils surprisingly do not inactivate enzymes [28, 29]. this feature extends enzyme-catalyzed reactions to a solvent polarity range that was previously inaccessible. the ability to use solvents with greater polarity increases the solubility of polar substrates, such as glucose, maltose or ascorbic acid [28], leading to faster reactions and changes in selectivity. for example, in the calb-catalyzed acylation of ascorbic acid with oleic acid in an ionic liquid the conversion was higher (83%) than the typical result in organic solvents (50%) [28]. the yield was higher in the case of some ionic liquids (80%) than in hexane (14%) during the esterification of la with ethanol [30]. there are some reports about using phosphoniumtype ils. extraction of la has been studied by marták et al. [31]. the phosphonium il with the 2,4,4-trimethylpentylphosphinic anion (called cyphos 104) is a new effective extractant of la with a considerably higher value of the distribution coefficient compared to liquid extractants. mainly the synergetic effect of the anion is responsible for the increased distribution coefficient of la in cyphos 104. separation of la is quite difficult due to its low volatility; hence distillation, liquid extraction, esterification, salt processes, electrodialysis, thermal methods and ion exchange can be used for obtain lactic acid from fermentation broth [32]. major et al. [30] studied esterification of la and used phosphonium-type ionic liquids for the first time in the process. the two substrates to produce ethyl-lactate (el) were lactic acid and ethanol and the applied biocatalyst was calb. the reactions were carried out in a shaking incubator (150 1/min) at 40 °c for 24 h. the enzymatic el synthesis was carried out in two different organic solvents (hexane and toluene) and in seven ils. the best yields were observed in cyphos 104 and cyphos 202 without catalysing the reaction themselves. five ils (cyphos 163, cyphos 166, cyphos 106, cyphos 102, and cyphos 110) showed high catalytic activity without enzyme loading. the substrates and products were completely miscible with the applied solvents, except for hexane and cyphos 110 resulting in the lowest ester yields of 14% and 36%. water content has a particular role in ester synthesis from organic acids and short alkyl alcohols in nonconventional media. esterification is an equilibrium reaction, hence the maximal yield can be influenced with the initial water content [30] or the control of the water content during the reaction by using zeolite [33] or pervaporation [34]. to reach high ester yield either one of the substrates (usually alcohol) should be used in excess or the product should be removed. applying la as substrate a new role of water content emerges, since in lower amount of water, la undergoes self esterification producing its open chain dimmer, lactoyllactic acid and other oligomers [35]. therefore the commercially available 90% la solution contains a significant amount of dimmer la beside the monomeric form. furthermore, dimerization/decomposition of la has to be considered as a side reaction in the reaction mixture beside ethyl lactate synthesis [30]. since la is a chiral molecule after esterification two molecules with the same consistence but different formation generates from industrial rla mixture. the ratio of the enantiomers strongly depends on the activity of the applied enzyme. enantioselectivity of enzymes is influenced by substrates and reaction conditions (water activity, temperature, ph, solvent, additives, etc.). in some experiments additional co-solvent increased activity, stability and enantioselectivity of the enzyme [36]. enantioselectivity is calculated by the following equation of enantiomeric excess: 421 %100.. × + − = sr sr ee , (1) where: ee enantiomeric excess r and s the ratios or values of the enantiomers our aim in this work was to achieve enantioselective lactic acid esterification in il as a solvent and to use biocatalysts to achieve enantioselectivity. with asymmetric esterification of rla it can be separated into the two enantiomers and after a cleaning procedure biodegradable pla can be polymerized. furthermore, the enzyme and the il can be recycled. lactic acid and ethanol are environmentally friendly materials, as well as enzymes and ils. with the application of these materials a novel green technology can be developed. four reasonable parameters (temperature, alcohol excess, added il, initial water content) were chosen to investigate their effects on enantioselectivity and yield. first the alcohol excess vs. temperature, then alcohol excess vs. il, and finally alcohol excess vs. initial water content were investigated. in each case the two other parameters were constant. materials and methods enzymes and chemicals enzymes: immobilized candida antarctica lipase b (novozym 435, triacilglycerol hidrolase, e. c. 3.1.1.3.) was a gift of novo nordisk (basvaerd, denmark). lipase from candida rugosa (liophylised, e. c. 3.1.1.3.) was from sigma-aldrich (buchs, switzerland) and amano lipase ps-im immobilised on diatomaceous earth from sigma-aldrich (st. louis, usa). solvents: trihexyl-tetradecyl-phosphonium-bis (2,4,4trimethyl-pentyl)-phosphinate (cyphos 104), sigmaaldrich, (germany), tributyl-tetradecylphsphoniumdodecylbenzenesulphonate (cyphos 201), iolitec gmbh, (germany). reagents: (d,l)-lactic acid (90%), reanal (hungary), absolute ethanol (>99%), merck (germany) were applied. reaction and analysis the reactions were carried out in 10 ml vials with ika ks 4000i shaking incubator at 150 min-1 in 24 hours. every mixture contained rla, ethanol and il. after preparing the mixture the initial water content was checked and set with karl-fischer method. 0.5 µl samples were analysed by hp 5890 gas chromatograph, fid, lipodex-e column (cyclodextrin) 30 m x 0.25 mm, head pressure 90 kpa at 90 °c constant temperature, injector 150 °c, detector 250 °c. fiberglass and high surface adsorbent material were inserted to the injector inlet to protect the column from contamination by the il. results and discussion selection of the reaction medium the reaction medium was selected so that it neither reduces nor enhances catalytic activity of the enzymes. therefore catalytic activities of two ils were investigated. previous report [30] shows that cyphos 104 and cyphos 202 were suitable solvents for lactic acid esterification with high ester yield. cyphos 202 is no more available from the producer. that is why cyphos 201 was applied, which is quite similar to cyphos 202, but its catalytic activity had to be determined. unfortunately, the catalytic activity of cyphos 201 was too high and the conversion was close to 100%. in the case of cyphos 104 the conversions without enzyme were low (<5%). these results were the start points for further investigations, hence the chosen solvent was cyphos 104. investigation of the enantioselectivity of enzymes in cyphos 104 ionic liquid the aim of the further experiments was to determine the optimal parameter combination to achieve the highest enantioselectivity and yield in the presence of enzymes. since alcohol:monomer la molar ratio, initial water content, temperature and the amount of il are the main parameters, which affect the activity of enzyme an experimental plan was composed with 13 measure points (table 1). first alcohol excess and il amount was combined to 5 measure points, the other parameters were constant. then the alcohol excess and temperature was combined, and in the end the alcohol excess and water content. the values of the parameters were: alcohol : monomer la molar ratio = 3 : 1 (14 mmol), 7 : 1 (6 mmol) and 11 : 1 (4 mmol) (calculated for 2 ml / 46 mmol of ethanol); initial water content: 8 w/w%, 12 w/w% and 16 w/w%; temperature: 30 °c, 50 °c and 70 °c; amount of added il: 0.5 g, 0.75 g and 1 g. table 1: experimental plan sample t (°c) alcohol molar excess initial water content (w/w%) added il (g) 1 50 3 8 0.5 2 50 3 8 1 3 50 7 8 0.75 4 50 11 8 0.5 5 50 11 8 1 6 70 3 8 1 7 70 11 8 1 8 30 3 8 1 9 30 11 8 1 10 50 7 8 1 11 50 3 16 1 12 50 11 16 1 13 50 7 12 1 422 using amano lipase ps-im as biocatalyst no enantioselectivity was observed, therefore the data are not published. fig. 1 and fig. 2 represent the values of enantioselectivity in the presence of the two further enzymes after the first and 24 hours reaction time, respectively. 0 10 20 30 40 50 1 2 3 4 5 6 7 8 9 10 11 12 13 sample en an tio m er ic e xc es s (% ) candida rugosa candida antarctica lipase b figure 1: values of enantioselectivity of the experimental design in the presence of candida rugosa and candida antarctica lipase b after 1 hour higher enantiomeric excess (e.e.) values were observed after 1 h reaction time than at the end of the reaction. there were parameter combinations where both enzymes showed reasonable selectivity almost as high as 40%. with time these high values began to reduce depending on the parameters. after 24 hours the selectivity values of candida rugosa catalysed measure points reduced almost to 0%, but at three points: 4, 5 and 9 the calb catalysed reactions kept their higher e.e. values of 14.74%, 18.95% and 22.09%, respectively. 0 5 10 15 20 25 1 2 3 4 5 6 7 8 9 10 11 12 13 sample en an tio m er ic e xc es s (% ) candida rugosa candida antarctica lipase b figure 2: values of enantioselectivity of the experimental design in the presence of candida rugosa and candida antarctica lipase b after the 24 hours determination of the optimal parameters for highest yield and enantioselectivity beyond selectivity a high ester yield is a requirement to obtain high amount of lla, as well. since the calb was the suitable enzyme among the three investigated ones, fig. 3 shows conversion calculated for monomer la and the e.e. values for the studied 13 points. two of the earlier mentioned three best parameter combinations for enantioselectivity showed also high conversion rate. conversion of 57% and 55% was measured for the points 5 and 9. 0 20 40 60 80 1 2 3 4 5 6 7 8 9 10 11 12 13 sample en an tio m er ic e xc es s (% ) co nv er si on (% ) conversion enantioselectivity figure 3: enantioselectivity and conversion of calb after 24 h to obtain more information about the optimal parameters for the required results the experiments were widened with some more points. one of the parameters was changed and the values of other parameters remained constant. the fundamental parameters were 50 °c, 11 : 1 alcohol : la molar ratio, 8 w/w% initial water content and 1 g il. the effects of the variables, which generally correlate with the selectivity and conversion, are represented from fig. 4 to fig. 7. 0 10 20 30 40 50 60 0 20 40 60 80 temperature (°c) en an tio m er ic e xc es s (% ) co nv er si on (% ) conversion enantioselectivity figure 4: effect of temperature on the enantioselectivity and conversion (11 : 1, 8 w/w% initial water content, 1 g il) 0 20 40 60 80 100 0 5 10 15 20 alcohol excess en an tio m er ic e xc es s (% ) co nv er si on (% ) conversion enantioselectivity figure 5: effect of alcohol excess on the enantioselectivity and conversion (50 °c, 8 w/w% initial water content, 1 g il) 423 0 20 40 60 80 100 0 5 10 15 20 initial water content (m/m %) en an tio m er ic e xc es s (% ) co nv er si on (% ) conversion enantioselectivity figure 6: effect of initial water content on the enantioselectivity and conversion (50 °c, 11 : 1, 1 g il) lower temperature values and initial water content, higher alcohol excess and amount of il were favourable. taking these results into account the optimal reaction parameters could be determined: temperature of 30 °c, 11 : 1 alcohol : la molar ratio, 8 w/w% initial water content and 1 g of il. the reason why enantiomeric excess decreases during the reaction is the calb catalyses the esterification faster with lla than with dla and during the reaction the amount of del gets closer to lel. to confirm our theory, pure lla was applied for a parallel reaction with the above mentioned optimal parameters (30 °c, 11 : 1, 8 w/w% initial water content, 1 g il). the initial reaction rates of the two reactions are 7.63·10-2 mmol product/hour and 5.92·10-2 mmol product/hour. 0 10 20 30 40 50 60 70 0 0,5 1 1,5 2 2,5 mass of added il (g) en an tio se le ct iv ity (% ) co nv er si on (% ) conversion enantioselectivity figure 7: effect of added il on the enantioselectivity and conversion (50 °c, 11 : 1, 8 w/w% initial water content) increasing the enantioselectivity of calb ohara et al. [25] accomplished the lactic acid recycling after the selective polymerization. after the separation of not polymerized lla it was reused and cleaned from pla. applying this method the produced ester was separated from other chemicals, hydrolysed and then the obtained lactic acid was recycled in our laboratory. the ratios of lla and dla in the further mixtures were set as they were observed after a 24 hours reaction. the reaction conditions were the same when the yield and the enantioselectivity were the highest: 50 °c, 11 : 1 alcohol : monomer la molar ratio, 8 w/w% initial water content and 1 g of ionic liquid. the reactions were carried out with the same amount of initial la (4 mmol) and with the e.e. values the previous reaction showed after 24 hours. the results can be seen in fig. 8 and fig. 9. the first sample was prepared with rla. after 24 hours enantiomeric excess of sample 1 reduced from 35% to 22%. the 2nd sample was prepared with the e.e. of 22% (3.3 mmol rla and 0.9 mmol lla). the initial e.e. of the 3rd sample was 51% (1.9 mmol rla and 2.1 mmol lla) and after one hour it was 73% and during the reaction it decreased to 65%. the last sample contained 1.4 mmol rla and 2.7 mmol lla, the selectivities were at the first hour and 24 hours 80% and 75%, respectively. in case of the yields the studied tendency could be observed, namely the more lla the mixture contained the faster the reaction was. 0,00 20,00 40,00 60,00 80,00 100,00 1 2 3 4 sample en an tio m er ic e xc es s (% ) 1 h 3h 5 h 24 h figure 8: enantiomeric excess values of each sample after recycling the la 0,00 20,00 40,00 60,00 80,00 100,00 1 2 3 4 sample co nv er si on (% ) 1 h 3h 5 h 24 h figure 9: conversion values of each sample after recycling the la conclusion esterification of racemic lactic acid was investigated using three types of biocatalysts. first a suitable solvent, cyphos 104 il was selected so that it neither catalyses the reaction itself nor reduces the activity of the enzyme. then investigation of three types of enzymes was the next step, where calb showed the highest enantioselectivity and yield by certain conditions. optimal reaction parameters were determined; which were temperature (30 °c), alcohol : monomer la molar 424 ratio (11 : 1), initial water content (8 w/w%) and the added ionic liquid to the mixture (1 g). finally, further investigations were carried out to increase selectivity by la reusing. in these experiments la was recycled to the start of the reaction three times. with this method e.e. value for the first hour increased from 35% to almost 80%. nomenclature pla: poly-lactic acid plla: poly-l-lactic acid la: lactic acid rla: racemic lactic acid lla: (l)-lactic acid dla: (d)-lactic acid lel: (l)-ethyl-lactate del: (d)-ethyl-lactate bulla: butyl-(l)-lactate budla: butyl-(d)-lactate calb: candida antarctica lipase b il: ionic liquid e.e.: enantiomeric excess acknowledgement this work was supported by the research programs “livable environment and healthier people – bioinnovation and green technology research at the university of pannonia támop-4.2.2-08/1/2008-0018” and 4.2.2/b-10/1-2010-0025. these projects are supported by the european union and co-financed by the european social fund. references 1. r. e. drumright, p. r. gruber, d. e. henton: polylactic acid technology, adv matera, 12 (2000) 1841–1846 2. r. datta, s. p. tsai, p. bonsignorea, s. h. moona, j. r. frank: technological and economic potential of poly(lactic acid) and lactic acid derivatives, microbiol rev 16 (1995) 221 3. d. j. garlotta: a literature review of poly(lactic acid), j polym environ, 9 (2001) 63–84 4. r. auras, b. harte, s. melke: an overview of polylactides as packaging materials, macromol biosci, 4 (2004) 835–864 5. k. e. perepelkin: chemistry and technology of chemical fibers. ploy(lactide) fibers: fabrication, properties, use, prostects, a review, fibre chem+, 34 (2002) 85–100 6. w. hoogsten, a. r. postema, a. j. pennings, g. t. brinke, p. 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word contents.doc hungarian journal of industry and chemistry veszprém vol. 40(1) pp. 33–38 (2012) synthesis, physico-chemical properties, and spectroscopic characterization of phenolic modified castor oil based polyol a.vazid1 , v. urvashi1 , k. jyotsna2 , s. a. alhadi faroun3, i. mohd3 1chaudhary devi lal university, department of chemistry, polymers and advanced materials research lab sirsa-125 055, haryana, india e-mail: kanikavashist2007@gmail.com 2chitkara university, department of applied sciences, rajpura, chandigarh 160014, india e-mail: jyotsna.kaushal@chitkara.edu.in 3jamia millia islamia university, department of mechanical engineering, new delhi, india physico-chemical properties and optical characterization of synthesized polyol explores the possibility to understand the mechanism and controlling the reaction parameters in a suitable manner during the production of polyurethane products. castor (ricinus communis) is generally grown for its oil yielding seeds, which contains ricinoleic acid and only the oil with hydroxyl group in molecular structure due to this castor oil can be exploited as modified polyol. in the present study, castor oil has been modified with blending phenolic resin and reacted with diethanolamine (dea) and diethyleneglycol (deg) to synthesize the polyol. various physico-chemical properties of synthesized polyol such as acid value, oh value, and moisture content have been measured. uv-vis, ftir and nmr spectroscopic studies of the synthesized castor oil based polyol are carried out. optical properties such as absorption coefficient (α), extinction coefficient (k) and optical band gap (eg) of polyols were determined. ftir studies show the information of changes in the functional group with changing concentration of diethanolamine (dea), diethyleneglycol (deg), and phenolic resin (ph. resin). infrared spectroscopy (ir) is used to understand the characterization worth with suitable standards in view of chemical and structural characterization of synthesized polyol. key words: phenolic resin, physico-chemical properties of polyol, optical properties and spectroscopic studies introduction studies based on experimental and spectroscopic characterization of polymeric materials may provide the information for versatile engineering applications. although many research works have been directed to petrochemicals based polyurethanes (pus), just a few studies have been reported on agro based products with formation and their spectroscopic characterization. polyurethanes are rapidly developing products especially in coating industry. thus, the important area of present day research in the surface protective coatings is to explore the potential utility of renewable and non conventional raw materials for preparation of resins. the most common among these materials are starch, cellulose, and various oils such as castor oil, soyabean oil etc. phenolic resins are one of the most important thermosetting polymers because of their good temperature and electrical resistance properties [1]. the traditional phenolic resins have various advantages [2] such as heat resistance, good electronic properties, and flame retardance. phenolic (resole) resins are used as cross-linkers for adjusting flexibility and improving surface contact in various types of coatings [3]. resole type phenolic resins have the capability to cure either by use of a curing agent or by heating only [4]. although the importance of phenolic resins has dwindled, they still have significant uses. their importance is likely to remain considerable because the used raw materials can be obtained at a reasonable cost. the individual development of phenolic resins is still continuing despite their long history [1]. in many industrial applications, amino resins are used as thermosetting polymers. despite possessing many attractive features, the acceptance of many engineering areas especially in the coating industry as paint binders is obstructed by some of its inherent qualities such as brittleness and poor water resistance (osemmeahon and barminas, 2006a; conner, 1996; 1990). the importance of synthesizing polymers containing moieties capable of participating in polymerization reactions continue to increase in today’s coating industry [5]. alkyd resins are complex network polyesters widely used in the paint and coatings industries [6]. polyols are alkyd resins with a specified high hydroxyl content that can react with compounds containing epoxy, isocyanate groups to produce hybrid coatings with superior performance [7]. a literature survey reveals that mostly petrochemicals-based polyurethanes have covered the polymer industries, which are costly raw materials as compared to vegetable oil based pus. 34 in the present investigation, attempt has been made to synthesizepolyols for polyurethane system by using castor oil, diethanolamine (dea) and diethyleneglycol (deg); modified oil based polyol with phenolic resin. physicochemical properties such as acid value, oh value, moisture content; and also spectroscopic techniques such as uv-vis, ftir and nmr have been used for the characterization of prepared phenolic modified polyol. experimental raw materials castor oil and phenolic resin supplied by shivathene ltd. parwanoo (hp) were used. diethanolamine and diethyleneglycol obtained from (qualigens fine chemicals, mumbai) were used. acetone (sisco research laboratory, ar grade) and koh solution were prepared for analysis (himedia laboratories pvt. ltd. mumbai). synthesis of modified polyol the reaction for the preparation of modified polyol from castor oil was carried out in a three-necked round bottom flask (equipped with nitrogen inlet, thermometer, stirrer, and reflux condenser). three sets of polyols were synthesized with repeated sets of conditions. in the first set, castor oil was taken into the three necked flask after heating it with added phenolic resin at varying concentrations keeping the quantity of castor oil constant. in the second and third set, castor oil and phenolic resin concentration were kept constant in all the three prepared polyol samples with varying concentrations of diethylene glycol and diethanolamine as shown in table 1. the mechanism of esterification was carried out via controlling the temperature of reaction. dehydration occurred from 150–2000c. the progress of condensation reactions were confirmed by checking hydroxyl and acid values. the time required to complete the reaction was 6 h, after this it was cooled and taken to the sample bottles. further, resulted synthesized polyols are characterized by measuring physico-chemical properties such as acid value, oh value, and moisture content. optical properties and spectroscopic studies of synthesized polyol samples were also carried out by using various spectroscopic techniques such as uv-vis, ftir, and nmr. proposed possible structures for all the three kinds of polyols as confirmed by ftir are given below in figure 1–3 respectively. *c. o. = castor oil, *ph. resin = phenolic resin, *deg = diethyleneglycol, *dea = diethanolamine table 1: physico-chemical properties of synthesized phenolic modified polyol (phmp). polyol samples acid value (mg koh/g) oh value (mg koh/g) moisture content (% moisture) 1. c.o. + ph. resin a. 180 + 15 g b. 180 + 10 g c. 180 + 7 g 2. c. o.+ ph. resin + deg a. 180 + 10 g b. 180 + 7 g c. 180 + 5 g 3. c.o. + ph. resin + dea a.180 + 10 g b.180 + 5 g c.180 + 3 g 66.37 ± 10 58.11 ± 10 41.44 ± 10 50.12 ± 10 41.41 ± 10 28.40 ± 10 28.05 ± 10 30.80 ± 10 36.46 ± 10 201.02 ± 10 195.93 ± 10 172.19 ± 10 218.90 ± 10 181.78 ± 10 179.94 ± 10 186.93 ± 10 221.80 ± 10 252.88 ± 10 0.05 0.06 0.02 0.02 0.02 0.04 0.017 0.074 0.132 results and discussion optical characterization in the present study, castor oil and phenolic resin modified polyol have been prepared. physico-chemical properties such as acid value, oh value, moisture content, optical and structural modifications using various spectroscopic techniques of the prepared polyol have been taken into consideration. physico-chemical properties of modified polyol shown in table 1 and uv-visnir (schimatzu spectrophotometer uv 1601) are used for the optical characterization of prepared modified polyol samples. the optical properties such as absorption coefficient (α), extinction coefficient (k), and energy band gap (eg) have been studied for all the castor oil based polyol samples. the relationship between optical band gap (eg), absorption coefficient (α), and the energy (hv) were estimated using the tauc relation [8]: (αhv) α (hv eg)n. (1) table 2: optical properties of phenolic modified polyol (phmp). where n = 1, 2, 3 for indirect transitions polyol samples band gap (eg) abs. coefficient (α) ext. coefficient (k) 1. c. o. + ph. resin a. 180 + 15 g b. 180 + 10 g c. 180 + 7 g 2.655 2.594 2.227 3.913 4 3.039 100.84 102.45 94.278 35 polyol samples band gap (eg) abs. coefficient (α) ext. coefficient (k) 2. c. o.+ ph. resin + deg a. 180 + 10 g b. 180 + 7 g c. 180 + 5 g 3. c.o. + ph. resin + dea a. 180 + 7 g b. 180 + 5 g c. 180 + 3 g 2.921 2.732 2.556 2.542 2.682 2.862 0.88 0.575 0.628 0.871 1.315 4 19.6 12.532 13.687 19.399 30.962 98 it has been observed by using the uv-visible spectra that all the polyol samples show indirect transitions. band gap for the indirect transitions has been determined by plotting (αhv) vs. hv as shown in figure 4. by plotting the graph it has been observed that the polyols prepared using phenolic resin show decrease in band gap with decreasing concentration. similar trend has been observed with diethyleneglycol (deg) modified polyols. interestingly, in the case of diethanolamine (dea) modified polyol increase in the band gap with decreasing concentration of dea has been observed. the extinction coefficient (k) and absorption coefficient (α) which are determined by using equation given below k = αλ/4π (2) show almost similar trend as shown for the energy band gaps. optical parameters such as band gap, absorption coefficient (α) and extinction coefficient (k) have been given in table 2 respectively. similar to that of band gap, extinction coefficient (k) and absorption coefficient (α) show decreasing trend with decreasing concentration in both the phenolic resin made polyol and deg modified polyol, while in case of dea modified polyol increase in extinction coefficient (k) and absorption coefficient (α) with decreasing concentration has been observed. oh o ch3 ch3 ch2 oh x ch2 hooc ch3 ch3 o o c ch3 h3c ch2 oh x ch2 ch3 ch3 o oh oh castor oil phenolic resin + phenolic resin modified polyol (phmp) -h2o figure 1: proposed possible structure of phenolic resin modified polyol (phmp) oh o ch3 ch3 ch2 ho x ch2 hooc ch3 ch3 o o c ch3 ch3 ch2 oh x ch2 ch3 ch3 o oh oh castor oil phenolic resin + diethyleneglycol modified polyol (phmp+deg) -h2o ho ch2ch2och2ch2oh + ch2ch2och2ch2 o diethyleneglycol figure 2: proposed possible structure of deg modified polyol (phmp + deg) oh o castor oil phenolic resin diethanolamine ch2ch2oh hn ch2ch2oh ch3 ch3 ch2 oh x ch2 hooc ch3 ch3 o ch2ch2oh n ch2ch2o ch3 ch3 ch2 oh x ch2 c ch3 ch3 o diethanolamine modified polyol (phmp+dea) oh oh -h2o + + figure 3: proposed possible structure of dea modified polyol (phmp + dea) ftir study absorption bands that are characteristic of organic molecular vibrations are seen throughout the spectrum of the sample, many occurring within relatively narrow wavenumber ranges that are associated with particular molecular groupings [9]. ftir spectra of the synthesized polyols were obtained using a perkin elmer 2000 spectrophotometer to see the effect of phenolic resin with deg and dea. the spectra show a broad peak at 3433 cm-1 indicating the hydroxyl group of polyols. at 2928 cm-1 and 2856 cm-1 peaks have been obtained for all the c-h stretching of ch2 group present in the compound. the peak at 1741 cm-1 gives strong evidence for ester formation. 1460 cm-1 shows peak for ch2 bending vibrations within the compound. at 1160 cm-1 peak obtained shows symmetric stretching of c-o-c group present in the compound. peak at 3007 cm-1 is due to c-h stretching vibration of aromatic ring. while the peak at 726 cm-1 is due to aromatic ring. in all the samples of synthesized polyol almost similar pattern has been observed as shown in figure 4–6 respectively. 36 figure 4: ftir spectra of phmp figure 5: ftir spectra of phmp + deg figure 6: ftir spectra of phmp + dea figure 7.: nmr spectra of phmp with highest concentration of phenolic resin figure 8: nmr spectra of phmp + deg with highest concentration of deg figure 9: nmr spectra of phmp + dea with highest concentration of dea nmr study nmr spectra of synthesized polyol and its characterization have been done using (bruker spectrospin dpx-300). 1h-nmr spectroscopy gives indirect information about the carbon skeleton of an organic molecule because most of carbon atoms have atleast one attached hydrogen. after analyzing the synthesized polyols the chemical shift (δ) shown within the range of 0.88–2.3 ppm indicates long aliphatic protons present in castor oil. peak at 3.6 ppm indicates for ch2oh. chemical shift at 4.2 ppm for acetate protons is shown in fig. 4–6 respectively. peak at 5.2 ppm is for c=ch and chemical shift of 7.2 ppm indicates phenolic protons. on interpreting the prepared polyol samples using nmr spectra obtained, it has been observed that as the amount of phenolic resin increases intensity of peak of aromatic protons increases. this has been observed in similar fashion in both the cases of phenolic resin and diethyleneglycol (deg) modified polyols. while in dithanolamine (dea) (i.e. 3% w/w) modified polyol this minimum amount of dea favours the enhancement of phenolic protons as the amount of dea increases from 3 to 5 and 10% w/w the intensity of absorption signal decreases. 37 conclusively, it has been shown by prepared polyol samples that optimum amount of resin and deg favours the polyol formation in first two cases of dithyleneglycol modified polyol and phenolic modified polyol. while minimum amount of dea favours the polyol formation in the third case of diethanolamine modified polyol. it has also been observed in nmr spectra that the aromatic peak at 7.2 ppm of aromatic protons of phenolic resin in fig. 7 is showing significant change by retarding the peak intensity which appeared in deg and dea modified polyols fig. 8, 9. the nmr spectra of the synthesi-zed polyol have been given in the fig. 7–9 respectively. conclusions in the present study modification of castor oil based polyol has been carried out by blending castor oil with phenolic resin, diethyleneglycol (deg) and diethanolamine (dea). they were then investigated for physicochemical properties and spectroscopic studies. on interpreting the physico-chemical properties such as acid value, hydroxyl value and moisture content it has been observed that acid value and hydroxyl value show almost similar trend. in case of phenolic modified polyol (phmp) and diethyleneglycol modified polyol (phmp + deg) acid value as well as the hydroxyl value (oh value) goes on decreasing with decreasing concentration of resin and deg. while diethanolamine modified polyol is showing contrary results to as those of resin and deg modified polyols i.e. with decreasing concentration of dea (diethanolamine) acid and oh value are increasing. moisture content in all the three cases of phmp, phmp + deg and phmp + dea are increasing with decrease in concentration of blending moieties. by studying uv-vis spectra’s of the modified polyol samples energy band gap, extinction coefficient and absorption coefficient, energy band gap of all the polyols show indirect kind of transitions. for confirming the results of band gaps all the samples were taken twice and then also almost similar band gap has been observed. in case of phenolic and deg modified polyols, band gap shows decreasing trend with decreasing concentration of phenolic resin and deg whereas, in case of diethanolamine modified polyol (phmp + dea) increase in band gap with decreasing concentration of dea has also been observed. extinction and absorption coefficient show similar trends as that of energy band gap in all the three synthesized polyols. ftir spectra of prepared polyol samples do not show any significant changes in the prepared polyol with changing concentrations of blending moieties. on studying the nmr spectra of polyol samples informative results have been obtained. in the first two cases of phenolic resin modified and deg modified polyols optimum amount of resin and deg favours the formation of polyols showing increase in the peak of aromatic protons of phenolic resin with increasing concentration while minimum amount of dea favours the formation of polyols, showing increase in the resonance intensity with decreasing concentration of diethanolamine (dea). references 1. s. attajariyakul, s. vanichseni: development of a kinetic model for resole type phenolic resin formation, thammasat int. j. sc. tech, (6) (2001) 3, pp. 13–18 2. a. m. motawie, e. m. sadek: adhesives and coatings based on poly(vinyl acetal)s, journal of applied polymer science, (70) (1998) pp. 1769– 1777 3. s. a. osemeahon, j. t. barminas: development of amino resin for paint formulation: copolymerization of methylol urea with polyester, african journal of biotechnology, (6) (2007) 12, pp. 1432–1440 4. a. spyros: quantitative determination of distribution of free hydroxyl and carboxylic groups in unstaturated polyester and alkyd resins by 31pnmr spectroscopy, journal of applied polymer science, (83) (2002) pp. 1635–1642 5. t. p. sharma, d. patidar, n. s. saxena, k. sharma: measurement of structural and optical band gaps of cd1-xznxs(x = 4 and 6) nanomaterials, indian j pure & appl physics, (44) (2006) pp. 125–128 6. v. ali, z. haque neelkamal, m. zulfeq-uar, m. husain: preparation and characterization of polyether based polyurethane dolomite composite, journal of applied polymer science, (103) (2006) pp. 2337–2342 7. h. s. park, j. p. wu, h. k. kim: synthesis and physical properties of two component polyurethane coatings using bromine-containing aromatic modified polyesters, journal of ind. & eng. chemistry, (3) (1997) 4, pp. 282–287 8. j. v. patel, s. d. desai, v. k. sinha: bioacrylic polyols for two pack polyurethane coating, journal of scientific & industrial research, (63) (2004) pp. 259–264 9. m. a. espinosa, m. galia, v. ca’diz: novel phosphorilated flame-retardant thermosets: epoxy benzoxazine-novolac systems, polymer, (45) (2004) pp. 6103–6109 10. a. m. motwie, m. m. badr, m. s. amer, h. y. moustafa, i. m. ali: some coating studies on phenolic epoxy/poly(vinyl acetal) resins, journal of applied sciences research, (4) (2008) 9, pp. 1043– 1051 11. v. isabelle, l. tighzert: biodegradable polymers, materials, (2) (2009) 2, pp. 307–344 12. s. n. suresh, y. jin, k. xiaohua: production of polyols from canola oil and their chemical identification and physical properties, j amer oil chem soc, (84) (2007) pp. 173–179 38 13. j. z. lin, y. t. jin, z. tong, z. y.yun: preparation of phenolic resin/silver nanocomposites via in situ reduction, chinese chemical letters, (14) (2003) 4, pp. 426–428 14. y. zhongren, e. james, b. gary: preparation and characterization of naoh activated carbons from phenolic resin, j. mater. chem., (16) (2006) pp. 1456–1461 15. c. l. chiang, ma m. chen-chi: synthesis, characterization, thermal properties and flame retardance of novel phenolic resin/silica nanocomposites, polymer degradation and stability, (83) (2004) pp. 207–214 16. linda, f. lorenz, w. christiansen alfred: interactions of phenolic resin alkalinity, moisture content and cure behavior, ind. eng. chem. res., (34) (1995) pp. 4520–4523 17. z. fahmina, s. eram, m. s. ashraf, a. sharif: studies on poly(styrene-co-maleic anhydride)modified polyesteramide based anticorrosive coatings synthesized from a sustainable resource, journal of applied polymer science, (92) (2004) 4, pp. 2538–2544 18. j. b. calvin: chemistry and physics of foam formation vol. i, (eds) plastic foam, john wiley and sons inc., new york, (1969) 19. j. h. saunders, k. c. frisch: polyurethane chemistry and technology, part ii, interscience publishers, new york, (1964) 20. j. h. saunders, k. c. frisch: polyurethane chemistry and technology, part i, interscience publishers inc., new york, (1962) microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 95-99 (2008) galacturonic acid recovery from pectin rich agro-wastes by electrodialysis with bipolar memranes e. molnár , n. nemestóthy, k. bélafi-bakó 1university of pannonia, research institute of chemical and process engineering egyetem u. 10., 8200 veszprém, hungary e-mail: emolnar@mukki.richem.hu pectin rich agro wastes can be utilised for manufacture of galacturonic acid. pectin is a complex polysaccharide found in the primary cell walls and intercellular regions of higher plants. backbone of pectin molecules is composed of galacturonic acid as a monomer. galacturonic acid and derivates are valuable raw materials in food and cosmetic industries as acidic agents and for production of vitamin c. in this work the aim was to produce galacturonic acid from citrus pectin and sugar beet pulp. the hydrolysate of pectin contains mainly carbohydrates (oligoand monosaccharides) and galacturonic acid. electrodialysis with bipolar membranes (edbm) represents an efficient technology to separate charged compounds from a solution. to remove galacturonic acid, edbm seems a suitable process, because galacturonic acid is present as a charged compound in the solution. to obtain galacturonic acid from hydrolysate of pectin laboratory experiments were performed, similar to the system applied by novalic et al. for recovery of other organic acids. an ed stack containing anion and cation selective and bipolar membranes was applied to obtain ga from hydrolysate. keywords: agro wastes, galacturonic acid, electrodialysis, bipolar membrane introduction pectin rich agro-wastes are available to manufacture galacturonic acid (ga). pectin is a complex polysaccharide found in the primary cell walls of higher plants. function of pectin is formation of bond in cells and between cell wall substances. the strength and structure of plants texture are determined also by this polysaccharide. the main component of pectin is backbone of α-1,4-linked galacturonic acid residues. galacturonic acid and derivates can be utilised in food industry (as acidic agents), chemical industry (as washing powder agent and nonionic or anionic biodegradable surfactants) and pharmaceutic of industry (for production of vitamin c) [1]. sugar beet pulp, apple pomace and other wastes (e.g. press cakes) from fruit juice industry are pectin rich raw materials. to obtain galacturonic acid, pectin is extracted from raw resources then its enzymatic hydrolysis results in galacturonic acid in diluted aqueous solution. in this work the plan was to produce galacturonic acid from citrus pectin and sugar beet pulp. for this purpose firstly pectin was extracted with hot water from sugar beet pulp then enzymatic hydrolysis was carried out using pectinex 100l enzyme preparation. the hydrolysate contains mainly carbohydrates (oligoand monosaccharides) and galacturonic acid. to recover galacturonic acid, electrodialysis with bipolar membranes (edbm) [2-4] seems to be a suitable process, because only galacturonic acid is present as a charged compound in the solution. electrodialysis with bipolar membranes (edbm) is an electromembrane process to separate ions and produce acids and basis. under electrical potential difference, charged compounds move in the direction of the oppositely charged electrode. anion(a) and cationselective (c) membranes let counter-ions cross and exclude co-ions. the function of bipolar membrane (bm) is to generate protons and hydroxyl ions which are removed from interphase of the membrane to outside phases. base is formed by hydroxyl ions and cations, acid is formed by protons and anions. uncharged components of salt solution are retained by bipolar membrane. to obtain galacturonic acid from hydrolysate electrodialysis with bipolar membranes was used [5]. galacturonic acid was separated and concentrated by edbm. the principle of our edbm shows fig. 1. when an electric field is applied, galacturonate ions migrate towards the anode. galacturonate ions leave the diluate solution and move through anion-selective membrane into acid compartment where galacturonic acid are formed by galacturonate ions and protons. sodium ions pass through cation-selective membranes and naoh is formed by generated hydroxyl and sodium ions. uncharged saccharide components are retained in the diluted solution. 96 anode + caustic solution (h2o) caustic solution (naoh) diluted solution (salt solution) cathode acid solution (h2o) acid solution (ga) diluted solution ohohohoh-h+ h+ h+ h+ na+ na+ na+ na+ gagagagana+ ac c a a ac c cbm bm bm bm anode + caustic solution (h2o) caustic solution (naoh) diluted solution (salt solution) cathode acid solution (h2o) acid solution (ga) diluted solution ohohohoh-h+ h+ h+ h+ na+ na+ na+ na+ gagagagana+ ac c a a ac c cbm bm bm bm figure 1: the principle of recovery galacturonic acid materials and methods the experimental set-up was purchased from fumatech (ft-ed-4-100-10 module). the electrodes were made of stainless steel. fumasep fkb, fumasep fab and fumasep fbm membranes, which are commercially available from fumatech gmbh (germany), were used. characteristics of membranes are shown table 1. the set-up composed of 10 anion-, 11 cation and 10 bipolar membranes. the effective membrane area was 0.31 m2. galacturonic acid applied as a standard and for model solution was purchased from sigma-aldrich, while sodium sulphate (electrolyte solution) from spectrum (hungary). firstly experiments were carried out with sodiumgalacturonate model solution, then secondly hydrolysate of sugar beet pulp was used to investigate removal of galacturonate. hydrolysis of pectin solution obtained from sugar beet pulp and citrus pectin was carried out by pectinase enzymes (pectinex 100l enzyme preparation) in a shaking incubator. the operation conditions were: 500 μl enzyme/ dm3 solution, 40 °c and 120 rpm. degradation of pectin was followed by acid titration (0.5 m naoh) and hplc, using perkin-elmer lc200 hplc. in order to recover ga, pretreatment of hydrolysate could be needed, because the membrane fouling is one of the main limiting factor of the process. large molecules can be removed by ultrafiltration or centrifugation. concentration of galacturonic acid in acid and diluted solutions was measured by colorimetrically with the dinitrosalicylic acid test (dna) method [6].in the acid solution, ph was followed by wtw microprocessor ph-meter. the data of conductivity in diluted, acid and base solutions, the electric current and voltage between electrodes was collected by data acquisition device (national instruments usb-6008/6009). the data were recorded by the program labview. table 1: main characteristics of membranes membrane characteristic fumasep fkb cation-exchange membrane peek-reinforced selectivity >98% electric resistance <4 ω*cm2 stability acid and caustic stable thickness 0,08–0,10 mm specific conductance >2 ms/cm ion exchange capacity 0,9–1,0 meq/g swelling 15% fumasep fab anion-exchange membrane peek reinforced selectivity >0,96% electric resistance <1 ω*cm2 stability 0–13 ph thickness 0,10–0,13 mm specific conductance >6 ms/cm ion exchange capacity >1,3 meq/g swelling 20% fumasep fbm bipolar membrane peek reinforced electric resistance <3 ω*cm2 thickness 0,2–0,25 mm thermal stability max 60 °c efficiency of water splitting >98% experiments were carried out at room temperature. 97 diluted, acid, caustic and electrode solution were circulated by peristaltic pumps. the flow rate of diluted, acid and caustic solution was 51 dm3/h, 44 dm3/h and 46 dm3/h. results voltagecurrent curves the voltage vs. current curves (u-i) were measured across the 31 compartment cell under different concentrations of na2so4 in electrode solution. the concentration of electrode solutions was 0.05/ 0.1/ 0.5/ 1 mol na2so4/dm3-solution. the results are plotted in fig. 2. three regions are observed on the experimental u-i curves: at low value of voltage, the increase of potential voltage does not cause electric current increase, because the electric field turns to generate protons and hydroxide ions by bipolar membrane. in second region, rise of voltage causes rising current, nearly linear relationship exist between applied voltage and electric current. at high voltage, the resistance increases drastically when a certain current is reached. the amount of protons and hydroxyl ions produced at the transition region becomes a limiting factor. during experiments the current should not exceed this certain value (limiting current) otherwise membranes will be destroyed. the limiting value of electric current increases with increasing concentration of electrode solution. although at high concentration of electrolyte, lower limiting current was measured because of evolved concentration polarization. by the grounds of experiments electrode solution of concentration 0.1 mol na2so4/dm3 was chosen, because the curve did not show limiting current in the voltage range studied. 0 0.5 1 1.5 2 2.5 3 0 5 10 15 20 25 30 35 40 voltage (v) el ec tri c cu rr en t ( a ) 0.05 m na-sulphate 0.1 m na-sulphate 0.5 m na-sulphate 1 m na-sulphate figure 2: potential drop as a function of electric current comparison of measurements at constant voltage with model solution the experiments with model solutions were carried out with constant voltage namely at 12 v, 24 v and 36 v. the diluate concentration was initially 20 g nagalacturonate/dm3. the volume of circulated diluted, acid and caustic solution was 0.4 dm3, 0.4 dm3 and 0.45 dm3. the driving force for the transport of ions is the electrical potential difference. increasing voltage obviously enhances the ion transport through the membrane. the current in the stack as a function of time are plotted in fig. 2. due to ohm's law, at he beginning of experiments higher electric current was measured at higher constant voltage. as ions were transported from diluate solution, the concentration of ions and conductivity in diluate solution decreases, the resistance of diluate increases therefore electric current drops. 0 0.2 0.4 0.6 0.8 0 50 100 150 time (min) el ec tri c cu rr en t ( a) 12 v 24v 36v figure 3: electric current in the edbm cell due to the transport of galacturonate ions and protons, galacturonic acid is formed in acid solution. the concentration of galacturonic acid (fig. 4) tends to a limiting value, independently of the value of voltage, as a function of time. 0 5 10 15 20 0 50 100 150 time (min) co nc en tra tio n (g g a/ l) 12v 24v 36v figure 4: concentration of galacturonic acid in acid compartment in acid solution the ph value rapidly decreases at beginning then it slightly increases (fig. 5). the ph drop depends generated protons and formed galacturonic 98 acid. protons are transported faster from interphase than galacturonate ions from diluate solution. at the beginning protons cause rapid ph drop. increase of ph shows galacturonic acid formation in acid solution. at lower applied voltage, ph has lower value because the transport of galacturonate ions is slower. 2 2.5 3 3.5 4 4.5 5 0 50 100 150 time (min) ph 12 v 24 v 36 v figure 5: ph vs. time in acid solution 0 2000 4000 6000 8000 0 50 100 150 time (min) co nd uc tiv ity (µ s ) 12v 24v 36v figure 6/a: conductivity of the diluate solution as a function of time 0 1000 2000 3000 4000 5000 6000 7000 0 50 100 150 time (min) co nd uc tiv ity (µ s ) 12v 24v 36v figure 6/b: conductivity of the acid solution as a function of time conductivity of diluate solution (fig. 6/a) decreases as a function of time due to the carried galacturonate and sodium ions. at the beginning conductivity in acid solution (fig. 6/b) increases rapidly at higher value of voltage (36 v). this increase is caused by protons, after 7.5 minutes the produced galacturonic acid decreases the conductivity. at lower value of voltage the water dissociation is slower, that causes less conductivity increase. our results shows measurements can be efficiently performed at voltage of 36 v. experiment with citrus pectin hydrolysate edbm with citrus pectin was carried out at 36v. the volume of citrus pectin hydrolisate was 2.95 dm3, the concentration of hydrolysate was 35.4 g nagalacturonate/dm3. the volume of acid and caustic solution was 1 dm3. results were agreement with results of model solutions. the concentration of ga in acid and diluate solution are shown in fig. 7. 0 10 20 30 40 50 60 0 100 200 300 400 500 600 time (min) co nc en tr at io n (g g a/ l) acid solution diluate solution figure 7: concentration of galacturonic acid in the acid and the diluate solution in an electrodialysis process not all of the current flowing through the stack can be utilized. average current efficiency [7] for galacturonic acid can be calculated as ni cqfδ =η where q is volume flux of acid solution, f is the faraday constant, δc is the concentration difference between acid solution in the feed of the entrance and that in the exit, n is the number of the cell units, and i is the average current. the change of current efficiency shows fig. 8 in the course of experiment with citrus pectin hydrolisate. as shown in fig. 8, the average current efficiency decreases with time therefore restricts the possibility of obtaining higher concentration of ga in acid solution. 99 0 0.1 0.2 0.3 0.4 0.5 0.6 0 100 200 300 400 500 600 time (min) cu rr en t e ffi ci en cy figure 8: the change of current efficiency as a function of time recovery of galacturonic acid from acid solution the saccharide composition (determined by hplc) of hydrolysate is 76% galacturonic acid, 3% partly hydrolysed pectin, 2.4% pectin, 8.2% glucose and 10.4% other monosaccharide, while acid solution is composed of 97.97% galacturonic acid and 2.03% partly hydrolysed pectin. to obtain galacturonic acid from the acid solution it was crystallised with methanol, then water and methanol were eliminated by vacuum filtration and vacuum drying. conclusion bipolar membrane electrodialysis can be applied for separation galacturonic acid. crystallised galacturonic acid has purity of 98%. references 1. kertesz z. i.: the pectic substances (1951), interscience publishers, new york 2. mulder m. h. v.: basic principles of membrane technology (1996), kluwer, dordrecht 3. hodúr c.: élelmezési ipar, 44 (1990) 270-272 (in hungarian) 4. gyura j., seres z., vatai gy., bekassy-molnar e.: desalination, 148 (2002) 49-56 5. novalic s., kongbangkerd t., kulbe k. d.: journal of membrane science, 166 (2000) 99-104 6. miller g. l.: analytical chemistry, 31 (1959) 426-428 7. strathmann h.: ion-exchange membrane separation (2004), elsevier, amsterdam hungarian journal of industrial chemistry veszprém vol. 33(1-2). pp. 31-42. (2005) high performance catalytic tubular membrane reactors owing to forced convective flow operation frerich j. keil*, uta flügge hamburg university of technology, chemical reaction engineering, eissendorfer str. 38, d-21073 hamburg, germany various tubular membranes were operated as catalyst supports whereby a radial convective flux of reactants through the pores was generated. a remarkable feature of convective flux through catalytic membranes is the very low catalyst loading necessary for a high conversion. additionally, this mode of operation allows a control of contact time of the reactants with the catalyst which can improve the reaction selectivity. the influence of catalyst preparation methods was investigated. very high conversions of h2o2 decomposition could be obtained for production plant waste water over a long period of time. a reactor model was used for simulations of the experiments. keywords: membrane reactor, forced convective flow, short-contact-time reactor, hydrogen peroxide decomposition *contact information: e-mail: keil@tu-harburg.de introduction membrane reactors combine reaction and separation in a single unit operation. in most cases the membrane removes one or more of the reaction or product species. the yield of reactions, which are limited by thermodynamic equilibrium, can be increased beyond their equilibrium values by removing the products. the membrane can act as a catalyst either being catalytic by itself or by being impregnated with a catalyst. in some cases packed or fluidized beds of catalysts exist inside or outside the membranes. membrane reactors are in use in biotechnology at a low temperature level. the first high-temperature catalytic membrane reactors in operation employed metallic palladium (or pd alloy) membranes. palladium membranes were the first to be used in catalytic membrane reactor applications because of their specific h2 permselectivity. micro-porous ceramic membranes can at best separate the various gases according to the knudsen diffusion law. their permeabilities are inversely proportional to the square root of molecular weights. zeolite or carbon membranes and some membranes manufactured by specialized techniques (e.g. cvd procedures) have molecular sieving properties. reviews on membrane reactors were presented by hsieh [1,2], zaspalis and burggraaf [3], saracco and specchia [4], zaman and chakma [5], dalmon [6] and coronas and santamaria [7]. models are reviewed by tsotsis et al. [8]. a comprehensive review of catalytic reactors was presented by marcano and tsotsis [9]. contrary to the previously mentioned mode of operation, in the present paper various tubular porous membranes will be employed as a catalyst support whereby radial forced convective flux of reactants through the pores is generated. in fact, it is a radial flow reactor with narrow pores. one can imagine this reactor as a radial flow reactor filled with catalytic pellets whereby the pellets were crushed such that the interstitial volume is reduced to narrow pores. the pore size distribution has to be optimized according to suitable criteria. the molecular sieve effect of the membrane is not used. owing to the forced convective flux, which is far higher than a diffusive flux, a very good contact between reactants and catalyst particles can be achieved which causes a high conversion even for very low catalyst loadings. this reactor concept was introduced in a thesis by flügge [10]. the concept of forced-flow membrane reactors with catalyst located inside the membrane pores was reported only in very few papers [11-14]. by varying the inlet pressure one can control the convective flux, and as a consequence the contact time of the reactants with the catalyst, which in turn allows one to control the reaction selectivity to a certain extent. this reactor can also be considered as a short-contact-time reactor. as an example the h2o2 decomposition at palladium catalyst on different membranes was chosen. the h2o2 content of waste water from h2o2 plants is quite high mailto:keil@tu-harburg.de 32 and has to be degraded. furthermore, this reaction should serve as an example for the testing of membrane catalysts under convective flow which, later on, should be used for the synthesis of high-grade chemicals. of course, h2o2 could be decomposed by suitable enzymes too. the objectives of the present paper are: various tubular membranes under radial flux were tested for the h2o2 decomposition reaction. the influence of the catalyst preparation methods was investigated (impregnation immobilization of the catalyst, reduction). the kinetics of the h2o2 decomposition was determined. table 1 properties of the membranes employed type of membrane pore radii [µm] inner diameter [mm] outer diameter [mm] pore volume [ml/g] isoelectric points (ph) 1) α-alumina 3.0 6 10 0.1038 7.4 2) α-alumina 0.2 6 10 0.112 7.9 3) carbon 0.14 6 10 0.215 5.75 4) carbon fiber min. 0.1 6 9 0.169 5.5 5) polyethylene 1.0 5 9 0.353 6) polypropylene 0.2 5.5 9 2.914 extensive investigations of different membranes in a pilot plant over a longer period of time should reveal the suitability of catalytic membranes under radial convective flux conditions. a two-dimensional model of the catalytic membrane was developed which represents the experimental results to a high degree of accuracy. the membranes were tested under real conditions by using production plant waste water. experimental membranes and catalyst five different membrane materials were employed: αalumina (from company porocer), carbon (carbosep m14 from techsep (rhone-poulenc)), carbon fiber (cfcc from deutsche carbone (le carbone loraine)), polyethylene and polypropylene (both from microdyn). the pore radii distributions, zero points of charge as a function of the ph-values, and the pore volumes were determined. mercury porosimetry was employed for the determination of the pore radii. the method suggested by brunelle [15] and jiratova [16] was used, modified according to a paper by ludwig and hönicke [17] for the determination of the isolectric points. the pore volumes were found by soaking the materials with ethanol. the data obtained are presented in table 1. tubular membranes were employed. the α-alumina membranes were temperature resistant up to 1000°c and pressure resistant up to 40 bar. the 0.2 µm membrane was fixed on a support which had a maximum of the pore radii distribution at 3 µm. the carbon membrane (carbosep m14 from the company techsep (rhone poulenc)) consisted of a carbon support and a zro2tio2 separation layer at the inner side of the tube. the membrane was temperature resistant up to 350°c and pressure resistant up to 15 bar. the carbon fiber membrane was a asymmetric carbon-carbon fiber tube with a thin separation layer of carbon. the maximum operation temperature was 165°c and the maximum pressure 40 bar. the spectrum of pore radii was rather broad with a minimum at 0.1 µm. the maximum operation temperature of the polyethylene and polypropylene membranes was 60°c, and the maximum operating pressures were 1.5 and 3.0 bar, respectively. palladium was employed as a catalyst for decomposition of hydrogen peroxide. the active component should be distributed evenly over the membrane cross section. for this purpose the membranes were impregnated over 1 hour with a solution of h2pdcl4 (0.5 wt-% pd). the membrane was put into such an amount of h2pdcl4 solution that the liquid filled the pore volume exactly. the membrane was dried for about 12 hours at room temperature. drying at high temperatures leads to a redistribution of the palladium to the outer surfaces of the membrane. a chemical immobilization of the palladium was done after the impregnation with h2pdcl4 by adding naoh (ph = 13.6) over 45 to 60 min. the following reaction occurs: (1) −−−− +→+ 4clpd(oh)4ohpdcl 2 4 2 4 owing to this treatment the palladium is immobilized. alternatively, naco3 (17 wt-%, ph = 11.7) was used or the dried pellets were additionally treated at 600°c. a liquid phase reduction was done at room temperature by means of nabh4: nabh4 + 2h2o → nabo2 + 4h2 (2) 2pd(oh )4 2 2 --------------------------------------------------------- 2− + 4h → 2pd + 8h o (3) 2pd(oh) + nabh−2 4 4 → nabo2 + 2pd + 6h2o (4) some palladium nuclei should be present for the reduction at room temperature. the reduction solution was set to a ph-value of 12 with naoh in order to precipitate the palladium. this measure prevents a migration of the palladium to the outer surface of the 33 membrane. alternatively, the reduction was done with hydrogen diluted with nitrogen over 3 hrs at 350°c: pd(oh) +2h−2 4 2 → pd + 4h2o (5) the preparation methods described above led to an evenly distributed palladium inside the membranes as was found by experimental checking. for the carbon membranes x-ray fluorescence was used for these investigations. kinetics of h2o2 decomposition mckee [18] investigated the disproportionation of diluted aquous h2o2 solutions with the aid of metal 0 -0,5 -1 -1,5 -2 -2,5 -3 -3,5 1/t[1/k] 0,00305 0,0031 0,00315 0,0032 0,00325 0,0033 0,00335 integralmethod differentialmethod ln ( ( )) k t yint = 6019,4x + 16,807− ydiff = 6439,4x + 18,643− fig. 1 arrhenius-plot for al2o3 powder of the viii group of elements. it was found that the activity of palladium was higher than of gold. furthermore, a strong dependence of the rate of reaction of the ph-value was detected (with a maximum at ph = 10 – 11). the kinetics was of first order and followed a postulated mechanism like this: ohohh oohohho ohohoohho ohhoohho ohhooh hhooh 2 222 22222 2222 22 222 →+ +→+ ++→+ +→+ +→ +→ •• •• •• •• •• •• (6) 2222 oo2ho2h +→ gossner et al. [19] investigated the kinetics of h2o2 decomposition with a silver catalyst for an h2o2 concentration of less than 5 mol/l. the authors observed that the reaction was first order for a h2o2 concentration below 0.3 mol/l and of second order for a concentration in the range of 0.3 – 1.2 mol/l. gossner and bischof [20,21] published also results on the dependence of the ph value of h2o2 at silver and gold catalysts. they found that the reaction rate for a silver catalyst was independent of the ph value for ph < 8 and increased with the ph value above ph = 8. at a gold catalyst the reaction rate increased with increasing ph value over the entire range of the ph scale. the reaction order for a gold catalyst was two over the whole range of h2o2 concentrations. eley and macmahon [22] investigated the decomposition of highly concentrated h2o2 solutions at wires of palladium, gold and their alloys. a significant higher activity of gold compared to palladium was detected. the authors found first order reactions. kreja [23] investigated the decomposition of h2o2 at platinum catalysts over a wide rage of h2o2 concentration (0.005 – 0.2 mol h2o2/cm3) and different specific catalyst surfaces. again a first order reaction was detected at lower and a second order reaction at higher h2o2 concentrations. the transition of the reaction order depends on the specific catalyst surface. schekhobalova [24,25] measured the kinetics of h2o2 decomposition at palladium and palladium/platinum alloys on alumina and silica supports. the alloys were more active than the pure metals. the reaction order was found to be about 0.7. the supports had no influence on the reaction rate. in order to determine the reaction kinetic expressions for each experiment two liters of a 5 wt-% h2o2 solution were filled into a continuously stirred retort and heated to a preset temperature. the ph-value was set to 7. before the experiment started the exact initial h2o2 concentration had been measured by titration with potassium permanganate. an exactly determined amount of catalyst powder (pd on membrane support) of about 2 g was filled into the retort. after certain periods of time samples of 5 ml of the reaction mixture were taken, and immediately separated from the catalyst powder by filtering in order to prevent the solution from further reaction. the present amount of h2o2 was again determined by kmno4 titration. these measurements were repeated at different temperatures in the range from 20 to 50°c. an arrhenius plot for an al2o3 membrane is presented in fig. 1. the experimental data were evaluated by means of the integral and differential method. both approaches gave nearly the same results. in table 2 some results are presented. as can be observed the reaction order with respect to the h2o2 concentration is equal to one for the present initial concentration. the activation energies are in the order of magnitude as found by schekhobalova [25] (about 50 (kj/mol)). the present authors found a transition from kinetics of first order to second order at a h2o2 concentration of about 65 g h2o2/l. h2o2 decomposition measurements for the h2o2 decomposition measurements an experimental set-up as given in fig. 2 was employed. the liquid is pumped from a storage tank via a filter through the membrane. two different pumps were used, a centrifugal pump (company hartmann) with 2800 revolutions/min with a volume flux of 13 l/min and a membrane pump (prominent g5) with a maximum volume flux of 9.54 l/min at a maximum counter pressure of 13 bar. the set-up can be either operated at a constant pressure or at a constant volume flux. the membranes (length 246 mm) were fixed into a tubular module by means of two o-ring seals (see fig. 1b). the seals separate the permeate volume from the retentate and feed. at both ends of the membrane module swagelok fittings were screwed on. for the experiments the membrane pump was used. the filter had a pore 34 diameter of 0.45 µm. valve v1 was closed such that the flux passed radially through the membrane. the fluxes and the h2o2 content were measured every 15 minutes. the loading of the membranes with palladium had nearly no influence on the fluxes compared to the original membranes. the results of the measurements will be discussed in a subsequent section. table 2 kinetic data type of membrane pore radii [µm] activation energy [kj/mol] reaction rate [g/(l ⋅ min)] 1) α-alumina1) 3.0 68.08 6.12 ⋅ 1010exp(-68.08/(8.314 ⋅ t)) ⋅ 22ohc 2) α-alumina2) 0.2 50.05 1.99 ⋅ 107exp(-50.05/(8.314 ⋅ t)) ⋅ 22ohc 3) carbon3) 0.14 50.05 1.99 ⋅ 107exp(-50.05/(8.314 ⋅ t)) ⋅ 22ohc 4) carbon4) 0.14 51.61 1.34 ⋅ 106exp(-51.67/(8.314 ⋅ t)) ⋅ 22ohc 1) 0.3 wt-% pd load 3) 0.3 wt-% pd load 2) 0.3 wt-% pd load 4) 0.06 wt-% pd load all the samples were treated with naoh and reduced with nabh4 reactant p1 p p pmembrane module productfilter p p2 a) feed swagelok-system membrane permeate retentate o-ring seal b) v1 v2 fig. 2a flowsheet of the test bench 2b tubular module of the membrane reactor modeling the model the membrane reactor consists of three regions: inside the tubular membrane, the membrane, and the annulus between the membrane and the shell (see fig. 3). for the membrane a two-dimensional model was introduced and for the other two regions a one-dimensional dispersion model was employed. these two regions are radially perfectly mixed. for the membrane a twodimensional dispersion model was introduced (see fig. 4). the fluid can be assumed as being incompressible such that there are no convective fluxes in axial direction inside the membrane. now we derive a general mass balance for the inner and shell region (see fig. 5). for a certain component we have the material balance (see notation section): ∑ = ⋅⋅++−= ∂ ∂ rn j jinoutin dvεrνsnn t n 1 &&& (7) for the axial terms a taylor expansion, truncated after the first term, gives: dx x n xndxxnn x out ∂ ∂ +=+= & &&& )()( (8) the sum of the inand outgoing fluxes therefore is: dx x nnn outin ∂ ∂ −=− & && (9) in axial direction one finds convection and dispersion: x cdaxcaxuxn rr ∂ ∂ −= )()()(& (10) the derivative with respect to the length coordinate x gives: ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ ∂ ∂ − ∂ ∂ + ∂ ∂ = ∂ ∂ 2 2)()()()()( x cd x xuxc x xcxua x xn r & (11) 35 radial mass transfer occurs owing to a mass transfer through the boundary layer and radial convection: in inp in in out outp out p m n m mrinm m n m outr n l lll auc aucccβas ∑ ∑∑ = + == + −−= , , 1 ,, 1 , 1 )(& (12) outside inside membrane ndiff ndispi ndispo n mt out n mt in nconv. nconv. ar3 ar1 ar2 x fig. 3 fluxes inside the reactor r r + dr dx nr n drr + fig. 4 two-dimensional dispersion model of the membrane the material balance around the element in fig. 5 then leads to: ∑∑ ∑∑ == + == ++ −−+ +⎥ ⎦ ⎤ ⎢ ⎣ ⎡ ∂ ∂ − ∂ ∂ + ∂ ∂ = ∂ ∂ r in inp in inin out outp out out p n j jm n m mrm m n m mr n l lll r dvεrνauc aucccβa dx x xcd x xuc x xcxua t cdvε 11 , 1 , 1 2 2 , , )( )()()()( (13) division by ε ⋅ dv = εardx gives the general expression for the material balance: ∑∑ ∑∑ == + == + ⎥ ⎥ ⎦ ⎤ + ⋅ ⎢ ⎢ ⎣ ⎡ −−+ +⎥ ⎦ ⎤ ⎢ ⎣ ⎡ ∂ ∂ − ∂ ∂ + ∂ ∂ = ∂ ∂ r in inp in inin out outp out out p n j jm n m mrm m n m mr n l lll r rνauc aucccβa aε x xcd x xuxc x xcxu εt c 11 , 1 , 1 2 2 , , )(1 )()()()()(1 ar dx nab szu nzu a fig. 5 material balance around an element this general expression can be applied to the inner region and the annulus, which results in: [ ]innerinnerrinner innermembrinnerinner r inner inner inner inner inner inner inner auc ccβa a x c d x u c x c u t c inner , ) 2 2 (1 − −⋅+ +⎥ ⎦ ⎤ ∂ ∂ − − ∂ ∂ ⎢ ⎣ ⎡ + ∂ ∂ = ∂ ∂ − (15) [ ]outerouterrmembr outermembrouterouter r outer outer outer outer outer outer outer auc ccβa a x c d x u c x c u t c outer ⋅⋅+ −⋅+ +⎥ ⎦ ⎤ ∂ ∂ − − ∂ ∂ ⎢ ⎣ ⎡ + ∂ ∂ = ∂ ∂ + , ) 2 2 (1 (16) for the membrane itself one has to introduce a twodimensional model. a material balance of a component is calculated over an arbitrary volume element dv (see fig. 4). dvεrνn nnn nn t n idiffradout diffradindiffaxoutdiffaxin convradoutconvradin ⋅+− −+−+ +−= ∂ ∂ ,, ,,,,,, ,,,, & &&& && (17) a taylor series expansion of the axial material flux, truncated after the first term, gives the following result: dx z n xndxxn ax axax ∂ ∂ +=+ & && )()( (18) 36 the reasonable assumption of no pressure gradients in axial direction results in a diffusive transport in axial direction only: x cdan rdiffax ∂ ∂ −=,& (19) thus the following result is obtained: rdrπ x cd x cda x n r ax 2 2 2 2 2 ∂ ∂ −= ∂ ∂ −= ∂ ∂ & (20) for the diffusive transport in radial direction one obtaines an analogous expression: dr r n rndrrn diffrad diffraddiffrad ⋅ ∂ ∂ +=+ , ,, )()( & && (21) the radial area depends on the position. therefore, the following expression for the radial diffusive flux is obtained: r cdxπdr r crdar diffrad ∂ ∂ −= ∂ ∂ −= 2)(, (22) partial derivation with respect to the radius results in: ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ∂ ∂ + ∂ ∂ ⋅−= ∂ ∂ r c r crdxπd r rn diffrad 2 2, 2 )(& (23) there is also a radial convective flux. therefore, the following relations are obtained: )()()( )()( )( )( )( )()()(,, rcrrarru rarc ra rra rru rarcrun iirad i irad radconvrad ⋅=⋅== = = ⋅== =⋅⋅=& (24) again we obtain for the taylor expansion: dr r xndrrn convradn convradconvrad ⋅ ∂ ∂ +=+ ,)()( ,, & && (25) partial derivation gives: r crrarru r n iiconvrad convrad ∂ ∂ =⋅== ∂ ∂ )()(, ,& (26) therefore, the material balance gets the form dvνεr r cdxdr x crπd rdxdrπ x cd dxdr r cπrrru t cdvε iirad +⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ∂ ∂ + ∂ ∂ + + ∂ ∂ + + ∂ ∂ =−= ∂ ∂ ⋅⋅ 2 2 2 2 2 2 2)( (27) with (28) rdrdxπdv 2= and recasting one obtains: rν x c ε d r c ε d rε rrru t c iirad + ∂ ∂ + ∂ ∂ +⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ⋅= −= ∂ ∂ 2 2 2 2)( (29) for the stationary case eq. (29) is an elliptical partial differential equation. in case the axial terms are dropped the equation turns to a parabolic pde. initially, a constant value for the concentration inside the inner ring of the membrane tube is assumed. the value is equal to the inlet concentration. inside the membrane and outside the tube (permeate side) initially the concentration is set to zero. this situation is the case during start-up. the tube inlet (x = 0) at the inner ring of the tube the concentration equals the inlet concentration all the time cin(x = 0) = co. furthermore, it is assumed that there is no concentration gradient at the inner and outer side of the membrane: 0 00 = ∂ ∂ = = ∂ ∂ = ∂ ∂ = ∂ ∂ = === lx out x out lx membr x membr x c x c x c x c (30) that means there is no diffusive and dispersive flux into the membrane. additionally, the concentration gradient at the inlet is set to zero. this boundary condition is quite well fulfilled. the model equations were solved by using the nag-library [26] routines d02nvf, d02nuf, d01ndf, and d02nxf. the integrator d01ndf is a general purpose routine for integrating the initial value problem for a stiff system of differential equations. it is designed specifically for the case where the jacobian is a sparse matrix. the program calls the sparse matrix linear algebra setup tourine d02nuf, and the backward differentiation formula (bdf) integrator routine d02nvf. d02nxf is a sparse linear algebra diagnostic routine. model parameters some model parameters have to be calculated. the diffusion coefficients of the pure components in water are calculated according to wilke and chang [27]: ( ) ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ ⋅⋅= − s cm104.7 2 5.0 5.0 8 ab bo ab vη tmφ d (31) for the association factor ϕ a value for water of 2.6 was taken. the molar volume va at the normal boiling point was calculated by means of a formula suggested by gunn and yamada [28]: )1(~ ~ γ−= ωv ν ν o r sc (32) whereby )0967.00292(~ ω p rtν c sc −= (33) (34) 43 2 11422.102512.2 51941.133953.033593.0 rr rr o r tt ttv ⋅+⋅− −⋅+−= for (0 ≤ tr ≤ 0.8). (35) 2 5.0 )1(91534.0)1(50879.0 )1lg()1(3.10.1 rr rr o r tt ttv −−−− −−−+= 37 for (0.8 < tr < 1). (36) 204842.009045.029607.0 rr tt ⋅−−=γ for (0.2 ≤ tr ≤ 1.0). table 3 data employed for the diffusivities of h2o2 and o2 tc [k] to [k] pc [bar] ω ( )mol m5 310~ −scν o rv γ [ ]mol m2~ν [ ]( )s m9oh, 2 2 10−ad h2o2 730.2 423.35 209.9 0.331 3.018 0.3811 0.2273 10.63 2.88 o2 154.6 90.2 50.4 0.025 4.309 0.3820 0.2268 16.37 2.8 ur uann uin x mo mperm mperm inside annulus membrane lr fig. 6 fluxes inside the membrane module lee-kessler formula [29] 6 6 1 1 43577.0ln4721.13 169347.0ln28862.1 6875.152518.15 09648.692714.5ln θθ θθ θ θp ω c +− −+ −− ++−− = − − (37) θ = tb/tc the values employed for h2o2 and o2 are given in table 3. the axial velocities in the membrane region, the radial velocities in the inner region, and the annulus are neglected. the fluxes are calculated as follows (see fig. 6). the permeate mass flow may be expressed by means of the ratio permm& (39) )(/)( tmtmχ operm &&= therefore, the total permeate flux, which passes through the membrane from the inlet up to the length x, is given by: (40) rorpermpx lxχtmlxtmtxm /)(/)(),( &&& == for the mass flux inside the tube one obtains: (41) )/1)((),( roin lxχtmtxm −= && assumed that the fluid has a constant density, and the tubular cross section is constant along the tube, the fluid velocity inside the tube is given by: (42) )/1)((),( roin lxχtutxu −= in the annulus is a permeate outlet at the position x = xout. therefore, we find for the mass fluxes in the annulus: out out out permrperm rperm ann xx xx xx tmlxtm lxtm txm > = < ⎪⎩ ⎪ ⎨ ⎧ − = )()( 0 )( ),( && & & (43) the fluid velocities in the annulus are given by: out out out ro ro ann xx xx xx lxθχtu lxθχtu txu > = < ⎪⎩ ⎪ ⎨ ⎧ −⋅ = )1()( 0 )( ),( (44) surface membraneouter surface membraneinner =θ (45) for the partial derivatives one obtains: ro in lχtu x tu /)( )( −= ∂ ∂ (46) ro ann lθχtu x tu /)( )( −= ∂ ∂ (47) for the velocity of the radial flow inside the membrane one obtains: )4()(),( 2 rior dldtuχtdu ⋅⋅= (48) the inlet velocity of the fluid is given by: uo(t) = v(t)/a (49) for the axial dispersion coefficient was calculated according to taylor and aris [30,31]: m mdisp d dudd 192 22 += (50) for the inner tube and the annulus the values of ddisp = 4.835 ⋅ 10-3 [m2/s] and ddisp = 2.15 ⋅ 10-4 [m2/s] were used, respectively. the mass transfer coefficient, β, was calculated according to: β = sh ⋅ d/d (51) whereby the sherwood number is given for the laminar region re < 5 ⋅ 105 by: 2 13 1 (re)332.0 cssh = (52) and the turbulent region by (53) 43.08.0re0296.0 scsh ⋅= 38 with the schmidt number sc = η/(ρd) (54) and the reynolds number re = (udρ)/η (55) the input data given in table 4 were used for all calculations. a porosity of 0.2779 was used for the al2o3 membrane, and of 0.1405 for the carbon membrane. table 4 input data for the calculation reactor length [m] 0.246 inner diameter of the membrane [m] 0.006 outer diameter of the membrane [m] 0.010 position of permeate outlet [m] 0.206 ratio of permeate flow to inlet flow [-] 1 density of the fluid [kg/m3] 1000 dynamic viscosity of the fluid [pas] 0.001002 diffusion resistance factor of the solid membrane [-] 11 diffusion coefficient in water [m2/s] h2o o2 2.88 ⋅ 10-9 2.80 ⋅ 10-9 inlet concentration [mol/l] h2o o2 0.15588 0.0 ratio of the inner cross section to the annulus cross section [-] 0.81818 diameter of the outer tube [m] 0.012 results and discussion conversions, fluxes and pressures were measured for the various membranes. an example of the results for the alumina membrane (see no. 1 in table 1; with 0.3 wt-% pd, immobilization of pd with naoh and reduction with h2) are given in fig. 7a/b. after 400 minutes the conversion is constant 98%, the pressure0.9 bar and the flux 16 l/h. for pore diameter of 0.2 µm (no. 2 in table 1) the conversion dropped c on ve rs io n % time [min] time [min] 100 95 90 85 800 200 400 600 800 1000 10 8 6 4 2 0 0 200 400 600 800 1000 pr es su re [b ar ] pressure flux fl ux [l /h ] 20 16 12 8 4 0 a) b) fig. 7 a) conversion and b) pressure as a function of time (alumina membrane) c on ve rs io n % pr es su re [b ar ] 100 80 60 40 20 0 0 100 200 300 400 500 600 0 100 200 300 400 500 600 10 8 6 4 2 0 pressure flux fl ux [l /h ] 20 16 12 8 4 0 a) b) fig. 8 a) conversion and b) pressure as a function of time (carbon membrane) after 900 minutes from 100% to 34% and the flux dropped owing to pore clogging. a reduction of membrane no. 1 in table 1 with nabh4 instead of h2 (0.3 wt-% pd, immobilization with naoh) gave a constant conversion of 65%, no pore clogging was observed. if the palladium content of this membrane was reduced from 0.3 wt-% to 0.06 wt-% the conversion was constantly 58% after 1500 min. if the 39 immobilization of palladium was done with soda the conversion dropped continuiously down to 27%. the carbon membrane (no. 3 in table 1, 0.3 wt-% pd, immobilization with naoh, reduction with nabh4) showed a constant conversion of 70% at a flux of 5.5 l/h and a pressure of 7 bar (see fig 8a/b). a reduction of the palladium content to 0.06 wt-% resulted in a decrease of the conversion to 8% at a flux of 6 l/h. a reduction by means of hydrogen (0.3 wt-% pd) decreased the conversion from 70% to 42%. the carbon fiber membranes (no. 4 in table 1) showed in all cases very low conversions (max. 3%). the polyethylen membrane (no. 5 in table 1, 0.3 wt% pd, immobilization with naoh, reduction with nabh4) gave a constant conversion of 20% at a flux of 14 l/h at a pressure of 4 bar. a reduction of the palladium content to 0.15 wt-% resulted in a decrease of the conversion to 5%. the polypropylen membrane (no. 6 in table 1; 0.3 wt-% pd, immobilization with naoh, reduction with nabh4) revealed a conversion of only 15% at a flux of 7.5 l/h at a pressure of 4.5bar. therefore, the polymer membranes gave rather low conversions. in all cases the 0.2 µm membranes showed a lower conversion compared to the 3 µm membranes, and clogged after a short time. as expected, a higher palladium content led to a higher yield. furthermore, 2500 2000 1500 1000 500 4 5 6 7 8 9 10 11 12 ph a ct iv ity [m gh o /g h ] 2 2 k at fig. 9 activity of the catalyst as a function of the ph value the membranes with a load of 0.06 wt-% pd deactivated over the first 200 minutes. the two methods of immobilization of palladium (naoh, naco3) showed no difference in case of the 3 µm alumina membranes, but for 0.2 µm alumina membranes an immobilization by means of naoh resulted in a higher conversion. the reduction with hydrogen was advantageous for the 3 µm alumina membrane compared to nabh4; for the 0.2 µm alumina membrane it was just the opposite. for the other membranes a higher palladium content gave also a higher conversion. the immobilization with naoh and reduction with nabh4 led for the carbon membrane to a twice as high conversion as an immobilization at 600°c followed by a reduction with h2. of considerable importance on the activity of the catalyst is the ph-value. in the range of a ph value of 5 – 11 the activity of the catalyst increased by a factor of about nine (see fig. 9) for the 3 µm alumina membrane (0.06 wt-% pd). for all other membranes also a nearly linear increase of the catalyst activity could be observed with increasing ph value. the reason for this behaviour may be explained by a mechanism in the alkaline ph region via a perhydroxylion, namely: (56) o2hohoh 0.5oo oohho hoho ohhoohoh 23 2(ads) (ads)(ads)2 (ads)2(aq)2 32222 ⇔+ ⇔ +⇔ ⇔ +⇔+ −+ −− −− −− ------------------------------------- 2222 0.5oohoh +⇔ furthermore, an oxide layer on the catalyst surface may be formed which reacts with perhydroxylions: (57) −− −− −+ +⇔+ ++⇔+ ⇔ ohmohom oohmhomo hohoh 2 22 222 0 41 82 123 164 205 246 0 6 8 1 19 1 70 22 1 6,00 5,00 4,00 3,00 2,00 1,00 0,00h o r es id ua l c on te nt [g /l] 2 2 length [mm] start time [s] end fig. 10 h2o2 content inside the membrane as a function of time and length inside outside length [mm] h o c on ve rs io n [% ] 2 2 0 2 3 4 5 6 7 8 9 10 100 90 80 70 60 50 40 30 20 10 0 radius 246,00 205,00 164,00 123,00 82,00 41,00 0,00 fig. 11 h2o2 conversion as a function of length and radius increasing the temperature leads to an increased decomposition rate, as expected from the kinetic 40 expression. a variation of the h2o2 inlet concentration between 0.25 [g/l] and 70 [g/l] had nearly no influence on the conversion of h2o2. this was tested for membrane number one in table 1, for which the immobilization was done with naco3 and reduction with h2. in the inlet concentration range between 0.25 [g/l] and 40 [g/l] the conversion dropped slightly from 100% to 90%; between 40 [g/l] and 70 [g/l] the conversion increased again to 100%. this may be explained by the change of the reaction order from one to two at higher concentrations. as expected, an increased volume flux, and therefore a shorter contact time, leads to a lower conversion. based on the kinetics and the model discussed in the previous sections several simulations were executed. examples are presented in figs. 10/11/12. in fig. 10 the residual content of h2o2 as a function of time and length inside the tube is presented for membrane no. 2 in table 1, where the immobilization was done with naoh and the reduction with nabh4. after about 17 [s] a stationary profile is achieved. stationary profiles of conversion as a function of the membrane radius and length are given in figs. 11/12. in fig. 11 the same membrane as in fig. 10 was calculated. in fig. 12 a carbon membrane (see no. 3 in table 1) with a pd load of 0.06 wt-% was employed. 10 9 8 7 6 5 4 3 2 1 01 3 5 7 9 246,00 205,00 164,00 123,00 82,00 41,00 0,00 inside outside length [mm] h o c on ve rs io n ln [% ] 2 2 radius fig. 12 h2o2 conversion as a function of length and radius 100 90 80 70 60 50 40 30 20 10 0 20 25 30 35 40 45 50 55 temperature [°c] c on ve rs io n [% ] calculated measured fig. 13 comparison of measured and calculated conversions the immobilization was done by heating to 600°c, and the reduction was executed with h2. in figs. 13/14 measured and calculated conversions are compared for various temperatures. as can be seen from the figures, the coincidence is quite good. in order to test the membranes under real conditions waste water from a plant in bernburg (solvay intox) was investigated. for this purpose the filter was removed from the pilot plant in order to investigate clogging effects. two alumina membranes were employed (3 µm, 0.2 µm). for both cases a palladium load of 0.3 wt-% was used. the membranes were reduced with nabh4, the immobilization of palladium was executed by means of naoh. for the 3 µm membrane a h2o2 conversion of 100% could be achieved at a flux of 2.3 l/h at a feed pressure of 1 bar and a flux of 6 l/h at 2 bar. in this case the conversion reduced to 96%. for the 0.2 µm membrane the conversion was 100% at a pressure of 1 bar and a flux of 2.5 l/h. typical results are presented in table 5. at a pressure of 1 [bar] nearly all h2o2 was decomposed and no pore blocking was observed. conclusions the radial convective flow is a promising alternative for catalytic reactions. owing to the possibility of varying the pressure one can, at least to a certain extent, control the yield and selectivity of reactions. this approach may be also useful for gas/solid reactions. 100 90 80 70 60 50 40 30 20 10 0 20 25 30 35 40 45 50 55 temperature [°c] co nv er si on [% ] measured calculated fig. 14 comparison of measured and calculated conversions table 3 waste water (solvay interox, bernburg) outlet after catalytic membrane* colour yellow, opaque clear ph 7 7 h2o2 [mg/l] 691 0 – 15 cod [mg/l] 943 866 tc [mg/l] 526 494 * 3 µm alumina membranes 0.3 wt-% pd, immobilization with naoh, reduction with nabh4. 41 symbols a area per unit of length [m] a area [m2] ar cross sectional area [m2] c concentration [mole/m3] d diameter [m] d dispersion or diffusion coefficient [m2/s] dm molecular diffusion coefficient [m2/s] i inner lr length of membrane [m] m& mass flow [kg/s] m mole weight [g/mole] n mole number [mole] n& mole flux [mol/s] axn& axial mole flux [mol/s] np number of components [-] nr number of chemical reactions [-] p pressure [pa] r radius [m] r rate of reaction [mol/cm3 ⋅s] re reynolds number [-] s& total radial flux between phases [mol/s] sc schmidt number [-] sh sherwood number [-] t time [s] t temperature [k] tr reduced temperature [-] u flow velocity [m/s] u average flow velocity [m/s] v volume [m3] va molar volume of diluted a at normal boiling point [cm3/mole] x length coordinate [m] β mass transfer coefficient [m/s] χ flow ratio [-] ε void fraction [-] γ coefficient [-] (see eq. 36) η dynamic viscosity [kg/(s ⋅ m)] ϕ association factor [-] v stoichiometric coefficient [-] ν~ molar volume νj stoichiometric factor [-] θ reduced boiling temperature [-] (see eq. 37), ratio of inner to outer membrane surface [-] (see eq. 45) ρ density [kg/m3] ω acentric factor [-] subscripts ann annulus ax axial c critical diff diffusive disp dispersion in into inner inner side of membrane membr membrane o inlet out out of outer outer side of membrane perm permeate r radial, reduced rad radial references 1. hsieh h.: catal. rev.-sci. eng. 1991, 33, 1 2. hsieh h., in: membrane science and technology series, vol. 3, elsevier, amsterdam, 1996 3. zaspalis v.t. and burggraaf a.j., in: r.r. bhare (ed.), inorganic membranes. synthesis, characteristics and applications, van nostrand reinhold, new york, 1991 4. saracco g. and specchia v.: catal. rev.-sci. eng. 1994, 36, 305 5. zaman j. and chakma a.: j. membr. sci. 1994, 92, 1 6. dalmon j.a., in: g. ertl, h. knötzinger, j. weitkamp (eds.), handbook of heterogeneous catalysis, vol. 3, wiley-vch, weinheim, 1997. 7. coronas j. and santamaria j.: catal. today, 1999, 51, 377 8. tsotsis t.t., minet r.g., champaigne a.m. and liu p.k.t., in: e.r. becker and c. pereira (eds.), computer-aided design of catalysts, marcel dekker, new york, 1993, p. 471. 9. marcano j.g.s. and tsotsis t.t.: catalytic membranes and membrane reactors, wiley-vch, weinheim, 2002 10. flügge u.: entwicklung und einsatz katalytischer membranen am beispiel der modellreaktion des wasserstoffperoxidabbaus. experimentelle und theoretische untersuchungen. dissertation, technische universität hamburg-harburg, 1998 11. ziegler s., theis j. and fritsch d.: j. membr. sci. 2001, 187, 71 12. vincenta m.j. and gonzaleza r.d.: aiche j. 2002, 48, 1257 13. kobayashi m., togawa j., kanno t., horinchi j. and tada k.: j. chem. technol. biotechnol., 2003, 78, 303 14. fritsch d., randjelovic i. and keil f.: catal. today, 2004, 98, 295 15. brunelle j.: pure and appl. chem., 1978, 50, 1211 16. jiratova k.: appl. catal., 1978, 1, 165. 17. ludwig s. and hönicke d.: chem.-ing.-tech., 1992, 64, 639. 18. mckee d.w.: j. catal., 1969, 14, 355 19. gossner k., heidrich h. and körner d.: z. f. phys. chem. n.f. 1969, 67, 220 20. gossner k. and bischof h.: z. f. phys. chem. n.f. 1972, 78, 277 21. gossner k. and bischof h.: z. f. phys. chem. n.f. 1972, 79, 28 22. eley d.d. and macmahon d.m.: j. coll. interface sci., 1972, 38, 322 23. kreja l.: z. f. phys. chem. n.f., 1984, 140, 247 24. schekhobalova v.i.: vestn. mosk. univ., ser. 2: khim., 1986, 27, 97 42 25. schekhobalova v.i. and voronova l.v.: vestn. mosk. univ., ser. 2: khim., 1989, 30, 63 26. numerical algebra group fortran library, mark 19, nag gmbh, garching 27. poling b.e., prausnitz j.m., and o’connell j.p.: the properties of liquids and gases, mcgraw hill, new york, 2001, chapter 11.21 28. vdi-wärmeatlas, vdi-verlag gmbh, düsseldorf, 1994 29. lee b.i., kessler m.g.: aiche j., 1975, 21, 510 30. taylor, g.: proc. royal soc. a, 1953, 219, 186 31. aris r.: proc. royal soc. a, 1956, 235, 67 microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 37(2) pp. 101-106 (2009) fuel production from triglycerides containing gas oils cs. tóth , p. baladincz, j. hancsók university of pannonia, institute of chemical and process engineering, department of hydrocarbon and coal processing h-8201 veszprém, p.o.box.: 158, hungary e-mail: tothcs@almos.uni-pannon.hu lately the development and the use of energy sources which are of bio-origin are required. the engine fuels have special importance. based on their origin they can be conventional, alternative or conventional + alternative. biofuels which can be produced from biomass, thus from a renewable energy source, are alternative fuels. the objective of our research work was to investigate the production of diesel fuel with excellent quality and/or of diesel fuel blending component by heterogeneous catalytic conversion of gas oil fraction containing 75% sunflower oil. furthermore, our aim was to determine the advantageous process parameters (temperature, pressure, liquid hourly space velocity, hydrogen/hydrocarbon ratio) during application of the selected nimo/al2o3 catalyst. based on the results obtained we determined that the main properties of these products were significantly better compared to the feed as diesel fuel components. the products which were made under desired combination of process parameters (t = 350–380 °c; p = 80 bar; lhsv = 1,0–1,5 h-1; h2/feed ratio: 600 nm3/m3) had lower than 10 mg/kg sulphur and nitrogen content, and the cetane numbers were significantly higher than it is specified in the msz en 590:2009 standard (minimum 51). keywords: vegetable oil, gas oil, mixtures, sunflower oil, biogasoil, heterogenous catalytic hydrogenation introduction for modern society, it is very important to maintain mobility, of which energy need is covered mostly with fossil derived energy sources. the depletion of crude oil stocks, the dependence of crude oil and import energy sources, and the need to reduce the environmental pollution necessitates the development and application of alternative energy sources. the energy sources include the paramount importance engine-fuels which, according to its origin, may be conventional, alternative, or conventional & alternative (fig. 1) [1-4]. bio-engine-fuels that belong to alternative enginefuels are produced from a renewable energy source as e.g. biomass. widely used alternative engine-fuels come into view, for example the derivatives of vegetable-oils (out of them esters) and furthermore nowadays products made with catalytic hydrogenation. the carbon-dioxide originating during the application of these fuels does not burden the environment, because it builds in again through the photosynthesis of the plants. as a result of the lower emission, the use of biofuels burdens the environment less than the use of fossil derived fuels [1-4]. in the directives and valid standards, the european union supports and orders more application of bioderived energy sources, among them bio engine-fuels. figure 1: classification of motor fuels the diesel fuel standard valid since 2000 (msz en 590:2000, then msz en 590:2004 and msz en 590:2009) permits the use of bio-derived blending components, but it specifies the composition (fatty-acid-methyl-esters) and sets limits to blended quantity (msz en 590:2009: maximum 7 v/v%). the european union confirmed and extended directive 2003/30/ec multiple times and fixed the ratio of bio engine-fuels in 10% till 2020 [5-8]. in hungary, the development and application of bioderived engine-fuels and blending components – among them mainly vegetable-oils and its derivatives – is very important, too. the engine-fuel consumption in the european union swings to diesel-fuel and according to the prognosis, more increase is probable in the rate of diesel-fuel and gasoline [9]. the engine-fuel market in 102 hungary exfoliates such as the european, but in our country, the usage of gasoline still increases, although more slightly than the use of diesel-fuel (figure 2) [10]. 0 0,5 1 1,5 2 2,5 3 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 year q ua nt ity o f f ue ls , 1 06 t gasoline diesel fuel figure 2: the change in the use of gasoline and diesel fuels in hungary therefore increasing the quantity and improving the quality of the bio-derived diesel-fuel blending components has great importance. in hungary, for this purpose nowadays the biodiesel (fatty-acid-methyl-ester), in the immediate future the bio gas oil (from the heterogeneous catalytic hydrogenation of triglycerides containing mainly normaland isoparaffins having a similar boiling point range as the traditional gas oil; the denomination and the notion was introduced at institute of chemical and process engineering, department of hydrocarbon and coal processing, university of pannonia at first [11-12]) and someday the synthetic bio gas oil (mainly a mixture of normaland isoparaffins from biomass based synthesis gas) will be available. the technologies produce biodiesels and the produced biodiesels also have a lot of problems and disadvantages (high unsaturated content causing bad thermal, oxidation, and thus storage stability; high water content causing corrosion problems; sensitivity to hydrolysis causing poor storage stability; unfavourable cold properties; low energy content; methanol) which damage the profit of the utilization and production [13-14]. to overcome these problems and to attain better quality, the alternative is the chemical conversion of triglyceride based feeds, mainly hydrocarbons rich in paraffins, which products can be utilized in dieselengines mixed with diesel gas oil or directly. from the available sources of triglyceride containing materials the most advantageously used are the oils made from oil-bearing vegetables. the heterogenous catalytic conversion of vegetable oil – gas oil mixtures can occur in two major ways. in the first way, shown in figure 3, the vegetable oil is pre-treated in a reactor first then it is deoxygenated in the hdo reactor. the product rich in n-paraffins, has a very high cetane number, but poor cold flow properties – is mixed with desulphurized gas oil stream after separation. in the second way, the vegetable oil is mixed in a gas oil stream in the refinery after pre-treatment. after it, the mixture is converted in a conventional (or slightly modified) desulphurization plant [15-17]. with further isomerisation or dewaxing, gas oil product can gain high cetane number and good cold flow properties. with these methods it is also possible to use the product as a blending component for quality boosting in gas oil streams with poor quality (low cetane number, high aromatic-, sulphurand nitrogen content). figure 3: options of the catalytic conversion of the vegetable oil-gas oil mixtures. (hdo: hydrodeoxygenation; hds: hydrodesulphurization) in the case of these methods, the pre-treatment of the vegetable oils is necessary, which step should be brought to effect by the building of a continuous, pre-treatment catalyst containing reactor. in the pre-treatment reactor the metal(ca, k, mg), the phosphorusand the solid impurities contents of the vegetable oil are removed [15-17]. for the time being, many leading corporations and departments of research examine the realization of these methods, respectively tailoring them for the regional capabilities [18-26]. the aim of the experimental work was the investigation of preparing high-quality products by the catalytic hydrogenation of mixtures of vegetable oil and crude gas oil distillate, which is useful in pure form as diesel fuel or as gas oil blending component as well. within this, our goal was to specify the favourable operation parameters (temperature, pressure, lhsv, hydrogen/feedstock volume ratio) on a commercial nimo/al2o3 catalyst. experimental work this paper presents experimental results obtained via the investigation of heterogeneous catalytic transformation of gas oil distillate containing sunflower oil in 75%, on nimo/al2o3 catalyst. beside this, our goal was to determine the favourable operation parameters (temperature, pressure, lhsv, hydrogen/feedstock volume ratio) applying a commercial nimo/al2o3 catalyst. during the experimental work, the influence of the process parameters on the yield of the organic and gas products, and on the yield and main physicalchemical properties and application impact of the gas oil boiling point range fraction of the product was studied. the combinations of process parameters were selected on the basis of the results of our pre-experiments, taking into account the physical and chemical properties of gas oil distillate and the sunflower oil. 103 experimental equipment the experiments were carried out in experimental equipment (figure 4) which contains all the main devices of a heterogeneous catalytic hydrogenation plant. this process equipment has a tubular reactor of 100 cm3 active volume capacity [27]. the experimental work was carried out in continuous mode in a single reactor array catalytic system. figure 4: simplified scheme of the test apparatus (1 reactor; 2 pre-heater; 3 oxygen converter; 4, 5 gas dryer; 6,10 gas filter; 7 gas flow meter; 8 gas flow meter; 9 demister; 11 compressor; 12, 13 burettes for liquid feed; 14 pump; 15, 18 cooler; 16 separator; 17 level meter; 19 closing valve; 20 control valve; 21 back valve; 22 manometer) feedstocks the feedstock of the heterogeneous catalytic experiment was gas oil-vegetable oil mixture with 75% vegetable oil content of properly pre-treated sunflower oil originating from a supplier in hungary. important properties of these mixtures are summarized in table 1. the catalyst was nimo/al2o3, which was chosen on the basis of other experiments previously performed by the department of hydrocarbon and coal processing at the university of pannonia. analytical and calculation methods the properties of the feedstocks and the products were specified as the specifications of the msz en 590:2009 standard, relevant for diesel-fuels and with standardised calculation methods. the ensued cetane numbers were specified with iqt apparatus according to standard astm d6890-03a. process parameters the experiments were carried out – on the basis of other experiments previously performed – on combinations of the following process parameters, t = 300–360 °c, p = 80 bar, lhsv: 1,0–3,0 h-1, h2/feedstock volume ratio: 600 nm3/m3. table 1: main properties of the feeds properties gas oil gas oilvegetable oil mixture density (15.6 °c), g/cm3 0,8513 0,8451 kinematic viscosity, (40 °c), mm2/s 5,36 24,73 iodine number, g i2/100 g 0,5 90 sulphur content, mg/kg 10370 2594 nitrogen content, mg/kg 228 58 flash point, °c 79 79 cold filter plugging point, °c 2 15 aromatic content, % 37,6 9,4 cetane number 49 43 104 results and discussion by the heterogeneous catalytic conversion of the gas oil containing vegetable oil, the product was separated to three main fractions as gas fraction, water fraction and organic fraction. in the gas phase, products besides the hydrogen are not used in the reactions, there is a high amount of gases formed through the hydrogenation reaction routes, such as carbon-oxides, propane arises from the triglyceride and lighter hydrocarbons originate from the cracking reactions (figure 5). the yield of the gas fraction significantly increases with the temperature, which is at first caused by the conversion of the vegetable oil, then at higher temperatures (>340 °c) boosts so that the hydrocracking reactions become conspicuous. 0 2 4 6 8 10 12 14 16 18 290 300 310 320 330 340 350 360 370 temperature, °c y ie ld o f g as p ha se , % 1.0 1.5 2.0 3.0lhsv, h-1 figure 5: the change of the yield of gas phase as a function of temperature the yield of the liquid organic product (c6+ fraction) decreased with increasing temperature and pressure as well as with decreasing lhsv (figure 6). this was caused by the higher conversion of vegetable oil – while water, co2, co and lighter products formed, decreasing the yield of the liquid product – and also the hydrocracking of the hydrocarbons. 78 80 82 84 86 88 90 92 94 290 300 310 320 330 340 350 360 370 temperature, °c y ie ld o f o rg an ic li qu id p ha se , % 11 1 1.0 1.5 2.0 3.0 lhsv, h-1 figure 6: the change of the yield of organic products (c6+) as a function of temperature. one of the main goals of the experiment was to convert the triglyceride molecule to a product which is in the gas oil boiling point range. for that very reason, it is important to know how the quantity of the products in boiling point range 180–360 °c – which was obtained via distillation –changed with the process parameters. the yield of the gas oil boiling point range product changes as the maximum-curve of the temperature (figure 7). till 320–330 °c the yield increased with the rate of the conversion, which can be seen well on the decrease of the residual fraction (figure 8), and with the further increase of the temperature the yield significantly decreases because of the hydrocracking reactions. with increasing lhsv, the yield of the main product increased because of the foreshortening of the contact time. 85 86 87 88 89 90 290 300 310 320 330 340 350 360 370 temperature, °c y ie ld o f m ai n pr od uc t, %1 11 1.0 1.5 2.0 3.0 lhsv, h-1 figure 7: the change of the yield of the gas oil boiling point range product as a function of temperature (p = 80 bar) while specifying the main product, the change in the sulphur and aromatic content was compared to the experiments with the gas oil used for the blending of the feedstock. 0 5 10 15 20 25 300 320 340 360 temperature, °c y ie ld o f r es id ua l p ha se , % 11 1 1.0 1.5 2.0 3.0lhsv, h-1 figure 8: the change of the yield of residue as a function of temperature. on the basis of the results, we determined that the desulphurization efficiency increased with increasing the temperature (figure 9), namely the sulphur content of the main product decreased. at the most severe process parameters (t = 360 °c, lshv = 1,0 h-1) a product, eligible for the valid diesel gas oil standard (msz en 590:2009) (<10 mg/kg) was produced. as it can be seen in the figure, the sulphur content of the gas 105 oil decreased more than in the case of the products made from mixtures, because the parallel reactions via the hydrogenation – saturation of double bonds, deoxygenation, dearomatization – the desulphurization confining as these reactions take place on the same catalytic places. 50 55 60 65 70 75 80 85 90 95 100 290 300 310 320 330 340 350 360 370 temperature, °c h d s, % 0 10 20 30 40 50 60 h d a , % 0% 75%vegetable oil content, % figure 9: the changes in desulphurisation(hds)and dearomatization(hda) efficiency as a function of temperature (p = 80 bar, lshv = 1,0 h-1) dearomatization efficiency changes as the maximum-curve in the case of both feedstocks. this is because with the increasing of the temperature, above 350 °c – the thermodynamic inhibition made by the exothermic reactions – the dearomatization is confined. one of the important attributes of diesel-fuels is the cold filter plugging point, which as we determined, decreases with the increasing temperature (figure 10), because on account of the hydrocracking reaction, more lighter hydrocarbon products formed and their cfpp is more favourable. via isomerisation and/or with additives, a product can be made of which cfpp satisfies the valid dieselfuel standards (summer grade: +5 °c, winter grade: -20 °c). -5 0 5 10 15 20 25 30 35 290 300 310 320 330 340 350 360 370 temperature, °c c fp p, °c 0% 75% vegetable oil content, % figure 10: the changes in cfpp value of the main fraction as a function of temperature. one of the most important quality properties for the gas oil boiling point range products is its cetane number. the cetane number of these products improves 24-29 points in the case of the preferential process parameters, which is significantly higher than the valid standards minimum specification, 51. summary and conclusion it was found that during the catalytic conversion, the properties of the products (first of all, the cetane number) were improved significantly comparing that to the properties of the feedstock. applying the desired combinations of process parameters (t = 350–380 °c; p = 80 bar; lhsv = 1,0–1,5 h-1; h2/feedstock ratio: 600 nm3/m3), the sulphur content of the products were less than 10 mg/kg and their cetane number were significantly higher than that in the valid diesel gas oil standards (msz en 590:2009). increase of the cetane number is caused by the high n-paraffin content of the products, which is produced mainly in the catalytic conversion of the vegetable oil portion of the feedstock. products were made which, with 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l. dobos 1, j. jäschke2, j. abonyi1, s. skogestad2 1university of pannonia, department of process engineering, egyetem str. 10 veszprém, 8200, hungary e-mail: dobosl@fmt.uni-pannon.hu 2norwegian university of science and technology, department of chemical engineering, no-7491 ,trondheim, norway the various governmental policies aimed at reducing the dependence on fossil fuels for space heating and the reduction in its associated emission of greenhouse gases such as co2 demands innovative measures. district heating systems using residual industrial waste heats could provide such an efficient method for house and space heating. in such systems, heat is produced and/or thermally upgraded in a central plant and then distributed to the final consumers through a pipeline network. in this work two main objectives will be considered: the first is to create a dynamic model which can represent the main characteristics of a district heating network and the second one is to design a non-linear model predictive controller (nlmpc) to satisfy the heat demands of the consumers in the heat exchanger network. as the model predictive controller is based on minimizing an objective function, it is totally perfect to find the way to reduce the superfluous energy consumption and make the best of using the freely applicable industrial waste heats. beside this environmental aspect, reducing the invested energy consumption can reduce the operational costs. keywords: district heating network, modeling, non-linear model predictive control, mpc introduction it has become natural for people today to have a network for the distribution of the electricity. however the picture is much different when it comes to heating. the majority of the buildings in western europe are heated with individual boilers that are fed either with natural gas or with oil. only in some cases, e.g. with waste incineration, a district heating network (dhn) is implemented to distribute the heat. district heating networks are for distributing heat generated in a centralized location for residential and commercial heating requirements. the heat can be obtained from cogeneration plants or waste incineration plants although to satisfy the periodically increased heat demand socalled heat-only/peak load boiler stations are also used. these stations can be suppliers of residential and commercial consumers for space heating and for hot tap water and if necessary it can provide heat for industrial consumers for a certain level. however, because of the numerous advantages of district heating systems, it would be beneficial to implement them in other areas too, since the main advantages of district heating systems are [12]: 1. fewer sources of emission in densely populated areas. 2. fewer individual boilers, thus increased the usable space in the buildings. 3. professional and on-going operating and maintenance of the centralized heating technology. since energy becomes a more and more competitive market nowadays, thus optimization of the energy production and distribution becomes an important task for energy companies. the district heating facility can provide higher economic and environmental efficiency compared to local boilers. this the reason why the importance of these networks are increasing, and the countries, which use local heat suppliers, such as the nordic countries, are switching to district heating networks instead. district heating networks exist in several variations: in the district heating network reported in [1] includes several consumers are located in different areas, but there is no energy storage and just one production unit. in [13], a storage tank is added to the network. in [6], a storage tank is also considered, but there is no thermal energy supply network. so the variety of the district heating networks are numerous. the operation of a district heating network is subject to operational constraints, e.g. assure the minimum inlet temperature of consumers this way satisfying their heat demand. the aim of the control strategies therefore is to meet these restrictions and at the same time to minimize the operational costs of the heat supplier. model predictive control methods an interesting alternative to conventional control structures since the formulation of the objective function and constraints takes both aspect into consideration. operating a district heating network implies to assign values to integer variables (status of production units, 38 status of pumps…) and to continuous variables (amounts of energy to produce). as a result, the optimization of the production and energy supply planning appears to be a huge, mixed integer and non linear optimization issue. consequently, most studies use a simplified model, leaving aside some of the district heating network aspects. simplifying the model may allow the use of one of the classical optimization methods listed in [11], but the solution can be strongly suboptimal when applied to the whole district heating network. our goal is to model a district heating network presented latter and at the same time we use the model in a model predictive controller to satisfy the heat demand of the consumers of the network. the work is organized as follows: in the modeling section the topology of the applied district heating network will be introduced and the applied model equations will be defined. in the control section first the general non-linear model predictive controllers will be described, then defining the purposes, introducing the applied mpcs and examining the control results. modeling section the models of a district heating network found in the literature are either a physical description of the heat and mass transfer in the network [8] or they are based on a statistical description of the transfer function from the supply point to the critical point considered. a statistical modeling approach is presented [10] where an ensemble of armax (auto-regressive moving average with exogenous input) models with different fixed time delays is set up, and depending on some estimated current time the models are switched. in [5] the grey-box approach for modeling combines physical knowledge with data-based (statistical) modeling; physical knowledge provides the main structure and statistical modeling provides details on structure and the actual coefficients/ estimates. the model in this work is developed with using the method of [7] so applying the physical description of the heat and mass transfer in the network. local models of the components of the network are established and then connected together. topology the topology showing fig. 1 was chosen to represent the main characteristics of a district heating network. the network contains two heat production units, three consumers, two pumps and a valve. the production unit, called producer 1, is the base load boiler, which may be considered a waste incineration plant. the other production unit, called producer 2, is the peak load boiler station, which has to satisfy the increased heat demand in the network, especially in case of the consumer 3. hx1 and hx2 heat exchangers are for transfer the produced heat from the primary circles to the secondary circle that is practically for distributing the heat for the consumers. figure 1: the topology of the examined district heating network during the modeling procedure the following simplifications and assumptions were made to avoid the excessive complexity of modeled network, while preserving important characteristics: ● since the system containes only pressurized water thermodynamical and material properties like heat capacities and densities are assumed constant. average values for the respective temperature intervals are used. ● isothermal flow is assumed through the pumps and valve. this is done due to the low pressure differences in the system. ● the pressure profile of the system changes much faster than the temperature profile, so it was modeled using steady-state equations, while the heat exchangers are modeled with dynamical assumption. the following model equations were applied to describe the network: valves the valve is modeled using the following equation: 2 2vpp inout ⋅ ⋅−= ρξ (1) where: pout – outlet pressure of the valve pin – outlet pressure of the valve ρ – density of water v – velocity of the fluid ξ means the valve coefficient that is calculated by the expression below: 100/(%)ngvalveopeni )dtotalopene(ξξ = (2) 39 as it was mentioned previously, there is no difference in value of the inlet and outlet temperature. pumps by neglecting any temperature rise in the water during travel through the pumps, they can be described using the bernoulli equation. the elevation difference is set to zero, and the pipe diameter was assumed equal before and after the pump, thus the following expression characterizes the pump: m ppp inout ηρ ⋅⋅ += (3) where p means the pump duty, η means the efficiency of the pump, m means the mass flow. mixers the mixing unit is modeled using the following expressions, under the assumption of instant and homogeneous mixing: ∑ = = n i iout mm 1 (4) out n i ii out m tm t ∑ = ⋅ = 1 (5) in modeling the mixers’ pressure, we assume: pin, i = pout (6) where: t – temperature p – inlet and outlet pressure. pipes in modeling the district heating networks taking the effects of pipelines into consideration is an important factor. the heat loss in the pipes can not be neglected, and the dead time between the ends of the pipe has to be accounted for. assuming one-dimensional flow, this leads to the partial equation: 0)),((2 ),()(),( 02 2 =− ⋅⋅ ⋅ + ⋅⋅ + ttxt rc tx x t r tmtx t t p ρ μ ∂ ∂ ρπ∂ ∂ (7) where: cp – specific heat capacity of the fuid r – the radius of the pipe μ – heat transfer coefficient on the wall t0 – the ambient temperature. this equation has the following solution: ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ − ⋅⋅ ⋅ − ⋅−−+= ))((2 000 0 )))((()( ttt rc inout petttttttt ρ μ (8) the varying time delay t – t0(t) is defined by: ld r mt t = ⋅⋅∫ τ ρπ τ 0 2 )( (9) l is the length of the pipe (m). as the thermal losses on pipes are assumed very low. thus the eq. 8 is approximated by the following expression: ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ − ⋅⋅ ⋅ −⋅−= ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ − ⋅⋅ ⋅ −⋅−−+= ))((21))(( ))((21)))((()( 00 0000 ttt rc tttt ttt rc tttttttt p in p inout ρ μ ρ μ (10) in eq. 10 constant time delay is assumed regarded to the high computation demand of calculating varying time delay. this approach yields a simple non-linear dynamic system, which can be quickly solved. the mechanical losses in pipes are modeled by: d lvp 2 2⋅ ⋅= ρξδ (11) δp – pressure drop of the pipe d – diameter of the pipe. heat exchangers in order model the proper dynamic behavior of the heat exchangers an approach using a cell model with ordinary differential equations is chosen [4]. this means that the heat exchanger is divided into perfectly and instantly mixed tanks. each cell featuring a hot side, a wall side, and a cold side element (fig. 2). the idea is that this approach will approximate the logarithmic mean temperature difference of the heat exchanger as the number of cells increases, while showing a realistic time delay behavior. in our model five cells were used on the hot side and five cells on the cold side. it is assumed that all cells are identical, and that no back-mixing occurres. in addition we assume that the mixing is instantaneous. figure 2: cell model of the heat exchanger 40 the following equations are applied to a cell: hot side: ))()(())()1(( )( ititauititcv dt itcdv chhhph hph −⋅⋅−−−⋅⋅⋅ = ⋅⋅⋅ • ρ ρ (12) cold side: ))()(())()1(( )( ititauititcv dt itcdv chhcpc cpc −⋅⋅+−+⋅⋅⋅ = ⋅⋅⋅ • ρ ρ (13) to avoid excessive complexity of the model the resistance of the wall is included to the heat transfer coefficient (u). the pressure drop of a heat exchanger is usually made up of the following parts: ● pressure drop of the inlet nozzle. ● pressure drop caused by the friction in the shell and in the tubes. ● pressure drop of the outlet nozzle. to model these areas separately it would be necessary to use complex equations. to reduce the number of the expressions (and because we do not have a real dhs we can fit the model to) the pressure drop of a heat exchanger is approximated with the model equation of a valve. this way it was possible to model the pressure drop as the function of the flow rate and at the same time keep the model simple. heat production units the approach for modeling the heat production units are similar to the model of the heat exchangers, however in this case just the cold side was divided into cells, following the scheme below: figure 3: cell model of the production unit the following equation is for representing the model of a cell on the cold side: n qititcv dt itcdv ccpc cpc +−−⋅⋅⋅= ⋅⋅⋅ • ))()1(( )( ρ ρ (14) where: q – invested heat n – the number of the cells. this simplification is introduced because in the aspect of the heating network it is not important how the heat was produced, just the quantity of the invested heat is significant. the previously introduced network was implemented in simulink. an other model of this network is implemented in matlab with the simplification of neglecting the time delay of the pipelines (in eq. 8). this was done to compare the performance of the two models in the mpc controller. control section model based control concepts the development of modern model based control concepts can be traced back to the early 1960s, to the linear quadratic regulator (lqr), which is designed to operate linear dynamic system. however, even though the concept of minimizing an objective function is very simple, the complexity of the controlled systems require advanced algorithms to solve the problem. at the early stage of model predictive controllers there were no sufficient computation facilities to realize complex optimization algorithms, so linear control algorithms were preferred [3, 9]. one example is dynamic matrix controller (dmc), because of the analytical solution to the objective function. with growing computation power more complex methods could be applied to solve nonlinear complex optimization problems in short time, and this way the non-linear model predictive algorithms could be born. model predictive controllers– theoretical basis mpc is a model based control algorithm where models are used to predict the behavior of dependent variables (i.e. outputs) of a dynamical system with respect to changes in the process independent variables (i.e. inputs). in chemical processes, independent variables are often setpoints of regulatory controllers that govern valve movement (e.g. valve positioners with or without flow, temperature or pressure controller cascades), while dependent variables might be constraints in the process (e.g. product purity, equipment safe operating limits), however it is not neccessary (e.g. in some cases temperature is measured but it is not a constraint). the mpc uses the models and current plant measurements to calculate future moves in the independent variables that will result in operation that minimizes the cost function and that satisfies all independent and dependent variable constraints. with the help of the fig. 4 the essence of the model predictive control is easily understandable. we formulate the objective function: min δu(k+ j ) (w(k + j) − y(k + j))2 + λ δu2 (k + j −1) j=1 hc ∑ j= h p1 h p 2 ∑ (15) where ∆u(k) denotes the change of the control signal, the hp1 and hp2 parameters are the minimum and maximum cost horizons and hc is the control horizon, which does not necessarily have to coincide with the maximum horizon. λ is a weighting factor, it is a 41 sequence that considers future behaviors, usually constant values or exponential sequences are used. w is the set point signal following the notation of fig. 4. figure 4: the essence of model predictive control generally predictive control uses the receding horizon principle. this means that after the computation of the optimal control sequence, only the first control action will be implemented, subsequently the horizon is shifted one sample and the optimization is restarted with new information about the measurements. in the presence of unmeasured disturbances and modeling errors the mpc controller can exhibit steadystate offset. one way of avoiding this is to design a disturbance estimator which gives the controller implicit integral action. the simplest method for incorporating integral action is to shift the setpoints with the disturbance estimates as depicted in fig. 5, where the corrected setpoints w′(k) = w(k) – d(k) are modified based on differences between the output of the system and its estimated value d(k) = y(k) – y′(k). figure 5: the imc (internal model control) scheme the scheme shown in fig. 5 is often referred as internal model control (imc) strategy. this disturbance model assumes that plant/model mismatch is attributable to a step disturbance in the output and that the disturbance remains constant over the prediction horizon. while these assumptions rarely hold in practice, the disturbance model does eliminate offset for asymptotically constant setpoints under most conditions. in practice all processes are subject to constraints. the actuators have a limited field of action as well as determined slew rate, as in the case of valves. constructive reasons, safety or environmental ones or even sensor slopes themselves, can cause limits in the process variables such as levels in tanks, flows in piping of maximum temperatures and pressures. all of this leads to the introduction of constraints in the mpc problem. usually, input constraints like umin ≤ u(k + j) ≤ umax, j = 1, ..., hc (16) ∆umin ≤ ∆u(k + j) ≤ ∆umax, j = 1, ..., hc (17) are hard constraints in the sense that they must be satisfied. coversely, output constraints can be often viewed as soft constraints because their violation may be necessary to obtain a feasible optimization problem: ymin ≤ y(k + j) ≤ ymax, j = j1, ..., hp (18) where j1 represents the lower limit for output constraint enforcement. because of the sequential solving method, some constraints can be implemented while solving the optimization problem. these constraints are for taking into consideration for example actual physical states of actuators or valves. these constraints can be defined as input constraints, represented by eq. 16-17. in this study the input constraint were introduced in the following form: u(k+j–1) – ∆u ≤ u(k+j) ≤ u(k+j–1) + ∆u, j = 1, ..., hc (19) using the fact that the value of ∆u is maximized. non-linear model based predictive controller non-linear model-based predictive control (nlmpc) algorithms should be applied in situations where the controlled process is inherently nonlinear, or where large changes in the operating conditions can be anticipated during routine operation, such as in batch processes, or during the start-up and shut-down of continuous processes. the advantages of non-linear predictive control include the following. ● manipulated and state variable constraints are explicitly handled. ● nonminimum-phase processes are easily handled. (if the prediction horizon is chosen adequately) ● knowledge of future setpoint changes is included that is useful for scheduled, coordinated operational changes. the main problem in nlmpc is that a non-linear often (non-convex) optimization problem must be solved at each sampling period in real-time. this hampers the application to fast processes where computationally expensive optimization techniques cannot be used, due to the short sampling time. several methods can be used to solve such constrained non-linear optimization problems. the most widely studied algorithms are described on [2]. using the sequential quadratic programming (sqp) method it is possible to minimize the value of the objective function, in each sampling period, varying the parameterized control signal values (u=[u(i)…u(i+hc)]) on the control horizon. hence the solution of the optimization problem is a control signal trajectory. the first element of the control signal trajectory is realized 42 in the next time sequent and the other elements are neglected. this is called recending horizon strategy. figure 6: the scheme of the non-linear model predictive controller model predictive control of a district heating network energy producer are compelled to reduce their rate of polluting emissions beside fulfilling consumers power demands with the lowest global costs. thus, technical, economical and environmental constraints have to be simultaneously dealt with. the optimization problem stated from this multifield area can hardly be solved as it is a non-linear programming problem, consists of numerous variables. the optimal control of district heating networks, for which propagation delays can not be neglected and mechanical and thermal losses have non-linear expressions, picks up all these harsh difficulties. managing a district heating network implies to assign values to integer variables (status of production units, status of pumps…) and to continuous variables (amounts of energy to produce). as a result, the optimization of the production and energy supply planning appears to be a huge, mixed and non linear optimization issue. however solving a non-linear mixed-integer optimization problem might have the ability to provide a control signal that may provide better performance than solving a non-linear optimization problem. in this work a non-linear sqp method with soft constraints will be introduced to avoid the complexity of mixed-integer non-linear programming. to take the different weights of the control variables into consideration the objective function is augmented with the absolute value of the control variables: ∑ ∑ ∑ = = =+ ++ +−+++−+ 2 2 1 1 2 1 22 )( )( )1())()((min p p p c h j h hj h jjku jku jkujkyjkw α λβ δ δ (20) it can also be important to define weights (β) for the error, the set points and manipulated variables, because the main task – keeping the manipulated variable equal to the set point – can be easily assured. this version of the objective function will be applied in this study. differences between the models with and without time delay in the case of the depicted (fig. 1) district heating network the possible control variables are: ● invested heat in production unit 1 ● invested heat in production unit 2 ● pump duty of p1 ● pump duty of p2 ● valve opening. since the pump p1 is chosen to compensate the pressure drop of the heat exchangers and pipelines, the p1 pump does not take part in satisfying the heat demand of consumers, so it is controlled by a local regulator. the split ratio between consumer 2 and consumer 3 can be adjusted using two control variables: valve opening and the pump duty of the p2 pump (as the pressure increase on the pump is the function of the pump duty (eq 3)). these control variables determine the flow in the two directions and thus the transferred heat to the consumers. comparing the model with and without time delay a main difference can be seen in the dynamics of the models. it is caused by the absent time delay. fig. 7 shows the difference between the two models (full line means the model without time delay, dot line means the model with time delay). naturally both simulations were run with the same inputs. in the initial moment there is no temperature profile in the network so the first 15 minutes show the temperature startup of the district heating network. after 15 minutes there is a step in the heat from producer 1. after the network is in steady state, there is a new step in the heat from the producer 2. in the 50th minute there is a step in the pump duty of pump 2 the last change in the inputs is changing the value of the valve opening in 63rd minute. these changes can be seen on the fig. 8. figure 7: transferred heat in model ‘a’ and ‘b’ model to the same input 43 figure 8: the input parameters of the district heating network related to fig. 7 from the fig. 7 it can be stated that the model without time delay can provide almost the same steady state than the model with time delay. the main difference is in the dynamical behavior. simulation scenarios the main goal is to satisfy the heat demand of the consumers. in this study the heat demand of the consumers is assumed to be known. it us to be tracked as the set points of the district heating network. to test the performance of the dhn the following set point trajectories were chosen: the set point changes are at the same time: at around 33rd minute and 60th minute. in order: ● consumer 1 (lower line) has 25000 kw – 60000 kw – 30000 kw heat demand ● consumer 2 (middle line) has 21000 kw – 55000 kw – 27000 kw heat demand ● consumer 3 (upper line) has 28000 kw – 55000 kw – 32000 kw. the main goal is to minimize the transition time as possible and at the same time fulfill the heat requirements of the consumers (follow the previously presented set point trajectory) considering to minimize of the use of the production unit 2 and the pump duty of p2 pump. this goal can be reached with minimizing the objective function presented in eq. 20. optimization model a contains time delays in the pipes: so the model and the process are identical. in this case it is not necessary to use the imc scheme, because there is no mismatch, and because there are no unmeasured disturbances. model b has no, so the plant-model mismatch seen in fig. 7 is expected to deteriorate control performance. because of this model mismatch simulation experiments will be carried out to test the performance of the mpc with imc scheme and without imc scheme. since the steady states of the two models should be equal the mpc was expected to reach the set point trajectories in both cases, but the dynamical behavior can not be predictable without simulations. simulation results control performance of mpc with a and b model the ise (integral square of error) criteria was chosen to compare the control performance of the two controllers (a and b model).additionally plots are used to compare quality of control. the set points are the same in all cases. the tuning parameters of model predicitve controllers are the lenght of the prediction and control horizon and the value of α, β and λ parameters (eq 20). to be able to compare the scenarios in both cases the same tuning parameters were chosen (prediction horizon: 4, control horizon: 1, sample time: 45 sec). the computation demand of the nlmpc controller is very high, since the sqp algorithm obtains gradient information via finite differences and the differential-algebraic model equations have to be solved for each perturbation. this solving method is very time-consuming and this is the reason why the tuning parameters of the nlmpc controller have not been optimized. control results using the ‘a’ model ‘a’ model means that the applied model during the optimization is the same as the model used as the operation process. thus there is no model mismatch is expected so there is no need to apply the imc scheme. the constraints are formulated like eq 19. the applied constraint can have serious effects on the computed control signal as seen the fig. 9 and fig. 10. analyzing the first transition: to assure a lower flow rate in direction of consumer 3 it was necessary to set the higher pressure drop of that section. to reach this goal infinite variations of valve opening-pump duty value pairs exist. by applying proper weight in objective function the biggest valve opening – the lowest pump duty pair can be applied. in the steady state of the system this condition is obviously determined. in the unconstrained case pump duty is decreased quickly to increase the pressure drop in the direction of flow, but at the same time the valve opening is set as high as possible – 100%. in the constrained case the controller handles the changes of these manipulated variables differently since it is not permitted to change them arbitrary. the increasing of that direction is handled by closing the valve and at the same time reduce the pump duty. closing the valve is a necessary action since the change of the pump duty is constrained. 44 figure 9: comparing the control performance of the unconstrained (dashdot line) and constrained (dot line) mpc figure 10: the manipulated variables regarding to the previous figure full line – constrained, dashed line – unconstrained mpc the quick and accurate control actions are not surprising since the most precise model was applied during the optimization, but at the same time this accuracy has enormous computational demand: simulation needs almost 8–10 hours to be finished. in the further cases only constrained mpcs will be described using the assumption that in unconstrained cases they would provide similar control action as it was recently shown. control results using the ‘b’ model using the ‘b’ model implies that the applied model in the optimization is not the same as the model used in as an operation process. for this scenario 3 different cases will be introduced: ● case 1: mpc without imc scheme ● case 2: mpc with imc scheme ● case 3: mpc, combination of the previous cases. case 1 – mpc without imc scheme here the control algorithm does not have any information about the model mismatch. the control performance mainly depends on the difference of the time delay. in the previous case this did not cause a problem since the model was identical, but in this case this requirement is not fulfilled. the control performance can be illustrated by fig. 11. as the fig. 11 shows, the existing model mismatch causes steady state offset, mainly detectable after the first transient. however this mpc has the advantage of avoiding any overshoot. the steady state offset – if it is converted to temperature difference – means 2–3 °c difference. since the same objective function was used in the optimization section in all cases – the same penalty weights were applied for the change of inputs – the control variable trajectories kept all the characteristics that were introduced in the case of using constrained mpc using ‘a’ model. the computational time was reduced to the half of the previous simulation, the simulation needs almost 3–4 hours to be accomplished. figure 11: the control performance of the model predictive controller in case 1, ‘b’ model without imc scheme 45 figure 12: the computed control signal corresponding to fig. 11 figure 13: the control performance of the model predictive controller in case 2 figure 14: the computed control signal regarded to the control scenario depicted on fig. 13 figure 15: the modified set point signal (by imc scheme) (full line) and the output of the network (dashed line) case 2 – mpc with imc scheme in order to eliminate steady state offset imc scheme is applied. after running a simulation using imc scheme, the following control result can be observed: in contrast to case 1 and simulation using ‘a’ model in this case some overshoot and oscillation occurres. a reason for this could be that the set point signal is modified with the error of the model and the plant fig. 15 shows the modified set point signal, which is the input of the optimization section and used in computing the minimum of the objective function. the oscillations are mainly caused by the absent time delay in the model and it is the most obvious during transitions. after the oscillations have died away at steady state there is no offset. case 3 – combination on case 1 and case 2 in this case an attempt will be made to combine the advantages of case 1 and case 2, avoiding overshoot and eliminating the steady state offset. to reach this goal the following strategy is applied: since the imc structure modifies the set point signals significantly during transitions, it is not advantageous to apply this scheme during the transitions. at the same time it is very useful to apply the imc scheme to eliminate the steady state offset. so in this case a trigger is implemented in the controller to switch on the imc scheme. the trigger is formulated with the following expression: 46 k n imeime ≤ −− 2))1()(( (21) where: me – the model error vector in ith and (i-1)th sample time n – length of the model error vector k – constant. so if the change of the model error is smaller than a previously determined constant, it means that the manipulated variable is relatively close to the steady state. if this condition is fulfilled the imc scheme is switched on and eliminate the steady state offset. by applying this method the following control result can be yielded: as the figures shows, this method can extract the advantage of imc – no steady state offset and at the same time exclude the disadvantage of imc – oscillations in the set point signal. figure 16: the control performance of the model predictive controller in case 3 figure 17: the computed control signal regarded to the control scenario depicted on fig. 16 performance evaluation of the different mpc systems in this section we compare the different mpc using a the integral of square error (ise), and graphical plots. additionally the control performance is examined in the point of view of settling time and the existence of overshoot during the control scenarios. furthermore we will explain the occurring differences. general comparison in this short section the controllers will be compared in some general aspects: ● performance index ● settling time and overshoot. performance index the integral square error (ise) is a measure of the control performance. it is obtained by integrating the square difference of set point signal and controlled variable over the time interval of the simulation. as the values of the controlled variables only known at sample times, the ise can be approximated with the following expression: ∑ = −= n i ii ywise 1 2)( (22) where wi means the value of the set point in ith moment, yi is the output of the system, n is the number of time steps. the constrained ‘a’ model provides the best performance in terms of ise. this is not surprising, since the controller uses the most accurate model to predict the reaction of the plant to a certain input. in cases that use ‘b’ model the controllers have worse performance because of plant – model mismatch. case 1 and case 3 has equal ise value, despite the combination of imc/noimc scheme. it is found that introducing switching strategy benefits only for consumer 2. settling time and overshoot next we consider the settling time and overshoot. in tables 2 and 3 the performance of the control scenarios is summarized. table 1 contains the ise value of the previously presented simulations. 47 table 1: comparing the performance of the applied mpcs by ise value ise (*109) consumer 1 consumer 2 consumer 3 mean % case 'a' model 1.7 1.45 1.6 1.58 100% case 1 2.54 2.31 2.72 2.52 159% case 2 2.52 2.12 3.14 2.59 164% case 3 2.56 2.27 2.74 2.52 159% table 2: comparing the applied mpcs by the existing of overshoot overshoot startup transient 1 transient 2 case 'a' model no yes no case 1 no no no case 2 yes yes yes case 3 no no no table 3: comparing the applied mpcs by settling time settling time (min) startup transient 1 transient 2 case 'a' model 7 7 9 case 1 11 12 13 case 2 25 28 24 case 3 15 15 13 analysis of the performance of the ‘b’ model the main advantage of applying this model – reduced computational time. next we highlight some important characteristics. because of the plant – model mismatch and the lack of imc scheme the mpc in case 1 can not reach the set point signal as it can be seen on fig. 12. to eliminate this phenomenon the imc scheme was applied. fig. 18 shows the result (for transient 1). as mentioned before, the overshoot of imc-mpc has been caused by the significant model error in the transients. taking model error into consideration is not a negligible fact since the performance of the model predictive control is a function of the model parameters, and model parameters can be the function of the time (eg. fouling in the heat exchangers can change the heat transfer coefficient). comparing the case a model and case 3 fig. 19 shows the difference of these two controllers. figure 18: graphical comparison of control performance of case 1 and case 2 controller figure 19: graphical comparison of control performance of case ‘a’ model and case 2 controller 48 figure 20: control variables of case ‘a’ model and case 3 the main difference is the settling time. the case 3 controller reaches the set point slower than the controller which uses the ‘a’ model. this happens because ‘a’ model and ‘b’ model have different dynamics (‘b’ model has no time delay). thus the ‘b’ model can reach the set point signals faster by the effect of the same input signal than ‘a’ model. that is why the ‘b’ model considers the transient finished sooner than it is realized by the operating process (‘a’ model). in steady state both models responsed with almost the same output (for the same input). to reach the set point signal without steady state offset the imc scheme switches on and eliminates the offset. summary in the previous sections detailed and general comparisons of the applied controllers was given. the case ‘a’ model was able to provide the highest accuracy that was confirmed by the lowest ise value and settling time. the most significant disadvantage of case ‘a’ model was the enormous computational demand that was reduced by using the ‘b’ model in the optimization. in case 1 it was observed, that a less accurate model was also useful for control purposes, however the performance was not as good as in case a, since there was a steady state offset and the settling time was higher than in case a. the case 1 controller had the drawback of the lack of the feedback of the difference of the model and plant. this feedback was realized in case 2 by introducing imc scheme. it had the advantage of eliminating the steady state offset of case 1, but unfortunately it accentuated the model mismatch in the dynamics. in case 3 the beneficial characteristics – eliminating the steady state offset caused by the model mismatch and avoiding the overshoot – of case 1 and case 2 were combined. this kind of solution could provide the most attractive performance. it can be difficult to predict the behavior the controller and the controlled system, compared to the case ‘a’ model. finally it can be stated that it is beneficial to use a model which is as accurate as possible but at the same time it is important to consider the fact that the computation demand is increasing with the increasing model accuracy. in case of plant – model mismatch the use of imc scheme can be useful since it can handle the mismatch and the effect of unmeasured disturbances at the same time. outlook and future work while designing the non-linear mpc framework it was very important to keep it modular, so changes are easy to implement. in this field the two most important characteristics of the control algorithms are: ● to have the opportunity to implement the control algorithm in the control system in a short time ● the ability of the control algorithm to provide a feasible control signal in a shorter time interval than the sampling time. for applying a non-linear model predictive algorithm it is very important to require that the optimization algorithm can find the (global) minimum of the objective function or at least a feasible solution in an certain time interval. considering that numerical optimization in each sequence can be very time consuming it is necessary to implement the methods which can reduce the computational demand of the optimization process. some possible approaches for this are: ● model reduction, which yield less states in the model ● applying the gradient of the objective function during the optimization. when it can be realized, these kind of control algorithms can be used widespread in the industrial practice as a real time optimization algorithm, regarding that the mpc algorithms can be applied in the advanced control level. ackowledgement jános abonyi is grateful for the support of the bolyai research fellowship of the hungarian academy of sciences. the financial support of the támop-4.2.208/1/2008-0018 project is gratefully acknowledged. references 1. benonysson a., bøhm b., ravn h. f.: (1995) operational optimization in a district heating system. energy conversion and management vol 36 (5) (1995), 297-314. 2. henson m. a.: (1998) nonlinear model predictive control: current status and future directions. computers and chemical engineering, 23, 187-202 49 3. marchetty j. l., mellchamp d. a., seborg d. e.: (1983) predictive control based on discrete convolution models, ind. eng. chem. res. dev., 22 488-495 4. mathisen k. w., morari m., skogestad s.: (1993) dynamic models for heat exchangers and heat exchanger networks, european symposium on computer aided process engineering 3 graz, austria 5. nielsen a. h., madsen h.: (2006) modelling the heat consumption in district heating systems using a grey-box approach energy and buildings 38 (2006) 63-71 6. ravn h. f., rygaard j. m.: (1994) optimal scheduling of coproduction with a storage. engineering optimization vol 22 (1994), 267-281. 7. sandou g., font s., tebbani s.: global modelling and simulation of a district heating network supélec, service automatique 8. sandou g., font s., tebbani s., hiret a., mondon c.: (2005) predictive control of a complex district heating network, proceedings of the 44th ieee conference on decision and control, and the european control conference 2005, seville, spain, december 12-15, 2005 9. shridhar r., cooper d. j.: (1997) a tuning strategy for unconstrained siso model predictive control, ing. eng. chem. res., 36, 729-746 10. søgaard h. t.: (1993) stochastic systems with embedded parameter variations – applications to district heating. ph.d. dissertation. technical university of denmark, institute of mathematical statistics and operations research. 11. subir s., kothari d. p.: (1998) optimal thermal generating unit commitment: a review. electrical power & energy systems vol 20 (7) (1998), 443-451. 12. weber c., marechal f., favrat d.: network synthesis for district heating with multiple heat plants, the international conference on energy and environment, ciem 2005 13. zhao h., holst j., arvastson l.: (1998) optimal operation of coproduction with storage. energy vol 23 (10) (1998), 859-866. microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 39-42 (2008) investigation of satureja hortensis l. as a possible source of natural antioxidants l. gontaru , s. plánder, b. simándi budapest university of technology and economics, department of chemical and environmental process engineering budapest 1111, budafoki út 6-8. f/ii. 1. floor, hungary e-mail: gontaru@vtp.rub.de natural antioxidants play important roles as health-protecting factors. antioxidants are also widely used as additives in fats and in food processing to prevent or delay spoilage of foods. spices have received an increased attention as natural sources of many effective antioxidants. in this study satureja hortensis l. (summer savory) was examined as a potential source of natural antioxidant compounds. for the isolation of the active components two extraction methods were investigated: conventional soxhlet extraction and supercritical fluid extraction. conventional soxhlet extraction was carried out with organic solvents with different polarities. supercritical fluid extractions were performed with neat co2 at two different pressures (300 and 450 bar) at 40 °c. to estimate the antioxidant activity of the extracts, 1,1-diphenyl-2picrylhydydrazyl (dpph) assay was used. the results were reported as ic 50%, where ic 50% was defined as the extract concentration required decreasing the initial dpph concentration by 50%. the antioxidant activity of the extracts obtained with organic solvents decreased in the following order: ethanol 50% > ethanol 96% > isopropanol > ethanol 100% > acetone > ethyl acetate > pentane. the highest antioxidant activity exhibited the extract obtained with ethanol 50% (with an ic 50% value of 14.48 ± 0.02 µg/ml), while the extract obtained with pentane showed the lowest antioxidant activity (with an ic 50% of 98 ± 0.1 µg/ml). the antioxidant activity of the extracts was also compared with the antioxidant activity of butylated hydroxytoluene (bht). the extract obtained with ethanol 50% showed approximately similar antioxidant activity as bht (with an ic 50% of 12.86 ± 0.19 µg/ml). although in the case of the supercritical extraction the antioxidant activity increased with increasing the pressure, it was lower than the antioxidant activity of the extracts performed with organic solvents. keywords: summer savory, extraction, antioxidant activity introduction recently the interest in natural antioxidants has increased dramatically due to: (1) concerns regarding the safety of the chronic consumption of synthetic antioxidants (butylated hydroxyltoluene and butylated hydroxylanisole), (2) the antioxidant efficiency of a variety of phytochemicals, (3) the consensus that foods rich in certain phytochemicals can affect the aetiology and pathology of chronically diseases and the ageing process and (4) the public’s conceived belief that natural compounds are innately safer than synthetic compounds and are thus more commercially acceptable [1]. herbs, spices and teas are the most important targets in research for natural antioxidants from the point of view of safety. satureja hortensis l. is an annual culinary herb belonging to the family labiatae. it is known as summer savory, native to southern europe and naturalized in parts of north america [2]. the leaves, flowers and stems of summer savory are frequently used as additives in commercial spice mixtures for many foods to confer aroma and flavour. this plant is also used in the traditional medicine to treat various ailments as cramps, muscal pains, nausea, indigestion, diarrhoea, and infection diseases [3]. besides, it was demonstrated that extracts from satureja hortensis l. exhibited antimicrobial, antioxidant, sedative, antispasmotic and antidiarrheal properties [2-8]. the objectives of the present study were first of all to select the plant material, and then to identify the most suitable solvent to recover the antioxidant compounds from this plant. in order to select the raw material a preliminary investigation on the quality was carried out. the antioxidant activity of natural extracts has been found to depend on the active components of the raw material, the type and polarity of extraction solvent and the isolation procedure [9]. in our study two extraction methods were compared: conventional soxhlet extraction and supercritical fluid extraction. 40 materials solvents and reagent for the laboratory extraction, co2 used was of 99.5% (w/w) purity and was supplied by linde gas hungary co. ltd. all other solvents (pentane, ethyl-acetate, isopropanol, ethanol 100%, ethanol 96%, acetone) used for the conventional soxhlet extractions were purchased from molar chemicals ltd, hungary. the ethanol 50% (50% water) used also for the conventional soxhlet extraction was prepared from ethanol 96%. 1,1pdipheny2-picryl-hydrazyl (dpph) free radical used for the estimation of the antioxidant activities of the extracts and bht used as a standard were purchased from fluka, switzerland. plant material four samples of dried summer savory plant (satureja hortensis l.) were bought from three different companies fitodry kft, rózsahegyi kft, biodrog-berta kft in hungary. in our work the samples are noted with savory 1, savory 2, savory 3 and savory 4, respectively. a preliminary investigation on the quality of the samples was carried out. the moisture content of every sample was measured. the moisture content decreased as follows: savory 1 (14.37%) > savory 2 (11.42%) > savory 3 (11.25%) > savory 4 (8.81%). for the characterization of the rubbed raw material sieving was performed using a vertical vibratory sieve shaker (labortechnik gmbh, ilmenau) for 20 min. the particle size of the rubbed raw material was approximately 0.8–1.2 mm. methods soxhlet extraction extractions with organic solvents of different polarities (pentane, acetone, ethyl-acetate, isopropanol, ethanol 100%, ethanol 96% and ethanol 50%) were carried out. samples about 15–20 g raw material were extracted in a soxhlet apparatus with 250 ml solvent, until totally depleted. the whole process took 22–24 h. after extraction the solvent was removed under vacuum using a rotator evaporator rotadest, type 2118. two parameters were measured: the yield% (w/w) (which was determined as the amount of the extract/100 g of dry material) and the antioxidant activity. every extraction was carried out in triplicate. supercritical fluid extraction the extraction experiments were performed in a high pressure pilot plant equipped with a 5 l volume extractor vessel (delivered by natex, austria). two extractions with neat co2 at two different pressures (300 and 450 bar) at 40 °c were performed. for each extraction about 1000 g rubbed savory plant was weighted accurately and filled into the extractor. the desired temperature and pressure were adjusted, and the co2 feed was started. the accumulated product samples were collected and weighed at certain time intervals. the co2 flow rate was measured with a micro motion rft 9729 type mass flow meter and it was about 7 kg/h in both cases. the extractions were carried on until the amount of the last product sample decreased for one hour under 0.1% of the raw material. a more detailed description of the equipment is given extensively elsewhere [10]. estimation of antioxidant activity by dpph assay to estimate the antioxidant activity of the extracts dpph (1,1-diphenyl-2-picryl-hydrazyl) assay was used. dpph is a stable free radical which is often used as an indicator in testing hydrogen-donation capacity and thus antioxidant activity. the dpph assay was carried out following the same method as reported elsewhere [11]. different concentrations of various extracts dissolved in methanol were added to 2.5 ml methanol solution of dpph. after 30 min incubation period at room temperature, the absorption was read against a blank at 517 nm using a uv/vis spectrophotometer m501 single beam – camspec. the inhibition of the free radical dpph was calculated in percent (i%) in the following way: i% = [(ablank asample)/ablank] · 100 where: ablank – is the absorbance of the control reaction (containing all reagents except the test compound), asample – is the absorption of the test component. results were reported as ic 50%, where ic 50% was defined as the extract concentration required decreasing the initial concentration by 50%. results and discussion selection of plant material in order to select the plant material for our experiments a preliminary investigation on the quality of four different samples of summer savory was performed. antioxidants are known to interrupt the free radical chain of oxidation by donating hydrogen from phenolic hydroxy groups and to form stable products, which do not initiate or propagate further oxidation [12]. the concentration of an antioxidant needed to decrease the dpph concentration by 50% is a parameter widely used to estimate antioxidant activity [13]. the 41 lower the ic50 value, the higher is the antioxidant activity [14]. the results of the extraction yield and antioxidant activity of the ethanol and pentane extracts are shown in table 1 and 2. table 1: yield and antioxidant activity of different samples of satureja hortensis l. extracted with ethanol 96% ethanol extract raw material ayield (%) aic 50% (μg/ml) savory1 28.96 ± 0.41 40 ± 0.1 savory2 24.83 ± 0.22 27 ± 0.3 savory3 17.92 ± 0.93 80 ± 0.1 savory4 15.27 ± 1.09 50 ± 0.6 amean value of three measurements ± sd (standard deviation) it can be observed that the ethanol extracts showed both antioxidant activities and the yields higher than the extracts obtained with pentane. among the extracts obtained with ethanol, the savory 2 extract exhibited the highest antioxidant activity (with an ic 50% of 27 ± 0.3 µg/ml), while the savory 3 extract showed the lowest antioxidant activity (with an ic 50% of 80 ± 0.1 µg/ml). in the ethanol extracts no correlation could be observed between the antioxidant activity and the yield. table 2: yield and antioxidant activity of different samples of satureja hortensis l. extracted with pentane pentane extract raw material ayield (%) aic 50% (μg/ml) savory1 3.19 ± 0.19 160 ± 0.2 savory2 3.51 ± 0.12 160 ± 0.2 savory3 2.27 ± 0.09 185 ± 0.8 savory4 2.44 ± 0.11 180 ± 0.3 amean value of three measurements ± sd (standard deviation) in the case of the extractions performed with pentane the extracts of savory 1 and savory 2 manifested a higher antioxidant activity (with an ic 50% of 160 ± 0.2 µg/ml) and higher yield than the extracts of savory 3 and savory 4 but less than the antioxidant activity of the same samples obtained with ethanol. it can be concluded that the best quality exhibited the extract of savory 2. this sample was used in our further experiments. in the attempt to increase the yield and the antioxidant activity, the savory 2 was subjected to the extraction with three different organic solvents in milled form and without milling. influence of the milling on the yield and antioxidant activity of different extracts of savory 2 is represented in table 3. although by the milling of the plant material the yield increased, the antioxidant activity decreased. therefore for the next experiments it was decided to use the plant material (savory 2) without milling. table 3: extraction yield and antioxidant activity of different extracts of savory 2 with and without milling ayield (%) aic 50% µg/ml s with milling without milling with milling without milling 1 26.91 ± 0.50 25.36 ± 1.07 35 ± 0.1 24 ± 0.1 2 25.77 ± 0.35 18.67 ± 0.90 60± 0.1 53 ± 0.7 3 11.48 ± 0.54 8.48 ± 0.44 90 ± 0.2 80 ± 0.3 amean value of three measurements ± sd (standard deviation) s solvent; 1: ethanol 96%; 2: ethanol 100%; 3: ethyl acetate. selection of the solvent in order to isolate the active compounds two extraction methods were investigated: conventional soxhlet extraction and supercritical fluid extraction. fig. 1 shows the effect of the polarity of the solvents on the antioxidant activity of different extracts of savory 2. 0 20 40 60 80 100 120 140 160 bht 1 2 3 4 5 6 7 8 9 solvent ic 5 0% (µ g/ m l) figure 1: antioxidant activity of different extracts of savory 2 and bht 1: ethanol 50%, 2: ethanol 96%, 3: isopropanol, 4: ethanol 100%, 5: acetone, 6: ethyl acetate, 7: pentane, 8, 9: supercritical fluid extracts performed at 450 and 300 bar, respectively at 40°c in the case of the extraction performed with organic solvents the antioxidant activity of the extracts decreased as follows: ethanol 50% > ethanol 96% > isopropanol > ethanol 100% > acetone > ethyl acetate > pentane. the extract obtained with ethanol 50% exhibited both the highest antioxidant activity (with an ic 50% of 14.48 ± 0.02 µg/ml) and the highest yield (34.67 ± 1.57 w/w) whereas the extract performed with pentane showed the lowest antioxidant activity (with an ic 50% of 98 ± 0.1 µg/ml) and the lowest yield (3.08 ± 0.1 w/w). the extraction yield of different extracts of savory 2 is represented in fig. 2. a correlation between the antioxidant activity and the extraction yield was found. 42 0 5 10 15 20 25 30 35 40 1 2 4 3 5 6 7 8 9 solvent y ie ld (% ) figure 2: yield of different extracts of savory 2. 1: 50% ethanol; 2: 96% ethanol; 3: isopropanol; 4: 100% ethanol; 5: acetone; 6: ethyl acetate; 7: pentane; 8, 9: supercritical fluid co2 at 450 and 300 bar, respectively at 40 °c supercritical fluid extraction was carried out with neat co2 at two different pressures, 300 and 450 bar at 40 °c. it was observed that by increasing the pressure both the antioxidant activity (with an ic 50% from 147.3 to 137.6 µg/ml) and the yield (from 2.23 to 3.02 w/w) increased. however, the antioxidant activity of the extracts performed with supercritical fluid co2 was lower than the antioxidant activity of the extracts obtained with organic solvents. the explication can be found in the polarity of the solvents, because the active compounds are usually polar compounds. since the co2 is non-polar solvent more non-polar compound can be extracted. more experiments with supercritical fluid co2 in present of different concentrations of a modifier are in progress in order to concentrate the active compounds. we assume that the maximum antioxidant activity was recovered with ethanol 50%. conclusions satureja hortensis l. was investigated as a potential source of natural antioxidant compounds. to recover the antioxidants two isolation methods, conventional soxhlet extraction and supercritical fluid extraction were compared. the best organic solvent to recover the antioxidant compounds was found to be ethanol 50% (with an ic 50% of 14.48 ± 0.02 µg/ml). the extracts obtained by using supercritical fluid extraction with neat co2 at two different pressures (300 and 450 bar) at 40 °c showed approximately 10 times lower antioxidant activity then the extracts obtained with organic solvents. to increase the polarity of the active compounds by using supercritical co2 a modifier is required. more extraction experiments with different concentrations of an entrainer are in progress. acknowledgements this research was financially supported through a european community marie curie fellowship (project mest-ct-2004-007767). for further information: http://www.cordis.lu/imprcong. references 1. dorman, d., hiltunen, r.: journal of food chemistry 88 (2004) 193-199. 2. sahin, f., karaman, i., güllüce, m., et al.: journal of ethnopharmacology 87 (2003) 61-65. 3. esquivel, m. m., ribeiro, m. a., bernardo-gil, m. g.: the journal of supercritical fluids 14 (1999) 129-139. 4. güllüce, m., sökmen, m., daferera, d., et al.: journal of agriculture and food chemistry 51 (2003) 3958-3965. 5. exarchou, v., nenadis, n., tsimidou, m., et al.: journal of agriculture and food chemistry 50 (2002) 5294-5299. 6. hajhashemi, v., sadraei, h., ghannadi, a. r. et al.: journal of ethnopharmacology 71 (2000) 187-192. 7. deans, s., svobova, k. p.: journal of horticultural science 65 (1989) 205-210. 8. madsen, h. l., andersen, l., christiansen, l., et al.: journal of food research and technology 203 (1996) 333-338. 9. cuvelier, m., richard, h., berset, c.: journal of american oil chemists’ society 73 (1996) 645-662. 10. simandi, b., deák, a., rónyai, e., et al.: journal of agriculture and food chemistry 47 (1999) 16351640. 11. blois, m. s.: nature 181 (1958) 1199-1200. 12. kouri, g., tsimogiannis, d., bardouki, h., et al.: innovation food science & emerging technologies 8 (2007) 155-162. 13. atoui, a. k., mansoury, a., boskou, g., et al.: journal of food chemistry 89 (2005) 27-36. 14. brand-williams, w., cuvelier, m. e., berset, c.: lebensmittel – wissenschaft und technologie 28 (1995) 25-30. hungarian journal of industrial chemistry veszprém vol. 33 (1-2). pp. 81-88. (2005) constrained pi(d) algorithms (c-pid) f. szeifert, l. nagy, t. chován* and j. abonyi department of process engeneering, university of veszprém, veszprém, egyetem u. 10, h-8200, hungary, www.fmt.vein.hu, chovan@fmt.vein.hu majority of control algorithms used in industrial processes is pid or pid modification and many of these is badly tuned. the reason for this is that the physical constraints of the manipulated variable are neglected. the pid algorithm, presented in the paper, is obtained by inverting the standard pid twice and it is able to handle the constraints. the first analytical inverting step results in a proper pid inverse. this is then transformed into a state-space model. the statespace model is then inverted again by using the same method which is applied in globally linearizing control and taking into account the physical constraints of the manipulated variable. the constrained pid (c-pid) algorithm obtained this way is an anti reset wind-up algorithm which can be readily implemented. a possible design methodology is also proposed. at the same time, regarding processes with not higher than second order dynamics, the solution a rigourous model-based one. keywords: constrained control, pid algorithm, model-based, constrained inverse introduction based on different surveys, 95% of control algorithms used in industrial processes is pid or pid modification and most of these is badly tuned. the consequence is that the dynamic performance is poor and in the worst cases even instability might occur. correct tuning is made difficult by several problems which are at the same time the reasons for the gap between the control engineering practice and the control theory. only a few of these are: on the practical side: • dynamics of the process is known only roughly. • dynamic properties can change with time (valve sticking, wearness, etc.). • the algorithm of the used pid modification is not known (because of the intellectual property rights, the documentation are non-algorithmic-level and superficial). • for the above reasons the “academic” tuning methods cannot be applied. • industrial implementation of algorithms established in control theory encounters difficulties. on the theoretical side: • most of the methods, thriving mathematical accuracy, start form assumption which are not satisfied in practice. • methods built on idealized models are preferred. • physical constraints are neglected (involving the constraints, the inherently linear models become non-linear). • the methods “in focus” are favoured. the paper defines a constrained pid algorithm which can be readily implemented in practice as well as discusses the limitations of pid-based algorithms and the possibilities of model-based design. the set of pid algorithms in spite of the two decades of industrial application and the intensive academic research providing the *correspondence concerning this article should be addressed to t. chovan (chovan@fmt.vein.hu) 82 theoretical bases, chemical processes are dominated by pid or pid-based controllers [1]. the main reasons for this dominancy are the role of pid controllers in the classical control technologies, their position in the engineering curriculum, their availability in dcs’s and not at least the efficiency of their application. on the top of these, certain model-based techniques, depending on the process model, often result in pid algorithms and therefore can be implemented as pid controllers. still the research and application of model-based control algorithms are rather important, first of all, in cases of processes where the application of pid is not efficient. the study of model-based control algorithms is getting more and more intensive as the technological possibilities are opening. at the same time the model of the controlled process gains more importance in the analysis. the input of the pid algorithm is the control error ( ), the output is the control signal ( ), and its continuous time ( ) model is: e u 0≥t sd t i u dt tdetde t tektu +⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ ++= ∫ )()(1)()( 0 ττ , (1) where di ttk ,, are the parameters (gain, integral and differential time constants) su is the steady-state control signal corresponding to setpoint )(tw design of the controller involves the determination of the three parameters, while the value of is often set to zero or sometimes to other constant (the i-term assures the settling without steady-state error). in case of more complex algorithms (e.g. for batch processes) the can be estimated more accurately: su su ),,(0 kzwffuus += , (2) where 0u is constant (in batch processes it can be used for initialization in the different phases) ),,( kzwff is a feed-forward term based on the setpoint and the measured disturbance(s) ( k,z ). in the process control systems usually different (i) modifications are implemented. transfer functions of the common solutions are the following: parallel pid (p-pid): ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ + ++== 1 11 )( )( st st st k se sug d d i pidp α , (3) serial pid (s-pid): 1 11 + ⋅⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ += st st st kg d d i pids α , (4) filtered parallel pid: 1 1 + ⋅= st gg f pidfpidf , (5) where ]5.0,1.0[∈α , constant ft is the time constant of the first order filter, it must be determined during the design. the above controllers are in continuous time. discretizing with an appropriate sampling time the corresponding discrete pid algorithms can be obtained. using a sampling time, orders of magnitude less than the characteristic time constant of the process, the discrete pid approximate the results the corresponding continuous algorithm with the required accuracy. the time constant for the great majority of chemical processes is several orders of magnitude larger than the (hardware) sampling time of 100 msec or 1 sec, realized in the process control systems. in case of relatively high sampling time, the discrete pid algorithms require special analysis. it is well known that in feedback loops, the zero steadystate error is maintained by the integrating term, therefore the i-term must included in most of the cases. at the same time, since the physical control signal is constrained, the application of the i-term can lead to saturation (wind-up) which is treated by different “backward integration” algorithms. pid blocks of the process control systems allow realization of a large variety of pid modifications by using different configuration parameters. this solution, however, makes the correct application of pid algorithms more difficult in itself, since it may require the specification further several tens of parameters above the three or four tuning parameters. model-based algorithms the fundamental problem of feedback control is that the effect of the actual control output – especially in case of higher order systems with dead-time – is delayed in time. the small change induces higher control output which ultimately can even cause instability. the mathematical model of the process allows estimating the future effect of the control output and this way determining the optimal output. the model predictive controllers (mpc) solving the optimal control problem over a discrete prediction horizon determine the optimal future values of discrete time control outputs. the first element is then realized and the calculation is repeated 83 in every sampling period. industrial application of mpc has two decades of history and software tools (e.g. rmpct) for considerably supporting the design have been introduced. mpc superposed on pid loops can be efficiently used, first of all, for multivariable (mimo) problems. in case of simple siso problems the performance of mpc is comparable to that of a pid, however its calculation requirements and implementation cost can be significantly higher [2]. one of the simplest model-based design methods is the direct synthesis technique [3]. its basic idea is that the dynamics of the closed loop is defined and the controller providing this response is calculated backward using the known process model. in case of simple process models, very often a pid variant, which can be readily implemented on any dcs, is obtained as a result. the results of the design for a few simple processes are summarized in table 1, where the closed loop is defined as a first order filter (with dead-time) and is the time constant of the closed loop. ct controllers applying the internal model control (imc) principle are very popular in academic studies. their essence is a feed-forward term containing the inverse of the process model. the control offset coming from the model error is corrected by feeding back the filtered model error. depending on the process model, often a pid algorithm, which can be used in the classical feedback scheme, is obtained in this case too. applying the imc method on the processes in table 1 and using first order filters, the same results given in the table are obtained [3]. investigating the results in table 1 it can be concluded that up to second order systems the linear-model-based methods also result in pid algorithms. it is well known too that a large number of simple chemical processes can be modeled as first (or second) order system with dead-time. these facts support the widely accepted experience that a considerable part of chemical process control problems can be solved by different pid variants. for systems with dead-time, the smith predictor which can also be well inserted into imc structures lives its renaissance. in case of batch systems it is practical to specify the pid algorithm by phases and often more complex solutions have to be applied (e.g. dual-mode control [4]). table 1 model-based pid algorithms direct synthesis or imc process model ckk ⋅ it dt 1+st k ct t t 0 ( )( )11 21 ++ stst k ct tt 21 + 21 tt + 21 21 tt tt + ⋅ s k ct 1 ∞ 0 ( )1+sts k ct 1 ∞ t 1+ − st ek sth hc tt t + t 0 ( )( ) hc tt tt + + 21 21 tt + 21 21 tt tt + ⋅ 11 21 ++ − stst ek sth investigating the results in table 1 it can be concluded that up to second order systems the linear-model-based methods also result in pid algorithms. it is well known too that a large number of simple chemical processes can be modeled as first (or second) order system with dead-time. these facts support the widely accepted experience that a considerable part of chemical process control problems can be solved by different pid variants. for systems with dead-time, the smith predictor which can also be well inserted into imc structures lives its renaissance. in case of batch systems it is practical to specify the pid algorithm by phases and often more complex solutions have to be applied (e.g. dual-mode control [4]). controller design the design of the control systems, in a broader sense, involves the selection of manipulated and measured variables based on the analysis of degree of freedom, sensitivity and dynamic behavior, as well as to select the control structure and method. more specifically the design means selecting the control algorithm and determining its parameters. this later, even now, is often solved by using classical methods (zieglernichols, cohen-coon, integral criteria, etc.) with appropriate computer aids and simulation tools. based on simulation, the optimal parameters of the controller can also be found by different search methods. there are known several modified versions of the classical techniques. model-based approaches (see e.g. table 1), starting from different types of models, derive the control equations using the techniques of the linear control theory and applying suitable approximations (e.g. dead-time: pade-approximation, nonlinearities: taylor-series). in this case the identified process model and the control rule determine the control structure and the controller parameters too; separate tuning rules are not needed. building in the identification of the applied model, in the framework of classical schemes (gain scheduling, model reference, self tuning), adaptive algorithm can be 84 constructed too. it is advisable to design the supervision of their operation in advance. in the controller design several practical problems emerge, making more difficult the efficient application of academic results. problems related to control valves, like hystheresis, sticking and nonlinear valve characteristic, are well known. since the problems of hystheresis and sticking must be solved by mechanical engineering techniques they are not considered in the design model. (their indication, at the same time is a model-based diagnostic problem). taking into account the strongly nonlinear valve characteristics is a prerequisite for the appropriate design. considering the practical controller design, an important element of the model is the allowable range of its variables, i.e. taking into account the related constraints. in mathematical sense, this changes the not constrained linear model into a nonlinear one and makes the detailed analysis more difficult (that is why it is often neglected in academic studies). a number of publication confirm that using adequate models containing the corresponding constraints, the model-based algorithms are more efficient than pid controllers tuned with classical methods [5]. constrained pi(d) algorithm taking into account the physical constraints on the control variable the saturation (wind-up) effect can be eliminated. especially in case of batch systems it is frequently occurs, that the requirement for fast settling generates such huge changes in the control output that cannot be realized. this may lead considerably high overshoots which prevent achieving good control performance. this was our main reason motivating the development a constrained pid variant. to take the physical constraints of the control variable into account, two consecutive inverting of a standard pid algorithm is applied, as follows: 1. the inverse of a standard pid is formed in the transformed domain. this can be solved reciprocating the transfer function. 2. a constrained inverse of the inverse pid is formed after converting the inverse transfer function (in time domain) into a state-space model. in details the following transformations are to be done. using a p-pid controller ( 0=α ) the starting transfer function is the following: ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ++== st st k se supid d i c 11 )( )( , (6) that defines an improper object. let us take its proper inverse: 2 1 1)( )( sttst s k t su sepid diic i ++ ⋅==− , (7) based on the transfer function, the inverse can be given as a time-domain input-output model: dt du k te dt det dt edtt c i idi ⋅=++2 2 , (8) let us transform the input-output model into the following input-output equivalent state-space model (using the ∫== e t xex i 1, 21 state definitions): uktx t tt dt xd cd i dd ⋅ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ +⋅ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ −− = 0 1 01 11 , (9) xey ⋅=≡ ]01[)( , (10) the state-space model given by eq.(9-10) is a proper inverse of a standard p-pid. the new c-pid algorithm is constructed by forming a constrained inverse of this model. to form a constrained inverse, let us consider the general scheme (fig.1) of globally linearizing control (glc) [6]. the idea is that an originally nonlinear object can be transformed into a linear one by a state feedback compensator. linear controller state feedback compensator process output map u y x vsetpoint + . . fig.1 globally linearizing control structure the order of the linear input-output model, where the input is v , the output is , is equal to the relative order of the state-space model, eq.(9-10). based on the linearization technique, the constrained inverse is formed according to the scheme shown on fig.2 [7]. the variables are interpreted in the following way: the input of the inverse is the setpoint ( ), its output is the manipulated variable ( ). let the relative order of of the state-space model, eq.(9-10) be y w u r . this means that the input of the process ( is not constrained, u is constrained) has a direct effect on the w r -order derivative of the output ( ). the not-constrained control output ( v ) is determined in such a way that the relationship between the setpoint ( ) and the controlled variable ( ) is defined by an rr dtyd / w y r -order linear input-output model. the time constant of this linear 85 model should be determined according to the time constants of the object given by eq.(9-10). relatively small time constants result in aggressive interventions; the control output ( v ) is often reaches the physical constraints (in this case u takes its minimal or maximal value). with relatively large time constants the system capacity is not exploited resulting in slow control settlings. constraint state feedback compensator u(t) x v(t) setpoint w process eq. (9) output map eq. (10) y constrained control output . . fig.2 formation of constrained inverse to invert according to the given scheme, the the output of eq.(9-10) is differentiated: u tk xx tdt dx dt dy dcd ⋅++⋅−== 1)(1 21 1 , (11) since the first order derivative contains the control output explicitly, the relative order of the inverse pid is one. hence the linear system can be defined in the following way: wy dt dytf =+⋅ , (12) substituting eq.(11) in place of the derivative, the value of the required control output is obtained (output of the feedback compensator): ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ ++−⋅⋅= 211)( xxxw t tkv f d c , (13) the output constraints are treated as follows: ⎪ ⎩ ⎪ ⎨ ⎧ > < ∈ = maxmax minmin maxmin , , ],[, uvifu uvifu uuvifv u , (14) where is the physically allowed range of control output. ],[ maxmin uuu∈ summarizing the steps above, the scheme of the constrained pid (c-pid) algorithm can be constructed (see fig.3). initial values of the differential equations are set to zero error and to zero output difference. constraint u(t) x1 e(t) + ck f d t t sti 1 ck 1 1 1 +std x2 + + + + cku / 0 + . . . . fig.3 scheme of the c-pid controller applying a similar reasoning or the limit value a c-pi algorithm can be elucidated too (see fig.4). here the relative order of the inverse is zero. 0→dt constraint u(t)e(t) + + ck 1 1 +sti ck 1 cku / . fig.4 scheme of the c-pi controller the non-constrained transfer functions can be easily constructed and the following results are obtained: c-pid: 1 111 + ⋅⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ++⋅=− st st st kg f d i cpidc , (15) c-pi: ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ +⋅=− st kg i cpic 11 , (16) it can be seen that c-pid not reaching the constraints is equivalent to a parallel pid with a filter, eq. (5), while a c-pi to a normal pi controller. hence it is clear that taking the constraints into account don’t makes the basic algorithms more complicated. this fact has a great importance for practical realizations. design of constrained pi(d) algorithms to determine the parameters of a c-pid it is practical to describe the controlled system as a second order object. the scheme of the closed loop for the non-constrained case is shown in fig.5. 86 y w + .21 ss k βα ++ 1+st pid f u fig.5 non-constrained closed loop this is equivalent to the closed loop given in fig.6. y w + 1 11 + ⋅ ⋅ sts kk t f c i .21 1 ss βα ++ 21 sttst dii ++ fig.6 equivalent loop the framed part shows well that the controller compensates the dynamics of the process if the controller parameters are chosen according to the followings: βαα /, == di tt . (17) the filter parameter should be selected at the possible smallest value ( ) allowed by the measurement noises, and then setting the time constant of the closed loop to , the controller gain can be given by the following expression: ft 0→ft ct c c tk k ⋅ = α . (18) in the direct synthesis method the time constant of the closed loop is selected as a half or fifth of the time constant of the process, therefore the gain can be estimates as: ]5,2[, ∈= γγ k kc , (19) the two parameters of a c-pi controller can be determined also according to the above reasoning. testing of constrained pi(d) algorithms the c-pid algorithm was physicaly tested on an electrical water heating system installed in our process engineering laboratory. the p&i diagram of the system is shown on fig.7; its technical specification is given in an earlier publication [8]. the temperature of the water ( ) leaving the heater system is controlled by manipulating the heater performance ( u ). the flowrate of the water and its feed temperature are considered as non-measured disturbances. the dynamic relationship is chosen as a second order inputoutput model with dead-time that provides a structuraly adequate description. open-loop experiments were conducted in order to determine the model parameters. the parameters were estimated by fitting to the measured data using matlab (see fig.8). ty ≡ ]10,0[∈ yu → fig.7 the laboratory system for testing 0 5 10 15 20 25 30 35 40 45 50 0 10 20 30 40 5 time (min) te m pe ra tu re (° c ), co nt ro l o ut pu t ( v ) 0 fig.8 identification of the process model 0 5 10 15 20 25 30 35 40 45 0 10 20 30 time (min) te m pe ra tu re (° c ), co nt ro l o ut pu t ( v ) 40 fig.9 simulation test of the p-pid controller mv water tin f t < heating pc < open close adam-5000 lan u 87 0 5 10 15 20 25 30 35 40 45 0 10 20 30 4 time (min) te m pe ra tu re (° c ), co nt ro l o ut pu t ( v ) 0 0 5 10 15 20 25 30 35 40 45 0 10 20 30 4 time (min) te m pe ra tu re (° c ), co nt ro l o ut pu t ( v ) 0 fig.10 simulation test of the anti wind-up pid controller fig.12 physical test of the p-pid controller 0 5 10 15 20 25 30 35 40 45 0 10 20 30 4 time (min) te m pe ra tu re (° c ), c on tro l o ut pu t ( v ) 0 0 5 10 15 20 25 30 35 40 45 0 10 20 30 4 time (min) te m pe ra tu re (° c ), co nt ro l o ut pu t ( v ) 0 fig.11 simulation test of the c-pid controller fig.13 physical test of the anti wind-up pid controller the c-pid algorithm was compared to a standard ppid algorithm as well as to an anti wind-up pid algorithm used in an industrial plc. the pid parameters are determined in each cases by the direct synthesis method based on the identified process model. in the simulation studies the mathematical model of the heater system was the process. the studies presents servo problems, however the load disturnbance compensation studies qualitatively showed similar results. simulation tests are illustrated on fig.9-11. fig.9 shows well that in those time periods when the control output approaches its physical limits, significant overshoots can be observed after changing the setpoint. overshoots can be considerably reduced by applying an anti wind-up compensator (see fig.10). fig.11 justifies that the c-pid algorithm completely eliminates the overshoot. 0 5 10 15 20 25 30 35 40 45 0 10 20 30 time (min) te m pe ra tu re (° c ), co nt ro l o ut pu t ( v ) 40 fig.14 physical test of the c-pid controller the same tests were conducted on the laboratory physical system. the results are given on fig.12-14. the physical experiments illustrates well the effect of measurement noises, still the relation of the different methods is the same in case of the physical tests as it was shown in the simulation studies. conclusions in industrial applications several versions of pid controllers can be found. because of the physical constraints on the control output only those supplemented with anti reset wind-up compensators can follow setpoint changes without overshoots. significant overshoots can involve safety risk especially in control of batch systems. the paper presents the so called c 88 pid algorithm which takes the physical constraints into account and provides settlings practically without overshoots. the algorithm does not make the standard pid algorithm more complex and it can be readily implemented in dcs’s. for the c-pid design, considering the potential capacity of pid algorithms, it is practical to describe the object as a second order process with dead-time. in case of systems with large dead-times the use of a smith predictor is suggested that does not limit the applicability of c-pid. acknowledgement this project has been financially supported in part by the chemical engineering institute cooperative research center, iii-2 project. references 1. luyben, w. l.: effect of derivative algorithm and tuning selection on the pid control of dead-time processes, ind. eng. chem. res., 2001, 40, 36053611. 2. bódizs á.: study of model predictive control (in hungarian), ph.d. theses, veszprém, 1998. 3. seeborg, d. e., edgar, t. f., mellichamp, d. a.: process dynamics and control, wiley, new york, 1989. 4. lipták, b. g. (ed.): instrument engineers' handbook. process control, 3rd ed., chilton book c., radnor, pe, 1995. 5. nagy, l.: simulation and control of batch reactors, ph.d. theses, veszprém, 2005. 6. madar, j., abonyi, j., szeifert, f: feedback linearizing control using hybrid neural networks identified by sensitivity approach, eng. appl. of artificial intelligence, 2005, 18, 343-351. 7. szeifert, f., nagy, l., chován, t., abonyi, j.: constrained inverse model-based control (in preparation). 8. bódizs á., szeifert f., chován t.: convolution model based predictive controller for nonlinear process, ind. eng. chem. res., 1999, 38, 154-161. microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 113-117 (2008) role of catalyst support (cs) in the growth of multi-walled carbon nanotubes (mwcnts) a. szentes , g. horváth university of pannonia, department of chemical engineering, h-8200 veszprém, egyetem u. 10., hungary e-mail: szentesa@almos.uni-pannon.hu since the first observation of carbon nanotubes in 1991, their synthesis by different techniques has been extensively investigated. several production methods have been developed aiming at the production of carbon nanotubes (cnt). main methods are laser vaporization, electric arc discharge and catalytic chemical deposition of hydrocarbons over metal catalysts (ccvd technique). this paper describes how to produce multiwalled carbon nanotubes (mwcnts) in pilot plant by ccvd technique. the aim of this investigation was to decide the intervals of reaction parameters with the most effective catalyst support on a large scale. the products were analysed by transmission electron microscopy (tem). analysis has shown the diameter and length of carbon nanotubes. key words: multi-walled carbon nanotubes, synthesis, ccvd technique, large scale production introduction carbon nanotubes (cnts) were discovered in the soot of arch discharge by iijima in 1991 [1]. carbon nanotubes are allotropes of carbon and members of the fullerene structural family. nanotubes are categorized as single-walled nanotubes (swcnts) and multi-walled nanotubes (mwcnts) (fig. 1). mwcnts consist in a variable number of graphene sheets rolled coaxially into a cylinder of nanometric diameter [2]. the interlayer distance in multi-walled nanotubes is close to the distance between graphene layers in graphite, approximately 0,34 nm. typical diameter of mwcnts are 10…20 nm typical length is above 20 μm. figure 1: swcnt and mwcnt nowadays carbon nanotubes are one of the most actively investigated materials. cnts are the most promising of all nanomaterials due to their unique electronic and mechanical properties which ensure themselves to a variety of applications, such as fieldemission displays [3], nanoscale sensors [4], nanostructured composite materials [5]. several production methods have been developed aiming at the production of carbon nanotubes in large scale, such as laser vaporization [6], electric arc discharge [7] and catalytic chemical vapor deposition of hydrocarbons over metal catalysts (ccvd technique) [8]. the first two methods are high temperature processes and can produce high quality nanotubes. however, the yields are poor and hence not adaptable for large-scale production. in contrast ccvd technique is a very efficient method to produce multi-walled carbon nanotubes (mwcnts) because this way could be a possibility to produce nanotubes at relatively low temperatures on a large scale at relatively low cost. this method is the most promising method to commercialize the carbon nanotubes growth. in ccvd method transition metals (fe, co or ni) supported on oxides, zeolite or silica are used as catalyst precursor [9]. the combinations of transition metals and supports can be changed depending on the characteristics required, for example the size of the tubes. bimetallic combinations of these transition metals are used for the synthesis of cnts and the relatively high yield and quality have been explained by characteristic behaviour of this alloy phase [10]. a very effective catalyst is a binary mixture co-fe. catalysts have been prepared by impregnation method using salts of fe and co. recently, several papers dealt with the mechanism of the formation of nanotubes. particularly the role of the catalyst support and the particle size of the metal have been discussed. the most frequently used catalyst support are silica, zeolites and oxides. the role of the 114 catalyst support is a difficult problem. reaction is influenced by interaction between the metal particle and the catalyst support [11]. if the interaction is strong, a metal particle does not budge from catalyst support. if the interaction is weak, a metal particle budge from catalyst support and growing of the tube starts from this point. due to weak interaction high quality and yield can be obtained [12]. during our investigation mwcnts were produced in a pilot scale equipment by ccvd technique. the aim of our investigation was to decide the intervals of the reaction parameters with the most effective catalyst support on a large scale. experimental catalyst and chemicals catalysts have been prepared by university of szeged, department of applied and enviromental chemistry. bimetallic catalysts (fe and co) were used with different supports (oxides, silicates). co-acetate and fe-acetate were impregnated in 2-5 w/w % on different supports. salts of fe and co were obtained from sigma-aldrich. reaction conditions were reductive in this way coand fe-acetat can reduce. as for the carbon source, a simple hydrocarbon (ethylene) was used. ethylene and nitrogen (as carrier gas) were obtained from messer. synthesis of carbon nanotubes simple hydrocarbons were decomposed in a catalytic reaction. cnhk → n c + k/2 h2 the scheme of pilot plant can be seen on fig. 2. figure 2: scheme of pilot plant after placing the catalyst (5-10 g) in metal reactor (5 dm3), the temperature was increased to 700 °c. during rising of temperature, carrier gas (nitrogen) flow was maintained through the reactor at the rate of 50 l/h. after reaching desired temperature hydrocarbon (ethylene) was introduced into the reactor at the rates of 10…40 l/h for 60…120 min. reaction parameters can be found on table 1. table 1: reaction parameters reaction temperature 700 °c reaction time 60…120 min amount of catalyst 5…10 g flow rate of hydrocarbon 10…40 l/h flow rate of carrier gas 10…40 l/h in our experiments the support material of catalyst, flow rates of ethylene and flow rates of carrier gas are the variable parameters for the controlled production of mwcnts because the morphology and the quality of carbon nanotubes depend on these parameters. the main parameters (reaction temperature, amount of catalyst, type of catalyst, type of hydrocarbons) were constant because these parameters were optimized in the course of preliminary research. the aim of our investigation was to decide the intervals of the reaction parameters with the most effective catalyst support on a large-scale. analysis the products were analysed by transmission electron microscopy (tem). analysis has shown the diameter and length of carbon nanotubes. outlet gas were analysed by gas chromatography system (gc). we followed up the hydrogen content of the outlet gas by gc therefore the end of the reaction and amount of formed hydrogen can be determined. results and discussion ethylene was decomposed in a catalytic reaction. formed carbon was analysed by tem and amount of formed hydrogen was analysed by gc. different experimental conditions (catalyst supports, c2h4 flow rate, n2 flow rate, reaction time) and results (diameter and length of tubes, density, conversion) are given on table 2. reaction temperature, type of catalyst, type of hydrocarbon were constant because these parameters were optimized in the course of preliminary research. the reaction temperature was 700 °c, bimetallic catalyst (fe and co) were used, source of carbon was ethylene. two different catalist support (a and b) were used in our experiments. conversion was calculated from amount of formed carbon and amount of formed hydrogen. these are equal. when support „a” was used, conversion was usually more than 70% in comparison with if support „b” was used conversion was fewer than 35%. density is a good indicator of quality of tubes and selectivity. carbon nanotubes have a very low density (~20 kg/m3) in contrast to other modifications of carbon (e.g. graphite: ~2200 kg/m3, active carbon 300…600 kg/m3). density was about 17 kg/m3 in presence of support „a” and about 80 kg/m3 in presence of support „b”. when support „b” was used a lot of amorphus carbon was formed (it can be seen from tem analysis). 115 hydrogen content of the outlet gas was followed up. it could be seen from fig. 3, fig. 4 and fig. 5 higher hydrogen contents were achieved when support „a” was used. when support „b” was used the reactions were finished sooner and hydrogen contents were lower than in presence of support „a”. 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 0 10 20 30 40 50 60 70 reaction time (min) c on ve rs io n a40 b40 figure 3: hydrogen content of the outlet gas (a40: support „a”, c2h4 flow rate 40 l/h; b40: support „b”, c2h4 flow rate 40 l/h) 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 0 10 20 30 40 50 60 70 80 90 100 reaction time (min) c on ve rs io n a30 b30 figure 4: hydrogen content of the outlet gas (a30: support „a”, c2h4 flow rate 30 l/h; b30: support „b”, c2h4 flow rate 30 l/h) 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 0 20 40 60 80 100 120 140 reaction time (min) c on ve rs io n a20 b20 figure 5: hydrogen content of the outlet gas (a20: support „a”, c2h4 flow rate 20 l/h; b20: support „b”, c2h4 flow rate 20 l/h) the best results were recieved in presence of „a” catalyst support. the main parameters were optimized in the course of preliminary research. change of c2h4 flow rate and reaction time does not influence significantly quality of the formed mwcnts but conversion is influenced by them. highest conversion has been obtained when c2h4 flow rate was 30 l/h and reaction time was 90 min. as long as these determined parameters are used high quality mwcnts can be produced and high conversion (85%) can be reached. diameter and length of tubes were determined from tem analysis (fig. 6 and fig. 7). similar results were achieved in all reactions in presence of support „a” as far as the quality of the tubes is concerned. the formed carbon nanotubes can be seen on fig. 6. the quality of the formed tubes in a batch was more uniform. diameter of tubes changed from 10 nm to 20 nm. length of tubes was usually longer than 30 μm. in contrast, when support „b” was used (fig. 7) diameter and length of tubes were variable. diameter of tubes changed from 10 nm to 100 nm and length of tubes was shorter than 10 μm. table. 2: experimental conditions and results catalyst support c2h4 flow rate (l/h) n2 flow rate (l/h) reaction time (min) diameter of tubes (nm) length of tubes (μm) density (kg/m3) conversion (%) a 20 40 120 10…20 10…40 17 72 a 30 30 90 10…20 10…40 16 85 a 40 20 60 10…20 10…40 18 77 b 20 40 120 10…100 1…20 74 33 b 30 30 90 10…100 1…20 83 28 b 40 20 60 10…100 1…20 75 31 116 figure 6: tem images of mwcnts produced by support „a” figure 7: tem images of mwcnts produced by support „b” 117 the best results were recieved in presence of „a” catalyst support. the main parameters were optimized in the course of preliminary research. change of c2h4 flow rate and reaction time does not influence significantly quality of the formed mwcnts but conversion is influenced by them. highest conversion has been obtained when c2h4 flow rate was 30 l/h and reaction time was 90 min. as long as these determined parameters are used high quality mwcnts can be produced and high conversion (85%) can be reached. in one batch 50 g multi-walled carbon nanotubes can be produced in pilot plant. density of this product is 16 kg/m3, diameter and lenght of tubes are almost uniform, diameter of tubes are between 10 and 20 nm and length of tubes are more than 30 μm. conclusion using the parameters determined in this study high quality mwcnts can be produced and high conversion (85%) can be reached. in one batch 50 g multi-walled carbon nanotubes can be produced in the pilot plant. density of this product is 16 kg/m3, diameter and lenght of tubes are constant, diameter of tubes are between 10 and 20 nm and length of tubes are more than 30 μm. references 1) iijima s.: nature 354 (1991) 56. 2) biró l. p., gyulai j., lambin ph., nagy j. b., lazarescu s., márk g., fonseca a., surján p. r., szekeres zs., thiry p., lucas a. a.: carbon 36 (1998) 689 3) yumura m., ohshima s., uchida k., tasaka y., kuriki y., ikazaki f., saito y., uemura s.: diamond and related materials 8 (1999) 785-791 4) chunyu li, erik t. thostenson, tsu-wei chou: composites science and technology 68 (2008) 1227-1249 5) xiao-lin xie, yiu-wing, xing-ping zhou: materials science and engineering 49 (2005) 89112 6) guo t., nikolaev p., thess a., colbert d. t., smalley r. e.: ž. chem. phys. lett. 236 (1995) 419. 7) ebbesen t. w., ajayan p. m.: nature 358 (1992) 220. 8) li w. z., xie s. s., qian l. x., et al.: science 274 (1996) 1701. 9) hernadi k., kónya z., siska a., kiss j., oszkó a., nagy j. b., kiricsi i.: materials chemistry and physics 77 (2003) 536-541 10) kónya z., kiss j., oszkó a., siska a., kiricsi i.: phys. chem. chem. phys. 3 (2001) 155 11) siska a., hernadi k., kiricsi i., rojik i., nagy b.: electronic propeties of novel materials – progress in molecular nanostructures, xii. international winterschool woodbury (1998) 20-24 12) hernadi k., fonesca a., nagy j. b., bernaerts d.: springer series in material science: supercarbon (1998) 81-79 13) thein-nga l., hernadi k., forro l.: adv. matter 13 (2001) 148. microsoft word b_30_a_r.doc hungarian journal of industrial chemistry veszprém vol. 38(2). pp. 207-210 (2010) sensorless rotor position detection of pmsm for automotive application d. fodor, h. medve, i. szalay, t. kulcsár automotive electronic systems group, institute of mechanical engineering, university of pannonia egyetem str. 10. veszprém, hungary e-mail: fodor@almos.uni-pannon.hu, hunor.medve@gmail.com, ifj_szalay_istvan@yahoo.com, trovo.st@gmail.com for correct operation of the permanent magnet synchronous motors is essential the knowledge of the rotor position, which is usually given by hall-sensors, encoders or resolvers. the aim of the present work is to set up such a general motor model, which takes into consideration the anisotropies in the magnetic structure of the motor. keywords: rotor position estimation, pmsm motor model, model validation, sensorless control methods introduction the electrical drives can be found in every field of the modern life from the cooling fans in computers to the most modern electric tractions. most of the cases where a variable-speed operation was required, dc motors were used extensively, since the flux and torque can be controlled easily by the field and armature current. however, the main problem of the conventional dc motors are the commutators and the brushes. the commutators have limited capability under high-speed operation. a good alternative to the conventional dc motors is the permanent magnet synchronous motor (pmsm), which are widely used in industrial applications due to their high efficiency, high torque-to-inertia ratio, high reliability, low maintenance and longer lifetime [1]. position sensors are placed in the motor for accurate control. for position sensing hall-effect sensors, different encoder types or resolvers are used. the construction of permanent magnet synchronous motors yields the advantages mentioned above but they do not have only bright side. the position sensors have many drawbacks: they increase cost and size of the motor, the operating temperature range is limited and need some external electronic circuits to transmit the correct position. thus in space restricted applications, in cost effective applications and in hostile environments the necessity of sensorless operation is brought up [1, 3, 6]. in this paper slotless motors will be analyzed, which are high power small size servo motors. these pmsms cannot be ranked in any conventional group because the rotor is one block magnet. the other special characteristic is the absence of the iron core in stator windings, which results ironless stator windings. this is not a common motor type, so far sensorless control of slotless pmsms is not discussed in literature. modelling the pmsms electric drives are complex electromechanical systems. their power supply and their control are usually electrical and their output is usually mechanical. therefore the modeling usually is done only for the electrical and mechanical phenomena. but if the magnetic structure of the motor is important (anisotropies, saturation, hysteresis and the combination of them is not negligible) then it should be taken into consideration thoroughly. our sensorless method is based on these magnetic phenomena, so their analysis is very important from both theoretical and experimental side. geometrical model usually more than one coordinate systems are used to describe the motor geometry. one of these systems is fixed to the stator (α – β) and the other to the rotor (d – q). their origins are the same. the angular position of the (d – q) system in the (α – β) system is defined by the angle θ. the modeled motors have 3 phase windings. the phases and their parameters usually are indexed with a, b and c. by fixing an axis to each phase can be created the 3 phase or natural (a – b – c) coordinate system of the motor. this system is fixed to the stator as the (α – β). it is comfortable to define the (α – β) in a way which grants the equality of the axes α and a. 208 electrical model the voltage equations of the phases (the voltage reference point is the start point): (1) the flux in phase i can be dissolved to flux components that are produced by the windings and the permanent magnet. for phase a: (2) in the above equation фij represents the flux component in phase i produced by phase j, and фmi represents the flux component in phase i produced by the permanent magnet. the voltage equation of phase a: (3) the flux derivatives can be dissolved into products of inductances and current derivatives: = (4) the change of the phase flux component induces the following voltage component, which can be considered proportional to the actual rotor speed: (5) voltage equations for the phases: (6) (7) (8) the flux equation, which describes the relation between the phase fluxes and phase currents: (9) (10) in the development of mathematical background of the sensorless method it is an important task to determine the [l] inductance matrix and its dependencies on the other physical quantities, especially the rotor position. in the magnetic modeling one of the main goals will be to write the inductance matrix into a form which uses the magnetic properties of the motor. the inductance matrix is also important because it is the mathematical object which describes the relationship between the electric and magnetic parts of the model. mechanical model the torque equation of the motor: (11) in the above equation θr is the inertia of the rotor, mm is the motor torque produced by the phase windings, and the mt is the load torque. the ksωm product is the torque produced by the friction forces. the mm motor torque can be computed from the equality of the incoming electrical energy and the outgoing mechanical energy (pelectr = pmech): (12) (13) solving the above equation system yields: (14) magnetic model the most important physical phenomena were the followings during the mathematical modeling of the motor’s magnetic structure: saturation: the rotor permanent magnets reluctance is flux dependent. hysteresis: permanent magnets’ b–h curve is a hysteresis loop. anisotropies: the rotor permanent magnets reluctance and probably the saturation and the hysteresis are anisotropic quantities. an other phenomenon, that should be considered is the eddy current on the surface of the permanent magnet. for geometrical reason the motor model should be divided into two parts: � stator and air gap model � rotor model. stator contains the air core windings, the air gap between the windings and the rotor, and the external iron cylinder. the air gap and the air cores can be discussed together as a simple reluctance. the external iron cylinder, the air cores and the air gap can be modeled as constant reluctances. the stator windings are magnetomotive forces in the magnetic circuit. the rotor is a permanent magnet, which is a cylindriform object. the permanent magnet can be modeled as a magnetic circuit that contains reluctances and magnetomotive forces. first, is practical to model separately the reluctances and the magnetomotive forces to create a reluctance model and a magnetomotive model, and then connect them. supposing the rotor is perfectly cylindriform, the magnetic field of the rotor permanent magnet is symmetrical to the plane defined by the axis and motor shaft. it is assumed that inside the magnet there is no leakage flux [2]. 209 reluctance model hypothesis: the reluctance between two circumferential points opposite each other depends on the point pair and the flux flowing from one to the other. with other words, using the symbols of fig. 1, the reluctance rab depends on the angle φ1 and rcd depends on φ3 and both reluctances depend on the actual ф flux flowing through the permanent-magnet. figure 1: reluctance between two surface points of a permanent magnet cylinder so any φ angle and ф flux defines a r(φ, ф) “passing through” reluctance value, which can be dissolved into two reluctance components: (15) where rm(φ, ф) is the rotor magnet’s “radial” reluctance function, which defines the “radial” reluctance between the center point and the surface point in the direction of the φ angle, when the flux flowing through is ф. the reluctance between non-opposite surface point can be dissolved to two “radial” reluctances. for example, the reluctance between the points a and c, when ф flux flows through from point a to point c, is computed in the following way using the rm(φ, ф) function: (16) the above method has some error, which is greater when the difference of the two angle (in the above example the difference of φ1 and φ3) is smaller. if the difference is 120° (between the center lines of the phase windings) the error of the method is acceptable. the rotor can be modeled as reluctances connected in star using the rm(φ, ф) function, see fig. 2. figure 2: reluctance circuit of the permanent magnet rotor. (in the αβ coordinate system) the phase reluctances and their pins are fixed in the standing coordinate system. the value of the phase reluctances can change because the rotor can rotate. describing the phase reluctances with the rm(φ, ф) function yields: (17) complete magnetic circuit the motor’s complete magnetic circuit with the inductances and phase windings is shown on fig. 3: s s sma θ mb θ mc θ mc θ,φ mb θ,φ ma θ,φ ea t eb t ec t g g g l1 θ,φ l3 θ,φl2 θ,φ φa φb φc figure 3: the magnetic circuit of the motor the merged phase reluctances: (18) using the above reluctance components the inductance matrix can be determined. flux equations the фaa flux component, which is produced by the fea magnetomotive force in phase a: (19) the фab flux component, which is produced by the feb magnetomotive force of phase b in phase a: (20) based on the above equations, flux equations can be written for the other two phases and can be written together in a vectorial form that contains the inductance matrix: (21) 210 mathematical description of standstill position detection at standstill is critical in sensorless methods, thus it has high priority. during the measurement only one phase winding was excited through the star point of the motor and the difference of the induced voltages in the two other phases was measured. the two induced voltages were not equal, and the amplitude of the difference was depending on the rotor position. the results can be seen on fig. 4. the above voltage measurements prove the presence of anisotropies. based on the amplitude of the difference in different rotor positions characteristic curves can be determined which are periodic with 180°, thus cannot give the exact rotor position. using the previously presented formalism, the following relation can be written for the exciting voltage, current and induced voltages: (22) similarly to (22) the voltage equations can be written for the other phases. altogether six equations can be obtained, from these with current measurement three reluctance value can be defined in one specified rotor position. from these the rm reluctance function can be defined. to do this further high precision measurements are necessary. figure 4: u1: exciting voltage, u2 and u3: voltages induced in phase 2 and 3, δu = u3 u2, the difference of the induced voltages. the u1 exciting voltage measured on the left-hand y axis. conclusions according to the phase geometry the phase characteristic curves are shifted with 120° to each other, however they are not really uniform. all three curves have a period of 180°, which means that the angular position only by voltage measurement cannot be done. in that way only the line defined by the rotor magnet poles can be found, but the two poles cannot be distinguished from each other. the line mentioned above can be determined with a relatively small error (5°–10°). the developed mathematical model and formalism makes possible a general description of permanent magnet synchronous motors. the formalism fits in the notation used by the literature. the main goal, to prove the existence of the anisotropies and their measurability has been reached. acknowledgements the work was partly supported by tamop-4.2.1/b09/1/konv-2010-0003: mobility and environment: researches in the fields of motor vehicle industry, energetics and environment in the middleand westtransdanubian regions of hungary. the project is supported by the european union and co-financed by the european regional development fund. references 1. p. vas: sensorless vector and direct torque control, oxford university press, inc., new york, 1998. 2. ec-32-118891_08_en_164.pdf 3. t. kim, h.-w. lee, m. ehsani: position sensorless brushless dc motor/generator drives: review and future trends. electric power applications, iet, 1(4), 2007, 557–564. 4. j. persson, m. markovic, y. perriard: a new standstill position detection technique for non-salient pmsm's using the magnetic anisotropy method (mam); industry app. conf., 2005. fourtieth ias annual meeting. conference record of the 2005, vol 1, 2-6 oct. 2005, 238–244. 5. j. shanlin, z. jibin, z. hongliang, s. jing: a novel method of detecting for rotor position of a sensorless brushless dc motor, icems. international conference on electrical machines and systems, 2007. 8-11 oct. 2007, 797–800. 6. m. linke, r. kennel, j. holtz: sensorless position control of permanent magnet synchronous machines without limitation at zero speed, iecon 02, industrial electronics society, ieee 2002 28th annual conference of the, 5-8 nov. 2002, vol.1, 674–679. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word 1_r.doc hungarian journal of industrial chemistry veszprém vol 37(1). pp. 27-30 (2009) investigation of modified pib-succinimides in low saps engine oils r. sági1 , l. bartha1, j. baladincz2 1university of pannonia, department of hydrocarbon and coal processing 8201 veszprém p.o. box 158, hungary e-mail: rsagi@almos.uni-pannon.hu 2mol plc, hungary along with the ever stricter economical, technical and mainly environmental regulations new types of low phosphorus, sulphur and metal containing multifunctional lubricant additives are required for formulating so-called low saps (sulphated ash, phosphorus and sulphur) engine oils. in the greatest volume dispersant additives, mainly polyisobuthylenesuccinimide types are used in the formulation of engine oils. by structural modification of the dispersants with molybdenum and sulphur containing compounds advantageous complementary effects could be achieved along dispersant efficiency. various modified pib-polysuccinimides with complementary antifriction and antiwear (af/aw), viscosity-index improver and enhanced detergent-dispersant properties were synthesized and investigated both in base oil and engine oil compositions. the detergent-dispersant and the high temperature deposit preventing effects, thermaland oxidation stability, af/aw properties and seal compatibility were studied in fully formulated, low saps engine oils with reduced zinc-dialkyl-dithiophosphate (znddp) content. based on the results it was found that by using suitable additive concentrations the conventional dispersant can be advantageously combined or replaced with these new additives to enhance the properties and to reduce the znddp concentration level of the experimental engine oils. keywords: modified pib-succinimide, low saps, seal compatibility, antifriction and antiwear properties. introduction in the last decade environmental regulations have been the key drivers in the automotive industry. new emission standards and engine design changes lead to changes also in the performance of the lubricants. additional new specifications are being introduced that restrict the level of sulphated ash, phosphorus and sulphur content (saps) to minimize the impact on the efficiency of the exhaust after treatment systems. the challenge for the lubricants industry is to provide both extended drain intervals and fuel economy while also formulating after treatment compatible engine oils. since higher quality base oils (group ii-vi) have very low sulphur content, the main contributors of saps emission are the functional additives such as zinc-dialkyl-dithiophosphate (znddp), detergents and friction modifiers. to meet the new emission standards and the requirements of the engine oil’s performance levels, low or non phosphorus, sulphurous and metal containing additives with higher efficiency have to be developed and produced [1-4]. on the other hand, engine oil seal compatibility tests have become more important and severe in the recent engine oil performance levels (api ci-4, cj-4; acea ax/bx, cx, ex; jaso dh-1 etc.). in these tests different elastomers (standard refrence elastomers) are immersed into engine oils for a given time and at a given temperature. after immersion the changes of mechanical properties and cracks are determined [2, 5]. due to the higher soot loading caused by exhaust gas recirculation (egr), higher flame temperatures, longer drain intervals etc. engine oils are formulated with higher detergent-dispersant concentrations to maximize the soot handling. in general for a given polyisobuthylenesuccinimide type ashless dispersant a higher nitrogen content gives better dispersancy and soot handling but poorer elastomer compatibility. the balance between soot handling and seal compatibility has provided lubricant formulators with significant challenges over the past ten years, especially as seal testing has become a major part of the engine oil approval process in europe [2, 3, 5, 6]. not only the detergent-dispersant, antiwear (aw) and antioxidant (ao) properties but also the seal compatibility must be highlighted in case of low saps engine oils with reduced znddp content because of the well known interactions between ashless dispersant and znddp which can prevent seal damages [7]. in our experimental work molybdenum and sulphur containing pib-polysuccinimides were prepared and investigated in an sae 10w-40 api sj partly synthetic engine oil formula. the possibility of the totally or partly replacement of the conventional dispersant and also the reduction of znddp and its impact on the properties, especially ao, aw and seal compatibility were investigated. 28 experimental methods during laboratory screening tests the properties of the additives and the engine oil compositions were measured by standard and proprietary methods [8, 9]. detergent-dispersant (dd) properties: based on centrifugation and paper chromatography; spot dispersancy. high temperature deposit preventing effect: modified panel coker (300 °c al plate, 3x3 h). thermal and oxidation stability: ip-48 method (200 °c, 12 h, 15 dm3/h air). af/aw properties: modified stanhope seta four ball equipment (600 n, 1 h). seal compatibility: vw pv 3344 (s3a test-pieces from ak-6 fluoroelastomer, pre-ageing: 150 °c, 24 h; immersion: 150 °c, 168 h). materials pib-polysuccinimide (psi) type commercial dispersant produced by mol-lub ltd. was used as reference additive. molybdenum (mo-psi) and molybdenum plus sulphur (mos-psi) containing pib-polysuccinimides prepared in our laboratory and a commercial sae 10w40 api sj/cf partly synthetic engine oil composition were used in the present research work. the main properties of the dispersants and the composition of the experimental engine oils are summarized in table 1 and 2. table 1: properties of the dispersants properties psi mo-psi mos-psi kin. viscosity at 100°c, mm2/s 496.9 283.4 310.6 diluent oil content, % 50 50 50 tbn, mg koh/g 14.1 10.2 11.8 n content, % 1.0 0.9 0.88 mo content (xrfs), % 0 0.3 0.37 s content (xrfs), % 0 0 0.12 3 % additive in sn-150 vie 118 108 111 pdde, % (max. 100) 82 84 89 table 2: composition of the experimental engine oils composition, % ref g1 g2 g3 g4 g5 g6 base oils balance part package 4.2 4.2 4.2 4.2 4.2 4.2 4.2 psi dispersant 10.5 5.25 5.25 2.5 2.5 mo-psi dispersant 5.25 10.5 8.0 mos-psi dispersant 5.25 10.5 8.0 znddp 1.1 0.55 0.55 0.55 0.55 0.88 0.88 results and discussion the potential detergent-dispersant efficiency (pdde) of the experimental engine oils was found to be high (>80%) and similar to each other, so the concentration of the experimental dispersants and znddp did not alter this property (fig. 1). in case of spot dispersancy test, where the carbon black suspensions of the engine oils were treated at different temperatures with and without water, greater differences can be observed among engine oils. at higher experimental dispersant concentrations (8 and 10.5%) the efficiency slightly decreased because of their higher polarity. in case of 0.55% znddp, 5.25% commercial and 5.25% modified dispersant (g1 and g2) the efficiency of the reference engine oil was achieved. in case of high temperature deposit preventing effect the low saps experimental engine oils were found to be analogous to the reference oil which contained 1.1% znddp. both the thermal and oxidation stabilities are very important due to the reduced znddp concentration and thus the reduced antioxidant capacity. after thermal treatment the samples with higher modified dispersant concentration showed better stability than the reference oil while g1 and g2 oils had similar results (fig. 2). after oxidation test higher changes in the viscosities could be observed but these changes did not exceed that of the reference oil. despite reducing the znddp level by 20 and 50% similar thermal and oxidation stabilities were detected in case of the engine oils with modified dispersants. antiwear (aw) and antifriction (af) properties were studied by modified four-ball method in which the af effect was characterized by the final temperature (tmax) achieved at the end of the test [9]. the most important conclusion of the tests that the reduction of znddp did not cause additional wear problems because the complementary af/aw effects of the modified dispersants could compensate the lower level of znddp concentration. when the ratio of modified dispersant and znddp was higher (g3 and g4) better af/aw properties could be observed (figure 3 and 4). it seemed that additive competition on the metal surfaces played important role thus at higher modified dispersant/znddp ratio the molybdenum containing dispersant could build up more efficient friction and wear reducing tribofilm. the reduction of znddp concentration can cause seal compatibility problems due to decreased interactions between succinimde type dispersant and znddp which can cause fluoroelastomer seal damage. vw pv 3344 seal tests of the low saps experimental engine oils with reduced znddp concentration showed no adverse effects on seal compatibility (table 3) even if the conventional dispersant was completely replaced by modified ones (g3, g4). its reason could be their lower tbn and higher polarity which could easily interact with the other additives and thus the seal damaging basic amino-groups were blocked. 29 0 20 40 60 80 100 ref g1 g2 g3 g4 g5 g6 ef fic ie nc y, % (m ax . 1 00 % ) pdde spot dispersancy deposit preventing effect figure 1: dd and high temperature deposit preventing effects of the experimental engine oils -25 -20 -15 -10 -5 0 5 ref g1 g2 g3 g4 g5 g6 c ha ng e in k v 10 0, % after thermal treatment after oxidation figure 2: thermal and oxidation stability of the experimental engine oils 0 0.2 0.4 0.6 0.8 1 ref g1 g2 g3 g4 g5 g6 w ea r s ca r d ia m et er , m m figure 3: antiwear properties of the experimental engine oils 30 50 60 70 80 90 ref g1 g2 g3 g4 g5 g6 tm ax , ° c figure 4: antifriction properties of the experimental engine oils table 3: results of the vw pv 3344 seal compatibility tests properties s3a* ref g1 g2 g3 g4 g5 g6 test limits tensile strength, mpa 15.5 10.5 11.7 12.1 12.5 12.8 13.2 13.5 ≥7 change in tensile strength, % -32 -25 -22 -19 -17 -15 -13 ≥-60 elongation at break, % 395 248 285 291 312 321 328 345 ≥160 change in elongation at break, % -37 -28 -26 -21 -18 -17 -14 ≥-50 hardness change (shore a), points 70.2** -3 -2 -2 -2 -2 -1 -1 surface cracks no no no no no no no no no * original s3a test-piece (without pre-ageing and immersion), ** shore a hardness, not the hardness change conclusions modified pib-polysuccinimide type dispersants containing molybdenum and molybdenum plus sulphur were investigated in fully formulated low saps (0.55 and 0.88% znddp content) engine oils. based on the results of the laboratory screening tests it was found: detergent-dispersant properties and the high temperature deposit preventing effect did not decrease, thermal and oxidation stability were unaffected despite reduced znddp content, complementary af/aw effects of the modified dispersants could compensate the reduction of znddp, low saps experimental engine oils passed the vw pv 3344 seal compatibility test. in this way it can be supposed but should be proved by engine tests that the modified dispersants may open up an opportunity for formulating low saps engine oils with reduced znddp content. references 1. the guide to euro 4 emission standards and lubrication, handbook (2005) lubrizol corp. 2. mang t., dresel w.: lubricants and lubrication (2007) wiley, mannheim 3. canter n.: additive challenges in meeting new automotive engine specifications, tribology & lubrication technology (2006) 62(9), 10-19 4. eachus a. c.: it is not your father’s motor oil, tribology&lubr. techn. (2006) 62(6), 38-44 5. http://www.infineum.com/information/tables.html (visited on 31 january 2008) 6. rudnick l. r.: lubricant additives, chemistry and applications (2003) marcel dekker, ny 7. sarpal a. s., bansal v., sastry m., mukherjee s., kapur g.: molecular spectroscopic studies of the effect of base oils on additive-additive interactions, lubrication science (2003) 16(1), 29-45 8. kis g., bartha l., baladincz j., varga g.: screening methods for selection of additive packages for engine oils, petroleum and coal (2003) 43 (3-4), 106-111 9. bubálik m., hancsók j., bartha l., sági r., kis g.: modified test method for characterization of af/aw properties, 8th int. conf. on tribology (2004) proceedings, 198-203 hungarian journal of industrial chemistry veszprém vol. 33(1-2). pp. 119-124. (2005) neumann boundary value problems with bem and collocation n. herrmann1 and v. karnjanatawee2 1institut für angewandte mathematik, universität hannover, hannover, germany 2dept. of mathematics, king mongkut university of technology thonburi, bangkok, thailand this paper is an introduction into the boundary element method (bem) with collocation to find the numerical solution of two different types of neumann problems. at first we start with the laplace equation and continue later with the heat equation on a bounded convex domain with smooth boundary in two dimensions. we will show how to transform the governing problem into a boundary integral equation which can be solved by dividing the boundary into a finite number of segments and applying the collocation method. we finish presenting an example of the heat equation. keywords: boundary element method, laplace equation, heat equation, neumann boundary value problem, collocation introduction let ω be a convex open domain in 2r with smooth boundary . consider the laplace equation: ω∂ in ω, ( ) 0=∆ y,xu ( ) ( y,xg n y,xu = ∂ ∂ ) on ω∂ , where 2 2 2 2 yx ∂ ∂ + ∂ ∂ =∆ and the heat equation ( ) ( ) ( ) , y t,y,xu x t,y,xu t t,y,xu 2 2 2 2 ∂ ∂ + ∂ ∂ = ∂ ∂ where ( ) ( ]t,t,y,x 0∈ω∈ with initial and boundary conditions, ( ) ( ,y,xf,y,xu =0 ) ( ) ω∈y,x ( ) ( ) ( ) ( ]t,t,y,x,t,y,xg n t,y,xu 0∈ω∂∈= ∂ ∂ by using the fundamental solution we will develop the boundary integral equation (bie) from the governing boundary value problem and will create a fredholm integral equation of the second kind. according to the fact that the solution of a neumann value problem is not unique the same is true for the approximate solution which we get by using bem and collocation. piecewise constant and piecewise linear functions will be used to form the ansatz functions which lead to a simple linear system of equations. neumann boundary value problem for the laplace equation let ω be a convex open domain in 2r with smooth boundary ω∂ . consider the neumann boundary value problem (nbvp): ( ) 0=∆ y,xu in ω, (1) ( ) ( y,xg n y,xu = ) ∂ ∂ on ω∂ . (2) it is well known that for two dimensions ( ) π ξ ξ 2 − −= xlog ,xe (3) is the green's function or the fundamental solution for the operator ∆, that means it is the solution of the problem ( ) ( ) 2r∈∀−−=∆ ξξδξξ ,xx,xe . (4) it can be seen that e is not defined at ξ=x , where e is singular. 120 boundary integral equation for we follow the definition of the distribution ω∈x δ, and with (1) and (4) ( ) ( )( )uxxu ξδ −= ( ) ( ) ( )( ) ( )(∫ω ∆−∆= ξξξξξ ξ du,xe,xeu ) the second green-gauß formula gives ( ) ( ) ( ) ( ) ( ) ω∈∀⎟ ⎠ ⎞ ⎜ ⎝ ⎛ ∂ ∂ − ∂ ∂ = ∫ ω∂ xdu n ,xe ,xe n u xu ξσξ ξ ξ ξ .(5) there is no singularity for . therefore for ω∈x ω∈x we can compute u(x) by knowing the boundary data u(x) and n u ∂ ∂ on . we will refer to this formula as the representation of the solution ω∂ u(x) for . ω∈x our neumann problem from above gives n u ∂ ∂ on . we have to find ω∂ u(x) = g(x) on . ω∂ both integrals in (5) ( ) ( ) ( ) ( )∫∫ ω∂ω∂ ∂ ∂ ∂ ∂ ξ ξ ξ σξξσξξ du n ,xed,xe n u and (6) are well defined for . but for we have a jump of magnitude ω∈x ω∂∈x ( ) 2 xu for the second integral : ( ) ( ) ( ) ( ) ( )∫∫ ω∂ω∂ω∂∈→ ∂ ∂ += ∂ ∂ ξ ξ ξ ξ σξ ξ σξξ du n ,xexu du n ,xelim xx 00 20 and so we obtain the boundary integral equation ( ) ( ) ( ) ( ) ( ) ( )∫ ω∂ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ ∂ ∂ − ∂ ∂ += ξ ξ σξ ξξ ξ du n ,xe n u ,xe xu xu 0 0 0 0 2 (7) ω∂∈∀ 0x then we get from (7) a fredholm integral equation of the second kind ( ) ( ) ( ) ( ) ( ) ξξ ξ σ ξ ξσξ ξ d n u ,xedu n ,xexu ∫∫ ω∂ω∂ ∂ ∂ = ∂ ∂ + 2 (8) ω∂∈∀x where u on the left hand side is unknown and ( ) ( )xg n xu = ∂ ∂ on is given. ω∂ collocation method the integral equation (9) does generally not admit a solution in closed form. we will show how to solve such a problem numerically using the collocation method. given ( ) ( ) ,x,xg n xu ω∂∈= ∂ ∂ solve for the unknown dirichlet data u(x), ω∂∈x from ( ) ( ) ( ) ( ) ( ) ,dg,xedu n ,xexu ξξ ξ σξξσξ ξ ∫∫ ω∂ω∂ = ∂ ∂ + 2 (9) ω∂∈∀x the solution of (9) is not unique since if we replace u(x) by ( ) ( ) cxuxu += where c is constant then u is a solution, too. we need a compatibility condition so that the neumann boundary value problem is well posed: g(x) should satisfy ( ) ( ) ( )∫∫∫ ω∂ω∂ω = ∂ ∂ =∆= σσ dxgd n xudxxu0 (10) we use now the collocation method to discretize the problem. we subdivide the boundary into n arcs and call the midpoints of the arcs with . we take the ansatz: ω∂ n,,, γγγ k21 nx,,x,x k21 1xxn = (11) ( ) ( )∑ = = n i ii xaxu~ 1 χ where ( )xiχ is the characteristic function on and are unknown parameters. that means iγ ia ( )xu~ is a piecewise constant approximation to u(x) on . as collocation points we use the midpoints. this leads to ω∂ ( ) ( ) ( ) ,dg,xed n ,xe a a j n i j i j i ∫∑ ∫ ω∂ = γ = ∂ ∂ + ξξ ξ σξξσ ξ 12 (12) nj ≤≤1 these are n linear equations with the unknowns , so that we have na,,a k1 n × n linear system of equations neumann boundary value problem for the heat equation let ω be a bounded convex domain with smooth boundary γ=ω∂ in 2r . consider the heat equation ( ) ( ) ( ) , y t,y,xu x t,y,xu t t,y,xu 2 2 2 2 ∂ ∂ + ∂ ∂ = ∂ ∂ (13) ( ) ( ]t,t,y,x 0∈ω∈ with initial and boundary conditions, ( ) ( ),y,xf,y,xu =0 ( ) ω∈y,x (14) ( ) ( ) ( ) ( ]t,t,y,x,t,y,xg n t,y,xu 0∈γ∈= ∂ ∂ . (15) the problem will be transformed into an integral equation by using the fundamental solution and will be solved by applying the collocation method in the same manner as for the laplace equation (1) and (2). boundary integral equation the well-known green’s function or fundamental solution for the heat equation 121 ( ) ( ) ( ) ⎪ ⎪ ⎩ ⎪⎪ ⎨ ⎧ ≤ > −= − −− τ τ τπτξ τ ξ t te tt,x;,e t x if0 if 4 1 4 2 , (16) is used as weight function to generate the integral equation ( ) ( ) ( )∫ ∫ ω =⎟ ⎠ ⎞ ⎜ ⎝ ⎛ ∂ ∂ −∆ t ddt,;,et,u,u 0ττ τ τ ξxξξξξ where ( t,u x ) is the unknown solution of the heat equation, ( ),, 21 ξξ=ξ ( ),y,x=x 2 2 2 2 1 2 ξξ ∂ ∂ + ∂ ∂ =∆ ξ . let ω be a bounded convex domain in 2r with smooth boundary ω∂=γ . by using the gauss-green formula the integral becomes: ( ) ( ) ( ) ( ) ( ) ( ) ( )∫∫ ∫ ∫ ∫ ωγ γ + ∂ ∂ − ⋅ ∂ ∂ = ξξξτστξτξ τστξτξ ξ ξ ξ ξ dt,x;,efdd n t,x;,e,u ddt,x;,e n ,ut,xu t t 0 0 0 for ( ) ( ]t,t,x 0×ω∈ the left hand side of the formula has to be replaced by the famous jump relation if x is on the boundary. so we are led to a boundary integral equation for γ∈x and . tt ≤<0 ( ) ( ) ( ) ( ) ( ) ( ) ( )∫ ∫ ∫ ∫ ∫ ω γ γ + ∂ ∂ − ⋅ ∂ ∂ = ξξξ τσ τξ τξ τστξ τξ ξ ξ ξ ξ dt,x;,ef dd n t,x;,e ,u ddt,x;,e n ,ut,xu t t 0 2 1 0 0 substitute the given boundary condition into ( ) ξ τξ n ,u ∂ ∂ the boundary integral equation becomes ( ) ( ) ( ) ( ) ( ) ( ) ( )∫∫ ∫ ∫ ∫ ωγ γ +⋅= ∂ ∂ + ξξξτστξτξ τσ τξ τξ ξ ξ ξ dt,x;,efddt,x;,e,g dd n t,x;,e,ut,xu t t 0 2 1 0 0 collocation method we divide the boundary into n segments as shown. ω∂=γ let . γ∈=+ 1121 xx,x,,x,x nnk define ( ){ }101 1 2 ≤≤−+=∈=γ′ + λλλ ,xxx:x iii r where n,,i k1= . then is a polygon in ω since ω is convex. nγ′γ′ uku1 let jn′v be the outer unit normal vector on iγ′ , in,,i maxh γ′= = k0 be the step width in space and for n∈m m tk = be the step width in time and we get the time steps ( ,m). jkt j = k,,j 10= using collocation method the piecewise linear spline functions ( ) n,,i, otherwise x, xx xx x, xx xx x i ii i i ii i i k1 0 1 1 1 1 1 = ⎪ ⎪ ⎪ ⎪ ⎩ ⎪ ⎪ ⎪ ⎪ ⎨ ⎧ γ′∈′ − ′− γ′∈′ − −′ =′ + + − − − ϕ are applied to space and the piecewise constant characteristic functions ( ) ( ] ( ] m,,j, t,tt t,tt t jj jj j k1 1 0 1 1 = ⎪⎩ ⎪ ⎨ ⎧ ∈ ∉ = − − χ are applied to time. with both we form the ansatz function ( ) ( ) (∑∑ = = ′=′ m j n i ji j i txut,xu~ 1 1 χϕ ) where u are the unknown coefficients which we have to find. j i at the time step p of segment i the boundary integral equation becomes xn+1=x1 x2 xi xi+1 xn γ γ' ni 122 ( ) ( ) ( ) ( ) ( ) ( )∫ ∫ ∫ ∫ ∫ ω′ γ′ ′ γ′ ′ ′ ′′′+ ′′⋅′= ′ ∂ ′∂ ′+ ξξξ τστξτξ τσ τξ τξ ξ ξ ξ dt,x;,ef ddt,x;,e,g dd n t,x;,e ,u~u pi t t pi t pip i p p 0 2 1 0 0 this is a system of linear equations. the coefficients can be written in short form as ( ) ( ) ∫ ∫ − γ′ ′ ′ ′ ∂ ′∂ ′= q q t t qi j pq ij dd n t,x;,e b 1 τσ τξ ξϕ ξ ξ ( ) ( ) ( ) ( )∫ ∫ ∫ ω′ γ′ ′ ′′′+ ′′⋅′= ξξξ τστξτξ ξ dt,x;,ef ddt,x;,e,gc pi t t pi p i p 0 0 the boundary integral equation at time step p of segment i is rewritten as: [ ] [ ] ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ + ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −= ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ ⎟ ⎟ ⎟ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎜ ⎜ ⎜ ⎝ ⎛ + ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ ∑ − = p n p q n q p q pq ij p n p pp ij c c u u b u u b mmmo 111 1 1 2 1 2 1 which should be solved to get the solution. example as example we consider the heat equation ( ) ( ) ( ) ( ) ( ]10 2 2 2 2 ,t,y,x, y t,y,xu x t,y,xu t t,y,xu ∈ω∈ ∂ ∂ + ∂ ∂ = ∂ ∂ with the following initial and neumann boundary conditions, ( ) ,,y,xu 10 = ( ) ω∈y,x (17) ( ) ( ) ( ]100 ,t,y,x, n t,y,xu ∈γ∈= ∂ ∂ (18) where ω is the unit circle. forming the boundary integral equation and substituting the data given in (17) and (18) we get ( ) ( ) ( ) ( )∫∫ ∫ ωγ = ∂ ∂ + ξτσττ ξ ξ dt,;,edd n t,;,e,ut,u t xξxξξx 0 2 1 0 , ( ) ( ]10,t,y,x ∈γ∈=x to apply the collocation method we divide the perimeter of the unit circle into 6 segments and discretize the time into 10 time steps. with piecewise linear functions used in space and piecewise constant functions ( 61 ,,i,i k=ϕ ) ( )101 ,,j,j k=χ used in time, the ansatz function is ( ) ( ) (∑∑ = = ′=′ 10 1 6 1j i ji j i txut,xu~ χϕ ) where u are the unknown constant collocation points. j i then the boundary integral equation at time step p becomes ( ) ( ) ( ) 610 2 1 0 ,,i,dt,;,e dd n t,;,e ,u~u pi t pip i k=′′= ∂ ′∂ ′+ ∫ ∫ ∫ ω γ′ ′ ′ ξ τσ τ τ ξ ξ xξ xξ ξ so at the first time step we have the equation ( ) ( )∫ ∫ ∫ ω γ′ ′ ′ ′′= ∂ ∂ +++ ξξ τσϕϕ ξ ξ dt,x,,e dd n e uuu i t i i 1 0 1 6 1 61 1 1 1 0 2 1 k , where i = 1, …, 6 and ( ) ξξ τξ ′′ ∂ ′∂ = ∂ ∂ n t,x;,e n e ii 1 1 . this is a system of linear equations ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ ∂ ∂ ∂ ∂ ∂ ∂ ∂ ∂ ∂ ∂ ∂ ∂ + ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ ∫ ∫∫ ∫ ∫ ∫∫ ∫ ∫ ∫∫ ∫ γ′∪γ′ ′γ′∪γ′ ′ γ′∪γ′ ′γ′∪γ′ ′ γ′∪γ′ ′γ′∪γ′ ′ 1 6 1 2 1 1 0 2 1 6 0 1 1 6 0 2 1 2 0 1 1 2 0 6 1 1 0 1 1 1 1 21 1 16 1 21 1 16 1 65 1 16 2 100 0 2 10 00 2 1 u u u dd n edd n e dd n edd n e dd n edd n e tt tt tt m m l mm l l omm l l τσϕτσϕ τσϕτσϕ τσϕτσϕ ξξ ξξ ξξ ( ) ( ) ( )⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ ′ ′ ′ = ∫ ∫ ∫ ω′ ω′ ω′ 16 12 11 ;0 ;0 ;0 t,,e t,,e t,,e x x x ξ ξ ξ m . the quantities ξ ′∂ ∂ n ei 1 with ( ) ( ) ( ) ⎪ ⎪ ⎩ ⎪⎪ ⎨ ⎧ ≤ > −=′ − −′− τ τ τπτξ τ ξ 1 1 4 11 if0 if 4 1 1 2 t te tt,x;, t x i i e are ( ) ( ) ( )τξ ξ ξ τπξ − −′ −′ ′ ′ − ⋅−′ −=⋅ ′∂ ∂ = ∂ ∂ 1 2 4 2 1 11 8 tiii i e t e n e xξnxξ n . the term ( ) ξξ ′⋅−′ nx i can be shown in the picture below ix y jx 1+jxξ′ ξ ′n 123 it is clear that ( ) ( ) ( )( ) ξξ ξξ ′′ ⋅−′+−=⋅−′ nn yxyx ii ji dxy =−= . jd are constant. then the elements of the coefficient matrix of above system are ( ) ( ) ( ) ( )∫ ∫ ∫ ∫∫ ∫ γ′ ′ − −′ − γ′ ′ − −′ − − γ′∪γ′ ′ − − − −= ∂ ∂ −− j i j i jj t j t x j t j t x j t j i dde t d dde t d dd n e 1 1 2 1 1 1 2 1 1 0 4 1 0 4 1 1 0 1 8 8 ξ τ ξ ξ τ ξ ξ στϕ τπ στϕ τπ τσϕ . we integrate analytically with respect to the time variable and get ∫ ∫∫ ∫ γ′ ′ −′ − γ′ ′ −′ − − γ′∪γ′ ′ −′ − −′ −= ∂ ∂ −− j i j i jj de x d de x d dd n e j t x i j j t x i j t j i ξ ξ ξ ξ ξ σϕ ξπ σϕ ξπ τσϕ 1 2 1 1 2 1 1 4 2 4 2 1 0 1 2 2 . we calculate each term numerically and obtain the system of linear equations ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ = ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ 3282980 3282980 3282980 3282980 3282980 3282980 1 6 1 5 1 4 1 3 1 2 1 1 . . . . . . u u u u u u a ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ = 0.50020200.000490000200.00049002020 0020200.50020200.000490000200.00049 0.000490020200.50020200.00049000020 0000200.000490020200.50020200.00049 0.000490000200.0004900202050002020 0020200.000490000200.000490020200.5 ... ... ... ... .... ... a the solution of the first time step is ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ = ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ 650050 650050 650050 650050 650050 650050 1 6 1 5 1 4 1 3 1 2 1 1 . . . . . . u u u u u u conclusions as shown in this paper the boundary element method (bem) can be applied to elliptic and parabolic differential equations. the benefit of the method compared to conventional methods such as finite different and finite element method is the reduction of dimension of the problem by one since the bem deals only with the corresponding boundary integral equation. moreover for applying the collocation method the unknown trial or ansatz function can be formed by simple functions i.e. piecewise constant and piecewise linear functions. however the disadvantage of the method is the knowledge of the fundamental solution. so its application is limited to linear differential equations symbols pq ij pq ij pq ij c,b,a parameters h space step k time step i, j index parameters m number of time intervals n number elements jnv unit normal vector p, q time parameters t time variable ( )t,y,xu solution n iu collocation parameters x, y space variable x space vector greek letters α a constant χ, ϕ trial function γ boundary of the domain γ' polygonal boundary ξ, τ integral variable ω domain ω' polygonal domain references 1. brebria c.a. and walker s.: boundary element techniques in engineering, newnes butterworths, london, 1980 2. costabel m.: boundary integral operators for the heat equation, integral equations operatortheory, 1990, vol.13, 498 552 3. costabel m., stephan e.p. :., on the convergence of collocation methods for boundary integral equations on polygons, mathematics of computation, 1987, vol.49, 461 -478 4. costabel m., onishi k., wendland w. l.: boundary element collocation method for the neumann problem of the heat equation, academic press inc., 1987 5. dyck u.: randelement-lösungen für die wärmeleitungsgleichung, master thesis in mathematics, hannover university, germany, 1992 6. friedman a.: partial differential equations of parabolic type, prentice hall. inc., 1964 7. herrmann n.: bem with collocation for the heat equation with neumann and mixed boundary 124 values, ams contemporary mathematics, 2002, vol.295, 265 277 8. herrmann n.: improved method for solving the heat equation with bem and collocation, ams contemporary mathematics, 2003, vol.329, 165 174 9. herrmann n.: time discretization of linear parabolic problems, hungarian journal of industrial chemistry, 1991, vol.19, 275 281 10. herrmann n.: numerical problems in determining pore-size distribution in porous material, workshop at the university of budapest, invited lecture, 1995 11. herrmann n., siefer j., stephan e.p., and wagner r., mathematik und umwelt, edition univ. hannover, theodor oppermann verlag, hannover, 1994 12. herrmann n. and stephan e.p., fem und bem einführung, eigendruck inst. f. angew. math., univ. hannover, 1991 13. iso y.: convergence of boundary element solutions for the heat equation, journal of computational and applied mathematics, 1991, vol.38, 201 – 209 microsoft word content.doc hungarian journal of industrial chemistry veszprém vol. 40 (2) pp. 69–75 (2012) effect of a new type of coupling agent on the mechanical properties of various multi-walled carbon nanotube/rubber composites cs. varga1 , b. tóth1, p. gergó1, l. bartha1 1university of pannonia, institutional department of mol hydrocarbon and coal processing, 10 egyetem str., 8200 veszprém, hungary e-mail: vcsilla@almos.uni-pannon.hu in our experimental work application of carbon nanotubes in rubbers have been investigated. the effects of the type of the rubber matrix, the concentration of the carbon nanotubes and the effects of a coupling agent on the mechanical properties of the composites have been studied. the strength of the rubber matrix had great influence on the strengthening behaviour of the carbon nanotubes. by application of surface treated carbon nanotubes the strength of the composites made from a rubber matrix having the tensile strength under 10 mpa could be improved by 35%. however, the composites from the rubber with higher tensile strength contained treated carbon nanotubes afforded balanced performance against fatigue stresses probably due to the effect of the coupling agent and the homogenous distribution of the carbon nanotubes. introduction rubbers reinforced with carbon black (cb) are used for numerous industrial applications, such as vibrationresistant structures, electromagnetic interface (emi) shielding materials, antistatic devices, etc. [1–4]. cb improves the mechanical properties (modulus and strength) of the rubber due to the interactions among the fillers and the fillers and the other components of the rubber. the cb particles were proven to form aggregates because of the strong bonding effects to each other. a part of the rubber is encapsulated in those aggregates because of the branched structures of the latter one and is shielded from macroscopic deformations [1]. small domain size is required for effective reinforcement. on the one hand only branched structures small enough (< 50 nm) can be trapped and thereby achieved a strongly bonded system, and on the other hand only the adequately small domains have high surface activity [1, 2]. in the last two decades researches focused on to substitute cb with another fillers (eg. caolin, sepiolite, sio2, zinc-disorbate, titania) also having reinforcing effects [4–6] and also on to reduce the particle size of the cb to improve their dispersion in the rubber matrix [2]. in the former step modification of the surface of the fillers had to be also solved because they are incompatible with the most organic matrices, therefore, coupling agents were being used [5, 7]. the fillers for substitution of cb like sio2 have been spread in the recent years especially due to the higher demand for non-black applications [7–11]. several solutions have been developed in the cb/rubber research area: as two step grinding technology, application of dispersants or coupling agents, pre-treatment of the carbon surface or chemical modification of the elastomer chains, moreover distribution of the cb in a latex solution instead of solid mixing [2]. not much significant improvements were achieved by the first three solutions. in case of the latter one the modification of the cb surface represented the largest difficulty in order to disperse them homogeneously in the water solution of latex [4, 12]. application of cb has been still significant because besides it can increase the strength of the vulcanized rubber; it also has a positive effect on the optical and electrical properties, and reduces production cost [3]. application of carbon nanotubes (cnt) may represent a breakthrough in rubber matrices either but only small quantities have been introduced because of their relatively high price. furthermore, by dispersion of the cnt arisen the same problems like the cb due to the high surface charge [13,114]. a lot of papers were published about cnt/epoxy and cnt/thermoplastic composites but only a very few about cnt/elastomers [4, 8, 15–18]. the most exciting challenge in the area of cnt containing composites was to solve the proportional dispersion of the cnt because absence of a well-homogenized morphology the distinguished mechanical improvements of the reinforcement can not be achieved in elastomers either. e.g. das and co-workers [19] used untreated and modified multi-walled carbon nanotubes (mwcnt) in a blend of styrene-butadiene rubber (sbr) and butadiene rubber (br) with 50/50 ratio. hydroxyl-groups were enacted to the surface of the modified mwcnt (nanocyl®3153), and bis(triethoxy-silylpropyl)tetrasulfone was applied as the coupling agent for bonding to the rubber. composites were manufactured by a two-roller mill and a stabilized non-ionic surfactant/ethanol solution was 70 used for mwcnt-treating. the coupling agent was applied in 2.5% related to the mass of the rubber. strength of composites containing 5% mwcnt could be enhanced from 1mpa to 4.5 mpa. the new process with the ethanol solution was more effective then other traditional methods in the given concentration range. similar properties were obtained by mwcnts having hydroxyl-groups. application of a silane type coupling agent did not significantly affect the mechanical properties. our research has been directed to the application of mwcnt in rubbers. the mwcnt has the same favourable effect in the point of view of the mechanical properties [20–22] as cb, and moreover by introduction of a proper coupling agent strong interaction can be established between the mwcnts and the rubber. as mwcnts have excellent mechanical properties they should have better strengthening effect than cb has. if mechanical properties of rubber composites can be improved to a large extent enough then the cost reduction can become less important. for the surface treatment of mwcnt an olefinmaleic-anhydride copolymer based coupling agent has been applied [24]. not only the possible effects of the coupling agent but also effects of the mechanical properties of the initial rubber matrix as raw material have also been investigated in mwcnt/rubber composites. 2. experimental 2.1. materials multi-walled carbon nanotubes (mwcnt) were produced at 700°c by chemical vapor deposition (cvd) process over fe-co bimetallic catalyst at the institutional department of chemical engineering (institute of chemical and process engineering, university of pannonia). purity of mwcnt was higher than 90 wt%, the diameter was between 10 nm and 20 nm, the average length was above 30 μm. natural rubber (nr) and styrene-butadiene rubber (sbr) based (r-i and rii) and nitrile-butadiene rubber (nbr) (acn content: 45%, mooney viscosity, 100°c: 60) based blends (riii) were used as matrix material. h n ch2 o o ch r2 o o ch2 ch3 ch3 n o ch2 o o r1 ch r2 o o ch2 ch3 ch3 k l m ch2 ch3 oh o ch2 ch3 o ch2 ch3 nh ch2 ch3 a a b b figure 1: structure of the ester-amide-imide derivative of the experimental olefin-maleic-anhydride copolymer (r1: alkyl group with length of the olefinic monomer (c16-c18); r2: alkyl group with r1-2 carbon number; a: 3-40, b: 3-32; k: 0,2-2; l: 1-7; m: 1-7 and n: 0,3-2) the coupling agent was produced at the institutional department of mol hydrocarbon and coal processing (institute of chemical and process engineering, university of pannonia) that was an ester-amide derivative of an experimental olefin-maleic-anhydride copolymer (figure 1). 2.2. preparation of composites compounds were prepared by a milling process. a tworoller mill was applied also for mixing the carbon nanotubes into the basic mixture of rubber. sheets of the mixtures were compression moulded at 180°c for 5 minutes vulcanization time. dog-bone samples for mechanical testing were cut from the sheets. compositions of the samples were given in table 1. table 1: composition of the different mwcnt/rubber composites sample rubber matrix type mwcnt content, wt% coupling agent, wt% c-1 r-i 0 c-2 r-i 1.0 c-3 r-i 1.0 0.2 c-4 r-ii 0 c-5 r-ii 1.0 c-6 r-ii 1.0 0.2 c-7 r-iii 0 c-8 r-iii 1.0 c-9 r-iii 1.0 0.2 c-10 r-iii 1.5 c-11 r-iii 2.4 c-12 r-iii 2.4 0.5 effects of the coupling agent were also studied by application with an experimental treating method developed for surface treating of mwcnts for pp [24]. surface of mwcnt was covered by the coupling agent from the hydrocarbon solution of the additive with stirring the mixture for 1 hour at 60°c then the solvent was distilled out. treated mwcnts were then dried at 110°c for 2 hours and were mixed into the basic mixture of rubber by a two-roller mill. r-i and r-ii matrices were nr and sbr based blends with lower and medium mechanical strength, riii matrix was an nbr based one with high mechanical strength. thus effects of the type of the rubber were also studied on the properties of the composites. mwcnts were applied in untreated and in treated form in order to investigate the influence of the coupling agent either. 2.3. measurement of tensile properties to determine the tensile and fatigue tensile properties (mainly stress, modulus and extension) (msz en iso 527-1-4:1999) an instron 3345 universal tensile 71 testing machine was used. the temperature in the laboratory was 23°c and the relative humidity was 50% during the mechanical tests which were carried out at 90 mm/min crosshead-speed both in case of tensile and fatigue tensile tests. structural information about the developed coupling agent was obtained by infrared technique with a tensor 27 type ftir1, illumination: sic globar light, detector: rt-dlatgs type) in the 400-4000 cm-1 wavenumber range. scanning electron microscopy (sem) was used to study the structure of fractured faces of the specimens and to follow the possible interaction between the reinforcements and the matrices. the applied apparatus was a phillips xl30 esem instrument. 3. results and discussion discussion of the results was divided into three parts. on the first hand effects of the type of the rubber matrix were detailed then on the second hand effects of the mwcnt concentration and finally the effects of the coupling agent were demonstrated. 3.1. effect of the change in the rubber matrix on the tensile properties in the present work effects of multi-walled carbon nanotubes (mwcnt) in three rubber matrices (signed as r-i, r-ii, r-iii) with different tensile strengths were investigated. different effects were measured for the rubber matrices (figure 2). introduction of mwcnts into the rubber either in treated or in untreated form resulted in both increase and in decrease of the tensile strengths. 0,0 4,0 8,0 12,0 16,0 20,0 r‐i r‐ii r‐iii te ns ile  s tr en gh t,  m pa sign of the rubber matrix rubber matrix untreated mwcnt treated mwcnt figure 2: effects of type of the rubber matrix on tensile properties (1wt% mwcnt-content) different effects were measured for the samples where treated mwcnts were incorporated. tensile strength enhanced from 8.6 mpa to 11.6 mpa meaning a 35% increase for the r-i matrix. meanwhile in the case of r-ii signed rubber the tensile strength reduced by 26% in the presence of untreated mwcnt. application of the coupling agent improved the tensile strength by 12% but tensile strength of the original matrix could not be achieved. tensile strengths of the mwcnt containing composites did not differ to that of the r-iii matrix having the highest tensile strength (19.2 mpa). 0,0 4,0 8,0 12,0 16,0 20,0 r‐i r‐ii r‐iii te ns ile  s tr en gh t,  m pa sign of the rubber matrix rubber matrix untreated mwcnt treated mwcnt figure 3: effects of type of the rubber matrix on fatigue tensile properties (1 wt% mwcnt, fatigue conditions: 100 cycles and 10 n) resistance of the samples against fatigue tensile stresses of 100 cycles and 10 n as loading force were also studied (figure 3). comparing the results of the fatigue tensile tests to those of the static tensile tests two important outcomes could be stated. first of all mwcnts in the rubber blends could either improve or deteriorate the mechanical properties depending on the type of the rubber matrices. on the second hand composites made from basic mixture of r-ii showed different behaviour than the others. fatigue tensile strength was found to have been deteriorated by 6.5% if the mwcnt was incorporated in untreated form. the opposite behaviour was experienced by mwcnts treated by the coupling agent since a 5% increase was measured. standard deviation (sd) was calculated to be 0.8 mpa for unteated and 1.0 mpa for surface treated mwcnt containing samples. elongation at break was also represented for both types of tensile tests (figures 4, 5). 0 50 100 150 200 250 300 350 400 r‐i r‐ii r‐iii el on ga ti on  a t  br ea k,  % sign of the rubber matrix rubber matrix untreated mwcnt treated mwcnt figure 4: effects of type of the rubber matrix on elongation at break (1 wt% mwcnt content) 72 considerations for the elongation at break were established similar to the tensile strength. type of the rubber was determinative in the evolution of the elongation at break (fig. 4) either. reinforcing rubber r-i with mwcnts the value of 250% of elongation at break significantly decreased due to the pristine mwcnts. changing the reinforcement to surface treated mwcnts an 18% improvement could be measured as the property increased to 290%. mwcnts even in coupling agent treated form deteriorated the elongation at break of r-ii rubber. 0 50 100 150 200 250 300 350 400 r‐i r‐ii r‐iii el on ga ti on  a t  br ea k,  % sign of the rubber matrix rubber matrix untreated mwcnt treated mwcnt figure 5: effects of type of the rubber matrix on elongation at break for fatigue tensile tests (fatigue conditions: 100 cycles and 10 n, 1 wt% mwcnt) elongation at break did not change if the matrix with the highest elongation was reinforced with mwcnts either in untreated or in surface treated form. regarding to the results for elongation at break after the fatigue tensile tests a more balanced picture could be drawn. approximately a 20% decrease was measured for r-i and r-ii matrices in the elongation at breaks for fatigue tensile testing compared to static tensile testing. but mwcnt containing composites had the same values for elongation at break both for r-i and for r-ii based samples even for fatigue tensile tests. there were not any significant effects of the coupling agent on the elongation at break of all the rubber matrices. 3.2. effect of carbon nanotube concentration in that chapter changes in tensile strength, tensile modulus and elongation at break of r-iii based composites was discussed in function of the concentration of the mwcnt. lower tensile strength was measured for r-iii matrix after fatigue tensile tests (figure 6). regarding to the static tensile strength approximately 1.5 wt% mwcnt was required for a slight increase. the fatigue tensile results were represented for the same fatigue load (10 n) with two different cycles: 100 and 1500 cycles (fig. 6). resistance of the rubber (riii) deteriorated with the duration of the fatigue test. the same trends were observed for carbon nanotube containing samples either. 2.4 wt% mwcnt was needed to exceed the tensile strength of r-iii after long time fatigue stresses. with lower concentration of mwcnts in the rubber there was no difference among the property at the same fatigue conditions. 14 16 18 20 r‐iii 1.0wt% mwcnt 1.5wt% mwcnt 2.4wt% mwcnt te ns ile  s tr en gh t,  m pa without fatigue 100 cycles 1500 cycles figure 6: effects of carbon nanotube concentration on the fatigue tensile strength (fatigue load: 10 n for both 100 cycles and 1500 cycles) figure 7 represented the effects of filler concentration on the tensile modulus. on the first hand, values of modulus by the static tensile test increased with the mwcnt content. the modulus of the samples containing 1 wt% mwcnt have been enhanced by 13% related to the reference. the same extent of improvement was measured for the other two mwcnt/rubber composites. fig. 7 showed the results for fatigue tensile test either. depending on the duration of the fatigue tests positive changes were getting lower with increasing mwcnt contents. in that case moduli for the fatigue conditions were compared to the results of the simple tensile test. all the reinforced samples performed higher tensile modulus than that of the rubber matrix, so toughness of the composites enhanced by incorporation of mwcnts. the modulus of the sample with 2.4 wt% mwcnt depended the less on the duration of fatigue stresses. that phenomenon could be related to orientation of the mwcnts into the direction of the periodic stresses based on previous experiments with carbon fibres. 0 2 4 6 8 r‐iii 1.0wt% mwcnt 1.5wt% mwcnt 2.4wt% mwcnt m od ul us , m pa without fatigue 100 cycles 1500 cycles figure 7: effects of carbon nanotube concentration on fatigue tensile modulus (fatigue load 10n) figure 8 reperesented changes in the elongation at break in the function of the mwcnt content. elasticity of the samples had been expected to decrease with the mwcnt content. thus, a reduction in elongation at 73 break was observed above 1 wt% mwcnts in the rubber. not a significant change was calculated for 1 wt% mwcnt/rubber samples. samples containing 2.4 wt% mwcnt had a value of 300% for elongation at break meanwhile the same property was 345% for the basic rubber. 0 50 100 150 200 250 300 350 400 r‐iii 1.0wt% mwcnt 1.5wt% mwcnt 2.4wt% mwcnt el on ga ti on  a t  br ea k,  % without fatigue 100 cycles 1500 cycles figure 8: effects of carbon nanotube concentration on fatigue elongation at break (fatigue load 10 n) 3.3. effect of surface treatment in that part of the paper effects of surface treatment were discussed on tensile and fatigue tensile properties. in figures either results of the unreinforced rubber matrix with composition r-iii or results of the composites containing 2.44 wt% mwcnt reinforcement were demonstrated. during the fatigue tensile tests a fatigue force of 10 n was applied with different duration times (100 and 1500 cycles). figure 9 represented the effects of untreated and coupling agent treated mwcnts on tensile strength and fatigue tensile strength of the unfilled rubber. changes for simple tensile test could be not significant both for untreated and treated mwcnt/rubber samples containing the same concentration of mwcnt. change was calculated to be below 5%. 14 16 18 20 r‐iii mwcnt 2.4% mwcnt 2.4% (treated) te ns ile  s tr en gh t,  m pa without fatigue 100 cycles 1500 cycles figure 9: effects of surface treatment on fatigue tensile properties (fatigue load: 10 n) the same trend was observed for the fatigue tensile tests. as fig. 9 clearly showed, values of fatigue tensile strength slightly decreased for the rubber matrix and the pristine mwcnt/rubber composites with the increasing number of fatigue cycles. however, the composite containing surface treated mwcnts afforded more balanced performance even for a long period of fatigue stress (1500 cycles) in the given range of concentration and the coupling agent has a higher stabilizing effect in the composite. 0 2 4 6 8 r‐iii mwcnt 2.4% mwcnt 2.4% (treated) m od ul us , m pa without fatigue 100 cycles 1500 cycles figure 10: effects of surface treatment on fatigue tensile properties of the composites (fatigue load: 10 n) in figure 10 the effects of the surface treated mwcnts were demonstrated on the tensile moduli in function of number of fatigue cycles. due to application of mwcnts in the rubber matrix the values of modulus enhanced compared to the rubber since the aforementioned reinforcing material can increase toughness of plastics, elastomers and rubbers. resistance against fatigue stresses were also showed in fig. 10. the values of modulus have been increased both for untreated and treated mwcnt containing samples compared to the initial rubber matrix independently from duration of the fatigue stress. almost the same moduli were determined for both mwcnt/rubber composites at the same level of fatigue conditions. surface treatment was concluded not to have significant effects on tensile modulus but more balanced behaviour was experienced for treated mwcnt/rubber samples. 0 50 100 150 200 250 300 350 400 r‐iii mwcnt 2.4% mwcnt 2.4% (treated) el on ga ti on  a t  br ea k,  % without fatigue 100 cycles 1500 cycles figure 11: effects of surface treatment on fatigue tensile properties of the composites (fatigue load: 10 n) figure 11 demonstrated the effects of both forms of mwcnts on the elongation at break for distinct fatigue duration. values of elongation at break for mwcnt/ rubber composites were measured to be below the value of the rubber matrix. the trends were the same both for simple and for fatigue tensile tests. results were observed to be more balanced for coupling agent treated mwcnt reinforced rubber in that point of view too. although elongation at break for the original rubber matrix was the highest among all the 74 samples regarding the tensile test but after a longer fatigue tensile test significant (13%) deterioration was obtained and the value of the treated mwcnt/rubber was less sensitive against fatigue stresses. 3.4. sem homogeneity of the samples based on r-i rubber was studied on the sem graphs of the broken surface of the composites (figure 12–14). figure 12: sem graph of the broken surface of the original rubber matrix figure 13: sem graph of the broken surface of the pristine cnt containing rubber composite figure 14: sem graph of the broken surface of the coupling agent treated cnt containing rubber composite components of the rubber formula were clearly remarked (white spots) on sem graph of all the samples. difference was observed between the carbon nanotube containing samples. composites with untreated cnts showed a less smooth surface after tensile test than samples with surface treated reinforcements. narrower and more homogeneous particle size distribution was experienced on the surface of coupling agent treated carbon nanotube/rubber samples indicating higher degree of compatibility of the components which could probably result the improvement of the mechanical properties. conclusion our research has been directed to the application of mwcnt in rubbers in which effects of an olefinmaleic-anhydride based coupling agent was also studied. the results were summarized as follows: application of carbon nanotubes in a rubber matrix could both enhance and deteriorate the mechanical properties of the composites depending on the types and strength of the original rubber mixture. difference in the behaviour in mwcnt containing composites could be experienced during the fatigue tensile test, which could be important especially for rubber products. at least 2.4 wt% mwcnt was required to achieve better performance during long time fatigue than the rubber matrix with the highest tensile strength (r-iii). acknowledgement we acknowledge the financial support of the work by the hungarian state and the european union under the támop-4.2.2/b-10/1-2010-0025 project. authors are also grateful to the project of baross gábor program (reg_kd_09_2-2009-0026) for the financial support. references 1. b. omnes, s. thuillier, p. 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page 408 page 409 page 410 page 411 page 412 page 413 page 414 page 415 page 416 page 417 page 418 page 419 page 420 page 421 page 422 page 423 page 424 page 425 page 426 page 427 page 428 page 429 page 430 page 431 page 432 page 433 page 434 page 435 page 436 page 437 page 438 page 439 page 440 page 441 page 442 page 443 page 444 page 445 page 446 page 447 page 448 page 449 page 450 page 451 page 452 page 453 page 454 page 455 page 456 page 457 page 458 page 459 page 460 page 461 page 462 page 463 page 464 page 465 page 466 page 467 page 468 page 469 page 470 page 471 page 472 page 473 page 474 page 475 page 476 page 477 page 478 page 479 page 480 page 481 page 482 page 483 page 484 page 485 page 486 page 487 page 488 page 489 page 490 page 491 page 492 page 493 page 494 page 495 page 496 page 497 page 498 page 499 page 500 page 501 page 502 page 503 page 504 page 505 page 506 page 507 page 508 page 509 page 510 page 511 page 512 page 513 page 514 page 515 page 516 page 517 page 518 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hungary, e-mail: gaborgal@freemail.hu 2gedeon richter ltd., h-1475 budapest po box. 27, hungary a promising solution for the separation of pharmaceutical enantiomers is the method of smb liquid chromatography (smb-lc). an optimised coupling of smb-lc and crystallization processes can improve the efficiency of enantioseparation. in the first process both enantiomers can be produced in enriched concentrations in extract and raffinate streams of simulated moving bed chromatograph suitable for crystallization. chromatographic investigations include the experimental determination of adsorption isotherms, bed voidage, ntp, hetp etc. on a suitable chiral stationary phase as well as the simulation and optimization of a the appropriate smb-lc process. mathematical models and joined computer programmes were published in our earlier papers had been developed and applied for the calculation of smb-lc. we assumed isotherm, isochor equilibrium adsorption (competitive multicomponent langmuir-adsorption equilibrium) in the mathematical model neglecting the effects of axial dispersion. the mathematical model was solved by finite differences, numerical mathematical method using pc. the smb-lc separations were carried out on a laboratory scale (i.d. = 1 cm, l = 25 cm) four-column open loop eluent system equipment at 1:1:1:1 column configuration. the process variables of the smb-lc (product purity, yield, productivity, specific solvent consumption) are favourable. the efficiency of the enantiomer separation can be increased by coupled crystallization of the enriched extract and raffinate fractions resulting >99% (w/w) pure enantiomer crystals. „mother liquids” recirculation from crystallization to the smblc process increases with great benefit the economical parameters of enantiomer separation. keywords: preparative liquid chromatography, simulated moving bed chromatography, pharmaceutical enantiomers, chiral chromatographic packing, crystallization introduction nowadays more than half of the registered medicals have got chiral structures owing special importance in pharmaceutical industry. from pharmaceutical points of view only one enantiomer has got good biological activity, meanwhile the other enantiomer is inactive or toxic. the conclusion is, that the enantiomer purity has determining effect. the classical resolution can be well applied for the production of optically active compounds. for example optically active compounds can be produced by stochiometric catalytic asymmetric synthesis starting from achiral compounds. enantiomers produced by synthesis can be separated by simulating moving bed liquid chromatography (smb-lc) process. this last process has growing importance in pharmaceutical industry as it is well applicable in case of the high purity separation of wide scale of racemic mixtures. the advantages of smb-lc compared to the traditional batch chromatography are: continuous process, constant product purity for both enantiomers, high yields, high productivities, low specific solvent consumptions. the chromatographic packing (csp) is used in full columns length, so the productivity and yield is high in case of smb-lc compared to batch chromatography. disadvantages of smb-lc are: high investment costs and process parameter sensitivity. in analytical, preparative and smb liquid chromatography the polysaccharide derivatives proved to be versatile among industrial chiral stationary phases (csp). the productivity of smb-lc in case of these csp packings are as high as 0.2-2 kg racemic mixture/kg packing/day. the coupled crystallization to smb-lc provides possibility to impurity removal, thus the valuable enantiomers can be achieved with more than 99% (w/w) purity [1-5]. the next crystallization methods can be applied: resolution by entrainment, separation via formation of diastereomer salts and crystallization from optically active solvents. the triangle solubility diagram of two enantiomers/one solvent system presents the possibility of enantiomer enrichment. the yield of crystallization process depends on the above mentioned triangle solubility diagram data and the inlet liquid concentration. this publication is on the smb-lc and the coupled crystallization of enantiomers. in the first step smb-lc process is used for enantiomer enrichment, then in the second step pure enantiomer is produced by crystallization. valuable 2 enantiomer crystallization mother liquid after evaporation was recirculated to the feed of smb-lc. determination of optimal concentration of the valuable enantiomer coming from smb-lc is an important task during the planning of hybrid process (smb-lc, liquid evaporation, crystallization with cooling, mother liquid recirculation, etc.). enantiomer separation by chiral liquid chromatography the first and significant step in planning of chiral chromatographic enantiomer separation is to determine the proper moving and stationary phases can be made by screening experiments in analytical scale. these data are used for smb-lc mathematical models, calculations helping previous planning and size increase of smb-lc process. fundamentals of smb-lc chromatography nowadays the smb-lc process is widely used and well applied in various separation problems. the large scale smb-lc process was developed by uop in 1960 and since this time it has gone over tremendous development. since 1980 it has been used especially in fine chemical industry and for the last decade in the field of pharmaceutical industry. on fig. 1. the classical four column open eluent loop smb-lc process is presented. the smb-lc chromatographic process is a multi column system with two inlet (fresh eluent and feed of enantiomers) and three outlet (extract, raffinate and outlet liquid) streams where the liquid and solid phases are moving in counter current direction. the counter current stream of liquid and solid phases is not real, but simulated as the stationary phase is moving by columns at each switching time. simulated solid phase movement is carried out at the switching time by the proper periodical change of inlet and outlet points of the equipment. these points divide the smb-lc equipment for four zones (i, ii, iii, iv). the enantiomer solution (a, b) for separation is fed (f = feed) into the equipment amidst ii and iii zones. as the component a adsorbs stronger on csp than component b, the previous is moving rather with the solid phase while the other one is moving with the liquid phase in the smb-lc equipment. components a and b in zones ii and iii separate from each because of their different adsorption affinity and the resulted pure a and b components can be got in extract and raffinate streams respectively (fig. 1) solid phase regeneration happens in zone i with fresh eluent, while in zone iv the eluent regeneration is carried out by retaining the less adsorbing component b. raffinate, r extract, e fresh eluent, d feed, f b a+b a iv iii ii i lr out fig. 1: simulated moving bed (smb) adsorber: i, ii, iii, iv-zones, respectively hplc columns; d-desorbent (solvent, eluent); e-extract stream with the stronger adsorbed component a; f-feed stream with the components a and b; r-raffinate stream with the less adsorbed component b; lr outoutlet liquid. working points and the separation range of smb-lc processes [6, 7] the main task in smb-lc planning is the proper choice of working conditions. obviously it means the determination of relative volumetric streams of liquid and solid phases in each zones. five parameters must be determined in a two component mixture separation task using smb-lc equipment. these are the liquid volumetric streams in four zones and the so called switching time. morbidelli and co-workers significantly contributed to the handling of this non trivial planning problem. according to the aboves morbidelli theory or triangle was used for the initial parameters calculation of smb-lc. assume the next component balance equation for equilibrium adsorption without component indexes. ( ) 01 =⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ∂ ∂ +⎟ ⎠ ⎞ ⎜ ⎝ ⎛ ∂ ∂ −+⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ∂ ∂ z f z f t f t ca t qa z cb εε 3 where bf = volumetric velocity (cm3/min), c = concentration in liquid phase (mg/cm3), z = axial distance (cm), t = time (min), ε = bed voidage (cm3 liquid/cm3 column), af = column cross section (cm2), q = concentration in solid phase (mg/cm3). assuming linear adsorption equilibrium isotherm: q=k · c the linear velocity of liquid element with c concentration, uc = (cm/min) after the de vault equation: ( )k a b u t z f f c c εε −+ ==⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ∂ ∂ 1 the column is packed with granular solid adsorbent, which does not fill the full volume. the column can be characterised by the bed voidage (ε). in our case “a” and “b” two component mixture was investigated with ka and kb adsorption equilibrium distribution coefficient. in our case ka >kb, k measure unit is (g component/cm3 solid)/(g component/cm3 liquid). determination of the morbidelli parameters [6,7] let examine the iii zone of the smb-lc equipment. presume, that the adsorbent have neither “a” nor “b” components and during “t” switching time “a” and “b” components are fed into the iii zone. as the volumetric velocity in the given iii zone is d-e+f, so the velocities of “a” and “b” components in iii zone are as follows (see fig. 1): a f a k a fed u )1( εε −+ +− = b f b k a fed u )1( εε −+ +− = the length of the iii zone is l (cm), the cross section of the column is af. “a” is not allowed to run out of the iii zone, but “b” must leave it. a f b k t l a fed k )1()1( εεεε −+< +− <−+ a f b k l lt a fed k < − − +− < )1( ε ε aiiib kmk << miii – morbidelli parameter, relative velocity for the iii zone the next can be written for the ii zone of the smblc equipment: “b” component must leave the ii zone and “a” is not allowed to get through: a f b k t l a ed k )1()1( εεεε −+〈 − 〈−+ a f b k l lt a ed k 〈 − − − 〈 )1( ε ε aiib kmk 〈〈 mii – morbidelli parameter, relative velocity for the ii zone in the i zone of the smb-lc equipment no “a” can be remained, so regeneration must be perfect. a f i k l lt a d m 〉 − − = )1( ε ε mi – morbidelli parameter, relative velocity for the i zone “b” component is not allowed to leave the iv zone of the smb-lc equipment. b f iv k l lt a rfed m 〈 − − −+− = )1( )( ε ε miv – morbidelli parameter, relative velocity for the iv zone these conditions are necessary for the separation of a two-component “a”, “b” mixture for pure “a” and “b” components. summary ka < mi kb < mii < ka kb < miii < ka miv < kb 4 fig. 2: morbidelli triangle in case of linear adsorption isotherms assuming independent adsorption: region 1: pure “a” and pure “b”, region 2: pure “b” in raffinate, impure “a” in extract, region 3: pure “a” in extract, impure “b” in raffinate, region 4: impure “a” in extract, impure “b” in raffinate. theoretical analysis in case of non linear adsorption isotherms [6,7] if linear adsorption equilibrium isotherms and independent adsorption conditions are not existing during the theoretical description of equilibrium adsorption described in the previous chapter, than the morbidelli triangle modifies. fig. 3: modification of morbidelli triangle in case of competitive langmuir isotherms it can be seen from the figure 3, that the modified morbidelli triangle is also divided into four regions: region 1: pure “a” and pure “b”; region 2 pure “b” in raffinate, impure “a” in extract; region 3: pure “a” in extract, impure “b” in raffinate; region 4: impure “a” in extract, impure “b” in raffinate let the two component competitive langmuir adsorption isotherm be valid: 22111 cbcb caq ii i ++ = 2,1=i where: qi – solid phase concentration (mg/cm3 adsorbent) ci – liquid phase concentration (mg/cm3) ai – langmuir constant (cm3 liquid/cm3 adsorbent) bi – langmuir constant (cm3 liquid/mg “a” or “b” component). the conditions of simultaneous production of pure “a” and “b” components are as follows: mi > ka mii,min (mii, miii) < mii < miii < miii,max (mii, miii) miv < miv, kr [ [ ] iiibiiiii f bbiiib iiiii f bbiiibkriv mammcbmk mmcbmkm 4)( )( 2 1 2 , −−++ −−++= where f means the feed of smb-lc equipment (cm3/min). explanation of fig 3: point a ka = ka point b kb = kb point f ωg = ωg point r [ ] ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ − −+−− )( )()()(, 2 faba fagbbagafg a g kkk kkkkk k ω ωωωωωω point w [ ] ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ − −+− )( )()(, fab fbbbafg a gb kk kkkk k k ω ωωωω where ωf and ωg (ωg > ωf > 0) are the roots of equation given below (1 + baca f + bbcb f)ω2 – [ka(1 + bbcb f) + +kb(1 + baca f)]ω + kakb = 0 it can be seen on fig. 3 that the shape and area of morbidelli triangle significantly changes caused by the competitive langmuir isotherm affected by feeding total and component concentrations, real effects as adsorption kinetics (component transfer resistances), axial mixing phenomena, column packing efficiency (fig. 4). 5 fig. 4: feeding concentration change on morbidelli triangle in case of racemic mixture (c0 f < c1 f < c2 f < c3 f < c4 f, c0 f ~ 0 g/dm3) increasing the feeding concentration the triangle area decreases and deforms at constant langmuir adsorption equilibrium parameters. it is unfavourable for enantiomer separation. the mathematical model of smb-lc from the above equations, it can be seen that the pure extract-pure raffinate area is smaller by higher feed concentration than the rectangular triangle, consequently we have less possibility by parameter variation. the morbidelli's area changes, when the following possibilities of intervention vary during the planning: temperature, changing adsorbent, and composition of the solvent (eluent). when we have already selected the chromatographic packing for the separation, the next task is to choose operating variables: fresh eluent, recirculated eluent, feed, and extract, raffinate flow rates, switching time. during calculation, the influence of a given parameter is to be investigated, the others must be considered as constants. better productivity, product purity, yield, and eluent consumption can be achieved by optimizing operating conditions by computer with the exact mathematical model of the smb. the basic equation of the mathematical model can be deduced from the component balance of the solid–liquid equilibrium system [8, 9]. the equal balance for the component “k” is: 0)()()1()(0 = ∂ + ∂ ∂ −+ z k z k t k t c t q z cv ∂ εε ∂ ∂ where v0 = velocity of fluid phase (cm/min), dck/dz = place derivative of liquid concentration of component k, dck/dt = time derivative of liquid concentration of component k, and dqk/dt = time derivative of solid concentration of component k. when we discuss a two-component equilibrium system the competitive multi-langmuir type isotherm can be written as: 2211 11 1 1 cbcb caq ++ = 2211 22 2 1 cbcb caq ++ = the denominator of this isotherm was replaced by “n”: 22111 cbcbn ++= considering the equal balance and concentration (c1, c2) derivatives of the above eq. can be written: t c n cba n cbana t c z cn vo ∂ ∂ − + − ∂ ∂ = ∂ ∂ − − 2 2 121 2 1111112 ) 1 ( 1 ε ε ε the derivatives were substituted with difference quotients: )() 1 ( 1 2 2 1 111 2 1 112 t c b t c bcanna t c z c n vo δ δ + δ δ − − + δ δ = δ δ − − ε ε ε difference eq. above was rearranged and written for component “k”: )) 1 ( 1 2 1 2 kkkk kk n k kkk ko cbanna t c t cbca z cnv − − + δ δ = δ δ + δ δ − − ∑ = ε ε ε the above eq. is the base of the numeric simulation software. the component transfer is calculated with this eq. between the so-called equilibrium cascades. in our model, the number of equilibrium cascades are compliant with the number of theoretical plates. based on the mathematical model, the krom-n and smb krom-n computer programs were written in delphi computer language [10]. frontal adsorption experiments and smb-lc measurements can be simulated by the computer programs. at 200 ntp/column the calculation time on a 3 ghz personal computer is 0,6% of the measurement time. the input data of the software: number of components, feed concentration, adsorption equilibrium properties (langmuir parameters), column geometrical data (average) ntp/column, total porosity, bulk density, volumetric velocities (eluent, feed, extract, raffinate, recirculation). the initial smb operating conditions were calculated with the equilibrium triangle method. we considered the maximal flow rate of eluent pump, and minimal column switching time was chosen. simulated moving bed liquid chromatography (smb-lc) coupling with crystallization [1-5] enantiomer purification by crystallization is based on their terner solubility diagrams. according to the type of saturation curves in the phase diagram, three fundamental types (conglomerate, racemic compound, pseudo racemate) forming systems can be identified. only 5-10% of racemates belong to the conglomerate forming group, 6 90-95% belong to the true racemates and the third group pseudo racemates are relatively few. on fig. 5 the solubility diagram of two, (s)and (r) enantiomers and solvent “h” can be seen on equilateral triangle at different temperatures. fig. 5: the solubility diagram of two enantiomers, (s) and (r) in “h” solvent. (s): less retained enantiomer, (r): more retained enantiomer, h: n-hexane solvent, 1. raffinate, 2. evaporated raffinate, 3. crystallization mother liquid, 4. (s) crystals, tc = -20 °c cooling temperature, te = 50 °c evaporation temperature, -.-.limiting evaporated liquid concentration curve of >99% (w/w) (s) crystals. smb-lc and joined crystallization processes are recommended for enantiomer separation according to fig. 5. the (s)-enantiomer in required purity can be achieved, if crystallization started from an asymmetric component content. joined smb-lc and crystallization process starts at point 1 (raffinate) with (s) enrichment. as the raffinate is a diluted unsaturated liquid (point 1), it must be evaporated to put point 2 between evaporation and cooling solubility curves. cooling the liquid (point 2) forms crystallization mother liquid (point 3) and pure (s) crystal is resulted (point 4). smb-lc, evaporation, cooling crystallization and crystallization mother liquid recycling the joint process can be seen on the fig. 6, where both enantiomers can be purified by crystallization. in our work only the (s)-enantiomer was crystallized and its crystallization mother liquid was recycled to the feed. in case of (r)-enantiomer only the eluent was recycled. the original (s) and (r) 50-50% (w/w) feed is to be changed because of the recirculation of (s) crystallization mother liquid and thus concentration of (s) increases over 50%. we have to work out an optimization method, which has got an objective function ((s) productivity maximalization, fresh solvent consumption minimalization) at higher than 99% (w/w) (s) purity, and higher than 99% (s) yield. fig. 6: smb-lc, evaporator, cooling crystallization and crystallization mother liquor recirculation. 7 purity and productivity are determined by the next equations in extract and in raffinate. 100⋅ + = rs s cc cpurity bc r s s v crp ρ4 ⋅ = bc e r r v cep ρ4 ⋅ = cs – (s) concentration in extract or raffinate streams (g/dm3) cr – (r) concentration in extract or raffinate streams (g/dm3) p – productivity (mg component/g packing/day) r, e – raffinate and extract volumetric streams (cm3/min) vc – column volume (cm3) ρb – bulk density (g/cm3) in case of the high purity production of (s)enantiomer only by smb-lc the (s) productivity is low. joining smb-lc and crystallization the (s) productivity can be significantly increased. experiments chiral racemic ester mixture separation was investigated as a model system. the two pure (s)and (r)enantiomers can not be reached in the market and no data can be found in special literature on them. during our research work both chromatographic and crystallization measurements were carried out. by previous analytical and preparative scale hplc measurements adsorption isotherms were estimated for chiral stationary phase-eluent systems. the terner system solubility (s, r, solvent) diagrams were determined at different temperatures in laboratory scale experiments. several laboratory scale smb-lc and joined crystallization experiments were carried out based on previous chromatographic and solubility data. further we describe in details the applied experimental methods. chiral chromatographic packing selection chiral racemic ester mixture separation was investigated by analytical hplc columns (i.d. = 0.46 cm, l = 25 cm, dp = 5-10 µm) at 20 °c. previous selection of csp was done by daicel handbook. accordingly the next csp of daicel were chosen: chiralcel od-h, chiralcel oj, chiralpak ad, chiralpak ia, chiralpak as. the applied eluents are as follows: n-hexane, ipa, et-oh, acn, me-oh, mtbe, dkm in different volumetric ratio with 1 cm3/min volumetric velocity. the 20 µl, 5 g racemic mixture/dm3 eluent concentration sample was separated by analytical hplc column. the enantiomers were detected by gilson type uv spectrophotometer at 254 nm wavelength. investigation of csp packing properties the supelco (i.d. = 1 cm, l = 25 cm) column was packed with the 20 µm chiralcel od by dry vibration method applying 60 min vibration time. air was removed by n-hexane:ipa = 95:5% (v/v) eluent. after that the ntp was determined by injection method. applied eluents were: n-hexane:ipa = 80:20, 90:10, 95:5% (v/v). reaching equilibrium condition with eluent, a 100 µl 50 g racemic mixture/dm3 eluent sample was injected to the column by a rheodyne type injector at 20°c temperature. detection of enantiomers happened by waters uv detector at 254 nm wavelength or chiralyser type chiral detector. applied eluent volumetric velocities: 2.5, 5, 10, 15, 20, 30 cm3/min. evaluation of residence time distribution curves were done by triangle method (determination of σ, tr, ntp, α values). the packing total porosity (ε) was determined by ttbb (tri-tert-butyl-benzene) method. bulk density of csp was calculated from weight measurements of dry packing. values of langmuir a* constants were calculated from k’ values. langmuir b constants were calculated from frontal adsorptionelution measurement data [11]. frontal adsorption-elution measurements measurements were carried out by supelco column (i.d.=1 cm, l=25 cm) packed with 20 µm chiralcel od at 20 °c temperature using n-hexane:ipa = 95:5, 95:7% (v/v) eluent. 2, 5, 10 g racemic mixture/dm3 eluent sample in 10 cm3 volume was injected to the column with 2.5, 5 cm3/min volumetric velocities. detection happened by gilson type uv spectrophotometer at 254 nm wavelength. based on the above data the langmuir adsorption isotherm a* and b values were calculated by felinger et al. [10] method. description of laboratory scale smb-lc equipment the smb-lc equipment with four columns (i.d. = 1 cm, l = 25 cm supelco type stainless steel, mounted with liquid distributor and porous stainless steel plates), four zones and open eluent loop was constructed in the central mechanical workshop of the pannon university. the joint pipes were made of 1/16” stainless steel material, the liquid stream controlled by valco 5 four-ways and 4 two-ways cocks, and by 4 gilson type hplc pumps with maximum volumetric velocity: one of them is 5 cm3/min, two are 10 cm3/min and one is 25 cm3/min. volumetric velocities (d, e, f, r) were measured by emx 100/211 type digital balance connected to a computer. pressure gauge was connected after the eluent pump. extract and raffinate outlet streams were detected on-line by uv or chiral detectors. 8 parameters of smb-lc measurements there is no liquid recirculation in open loop smb-lc equipment, but the liquid from iv zone is collected (lr out) separately. the feed composition is 2.5 g (s)/dm3 eluent and 2.5 g (r)/dm3 eluent. the eluent composition is: n-hexane:ipa = 95:5% (v/v), 20 °c temperature, column configuration 1:1:1:1. volumetric velocities adjusted on different pumps: fresh eluent d = 20 cm3/min, feed f = 0.5-1.5-2.9 cm3/min, extract e = 4 cm3/min, raffinate r = 6 cm3/min. switching time is 5 min. the smb-lc equipment was working by the usual fourzone process, in each 5 minutes inlet and outlet points were changed. examination of smb-lc product streams extracts, raffinates and lr out liquid streams were collected in the 1st, 2nd, 3rd and 4th cycle separately through 20-20 minutes. during the first switching time of the 5th cycle extract, raffinate and lr out streams were fractionated in each 75 seconds for studying concentration transients. the above samples were analysed by gilson hplc equipment, on chiralcel od-h packing at 20 °c temperature, at uv 254 nm wavelength using n-hexane:ipa = 95:5% (v/v) eluent. solubility investigations 20 mg 80:20, 85:15, 90:10, 95:5, 100:0% (w/w) (s):(r) samples were solved in 4 cm3 n-hexane at 20 °c temperature, later cooled to -22 °c and kept staying for 8 hours. crystals and crystallization mother liquid were separated from each other and analyzed by gilson analytical hplc equipment. crystal purity in each case was higher than 99% (w/w) (s). the solubility of pure (s)-enantiomer in n-hexane at -22 °c was 1.2 g/dm3, at 20 °c it was 28.5 g/dm3. solubility of pure (r) in n-hexane at -22 °c was also 1.2 g/dm3. solubility of “sr” racemate at -27 °c was 0.735 g/dm3, at 20 °c was 25.45 g/dm3. solubility of (s) and (r) was examined in n-hexane-ipa mixtures at 0, 5, 10, 20% (v/v) ipa content too. crystallization investigations extract and raffinate fractions of the smb-lc measurements were separately evaporated in vacuum at 40-60 °c temperature in rotadest equipment according to fig. 5. because of the n-hexane-ipa vapour liquid equilibrium data at 95:5% (v/v) n-hexane:ipa concentration during evaporation only n-hexane remained in liquid phase. evaporation was done on the way, that enantiomer concentration was about 5 g/dm3 in the evaporated liquid. the evaporated liquid was kept in a -20…-27 °c freezer through 8 hours. crystals and crystallization mother liquid were separated from each other and analyzed by gilson analytical hplc equipment. results csp packing selection capacity relations and selectivity coefficients were calculated from analytical hplc measurements. 0 0' t ttk r −= ' ' s rr s k k =α 0 2 4 tf ld ⋅ ⋅ = π ε where tr – retention time of the given enantiomer (min) t0 – dead time (min), d = 0.46 cm, inner diameter of column, l = 25 cm, length of column, f = 1 cm3/min, eluent volumetric velocity ε – bed voidage, total porosity (determined by ttbb method) on table 1 are summarized the experimental data. the best αr s selectivity was given in case of chiralcel od-h packing and n-hexane-ipa eluent. thus this system was used in further experiments. 9 table 1: screening measurement results by analytical hplc equipment concentration (% v/v) chiralcel od-h chiralcel oj chiralpak as chiralpak ad chiralpak ia n-hexane:ipa 70:30 αr s=1 n-hexane:ipa 80:20 αr s=1.17 αr s=1.196 n-hexane:ipa 90:10 αr s=1.173 αr s=1 αr s=1 n-hexane:ipa 97.5:2.5 αr s=1.06 n-hexane:ipa 95:5 αr s=1.19 αr s=1 αr s=1.03 n-hexane:et-oh 95:5 αr s=1.122 n-hexane:ipa:acn 80:10:10 αr s=1 acn 100 k's=0.24 αr s=1 acn-me-oh 80:20 αr s=1 αr s=1 ethanol 100 αr s=1 n-hexane:mtbé 80:20 k's>20 n-hexane:mtbé 60:40 k's=6.10 n-hexane:mtbe:et-oh (60:40)+5% et-oh k's=1.086 n-hexane:ipa αr s=1.08 n-hexane:met-oh 99:1 αr s=1.12 n-hexane:et-oh 99:1 αr s=1.11 n-hexane:dkm 75:25 αr s=1.03 n-hexane:ipa:etoh 95:2.5:2.5 αr s=1.15 n-hexane:ipa:metoh 95:2.5:2.5 αr s=1.05 n-hexane:etoh:metoh 95:2.5:2.5 αr s=1.05 packingeluent investigation of csp packing properties 0 50 100 150 200 250 300 350 400 450 0 5 10 15 20 25 30 f (cm3/min) n tp / 25 cm n-hexane:ipa=95:5% (v/v), (s)-enantiomer n-hexane:ipa= 90:10% (v/v), (s)-enantiomer n-hexane:ipa= 80:20% (v/v), (s)-enantiomer n-hexane:ipa= 95:5% (v/v), (r)-enantoimer n-hexane:ipa= 80:20% (v/v), (r)-enantiomer n-hexane:ipa= 90:10% (v/v), (r)-enantiomer fig. 7: results of elution chromatographic experiments, supelco hplc column (i.d. = 1 cm, l = 25cm), chiralcel od (particle size: 20 μm) packing, t = 20 °c, sample: 50 g chiral racemic mixture/cm3 eluent, 100 μl injection, eluent: n-hexane:ipa. for example the n-hexane:ipa = 95:5% (v/v), (s) isomer experimental curve can be described by the next fitting equitation. 3876,036.643 −= fntp where f – volumetric velocity (cm3/min), ntp – number of theoretical plates/25 cm column, ε = 0.67 bed viodage, total porosity ρb = 0.6 g dry csp/cm3 column volume, bulk density 10 frontal adsorption-elution measurement and simulation on the basis of k’ capacity relation values determined by elution measurements (chiralcel od-h, 95:5% (v/v) = n-hexane:ipa) k morbidelli parameters and langmuir adsorption a* values were determined at 20 °c temperature, b values of langmuir adsorption isotherm were calculated by felinger et al. [11] method using the krom-n simulation program (table 2). table 2: input data of krom-n software data input to the krom-n software number of components: 2 column inner diameter: i.d. = 1 cm column length: l = 25 cm free volume coefficient: ε = 0.67 cm3 liquid free volume/cm3 column bulk density: ρb = 0.6 g packing/cm3 column langmuir constants: as given volumetric velocity: 2-2.5-5 cm3/min sample feeding time: 2-4-5-6 min (10 cm3) sample concentration: g (s ) component/dm3 liquid g (r ) component/dm3 liquid number of theoretical plates: ntp = 200/25 cm column end of calculation time: 400 min 55.21f b −−=c 55.21f a −−=c adsorbentcm liquidcmkk rara 3 3 )()( 998.12 1 ' = − = ε ε adsorbentcm liquidcmkk sbsb 3 3 )()( 058.10 1 ' = − = ε ε columncm packingg bulk 36.0=ρ 29.1=r sα method) benzol-butil-tert-tri(67.0 3 3 columncm liquidcm =ε packingg volumefreeliquidcmka bulk rara 3 )( * )( 1489.71 = − = ρ ε componentamg volumefreeliquidcmb ra 3 )( 016.0= packingg volumefreeliquidcmka bulk sbsb 3 )( * )( 5320.51 = − = ρ ε componentbmg volumefreeliquidcmb sb 3 )( 012.0= krom-n simulation program was used for simulation and compared to the measurement results. the conclusion is, that small concentration (2 g/dm3 sample) measurements provide the best separation. results of smb-lc simulations we examined the inlet concentration effect on morbidelli triangle. enantiomers in feed are in equal ratio, (r)=(s) as a racemic mixture. by data given in previous chapter. adsorbentcm liquidcmkr 3 3 998.12= adsorbentcm liquidcmks 3 3 058.10= fig. 8 shows, that increase of inlet concentration decreases deforms the pure components separation area of morbidelli triangle. 7 8 9 10 11 12 13 14 15 7 8 9 10 11 12 13 14 15 mii m iii cf=0,0 g/dm3 cf=2,5 g/dm3 cf=5,0 g/dm3 cf=7,5 g/dm3 cf= 10,0 g/dm3 cf = 0.0 g/dm3 cf = 2.5 g/dm3 cf = 5.0 g/dm3 cf = 7.5 g/dm3 cf = 10.0 g/dm3 fig. 8: changes in morbidelli triangle in function of feed concentration, cf = cs+cr, cs = cr in feed. the smb-lc process volumetric velocity by zones and the switching time were determined in linear adsorption isotherm region using the morbidelli theory. on the basis of that the next relations must be true to produce pure (s)and pure (r)-enantiomers respectively in product streams: 12.998 = kr < mi 10.058 = ks < mii < kr = 12.998 10.058 = ks < miii < kr = 12.998 miv < ks = 10.058 assuming 5 min switching time by the above relations the fresh eluent (d) must be over 19.47 cm3/min, extract stream between 0.53 and 4.34 cm3/min, the feed stream between 0 and 3.47 cm3/min values. the minimal raffinate stream was 3.24 cm3/min value. during simulation the aim was to achieve 80, 85, 90, 95, 99% (w/w) (s) pure raffinate at >99% (s) yield. the fresh (d) volumetric velocity can not be higher than 20 cm3/min because of the allowed highest 50 bar pressure (csp packing specification). the working points of the simulations can be found in morbidelli triangle on fig. 9, the parameters in table 3 and the results in table 4. 11 table 3: input data of smb krom-n software number of components: 2 column inner diameter: i.d. = 1 cm column length: l = 25 cm number of columns: n = 4 free volume coefficient: ε = 0.67 cm3 liquid free volume/cm3 column bulk density: ρb = 0.6 g packing/cm3 column sim 1. sim 2. sim 3. sim 4. sim 5. sim 6. sim 7. feed: cm3/min 3.47 3.2 2.9 2.6 2.35 1.5 0.5 fresh eluent: d = 20 cm3/min extract: e = 4 cm3/min raffinate: r = 6 cm3/min recycling: rec = 0 cm3/min langmuir constants: as given feed concentration: g (s ) component/cm3 liquid g (r ) component/cm3 liquid number of theoretical plates: ntp = 200/25 cm column switching time: 5 min calculation time: 400 min data input to the smb-krom-n software 5.2=f bc 5.2=f ac table 4: results of simulations s % (a/a) r % (a/a) s (%) r (%) (mg s / g packing/day) (mg r / g packing/day) (cm3 eluent/mg s ) (cm3 eluent/mg r ) sim 1. 76.44 99.61 99.97 68.84 268.31 184.16 2.27 3.32 sim 2. 80.43 99.63 99.97 75.29 245.40 184.15 2.49 3.32 sim 3. 85.88 99.65 99.98 83.04 222.50 184.06 2.74 3.33 sim 4. 93.18 99.66 99.98 91.77 199.63 182.37 3.06 3.35 sim 5. 97.43 99.64 99.97 96.10 180.54 173.61 3.38 3.54 sim 6. 99.73 99.35 99.96 98.06 115.32 112.43 5.3 5.44 sim 7. 99.98 98.38 99.96 97.98 38.55 37.41 15.86 16.34 eluent consumption simulation prodictivityyieldpurity 5 10 15 5 10 15 mii m iii sim 1 sim 2 sim 3 sim 4 sim 5 sim 6 sim 7 fig. 9: the working points of the smb simulations, simulated with smb krom-n program, dash line: non-linear morbidelli triangle at cf = 5 g/dm3. summarized results for (s)-enantiomer (purity, yield, productivity, eluent consumption) can be seen on fig. 10. 0 50 100 150 200 250 300 0 1 2 3 4 feed (cm3/min) 0 2 4 6 8 10 12 14 16 18 purity s% (a/a) yield (%) productivity (mg s/g packing/day) fig. 10: summarized results for (s)-enantiomer in raffinate stream. evaporation of raffinate streams, crystallization, crystallization mother liquid recirculation simulation calculation were done. solubility of both (s)and (r)-enantiomers at -20 °c temperature were 1.2 g/dm3. raffinates of smb-lc were evaporated until 5 g (s)+(r)-enantiomers/dm3 concentration followed by cooling to -20 °c temperature. purity of crystal (s) was assumed 99.9% (w/w). on table 5 are summarized data for the calculation of crystallization. 12 table 5: summarized data for the calculation of crystallization s (g/dm³) r (g/dm³) s :r s (g/dm³) sr (g/dm³) s (g) s (%) 4.00 1.00 80:20 1.2 2.0 1.8 45.0 4.25 0.75 85:15 1.2 1.5 2.3 54.1 4.50 0.50 90:10 1.2 1.0 2.8 62.2 4.75 0.25 95:5 1.2 0.5 3.3 69.5 4.90 0.10 98:2 1.2 0.2 3.6 73.5 5.00 0.00 100:0 1.2 0.0 3.8 76.0 crystal ή solution to cooling +20°c, 5 g/dm³ total concentration solution at -20°c crystallization mother liquid was evaporated to 5 g (s)+(r)-enantiomers/dm3 concentration, which was mixed to the smb-lc feed. in the recycled evaporated mother liquid ipa concentration was adjusted at 5% (v/v) value. evaporation of raffinate streams, crystallization, crystallization mother liquid recirculation was repeated by this modified feed concentration twice and three times. after the third full calculation quasi-stationary condition was reached. calculated data can be found in table 6 and 7. table 6: first step crystallization calculated data cf s cf r (g/dm3) (g/dm3) c i.01 3.80 1.50 1.97 2.82 2.18 c i.02 4.07 1.18 2.02 2.81 2.19 c i.03 4.38 0.81 2.09 2.79 2.21 c i.04 4.65 0.47 2.13 2.77 2.23 c i.05 4.59 0.32 2.03 2.76 2.24 c i.06 3.00 0.15 1.35 2.75 2.25 c i.07 1.00 0.00 0.50 2.50 2.50 crystallization code 99,9% purity crystal (mg/min) recirculation (cm3/min) fresh feed (cm3/min) table 7: calculated data after the third full calculation raffinate purity fresh eluent consumption productivity rec. fresh cf s cf r s % (w/w) (cm3 eluent/mg s ) (mg s /g packing/day) sim. iii.01. c iii.01. sim._iii.02. c iii.02. szim. iii.03. c iii.03. szim.iii.04. c iii.04. szim. iii.05. c iii.05. szim. iii.06. c iii.06. szim. iii.07. c iii.07. simulation, crystallization code feed (cm3/min) concentration (g/dm3) 1.37 2.10 2.85 2.15 81.71 3.80 160.96 1.08 2.12 2.83 2.17 84.67 3.77 162.01 0.77 2.13 2.81 2.19 89.07 3.74 163.50 0.47 2.13 2.79 2.21 94.70 3.73 163.43 0.33 2.02 2.78 2.22 97.82 3.94 155.33 0.17 1.33 2.77 2.23 99.76 6.00 102.05 99.98 15.86 38.550.00 0.50 2.50 2.50 on the basis of the above data productivity maximum was at values 2.13 cm3/min fresh feed and 0.77 cm3/min recirculation feed, when raffinate purity was 89.07% (w/w) (s). fresh eluent consumption (calculated for the total smb+crystallization system) was 3.74 cm3 fresh eluent/mg (s). considering the pure (s)-enantiomer 28.5 g (s)/dm3 solubility in n-hexane at 20 °c temperature and (r) and (s) 1.2 g/dm3 solubility in n-hexane at -20 °c temperature, crystallization process was recalculated (see table 8). during calculation purity of (s) 99.9% (w/w) was assumed in crystals. the so called limiting curve belonging to the 99.9% (w/w) (s) crystal value can be drawn (fig. 11). table 8: summarized data for the calculation of crystallization of 99.9% (w/w) pure (s) s (g/dm³) r (g/dm³) s :r s (g/dm³) sr (g/dm³) s (g) s (%) 4.80 1.20 80:20 1.2 2.40 2.40 50.0 6.80 1.20 85:15 1.2 2.40 4.40 64.7 10.80 1.20 90:10 1.2 2.40 8.40 77.7 22.80 1.20 95:5 1.2 2.40 20.40 89.4 27.93 0.57 98:2 1.2 1.14 26.16 93.7 28.50 0.00 100:0 1.2 0.00 27.30 95.7 crystal ή solution to cooling +20°c solution at -20°c 0 5 10 15 20 25 30 0 5 10 15 20 r enantiomer in solution to cooling (% w/w) li m iti ng c on ce nt ra tio n (g /d m3 ) total concentration s concentration r concentration fig. 11: concentration limiting curve of 99.9% (w/w) (s) crystals, calculated. using the above so called limiting curve data belonging to the 99.9% (w/w) (s) crystal product this hybrid process (evaporation of raffinate streams, crystallization, crystallization mother liquid recirculation) were recalculated three times. data can be seen on table 9 and fig. 12. by these data the optimum of hybrid system was at 2.32 cm3/min fresh feed, 0.18 cm3/min recirculated feed and 95.6% (w/w) (s) raffinate purity. at optimum value productivity was 177.83 mg (s)/g packing/day, fresh eluent consumption (calculated for the total smb+crystallization system) was 3.44 cm3 fresh eluent/mg (s). 13 table 9: the data of hybrid system at optimized evaporation, quasi-stationary state raffinate purity fresh eluent consumption productivity rec. fresh cf s cf r s % (w/w) (cm3 eluent/mg s ) (mg s /g packing/day) sim. iii.08. c iii.08. sim._iii.09. c iii.09. szim. iii.10. c iii.10. szim.iii.11. c iii.11. szim. iii.12. c iii.12. 99.52 4.18 134.370.05 1.75 2.54 2.46 95.60 3.44 177.83 0.11 2.24 2.55 2.45 97.43 3.64 167.97 0.18 2.32 2.56 2.44 83.81 3.68 166.2 0.44 2.30 2.64 2.36 90.73 3.47 176.01 simulation, crystallization code feed (cm3/min) concentration (g/dm3) 1.03 2.17 2.77 2.23 0 50 100 150 200 80 82 84 86 88 90 92 94 96 98 100 s% (w/w) 0 5 10 15 20 productivity at c=5g/dm3 (mg s/packing/day) productivity at optimized c (mg s/packing/day) fig. 12: the calculated data of hybrid system at optimized evaporation presented on figure. smb-lc measurements table 10 shows planned volumetric velocities. specific values of smb-lc processes were calculated after data of 4th full cycle. difference between the measured and simulated values was caused by the relatively short measuring time (80 min), so the smb-lc quasistationary condition could not be reached. the calculated and measured working points are shown on fig. 13. evaporation crystallization joined to smb-lc (smb 01 measurement) resulted from 96.68% (w/w) (s) raffinate the 99.33% (w/w) (s) crystal. in case of the smb 02 and smb 03 measurements the 99% (w/w) (s) purity could not be reached. table 10: results of smb measurements identifier eluent sample switching time (min) d e f r lr out (s ) (r ) (s ) (r ) (s ) (r ) purity % (w/w) 96.68 85.7 87.22 84.7 77.43 96 yield (%) 98.2 99.9 97.4 74 98.7 28 49.3 213.7 61.1(mg product/g packing/day) productivity 32.7 30.7 74.7 12.38 2.9 10.2 (cm3 eluent/mg product) eluent consumption 18.9 20.1 8.18 10.5 11.5 12.9 enantiomer 0.5 1.5 2.9 6 6 6 n-hexane:ipa = 95:5% (v/v) 5 g racemic/cm3 n-hexane:ipa = 95:5% (v/v) 5 (cm3/min) 20 20 20 4 4 4 smb 01-03 measurements smb 01 smb 02 smb 03 5 10 15 5 10 15 mii m ii i non-linear morbidelli triangle smb01 sim. smb01 meas. smb02 sim. smb02 meas. smb03 sim. smb03 meas. fig. 13: the calculated and measured working points in morbidelli triangle. measurement results can be seen on fig. 14 showing the earlier measurement results done at richter gedeon ltd. and pannon university, together with the limiting curve belonging to the 99.9% (w/w) (s) crystal value. table 11: results of evaporation and crystallization measurements (s ) (r ) (s ) (r ) (s ) (r ) (s ) (r ) (s ) (r ) (s ) (r ) raffinate 96.68 3.32 5.08 0.17 87.22 12.78 5.72 0.84 77.43 22.57 4.21 1.23 e+lrout 28.81 71.19 1.57 3.88 34.12 65.88 1.69 3.25 raffinate 86.25 13.75 0.99 0.16 66.35 33.65 0.95 0.48 67.98 22.84 1.28 0.38 e+lrout 37.83 62.17 0.48 0.79 raffinate 99.33 0.67 92.44 7.55 83.29 22.31 2.65 0.76 e+lrout 27.49 72.51 crystals purity % (w/w) c (g/dm3) evaporated liquid crystallization mother liquor purity % (w/w) c (g/dm3) purity % (w/w) c (g/dm3) evaporation and crystallization smb 01 smb 02 smb 03 14 0 10 20 30 40 50 60 70 80 90 100 0 5 10 15 20 25 r enantiomer in solution before cooling (% w/w) ef fic ie nc y of c ry sta lli za tio n (% ) smb 01 (>99% (w/w) purity product) smb 02 (92% (w/w) purity product) smb 03 (83% (w/w) purity product) experiment of pannon university >99% w/w product experiment of gedeon richter ltd. >99% w/w product efficiency of cristallyzatoin at optimized limiting concentration efficiency of crystallization at 5g/dm3 fig. 14: measurement results and the earlier measurement results done at richter gedeon ltd. and pannon university, together with the optimized limiting curve belonging to the 99.9% (w/w) (s) crystal value. summary in this work separation of pharmaceutical enantiomers coupling with crystallization using smb-lc joined crystallization hybrid system were studied. the aim of this work was the production of valuable (s)-enantiomer of racemic ester mixture from raffinate with higher than 99% (w/w) (s) purity and higher than 99% (s) yield for getting maximal (s) productivity and minimal fresh solvent consumption. the main parts of hybrid system and processes are: enrichment of (s) in smb-lc raffinate stream, evaporation of raffinate, cooling, separation of (s) crystals and crystallization mother liquid, recirculation of crystallization mother liquid to the feed after (s)+(r) and eluent concentration adjustment. evaporated eluent was recirculated from raffinate and extract streams to the smb-lc equipment inlet. after total evaporation of extract stream (r) component was produced could be transformed to (s)-enantiomer by chemical or other processes outside the smb-lc crystallization hybrid system. by previous laboratory scale measurements fundamental data of smb-lc and joined crystallization necessary for computer simulation were determined. we concluded, that in smb-lc crystallization hybrid system productivity could significantly be increased from 115.32-177.83 mg (s)/g packing/day compared to the separation method using only smb-lc equipment at higher than 99% (w/w) (s) purity and higher than 99% (s) yield. the above hybrid system applicability was proven by laboratory and industrial scale smb-lc, crystallization experiments. acknowledgements the research was financed by the chemical engineering institute cooperative research center of the pannon university, upon the request of richter gedeon ltd. the authors express their thanks to these institutions. references 1. lorenz h., sheehan p., seidel-morgentern a., j. chromatogr. a, 908 (2001) 201-214 2. lorenz h., perlberg a., sapoundjiev d., elsner m. p., seidel-morgenstern a., chemical engineering and processing 45 (2006) 863–873 3. kaspereit m., gedicke k., zahn v., mahoney a. w., j.chromatogr. a 1092( 2005) 43-54 4. strube j., gartner r., schulte m., chem. eng. j. 85(2002), 273-288 5. huthmann e., juza m., j. chromatogr. a, 908 (2001) 185–200 6. szánya t., hanák l.: simulated moving bed liquid chromatography (smb-lc), post-graduate engineer course book, university of veszprém (2001) 7. migliorini c., mazzotti m., morbidelli m., j. chromatogr. a, 827 (1998) 161 m. 8. g. guiochon, j. chromatogr. a. 965 (2002) 129-161. 9. heuer c., küstens e., plattner t., seidelmorgenstern a., j. chromatogr. a 827 (1998) 175. 10. szanya t., argyelan j., kovats s., hanak l., j. chromatogr. a, 908 (2001) 265–272 11. felinger a., cavazzini a., guiochon g., j. chromatogr. a 986 (2003) 207–225 12. herseczki zs., diploma piece: separation of optical isomers with preparative liquid chromatograph (2006) << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb 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(adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice hungarian journal of industrial chemistry veszprém vol. 33(1-2). pp. 75-80. (2005) spline functions in evaluation of explosion limit curves for gas mixtures m. molnárné-jobbágy, k. kollár-hunek1 federal institute for materials research and testing, bam, d-12200 berlin, germany 1dept. of chemical information technology, bp. univ. of technology and economics, h-1521 budapest, pf.91. hungary the paper discusses a new method to approximate the sometimes missing apex point of the explosion limit curves of flammable substances with diluents in air. the base of the new method is to vary the frame points of the co-monotonic splines using de casteljau algorithm. we show several examples for flammable/inert/oxidising gas containing systems – selected by the program triangle – where the method was applied. due to the definition of the frame of splines it can be stated that the new method never restricts the explosion range around the apex and shifts the explosion limit curve into the direction of higher inert gas concentrations. this means that the new method can correct the highly “cut down nose” of the co-monotonic splines and gives a safer explosion range of these systems. keywords: ternary flammable systems, inerting, explosion areas, co-monotonic spline curves introduction inerting of explosive fuel-air mixtures is a frequently applied method in the chemical and related industries to prevent fires and explosions. for this purpose the exact knowledge of the explosion range is required as a function of the flammable, oxidizer and inert gas concentrations. the chemsafe® database [1], which is world wide available through stn international and internet, contains rated safety characteristics of flammable liquids, gases, dusts and their mixtures, such as explosion limits, flash points, ignition temperatures, etc. the in-house version of chemsafe® allows a graphical representation of the measured explosion range of ternary systems in triangular diagrams as a function of the concentration of flammable (combustible), oxidising or inert gases. the triangle program [6,7,9,10], created by bam and extended by the common research group of bme and bam, is used for processing measured values of ternary systems, it provides 2d triangular diagrams for the data processing phase of the explosion area of the gas mixtures. in our latest research we created a new test method to investigate whether the (last) measured connection point between the upper and lower explosion limit curves – the so called apex point – is the real apex point, or it is not the last point of the limiting curves. description of the explosion range of ternary systems beside the explosion limits and the explosion range other characteristics can be also deduced from triangular or cartesian explosion diagrams, which parameters explicitly define the dangerous area as they are shown on fig 1. the iar (minimum inert gas / air (oxidising gas) ratio) and icr (minimum inert gas / combustible ratio) lines represent limits in the ternary flammable system: the points lying on the right hand side of iar line or below the icr line will not cause an explosion regardless of the added amount of flammable gas. mai (minimum required amount of inert gas) and mxc (maximum permissible amount of combustible) points are intercepts of iar/icr lines and the corresponding binary triangle sides. the moc (maximum oxidising gas content) is given by the 76 tangent line of the explosion limit curve parallel with the flammable-inert side of the triangle. in some cases this line passes through the apex point . fig. 1: characteristics of the explosion area the lel (lower explosion limit) and uel (upper explosion limit) curves are generated around the explosion area by applying numerical interpolation on the measured data. having evaluated the characteristic values of the system the triangle program returns the results in tables and in ternary diagrams both in cartesian and in triangle co-ordinates. most of the above mentioned characteristics are deduced from the common point of the lel and uel curves, from the so called apex point, and for the icr line and the mxc point we use a tangent line of the lel curve. these calculations require the best possible numerical approximation of the explosion limit curves and of their apex point. application of co-monotonic vector splines co-monotonic parametric vector splines possess the best numerical properties for the approximation of ternary explosion limit curves [2,3,4,5,8]. the earlier used akima splines failed to describe several systems, where the lel or the uel curve was not monotonic or the concatenation of the two explosion curves couldn’t be considered as an only function of the flammable gas concentration. as a result of our previous research [6,9], we created subroutines for the co-monotonic parametric vector splines and built them in the triangle program. testing this extension of the software we have found several ternary data sets, which didn’t contain enough measurements around the most critical apex of their explosion curves. to select these data sets, we made the program to give an alert in these cases, and to offer the user the possibilities of sketching an “open apex” curve, typing in an apex from another source, or trying to make up the apex based on the last two points of the lel and of the uel curves. the make up of the apex, based on the last two points of the lel and of the uel curves gives also a possibility to investigate other “full” data sets whether the “common” point of the lel and uel can be considered as a real apex point, or it rather belongs only to the lel or only to the uel curve. the theoretical background of the apex-make-up is the de casteljau algorithm. this algorithm offers a numerically very simple way to evaluate an ndimensional point of a parametric (cubic) co-monotonic spline curve. the algorithm and the resulted point are shown on fig.2. t=1/3 p2 p3 p1 1 p2 1 p1 2 p0 3 p0 p1p0 1 p0 2 32 1 2 21 1 1 10 1 0 )1()( )1()( )1()( ptpttp ptpttp ptpttp ⋅+⋅−= ⋅+⋅−= ⋅+⋅−= 1 2 1 1 2 1 1 1 1 0 2 0 )1()( )1()( ptpttp ptpttp ⋅+⋅−= ⋅+⋅−= ⎣ ⎦1;0 )1()( 2 1 2 0 3 0 ∈ ⋅+⋅−= t ptpttp fig. 2.: the four frame points of a co-monotonic spline and evaluating p0 3 at t=1/3 to determine the p0, p1, p2 and p3 frame points of the co-monotonic spline we have used the last two points of the uel curve, and the last two points of the lel curve. if the measured data set contained an (assumed) apex point, in the first step of our algorithm we truncated the data set by this assumed apex. we evaluated a co-monotonic spline based on the remained last four points. in tables 1 and 2 we show the steps of the frame point calculations for the systems nh3+n2+air and ch4+co2+air, in this second case we give a description of the steps in every detail. one can see the frame points (black squares), and the result of the apex test for the nh3+n2+air system on fig 3, and for the ch4+co2+air system on fig. 4. nh3+n2+air t=24c p=1,03 bar for the secant-intercept: n2 nh3 14 15,8 lel 16 16,15 16 16,9 uel 14 18,05 de casteljau frame t*= 0,66 xo yo slope x y secant1 16 16,15 0,175 p0 16 16,2 secant2 16 16,9 -0,58 p116,7 16,3 intercept 17 16,325 p216,7 16,5 delta(x)1,00 p3 16 16,9 1,00 ratio(2/1)1,00 slope ratio3,3 table 1: frame point calculation (symmetric case) 77 nh3 + n2 + air 15,5 16,5 17,5 18,5 14 15 16 17 nh3 mpoint fig. 3: apex test (result: the real apex was measured) in the case of nh3+n2+air system the skipped apex lies on the approximating spline as a real apex – this means that the measured apex is a real one. the apex test suggests for the ch4+co2+air system that the assumed apex is not a real one. the measured point lies on the uel curve, and a new apex point is offered showing 1% relative difference in the inert gas concentration. in this case the steps of the frame point calculations show asymmetry because the inert gas differences of the last two points on the lel and uel curves are not equal. the slope ratio is also in this system not too big, what means that the asymmetry is only in the different distances of the measured points. ch4+co2+air t=24c p=1 bar for the secant-intercept: co2 ch4 25 5,7 lel 28,5 6 27,8 7 uel 25 7,9 de casteljau frame t*= 0,75 xo yo slope x y secant1 28,5 6 0,086 p0 28,5 6 secant2 27,8 7 -0,32 p1 29,5 6,1 intercept 30,40 6,16 p2 29,8 6,4 delta(x)1,90 p3 27,8 7 2,60 ratio(2/1)1,37 slope ratio3,75 table 2: frame point calculation (asymmetric case) to see clearly the meaning of the results now we show step by step the frame point algorithm and the apex calculation of the asymmetric case. the bold points of table 2 on lel / uel (28,5 ; 6) and (27,8 ; 7) are chosen for the frame points p0 and p3. using the other two points – (25 ; 5,7) on lel and (25 ; 7,9) on uel – we determined the equation of the lines passing through the given points of lel/uel. the intercept (pm) and the slopes (s1 and s2) of the two lines and the ratio of the two slopes contain the shaded cells of table 2. the next step is to calculate the t* parameter that determines the p2 frame point on the line segment of p3 and pm: if abs(s2/s1)<5 then t*=abs(s2/s1)/5 else t*=0,99 with this t* : p2 = p3 + t*⋅(pm-p3) (1/a) now we calculate the ratio of the horizontal distances between the secant line intercept and p0 / p3 lel / uel points: ratio(2/1)=2,6/1,9=1,37=a21 with this a21 : p1 = p0 + t*⋅(pm-p0)/a21 (1/b) having determined the missing two frame points, any arbitrary point of the interpolating co-monotonic spline can be calculated by the de casteljau algorithm. ch4 + co2 + air 5 6 7 8 25 26 27 28 29 30 ch4 mpoint fig. 4: apex test (result: not the real apex was measured) the apex calculation is very simple: we have to determine the maximal abscissa of the co-monotonic spline. the key of this apex calculation lies in the parameter t* that determines by the missing two frame points the apex, too. the original formula for t* is the following: if abs(s2/s1)<c then t*=abs(s2/s1)/c else t*=1-k (2) the values of parameters c and k can be determined by minimising the function given in eq. 3 ( )( )∑ = −= sysnum j meas k,csplineapexcetandis)k,c(f 1 (3) naturally, we have the better c and k parameters the more complete system we involve into the minimisation. in eq. 1/a we used c and k determined by the systems shown in table 3 (group 1/a). the above investigated nh3+n2+air and ch4+co2+air systems consist of enough measured points at the apex area, because the interpolating spline based on the truncated system passes through the skipped “apex”. the next two systems shown on figs 5 and 6 don’t have this property. the ethene + co2 + air system was measured at t=20 c temperature and p=100 bar pressure. the truncated data set doesn’t contain enough information to evaluate the frame points for an interpolating function passing through the skipped apex. 78 ethen + co2 + air 0 10 20 30 40 50 20 25 30 35 40 45 50 55 ethen mpoint fig. 5: apex test (after truncation the skipped apex is in the explosion area) quite the same thing occurs in the case of propane + c2h2f4 + air system, measured at t=20 c and p=1 bar. the only difference is between the two last systems, that in the first system the acceptance of the new apex is uneconomic, while in the second one it is dangerous. c3h8 + c2h2f4 + air 1 2 3 4 14 15 16 17 18 c3h8 mpoint fig. 6: apex test (after truncation the skipped apex is out of the explosion area) in both last cases we have got the information that the truncation is not allowed. so we have to repeat the procedure, but now without truncation. application of the new apex test for different systems the two-step apex test we have applied for 45 different ternary systems selected by the triangle program. first we investigated 23 systems where in the most cases we considered the systems as at the apex area fully measured ones. we summarize the test results in tables 3, 4, 5 and 6. the group 1/a contains 8 systems where after truncation the spline passes through the original apex point. however, the apex test results only for the first system that the measured apex was a real one. for the other 7 system a safer apex (bigger inert and smaller flammable gas concentration) is offered. system t[c] p[bar] 1 nh3+n2+air 24 1,03 2 ch4+co2+air 24 1 3 c2h6+co2+air 24 1 4 co+(co2+h2o)+air 110 1 5 co+(n2+h2o)+air 400 1 6 ch4+ar+air 340 1 7 (99%co+1%h2)+n2+air 20 1 8 isobutene+n2+air 200 1 table 3: systems of 1/a group measured apex apex calculations inert (%) flamm (%) trunc. in(%) new fl(%) new rel diff% 1 16,5 16,4 pass old 2 29 6,5 pass 29,3 6,3 1,0 3 39,7 4 pass 41,1 3,6 3,5 4 53,88 17,05 pass 53,92 16,34 0,07 5 83,62 5,27 pass 84,9 5,94 1,5 6 70,86 2,15 pass 73,1 2,32 3,2 7 64 11,5 pass 66 12,4 3,1 8 55 1,6 pass 57,3 1,7 4,2 table 4: apex results of 1/a group the group 1/b consists of 15 systems where after truncation the spline doesn’t pass through the original apex point. after the first step of the apex step in the group 1/b the second step (without truncation) is carried out, too. the result of the second step is that for 10 systems the data set contains the real apex, and only in the remained 5 cases is a safer apex offered. system t[c] p[bar] 1 acetone+n2+o2 20 1 2 c3h8+c2h2f4+air 20 1 3 c3h8+n2+air 20 1 4 ethene+n2+air 20 1 5 ethene+n2+air 20 100 6 ethene+co2+air 20 1 7 ethene+co2+air 20 100 8 ethene+n2+air 100 100 9 po+co2+air 20 1 10 co+(co2+h2o)+air 70 1 11 co+(co2+h2o)+air 200 1 12 co+(ar+h2o)+air 100 1 13 2me-1propene+co2+air 20 1 14 isobuten+h2o+air 100 1 15 2me-1propene+h2o+air 200 1 table 5: systems of 1/b group 79 measured apex apex calculations inert (%) flamm (%) trunc. in(%) new fl(%) new rel diff% 1 82,92 3,11 in old 2 17,1 2,6 out old 3 53 2,4 in old 4 55,5 3,4 out old 5 58 10 in old 6 41,5 4,7 out old 7 47,5 10 in old 8 62 12,3 in old 9 47,2 3,7 in old 10 52,78 17,04 out old 11 59,23 16,61 out 59,56 15,52 0,6 12 75,5 10,14 in 77,2 8 2,3 13 32,9 2,5 out 33,6 2,6 2,1 14 32,3 2 in 33,2 2,4 2,8 15 36,2 1,9 in 37,4 2,3 3,3 table 6: apex results of 1/b group system t[c] p[bar] 1 ethane+n2+air 20 1 2 2me-propane+h2o+air 100 1 table 7: systems of 2/a group measured apex apex calculations inert (%) flamm (%) trunc. in(%) new fl(%) new rel diff% 1 53,9 2,9 pass 54,5 2,7 1,0 2 35,6 2,0 pass 36,4 2,2 2,2 table 8: apex results of 2/a group system t[c] p[bar] 1 1-butene+n2+air 24 1 2 methane+h2o+air 100 1 3 methane+co2+air 300 1 4 methane+co2+air 340 1 5 methane+co2+air 400 1 6 methane+h2o+o2 200 1 7 ethane+co2+air 20 1 8 propane+co2+air 20 1 9 propane+co2+air 100 1 10 propane+co2+air 250 1 11 propane+co2+air 400 1 12 propane+h2o+air 200 1 13 isobutane+n2+air 20 1 14 isobutane+n2+air 100 1 15 2me-propane+co2+air 100 1 16 isobutane+h2o+air 250 1 17 propene+n2+air 100 1 18 propene+n2+air 250 1 19 propene+co2+air 20 1 20 propene+co2+air 100 1 table 7: systems of 2/b group measured apex apex calculations inert (%) flamm (%) trunc. in(%) new fl(%) new rel diff% 1 51,0 1,8 pass(brd) 51,3 2,0 0,6 2 34,2 6,5 out 34,8 6,2 1,8 3 38,5 5,6 in old 4 40,5 5,3 in 40,6 5,4 0,2 5 43,7 4,9 out old 6 76,3 9,0 out old 7 38,1 3,4 pass(brd) 40,4 3,6 6,0 8 37,1 2,8 in 37,7 3,0 1,7 9 34,0 2,4 pass(brd) 40,9 2,9 20,2 10 42,1 2,1 out 47,1 2,3 11,8 11 54,0 1,7 out 56,0 1,9 3,7 12 42,0 2,8 out 42,5 2,6 1,3 13 47,9 2,6 out 50,4 2,2 5,3 14 53,0 1,8 in 53,8 2,1 1,6 15 36,1 3,2 out 36,9 2,8 2,1 16 39,0 1,6 in 39,7 1,8 1,7 17 55,1 1,9 out 60,5 2,0 9,9 18 50,0 4,0 out 61,8 1,9 23,6 19 35,0 2,8 out 39,1 3,0 11,6 20 40,1 2,8 in 42,1 3,1 4,9 table 10: apex results of 2/b group the second group of systems investigated consists of 22 ternary systems selected by the triangle program. among these systems there were several ones on higher temperature measured systems and some ones where the triangle gave the “open apex” alert. as we see in tables 9 and 10, for 20 systems the two-step apex test was necessary. in the case of three systems (group 2/b, systems 1, 7 and 9) even the approximating spline evaluated from the truncated system passed through the skipped measured “apex”, the measured apex was not a real one, and the apex-make-up offered such a different new apex (relative difference in inert gas concentration was bigger than 5%), that its acceptance would be too expensive. also in these cases we continued the apex test by its second step. it gave a quite good result for the first system, but for the seventh and ninth the big difference remained. in these cases, as well as for the 10, 13, 17, 18, 19 systems additional measurements are suggested. on the fig. 7 we show the 1-propene + n2 + air system (18), measured at t=250 c, p=1 bar. considering, that in the measured data set the smallest flammable concentration on the lel curve is 0,9 mol%, and the biggest on the uel curve is 13,6 mol%, none of the last two measured points on the lel or uel (1,3 mol% and 4 mol%) can be assumed as a real apex point. 80 1-propen+n2+air 1 2 3 4 5 6 40 45 50 55 60 65 1-propen mpoint fig. 7: 2/b group, 18. system: open apex in the measured data conclusions for correct description of explosion areas for ternary gas mixtures containing flammable gas, we created a new test method to investigate whether the (last) measured connection point between the upper and lower explosion limit curves – the so called apex point – can be accepted as the real apex point, or it is safer to reject this hypothesis and try to measure more point around the apex. we tested by the new method several flammable/inert/oxidising gas containing systems – selected by the program triangle. as result we can state, that using all the information hidden in the measured data, by the new method we can either correct the highly “cut down nose” of the co-monotonic splines or recognize that more measured data are necessary. the application of our new method gives a safer explosion range for the investigated systems. the here presented algorithm also shows promising results for using as a tool for planning experiments. according to the new ec standard pren 14756, “determination of the limiting oxygen concentration (loc) for gases and vapours", which is now under approval, offers two experimental methods for determination of loc, the so called "short procedure" for substances with small explosion range and the "extended procedure" for substances with a large explosion range. in this last case a spline approximation is needed for the determination of the apex of the explosion curve and the loc value from the upper explosion limits. the akima spline overestimates many times the apex area, which is very uneconomic. also in these cases an application of the new method would be very desirable. acknowledgements the authors wish to express their gratitude to dr. norbert herrmann (univ. of hannover) and to dr. gergely viczián (bme). the work has been supported by the bam (berlin) and by the varga józsef foundation of the chemical engineering faculty, bme. list of symbols a21 inert concentration differences’ ratio brd big relative difference in meas./calc. apex c and k parameters for apex calculation iar minimum inert gas / air (oxidising gas) ratio icr minimum inert gas / combustible ratio lel lower explosion limit mai minimum required amount of inert gas moc maximum oxidising gas content mxc maximum permissible amount of combustible gas p pressure, bar p0,p1,p2,p3 spline frame points pm secant lines’ intercept s1, s2 slopes t temperature, k or c t* frame points’ parameter uel upper explosion limit (x,y) cartesian co-ordinates references 1. chemsafe®-database for safety characteristics, bam, berlin, ptb, braunschweig, dechema, frankfurt am main, v1.4, 2001 2. fasshauer, g.e., schumaker, l.l.: computer aided geometric design, 1996, (13), 45 3. gronewold, g.: hung journal of ind. chem. 1996, (25), 59 4. herrmann, n.: hung journal of ind. chem. 1996, (25) 263 5. kollár-hunek, k., láng-lázi, m., herrmann, n., miklós, d., kovács, i.: hung journal of ind. chem. 1998, (26), 269 6. molnárné m., bulin m., viczián g., kollárhunek k.: technische überwachung (tü), springer-vdi verlag, 2003, (44, nr.1/2) 32 7. molnárné m., schendler th., schröder v.: sicherheitstechnische kenngrößen, band 2: explosionsbereiche von gasgemischen, isbn 389701-746-6, wirtschaftsverlag nw verlag für neue wissenschaft gmbh, berlin, 2003 8. shikin, e.v., plis, a.i.: handbook on splines for the user; crc press, boca raton, fl, usa, 1995 9. viczián g., molnárné-jobbágy m., heszberger j., kollár-hunek k.: hung. journal of ind. chem., 2001, (29), 143 10. http://www.bam.de/english/expertise/areas_of_exper tise/department_2/division_22/div_22_wg6c_i.htm microsoft word 2012_dr_bodor_endre_hjic.doc hungarian journal of industrial chemistry veszprém vol. 39(3) pp. 427-431 (2011) effects and changes of zearalenone and fumonisin contamination in corn-based bioethanol process zs. prettl , a. lepossa, é. tóth, i. kelemen-horváth, á. sz. németh, e. nagy university of pannonia, faculty of information technology, institute of chemical and process engineering h-8201 veszprém, egyetem u. 10, hungary e-mail: prettl@mukki.richem.hu bioethanol production is a growing industry nowadays. in this work dry-grind ethanol production was carried out from different corn samples (uncontaminated; zearalenone; fumonisin b1+b2 contaminated) and the changes of the ratio of the solid-liquid phase as well as toxin concentrations were examined in laboratory scale. the ethanol yields of mycotoxincontaminated corn-mashes were 27% lower, due to 10% less produced glucose-concentrations from these raw materials, compared to uncontaminated ones. by the end of the whole process, the initial 20% solid content was reduced below 7% both in contaminated and uncontaminated corn-mashes. differences were observed in the concentration changes of examined toxins. zearalenone was localized in the solid phase, and its concentrations did not alter during the ethanol production process. fumonisin concentration increased 3 times at the end of the process, and it dissolved in the liquid phase in significant amount. keywords: mycotoxins, bioethanol, zearalenone, fumonisin introduction there is a growing significance of corn usage for industrial purpose along the human and animal nutrition since this can be produced relatively cheaply. for this reason the mainly used source for bioethanol production is corn. the mouldy attach of cereals is not only a yield influencing factor. the mycotoxin producing deuteromycota (mainly aspergillus, fusarium, penicillium and alternaria species) found both on fields and during crop-storage can cause serious food safety and health risk to vertebrates. the effects of the most important fungi metabolites – aflatoxins, fusarium toxins (trichotechenes, zearalenone, fumonisin), ocharoxin a – on the living organisms are well studied and this is a continuously developing field of science, as well as their analyzing techniques and decreasing possibilities of their occurrence [1-6]. several fusarium fungi, which are common soil fungi, produce different mycotoxins of the class of trichothecenes (t-2 toxin, ht-2 toxin, deoxynivalenol (don) and nivalenol and some other toxins (zearalenone and fumonisins). the fusarium fungi are probably the most prevalent toxin-producing fungi of the northern temperate regions and are commonly found on cereals grown in the temperate regions of america, europe and asia. fusarium toxins have been shown to cause a variety of toxic effects in both experimental animals and livestock. on some occasions these mycotoxins also been suspected to cause toxicity in humans [7]. zearalenone (zea) – also known as f-2 toxin –, a lactone of the derivative of the resorcylic acid (fig. 1) has estrogenic effect [8]. it is found worldwide in a number of cereal crops such as maize, barley, oats, wheat, rice and sorghum, and also in bread. zea is a stable compound, both during storage/milling and the processing/cooking of food, and it does not degrade at high temperatures. wet milling of corn concentrates zea in the gluten fraction (2-7 fold concentration) [9] figure 1: structure of zearalenone (www.fermentek.co.il) fumonisin b1 (fb1) (fig. 2) – discovered in 1988 – belongs to fumonisins, which have been reported to cause various diseases in animals, such as liver and kidney cancer in rodents, leukoencephalomalacia in equines, pulmonary oedema in pigs. fumonisin b2 (fig. 3) is more cytotoxic than fumonisin b1, both are carcinogenic mycotoxins. they are produced by fusarium verticilloides that commonly contaminate maize. fb1 has been found as natural contaminant in maize and maizebased food worldwide. 428 figure 2: molecular structure of fb1 (www.fermentek.co.il) figure 3: molecular structure of fb2 (www.fermentek.co.il) fb1 is stable during most types of processing. dry milling of maize results in the distribution of fb1 into the bran, germ and flour. fb1 is stable in polenta (maize porridge). however, the concentration of fb1 is reduced during the manufacture of cornstarch by wet milling, since fb1 is soluble in water [10]. the simultaneous occurrence of two or more toxins in cereals has also been frequently documented in the literature, e.g. maize contaminated with fb1, zea, don and t-2 toxin [11]. there are different limit values recommended of several legislations in food safety. table 1 indicates the eu health regulation of the mycotoxins studied in this work. zearalenone has a stronger impact on vertebrates so its regulation limit is lower than fumonisin's. table 1: recommended limit values of mycotoxins upper limit (μg/kg crop) zea fumonisin b1 and b2 grains for human consumption 350 [12] eu: 1,000 (b1+b2) [12]; us: 2-4,000 (b1+b2+b3) [13] ground grains (>500 μm) for not direct human consumption (19041010 kn-code) 200 [12] 1,400 (b1+b2) [12] feed 3,000* [5] 20,000 (swine, b1+b2+b3) [14]; 60,000* (b1+b2) [5] * reference value wet-milling and dry-grinding are the two major technologies used to convert corn grain into ethanol [15]. the wet-milling process is designed for the best utilization of the corn grain while dry-grinding process is designed to be cost effective. in wet-milling process corn is fractionated into its individual components of starch, protein, fibre, germ and soluble, so there are more products beyond the ethanol (e.g. corn syrup, dextrose, glucose). however, in conventional dry-grinding process there is no fractionation; the whole corn kernel is ground, mixed with water and convert to alcohol. distillers grains with solubles (dgs) are the main byproduct feeds produced, which have a good nutritional value. its starch content less than 5% of dry matter, these can be marketed in the original wet form (~33% dry matter, wdgs), dried partially and called modified (~48% dry matter, mdgs), or dried (~90% dry matter, ddgs). nutrient composition of dgs, consequently its quality can be highly variable. it consists of mainly protein and fibre (lignocellulose, hemicellulose, pectin): approximately 31% cp (crude protein) (70% undegradable intake protein), 11.9% ether extract, 33% ndf (nondegradable fibre), 4.5% ash, 0.84% p, and 0.77% s [16]. the current study was undertaken to examine the changes of the mycotoxin content in both the solid and liquid phase of the naturally contaminated substrate during the dry-grinding bioethanol process. we also compared the maximum ethanol yield achieved to the end of the fermentation from naturally contaminated and control corns. materials and methods preparation and fermentation of corn for the experiments uncontaminated and naturally mycotoxin contaminated corns (1,170 μg/kg zearalenone and 760 μg/kg fumonisin b1+b2) were processed. corn grains were ground in two steps: at first step it was ground in a hammer mill with a 2 mm screen size, and then in a coffee grinder under the particle size of 1 mm of the ground flour. the starch-hydrolysis was carried out from 2,000 g ground corn slurry (20% solids content) in a completelystirred glass reactor. for the starch liquefaction α-amylase (liquozyme scdc, novozyme) was used in the amount of 0.88 mg/g dry corn source. the saccharification was performed with gluco-amylase (spirizyme fuel, novozyme) in the amount of 1.1 mg/g dry corn source. for the ph adjustment 20% naoh and 25% h2so4 were used. the fermentation process was achieved in biostat aplus fermentor with 2 dm3 useful volume, with ethanol red® (fermentis, product-code: 42138) dry alcohol yeast in 7 g/kg dry corn source during 62 hours on 34 °c. after fermentation, ethanol was distilled from the stillage by a laboratory distillation apparatus equipped with a 20 cm long separating column. samples were taken for analyze glucose, toxin and ethanol concentrations. the known weight samples were centrifuged (12,000 rpm, 4 °c, 1 h) and the ratio of their liquid and solid phase was measured. the whole process as well as sampling points (s.i.-s.v.) according to table 2 are shown in fig. 4. 429 table 2: analyzed parameters at different sampling points analyzed parameters s. i. s. ii. s. iii. s. iv. s. v. glucose + toxins + + + + + ethanol + + + not analyzed; + analyzed figure 4: flowchart of the bioethanol process analyses glucose concentrations were determined by highperformance liquid chromatography (hplc). samples for hplc analyses were prepared by filtration through a 0.2 μm pore size cellulose acetate filter (sartorius stedim biotech gmbh, germany). for the analysis yl 9100 type of liquid chromatograph (young lin, rep. korea), aminex-87p column and pre-column hyperrez xp pb were used at 35 °c with bidistilled water as mobile phase at 0.3 ml/min flow rate. a refractive index detector was applied for detection of monosaccharides. ethanol concentrations of the produced mash and alcohol distillate, as well as the remained alcohol content of the wdgs were determined by gas chromatography (gc). samples for gc analyses were prepared by filtration through a 0.2 μm pore size cellulose acetate filter (sartorius stedim biotech gmbh, germany). for the analysis yl acme 6000 type of gas chromatograph (young lin, rep. korea) equipped with flame ionization detector and autosampler was used. db-ffap (agilent j&w) gc column was used at 200 °c (injector) and 250 °c (detector) with n2 carrier (6 ml/min, 20:1 split ratio). during the run an oven temperature program was applied [60 °c (3 min) → 10 °c/min → 200 °c (10 min)]. msz en 12955:2000 sample preparative method, aoac 985.18.:1988 (zea) and msz en 13585:2002 (fb1+b2) analysis standards were used for measuring the mycotoxin contents. results and discussion fermentation glucose concentration after the starch-hydrolysis of mycotoxin contaminated corn stock was 10% lower than of uncontaminated ones. similar conversion efficiencies could be observed at the end of the fermentation process, though the specific ethanol yield was 27% lower in the case of contaminated corn stock (table 3). table 3: fermentation results corn initial glucose concentration (g·dm-3) ethanol conversion (%) specific ethanol yield (g etoh· g corn dry matter-1) 169 85 0.34 uncontaminated 171 82 0.32 zea+fb1+b2contaminated 151 84 0.25 the ratio of solid and liquid phase of both contaminated and uncontaminated corn suspensions changed similarly in each technological steps (fig. 5). dry matter content decreased from 20% to 5-7% during the bioethanol production process. figure 5: changes of the ratio of solid and liquid phase at the end of each technological steps 430 mycotoxin monitoring zearalenone was localized principally in the solid phase of corn mash due to hydrophobic characteristics of the toxin. its concentration did not alter (fig. 6), what shows thermal stability and low chemical reactivity of the molecule under applied circumstances. fumonisin concentration increased three times at the end of distillation (fig. 7). the “multiplication” can be explained by appearance of starch-bound fumonisins after saccharification and getting more concentrated suspension after distillation, since there was no any toxin in distillate. maize like other cereals is a complex matrix, where polysaccharides, proteins and lipids can form different bonds with fbs changing the structure and toxicity of the molecule. accurate knowledge of this masking mechanism is not available yet [17]. in contrast to zea, significant amount of fb getting out in the liquid phase can be due to the chemical structure of this toxin molecule: the four carbonyl groups, amino and hydroxyl groups located on carbon structure also facilitate good solubility in water. zearalenone and fumonisin concentrations of dried out solid phase increased 1,402 to 3,173 μg/kg and 911 to 3,434 μg/kg, respectively. figure 6: changes of zearalenone concentrations calculated to corn suspension figure 7: changes of fumonisin concentrations calculated to corn suspension acknowledgements this work was supported by national office research and technology (nkth tech_08a3/2-2008-0385). the authors are grateful to dr. sándor kovács and †dr. levente kotsis for their useful professional and technical assistance and would like to thank to wessling hungary ltd. for the mycotoxin analyses as well as to novozymes (denmark) for providing enzymes. references 1. scientific report submitted to efsa, cfp/efsa/ feedap/2009/01. pp. 1–192 2. j. r. wilkinson, h. k. abbas: aflatoxin, aspergillus, maize and the relevance to alternative fuels (or aflatoxin: what is it, can we get rid of it, and should the ethanol industry care?), toxin reviews, 27(3) (2008) 227–260 3. b. kabak, a. d. w. dobson, i. var: strategies to prevent mycotoxin contamination of animal feed: a review, critical reviews in food science and nutrition, 46 (2006) 593–619 4. j. w. bennett, m. klich: mycotoxins, clinical microbiology reviews, 16(3) (2003) 497–516 5. m. szeitzné szabó (szerk.): gabonaalapú élelmiszerek fuzárium toxin szennyezettségének csökkentési lehetőségei. magyar élelmiszer-biztonsági hivatal, (2009) pp. 1–33 6. n. w. turner, s. subrahmanyam, s. a. piletsky: analytical methods for determination of mycotoxins: a review, analytica chimica acta, 632 (2009) 168–180 7. european commission: opinion of the scientific committee on food on fusarium toxins part 2: zearalenone (zea), 22 june 2000. http://ec.europa.eu/food/fs/sc/scf/out65_en.pdf 8. j. fink-gremmels, h. malekinejad: clinical effects and biochemical mechanism associated with exposure to the mycoestrogen zearalenone, anim. feed. sci. tech., 137 (2007) 326–341 9. d. r. lauren, m. a. ringrose: determination of the fate of three fusarium mycotoxins through wetmilling of maize using an improved hplc analytical technique, food addit. contam., 14 (1997) 435–443 10. european commission: opinion of the scientific committee on food on fusarium toxins part 3: fumonisin b1 (fb1), 17 october 2000. http://ec.europa.eu/food/fs/sc/scf/out73_en.pdf 11. b. fazekas, m. kis, e. tóth-hajdu: data on the contamination of maize with fumonisin b1 and other fusariotoxins in hungary, acta veterinaria hungarica, 44 (1996) 25–37 431 12. commission regulation (ec) no 1126/2007, amending regulation (ec) no 1881/2006 setting maximum levels for certain contaminants in foodstuffs as regards fusarium toxins in maize and maize products, official journal of the european union, l 255 (2007) 14–17 13. cast, mycotoxins: risks in plant, animal, and human systems, task force report, no. 139., ames, iowa, (2003) pp. 1–191 14. fao: worldwide regulations for mycotoxins in food and feed in 2003, food and nutrition papers, 81 (2004) 1–180 15. a. a. vertés, n. qureshi, h. p. blaschek, h. yukawa, (eds): biomass to biofuels. strategies for global industries, wiley, chippenham, (2010) pp. 187–198 16. c. d. buckner: ethanol byproduct feeds: determining accurate fiber content, nutrient composition and variability, storing with lowquality forages, and fiber utilization in finishing diets, thesis and dissertation in animal science, univ. nebraska, lincoln, (2010) p. 131 17. m. mangia: free and hidden fumonisins in maize and 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word a_03_r.doc hungarian journal of industrial chemistry veszprém vol. 38(1). pp. 9-13 (2010) microalgae production in service of fuel production r. bocsi , g. horváth, l. hanák department of chemical engineering sciences, university of pannonia 8200 veszprém, egyetem u. 10, hungary e-mail: bocsirobert@almos.uni-pannon.hu driven by the rising need for biofuels because of the constant rise in the world market price of crude oil, and by the necessity to capture carbon dioxide, autotroph organisms got into the spotlight of energetic research. algae production is the most promising solution amongst the alternatives because of its specific area necessity and high reproduction rate. research on the whole range of algae cultivation and processing is done at the department of chemical engineering of the university of pannonia. the utilization of algacultures in experimental photobioreactors is examined, together with the optimization of the operational conditions both for artificial and natural light and with different fertilizers. the various parameters of alga-processing is also determined. based on literature data and experiments conducted in veszprém, in this paper we give an overview of the planning, operation and processing principles connected to algae reactors. keywords: algae, oilgae, algae photobioreactor introduction carbon-dioxide emission volume is one of the highest of air pollutants in the world. carbon capture and storage needs rise year by year. there are spoantaneous environmental procedures to feed co2. using these procedures we can feed back the carbon content of co2 into biological systems and we can get a number of valuable organic compounds, among others biofuel, to reach ecological and economical benefits. algae research is not as novel as it seems at first. algae growing began in about the first quarter of last century. scientist thought the food source of the future could be green algae farms. although the vision falls by insufficient sponsorship, but most of general rules of growing was discovered. algae based fuel technology first mentioned in the beginning of the 1950’s. some pilot plant to grow algae as energy source was built in 1970’s. algae oil production for fuel technology first mentioned in the 1980’s and lives its renessaince 21st century [1, 2]. autotrophic organisms as energy sources autotrophic organisms synthetizes complicated organic compunds which need them to build up their own cells. these organisms can be monocytae (microalgae) or other differentiated autotrophics (e.g. corn, soy beans). the needs of these photosynthetizing creatures can generally be categorized in five groups. in the first group there are the environmental parameters. light has a special function since it supplies the energetic background of the biochemical reactions in the light period the second gruoup is the concentration of co2 and its derivatives in aquenous solution. these contents supply the great majority of carbon content of the photosynthetics cell. we use co2 as a fetilizer to reach higher biomass productivity [3]. the third group is primary macronutrients (npk). nitrogen (n) is a major component of proteins, hormones, chlorophyll, vitamins and enzymes essential for plant life. phosphorus (p) is necessary for photosynthesis, protein formation and almost all aspects of growth and metabolism. potassium (k) is necessary for the formation of sugars, starches, carbohydrates, for protein synthesis and cell division in plants. the fourth group is primary macronutrients (ca, s, mg). sulfur (s) is a structural component of amino acids, proteins, vitamins and enzymes and is essential to produce chlorophyll. magnesium (mg) is a critical structural component of the chlorophyll molecule and is necessary for functioning of plant enzymes to produce carbohydrates, sugars and fats. calcium (ca) plays a role in the functioning of enzymes, is part of the structure of cell walls, helps control the water content of cells, and is necessary for cell growth and division. the fifth group is micronutrients or trace minerals. iron (fe) is necessary for enzyme functionality and is important for the synthesis of chlorophyll. manganese (mn) is involved in enzyme activity for photosynthesis, respiration, and nitrogen metabolism. boron (b) is used in cell wall formation, for membrane integrity within 10 cells, for calcium uptake and may aid in the transfer of nutritional sugars between plant parts. zinc (zn) is a component of enzymes or as an important aid in the functioning of them. copper (cu) takes part in nitrogen metabolism. molybdenum (mo) is a structural component of the enzyme that reduces nitrates to ammonia. without it, the synthesis of proteins is blocked. nickel (ni) is required for iron absorption. cobalt (co) is required for nitrogen fixation, so a deficiency could result in nitrogen deficiency symptoms. sodium (na) and chlorine (cl) are involved in the osmotic (water movement) and ionic balance in plants (much as is people). there is the annual oil productivity specification of autotrophic organisms in table 1. these organisms are potentially used for oil production. the microalgae oil productivity in prosperous circumstances is at least 8 times higher than others. table 1: oil productivity of autotrophic organisms organism oil, liters/hectare/year soya 440 sunflower 900 rapeseed 1 150 palmoil 5 400 microalgae 40 000–135 000 nowadays algae growing is in limelight due to its high productivity. additional benefits are that there is no need to use growing fields and some wastewater may be used with nutrient supplementation. algae species for oil production algae are a large goup of simple, typically autotrophic organisms. they are eucaryotic, autotrophic, unicellular or multicellular form. their size can change wide range (micrometers to meters). algae have nuclei enclosed in membrane and plastids bound in one or more membranes. there are chloroplastics in the cell, which contain bioactive compounds for photosynthesis. these compounds function is transferring the energy of light to biochemical reactions. hereinafter parameters are about freshwater algae, but some observations might be applicable to seawater species. algae species are applicable for energetic purposes wich produce lipids as more as it possible in their whole growing period. some of these species’ lypide content may be more than 40 percent of their own weight. these lypides mostly contents glycerine esthers of various c16-c20 fatty acides. these compounds are applicable for biodiesel production. [4] table 2 shows the organic composition of some algae. it is important that these parameters are only valid at properly equal conditions of the source. in case of changing culturing, environmental and other parameters productivity may shows such enormous difference. it is important to notice that high lipid content does not necessarily mean a high biomass growing potential. [6, 7, 8, 9, 10, 11]. table 2: common alga species used for energy biomass and energy production (contents in wt.%) [5] microalga protein carbohydrate lypides primnesium parvum 28–45 25–33 22–38 scenedesmus dimorphus 8–18 21–52 16–40 chlorella vulgaris 51–58 12–17 14–22 dunaliella bioculata 49 4 8 euglena gracilis 39–61 14–18 14–20 spirulina maxima 60–71 13–16 6–7 circumstances of growing algae get nutrients and other compounds from aqueous solution. on one hand they consume inorganic compounds and simple organic compounds, on the other hand they feed co2 in the form of hydrogencarbonate from dissolved gas mixture. choosing the right growing conditions has a positive effect on the whole process. continous measuring of all parameters are not necessary. a proper routine for the analytics can give as enough information as we need. for example a photometric test can give information about population and partially about the composition of the cells. environmetal parameters where environmental parameters are same at the major part of the year growing is so easier to manage than continental areas where weather is more complicated. we should keep on eye on weather forecast to plan procedures and the whole supply chain. available light is an essentially limiting factor for photosynthetic organisms. at natural conditions numerous alga species can live together in the same medium. in these media each species have competitive advantage beacause of the change of daylight spectra and intensity. the diversity of species remains because the light parameters change in every part of the day. green algae produce biomass by photoautotrophic production. in this method absorbed solar energy is transformed to chemical energy. for further energetic inspection this process can be drawn as given below (the nitrogen source is ammonia): 1 co2 + x nh3 + y h2o → 1 ch1,78o0,36n0,12 theoretically at least 14 moles of photones is necessary to build 1 mole of co2 for biomass production. this rate is the same for microalgae too. assimilating 1 mol of co2 produces 1 mol of biomass. its molar mass is about 21.25 g/mol and its heat of combustion is 547.8 kj/mol (25.8 kj/g biomass). 11 autotrophic organisms use only a part of total sunlight spectrum (400–700 nm) for photosynthesis. this range is 42.3 % of the total spectrum. this is called photosynthetic active radiation (par). the average energy of the photones is 218 kj/mol in this interval. the maximum theoretical photosynthetic energy efficience (pe) can be determined from these data given above. pe is 9 % for the total spectrum of sunligh and it is 21.4 % for the range of par. another environmental parameter is the ambient temperature and its effect on the reactor. warming up of a dense algae suspension without cooling can reach much higher temperature than ambient temperature. increasing suspension density causes increasing heat absorbtion from sunlight. algae optimally proliferate between 20–40 °c. below this range their metabolism is slowed down. above this range their decomposition by heat shock is rising with the rise of the temperature. fertilizing with co2 co2 feed means that the bubbling of a gas mixture into the algae suspension. generally, this mixture contains about 5–30 vol% co2 and air is the rest. it is possible to grow algae in gas mixtures without air, but their oxygen content for the dark period is an essence. the applicable co2 concentration depends on the temperature and liquid fertilizer concentration too. althogh the liquid concentration of co2 decreases by the rise of temperature but solved gas is used higher efficiency by the rise of metabolism than at lower temperature. in case toxic components are in the co2 source (eg. sox, nox), then air mixing might be essential. the air supply must be free of dust, mineral oil and other harmful particles (e. g. microbes). the medium there are significant differences in nutrient requirement among species of the same alga genus. accordingly, an optimal nutrient composition for a specified alga might not be applicable for another species in the same genus. commonly an optimized medium composition is only valid and applicable in the same circumstances as observed. it is an important to mention that in these systems single nutrient composition changes do not have effets of the same intensity than in combination with another nutrient(s). there are multilateral effects between nutient component concentrations, these connections might be a relevant information. there are a lot of media recipes accessible. there are recommendations for the most algae species. athough media for smaller volumes are more complicated than media used for higher volumes of algae suspension. an important point is to use some kind of comlplex formula to keep micronutrients accesible for algae. photobioreactors we use special photobioreactors to keep specified cultivation parameters. common expectations are specified below. it is important that as much par type light as possible be accesible for the algae. input and output streams must be safeand well measured for co2 content of the gas mixture. these reactors must be designed to resist environmental effects (wind, rain, sunlight, insects etc.). these algae suspensions must be well stirred, because degradation might be started in subsided algae conglomerate. these reactors must be designed for local microclimate and mostly mounted with cooling system. the planned cultivating volume affects the reactor geometry. the largest volume can be reached in open pond systems. in this case we can keep those type of algae which are resistant against local microbes and environmetal effects. to avoid invasive species proliferation parameters must be well monitored. generally, mechanical stirring is applied to maintain aeriation and stirring. another open type cultivation is the raceway system. in this case algae suspension flows in a canal. the thickness of the layer is between 100–500 mm. another type of cultivation can be in closed photobioreactors. these reactors have a well-defined area of light trasmitting wall. this is critical to the design. we should reckon with shadows of statically necessary elements on the light side. inner or outer contaminations of walls must be regularly eliminated. source of outer contaminations origin can be technical (e. g. scratches) or other environmental (e. g. dust). important is the choice of optimal thickness of layer to reach sufficient mixing. a thoughtful reactor design and monitored inputs can assure a well balanced algae cultivating system with low risk of unwanted external effects. closed photobioreactors are built in two designs. the first is the pipe system, with the advantages of simple geometry and few shading element but it has the disadvantage of low area by volumetric unit. the second type is the panel with the advantage of high area of volumetric unit and the disadvantage of evolving idle spaces. the harvest harvest is a critical phase of the technology. this is the limit between the active and inactive phase of algae. its time must be determined by the quality of the algae suspension. to choose the appropriate date, we should know the algae’s behaviour at the current parameters. following biologists instructions in case of ideal parameters an algae culture goes through four main growth phases. 12 the first is getting acclimatized. it can lasts from a few hours to 1-2 days. it is probably affected by the change of environmental parameters. the second is the quick growth or exponentional phase when significant biomass multiplication is shown. in this phase batch harvesting is too early. after this, a maximum is reached in biomass concentration. the next phase is the decrease of biomass comcentration. in this phase algae should be harvested. at the end of this phase there are a few algae in population and the chances are that other harmful microorganisms have been proliferated. figure 1: population vs. age of population we can choose from two opposite harvesting strategies. one of them is the batch type when total harvest and refill periods follow each other. in this case we use a new sterile starter culture. its advantage is that the previous batch does not affect to the next but its disadvantage is the need of a separate infrastructure to supply eligible quality and quantity starter culture. the other leads to quasi-continious systems. in this case part of the culture is harvested and restored with fresh medium. its advantage is the ability of simple automation system but the disatvantage is the need of a proper harvesting schedule. it is important to avoid the proliferation of harmful microbes and important to monitor the accumulation of metabolites. concentrating algae suspension, oil extraction (13-18) algal oil extraction consists of 2 necessary steps. one of them is the concentration of the alga biomass and the other is the lipid extraction. lots of techniques are applicable for this purpose. the most common types of techniques and their tipical examples are summarized below. if any of these is to be chosen it is important to consider that we should get the most biocomponent by using the least energy consumption as possible. concentrating the algae suspension although settling has the least energy consumption of concentration but mostly the rest of dry content cannot be precipitated. in this case some kind of pre-treating is necessary. flocculation is a widely applicated technology in wastewater treatment technologies. cationic polyelectrolytes are used for algae flocculation. after addition of these polyelectrolytes settling and filtering of evolved flocks becomes easier. it is important to notice that the use of polyelectrolytes may affect the oil extraction. in case of insufficient flocculation centrifugation is also used but it is important to reconsider since it means investing more energy. at the end of the concentrating phase we get a biomass with a low moisture content. it is important to know that this material should be processed as soon as possible. it can be stored after drying in inert atmosphere or frozen. algal oil extraction algal oil extraction can be carried out in two startegies. one of them is to extract oil from dry or moist material. the other is cell degradation come before extraction. the latter can be made by ultrasonic, microwave radiation, chilling shock, cell blast, enzymatic process. the aim of these methods that let intracellular compounds achievable for extracting material. in table 3 we present some common used solvent systems. in complex solvent systems, the polarity order is kept. table 3: common solvent systems for algae extraction extraction solvent1 solvent2 solvent3 chloroform methanol water hexane i-propanol water hexane ethanol water ethanol 1buthanol water solid-liquid acetone hexane superchritical fluid co2, water, methanol, buthane, penthane novel techniques ultrasonic, microwave, ase, cell-milking, liquid dimethyl-ether use of supercritical extraction is not so competitive but there are researches to get the optimal fluid-cosolvent pair. there are more and more new algal oil extraction can be reached. some of these keeps to solvent free technologies [19] others lead to new solvent base ones. [20, 21, 22]. algae technology research at the university of pannonia research in algae cultivation and algal oil extraction is carried out at the department of chemical engineering at the university of pannonia. together with industrial partners, we deal with the selection and testing of lipids, other bioactive compounds and alga species capable of biomass production. we also deal with the examination of optimal operational conditions of photobioreactors and the development of algae processing technologies. the available photobioreactors make the examination of different alga species with natural and artificial illumnation and with the intake of gas mixtures of different composition possible. 13 conclusion cultivation and processing of algae for fuel production is a promising research area because of the potentially high yield. however, most of the present technological solutions require development. the most important goal is to get the best yield with the lowest investment of materials and energy. a possible experimental path which has not been described in detail above is gmo, the introduction of which to industrial production has possible benefits, but also needs caution in order to prevent the natural ecosystem. the other important question – as for all novel processes – is the rate of return. at this point the utilization of the algal oil is not sufficient on its own, but the alga cells contain compounds that can be used in pharmaceutics (carotinoids), biogas synthesis (starch, sugars) or even in the agricultural industry (mirco and macro elements). references 1. n. g. carr, b. a. whitton: the biology of bluegreen algae, university of california press, 1973, isbn 0520023447. 2. nabors, w. murray: introduction to botany, san francisco, ca: pearson education, inc., 2004, isbn 0805344160. 3. c. körner: plant co2 responses: an issue of definition, time and resource supply, institute of botany, university of basel, switzerland, 2006, http://se-server.ethz.ch/staff/af/ar4-ch4_grey_lit/ ko110.pdf. 4. a. s. carlsson, j. b. van bilen, r. möller, d. clayton: mircroand macroalgae: utility for industrial applications, 2007, http://www.epobio.net/pdfs/0709aquaticreport.pdf accessed june 2008. 5. becker: algal chemical composition, 1994, http://www.castoroil.in/reference/plant_oils/uses/fuel /sources/algae/biodiesel_algae.html. accessed february 2008. 6. b. wang, y. li, n. wu, c. q. lan: co2 biomitigation using microalgae, applied microbiology and biotechnology, 79(5), 2008, 707–718. 7. y. chisti: biodiesel from microalgae, biotechnology advances, 25(3), 2007, 294-306. 8. y. li, m. horsman, n. wu, c. q. lan, n. duboiscalero: biofuels from microalgae, biotechnology progress, 24(4), 2008, 815–820. 9. j. pratoomyot, p. srivilas, t. noiraksar: fatty acids composition of 10 microalgal species, songklanakarin journal of science and technology, 27(6), 2005, 1179–1187. 10. s. m. renaud, l. v. thinh, d. l. parry: the gross chemical composition and fatty acid composition of 18 species of tropical australian microalgae for possible use in mariculture, aquaculture, 170, 1999, 147–159. 11. q. hu, m. sommerfeld, e. jarvis, m. ghirardi, m. posewitz, m. seibert et al.: microalgal triacylglycerols as feedstocks for biofuels production: perspectives and advances, the plant journal, 54, 2008, 621–639. 12. j. r. benemann: biofixation of co2 and greenhouse gas abatement with microalgae – technology roadmap 2003. http://www.co2captureandstorage.info/networks/ biofixation.htm accessed july 2008. 13. x. meng, j. yang, x. xu, l. zhang, q. nie, m. xian: biodiesel production from oleaginous microorganisms, renew. ener., 34, 2009, 1–5. 14. e. m grima, e. h. belarbi, f. g. a. fernández, a. r. medina, y. chisti: recovery of microalgal biomass and metabolites: process options and economics, biotechnology advances, 20, 2003, 491–515. 15. e. g. bligh, w. j. dyer: a rapid method for total lipid extraction and purification, can. j. biochem. physiol., 37, 1959, 911–917. 16. m. cooney, g. young, n. nagle: extraction of bio-oils from microalgae, sep. pur. rew., 38, 2009, 291–325. 17. f. smedes, t. k. askland: revisiting the development of the bligh and dyer total lipid determination method, mar. poll. bull., 38, 1999, 193–201. 18. j-y. lee, et al.: comparison of several methods for effective lipid extraction from microalgae. bioresour. technol., 101, 2010, s75–s77. 19. low cost extraction, live extraction. http://www.originoil.com/technology/low-cost-oilextraction.html http://www.originoil.com/technology/liveextraction.html accessed: 2010. 05. 19. 20. b. e. richter, b. a. jones, j. l. ezzell, n. l. porter, n. avdalovic, c. pohl: accelerated solvent extraction: a technique for sample preparation, anal. chem., 68, 1996, 1033–1039. 21. n. m. d. courchesne, a. parisien, b. wang, c. q. lan: enhancement of lipid production using biochemical, genetic, and transcription factor engineering approaches, j. biotechnol., 141, 2009, 31–41. 22. hideki kanda: successful extraction of „green crude oil” from blue-green algae high yield extraction at room temperature without drying nor pulverizing process (criepi) press release http://criepi.denken.or.jp/en/activities/pressrelease/ 2010/03_17.pdf 2010.03.17. 23. e. h. belarbi, et al.: a process for high yield and scaleable recovery of high purity eicosapentaenoic acid esters from microalgae and fish oil. enzyme and microbial technology, 26, 2000, 516–529. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 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<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> /enu (use these settings to create adobe pdf documents best suited for high-quality prepress printing. created pdf documents can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word szolcs_eloszo.doc hungarian journal of industrial chemistry veszprém vol. 32. pp. 57-64 (2004) separation by ion exchange and adsorption parametric pumping iv. theoretical cycle, number of theoretical cycles for batch, thermal ion exchange parametric pumping l. hanák, t. szánya and p. szolcsányi department of chemical process engineering, university of veszprém, veszprém, hungary the best component separation can be achieved by the application of theoretical cycles. a local equilibrium analysis is provided, which gives, ideal efficiencies through either graphical or numerical calculations. as the calculations presented here ignore non-equilibrium ion exchange, the mixing phenomena and the “run out” of characteristics, they are significant mainly in relation to one another. nevertheless, the effects of process and operation variables found here should be valid for actual system, especially in the production of high purity materials. introduction the so-called equilibrium theories or models are the simplest variants of the theoretical analysis and mathematical modelling of parametric pumping processes. there are two determining theories in literature dealing with this subject. the first assumes continuous flow and column and uses the basic equation of chromatography for the mathematical description of the operation. by the second theory the column is separated to parts, to well mixed cascades and also the flow is discontinuous. for the mathematical description of the cyclic operation, the equilibrium cascade model is applied, this, regarding the computation technique, can easily be treated. the first mathematical description of parametric pumping was given by wilhelm and co-workers [1], together with the basic idea of a new component separation moreover, the first experimental data were published. pigford and co-workers [2] elaborated the chromatographic model of the operation and called it “equilibrium theory of parametric pumping”. this equilibrium model consisting of linear isotherms was generalized by aris [3]. camero and sweed [4] expanded this theory and extended it to the domain of non-linear isotherms. this was applied by chen and co-workers [5, 6, 7, 8] for the description of multi-component systems, for continuous and semi-continuous processes. these models have the considerable advantage, that in their use, a computer is superfluous, the results can be calculated by simple relationships which present the concentrations of the reservoirs and the separation factors in the function of the cycle number. another variation in the description of operation is the so-called “cascade model”, this was parallelly elaborated with the previously discussed one. sweed and wilhelm [9] developed the so-called stop-go algorithm for the flow without component transfer, and later the component transfer without flow. the calculation of the operation was carried out by the help of a computer, successively, from cycle to cycle. grevillot and tondeur [10, 11] showed the analytical and graphical solution of the equilibrium cascade model of cyclic operation, the result is similar to the well known fenske 58 equation, used in rectification. they recognized the analogy between the rectification and parametric pumping, and they extended it for the solution of continuous operations [12]. our previous paper [13] dealt with the separation theory of batch thermal ion exchange parametric pumping operations. the conditions of the theoretically best separation were given. in the practice this high degree of separation is hardly to attain because, the theory greatly simplifies and idealizes the real cyclic operation. its advantage lies in the simple presentation of the component separation on an equilibrium diagram, on this, the separation mechanism of the cyclic operation is easy to understand. in this paper the effects of some parameters of the equilibrium model on the component separation will be examined in details. for the comparison of the theoretical and the experimental results the notion of cycle efficiency is introduced, which shows very clearly the effects of operation variables on the component separation. the determination of reservoir concentration in relation of theoretical cycle number in the batch, thermal ion exchange parametric pumping, as it was shown in previous paper [13] the best separation can be achieved if the theoretical cycles are repeated. if the “stepping up construction” is made between the equilibrium isotherms )tt( c,i j h,i j 〉 formed at two temperatures, between xi,0 and xi=0 interval, the concentrations of the cold reservoir, and between 0,ix and xi=1 interval, the concentration of the hot reservoir can be determined in function of the cycle number )tt( c,i j h,i j 〉 , being equal with the number of steps. this is shown on figure 1. one step means a half cycle: the perpendicular section (xi=constant) presents the frontal ion exchange during the flow, the inclined section gives the compositions formed during the thermostation period. the slope of the inclined section can be calculated with the help of the following balance equation, which includes the amounts of i component being in the liquid and in the resin phases, before and after the thermostation periods k 1 ik 1 i0k 0 ik 0 i0 vyq)1(vxcvyq)1(vxc ε−+=ε−+ (1) xc i,3 xc i,2 xc i,1 x0 i xh i,1 xh i,3 xi cold hot reservoir tj i,h tj i,c figure 1. the change of reservoir concentrations with the theoretical cycle number after simplification and rearrangement, the slope of the thermostation section (m) is: q)1( c xx yy m 0 1 i 0 i 1 i 0 i ε− ε −= − − = (2) starting from the composition of 0,ix and knowing the equilibrium composition and the value of m, the „stepping up construction” can easily be made. if graphic construction is needed, the slope of equilibrium isotherms can be optional. if the concentration domain lies over several order of magnitudes, this method is inconvenient. in case of constant ion exchange selectivity coefficients, the equilibrium, relationship for ion exchange of two components is as follows: ( ) i i j i i j i xt xt y 11 −+ = (3) where i jt is constant in the function of composition and it depends definitely on the temperature. in this case the concentrations of the reservoir can directly be calculated in the function of the cycle number, but the equation is fairly complicated and can rarely be used for real systems. if the ion exchange selectivity coefficients vary with the composition, the reservoir concentration can only be determined with iterations or by the approximation of isotherms with linear sections. in our calculations the latter method was used, giving a base for a computer programme development. 59 the computer programme for the calculation of theoretical cycles in the study of parametric pumping operation, being a novel component separation possibility, one of the most important questions is, how the component separation varies during the cycles, and on the other hand when repeating cycles what the value is of the theoretically attainable separation depending only on the model parameters discussed below: − the slope and the temperature dependence of ion exchange equilibrium isotherm, which are taken into account with the temperature dependence of ion exchange selectivity coefficients; these are the function of ion exchange resin quality and the ions to be separated, of the solution total concentration and of the applied temperature values. − the slope “m” operating line; − the 0,ix initial ion composition. to examine these parameters, a computer programme was prepared, its essence is as follows: using the equilibrium )y(tt i i j i j = relationships, the equilibrium isotherms are divided into small sections and are approximated with linear sections. starting from the initial 0,ix composition, in both direction, between the isotherms, the „stepping up construction” is made until the previously given cycle number is reached. the new xi composition is given by the intersection of the straight line (thermostation) of “m” slope and the appropriate linear section of the isotherm. the equilibrium relations can be optional, in the calculations of real systems, third order polynoms are used, fitted previously on experimentally determined data points, with the required accuracy [21]. in these calculations, as constants were taken the free volume coefficient of fixed bed ion exchange resin column (ε=0.35) and the resin capacity (q=2.36 mequ/cm3), these data were determined with ca2+ loaded varion ksm ion exchange resin particles, settled in water. in these calculations, the isotherms were approximated with linear sections, the yi coordinate was splitted to sections, these sections were shortened until the concentration difference of the reservoirs went below 1%. depending on the shape of the isotherms, the number of the sections reached 50 to 100. outputs of the program are: the compositions of the cold and hot reservoirs in the function of theoretical cycle number, and the separation factors. the result of calculations parameter sensitivity investigation selecting constant ion exchange selectivity coefficients in the function of resin composition, the effects of the following parameters were investigated: − the ratio of selectivity coefficients, formed on ion exchange on two temperature values (figure 2.); 1.e-10 1.e-08 1.e-06 1.e-04 1.e-02 1.e+00 0 5 10 15 20 25 30 cycle number c ol d re se rv oi r, x i 1 4 1 2 1 1.5 1 1.2 1 1.1 ti/j,c ti/j,h co=1.0equ/dm3 xi,o=0.5 1.e-10 1.e-08 1.e-06 1.e-04 1.e-02 1.e+00 0 5 10 15 20 25 30 cycle number h ot re se rv oi r, x j figure 2. the effect of the ratio of selectivity coefficients on the change of reservoir concentration 60 − the absolute value of selectivity coefficients (figure 3.); 1.e-10 1.e-08 1.e-06 1.e-04 1.e-02 1.e+00 0 5 10 15 20 25 30 cycle number c ol d re se rv oi r, x i 1 2 2 4 4 8 8 16 16 32 32 64 ti/j,c ti/j,h co=1.0equ/dm3 xi,o=0.5 1.e-10 1.e-08 1.e-06 1.e-04 1.e-02 1.e+00 0 5 10 15 20 25 30 cycle number h ot re se rv oi r, x j figure 3. the effect of absolute values of selectivity coefficients on the reservoir concentration − the total concentrations of solutions (figure 4.); 1.e-10 1.e-08 1.e-06 1.e-04 1.e-02 1.e+00 0 5 10 15 20 25 30 cycle number c ol d re se rv oi r, x i 0.01 1 4 ti/j h xi,o=0.5 ti/j,c=1.0 ti/j,h=2.0 co,equ/dm3 1.e-10 1.e-08 1.e-06 1.e-04 1.e-02 1.e+00 0 5 10 15 20 25 30 cycle number h ot re se rv oi r, x j figure 4. the effect of solution total concentration on the reservoir concentration − initial ion composition (figure 5.). 1.e-10 1.e-08 1.e-06 1.e-04 1.e-02 1.e+00 0 5 10 15 20 25 30 cycle number c ol d re se rv oi r, x i 0.01 0.1 0.5 0.9 0.99 co=1.0equ/dm3 ti/j,c=1.0 ti/j,h=2.0 xi,o 1.e-10 1.e-08 1.e-06 1.e-04 1.e-02 1.e+00 0 5 10 15 20 25 30 cycle number h ot re se rv oi r, x j figure 5. the effect of initial ion concentration on the change reservoir concentration on the figures the logarithmic values of ion composition of reservoirs are shown in the function of cycle number. it can be seen that if xi, xj<0.1, then the compositions exponentially decrease with the cycle number. from the results, the following deductions can be made being valid for thermal parametric pumping operations; 1 1.5 2 2.5 3 3.5 4 4.5 5 0 2 4 6 8 10 12 14 h, kj/equ k 1/k 2 288k/333k 278k/368k ∆ figure 6. the ratio of ion exchange equilibrium constants in the function of the enthalpy change of ion exchange reactions 61 1. the value of selectivity coefficients ratio determines basically the variation of reservoir composition in function of the cycle number. (figure 2.) the temperature dependence of the selectivity constants is basically related to the energy changes following the ion exchange processes. the temperature dependence of the equilibrium constant of ion exchange reaction can be described by van’t hoff’s equation, its integral form is: c rt hkln + ∆ = (4) it is evident that the enthalpy change of the ion exchange reaction, is an essential postulation of the realization of parametric pumping operation. on figure 6., using equation (4), the ratio of equilibrium constants is plotted against the ion exchange reaction enthalpy change. in case of exchange of ions having the same valence number, the ratio of equilibrium constants is approximately the same as the ratio of selectivity coefficients. the enthalpy changes of some ion exchange reactions are listed in table 1. [14, 15, 16, 17, 18, 19, 20]. it shows that in most cases, especially if 90k temperature difference is applied, the separation of ion pairs with thermal parametric pumping seems to be very attractive. 2. the absolute values of selectivity coefficients have considerable influence on the decrease of ion ratio of unfavourably bonding components, but they are ineffective for the same one of the well bonding components (figure 3.). these phenomena can be explained by the slope “m” of operating line, being constant with the composition and, with the slope of isotherms, depending strongly on the composition and the absolute value of selectivity coefficients. the logarithmic values of reservoir compositions, shown on figures 2. to 5. in the case of xi, xj<0.1, are inversely proportional to the cycle number, if half-logarithmic log x scale is selected. in the concentration intervals of 0 < xi <0.1 and 0.9 < xi <1, the ion exchange isotherms are nearly linear. this shows that the computation can greatly be simplified (figure 7.). y=i 1 tj i,h x+const.i y=i 1 tj i,c x+const.i m m m m 1 yi 0 0 0.1 0.9 xh i,m xh i,m+1 xh i,m+2 xi 1.0 figure 7. the linearization of ion exchange isotherms and the reservoir concentrations in the case of xj, xi <0.1 62 table 1. the enthalpy changes of some ion exchange reactions ion pair ion exchanger resin ∆h kj/equ ion pair ion exchanger resin ∆h kj/equ na+-h+ dowex 50×12 4,64 y3+-ce3+ dowex 50×8 -2,33 k+-h+ “ 8,96 la3+-na+ dowex 50×4 7,37 rb+-h+ “ 11,68 la3+-ce3+ dowex 50×8 -0,19 cs+-h+ “ 14,23 ce3+-k+ “ -8,10 be2+-h+ “ -2,59 ce3+-be2+ “ 2,60 be2+-h+ “ 4,56 ce3+-cr3+ dowex 50×2 0,77 co2+-h+ “ -0,42 “ dowex 50×8 1,15 zn2+-h+ “ -0,42 “ dowex 50×16 1,36 cu2+-h+ “ 2,52 pr3+-ce3+ dowex 50×8 0,16 la3+-h+ “ 2,39 nd3+-ce3+ “ 0,092 eu3+-h+ “ 3,60 sm3+-ce3+ dowex 50×4 1,22 pm3+-h+ “ 1,23 eu3+-ce3+ dowex 50×8 -1,82 tm3+-h+ “ 1,97 gd3+-ce3+ “ -2,36 lu3+-h+ “ 1,73 tb3+-ce3+ “ -2,89 k+-na+ “ 3,78 dy3+-ce3+ “ -2,75 rb+-na+ “ 2,42 ho3+-ce3+ “ -2,49 cs+-na+ “ 3,24 er3+-ce3+ “ -1,98 ba2+-na+ “ 3,51 tm3+-ce3+ “ -1,43 izotópok j/eq yb3+-ce3+ “ -1,08 6li+-7li+ dowex 50×12 -9,46 lu3+-ce3+ -0,64 22na+-24na+ “ -1,72 cl–−2 4so amberlite ira400 15,0 40ca2+-48ca2+ “ -2,9 35cl––37cl– biorad ag1-x10 -6,1 (0-10°c) “ “ -0,61 (20-60°c) 63 instead of the relationship, generally describing the equilibrium of ion exchange reaction in the interval of 0 < xi< 0.1, the i i ji xty = (5) and in the interval of 0.9 < xi <1, the cx t 1y ii j i += (6) relationships can be used, these were derived from eq.(3), taking the limits of x → 0 and x → 1. with its help it is easy to show that the following simple relationships can be used for the description of the alteration of reservoir concentrations; in the case of ,1tt c,i i h,i j >> for the subsequent cycles: the concentration of “i” ions in the cold reservoir is: mt mt xx h,i j c,i jc n,i c 1n,i − − =+ (7) the ion ratio of “j” in the hot reservoir is: m t 1 m t 1 xx c,i j h,i jh n,j h 1n,j − − =+ (8) equation (7) describes the alteration of ion ratio of “i” ions bonding advantageously, during the theoretical cycle, in the cold reservoir. it can be seen that the increase of the absolute values of selectivity coefficients increases the attainable separation within a theoretical cycle. it is noted that the usual values of i jt are between 2 and 50; the value of “m” lies between (-0.01) and (-0.2); in these cases the theoretically attainable separation increases only slightly with the growing values of selectivity coefficient. equation (8) describes the alteration of ion ratio of unfavourable bonding “j” ions within a theoretical cycle, in the hot reservoir. it can be seen that reciprocal values of the selectivity coefficients are present in the fraction, these values can be compared to values of “m”, and the increase of selectivity coefficients considerably decreases the separation attained within a step. 3. from equations (7) and (8), it can be seen that the growing value of “m” decreases the separation in both reservoirs attained within a step (figure 4). the value of “m” is given by equation (2). while decreasing the absolute value of “m” the separation is better, therefore it is advantageous to use for the separation high capacity ion exchange resin. the free volume coefficient (ε) of ion exchange columns is usually between 0.3 and 0.4. decreasing the total concentration of the solution, the attainable separation within a step is better, but the amount of ions processed in unit time, generally decreases. 4. investigating the effect of initial ion composition from the viewpoint of theoretical cycles it can be concluded that fewer cycles are needed to reach the same separation at smaller initial compositions. (figure 5.). summarizing, for the calculation of component separation, based on theoretical cycles, the following simple relationship can be used. this presents the concentration of the reservoirs in the case of xi, xj< 0.1 ion ratios, with less than ±5% error. in case of cold reservoir, for advantageously bonding “i” ions: ( )1,, , , 0,, >>         − − = ci j hi j n hi j ci j i c ni tt mt mt xx (9) in the case of hot reservoir, for weakly bonding “j” ions: ( )1tt m t 1 m t 1 xx c,i j h,i j n c,i j h,i j 0,j h n,j >>               − − = (10) it is noted, if the selectivity coefficients ( )h,i j c,i j t,t are dependent on the ion composition of the resin and/or the liquid phases, then in the intervals of 0 < xi < 0.1 and 0 < xj < 0.1 (equ. 10), the mean values of c,i jt and h,i jt should be used. 64 summary in this paper the component separation theory is presented, which describes the batch, thermal ion exchange parametric pumping process. in the frame of this, simple relationships are presented; these describe the alteration of reservoir concentrations in the function of the theoretical cycle number. calculations were made to investigate the effects of the ratio and absolute value of ion exchange selectivity coefficients, the total concentration of solution and the initial ion composition on the component separation. the simplified model gives only rough estimation of the transient concentration changes and elucidates the effects of some process and operation parameters playing an important role in the production of high purity compounds. one major benefit of the equilibrium model is that it provides view in the mechanism of the separation. symbols m variable, defined by equ. (2) xj ion ratio of component “j” in the liquid phase xj,0 initial ion ratio of component “j” in the liquid phase c n,i h n,i xx ion ratio in hot and cold reservoirs, in the nth theoretical cycle yj ion ratio of component “j” in resin phase c0 total concentration of liquid phase ∆h enthalpy change of ion exchange process k1, k2 equilibrium constants of ion exchange reaction on two, different temperatures l the length of ion exchange column n theoretical cycle number q capacity of ion exchanger resin, related to volume unit c,i jt h,i jt ion exchange selectivity coefficient of ion “i”, related to ion “j”, on “cold” and “hot” temperatures vk volume of ion exchanger resin charged into the column ε free volume coefficient of the ion exchanger resin column references 1. wilhelm r. h., rice a. w and bendelius a. k.: ind. eng. chem. fund.,1966, 5(1), 141144 2. pigforg r. l., baker b. and blum d. e.: ind. eng. chem. fund., 1989, 8(1), 144-149 3. aris r.: ind. eng. chem. fund., 1969, 8(3), 603-604 4. camero a. a. and sweed n. h.: aiche journal, 1974, 22(2), 369-376 5. chen h. t. et al.: aiche journal, 1974, 20(2), 306-310 6. chen h. t. and manganarov j. a.: aiche journal, 1974, 20(5), 1020-1022 7. chen h. t. and hill f. b.: sep. sci., 1971, 6(3), 411-434 8. chen h. t. et al.: aiche journal, 1972, 18(2), 356-361 9. sweed n. h. and wilhelm, r. h.: ind. eng. chem. fund., 1969, 8(2), 221-231 10. grevillot g. and tondeur d.: aiche journal, 1976, 22(6), 1055-1063 11. grevillot g. and tondeur d.: aiche journal, 1977, 23(6), 840-851 12. grevillot d.: aiche journal, 1980, 26(1), 120-131 13. szánya t., hanák l. and szolcsányi p.: hung. j. ind. chem., 1985, 13(2), 155-161 14. inczédy j.: analytical application of ion exchangers. műszaki könyvkiadó, budapest, pp. 85-87. 1963 15. gmelins handbook of inorganic chemistry. 8th edit. d6, pp. 4-10. 1983 16. rao t. s. and bonde s. l.: z. phys. chemie, leipzig, 1980, 261(2), 352-358 17. bonner o. d. and smith l. l.: j. phys. chem., 1957, 61, 1614-1617 18. heumann k. g. and klöppel h.: z. anorg. allg. chem., 1981, 472, 83-88 19. glueckauf e.: trans. faraday soc., 1958, 54, 1203-1205 20. lee d.a.: j. phys. chem., 1960, 64, 187-188 21. hanák l., szánya t. and szolcsányi p.: hung. j. ind. chem., 1988, 16, 253-260 22. szánya t., hanák l., mohilla r. and szolcsányi p.: hung. j. ind. chem., 1988, 16, 261-271 microsoft word contents_2.doc hungarian journal of industrial chemistry veszprém vol. 31. pp. 37-45 (2003) investigation of the deep hydrodesulphurization of gas oil fractions z. varga, j. hancsók, g. nagy department of hydrocarbon and coal processing, university of veszprém, h-8201 veszprém, p.o. box 158, hungary the sulphur content of automotive diesel fuels was tightened all over the world, for example a sulphur content limit of 350 ppm came into force in the european union in the year 2000 and this value will be 50 ppm in the year 2005, even 10 ppm from the end of this decade. one of the reasonable solutions for refineries to satisfy these strict requirements is deep hydrodesulphurization of the gas oils fractions. in this paper the experimental results of the hydrodesulphurization of gas oils with different sulphur, nitrogen and aromatic contents on nimo/al2o3/promoter catalyst are presented. effect of the key process parameters and composition of the feeds on the yield and the quality of products are discussed. in addition to this, hydrogenation reactions of aromatic compounds taking place during the hydrodesulphurization are covered. on the basis of experimental results the advantageous process parameters were determined for producing diesel fuel blending components of sulphur content lower than 50 ppm and lower than 10 ppm. keywords: hydrodesulphurization, hydrodearomatization, nimo/al2o3, feed quality introduction the quality requirements of diesel fuels became stricter and stricter all over the world in the last years and this tendency will continue in the near future, too. the most pronounced changes were introduced in the maximum allowable sulphur content, for example its value was limited to 350 ppm in 2000 and 50 ppm from 2005, furthermore fuel having maximum 10 ppm sulphur content should be regionally available from this date and all automotive diesel fuels must be sold with less than 10 ppm sulphur content after january, 2009 [1]. reduction in the sulphur content of diesel fuels contributes to the decrease of so2 (acid rain precursor) sulphate particles and emission of particulate matter, but the most important reason for this reduction is to preserve the efficiency of modern exhaust gas treating systems e.g. nox traps, nox converters, particulate filters for a long time, because these systems are greatly sulphur sensitive [2]. production of diesel fuels with lower than 50 ppm and mainly 10 ppm sulphur content gave a headache for the refining industry and initiated extensive research and development activities on both the conventional hydrodesulphurization technology and the alternative methods e.g. desulphurization by selective adsorption (phillips 66 co. “s zorb process”), chemical oxidation followed by extraction (uni-pure and texaco “asr-2 process”), biological desulphurization and production of fischer–tropsch diesel fuel [3-5]. the main difficulty in producing low sulphur (< 50 ppm sulphur content) and practically sulphur-free diesel fuels (< 10 ppm) arises from the sterically hindered dibenzothiophenes content of gasoil fractions. it is known that there are two possible reaction pathways for the removal of sulphur. the first is direct extraction of the sulphur atom from the molecule, and the second, hydrogenation of aromatic rings followed by extraction of the sulphur atom. the sterically 38 hindered heterocyclic sulphur compounds contain one or two alkyl groups adjacent to the sulphur atom (4 and/or 6 position) which restricts the vertical adsorption of molecules to the hydrogenolysing active sites of the catalyst and promote the flat adsorption to the hydrogenating active sites of the catalyst, see figure 1 [4]. hence it follows that the removal of these compounds requires the application of catalysts having relatively high hydrogenating activity, for example nimo/al2o3. figure 1 adsorption of a sterically hindered dibenzothiophene to the active sites of catalyst beside proper selection of the catalyst optimalization of process parameters contribute to the successful implementation of hydrodesulphurization too. the optimal parameters are the following: • higher partial pressure of hydrogen, especially in case of applying nimo/al2o3 type catalyst. • lower partial pressure of hydrogen sulphide, because this compound inhibits hydrodesulphurising reactions. • lower liquid space velocity corresponding to longer residence time, and higher volume ratio of hydrogen-to-hydrocarbon. the aim of this present study was to identify and quantify the key process parameters for the hydrodesulphurization of gas oils of different sulphur, nitrogen and aromatic content on nimo/al2o3/promoter catalyst. effect of the key process parameters (temperature, pressure, lhsv, hydrogen/hydrocarbon volume ratio) and composition of the feeds on the yield and quality of products were investigated. in addition, hydrogenating reactions of aromatic compounds taking place during the hydrodesulphurization were studied as well. on the basis of experimental results the advantageous process parameters were determined for producing diesel fuel blending components of sulphur content lower than 50 ppm and lower than 10 ppm. possible applications of the obtained diesel fuel blending components in themselves or together with others were examined with the objective of satisfying standard specifications of commercial products. experimental the hydrodesulphurizing experiments were carried out at the university of veszprém, department of hydrocarbon and coal processing. apparatus the experiments were carried out in a high pressure reactor system. this system consists of a tubular reactor of 100 cm3 efficient volume free from back-mixing, as well as equipment and devices applied in the reactor system of hydrotreating plants (pumps, separators, heat exchangers, temperature and pressure regulators and gas flow regulators). the experiments were carried out on a catalyst of constant activity and in continuous operation. repeatability of the experimental results was higher than 95% considering the total errors of both the technological experiments and the tests methods. 39 materials catalyst the hydrodesulphurizating experiments were carried out on a commercially available nimo/al2o3/promotor type catalyst which was pre-treated according to the recommendation of the supplier. feedstock the feeds were two straight run light gas oils (“a1” and “a2”) and two straight run heavy gas oils (“b1” and “b2”). feeds “a1” and “b1” were derived from crude oil exploited in hungary while feeds “a2” and “b2” were produced from russian crude oil. their main properties are given in table 1. these data show that the quality of gas oil produced from domestic source (“a1” and “b1”) is better compared to those derived from russian crude, regarding especially sulphur, nitrogen and aromatic contents of which properties influence the efficiency of hydrodesulphurization in a large extent. table 1 main properties of the feeds feed property a1 a2 b1 b2 density at 15 °c, kg/m3 797.1 835.2 820.0 860.0 sulphur, ppm 600 5100 1200 9300 nitrogen, ppm 5 9 114 217 aromatics, % mono 8.9 16.6 8.5 18.9 di 4.2 8.0 3.9 8.1 tri+ 0.7 1.0 2.1 3.2 total 13.8 25.6 14.4 30.2 cfpp, °c <-24 -23 8 5 flash point, °c 52 59 64 70 distillation, °c initial boiling point 169 154 172 188 10 vol. % 197 233 248 284 30 vol. % 215 254 275 309 50 vol. % 224 266 291 324 70 vol. % 237 278 307 336 90 vol. % 263 284 336 354 95 vol. % 278 301 354 366 end boiling point 291 306 361 369 cetane index 57.2 52.8 68.2 58.5 methods properties of the feeds and products were determined by standard test methods which are summarized in table 2. for example sulphur and nitrogen content was measured by oxidative combustion and electrochemical detection (aps-35 equipment) and aromatic content by high performance liquid chromatography (hplc) (en 12916:2000). table 2 applied test methods properties standards density, at 15°c msz en iso 12185 cetane index msz 13166 flash point msz en 22719 sulphur content astm d 6428 nitrogen content astm d 6366 aromatic content en 12916:2000 distillation data astm d86-97 the experiments were carried out on a catalyst of constant-state activity, in continuous operation. hydrodesulphurising (hds) and aromatic saturating (hda) activities of the catalyst were determined on the basis of equations 1-2. hds activity: hds% = 100 (sfeed-sproduct) / sfeed eq. 1 where sfeed: sulphur content of the feed, ppm sproduct: sulphur content of the product, ppm hda activity: hda% = 100 (afeed-aproduct) / afeed eq. 2 where afeed: total aromatic content of the feed, % aproduct: total aromatic content of the product, %. process parameters the applied process parameters are summarized in table 3. table 3 applied process parameters parameters temperature, °c 300-360 pressure, bar 40-60 liquid hourly space velocity, (lhsv), h-1 1.0-2.0 h2 to hydrocarbon volume ratio, m3/m3 400 40 results and discussion hydrodesulphurizing (hds) experiments after each experiment we determined first the yield of the stabilized liquid products. the yield was higher than 98% in every case. however, the amounts of the gas and gasoline fractions were higher at higher temperatures and lower liquid hourly space velocities (lhsv), due to the stricter process parameters. experiments applying straight run light gas oils (feed “a1” and “a2”) results of hds experiments applying straight run light gas oils (feed “a1” and “a2”) are summarized in figures 2-5, showing the change of sulphur content of the products and the variation of hds activities of the catalyst as a function of temperature at a lower and a higher value of pressure (40 bar and 60 bar) and of lhsv (1.0 h-1 and 2.0 h-1) in case of both feeds, respectively. 0 10 20 30 40 50 60 70 290 300 310 320 330 340 350 360 370 temperature, °c su lp hu r c on te nt , p pm lhsv=1(40bar) lhsv=2(40bar) lhsv=1(60bar) lhsv=2(60bar) figure 2 effect of temperature on the reduction of sulphur content (feed “a1”) 90.0 91.0 92.0 93.0 94.0 95.0 96.0 97.0 98.0 99.0 100.0 290 300 310 320 330 340 350 360 370 temperature, °c h d s, % lhsv=1(40bar) lhsv=2(40bar) lhsv=1(60bar) lhsv=2(60bar) figure 3 effect of temperature on the hds activity (feed “a1”) the highest rate of the reduction of sulphur content occurred in the temperature range of 300340°c in case of both feeds and at every process parameter applied, where it decreased practically linearly with increasing temperature; above this range the sulphur content further decreased, but the rate of reduction decreased in a large extent. figures 3 and 5 show that hds activities exceed 98% (even 99% in case of feed “a2”) at 340°c suggesting that most sulphur compounds were converted at this temperature, and only the most refractory ones remained in the products. 0 50 100 150 200 250 300 350 400 290 300 310 320 330 340 350 360 370 temperature, °c su lp hu r c on te nt , p pm lhsv=1(40bar) lhsv=2(40bar) lhsv=1(60bar) lhsv=2(60bar) figure 4 effect of temperature on the reduction of sulphur content (feed “a2”) 41 92.0 93.0 94.0 95.0 96.0 97.0 98.0 99.0 100.0 290 300 310 320 330 340 350 360 370 temperature, °c h d s, % lhsv=1(40bar) lhsv=2(40bar) lhsv=1(60bar) lhsv=2(60bar) figure 5 effect of temperature on the hds activity (feed “a2”) figures 2 and 4 show the pressure and lhsv effects and the attainable sulphur content. increasing the pressure and decreasing the lhsv (longer mean residence time) had advantageous effect on the sulphur content of the products at a given temperature, especially in case of feed “a2” and lower temperatures (300°c and 320°c). effect of decreasing the lhsv from 2.0 h-1 to 1.0 h-1 was more pronounced than that of the increasing the pressure from 40 bar to 60 bar. this suggests that the applied feeds contain such types of heterocyclic sulphur compounds (probably alkyl benzothiophenes) which are preferably converted by direct desulphurization route. this reaction pathway is influenced by the partial pressure of h2 (ph2) in a less extent than the hydrogenating route. besides the increase of ph2 is essentially favourable for “direct” reaction route because it decreases the partial pressure of h2s which compound exerts negative effect on the rate of the reaction. concerning values of maximum allowable sulphur content of diesel fuels coming into force in year 2005 (50 ppm) and in year 2009 (10 ppm) it can be stated that products having sulphur content lower than 50 ppm can be obtained even at a temperature as low as 300°c and lhsv = 1.0 h-1 at 40 bar and lhsv = 1.0 h-1 and 2.0 h-1 at 60 bar applying feed “a1”. products below 10 ppm sulphur content can be produced at 340°c and in all cases, except pressure of 40 bar and lhsv of 2.0 h-1. on the contrary, products below 50 ppm sulphur can only be produced at significantly higher temperature (at 340°c and above) in case of feed “a2” and product below 10 ppm sulphur content can only be obtained at the highest temperature and pressure (360°c and 60 bar) and the lowest lhsv (1.0 h-1). the reason of this is that feed “a2” contains sulphur in higher concentration originally, and it is postulated fact that sulphur compounds exert self-inhibition effects on the desulphurising reactions, and higher amount of sulphur leads to the formation of more h2s. besides the feed “a2” contains significantly more aromatics (see table 1) which also inhibit the desulphurizing reactions (especially direct desulphurization) by competitive adsorption. in consequence of all these effects the attainable reduction in sulphur content is less. experiments applying straight run heavy gas oils (feed “b1” and “b2”) figures 6-9 show the results of hds experiments carried out applying straight run heavy gas oils (feed “b1” and “b2”), that is the change of sulphur content of the products and variation of hds activities of the catalyst as a function of temperature at a lower and a higher pressure (40 bar and 60 bar) and of lhsv (1.0 h-1 and 2.0 h-1) for both feeds, respectively. figures 7 and 9 show that significant reduction in the sulphur content took place even at the temperature of 300°c in case of feed “b1” (above 90% hds activity) and a further increase of temperature resulted in a relatively low improvement (about 6%). on the contrary, in case of feed “b2” significant improvement on hds activity (between 18% and 30% depending on process conditions) was experienced in the applied temperature range. 42 0 20 40 60 80 100 120 140 280 300 320 340 360 380 temperature, °c su lp hu r c on te nt , p pm lhsv=1(40bar) lhsv=2(40bar) lhsv=1(60bar) lhsv=2(60bar) figure 6 effect of temperature on the reduction of sulphur content (feed “b1”) 90.0 91.0 92.0 93.0 94.0 95.0 96.0 97.0 98.0 99.0 100.0 290 300 310 320 330 340 350 360 370 temperature, °c h d s, % lhsv=1(40bar) lhsv=2(40bar) lhsv=1(60bar) lhsv=2(60bar) figure 7 effect of temperature on the hds activity (feed “b1”) 0 400 800 1200 1600 2000 2400 2800 290 300 310 320 330 340 350 360 370 temperature, °c su lp hu r c on te nt , % lhsv=1(40bar) lhsv=2(40bar) lhsv=1(60bar) lhsv=2(60bar) figure 8 effect of temperature on the reduction of sulphur content (feed “b2”) 65.0 70.0 75.0 80.0 85.0 90.0 95.0 100.0 290 300 310 320 330 340 350 360 370 temperature, °c h d s, % lhsv=1(40bar) lhsv=2(40bar) lhsv=1(60bar) lhsv=2(60bar) figure 9 effect of temperature on the hds activity (feed “b2”) 43 regarding other process parameters (pressure and lhsv) it can be stated that the increase of pressure and the decrease of lhsv exerts advantageous effect on the attainable sulphur reduction at a given temperature, especially in case of feed “b2” and at lower temperatures. studying the effects of pressure and lhsv showed an interesting picture. namely, the decrease of lhsv from 2.0 h-1 to 1.0 h-1 caused higher improvement on the reduction of the sulphur content than the increase of the pressure from 40 bar to 60 bar at constant temperature in case of feeds “a1”, “a2” and “b1”. on the contrary, in case of feed “b2” the advantageous effect of the increase of the pressure was higher than that of the reduction of lhsv above 330°c. this suggests that distribution of the sulphur compounds greatly differs in the latter one compared to the former ones. feed “b2” contains presumably higher amount of sterically hindered heterocyclic sulphur compounds (e.g. dibenzothiophenes alkylated in 4 and 6 positions) and the conversion of these refractory sulphur compounds takes place mainly in the “indirect” reaction route involving hydrogenation of the aromatic ring in the first step. this is an equilibrium reaction and exothermic process, and the increase of the pressure, especially of the partial pressure of hydrogen, shifts the equilibrium towards saturation of aromatics which implies higher reduction in sulphur content, too. concerning present (350 ppm) and future (50 ppm from 2005 and 10 ppm from 2009) sulphur content regulations of diesel fuels it can be stated that products having sulphur content lower than 350 ppm can be produced even at less severe operating conditions (300°c, 40 bar and lhsv = 2.0 h-1) applying feed “b1”. products having sulphur content below 50 ppm can be produced at 340°c and in all cases except at pressure of 40 bar and lhsv of 2.0 h-1. on the contrary, products having sulphur content below 350 ppm can only be produced at significantly higher temperature (at 340°c and above) in case of feed “b2”, and products below 50 ppm sulphur content could not be obtained even at the highest temperature and pressure (360°c and 60 bar) and the lowest lhsv (1.0 h-1) applied. the main reason of this is probably that this feed contains considerable amount of sterically hindered heterocyclic sulphur compounds. besides the heavy gas oil obtained from russian crude contains originally higher sulphur which would contribute to the evolvement of strong self-inhibition effect on the desulphurising reactions, furthermore, the higher amount of sulphur leads to the formation of more h2s which inhibits these reactions, too. the high amount of nitrogen and aromatics (see table 1) contained in feed “b2” also inhibits the desulphurising reactions. experiments for hydrodearomatisation (hda) the reduction of the aromatic content taking place collaterally with the hydrodesulphurization was investigated as well. since the primary purpose of this study was to investigate the reduction of the sulphur content, the results of only those hda experiments are presented which are obtained at process conditions required for the production of gas oils having sulphur content meeting the present (350 ppm) and future (50 ppm from 2005 and 10 ppm from 2009) quality requirements. these results are summarized in table 4. table 4 aromatic contents of selected products properties feeds a1 a1 a2 a2 sulphur, ppm 45 6 41 7 pressure, bar 40 60 40 60 temperature, °c 300 340 340 360 lhsv, h-1 1 1 1 1 aromatics, % mono 12.7 8 19.7 16.0 di+ 0.8 1.2 3.0 2.7 total 13.5 9.2 22.7 18.7 hda, % 2.2 33.3 11.3 27.0 feeds b1 b1 b2 b2 sulphur, ppm 43 34 100 81 pressure, bar 60 40 60 60 temperature, °c 340 340 360 360 lhsv, h-1 2 1 2 1 aromatics, % mono 10.2 10.7 18.8 16.0 di+ 3.3 3.1 3.1 2.7 total 13.5 13.8 21.9 18.7 hda, % 6.2 4.2 27.5 38.1 the valid standard regarding the commercial type diesel fuel (en 590) contains regulation of aromatics only for the polyaromatic content with maximum allowable value of 11%. this value will not change in 2005 counter to sulphur content and it will be tightened presumably from 2009. 44 comparing the polyaromatic content of feeds (table 1) to the required value it can be stated that both light gas oils and one of the heavy gas oils that is produced from domestic crude satisfy this value, and only the other heavy gas oil contains polyaromatics in a little bit higher concentration. data of table 4 show that products manufactured to satisfy different requirements of sulphur content have low polyaromatic content even in case of feed “b2”, and all values meet the requirement of the standard en 590. this indicates that satisfying the requirement of polyaromatic content can be reached more easily than that of the sulphur content. these data also demonstrate that hda activity of the catalyst was relatively low (between 2.2% and 11.3%) at process conditions for obtaining products of lower than 50 ppm (feed of “a1”, “a2” and “b1”), and this is advantageous from the point of view of hydrogen consumption. these results also show that mainly the reduction of the polyaromatic content took place in these conditions, and the products contain mono aromatics in higher concentration than the feeds, which means that saturation of the mono aromatics to naphthenes takes place with a lower rate of reaction than their formation from diand polyaromatics by consecutive ring opening hydrogenation. on the basis of the experimental results presented it can be seen that products having sulphur content lower than 10 ppm can only be produced from feed “a1” and “a2” at strict process conditions (high pressure and temperature, as well as low lhsv). the hda activity of the catalyst was relatively high in these conditions (27.0% and 33.3%) and not only the reduction in polyaromatic content but the decrease in mono aromatic content took place. the reduction of the aromatic content of gas oils is advantageous from the aspects of environmental protection and engine operation. however, if the primary purpose of the hydrotreatment is the reduction of the sulphur content, high hda activity involves growing hydrogen consumption that is not beneficial from the point of view of economy. besides, the use of more hydrogen causes more fuel consumption consequently higher flue gas emissions in the steam-reforming process, so some parts of the emissions are shifted from the cars to the refinery. quality parameters of feed “b2” are the worst of all examined feeds (high aromatic, sulphur and nitrogen contents), and to obtain products with relatively low sulphur content strict process conditions (high temperature and pressure low lhsv) should be applied. the degree of the saturation of aromatics was high in these conditions (from 27.5% to 38.1%, depending on process parameters), which is unfavourable from the point of view of hydrogen consumption and it leads to the problems mentioned before. one of the possible solutions of processing this feed can be the application of the two-step hds. in the first step of this process more selective desulphurising catalyst (e.g. como) can be applied for converting a predominant part of sulphur compounds, and in the second step the remaining sulphur compounds can be removed on a type of catalyst having high hydrogenating activity (for example noble metal/zeolite) in mild process conditions. summary the sulphur content of automotive diesel fuels was tightened all over the world, for example sulphur content limit of 350 ppm came into force in the european union in the year 2000 and this value will be 50 ppm in the year 2005, even 10 ppm from the end of this decade. this paper summarized the results of experiments of hydrodesulphurizing of feeds having different qualities (sulphur, nitrogen and aromatic content, boiling point range, etc.) on nimo/al2o3/promoter catalyst. the feeds were two straight run light gas oils (“a1” and “a2”) and two straight run heavy gas oils (“b1” and “b2”). feeds “a1” and “b1” were derived from crude oil exploited in hungary while feeds “a2” and “b2” were produced from russian crude oil. the highest rate of the reduction of sulphur content occurred in the temperature range of 300340°c in case of both feeds and in all cases, where it decreased practically linearly with increasing temperature, above this range the sulphur content decreased further, but the rate of the reduction decreased in a large extent. pressure and lhsv also influence the attainable sulphur content. increasing pressure and decreasing the lhsv (longer mean residence time) had advantageous effect on the sulphur content of products at a given temperature. studying the effects of the pressure and lhsv showed an interesting picture. namely, decreasing lhsv from 2.0 h-1 to 1.0 h-1 caused higher improvement on the reduction of the sulphur content than the increase of the pressure from 40 bar to 60 bar at constant temperature in case of feeds “a1”, “a2” and “b1”. on the 45 contrary, in case of feed “b2” the advantageous effect of the increase of pressure was higher than that of the reduction of lhsv above 330°c. this suggests that distribution of the sulphur compounds greatly differs in the latter one compared to the former ones. concerning values of maximum allowable sulphur content of diesel fuels coming into force in year 2005 (50 ppm) and in year 2009 (10 ppm) it can be stated that products having sulphur content lower than 50 ppm can be obtained even at a temperature as low as 300°c and lhsv = 1.0 h-1 at 40 bar and lhsv = 1.0 h-1 and 2.0 h-1 at 60 bar applying feed “a1”, products below 50 ppm sulphur can only be produced at significantly higher temperature (at 340°c and above) in case of feed “a2”. applying feed “b1” products having sulphur content below 50 ppm can be produced at 340°c and in all cases except at pressure of 40 bar and lhsv of 2.0 h-1, but in case of feed “b2” product below 50 ppm sulphur content could not be obtained even at the highest temperature and pressure (360°c and 60 bar) and the lowest lhsv (1.0 h-1) applied. products below 10 ppm sulphur content can be produced at 340°c and in all cases, except pressure of 40 bar and lhsv of 2.0 h-1 in case of feed “a1”, on the contrary, product below 10 ppm sulphur content can only be obtained at the highest temperature and pressure (360°c and 60 bar) and the lowest lhsv (1.0 h-1) in case of feed “a2”. however, products containing lower than 10 ppm sulphur could not be obtained applying heavy gas oils even at highest temperature and pressure and the lowest lhsv applied. the reduction of the aromatic content taking place collaterally with the hydrodesulphurization was investigated as well. the polyaromatic content of products was well below the required value (11%) of en 590 standard, which indicates that satisfying the requirement of polyaromatic content can be reached more easily than that of the sulphur content. the hda activity of the catalyst was relatively high in conditions to be applied to obtain products having the lowest sulphur content for every applied feeds, and not only the reduction in polyaromatic content but the decrease in mono aromatic content took place. the reduction of the aromatic content of gas oils is advantageous from the aspects of environmental protection and engine operation. however, if the primary purpose of the hydrotreatment is the reduction of the sulphur content, high hda activity involves growing hydrogen consumption that is not beneficial from the point of view of economy. besides, the use of more hydrogen causes more fuel consumption consequently higher flue gas emissions in the steam-reforming process, so some parts of the emissions are shifted from the cars to the refinery. references 1. dixson-decleve s.: global automotive fuel quality trends 4th int. colloquium on fuels, 2003, esslingen, germany, pp. 1-18 2. kašpar j. et al.: automotive catalytic converters: current status and some perspectives catalysis today, 77, 419-449, 2003. 3. babich i. v. and moulijn j. a.: science and technology of novel processes for deep desulfurization of oil refinery streams: a review fuel, 82, 607–631, 2003. 4. song ch. and ma x.: new design approaches to ultra-clean diesel fuels by deep desulfurization and deep dearomatization, applied catalysis b: environmental, 41, 207238, 2003. 5. ma x., sun l. and song ch.: a new approach to deep desulfurization of gasoline, diesel fuel and jet fuel by selective adsorption for ultraclean fuels and for fuel cell applications, catalysis today, 77, 107-116, 2002. hungarian journal of industrial chemistry veszprém vol. 33(1-2). pp. 57-67. (2005) fuzzy association rule mining for data driven analysis of dynamical systems f.p. pach, f. szeifert, s. nemeth, p. arva and j. abonyi* department of process engeneering, university of veszprém, veszprém, egyetem u. 10, h-8200, hungary, www.fmt.vein.hu/softcomp, abonyij@fmt.vein.hu in system identification a key step is to find a suitable model structure. the utilizations of prior knowledge and physical insight about the system are very important when selecting the model structure. in nonlinear black-box modeling no physical insight is available we have “only” observed inputs and outputs from the dynamical system. association rule mining is one of the widely used data mining tools. it finds interesting association or correlation relationships among a large data set. the aim of this paper is to demonstrate that this data mining tool can be effectively applied for the datadriven modeling and analysis of dynamical systems. the detected association rules can be interpreted as simple local input-output models of the modeled process. hence, the analysis of the mined association rules (models) can provide useful information about the structure and the order of the model that can adequately describe the dynamical behavior of the process. in this paper a fuzzy association rule mining algorithm is introduced and a rule-base simplification algorithm is presented for the generation of a set of “rule-based models” that can be directly used as a qualitative model of the system. the general applicability of the developed tool is illustrated by the analysis of the input-output data of a continuously stirred styrene polymerization reactor. the detected association rules is used for the selection of the structure of a linear and nonlinear (neural network) models for this process and determine the most relevant process variables. keywords: process modeling, model structure selection, association rules, rule base systems, polymerization introduction in process modeling the a priori knowledge, experimental data and experiments are crucial. the process of modeling from experimental data is known as system identification by ljung [1]. the main steps of the system identification process are summarized well by petrick and wigdorowitz [2]: 1. design an experiment to obtain the physical process input/output experimental data sets pertinent to the model application. 2. examine the measured data. remove trends and outliers. apply filtering to remove measurement and process noise. 3. construct a set of candidate models based on information from the experimental data sets. this step is the model structure identification. 4. select a particular model from the set of candidate models in step 3 and estimate the model parameter values using the experimental data sets. 5. evaluate how good the model is, using an objective function. if the model is not satisfactory then repeat step 4 until all the candidate models have been evaluated. 6. if a satisfactory model is still not obtained in step 5 then repeat the procedure either from step 1 or step 3, depending on the problem. a key step (step 3) is to find a suitable model structure which is capable of representing the dynamical behavior of the system. therefore effective methods for structure selection are necessary. consider the main aspects influencing the choice of a model structure: what type of model is needed, nonlinear or linear, static or dynamic, distributed or lamped? *correspondence concerning this article should be addressed to j. abonyi (abonyij@fmt.vein.hu) 58 how large must the model set be? this question includes the issue of expected model orders and types of nonlinearities. how must the model be parameterized? this involves selecting a criterion to enable measuring the closeness of the model dynamic behavior to the physical process dynamic behavior as model parameters are varied. large number of model structure selection methods has been introduced. for linear models, for example correlation analysis and multivariate structure selection techniques [3] such as principal component analysis (pca) are proposed. several information-theoretical criteria have been also proposed for the structure selection of linear dynamic input-output models. these methods are based on the minimization of a criterion function which involves the estimation of the one-step-prediction error plus some penalty function. the classical criteria are the final prediction error (fpe), the akaike information criterion (aic) [4], the minimum description length (mdl) criterion [5], the schwarz criterion (bic) [6] and the hannan-quinn criteria (hic) [7]. they only differ on the employed penalty function, but in [8] a new criterion function is introduced based on the decomposition of the variance of the innovations of the model in terms of their frequency components. the information criteria have been used in a context of regression models [9, 10], in distributed lag regression models [11], or in selection of the order an autoregressive and autoregressive moving average model [12, 13, 14]. in paper [15] the effects of the model selection problem, and in paper [16] the variable selection problem are studied. determining the structure of linear systems is a rather straightforward task with these tools, but for nonlinear systems other structure selection methods are need. aguirre and billings [17] defined the concepts of term clusters and cluster coefficients and used in the context of system identification. this approach is used for the structure selection of polynomial models in the paper of aguirre and mendes [18]. in [19] an alternative solution is introduced by initially conducting a forward search through the many possible candidate model terms before performing an exhaustive all-subset model selection on the resulting model. a backward search approach based on orthogonal parameter estimation is also applied to structure selection [20, 21]. the paper [22] discusses several model structures selection methods and nonlinear input-output models that are suitable for implementation of feed-forward neural networks. a systematic method for the selection of model order and time delay is presented in [23]. the method is applied to the neural network modeling of a multivariable chemical process rig. a deterministic suitability measure is introduced in [24] that quantifies the capably of a particular model class to capture the control relevant i/o-behavior of a nonlinear system. this suitability measure can be used for the purpose of model structure selection prior to the actual parameter identification. the fast bootstrap (fb) methodology to select the best model structure is presented in [25]. the methodology is applied to a regression task. in [26] a methodology for model structure selection based on a genetic algorithm was introduced and applied to nonlinear discrete-time dynamic systems. a modified genetic programming approach for model structure selection is introduced in [27]. it is combined with a classical technique for parameter estimation. hong and harris [28] introduced a learning algorithm for model subset selection which based on a new composite cost function that simultaneously optimizes the model approximation ability and model adequacy. in [29] a cost functional is evaluated for each identified model and the model with minimum cost is preferred. suboptimal search strategies are adopted, forward and stepwise strategies are considered. we introduce in this paper a new data-driven structure selection method. the new method is based on fuzzy association rule mining and it is called mossfarm (model structure selection by fuzzy association rule mining). association rule mining finds interesting association or correlation relationships among a large data set. the problem of mining association rules was introduced over supermarket basket data in [30]. it helps to learn more about the buying habits of the customer. it gets information and answers for the market questions. but the market basket analysis is just one application of association rule mining this paper presents a new application area, the model structure selection. this paper is organized as follows. the first section introduces the system identification problem in nonlinear black box modeling. association rule mining theory is presented in the second section. in third section the fuzzy association rule mining is detailed. our new method based on fuzzy association rule mining is introduced in the fourth section. the last fifth section illustrates how the mossfarm method select the most important model structures of a linear (least square method) and a non-linear (neural network) model of a styrene polymerization cstr. system identification in nonlinear black box modeling to be successful the entire modeling process should be given as much information about the system as is practical. the utilization of prior knowledge and physical insight about the system are very important, but in nonlinear black-box situation no physical insight is available, we have “only” observed inputs and outputs from the system. this paper concentrates on structure selection task in case of the black-box modeling. 59 in a system identification problem in case of black-box modeling [31] we have only input, and output, data from the process (system), ku ky (1) [ kk uuu ,,21 k=u ] (2) [ ]kk yyy ,,21 k=y we are looking for a relationship between past observations and future outputs, ],[ 11 −− kk yu , (3) kkkk efy += −− ),( 11 yu where represents an error value, because will not be an exact function of past data. however, a goal must be that is small, so that we may think of function as a good prediction of . ke ky ke (.)f ky eq. 3 models general discrete time dynamic systems, but nonlinear static processes can be also represented by the following regression model: (4) )( kk fy x= the is a non-linear function, represents its input vector and denotes the k-th input-output data. the model regression vector in a narx (non-linear auto-regressive models with exegoneus inputs) model contains the past values of the process outputs and the process inputs as regressors: (.)f kx nk ,,1k= kx ky ku t nkkkmkkkk uuuyyy ],,,,[ ,2,12,1 −−−−−−= kkx (5) the m determines the number of past outputs and n represents the past inputs (model order). while the output of the regression model, is the one-step-ahead prediction of the process. this siso form of the narx models could be extended to the mimo case. ky association rule mining one of the widely used research tasks in data mining is the discovery of frequent item sets and association rules. the problem originates in market basket analysis which aims at understanding the behavior of retail customers, or in other words, finding associations among the items purchased together. a famous example of an association rule in such a database is “diapers => beer”, i.e. young fathers being sent off to the store to buy diapers, reward themselves for their trouble. because of the practical usefulness of association rule discovery, this approach can be applied in various research areas. how can we search association rules? the association rule mining is based on frequent item set searching. an item could be for example one product in the supermarket example, e.g. {beer}, and an item set is a set of items (products), e.g. {milk, beer, diapers}. the occurrences of an item (item sets) in a data set are called support. the support value of an item (item set) could be seen as a probability value. the support gives in how many percent of the transactions is the item (are the items of an item set together)? be the x an item set, the support value of x is calculated as follows: nstransactio of with nstransactio of # #)()supp( xxpx == (6) an item x (or the item set x) is called frequent item (item set) if its support is higher than a given (user defined) threshold, namely the minimal support (σ ). see table 1 which includes an example supermarket transaction data set, where each row represents a transaction. the first column contains the transaction number (tid transaction identifier) and in the second column the purchased products are listed in the transaction. table 1 example transaction data set tid items 1 bread, milk 2 beer, bread, diaper, eggs 3 beer, coke, diaper, milk 4 beer, bread, diaper, milk the frequent item set searching is a very easy task for this example data set, because the number of transactions is only four. if the minimum support is equal to 50 percent (σ = two occurrences), we can search all the frequent items and item sets, e.g. a frequent item is the {milk} (with 75 % support), or a frequent item set is the {diaper, beer} (with 75 % support). but if we have a large data set (database) with many transactions and several items the frequent item set searching demands to use an efficient algorithm. a widely used frequent item set searching algorithm is the apriori algorithm (was introduced in [30]). the name of algorithm is based on the fact that the apriori uses prior knowledge of frequent item sets already determined. it is an iterative, breadth-first search algorithm, based on generating stepwise longer candidate item sets, and clever pruning of non-frequent item sets. pruning takes advantage of the so-called apriori (or upward closure) property of frequent item sets: all subsets of a frequent item set must also be frequent. each candidate generation step is followed by a counting step where the supports of candidates are checked and non-frequent ones deleted. generation and counting alternate, until at some step all generated candidates turn out to be non-frequent. if we searched all the frequent item sets by the apriori algorithm, we can generate association rules from them. an association rule has two parts: the rule antecedent 60 (denoted by x) and the rule consequent (denoted by y), and both of them contain items. therefore an association rule is represented by the form x => y. from a frequent item set we can generate all the possible rules. each item and sub item set could be placed in both parts of a rule. in the previous example, we can generate six rules from the frequent item sets {beer, bread, diaper} (see the possible rules in figure 1). fig.1 example for association rule generating it is very important to know which association rules are well usable, namely which gives the most information about the data. two basic measures are used to calculate how “important” an association rule. first one is the previously defined support measure. the support of an association rule is the support of the set of its items. for example, the support of the rule “{bread, diaper} => {beer}” is equal to the support of the item set {beer, bread, diaper}. the second one, the confidence measure of a rule is calculated as follows: )supp( )supp()( x yxyxconf ∪ ==> (7) because the confidence measure is a conditional probability (the quotient of the rule and antecedent supports) it serves information about the relationship of the antecedent and consequent parts of a rule. a rule x => y is called important, or strong rule if its support and confidence are higher than the minimum support (σ ) and the minimum confidence thresholds ( γ ). the confidence is a basic rule interestingness measure, but many other measures are also can be used to determine the importance and ordering the mined rules (e.g. ri – rule interesting, lift, correlation, jaccard, piatetskyshapiro, etc. measures). the number of the possible association rules is very high in case of an item set with many elements (e.g. if ten items are in an item set, the number of possible rules is ). therefore it is well worth using the antimonotonic feature. for generating of the (n-1)-large rules we can use in the previous step selected frequent (n)-large rule. for example be the z a frequent item set. the following two association rules are generated from z: 1) x => z \ x and 2) x => z \ x, where . if the first rule does not fulfil the support criteria, the second rule is also can not to be frequent. 2210 − xx∈ the importance of an association rule can be determined not only by objective way. the determination can be also subjective. the users can add the “right” form of the rules. suppose that a user wants to search only rules with a distinguished item in consequent part. for example be this item a productfamily, books. in this case, only the rules where a book is placed in the consequent part will be strong rules. to increase the usability of the association rule, fuzzy association rules are proposed. in the next section, the basic definitions of fuzzy association rule theory are presented. fuzzy association rule mining the fuzzy association rules can be discovered in also two steps as we showed in crisp case: 1) mining frequent item sets, and 2) generating fuzzy association rules from the discovered set of frequent item sets. a dataset (database) includes records (data rows) via the data fields (columns). the fields are frequent called as attributes. because in fuzzy association rule theory the items are fuzzy sets, a partition method is necessary which transforms the crisp data set into fuzzy data set for all attributes. for the numerical attributes (as for example the temperature, pressure, etc.) of the data set, fuzzy sets can be defined with gaussian, sigmoid, or piecewise linear fuzzy dichotomies. therefore triangular, trapezoidal type of fuzzy sets (intervals) can be used for data partition. see the figure 2 for an example, where the attributes and are partitioned by two-two trapezoidal fuzzy sets. 1z 2z fig.2 a fuzzy partition of data space ( , ) 1z 2z let be a transformed (partitioned) fuzzy dataset of n tuples (data records ~ data points) with a set of attributes },,,{ 21 ntttd k= },,,{ 21 qzzzζ k= and let be an arbitrary fuzzy interval (fuzzy set) associated with attribute in z where q denotes the number of attributes. from this point, we use the notation jic , iz jii cz ,: for an attribute-fuzzy interval pair, or simply 61 fuzzy item. an example could be youngage : . for fuzzy item sets, we use expressions like cz : to denote an ordered set of attributes (ζ⊆z ζ denotes the set of the all possible attributes) and a corresponding set of some fuzzy intervals, one per attribute, i.e c ]:::[: ,,, 2211 jiijiijii qq czczczcz ∪∪∪= k . in the literature, the fuzzy support value has been defined in different ways. some researchers suggest the minimum operator as in fuzzy intersection, others prefer the product operator. they can be defined formally as follows: value for attribute , then the fuzzy support of )( ik zt iz 2: cz with respect to d is defined as n zt czfs n k ikczcz jii ∑ λ = = ∈1 :: )( ):( , (8) where the is an operator set. in this paper we prefer the product form. a fuzzy support reflects how the record of the identification data set support the item set. a fuzzy item set },{min, kπ=λ cz : is called frequent if its fuzzy support value is higher than or equal to a user-defined minimum support (σ ). the following example illustrates the calculation of the fuzzy support value. let ]high : income medium : balance[: u=ax be a fuzzy item set and the example dataset is shown in table 2. table 2 example database containing memberships the fuzzy support of ax : is calculated as follows: 0.3367= ⋅+⋅+⋅ = 3 7.07.04.08.04.05.0):( axfs since the rules are generated from the frequent item sets, the generation of fuzzy association rules becomes relatively straightforward. more precisely, each frequent item set cz : is divided into the consequent by : and antecedent ax : , where and . with the use of this notation a fuzzy association rule can be represented in the form of caxzyzx ⊂−=⊂ ,, acb −= if x is a, then y is b, (9) or in more compact form, byax :: ⇒ . (10) a fuzzy association rule is considered strong if its support and confidence exceeds the given minimum support (σ ) and minimum confidence ( γ ). since the rules are generated from frequent item sets, they satisfy the minimum support automatically. the fuzzy confidence of a fuzzy association rule byax :: ⇒ is defined as ):( )::( )::( axfs byaxfs byaxfc ⇒ =⇒ (11) and it is a conditional probability of the parts of the rule: ( )axbyp :|: . fuzzy association rules mined using the above fuzzy support-confidence framework are useful for many applications. however, a rule might be identified as interesting when, in fact, the occurrence ax : does not imply the occurrence of by : . the occurrence of a fuzzy item set ax : is independent of the item set by : if b), : fs(y a) : fs(x c) : fs(z ⋅= otherwise item sets ax : and by : are dependent and correlated as events. the correlation between the occurrence of ax : and by : can be measured by computing the interestingness of a given rule: ( ) ):():( ):(:,: byfsaxfs czfsbyaxfcorr ⋅ = (12) balance: med. credit: high income: high 0.5 0.6 0.4 0.8 0.9 0.4 0.7 0.8 0.7 if the resulting value of eq. 12 is less than one, the occurrence of ax : is negatively correlated with the occurrence of by : . if the resulting value is greater than one, ax : and by : are positively correlated. it means the occurrence of one implies the other. if the resulting value is near to one, then ax : and by : are independent and there is no correlation between them. after the review of basics of association rule mining, the next section presents how use the fuzzy association rules for model structure selection. mossfarm model structure selection by fuzzy association rule mining since in the previous section all of the necessary definitions and methods to mine fuzzy association rules were considered, this section will focus on the main steps of our method that are needed to solve the studied model structure (order) selection problem in case of narx model. 62 suppose that we have only measured input-output data from a siso process. in a narx model of the process, from this i/o data set we can construct a regression vector from each input-output data pairs by the following way, similar for eq. 5: nk ,,1k= t nkkkmkkkk uuuyyy ],,,,[ ,2,12,1 −−−−−−= kkx where the past values of the process outputs and the process inputs are the regressors. the number of past inputs (n) and past outputs (m) are often referred to as model order. ky ku the question is how to select the right model order? an answer could be our method, the mossfarm. the method consists of the following five steps: 1) generate a fuzzy database 2) mine frequent fuzzy item sets 3) generate fuzzy association rules 4) prune the fuzzy rule base 5) aggregate the mined rules, select the model structure step 1) observed (measured) input-output data are general crisp values. in the first step the “attributes” (regressors in the regression vector) need to partition to get fuzzy valued data set. the fuzzy gustafson-kessel (gk) [33] clustering algorithm partitions the initial data on every attribute (dimension of data ~ all the candidate regressors). the resulted membership functions are transformed into trapezoidal membership functions (see an example in fig. 4 where on two attributes are four and three fuzzy sets, respectively). 0 0.5 1 0 0.5 1 0 0.5 1 0 0.5 1 0 1 1 fig.4 trapezoidal membership functions step 2) the resulted fuzzy data set includes the membership function values of each data points on each attributes, and the index of fuzzy set which give the highest membership value for the data point in a given attribute. these indices can be the items and the set of them are the item sets. the frequent item set searching is based on a fuzzy implementation of the apriori algorithm. the fuzzy support values are calculated as the eq. 8 shows. step 3) the mined frequent item sets are the base of fuzzy rule generation step. every fuzzy rules are generated, but only the rules with high support (fs > σ ) and confidence (fc > γ ) values are the relevant rules. the fuzzy support and confidence values are calculated as the eq. 8 and 11 show. the interesting value of the rules are determined by the correlation factor (fcorr, calculated by eq.12). step 4) the advantage of the application of the correlation measure for the analysis of the quality of the rules is that it is upward closed. based on this, a rule based pruning algorithm has been developed that removes the unnecessarily complex rules. such rules contain input variables that do not significantly improve the correlation of rules. step 5) we have to analyze the mined association rules to determine model structures. the rules where the first indices of the fuzzy sets are equal in the antecedent parts, give identical model structures. therefore it is necessary to aggregate the support, the confidence, and the correlation measures of these individual rules. after the aggregation the given model structures must be ordered by the correlation (calculated by eq. 12) measure (or by other rule interesting measures) and accordingly the first structures will be the most interesting structures of the models. in the next section an application study is showed to illustrate how this method determines the structures of the models for a dynamic system and selects the most relevant process variables. application study model of styrene polymerization cstr the data-driven modeling of styrene polymerization in a continuously stirred tank reactor is considered as a case study to demonstrate the applicability of the proposed method. the schematic diagram of the polymerization process is shown in fig. 5. qm cmf tf qc qt ci cmt tc tc ci qs qi cif tf tf cm t tcf qm cmf tf qc qt ci cmt tc tc ci qs qi cif tf tf cm t tcf fig.5 scheme of the styrene polymerization cstr with a cooling jacket on figure 5, , , , denote the monomer flowrate, the monomer feed concentration, the feed mq mfc ft mc 63 temperature, and the monomer concentration, respectively. the solvent flowrate is represented by , while , , are the initiator flowrate, the initiator feed concentration, and the concentration of the initiator in the reactor, respectively. , and are the coolant feed temperature, the coolant flowrate, and the coolant temperature. the total flowrate is denoted by and t is the reactor temperature. the initiator is azobisisobutyroitrile (aibn) dissolved in benzene, while the monomer is styrene and the solvent is benzene. sq iq ifc ic cft cq ct tq for the simulation of this system the model of hidalgo and brosilow [33] is applied: id ismiifii ck v cqqcq dt dc − +− = )( q+ (13) gpmp msmimfmm cck v cqqqcq dt dc − ++− = )( (14) )( )( ))(( c p gpmp p fsmi tt vc au cck c hr v ttqqq dt dt −− − + −++ = ρρ (15) )( )( c pc ccfcc tt vc au v ttq dt dt −+ − = ρ (16) ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ = t id gp k cfk c 2 (17) where represents the concentration of the growing polymer. gpc the dimensionless model and its nominal parameter values are detailed in [34]. the dynamical behavior of this dimensionless model is illustrated in figure 6, where the coolant flowrate (qc) is considered as an input variable. the steady-state input-output relationship of qc and the reactor temperature (t) confirms the nonlinear behaviour of the model (see figure 7). suppose we have only input output simulated data taken from the above cstr model, and we want to identify a linear arx or a neural network based narx model with some model structure. to determine (select) the structure of these models the proposed fuzzy association rule based method will be followed in the next session. 0 50 100 150 200 250 300 0 0.005 0.01 c i 0 50 100 150 200 250 300 0 0.2 0.4 c m 0 50 100 150 200 250 300 0 1 2 3 tr 0 50 100 150 200 250 300 -1 0 1 tc 0 50 100 150 200 250 300 0 5 q c time fig.6 dynamical behavior of the dimensionless model of the styrene polymerization reactor 0.2 0.6 1 1.4 1.8 2.2 2.6 0 1 2 3 4 5 6 coolant flowrate (qc) re ac to r t em p. (t ) fig.7 steady-state input-output relationship of the coolant flowrate and the reactor temperature model structure selection by mossfarm a siso narx model of the previous system is considered where the output of model (y) is the reactor temperature, and the input (u) is the coolant flowrate. the maximal number of lagged inputs and outputs is four-four, therefore the more complex model is: ]),,,([ 4,,14,,11 −−−−+ = kkkkkkk uuuyyyfy kk (18) if the original (the full, see eq. 18) model structure is used for a linear and a neural network (nn) based model, the mean square error (mse) values are 0.00047 and 0.00008, respectively. in the linear model least square method is used. at the nn model the number of regressors in the structure is used for set the number of neurons in input, hidden and output layers (e.g. for the structure [yk, yk-1, yk-2, yk-3, uk] input: 5, output: 1, hidden: 3). the applied learning method was the backpropagation method. the structures with highest correlation factor (selected by mossfarm with σ =1 %, γ = 95 %) are listed in table 3. 64 table 3 the selected model structures # structure fs fc fcorr 1. yk, yk-1, yk-2, yk-3, uk 8.1 96.3 822 2. yk, yk-1, yk-3, uk 8.2 95.9 819 3. yk, yk-2, yk-3, uk 8.2 95.7 817 4. yk, yk-1, yk-2, yk-3, uk-1 8.7 95.3 814 5. yk, yk-3, uk, uk-2, uk-3 8.3 95 811 table 4 shows the selected model structures for several minimal support and confidence conditions. the selected model structures (e.g. in table 3) can be used to identify the linear and the nn model. table 4 the selected model structures for several searching condition (support, confidence) σ γ best structure 1 95 yk, yk-1, yk-2, yk-3, uk 1 80 yk-3, uk 1 70 yk, yk-1, yk-3, uk, uk-2 1 60 yk, yk-1, yk-2, yk-3, uk, uk-1 1 50 yk-1, yk-3 uk, uk-1, uk-2, uk-3 5 50 yk, yk-3, uk 8 60 yk, yk-3, uk 3 70 yk, yk-3, uk the results are showed in figures 8-11. we can see that the nn model gives lower mse values in all cases. the mse values are lower at the using of first structures as the other structures in both model (linear and nn). the resulted mse values are higher than the original (the full) structures, but the differences are not considerable and these structures are smaller than the original model structure. therefore mossfarm can be an efficient method for determining the model structure for inputoutput models. 0.00040 0.00050 0.00060 0.00070 0.00080 0.00090 1 2 3 4 5 structure # m se fig.8 the mse values for the linear model with the selected model structures 0.00004 0.00009 0.00014 0.00019 0.00024 0.00029 1 2 3 4 5 structure # m se fig.9 the mse values for the nn model with the selected model structures 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 -0.2 0 0.2 0.4 0.6 0.8 1 1.2 y(k) data ym (k ) li ne ar m od el fig .10 the linear model output values ym(k) in function of the simulated output values y(k) 65 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 y(k) data ym (k ) n n m od el fig.11 the nn model output values ym(k) in function of the simulated output values y(k) table 5 the effects of the rule pruning step original r. base pruned r. base first structure yk, uk, uk-1, uk-2, uk-3 yk, yk-3,uk rules 714 27 conditions 3157 77 mse of lin. 0.001 0.0008025 mse of lin. free 0.0352 0.0141 mse of nn 0.00039197 0.00030913 mse of nn free 0.03 0.0093 table 5 shows the results of the rule base complexity analysis. the searching conditions were followings:σ = 3 %, γ = 90 % for the original simulated (with the regressor in eq. 18) data. the rule pruning step give smaller, but well usable model structures both in linear and nn models. the pruned rule base has 97.56 percent less complexity than the original rule base and lower mse values. if the structures are ordered by the number of aggregated rules, the first structures are the yk, yk-1, yk-2, uk-1, uk-2 (with the original rule base), and the yk, yk-3,uk (with pruned rule base, all other searching parameters are equal as was in case of table 5). for the structure yk, yk-1, yk-2, uk-1, uk-2 the mse values of the linear and the nn model in the case of free running are 0.0223, 0.0192 respectively (the results are depicted in fig. 12 and fig. 13). for structure yk, yk-3,uk lower mse values are resulted: 0.0141 at free running of linear model and 0.0174 at free running of nn model. 0 200 400 600 800 1000 1200 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 linear input-output modell (free run) y: output ym: modell output (free run) fig.12 results of the free run of linear model for yk, yk-1, yk-2, uk-1, uk-2 structure 0 200 400 600 800 1000 1200 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 neural network modell (free run) y: output ym: modell output (free run) fig .13 results of the free run of neural model yk, yk-1, yk-2, uk-1, uk-2 structure feature (variable) selection by mossfarm the proposed method also can be used for select the most relevant variable which determine the output variable. the four state dimensionless form of the model hidalgo and brosilow could be extended with the dimensionless moment equations. a new dataset is based on the simulation of this extended dimensionless model with six state variables. the dimensionless number-average molecular weight (namw) is the ratio of the last two state variables of the model [35]. the relevant variables which determine the value of the namw are selected by the mossfarm method. the new initial model structure is: ]),([ 7,,211 kkkk xxxfy k=+ (19) where the dimensionless variables are the following: y : model output namw, x1 : the initiator concentration, x2 : monomer concentration, x3 : reactor temperature, x4 : jacket temperature, x5 : the first variable in the moment equations, x6 : the second variable in the moment equations and x7 : cooling jacket flowrate. if the searching conditions were the followings: number of 66 partitions (~ clusters) for the output variable: 5, the number of partitions in the regressor variables: 3, σ = 10 %, γ = 50 %, the mossfarm selects the structure x1k, x3k (“aggregated” from one rule) as first (ordered by the correlation). this result says that the initiator concentration and the reactor temperature determine the number-average molecular weight. if the ordering is based on the number of aggregated rules, the first selected structure is the x6k, x7k. (aggregated from two rules). the results are summarized in table 6. table 6 linear and nn model for estimate number-average molecular weight ordering by corralation ordering by rule number first structure x1k, x3k x6k, x7k mse of lin. 0.0103 0.0049 mse of lin. free 0.0106 0.576 mse of nn 0.0001723 0.000416 mse of nn free 0.2080 0.576 conclusions this paper showed a new model-free, fuzzy association rule mining based method for model structure selection for input-output data-driven models. the results show that the developed tool provides an efficient method for determining the model structure of both linear and neural network based input-output models. moreover this method is also can be used to selection of the most relevant process variables (feature selection problem). the proposed approach has been implemented as a matlab program called mossfarm (model structures selection by association rules mining), it will be free available from: www.fmt.vein.hu/ softcomp. acknowledgement this 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operating points, comp. chem. eng., 1990, 14, 481-494 34. russo l. p. and bequette b. w.: operability of chemical ractors: multiplicity behavior of a jacketed styrene polymerization reactor, chem. eng. science, 1998, 53 (1), 27-45 35. rendszergazda rectangle microsoft word a_01_r.doc hungarian journal of industrial chemistry veszprém vol. 38(1). pp. 1-7 (2010) expanding feedstock supplies of the second generation bio-fuels of diesel-engines p. baladincz, cs. tóth, j. hancsók department of hydrocarbon and coal processing, university of pannonia h-8201 veszprém, p.o. box 158., hungary e-mail: hancsokj@almos.uni-pannon.hu nowadays the first generation bio-fuels are already introduced in the european union and amongst them the one used in diesel-engines is the triglyceride containing feedstock derived product, the so-called biodiesel. however these fatty-acidmethyl-esters have multiple disadvantages (e.g.: poor oxidation and heat stability, lower energy content than the fossil derived diesel fuels, etc.) because of their chemical structure. therefore it has become necessary to develop new bio-derived fuels on triglyceride supply, with other chemical structure. these bio-derived fuels are the second generation bio-fuels and amongst them the most promising product is the bio gas oil. the bio gas oil is a mixture of nand i-paraffins (these are the primal components of the fossil diesel fuels also) in the gas oil boiling point range made from triglyceride containing feedstock. to ensure the eligible quantity and quality of bio gas oils, it is necessary to examine the utilization of other feedstocks with high triglyceride content. the european union also urges the expanding of the feedstock supplies of the bio-derived motor fuels [com(2006)34]. during our experimental work we examined the possibilities of the catalytic hydrogenation of mixtures of gas oil and lard or vegetable oil respectively, on nimo/al2o3 catalyst. besides the examination of the reaction parameters (temperature: 360 °c, pressure: 80 bar, lhsv: 1.0 h-1 , h2/feedstock ratio: 600 nm3/m3) which were found to be congenial for the catalytic conversion of vegetable oils for the conversion of the different, respectively lard or vegetable oil containing (0–10–20–30–50–100%) gas oil feedstocks we investigated the convertibility of the triglyceride part and the effect of the feedstock on the quality and the quantity of the product, furthermore the effect of the triglyceride in the feedstock on the desulphurisation, denitrification and dearomatisation. we determined that in the case of respectively 10% vegetable oil or lard containing feedstocks, the product was already an excellent bio-constituent containing diesel fuel blending component. keywords:, bio gas oil, lard, sunflower oil, bio-derived blending component, catalytic co-processing introduction mobility is a keystone of great importance in the modern human society. it is essential for maintaining and developing the economy and thus the standard of living, and for meeting the social demands. the material equipment of mobility is the vehicles, nowadays almost every one of them (>97%) operates with fossil derived fuels. the limited amount and the unequal distribution of the available oil reserves is a source of international tensions, therewith to ensure the life standard of their citizens, most countries rely on import. besides, there are more and more vehicles, so to ensure the mobility means more and more intense environmental pollution. for this reason, on the whole world research has started for the development and utilization of cleaner and more available energy sources. among these alternative fuels, there are the renewable, agricultural-derived fuels from biomass and amongst them the bio-derived motor fuels (agro-motor fuels) [1, 2, 3]. bio-derived motor fuels in the european union because of environmental consideration and its intense rely on import energy sources (>55%) the european union treats the research of agriculture-derived, renewable energy sources with great attention and urges their utilization in greater volumes [4, 5, 6]. the 2003/30/ec directive is the first where the european union literally declared the necessity of the production of bio motor fuels and their extensive utilization [4]. as an effect of this, the diesel fuel standards validated from 2004 allow the blending of bio-components (biodiesel maximum 5 v/v%, then 7 v/v% from 2009). the european council in the com(2006) 34 strategy of the union announced seven political keystones and one of them is the effort to expand the feedstock supplies of bio motor fuels [5]. besides this, the european union in the com(2006)845 report specified those steps which must be taken in the interest to increase the 1% share of bio-derived automotive fuels to 10% till 2020. 2 in this report it was determined that the research and development of the second generation bio motor fuels could help to boost the innovation and to preserve the competitiveness of the european union in the renewable energy sector, and also, with the partial utilization of the second generation bio motor fuels it becomes achievable to increase the share of bio motor fuels to 10% till 2020 [6]. in the 2009/28/ec directive of the european union, the european council confirmed the content of the com(2006)845 report, namely that the average share of the renewable energy sources must be raised to 20% until 2020, and in it the average content of renewable fuels must be raised to 10% in all automotive fuels in the european market until 2020. besides, it affirms that the suggested blending amount of bio fuels must be set at minimum 5.75% until 2010 calculated on the basis of the energy content [6]. to suit the valid 2009/28/ec directive, the valid diesel fuel standard also changed. therefore in the currently valid en 590:2009+a1:2010 diesel gas oil standard the blendable amount of biodiesel was increased from 5 v/v% to 7 v/v%. thus the suggested blending amount – 5.75% until 2010 – urged by the european committee became achievable. among the motor fuels, the use of diesel-fuels decreased at present as a consequence of the worldwide economic crisis, but the long-distance tendency shows increase such as the total use of motor fuels increases and within it the share of the middle distillates increases. the tendency of the automotive fuel market in the european union – before the worldwide economic crisis – showed a probable increase in the demand [7] for diesel fuels. therefore the research and development of the agriculturederived bio motor fuels is coming to the front. triglycerides and their derivatives the main constituents of the vegetable oils and animal fats are the triglycerides, which are esters of a polyvalent alcohol, the glycerine, and fatty acids with different carbon number (fig. 1 and 2). since they are natural triglycerides, their carbon number of the chain is always paired and they contain unsaturated bonds in different measure. for the sake of satisfying the continuously increasing gas oil demand, vegetable oils and their different percentage mixtures with gas oil are attempted to be utilized. however the differences between the physical and utilization properties of the vegetable oils and the conventional diesel fuels do not permit to simply replace the conventional gas oils with vegetable oils [1, 2, 3, 8]. therefore it is necessary to convert them with different conversion pathways. these conversion pathways can be: ● thermal and ● catalytic pathway. in practice, the more important is the latter one. from these types of conversions the most important ones are the esterification (specifically esterification with alcohols) and the hydrogenating with motor fuel purpose. biodiesel nowadays, the agriculture-derived bio motor fuel and bio blending component that is produced and utilized in the greatest volume is the biodiesel from the first generation biofuels. this is made by the catalytic esterification of vegetable oils and other fats (fig. 1) [1, 2, 3, 9]. triglycerides (e.g.: vegetable oils, animal fats) glycerine fame (fatty-acid-methyl-ester) methanol catalyst figure 1: the reaction pathway of the esterification of an average triglyceride molecule (vegetable oil) (r1, r2, r3: carbon chains with c11-c23 carbon number) however the technologies producing biodiesel and the product itself also have numerous disadvantages [1, 2, 3, 9]: ● high unsaturated content (causing bad thermal-, oxidation-, and thus storage stability), ● high water content (corrosion problems) ● sensitivity to hydrolysis (poor storage stability), ● methanol content (toxic), ● reactive oh-group (corrosion of coloured metals), ● low energy content that results in greater fuel consumption (~10-15%), ● unfavourable cold properties (cold-start and pulverizing, cfpp). bio gas oil the most suitable for the utilization in diesel engines and the most valuable compounds of the fossil derived gas oils are the normaland iso-paraffins with high cetane number and with good cold flow properties. [1, 2, 3, 10, 11, 12, 13, 14], therefore intense research has started to produce products with similar chemical structure on triglyceride (as a renewable agriculturederived feedstock) base. one of the alternatives to produce such a product rich in iso-paraffins on triglyceride base is the catalytic hydrogenation and if necessary, their isomerization. then the conversion of triglycerides to a product rich in iso-paraffins is recommended by multistage catalytic process (fig. 2). through the reaction pathway, in the first step the hydrogenating of the unsaturated bonds of the triglycerides takes place. then deoxygenating reaction occurs. in this reaction, monoglycerides and carboxylic acids form and then these intermediates are converted to paraffins by three different pathways: decarboxylation, decarbonylation and hydrodeoxigenation (reduction, hdo). as the next possible step in the process isomerization reactions can occur, of which measure 3 depends on the applied catalyst and process parameters. cracking reactions may occur in the course of the whole process [3, 10, 11, 12, 13, 14]. catalyst hydrogen, t, p n-parraffins i-parraffins oxygen containing compounds byproducts:vegetable oil (triglycerides) co + co2 + ch4 + c3h8 + h2o figure 2: the reaction pathway of the bio gas oil production (r1,r2,r3: carbon chains with c11-c23 carbon number) the product of the reaction is the so called bio gas oil, of which concept was introduced by the mol department of hydrocarbon and coal processing of the university of pannonia [3, 12, 13]. according to its definition, the bio gas oil is a mixture of nand i-paraffins in the gas oil boiling point range, made with specific catalytic hydrogenating process of raw materials with high triglyceride content (vegetable oils, fats, used frying oils, etc.). to produce bio gas oil and products containing it, there are different technological methods according to our experiments and the literature data. it is possible to pre-treat the triglyceride containing feedstock in a pretreater reactor and then hydrodeoxygenate it, in other words convert it in a second hdo reactor. the obtained product in this technology is rich in normal-paraffins, has very high cetane number but besides it, the product needs to be isomerized after the separation to improve its poor cold flow properties. the bio gas oil obtained with such technology can be blended to deeply desulphurized gas oil stream and thus gas oil with bio-component content can be made. beyond that, through blending the pre-treated triglyceride containing feedstock to a straight run gas oil stream and process this feedstock mixture in an existing (or slightly modified) desulphurization plant, bio-component containing gas oil can be obtained [11, 12, 13, 14, 15]. experimental during our experimental work our aim was to expand the feedstock supplies of the bio gas oils. in the course of it, the possibility of processing the lard as an agriculture-derived, renewable feedstock was investigated to make a product which can be utilized in diesel-engines by itself or as a bio-blending component to conventional gas oils. therefore we investigated the possibilities of heterogeneous catalytic conversion of 0%, 10%, 20%, 30%, 50%, 100% lard or sunflower oil containing gas oil feedstock, respectively, on nimo/al2o3 catalyst. the process parameters were chosen on the basis of our previous experimental results considering the physical and chemical properties of the feedstocks. experimental equipment the experiments were carried out on experimental equipment with a tubular reactor of 100 cm3 active volume capacity. the experimental work was carried out in continuous mode. the equipment contains all of the main apparatus of a heterogeneous catalytic hydrogenation plant [15]. applied feedstocks and catalyst as the base stock of the heterogeneous catalytic hydrogenating experiments we used lard and sunflower oil (fatty acid composition is in table 1) of hungarian origin and straight run gas oil stream – derived by mol plc. – obtained from russian crude. as feedstocks we used 0%, 10%, 20%, 30%, 50%, 100% mixtures of gas oil and lard or sunflower oil, respectively. table 1: the typical fatty acid composition of the applied lard and sunflower oil fatty acid lard (l) sunflower oil (so) c12:0 1.70 0.00 c16:0 26.00 0.09 c16:1 2.30 6.33 c18:0 16.50 3.45 c18:1 36.60 21.64 c18:2 11.30 67.28 c18:3 0.70 0.09 c20:0 0.20 0.23 c20:1 0.80 0.13 c22:0 0.20 0.72 other 3.60 0.04 *cx:y, where x: carbon number of the fatty acid, y: number of the unsaturated bonds in the fatty acids. **other – fatty acids with higher carbon number than c22 in the case of pure sunflower oil and lard, the sulphur content of the feedstock was adjusted to 1000 mg/kg with the use of sulphur containing chemical (dimethyldisulphide) in the interest of preserving the sulphide state of the catalyst, otherwise, the sulphur content was covered by the gas oil part. table 2: the heteroatom and aromatic content of the feedstocks properties gas oil l so sulphur content, mg/kg 10370 20 3 nitrogen content, mg/kg 228 61 9 aromatic content, % 33.0 poliaromatic content, % 12.7 0.0 0.0 as catalyst we applied in-situ sulphided nimo/al2o3 catalyst which was chosen on the basis of our previous experimental results. 4 process parameters the series of experiments were carried out at process parameters based on previous experimental results: t: 360 °c, p: 80 bar, lhsv: 1.0 h-1, h2/feedstock ratio: 600 nm3/m3. by applying these process parameters high triglyceride conversion with high selectivity can be achieved [16], the dearomatization efficiency of the catalyst reaches its maximum at 350–360 °c [17], the desulphurization and denitrification activity of the catalyst is high too, while its hydrocracking activity is very low [17]. analytical methods the properties of the feedstocks and the products were specified according to the specifications of the valid en 590:2009+a1:2010 diesel fuel standard, and with standardised calculation methods. the obtained liquid organic product’s composition was identified by gas chromatography. obtaining the main product the fractionating of the product mixture was carried out as it can be seen in fig. 3. in the course of the experiments, the product mixture was separated into gaseous and liquid phase in the separator unit of the experimental equipment. after separating the water from the obtained liquid product mixture, we separated the light, c5-c9 hydrocarbon products by distillation up to 180 °c from the organic liquid phase. their amount was negligible in each case (less than 0.1% compared to the feedstock). the fraction above the boiling point of 180 °c was separated to gas oil boiling point range main product (c10-c22 hydrocarbons up to the boiling point of 360 °c) and to residual fraction by vacuum-distillation. product mixtures gas phase (co, co2, c3h8, c3h6, c1-c4 hydrocarbons h2s, nh3) water phase organic phase (c5+) light hydrocarbons (c5-c10) gas oil fraction (180-360°c) residue (triglycerides , diglycerides , monoglycerides , hydrocarbons with higher carbon number , carboxylic acids , esters) figure 3: the method of the product fractionating results and discussion the gaseous phase contained carbon-oxides formed during the deoxygenation, propane originated from the triglyceride molecule, hydrogen sulphide and ammonia formed in the course of heteroatom removal and a very small amount of lighter hydrocarbons (c4–) originated from the hydrocracking reactions. the latter one shows the low hydrocracking activity of the applied catalyst. as it can be seen in fig. 4, the yield of the gas oil boiling point range main product fraction decreased with increasing the triglyceride content of the feedstock, because in the course of the catalytic hydrogenating of the triglycerides, a large amount of propane and water forms too. in the case of lard containing feedstocks the yield of the main fraction decreased with the increasing lard content of the feedstock compared to the feedstocks containing sunflower oil. the cause of this was partially the higher oxygen content of the lard, which is the consequence of the lower carbon number fatty acids in the lard. besides this, the lard contains fatty acids with higher carbon number than c22 which are not in the boiling point range to 360 °c (boiling point of n-c24: 391 °c). 70 75 80 85 90 95 100 0 10 20 30 40 50 60 70 80 90 100 triglyecride content of the feedstock, % y ie ld o f t he g as o il bp . r an ge m ai n pr od uc t fr ac tio n, % lard sunflower oil figure 4: the yield of the gas oil boiling point range main product as the function of the triglyceride content of the feedstock the yield of the residual fraction (fig. 5) shows that to 50% sunflower oil content of the feedstock, the sunflower oil part was converted entirely, while in the 5 case of lard, above 30% lard content of the feedstock the conversion was not complete. that is also due to the fatty acid chains with higher than c22 carbon number of the lard, since they are not in the boiling point range of the main product fraction. 0 1 2 3 4 5 6 7 0 10 20 30 40 50 60 70 80 90 100 triglyceride content of the feedstock, % y ie ld o f t he r as id ua l f ra ct io n, % lard sunflower oil figure 5: the yield of the residual fraction as a function of the triglyceride content of the feedstock the differences between the products originated from the different fatty-acid composition of the sunflower oil and the lard are shown in fig. 6 and 7. while the sunflower oil contains mainly c18 fatty-acids, and thus mainly c18 and c17 paraffins form during the catalytic hydrogenation, in the case of lard the amount of c18 fatty-acids is lower in it and in the feedstock, so that means less c18 and c17 paraffins in the product mixture. 20 30 40 50 60 70 80 90 0 10 20 30 40 50 60 70 80 90 100 triglyceride content of the feedstock, % t he y ie ld o f c 17 +c 18 p ar af fin s, % lard sunflower oil figure 6: the yield of c17 and c18 paraffins as a function of the triglyceride content of the feedstock 5 10 15 20 25 30 0 10 20 30 40 50 60 70 80 90 100 triglyceride content of the feedstock, % y ie ld o f t he c 15 +c 16 p ar af fin s, % lard sunflower oil figure 7: the yield of c15 and c16 paraffins as a function of the triglyceride content of the feedstock the lard contains c16 fatty-acids in high concentration, so the amount of c15 and c16 paraffins increased the yield of the gas oil boiling point range main fraction with increasing the lard content of the feedstock. on the other hand, the triglycerides forming the sunflower oil contain only a small amount of c16 fatty-acids (table 1), and so the yield of the c15 and c16 paraffins (fig. 8) decreased with the increasing sunflower oil content of the feedstock. in the case of pure gas oil (22 mg/kg), sunflower oil (28–49 mg/kg) and as regards feedstocks up to 20% lard content (35–47 mg/kg), the sulphur content of the gas oil boiling point range main products was below 50 mg/kg, however we were not able to reach sulphur content below 10 mg/kg specified by the valid diesel fuel standard in either case. for the main products obtained in the case of feedstocks with lard content higher than 20%, the sulphur contents were 75 and 148 mg/kg, respectively. we did not find any significant difference between the sulphur contents (25 and 27 mg/kg) of the main product fractions obtained from pure sunflower oil or lard. this was caused by the process temperature, which entailed that the desulphurisation efficiency was not high enough. the polyaromatic content of the products fulfilled the specification of maximum 8% of the valid diesel gas oil standard in every case. as it can be seen in fig. 8, 9 and 10, the desulphurization, denitrification and dearomatization efficiency decreased with the increasing triglyceride content of the feedstock, because these reactions occur on the same active sites of the catalyst as the deoxygenating of the triglycerides. 95 95,5 96 96,5 97 97,5 98 98,5 99 99,5 100 0 10 20 30 40 50 triglyceride content of the feedstock, % d es ul ph ur iz at io n ef fic ie nc y of th e ca ta ly st , % lard sunflower oil figure 8: the desulphurization efficiency of the catalyst as a function of the triglyceride content of the feedstock 70 75 80 85 90 95 100 0 10 20 30 40 50 triglyceride content of the feedstock, % d en itr ifi ca tio n ef fic ie nc y of th e ca ta ly st , % lard sunflower oil figure 9: the denitrification efficiency of the catalyst as a function of the triglyceride content of the feedstock 6 40 42 44 46 48 50 52 54 56 58 60 0 10 20 30 40 50 triglyceride content of the feedstock, % d ea ro m at iz at io n ef fic ie nc y of th e ca ta ly st , % lard sunflower oil figure 10: the dearomatization efficiency of the catalyst as a function of the triglyceride content of the feedstock in the case of lard containing feedstocks the efficiency of desulphurization, denitrification, dearomatization fell behind compared to the feedstocks with sunflower oil content. the lard’s higher heteroatom content (table 2) compared to the sunflower oil’s causes higher heteroatom concentration at the active sites which means the inhibition of the reactions. the cold filter plugging points (cfpp) of the gas oil boiling point range main products obtained from lard containing feedstocks were more favourable (with 2–3 °c) compared to the sunflower oil containing feedstocks (fig. 11). this effect was due to the high concentration of the forming c15 and c16 paraffins from the lard part of the feedstock. the cfpp values of these are more favourable than the cfpp values of the c17 and c18 paraffins. 0 5 10 15 20 25 0 10 20 30 40 50 60 70 80 90 100 triglyceride content of the feedstock, % c fp p va lu e of th e ga s o il bp . r an ge m ai n pr od uc t f ra ct io ns , ° c lard sunflower oil figure 11: the cfpp value of the gas oil boiling point range main product fractions as a function of the triglyceride content of the feedstock in spite of this, we obtained products that meet the maximum +5 °c cfpp value specified by the valid diesel fuel standard only in the case of pure gas oil and feedstock containing 10% triglyceride because mostly n-paraffins form during the conversion of triglycerides, of which cold flow properties are unfavourable (+15(-)+25 °c). summary and conclusions on the basis of our experimental results we determined that in the case of lard the triglyceride conversion is lower (more residual fractions) compared to sunflower oil, because of the higher heteroatom concentration of the lard, and in consequence of the higher than c22 carbon number fatty-acid content (3.6%) of the lard, of which boiling point is above 360 °c. the yield of the c17 and c18 paraffins was essentially higher (50% no – 63.57% and 50% szs – 48.72% respectively) in the case of sunflower oil containing feedstocks, because the sunflower oil builds up with mainly c18 fatty-acids. the yield of the c15 and c16 paraffins was higher (50% no – 10.30% and 50% szs – 18.9% respectively) in the event of lard containing feedstocks since the lard contains c16 fatty-acids in high concentrations. this surplus c16 in the case of lard containing feedstocks supplements the amount of c15 and c16 dropped out by the blending of the bio-component sunflower oil as a consequence of the lower gas oil (in the case of pure gas oil the c15 and c16 content is 12.49%) content of the feedstock and it even means a surplus in the yield. because of the effect of the higher heteroatom concentration of the lard, the dearomatization (50% szs – 45.3% and 50% no – 47.3% respectively), the desulphurization (50% szs – 97.1% and 50% no – 99.0% respectively) and the denitrification (50% szs – 72.9% and 50% no – 81.8% respectively) efficiency was higher in the case of feedstocks containing sunflower oil. the obtained main product fractions – except for their cfpp values and sulphur contents – met the valid msz en 590:2009+a1:2010 diesel gas oil standard. the obtained products can be excellent diesel gas oil blending components because of their low aromatic content and beside it their high cetane numbers (65–90) provided by the n-paraffins formed during the conversion of the triglycerides. the cfpp values of the products obtained in the case of lard containing feedstocks were more favourable (with 2-3 °c) compared to the sunflower oil containing feedstocks, however it is necessary to improve these values (e.g.: by the catalytic isomerization of the nparaffins). on the whole, we found that the lard is suitable for the production of high quality agricultural-derived diesel gas oil blending component through catalytic hydrogenation. acknowledgement we acknowledge the financial support of this work by the hungarian state and the european union under the tamop-4.2.1/b-09/1/konv-2010-0003 project. 7 references 1. j. hancsók, j. baladincz, j. magyar: mobilitás és 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(editor) silica and silicates in modern catalysis, transworld research network, india, kerala isbn 978-817895-455-4, 435–455. 16. m. krár, s. kovács, l. boda, l. leveles, a. thernesz, i. wáhlné horváth, j. hancsók: fuel purpose hydrotreating of vegetable oil on nimo/γ-al2o3 catalyst, hungarian journal of industrial chemistry, 37(2), 2009, 107–111. 17. z. varga, j. hancsók, g. nagy, gy. pölczmann: quality improvement of heavy gas oils on nimo and como catalysts, 7th international symposium motor fuels 2006, slovakia, tatranské matliare, 19-22. june 2006., in proceedings (isbn 80-968011-3-9), 328–339. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 37(2) pp. 153-158 (2009) mathematical models for a closed-circuit grinding p. b. kis1 , cs. mihálykó2, b. g. lakatos2 1college of dunaújváros, department of applied mathematics, dunaújváros, táncsics m. u. 1/a, hungary e-mail: buzane.kis.piroska@mail.duf.hu 2university of pannonia, veszprém, egyetem u. 10, hungary new continuous and discrete mathematical models are elaborated for describing some types of closed-circuit grinding mill-classifier systems. based on the discrete model computer simulation is also developed for investigation of grinding processes. the starting point in developing the model is the continuous grinding equation for the open-circuit grinding which is a partial integro-differential equation describing axial mixing and breakage of particles in the grinding mill. the convective flow in the mill is modeled as particle size-dependent process. the boundary conditions at the inlet and outlet of the mill, the initial conditions, and the equations describing the operation of the classifier and its mass balance are the additional equations of the model. the properties and capabilities of the new computer model are demonstrated and analyzed by simulation developed in matlab environment. the effects of all parameters of the grinding process, among others of parameters of the classifier, are studied via simulation. the main statistical characteristics of the steady states, the hold-up of the grinding device and the operation of the classifier are also studied. the models presented appear to be very flexible and useful tools for analysis and design of closed-circuit grinding processes, and are suitable for the deeper understanding of the aimed processes. keywords: closed-circuit grinding, computer simulation, grinding-classifying system, mathematical modeling, millclassifier system. introduction grinding is a widely used operation in the industrial processes. due to the fact that there are numerous types of grindings many kinds of grinding devices have been developed based on various operation principles. at the same time, grinding is an energy consuming operation therefore the cost-efficiency of the operation can be improved by the decreasing the grinding energy. one of the main urgings of the mathematical description and modeling of grinding is exactly the improvement of the cost-efficiency. numerous excellent papers have been devoted to the description of the batch grindings [1, 2, 3]. mihálykó, blickle and lakatos [4] developed deterministic continuous and discrete models for the open circuit grinding describing processes in long ball mills. further development and generalization of these models provided mathematical description also for closed-circuit grinding systems with classifying devices [5, 6]. in the literature, grinding with internal classification of the product has also been modeled [7, 8]. the aim of this paper is to present continuous and discrete mathematical models for describing some further types of closed-circuit grinding mill-classifier systems. the model is formed by a continuous grinding equation for the open-circuit grinding process, being a partial integro-differential equation describing axial mixing and breakage of particles in the mill. the convective flow of ground material in the mill is modeled as sizedependent process. the boundary conditions at the inlet and outlet of the mill, the initial conditions, and the equations describing the operation of the classifier and its mass balance are the additional equations of the model. using the discrete model computer simulation is carried out investigating the effects of parameters and operational conditions of the grinding system. continuous and discrete mathematical models the closed-circuit grinding models of the authors which have been previously published describe such a grindingclassifying system which returns the large particles from the classifier to the inlet of the mill [5, 6, 9]. this paper presents mathematical models referring to another group of the closed-circuit grindings. the considered process is as follows: the fresh particles to be ground are entered into the mill through the inlet of the mill; the particles are grinding while they are flowing along the mill; the particles are classified; only the fine 154 particles are allowed to leave the mill through the outlet; due to the classification the large particles are retained in the mill. let symbol x stands for the particle size, let symbol xmax denote the largest particle size. the convective flow of the particles along the device is characterized via the convective flow velocity and denoted by u(x), while symbol d stands for the axial dispersion of the particles. the operation of the classifier is characterized by the classification function ψ(x). let the mass density function m(x, y, t) characterize the size distribution of the particles where m(x, y, t)dx expresses the mass of the particles at the axial coordinate y of the mill at time t within the particle size interval (x, x+dx) in a unit mass of the particles. at the model-construction let us suppose that 1) the transport of the particles in the mill is described by the axial dispersion model; 2) the grinding kinetics is described by the first order law of breakage. the continuous mathematical model is given by the following equations (1) – (6). the operation of the grinding mill is described via equation (1) which is a partial integral-differential equation: y tyxmxu y tyxmd t tyxm ∂ ∂ − ∂ ∂ = ∂ ∂ ),,()(),,(),,( 2 2 .d),,(),()(),,()( max ∫+− x x ltylmlxblstyxmxs (1) equations (2) and (3) – (4) express the initial and the boundary conditions, respectively: ),,()0,,( 0 yxmyxm = (2) ,0if,),,(),,()(),( = ∂ ∂ ⋅−⋅= y y tyxmdtyxmxutxf f (3) ,0),,( = ∂ ∂ y tyxm if y = y. (4) in equation (1) function s(l) represents the rate of breakage of particles of size l , usually termed selection function, while function b(x, l) is the breakage density function. in equation (3) function ff(x, t) denotes the mass flow rate of the feed to the mill. equation (3) expresses the assumption that there is no back-mixing from the mill into the transfer pipe. symbol y stands for the length of the mill, therefore y = 0 expresses the inlet of the mill in equation (3) and y = y means the outlet of the mill in equation (4). equations (5) and (6) describe the operation of the classifier. the mass flow of the large particles is given by equation (5): fr(x, t) = ψ(x) · f(x, t) = ψ(x) · u(x) · m(x, y, t). (5) in equation (5) f(x, t) is the mass flow density function at the outlet of the mill. we suppose that the large particles – which are not allowed to leave the mill due to the operation of the classifier – remain in the grinding device. this assumption is expressed by equation (6): f(x, t) = fl(x, t) + ψ(x) · f(x, t), (6) where function fl(x, t) is the mass flow density function of that particles which flowed in the grinding device to the outlet of the mill. using the continuous model – equations (1) – (6) – a discrete mathematical model has been derived similar way involved in the paper [6]. let δt denote the length of the time step, let tn stand for tn = nδt. let us subdivide the mill into j equal sections and denote hy the length of a section of the mill, thus hy = y/j. let us sort the particles into size fractions. let xmin denote the smallest particle size. if i denotes the total number of size fractions of particles and we introduce the notation hx = (xmax – xmin)/i, then xi = xmin + ihx stands for the ith particle size fraction. let symbol ix denote the mean size of the ith size fraction, i.e. ix = (xi-1 + xi)/2 and let )( ixt stand for the mean residence time of particles belonging to the ith size interval, i.e. )(/)( ii xuyxt = . let µ(xi, yj, tn) denote the mass of the particles belonging to the ith size fraction and the jth section at the moment of time tn. let us introduce symbols )( if xv and )( ib xv (i=1, 2, …, i) via the following formulae: , )( )(1)( )( 2j xpe j xpex xv i i i if ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ + = τ , )( )( )( 2j xpe x xv i i ib τ = where )(/)()( iii xdyxuxpe = is the peclet number for the ith size fraction of particles. in the above formulae )( ixu and )( ixd denote the convective flow velocity and the axial mixing coefficient of that size fraction, respectively, while )(/)( ii xttx δ=τ . the breakage distribution function – let it denote symbol b(x, x) – describes of the rubbles when the particle of size x breaks. the connection between the breakage distribution function and the density function is as follows: ∫= x x dlxlbxxb min ),(),( . after introducing the notation )],(),()[( 1, −−= ikikkik xxbxxbxtsp δ then the equations of the discrete model can be described by equations (7) – (9). the development of the discrete model can be manipulated similarly to those published in the paper [6]. the left-hand sides of equations (7), (8), (9) contain the mass of the particles belonging to the ith size fraction at the moment of time tn+1. the first group of equations describes the size composition of particles in the first section; the second group reflects to the inner sections 155 of the mill; finally, equation (9) expresses the size composition in the last section of the mill. =+ ),,( 11 ni tyxμ = +−− ),,())()()()(1( 1 niiiiif tyxxsxtxxv μτ + +),,()( 2 niib tyxxv μ + )(),,( 1, nink i ik ik tatyxp +∑ = μ i=1, 2, …, i. (7) the first term on the right-hand side of equation (7) expresses the mass of particles belonging to the ith size interval at the moment of time tn which neither moved forward nor broke; the second term represents that particles of the same size interval that moved backwards from the second section; the third term gives the mass of particles that remained in the first section and broke from some greater or equal size than xi to this very size interval; the last term denotes the mass of the feed particles belonging to the ith size interval. =+ ),,( 1nji tyxμ = ))()()()()(1( iiiibif xsxtxxvxv τ−−− ++× − ),,()(),,( 1 njiifnji tyxxvtyx μμ + ++ ),,()( 1 njiib tyxxv μ + ),,(, njk i ik ik tyxp μ∑ = j=2, …, j–1, i=1, 2, …, i. (8) the first term on the right-hand side of equation (8) gives the mass of particles of the ith size fraction that did not changed at all during a unit of time; the second term represents the fraction of particles belonging to the ith size interval that moved forward from the previous section; the third term expresses that part of particles which moved backward from the next section; while the last term means the mass of those particles that remained in the section and broke from some size greater or equal than xi to the interval in question. finally, equation (9) describes the size composition of the particles as =+ ),,( 1nji tyxμ = +−− ),,())()()()(1( njiiiiib tyxxsxtxxv μτ + +− ),,()( 1 njiif tyxxv μ + +∑ = ),,(, njk i ik ik tyxp μ + ),,())()()(( njiibifi tyxxvxvx μψ − i=1, 2, …, i. (9) where the first term on the right-hand side describes the mass of those particles which did not changed at all; the second term represents the particles which moved forward from the last but one section; the third term represents the mass of particles that remained in the last section and broke to the interval in question; the last expression, i.e. ),,())()()(( njiibifi tyxxvxvx μψ − gives the mass of that particles of that size were retained in the mill due to the classification. the set of recursive equations (7), (8), and (9) provide, in principle, the discrete mathematical model of the closed-circuit grinding system. in the model the constitutive relations d(x), u(x), and ψ(x) are of arbitrary form, and can be formulated arranging the simulation in accordance with the equipment and operational conditions. numerical experiments and results based on the discrete mathematical model computer simulation has been elaborated in matlab environment for examination the capabilities and properties of the model. the particle size distribution of the material to be ground was chosen from the literature [10] as well as the parameters in the model which are the kinetic and process parameters. the parameters of the selection function and breakage distribution function form the kinetic parameters, while the convective flow velocity, the axial dispersion, and the parameters of the classification function constitute the process parameters. the forms of the selection function and breakage distribution function are as follows: s(x) = ks⋅xα, where ks and α are the parameters of the function; βγ ⎟ ⎠ ⎞ ⎜ ⎝ ⎛⋅−+⎟ ⎠ ⎞ ⎜ ⎝ ⎛⋅= x x x xxxb )1(),( φφ , where β, γ, φ are the parameters [11]. the size dependency of the convective flow velocity of particles was characterized via the formulae u(xi) = ki · u(x1), (i=1, 2, …, i) where λ)/(1 1 50xx k i i + = 0 ≤ ki ≤ 1, where u(x1) stands for the velocity of flow of the finest particles. in the formula for ki symbol x50 denotes that particle size for which the convective flow velocity is 0.5u(x1), and λ is an appropriate constant [12]. the classifier was modeled using the molerus curve approach so the operation of the classifier was characterized by the following efficiency curve [13]: . 1 11)( )1( cutx xc cut e x x x −− ⋅+ −=ψ in the formula for ψ(x) symbol x denotes the particle size. function ψ(x) has two parameters; c and xcut. parameter c characterizes the classifier, while xcut means the cut size. it is very likely that the classifier retains a particle in the mill if the size of a particle is greater than the cut size. parameter c expresses the sharpness of the cut. with the aid of the computer simulation the operation of the grinding-classifying system was investigated via 156 numerical experiments. the effects of both the kinetic and process parameters were examined. the statistical characterization of the ground material at the steady state was also performed. let us see an example, i.e. an experiment which demonstrates the effect of the classification to the steady state characteristics of the material at the outlet from the mill. the aim of the numerical experiment is to show the influence of the cut size of the classifier to the mean particle size and dispersion of the particle size distribution of the ground material which leaves the mill at the outlet. the calculation results are involved in the table 1 and table 2. in the numerical experiments the value of the parameter c was 5 and 10, respectively. the grade efficiency curves of the classifier is illustrated by fig. 1, while fig. 2 shows the distribution of the feed material and the distribution of the ground material at the outlet from the mill at the steady state. the values of the remaining parameters were: y = 5.4 m, α = 1.2, β = 2.6, γ = 0.8, φ = 0.4, ks = 0.028 s-1, xmin = 0 µm, xmax = 1540 µm, u(x1) = 0.090 m/s, d = 0.002 m2/s, λ = 3.5, x50 = 650 µm. table 1: the steady state characteristics of the material at the outlet from the mill depending on the cut size of the grade efficiency curve, where c = 5 the steady characteristics of the material at the outlet from the mill cut size (μm) (c = 5) mean particle size (µm) dispersion of the particle size distribution (μm) 200 136 103 300 171 138 400 191 162 table 2: the steady state characteristics of the material at the outlet from the mill depending on the cut size of the grade efficiency curve, where c = 10 the steady characteristics of the material at the outlet from the mill cut size (μm) (c = 10) mean particle size (μm) dispersion of the particle size distribution (μm) 200 117 83 300 155 119 400 180 147 table 1 and table 2 illustrate well how the average particle size and dispersion at the outlet from the mill keep growing with increasing the cut size of the classifier. at the same time, the tables show the effect of the sharpness of the classification. the greater is the value of parameter c the sharper is the classification function, i.e. the better is the classification. in the case of a good classification the large particles have a very little chance to leave the mill. therefore the greater value of the parameter c yields smaller mean particle size and dispersion of the particle size distribution. this fact is also demonstrated by the data involved in the table 1 and table 2. figure 1: grade efficiency curves of the classifier, c = 5 and c = 10 figure 2: the size distribution of the feed material and the size distribution of the ground material at the outlet from the mill where xcut = 200, and c = 10 the hold-up of the grinding device can also be investigated via numerical experiment. let us see how the operation of the classifier and one of the kinetic parameters – ks – influence the hold-up of the mill at the steady state. the effects of the cut size, sharpness of the cut, and parameter ks were studied. it was supposed that the amount of the particles in the mill was a unit at the start of the grinding process. the results of the calculations are seen in the table 3 and table 4 where ks = 0.005 s-1 and ks = 0.050 s-1, respectively. fig. 3 and fig. 4 also illustrate the hold-up of the mill at the steady state. the values of the remaining parameters were: y = 5.4 m, α = 1.2, β = 2.6, γ = 0.8, φ = 0.4, xmin = 0 µm, xmax = 2000 µm, u(x1) = 0.090 m/s, d = 0.002 m2/s, λ = 3.5, x50 = 650 µm. comparing table 3 and table 4, the results indicate that the increase of the value of parameter ks causes the decrease of the hold-up of mill. 157 table 3: the hold-up of the grinding device at the steady state depending on the cut size and sharpness of the cut, where ks = 0.005 s-1 the hold-up of the mill at the steady state cut size (μm) sharpness of the cut c = 3 sharpness of the cut c = 5 sharpness of the cut c = 10 220 2.8 3.8 3.8 240 2.4 3.7 3.8 260 2.1 3.1 3.8 280 1.8 2.7 3.8 300 1.7 2.4 3.8 320 1.5 2.1 3.4 table 4: the hold-up of the grinding device at the steady state depending on the cut size and sharpness of the cut, where ks = 0.050 s-1 the hold-up of the mill at the steady state cut size (μm) sharpness of the cut c = 3 sharpness of the cut c = 5 sharpness of the cut c = 10 220 2.1 2.9 3.7 240 1.8 2.5 3.7 260 1.6 2.2 3.2 280 1.5 2.0 2.8 300 1.4 1.8 2.5 320 1.3 1.6 2.3 table 3 and table 4 show well that the increase of the cut size induces the decrease of the hold-up for a fixed value of the sharpness of the cut generally; as well as the increase of the sharpness of the cut gives the increase of the hold-up for a fixed cut size mostly. figure 3: the hold-up of the grinding device at the steady state depending on the cut size and sharpness of the cut, where ks = 0.005 s-1 figure 4: the hold-up of the grinding device at the steady state depending on the cut size and sharpness of the cut, where ks = 0.050s-1 we can find some equal values of the hold-ups in table 3 and table 4 for just the same value of parameter c, for example, c = 3 and the hold-up is 2.1. table 5 contains the statistical characteristics at the outlet from the mill in both cases, i.e. ks = 0.005 s-1 and ks = 0.050 s-1. in order to produce equal hold-ups the higher value of the parameter ks connects to smaller cut size. as a consequence the values of the mean particle size and the dispersion of the particle size distribution are also smaller as it is seen in table 5. table 5: the values of the mean particle sizes and the dispersions of the particle size distribution where c = 3 and the hold-up is 2.1 parameter ks cut size mean particle size dispersion 0.005 260 222 180 0.050 220 193 153 summary numerous papers have been devoted to the mathematical description of the batch grindings. at the same time the mathematical description and modeling of continuous grinding processes, in particular the closed-circuit grindings still offer a lot of work for the process engineers and experts who investigate this area. the newly elaborated continuous and discrete mathematical models proved to be suitable to the description and analysis of some types of closed-circuit mill-classifier systems. in particular, the newly developed mathematical models presented in the paper involve the description of both the batch grinding and the open-circuit grinding systems. notice that the discrete mathematical model of the closed-circuit grinding system, i.e. the set of recur 158 sive equations (7), (8), and (9), can also be written in matrix form. the matrix form of the model is suitable for some further, among others stability investigations. references 1 kostoglou m., karabelas a. j.: an assessment of low-order methods for solving the breakage equa-tion, powder technology 127 (2002), 116–127 2 reid k. j.: a solution to the batch grinding equation, chem. eng. sci., 20 (1965), 953–963 3 fan l. s., srivastava r. c.: a stochastic model for particle disintegration, chem. eng. sci., 36 (1980), 2289–2291 4 mihálykó cs., blickle t., lakatos g. b.: a simulation model for analysis and design of continuous grinding mills, powder technology 97 (1998), 51–58 5 buzáné kis p., mihálykó cs., lakatos g. b.: computer simulation for closed-circuit grindings (in hungarian), proc. of conference of chemical engineering ’05 (2005), 180–183 6 kis p. b., mihálykó cs., lakatos g. b.: discrete model for analysis and design of grinding mill-classifier systems, chemical engineering and processing 45 (2006), 340–349 7 mizonov v. e., berthiaux h., zhukov v. p., bernotat s.: application of multidimensional markov chains to model kinetics of grinding with internal classification, proc. of 10th european symposium on comminution, heidelberg, (2002) cdrom, a3. 8 hintikka v., mörsky p., kuusisto m., knuutinen t.: continuous classifying laboratory mill – new possibilities for research work, minerals eng-ineering, 9 (1996), 1157–1164 9 kis p. b., mihálykó cs., lakatos g. b.: mathematical models for simulation of continuous grinding process with recirculation, acta cybernetica, 15 (2002), 529–545 10 braun r. m., kolacz j., hoyer d. i.: fine dry comminution of calcium carbonate in a hicom mill with an inprosys classifier, minerals engineering, 15 (2002), 123–129 11 austin l. g.: a discussion of equations for the analysis of batch grinding data, powder technology 106 (1999), 71–77 12 cho h., austin l. g.: a study of the exit classification effect in wet ball milling, powder technology 143-144 (2004), 204–214 13 molerus o., hoffmann h.: darstellung von wind-sichtertrennkurven, chemie-ing. techn., 41 (1969), 340–344 microsoft word b_16_r.doc hungarian journal of industrial chemistry veszprém vol. 38(2). pp. 133-136 (2010) tool life of cutting tool in case of hard turning l. ráczkövi department of production engineering, university of miskolc, 3515 miskolc egyetemváros, hungary e-mail: laszlo.raczkovi@uni-miskolc.hu the wear and tool life of tools applied to precision cutting have huge significance, because we perform the finishing of parts with expensive tool materials and the advantageous chip removal properties of these materials are valid in a narrow range of technological parameters. until recently grinding was used in finish machining; nowadays hard turning is used instead of or in addition to grinding. grinding requires a lot of cooling and lubricating liquid, whereas hard turning is dry machining, therefore it is very advantageous from the point of view of environmental load. this paper presents the examination of the wear of pcbn tools and the results of determining the tool life of these tools. the experimental results were processed using the tool life relation, valid in the whole range of cutting speed. keywords: pcbn; cutting tools; tool life introduction increasing the lifetime of parts requires the formation of more hard surface. creating the hard surface of parts needs higher expenditure and more operations, but after tempering, the fatigue limit is also increased in addition to strenght and hardness. therefore, after the appropriate finishing, the parts are much more chargeable, abrasionresistant, and the lifetimes will be longer. [1] the quality of worked parts is influenced by finishing. working of very hard materials can be finished by grindig, turnig or the combination of the two processes. during manufacturing the requested quality of the part can be achieved by hard turning so that the working process can satisfy certain economic conditions at the same time. the wide-spread use of hard turning requires the more accurate description of the wear and tool life of cutting tools [2, 3, 4]. determining the tool life is necessary for economic analisys and for creating the mathematical model to specify the cutting parameters. during the cutting process, the cutting tools are subject to wear. the intensity of wear depends on the conditions of the cutting process. up to the permitted limit of wear – which is called lifetime criterion – the time spent in the process of cutting is the tool life, which depends on the changes of cutting speed. the oldest and still used tool life equation originates from 1901 and it was published in 1904 by f. w. taylor [5]. taylor determined the tool life, belonging to the different cutting speeds, with the vc-t tool life curve (“taylor curve”). the equation published by taylor is only valid in a narrow range of cutting speed. this equation is called the simple taylor equation, differentiated from its later, improved version, which also reflects the effect feed-rate and the depth of cut plays on tool life. the simple and improved taylor equations can only provide a relatively good approximate on the descending branch of the tool life curve in a narrow range of cutting speed and it can be characterized with a group of straight lines. clearly, it has a serious practical significance that these equations can take into consideration all of three cutting parameters but the possible extrapolation is very limited. this tool life equation is used most generally in practice because it has a huge experimental database and it can be handled in a simple way [6, 7]. however, it can be noticed that, in a wider range of the cutting parameters, especially the speed of cutting, the tool life which is calculated with the taylor equation is different from the actual, measured tool life. it is almost natural if we take into consideration that the wear determining the tool life is evolved through a very complicated mechanical-, chemical-, electric-, etc. process. as the conditions of cutting change, the mechanical and heat load of the cutting tool also change, the ratio of the components of wear are modified and their mathematical handling becomes difficult. cutting experiments and their results during the cutting experiments, the surfaces of workpieces were cut by pcbn hard turning. these surfaces were previously cut with grinding. the experiments designed to determine tool life were accomplished using pcbn tool with different cutting speeds and values of federating and depth of cutting. 134 the experimental conditions were as follows [8]: cutting tool: composite 01; tool edge geometry: γ = -5°; α = α’ = 15°; λs = 0°; κr = 45°; κ'r1 = 2°; κ'r2 = 15°; bε = 0.3 mm workpiece: tempered steel: 100cr6 hrc 62±2; diameter of workpiece: d = 45 mm machine – tool: e400-1000 universal centre lathe; cutting parameters: f = 0.025–0.125 mm/rev; depth of cut: ap = 0.05–0.25 mm; vc = 11–120 m/min wear criterion vb = 0.4 mm. table 1 contains the combination of cutting parameters which was measured the wear of cutting tool [8]. the wear criterion was chosen to 0.4 mm and we measured the tool life along this value of wear. table 1: the measured tool life during cutting experiments measured tool life t [min] vc [m/min] f [mm/rev.] ap [mm] 11 20 29 40 50 68 92 105 120 0.025 0.1 357 241 230 249 276 220 81 50 33 0.075 0.1 249 198 209 209 157 66 18 10 7 0.125 0.1 203 183 184 167 103 30 8 5 4 0.5 0.05 328 238 246 246 258 142 43 25 19 0.5 0.15 258 194 203 216 216 93 25 14 10 0.5 0.25 229 179 184 202 183 70 18 10 7 evaluation of the experimental results with new tool life equation in the cutting process it often means a difficulty that some phenomena change the characteristic of vc–t curves. the layers with different origin and thickness that appear on the face of the tool (e.g. metallic and non – metallic accumulation) can seriously increase the tool life in a specified range of cutting speed. a wide range tool life experiments proved that the change of real tool life can be described with a rational fractional function of cutting speed (which has the most intensive influence on tool life) with a relative maximum and a relative minimum. [8, 9] we can see from the data of table 1 that the relation between cutting speed and tool life is not monotonous, it can be described with a function which has two extreme values, through which the whole range of cutting speed can be divided into three parts. these three parts are shown in fig. 1. the equation, which is valid in the whole range of cutting speed and suitable to describe the changing of tool life – in other words the tool life equation – is the following [10]: ctctc t vcvcv ct 2 2 2 3 1 ++ = (1) where: t – tool life vc – cutting speed ct1, ct2, ct3 – constants depending on the technological conditions of cutting based on the measured values, the constants of equation (1) can be determined by regression calculation. the calculation is performed using mathcad software that applies the principle of nonlinear least squares. the software has its own built-in function applying the levenberg – marquardt algorithm [11] to minimize the residual error. figure 1: the effect of cutting speed on tool life figure 2: determining the ct1, ct2, ct3 constants with mathcad 135 the levenberg – marquardt (lm) algorithm is an iterative technique that locates the minimum of a multivariate functions, expressed as the sum of squares of nonlinear real-value functions. the application of the software is shown by fig. 2 for the highlighted values of table 1. the measured tool life points and the calculated tool life curve are shown by fig. 3. figure 3: comparison of the measured tool life points and the calculated tool life curves we can see from fig. 3 that the calculated tool life curve well suits the measured points. applying the calculation to the rest of the given measured values of feedrate and depth of cut, we can determine the sought constants, which are comprised in table 2. table 2: the calculated ct1, ct2, ct3 constants composite 01 f [mm/rev.] ap [mm] ct1 ct2 ct3 0.025 0.1 1.317·107 -124.18 4687 0.075 0.1 4.422·106 -88.27 2463 0.125 0.1 2.631·106 -77.50 1893 0.5 0.05 8.914·106 -106.90 3551 0.5 0.15 5.784·106 -100.08 3055 0.5 0.25 4.595·106 -95.32 2777 we described the calculated tool life values, belonging to constant feedrate and depth of cut, on two diagrams depending on which cutting parameter is constant. fig. 4 shows the calculated tool life values in case of constant ap = 0.1 mm depth of cut and different feedrates. it can be seen from the diagram that as the feedrate is increased, the tool life curve moves downwards, i.e. the tool life decreases. it can also be observed that the local extreme values of the curves move both in the vertical and horizontal direction towards the decreasing values of tool life and cutting speed. therefore, the effect of increasing feedrate can be compensated by decreasing the cutting speed. fig. 5 shows the calculated tool life values in case of constant f = 0,5 mm/rev feedrate and different depth of cut values. figure 4: the calculated tool life values with different feedrates 1. f=0,025 mm/rev., 2. f=0,075 mm/rev., 3. f=0,125 mm/rev. figure 5: the calculated tool life values with different depth of cut values 1. ap=0,05 mm, 2. ap=0,15 mm, 3. ap=0,25mm. it can be seen in fig. 5 that the range bordered by local extreme values is less extended in the horizontal direction, with both extreme values moving in a narrow range of cutting speed. as a result of varying the depth of cut, the curves move in a vertical direction. the effect of increasing the depth of cut cannot be significantly influenced by changing the cutting speed. conclusions the measured tool life values can be evaluated with the chosen relation. the changes that can observed in the whole range of cutting speed in case of cutting with pcbn tools can be described appropriately. with the help of the mathcad software, we can determine the constants of tool life relation and this way we can predict the tool life in the whole range of cutting speed values. 136 with the help of calculated tool life curves, it is possible to determine the range of optimal cutting parameters with maximum tool life in case of pcbn tools. references 1. j. kundrák: a furatátmérő hatása a szerszám éltartamára keményesztergálásnál, x. országos gépész találkozó (ogét 2002) erdélyi műszaki tudományos társaság székelyudvarhely, 2002. április 2528., 169–174 issn 1454-0746. 2. j. kundrák: tool life equation and its application in hard turning, rezanie i instrument, 57, 2000, 145–151. 3. j. kundrak: tool life in hard boring, strojirenska technologie 3, 2002 4–10 (issn 1211-4162). 4. j. kundrák: tool life of different cbn cutting tools in boring, scientific works ntu, „khpi”, 9’2002, kharkiv, (no10) manufacturing technology, 103–108. 5. f. w. taylor: “on the art of metal cutting”, transactions asme. 28, 1901. 6. m. horváth: alkatrészgyártási folyamatok automatizált tervezése, akadémiai doktori értekezés, mta sztaki, budapest, 169/1985, 205 p. 7. t. tóth: automatizált műszaki tervezés a gépgyártástechnológiában, akadémiai doktori értekezés, miskolc, 1988. 8. a. g. mamalis, j. kundrák, m. horváth: wear and tool life of cbn cutting tools int. j. adv. manuf. technol., 20, 2002, 475–479. 9. a. g. mamalis, j. kundrak, m. horvath: on a novel tool life relation for precision cutting tools, journal of manufacturing science and engineering transactions of the asme, 127 (2), 2005, 328–332. 10. j. kundrák: the scientific principles of increasing the effectiveness of inner surfaces' cutting with cbn tools, harkov, 1996, 368 p. 11. manolis i. a. lourakis: a brief description of the levenberg marquardt algorithm implemented by levmar, institute of computer science, foundation for research and technology hellas, heraklion, crete, greece, 2005. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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<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> /enu (use these settings to create adobe pdf documents best suited for high-quality prepress printing. created pdf documents can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word contents_2.doc hungarian journal of industrial chemistry veszprém vol. 31. pp. 23-29 (2003) vapor pressure, density, viscosity and refractive index of dimethyl sulfoxide + 1,4-dimethylbenzene system o. ciocirlan, o. iulian department of applied physical chemistry and electrochemistry, faculty of industrial chemistry, “politehnica” university of bucharest, 313 splaiul independentei, 060042, romania this work reports the experimental results of the isothermal vapor-liquid equilibrium data between 303.15 k and 333.15 k, densities, viscosities and refractive indices from 298.15 to 323.15 k of the dimethyl sulfoxide + 1,4-dimethylbenzene system over the entire range of mixture composition. the obtained ptx data were correlated and estimated by the wilson, nrtl and unifac models. the excess gibbs energy and activity coefficients were calculated and compared with the others excess properties. excess molar volumes, viscosity deviations and deviations in refractivity were calculated from experimental data; all the computed quantities were fitted to the redlich-kister equation. the resulting excess functions were interpreted in terms of the interactions between the molecules in the binary system. keywords: vle data, mixture properties, correlative and predictive methods, molecular interactions introduction continuing our work on the thermodynamic of the nonelectrolite systems, the present paper is a part of a study of the binary systems containing dimethyl sulfoxide (dmso) and aromatic hydrocarbons, interesting as mixed solvents [1]. dimethyl sulfoxide is a versatile nonaqueous, aprotic, highly polar self-associated solvent (having a dipole moment µ =3.90 d at 298.15 k) used extensively in kinetic studies, electrochemistry and as a solvent for polymers. binary mixtures of dmso with aromatic solvents are interesting in studies of polymer miscibility, polymer phase diagrams, and preferential interactions in mixed solvents [2]. this work reports isothermal experimental vapor liquid equilibrium (vle) data at temperatures in the range from 303.15 k to 333.15 k and experimental data of density, viscosity and refractive index in the temperature range from 298.15 to 323.15 k for the dimethyl sulfoxide + 1,4-dimethylbenzene system. the vle data were correlated by means of wilson [3] and nrtl [4] models; this work has also served to test the predictive capacity of the group contribution methods: original unifac [5] and unifac-dortmund [6,7]. excess molar volumes, viscosity deviations and deviations in refractivity were calculated from experimental data; all the computed quantities were fitted to the redlich-kister equation. after our knowledge, vle data for this binary system are not numerous [8]; there is only one source in the literature [9]. no literature data on densities, viscosities and refractive indices are available for this system, except on densities at 303.15 k [10]. experimental materials the used substances were purified by distillation. dimethyl sulfoxide was distilled under vacuum at 0.8-0.9 kpa and 338.65 k. the analytical-reagentgrade 1,4-dimethylbenzene from fluka (p.a.) was used without further purification. the purity was checked by refractive index, density and gas chromatography. it was better than 99.5 mass per 24 cent. the experimental values of density, refractive index and viscosity of the pure components are presented in table 1 and compared with literature values. table 1. experimental and literature values for density (ρ), refractive index (nd) and viscosity (η) of the pure components 10-3 ρ, kg·m-3 nd η, mpa·s t, k lit. exptl lit. exptl lit. exptl dimethyl sulfoxide 293.15 1.1005013, 1.1005314 1.10073 298.15 1.096211, 1.095412 1.09574 1.477011 1.4768 2.0388 303.15 1.0905015 1.09074 1.475214 1.4733 1.83014 1.8405 313.15 1.0804616 1.08075 1.470014 1.4694 1.53414 1.5373 1,4-dimethylbenzene 293.15 0.861017 0.86144 298.15 0.856519, 0.8567020 0.85712 1.4932010, 1.4928619, 1.493021 1.4930 0.60318 0.6281 vapor pressure the total vapor pressure of the binary mixture was measured at temperatures between 303.15 k and 333.15 k by a static method, with a glass isoteniscope of the smith and menzies type, with some modifications [22], which allows the measurements of vle at subatmospheric pressures at temperatures up to 423.15 k. vapor pressures are measured by means of a hg manometer and a cathetometer, readings accurate to within 0.026 kpa. the temperature was controlled by a u-10 type thermostat and measured with an hg thermometer with an estimate accuracy of 0.05 k. the substances were degassed prior to the measurements by freezing-thawing processes under vacuum. the vapor phase volume of the apparatus being relatively small, calculation showed that the error in composition due to vaporization is within this limit. density, viscosity and refractive index densities, ρ, of the pure solvents and the mixtures were measured with an anton paar dma 4500 densimeter with a precision of ±0.00005 g cm-3, between 298.15 and 323.15 k. the dma cell was calibrated with ultra pure water at atmospheric pressure. the sample size was 0.7 cm3, and the sample thermostat was controlled to ±0.01 k. kinematic viscosities, ν, of the pure components and their mixtures were determined at 298.15, 303.15, 313.15 and 323.15 k using an ubbelohde capillary viscosimeter for which the uncertainty of the flow time measurement was ±0.1 s; the corresponding uncertainty in the kinematic viscosity was ± 0.001 10-6 m2 s-1. at least four times flow measurements were performed for each composition and temperature, and the results were averaged. the viscosimeter was calibrated using double distilled water; it was placed in a thermostat maintained constant within ± 0.05 k. refractive indices values for the d-line, nd, were measured with a thermostated abbe refractometer with a precision of ±0.0001. all measurements were done in a thermostat maintained at ± 0.05 k. the binary mixtures were prepared by mass; the precision of the mole fraction is estimated to be better than ± 0.0002. results and discussion the measurements of the total pressure were carried out at various compositions on the large temperature range. for each binary mixture the dependencies between experimental pressure and temperature were established. the functions p = f(t) obtained by polynomial regression were used to calculate the vle data at 303.15 k, 313.15 k, 323.15 k and 333.15 k. the smoothed data resulted from experimental measurements are reported in table 2. table 2 vapor-liquid equilibrium data for the binary dimethyl sulfoxide (1) + 1,4-dimethylbenzene (2) system from 303.15 to 333.15 k. smoothed values of the pressure by polynomial regression p, kpa t, k x1 303.15 313.15 323.15 333.15 0.0000 1.55 2.65 4.34 6.86 0.1235 1.67 2.50 4.33 7.21 0.2098 1.50 2.41 4.37 7.20 0.3029 1.19 2.19 4.00 6.93 0.4059 1.36 2.10 3.86 6.64 0.6348 1.09 1.91 3.60 6.17 0.8022 1.09 1.71 3.05 5.11 0.9078 0.74 1.40 2.35 3.59 0.9554 0.64 0.85 1.47 2.48 1.0000 0.11 0.22 0.41 0.73 the temperature dependence of the pure component vapor pressures, pi o, was calculated using the antoine equation: i i i o i ckt b akpap − −= )( )(ln (1) where the antoine constants ai, bi and ci are reported in table 3. 25 table 3 result of correlation and prediction with wilson, nrtl and unifac models for dimethyl sulfoxide (1) + 1,4dimethylbenzene (2) system compound ai bi ci dimethyl sulfoxide23 15.86168 4717.396 41.59 1,4-dimethylbenzene24 14.08127 3346.646 57.84 the various models are used for correlation and prediction of binary vle data: the equations based on local composition concept (wilson and nrtl) and the group contribution methods unifac. the results of correlation with wilson and nrtl models are presented in table 4, which includes the model parameters values and the statistical parameters: average percentage deviation in pressure, ∆p, and standard deviation, σ. prediction of vle for the binary system at 303.15, 313.15, 323.15 and 333.15 k has been carried out by the original unifac method and its modification, unifac-dortmund. the group interaction parameters were those published by reid [25], hansen [26] and gmehling [6,7]. the results of prediction are also presented in table 4. the wilson and nrtl give a similar and good representation of experimental data (except at 303.15 k temperature); σ and ∆p characterise the data as satisfactory. it can be observed that the description of this system by the original unifac method shows good agreement with the experimental data, like wilson and nrtl models; the modified unifac gives less satisfactory results, especially at high temperature. the experimental and calculated (with wilson model) total pressures vs. liquid and vapor compositions for 303.15 k, 313.15 k, 323.15 k and 333.15 k are presented in figure 1. in the same phase diagram the curves represent calculated data and the points, experimental data. the activity coefficients were calculated with wilson equation for binary systems. figure 2 presents the dependence of the activity coefficients of the composition at 313.15 k, the limiting values at infinite dilution of these coefficients being given. we have also computed and represented the variation of the excess gibbs energy of the system, which shows positive deviations from the ideal. the comparison of maximum obtained value of ge with literature, at 313.15 k, is satisfactory [9]. table 4 experimental values of density, kinematic viscosity and refractive index of dimethyl sulfoxide (1) + 1,4dimethylbenzene (2) system from 298.15 to 323.15 k statistical parameters model parameters, j mol-1 σ a, mmhg ∆p b, % 303.15 k wilson ∆λ12=4143.8± 770 ∆λ21=2412.5±1004 0.86 7.14 nrtl (α=0.3) ∆g12=4067.7±1113 ∆g21=1442.6± 891 0.91 7.54 unifac original unifac unifac-dortmund 6.25 9.92 313.15 k wilson ∆λ12=3764.3±217 ∆λ21= 346.4±326 0.41 2.64 nrtl (α=0.3) ∆g12=4444.2±309 ∆g21= 969.4±222 0.37 2.10 unifac original unifac unifac-dortmund 7.99 4.54 323.15 k wilson ∆λ12=6261.8±431 ∆λ21=1163.9±284 0.86 2.27 nrtl (α=0.3) ∆g12=2620.0±435 ∆g21=3451.0±535 1.15 2.93 unifac original unifac unifac-dortmund 3.79 10.20 333.15 k wilson ∆λ12=9770.9±728 ∆λ21= 455.2±172 1.07 1.91 nrtl (α=0.3) ∆g12=1649.8±343 ∆g21=5777.3±636 2.00 3.85 unifac original unifac unifac-dortmund 3.48 14.20 a standard deviation σ ={σi n (pcalc(i)pexp(i))2/(n-m)}0.5 (n: number of data points and m: number of estimated parameters). b average percentage deviation in pressure ∆p=(100/n)·σi n |pcalc(i)pexp(i)|/ pexp(i) 0 2 4 6 8 0 0.2 0.4 0.6 0.8 1 x2, y2 p, k pa fig. 1 experimental vapor pressures of dimethyl sulfoxide (1) + 1,4-dimethylbenzene (2) system at 303.15 k (□); 313.15 k (∆); 323.15 k (o); 333.15 k (×); correlation with wilson model (―) 26 0 1 2 3 4 5 6 7 8 9 10 0 0.2 0.4 0.6 0.8 1 x2 1, 2 0 200 400 600 800 1000 1200 g e , j m ol -1 fig. 2 activity coefficients and excess gibbs energy for the dimethyl sulfoxide (1) + 1,4-dimethylbenzene (2) system calculated with wilson model at 313.15 k densities, viscosities and refractive indices were measured in the temperature range from 298.15 to 323.15 k and the measured values were listed in table 5. the values of excess molar volume, ve, viscosity deviation, ∆ν, and deviation in molar refractivity, ∆r, were calculated from the experimental data according to the following equations: ∑ = −= 2 1i iim e xvvv (2) ∑ = −=∆ 2 1i iim xννν (3) ∑ = −=∆ 2 1i iim rrr ϕ (4) where xi and φi represent the mole fraction and volume fraction, respectively; vm, νm, rm, the properties of mixtures, vi, νi, ri, the properties of the pure components. the values of r were calculated from the lorentz-lorenz equation [27]. the experimental values of ve, ∆ν, and ∆r have been fitted to the redlich-kister [28] type polynomials: ( ) kn k k xaxxy ∑ = −= 0 121 12 (5) where y represent the excess molar volume, viscosity deviation and deviation in molar refractivity, and ak represents the parameters. a nonlinear least-squares method was used to estimate the adjustable parameters ak. the values of ak and standard deviation σ are given in table 6. table 5 parameters of eq. 5 and standard deviations of excess functions of dimethyl sulfoxide (1) + 1,4-dimethylbenzene (2) system x1 10-3·ρ, kg·m-3 106·ν, m2·s-1 nd x1 10-3·ρ, kg·m-3 106·ν, m2·s-1 nd 298.15 k 0.0000 0.85712 0.855 1.4930 0.5969 0.96896 1.236 1.4858 0.1056 0.87326 0.902 1.4927 0.7009 0.99631 1.337 1.4836 0.1975 0.88813 0.950 1.4920 0.8022 1.02625 1.447 1.4813 0.2988 0.90577 1.010 1.4908 0.8978 1.05785 1.561 1.4791 0.4033 0.92574 1.079 1.4893 1.0000 1.09574 1.698 1.4768 0.5126 0.94902 1.163 1.4875 303.15 k 0.0000 0.85277 0.692 1.4907 0.5969 0.96423 1.110 1.4835 0.1056 0.86880 0.745 1.4901 0.7009 0.99151 1.227 1.4813 0.1975 0.88363 0.797 1.4893 0.8022 1.02138 1.360 1.4790 0.2988 0.90121 0.861 1.4882 0.8978 1.05292 1.506 1.4765 0.4033 0.92112 0.936 1.4868 1.0000 1.09074 1.687 1.4733 0.5126 0.94434 1.028 1.4851 313.15 k 0.0000 0.84405 0.746 1.4854 0.5969 0.95490 1.012 1.4792 0.1056 0.85999 0.782 1.4847 0.7009 0.98205 1.079 1.4772 0.1975 0.87472 0.816 1.4840 0.8022 1.01179 1.152 1.4749 0.2988 0.89220 0.858 1.4831 0.8978 1.04318 1.227 1.4723 0.4033 0.91200 0.906 1.4820 1.0000 1.08075 1.316 1.4694 0.5126 0.93510 0.963 1.4805 323.15 k 0.0000 0.83526 0.578 0.5969 0.94543 0.857 0.1056 0.85108 0.612 0.7009 0.97244 0.934 0.1975 0.86571 0.647 0.8022 1.00203 1.020 0.2988 0.88308 0.690 0.8978 1.03326 1.113 0.4033 0.90276 0.740 1.0000 1.07075 1.227 0.5126 0.92574 0.802 table 6 function a0 a1 a2 a3 σ a 298.15 k 106·ve, m3·mol-1 -0.7875 0.0235 -0.7956 0.1458 0.0007 106·∆ν, m2·s-1 -0.4946 -0.0705 0.0004 106·∆r, m3·mol-1 -8.6332 2.0491 -0.5638 0.1739 0.0022 303.15 k 106·ve, m3·mol-1 -0.7718 0.0122 -0.7718 0.1051 0.0011 106·∆ν, m2·s-1 -0.4112 -0.1051 0.0130 0.0002 106·∆r, m3·mol-1 -8.6048 2.2879 -0.7394 0.0058 313.15 k 106·ve, m3·mol-1 -0.7908 -0.0116 -0.8715 0.0009 106·∆ν, m2·s-1 -0.3002 -0.0443 0.0002 106·∆r, m3·mol-1 -8.5246 2.1822 -0.8037 0.5005 0.0041 323.15 k 106·ve, m3·mol-1 -0.7815 -0.0221 -0.9102 0.0026 106·∆ν, m2·s-1 -0.2340 -0.0220 0.0017 0.0001 106·∆r, m3·mol-1 a standard deviation σ ={σi n (ycalc(i)yexp(i))2/(n-m)}0.5 (n: number of data points and m: number of estimated parameters). the dependence of excess molar volume ve on the mole fraction of dmso is presented in figure 3. the negative values of ve suggest the presence of specific interactions between the mixing components. ve shows negligible temperature dependence. plots of excess viscosity versus the mole fraction of dmso are shown in figure 4. the ∆ν are negative over the whole composition range; a 27 -0.25 -0.2 -0.15 -0.1 -0.05 0 0 0.2 0.4 0.6 0.8 1 x2 10 6 v e , m 3 m ol -1 -0.13 -0.11 -0.09 -0.07 -0.05 -0.03 -0.01 0 0.2 0.4 0.6 0.8 1 x2 6 , m m 2 s-1 -2.5 -2 -1.5 -1 -0.5 0 0.5 0 0.2 0.4 0.6 0.8 1 x2 6 r, m 3 m ol -1 rise of temperature makes an increase of ∆ν. the viscosity of a mixture depends on the molecular interactions between components: generally, mixtures with strong interactions between different molecules show positive viscosity deviations, while for mixtures without specific strong interactions, viscosity deviations are negative. in our mixtures the breaking of dipole-dipole interactions of dmso contributes to the reduction of the viscosity during the mixing process. on the other hand, self-association of dmso and “π electron interactions” in dmso + 1,4-dimethylbenzene system [29] increase the viscosity, but the effect is not as important as the breaking of selfinteractions. consequently, the excess viscosity of all our mixtures is moderately negative; similarly, ve values remain negative. the presence of intramolecular interaction is reflected in positive deviations from raoult’s law, therefore, positive values for ge. the excess molar refractivity is shown in figure 5. the ∆r values are negative for the whole composition range for all mixtures. the values are independent of temperature, as predicted by the theory, the molar refractivity depending only on the wavelength of light used for measurement. fig. 3 excess molar volumes for dimethyl sulfoxide (1) + 1,4dimethylbenzene (2) system at 298.15 (◊); 303.15 k (□); 313.15 k (∆); 323.15 k (o); correlation with redlich-kister equation (―) fig. 4 viscosity deviations for dimethyl sulfoxide (1) + 1,4dimethylbenzene (2) system for the temperatures given in figure 3; correlation with redlich-kister equation (―) fig. 5 deviations in molar refractivity for dimethyl sulfoxide (1) + 1,4-dimethylbenzene (2) system for the temperatures given in figure 3; correlation with redlich-kister equation (―) conclusions the experimental data concerning the isothermal vapor-liquid equilibria in the binary 1,4dimethylbenzene + dmso system have been presented. eight various mixtures containing 1,4dimethylbenzene + dmso have been analyzed. a good agreement between experimental and calculated values of the pressure has been observed for wilson and nrtl correlative methods and for original unifacpredictive method. experimental densities, kinematic viscosities and refractive indices data for the binary system dmso + 1,4-dimethylbenzene have been measured at atmospheric pressure between 298.15 k and 323.15 k. excess functions have been calculated and fitted to the redlich-kister equation. the behaviour of this mixture has been discussed in terms of inter and intramolecular interactions. 28 symbols ai, bi, ci antoine’s equation parameters ak redlich-kister’s parameters g e excess gibbs energy gij parameters of nrtl equation m number of model parameters n number of experimental points nd refractive index ∆p average percentage deviation in pressure expp experimental total pressure calcp computed total pressure o ip vapor pressure of i-th pure component ∆r deviation in molar refractivity rm molar refractivity of mixture ri molar refractivity of the i-th pure component t absolute temperature ve excess molar volume vm molar volume of mixture vi molar volume of the i-th pure component xi liquid-phase mole fractions γ k activity coefficients λ ij parameters of wilson equation µ dipole moment η, ν dynamic and cinematic viscosity, respectively ∆ν viscosity deviation νm kinematic viscosity of mixture νi kinematic viscosity of the i-th pure component ρ density σ standard deviation φi volume fraction references 1. ciocirlan o., iulian o. and catrinciuc m.: 13th romanian international conference on chemistry and chemical engineering, bucharest, sept. 2003, (in press) 2. aminabhabi t. m. and munk p.: macromolecules, 1979, 12, 607 3. wilson g. m.: j. am. chem. soc., 1964, 86, 127-130 4. renon h. and prausnitz j. m.: aiche j, 1968, 1, 135-144 5. fredenslund a. a, gmehling j. and 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equilibrium data, p.w.n, warszawa, vol. 6, 1982 25. reid r. c., prausnitz j. m. and pooling e. b.: in properties of gases and liquids, 4-rd, mcgraw hill book co., new york, pp. 314, 1988 26. hansen h. k., rasmussen p., fredenslund a. a. and schiller m.: ind. eng. chem. res., 1991, 30, 2352-2355 27. lorentz h. a.: theory of electrons, teubner, leipzig, 1909 28. redlich o. and kister, a. t.: ind. eng. chem., 1948, 40, 345-348 29. fenby d. v., billing g. b. and smythe d. b.: j. chem. thermodynamics, 1973, 5, 49-56 microsoft word b_28_r.doc hungarian journal of industrial chemistry veszprém vol. 38(2). pp. 197-200 (2010) mechanical and thermal treatments influencing the grain boundary character distribution p. j. szabo1, p. varga2 1department of materials science and engineering, budapest university of technology and economics 1111 budapest, bertalan l. u. 7. mt, hungary e-mail: szpj@eik.bme.hu 2department of materials science and technology, óbuda university, 1081 budapest, népszínház u. 8., hungary e-mail: varga.peter@bgk.uni-obuda.hu random high angle grain boundaries could be transformed into special, low energy boundaries (so called csl boundaries), which affect the properties of materials. the formation of these special boundaries could be obtained through various combinations of thermal and mechanical treating. changing the parameters of the treatments will strongly affects the quantity and quality of the special boundaries. because of that it is essential to have a thorough knowledge and control over the conditions of the samples, such as the effective temperature and the strain field. mapping these parameters could be accomplished by experimental and computational methods. in this paper the mapping of the effective temperature and the true strain field of a cylindrical pure copper sample via experimental and computational methods will be introduced. in addition it will be presented how the obtained data could be used in the further work. keywords: upsetting, finite element simulation, strain field, copper, csl grain boundaries, heat treatment introduction the macroscopic properties of materials are strongly affected by both the density and type of microstructural elements, such as dislocations and interfaces. it is known for many decades that these properties may be improved by the presence of interfaces having appropriate structures. grain boundary design and control, the so called grain boundary engineering, is a concept for obtaining improved materials properties [1, 2]. the characterization of grain boundaries is generally carried out using geometrical models such as the coincidence site lattice (csl) model [1]. controlling the frequency of csl boundaries and csl triple junctions through grain boundary engineering may improve the resistance of materials to intergranular degradations such as intergranular stress corrosion cracking and creep deformation [1, 2]. control and optimization of special grain boundary distribution may be achieved by thermal and mechanical processing. to achieve this goal studying the effects of the parameters of these processes on the grain boundary character distribution is vital. as for the forming process the well definable strain rate is the key factor, while in case of the following heat treatment these are the temperature and the soaking time. the effects of such processes of course are strongly affected by the microstructure of the metal prior to them [3, 4]. we are examining these matters using pure copper specimens by altering the treatment methods and the initial conditions. to be able to reproduce the experiments and compare the results taken from different treating methods, the exact description of the parameters of treatments is needed. these parameters could be pre defined (such as the temperature of the furnace or the dimensional changing of the specimen), measured (the effective temperature of the specimen, or the grain size after the heat treatment), or calculated from the results of the treatments (for example the true strain of the specimen after the forming process). as for the forming process, in an ideal state, disregarding the friction, the strain field would be homogeneous and precisely and easily predictable. in this case only the parameters of the flow curve are needed, which could be determined with a help of a few tests. in reality it is more than questionable that we could reach this ideal state (as the friction will take its effect), therefore some pre-calculations are needed to determine the effective strain field. considering the formation of special grain boundaries, heat treatments with different parameters are also needed. among these parameters temperature has the most significant effect on the microstructure. determined by their role there are two kinds of annealing: the one used for developing the initial microstructure, and the other following the forming process, directly affecting the formation of the special grain boundaries. the annealing temperature could vary in a wide range of 400 to 900 °c, in relation to the strain rate applied. it is vital to gain information on the real temperature of the specimen to see if there are significant differences compared to the 198 furnace temperature, and to check if the temperature field is homogeneous. experiments investigating the forming process finite element analysis was used. for the simulation we used qform 2.2 software, where upsetting was applied as the forming process. because of the axisymmertic cylindrical specimen, the origin of the coordinate system was placed in the centre of the specimen (fig. 1), and also it was sufficient that the quarter of the plane section of the specimen was taken into consideration. figure 1: the dimensions of the specimen and the applied coordinate system the inhomogeneity of the strain field was investigated where the friction coefficient (according to kudo) and the displacement were altered. describing the flow curve of copper we used the following equation (alder-philips formula): m )a(ö ön öf ck ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ λ λ ⋅λ⋅= & & where: kf – flow stress [n/mm2] c – strenght coefficient [n/mm2] n – strain-hardening exponent m – strain-rate sensitivity exponent λö – effective strain öλ& – effective strain rate [1/s], )a(öλ& = 1 [1/s] for describing the temperature field during annealing the same kind of specimens were used as for the forming purpose. the annealings were carried out in an electricresistance box furnace and in an induction furnace. we varied the temperature from 400 °c to 600 °c for the box furnace (where the specimens were put into the preheated chamber) and from 400 °c to 930 °c for the induction furnace. for measuring the temperature we used k type (nicr-ni) thermocouples and a dataq di-710-uls data logger. two thermocouples were installed, one of them was put in the center of the specimen, and the other was placed below the surface of the specimen. results simulation of the forming process the following diagrams (fig. 2) show the effective strain (λö) as a function of the radius (ρ) at different heights (z), where “z” counts from the middle of the samples. please note that the diagrams were taken at different displacement (δh = 2, 6, 10 mm) and friction coefficient values (m = 0.05, 0.8). it can be seen, that even at near ideal state where the friction coefficient value is very low (m = 0.05) the strain field is considered to be homogeneous only in case of low displacement values (δh = 2 mm). at higher displacement and strain values the differences in the values of effective strain are increasing, and as a consequence they are deviate from the theoretical values where the friction coefficient is zero. at a high friction coefficient value (m = 0.8) besides the big differences in the values of effective strain, its nearly linear change can be observed at zero height value (z = 0). investigating the effective temperature of the samples during heat treatment fig. 3 shows the development of the temperature of a sample which was put into a preheated box furnace. the temperature of the chamber was 400 °c and 600 °c. as it can be seen the heating up of the specimen to the desired temperature took about forty minutes in case of 400 °c and thirteen minutes in case of 600 °c. in case of the induction furnace at maximum heating power these values were around forty and fifty five seconds, while the heating up to 850 °c took seventy five seconds. regarding the rapid heating up and the lack of temperature control of the induction furnace, we find it difficult to keep the sample at a constant temperature especially at lower temperatures. the differences in temperature between the center and the surface of the sample were negligible in both cases. 199 figure 2: the effective strain (λö) as a function of the radius, the friction coefficient, the displacement, and the height values figure 3: development of the sample temperature in a box furnace 200 discussion analyzing the forming process we found that in this case upsetting is the most suitable method for the forming process. its mathematical background is well developed; it is easy to perform experiments with the same parameters; the samples could be manufactured easily and precisely; and it is well controllable. the advantage of the ideal state forming (where the friction coefficient is disregarded) is that the desired strains are easily realizable and computable. but these kinds of circumstances cannot be put into practice, and even at very low friction coefficient values the strain field remains nearly homogeneous only at low strain values. on the other hand at higher friction values the simplified equations do not work which means it is hard to determine the exact strain values. the differences in the strain field in the volume could be characterized with micro hardness testing. this hardness map of the sample could be transformed into a strain map by computing the theoretical strain values and doing forming experiments as close to the ideal state as possible, and then pairing the related strain and hardness values. as mentioned before the ideal state cannot be reached in the practice, so the real strain values of the formed samples will deviate from the results obtained by computing. transforming the strain levels to hardness values needs lots of experiments, but once it is done, the result could be applied in the further work. of course this method could give correct results only if the initial microstructures of the samples are identical. on the last three diagrams in fig. 2 (where the friction coefficient m = 0.8) it can be observed that the effective strain have changed nearly linearly at the middle section of the specimen (where the height value z = 0), and through the three different displacements (δh = 2, 6, 10 mm) its value covered a wide range. in addition the specimens are axisymmertic cylinders; therefore investigating the middle section of the samples along a line from the origin to the surface will provide sufficient information. as a result of the widely varying effective strain values, the number of the necessary samples (and therefore the number of the experiments) could be significantly reduced, and there is no need for the value of the friction coefficient to be precisely determined (we not even need to know its value). investigating the heat treatment methods we learnt that the temperature field is homogeneous in the whole volume of the copper samples during heating regardless of the method. in case of heating in a box furnace the heating rate is low, and therefore it is possible that at shorter annealing times the temperature of the sample would not even reach the desired value. on the other hand the induction furnace is capable of rapid heating but the proper control of its heating power is still unaccomplished. conclusions ● as for the forming process we found upsetting to be the most suitable. ● as the ideal state forming could not be accomplished we found high friction coefficient to be the most effective as a forming parameter. ● at high friction values it is hard to determine the exact strain values, therefore extended examination is needed, but once it is done, its results could be applied in the further work. and also because of the widely varying effective strain values the number of the necessary samples and experiments could be significantly reduced. ● standardizing the initial microstructure of the samples is a key factor to get precise and comparable results. ● as for the annealing of the samples using inductional tempering seems to be more satisfying, despite the proper control of the specimen temperature is still needs to be solved. references 1. p. fortier, w. a. miller, k. t. aust: triple junction and grain boundary character distributions in metallic materials, acta materialia, 45 (8), 1997, 3459–3467. 2. s. tsurekawa, s. nakamichi, t. watanabe: correlation of grain boundary connectivity with grain boundary character distribution in austenitic stainless steel, acta materialia, 54, 2006, 3617–3626. 3. v. randle, r. jones: grain boundary plane distributions and single-step versus multiple-step grain boundary engineering, materials science and engineering a, 524, 2009, 134–142. 4. m. kumar, a. j. schwartz, w. e. king: microstructural evolution during grain boundary engineering of low to medium stacking fault energy fcc materials, acta materialia, 50, 2000, 2599–2612. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 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<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> /enu (use these settings to create adobe pdf documents best suited for high-quality prepress printing. created pdf documents can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word 01_r.doc hungarian journal of industrial chemistry veszprém vol. 35. pp. 75-84 (2007) what happens to process data in chemical industry? from source to applications – an overview b. balasko, j. abonyi university of pannonia, dept. of process engineering, h-8201, veszprem, p.o.box 158, hungary it is globally accepted that information is a very powerful asset that can provide significant benefits and a competitive advantage to any organization, like production technologies in the chemical industry, which was driven by market forces, customer needs and perceptions, resulting in more and more complex multi-product manufacturing technologies. these technologies, due to their highly automated level, provide mountains of process data, which is applied only in daily operation and control, but it definitely can give access to the underlying structure of any system. to enhance this automation level while keep operation safe and efficient, one needs more information, i.e. knowledge about the process, which can be extracted from process data, and more tools, which can extract effectively this knowledge. to meet the growing expectations for future chemical engineering tasks, like multi-scale modelling, simulation and control or process and product design, advanced data analysis techniques can lead a way to solution. this paper briefly overviews some of the commercial products on market and the applicable data analysis techniques which guide process data from source to its application: from technology to expert knowledge with the help of knowledge discovery in databases (kdd) process. numerous citations and their evaluation are given to show that data mining in chemical engineering can efficiently solve many data analysis related problems. keywords: process data, data analysis, data mining, chemical engineering, review introduction chemical engineering is said to be a profession of applied natural science, but besides applying the common practice for design, maintenance and control of industrial processes, it always faces challenges to continuously improve these techniques, thus improve the efficiency, effectiveness and reliability of all the chemical engineering activities. charpentier defines the future main objectives of chemical engineering in four areas: (1) total multi-scale control of the process to increase selectivity and productivity; (2) equipment design of based on scientific principles and new operation modes and methods of production: process intensification; (3) product design; (4) an implementation of the multi-scale and multidisciplinary computational chemical engineering modelling and simulation to real-life situations [1]. it is clear that in every area, process data plays an essential role to fulfil these high expectations, hence it needs to be well structured and reliable. the boom of the information systems in the past decades had its effect in every field of life, which is especially true for chemical industry, where a high level of automation and integration takes place. the high automation level provides the opportunity to collect more information (more variables) from the process and due to the integration of these components of the technology, the collected information in chemical industry can be larger than ever before. additionally, due to the large developments in data storage capacities, the sampling frequency of the collected data has increased significantly as well. on the other hand, the availability of these modern data acquisition systems has increased as well: compared to a system 20-25 years ago, modern data acquisition systems cost 20 times less while running on higher performance level [2]. to serve this horizontal and vertical increase in data amount – it doubles every year – an exceptional hardware and software development takes place for a huge amount of application fields, and from being under-informed in the past we turned into over-informed: information mountains have arisen, but only ten percent of the enormous amount of collected and stored data is analyzed for further aims [3]. this means that there is a clear need for tools and applications that are able to handle all the relevant tasks regarding data produced in a process. this paper aims to review the available solutions in the areas of data acquisition and data analysis for the above mentioned problems, highlighting the importance of process data analysis in chemical engineering. the first half of the paper presents recent solutions to data acquisition in industrial environments while the second half provides the various ways how these data can be analyzed to achieve process-related knowledge and meet the continuous development requirements in chemical industry. 76 data acquisition and retrieval the two main weaknesses of data acquisition systems are not handling heterogeneity and data inaccessibility: 1. data from different sources and in different format cannot be handled in one environment, e.g. a priori knowledge, empirical or phenomenological knowledge cannot be incorporated into sampled data. lots of research has been done on these problems: data compression and data integrity, the next section deals with several solutions to these problems. 2. a mid-size chemical plant has about few thousand measured variables sampled from seconds to hours, a hundred manipulated variables to control a few critical product quality related variables, which results in terabytes of data every year. it would mean inefficiently large data storage capacity if one wants to analyze not only prompt but historical data. in this section solutions to these problems and already available commercial products on market are presented. integrated information storage and query to solve the problem of heterogeneous data integrity several approaches have been developed. complexity of integrating the information with their various describing models is not easy to handle, hence solution methods are different. two main solution groups can be identified: where the integrality problem is solved at the query level or at the construction level of the integrated information system. collins et al. developed an xml based environment [4], while wehr suggests an object-oriented global federated layer above information sources [5]. in [6], bergamaschi et al. presents an object-oriented language as well with an underlying description logic, which was introduced for information extraction from both structured and semi-structured data sources based on tool-supported techniques. paton et al. developed a framework for the comparison of systems, which can exploit knowledge based techniques to assist with information integration [7]. another approach to handle the heterogeneity of information sources is the application of data warehouses (dws) to construct an environment filled by consistent, pre-processed data [8]. the main advantage of a dw is that it can be easily adapted to a dcs and other process information sources of a process while it works independently. table 1 shows a comparison of a dcs related database and a data warehouse [9]. table 1: main differences of a dcs related database and a data warehouse [9] dcs related database data warehouse function day-to-day data storage for operation and control decision supporting data actual historical usage iterative ad-hoc unit of work general transactions complex queries user operator plant manager, engineer, design application-oriented subject-oriented accessed records decimal order million order size 100 mb-gb 100 gb-tb degree transactional time inquiry time region unit, product line product obviously, beside database integration among particular parts of the whole process, there is a need for information integration in the level of the whole enterprise as well for the purpose of optimal operation and planning. this task cannot be fully automated, there is a need for permanently improved methods and approaches for creation, storage and dissemination of experience, know-how and judgment embedded in the organization [10]. appropriate time-series representation for data compression data compression is rather a contribution of the signal and image processing society where lossless information transmission is a key feature within limited time or bandwidth, in chemical engineering society data compression has beside storage capacity rationalization another important issue: retrieve the data in a manner that renders it easily interpretable for the execution of later engineering tasks. in this manner, data compression problem is turned into trend representation problem. lin et al. gave a classification of process trend representation methods in [11], which can be seen in fig. 1. many of these representation techniques refer to segmentation of time series, which means finding time intervals where a trajectory of a state variable is homogeneous [12], representing data by its segments and storing only the segments instead of raw data. 77 figure 1: hierarchy of various time series representations for data mining [11]. products on the market the modern distributed control systems (dcss), which are widely implemented in modern, automated technologies have the direct access to the field instrument signals and measurements, while have data storage functions as well. today several software products in the market provide the capability of integration of historical process data of dcs’s: e.g. intellution i-historian [13], siemens simatic [14], the plantweb system of fisher-rosemount [15], wonderware factorysuite 2000 mmi software package [16] or the uniformance phd modul (process history database) from honeywell [17], which structural components are shown in fig. 2. these elements are typical in modern data collection systems. figure 2: structure of the data flow in honeywell uniformance phd software. there are two main operations: ● data collection: data originates from real-time system and is collected by a real-time data interface (rdi). tag parameters for all the variables are stored in a reference database. a tag contains all important information about a process variable (name, type, unit, etc.). rdi sends data to phd server which places the collected data for a tag in the raw data queue and applies data processing, such as smoothing, compression, and so on, to move raw data queue entries to the data queue of the tag. data queue of the tag then holds processed data that is ready for insertion into the active logical archive files using the continuous store thread. ● data retrieval: an application program makes a call to the phd application programming interface (api) indicating the desired tag and time range for data. the phd system checks the data queues to see if the data is still held in the queues, otherwise phd accesses the data from the connected archive files. data flow goes as follows: first, the tag names of the relevant process variables are selected from all the possible tags in the plant. process data belonging to the selected tags are accessed in phd by the uniformance desktop application program (by honeywell). while the uniformance runs as an ms excel add-in, the results of data queries are saved in excel files. concluding, modern data acquisition systems need to be capable to handle diverse types of data in a way that data is applicable for further analysis. rationally constructed data warehouses are needed for these purposes. some of the above mentioned commercial historical data handling products assist dw maintenance interfaces as well, but in most cases there is no integrated software solution. moreover, to get valuable knowledge that guides process development, appropriate information storage is not sufficient, process data analysis indispensable. the next section deals with this topic where a widely-applied procedure is presented. information extraction from process data knowledge discovery in databases (kdd) integration of heterogeneous data sources is highly related to knowledge discovery and data mining [18, 19], all in all this is one of its main purposes: store data in such a logically constructed way that some deeper information and knowledge can be extracted through data analysis. knowledge discovery in databases (kdd) is a well known iterative process in the literature, which involves several steps that interactively take the user along the path from data source to knowledge [20]. 78 figure 3: knowledge discovery in databases process (left) and the data-driven process development scheme (right). fig. 3 shows the kdd process and its connection to the process development scheme: kdd can be considered as the analysis step of the process development process. this connection was published by many researchers who used the elements of kdd for solving several engineering tasks, like system identification, process monitoring and fault diagnosis, time-series analysis. in the following, we go through the steps of kdd highlighting the presence of “data mining in chemical engineering” (note, that although data mining is a particular step of kdd, it is often associated to it as an independent technique). 1. data selection. developing and understanding of the application domain and the relevant prior knowledge, and identifying the goal of the kdd process. 2. data pre-processing. this step deals with data filtering and data reconciliation. in process data warehouses and integrated kdd environments it is made preliminary during collection of relevant data. 3. data transformation. finding useful features to represent the data depending the goal of the task. dimensionality reduction or transformation methods are applied to reduce the effective number of variables under consideration or to find invariant representation of data. data selection, pre-processing and transformation activities are often referred to as the data preparation step. it corresponds to the feature selection step of the pattern recognition process, which means to select a subset of original features that is good enough regarding its ability to describe the training data set and to predict for future cases. a wealth of approaches have been used to solve the feature selection problem, such as principal component analysis [21], walsh analysis [22], neural networks [23], kernels [24], rough set theory [25, 26], neuro-fuzzy scheme [27], fuzzy clustering [28], selforganizing maps [29], hill climbing [30], branch and bound algorithms [31], and stochastic algorithms like simulated annealing and genetic algorithms (gas) [32-33]. process data have several undesirable attributes which need to be handled before any analysis can take place: time-dependent, multi-scale, noisy, variant and incomplete. all these problems need to be solved in the data preparation steps, hence it takes the largest part, approx. 60 % of the efforts in the whole kdd process. for industrial data reconciliation, osisoft and invensys have developed packages such as sigmafine and datacon [34, 35]. 4. data mining. it is an information processing method, the extraction of interesting (non-trivial, implicit, previously unknown and potentially useful) information or patterns from data (corresponds to feature extraction in pattern recognition). a) the goals of data mining are achieved by various methods: ● clustering. cluster is a group of objects that are more similar to one another than to members of other clusters. the term “similarity” should be understood as mathematical similarity, measured in some well-defined sense. in metric spaces, similarity is often defined by means of a distance norm, which can be measured among the data vectors themselves, or from a data vector to some prototypical object of the cluster. the prototypes are usually not known beforehand, and are sought by the clustering algorithms simultaneously with the partitioning of the data. the prototypes may be vectors of the same dimension as the data objects, but they can also be defined as “higherlevel” geometrical objects, such as linear or nonlinear subspaces or functions. data objects belong to a cluster by their membership value, which is zero or one for hard clustering and between zero and one for fuzzy clustering techniques. note, that in the case of fuzzy clustering the sum of the membership values equals one, i.e. a data object is more or less part of every cluster. on fig. 4, clustering of data of a dynamic crystallizer cascade model (reconstructed in a 4-dimensional state space) projected by pca is shown to analyze the cyclic operation [36]. 79 figure 4: fuzzy clustering of crystallizer cascade model data. data points are denoted by dots, cluster prototypes by stars, cluster membership value levels by lines (darker means lower). clustering is widely used for feature selection [28], feature extraction method, which is applied in operating regime detection [36, 37], fault detection [38, 39] or system identification, like model order selection [40-42], state space reconstruction [43]. ● segmentation. time series segmentation means finding time intervals where a trajectory of a state variable is homogeneous. in order to formalize this goal, a cost function with the internal homogeneity of individual segments is defined. this cost function can be any arbitrary function, usually it is defined by distances between the actual values of the time-series and the values given by a simple function (constant, linear or a polynomial function of a higher but limited degree) fitted to the data of each segment. hence, the segmentation algorithms simultaneously determine the parameters of the describing models and the borders of the segments by minimizing the sum of the costs of the individual segments. the linear, steady-state or transient segments can be indicative for normal, transient or abnormal operation, hence segmentation based feature extraction is a widely known technique for fault diagnosis, anomaly detection and process monitoring or decision support [44-47]. fig. 5 shows a second-order segmentation of 1-d polymerization data during a process transition. second-order means, segment borders are captured where the first or second derivative of a trend changes sign, thus at extrema and inflexion points. ● classification. map the data into labelled subsets, i.e. classes, which are characterized by their specific attribute called the class attribute. the goal is to induce a model that can be used to discriminate new data into classes according to class attributes. the induction is based on a labelled training set. the objective of the 0 50 100 150 200 250 300 350 400 450 500 -0.02 -0.015 -0.01 -0.005 0 0.005 0.01 0.015 0.02 data points y c d a d a d a b c d a figure 5: second-order segmentation of filtered process transition data of polypropylene plant projected into 1-d by pca. segment boundaries are noted as vertical lines at extrema or inflexion points. classification is to first analyze the training data and develop an accurate description or a model for each class using the attributes available in the data. such class descriptions are then used to classify future independent test data or to develop a better description for each class. many methods have been studied for classification, including decision tree induction, support vector machines, neural networks, and bayesian networks [20]. in chemical engineering problems, classification is used in fault detection, anomaly detection problems [27, 45, 47-50]. on fig. 6, a typical classification example is shown, where a decision tree was applied for the problem of the classification of operating regions related to the runaway of a chemical reactor. in [51] a new approach has been proposed, which is allows the transparent and interpretable representation of the boundaries of the operating regions. 285 290 295 300 305 310 315 320 1.05 1.1 1.15 1.2 1.25 1.3 1.35 1.4 1.45 1.5 tw,in p g ,in figure 6: classification example for the classification of operating conditions regarding the runnaway of a chemical reactor. the decision tree representation of the related classifier is shown in fig. 8 80 figure 7: cubic spline interpolation of a semimechanistic model for online melt index prediction in a polyethylene process. ● regression. the purpose of regression problems is to give prediction for process or so called dependent variables based on the existing data (independent variable), in other words, regression learns a function which maps a data item to a real-valued prediction variable and the discovers functional relationships between variables [52-53]. uses of regression include curve fitting, prediction (forecasting), modelling of causal relationships and testing scientific hypotheses about relationships between variables. applied mainly in system identification problems, e.g. [54]. in [55], cubic spline interpolation-regression is applied to estimate variable derivatives for a semi mechanistic neural network model (fig. 7). b) representation, i.e. output of data mining, of patterns of interest can be in form of several techniques as well: ● regression models. model interpretation of a system’s behavior is possible by several techniques for numerous tasks. the extracted model structure can be various: from linear autoregressive models [53] to artificial neural networks [27, 45, 48], semi mechanistic models [37], self-organizing maps [29, 50], etc. on fig. 8 component planes of a som model for melt index prediction of a polypropylene polymer grade are presented for 8 independent variables of the technology [56]. ● association rules. general form of association rules is an ‘if x … then y …’ (noted as x�y) implication. the two parts of a rule are the antecedent (x) and the consequent (y). the association rules are constructed from frequent item sets [57]. the occurrences of an item (or item sets) in a data set are called support, which value could be seen as a probability value: how many percent of the transactions is the specific item (are the items of an item set together). an item is called frequent item if its support is higher than a given (user defined) threshold, namely the minimal support. the support of a u-matrix 0.0289 3.65 7.28 melt index n -0.962 1.52 4.01 h2 conc(r201) n -0.742 1.92 4.58 h2 conc(r202) n -0.783 1.91 4.61 h2 inlet(r201) n -0.962 1.62 4.21 h2 inlet(r202) n -1.06 1.46 3.98 cat inlet n -2.49 -0.244 2 temp.(r200) n -1.45 -0.296 0.856 temp.(r201) n -4.88 0.129 5.13 temp.(r202) n -4.88 0.0809 5.04 slurry dens.(r201) n -2.5 -0.619 1.27 slurry dens.(r202) n -2.61 -0.701 1.21 figure 8: self-organizing map representation based regression of process variables for melt index prediction in a polypropylene plant. rule is equal to the support of the item sets contained in the rule. while support says only the probability of joint occurrence of x and y, the confidence (conditional probability) of an x�y rule serves information about relationships between the x and y. association rules are applied in the field of decision support, process monitoring, process control [58]. ● decision trees. common representation for classification problems [47, 49]. the goal of tree induction method is to get an input attribute partitioning which warrants the accurate separation of the samples. a decision tree has two types of nodes (internal and terminal) and branches between the nodes. the possible outputs for an internal node (cut) are represented by the branches. the terminal nodes of the tree are called leaves where the class labels are represented. the paths from the root to the leaves (sequences of decisions, or cuts) represent the classification rules. therefore, as data partition representation, it represents the data as a hyperrectangle. the most of the decision tree induction algorithms (e.g. id3, c4.5) are based on the divide and conquer strategy. in every iteration steps the cut which serves topically the highest information gain (greedy algorithms) is realized. in fig. 9. a decision tree is presented for reactor runaway detection of a fixed bed tube reactor [59]. there are two class attributes: class attribute 1 and 2 refers to reactor conditions where reactor runaway takes (1) and takes not place (2). decision variables are: cooling water inlet temperature (tw,in), reactor mixture inlet temperature (tw,in), inlet pressure of reactor mixture (pg,in) and mass feed flow of reactants (bg,inca g,in and bg,incb g,in). 5. interpretation of mined patterns, i.e. discovered knowledge about the system or process. the interpretation depends on the chosen data mining representation. 81 figure 9: example of decision tree representation of a two-class problem for classification of reactor conditions regarding if there is (1) or is not reactor runaway (2). tw,in: cooling water inlet temperature; tg,in: reactor mixture inlet temperature; pg,in: inlet pressure of reactor mixture; bg,inca g,in and bg,incb g,in: mass feed flow of reactants. for visualization of the mined patterns, exploratory data analysis (eda) has been developed. although it is often stated as an independent analysis technique, it can be considered as a special application of the kdd process, where the knowledge is presented by the information embedded into several types of visualization tools. it focuses on a variety of mostly graphical techniques to maximize insight into a data set. the seminal work in eda is written by tukey [60]. over the years it has benefited from other noteworthy publications such as data analysis and regression by mosteller and tukey [61], and the book of velleman and hoaglin [62]. data preprocessing step in eda refers to several projection methods in order to be able to visualize high dimensional data as well: techniques of principal component analysis (pca) [63], sammon-mapping [64], projection to latent structure (pls) [65], multidimensional scaling (mds) [66] or self-organizing map (som) [67] are applied. data mining methods also use these techniques, but in eda, projection is used for visualization purpose hence in most cases into two or three dimensions. the graphical techniques of eda have a wide spectrum including plots of raw data (histograms, probability plots, block plots), basic statistics (median, quantile plot, quantile-quantile plot, box plot) or advanced multidimensional plots (scatterplot matrices, radar plots, bubble charts, coded maps, etc.). in fig. 10, fig. 11 and fig. 12, some examples are presented. figure 10: example of a process variable (reactor temperature) and its cumulated distribution function (q0.25, q0.50, q0.75 refer to quantiles) plotted by matlab figure 11: box-plot of variable on fig. 5 plotted by matlab, i.e. 5-number-summary from tukey: minimum, maximum, median (q0.50), 1st and 3rd quartile(q0.25 and q0.75) mg srmn ba ti zr zn v figure 12: star plot of a south african clinker (code number 159sa17). the standard on the right side can be used as comparison [68] the most common software for eda is ms excel with free add-ins, but there are several products on the market as well: ibm’s db2 intelligent miner (which is no longer supported), mathworks’s matlab statistics toolbox [69] and the open-source weka developed by waikato university [70]. note, that most eda techniques are only a guide to the expert to understand the underlying structure in the data in a visual form. hence their main application is process monitoring [71, 72], but these tools are already used for system identification [73], ensuring consistent production [74] and product design as well [75]. 82 conclusions chemical industry is a highly automated industry, which produces a huge amount of production related data in every minute, which obviously has the potential to mine useful information and knowledge about the whole process. this paper reviewed how process data is stored and what types of scientific approaches are developed to guide this knowledge discovery. the brief description of kdd and eda techniques is presented, emphasizing their high correlation to chemical engineering tasks. from all the results in these scientific areas, one can conclude, that process data analysis has high contribution to the solution of problems that chemical engineers will face in the near future: optimal multi-scale control, process and product intensification, modeling and simulation of complex systems. kdd gives users tools to shift through vast data stores to learn and recognize patterns, make classifications, verify hypotheses, and detect anomalies. these findings can highlight previously undetected correlations, influence strategic decision-making, and identify new hypotheses that warrant further 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10., veszprém, hungary e-mail: kiss@mukki.richem.hu hydrolysis of pectins from various sources by a polygalacturonase (pg) enzyme was studied from a kinetic point of view. pectin substrates – which are commercially not available – were extracted from sugar beet pulp, apple, red currant and black currant. strong product inhibition was found in each pectin preparations that could be described by a competitive mechanism. the kinetic parameters (michaelis-menten constants, maximal reaction rates and inhibition constants) were determined and compared. differences in the parameters imply distinctions in structure of the pectins studied. keywords: product inhibition, enzymatic hydrolysis, galacturonic acid, introduction in the fruit-processing industry pectolytic enzymes are used to increase yields, improve liquefaction and clarification [1,2], moreover to produce d-galacturonic acid (monomer of pectin), which is an important compound, raw material in the food, pharmaceutical and cosmetic industry to manufacture e.g. vitamin c, or acidifying, tensioactive agents [3]. hydrolysis of pectin can be carried out by pectinases that are classified into three main groups: • pectinesterases – catalysing deesterification of the methoxyl group of pectin; • depolymerising hydrolytic enzymes (including polymethyl-galacturonases and polygalacturonases) – catalysing the hydrolytic cleavage of 1,4glycosidic bonds; • lyases – catalysing the cleavage of glycosidic bond by transelimination. among the pectin hydrolysing enzymes (endo)polygalacturonases are probably the most important biocatalysts. polygalacturonase enzymes (pg, e.c. 3.2.1.15.) are able to hydrolyse pectin and/or pectic acid. although pg enzymes play a key role in pectin hydrolysis, their actions have not been studied in details from kinetics point of view so far, while kinetic behaviour of many soluble and immobilized pectinase enzymes and enzyme-mixtures have been already characterised [4,5,6]. kulbe et al. [7] have assumed that the pg enzyme from aspergillus niger was inhibited by its monomer, but no experiments were carried out to prove it and determine the mechanism. we have studied the kinetics of pectin hydrolysis by polygalacturonase enzyme from aspergillus niger in details using a commercially available, low esterification degree lm-5cs pectin substrate and the kinetic parameters were determined [8]. the aim of this work is to study the kinetics of enzymatic hydrolysis of other pectins, which are commercially not available. these pectins, therefore, should be prepared in our laboratory by extraction from plant substances containing considerable amount of pectin. materials and methods polygalacturonase enzyme (pg) from aspergillus niger was purchased from sigma (usa), its activity was 1.7 u/mg. activity definition: one unit is defined as the amount of enzyme which is able to produce 1 μmol galacturonic acid from polygalacturonic acid in one minute in ph = 4.1 and 50 °c. the enzyme is able to hydrolyse pectin molecules, as well. all the other chemicals (analytical grade) were purchased from fluka (germany). pectin substrates were extracted from sugar beet pulp, apple, red currant and black currant by boiling water [9]. the substance-water mass ratio was 1:4, the extraction time was 4 hour. as a result, majority of the pectin was obtained in the aqueous phase. ultrafiltration was used then to clarify the extracted solution, and the diluted aqueous pectin solution was concentrated partly by membranes (ultrafiltration, polyethersulfone membrane, cut off 45 kda) up to 5 % tss, partly by evaporation up to 30 % tss. then pectin in powder form was obtained 56 from the concentrated pectin solution after precipitation with alcohol. pectin purity was determined by hplc (merck system) equipped with biorad aminex hpx42-a column and ri detector, ultrapure water was used a mobile phase. purified citrus pectin was used as a standard for comparison. in the kinetic experiments purified apple and sugar beet pectins were used to compare to the other pectin preparations. to study the kinetics of the reaction, shaking flask experiments (three parallel each) were carried out in a new brunswick scientific (usa) shaking incubator. citrate buffer was used (ph = 4.1) to prepare the substrate solutions with various concentrations, and the operational conditions of the experiments were 50 °c and 150 rpm. to determine the product inhibition, galacturonic acid (product) was added initially to some of the substrate solutions. the hydrolytic reaction was followed by measuring the reducing sugar content using the dinitro-salicylic test (dns standard method – miller (1959) [10]) which is based on the formation of a chromophore between dns product and reducing groups of the (oligo)galacturonic acid molecules. degree of esterification was determined by the titration method [11] involving the titration of the pectin suspension with sodium hydroxide before and after the saponification step. in the de-esterification procedure the carboxyl groups of the pectin were hydrolyzed, while the ph of the pectin solutions was maintained at 12, using 0.1 m naoh. after saponification 0.1 m citric acid was added to the mixture to adjust the ph at 4.1. results pectin extraction pectin substrates were extracted from various sources, the average yields obtained were summarized in table 1, and data on original pectin content [12] of the fresh substances are presented for comparison, as well. it can be seen that majority of the pectin content was successfully recovered from the tissues. the average purity of the various pectin preparations was determined by hplc and the initial substrate solutions for the kinetic study were prepared taking into account the exact pectin content of the preparations. table 1: pectin yields and purity substance yield of extraction [%] purity [%] original pectin content [%] apple 0.93 82.9 1.5-1.6 [2] red currant 0.95 85.4 1.2-1.4 [13] black currant 1.25 90.6 1.4 [12] sugar beet 11.35 93.4 13.1[2] study on the kinetics in the shaking flask experiments firstly progress curves on hydrolysis of pectin solutions were measured, where the reducing sugar contents (galacturonic acid) in the reaction mixtures as a function of time were determined with different initial substrate concentrations. as an example, experimental data on various initial substrate concentration (using 0.01 g enzyme) for red currant pectin preparations are presented in fig. 1. 0 0,2 0,4 0,6 0,8 1 1,2 1,4 1,6 0 20 40 60 80 100time (min) re du ci ng s ug ar (g /l) 1 g/l 2 g/l 4 g/l figure 1: progress curves of pectin hydrolysis by polygalacturonase from aspergillus niger (reaction conditions: ph 4.1, 150 rpm, 50 °c, 0.01 g enzyme, red currant pectin) since earlier measurements for citrus pectin have proven that product inhibition occurs during the reaction, another series of experiments were carried out to study the effect of the product on the process. various amounts of galacturonic acid were added initially to the reaction mixture using different substrate concentrations and the reducing sugar content was measured as a function of time (fig. 2). in fig. 2 it is clearly shown that the galacturonic acid present had a significant inhibition effect on the reaction. the more product to the reaction mixture was added, the slower initial reaction rate was observed. investigating the hydrolysis of pectins from different sources similar progress curves were obtained. from the experimental data (progress curves) initial reaction rates were calculated which were then transformed according to lineweaver-burk method (double reciprocal method). the 1/v intercepts of all the lines were in the same section, thus it can be concluded that the type of inhibition was competitive. 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0 20 40 60 80 100 time (min) re du ci ng s ug ar (g /l) i= 0.5 g/l i= 1 g/l i= 2 g/l i= 0 g/l figure 2: example for progress curves on studying the product inhibition (reaction conditions: ph 4.1, 150 rpm, 50 °c, 2 g/l red currant pectin, 0.01 g enzyme) 57 the michaelis-menten model for the reaction rate completed with competitive product inhibition describes the process as follows: (s) k (i)kk (s)vv i i m max i + + = where vi reaction rate s substrate concentration i inhibitor (product) concentration vmax maximal reaction rate km michaelis-menten constant ki inhibition constant applying the lineweaver-burk method, the parameters of the model were determined (which were checked by numerical methods, as well) and their statistical analysis was carried out by sigmastat program. the parameters obtained are summarised in table 2. table 2: kinetic parameters obtained for hydrolysis of various pectin preparations by pg from aspergillus niger pectin km [g/l] vmax [g/l*min] ki [g/l] sugar beet 1.47 0.31 1.16 sugar beet* [14] 3.0 0.43 0.16 citrus 8.3 1.06 3.13 citrus*[14] 3.5 0.23 1.05 red currant 0.48 0.19 0.88 red currant (after de-esterification) 0.48 0.47 0.93 black currant 0.79 0.31 0.94 black currant (after de-esterification) 0.95 0.82 1.04 apple 0.15 0.08 0.58 firstly the kinetic parameters of the pectins were compared with data found in literature [14]. these data are marked by asterisk. it can be concluded that the value of the data are in one order of magnitude. however full comparison is not possible through another enzyme preparation was used during the reactions. it also implies – regarding pectins from other sources (including citrus pectin studied and described in our earlier paper) – that the considerable differences existing in the parameters for various pectins might be caused by the structural differences between the pectins. it is known that pectins from citrus fruits have low esterification degree, while sugar beet pectin contains not only large amount of methanol (esterified), but acetic acids, as well, bound to the backbone [9]. pectins from berry fruits less information is available on the structure of pectins, therefore a study on the structure details should be accomplished. nevertheless higher initial reaction rate was observed in case of de-esterified pectins compared to natural pectins. summary hydrolysis of various pectin preparations by polygalacturonase from aspergillus niger was studied in details. it was found that strong product inhibition occurred during the process. the product, galacturonic acid is a competitive inhibitor of the enzyme, and the kinetic parameters (including inhibition constants) were determined experimentally as a new finding for each pectin substrates. considerable differences in the constants were found for the various pectins implying significant differences in pectin structure. now our aims are (i) to explore and determine structural differences in pectin from various sources by special analytical methods, instrumental analysis (e.g. nmr, sem, ms…etc.) and (ii) to extend the research work for other, cheaper substrates, like agro-waste material e.g. press cake formed in fruit juice production. thus the processing of pectin containing fruits can be completed with a waste utilization step: manufacturing a valuable product, d-galacturonic acid by pectin extraction followed by enzymatic degradation. to avoid inhibition, membrane bioreactor should be applied for continuous pectin hydrolysis to enhance productivity. finally the galacturonic acid can be recovered and concentrated by electrodialysis, to study and characterize this process is also one (iii) of our aims in this project. acknowledgements the research work was supported by gak (membran5) project, grant no. omfb-00971/2005. and gvop project, grant no. 0421/3.0. references 1. pilnik, w., voragen, a. g. j.: pectic enzymes in fruit juice and vegetable juice manufacture. in g. reeds (ed.), food and science technology, enzymes in food processing (pp. 363-399). academic press, new york, (1993) 2. kashyap, d. r., vohra, p. k., chopra, s., tewari, r.: bioresource technology 77, 215-227 (2001) 3. jörneding, h. j., baciu, i. e., berensmeyer, s., buchholz, k.: zuckerindustrie 127, 845-853 (2002) 4. gillespie, a. m., coughlan, m. p.: biochemical society transactions 17, 384-385 (1989) 5. todisco, s., calabro, v., iorio, g.: journal of molecular catalysis 92, 333-346 (1994) 6. sarioğlu, k., demir, n., acar, j., mutlu, m.: journal of food engineering 47, 271-274 (2001) 7. kulbe, k. d., heinzler, a., knopki, g.: annals of the new york academy of sciences 506, 543-551 (1987) 58 8. bélafi-bakó, k., eszterle, m., kiss, k., nemestóthy, n., gubicza, l.: journal of food engineering 78, 438-442 (2007) 9. kertesz, z. i.: the pectic substances, intersciences publishers, new york, (1951) 10. miller g. l.: analytical chemistry 31, 426-428 (1959) 11. food chemical codex, washington, dc, national academy of science pp. 283-286 (1981)] 12. hilz, h., bakx, e. j., schols, h. a. voragen, a. g. j.: carbohydrate polymers 59, 477-488 (2004) 13. poutanen, k.: maxfun – tools for increased bioactivity in berry and grape processing. 3rd international conference biocatalyis in the food and drinks industries, wageningen, the netherlands, book of abstracts, p. 16. (2006) 14. baciu, i. e., jördening, h. j.: enzyme and microbial technology 34, 505-512 (2004) microsoft word b_23_r.doc hungarian journal of industrial chemistry veszprém vol. 38(2). pp. 169-173 (2010) research of roughness of hard turned bores k. szakács department of production engineering, university of miskolc, 3515 miskolc, egyetemváros, hungary e-mail: kati873@freemail.hu this paper reports an extensive characterization of the surface roughness generated during hard turning operations performed with conventional pcbn tools and during combination turning and grinding machining. hard turning has been applied in many cases such as producing bearings, gears, axles and other mechanical components. the pcbn is widely used for finish machining of hardened steel parts (hrc 45–65). the special condition of dry hard cutting is the required cutting speed must be ranged from 90 to 180 m/min. after the hard turning and combination machining tests, the relevant changes of surface profiles and surface roughness parameters were successively registered and measured by a profilometer. based on the experimental results, this paper shows and analyse the modification of the surface roughness parameters in case of hard turning and combination machining[1]. keywords: hard turning, grinding, surface roughness, combination machining introduction this work aims to investigate the machining of hardened steels using cubick boron nitride (cbn) the combining of processes in the machining of high-precision hardened workpieces is catching on. since the introduction of the first combined turning and grinding center at metav 1998 the new technology has found wide-ranging acceptance. one of the leading exponents is the emag group experimental set-up, cutting parameter control is shown by fig. 1. table 1 contains the parameters of surface roughness and the tool edge geometry [2, 3]. table 1: nomenclature ap – cutting depth (mm) f – feed rate (mm/rev) vc – cutting speed (m/min) ra – arithmetical roughness (μm) rm – equivalent mechanical resistance (ηm) rz – rougness (ηm) rq – quadrotic roughness (ηm) kr – tool cutting edge angle (°) αr – rake angle (°) γr – relief angle (°) vb – flank wear (mm) work piece material geometry machined surface cutting operation cutting speed feed rate cutting depth lubrification tool wear coatingl geometry machine tool power precision rigidity cutting forces wear figure 1: experimental set-up, cutting parameter control [4] experimental conditions work pieces all the tests were carried out with parts machined under industrial. the cutting parameters were taken from the practice. the machined material was the steel din 20mncr5, quenched to 62 hrc. the machined work piece was on gear with a cylindrical section with a diameter of 53 mm and length of 49.3 mm and the other gear was diameter of 60 mm and length of 45.3 mm. 170 table 2 shows the chemical composition of the material [2]. table 2 cemical composition % c 0.17/ 0.22 mn 0.15/ 0.40 p 0.02 0.035 s 0.035 max. si 0.15/ 0.4 cr 1.00/ 1.30 al 0.020 min. tool the inserts conformed to the iso cod. hard turning: conventional mitsubishi: np-cnga120408ta2 mb8025 (roughing) and the tool holder c5-pclnr/l17090-12 and smoothing wiper: np-cnga120408gsw2 mbc010 and the tool holder c5-pclnr/l-17090-12. combinated machining: somitomo: 4nccnga120412, and the tool holder c5-pclnr/l17090-12 grinding wheel: 97a 602 i 5 v112 cnc turn it was employed a turn pvs pittler, this equipment presents the stiffness and accuracy enough for the demands of the hard turning operations. combinated turn and grinding machine improved component and end product quality, as the workpiece is machined in a single setup, whereby the rough hard turning operation leaves a grind-finishing allowance of just 0.02 mm (relative to the diameter). compared to conventional grinding methods the minute grinding allowances required for the application of hds-technology allow you to grind with a minimum of coolant and even dry, in which case there is no need for costly grinding sludge disposal measures [3]. figure 3: pgk 120 prfilometer [2] surface roughness measurements after each individual test, part surface finish was measured with a stylus profilograph. in this investigation, a shop floor pgk 120 profilometer (fig. 3) with a 5 μm diamond stylus radius was used. i used a special computer programs. conclusion significant difference could be found among the surface roughness number as the function of number of pieces on the worpieces surface machined by hard turning and by combined machining (fig. 4). in case of hard turning significant fluctuation can be seen in the values of surface roughness, which makes uncertain the planning of the machined roughness. this manifestation can be disadvantageous in case of production certain machine elements. this can be explained by the tool wear mechanism of pcbn single point cutting tools, because the tool is machining on one point, and its geometrical errors can be copied into the workpieces. in spite of this in the case of combined machining roughness height mad by hard turning can be grinded by the grinding wheel truined at each worpiece (fig. 5). so, the surface roughness to be produced can be regular, can be planned. furthermore the micro-thread can be avoided which occurs in hard turning. however, hard turning can be pretend to quasy absolute environmentally friendly procedure for neglecting of coolants and lubricants, but because of fluctuation of surface roughness its change to combined machining is suggested, which involves a little load of environment. 171 0 0,1 0,2 0,3 0,4 0,5 1 10 20 30 40 50 60 70 80 90 100 110 120 ra work pieces combined machinig hard turning a, 0 0,1 0,2 0,3 0,4 0,5 1 10 20 30 40 50 60 70 80 90 100 110 120 work pieces rq combined machinig hard turning b, 0 0,5 1 1,5 2 2,5 1 10 20 30 40 50 60 70 80 90 100 110 120 work pieces rz combined machinig hard turning c, 0 0,5 1 1,5 2 2,5 1 10 20 30 40 50 60 70 80 90 100 110 120 work pieces rm combined machinig hard turning d, figure 4: roughness parameters as a fuction of work pieces for different machining conditions 172 hard turned profile combining machined profile workpieces 1 workpieces 40 workpieces 50 workpieces 90 workpieces 120 figure 5: charasteristic surface profiles 173 references 1. w. grzesik: influence of tool wear on surface roughness in hard turning using differently shaped ceramic tools, wear, 265 (3-4), 2008, 327–335. 2. g. de s. galoppi, m. s. filho, g. f. batalha: hard turning of tempered din 100cr6 steel with coate and no coated cbn inserts, journal of materials processing technology, 179, 2006, 146–153. 3. http://www.emag.com/de/maschinen/schleifmaschi nen/innenrundschleifen/vsc-dsdds-baureihe.html 4. m. remadna, j. f. rigal: evolution during time of tool wear and cutting forces in the case of hard turning with cbn inserts, journal of materials processing technology, 178 (1-3), 2006, 67–75. 5. acélkalauz, szabványkiadó, budapest, 1983, p.110. 6. r. pavel, i. marinescu, m. deis, j. pillar: effect of tool wear on surface finish for a case of continuous and interrupted hard turning, journal of materials processing technology, 170 (1-2), 2005, 341–349. 7. j. kundrak, k. gyani, v. bana: roughness of ground and hard-turned surfaces on the basis of 3d parameters, international journal of advanced manufacturing technology, 38 (1-2), 2008, 110–119. 8. j. kundrak, a. g. mamalis, a. markopoulos: finishing of hardened boreholes: grinding or hard cutting? materials and manufacturing processes, 19 (6), 2004, 979–993. 9. j. kundrak, k. gyani, v. bana: qualification of hard bored surfaces with 3d parameters, daaam international scientific book, vienna 2005, 371–384. 10. a. g. mamalis, j. kundrak, k. gyani: on the surface integrity of precision-ground steel cylindrical parts, materials and manufacturing processes, 18 (5), 2003, 835–845. 11. j. kundrak, v. bana: investigation of surface roughness in turning of hardened and 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word a_06_r.doc hungarian journal of industrial chemistry veszprém vol. 38(1). pp. 27-33 (2010) power conditioning with electric car battery charging from renewable sources p. görbe , a. magyar, k. m. hangos department of electrical engineering and information systems, university of pannonia veszprém egyetem u. 10. 8200 hungary e-mail: gorbep@almos.vein.hu a control method for electric car battery charging combined with small domestic power plants using renewable energy is described in this paper. this method is not only capable of optimizing the working point and charging current of the system but also implements robust energy flow control to balance the convenient process variables.the proposed controller has been investigated by simulation in matlab environment, and as a result, succesful combination of a grid synchronised inverter and a electric car battery charger robust operation could be achieved in changing operational modes. keywords: power quality, electric car, battery charging, simulation, nonlinear distortion, renewable power sources introduction with the price of electrical energy rising the small domestic power plants are coming into general use in the european union too (in the range of 1–5 kva). the isolated working mode of these plants is not an efficient way since the cost effective energy storage is not a solved problem yet. on the other hand the electric cars development turns to be general in vehicle industry. these two problems can be handled jointly, since the optimal working point of the renewable power source (photovoltaic panel or wind generator) and the optimal charging current of the li-ion battery can only be optimized jointly. the optimal working point is important for the economical operation, the optimal charging current is important for extending the lifetime of the expensive electric car batteries. the optimal working mode sometimes needs additional electrical power, sometimes gives remaining efficient power and theese need additional storage capacity. grid tie inverter systems can be used to inject the spare power to the local low voltage mains. this power is utilized in the local neighborhood, not far from the injection point so the loss is small. in addition, the construction of this type of inverters makes them suitable for conditioning the line, correcting the accurate voltage forms, and repairing the reactive power in the mains. therefore, this additional functionality doesn't need expensive change of the constructions, we should only modify the control methods and regulators to develop the ability of line conditioning. the cost of changing the controlling processor and control software negligible to the cost of equipment. on the other hand with high percentage of fluctuating renewable energy sources the connected electric car batteries can absorb peaks of power production or feed the power into the grid [12]. several papers deal with power injection to the grid, see e.g. [1] for a recent survey. the possibility of power factor correction in conjunction with power injection has also been realized [2, 3, 5]. furthermore, its connection with nonlinear distortion reduction has also been explored [6] and [8]. in [6] and [8] the authors use the dsp based current control technique for distortion reduction with active power filters (apf) for compensating an exact nonlinear load. sensing the nonlinear current time function and the ideal sinusoid current with phase locked loop (pll) technique, they inject the exact deviation current into the grid with radical distortion reduction. the aim of our work has been to develop and investigate control methods for performing active power factor correction and lowering the extant harmonic distortion in the line without the need for current measurement. as our earlier papers show [9, 11], this aim can be achieved in addition to control the maximum power operating point from the renewable source (wind generator or photovoltaic panel) by adding new elements to the schematic construction designed for the built-in elements. the aim of this paper is to develop an improved construcion of combination of a small domestic power plant and battery charger components and to investigate the robustness of the proposed method with respect to working mode changes of the system consisting of a renewable source, an electric car battery charger and the nonlinear distorted low voltage electric network. 28 background and motivation the use of low consumption equipments with simple switching power supplies (mobile phone chargers, notebooks, networking products, small variable frequency motor drives, telecommunication consumer electronics) a capacitive load with high nonlinearities creates significant 3rd and 5th upper harmonic current components, which cause serious distortion in the voltage shape. it is well-known, that it is difficult to compensate the reactive power of this type of nonlinear distorted voltage shape with traditional shunt capacitances (compensator). the distortion of the voltage shape is commonly characterized by the overall reactive power 2 )(sin|)(ˆ||)(ˆ|== =1=1 kkikvqq ls n k k n k b φ∑∑ where the positive integer n is the (highest) number of harmonics of interest, qk, v ˆ s(k), iˆl(k) and φ(k) are the the reactive power, the source (s) peak voltage, the load (l) peak current and the phase-angle difference of the k-th harmonic, respectively. the power factor (pf) of the source is defined by [3] as |||||||| ,= ss ss iv ivpf ⋅ 〉〈 where 〉〈 ss ivp ,= is the active (real) power and the product s = ║vs║·║is║ is the apparent power calculated from effective values. from the cauchy-schwartz inequality, it follows that p ≤ s. hence 1,1][−∈pf is a dimensionless measure of the energy-transmission efficiency. the total harmonic distortion (thd) is defined as [5]: 2 1 2 2= || )|(| = v v thd k k ∑ ∞ where v1 equals to the voltage amplitude of the fundamental frequency and vn is the voltage amplitude of the n-th harmonic. in applications with capacitive input stage, thd > 0 holds. upper harmonic components have many undesirable effects on power grid [11] causing faulty operation of the network. problem statement as it is indicated in the above discussion, it is desirable to develop a control method that can compensate the distortion caused by the capacitive nonlinear load using the built-in and available controller of electric car battery charger combined with small domestic power plants. the controller unit of these plants can be extended with three new elements to form a complex multifunctional controller unit. the first function of this complex control unit is a conventional maximum power controller that is used to inject base harmonic in phase with the sinusoid current to the mains. the second function is a conventional charger controller that controls the convenient charging current value. the third function, that is to be implemented, is the compensation of the undesirable effects of the linear network with production base harmonic current being not in phase, by injecting reactive power to compensate the inductive and capacitive loads. the third function to be implemented would be the compensation of the nonlinear distortion that is intended to achieved by injecting upper harmonic (mainly 3rd and 5th, but possibly higher) sinusoid current components to reduce the harmonic distortion and to lower the reactive power of the upper harmonic load currents. our aim has been to implement the missing three elements and their relationship, the simplest possible way. the main goals of the three new elements are to approach unity power factor for the overall system for the range of the possible loads and working modes, and to reduce thd. there is a trade-off between these goals that should be taken into account. the intervention to these factors is limited by the renewable source maximum power point, the semiconductors of the bridge and the serial inductances, as well as by the speed and cycle time and the computational capacity of the control device. the optimum would be to have a unit pf and zero thd, but unfortunately, this optimum is not achievable in practice, just approachable. the practical aim is to compensate the upper harmonic component. these values will be used to reduce the nonlinear distortion at the output. structure of the multifunctional complex controller a simple model of the grid tie inverter [2] is used for the controller structure design, that is shown in fig. 1. it contains a simple booster stage with an igbt bridge, connected to the grid through serial inductance. the control system is divided to six main functional parts as shown in fig. 2 in shadowed boxes. • maximum power controller it is a general part of the control system, independent from the other control parts. its' only task is to operate the renewable power source (photovoltaic panel or wind generator) at the optimal working point in any wind and solar condition to get the maximal amount of electric power from the source. the output of the maximum power controller is the input current setpoint of the inverter. the input current control is a simple on/off switching nonlinear hysteresis controller [6]. • charger controller this part of the control system is also independent from the other control parts. it is responsible for controlling the bulk converter's switching element s6 (fig. 3) to adjust the convenient charging current value of the li-ion 29 battery. the current control is also a simple on/off switching nonlinear hysteresis controller [6]. • intermediate voltage controller it senses the intermediate voltage, and observes the difference between the measured and the setpoint value. the controller changes the fundamental harmonic amplitude of the injected current using a simple p controller based on the difference. upper harmonic components have no effect on the intermediate voltage so they are not used by the upper harmonic controller. the controller adjusts the effective power injection to the grid in each 20 ms cycle. • upper harmonic controller the main controller of the complex multi-functional unit is the upper harmonic controller. its' inputs are the computed 3rd, 5th, 7th, 9th and 11th upper harmonic component amplitudes of the measured voltage, the outputs are the output current base, and its 3rd, 5th, 7th, 9th and 11th upper harmonic components' amplitudes and phases. these currents are used for compensating the nonlinear distortion using an advanced controller (see details in [9, 11]). • current waveform generator this block will calculate the necessary exact time function of the output current setpoint, which is the setpoint of the bridge current controller. • bridge controller it calculates the difference between the measured output current and the output current setpoint, and switches the igbt bridge two half's control signal (s1s4, s2-s3) on and off in alternate way using a simple schmitt trigger comparator, that realizes a simple on/off switching hysteresis controller [6]. the above blocks influence each other directly, and also through some measurable voltages and currents of the inverter (see fig. 4). figure 1: grid tie inverter model 30 figure 2: control flow chart diagram figure 3: system matlab simulink model 31 modeling and simulation the mathematical model of the nonlinear distorted network has been implemented in matlab simulink using the power electronics toolbox [7]. the control flow chart of the complete model can be seen in fig. 3. modeling the nonlinear network and the battery three type of loads have been modeled: (i) an ohmic one, that represents, for example, heating devices, traditional bulbs, (ii) an ohmic with serial inductance representing motors and rotating household appliances (washing machine, lawnmower etc.) and (iii) a capacitive input stage load for representing the simple nonlinear switching mode power supplies. table 1: load parameter values load nl1 nl2 nl3 resistance 25 ω 50 ω 35 ω capacitance 10 mf 5 mf 7 mf the battery has been modeled by the battery block of matlab simulink power electronics toolbox using the following parameters: nominal voltage 153.6 v, rated capacity 200 ah. simulation experiments as a first step of model verification, the basic elements of the system, the load part, the maximum power controller, and the intermediate voltage controller have been tested. these results served as reference values for comparison. fig. 4 shows these simulated voltage and current values as functions of time. figure 4: voltage and current with inverter on robustness analysis against the energy flow the robustness of the intermediate voltage controller against the changing of the energy flow from the sources to the different loads has been examined using the following four cases: ● normal inverter mode the energy flows from the renewable source to the grid only (fig. 5). ● normal inverter and battery charger mode the energy flows from the renewable source to the li-ion battery and to the grid too (fig. 6 and 7). ● battery charger mode the energy flows from the grid to the li-ion battery only (fig. 8). ● distortion reduction mode the energy flows from the grid into the intermediate capacitance and from the intermediate capacitance into the grid. the energy balance is zero for a whole period, the active power is zero (fig. 9) [9, 11]. figure 5: energy flow: normal inverter mode figure 6: energy flow: normal inverter and battery charger mode 32 the robustness analysis has been performed by changing the energy flow modes in subsequent time intervals as seen in table 2 implemented by changing the source (u0pv) and load (ibattcharge) parameters. the simulation results can be seen in fig. 13, where uintermediate (the intermediate voltage value of the puffer capacitor) and ibaseampl (the amplitude of the base harmonic current component injected to the grid) are plotted as a function of time. figure 7: energy flow: normal inverter and battery charger mode figure 8: energy flow: battery charger mode figure 9: energy flow: distortion reduction mode the controller has been found very robust and tolerant against changing the energy flow mode; the operating mode change transients are monotonous without overshoot. the castor time is less than 0.1 second. a preliminary distortion reduction performance has also been computed in normal inverter mode, the results are seen in fig. 10 and table 3. figure 10: robustness analysis of the controller table 2: parameters of the robustness analysis time 0–0.5 sec 0.5–1 sec 1–1.5 sec 1.5–2 sec u0pv 300 v 300 v 0 v 0 v ibattcharge 0 a 30 a 30 a 0 a table 3: preliminary performance analysis results in normal inverter mode mode irms error thd inverter off ni 39.63 14.26% upper h.contr on 5.74 a 3.87 5.23% conclusion a novel control structure for small domestic power plants integrated with electric car battery charger using renewable energy is described in this paper. it is capable of optimizing the working point of the plant and maintaining the convenient energy balance. the proposed controller has been investigated by using matlab simulation, and a stable and robust operation has been achieved. preliminary analysis showed that the extended controller was able to reduce voltage thd almost as much as our previous inverter controller [11]. future work will be directed towards investigating the effect of the upper harmonic compensation in this combined application using the different source-load modes on the thd and effective current values. furthermore, a new connection type will be defined to allow the injection of the electric power into the grid from the stored reserve in battery in case of highly fluctuating needs [12]. acknowledgement we acknowledge the financial support of this work by the hungarian state and the european union under the tamop-4.2.1/b-09/1/konv-2010-0003 project. the work has also been partially supported by the hungarian national science fund through grant no. k67625. 33 references 1. a j. m. carrasco, l. g. franquelo, j. t. bialasiewicz, e. galván, r. c. p. guisado, ma. á. m. prats, j. i. león, n. m. alfonso: powerelectronic systems for the grid integration of renewable energy sources: a survey, ieee transactions on industrial electronics, 53(4), 2006, 1003–1015. 2. y. k. lo, t. p. lee, k. h. wu: grid-connected photovoltaic system with power factor correction, ieee transactions on industrial electronics, 55(5), 2008, 2224–2227. 3. e. gar e. garcía-canseco, r. grino, r. ortega, m. salichs, a. m. stankovic: power-factor compensation of electrical circuits, a framework for analysis and design in the nonlinear nonsinusoidal case, ieee control 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a. magyar, k. m. hangos: line conditioning with grid synchronized inverter's power injection of renewable sources in nonlinear distorted mains, 10th international phd workshop on systems and control (sept. 2009.) isbn:97880-903834-3-2, on cd. 10. r. c. dugen, m. f. mcgranaghan, s. santozo, h. w. beaty: electrical power systems quality, second edition, mcgraw-hill 2003. 11. p. görbe, a. magyar, k. m. hangos: thd reduction with grid synchronized inverter’s power injection of renewable sources, 20th international symposium on power electronics, electrical drives, automation and motion (speedam) (2010) isbn:978-1-4244-7919-1, on cd, 1381–1386. 12. c. binding, o. sundström, d. gantenbeim, b. jansen: integration of an electrical vehicle fleet into the power grid, european research consortium for informatics and mathematics news nr 82, july 2010, 57–58. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word contents_2.doc hungarian journal of industrial chemistry veszprém vol. 31. pp. 3-8 (2003) chemical utilization of biomass i: starch modification in batch type solid phase reactor j. dencs*, b. dencs**, g. marton* *department of chemical engineering science, university of veszprém, h-8201 veszprém, pob 158. hungary ** cooperative research centre, university of veszprém, h-8201 veszprém, pob 158. hungary anionic flocculants were produced by chemical modification of starch. on the basis of their favourable properties (non-toxic, environmentally degradable) their application is very advantageous in drinking water treatment, food industry and pharmaceutical industry for removing colloid size particles from suspensions. the greenfloc 213a flocculant developed at the department of chemical engineering science of the university of veszprém was successful both in laboratory and industrial scale experiments. a pilot scale plant was built for the production of the flocculant. the main part of the plant is a multifunctional batch type reactor in which all steps of the dry modification technology can be carried out. the scaling-up of the reactors requires thorough knowledge of the kinetics of the reactions taking place in the equipment. the starch modification reaction consists of the phosphorylation and degradation of the starch. the results of the kinetic investigation and the bath type pilot scale plant will be presented in this paper. introduction flocculants are so called polyelectrolytes, watersoluble polymers with ionic charge. the particles in aqueous suspension can be agglomerated by various mechanisms. flocculants neutralise the identical charges of repelling particles and hence stop repulsion. another mechanism is bridge forming, where the big polymer molecule binds particles to itself by its functional groups. cationic flocculants are suitable for the neutralisation of particles with a negative charge, while anionic ones are for those with a positive charge. the flocculants used in today’s industry are mostly synthetic products, such as polyacrylamid, polyethylene-oxide, etc. these are very effective, but may contain toxic monomer residuals and after disposed of in the environment they are not biodegradable. starch in its original form is not water-soluble and has no functional groups with charges. it is a mixture of two polymers: amylose and amylopectin, and the mass of molecules ranges from 50,000 to millions. starch can be converted into flocculants by substituting some of the oh−-groups in the monomer units of the polymer chain with ionic functional groups. as a result of the substitution the water-solubility of the starch derivative increases. depending on whether we build anionic or cationic functional groups into the starch chain, we will get anionic or cationic flocculants. the starch derivative if produced with the proper reagent is non-toxic and indeed biodegradable. the objective then is to produce natural based flocculants for those fields where their beneficial properties are really advantageous. such a field is drinking water treatment, where in the clarification step anionic flocculants are used. al3+ or fe3+-salts are added to the water to be treated, and polyelectrolytes improve the sedimentation of the forming flocs. by building phosphate groups into the starch anionic derivatives can be produced: h2po4 -ohst na + st o p o oh o na + 4 the building-in of phosphate groups can be made more effective by the use of n-containing catalysators. lab-scale experiments for the development of the starch based anionic flocculant at the department of chemical engineering science of the university of veszprém a research group has been involved in chemical processing of the ingredients of plant biomass for a long time. the aim of the work is to produce chemicals based on renewable raw materials, which can substitute the commercial products synthesized from fossil raw materials. the laboratory experiments related to the development of starch based flocculants were of two kinds, preparation of polyelectrolytes and testing of the best products in different applications. the starting materials of the modification procedures were native corn starch, wheat starch and waxy corn starch. phosphoric acid and phosphate salts were used to build the phosphate groups into the starch molecule, and different kind of n-compounds were used to catalyse the phosphorylation reactions. wet (slurry phase) and dry (solid phase) reactions were carried out. the reaction parameters (temperature, concentration, etc.) were chosen so that we could prepare polyelectrolyte with solubility as high as possible, satisfactory ionic character and high molecular weight. the best flocculant was a starch phosphate with an average molecular weight of mw≈1.8*106 da, and a degree of substitution ds≈0.01. the phosphorylation reaction was carried out in solid phase. the product was registered by the name of greenfloc 213a. we recommend greenfloc 213a to use it as a coagulant aid in the drinking water treatment together with alor fe-salt coagulants. industrial scale application tests [1]: the experiments related to the applicability of the greenfloc 213a were conducted in lazberc at the north-hungarian waterworks ltd. in this area the environmental protection is especially important: lazberc is in the heart of the bukk mountains − a natural park. the objective of the experiments in the waterworks was to find out whether the flocculant developed by us is suitable for the substitution of the synthetic agent in the coagulation-flocculation step of water treatment. at these waterworks coagulation was followed by sedimentation. from the characteristics (turbidity and cod removal, al-residue and algae removal) this time the algae removal has been followed with special attention. the sedimentation is made difficult not only by the high number of algae, but by the variety of algae types. with the coming winter this is accompanied by the increasing viscosity of water. table i: results of the experiment in lazberc (1 november 31 december 2003)* removal percent after sedimentation property 1-16 nov. by synthetic flocculant 17 nov. 8 dec. by greenfloc 213a 9-31 dec. by synthetic flocculant turbidity, ntu 89.6 87.5 84.0 cod, mg/l 43.8 43.2 32.4 algae, 106/l 92.8 93.6 92.0 al(iii), mg/l 99.96 99.96 99.94 temperature, oc 6-7 4-6 3-4 *coagulant: bopac (poly-aluminium-chloride) the figures in table i. and in charts in fig. 1. show that the characteristics of the water produced using greenfloc 213a are similar to those that were measured before and after the experiment. after the successful industrial scale experiments we decided to build a pilot scale plant for the production of the starch based flocculants. the scaling up of a reactor requires special attention since because of the larger quantities the manipulation times are longer in the larger pilot scale reactor than in the laboratory reactor. that is why we have to investigate thoroughly the kinetics of the phosphorylation process. kinetics of the modification during the chemical reaction the building-in of phosphate groups and the degradation of polymer molecules take place simultaneously. however flocculants have to be of high molecular weight for bridge-forming. therefore the temperature and time of the reaction have to be optimised. the optimal reaction conditions were defined by parallel investigation of the two chemical reactions and flocculation properties. the phosphorylation reaction was carried out at different temperatures, and the quality of the products was followed by determining the bound and free phosphorus in the starch phosphate. at the same time the degradation reaction was examined through the analysis of the molecular weight 5 0 1 2 3 4 5 6 7 8 1. 11 4. 11 7. 11 10 .1 1 13 /1 1 16 /1 1 19 /1 1 22 /1 1 25 /1 1 28 /1 1 1. 12 4. 12 7. 12 10 .1 2 13 /1 2 16 /1 2 19 /1 2 22 /1 2 25 /1 2 28 /1 2 31 /1 2 d ate a lg ae c on c. , 1 06 /l 20 30 40 50 60 70 80 90 100 a lg ae re m ov al p er ce nt in itia l r esidua l r em oval, % s yn th e t ic flo c c u la n t b reakdown g r e e n flo c 213a s yn t h e t ic flo c c u la n t figure 1: algae removal in the lazberc water treatment plant distribution of the derivatives. the flocculation properties were tested by settling standard kaolin suspension. materials and methods the raw material meritena 300 starch was supplied by hungrana (hungary), all of the other ingredients used at the phosphorylation were of analytical grade. the chemicals used at the analysis were bought from merck ag in analytical reagent grade. analysis of the bound and free phosphoruscontent: the free phosphate content of the samples was separated from the bound phosphate by extraction with 80% aqueous methanol. all organic materials of the solid residue were burnt, and the p-content was determined from the ash as molybdivanado-phosphoric acid spectrophotometrically [2] by biochrom 4060 spectrophotometer (pharmacia ag) at 460 nm. the liquid phase was evaporated and the free p-content was determined from its residue in a similar way. determination of the molecular weight distribution: in the standard method the starch phosphate samples were dissolved in 90% aqueous dimethyl-sulfoxid solution for 24 hours. (the native starch samples were dissolved for 94 hours.) the molecular weight distribution was measured by hpsec analysis: gilson hplc system, 30 cm × 7,8 mm ×10 µm tsk-gel g5000pwxl column, 20 µl sample injected, 0.6 ml/min ph 11 puffer eluent [3], 60 oc thermostat, rid detector. the parameters of the molecular weight distribution were determined by a microsoft excel program. flocculation characteristics: the flocculation properties of the derivatives were measured by a quick test developed at our department. 10 ml of kaolin suspension (5 g/l) was filled into test-tubes and 0.1-0.5 ml of flocculant solution (1 g/l) was added and the mixture was thoroughly mixed. some seconds after the stoppage flocs appeared and settled into the lower part of the tubes. the time of the appearance of the flocs and the time of their settling were measured. the flocculation characteristics of the flocculants in a particular application were determined by jar tests and followed common water analytical methods. results and discussion as a result of the preliminary laboratory experiments we had a receipt and a method for 0 1 2 3 4 5 6 0 100 200 300 400 500 time of the heat treatment, min pco nt en t, m g/ g 120 oc 130 oc 140 oc 145 oc 150 oc 160 oc figure 2: bound p in the modified starch 6 0 1 2 3 0 100 200 300 400 500 time of the heat treatment, min a ve ra ge m ol ec ul ar w ei gh t, 10 6 d a 120 oc 130 oc 140 oc 145 oc 150 oc 160 oc figure 3: molecular weight decrease during the heat treatment preparation of the greenfloc 213a flocculant. the objective of this kinetic investigation was to clear up the influence of the longer residence time and possibly irregular temperature on the quality of the product. the raw material starch was impregnated with the additives according to the receipt, and the wet material was treated at temperatures 120-160 oc. the duration of the heat treatments ranged 45-1440 minutes depending on the temperature. the reaction products were analysed and tested. all product samples could be dissolved by the standard hpsec method. fig. 2 shows the building-in of the phosphorus into the starch during the time at different temperatures. in fig. 3 the degradation of the starch polymers is displayed by an average molecular weight versus time diagram. 0 0.5 1 1.5 2 2.5 0 1 2 3 4 5 6 p-content, mg/g a ve ra ge m ol ec ul ar w ei gh t, 10 6 d a 120 oc 130 oc 140 oc 145 oc 150 oc 160 oc figure 4: molecular weight vs. p-content diagram 20 25 30 35 40 45 50 55 60 0 1 2 3 4 5 6 p-content, mg/g se ttl in g tim e, s ec 120 oc 130 oc 140 oc 145 oc 150 oc 160 oc figure 5: flocculation properties of the products based on these data we can draw an average molecular weight versus bound p-content diagram (fig. 4.), in which a limited area contains the characteristics of the products resulted from the given raw material composition. in the diagram we can determine the range where the "best products" can be found. fig. 5 shows the results of the flocculation test at 20 ppm dosage. applying the best flocculants the kaolin suspension settled in under 30 sec. the average molecular weights of these derivatives range from 1.5-2*106 da, the pcontent is 2-3 mg/g. the products of 1-1.5*106 da molecular weight and 3-4 mg/g p-content showed rather good flocculation effect, but the flocs were smaller. in this way we can state that • the best flocculant can be prepared at 140 oc and 90 min; • the time of the heating up from the drying to the reaction temperature must be short; • the conversion under the heating up can be determined from the results. pilot scale reactor we have developed and constructed a pilot scale batch type reactor of 100 kg/charge (fig. 6), which is suitable for performing solid phase reactions especially when the main component is a fine grain solid material (generally lower than 200 µm). the shape of reactor is a horizontal cylinder closed at both ends. its diameter is d=0.9 m, length is l=0.9 m, and volume is v=0,45 m3. the adequate motion of the particles is ensured by an impeller. the rotation speed of the impeller can be set in an 8-90 rpm range depending on technological aims. the even distribution of the dissolved reagents on the surface of particles of the main component is carried out by a pneumatic nozzle. in the course of spraying the agglomeration of particles also takes place. over-agglomeration is prevented by a high rotation speed chopper (2440 rpm) placed at the bottom of the reactor. 7 5 67 2 3 1 84 a b figure 6: flow sheet of the pilot scale plant 1 reactor, a-impeller, b-chopper; 2 liquid tank; 3 -liqiud pump; 4 compressor; 5 condenser; 6 container for condensed vapour; 7 vacuum pump; 8 container for product the reactor is equipped with proper insulation and an electric heating jacket to ensure the heat energy input required for the reaction. the maximum temperature is 180 oc. a liquid tank belongs to the reactor with a heating jacket to dissolve reagents and a compressor to provide compressed air for spraying. the vapour formed during the heat treatment (drying, heating, chemical reaction) is eliminated by a vacuum pump and then it is condensed. production of modified starch in the pilot scale reactor the chemical reaction is performed in the solid phase. apart from the starch all other components are water-soluble; therefore we add their aqueous solution to the starch before the reaction. the steps to be carried out in the reactor are the following: • spraying in the aqueous solution of the reagents and mixing it with the starch; • drying the impregnated starch; • heating up to the optimal reaction temperature; • performing the phosphorylation reaction. at the first step it is very important to add as little water as possible into the reactor to keep the flowability of the particles during the operation as well as to reduce the energy demand of drying. the temperature of drying and hence the speed of drying is restricted by the fact, that starch, in presence of water, gelatinises at a higher temperature. (native starch at ca. 70 oc, modified could differ.) gelatinised starch is impossible to handle in such an apparatus. during the experimental production of greenfloc 213a we have measured anionic flocculant and controlled the temperature of the reactor wall as well as the temperature inside the reactor. during the drying period the wall temperature was set to 80 oc, and no significant gelatinisation was experienced. the remaining (3-5 m%) humidity was eliminated in the heating-up phase at a wall temperature of 120 oc. the phosphorylation reaction was performed at a wall temperature of 140 oc. properties of the greenfloc 213a flocculant fig. 7 shows the size exclusion (hpsec) chromatograms of the native starch and the greenfloc 213a anionic flocculant derived from it. at first the native starch was dissolved according to the standard method described above. the area beneath the curve is proportional to the amount of material that can be dissolved. only a small part of the native starch – mainly the polymers of lower molecular weight – could dissolve in this way. the diagrams show that the solubility of the polymers of higher molecular weight was increased by the phosphorylation. the chromatogram of the native starch after a more intensive dissolution is also displayed in fig. 7. during the modification reaction the rate of the polymers of lower molecular weight is increased, but the degradation is not significant. the main characteristics of the greenfloc 213a produced in the pilot scale plant are: • average molecular weight (mw ) – 1.74*106 da • bounded p-content – 2.74 mg/g • settling time at 20 ppm – 26 sec 10 ppm – 28 sec. molecular weight, da 106 105 104 103 102 0 100 200 300 400 500 600 0 500 1000 1500 2000 retention time, 10-2 min si gn al , 1 0-2 m v modified starch native starch figure 7: size exclusion chromatograms of the modified starch (greenfloc 213a) and the native starch after standard and intensive dissolution 8 conclusions • the flocculant, produced by the reactor had the same characteristics and efficiency as the product made in the laboratory • the greenfloc 213a is a really tailor-made product; it has optimal molecular weight and pcontent. • the reactor could be operated without any problem, and all steps of the technology could be carried out according to the expectations. references 1. dencs b., dencs j. and marton g.: conference proceedings, hung. j. ind. chem. veszprém, 1999. vol. 1. 12. 2. radley j. a.: examination and analysis of starch. applied science publishers ltd. london, 1976. 3. lehtonen p.: chromatographia, 1988. vol.26. 157. hungarian journal of industrial chemistry veszprém vol. 33(1-2). pp. 105-111. (2005) optimization of food logistic processes by simulation technique é. hajnal and g. kollár1 1bp. corvinus university, postharvest department h-1118. budapest, ménesi út 45, hungary e-mail: hajnal.eva@axing.hu existing warehouse operations can be audited, reviewed and benchmarked for productivity. the effects of different operational and racking configurations can then be tested in a safe environment before any capital expenditure is made. modelling is based on computer programs, which are able to mimic the warehouse operations and allow many different scenarios to be tested quickly and easily. series of experiments carried out on the constructed model is simulation. in our paper we discuss what process approach means in logistics, why important to model and optimize the members of the warehouse process network, how a process simulation looks like in a distribution centre, how can we measure changes during simulation runs and finally what results can we achieve. keywords: food logistics, optimizing, modelling, core process, discrete event model, key performance indicators, intake process, simulation technique, queuing introduction distribution centres are important elements of the food supply chain. in a dc there are coreand additional processes and they all together form process network. to identify these processes, the first step is process mapping the second is modelling. in business a common goal is to optimize a system such that it processes the most things using the least amount of resources and time. this time of system is often modelled using discrete event queue/server concepts. process approach every company is a network of processes, which are describable, documentable, monitorable and improvable. to find the processes to be optimized, we should do process mapping ranging over the whole organization to define and document all processes necessary for the normal operation. connections of processes only after this mapping can be defined, and the process network described. in the network there are basic –so called coreprocesses, which are essential for the success of an organization. to define core processes we need goals determined by the company management. [1] after process network is known, the whole process can be decomposed into subprocesses, where the output of one subprocess is the input of one or more other subprocesses. it is important, that every subprocess’ contribution to the whole service should be measurable. this forms a distribution chain, where time-based approach is dominating. delivery time of subprocesses are summing considering the whole process. why is it worth to optimize? there are several reasons, basically to reach more efficiency in operation using the least amount of resources and time. some additional reasons are listed below: changes in connection with customers new customer arrival, change in customer needs (e.g. control degree), change in product assortment, change in packaging units, change in frequency of intake/delivery. internal reasons economic rationalization (cost and resource efficiency), need of continuous improvement, change in size of the company (increase/decrease storing capacity), change in human resources (newcomers, discharges, trainings), change in number of docks, change in other resources (it system development, equipment capacity change etc.), change in resources shared with other warehouse operations/processes. external reasons improve food safety, change in laws and legal regulations, change in authority demands (e.g. tight control because of epidemic hazard). environmental reasons decrease integrated contamination level, primary task of environment protection is to decrease economic origin environment pollution. the goal to achieve more ecologyeffective company operation, which uses fewer raw materials and emits less poisonous and waste material. the economical expansion should not accompany by the increase of causeless environmental burdens and occurrence of preventable damages. decrease traffic origin contaminant outputs, hungary’s carbon dioxide quota is 93 million tons, from which 97.5% is distributable between companies responsible most of all for the environment pollution (stokers, oilrefineries, coking plants, iron industry, steel industry, paper industry, and cement-, glassor building material producers). this does not mean that traffic origin carbon dioxide emission is negligible. everyone in this country can feel the burden of the crescive traffic on the roads day by day. improve noise protection (first of all traffic origin, but industrial and commercial noise is also significant), eu initiation that hungary should prepare noise-maps until 2007 about the capital, some other cities, 400km heavy-traffic roads, 20km railways and the national airport. this map will point out the problematic places, where there will be lot of tasks to do within short time period to decrease noise contamination. [3] modelling processes collected during process mapping should be recorded and modelled. in a qualified sense we can call modelling the mathematical model building. models are simplified versions of real life processes or systems, which enhance relevant features of them. this definition shows that models never can entirely substitute the real life processes. their essence is that they can give rather exact answer to our previously asked questions, but in the case further questions they need refinement or we should build another model. fig 1 shows the modelling process in the case of discrete events. it is generally true that all models proceed from the reality and always come back to it. they work with empirical data, and fill the remaining gaps with hypotheses. goodness of a model is verified only by compare against reality. series of experiments carried out on the constructed model is simulation. during simulation we mimic/simulate real life events by experimental methods. we examine the effect of different inputs and disturbing signs upon the formed state variables and outputs while generally we are seeking optimal solutions (optimization). [7] the object of the simulation generally is to determine where there are bottlenecks in the process and to see which parts of the process might be improved. in many models, you are interested in the time required for an item to move from one end of the model to the other. data collection results analysis experiment initial tests (incremental) built modification/refinement fig 1 modelling process in the case of discrete event simulation [sommerville, 1992] benefits of simulation modelling basic description of the process is enough to start simulation, the model can be refined step by step as we understand the process better, we can give exact estimation within short time period, applicable even in the case of the most complicated problems, this method is applicable as a part of both bpr and tqm, analysis can be done with the help of existing data before organizational or operational changes, 107 not necessary useless expenditure of time, energy or money to realize interim -sometimes wrongsolutions, the result is applicable to verify current method or proposing new method, appropriate to perform unrealisable or very expensive experiments. some of the application areas of simulation models queuing, routing, activity based costing, resource planning etc. computer modelling, simulation there are several modelling methods. advisable to choose from them the one that can be most effectively used in description of the examined processes. continuous time models describe a smooth flow of homogenous values; time changes in equal increments and values change based directly on changes in time. values reflect the state of the modelled system at any particular time, and simulated time advances evenly from one time step to the next. discrete event models (fig 2) track individual and unique entities, known as items. these items change state as event occurs in the simulation. the state of the model changes only when those events occur; the mere passing of time has no direct effect. for a discrete event model, simulated time advances from one event to the next and it is unlikely that the time between events will be equal. [2] start event load machine time activity unloadrun process stop event fig 2 discrete event simulation scheme [pidd, 1992] it is important that a system can be modelled in any number of different ways, depending on what is you want to accomplish. in general, how you model the system depends on the purpose of the model: what type, level, and accuracy of the information you want to gather. table 1 shows the differences and the some fields of application of continuous time and discrete event models. table 1 summary of continuous and discrete event differences [diamond, 2002] factor continuous time modelling discrete event modelling what is modelled flows („stuff”) discrete items („things”) characteristics random number „simulates” characteristics of flows. attributes and unique characteristics are assigned to items. time steps constant. model recalculations are sequential and time dependent. dependent. model only recalculates when events occur. ordering fifo order. fifo, lifo, priority, or customized order. routing flows can go to multiple places at the same time. items can only be in one place at a time. statistical detail general statistics: amount efficiency, transit time etc. general statistics+ individual tracking: count utilization, cycle time etc. common uses scientific, engineering, bulk processes, system thinking, economics, system dynamics. manufacturing, service industries, business processes, strategic thinking, networks, system engineering. there are 3 basic methods to handle dynamic simulation: 1. event driven, 2. acivity driven, and 3. process driven method. compared to each other, most effective is the event driven programming. on the other hand the structure of the original modelled system and the simulation modell is more similar in case of the process driven method. it has the benefit that people is not experienced in simulation techniques but familiar with operation problems of the modelled system can easily overview the simulation program. [8] advisable to use such simulation tool which modeldescriptive language can be fitted to the modeler’s needs, while model running is managed by an executive system which fits to computer representation. [8] optimization of food logistic processes defining core processes in logistics we can simplify and define the core process in a distribution centre as follows: intake delivery checking marshalling product handling fig 3 core process in a distribution centre naturally we can add to this process line other blocks, like ordering, routing etc., but here in details we do not take them into consideration. the effectivity (efficiency) of the processes can be measured with the process specific key performance indicators. watching the course of events with kpis is monitoring. these indicators are very important in the case of initial state examination and during process change monitoring (optimization). examining processes as a whole unit, one of the most important performance indicator is cycle time, which necessary to transform inputs to outputs. [4] some additional kpis in logistics: intake: intake time parking place utilization time of unload lorries product handling: stock turning speed average stock level (warehouse occupancy) inventory records (stockloss, pallet-loss) marshalling: picking rate picking speed picking accuracy checking: checking ratio % delivery: delivery time time of load lorries wait at the customer on-time delivery case-fill rate all parts of the process: workforce efficiency (piece rates) material handling equipments utilization. optimization by simulation technique main objectives to achieve shorten the intake time, decrease air-contaminants released by the lorries, and also decrease noise contamination. process for optimization intake process; ambient operation. model type discrete event model. method used for optimization queuing. building discrete event model after collecting empirical data, building the model itself with the help of simulation software is the next step in the optimization process. we used message-based discrete event simulation software (extend). this system eases the model building process by allowing the modeller to put the model together in an intuitive manner. the architecture based on a messaging system. instead of a centrally located simulation program executing subroutines based on simulation data, this architecture sends messages from one simulation block to another. the central simulation engine performs only event scheduling and selection. the bulk of the simulation execution is performed by blocks sending messages to one another. [9] in the model items are passed from block to block through item connectors, which passes not just the items, but also all the related information. in the software the typical blocks of the chosen model type are already predefined. output connectors can be connected to more than one input connector. you cannot, however, connect more than one output to a single input. this difference makes sense because the information flowing out of an output connector can be useful in many places, but each input connector can only have one source of information. [2] fig 4 shows the model of intake process set up from blocks. it shows items standing in the queue and waiting for their turn at the docks. items in the queue are the lorries, which are waiting for unload. servers are the mechanisms by which the members of the line are processed, and then sent on their way. servers here are the warehouse personnel (warehouse keeper, reach truck driver etc.), the machines and the computers. it takes some time to process the members of the line. 109 count event 3v 1 2 item generator dock 1 exit # 80 exit 1 dock 2 exit # 79 exit 2 dock 3 exit # 78 exit 3 f l w 39 fifo queue fig 4 intake process model [extend simulation software] in our model the executive block at the upper left corner of the model window has two tasks: first, it maintains a data structure of information about the items; second, it takes control of the time clock from the application, scheduling events, sending messages to the blocks that scheduled the event, and moving the clock forward to the appropriate time for the next event. [2] the item generator block generates items with an interarrival time according to an exponential distribution. analysing the arriving lorries, this distribution seems to fit the real values. we can see the items’ distribution plot on fig 5. 1,132019e-05 0,2310821 0,4621528 0,6932236 0,9242943 0 3,75 7,5 11,25 15 interarriv al time percent items items' distribution % items 1 fig 5 incoming lorries’ distribution plot we work with one queue, and will choose fifo queuing discipline for the ambient operation, and do not use any other priorities. we also do not use balking (when the lorry does not enter the line, because its length), reneging (when the lorry leaves before being served because too much time has passed), or blocking (when an empty lorry stick in the dock) etc. our fifo queue block holds items until their turn. this block calculates the average queue length, average wait time, and utilization of the queue. exit blocks count lorries leaving the docks. the processing itself goes on at docks. fig 6 shows the details of the main model’s central dock blocks, which are hierarchic blocks in the system. number of the docks can be varied; the service time per unit (time of unload a single unit) is now a constant value and same for all the docks. of course this is ideal assumption, but the first model can work with this. eqn equation demand # condition block exit # 61 exit block f l w 17 fifo queue d t u activity delay use # change u0 stockroom demand a b c unbatch items con1incon1in con2outcon2out fig 6 intake process: dock unloading [extend simulation software] the condition block serves as a conditional wait. it accumulates demand based on the values at the demand connector. it passes the next item only when a certain condition exist. in our case when the calculation of the equation block results that there are no more pallets waiting at the marshalling place, the condition block will release the next lorry. unbatch block separates an incoming item into multiple quantities of output items. in this case one incoming lorry carries pallets (full lorry=pallets+empty lorry). exit block counts empty lorries, pallets go to fifo queue block. they should wait until being carried to their final location in the warehouse, and the dock will be empty. activity delay block holds an item for a specified amount of time. stockroom block provides and stores stockroom items. the next figure shows on a flow chart the algorithm of the general intake process, represented on fig 4, including the subprocess of dock unloading, represented on fig 6. start lorry coming in generated by exp. dist. registration of lorry parameters is a free dock available? call lwp using wcost ofunc stop docking read actual parameters and call ulp is the ma free? call dwp using duse ofunc db subprocess of fig. 6 yes yes no no fig 7 the flow chart of intake process running simulation, choosing optimal solution during running this first model, we can check the following kpis: time of unloading lorries, average and maximal queue length, average and maximal wait before intake, dock and parking place utilization, whole cycle time etc. the model runs much faster than the real operation, so performance over hours, weeks, months or years of production can quickly be simulated. our simulation time was 24 hours. optimization is a useful technique to automatically find the best answer to a problem. the problem is usually stated as an objective function. most optimization algorithms that can solve stochastic models use an initial population of possible solutions. each solution is tried by running the model several times, averaging the samples, and sorting the solutions. the best solution sets of parameters are used to derive slightly different solutions that might be better. the problem with all optimization algorithms stem from the inability to tell when the best solution has been found. a good approach is to allow the optimization to continue for a “long enough” time and check to see if the population of solutions converge. after that, the user could try the optimization procedure several times to make sure that the answer agree and that the first answer is not a false or sub-optimal one. [2] models have parameters that are specified by the modeller and shouldn’t vary, and some parameters could vary and change the efficiency of the model. though we have not just constant variables, but distributions, we have to take it into consideration. optimization can be carried out by simple building an optimizer block into our model. in most cases optimizer would like to minimize the cost or maximize the profit to get a benefit from optimization. in our case we would like to maximize our profit while decrease wait of lorries before intake. the waiting cost in logistics is high, and our original problem was air pollution and noise. because none of the parameters can be varied except the number of docks in our simplified model, our objective function can be: maxprofit = exitnum*lprof-avewait*wcost-docknum*duse where lprof, wcost and duse are objective functions too, which results multiple objective function optimization. in the original model we had 3 docks, and we found it not enough, because during simulation the queue length increased continuously and the average waiting time of the lorries was more than 5 hours. (fig 8) 0 6 12 18 24 0 22,5 45 67,5 90 time value plotter, discrete event numberexited numberexited numberexited queuelength 1 fig 8 simulation result [extend simulation software] 0 6 12 18 24 0 50 100 150 200 time value plotter, discrete event numberexited numberexited numberexited queuelength 1 fig 9 simulation result after optimization [extend simulation software] during optimization we varied the number of docks between 1 and 10. we found the optimum at docknum=5. running the simulation with this new parameter by the end of the simulation only 3 lorries remained unprocessed, the average wait was approximately half an hour, though the parking place utilisation decreased. (fig 9) model refinement generally true: the more accurate input data we have, the more accurate results we can get. the input data can also be refined upon the empirical data (curves can be fitted to empirical data points to find the correct distribution). we can refine the interarrival time (mean etc.), with lot of more empirical data, we can find seasonality examining daily, weekly, monthly or yearly distribution. in our model queuing discipline is fifo, but in the real life there are priorities. for example chilled or frozen products have priority over ambient products, or also products being out of stock. there can be differentiation in service times between clients, sometimes authority require priority because of food safety reason or any other consideration. extreme cold weather can explain the priority of not freezingresistant ambient products etc. the number of the docks can vary, depending on queue length, technical problem, priority of other internal 111 operational process, limited resource capacity, or any other reason maybe some of them is not working. happens, that not all of the lorries can use all of the docks, because of size problems (too large or small vehicles compared to dock sizes), or simply because the product itself carried by the lorry (e.g. chilled or frozen products are stored separately, they can not be stored in at the same docks as ambient products). in an advanced model we can get service time per lorry by multiplying service time per unit with the number of units per lorry. to get this result we should know in advance, how many units are there in the following cargo. this requires good prediction from the product owner. in the real life even service time per unit is not constant, as we assumed in the first model. this value depends on the product itself, the processing personnel or the processing method (paper based operation or radio frequency it system). discussion building model allows us to optimise logistics processes by using computer experiments rather than costly plant time. modelling is a tool for understanding why problems are occurring in a process when direct measurement is too difficult. the basis of process simulation is a very detailed process mapping. processes should be well defined, documented, up to date and the kpis, which describe the process, also should be known. first step is the core process description. during simulation the kpis will show the differences of each setup. all changes should be documented, though the optimization will be reproducible. in this paper we introduced how process building, simulation run and optimization can be carried out with simulation software. although optimization of our extremely simplified model was successful, we can see that in the real life this is still not a liveable model. before optimization we should refine our model until it perfectly simulates the real process. above all, while the question concerned only the intake process, we cannot give correct and exact answer without knowing in details the other elements of the whole operational network in the distribution centre. resource planning, marshalling, outbound deliveries, or other processes bear importantly upon the answer to the original question. the interactions between this process and the other ones are so tight, that the estimation would be inaccurate taking not into consideration them. acknowledgements the authors wish to express their gratitude to gábor tóth (axing ltd) and klára kollár-hunek (bme) acronyms dc distribution centre bpr business process reengineering tqm total quality management kpi key performance indicator fifo first in first out lifo last in first out it information technology exitnum number of lorries leaving docks lprof income per lorry avewait average wait of lorries before intake wcost cost of one hour waiting docknum number of docks duse cost of dock using lwa lorry waiting procedure ulp unloading procedure ma marshalling area dwp dock waiting procedure ofunc objective function db database references 1. a. r. tenner, i. j. detoro l.: bpr (in hungarian), műszaki könyvkiadó, budapest, 1998 2. diamond, b.: simulation overview, imagine that inc, 2002, www.imaginethatinc.com 3. hajnal é.: application of eu environmental regulations in logistics (in hungarian), logisztikai évkönyv, vol 2004, p. 61-66, 2004 4. hajnal é., kollár g.: process optimalisation and monitoring in logistics (in hungarian), proc. of conf. mkn 2004, veszprém, hungary 5. pidd, m.: 'computer simulation in management science', john wiley & sons, inc., 1992 6. sommerville, i.: 'software engineering, fourth edition', addison-wesley publishing company, inc., 1992 7. dr. benyó z., szűcs b.: folyamatszabályozás, bme-sote-áote orvosbiológiai mérnöki szak egyetemi jegyzet, budapest, 1995 8. dr. jávor a.: diszkrét szimuláció, szifuniversitas kft., győr, 2000 9. krahl d., lamperti j. s.: a message-based discrete event simulation architecture, proceedings of the 1997 winter simulation conference ed. s. andradóttir, k.j. healy, d.h. withers and b.l. nelson http://www.imaginethatinc.com/ microsoft word content.doc hungarian journal of industry and chemistry veszprém vol. 40 (2) pp. 113-119 (2012) magnetorheological fluid brake – basic performances testing with magnetic field efficiency improvement proposal a. poznić1 , a. zelić1, l. szabó2 1university of novi sad, 6 trg dositeja obradovića, 21 000 novi sad, serbia e-mail: alpoznic@uns.ac.rs 2university of pannonia, 18 zrínyi str., 8800 nagykanizsa, hungary a review of all magnetorheological brake types was presented. based on overall braking torque analytical comparison for all magnetorheological brake types and other relevant parameters, the most promising design was selected. a test rig, utilizing selected brake type filled with magnetorheological fluid – basonetic 5030 was manufactured and then tested. to analyze the effect produced by magnetic field on magnetorheological fluid and hence at overall braking torque, the authors used amplification factor. results were discussed and the magnetic field efficiency improvements were proposed. keywords: magnetorheological brake, basonetic 5030, test rig, amplification factor, efficiency improvements introduction the convectional friction brake (fb) is the most commonly used brake type in almost any mechanical system today. however, it is characterized by drawbacks such as periodic replacement due to wear, large mechanical time-delay, bulky size etc. [13, 29], partially altered. electromechanical brakes (embs) have potential to overcome some of these drawbacks and are a suitable fb replacement. today embs are applicable in almost any mechanical system. application of intelligent materials is the next step in the development of emb. magnetorheological (mr) fluids belong to a class of intelligent materials that respond to applied magnetic field with fast, continuous, and reversible change in its rheological behaviour [3, 7, 28], partially altered. mr fluids are a type of suspensions, with carrier fluid usually mineral or synthetic oil, water, kerosene and micro size magnetizable particles dispersed in it. when exposed to external magnetic field particles form a chain-like structures thus changing the viscosity of the fluid. in this study, authors used basf’s magnetorheological fluid, basonetic 5030. mr fluids have attracted extensive research interest in recent years since they can provide simple, quiet and fast response interface between electronic control and mechanical system [11, 20, 22]. a lot of work was done on mr fluid brakes modelling, properties investigation and control [3, 6, 11]. a wide range of mr fluid devices have also been investigated for their potential applications in different systems, such as: clutch system, vibration control, seismic response reduction, etc. [9, 10, 26]. mr fluid brakes have also been used in actuators due to their distinguished force control and power transmission features [5, 15]. by applying a proper control effort, viscosity with large varying range is achievable with the mr fluid brake. currently, there are many solutions for mr fluid brake design. some mr fluid brakes with attractive properties, such as high yield stress and stable behavior, have been developed and commercialized [4, 16]. the objective of this work was to compare overall braking torque analytical expressions and design complexity for all mr fluid brake types. based on results obtained from these comparisons, mr fluid brake type with the most promising properties was manufactured and tested on a specially designed test rig. results were discussed and a proposal for new mr brake design with higher magnetic efficiency was presented. magnetorheological effect mr fluids are suspensions composed out of three major components: carrier fluid usually mineral or synthetic oil, magnetizable particles carbonyl iron powder and set of additives [2, 17], partially altered. when exposed to an external magnetic field (on state), change in mr fluid’s viscosity occurs. in the absence of an external magnetic field (off state), mr fluid acts as newtonian fluid [7, 11] and can be described as: τ η γ= ⋅ & (1) in (1) τ represents shear stress, η the viscosity of the fluid and γ& shear rate. often, for mr fluid brakes, 114 denoted as r / gγ ω= ⋅& , where r is rotor radius, ω and g are angular speed and mr fluid gap length, respectively. when in on state, mr the rheological properties of mr fluid change. magnetizable particles induce polarization and form chain-like structures in magnetic flux path direction, thus changing apparent viscosity of the fluid. on state behavior of mr fluid is often represented as a non-newtonian [1, 3, 5], having a variable yield strength. the usage of bingham’s model (2), in this situation, gives reasonably good results, [1, 11, 20, 22]: bτ τ η γ= + ⋅ & , (2) where τb is the yield stress, developed in response to the applied magnetic field. its value is a function of the magnetic field induction b. when used in a device, mr fluid can be in one of four modes: shear, flow (pressure), squeeze and pinch, [8, 18, 28]. in brake i.e. torque transfer applications, mr fluid operates in shear mode [1]. braking torque values are adjusted continuously by changing the external magnetic field strength. magnetorheological brakes mr brake consists out of four main parts: rotor, housing i.e. stator, coil and mr fluid, figure 1. the shape of the rotor is what differentiates mr brake types from each other. one needs the quantitative parameters of mr brake, to be able to determine its specific application suitability. mr brake types, mechanical model, quantitative parameters comparison for all mr brake types are presented in next section. magnetorheological brake types through literature research [9, 14, 22, 23, 24], authors of this paper have identified five major mr fluid brake designs: drum brake, inverted drum brake, disk brake, t-shape rotor brake and multiple disks brake, fig. 1. drum brake along with the disk brake is the easiest designs to manufacture. however, large inertia is its major drawback compared to disk brake design [1]. the disk brake design is the most common mr brake design found in literature today and was the first one to be investigated [25]. it is the easiest one to manufacture and gives reasonably good results in terms of weight and compactness [14]. there are some variations in mr disk brake design such as: the use of two coils instead of one in order to increase the magnetic pole area and/or relocation of the coil on top of the disk in order to reduce its external diameter [22], but the basics remain the same. it is also interesting to note that the mr disk brake design is currently the only one commercially available as a standard product, manufactured by lord corporation [16] and that it was used in several studies [7, 19, 21]. in order to increase compactness of the mr disk brake design, several disk-shape rotors can be used instead of one, with segments of stator located in between each rotor disk, fig. 1.d. this multiple disk design is very popular in literature and was used in several applications that required high torque in limited space and weight [13, 22, 23]. the equations describing this particular design are very similar to those of the single disk brake, presented paper’s sequel. the t-shape rotor brake design (fig. 1.e), is more compact than all other designs but is also more complex to manufacture. despite its advantages, this design is not so common in literature [22]. figure 1: types of mr brakes: a) drum, b) inverted drum, c) disk, d) multiple disks, e) t-shaped rotor, [28] for all aforementioned mr brake types, the rotor has a cylindrical shape and the magnetic flux lines run in the radial direction, fig. 1. to author’s knowledge, an in-depth comparison of all these architectures is not yet available. mechanical model the key objective in mr fluid brake design is to establish the relationship between the overall braking torque, magnetic field strength and design parameters. interaction of mr fluid and inner surfaces of the brake will generate the braking torque. based on eq. (2) and the specific geometrical configuration of mr brake, for all mr brake types, it applies: 2d 2 dt n r rπ τ= , (3) where: n – number of surfaces of the rotor, perpendicular to the magnetic flux lines and in contact with mr fluid, r – the radius of the rotor. the overall braking torque toverall, consists of three components: the magnetic field induced component tb, due to the field-dependent yield stress, the fluid viscosity dependent component tvis and the friction induced component tfric.. thus, the overall brake torque: 115 overall b vis frict t t t= + + (4) the sum of the first two components tb and tvis i.e. the braking torque can be obtained by the following integral: 22 d o i r b vis r t t n r rπ τ+ = ∫ , (5) where ro and ri are the brake’s rotor outer and inner radii respectively. considering practical conditions, for all mr brake types, the value of the ri can be ignored because the ro is several order of magnitude of the ri (figure 2). figure 2: mr fluid disk brake simplified representation based on eq. (5), the authors formed the final analytical expressions for all five mr brake designs. expressions were adopted from several different literature sources [1, 6, 12, 13, 21, 27, 29] and were partially altered in order to make the comparison easier. the last part of torque, tfric can be precisely obtained only by torque gauge. 3 44( ) 3overall o o frict r r t g ωπ τ η= + + , (6) 3 44( ) 3overall o o frict n r r t g ωπ τ η= + + , (7) 2 34 ( )overall o o frict h r r t g ωπ τ η= + + , (8) 2 38 ( )overall o o frict h r r t g ωπ τ η= + + . (9) variable h is the height of the rotor. it is now easy to distinguish components of overall braking torque in eq. (6–9), for disk, multiple disks, drums and t-shaped rotor, respectively. the yield stress τb given in eq. (2), varies with magnetic induction, but can reasonably be fitted with the third-order polynomial [12], as follows: 2 3 1 2 3b k b k b k bτ = + + , (10) where ki represents coefficients of regression. performances comparison mr brakes can be compared on several different aspects e.g. overall braking torque, dynamic range, mechanical simplicity, inertia, electric power consumption, torque to volume ratio, compactness, etc. authors of this paper compared level of mechanical simplicity for all five mr brake types and the overall braking torque based on analytical expressions, given in eq. (6–9), table 1. in addition, the dynamic range and inertia were consider and presented in the same table. table 1: characteristics of various mr brake designs b ra ke ty pe t o ve ra ll le ve l o f m ec ha ni ca l si m pl ic ity d yn am ic ra ng e t b /t vi s in er tia (1) m h b i g r τ ηγ ⋅ & 21 2 omr * (2) m l 4 3 b o g r τ ηγ ⋅ ⋅ & 21 2 omr (3) h l 4 3 b o g r τ ηγ ⋅ ⋅ & 21 2 o dmr n (4) h h b o g r τ ηγ ⋅ & 2 2 2 i i o m r mr − explanations: brake types: (1)drum and inverted drum, (2) disk, (3) multiple disks, (4) t-shaped rotor. level of mech. simplicity: h – high, m medium, l – low. * for inverted drum brake design, expression is the same as for the t-shape rotor design. nd – the number of rotor disks, mi – missing inner mass of the disk. dynamic range represents ratio of field induced component tb and viscous component tvis (friction torque component not considered). t-shaped rotor brake performs best dynamic and can offer biggest overall braking torque, however it has a large inertia, and is considered difficult to manufacture. the other four designs are globally less compact than the t-shaped rotor design. the two drum based designs have comparable performances but are burdened with even larger inertia for same rotor radius. finally, the disk and multiple disks designs offer a good alternative, being mechanically the simplest, with smaller inertia and giving reasonable dynamic range and the overall braking torque. test rig based on test rigs literature research [10, 15, 20, 27] and mr brake properties comparison (eq. (6–9) and tab. 1), 116 the authors of this paper selected the most promising mr brake design and manufactured it. with lowest inertia, good dynamic range and the highest mechanical simplicity, the disk type promised the biggest potential. for performance evaluating of the selected mr brake type a rig was set up. the test rig was designed and manufactured at faculty of technical sciences, novi sad – serbia, and is presently at its laboratory for engines and vehicles. the test rig with its parts is depict in figure 3 and 4, and consists of four main parts: drive, power supply, mr brake and measuring and data acquisition equipment. an 8-pole ac squirrel cage motor with 0.75 kw and nominal speed of 700 rpm, model 5 az 100 la – 8 (končar) was placed at one end of the support-frame, of the test rig. the inverter micro master (siemens), fig. 4, position 2, controls the direction and variablespeed of the ac motor. speed range was from 150 rpm to 750 rpm with 50 rpm increment. these two elements form a drive part of the test rig. the flexible coupling connects ac motor and the shaft of the mr brake. mr brake rests on two self-aligning ball bearings into housings p203 (fk bearing group). to avoid leakage of mr fluid, nitrile rubber lip seals, suitable for mr type application, have been used. torque transfer from the mr brake to a measurement device was done indirectly. a load arm, connected to the mr brake housing at one end, rests on top of the load cell on the other end, fig. 3. thus, by measuring the force on the load cell, the value of transmitted torque was obtained. load cell was internally calibrated by calibration weights. the capacity of the load cell, 1030 (tedea), was 15 kg. figure 3: demonstrating the test rig for mr brake 1. drive, 2. coupling, 3. self-aligning ball bearing, 4. mr fluid brake, 5. self-aligning ball bearing, 6. optical encoder, 7. load arm, 8. load cell, 9. data acquisition card the optical encoder, model amt102-v-rev-c (cui inc.), was connected to the shaft of the mr brake, at the opposite side of the ac motor and rotated at the same speed sample rate was 2048 per rotation. the signals were processed by universal amplifier, kws 673.a2 (hbm), fig. 4, position 3. the dc power supply, ea ps 2016-100 (elektro-automatik), was connected to the leads of the coil to provide flux generation. this was the control current, with range of 0 a to 2 a and 0.2 a increment. the coil, made of copper wire with diameter of 1 mm (18 gauges) has been coiled on outer radius of the mr brake housing. the mr fluid used in this experiment was basonetic® 5030, from basf® [17]. it is a carbonyl iron powder based mr fluid. figure 4: measurement and data acquisition equipment: 1. stabilized power supply, 2. inverter, 3. universal amplifier a typical testing procedure was as follows. first, the mr brakes shaft was set to a certain speed for 1 min as an initial condition, which stirred the mr fluid in the brake to distribute it uniformly. the desired magnetic field was then applied by setting the coil current i.e. control current and waiting for 1 min. this ensured stable structure forming of the mr fluid. the load cell detected transmitted torque. finally, the signal from the load cell was processed and recorded. experimental results and improvement proposal the goal of this experiment was to determine overall braking torque capabilities of selected mr brake design. the experiment was conducted on a specially designed test rig, with different control currents and speed sets. to eliminate the effects of previous observations, different combinations of control current and rotational speed were set for each reading. to bring repeatability in the reading, every speed set was carried out twice at different instance of time. for every reading, approximately 1 min time, before torque data recording, has been allotted to distribute the carbonyl iron particles uniformly in the mr fluid and form a stable structure. experimental results the experiment itself consisted out of tree parts. the first part was to determine the influence of the supporting ball bearings and seals, without mr fluid inside the brake and no control current applied. this was a friction braking torque component. second part of the experiment had the same setup but it included mr fluid inside the brake. viscous torque data was then 117 recorded, assuming that bearings and seals did not change their friction characteristics in time. aforementioned recordings were needed in order to get clear and precise information about field induced component. this was the third part of the experiment and it included mr fluid inside the brake and application of the control current. the same speed sets were used for the friction and the viscous torque component measurements were repeated. for each speed set, a 2 minute recording time was used. some field induced component results are depict in figure 5. magnetic field influence is apparent. a) b) figure 5: samples of overall braking torque results: a) 0,2 a at 150 rpm, b) 1,6 a at 300 rpm because of the large number of data obtained in this experiment, authors decided to use amplification factor to determine the effect produced by magnetic field. amplification factor (af) represents relation between overall braking torque and sum of friction and viscous torque, i.e. relation between the on and off state of the mr fluid. at current at zero current overall overall t i af t = (11) amplification factor curves for all 13 speed sets are plotted in figure 6. this figure shows linearity in amplification factor with increase in control current. this was expected, since the higher the current, the higher the field induced torque should be. results are presented with rotational speed variation as well. figure 6 indicates that the amplification factors for speeds 150, 200, 250, 300 and 350 were much larger than the ones for 450, 500, 550, 600, 650, 700 and 750 rpm. transition rpm value for this mr brake was 400 rpm. this was somewhat opposite to the torque predicted by eq. (6) where the toverall should increase with angular speed. this was not the case here. however, other authors have also reported the same trend – reduction of amplification factor with increment of speed [20, 27]. this may be due to the possible shear thinning effect of the mr fluid at high shear rates. this reduces the effectiveness of mr brake at higher speeds. therefore, to make mr brake effective at higher speed operation, one needs to think of „shear stable mr fluid“. figure 6: variation in amplification factor with control current mr brake improvement proposal in order to increase the overall braking torque of any mr brake type its geometry needs to be optimized [14]. state of the art mr brake designs base their torque generation on the inner section of the coil [4, 10, 13]. these designs are rather inefficient, because the magnetic field is not used to its full potential and active mr area is small. flux mostly travels through the housing of the mr brake. in this configuration, magnetic field is concentrated on small area of the mr fluid. figure 7: novel mr brake design with enhanced magnetic field efficiency by altering earlier mr brake designs, it is possible to concentrate magnetic field effect. one such design has been presented in figure 7. compared to the dimensions of the tested mr disk brake, radius of the coil was reduced so that it could be placed in a more suitable position inside new mr brake design. new coil position allows for magnetic flux to be 118 used more efficiently. now, the magnetic flux inside mr brake passes through mr fluid several times. based on analytical comparison, presented in eq. (6–9) and tab. 1, new design features two disks in order to create more mr fluid active area. greater number of disks creates more mr fluid gaps thus the volume of mr fluid can be increased. conclusion authors compared all mr brake types on several different aspects. based on this information, the most promising mr brake type was selected, manufactured and tested on a specially designed test rig. the mr brake produced desirable results, which coincide with literature sources. approximately linear relation between the overall braking torque and the control current intensity was observed. to present results in more readable manner, the amplification factor was introduced. the experiment showed that the tested mr brake has potential for practical applications due to easiness and accuracy of control. however, the value of the overall braking torque is still small. to increase it, better utilization of the existing magnetic field is needed. the authors suggested different approach in comparison to the conventional mr brake design that would increase the overall braking torque by increasing the magnetic field efficiency and the contact area of the mr brake fluid. by multiplying the number of the disks in contact with mr fluid, value of the overall braking torque will multiply as well, eq. (7). in order to maximize the potential of the proposed mr brake, further investigations on magnetic field propagation is needed as well as design optimization. finite element method model of the novel mr brake is the next step in this process. acknowledgments this research was done as a part of project tr31046 “improvement of the quality of tractors and mobile systems with the aim of increasing competitiveness and preserving soil and environment”, supported by serbian ministry of science and technological development. mr fluid used in this experiment was provided by basf® company, under commercial name basonetic® 5030. the authors of this paper would like to express their sincere gratitude to basf company as well as to the project manager dr. christoffer kieburg for all the supports. references 1. t. m. avraam: mr-fluid brake design and its application to a portable muscular rehabilitation device, phd thesis, active structures laboratory, department of mechanical engineering and robotics, universit´e libre de bruxelles, bruxelles (2009) 2. g. bossis, s. lacis, a. meunier, o. volkova: magnetorheological fluids, journal of magnetism and magnetic materials, 252 (2002), pp. 224–228 3. j. d. carlson, m. r. jolly: mr fluid, foam and elastomer devices, mechatronics, 10 (2000), pp. 555–569 4. j. d. carlson, d. m. catanzarite, k. a. clair: commercial magnetorheological fluid devices, in proceedings of the 5th international conference on er fluids, mr suspensions and associated technology (ed. w. a. bullogh), singapore (1996), pp. 20–28 5. e. d. ericksen, f. gordaninejad: a magnetorheological fluid shock absorber for an off-road motorcycle, international j. vehicle design, 33 no 1-3 (2003), pp. 139–152 6. a. farjoud, n. vahdati, y. f. fah: mathematical model of drum-type mr brake using hershelbulkley shear model, journal of intelligent material systems and structures (2007), pp. 1–8 7. d. g. fernando: characterizing the behavior of magnetorheological fluids at high velocities and high shear rates, phd thesis, faculty of the virginia polytechnic institute and state university, blacksburg,virginia (2005) 8. f. d. goncalves, j. d. carlson: an alternate operation mode for mr fluids – magnetic gradient pinch, journal of physics: conference series, 149 (2009), pp. 1–4 9. k. h. gudnundsson, f. jonsdottir, f. thorsteinsson: a geometrical optimization of a magneto-rheological rotary brake in a prosthetic knee, smart materials and structures, 19 (2010) pp. 1–11 10. z. herold, d. libl, j. deur: design and testing of an experimental magnetorheological fluid clutch, strojarstvo, 52 no. 3 (2010), pp. 601–614 11. j. huang, j. q. yhang, y. yang, y. q. wei: analysis and design of a cylindrical magnetorheological fluid brake, journal of material processing technology, 129 (2002) pp. 559–562 12. a. jinung, k. dong-soo: modelling of magnetorheological actuator including magnetic hysteresis, journal of intelligent material systems and structures, 14 (2003) pp. 541–550 13. k. karakoc, j. e. park, a. suleman: design considerations for an automotive magnetorheological brake, mechatronics, 18, no. 8 (2008), pp. 434–447 14. k. karakoc: design of a magnetorheological brake system based on magnetic circuit optimization, phd thesis, department of mechanical engineering, university of victoria, victoria, canada (2007) 15. b. m. kavlicoglu, f. gordaninejad, c. a. evrensel, n. cobanoglu, y. lui, a. fuchs, g. korol: a high-torque magneto-rheological fluid clutch, proceedings of spie conference on smart 119 materials and structures, march 2002, san diego, pp. 1–8 16. k. kayler: lord corporation expands production of steer-by-wire tfd brakes to meet demand, available from: http://www.lord.com/newscenter/press-releases/lord-corporation-expandsproduction-of-steer-by-wire-tfd-brakes-to-meetdemand-.xml. 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da luz, a. suleman: a performance evaluation of an automotive magnetorheological brake design with a sliding mode controller, mechatronics, 16 (2006), pp. 405–416 24. n. phuong-bac, c. seung-bok: a new approach to magnetic circuit analysis and its application to the optimal design of a bi-directional magnetorheological brake, smart materials and structures, 20 (2011), pp. 1–12 25. j. rabinow: magnetic fluid torque and force transmitting device, us patent 2,575,360, 1951. 26. b. f. spencer, s. j. dyke, m. k. sain, j. d. carlson: phenomenological model of a magnetorheological damper, asce journal of engineering mechanics, 123, no. 3 (1996), pp. 1– 23 27. v. k. sukhwani, h. hirani: design, development, and performance evaluation of high-speed magnetorheological brakes, proceedings of the institution of mechanical engineers, part l: journal of materials design and applications, 222 (2008), pp. 73–82 28. j. wang, g. meng: magnetorheological fluid devices: principles, characteristics and applications in mechanical engineering, proceedings of institution of mechanical engineers – part l – journal of materials: design and application, 215 (2001), pp. 165-174 29. z. a. zainordin, a. m. abdullah, k. hudha: experimental evaluations on braking responses of magnetorheological brake, international journal of mining, metallurgy & mechanical engineering, 1, no. 3 (2013), pp. 195–199 microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 83-88 (2008) investigation and production of bioethanol/gas oil emulsions g. marsi, g. nagy , j. hancsók university of pannonia, institute of chemical and process engineering, department of hydrocarbon and coal processing h-8201 veszprém, p.o.box.: 158, hungary e-mail: nagyg@almos.uni-pannon.hu directive 2003/30/ec contains the recommendation of the european union regarding the increase of the use of bioderived fuels. according to the directive fuels have to contain 5.75% bio-derived component – regarding the total energy content – by 2010. nowadays in the european union as renewable blending component biodiesel is applied in the highest amount, however further increase of its quantity is inhibited by many reasons. one possible solution for the increase of renewable gas oil blending components is the application of bioethanol/gas oil emulsions; however their spread is inhibited by their stability, analytical and performance properties. in this paper the effect of temperature and the presence of biodiesel on the stability of bioethanol/gas oil blends were investigated. besides, analytical and performance properties of these emulsions were compared to the regulations of the diesel fuel standard (msz en 590:2004) and to that of the applied base gas oil. it was found, that decrease of temperature worsened the stability of these emulsions in a great manner. decrease of viscosity and lubricity caused by bioethanol were compensated until 6 v/v% bioethanol content by blending 5 v/v% biodiesel into the base gas oil. it was established that the decrease of cetane number caused by the bleding of bioethanol can be partially compensated by the application of high cetane number biodiesel. in conclusion, by the application of 5 v/v% biodiesel – produced by the transesterification of expediently improved sunflower oil having high cetane number – bioethanol/gas oil/biodiesel emulsion with 6 v/v% bioethanol content could be produced, that was stable at low temperature, had adequate lubricity and cetane number. keywords: gas oil, emulsion, bioethanol, biodiesel. introduction in the last couple of years we have been facing several new challenges about the mobility, one of the most important pillars of sustainable development, both in the automobile manufacturing industry and in the oil industry [1-3]. among other things, these changes were driven by regulated emission reduction of vehicles and that of greenhouse gas emissions, the tightening fuel specifications, the significantly higher crude oil prices, the efforts to reduce the dependency on imported crude oil and the increasing utilization of renewable energy sources [2-5]. out of the biomass-based engine fuels, which are suitable to operate diesel engines, biodiesel (vegetable oil fatty acid methyl esters) became the most widespread in the european union [6-8]. however, the investigation of bioethanol-diesel fuel and/or biodiesel emulsions as possible fuels to be applied in diesel engines is also of increasing importance [7, 8]. this is constrained by the stability and the other problems derived from the analytical and performance properties of these emulsions [9-19]. the stability of these emulsions is influenced by several factors, which are the followings: hydrocarbon composition of base gas oils [10, 11], water content of bioethanol [12-15] and quality and quantity of emulsive additive [16]. the most important disadvantageous derived from their analytical and performance properties are: flash point, cetane number, viscosity and lubricating properties [17-19]. due to these disadvantageous properties low quantity of bioethanol/gas oil emulsions have benn used as fuel in diesel powered vehicles (mainly in case of urban bus or agricultural vehicles). various techniques involving bioethanol-gas oil fuel operation have been developed to make diesel engine technology compatible with the properties of ethanolbased fuels. they can be divided into the following categories: • bioethanol/gas oil emulsions, • injection of bioethanol (vaporization), • dual injection of bioethanol and diesel fuel, • application of bioethanol alone with cetanebooster additive, • transformation of diesel-engines to be operated with bioethanol. in case of the first three options about 5–90% of diesel fuel can be substituted with bioethanol. the last two options mean the application of bioethanol alone. 84 in the european union diesel-vehicles fuelled by bioethanol could not be spread in wide range; currently these engines are used in sweden in case of urban transport or agricultural fleets [19]. in pursuance of previous observations the main objective of our research work was to study the effect of temperature, presence of biodiesel and quantity of stabilizing additive on the stability of bioethanol/diesel fuel and/or biodiesel emulsions. additionally the properties (density, kinematic viscosity, lubricity, reid vapour pressure, cold properties, distillation properties, cetane number) of the bioethanol/diesel fuel micro emulsions in function of bioethanol content, in comparison with the specifications of the diesel fuel standard (msz en 590: 2004) and with the corresponding properties of the base diesel fuel were investigated. experimental characteristics of the applied bioethanol and biodiesel used to prepare the studied samples are summarized in table 1-3. tridecanol based additive was used to prepare bioethanol/gas oil emulsions. characteristics of the prepared samples, base gas oil, bioethanol and biodiesel were determined or calculated by standard test methods, which are listed in table 4. table 1: main properties of base gas oil properties value density at 15.6 °c, kg/m3 837.2 sulphur content, mg/kg 5 nitrogen content, mg/kg 1 aromatic content,% mono 21.9 mi 2.0 poly 0.3 total 24.2 kinematic viscosity at 40 °c, mm2/s 2.60 cfpp, °c -10 flash point, °c 64 distillation range, °c 184-356 cetane index 51.1 cetane number 52.5 cfpp: cold filter plugging point preparation of the emulsions was carried out with a magnetic agitator equipment at medium speed (600–700 rpm). the duration of agitation was 10 minutes in case of all samples. after the agitation, the samples were left alone at room temperature for 7x24 hours in a measuring tube of 100 cm3 closed with a glass stopper. the tridecanol based additive was used in 0.5–2.0 m/m% concentration referring to base gas oil, bioethanol in 1–15 v/v% and biodiesel in 3–21 v/v% concentration referring to base gas oil. the stability of the samples was investigated in the temperature range of 1–20 °c. table 2: main properties of bioethanol properties value relative molecular mass, g/mol 46.07 carbon content, % 52.14 hydrogen content, % 13.13 oxygen content, % 34.73 sulphur content, mg/kg <1 density at 15.6 ºc, kg/m3 789.3 boiling point at 101.3 kpa, ºc 78.5 heating value, mj/l 21.1 flash point, ºc 12.8 reid vapour pressure, kpa 15.9 table 3: main properties of biodiesel properties value ester content, % 99.2 density at 15.6 °c, kg/m3 885.0 kinematic viscosity at 40 °c, mm2/s 4.5 flash point, °c 132 oxidation stability at 110 °c, h 13 acid value, mg koh/g 0.3 iodine value, g iodine/100 g 84 cfpp, °c -12 cetane number 56 cfpp: cold filter plugging point table 4: standard test methods characteristics standard method density at 15.6 °c msz en iso 3675 kin. viscosity at 40 °c msz en iso 3104 flash point msz en iso 2719 cfpp msz en 116 cloud point msz en 23015 reid vapour pressure msz en 13016-1 lubricity (four ball test) astm d 2783-88 sulphur content msz en iso 20846 aromatic content msz en 12916 distillation properties msz en iso 3405 cetane index msz en iso 4264 cetane number msz en iso 5165 ester content msz en 14103 oxidation stability msz en 14112 acid value msz en 14104 cfpp: cold filter plugging point results and discussion investigation of the stability of bioethanol/gas oil emulsions first, the effect of quantity of tridecanol based additive on stability of bioethanol/gas oil emulsions was investigated (fig. 1). fig. 1 indicates that the concentration of the additive strongly affected the volume of bioethanol kept dissolved. the base gas oil alone 85 without any additive was only able to keep maximum 3 v/v% bioethanol in solution. this value increased to 8.5% with increasing concentration of the additive. the stability of emulsions was strongly influenced by the temperature. the decrease of temperature had negative effect on the amount of dissolved bioethanol, as it was expected. the bioethanol kept in emulsion decreased from 8.5% to 5.3% with decreasing the temperature from 20 °c to 1 °c. 0 2 4 6 8 10 0 2 4 6 8 10 12 14 16 blended bioethanol, v/v% c on ce nt ra tio n of b io et ha no l i n em ul si on , v/ v% 0,5 0,75 1 1,5 2concentration of additive, % figure 1: stability of bioethanol/gas oil emulsions as a function of quantity of additive (temperature: 20 °c) beside the effect of additive concentration and temperature, as a potential co-solvent biodiesel was also investigated. these results are presented in figs 3-5. the biodiesel co-solvent significantly enhanced the stability of the blend, thus a defined amount of base gas oil was able to dissolve a higher amount of bioethanol. this is caused by the unlimited solvency of bioetanol and biodiesel [10,19]. the stability of emulsions increased with increasing the quantity of the additive (fig. 4). it can be observed that the reduction of temperature had a negative effect on the amount of dissolved ethanol even in the presence of biodiesel. without the use of additive, bioethanol did not dissolve into the base gas oil at 1°c, but the presence of 5% biodiesel facilitated the admixture. figs 2-5 indicate that the stability of emulsions increased due to the application of biodiesel in low quantity (5–7%). 4.4v/v biodiesel containing base gas oil was able to keep 1.5% more bioethanol in emulsion under the same conditions compared to the base gas oil without biodiesel. 0 2 4 6 8 10 12 14 16 0 5 10 15 20 25 concentration of biodiesel in base gas oil, % se pa ra te d bi oe th an ol , cm 3 20°c 3°c 1°c temperature, °c figure 2: stability of bioethanol/gas oil emulsions as a function of temperature (without additive, 15 v/v% bioethanol) 0 2 4 6 8 10 12 14 0 5 10 15 20 25 concentration of biodiesel in base gas oil, v/v% se pa ra te d bi oe th an ol , c m 3 20°c 3°c 1°c temperature, °c figure 3: stability of bioethanol/gas oil emulsions as a function of temperature (1% additive, 15 v/v% bioethanol) 0 2 4 6 8 10 12 14 0 5 10 15 20 25 concentration of biodiesel in base gas oil, v/v% se pa ra te d bi oe th an ol , c m 3 20°c 3°c 1°c temperature, °c figure 4: stability of bioethanol/gas oil emulsions as a function of temperature (2% additive, 15 v/v% bioethanol) 0 2 4 6 8 10 12 0 5 10 15 20 25 concentration of biodiesel in base gas oil, % se pa ra te d bi oe th an ol , c m 3 without additive 1% additive 1,5% additive 2% additive figure 5: stability of bioethanol/gas oil emulsions as a function of quantity of additive (temperature: 20 °c, bioethanol content: 15 v/v%) this finding is important, because diesel fuels containing at least 4.4 v/v% biodiesel can be marketed with tax incentives in hungary beginning with january 1, 2008. biodiesel acts as a co-solvent and can improve the stability of bioethanol/diesel fuel emulsions meaning that the low temperature (1–20 °c) might occurring during the storage or transportation will not cause phase separation in case of bioethanol content between 1–8 v/v%. 86 investigation of the analytical and performance properties of bioethanol/gas oil emulsions the usability of bioethanol/gas oil emulsion is not only affected by their stability but also by their analytical and performance properties. that’s why their analytical properties were also investigated according to the specifications of the diesel fuel standard (msz en 590: 2004) and the corresponding properties were compared to those of the base diesel fuel. density of the base gas oil used for the blending was 0.8372 g/cm3 at 15 °c-on. density of the blends was lower due to the addition of ethanol having a lower density (fig. 6). density of the blends containing up to 10 v/v% bioethanol has met the specification (0.820–0.845) of msz en 590:2004 standard. kinematic viscosity of the base gas oil measured at 40 °c was 2.60 mm2/s, which dropped to 2.18 mm2/s after blending 10 v/v% bioethanol. the presence of biodiesel slightly increased the kinematical viscosity, as expected (fig. 7). the measured viscosity values have met the specifications (2.0–4.5 mm2/s) of the diesel fuel standard. it can be seen that the presence of biodiesel in 5.5 v/v% concentration increased the kinematic viscosity of the base gas oil. 0.816 0.82 0.824 0.828 0.832 0.836 0.84 0 2 4 6 8 10 12 concentration of bioethanol, v/v% d en si ty a t 1 5, 6° c , g /c m 3 figure 6: change of density of bioethanol/gas oil emulsions as a function of bioethanol content 2 2.2 2.4 2.6 2.8 0 2 4 6 8 10 12 concentration of bioethanol, v/v% k in em at ic v is co si ty a t 4 0° c , m m 2 /s bioethanol/gas oil emulsions bioethanol/gas oil emulsions + 5v/v% biodiesel figure 7: change of kinematic viscosity of bioethanol/gas oil and/or biodiesel emulsions as a function bioethanol content flash point (as of pensky-martens) of the base gas oil was 64 °c, which decreased to an average of around 14 °c (± 1 °c) as a result of adding 5% bioethanol (fig. 8). this value was not affected by the presence of biodiesel. this flash point is much lower than the max. limit specified in the standard, therefore, ethanol/diesel fuel blends/emulsions have to be categorized into a higher class of flammability group than the base gas oil. as a result, the air/hydrocarbon mixture is within the range of the explosive limit at a temperature of 12–35 °c. in order to overcome this problem, the literature suggests the installation of a flame arrester in the fuel tank of the vehicle [9,10]. 0 10 20 30 40 50 60 70 base gas oil base gas oil + 5v/v% biodiesel 2 4 6 8 10 concentration of bioethanol, v/v% fl as h po in t, °c base gas oils emulsions figure 8: change of flash point of bioethanol/gas oil and/or biodiesel emulsions as a function of bioethanol content normally, vapour pressure of gas oils is not measured, because it is very low. however, the blending of bioethanol has significantly increased the vapour pressure of the base fuel as already projected in the literature. reid vapour pressure of the base feedstock was 0.6 kpa, while those of the blends containing 5% bioethanol were about 13.2 kpa in average, also in the presence of biodiesel. the about twenty times higher rvp of the gas oil/ethanol blend can even result in vapour lock formation in the fuel supply chain of vehicles. among cold properties the cfpp values decreased only slightly, pour point also decreased, but greatly and cloud point increased greatly as a result of bioethanol blending. cfpp values became higher by 2–3 °c in the presence of biodiesel (table 5). the increase of cloud point was caused by the growing micelles due to the lower temperature in micro emulsions. table 5: change of cold flow properties of bioethanol/gas oil and/or biodiesel emulsions as a function of bioethanol content bioethanol content, v/v% cfpp, °c cloud point, °c pour point, °c base gas oil -10 -10 -22 2 -11 -8 -24 4 -11 -6 -25 6 -13 -5 -26 8 -14 -4 -28 10 -14 -2 -31 87 the lubricity of fuel can be an issue in the vehicles, where the lubrication of the fuel pump is provided by the fuel itself. lubricity of the bioethanol/gas oil emulsions was studied with a four ball equipment available at our department. the samples were examined in the four ball test under 300 n load for 1 hour. the obtained results are presented in fig. 9 and 10. as expected, the ethanol has considerably decreased the lubricating properties of the base gas oil. the size of wear scar increased from 0.78 mm to 1.2 mm after blending ethanol, i.e. the anti-wear effect of the mixture substantially dropped. the temperature varied between 55.5–57 °c, which was not a significant change but increased in tendency, indicating that the anti-friction effect of the fuel mixture also worsened. 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 base gas oil 2v/v% bioethanol 4v/v% bioethanol 6v/v% bioethanol w ea r sc ar e di am et er , m m 40 42 44 46 48 50 52 54 56 58 60 t m ax , ° c wear scare diameter tmax figure 9: change of lubricity of bioethanol/gas oil emulsions as a function of bioethanol content 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 base gas oil+5v/v% biodiesel 2v/v% bioethanol+5v/v% biodiesel 4v/v% bioethanol+5v/v% biodiesel 6v/v% bioethanol+5v/v% biodiesel 8v/v% bioethanol+5v/v% biodiesel w ea r sc ar e di am et er , m m 40 45 50 55 60 65 70 t m ax , ° c wear scare diameter tmax figure 10: change of lubricity of bioethanol/gas oil/biodiesel emulsions as a function of bioethanol content (biodiesel content of base gas oil: 5 v/v%) the loss of lubricity could be compensated with biodiesel in case of maximum 6 v/v% bioethanol (fig. 10). the distillation properties of base gas oil greatly changed due to the lower boiling point of bioethanol (78.5 °c at 101.3 kpa) (fig. 11). cetane number is an important property of diesel fuels. due to the blending of 10v/v% bioethanol with base gas oil the cetane number decreased by about 10 units (fig. 12). the loss of cetane number would be compensated by: − use of high cetane number base gas oil, − cetane booster additives (ethyl-hexyl-nitrate), − higher carbonand cetane number and more soluble alcohol (biobutanol, cetane number: 36), − high cetane number biodiesel produced from improved vegetable oil. 0 50 100 150 200 250 300 350 400 0 20 40 60 80 100 quantity of distillated product, ftf% t em pe ra tu re , ° c base gas oil base gas oil + 5v/v% bioethanol base gas oil + 10v/v% bioethanol base gas oil + 15v/v% bioethanol figure 11: change of the distillation properties of bioethanol/gas oil and/or biodiesel emulsions as a function of bioethanol content (biodiesel content of base gas oil: 5 v/v%) 40 44 48 52 56 base gas oil 2 v/v% bioethanol 4 v/v% bioethanol 6 v/v% bioethanol 8 v/v% bioethanol 10 v/v% bioethanol c et an e nu m be r without biodiesel 5v/v% biodiesel figure 12: change of cetane number of bioethanol/gas oil and/or biodiesel emulsions as a function bioethanol content (biodiesel content of base gas oil: 5v/v%) cetane number of 6v/v% bioethanol containing bioethanol/gas oil emulsion could be increase from 48 to 51 units by the application of high cetane number biodiesel produced from improved vegetable oil. summary application of bioethanol/gas oil emulsions as fuels will probably increase in the european union in the following decades mostly in the urban bus fleets and in the agricultural vehicle fleets. we established that stability problems of bioethanol/gas oil emulsions can be partially compensated by the application of biodiesel. 6 v/v% bioethanol containing bioethanol/gas oil/biodiesel emulsions were stable at lower temperature due to the 5 v/v% biodiesel applied in the base gas oil. analytical and performance properties of bioethanol/gas oil emulsions were in many cases different from that of 88 the base gas oil and that of the regulations of the msz en 590:2004 diesel fuel standard. we established that the decrease of kinematic viscosity and lubricity of bioethanol/gas oil/biodiesel emulsions containing 6 v/v% bioethanol were compensated by blending 5 v/v% biodiesel into the base gas oil. furthermore, it was found that the decrease of cetane number caused by the blending of bioethanol can be partially compensated by the application of high cetane number biodiesel. in case of blending 6 v/v% bioethanol density and kinematic viscosity of bioethanol/gas oil emulsions satisfied the requirements of the msz en 590:2004 standard. however, flash point and reid vapour pressure values of the emulsions were off the limits. in order the overcome this problem, the literature suggests the installation of a flame arrester in the fuel tank of the vehicle references 1. merritt p. m., ulmet v., mccormick r. l., mitchell w. e., baumgard k. j.: sae technical paper 2005-01-2193 (2005) 2. directive 2003/30/ec of the european parliament and of the council of 8 may 2003 on the promotion of the use of biofuels or other renewable fuels for transport. 3. hamelinck c. n., faaij a. p. c.: energy policy, 34 (2006) 3268-3283. 4. rakopoulos c. d., antonopoulos k. a., rakopoulos d. c., kakaras e. c., pariotis e. g.: int. j. vehicle design (2008) in press. 5. demirbas a.: progress energy combust science, 33 (2007) 1-18. 6. satge de caro p., mouloungui z., vaitilingom g., berge j. c. h.: fuel, 80 (2001) 565-574. 7. rosenberg a., kaul h. p., senn t., aufhammer w.: ind. crop. prod., 15 (2002) 91-102. 8. malca m., freire f.: energy, 31 (2006) 3362-3380. 9. he b. q., shuai s. j., wang j. x., he h.: atmospheric environmental, 37 (2003) 4965-4971. 10. hansen a. c., zhang q., lyne p. w. l.: bioresource technology, 96 (2005) 277-285. 11. xing-cai l., jian-guang y., wu-gao z., zhen h.: fuel, 83 (2004) 2013-2020. 12. noguchi n., terao h., sakata c.: bioresource technology, 56 (1996) 35-39. 13. can o., celikten i., usta n.: energy conversion management, 45 (2004) 2429-2440. 14. xingcai l., jianguang y., wugao z., zhen h.: fuel, 83 (2004) 2013-2020. 15. chen h, shuai s, wang j.: proc. combust. inst., 31 (2007) 2981-2989. 16. de menezes, e. w.: fuel, 85(3) (2006) 815-822. 17. fredriksson, h.: agricultural systems, 89 (2006) 184-203. 18. de-gang l.: renewable energy, 30 (2005) 967-976. 19. varga z., hancsók j., lengyel a.: hungarian chemical journal, 61(9-10) (2006) 315-320, (in hungarian). microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 101-106 (2008) ion transport via electrosorption d. pethő1 , gy. gáspár1, g. horváth1, j. liszi2, r. szakály1, i. tóth1 1university of pannonia, department of chemical engineering, h-8201 veszprém, hungary e-mail: pethod@almos.vein.hu 2university of pannonia, department of chemical physics, h-8201 veszprém, hungary the aim of this study was the metal ion removal of the gas scrubber effluents of an olefins plant by electro swing adsorption. this electrochemical method has an advantage it does not use hazardous chemicals and it does not produce pollution. this paper is a report about preparation of nickel electrodes with high specific surface area, estimating the electrochemically accessible surface area, and experimentally demonstrating the existence of the double-layer, determination of the capacity of the electric double-layer, demonstrating the ion transport by electrosorption. moreover an attempt is made at the determination of the relative role of the physical adsorption and the electrosorption in the ion transport. measurements were carried out on an automated electro swing adsorption apparatus. finally optimal operating parameters were determined by maximizing the removal efficiency. keywords: electrosorption, physical adsorption, “nickelized” nickel electrod, porous nickel electrode, mass transfer introduction environmental pollution is one of the most challenging problem of the continuously developing, industrialized world. recycling of the effluents containing large amount of impurities can only be realized by appropriate treatment. effluents from caustic scrubbers of pyrolysis gases are heavily loaded with metal ions of which the removal is not yet solved. we aimed to develop a process for reducing the metal ion content in spent caustic effluents to minimize the environmental effect. the basis of the proposed process was ion transport via electrosorption.the electrosorption is a kind of adsorption, which takes place on the surface of charged electrodes [1]. the electric polarization can be carried out galvanostatic or potentiostatic ways [2]. in practise the galvanostatic method is preferred [2-4]. the electrosorption of cations takes place on the cathodic polarized (negative) electrode. this electrosorption is superimposed on the physical adsorption (on non-charged electrode). in case of reversed electric polarization the cations desorb. when the ionadsorption is carried out in a given solution and the desorption in another solution, then ions can be transported from one solution to another [5-8]. this is called ion transport via electrosorption. in the electrosorption an electric double-layer comes into being at the electrode-solution interface. the electric double-layer consists of two parts: the helmholtz-layer and the diffuse layer. if the electrode moves the diffuse layer can break and a zeta-potential appears between the fixed and the moving parts. the electrosorption, as it is an electrochemical method, has an absolute advantage: it does not use hazardous chemicals, but only inert electrodes. in addition it does not produce pollution, and the electrochemical parameters can be measured and controlled easily. the electrosorption is a surface phenomenon. its efficiency grows with the electrode surface area. the applied electrodes are mostly porous carbon-electrodes with high specific surface area [1, 3, 9-14]. electrode with high specific surface area also can be prepared from metals, several methods of this procedure are known. macroporous ni, co and fe can be prepared via reduction of nio, co3o4 and fe2o3 by hydrogen [15]. heating of metal-oxalates in nitrogen also can result in high specific surface area metals [15]. porous ni, cu, ag, pt and au can be prepared via precipitation of metal on colloidal silica, and after calcinations the silica is removed with hf [16]. among the electrochemical methods the preparation of platinated platinum is well known. accordingly “black” or “grey” nickel electrode also can be prepared with high specific surface area [1719]. the high surface in itself area is not sure enough, because in case of insufficient pore-size distribution not the whole surface will be accessible electrochemically. inorganic ions can be removed from aqueous solution by means of electrosorption [20]. numerous examples are known of removing of organic compounds from dilute aqueous solution, e.g. phenols and derivates [10], pyridine [2], aniline and bipyridines [3], tiocianate [1] or even colloidal particles [21]. the electrosorption is applied at industrial level in wastewater treatment [2, 3, 10, 19] and water desalination [22-29]. 102 preparation of nickel electrodes of high specific surface area the preparation was carried out by two different techniques: by electrochemical and powder metallurgic methods. the nickel coated nickel was prepared by electrolysis, and the porous disc electrode was made by powder metallurgic technique. preparation of nickel coated nickel electrodes by electrolysis nickel was precipitated on the surface of nickel sheet. before the electrolysis the nickel sheet was prepared: mechanical polishing, degreasing by sodium hydroxide solution (10 m), washing by water, drying, soaking in chloroform or carbon tetrachloride, and finally acidic etching in boiling hydrochloride acid (30 wt%). the electrolytes applied in the former papers contain niso4 (33 g dm-3), (nh4)2so4 (33 g dm-3) and k-natartarate (14 g dm-3) with ph 5.1. in accordance with our experience by this solution it can not prepared smooth, stable coating. it was found that the properties of the nickel layer precipitated via electrolysis strongly depend on the ph. at ph 7.0 a bright, gleaming grey surface forms, while at ph 8.0 a black and cracking surface evolves. nh4oh was used to increase the ph. at ph 7.5 some opalescence was observed due to the formation of ni(oh)2 precipitation, that can be taken into complex by edta. in the ph range of 9.5–10.0 the solution is dark blue, and from this solution smooth, black, stable coating can be precipitated. the current density of the electrolysis has to be less than 0.1 a cm-2. the ph of the solution can change during the electrolysis that results in deterioration of the surface. the ph can be kept constant with application of sufficient solution volume or nh4oh feeding. preparation of porous nickel electrodes by powder metallurgic technique porous electrodes were made by this method, the porosity guarantees higher surface area. the initial powder contains raney-nickel (90–93 wt%, glowed at 60 °c), silver chloride (2–5 wt% referred to the silver) and paraffin (5 wt%). the paraffin needed to prepare to get the required homogeneity and porosity. it was melted in warm water (70 °c) and surfactant (dish-washing agent) was added with strong mixing. the emulsion was cooled quickly pouring onto ice, then the paraffin particles were dried at room-temperature. after then the powder was pressed (6–8 ton) in a steel ring by means of a hydraulic pressing machine and pastille was formed. the pastilles were treated by heat and reduction. the heat treating had two stages. first the whole organic substance was fired out in oxidative atmosphere. the heating rate was approximately 200 °c h-1. the pastilles were kept between 400–450 °c for 30 minutes. this way the solid paraffin melted then turned into cracking gas. in case of higher heating rate the forming gases can break the pastille. in the second stage the pastilles were kept between 960–1100 °c for 30 minutes in inert atmosphere (nitrogen). under these conditions the silver and the nickel form an alloy, that has increased electric conductivity and provides enhanced disc electrode with better mechanical properties. if the first stage misses, the porous electrode will be useless because of the surface cracks. the reduction was carried out in hydrogen atmosphere at 550 °c. at the end of the reduction process the output gas of the reactor does not contain water. nickel electrodes tested the electrochemically accessible surface area an electrolytic double-layer forms at the electrodesolution interface, that consists of a helmholtz-layer and a diffuse layer. the helmholtz-layer is independent of the ion concentration (contrasted) in contradiction with the diffuse layer. the double-layer regards as a capacitor. when electric current flows in an ideally polarisable electrode, the current changes only the charge of the capacitor and there is no charge transition. tc dε idt dε dq == (1) where: q – charge, ε – potential, i – current intensity, t – time, ct – polarisation capacity at a given t. in case of partially polarisable electrode ct is the electrode capacity of the double-layer at t=0. under constant current intensity the potential of the electrode was measured compared to a saturated calomel electrode (δε = ε εcalomel) in the function of time. the counter electrode was graphite. the slope of the curve δε vs. t: ( ) dt d dt dtg εεα == δ (2) the polarisation capacity from the equations (1) and (2): ( ) αε tg di d tdidct == δ (3) supposing flat condenser (4): d a c 0 t ε = (4) where: ε0 – the permittivity of the vacuum, a – the area, 103 d – the distance between the condenser plates. considering the equation (4): α ε tg i d a0 = (5) comparing the electrochemically active surface area of two electrodes under the same conditions where index 1 and 2 refer to the electrodes: 1 2 2 1 tg tg a a α α = (6) on the basis of the above-mentioned consideration the high surface area of the electrodes were compared to the nickel electrode’s flat surface (polished). the constant current intensity was 10 ma. the solution contained naoh (0.2 wt%). the electrode distance was 10 mm. referring to the flat nickel surface area, the electrochemically accessible surface area for nickel coated nickel (nickel-soot coated nickel) and for the porous nickel electrode are 50 and 214, respectively. these values are in accordance with the data measured by others with different methods in case of copper coated copper [4, 30] or nickel coated nickel [18]. bet surface area analysis was carried out by nitrogen adsorption in a micromeritics asap 2000 instrument. the ratio of the bet surface area and the geometric surface area for the nickel coated nickel and for the porous nickel were 31370 and 38680, respectively. it means that only a part of the bet surface area is accessible electrochemically: this value is 0.16% for the nickel coated nickel, and 0.52% for the porous nickel. diffuse part of the electric double-layer the electrode has to be moved to transport ions with electrosorption from a solution to another. moving the electrode (compared to the “stationary” solution) the diffuse part of the double-layer breaks and zeta-potential evolves. the zeta-potential depends on the rate of the relative moving. on the other hand the place of the breaking has effect on the efficiency of the ion transport. the higher part of the double-layer gets from one solution to another, the more efficient the ion transport is. it seems reasonable to examine how the zeta-potential (and this way the place of the double-layer breaking) changes with the relative rate. the applied instrument for the zeta-potential measurements can be seen in the fig. 1. the solution containing naoh (0.2 wt%) flowed in a plastic tube (r = 15 mm) in the direction as the arrow shows. r 1800 mv v 1 d3l3 2 r + figure 1: measurement of the zeta-potential 1800 mv potential-difference was switched on the cathode (1) and on the anode (2). the electrode distance, d was 15 mm. the potential-difference was measured between the reference electrodes (3) by a voltmeter (v). the reference electrode distance, l was 40 mm. a series of measurement can be seen in the fig. 2. the reference electrode distance is plotted in the function of the laminar rate of flow. the zeta-potential, ζ does not change significantly over flow rate of 25 cm s-1. this way it is not reasonable to apply higher relative rate. 0 10 20 30 40 50 60 70 80 0 10 20 30 40 50 60 70 80 90 v (cm s-1) z et apo te nt ia l ( m v ) figure 2: zeta-potential vs. flow rate of the solution the capacity of the double-layer and the electrosorption of the sodium ions f. béguin et al. [11] investigated the electrosorption of lithium on activated carbons using the flowing model cell (fig. 3)z. re rt cd figure 3: the model cell where: re – the resistance of the electrolyte solution, rt – the charge transport resistance cd – is the capacitance of the double-layer. it was found that under constant current intensity the potential difference, u changes in time as follows: e irir ir u dtcr t tte += (7) if t = 0, then considering equation (7): u (t = 0) = re i (8) re is coming from (8). if t → ∞ , then u (t = ∞) = (re+ rt)i, (9) rt is coming from (9). the derivative of potential with respect to time under constant current intensity, i: 104 dtcr t d0t e i c 1 dt du = = (10) if t = 0, then c i dt du d0t = = (11) i.e. the capacitance of the double-layer, cd can be calculated from the initial slope of the u vs. t curve. the potential-difference in time can be seen in the fig. 4 for the nickel coated nickel under current intensity i = 0.01 a. the solution contained naoh (0.2 wt%), the counter electrode was graphite. the parameters of the electrochemical cell: re = 122 ω, rt = 225 ω, cd = 1.84 f. 1,2 1,4 1,6 1,8 2 2,2 2,4 2,6 0 25 50 75 100 125 150 175 200 225 250 t (s) u (v) figure 4: u vs. t curve for the nickel coated nickel the u vs. t curve for porous nickel electrode can be seen in the fig. 5. the parameters of the electrochemical cell: re = 63 ω, rt = 109 ω, cd = 5.08 f. 0,6 0,8 1 1,2 1,4 1,6 1,8 0 50 100 150 200 250 300 350 400 450 500 t (s) u (v) figure 5: u vs. t curve for porous nickel electrode knowing the capacitance, cd and the potentialdifference between the two electrodes, u the charge can be determined on the electrodes: q = cd u (12) the charge, q was calculated from the u at 25 s. knowing the charge, q considering the faraday’s law the amount of the sorbed sodium ions can be determined, that was 298 mg na+ for nickel coated nickel and 127 mg na+ for the porous nickel electrode. electrosorption and physical sorption in electrosorption assisted ion transport the ion adsorption takes place in a solution and the desorption is carried out in another solution. this way the physical adsorption is superimposed on the electrosorption, and in addition the hydrodynamic adhesive layer also takes part in the ion transport. the relative extent of three effects was estimated. the electrode was immersed in a solution containing naoh 0.2 wt% . the physical adsorption of the sodium ions took place. the desorption was carried out in distilled water. the extent of the sodium ion transported with physical adsorption was 320 mg m-2 for the nickel coated nickel, and 120 mg m-2 for the porous nickel. after this the desorption was carried out by switching 1800 mv potential-difference between the studied electrode and the counter electrode. the desorption took place in also distilled water, but the polarity of the electrodes was reversed. it is supposed that under this conditions the electrosorption and the physical adsorption take place simultaneously. in this later case the quantity of the transported sodium ions was 500 mg m-2 for the nickel coated nickel, and 160 mg m-2 for the porous nickel. the extent of the sodium ions transported by electrosorption could be calculated from the difference of the two solutions (measured with and without potential-difference). this value was 180 mg m-2 for the nickel coated nickel, and 40 mg m-2 for the porous nickel. these values are less than the calculated ones from the capacity of the double-layer, but considering the roughness of the measurement it can be said that they are comparable with each other. it is necessary to explain the effect of the hydrodynamic adhesive layer, as well. the hydrodynamic adhesive layer moving with the electrode could carry some ions with itself even without any ion adsorption. in this case the sodium ion concentration is the same in the hydrodynamic adhesive layer as in the bulk. the effect of the hydrodynamic adhesive layer was determined by distilled water. using the bulk concentration the quantity of the sodium ion transported by the adhesive layer was calculated. this value was 90 mg m-2 for the nickel coated nickel, and 45 mg m-2 for the porous nickel. thus the effect of the hydrodynamic adhesive layer is much less than the effect of the adsorption, but it is still not negligible. mass transfer by electrosorption apparatus a fully automated electrosorption apparatus was designed and built. measurements were carried out on this apparatus. the used parameters are summarised in table 1. table 1: parameters of the measurements parameters polarization potential 1000–2400 mv distance between the electrodes 2.5–40 mm time 25–600 s 105 parameters can be changed fast and in wide range due to the structure of apparatus. experimental setup can be controlled easily and it works reliable. purification of used model solutions was carried out by cyclic procedure. this purification is based on electro swing adsorption. 4 wt% naoh solution was used instead of the effluent and porous nickel electrode was used in the experiments. the latter was prepared by powder metallurgic techniques. optimal operating parameters were determined by maximizing the removal efficiency. the amount of ions removed in one cycle was determined as a function of the number of cycles, concentration of sodium ions, polarization potential and desorption time. fig. 6 illustrates the influence of polarization potential on the mass transfer. the polarization potentialts have been varied from 1000 mv to 2400 mv. at first high polarization potential was used however in this case a huge enegy consumption appeared because of hydrolysis. it was proved that a good mass transfer can be reached with lower polarization potentials when the enegy consumption is lower. 0 100 200 300 400 500 600 700 800 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 polarization potential [mv] m as s tr an fe r [m g n a + m -2 c yc le -1 ] figure 6: mass transfer for porous nickel electrode 25 s adsorption time, and 120 s desorption time previously we have demonstrated that adsorption process is faster than desorption process. if porous nickel electrodes are used pore diffusion inhibition will occur. in fig. 7 it can be seen that desorption time have to be more than 300 s, in this way a more efficient mass transfer can be reached. 0 200 400 600 800 1000 1200 1400 0 100 200 300 400 500 600 700 desorption time [s] m as s t ra nf er [ m g n a + m -2 c yc le -1 ] figure 7: mass transfer for porous nickel electrode 1200 mv adsorption and desorption polarization potential in the early part of the investigations electrical efficiency was 30–35% but after the optimalization of the parameters it has improved to 60%. summary nickel electrodes were prepared with high specific surface area to produce ion transport by electrosorption. nickel coated nickel electrode was prepared by electrolysis and porous nickel electrode was made by powder metallurgic method. it was found that the electrochemically accessible surface area of the electrodes is much less than their bet surface area. measuring the zeta-potential it was shown that it is not worth-while to apply higher relative moving rate than 25 cm s-1 between the solution and the electrode. using graphite counters electrode the parameters of the electrochemical cell were determined. knowing faraday’s law and the capacitance of the electrolytic double layer the extent of the adsorbed sodium ions (by electrosorption) was calculated. this value was 298 mg m-2 for the nickel coated nickel, and 127 mg m-2 for the porous nickel. the role of the electrosorption, the physical adsorption and the hydrodynamic adhesive layer was estimated via independent measurements. it was found that all of the three effects take part in the ion transport. under the experimentally determined optimal conditions electric efficiencies up to 60% were achieved. removed sodium ion was 1200 mg m-2 cycle-1 from a 4 wt% naoh solution, using a polarization potential of 1200 mv and a distance of 2,5 mm between the electrodes with an adsorption and desorption time set to 25 and 300 s, respectively. we can conclude that our laboratory scale electrosorption apparatus fulfilled the requirements and measurements were reproducible. on the basis of the lab-scale results the scale-up of the process to pilot scale seems to be possible. acknowledgement the authors express their gratitude to chemical engeering institute cooperative research center of the university of pannonia for financial support of this research study. references 1. chen rong, hu xien: j. colloid and interface science, 290 (2005), 190. 2. jianjun niu, conway b. e.: j. electroanal chem., 521 (2002), 16. 3. jianjun niu, conway b. e.: j. electroanal chem., 536 (2002), 83. 4. vaškelis a., norkus e., stalnioniene j., stalnionis g.: electrochim. acta, 49 (2004), 1613. 5. afkhauni a., conway b. e.: j. colloid and interface science, 251 (2002), 248. 106 6. 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sssr, 77 (1951), 53. 18. horányi g., rizmayer e. m.: j. electroanal. chem., 180 (1984), 97. 19. ganesh v., lakshminarayanon v.: electrochim. acta, 49 (2004), 3561. 20. genders j. d., chai d., hobbs d. t.: j. appl. electrochem., 30 (2000), 13. 21. hall d., priel z., osen y., soffer a.: separation sci. and technol., 22 (1987), 1017. 22. oren y., soffer a.: j. appl. electrochem., 13 (1983), 473. 23. oren y., soffer a.: j. appl. electrochem., 13 (1983), 489. 24. oren y., soffer a.: j. electrochem. soc., 125 (1978), 869. 25. oren y., egozy y.: desalination, 86 (1992), 155. 26. ginffrida a. j., jha a. d., ganzi g. c.: us patent num. 4632745. 27. ginffrida a. j., ganzi g. c., oren y.: us patent num. 4956071. 28. oren y., a. ginffrida j., ciaccio s.: us patent num. 5154809. 29. johnson a. m., newman j.: j. electrochem. soc., 118 (1971), 51. 30. norkus e., vaškelis a., staluioviene j.: j. solid state electrochem. 4 (2000), 337. microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 37(2) pp. 131-137 (2009) preparation and characterization of zno and tio2 sol-gel thin films deposited by dip coating r. baranyai, á. detrich, e. volentiru, z. hórvölgyi department of physical chemistry and materials science, budapest university of technology and economics 1111 budapest, budafoki út 6-8., building f, staircase 1, high ground floor, centre for colloid chemistry, hungary e-mail: zhorvolgyi@mail.bme.hu zno and tio2 thin films were prepared by sol-gel technique. dip coating was applied for film deposition and withdrawal velocity was varied in order to control the film thickness. the deposited films were annealed to remove additives and obtain oxide layers. large silicon and glass substrates were coated with homogeneous, reflective semiconductor layers of different refractive index values. uv-vis spectroscopy and scanning angle reflectometry measurements were performed to determine refractive index and thickness values. the using of different stabilizers for zno precursor sol preparation resulted in different layer thicknesses and very different response to the varying of the withdrawal speed. according to photoluminescence measurements zno films are of good crystallinity. thicknesses of deposited films were found to be in the range of 6-200 nm. tio2 coatings show strong interference colours due to their high refractive index. keywords: zno, tio2, sol-gel coating, scanning angle reflectometry, uv-vis spectroscopyintroduction nanostructured wide gap semiconductors emerged in the last decade and many researchers [1, 2, 3, 4] began to pay attention to unique properties of these materials. oxide semiconductor thin films, aerogels and nanocrystals can be used in photonic devices, drug delivery, sensors, solar cells, wastewater treatment etc. among these promising materials zno and tio2 are the most versatile ones, since their non-toxicity, stability and ease to prepare. zno has been recently used in uv leds as light emitting material [5, 6] and in solar cells as transparent conductive oxide [7, 8], while tio2 plays the basic role as electron acceptor in the grätzel cell [9, 10], and also used as antimicrobal and self-cleaning coating [11] because of its photocatalytical property [12, 13, 14]. thin films of zno and tio2 can be deposited by many methods, e.g. chemical bath deposition [15, 16], spray pyrolysis [17, 18], rf magnetron sputtering [19, 20]. among them sol-gel technique [21, 22] and dip coating provide low-cost deposition method which can be applied in large scale production and allows the possibility to tailor the film properties. refractive index and thickness of thin films used in optical devices have to be adequately controlled. determining these parameters is of great importance in many optical applications [23, 24] and particularly in the semiconductor industry [25, 26]. ellipsometry provides means to perform fast and non-destructive measurements [27, 28] on thin films however for very thin coatings (e. g. film with thickness below 100 nm, nanoparticulated layers and monomolecular coatings) scanning angle reflectometry (sar) [29, 30, 31] can be an other appropriate choice. this method possesses the capability to determine those important parameters very precisely since it operates with polarized monochromatic light and measurements are usually performed in angle range around the brewster angle of the substrate/air interface providing good sensitivity due to the lack of reflected light from the substrate. sar also can be used for measurement of layers on transparent substrates. our investigation focused on the preparation of oxide semiconductor coatings and adjusting their thicknesses and refractive indices. deposition method and starting precursor sol have obvious influence on sol-gel film properties. several additives such as monoethanolamine [32], triethanolamine [33] and acetic acid [34] are used for zno precursor sol preparation to stabilise the sol and control the hydrolysis. in this work two different zno precursor sols were prepared and thin films were deposited from each sol by dip coating using different withdrawal velocities. the influence of chemical composition of precursor sols on the optical properties and thickness of mono and multilayered coatings were investigated by optical methods. since tio2 possesses many properties similar to zno our investigation was extended to tio2 thin films. tio2 precursor sol was prepared and tio2 films were deposited and characterized on the same way as zno films. 132 experimental details preparation of precursor sols different zno precursor sols were prepared using polyvinylpyrrolidone (pvp) [35] or diethanolamine (dea) [36] as stabiliser. in the former case 1.098 g zinc acetate dihydrate (a.c.s. reagent, 98+%, sigmaaldrich) was added to 50.0 ml ethanol (a. r. >99.7%, reanal). under vigorous stirring 0.450 ml distilled water (conductivity: 18.2 ms/cm, purified with millipore simplicity 185 filtration system) was added drop by drop to the solution in order to promote the hydrolysis. after 15 minutes 2.000 g pvp k90 (m.w. 360000, fluka) was added to the solution in small portions. the sol became clear after 20 minutes. the sol was aged for 24 hours under continuous stirring at room temperature then it was labelled as pvp-zno and was stored in the dark. precursor sol containing diethanolamine was prepared by dissolving 5.488 g zinc acetate dihydrate in 50 ml ethanol. after 30 minutes of vigorous stirring 2.4 ml dea (for synthesis, ≥98%, merck) was added dropwise to the solution. in a few minutes after adding dea the solution became clear. it was aged for 24 hours under continuous stirring at room temperature before film deposition. the sol was labelled as dea-zno and was kept in the dark. in order to obtain tio2 precursor sol [37], 11.74 ml tetrabuthyl orthotitanate (purum, ≥97.0%, fluka) was dissolved in 55.40 ml ethanol under continuous stirring at room temperature. it was followed by addition of 65% hno3 (rpe, carlo elba) to adjust the ph of the sol to ~1.5. then 0.453 ml distilled water was added to the solution then it was stirred with 400 rpm. at 60 °c for 2 hours before film coating. precursor sols were stored in closed containers to prevent evaporation. zno sols can be used for film coating even after 2 months, but tio2 sol showed slow gelation resulting in solidification in two weeks. deposition of thin films thin films from different precursor sols were deposited by dip coating (dip coater, mfa, hungary). this equipment provides withdrawal velocities between 0.1–18.0 cm/min. glass microscope slides (menzel-gläser, 76×26 mm, refractive index: 1.517) were used as substrates for purposes of sar and spectroscopy measurements. thin films for photoluminescence investigations were coated onto si (100) substrates. prior to dip coating all substrates were cleaned consecutively with detergent, cc. hno3, distilled water and ethanol. after cleaning they were dried in dust free environment. after preliminary tests a range of withdrawal velocities were applied, films from pvp-zno sol were deposited with rates of 1, 4, 8 and 12 cm/min, while films from dea-zno and tio2 sols were prepared using 12, 15 and 18 cm/min withdrawal velocities. all films were deposited from freshly prepared precursor sols. after coating pvp-zno films were dried at room temperature for 5 min then annealed at 500 °c for 1 h. tio2 films also were dried at room temperature for 5 min then treated at 450 °c for 30 min. dea-zno films were placed into hot (250 °c) furnace immediately after coating and annealed at 500 °c for 1 h. all films were heated up with 5 °c/min heating rate. investigation methods refractive indices and thicknesses of thin films were determined by uv-vis spectroscopy and scanning angle reflecometry (homemade sar device, he-ne laser, wavelength: 632.8 nm, power: 17 mw, melles-griot). measured reflectance curves were smoothed before evaluating to eliminate the effect of interference. refractive index and thickness values were obtained by fitting simulated reflectance functions [38]. uv-vis spectroscopy measurements were performed by agilent 8453 spectrophotometer. crystalline quality was investigated with photoluminescence measurements performed by perkin elmer ls50b fluorimeter. results and discussion the resulted thin films were found to be transparent, visually homogeneous and reflective as can be seen in fig 1. figure 1: smooth and reflective surface of tio2 film on a piece of 3” si wafer uv-vis transmittance spectra of pvp-zno films prepared with different withdrawal speeds are shown in fig. 2. decrease of transmittance around 380 nm (transmittance edge) is related to the band gap of zno. transmittance around this wavelength decreases with increasing velocities indicating increase of thickness of the thin film. theoretically, in case of ideal fluids the thickness of fluid film stacked onto the substrate increases with ascendent velocity [39]. therefore the 133 growing tendency of film thicknesses is expected for films prepared with increasing velocities. uv-vis spectra seem to confirm our expectation. for further confirmation sar measurements were performed. they are shown in fig. 3. results can be found in table 1. thickness values grow with increasing velocities and refractive index values are lower in comparison to one of the substrate except for film prepared with 1 cm/min. low refractive indices can be attributed to interstices formed due to the burnout of the polymer (pvp) during annealing. low refractive indices resulted in faint antireflection effect. transmittance maxima corresponding to this effect can be recognized in spectra of films prepared with rates of 8 and 12 cm/min, however the interference is not severe enough for the correct quantitative analysis. figure 2: transmittance spectra of pvp-zno films prepared with different withdrawal velocities figure 3: result of sar measurements on pvp-zno films prepared with different withdrawal velocities table 1: results of sar measurements on pvp-zno films withdrawal velocity refractive index thickness 1 cm/min 1.684 6.2 nm 4 cm/min 1.338 16.7 nm 8 cm/min 1.420 45.4 nm 12 cm/min 1.404 72.9 nm effect of varying withdrawal speed on film thickness was also studied for films prepared from dea-zno and tio2 precursor sols. in both cases it was found that those precursor sols are not appropriate for the preparation of films at velocities below ~10 cm/min. films prepared with lower velocities were inhomogeneous, which might be caused by contraction of thin fluid film before gelation. therefore films were deposited at higher velocities. withdrawal speed did not influence significantly the light transmittance of dea-zno films. transmittance at 380 nm, as can be seen in fig. 4, only decreases few percents with growing velocity, indicating only slight increase of film thickness. probably because of material properties of that precursor sol the differences between applied speeds are too small to observe notable change in film thickness. for preparation of multilayered films 15 cm/min speed was applied. figure 4: transmittance spectra of dea-zno films prepared with different withdrawal velocities dea-zno films containing 1, 2 and 3 layers were prepared. heat treatment was repeated and uv-vis as well as sar measurements were performed after deposition of each layer. measured spectra and reflectance curves are shown in figs. 4 and 5, respectively. transmittance spectra of films containing two and three layers show interference extrema, hence refractive indices and film thicknesses can be calculated by analyzing the positions of extrema [40]. results can be found in table 2. since transmittance of the threelayered film at the maxima is higher than transmittance of the substrate (~92%), this film is thought to be optically inhomogeneous [41] and its refractive index should decrease towards the outer layer. this phenomenon can be caused by consecutive annealing steps: the inner layer was treated at high temperature three times, while the outer one just once. therefore the inner parts of the film can be denser and possess higher refractive index. to confirm these results, sar measurements were performed. as can be seen in table 2 values obtained by applying different measurement methods are in reasonable agreement for the two layered film, but there is notable difference between refractive index values calculated from uv-vis and sar measurements in case of the three-layered film. this deviation is probably caused by the aforementioned refractive index inhomogeneity of that film. these refractive index values 134 are only reported as rough estimation. this phenomenon must be subjected to further investigations and analysis. figure 5: transmittance spectra of dea-zno films containing 1, 2 and 3 layers figure 6: results of sar measurements on dea-zno films containing 1, 2 and 3 layers in case of tio2 thin films transmittance spectra show interference extrema due to high refractive index of the films. (refractive index of anatase (rutile) is 2.52 (2.72) [42], while bulk zno possesses refractive index of 2.08. [43]) therefore refractive indices and film thicknesses were calculated by analyzing positions of interference extrema. transmittance spectra of tio2 films deposited at different withdrawal velocities are shown in fig. 7. as can be seen in table 3 film thicknesses rise with ascendent velocity. refractive index values show slight decrease. much like in the case of zno, tio2 films containing 1, 2 and 3 layers were prepared and examined. transmittance spectra and measured reflectance curves are reported in figs. 8 and 9, respectively. as can be seen in table 3, film thickness can be risen up to ~200 nm by repeating layer deposition three times. on the three-layered film there was no sar measurement performed, since it was too thick to obtain precise results. values obtained by different methods are in reasonable agreement. no sign of optical inhomogeneity could be observed. table 2: results of sar and uv-vis spectroscopy on multilayered dea-zno films nr. of layers thickness (sar) thickness (uv-vis) 1 27.2 nm 2 88.0 nm 74.8 nm 3 129.3 nm 136.9 nm nr. of layers refractive index (sar) refractive index (uv-vis) 1 1.653 2 1.719 1.725 3 2.278 1.724 figure 7: transmittance spectra of tio2 film prepared with different withdrawal velocities table 3: results of sar measurements and uv-vis spectroscopy on tio2 films withdrawal velocity refractive index thickness 12 cm/min 2.073 57.0 nm 15 cm/min 2.044 65.9 nm 18 cm/min 2.023 79.6 nm nr. of layers thickness (sar) thickness (uv-vis) 1 60.6 nm 58.5 nm 2 133.9 nm 128.7 nm 3 201.6 nm nr. of layers refractive index (sar) refractive index (uv-vis) 1 1.994 2.073 2 1.978 1.998 3 2.079 135 figure 8: transmittance spectra of tio2 films containing 1, 2 and 3 layers figure 9: results of sar measurements on tio2 films containing 1 and 2 layers films prepared from the same sol, under the same conditions were found to be highly uniform. uv-vis measurements were performed for comparison. according to our estimation thin films can be prepared with max. 2% standard deviation of average thickness. sol-gel zno thin films generally consist of nanosized wurtzite crystals. for comparison of crystalline quality of the dea-zno and the pvp-zno films photoluminescence measurements were performed. excitation wavelength was 310 nm; spectra were recorded using a 350 nm cut-off filter. normalized pl spectra are displayed in fig. 10. both samples showed strong violet emission peak at 386 nm, indicating good crystallinity. this peak is related to band edge emission [44]. in the pl spectrum of dea-zno a broad band centered at ~650 nm can be observed, which is related to carrier recombination due to defects, possibly interstitial oxygen ions [45]. the defect-related orange band is absent in the pl spectrum of pvp-zno, however a violet-blue peak is observable around ~430 nm, which can be ascribed to zinc-related defects [46].therefore we can draw the conclusion, that different stabilisers for sol preparation result in diverse defect structures of zno thin films. figure 10: photoluminescence spectra of dea-zno and pvp-zno films conclusions zno thin films were prepared from precursor sols containing diethanolamine or polyvinylpyrrolidone as stabiliser. effect of varying withdrawal speed on refractive index and film thickness values were studied by means of uv-vis spectroscopy and scanning angle reflectometry. thicknesses of zno-pvp films were found to be in range of 6–74 nm, depending on the withdrawal speed. refractive indices are low, indicating porous films and resulting in antireflection effect. withdrawal speed seems to provide good control over thickness of pvp-zno layers in contrast with dea-zno layers. in latter case the speed does not seem to possess severe influence on film thickness. tio2 thin films were also prepared at different withdrawal velocities and their thicknesses were found to be in the range of 43–80 nm depending on velocity. multilayered dea-zno and tio2 films were prepared; hence film thickness could be elevated up to ~130 nm in case of zno films and up to ~200 nm in case of tio2 films. multilayered zno was found to be of in-depth optical inhomogeneity. photoluminescence measurements revealed good crystalline quality and diverse defect structures of films prepared from different precursor sols. it is apparent that refractive index and film thickness can be properly tailored by using appropriate starting precursor sol, withdrawal velocity and/or by repeating film deposition. therefore sol-gel technique and dip coating seem to provide powerful means to fabricate wide gap semiconductor structures with unique optical properties. acknowledgements the authors would like to thank to dr. erzsébet hild for her help by optical calculations. we gratefully he financial support of the hungarian scientific research fund (otka ck 78629). 136 references 1 fernandes d. m., silva r., winkler hechenleitner a. a., radovanovic e., custódio melo m. a., gómez pineda e. a.: synthesis and 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of solgel silica coating obtained by dipping, journal of non-crystalline solids 121 (1990) 1-3, 303 40 hild e.: period. polytech., chem. eng. 19 (1975) (4), 291 41 hild e., deák a., naszályi l., sepsi ö., ábrahám n., hórvölgyi z.: use of the optical admittance function and its wkb approximation to simulate and evaluate transmittance spectra of graded index colloidal films, j. opt. a: pure appl. opt. 9 (2007), 920 42 wells a. f.: structural inorganic chemistry, 5th ed.; claredon press: oxford, 1984 43 wypych g.: handbook of fillers, 2nd ed., chem. tech. publishing, canada, 1999 44 sagar p., shishodia p. k., mehra r. m., okada h., wakahara a., yoshida a.: photoluminescence and absorption in sol–gel-derived zno films, journal of luminescence 126 (2007) 2, 800 45 o'brien s., koh l. h. k., crean g. m.: zno thin films prepared by a single step sol–gel process, thin solid films 516 (2008) 8, 1391 46 valerini d., caricato a. p., creti a., lomascolo m., romano f., taurino a., tunno t., martino m.: morphology and photoluminescence properties of zinc oxide films grown by pulsed laser deposition, applied surface science 255 (2009) 24, 9680 microsoft word 01_r.doc hungarian journal of industrial chemistry veszprém vol. 35. pp. 31-37 (2007) the effect of a ziegler-natta catalyst and the polymerization parameters on the basic properties of polyethylene p. suba1, p. árva2, s. németh2 1tisza chemical group plc., product and application development, h-3581 tiszaújváros p. o. box 20, hungary 2university of pannonia, department of process engineering, h-8201 veszprém, p. o. box 158, hungary in our article, some of the basic correlations concerning the polymerization behaviour of a ziegler-natta catalyst are presented. we have examined a general, commercial mgcl2 supported catalyst, the effect of the main polymerization parameters, such as hydrogen concentration, al/ti mol ratio, monomer (ethylene) concentration and residence time on the productivity of the catalyst and the properties of the final polyethylene product. keywords: olefin polymerization, ziegler-natta catalyst, polymer properties, polyethylene introduction one of the biggest achievements in the history of polyolefin production is connected with the names of ziegler and natta. in 1953 it was discovered in the laboratory of ziegler, that with the mixture of metalalkyl and transition metal salts, it is possible to produce high density polyethylene (hdpe) at low pressure. as an addition, natta and his coworkers justified that the same catalyst system is capable for the production of isotactic polymers, based on different α-olefins. the two scientists were awarded by noble-price for their discovery in 1963. heterogeneous ziegler-natta catalysts usually consists of tior v-trichloride and some kind of al-organic compound, and are used already more than half century for the polymerization of α-olefins and dienes. in the past decades the development of these catalysts is continuous. nowadays, the most “state of the art” types are referred as 5th generation catalysts, and although they also inherit the basics of their ancestors, also contain a lot of improvements. these improvements (for example: new methods in catalyst production, application of carriers, electron donors – that are essential in case of monomers with atactic carbon – and of course new technological solutions ensure still the importance of this catalyst family. table 1: generations of ziegler-natta catalysts generation catalyts productivity g/g isotact. index % i. δ-ticl3. 0,33alcl3 + deac 1500 90-94 ii. γ-ticl3 + deac 4000 94-97 iii. ticl4/mono-ester(id)/mgcl2+teal/ester(ed) <20000 90-95 iv. ticl4/di-ester(id)/mgcl2+teal/silane(ed) >25000 95-99 v. ticl4/di-ether, succiante(id)/mgcl2 + teal (silane(ed)not essential) >50000 95-99 deac: diethyl-aluminum-chloride; teal: triethyl-aluminum; id: internal (electron) donor; ed: external (electron) donor the variety of ziegler-natta catalyst systems is very wide. they can differ in transition metal, metal-alkyl (so called cocatalyst), structural properties (particle size, morphology, porosity, stiffness, etc.), composition (ti content, id content) [1-6], but the commercial catalysts usually are based on ticl4 on mgcl2 carrier with teal cocatalyst. the mechanism of the polymerization is still not absolutely clear, although in the literature we can find several theories in this topic. the most common ones are the bimetallic model by natta, patat and sinn [7-10], the monometallic model by arlman and cossee [11-12] and the trigger mechanism by ystenes [3, 13]. although the importance of electron donors is also very considerable, within the polymerization of ethylene they do not have a big concern [1-6]. in industrial sizes the most paramount parameters that have to be taken into consideration to make different, tailor-made polyolefin products with special 32 properties, are for example reaction temperature, concentration of monomer, comonomer, cocatalyst, hydrogen, and residence time in the reactor, etc. the effects of the parameters we have investigated in our project are as follows [1, 3, 4, 15-16]: 1. hydrogen concentration: hydrogen is used as molecular weight (mw) controller substance via chain transfer. with increasing hydrogen concentration the weight of chain transfer reactions increase and the molecular weight of the macromolecule decrease. because all base properties are in connection with mw, the structure of the chain, this also affects actually every properties of the final product (mechanical, optical, thermal). notable fact is that the concentration of hydrogen also affects the productivity of the catalyst, but differently with different monomers. for example with increasing hydrogen concentration the productivity increases in case of propylene, and decreases in case of ethylene monomer. 2. al/ti mol ratio: this ratio comes from the ratio of cocatalyst (triethyl-aluminum) and the catalyst (ti content). the cocatalyst has a double effect. first it eliminates impurities from the different reaction components, and second, it activates the catalyst (reduces ti4+ to the active ti3+) form. based on these effects the concentration of the cocatalyst has a very sensitive role. with increasing amounts, as more impurities can be eliminated, and more active sites can be formed, the productivity of the catalyst increases. after an optimal value, the productivity decreases due to over reduction of ti3+ to the inactive ti2+ form. 3. monomer concentration: with increasing monomer concentration, as the ratio of monomer/active sites is increasing, the productivity of the catalyst increases, and also the mw. 4. residence time: the produced amount of polyethylene increases with increasing residence time. this connection is not similar for all catalysts, as it is based on kinetic behaviour. some types are starting with high initial rates that decrease in time, some others are able to maintain an almost constant value. experimental within our experiments we have investigated a mgcl2 supported ticl4 based ziegler-natta catalyst, with 4.5% titanium content. as cocatalyst, we have used teal. the polymerization tests were carried on in a 20 litre volume batch-scale laboratory reactor in isobutane media. along the project we have measured the effect of the above mentioned parameters on the productivity of the catalyst, and the properties of the final product. the following measurements were carried out: 1. mfr (melt flow rate): with different weights based on iso 1133, 2. density based on iso 1183, 3. molecular weight (mn, mw) with gpc (pl-gpc 210), 4. thermal measurements (melting and crystallization temperatures, enthalpies) were made on a netzch dsc 2004 phoenix scanning micro calorimeter, 5. micro-structure characteristics (number of methyl, vinyl, vinylidene, vinylene groups) were carried out on a mattson galaxy 3020 ftir spectroscope, 6. particle size distribution based on astm d 1921. results and evaluation effects of different hydrogen concentrations to be able to see only the effect of hydrogen in our experiments, all the other parameters were constant, even monomer concentration in the liquid phase (this means, that experiments with different hydrogen concentrations were carried out on different polymerization pressure with the same ethylene concentration). the needed component amounts were calculated by a software developed by department of process engineering at university of pannonia. referring to our literature summary, it is clear, that at hdpe production with increasing hydrogen concentration the activity of the catalyst is decreasing. the cause of this is the slow addition of a new monomer to the ti-h bond, formed at the previous chain transfer reaction. the amount of hydrogen was changed between 0 and 200 nl (normal litre). the tests were carried out at standard al/ti mol ratio (100), temperature (80 °c) and stirring (500 1/min) for 2 hours. on the next figures we present the correlation between hydrogen amount and catalyst productivity, and the kinetic flow of the reaction (ethylene feed to maintain standard pressure in the reactor). as it can be seen, that at lower rates the productivity of the catalyst is increasing, and after a certain amount it decreases as it is awaited based on the literature. the cause of the difference from the logical tendency at the point without any hydrogen is linked also to the effect of hydrogen. because there is no hydrogen, the productivity of the catalyst is very high at the beginning of the reaction. this increased productivity is so high, that the heat and stress that appears at the catalyst particle, destroys partially the structure of the catalyst itself, so after a short period the productivity decreases more dramatically then in the case of some hydrogen. because of this, the overall, average productivity will be lower, than “expected”. in all other cases when there is hydrogen in the system, it controls the catalyst, and this damage doesn’t occur. concerning to the base properties of the polymer the effect of hydrogen as chain transfer agent can be seen at all of our data. with increasing hydrogen amount, the average molecular weight of the chains is decreasing (that causes higher melt flow rates) that also affects the density (shorter chains increase the density via overall crystallinity). the effect of hydrogen can be seen on the results of our other analytical measurements (ftir, gpc, dsc), that are not detailed here. 33 table 2: test parameters with different hydrogen amounts reactor pressure (barg) hydrogen amount (nl) hydrogen concentration in liquid phase (mol%) ethylene amount (for filling up to pol. pressure) (g) ethylene concentration in liquid phase (mol%) 17 0 0 152 4,5 18,4 14,7 0,3 152 4,5 21,8 50 1,0 153 4,5 26,7 100 2,0 155 4,5 31,7 150 3,0 157 4,6 36,8 200 4,0 159 4,6 0 5 000 10 000 15 000 20 000 25 000 30 000 35 000 40 000 0 20 40 60 80 100 120 140 160 180 200 h2 amount (nl) pr od uc tiv ity (g /g 2 h) figure 1: productivity vs. hydrogen amount 0 0,5 1 1,5 2 2,5 3 3,5 4 4,5 5 0:00:00 0:25:00 0:50:00 1:15:00 1:40:00 2:05:00 time (from the start of ethylene feed) (min) et hy le ne fl ow (k h/ h) 14,7 nl h2 (008) 0 nl (017) figure 2: ethylene flows at different hydrogen amounts 34 0 20 40 60 80 100 120 140 0 20 40 60 80 100 120 140 160 180 200 h2 amount (nl) m fr /2 ,1 6k g 19 0° c (g /1 0 m in ) 0,9350 0,9405 0,9460 0,9515 0,9570 0,9625 0,9680 0,9735 d en si ty (g /c m 3) figure 3: effect of hydrogen amount on the mfr and density of the hdpe product the effects of different al/ti ratios as we explained before, the optimal al/ti mol ratio is very important in the polymerization reactions, due to its double function (elimination of impurities, reduction of ti4+). in our experiments we have changed the ratio between 0 and 400, while the other parameters were constant (hydrogen: 50 nl, temperature: 80 °c, pressure: 21,8 barg, stirrer: 500 1/min, residence time: 2 hours). as it can be seen on the figure below, the optimal al/ti mol ratio was 25, this value resulted the highest productivity. the al/ti mol ratio has of course other effects also on the properties of the polymer, but they are not very important. with high redundancy it decreases molecular weight, as it has also minor chain transfer function. 0 5000 10000 15000 20000 25000 30000 35000 40000 0 50 100 150 200 250 300 350 400 al/ti mol ratio (mol/mol) pr od uc tiv ity (g /g 2 h) figure 4: effect of al/ti mol ratio on the productivity of the catalyst 35 effects of monomer (ethylene) concentration to be able to examine a wider concentration interval, we had to do some changes at our tests. the cause of this is, that at higher concentrations with the standard amount of catalyst and residence time, the amount of the polymer powder was too much for the reactor to handle, and the efficiency of the temperature control decreased heavily. so beside of the untouched standard parameters (hydrogen amount: 50 nl, temperature: 80 °c, al/ti mol ratio: 100, stirrer: 500 1/min) we decreased residence time to 1 hour, and at the tests with the highest ethylene concentrations, we also decreased the amount of the catalyst. our changes in ethylene concentration and catalyst amount increased the c2/ti ratio that is the monomer/active site ratio. the main affect of this can be seen in catalyst productivity and molecular weight increase (decreased mfr values). table 3: test parameters with different ethylene amounts pressure (barg) 20,1 21,8 25,2 25,2 25,2 ethylene amount (for filling up to pol. pressure) (g) 75,1 153 313,5 313,5 313,5 ethylene concentration in liquid phase (mol%) 2,27 4,52 8,96 8,96 8,96 catalyst amount (g) 0,1 0,1 0,1 0,05 0,025 c2/ti ratio in liquid phase (mol/mmol) 22,5 46,0 95,9 191,9 383,8 0 10000 20000 30000 40000 50000 60000 0 50 100 150 200 250 300 350 400 450 500 c2/ti ratio (mol/mmol) pr od uc tiv ity (g /g 2 h) figure 5: effect of monomer concentration on the productivity of the catalyst the reason of productivity increase is, that the speed of the chain growing reaction changes linear with monomer concentration (the difference here can be the result of the maximal surface cover), whereas the increase of molecular weight is the result of the previous cause, and that the speed of chain transfer reactions to monomer are neglectable. the decrease of density (crystallinity) is the outcome of the increase of molecular weight. effects of polymerization time with the increase of polymerization (residence) time, the amount of the produced polymer is increasing obviously, but among the kinetic behaviour of different catalysts, there can be essential variations. this is very important in industrial processes, where the residence time can be quite long, and the catalyst along its production time, progresses through more reactors (e. g. spheripol pp technology, or mitsui cx pe process). generally we can say that the productivity of the catalyst along the polymerization process is decreasing. on the figure below, we can see the kinetic profiles (ethylene flow to maintain constant pressure) and productivities of reactions with different polymerization times (from 30 to 180 min). as usual, the other parameters were constant (hydrogen amount: 50 nl, temperature: 80 °c, pressure: 21,8 barg, stirrer: 500 1/min, al/ti ratio: 100). 36 0 2 4 6 8 10 0 50 100 150 200 250 300 350 400 450 500 c2/ti ratio (mol/mmol) m fr (g /1 0 m in ) 2 ,1 6k g 0,957 0,9585 0,96 0,9615 0,963 0,9645 d en si ty (g /c m 3) figure 6: effect of monomer concentration on the product mfr and density 0,0 0,5 1,0 1,5 2,0 2,5 3,0 0 0,020834 0,041668 0,062502 0,083336 0,10417 0,125004 time (min) et hy le ne fl ow (k g/ g) 0 5500 11000 16500 22000 27500 33000 pr od uc tiv ity (g /g ) 30 min 60 min 90 min 180 min120 min figure 7: kinetics of tests with different polymerization time the possible cause of the productivity decrease within time could be the spontaneous deactivation of the active sites on one hand, and the higher diffusion resistance for ethylene in the bigger polymer particle. the scale of the decrease depends on the catalyst type also (structure). in our case we couldn’t observe any effect of the residence time on the properties of the final product. 37 summary the aim of our paper was to introduce the basic properties, behaviour of ziegler-natta catalysts, and highlight the most paramount parameters that can play a major role in forming the productivity of the catalyst, and/or the properties of the final product. we have shown these effects through the experiments with a traditional ziegler-natta catalyst for hdpe production. references 1. boor j. jr.: ziegler-natta catalysts and polymerizations, academic press, new york, usa, 1979 2. minsker k. s., karpasas n. r.: macromol. chem. phys., 1987, c27(1), 1-90 3. huang j., rempel g. l.: prog. polym sci., 1995, 20, 459-526 4. hogan j. p., myerholtz w.: olefin polymers, 1967, 14, 259-308 5. moore e. p. jr.: the rebirth of polypropylene: supported catalysts, hanser gardner publications, 1998 6. polypropylene: past, present and future: the challenge continues ferrara 19th-20th october 1998. 7. natta g.: macromol. chem., 1955, 16, 213 8. natta g.: j. polym. sci., 1960, 48, 219 9. natta g.: j. inorg. nucl. chem, 1958, 8, 589 10. patat f., sinn, h.: angew. chem., 1958, 70, 496 11. arman e. j., cossee, j.: j. catal., 1964, 3, 99 12. arman e. j.: ibid., 1966, 5, 178 13. ystenes m.: macromol. chem., macromol. symph., 1993, 66, 71-82 14. pater j., weickert g., loos j., van swaaij w.: chem. eng. sci., 2002, 57, 3461-3477 15. garoff t, johansson s., pesonens k., waldvogel p., lindgren d.: european polymer journal, 2002, 38, 121-132 16. chu k. j., soares j., penlidis k., ihm s. k.: european polymer journal, 2000, 36, 3-11 microsoft word a_09_r.doc hungarian journal of industrial chemistry veszprém vol. 38(1). pp. 47-51 (2010) comparison of physical and chemical measurements of séd stream in veszprém and holt-sebes-körös together with sebes-körös in békés zs. kovács1 , cs. szalkay3, z. zsilák2, á. rédey1 1department of environmental engineering, university of pannonia, h-8200 veszprém, 10 egyetem str. hungary e-mail: zsofiakovacs@almos.uni-pannon.hu 2department of general and inorganic chemistry, university of pannonia, h-8200 veszprém, 10 egyetem str, hungary 3department of landscape ecology, szent istván university, h-2103 gödöllő, 1 páter str, hungary the most essential purpose of the modern society is that it’s able to handle and find solution for environmental problems especially water pollution which is serious problem not only for present but future generation as well. as the load to our surface water has become more significant consequently a continuously increasing demand has been created for adequate water quality and quantity water. the water framework directive is a long-term water policy of the european union. aim of wfd is the classification and protection of the water according to consistent viewpoints. objectives of the researches are the identification and testing of the effects of the potential pollutants sources and critical sites in séd (veszprém) and in sebes-körös in békés. keywords: séd stream, sebes-körös, physical and chemical parameters, water classification introduction nowadays there is a reduction in water management. the most significant aspects are estimation of water in viewpoint of society and change of demands. alteration of approach sustainability and ecological viewpoints are in priority question furthermore water management, environment and nature protection. regional development are also significantly important to be integrated. these are legalized by european union. entire water policy has been installed in 2000 its run under the directive of water framework directive. water framework directive (wfd) provides the solution and wfd is one of the most significant manifestations of water management [2]. the wfd (2000/60/ec) was created as a long-term water policy of the european union. member states are required to achieve good ecological and chemical status in all bodies of surface water by 2015 [1]. it provides a framework for member states and to be applied taking into consideration local features. the basis of implementing the wfd is the elaboration of the typology of water bodies [6]. hungarian typology based on four parameters altitude, geology, structure and substrate of bed material and size of the catchment area. a further requirement of wfd water management plan has to be submitted by all member states. by 2009 standard water management plan has to be developed for the whole territory of hungary. in this project cooperation with neighbour countries are essential. this plan should include arrangements for maintenance of good water condition and water monitoring. examination units have been defined in water management plan according to this territory of hungary has been divided into 42 units. séd situate in veszprém county is included within category 1-13. this called észak-mezőföld és keletibakony. holt-sebes-körös just as sebes-körös in békés county is included within category 2-14 [7]. this called sebes-körös (fig. 1). the competent authority according to the instructions of the wfd in hungary marked out monitoring sampling sites such as streams in veszprém and in békés. two different area were appointed where polluted resources were investigated in point of view how they influence surface water according to wfd. the most significant purpose of the project is to define water quality of séd and holt-sebes-körös just as sebes-körös. in the second place the most significant physical and chemical parameters of the streams were compared. the water capacity of séd has been decreased year by year although the volume of incoming sewage water has been increased. in summer several parts of the stream became dry which means its favourable to enter the sewage water into dolomitic water. marshy areas can be found in large numbers in the area of holt-sebes-körös and sebes-körös. those areas that did not have permanent water cover but effected by the change in the level of groundwater went through salinization due to leaching of sodium ions [3]. impacts of sewage and animal farms have to be taken into 48 consideration in these areas. furthermore the effects of the human activities exercise also significant influence on the ecosystem. figure 1: catchment area of séd and sebes-körös according to the results of the examined water the followings were determined. séd and sebes-körös are loaded by direct and diffuse pollutants. water pollution comes from close gardens, cultivated lands, sewage water treatment plants where sewage and cleaned water contain high concentration level of nitrate, nitrite, ammonium ion and orthophosphate. an additional pollutant source is the urban drainage water. séd and also sebes-körös run through water bases so they have their effects on subsurface water. it is important to measure the pollutants regularly in order to be able to follow the quantity and quality of pollution tendency. material and methods séd stream runs through limestone area in transdanubian region. its length reaches the 70 km. körös coming from the transylvanian mountains has been forming the surface of the area for thousands years. according to typological categorization (wdf) séd belongs to high altitude calcareous streams with coarse bed material while körös area belongs to lowland calcareous medium sized streams with moderately fine bed material. physical and chemical tests were taken three times at urban part of séd in spring. at selection of the sampling sites the following direct pollution sources have been taken into consideration: 20 sampling site and 7 polluted locations were appointed along the stream that have strong effect to water quality. these polluted locations are spring-water, output pipe of bus service station, output of urban drainage, output pipe of sewage treatment, békatói stream and branches. two villages were marked (okány and mágor) at part of holt-sebes-körös and three villages (körösszakál, körösladány and komádi) at part of sebes-körös, where some important physical, chemical measurements [8] were taken three times in spring so far (fig. 2). figure 2: sampling sites in veszprém and in békés calibrated and portable devices were applied to take outside measurements like temperature, ph-value, conductivity. alkaline and codps were analyzed by titrimetry. the so4 2-, po4 3-; nh4 +; no3 -; no2 were analyzed by spectrophotometer [4]. na+; k+; ca2+; mg2+ concentrations were defined using aas methods. on the base of the results of field and laboratory measurements surface water has been qualified according to msz 12749:1993 standards (excellent, good, tolerable, polluted, extremely polluted) [5]. 49 results and discussions measurements taken on field examination of the temperature in spring (10–17 °c) meets expectation. fig. 3a, b represents clearly the daily changeability of the temperature. the temperature measured at the output pipe of sewage treatment is higher than average temperature of the stream so it causes continuous heat load to certain sampling sites. 0 2 4 6 8 10 12 14 16 18 20 1 sp ri ng 2 3 4 o ut pu t o f b us  s er vi ce  s ta tio n 5 6 7 8 9 o ut pu t o f u rb an  d ra in ag e  10 11 12 bé ka tó i s tr ea m   13 14 o ut pu t o f s ew ag e  tr ea tm en t 15 br an ch  o f s éd 17 br an ch  o f s éd 19 20 te m pe ra tu re ( c ) sampling sites 2009.04.20 2009.04.27 2009.05.06 figure 3a: temperature values measured in séd 0 2 4 6 8 10 12 14 m ág or o ká ny kö rö ss za ká l ko m ád i kö rö sl ad án y te m pe ra tu re (° c) sampling sites 2008.04.18 2008.04.26 2009.04.10 figure 3b: temperature values measured in körös along downstream ph-level is between (7–9) so the water is defined as smoothly alkaline (fig. 4a, b). 0 2 4 6 8 10 12 1 sp ri ng 2 3 4 o ut pu t o f b us  s er vi ce  s ta tio n 5 6 7 8 9 o ut pu t o f u rb an  d ra in ag e  10 11 12 bé ka tó i s tr ea m   13 14 o ut pu t o f s ew ag e  tr ea tm en t 15 br an ch  o f s éd 17 br an ch  o f s éd 19 20 ph -le ve l sampling sites 2009.04.20 2009.04.27 2009.05.06 figure 4a: ph-level in séd 7,5 7,6 7,7 7,8 7,9 8 8,1 8,2 m ág or o ká ny kö rö ss za ká l ko m ád i kö rö sl ad án y ph le ve l sampling sites 2008.04.18 2008.04.26 2009.04.10 figure 4a: ph-level in körös the tendency of conductivity in séd was constant (800–900 µs cm-1), extremely high values (1400 µs cm-1) were taken at békatói stream. average value of the conductivity is 894 µs cm-1 so low values were measured at output side of bus service station (600 µs cm-1) and in the cleaned water of sewage treatment (340 µs cm-1) (fig. 5a). the tendency of conductivity in körös was also permanent, but lower than in séd (400– 600 µs cm-1). the highest values (800 µs cm-1) was measured in mágor (fig. 5b). the reason of the different values of conductivity is due to different bed material (calcareous or salinated). 0 200 400 600 800 1000 1200 1400 1600 1 sp ri ng 2 3 4 o ut pu t  of  b us  s er vi ce  s ta ti on 5 6 7 8 9 o ut pu t  of  u rb an  d ra in ag e  10 11 12 b ék at ói  s tr ea m   13 14 o ut pu t  of  s ew ag e  tr ea tm en t 15 b ra nc h  of  s éd 17 b ra nc h  of  s éd 19 20 c on du ct iv ity (µ s cm -1 ) sampling sites 2009.04.20 2009.04.27 2009.05.06 figure 5a: changeability of the conductivity in séd 0 200 400 600 800 m ág or o ká ny kö rö ss za ká l ko m ád i kö rö sl ad án y co nd uc ti vi ty  ( µs  c m ‐1 ) sampling sites 2008.04.18 2008.04.26 2009.04.10 figure 5b: changeability of the conductivity in körös 50 measurements taken in laboratory the ammonium ion concentration was measured between 20–250 µg l-1. fig. 6a shows the high concentration values taken in békatói stream (760 µg l-1) and central urban drainage in veszprém (1900 µg l-1). fig 6b shows the highest concentration values measured in vésztő-mágor (1010 µg l-1) due to direct pollution [8]. 0 200 400 600 800 1000 1200 1400 1600 1800 2000 1 sp ri ng 2 3 4 o ut pu t o f b us  s er vi ce  s ta tio n 5 6 7 8 9 o ut pu t o f u rb an  d ra in ag e  10 11 12 bé ka tó i s tr ea m   13 14 o ut pu t o f s ew ag e  tr ea tm en t 15 br an ch  o f s éd 17 br an ch  o f s éd 19 20 a m m on iu m io n (µ g l-1 ) sampling sites 2009.04.20 2009.04.27 2009.05.06 figure 6a: concentration of ammonium ion in séd 0 200 400 600 800 1000 1200 mágor okány körösszakál komádi körösladány a m m on iu m  io n  (µ g  l‐1 ) sampling sites 2008.04.18 2008.04.26 2009.04.10 figure 6b: concentration of ammonium ion in körös nitrate concentration level has been increased (3,4–5,2 mg l-1) continuously in the town. its level is higher inside the town than outside of the town. in séd and vésztő-mágor extremely high concentration level (14,4 mg l-1, 10 mg l-1) were measured from cleaned water of sewage treatment (fig. 7a). 0 2 4 6 8 10 12 14 1 sp ri ng 2 3 4 o ut pu t o f b us  s er vi ce  s ta tio n 5 6 7 8 9 o ut pu t o f u rb an  d ra in ag e  10 11 12 bé ka tó i s tr ea m   13 14 o ut pu t o f s ew ag e  tr ea tm en t 15 br an ch  o f s éd 17 br an ch  o f s éd 19 20 n itr at e (m g l-1 ) sampling sites 2009.04.20 2009.04.27 2009.05.06 figure 7a: range of nitrate concentration in séd in case of vésztő-mágor always higher nitrate concentration was measured 10 mg l-1 than other sampling sites 2–6 mg l-1 fig. 7b. 0 2 4 6 8 10 12 mágor okány körösszakál komádi körösladány n it ra te  (m g  l‐1 ) sampling sites 2008.04.18 2008.04.26 2009.04.10 figure 7b: range of nitrate concentration in körös the level of the orthophosphate concentration in séd in veszprém was changed between 50–100 µg l-1 but high concentration level was taken at urban drainage (790 µg l-1) and output pipe of sewage treatment (690 µg l-1) that caused by heavy raining. high concentration (1020 µg l-1) was measured at békatói stream (fig. 8a). 0 200 400 600 800 1000 1200 1 sp ri ng 2 3 4 o ut pu t o f b us  s er vi ce  s ta tio n 5 6 7 8 9 o ut pu t o f u rb an  d ra in ag e  10 11 12 bé ka tó i s tr ea m   13 14 o ut pu t o f s ew ag e  tr ea tm en t 15 br an ch  o f s éd 17 br an ch  o f s éd 19 20 o rt ho ph os ph at e (µ g l-1 ) sampling sites 2009.04.20 2009.04.27 2009.05.06 figure 8a: orthophosphate concentration in séd high concentration (600 µg l-1) was measured at sebes-körös stream (körösszakál) (fig. 8b). 0 100 200 300 400 500 600 700 mágor okány körösszakál komádi körösladány o rt ho ph os ph at e  (µ g  l‐1 ) sampling sites 2008.04.18 2008.04.26 2009.04.10 figure 8b: orthophosphate concentration in körös the average orthophosphate concentration level in körös is higher than in séd because of fertilizer and animal husbandry. results of the measured 8 main ions have supported that séd runs through calcareous and karstic base rock and körös is in salinated area. maucha diagram represents the concentration level of the 8 main ions in séd and körös. fig. 9a presents clearly 51 the high concentration of hco3-, ca2+, mg2+. relative high concentration of na+ was measured in körös (fig. 9b). figure 9a: maucha diagram referring to séd figure 9b: maucha diagram referring to körös water classification categorization of surface water was performed according to hungarian standards [5]. in point of conductivity the tested part of séd can be classified as moderate stream. békatói stream and holtsebes-körös at mágor have been ranked as polluted stream according to water classification. ammonium ion concentration has been changed between good and tolerable. in séd the most critical concentration level was indicated at output of urban drainage where the water quality was classified as polluted. the water in mágor is different from the other points in körös, due to pollutants caused by an animal farm and sewage treatment transmitted into freshwater. in most cases ion concentration of water in okány is the lowest, because this point was situated far from the town. water quality at békatói stream holt-sebes-körös in mágor has been considered as moderate. in both cases polluted water have been likely emitted. in case of nitrate concentration good and tolerable categories were distinguished (inside the town and outside of the town). furthermore excellent water quality was determined in okány and komádi and water quality measured at other sampling sites were ranked as tolerable [8]. conclusion according to measurement taken on field and laboratory the water quality of séd and körös is classified excellent and good [okány; bus service station] but in some cases water quality is categorized as tolerable [körösszakál; békatói stream]. several parameters refer to direct flowing of sewage that requires further detailed measurements. six sampling sites are emphasised according to volume of pollutants. bus service station and sewage treatment are the only public utilities that possess unique permission in case of water limit values. but some tests have approved that the water is loaded with pollutants emitted by above mentioned public utilities. urban drainage should be also enhanced as contamination source as it takes pollutants to séd. finally békatói stream is also stressed as a loading source. orthophosphate and nitrate concentration in békatói stream are rather high so this water is considered polluted stream. the measurements taken in mágor indicate high concentration level of ions (orthophosphate, nitrate and ammonium) and it refer contamination caused by local husbandry. in körösszakál and körösladány the measured data of orthophosphate is higher than the average value in the sampling point because sewage of the townships are transmitted into freshwater. the nitrite and nitrate concentration in water is lower than the values taken in the past. this is because the area is protected by regulation and the farm production is limited [8]. in conclusion in both cases the pollution resources originated from point sources such as sewage treatment, husbandry. these activities have significant effect on the quality of surface water. further measurements are required that pollutants sources to be easily identified. information about water quality in séd and körös are available at local governments. the critical polluted sites have been assigned so collective action plan have to be worked out based on wfd instruction. acknowledgement this work is financially supported by the hungarian state and the european union under the tamop4.2.1/b-09/1/konv-2010-0003 project. references 1. directive 2000/60/ec of the european parliament and of the council. 2. d. zikos, k. bithas: the case of a “weak water” governance model: athens-greece, proceedings of the 2006 iasme/wseas int. conf. on water resources, hydraulics & hydrology, chalkida, greece, may 11-13, 2006, 161–166. 3. execution of wfd in hungary 2-14 sebes-körös subcategory 2010. 4. j. inczédy: analytic laboratory practice i. published by the of university of veszprém, veszprém, 1981. 5. msz 12749:1993 standards water classification. 6. z. simonffy: object of water framework directive. hungarian academy of sciences, water management researcher team, 2001. 7. schedule of water management plan 2006–2009. 8. cs. szalkay: water chemical and hydrological measurements taken in sebes-körös and holt sebeskörös (2007–2009). << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 /colorconversionstrategy /cmyk /dothumbnails false /embedallfonts true /embedopentype 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 5-9 (2008) techno-economic aspects of on-site cellulase production zs. barta1 , p. sassner2, g. zacchi2, k. réczey1 1budapest university of technology and economics, department of applied biotechnology and food science h-1111 budapest gellért tér 4, hungary e-mail: zsolt_barta@mkt.bme.hu 2lund university, department of chemical engineering, p. o. box 124, s 221 00 lund, sweden on-site cellulase production for lignocellulosic ethanol production based on so2-impregnated steam pretreatment followed by simultaneous saccharification and fermentation was investigated from a techno-economic aspect using aspen plus and aspen icarus softwares. the enzyme fermentation was assumed to operate batch-wise with a cycle time of 100 hours. the base case included sixteen 343 m3 aerated fermentors arranged in four lines operating according to a merry-go-round pattern. besides the base case, three cases, with improved productivities, were investigated. the cost of the on-site enzyme production was estimated to range between 6.7-16.5 eurocent/l ethanol. the cost of carbon source was not included in the total production cost, since the pretreated material was produced in the process. keywords: process simulation, cellulase fermentation, on-site, ethanol production, economics introduction the second generation fuel-ethanol production has not been demonstrated on full-scale so far, although some pilot plants already exist in europe and north-america. the lignocellulosic ethanol production is the most complex technology compared to sugarand starch-based processes, which are already well-known and mature. due to their complex structure the lignocellulosic feedstock require pretreatment prior to the cellulose hydrolysis and ethanol fermentation, that adds one more step to the process. one alternative of cellulose hydrolysis is the enzymatic way. although substantial improvements have been made in the last decades, the cost of enzyme is still a major problem in the enzymatic process. in this study on-site cellulase fermentation was modeled and economic evaluation for the enzyme production was conducted. materials and methods the simulation software the process was modeled by aspen plus flow-sheeting software (aspen tech inc, cambridge, ma, usa) capable to solve mass and energy balances. it is a powerful tool in comparing different process configurations in terms of efficiency, energy demand or – coupled with aspen icarus process evaluator (aspen tech inc, cambridge, ma, usa) – production cost. the later software is able to evaluate the process economics, nevertheless in our case it was used for sizing and estimating the capital investment. the built-in databases of aspen plus did not contain all the chemical components e.g. the ones of wood such as cellulose, lignin etc. they were obtained from the biomass databank of nrel. economic evaluation before performing economic evaluation the process equipments had to be sized. most of them were sized manually on excel worksheets except the heat exchanger which was sized by icarus using the report file from aspen plus containing the results of material and energy balances. the manual sizing was also based on aspen plus simulation data. the fixed capital investment – both the direct and indirect costs – was estimated by icarus, where equipments not present in the aspen plus flowsheet, such as pumps, compressors and additional vessels were also included. the built-in database of icarus was used for cost estimation of all the process components except the fermentors where modifications were made introducing factors to obtain the costs given by a swedish supplier. the fermentors, however, were cost-estimated as stainless-steel (ss 304) storage tanks and their agitators as well as cooling coils were added separately. the annual fixed capital investment was calculated by use of an annuity factor of 0.110, corresponding to 15-year life of the plant, 7% interest rate, linear 6 deprecation and zero scrap-value. the reference year was 2008 and 8000 working hours per year were assumed. the working capital investment was calculated according to the recommendation of peters and timmerhaus [1]. to obtain its annual representation the working capital was multiplied by the interest rate. table 1 summarizes the specific costs employed in the operating cost estimation. table 1: cost used in the evaluation chemicals, nutrients soy-meal (48% protein) 0,16 €/kg (nh4)2so4 0,10 €/kg kh2po4 0,10 €/kg feso4*7h2o 0,11 €/kg nh3 (25%) 0,22 €/kg cc. h2so4 0,05 €/kg defoamer 2,15 €/kg utilities electricity 48,4 €/mwh cooling water 0,02 €/m3 other costs insurance 1% of fixed capital maintenance 2% of fixed capital by-product credit co2 3,2 €/t base case description the enzyme production step was based on literature data [2,3], and the process step was implemented in an aspen plus model including all major process steps shown in fig. 1 described in detail in a previous study [4]. the ethanol plant was assumed to be located in sweden, with the capacity to process 200 000 dry tons of spruce annually. the pre-treated material stream was divided into a major stream fed directly to the simultaneous saccharification and fermentation (ssf) step and a minor stream (7.5% in the base case) led to the trichoderma fermentation where the enzyme amount required by ssf assumed to be 15 fpu/g wis (filter paper unit/g water insoluble solid) was obtained. the whole broth could be added to ssf since it was carried out at 37 °c and above 35 °c the growth of mycelia is entirely inhibited. using the whole culture had several advantages: i) no additional separation was needed, which decreased the cost; ii) the enzymes adsorbed on the surface of the lignin and the cells as well as the ones trapped in the cytoplasm could also be utilized. all the sugars present in the fermentation medium were taken into account in anhydro equivalent i.e. the polymer and monomer sugars in the pretreated material and the carbohydrate content of the soy-meal (26%) were assumed to be consumed entirely. the yields were the same for the hexosans and pentosans (table 2). it must be mentioned that the fermentation whose results were used in the model was carried out on sulphitepulp [2]. in order to apply these data key-assumptions had to be made: the lignin content did not affect the enzyme production, which was concluded in the same article, furthermore the monomer sugars present in the medium did not result in catabolite repression. the base case included 16 aerated agitated fermentors, each 343 m3 in volume, arranged in four lines. the working volume was 72% of the total one. cooling was performed by use of cooling coils. the fermentors operated in atmospheric pressure, and were not pressure-rated for steam sterilization. the pretreated material and the makeup water coming entirely from the evaporation step were considered sterile, hence only cleaning-inplace was applied in the tanks. the cost of nutrient sterilization was assumed to be negligible. feedstock handling steam-pretreatment simultaneous saccharification and fermentation (ssf) enzyme production yeast cultivation distillation separationevaporation drying pellet productioncomb. heat&powerwastewater treatment ethanol stillage liquid solid so2 steam water condensate molasses liquid syrup steam solid fuel methane spruce electricity a.) b.) c.) figure 1: boundary conditions of the modelled wood-to-ethanol process (a. steam pre-treated spruce slurry, b. condensate recycled to enzyme fermentation, c. fermentation broth) 7 table 2: the features of t. reesei mcg-77 fermentation temperature 30 °c [2] ph 6 [2] fermentation time 90 h [2] cycle time 100 h [5] aeration rate 0.5 vvm 1 [2] power to the broth 0.5 kw/m3 [5] mycelium yield 0.27 g/g ch [3] soluble protein yield 0.26 g/g ch [3] activity yield 185 fpu/g ch [2] specific activity 0.71 fpu/mg protein * ch concentration 2 2 % [2] productivity 61 fpu/(l*h) [2] *calculated 1 air volume/working volume/minute 2 carbohydrate concentration given in anhydro equivalent compressed air(2,7 bar) fermentation broth medium 1. 2. 3. 4. figure 2: schematic flowsheet of kornuta process (1 line – 4 fermentors) the four fermentors in a given line followed the same schedule, however they started being shifted in 25 hour intervals. at 25 hour 10% of the culture in the first vessel was transferred to the second one and used as inoculum (the second one gave inoculum to the third one etc.). the culture was at its peak growth and the cellulase concentration was low enough, hence fast sugar formation i.e. catabolite repression in the second vessel could be avoided. the fermentation lasted for 90 hours and was followed by a 10 hour harvesting, cleaning, charging period giving a 100 hour cycle time. after 100 hours from the start of the first fermentation the fourth vessel was ready to transfer inoculum to the first one closing the line to a loop (fig. 2). this operation pattern was referred as “kornuta merry-go-round” [5]. in case of contamination inoculum could be transferred from a vessel in another line and both lines could continue uninterrupted. the air supply was provided by compressors, one for each line. the four lines had a common medium preparation vessel that received the pretreated material, the makeup water and the nutrients whose concentrations were the following: 0.5% soy-meal, 0.15% (nh4)2so4, 0.07% kh2po4, 0.001% feso4·7h2o. the outlet stream before being fed to the fermentors was cooled down to 30 °c in a heat exchanger. the system contained 16 inlet and 16 outlet pumps. other investigated cases besides the base case (a) three hypothetical cases with improved productivities were investigated (table 3). in case b the activity yield was enhanced by 50%, which also connoted 1.5-fold productivity. in case c the carbohydrate content (ch) was increased to 4% and the same yield with doubled productivity was assumed. in case d both parameters was enhanced, which resulted in tripled productivity. table 3: modified parameters in the various cases base case (a) enhanced yield (b) enhanced ch conc. (c) enhanced yield, ch (d) activity y., fpu/g ch 185 278 (1,5x) 185 278 (1,5x) ch conc. 2% 2% 4% (2x) 4% (2x) prod., fpu/(l*h) 61 92 (1,5x) 122 (2x) 183 (3x) results and discussion while according to the model the trichoderma fermentation consumed all the sugars being fed, it did not alter the amount of other substances (lignin, inhibitors etc.). the water consumption declined monotonous from a to d, whereas the other components had two levels. table 4: component flows entering and departing the enzyme fermentation flow, kg/h a b c d in hexosans 782 535 782 535 pentosans 15 11 15 11 hexoses 352 241 352 241 pentoses 63 43 63 43 lignin 439 300 439 300 water 55814 38167 27031 18485 produced enzyme 304 208 304 208 mycelium 317 217 317 217 co2 712 487 712 487 they were higher in scenario a/c and lower at b/d (table 4). it can be due to the two activity yields applied which determined the carbon source demand as well as the product formation. the total capital investment, i.e. the sum of fixed and working capitals varied in a range between 16 and 34 m€ which multiplied by the annuity factor gave the annual capital cost of 1.8–3.7 m€/year (table 5). 8 table 5: total capital investment and the annual costs in m€ a b c d total capital investment, m€ 34 25 19 16 costs, m€/year capital 3.72 (41%) 2.74 (43%) 2.06 (41%) 1.75 (46%) chemicals, nutrients 0.49 (5%) 0.34 (5%) 0.44 (9%) 0.30 (8%) utilities 3.89 (43%) 2.62 (41%) 1.96 (39%) 1.28 (34%) other costs 1.02 (11%) 0.75 (11%) 0.56 (11%) 0.48 (12%) by-product credit, m€/year co2 -0.02 -0.01 -0.02 -0.01 total, m€/year 9.09 6.44 5.00 3.81 besides the capital the utilities namely the electricity used by agitators, compressors, pumps was found the other largest contributor in production cost. the cost of cooling water was negligible. the carbon-dioxide credits were two order smaller than the costs. the sum of chemicals, nutrients and other costs were estimated not being more than 20% of the total. it must be pointed out, that the cost of carbon source was not included in either the annual or the specific enzyme production cost, since the pre-treated material was produced in the process. the on-site cellulase production reduced the produced ethanol amount providing the same feedstock utilization, since the carbohydrates were consumed partially by the enzyme fermentation. the ethanol plant using commercial enzyme produced 59 563 m3 ethanol per year, whereas the base case (a) and case c merely 55 000 m3. the cases b/d with enhanced activity yield produced more ethanol (56 441 m3/year), since less pre-treated material was needed for the cellulase fermentation. y = 464.032x-0.815 r2 = 0.997 0 2 4 6 8 10 12 14 16 18 50 100 150 200 produktivitás, fpu /(l*h) cent/l e toh figure 3: specific enzyme cost as a function of productivity by increasing the productivity the specific enzyme cost reduced monotonously. the fitted curve was close to hyperbola having the index of 0.8 (fig. 3). the breakdown of specific enzyme cost also shows that the main contributors were the capital and the utilities (fig. 4). in the base case 16.5 eurocent/l etoh was found. at tripled productivity (d) the specific enzyme cost was 6.7 eurocent/l (41% of the base case). 11.4 6.7 9.1 16.5 0 2 4 6 8 10 12 14 16 18 a b c d cent/l etoh total capital chemicals utilities other figure 4: breakdown of specific enzyme cost (produced ethanol: 55 000 m3/year at a/c, 56 441 m3/year at b/d) summary the total cost of on-site cellulase production (diminished with cost of carbon source) was estimated to range between 6.7–16.5 eurocent/l ethanol for the four investigated scenarios. capital investment and electricity were found the main contributors. acknowledgement the 6th framework programme of the european commission is gratefully acknowledged for its financial support (nile-project, contract no. 019882). 9 references 1. peters, m. s., timmerhaus, k. d.: plant design and economics for chemical engineers, mcgrawhill, new york (1991) 2. doppelbauer, r., esterbauer, h., steiner, w., lafferty, r. m., steinmüller, h.: applied microbiology and biotechnology 26 (1987) 485-494 3. esterbauer, h., steiner, w., labudova, i., hermann, a., hayn, m.: bioresource technology 36 (1991) 51-65 4. sassner, p., galbe, m., zacchi, g.: biomass and bioenergy 32 (2008) 422-430 5. nystrom, j. m., allen, a. l.: biotechnology and bioengineering symposium 6 (1976) 57-74 microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 37(2) pp. 123-130 (2009) comparison of the structure and the stability of single enzyme nanoparticles i. hegedüs, e. nagy research institute of chemical and process engineering, fit, university of pannonia, egyetem u.10. h-8200 veszprém, hungary, tel.: +3688-624-040, fax: +3688-624-038 e-mail: nagye@mik.vein.hu single enzyme complex nanoparticles were synthesized following the method of kim et al [1]. the enzyme complex used was cellulosome that is a large spatial association of enzymes. single enzyme nanoparticle of celluclast bg cellulase enzyme complex (sen-ck) can degrade as great substrates as natural cellulose. it was proved that the stability of sen-ck enzyme complex is significantly better than that of native enzyme complex (enzyme without pretreatment). significant portion of the activity of sen-ck is remaining at 80 °c for 1 hour time. keywords: enzyme activity, improvement of enzyme stability, single enzyme nanoparticle, effects of temperature on enzyme stability introduction the enzymatic fermentation of cellulose to glucose under industrial conditions is a crucial point in industrial bioethanol synthesis [2]. the most interesting step of the bioconversion is the enzymatic fermentation of cellulose molecules under industrial conditions. cellulose is one of the most stable biopolymers. the polymer chains in natural cellulose build up crystalline and amorphous regions (fig. 1), [2]. figure 1: the spatial structure of natural cellulose. polymer chains build up crystalline domains cellulases comprise three types of enzymes: endoglucanases, which cleave internal β-1,4-glucosidic bonds; exoglucanases, which processively act on the reducing and non-reducing ends of cellulose chains to release short-chain cello-oligosaccharides; and β glucosidases, which hydrolyze soluble cellooligosaccharides (e.g. cellobiose) to glucose (fig. 2) plant cell-wall degrading enzymes exist either in complexed or non-complexed systems [2, 3]. cellulosome is one type of hyperstructures. a hyperstructure is a large, spatial association of cellular constituents such as molecules, macromolecules, and ions that performs a particular function because the constituents are associated with one another [4]. a hyperstructure interacts with other hyperstructures at a level of organization intermediate between the macromolecule and the bacterial cell (fig. 2). exoglucanase (4x) endoglucanase β-glucosidase = glucose = cellobiose exoglucanase (4x) endoglucanase β-glucosidase = glucose = cellobiose figure 2: the structure and function of cellulose multienzyme complex from t. reesei 124 3. single enzyme nanoparticles:individual enzyme molecules surrounded by α) organic/inorganic hybrid polymer e γ) magnetic nanolayer e 3 o 4ef β) mezoporous silica β) organic nanogel e e a) polymer layer: b) inorganic layer: e e e α) hollow metal sphere 3. single enzyme nanoparticles:individual enzyme molecules surrounded by α) organic/inorganic hybrid polymer ee γ) magnetic nanolayer e 3 o 4ef γ) magnetic nanolayer e 3 o 4ef e 3 o 4e e 3 o 4ef β) mezoporous silica β) organic nanogel eee ee a) polymer layer: b) inorganic layer: e e e α) hollow metal sphere e e e ee ee ee α) hollow metal sphere a) hyperbranched polymers cds e e e e e e cdscds ee ee ee ee ee ee au ee e e e e auau eeee ee ee ee ee fe3o4 e e e e e e e fe3o4 ee ee ee ee ee ee ee e eeee ee 2. immoblization into nano-size carriers 1) nanoparticles as carriers on the surface a) metal nanoparticles b) magnetic nanoparticles b) dendimers ee e e e e e ee e e e e 3. single enzyme nanoparticles:individual enzyme molecules surrounded by α) organic/inorganic hybrid polymer e γ) magnetic nanolayer e 3 o 4ef β) mezoporous silica β) organic nanogel e e a) polymer layer: b) inorganic layer: e e e α) hollow metal sphere 3. single enzyme nanoparticles:individual enzyme molecules surrounded by α) organic/inorganic hybrid polymer ee γ) magnetic nanolayer e 3 o 4ef γ) magnetic nanolayer e 3 o 4ef e 3 o 4e e 3 o 4ef β) mezoporous silica β) organic nanogel eee ee a) polymer layer: b) inorganic layer: e e e α) hollow metal sphere e e e ee ee ee α) hollow metal sphere a) hyperbranched polymers cds e e e e e e cdscds ee ee ee ee ee ee au ee e e e e auau eeee ee ee ee ee fe3o4 e e e e e e e fe3o4 ee ee ee ee ee ee ee e eeee ee 2. immoblization into nano-size carriers 1) nanoparticles as carriers on the surface a) metal nanoparticles b) magnetic nanoparticles b) dendimers ee e e e e e ee e e e e figure 3: nanotechnological methods for enzyme stabilization. the new approach is the reducing the size of the enzyme carriers using 1) a) metal or b) magnetic nanoparticles as carriers 2) encapsulation into a) hyperbranched polymers b) dendrimers. 3) single enzyme nanoparticles means single enzyme molecules encapsulated with a) polymer network [α)organic/inorganic hybrid polymer or β) nanogel] b) inorganic layer [α) hollow metal sphere, β) mezoporous silica or γ) magnetic nanolayer.] we investigated celluclast enzyme systems. this enzyme systhem not contains covalent linkage among different enzymes of the complex but each individual enzymes have a well definied spatial order and arrangement in the hyperstructure [3]. improvement in enzyme stability enable further practical applications. classical techniques for improving the stability of the enzymes are enzyme immobilization to the surface or inner cavity of the carrier, modification of the surface of the enzyme, protein engineering, reaction medium engineering and cross-linked enzyme crystals. recently growing interest has been shown in using nanoparticles as carriers to achieve enzyme immobilization in order to increase enzyme stability. the new approach is reducing the size of the enzyme carriers using metal [6, 7], or magnetic nanoparticles [8] as carriers, encapsulation into hyperbranched polymers [9] dendrimers [10, 11]. single enzyme nanoparticles means single enzyme molecules encapsulated within polymer network (nanogel) [12] of inorganic layer. the inorganic layer could be hollowed metal or silica nano-sphere [13, 14] mezoporous silica [15] or magnetic nanolayer [16] (fig. 3). single enzyme nanoparticles (sens) represent a new approach in industrial enzyme research (fig. 3) [1, 19]. form of sen means, that each enzyme molecule is surrounded by a nanometer-size polymer matrix layer, resulting in stabilization of enzyme activity without any serious limitation for the substrate transfer from solution to the active site of the enzyme. the synthesis of sen particles is available via more or less simple laboratorial technique. previously we have decided to apply this technique for industrial bioethanol synthesis. the steps of the synthesis of sen-molecules comply with the requirements of green chemistry. we would like to investigate how can the sen-enzymes digest highersize substrates. we have tried to prepare single enzyme-complex nanoparticles where the functional level is not only a single enzyme, but a multifunctional supramolecular enzyme complex which can have a hyperstructure. we tried to investigate that supramolecular hyperstructures as single nanoparticles has similar behaviour as the monomolecular single enzyme nanoparticles, under extremely conditions. materials and methods the following chemical compounds were used: celluclast bg enzyme complex from t: reesei (novozymes), acryloyl chloride, 1,3-bis[tris(hydroxymethyl)methylamino]propane or bis-tris propane (sigma), sodium bis(2-ethylhexyl) sulphosuccinate or aerosol ot (aot) (fluka), disodium hydrogen phosphate, potassium dihydrogen phosphate, calcium chloride, 2-propanol, n-hexane (spektrum-3d, scharlau), methacryloxypropyltrimetoxysilane (maps), 2,2-azobis(2,4-dimethylvaleronitrile) (fluka), n-acetyl-l-tyrosine ethyl ester (sigma), 3,5-dinitro-salicylic acid (sigma). julaba f12 cryostate was used to keep the reaction mixture at 0 °c. a gas chromatographic syringe (volume 5 μl) was used for the addition of a few microlitres of acryloyl chloride to the enzyme solution. the polymerization step in the synthesis of single enzyme nanoparticles of ck enzyme (sen-ck) was carried out in a double-walled stirring vessel (fig. 4). the solution was irradiated by a uv-lamp made by vilber lourmat. filtration of the surface-polymerized 125 enzymes was carried out with a syringe filter (pore size 0.1 μm) made by millipore. uv-spectra were recorded and enzyme activity measurements carried out by means of a biochrom 4060 spectrophotometer made by pharmacia. a new brunswick scientific g24 incubator shaker was used for the stability measurements. malvern zeta-sizer was applied for detection of size distribution of the enzyme nanoparticles. preparation of single enzyme nanoparticles the preparation process of single enzyme nanoparticles (sen) has three steps (fig. 5). the detailed description of the procedure was given earlier [1, 17, 19]. the first step is a modification of ck enzyme complex and its solubilization in a hydrophobic medium. the second step is the polymerization of the vinyl group in hexane, and the final (third) step is hydrolysis and condensation of the trimethoxysilyl functional group (tms). for the polymerization step, the enzyme should be dissolved in a hydrophobic medium (n-hexane). polymerization on the surface of the enzyme can only be achieved if there is direct contact between the enzyme surface and the hexane medium. for this reason, the specific solubilization method of hydrophobic ion pairing may be used (fig. 6). in this process, vinyl groups on the enzyme surface (synthesized in the first step) are well exposed to the organic solvent (and reagents). side view 365 nm uv irradiation magnetic stirrer uv lamp thermometer hexane phase water cooling double-walled vessel side view 365 nm uv irradiation magnetic stirrer uv lamp thermometer hexane phase water cooling double-walled vessel 365 nm uv irradiation magnetic stirrer uv lamp thermometer hexane phase water cooling double-walled vessel 15 c m 8 cm doublewalled wessel watercooling magnetic stirrer hν uv-lamp plan view 15 c m 8 cm doublewalled wessel watercooling magnetic stirrer hν uv-lamp 15 c m 8 cm doublewalled wessel watercooling magnetic stirrer hν uv-lamp plan viewside view 365 nm uv irradiation magnetic stirrer uv lamp thermometer hexane phase water cooling double-walled vessel side view 365 nm uv irradiation magnetic stirrer uv lamp thermometer hexane phase water cooling double-walled vessel 365 nm uv irradiation magnetic stirrer uv lamp thermometer hexane phase water cooling double-walled vessel 15 c m 8 cm doublewalled wessel watercooling magnetic stirrer hν uv-lamp plan view 15 c m 8 cm doublewalled wessel watercooling magnetic stirrer hν uv-lamp 15 c m 8 cm doublewalled wessel watercooling magnetic stirrer hν uv-lamp plan view figure 4: uv-irradiation for the polymerization on the surface of the single enzyme molecules enzim felület módosítás polimerizáció réteg képzés polimer rétegge beburkolt enzim enzim felület módosítás polimerizáció réteg képzés polimer rétegge beburkolt enzim enzyme surface modification polymerization layer formation enzyme surrounded by polymer layer enzyme surface modification polymerization layer formation enzyme surrounded by polymer layer figure 5: synthesis steps of single enzyme nanoparticles 126 hydrophobic ion pairing (self assembling on the surface of the enzymes) ═ aerosol ot surfactant ═ acryloylated (hydrophobic) surface group of the enzyme ═ phase transfer from the water to the hexan phase ═ positively and negatively charged parts of the enzyme aot water hexane enzyme+ca+ +ca+ + ca+aot aot aot aot aot aot water hexane enzyme+ca++ca+ +ca+ +ca+ + ca+ + ca+aot aot aot -aot aot aot aotaot aotaot aot aot water hexane ca++ ca++ ca++ aot aot aot aot aot aot enzyme water hexane ca++ca++ ca++ca++ ca++ca++ aot -aot aot -aot aot -aot aot -aot aot -aot aot -aot enzymeenzyme hydrophylic (charged) part of the molecules hydrophobic part of the molecules enzymeenzyme aot -aot hydrophobic ion pairing (self assembling on the surface of the enzymes) ═ aerosol ot surfactant ═ acryloylated (hydrophobic) surface group of the enzyme ═ phase transfer from the water to the hexan phase ═ positively and negatively charged parts of the enzyme aot -aot water hexane enzyme+ca+ +ca+ + ca+aot aot aot aot aot aot water hexane enzyme+ca++ca+ +ca+ +ca+ + ca+ + ca+aot aot aot -aot aot aot aotaot aotaot aot aot water hexane ca++ ca++ ca++ aot aot aot aot aot aot enzyme water hexane ca++ca++ ca++ca++ ca++ca++ aot -aot aot -aot aot -aot aot -aot aot -aot aot -aot enzymeenzyme hydrophylic (charged) part of the molecules hydrophobic part of the molecules enzymeenzyme aot -aot hydrophylic (charged) part of the molecules hydrophobic part of the molecules enzymeenzyme aot -aot figure 6: mechanism of hydrophobic ion pairing characterization of single enzyme nanoparticles the morphology and the size of resulting sens were examined by a jeol-1200x transmission electron microscopy (tem) at an accelerated voltage 80 kv. the procedure of the imaging was rather simple, the sample did not need specific preparation for their measurement. one drop of the sen-ct solution was enough to get detectable image by tem. the drops of sen-ct samples were dried and after the drying the sen-particles were detected. measurement and calculation of enzyme concentration the concentration of native ck was determined by taking calibration measurements of the enzyme absorption at 280 nm. there was also no difference between the absorption properties of modified and native enzymes. the concentration of sen-ck could not be obtained from measurement of the uv-light absorption, because the polymer layer prepared around the enzymes also has high absorption at wavelength 280 nm. the sen-ck concentration in water was therefore calculated from the initial concentration of modified ct in hexane (in this case the absorption was measurable), assuming that after the polymerization step the full amount of senck was transferred from the hexane into the water phase, and the amount of sen-ck precipitated during the phase transfer process was negligible. measurement of enzyme activity whatman filter paper was used as substrate (filter paper unit, fpu) and total cellulase activity was measured using dns-probe according the instructions of ghose [20]. measurement of enzyme stability the heat stability of native and prepared enzymes was measured at the following method: 1 ml 0.05 m citrat buffer (ph = 6,00) and 0.5 ml of the enzyme stick solution was mixed and filter paper sample was added into the mixture (1 cm x 6 cm whatman no. 1. standard filter paper) and the mixture was incubated for 60 min at the desired temperature (from 50 °c to 80 °c) without shaking. after the incubation, the enzyme-substrate mixture was cooled and the next steps were the standard activity measurement [20]. the relative activity was calculated as the ratio of residual activity to initial activity. results and discussion in this section it will be enlight the relations among the thickness of the polymer layer on the surface of the prepared sen-enzymes and the structure, size and stability of the resulting sen-enzymes. 127 figure 7: size distribution of different type of single enzyme nanoparticles after the solvatation in hexane using hydrophobic ion pairing (ct =chymotrypsin, ck = celluclast enzyme complex, msz = mannosynthase enzyme) size distribution of sen-ck during the preparation process the size distribution of the sen-ck enzyme complex was measured during the preparation. it was detected by zeta sizer. the results show that the range of the size of the enzyme nanoparticles on the hexane phase after the hydrophobic ion pairing process are between 2–10 nm (fig. 7). we measured three different enzymes (ck = chymotrypsin enzyme, ck = celluclast bg enzyme complex and msz = mannosynthase enzyme). in the case of ck enzyme complex during the solvatation process in hexane enzyme particles with size higher than 10 nm can not be detected. structural caracterization of sen-ck enzymes the structural and size characteristics of sen-ct were detected by transmission electron microscopy (tem). the size of monomeric enzyme is about 2–8 nm (fig. 7). fig. 8 shows that the resulting single enzyme nanoparticles have hollow spherical structures on the electron microscopic images. the surrounding silica-containing nano-gel is electrodense and results dark layer around the enzyme molecules on the picture. but these sen nanoparticles was aggregated into greater structures. the diameter of the resulting sen-ck molecules falls usually between 10 and 100 nm. it can be seen a great difference of the structures of the sen enzyme aggregates when the size of the polymer layer around the sen particles was half (0.5x) or four times (4x) thicker than the originally described [1, 19]. the shape of the originally desribed thickness of polymer layer (fig. 8, 1x) seems to be more spherical than that of the natural ck enzymes. but in the case of the half thickness (fig. 8, 0.5x) we can see non-sperical objects, ellyptoid, rhomboid shapes and enzyme strings. in the case of 4x thickness (fig. 8, 4x) there are a greater, shadowed layer around the enzyme aggregates. we can see white spot on the darker halo of the darker thick layer around the enzyme aggregates. it is very likely that these white spots are “enzyme footprints” of enzymes existing on the sample without polymer layer. 500 nm 0,5x 500 nm500 nm 0,5x 500 nm 1x 500 nm500 nm 1x 500 nm 4x 500 nm500 nm 4x 500 nm 0,5x 500 nm500 nm 0,5x 500 nm 1x 500 nm500 nm 1x 500 nm500 nm 4x 500 nm500 nm 4x figure 8: tem images of the sen-ck enzyme complexes with 0.5x, 1x and 4x quantity of monomers of the polymer layer 128 results obtained confirm that this technique is suitable to realize not only single enzyme nanoparticles but also single enzyme complex nanoparticles (make polymer layer around each single enzyme molecules of the enzyme complex) which are separable (little particles in fig. 10) or in some cases a few number of enzymes can be included in the nanoparticles (greater particles in fig. 10). the filtration of the nanofluid, applying filter paper with cutoff of 10 000 d, could not be carried out during our preparation procedure. the thickness of the polymer layer can be estimated to be about 3–7 nm according to fig. 10. the larger particles with size of 10–100 nm can not cause practically diffusion resistance against the substrate molecules diffusing to the active centre of the enzyme. activity change of enzyme complexes with the changes of the thickness of the polymer layer preliminary results show that the thickness of the crosslinked polymer layer around the enzyme complex can also reduce the activity of the single enzyme nanoparticles of celloclast bg enzyme complexes (sen-ck). but this reducing effect is not dramatical because when the polymer layer around the enzyme complex is 4 times thicker, the activity of the sen-ck composite decreases to about 60%, of its original value. (we assume here, that the thickness of the polymer layer is proportional to the quantity of monomer given in fig. 9). 0 0,2 0,4 0,6 0,8 1 0 1 2 3 4 quantity of monomers [100 μl/mg enzime] r el at iv e ac tiv ity figure 9: the change of the enzyme activity in the function of the quantity of monomers (maps) heat stability of ck and sen-ck enzyme compexes according to our previous investigations carried out by chymotrypsin enzyme, the prepared chymotrypsin enzyme (sen-ct) is more stable than the natural one [17, 19]. similarly to it, the sen-ck particles are really more stable than natural ones (ck) at room temperature as well as under extreme conditions (50–80 °c, fig. 10). the native enzyme complex loses about 90% of its activity at 80 °c after 1 h incubation, but in the case of sen-ck particles using an originally described amount of monomer in the polymerization step (fig. 10, 1x layer) there is no significant change in its thermal stability between 50–80 °c (fig. 10). 0 0,2 0,4 0,6 0,8 1 50 60 70 80 t [oc] r el at iv e ac tiv ity natural ck 0.5 x layer 1 x layer 4 x layer senck 0 0,2 0,4 0,6 0,8 1 50 60 70 80 t [oc] r el at iv e ac tiv ity natural ck 0.5 x layer 1 x layer 4 x layer senck figure 10: heat stability of the ck enzyme complex using different amount of monomer during the polymerization of the layer on the surfaces of the enzymes there is no significant difference among the stability of sen-ck enzymes, when the amount of the monomer is four times higher (4x layer, fig. 10) but if the thickness of the polymer layer is lower than the originally described (0.5x, fig. 10), then the heat stability of the sen-ck enzyme complex converges to the heat stability of the naurtal ones (ck) without polymer layer. conclusions single enzyme complex nanoparticles was synthesized following the method of kim et al [1]. the enzyme complex was cellulosome that it is a large spatial association of enzymes. single enzyme nanoparticle of celluclast bg cellulose enzyme complex (sen-ck) can degrade substrates with large molecules as natural cellulose. it means that four different types of cellulolytic enzymes are located at the well defined place in the enzyme complex during the degradation of cellulose substrate. the diameter of cellulosome in the case of c. thermocellum is about 18 nm [21]. during the solvatation process of ck enzyme complex in hexane enzyme particles with size higher than 10 nm are not detectable. it means that the hydrophobic ion pairing process can solve the different enzymes of ck enzyme comlex separately and the ionic interactions between the different enzymes and the detergent molecules on the surface of the enzymes seemed stronger than the interactions between the different functional parts of the enzyme complex. the results suggest, that self-arrangement mechanism takes place in the third step of the preparation of sen-ck enzyme complexes. after the polymerization step and the cross linkage between the polymer fibers on the surface of the 129 enzymes the resulting sen-ck enzyme complexes have at least one order of magnitude higher average size (fig. 7). it means that during the third step of the preparation of sen enzyme complexes, the separated enzyme nanoparticles, containing polymer fibers on the surfaces of the enzyme molecules, can aggregate into larger structures. it was assumed that the altering size distribution of the resulting sen-ck enzyme complex was caused by the higher concentration of monomer at the third step of the synthesis of sen-ck. (crosslinkage between the polymer chains). the probability of the intermolecular binding is higher and the size of the resulting partiles will be longer due to the higher concentration of enzymes. it was proved that the stability of sen-ck enzyme complex is significantly better than that of native enzyme complex (enzyme without pretreatment). activity of sen-ck does not decrease practically at 80 °c for 1 hour incubation time. abbrevations aot: sodium bis(2-ethylhexyl) sulfosuccinate or aerosol ot ct: α-chymotrypsin enzyme ck: celloclast bg enzyme complex (novozymes) sen: single enzyme nanoparticles maps: methacryloxypropyltrimethoxysilane tem: transmission electron microscope aknowledgements this work was realized as a project of national office for research and technology (nkth tech_08_a3/22008-0385). the authors wish to thank józsef takács (department of anatomy, histology and embryology of semmelweis university, budapest) for tem images. references 1. kim j., grate j. w., wang p.: nanostructures for enzyme stabilization, chemical engineering science 61 (2006) 3, 1017–1026 2. lynd l. r, weimer p. j., van zyl w. h., pretorius i. s.: microbial cellulose utilization: fundamentals and biotechnology, microbiology and molecular biology reviews 66 (2002) 3, 506–577 3. schwarz w. h.: the cellulosome and cellulose degradation by anaerobic bacteria, applied microbiology and biotechnology 56 (2001) 5-6, 634–649 4. norris v., den blaauwen t., doi r. h., harshey r. m., janniere l., jiménez-sánchez a., jin d. j., levin p. a., mileykovskaya e., minsky a., misevic g., ripoll c., saier m. jr., skarstad k., thellier m., toward a hyperstructure taxonomy, annual review of microbiology 61 (2007), 309–329 5. mattinen m.-l., linder m., drakenberg t., annila a., solution structure of the cellulosebinding domain of endoglucanase i from trichoderma reesei and its interaction with cellooligosaccharides, european journal of biochemistry 256 (1998) 2, 279–286 6. hong r., fischer n. o., verma a., goodman c m, emrick t, rotello v. m: control of protein structure and function through surface recognition by tailored nanoparticle scaffolds, journal of american chemical society 126 (2004) 3, 739–743 7. hong r., emrick t., rotello v. m.: monolayercontrolled substrate selectivity using noncovalent enzyme-nanoparticle conjugates, journal of american chemical society 126 (2004) 42, 13572– 13572 8. hong j., xu d., gong p., ma h., dong l., yao s.: conjugation of enzyme on superparamagnetic nanogels covered with carboxyl groups, journal of chromatography b 850 (2007) 1-2, 499–506 9. ge y., ming y., lu d., zhang m., liu zh.: hyperbranched polymer conjugated lypase with enhanced activity and stability, biochemical engineering journal 36 (2007) 2, 93–99 10. zeng y.-l., huang h.-w., jiang j.-h., tian m.-n., li ch.-x., shen g.-l., yu r.-q.: novel looped enzyme-polyamidoamine dendrimer nanohybrids used as biosensor matrix, analytica chimica acta 604 (2007) 2, 170–176 11. yao k., zhu y., yang x., li c.: enfet glucose biosensor produced with dendrimer encapsulated pt nanoparticles, materials science and engineering: c 28 (2008) 8, 1236–1241 12. ming y., ge y., liu z., ouyang p. k.: encapsulation of single enzyme in nanogel with enhanced biocatalytic activity and stability, journal of american chemical society, 128 (2006), 11008– 11009 13. kumar r., maitra a. n., patanjali p. k., sharma p.: hollow gold nanoparticles encapsulating horseradish peroxidase, biomaterials 26 (2005), 6743–6753. 14. kumar r. s., das s., maitra a.: enzymes in the cavity of hollow silica nanoparticles, journal of colloid and interface science 284 (2005), 358–361 15. naik r. r., tomczak m. m., luckarift h. r., spain j. c., stonea m. o.: entrapment of enzymes and nanoparticles using biomimetically synthesized silica, chem. commun. (2004), 1684–1685 16. yang z., shihui s., chunjing z.: magnetic singleenzyme nanoparticles with high activitíy and stability, biochemical and biophysical research communications, 367 (2008), 169–175 17. hegedűs i., nagy e., kovács s.: műszaki kémiai napok ‘07 kiadvány, veszprém (2007), 280. 18. hegedűs i., nagy e.: műszaki kémiai napok ‘09 kiadvány, veszprém (2009), 7. 130 19. hegedűs i., nagy e.: improvement of chymotrypsin enzyme stability as single enzyme nanoparticles, chemical engineering science, 64 (2009), 1053– 1060 20. ghose t. k.: measurement of cellulase activities, pure and applied chemistry 59 (1987) 2, 257–268 21. uversky v., kataeva i. a.: cellulosome in: molecular anatomy and physiology of proteinaceous machines, nova science, new york (2006) microsoft word a_21_r.doc hungarian journal of industrial chemistry veszprém vol. 38(1). pp. 71-76 (2010) investigation of isomerization of sulphur containing hexane fractions zs. szoboszlai , j. hancsók department of mol hydrocarbon and coal processing, university of pannonia 8200, veszprém egyetem u. 10, hungary, e-mail: szzsolt@almos.uni-pannon.hu the main activations of gasoline r&d activities simultaneously the stricter environmental requirements and quality specifications based on increased activity catalysts which saving more energy and feedstock. in the eu the gasoline sulphur content was limited to 10 mg/kg and aromatic content was reduced to 35 %v/v in the year of 2005. the benzene concentration was maximized in 1.0%. these specifications with vehicle r&d contributing to the cleaner environment opposing the constantly increase vehicle number/population. at present only cycloand isoparaffin concentration are not limited because these components burn cleaner have high octane number, low sensibility, and better combustion properties than the aromatic and olefin hydrocarbons. the scientific articles and papers did not concerned with the long term effect of sulphur species on isomerization activity, the effects with higher sulphur concentration than the real industrial feedstock was investigated and after the deactivation they do not give any further information that the feedstock quality (distillation properties, hydrocarbon composition, heteroatom content) how influenced long term activity of the catalyst, additionally the economy and safety operation of the technology. one of main objectives of the research work was to select catalysts that applicable for isomerization and desulphurization in one step. other objectives of our research work were the catalyst selection and process parameters estimation, which could be used in sulphur-containing n-hexane fractions economically feasible, one-step isomerization and desulphurization. in addition, our goal was to determine and estimate those sulphur concentrations, which cause not or only reversible changes in the isomerization activity of the applied catalysts, thereby contributing to faster and safer operational response because of the unexpected change (e.g. increase) in sulphur content of the feedstock. our results indicated that relationships were identified between the material composition the catalytic properties and the applied operational combinations (t, p, lhsv, h2/hc), and available of product qualities. investigation of the activity of three naphtha isomerization catalysts was studied. we studied the changes in the catalytic activities and selectivities in case of the pt/al2o3/cl catalyst, different platinum containing pt/h-mor catalysts (metallic/acid sites ratio changes) and the pt/so4 2-/zro2 catalyst in case of different sulphur containing (<1–120 mg/kg) hexane fractions under the applied process parameters. the range of process parameters were t: 140-280 °c, p: 30 bar, lhsv: 1.0–4.0 h-1, h2/hc: 1:1-3:1. the main conclusions were that both the pt/al2o3/cl and pt/so4 2-/zro2 catalysts isomerization activity was substantially reduced in case of low sulphur containing feed (5–20 mg/kg), after a short period of time (20–50 hours). the practically sulphur free feedstock (≤0.5 mg/kg) increased the isomerization activity, but it did not regained the starting activity, so deactivation was partly irreversible. h-mor catalysts with increased (0.4 to 0.6%) pt-containing was found to be most appropriate, so a slight increase in the concentration of pt (0.35 and 0.40% to 0.45%) significant (hydrogenation) activity change could be achieved. according to the in case of high sulphur content (~100 mg/kg) feedstock the isomerization activity did not decreased significantly in activity, as well as the sulphur content of the gained liquid products was less than 10 mg/kg for the favorable parameters. this is mainly due to the interaction between pt and acid sites explained resulting in sulphur-containing compounds weakly bound to pt surface. we found that the tested catalysts were economically feasible in the one-step isomerization and desulphurization so the increased pt-containing h-mor catalysts are the most appropriate, they can significantly increase the flexibility and economy of technology with low cost, as opposed to non-modified catalysts (not integrated into the feed). on the modified, improved pt-containing h-mor catalysts the octane number of gained liquid products 30-35 units higher than the feed for the favorable operational parameters (t: 260–270 °c; lhsv: 1.0 to 1.5 h-1, p: 30 bar). keywords: isomerization, desulphurization, one step, light naphtha 72 introduction the most valuable engine gasoline blending components are the isoand cycloparaffins, because their application causing lower environmental-, human biology risks, that the aromatic or olefin hydrocarbons. however, the availability of isoand cycloparaffins is limited. light naphtha yields of different types of crude are different, and these fractions (c5-c7) having different amounts of heteroatoms (mainly sulphur compounds), as well as normaland isocycloparaffins, and benzene. the modern motor gasoline and stricter quality requirements become more stringent around the world (reduced sulphur, olefin and benzene concentration). these requirements, together with the vehicle and powertrain developments have being contributing to a cleaner environment. currently, only the cycloand isoparaffins do not limit the amount of engine gasoline because their relatively clean burning, high octane, lower sensibility and better combustion properties, such as aromatic or olefin hydrocarbons. therefore, demand is growing in number [1, 2, 3]. under the catalytic conversion of sulphur containing light naphthas the sulphur species was more strongly bonded to the catalytic metal (hydrogenation/dehydrogenating) functional spaces, which causes coke formation on catalysts, so it may lead to rapid deactivation. experimental the main purpose of the experimental work to study the catalytic conversion of desulphurization and the isomerization reaction was to study side by side in laboratory scale equipment with different sulphur containing naphtha fractions rich in n-hexane, continuous operation, and to the steady catalytic activity of desulphurization and isomerization [3, 4, 5, 6, 7, 8, 9, 10, 11]. the reason for this was that about, the catalysts of the real (industrial), 20–150 mg/kg of sulphurcontaining material only a few results have been released, and their reliability is questionable. based on the results of experiments with different compositions of catalysts were determined the advantageous composition of the catalysts and the advantageous parameter combinations, where the favorable properties (practically sulphur free <10 mg/kg, and high-octane number) with appropriate liquid product yield process can be reached. experimental eqipment the experiments were made a 200 cm3 free volume, vertical, high pressure tubular reactor. it contained all the units, which can be found in a desulphurisation and/or isomerization plant [3]. the experimental system contains a gas-control system and the reactor directly (on-line) contacted to gas chromatograph. materials the volume of the catalyst was 80 cm3, the free volume was filled with inert material (raschig ring). ar (96%+) ccl4, propyl-mercaptan, n-hexane (their mixtures), was used as feedstock. these sulphur content changed between <1–120 mg/kg. linde 4a molecular sieve was used as moisture trap. catalysts and test methods the catalysts were tested for isomerization: pt/al2o3/(7–9%) cl catalyst (in situ chlorinated with ccl4), pt/h-mor catalysts, which noble metal composition/concentration (increased hydrogenation function) from 0.3 to 0.7% ranged between [3, 4, 5, 6, 7] and non-modified pt/so4 2-/zro2 catalyst. the main properties of catalysts are showed in table 1. standard test and calculation methods were used in the study. the platinum and chlorine content of catalysts was determined according to the uop-274 and uop 291-76 standard. the surface and the acidity of the catalysts with nh3 adsorption method and the pore volume and pore size (distribution) with mercury penetration method were determined. the hydrocarbon composition of feedstocks and products with astm d5134 (2003) standard was determined. the sulphur content of all materials and products (greenlab ltd./analytik-jena multi ea 3100-type device) with en iso 20846 (2003), water content (greenlab ltd./kem mka-610-type device) with iso 12937:2001 standard was determined. table 1: the main characteristics of applied catalysts catalyst pt/so4 2/zro2 *pt /h-mor **pt/al2o3 /cl properties pt-content, % 0.415 0.450 0.380 pt-dispersion, % 69 86 92–96 acidity, mmolnh3/g 0.56 0.81 sametalic (metal (pt) surface on the catalyst), m2/g metal 25.91 37.84 smetal (specific metal surface), m2 metal/g cat. 0.108 0.170 aps (average particle size f the metal), nm 2.01 5.12 specific acidity, mmolnh3/m2 cat. 0.0043 0.0021 bet surface, m2/g 130 395 360–430 microporus surface, m2/g 12.2 307.6 micropore volume, cm3/g 0.0045 0.1428 mezopore volume, cm3/g 0.2874 0.2641 mezo-/micropore volume ratio 63.9 1.85 average pore size, nm(å) 8.5(85) 2.9(29) * a modified catalyst properties ** in-situ chlorinated catalysts, so that the modified catalyst in a number of properties can only be estimated 73 due to the large number of results on the most important product properties and the best performance is discussed and presented. to demonstrate the effectiveness of the isomerization of 2,2-dimethylbutane (hereinafter referred to as 2,2-dmb) thermodynamic equilibrium concentration level approach was used (datec), because this is the lowest rate from the component, and the equilibrium concentration of the test range varies almost exponentially [3, 10], so the changes are clearly traceable. with iae the efficiency of isomerization values can be monitored, though it is well to approach the equilibrium concentrations, meanwhile the part of the product (isoparaffins) cracked undesired side reactions reducing the rate of return and hence the economy. teqdmb dmb tdmb c c datec .;2,2 2,2 ,2,2 − − = where datec2,2-dmb,t: 2,2-dimethyl-butane degree approach of thermodynamic equilibrium concentration at a temperature t; c2,2-dmb: 2,2-dmb concentration in the hexane fraction (%); c2,2-dmb;eq.t: 2,2-dmb thermodynamic equilibrium concentration (%) at a temperature t. 100 ronyield iae )c-cc-(i)c-cc-(i xxxx ++ × = where iae: the absolute efficiency of isomerization, yield(i-cx + c-cx): the yield of iso-and cycloparaffins ron(i-cx + c-cx): iso-octane number and cycloparaffins (practically 100% separation of the n-paraffins) process parameters the experiments were made on started steady state activity catalysts. based on preliminary results in the experiments 20–30 bar total pressure, 1.0 to 4.0 h-1 liquid hourly space velocity and 1,0:1,0–3.0:1.0 h2:hydrocarbon molar ratio (industrially relevant conditions) was applied. with the systematic changes in the parameters we tried to find combinations, where feeds with various compositions the desulphurization and the isomerization activity/selectivity good as far as it takes place. rersults and discussion the expediently blended sulphur compounds in higher concentrations to n-hexane have significantly changed isomerization reactions especially the isomerization rate and the effectiveness in case of all three (not modified) base catalysts. mainly in case of the zro2-based catalyst significant isoparaffin content decrease of the liquid products (primarily decreased concentrations of 2,2-dmb) was obsereved, but positive effect of the increase in sulphur content (table 2) was found. the concentration of isoparaffins in liquid products ranged from 68.9 to 84.6%. this value strongly depended on the applied catalyst and the sulphur content of the feed. in case of the lowest temperature active catalytic system (pt/al2o3/cl) was the most appropriate to the isomerization of hexane fraction with low sulphur content was confirmed. the modified catalysts with differently increased pt content were much less sensitive to response the changes of feed sulphur concentration so the decrement the yield of isoparaffins were less therefore the octane number decrement were insignificant (that of the sulphur less feeds). increasing the yield of the liquid product simultaneously with both the small decrement of isoparaffin yield and octane number was just slightly reduced the octane number mass (liquid yield x octane number). 50 55 60 65 70 75 80 0 40 80 120 160 200 time, hour ia e, % elméleti <1mg/kg 2mg/kg 5mg/kg 9mg/kg 15mg/kg 31mg/kg 54mg/kg 76mg/kg 93mg/kg 122mg/kg figure 1: isomerization absolute efficiency vs. time in case of different sulphur containing n-hexane feeds on pt/al2o3/cl catalyst (t: 160 °c, p: 30 bar, lhsv: 1,5 h-1, h2/ch-2:1) 0 5 10 15 20 25 210 220 230 240 250 260 270 280 temprature,°c su lp hu r c on te nt , m g/ kg 0,40 0,45 0,50 0,55 0,60 figure 2: sulphur content of desulphurised and isomerised n-hexane fraction (85 mgs/kg) vs temperature on different pt containing h-mor catalysts (p: 30 bar, lhsv: 1,5 h-1, h2/ch-2:1) in case of high sulphur containing hexane fractions the stricter process parameters were favourable to higher liquid product yields. the concentration of 2,2-dmb in all case were decreased with increasing the sulphur concentration of the feed, while in case of zro2 base catalyst the decrement was much less than the thermodynamic equilibrium concentration. based on the yield values (table 2) the best results were gained on pt/al2o3/cl catalyst (practically sulphur free feed) in all 74 case, the good choice of chlorine content of the catalyst contributes to the lowest available temperature during isomerization was done, and to reach minimal cracking and more favorable equilibrium product composition. beyond the change of octane number it is important to note that in case the low sulphur concentration feed (5–10 mg/kg) the selectivity of isomerization reaction was slightly increased nevertheless the conversion rate of isomerization was decreased only a little. these effects and their changes was well correlated the iae values, which involve both the gained liquid yield and octane number of isoand cycloparaffin products. with different sulphur containing hexane fractions on 160 °c, 30 bar pressure, 1.5 h-1 lhsv, and 2:1 hydrogen/hydrocarbon molar ratio experiments were done, some important results were shown on fig. 1 and table 2. table 2: products from different sulphur containing hexane fractions preferable to find more important features of the operating parameters properties catalysts pt/al2o3/cl pt/so4 2/zro2 pt(0.45%)/hmor *chlorine content of catalyst, % 7.1–9.1 sulphur content of the feed, mg/kg <1–120 <1–50 <1–85 temperature, °c 150–160 195–200 260–270 lhsv, h-1 1.0–1.5 1.0–1.5 1.0–1.5 pressure, bar 30 30 30 h2/ch molar ratio 2:1 2:1 2:1 **maximum allowable sulphur concentration of the feed, mg/kg <3 <10 ≤~100 liquid product(c5+) yield, % 99.4–98.6 94.5–90.6 96.2–93.7 sulphur content, % <1 <1 <10 2,2-dimethylbutane (2,2-dmb), % 27.9–29.8 9.7–11.2 10.8–13.7 datec2,2-dmb, % 67.0–78.2 34.0–40.5 48.9–66.4 ron 78.0–74.9 68.2–72.6 71.7–72.8 mon 78.5–75.0 68.3–72.5 71.9–72.5 δron** 44.1–37.6 37.8–33.3 38.0–35.2 separation of n-paraffins from the liquid product theoretically 100% efficiency yield, % 84.6–77.6 72.5–68.9 75.8–71.9 ron 86.0–86.3 80.0–82.0 82.4–84.6 mon 86.7–86.6 79.7–82.0 82.9–84.4 δron*** 53.9–49.9 47.8–46.2 49.0–47.1 * in situ chlorinated catalysts, such as chlorine content and acidity under the measurement can only be estimated, after measuring with the above mention standard test methods ** the highest sulphur content, which is a catalyst capable of reversibly tolerate and the resulting low activity decrement to the technology operate economically *** the increment of octane number in relation to feedstock on fig. 1 the time of isomerization vs. iae change in case of different sulphur containing hexane feeds shown. it is well illustrated that with less than 5 mg/kg sulphur concentration the isomerisation efficiency just slightly reduced until 100 hour contact time and after that it was nearly constant. up to 31 mg/kg sulphur concentration of hexane fraction the isomerization activity and efficiency was clearly decreased versus the time. at 54 mg/kg and higher concentration the isomerization efficiency already in the starting period significantly decreased moreover ca. after 150 hour (54 mg/kg), ca. after 90 hour (76 mg/kg), ca. after 60 hour (93 mg/kg), ca. after 40 hour (122 mg/kg) strongly decreased so the catalyst was deactivated. the pt/al2o3/cl catalyst only works with very low sulphur containing feeds or it has limited applicability [3, 4, 5, 6, 7]. differently increased pt containing (0.3–0.7%) hmor catalysts activity and selectivity changes were investigated in case of sulphur containing hexane fractions. hereinafter the 85 mg/kg sulphur containing hexane feed results of one step desulphurization and isomerization is presented. wit the expediently modified catalysts and the selected process/operational parameters combination (temperature: 220–270 °c, lhsv: 1.0–3.0 h-1, pressure: 30 bar, h2/hydrocarbon molar ratio 2:1) the result were nearly the same with the results with practically sulphur free feedstock. simultaneously with the high isomerization activity the catalysts have high desulphurization activity. because of the acid support electron draw effect the pt bond strength decreased the sulphur substituent causing the desulphurization to take place rapidly without irreversible poisoning. based on the datas of table 2 and fig. 2 it was concluded that the desulphurization and isomerization efficiency increased with higher temperature, so the favorable process parameters were temperature: 260 °c, lhsv: 1.5 h-1, pressure: 30 bar, h2/hydrocarbon molar ratio 2:1. with the applied pt(0.45%)/hmor catalyst high octane number, high quality, low sulphur isomerised light naphtha could be produced without long term activity change. in case of the pt/hmor catalysts the liquid product octane number were significantly increasing with increased metal/acid site ratio was observed although 0.6, 0.7% pt content has no significant changes than 0.3 to 0.4–0.5% were 75 raised. we concluded that because of the pt has high stock price causing relatively high catalyst cost that indicate higher revamp cost and lower return so the higher pt concentrations are uneconomical. the other tested catalyst was pt/sulfated zirconia without any modification so the application was strongly limited or ultra low sulphur naphtha (10 mg/kg) has to be used. its surface area, specific acidity, pore size and pore volume distributions unbeneficial to forming multibranched isoparaffin mainly the 2,2-dmb were influenced. increasing the concentration of 2,2-dmb simultaneously increased the gas product yield so the catalyst cracking activity increased which was mainly caused by its physical properties than kinetic effects. in the next section, iae of the pt/sulfated zirconia catalyst were presented. fig. 3 showed the iae values in function of time. the explanation of tendency fig. 3 is that the increasing iae values of starting period/term of the measurement was the consequence of the decreasing sulphur concentrations (46→0.5 mg/kg), so the catalyst regained (30→48 h) the starting isomerization activity (iae 62–64% before the measurement, in steady state activity). repeating the sulphur concentration increasing and decreasing in several periods observed that the iae values not reached the starting values and isomerization effectiveness consequently the sulphur poising effect was very significant. while the starting period of the iae reached the 60% (theoretically the highest value: 73%) after in case of sulphur free feedstocks the reduced hydrogenation effect causing relatively high decrement in iae values. activity of the metal sites was decreased more and more to a constant value 30%. 0 10 20 30 40 50 60 70 30 36 42 48 54 60 66 72 78 84 90 96 102 108 114 120 126 132 138 144 150 156 162 168 174 180 186 192 198 204 time, h ia e, % increasing sulphur conc. decreasing sulphur conc. increasing sulphur conc. decreasing sulphur conc. sulphurless feed sulphurless feed 13 mgs/kg feed figure 3: isomerization absolute efficiency on pt/sulphated zro2 catalyst (t: 195 °c, p: 30 bar, lhsv: 1,5 h-1, h2/ch-2:1) the increase of effectiveness in the period was due to the sulphur free feedstock. in the starting period the in case of sulphur free feedstock slightly activity decrement was observed after the sulphur containing feedstock, further the poising effect in short term was mainly reversible, though these few amount of sulphur was caused a little less isomerization activity decrement but there were increase in the liquid product yield. the relatively high sulphur concentration (20–46 mg/kg) caused rapid isomerization activity decrease, while the desulphurization efficiency (the amount of removed sulphur / sulphur content of feedstock) was not reduced significantly. in this case, the poisoning effect of sulphur typically occurs irreversibly (short term) of isomerization. based on the results, in case of the pt/so4 2-/zro2 catalyst one-step isomerization and desulphurization the favorable combination of operational parameters and the maximum allowable sulphur content of the feed are: temperature: 195 °c, pressure: 30 bar, space velocity 1.0 h-1 feedstock sulphur content: <~10 mg/kg. through the measurement period in case the 13 mg/kg of sulphurcontaining feedstock although not the same extent as the other two sulphur-containing feeds, but also showed some degree of decrease of the isomerization, a longer measurement period the feedstock also may be caused isomerization activity decrement. in fact, the sulphur adsorption took place in case of low concentration of sulphur, so increasing the amount of sulphur in the catalyst. 76 conclusions only the modified, increased pt containing h-mor catalysts of the three investigated isomerization catalysts may be capable of sulphur-containing n-hexane fractions of long term, one-step isomerization and desulphurisation (>20,000 hours) while maintaining profitability. the application pilot plant equipment the investigated catalysts and increased sulphur-containing feeds in industrially relevant conditions made it possible to investigate the conditions and testing examination of the isomerization reactions that affect the effectiveness of the impact study. that kind of catalyst research and results may help the existing processes – flexibility with the changes in feed quality, wide parameter range – for more economical and safer operation. the liquid products yield and octane number can vary considerably, depending on the composition of hydrocarbons (boiling range) and heteroatom containing (sulphur and nitrogen) feedstocks are applied. the investigated catalysts one-step isomerization and desulphurization activity on the favorable technological conditions were as follows: pt/h-mordenite (increased pt content) > pt/al2o3/cl > pt/sulfated zro2. the one-step catalytic isomerization and desulphurisation activity was mostly affected by appropriate changing metallic and acid sites ratio. even deeper known of the physical properties of the catalysts to recognize, and thereby to change the acidity and the specific acidity of the catalysts, metal dispersion and particle size has very significant effect on the catalytic activity showed a primary event. the catalyst had a positive effect by increasing the pt content of the edensity of the catalyst active site, and thus the hydrogenation of sulphur compounds takes place more quickly, and the hydrogenation of iso-carbenium ions are less inhibited, so that the products obtained by octane number (composition) is very beneficial to addition to practically sulphur free (<10 mg/kg) as well. acknowledgment we acknowledge the financial support of this work by the hungarian state and the european union under the tamop-4.2.1/b-09/1/konv-2010-0003 project. references 1. u. szalkowska: fuel quality global overview, 7th international colloquium on fuels 2009, tae, stuttgart/ostfildern (germany). 2. h. weyda, e. köhler: modern refining concepts an update on naphtha-isomerization to modern gasoline manufacture, catalysis today, 2003, 81(1), 51–55. 3. j. hancsók, sz. magyar, zs. szoboszlai, d. kalló: investigation of energy and feedstock saving production of gasoline blending components free of benzene, fuel processing technology, 88 (4), 2008, 393–399. 4. j. hancsók, gy. gárdos, j. perger: isomerisation of paraffine hydrocarbons at low temperature, hung. j. ind. chem., 15(3), 1987, 309–316. 5. j. hancsók, g. gárdos, m. baumann: the effect of platinum dispersion on the isomerization of n-pentane, hung. j. ind. chem., 17(1), 1989, 131–137. 6. j. hancsók, gy. gárdos, b. juhász: development of a low temperature isomerization catalyst, j. appl. chem. (plenum publ. corp.), 62(3), 1989, 569–573. 7. j. hancsók: izomerizáló katalizátorok savas tulajdonságainak hatása az aktivitásra, műszaki kémiai napok'92, veszprém, 1992, április 22-24. kiadvány 108. 8. j. m. serra, a. chica, a. corma: development of a low temperature light paraffin isomerization catalysts with improved resistance to water and sulphur by combinatorial methods, applied catalysis a: general, 239(1-2), 2003, 35–42. 9. g. d. yadav, j. j. nair: sulfated zirconia and its modified version as promising catalysts for industrial processes, microporus and mesoporus materials, 33, 1999, 1–48. 10. j. hancsók, sz. magyar k. v. s. nguyen, zs. szoboszlai, d. kalló, a. holló, gy. szauer: simultaneous desulphurization, isomerization and benzene saturation of n-hexane fraction on pth/mor, studies in surface science and catalysis porous materials in environmentally friendly processes 158, 2005, 1717–1724. 11. w. takemi, m. hiromi: reaction of linear, branched, and cyclic alkanes 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word 01_r.doc hungarian journal of industrial chemistry veszprém vol. 35., pp. 95-99 (2007) decision tree based qualitative analysis of operating regimes in industrial production processes* t. varga1, f. szeifert1, j. réti2, j. abonyi1 1university of pannonia, department of process engineering, h-8201 veszprém, p.o.box 158, hungary 2borsodchem ltd., h-3700, kazincbarcika, bolyai square 6., hungary the qualitative analysis of complex process systems is an important task at the design of control and process monitoring algorithms. qualitative models require interpretable description of the operating regimes of the process. this work shows a novel approach to discover and isolate operating regimes of process systems based on process models, time series analysis, and decision tree induction technique. the novelty of this approach is the application of time series segmentation algorithms to detect the homogeneous periods of the operation. advanced sequence alignment algorithm used in bioinformatics is applied for the calculation of the similarity of the process trends described by qualitative variables. decision tree induction is applied for the transformation of this hidden knowledge into easily interpretable rule base to represent the operation regions of the process. the whole methodology is applied to detect operating regimes of an industrial fixed bed tube reactor. keywords: qualitative analysis, decision tree, operating regime, sequence alignment * an extended version of the lecture presented in 18th escape conference, lyon, france, june 1-4, 2008 introduction the improvement of product quality, the need for the reduction of energy and materials waste, and the increased flexibility and complexity of the production systems, process operators require more and more insight into the behaviour of the process. next to these requirements supporting expert systems should also be able to detect failures, discover the source of each failure, and forecast false operations (e.g. thermal runaway) to prevent from the development of production breakdowns. data mining of historical process data along advanced process modelling and monitoring algorithms can offer effective solution for this problem. quantitative data intensive methods are widely applied because of their statistical nature, but it always claims prior knowledge to analyze the results. usually prior knowledge is available in the form of qualitative or tendency models of the process. hence, qualitative analysis of complex process systems is an important task at the design of control and process monitoring algorithms. qualitative models require the interpretable description not only the historical process data but also the operating regimes of the process. a common method for decreasing the size of a data set and to get qualitative instead of quantitative information is time series segmentation. segmentation means finding time intervals where a trajectory of a state variable is homogeneous [1]. segments can be linear, steady-state or transient, indicative for normal, transient or abnormal operation. cheung and stephanopoulos in [2] proposed a second order segmentation method for process trend analysis, the application of episodes with a geometrical representation of triangles. triangular episodes use the first and second derivatives of a time series on a geometrical basis, hence seven primitive episodes can be achieved as characters. to extract useful feature from time series of the state variables one needs to lower the size and dimension of the data and define a distance measure from a theoretically optimal solution to help operators in their work (i.e. the process trends can be easily compared and evaluated with comparing each sequence of primitive episodes). for sequence comparement, in [3] it was shown as an example that dynamic time warping (dtw) is able to compare dna sequences if mutation weights (as distances) exist. going towards this dynamic alignment technique, we applied global pairwise sequence alignment, a wellknown technique in bioinformatics developed by [4], to handle not only mutation and substitution but injection and deletion operators in a sequence. decision trees are widely used in pattern recognition, machine learning and data mining applications thanks to the interpretable representation of the detected information. this is attractive for a wide range of users who are interested in domain understanding, classification capabilities, or the symbolic rules that may be extracted from the tree and subsequently used in a rule-based decision system. to emphasize how decision trees can be applied to extract useful information from the sequences of process trends, and how they are able to represent the 96 operating regimes, an industrial heterocatalytic reactor was analyzed. the results show that the proposed hybrid quantitative qualitative modelling approach can be effectively used to build a process monitoring and operation support system for industrial reactors. the paper is organized as follows: in section 2 the method of qualitative analysis of process trends is briefly introduced, it is followed by the introduction of the developed algorithm for detection of operating regimes. further sections show an application example and results of the analysis. a novel qualitative time series analysis algorithm for the detection of operating regimes qualitative analysis of process trends as described in [2], to get from a quantitative to a qualitative representation of a real-valued x(t) function, it has to be reasonable function. it is clear that all the psychical variables in a plant operation are reasonable. it is considered, if we know the value and derivatives of a reasonable function, the state of that function is completely known. the continuous state (cs) over a closed time interval can be defined as a point value, which is a triplet (if x(t) is continuous in t) cs(x, t) ≡ point_value(x, t) = = <x(t), x’(t), x”(t)> consequently, a continuous trend can be defined as continuous sequence of states. for discrete functions, as an approximation, an underlying continuous function has to be known since the derivatives of single points cannot be performed. these definitions lead to a qualitative description of a state (qs) and trend if x is continuous at t, otherwise it is undefined. qs(x, t) = <[x(t)], [x’(t)], [x”(t)]> where [x(t)], [x’(t)] and [x’’(t)] can be {–; 0; +}, depending if they have negative, zero or positive values. obviously, a qualitative trend of a reasonable variable is given by the continuous sequence of qualitative states. qs(x; t) is called an episode if it is constant for a maximal time interval (the aggregation of time intervals with same qs), and the final definition of a trend of a reasonable function is a sequence of these maximal episodes. an ordered sequence of triangular episodes is the geometric language to describe trends. it is composed of seven primitive notes as {a, b, c, d, e, f, g} illustrated in fig. 1. sequence alignment to determine the similarities of the segmented process trends sequence alignment is typical expression of bioinformatics, where amino acid or nucleotide sequences have to be compared, how far the evolved new sequences are from the elders, i.e. how old they are, and how many mutation steps were needed to result in the new sequence. the algorithm tries to find the least mutation steps between the elder and offspring sequence applies, that is called minimal evolution. in this paper the most advanced algorithm was used (incorporated in the matlab bioinformatics toolbox) to determine the minimal sum of transformation weights (which means the similarity of the sequences). for this project therefore we extended the toolbox so it is now not only able to handle amino acid sequences, but the sequences of episodes of time series. for this purpose the similarity of the episodes had to be defined, which becomes the elements of the new transformation matrix. visualization and characterization of segments of process trends based on these alignment scores (i.e. matching scores), one is able to compare and classify process trends to get a qualitative analysis. the multidimensional scaling algorithm (mds) was applied to visualize the similarity of each process trend to other so the operator can easily check a new trend and in the possession of the necessary a prior knowledge the operator is able to improve the process performance. mds is a statistical technique for taking the preferences and perceptions of respondents and representing them on a visual grid, called perceptual maps. mds is a good tool to "rearrange" objects (in our case the process trends) in an efficient manner, so as to arrive at a configuration that best approximates the observed distances (in our case similarities of time series). it actually moves objects around in the space defined by the requested number of dimensions (in our case in three dimension), and checks how well the distances between objects can be reproduced by the new configuration. { } { }−=∂∂ +=∂ x x { } { }+=∂∂ −=∂ x x { } { }−=∂∂ −=∂ x x { } { }+=∂∂ +=∂ x x { } { }0x x =∂∂ +=∂ { } { }0x x =∂∂ −=∂{ }0x=∂ figure 1: seven primitive episodes proposed by cheung and stephanopoulos 97 calculating temperature profiles learning phase classification of sequences generating inlet conditions inducting the decision tree segmentation of temperature profiles sequence alignment multidimensional scaling measuring inlet conditions application phase forecasting the temperature profile making suggestion coolant in coolant out reagents product x = 0 x = l ( )wout,w b,t ( )win,w b,t ( )out,gout,g i out,gout,g p,c,b,t ( )in,gin,g i in,gin,g p,c,b,t figure 2: (a) the developed algorithm. (b) simplified scheme of the studied reactor qualitative analysis of operating regimes the obtained virtual space (shown in fig. 2a) can be easily used to reveal how the process trends are clustered. since the aim of the proposed methodology is the classification of these process trends and the characterization of the operating regimes of the process variables that affects the shape of these trends, the application of decision trees seems to be a straightforward solution. binary decision trees consist of two types of nodes: (i) internal nodes having two children, and (ii) terminal nodes without children. each internal node is associated with a decision function to indicate which node to visit next (e.g. if the temperature is smaller than 235° visit node 25, otherwise visit node 26). each terminal node represents the output of a given input that leads to this node, i.e. in classification problems each terminal node contains the label of the predicted class (e.g. the 25th terminal node represents reactor runaway). the algorithm has the following basic steps (as shown on fig. 2a): ● randomly generating inlet conditions and calculating the temperature profiles; ● time series segmentation into a sequence of triangular episode primitives; ● alignment of two episode chains and determining the distance of sequences in a three dimensional virtual space; ● classifying the time series by a decision tree and based on inlet conditions and the corresponding class of sequence another decision tree is inducted. 0.1 0.2 0.3 0.4 0.5 0.6 0.7 300 350 400 450 500 550 600 650 reactor length [m] te m pe ra tu re [k ] 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 320 340 360 380 400 420 de a c b reactor length [m] te m pe ra tu re [k ] figure 3: (a) calculated temperature profiles at some inlet conditions. (b) example for a segmented process trend. the alphabetic codes of the episodes are also shown. 98 -0.4 -0.2 0 0.2 0.4 -0.4 -0.2 0 0.2 0.4 -0.2 -0.1 0 0.1 0.2 33 agcfbfgagcfbfg 11 daedeacbfgdaedeacbfg 11 77eagcfbfgeagcfbfg 3232 1515 dagcfbfgdagcfbfg dacbfgdacbfg deagcfgdeagcfg 11 55 11 dedacbfgdedacbfg dacfbfgdacfbfg daedacbfgdaedacbfg 1515 deagcfbfgdeagcfbfg 44 55 11 deacfbfgdeacfbfg deaedacbfgdeaedacbfg deacbfgdeacbfg 99 z 3 cfbfgcfbfg z1 z2 tw,in <= 289.154 : | pg,in <= 1.69487 : 4 | pg,in > 1.69487 : 3 tw,in > 289.154 : | tw,in <= 295.308 : | | pg,in <= 1.69487 : 2 | | pg,in > 1.69487 : 1 | tw,in > 295.308 : | | nb,in <= 573.077 : 4 | | nb,in > 573.077 : 1 tw,in – inlet temperature of cooling media [k] pg,in – inlet pressure of reactor [bar] nb,in – inlet mass flow rate of component b [mol/s] figure 4: (a) sequences mapped into a three dimensional “virtual” space based on their similarity. (b) the extracted decision tree that represents the operating regimes and able to estimate the class (1-4) of the temperature profiles (shown in fig. 5). 0 0.5 1 1.5 2 2.5 3 3.5 4 300 350 400 450 500 550 600 650 700 reactor length [m] te m pe ra tu re [k ] 0 0.5 1 1.5 2 2.5 3 3.5 4 280 300 320 340 360 380 400 420 reactor length [m] te m pe ra tu re [k ] 0 0.5 1 1.5 2 2.5 3 3.5 4 280 290 300 310 320 330 340 reactor length [m] te m pe ra tu re [k ] 0 0.5 1 1.5 2 2.5 3 3.5 4 280 300 320 340 360 380 reactor length [m] te m pe ra tu re [k ] dacbfg daedacbfg daedeacbfg deaedacbfg dedacbfg deacbfg deacfbfg deagcfbfg deagcfg eagcfbfg agcfbfg cfbfg dacfbfg dagcfbfg figure 5: classified temperature profiles. four classes of the temperature profiles were detected and the decision tree is able to assign the classes based on the inlet conditions of the reactor. application to an industrial fixed bed tube reactor process description to emphasize how decision trees can be applied to extract the relevant information from process trends and how the rules characterize the operating regimes a detailed case study has been worked out based on a sophisticated model of an industrial catalytic fixed bed tube reactor. the studied vertically build up reactor contains a great number of tubes with catalyst (as shown on fig 2b). highly exothermic reaction occurs as the reactants rising up the tube pass the fixed bed of catalyst particles and the heat generated by the reaction escapes through the tube walls into the cooling water. due to the highly exothermic reaction which takes place in the catalyst bed makes the reactor very sensitive for the development of reactor runaway. reactor runaway means a sudden and considerable change in the process variables. the development of runaway is in very close relationship with the stability of reactor/model. runaway 99 has two main important aspects. in one hand runaway forecast has a safety aspect, since it is important for avoiding the damage the constructional material or in the worst case scenario the explosion of reactor; on the other hand it has a technology aspect, since the forecast of the runaway can be used for avoiding the development of hot spots in catalytic bed. the selection of operation conditions is important to avoid the development of reactor runaway and to increase the lifetime of catalyst at same time. the worked out mathematical model has been presented in the previous escape conference by the authors [5]. the model has been implemented in matlab and solved with a low order runge-kutta method. the obtained simulator was applied to calculate profiles in case of randomly generated inlet conditions. results and discussion example for learning samples are plotted on fig. 3a where the vertical lines present where runaway occurs. such process trends can be easily segmented as it is shown in fig. 3b. it is interesting to note that the algorithm detected that in this case there was no runaway, since it has inserted an e type episode between the d and a episodes, otherwise d-a episodes would mean the change of the sign of the second derivative of the profile that would indicate runaway according to the classical inflection point based runaway detection method. 100 process trends were analyzed. the similarities of the sequences of the episodes generated from these trends were determined by the previously presented sequence alignment. these similarities were used to map the sequences into a three dimensional space to evolve the hidden structure of the trends. a decision tree was inducted to characterize the trends. four classes were detected. the tree generated based on these new class labels can be seen on fig 4b. on this figure the branches of the tree leading from the root to the leaves should be followed from left to right. in a decision tree the leaves contain the label of the class of the typical temperature profiles. runaway occurs in case of the first class as shown of fig 5. based on this tree the instability regime can be determined (pg,in > 1.69 bar and tw,in > 289 k). the secondary reduction is directed to the implicit part of the model, only. conclusions this work demonstrated how advanced data mining techniques such as time series segmentation, sequence alignment, and decision tree induction can be used to determine the operating regimes in a heterocatalytic reactor. the results show that the proposed approach is able to distinguish between runaway and non-runaway situations based on a set of linguistic rules extracted from classified process trends obtained by the segmentation of time series generated by the model of the process. the analysis of the extracted rules showed the critical process variables determine the shape of the temperature profiles. acknowledgement the authors would like to acknowledge the support of hungarian research found (otka t049534) and the cooperative research centre (vikkk) (project iii/2). jános abonyi is grateful for the support of the bolyai research fellowship of the hungarian academy of sciences. references 1. keogh e., chu s., hart d., pazzani m.: ieee international conference on data mining, 2001, 289-296. 2. cheung j. t., stephanopoulos g.: computers and chemical engineering, 1990, 14, 495-510. 3. srinivasan r., qian m. s.: chemical engineering science, 2006, 61, 6109-6132. 4. needleman s. b., wunsch c. d.: journal of molecular biology, 1970, 48, 443-453. 5. varga t., szeifert f., réti j., abonyi j.: computer-aided chemical engineering, 2007, 24, 751-756. microsoft word 1_r.doc hungarian journal of industrial chemistry veszprém vol. 37(1). pp. 31-36 (2009) cumulative lopa method gy. baradits sr. , j. madár sil4s ltd., h-8200 veszprém, p.o. box 1297, hungary e-mail: bgs@sil4s.hu lopa (layer of protection analysis) is a simplified risk assessment method that is uniquely useful for determining how “strong” sif (safety instrumented function – “interlock”) should be designed. lopa is a semi-quantitative tool which is readily applied after the process hazard analysis (pha) – for example, hazop – and before fault tree analysis/quantitative risk assessment if needed. in most cases, the sif’s safety integrity level requirements can be determined by lopa without using the more time-consuming tool of fault tree analysis or quantitative risk assessment. the problem of classical lopa approach is that it takes into consideration only one hazard scenario at a time. however a sif may exist in several hazard scenarios, so in practice there is a need for a cumulative lopa method where we can take into account all hazard scenarios in lopa calculation which have identical sif as a safety instrumented independent protection layer. we lay down the mathematics of cumulative lopa, and developed software called tool4s which uses this mathematics. the article shows some example of the sw application. keywords: process hazop, process risk, risk matrix, lopa, cumulative lopa, sil, sil calculation, cost reduction, tool4s sw introduction in the 1990s, companies and industrial groups developed standards to design, build, and maintain, that time called, esd system focusing only the plc part of the system. the plc, in safety application, was classified according the german standards [1-7]. the first general safety standard, the iec 61508 1-7 [8], was issued in 1998, which in this topic dramatically changed the safety thinking both in general and industrial segment specific. in 2004 was published the iec 61511 1-3, process industry sector safety standard [9], which is valid for chemical, petrochemical, oil and gas industry. this standard firstly introduced the principle of safety instrumented systems (sis) and safety instrumented function (sif). a key input for the tools and techniques required to implement these standards was the required probability of failure on demand (pfd) for each safety instrumented function (sif). process hazard analysis (pha) teams and project teams struggled to determine the required safety integrity level (sil) for the sifs (“interlocks”). within these techniques, the concept of layers of protection analysis (lopa) – an approach to analyze the number of layers needed to protect the process against the unwanted consequences of the hazards – was first published by the center for chemical process safety (ccps) in the 1993 book guidelines for safe automation of chemical processes [12]. from those concepts, several companies developed internal procedures for layer of protection analysis (lopa) [13], and in 2001 ccps published a book describing lopa [12]. this paper briefly describes the lopa process, and discusses experience in implementing the technique. procedure of sil calculation based on the safety life cycle, it is necessary to get convinced that the existing / designed sis is appropriate for the particular process from the viewpoint of safety (pre-validation, validation). how does one get convince about it? based on the iec-61511 standard, one should perform the following steps: ● hazard and risk analysis ● ipl allocation and sil calculation of sifs ● safety requirement documentation the following figure shows this procedure (see fig. 1). what is lopa? both in the iec 61508 and iec 61511, lopa is mentioned as one of the methods, which gives possibility of calculation the required sil value of sif. lopa [14, 15] is a semi-quantitative risk analysis technique that is applied following a qualitative hazard identification tool such as hazop. 32 input datahazop study cause is bpcs? scenario yes no next scenario hazop, lopa study finished yes no decision about case frequency decession about consequences allocation of ipl with condition allocation of ipl company risk matrices decesion about safety target pfd value of ipl for lopa calculation of sil sil value, lopa human environment business frquency target frequency safety requirement specification target sil and rrf calculated sil and rrf pre-validation figure 1: method of sil calculation we describe lopa as a semi-quantitative method because even if the technique does use numbers and generates a numerical risk estimation, the input numbers are approximate estimates, their accuracy is about at the order-of-magnitude level; and the result is intended to be conservative (overestimating the risk). but even if the lopa is semi-quantitative, the estimated risk is usually adequate to understand the required sil for the sifs. if a more complete understanding of the risk is required, more rigorous quantitative techniques such as fault tree analysis or quantitative risk analysis may be required. the main goal of lopa to evaluate the risk of selected hazardous scenarios. practically, the lopa is used to determine that the identified (existing and/or proposed) protection layers are “strong” enough or not. i.e. the lopa is used to make risk avoiding (protection and preventive) decisions. lopa starts with an undesired consequence – usually, an event with environmental, health, safety, business, or economic impact. the severity of the consequence is estimated using appropriate techniques, which may range from simple “look up” tables to sophisticated consequence modelling software tools. a consequence always has one or more initiating events (causes). each cause-consequence pair is called as scenario, and the lopa focuses on one scenario at a time. the frequency of the initiating event is also estimated (usually from look-up tables or historical data). after identifying all causes and consequences, the possible safeguards (protections layers) are evaluated for two keys characteristics: ● is the safeguard enough effective in preventing the scenario from reaching the consequence? ● and, is the safeguard independent of the initiating event and the other ipls (independent protection layers)? if the safeguard meets both of these criteria, it is an independent protection layer (ipl). lopa estimates the likelihood of the undesired consequence by multiplying the frequency of the initiating event by the product of the probability of failure on demand (pfd) of applicable ipls: ∏⋅= j jinitiatingmit pfdff . pfd gives the probability that the given ipl cannot prevent against the scenario to reach the unwanted consequence. the smaller that value, the better the ipl. the estimated likelihood of the undesired consequence is called as “mitigated consequence frequency” because the frequency is mitigated by the independent protection layers. that value should be compared to the company criteria for tolerable risk for the particular consequence severity. if additional risk reduction is needed, more ipls must be added to the design. the estimated likelihood of the undesired consequence is called as “mitigated consequence frequency” because the frequency is mitigated by the independent protection layers. that value should be compared to the company criteria for tolerable risk for the particular consequence severity. if additional risk reduction is needed, more ipls must be added to the design. fig. 2 shows a simple diagram to illustrate how the probability of occurrence of the unwanted consequence decreases by using ipls. ipl ipl iplipl ipl iplipl1 ipl2 ipl3 consequence occur figure 2: lopa method why is lopa? the suggested methods in the iec 61508 and iec 61511 which gives possibility of calculation the target sil value of sif are split into three groups: ● qualitative, like risk matrix, risk graph ● semi quantitative, like lopa ● quantitative, like failure mode and effect analysis (fmea) or markov modelling 33 the qualitative methods are simply, inaccurate and too subjective, that is why they are not widely applied in the practice. on the other hand, the quantitative methods are just too complex and slow for practical usage. that is why the semi-quantitative methods, lopa seems to be a good compromise. however while the lopa is semi-quantitative, we have some argument why using of lopa is preferable: ● it is not as subjective as the qualitative methods. ● it needs company target risk matrix, so it increases the safety culture of the given company as the company needs to build up the functional safety quality manual. ● lopa is the only method that is able to take into consideration the non-instrumented protection layers. ● lopa gives the possibility of discovering all non-instrumented protection layers. ● lopa gives the possibility of building up the most cost effective protection system including instrumented and non instrumented protection layers. general method of lopa the lopa main objectives are the following [16]: ● identify the non instrumented safety protection layers. ● allocate the safety functions to the protection layers. ● determine if one or more safety instrumented functions (sif) are required to achieve the target risk reduction. ● determine for each sif, if required, the safety integrity level (sil). main steps of lopa are the following: ● develop each impact event scenario based on hazop. ● evaluate the severity consequences for human, business and environment of the impact event scenario. ● set the impact event scenario target likelihoods after mitigation, to meet the company’s functional safety quality management (fsqm) target safety matrix for human, business and environment. ● identify and set the initiating event(s) and related enabling factors. ● calculate the enabled initiating event(s) likelihood. ● add independent protection layers (ipl) to mitigate the impact event scenario. ● set the probability of failure on demand (pfd) values of ipls. ● set the impact event scenario mitigation credit factors. ● calculate the likelihood of the impact event scenario after mitigation; and check if the likelihoods meet the company’s target safety matrix. if one or more target likelihoods are not met, go back to beginning. ● if all the target likelihoods are met, assess the next impact event scenario (see also fig. 1). problems with the simple lopa method the fundament of the lopa calculation is the tolerable risk criteria. the typical risk criteria give the tolerable risk for a person, for a plant, etc. during the lopa, one always compares the mitigated risk to the tolerable risk. if the mitigated risk is lower than the tolerable risk or at least it is “low as is reasonably practicable” there is no need for other protection layers. if not, there is a need for new protection layers and/or other risk reduction methods (see the “main steps of lopa” in the previous chapter). the tolerable risk categories are always set up by the given company and they must be involved in the company safety policy. as the corporate criteria determine the tolerable risk values, practically the lopa focuses on the calculation of the mitigated risk for the goal to determine the necessary risk reduction factor. however because the tolerable risk is based on a unit such as person, it is not enough to calculate the mitigated risk for every scenario and compare them to the tolerable risk value(s). this so-called “per scenario” method has the disadvantage that it cannot take into consideration that a hazard may contain several scenarios with the same consequence and same protection layer (a sif, for example). in this cases, instead of “per scenario” method, one should use the “cumulative” risk calculation method. cumulative lopa method because of the problems of “per scenario” method, we suggested here the “cumulative” method which can take into consideration all hazard scenario which is protected by the same sif. let see an example about the difference between the “per scenario” and the “cumulative” method. let assume that the hazard is high pressure of a vessel and there are two possible initial events: ● the pressure control fails. the frequency is f1. ● the downstream line is blocked. the frequency is f2. let us assume that the consequence is vessel rupture in both cases. also let assume that there is an independent high pressure trip, i.e. a sif which can protect against the high pressure in both cases, and there is no any other ipl. if the “per scenario” method used, one will calculate in the following way: the necessary risk reduction factor (target risk reduction factor) for the first scenario is: rrf1 = f1 / ftol, where the ftol is the tolerable frequency for the given consequence based on the company safety policy. the target risk reduction factor for the second scenario is: rrf2 = f2 / ftol. the final 34 target rrf for the sif is the higher rrf value. e.g. if rrf2 > rrf1, the final rrf will be: 2rrfrrf scenarioper =− . in contrast, the “cumulative” method adds up all the rrf values, so the target rrf for the sif will be: 21 rrfrrfrrfcumulative += . this is higher value than the result of “per scenario” method. that above mentioned difference is important because the iec-61511-3 suggests calculating the total risk: “the last step is to add up all the mitigated event likelihood for serious and extensive impact events that present the same hazard”. it means that the standard suggests the cumulative lopa instead of the perscenario lopa. the difference between the results of the two lopa techniques may be very high when the given sif can be found in several scenarios as ipl. this difference is usually much more than the uncertainty of the lopa method, so the neglect of cumulative lopa may lead to totally wrong sil calculation. in the next chapter, we will show how the cumulative lopa is implemented in our tool4s software tool. cumulative lopa method sw: the tool4s there are several software tools for making hazop and lopa, but our experience has showed that most of them only can calculate the rrf value for a scenario (per scenario method) but do not accumulate them. so it is the task of the user. our experience has showed that a sif can occur in several hazards in the process industry. if a user uses software which does not support the cumulative lopa method, finally he/she will make mistakes or try to forget the cumulative lopa method just because it is too tiresome. hence, we built the cumulative lopa into our tool4s software making the calculation automatic. in the following, it will be presented how the cumulative lopa is realised in our software. the calculation is based on the “non-mitigated frequencies” matrix for causes and the “tolerable frequencies” matrix of the given company. the nonmitigated frequencies matrix can contain one or more pre-defined likelihood values for the initial events (causes). fig. 3 illustrates an example. it is the user task to define this values, he/she can easily add or remove items to/from the matrix. certainly it is not necessary to use this matrix for every case; the user can give a unique frequency value for every initial event if the predefined values do not fit to the given case. figure 3: definition of non-mitigated frequency matrix of causes the tolerable frequencies are also user defined. the user can define the number of consequence types (the default is three: for human, for business and for environment), the possible severity categories, and the specific tolerable frequencies for each severity. fig. 4 shows an example. figure 4: definition of tolerable frequency matrix every pre-defined non-mitigated frequency and tolerable frequency value has a code. the user can easily do the risk ranking by only selecting the appropriate code; fig. 5 shows an example. figure 5: example for risk ranking the risk ranking must be done for every causeconsequence pair, but if the consequence is the same for more causes, the software will copy the consequence ranking information to save manual work. the main concept in the software is that every sif has a unique tag name and own srs (safety requirement specification). when a sif is added into the hazop, the software automatically collect every scenario in which the sif can be found, and calculates the cumulative rrf. the following figure (fig. 6) shows an example from the software: 35 where the sif can be foundcumulative lopa results figure 6: example for result of a cumulative lopa in the followings, the algorithm of cumulative lopa will be presented as it is realised in the tool4s software. cumulative lopa algorithm first step in the first step, the software takes the frequency of the cause. this is called as non-mitigated frequency. the software takes the cause frequency category and looks for the non-mitigated frequency value from the qtrm (qualitative tolerable risk matrix). the attributes of non-mitigated frequency: sign : fnon-mit name : non-mitigated frequency unit : 1/year range : real number, 0 ≤ fnon–mit second step the software takes the severity categories of the consequence, and look for the tolerable frequency value from the qtrm. in the qtrm, there are tables which inform about the tolerable frequency of different types of consequences. typically there are three types of consequences: ● human ● business ● environment in the followings, we assume that these three consequence types are used. the attributes of tolerable frequencies: sign : tenvironmenbusinesshuman ,, toltoltol fff name : tolerable frequency (target frequency to be reached) unit : 1/year range : real number, ...0 tolf≤ third step the software calculates the scenario risk reduction factor (without sif) based on the pfd values of safeguards. the pfd values are manually given by the user in the hazop (fig. 7 illustrates an example). the attributes of pfd: sign : pfd name : probability of failure on demand unit : range : real number, 0 ≤ pfd ≤ 1 the attributes of scenario risk reduction factor: sign : rrfscen name : scenario risk reduction factor (without sif) unit : range : integer, 0 ≤ rrfscen the calculation of scenario risk reduction factor is: ( )tolmitscen ffrrf /int up= where intup is an integer round up function (“ceil function”), and the ftol and fmit are calculated as: ( )tenvironmenbusinesspeople ,,min toltoltoltol ffff = ∏⋅= − j jmitnonmit pfdff where j is a running index for the safeguards in the given hazard scenario. figure 7: edit safeguards in tool4s sw fourth step finally the software calculates the cumulative target risk reduction factor and sil value. both values are calculated automatically for a given sif based on all referenced hazard scenarios (see fig. 6). the attributes of target risk reduction factor: symbol : rrftar name : target risk reduction factor unit : range : integer, 0 ≤ rrftar the calculation of cumulative target risk reduction factor: ( )⎟ ⎠ ⎞ ⎜ ⎝ ⎛ = ∑ i i tol i mittar ffrrf /int up where i is running index for hazard scenarios in which the given sif can be found as safeguard. the attributes of target sil: sign : siltar name : target safety integrity level unit : range : integer the calculation method of target sil: 36 ( )( )tartar rrfsil 10down logint= where intdown is an integer round down function (“floor function”). conclusions in this article, we evaluated the existing methods which calculate the sil value of sifs within a hazop study using lopa method. we has analysed the traditional lopa method called “per scenario” in which only one scenario/sif is taken into consideration. we showed that the result of this calculation is far away from to be considered as correct. we suggested and analysed the “cumulative lopa method” that takes into consideration all hazard scenario which contain the same sif as an independent protection layer. this method has only one disadvantage that it is not easy to realise manually. that is why we developed our tool4s hazop/lopa study program, which automatically calculates the result of the cumulative lopa method. the tool4s sw overcomes the problem of manual and very slow calculation, where the result is not always correct, mainly in case when the technology is difficult. the tool4s was tested over more than 100 hazop and lopa study and proved that is fast, correct with high reliability. acknowledgements here we would like to express our acknowledgement to our colleges at sil4s ltd. for their continuous contribution to this development and the department of process engineering of pannon university, veszprém taking part in the test of our sw and giving some development idea to us. references 1. tüv book, microcomputer in safety application, safety classes 1…5 level, 1972 2. din 3100 – general requirement, ak 1…8 3. din v vde 081 microprocessors in safety application 4. din v 19250 basic safety evaluation for measurement & control 5. din v 19250 requirements & measures, qualitative consideration 6. vde 0116 electrical equipment for burner application 7. din en 954 safety for machinery 8. iec 61508 1–7: functional safety of electrical / electronic/programmable electronic safety related systems. 9. iec 61511 1–3: functional safety: safety instrumented systems for the process industry sector 10. iec 61882: hazard and operability (hazop) studies 11. arthur m. (art) dowell, hendershot d. c.: simplified risk analysis – layer of protection analysis (lopa), aiche 2002 national meeting, paper 281a 12. safety line institute: occupational health & safety practitioner, management of major hazard facilities, london, 1998 13. layer of protection analysis – simplified process risk assessment, american institute of chemical engineers, new york, ny, 2001 14. centre for chemical process safety (ccps), guidelines for safe automation of chemical processes, american institute of chemical engineers, new york, ny, 1993. 15. the instrumentation, systems, and automation society (isa), ansi/isa 84.01-1996, application of safety instrumented systems to the process industries, the instrumentation, systems, and automation society, research triangle park, nc, 1996. 16. risk guidelines as a risk management tool, prepared for presentation at the 1996 process plant safety symposium houston, texas april 1-2, 1996 session 3 microsoft word a_53_tofalvi_r.doc hungarian journal of industrial chemistry veszprém vol. 39(1) pp. 95-99 (2011) environmental significance and identification of metal-chelate complexes using ion chromatography r. tófalvi , a. sepsey, k. horváth, p. hajós university of pannonia, department of analytical chemistry, 8200 veszprém, egyetem u. 10., hungary e-mail: tofalvir@freemail.hu, hajosp@almos.uni-pannon.hu the trace analysis of metal-complexes has long been an area of interest for analytical chemists and environmental researchers due to the biological and toxic properties of these compounds. the method for the simultaneous separation of the metal cations and organic and inorganic anions is based on the use of strong chelating anion with high charge. when basic solution contains an excess of strong complexing anion of high charge, such as ethylenediaminetetraacetate (edta) or trans-1,2-diamine-cyclohexane-tetraacetic acid (dcta) ion, most heavy and transition metal ions will occur as anionic complexes. hence this method provides simultaneous metal and anion separation. the edta and dcta chelating agents exhibit strong complexing power. these aminopolycarboxylic acids can remobilize metals in nature. because aminopolycarboxylic acids are a potential risk to the environment, it is important to develop an effective analytical technique for their determination. several factors affect the retention in the separation of the complex anions: complex formation reactions, ion-exchange equilibria and protolysis depending on ph. the aim of this work is the optimization of a simultaneous chromatographic separation and identification of metal ions complexed by the ligand edta or dcta. the method was utilized to separate cuedta2-, cudcta2-, znedta2-, zndcta2-, aledta-, aldcta-, cl-, piruvate and maleate anions. an advantage of the developed method is that the same basic ph-range is favourable to the stability of the metal complexes and to the elution. keywords: transition metal complexes, edta, dcta ligands, ion exchange chromatography introduction metal ion speciation and the environment the presence of transition and heavy metals in the environmental and biological materials justifies the importance of high performance environmental qualitative and quantitative analysis of these species [1]. the transition metals exist in different oxidation states possessing different physical and chemical properties and different toxicity. the main sources of metalcontamination of the environment are the industrial emission, vehicle exhaustion, corrosion processes, households, agriculture, hazardous storage tanks, and waste disposal sites. the presence of inorganic pollutants, especially toxic metal ions, is a serious issue, as metal ions may often be carcinogenic in nature. the identification of pollutants in environmental matrices is a difficult task because of strong interference from other components of the sample. the extended use of palladium in automotive catalytic converters and in the chemical industry has also led to increasing concentrations of this metal in environmental compartments. platinum group and heavy metals may enter the environment and interact with complexing materials, such as humic substances. determination of palladium by ion chromatography with icp-ms detection was developed by m. c. bruzzoniti et al. [2] aluminium plays probably a role in the development of alzheimer’s disease [3]. the route of these toxic metal ions to the human body is through water and other foodstuffs. therefore, the monitoring of metal ions with different oxidation states in water bodies and foodstuffs is essential and important. some toxic metal ions are also present in the atmosphere and indirectly affect our health. some metal ion in oxoanion forms (aso4 3-, cro4 2-) are transported across cell membranes. copper and zinc within those metals that are essential to life although inherently toxic. the characteristic oxidation forms of copper are: cu(i) and cu(ii). in case of zinc the most frequent forms are zn(i) and zn(ii). the change of oxidation state of an element affects the degree of its bio-availability and toxicity. the different oxidation states of a particular metal ion possess different physical and chemical properties. these oxidation states differ in their redox potential, complexation, and hydration properties. therefore the speciation analysis can differentiate the complexed and free forms of metal ions. measuring the total concentration of metal ions gives no information about the actual chemical forms it exist, that is important to understand its toxicity and biotransformation. therefore the speciation of elements can not be omitted. 96 aminopolycarboxylic acids as ligands can remobilize heavy and transition metals and their release in nature may cause release of metals into ground water and their uptake by plants. degradation of chelating agents is controversial. while excessive uptake of heavy metals was viewed as a deterrent for the use of edta in agriculture, the same process is now being researched because of the possibility that it could be applied to the phytoremediation of heavy-metal contaminated soils. however, due to the lack of selective analytical techniques, the mechanisms of metal uptake by plants in the presence of edta still remain largely speculative. since aminopolycarboxylic acids are a potential risk to the environment, it is also important to develop a selective analytical technique for their determination. chelate chromatography chelate chromatography is a special type of ionchromatography in which chelating agents as eluent additives are employed. the ion chromatography is a suitable speciation technique and it offers reproducible results. simultaneous separation of metals and anions is based on the use of a strong complexing anion of high charge [4]. ethylenediaminetetraacetic acid (edta) and trans-1,2-diamincyclohexanetetraacetic acid (dcta) are excellent chelating agents that are able to form sufficiently stable chelates with different metal ions. the strong complex-forming anions with high charge react with most of the diand trivalent metal cations and they form complexes with one or two negative charge that makes the simultaneous separation of metal cations, organic and inorganic anions possible. several factors affect the chromatographic retention of complex anions. these are the (1) complex formation reactions, (2) the ion-exchange equilibria, and (3) the protolysis that depends on the ph of elution. retention models have been developed by hajos et al. in order to study the retention behavior of metal-complexes in anion exchange chromatography [4, 5]. the theory [5] is based on the generalized ion-exchange-, protonation and complex-formation equilibria. the unknown ionexchange equilibrium constants for the sample and the eluent species can be determined from experimental retention data [6] by iterative minimization, using a non-linear regression algorithm. the model was utilized to predict the retention behavior of cdedta2-, coedta2-, mnedta2and niedta2ions. it was concluded that the chromatographic separation of these species are strongly influenced by the size of ion, the type, concentration, and ph of eluent, and the stability of complex. experimental instrumentation a dionex dx-300 ion chromatograph (sunnyvale, ca, usa) equipped with a conductivity detector and a dionex amms-i cation micromembrane suppressor was used during the work. the separations were carried out by as9-hc and as4a-sc separator columns (250 x 4 mm i.d.) packed with anion-exchangers functionalized with alkyl/alkanol quaternary ammonium ions. the recommended ph-range for the columns was 2–13. all chromatograms were obtained at room temperature at a flow rate of 1.2 ml min-1. the injection volume was 50 μl. the micromembrane suppressor was regenerated with sulphuric acid (0.025 m) at flow rate 3,5 ml min-1. reagents and solutions eluents were prepared by using analytical grade na2co3 and nahco3 (fluka, switzerland). high purity water was obtained by using a milli-q system (millipore, bedford, ma). the specific resistance of the water was 18.2 mω cm-1. sample solutions of metals, organic and inorganic anions and the chelating agents (edta and dcta) were prepared by dilution of a concentrated stock solution of analytical-grade salts (fluka). the sample solutions contained chloride salts of metal cations and complex forming ligands. before analysis, all eluents were treated in an ultrasonic bath for 5 mins in order to remove air. basic components and practice of chelatechromatography the basic components of chelate chromatography are presented in fig. 1. the delivery system consists of an eluent container (na2co3, nahco3, ph 8–11), liquid transfer lines, eluent and sample selection valves and a pump. the sample components (metal-halogenides, oxoanions) together with complexing agents (edta, dcta) are injected into the separation system via a valve injector. plastic valves made of chemically inert materials are used. typical injection volumes are between 10–100 μl. the separator columns are packed with pellicular anion exchanger in order to obtain optimum separation condition for ionic components (medta2-, a-) with an adequately short analysis time. after leaving the separator column, the separated species pass into the conductivity detector. the suppressor-type ion chromatography systems has a unique detection system in which an ion-exchange membrane enhances the sensitivity of analysis. the main function of the suppressor is to chemically reduce the high background conductivity 97 of the electrolyte used as eluent (naoh → h2o; na2co3 → h2co3), and to convert the sample anions into a much more conductive form (nacl → hcl). a major advantage of chelate-chromatography – in contrast to other instrumental analysis such as atomic spectroscopy – is its ability to detect different species of anions and cations simultaneously. figure 1: schematic flow diagram of chelate chromatography results and discussion by adding negatively charged edta or dcta ligand to positively charged metal ions complex anions with negative charge form in the solution according to the following equilibria: edta4+ m2+ ↔ [medta]2(1) dcta4+ m2+ ↔ [mdcta]2(2) the conjugate bases of edta and dcta are 6-dentate ligands. in case of complex formation, the 6 donoratoms of the ligand (4 oxygen and 2 nitrogen atoms) are located at octahedron vertices around the central metal ion. the high stability of the metal chelates is due to the fact that the ligand surrounds fully the metal ion and isolates it from molecules of the solvent. the stability of the complexes depends on the ph. when the ph increases, the chelating agents are more and more deprotonated and exhibit their complexing power. during the formation of metal chelates ph-dependent side-reactions occur. at the eluent ph range investigated edta and dcta exist in two forms: hy3and y4-. in this work, carbonate/hydrogencarbonate electrolyte was used as eluent at various concentrations and phs. the separation system contains three ionic species in the eluent (co3 2-, hco3 and oh-) and various forms of organic, inorganic and complex ions in the sample. during elution, the following simultaneous equilibria take place in the separator column: 2r-e + medta2↔ r2-medta + 2e(3) r-e + mhedta↔ r-mhedta + e(4) 2r-e + mdcta2↔ r2-mdcta + 2e(5) r-e + mhdcta↔ r-mhdcta + e(6) where: r – the charged functional group of the ionexchanger e – the anion of the eluent. in the suppressor reaction carbonic acid is formed from the eluent anions: co3 2+ 2 h+ ↔ h2co3 (7) the retention factors (log k’) of the investigated anions at different eluent concentrations and phs can be seen in table 1. the result shows clearly that the increasing eluent concentration decreases the retention of anions. at the same time, the changing eluent ph affects the sample composition by changing the fractions of differently protonated species. it can be seen in fig. 2 (ph vs. φ) that at the ph of elution the edta can exist in two distinct forms with triand four negative charges. it is important to note that the changing ph of the eluent does not affect the order of elution of the metal complexes. an advantage of the applied method is that the same basic ph-range is favorable to the stability of the metal complexes and also to the elution. figure 2: partial molar fractions of edta in the eluent at different phs. the cross-hatched area represents the ph region of the eluents used with this separation method, complexes with different ligands and the complexes of different metal ions can be separated in the same run (fig. 3-5). the simultaneous separation of negatively charged metal chelates and carboxylate anions can be performed as well (fig. 4). the results indicate that the retention is influenced by the ph of eluent (table 1). increasing eluent ph leads to decrease in retention (k’) because the predominant form of eluent species is the divalent carbonate above ph 10 that has higher elution strength than the monovalent hydrogen carbonate anion. this important factor has to be considered during the optimization of separation. 98 table 1: the effect of ph and eluent concentration on the retention of complexes and ligands k’ celu [mm] 5.0 6.5 8.0 9.0 ph 10.27 10.86 11.03 9.90 10.27 10.50 10.86 9.44 10.27 10.86 11.03 cl3.88 3.45 3.60 4.20 3.56 3.42 3.08 5.34 3.53 3.14 2.85 edta412.00 8.06 9.00 11.89 8.16 6.93 5.95 12.27 6.29 5.38 3.92 edta326.09 19.38 20.16 25.18 17.78 15.81 14.63 17.29 14.73 12.68 10.58 dcta412.80 9.28 9.81 13.54 10.04 8.73 7.11 n.r. 7.96 6.32 5.07 dcta315.86 11.23 11.93 14.36 12.10 10.55 8.62 21.01 16.96 13.27 10.84 cuedta230.27 25.98 25.95 22.53 21.67 19.92 18.87 n.r. 17.55 15.86 14.28 znedta222.87 19.30 19.95 n.r. 17.84 16.12 14.54 18.20 14.62 12.77 10.72 cudcta227.60 19.14 20.84 n.r. 20.41 17.08 14.66 20.22 16.96 13.27 10.65 zndcta228.58 20.01 21.31 n.r. 21.45 17.84 15.30 21.90 17.60 13.72 10.50 n.r.: no retention data figure 3: simultaneous separation of al and zn complexes with edta and dcta chelating agents. peaks: 1. cl-, 2. edta4-, 3. dcta4-, 4. [aledta]-, 5. [aldcta]-, 6. [znedta]2and [zndcta]2-. eluent: 9.0 mm na2co3, ph = 11.027. column: as9-hc anion exchanger. calibration data (table 2) demonstrate that the simultaneous ic analysis of metal-chelate complexes and ligands is sensitive and can be used for quantitation as well. figure 4: chromatogram of simultaneous separation of aliphatic carboxyl acids and copper-edta complex. peaks: 1. piruvate, 2. cl-, 3. edta4-, 4. maleate, 5. [cuedta]. eluent: 0.7 mm na2co3 + 1.8 mm nahco3; ph=9.66. column: as4a-sc. figure 5: chromatogram of edta-metal complexes. peaks: 1. cl-, 2. edta4-, 3. [cuedta], 4. [znedta]. eluent: 8.0 mm na2co3+ nahco3, ph = 10.27. column: as9-hc anion exchanger. table 2: calibration data of edta and dcta chelating agents and their complexes. sample sensitivity (μs sec l mg-1) linearity (r2) edta43×108 0.8645 edta33×108 0.8442 dcta44×108 0.8771 dcta32×107 0.7558 [cu-edta]2109 0.9931 [cu-dcta]2109 0.9894 conclusion our experiments verified that the simultaneous analysis of anions and metal cations can be achieved and the change of concentration of components can be detected, the metal complexes and their ligands can be identified. the retention data of chelate-complexes (cu2+, zn2+, edta, dcta) were given by the use of anion exchange column packed with pellicular stationary phase, and by the use of carbonate-hydrogencarbonate eluent and suppressed conductivity detection. the effective parameters of the separation were determined considering the composition of eluent. 99 acknowledgements present article was published in the frame of the projects támop-4.2.1/b-09/1/konv-2010-0003 and támop-4.2.2/b-10/1-2010-0025. the projects are realized with the support of the hungarian government and the european union, with the co-funding of the european social fund. financial and infrastructural support of the hungarian scientific research fund (otka k 81843), and the ntp_oka_viii_a_85 student grant is also gratefully acknowledged. references 1. i. ali, h. y. aboul-enein: instrumental methods in metal ion speciation, chromatographic science series; taylor & francis, 2006, 1–16 2. m. c. bruzzoniti, s. cavalli, a. mangia, c. mucchino, c. sarzanini, e. tarasco: ion chromatography with inductively coupled plasma mass spectrometry, a powerful analytical tool for complex matrices. estimation of pt and p din environmental samples, journal of chromatography a, 997, (2003), 51–63 3. m. c. bruzzoniti, e. mentasti, c. sarzanini: simultaneous determination of inorganic anions and metal ions by suppressed ion chromatography, analytica chimica acta 382, (1999), 291–299 4. p. hajos, g. revesz, o. horvath, c. sarzanini: the simultaneous analysis of metal-edta complexes and inorganic anions by suppressed ion chromatography, journal of chromatographic science, 34(6), (1996), 291–299 5. p. hajos, g. revesz, c. sarzanini, g. sacchero, e. mentasti: retention model for the separation of anionic metal-edta complexes in ion chromatography, journal of chromatography, 640, (1993), 15–25 6. p. hajos, o. horvath, g. revesz: advances in chromatography, 38., marcel dekker inc., new york (1997) << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false 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<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> /enu (use these settings to create adobe pdf documents best suited for high-quality prepress printing. created pdf documents can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 59-63 (2008) investigation of enzyme-catalyzed transesterification of used frying oils s. kovács , m. krár, j. hancsók university of pannonia, institute of chemical and process engineering, department of hydrocarbon and coal processing veszprém, h-8201, p.o.box.: 158, hungary e-mail: kovacss@almos.uni-pannon.hu investigation of the possibility to convert used frying oils to less harmful but more valuable products is driven by the protection of environment and human health as well as economical reasons. one solution could be the conversion of these oils to transportation fuels and their application in diesel engines in “pure” form or as blend stocks of diesel fuels. the conversion to biodiesel can be realized by transesterification with various catalysts. this paper presents the results of some experiments made by applying used frying oils and a process which is studied less intensively in the literature. the main goal of our experiments was to compare the transesterification efficiency of the three commercially available immobilized lipases [candida antarctica (novozym 435), rhizomucor miehei (lipozyme rm im) and thermomyces lanuginosus (lipozyme tl im)] which were applied under the same conditions and using the same feed. based on our experimental results we established that we achieved the highest methyl ester content (>94%) approaching well the theoretical yield when we applied candida antarctica (novozym 435) among the investigated lipase enzymes. keywords: lipase, enzyme-catalyzed transesterification, used frying oil, biodiesel introduction nowadays the amount of vegetable oils used for human consumption has increased significantly. this causes the increase of quantity of the used frying oils and cooking greases which can no more be used in the food industry. the gathering, deposition, recycle or treatment of this high amount of used frying oils are becoming more important in these days. this is caused by the need for decreasing the quantity of wastes, saving our resources, lowering the load of the sewages and dumps, and economical aspects as well [1]. currently many applications of the used frying oils which can no more be used for edible purposes are known. the appropriately pre-treated used frying oil is an important feedstock for the colour industry, cosmetic industry and road-building industry. additionally it was used as a feed additive for animals, but now it is forbidden [2, 3, 4, 5]. beside the above mentioned areas the pre-treatment and purification of used frying oils and their use as fuels (or heating oils) with or without conversion are very important research areas nowadays. the application of used frying oils as fuels is favored by the european union. by 2005 1% of the fuels consummated by the eu was biomass derived, thanks to the 2003/30/ec directive of the european union which helped to merge the use of biofuels [6]. the „eu strategy for biofuels” [7] was a milestone in the application of used frying oils, because the european union declared the need for using new kind of feedstock [7]. according to the latest aims of the european union the quantity of the biofuels used should be 10% by 2020 [8]. this can also help the application and conversion of used frying oils. this proposed value can be accomplished by utilization of different vegetable oils, used frying oils and its derivatives as fuels. the utilization options of triglycerides as fuels can be the following: • direct blending into diesel fuels, • transesterification to biodiesel fuels, • production of fuel blending components by different cracking processes (engine gasoline, jet, diesel fuel). recently, among these methods the use of biodiesels obtained the transesterification of triglycerides with methanol is the most preferred. chemical transformation of used frying oils is not possible by the conventional method (alkali catalyst), because of its high free fatty acid content (5–35%). the adequate amount of alkali catalyst immediately reacts with the free fatty acids found in used frying oils resulting in soap formation and it is not able to catalyze the reaction. a possible way is the conversion of the used frying oils with acid catalyst (hydrochloric acid, sulphuric acid, acid ion-exchange resin). substantial amount of acid catalyst and significantly higher reaction time is 60 necessary for the transesterification, compared to the alkali catalyzed method [9, 10]. another option is the conversion of used frying oils by combined acid and alkali catalyzed transesterification. in this process the free fatty acid content of the used frying oils are first pre-esterified in the presence of acid catalyst, then the transesterification is completed by alkali catalyst [10, 11]. another possible way is the enzyme-catalyzed transesterification of used frying oils, because lipase enzymes can transform free fatty acids into esters. the application of enzyme catalysts compared to alkali catalysts has several advantages: it is carried out under mild temperature-, pressure-, ph-conditions and no hazardous by-products or wastes are formed (e.g. waste water, soaps), furthermore methyl esters are formed from also the free fatty acids of the raw materials. however, in all cases it is very practical to separate all undesired components present in the used frying oils before their use or conversion. these undesired components are for example the solid oxidation compounds which form during frying (oxidized triglycerides, epoxides, etc.), oxidized oligomers, nonpolar dimers and non-polar polymers, etc [12]. many processes are known to eliminate these undesired components, thus to clean the used frying oils [13, 14]. for example adsorbents (eg: calcite, sepiolite, montmorillonite, attapulgite), supercritical carbon-dioxide, ozone, water and inert gases can be used. after adequate pre-treatments the used frying oils can be converted with the similar method as the vegetable oils. this gives many advantages. the most important is that valuable product can be produced of a material that is concerned as waste, so the load of the dumps and the environment decreases. from economical point of view it can be attractive that the price of the used frying oils and that of the methyl-ester produced from them is lower than the price of the vegetable oils and of the vegetable oil fatty acid methyl-esters [13]. experimental the main goal of our experiments was to compare the transesterification efficiency of the three commercially available immobilized lipases [candida antarctica (novozym 435), rhizomucor miehei (lipozyme rm im) and thermomyces lanuginosus (lipozyme tl im)] which were applied under the same conditions and using the same feed. the operational parameters during our experimental work were based on our previous results [15-18]. experimental apparatus the enzyme catalysed transesterification was carried out in a heated shaker equipment with a capacity of 9 erlenmeyer flasks (new brunswick g24). simultaneously all feedstocks can be put into the shaker, so the same parameters can be assured. the temperature in the shaker equipment was controlled manually with a precision of ±1 °c. materials and their preparation durig our experimental work the feedstocks were hungarian sunflower oil with high oleic acid content (hoso), used frying oil (ufo) and the 50-50% mixture (mix) of the previous materials. the main characteristics of the different feeds is given in table 1 and their fatty acid composition in table 2. table 1: the main properties of the feeds properties ufo hoso mix density, 15°c, g/cm3 0.9216 0.9145 0.9195 kinematic viscosity, 40°c, mm2/s 39.8 33.7 35.6 sulphur content, mg/kg 10 5 8 nitrogen content, mg/kg 12 6 8 cfpp, °c 42 36 39 acid value, mg koh/g 2.3 0.5 1.5 iodine number, g i2/100g 132 89 103 ufo: used frying oil hoso: sunflover oil with high oleic acid content mix: 50-50% mixture of the previous cfpp: cold filter plugging point table 2: the fatty acid composition of the feeds fatty acid composition, %* ufo hoso mix c14:0 0.1 0.0 0.1 c16:0 7.9 3.3 4.8 c16:1 0.2 0.1 0.1 c18:0 3.8 3.3 3.5 c18:1 26.3 87.4 59.7 c18:2 60.3 4.2 30.2 c18:3 0.2 0.0 0.1 c20:0 0.2 0.3 0.3 c20:1 0.2 0.2 0.2 c22:0 0.6 0.9 0.8 c22:1 0.0 0.0 0.0 c24:0 0.2 0.3 0.2 c24:1 0.1 0.0 0.1 *the first number represents the number of carbon atoms and the second means the number of double bonds in the molecule ufo: used frying oil hoso: sunflover oil with high oleic acid content mix: 50-50% mixture of the previous during the transesterification reactions analitycal grade methanol (spektrum 3d) was used. the investigated enzyme catalysts were the macroporous resin immobilized lipase candida antarctica (novozym 435) (activity: 7000 plu/g), acrylic resin 61 immobilized thermomyces lanuginosus (lipozyme tl im) (activity: 250 iun/g) and anion-exchange resin immobilized rhizomucor miehei (lipozyme rm im) (activity: 150 iun/g) received as a kind gift from novozymes a/s (bagsvaerd, denmark). before the transesterification the first step was the pretreatment of the used frying oils and vegetable oils with tonsil® adsorption clay and adequate volume of pertfil filter aid. test method the methyl ester content of the products were determined according to the en 14103: 2004 standard [fat and oil derivatives – fatty acid methyl esters (fame) – determination of ester and linolenic acid methyl ester contents]. during the measurements we used gas chromatograph and we applied methyl heptadecanoate as an internal standard. the conditions of the gas chromatograhic measurements are summarized in table 3. table 3: the conditions of the gas chromatograhic measurements injector split/splitless injector, 260 °c, 200 ml/min column supelco omegawax-250 capillary column, 30 m x 0.25 mm x 0.25 μm furnace program 120 °c (1 min) initial temperature 240 °c (10 min) final temperature 5 °c/min detector fid detector, 260 °c amount of sample 1 μl experimental method the feeds in erlenmeyer flasks were shaken by the shaker equipment in the presence of immobilized enzyme catalyst at 50±1 °c, atmospheric pressure for a defined time. every flask contained 44 g of vegetable/used frying oil and 6g of immobilized lipase (12% of the total amount of reactants). methanol was added to the reaction mixture in 8 parts by applying a methanol-totriglyceride molar ratio of 4:1 (6.4 g methanol) instead of the stochiometric ratio of 3:1, considering that excess methanol favors the progress of the reaction. the stepwise addition is necessary to prevent the inhibiting effect of the methanol. all transesterification reactions were carried out under the same conditions, the reaction times were 4, 8, 12, 16 hours. after the reactions the ester containing phase was separated and the excess of methanol was removed by vacuum destillation. thereafter, the amount of the product and the methyl ester content of the ester phase obtained through the enzymatic transesterification were determined. results and disscussion in case of all feedstock the yield of the methyl-ester phase was 96–99% of the theoretical value using candida antarctica (novozym 435) immobilized lipase enzyme. methyl ester content of the products as a fuction of the reaction time is shown in fig. 1. it can be seen that methyl ester contents in case of a given reaction time differ only by few percents. after 16 hours reaction time methyl ester content of the product obtained form used frying oil (ufo) was the smallest (94.1%), is probably caused the oxided compounds present in the used frying oil, can not be converted by candida antarctica. yield of the product prepared from high oleic sunflower oil (hoso) approached the theoretical value by 99.8%, its methyl ester content was 99.0%, meanwhile methyl ester content of the mixture (mix) was 96.9% after 16 hours reaction time. methyl ester content of these two products fulfilled the requirements (>96.5%) of the en 14214:2004 standard. 0 10 20 30 40 50 60 70 80 90 100 0 2 4 6 8 10 12 14 16 reaction time, h m et hy l e st er c on te nt , % hoso mix ufo figure 1: methyl ester content of products as a function of transesterification time (catalyst candida antarctica (novozym 435)) in case of the transesterification carried out in the presence of thermomyces lanuginosus (lipozyme tl im) immobilized lipase enzyme methyl ester content of the products differed by only few percents (fig. 2) as a function of the reaction time. however, methyl ester contents at a given reaction time were much lower than in case of candida antarctica (novozym 435). after 16 hours reaction time methyl ester content of the product prepared from high oleic sunflower oil (hoso) was the highest (77.3%), that of the mixture (mix) was 74.4%, menawhile that of the used frying oil (ufo) was only 71.1%. methyl ester content as a function of reaction time in case of rhizomucor miehei (lipozyme rm im) is shown in fig. 4. after 16 hours reaction time methyl ester content of the product prepared from used frying oil (ufo) was the smallest (63.8%), that of the high oilec sunflower oil (hoso) was 74.8%, meanwhile that of the mixture (mix) was 70.2%. methyl ester content of the mixture was between the results of the high oleic sunlfower oil and the used frying oil (fig. 3). 62 0 10 20 30 40 50 60 70 80 90 100 0 2 4 6 8 10 12 14 16 reaction time, h m et hy l e st er c on te nt , % hoso mix ufo figure 2: methyl ester content of products as a function of transesterification time (catalyst thermomyces lanuginosus (lipozyme tl im)) 0 10 20 30 40 50 60 70 80 90 100 0 2 4 6 8 10 12 14 16 reaction time, h m et hy l e st er c on te nt , % hoso mix ufo figure 3: methyl ester content of products as a function of transesterification time (catalyst rhizomucor miehei (lipozyme rm im)) methyl ester content of the products after 16 hours reaction time prepared by the three different immobilized lipase enzymes is summarized in fig. 4. based on the results shown in the figure it can be established that there is significant difference between the methyl ester contents of the products prepared from the same feedstock but with different lipases. methyl ester content (94–99%) was the highest in case of candida antarctica (novozym 435) immobilized lipase enzyme in case of all three feedstocks. the lowest values (63–75%) were obtained by applying rhizomucor miehei (lipozyme rm im) in all case. methyl ester content of the products (71–78%) prepared by thermomyces lanuginosus (lipozyme tl im) was between that of the previously mentioned two enzymes, but it is closer to the results obtained by applying rhizomucor miehei (lipozyme rm im). based on our results it was found that in case of all three enzyme catalysts the highest methyl ester contents were achieved from high oleic sunflower oil (hoso) and the lowest in case of the used frying oil (ufo). 94.196.999.0 73.975.277.3 63.8 70.2 74.8 0 10 20 30 40 50 60 70 80 90 100 hoso mix ufo m et hy l e st er c on te nt , % candida antarctica thermomyces lanoginosus rhizomucor miehei figure 4: methyl ester content in case of different feeds and enzymes after 16 hours reaction) summary after the transesterifications carried out at the presence of three different immobilized enzyme catalysts we found that methyl ester content of the products prepared by candida antarctica (novozym 435) was the highest in all case. methyl ester content of the products prepared from high oleic sunflower oil (hoso) and from the 50-50% mixture (mix) of high oleic sunflower oil and used frying oil satisfied the requirements (≥96.5%) of the standard (en 14214:2004). however, the products prepared from used frying oil (ufo) did not reach this limit. theoretical yield of the methyl ester containing phase was approached by 96–99%. by the application of rhizomucor miehei (lipozyme rm im) and thermomyces lanuginosus (lipozyme tl im) immobilized lipases methyl ester content of the products was significantly lower, thus it did not satisfy the limit of the standard. in case of all three enzymes methyl ester content of the products prepared from high oleic sunflower oil (hoso) was the highest, meanwhile that of used frying oil (ufo) was the lowest. methyl ester content of the product prepared from the 50-50% mixture (mix) of high oleic sunflower oil and used frying oil was between the results of the previous two. methyl ester content of the products clearly depended on the used frying oil content of the feedstock. references 1. gaio t., cordeiro j.: report of the oilprodiesel project, (2006) 2. canaki m.: bioresource technology 98 (2007) 183-190 63 3. kulkarni m. g., dalai a. k.: ind. eng. chem. res. 45 (2006) 2901-2913 4. keöves s., sárfalvi n., lakatos á., gubicza l., bélafi-bakó k.: proc. 2nd int.conf. env. eng. veszprém, (1999) 248-250 5. nemestóthy n., lakatos g., bélafi-bakó k., gubicza l.: proc. 29th int. conf. ssche, tatranska matliare, (slovakia), 2002, cd-rom 6. commission of the european communities, com(2006) 845 final, (2007) 7. commission of the european communities, com(2006) 34 final, (2006) 8. commission of the european communities, com(2006) 848 final, (2006) 9. canakci m., gerpen j.v.: transactions of asae 42 (1999) 1203-1210 10. hancsók j., kovács f., krár m.: petroleum & coal 46 (2004) 36-47 11. boocock d. g. b.: 53rd canadian chem. eng. conf. (2003) 12. riera j. b., codony r., rafecas m., guardiola f.: working document for the stoa panel (2000) 13. cvengroš j., cvengošova z.: biomass and bioenergy 27 (2004) 172-181 14. canakci m., van gerpen j.: transactions of the asae 44 (2001) 1429 15. krár m., hancsók j., kovács f., holló a., boda l.: in proceedings of interfaces’05 (2005) 17-24 16. kovács f., hancsók j., bélafi-bakó k.: in proceedings of 4th international colloquium on fuels (2003) 147-154 17. bélafi-bakó k., kovács f., gubicza g., hancsók j.: biocatalysis and biotransformation 20 (2002) 437-439 18. kovács s., krár m., beck á, hancsók j.: 15th european biomass conference & exhibition. biomass for energy, industry and climate protection, in proceedings (isbn 978-88-89407-59-x) (2007) 1747-1750 hungarian journal of industrial chemistry veszprém vol. 33(1-2). pp. 43-48. (2005) mathematical modelling in osmotic dehydration a. matusek1, b. czukor1, p. merész2, f. örsi2 1central food research institute, unit of technology h-1022 budapest, herman o. út 15., hungary 2budapest university of technology and economics, department of biochemistry and food technology h-1111 budapest, műegyetem rkp. 3., hungary e-mail: a.matusek@cfri.hu this paper was presented at the 10th international workshop on chemical engineering mathematics, budapest, hungary, august 18-20 2005 mass transfer parameters during osmotic dehydration of apple cv. idared has been studied. the solution of fick’s law for unsteady state mass transfer in rectangular configuration has been used to calculate the apparent diffusion coefficient of fructo-oligosaccharides (fos) used as osmotic agent and water. apple cubes were blanched and osmotically treated (0-60 min) in 60 % fos solution at 40 °c, sample-to-solution ratio was 1:10. total solid (ts) content of the samples was determined by gravimetric method, total soluble solid (tss) content was measured by refractometer and fos content was measured by polarimeter. the apparent diffusion coefficient of fos and water were found to be of the order of 10-9 m2/s. the model of the osmotic dehydration process is better for the water than for the fos. keywords: mathematical modelling, osmotic dehydration, diffusion coefficient, apple 1. introduction osmotic dehydration is a water removal process by immersing the fruit or vegetable in a hypertonic solution. two simultaneous counter current flows take place because of the semipermeable property of the plant cell structure: a water flow from the tissues into the solution and a simultaneous transfer of solute from the solution into the food (salvatori et al., 1999a,b). since the membrane is not perfectly selective, other solutes (minerals, vitamins, and flavours) present in the food are also leached into the osmotic solution (taiwo et al., 2002). the driving force of diffusion is the gradient of chemical potential. in practice osmotic dehydration is used for partial dehydration of foods, especially fruits and vegetables as a pre-treatment step before different drying methods or freezing (torreggiani, 1993). the rate of mass transport depends upon many factors such as concentration, temperature and the kind of osmotic solution, time of treatment, level of agitation, sample-to-solution ratio, vacuum level and different pre-treatments if applied. several studies in the literature describe the effect of these variables (lerici et al., 1985; beristain et al., 1990; lazarides et al., 1997; park et al., 2002). the conventional used osmotic agents are sucrose and sodium chloride. the purpose of present work was to study mass transfer parameters during osmotic dehydration of apple and to develop a model based on fick’s second law describing the transport phenomena in longitudinal direction. 2. mathematical modelling most of the available models proposed are based on fick’s law of diffusion and use the particular solution given by crank (1975) for one-dimensional unsteady state mass transport (salvatori et al., 1999a): 2 2 x cd t c ∂ ∂ = ∂ ∂ (1) where c is the concentration of the diffusing component, d is the diffusion coefficient, t is the time coordinate, x is the space coordinate, the diffusion path. the double mass transfer is reduced this way to only one transport process, either of water or solute. lenart & flink (1984) proposed a model that was able to predict osmotic mass transport data and water activity data for short, non equilibrium osmosis time. solution of fick’s law for short contact time diffusion was used by hawkes & flink (1978) and magee et al. (1983). kaymak-ertekin & sultanoglu (2000) developed a model for od of fruits with limited sample-to-solution ratio applying fick’s law. in order to analyse the data 44 and indicate the overall exchange of solutes and water between the apples and the osmotic solution, different parameters were determined for each sample, as water loss (wl), solid gain (sg), weight reduction (wr), soluble solid concentration (ssc). they investigated apple slices with thickness 5 mm. they used the following assumptions in the development: 1. apple slices are infinite slabs of width = 2r. 2. initial water and ssc in the apple are uniform. 3. apparent diffusion coefficient is constant (d ≠ f (c)). 4. the process is isothermal. 5. simultaneous counter-current flows; the diffusion of water from the apple and the diffusion of sugar into the apples are only considered. 6. a sugar solution film is thought to be at the surface of the apple as a boundary layer. being a part of the apple, this film is assumed to the equilibrium concentration and the process is directly proceeded by diffusion. 7. shrinkage is neglected. in this model, using a mass balance on water movement inside the food, the rate of water loss was obtained as a function of time (azuara et al., 1992): ts wltswl 1 1 1 )( + = ∞ (2) where wl is the fraction of water loss at time t, wl∞ the fraction of water loss at equilibrium, s1 the model constant related to the rate of water loss and t is the time. 100 0 00 m xmxm wl w tt w − = (g/100g fresh sample), where m0 is the initial mass of sample, m1 the mass of the sample at time t, x0 w the initial water concentration of sample, xt w the water concentration of sample at time t. similarly for solid gain, it can be written as: ts sgts sg 2 2 1 )( + = ∞ (3) where sg is the fraction of solid gain at time t, sg∞ the fraction of solid gain at equilibrium, s2 the model constant related to the rate of sg. 100 0 00 m xmxm sg tsts tt − = (g/100g fresh sample), where x0 ts the initial total solids concentration of the sample and xt ts is the total solids concentration of the sample at time t. using wl and sg values calculated from the experimental data at different processing times, the wl∞, s1 and sg∞, s2 can be estimated from the slope and intercept of the plot t/wl or t/sg vs t of the linearized form of eq.(2) and eq.(3) respectively. therefore the equilibrium solute concentration can be estimated from a mass balance equation derived as: ∞ ∞ ∞ +− − = wlmws sgmws w s s s 000 000 )1( (4) where s0 is the mass of the initial osmotic solution, w0 s the initial ssc and w∞ s is the ssc at equilibrium. solving eq.(1) numerically by the crank-nicholson method – at each time step the concentration profiles can be calculated numerically without considering the other component. then concentration at each time step could be adjusted considering the other component changes in the same step calculated numerically from the eq.(1). if t and x are the subscripts indicating the time and position, at time t or at time t+1 the concentrations can be given as: s xt w xt w xtw xt mm m c ,, , , + = s xt w xt w xtw xt mm m c ,1,1 ,1 ,1 ++ + + + = (5) s xt w xt s xts xt mm m c ,, , , + = s xt w xt s xts xt mm m c ,1,1 ,1 ,1 ++ + + + = (6) since the concentrations can be calculated and the masses of water and soluble solids at each position are known, m values at time t+1 can be calculated from eqn.(5) and (6); total mass of water and soluble solids of fruit are estimated by sum of the masses at different positions. the wl and sg values were calculated from the experimental data. the concentration at time t is obtained from a mass balance equation derived as sgwl xsg x ts ts t +− + = 1 0 (7) where xt ts is the total solids concentration at time t and x0 ts is the initial total solids concentration. a model fitted to the experimental values and the apparent diffusivities of solute and water can be obtained by the trial and error method. both diffusion coefficient representing water loss and solid gain are found to be in the range of 10-10 – 10-11 m2/s. beristain et al. (1990) developed a model based on crank’s equation. they also used the solution of eqn.(1) gave by crank (1975): ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ − ++ + σ−= ∞ = ∞ 2 2 221 exp 1 )1(21 l tdq qwl wl n n n t αα αα (8) where wlt is the weight of water loss at time t; wl∞ is the water loss at time ∞; α is the volumetric ratio of syrup to sample; qn positive roots other than zero of equation: tan qn = -αqn. the maximum fraction of water that a sample (pineapple ring) can lose, for given concentration of sucrose solution was determined; diffusion coefficients were calculated using park’s method (crank, 1975). the main limit of models based on fick’s law of diffusion is that the resulting diffusivities are a combination of the respective water and solute diffusivities and the probably interaction of the flows. furthermore these methods neglect spatial distribution of the osmotic effect (salvatori, 1999a). salvatori developed a model in terms of the advancing rate of 45 disturbance front in the osmosed plant tissues. diffusion coefficient was calculated by using a non simplified fick’s equation in terms of concentration profiles. they described the changes in plant tissues with the “advancing disturbance” front (adf), later they (salvatori et al., 1999b) developed generalised equations – on the base of the adf – to describe the concentration profiles and the average concentration during od process. regarding to the geometry of the food the mass transport phenomena occur during osmotic dehydration can be analysed in rectangular and in cylindrical configurations. rastogi et al. (1997) studied the effect of temperature and concentration of the osmotic solution on the od of banana, they determined the effective diffusion coefficient of water by the use of fick’s ii law in terms of cylindrical coordinates (r, θ, z, crank, 1975): ⎭ ⎬ ⎫ ⎩ ⎨ ⎧ ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ ∂ ∂ ∂ ∂ +⎟ ⎠ ⎞ ⎜ ⎝ ⎛ ∂ ∂ ∂ ∂ +⎟ ⎠ ⎞ ⎜ ⎝ ⎛ ∂ ∂ ∂ ∂ = ∂ ∂ z crd z c r d r crd rrt c θθ 1 (9) for long cylinders (∂c/∂z=0), assuming the diffusion to be radial (∂c/∂θ=0) and concentration (c) to be a function of radius (r) and time (t) only, eqn.(9) reduces to: ⎭ ⎬ ⎫ ⎩ ⎨ ⎧ ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ ∂ ∂ ∂ ∂ = ∂ ∂ r crd rrt c 1 (10 ) considering boundary condition for t>0, c=c0, at r=a and initial condition for t=0, c=c1, 0<r<a, the solution of eqn.(10) can be written as (crank, 1975): )( )()exp(21 0 2 1 10 1 ntn nn t n aj rjtd acc cc αα αα− σ−= − − = (11) where j0 is the flux of diffusion (fick i.), aαn are the roots of the equation j0(aαn)=0. if mt and m∞ denote the amount of water diffused from banana at times t=0 and t=∞ respectively, in the case of osmotic dehydration eqn.(11) can be rewritten for the diffused moisture ratio (mt/m∞) in terms of an effective diffusion coefficient (de), which accounts for the variation in diffusion coefficient (d) due to changes in the physical structure of the food, as: ( ) (12) td am m ne n n t 2 221 exp41 α α −σ−= ∞ = ∞ if the fourier number of diffusion (f0) is given by the equation (13) 2 0 / atdf e= where de is the effective diffusion coefficient, eqn.(12) can be written as ( ) [ ] (14) 2 021 )(exp41 n n n t af am m α α −σ−= ∞ = ∞ in our earlier study the mass transport was investigated during osmotic dehydration of carrot cylinders in longitudinal and also in radial direction (matusek & merész, 2002). in the case of radial diffusion the equation derived from fick first law (eqn.15) and second law (eqn.16) in a cylindrical coordinate system was used to describe the diffusion coefficient (dr,s): r rcdj srr ∂ ∂ −= )( , (15) ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ∂ ∂ + ∂ ∂ = r c rr cd dt dc sr 1 2 2 , (16) where jr is the flux density of soluble solid at radius r. if the diffusion was constant, eqn.(16) equal to zero. the equation is referred as: 01 2 2 = ∂ ∂ + ∂ ∂ r c rr c (17) if z r c = ∂ ∂ , is substituted, than z rr z 1 −= ∂ ∂ , (18) that can be transformed to eqn.: r r z z ∂ = ∂ (19) solution is: (20) )ln()ln( 1 rkz −= back-substitution of z lead to the eqn.: r k r c 1 2= ∂ ∂ (21) that gives a logarithmic solution for the distribution of the concentration in the media: )ln(20 rkcc =− (22) solving the fick’s second law for stationary diffusion in descartes system assuming finite diffusion, substituting in the eqn.(1) the expression: c(t,x)=ct(t)cx(x), can be : 2 2 dx cddc dt dcc x t t x = (23) solution of the eqn.(23) gives: 0 2 4 .)ln( 2 2 x dkonst c d dt cd x dx cd t x π −=== (24) substitution of cx: ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ = 02 cos: x xcx π (25) leads to the differential eqn.: x x c xdx dc 2 0 2 4 π −= (26) than the changes of concentration distribution can be expressed as a function of time: 46 ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −= 2 0 2 4 exp. x tdkonstct π (27) the eqn.(27) can be transformed to cylindrical coordinate system considering the bessel function is the equivalent of the cos function in the cylindrical system: ( ) ( ) ),(0 24 2 , rtcrie brr tisrd =− ∞ (28) where i∞ is the abscissa value at first zero ordinate value of the zero order bessel function (i∞=2,4048), dr,s is the radial diffusion coefficient of the solid, r is the radius of the cylindric sample, rb is the radius of the plastic tube in the centre of the sample cylinder, (r – rb) difference is the geometric parameter, the diffusion distance. the linearized distribution of concentration in the eqn.(28) and the slope of the linear function presenting the concentration differences as a function of time give the apparent diffusion coefficient: 2 2 , )( b sr rr i ds − −= ∞ (29) where s is the slope of the linear function fit to observed data: ts c cc t ⋅=⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ − ∞ ∞ln (30) in this study we used the solution of fick law ii. in a rectangular coordinate system eqn.(27) to determine the diffusion coefficient of fos and water in the apple samples (matusek & merész, 2002): ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ⋅−= 2 0 2 , 4x ds sl π (31) where s is the slope of the linear function fit to observed data eqn.(30), and dl,s is the longitudinal diffusion coefficient of the solved component, xo: is the geometric parameter: the diffusion distance. the apparent diffusion coefficients dr,s and dl,s can be calculated having known the other variables in the eqn.(29) and eqn.(31) in the case of radial or longitudinal diffusion respectively. 3. materials and methods apples of the idared variety (86% w/w moisture content, soluble solids content ≅ 13 r%) were purchased from the local market and stored at 1-4 °c, 94-96 rh until use. raftilose® p95, (orafti) was used as osmotic agent. raftilose® p95 is a fructooligosaccharide product from chicory inulin. the carbohydrate composition of the product is: oligofructose (degree of polymerisation: 2-8) ≥ 93,2 %; glucose + fructose + sucrose ≤ 6,8 %. a few hours prior to use the apples were left to equilibrate at room temperature. they were peeled manually and cut into 1x1x1 cm cubes after removing the pericarp. apple cubes were immersed into a 1% citric-acid solution to inhibit enzymatic browning. blanching was carried out under atmospheric conditions at 70 °c, for 5 minutes, the sample-tosolution ratio was 1:10. continuous agitation was used (ν = 140 1/min). osmotic dehydration was carried out also at atmospheric pressure at 40 °c, sample-tosolution ratio was 1:10, and the level of agitation was 140 1/min. samples were taken out from the solution in every 5 minutes till 60 minutes. they were blotted on a filter paper and weighed. moisture content (mc) of the samples was measured gravimetrically, total soluble solid (tss) content was determined by refractometer (carl zeiss, jena) and fos content was measured by polarimeter (carl zeiss, jena). for the polarimetric method apple samples were rehydrated and homogenized with distilled water, carrez i. and ii. solutions and ethanol were add to precipitate the macromolecules. after 18 hours cooling the sample was filtrated under vacuum and the solution was measured by polarimeter. 4. results and discussion it was observed, that increased od time result in increased tss by logarithmic curve (fig. 1), as well as fos content and it decreased moisture content (fig. 2). the apparent diffusion coefficient of fos and water were found to be of the order of 10-9 m2/s (table 1). table 1: apparent diffusion coefficients apparent diffusion coefficient [m2/s] fos 3,14 ⋅ 10-9 10 15 20 25 30 35 0 5 10 15 20 25 30 35 40 45 50 55 60 time of od process [min] re fr ac tio n [r e ] water 2,57⋅ 10-9 a correlation analysis for calculated (c-fos) and measured (m-fos) fructo-oligosaccharides content gives high correlation coefficient (r2 = 0,863). the relationship for apple cubes (fig. 3): 40 f % figure 1. effect of od process time on tss content 47 m-fos = -0,4123 + 1,0151 (c-fos) (32) the correlation analysis for calculated (c-mc) and measured (m-mc) moisture content gives high correlation coefficient (r2 = 0,988). the relationship for apple cubes (fig. 4): 60 65 70 75 80 85 90 0 5 10 15 20 25 30 35 40 45 50 55 60 time of od process [min] m c [% ] m-mc = 5,5084 + 0,9218 (c-mc) (33) conclusion the model describes the osmotic dehydration process better in the case of fos than in the case of water. the correlation analysis for measured and calculated values gives higher coefficient for water diffusion regarding to the better deviation attribute of the moisture determination, but the deviation attribute of the refraction is lower, as higher the standard error of prediction (sep). the lower value of the fos correlation coefficient appoints that the fos intake is a complex phenomenon containing diffusion and other mechanisms too. the presumed hypothesis that the water leakage from the fruit tissue is characterised by diffusion mechanism based on fick laws is verified by the relationship between the measured and calculated data. the slope of the relationship is very closed to the value 1 and the axis section is closed to zero that shows the better applicability of the model for the prediction of fos diffusion than that of water. figure 2. effect of od process time on moisture content 30 s acknowledgement the authors thank to dr. j. bódiss helping in numerical analysis. references 1. azuara, e., cortes, r., garcia, h.s. & beristain, c.i. (1992); kinetic model for osmotic dehydration and its relationship with fick’s second law. international journal of food science and technology, 27, 239-242. 2. beristain, c.i., azuara, e., cortés, r. & garcia, s. (1990); mass transfer during osmotic dehydration of pineapple rings. international journal of food science and technology, 25, 576-582. 5 10 15 20 25 5 10 15 20 25 30 c-fos m -f o figure 3: relationship of measured (m-fos) values and calculated (c-fos) values 3. crank, j. (1975); the mathematics of diffusion (2nd ed.). uk: oxford university press. 65 70 75 80 85 65 70 75 80 85 c-mc m -m c 4. hawkes, j. & flink, j. m. (1978); osmotic concentration of fruit slices prior to freeze dehydration. journal of food processing and preservation., 2, 265-284. 5. kaymak-ertekin, f. & sultanoglu, m. (2000); modelling of mass transfer during osmotic dehydration of apples. journal of food engineering, 46, 243-250. 6. lazarides, h. n., gekas, v. & mavroudis, n. (1997); apparent mass diffusivities in fruit and vegetable tissues undergoing osmotic processing. journal of food engineering, 31, 315-324. 7. lenart, a. & flink, j. m. (1984); osmotic concentration of potato. i. criteria for the endpoint of the osmosis process. journal of food technology, 19, 45-63. figure 4: relationship of measured experimental m-mc values and calculated c-mc values 48 8. lerici, c. r., pinnavaia, g., dalla rosa, m. & bartolucci, l. (1985); osmotic dehydration of fruit: influence of osmotic agents on drying behaviour and product quality. journal of food science, 50, 1217-1219. 9. magee, t. r. a., hassaballah, a. a. & murphy, w. r. (1983); internal mass transfer during osmotic dehydration of apple slices in sugar solutions. irish journal of food science and technology, 7, 147-155. 10. matusek, a. & merész, p. (2002); modelling of sugar transfer during osmotic dehydration of carrots. periodica polytechnica ser. chem. eng., 46, 83-92. 11. park, k. j., bin, a., brod, f. p. r., brandini park, t. h. k. (2002); osmotic dehydration kinetics of pear d’anjou (pyrus communis l.). journal of food engineering, 52, 293-298. 12. rastogi, n. k., raghavarao, k. s. m. s. & niranjan, k. (1997); mass transfer during osmotic dehydration of banana: fickian diffusion in cylindrical configuration. journal of food engineering, 31, 423-432. 13. salvatori, d., andrés, a., chiralt, a. & fito, p. (1999a); osmotic dehydration progression in apple tissue i: spatial distribution of solutes and moisture content. journal of food engineering, 42, 125-132. 14. salvatori, d., andrés, a., chiralt, a. & fito, p. (1999b); osmotic dehydration progression in apple tissue ii.: generalized equations for concentration prediction. journal of food engineering, 42, 133-138. 15. taiwo, k. a., angersbach, a. & knorr, d. (2002); influence of high intensity electric field pulses and osmotic dehydration on the rehydration characteristics of apple slices at different temperatures. journal of food engineering, 52, 185-192. 16. torreggiani, d. (1993); osmotic dehydration in fruit and vegetable processing. food research international, 26, 59-68. 17. rendszergazda rectangle microsoft word 2012_dr_bodor_endre_hjic.doc hungarian journal of industrial chemistry veszprém vol. 39(3) pp. 341-348 (2011) cellulase and hemicellulase enzymes as single molecular nanobiocomposites i. hegedüs1, e. nagy 1, j. kukolya2, t. barna3, cs. a. fekete3 1university of pannonia research institute of chemical and process engineering egyetem u. 10. h-8200 veszprém, hungary, tel.: +3688-624040, fax: +3688-624038 e-mail: nagye@mik.vein.hu 2szent istván university, department of environmental protection & environmental safety páter k. u. 1. h-2100, gödöllő, hungary 3university of debrecen, research institute of genetics and applied microbiology egyetem tér 1. h-4032, debrecen, hungary we have worked out two different stabilization procedures for glycolytic enzymes with significant biotechnology relevance: for the commercial novozyme cellulase complex (celluclast) and for recombinant thermobifida fusca hemicellulases (β-d-xylosidase and β-d-mannosidase). in the applied methods, individual cellulase and hemicellulase enzyme molecules were conjugated with a polymer nano-layer providing nanobiocomposites (single enzyme nanoparticles, sens) that exihibit an excellent stability under extreme conditions. the first method that we have been successfully used earlier on chymotrypsin [3], creates a polymer layer around the enzyme molecules with trimethoxysilyl (tms) functionalities in three steps [4]. the second stabilization method is a novel one pot reaction resulting in an acrylamide-bisacrylamide (aa) copolymer layer around the enzyme molecules in two steps. the heat stability of the developed single enzyme nanoparticles with tms and aa nanolayers were tested at two different temperatures (+4 °c; 80 °c) following the residual activities of the modified enzymes in regular time interval. upon incubation of the cellulase complex nanoparticles with tms and the non-modified cellulase at 80 °c, the nanoparticle has kept its 40% of its starting cellulase activity after 6 hours, whereas the non-modified enzyme lost its activity completely in half an hour. the relative activity of sens with aa is about 50% of the initial activity. after 12 hours under 80 °c the activity of nck is reduced to 14%, while the activity of ncka is 24% of the activity of the native enzyme at the start of the incubation. the nanoparticles of the thermobifida fusca hemicellulases (β-d-xylosidase and β-d-mannosidase) obtained from both tms and aa nanolayers have exhibited concomitant stability increase. tms nanoparticles of β-xylosidase has lost 60% of its activity after 120 days during an incubation procedure at +4 °c, whereas the non-modified β-xylosidase lost all its activity in 40 days during the same conditions. the 40% of the starting enzyme activity of β-d mannosidase with aa has remained after 6 hours, during an incubation process at 80 °c, the activity of the non-modified enzyme has lost in one hour. keywords: thermostable enzymes, single enzyme nanoparticles, hemicellulases, thermobifida fusca species. introduction extremophilic organisms require physically or geochemically extreme conditions that are harmful for most other organisms on earth. thermophilic organisms are a type of extremophile organisms that lives at relatively high temperatures, between 45 °c and 80 °c. cellular components of thermophilic organisms (enzymes, proteins and nucleic acids) are also thermostable. thermostable enzymes are highly specific and thus have considerable potential for many industrial applications [1]. thermobifida spp. are gram-positive, compostand soil-inhabiting bacteria with broad decomposing activity on plant cell wall constituents. thermobifida fusca, the most extensively studied species of this genus, is the model organism of thermophilic, aerobic cellulolytic bacteria. thermobifida fusca produces multiple extracellular enzymes including cellulases that are responsible for the decomposition of cellulose and lignocellulose residues, which make up the bulk of agricultural and urban wastes (fig. 1). while there are several data on the cellulolytic system of t. fusca, the hemicellulolytic enzyme system of this species is still poorly characterized [1]. hemicelluloses act as linkers between lignin and cellulose. the high percentage of hemicellulose fraction in the cell wall of higher plants makes this material the second most abundant biopolymer in nature. single enzyme nanoparticles (sens) represent a new approach in industrial enzyme research [2, 3] (fig. 2). 342 figure 1: hyphal surface of thermobifida fusca tm51 a) smooth surface of mycelium grown on glucose b) cellulosome-like structures emerged upon induction by cellulose c) cellulosome-like structures at higher magnification 3. single enzyme nanoparticles:individual enzyme molecules surrounded by α) organic/inorganic hybrid polymer e γ) magnetic nanolayer e 3 o 4ef β) mezoporous silica β) organic nanogel e e a) polymer layer: b) inorganic layer: e e e α) hollow metal sphere 3. single enzyme nanoparticles:individual enzyme molecules surrounded by α) organic/inorganic hybrid polymer ee γ) magnetic nanolayer e 3 o 4ef γ) magnetic nanolayer e 3 o 4ef e 3 o 4e e 3 o 4ef β) mezoporous silica β) organic nanogel eee ee a) polymer layer: b) inorganic layer: e e e α) hollow metal sphere e e e ee ee ee α) hollow metal sphere a) hyperbranched polymers cds e e e e e e cdscds ee ee ee ee ee ee au ee e e e e auau eeee ee ee ee ee fe3o4 e e e e e e e fe3o4 ee ee ee ee ee ee ee e eeee ee 2. immoblization into nano-size carriers 1) nanoparticles as carriers on the surface a) metal nanoparticles b) magnetic nanoparticles b) dendimers ee e e e e e ee e e e e 3. single enzyme nanoparticles:individual enzyme molecules surrounded by α) organic/inorganic hybrid polymer e γ) magnetic nanolayer e 3 o 4ef β) mezoporous silica β) organic nanogel e e a) polymer layer: b) inorganic layer: e e e α) hollow metal sphere 3. single enzyme nanoparticles:individual enzyme molecules surrounded by α) organic/inorganic hybrid polymer ee γ) magnetic nanolayer e 3 o 4ef γ) magnetic nanolayer e 3 o 4ef e 3 o 4e e 3 o 4ef β) mezoporous silica β) organic nanogel eee ee a) polymer layer: b) inorganic layer: e e e α) hollow metal sphere e e e ee ee ee α) hollow metal sphere a) hyperbranched polymers cds e e e e e e cdscds ee ee ee ee ee ee au ee e e e e auau eeee ee ee ee ee fe3o4 e e e e e e e fe3o4 ee ee ee ee ee ee ee e eeee ee 2. immoblization into nano-size carriers 1) nanoparticles as carriers on the surface a) metal nanoparticles b) magnetic nanoparticles b) dendimers ee e e e e e ee e e e e figure 2: nanotechnological methods for enzyme stabilization the form of sen means, that each enzyme molecule are surrounded with a nanometer scale polymer matrix layer, resulting in stabilization of enzyme activity without any serious limitation for the substrate transfer from solution to the active site of the enzyme. the synthesis of sen particles is available via more or less simple laboratorial technique. previously we have decided to apply this technique for industrial bioethanol synthesis able to comply with the requirements of green chemistry. we would like to investigate that how can the senenzymes digest higher-size substrates. single enzyme nanoparticles can be used for stabilization of enzymes in industrial enzyme research. using mesoporous silica gels single enzyme nanoparticles can be fixed into the inner wall of the mezoporous gel and it means that nanoreactors can be fabricated [2]. the polymer layer of the single enzyme nanoparticles is electrodense to transmission electron microscopic detection the structures of the enzyme complexes can be realized easily. polymers composed with maps monomers have a good biocompatibility and has no toxicity [14, 16]. we investigated the chemical stability of different enzymes and enzyme complexes in the form of sen. otherwise a numerous types of enzymes and proteins (lipases, bovine serum albumin and hemicellulases from thermobifida fusca) can not be solved in hexane. recently a new technique was found, which does not need any specific solution 343 technique in hexane because the polymerization of the nano-layer around the enzyme molecules can be realized in water media. for the polymerization we used a mixture of mono and bifunctional monomers (acrylamide and bisacrylamide mix), the preparation of enzyme nanoparticles can reduced to one-pot reaction with two steps [4]. materials and methods enzymes novozyme celluclast bg cellulase enzyme complex (ck) and thermobifida fusca wild type endomannanase (em), β-xylosidase (xi), β-mannosidase (mn) and mutant β-mannosidase (mm) glycolytic enzymes were used in these experiments. hemicellulase enzymes were hererologously expressed as his-fusion protein constructs in escherichis coli bld21 host and were further purified by affinity chromatography on ninta-agarose beads and isolated as a 95% homogeneous, highly active enzyme sample by józsef kukolya (szent istván university, faculty of agriculture and environmental sciences) and terez barna and csaba attila fekete (university of debrecen; department of genetics and applied microbiology). other chemicals acryloyl chloride, 1,3-bis[tris(hydroxymethyl)-methylamino]propane or bis-tris propane (sigma), sodium bis(2-ethylhexyl) sulphosuccinate or aerosol ot (aot) (fluka), disodium hydrogen phosphate, potassium dihydrogen phosphate, calcium chloride, 2-propanol, n-hexane (spektrum-3d, scharlau), methacryloxypropyltrimetoxysilane (tms), 2,2-azobis(2,4-dimethylvaleronitrile) (fluka), 3,5-dinitro-salicylic acid (sigma), acrylamide (sigma), bisacrylamide (sigma), tetraethylorthosylicate (teos, sigma), ammoniumperoxodisulphate (sigma), paranitrophenyle-β-d-mannopyranoside (sigma), paranitrophenyle-β-d-xylopyranoside (sigma). h2o (hydrolysis) (sylanol condensation) protein modification on the surface nh2 o cl nh c o nh c o polymerization on the surface o o si (ome)3 nh c o o o si (ome)3 n protein with polymer chains modified protein protein with electrodense polymer layer protein modified protein p protein with polymer chains nh c o oo si (ome) 3 n = = electrondense parts of the polymer layer = = modified parts on the surface of the protein p pp pp figure 3: thee-step method to synthesize single enzyme nanoparticles instruments cryostate was used to keep the reaction mixture at 0 °c. a gas chromatographic syringe (volume 5 μl) was used for the addition of a few microlitres of acryloyl chloride to the enzyme solution. the polymerization step in the synthesis of single enzyme nanoparticles (sen) was carried out in a double-walled stirring vessel. the solution was irradiated by a uv-lamp made by vilber-lourmat. filtration of the surface-polymerized enzymes was carried out with a syringe filter (pore size 0.1 μm) made by millipore. uv-spectra were recorded and enzyme activity measurements carried out by means of a biochrom 4060 spectrophotometer made by pharmacia. a new brunswick scientific g24 incubator shaker was used for the stability measurements. for the detection of the size distribution of the enzyme nanoparticles malvern zeta-sizer was used. 344 e + acrylamideacrylamide bisacrylamidebisacrylamidee enzymeenzyme moleculemolecule ((modifiedmodified onon thethe surfacesurface)) singlesingle enzymeenzyme nanoparticlenanoparticle ee + acrylamideacrylamide bisacrylamidebisacrylamideee enzymeenzyme moleculemolecule ((modifiedmodified onon thethe surfacesurface)) singlesingle enzymeenzyme nanoparticlenanoparticle figure 4: one-pot reaction to synthesize single enzyme nanoparticles methods synthesis of sen: we used two methods for the preparation of single enzyme nanoparticles (sen). the first method has three steps (fig. 3). the description of the procedure was detailed earlier [2, 3]. the first step is a modification of ck enzyme complex and its solubilization in a hydrophobic medium. the second step is the polymerization of the vinyl group in hexane, and the final (third) step is hydrolysis and condensation of the trimethoxysilyl functional group (tms). for the polymerization step, the enzyme should be dissolved in a hydrophobic medium (n-hexane). the surfaces of the enzymes have hydrophobic and hydrophilic regions. if hydrophilic parts of the surface of the enzymes are covered by surfactant molecules, the enzyme lost its hydrophilic characteristic and became hydrophobic, so hydrophobic solvents, e.g. hexane can solve it easily. during this complexation ion-pairs make bounds between the ionic part of the surfactant and the ionic part on the surface of the enzyme. for the polymerization on the surface of the enzyme direct contact is necessary between the enzyme surface and the hexane medium (fig. 3). in this process, vinyl groups on the enzyme surface (synthesized in the first step) are well exposed to the organic solvent (and reagents). preparation of single enzyme nanoparticles can be realized also using a one-pot reaction (fig. 4) [4]. this method has two steps. the first step is the modification of the surface of the enzymes (this step is similar in both method). the second step is a polymerization in water media using acrylamide and bisacrylamide substrates as mixtures (9: 1 molar ratio of acrylamide: bisacrylamide). measurement of enzyme activities: in the case of cellulase enzymes whatman filter paper was used as substrate (filter paper unit, fpu) and total cellulase activity was measured using dns-probe [17]. activities of hemicellulase enzymes was measured using chemically modified substrates. the activity of β-d-mannosidase was measured using paranitrophenyle-β-d-mannopyranoside as substrate. activity was calculated by the absorbance changes at 400 nm. activity of β-d-xylosidase was measured and calculated in similar way using paranitrophenyle-β-d-xylopyranoside as substrate. (enzyme concentrations were calculated by absorbance at 280 nm using molar extinction coefficients.) results and discussion two methods were used to synthesize enzyme nanoparticles. the first method (by kim at al., [2, 3]) contains three steps and the second method (by yan et al., [4]) is a one-pot reaction. enzyme nanoparticles using β-mannosidase and cellulase enzymes were created by both methods and therefore we can compare the yields of the enzyme nanoparticles using these methods. effectivity of methods during the synthesis steps of the kim method, the yields of the products at the end of each step could be less and less than the initial amount of enzymes before the stabilization processes. hemicellulase enzymes from thermobifida fusca species precipitated at the first step because these enzymes are very sensitive for phchanges. therefore the yields of the enzyme nanoparticle products from these hemicellulase enzymes are very low, less than 5 percent (except β-xylosidase enzyme, where the yield of enzyme nanoparicle is about 12%, table 1). but even in the case of cellulose enzyme complex from t. reesei (celluclast bg from novozymes), where each step has resulted in a relatively good yield (more, than 60%), at the end of the whole process the yield became only 15–25% (table 2, first column). the second method (by yan et al.) does not contain phase transfer or solution change steps [4], therefore much higher yield could be achieved at the end of this stabilization process than that of the kim’s method (table 2). table 1: yields of enzyme nanoparticles of thermostable hemocellulase enzymes (from thermobifida fusca) using method by kim et al. type of enzymes β-mannosidase mutant β-mannosidase β-xylosidase endomannanase sign mn–12 mm–2 xi–6 em–4 amount [mg] and yield (η) of enzyme nanoparticles 0.525 (η = 3.50%) 0.782 (η = 4.01%) 3.712 (η = 12.37%) 0.280 (η = 4.15%) 345 table 2: comparison of the yields of enzyme nanoparticles using two methods methods kim et al. (3 step process) yan et al. (one pot reaction) β-mannosidase 7%*70%*60%= =3% 2211%% y ie ld s [ % ] cellulase enzyme complex 60%*70%*60%= =15-25% 4477%% size distribution we have examined and followed the size distribution of endomannase nanoparticles with aa monolyers and tms monolayers. the peak of the size distribution of the non modified endomannanase enzyme (em/water) was about 6 nm. there was no difference between the size of the non-modified em enzymes and the surfacemodified acrylated em enzymes. in contrast, using the three step kim method, the size distribution of the endomannanase enzyme nanoparticles were varied during the preparation using the kim’s method. the range of the size distribution of the em nanoparticles after the hydrophobic ion pairing process measured in the hexane phase are between 5–11 nm (em/hexane, fig. 5a). after the third step (polymerization with tms) there was a further increase in the size and the peak of the size distribution of the sen-endomannanase (sen– em/water) is about 15 nm (fig. 5a). in fig. 5b we compared the size distributions of sen-products in the case of three different enzymes (em = endomannanase, mm = mutant mannosidase, mn = β-mannosidase, xi = β-xylosidase enzyme, fig. 5b). sen–em and sen–mm products have about same size but sen–mn and sen–xi have higher peak of their size distribution (about 60 nm). for a good enzymatic function of β-xylosidase enzymes has a quaternary structure it is a homotetramer. the monomeric form of β-xylosidase has no enzymatic activity. results suggest that this technique could preserve the fine interactions between the enzyme molecules and the quaternary structures could remain during the process. figure 5: a) size distribution of endomannanase enzyme (em) during the three step process of preparation. b) size distribution of different type of single enzyme nanoparticles after the solution in hexane using hydrophobic ion pairing (em = endomannanase, mm = mutant mannosidase, mn = β-mannosidase, xi = β-xylosidase enzyme) stability measurements incubating the single enzyme nanoparticles from βxylosidase enzyme with tms at +4 °c for a long period of time, 40% of the enzyme activity has remained after 120 days, while the non-modified β-xylosidase enzyme lost its activity after about 40 days (fig. 6). incubation of the enzyme nanoparticles from β-mannosidase with aa at high degree (80 °c), has decreased the mannosidase starting activity to 40% in 6 hours, whereas the nonmodified enzyme has lost its activity after a half an hour under the same conditions (fig. 7). in both cases after a short period of the intensive reduction in the sen’s activity was observed, then there were no further activity loss, and 40% of initial activity was remained. 346 figure 6: stability of sen β-xylosidase enzymes (with tms) and control β-xylosidase enzymes at +4 °c 0,0 0,5 1,0 0,0 1,0 2,0 3,0 4,0 5,0 6,0 time [hours] re la ti ve  a ct iv it y  [% ] �  = sen,  ■ = native enzyme figure 7: stability of sen β-mannosidase enzymes (with aa) and natural β-mannosidase enzymes at 80 °c cellulase enzymes (celluclast bg enzyme complex from novozymes) nanoparticles were prepared with both methods and the resulted activities and the stabilities of the modified enzymes were compared. nck is the designation for the enzyme nanoparticles using tms based nanolayer and ncka refers to the enzyme nanoparticles using acrylamide-bisacrylamide mixture (aa) for the polymerization. when double amount of monomers incorporated in the nanolayer, the resulted enzyme nanoparticle is distinguished as ncka–1 from ncka–2, where the layer contains the usual amount of monomers. we summarize the heat stability of the cellulose nanoparticles obtained by the different methods incubating them at 80 °c, in fig. 8. both method is able to stabilize the cellulase enzyme complexes at 80 °c. although the greatest stability increase has obtained in case of ncka–2 enzyme nanoparticles when 50% of the initial activity has remained after 12 hours incubation at 80 °c. we also compared the specific activities of the different cellulose enzyme complex nanoparticles (fig. 9). the results show that the specific activity of nck (polymer layer around the enzymes with tms) is more, than 20% of the non-modified enzyme at the start of the incubation. in the case of ncka–2 its activity is 47% of the non-modified ck enzyme at the start of the incubation. after 12 hours incubation at 80 °c, the activity of nck is reduced to 14%, whereas the activity of ncka–2 is 24% of the activity of the non-modified enzyme at the start of the incubation. the initial activity of ncka–1 (double amount of monomers in the layer) is about 12% and does not changed during the incubation period. the stability of β-d mannosidasesen of thermobifida fusca strain tm51 under 80 °c is also higher than that of the non-modified enzyme. the nmna (single enzyme nanoparticles from β-d mannosidase using polymer layer around the enzymes with aa) has about 40% of its original activity, while the native enzyme lost its activity after one hour incubation. figure 8: stability of cellulase enzyme nanoparticles (ck = native cellulase enzyme complex, ncka–2 cellulase enzyme nanocomposites with aa at 80 °c) figure 9: comparison of the activities of cellulase enzyme complex using different methods to stabilize them as enzyme nanoparticles (ck = natural cellulase enzyme complex, nck = cellulase enzyme nanoparticles with tms, ncka–1 cellulase enzyme nanoparticles with aa (higher thickness), ncka–2 cellulase enzyme nanocomposites with aa (usual thickness) at 80 °c conclusions cellulase and hemicellulase enzyme nanoparticles were synthesized to stabilize the enzymes under industrial conditions. thermostable enzymes from thermobifida fusca (β-d-mannosidase, β-d-xylosidase, endomannanase and mutant β-d-mannosidase enzymes) are sensitive for ph-changes and became precipitated during the synthesis 347 steps using the kim’s method [3]. although using a one pot process to stabilize enzymes as single enzymes nanoparticles (yan’s method [4]), the stabilization was successful. size distribution of em enzyme shows that after each step of stabilization process the size of the enzyme nanoparticles change from 6 nm to 9 nm and 11–12 nm. we can compare the specific activities of the obtained nanoparticles, the results show that in the case of tms layer the specific activity is 20% of the native enzyme at the start of the incubation. in the case of sens with aa layer its activity is 47% of the native ck enzyme at the start of incubation. the stability of sen β-xylosidase is higher than that of the non-modified enzyme at 4 °c (with tms) and 80 °c (with aa). while the non-modified enzyme lost its activity in 15 min at 80 °c without stirring, the sen–xi remains 40% of its activity after 6 hour incubation. both types of layers are able to increase the β-xylosidase heat stability even at 80 °c. the heat stability of β-mannosidase (with aa) and cellulase enzyme complex (ck with tms and aa) was investigated at 80 °c without stirring. whereas the nonmodified enzymes lost their activity after a 0.5-1 hour time period incubation at 80 °c, the stabilized enzyme complexes (mn with aa, ck with tms and aa) still possess their activities after a 6 hour time period incubation. β-mannosidase enzyme (stabilized with aa) has kept the 40% of its initial activity. cellulase enzyme complex (ck) with aa layer showed a slightly better stability at 80 °c during 12 hour incubation period, since its starting actvity has reduced only to 50%. abbrevations aa acrylamide-bisacrylamide aot sodium bis(2-ethylhexyl) sulfosuccinate (aerosol ot) ck celluclast bg cellulase enzyme complex (novozymes) em endomannanase mm mutant mannosidase sen single enzyme nanoparticles mn β-mannosidase nck cellulase enzyme nanobiocomposites from ck (method kim et al.) ncka cellulase enzyme complex nanobiocomposites from ck (method yan et al.) tem transmission electron microscope tms methacryloxypropyltrimethoxysilane, or trimethoxysilyl functional group xi β-xylosidase acknowledgments this work was supported by the national development agency grant (támop-4.2.2/b-10/1-2010-0025). references 1. j. kukolya, i. nagy, m. láday, o. oravetz, k. máraligeti, l. hornok: thermobifida cellulolytica sp. nov., a novel lignocellulosedecomposing actinomycete, international journal of systematic and evolutionary microbiology, 52 (2002) 1193–1199 2. j. kim, j. w. grate, p. wang: nanostructures for enzyme stabilization, chemical engineering science, 61(3) (2006) 1017–1026 3. i. hegedüs, e. nagy: improvement of chymotrypsin enzyme stability as single enzyme nanoparticles, chemical engineering science, 64, (2009) 1053–1060 4. m. yan, y. ge, z. liu, p. k. ouyang: encapsulation of single enzyme in nanogel with enhanced biocatalytic activity and stability, journal of american chemical society, 128 (2006) 11008–11009 5. r. hong, n. o. fischer, a. verma, c. m. goodman, t. emrick, v. m. rotello: control of protein structure and function through surface recognition by tailored nanoparticle scaffolds, journal of american chemical society, 126 (2004) 739–743 6. r. hong, t. emrick, v. m. rotello: monolayercontrolled substrate selectivity using noncovalent enzyme-nanoparticle conjugates, journal of american chemical society, 126(42) (2004) 13572–13572 7. j. hong, d. xu, p. gong, h. ma, l. dong, s. yao: conjugation of enzyme on superparamagnetic nanogels covered with carboxyl groups, journal of chromatography b, 850(1-2) (2007) 499–506 8. y. ge, y. ming, d. lu, m. zhang, z. liu: hyperbranched polymer conjugated lypase with enhanced activity and stability, biochemical engineering journal, 36 (2007) 93–99 9. y-l. zeng, h-w. huang, j-h. jiang, m-n. tian, c-x. li, g-l. shen, r-q. yu: novel looped enzyme-polyamidoamine dendrimer nanohybrids used as biosensor matrix, analytica chimica acta, 604 (2007) 170–176 10. k. yao, y. zhu, x. yang, c. li: enfet glucose biosensor produced with dendrimer encapsulated pt nanoparticles, materials science and engineering: c, 28(8) (2008) 1236–1241 11. y. ming, y. ge, z. liu, p. k. ouyang: encapsulation of single enzyme in nanogel with enhanced biocatalytic activity and stability, journal of american chemical society, 128 (2006) 11008–11009 12. r. kumar, a. n. maitra, p. k. patanjali, p. sharma: hollow gold nanoparticles encapsulating horseradish peroxidase, biomaterials, 26 (2005) 6743–6753 13. r. s. kumar, s. das, a. maitra: enzymes in the cavity of hollow silica nanoparticles, journal of colloid and interface science, 284 (2005) 358–361 348 14. r. r. naik, m. m. tomczak, h. r. luckarift, j. c. spain, m. o. stonea: entrapment of enzymes and nanoparticles using biomimetically synthesized silica, chemical communications, (2004) 1684–1685 15. z. yang, s. shihui, z. chunjing: magnetic singleenzyme nanoparticles with high activity and stability, biochemical and biophysical research communications, 367 (2008) 169–175 16. a. mori, c. ohtsuki, t. miyazaki, a. sugino, m. tanihara, k. kuramoto, a. osaka: synthesis of bioactive pmma bone cement via modification with methacryloxypropyltrimethoxysilane and calcium acetate, journal of materials science: materials in medicine, 16 (2005) 713–718 17. t. k. ghose: measurement of cellulase activities, pure applied chemistry 59(2) (1987) 257–268 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 /colorconversionstrategy /cmyk /dothumbnails false /embedallfonts true /embedopentype false 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word contents_2.doc hungarian journal of industrial chemistry veszprém vol. 31. pp. 31-35 (2003) education in chemical process control using the supervisory laboratory application c. vasile-mircea, l. dan, a. şerban paul babeş-bolyai university, faculty of chemistry and chemical engineering, 11 arany janos, 400028 cluj-napoca, romania, tel: +40264593833, ext. 5689, fax:+40264590818, e-mail: mcristea@chem.ubbcluj.ro the developed cape (computer aided process engineering) application provides a helpful tool for performing the student laboratory works of the chemical process control program of study, allowing an efficient transfer from theoretic concepts to practical exemplification. different pilot plants, such as: liquid accumulation in a tank, heat transfer in a jacketed reactor, gas accumulation in a set of reservoirs or flow of liquid in a pipe-network, are fitted with specific instrumentation. by means of the special developed application and built in serial communication facility of the µp-based rex f-400 local controllers (with rs485-rs232 converter) the pilots are connected to the pc. application makes the practical demonstration of the different steps of the chemical process control curriculum possible: mathematical modelling coupled with process identification; frequency response; stability; dynamic behaviour of transducers and actuating elements; p, pi, pd, pid controller response and tuning. introduction developments of information technology and computer sciences make teaching and learning concepts change rapidly in the attempt to capture their spectacular progress. in the last years a set of new education systems have emerged, such as: computer aided e-learning, long-distance (spacedistributed) learning, teaching systems for life-long learning, interactive teaching systems, electronic courses, all using the computer as the main targetoriented tool. soon, the new learning methods will replace the traditional education methods. modern education processes are also assumed in chemical engineering education. computers can play different roles in chemical engineering education, such as: simulation, data acquisition and monitoring, computer aided testing, visualization, virtual reality. using special applications, the correlation between theoretical concepts and practical examples becomes possible, having continuously growing hardware and software support. the paper presents the results of implementing cape tools in the education process of chemical engineers at “babes-bolyai” university of clujnapoca, faculty of chemistry and chemical engineering, in the field of chemical process control. the use of a special developed application provides a helpful tool for performing the laboratory works of chemical process control programme of study, allowing an efficient transfer from theoretic concepts to their practical exemplification. experimental laboratory set-up the laboratory equipment consists of different pilot plants where processes such as: liquid accumulation in a tank, heat transfer in a jacketed reactor, gas accumulation in a set of reservoirs or flow of liquid through a pipe-network may be investigated by experiments. 32 a schematic illustration of the pilot plants with related instrumentation is presented in figure 1. figure 1. schematic representation of the pilot set-up. each of the pilots is fitted with specific measuring, actuating and control instrumentation [1]. the µp-based rex f-400 local controllers, connected by serial rs485-rs232 converter to a pc, represent the regulatory control level. the pc represents the upper supervisory control and the monitoring level of the two-level distributed control hierarchy. pc – local controller communication the computer-aided process engineering (cape) application performs several tasks. the first task allows the bi-directional communication between the local controllers and the pc, using a specific protocol [2, 5, 6]. this application achieves the serial link between a pc and the pilot plants fitted with µp-based rex f-400 controllers, with the help of an rs485-rs232 converter. in order to attain the communication, a specific transmission control procedure has been implemented. when data are needed to be read from the controller, the computer has to send a polling sequence in a ten-character format shown in figure 2. the meaning of the characters is: eot – character used for initialising the data link; 1 – two characters used for selecting the device address; 2 – two characters used for selecting the controller memory area; 3 – two characters used for specifying the identifier group; 4 – two characters used for identifying requested data and enq – character indicating the end of the polling sequence. figure 2. format of the polling sequence. the answer of the controller to the polling procedure has the format presented in figure 3: figure 3. format of the answer sequence to the polling procedure. where the eleven characters structure has the following significance: stx – character used to indicate the beginning of a text; 1 – two characters used for identifying the transmitted data; 2 – six characters used for representing the transmitted data, including the sign and the decimal point; etx – character used to indicate the text ending and bcc – character used for error detection, calculated by using horizontal parity. when transmitting data to the controller, the computer has to send the sequence in a format shown in figure 4: 0figure 4. format of the data sequence sent to the controller. where the eleven characters structure has the following significance: stx – character used to indicate the beginning of a text; 1 – two characters used for identifying the controller memory area; 2 – two characters used for identifying the transmitted data; 3 – six characters used for representing the transmitted data, including the sign and the decimal point; etx – character used to indicate the end of the sequence and bcc – character used for error detection. when receiving data, either the controller or the computer sends an ack (acknowledge) character or nak (not acknowledge) character to inform the sender about the integrity of the e o t e n q 1 2 3 4 s t x e t x 1 2 b c c s t x 1 2 3 e t x b c c 33 received data. in case the nak character is received the sender resumes the transmission. the communication application is developed using labview software environment in order to provide compatibility with other modules of the application. monitoring and supervisory control the basic task of the cape application allows the monitoring operation of the pilot plants, offering a general overview on the pilot processes and being also provided with override alarm functions. this task is accomplished by using the polling procedure. the computer sends the polling sequence and receives in return all requested process information together with controller status from the rex f-400 controllers belonging to each pilot plant. the main window of the application performing the monitoring task is presented in figure 5. figure 5. monitoring application window. main pilot parameters of the pilot plants are: level, temperature, pressure and flow rate are displayed together with the associated control variable and the state of the two point alarm. by the operation of the visualisation button another task, the main task of the cape application, allows acquisition and display of the detailed information on each particular pilot plants dynamic behaviours and their controller status. the main task also offers the means for sending control actions to the corresponding pilot plant. the functions of the main task are achieved by using both the polling and data transmission procedures. the first step is checking the status of local mode/computer mode identifier. if the controller is set in local mode, polling procedures are used for achieving the communication. for this case, only a detailed monitoring operation is allowed because the user intervention on the pilot plant is permitted merely from the on-site controller panel. the control actions that may be performed by the user from the cape application window become active only in computer mode. this way choosing the preference of the command source sets the priority for the local controller panel against the computer application, as it is commonly required in practice in the usual applications. the application window accomplishing the main task is presented in figure 6 with exemplification for the pilot plant of liquid accumulation in a tank and the control of the tank level by manipulating the outlet flow rate. figure 6. main application window. this task achieves several functions. the first one is the waveform graph visualization of the most important variables: the controlled variable and the setpoint, on a two-point chart and the manipulated variable, on a separate chart. the twopoint led alarm (alarm1 and alarm2) is also presented on the main application window in order to keep track of any violation of the particular security thresholds. the local/computer indicator displays the status of the local/computer mode. the application has special functions for the control combined with the display of the important application variables. it is the case of the start/stop (oprire program) control of the application, the manual/automat switch and the sampling time (interval de timp) control. the setpoint variable (xref in engineering units) and the control variable (xc in %), the latter only for manual mode, may be changed by using special slide controls/indicators fitted also with combined numeric command and 34 display. the process variable (xe in engineering units) is only displayed using a dual slide-numeric indicator. the pid tuning parameters may be changed by using the distinctive controls for proportional band (banda de proportionalitate), integral (timp de integrare) and derivative (timp de derivare) time constants. visualization of historical process information may be used for on line or off line data interpretation and processing. when the history (istoric) control is activated all acquired data is displayed, up to the current time, allowing zooming for detailed graphic representation, analysis or plotting. a special function of the application performs on line saving and storing of the acquired data in specific text files. this action is carried out when the save (salvare) control is activated from the application window. postprocessing of data saved in the file may be done with usual text editors. a sample of the historical window and visualization of the saved data opened from the text file with notepad editor are presented in figure 7. figure 7. historical application windows and saved data opened in notepad editor. operations such as sending data to the controller, receiving data from the controller, controlling errors that may occur during data transmission, saving data in a file and analysing the historical evolution are all accomplished in separate application modules. this application structure allows an immediate extension and adaptation of the application to other pilot plants. when operating the pilot plants from the application it is possible to change interactively the setpoint value for each pid controller generating a two-level hierarchical control system. incentives for process control education for the mathematical modelling purpose the cape application serves as a useful provider of accurate process experimental data and a versatile process input (manipulated) variable function generator [3]. the investigation step shaped process input variable is easily generated with the application, synchronization with acquisition of the process response being directly accomplished. the experimental data, e.g. the step response of the process output variable to the different input variables, are used for building the experimental based model. this experimental model is compared with the first principle model obtained on the basis of mass, energy and momentum conservation principles. fitness or mismatching between the two models reveals the way student has succeeded to gain knowledge on theoretical versus practical approach of system modelling, considering the linear or nonlinear behaviour. when studying the frequency response of the process the sine wave generation used for investigation is performed by the cape application and the response is displayed, saved for subsequent study or analysed on-line. concepts as bandwidth, crossover frequency, gain or phase margin get a practical insight. as a result, the stability may be further addressed both in an open and closed loop. the cape application also assists the study of different measuring and actuating instruments of the pilot plants based on the accuracy of data acquisition, especially for the case of the rapid change of the measured or manipulated variables, and when revealing aspects of nonlinear behaviour. understanding the time evolution of open loop step response of p, pi, pd and pid controller is important from the educational point of view in the perspective of closed loop feedback control. the supervisory cape application may perform the step change and record the open loop step response of the classical control laws incorporated in the rex f-400 controller together with the specific functions usually present at the industrial controllers. controller tuning may be carried out either on experimental basis or with analytical methods; comparative analysis between the obtained control performance results may show the incentives and drawbacks of these alternative approaches. the application serves as a convenient tool for manipulating the tuning parameters and for 35 revealing their effectiveness in different cases of pilot process control. the supervisory cape application allows centralization of the information from all pilot plants offering the supervisory control ability when changing setpoint values for each of the controlled pilots [4]. extending the application for performing a multivariable control strategy, with model predictive control at the higher level of the control structure and pid controllers at the regulatory control level, is straightforward. conclusions the flexibility of the application makes the practical demonstration of the different steps of the chemical process control curriculum possible, such as: mathematical modelling coupled with process identification (first principle and experimental based modelling), frequency response, stability, dynamic behaviour of transducers and actuating elements; p, pi, pd, pid controllers response and tuning, process monitoring and demonstration of the supervisory or multivariable control strategy (e.g. model predictive control). implementation of this cape application in the education process of chemical engineering offers an efficient transfer from the theoretical concepts to their practical exemplification. cape application is assembled in a modulebased structure offering both an easily extending facility and direct adaptation to other pilot plants for performing the laboratory works in other fields of engineering education. references 1. mcmillan g. k.: process/industrial instruments and controls handbook, 5th edition, mcgrawhill, 1999. 2. new f series (rex-f400, f700, f900) – communication instruction manual, rkc instrument inc.,1999. 3. agachi s. p. and cristea v. m.: lucrari practice de automatizarea proceselor chimice, 1996. 4. marlin t. e. : process control – designing processes and control systems for dynamic performance, 2nd edition, mcgraw-hill, 2000. 5. http://camiressearch.com 6. http://www.arcelect.com hungarian journal of industrial chemistry veszprém vol. 33(1-2). pp. 23-30. (2005) simulated moving bed (smb) separation of pharmaceutical enantiomers g. gál1*, l. hanák1, j. argyelán1, a. strbka1 and t. szánya1 a. aranyi2, k. temesvári2 1university of veszprém, department of chemical engineering processes 8201 veszprém, p.o.box 158, hungary, *e-mail: gaborgal@freemail.hu 2gedeon richter ltd., 1475 budapest p.o.box. 27, hungary authors investigated the separation of chiral racemic mixture pharmaceutical enantiomers in a laboratory scale smb equipment. they chose the proper chiral chromatographic packing and eluent for the separation of smb with the help of previous analytical hplc investigation. this was followed by frontal adsorptionelution measurements on the chosen chiralcel od packing (20µm particle size) in n-hexane-ipa eluent at 20°c. the measurements of adsorption equilibrium (k’ values) and ntp, hetp data were carried out with laboratory scale preparative hplc equipment (l=25 cm, id=1 cm). the parameter planning, previous estimation of smb operation was carried out with krom-n and smb-krom-n simulation programs. this was followed by the experimental study of the smb preparative liquid chromatographic operation (laboratory scale open loop eluent circle 4 column (l=25 cm, id=1 cm) equipment), and the comparison of the mathematical simulation with the results achieved in practice. the prescribed 99,9 % m/m purity for the „s” component of raffinate can be reached. at the optimum experiment the yield for „s” was over 99 %, the productivity was 62 mg s g-1 packing day-1 and the eluent consumption was 5,4 ml eluent mg-1 s. keywords: preparative liquid chromatography, simulated moving bed chromatography, pharmaceutical enantiomers, chiral chromatographic packing introduction nowadays almost half of the registered pharmaceutical products have chiral structure, accordingly they are of importance in pharmaceutical industry [1]. pharmacologically, most often only one optical isomer has proper activity, while the other one is inactive, possibly toxic. as a consequence the optical purity of enantiomers have got significant importance. as the enantiomers have the same physicochemical features and they show different characters only in optically active surroundings, the separation of them is unachievable without chiral interactions. chiral stationary phases can be produced by chiral selectors modifying the next natural materials (proteins, cyclodextrins, saccharides, antibiotics), synthetic polimers, and small, completely synthetic chiral compounds. nowadays the production and separation of enantiomer can be done by asymmetric catalysis, biotransformation, liquid-liquid extraction, capillary electrophoresis, membrane separation, crystallization, chromatography, and within chromatography: with capillary electrochromatography (cec), supercritical fluid chromatography (scf), gas chromatography (gc) and liquid chromatography (lc). that is thin-layer chromatography (tlc), countercurrent chromatography (ccc) and simulated moving bed chromatography (smb). the advantage of the smb method is that the procedure can be made continuously, the columns are completely used, the productivity and yield is higher, and the consumption of the eluent is lower compared to the batch chromatographic process. the disadvantage is the high investment cost, and the considerable sensitivity of the operational parameters. in the traditional batch elution chromatography the sample is injected on the top of the column and the components get separated after a certain time by moving through the column forced by the mobile phase [2]. however, this process is not very efficient as during the chromatography only a small part of the whole stationary phase is used for separation. a possibility to improve the packing utilization, is given by the true moving bed chromatography (tmb) principle. this chromatographic process was first introduced in the late 1960s by the universal oil product company [3-5] and mailto:gaborgal@freemail.hu 24 was intensively investigated by ching and co-workers [6-11]. according to this concept, not only the liquid phase is moving but the solid phase as well (tmb, fig. 1). for example, at a given counter current liquid phase and solid phase velocities, the faster eluting compound (raffinate, „b”) moves forward in the liquid direction and the slower eluting compound (extract, „a”) moves in the opposite direction together with the solid phase. under this condition, the full mass of the solid phase contributing to the separation is continuosly used, thus improving considerably the productivity of the system. obviously, this principle is particularly suitable for a binary mixture, especially for racemates (optical isomer mixtures). however, it is technically difficult to move a solid phase, thus the solid phase movement is simulated (smb, fig 2). in fact, it is a continuous process, the system consists of a number of small columns arranged in series in practice, as shown schematically in fig 2. as the inlet and outlet points are regularly changed (switching time), the net result is the same as it would be if the stationary phase were moving. in the last decades simulated moving bed processes were widely spread in preparative chromatography on the field of high-purity materials production in the pharmaceutical, fine chemical and biotechnology industries. if materials are difficult to be separated (α ≈ 1) the process efficiency is disadvantegous. otherwise if a component of a mixture was strongly adsorbed, the process would become uneconomical because a large volume of eluent should be used. experimental examination of adsorbent packings during examination chiralcel od-h, chiralcel oj, chiralpak ad, chiralpak ia, chiralpak as chiral packings were compared. selection of chiral chromatographic packings and eluents the selection of the chiral stationary packings (csp) and eluents carried out by a reference book published by daicel. these materials are coated or immobilised polysaccharide-derived csps. the chiral stationary packings tested by analytical hplc are the follows (fig. 3): • chiralcel od-h: cellulose tris(3,5-dimethylphenylcarbamate), coated on a 5 µm silica support, particle size 5 µm, • chiralcel od: cellulose tris(3,5-dimethylphenylcarbamate), coated on a 20 µm silica support, particle size 5 µm, • chiralcel oj: cellulose tris(4-methylbenzoate), coated on a 20 µm silica support, particle size 20 µm, • chiralpak ad: amylose tris(3,5-dimethylphenylcarbamate) coated on a 20 µm silica support, particle size 20 µm, • chiralpak ia: amylose tris(3,5-dimethylphenylcarbamate) immobilized on a 5 µm silica support, particle size 5 µm, • chiralpak as: amylose tris[(s)-phenylethylcarbamate] coated on a 5 µm silica support, particle size 5 µm. fig. 1: column disposition in the true moving bed chromatography (tmb) fig. 2: column disposition in the simulated moving bed chromatography (smb), short columns in series 25 fig. 3: chiral packings tested by analitycal hplc the measurements were done by gilson type analytical hplc. detection was carried out at 254 nm uv wavelength, at 20°c. as can be seen in table 1, the n-hexane-ipa eluent and the chiralcel-od chiral stationary packing proved to be the most appropriate according to the selectivity ( ), so this system was chosen for further examination. r sαα = determination of the number of theoretical plates (ntp) – height of equivalent theoretical plate (hetp) and selectivity ( ) r sα the definition of the equilibrium data of „s”(b) and „r”(a) optical isomers was carried out on supelco product preparative hplc column (i.d. = 1 cm, l = 25 cm), filled with chiralcel od (particle size: 20µm) packing, with the aid of a column-packing vibrator, at 20°c. air was removed from the column by means of 95:5 (v/v) n-hexane-ipa and an lmim d-167 pump. a rheodyne injection valve with 100µl loop was connected to the column inlet and a waters uv detector to the outlet, where we monitored the signal of optical isomers. the elution residence-time curve was recorded by uv spectrophotometer (λ = 254 nm). the sample was 541/bk chiral racemic mixture soluted in eluent in 50 mg ml-1 concentration, from which 100µl was injected into the column. the eluent was n-hexane-ipa used in three different volumetric ratio with five different volume flow rates. the results of the measurements are shown in table 2. the residence time curve was evaluated by the triangulation method determining σ and tr values: 0 0' t ttk r − = s r r rr s k k tt tt s r ' ' 0 0 = − − =α 2 r σ t ⎟ ⎠ ⎞ ⎜ ⎝ ⎛=ntp ntp l =hetp frontal adsorption elution measurements the langmuir constants and the data of the adsorption isotherm were calculated from the k’ values: ε ε − = 1 ' )()( sbsb kk ε ε − = 1 ' )()( rara kk columnml liquidml67.0=ε columnml packingg bulk 6.0=ρ bulk sbsb ka ρ ε− = 1 )()( bulk rara ka ρ ε− = 1 )()( )()( rasb bb = (computative data) packingg volumefreeliquidmla 3366.5* b = componentbmg volumefreeliquidmlb 016.0b = packingg volumefreeliquidmla 4405.6* a = componentamg volumefreeliquidmlb 016.0a = thus enough information was assembled to do the computer simulations (with krom-n software) of the frontal adsorption-elution. the data input to the software is shown on table 3. hereby there was a possibility to compare the simulation and the laboratory measurements. the laboratory measurements were performed with the column used before. air was removed from the column by means of 95:5 (v/v) nhexane-ipa at 20°c, directed downwards by means of an lmim-d167 piston pump. during the frontal adsorption a 10 ml of 50:50 (m/m) mixture of chiral mixtures s+r (total conc. 2-5-10 g l-1) was applied downwards to the column at a flow rate 2-2,5-5 ml min-1 at 20°c. feeding of the mixture s and r was stopped after 10 ml and pure eluent (95:5 and 93:7 nhexane-ipa) was pumped into the column at a flow rate of 2-2,5-5 ml min-1 (table 4). the eluent was collected in sample collectors and concentration analysed on-line by uv spectrophotometer. the concentration of the given samples were measured by analytical hplc. the frontal adsorption-desorption simulation and laboratory measurement results are shown in (fig. 4.). it’s remarkable that the separation of “s” and “r” optical isomers are favourable at small total contrantrations compared to the high ones. 26 the estimation of the smb measurements with computer simulations the simulations were calculated by smb-krom-n software. the model of the software uses the physical and chemical data of chemicals, the number of theoretical plates (ntp), volumetric flow rates, adsorption equilibrium data, switching time, etc. published by morbidelli [12] and his partners. the software of the simulation solves the differential equations by the numerical method of finite differencies [13]. determination of morbidelli parameters on the bases of a theoretical method assuming independent adsorption and linear isotherms, published by massimo morbidelli [12] and his team, the right values of volumetric stream can be well estimated. values of distribution quotient: silicagelsolidml liquidvolumefreeml 703.9 )(1 h * b b = − ⋅ = ε ρa k silicagelml liquidvolumefreeml3366.5* =ba silicagelsolidml liquidvolumefreeml71.11 )1( h * a = − ⋅ = ε ρa k a silicagelml liquidvolumefreeml4405.6* =aa by the morbidelli criteria the next relations must be true for producing pure „s” (b component) and „r” (a component) isomers: 11.71 = ka < mi 9.703 = kb < mii < ka = 11.71 9.703 = kb < miii < ka = 11.71 miv < kb = 9.703 the following parameters were chosen for the purpose of measurement, because these parameters accomplish morbidelli criteria providing adequate results during simulations. further data can be seen in the next chapter. f = 0.3 ml min-1 e = 4.4 ml min-1 r = 4.4 ml min-1 s = 12 ml min-1 lr out = 3.5 ml min-1 d = s + rec = 12 ml min-1 t = 10 min (switching time) l = 25 cm (column length) 4 πda 2 f = values of morbidelli parameters: 7108.114989.16 )1( >= − − = ε ε l lt a d m f i 7108.117049.9 )1( 7028.9 <= − − − =< ε ε l lt a ed m f ii 7108.111681.10 )1( 7028.9 <= − −+− =< ε ε l lt a fed m f iii 7108.111681.10 )1( 7028.9 <= − −+− =< ε ε l lt a fed m f iii data input to the smb-krom-n software number of components: k = 2 column inner diameter: i.d. = 1 cm column length: l = 25 cm number of columns: n = 4 free volume coefficient: eps = 0.67 ml liquid free volume ml-1 column bulk density: ρbulk=0.6 g packing ml-1 column feed: f = 0.3 ml min-1 fresh eluent: s = 12 ml min-1 extract: e = 4.4 ml min-1 raffinate: r = 4.4 ml min-1 recycling: rec = 0 ml min-1 langmuir constants: as given above feed concentration: mg b component ml 5.2f b =c -1 liquid 5.2f a =c mg a component ml-1 liquid number of theoretical plates: ntp = 200 per 25 cm column switching time: 10 min calculation time: 400 min smb equipment planning, construction and installation the smb preparative liquid chromatographic equipment with four columns, four sectors and open eluent circle was constructed in the central mechanical workshop of the university of veszprém (figs. 5 and 6). during installation the four preparative liquid chromatographic columns (i.d. = 10 mm, l = 250 mm) were filled with chiralcel-od packing by the vibration method (~30 min filling time). the column packing density was 0.6 g ml-1, the free volume factor was 0.67. each column was filled with approximately 11.77 g packing. stainless steel frits (2µm) were placed at the top and the bottom of each column. before measurements air was removed with eluent. 27 fig. 5: photograph of the smb equipment fig. 6: the block diagram of the smb equipment with four columns, four sectors, and open eluent cycle smb measurements out of the 22 executed simulations the best ones were chosen, according to which four measurements were done with the laboratory scale 1:1:1:1 column configuration, open eluent circle smb equipment of the department of chemical engineering processes. the conditions and the results of the smb measurements are included in table 5 and in the graphs (fig.7). results measurement results of smb compared to simulation results columns of the four-column smb equipment, previously equilibrated at 20°c with 95:5 (v/v) nhexane-ipa as eluent, were used to separate a racemic mixture of 2.5 g l-1 isomer a (r) and 2.5 g l-1 isomer b (s) in the same solvent mixture. the mixture to be separated was fed at the top of column iii. up to 10 min at a flow rate of 0.3 ml min-1. (the other volumetric ratios: e = 4.4 ml min-1, r = 4,4 ml min-1, fresh eluent: 12 ml min-1). it was followed by switching columns were exchanged according to the smb process and the eluent was not recirculated. flow rates were controlled by digital balances with the help of computer during the 10 min switching time. fig. 7 shows the eluent consumption, productivity, purity and yield for component “s” in the raffinate fraction at quasi-stationary state. our conclusion on the bases of laboratory measurements is that the smb-krom-n software is very adaptable to optimalize smb operation. the prescribed 99,9 % m/m purity for the „s” component of raffinate can be reached. at the optimum experiment the yield for „s” was over 99 %, the productivity was 62 mg „s” g-1 packing day-1 and the eluent consumption was 5,4 ml eluent mg-1 „s”. with the help of experimental and theoretical optimization of smb process (switching time decrease, feed concentration increase, volumetric flow-rate change, gradient methods application, column number increase, column configuration change etc.) markedly can be improve the specific values of the smb process. the investigation is in progressive state at the university of veszprém and at the gedeon richter ltd. acknowledgement the authors express their gratitude to chemical engineering institute cooperative research center of the university of veszprém and the gedeon richter ltd. for financial support of this research study. 28 rg od fr 01 0,0 0,5 1,0 1,5 2,0 2,5 0 20 40 60 80 100 120 140 v (ml) c (m g m l -1 ) s measured r measured s calculated r calculated eluent: n-hexane:ipa=95:5 (v/v ) csample= 5 mg ml-1 f= 5 ml min-1 rg od fr 02 0,0 0,5 1,0 1,5 2,0 2,5 0 20 40 60 80 100 120 140 v (ml) c (m g m l -1 ) s measured r measured eluent: n-hexane:ipa=95:5 (v/v ) csample= 5 mg ml-1 f= 2 ml min-1 rg od fr 05 0,0 0,5 1,0 1,5 2,0 2,5 0 20 40 60 80 100 120 140 v (ml) c (m g m l -1 ) s measured r measured eluent: n-hexane:ipa=95:5 (v/v ) csample= 2 mg ml-1 f= 2.5 ml min-1 rg od fr 07 0,0 1,0 2,0 3,0 4,0 5,0 0 20 40 60 80 100 120 140 v (ml) c (m g m l -1 ) s measured r measured eluent: n-hexane:ipa=95:5 (v/v ) csample= 10 mg ml-1 f = 2.5 ml min-1 rg od fr 03 0 1 2 3 4 5 6 7 0 20 40 60 80 100 120 140 v (ml) c (m g m l -1 ) s measured r measured s calculated r calculated eluent: n-hexane:ipa=93:7 (v/v ) csample= 10 mg ml-1 f= 2.5 ml min-1 rg od fr 04 0 1 2 3 4 5 6 7 0 20 40 60 80 100 120 14 v (ml) c (m g m l -1 ) 0 s measured r measured eluent: n-hexane:ipa=93:7 (v/v ) csample= 5 mg ml-1 f= 5 ml min-1 rg od fr 06 0,0 0,5 1,0 1,5 2,0 0 20 40 60 80 100 120 140 v (ml) c (m g m l -1 ) s measured r measured eluent: n-hexane:ipa=93:7 (v/v) csample= 2 mg ml-1 f= 2.5 ml min-1 fig. 4: the results of frontal adsorption-desorption simulation and laboratory measurements 29 0 1 2 3 4 5 6 7 8 9 10 rg od smb 01 rg od smb 02 rg od smb 03 rg od smb 04 el ue nt c on su m pt io n (m l el ue nt m g-1 s) r calculated r measured 0 10 20 30 40 50 60 70 rg od smb 01 rg od smb 02 rg od smb 03 rg od smb 04 pr od uc tiv ity (m g s g-1 p ac ki ng d ay -1 ) r calculated r measured 0 10 20 30 40 50 60 70 80 90 100 rg od smb 01 rg od smb 02 rg od smb 03 rg od smb 04 pu rit y (% ) r calculated r measured 0 10 20 30 40 50 60 70 80 90 100 rg od smb 01 rg od smb 02 rg od smb 03 rg od smb 04 yi el d (% ) r calculated r measured fig. 7: results of 4 measurements and 1 simulation: eluent consumption, productivity, purity and yield for component “s” in the raffinate concentration [% v/v ] chiralcel od-h chiralcel oj chiralpak as chiralpak ad chiralpak ia n-hexane:ipa 70:30 α=1 n-hexane:ipa 80:20 α=1.17 α=1.196 n-hexane:ipa 90:10 α=1.173 α=1 α=1 n-hexane:ipa 97.5:2.5 α=1.06 n-hexane:ipa 95:5 α=1.19 α=1 α=1.03 n-hexane:et-oh 95:5 α=1.122 n-hexane:ipa:acn 80:10:10 α=1 acn 100 α=1.31 α=1 acn-me-oh 80:20 α=1 α=1 ethanol 100 α=1 n-hexane:mtbé 80:20 k'1,2>20 n-hexane:mtbé 60:40 k'1,2=6.10 n-hexane:mtbe:et-oh (60:40)+5% et-oh k'1,2=1.086 n-hexane:ipa α=1.08 n-hexane:met-oh 99:1 α=1.12 n-hexane:et-oh 99:1 α=1.11 n-hexane:dkm 75:25 α=1.03 n-hexane:ipa:etoh 95:2.5:2.5 α = 1.15 n-hexane:ipa:metoh 95:2.5:2.5 α = 1.05 n-hexane:etoh:metoh 95:2.5:2.5 α = 1.05 packingeluent table 1: hplc measurements on different charges eluent: n-hexane:ipa=95:5 [% v/v] b t0 4σ hetp 4σ hetp pressure pressure [ml min-1] [sec] tr,1 k'1 [s] [mm] tr,2 k'2 [s] [mm] [psi] [bar] 2.5 316 1902 5.027 378 405 0.617 2 532 7.023 510 394 0.634 1.397 42 3.0 5 158 912 4.779 192 361 0.693 1068 5.768 264 262 0.955 1.207 66 4.6 10 79 468 4.932 108 300 0.832 576 6.300 150 236 1.060 1.278 110 7.7 15 53 306 4.817 78 246 1.015 378 6.186 108 196 1.276 1.284 168 11.8 20 39 228 4.779 66 191 1.309 282 6.148 90 157 1.592 1.286 240 16.9 30 26 168 5.388 54 155 1.614 210 6.985 90 87 2.870 1.296 336 23.6 eluent: n-hexane:ipa=90:10 [% v/v] b t0 4σ hetp 4σ hetp pressure pressure [ml min-1] [sec] tr,1 k'1 [s] [mm] tr,2 k'2 [s] [mm] [psi] [bar] 2.5 316 1248 2.954 258 374 0.668 1 530 3.848 336 332 0.754 1.302 30 2.1 5 158 612 2.878 126 377 0.662 732 3.639 192 233 1.075 1.264 48 3.4 10 79 303 2.840 72 283 0.882 366 3.639 102 206 1.214 1.281 100 7.0 15 53 204 2.878 56 212 1.177 242 3.601 80 146 1.708 1.251 144 10.1 20 39 152 2.853 48 160 1.558 182 3.613 72 102 2.445 1.267 210 14.8 30 26 102 2.878 40 104 2.403 120 3.563 72 44 5.625 1.238 336 23.6 eluent: n-hexane:ipa=80:20 [% v/v] b t0 4σ hetp 4σ hetp pressure pressure [ml min-1] [sec] tr,1 k'1 [s] [mm] tr,2 k'2 [s] [mm] [psi] [bar] 2.5 316 1008 2.194 210 369 0.678 1 218 2.859 249 383 0.653 1.303 0 0.0 5 158 492 2.118 102 372 0.672 588 2.726 138 290 0.861 1.287 0 0.0 10 79 242 2.067 58 279 0.898 288 2.650 78 218 1.146 1.282 54 3.8 15 53 162 2.080 46 198 1.260 192 2.650 58 175 1.426 1.274 108 7.6 20 39 120 2.042 40 144 1.736 142 2.599 58 96 2.607 1.273 168 11.8 30 26 81 2.080 35 88 2.835 94 2.574 40 88 2.829 1.238 306 21.5 ntp s (-) r (+) α (k'+/k'-) α (k'+/k'-) α (k'+/k'-)ntp ntp ntp ntp ntp s (-) r (+) s (-) r (+) table 2: the parameters and the results of the elution measurements 30 number of components: k = 2 column inner diameter: i.d. = 1 cm column length: l = 25 cm free volume coefficient: eps = 0.67 ml liquid free volume ml-1 column bulk density: ρb= 0.6 g packing ml-1 column feed: f = 2-2.5-5 ml min-1 langmuir constants: as given above sample feeding volume: 10 ml sample concentration: mg b component ml 1052f b −−=c -1 liquid 1052f a −−=c mg a component ml-1 liquid number of theoretical plates: ntp = 200 calculation time: 70 min table 3: data input for the krom-n software identifier feed [ml min-1] csample [mg ml-1] eluent, (v/v) n-hexane-ipa rg od fr 05 2.5 2 95:5 rg od fr 02 2 5 95:5 rg od fr 01 5 5 95:5 rg od fr 07 2.5 10 95:5 rg od fr 06 2.5 2 93:7 rg od fr 04 5 5 93:7 rg od fr 03 2.5 10 93:7 table 4: the parameters of the frontal adsorptionelution measurements identifier eluent sample switching time (min) d e f r lr out simulation raffinate cs (mg ml-1) 0,0468 0,5702 purity (%) 99,66 100,00 yield (%) 99,95 100,00 4,22 2,94 7,5 15,76 6,59 0,50 6,01 3,64 10 11,93 "s" isomer productivity (mg s g-1 packing day-1) (ml min-1) eluant consumption (ml eluent mg-1 s) rg od smb 01 10 11,55 4,29 0,23 3,59 3,72 rg od smb 02 rg od smb 03 rg od smb 04 rg od smb 01-04 measurements n-hexane:ipa = 93:7 (v/v) 5,23 5,39 0,3442 10 12,01 4,29 0,30 5,06 0,33 57,50 100,00 100,00 5 g racemic ml-1 in n-hexane:ipa = 95:5 (v/v) 5 g racemic ml-1 in n-hexane:ipa = 93:7 (v/v) 59,00 61,96 34,98 3,91 3,72 raffinateraffinate 0,2983 9,48 7,62 100,00 100,00 raffinate 0,3477 9,25 34,69 100,00 100,00 table 5: the conditions and the results of the smb measurements symbols ε – free volume coefficient [ml liquid free volume ml-1 column] f – volume flow rate of eluent [ml min-1] t0 – dead time [min] tr – retention time [min] k’ – retention factor s(–) – the „s”, l-isomer, bonds weakly to adsorbent (b) r(+) – az „r”, d-isomer, bonds stronger to adsor bent (a) r sα – separation factor ntp – number of theoretical plates hetp – height of theoretical plates [mm] references 1. ilona horvath, sandor kovacs: days of technical chemistry (2004) 91-94 2. eric r. francotte, paul richert: j.chromatogr a, (1997) 769:101-107 3. d.b. braughton and c.g gerhald: us pat, (1961) 2985589 4. d.b. braughton and s.a. gembicki: a.i.ch.e. symp.ser. 5. p.e. baker and g.ganestos: sep. sci. technol., 22 (1987) 2011 6. c.b. ching, b.g. lim, e.j.d. lee and s.c. ng: j. chromatogr, 634 (1993) 215 7. b.g. lim, c.b. ching, r.b.h. tan and s.c. ng: chem. eng. sci., 50 (1995) 2289 8. c.b. ching, d.m. ruthvenand k. hidajat: chem. eng. sci., 40 (1985) 141 9. c.b. ching, c. ho and d.m. ruthven: chem. eng. sci., 43 (1988) 703 10. c.b. ching, k.h. chu.,k. hidajat and d.m. ruthven: chem. eng. sci., 48 (1993) 1343 11. c.b. ching and d.m. ruthven: a.i.ch.e. symp.ser. 38 (1992) 1744 12. migliorini c, mazzotti m, morbidelli m.: j chromatogr a, (1998) 827:2:161-173 13. m. miron, t. szánya, l. hanák, j. argyelán and gy. marton: hung. j. ind. chem. (1995) 23:293-298 editorial hungarian journal of industrial chemistry veszprém vol. 42(1) 7–12 (2014) improving the interfacial properties of glass fibre reinforced and unreinforced waste sourced low density polyethylene/acrylonitrile butadiene styrene/polystyrene composites jános sója,1 vladimir sedlarik,2 pavel kucharczyk,2 and norbert miskolczi1! 1 mol department of hydrocarbon & coal processing, institute of chemical engineering and process engineering, faculty of engineering, university of pannonia, egyetem u. 10, veszprém, h-8200, hungary 2 centre of polymer systems, university institute, tomas bata university in zlin, nad ovcirnou 3685, zlín, 76001, czech republic !e-mail: mnorbert@almos.uni-pannon.hu this work is focused on compatibilization of immiscible waste sourced low density polyethylene (ldpe), acrylonitrile butadiene styrene (abs), and polystyrene (ps) blends by different surface modifying routes. to reach better mechanical properties of the given reused waste blends 20% glass fibre was used. the ratio of waste ldpe/abs/ps was 3.6/2.0/1.0 both in the presence and absence of glass fibre, while the applied concentration of the surface modifying routes was 1% in each case. blends of raw materials had been manufactured by two roll mill, and specimens were obtained by the press moulded plates. the properties of samples were studied by mechanical testing. results show that blending of the three kinds of waste polymers without compatibilizers resulted immiscible blends with poor mechanical properties. this could be significantly improved by the application of the commercial and synthetic surface treatment additives. generally, favourable properties were found in the presence of 20% glass fibre. especially ad-1 and ad-2 experimental and commercial γ-aminopropylsilane additives showed the best results. keywords: immiscible, compatibilizer, waste mechanical recycling, tensile strength introduction owing to the increasing application of polymers, the utilization of wastes plastics causes serious challenges. according to reports the energetic utilization of polymer wastes were mainly investigated, such as incineration, chemical recycling, and/or mechanical recycling [1–7]. it is also well known that the industrially used plastics are not exchangeable with other constructional materials (glass, metals, etc.). excess energy use and/or more greenhouse gas emissions would be incurred upon replacement of plastics with other materials. therefore most of the key industrial segments, such as transportation, aviation, packaging, civil engineering, cannot function without polymers. from the 50s' the plastic industry went through a significant development, which is a reason for their wide-spread and diverse applications often for highly specific purposes. in the case of plastic composites, they provide alternative solutions to problems of increasing strength, maintaining compatibility and malleability [2, 4, 6–14]. the mechanical recycling of polymers is a reshaping process using waste polymeric materials or even the mixtures of unused and waste polymers. basically the waste polymer can be originated from two sources. in “closed-loop” recycling, the same product is manufactured from the same recycled components. for instance, the material of bottles (in some cases) can be recycled. in contrast, there is a recycling route, when the repeated remanufactured products are becoming less valuable [10–12, 15, 16]. a major challenge in mechanical recycling of polymers is immiscibility that leads to phase separation causing significant reductions in mechanical properties of the polymer mixtures. there are specific kinds of polymers that are immiscible with each other, such as polyolefin-pa, polyolefin-abs, polyolefin-pet. therefore, polymer blends may contain two phases, such as disperse and continuous. generally, the difference in chemical and physical properties of phases are the source of the above mentioned immiscibility problem. therefore, coupling agents with special chemical structure can be used to create adequate chemical/physical interaction between the constituents of polymer mixtures. for this purpose grafted-ma or silane based compounds are widely used. these compatibilizers are able to increase the interfacial tension in boundary layer of polymer blends, which results in better chemical/physical interactions [17, 18]. 8 in this work, the feasibility of mechanical recycling of automotive industry waste mixtures of low-density polyethylene (ldpe), acrylonitrile butadiene styrene (abs), and polystyrene (ps) were studied. the effects of various compatibilization techniques on mechanical properties of the prepared ternary abs/lspe/ps systems were studied. materials and methods raw materials waste polymers used as raw materials in our experimental work were selectively collected directly from automotive industry. the main properties of the plastic wastes are summarized in table 1. the ldpe has the lowest tensile strength (15.8 mpa), which is followed by the polystyrene (25.6 mpa), and the abs (34.4 mpa). tensile modulus showed similar order as well. due to the chemical structure of plastics, the ldpe had the highest elongation (351.5%), while abs the lowest (4.7%). the average particle size for each tested plastic wastes were in the range of 4–5 mm, with moisture content of 0.7–0.8 %. moreover, significant differences were noticed in the charpy impact strength of samples; because the maximum value was measured in the case of abs (10.5 kj mm-2), while the smallest regarding ldpe (3.8 kj mm-2). as known, blends of abs and ldpe are immiscible phases in the most cases. therefore, the mechanical properties of abs and ldpe blend are significantly worse than that of the constituents, either abs or ldpe. in order to enhance their properties, the interfacial forces must be improved between the constituents. in our work, different commercial and synthetic compatibilizers were used for improving the interfacial properties and decrease the interfacial tension of composites. two commercially available compounds of γ-aminopropyl silane (c-1) (aldrich chemistry), and polyethylene grafted with maleic anhydride (c-2) (viba spa) were used as compatibilizer agents. the synthetic agents were maleic anhydride intermediates made from different olefins at the department of mol hydrocarbon and coal processing, university of pannonia with significantly different physical and chemical properties. the main properties of the four additives are summarized in table 2. sample preparation blends of waste ldpe/abs/ps were prepared by two roll mill. then sample plates were manufactured by press moulding. fig.1 demonstrates the flow of the experimental work. for composite manufacturing a labtech two roll mill (labtech ltd, thailand) was used. the temperatures of the rolls were 170 °c and 190 °c with friction ratio of 0.5. the compositions of samples are summarized in tables 3 and 4. in selected cases e-type unsized glass fibre with 4–5 cm average length was also added to the composites in its 20%. the e-type gf was produced by ovens table 1: the main properties of waste polymers ldpe abs ps tensile strength, mpa 15.8±1.4 34.4±2.5 25.6±1.9 tensile modulus, mpa 420±33 1750±88 1720±95 elongation, % 351.5±35.5 4.7±0.3 189.6±10.2 flexural strength, mpa 29.0±2.2 21.0±1.7 flexural modulus, mpa 1820±79 1140±73 charpy strength, kj mm-2 3.8±0.4 10.5±1.1 5.9±0.4 table 2: the main of experimental coupling agents ad-1 ad-2 ad-3 ad-4 appearance solid dense liquid solid solid side chain c16-c18 polyisobutylene styrene c20-c22 figure 1: sample preparation and testing table 3: sample compositions without glass fibre in weight % sample no. 1 2 3 4 5 6 7 8 ldpe 55 54 54 54 54 54 54 54 abs 30 30 30 30 30 30 30 30 ps 15 15 15 15 15 15 15 15 c-1 1 c-2 1 ad-1 1 ad-2 1 ad-3 1 ad-4 1 peroxide 1 9 corning and it contained mainly sio2, cao and al2o3. the ratio of waste ldpe/abs/ps was 3.6/2/1 both in the presence and absence of glass fibre, while the applied concentration of the additives was 1% in each case. the additives were directly added to the molten polymer during the sample sheet manufacturing. in two cases organic peroxide (di-tercier-butyl-peroxide) was used to modify the interfacial surface of composites. the sample blending composites were press moulded at 180 °c using 6.8 ton loading and then specimens with dimension of 1 mm x 10 mm x 100 mm were cut from the composite plates. determination of tensile strength the tensile properties of the composites were determined by instron 3345 universal tensile machine using 90 mm/min crosshead displacement rate. during the tests, the ambient temperature was 23 °c, and the relative humidity was 35 % in all cases. preloading was not applied. determination of flexural strength the three point flexural tests were performed by also the before mentioned instron 3345 universal tensile tester. the crosshead displacement rate was 20 mm min-1 in all cases. determination of charpy impact properties a ceast resil impactor was used for determination of charpy impact strength. the machine was equipped with a 4j hammer, while the specimens were cut. results and discussion tensile properties fig.2 compares the tensile strength of samples. it can be seen that the tensile strength has changed in the range of 13.8 and 24.1 mpa. however, the reinforced composites have significantly better resistance against constant tensile loading (13.8–24.1 mpa), than that of unreinforced (14.2–18.5 mpa). according to data the highest values were obtained in the case sample containing a-1 surface modifier agent in the presence of gf (24.1 mpa), while that was the highest in using ad3 additive without gf (18.5 mpa). from table 1, the raw materials had 34.4 mpa (abs), 25.6 mpa (ps) and 15.8 mpa (ldpe) tensile strength. on the contrary, the untreated ldpe/abs/ps composites have tensile strength of 15.3 mpa without fibres, and 16.8 mpa in the presence of 20% glass fibre. it means that presumably owing to the immiscible phases the ldpe/abs/ps composites without surface modifying additive has lower strength than its constituents. in three samples (c-1, ad-2, and ad-4) the tensile strength of glass fibre free, but treated composites was lower than that of untreated. this is probably due to the reason of the additive has been disadvantageously altered in surface characteristics of the plastic mixture. the largest increase in the tensile strength occurred for ad-1 (+12%) and ad-3 (+21%) additives without gf, while the peroxide (+23%), and ad-1 (43%) samples have resulted the best properties using 20% glass fibre, as well. the young’s modulus, as the measure of the elastic property of sample, changed in the range between 1015 and 1685 mpa in the presence of glass fibre, while the values were between 937 and 1579 mpa without gf reinforcing (fig.3). the maximum value of tensile modulus was found by the using ad-1 surface treating agent both presence and absence of gf (1579 mpa and table 4: sample compositions with glass fibre in weight % sample no. 10 11 12 13 14 15 16 ldpe 43 43 43 43 43 43 43 abs 24 24 24 24 24 24 24 ps 12 12 12 12 12 12 12 gf 20 20 20 20 20 20 20 c-1 1 c-2 1 ad-1 1 ad-2 1 ad-3 1 ad-4 1 peroxide 1 figure 2: tensile strength of samples figure 3: tensile modulus of ldpe/abs/ps samples 10 1685 mpa). on the basis of data in table 1, the tensile modulus of ldpe, abs and ps raw materials were 420, 1750 and 1720 mpa, respectively. the untreated ldpe/abs/ps samples had significantly lower tensile moduli with 937 mpa and 1173 mpa in the presence and absence of gf, respectively. presumably it was the consequence of the phase separation occurring the immiscible polymers. the compatibility of immiscible polymer blends could be significantly improved by the above mentioned additives, because not only the tensile strength, but also the tensile modulus was significantly increased e.g. by the application of ad-1 additive (+44 % with gf and +69% without gf). in general, the tensile modulus was higher in the presence of glass fibre than without that. the relative elongation refers to the change in sample length during the tensile tests. rigid materials (polyamide, abs, etc.) have low value of elongation, while that of significantly higher in case of soft or rubber like elastic polymers (polyethylene, pp, ps, rubber, etc.). the relative elongation (fig.4) follows the opposite trends than tensile strength or modulus. it is changed in the range of 2.33 and 4.29% without gf, or 2.09 and 3.16% with gf. it means that the glass fibre presence resulted lower values of relative elongation. the surface treating agents have only slight effect to the elongation apart from ad-1 sample, because the difference between the treated and untreated samples was 63% in case of ad-1. in any other cases this value was less than 20%. flexural properties results from flexural tests are summarized in figs.5 and 6. the flexural strength was in the range of 17.3 and 22.6 mpa in case of gf reinforced ldpe/abs/ps composites and between 13.7 and 19.9 mpa in case of unreinforced specimens. the best result was found when the interfacial surface of ldpe/abs/ps composite and/or the glass fibre surface were modified by ad-3 additive (22.6 mpa). in the presence of ad-3 additive the unreinforced ldpe/abs/ps blend had 19.9 mpa flexural strength value. generally, the tensile properties were favourable in case of reinforced, than that of unreinforced samples. according to table 1, the waste abs and ps raw materials had flexural strength of 29.0 mpa and 21.0 mpa, respectively. on the other hand, the flexural strength of unreinforced ldpe/abs/ps was 15.3 mpa, which can be increased to 17.3 mpa in the presence of gf. it means that the flexural strength was below the lowest value of constituent (ps, 21.0 mpa) even in the presence of gf. co mparing tensile and flexural strength, it can be concluded that the effect of the surface modifying agents were more significant to the tensile than to the flexural properties. the negative effect of surface modifying agents was observed in some cases. for instance, flexural strength was reduced in case of c-1 and peroxide additives. regarding the flexural strength the largest increase occurred in the presence of ad-3 (+30%) and c-2 (+22%) additives without glass fibre reinforcements. the increasing in flexural strength was 30% (without gf) and 31% (with gf) in case of ad-3 additive, while that of was 22% (without gf) and 17% (with gf). regarding flexural modulus, similar results were obtained as discussed above. abs and ps raw materials have 1820 and 1140 mpa flexural modulus, respectively. according to fig.6, the flexural modulus was 1080 mpa and 1285 mpa in case of unreinforced and reinforced ldpe/abs/ps composite without surface treating agents. the flexural modulus indicates the rigidity. higher modulus means greater rigidity. results demonstrate that the flexural modulus changes in the range 1285 and 2015 mpa in the presence of gf, whereas values were between 1040 and 1637 mpa in case of the non-reinforced composites. the maximum value of flexural modulus was given specimens figure 5: flexural strength of ldpe/abs/ps samples figure 6: flexural modulus of abs/ldpe/ps samples figure 4: elongation of samples measured at tensile test 11 containing c-2 surface treating additives both with and without glass fibres. charpy impact strength the charpy impact test determines the amount of energy absorbed by a material during fracture. fig.7 summarizes the charpy impact strength of samples as a function of surface treatment additives. the impact strength of the samples ranged from 4.7 to 9.1 kj mm-2, in which reinforced composite materials was between the higher range of 5.9 and 9.1 kj mm-2. the highest value was in a sample including ad-1 surface modification agent, and glass fibre (9.1 kj mm-2). in case of the same additive without reinforced fibre the impact strength was 7.1 kj mm-2. results show that the impact strength could be increased in each case due to surface treatment. the impact strength of ldpe/abs/ps composite was 4.7 kj mm-2 without reinforced and 6.8 kj mm-2 in reinforced by glass fibres. the largest growth was observed in the case of the sample containing c-2 (+53%) and ad-1 (+51%) additives for samples without glass fibres. contrary, the least growth was observed in the case of the sample containing ad-2 (+4%) additives. regarding the gf reinforced samples, the largest growth was observed when the ad-1 (+34%) and c-2 (+29%) additive were used. only the ad-2 additive resulted in lower impact strength, than abs/ldpe/ps excluding any additive (-13%). conclusion in this paper the efficiency of different compatibilizers in waste sourced ldpe/abs/ps composite were investigated both in absence and presence of 20% etype glass fibre. it was found that both the tensile and flexural properties of samples could be significantly improved by both synthetic and commercial coupling agent. the tensile strength and elastic modulus were the best when ad-1, a c16-c18 olefin containing polyakenyl polymaleic anhydride compatibilizers and 20% gf were applied. thus, compared to the ldpe/abs/ps composite without glass fibre and surface modifying additives, the tensile strength showed 58 %, and the elastic modulus showed an 80 % increase. regarding flexural properties similar result were observed, but not with ad-1, rather than ad-3, a polyakenyl polymaleic anhydride additive that resulted in the best properties, such as increase of 22.6 mpa in flexural strength. charpy impact strength increase was the largest (9.1 kj mm-2) in a sample containing ad-1 agent in the presence of glass fibres, which converts to about 90% increase relative the ldpe/abs/ps blend without gf and compatibilizing additives. synergistic effect of glass fibres and some of the compatibilizers can lead to increase of charpy impact strength 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e-mail: polczmann@almos.uni-pannon.hu 2slovnaft, a.s., vlčie hrdlo 1, 824 12 bratislava, slovakia modern lube oils are prepared from base oils (base oil mixtures) and additives. the allotted quality parameters and the proper application properties are assured by the harmonical integration of these components. some key lube oil properties depend on the quality of the base oil. for example a new demand has raised in the area of engine oils in the last couple of years: the demand is to contribute to the lower emission of the vehicles. this means the development of engine oils with low sulphated ash, low metal, sulphur and phosphorous content (“low saps” engine oils). in order to reach the adequate properties, the base oil (which is the main component of the engine oils) has to be produced with modern and advanced processes. the conventional base oil production line has its own disadvantages and limitations, so the catalytic processes were spread to enhance the viscosity index and to reduce the pour point of the base oils. it was necessary to develop and apply base oil production processes and technologies which are flexible to the crude oil quality and can produce environmentally friendly base oils with high viscosity index. to reach these goals the most adequate technologies are the catalytic base oil production processes. in the experimental section of this paper the results of hydroisomerization of wax from hungarian crude oil on pt/zeolite/al2o3 catalyst are presented. based on our experiments we established that with hydroisomerization base oils with very high or extra high viscosity index and low pour point can be produced from high molecular weight paraffinic hydrocarbon mixture. these base oils with low sulphur and aromatic content are appropriate, for example to produce energy efficient and environmentally friendly engine oils. keywords: modern base oils, slack wax, hydroisomerization, pt/sapo-11 introduction modern lubricants are prepared basically from base oils (base oil mixtures) and additive(s). the allotted quality parameters and the proper application properties are assured by the harmonical integration of these components. some key lube oil properties depend on the quality of the base oil. for example a new demand has raised in the area of engine oils in the recent years: the demand to contribute to the lower emission of the vehicles. this means the development of engine oils with low sulphated ash, low metal, sulphur and phosphorous content (“low saps” engine oils). [1-4]. to reach the adequate properties, the base oil (which is the main component of the engine oils) has to be produced with modern and advanced processes. table 1 shows the api classification of base oils [5]. the future demand for different quality base oils in the world can be seen in fig. 1 [6]. based on this diagram, it can be concluded that the demand for higher quality base oils will slightly increase in the future. the main requirements of the base oils to make environmentally friendly and high performance level engine oils are [7,8]: • availability in the proper viscosity grades, • good viscosity-temperature behaviour • high viscosity index • good lubrication properties • good lubrication quality at low viscosity • good friction behaviour in wide range of stress, • good antiwear effect, • low pour point, • high flash point, • good cold flow properties, • good additive sensitivity, • low foaming, • low sulphur content, • good thermal and oxidation stability in the working range, • low volatility, • chemical stability, • good hydrolytic stability, • anticorrosion effect, • non-toxic, 108 0 5 10 15 20 25 30 35 2006 2007 2008 2009 2010 b as e oi l d em an , 1 06 t/ ye ar api group i api group ii api group iii figure 1: the evolution of world demand for different quality base oils table 1: api classification of base oils group properties i. ii. iii. iv. v saturated content, % <90 and/or ≥90 and ≥90 and sulphur content, % >0.03 ≤0.03 ≤0.03 viscosity index (vi) 80≤vi≤120 80≤vi≤120 >120 poli(alfa-)olefins (paos) every base oil except group i-iv typical production technology solvent refining hydrocracking severe hydrocracking, isomerization chemical synthesis chemical synthesis • clean ignition (ashless if possible), • high additive solvency, • compatibility with metallic and non-metallic structural materials, • environmental friendliness and good biodegradability, • real price etc. if the engine oil is produced from base oil which fulfils these requirements, the engine will be cleaner and work longer, the oil change period will increase, the fuel consumption will decrease and the activity of the aftertreatment catalytic system will last longer. today, these properties can be reached with the application of mainly catalytic technologies. modern base oils from crude oil the general process of conventional base oil production contains the following technologies: the vacuum distillation of the atmospheric residue and deasphalting as feedstock production step, solvent refining, solvent dewaxing and a hydrofinishing. however, base oils produced by this technology line have several disadvantages [5]: • the yield and the quality of the target product depends on the composition of the crude oil, so the paraffinic crude is strongly preferred; • the produced base oils have only 100–110 viscosity index, and their pour points are not good enough; • to produce high performance level (e.g. viscosity index >130–150; volatility <10%) and environmentally benign (low sulphur content, good biodegradability) engine oils very expensive synthetic base oils have to be used, • from naphtenic crude oil only base oils of low viscosity index can be produced; • in case of solvent refining the extract can only be used as low value heating oil. this is the reason why in the last couple of years the catalytic processes kept on spreading in the base oil industry to produce base oils with high viscosity indexes and low pour points. industry needs base oil production processes which are very flexible to the quality of the feedstocks and can be applied to produce environmentally friendly base oils with high viscosity index. 109 base oils with good lubrication properties, containing high amount of multi-branched isoparaffins, having high viscosity index, reduced sulphur and aromatic content (chemically stable), low volatility and good biodegradability can be produced with the following catalytic technologies: • hydrocracking, • catalytic dewaxing (n-paraffin conversion), • isomerization of high molecular weight paraffins, • hydrotreating and hydroisomerization of the residue of fuel hydrocracking plant, • severe hydrofinishing. nowadays the modern way of base oil production is the application of catalytic processes only (e.g. hydrocracking – catalytic n-paraffin conversion – hydrofinishing) (fig. 2). the product obtained by this way was found to be clean and stable because the molecules with poor lubrication properties are converted to high quality molecules. the value of the pour point and the viscosity index can be controlled properly in the different catalytic steps. moreover, this kind of technology is flexible, and less sensitive to for the quality of the crude oil [9]. base oil production from fischer-tropsch waxes the new group of the base oils are the fischer-tropsch base oils. the fischer-tropsch synthesis is a hydrocarbon producing technology first described in 1923 [10]. the synthetic crude is at normal conditions is a high pour point (>30–50 °c) hydrocarbon mixture (containing high molecular weight n-paraffins) with zero sulphur and aromatic content. the synthesis and the catalytic conversions can be done with special conditions (reactor structure, catalyst, operating parameters) to produce high amount (10–15%) and high quality feedstocks to produce base oils. experimental in our experiments hydroisomerization of a hungarian crude slack wax on pt/sapo-11/al2o3 catalyst have been carried out. main goals of these experiments were to produce high quality base oil and high quality gas oil as co-product. through this process we investigated the effect of the operating conditions on the product yield and quality. apparatus the experiments were carried out in a high-pressure reactor system. this consists of a tubular down-flow reactor of 100 cm3 efficient volume and it is free of back-mixing; it contains equipments and devices applied in the reactor system of industrial plants (pumps, separators, heat exchangers, as well as temperature, pressure and gas flow regulators). the experiments were carried out in continuous operation (fig. 3). hydrogen heavy vacuum distillate fuel blending component base oil tank base oil hydrocracking catalytic nparaffin conversion pre-reactor hydrocracking reactor vacuum distillation catalytic dewaxing hydrotreating reactor fuel blending component hydrogen figure 2: base oil production by catalytic technologies (simplified scheme) 110 v-1 v-2 v-3 v-4 pi1 pi2 pi3 v-5 v-6 f fic-1 pi4 v-7 p-1 v-8 v-9 v-10 v-11 v-12 ti1 v-13 v-14 v-15 p pic-1 v-16 v-17 f fi-1 v-18 v-19 tic1 tic2 gas bottles 1 2 3 4 5 6 7 8 9 10 11 liquid products purge pir-1 tic3 figure 3: high pressure catalytic experimental apparatus catalyst the experiments were carried out on pt/sapo-11/al2o3 catalyst. we chose the ratio of metallic (deand hydrogenating function) and acidic (skeletal rearranging and selective cracking function) sites of catalyst to produce a low amount of gaseous and naphta products as co-product [11]. before the experiments the catalyst was activated and dried properly with the method elaborated by us. feedstock the feedstock was crude slack wax obtained from hungarian crude oil (rich in c22-c40 n-paraffins), which was in solid condition at ambient temperature. the main properties of the feedstock are presented in table 2. table 2: major properties of the feedstock properties value c20hydrocarbon content, % 9.8 c20+, hydrocarbon content, % 90.2 i-/n-paraffin weight ratio 0.41 pour point , °c +39 sulphur content, mg/kg 94 aromatic content, % 8.5 process parameters the applied process parameters were chosen based on the results of previous experiments. they were as follows: temperature: 300–380 °c pressure: 4.0–8.0 mpa liquid hour space velocity: 0.75–3.0 cm3/cm3 cath h2/hydrocarbon ratio: 200–600 nm3/m3 results and discussion based on our experimental results, it is concluded that the pt/sapo-11/al2o3 catalyst is applicable to the hydroisomerization of hungarian slack wax. the degree of hydroisomerization and hydrocracking changed as a function of operational conditions. the yield of pentanes and heavier products (c5+) were 99.5% at the mildest conditions and 73.5% at the strictest conditions. this product was fractionated to naphta, gas oil, base oil and residue fractions. after the gas oil fraction, the base oil fraction was cut in a similar way as their properties fulfil the requirements of api group iii base oils. the yield of the gaseous and liquid products as a function of process parameters are shown in fig. 4. these data are typical to the conversion as well. 111 0 10 20 30 40 50 60 70 80 90 100 300 310 320 330 340 350 360 370 380 temperature, °c fu el g as + n ap ht a + ga s o il + ba se o il yi el d, % 40 60 500 500 500 600 0,75 -■-●-○--1,0 -δ1,5 -▲-□2,0 -x80 lhsv, h-1 pressure, bar h2/ch, m3/m3 figure 4: product yields (fuel gas + naphta + gas oil + base oil fraction) as a function of temperature the nearly s-shaped curves show that the depth of conversion increased definitely, but the rate varied in the function of other process parameters. increase of pressure had positive influence on the catalytic conversion. decreasing the liquid hour space velocity caused the same tendency. under the following reaction conditions, namely at 350 °c (and above), 0.75–3.0 h-1 lhsv and 70–80 bar pressure, the products contained no more residue components. the yield of gaseous products in case of some key process parameter combinations are presented in fig. 5. the figure shows that with increasing temperature – at constant other parameters – the gaseous product yield increased near exponentially. increasing the liquid hour space velocity, the gaseous product yield decreased at constant other parameters. using higher pressures, the formation of gaseous products (with significant increasing number of moles) is limited. increase of the hydrogen/hydrocarbon volume ratio caused the same effect. in the tested process parameter range the amount of gaseous products changed between 0,5% (300 °c, 40 bar, lhsv 3 h-1, 600 m3/m3 hydrogen/hydrocarbon ratio) and 26.5% (380 °c, 40 bar, lhsv 0.75 h-1, 200 m3/m3 hydrogen/hydrocarbon ratio). there has been adverse tendency of changes in the yield of the c5+ products, of course. 0 5 10 15 20 25 30 330 340 350 360 370 380 temperature, °c g as eo us p ro du ct y ie ld , % 60 70 200 600 600 500 500 600 0.75 --+ ◊ -○-δ1.5 -□-x2.0 -●3.0 -■-▲lhsv, h-1 8040 h2/ch, m3/m3 pressure, bar figure 5: gaseous product yield as a function of process parameters 112 as example, the main properties of base oil products, which were produced at advantageous process parameters are presented in table 3. it can be seen, that at optimal process parameters (temperature: 350–355 °c, pressure: 70–80 bar, lhsv: 0.75–1.3, hydrogen/hydrocarbon volume ratio: 500–600 cm3/cm3) base oils having high viscosity index, good cold flow properties, ultra low sulphur content (3–5 ppm) and strongly reduced aromatic content (1.0–3.8%) were produced. these base oils fulfill the requirements of api group iii base oils, and they can be applied to produce lubricants with low sulphur and aromatic content, for example to manufacture “low saps” engine oils. the gas oil products obtained are excellent blending components and fulfil the most severe quality requirements (sulphur content: <2 ppm; cetane number: 61–64, aromatic content: 0.5–1.1%). so they are appropriate to manufacture environmental friendly diesel fuels. the naphta fractions, produced in low amount, have high isoparaffine content (>70%) and they are free of sulphur, thus they are considered as excellent naphta blending components. table 3 main charachteristics of isomerized base oils (temperature: 350–355 °c, pressure: 70–80 bar, lhsv: 0.75–1.3, hydrogen/hydrocarbon volume ratio: 500–600 cm3/cm3) properties value c20hydrocarbon content, % 16.9–14.6 c20+, hydrocarbon content, % 83.1–86.4 i-/n-paraffin weight ratio 3.29–3.94 kinematic viscosity (100°c), mm2/s 3.9–4.15 viscosity index 136–142 pour point , °c -17 (–) -12 volatility, (noack), % 14–10 sulphur content, mg/kg 3–5 aromatic content, % 1.0–3.8 conclusions the principal motivation force behind the base oil development is the growing demand of base oils for the economical production of highly efficient engine oils with practically zero sulphur-, nitrogenand aromatic content. base oils possessing these advantageous properties can be produced mostly by catalytic technologies. based on the results it can be concluded, that base oils with very high viscosity index and low pour point can be produced from high molecular weight hungarian crude slack wax with hydroisomerization over the pt/sapo-11/al2o3 catalyst. these base oils with low sulphur and aromatic content are appropriate to produce energy efficient and environmentally friendly engine oils. references 1. cock n.: conference of the institute of quarrying & aggregates association, waiangi, july 14-15., (2005) 2. “report of oil working group”, 4th jcap conference, june 1st, (2005) 3. stow c.: icis-lor conference, february 17th, (2005) 4. bardasz e. a.: 11th diesel engine emissions reduction, chicago, august 21-25, (2005) 5. auer j., borsi z., hancsók j., lakics l-né, lenti m., nemesnyik á., valasek i.: tribológia 2., kenőanyagok és vizsgálataik, tribotechnik kft., budapest, (isbn 963 00 8689 1), (2003) 6. rodera, j. m.: ueil congress, 2007 october 7. rousmaniere, j.: lubricants world, 10 (5), (2000) 38. 8. sanchez, p. m. m.: europia general information meeting, brussels, may 21st, (2003) 9. kramer, d. c., lok, b. k., krug r. r., rosenbaum, j. m.: machinery lubrication, 2003 may 10. magyar j., hancsók j., krár m., pölczmann gy.: magyar kémikusok lapja, 61(9-10), (2006), 309-314. 11. hung. pat. 225 912 (2001) microsoft word 01_r.doc hungarian journal of industrial chemistry veszprém vol. 35. pp. 101-108 (2007) interpetable support vector machines in regression and classification – application in process engineering t. kenesei, j. abonyi university of pannonia, department of process engineering, h-8201 veszprém, p.o.box 158, hungary abonyij@fmt.vein.hu, www.fmt.vein.hu/softcomp tools from the armoury of soft computing have been in focus of researches recently, since soft computing techniques are used for fault detection (classification techniques), forecasting of time-series data, inference, hypothesis testing, and modelling of causal relationships (regression techniques) in process engineering. these techniques solve two cardinal problems: learning from experimental data by neural networks and support vector based techniques and embedding existing structured human knowledge into fuzzy models. support vector based models are one of the most commonly used soft computing techniques. support vector based models are strong in feature selection and to achieve robust models and fuzzy logic helps to improve the interpretability of models. this paper deals with combining these existing soft computing techniques to get interpretable but accurate models for industrial purposes. the paper describes that trained support vector based models can be used for the construction of fuzzy rule-based classifier or regression models. however, the transformed support vector model does not automatically result in an interpretable fuzzy model because the support vector model results in a complex rulebase, where the number of rules is approximately 40-60% of the number of the training data. hence, reduction of the support model-initialized fuzzy model is an essential task. for this purpose, a three-step reduction algorithm is used on the combination of previously published model reduction techniques. in the first step, the identification of the sv model is followed by the application of the reduced set method to decrease the number of kernel functions. the reduced sv model is then transformed into a fuzzy rule-based model. the interpretability of a fuzzy model highly depends on the distribution of the membership functions. hence, the second reduction step is achieved by merging similar fuzzy sets based on a similarity measure. finally, in the third step, an orthogonal least-squares method is used to reduce the number of rules and re-estimate the consequent parameters of the fuzzy rule-based model. the proposed approach is applied for classification problems and applied for hammerstein system identification to illustrate the effectiveness of the technique. introduction tools from the armoury of soft computing have been in focus of researches recently, since soft computing techniques are used for fault detection (classification techniques), forecasting of time-series data, inference, hypothesis testing, and modelling of causal relationships (regression techniques) in process engineering. as mankind use, store and maintain enormous size of information in databases (the amount of data used doubles almost every year) modelling techniques getting more and more important. this phenomenon implies the need of new generation computational techniques to support knowledge extraction from data sources. historically the notion of finding useful patterns in data has been given a variety of names including data mining, knowledge extraction, information discovery, and data pattern processing. the term data mining has been mostly used by statisticians, data analysts, and the management information systems (mis) communities. [1] the term knowledge discovery in databases (kdd) refers to the overall process of discovering knowledge from data, while data mining refers to a particular step of this process. data mining is the application of specific algorithms for extracting patterns from data. the additional steps in the kdd process, such as data selection, data cleaning, incorporating appropriate prior knowledge, and proper interpretation of the results are essential to ensure that useful knowledge is derived form the data [2]. soft computing techniques are one of the cornerstones of the kdd process. this paper gives a method how the techniques of soft computing can be combined to get interpretable and robust models for the kdd process. the meaning of soft computing was originally tailored in the early 1990s by dr. zadeh [3]. soft computing refers to a collection of computational techniques in computer science, artificial intelligence, machine learning and some engineering disciplines, to solve two cardinal problems: ● learning from experimental data (examples, samples, measurements, records, patterns) by 102 neural networks and support vector based techniques ● embedding existing structured human knowledge (experience, expertise, heuristic) into fuzzy models [2] these approaches attempt to study, model, and analyze very complex phenomena: those for which more conventional methods have not yielded low cost, analytic, and complete solutions. earlier computational approaches (hard computing) could model and precisely analyze only relatively simple systems. as more complex systems arising in biology, medicine, the humanities, management sciences, and similar fields often remained intractable to conventional mathematical and analytical methods. where the hard computing schemes, which strive for exactness and full truth, fail to render the problem, soft computing techniques exploit the given tolerance of imprecision, partial truth, and uncertainty is inherent in human thinking and in real life problems, to deliver robust, efficient and optimal solutions and to further explore and capture the available design knowledge. generally speaking, soft computing techniques resemble biological processes more closely than traditional techniques, which are largely based on formal logical systems, such as sentential logic and predicate logic, or rely heavily on computer-aided numerical analysis. support vector based models and neural networks are one of the most commonly used soft computing techniques. however it should be pointed out that simplicity and complexity of these systems is a challenging task to perform. neural networks, support vector machines are universal approximators of any multivariate function; they are widely-used to model highly nonlinear, unknown or partially known complex systems plants or processes. the identification of the proper structure of nonlinear neural networks (nns) and support vector based techniques (svm, svr) is a challenging task, since these black-box models are too complex and not interpretable. complexity and interpretability issues are connected with each other: achieve the less complex more interpretable model with the best accuracy. other problem is how a priori knowledge can be utilized and integrated into the black box modelling approach, and how a human expert can validate the identified black box model or more favourably, follow the identification process to interfere in it if it is needed (e.g. to avoid over parameterization) neural networks and support vector machines are strong in feature selection and to achieve robust models and fuzzy logic helps to improve the interpretability of models. with the combination of these techniques accurate, but interpretable models can be achieved. this paper describes a three-step technique how to use reduction techniques on trained svm and svr models to acquire transparent, but accurate fuzzy rule based classifier and fuzzy regression models. the steps are the following: step 1. reduced set method the identification of the svm/svr model is followed by the application of the reduced set (rs) method to decrease the number of kernel functions. originally, this method has been introduced by [4] to reduce the computational complexity of sv models. step 2. similarity-based fuzzy set merging the gaussian membership functions of the fuzzy rulebased models are derived from the gaussian kernel functions of the sv models. the interpretability of a fuzzy model highly depends on the distribution of the membership functions. hence, the next reduction step is achieved by merging fuzzy sets based on a similarity measure. [5] step3. rule-base simplification by orthogonal transformations finally, an orthogonal least-squares method is used to reduce the number of rules and re-estimate the consequent parameters of the classifier. the application of orthogonal transforms for reducing the number of rules has received much attention in the recent literature [6, 7]. these methods evaluate the output contribution of the rules to obtain the order of importance. the less important rules are then removed according this ranking to further reduce the complexity and increase the transparency. this article organized as follows. firstly basic notations of support vector machines and the connection between the fuzzy rule-based classifiers is described, later on the connection between support vector regression and fuzzy regression is introduced. after detailed description of the three-step reduction algorithm examples indicate the power and the usage of the described techniques either on classification and regression problems. support vector machines for classification formulation of the fuzzy rule-based classifier as a kernel machine svm has been recently introduced for solving pattern recognition and function estimation problems. svm is a nonlinear generalization of the generalized portrait algorithm developed in russia in the 1960s. in its present form, the svm was developed at at&t bell laboratories by vapnik and co-workers.[8] due to this industrial context, svm research has up to date had a sound orientation towards real-world applications. svm learning has now evolved into an active area of research. moreover, it is in the process of entering the standard methods toolbox of machine learning. the basic idea behind svm is that with a kernel function k(xi, xj) which for all data pairs {x1, ... xnd} ⊂ χ × rni give rise to positive matrices kij := k(xi, xj). [9] using k instead of a dot product in rni corresponds to mapping the data into a possibly high dimensional space f, by a 103 usually nonlinear map φ : rni → f and takes the dot product there k(zi, x) = (φ(zi), φ (x)) (1) the structure of the fuzzy rule-based classifier one widely used approach to solve non-fuzzy nc-class pattern recognition problems is to consider the general problem as a collection of binary classification problems. accordingly, nc classifiers can be constructed, i.e. one for each class. the c-th classifier, c = 1 ... nc, separates class c from the nc other classes. this one-against-all method results in a hierarchical classifier structure that allows for a sequential model construction and evaluation procedure. based on this the classifier consist of nc fuzzy subsystems with a set of takagi-sugeno-type fuzzy rules [10] that describe the c-th class in the given data set as: ri c if x1 is c ia1 and ... xn is c ina then c i c iy δ= (2) where ri c is the i-th rule in the c-th fuzzy rule-based classifier and nr c denotes the number of rules. c n c i i aa k,1 denote the antecedent fuzzy sets that define the operating region of rule in the ni dimensional input space. the rule consequent δi c is a crisp number. the connective is modelled by the product operator. hence the degree of activation of the i-th rule is calculated as ( ) ( )∏ = == in j c rj c ij c i nixax 1 ,,1, kβ (3) the output of the classifier determined by the following decision function ( ) ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ += ∑ = cc i n i c i c bxy c r δβ 1 sgn (4) where bc is a constant threshold. if yc = –1, then it is not an item in class c. the main principle of kernel-based support vector classifiers is the identification of a linear decision boundary in this high-dimensional feature-space. the link to the fuzzy model structure is the following: the fuzzy sets are represented in this paper by gaussian membership functions ( ) ( ) ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ − = 2 2 2 exp σ ijj jij zx xa (5) ( ) ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ − == σ β 2 exp),( 2 i ii zx xzkx (6) the degree of fulfilment βi(x) can be written in a more compact form by using the gaussian kernels. this kernel interpretation of fuzzy systems shows that fuzzy models are effective in solving nonlinear problems because they map the original input space into a nonlinear feature space by using membership functions similar to the svm that utilizes kernel functions for this purpose. support vector machines for regression svms can also be applied to regression problems as described in the following paragraphs. suppose we have the training data {(x1, y1) ... (xnd, ynd)} ⊂ χ × rni, where χ denotes the space of input patterns. our goal is to find function f(x) that has at most ε deviation from the actually obtained targets yi for all the training data. in other words we do not care about errors as long as they are less than ε, but will not accept any deviation larger than this [9]. the linear case is the following: ( ) inbzwithbxzxf r∈∈+= ,, χ ⎩ ⎨ ⎧ ≤−+ ≤−− ε ε ii ii ybxz bxzy ts z , , .. 2 1min (7) sometimes however we want to allow some errors. this could be done by the introduction of an alternative loss function. the loss function must be modified to include a distance measure. figure 1: loss functions the loss function in fig. 1(a) corresponds to the conventional least squares error criterion. the loss function in fig. 1(b) is a laplacian loss function that is less sensitive to outliers than the quadratic loss function. huber proposed the loss function in fig. 1(c) as a robust loss function that has optimal properties when the underlying distribution of the data is unknown. these three loss functions will produce no sparseness in the support vectors. to address this issue vapnik proposed the loss function, also called ε-insensitive loss function in fig. 1(d) as an approximation to huber’s loss function that enables a sparse set of support vectors to be obtained [11]. the nonlinear svr problems with the ε-insensitive loss function (fig. 1(d)) is given by: a b c d 104 ( ) ( ) ( ) ( ) [ ]cand tosubject y xxk maximize ji n i ii n i iii n i ii n ji jijjii d dd d ,0 0 ,))(( 2 1 , 1 11 1, ∈ =− ⎪ ⎪ ⎩ ⎪⎪ ⎨ ⎧ −++− −−− ∑ ∑∑ ∑ = ∗ = ∗ = ∗ = ∗∗ αα αα ααααε αααα (8) where α is the lagrange multiplier (α* is the dual variable); the kernel function k; c > 0 represents the trade-off between the flatness of f and the deviation tolerance. we can rewrite the equation above to formulate the so called support vector expansion: ( ) ( )∑ = ∗ +−= dn i iii bxxkxf 1 ,)( αα where ( ) ( )∑ = ∗−= dn i iii xz 1 φαα (9) formulation of the fuzzy regression model based on support vector regression the link between support vector based techniques and fuzzy models is established in the earlier sections through equations 1-6. to get a fuzzy-rule based regression model from the support vector regression model the following interpretation is needed: ( ) bxy i n i i r +=∑ = δβ 1 (10) where βi is the firing strength and δi is the rule consequent. reduction of the number of fuzzy sets in the previous section, it has been shown how kernelbased models with a given number of kernel functions nr, can be obtained. because the number of the rules in the transformed fuzzy system is identical to the number of kernels, it is extremely important to get a moderate number of kernels in order to obtain a compact fuzzy rule-based model. from (6) it can be seen that the number of fuzzy sets in the identified model is ns = nr · ni. the interpretability of a fuzzy model highly depends on the distribution of these membership functions. with the simple use of (6), some of the membership functions may appear almost undistinguishable. merging similar fuzzy sets reduces the number of linguistic terms used in the model and thereby increases the transparency of the model. this reduction is achieved by a rule-base simplification method [12, 13], based on a similarity measure s(aij, akj), i, k, = 1, ..., n; and i≠j. if s(aij, akj) = 1, then the two membership functions aij and akj are equal. s(aij, akj) becomes 0 when the membership functions are non-overlapping. during the rule-base simplification procedure similar fuzzy sets are merged when their similarity exceeds a user-defined threshold θ ∈ [0, 1]. the set-similarity measure can be based on the settheoretic operations of intersection and union [12]: ( ) kjij kjij kjij aa aa aas ∪ ∩ =, (11) where |·| denotes the cardinality of a set, and the ∩ and ∪ operators represent the intersection and union, respectively, or it can be based on the distance of the two fuzzy sets. here, the following expression was used to approximate the similarity between two gaussian fuzzy sets [13]: ( ) ( ) ( ) ( )221 1 ,1 1, kjijkjijkjij kjij zzaad aas σσ −+−+ = + = (12) reduction of the number of rules by orthogonal transforms by using the previously presented sv model identification and reduction techniques, the following fuzzy rule-based models have been identified. for classification: ( ) ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ + ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ − = ∑∏ = = b zx y i n i n j ijjr i δ σ1 1 2 2 2 expsgn (13) for regression: ( ) b zx y i n i n j ijjr i + ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ − = ∑∏ = = δ σ1 1 2 2 2 exp (14) because the application of the rs method and the fuzzy set merging procedure the obtained membership functions only approximate the original feature space identified by the sv based model. hence, the δ = [δ1, δ2, ..., δnr]t consequent parameters of the rules have to be re-identified to minimize the difference between the decision function of the support vector machine and the fuzzy model (13, 14): ( ) ( ) 2 1 2 1 1 ,∑ ∑ ∑ = = = −=⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −= d i rn j s n i n i jiiiji xxxkmse δβδγ by (15) where the matrix rd nn ×∈= rb,,bb rn1 ][ k containing the firing strength of all nr rules for all the input xi, where bj = [βj(x1), ..., βj(xnd)] t. as the fuzzy rule-based model (13, 14) is linear in the parameters δ, (15) can be solved by a least-squares method δ = b+ ys (16) where b+ denotes the moore-penrose pseudo inverse of b. the application of orthogonal transforms for the above mentioned regression problem (15) for reducing the number of rules has received much attention in recent literature [14]. these methods evaluate the output contribution of the rules to obtain an importance ordering. for modelling purposes, the orthogonal least squares 105 (ols) is the most appropriate tool [7]. the ols method transforms the columns of b into a set of orthogonal basis vectors in order to inspect the individual contribution of each rule. to do this, gram-schmidt orthogonalization of b = wa is used, where w is an orthogonal matrix wt w = i and a is an upper triangular matrix with unity diagonal elements. if wi denotes the i-th column of w and gi is the corresponding element of the ols solution vector g = aδ, the output variance ys t y/nd can be explained by the regressors d n i i ng r / 1 i t i ww∑ = . thus, the error reduction ratio, ρ, due to an individual rule i can be expressed as s t s i t iu i yy wwg 2 =ρ (17) this ratio offers a simple mean for ordering the rules, and can be easily used to select a subset of rules in a forward-regression manner. evaluating only the approximation capabilities of the rules, the ols method often assigns high importance to a set of redundant or correlated rules. to avoid this, in [7] some extension for the ols method were proposed. in the previous sections it has been shown how an sv based model, that is structurally equivalent to a fuzzy model, can be identified. unfortunately, this identification method cannot be used directly for the identification of interpretable fuzzy systems because the number of the support vectors is usually very large. typical values are 40-60% of the number of training data which is in our approach equal to the number of rules in the fuzzy system. therefore, there is a need for an interpretable approximation of the support vector expansion. for this purpose the three-step algorithm described will be used in the examples section examples example for classification to show the power of the described technique is applied to the wisconsin breast cancer data, which is a benchmark problem in the classification and pattern recognition literature. the data is divided into training and an evaluation subset that have similar size and class distributions (we used 342 cases for training and 341 cases for testing the classifier). first, the advanced version of c4.5 was applied to obtain an estimate for the useful features. this method gave 36 misclassification for the problem (5,25 %). the constructed decision-tree model had 25 nodes and used mainly three inputs; x1, x2 and x6. based on this pre-study, only the previous three inputs were applied to identify the svm classifier with nx = 71 support vectors. the application of this model resulted in 3 and 15 misclassifications on the training and testing data, respectively. this model has been reduced by the rs method, by which we tried to reduce the model by a factor of 10, nr = 8. by this step, the classification performance slightly decreased on the training set to 12 misclassifications, but the validation data showed a slightly better result with 14 misclassifications. next, the reduced kernelclassifier was transformed into a fuzzy system. fig. 2 shows the membership functions that were obtained. the obtained model with eight rules is still not really well interpretable; however, some of the membership functions appear very similar and can probably be merged easily without loss in accuracy. figure 2: non-distinguishable membership functions obtained after the application of the rs method figure 3: interpretable membership functions of the reduced fuzzy model table 1: classification rates and model complexity for the constructed classifiers method # miss. train #miss test # rules # conditions svm 3 15 71 213 rs method 12 14 8 24 merging 11 13 8 10 ols 14 16 2 4 106 the performance of the classifier slightly increased after this merging step (table 1). subsequently, using the ols method, the rules were ordered according to there importance. then, we reduced the number of rules one-by-one according the ols ranking, till a major drop in the performance was observed. to our surprise, only two rules and four membership functions were necessary to have a good classification performance on this problem: 14 and 16 misclassification on the learning and validation data, respectively (table 1, fig. 3). the obtained rules are: r1. if x1 is small and x2 is small and x6 is small then class is benign; r2. if x1 is high then class is malignant; where x1 is the clump thickness, x2 the uniformity of cell size, and x6 a measure for bare nuclei. example for regression to demonstrate the potential of support vector regression techniques two examples are introduced. firstly a simple regression problem called regress is solved. regress is a simple dataset containing 51 samples (fig. 4). figure 4: the regress dataset with model output, support vectors and the insensitive region. the svr technique obtained nx = 14. this model has been also reduced by the rs method, by which we tried to reduce the model to nr = 10. after doing the modelling steps described in the classification example we achieved the following results (described in table 2) table 2. svr results on regress data method rmse # rules svm 0,0840 14 rs 0,0919 10 ols 0,2261 9 merging 0,2415 6 the ols reduction indicated, that reducing with one rule results the increase of modelling error at this example, for an interesting point we mention that using extreme reduction steps in this example (nr = 4, after ols ranking nr = 2) gives also reasonable results (rmse = 1.241). identification of a hammerstein system in this example, the support vector regression is used to approximate a hammerstein system that consists of a series connection of a memory less nonlinearity, f, and linear dynamics, g, as shown in fig. 5 where v represents the transformed input variable. figure 5: hammerstein system for transparent presentation, the hammerstein system to be identified consists of a first-order linear part, y(k+1) = 0,9·y(k) + 0,1·v(k), and a static nonlinearity represented by a polynomial, v(k) = u(k)2. the identification data consists of 500 input-output data. a support vector regression model was identified with the efficiency summarized in table 3. table 3: svr results on hammerstein system identification method rmse # rules svm 0,0533 22 rs 0,0604 15 applying ols 0.0650 13 merging 0.0792 12 figure 5: identified hammerstein system support vectors and model output after reduction. as fig. 5 and table 3 conclude, support vector regression is able to give accurate model for hammerstein system with, however the results are not interpretable. hereby the three-step reduction algorithm is used to acquire interpretable fuzzy regression model. after applying the rs method we were able to reduce the number of support vectors to 15 without the loss of the modelling error, but the obtained results are still not interpretable as it can be seen on fig. 6. using further reduction with the second and third step of the algorithm ols and fuzzy membership function merging finally results interpretable (fig. 7) and accurate (table 3) fuzzy model. -2 0 2 -1,5 0 1,5 regress data model output support vectors insensitive region 250 500 0 1 hammerstein data model output support vectors model output after reduction 107 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0 0.2 0.4 0.6 0.8 1 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0 0.2 0.4 0.6 0.8 1 figure 6: non-distinguishable membership functions obtained after the application of the rs method 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0 0.2 0.4 0.6 0.8 1 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0 0.2 0.4 0.6 0.8 1 figure 7: interpretable membership functions of the reduced fuzzy model conclusion it has been shown in a mathematical way that support vector based techniques and fuzzy rule-based models work in a similar manner as both models maps the input space of the problem into a feature space with the use of either nonlinear kernel or membership functions. the main difference between support vector based and fuzzy rule-based systems is that fuzzy systems have to fulfil two objectives simultaneously, i.e., they must provide a good modelling performance and must also be linguistically interpretable, which is not an issue for support vector systems. however, as the structure identification of fuzzy systems is a challenging task, the application of kernel-based methods for model initialization could be advantageous because of the high performance and the good generalization properties of these type of models. accordingly, support vector-based initialization of fuzzy rule-based model is used in this paper. first, the initial fuzzy model is derived by means of the support vector learning algorithm. then the support vector model is transformed into an initial fuzzy model that is subsequently reduced by means of the reduced set method, similarity-based fuzzy set merging, and orthogonal transform-based rule-reduction. because these rule-base simplification steps do not utilize any nonlinear optimization tools, it is computationally cheap and easy to implement. the application of the proposed approach is shown for the wisconsin breast cancer as a classification problem and regress data and hammerstein system identification as a regression problem. the obtained models are very compact but their accuracy is still adequate. besides, it might be clear that still real progress can be made in the development of novel methods for feature selection. we intend this paper also as a case study for further developments in the direction of a combination-of-tools methodology for modelling and identification, aiming at models that perform well on multiple criteria, considering here different soft-computing tools, namely support vector machines and fuzzy techniques are combined to achieve a predefined trade-off between performance and transparency. acknowledgement the authors would like to acknowledge the support of the cooperative research centre (vikkk) (project 2004-i) and hungarian research found (otka t049534). jános abonyi is grateful for the support of the bolyai research fellowship of the hungarian academy of sciences. references 1. abonyi j., feil b.: computational intelligence in data mining, informatica 29 (2005) 3-12 2. kecman v.: learning and soft computing, mit press 2001 3. zadeh l. a.: fuzzy logic, neural networks, and soft computing, communications of the acm, vol. 37 (1994), issue 3, 77-84 4. schölkopf b., mika s., burges c. j. c., knirsch p., müller k.-r., ratsch g., smola a.: input space vs. feature space in kernel-based methods, ieee trans. on neural networks, vol. 10(5) (1999) 5. setnes m., babuska r., kaymak u., van nauta lemke h. r.: similarity measures in fuzzy rule base simplification, ieee trans. smc-b, vol. 28 (1998), 376-386 6. yen j., wang l.: simplifying fuzzy rule-based models using orthogonal transformation methods, ieee trans. smc-b vol. 29, (1999), 13-24 7. setnes m., hellendoorn h.: orthogonal transforms for ordering and reduction of fuzzy rules, in fuzzieee 700-705,san antonio, texas, usa 2000 8. cortes c., vapnik v.: support-vector networks, at&t research labs, usa 1995 9. smola a. j., schölkopf b.: a tutorial on support vector regression, statistics and computing 14, 199-222, 2004 10. takagi t., sugeno m.: fuzzy identification of systems and its application to modelling and control, ieee trans. smc vol. 15 (1985) 116-132 11. gunn s. r.: support vector machines for classification and regression, technical report 1998 108 12. setnes m., babuska r., kaymak u., van nauta lemke h. r.: similarity measures in fuzzy rule base simplification 13. jin y.: fuzzy modelling of high-dimensional systems, ieee trans. fs vol. 8 (2000) 212-221 14. yen j., wang l.: simplifying fuzzy rule-based models using orthogonal transformation methods, ieee trans. smc-b vol. 29 (1999) 13-24 hungarian journal of industrial chemistry veszprém vol. 33(1-2). pp. 1-9 (2005) basic principles of process modelling g. a. almásy and k. kollár-hunek1 university of veszprém, h-8201 veszprém, p.o. box 158, hungary 1budapest university of technology and economics, h-1521 budapest, p.o. box 91, hungary the principle of systems and process engineering was introduced into mathematical modelling in the middles of 20-th century by bertalanffy, mesarovič, kalman, zadeh, benedek and others [1,2,7,9]. himmelblau and bischoff showed that population balance problems, i.e., processes described with another independent variable than a physical space variable, can be solved by differential equations similarly to the transport equations. essentially the same concepts are used – even with different names – in the theory of chemical, petrochemical, ceramic, food, biochemical process engineering, building material production, metallurgy, nuclear engineering and maybe in other fields of applied chemistry or physics. the differences in the nomenclature and treatment make difficulties transferring the theoretical bases and ways of solution of different problems from one field already solved to an other one. the aim of this paper is to define the processes, so that all models shall be given a common mathematical background, all models can be deduced therefrom. the postulates listed here can also serve as definitions of processes, process engineers deal with. to sum up the main concepts of process engineering is also worthwhile to identify and support the most important i/o elements in a process approached quality management system for different fields of industry. keywords: process modelling, principles of systems and process engineering introduction in the middles of 20-th century as the principle of systems and process engineering was introduced into mathematical modelling, bertalanffy [2] called the attention to the fact that the models describing processes functioning differently, have sometimes similar mathematical descriptions. mesarovič [9] was the first, attending to formulate this mathematically. the mathematical system theory that could be first applied in linear cases can be regarded to kalman [7], mostly used in control theory. the concepts of state, of the mathematical process modelling and computer simulation can also be regarded to him. himmelblau and bischoff [6] showed that population balance problems can be solved by differential equations similarly to the transport equations. fan and friedler [8], grossman [4] and floudas [3] have recently dealt with optimization of processes. essentially the same concepts are used – even with different names – in the theory of processes in different fields of applied chemistry and physics. the 1 to 3dimensional physical spaces (length, width and depth), and other independent variables of process description, either continuous or discontinuous (like particle size, transition between phases, microorganism age, grade of polymerization, etc.) or combination thereof can be mathematically handled similarly. even the iso 9001:2000 standards encourage the adoption of the process approach for the management of the organisations [5]. in the standard there is explicitly written, that “any activity that receives inputs and convert them to outputs, can be considered as a process.” in our paper we give some postulates which are necessarily valid for ordinary processes. we use in the following the term process for all real or theoretical systems, that satisfy the given postulates. according to our concepts a correct process model describes process activities independently of personal wills (except environmental impacts) and do not contradict the accepted laws of classical physics. those of relativistic and quantum physics are not taken in consideration here. concepts our aim is to present some properties of process models necessary to be correct in the sense that they obey the postulates below, i.e., the obvious rules of classical 2 newtonian physics. the first question is whether it is a necessary condition for process models to fulfil the condition not to contradict the rules of conservation. there are two logical arguments to accept this. first: nobody wants to have such a process model that produces anything from nothing that is possible according to a model contradicting the rules of conservation of material. similarly, a model contradicting the first law of thermostatics is worthless when it is applied to simulate the energy scheme of a plant. according to such a model it would be the most profitable action to produce only energy from nothing. secondly: models, contradicting the rules of classical physics are valid of zero probability in practical, nonmicrophysical processes. it is a logically acceptable conjecture for all realistic models that parameters, estimated according to the maximum probability principle, give a better approximation of the reality also extrapolating out of their validity range. all changes during the process operation1 are due to the state of the process and its environment. the components of the state are the conserving substances (like mass, energy, momentum, and other conserving physical substances) that change in a process influenced only by the environmental streams (se,·,·). in some practical cases also other categories may be chosen as entity components, conserving their quantity during the process, changing only on environmental influences as well. such are composition in separation or disintegration processes, the amount of chemical elements in chemical reactions, the amount of elementary nuclear particles in nuclear processes, etc.. all they are nominated as entities. in our formulation, we say their time–dependent distribution over the space of process coordinates the process state ei(t). the consequence of the above is that a certain process is totally specified by the initial state and by the (not necessarily time dependent) environmental streams in the time period of simulation. the independent variables of process description are the process variables (x) and time (t). process variables span the space of process coordinates (x∋x). the elements of the space of process coordinates are n-element variables, where n means the number of the process variables. they may be considered as continuous (i.e., physical space coordinates), equidistant discrete (i.e., grade of polymerization, serial number of units, etc.) or abstract variables (i.e., physical phases, crystal forms, chemical compounds, etc.). for shortness we say for them n-dimensional vectors. time may be considered as continuous, equidistant discrete, non– equidistant discrete or general time (continuous mixed with discrete events). continuous variables are described by continuous functions, discrete variables by sets of integer numbers, abstract variables by some single points. the set of process variables is a direct product of them, used in the process modelling. 1 in the following: operation, where a unit operation in principle corresponds to exactly one correct mathematical operation considering the level of decomposition. the cardinality of the sets, both that of process variables (i) and of entity (m) is considered as finite. decomposition is cutting the space of process variables into two or more disjoint process variable subspaces, said subprocesses. their elements are interconnected by inner entity streams. processes are encircled by environment. streams from or to it, the so-called environmental streams influence its operation. a process model including the environmental parameters, possibly also timedependent, describe the dependence of their variables. subprocesses are linked by inner entity streams depending on the states of the connected subprocesses. they are environmental streams from the view of the subprocesses. naturally, other variables, necessary to compute the operation or streams between the subprocesses maybe introduced within the model but not between the subprocesses, as necessary. subprocesses have similar properties as the processes themselves. when decomposing continuous variable processes into two or more discrete environmental variable processes at least one of them has to consist again of a continuous one. composition is the contrary of decomposition, i.e., building a composite model from more processes that will be subprocesses of the composed one. the process coordinates of the composed model will be the union of each subprocesses, the states are the union of subprocess states and the parameters are the union of the subprocess parameters. cutting a process into subprocesses has practical reason; generally only models of parts of a process can be described by an elementary or comparatively simpler model and the full process model has to be composed by them. in order to simplify the process model, usually the number of entities, process variables and parameters is reduced. this reduction results naturally in another, more inaccurate, less generally applicable model. the operation of processes are described by operation models and, if they are composed of more subprocesses, by transfer models between them. operation models describe the distribution of entity streams depending on the state and environmental streams. transfer models describe the dependence of streams on the state of the connected subprocesses and some entity–independent subprocess. transfers are monotonic functions of the driving forces i.e., of the differences/differential quotients2 for each potential, that depends on the entity content/density of the submodel. the other factor of transfer is the transfer coefficient depending on the operation parameters of the submodel and on material properties, of the streams between the points connected. the inputs of operation models are the initial state (e(0)) and their time–dependent environmental streams. the outputs of the operation model are either the actual model’s state change or any functions of them. 2 we write as ⋅/⋅ (e.g., content/density) if we refer to a notion, differing in our discrete/continuous treatment. the character ∅ shall not be read in the text, as in (e.g., ∅/density). 3 we deal only with reproducible processes. reproducibility is understood that the states of processes are independent of start time: with identical state at the start time and identical environmental streams, the states of the processes are identical in any times related to the initial. this is only an abstraction; true exactly reproducible processes don’t exist in the reality but can be well applied in practical modelling processes. the second rule of thermostatics, the criterion of the increase of entropy is not dealt here with explicitly. in order to treat it, energy should divided into two kinds, regular and irregular and its motion should be constrained to one-sided. from the side of the theory, its validity is scale-dependent, what is regarded as irregular motion of particles. also the molecular or brownian motion of particles could be described as regular, seeing them from a molecular order of magnitude and stellar motion (movement of stellar objects) may be regarded as irregular, seeing it from a point of a higher magnitude. we omit handling these kinds of inequality constraints here. all of it is considered here is prescribing the rule that the direction of streams be always from higher potentials toward the lower. all other consequences of the second law are considered to be fulfilled by the operation models of the subprocesses. naturally, rules of less importance seen from the point of view of the actual problem, may be neglected in order to simplify the model. but if it has been neglected in one of the subprocesses the whole composed process model becomes more or less incorrect, concerning the left entity component dependent variables of a process are a finite set of entities in the case of discrete process variable functions; they are density distributions in the case of continuous process variable functions of the independent process variables. in most of the problems there are combined discrete and continuous processes. postulates the first assumption put is that with correctly posed and unbounded number of measurements a process model approximates the mapping of reality. we deal only with correct models, fulfilling this assumption. the postulates 1 to 5 are the comprised and most important component–independent features, generally accepted in the macroscopic real world. it is claimed that postulate 1 actual properties of a process depend only on its actual state. postulate 2 actual changes of a process state depend only on the actual state and on the environmental streams. postulate 3 each process model shall obey the conservation laws for each entity component at any time. postulate 4 there exists at least one set of linearly independent process variables one–to–one mapping any subspace of process variable space to the space of entity content/density and to the potential functions. postulate 5 processes shall obey the principle of causality. the next postulates express the trivial aim to the model application that results should be independent on the model users’ subjective decision. postulate 6 if a field of process variables is built up as a union of more than one subspaces, it can be decomposed into subprocesses of the same independent variables and/or those of the same time variable. postulate 7 it is claimed that decomposition– composition fulfils by definition that the composition or decomposition of a process model with any initial state and environmental stream functions must result into the same environmental variable relations, independently of the mode of decomposition into any submodels. postulate 8 processes are only relative–time dependent and they are independent on the zero and unit choice of time in the model. postulate 9 the model must be measurement–unity– invariant in time, in all its process variables and entities. reasons and physical background of postulates reason and consequence of postulate 1: it is assumed that all material properties necessary to describe the process depend only on the actual entity content/density in the process. simply practically there are no other impact possibilities and there is no other way of remembering on past events influencing the present or the future but the material state3. the fulfilment of this postulate is important in formulating models of composed processes as a complex, multivariate system of algebraic, partial difference/differential and integral equations. reason and consequence of postulate 2: streams depend on the process states and parameters – named in some cases transfer coefficients, but also rate coefficients, etc. – between the connected subprocesses. referring to postulate 1 we obtain postulate 2. this postulate is fulfilled also for controlled processes if set points and other control variables are ordered to the process parameters. reason and consequence of postulate 3: this condition is equivalent to the laws of conservation of entities, stated by definition. the sum/integral of entity changes in any process must be equal to the algebraic sum/integral of its environment streams in any time–interval/any actual time. any sum/integral of streams must be equal zero at its junction points. 3 this statement is difficult to see in biological processes, but sometimes it has its importance in these cases, as well [11]. 4 reason and consequence of postulate 4: this postulate is a necessary condition to observe and to simulate the operation of a submodel. reason and consequence of postulate 5: this postulate is trivial in everyday life. no actual or past event or observation is influenced by future environmental impacts. reason and consequence of postulate 6: this postulate is valid by definition of decomposition. contradicting this postulates the result depended on the cut, i.e., the result of simulation would depend on the subjective choice of model decomposition. process models of the decomposed models’ submodel are not necessarily of similar structure. the model state is the union of each/all its subprocess states; parameters are the union of submodel parameters. the sum/lebesque–integral of inner streams between each/all subprocesses is zero for each entity component. long–distance effects in process engineering are electromagnetic radiation, i.e., light and heat radiation, microwave heating, etc.4. these can be simulated by no–time–delay algebraic equations, while others by difference/differential equation increment models. reason and consequence of postulate 8: it is a necessary condition in the everyday life. no event is influenced by the fact, whether the time is measured from the zero of the time scale, whether it is counted according to the time according to the buddhist, christian, jew, muslim, etc. calendar, or from the beginning of the operation of the invested process or from the beginning time instance of a batch process. reason and consequence of postulate 9: measurement units are on the model builder’s choice, so it is impossible to influence the real operation. it is trivial that real processes are independent on the time scale shift, like in case of postulate 8. it should be noted that fulfilment of all the postulates is only necessary condition of practical correctness of the model. it depends also on the exactness of constitutive equations. in all of our next treatment their validity is assumed. process models according to the above postulates, processes may be described by operation, composed processes by operation and transfer models between them. operation of a composed unit would depend on the operation of all of its subprocesses. decomposition is possible applying the philosophy of postulate 6, in the praxis if the process can be clearly decomposed in selfstanding operation models, and in transfers connecting them. we consider all processes possible subprocesses of a more general process, what means, it is enough to discuss process models, it includes subprocess models, as well. 4 i.e., the speed of light is considered as infinity. in general, to simulate both the process and transfer models, the knowledge of a lot of state–property functions is needed. these functions are generally called constitutive equations. all of their knowledge is supposed in this treatment. according to postulate 1, actual properties of a process, depending on material quality, are depending only on their actual entity content/density according to postulate 2, actual changes of processes are depending only on the actual state of the given process, it means, on their x-space distribution. as a corollary of postulate 3, the sum/integral of streams or stream densities of entities is given by the sum/integral of connected streams or stream densities in any arbitrary (x,t) point of the process space, regardless to the direction of the streams. for the model of a process decomposition it is necessary to take in account postulate 6, it means the process should be decomposed into subprocesses of the same independent variables and those of the same time variable. at last, the operation model has to fulfill postulate 9, e.g. the operation model should be dimensionally correct. a part of the streams of the process from or to the environmental points is known, other part is unknown and we have to evaluate them. according to postulate 6 we may assume that the equation describing the operation model fulfils the conditions for existing solution, and so it makes possible to determine the potentials of the unknown streams and the differences/derivatives of the entities with respect to the time. the trajectories of the process – e.g. the solution of composed model – will be given by the time sum/integration of the simultaneous equation system of each operation model and of each stream model, including their initial and boundary conditions. one of the steps is to determine all potentials depending on the density content/density of entities, that are necessary to the calculation of connected streams by the stream models. some of the connected streams are known, others are unknown and are to be evaluated. we again assume, that the equation describing the operation model fulfils the conditions for existing solution, and so it makes possible to determine the unknown streams. the operation model – of course – depends on the material properties, too, but they are considered as properties of the functions describing the model, so we don’t discuss it in details. but we assume – according to postulate 4 – that the functions that connect potentials and entity contents/densities are known one–to one (invertible) functions. to simulate a process, its model has to solve the following problem: it is necessary to determine the potentials and driving forces between the connected environmental points, based on the entity content/density of the process and its environmental points, then to determine the entity content/density corresponding to a ∆t time step, using the sum/integral of the potentials and driving forces with respect to the process variables. 5 by repeated application of this step, the operation model of the process can determine the entity content/density on any time–interval, also for non constant environmental streams. operation models an operation model is a set of relations, describing the time dependent state change and the potentials necessary to compute the driving forces of the process toward or from its environment. the distribution of the entity content/density streams is influenced by the constitutive relations, by the equipment parameters of operation and by every/all streams entering and leaving the model. operation models have to based on the constitutive equations. describing an operation model by its equations, in a discrete process space we have to determine the hj(ei,t) potentials from i transfers the j subsystems and the stream rates toward or from the environment denoted by vi(t). using the notation above we get the equation for the ∆ei(t) entity change: ( ) ( )( )( ) ( ) itttt i ∈∆⋅⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ +=∆ ∑ ∈ i j iijji,i vele h (1) the first term on the right side is a sum regarding all subprocesses, defined so, that the stream is zero between subprocesses having no contact, or in the case i=j. in continuous process space the corresponding functions are g and ki,j , similarly as the streams and the density of entities are denoted by d(x,t). the derivative of the density function with respect to the time is given by ( ) ( ) ( )( )( ) ( ) xttx t t x ∈+= ∫ ∈ xxuξξdkxd ξ ξx, ,d,,g d ,d (2) it is important to see that postulate 3 is fulfilled if the submodels fulfil it and the composed operation models are sums/lebesque integrals of entity on the space of process variables at any considered time. postulate 8 and postulate 9 are fulfilled on any time interval if the submodels fulfil them and if the composed operation models are sums/lebesque time integrals of entity of environmental streams. the sufficiency is clear, the necessity has not been proven according to author’s knowledge, but it is of less practical importance. it is obvious in the case of transport equations. the necessary condition of fulfilling, the laws of conservation according to postulate 3, is given for discrete processes in equation 3, and for continuous processes in equation 4. ( ) ( ) ( ) ttitttt i ∈∈∀∆⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ +=∆ ∑ ∈ ii j jii vre , (3) ( ) ( ) ( ) ttxdttdtt tt t x ∈∈∀⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ +=∆ ∫ ∫ ∆+ ∈ xxxx ξ ,,,, uξqd ξ (4) for discrete processes, the entity increase of each entity component in any process space element i must be the sum of all entering–leaving streams j connected to it; the entity increase of each entity component in any continuous process space element x must be the integral of entering–leaving streams on the whole process variable space and that of environmental stream connected to it. stream/stream density and velocity of transfers environmental streams in a composed model are computed by transfer models, and have to undergo the conservation rules. transfer between discrete submodels is interpreted as transfers of each entity belonging to them. transfer models of a composed process describe the dependence of transfer streams on the environmental potentials and on some entity–independent and eventually time–dependent parameters. transfer potentials are assumed to be one–to–one functions of the entity content/density according to postulate 2 and postulate 4. they have to be computed either from the environment entity content/density or the potential itself by the operation models, depending eventually on the entity independent parameters of the constitutive equations. if the environmental entity capacity is considered infinite, then the potential itself has to be specified. transfer models are usually described as functions – mostly, but not necessarily – as products of state– dependent driving forces between the connected models and an approximately but not necessarily state– independent transfer coefficient. this is a somewhat redundant way of the stream–entity function description but is practical when the dependence is linear: the driving force equals approximately the difference of connected submodel transfer potentials, and the transfer coefficient an entity–independent constant. in this way the transfer streams depend on the driving forces that monotonously depend on the differences/derivatives of each potential and equal zero if the difference between the connected potentials is zero. note that such rules were motivating the first steps of physical chemistry and fluid mechanics. they are only linear approximating rules (like the newtonian rules of heat and impulse transfer, henry’s raoult’s, rule of component transfer between fluid phases, rules of fourier, fick, etc.). also such relation is for first order isothermal chemical reaction, but other reaction mechanisms are essentially non–linear. the potentials (chemical potential, temperature, etc.) of the environment entity variables must coincide with the entity variables of the process. environmental streams may be either time independent or dependent variables, according to the process specification. eq. 5 defines the velocity of entity-transfer between the points i and j in case of discrete-time processes having discrete process variables: 6 ( ) ( ) ( ) ( )( ) ( ) ( )( ) ( ) ( ) i t t t t ttt t ttt t t t ij constjconstj consticonsti ji ∈∀ −=⎟ ⎠ ⎞ ⎜ ⎝ ⎛ ∆ ∆ −=⎟ ⎠ ⎞ ⎜ ⎝ ⎛ ∆ −∆+ −≡ ≡⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ∆ −∆+ =⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ∆ ∆ = == == ji iii jjj , , , r eee eee r (5) as one can see, the velocity in equation 5 is defined by the partial difference quotients of ei or ej with respect to the time, according to this, the dimension of r is entity/time. this definition contains also the fulfilling of postulate 3. similarly, for discrete-time processes having continuous process variables, the velocity of entitydensity transfer is given in equation 6) ( ) ( )( ) ( )( ) ( x t t t t tt x ∈∀ −= ∆ ∆ −≡ ∆ ∆ = ξ ξqξddξq ξ x, xxx ,,,,,, constconst ) (6) the dimension of q is entity/(generalized volume×time), the dimension of d is entity/generalized volume. in eq. 7 and 8 is given the definition of the entity density, d , and the generalized volume, ∆v: ( ) ( ) v tt ∆ ∆ = → ,lim, 0 xx ed ζ (7) where ∏ ∈ ∆≡∆ ii iv x and { ii i ∈ ∆= xsupζ } (8) equation 9 and equation 10 express the velocity of entity/density -transfer for time-continuous processes having discrete/continuous process variables. ( ) ( ) i t t t consti j ji ∈⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ∂ ∂ = = ji,, e r (9) ( ) ( ) x t tt const ∈⎟ ⎠ ⎞ ⎜ ⎝ ⎛ ∂ ∂ = = ξξdξq ,,,,, xxx ξ (10) phenomenological description of stream/stream density the q(x,ξ,t) entity density-transfer stream velocity between points x and ξ is defined usually as the product of an entity-transfer coefficient and of the driving force. the entity-transfer coefficient is usually – but not in all cases – described by the li,j(hj(ei(t)) transfer coefficient, depending on the entity content of the subprocesses and on the geometry describing their contacts (for example heat transfer coefficient in discrete state space or heat conduction coefficient in continuous state space.), and by the potential difference vectors – called the driving force vectors – as their component–by component product. the above mentioned decomposition is not a unique one, but it is very useful for linearization, because the entity-transfer coefficient may be regarded often constant, and the driving force can be considered as proportional with the entity-differences, which means a considerable simplification in the numerical steps of the simulation. considering the above mentioned, the transferred entity stream/density between any arbitrary two discrete time points from x2 toward any x1 points is given by ( ) ( ) ( )( ) ( )( )( ) iitttttt ij ijijjiji ij jii ∈∀∆⋅⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −=∆⋅=∆ ∑∑ ∈∀∈∀ ,h,h ,,, elelre (11) the number of equations describing these conditions is n(i)2. in the case of i=j equation 11 is an identity, thus is meaningless. similarly, equation 12 describes the entity-change rate in case of continuous process variables: ( ) ( ) ( )( )( ) ( )( )( )( ) ttgtg ttt v v ∆⋅−= =∆⋅=∆ ∫ ∫ ∆∈ ∆∈ ξ ξ d,, d, , ξ ξξ ξ dkdk qd x,ξξx, ξ,x,x xx, (12) the functions k and l are nonnegative, and invariant to interchanging of the points 1 and 2 , necessarily for all entity components of any subsystems. streams can belong to more than two contact points, as well. (like in chemical reactions between more than two molecules). primary model here we don’t deal with functions describing operation of elementary models. we assume, those are well known either from the theoretical background of the process or from some empirical equations. but fulfilling the postulates discussed above, is required for the primary models, as well. composed model the solution of a composed model means that we know all the trajectories of the subprocesses, i.e. the entity contents and all the streams at all possible time point is determined. in case of a composed model the solution is given by the simultaneous solution of a multidimensional, usually non–linear, perhaps in closed form not known, partial integro–differential equation (including initial and boundary values). this integro–differential equation is given by all of the operation models and by all of the stream models. the simultaneous solution of this p.d.e. gives the derivative of the processes, from that the trajectories can be determined. usually we don’t have general solution in closed form, but only numerical ones by euler, newton, broyden, etc. methods. 7 some usual notions velocity: entity/density velocity is an often-occurring concept in process engineering. it is difficult to define in the process variable spatial description but may be defined as the absolute value of the difference– quotient/gradient of the mass components of entity on the process subspace: length, width and deepness. the gradient direction of energy–stream and velocity are often but not necessarily taken as equal to the former. generally speaking, each entity component has its own velocity. conductive streams: conductive streams (like molecular diffusion, heat conductivity, etc.) are often occurring in the so–called transport equations as second order difference/differential terms. the description of such conductive streams is possible, taking into consideration the entity contents/densities in all points of the considered space with proper weights. in the practice they can be simplified into the usual second order differential equations (divergence or rotation). this way of describing conductive streams is strongly exhausted in the so called transport equation in the theory of chemical process engineering. in our further treatment it will be not discussed; it is left for the future. cross effects: in most of the cases the so–called cross effects can be neglected between the component entity ø/density and the energy or impulse transfer streams5. in some cases they are also applied in industrial processes, like thermodiffusion in isotope separation. if necessary, they can be taken into consideration using vector–vector equations instead of particular relations to compute each transfer coefficient. pressure, pressure drop: the theoretical base of pressure and pressure drop computation is the law of conservation of momentum, transferring the momentum change by the pressure drop to the ground. its value is computed from the state, its change by the navier– stokes equation. in most of the cases, however, the change calculation is simplified calculating the pressure drop by friction factors. linear models in the space of process coordinates linearity in the space of process coordinates a process model is said to be linear in the space of process coordinates (further l.p.c.) if the equation 13 ( ) ( ) ( )22112211 zzzz eee ⋅+⋅=⋅+⋅ cccc holds for any two z∈x∪u points of the union of the space of process and environment variables. according to this definition is easy to see that if an operator l.p.c. contains parameters, they have to be independent of z. if such a model is a linear approximation of a continuous and differentiable non–linear model its coefficients become the corresponding partial difference/differential quotients of the variables on the corresponding (discrete or continuous) time variable. the simulation result becomes the sum of the state changes in time differences in discrete processes, and the time integral of the state changes in time in continuous time processes. it is easy so see that time independent processes have to be time independent as well. in all cases the models can be discrete or continuous in time. nothing is against that subprocesses of a l.p.c. process be nonlinear, supposed that their corresponding partial difference/differential quotients are approximated by state independent values. the coefficients of the linear system are given by the equation 11 and equation 14: ( ) ( )( ) ( ) ( )( ) ijitttt iijjijijji ∈∀⋅−⋅= ,h,,h,, ,, eeeleeel0 (14) ( ) ( ) ( ) ( ) x tttt ∈∀ ⋅−⋅= ξ dddkdddk0 ξξξξξ , ,g,,,g,, ,, x xxxxx (15) if the problem is linearized, all coefficients li,j⋅h(ej) of equation 11 and equation 14 are constants. it can be described clearly by hypermatrix – hypervector notation. for lack of space, it is omitting here. one of the most problematic cases is dividing homogeneous streams, that needs a prescription of entity stream ratios. it has to be described by bilinear equations that restricts the validity of the linearized equations into small time steps. that’s why networking programs have to iterate the concentration at each stream recirculation, too. an algorithm for the solution considering the above mentioned model descriptions, we suggest the following algorithm for the solutions: 1. having determined the derivatives of each entity content and each entity stream functions for each subprocess, we have to solve the corresponding system of linear equations. these procedures result an approximating linear system, whose accuracy depends on the length of the applied steps. this linear system won’t be more complicated if we consider as variables not only the entity contents of the subprocesses, but those of the higher level processes, too. 2. the next procedure is to evaluate the roots of the approximating linear system, that makes possible to approximate the next time-step values of the streams using euler, newton, broyden, or other methods 3. we add the resulted entity changes to the corresponding previous entity values. 8 4. we do this procedure until the last time point will be reached. theoretically the method offers the possibility for the numerical approximation of the trajectories also in the case of non–constant environmental streams. of course, the numerical differentiation in each step could require a long computer time if the number of subprocesses is high. the goal of the most computer engineering problems is to determine the stationary state of a stable system. this goal, considering constant values of the environmental variables (theoretically) can be reached if we know the coefficient matrix of the linear model: it requires the numerical solution of the eigenvalue– eigenvector system corresponding to the coefficient matrix of the dynamic simulations equation system. we don’t suggest any method to determine the process variables or to carry out the decomposition. both problems need special engineering aspects for each individual problem. the regularity of the corresponding jacobian matrix offers only a checking possibility. decomposition usually expands the number of parameters, but in case of linear models the huge equation system splits into several smaller ones, so that it offers bigger accuracy of numerical approximation. inversely, if we patch up subprocesses, the number of parameters decreases. sometimes it is necessary to shorten the intolerable long computing time, satisfied with lower accuracy of numerical approximations. these models are important, showing the theoretical possibility of simulation and optimizing complex processes, built up from subprocess models. we can also see the problem inversely: how a process may be seen from above, yielding a product wanted, decomposing it into subprocesses such detailed as it is necessary to reach the accuracy wanted. we are continuously working on some examples describing very different fields of process engineering, which show well the common bases and sometimes different ways of solving the complex process simulation and optimization problems. conclusions however, processes have been designed and industrially applied for centuries, the theory of their simulation, based on correctly formulated and defined basis, has not clearly put yet, according to the authors knowledge. the postulates put in this paper show some theoretical bases of simulation and process design and inspire a theoretically exactly based way of computing. the reason, not to formulate these rules is possibly due to the difficulty of executing such a calculation. this seemed to be impossible by human forces and to computers too up to the last decades. however, the computation possibilities reached in last years such a speed and memory capacity that the computation, necessary to such a simulation is over or shall reach them in few years. this paper tries to give basic postulates, some of them based on the well–known rules of physics and others on trivial logical statements. naturally, the question on the knowledge of constitutional equations remains. applying the algorithm outlined would be able to simulate, design, optimize processes, design their control system, their sensitivity on input, their stability. the stochastic simulation has not been treated here, in that case the objects are not numeric but probability distributions and the theoretical treatment becomes more complicated. one must not forget applying also the deterministic simulation model the chaotic uncertainty of the result due to the inherent sensitivity on initial conditions of such systems. acknowledgement authors are indebted to tamás sztanó for his valuable help in controlling the mathematic correctness of the paper. list of symbols cont. pr. continuous process disc. pr. discrete process d(x,t). density of an entity ei(t) time dependent distribution of an entity g(d(x,t)) potential in a cont. pr. h(ei(t)) potential in a discrete process i or j a discrete process variable vectors i the set of disc. proc. variable vectors m the set of entities li,j entity transfer coefficient for disc. proc. variables kx,ξ entity transfer coefficient for cont. proc. variables ri,j(t) velocity of entity transfer q(x,ξ,t) velocity of entity density transfer s, σ streams t time t the set of time values vi(t) environmental stream vector (discr. pr.) u(x,t) environmental stream vector (cont. pr.) x or ξ process coordinate vectors x the set of cont. proc. variable vectors ∆v generalized volume ζ factor for the definition of d(x,t). references 1. benedek p., lászló a.: a vegyészmérnöki tudomány alapjai, műszaki könyvkiadó, budapest, 1964 2. bertalanffy, l.: general system theory, braziller, new york, 1972 3. floudas, c, a.: computers and chemical engineering, 1999 (23) 963 4. galán, b., grossmann, l.e.: computers and chemical engineering, 1999 (23) 161 9 5. hajnal, é., kollár g., láng-lázi m.: periodica polytechnica, ser. chem. eng., 2004 (48) 41 6. himmelblau, d.m.: basic principles and calculations in chemical engineering, prentice-hall, englewood cliffs, n.j., 1982 7. kalman r.e., falb, p.l., arbib, m.a.: topics in mathematical system theory, mcgraw-hill, new york, 1969 8. kovács, z., ercsey, z., friedler, f., fan, l.t.: exact super-structure for the synthesis of separation-networks with multiple streams and sharp separators, computers and chemical engineering, 1999 (23) 1007 9. mesarovic, m.d., yasukiho takahara: general systems theory: mathematical foundations, acad. pr., new york, 1975 10. prigogine, i.: etude thermodynamiqe des phénomènes irréversibles, paris: dunod and liége: desoer 1947 11. viczián, zs., herrmann, n., kollár-hunek, k., zsíros l.: hungarian j. of ind. chem, 1999 (27) 311 01_modalmasy.pdf 01_modalmasy.pdf operation models stream/stream density and velocity of transfers phenomenological description of stream/stream density primary model composed model velocity: entity/density velocity is an often-occurring conc conductive streams: conductive streams (like molecular diffu linearity in the space of process coordinates an algorithm for the solution 04_modkeilh2o2paper.pdf table 1 properties of the membranes employed 05_modmatusek-hung j of ind chem.pdf abstract 07_mossfarm_styrene_hjic2005_jav.pdf acknowledgement 09_statracape_2_cikk_mari.pdf application of co-monotonic vector splines ch4+co2+air application of the new apex test for different systems conclusions acknowledgements list of symbols references 12_conthjich_paper_of_mnlb.pdf dimensionless equations. scaling controllability and observability 13_optim.pdf introduction process approach why is it worth to optimize? internal reasons external reasons environmental reasons modelling computer modelling, simulation fig 2 discrete event simulation scheme [pidd, 1992] optimization of food logistic processes defining core processes in logistics optimization by simulation technique main objectives to achieve process for optimization model type discrete event model. method used for optimization building discrete event model we work with one queue, and will choose fifo queuing discipl fig 6 intake process: dock unloading [extend simulation soft the condition block serves as a conditional wait. it accumul running simulation, choosing optimal solution during running this first model, we can check the following fig 8 simulation result [extend simulation software] fig 9 simulation result after optimization [extend simulatio discussion acknowledgements dc distribution centre bpr business process reengineering microsoft word b_14_r.doc hungarian journal of industrial chemistry veszprém vol. 38(2). pp. 123-126 (2010) the application of probability theory for drilling r. monostori, i. dudás department of production engineering, university of miskolc, h-3515 miskolc, egyetemváros, hungary e-mail: renata.horcsik@uni-miskolc.hu, illes.dudas@uni-miskolc.hu boring is presented in the article as well as drilling, errors in the drilling shape and position, and their control. the position of the holes is determined. it is possible to give the position of the holes in many ways. we are analysing the measurement results with a statistical method in the article. for example, we use distribution analysis, that is we apply a standard χ2 test to check if it is possible to define the measured variables according to a normal distribution. finally, histograms and χ2 tests enable us to make a conclusion considering the errors, and we also propose the correction. key words: boring, definition of position, statistics, histograms introduction during the production of the components – particularly the hollow components – keeping the position tolerances as well as studying how the position errors in the finished bores evolve, and what kind of requirements are met, is very important considering the lifespan of the component. the position errors in the bores influence their function and assembly. under the position of the bores we mean how the hole occupies a position as compared to the geometrically limited surfaces, as well as what the position of bores is like as compared to each other. we characterize the hole with the position of its axis line. the latter one is provided with accurate measurements on the component drawings and the sizes are compared to a geometrically accurate central line – or surface or base. the values of the position of the holes can be described on the drawing with a certain deviation, but it should be kept within the so called tolerance field. the value of tolerance is based on the standards selected on the basis of various shaping methods and the operating conditions of the workpiece. boring boring means shaping inner cylindrical surfaces with big tools (with drills, countersinks, reamers and with tap drills) or single edge tools. this way chipping procedures belong to the boring method that have one common feature, that is cutting tools with several edges rotate around their own axis and along its axis it makes a straight movement, which is identical with the pushing motion. in the course of boring the chipped surface is an inner cylinder or cone surface, plane and general rotation surface. the above grouping can only provide us with general criteria for boring, and there may be exceptions there. it is necessary to take the following aspects into consideration in the course of the preparation of the boring: the material of the workpiece; the technology of the operation; the selection of the tools; the selection of tool material; the selection of the machine tool and the consideration of its performance [1]. the operations of boring are as follows: drilling; sinking; reamer. drilling through hole drilling is the procedure when we make a hole into a standing or rotating brief workpiece. it is necessary to be careful that – despite the apparently simple operation – various errors may occur. this way, for example, in the case of a standing workpiece, the spiral drill can drill in an inappropriate way if the material of the workpiece is faulty. however, if the drilling is done into a rotating workpiece and the start falls into the rotation axis of the component, the spiral drill makes a uniaxial hole with an axis equivalent with the rotation axis of the workpiece, even in the case of a faulty material. shape and position errors (fig. 1) may arise if we make a hole in a standing or rotating workpiece with a spiral drill. the error(s) may occur due to, for example, wrong harnessing or setting [1]. 124 figure 1: shape and position errors during drilling in picture (a) the axis of the drill and the direction of the feeding form a certain angle, the drill is subjected to a sideway pressure, so the hole will be a crooked. in picture (b) the direction of the feeding and the axis direction tally, but the setting of the workpiece is wrong, the consequence of this is that the axis of the hole is aslope. in (c) the axis of the drill and the direction of the feeding form an angle, and this time only one of the spiral drill edges chips, and the shape of the hole is wrong. picture (d) indicates the situation when the drill axis and the direction of the feeding forms an angle with the axis of the workpiece. the arising hole is tapered. the main factors defining the accuracy of the hole: the quality of the substance to be holed; the diameter of the drill and the state of his edges; the state of the drill and a tool leg [3]. the definition of the position of holes it is possible to determine the position of the holes in many ways. under the position of the bores we mean how the hole occupies a position as compared to the geometrically limited surfaces, as well as what the position of bores is like as compared to each other. we characterize the hole with its position of its axis line. the latter one is provided with accurate measurements in the component drawings and the sizes are compared to a geometrically accurate central line – or surface or base (fig. 2). figure 2: rectangular scaling of holes the values of the position of the holes can be described on the drawing with a certain deviation, but it should be kept within the so called tolerance field. the value of tolerance is described according to the standards selected on the basis of various shaping methods and the operating conditions of the workpiece. the control of the uniaxial of holes if there is a component on which there are several cylindrical surfaces, and between them there is also a hole, uniaxiality plays a considerable role (coaxiality). here we have to pay attention not only to the cylindrical surfaces, but also to the position of tapered and other surfaces as compared to each other. in the course of the check-up we can speak about: uniaxiality (fig. 3); deviation from parallelism; deviating of axes. figure 3: checking the hole concentricity measurement methods should be chosen adequately. the basic principle of the measurement is that one of the cylinder surfaces (holes) is considered to be basic (this is the so called base), and we compare the deviation of the rest of the surfaces with it. main methods: a. the base is the component of the hole; b. we consider one of the hole diameters as a base, and we focus on it; c. we give accurate data referring to the hole axis in certain planes. in the first case we place the hole of the component to be examined on the so-called compass tap of the measuring apparatus standing motionlessly in the case. it is important that there should not be a gap between them because this is an error source during the check-up of the additional surfaces. it spoils the accuracy of the measurement if the hole has a shape error. we make the workpiece revolve around the tap of the instrument in the course of the measurement and meanwhile – with other parts of the instrument – we fix the coaxiality for the surfaces and axes of the workpiece to be examined. within the 3rd method the orientation accuracy is growing in the recorded plane significantly, however, in the perpendicular plane we may expect smaller accuracy. it is a modern method of measurement to use the coordinate gauge machine, with which we can check the surface where the tool (drill) enters the substance and 125 the one where it gets out of the surface. we can make a conclusion regarding e.g. the excentricity, which we cannot be measured with simple measuring devices [3]. checking the hole diameters the aim of all measurements is defining of the indexnumber. during the measurement of a hole, as in the case of all solid shapes, it is necessary to consider not only one size, but several sizes. a number of factors may cause the errors of the boring. i am examining the methods of boring in order that it would be more possible to choose the sources of dangerous errors out of several possible causes. boring is done with the help of mkc-500 type working centre. the equipment works with a program control. the machine tool working accuracy is it6. i studied the component called arched arm (fig. 4). figure 4: arched arm the technological plan of the arched arm: ● centre drilling, done with a standard centre drill with a diameter of 2.5 mm at all holes; ● multiple drilling happens with figural spiral drill (nominal size) -2 mm; ● sinking: (nominal size) -0.2mm; ● finisher shaping with the size being equal to the holes and tolerance (20h7, 28 h7), done with a traditional reamer; ● the edge breaking is done with a tapered countersink. based on the faulty workpieces and the examination of the technological process it can be stated that the error of the relative position of the holes may not be caused by the error of the device and the deficiency of a centre's accuracy; the insufficient hole protection may not cause the error of the hole diameter at painting, as there is no sign of it on the faulty pieces. thus, the two most frequent reasons can be unambiguously traced back to the types and lengths of the tools and the quality of the reamer. this way my further investigation considers only the two most important causes. making a use of the measurements of all manufactured workpieces i apply statistical evaluation [2]. the statistical analysis of the data the measurement results were expanded on the 162 workpieces used in the course of the experimental production. the analysis of the data of the position of the holes in figs. 5 and 6 we can see data for the 5-6 and 6-7 holes in y direction, while in figs. 7, 8, 9 three holes in x direction are shown according to the descriptive statistical processing of error data. the statistical values necessary for the χ2 test can be seen in table 2. table 1: measured values class middle 40 32 24 16 8 0 -8 -16 -24 -32 -40 relative frequency 1 2 5 23 47 40 28 11 4 1 0 figure 5. the evaluation of a difference measured in y direction figure 6. the evaluation of the difference measured in y direction figure 7. the evaluation of the difference measured in x direction 126 figure 8. the evaluation of the difference measured in x direction figure 9. the evaluation of the difference measured in x direction table 2: the calculated features of the five diagrams n x r s a figure 5 162 2.71 68 11.7 -450 figure 6 162 1.73 71 11.8 453 figure 7 162 4 54 10.2 390 figure 8 162 0.44 48 9 50 figure 9 162 74 64 10 7.4 table 3: the χ2data of the test class middle frequency χ2 -36.1 -28 1 0.1697 -28.1 -20 4 0.0492 -20.1 -12 11 0.1963 -12.1 -4 28 0.0526 -4.1 4 40 0.0988 4.1 12 47 1.5859 12.1 20 23 0.0123 20.1 28 5 1.605 28.1 36 2 0.0089 36.1 44 1 1.556 we apply a fitting test after defining the frequency distribution of the distances and graphical representation of holes, with the help of a statistical test – the χ2 test (table 3) –, so that the distances between the holes should follow a normal distribution. the data are divided to k columns for the determination of the χ2 test and the exanimation statistics is defined similarly to the previous method: χ2 = ( )∑ = −k i i ii e eo 1 2 , where oi is the observed frequency for column i and ei is the probable frequency of column i. χ2 sz = 5.334 < χ2 table = 15.1; so the distribution is normal. considering the data about the machine, the apparatus and the circumstances of the shaping, and also taking the data in the tables into consideration, we can state that the big extent and scattering and the big number of waste products originating from the position of the holes are caused by the splay of the drill, asymmetric grinding and other factors linked to a tool. proposal for the correction of the quality about the situation after the change we do not have additional data, but the number of faulty products deriving from this error is expected to fall to a level that there will be no need for any additional intervention. summary we presented boring, as well as its steps and the checkup of the holes. we analysed the data of an experiment in a statistical way, which determined what error may arise during the shaping. after it we proposed the correction of the quality. acknowledgements this work was supported by otka project k 63377. entitled ”complex analysis of the features of production geometry and meshing in case of up-to-date application”. (research leader: dr. illés dudás) references 1. dudás: gépgyártástechnológia i., gépgyártástechnológia alapjai, miskolci egyetem, 2002, university book in hungarian. 2. i. pap, et al.: 3d mérőgép honosítása alkalmazástechnikai referencia helyének kiépítése és dokumentálása, miskolc, 1990. szeptember, study in hungarian. 3. r. hörcsik: koordináta méréstechnika elmélete és gyakorlati alkalmazása, miskolc, 2003, thesis in hungarian. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 /colorconversionstrategy /cmyk /dothumbnails 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/pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word contents.doc hungarian journal of industry and chemistry veszprém vol. 40(1) pp. 15–18 (2012) algae cultivation for energetic purposes, research on algae technolgy at the university of pannonia r. bocsi1 , l. hanák, g. horváth, z. hodai, d. rippel-pethő, b. szabó-ravasz, l. szokonya, gy. takács 1university of pannonia, department of chemical engineering, 10 egyetem str., 8200 veszprém, hungary e-mail: bocsirobert@almos.uni-pannon.hu biotechnology and renewable materials are very popular research projects nowadays. the increasing attendance of industrial participants enhances the significance of these projects. we started cultivating microalgae a few years ago. under the supervision of our biologist partner and based on the literature, we built our photobioreactor system on a laboratory scale. our first objectives were algae cultivation for energetic purposes in addition to carbon-dioxide capture. it is reasonable to conclude that the extraction of bioactive compounds is worth consideration. keywords: alga technology, cultivation, lipid introduction driven by the rising need for biofuels and the necessity to capture carbon dioxide, autotrophic organisms got into the spotlight of energetic research. with the cultivation of these organisms we can feed back the carbon content of co2 into biological systems and we are able to get a number of valuable organic compounds – among other biofuels – to reach ecological and economical benefits. [1] algae production is the most promising solution amongst the alternatives due to its low specific needs of land use and high reproduction rate. additional benefits are that there is no need to use agricultural land and some wastewater may be used for nutrient supplementation. we have studied the technology of algae cultivation and processing at the department of chemical engineering at the university of pannonia. the utilization of algae cultures in experimental photo-bioreactors was examined together with the optimization of the operational conditions with both artificial and natural light and different fertilizers. several densification processes of algae have been studied and numerous extraction experiments were carried out, where dried algae were made. this article is a cross-sectional review presented about this diversified work. determining the key points of the technology in order to examine this technology operated under the local climatic circumstances, we had to construct it all the way from the cultivation of algae to the preparation of the end product. investigating the whole process is important because the composition of the algae suspension, as a raw material, affects the parameters of the technologies to be used in the later phases. the laboratory and outdoor conditions of the cultivating algae were determined by the algae breeding examinations. a subsystem was created to provide raw material for further examinations. adaptations of existing analytic methods, as well as development of new ones, were necessary in order to determine the quality of the algae suspension. therefore, development of the analytical instrumentation had top priority. algae suspension of acceptable quality has to be produced in order to gain the required product. processing has been concentrated on three critical operations. these were: densification, extraction, and processing of the residues. the next goal was to automate the technological process, such as temperature control in the reactor, controlling the gas supplementation, etc. the project outlined above is illustrated in figure 1. 16 figure 1: the four phases of technology setup and research subjects examinations of algae cultivation the algae cultivation technology was investigated in a closed photobioreactor, according to the local microclimate. figure 2: algae requirements for a successful breeding, the basic needs of algae have to be met. for optimal processing, a high density algae suspension is necessary, in which high lipid content algae exist. the alga cultures were propagated in purpose-built flat panel photo-bioreactors. for the tests, closed photobioreactors were chosen since they allow fast and easy setting of the parameters [2]. flat panel reactors were chosen because of the following advantages: the closed design minimizes the probability of infection light distribution is easily definable in the reactor high-area volume ratio the area/volume ratio can be modified by small changes of the construction flat panel reactors were also installed for the laboratory pre-experiments, the outdoor, scaled up laboratory reactor, and the pilot reactors. cultivation parameters at first, a modified bg-11 nutrient solution formula was used, where a final algae concentration of 5–7 g/dm3 could be reached. at the same time, the lipid concentration of the dried algae exceeded 20 (m/m%). these values are also true for the photo-bioreactors operating by natural light. ‘cool white’ and other special-spectrum fluorescent lamps were used as light sources in the laboratory. natural light was used for the open-air experiments exclusively. biomass output can be influenced by the amount of carbon dioxide inlet. although experiments were carried out in the 0–100% (v/v%) range, most of the measurements used air with 6–15% co2 content. a flat panel photo-bio reactor system was constructed which could be operated stably. this system proved capable of determining whether the algae species could be introduced to an open-air cultivation system. analytical methods the applied analytical methods can be characterized on the basis of the following three aspects: 17 algae cell content and concentration in the suspension characterization of the nutrient solution composition of the product and the by-products characterization of the algae almost continuous measurement is required to get information about the state of the algae cultivation. short measurements are necessary because during the propagation experiments gaining more than 30 samples are performed occasionally. as a result of this, a propagation index was introduced, which is equal to the absorbance of the suspension at 681.5 nm. the ph of the suspension has to be measured too. if the propagation index of the suspension shows a decreasing trend, the system needs intervention. at the initialization of the reactor and in the days before the harvest, determination of the exact algae concentration is usually followed by the dry matter content measurement. the composition of the algae cells was determined after drying and extracting the samples taken from the algae suspension. this extract was analyzed according to the methods described in the section ‘analysis of the product contents’. parameters of the nutrient solution the nutrient solution contains both micro and macro elements. there are at least 2 orders of magnitude difference in their concentrations. nitrogen is an important macroelement which is advantageous mainly in the form of no3 -, but can also be present in the nutrient solution as ammonia or urea. another important ingredient is phosphate, the quantity of which also influences the final biomass concentration. the presence of micro elements is significant for the biocatalysts needed for the algae to function. their application involves a rather small concentration interval. nitrate and phosphate concentration have to be checked at constant intervals during the propagation cycle. this can be done by an appropriate photometric method. if the quantity of the nutrient solution components drops below a critical level, the propagation process stops and adequate measures have to be taken. these measures include the supplementation of missing components, harvest, or starvation. if the required biomass concentration has been reached, starvation can be useful. at this point, nitrogen-starvation causes the rise of lipid-concentration in the cells. analysis of the product contents the primary product is the extract, the contents of which essentially affect the type of method we choose to produce biofuel. the samples were analyzed according to the en 14105 standard and some individual components were determined by gc-ms. with the instrumentation available at the clean world laboratory of the university of pannonia, we were able to gain a considerable amount of information about the individual algae species as well as the processes. processing the algae suspension since the algae are cultivated for energetic purposes, the energy balance has to be considered. the main objective for energy input is not to exceed the amount of maximally retrievable energy. processing can be divided into three important steps. in the first step, dry algae powder is to be made from a relatively dense aqueous suspension. then the key components are extracted from the dry algae powder. at the end, the main task is to process the residue in the third step. densification the main objective of the densification methods was to gain dry algae in the shortest time and at the lowest energy cost. experiments were carried out with chemical flocculation, which proved to be simple a method, but it was rather sensitive to the quality of the algae input. the applicability of ultrafiltration was also examined. this process proved advantageous for being insensitive to the quality of the algae input. its drawback is the relatively high investment cost. further combined methods were also examined (e. g. autoflocculation) which are useful due to their low energy needs. the possibility of scaling up these methods is being examined at the present. extraction the other important step in processing dry algae is the extraction. the lipid components are extracted in this step. this is the raw material for biodiesel production [3, 4]. there are various ways of extracting lipids. the amount of neutral lipids is determined by extraction with n-hexane. the bligh-dyer method is a widely used method for determining the total lipid content. these techniques are used for both analytics and processing. in addition, a number of other industrial solvents and solvent mixtures have been tested. the highest extract yield can be reached with the bligh-dyer chloroformmethanol mixture. the drawback of the method is that additional components are extracted along with the non-polar lipids. solvent mixtures consisting only paraffins give products of higher purity, but at the cost of a lower specific yield. it is worth to consider the 18 fractional distillation of the extract when choosing the appropriate extraction method. in addition to simple solvent extraction, the applicability of supercritical carbon-dioxide extraction (scf) was also examined. the main advantage is that we can control the composition of the extract with appropriately chosen operational parameters and cosolvent. its drawback is the high investment cost and the need of high pressure (in order to reach the supercritical state of co2). residue processing residue processing is necessary because the liquid phase separated at the densification step can be either recycled or purified, depending on the processing steps. if membrane separation was used as the first step of densification, the permeate can be reused to make nutrient solution because of the remaining salt contents. direct recycling is not always possible. in the case of chemical flocculation, a purification step is often necessary. it is also reasonable to utilize the raffinate produced by the extraction, as it can contain sugar, starch, dyes, and other bioactive components. a number of possibilities arise for secondary energy retrieval when processing the raffinate. on one hand, it can be used for the production of biogas, on the other hand, bioethanol can be produced from it by fermentation. experiments were carried out for biogas production, which prove that the raw algae mass and the raffinate can be used for the production of biogas within certain limitations. conclusions a number of algae species were tested and processed as part of the algae cultivation experiments. below is given the essence of our experience in the various examination phases. phase 1. operation temperature is one of the most important parameters to control. application of artificial light was only considered in the laboratory scale reactors. algae strain cultivation was observed to be better than the cultivation of special alga species. phase 2. daily analysis of the algae suspension was sufficient by measuring the propagation index (enhanced optical density) and ph. the recirculation of nutrient media residue is to be considered. the number of recirculation cycles depends on the densification processes. phase 3. algae suspension is an expensive but valuable material. the processing of algae suspension needs energy and economic analysis in order to reach optimal processing. phase 4. scale-up and automation need special considerations which are part of the current working phase. acknowledgement the financial support of this work by the hungarian state and the european union under the támop4.2.1/b-09/1/konv-2010-0003 project is kindly acknowledged. references 1. l. brennan, p. owende: biofuels from microalgae – a review of technologies for production, processing, and extractions of biofuels and co-products, renewable and sustainable energy reviews, 14 (2010) pp. 557–577, doi:10.1016/j.rser. 2009.10.009 2. r. lau, x. chen, q. yvonne goh, w. tan, i. hossain, w. n. chen: lumostatic strategy for microalgae cultivation utilizing image analysisand chlorophyll a content as design parameters, bioresource technology 102 (2011) pp. 6005– 6012, doi:10.1016/j.biortech.2011.02.061 3. j. pruvost, g. van vooren, b. le gouic, a. couzinet-mossion, j. legrand: systematic investigation of biomass and lipid productivity by microalgae in photobioreactors for biodiesel application, bioresource technology 102 (2011) pp. 150–158, doi:10.1016/j.biortech.2010.06.153 4. l. c. seefeldt, b. d. wahlen, r. m. willis: biodiesel production by simultaneous extraction and conversion of total lipids from microalgae, cyanobacteria, and wild mixed-cultures, bioresource technology 102 (2011) pp. 2724– 2730, doi:10.1016/j.biortech.2010.11.026 microsoft word b_06_r.doc hungarian journal of industrial chemistry veszprém vol. 38(2). pp. 99-105 (2010) environmental-friendly cutting of automotive parts made of aluminium castings r. horváth, b. palásti-kovács, s. sipos bánki donát faculty of mech. eng., university obuda, hungary e-mail: horvath.richard@bgk.uni-obuda.hu, palasti@uni-obuda.hu, sipos.sandor@bgk.uni-obuda.hu through an example of an automotive component, the lecture introduces difficulties, arising during the turning operations of high silicon content aluminium castings. it evaluates the production, running currently with cutting fluid flood-type application; introduces the preliminary tests, carried out before change-over to the green manufacturing; furthermore, the circumstances of the tests, carried out with the method of doe at high speed machining. the results of measurements, carried out with different tool materials and edge constructions, will be evaluated from the point of view of surface roughness minimisation. the results of topographic (3d) measurements of the machined surface will be compared with the results, gained with the electron-microscope; the disturbing phenomena, arising during the turning operation with diamond tool, will be analysed. finally, the production circumstances will be determined in order to ensure the prescribed surface roughness despite the increased productivity and the environmentally friendly cutting. keywords: machinability, green machining, aluminium castings, polycrystalline diamond turning, cvd coated thick diamond layer introduction one of the determinant characteristics of modern production is that the quality of the products is improving continuously: on of its cause can be the development of the machine tools, the other important reson is the development of new geometries and tool materials. this progress is accompanied by an ever-increasing productivity (reduced productive time, shorter non-productive times and production period) as well. this process can also be noticed especially in the case of high level technologies, characteristical for the modern automotive industry, defense industry, aircraft industry and aerospace industry. another determinant factor, to be considered during the production, is the increased consideration of the effects, carried out on the environment: we must abstain from processes, harmful to the environment; and the safe treatment, storage and desposal of waste materials are also our tasks to be solved. the manufacturing intermediates (cooling liquids, emulsions of different concentrations, lubricants) can cause huge danger to the environment. the fact is that there are always more and more strict regulations in favour of the environmentalfriendly production. in this article we are going to present the difficulties, arising during the turning operations of the fixture of a large-scale produced compressor. the paper will also present possible solutions and determines the circumstances, meeting all the three segments of the concepts of “quality-environment-productivity”. machinability of high silicon content aluminium alloys the industries, mentioned earlier, use preferred aluminium cast alloys, especially versions, alloyed with silicon, copper, magnesium. in these alloys excellent mechanical features (hardness, strength) and appropriate technological advances (excellent castability, machinability, corrosion resistance, weldability) are combined. parts, made in the 80’ and made of aluminium with high silicium content, have spread in the automobile industry (for example, fixtures of engines, compressors, steering devices) and their unfavourable machinability causes several problems. the aluminium alloys, having a silicon content of higher than 11.8% are called hypereutectic, and almost all of them have good strength characteristics, higher fatigue limits and excellent wear resistance. one of the circumstances, making the machining difficult, is that aluminium is an easy-to-machine material, soft and ductile; but with increasing the si-content, the abrasive effect of the alloys increases and the difficulties, arising during the machining, are on the increase. because of the primary silicon crystals, embedded in the aluminium matrix, the chips breaks off easily; however, the presence of these hard particles leads to the quick wear of the insert, due to their strong adhesion and chemical reactions as well as low abrasive resistance with al-si alloys. in case if the primary si-particles contact the tool edge in the cutting zone, then they wear it; furthermore, due to their hardness they hinder the formation of good quality surfaces. therefore, the precondition of the favourable 100 surface roughness is the even dispersion, small grain size and favourable shape of the primary si-particles, otherwise the particles, adhered to the edge on the “adhesion way”, can “plough” the surface completely, to be machined. the situation can be even more complicated if the interdendritic region contains a high number of resistant intermetallic precipitates and inclusions. the causeeffect diagram (the so called ishikawa diagram) of the unfavourable machinability of these cast alloys can be seen in fig. 1 [1, 2]. figure 1: machinability of high silicon content aluminium casts only tool materials with the highest performance can overcome the difficulties, as illustrated in fig. 1. as already presented in [3, 4, 5], the polished types of iso cemented carbide, belonging to k-group, are convenient for it only in limited degree. the most appropriate solution is to use monocrystallic, natural and artificial, polycrystalline diamonds and diamond layers, deposited with cvd. these tools appeared in the market recently. in the production of the manufacturer, flood type application of cutting fluid has been applied untill now. these were water soluble mineral oil, free from amine, sometimes cooling-lubricating liquid, containing ep additives. although this medium enables the most convenient occupational health and safety conditions (its ph-value is 7.5–8.8), there is a huge consumption of it, nearly 30 l, calculated to one piece in case of turning with a diamond edge tool; furthermore, the coolinglubricating liquid costs 5 huf per each part. therefore the company has made a decision about technology change to the environmental-friendly cutting: the casts, produced till now in millions of items, will be machined by dry turning. description of the goals and circumstances of the tests the main goal of the tests was to get clear picture how the tools of different materials and with different construction can meet the extremely rigorous roughness standards, applied in the automobile industry. the difficulties have been increased further by the fact that we had to carry out the trial tests without coolinglubricating liquid. measured surface roughnesses, made with polycrystalline diamond of different compositions, have been compared, where the dry turning operations have been performed with tools with different point angles and nose radiuses; the cutting speed has been varied in a very wide range (vc = 500…2000 m/min). the depth of cut – due to reason of saving materials – has been kept on a constant value (a = 0.5 mm), other testing conditions can be seen in table 1. table 1 m ac hi ne to ol type: euroturn 12b (nct kft.) control: nct2000 w or kp ie ce material: as17 (rencast reyrieux) contents: si 16.8%, cu 4.1%, zn 1%, fe 0.8%, mg 0.5%, mn 0.2%, other components: pb, sn, ni, ti (<0.08%) a pp lie d tu rn in g in se rt s m ad e of d ia m on d ccgw09t304fst kd1425 (kennametal) ccgw09t308fst kd1400 (kennametal) ccgw09t308fst kd1425 (kennametal) cpgw09t308fwstkd1425 (kennametal) cpgw09t304fst kd1425 (kennametal) ccgt 09t304 cb1 pdc (wnt deutschland gmbh) ccgt 09t304-w cb1 pdc (wnt) ccgt 09t304 cb1 cvd (wnt) ccmw09t304 md220 (mitsubishi) dcmt11t304 id5 (iscar) dcmw11t304fp cd10 (sandvik) dcmw09t304 md220 (mitsubishi) t es tin g ci rc um st an ce a = 0.5 mm (constant) vc = 1000 … 2000 m/min (varied) f= 0.05-0.063-0.08-0.1 mm (iso) f=0.1-0.125-0.16-0.2-0.25 (wiper) m ea su ri ng de vi ce s surftest sj301 (mitutoyo, japan) perthometer concept 3d (perthen-mahr, germany) electron microscope jsm-5310 (jeol co., japan) test results due to space limitations it is not possible to present the complete results of our systematically performed tests; the research experiences of our far-reaching examinations will be summarised later. the description below contains the surface roughness values, measured along 3 different measuring lines, by setting every single test values. 101 effects of the tool geometry the most important features of the tool edge geometry are the point angle, rake face angle and design (with and without chipbreaker), flank face angle, nose radius of the insert and the tool edge quality. the selection of the insert with optimal design influences significantly the expectations, concerning the quality and efficiency during the cutting machining process [6]. in case of light metal alloys it is a general accepted principle to apply the point angle as small as possible: during the turning operation the surface roughness is considerably better if the chip has enough free space to leave the process, with other words: the chip space is wide (is not limited) [3]. this value of angle is in case of ccmw insert 80°, while in case of dcmw it is only 55°. the tests, carried out with the inserts of famous tool manufacturers, have confirmed that the average surface roughness values (ra) can be significantly affected not only by the feed rate, but by the point angle of the insert as well. as it can be seen on fig. 2, the value of ra (average surface roughness) is by 20–40% smaller in case of application of sharper point angles. furthermore, the ra value of <0.4 μm can be achieved without any difficulties under reasonable defined machining conditions, even in case of inserts with small nose radius applied by us. what is surprising in this fact is the rate and this phenomenon can be noticed so significantly even in case of hypereutectic al-si alloys, this type of material has been also tested by us. a) insert code: ccmw (εr = 80°) b) insert code: dcmw (εr = 55°) figure 2: surface roughness under high speed cutting conditions cutting conditions: vc = 1000–2000 m/min; rε = 0.4 mm an important factor, to be considered during the design of the insert, is the nose radius, its increase affects favourably the surface roughness. in fig. 3a the different (measured and calculated) surface roughness values can be seen: the rtheor value means the surface roughness data, calculated with the well-known bauer-formula: [ ]m r frr s ztheor μ 2 125 ⋅≈≈ (1) another known and used formula (see (2)) has been created by brammertz: [ ]m f rhh r fr s s thbr μ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ⋅ +⋅+⋅= 2 minmin 2 1 2 125 (2) this (2) relationship can be convenient to provide a basis for the determination of a reasonable feed rate during the technological design process, provided that we use the formula, applied by us, as the method of continual approaches. the aim is to define the value of the minimum undetachable chip thickness (hmin) [1] with a computer program. other tests, carried out by us, have confirmed that in case of change in cutting speed values, very diverse average surface roughness values have been measured by applying inserts with relatively small (e.g. rε = 0.4 mm) nose radius. in case of inserts with bigger nose radius (e.g. rε = 0.8 mm) much more regular, better predictable surfaces have been produced. beside the tests, carried out on traditional designed rake face, we have had the possibility to test the version with chip-breaker as well [7]. as it can be seen in fig. 3b, the chip-breaker, produced with laser, is extremely efficient and it reduces the value of rz (so called maximum height of profile) almost by 100%. it can be seen as well that the so called bauerformula can describe the real surface roughness only in limited degree. the insert selection determines the value of relief angle, to be applied during the cutting process and it significantly influences all characteristics of surface roughness. based on our tests, we can observe that bigger relief angle produces much more regular surface roughness profile as the edge of the diamond tool creates much more characteristic mark on the workpiece, preventing the development of adhesion layer (deceptive chip formation) on the flank land. analysing the fig. 4a, we can notice that all values of 102 maximum height of profile (rz) are significantly lower in case of each test setting. beside this fact, the components, turned with cpgw coded insert, have much more favourable behaviour (smaller wear, longer life time) than in case of workpieces, machined with ccgw coded insert (relief angle: 7°). from the surface roughness parameters, the kurtosis of profile informs us about it: the kurtosis of profile (rku) is the quotient of mean quadric of the ordinate values, within the sampling length. fig. 4b shows that the texture of surface profile has much more favourable distribution (so called full surface profile), if the machining is carried out with great relief angle, at increased feed rate. for example, if rku-value is higher than 3, then the machined surface has a many outstanding peaks, so the working surfaces, sliding away on each other, can be characterised by really intensive wear [7]. due to space limitations it is not possible to analyse the tool edge quality (surface roughness values on the rake face and flank land of the inserts, roughness of main cutting edge, edge sharpness, edge radius etc.) a) different nose radii (rε = 0.4 and 0.8 mm) b) different versions of rake face figure 3: surface roughness vs. insert geometry cutting conditions: vc = 1400 m/min a) maximum heights of profile b) profile kurtosis figure 4: surface roughness versus relief angle the effect of the tool material the first material, coming into question, is the polycrystalline diamond (pcd): it has anti-adhesion characteristics, chemical inertness, compared to cemented carbide better abrasive wear resistance and low friction coefficient. these technological characteristics make it possible, and, the expensive tool materials requires to use pcd inserts at increased cutting speed values, especially if the component is produced in large scale, with high quality expectations, in environmental-friendly way. the size and structure of the grains of pcd significantly affect the rz value of the machined surface. as it can be seen on fig. 5a the kd1400 grade is finegrained (~2 μm), the wear resistance of the kd1425 grade, having a grain size of 2…30 μm, is greater as it has a multi-modal structure. the measured rz values inform us that the use of diamond inserts is not effective enough at low cutting speed values. this last version can withstand moderate interruptions, appearing – in the case of machining aluminium alloys – in the form of microporosity, caused by the hydrogen gas. at low cutting speed values and feed rates it is recommended to use the grade with higher wear resistance, in case of higher 103 cutting speed values the recommendation “for high speed finishing”, given for the kd1400, can prevail. other tool material, coming into question is an approximately 1 mm thick diamond layer, deposited with cvd: compared to the polycrystal it has different behaviour. this layer, deposited at very low pressure, can be characterised by a really low friction coefficient, (built-up edge, deceptive chip formation), connected with the adhesion of the machined material, will not even develop. based on fig. 5b, summing up the results of the tests, it can be noticed that (to our surprise) the pcd insert has permanently achieved rz value of approx. 2 μm, while diamond layer, deposited with cvd, has “produced” greater surface roughness by 50–130%. a) various types of polycrystalline diamonds b) various origin of diamonds (rε = 0,8 mm; vc = 500 m/min) (rε = 0.4 mm) figure 5: surface roughness versus insert material the micromechanisms of cutting operations have been confirmed by the photos, taken with electron microscope (type jeol jsm-5310). with the help of 3d surface roughness (i.e. microtopographical) measurements we can get even more detailed picture about the textures of surfaces, machined with polycrystalline diamond tool. fig. 6 shows a photo with 1000 magnification, taken of a surface, turned with a pcd tool. it shows the photosimulation visualisation of the machined surface, filtered from the waviness and cylindricity, the most important parameters of the p-topography. some 3d roughness parameters can be seen in this figure (for example arithmetical mean deviation, spa; total height of profile, spt; the profile peak heights, spp; the profile valley depths, spv etc.). the profile peak heights, machined with pcd tool, are significant lower (spp), the profile valley depths are much higher (spv). it means that diamond tool produces much more even surfaces and it “machines” the surface in its real meaning. it is confirmed by the kurtosis value of profile (spku < 3), characterising the topography height distribution of the 3d surface roughness values as well. on the examined section of surface, machined with pcd tool, whole “series” of primary si-crystalls can be observed in the feed grooves. 2 mm × 2 mm (1000 × 1000 points) results of 3d surface representation figure 6: microtopography of surface, machined with polycrystalline diamond cutting conditions: vc = 1000 m/min; f = 0.05 mm; rε = 0.4 mm 104 tests of up to date constructions diamond inserts we have managed to purchase diamond inserts with different materials and different edge constructions (fig. 7) from the same company. the common characteristic of the tested inserts is the chip-breaker, produced with laser: its design can be seen well on the photo, taken with an electron microscope with 150 magnification. the material and design of the tool edges, differing from the traditional ones, have had undoubtly positive effect on the results, gained with the presented inserts. all results, introduced till now, refer to iso shaped inserts (where nose radius is surrounded by two straight edge sections). if the main and minor cutting edges have been made with great radius (it means the insert has wiper edge form), then the surface is machined mostly by nose radius and by minor cutting edge. the amplitude parameters of the surface texture (for example, average surface roughness (ra), maximum heigth of profile (rz) etc.), machined this way, are significantly lower, with the same test settings. as it can be seen in fig. 8, it is also possible to set data, enabling two and a half times greater productivity – the surface roughness values are the same. in case of inserts with wiper edge form, the expectable results can be influenced by deceptive chip formation, developed as a result of increased cutting speed values: it contacts the machined surface as well. iso (magnification: 150x) wiper (magn.: 150x) iso cvd (magnification: 150x) figure 7: several diamond inserts with up-to-date constructions figure 8: development of surface roughness in case of iso shaped and wiper insert summary during our short term tests, carried out to examine the machinability of the grade, mentioned earlier, we can get picture about the roughness parameters of surfaces, machined with tools, having different materials, shapes, constructions and produced by different manufacturers. we have carried out 2d and 3d measurements; and also, our tests have been extended by electron-microscopic analyse as well. not having the approval from the manufacturers, we do not wish to publish the results of our research in details. the most important conclusion of our investigations is that in case of diamond insert with appropriate tool material, design and edge geometry it is possible to meet the requirement of the average surface roughness ra ≤ 0.2 μm, even under conditions of environmentalfriendly machining. the circumstances of the application can be seen in the diagrams, presented earlier. in case of insert with wiper edge form, the productivity can be increased by twofold or more. the strategy and exact steps how to avoid disturbing phenomena (built-up edge, deceptive chip formation), developing during the cutting process of aluminium parts, will be presented in our next paper. 105 acknowledgments authors wish to thank mr. tornyi, mr. nagy and mr. benkó, working at delphi thermal hungary kft. in balassagyarmat, for their valuable comments and for the company as well, having provided us with the casting components. references 1. www.forgacsolaskutatas.hu/elmélet/forgácsolhatóság 2. h. ye: an overview of the developement of al sialloy based material for engine applications jmepeg (2003) 12:288-297. 3. r. horvath, s. sipos: machinability of high silicon content aluminum alloys, microcad 2010 international scientific conference, miskolc, 18-20 march 2010. section n: production engineering and manufacturing systems, 75–82, isbn 978-963661-918-3. 4. r. horváth, s. sipos: nagy szilíciumtartalmú alumíniumötvözetek forgácsolhatósága, xv. fiatal műszakiak tudományos ülésszaka, kolozsvár, 2010. március 25-26., 135–138. issn 2067-6808 5. r. horváth, s. sipos: nagy szilíciumtartalmú alumíniumötvözetek forgácsolhatósága gyártóeszközök, szerszámgépek, szerszámok, 15, 2010. 44–48. 6. www.fogacsolaskutatas.hu/szerszámválasztás 7. b. palásti kovács, á. czifra, s. horváth, s. sipos: műszaki felületek mikro-geometriájának, mikrotopográfiájának vizsgálata és értékelése, gép, 2010. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word a_11_kodrik_r.doc hungarian journal of industrial chemistry veszprém vol. 39(1) pp. 15-19 (2011) the effect of highway traffic on heavy metal content of cow milk and cheese l. kodrik1 , l. wagner1, k. imre2, k. f. polyak2, f. besenyei3, f. husveth1 1university of pannonia, department of animal sciences and animal husbandry 8360 keszthely, deak ferenc u.16, hungary e-mail: kodriklaszlo@gmail.com 2university of pannonia, department of earth and environmental sciences, 8200 veszprem egyetem u. 10, hungary 3pannontej zrt., 8900 zalaegerszeg platan sor 6, hungary human exposure to heavy metal elements through milk and dairy products may have influences on food safety. although certain elements such as zinc, chromium are essential in small quantities, in high amount they can result in toxic effects on animal and human health. in this experiment samples of raw cow milk were collected from dairy farms close to highways in the central region of hungary, and in rural green regions in west hungary. concentrations of selected heavy metals such as as, cd, cr, cu, fe, mn, v, ni, pb and zn in cow milk and cheese were determined using inductively coupled plasma mass spectrometry and inductively coupled plasma-optical emission (spectrometry). chrome, copper, iron, vanadium, manganese, cadmium, arsenic, and lead content showed higher concentrations in the milk from intensive traffic areas than those in the milk from non-polluted green areas. however, in the cheese only copper, chrome, iron and lead concentrations were found significantly higher in the highway samples than those in non-polluted green samples. keywords: food safety, dairy products, heavy metal pollution introduction the rapid development of industrial production and traffic system may result in the contamination of food sources. pesticides, industrial by-products, fertilizers and the increasing number of vehicles using highways, roads are important sources of heavy metals. the potential environmental factors affecting animal production (soil, water and air) are polluted with toxic metals [8] as well. different levels of these elements have been measured in many countries in soil, vegetation, and the atmosphere. lead, cadmium, nickel, and zinc concentrations in earthworms were found high by scanlon [16], mushrooms tended to accumulate some metals [12]. transport of heavy metal contaminants in the air has been also observed [17]. according to coni et al. [3] different environmental conditions, rather than animal species, tend to affect the concentration of certain elements in three types of milk (sheep, goat and cow). heavy metals are well known, mostly because of potential hazards to the health of living organisms. they can accumulate in tissues of the body, can be toxic even at low level of exposure [11] and can be transferred through food chains. interest in this subject has led some scientists to the use of plants to clean up contaminated soil and water [15, 19] or to the use of zeolites to remove metals from wastewater [10]. milk and milk products are important as human foodstuffs; they are essential sources of protein, fat and minerals. the principal type of milk used throughout the world is cow milk. dairy cattle are fed mostly locally grown forages and preserved feedstuffs and therefore they are exposed to metal contamination if the field is located nearby an industrial area or highway. this is the reason why the concentrations of certain metals in dairy cattle products have been measured from in several countries [18, 4, 6, 5]. the objective of this study was to study the toxic metal concentrations in cow milk and cheese from two different environmental regions in hungary. the studied regions included polluted industrial and traffic intensive areas as well as in green non-polluted areas. materials and methods sample collection and preparation cow milk was collected at different dairy farms during the summer of 2011. two farms were located in polluted areas (near highways m6 and m7; central hungarian region), where density of the road traffic was high. the other two sampling areas were located in non-polluted green areas (őrség and hetés, west hungary), where the number of roads and traffic density were very low. mixed milk samples starting from morning milking were taken from each cow. 16 cows were fed twice daily with a total mix ratio (tmr) diet formulated to meet the requirements of lactating cows [14]. tmr consisted of corn silage, grass hay, and cereals produced in the indicated areas respectively as main components. heavy metal contents of the ingredients were measured by the methods indicated later. the concentrations of the metals in the feed ingredients are shown in table 1. table 1: heavy metal contents (mg kg-1) in the ingredients of the diet fed with lactating cows kept in non-polluted green or highway conditions non-polluted green area elements corn silage grass hay cereals zn 9.33 6.31 13.11 v 0.09 0.07 nd cd nd nd 0.02 cr 0.10 0.09 0.10 pb 0.12 0.10 0.01 ni 0.42 0.62 0.21 highway area elements corn silage grass hay cereals zn 14.61 6.82 13.81 v 0.15 0.09 0.09 cd 0.02 0.02 0.02 cr 0.23 0.23 0.01 pb 0.22 0.20 0.14 ni 0.42 0.81 0.22 nd: not detectable milk of ten cows was collected at each farm (a total of 40 samples) into plastic tubes. aliquot volumes of milk were carried separately from each farm to a milk processing factory (pannontej zrt.) where a popular hungarian cheese type (trappista) was produced from the cow milk according to the technology of the factory. after the second month of cheese processing, 400 g samples were collected from each cheese roll respectively and the samples were packed in polyethylene bags. both milk and cheese samples were stored refrigerated until chemical analyses. analytical measurements all sample treatment and analytical processes were performed in clean conditions to avoid exogenous contamination. milk, cheese and dietary ingredients were digested by acidic digestion in microwave oven (ethos 1, milestone). approximately 0.5 g of both cheese and feed, and 5 ml of milk samples were transferred into teflon vessels and 8 ml of nitric acid (hno3, 65% suprapur®, merck) and 2 ml of hydrogen peroxide (h2o2, traceselect® ultra) were mixed. details of the microwave degradation conditions are shown in table 2. table 2: microwave digestion program of the milk, cheese and feed samples program step time (min) power (w) temp. (°c) 1 03:00 800 85 2 05:00 800 145 3 05:00 800 180 m ilk , c he es e 4 12:00 800 200 program step time (min) power (w) temp. (°c) 1 03:00 800 85 2 04:00 800 145 3 07:00 800 200 fe ed 4 11:00 800 200 microwave degradation was followed by a cooling period at room temperature, and then the sample solutions were transferred into volumetric flasks and adjusted to 25 ml up with high purity, double deionised water. the digested solutions were then stored at room temperature until analyses. blank digest was made in the same way without milk, cheese or feed samples. analyses of the elements were carried out by inductively coupled plasma-optical emission spectrophotometer (perkinelmer elan drc ii) and inductively coupled plasma mass spectrometer (perkin elmer optima 2000 dv). at lower levels of contamination, icp-ms provided lower detection limits for measurement (as, cd, cr, cu, mn, v, ni and pb), while icp-oes was used for measuring higher concentrations of metals such as fe and zn. the instrumental conditions and operating variables of the instruments are summarized in table 3. table 3: variables and conditions of icp-ms and icp-oes perkinelmer optima 2000™ dv rf power 1450 w plasma flow 15 l/min nebulizer flow 0.65 l/min auxilliary flow 0.5 l/min sample pump flow 1.5 ml/min neb. gemcone™ low-flow nebulizer chamber cyclonic injector alumina, 2 mm processing mode area perkinelmer optima 2000™ dv rf power 1550 w plasma gas 15 l/min nebulizer gas 0.54 l/min auxilliary gas 0.975 l/min sample uptake 0.7 ml/min nebulizer meinhard type k3 sampler and skinner platinum injector alumina, 0.85 mm reaction gas nh3 17 statistical analysis all statistical analyses were carried out with the computer software spss statistics 17.0. the data were statistically analyzed using one-way analysis of variance (anova) and t-test to examine statistical significance of differences in the mean concentration of heavy metals obtained in milk and cheese samples. the levels were found significantly different at p < 0.05. results and discussion metal concentrations in milk samples ten heavy metals were detected in the cow milk: as, cd, cr, cu, fe, mn, v, ni, pb and zn. total concentrations of elements in the 40 samples analysed (20 from highway, and 20 from non-polluted green areas) are shown in table 4. the content of lead, copper, vanadium, arsenic in milk collected from traffic intensive areas was significantly high, almost twice to three times as much as in that collected from green rural areas. lower, but significant difference was detected in the concentrations of iron, however, milk from highway areas showed similar ni concentrations to those observed in milk collected from non-polluted green areas. the contents of zn reached the highest value of all the elements tested in both groups. in cow milk, about the same concentrations of this element have previously been observed by some authors [7]. the higher concentrations of zinc in milk results mainly from metal pesticides according to watson [1], or zinc can be transferred from machines and tools used in milk collection procedure. no cadmium pollution could be detected in the milk from the green areas, however, 5.18 µg kg–1 cd content was measured in the milk of highway areas. in the milk collected from the highway areas, the concentrations of vanadium were measured three times higher than in the milk from non-polluted green areas. the concentrations of cr and fe detected in this study were quite similar to those measured under similar conditions in poland [9], however as and pb contents were detected higher in our study. metal concentrations in cheese samples the concentrations of metal elements measured in semihard cheese (trappista) are shown in table 5. the sequence of heavy metals in the cheeses made from milk collected in non-polluted green or highway areas were as follows: as, cd < v < pb < cr < mn <cu<ni< fe < zn, and as, cd < v < pb < mn < cr < cu < ni < fe < zn, respectively. arsenic and cadmium concentrations in both groups of cheese samples were below detection limits. chrome, copper, iron, and lead showed significantly higher concentrations in the cheese from highway areas, than in the cheese from non-polluted green areas. the treatment and the process of dairy production as well as the equipment used can influence the element concentrations [13]. the range of other trace elements, ni and fe were found similar in both cheese samples. the highest amount of v was detected in cheese made of milk collected from highway areas (119.9 µg kg–1), the level of this element was significantly lower (75.3 µg kg–1) than that of the cheese from green area. among all the elements detected in this study zn had the highest concentration in both treatments. high level of zinc and iron can be also explained by manufacturing processes. the mean concentrations of heavy metals obtained for cheese samples in this study were similar, however cr level was higher than those published in other literature [2, 3]. table 4: heavy metal contents (µg kg–1) of cow milk from lactating cows kept in non-polluted green or highway conditions (n=20 in each area) non-polluted green area highway area elements mean sd* mean sd* p-value (p<0.05) cr 14.7 2.2 18.3 0.9 0.04 cu 137.1 22.7 336.2 7.9 <0.01 fe 778.0 145.6 797.2 83.1 0.03 v 30.1 4.5 90.8 10.0 <0.01 zn 2240.5 517.4 1493.7 124.5 0.01 mn 25.8 9.7 16.9 2.0 0.01 cd nd* 5.2 1.6 0.02 as 23.3 7.8 52.1 5.2 <0.01 pb 11.7 5.1 24.9 12.4 0.05 ni 24.1 3.0 25.5 2.5 0.08 nd: not detectable sd: standard deviation 18 table 5: heavy metal contents (µg kg–1) of cheese (trappista) made of milk from lactating cows kept in non-polluted green or highway conditions (n=20 in each area) non-polluted green area highway area elements mean sd* mean sd* p-value (p<0.05) cr 314.1 93.9 528.5 141.2 0.05 cu 455.5 77.9 695.4 62.2 <0.01 fe 7258.0 45.7 7979.3 63.6 0.03 v 75.3 22.3 119.9 49.4 0.09 zn 23890.6 1783.5 19246.5 2066.6 <0.01 mn 366.6 74.2 417.9 45.1 0.09 cd nd* nd* as nd* nd* pb 125.7 51.0 148.9 42.4 0.05 ni 929.5 213.6 902.7 149.7 0.13 nd: not detectable sd: standard deviation conclusion differences in the concentrations of major and minor chemical elements in milk depend on many circumstances which are related to geographical location, soil type, nutrition, breed, age, lactation period, geographical location, mineral status of animals. however, certain heavy metal concentrations in milk from polluted areas are high compared to milk from non-polluted areas. these differences can be detected even in milk products such as cheese. our results confirm that attention must be paid to circumstances entailing continuous emission of heavy metal elements into the environment. the method of technology and quality control of milk and dairy product processes should be monitored regarding certain toxic elements in both fresh milk and milk products. acknowledgement we acknowledge the financial support of this work by the hungarian state and the european union under the tamop-4.2.1/b-09/1/konv-2010-0003 project. references 1. d. h. watson: food chemical safety, crc press broca raton fl, 1, (2001), 1–12 2. d. mendil: mineral and trace metal levels in some cheese collected from turkey, food chemistry, 96, (2006), 532–537 3. e. coni, a. bocca, p. coppolelli, s. caroli, c. cavallucci, m. trabalza marinucci: minor and trace element content in sheep and goat milk and dairy products, food chemistry, 57(2), (1996), 253–260 4. i. pavlovic, m. sikiric, j. l. havranek, n. plavljanic, n. brajenovic: lead and cadmium levels in raw cow's milk from an industrialised croatian region determined by electrothermal atomic absorption spectrometry, czech journal of animal science, 49(4), (2004), 164–168 5. j. a. nobrega, y. gelinas, a. krushevska, r. m. barnes: direct determination of major and trace elements in milk by inductively coupled plasma atomic emission and mass spectrometry, journal of analytical atomic spectrometry, 12(10), (1997), 1243–1246 6. l. pilsbacher, f. grubhofer: mercury, lead and cadmium in austrian raw milk – a comparison to earlier analyses and to 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dairy products, j. am. diet. assoc., 72, (1978), 608–611 14. nrc: nutrient requirements of dairy cattle, 7th rev. ed. national research council, washington dc. 15. p. b. a. n. kumar, v. dushenkov, h. motto, i. raskin: phytoextraction: the use of plants to remove heavy metals from soil, environmental science and technology, 29(5), (1995), 1232–1238 16. p. f. scanlon: heavy metals in small mammals in roadside environments: implications for food chains, science of the total environment, 59, (1987), 317–323 17. s. l. l. celine, l. xian-dong, g. zan, l. jun, d. ai-jun, w. tao: heavy metals and pb isotopic composition of aerosols in urban and suburban areas of hong kong and guangzhou, south china evidence of the long-range transport of air contaminants, science of the total environment, 41(2), (2007), 432–447 18. s. m. farid, m. a enani, s. a. wajid: determination of trace elements in cow's milk in saudi arabia, jkau: eng. sci., 15(2), (2004), 131–140 19. v. dushenkov, p. b. a. n. kumar, h. 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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<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> /enu (use these settings to create adobe pdf documents best suited for high-quality prepress printing. created pdf documents can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word 01_r.doc hungarian journal of industrial chemistry veszprém vol. 35. pp. 47-55 (2007) control structures based on constrained inverses f. szeifert, t. chován, l. nagy university of pannonia, department of process engineering, h-8201 veszprém, p.o. box 158, hungary the widespread use of the pid algorithms in the classical feedback scheme is due to the following to basic reasons: the role of pid-controllers in the traditional process control profession, and the good control performance achieved at the local control level. present paper proposes a well structured control solution for the local control level allowing the integration of different types of engineering information into the control algorithm. based on a comparative study of the structures of pid and imc controllers a novel control structure with two degrees of freedom (or three if the possibility of adaptation is considered too) is defined. the application of the new control structure is illustrated by the example of the temperature control in a laboratory water heater system. keywords: pid, imc, constrained inverse introduction more open control solutions which, at the same time, allow taking into account the inherent steady-state and unsteady-state (dynamic) characteristics of the process are recently introduced for chemical processes, too. in spite of the fact that the ifac technical committee on “chemical process control” has already outlined the necessity of the integration of process design and control design at its world congress in 1994, the broader application of control solutions mapping all the aspects of process characteristics directly requires much more time. this integration can assure that the a priori chemical engineering knowledge used in the process design could be employed in the development of the control algorithms in an explicit way. the introduction of this methodology is slowed down by several factors: ● it is well known that in the most part of chemical process control pid controllers, that map the model of the traditional instrumental controllers, are used. the digital technology allowed the implementation of several pid-modifications softening the difficulties of the application of common pid-algorithms in many cases. the consequence is that configuring a real control loop on the control system involves determining numerous structural and calculation parameters beside the three original control parameters. this way the simple algorithm loses its transparency and makes it almost impossible for the personnel operating the process application carefully the tuning methods of the control theory enforcing the application of empirical tuning techniques. according to an estimation, the ratio of pid controllers is 98 % in an average chemical process and only 5-10 % can be considered as more advanced solution. among these, 80 % of industrial pid-controllers are poorly tuned, 30 % of them are operated in manual mode and 30 % of them use the parameters set at commissioning [1]. limited competitors of pid-controllers are the mpc techniques which are mainly applied at the hierarchy level above the pid-controllers. ● control theory has a wide range of linear techniques, however thorough investigation the prerequisites of the practical applications has started only recently. measurement noises got a large attention from the beginning; while the dead-time, steady-state characteristics (e.g. nonlinearity of valves), the constraints of control outputs, the model error and the effect of the non-measured disturbances are getting into the researchers’ interest only recently. ● the chemical engineering knowledge regarding the process is principally given in form of balances for the phase masses, the component masses, the enthalpy (heat) and maybe the momentum which is a complex set of partial differential equations supplemented with the constitutive algebraic equations. in process design generally the simplified steady-state form of the equation set is used. the chemical engineering approach can be mainly tied to the steady-state models. the unsteady-state model is usually too complex to be employed directly in the control. on the other hand the black box models applied in control theory do not include any information regarding the structure of the controlled process. recently published approaches use models reflecting the structure of the controlled process to some extent while maintaining a simplified 48 form of the model (tendency models [2], grey box model, etc). present paper proposes a well structured form of the local control level which allows the integration of different types of engineering information in the control algorithm. comparison of control structures the widespread use of the pid algorithms in the classical feedback scheme is due to the following to basic reasons: 1. the role of pid-controllers in the traditional process control profession. 2. the good control performance achieved at the local control level. the second one is accounted for in a bit more details. the algorithm is transformed as follows: )1(1)11( 2 ++∗=++= ststt t tk st st st kg idi i cc c d i cc (1) i.e. the pid-controller can be interpreted as a serial system of an integrator and the inverse of a second order system (see fig. 1). if the dynamics of the process is second order then the transfer function of the part in dotted frame could be set to unity by appropriately tuning the pid parameters. this way the transfer function of the closed loop is a first-order filter and its time constant can be set arbitrarily. since many of the chemical processes can be well approximated by first or second-order dynamics, in such cases the excellent performance of pid controllers is not surprising. it should be emphasized, that the same results are obtained with model-based design techniques (direct synthesis, imc, etc.), in case of nonlinear systems the results are not equivalent rather they are only similar. figure 1: classical feedback scheme fig. 1 illustrates well the functions of the two parts of the controller used in the feedback loop. the inverse part compensates for the dynamics of the process, while the integrator eliminates the control error (and ultimately the final control error completely). the feed-back part can compensate for the influence of both the changes of the setpoint and disturbances (causes) by feeding back the output (time-delayed effect). measuring the dominant disturbances, the dynamics of the compensation can be significantly improved by applying a feed-forward part. the feed-back and feed-forward parts can be synthesized in the imc structure (see fig. 2). the applied filter has two functions; on the one hand it filters the noises, and on the other hand assures the operability of the scheme (without a filter a short circuit can be obtained). applying a first-order filter, the scheme can be transformed according to fig. 3. taking into account that the product of the transfer functions of the model and the inverse is unity, the transfer function of the part in dotted frame is the following: inverse stmodelinverse st inverse st g c c c ∗= ∗∗ + − ∗ + = 1 1 11 1 1 (2) figure 2: the imc structure filter inverse process model + + inverse of the second order system process + 1=sg stc 1 49 figure 3: the transformed imc this gives the same result shown on fig. 1, except that there was not any assumption made for the model. therefore the part in dotted frame fulfils both the inverting and the error elimination functions. the above analyses are valid for linear system models. the imc structure allows taking into account the effect of the measured disturbances in the model construction as well as in the model-based inverse formation. the model error and the effect of the unmeasured disturbances are measured together by the model error. therefore the accuracy of the model is known by very instant by calculating the model error. in the original imc structure the model error is compensated by feeding back the model error to the input of the feed-forward inverse model. this way the model approximates the real system. in the structure shown on fig. 2 the input of process and the model are the same, consequently it can be used for the control of stable systems only. new control structure in the construction of the new structure related to the above ones the following starting assumptions are made: 1. the system model includes all important properties regarding the process dynamics and it maps the manipulated variables, the measured disturbances and the parameters of the model to the controlled variables. 2. based on the model a constrained inverse model is constructed. the constrained inverse maps the setpoints, the measured disturbances and the parameters of the inverse model to realizable (constrained) manipulated variables. sound knowledge of the process is utilised in feedforward form. 3. the difference between the dynamics of the process and model is to be eliminated by applying a model-error compensator. as it was shown earlier, the model error comes from the direct error of the applied model and from the unmeasured disturbances. missing knowledge about the process is compensated for by feeding back the model error obtained from the measurements and the calculations. based on the above assumptions a control structure shown on fig. 4 can be constructed. the manipulated variable which is the feed-forward part of the real (physical) manipulated (uff) variable is calculated from the setpoint and the measured disturbances by forming the constrained inverse. from this signal the controlled variable which serves as reference signal for the process output can be calculated using the model. the difference (control error which is not equivalent with control deviation calculated directly from the setpoint) is due to the different dynamics of the model and the process. in the imc scheme this error can be compensated for by correcting the setpoint (see fig. 2, the correction is on the input of the inverse model, i.e. this correction approaches the model to the process). another option is to apply the correction on the input of the process (i.e. the output of the inverse model) using a compensator (this approaches the process dynamics to the model by correcting on its physical input). this correction is the feed-back part of the physical manipulated variable (ufb). the compensator is required to eliminate the difference (control error) between the controlled variable and the reference signal, i.e. it has an integrating character. the imc scheme synthesises the feed-back and feed-forward parts and makes the correction on the input of the inverse model. in the above structure, defining distinct functionalities, the feed-forward and feed-back terms are firmly separated, hence the degrees of freedom of the controller increases. the feed-forward part treats the servo problem while the feed-back part provides the “noise” compensation. the design of the above two parts of the controller can be separated. inverse model process 1 1 +stc + + + g 50 figure 4: the control scheme using feed the control error relative to the reference signal arising from the different dynamics of the model and the process can be set to zero. the actual model error is generated in a parallel scheme of the process and the model. based on the model error the model parameters can be refined too (adaptive systems). this involves a secondary feed back with a much larger time constant than that of the primary feed back. the different adaptation possibilities are not discussed in this paper. construction of the constrained inverse the function of the inverse term is to generate the input for the specified output. this is interpreted on fig. 5. the model of the process to be controlled maps the manipulated variable(s), the measured disturbance(s) (inputs) and the parameter(s) to the controlled variable(s) (outputs). this is a cause-effect relationship inferring that a physically feasible output can always be generated for every physically realizable input. the inverse model maps the physically possible disturbances, the references given independently from process and the parameters to the process inputs. this is a goal-cause relationship, i.e. the suitable system inputs must be find for the given system outputs. it is not always guaranteed that the specifications can be satisfied. this is the basic problem of composing the inverse. the impractical specifications can be corrected by applying constrained inverses. the details of this method are discussed in the following. let us define the model of the process to be controlled in the following state-space form (the principle of the method is not affected when, for the sake of simplicity, only one manipulated and one controlled variable considered in the calculations in the continuous time domain): ),,( zuxf dt dx = , state-transition function (3) y = g(x, u, z), output function (4) where u input signal, z measure disturbance(s), y controlled variable, x state variables t time. figure 5: interpretation of the constrained inverse constrains model inverse manipulated variable, u constrained manipulated variable input, u output, y measured disturbance, z reference signal, w constrained inverse model process compensation model adaptation model setpoint disturbance manipulated variable controlled variable parameters 51 the relative order of (3-4) system has an important role in the invertation [3]. the relative order basically means the smallest order differential of the output signal which is affected by the manipulated variable directly. therefore if the relative order of the system is r, then the following applies: ),,( xzu dt yd r r ϕ= , (5) while the (r-1)-differential is not a direct function of u. function φ(u, z, x) can be obtained by differentiating equation (4) r-times and taking into account the statetransition function too. the ideal form of inverting was, if the output followed the reference signal without any time delay (y = w). apart from the zero-order systems without any time delay, this is impossible in case of finite manipulated variables. consequently an r-order filter can be applied as inverting rule: ,... 11 1 10 wy dt dya dt yda dt yda rr r r r =++++ −− − (6) where a0, a1, ..., ar–1, altogether r pieces of parameters of the inverse formation. the r-order filter can be given as cascading r first-order filter. in this case the inverting has only one parameter. substituting relationship (5) into specification (6) and ordering the equation, φ(u, z, x) can be expressed as: )...(1),,( 1 1 11 0 − − − −−−−= r r r dt yda dt dyayw a xzuϕ (7) the manipulating variable can be expressed by inverting φ(u, z, x) with respect to u: u = φ-1(u, z, x) (8) the smaller is the time constant of the inverse, the more aggressive is the control action, at the same time the higher is the risk that the manipulated variable gets outside the physical constraints. conversely, at higher time constants, the physical constraints of the manipulated variable are more rarely attained. the physical realization of the manipulated variable calculated according to equation (8) cannot be guaranteed, hence usually the constraints are considered: u = {umin, if u < umin; umax, if u > umax; u otherwise} (9) where the allowable range of u: u ∈ [umin, umax]. the constrained manipulated variable calculated according to equation (9) can always be realized; however during the cutbacks the invertation rule (6) cannot be applied. model error compensation the design of the model error compensator is based on fig. 4 and the scheme of the constrained inverse based feed-back controlled process given on fig. 6. the input of the constrained inverse is the setpoint and the measured disturbance and its output is the feedforward manipulation variable (uff) and the reference signal calculated from the model. the model error is compensated by correcting the physical input of the process (u), while the control error (y) is calculated from difference of the reference signal and the measured output. the model for calculating the model error (merr) describes the relationship. the error model can be derived from the process model (3-4); however an autonomous black-box model can also be identified. e.g. if the error model is a maximum second-order input-output model, then a constrained pid controller (c-pid, [3], see fig. 7) can be well applied. the model error can also be compensated in imc structure, assuming that the constrained inverse which makes unnecessary the application of a separate filter and discussed in the previous part, is used. eliminating the model error, the setpoint is implicitly zero; therefore the scheme becomes simpler as shown on fig. 8. it is well known, that the model is required to be selfadjusting in the imc structure. figure 6: classical feedback scheme constrained inverse model process + fbu+ ffu+ control error y correction u 52 figure 7: model error compensation with c-pid controller figure 8: model error compensation with c-pid controller application of the method the application of the new control structure is illustrated by the example of the temperature control in a laboratory water heater system. the scheme of the system is shown on fig. 9. the feed flow rate can be controlled; the discharge temperature of the water can be controlled by the performance of the electric heater [4] figure 9: scheme of the laboratory water heater system the objective is to control the discharge temperature of the water while the feed flow rate and the feed temperature can fluctuate. accordingly, the controlled variable (y) is the discharge temperature, the manipulated variable (u) is the performance of the electric heater, the measured disturbances are the feed temperature (z1) and the feed flow rate (z2). the model of the process is the following heat balance of the tubular equipment: )( hpp ttku x tcb t tcv −= ∂ ∂ + ∂ ∂ ρρ (10) where x ∈ [0, 1] dimensionless length coordinate, t(t, x) temperature function, th pure time delay, b volumetric flow rate, disturbance signal (z2), v total volume, ρcp heat capacity of the liquid, ku(t – th) source density of electric heating, manipulated variable. the necessary initial and boundary conditions: t(0, x) given, t(t, 0) = z1 temperature of liquid feed (disturbance signal), y = t(t, 1) controlled variable. the heat balance (10) is a partial differential equation (distributed-parameter model) which is practical to be spatially discretized. the so called cascade model, obtained this way, can be transformed into the following state-space model: )]([ 211 1 21 httupxz p z dt dx −+−= )]([ 21 1 2 hii i ttupxx p z dt dx −+−= − , i=2,…,n, (11) y = xn, where n the number of cascade elements (the order of the state-space model), n kp n vp == 21 , parameters. the state-space model (11) has four parameters (p1, p2, th, n) which can be determined from a priory knowledge or by parameter estimation from experimental data. based on the experimental and simulation studies it was concluded that the model adequately reflects the experimental data; therefore it is suitable for the controller design. mv water t in f t < heating pc < open close adam-5000 lan u process for feed back constrained inverse error model control error c-pid process for feed back 53 the first step of controller design is the development of the constrained inverse model. since y does not directly depend on u, the output signal is differentiated according to equation (5): )]([ 21 1 2 hnn n ttupxx p z dt dx dt dy −+−≡= − . (12) the differential of the output is a direct function of u; therefore the relative order of the system is one. according to equation (6) the rule for inverting is the following: wy dt dy c =+τ , (13) where w setpoint, τc time constant. substituting relationship (12) regarding the differential into equation (13), the manipulated variable can be calculated based on equations (7-8): ])([1 1 2 1 2 −−+−= nnn c xxxw z p p u τ . (14) since the system is time-delayed, the variables on the right hand side of equation (14) can be considered as the values predicted for time t + th. the constraints corresponding to equation (9) are the following: if u < 0, then u = 0; if u > 10, then u = 10. (15) this way the constrained inverse model is completely defined. the scheme given on fig. 8 is applied for compensating the model error. since the state-space model (11) can be considered as a linear system with changing parameters for variables u, x, y, a model which is isomorphic to model (11) can be used as error model too. the difference is that in this case the input is the correction feed back while the output is negative control error (with respect to the reference signal). zero initial values are used as initial conditions involving that there is not any the control error initially. due to the isomorphism of the two models, the constrained inverse error model is isomorphic to the constrained inverse model. the input, output and state variables as well as the constraints are different, while the disturbances and the parameters are the same. the scheme of the controller constructed according to the above reasoning is shown on fig. 10. the control algorithm based on the scheme on fig. 10 was implemented in matlab/simulink programming environment. the algorithm was tested in several simulation and physical experiments. the results of a representative simulation study are presented on fig. 11. while the temperature of the feed is constant, a simulated disturbance is generated by applying a step function on the setpoint of the ideal flow controller. the controlled system is excited by step-wise changes of the temperature setpoint and the disturbance signal. the controller parameters can be directly estimated on the basis of the parameters of the a priori model. the control performance is significantly better than that of a pid controller; the tuning is much simpler; however the construction of the model is much more time consuming. after acquiring simulation experiences physical experiments were conducted (see fig. 12). in this case the flow control of the system was not ideal either due to other (unpredictable) disturbances affecting the system disturbances. in spite of the poor performance of the flow controller the experience collected in the simulation studies regarding the temperature control are still valid. figure 10: temperature control of the water heater system calculation of uff (14) constraint (15) constraint (15) model (11) error model (11) calculation of ufb (14) water heater delay (th) delay (th)) setpoint disturbance constrained inverse error model constrained inverse model controlled cariable manipulated variable 54 0 5 10 15 20 25 30 0 5 10 15 20 25 30 35 40 45 50 55 60 time (min) te m pe ra tu re (° c ) 0 50 100 150 200 250 300 fl ow ra te (l /h ), h ea tin g (% ) wtout tout u f figure 11: results of the simulation study 0 5 10 15 20 25 30 0 5 10 15 20 25 30 35 40 45 50 55 60 time (min) te m pe ra tu re (° c ) 0 50 100 150 200 250 300 fl ow ra te (l /h ), h ea tin g (% ) wtout tout f u figure 12: results of the experimental study 55 conclusions based on a comparative study of the structures of pid and imc controllers a novel control structure with two degrees of freedom (or three if the possibility of adaptation is considered too) is defined. at the given setpoint and measured disturbances, the firm knowledge regarding the controlled process is fed forward through a constrained inverse model (i.e. the feed-forward solution of the servo problem). the difference between the reference signal and the measured controlled variable is a control error coming from the model error and the effect of the unmeasured disturbances which is not accounted for. this error represents the lack of knowledge regarding the process to be controlled that can only be compensated for in feed-back scheme (i.e. the feed-back solution of the noise compensation). this can be designed on the basis of model error in several ways. the application of imc structure is advantageous in case of stable systems. simulation and physical experiments conducted on a water heater system, which can be described by a distributed parameter model, justified the feasibility and good performance of the proposed scheme. references 1. luyben w. l.: effect of derivative algorithm and tuning selection on pid control of dead-time processes, ind. eng. chem. res., 2001, 40, 36053611 2. filippi-bossy c., bordet j., villermaux j.: marchal-brassely s., georgakis c.:, batch reactor optimization by use of tendency models, comp. chem. eng., 1989, 13, 35-47 3. szeifert f., nagy l., chovan t., abonyi j.: constrained pi(d) algorithms (c-pid), hung. j. ind. chem., 2005, 33, 81-88 4. bodizs a., szeifert f., chovan t.: convolution model based predictive controller for nonlinear process, ind. eng. chem. res., 1999, 38, 154-161 microsoft word b_33_r.doc hungarian journal of industrial chemistry veszprém vol. 38(2). pp. 219-222 (2010) automatic robotic assembly system in the service of the vehicle industry and the environment i. sztankovics 1department of production engineering, university of miskolc, 3515 miskolc egyetemváros, hungary, e-mail: sztanisti@gmail.com i present an automatic assembly system in this article. i search out the main methods of assembly first. than i describe the system found in the department of production engineering at the university of miskolc. next i choose one of the used robots, and i describe it from the viewpoint of productivity and flexibility. keywords: robotic assembly, scara robot. introduction nowdays machine industry consists of 3 main sections: preproduction, component production and assembly. these three primary groups have the most considerable effect on the quality of the product although the product gets in contact with other areas, for example logistics or design. assembly grants the final form of the product from the 3 areas, althrough this section receives the least attention and it is not as advanced in most cases. so it is worth examining what kind of development we can observe in this area. before the examination of the topic it is useful to define the concept of the robot. this mechanism has an open kinematics chain, which is capable of directed motion, its part handler can be flexibly programed, and it has artificial intelligence functions. the difference between robots and manipulators can easily be seen. robots can be divided into 3 main groups from the viewpoint of the provided task. there are logistical, functional and mounting robots. in addition, the tasks one robot can perform can be extended if the head of the robot is changeable and the machine is able to do this exchange according to program instructions. the main area of the application of robots is the mass production lines or such areas where employees’ health is endangered, the tasks are too monotonous and where a human worker cannot fulfil the quality expectations. material handler robots are applied in the service of manufacturer or gauging machines, or they can carry the workpieces between positions. for robots, welding is a typical operation. they work more punctually and with the right quality, and they do not have to carry coveralls. painter robots are applied for similar reasons since harmful substances get into the air during the operation. it can accelerate the process of the operations or improve the quality if we apply robots in assembly areas. the monotony of mending operations would significantly influence the efficiency of the human workforce. methods of assembly in the next section i introduce the main groups of mounting methods. the designer needs this alignment at the time of planning so that he can decide whether to use robots and what kind of opportunities are available. we can group them according to the place of the mending operation and the degree of automation. classification according to the location of the assembly mounting processes can be divided into two groups according to the location of the assembly. the operations can take place in one or more areas. if mounting is performed in one place, the workpiece does not change its position in the course of the process. components and mounted units are transported into a single area and the workers come to this location. the assembly of products mostly takes place in this group. there are difficulties to automate this process since the application of robots would be expensive. another solution is when the product changes its position. it is defined at the time of planning, what kind of operations should be executed in which position. they apply this method in case of small, light products. the opportunities of automation are big as single positions can be completely robotized. 220 classification according to the degree of automation three main groups can be distinguished in automation. mounting can be processed non-automatically, semiautomatically and in a fully automated way. workers perform all the operations in case of manual assembly. small machines may assist them in his work. in semi-automatical assembly, machines perform certain operations, but they have no automatic functions. there is no need for human workers in case of an automatic assembly line; one man can handle the entire line, providing the proper conditions for the machines. presentation of an assembly line i present the system located in the workshop of the department of production engineering at the university of miskolc. to demonstrate robotized assembly, the line is able to accomplish the production of the following products: fly 525 type mikromotor mcdc 35-s-1 type mikromotor tk 422 type plate horn the most frequent mounting technologies and material handling operations can be demonstrated on these products. they can also present the main abilities of the robots that play an important role in the automation. a main viewpoint in the construction of the system was to plan a system layout that is mostly used in production. the line has its palette carrying-system in the middle, which increases the utilisation of the place. this is surrounded by the necessary positions. in this case it poses no difficulties to supply the components and tools for the system and the necessary maintenances are easy to perform on the line. to sum it up we can divide the flexible robotic assembly system into these main units (presented in fig. 1): workpiece handling conveyor system, 2 robotic assembly cells, 2 manual workplaces. workpieces are carried with palettes. inaccuracy in the position of workpieces cannot be allowed if robots are applied and with a high level of automation. these problemes can easily be solved with the use of palettes. in addition, an identification system can be found on the carrying elements. the system reads it at defined points of the line so the computer knows which mounting operations were made on the workpieces carried by the read palette. this i necessary because the buffer of each position is created on the middle conveyor. the auxilliary elements of the system are driven with pneumatics. this solution is safe enough, it does not pollute the environment, it can be built easily, and in case of a mistake it is simple to repair. for a more detailed view, i itemize the main parts of the assembly system: a) orimat material movement system 3 twin belt conveyor belts 2 overband lintra-s transferer 1 chain transferer parts carrier palettes fitted with equipment mechatronika plc control b) bosch sr 450 scara type assembly robot desoutter automated screwdriver feeding system construction capable of switching tools tool magazine for 3 tools c) poly-p 42 scara type assembly robot pneumatic cracking machine, d) central computer figure 1: sketch of the assembly system 221 presentation of a robot in the system the most important element of the system is the bosch sr scara 450 type robot. the main operations are carried out with this, so i describe it in more detail. we can see the construction of the robot in fig. 2. figure 2: structure of the bosch sr 450 the scara type (selective compliance assembly robot arm) robot from the sr family (sr450, sr600, sr800) is the smallest in the family. the construction of the arm matches the requirements of the assembly technology. it has a short cycle time and great accuracy. its price-performance proportion is beneficial. its design is adequatly robust and it is dependable. the construction ensures easy maintance. the robot has 4 controllable axes with electric drives. it has the opportunity for ptp, circle and lineal interpolation. it has free plc inand outputs. there is an m/60342/11 type paralel handler in the head. (martonair product, with pneumatic operation, max. stroke 20 mm). it has pneumatic and electric connections for the installed units on the robot body (screwing machine, snatching tools…) technological parameters of the robot: repetition accuracy ±0.05 mm maximum speed by axis: a1: 1–325 mm /and, a2: 2–510 mm/s a3: 3–800 mm /and, a4: 4–600 mm/s turning capability around the axes, and linear movement capability along the 3rd axis: a1: ±90°, a2: ±120°, a3: 360 mm, a4: 1028° maximum liftable weight: 2 kgs maximum liftable weight at reduced speed: 5 kgs opportunities for programming the motion of the robot is possible in descartes (x,y,z,c) and in mechanical (a1,a2,a3,a4) coordinate systems. the coordinates of the programmed dots can be taught. it is programmable with the baps language. the program can be launched from the terminal, from the controller board or from the manual handler. it has a testing opportunity with or without robot motion. during operation the technical features (speed, acceleration, actual position) can be read. the work area can be determined from the software. it is possible to use different interfaces (video camera, printer) through the data distributor. screwdriver tool with the help of its preferias, the screwdriver tool sorts the screws, moves them to the mounting positions and fastens them with the preset momentum. the phases of the operation are presented in fig. 3. figure 3: phases of the operation summary the opportunities in the automation of assembly can be observed from this article. mounting operations expectedly head in this direction of development, mainly in mass production. with the usage of an automatic system we can eliminate the chances of error due to the human factor. subjective errors in case of calculations are completely negligible. productivity grows significantly with the use of automation. nowdays this is very important because in the production of a component, a few seconds mean a lot. with shorter production it is possible to reduce the environmental load caused by one product. robots can perfrom work with adequate punctuality so they can live up to the strickest quality requirements. continuous supervision is not needed so one worker can handle several machines. a system with a robot has great flexibility. we can write the program far from the machine, then just upload it into the machine and we have already taught a new motion cycle to the robot. this way a robot can be easily switched to new products. nowadays this is an important requirement as it is necessary to respond to the customer demands promptly. besides, robots are safe enough. with suitable programming they cannot possibly damage the surrounding equipment as inappropriate motions can be banned. 222 they can control the auxiliary equipment which are found next to the robot with their inbuilt controls. so the plc of the whole system can be a smaller version. this increases the flexibility and new assembly positions can can be easily built in the system. references 1. i. deszpoth, j. kundrák, j. szűcs, t. papp: robotos szerelőcellában alkalmazható szerszámok. proc. on the viiith international conference on tools, miskolc, hungary, 1993, 648–653. 2. j. kundrák, t. papp: fine mechanical assembly in a robotized cell. proc. on the 2nd international scientific conference mtm´93, cugir, romania, 1993, 12–14. 3. j. kundrák, t. papp, l. kovács, l. pap: lehre und forschung zur montage-automatisierung an der universität miskolc, gép, 8, 1992, 25–33. 4. j. kundrák, t. papp, l. kovács, l. papp: lehre von der automatisierung in der ausbildung von maschinenbauingenieuren. proc. on the 3th international daaam symposium, budapest, hungary, 1992, 103–104. 5. j. kundrák, t. papp, l. kovács, l. papp: szerelésautomatizálás oktatása és kutatása a miskolci egyetemen. proc. on the mechatroninfo'92 international conference, budapest, hungary, 1992, 233–244. 6. l. kovács, j. kundrák, j. szadai, j. varga: flexible assembly model system at the university of miskolc. proc. on the 2nd international daaam symposium, strbske-pleso, czecho-slovakia, 1991, 128–131. 7. t. papp, l. strelecz, j. kundrák: flexible robot control system with image processing. proc. on the 8th international daaam symposium, dubrovnik – croatia, 1997, 251–252. 8. j. kundrák: robotized assembly systems: research and education. proc. on the microcad´97 international computer science conference, kharkov, ukraine, 1997. i. 312–314. 9. j. kundrák, t. papp, l. strelecz: flexible automatization by robots and vision system. proc. on the raad'96 5th international workshop on robotics in alpe-adria-danube region, budapest, hungary, 1996, 265–268. 10. j. kundrák, t. papp: die flexible automatisierung der montage in einem mustersystem. proc. on the 6th international daaam symposium, krakow, poland, 1995, 199–200. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice hungarian journal of industrial chemistry vesprém vol. 33(1-2)., pp. 69-73. (2005) estimation of parameters in 3-parameter weibull probability distribution functions r. luus and m. jammer department of chemical engineering, university of toronto, toronto, on m5s 3e5, canada this paper was presented at the 10th international workshop on chemical engineering mathematics, budapest, hungary, august 18-20, 2005 three-parameter weibull probability distribution function is used to represent the time-to-failure data. for parameter estimation, the errors-in-variables, maximum likelihood, and least squares methods are compared. the results obtained from five data sets show that maximum likelihood method gives the most reliable parameter estimates which are close to those obtained by errors-in-variables approach. the least squares method gave the poorest results in most cases. for parameter estimation, the luus-jaakola direct search optimization procedure yielded the optimal parameter values in negligible computation time, taking less than a second of computation time on a pentium4/2.66mhz personal computer for 50 data points. keywords: parameter estimation, weibull, maximum likelihood, least squares, errors-in-variables introduction similar items, such as 100-watt incandescent light bulbs produced by the same company, subjected to similar environmental conditions tend to fail at different times. to predict the life of such items, the three-parameter weibull probability distribution function has been found to represent the time-to-failure data reasonably well. the weibull cumulative distribution function is tttf < − −−= µ α µ β ],)(exp[1)( (1) and its derivative is the weibull probability density function ].)(exp[))(()( 1 ββ β α µµ α β − −−= − tttf (2) the data are in the form of time to failure for n similar items arranged in order so that t1 is the time to failure of the first item and tn is the time to failure for the nth item. statistically, a good estimate for the weibull cumulative distribution function for n data points, as suggested by o’conner [1] and used recently by hung [2], is 4.0 3.0)( + − = n iifs . (3) the problem is to estimate the parameters µ, α, and β from a given reliability data set. there are three approaches that may be used to obtain the parameters, depending on the criterion used for optimization. errors-in-variables estimation (eiv) recently, errors-in-variables approach has been found useful for parameter estimation where there is a significant error in the independent variables [3]. instead of estimating only the parameters, the method also estimates the values of the independent variables. here we choose the performance index to be minimized as ∑ −= = n i sii tti 1 2)( (4) where ti are the actual measured times to failure and (5) βαµ /1))](1ln([ ift ssi −−+= which, with the use of eq.(3), becomes 70 βαµ /1)] 4.0 3.01ln([ + − −−+= n itsi . (6) maximum likelihood estimation (ml) the likelihood function is the product of the individual probability density functions. thus the aim is to maximize the likelihood function ∏= = n i itfl 1 )( (7) which is written as ].)(exp[))(( 1 1 ββ β α µ µ α β − −−∏= − = i i n i t tl (8) to prevent computational difficulties, it is further specified that β ≥ 1. otherwise, if β < 1 and if µ is very close to t1, the term (t1 µ) β-1 becomes very large. least squares estimation (ls) an alternative to the above two methods is to consider as a performance index the sum of squares of deviations of the cumulative distribution functions ∑ −= = n i si iftfs 1 2)]()([ (9) substituting eq.(1) and eq.(3) into eq.(9) gives ∑ + − − − −−= = n i i n it s 1 2] 4.0 3.0])(exp[1[ β α µ . (10) the values of the three parameters α, β, and µ obtained from a set of data will depend on the choice of the performance index. the goal here is to examine the parameters obtained by these three performance indices i, l, and s. optimization procedure to obtain the three parameters, we decided to use direct search optimization, so that no transformations or auxiliary variables would have to be calculated. there are numerous direct search optimization procedures that may be used. recently, genetic algorithm has been favored by some, but recent comparison of the genetic algorithm to the direct search procedure introduced by luus and jaakola [4], and refined recently by luus [5-7], showed that the lj optimization procedure tends to be somewhat faster and more reliable than the genetic algorithm [8]. therefore, we used the lj optimization procedure for the optimization. the lj optimization procedure involves taking a number of random sampling points over a region, finding the best point, and then using the best point as the centre of the region for the next iteration. however, at the beginning of this iteration the region size is reduced by a factor γ < 1 to make the search more intensive around the best point. this procedure is continued for a number of iterations to finish a pass. since it is desirable to obtain the optimum value of the performance index very accurately, a number of passes is usually necessary. the algorithm for the lj optimization procedure is given by luus [9]. we used a multi-pass procedure, involving 25 passes, each consisting of 21 iterations. the initial values for the parameters were: µ = 0.5 t1, α = t1, β = 2.0, and the initial region size for the first pass was taken as 0.5 times the initial value. after every iteration the region sizes were reduced by γ = 0.95. at the beginning of the second pass, the region sizes were put to 0.01 times the parameter values. for the remaining passes, the region size for each parameter at the beginning of the pass was put equal to the amount by which the parameter changed during the previous pass. if this change, divided by the parameter value, was less than 10-6, then the region size was put to 10-6 times the parameter value. the parameter estimates were run with r = 25 and with r = 100 random points per iteration. numerical results all computations were done in double precision using watcom fortran compiler version 9.5 on a pentium4/2.66ghz personal computer. example 1: lifetime of light bulbs as the first example we chose the data of walpole and myers [10] relating to the lifetimes of 50 internally frosted incandescent 40-watt 110-volt light bulbs. the shortest lifetime was 702 h, so we chose the initial values: µ = 351, α = 702, and β = 2. using the eiv approach, after 25 passes, we obtained the minimum value i = 1.754306594335 × 104 with r = 100 in a total computation time of 0.83 s, and i = 1.754306594336 × 104 with r = 25 in a computation time of 0.22 s. the convergence profile given in fig.1 shows that 25 randomly chosen test points per iteration are quite sufficient to get accurate values for the parameters within 25 passes. however, when 100 points are used, convergence to 12 figures is obtained already in 11 passes. maximization of the likelihood function given in eq.(8) yielded with r = 100 in a computation time of 1.49 s the maximum value l = 1.0285396 × 10-139 with parameter values which are very close to those obtained by eiv, as is shown in table 1. to calculate such a small number, each probability density function was multiplied by 103 and then the resulting likelihood function at the end was multiplied by 10-150. this avoided any possibility of underflow problems. minimization of the sum of squares of deviations given in eq.(9) yielded with r = 100 in a computation time of 0.50 s the minimum s = 5.6267167 × 10-2 with parameter values given in table 1. these values are quite 71 different from those obtained from the other two methods. also, the deviations of the estimated times to failure and the measured times to failure are substantially higher, as is shown in the last column of table 1. it is natural for eiv to outperform the other two methods if the deviations of the same data points are used for estimating the parameters and then used for the evaluation, since in eiv the evaluation function is used for estimating the parameters. we therefore used only half of the data to obtain the parameters. starting with the first data point, every second data point was used, plus the last data point, giving 26 data points. fig.1 convergence profile for example 1, showing the effect of the number of random points used per iteration for evaluation of the results, the entire data length was used. as is shown in table 2, the maximum likelihood method yielded the best results. such evaluation was carried out with several additional data sets available in the literature. example 2: lifetime of batteries we now consider the lives of 40 similar batteries recorded to the nearest tenth of a year, as reported by walpole and myers [9]. convergence was easily obtained, yielding i = 0.36569261, l = 7.5001463 × 10-19, and s = 3.724944 × 10-2 with the parameter values given in table 3 for all the data. table 1 parameters obtained for example 1 with the use of 50 time-to-failure data points: 702, 765, 785, 811, 832, 855, 896, 902, 905, 918, 919, 920, 923, 929, 936, 938, 948, 950, 956, 958, 958, 970, 972, 978, 1009, 1009, 1022, 1035, 1037, 1045, 1067, 1085, 1092, 1102, 1122, 1126, 1151, 1156, 1157, 1157, 1162, 1170, 1195, 1195, 1196, 1217, 1237, 1311, 1333, 1340 µ α β ∑ = − 50 1 2)( i sii tt eiv ml ls 626.155 623.527 702.000 450.129 452.020 371.347 2.90623 3.00294 2.25438 1.7543×104 1.8188×104 2.3295×104 table 2 parameters obtained for example 1 with the use of every second data point and the last one (26 data points) but evaluated with all data points µ α β ∑ = − 50 1 2)( i sii tt eiv ml ls 577.18 590.06 702.00 510.72 495.22 380.64 3.0347 3.0953 2.1505 2.8713×104 2.1177×104 4.0526×104 table 3 parameters obtained for example 2, given the time-tofailure data: 1.6, 1.9, 2.2, 2.5, 2.6, 2.6, 2.9, 3.0, 3.0, 3.1, 3.1, 3.1, 3.1, 3.2, 3.2, 3.2, 3.3, 3.3, 3.3, 3.4, 3.4, 3.4, 3.5, 3.5, 3.6, 3.7, 3.7, 3.7, 3.8, 3.8, 3.9, 3.9, 4.1, 4.1, 4.2, 4.3, 4.4, 4.5, 4.7, 4.7 µ α β ∑ = − 40 1 2)( i sii tt eiv ml ls 0.00000 0.10346 1.60000 3.69330 3.58331 2.05230 5.51662 5.49813 3.18526 0.36569 0.38317 0.82921 in table 4 are the parameter values for half of the data. by comparing the estimates in these two tables, again the maximum likelihood method is seen to give the best results if half of the data are used to obtain the parameters, and the parameter values are evaluated with the entire data length. again, the least squares method yielded the worst results. table 4 parameters obtained for example 2 with the use of every second data point and the last one (21 data points) but evaluated with all data µ α β ∑ = − 40 1 2)( i sii tt eiv ml ls 0.00000 0.00000 1.60000 3.7487 3.7382 2.1089 4.9521 5.2934 2.8953 0.65398 0.45611 0.85610 72 example 3: data used by lockhart and stephens the data given by cox and oakes [11], and used by lockhart and stephens [12] gave i = 261.79902, l = 9.0746400 × 10-22, and s = 2.0017367 × 10-2 with a wide range of values for the parameters, as is seen in table 5. the ml values obtained here correspond very closely to the ml values obtained by lockhart and stephens, namely, 99.02, 78.23 and 2.38. table 5 parameters obtained for example 3, given the time-tofailure data: 117, 135, 135, 162, 162, 171, 189, 189, 198, 225 µ α β ∑ = − 10 1 2)( i sii tt eiv ml ls 71.5445 99.0109 13.9179 108.641 78.240 167.491 3.0214 2.3755 4.7922 261.799 412.692 321.376 when only half of the data were used, we see in table 6 that the maximum likelihood method yielded the most consistent values for the parameters. table 6 parameters obtained for example 3 with the use of every second data point and the last one (6 data points) but evaluated with entire data length µ α β ∑ = − 10 1 2)( i sii tt eiv ml ls 17.323 102.506 0.000 169.824 77.016 188.474 3.8339 1.8877 4.0675 1068.61 423.78 1499.66 example 4: lifetime of fruit flies for the data on the lives of 50 fruit flies in seconds when exposed to a spray in a controlled laboratory experiment as given by walpole and myers [10], we obtained the parameter values shown in table 7 with i = 18.879469, l = 4.8751765 × 10-18, and s = 3.8023533 × 10-2. table 7 parameters obtained for example 4, given the time-tofailure data: 3, 4, 5, 6, 6, 6, 7, 7, 7, 7, 7, 7, 7, 8, 8, 9, 9, 9, 9, 10, 10, 10, 10, 10, 10, 11, 12, 12, 13, 13, 13, 13, 13, 14, 14, 15, 15, 16, 16, 17, 18, 18, 18, 19, 19, 20, 23, 24, 27, 32 µ α β ∑ = − 50 1 2)( i sii tt eiv ml ls 3.0000 2.6548 3.0000 10.3405 10.8189 10.3032 1.4947 1.6606 1.5949 18.879 28.646 27.829 when only half of the data were used, as is seen in table 8, the best results were obtained with the least squares method. table 8 parameters obtained for example 4 with the use of every second data point and the last one (26 data points) but evaluated with entire data length µ α β ∑ = − 50 1 2)( i sii tt eiv ml ls 3.0000 2.5974 3.0000 10.6904 11.2482 10.6047 1.3285 1.5300 1.4892 84.548 36.322 23.355 example 5: lifetime of fuel pumps for the data on the lives in years of 30 similar fuel pumps as presented by walpole and myers [10], convergence to i = 14.135236, l = 3.456841 × 10-26, and s = 6.2525950 × 10-2 was easily obtained, yielding the parameter values in table 9. when only half of the data were used, table 10 shows that eiv yielded the best results. here it is noted that for the maximum likelihood method µ is very close to t1 and β is very close to 1, so the maximum likelihood estimation procedure is not very reliable. for this example, therefore, the errors-in-variables approach gives the most reliable parameter estimates. table 9 parameters obtained for example 5, given the time-tofailure data: 0.2, 0.2, 0.2, 0.3, 0.3, 0.4, 0.5, 0.7, 1.0, 1.2, 1.3, 1.5, 1.5, 1.8, 2.0, 2.3, 2.5, 3.0, 3.3, 4.0, 4.5, 4.7, 5.0, 5.5, 5.6, 5.9, 6.0, 6.0, 6.0, 6.5 µ α β ∑ = − 30 1 2)( i sii tt eiv ml ls 0.00000 0.20000 0.00000 3.2353 2.5965 3.1446 1.4346 1.0000 0.9248 14.135 26.517 68.778 table 10 parameters obtained for example 5 with the use of every second data point and the last one (16 data points) but evaluated with entire data length µ α β ∑ = − 50 1 2)( i sii tt eiv ml ls 0.00000 0.20000 0.00000 3.3732 2.6999 3.2830 1.3757 1.0000 0.8826 15.642 28.337 105.122 73 conclusions the luus-jaakola optimization procedure is easy to use for parameter estimation for the weibull distribution, since no transformations are required. the optimal parameter values are readily obtained in negligible computation time on a personal computer. errors-in-variables approach is easy to use with direct search optimization, and no computational difficulties were encountered with the use of the lj optimization procedure. however, with the maximum likelihood function, great care is required if β < 1, and µ is very close to t1. the parameter estimates obtained by eiv are closer to those obtained by maximum likelihood than by least squares. the least squares approach tends to give the least reliable parameter estimates. for most of the data sets, the maximum likelihood method gave the most consistent estimates for the parameters when a shorter data length was used. it is recommended to use both the errors-in-variables and the maximum likelihood methods to obtain the parameters in the weibull distribution and then to examine and evaluate the results. acknowledgement financial support from the natural sciences and engineering research council of canada is gratefully appreciated. symbols f weibull probability density function f weibull cumulative distribution function fs statistically determined weibull cumulative distribution function i performance index for errors-in-variables l likelihood function n number of items tested r number of random points used in each iteration s sum of squares of deviations of cumulative distribution functions ti time for the ith item to fail α parameter to be determined β parameter to be determined γ region size reduction after every iteration in the lj optimization procedure µ parameter to be determined acronyms eiv errors-in-variables estimation lj luus-jaakola optimization procedure ls least squares estimation ml maximum likelihood estimation references 1. o’conner p.d.t.: practical reliability engineering, wiley, new york, 1985 2. hung w.l.: quality and reliability engineering international, 2001,17(6),467-469 3. luus r. and hernaez h.: hungarian j. industrial chemistry, 2000, 28(3), 201-206 4. luus r. and jaakola t.h.i.: aiche j., 1973, 19(4), 760-766. 5. luus r.: recent research developments in chemical engineering, 2000, 4, 45-64. 6. luus r.: iterative dynamic programming, chapman & hall/crc, london, uk, 2000 7. luus r.: direct search luus-jaakola optimization procedure, lj optimization procedure, in floudas c.a. and pardalos p.m. (eds.), encyclopedia of optimization, kluwer, dordrecht, the netherlands, 2001, vol. 1, 440-444 8. liao b. and luus r.: engineering optimization, 2005, 37(4), 381-398 9. luus r.: hungarian j. industrial chemistry, 2000, 28(3), 217-223 10. walpole r.e. and myers r.h.: probability and statistics for engineers and scientists, macmillan, new york, 1993 11. cox d.r. and oakes d.: analysis of survival data, chapman and hall, london, uk, 1984 12. lockhart r.a. and stephens m.a.: j. royal statistical society, series b, 1994, 56(3), 491-500. microsoft word content.doc hungarian journal of industrial chemistry veszprém vol. 40 (2) pp. 87–91 (2012) biocatalytic hydrogen sulphide removal from gaseous streams g. tóth , é. lövitusz, n. nemestóthy, k. bélafi-bakó university of pannonia, research institute on bioengineering, membrane technologies and energetics, 10 egyetem str., 8200 veszprém, hungary e-mail: tothgabor2@gmail.com hydrogen sulphide is one of the most important substances responsible for unpleasant odour emissions in gas phase. it is often formed in higher concentration beyond other sulphur containing volatile compounds like methane thiol (mt), dimethyl sulphide (dms) and dimethyl disulphide (dmds). removal of hydrogen sulphide is usually carried out by physical-chemical methods (e.g. adsorption), but nowadays some bio-processes may be considered as promising alternatives. certain sulphur oxidising thiobacteria can be successfully applied for hydrogen sulphide conversion from gaseous streams like biogas. various strains have been applied so far for degradation of hydrogen sulphide, they belong mostly to the group of thiobacillus, which are autotrophic microorganisms. these autotrophic bacteria have the drawback in application that they grow slower than the heterotrophic ones and it is more difficult to control their growth. a number of chemotrophs are suitable for the biodegradation of h2s. these bacteria grow and produce new cell material by using inorganic carbon (co2) as a carbon source and chemical energy from the oxidation of reduced inorganic compounds such as h2s.the objective of the work described here was to study the ability of elimination of hydrogen sulphide by two chemotrophic microorganisms (thiomonas intermedia, thiobacillus thioparus) in a batch bioreactor. the other aim was the study of the immobilization of these bacteria to different supports. keywords: hydrogen sulphide, chemotrophic, biological oxidation thiomonas intermedia, thiobacillus thioparus, batch reactor, support introduction volatile sulphuric compounds like methane thiol (mt), dimethyl sulphide (dms), dimethyl disulphide (dmds) are harmful, corrosive components, and present in various gas streams, e.g. biogas [1, 2], among them hydrogen sulphide can be found in relatively high concentration. the concentration of hydrogen sulphide varies between 0,1 és 2% and depends on the quality of feed substance [3]. utilisation of biogas is mainly hindered by its hydrogen sulphide content, therefore its removal is essential. the current technologies based on chemical removal are quite expensive, thus usage of biogas in power plants is not supported [4]. yet, in most cases physico-chemical methods are used. recently biological processes received some attention due to their effectiveness and low operational and maintenance costs [2], [4]. biological removal of hydrogen sulphide can be carried out by autotrophic and heterotrophic ways. from the operation point of view heterotrophic strains are more beneficial, but mos chemoautotrophic bacteria seem suitable for degradation of the compound. these bacteria can live using inorganic carbon (e.g. co2) as carbon source, while energy is obtained by oxidation of reduced compounds (e.g. h2s) [5]. the aim of this work was to study a suspended batch bioreactor, where chemoautotrophic aerob bacteria (thiomonas intermedia, thiobacillus thioparus) are able to use carbon dioxide present as carbon source, while hydrogen sulphide is converted into sulphur powder or oxidised sulphur compounds. the investigations were conducted in liquid phase by using free and immobilised cells. materials and methods microorganisms thiomonas intermedia is an aerobic, chemoautotrophic bacterium, purchased in lyophilised state from the national collection of agricultural and industrial microorganisms (ncaim budapest, hungary). for its growing thiomonas intermedia broth elaborated by dsmz (deutsche sammlung von mikroorganismen und zellkulturen gmbh, germany) was used [6]. its composition is (g/l): nh4cl 0.1, kh2po4 3.0, mgcl2*6 h2o 0.1, cacl2 0.1, na2s2o3*5 h2o 5.0, yeast extract 1.0, 1000 ml distilled water. during the growing period ph was adjusted to 5.5–6.0, then it was incubated at 33°c temperature and 120 rpm. 88 the other, also chemoautotrophic aerobic bacterium is thiobacillus thioparus, which was purchased from dsmz (germany) strain collection. its growing parameters are the same as given in thiomonas intermedia. the features of microorganisms are summarized in table 1. table 1: the features of thiomonas intermedia és a thiobacillus thioparus thiobacillus thioparus thiomonas intermedia optimal ph 5–9 5–7.5 optimal temperature [°c] 33–35 30–35 cell type gram negative gram negative shape, size rod, 0.9–1.8 μm trophity obligate chemoautotrophic facultative chemoautotroph energy source thiosulphate, sulphide thiosulphate, sulphide oxygen demand aerob aerob source [7] [8] analysis to follow the concentration of hydrogen sulphide in the liquid phase a photometric method was applied. the principle of the measurement is that the sulphide in acidic environment gives a colourful reaction with n,n dimethyl-p-phenilene diamin resulting in methylene blue, which can be measured by photometer in 670 nm after 20 min reaction time, using 5 cm cuvette (hachlange dr 3800) [9]. the advantages of the method are that easily applicable, having good reproducibility and the measuring range is wide: between 0.1 and 1.2 mg s2-/l. the composition of the gas phase was determined by dräger x-am 7000, which is a mobile electrochemical device, able to detect hydrogen sulphide and carbon dioxide. the experiments were carried out in 250 ml, jacketed, thermostated reactor (figure 1), where the total volume of the liquid phase was 200 ml. its composition was: 10% inoculum, 5%, water containing 2500 mg/l hydrogen sulphide and 85% broth. the optical density of the samples were measured by a photometer (hachlange dr 3800), in 620 nm. the biochemical reactions in the reactor resulted in a decrease of sulphide content in the liquid phase. the water vapour in the gas phase disturbs the optimal operation of the gas analysis equipment, therefore the vapour had to be condensed before. samples were taken every half an hour during the exponential growing period of the bacterium, otherwise it was taken every hour, and dissolved sulphide concentration and optical density were determined. figure 1: set-up of the batch reactor immobilization the strains were immobilised in three types of supports and the process was checked in a serial of measurements. mavicell-b cellulose beads, alginate beads and granulated activated carbon were used in the experiments. mavicell-b (table 2) is cellulose beads, widely used for immobilization of various microbes, having large adsorption surface area, thus a highly suitable support, moreover it can withstand to the corrosive effect of hydrogen sulphide. the cells can be bound on the surface of the support by adsorption. table 2: features of mavicell-b feature regenerated cellulose content 45–55% ash 35–40% particle size 2–3.5 mm aggregate thickness 250–300 g/dm3 water uptake at 25ºc 150–200% special pore volume 1.5–2 cm3/g special pore surface area 8–10 m2/g swelling increase in diameter 1.5 fold increase in volume 3 fold the other support used was alginate beads, widely used in biotechnology for immobilization of cells and enzyme, (figure 2) by the so called entrapment technique. during jellification small hollows are formed in alginate where biocatalysts (enzymes and cells) can be entrapped. the structure of the gel is compatible with the biocatalysts, thus no chemical modification is needed [10]. finally the granulated activated carbon (gac) support was purchased from airwatec s.a. (belgium). 89 figure 2: alginate beads containing cells due to its high surface area it seems also a promising support material for immobilisation of microorganisms. the features are listed in table 3. table 3: features of activated carbon parameter value total surface area (bet) (m2/g) 1080 ph 7.0 water content (%) 1,1 ash content (%) 8.6 granules diameter (mm) 1.0 during the experiments immobilised strains were kept in two vessels (for the two strains) and a blind one was used as a control, for all the three types of immobilization. samples were taken from all vessels regularly, and sulphide contents were determined. then fresh broth was given to the strains. in the end of the experiments the amount of immobilised cells (on the surface of mavicell and activated carbon particles, as well as in the alginate beads) – or more precisely the protein content – was measured by the modified folin-method. results firstly 24 h long batch fermentations were carried out by free thiomonas intermedia and thiobacillus thioparus microbes. the results are shown in figure 3 and figure 4. as it can be seen from figure 3 and figure 4 after a 8–12 h lag phase bacteria started to grow, the exponential growing period was found from around 10th h till 15-16th h, then a the rate of growing was slower. all the four parameters measured confirmed that the maximal growing rate of both bacteria was at the 12–13th h of the fermentations. a b figure 3: concentration of hydrogen sulphide and carbon dioxide (a), dissolved sulphide and optical density of thiomonas intermedia (b) as a function of time moreover it can be established that both thiomonas intermedia and thiobacillus thioparus reduced the concentration of hydrogen sulphide in the reaction mixture, i.e. they mostly obtained energy from degradation of hydrogen sulphide (dissolved sulphide) during the metabolisms. in both figures 3/b and 4/b dissolved sulphide concentration as a function of time shows some discrepancy, which is difficult to explain. we think that the analytical method (by photometer) may be disturbed by some nutrient compound present in the liquid phase, therefore another method should be found in future. another reason of the strange behaviour might be that certain metabolic products were formed during the fermentation which resulted it in the second half of the experiments. 90 a b figure 4: concentration of hydrogen sulphide and carbon dioxide (a), dissolved sulphide and optical density of thiobacillus thioparus (b) as a function of time operational stability in the liquid phase the bacteria were immobilised in three different support: mavicell-b cellulose beads, alginate beads and granulated activated carbon. to check their work they were kept in reaction mixtures, containing nutrients and hydrogen sulphide, and samples were taken regularly. figure 5 presents the experimental results: the variation of hydrogen sulphide concentration [mg s2-/l] compared to the control (bind) one as a function of reaction time in cases of mavicell-b cellulose beads (fig. 5/a), alginate beads (5/b) and granulated activated carbon (5/c). it can be observed that a decrease in hydrogen sulphide concentration compared to the blind was measured, due to the activity of the bacteria immobilised on the support. to check this phenomenon protein content of the supports (measured in the end of the experiments by washing out the microbes from the surface of the support, or – in case of alginate – destroying the gel structure) was determined. the results are summarized in table 4. a b c figure 5: operational stability of bacteria immobilised in mavicell-b (a), ca-alginate (b) and activated carbon granulates (c) from the table 4 it can be seen that the protein measurement confirmed our experimental results: considerable amount of microbes were immobilised on all of the supports. since bacteria were entrapped in 91 alginate (not only adsorbed on the surface), much higher protein content was found in that case. table 4: the amount of protein (microbes) measured in the various support mavicell-b caalginate ga c thiomonas intermedia [mg dm/g carrier] 0.12 6.3 0.15 thiobacillus thioparus [mg dm/g carrier] 1.83 7.1 2.05 it can be stated that the bioconversion processes can be followed by measuring the hydrogen sulphide concentration in the liquid phase, but the photometric determination of the total sulphide content can not be applied here. based on the protein determination it is obvious that the microbes were able to immobilise in the supports and worked properly to reduce hydrogen sulphide concentration in the liquid phase. evaluation as a summary it can be stated that our experiments proved: the two microbes investigated are suitable for the biological degradation, removal of hydrogen sulphide. however, the analytical method to follow the bioconversions should be improved and we should continue the experiments in gas phase. based on the successful immobilisation and measurements in liquid phase, the bioreactor system should be redesigned to be able to operate in gas phase and to determine exactly the ability and effectiveness of the bacteria. acknowledgement the research work was partly supported by the „social renewal operational programme” (new széchenyi plan) in the frame of támop-4.2.2.a-11/1/konv2012-0038 project, entitled „complex multidisciplinary investigation of the effects of human activity and the related social conflicts on a sensitive geographical area pertaining to a shallow lake (the water body of lake balaton and its southern catchment area). the project is supported by the european union and co-financed by the european social fund. references 1. k. s. cho, m. hirai and m. shoda: degradation of hydrogen sulfide by xanthomonas sp. strain dy44 isolated from peat, appl. environ. microbiol., 58 (1992), pp. 1183–1189 2. e. szentgyörgyi, n. nemestóthy, k. bélafibakó: application of membranes in biogas production, desalination and water treatment, 14 (2010), pp. 112–115 3. g. lastella, c. testa, g. cornacchia, m. notornicola, f. voltasio, v. k. sharma: anaerobic digestion of semi-solid organic waste: biogas production and its purification, energy conversion and management, 43 (2002), pp. 63–75 4. g. tchobanoglous, f. l. burton, h. d. stensel: wastewater engineering. treatment and reuse, 4th edition mcgraw-hill companies, new york (2003), cap. 14., 1505–1532 5. m. l. prescott, p. j. harley, a. d. klein: microbiology, 5th edition. mcgraw-hill companies, new york (2003) 6. www.dsmz.de 7. l. vlasceanu, r. popa, k. b. kinkle: characterization of thiobacillus thioparus lv43 and its distribution in a chemoautotrophically based groundwater ecosystem, applied and environmental microbiology 63(8) (1997), pp.3123–3127 8. s. k. panda,v. jyoti, b. bhadra, k. c. nayak, s. shivaji, f. a. rainey, s. k. das: thiomonas bhubaneswarensis sp. nov., an obligately mixotrophic, moderately thermophilic, thiosulfateoxidizing bacterium int. j. syst. evol. microbiol., 59 (2009), pp. 2171–2175 9. j. d. cline: spectrophotometric deter-mination of hydrogen sulfide in natural waters, department of oceanography, university of washington seattle, 14 (1969), pp. 454–458 10. l. boross, cs. sisak, b. szajáni: szilárd fázisú biokatalizátorok – előállításuk, tulajdonságaik és gyakorlati alkalmazásuk, akadémiai kiadó, budapest (2008), pp. 53–54 page 1 page 2 page 3 page 4 page 5 page 6 page 7 page 8 page 9 page 10 page 11 page 12 page 13 page 14 page 15 page 16 page 17 page 18 page 19 page 20 page 21 page 22 page 23 page 24 page 25 page 26 page 27 page 28 page 29 page 30 page 31 page 32 page 33 page 34 page 35 page 36 page 37 page 38 page 39 page 40 page 41 page 42 page 43 page 44 page 45 page 46 page 47 page 48 page 49 page 50 page 51 page 52 page 53 page 54 page 55 page 56 page 57 page 58 page 59 page 60 page 61 page 62 page 63 page 64 page 65 page 66 page 67 page 68 page 69 page 70 page 71 page 72 page 73 page 74 page 75 page 76 page 77 page 78 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525 page 526 page 527 page 528 page 529 page 530 page 531 page 532 page 533 page 534 page 535 page 536 page 537 page 538 page 539 page 540 page 541 page 542 page 543 page 544 page 545 page 546 page 547 page 548 page 549 page 550 page 551 page 552 page 553 page 554 page 555 page 556 page 557 page 558 page 559 page 560 page 561 page 562 page 563 page 564 page 565 page 566 page 567 page 568 page 569 page 570 page 571 page 572 page 573 page 574 page 575 page 576 page 577 page 578 page 579 page 580 page 581 page 582 page 583 page 584 microsoft word contents_2.doc hungarian journal of industrial chemistry veszprém vol. 31. pp. 47-55 (2003) conversion of waste hdpe and ldpe into feed stocks in tube reactor n. miskolczi1, l. bartha1, gy. deák1, b. jóver2 1 university of veszprém, department of hydrocarbon and coal processing 2 mol hungarian oil and gas plc, r&d, hungary the thermal degradation of waste polyethylenes (hdpe and ldpe) was investigated in a horizontal tube reactor at temperatures of 500, 525 and 550 °c. by thermal cracking, the hdpe and ldpe were converted into gas, liquid and wax-like hydrocarbon products with the yields of 3.1-6.0%, 5.9-22.4 and 70.6-91%, resp. the liquids were further separated with atmospheric and vacuum distillation into naphthaand diesel-like products. these fuel-like products consisted of hydrocarbons of c5-c10 and c11-c27 in case of lighter and heavier products resp., which might be used as feed stock materials. differences in the properties of volatile products could be observed with increasing temperature, but not significant differences were noticed between various waste polymers. subsequent distillation of the products, fuel like liquids that had low sulphur and nitrogen content and high cetane index was carried out. the olefin content of the fractions and the distribution of the double bonds were determined by infrared spectroscopy and the distribution of carbon atoms by gas-chromatography. the gas and liquid products contained a significant amount of unsaturated hydrocarbons, mainly terminal olefins. keywords: tube reactor, chemical recycling, waste polyethylenes, cracking temperature, gas-chromatography, olefin content, carbon atom distribution introduction the suitable treatment of plastic wastes got the focus of interest in modern society, because of increasing production of polymers, which generates enormous amounts of wastes from them. the question of recycling and reusing is important both from the environmental and energetic aspects. however, the global reserves of fossil fuels are limited; therefore there are efforts to convert wastes into valuable feed stocks. some legal measures stimulate the higher rate of recycling e.g. in the member countries of the eu recycle of 20% of plastic wastes is aimed at in 2005, and 30% in 2010. the present amount of recycled waste plastics is less than 10% [1]. thermal degradation of waste polymers is only one way of their utilization. in cracking reactions of plastic materials c-c bonds are cracked resulting in lighter and more valuable hydrocarbons. according to production data the main constituents of the plastic wastes are low-density polyethylene, high-density polyethylene and polypropylene, which represent about 20-20% of the wastes [2]. this is one of the reasons that their thermal or catalytic degradation was widely investigated. the reaction of decomposition resulted gases, liquids and heavier hydrocarbons. further application of decomposed wastes can be as fuels or raw materials for the petrochemical industry. in fact, several researchers have investigated the route of thermal degradation of waste polymers to valuable products, and several methods have been suggested for solving of this problem. however, it is often complicated. the most investigated way of the degradation is the thermal and/or catalytic cracking in batch reactors. the weight of the used materials is generally not more than 100-200g, although the preferred technique is thermal-gravimetry connected with an analysis e.g. tg-ms using 1-2g of polymers [3-9]. cracking parameters are most important in respect of products properties [10-13]. higher yields of gas 48 and coke were observed at higher temperatures; moreover the liquid fraction had significant aromatic and cyclic hydrocarbon content. at lower temperatures the main product is liquid of high olefin content. the liquid can be further saturated with hydrogen, and perhaps isomerised by the use of catalysts and can be used as good quality synthetic diesel oil or lubricants. cracking reactions are endothermic, and need lot of energy. heat requirements can be reduced with catalysts, but the disposal and the activation loss or regeneration of the catalysts could cause some other problems. the cracking of ldpe and hdpe was studied also in fluidized bed reactor [14-16]. the pyrolysis of ldpe in an internally circulating fluidized-bed reactor [14, 15] using short residence time at 850°c resulted 90% of gas yields with 75% of olefins in the gases. williams et al. [16] have evaluated the pyrolysis of ldpe in a fluidized bed reactor at temperatures of 500–700 °c. according to gc-ms analysis alkyldienes, alkenes and alkanes are found in the products. the carbon number range of the wax sample was c11-c57, whilst the oil sample was c8-c44. the wax-like product was very pure aliphatic material, with no aromatic content. it has the potential to be used in a conventional steam cracker or fluidised catalytic cracker in the petrochemical industry as substitutes for petroleum derived feed stocks. ng et al. [17] have investigated the conversion of pe with vgo into fuels by catalytic cracking in a fixed bed reactor at 510 °c. different ratios of pe/vgo were used, and the highest yield of gasoline was found when 10% waste pe was used. in the present paper, we report the thermal cracking behaviour of a waste low-density polyethylene (ldpe) and high-density polyethylene (hdpe) in a horizontal tube reactor. the aim of this study is to investigate the effect of the cracking parameters (temperature and feed materials) on the properties of the products. the change of aliphatic species (n-olefin and nparaffin) and their distribution were investigated in function of cracking parameters. liquid fractions were separated into two fractions, and their application possibilities as fuel were studied. experimental raw materials commercial highand low-density polyethylenes (hdpe and ldpe) were used as raw materials. the hdpe waste was obtained from motor oil flasks, which were crashed to 5-7 mm pieces and used as raw material, and the ldpe waste was regranulated pellets of ldpe from the packaging industry. their main properties are summarized in table 1. each polyethylene waste has ca, ti, zn content from filler materials and pigments such as caco3, tio2 and zno. the used raw materials had sulphur and nitrogen content from additives of polymer (e.g. anti oxidant, fire-retardant and antifuming additives). table 1 the properties of waste polymers properties hdpe ldpe grain size, mm 4-6 5-6 density, g/cm3 0.962 0.923 melt-flow index, g/10min. (1) 0.538 0.551 ash content, % 1.14 1.03 humidity, % 0.13 0.10 metals, ppm ca 55 89 zn 21 44 ti 545 417 (1) at 190 °c with 2160 n load cracking apparatus the experiments were carried out in a horizontal tube reactor, which is schematically shown in fig. 1. the cracking equipment consisted of four main parts: a feeding, a thermal degradation, a preliminary separation and a distillation part. wastes with suitable grain size were fed in an extruder. in the extruder the raw material was preheated up to 250-280 °c. from the extruder the preheated polymer was directly driven in the reactor, where it was cracked at 500-550 °c into volatile products and wax-like residue. the reactor was connected to a separator and a distillation unit. in the separator, the hydrocarbons were separated into volatile products and residue. the volatile fraction was further separated in a condenser to gas and liquid. cooling water at 20 °c was used for condensation. non-condensable gases were passed through a flow meter and then flared. gases and liquids were sampled and analysed by a gaschromatograph. at room temperature solid residue was collected as a bottom product. the distillation 49 took place under inert nitrogen atmosphere using atmospheric pressure and vacuum (15 hgmm). 2 waste residue liquid gases 9 9 9 5 6 f2 f1 33 34 6 7 8 9 10 11 f3 volatile products 1 distillation preliminary separation thermal degradation feeding 1 fig. 1 cracking apparatus for cracking of waste polymers 1. motor, 2. extruder, 3. reactor, 4. separator, 5. condenser, 6. separator, 7. gas-flow meter, 8. flare, 9. atmospheric distillation, 10. vacuum distillation, 11. thermometer analysis of products in the present work the change of product properties was studied as function of cracking parameters. gas and liquid products formed in cracking reactions were analyzed with the use of the following methods: liquid density measurement (msz en iso 12185), determination of the –ch2–/–ch3 ratio in liquid fractions with ir spectroscopy, determination of the olefin double bond distribution with shimadzu ir-470 type spectrometer, gas analysis using a carlo erba vega series gc 6000 gas-chromatograph (gc) provided with a 50 m × 0.32 mm fused silica column with al2o3/kcl coating, at 40 °c, liquid analysis using a trace gc gaschromatograph provided with a 30m x 0.32mm rtx®-1 (crossbond® 100% dimethylpolysiloxane) column. the temperature program of the analysis started at 40 °c (2 min.), then the temperature was raised to a rate of 15°c/min. to 330°c, determination of sulphur and nitrogen content of liquids (astm d 6428 99 and astm d 6366 99). results and discussion yields the cracking behaviour of various waste polyethylenes was investigated in a horizontal tube reactor at 500, 525 and 550 °c temperature. the cracking reactions of wastes gave off three different products: gas, liquid and residue, which consisted of hydrocarbons of different lengths. the yields of products are shown in table 2. table 2 the yields of products formed in thermal degradation of waste hdpe and ldpe (%) polymer hdpe ldpe temperature, °c 500 525 550 500 525 550 gas 3.1 3.9 4.7 4.0 5.5 6.0 liquid 5.9 10.8 21.7 8.6 12.4 23.4 residue 91.0 85.3 73.6 87.4 82.1 70.6 it was found that the yield of volatile products is increased with temperature in case of both polyethylenes. with increasing temperature the thermal stability of carbon chains decreases, therefore in case of higher temperature (550 °c) the possibility of cracking of c-c is greater than at lower temperature (500 °c). this results in a growing amount of the volatile products. from ldpe higher liquid yields were observed (8.6, 12.4, 23.4%) in contrast to hdpe (5.9, 10.8, 21.7%). this fact can be explained by the difference in the structure of polyethylenes. the ldpe polymer has lower density, because of its structure, which contains more branch chains than the hdpe. it means that ldpe has more tertiary carbon atoms, which have considerably lower resistance against thermal degradation. it was found that under the same circumstances (cracking temperature, residence time, etc.) the ldpe can be degraded a little easier than hdpe, therefore the cracking of ldpe could result in higher amount of liquids and gases. structure of products gases the change of composition of gases with different cracking temperature is compared in table 3. significant differences are not observed between various gas compositions obtained at different temperatures, and the various densities of raw materials did not cause differences either. gases formed in the degradation of both ldpe and hdpe contained high amounts of c2 and c4 50 hydrocarbons. this is consistent with results of previous papers [18, 19]. the concentration of olefins was higher than that of the paraffins of the same carbon number. it was earlier described that the possibility of β-scission reactions is greater than hydrogen transfer reactions in thermal degradation. it is well known that the thermal degradation of polymers takes place by radical mechanism and results mainly in monomers and oligomers. pe is built up from monomers of two carbon atoms –(ch2-ch2)–, which cracked into statistically determined fragments, e.g. ethane, ethane or butane, butane, etc. the possible scheme of the degradation is shown in fig. 5. table 3 the composition of gases obtained in the cracking of hdpe and ldpe waste (%) initiation r1ψ ψ -r2 ⇒ r1-ψ· + ·ψ-r2 propagation r1-ψ· + r1-ψ-ψ-r2 ⇒ r1-ψ + r1-ψ-ψ·-r2 (intermolecular hydrogentrasfer) r3-(k)m-ψ-ψ-ψ-(ψ)n-ψ·⇒ r3-(ψ)m-ψ-ψ·-ψ-(ψ)n-ψ (intramolecular hydrogentrasfer) r3-(ψ)m-ψ-ψ·-ψ-(ψ)n-ψ⇒ α-olefin + r3-(ψ)m-ψ· (β-scission) r3-(ψ)m-ψ-ψ·-ψ-(ψ)n-ψ⇒ α-olefin + r3-(ψ)n-ψ· (β-scission) termination r5-ψ· + ·ψ-r4 ⇒ r5-ψ-ψ-r4 where ψ = –(ch2-ch2)– r1, r2, r3, r4, r5 = alkyl group ψ· = radical from ψ fig. 5 the scheme of cracking of polyolefin wastes liquid fractions the liquid fractions and residues obtained in the cracking reactions were measured and analyzed also as fuel-like products. for the sake of investigation of this possibility, after thermal degradation the liquid products from the waste polymers and their residues were mixed and then separated with atmospheric and vacuum distillation into further fractions: white spirit like wsl, diesel like dl fractions and bottom products. table 3 represents the main properties of each distillate fraction in case of hdpe and ldpe wastes. polymer hdp e ldpe temperatur e. °c 500 525 550 500 525 550 methane 6.44 6.06 6.02 7.33 6.90 7.40 ethene 28.2 9 27.2 7 27.7 8 25.84 26.55 27.28 ethane 15.1 2 16.2 6 13.1 5 15.04 16.09 14.40 propene 8.78 9.29 8.70 8.54 8.42 7.61 propane 6.05 6.16 5.93 6.81 6.10 6.49 butene 23.4 1 23.2 3 25.0 0 24.05 21.49 24.75 butane 11.9 0 11.7 2 13.4 3 12.40 14.46 12.07 51 table 3 the properties of fractions after distillation polymer hdpe ldpe temperature, °c 500 525 550 500 525 550 fraction wsl dl wsl dl wsl dl wsl dl wsl dl wsl dl yield (1) 8.00 13.70 15.74 28.93 13.98 34.09 10.85 16.28 19.30 31.99 21.46 37.22 density. g/cm3 0.738 0.795 0.747 0.801 0.741 0.802 0.733 0.789 0.752 0.801 0.748 0.796 ch2 (2) 7.1 15.9 7.6 15.3 7.0 15.1 7.6 15.5 7.3 15.0 7.8 15.8 ch3 (2) 1.8 2.3 1.9 2.4 1.8 2.1 2.7 2.8 2.6 2.9 2.5 2.7 olefin content vinyl 52.3 37.4 49.6 39.1 49.1 35.6 45.1 32.8 44.3 31.4 44.6 31.5 vinylidene 1.7 4.1 2.8 2.9 2.3 2.1 6.5 6.3 6.1 7.4 6.9 6.6 internal 3.6 4.0 4.0 3.0 4.0 4.7 2.3 3.6 3.9 2.5 3.8 4.4 vk40, mm2/s 4.43 4.54 4.20 4.52 4.51 4.63 corrosion test group1 group1 group1 group1 group1 group1 pour point, °c 8 10 8 5 5 3 flash point, °c 105 101 98 96 99 95 diesel index 71 72 72 69 70 70 s content, ppm 18 19 18 23 23 28 16 13 18 20 20 25 n content, ppm 10 14 9 12 10 11 9 9 13 11 12 8 (1) the yield applies to the weight of the raw material (2) groups in average molecule considerable differences could be noticed in liquid yields obtained only in thermal cracking and separation with distillations. the yield of wsl and dl fractions was 5.9-22.4% obtained in the cracking process (table 3) depending on the temperature, in consequence of the decreasing thermal stability of the c-c bonds. using further separations (atmospheric and vacuum distillation) the summarized yields of fuel like fractions wsl and dl were 21.7-49.68%. it means that further valuable liquids could be separated by distillation from residues obtained in thermal cracking. on the other hand some differences were observed between the characteristics of the two fractions (white spirit like wsl and diesel like dl), because wsl consists mainly of lighter hydrocarbons c5c10 and the dl c 10+. the olefin concentration of liquids and the distribution of double bonds were determined by infrared spectra. the vinyl double bonds gave two intensive ir adsorption bands at 910 and 990cm-1 while vinylidene and internal double bonds have peaks at 890 and 956 cm-1, resp. the analysis of liquid products obtained by thermal degradation gave an intensive adsorption band at 720cm-1, which is proportional to the length of the carbon chain when the carbon number is higher than 6. adsorption bands at 910 and 990cm-1 were more intensive in case of hdpe, and less notable in ldpe. however, the adsorption band at 890cm-1 was more intensive in case of ldpe than hdpe. this peak was observed from the deformation vibration of the vinylidene group in rr’c=ch2 compounds. this phenomenon could be attributed to the various carbon chain structures of the raw materials. ldpe contained more branches therefore the formation of vinylidene type terminal olefins was stronger. fig. 6/a ir spectra of wsl fraction from ldpe (500°c) fig. 6/b ir spectra of wsl fraction from hdpe (500°c) 52 the number of –ch2– and –ch3 groups was also determined by ir technique in the range of 2800-3100cm-1. the number of the –ch2– groups is proportional to the intensity of asymmetric stretching vibration band at 2927 cm-1 and the number of the –ch3 groups to that of asymmetric stretching vibration band at 2958 cm-1. it was found that ldpe waste degradation products have a little higher –ch3 content, because of their chemical structure. from the other hand, the pour and flash point of dl from ldpe was lower than dl from hdpe, because of ramification. fig. 7/a ir spectrum of wsl fraction wavelength range of 2800-3200 cm-1 from ldpe (500°c) fig. 7/b ir spectrum of wsl fraction wavelength range of 2800-3200 cm-1 from hdpe (500°c) the heteroatom content is an other important parameter for further application of liquids. therefore the concentration of sulphur and nitrogen was measured according to astm d 6429 99 and astm d 6366 99 standards. it was observed that the nitrogen content was lower than 15 ppm and the sulphur content was lower than 30 ppm. these properties are favourable for further fuel-like application of wsl and dl fractions. liquids obtained from thermal degradation of waste polyethylenes were analyzed by gaschromatography. a 30m x 0.32mm column was used, coated with dimethyl-polysiloxane, which separated the hydrocarbons according to polarity under the applied circumstances. they have not distinguished those segments of the molecules parts, where the stability against the thermal degradation might be lower than in other parts of the carbon chain, therefore n-alkanes and n-alkenes were formed from c5 to c10 in case of wsl fractions and from c8 to c26 in case of dl fractions. the composition of liquid fractions wsl and dl was demonstrated in table 4/a and b. in these tables the summarized n-paraffin and n-olefin content and the calculated average molecular weight of each fraction were indicated. the average molecular weight of fractions was calculated from the composition. 53 table 4/a. the composition of liquids obtained in the cracking of hdpe and ldpe waste (wsl) (%) polymer hdpe ldpe temperature. °c 500 525 550 500 525 550 n-pentene 2.26 3.15 4.45 2.15 2.86 3.18 n-pentane 1.24 2.36 3.36 2.31 2.51 3.08 n-hexene 13.29 15.58 17.40 12.41 13.73 16.00 n-hexane 11.11 13.39 15.14 10.13 12.14 13.78 n-heptene 20.23 20.19 18.92 16.43 19.57 20.24 n-heptane 14.78 16.78 15.94 15.13 17.41 17.73 n-octene 13.61 12.43 9.99 15.03 113.88 12.49 n-octane 13.22 11.21 10.18 12.51 10.88 9.40 n-nonene 4.48 2.21 1.96 6.29 4.30 1.67 n-nonane 4.10 1.80 1.93 4.19 1.85 1.99 n-decene 1.26 0.81 0.54 1.84 0.77 0.16 n-decane 0.40 0.10 0.19 1.58 0.10 0.30 n-paraffin 44.87 45.63 46.74 43.84 44.89 46.27 n-olefin 55.13 54.37 53.26 56.16 55.11 53.73 m, g/mol 101.4 98.1 96.4 102.6 99.3 97.3 table 4/b. the composition of liquids obtained in the cracking of hdpe and ldpe waste (dl) (%) polymer hdpe ldpe temperature, °c 500 525 550 500 525 550 n-octene 0.00 0.74 1.08 0.00 0.72 0.88 n-octane 0.00 0.28 0.72 0.00 0.32 0.41 n-nonene 2.05 2.00 2.75 1.11 1.59 1.85 n-nonane 1.22 2.36 2.38 1.41 2.11 2.86 n-decene 3.69 3.47 3.52 2.88 3.56 3.07 n-decane 2.31 2.82 3.33 1.20 1.99 2.65 n-undecene 3.22 3.91 4.71 3.99 2.91 4.77 n-undecane 2.64 3.72 3.77 2.96 3.50 3.81 n-dodecene 3.24 4.03 4.77 3.69 4.07 4.31 n-dodecane 3.75 4.67 5.25 3.10 4.76 4.91 n-tridecene 4.57 4.54 5.04 4.42 4.45 5.11 n-tridecane 3.08 5.07 5.59 4.32 5.04 5.81 n-tetradecene 5.10 5.20 5.22 4.93 5.33 5.13 n-tetradecane 4.96 5.89 6.01 5.15 5.60 6.08 n-pentadecene 4.97 5.38 5.31 5.17 5.52 5.38 n-pentadecane 5.73 6.50 6.40 5.95 5.85 6.52 n-hexadecene 5.53 5.92 4.93 5.29 5.72 5.75 n-hexadecane 5.77 5.76 5.71 5.82 5.91 5.78 n-heptadecene 4.11 3.83 3.69 4.27 4.14 3.86 n-heptadecane 5.60 4.87 4.65 5.67 5.44 4.51 n-octadecene 3.75 3.05 2.71 4.01 3.77 3.10 n-octadecane 5.33 3.60 3.22 5.05 4.42 3.37 n-nonadecene 2.81 1.61 1.11 3.71 2.00 1.37 n-nonadecane 3.85 2.89 2.13 4.00 2.69 2.20 n-eicosene 2.03 1.39 0.36 1.97 1.43 0.36 n-eicosane 3.63 1.76 1.71 2.04 1.84 1.05 n-uneicosene 1.46 1.05 0.65 1.15 0.89 0.66 n-uneicosane 1.52 1.08 0.90 1.74 1.11 1.18 n-dodeicosene 1.04 0.53 0.36 0.87 0.54 0.49 n-dodeicosane 1.42 0.98 0.89 1.42 1.00 0.91 n-trieicosene 0.52 0.33 0.36 0.54 0.60 0.84 n-trieicosane 0.81 0.65 0.50 0.87 0.84 0.61 n-tetraeicosene 0.12 0.05 0.09 0.14 0.05 0.13 n-tetraeicosane 0.19 0.09 0.09 0.61 0.10 0.24 n-pentaeicosene 0.00 0.00 0.00 0.00 0.10 0.00 n-pentaeicosane 0.00 0.00 0.09 0.00 0.10 0.05 n-paraffin 51.79 52.97 53.33 51.88 52.60 52.94 n-olefin 48.21 47.03 46.67 48.12 47.40 47.06 m, g/mol 212.7 202.9 198.2 215.2 206.8 201.3 54 high olefin content was observed in liquids because of β-scission reactions. it was found that the content of olefins in case of f1 fraction obtained from both hdpe and ldpe was higher than the concentration of paraffins. the concentration of olefins decreased with increasing temperatures. it is consistent with earlier experimental results. j. puente et al. published earlier that the yield of olefins decreased both with increasing cracking temperature and its reaction time in case of batch cracking [20]. this phenomenon could be attributed to the greater possibility of the intermolecular hydrogen transfer reactions and termination reactions with recombination at higher temperature. figs 8/a-b and figs 9/a-b show total carbon atom distribution (n-paraffins and n-olefins) in fuel-like hydrocarbon fractions. it is well observable in these figs that the concentration of lighter hydrocarbons increased with increasing cracking temperature in case of both white spirit like wsl and diesel like dl fractions. it is supposed to be the consequence of decreasing thermal stability of the c-c bonds. with increasing temperatures more and more c-c bonds are cracked resulting in lighter hydrocarbons. this phenomenon could be well followed with the average molecular weights. 0,0 10,0 20,0 30,0 40,0 5 6 7 8 9 10 11 12 13 carbon number c om po si tio n, % 500°c 525°c 550°c fig. 8/a the carbon number distribution in liquids obtained by the cracking of hdpe waste (wsl) 0,0 3,0 6,0 9,0 12,0 15,0 6 9 12 15 18 21 24 27 carbon number c om po si tio n, % 500°c 525°c 550°c fig. 9/a the carbon number distribution in liquids obtained by the cracking of hdpe waste (dl) 0,0 10,0 20,0 30,0 40,0 5 6 7 8 9 10 11 12 13 carbon number c om po si tio n, % 500°c 525°c 550°c fig. 8/b the carbon number distribution in liquids obtained by the cracking of ldpe waste (wsl) 0,0 3,0 6,0 9,0 12,0 15,0 6 9 12 15 18 21 24 27 carbon number c om po si tio n, % 500°c 525°c 550°c fig. 9/b the carbon number distribution in liquids obtained by the cracking of ldpe waste (dl) conclusions the degradation of different waste polyethylenes (hdpe and ldpe) in a horizontal tube reactor at 500-500 °c was studied. it was found that the cracking temperature had a significant effect both on the yields and structure of the products, because higher yields of volatile products were observed at higher temperature. the yields of valuable volatile fractions could be increased by vacuum distillation of the residue. gas products of cracking consisted mainly of c2 and c4 hydrocarbons because of the chemical structure of the wastes. in liquid fractions basically aliphatic compounds (n-olefins and nparaffins) were observed. the cracking temperature and composition of waste polymers (ldpe and hdpe) had a significant effect on the qualitative and quantitative properties of the products. the ldpe waste degradation products have a little higher branched hydrocarbon content, lower pour and flash point because of their chemical structure. it is important for the further application of the products. other favourable properties for further fuel-like application were also found, such as nitrogen and sulphur content under 30ppm or high diesel index, etc. 55 acknowledgement the authors would like to thank chemical engineering institute’s cooperative research center (especially ministry of education of hungary and the hungarian oil and gas (mol) plc) for the financial support received for this work. references 1. sartorius i.: development plastics manufacturing industry in europe, icsunido conference, trieste, italy, september 5-6 (2002) 2. tno report (stb-99-55): chemical recycling of plastic waste (pvc and other resins), (1999) 3. wong a. c.-y. and lam f.: polymer testing, 2002, 21, 691-696 4. yanga j., mirand r. and roy c.: polym. degr. and stab., 2001, 73, 455-461 5. breen c., last p. m., taylor s. and komadel p.: thermochimica acta, 2000, 363, 93-104 6. hwang e. y., kim j. r., choi j. k., woo h. c. and park d. w.: j. anal. appl. pyrolysis, 2002, 62, 351-364 7. kim j. r., yoon j. h. and park d. w.: polymer degradation and stability, 2002, 76, 61-67 8. ucar s., karagoza s., karayildirim t. and yanik j.: polym. degr. and stab., 2002, 75, 161-171 9. bertini f., audisio g., kiji j. and fujita m.: j. anal. appl. pyrolysis, 2003, 68/69, 61-81 10. ballice l. and reimert r.: chem. eng. and processing, 2002, 41, 289-296 11. gensler r., plummer c. j. g., kausch h.-h., kramer e., pauquet j.-r. and zweifel h.: polym. degr.n and stab., 2000, 67, 195-208 12. fourcadea e., hoefsloota h. c. j., vlietb g. van, bungeb w., mutsersb s. m. p. and iedema p. d.: chem. eng. science, 2001, 56, 6589-6603 13. sawaguchi t., saito h., yano s. and seno m.: polym. degrad. and stab., 2001, 72, 383391 14. luo g., suto t., yasu s. and kato k.: polyme. degrad. and stab., 2000, 70, 97-102 15. predel m. and kaminsky w.: polym. degrad. and stab., 2000, 70, 373-385 16. paul t., williams p. t. and williams e. a.: j. anal. appl. pyrolysis, 1999,51, 107-126 17. karagöz s., karayildirim t., uçar s. yuksel m. and yanik j.: fuel, 2003, 82, 415423 18. suto l. g., yasu t. and kato k.: polym. degrad. and stab., 70, 2000, 97-102 19. mccaffrey w. c., kamal m. r. and cooper d. g.: polym. degrad. and stab., 47, 1996, 64-73 20. puente g., klocker c. and sedran u.: applied catalysis b: environmental, 2002, 36, 279-285 microsoft word b_19_r.doc hungarian journal of industrial chemistry veszprém vol. 38(2). pp. 149-153 (2010) models and methods to detect similarity of manufacturing machines o. hornyák1 , g. sáfrány2 1department of information engineering at university of miskolc, hungary e-mail: hornyak@ ait.iit.uni-miskolc.hu 2evopro ltd., hungary this paper focuses on detecting similarity of manufacturing machines. it discusses the application of the group technology (gt) concept in the case of producing controller software for manufacturing machines. an overview on the modular machines is given. the paper presents a new concept for the development of the controllers’ software. the advantages of gt are presented. two grouping approaches are detailed: the bottom-up approach and the top-down approach. a genetic algorithm clustering is presented for the automatic grouping. the second part of the paper deals with the similairity of plc code. smith and waterman local allignment search algorithm is used to detect similar code paths in plc programs keywords: group technology, genetic algorithm clustering, code similarity, smith waterman algorithm introduction the design, assembly, starting up, monitoring and maintenance of industrial manufacturing devices have become very complex tasks over the time. according to the predictions for the future the complexity will not decrease. simultaneously, the demands for and expectations of the quality of the products and processes have been growing. it is a well known fact that the cost price is an important factor in today’s competitive manufacturing. another important factor is the lead-in time spent on the aforementioned activities. engineers need to revise the activities required for producing a manufacturing design to be able to meet today’s needs and to take a step towards future manufacturing devices. the manufacturing machine producers need to develop the code used by their controllers. in case of process control the programmable logic controller (plc) based solutions are very widespread as the controlling algorithms are stored in a program. at the moment the engineering tools used for creating such controller codes do not utilize the opportunities of group technology (gt), i.e. the reorganization and grouping of the similar hardware and software modules, and creating developer databases. so the engineering tools offer only a static help in the software development process. industrial experience shows the fact, that highly qualified engineers are required for working confidently with such tools. modern software engineering tools have the capability to generate code automatically, see for example the recent releases of developer studio of microsoft or eclipse. some graphical user interface (gui) design tools or some database design tools can also generate code snippets or scripts. software engineering companies tend to have coding standards to enforce similar coding style among their staff. descriptions of algorithms are widespread through the internet; the implementations of these can be very similar. the code copied from external sources can be either authorised or plagiarised. overview on modular machines the design of manufacturing machines – both in the hardware and software aspects – is undergoing a sensible change. the solutions which offer customizations required by the merchant at the designing phase receive the attention of engineers. ● the use of modular building techniques – including mechanical parts, standardized communication, standard software modules, and generation of software modules – have been increased. ● it is expedient to use automated tools to develop such a customer-specific controller code which very often includes motion control modules as well. automated controller creation tools have the advantage of: ● increasing the precision of repeated tasks, ● reducing the dependency on engineers experience, ● improving the quality of the process and product documentation, ● reducing the preparation time of tendering, ● improving the flexibility of the preparation of the engineering work. 150 automated generation of project variants besides the modular design of the manufacturing machines there is an increased need for implementing methods and tools by which the automated generation of the controller algorithms and project databases can be executed, especially without expert knowledge of the system. it is not necessary for the involved engineers to have an overall knowledge about the controller details. however, a generic change request or a call for a tender may require prompt action to develop the required machines, including the controller’s software. those machines are made to order or engineered to order, which means a high level of custom needs. to give a high service level for such customers there should be methods and tools for non expert engineers, marketing and sales staff which enable them: ● to combine the requested product (i.e. the generation of the product descriptor database, the automated generation of the controller code, the feasibility checks and availability of the required stock); ● to generate some software modules based on the existing project code library; ● to use an easy to understand, non technical workflow description language; ● to support the developer engineers in executing their repeated tasks; ● to support open source development. group technology group technology is a management theory based on the principle that similar things should be done similarly. products requiring similar operations, having similar attributes or needing a common set of resources are grouped into product families [3]. a key factor is the coding, which is an activity to create an – usually – alphanumeric key that describes the product and its attributes. the code must be exact and unambiguous. the literature identifies three kinds of codes: ● monocode (hierarchical code), where each character is restricted by the previous character, ● polycode (attribute), where each character has its own piece of information, ● hybrid (mixed code). feasibility of group technology for manufacturing machine controllers the development process of creating a new manufacturing machine is a complex task. it is expedient to use the experience from former machine development projects. it is not an acceptable approach which does require the rewriting of an existing functional block of the controller software. engineers need to split complex projects into small modules which can operate alone. complex systems need to be built from these bricks according to predefined rules. fig. 1 depicts a development office, where engineers develop modules, hardware descriptor tables, and units made from modules. fig. 2 refers to the process in which new manufacture machine controller software can be automatically generated. component database units hardware list softwaremoduls development figure 1: development process of a new project orders component database integrator machine-project database units hardware description table softwaremodules first commissioning connect plan project description table a f e c d b figure 2: simplified workflow of a project realization following the order a: the customer specific production machine description is presented. b: the technician doing the integration checks the components repository c for the required components in an automated way. then a software tool generates the project database and the connected plan e for the machine controller. these passed to the installer staff f. after the integration there can be some feedback d. note, that the suggested development process implements the modules only once. these form a module repository so that the aforementioned advantages can be achieved. when a new module is required to be developed the first step is to analyze the functionality. experiments show that projects including similar modules have the same level of similarity. if the similar functions are implemented separately then it leads to redundant work and more opportunity of errors. 151 engineers would need a tool which finds similar existing modules which implement the required functionality. the use of group technology can accomplish this to replace the human expertise. as manufacturing machines have been created for many years now, group technology can be suitable for analyzing existing projects. very likely a project analysis including module similarity check will exhibit a high level of redundancy. in the following chapter the computer tools and mathematical models supporting these analyses will be detailed. automated clustering methods automated clustering methods should be computer algorithms with the capability of clustering the controller code of the machines. there can be two different approaches. the top-down approach uses the project description table and extracts the module information. then it codes the functional components and tries to find similarity in the module/unit repository. this approach can be used during the tendering phase of a project, when the actual machine and its controller do not exist. the other approach is the bottom-up approach, where the controller code should be investigated. plc coding can be made in various ways; some uses icons like relay ladder diagram (rld). some codes have textual format like the structured text (st) form. this is suitable for gt clustering. groups existing projects groups code code requirements figure 3: top-down and bottom-up approaches plc code the most widespread plc programming languages are as follows: cp – contact plan: a plc programming language with the support of net-and relay switch plans. fbd – function block diagram: fbd is another graphical programming language. the main concept is the data flow that starts from inputs and passes in block(s) and generate the output. ld – ladder diagram: ladder diagrams are specialized schematics commonly used to document industrial control logic systems. they are called “ladder” diagrams because they resemble a ladder, with two vertical rails (supply power) and as many "rungs" (horizontal lines) as there are control circuits to represent. il – instruction list: instruction list programming is defined as part of the iec 61131 standard. it uses very simple instructions similar to the original mnemonic programming languages developed for plcs. st – structured text: structural text is a high level plc programming language such as pascal. sfc – sequential function charts: sequential function charts have long been established as a means of designing and implementing sequential control systems utilising programmable controllers. the programming standard iec 61131-3 includes a graphical implementation of sfc’s in its suite of programming languages. mathematical formulization of the top-down problem let’s assume a binary polycode coding system. each bit of the k bit long code represents a feature. 0 means that the controller does not implement the feature, 1 means that the feature is realized. let’s investigate n projects. the problem can be represented by an n x k matrix m, see for example (1). ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ 1100000000 0011100000 0000010111 0001100000 1000011011 0110000000 0001100000 0000111110 0000101111 0010100000 10 9 8 7 6 5 4 3 2 1 (1) let pi represent the ith row. we can define a distance function by which we can evaluate how similar is one project to the other. for the sake of simplicity we assigned the decimal representation of the pi vector. let dec(pi) denote this assignment. note, that this calculation is easy to execute, however it may give wrong result. for example p1 = 0111111111 is closer to p2 = 1000000000 than to p3 = 0111111001. so clustering the distance function dec(pi) will not give us a correct result, however, if we order the pi vectors according to their decimal representation then this can be a starting point for further clustering. this method, however, will find it easily if two vectors are exactly the same: pi= pj if dec(pi)= dec(pj). 152 genetic algorithm clustering the rows in matrix m need to be rearranged so that there will be block of 1s near in the p distance of the diagonal item. [4] details two measures of the goodness of the grouping, called grouping efficiency and grouping efficacy. grouping efficiency is calculated as η = q·η1 + (1 – q)·η2 (2) where η1 is the proportion of 1s in the diagonal block, η2 is the proportion of 0s in the off-diagonal block, q is a weight coefficient. grouping efficacy is calculated as in out nn nn 01 11 + − =μ (3) where n1 is the total count of 1s in the matrix, n1 out is the count of 1s outside the diagonal blocks, n0 in is the count of 0s inside the diagonal blocks. a genetic algorithm clustering (gac) was implemented in the form of matlab code. both the grouping efficiency and grouping efficacy were implemented as a fitness function. the n number of rows and k number of columns had been split to y and x number of block w1, w2, …, wy and u1, u2, …,ux so that kuandnw x j y i == ∑∑ 11 (4) if the gac creates an instance which does not meet (4) then the fitness function will be 0. otherwise the fitness function is calculated as described above. the pseudo code of the gac is as follows create the initial set of the population. evaluate each of them while not to stop do select two random elements crossover random genes of those two mutate the new specimen randomly evaluate the new specimen the new population will be the top elite of the previous population plus the best ones of the new specimens end while after the block diagonalization process the (1) matrix should look as in (5). ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ 1100000000 0110000000 0001100000 0011100000 0010100000 0001100000 0000101111 0000111110 1000011011 0000010111 10 5 7 9 1 4 2 3 6 8 (5) you can see three groups identified by the algorithm here: group 1 consists of (8, 6, 3, 4), group 2 consists of (1, 9, 7), group 3 consists of (5, 10). computer algorithms for detection of similarity let’s consider the bottom up approach, i.e. check the plc code for similiarity. the structured text format discussed above is can undergo such an investigation because that is textual format of the code. in the past, many computer algorithms were introduced for detecting software similarity, mainly for detecting plagiarism. [2] defines seven layers of code modification in a plagiarism spectrum. some recommended using software metrics to detect similarity. [4] was among the pioneers: its metric used the following quantities: n1 = number of unique or distinct operators. n2 = number of unique or distinct operands. n1 = total usage of all the operators. n2 = total usage of all the operands. using these metrics we can calculate: v = (n1 + n2)log2(n1 + n2) (6) e = (n1n2(n1 + n2)log2(n1 + n2))/2n2) (7) where v refers to the volume of the program and e refers to the efforts to create the program. you may find the logarithmic function odd at first sight. in this metric they found a correlation between the number of bugs in the program, programming or debugging time of the program and the complexity of the program. 153 local alignment detection using smith-waterman algorithm smith and waterman developed their algorithm to detect common molecular subsequences. they compared two molecular sequences: a=a1 a2 ... an and b=b1 b2 ... bm. the algorithm works as follows: set up a hn+1 m+1 matrix whose first row and column have the 0 index and are zeroed. hk0 = h0l = 0 for 0 ≤ k ≤ n and 0 ≤ l ≤ m then hij is the maximum similarity of two segments ending in ai and bj respectively. it is calculated as { } { } ⎪⎪⎭ ⎪⎪ ⎬ ⎫ ⎪ ⎪ ⎩ ⎪⎪ ⎨ ⎧ − − + = −≥ −≥ −− ljil kjkik jiji ij wh wh bash h 1,1 1 1,1 max ,max ),,( max (8), where s(ai,bj) is a score function for similarity, wk is a weight (cost) function for a k-long deletion and wl is a cost function for inserting l length of new sequence. the highest score in the matrix indicates the maximum local alignment of the two sequences. once the matrix elements are calculated the maximum element has to be found. that refers to the end of the maximum alignment. the traceback algorithm will find the way back. find the next highest score. – a diagonal jump implies there is an alignment (either a match or a mismatch). – a top-down jump implies there is a deletion. – a left-right jump implies there is an insertion. figure 4: trace back from the maximum element references 1. o. hornyak, g. safrany: group technology for automated generation of machine controller code. 5th international symposium on applied computational intelligence and infromatics. (2009), timisoara, romania, 17–21. 2. j. a. w. fahidi, s. k. robinson: an empirical approach for detecting program similarity and plagiarism within a university programming environment, compter education, 11, 1987, 11–19. 3. a. parker, j. o. hamblen: computer algorithms form plagiarism detection, ieee transactions on education, 32 (2), 1989, 94–99. 4. m. h. halstead: elements of software science, north holland, new york, 1977. 5. t. f. smith, m. s. waterman: identification of common molecular subsequences, journal of molecular biology, 147, 1981, 195–197. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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/pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word a_19_morauszki_r.doc hungarian journal of industrial chemistry veszprém vol. 39(1) pp. 27-30 (2011) simulation of fluid flow, combustion and heat transfer processes in internal combustion engines t. morauszki1 , p. mándli1, z. horváth1, m. r. dreyer2 1széchenyi istván university, department of mathematics and computer sciences 2széchenyi istván university, audi hungaria department of internal combustion engines 9026, győr, egyetem tér 1, hungary e-mail: mtamas@sze.hu the better understanding and optimization of fluid flow, injection, mixing and combustion processes in internal combustion engines are of critical importance in regard to compliance of the emission standards. presented here is a complex simulation method, which provides transient fluid flow results in a cylinder of a gasoline engine. the model includes moving boundaries. through the intake port and open intake valve, air is flown into the combustion chamber. fuel is injected. in the compression stroke, after closing the intake valve, the mixing process is shown. at the top dead center (tdc) ignition is set, which results in combustion of the fuel-air mixture in the power stroke. in the exhaust stroke the burnt gases leave the combustion chamber through the open exhaust valve and the exhaust port. with the results of this simulation, it is possible to determine the temperature and heat transfer coefficients on the walls of the combustion chamber, and to define the thermal load. this load can later be used in a structural analysis of the parts of the combustion chamber, where heat transfer and expansion is calculated. keywords: internal combustion engines, air flow simulation, direct-injection, spark ignition, combustion introduction although internal combustion engine development has in certain aspects already approached its limits, just by looking ahead to the upcoming tightening of the emission norms, it is clear that further optimization is inevitable. by now numerical simulations such as structural, thermal or fluid flow calculations have become fast, reliable and inexpensive tools in all fields of the vehicle development process. to further broaden the frontiers, recently complex simulation methods have been developed, which simultaneously use more software and provide results of more interacting physical phenomena. these are sometimes called multiphysics applications, fluid-structure interaction (fsi) being a good example. the main goal of this work is to develop and present a complex simulation method for evaluating important physical properties in the combustion chamber of a gasoline direct injection engine, such as air flow in the combustion chamber, direct injection of gasoline, mixture formation, spark ignition and combustion processes, heat generation and heat transfer from hot air to the surrounding solid walls. these tasks were solved by one of the computational fluid dynamics (cfd) software, ansys fluent. it should be noted that the presented methodology is capable to include combustion of different fuel materials under realistic operating conditions. in-cylinder air flow with moving boundaries as a slight simplification, a one-cylinder part is taken from a 2-liter inline four-cylinder naturally-aspirated gasoline direct injection spark ignition engine. the extent of the model is therefore limited to an intake and an exhaust port – with two intake and two exhaust valves – and a combustion chamber. the latter is bounded by the piston top surface and walls of the cylinder and cylinder head. fig. 1 shows the computational domain at a midstroke stage. the intake port is on the left side, while the exhaust port is to the right of each picture. figure 1: shaded and partly transparent view of the computational domain 28 construction of the fluid flow model transient, highly compressible and turbulent air flow has to be considered inside the cylinder. this makes the numerical simulation rather demanding in regards to computing power and time. further complications arise because of the moving boundaries: some parts of the discretised model have to be remeshed in each and every time step. to keep the calculation speed within reasonable limits, the varying number of elements is kept in the 200–400.000 range during the whole calculation. with these restrictions it is possible to run a complex simulation (including combustion) in one day time, using 16 processor cores. further refinement of the mesh might help to achieve better results, which in turn might slow the computation speed to unacceptable levels. the chosen refinement level of the mesh does not allow boundary layers to be meshed properly therefore losing information on turbulence is inevitable. this effect was reduced by using the two-equation realizable k-ε turbulence model with enhanced wall functions [1]. during the calculation one four-stroke cycle is computed, this corresponds to a rotation of 720° crankshaft angle. on fig. 2 the events of the cycle are shown. the starting angle is 360°: piston is at the tdc, intake stroke starts and the intake valve opens, following the valve lift curve (as seen on fig. 2, part a). air is passing through the inlet of the intake port, where freeflow pressure inlet boundary condition is defined, which corresponds to the intake process of a naturally-aspirated engine. figure 2: timeline of events during the simulation; a: intake valve is open, b: gasoline injection, c: exhaust valve is open at 550° the intake valve closes and during the compression and power stroke no air enters or leaves the combustion chamber, the air flow is guided by the piston motion and the effects of injection and combustion process. in the exhaust stroke, starting at 900°, the exhaust gas leaves through the open exhaust valves. in the computation free-flow pressure outlet was applied at the end of the exhaust port. the lift curve of the exhaust valve can be seen on fig. 2, part c. the events end at 1080°. dynamic mesh the aforementioned events predispose the structure of the model: a dynamic mesh has to be generated, which consists of tetrahedral and hexahedral elements and continuously changes during the steps of the computation. the dynamic mesh system has three types of meshes. stationary parts are not involved in any movement (e.g. most of the intake and exhaust ports meshed with tetra elements). rigid parts are moving, but not deforming (e.g. a layer of elements above the piston top surface). deforming parts can change shape (e.g. regions around the valves). here either tetra elements are created by remeshing or hexa elements are created by layering. on fig. 3 the process of mesh deformation can be seen. on the left picture the exhaust valve is closed, while on the right it is open: its walls are moved, the tetra mesh under it is remeshed and the hexa layers above it are multiplied as needed. figure 3: two states of the dynamic mesh at the region of the valves piston movement is governed by basic engine data: crankshaft speed is 2000 rpm, piston stroke is 90 mm and connecting rod length is 150 mm. intake and exhaust valve timing and lift is subject to change depending engine settings (e.g. speed, load) and has to be defined for each case with movement profiles. results of the fluid flow simulation examination of the fluid flow results at several stages of the cycle shows that the events happened as planned and are in balance with the normal behavior of a four-stroke engine. fig. 4 shows path lines of the airflow from all four strokes. on fig. 4/a the air intake process is visible: the vacuum-effect of the downward moving piston sucks air through the intake valve. the shape of the piston top surface aids the development of a swirling flow. in the compression stroke all valves are already closed and the piston moves upward. as the volume of the airspace becomes smaller, the results show the inevitable rise in the density of the material. at this stage work is done on the system through the crankshaft. as a consequence the internal energy, i.e. the mean temperature of the air goes up to 400 °c by the end of compression. 29 as fig. 4/b and 4/c show, the air flow pattern continues to evolve, maintaining a high-swirl profile both in the compression and power stroke. fig. 4/d is a good example of the exhaust process: gas leaves the combustion chamber through the open valves. figure 4: path lines of fluid flow in a, intake; b, compression; c, power and d, exhaust stroke as a short summary of the fluid flow process it can be said, that the results are as expected. further evaluation and model possible refinement is necessary. other engine setups are also to be computed and compared. combustion process construction of the combustion simulation as the combustion model is introduced to the air flow simulation, the timeline of events can be further divided. on fig. 2, part c is bounded by the start and end time of gasoline injection (in this engine setup it is between 600° and 700° in the compression stroke). injection is provided through the discrete phase model, where in the compression stroke 40 mg of gasoline droplets, discrete particles are injected with a relatively high velocity of 120 m/s [2]. although the actual injector geometry is not modeled, the injection is parameterized as a solid cone with four particle streams and 25° cone angle. the injected material is octane, which is a major part of gasoline and its combustion properties are closely linked to gasoline itself. the mixture formation in direct-injection engines happens in a relatively short duration of the compression stroke. shortly after injection – at 708°, i.e. 12° before tdc – the spark ignition is modeled. spark is defined as a sphere at the position of spark plug (which itself is not included in the model). it has sufficient energy (0.1 j) to initiate combustion 12° before tdc. combustion is modeled with the partially premixed combustion model, which is a simple combination of the non-premixed [3] and the premixed [4] combustion models. as the software provides good initial settings to these combustion models, it is possible to calculate the flame front position, heat generation, unburnt and burnt mixture fraction properties without detailed knowledge of the combustion model. in order to further optimize the method, a deeper understanding of these models is desired. it should also be noted, that with user defined functions it is possible to include custom written extensions in the combustion calculations. results of the combustion simulation the high-speed discrete octane-particles entering the combustion chamber have to be mixed with the highswirl air flow. despite the short duration (only 108° crankshaft angle) until the spark at 708°, the result shows a relatively even distribution of the injected particles. this makes it possible, that after the spark initiation a smooth combustion process can happen. as the results of fig. 5 show, the flame front is constantly evolving after the spark ignition. figure 5: evolution of the flame front: 8° after spark initiation (a,) and further 10-20-30° later (b, c, d,) figure 6: mean pressure in the combustion chamber during the compression (540–720°) and power (720–900°) stroke as seen in fig. 6, the mean cylinder pressure has its peak at tdc, right after spark ignition at 25 bar. for a naturally-aspirated engine running at 2000 rpm, midload these results are in the expected range [5]. so is the 30 cylinder mean temperature, which rapidly rises to 1100° c. conclusions and outlook a simulation method was developed to model in-cylinder fluid flow processes bounded by moving walls. injection, mixture formulation, spark ignition and combustion was also included. delivered results show good correlation with literature values. further evaluation of the method is necessary: mesh refinement possibilities should be considered, important parameters need fine-tuning and the extent of human interventions during the calculation should be reduced. comparison to measurements and parametric studies should be carried out. method extension possibilities include implementation of custom defined combustion methods. a model for turbocharged engines is of great interest, too. in this case, overpressure has to be defined at the intake inlet. in every simulation case, the results can further be used: wall temperatures and heat transfer coefficients can be exported to a finite element (fe) solver. mapping cfd-results to similar but not identical fe-meshes can also be done. with fe-calculations heat transfer and thermal expansion of the surrounding parts (e.g. piston, engine block) can be calculated. expansion has a significant role in piston and piston ring dynamics. it can and will influence the mechanical friction losses of the pistonrings-liner system, therefore taking expansion into consideration while doing friction simulations is of great importance. acknowledgements tamop-4.2.1/b-09/1/konv-2010-0003: mobility and environment: research in the fields of motor vehicle industry, energetics and environment in the centraland western-transdanubian regions of hungary. the project is supported by the european union and co-financed by the european social fund. references 1. h. c. chen, v. c. patel: near-wall turbulence models for complex flows including separation, aiaa journal, 26(6), (1988), 641–648 2. f. zhaoa, m.-c. laia, d. l. harrington: automotive spark-ignited direct-injection gasoline engines, progress in enegry and combustion science, 25, (1999), 437–562 3. y. r. sivathanu, g. m. faeth: generalized state relationships for scalar properties in non-premixed hydrocarbon/air flames, combustion and flame, 82, (1990), 211–230 4. v. zimont, w. polifke, m. bettelini, w. weisenstein: an efficient computational model for premixed turbulent combustion at high reynolds numbers based on a turbulent flame speed closure, j. of gas turbines power, 120, (1998), 526–532 5. j. b. heywood: internal combustion engine fundamentals, mcgraw-hill, 1988, 371–383 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 /colorconversionstrategy /cmyk /dothumbnails false /embedallfonts true /embedopentype false /parseiccprofilesincomments true 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 37(2) pp. 107-111 (2009) fuel purpose hydrotreating of vegetable oil on nimo/γ-al2o3 catalyst m. krár1, s. kovács1, l. boda2, l. leveles2, a. thernesz2, i. wáhlné, horváth, j. hancsók1 1university of pannonia, institute of chemical and process engineering, department of hydrocarbon and coal processing h-8201 veszprém, p.o.box.: 158, hungary e-mail: hancsokj@almos.uni-pannon.hu 2mol plc. ds development, százhalombatta 2443, p.o.box 1, hungary the application of biofuels has become more important in the whole world since the last decades. intensive research has been started for the production of biofuels which can be applied in diesel engines and has different chemical composition from the previously used ones. among these fuels the most important one is biogasoil (normal and iso-paraffins) produced from triglycerides with catalytic hydrotreating (special hydrocracking). the aim of present study was to investigate the applicability of commercial nimo/γ-al2o3 catalyst for conversion of specially pretreated hungarian sunflower oil to produce motor fuel components. the change in the hydrotreating activity of applied catalyst, the pathways of hydrodeoxigenation reactions and the effect of process parameters (t= 300–360 °c, p= 20–60 bar, lhsv= = 0.5–2.0 h-1, h2/sunflower oil volume ratio: 400 nm3/m3) on the yield and composition of the products were also investigated. it was concluded that on the investigated nimo/γ-al2o3 catalyst products with relatively high (>50%) paraffin content (t = 360–380 °c, p = 60 bar, lhsv = 0.5–1.0 h-1) could be produced. the yield of the produced target fraction was 50.7–54.5% at these advantageous process parameters. so it is necessary to separate and recirculate the heavy fraction. in case of every investigated process parameter c18-, c17-, c16and c15 normal paraffins were formed, i.e. both the hdo and the decarboxylation/ decarbonylation reactions took place. the cetane number of the target fractions, are very high (>80, en standard: ≥51), but the cold flow properties of this fraction are disadvantageous. to improve this disadvantageous property it is necessary to carry out selective isomerization of the target fraction. keywords: sunflower oil hydrotreating, biogasoil, paraffinic hydrocarbons introduction the application of biofuels has become more important in the whole world since the last decades. in europe the production and application of diesel fuels and/or blending components derived from biomass have been emerged into the focus due to the climate, geographical conditions and the increasing demand for diesel fuel [1]. actually the biodiesel (fatty acid methyl esters) is practically the only bio derived component used in crude oil derived diesel fuels, however it and the biodiesel technologies, which applied alkali catalyst, have numerous disadvantages [2-6]. because of these facts and to reach better quality, intensive research has been started for the production of biofuels, which can be applied in diesel engines and has different chemical composition from the previously used ones [6-13]. among these fuels the most important ones are in the near and medium future the biogasoils produced from triglycerides with catalytic hydrotreating (special hydrocracking). the biogasoil is a second generation biofuel, therefore their research, production and use are strongly supported by the european union. the biogasoil contains mainly normal and isoparaffins having similar boiling point range as the conventional gas oil [6, 10, 11]. the normal and isoparaffins are the most advantageous components of crude oil derived diesel fuels because of their chemical structure, as they have cetane number and advantageous application technology properties at low temperature, too [15, 16]. through the reactions of special hydrocracking of triglycerides primarily normal and isoparaffins, propane, co2, co, water and oxygenate compounds are formed on the applied catalyst(s) and process parameters. through this process the triglyceride molecules transform according to the following reactions [17-19]: • saturation (hydrogenation) of double bonds, • heteroatom removal, deoxygenation, hydrodeoxygenation (hdo reaction, reduction), (hydro)decarboxylation, (decarbonylation), • different side reactions: hydrocracking of fatty acid chain of triglycerides, water-gas-shift, etc. • isomerization of produced normal paraffins from deoxygenation. 108 c ch2 o och2 ch c o och2 c o o ch2 ch3ch2 ch ch 76 ch2 ch2 ch3ch2 ch ch 76 ch2 ch2 ch3ch2 ch ch 76 + 15 h2 3 n-c18h38 + c3h8 + 6 h2o + 6 h2 3 n-c17h36 + c3h8 + 3 co2 + 9 h2 3 n-c17h36 + c3h8 + 3 co + 3h2o i. iii. ii. figure 1: possible reaction pathways for oxygen removal from trioleic triglycerides through the deoxygenation (fig. 1) of tryglicerides in the hdo reaction (reaction route i.) 1 mol triglyceride molecule is converted to 3 mol n-paraffins having the same chain length as the fatty acid. the carbon number of the produced normal paraffins by decarboxylation (reaction route ii.) and decarbonylation (reaction route iii.) reactions are lower by one compared to the fatty acid chains of triglycerides [17, 19]. the produced mixture having high n-paraffin content (cold filter pluggin point – cfpp: 18–28 °c) has to be isomerized after separation to the necessary level to improve the flow properties. the biogasoil can be also used alone in diesel engines, but in conventional utilization it is unnecessary to apply this excellent product. furthermore, due to the limited availability of the currently used feedstock and the amount of the produced biogasoil allows limited application. therefore the application of biogasoil as gas oil blending components will be primarily of practical significance. for the production of biogasoil several technologies are proposed in the literature: neste oil nexbtl [20], uop/eni ecofiningtm technology [18] and the supercetane process [9]. in the last couple of years our widespread and systematic research and development activity has been focused on the field of conversion of natural triglycerides to diesel fuels. in this paper the most important results of triglycerides hydrotreating obtained on commercial nimo/γ-al2o3 catalyst are presented. experimental work based on the introduction the aim of our experimental work was to determine the applicability of the commercial nimo/γ-al2o3 catalyst in the fuel purpose (hydrocarbons with high n-paraffin content in gas oil boiling range) hydrotreating (special hydrocracking) of properly pretreated hungarian sunflower oil. our objective was to study the change of the hydrocracking activity (deoxygention activity) and the effect of the operating parameters (temperature, pressure, lhsv) on the yield and the composition of products. apparatus the experiments were carried out in an apparatus containing a tubular down-flow reactor of 100 cm3 effective volume. it contains all the equipment and devices applied in the reactor system of an industrial heterogeneous catalytic plant. the experiments were carried out in continuous operation [21]. the products of the experiment were fractionated to three main fractions: gaseous-, waterand liquid organic fractions. the liquid products which were separated in the separator of the apparatus contained water, hydrocarbons (c5 and larger) and compounds with oxygen content. the organic phases were separated from the water phase and analyzed without phase separation. feedstock and catalyst the feedstock of the hydrotreating experiments was properly pretreated hungarian sunflower oil (table 1). table 1: the main properties of the feedstock of hydrotreating properties value density (15°c) g/cm3 0.9252 acid number, mgkoh/g 2.2 iodine number, g i2/100g 136 water content, mg/kg 244 fatty acid composition, % c16:0 6.5 c18:0 3.8 c18:1 20.7 c18:2 68.4 c22:0 0.6 the catalyst was an expediently chosen and commercial nimo/γ-al2o3 catalyst. the bet surface area of the catalyst was 115 m2/g, mo-content was 2.9% and the ni-content was 1.5%. before the experiments we increased the temperature of catalyst “in-situ” with 25 °c/hour to 400 °c, then we held the temperature at 400 °c for 2 hours at a gas flow-rate of 40 dm3/h. thereafter we decreased the temperature of the catalyst to the temperature of the first experimental point. 109 process parameters the range of the chosen process parameters – based on our pre-experimental results – were the following: temperature 300–360 °c, total pressure 20–60 bar, liquid hourly space velocity (lhsv): 0.5–2.0 h-1 and h2/sunflower oil volume ratio: 400 nm3/m3. analytical methods the properties of the feedstock and the products were measured according to standard methods (table 2). the compounds of the products were determined with high temperature gas chromatograph on special column (6m x 0,53mm x 0,1 μm, db5-ht aluclad column). table 2: the applied analytical methods properties method density en iso 12185:1996 iodine number en iso 3961:2000 acid number en 14104:2003 water content en iso 12937:2001 hydrocarbon composition en 15199-2:2007 fatty acid composition en iso 5509:2000 en 14103:2003 results and discussion the main aim of the fuel purpose hydrotreating experiments of sunflower oil was – besides the saturation of double bonds – the removal of the oxygen atom from the sunflower oil and the production of the target fraction (primary c15-c18 nand i-paraffins) in gas oil boiling range with the highest yield. based on our results it can be concluded that the yield of the liquid organic fraction was higher than 88% in every case related to the weight of the feedstock (depending on the process parameters). the cause of this is the conversion of the oxygen content of the sunflower oil to water and co2 (and co) in different amounts, the elimination of propane and the lower carbon number (≤4) gas products formed by cracking reactions. the conversion of triglycerides increased with increasing temperature. the amount of the not conversed triglyceride was below 10% at 380 °c temperature, at 60 bar pressure and at every lhsv (fig. 2). the conversion of triglycerides significantly increased with increasing pressure (if the other process parameters were constant) (fig. 3). but at 300 °c the hydrocrack reactions took place only to produce carboxylic acids. accordingly the organic fraction contained primarily carboxylic acids (methyl esters) and other esters, diglycerides and triglycerides and the amount of the target fraction was below 5%. the conversion of triglycerides decreased with increasing the lhsv (and decreasing the time on stream) so the content of triglyceride was higher in the product mixture (fig. 4). but at 300 °c and 60 bar the deoxygenation reactions took place only in a little extent because the target fraction was formed in a small amount. 0.0 10.0 20.0 30.0 40.0 50.0 60.0 280 300 320 340 360 380 400 temperature, °c y ie ld , % paraffins up to c16 c17 paraffins c18 paraffins carboxylic acids + fames other esters diglycerides triglycerides lhsv: 1.0h-1, p = 60 bar figure 2: the yield of important compounds in organic phase as a function of the temperature (lhsv: 1.0 h-1; p = 60 bar) 0 5 10 15 20 25 30 35 40 45 50 10 20 30 40 50 60 70 pressure, bar y ie ld , % paraffins up to c16 c17 paraffins c18 paraffins carboxylic acids + fames other esters diglycerides triglycerides t=300°c, lhsv: 0.5h-1 figure 3: a the yield of important compounds in organic phase as a function of the pressure (lhsv: 0.5 h-1; t = 300 °c) 0 10 20 30 40 50 60 70 0.0 0.5 1.0 1.5 2.0 2.5 lhsv, h-1 y ie ld , % paraffins up to c16 c17 paraffins c18 paraffins carboxylic acids + fames other esters diglycerides triglycerides t=300°c, p=60 bar figure 4: the yield of important compounds in organic phase as a function of the lhsv (p = 60 bar; t = 300 °c) 110 the yield of the target fraction (50.7–54.5%) was significantly lower at advantageous process parameters (370–380 °c, 60 bar, 0.5 h-1) than the theoretical values (82–86%). so it is necessary to separate the target fraction from the not converted triglyceides and from the produced intermediates. the heavy fraction has to be recirculated to the reactor after the separation. one of the intermediates, which were formed by the special hydrocracking reactions, is the different carboxylic acids. the yield of this intermediate at the applied pressure and lhsvs changed according to maximum curve as a function of temperature. the maxiumal yield of carboxylic acids were between 320–340 °c (lhsv: 0.5 h-1), about 340 °c (lhsv: 1.0 h-1), and about 360 °c (lhsv: 1.5 h-1 and 2.0 h-1) (fig. 5). consequently it is necessary to apply properly high temperature in order to convert the intermediates to valuable components (target fraction) in further reactions. 0 5 10 15 20 25 30 35 40 280 300 320 340 360 380 400 temperature, °c y ie ld o f c ar bo xy lic a ci ds , % . p=60 bar, lhsv=2.0h-1 p=60 bar, lhsv=1.5h-1 p=60 bar, lhsv=1.0h-1 p=60 bar, lhsv=0.5h-1 figure 5: the yield of the produced carboxylic acids as a function of the temperature (p = 60 bar) based on the hydrocarbon composition (determined by gas chromatograph) it can be concluded that these intermediates are converted primarily to c16 and c18 paraffins in hdo reaction and to c15 and c17 paraffins in the decarboxilation/decarbonylation reaction and in a lower amount to c14 and shorter hydrocarbons (with cracking of c–c bonds) the yield of the c18 paraffins which were formed in hdo reaction – similarly to the yield of carboxylic acids – changed according to maximum curve as a function of temperature (fig. 6) so the amount of c18 paraffins significantly decreased with further strictening of the process parameters due to the chain crakcing reactions. the yield of c17 paraffins which were obtained by decarboxylation/decarbonylation reactions changed similarly to the yield of c18 paraffins for example at the lowest lhsv (0.5 h-1) (fig. 7). the yield of c17 paraffins increased with increasing the temperature at higher lhsvs. the further increase of the temperature will probably increase the rate of chain cracking reactions and the yield of c17 paraffins will be lower, too. 0.0 5.0 10.0 15.0 20.0 25.0 30.0 280 300 320 340 360 380 400 temperature, °c y ie ld o f c 18 p ar af fs , % . p=60 bar, lhsv=2.0h-1 p=60 bar, lhsv=1.5h-1 p=60 bar, lhsv=1.0h-1 p=60 bar, lhsv=0.5h-1 figure 6: the yield of the c18 paraffins as a function of the temperature (p = 60 bar) 0 2 4 6 8 10 12 14 16 280 300 320 340 360 380 400 temperature, °c y ile d of c 17 p ar af fin s, % . p=60 bar, lhsv=2.0h-1 p=60 bar, lhsv=1.5h-1 p=60 bar, lhsv=1.0h-1 p=60 bar, lhsv=0.5h-1 figure 7: the yield of the c17 paraffins as a function of the temperature (p = 60 bar) to summarize the results we concluded that in case of every investigated process parameter the c18-, c17-, c16 and c15 paraffins were formed, i.e. on the applied catalyst both the hdo and the decarboxylation/decarbonylation reactions took place. we obtained the target fraction (gas oil boiling range fraction) with destillation of organic fractions. these target fractions, which were produced under optimal process parameters (360–380 °c, 60 bar, 0.5 h-1, 400 nm3/m3), contained more than 95% normal paraffins (from this 5.3–6.9% n-c15, 19.2–29.1% n-c16, 16.5–18.0% n-c17, 20.3–34.0% n-c18) and <5% isoparaffins. the use of the target fraction as engine fuels (diesel) is limited, because its cetane number is high (>80) but its cfpp value is also high (>20 °c). so to improve this disadvantageous property it is necessary to carry out selective isomerization of the target fraction. summary to summarize the results, it can be concluded that with the hydrotreating (special hydrocracking) of sunflower oil high paraffin containing (>50%) product mixtures 111 (target fraction) with high yield can be produced on the applied nimo/γ-al2o3 catalyst. but it is necessary to apply high pressure (p = 60 bar), high temperature (t = 360–380 °c) and low lhsv (lhsv = 0.5–1.0 h-1); for example 370–380 °c, 60 bar, 0.5 h-1. the yield of the produced target fraction (gas oil boiling range fraction) was significantly lower (50.7– 54.5%) at advantageous process parameters (370–380 °c, 60 bar, 0.5 h-1) than the theoretical values (82–86%). that is why it is necessary to separate and recirculate the heavy fraction. the conversion of triglycerides significantly increased with increasing pressure, but at lower temperature (300 °c) the hydrocracking reactions took place only until the formation of carboxylic acids. the yield of produced intermediates (esters, carboxylic acids) and the target fraction changed according to maximum curve as a function of temperature in every lhsv. in case of every investigated process parameter the c18-, c17-, c16and c15 paraffins were formed, i.e. on the applied catalyst both the hdo and the decarboxylation/decarbonylation reactions took place. the cetane number of the target fractions which were obtained from organic fraction with distillation are very high (>80, en standard: ≥51), but the cold flow properties of this fraction are disadvantageous. so to improve this disadvantageous property it is necessery to carry out selective isomerization of the target fraction [8, 11]. references 1. larivé j. f.: concawe review, 15 (2) (2006) 2. demirbas a.: progress and recent trends in biodiesel fuels, energy conversion and management, (2009) 50, 14–34 3. meher l. c., vidya s. d., naik s. n.: technical aspects of biodiesel production by transesterification a review, renew. and sust. energy reviews, (2006) 10, 248–268 4. knothe g., van gerpen j., krahl j.: the biodiesel handbook. the american oil chemists' society, champaign, il usa, (2005) 303 pp 5. hancsók j., krár m., holló a., thernesz a.: újgenerációs bio-motorhajtóanyagok i., magyar kémikusok lapja, (2006) 61(8), 260–264 6. hancsók j., krár m., magyar sz., boda l., holló a., kalló d.: investigation of the production of high cetane number biogasoil from prehydrogenated vegetable oils over pt/hzsm-22/al2o3, microporous and mesoporous materials, (2007) 101, 148–152 7. twaiq f. a., zabidi n. a. m., mohamed a. r., bhatia s.: catalytic conversion of palm oil over mesoporous aluminosilicate mcm-41 for the production of liquid hydrocarbon fuels, fuel processing technology, (2003) 84, 105–120 8. kloprogge j. t., duong l. v., frost r. l., a review of the synthesis and characterisation of pillared clays and related porous materials for cracking of vegetable oils to produce biofuels, environmental geology, (2005) 47, 967–981 9. stumborg m., wong a., hogan e.: hydroprocessed vegetable oils for diesel fuel improvement, bioresource technology, (1996) 56, 13–18 10. krár m., magyar sz., thernesz a., holló a. boda l., hancsók j.: study of the hydrodeoxygenation of vegetable oils, 15th european biomass conference proceedings, (2007), 1988– 1992 11. hancsók j., krár m., magyar sz., boda l., holló a., kalló d.: investigation of the production of high quality biogasoil from pre-hydrogenated vegetable oils over pt/sapo-11/al2o3, studies in surface science and catalysis, (2007) 170, 1605– 1610 12. van vliet o. p. r., faaij a. p. c.: fischer-tropsch diesel production in a well-to-wheel perspective: a carbon, energy flow and cost analysis, energy conversion and management, (2009) 50, 855–876 13. chew t. l., bhatia s.: catalytic processes towards the production of biofuels in a palm oil and oil palm biomass-based biorefinery, bioresource technology, (2008) 99, 7911–7922 14. commission of the european communities, an eu strategy for biofuels, com(2006) 34 final, (2006) 15. corma a.: zeolites in oil refining and petrochemistry, zeolite microporous solids: synthesis, structure, and reactivity, (1992), 373–436 16. murphy m. j., taylor j. d., mccormik r. l.: nrel/sr-540-36805, (2004) 17. huber g. w., o’connor p., corma a.: processing biomass in conventional oil refineries: production of high quality diesel by hydrotreating vegetable oils in heavy vacuum oil mixtures, applied catalysis a: general, (2007) 329, 120–129 18. kalnes t., marker t., shonnard d. r.: green diesel: a second generation biofuel, international journal of chemical reactor engineering, (2007) 5, article a48, 19. krár m., hancsόk j.: investigation of the transformability of vegetable oil containing gas oils with heterogenous catalyst, 7th international colloquium fuels proceedings, (2009), 507–514 20. turpeinen h.: renewable nexbtl diesel, biofuel 2g conference, pamplona, navarra, 24.01.2008. 21. nagy g., hancsók j., varga z., pölczmann gy., kalló d.: investigation of hydrodearomatization of prehydrogenated gas oil fractions on pt-pd/h-usy catalysts, topics in catalysis, (2007) 45, 195–201 microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 27-34 (2008) recent trends on application of ionic liquids in organic synthesis p. cserjési , k. bélafi-bakó, n. nemestóthy, l. gubicza university of pannonia, research institute of chemical and process engineering veszprém, egyetem u. 10. h-8200, hungary e-mail: cserjesi@mukki.richem.hu ionic liquids have been identified as one of the new classes of solvents that offer opportunities to move away from traditional chemical processes to new, clean technologies in which waste streams are minimized. ionic liquids are salts composed of organic cations and organic or inorganic anions. they are liquid at room temperature and by definition have low melting points (<150 °c). compared to conventional organic solvents, the use of ionic liquids for synthesis, catalysis and extraction has a number of advantages determined by the unique combinations of their properties. these properties are significant when addressing the health and safety concerns associated with many solvent applications. this work reviews the latest trends on the application of ionic liquids in organic reactions. keywords: ionic liquid, organic synthesis introduction the green chemistry movement, which encompasses the application of environmentally sound chemicals and chemical processes, has widespread quickly in the last decades. one of its most important goals is to replace the hazardous volatile organic compounds required for mixing and dissolving with benign solvents. a wide range of solvent application have been investigated and in many cases the ionic liquid media, that are now studied because of their specific advantages in rate, specificity, and yield rather than simple voc replacement, proved to satisfy the given requirements [1]. generally, the term “ionic liquids” (il) stands for liquids composed of ions. these are usually molten salts or molten oxides. inorganic salts such as the sodium halogens are solid with melting point well above 500 °c. the novelty of ils is the low melting temperature; they usually have a melting point arbitrarily fixed at or below 100 °c. if the melting point is below room temperature (~25 °c), the il is called room-temperature ionic liquid (rtil) [2]. it has been noted that the properties of molten salts as a solvent for chemical processes differ from those of aqueous and organic solvents. some processes, for instance, the electrochemical reduction of aluminium from alumina, can be conducted only in molten salts and are impossible in aqueous solutions [3]. a book titled ionic liquid for synthesis was published by wasserschied and welton [4] in 2007. it contains information about the physicochemical properties of ils and the role of ils in organic, inorganic and biocatalytic reactions. the objective of our work is not to exceed a book concerning ils but to draw attention to the recent trends of il application focusing mainly on organic synthesis reactions, such as acylation, alkylation, condensation, esterification, hydrogenation, hydroformylation and oxidation. acylation friedel-crafts acylation reactions are of great importance in the industrial manufacture of aryl ketones, and are used extensively in the production of pharmaceuticals such as the nonsteroidal anti-inflammatory drugs ibuprofen and naproxen. conventionally, these reactions are catalysed by aluminium trichloride, using an acylating agent such as an acid chloride in a volatile organic solvent the friedel-crafts benzoylation of anisole with benzoic anhydride to yield 4-methoxybenzophenone has been carried out in a range of ils using zeolite catalysts [5], as shown in fig. 1. the rates of reaction were found to be significantly higher using ils compared with organic solvents. continuous-flow studies of successful il systems indicate that the bulk of the catalysis is due to the formation of an acid via the ion exchange of the cation with the protons of the zeolite. the acid liberated was quantified using both titration experiments and ionexchange experiments using sodium-exchanged zeolites. 28 o o o ome meo o cooh + + zeolite solvent figure 1: scheme of the friedel-crafts benzoylation many acylation reactions have been demonstrated in acidic chloroaluminate(iii) (cl·alcl3) ils. as with the conventional processes, difficulties remain from the reaction being noncatalytic in aluminium chloride (alcl3) which necessitates destroying the il catalyst by quenching with water to extract the products. however, regioselectivity and reaction rates observed from acylation reactions in ils were equal to the best published results. friedel-crafts acylation of benzene is promoted by franklin acidic cl·alcl3 ils [6]: as is typical for acylation reactions, selectively monoacylated products are formed through deactivation of the aromatic ring by the first acyl substituent. the acylated products of these reactions show high selectivities to a single isomer: for example toluene, chlorobenzene and anisole are acylated in the 4-position with 98% specificity. naphthalene is acylated in the 1-position which is the thermodynamically unfavoured product under conventional friedel-crafts acylation conditions compared to the derivatisation at the 2-position, the “normal” product [7]. alkylation amines and their derivatives have many functions in various natural products and unnatural synthetic targets. because of their unique biological properties, substituted amines are widely used clinically as antihypertensive, antihistamine, and antiinflammatory drugs. the synthetic approaches to make secondary and tertiary amines include reductive alkylation the use of protecting groups, and direct n-alkylation. these traditional methods for the synthesis of amines typically require highly polar solvents such as dimethyl sulphoxide and dimethyl formamide at high temperatures with excess of alkyl halide or amine and harsh reaction conditions. the selective alkylation of amino groups within amine derivatives with a variety of alkyl halides was reported using ils; 1-butyl-3-methylimidazolium iodide ([bmim]i) (fig. 2) and 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][pf6]) in the presence of triethylamine. the reaction was found to proceed under relatively mild conditions with excellent conversions and selectivities. the ils, which could replace the high temperature use of highly polar organic solvents such as dimethyl formamide, 1,3-dimethyl-2 imidazolidinone, and dimethyl sulphoxide, were recycled and reused [8]. nh2 + r' x net3 [bmim]i r r nhr' figure 2: n-alkylation of aniline derivatives in [bmim]i so3h-functionalized ils were synthesized and their catalytic performance for the tert-butylation of m-cresol with tert-butanol (tba) were investigated. the reaction time, reaction temperature, molar ratio of m-cresol to tba and the recycle number of the spent il were examined. under optimum reaction conditions, the conversion of m-cresol and the selectivity to 2-tertbutyl-5-methyl phenol (2-tbc) were 81% and 96%, respectively. no apparent loss of activity and selectivity of the il were observed after four recycles. 2-tbc is a precursor for a number of commercially important antioxidants and a light protection agent for the bisphenos and thiobisphenols [9]. the optically active orthopalladated phenanthrylamine phase transfer catalyst has been produced and explored for asymmetric glycine alkylation by mukherjee [10]. the catalyst (10 mol%) in toluene/chloroform with 50% aqueous koh (25 °c) promoted benzylation of benzophenone imine tert-butyl glycine. the product was obtained in 85% yield and 15% enantiomeric excess (ee). addition of the chiral il n,n-dimethyl ephedrinium bis(trifluoromethansulfon)imidate enhanced reactivity and selectivity for ptc glycine alkylation. it appeared that the chiral il had a cooperative effect to boost the ee content of an asymmetric reaction. alkylation of indole salts in different ils was also reported. ils increased the alkylation reaction rate of ambident indole anion and reduced the effects of counter ions and/or additives, the alkylation reaction rates being independent of the presence of small amounts of protic solvents or water [11]. condensation condensation reactions are a useful way of making c–c bonds, with the elimination of a small molecule byproduct [12]. a number of lewis acid condensation reactions have been tried in cl·alcl3 ils. these are the pechmann reaction [13], the knoevenagel reaction [14], the fischer indole synthesis [15], and the baeyer condensation [16]. while these have all given high conversions of starting materials under the best conditions, they suffer from having water as a principle by-product. any water generated by the reaction reacts with the cl·alcl3 species in the il, so reducing its acidity and eventually destroying the il. other lewis acid mediated reactions that have been conducted in cl·alcl3 ils include the cleavage of aromatic methyl ethers [17], acylative cleavage of ethers [18], esterifications [19], diels-alder cycloadditions [20], and the formation of 4-chloropyrans during an attempted prins reaction [21] but, once again, the il is consumed in the reaction or during product isolation. this problem, that the il is consumed and cannot be considered to be a true catalyst for the reactions has arisen repeatedly with the use of cl·alcl3 ils. the air stable 1-ethyl-3-methylimidazolium tetrafluoroborate ([emim][bf4]), 1-ethyl-3-methylimidazolium hexafluorophosphate ([emim][pf6]), 1-ethyl-3-methylimidazolium nonafluoro-1-butanesulfonate ([emim][nfo]) and 3-(5-carboxy-pentyl)-1-methylimidazolium tetrafluoroborate ([capemim][bf4]) ils were investigated [22] in the 1,3-dipolar cycloaddition of diethyl amiono 29 malonate derived imidate and 2-ethoxybenzaldehyde. the first three ils gave significant rate acceleration and good isolated cycloadduct yields when compared to solvent-free cycloaddition reaction conditions. the knoevenagel reaction is well known for its immense potential in the synthesis of electrophilic olefins from active methylene and carbonyl compounds. more than a century old now, a wide array of catalysts have been employed to accomplish this reaction, each affording variable yields of olefins. the knoevenagel condensations of benzaldehyde and substituted benzaldehydes with diethyl malonate in lewis acidic 1-butyl3-methylimidazolium chloroaluminate, ([bmim]cl·alcl3) and 1-butylpyridinium chloro-aluminate, ([bpy]cl·alcl3) ils (fig. 3) was reported. co2et co2et r co2et co2et cho r r co2et co2et ch(co2et)2 + minor + [bpy]cl.xalcl3 [bmim]cl.xalcl3 or figure 3: reaction of benzaldehyde and substituted benzaldehydes with diethyl malonate in the lewis acidic [bmim] cl·alcl3 and [bpy]cl·alcl3 ils the two ils [bmim]cl·alcl3 and [bpy]cl·alcl3, served as an alternative media that catalysed knoevenagel reactions. the synthesis of coumarins via knoevenagel route was also demonstrated in these liquids. considerable control over various products in these reactions can be exercised by variation of the parameters associated with the il. the experimental procedure is simple and timesaving, avoiding cumbersome water removal steps [14]. a task-specific il, [h3n+–ch2–ch2–oh][ch3coo-] was synthesized and used as catalyst in the knoevenagel condensation reaction of various kinds of aromatic aldehydes with ethyl cyanoacetate or malononitrile by yue [23]. α,β-unsaturated carbonyl compounds were obtained in reasonable yields when the [h3n+–ch2– ch2–oh][ch3coo-] catalyzed knoevenagel reaction was carried out at room temperature for 60 min under solvent-free conditions. only e-isomers were detected. after the removal of water the task-specific il could be recycled and reused for five times without noticeably decreasing the catalytic activity. singer et al. conducted acylative cleavage of cyclic ethers in lewis acidic 1-ethyl-3-methylimidazolium halogenoaluminate ([emim][x·alx3]) ils and reported that these cleavages were sensitive to the ‘bulk’ lewis acidity of the ionic solvent system [18]. the results support a mechanism in which there is initial formation of a polarized complex between lewis acidic halogenoaluminate or alcl3 species present in solution and benzoyl chloride or the formation of benzoyl cation upon addition of benzoyl chloride to the system. o-acylation of the ether then occurs to give an oxonium ion species that cleaves to give the most stable carbonium ion or which undergoes nucleophilic attack by iodine present in these systems. the lack of chlorine in any of the products isolated in this study indicates the latter of these two mechanistic possibilities is more likely. the differential results observed using ionic solvents of variable lewis acidity suggest that this mechanism may be hindered by occupation of the etherial oxygen by some lewis acidic species (i.e. al2x7 -) other than acylinium ion when the strictly acidic solvent system is used. high molecular weight aliphatic polyesters were synthesized in [cnmim][pf6] and [cnmim][ntf2] (where ntf2: bis(trifluoromethylsulfonyl)imide) ils (n = 4, 6, 8, 10, 12) via two-step polycondensation [24]. an oligoester with diol/diacid ratio higher than unity was essential for achieving high molecular weight product. moreover, the molecular weight of the resulting polyesters was found to depend on the activity of the catalyst in the ils and the miscibility of aliphatic polyester/il. the former factor was dominated by the anion of the ils. the latter factor could readily be tuned by varying the anion and/or the cation of the ils. a clear correlation was found between the miscibility of aliphatic polyester/il and the extent to which their solubility parameters matched. when the temperature dropped below the polyesters’ melting points they formed crystals and were separated from the ils. this crystallization-induced phase separation simplified the purification process. by simply removing the il using methanol, then washing for 4 times, high-purity (>99%) polyester was obtained at yield up to 96.3%. diels–alder reactions offer a powerful synthetic methodology to construct six-membered cycloadducts of biological importance with a fine control over their stereoselectivities. sarma and kumar [25] reported the combined effect of triflates (otf) and ils, such as 1-octyl3-methylimidazolium tetrafluoroborate ([omim][bf4]), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) ([emim][ntf2]), 1-ethyl-3-methylimidazolium trifluoroacetate ([emim][tfa]), 1-butyl-3methylimidazolium tetrafluoroborate ([bmim][bf4]), [bmim][pf6], and [emim][bf4], in the reactions of cyclopentadiene with methyl acrylate, methyl methacrylate and methyl trans crotonate. it was stated that diels– alder reactions carried out in ils can be further accelerated by rare earth metal otfs. it is possible to achieve good yields even after six recycles of ils with otfs. the chiral bis(oxazoline)–copper complex catalyzed asymmetric diels–alder reaction of cyclopentadiene and 3-(acryloyl)oxazolidin-2-one was investigated in [bmim][bf4], [bmim][pf6], 1-butyl-3-methylimidazolium triflate ([bmim][otf]) and 1-butyl-3-methylimidazolium antimonyfluoride ([bmim][sbf6]) ils [26]. for the study, inda-box (fig. 4) was chosen as a chiral ligand. a copper salt and slightly excess ligand were mixed in il to form a ligand–metal complex. ils were used for significant reactivity enhancement, stereoselectivity improvement and for the efficient recycling of the catalyst. with il only, the reaction proceeded to some extent yielding a 91:9 endo/exo mixture of the racemic adduct in 15% yield and in the presence of 8 mol% cu(otf)2, reaction was complete (90% yield) within 10 min, also providing racemic products in a similar diastereoselectivity (endo/exo = 91:9). it was concluded that the reaction could be catalyzed by the il and the copper reagent itself and below a critical amount of the 30 ligand–metal complex (0.85 mol% ligand and 0.6 mol% cu(otf)2) the nonselective reaction would prevail. n o n o figure 4: structure of inda-box esterification esterifications of alcohols with carboxylic acids in ils as green reaction medium in catalytic quantities have been investigated. the application of ils in esterification is advantageous because of three reasons; (1) ils catalyse the esterification, (2) the resultant esters do not dissolved in the il and therefore can be isolated easily, (3) the il could be recovered and reused again with the evacuation of the reactor system containing il [27]. excellent conversion and selectivities were achieved, and the most of resultant esters could be easily recovered due to immiscibility with the ils [19]. the esterification results of several alcohols with acetic or anchoic acids in the [bpy]cl·alcl3 il and in concentrated sulfuric acid were compared. for the esterification of iso-propyl, iso-pentyl, and benzyl alcohols with acetic acid the catalytic activities of il were proved to be higher than that of the corresponding sulfuric acid, and there was not much difference in selectivities. for esterifications of benzyl alcohol, some by-products, i.e. benzyl chloride (~3%) in il and phenymethylether (~4%) in sulfuric acid were found, respectively. it was indicated that the il as esterification catalyst could be reused although the conversion is slightly decreased after the first esterification. hydrogenation the new ‘air-stable’ ambient temperature ils were used for the first time in 1995, liberating the worker from the constraints of working with solvents that were difficult to handle [28]. these experiments used osborne’s catalyst, [rh(nbd)pph3][pf6] (where nbd: norbornadiene) for the hydrogenation of pent-1-ene. in both [sbf6] and [pf6] ils, the hydrogenation rates were significantly greater than in acetone. the separation of the product alkenes from the reaction mixture was simple and the catalyst containing il solution could be recycled. at almost the same time a paper that is often overlooked came from dupont and co-workers [29], using rhcl(pph3)3 and [rh(cod)2][bf4] (where cod: cyclooctadiene) for the hydrogenation of cyclohexene in [bmim][bf4]. here, the advantage claimed was effective recycling of the catalyst solution. the promise that ils hold for providing systems for the reuse of expensive catalyst solutions and ligands is particularly appealing in this area and a number of reactions have been investigated. the hydrogenation of benzene and other arenes by molecular catalysts is a fascinating and controversial area of research, in which many highly innovative catalysts have been evaluated. arene hydrogenation is not just a topic of academic interest, but has industrial application such as the synthesis of cyclohexane (a precursor to adiptic acid used to produce nylon), removal of aromatic compounds from fuels, and as a way to prevent paper from yellowing without addition of bleaches, since the compounds responsible for the yellowing are aromatic macromolecules [30, 31]. all industrial arene hydrogenation catalysts are heterogeneous, including a system that converts benzene to cyclohexene, which is subsequently converted into cyclohexanol. ionic-liquid-like copolymer poly[(n-vinyl-2 pyrrolidone)-co-(1-vinyl-3-butylimidazolium chloride)] (nvp-co-vbimcl) stabilized rhodium nanoparticles were used to catalyze the hydrogenation of benzene and other arenes in ils [32]. the nano particle catalysts can endure forcing conditions (75 °c, 40 bar h2), resulting in high reaction rates and high conversions compared with other nano particles that operate in ils. the hydrogenation of benzene attained record total turnovers of 20000, and the products were easily separated without being contaminated by the catalysts. other substrates, including alkyl-substituted arenes, phenol, 4-n-propylphenol, 4-methoxylphenol, and phenyl-methanol, were studied and in most cases were found to afford partially hydrogenated products in addition to cyclohexanes. indepth investigations on reaction optimization, including characterization of copolymers, transmission electron microscopy, and an infrared spectroscopic study of nanocatalysts were also undertaken. a very effective and simple il based system for arene hydrogenation based on k2ptcl4 and [n-octyl-3picolinium]cl·alcl3 was identified by geldbach and dyson. benzene is partially miscible in the il phase whereas the cyclohexane product is immiscible. this gives rise to the ideal situation of high reactions rates, not impeded by phase problems, with the ideal separation properties. it is likely that further optimization of this system will be possible, for example, by using mixtures of different salts which may lead to heteronuclear nanoparticles catalysts with greater activity [30]. the selective heterogeneous catalytic reduction of phenyl acetylene to styrene over palladium, supported on calcium carbonate, is reported in both an il and a molecular solvent [33]. in the case of il experiments, the 1-butyl-3-methyl imidazolium bis(trifluoromethylsulfonyl)imide ([bmim][ntf2]) was recycled after reaction by solvent extraction with diethyl ether until no reagents or products could be observed by either 1hnmr or raman spectroscopy. good reproducibility was found with fresh il and fresh catalyst compared with recycled il and recycled catalyst. no palladium was detected in the il reaction mixture and no reaction was observed in the absence of catalyst either in the fresh or recycled il. overall the comparison of the resistances in the il and the heptane showed that the lower reaction 31 rates when using il was attributed to the mass transfer of hydrogen within the liquid. structured supported il-phase (ssilp) catalysis, which is a new concept with the advantages of ils used as solvents for homogeneous catalyst and the further benefits of structured heterogeneous catalysts, was studied [34]. it was achieved by confining the il with the transition metal complex to the surface of a structured support consisting of sintered metal fibers (smfs). in an attempt to improve the homogeneity of the il film, the smfs were coated by a layer of carbon nanofibers (cnfs). the il thin film immobilized on cnf/smf supports presented a high interface area, ensuring efficient use of the transition metal catalyst. the regular structure of the support with high porosity (>80%) allowed a low pressure drop and even gas-flow distribution in a fixed-bed reactor. the high thermoconductivity of the cnf/smf support suppressed the formation of hot spots during exothermic hydrogenation reactions. the selective gas-phase hydrogenation of 1,3cyclohexadiene to cyclohexene over a homogeneous rh catalyst immobilized in il supported on cnf/smf was used as a test reaction to demonstrate the feasibility of the ssilp concept. the catalyst [rh(h)2cl(pph3)3/il/ cnf/smf] showed a turnover frequency of 150-250 h-1 and a selectivity of >96%. high-pressure 1hnmr and 1h{31p} nmr spectroscopy was used to provide insights into the nature of the active catalytic species. according to xu significant improvements could be achieved in the hydrogenation of halonitrobenzenes to the corresponding haloanilines over easily available catalysts in [bmim][bf4] and [emim][bf4] ils with excellent selectivity of lower dehalogenation. the selective hydrogenation of halonitroaromatics could be applicable to monohaloand polychloro-substituted nitrobenzenes as well [35]. hydroformylation even though there is already a highly efficient aqueous or organic biphasic industrial process for the hydroformylation of olefins, hydroformylation in ils is extensively studied. this process can only be used with short-chain (≤ 5 c) olefins because heavier olefins are insufficiently soluble in water for an effective reaction to occur. ils with higher solubilities for these higher olefins can offer the possibility of replacing the water layer and extending the usefulness of the biphasic technique [2]. olivier-bourbigou and co-workers [36] investigated the hydroformylation of 1 hexene in a variety of ils with imidazolium and pyrrrolidinium cations and a range of different anions. initially they introduced the rhodium as [rh(co)2(acac)] (where acac: acetylacetonate) with four equivalents of the charged triphenylphosphine monosulfonate (tppms) and measured the turnover frequency (tof) of the catalyst in the different ils. for the [bf4], [pf6], [otf], and trifluoroacetate ([cf3co2]) ils they found that the tof of the reaction was dependent upon the solubility of the 1-hexene in the il, possibly suggesting a mass transfer limited process. however, when they used three different trifluoromethanesulfonimid ([(cf3so2)2n]) based ils the tof did follow the solubility of the 1-hexene in these ils, but the tof’s of the whole set were lower than expected when compared to the other ils. it is not at all clear why this discrepancy exists. given that the [(cf3so2)2n] ion is one of the least basic of the anions used [37], and that [(cf3so2)2n] ils are generally at the low end of il viscosities [38], one might have expected any deviation to be in the other direction. when this puzzle is solved it may be possible to design ils that will give greater reactivities. the ils [bmim][bf4], [bmim][pf6] and 1,2-dimethyl3-butyl-imidazolium hexafluorophosphate ([bdmim][pf6]) were investigated as potential media for hydroformylation catalysis in a liquid–liquid biphase reaction environment [39]. the study used the rhodium/tppti* (tppti* = tri(m-sulfonyl) triphenyl phosphine [bdmim] salt) system as the catalyst and hexene-1 as the substrate, which enabled the produced heptanal to be conveniently isolated from the il by phase separation. all catalyst evaluations were carried out in high-purity ils to avoid any decomposition of the catalyst, substrate and/or il. the activity of the biphasic il system containing the rh/tppti* catalyst was approximately one order of magnitude lower than that observed for the conventional rh/pph3 catalyst in toluene. the rh/tppti* catalyst system showed a decrease of activity in the semicontinuous hydroformylation of hexene-1 due to catalyst deactivation and/or metal loss. the loss of rhodium metal from the il phases appears to be correlated to the solubility characteristics of the il and the concentration of the aldehyde in the organic phase. in support of this theory, the il [bmim][pf6] gave the best results due to its very low miscibility with polar substances. a high-pressure nmr (hp-nmr) study revealed that the solution structure of hrh(13co)(tppts)3 (tppts = tri(msulfonyl) triphenyl phosphine sodium salt) in [bmim][bf4] was similar to that of hrh(13co)(pph3)3 in toluene-d8. the hp-nmr investigation at elevated syngas pressures showed that hrh(13co)(tppts)3 lies in equilibrium with hrh(13co)2(tppts)2. in 2006 yan and zhang [40] developed new hybrid phosphine–phosphoramidite ligands for the rh-catalyzed aymmetric hydroformylations of styrene and vinyl acetate, where excellent enantio-selectivity as high as 99% was achieved. nevertheless, chiral ligands are usually expensive, mainly due to the tedious synthesis pathways. the investigation of asymmetric catalytic reaction associated with the biphasic system is of significant importance from both the fundamental and industrial points of view. yuan and co-workers [41] developed a biphasic catalytic system with water-soluble rhodium complexes of sulfonated (r)-2,2’-bis(diphenylphosphino)-1,1’binaphthyl ((r)-binaps) in [bmim][bf4] il for the asymmetric hydroformylation of vinyl acetate under mild conditions. the biphasic asymmetric hydroformylation of vinyl acetate (fig. 5) provided 28.2% conversion and 55.2% enantiomeric excess when [bmim][bf4] toluene was used as the reaction medium at 333 k and 1 mpa for 24 h. 32 r + r cho cho r(r)-binaps-rh / ionic liquid co/h2 figure 5: asymmetric hydroformylation of vinyl acetate and styrene the biphasic asymmetric hydrogenation of dimethyl itaconate in [bmim][bf4] at 333 k and 2 mpa afforded 65% enantiomeric excess with an activity similar to the homogenous analogs. both biphasic catalytic systems with (r)-binaps ligand could be reused several times without significantly decrease in the activity, enantio and regio selectivities. oxidation although most ils currently in use are stable to oxidation, and so they provide ideal solvents for oxidation processes, this chemistry has only developed in the last few years. ni(acac)2 has been used as the catalyst for a number of aerial oxidations of parasubstituted benzaldehydes with moderate yields of the corresponding acids in [bmim][pf6] [42]. in the absence of the catalyst very little oxidation was observed. the same combination of catalyst, il and oxidant has also been used in the synthesis of ethylbenzene hydroperoxide from ethylbenzene [43]. however, in this case it is more accurate to describe the reaction system as a solution of the catalyst and il in ethyl benzene. the two principle advantages of the il are that it has a greater solubility in the ethylbenzene and the poorly coordinating anion competes less well for the metal centre than the previously used tetraalkylammonium halide salts. jacobsen’s catalyst has been used for asymmetric epoxidations with aqueous naocl in [bmim][pf6]/ch2cl2 (1:4) mixtures [44]. the mixed solvent system was used because the il itself was solid at the reaction temperature. yields and selectivities were similar to those in the absence of the il, but the use of the il gave faster reactions. the il and the reaction products were found in the organic phase, which was separated from the aqueous phase. the ch2cl2 was removed from the il–catalyst–product mixture in vacuum, before the product was washed from the il with hexane. the resultant solution of the catalyst in the il could then be reused with a small drop in enantioselectivity. canoira and co-workers [43] carried out the air catalysed liquid-phase oxidation of ethylbenzene (eb) to ethylbenzene hydroperoxide (ebhp) by ni2+ complexes. the use of a nickel soluble complex without acetylacetone ligands gave unsatisfactory results. quaternary ammonium salts (r4nbf4) (r = n-bu, me) were used as co-catalysts, and the ammonium salt with the longer radical n-bu gave better results. on the other hand, a catalytic system has been designed based on ni(acac)2 and [bmim][pf6] and its reactivity has been explored in the oxidation with air of ethylbenzene at atmospheric pressure, showing that this catalytic system could be at the moment an alternative to the catalysts in use for this oxidation process. the oxidation of aromatic aldehydes was reported [40] using the catalyst [ni(acac)2] and molecular oxygen at atmospheric pressure, as the oxidant, in the il [bmim][pf6], as shown in fig. 6. the catalyst and il could be recycled after extraction of the carboxylic acid product. r h o r oh o [bmim]pf6, 60oc (3 mol%), o2 figure 6: oxidation of aldehydes metal-containing zsm-5 (mzsm-5) molecular sieves catalysed cyclohexane oxidation with tert-butylhydroperoxide (tbhp) in [emim][bf4] il was carried out under mild conditions [45]. in [emim][bf4] much higher activity was observed than in either the conventional molecular solvent or in the absence of a solvent. the as-received hydrogen-containing zsm-5 (hzsm-5) was active, giving a conversion of 15.8% and selectivity of desired products (97.0%), which was higher than the best values reported for 4% conversion in the industrial oxidation process. in the oxidation two competing reactions occur, the decomposition of tbhp and the oxidation of substrate. the conversion and efficiency of tbhp had also been studied; the tbhp conversion was high for the catalysts used, while the efficiency of the oxidant was very low. the tbhp conversion was 74% and the tbhp efficiency was only 15.4%. around 80% of the oxidant was unselectively decomposed after 12 h. it is important to note that the il/mzsm-5 systems are very easily separated from the product mixture by simple decantation. catalyst recycling experiments were carried out with repeated use of il/mzsm-5 system. after each run, the separation step was operated carefully in order to ensure that there was no loss of the catalyst used in il. the total amount of the recovered il phase containing catalyst was measured accurately. fresh il, which was equivalent to the amount of il being losed (about 2%), was added to the recovered il/catalyst phase to make up to the initial concentration of il, and then the next run was performed by adding 27.8 mmol cyclohexane and 55.6 mmol tbhp (85% in h2o). it can be concluded that the desired product were obtained in the similar conversion, selectivity, and yield, indicating that both the il and the catalyst were recoverable and reusable. a number of ils have been used as co-solvents for the 2-methyl-3,4 dihyroisoquinoliunium ([mdhqm]) catalyzed epoxidation of alkenes. water miscible ils gave systems with similar reactivities to the conventional acetonitrile based systems. attempts to produce an aqueous/il biphasic system that could be used to recycle the catalyst failed due to a lack of phase transfer between the aqueous and il phases. epoxidation of 1phenyl-cyclohexene with [mdhqm][ntf2] as catalyst in different co-solvent/water solvent systems applying the ils [bmim][bf4], [bmim][otf], [bmim][sbf6], [bmim][ntf2] and 1-butyl-3-methyl pyridinium bis(trifluoromethylsulfonyl)imide ([bmpy][ntf2]) was investigated [46]. although both [bmim][bf4] and [bmim][otf] gave 33 good conversions, only marginally lower than for the water/acetonitrile system, [bmim][otf] gave the higher ones and was selected for subsequent investigations. it was found that the counter ion of the catalyst had no significant effect on the measured conversions in [bmim][otf]. this is probably due to total fast exchange of the catalyst counter anion with the anion of the il leading to the iminium cation being only associated with the [otf] anion. this ion scrambling has been noted in polymerisation catalysis, and on the reactivity of anionic nucleophiles, where it was found that the counter cation of the nucleophile had no significant effect upon its reactivity and that cation of the il determined its reactivity conclusion ils are salts composed of organic anions and organic or inorganic anions, which have low melting point. their physical and chemical properties can be adjusted by the variation of the ions. the fine adjusting of properties is possible by the variation of the length and branching of the alkyl groups incorporated into the cation. ionic liquids have interesting advantages; they are non-flammable and have extremely low vapor pressure. these properties are significant when addressing the health and safety concerns associated with many solvent applications. negligible vapor pressure solvent evaporation is eliminated, reducing the need for respiratory protection and exhaust systems. they have liquid range more than 400 k. while many solvents will freeze or boil across such a large temperature range, ionic liquids maintain their volume and fluidity. this wide range of thermal stability allows for tremendous kinetic control of chemical processes. the wide temperature range is also helpful in temperature dependent separation processes. ionic liquids have higher density than water and miscible with substances having very wide range of polarities and can simultaneously dissolve organic and inorganic substances. these features of rtils offer numerous opportunities for modifications of existing and for the development of new processes. in such cases, such processes would be impossible with conventional solvents because of their limited liquid range or miscibility. as a replacement of classical organic solvents, the application of ils offers a new and environmentally benign approach toward modern synthetic chemistry. il technology has been successfully applied in several classical organic chemical reactions, such as hydrogenation, hydroformylation, condensation, oxidation, etc. recently ionic liquids have been successfully employed as dual reagent (solvents + catalytic activity) for a variety of reactions, but their use as catalyst under solvent-free conditions still need to be given more attention. references 1. forsyth s. a., pringle j. m., macfarlane d. r.: aust. j. chem, 57 (2004) 113-119 2. welton t.: chem. rev. 99 (1999) 2071-2083 3. marsh k. n., boxall j. a., lichtenthaler a.: fluid phase equilibria 219 (2004) 93-98 4. wasserschied p., welton t.: ionic liquids in synthesis second edition vch–wiley, weinheim, (2007) 5. hardacre c., katdare s. p., milroy d., nancarrow p., rooney d. w., thompson j. m.: j. catal. 227 (2004) 44-52 6. boon, j. a. levisky j. a. pflug j. l., wilkes j. s.: j. org. chem. 51 (1986) 480-483 7. adams c. j., earle m. j., roberts g., seddon k. r.: chem. commun. (1998) 2097-2098 8. gök y., özdemir i., cetinkaya e.: chin j catal. 28(6) (2007) 489-491 9. liu x., liu m., guo x., zhou j.: cat. commun. 9 (2008) 1-7 10. mukherjee d. k., ghosh n.: cat. comm. 9 (2008) 40-44 11. zicmanis a., vavilina g., drozdova s., mekss p., klavins m.: central european journal of chemistry 5 (2006) 156-168 12. welton t.: coordination chemistry reviews 248 (2004) 2459-2477 13. khandekar a. c., khadilkar b. m.: synth. lett. 1 (2002) 152-154 14. harjani j. r., nara s. j. salunkhe m. m.: tetrahedron lett. 43 (2002) 1127-1130 15. rebeiro g. l., khadilkar b. m.: synthesis (2001) 370-372 16. poole c.f., kersten b. r., ho s. s. j., coddens m. e., furton k. g.: chromatogr., 352 (1986) 407425 17. kemperman g. j., roeters t. a., hilberink p. w.: eur. j. org. chem. 9 (2003) 1681-1686 18. green l., hemeon i., singer r. d.: tetrahedron lett. 41 (2000) 1343-1346 19. deng y., shi f., beng j., qiao k.: j. mol. catal. a 165 (2001) 33-36 20. lee c. w.: tetrahedron lett. 40 (1999) 2461-2464 21. yadav j. s., reddy b. v. s., reddy m. s., niranjan n., prasad a. r.: eur. j. org. chem. (2000) 1779 22. dubreuil j. f., bazureau j. p.: tetrahedron lett. 41 (2000) 7351-7355 23. yue c., mao a., wei y., lü m.: catalysis communications 9 (2008) 1571-1574 24. fu c., liu z.: polymer 49 (2008) 461-466 25. sarma d., kumar a.: applied catalysis a 335 (2008) 1-6 34 26. yeom c. e., kim h. w., shin y. j., kim b. m.: tetrahedron lett. 48 (2007) 9035-9039 27. gubicza l., nemestóthy n., fráter t. bélafibakó k.: green chem. 5 (2003) 236-239 28. chauvin y., mussmann l., olivier h.: angew. chem. int. ed. engl. 34 (1995) 2698-2700 29. suarez p. a. z., dullius j. e. l., einloft s., de souza r. f., dupont j.: polyhedron 75 (1996) 1217-1219 30. geldbach t. j., dyson p. j.: journal of organometallic chemistry 690 (2005) 3552-3557 31. holbrey j. d., seddon k. r.: clean products and processes 1 (1999) 223-236 32. zhao c., wang h., yan n., xiao c., mu x., dyson p. j., kou y.: journal of catalysis 250 (2007) 33-40 33. hardacre c., mullan e. a., rooney d. w., thompson j. m., yablonsky g. s.: chem. eng. sci. 61 (2006) 6995-7006 34. ruta m., yuranov i., dyson p. j., laurenczy g., kiwi-minsker l.: j. cat. 247 (2007) 269-276 35. xu d. q., hu z. y., li w. w., luo s. p., xu z. y.: j. mol. catal. a 235 (2005) 137-142 36. olivier-bourbigou h., magna l.: j. mol. catal. a, 182–183 (2002) 419-437 37. crowhurst l., mawdsley p. r., perez-arlandis j. m., salter p. a., welton t.: phys. chem. chem. phys. 5 (2003) 2792-2794 38. wasserschied p., welton t.: ionic liquids in synthesis, vch–wiley, weinheim, (2002) 39. mehnert c. p., cook r. a., dispenziere n. c., mozeleski e. j.: polyhedron 23 (2004) 2679-2688 40. yan y., zhang, x.: j. am. chem. soc. 128 (2006) 7198-7202 41. deng c., ou g., she j., yuan y.: mol. catal. al 270 (2007) 76-82 42. howarth j.: tetrahedron lett. 41 (2000) 66276629 43. alcántara r., canoira l., guilherme-joao p., pérez-mendo j. p.: applied catalysis a 218 (2001) 269-279 44. song c. e., roh e. j.: chem. commun. (2000) 837-838 45. wang j. y., zhaob f. y., liu r. j., hua y. q.: j. mol. catal. a 279 (2008) 153-158 46. crosthwaite j. m., farmer v. a., hallett j. p., welton t.: j. mol. cat. a 279 (2008) 148-152 microsoft word 1_r.doc hungarian journal of industrial chemistry veszprém vol. 37(1). pp. 1-4 (2009) examination of the use of support materials of natural origin in wastewater treatment b. fazekas , v. pitás, p. thury, á. kárpáti university of pannonia, institute of environmental engineering, 8200, veszprém egyetem str. 10, hungary e-mail: fazekasb@almos.vein.hu wastewater has become continuously concentrated since 1990 in hungary as the price of drinking water started to increase intensively from that year. adding to that, reject water, leakages from landfills, and technological effluents of meat waste processing resulted in high specific nitrogen removal requirements at waste liquids of low cod/tkn ratio. separated treatment of such waste streams is strongly recommended. we applied zeolite and alginite (supporting materials of natural origin and low price) in three parallel experiments to examine their effects on nitrogen removal using synthetic wastewater in these trials. first we measured the efficiency of a cyclically aerated biofilter (zeolite bed). then we studied the efficiency of an as sbr (zeolite powder containing activated sludge unit, operated as sequencing batch reactor), finally we substituted zeolite with alginite. the last one has not been examined for improving nitrogen removal in wastewater treatment in our country till now. we tested the three versions parallel with their proper controls. that is why one of the reactors always contained the seeding activated sludge exclusively to compare the effect of the subsidiary component (zeolite/alginite). the best results were received with using zeolite to the activated sludge. it improved both nitrogen removal and sludge settling. addition of alginite to the as also considerably improved sludge settling even at low dosages; therefore further pilot plant controls are recommended before any industrial application of the two support material. keywords: zeolite, alginite, sbr, wastewater introduction water consumption started to decrease at the beginning of 1990 in hungary. the main reason for this was the significant change in the price of water. the average personal water consumption is 80–120 liters/day in the cities and 50–60 liters/day in the country (it is 150 liters/day in average in europe). in spite of that the amount of collected and purified sewage in the country has not decreased, moreover it slightly has increased because considerable areas have been canalized in the meantime. increase of concentration of the sewage is not serious problem in cod or bod removal, but it is for fulfilling the strict nutrient limits of the recipients or the discharge regulation especially in the tn figures. biological systems for nitrogen removal can be improved by separate treatment of highly concentrated waters, such as supernatant produced during dewatering of digested sludge, effluents from the fertilizer and fish canning industry, manure systems and landfill leachates. in wastewater treatment plants (wwtp) with anaerobic sludge digestion, a recirculated supernatant contributes to 10–15% of the influent nitrogen load. therefore, it is proposed to treat the supernatant separately rather than return it to the wwtp inlet for treatment as a part of the main flow [1–3]. as the specific nitrogen uptake and oxidation capacity of the activated sludge in the main stream can hardly be increased, this increase of ammonium load requires similar increase in treating volumes and biomass, or mixed liquid volumes. on the other hand the extra ammonium load of the highly concentrated reject water (0.5–1.5 g nh4-n/l in about 1 % of the main sewage flow) can separately be treated with sophisticated technologies nowadays [4–6]. aim of the experiments the aim of our experiments was to establish whether support materials of natural origin and low price (like zeolite and alginite) are suitable to be used as biofilm carriers. besides we were about to determine the capacity of ammonium fixation on zeolite in various surroundings and granulation size. we wanted to examine the influence of possibility of the zeolite used in sewage purification in various reactor constructions. for this reason we examined both biofilter and moving bed reactors [7-9]. we carried out measurements in terms of the efficiency of toc and nitrogen removal and sludge 2 settling. furthermore we studied the suitability of using alginite for the same purpose. support materials used synthetic wastewater was prepared using demineralized water, a nutrient mix necessary to maintain the bacterial growth. composition of the synthetic wastewater composition is shown in table 1. table 1: composition of synthetic wastewaters raw materials concentration (mg/l) milk-powder 0.52 urea 0.08 (nh4)2so4 0.10 caco3 0.05 na3po4·12 h2o 0.18 ch3coona.·3 h2o 0.03 c6h12o6 0.06 nh4cl 2.88 zeolites are aluminosilicates containing certain amount of water. their use in wastewater treatment is cited in several foreign and some hungarian publications. the main reason for their application is their considerable ion exchange capacity and selectivity to ammonium. the hungarian zeolite applied in the experiments had 82–84 % clinoptilolite content. when investigating the ammonium fixation capacity we intensively mixed certain grain sizes of zeolite in solutions with known ammonium content and finally measured the remaining ammonium concentration in the solutions. from that the amount of adsorbed ammonium was determined. the results can be seen in table 2. fraction of zeolite with bigger grain size was able to adsorb less than half of the amount of ammonium. table 2: capacity of ammonium fixation of zeolite fractions with various grain size grain size (mm) capacity of ammonium fixation (mg/g) >2 3.0625 0,5–1 7.3125 <0.5 6.8750 alginite is a rock with considerable organic material content formed of fossil biomass, basaltic tuff and limestone. it is rich in micro-, and macro-components, therefore we supposed that it can result in improving the nutrient supply of the activated sludge as well. we made a dissolution experiment with alginite. the results showed that organic material, equivalent of 40 mg cod/g alginite dissolved into a solution at 0.5 g alginite/liter dosage with intensive mixing. experimental device the experiments were carried out in sequencing batch reactors (sbr – fig. 1) with a parallel control unit containing only seeding activated sludge. the feed solution was synthetic sewage with high nitrogen (700– 800 mg nh4/l) and organic material (800–900 mg cod/l) content. figure 1: experimental reactor analytical methods all analyses were performed on grab samples taken from the reactors (once a day at the same time from the control and the test reactor) and completed in accordance with standard methods from filtrated samples. ammonium concentration was determined by lovibond 535650 vario am tube test reagent set hr 0–50 mg/l nh3-n and with lovibond pc multidirect spectrophotometer. chemical oxigen demand was measured after a destruction with potassium-dichromate by lovibond pcspectro spectrophotometer. the concentration of nitrate-nitrogen was measured according directions of msz 12750/18-74 standard. biomass concentrations were determined by measuring mlss and mlvss after desiccation of sludge on 105 °c and ignition on 600 °c. tn concentrations were measured by teledyne tekmar tn analyzer, while toc concentration by tekmar dohrmann apollo 9000 analyzer. ph and do was measured by specific electrodes. discussion and conclusions figure 2 shows the nitrogen removal of the test and control reactor and the theoretical ammonium concentration in the reactors formed by the influent. as it can be seen on the figure, the ammonium removal capacity of the biofilter made of zeolite grains was about twice as the control reactors. it might be due to the ammonium fixation of the zeolite or an advantageous surrounding for activity of the nitrifiers on the surface of zeolite grains. the reactor containing zeolite was able to remove almost the whole amount of influent ammonium. although the biofilter we made with the zeolite grains improved nitrogen removal it can not be used in practical application because the zeolite bed churned very fast and the sludge without mixing and aeration turned to anaerobic and began to rot. in the experimental period of the moving bed reactor (practically as) with zeolite we applied 1 g/l zeolite 3 concentration. it improved the nitrogen removal as can be seen in fig. 3. besides the previously mentioned facts it is important to note that the zeolite added to the activated sludge had a favourable effect even on sludge settling parameters. figure 2: nitrogen removal with the zeolite grains figure 3: nitrogen removal in moving bed reactor with zeolite the sludge of the reactor containing zeolite concentrated better then that of the control unit (with averagely 0.5–1 liters in the volume of 12 liters) during the settle phase of the sbr cycle. the incremental mass of sludge was not considerable, but the difference between the sludge concentration in the test and the control reactor remained the same during the whole experimental period. the sludge in the reactors is regarded to be underloaded with toc (that is the reason why the sludge degradation happened) but it is strongly overloaded with ammonium. the seeding sludge was not especially adapted for this application. nitrifying sludge with far better specific ammonium oxidation capacity is used at our simultaneous pilot-plant tests where the biofilm carrier is kaldnes ring support. using zeolite in this concentration and grain size can easily be realized in industrial application because on one hand the price of the amount of zeolite needed to form the 1 g/l concentration in the reactor is much less than that in the biofilter and on the other hand the possibility of rotting is not considerable in this configuration. longer experimental periods are recommended to make sure that biology is capable of the regeneration of zeolite saturated with ammonium and being a perfect carrier of well-nirtifying biofilm (as it is stated in several publications). the industrial application however is preferred for municipal wastewater treatment plants where a slight improving in the nitrogen removal with zeolite can be enough to fit the limit values or where the slow settling of sludge should be improved. zeolite as a support material might be suitable to reduce the amount of suspended solids in the effluent that is caused by biofilm detachment from the carrier, because the concentration of suspended solids in the effluent of the reactor containing zeolite was far lower than in the treated effluent of the control reactor. further experiments are needed to final proposal of the correct dosing of the zeolite. we measured in our next trials whether the dissoluble components of the alginate will disturb the toc or the ammonium removal. dosing of 0.5 g alginite/l obviously improved sludge settling which is shown in fig. 4 figure 4: sludge settling with and without alginite the results of our experiments show that the alginite is similarly useful material in wastewater treatment as zeolite is. however the price of the alginite is much lower. so it can be preferred as flocculating aid and biofilm support in hybrid as-biofilm sewage treatment systems. alginite costs 18 €/tons while zeolite costs 100–120 €/tons. its addition in such systems will also decrease the amount of suspended solids remaining in the effluent. further pilot plant experiments are designed to determine the right dosage requirements. references 1. gut l., płaza e., trela j., hultman b., bosander j.: combined partial nitritation/ anammox system for treatment of digester supernatant, water sci. technol. 53 (12) (2006) 149-159. 2. beun j. j., heijnen j. j., van loosdrecht m. c. m.: n-removal in a granular sludge sequencing batch airlift reactor, biotechnol. bioeng. 75 (1) (2001) 82-92. 3. wett b., rostek r., rauch w., ngerle k.: phcontrolled reject-watertreatment, water sci. technol. 37 (12) (1998) 165-172. with alginite without alginite 4 4. aneliak a., piaskowski k.: influence of zeolites on kinetics and effectiveness of the process of sewage biological purification in sequencing batch reactors. environment protection engineering, 31 (2005) 31-25. 5. he s-b., xue g., kong h-n.: the performance of baf using natural zeolite as a filter media under conditions of low temperature and ammonium shock load. journal of hazardous materials, 143 (2007, l -2) 291-295. 6. he s-b., xue g., kong h-n., li x.: improving the performance of sequencing batch reactor (sbr) by the addition of zeolite powder. journal of hazardous materials 142 (2007, 1-2) 493-499. 7. miladinovic n., weatherley l. r.: intensification of ammonia removal in a combined ion-exchange and nitrification coloumn. chemical engineering journal 135 (2008, 1-2) 15-24. 8. sarioglu m.: removal of ammonium from municipal wastewater using natural turkish (dogantepe) zeolite. separation and purification technology 41 (2005, 1) 1-11. 9. wu z., an y., wang z., yang s., chen h., zhou z., mai s.: study on zeolite enhanced contactadsorption regeneration-stabilization process for nitrogen removal. journal of hazardous materials (2008) << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word contents_2.doc hungarian journal of industrial chemistry veszprém vol. 31. pp. 9-12 (2003) chemical utilization of biomass ii: preparation of adsorbents from wheat straw to eliminate cupric and zinc ions of industrial wastewaters j. dencs, z. marton, b. dencs and g. marton university of veszprém, cooperative research centre h-8201, veszprém, pob 158. hungary agricultural residues represent a cheap and environmentally safe source of raw material for the preparation of ion exchangers and adsorbents that may be useful for removal of metals and/or colour from different wastewaters. metal ions (cd, cr, co, cu, fe, pb, mn, ni and zn) are known to contaminate the industrial effluents, water supplies, as well as mine waters. fish and textile plants may apply this method to eliminate contaminants in case of low ion concentrations far away from their source. the simultaneous biosorption of cu and zn ions from aqueous solution by straw based oxidised cellulose was studied. the adsorption equilibrium was attained in 24 h at room temperature. the adsorption was found to fit the modified langmuir type isotherms, and the parameters of the maximum adsorbent capacity and the adsorption intensity were calculated. keywords: adsorbents, straw, bio-based products introduction the sorption of heavy metal ions onto biosorbents from aqueous solution has been studied for single systems (xie, chang & kilbane, 1966). the influence of a second metal has also been investigated (trujillo, jeffers, ferguson & stevenson, 1991). chong and volesky (1996) reported a description of a two metal biosorption equilibrium using langmuir-type models. there have been several extended langmuir models applied to multicomponent sorption systems. jain and snoeyink (1973) developed an extended langmuir model by adding a term based on the hypothesis that in a multicomponent system adsorption occurs both with and without competition. a two-term expansion of the isotherm for competition equilibrium of the two components of a binary mixture has also been reported (levan & vermeulen, 1981). the present paper investigates the binary sorption of copper and zinc ions onto oxidised cellulose using three molar ratios of cu:zn. the model has been developed by incorporating an interaction factor correlation into the multicomponent langmuir equation. this model was originally developed by marton et al. (1981). materials and methods the batch sorption experiments for singlecomponent systems were carried out using a constant temperature shaking water bath and a series of capped 125 ml conical flasks. in the sorption isotherm tests, 0.5 g of straw sample was thoroughly mixed with the metal ion solution (125ml). the concentrations of the two metal, copper and zinc ions system ranged from 0.2 to 3 mmol/dm3. a similar procedure was used for the bi-component studies. three different systems were examined using copper and zinc in the molar ratios of 1:1, 1:2 and 2:1 (cu:zn) and in the concentration range of 0.5-4 mmol/dm3 for both cu and zn ions. 10 materials stock solutions of cuso4 and znso4 were prepared in distilled water. wheat straw was obtained from a local agro-refinery with the fraction 60-80 mesh particle size. pretreatment procedure consists of a cc. hno3 and h3po4 (1:1) treatment at 80 °c for 120 min and water washing. preparation of oxidized cellulose (oc) nitric acid (69.7%w/w) and phosphoric acid (85% w/w) were mixed in a 1:1 ratio. 5.0 g of straw sample was added to a 70 ml solution of the acid mixture. it was completely soaked and 1.0 g of sodium nitrate was added. an immediate formation of reddish brown fumes occurred. to prevent the release of these fumes into the air, the reaction container was covered with a petri dish. the reaction mixture was allowed to react at room temperature, with occasional stirring using a glass rod, for 12, 24, 36 or 48 h. the reaction mixture, which appeared green, was diluted by adding an excess of water (about five times the volume of the reaction mixture). the diluted reaction mixture was filtered, and washed with water until the filtrate showed a ph of about 4. it was finally washed with acetone and then air-dried at room temperature. the dried oc was ball milled for 24 h and then sieved. the solid product of the reaction contained particles ranging between 74 and 105 µm was used for the adsorption investigation. determination of carboxyl content this was performed according to the method described in the united states pharmacopoeia (usp, 1995). approximately 0.5 g of the sample was weighed and suspended in 50 ml of a 2% (w/w) calcium acetate solution for 30 min. the mixture was titrated with 0.1m naoh using phenolphthalein as an indicator. the volume of naoh solution consumed was corrected for the blank. the carboxyl content in the sample was calculated using the following relationship: 100 (mg)sampleofweight vm49w/w)(%groupscarboxyl ⋅ ⋅⋅⋅ = where m is the molality of naoh, and v is the volume of naoh in ml consumed in titration, after correcting for the blank. the carboxyl content of our product was 18.2%. isotherms equilibrium sorption studies provide the capacity of the sorbent, which can be described by a sorption isotherm characterised by certain constants whose values express the surface properties and affinity of the sorbent. sorption equilibrium is established when the concentration of sorbate in the bulk solution is in dynamic balance with that of the interface. equilibrium relationships between sorbent and sorbate are described by sorption isotherms. the data were determined and analysed in accordance with some of the most frequently used isotherms. the langmuir sorption isotherm (langmuir, 1916) is the best known and the most often used isotherm for the sorption of a solute from liquid solution: q c qb 1 q c e 1e e += (1) where qe is the sorption capacity at the equilibrium solute concentration ce (mmol/g); ce is the concentration of sorbate in solution (mmol/dm3); q is the maximum sorption capacity corresponding to complete monolayer coverage (mmol/g); bl is a langmuir constant related to the energy of sorption (dm3/mmol). butler and ockrent (1930) developed a model for competitive sorption based on the langmuir equation. this isotherm is applicable when each single-component obeys langmuir behaviour in a single-component system. it is widely used to calculate the langmuir constant q, the amount of solute sorbed per unit weight of the sorbent, in the multicomponent systems. the common form for depicting the sorbate distribution is to correlate the amount of solute sorbed per unit weight of the sorbent with the residual solute concentration remaining in an equilibrium state. if there are two solutes present together in the sorption system the extended langmuir isotherms are: 2211 111 1 cbcb1 cbq q ++ = (2) 2211 222 2 cbcb1 cbq q ++ = (3) where q1 and q2 are the amounts of solutes 1 and 2 sorbed per unit weight of the sorbent at equilibrium concentrations c1 and c2 respectively. 11 q1 and q2 are the maximum sorption capacities of 1 and 2, respectively. these are determined from single-component systems and, therefore, correspond to a monolayer coverage of the sorbent. b1 and b2 are the langmuir constants and are a function of the energy of sorption of solutes 1 and 2, respectively. these are also determined from single-component systems. these langmuir equations are simple extensions of the singlecomponent isotherms to multicomponent sorption. they assume that each component adsorbs onto the surface according to the ideal solute behaviour under homogenous conditions with no interaction or competition taking place between the molecules. extension of the langmuir and bet theory for the description of multicomponent liquid-phase adsorption according to the original langmuir hypothesis, the free area available for adsorption of component i is:         −στ= ∑ = n 1j iii0ii1 sqnzs (4) let us assume that the ratio of free and occupied area of the adsorbent is: ( )∑∑ == δ−στ στ = n 1j ijjj0jj ii0ii n 1j j i qzn qzn s s (5) where δij is the surface-area-excess accounting for the difference in size and energy-state of the competing adsorbing components. by definition δij = 0 for each i = j, while for i ≠ j it may be a positive or negative number, or zero. by substituting eq. 5 into eq. 4 we obtain: ( )             δ−στ στ −στ= ∑ = = n 1i 1j ijjj0jj ii0ii i ii0iii qzn qzn sqnzs (6) let us introduce: iii0ii cbnz =στ (7) let us make use of the statement of bet theory, i.e. that at low concentration of the adsorbent component: i n 1i iii qck1s         −= ∑ = (8) by substituting eq. 7 and 8 into eq. 6 we obtain: ( )         − ⋅ δ−+ = ∑∑ = = = n 1i ii n 1i 1j ijjjj i iii i ck1 1 qcb q 11 qcbq (9) let us introduce: ( ) i ijjj ji q qb b δ− = (10) for two components eq. 9 becomes: 22112211 111 1 ckck1 1 cbcb1 cqbq −− ⋅ ++ = (11) 22111122 222 2 ckck1 1 cbcb1 cqbq −− ⋅ ++ = (12) k1 and k2 in the equations 11 and 12 are so called interaction factors. results and discussion the data were examined by linear regression analysis using equations 11 and 12. table 1 shows the modified langmuir parameters for the adsorption of cu(ii) and zn ions. comparison of measured and calculated data (fig 1) produced an excellent (>0.98) correlation coefficient for the bicomponent system. table 1: modified langmuir parameters for the adsorption of cu(ii) and zn(ii) for the eq. 11 and 12. sample q1 q2 b1 b2 k1 k2 mmol/g dm3/mmol untrd. straw 0.072 0.066 0.52 0.37 0.021 0.013 oxidized straw 0.321 0.293 0.98 0.83 0.043 0.080 12 0 50 100 150 200 250 300 350 400 450 500 0 50 100 150 200 250 300 350 400 450 measured q1 (mmol/kg) pr ed ic te d q 1 (m m ol /k g) cu:zn = 1:2 2:1 figure 1: the relationship between measured and predicted amount of adsorbed component of cu ion in the presence of zn ion. conclusions a series of modified extended multicomponent langmuir isotherms have been used to correlate binary copper-zinc equilibrium sorption study results using oxidised wheat straw. because of complexity of the mechanism of biosorption a new interaction factor-combined equilibrium model has been developed. symbols a specific surface area of adsorbent, m3/kg b adsorption energy coefficient, m3/mol c1 concentration of i-th component, mol/m3 k1 bet constant, m2/mol n avogadro’s number, 1/mol qi amount of adsorbed component, mol/kg q ultimate uptake capacity, mol/kg r universal gas coefficient, m2 bar/k mol si surface covered by i-th solute, m2 zi collison frequency factor of i-th solute σ0i actual area of one adsorbed molecule, m2 τi residence time on the surface of i-th solute, h subscripts i, j …, …, n component c calculated m measured references 1. xie j. z. and chang h. l.: (1996) biores. techn. 57, 127-136 2. trujillo e. m; jeffers t. h.; ferguson and stevenson, h. q.: (1991) environ. sci. and technol. 25, 1559-1565 3. le van m. d. and vermeluen t.: (1981) journ. of phys. chem. 85, 3247-3250 4. marton g.; dencs j.; szokonya l. and illés z.: hung. journ. ind. chem. (1981), 9, 251-262 microsoft word b_13_r.doc hungarian journal of industrial chemistry veszprém vol. 38(2). pp. 117-121 (2010) photofermentative production of hydrogen by thiocapsa roseopersicina from simple organic substrates é. molnos1,2 , a. nyilasi1,3, g. rákhely1,3, o. muntean2, k. l. kovács1,3 1department of biotechnology, university of szeged, 6726 szeged, közép fasor 52., hungary e-mail: harai_eva@yahoo.com 2faculty of applied chemistry and material science, politehnica university of bucharest 060042 bucureşti, spl. independenţei 313., românia 3institute of biophysics, biological research centre, hungarian academy of sciences 6726 szeged, temesvári krt. 62, hungary, e-mail: kornel@brc.hu h2 is an ideal, clean and potentially sustainable energy carrier for the future due to its large energy content per weight, abundance and non-polluting nature. the selection of optimal h2 production technology depends on the h2-producing enzymes available. thiocapsa roseopersicina contains a nitrogenase and several [nife] hydrogenases, which participate in h2 metabolism. in the present study, h2 production by the hox1 soluble hydrogenase and the nitrogenase were investigated. the amount of h2 evolved by the nitrogenase enzyme was much higher than the amount produced by the hox1 hydrogenase enzyme. by comparing the h2 production by nitrogenase from five short-chain organic acids (acetate, citrate, pyruvate, succinate, formate) the highest productivity of h2 (~3 times) was observed in the presence of 4 g/l pyruvate. in this case, the pyruvate consumption was 100%, the biomass growth was equal to that of the control, therefore the produced h2 derived from pyruvate. keywords: hydrogenase, nitrogenase, photofermentation, thiocapsa roseopersicina, biohydrogen introduction biohydrogen can be produced by anaerobic microorganisms and considered as a potential energy carrier of the future [1]. the anaerobic, non-photosynthetic bacteria decompose organic compounds (most frequently carbohydrates) into organic acids, carbon dioxide and h2, but the subsequent anaerobic conversion of the organic acids is not feasible energetically in dark fermentation [2]. however, some photosynthetic bacteria manage to further exploit these organic acids, driven by solar energy due to the light-harvesting pigments found in the bacterial cell membrane. being intimately linked to light energy, the process that makes possible the decomposition of organic acids into h2 and carbon dioxide is called photofermentation [3]. hydrogenase enzymes play pivotal role in photofermentative h2 production as a biocatalyst of the reversible oxidation of molecular h2. h2 is also generated by nitrogenases, which catalyze the reduction of molecular nitrogen into ammonia and that is accompanied by the reduction of protons to h2 [4, 5]. photosynthetic bacteria have long been studied for their capacity to produce h2 [1]. the nitrogenase based h2 production in purple non-sulphur bacteria is the major field of research [6], while the study of nitrogenase mediated h2 production in purple sulphur bacteria seems to be a novel approach. our model organism, thiocapsa roseopersicina bbs is an anaerobic, purple sulphur phototrophic bacterium which contains at least four distinct and active [nife] hydrogenases: two membrane-bound (hynsl, hupsl) and two soluble (hox1efuyh, hox2fuyh) enzymes as well as a nitrogenase enzyme [7, 8]. in this study, the h2 productivity of the hox1 soluble hydrogenase and the nitrogenase were compared. moreover, the basic growth medium was supplemented with various organic carbon substrates in order to identify the ones the bacteria could use as electron source to produce h2. the organic acids are utilized in diverse metabolic pathways. electrons formed by biochemical reactions are transferred by cofactors as long as they get to the enzyme and become reduced to h2. materials and methods bacterial strains and growth conditions mutant strains of t. roseopersicina bbs (wild type) used in this study were gb1121 (δhynsl, δhupsl) and m539 (δhypf) [9] for hox1-mediated and nitrogenasebased h2 production measurements, respectively. as negative control gb112131 (δhynsl, δhupsl, δhox1efuyh) and m539 (δhypf) under non-nitrogen fixing conditions were applied. hypf is an accessory 118 protein that is required for the biosynthesis of all active [nife] hydrogenases. all strains were grown anaerobically in liquid cultures with continuous illumination (35 μmol photons·m-2·s-1 light intensity) at 25ºc in pfennig's mineral medium (2% nacl, 0.1% kh2po4, 0.1% mgcl2, 0.1% kcl, 0.1% nh4cl as nitrogen source, 0.2% nahco3 as carbon source, 0.4% na2s2o3, 20 μg/μl vitamin b12, 3.3 mg/l fe-edta, 2.975 mg/l na2-edta, 0.3 mg/l h3bo3, 0.2 mg/l cacl2, 0.1 mg/l znso4, 0.03 mg/l mncl2, 0.03 mg/l na2moo4, 0.713 mg/l nicl2, 0.01 mg/l cucl2). for nitrogen-fixing conditions, the nh4cl was omitted. the growth media were supplemented with various carbon sources (acetate, citrate, formate, pyruvate, succinate) and tested at different initial concentrations (2 g/l, 4 g/l, 6 g/l). in vivo h2 evolution activity measurements cultures (20 ml and 60 ml) were grown in 27 ml and 100 ml hypovials; the gas phase was flushed with n2 after inoculation. the produced h2 was determined daily by gas chromatograph [9] (agilent technologies 6890n equipped with molesieve 30 m x 0.53 mm x 25 μm column and thermal conductivity detector; oven and detector temperature 160 °c, mobil phase: n2). organic-acid analysis in order to determine the residual organic acid concentrations in the culture medium, 1 ml of cell suspension was centrifuged at 13000 rpm for 10 min, and 50 μl of the supernatant was analyzed by hplc (hitachi elite, equipped with icsep ice-coregel 64h column and refractive index detector l2490) using the following parameters: solvent 0.1 n h2so4, flow rate 0.8 ml/min, column temperature 50 °c, detector temperature 41 °c. results and discussion biohydrogen production by hox1 hydrogenase and nitrogenase enzymes the h2-evolving enzymes used by most biohydrogen evolving systems are nitrogenases and hydrogenases. in order to compare the h2 productivity of the hox1 [nife] hydrogenase and the nitrogenase enzymes in t. roseopersicina, two mutant strains were used. 0 1 2 3 4 5 6 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 days m l h 2 /l cu ltu re hox1 hydrogenase negative control 0 5 10 15 20 25 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 days m l h 2/l cu ltu re nitrogenase negative control figure 1: in vivo daily h2 production by hox1 hydrogenase (a) and by nitrogenase (b) the quantity of the h2 produced by hox1 hydrogenase (gb1121 strain) and nitrogenase (m539 strain) enzymes was measured daily. it has to be noted, that although the gb1121 strain contains the genes encoding the hox2 hydrogenase too, this enzyme does not evolve h2 in the circumstances studied [8]. it was observed that the amount of h2 produced by the nitrogenase enzyme under nitrogen-fixing conditions was much higher than the amount produced by the hox1 hydrogenase enzyme under nitrogenase repressed conditions (fig. 1). however, almost no nitrogenase-based h2 production was observed after the 7th day, while the hox1 hydrogenase-based h2 production lasted for two more weeks. moreover, the daily removal of h2 from the headspace of the culture (a) (b) 119 which produces h2 via hox1 hydrogenase resulted in a relatively high h2 production rate (1.018 ml h2/l culture/day). it has to be noted that, in all experiments, the strains used as negative control did not produce detectable amounts of h2. substrates for biohydrogen production photosynthetic bacteria are able to produce h2 from various reduced compounds; therefore, they are favourable substrates for biological h2 production. the bacteria are capable of evolving h2 from a wide range of organic acids, as well as from hydrogen sulphide, elemental sulphur or thiosulphate if co2 is supplied as carbon source. the conversion of different organic acids into h2 – which would be advantageous for coupling clean, bioenergy production with organic waste-treatment – by different purple non-sulphur bacteria is well documented [10, 11], but little is known about the affinity of the purple sulphur bacteria to these organic acids. therefore, by supplementing the growth medium (20 ml) with various organic acids, the conversion efficacies of these substrates by t. roseopersicina strains were tested. the experiments were repeated 3 times (except the asterisk labeled data in table 1) using different initial concentrations of the substrates as listed in table 1. the values given in table 1 are the mean value of the data measured at day 9 of growth. the relative h2 production refers to the h2 produced by the same culture without supplementation. the h2 produced by the cultures without supplementation in different runs are taken as 100%. the data clearly show, that the hox1 hydrogenase mediated h2 production was negatively influenced by the organic acids present in the culture medium containing elevated amount of thiosulphate. however, at lower thiosulphate concentration, acetate driven hydrogen production could be observed (data not shown). supplementation of the nitrogen-fixing medium used for nitrogenase-based h2 production with different organic acids resulted in higher h2 production in case of the pyruvate and succinate. the increase of the initial concentration of pyruvate from 2 g/l to 4 g/l, increased the amount of h2, but further increase of the substrate concentration to 6 g/l decreased the h2 production. additionally, almost all of the added pyruvate was consumed in the first two cases (2 g/l and 4 g/l), while in the third case (6 g/l) the substrate consumption was only 77% in the first 9 days of the experiment. similar results were found in case of supplementing the growth medium with succinate with the difference that the volumes of h2 produced were less, and the substrate consumption rates were lower, too. in the course of experiments, the bacterial growth was measured beside the h2 production. the application of 2 and 4 g/l pyruvate did not result in higher biomass growth (8.65 g cell/l culture and 8.4 g cell/l culture, respectively) compared to the pyruvate-free control (8.8 g cell/l culture); therefore it is likely that the extra h2 derived from the pyruvate. nevertheless, in the case of 6 g/l pyruvate not only the biomass concentration was increased (18.5 g cell/l culture), but also the specific h2 production was enhanced. table 1: hydrogen production by hydrogenase (hox1) and nitrogenase (n2ase) h2 production (ml h2/l culture) relative h2 production (%) relative substrate consumption (%) organic compound initial conc. (g/l) hox1 n2ase hox1 n2ase hox1 n2ase 2 0.51 110 16 90 74 74 4 0.59 49 9 68 54 53 acetate 6 0.46* 17* 46* 2 2.27 110 65 94 -36 -30 4 4.60 76 60 97 13 18 citrate 6 0.90* 33* 44* 2 2.48 219 63 185 100 99 4 0.55 251 9 307 85 97 pyruvate 6 0.59* 227* 22* 211* 97* 77* 2 1.19 178 39 151 98 40 4 2.31 214 30 263 71 32 succinate 6 0.85* 226* 32* 209* 70* 31* 2 0.60 62 17 53 39 34 formate 4 0.81 33 14 45 45 47 the effect of pyruvate addition on the nitrogenase-based biohydrogen evolution in order to test the observation that in the case of nitrogenase, the extra h2 was derived from the pyruvate, the same experiment was repeated with 2 g/l pyruvate in 60 ml culture volume. on day 13, when no h2 production was observed, further pyruvate was added. during the experiments the total h2 production, pyruvate concentration and the amount of biomass were measured daily. fig. 2a illustrates the h2 production with or without pyruvate and the variation of pyruvate concentration in time. visible improvement in the h2 evolution was observed after supplementing with pyruvate, moreover the in vivo h2 generation started at day 3, 2 days earlier than the control. this result is in agreement with the tendency of the bacterial growth (fig. 2b). 120 the supplementation with pyruvate enhanced the bacterial growth, but at day 9 both culture reached the same level. further addition of pyruvate to the culture in stationary phase (day 13) resulted in a lower rate increase of h2 production, which is caused by the repression of nitrogenase due to the production of organic nitrogen compounds. remarkably, a 2-fold difference in the amount of h2 produced by nitrogenase from 2 g/l pyruvate in 20 ml and 60 ml cultures (220 ml h2/l culture and 420 ml h2/l culture, respectively) was observed. the pyruvate-free control did not show any difference in 20 ml and 60 ml culture (98 ml h2/l culture and 96 ml h2/l culture, respectively). these results indicate that accumulation of h2 in the headspace may have an inhibitory effect on biohydrogen production, which has to be considered in scale-up experimental design. 0 20 40 60 80 100 120 140 0* 1 2 3 4 5 6 7 8 9 10 11 12 13* 14 15 16 17 18 19 days m l h 2/l cu ltu re 0 0.5 1 1.5 2 2.5 3 py ru va te c on ce nt ra tio n, g /l without pyruvate with 2g/l pyruvate pyruvate concentration 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 days o d 68 0 nm without pyruvate with 2g/l pyruvate figure 2: effect of 2 g/l pyruvate on in vivo h2 production by nitrogenase (a) and biomass growth (b) in summary both nitrogenase and hox1 hydrogenase can catalyze biohydrogen production from simple and inexpensive organic substrates in photoheterotrophic mode of growth. the overall h2 yield generated by the nitrogenase system is higher, i.e., about 55 ml h2/l culture compared to the 25 ml h2/ l culture for hox1. nitrogenase evolves h2 intensively in short term while hox1 [nife] hydrogenase is capable of sustained in vivo biohydrogen production, which may have important ramification for large scale exploitation. acknowledgements this work was supported by eu projects hyvolution fp6-ip-ses6 019825 and fp7 collaborative project solar-h2 fp7-energy-212508, and by domestic funds (gop-1.1.2.-07/1-2003+8-0007, asbóth-damec-2007⁄09, baross_da07_da_ tech-07-2008-0012, and kn-ret07⁄2005). the financial assistance from the sectoral operational programme human resources development 2007–2013 of the romanian ministry of labour, family and social protection through the financial agreement posdru/6/1.5/s/19 is gratefully acknowledged by éva molnos. references 1. d. das, n. khanna, t. n. veziroğlu: chemical industry and chemical engineering quarterly, 14(2), 2008, 57–67. 2. p. c. hallenbeck: international journal of hydrogen energy, 34, 2009, 7379–7389. 3. a. asada, j. miyake: journal of biosciences and bioengineering, 88(1), 1999, 1–6. 4. p. tamagnini, r. axelsson, p. lindberg, f. oxelfelt, r. wünschiers, p. lindblad: microbiology and molecular biology reviews, 66(1), 2002, 1–20. 5. k. l. kovács, g. maróti, g. rákhely: international journal of hydrogen energy, 31, 2006, 1460–1468. (a) (b) 121 6. n. basak, d. das: world journal of microbiology and biotechnology, 23, 2007, 31–42. 7. k. l. kovács, á. t. kovács, g. maróti, l. s. mészáros, j. balogh, d. latinovics, a. fülöp, r. dávid, e. dorogházi, g. rákhely: proceedings of 7th international conference on hydrogenases, 2004, 61–63. 8. j. maróti, a. farkas, i. k. nagy, g. maróti, é. kondorosi, g. rákhely, k. l. kovács: applied and environmental microbiology, 76(15), 2010, 5113–5123. 9. b. fodor, g. rákhely, á. t. kovács, k. l. kovács: applied and environmental microbiology, 67, 2001, 2476–2483. 10. m. j. barbosa, j. m. s. rocha, j. tramper, r. h. wijffels: journal of biotechnology, 85, 2001, 25–33. 11. h. koku, i̇. eroğlu, u. gündüz, m. yücel, l. türker: international journal of hydrogen energy, 27, 2002, 1315-1329. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 119-123 (2008) mass transfer characteristics of isopropanol pervaporative dehydration through cmc-ca-01 membrane l. takács, gy. vatai corvinus university of budapest, department of food engineering, h-1118 budapest ménesi út 44., hungary e-mail: gyula.vatai@uni-corvinus.hu pervaporation can subsitute conventional azeotropic distillation as an alternative dehydration process. applying this technique, the azeotropic point of azeotrope can be exceeded without any additives under boiling temperature. the entire energy used for dehydration is substantially lower in comparison with azeotropic rectification, furthermore, this modern separation process without additives can be part of an enviromentally conscious technology. in the course of our experiments we described with the pervaporational behavior of isopropyl alcohol from experimental data of model solutions. at the corvinus university of budapest, department of food engineering the matemathical modeling was carried out, using our earlier experimental data whith cmc-ca-01 membrane [1]. the aim of this calculations was the definition of the mass transfer properties of the membrane and development of design eqauations for industrial application. as the results are demonstrated, that membrane characteristic defined by resistance in series model provides fundamentals for technological design to industrial application and for the economical examination. and it also provides data for the process simulation of hybrid technology. keywords: pervaporation, isopropanol, membrane, modelling, dehydration introduction isopropyl alcohol is a solvent, which is widely used in chemical and pharmaceutical industry. it is used as an organic solvent in the pharmaceutical industry, in the process of esterification, and in electronics it is the cleaning agent of fine pieces. it is a well known phenomenon, that isopropyl alcohol composes azeotrope with water, which makes the recovery of water from industrial byproducts more difficult in conventional distillation [2]. the conventional industrial processes needs the application of further additives. in the course of azeotropic destillation they use di-isopropyl-ether, benzene or cyclohexane [3], and in case of extractive distillation ethylene-glycole as the carrier agent [4]. the advantage of pervaporation is that azeotrope can be separated simply whithout additives forming terner. in addition to applying this process in chemical industry, this method of dehdydration of isopropanol by pervaporation of azeotrope can be prepared to substitute the solvent for extraction of edible oils in edible oil processing industry. the isopropanol has the sufficient properties, although its oil absorbing capacity is lower than that of the hexane, it can not be neglected as an organic solvent in the process of extraction [5]. as the oil absorbing capacity of isopropanol is substantially higher than the azeotrope, its absolutization is very important, and it can be carried out economically by pervaporation [1]. the industrial application of this process can be justified by the technologyand costefficiency of pervaporation. in the centre of the scientific and industrial development stands the hybrid separation technology. to reach the azeotropic point the technology based on the conventional distillation technique and the pervaporational dehydration is applied effectively in the branches of chemical industry [6]. a lot of researchers deal with the optimization of hybrid technology. the optimization is based on experimental results, which is followed by an optimization program on pc and process simulation using theoretical and half-empirical mathematical models, determining the parameters of the applied model [7]. however the characteristics of the applied membrane has to be known to put the pervaporation into process simulation environment [8]. the characteristic of pervaporation membrane can be evaluated from the view of capacity/permeability and the separation efficiency of the membrane. permeate flux is the permeate pervaporated and condensed in the pervaporative system during time unit through the membrane surface. τ⋅ = a mj p (1) where: j – the permeate flux (kg/(m2h)), a – the membrane surface (m2), τ – the pervaporation time (h). the selectivity shows in which the component, permeating through the membrane is enriched in comparison with the feed solution. 120 if ip i x x , ,=β (2) where: βi – selectivity of (i) component (-), xf,i – feed concentration of (i) component (kg/kg), xp,i – permeate concentration of (i) component (kg/kg). the separation factor shows how effectively the membrane can separate the two components. )1( )1( ,, ,, ifip ipif i xx xx −⋅ −⋅ =α (3) where: αi – selectivity of membrane concerning to (i) component (-). the pervaporation separation index describes the effectiveness of the process as overall effect of permpeate flux and separation factor. ii jpsi α⋅= (4) where: psii – pervaporation separation index of (i) component (kg/(m2h)). material and method to modeling of the behavior of izpropil alcohol pervaporation is based on the results of the experiments of isopropanol water model solutions examined by atra et al. (1999) [1], which had feed concentration close to azeotropic composition. the experiments were carried out in a laboratory pervaporation equipment with cmc-ca-01 type membrane made by the swiss celfa membrantechnik firm. the feed was circulated over the 110 cm2 active hydrophyl membrane surface at 45, 55, 65 °c temperature with 200 l/h recirculation bulk flow rate, while 30 mbar pressure was set on permeate side. the amount, and the compositon of the gained pervaporation products were measured, and the flux of permeate was determined from a 200 ml feed model solution in a five-hour interval in the course of our experiments we calculated the characteristics of pervaporation from the entire, 25 hour pervaporation period. mathematical modeling of pervaporation to describe the mass transfer of the membrane both the concentration and partial vapour pressure are suitable. however, in case of pervaporation, partial vapour pressure as a driving force characterises better for the process description [9]. )( ,,, igiliovi ppaqj −⋅⋅= (5) where: ji – mole stream of (i) component through the membrane [mol/s], qov,i – overall mass transfer coefficient of (i) component with driving force of partial vapour perssure (mol/m2pas), a – the membrane surface (m2), pl,i – partial vapour pressure of (i) component at feed side (pa), pg,i – partial vapour pressure of (i) component at permeate side (pa). l iiil il pc p ρ γ 0 , , ⋅⋅ = (6) where: cl,i – molar concentration of (i) component at liquid side (mol/m3) γi – activity coefficient of (i) component at liquid side calculated by nrtl method [10], pi o – saturated vapour pressure of (i) component (pa) [11], ρl – molar density of liquid (mol/m3). g ig ig pc p ρ ⋅ = , , (7) where: cg,i – molar concentration of (i) component on permeate side (mol/m3), p – entire pressure of solution at permeate side (pa), ρg – molar density of vapour phase at permeate side (mol/m3). assuming that the resistance at permeate side is negligible [7-9], the mass transfer through the membrane can be desribed by linear resistance model as follows [12]: ilimiov qqq ,,, 111 += (8) where: qov,i – overall mass transfer coefficient of (i) component with driving force of partial vapour perssure (mol/m2pas), ql,i – mass transfer coefficient of (i) component with driving force of partial vapour perssure at liquid side (mol/m2pas), qm,i – mass transfer coefficient of (i) component with driving force of partial vapour perssure in membrane (mol/m2pas). the mass transfer coefficient of liquid side with the driving force of partial vapour pressure: il ii il il k p q ,0 , , ⋅ ⋅ = γ ρ (9) where: kl,i – mass transfer coefficient (i) component with driving force of concentration-difference at liquid side (m/s). 121 e ji il d dsh k , , ⋅ = (10) where: sh – sherwood-number, di,j – diffusivity of (i) component in (j) solvent by wilke-chang equation (m2/s) [13], de –equivalent diameter calculated by the geomethric relations of the membrane modul (m). the sherwood-number can be described with the equation below in case of laminar bulk flow [14]: 3 1 re85,1 ⎥⎦ ⎤ ⎢⎣ ⎡ ⋅⋅⋅= l dscsh e (11) l lel dv η ρ⋅⋅ =re (12) where: vl – flow rate of liquid/feed (m/s), ηl – dynamic viscosity of liquid (pas). results and evaluation by similar settings, water fluxes on different temperatures become more dynamic if we rise feed concentration (fig. 1). higher feed concentration results higher driving force, which helps favourable membrane permeation. permeate yield also rises with temperature. on the one hand the liquid side partial pressure rising with temperature has strengthening effect on driving force due to the rise of saturation pressure, the water molecules diffuse more intensively on a higher temperature on the other hand. [15]. flux values vary in the lowest range at 45 °c on cmc-ca-01 membrane, but there is no significant difference between 55 and 65 °c. however during the pervaporative process the concentration-polarisation of the accumulating molecules in the boundary-layer close to the membrane intensifies on every temperature. this has a counter-effect on mass transfer and it is presented in the variation of the entire mass transfer coefficient of water through the membrane (fig. 2). this effect leads to a rising resistance in the hydrodinamic boundary-layer at liquid side, which becomes more intense by lower feed concentraiton which means the end of pervaporative dehydration. this can also be observed in case of water, in the variation of mass transfer coefficients, at liquid (feed) side with the driving force of concentration difference, as a function of pervaporation time (fig. 3). it can be determined that the mass transfer coefficient of water at liquid side is higher with orders of magnitude than the overall and the membrane mass transfer coefficient regarding to values studied at different temperatures with the driving force of partial pressure (fig. 4). thus it has no effect on overall mass transfer, and the function in pervaporative resistance in serial resistance model is negligible. it can be seen in fig. 4, that the mass transfer coefficient of membrane is equal to the overall mass transfer coefficient, hereby the mass transfer is determined by the membrane and its structure in each case [16]. figure 1: water flux as a function of water content of feed at different temperatures figure 2: overall mass transfer coefficient calculated for water as a function of pervaporation time figure 3: mass transfer coefficient at liquid side as a function of pervaporation time with the driving force of concentration difference at different temperatures all this phenomenon is a results of the favourable hydrodinamic conditions, which make prosperous circumstances. on the one part it affects favourably the mass transfer through the well-known material and hydrodynamic characteristics, on the other part the 122 continous intensive flux inpedes the formation of partition balance between boundary-layer and the membrane and lowers the degree of concentration polarisation, which rises the resistance at liquid side. figure 4: coefficients in mass transfers a function of feed concentration at different temperatures figure 5: separation factor of water as a function of feed concentration at different temperatures the vapour phase containes more isopropanol through the progress in view of applied temperatures during dehydration experiments. this phenomenon can be noticed at every temperature which decreases the separation effeciency. all these reveal themselves in the decreasing tendency of separation factor in case of water. water separating ability of the membrane is decreasing by the feed concentration (fig. 5). the phenomenon can be explained by the theory of “free volume” [17]. the polimer chaines setting up the membrane, on account of accelerating heat movement, create free volumes open for the diffusing molecules. the flexible volume enlargement decreases energy need to diffusive mass transfer, hereby enables faster movement of water molecules inside the membrane resulting in a mending pervaporative yield. at the same time all these facilitate the permeation of more undesired isopropylalcohol molecules lowering the efficiency of dehydration. by the decreasing feed concentration the membrane selectivity and separation ability referred to water lowers by the reasons mentioned before. the pervaporation separation index follows a decreasing tendency as well, however at a higher temperature it moves a in higher range because of the more favourable flux (fig. 6). flux and separation coefficient changes opposite direction to the increase of temperature. nevertheless, the degree of the change is higher in case of permeate flux, so because of its rising, the increase in pervaporation separation index can be noticed. figure 6: pervaporation separation index of water as a function of feed at different temperatures conclusion the characteristic of cmc-ca-01 type hydrophyllic pervaporation membrane defined by serial resistance model provides principles to mechanical, technological design and to the economical examination of the process for industrial application, together with provides model for the computerized process simulation of hybrid technology [17-22]. the proposed equations are suitable for optimization of the industrial process. the efficiency of dehydration decreases with feed concentration, so continous technology can be preferred. rising the temperature gets better productivity of the process, however the selectivity and the separation factor decrease. so the energy investment into the pervaporation rises the yield of the process, but over a certain feed temperature the dehydration efficiency decreases. regarding to the mass transfer characteristics and the connection among these, the liquid side resistance in the pervaporation process is negligible, so the pervaporative resistance is influenced by only the material and the structure of the membrane. references 1. atra r., vatai gy., békassy-molnar e.: isopropanol dehidration by pervaporation, chemical engeneering and processing 38 (1999) 149-155. 2. lee y. m., nam s. y., lee b. r., woo d. j., lee k. h., won j. m.: dehydration of alcohol solutions through crosslinked chitosan composite membranes; preparation of chemically crosslinked chitosan composite membranes and ethanol dehydration, membrane (korea) 20 (1996) 37-43. 123 3. van hoof v., van den abeele l., buekenhoudt a., dotremont c., leysen r.: economic comparison between azeotropic distillation and different hybrid systems combining distillation with pervaporation for the dehydration of isopropanol, sep. purif. technol. 37 (2004) 33-49. 4. sommer s., melin t.: design and optimization of hybrid separation processes for the dehydration of 2-propanol and other organics, ind. eng. chem. res. 43 (2004) 5248-5259. 5. lusas e. w., watkins l. r., köseoglu s. s.: isopropyl alcohol to be tested as solvent, inform, 2 (1991), 970-976. 6. kreis p., gorak a.: process analysis of hybrid separation processes combination of distillation and pervaporation, chemical engineering research and design, 84 (2006) (a7): 595-600 7. gómez p., ibáñez r., ortiz i., grossmann i.: optimum design of pv processes for dehydration of organic mixtures, desalination 193 (2006), 152-159. 8. verhoef a., degreve j., huybrechs b., van veen h., pex p., van der bruggen b.: simulation of a hybrid pervaporation–distillation process, computers and chemical engineering 32 (2008), 1135-1146. 9. ji w., sikdar s. k., hwang s.-t.: modeling of multicomponent pervaporation for removal of voc’s from water, j.membr. sci. (1997) 128, 195 10. reid r. c., prausnitz j. m., poling b. e.: the properties of gases and liquids fourth edition mcgrw-hill book company (1985) 247-263 11. shuzo o.: computer aided data book of vapor pressure, (1976) data book publishing company tokyo-japan 12. oliveira t., scarpello t., livingston a.: pervaporation-biological oxidation hybrid process for removal of volatile compounds from wastewaters, journal of membrane science, 195 (2002) 75-88. 13. wankat p. c.: rate-controlled separations. glasgow: blackie academic & professional (1994). 14. hwang s. t., kammermeyer k.: boundary layer phenomenon membranes in separations. john wiley and sons, (1975). 15. huang r. y. m.: pervaporation membrane separation processes. amsterdam – oxford – new york – tokyo, elsevier, (1991). 16. mora j. m., meszaros p., vatai gy., békássyné-molnár e.: eliminación del etanol de solución modelo y del agua residual farmacéutica por pervaporación (in spanish), tecnología en marcha 15 (2003)1-9. 17. atra r.: application of membrane separation processes in dairy and distillery industry (in hungarian), phd thesis, szent istván university, budapest, (2000). 18. bélafi-bakó k., kabiri-badr a., dörmő n., gubicza l.: pervaporation and its application as downstream or integrated process, hung. j. ind. chem. 28, (2000)175-9. 19. koszorz z., nemestóthy n., dörmő n., ziobrowski z., bélafi-bakó k., gubicza l.: enzymatic esterification enhanced by pervaporation, proc. 4th sci. conf. membranes and membrane processes in environmental protection, zakopane (poland), (2002), pp. 189-195. 20. bélafi-bakó k., dörmő n., rodrigues c., schäfer t., crespo j. g., gubicza l.: enzymatic esterification coupled with pervaporation for natural flavour ester production, proc. engineering with membranes, granada (spain) vol. i. (2001) pp. 287-291. 21. figoli a., donato l., carnevale r., tundis r., statti g. a., menichini f., drioli e.: bergamot essential oil extraction by pervaporation, desalination, 193, (2006), 160-165. 22. vauclair c., schaetzel p., nobrega r., habert c.: dehydration of light oil by pervaporation using poly(vinyl alcohol)-poly(acrylic acid-co-maleic acid) membranes, journal of applied polymer science, 86, (2003) 1709-1716. microsoft word b_26_r.doc hungarian journal of industrial chemistry veszprém vol. 38(2). pp. 187-191 (2010) autonomous mapping in polluted environments i. szőke , a. majdik, d. lupea, l. tamás, gh. lazea department of automation, technical university of cluj-napoca, c. daicoviciu 15 cluj-napoca, romania e-mail: istvan.szoke@aut.utcluj.ro the need of ecological robots is imposed by the nowadays trend towards protecting the environment and the human factor. new researches in this area have arisen in the past years. in the next few lines an overview of the state of the art in this domain will be made, proposals go from robots designed to repair power line damage to robots for capturing photos of animals in the wild without human intervention. the main objective in this paper is to demonstrate the autonomous navigation of a mobile robot in a polluted environment. so far the research on robots used for detection of gas sources was focused mainly on indoor environments, but, in the recent years, a constant move towards the outdoor environment can be observed. there can be found several researches with different applications in the area of ecological robots. keywords: autonomous mobile robots, mapping, navigation, polluted enviromnets. introduction there are many kinds of environmental robots which have various usage in order to detect failures in proximity of the robot excluding the human being from a possible dangerous situation. describing a few prototype examples would demonstrate the utility of the research in this field. a first example would be a robot that is able to detect defects on power lines. the device uses rollers to clamp onto and move along a power line. the robot will do image analysis to see if there is something different with the structure compared to an earlier picture taken from the exact same spot, being able to remotely spot high-risk trees, which are the top cause of electrical outages. the prototype robot will also make sure there are no faulty connections that can cause overheating, and listen for electromagnetic "noise" that might indicate other problems with the equipment. figure 1: electric power research institute prototype another proposal is the traffic regulating robots powered by solar energy. qatar’s public works authority with support from the qatar science club will soon be developing new robots that will replace the manual methods used in guiding traffic at varies road project sites. the green robots will be powered by solar energy harvested by onboard solar panels. the robots will control traffic at major ongoing road projects in the main cities. the us scientists developed a solar-powered prototype and tested it in greenland. these are the next generation of antarctic explorer robots capable of driving hundreds of kilometers and doing scientific experiments alone. these could perform scientific experiments where access is currently difficult or expensive. there are two basic types of mission scenario one would be to stop the robot on the driving trajectory and take the data you need things like sampling for bacteria in the snow, measuring the atmosphere, or doing a glaciological survey with ground-penetrating radar [3]. another environmental robot, the dustcart , was developed by numerous european companies and universities, who aims to be a collecting and segregating garbage robot. what’s more, it can go door to door playing garbage man and can be summoned by a cell phone. to top it all off, it can also act as a mobile pollution monitor by monitoring atmospheric pollution levels. figure 2: the dustcart 188 research on using chemical sensors in robotic systems started in early nineties focusing on the development of two typologies of robots: the first typology is able to follow odor trails marked on the ground as ants follow a pheromone trail [1]; the second one is able to track odor trails formed in fluid media to find a chemical source [20, 9, 2]. nowadays this research field of finding places where chemical sources are present or in the air or on the ground surface or underground, has been widely spreaded. other robots for monitoring gas pollution in areas of interest have been proposed in literature. there are robots designed to monitor ammonia pollution near animal farms [11], robots designed to go into old mines and detect dangers of gas intoxication and so on. in case of the underground search finding unexploded ordinance, land mines, and sources of leaks from pipes and tanks are some examples. our project proposal is related to a mine exploration situation, where an autonomous robot is sent to explore the area in order to detect places where the air contains more chemical components than the normal values. the robot is creating the map of the environment, which is explored at exact intervallums. in case of pollution detection the robot is sending a warning signal to the server by wireless network. the warning message contains the position of the robot and the quantity of the pollution. using all these informations the rescue team can be sent to avoid more tragic events, explosions which can harm the mine workers. in fig. 3 can be seen a mine scene together with the pioneer robot, a four wheeled mobile robot which is used in our research project. figure 3: mine scene with the p3-at robot in the following sections the theories of the visual and laser system is described. these two systems are combined at different steps of the robots behaviour like the mapping, localization stages. theoretical background of the visual system building feature based maps in fig. 4 is shown the diagram of the visual feature based mapping algorithm. the visual data and the laser scans need to be taken synchronously. after the data acquisition is done from the displacement of the consecutive laser scans the robots displacement (translation and rotation) is computed with a standard iterative closest point algorithm [22] between two consecutive scans. because the test environment is relatively small a more complex scan registration method is not needed like in [14], where the problem of mapping a large mine is addressed. figure 4: diagram of the mapping algorithm in the mean time another task is to detect the image features on both of the stereo image pair synchronously. our algorithm uses image features detector and descriptor called surf. surf is an abbreviation from speeded up robust features; it is a method, known in the field of computer vision to detect interest points on images. surf was first introduced by [7], the advantage of this algorithm is the computational speed compared with other performing image feature detectors like scaleinvariant feature transform (sift) presented by [17], maintaining approximately the same or even better performances regarding: repeatability, distinctiveness and robustness. in [22] is concluded that surf is one of the most suitable descriptor for visual simultaneous localization and mapping applications. the algorithm and the performances are largely discussed in [6] and [16], whereas hereby only a short overview is presented. the main reason why the algorithm decreases the computational time is because surf uses integral images [16] as intermediate representation, in this way the sum of intensities over any upright, rectangular region is calculated with only four additions. the surf algorithm is based on the fast-hessian detector, which computes the determinant of the hessian matrix: ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ σσ σσ = ),(),( ),(),( ),( yyxy xyxx pp pp σp ll ll h (1) where with lxx(p,σ) is denoted the convolution of the second order gaussian derivative 2 2 )( x σg ∂ ∂ of the image at point p(x,y) and scale σ in the x direction. lxy(p,σ) and lyy(p,σ) are calculated similarly, these derivatives are known as laplacian of gaussian. another reason why the surf algorithm performs fast is that it approximates the laplacian of gaussian with a box filter representation. the box filter allows a performance increase in time when they are computed on integral images the features must be detected on both images of the stereo pair to calculate the local 3d feature map using the stereo geometry of the stereo camera system. in every robotic application it is desirable to limit the amount of 189 data to decrease computational time as much as possible. for this reason the prior map shouldn’t be overpopulate, but in the mean time the distinctiveness of the data is important. therefore the 3d image features that are already in the global map or the similar ones to these are filtered out based on the surf descriptor. in the final step the local feature point cloud coordinate system is updated with the global position of the robot computed by the laser scan registration algorithm and the new distinctive features are recorded in the global 3d feature map. theoretical background of the laser system gaussian mixture models are widely used in data mining, pattern recognition, machine learning and statistical analysis. in order to build complex probability distributions, mixture models can also be used to cluster data. the problem of finding clusters in a set of data points can be resolved by a non-probabilistic technique, the k-means algorithm. k-means clustering the main usage of the method created by [15] is to identify groups, or clusters of data points in a multidimensional space. the inputs of the method are a data set {x1, ..., xn} consisting of n observations of a random d-dimensional euclidean variable x, and k the number of clusters which we would like to obtain. in common words a cluster can be described as comprising a group of data points whose distances between the points are less than the distances between the points outside from the cluster. we note μk as the representation of the centers of the clusters. finding an optimal solution to the data set clustering problem is not straightforward. a relative good solution has been found when the sum of the squares of the distances of each data point to its closest center is a minimum. for each data point xn is introduced a corresponding set of binary indicator variables rnk ∈ {0,1}, where k = 1, ..., k describing which of the k clusters the data point xn is assigned to. each point can be assigned just to one cluster, this can be described as follows if rnk = 1 ∧ rnk = 0, then j ≠ k, this is called the 1-of-k coding scheme. ∑∑ == μ−= k 1k 2 knnk n 1n xrj (2) the objective function (9) represents the sum of the squares of the distances of each data point to its assigned vector μk. the solution is optimal when the values found for rnk and μk are minimizing j. these values can be obtained developing an iterative procedure, it involves two successive steps in which rnk and μk are optimized. in the beginning initial values are chosen for μk, j is minimized with respect to rnk, keeping the μk fixed. in the following step j is minimized with respect to μk, rnk is kept fixed. these two stages correspond to e(expectation) and m(maximization) steps of the em algorithm, which steps are repeated until convergence [12]. expectation-maximization algorithm the goal of the em algorithm is to find maximum likelihood solutions for models having latent variables [9]. table 1: description of the em algorithm experimental results in order to achieve an autonomous navigation for the p3-at in a mine scene, first we tested our algorithms in an indoor environment, which is the office building where the research is done. the 2d laser map and the map built using the images taken by the stereo camera are well combined. the feature based map is built iteratively with the presented algorithm above by navigating the robot in the test environment which is an indoor office building. a selected image sequence can be seen on fig. 5 from the 155 stereo pair image sequences that were taken in the office, corridor and staircase of our laboratory. figure 5: selected images from the data set the obtained 3d feature map is plotted on fig. 6, where with black spheres are represented the 3d feature landmarks obtained in the whole test environment, divided in the three main rooms. 1. chose initial values for θold 2. e step evaluate ),|( oldxzp θ 3. m step evaluate θnew, where ),(maxarg oldnew θθφθ θ = we know that, ∑= z oldold zxpxzp ).|,(ln),|(),( θθθθφ 4. check the convergence of the parameter values, if the convergence is not achieved then θold = θnew and return to step 2. 190 figure 6: the obtained 3d feature based map of the environment with the red disk are denoted the positions of the robot, where the stereo image pares were taken. the origin of the map, the first robot location is the dark red one. the fade color of the disks shows the path travelled by the robot. the point clouds acquired by the 2d laser system can be computed for different usage in the navigation process. the first objective would be to create an apriori static map, which is done using the above described algorithms, k-means and em algorithm. in fig. 7 the map of the office environment can be seen, which will be clustered in equal rectangles. the objective is to clusterize all the separate objects and to detect the dynamic ones. figure 7: 2d laser map of the office in fig. 8 the map is separate in rectangles, for each rectangle the same algorithms are applied. figure 8: clustered map of the office in each rectangle the data set is clustered in separate parts by both of the algorithms in order to detect the dynamic ones. in fig. 9 from the two separations the one with the most clear one is chosen. all the separate data set will be encontoured by geometrical shapes, like ellipsoids and different contours. figure 9: the separated data set by k-means and em algorithm after all these steps will be made to each rectangles, the objective is to put together the data points which are part from the same object. the data set which will change its original cluster will be included in a new geometrical form. these newly created forms will be put in cells, of which size will be deducted by the size of the object. using the markovian properties an optimal trajectory will be find and in collaboration with the vision system the localization process will work more efficiently. future work our future objective is to develop the visual system to be capable of building large scale image feature based maps. to accomplish this goal in an efficient data management manner the bag of words representations will be used. the laser system will be combined with the markovian properties. another interest of our research is focused on the possibility of putting the visual mapping system in a probabilistic framework to be able to perform simultaneous localization and mapping. references 1. g. ferri, a. mondini, a. manzi, b. mazzolai, c. laschi, v. mattoli, m. reggente, t. stoyanov, a. lilienthal, m. lettere, p. dario: dustcart, a mobile robot for urban environments: experiments of pollution monitoring and mapping during autonomous navigation in urban scenarios, icra workshop, 2010. 2. g. ferri, e. caselli, v. mattoli, a. mondini, b. mazzolai, p. dario: spiral: a novel biologicallyinspired algorithm for gas/odor source localization in an indoor environment with no strong airflow, robotics and autonomous systems, issue 4, april, 2009. 3. m. k. muezzinoglu, a. vergara, r. huerta, n. rulkov, m. i. rabinovich, a. selverston, h. d. abarbanel: acceleration of chemosensory information processing using transient features, sensors and actuators b: chemical, 2009. 191 4. c. stachniss, c. plagemann, a. lilienthal: learning gas distribution models using sparse gaussian process mixtures, autonomous robots, 2009. 5. a. gil, et al.: a comparative evaluation of interest point detectors and local descriptors for visual slam, machine vision and applications, springer, 2009. 6. c. evans: notes on the opensurf library, university of bristol, technical report: cstr-0900, 2009. 7. h. bay, a. ess, t. tuytelaars, a. van gool: surf: speeded up robust feature, computer vision and image understanding, 110, 2008, 346–359. 8. g. ferri, m. v. jakuba, e. caselli yoerger, p. dario: localizing multiple gas/odor sources in an indoor environment using bayesian occupancy grid mapping, ieee/rsj international conference on intelligent robots and systems, 2007. 9. c. laugier, r. chatila: autonomous navigation in dynamic environments, springer tracts in advanced robotics, 35, 2007. 10. a. lilienthal, a. loutfi, t. duckett: airborne chemical sensing with mobile robots, sensors, 2006. 11. d. martinez, o. rochel, e. hughes: a biomimetic robot for tracking specific odors in turbulent plumes, autonomous robots, june 2006. 12. c. m. bishop: pattern recognition and machine learning. information science and statistics, 2006. 13. h. r. olesen, r. berkowicz, m. ketzel: regulatory odour model development: survey of modelling tools and datasets with focus on building effects, technical report 541, denmark 2005. 14. l. marques, a. martins, a. de almeida: environmental monitoring with mobile robots, conference on intelligent robots and systems, iros 2005. 15. j. a. farrell, s. pang, w. li: plume mapping using markov methods, ieee transactions on systems, man and cybernetics part b: cybernetics, 2003. 16. s. thrun et al.: a system for volumetric robotic mapping of abandoned mines, ieee international conference on robotics and automation, 2003, 4270–4275. 17. a. t. hayes, a. martinoli, r. m. goodman: distributed odor source localization, ieee sensors journal, 2, 2002. 18. p. viola, m. jones: rapid object detection using a boosted cascade of simple features, computer vision and pattern recognition, 2001. 19. d. g. lowe: object recognition from local scaleinvariant features, international conference on computer vision, 1999, 1150–1157. 20. h. ishida, t. nakamoto, t. moriizumi: remote sensing of gas/odor source location and concentration distribution using mobile systems, sensors and actuators b 1998. 21. r. a. russell: laying and sensing odor markings as a strategy for assisting mobile robot navigation tasks, ieee robot. mag., 2, 1995. 22. h. ishida, k. suetsugu, t. nakamoto, t. moriizumi: study of autonomous mobile sensing system for localization of odor source using gas sensors and anemometric sensors, 45, 1994. 23. p. j. besl, n. d. mckay: a method for registration of 3-d shapes, ieee transactions on pattern analysis & machine intelligence, 14, 1992, 239–256. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word contents_2.doc hungarian journal of industrial chemistry veszprém vol. 31. pp. 57-70 (2003) non-equilibrium model and experimental validation for reactive distillation d. rouzineau1, m. meyer1, m. prevost1, j. m. reneaume2, f. druart2 1 laboratoire de génie chimique, ecole nationale supérieure des ingénieurs en arts chimiques et technologiques, institut national polytechnique de toulouse, (france) e-mail: david.rouzineau@ensiacet.fr 2 laboratoire de génie des procédés de pau, ecole nationale supérieure en génie des technologies industrielles, université de pau et des pays de l’adour, (france) e-mail: jean-michel.reneaume@univ-pau.fr firstly, a non-equilibrium model is implemented in order to simulate non-ideal multi-component reactive separation processes. this model is characterised by mass and energy transfer description and is completed up by considering hydrodynamics using the film theory model. the maxwell stefan approach is used for the description of mass transfer without restrictive hypotheses. moreover, there are no restrictive hypotheses about the type and localisation of the chemical reactions. secondly, the numerical analysis of this model ends in setting up a sure and stable strategy, especially to the differentiation index and the initialisation coherence. thirdly, an experimental apparatus is set up in order to validate the numerical results. it represents a section of a packing distillation column fed by two fully controlled flows. the experiments were performed for the homogeneously catalysed etherification of acid acetic and methanol to produce methyl acetate and water. several runs have been realised by varying the flow rates and compositions of the feeds, as well as the concentration of the catalyst. for each one, the simulation results are in good agreement with the vapour composition and the liquid temperature profile, without any parameter adjustments. in addition, the need of taking into account the reaction contribution in the diffusional layers is clearly shown. introduction the reactive distillation processes, which combine reaction and gas liquid separation, are of an increasing interest for scientific investigations and industrial applications. simulation and design of this process is usually carried out by using the equilibrium stage model. the limitation of conventional equilibrium stage efficiency calculations is discussed by lee & dudukovic [1], baur & al. [2], taylor & krishna [3], and wesselingh [4]. these authors assume that the generalised non-equilibrium model should be preferred for the simulation of a column for reactive distillation to the equilibrium model, because the accurate prediction of individual murphee tray efficiencies (or hept for packing) is very difficult in case of the simultaneous multicomponent separation and reaction. moreover, they outlined the limitations of the equilibrium stage modelling, especially with respect to the realisation of multiple steady states phenomena [5]. but the complexity of the non-equilibrium model pushes some teams to make restrictive assumptions to solve the generated equations. indeed, the analysis of the models suggested in the literature shows differences concerning the writing of the model and its resolution (see table 1). a complete model must not, for mixing together the transfer and energy transfer, make any restrictive assumption on the relations of maxwellstefan and must consider the equilibrium and controlled reaction in the phase and film, like the gorak a. and kenig e.y. approach. our model is 58 table 1 : different approaches for the non equilibrium model authors university hydrodynamic model reactions in the film type of reactions maxwell-stefan resolution heat transfer taylor r. krishna r. holland amsterdam postdam film theory + cell model yes controlled numerical yes lee j.h dudukovic m.p. usa washington film theory no controlled analytical yes pagani g. bianchi g. italy novara film theory yes controlled and equilibrium numerical no kenig e.y. gorak a. germany dortmund film theory yes controlled and equilibrium numerical yes implemented in the same way except for the numerical resolution (see paragraph 3.2). compared to this complete approach, taylor r. and krishna r. [6] do not consider the instantaneous equilibrium reaction. lee j.h. and dudukovic m.p. [1] do not take into account the reaction on the film. or, pagani g. and bianchi g. [7] neglect the heat transfer. moreover, the type of resolution carried out by some authors can generate uncertainties about the precision of the results without a large investigation, such as the linearisation of film. experimental validation of the non-equilibrium model was also carried out by various authors [7,8,9,10,11]. nevertheless, accurate experimental work on reactive distillation is necessary. indeed, on the articles, it is difficult to have the complete parameter of the model to reproduce these experiments by simulation, like diffusion coefficients, all internal column characteristics ( hold up, specific area,…), kinetic (often depending on the catalyst quantity but is not described like such) or error estimation of analysis measurement. moreover, the experimental results are not available as data but only presented on graphs. lastly, many parameters must be measured along the column in order to get a pilot process of reactive distillation. too many times, the measurements taken on the pilots are confined to input and output data, as mentioned by taylor r. and krishna r. [6] in their conclusion of the review on modelling reactive distillation : “...there is need for more experimental work with the express purpose of model validation. in such process studies, parameters need to be measured along the height of rd columns. too often measurements are confined to feed and product stream conditions. such data cannot serve as a reliable discriminant of computer-based process models.” the objectives of our study are thus to propose a model without any restrictive assumption but with a reliable and powerful resolution, as well as to develop an experimental pilot for validation. thus, this article is divided into three parts. the first part is dedicated to the writing of the nonequilibrium model. first of all the column is described from a macroscopic point of view where it is focused on the interface vicinity to quantify the various transfers between phases. the numerical resolution of the model equations is also briefly exposed in this part. the second part deals with the experimental pilot and the reasons of the material choice. its design features and its settings are also evoked. the various measurement techniques are thoroughly described and the operational protocols are specified. the experimental validation is the final topic. the numerical results of the model are compared with the experimental values resulting from the pilot of the laboratory for reactive multi-components mixtures. 59 non-equilibrium model theory some limits must be fixed to define the limits of our investigation. the implemented model can be applied to any fluid-fluid contactor in which a twophase transfer takes place. however, this work is focused on reactive distillation and absorption, for which a liquid phase and a vapour phase are in contact. the study is carried out in a steady state and the mixture is considered as a non-ideal multicomponent mixture. the reactions can be multiples. there is no assumption concerning the nature and the localisation of the reactions; they can be considered as being instantaneously in equilibrium or controlled by kinetics, and can be slow, therefore they would take place primarily in the bulk of the phases or can be fast, therefore they would take place primarily in the diffusional layer. figure 1 : non equilibrium model column level model first of all, the “column” model is described, with two kinds of equations: bulk equations and interface equations. bulk equations the stage equations are the traditional equations based on mass balances and energy balances in the bulk phase for each stage [3]. these equations take into account the reactions, and there are no restrictive hypotheses regarding the nature and the localisation of the chemical reactions. the bulk variables (composition, molar flux, temperature, energy flux) are different to the interface variables. the temperature of the vapour and the liquid phases are not assumed to be equal. the modelling leads to a system of algebraic equations. j represents the stage number. energy balance for vapour and liquid phase ( ) 0)()().()( )(.)()()1().1( =−++ ++−−− jqjhjfje jhjsjljhjl l f lll lll ( ) 0)()().()( )(.)()()1().1( =−++ ++−++ jqjhjfje jhjsjvjhjv v f vvv vvv partial mass balance for vapour and liquid phase for the component i (i ∈ [1,n]) ( ) 0),().(),( ),(.)()()1,().1( 1 =+++ ++−−− ∑ = nrc k ikiklll l rjizfjfjin jixjsjljixjl υ ( ) 0),().(),( ),(.)()()1,().1( =++ ++−++ jizfjfjin jiyjsjvjiyjv vvv v interface equation the interface equations link the two phases. thermodynamic equilibrium is considered at the vapour liquid interface for each component. moreover, the mass and energy transfer fluxes through the interface should be continuous. energy fluxes conservation 0)()( =+ jeje i v i l summation equation for the liquid and vapour thin films resistances for mass and heat transfer l(j) qv(j) ql(j) ev el interface v(j) v(j+1) l(j-1) plate or packing l1 li j=1 condenser j=2 j=i j=n-1 j=n boiler v2 vi vn-1 vn l2 ln-1 sl(j) sv(j) 60 ∑ = = n i i jix 1 1),( ∑ = = n i i jiy 1 1),( equilibrium equations 0),(.),( =− jixkijiy i eq i i ∈ [1,n] mass flux conservation 0),(),( =+ jinjin i v i l i ∈ [1,n] chemical equilibrium ∏∏ == =− n i i n i ij p ij r ij aamkeq 11 0αα i ∈ [1,n] diffusional layer model a complete model is used to compute heat and mass transfer through the diffusion layer considered in the film theory [11]. indeed, the fluid is considered as an n component reactive non-ideal mixture. the balance equations for simultaneous heat and mass transfer are written in steady state, taking into account the reactions. for mass transfer, the maxwell stefan diffusion law is used. neither the diffusion coefficients nor the molar flux are considered to be constant due to the reaction. the complete formulation for mass transfer for n non-ideal components is: mass transfer continuity (1) : ∑∑ == =++ ∂ ∂ − nre j jij nrc j jij i r z n 1 ' 1 0ξυυ i ∈ [1,n] maxwell stephan diffusion law (2): ( ) ∑∑ ≠ == − −= ∂ ∂         ∂ ∂ + n ij 1j ijt ijji n 1j j p,tj i iij dc nxnx z x x ln x γ δ i ∈ [1,n] equilibrium equation (3) : ∏∏ == =− n i i n i ij p ij r ij aamkeq 11 0αα j ∈ [1,nre] the dimension of system (i) is 2n+nre in a traditional model, only n-1 equations of (2) are conserved because of equation dependence. indeed, equation (4) is obtained by summing the n terms in equation (2): ∑∑ == + ∂ ∂         ∂ ∂ ++ ∂ ∂         ∂ ∂ + n i pt i i n i ptj i i z x x x z x x x 1 2 ,21 1 , ln 1 ln 1 γγ ( ) ∑∑∑ = == − −= ∂ ∂         ∂ ∂ +++ n i n j ijt ijjin i n ptn i i dc nxnx z x x x 1 11 , ln 1... γ (4) with the gibbs duhem relation 0 ln 1 = ∂ ∂∑ = n i j i i x x γ and the coefficient symmetry dij=dji, equation (4) becomes:∑ = = ∂ ∂n i i z x 1 0 (5) which is the differential form of equation 6 ∑ = = n i ix 1 1 (6). in our model, the n components formulation is conserved because equation (6) is never written. this formulation is a great advantage; the molar fluxes are needed because they appear in the material balance. with the n components formulation, molar fluxes in a fixed reference are directly derived; we do not need other information [3] unlike the traditional models do. no assumption is made about the kind or the number of reactions, thus they can be controlled by kinetics or instantaneously equilibrium. in addition, the mass transfer rate changes due to the chemical reaction. for the heat transfer, the dufour and soret effects are neglected and the diffusion heat rate is evaluated by fourier’s law. heat transfer continuity 0= dz de (7) energy definition ∑ = +∇−= n i ii hnte 1 λ (8) the diffusional layer model is formed by equations (1),(2),(3),(7) and (8). numeric resolution the complete model consists of partial and algebraic equations and we can find different resolution methods in the literature. lee j.h. and dudukovic m.p. [1] write an approximate analytical solution for the diffusional layer model 61 described by maxwell stefan diffusion. discretisation is used to write the bulk phase equations with the set of model equation, newton’s method and homotopy continuation are used. the homotopy-continuation method was found superior to the newton-raphson method in guaranteeing the desired solution for the non-equilibrium model. but this kind of approach is not acceptable for the complete model without assumptions. gorak a. [12,13] and taylor r. [14] suggest that in order to obtain a numerical solution of such a problem, discretisation in regard to the axial (column height) and normal (film thickness) coordinates should be carried out. with this kind of resolution, a step discretisation analysis in the film is needed. indeed, several discretisations should be tested for the determination of the required number of film grid points. these number segments depend on the reaction kinetic rate. moreover, the segment width should be varied to take into account the large variable profiles and to optimise time calculation and numerical convergence. in our case, this problem is avoided. even if the discretisation in regard to the axial is used, the diffusional layer model equations are solved by integration based on the gear method extended by petzold l. r. [15] to dae systems. with this numerical tool the integration step and method order are automatically adjusted. so, the numeric resolution was achieved in two steps according to the model. this resolution was thoroughly described in a previous article [11]. resolution of the diffusional layer model the diffusional layer model equations (dae system) are solved by a dae integration based on the gear method and implemented by le lann j.m. [16]. the integration of system dae is made from the interface to the bulk by using interface variables as boundary conditions (molar compositions, mass and energy fluxes, temperature). the outcomes are: the molar and energy fluxes, temperature and the compositions in the diffusional layer. in order to use a dae integrator effectively there are two main numerical problems to overcome: initialisation procedure (figure 2) first of all, a hardy procedure leading to a coherent initial state (i.e. all algebraic equations must be satisfied at z=0) before starting the integration has to be used. the algebraic equations are the chemical equilibrium equations (eq3). the boundary values which must thus check these equations are the molar fractions and enhancement of equilibrium reaction. this calculation procedure is used to evaluate these boundary variables if the equilibrium reactions are present in the film. if not, the diffusional layer model consists of a pure differential system without any consistency problems of the boundary values. figure 2 : consistancy of boundary values our procedure is based on the transformation of a set of fraction x0 in a set of fraction xeq satisfying equation (3). to perform this calculation the following system is solved: 00 0 =+− ∑ nre j j ' ij eq ii fxxf ξυ i ∈ [1,n] (9) ∏ = = n i i eq j ijxk 1 α j ∈ [1,nre] (10) 01 1 =−∑ = n j eq jx (11) then, at z=0, xeq are used as boundary values. index reduction secondly, an automatic substitution procedure is used to reduce the number of mass balances in order to take into account the chemical equilibrium constraints and also to reduce the differentiation index to 1 (see annex). 0 ix done before started initialisation 10 =f dummy flowrate eq ix calculated in agreement with the equilibrium reaction jξ calculated f calculated but not used initialisation procedure 62 resolution of the column level model equations of the column level model lead to a system of differential and algebraic equations with boundary conditions at each end. discretisation method is used and the resulting algebraic system is solved by newton’s method. those general balances use the values resulting from the integration of the diffusional level model equations. results a fortran code was implemented in the prosim plus simulator. this simulation software is able to give results in terms of profiles along the column of various variables such as the molar compositions, temperatures and flow-rates. experimental validation an experimental pilot plant was developed in order to validate the simulation results. materials the glass column consists of four packed sections with glass raschig rings. the total packing height is about one meter and the column diameter is 8 cm. this column has no boiler and no reflux. it represents the reactive section where the top liquid flow and bottom vapour flow are totally controlled. the experimental pilot plant is shown in figure 3. the top liquid flow is pre-heated close to its bubble temperature by an electric preheater and a dry evaporator (power 8 kw) generates the bottom vapour flow (see figure 3). a vapour sample and the liquid temperature can be measured at each end of the packing sections. the vapour sampling is done via a gutter placed on the lower part of a teflon support. this shelters a capillary needle from the down flowing liquid. for the liquid temperature measurement, a gutter is placed on the higher part so that it can collect the falling liquid where a thermocouple of type j is placed. therefore, the liquid temperature and vapour compositions are measured along the column. the samples analysis is done by gas chromatography with an fid detector. the absolute error generated by this method is ± 0.015 of the mass fractions. the measurement error on the liquid temperature is evaluated according to the type of thermocouple and the calibration with ).t*.(t 2000250 +±=∆ . the operational variables such as the feed flow rate, the feed temperature, and the column temperature profile are measured by a process control unit. figure 3 : experimental pilot plant évaporateur condenseur anneaux rashig vrac préchauffeur électrique contrôle de débits pompes d’alimentation echangeur garde hydraulique distributeur prise d’échantillon thermocouple p o m p o m r 63 experiments specific experiment for heat losses determination in spite of the heat insulator around the column, heat losses are inevitable. it is significant to evaluate them for simulation. the evaporator is supplied by the pump of constant water flow. the column is not fed at the head of the column. if there is no loss, all the vapour generated by the evaporator must be recovered at the head of the column to condenser . on the other hand, in case of heat losses, part of the vapour condenses in the column and is recovered in the bottom of the column. this residue flow-rate corresponds to the heat losses which can be evaluated at 250 watts. the experiments were performed for the homogeneously catalysed etherification of acid acetic and methanol to produce methyl acetate and water. sulphuric acid is chosen as the homogeneous catalyst. the catalyst is fed into the column through the liquid feed in the top of the column with a shower . four experiments have been carried out by changing the flow rates (ranging from 4.34 kg/h to 8.35 kg/h for the liquid feed and from 2.89 kg/h to 6.34 kg/h for the vapour feed), as well as the concentration of catalyst, in order to modify the rate of the reaction. experiment 5 is carried out to represent a section of the simulated column. the different conditions of the experiments are shown in table 2. for each run, the partial and global mass balance is tested in order to validate the consistency of the measurements. table 2 : operating conditions for the five experiments experiments exp.1 exp. 2 exp.3 exp.4 exp. 5 liquid vapour liquid vapour liquid vapour liquid vapour liquid vapour flow (kg/hr) 4.84 5.63 4.34 2.89 4.34 2.89 8.35 6.34 7.74 6.129 acid mass meoh fraction ester h2o 0.760 0.000 0.000 0.240 0.000 0.980 0.000 0.020 0.760 0.000 0.000 0.240 0.000 0.980 0.000 0.020 0.760 0.000 0.000 0.240 0.000 0.980 0.000 0.020 0.760 0.000 0.000 0.240 0.000 0.980 0.000 0.020 0.519 0.095 0.121 0.265 0.043 0.587 0.249 0.121 k0[h+] (l/mol/s) 400 550 1100 1100 200 simulation simulations were made by our non-equilibrium model. the thermodynamics data specifications are provided by the dechema database. the uniquac model is used to represent the nonideal liquid phase. dimerisation is considered for the vapour phase. the reaction is considered as a reaction controlled by kinetics and the rate constant depends on the catalyst quantity [ref]: [ ]       −      −= + e méthanolacide eauacétate a k cc cc rt e hkr exp0 with [h+] in ml/lsolution and ea=10000 cal/mol , 0k =333.3 l/mol/s, ke=5.2 the value for the different experiments are given in table 2. the film thickness estimation is obtained from the average values for the binary mass transfer and diffusion coefficient, estimated by the traditional correlation (table 3). the different parameters for the simulation can be found in table 3. results and exploitation for each run, the experimental and calculated values of the outputs (flow rates, concentrations), the vapour composition and the liquid temperature profiles are compared. a good agreement is systematically seen without the need of any 64 table 3 : simulation parameters _______________________________________________________________ mixture: number of components: 4 components: acetic acid – methanol – methyl acetate – water thermodynamic model: heat of vaporization: clausius clapeyron equation of state: association (polymerisation) vapour tension: antoine activity coefficient: uniquac binary interaction parameters (cal/mol) 1 2 -23.094 30.803 1 3 -449.604 747.594 1.4 -383.266 601.033 2 3 -115.025 676.392 2.4 54.337 47.106 3.4 789.996 117.211 reaction: number of reaction: 2 reaction: acetic acid + methanol methyl acetate + water 1 methyl acetate + water acetic acid + methanol 2 kinetics: [ ] méthanollacetiquecc* rt exph.r      −= + 10000333331 r mol/l/s and r cal/mol/k [ ] eauacétatecc* rt exph.r      −= + 1000010642 [h+] ml for litre of solution type of column: column: raschig packing diameter: 0.08 m numeric discretisation: 30 non equilibrium stages losses thermal: 250 w in liquid phase correlations : mass transfer coefficients : onda [17] binary coefficients diffusion : fuller for vapour phase wilke et chang for the liquid phase hold-up : mersmann et deixler (kister, [18]) inter facial area : onda [17] _______________________________________________________________ 0.08 metre 65 table 4 : experimental measurement and mass balances global mass balance (kg/h) liquid vapour total input 4.34 2.89 7.23 output 5.00 2.20 7.20 absolute error 0.03 relative error 0.41% partial mass balance acid acetic methanol methyl acetate water temperature °c liquid input 95.1 mass fraction 0.760 0.000 0.000 0.240 partial flow rate g/h 3298.400 0.000 0.000 1041.600 partial flow rate mol/h 54.973 0.000 0.000 57.867 vapour input mass fraction 0.000 0.980 0.000 0.020 partial flow rate g/h 0.000 2832.200 0.000 57.800 partial flow rate mol/h 0.000 88.506 0.000 3.211 liquid output 73.9 mass fraction 0.371 0.408 0.054 0.167 partial flow rate g/h 1855.000 2040.000 270.000 835.000 partial flow rate mol/h 30.917 63.750 3.649 46.389 vapour output mass fraction 0.243 0.166 0.360 0.231 partial flow rate g/h 534.600 365.757 792.110 507.533 partial flow rate mol/h 8.910 11.430 10.704 28.196 input output difference molar -15.147 -13.326 14.353 13.507 molar error relative error / reactive average -14.237 13.930 -0.306 2.15% conversion acetic acid 26.11% global energy balance liquid vapour total input (watt) -11411.23 -5178.82 -16590.05 output (watt) -10697.72 -6166.67 -16864.39 difference -274.34 energy lost (watt) 250.00 absolute error -39.34 relative error 8.87% vapour mass fraction and liquid temperature measerement aloung the column t = 84.0 °c mass fraction aa 0.076 mét. 0.465 ester 0.308 water 0.151 t = 88.0 °c mass fraction aa 0.160 mét. 0.292 ester 0.377 water 0.171 t = 78.8 °c mass fraction. aa 0.043 mét. 0.667 ester 0.170 water 0.120 experimental measurement 66 parameter adjustment. the comparison between the predicted and measured mass fraction for all five experiments is provided in figure 4. the maximum absolute deviation is 0.026 and the average absolute deviation is 0.0096. this is satisfactory considering the measurement experimental error, which is more or less 0.015 of these mass fractions. for illustration, experiment 3 is analysed. the liquid feed is water and acetic acid (0.76 mass) mixture with a flow rate of 4.34 kg/hr, and the vapour feed is pure methanol with a flow rate of 2.89 kg/hr. the flow rate of the catalyst is about 32g/hr. the following table 4 shows the different experimental measurements and the different mass and energy balances. the global mass balance error for this experiment is 0.4 % and 2.1 % for the partial mass balance. the output vapour temperature is not measured, so the energy balance can only be carried out by admitting that the top vapour exit is dew. these results guarantee us the quality of the experiment as well as the control of the operating conditions. the error on this energy balance is 8.87 %. figure 4 : predicted versus experimental mass fraction along the column for the five experiments the conversion of acetic acid is about 26%, therefore the reaction is shown and the concentration gradients are important along the column height. figure 5 shows composition profiles along the column for run 3 and for the simulation. the nonequilibrium model shows quite good agreement with the experiment, considering the measurement error. a maximum deviation of 1°c appears between the experimental and calculated profiles of the liquid temperature (figure 6). this remains acceptable considering the precision of the thermocouples. the simulation also gives acceptable results in terms of output flow rates (average deviation of 2%). an other simulation is done without taking into account the reaction results in the diffusional layers. the profiles are compared with the experimental and simulated results with reaction in the film, as shown in figure 7. it is clear that the results are different, so the importance of taking into account the reaction in the diffusional film is obvious. furthermore, the faster the reaction is, the greater the gap is between these two cases. 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 experimental mass fraction c al cu la te d m as s fr ac tio n 67 figure 5 : experimental and calculated composition profile figure 6 : experimental and calculated liquid temperature profile figure 7 : composition profile with and without reaction in the film 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 1,1 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 vapour mass fraction pa ck in g he ig ht (m ) methanol methyl acetate water calculated profile experimental values • 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 1,1 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 liquid temperature (°c) h ei gh t o f p ac ki ng (m ) calculated profile experimental values • 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 1,1 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 vapour mass fraction pa ck in g he ig ht (m ) methanol methyl acetate water calculated with reaction in the film calculated without reaction in the film• 68 conclusion we have developed a non-equilibrium model for multi-component reactive separation techniques. this model is solved numerically by a hardy strategy. the originalities of this model are the maxwell stefan formulation, which is solved in the complete formulation and the absence of restrictive assumptions concerning the reaction. to validate the model, an experimental pilot has been developed. it is a part of the column where inlet fluxes are controlled, and local temperatures and compositions profiles are measured accurately. for each experiment, which concerns the production of methyl acetate, the results of the steady state simulation are in good agreement with the experimental data and demonstrate the importance of taking into account the reaction in the diffusionnal layer. therefore, the non-equilibrium model seems to be a well-adapted tool for the simulation, design and optimisation of reactive distillation. symbols λ thermal conductivity of the mixture (cal/m/k/hr) ν’ ij stœchiometric coefficients of component i for equilibrium reactions control j γi activity coefficient component i αij order of component i in equilibrium reaction j δij kroneker symbol νij stœchiometric coefficients of component i for control reactions j ξj enhancement of equilibrium reaction j (mol/m2/hr) ai activity component i ct total concentration (mol/m3) dij maxwell stefan binaries diffusion coefficient i-j (m2/hr) e density of energy flux (cal/m2/hr) e(j) energy flux of stage j (cal/hr) e(j) energy flux of stage j (cal/hr) ea activation energy el liquid film thickness (m) ev vapour film thickness (m) f(j) molar flow rate of the stage alimentation j (mol/hr) h(j) molar enthalpy of mixture of stage j (cal/mol) hf(j) molar enthalpy of mixture alimentation of stage j (cal/mol) ke equilibrium constant for etherification keqj chemical equilibrium constant of the equilibrium reaction j kj equilibrium constant for equilibrium reaction j l(j) liquid molar flow rate for the stage j (mol/hr) n number of components n(i,j) molar flux of component i of the stage j (mol/hr) ni molar flux component i (mol/m2/hr) nrc number of control reactions nre number of equilibrium reactions q(j) heat release of stage j (cal/hr) r constant perfect gas = 1.989 cal/mol r reaction rate of estherification (mol/l/hr) rik rate of reaction for the constituent i in the reaction k (mol/hr) rj rate of reaction j (mol/m3/hr) s(j) output flow rate of side stream of stage j (mol/hr) t temperature (k) v(j) vapour molar flowrate for the stage j (mol/hr) x(i,j) liquid molar fraction of component i of stage j xi molar fraction component i y(i,j) vapour molar fraction of component i of stage j z space coordinate (m) zf(i,j) molar fraction of component i for the feed of stage j index l : variable concerning the liquid phase v : variable concerning the vapour phase 69 exponent i : variable concerning the interface p : products r: reactive annex: substitution procedure to reduce the number of mass balances in order to take into account the chemical equilibrium constraints and to reduce the differentiation index to 1. the equation (1) of mass balance is: ∑∑ == =ξυ+υ+ ∂ ∂ − nre 1j j ' ij nrc 1j jij i 0r z n with the matrix formulation: 0 ................ . . . ............... r r .................. . . . ................... dz dn dz dn 1 1 nre 1 ' nre,n ' 1,n ' nre,1 ' 1,1 nrc 1 nrc,n1,n nrc,11,1 n 1 =                 ξ ⋅ ⋅ ⋅ ξ                   υυ υυ +                 ⋅ ⋅ ⋅                 υυ υυ +                   ⋅ ⋅                − with a pivot strategy, we can obtain equation (1) with this formulation: ( ) ( )                     ⋅ ⋅ ⋅ ⋅ +                       ⋅ ⋅ ⋅ =                       ξ ⋅ ⋅ ⋅ ⋅ ⋅ ξ                           nrc 1 n 1 nre 1 nre-n 1 r r b dz dn dz dn a a 0 0 a 1 0 0 0 1 0 0 0 1 so, the advancement of the equilibrium reaction becomes explicit, and we can substitute their value in the other equation. so, the 2n+nre dimensional system (1) is reduced to a 2n dimensional system. moreover, the differentiation index of the dae system is reduced to 1. references 1. lee j-h. and dudukovic m. p.: 1998, a comparison of the equilibrium and nonequilibrium models for a multicomponent reactive distillation column, computers and chemical engineering, 23, pp 159-172. 2. baur r., higler a. p., taylor r. and krishna r.: 2000, comparison of equilibrium stage and nonequilibrium stage models for reactive distillation, chemical engineering journal, journal 76, 33-47. 3. taylor r. and krishna r.: 1993, multicomponent mass transfer, wiley series in chemical engineering, (new york). 4. wesselingh j. a.: 1997, non-equilibrium modelling of distillation, distillation and absorption, vol. 1, 1-21. 5. higler a. p., taylor r. and krishna r.: 1999, nonequilibrium modelling of reactive distillation: multiple steady states in mtbe synthesis, chemical engineering science, 54, pp 1389-1395, 6. taylor r. and krishna r.: 2000, modelling reactive distillation, chemical engineering science, 55, pp 5183-5229. 7. pagani g., arminio monforte a. and bianchi: 2001, transfer-based models implementation in an equation oriented package, computers and chemical engineering, 25, 1493-1511. 8. noeres c., kebig e. y. and gorak a.: 2003, modelling of reactive separation processes reactive absorption and reactive distillation, chem. eng. process, pp. 157178. 9. kenig e. y., baeder h., gorak a., bessling b., adrian t. and schoenmakers h.: 2001, investigation of ethyl acetate reactive distillation process, chemical engineering science, 56, pp 6185 – 6193. 0 0 70 10. gorak a. and hoffmann a.: 2001, catalytic distillation in structured packings: methyl acetate synthesis, aiche journal, 47, pp 10671076. 11. rouzineau d., prevost m. and meyer m.: 2001, evaluation of coupled reactive distillation performances by means of a rigorous simulation procedure, european symposium on computer aided process engineering, escape 11, computer – aided chemical engineering, vol. 9, page 267 – 272, denmark. 12. kucka l., muller i., kenig y. and gorak a.: 2003, on the modelling and simulation of sour gas absorption by aqueous amine solutions, chem. eng. science, 58, pp 3571 – 3578. 13. shneider r., sander f. and gorak a.: 2003, dynamic simulation of industrial reactive absorption processes, chem. eng. and proc., 42, pp 955-964 14. higler a., krishna r. and taylor r.: 1999, nonequilibrium cell model for multicomponent reactive separation processes american institute of chemical engineers journal, 45, pp 2357 – 2370. 15. petzold l. r.: 1982, differential/algebraic equations are not ode, soc. ind. appl. math. j. sci. stat. comp., vol 3 n° 3 , 367-384. 16. le lann j. m.: 1998, habilitation à diriger les recherches, 80 pages. 17. onda k., tackeuchi h. and okumoto y.: 1968, mass transfer coefficient between gas and liquid phases in packed columns, j chem eng jpn., 1, 56-62. 18. kister h. z.: 1992, distillation design microsoft word szolcs_eloszo.doc hungarian journal of industrial chemistry veszprém vol. 32. pp. 13-21 (2004) study of open–looped simulated moving bed (smb) chromatographic process m. nagy1, z. molnár1, l. hanák1, j. argyelán1, t. szánya1, b. ravasz1, g. turza1 a. aranyi2 and k. temesvári2 1university of veszprém, department of chemical engineering pob 158, veszprém, h-8201, hungary 2gedeon richter rt., pob 27 budapest 10, h-1475, hungary in this experimental work laboratory scale four-column simulating moving bed (smb) equipment (l=25 cm, id=1 cm) was planned and constructed for separation of a steroid mixture [1] using ymc s-50 silica gel as adsorbent, with the co-operation of central mechanical workshop, university of veszprém. the effect of switching time change (5.5 min, 9 min, 11.5 min, 22.5 min) on component separation was examined. during our measurements the amount of acetone in dichloromethane was 55 % v/v in the fresh eluent and pure dichloromethane in the feed. product purity and other specifications (yield, productivity, eluent consumption) were measured by gas chromatography. an equilibrium mathematical model of the smb process for open and closed eluent loops was constructed by means of a computer program [2, 3]. adsorption equilibrium, and kinetic data, theoretical plate number measurement, frontal and elution adsorption-desorption measurements for determination of the optimum conditions for the smb process and for construction of the mathematical model were measured by means of laboratory experiments. finally results coming from simulation program were compared to measurement results. our conclusion is that the measured and the calculated data agreed well and we have produced more than 99.9 % m/m purity and 90 % yield, at productivity 1300-3000 g “b” component/ kg adsorbent within a day using 60 g dm-3 inlet steroid composition in case of 1:1:2:0 column configuration. keywords: smb, preparative liquid chromatography, simulated moving bed chromatography, introduction the most recent developments in preparative chromatographic processes are the simulated moving bed processes; these will probably be widely used, mostly for the production of high purity materials or materials otherwise difficult to isolate in pharmaceutical industry, fine chemical and biotechnological separation tasks. if materials are difficult to separate (α ≈1), the process efficiency is disadvantageous, as in case of a component of a mixture being strongly adsorbed (k’»). the process becomes uneconomical when a large volume of eluent must be used. the smb process was developed in the early 1960s by brougthon and gerhold [4] and has been used for many years in the petrochemical and sugar industries for large scale separation. recently, the separation of enantiomers due to the demand for high purity products becomes necessary [5]. the smb (fig.2.) is a continuous unit operated mode in cyclic which reproduces the performance of the equivalent true moving bed (tmb) unit (fig.1.). the smb is divided into four sections, each constituted of a counter current adsorption column which plays a specific role in the separation. let us consider a feed mixture consisting of a more retained species (a) and a less retained one (b) dissolved in the eluent. the separation is obtained in the two central sections, where b is carried by the mobile phase to the raffinate outlet. the fresh eluent is fed to the bottom of the section i, so as to desorb a and regenerate the adsorbent solid, before it is recycled to section iv. on the other hand b is 14 fig. 1. true moving bed (tmb) fig. 2. simulated moving bed (smb) retained in section iv and the pure eluent is recycled to section i. in practice the movement of the solid is not feasible and the tmb is replaced by the smb configuration where the adsorption beds are fixed and the counter-current solid-liquid movement is simulated by periodical switching the inlet and outlet ports of the unit [6]. use of gradient elution is recommended, likewise the conditions change during the separation. the applied gradient can be the pressure, temperature or solution composition. the third out of theses is usually chosen, and the process is known as solution composition changing gradient smb. the literature reveals that four scientific „schools” study this subject, the kluyer laboratory for biotechnology at delft university of technology in the netherlands [7-9], eth zürich, inst. verfahrenstechnik in switzerland [10,11], the mpi magdeburg inst. dyn. komplex techn. system in germany [12,13] and there are significant scientific results in france, too. we calculated the initial parameters with the method of morbidelli et al. [14]. after the authors in a two components system can be determined a mii-miii area from the geometric data of the smb equipment, the volumetric velocities, the parameters of langmuir-type isotherms and the concentrations of the mixture to be separated. the actual operating conditions determined a point on the mii-miii diagram. the variable operating conditions are: fresh eluent, recirculated eluent, feed, extract and raffinate flow rates, switching time. experiments equilibria measurements adsorption equilibria data for acetone (fig. 3.) and for steroids “a” and “b” (fig. 4.) were determined on ymc s-50 silica gel with 1:1 (v/v) acetonedichloromethane at 293 k at richter rt, department of preparative chromatography. monitoring happened by analytical hplc with a multistepped frontal saturating method. 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0 200 400 600 800 1000 c acetone (g dm-3 eluent) q ac et on e (g g -1 si lic a ge l) q acetone measured q acetone calculated a*acetone= 1.543 cm3 liquid cm-3 solid silica gel b*acetone= 0.001517 cm3 liquid mg-1 acetone fig. 3. adsorption equilibria measurement of acetone acetone in dichloromethane ymc s-50 silica gel, 20°c, measurements of g. r. i. feed (a+b) extract (a) raffinate (b) iv. iii. ii. a ds or be nt r ec ir cu la tio n l iq ui d re ci rc ul at io n s (e-f+r) d=s+rec rec fresh eluent i ii iii iv d=s+rec e (a) f (a+b) r (b) liquid phase adsorbent phase 15 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.20 0 5 10 15 20 25 30 35 40 45 c (g dm-3 eluent) q b , q a (g g -1 a ds or be nt ) qb calculated qb measured qa calculated qa measured ab= 6.4747 cm3 liquid g-1 adsorbent bb= 0.016711 cm3 liquid mg-1 b steroid aa= 14.4086 cm3 liquid g-1 adsorbent ba= 0.041481 cm3 liquid mg-1 a steroid fig. 4. adsorption equilibria measurement of „a” and „b” components steroid a, b adsorption, ymc s 50 silica gel in 1:1 (v/v) acetone-dichloromethane, 20°c, measurements of g. r. langmuir constants used for calculations are given below (table 1.): calculation for the three-component mixture: adsorption isotherm of acetone: 1 acetone acetone acetoneacetone acetoneacetone acetone gmg 0.0015171 1.543 1 − + = + = c c cb ca q (1) adsorption isotherm for steroid b in 1:1 (v/v) acetone-dichloromethane: 1 b b b gmg 0.0016711 6.474 − + = c c q (2) for the competitive langmuir: bbacetoneacetone bb b 1 cbcb caq ++ = (3) if cb ≈ 0, the first derivative of the isotherm is: acetoneacetone b b b d d cb a c q + = 1 (4) we obtained new langmuir constants when the acetone-dichloromethane volume is additive and cacetone=396 g dm-3 : 13* b * b g36.10 396001517.01 474.6 −= ⋅+ = cma a (5) 13* b * b mg02675.0 396001517.01 01671.0 −= ⋅+ = cmbb (6) calculation method for steroid a is similar. table 1. adsorption isotherms on ymc-s-50 silica gel langmuir constants for acetone in dichloromethane silicagelg volumefreeliquid .* acetone 3 5431 cm a = neacetomg volumefreeliquid.* acetone 3 0015170 cmb = langmuir constants for steroids 1: 1 (v/v) acetone -dichloromethane silicagelg volumefreeliquid .b 3 4746 cm a = componentbmg volumefreeliquid .b 3 016710 cm b = silicagelg volumefreeliquid .a 3 08614 cm a = componentamg volumefreeliquid .a 3 041480 cm b = langmuir constants of three-component compound silicagelg volumefreeliquid .* acetone 3 5431 cm a = neacetomg volumefreeliquid.* acetone 3 0015170 cmb = silicagelg volumefreeliquid .* b 3 3610 cm a = componentbmg volumefreeliquid .b * 3 026750 cmb = silicagelg volumefreeliquid .* a 3 5522 cm a = componentamg volumefreeliquid .a * 3 066400 cm b = determination of number of theoretical plates (ntp) – height of equivalent theoretical plate (hetp) a supelco chromatographic column (id=1 cm, l=25 cm) was filled with ymc s-50 silica gel (8 g) with the aid of a column-packing vibrator. air was removed from the column by means of 1:1 16 (v/v) acetone-dichloromethane and an lmim d167 pump. a rheodyne injection valve with 100 µl loop was connected to the column inlet and a waters uv detector to the outlet, where we monitored the signal from 0.2 % (v/v) acetophenone in eluent on 300 nm wavelength. we evaluated the retention time density function with the triangle method. the flow rates during the measurements were in the range of 1-13 cm3 min-1. the equation of the trendline is ntp/25(cm)= 1522.4v0(cm3 min-1)-0,707 , the regression value is r2= 0.9639. frontal adsorption elution measurement measurement was performed with a chromatographic column (id=0.735 cm, l=42 cm) packed with ymc s-50 silica gel. air was removed from the column by means of 1:1 (v/v) acetonedichloromethane at 293 k, directed upwards by means of an lmim-d167 piston pump. 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 0 50 100 150 200 250 30 v (cm3) c (g d m -3 ) measured "b" measured "a" calculated "b" calculated "a" 50 % v/v acetone 50 % v/v dichloromethane 4 g b dm-3 1 g a dm-3 135 cm3 50% v/v acetone, 50% v/v dichloromethane fig. 5. frontal adsorption-desorption measurement of steroids 385 390 395 400 405 0 50 100 150 200 250 v (cm3) c ac et on e ( m g cm -3 ) aceton konc. számított aceton konc. mért acetone calculated acetone measured fig. 6. frontal adsorption-desorption measurement of acetone during frontal adsorption an 80:20 % (m/m) mixture of steroids b+a (total concentration 5 g dm-3) was applied downwards to the column at a flow of 2.47 cm3 min-1 at 293 k. application of the mixture of a and b was stopped after 55 min (135 cm3 liquid) and pure eluent (1:1 (v/v) acetonedichloromethane) was let to the column at a flow rate 2.85 cm3 min-1 (fig. 5. and fig. 6.). the outlet liquid was collected in cooled (273 k) sample collectors and the concentration was measured by analytical gas chromatography. frontal adsorption desorption simulation data parameters in krom-n software with solvent adsorption-desorption (table 2.). table 2. input data of the software number of components: k = 3 column inner diameter: id=0.735 cm column length: l=42 cm free volume coefficient: eps= 0.8018 cm3 liquid free volume cm-3 column feed: b=2.47 cm3 min-1 bulk density: roh= 0.4045 g silica gel cm-3column langmuir constants: (same as in table 1 ) sample feeding time: 55 min (135.85 cm3) sample concentration: cacetone=396 mg cm-3 cb=4 mg cm-3 ca=1 mg cm-3 eluent concentration: cacetone=396 mg cm-3 cb=ca=0 mg cm-3 number of theoretical plates ntp=400 end of elution time: 112 min smb equipment planning, construction and installation the smb preparative liquid chromatographic equipment with four columns, four sectors and open eluent loops were constructed in the central mechanical workshop of university of veszprém (fig. 7.). 17 fig. 7. smb equipment photo during installation the four preparative liquid chromatographic columns were filled with ymc s-50 silica gel applying vibration method ( ~ 60 min filling time). the column packing density was 0.405 g cm-3, the free volume factor was 0.8018. each column was filled with approximately 7.95 g silicagel. stainless steel fritts (2 µm) were placed at the top and bottom of each column. before measurements air was removed with dichloromethane. parameters of smb-lc measurements we applied an 1-1-2-0 column configuration in smb system. this way the steroid b has “bigger space” along the length of the columns. in this case we did not use the raffinate pump, we adjusted the flow rate in segment iii so that the steroid b appeared in the lrout flow in the open-looped smb system. the function of segment i is the regeneration of the adsorbent and the production of the steroid a in the extract. we used 1,2:1 (v/v) acetone dichloromethane (gradient) like fresh eluent in the segment i. the function of segment ii is the separation of steroid a and b and the extraction of the steroid a in this segment. the function of segment iii is to separate steroid a and b and to produce steroid b in the lrout flow. we fed the mixture of steroid a and b into the third segment, the steroids were soluted in pure dichloromethane because this improved the solution of the steroids and helped us to use gradient smb. each of the columns in the four-column smb equipment were previously equilibrated with pure dichloromethane at 293 k, we wanted to separate the mixture of 42 g dm-3 steroid b and 18 g dm-3 steroid a in the same solvent. the flow rate of the steroid sample input was 0.8 cm3 min-1. steroid a was extracted with 2.2 cm3 min-1 parameter, so the lrout flow was 4.25 cm3 min-1 and the switching time was 22.5 min. process parameters have been determined by morbidelli method (fig. 8.). fig. 8. the measurements points placed in the morbidelli triangle at different switching times when we decreased the switching time to 11.25 min, we doubled the original flow rates. when we used 5.5 min for switch time, we doubled once again the flow rates. in case of 9 min switching time, we used computer simulation to optimize the work point to get as close to the points of morbidelli triangle as it was possible. simulation data of 1:1:2:0 column configuration smb simulation was done by smb-krom-n software. the input data are summarized in table 3. the software takes into account the solvent adsorptiondesorption phenomena, too. 18 table 3. input data of the software number of components k = 3 column inner diameter id.=1 cm column length l=25 cm number of columns n=4 free volume coefficient eps= 0.8018 cm3 liquid free volume cm-3 column bulk density roh= 0.4045 g silica gel cm-3 column langmuir constants (same as on page ) feed concentration liquid cmacetonemg -3f acetone 0=c liquid cmcomponentbmg -3f b 42=c liquid cmcomponentamg -3f a 18=c flow rates * optimized by simulation liquidmlcomponentaorbmg0 1s a s b −== cc simulation smb 8/41 smb 8/42 smb 8/46* smb 8/44 switching time(min) 22.5 11.25 9 5.5 f (cm3 min-1) 0.8 1.6 1.8 3.2 d (cm3 min-1) 4.25 8.5. 14.4 17.0 e (cm3 min-1) 2.2 4.4 7.8 8.8 r (cm3 min-1) 0 0 0 0 fresh eluent liquid cmacetonemg. -3f acetone 6435=c number of theoretical plates ntp=200 / 25 cm column calculation time 585 min results measurement results of 1:1:2:0 column configuration smb compared to simulation in the figs. 9. 10. 11. 12. those measurements are marked with grey colour where the desired results can be seen, with white colours the measurements which are out of our requirements. the result of the experiments shows that the decrease of the switching time highly improves the productivity, especially at the optimized 9 min switching time experiment. in this case the eluent consumption is also properly low. numerically describe the above gsmb 8/41 and gsmb 8/46, the productivity was increased from 0.95 mg steroid b g-1 adsorbent min-1 to 2.64 mg steroid b g-1 adsorbent min-1. the eluent consumption was changed from 0.12 cm3 eluent mg-1 steroid b to 0.18 cm3 eluent mg-1 steroid b. 0 20 40 60 80 100 prep. hplc gsmb8/41 (22.50 min) gsmb8/42 (11.25 min) gsmb8/44 (5.50 min) gsmb8/46 (9.00 min) pu ri ty " b "( % m /m ) raffinate > 99.9 % m/m b ηb > 90 % raffinate < 99.9 % m/m b vagy ηb < 90 % fig. 9. comparing the purity of steroid b in different measurements 19 0 10 20 30 40 50 60 70 80 90 100 prep. hplc gsmb8/41 (22.50 min) gsmb8/42 (11.25 min) gsmb8/44 (5.50 min) gsmb8/46 (9.00 min) yi el d "b "( % ) raffinate > 99.9 % m/m b ηb > 90 % raffinate < 99.9 % m/m b vagy ηb < 90 % fig. 10. comparing the yield of steroid b in different measurements 0.0 0.5 1.0 1.5 2.0 2.5 3.0 prep. hplc gsmb8/41 (22.50 min) gsmb8/42 (11.25 min) gsmb8/44 (5.50 min) gsmb8/46 (9.00 min) p b (m g b g -1 si lic a ge l m in ) raffinate > 99.9 % m/m b ηb > 90 % raffinate < 99.9 % m/m b vagy ηb < 90 % fig. 11. comparing the productivity of steroid b in different measurements 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 prep. hplc gsmb8/41 (22.50 min) gsmb8/42 (11.25 min) gsmb8/44 (5.50 min) gsmb8/46 (9.00 min) sf b (d m 3 e lu en t g -1 b ) raffinate > 99.9 % m/m b ηb > 90 % raffinate < 99.9 % m/m b vagy ηb < 90 % fig.12. comparing the eluent consumption of steroid b in different measurements we achieved the best favourable result in the rg-1040-gsmb 8/46 measurement at 9 min switching time. in this case calculated values of measurement were compared to data given in table 4. we note that the lrout 1, 2 are given by halving the lrout liquid stream for 0-4,5 min and 4,5-9 min fractions. conclusion our conclusion on the basis of laboratory measurements is that varying the switching time of smb process results big changes in productivity. in our case we get the highest productivity at 9 min switching time. we significantly increased the operation results according to the preparative hplc measurement (table 5.). we achieved 700% productivity increase and 50 % eluent consumption decrease beside more than 99.9 % m/m b purity and 90 % b yield. it could be seen, that the developed smb process was outstandingly economic, the value of the productivity was successfully increased to 3.082 kg b/ kg silica gel within a day. acknowledgement the authors express their gratitude to the chemical engineering institution co-operation research centre, veszprém, the széchenyi project of national research and development project, and the gedeon richter ltd. for financial support of this research. 20 table 4. results of the rg 1040 gsmb 8/46 measurement compared to result of the simulation measurement simulation purity of raffinate (lrout) lrout1 96.96 %m/m b lrout2 > 99.9 %m/m b lrout 1 +lrout 2 > 99.9 %m/m b purity of extract (e) 88.89 %m/m a 93.5 %m/m a yield lrout1 6.46 %b lrout2 92.6 %b extract 68.1 %a lrout 1 +lrout 2 > 99.99 % 98.3 % productivity lrout 2 2.14 mingelsilicag bmg extract 0.54 mingelsilicg amg lrout 1 +lrout 2 2.16 mingelsilicag bmg extract 0.69 mingelsilicg amg eluent consumption lrout 2 0.134 bmg eluentfreshcm3 extract 0.403 amg eluentfreshcm3 lrout 1 +lrout 2 0.197 bmg eluentfreshcm3 extract 0.61 amg eluentfreshcm3 table 5. results of the rg 1040 gsmb 8/46 measurement compared to preparative hplc measurement preparative hplc rg1040 smb8/46 measurement (9 min) purity of raffinate (lrout 2) >99.9 % m/m b >99.9 % m/m b yield (lrout 2) ~ 95 % b >92.6 % b productivity (lrout 2) 0.303 mingelsilicag bmg 2.14 mingelsilicag bmg eluent consumption (lrout 2) 0.354 bmg eluentfreshcm3 0.134 bmg eluentfreshcm3 21 symbols qacetone adsorbent concentration of acetone, mg g-1 aacetone langmuir constant of acetone, cm3 liquid free volume g-1 silica gel bacetone langmuir constant of acetone, cm3 liquid free volume mg-1 acetone cacetone concentration of acetone, g dm-3 qb adsorbent concentration of steroid b, mg g-1 ab langmuir constant of steroid b, cm3 liquid free volume g-1 silica gel bb langmuir constant of steroid b, cm3 liquid free volume mg-1 b component cb concentration of steroid b, g dm-3 qa adsorbent concentration of steroid a, mg g-1 aa langmuir constant of steroid a, cm3 liquid free volume g-1 silica gel ba langmuir constant of steroid a, cm3 liquid free volume mg-1 a component ca concentration of steroid a, g dm-3 k number of components k’ capacity factor id column inner diameter, cm l column length, cm f flow rate of feed, cm3 min-1 d flow rate of fresh eluent, cm3 min-1 e flow rate of extract, cm3 min-1 r flow rate of raffinate, cm3 min-1 lrout outlet liquid at 1:1:2:0 column configuration at r=0 t switching time, min ε free volume coefficient, cm3 liquid free volume cm-3 column roh bulk density, g silica gel cm-3column ntp number of theoretical plates references 1. szanya t., argyelan j., kovats s. and hanak l.: j. chromatogr. a, 2001, 908:265272 2. miron m., szanya t., hanak l., argyelan j. and marton gy.: hung. j. ind.chem. 1995, 23:293-298. 3. kovats s., csukas b., aranyi a. and pozna e.: hung. j. ind.chem. 1998, 26: 44-53. 4. broughton d. b. and gerhold c. g.: us pat. 2 985589, 1961. 5. jupke a., epping a. and schmidt-traub h.: j. chromatogr. a, 2002 944:93-117 6. giovanni o., mazzotti m., morbidelli m., denet f., hauck w. and nicoud r.: j. chromatogr. a, 2001, 919:1-12 7. jensen t., reijns t., billiet h. and wielen l.: j. chromatogr a, 2000, 873:149-162 8. houwing j., billiet h. and wielen l.: j. chromatogr a, 2002, 944:189-201 9. houwing j., hateren s., billiet h. and wielen l.: j. chromatogr a, 2002, 952:85-98 10. abel s., mazzotti m. and morbidelli m.: j. chromatogr a, 2002, 944:23-29 11. giovanni o., mazzotti m., morbidelli m., denet f., hauck w. and nicoud r.: j. chromatogr a, 2001, 919:1-12 12. antos d. and morgenstern a.: j. chromatogr., 2002, 944:77-91 13. antos d. and morgenstern a.: chem. eng. sci., 2001, 56:6667-6682 14. migliorini c., mazzotti m. and morbidelli m.: j. chromatogr. a, 1998, 827:2:161-173 microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 37(2) pp. 77-81 (2009) enzyme facilitated enantioselective transport of (l)-lactic acid through membranes e. kulcsar, e. nagy university of pannonia, department of research institute for chemical and process engineering h-8200 veszprem egyetem u. 10, hungary e-mail: nagy@mukki.richem.hu production of ethyl lactate in esterification reaction by candida antarctica lipase enzyme was studied the optimal conditions of the synthesis of ethyl lactate was obtained to be: 20 μl/ml lactic acid, 160 μl/ml ethanol, 15 mg/ml novozym 435 lipase enzyme. the yield obtained is over 90% and the enantiomeric exess is about 20% at temperature of 40 °c in case of 24 hours reaction time under 150 rpm revolution rate . in the present study, the enantioselective transport of the (l)-enantiomer from racemic lactic-acid has been presented through a lipase-facilitated supported liquid membrane (slm) containing ionic liquids keywords: d,l-lactic acid, enantioseparation, esterification, supported liquid membrane. introduction a growing interest has been developed for the synthesis and production of environmentally benign solvents and green chemicals. the significance of lactic acid arises from its utility as a monomer for biodegradable solvents and polymers in which the hydroxyl and the carboxyl functional groups permit it to participate in a wide variety of chemical reactions [1]. the reactivity of an alcohol as lactic acid (or its esters or amides) may undergo xanthation reaction with carbon bisulphide, esterification with organic acids and dehdrogenation or oxygenation to form pyruvic acid or its derivatives. the acid reactions of lactic acid are those that form salts. it can also undergo esterification reactions with various alcohols [2]. lactic acid, occurrence of which is widespread in nature, can be produced in large quantities by fermentation at low cost and its esterification is an important step for both lactic acid purification and for the production of the environmentally benign solvents. lactic acid esters are nontoxic and biodegradable materials having excellent solvent properties and could potentially replace toxic and halogenated solvents for a wide range of industrial and consumer uses [3, 4]. lactic acid has many pharmaceutical and cosmetic applications as formulations in topical ointments, lotions, anti acne solutions, humectants, parenteral solutions and dialysis applications, for anti carries agent. calcium lactate can be used for calcium deficiency therapy and as anti caries agent. its biodegradable polymer has medical applications as sutures, orthopaedic implants, controlled drug release etc. polymers of lactic acids are biodegradable thermoplastics. these polymers are transparent and their degradation can be controlled by adjusting the composition, and the molecular weight. their properties approach those of petroleum derived plastics. lactic acid esters like ethyl/butyl lactate can be used as green solvents. they are high boiling, non-toxic and degradable components [5]. an enzyme often shows a high selectivity for a target substrate; therefore, we can utilize the enzyme as a biocatalyst for the resolution of optically active materials. in an aqueous solution, lipase catalyzes the hydrolysis reaction of ester compounds however, the use of lipase in nonaqueous media enables its reverse reaction namely esterfication [6]. this property can be utilized for the resolution of racemic alcohols or carboxylic acids through the esterification by lipase. only a few reports have been published concerning the enzymatically catalyzed esterification reaction of lactic acid and alcohols [7]. in these reactions there is a potential risk that lactic acid will act both as acyl and nucleophile donor, thus yielding dimers and oligomers of lactic acid. to avoid this, one could either protect the hydroxyl group of the lactic acid or use an enzyme with which lactic acid is not effective as a nucleophile agent. here, the second alternative was utilised using a commercially available lipase from candida antarctica as catalyst [8]. moreover, lipases have been employed in preparing many flavour and fragrance esters under conditions that are milder than those used in the industry. in particular, the lipase from candida antarctica fraction b (cal-b) is a robust lipase in organic syntheses, showing high catalytic efficiency in the resolution of chiral esters and 78 amines via esterification, transesterification [9], aminolysis, and ammonolysis reactions, including regiochemo-, and geometric selectivity [10]. nowadays, enantioseparation of l(+)-lactic acid from the racemic mixture is important and challenging task for food and pharmaceutical industries. among various alternatives for lactic acid recovery, the supported liquid membrane (slm) appears to be a promising method because it potentially offers high flux and very selective separation. in addition, only small amounts of expensive carriers are required [11]. membrane separation methods, involving liquid membranes, are very promising new processes for enantioseparation [12–15]. however, only a little work has been conducted in the liquid membrane area engaging with the separation of lactic acid enantiomers: hadik et al. [16, 17] studied the enantioselective transport of d,l-lactic acid facilitated by their synthesized chiral selector n-3,5-dinitrobenzoyl-l-alanine octylester through supported liquid membrane or solid chiral membrane. tailoring of ionic liquids (il) to achieve good partitioning of target solutes and acceptable viscosity of il may lead to interesting results. the reactive mechanism of the solute extraction promotes partitioning and the separation selectivity. water extraction highly influences solvent extraction [18, 19]. a dual mechanism with the formation of reverse micelles and the formation of a hydrated complex has been proposed. kinetics of these processes may greatly influence the transport rate. influence of an anion structure of ils on the extraction by them is discussed in papers of martak et al. [20]. employing ionic liquids as a liquid membrane phase resulted in the stabilization of the slm, because ionic liquids have negligible vapor pressure and are waterimmiscible [21]. in the present study, we have investigated in the enantioselective transport of the (l)-enantiomer from racemic lactic acid through a lipase-facilitated slm based on ionic liquids. materials and methods materials enzyme: triacilglicerol hydrolase, e.c. 3.1.1.3. novozym 435, novo nordisk (basvaerd, danmark), 1u = 7000 μmol plu/g, 15 min, 1 atm (plu: propyllaurate, water content: 1–2%, lipase from porcine pancreas type vi-s, lyophilized powder from sigma , (d,l)-lactic acid 90% (reanal, hungary), ethanol (spektrum 3d, hungary). ionic liquid: trihexyltetradecylphosphonium bromide, >95%, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide 99%, triisobutylmethylphosphonium tosylate,>95% from iolitec. gas chromatograph: acme 6100, column: lipodex e 0,2 μm 25 m x 0,25 m, fid detector, shaking incubator: gfl 3031. ethyl lactate synthesis reactin mixtures contained 20 μl/ml lactic acid and 160 μl/ml ethanol. enzyme preparations were added to 15 mg/ml reaction solution. reactions were performed in 10 ml screw-capped glass bottles, at temperature of 40 ◦c for 24 hours. solution was shaked at 150 rpm. samples were taken from the reaction solutions at intervals of time and analyzed. c h 3 c h 2 o h o c h 3 c h o h o h o c h 3 c h o h o c h 2 c h 3 o c h 3 c h o h o h o h 2 * ++ etoh (d, l)-lactic acid enzyme (l)-ethyl lactate + (d)-lactic acid water * solution figure 1: reaction scheme for the enantioselective esterification of lactic acid with ethanol membrane hydrophobic poly(propylene) membrane filter (47 mm diameter, 0.2 μm pore size, 170 μm thickness) supplied by sterlitech. (kent, usa) were used as supporting membranes. membrane module using a pair of plastic cells (each cell had a volume of 25 ml). immobilization of the liquid membrane: the porous supporting membrane was submerged in 5 ml of il and a vacuum from a rotary pump was applied for 1 h to remove all of the air from the pores of the membrane. after procedures, the membrane was left to drip overnight to remove excess ionic liquid from the membrane surface. to determine the amount of ionic liquid immobilized in the supporting membrane, all the membranes were weighted before and after impregnation. analysis the enantiomers of ethyl lactate were analyzed by gas chromatograph 6100 model from acme (the republic of korea) with fid detector and chiral column (lipodex e 0,2 μm 25 m x 0,25 m). the selectivity was calculated in terms of the percentage enantiomeric excess (ee., %) and the separation factor (a) where ,100*)%.(. dl dllee + − = l is l-lactic acid concentration, d is d-lactic acid concentration. 79 results and discussion production of ethyl lactate in esterification reaction by candida antarctica lipase was studied. novozyme 435 (immobilized candida antarctica lipase b) was used for the present study as a biocatalyst, because this enzyme has been confirmed, in the previous observation, to be the most effective to esterify lactic acid. the influence of ethanol, lactic acid and enzyme concentration, initial water content and reaction time have been studied on both the ester yield and enantiomeric excess. effect of molar ratio of lactic acid to alcohol ratio between the lactic acid and ethanol was varied while the other parameters were held constant. an enzyme concentration of 15 mg/ml was used for all experiments. the lactic acid concentration was then held constant while the ethanol concentration was increased to obtain a ratio of 10:1, and vice versa, to obtain a ratio of 1:10 (fig. 2). results, shown in fig. 1, indicate that the most favorable ethanol to lactic acid ratio was equal to 7, where the conversion of the ester formation reached the value of 85%. the highest value of the enantimeric excess was obtained at alcohol to lactic acid ratio of 5. this can be regarded as optimal value. 0 10 20 30 40 50 60 70 80 90 100 1 2 3 4 5 6 7 8 ethanol(mg)/lactic acid (mg) % ee% yield % figure 2: effect of the molar ratio of alcohol to lactic acid on enantioselectivity of esterification of racemic lactic acid with ethanol, catalyzed by candida antartica effect of the temperature on activity of lipase the heat energy from the reaction temperature may affect enzymatic rate and functional group of substrate involved in the reaction, and therefore, reactions must be experimented to find the optimum temperature in order to obtain the best yield (fig. 3). the effect of reaction temperature using novozyme 435 on the esterification activity is shown in fig. 2. the results show that the highest value of activity of lipase was obtained at 40 °c, which can be regarded as the optimal reaction temperature. the relative activity was found to be increased with the temperature between 30 °c to 40 °c. in temperatur range above 50 °c, the relative yield was drastically decreased and it further decreased with an increase of temperature up to 70 °c, probably due to inactivation of the catalyst. 0 10 20 30 40 50 60 70 80 90 100 30 40 50 60 70 temperature [oc] es te r yi el d [°% ] figure 3: effect of temperature on the relative value of esterification activity of immobilized lipase effect of the enzyme concentration reactions were carried out at different enzyme levels (5–20 mg/ml) using constant concentrations of alcohol and acid substrates. when enzyme concentration was increased the ester yield increased but the enantiomeric excess was constant (fig. 4). 0 10 20 30 40 50 60 70 80 90 100 5 8 11 14 17 20 enzyme (mg/ml) % ee% yield % figure 4 : effect of enzyme concentration on the enzymatic esterification of lactic acid by ethanol influence of the initial water activity it is well known that while water is essential for the catalytic activity of enzymes in organic media, excess of water molecules reverses the direction of the esterification reaction. as a consequence, there is an optimal water level that maximizes the enzyme activity in organic media; control of the water content is thus important for optimizing esterification reactions in organic solvents. 80 the highest enantioselectivity was observed at 4 w/w % water concentration. this is the consequence of different effects of water activity on the reaction rates with the two isomers (fig. 5). according to our results, it appears that the lower the water activity is, the higher is the synthetic activity of c. antarctica lipase. best conversion was achieved for water concentration less than 2 w/w %. 0 10 20 30 40 50 60 70 80 90 100 1 2 3 4 5 water (w/w%) % ee% yield% figure 5: effect of water activity on the enantioselectivity and ester yield in the esterification of lactic acid 0 10 20 30 40 50 60 70 80 90 100 0 5 10 15 20 25 30 time (h) % ee% yield % figure 6: a time course of the esterification between lactic acid and ethanol by novozymes 435 the optimal conditions of the synthesis of ethyl lactate were 20 μl/ml lactic acid, 160 μl/ml ethanol, 15 mg/ml novozym 435 lipase enzyme. after shaking the reaction mixture with 150 rpm at 40 °c. the measured yield is over 90%. a high enantiomeric excess 20% is seen up to 4–6 h of reaction. results are shown in fig. 6. membrane separation lipase from candida antarctica (crl) is applicable for catalyzing esterification in the feed phase and another lipase from porcine pancreas (ppl) is an ester hydrolysis catalyst in the receiving phase. lipases are usually known as ester-hydrolysis catalysts, however, some of them, such as crl are able to catalyze ester synthesis. (l)-lactic acid is selectively esterified by crl in the feed phase, and the resulting ester dissolves into the ionic liquid phase of the slm and diffuses across the slm. in the receiving phase, ppl catalyzes the ester hydrolysis to produce the initial lactic acid and ethanol, which are water soluble. finally, the (l)-lactic acid is selectively transported through the slm, based on the enantioselectivity of lipases [21]. slm (ionic liquid phase) interface 1 interface 2 (l)-lactic acid + etoh (l)-lacticacid + etoh (d)-lactic -acid e1 e2 e1: candida anatrtica e2: porcine pancreas -h2o +h2o l-ethyl lactate figure 7: schematic diagram of enantioselective transport of (l)-lactic acid through a lipase-facilitated slm based on an ionic liquid 0 500 1000 1500 2000 2500 3000 3500 127 797 2680 2686 2895 time (day) et hl y la ct at (m g/ m l) l-ethyl lactate in the feed phase d-ethyl lactate in the feed phase l-ethyl lactate in the receivning phase d-ethyl lactate in the recivning phase figure 8: lipase-facilitated transport of lactic acid through the slm based on trihexyltetradecylphosphonium bromide the results of experiments in fig. 8 show the transport of both la enantiomers. when only the candida antartica lipase were present in the feed and porcine pancreas weren’t in the receiving phase, the concentration of (l)-ethyl lactate and (d)-ethyl lactate increases with time in the feed and receiving phases. the increasing rates of l-ethyl lactate in the phases were higher than those of d-ethyl lactate meaning that the lipase catalyzed reactions drove the selective transport of l ethyl lactate through the slm. the highest enantiomeric excess was 20% in all the used ionic liquid were almost the same effects of lactic-acid enantioselectivity. conclusion the resolution of lactic-acid by esterification with ethanol catalysed by a commercial immobilized candida antarctica lipase b was succesfully carried out in a membrane bioreactor containing an slm based on ionic liquids. this system integrated the enantioselective 81 catalytic action of the enzyme and the selective permeability of the isomers through the slm. various process variables such as the nature of the liquid membrane phase, the enzyme concentration in the feed compartment, temperature and the nature of ethanol used as acyl-donor were investigated in order to optimize the integrated reaction/separation process. in conclusion, our investigations demonstrate that the coupling of lipases with an slm based on il provides a promisingbasis for the development of environmentally friendly methodologies for practical production of enantiomerically pure or enriched compounds. acknowledgement this work supported by the hungarian reserach foundation under grants otka 63615/2006 references 1. holten c. h.: lactic acid; properties and chemistry of lactic acid and derivatives (1971), verlag chemie, weinheim 2. niju n., pradip r. k., aradhana s.: l (+) lactic acid fermentation and its product polymerization, electronic j. biotechnol. 7 (2004) 2, 167–178 3. jafar j. j., budd p. m., hughes r.: j. membr. sci. 199 (2002), 117–1213 4. tanaka k., yoshikawa r., ying c., kita h. okamato k.: chem. eng. sci. 57 (2002), 1577– 1584 5. datta r.: technological and economical potential of polylactic acid and lactic acid derivatives. fems microbiology reviews 16 (1995) 1-3, 221–231 6. kazandjian r. z., dordich j. s., kilbanov a. m.: enzymatic analysis in organic solvents, biotechnol bioeng. 28 (1986), 417–421. 7. torres, c., otero c.: enzymatic synthesis of lactate and glycolate esters of fatty alcohols, enzyme microb. technol. (1999). 25:745–752. 8. from m., adlercreutz p., mattiasson b.: lipase catalyzed esterification of lactic acid, biotechnol. lett. 19 (1997), 315–317 9. paiva a. l., van rossum d., malcata f. j.: kinetics of lipasemediated synthesis of butyl butyrate in n-hexane. biocatal. biotransfor. 20 (2002), 43–51 10. gotor v.: biocatalysis applied to the preparation of pharmaceuticals. org. proc. res. dev. 6 (2002), 420–426 11. yang q, chug t. s.: j. membr. sci. 294 (2007) 1-2, 127–131 12. baker r. w., cussler e. l., eykamp w., koros w. j., riley r. l., strathmann h.: membrane separation systems: recent developments and future directions park ridge, noyes data corporation, new jersey, 1991. 13. keurentjes j. t. f., nabuurs l., vegter e. a.: liquid membrane technology for the separation of racemic mixtures, j. membr. sci. 113 (1996), 351– 360. 14. bryjak m., kozlowski j., wieczorek p., kaferski p.: enantioselective transport of amino acid through supported chiral liquid membranes, j. membr. sci. 85 (1993), 221–228 15. clark j. d., han b. b., bhown a. s., wickramasinghe s. r.: amino acid resolution using supported liquid membranes, sep. purif. technol. 42 (2005), 201–211 16. hadik p., szabo l. p., nagy e., farkas z.: enantio separation of d,l-lactic acid by membrane techniques, j. membr. sci. 251 (2005), 223–232 17. hadik p., szabo l. p., nagy e.: d,l-lactic acid and d,l-alanine enantio separation by membrane process, desalination 148 (2002), 193–198 18. marták j., schlosser s.: phosphonium ionic liquids as new, reactive extractants of lactic acid, chem. papers 60 (2006), 395 19. martak j., schlosser s.: extraction of lactic acid by phosphonium ionic liquids, sep. purif. technol. 57 (2007), 483 20. marták j., schlosser s., vlcková s.: journal of membrane science 318 (2008), 298–310 microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 37(2) pp. 89-94 (2009) probability and expected time of emptying of intermediate storages under stochastic operation é. orbán-mihálykó1 , b. g. lakatos2, cs. mihálykó1, l. lucz1 1university of pannonia, department of mathematics, h-8200 veszprém, egyetem u. 10. hungary e-mail: orbane@almos.uni-pannon.hu 2university of pannonia, department of process engineering, h-8200 veszprém, egyetem u. 10. hungary a mathematical model for the operation of an intermediate storage under stochastic operational conditions is presented. the material input of the storage occurs at randomly, both in terms of time and amount of material, while the output is of constant volumetric rate. the main practical question is the required initial amount of material in the storage allowing no emptying of storage. in order to determine that we define a two variable function. we develop an equation satisfied by this function and present solution for the case of erlang(n) distributed inter-arrival time. we provide numerical examples and apply this function for solving the original problem. keywords: process system, random operation conditions, intermediate storage, reliability, integro-differential equation. introduction intermediate storage is frequently used in processing systems. in chemical engineering, the material produced by batch operational units is often collected in a storage system from which it is withdrawn for further processing in the subsequent plant units. the reasons of applying storage may be the different operational characteristics of the input and output subsystems, or necessity of sparing the processed material in case of failures during the operation. it seems to be an important question to determine the necessary size of the storage in order to avoid the overflow and the necessary initial amount of material not to run out the material stored. this is to ensure the work without failure of the continuously operated subsystem supplied by material from the storage system. investigating the operation of intermediate storage, researchers realised that the operation is rather stochastic than deterministic [2]. general stochastic model was set up for batch-batch systems [3], and a method was given for determining the size and the initial amount of material required for operation of the system without failures at a given reliability level. in this paper we investigate such a model in which the input of the storage system is formed by a processing system of a large set of batch operational units while the output of the storage occurs continuously, i.e. the material from the storage is withdrawn at a constant rate. in previous work [4], we investigated this problem assuming poisson input process. we have set up the equations modelling the behaviour of the system which were solved analytically in some special cases, and we have given a method for solving the sizing and initial amount problem based on these solutions or computer simulation. in this paper we deal with the problem of initial amount of material under more general conditions. we determine the probability of running out of material in the storage as a function of the initial amount of material. on the other hand it is interesting to also know the expected time of this event. in order to handle these problems together, we introduce a general function which at the value zero provides the probability of running out of material, and its derivative provides the expected time of emptying as well. applying the tools of probability theory we set up an integro-differential equation satisfied by this function. we show some qualitative properties of the solution and in some cases we determine analytical solutions for it. furthermore, we present numerical examples of solutions which are applied for solving the practical problem. the model: basic assumptions and notations consider a processing system consisting of a batch and a continuous subsystem that are connected by means of an intermediate storage system, shown schematically in fig. 1. the material to be processed is filled into the storage by the input sub-systems. the filling happens randomly, both in terms of time and amount of material. the investigation starts at t0 = 0 and the time intervals between the consecutive filling points are described by random variables ...3,2,1,kt therefore, the ith filling is at time ∑ = i k kt 1 . 90 figure 1: intermediate storage connecting the batch and continuous subsystems let the random variables ti be assumed to be nonnegative, independent, identically distributed random variables, hence the input process is a renewal process. if the random variables are exponentially distributed, then the input process is a poisson process. in a general case let their common distribution function be denoted by f(t), while the density function be denoted by f(t). let μf be their finite expectation. let n(t) denote the (random) number of fillings in the time interval [0, t]. in the ith filling event, the amount of material filled into the storage is random as well, and it is described by the nonnegative random variable yi, i = 1, 2, …. these are supposed to be independent of each other. their distribution function is denoted by g(y), the density function is g(y), while the finite expectation is μg. furthermore, we assume that the input process n(t) and yi are independent as well. the output process is a deterministic process with constant output rate c. the main goal is to determine the initial amount of material necessary at a given reliability level, which means that there occurs no running out of the material with a given probability. for this purpose it is worth investigating the change of material in storage as a function of time. the change of material is the difference of the filled and the withdrawn material. if we denote the initial amount of material by x, which is the amount of material at t = 0, and we sum up the change to the initial amount of material x, we get the function describing the amount of material in the storage in terms of time. this is a random function, which means that considering it in terms of time provides a stochastic process. in order not to run out of material it is necessary to satisfy the following inequality 0)( )( 1 ≥−+= ∑ = ctyxtv tn i i (1) for any value of t ≥ 0 where v(t) denotes the amount of the material in the storage at time t. as v(t) is a stochastic process, the inequality (1) holds for some realization and does not hold for other ones, i.e. it holds only with a given probability (reliability). let us introduce a function describing reliability, i.e. the probability of not emptying as a function of the initial amount of material. if x is the initial amount of material then we define ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ ⎭ ⎬ ⎫ ⎩ ⎨ ⎧ ≤∀−+≤= ∑ = )( 1 0:0)( tn i i ttctyxpxr . the probability of running out of the material is given by ψ(x) = 1 – r(x), and the time of emptying is expressed as }{⎩ ⎨ ⎧ <≥<≥ ≥≥∞ = 0)(:0existsthereif,0)(:0inf 0anyfor0)(if, )( tvttvt ttv xtv furthermore let the function φ(x,δ) be defined as follows. for 0 ≤ x and 0 ≤ δ we have )1(),( )( )( ∞< −= xt xt v veex δδφ . this function is, in essence, the laplace transform of the probability density function of the finite time of running out of the material. it can be easily shown that φ(x,δ) = ψ(x), and )1(),( )( )( 0 ∞< − = = ∂ ∂ − xt xt v veex δ δδ δφ , hence the function φ(x,δ) is a suitable tool for determining the reliability and the expectation as well. consequently, we will deal with the function φ(x,δ). we mention that similar function was introduced in insurance mathematics to investigate the ruin probability in [1] called gerber-shiu discounted penalty function. equations for the function φ(x,δ) first we note that the function φ(x,δ) is monotonic decreasing in both variables. it is continuous and the inequality 0 ≤ φ(x,δ) ≤ 1 holds. furthermore it can be proved that: theorem 1: for any x ≥ 0 and δ ≥ 0 function φ(x,δ) satisfies the following integro-differential equation: +−+= ∫ ∫ ∞ − dtdyygtfctyxex c z t )()(),(),( 0 0 δφδφ δ ∫ ∞ − + c x c x dttfe )( δ . (2) batch units continuous subsystem intermediate storage input output 1 k q(t)=c y1i, t1i yki, tki yi, ti 91 theorem 2: equation (2) has a unique solution for δ > 0 in the set of bounded functions. this solution tends to zero in exponential order. namely φ(x,δ) ≤ ke–rx for suitable constants 0 < k and 0 < r, depending on δ. in the case of δ = 0 the bounded solution of equation (2) is not unique, as the heaviside function, i.e. constant of value one for all x ≥ 0 is a solution to equation (2) and, if c f g > μ μ and ∫ ∞ −≤ x rxekdttf 2)( , r > 0, then there exists such a solution as well for which φ(x,0) ≤ k1e–rx with a suitable constant k1 > 0. remark: condition c f g > μ μ means that during a unit time interval the expectation of the amount of filled material is more than the amount of withdrawn material. in the opposite case it can be proven that the solution of the processing problem is φ(x,0) ≡ 1, x ≥ 0. theorem 2 ensures that in the case c f g > μ μ for any 0 < α < 1 there exists such an initial amount of material x for which the material in the intermediate storage will not run out with probability 1 – α hence the processing problem can be solved theoretically. the solution will be provided by taking the inverse function of φ(x,0) = ψ(x) at point y = α. consequently we want to determine the solution of equation (2). theorem 3: let the random variables be the sum of n independent, exponentially distributed random variables with parameter λ, that is erlang(n) distributed. now, one can prove that equation (2) can be transformed into the following form: ∫ ∑ ∞ − = +⎟ ⎠ ⎞ ⎜ ⎝ ⎛= =⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ + ∂ ∂ 0 0 )(),( ),( dyygyx c i n cx x n inn i i i δφλ λδδφ (3) with initial conditions i x i i cx x ⎟ ⎠ ⎞ ⎜ ⎝ ⎛−= ∂ ∂ = δδφ 0 ),( 1,...,1,0 −= ni (4) if δ > 0, then the function ∑ ∑ = − = −= m i n j xkj ij i iexcx 1 1 0 )()(),( δδδφ (5) is the unique solution of equation (3) where ki(δ) is the root of the equation ∫ ∞ − =⎟ ⎠ ⎞ ⎜ ⎝ ⎛−⎟ ⎠ ⎞ ⎜ ⎝ ⎛ − + 0 0 )( dyyge c k c ky nn λλδ , (6) which is the characteristic equation of equation (3). the multiplicity of ki(δ) is ni, and ∑ = = m i i nn 1 . the constant values cij(δ) can be uniquely determined from (4) by solving a system of linear equations. if the limit )(lim)0( 0 δ δ ii kk +→ = (i=1, …, m) exists, then ∑∑ = − = −= m i n j xkj ij i iexcx 1 1 0 )0()0()(ψ and )(lim)0( 0 δ δ ijij cc +→ = . corollary: if the assumptions of theorem 3 are valid and the roots of characteristic equation are of multiplicity 1, then ∑ = −= n i xk i iecx 1 )()(),( δδδφ and ∑ = −= n i xk i iecx 1 )0()0()(ψ . now xk n i iiixtv i v ecxkcxte )0( 1 '' )( ))0()0()0(()1)(( − = ∞< ∑ −−= where 1 0 )0( 1 ' )0()( )0( )0( −∞ − − ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ −−⎟ ⎠ ⎞ ⎜ ⎝ ⎛ ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ − = = ∫ n i yk n n i i k c ndyyyge c k cc n k i λλ λ especially, if n = 1, that is the inter-arrival times are exponentially distributed, then xkex )(1),( δδφ −= (7) xkex )0(1)( −=ψ (8) xk yk tv e dyyygec xxte i v )0( 0 )0( 1 )( )1)(( − ∞ − ∞< ∫− = λ . (9) if yk is exponentially distributed, that is 0,1)( 1 ≥= − yeyg y g gμ μ , then 92 x c ccc ggg ex 2 4)()( 2 ),( μ δδλ μ δλ μ δφ +−−+−−− − = (10) x c gex ) 1 ( )( μ λ ψ −− = (11) x c g g tv g v e cc x xte )1( )( )1)(( μ λ λμ λμ −− ∞< − = . (12) in the case when g(y) is a dirac-delta function at y = 1, that is yk ≡ 1, then an equation corresponding to equation(2) can be set up by similar argumentation and its solution expressed as xkex )(1),( δδφ −= (13) xkex )0(1)( −=ψ (14) xk tv e kc xxte v )0( 1 1 ))0(1( )1)(( − ∞< −+ = λ , (15) where k1(δ) is the unique root with positive real part of the characteristic equation 0=−− + −ke c k c λλδ (16) for δ ≥ 0. we note that as ψ(x) is exponential function in both cases, consequently its inverse function can be analytically determined easily. numerical results we discuss some examples of functions presented in the previous sections. fig. 2 shows the function φ(x,δ) determined by expression (13) in the case of exponentially distributed time interval tk with expected value μf = 0.5 (λ = 2), constant amount of filled material yk = 1 and constant withdrawing rate c = 1. here, x is the initial amount of material and δ is a parameter. the exponent k1(δ) was computed numerically from formula (16). figure 2: the form of function φ(x,δ) depending on the initial amount of material x and parameter δ fig. 3 demonstrates φ(x,0) = ψ(x) using the previously given parameters. the exponent in expression (14) is actually 1.5936. 0 0.5 1 1.5 2 2.5 3 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 figure 3: diagram of function ψ(x) describing the probability of running out of the material depending on the initial amount of material the inverse function of ψ(x), i.e. ψ–1(α), provides the necessary initial amount of material in the function of variable α, where α provides the probability of running out of material in storage. function ψ–1(α) is shown in fig. 4 depending on the parameter α. 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0 1 2 3 4 5 6 7 8 figure 4: the initial amount of material as a function of the probability of emptying the storage the expectation of the time of emptying given by formula (15) as a function of the initial amount of material can be seen in fig. 5. the function φ(x,δ) given by expression (10) is shown in fig. 6 in the case of exponentially distributed consecutive filling times with parameter μf = 0.5 and exponentially distributed filled amount of material with parameter μg = 1. φ(x,δ) x δ μf = 0.5 yk ≡ 1 c = 1 ψ(x) x α ψ–1(α) μf = 0.5 yk ≡ 1 c = 1 μf = 0.5 yk ≡ 1 c = 1 93 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 figure 5: the expectation of the time of emptying the storage depending on the initial amount of material figure 6: function φ(x,δ) in the case of poisson filling process and exponentially distributed filled material into storage the functions expressing the probability of emptying can be seen in fig. 7 using different values for the expectation of the filled material. figure 7: the probability of emptying storage ψ(x) as a function of initial amount of material in fig. 8 we represent the function φ(x,δ) in case of erlang(2) distributed consecutive input times with λ = 0.3, that is 3.0 2)( =ite , and lognormal distri-bution of the filled amount of material. parameter m equals 2, the standard deviation of the normal distribution is σ = 1, hence the expectation of the lognormal distribution is 18.12)( 2/2 == +σm i eye . the solution of the integrodifferential equation (3) is given by expression (5). the exponents were determined numerically from the equation (6). the integral for the case of lognormal distribution of the filled amount of material, i.e. the laplace transform of the lognormal density function can not be computed analytically. it was determined numerically by using gauss-laguerre quadrature formulas based on polynomial of degree 20. for this case, the bivariate function φ(x,δ) is presented in fig. 8. figure 8: function φ(x,δ) in case of erlang (2) distributed inter-arrival times and lognormal distribution of filled amount of material finally, let us see an example in details how to determine the initial amount of material according to the reliability level 1 – α = 0.95, i.e. we would like to determine how much initial amount of material is needed if we want to assure the operation of the system without running out of material with probability 0.95. it means that the initial amount of material in the storage x is to be determined corresponding to r(x) = 1 – α = 0.95. let us suppose that the distribution of the consecutive filling times is erlang(2) distribution with parameters λ = 2.1, c = 1 and yi ≡ 1. first we determine the roots of the equation ψ(x) = α. as ψ(x) = φ(x,0), we deal with the function φ(x,δ), which is of the form (5). now g(y) is a dirac-delta function at y = 1, hence equation (6) takes the form 0 22 =⎟ ⎠ ⎞ ⎜ ⎝ ⎛−⎟ ⎠ ⎞ ⎜ ⎝ ⎛ − + −kye c k c λλδ . this equation has two positive roots, one lies in the interval (0, λ + δ), and the another one is in the interval (λ + δ, ∞) with multiplicities equal 1. these roots were )1)(( ∞<vtv xte μf = 0.5 μg = 1 c = 1 δ φ(x,δ) x μg = 1 μg = 2 μg = 3 μf = 0.5 c = 1 φ(x, δ) x λ = 0.3 n = 2 m = 2 σ = 1 c = 2 x δ x μf = 0.5 yk ≡ 1 c = 1 ψ(x) 94 determined numerically by the newton method. the solution is of form )( 2 )( 1 21 )()(),( δδ δδδφ kk ececx −− += where the constants c1(δ) and c2(δ) are expressed from the initial conditions for i = 0 and i = 1, that is from the system of linear equations c1(δ) + c2(δ) = 1 and c ckck δδδδδ −=−− )()()()( 2211 . the function φ(x,δ) is shown in fig. 9. figure 9: function φ(x,δ) in the case of erlang (2) distributed inter-arrival times and constant amount of filled material the numerical computations provided the values k1(0) = 0.1968, k2(0) = 2.6564, while the constants are c1(0) = 1.0800, c2(0) = –0.0800, hence finally xx eex 6564.21968.0 0800.00800.1)( −− −=ψ . the function ψ(x) = 1 – r(x) = φ(x,0) can be seen in fig. 10. this function is shown together with the function ψ(x) equals 0.05 for x = 15. we numerically determined the roots of equation ψ(x) = 0.05, which is x = 15.61 and ψ(x) = 0.01 which holds for x = 23.7945. therefore, if we want to ensure operation of the continuous processing system without emptying of the intermediate storage with probability 0.95 we have to start to operate the system with initial amount of material equal to 15.6154 units. 0 2 4 6 8 10 12 14 16 18 20 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 figure 10: function ψ(x) in case of erlang (2) distributed inter-arrival times and constant amount of material however, in spite of having this amount of material the storage may still become empty with probability 0.05. the expected time of this event is 5398.12)1( = ∞<vtvte units. references 1. gerber h. u.,shiu e. s. w.: on the time value of ruin, north american actuarial journal 2 (1998), 48–78. 2. lee e. s., reklaitis g. v.: intermediate sto-rage and operation of batch processes under batch failure. comp. chem. eng., 13 (1989), 411–498. 3. odi t. o., karimi i. a.: a general stochastic model for intermediate storage in non-continuous processes. chem. eng. sci., 45 (1990), 3533–3549. 4. orbán-mihálykó é., lakatos g. b.: intermediate storage in batch/continuous processing systems under stochastic operation conditions. comp. chem. eng., 28 (2004), 2493–2508. x φ(x,δ) x λ = 2.1 n = 2 c = 1 yi ≡ 1 x ψ(x) δ λ = 2.1 n = 2 c = 1 yi ≡ 1 microsoft word contents.doc hungarian journal of industry and chemistry veszprém vol. 40(1) pp. 53–56 (2012) comparative study on concentration of juices from colourful wild berry fruits by membrane osmotic distillation k. bélafi-bakó , a. boór, n. nemestóthy university of pannonia, research institute on bioengineering, membrane technology and energetics 10 egyetem str., 8200 veszprém, hungary e-mail: bako@almos.uni-pannon.hu concentration of fruit juices by membrane osmotic distillation (mod) was studied. for the experiments, fresh juices were obtained from colourful wild berries: cornelian cherry, blackthorn, and whitebeam, which can be considered as valuable, highly nutritive beverages and characterized by high level of vitamins and antioxidant capacity. these beneficial properties may be preserved if mild but effective, environementally-safe membrane processes are applied for the concentration. mod is a coupled operation of membrane distillation (md) and osmotic evaporation (oe), where a hydrophobic membrane is used, while the osmotic agent was concentrated cacl2 solution. as a result of our experiments, we found that high concentration was possible to reach in the fruit juices studied, while the flux was between 0.3 and 2.4 lm-2h-1. comparing the analytical results of the fresh and concentrated juices, it has turned out that the antioxidant capacities were almost completely preserved during the concentration process. keywords: membrane processes, antioxidant capacity, cornelian cherry, blackthorn, whitebeam introduction fruit juices have been traditionally concentrated by multi-stage vacuum evaporation, resulting in a loss of fresh juice flavors, color degradation and a ”cooked” taste due to the thermal effects. the promising membrane alternatives (membrane separation processes, [1, 2]) offer potential advantages over the evaporation technique, such as improved product quality, easy scaleup and lower energy consumption, however, they are generally limited by the low flux and fouling. reverse osmosis (ro) is one of the membrane processes suitable for concentration of juices [3], but it cannot reach concentrations more than 25–30 °brix with a single-stage ro system due to high osmotic pressure limitation, which is quite below the value of 45–65 °brix for standard products obtained by evaporation. membrane osmotic distillation (mod) is a relatively novel process, where membrane distillation and osmotic evaporation is coupled; thus, the water vapor pressure difference across the membrane is added and higher driving force is obtained. in our earlier works, mod was used to concentrate juices from various fruits (e.g. apple) [4, 5], then the research was focused on colourful fruits like raspberry, black currant, and elder berry due to their higher antioxidant capacity and other beneficial features (high level of vitamins, anthocyanins... etc.) [6]. recently, the research work was extended to other colourful berries, which are mainly wild grown and can be found in the woods of hungary. in this work the following fruits were studied: cornelian cherry (cornus mas, l.) blackthorn (prunus spinosa, l.) common whitebeam (sorbus aria). the fruit of cornelian cherry is red (figure 1), 1-2 cm long, elongated and edible drupe, containing a single seed and ripens in the end of august [7]. the berries contain a great amount of vitamins, glucose, fructose, organic acid, tannin, pectin, fragranceand painting materials, and carotenoids. figure 1: cornelian cherry the fruit of blackthorn (figure 2), called a ”sloe”, is a drupe 10–12 millimeters (0.39–0.47 in) in diameter, black with a purple-blue waxy bloom, ripening in autumn [8], and harvested traditionally in october or 54 november after the first frosts. sloes are thin-fleshed, with a very strongly astringent flavour when fresh. figure 2: blackthorn common whitebeam (sorbus aria) is a deciduous tree [8], the fruits are scarlet berries (figure 3) similar to rowan berries, but less juicy, often eaten by birds. figure 3: common whitebeam all these fruits can be consumed fresh and often used to manufacture jam, marmalade, syrups, sweets, and soft drinks. all of them are rich source of natural antioxidants, phenolics, and flavonoids. the goal of this work was to compare the juices of these fruits from the concentration by mod point of view on one hand, and to study the preservation level of valuable compounds (antioxidant capacity and total polyphenol content) during the concentration process. materials and methods materials fresh raw fruits were collected in the forests of middlewest hungary and were stored in a freezer. calcium chloride dihydrate was technical grade from spektrum 3d, hungary, all other chemicals were analytical grade and purchased from sigma-aldrich, germany. experimental set-up the fresh, raw fruit juices were obtained by a hand pressing process which was then ultra-filtered by a 3dta (uwatech) test equipment for clarification. the uf cell was supplied with a 0.9 l feed tank and a cylindrical-shaped membrane module equipped with flat-sheet membrane (type polyethersulfone, nominal molecular weight cut-off 45 kda, active membrane surface area 150 cm2), operated in a cross-flow mode at 1.2–1.5 bar and room temperature, with 10 l/h axial flow rate. for the mod experiments, 6 mol/dm3 aqueous osmotic solution was prepared from calcium chloride dihydrate and was used in five-fold initial volume excess to prevent dilution. the membrane contactor used contained 34 polypropylene capillary membranes (microdyn) with a total effective internal area of 68 cm2, nominal pore size of 0.2 μm, 70% porosity, 0.8 mm outer and 0.6 mm inner diameter, thickness of 0.2 mm, and a length of 80 mm. the solutions were pumped through the shell side (osmotic circle) and the lumen of fibers (product circle) in a counter-current mode, using peristaltic pumps at 10.0 l/h flow rate. constant bulk temperature was maintained employing a heat exchanger on each side: 30°c and 17°c in the feed and osmotic side, respectively [6]. during the process the mass loss of the reservoir comprising diluted solution was acquired over time. analytical methods the experiments were followed mainly by measuring the total suspended solid (tss) of the samples taken. benzie and strain’s spectrophotometric method was used for determination of the antioxidant capacity in the samples [9]. the frap assay was developed to measure the ferric reducing ability of plasma (frap) at low ph by using 2,4,6-tripyridyl-s-triazine and fecl3 reagents in acetate buffer (ph 3.6). the absorbance was measured at 593 nm using a calibration curve for ascorbic acid (aa) and the results were expressed as mg aa/l. the total poly-phenol content was determined by the singleton and rossi spectro-photometric method, with the help of folin-ciocalteu reagent. the base of the determination is a complex making reaction between the hydroxide group of poly-phenols and the reagent. the absorbance of the blue coloured solution is proportional to the poly-phenol content of the extract. the total polyphenol content is referred to gallic acid [10]. results and discussion concentration of fruit juices the concentration experiments of the juices from the three fruits (cornelian cherry, blackthorn and common whitebeam) were carried out in the mod apparatus. the tss values of the three juices as a function of time are presented in figure 4. as it can be seen, the fastest process was found in case of blackthorn juice, probably due to its lower initial tss value. the runs were quite long (100-250 hours) because of the relatively small membrane surface area. 55 high final concentration (around 60%) was achieved for all the three juices. figure 4: tss values versus time the flux data are summarized in figure 5, where significant differences can be observed. higher fluxes were found in case of cornelian cherry than the other two juices, which may be explained by the much lower initial tss value in the beginning of the process. figure 5: flux values for the juices the antioxidant capacity and the total phenol content of the fresh, concentrated, and rediluted juices were determined and shown in figure 6 and 7. figure 6: antioxidant capacity of the juices figure 7: total polyphenol content of the juices it can be seen that both values for the fresh and rediluted juices were found similar, which means that it was possible to preserve majority of the valuable compounds in the juices and the concentration process can be considered mild enough. conclusion in this work, concentration of three colourful juices by membrane osmotic distillation was studied. we found that around 60 tss was achieved by the process and both the antioxidant capacity and the total polyphenol content were almost completely preserved confirming the advantages of the mild membrane process. acknowledgements this work was supported by the european union and co-financed by the european social fund in the frame of the támop-4.2.1/b-09/1/konv-2010-0003 and támop-4.2.2/b-10/1-2010-0025 projects. references 1. c. gostoli, s. bandini, a. r. di franscesc, g. zardi: concentrating fruit juices by reverse osmosis. the low retention/high retention method, fruit processing, 6 (1995) pp. 417–421 2. s. beszédes, zs. lászló, g. szabó, c. hodúr: hung, j. ind. chem., 36 (2008) pp. 11–16 3. l. takács, gy. vatai: hung, j. ind. chem., 36 (2008) pp. 119–123 4. k. bélafi-bakó, b. koroknai: enhanced flux in fruit juice concentration: coupled operation of osmotic evaporation and membrane distillation, journal of membrane science, 269 (2006) pp. 187–193 5. z. wang, f. zheng, y. wu, s. wang: membrane osmotic distillation and its mathematical simulation, desalination, 139 (2001) pp. 423–428 6. b. koroknai, zs. csanádi, l. gubicza, k. bélafi-bakó: preservation of antioxidant capacity and flux enhancement in concentration of 56 red fruit juices by membrane processes, desalination, 228 (2008) pp. 295–301 7. f. demir, i. h. kalyoncu: some nutritional, pomological and physicalproperties of cornelian cherry (cornus mas l.), journal of food engineering, 60 (2003) pp. 335–341 8. k. rushforth: trees of britain and europe, collins (1999) 9. i. f. f. benzie, j. j. strain: the ferric reducing ability of plasma (frap) as a measure of “antioxidant power”: the frap assay, anal. biochemistry, 239 (1996) pp. 70–76 10. v. l. singleton, r. orthofer, r. m. lamuelaraventos: analysis of total phenols and other oxidation substrates and antioxidants by means of folin-ciocalteu reagent, method enzymology, 299 (1999) pp. 152–178 microsoft word a_10_r.doc hungarian journal of industrial chemistry veszprém vol. 38(1). pp. 53-57 (2010) investigation of the oligomerization of light olefins on ion exchange resin catalyst e. kriván, g. marsi, j. hancsók department of mol hydrocarbon and coal processing, university of pannonia egyetem street 10, h-8201 veszprém, p.o. box 158., hungary e-mail: hancsokj@almos.uni-pannon.hu the requirements against the quality of motor fuels were rendered more rigorous in the past decade; the most important ones were the major reductions of the sulphur and aromatic content. besides the changing of the regulation of the motor fuels, the harmful material emission of the ottoand diesel-engine built vehicles was also limited significantly. these effects make necessary the greater use of the environmentally friendly, relatively “clean burning”, technically heteroatom and aromatic free, great nand i-paraffinic containing blending components in the case of gasoline and diesel gas oils. during our experimental work we studied the possibilities of producing motor fuel blending components like these blending components with the oligomerization of the olefin content of light fcc-naphtha – assuming later industrial application – on amberlyst-15 acidic ion exchange resin type catalyst. this topic is very important in a modern oil refinery, because different isoparaffin-rich motor fuel blending components can be produced (depending on the catalyst and the process parameters), and this technology can grow considerably the gasolineand diesel gas oil flexibility of the oil refinery, too. the aim of our experiments was to produce motor fuel blending components with the oligomerization of c4-c6 olefins in light fcc-naphtha matrix. working on the acidic ion exchange resin catalyst under different process parameters (t: 80–130 °c, p: 15–30 bar, lhsv: 0.5–3.0 h-1) we determined that in the studied process parameter range in preferable case (t: 100–110°c, p: 25–30 bar, lhsv 0.5–1.0 h-1) the liquid product yield was: greater than 95%, the conversion of olefins: 90–92%, the selectivity of c8-c11: 70–76%, while the selectivity of c12+: 24–30%. keywords: oligomerization, ion exchange resin, light olefin, fcc naphtha introduction during the fluid catalytic cracking (fcc) of heavy distillates and other thermal technologies light olefins (carbon number: 3-6) are formed as side products. due to the more rigorous regulations the blending of the fccnaphtha to motor fuel is limited, because it has great olefin content and vapour pressure, therefore it is necessary to convert these olefins. the growing demands for motor fuels in the world make it necessary to develop new technologies or make technologies perfect that would be suitable for producing different motor fuels (gasoline, jet, diesel gas oil). therefore against the conventional solutions (alkylation, producing of ethers) the oligomerization technologies have a greater importance, because they have greater flexibility from the aspect of product composition. during the oligomerization, olefins can be produced with different boiling point range (components are formed with gasoline, jet, diesel gas oil boiling point range depending on the grade of oligomerization), which can be convert to isoparaffins after hydrogenation. until now the oligomerization was studied with the application of different catalysts, like zeolits [1, 2], ionic liquids [3], metal-oxides [4, 5], and sulphated metal-oxide catalysts [6]. a part of the olefins, which is formed in oil refineries, is used for producing ethers (e.g.: methyl-tercier-buthylether – mtbe). the importance of mtbe has been reduced due to the environmental and health risks [7, 8]. the application of the acidic cation exchange resin catalysts can be a good solution from that aspect that with the limited mtbe use there is a great quantity of unused product capacity with the ion exchange catalyst, of which only a part will be converted to bio-etbe (ethyl-tercierbuthyl-ether) plant. the ion exchange resins are catalysts that are regenerative and applied in different hydrocarbon processes. the acidic ion exchange resins, which are available commercial, have different acidic strength, depending on the type of the contained acidic group (e.g.: -so3h, -cooh). first of all the sulphonic acid group containing catalysts can be the most suitable for the aim of oligomerization from these catalysts. the studies of the oligomerization of isobutene were carried out with different commercial ion exchange resin catalysts. on the studied catalyst they reached different conversions (90–100%), and different selectivity of dimers (5–10%), trimers (75–95%), and tetramers (2–6%) [8]. the achieved results correlated with the acidic capacity, the type of the function group and the structure of the applied catalysts. some papers studied especially the possibilities 54 of producing dimers [9, 10], but there are some papers which worked on the possibilities of producing trimers, too [8, 11]. but these experiments were carried out with model compounds (isobutene), not with the materials available in the industry. experimental the aim of our experimental work was to produce isoolefin-rich products with great yield from light fccnaphtha with oligomerization on an acidic ion exchange resin catalyst; which products can be used as blending components for different motor fuels after hydrogenation. apparatus we carried out the experiments in a great laboratory, high pressure reactor system. the effective volume of the fixed bed reactor was 100 cm3. this equipment included the main apparatus and machines which can be found in an industrial plant also. the simplified theoretical process system is shown in fig. 1. we have determined the process parameters based on literature data and our earlier experiments. the examined temperature range was: 80–130 °c, pressure range: 15–30 bar, liquid hour space velocity: 0.5–3.0 h-1. thereinafter we show the results of the measurements with two different feedstocks. figure 1: simplified scheme of the test apparatus (1 oxygen converter; 2 gas dryer; 3, 11 gas filter; 4, 5 burettes for liquid feed; 6 pre-heater; 7 reactor; 8, 10 heat exchangle; 9 separator; v-1, v-3, v-7, v-8,v-9, v-10, v-15, v-16, v-18 closing valve; v-2, v-4, v-5, v-6, v-13, v-14, v-17, v-19 control valve; v-11, v-12 back valve; pi1, pi2, pi3, pi4 manometer; p-1 pump; fic-1 gas flow meter/ controller; pir-1 pressure register; fi-1 gas flow meter; pic-1 pressure meter/ controller) materials assuming a later industrial application we carried out our experiments not with individual olefins, but with light fcc-naphtha from a refinery, and with the part of the fcc-naphtha, distillated to 60°c (table 1). the applied redistillated feedstock contained 34% unsaturated components (mainly c5-c6 hydrocarbons), which were important from the point of view of oligomerization. we carried out the experiments on an amberlyst-15 type catalyst (table 2). we loaded 80 cm3 catalyst into the reactor. table 1: the composition of the applied feedstocks composition, % hydrocarbons total fcc naphtha light fcc naphtha distillate butenes 2.1 2.7 i-pentane 25.6 36.7 pentene 3.7 4.6 n-pentane 3.4 4.2 dimethyl-butene 18.8 20.6 2-methyl-pentene 1 1 methyl-pentane 14.2 16.8 hexene 1.6 2.2 hexane 1.3 1.7 methyl-cyclopentene 1.3 1.7 methyl-cyclopentane 2.1 2.7 cyclohexene 0.6 0.8 cyclohexane 0.4 0.7 other hydrocarbon 22.9 3.6 total olefin 29.1 33.6 55 table 2: main parameters of the amberlyst-15 ion exchange resin properties amberlyst-15 acidity, meq h+/g (dry) 4.75 humidity content, % 53.1 apparent density, g/cm3 0.77 specific surface area, m2/g 45 particle size (95%-os volume), mm 0.63–1.25 porosity, cm3/g 0.3 testing and calculating methods we thermostated the feedstock at nearly 0–5 °c in the storingand feeding burettes for all of the experiments. the measurements on the ion exchange resin were carried out in nitrogen atmosphere. at first for the dehydratation of the catalyst, we increased the temperature to 105 °c with nitrogen flow, and we held this temperature for 2 hours, after that we set the temperature to the temperature of the first experimental point. after that we increased the pressure to the adequate value. we started the experiment when the system was in steady-state. we examined the liquid hydrocarbon products with gas chromatography method (thermo finnigan trace gc), which contained a pona column (varian cp-sil pona cb fs 50×0.21×0.5). based on the achieved results we determined the value of the transformation of the olefin content of the feedstock (conversion), and the quantity of the c8-c12, and the c12+ fraction (selectivity). results and discussion at the first experiment we carried out our measurements with light fcc-naphtha feedstock, in a temperature range of 80–130 °c, the pressure was 15 and 30 bar, and with a liquid hourly space velocity range of 0.5–3.0 h-1. based on the results we determined that at all measure points the liquid product yield was greater than 95%. the value of the olefin conversion changed between 5 and 16.5%. in fig. 2 and 3 we show the values of the olefin conversion, measured at constant pressure, 20 and 30 bar. 0 2 4 6 8 10 12 14 16 18 70 80 90 100 110 120 130 140 o le fin co nv er sio n, % temperature, °c lhsv=0.5 1/h lhsv=1.0 1/h lhsv=2.0 1/h lhsv=3.0 1/h figure 2: conversion of olefins as a function of the temperature and pressure (p = 20 bar, light fcc-naphtha) 0 2 4 6 8 10 12 14 16 18 70 80 90 100 110 120 130 140 o le fin co nv er sio n, % temperature, °c lhsv=0.5 1/h lhsv=1.0 1/h lhsv=2.0 1/h lhsv=3.0 1/h figure 3: conversion of olefins as a function the temperature and pressure (p = 20 bar, light fcc-naphtha) we found that with the changing of the temperature, the conversion of olefin had a maximum value at 100–110 °c, while with the reduction of the liquid hourly space velocity the value got greater. at 30 bar pressure the measured conversion was greater than the measured conversion at 20 bar. we also found that during the experiments with light fcc-naphtha the conversion concerning to the olefin content of the feedstock is only 5–16.5%. the reason was that the heavier components of the feedstock, like the aromatic compounds and cyclic compounds, were adsorbed to the active spaces of the catalyst, so they reduced the activity of the catalyst. so, in case of the referred experiment we could not reach the expected conversion, therefore during the following experiments we cut the feedstock with distillation, so that the feedstock distillated to 60 °c should contain less compounds affecting the activity of the catalyst harmfully. in case of the following experiment we studied the quantity of the olefin content of the narrower boiling point ranged feedstock under the process parameters applied earlier. based on the results, we found that in all points of the measurement, the yield of the liquid products was greater than 95%. the conversion of the olefin depended on the process parameters considerably. we compared the values of the conversion of olefin achieved at 20 and 30 bar pressure, in fig. 4 and 5. based on this we found that at constant pressure the conversion of olefins increased considerably, with the increase of the temperature, it was the greatest at 110 °c, and over 110 °c it reduced, while the reduction of the liquid hourly space velocity increased the conversion. the colour of the catalyst taken off from the reactor was darker than the colour of the new catalyst. the applied acidic ion exchange resin deactivated quickly at greater temperature, because it lost a part of its sulphonic groups [12]. the selectivity of c8-c11 (70–76%) and c12+ (24–30%) changed as a function of the temperature similarly to the conversion of olefins (fig. 6). we reached the greatest selectivity of c12+ (29.8%) at temperature 110 °c, 30 bar pressure, and 1.0 h-1 liquid hourly space velocity. due to the relatively weak acidity of the acidic ion exchange resin tetramers formed in a little quantity, it is preferable from that aspect that the catalyst deactivates slower. 56 0 10 20 30 40 50 60 70 80 90 100 70 80 90 100 110 120 130 140 o le fin co nv er sio n, % temperature, °c lhsv=0.5 1/h lhsv=1.0 1/h lhsv=2.0 1/h lhsv=3.0 1/h figure 4: conversion of olefins as a function of the temperature and pressure (p = 20 bar, feedstock: prefraction of light fcc-naphtha) 0 10 20 30 40 50 60 70 80 90 100 70 80 90 100 110 120 130 140 o le fin co nv er sio n, % temperature, °c lhsv=0.5 1/h lhsv=1.0 1/h lhsv=2.0 1/h lhsv=3.0 1/h figure 5: conversion of olefins as a function of the temperature and pressure (p = 30 bar, feedstock: prefraction of light fcc-naphtha) 10 12 14 16 18 20 22 24 26 28 30 32 70 80 90 100 110 120 130 140 c 12 + se le ct iv ity , % temperature, °c lhsv=0.5 1/h lhsv=1.0 1/h lhsv=2.0 1/h lhsv=3.0 1/h figure 6: the changing of part of c12+ products as a function of the temperature and the liquid hour space velocity (p = 30 bar, prefraction of light fcc-naphtha) with the increase of the liquid hourly space velocity the growing number of the olefin molecules increases the possibility of the forming of heavier oligomers, at the same time the greater volume flow „washes out” the intermedier products from the surface of the catalyst. the selectivity of c12+ changed as resultant of these effects as a function of the liquid hourly space velocity. with the increase of the pressure the conversion of olefins increased in the examined ranges (fig. 7). after reaching the liquid state (20.2 bar at 100 °c, 24.2 bar at 110 °c, determined with soave-redlich-kwong (srk) method), the following increase of the pressure had less effect on the conversion of olefins. with the increase of the pressure the parts of the c12+ hydrocarbons got greater. 0 10 20 30 40 50 60 70 80 90 100 10 15 20 25 30 35 o le fin c on ve rs io n/ c 12 + se le ct iv ity , % pressure, bar conversion t=100 °c conversion t=110 °c c12+ selectivity t=100 °c c12+ selectivity t=110 °c figure 7: the effect of the pressure on the conversion of olefins and the selectivity of c12+ (lhsv = 1.0 h-1, feedstock: prefraction of light fcc-naphtha) we found that the conversion of olefins was lower than experienced by others in experiments with model compounds. the reason is that the industrial feedstock contained a relatively high quantity of inert materials from the aspect of oligomerization (66% paraffin and cyclic compounds), which obstructs the access to the active sites, or adsorbs to the active sites of the catalyst. summary the growing degree of the use of motor fuels makes necessary the research and development of those new technologies that can produce adequate quality blending components from lower value feedstock. during our experimental work we studied the possibilities of converting the olefin content of light fcc-naphtha with oligomerization to greater carbon number isoolefin-rich products that can be applicable as blending components of motor fuels after hydrogenation. we studied the effect of the process parameters (temperature, pressure, liquid hourly space velocity) on the conversion of olefins and the selectivity of the products on amberlyst-15 ion exchange resin catalyst. in the course of the experiments carried out with acidic ion exchange resin, we successfully produced preferable products at 100–110 °c temperature, 25–30 bar pressure and 0.5–1.0 h-1 liquid hourly space velocity (conversion of olefin was 90–92%, c12+ selectivity 24–30%). in all cases the selectivity of the c12+ products was lower than the selectivity of c8-c11, the greatest value was 30%. we also found that the light fcc-naphtha applied as feedstock contained non-olefinic compounds that adsorbed to the active sites of the catalyst, therefore a distillation step is necessary to separate them and to increase the olefin content of the light fcc-naphtha, too. the achieved products cannot be applied directly as motor fuel blending components, because of their great olefin content. but with catalytic hydrogenation isopraffinrich products can be produced with preferable quality. so with these two catalytic steps valuable products can 57 be produced from light olefin containing side products of an oil refinery. acknowledgement we acknowledge the financial support of this work by the hungarian state and the european union under the tamop-4.2.1/b-09/1/konv-2010-0003 project and the ion exchange catalysts by hsh chemie distribution group. references 1. j. w. yoon, s. h. jhung, d. h. choo, s. j. lee, k. y. lee, j. s. chang: oligomerization of isobutene over dealuminated y zeolite catalysts, applied catalysis a: general, 337, 2008, 73–77. 2. r. van grieken, j. m. escola, j. moreno, r. rodriguez: nitrogen and sulphur poisoning in alkene oligomerization over mesostructured aluminosilicates (al-mts, al-mcm-41) and nanocrystalline n-hzm-5, applied catalysis a: general, 337, 2008, 173–183. 3. r. f. de souza, d. thiele, a. l. monteiro: effect of phosphine–cs2 adducts on the nickel-catalyzed butenes oligomerization in organochloroaluminate imidazolium 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45, 2000 19–27. 9. m. marchionna, m. di girolamo, r. patriani: light olefins dimerization to high quality gasoline components, catalysis today, 65, 2001, 397–403. 10. t. ouni, m. honkela, a. kolah, j. aittamaa: isobutene dimerisation in a miniplant-scale reactor, chemical engineering and processing, 45 (5), 2006, 329–339. 11. j. w. yoon, j.-s. chang, h.-d. lee, t.-j. kim, h. jhung: trimerization of isobutene over cation exchange resins: effect of physical properties of the resins and reaction conditions, journal of molecular catalysis a: chemical, 260, 2006, 181–186. 12. k. hauge, e. bergene, d. chen, g. r. fredriksen, a. holmen: oligomerization of isobutene over solid acid catalysts, catalysis today, 100, 2005, 463–466. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 37(2) pp. 159-164 (2009) mathematical modeling of diafiltration z. kovács1 , m. fikar2, p. czermak1,3 1institute of biopharmaceutical technology, university of applied sciences, giessen-friedberg, giessen, germany e-mail: kovacs.zoltan@tg.fh-giessen.de 2department of information engineering and process control fcft, slovak university of technology, slovakia 3department of chemical engineering, kansas state university, manhattan, kansas, usa the main objective of this study is to provide a general mathematical model in a compact form for batch diafiltration techniques. the presented mathematical framework gives a rich representation of diafiltration processes due to the employment of concentration-dependent solute rejections. it unifies the existing models for constant-volume dilution mode, variable-volume dilution mode, and concentration mode operations. the use of such a mathematical framework allows the optimization of the overall diafiltration process. the provided methodology is particularly applicable for decision makers to choose an appropriate diafiltration technique for the given separation design problem. keywords: membrane separations, diafiltration, mathematical modeling, optimization introduction the objective of industrial purification processes is usually dual: (1) to separate certain solutes from the process liquor and (2) to concentrate the purified solution in order to obtain a final product. in this work we examine a batch diafiltration process that is designed to fulfill these objectives simultaneously. in the following we consider a binary aqueous solution consisting of two solutes, namely a macrosolute and a microsolute. diafiltration is known as a conventional process technique to achieve high purification of macrosolutes with an economically acceptable flux [1]. the requirement for an effective separation is the utilization of a membrane which has a high rejection for the macrosolute and a low rejection for the microsolute. the terms macrosolute and microsolute are widely-used in the literature dealing with membrane diafiltration. in order to eliminate ambiguity, we would like to point out, that the separation is not necessarily based on solely size exclusion as it might be suggested by this nomenclature. membrane filtration also allows separation of solutes of similar molecular weights but having different charges as reported in many studies, for example in [2, 3]. there have been many published works on batch diafiltration. however, there is no exact and uniform definition for the term diafiltration. indeed, the terminology currently being used is somewhat conflicting. in this paper, we use the term diafiltration in its broad sense referring to the actual technological goal. thus, diafiltration is a membrane-assisted process that can be used to achieve the twin-objectives of concentrating a solution of a macrosolute, and removing a microsolute by the utilization of a diluant. in this context, batch diafiltration is a complex process that may involve a sequence of consecutive operational steps. we consider three frequently used operational modes. these are the concentration mode (c), the constant-volume dilution mode (cvd), and the variable-volume dilution mode (vvd). they differ from each other in the utilization of wash-water as it is discussed in more details later in this paper. note that an operation mode does operate with fixed operational settings. a diafiltration process, in contrast, is usually constructed by changing the settings of wash-water addition (i.e. switching to another operational mode) according to a pre-defined schedule. in the following, we examine two frequently used diafiltration techniques: the traditional diafiltration (td) and the pre-concentration combined with variablevolume dilution (pvvd). the most commonly used concept of diafiltration is the td process that involves three consecutive steps (i.e. operational modes). first, a pre-concentration is used to reduce the fluid volume and remove some of the microsolute. then, a constant-volume dilution step is employed to “wash out” the micro-solute by adding a washing solution (e.g. diluant) into the system at a rate equal to the permeate flow rate. thus, the volume of the solution in the feed tank is kept constant during this operational mode. finally, a post-concentration is used to obtain the final volume and concentrate the macrosolute to the final concentration due to the specific technological demands. the vvd is an operation mode in which fresh water is continuously added to the feed tank at a rate that is proportional but less than the permeate flow. this causes a simultaneous concentration of macrosolute and removal 160 of microsolute. this operation has been proposed by jaffrin and charrier [4], analyzed in some detail by tekić et. al and krstić et. al [5, 6], and recently revised by foley [7]. a modification of vvd is pvvd, i.e., a two step process in which the solution is first preconcentrated to an intermediate macrosolute concentration and then subjected to vvd to reach the final desired concentrations of both solutes. this concept is credited to foley [8]. several studies have examined the different types of diafiltration techniques in terms of process time and wash-water requirement [1, 4-11]. however, only a few works have considered concentration-dependent rejections in the optimization procedure [12]. assuming constant rejections might lead to inaccurate simulation and subsequent optimization results under conditions where the rejections of solutes are strongly vary depending on their feed concentrations and a considerably interdependence in their permeation occurs. in this work, we attempt to enlarge our perspective on how engineers in general should cope with the complexity of a diafiltration design problem. we present a general mathematical model in a compact form for batch diafiltration techniques. from this perspective we discuss the model limitations when simplifying assumptions on solute rejections are being used. we consider a common separation objective and through a specific example we demonstrate the power of the presented modeling methodology. finally, we present some specific ideas of how optimization should support decision makers in finding the best wash-water utilizing profile for the given engineering design problem. theory configuration of diafiltration the schematic representation of membrane diafiltration setting is shown in fig. 1. figure 1: schematic representation of diafiltration settings in a batch operation, the retentate stream is recirculated to the feed tank, and the permeate stream q(t) is collected separately. during the operation, fresh solute-free diluant stream u(t) (i.e. wash-water) can be added into the feed tank to replace solvent losses. general mathematical framework in this section we derive the governing differential equations for diafiltration. the proportionality factor α(t) is defined as the ratio of diluant flow u(t) to permeate flow q(t): )( )()( tq tut =α (1) where the diluant flow u(t) is given as a product of the membrane area a and the permeate flux j(t). the change in the volume in the permeate tank vp is given by the permeate volumetric flow-rate q: )( )( tq dt tdvp = (2) the change in the feed volume during the operation is given as )()( )( tqtu dt tdv f −= (3) considering two solutes and assuming that the diluant consists of no solutes, the mass balance for the solute concentrations yields 2,1)()()()( ,, =−= itctqtctv dt d ipiff (4) where cp,i(t) denotes the permeate concentration of solute i at time t. equation (4) can be rewritten in the following way: 2,1)()( )( )()( )( , , , =−=+ itctq dt tdc tvtc dt tdv ip if fif f using eq.(3) and recalling that cp,i(t) = cf,i(t)(1–ri(t)), where ri(t) is the rejection of solute i at time t, we obtain, for i = 1, 2, ... [ ])()()()( )( )( , , tutrtqtc dt tdc tv iif if f −= thus, we have the following initial-value problems: ⎪ ⎩ ⎪ ⎨ ⎧ = −= 0)0( )()( )( ff f vv tqtu tdt dv (5) and, for i = 1, 2, ... [ ] ⎪ ⎩ ⎪ ⎨ ⎧ = −= 0 ,, , , )0( )()()()( )( )( ifif iif if f cc tutrtqtc dt tdc tv (6) which describe the evolution in time of the volume in the feed tank vf and of the feed concentration cf,i. vf 0 and cf 0 ,i denote respectively the initial feed volume and the initial feed concentration of the solute i. in the next two sections, we briefly describe discuss the possible strategies to determine flux and rejection. 161 later we formulate an optimization problem that represents a frequent industrial separation flask. then, to examine and compare the td and pvvd processes, we make a use of the filtration data from our earlier work [14]. rejection and permeate flow the separation behaviour of the membrane can be characterized in terms of permeate flux and solute rejections. the estimation of the flow q(t) and of the rejection ri(t) can be carried out separately using the most convenient approach for the problem at hand. possible strategies to determine flux and rejection are presented in our previous study [13]. in brief, either mechanism-driven or data-driven models can be employed. mechanism-driven models are based on a physical understanding of the transport phenomenon. in contrast with that, data-driven models make a direct use of the experimental data obtained from filtration tests with the process liquor. the main challenges in employing a data-driven model are the minimization of necessary a-priori experiments and the conversion of raw data into useful information. in this study, we consider the following empirical relations which were reported earlier in [14]: 1,62,5 2 2,4 )( 32,2 2 2,1 )( fff cscscs ff escscsq ++++= (7) )()( 42,31,22,11 zczczczr fff +++= (8) 1,62,5 2 2,4 )( 32,2 2 2,12 )( fff cwcwcw ff ewcwcwr ++++= (9) where s1, ..., s6, z1, ..., z4, w1, ..., w6 are suitable coefficients that were previously determined from laboratory experiments with the test solution as described later. special cases and analytical solutions the complexity of the modelling problem originates from the fact that in most of the membrane filtration processes the solute rejections are concentrationdependent quantities. since the concentrations are due to change while processing the feed, the rejections of both microsolute and macrosolute are affected by the extent to which the microsolute concentration is reduced and also to which the macrosolute is concentrated. analogously, the permeate flux also depends on the actual feed concentration of both components. in general, the model equations require numerical techniques to solve them, since no closed form solutions exist. however, when the effect of the feed concentrations on the rejections is neglected, then a constant rejection coefficient σ can be introduced such that ri(t) = σi = constant for i = 1, 2. when introducing this simplifying assumption on the rejections, the differential equations can be reduced to simple algebraic equations, the resulting exact solutions are reviewed below: 1. concentration mode: since no diluant is applied, u(t) = 0 and cd,i = 0. the concentration of component i at the end of the operation is given by (10) where the expression )( )0( ff f tv v is by definition the concentration factor n. 2. constant-volume dilution mode: the solute free diluant is continuously added to the feed tank in a rate equal to the permeate flow. thus, cd,i = 0 and u(t) = q(t). the component concentration is related to the total volume of wash-water vw can be written as )( )1( ,, )0()( ff iw tv v iffif ectc − = σ i = 1, 2, ... (11) where the expression )( ff w tv v is by definition the dilution factor d. 3. variable-volume dilution mode: solute-free washwater is added at a rate αq(t) , where α is a parameter with value 0 ≤ α ≤ 1. assuming that the permeate flux remains unchanged during the process, krstić et al. [6] gave the expression for the component balance: α ασ α − − ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ − − = 1 , , )0( )()1( 1 )0( )( i f fp if fif v tv c tc i =1, 2, ... (12) note, that the main pitfall of the commonly used modelling approaches is often the assumption of constant rejection coefficients. these simplifying assumptions can easily be misused when their appropriateness is not carefully checked for the given separation process. for instance, a typical rejection profile of an inorganic salt nanofiltration is illustrated in fig. 2. figure 2: rejection of the membrane desal-dk5 for nacl as a function of feed concentration (30 bar, 25 ºc, 0.55 m2 spiral-wound element, 1.0 m3h-1 recirculation flow-rate). solid line is for eye guidance 162 the complexity of the problem further increases in the presence of more than one solute, due to their interdependent permeation. optimization problem formulation we define the optimization problem as follows: minimize (j = cf,2(tf)) (13) such that tf ≤ 6 (14) n = 3. (15) thus, the objective of the separation is to reduce the concentration of component 2 in the final product as much as possible with the restriction that the total operation time should not exceed 6 hours and a total concentration factor 3 is achieved. in the case of td, the objective is to find the optimal set of variables of pre-concentration factor n1, dilution factor d, and post-concentration factor n2. in the case of pvvd, the optimal set of variables n1 and α is to be determined. note that the numerical values of the constraints in eqs. (14) and (15) are chosen according to the processing conditions and the specifications of our laboratory system. however, the concept itself can find a general interest. industrial problems can be handled in an analogous way, when the optimal operational parameters of an existing membrane plant with a defined membrane area are to be found. experimental in this study we use the filtration data from our earlier work [13]. these data serve as input for the mathematical analysis. the laboratory apparatus, applied chemicals, and sample analysis have been described in details earlier. in brief, nanofiltration experiments were carried out with the membrane desal-dk5 separating a binary aqueous solution at constant temperature and pressure. the process liqueur was a test system consisting of sucrose (hereafter called component 1) and sodium chloride (component 2). a limited number of a-priori experiments were used to determine the dependence of r and q on concentration. the resulting functions are reported in section “rejection and permeate flow”. results the dynamics of a diafiltration process can be evaluated by simultaneous solving of eqs. (5) and (6). considering a td process with a fixed pre-concentration factor n1, the post-concentration factor n2 is readily given with the use of the constraint on the total concentration factor as n2=n/n1. it is evident that longer dilution results in lower final microsolute concentration. thus, for each preconcentration factor, a maximal dilution factor can be found so that the given constraint on the total operation time is still satisfied. for instance, when the initial solution is pre-concentrated with a factor 2, then a maximal operational time for cvd can be calculated so that the total operation time including the postconcentration step does not exceed the given 6 hours. this example is illustrated in figs. 3a and 3b. figure 3: the estimated 6-hour time-course of the concentrations and the volumes of feed and permeate for a traditional diafiltration process with a preconcentration-factor of 2 the optimization problem of pvvd is analogous to td. here, an optimal α has to be found for each fixed n1 so that the objective function is minimized while satisfying the constraints. fig. 4 shows the calculated values of α for fixed n1 values. obviously, when n1=n, α must be 1 in order to satisfy the constraint on n. in both cases of td and pvvd, the respective operation parameters of d and α for a fixed n1 were found by applying iterative methods similar to as reported in [13]. the optimization results obtained by varying n1 stepwise form 1 to n are illustrated in figs. 5 and 6. 163 figure 4: optimized α values as a function of preconcentration factor for the pvvd process figure 5: optimization diagram for traditional diafiltration. final microsolute concentration (dashed line) and required wash-water volume (continuous line) are plotted versus pre-concentration factor figure 6: optimization diagram for diafiltration involving pre-concentration combined variable-volume dilution. final microsolute concentration (dashed line) and required wash-water volume (continuous line) are plotted versus pre-concentration factor when comparing the td and the pvvd processes, from the optimization diagrams shown in figs. 5 and 6, we can conclude that the best diafiltration strategy is a specific case when n1 = n and α = 1. in other words, the optimal strategy is to pre-concentrate the process liqueur to its minimum volume and then to apply a constant-volume dilution without a post-concentration step. we would like to draw attention to the fact that a great care is needed when interpreting and generalizing such finding. the here presented methodology for choosing an appropriate diafiltration technique is general in the sense that it can be readily adopted for different solute/membrane systems without the need of major changes in the provided procedure. however, the output of the optimization is unique for each application. the choice of td versus pvvd depends primary on 1. the response of the particular membrane to the specific solution that is expressed in terms of rejection ri and permeate flow q, 2. the terms involved in the objective function (i.e. the definition of the separation goal), 3. the involved constraints (technological demands) and their numerical values that need to be satisfied. any changes in these above listed specifications may modify the output of the optimization, and lead to a different optimal strategy of diafiltration. further optimization aspects it should be pointed out that the main difference between the various types of operational modes is due to the quantity and the duration of the diluant stream introduced in the feed tank during the entire operation. in this context, diafiltration techniques differ in their strategies for controlling the introduction of the diluant stream u(t). in the widely applied conventional diafiltration processes, such as td or pvvd, the trajectory of the control variable u(t) is arbitrarily predefined for the entire operational time. however, it may happen that the optimal time-dependent profile of the diluant flow is not among these arbitrarily constructed scenarios. the optimal control trajectory can be determined by formulating an optimization problem subject to process model described by differential equations. using a dynamic optimization solver called dynopt developed by čižniar et. al [15], we are currently developing a unified technology for water utilization control that addresses generality versus special cases. this approach is currently under investigation and will be published soon. conclusions we provide a methodology that is useful for the design of batch diafiltration processes. a general mathematical model in a compact form is presented. it unifies the existing models for constant-volume dilution mode, variable-volume dilution mode, and concentration mode operations. a rich representation of the separation process is given due to the employment of concentration 164 dependent solute rejections in the design equations. thus, a formal tool is provided for describing the engineering design that supports the disciplined use of data-driven and mechanism-driven permeation models. the use of such a mathematical framework allows the optimization of the overall diafiltration process. the provided methodology is particularly applicable for decision makers to choose an appropriate diafiltration technique for a given separation design problem. further research effort is directed at the dynamic optimization of diafiltration processes. acknowledgment this research is a cooperative effort. the first author would like to thank the hessen state ministry of higher education, research and the arts for the financial support within the hessen initiative for scientific and economic excellence (loewe-program). the second author acknowledges the support of the slovak research and development agency under the contract no. vv-0029-07. list of symbols a − membrane area (m2) c – concentration (mol m-3) d − dilution factor j − permeate flux (m h-1) n – concentration factor q – permeate flow-rate r – rejection t – operation time (h) u – diluant flow-rate (m3 h-1) x – state variables (mol m-3) v – volume greek symbols α – proportionality factor of diluant flow to permeate flow subscripts d – diluant f – feed i – component (i = 1 macro-solute, and i = 2 microsolute) p – permeate w − wash-water abbreviations c − concentration mode cvd – constant-volume dilution mode vvd – variable-volume dilution mode pvvd − diafiltration involving pre-concentration and variable-volume dilution mode td – traditional diafiltration references 1. wang x.-l., zhang c., ouyang p.: the possibility of separating saccharides from a nacl solution by using nanofiltration in diafiltration mode, j. membr. sci. 204 (2002), 271–281. 2. borbély g., nagy e.: removal of zinc and nickel ions by complexation-membrane filtration process from industrial wastewater, desalination 240 (2009), 218–226. 3. kovács z., samhaber w.: contribution of ph dependent 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diafiltration processes, sep. purif. technol. 59 (2008), 206–213. 10. van reis r, saksena s.: optimization diagram for membrane separations, j. membr. sci. 129 (1997), 19–29. 11. wallberg o., joensson a., wimmerstedt r.: fractionation and concentration of kraft black liquor lignin with ultrafiltration, desalination 154 (2003), 187–199 12. bowen w., mohammad a.: diafiltration by nanofiltration: prediction and optimization, aiche journal 44 (8) (1998) 1799–1812. 13. kovács z., discacciati m., samhaber w.: numerical simulation and optimization of multistep batch membrane processes, j. membr. sci. 324 (2008), 50–58. 14. kovács z., discacciati m., samhaber w.: modeling of batch and semi-batch membrane filtration processes, j. membr. sci. 327 (2009), 164–173. 15. čižniar m., fikar m., latifi m. a.: matlab dynamic optimisation code dynopt, tech. rep., bratislava, user’s guide, 2006. microsoft word 01_r.doc hungarian journal of industrial chemistry veszprém vol. 35. pp. 65-74 (2007) control of a continuous vacuum crystalliser in an industrial environment: a feasibility study – comparision pid to model predictive control solution n. moldoványi1, j. abonyi2 1honeywell process solutions, h-1139 budapest petneházy u. 2-4 hungary, 2university of pannonia, department of process engineering, h-8201 veszprém, p.o. box 158, hungary crystallisers are essentially multivariable systems with high interaction amongst the process variables, that’s why it is a difficult control problem. in the absence of a real continuous crystalliser, a detailed momentum-model was applied using the process simulator in matlab simulink. the relative gain array was calculated to try to decouple the input and output variables for the setup of single input single output (siso) pid controllers. the pids were tuned, but the control performance is not satisfying. model predictive controllers (mpc) can handle such highly interacting multivariable systems efficiently due to their coordinated approach. the feasibility study illustrated that the applied identification tool gave an accurate and robust model, and that the non-linear crystalliser can be controlled and optimised very well with the honeywell profit® suite package. the developed system – engineering model in matlab is connected to an mpc used in the industry via opc (originally ole-object linking and embedding for process control) is proven to be useful in research and development. keywords: continuous crystalliser, feasibility study, model predictive control introduction crystallization is a widely used cleaning, separation and grain-producing technique in the chemical industry, particularly within the pharmaceutical industries. the main quality criteria (from the point of view of controlling a crystalliser) are the properties of the produced crystals—let us first consider size-distribution and size. crystallisation is a multi-variable system, with multi-input and multi-output (mimo), often with strong coupling. thus a good, modern approach to control is possible using a model-based mimo control system. there are only a few examples in the literature for this [1–5]. a predictive type of control would be better than the corrective (feedback) type, because crystal size cannot be decreased under crystallization conditions. one of the main problems is that (because of the mentioned properties of the population balance equation), for a proper model-based control of this size-distribution, a high-order control solution is required, which leads to technical difficulties. the crystallisers are dissipative systems [6]; hence, a crystalliser as a dynamical system possesses finite-dimensional global attractors [7] that create an adequate basis for the synthesis and use of a good quality, low order model-based control system. at the same time, it means that for the synthesis of the model based control system of the crystallisers, the momentum-model—generated from population balance equations as linear differential equations—can be used with close approximation. chiu and christofides [8] applied this property to design a non-linear single input single output (siso) controller. to select a proper controller structure first siso pid controllers after a model predictive mimo control systems of a crystalliser are presented in this paper. one main advantage the mpc to the set of pids is that the structural problems are solved inherently, mpc handles the assigning loops. for the synthesis of the control system, instead of a real continuous crystalliser, a moment model of the vacuum crystalliser was composed (section 2, appendix). the control problem (section 3) and the dynamic analysis of the model (section 4) was presented. in section 5 the crystalliser was tried to control with pid controllers. another kind, more adequate controller, the model predictive controller is presented is section 6. for the simulation the detailed model and the mpc of honeywell, the profit controller was connected via opc (originally ole-object linking and embedding for process control); the simulation results (which gave very satisfactory results) are presented in section 7. in the end some comparison is made to pid controller and mpc. 66 mathematical model of a vacuum crystalliser consider a continuous msmpr (mixed suspension mixed product removal) crystalliser in which supersaturation is generated using a vacuum. in this case, the crystalliser is considered as a three-phase operational unit; having liquid, solid and vapour phases, in which, under usual conditions, only two chemical species, the solvent and solute, take part in the crystallization process. (see fig. 1.) figure 1: schematic of a vacuum crystalliser then, the set of process level equations, termed rigorous model of the crystalliser, consists of the following balance equations: ● population balance equation for crystals governing the crystal size dynamics ● mass balance equation for the crystallizing substance ● mass balance equation for the solvent ● energy balance equation for the vapour phase it is assumed that the following conditions are satisfied: (1) the volumetric feed and withdrawal rates of the crystalliser are constant and equal, thus the working volume is constant during the course of the operation; (2) the crystals can be characterized by a linear dimension l; (3) all new crystals are formed at a nominal size ln ≅ 0 so that one can assume ln = 0; (4) crystal breakage and agglomeration are negligible; (5) no growth rate fluctuations occur; (6) the overall linear growth rate of crystals g is size-dependent and has the form of the power law expression of supersaturation ( ) )()(),( lwwklwwg g ecgec φφγ −== ; (1) (7) the primary nucleation rate bp is described by volmer’s model: )()( ln exp 2 npn e c e pp llll w w kkb −=− ⎟ ⎟ ⎟ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎜ ⎜ ⎜ ⎝ ⎛ ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −= δβδ (2) the secondary nucleation rate bb is the following: ( ) )()(3 nbn jb cecbb llllwwkb −=−−= δβδμ (3) where: ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −= rt e kk g gg exp0 ; ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −= rt e kk p pp exp0 ; ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ −= rt e kk b bb exp0 (4) where μ3 is the third of the ordinary moments of the population density function n, which are defined as: ...3,2,1,0,),( 0 == ∫ ∞ mdltlnlm mμ (5) the model variables are: μ0, μ1, μ2, μ3, wc, msv, t, ρv, tv i.e. the zero, first, second and third order moments of the crystal size, concentration of the solute, the solvent mass, the temperature of suspension, the vapour density and the temperature of vapour respectively. the final moment equation model is summarised in the appendix; the details can be found in the paper of ulbert and lakatos [9]. the control problem the goal of the above presented crystalliser is to produce crystals with a certain quality as far as possible using the minimum amount of energy. from the point of view of controlling a crystalliser the main quality criteria are the properties of the produced crystals, the size and the size-distribution. the delivery of the crystalliser can be also controlled. so, the outputs, the variables to be controlled (called cvs), calculated from the moments are the following: mean crystal size, calculated from the moments μ1/μ0 = (x1/s1)/(x2/s2) standard deviation of the crystal size distribution computed as: σ2 = μ2/μ0 – (μ1/μ0)2 = (x2/s2)/(x0/s0) – ((x1/s1)/(x0/s0)) μ3, delivery of the crystalliser, where kv *μ3 is the volume of the produced crystals where st, st, s0, s1, s2 are dimensionless parameters, x0, x1, x2 are the dimensionless moments. from the process point of view, in a continuous vacuum crystalliser, the pressure, the temperature and the residence time can be changed in practice. in the environment of the model the inputs, the variables to be manipulated (called mvs), are the following: pressure; can be changed with partial pressure, by the valve constant ks of the vapour outlet temperature; can be changed with x7in dimensionless inlet suspension temperature, where x7in = tsus, in·st residence time; can be varied with ξav dimensionless residence time, where ξav = τmean·st 67 dynamic analysis of the models instead of a real unit, the model of the crystalliser – presented above – was stepped in matlab simulink environment to collect data for the identification of the model matrix. the overall process model is composed of a matrix of dynamic sub-process models, each of which describes the effect of one of the independent variables on one of the controlled variables. a subprocess model describes how the effect of an independent variable on a control variable evolves over time. it is called the matrix of linear dynamic sub-process models, the linear model matrix. each manipulated variable (pressure, temperature, residue time) was stepped many times one by one considering the time to steady state, as would be carried out in an industrial project environment. the object was stepped around a stable operating point with reasonable step sizes as tested before. with the collected data the automated method was use for the model identification in profit® design studio of honeywell. [10] the identification result is shown in fig. 2. the manipulated variables (mv1 = ks, mv2 = x7in, mv3 = ξav), are in columns, the controlled variables (cv1 = μ1/μ0, cv2 = σ2, cv3 = μ3) are in the rows. for better conditioning of the problem, the magnitudes of the cvs were changed; multiplied by 103, 107, 103 respectively. the model is the darker line; the data is the lighter, covered. profit design studio found good models quickly with an automated identification method. all sub-models’ qualities are good, rank 1 or 2 in the range of 1-5, where 1 is the best (model ranking is a standard feature of the package and uses a variety of measures to give an overall rank or “goodness of fit” [10] the settling time for the process data and the settling time from the calculated transfer function, settle t and tfsettle respectively, are close to each other for all submodels. in this case the model matrix is full, all the cvs are in connection to all the mvs. with pressure (mv1), the size (cv1) and the size-distribution (cv2) models have a highly inverse response, by increasing the pressure, the size and size-distribution decreases first and then increases, because the nucleation is changing. with this accurate identification the high order sub-models can follow the special behaviour of the object. the inlet temperature (mv2) delivery (cv3) model also appears to be an inverse response model, because by increasing the temperature, the discharge temporary increased. but the overshoots and high order models would be too sensitive to model error and it would not work in model based controller. these responses are all real but even a slight error in these models (and they will vary in practice as the model is never perfect) will lead to out of phase control which will lead to oscillation. so the oscillation of the models were removed, the simplified robust model is presented in fig. 3, the model is the darker line, the data is the lighter. figure 2: the accurate model matrix 68 figure 3: models used for the control study the relative gain array was calculated to decide the best pairings. since its proposal by bristol in 1966 [11], the relative gain technique has not only become a valuable tool for the selection of manipulative-controlled variable pairings, it has also been used to predict the behaviour of controlled responses. the relative gain array (rga) can be easily calculated from the gains of the model matrix (k): 1)(. −∗= tkkλ (6) the result of the calculation from the used model matrix (see fig. 4): ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ − − − = 181.0018.1163.0 832.2669.2837.0 651.1651.20 λ (7) it is an obvious proof of strong coupling. since the best value for pairing is 1 but it shouldn’t be negative and 0 [12] the only pairing is the following, showed with bold numbers: ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ − − − = 181.0018.1 669.2837.0 651.10 0.163 2.832 2.651 λ (8) so mv1 controls cv3, mv2 controls cv1 and cv2 is controlled by mv3. control with pid controllers first pid controllers were set up and tuned for the vacuum crystalliser. pid is a single input single output (siso) controller and as it is showed in that the crystallisers are mimo object with strong coupling. the starting points of the pid tunings were calculated with the strategy based on internal model control (imc). [12] pid controller in imc structure: ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ ++= s s ksg d i cc τ τ 11)( (9) the filter: 1 1)( + = s sf cτ (10) in case of a first order model ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ +1s k τ c c kk τ τ = , ττ =i and 0=dτ . (11, 12, 13) the parameters of the pid controllers were finetuned, the mvs were limited, the control structure can be seen in fig. 4. the result shows (figs 5 and 6) that the coupling is strong, pid controllers can not really handle this mimo object. the new setpoint of cv1 couldn’t reach, but for cv3 it is good. 69 figure 4: the structure of pid control of the crystalliser model 1.10e-01 1.20e-01 1.30e-01 1.40e-01 1.50e-01 1.60e-01 1.70e-01 1.80e-01 22:30 23:30 0:30 1:30 2:30 3:30 4:30 5:30 1.50e-01 1.70e-01 1.90e-01 2.10e-01 2.30e-01 2.50e-01 2.70e-01 2.90e-01 3.10e-01 3.30e-01 3.50e-01 cv1*10^3 (left axis) cv1 setpoint (left axis) cv2*10^7 (right axis) cv3*10^3 (right axis) cv3 setpoint (right axis) cv2 setpoint (right axis) figure 5: simulation results with pid controllers, controlled variables (cv1=crystal size, cv2=crystal size-distribution, cv3=delivery of the crystalliser) 70 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 22:30 23:30 0:30 1:30 2:30 3:30 4:30 5:30 1.00e+03 1.02e+03 1.04e+03 1.06e+03 1.08e+03 1.10e+03 1.12e+03 1.14e+03 1.16e+03 1.18e+03 1.20e+03 1000*mv1 (left axis) mv2 (left axis) mv3 (right axis) figure 6: simulation results with pid controllers, manipulated variables (mv1=pressure, mv2=temperature, mv3=residence time) it is proved that there is a strong coupling between the inputs and the outputs, for example by changing the residence time in the vacuum crystalliser not only the size but the size distribution (and of course the delivery) changes. to summarise, the above analysed crystalliser is a non-linear object, with a high degree of interaction between the process variables. one can do nothing if the crystals grow beyond a certain size. for all of these problems, a model predictive controller (mpc) presents a good solution. mpc can handle the mimo object; and it is predictive, so the controller “prevents” over-size crystals. for non-linearity within a certain range, a robust controller is adequate as it presented below. model predictive control model predictive control (mpc) refers to a class of computer control algorithms that utilise an explicit process model to predict the future response of the plant. [13] originally developed to meet the specialised control needs of power plants and petroleum refineries [14], mpc technology can now be found in a wide variety of application areas including chemicals, food processing, automotive and aerospace applications. the presented work is an opening to another new application, the mpc control of continuous crystallisers. in model predictive control, the control action is provided after solving – on-line at each sampling instant – an optimisation problem, and the first element in the optimised control sequence is applied to the process (receding horizon control). the “moving horizon” concept of mpc is a key feature that distinguishes it from classical controllers, where a pre-computed control law is employed. a major factor in the success of model based predictive control is its’ applicability to problems where analytical control laws are difficult, or even impossible to obtain. a model is used to predict the future plant outputs, based on past and current values and on the proposed optimal future control actions. these actions are calculated by the optimiser, taking into account the cost function (where the future tracking error is considered) as well as the constraints. the methodology of all the controllers belonging to the mpc family is characterised by the following strategy, represented in fig. 7 (u is the input y is the output and w is the set-point). from the section 3 with this classical notation u = (ks, x7in, ξav), and the y = (μ1/μ0, σ2, μ3). for mpc the prediction horizon (hp) represents the number of samples taken from the future over which mpc computes the predicted process variable profile and minimises the predicted error. the control signals change only inside the control horizon, hc remaining constant afterwards: u(k + j) = u(k + hc – 1), j = hc, ..., hp – 1 futurepast control horizon prediction horizon u(.) w(.) y(.) k k+1k-1k-2 k+2 figure 7: mpc horizons 71 the basic steps: 1. in the mpc future outputs for a determined prediction horizon hp are predicted at each instant k using a prediction model. these predicted outputs phjkjky ,...1),(ˆ =+ (means the value at the instant k+j, calculated at instant k) depend on the known values up to instant k (past inputs and outputs) and the future control signals u(k+j|k), j = 0,..hp-1., which are those to be sent to the system and to be calculated. 2. the set of control signals is calculated by optimising a cost function in order to keep the process as close as possible to the reference trajectory w(k+j), j = 1,..hp or to keep inside the range. 3. the control signal u(k|k) is sent to the process whilst the next control signals calculated are rejected, because at the next sampling instant y(k+1) is already known and step 1 is repeated with this new value and all the sequences are updated. thus the u(k+1|k+1) is calculated (which in principle will be different to the u(k+1|k) because of the new information available) using a receding horizon concept. the details of mpc are presented by moldoványi and lakatos. [15] honeywell’s profit controller controls the process using the minimum manipulated variable movement necessary to bring all of the process variables within limits or to setpoints; and to optimise the process with the remaining degrees of freedom in order to drive the process to optimum operation. profit controller uses the honeywell patented range control algorithm (rca) [10]. rca minimises the effects of model uncertainty while determining the smallest process moves required to simultaneously meet control and optimisation objectives. the robustness of the controller is tested in this study, since a non-linear object was controlled with a linear mpc. the issues of using a linear controller in order to control a non-linear process may not be as big an issue as is first expected. there are two reasons for this. firstly, the non-linearity, non-linear region or nonlinear variable(s) may sometimes be linearised where it is well understood. secondly, within the relatively narrow range of normal operation of a process, the process may be said to act linearly within these limits. profit controller application includes the necessary tools to design, implement and maintain mimo applications. control with mpc the integration of a process simulator and the mpc of honeywell was performed with opc (originally oleobject linking and embedding for process control). this standard specifies the communication of real-time plant data between control devices from different manufacturers. opc was designed to bridge windowsbased applications and process control hardware and software applications. in the absence of a real crystalliser, the engineering model acts like the unit, connected to the controller via opc. for the non-linear model in matlab the inputs are the mvs, which are the controller outputs. the matlab model calculates the cvs and sends them to the controller via opc every minute, see fig. 8. profit controller crystallizer (model) mvs cvs opc figure 8: the control shame with profit controller the control horizon (where the manipulated variables changes in the prediction) contains 10 movements of the mvs, in the honeywell controller, the control horizon for each cv is based on a gain weighted average of the individual models in that row of the matrix. the prediction horizon (where the prediction is calculated) is the closed loop response interval, this is about 1.5 hours in this case. weights, rate of change limits and ramping limits, and other tuning parameters were set up in profit controller. the size was controlled to a setpoint, it followed the changes that were made correctly. the standard deviation of the size distribution was minimised within a range, but the maximisation of the volume was set to be a more important priority. the cost function is j= σ2-10·μ3, quadratic coefficients and optimisation of the manipulated variables were not set up. the optimisation speed factor is 3 (fast), which results in an optimisation horizon approximately 6/3=2 times the cv overall response time. the cv overall response time is defined as the average of the longest cv response time and the average cv response time, 123 minutes in this case. the simulation results are shown in figs 9 and 10. the dashed lines are the setpoint for cv1 and the minimum and the maximum limits of cv3. the limits of cv2 are irrelevant. in the test run the optimiser was turned on at 23:00, from that time the cv3 (delivery) increased significantly, the cv2 (size distribution) deceased a little to the optimal values. cv1 setpoint change is solved after a little overshoot, the changes of mvs (fig. 10) show that the controller reacts rapidly. when the range of cv3 is changed, the mvs change fast, and the control problem is solved. cv1 also changed significantly due to interaction, but it calms down after a while. 72 0.11 0.12 0.13 0.14 0.15 0.16 0.17 0.18 22:30 23:30 0:30 1:30 2:30 3:30 4:30 5:30 6:30 7:30 8:30 9:30 10:30 11:30 12:30 13:30 0.15 0.17 0.19 0.21 0.23 0.25 0.27 0.29 0.31 0.33 0.35 cv1*10^3 (left axis) cv1 setpoint (left axis) cv2*10^7 (right axis) cv3*10^3 (right axis) cv3 highlimit (right axis) cv3 lowlimit (right axis) figure 9: simulation results for the controller, optimiser, with controlled variables (cv1=crystal size, cv2=crystal size-distribution, cv3=delivery of the crystalliser) 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 22:30 23:30 0:30 1:30 2:30 3:30 4:30 5:30 6:30 7:30 8:30 9:30 10:30 11:30 12:30 13:30 900 1000 1100 1200 1300 1400 1500 1000*mv1 (left axis) mv2 (left axis) mv3 (right axis) figure 10: simulation results for the controller, optimiser, with manipulated variables (mv1=pressure, mv2=temperature, mv3=residence time) the results shows that the controller optimises and solves the changes in the range, the mvs react rapidly, but smoothly, and the controller is robust. one main advantage the mpc to the set of pids is that the structural problems are solved inherently, mpc handles the assigning loops. there is a difference in complexity between the two controllers. according to engineering experience the more complex the technology the more complex the control system, but the slope of the relation depends on the kind of controller. see fig. 11. for simple cases, pid is easier, but for a difficult one mpc can be the easier controller to implement. already for this 3 input, 3 output case the decoupling is difficult, mpc can handle the mimo object without problem. 73 complexity of the technology complexity of the controller pid mpc figure 11: the relationship between the complexity of the technology and the controller conclusion crystallisers are multivariable objects with coupling among the process variables. the relative gain array was calculated to try to decouple the input and output variables for the setup of single input single output (siso) pid controllers. the pids were tuned, but the control performance is not satisfying. model predictive controllers (mpc) can handle such highly interacting multivariable systems efficiently due to their coordinated approach. the feasibility study illustrated that the applied identification tool gave an accurate and robust model, and that the non-linear crystalliser can be controlled and optimised very well with the honeywell profit® suite package. the developed system – engineering model in matlab is connected to an mpc used in the industry via opc is proven to be useful in research and development. acknowledgements special thanks to professor béla lakatos from the university of pannonia and colleagues in honeywell, howard boder and peter kiss for their good ideas and review. appendix the moment equation model of a continuous vacuum crystalliser is formed by the following equations [9]. zero order moment: ( ) bpv sv in sv insv bbbw m b m f dt d +=++−= ,0 00 ,0 μ μμ μ (a1) first order moment: ( ) ( )( ) v sv ecin sv insv w m aww m f dt d 1 101,1 ,1 , μμμγμμμ +++−= (a2) second order model: ( ) ( )( ) v sv ecin sv insv w m aww m f dt d 2 212,2 ,2 , μμμγμμμ +++−= (a3) third order model: ( ) ( )( ) v sv ecin sv insv w m aww m f dt d 3 323,3 ,3 , μμμγμμμ +++−= (a4) mass balance for solute: ( ) v sv scvcinc sv insvc w m cacwkww m f dt dw ++−−−= ))((3 32, , μμργ (a5) mass balance for the solvent: vsvsvin sv wff dt dm −−= (a6) energy balance equation for the crystal suspension: ( ) svav v vinavin svav svin mc w httc mc f dt dt δ−−= av c sv c hacck δ +−+ ))((3 32 μμργ (a7) where cav = csv + cc + kv ρcμ3 and cavin = csv + ccin + kv ρcμ3in. mass balance equation for the vapour phase: ⎢ ⎣ ⎡ ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ +++−⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −= inv in sv svinvvvv sv v v v kcfqw vdt d 3 111 μ ρρ ρρ ρ ρρ ⎥ ⎦ ⎤ ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ++− 3 1 μ ρρ ρ v sv svv kcf (a8) where the steam removal of the evaporated solvent was modelled by a controlled valve having characteristics ( )outvvsvvvv pppkqf −== ρρ . (a9) energy balance equation for the vapour phase: ( ) ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −+ − −= v v vvvv vvvv dt dc ttcv wttc dt dt ρ )( . (a10) where: ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ++−= 3 1 μ ρρ v sv svv kcmvv (a11) the constitutive equations associated with the moment, mass and energy balance equations were as follows. temperature dependence of the solubility: ( ) 2 210 tataatcs ++= (a12) evaporation rate of the solvent: ( )∗−= vvevapv ppkw (a13) where the vapour pressure was computed by the antoineequation: a a av ct bap + −=∗log (a14) 74 while the state of vapour was predicted by the ideal gas law: v v v v rtp = . (a15) notation a constant of the crystal growth rate [m-1] b exponent of secondary nucleation rate bp primary nucleation rate [no m-3s-1] bb secondary nucleation rate [no m-3s-1] c concentration of solute [kgm-3] cs equilibrium saturation concentration [kgm-3] dap dimensionless parameter for primary nucleation dab dimensionless parameter for secondary nucleation g exponent of crystal growth rate g crystal growth rate [ms-1] j exponent of secondary nucleation rate ke parameter of primary nucleation rate kg rate coefficient of crystal growth [m3g+1 kg-g s-1] kp rate coefficient of primary nucleation [no m-3s-1] kb rate coefficient of secondary nucleation [no m3b-3 kg-b s-1] kv volume shape factor l linear size of crystals [m] n population density function [no m-4] sc scale factor of the concentration [kg-1m3] sm scale factor of the mth order moment of n (m = 0,1,2,...) xm mth order dimensionless moment (m = 0, 1, 2, ...) y dimensionless concentration of solute greek letters ε viodage of suspension μm mth order moment of n [mm-3] ρc density of crystals [kgm-3] ξ dimensionless time subscripts 0 initial value in inlet value p primary nucleation b secondary nucleation s steady state references 1. qin s. j., badgwell t. a.: control engineering practice, 11 (2003) 733 2. myerson a. s. et al.: proc. 10th symposium. industrial crystallization. academia, praha, 1987 3. jager j., et al.: powder technology 69 (1992) 11 4. miller s. m., rawlings j. b.: aiche journal, 40 (1994) 1312 5. rohani s. et al.: computers and chemical engineering, 23 (1999) 279. 6. lakatos b. g., sapundzhiev ts. j.: bulgarian chemical communications, 29 (1997) 28 7. temam r.: infinite-dimensional dynamical systems in mechanics and physics. springerverlag, new york, 1988 8. chiu t., christofides p. d.: aiche journal, 45 (1999) 1279 9. ulbert zs., lakatos b. g.: simulation of cmsmpr vacuum crystallisers. computers and chemical engineering, 23 (1999) s435 10. r300 profit suite documentation, identifier user’s guide ap09-200, honeywell international inc., 2007 11. bristol e. h.: ieee trans. on auto. control, ac11, 1966, pp 133-134, 12. cooper d.: practical process control using control station, control station, inc, storrs, (2004).ct 13. meadows e. s., rawlings j. b.: model predictive control, chapter 5. pp 233-310. englewoods cliffs. nj: prentice-hall, 1997 14. joe qin s., badgwell t. a.: control engineering practice 11 (2003) 733 15. moldoványi n., lakatos b. g.: hungarian journal of industrial chemistry, 33 (2005) 97 microsoft word a_18_r.doc hungarian journal of industrial chemistry veszprém vol. 38(1). pp. 63-66 (2010) municipal environmental-monitoring system f. speiser , i. magyar, k. enisz university of pannonia, h-8200 veszprém, egyetem str. 10, e-mail: ferenc.speiser@gmail.com nowadays protection of our environment is playing more and more significant role and within this topic the protection of the human aspects is even more important. the continuous monitoring of the municipal environment came into foreground in hungary also through the past years. within the faculty of engineering of the university of pannonia a unique organizational unit was established under the name “sustainable development environmental an informatics cooperative research centre”. this centre started an r+d project on the main topic of environmental protection and its technologies. the goal of this paper is to summarize a measuring method of municipal-environmental parameters (e.g.: co, o3, nox, no2, c6h6) using low-cost monitoring devices and open source visualization software. the system integrates the measured data in a gis for further processing and publishing. the sample-area was given by the location of the university. hence, the test-measurements were carried out in veszprém, hungary. the developed system gives the power of data integration so the user can manage one uniform user interface for processing the data gained from the environmental measurements. on the whole it can be stated that the system is suitable for collecting environmental data with specific low costs at minimal infrastructural build-up. further measurements and modeling will be managed in the future using the developed system in order to compare the present results of air quality of veszprém to the collected environmental parameters in other cities and counties. keywords: gis, environmental monitoring, airpollution, environmental modeling introduction the permanent monitoring of the municipal environment becomes more important in hungary recently. this aim can be realized by modern monitoring stations, but the involvement of local groups, ngos and, people living there in the control of the environmental parameters is very rare. the best solution for this problem is to publish the available environmental data on-line, through the internet. our r+d project targets to work out the measurement methodologies of environmental pollution data [1]. the main goal is to make it possible to setup and operate an information system based on the collected data that can publish environmental data trough the internet. in connection with the information system mentioned above, the local government/authority can elaborate an attractive, informative, up-to-date information service that provides data on the state of their environment for the inhabitants' purpose. the database obtained from the measurements is a kind of data source possessed by the local authority that can be effectively used for preparing the annual environmental report, as well as for supporting decision making in fields, where displaying of spatial information on maps plays an important role. nevertheless, during the further development of the system there are several possibilities to optimize the process. for example the integration of the dustconcentration meter to the data-collector could be a possible solution. on the basis of this the measured dust-data could be sent via e-mail to the processing server. furthermore it would be practical to analyze more comprehensive also the (under) surface waters. the goal as a result of the measurements carried out by the university of pannonia, the university earns special measurement experiences and data, which results leading position among the similar faculties in hungary and also among universities and educational institutes of neighboring countries. the goal is to develop an information system which is suitable for integrating, processing of data (average, statistics, limit) and then publishing environmental parameters (air, noise, water, soil, and weather attributes) in database tables, diagrams, graphs, and maps in the same way. the information system is available through the web. the system provides other related environmental data like environmental infrastructure (e.g. treatment of waste) and can offer various environmental events as well. 64 novelty of the system during the preliminary consumer research and surveying the existing monitoring systems and services it was apparent that the air pollution-monitoring is the most important in the city-environment. therefore the processing and representation of measured data is limited only to these parameters. however, the planned system gives the possibility to manage series of environmental parameters and – after loading – publish them immediately. the managed data is stored in a scalable, fast geodatabase by the system, which means it is easy to search and browse, so a tool is available to achieve data for modelling, spatial statistics, queries, and surveys. since the same database stores all type of the environmental data, the diversity of formats used by different measurement systems is eliminated – this makes the data collection faster. furthermore, the user can obtain the proper dataset executing a definite query on a uniform interface. the application differs from the other services in the mobility of measurements too. the measurements performed by a mobile monitoring station equipped by the proper measurement tools and devices. it is possible to make daily or monthly measurements by this equipment during an optional time period, so conclusions can be drawn; maps regarding the tendencies of the examined area can be prepared as well. protection of municipal environment the work of our world is complex and is getting more and more complicated, people are moving to overcrowded metropolises, so the environmental impacts of the city is significantly influence the human health. the energy and food demand is increasing and for supplying it a device with an appropriate logistic background and adequate trend-prediction is needed. the number of national disasters (rain, fire or earthquake) is increasing in the counties of the world. the geoinformatics as tool can help with forecast, modeling and can help to manage the problems, support the decision-making and preparing for corrective and preventive plans [2, 3]. there are efforts to manage for example the following fields in hungary for that gi is applied: human health, food quality, epidemiology, ragweed mapping, flood protection. in addition to these areas, the monitoring and protection of the municipal environment – as the most important fields – are our important tasks too and with the system elaborated by us we try to realize these goals. the system architecture the components of the system are working on a windows 2003 server (not open source) operating system. the program components are open source (http://www.opensource.org) softwares. the developerteam decided to use the following tools: ● mapserver (http://mapserver.gis.umn.edu/), ● ms4w application (http://www.maptools.org/ms4w/), ● php/mapscript (http://mapserver.gis.umn.edu/doc44/), ● apache web server (http://www.apache.org/), ● postgresql (http://www.postgresql.org), ● postgis (http://postgis.refractions.net). if appropriate logic is assigned to the components and a data model then a link can be established to even to a local government information system, providing environmental information. fig. 1 shows the communication between the components of the system. figure 1: system components and connections the portal consists of two main modules: the starting page gives general information and a menu-system grouping environmental data regarding the specified area of the municipality. navigating through this menu, information about the environmental parameters can be obtained as static html pages by selecting a phrase. after starting the service in the window of the browser it is allowed to browse among the classical formed – in tree structure – and stored data. selecting from this list, html-contents appears in the right side of the page. the menu of the homepage is sorted according to the following environmental aspects (see below). these are about the environmental status of the given municipality. environmental status: air pollution – information on air-quality, pollen status – general information on pollen, tick infection – tick frequency in the given territory, water – surface-, subsurface-, drinking-water properties, soil – generally about role and protection of soils, noise – noise load of the municipality. 65 environmental infrastructure: waste management – general information on waste handling, drainage – information on drainage, rainwater network – drainage maps, sewage works – sewage farms of the area, environmental protection – natural reserves, ragweed – general information on ragweed, street network – street map of the city. environmental information: programs, news, call for a tender, associations – information on the city. there is an opportunity to display a map, which serves dynamic information from the database. on the map commonly used navigation tools can be applied to browse the specific measured parameters and data. measuring method it was decided to develop a system for measuring environmental parameters, which are extremely important considering the human health. the system was planned to be mobile and capable to measure most of the parameters collected by a normal monitoring station (measuring container). the defined requirements of our system are the followings: it should be significantly better in cost effectiveness; it should be capable to transmit the collected data to the server in a reliable way immediately; the system should be installable at any site of the country. on the contrary costs would be serious to establish in case of a normal monitoring station. in addition to collecting the air quality and meteorological information, an attempt was made to apply on-site water-analytical methods, which are fast, cost effective and suitable to provide reliable information about our surface waters. on the basis of the acquired information it turned out that the cheaper absorption measuring procedure is appropriate only in the case of two parameters. moreover the chemical demand of the method is high and it can only provide few information about the given parameters. the air-quality monitoring appliances installed into the automatic monitoring stations and the well-equipped monitoring vehicles are precise, providing a lot of data, but they are extremely expensive. the chemiluminescent measurement of no and no2, the ndir meter for measuring co and the gaschromatographic measurement of btx (benzene, toluene and xylene) compounds exhibit high costs. the definition of pm10 based on discolouring of the filter-paper. it is slow and material demanding. on the basis of the calculations it can be concluded that costs are mainly come from the immission measurement of the air quality. hence, first of all special focus was put on the air analytical measuring system during the system development. development of a method was envisaged in order to reach a compromise between the cheap and mobile data acquisition and the numerous, relative reliable datasupply. fig. 2 below shows the measuring system. figure 2: the structure of the measurement system experience of the pilot project during the planning of the measurements unexpected difficulties were comeing up, while our initial expectations were not confirmed in all of the areas. it can be stated that the elaborated system is proper to measure environmental parameters also at remote areas. by means of low initial, operational and maintenance costs the system is possible to be installed at several sites. the results supplied by the device are proper for static measurements, for mobile-measurements further experiments are needed. however, it is interesting to get a snapshot of the air pollution of the city by driving around on the main streets. although it is not an authenticated measurement method that the air-monitoring system uses, the measured values give a proper image about the actual environmental status. for testing the system more routes were selected in veszprém, hungary to represent the area. one of them depicted in fig. 3. the paper only deals with air pollution and meteorology monitoring but the system is able to measure water parameters too. meteorology parameters are necessary for calculating the distribution utilizing the known points. considering that the chosen etl2000 air quality monitoring device is not widely used in hungary, reference data were requested for reliable operation. hence, prior to the measurements a calibration procedure was carried out with using the system of the hungarian air quality network. after calibration measurements the environmental data provided by the etl2000 were evaluated regarding the necessary correction to be done. as a result of the calibration the data measured by the two different technologies are correlating well. pressure on the blue distribution maps is principally defined by the relief of the town, hence, they are similar, although they show different time period. it can be stated about the benzene pollution that it is higher in the southeastern part of the town. the hypothetical causes could be the following: the high traffic routes of the area, the prevailing north-western wind direction, the relief. dark-red colours of fig. 4 on the south-eastern part of the town are in good correlation with the well-known high traffic roads. on the west side of the city is a familyhouse area with lot of parks; the pollution is significantly smaller in this area. in addition to the on-line data supply, this technique provides chemical-free, environmentally sound and it is cheaper at site analysis. on the whole it 66 can be stated that the system is suitable for collecting environmental data with specific low costs at minimal infrastructural build-up. figure 3: dynamic measurement figure 4: dispersion map from the collected data environmental modelling there are a lot of efforts to develop an appropriate framework or an easy to use method to control and simulate the urban environment for supporting effective urban air pollution control and management [3, 4]. as the above mentioned experience shows, our system can be used as a primary data source (monitoring system) for an environmental quality modelling system, that uses various algorithms to assess the impact of the environment on the human inhabitants in a city. the elaborated system is able to collect traffic pollution data, that can be used for deeper traffic situation modelling. conclusion the environmental data displayed on maps provided by the information system are beneficial for the local governments and on regional level in environmental protection and also for inhabitants by publishing the information. at public administration level the collected data are used for supporting investments, development policies, and environmental decisions. every system produced up to the present was specialized to monitor one specific environmental parameter category (air-, soil-, water quality monitoring), hence it was more complicated if all components were requested to be monitored because of the variety of the user interfaces and data formats. in contrast to this the developed system gives the power of data integration so the user can manage one uniform user interface for processing the data gained from the environmental measurements. the strengths of the monitoring system is the integration since every measured data of environmental parameters are loaded to a database, so the publication, retrieval and the later utilization is getting easier. the people can get information on the actual environmental conditions through a continuously available internet portal. acknowledgements we acknowledge the financial support of this work by the hungarian state and the europen union under the tamop-4.2.1/b-09/1/konv-2010-0003 project. references 1. i. magyar, f. speiser: municipal monitoring from university of pannonia, geoinformatics 2007/1 (p19-20, in hungarian). 2. h. s. gorman, e. m. conway: monitoring the environment: taking a historical perspective, environ. monit. assess., 106 (1-3), 1-10. jul. 2005. web of science/isi. 3. g.-j. liu, e.-j. fu, y.-j. wang, k.-f. zhang, b.-p. han, c. arrowsmith: a framework of environmental modelling and information sharing for urban air pollution control and management, journal of china university of mining & technology, 2007, 17 (2), 172–178. 4. leorey o. marquez, nariida c. smith: a framework for linking urban form and air quality, environmental modelling & software, 14, 1999, 541–548. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 /colorconversionstrategy /cmyk 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 137-142 (2008) improving the compatibility of man-made fibre reinforced composites cs. varga1 , n. miskolczi1, l. bartha1, g. lipóczi2, l. falussy3 1university of pannonia, institute of chemical and process engineering, department of hydrocarbon and coal processing egyetem u.10, veszprém, h-8200 hungary e-mail: vcsilla@almos.uni-pannon.hu 2balatonplast ltd., petőfi u. 26, felsőörs, h-8227 hungary 3dr. falussy engineering office, ibolya u. 14., kaposvár-kaposfüred, h-7400 hungary composites are made of two or more different materials which constitute the modernest family of construction materials for technical applications. fibre reinforced composites are unique materials and are heterogeneous in composition. high strength/weight ratio is characteristic for them which is advantageous in many points of view. e.g. cost for moving them is much more lower than for conventional materials, they are advantageous environmentally either, do not need high maintenance costs and allow high creativity in shapes and functions. for properties of fibre reinforced composites interaction between the fibres and the matrix is especially important beside the mechanical properties of the building parts. as their chemical compositions significantly differ from each other the proper adhesion could be achieved by application of compatibility improving so called compatibilizing additive which is able to connect either to the fibres or the matrix due to its chemical composition. such compatibilizing additives were produced, which are able to solve or at least reduce the incompatibility problem in carbon fibre reinforced thermoplastic and glass fibre reinforced thermoset composite systems. keywords: reinforced composites, carbon fibre, glass fibre, thermoplast, thermoset introduction a lot of new construction materials, characteristically combined materials or composites have appeared in car industry and other areas. in case of these materials one of the properties is advantage but another one is disadvantage in the point of view of application. in homogenous metals improving the strength involves high weight increase which may considerably increase investment and operational costs. composites especially polymer composites may mean the solution for that problem according to the extent of progress. that could be traced back to the availability of polymers in great volumes at low prices and to the excellent properties (good resistance against corrosion, advantageous strength/weight and stiffness/weight ratios…) of composites made of them. so they are getting to substitute conventional construction materials (e.g. steel, aluminium) in many fields due to their high strength, stiffness and low weight. improving the properties of composites can be obtained by combination of two or more continuous phases. in fibre reinforced composites the phases strengthen each others effect due to the interaction between the fibres and the matrix compensating the worse properties of the clean components. the compatibility of the matrix and the reinforcing material plays an important role during processing. reducing the incompatibility problems compatibilizing additives are used that can help to considerably enhance the fibrematrix interaction both in chemical and in physical ways. in literature mainly such publications are to be find that discuss the reducing of the incompatibility of the thermoplastic fibre reinforced polymers [1-6] and only a few are about the fibre-matrix interaction in fibre reinforced thermoset composites [7-8] because such problems come up much more rarely in the latter systems. in quite lots of cases when reinforcement and thermoplastics are used together the properties of composites became worse without coupling agent that is presumed to be the cause of the incompatibility of the constitutive. in fibre reinforced thermoplastics maleicanhydride-grafted-polyolefins (ma-g-pos), with molecular weights similar to the base plastics, are generally applied. the presence of plasticizing components retained in the ma-g-po additives after grafting process is the main problem so the compatibilisation can be improved but plasticizing effects also occur besides. in case of reinforced thermoset composites different silane type agents, titanates and zirconates are generally used [9] as coupling agent or fibre surface modifying agent. those additives can connect the matrix to the fibres with hydrogen or even covalent bonds [10], so they have great effects on improving the adhesion between the components. organosilanes are the most 138 widely used coupling agents for improvement of the interfacial adhesion in glass reinforced materials. according to literature their effectiveness depends on among others the nature and pre-treatment of the substrate, the type of silane used, the thickness of the silane layer and the process by which it is applied [10-11]. in our experimental work incompatibility problems of carbon and glass fibre reinforced polymer composites have been investigated. thermoplastic and thermoset polymers have either been applied as matrices and as compatibilizing additive such experimental surface modifier additives (polyalkenyl-poly-maleic-anhydrideester, polyalkenyl-poly-maleic-anhydride-amide and polyalkenyl-poly-maleic-anhydride-ester-amide) have been used that were produced according to our prior experiments and researches. materials and processing for carbon fibre reinforced thermoplastic composites commercially available polyethylene (finathen 6006 pe) and panex®35 type carbon fibres (σt = 3800 mpa; εt = 242 gpa; ρ = 1,81 g/cm3; ød = 7,1 μm) supplied by zoltek plc. were used. geogrids applied in dam strengthening were produced at rex international ltd. for glass fibre reinforced thermoset composites e-type chopped glass fibre mat with 450 g/m2 specific density (supplied by former vetrotex, now owens corning) and polyester (aropol m105 tb, (ashland inc., usa)) were applied. sample sheets were made from the chopped glass fibre mats and polyester at balatonplast ltd. by hand lay-up laminating technique. before application, the reinforcing fibres and chopped glass fibre mats were impregnated with the solution of the experimental compatibilizing additives produced at university of pannonia, institute of chemical and process engineering, department of hydrocarbon and coal processing. for carbon fibre treating polyalkenyl-poly-maleic-anhydride-ester-amide (amaea) type compatibilizer, for chopped glass fibre mats polyalkenyl-poly-maleic-anhydride-ester (amae), polyalkenyl-poly-maleic-anhydride-amide (amaa) and polyalkenyl-poly-maleic-anhydride-ester-amide (amaea) agents were used. experimental results carbon fibre reinforced polyethylene composites resistance against tensile stresses and relaxation tests of specimens cut out from the geogrid were determined with an instron 3345 universal tensile testing machine. in case of carbon fibre reinforced polyethylene grid three characteristic directions were defined: process direction, perpendicular to process direction and diagonal direction (fig. 1). it is important because the grid is exposed to stresses in different directions during its application. process direction perpendicular to process direction diagonal direction figure 1: testing directions of geogrid tested geogrid samples contained experimental polyalkenyl-poly-maleic-anhydride-ester-amide treated carbon fibres in 0%, 1%, 2% and 5% concentrations. in case of long carbon fibre reinforced thermoplastic composites fibres could not be introduced into the polymer matrix without additive treating neither by injection moulding nor by extrusion. therefore, the properties of geogrids containing additive treated carbon fibres were compared to the properties of commercially available product containing no carbon fibres. carbon fibres could be easily introduced into the polymer by extrusion when the fibres were treated with our compatibilizing agent and the fibres respectively remained in long fibre form (l = 3-4mm). tensile strength, modulus and elongation values of the geogrid in the different directions were shown in table 1. tensile strengths and elongations differed within the error of measurement in case of samples containing no and 1% carbon fibres in all testing directions but the differences in tensile moduluses were enormous in diagonal direction. the mechanical properties of the simple tensile tests of the additive treated carbon fibres containing composites showed upward tendency compared to the unreinforced samples. with the relaxation tests the process of shaperestitution was investigated at three different loads (100 n, 200 n and 300 n). relaxation curves of specimens, perpendicular to process direction, at 200 n load was shown in fig. 2. fig. 3 showed the load values after 180 sec relaxation in case of the different loads and different directions. relaxation of the specimens did not show significant tendencies, the results changed within the error of measurement. the load values at given time after the load passed off did not show significant differences in the various specimen directions. the decrease of load fell down from ~45% to ~30% with increasing relaxation load. only the specimens perpendicular to process direction made from the virgin polymer and the specimens in process and perpendicular to process direction made from the 1% carbon fibre containing composites could be measured at 300n relaxation load, the others could not bear the applied relaxation stress. 139 table 1: mechanical properties of geogrid in the different specimen directions tensile strength at max. tensile elongation maximum tensile elongation tensile modulus mpa mm mpa p.d. 23.3±1.1 8.2±0.4 15.1±1.8 p.p.d. 35.0±0.7 13.0±0.5 45.1±0.8 0% carbon fibre d.d. 25.0±1.4 10.5±0.5 24.8±0.5 p.d. 24.0±1.2 8.1±0.5 15.3±1.6 p.p.d. 35.0±0.6 12.8±0.5 43.4±0.3 1% carbon fibre d.d. 22.7±1.1 11.2±0.6 29.4±0.4 p.d. 30.0±0.8 8.2±0.5 16.0±0.3 p.p.d. 34.4±0.6 14.6±0.3 34.2±1.2 2% carbon fibre d.d. 9.5±0.9 18.0±0.5 36.0±0.4 p.d. 31.3±0.4 8.5±0.3 15.0±0.2 p.p.d. 25.8±0.3 14.5±0.3 54.9±1.5 5% carbon fibre d.d. 12.8±0.7 18.3±0.2 42.8±0.3 p.d.– process direction, p.p.d.– perpendicular to process direction, d.d.– diagonal direction 0 50 100 150 200 0 50 100 150 200 time, sec l oa d, n 1% carbon fibre 0% carbon fibre figure 2: relaxation curves (at 200n relaxation load, specimens perpendicular to process direction) pr oc es s di re ct io n pe rp . t o pr oc es s d. di ag on al di re ct io n pr oc es s di re ct io n pe rp . t o pr oc es s d. di ag on al di re ct io n pr oc es s di re ct io n pe rp . t o pr oc es s d. di ag on al di re ct io n0 50 100 150 200 250 300 l oa d af te r re la xa tio n, n 0% carbon fibre 1% carbon fibre 100n 300n 200n figure 3: results of relaxation tests after simple tensile tests different fatigue conditions were applied and tensile properties were also determined. according to relaxation tests two different loads (100 n and 250 n) and three different numbers of cycles were used during fatigue tests then tensile properties were measured. 50, 100 and 150 numbers of cycles were applied in case of 100 n and 100 numbers of cycles at 250 n pre-load at 90 mm/min crosshead speed. results of fatigue tests were shown in figs 4-7. as the figs 4 and 5 showed significant differences were experienced in case of tensile strengths in the various specimen directions. rising tendency could be observed comparing to the results of fatigue tensile tests, however, the specimen direction also influenced the differences between the polymer and the 1% carbon fibre containing composite. the differences varied within the range of 0.5-29.7%. the worst results were experienced with specimens in process direction either as in case of simple tensile tests. tensile strength of 1% carbon fibre containing composites decreased with the numbers of pre-cycles in each direction which is probably because fibre orientation can not compensate the stress after a given degree of pre-stress. tensile strength of the virgin polymer slightly increased with numbers of cycles which was probably due to the higher elasticity of the polyethylene than of the carbon fibre reinforced composites. pr oc es s di re ct io n pe rp en di cu la r to p ro ce ss d . di ag on al di re ct io n pr oc es s di re ct io n pe rp en di cu la r to p ro ce ss d . di ag on al di re ct io n pr oc es s di re ct io n pe rp en di cu la r to p ro ce ss d . di ag on al di re ct io n0 5 10 15 20 t en si le st re ng th , m pa numbers of cycles (in case of 100n pre-load) 0% carbon fibre 1% carbon fibre 50 100 150 figure 4: results of fatigue tests in the different specimen directions pr oc es s di re ct io n pe rp en di cu la r to p ro ce ss d . di ag on al di re ct io n pr oc es s di re ct io n pe rp en di cu la r to p ro ce ss d . di ag on al di re ct io n0 5 10 15 20 t en si le st re ng th , m pa pre-load (in case of 100 numbers of cycles) 0% carbon fibre 1% carbon fibre 100n 250n figure 5: results of fatigue tests in the different specimen directions 140 a further advantage of the carbon fibre reinforced composites was that better tensile strength could be measured with applying pre-stress compared to the results of the grid made of polyethylene where application of pre-stress decreased the tensile strengths of the specimens in each direction. that phenomenon was probably due to fibre orientation. the highest increase was observed with specimens in diagonal direction. similar results were obtained with the other properties (tensile elongation, modulus, properties at break) in fatigue tests. the effects of fibre content on the fatigue properties were also examined. according to figs 6-7 tensile strength increased when the fatigue conditions became stricter in case of higher carbon fibre content. a decrease could be observed in case of 2% carbon fibre content compared to 1% carbon fibre content which was probably due to processing failure as the specimens showed the trends described in the previous paragraphs. 50 100 150 0 5 10 15 20 t en si le st re ng th , m pa numbers of cycles (in case of 100n pre-load) 0% carbon fibre 1% carbon fibre 2% carbon fibre 5% carbon fibre figure 6: results of fatigue tests in case of different carbon fibre content 100 n 250 n 0 5 10 15 20 t en si le st re ng th , m pa pre-load (in case of 100 numbers of cycles) 0% carbon fibre 1% carbon fibre 2% carbon fibre 5% carbon fibre figure 7: results of fatigue tests in case of different carbon fibre content figure 8: sem graph of the fractured surface of the 5% carbon fibre containing composite fibre-matrix interaction was followed by scanning electron microscopy. fig. 8 showed the fibre-matrix connection and represented that the fibres were just broken at the surface and fibre-pullout was not experienced so the additive could establish good connection between the elements. chopped glass fibre mat reinforced polyester composites results of tensile tests were shown in figs 9-11 while charpy impact properties in fig. 12. tensile properties of the samples were determined according to msz en iso 527-1-4:1999 and charpy impact properties according to iso 179-2:1997 standard. as glass fibre content can considerably influence the mechanical properties glass fibre contents of the samples were determined. measurements were carried out according to msz en iso 3451-1:1999 standard so ash contents were measured after 800 °c heating. the glass fibre contents of the samples with and without additive were 35.5±2.4%. fig. 7 showed tensile strength at break. properties at maximum tensile elongation and at break were the same because of the physical characteristics of the polyester composites. during the mechanical tests the samples showing the best properties were compared to the reference samples. amae amaea amaa 0 25 50 75 100 t en si le st re ng th , m pa additive sign without additive (73 mpa) figure 9: changes in tensile strength according to the results of tensile tests it could be stated that such surface modifier additive could be produced with which better mechanical properties could be realized than with untreated fibres reinforced composites. tensile strength was 9.7% better with amae additive, and 23.7% better with amaea than the tensile strength of the untreated fibres containing composite. but with amaa additive the tensile strength decreased with almost 13% which showed that the high nitrogen-content and the absence of ester groups influence the fibre-matrix interaction disadvantageously. amae amaea amaa 1,5 1,7 1,9 2,1 2,3 2,5 e lo ng at io n at b re ak , m m additive sign without additive (2.2 mm) figure 10: changes in elongation at break 141 similar results were obtained in case of elongation at break either where the positive changes were 4.5% and 9.1% but in case of amaa agent with 2.3% lower value of elongation could be observed. amae amaea amaa 0 1000 2000 3000 4000 5000 6000 y ou ng m od ul us , m pa additive sign without additive (3980 mpa) figure 11: changes in young-modulus young-modulus increased with almost 27% applying the amaea additive but in case of the additive containing no ester groups 4% decrease was experienced compared to the reference sample. dynamic tests were carried out with a ceast resil impactor machine according to the iso 179 standard using a type cut specimens. as fig. 12 showed in the first two cases the specific work was 16.5% and 20.6% higher than without additive. with the third additive that property decreased with 3%. amae amaea amaa 0 30 60 90 120 150 180 c ha rp y im pa ct st re ng th , k j/ m m 2 additive sign without additive (127 kj/mm2) figure 12: changes in charpy impact strength the broken samples were examined because the fibre pull-out is the most visible in that case. figs 13-15 represented the fibre-matrix interaction shown on the sem graphs. in case of untreated fibres containing composites the matrix covered the fibres in many places (fig. 13) but at the fractured faces the fibres separated from the matrix. figure 13: fibre-matrix interaction in untreated chopped glass fibre mat reinforced polyester composites according to the sem graph about the samples showing best mechanical properties (fig. 14) the compatibility of the glass fibres and matrix was improved because the fibres pulled out less from the matrix and were broken at the surface, and the surface was covered with the polymer even after break in many places. figure 14: fibre-matrix interaction in chopped glass fibre mat reinforced polyester composites applying amaea compatibilizing additive fig. 15 showed the fractured face of the samples showing worse mechanical properties where it can be seen that the surface of the glass fibres became smooth because they separated easily from the matrix. the glass fibre bundles functioning as reinforcing materials easily moved out from the starched resin so they could not supply their objectives. figure 15: fibre-matrix interaction in chopped glass fibre mat reinforced polyester composites applying amaa compatibilizing additive summary with our compatibilizing additives the mechanical properties of carbon fibre reinforced thermoplastic and glass fibre reinforced thermoset composites could be enhanced. applying our experimental compatibilizing additive carbon fibre reinforced geogrid could be produced by extrusion. while the mechanical properties of the additive treated carbon fibres containing composites did not show significant difference compared to the virgin polymer in case of simple tensile tests considerable differences were experienced in case of fatigue properties. 142 either with increasing pre-load or with numbers of cycles deteriorative trends could be marked in case of unreinforced geogrid samples in opposition with the carbon fibre reinforced ones where the rising tendency was probably due to the orientation of the fibres. convenient adhesion was developed in the composites as sem graphs proved. according to the tensile and dynamic mechanical properties of compatibilizing additive impregnated chopped glass fibre mat reinforced laminated polyester composites such compatibilizing additive could be produced by which better mechanical properties could be achieved than the untreated glass fibre reinforced composites. fibrematrix adhesion was investigated by sem in glass fibre reinforced composites either. in untreated fibres containing systems there are places where convenient adhesion was developed between the fibres and the matrix so the resin surrounded the fibres well but somewhere the components separated. the resin adhered to the fibres even after break in case of effective additive as represented on the sem graphs. references 1. thomason j. l.: composites part a 36 (2005) 995-1003 2. soutis c.: materials science and engineering a 412 (2005) 171-176 3. arib r. m. n., sapuan s. m., ahmad m. m. h. m., paridah m. t., khairul zaman h. m. d.: materials and design 27 (2006) 391-396 4. abdelmouleh m., boufi s., belgacem m. n., dufresne a.: composites science and technology 67 (2007) 1627-1639 5. karmarkar a., chauhan s. s., modak j. m., chanda m.: composites: part a 38 (2007) 227-233 6. park s.-j., jin j.-s.: journal of colloid and interface science 242 (2001) 174-179 7. malchev p. g., david c. t., picken s. j., gotsis a. d.: polymer 46 (2005) 3895-3905 8. kaynak c., orguna o., tincer t.: polymer testing 24 (2005) 455-462 9. chung d. d. l.: butterworth-heinemann, newton, (1994) 88-92 10. dibenedetto a. t.: materials science and engineering a 302 (2001) 74-82 11. park s.-j., jin j.-s.: j colloid interf sci 242 (2001) 174-179 microsoft word content.doc hungarian journal of industrial chemistry veszprém vol. 40 (2) pp. 65–67 (2012) comparative study on electrodialysis systems for galacturonic acid recovery k. bélafi-bakó , e. molnár, z. csanádi, n. nemestóthy university of pannonia, research institute on bioengineering, membrane technology and energetics, 10 egyetem str., 8200 veszprém, hungary e-mail: bako@almos.uni-pannon.hu electrodialysis (ed) is an electromembrane separation process suitable for recovery of organic acids. in this work galacturonic acid (ga) obtained by enzymatic hydrolysis of pectins from various sources was separated by a laboratory scale, two-step ed stack and a scaled-up, complex ed system. the experimental results from the two systems were compared. keywords: electrodialysis, pectin, galacturonic acid introduction galacturonic acid is the monomer of pectin, a polysaccharide [1] often occurred in agro-wastes, like sugar beet pulp, apple pomace, press cakes of fruits... etc. pectin can be hydrolyzed by enzymes and the process results a galacturonate (gat) solution. since it is an acidic (charged) compound, its recovery and separation can be carried out by electrodialysis (ed). electrodialysis is an electro membrane process, where charged components move in the direction of the oppositely charged electrode under electrical potential difference [2, 3]. ed has already been applied to separate various organic acids like citric acid, lactic acid, acetic acid, propionic adic, gluconic acid, maleic acid [4–8]. in case of pectin hydrolysates ed can be used for recovery and desalination of galacturonate ions (the counter ion is usually na). a laboratory scale, two step ed stack and a fumatech ft-ed-4-100-10 scaled-up complex module were applied in our laboratory to recover ga ([9 ,10]. in this work the stacks are compared from the aspects of yield, operation parameters, energy requirement and average current efficiency. material and methods galacturonic acid (ga) applied in the model solutions was purchased from sigma-aldrich, while sodium sulphate from spectrum (hungary). cation(fumasep fkb), anion-selective (fumasep fab) and bipolar (bp) membranes were purchased from fumatech. hydrolysis of pectin solutions from sugar beet pulp and citrus was carried out by pectinase enzymes (pectinex 100l enzyme preparation) in a shaking incubator. the process was followed by acid titration (0.5 m naoh). the laboratory scale ed set up consisted of two stacks (one conventional and the other contains bipolar membrane) was constructed in our workshop. the first stack was an symmetric ed cell (described in [9]), with 0.0225 m2 membrane surface area. here the galacturonate ions from the hydrolysate moved toward the anode and passed through the anion selective membrane, while sodium ions are transported in the other way. thus a concentrate stream containing mainly na-galacturonate was formed. then its desalination was carried out in the second ed cell, where 2 cation selective and a bipolar membrane were built in (figure 1) altogether with 0.0135 m2 membrane surface area. separation of sodium and galacturonate ions was possible: galacturonate anions remained in the feed solution forming an acid solution, while na ions passed through the cation selective membrane into the alkali solution forming naoh. figure 1: set-up of the second laboratory scale ed module 66 the scaled-up complex module containing cation, anion selective and bipolar membranes was described in [10], its membrane surface area was 0.31 m2. both ed stacks were operated by recirculation, using na2so4 solution (electrode solution). the experiments were followed by measuring the concentration of ga (dns test [11]) in various streams, conductivity, ph, electric current and voltage, the data were collected by a data acquisition device (national instruments usb6008/6009) and recorded by the program labview. the important stack and operation parameters for the laboratory scale stacks and the scaled-up complex ed module were summarized in tables 1 and 2, respectively. table 1: parameters of the two-step ed system for galacturonic acid recovery and desalination features of the modules conventional asymmetric ed combined with bp membrane membranes 3 cation selective, 2 anion selective 2 cation selective, 1 bipolar membrane surface area 0.0225 m2 0.0135 m2 volumes of solutions feed (diluate): 100 ml, concentrate: 150 ml feed (acid): 100 ml, alkali: 150 ml recirculation rate 32 ml/min 32 ml/min electrode solution 200 ml 0.5 mol/l na2so4 200 ml 0.5 mol/l na2so4 recirculation rate 60 ml/min 60 ml/min applied voltage 5 v 5 v processes galacturonate anions and na cations pass through the membranes to accumulate in the concentrate galacturonate anions remain, bp provides h+, acid formation na cations pass through the membranes, form alkali solution final results concentrate rich in na-galacturonate formation of galacturonic acid and naoh solutions table 2: parameters of the scaled-up complex ed system features of the module scaled-up complex module membranes 10 anion selective, 11 cation selective, 10 bipolar membrane surface area 0.31 m2 volumes of solutions feed (diluate): 400 ml, acid: 400 ml, alkali: 450 ml recirculation rate 380 ml/min electrode solution 500 ml 0.1 mol/l na2so4 recirculation rate 500 ml/min applied voltage 36 v processes both galacturonic anions and na cations pass through the membrane, formation of acid and alkali solutions final results recovery and desalination of galacturonic acid in one step results pectin hydrolysates from sugar beet pulp and citrus were studied by using the two ed systems. the experimental results are compared in table 3. from the table it can be seen, that higher initial concentration feed was applied in case of the two-step laboratory module, since in the second step we had to use the result of the first step: the na-galacturonate solution (recovered from the hydrolysate). it was desalinated in the bp module. in the scaled-up complex system the separation process (recovery and desalination) was achieved in one single step. though the energy consumptions were much higher in the scaled-up system and the current efficiencies were lower (than in the laboratory scale stack), but larger amount of product solutions (pure galacturonic acid) were manufactured. if the product acid obtained were related to the energy consumption, we found that – in case of ed separation of sugar beet pectin hydrolysate – 1 wh energy resulted in 0.09 g and 0.13 g ga production by the two-step, laboratory and the scaled-up, complex system, respectively. the scaled-up system worked with higher effectiveness, moreover it should be taken into account that its operation can be further optimised, and the energy consumption might be reduced even more. 67 table 3: comparison of the two ed systems two-step laboratory ed system hydrolysate asymmetric ed bp module scaled-up complex ed system from sugar beet pulp pectin feed volume feed conc. yield current eff. energy final result 100 ml 36.5g/l 63% 56% 9.2 wh 150 ml 15.4 g/l nagat solution 100 ml 15.4 g/l desalination – 4.6 wh 100 ml 12.1 g/l desalinated ga solution 400 ml 15 g/l 65% 41% 31 wh 400 ml 9.8 g/l desalinated ga solution from citrus pectin feed volume feed conc. yield current eff. energy final results 100 ml 48.9 g/l 78% 63% 8.9 wh 150 ml 25.4 g/l nagat solution no data 400 ml 39 g/l 86% 54% 39 wh 400 ml 33.5 g/l desalinated ga solution the yield, current effectiveness values are better for citrus pectin hydrolysate than for sugar beet pulp pectin hydrolysate, which may be explained by the higher purity of the citrus pectin preparation. as a summary, we concluded that electrodialysis is a suitable method for recovery, desalination and purification of galacturonic acid from hydrolysates of various pectins. the complex module was able to separate the product in one step and it seems that the scaled-up system worked more efficiently: higher yield was achieved by less energy consumption. therefore the complex ed system is suggested to apply for further experiments, aiming to study the possibilities of industrial applications. acknowledgement this work was partly supported by the támop4.2.1/b-09/1/konv-201-0003 and támop-4.2.2/b10/1-2010-0025. references 1. z. i., kertész: the pectic substances, interscience publishers, new york (1951) 2. h. strathmann: ion-exchange membrane separation processes, elsevier, amsterdam (2004) 3. s. beszdes, zs. lászló, g. szabó, c. hodúr: enhancing of biodegradability of sewage sludge by microwave irradiation, hungarian journal industrial chemistry, 36 (2008), pp. 11–16 4. s. novalic, j. okwor, k. d. kulbe: the characteristics of citric acid separation using electrodialysis with bipolar membranes, desalination, 105 (1996), pp. 277–283 5. m. cytko, k. ishi, k. kawai: continuous glucose fermentation for lactic acid production: recovery of acid by electrodialysis, chemie ingenieur technik, 59 (1987), pp. 952–954 6. n. yoshiyuki, i. masayoshi, h. motoyoshi: acetic acid production by an electrodialysis fermentation method with a computerized control system. applied environmental microbiology, 54 (1988), pp. 137–142 7. s. novalic, t. kongbangkerd, k. d. kulbe: recovery of organic acids with high molecular weight using a combined electrodialytic process, journal of membrane science, 166 (2000), pp. 99–104 8. k. bélafi-bakó, n. nemestóthy, l. gubicza: study on application of membrane techniques in bioconversion of fumaric acid to l-malic acid, desalination, 162 (2004), pp. 301–306 9. e. molnár, m. eszterle, k. kiss, n. nemestóthy, j. fekete, k. bélafi-bakó: utilisation of electrodialysis for galacturonic acid recovery, desalination, 241 (2009), pp. 81–85 10. e. molnár, n. nemestóthy, k. bélafi-bakó: utilisation of bipolar electrodialysis for recovery of galacturonic acid, desalination, 250 (2010), pp. 1128–1131 11. g. l. miller: use of dinitro-salicylic acid reagent for determination of reducing sugar, analytical chemistry, 31 (1959), pp. 426–428 microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 11-16 (2008) enhancing of biodegradability of sewage sludge by microwave irradiation s. beszédes, zs. lászló, g. szabó, c. hodúr university of szeged, institute of mechanical and process engineering moszkvai krt. 5-7, hu-6725 szeged, hungary e-mail: hodur@mk.u-szeged.hu in our work we focused on the effect of the microwave energy at the aerobic and anaerobic biological degradability of sewage sludge. the sewage sludge is a multiphase system with high water content. because of the presence of water molecules sludge is able to absorb the microwave energy efficiently. because of the variable dielectric properties the different component of sludge heat differently, these effects cause „thermal shock”. during the microwave treatment the configuration of macromolecules are varied and the cell walls of the microorganisms are opened by the thermal shock, it means the organic compounds are accessible for further biological degradable. in our experiments digested municipal sewage sludge and undigested dairy-sludge were used. labotron 500 professional microwave equipment was used for the microwave treatment at 2450 mhz frequency. the specific microwave power level was changed between 1 to 5 w/g. oxitop pm barometrical measurement system was used for determination of the biogas production at 40 °c, the measurement of the chemical oxygen demand (cod) of sludge was based on a potassinium-bichromate method, and a respirometric bod meter was used for the biochemical oxygen demand (bod) measurement (20 °c). our results showed that, the microwave energy could be a practical and effective alternative technique to enhance the biodegradability of sludge, because after microwave treatment increases the biodegradability from 7 up to 40% by diary sludge and from 12 up to 48 % by municipal sludge. it was found, that the originally resistant sludge after a microwave pre-treatment became more degradable, and its biogas production increased from 20-30 ml/g dry weight up to 500 ml/ gdry weight. the highest microwave power level effects the highest biogas yield, but the energy balance at lower specific power level (1-2 w/g) and longer treatment time gave just notable net energy production compared to the control sample. keywords: sewage sludge, biodegradability, biogas, microwave pre-treatment introduction nowadays, the most limiting factor of human being has been the clear water, and for this reason the efficiency of wastewater treatment technologies has increased. but the development and the widespread using of waste water technologies causes a large increasing in the municipal and industrial sewage sludge production. sludge represents the major solid waste from biological and physico-chemical waste water treatment processes. handling of this waste is difficult, and gives rise to secondary collateral environmental pollution. so the amount and the environmental risk of sludge have growing. the most common alternatives of treatment of sewage sludge are sludge landfill, cropland application, ocean dumping and incineration. but for example by agricultural using the existing landfill sites are running out of space, however secondary pollution is becoming a serious problem. for these reasons it is the most urgent challange to improved novel process to minimized final sludge quantity. environmental problems of sewage sludges the municipal and for instance the food industrial sludge, because of high organic content, is a special type of biomass, thus it may be utilized in biogas production. in the case of sludge it is some limiting compounds for example hazardous heavy metals and pathogen microorganisms. the anaerobic conditions in presence of methanogenic microorganisms lead to sludge stabilization by converting a part of organic substance into biogas [1]. the carbohydrates and the lipids of sludge are easily degradable by microorganisms, while the proteins normally less accessible for biological degradation. the anaerobic digestion of sewage sludge has many advantages for example the produced biogas can be used as renewable energy source, digestion has low energy requirement (if the produced biogas is used for heating of reactor), the pathogenic microorganisms are efficiently killed and digested sludge is harmless to dispose [2-4]. the main structure of sludge consists of extracellular polymeric substance (polysaccharide, proteins), other organic and inorganic matter and microbial cells which 12 agglomerated together. this complex flock structure of sludge is resistance to a direct anaerobic degradation since cell walls and polymeric conformation present physical and chemical barriers for microbial and enzymatic degradation [5]. the non-biodegradable polymeric structure does not only originate from cell autolysis and sludge bacterial cell but also originates from the raw wastewater. so besides the dosed chemical, the organic matter removal efficiency of applied waste water technology is determinative too. but the amount of biological degradable component of organic matter is essential not only in anaerobic digestion but in aerobic process for example in composting or in soilbioremediation, also. there are many possibilities to improve the digestibility and aerobical biodegradability of sludge. mechanical, thermal, ultrasound, chemical, thermochemical and enzymatic pre-treatment methods can enhance the extent and the rate of biological degradation [6-8]. it is verified the thermal pretreatments improve pathogen destruction and dewaterability process of sludge, too [9, 10]. the value of biodegradability (bd) is commonly characterized by the bod/cod ratio. cod is the chemical oxygen demand; the quantity of oxygen required oxidation by chemical oxidant. the soluble cod (scod) indicate the water soluble part of cod. bod is the biochemical oxygen demand, the quantity of oxygen consumed by aerobic microorganisms due to carbonaceous oxidation at a standard temperature (20 °c). the anaerobic degradability batch mesophilic biochemical methane potential (bmp) tests are used with applying of acclimated inoculums of methanogenic bacteria at mesophilic temperature range (25–45 °c). possibilities of microwave technic in sewage sludge treatment microwave heating is used as a popular alternative to conventional heating mainly due to considerable reaction time reducing effect. in conventional heating a large part of process time is needed to heat the vessel before the heat is transferred to the sample, while microwave irradiation heats matter directly. the microwave equipment generally uses 2450 mhz frequency with a 12.24 cm operating wavelength. the microwave magnetron with 900 mhz operating frequency is used for industrial scale heating and drying of solid and low water content matter on the ground of larger penetration ability [11]. nowadays microwave digestion methods have been developed for different sample types such as environmental, biological, geological and metallic matrices [12]. applications of microwaveassisted techniques in many fields of analytical methods, such as sample drying, moisture measurements and extraction processes are used. besides the examination of microwave irradiation on biological system the microwave oven reaction engineering (more) demonstrates promising results, for example in synthesis of organic molecules. the microwave irradiation has thermal and athermal effect. the thermal effect can be attributed heat generation in the matter due to rotation of dipole molecules or ionic conduction. ionic conduction is the electrophoretic migration of ions when an electromagnetic field is applied. dipole rotation means realignment of dipoles with the applied fields, for example at 2450 mhz the dipoles align and randomized 4.9·109 times per second and this forced molecular motion results heat. in many applications these two mechanisms have been applied simultaneously. due to high water content the sewage sludge can absorb microwave energy efficiency. microwave irradiation causes increasing of kinetic energy of water molecules, thus the boiling point is reached rapidly. although the quantum energy of microwave radiation is too low (1.05·10-5 ev) to break the chemical bounds but some structures can be altered by the energies carried by microwaves. for example the athermal effect of microwave radiation is caused by polarized parts of macromolecules, it results breakage of hydrogen bound. therefore, for instance the microwave irradiated microbial cell shows greater damage than convective heating cells to a similar temperature. a sample with non-homogenous structural characteristics and different dielectric properties is possible to produce a selective heating of some areas or components of material, it is known as superheating effect. the intensive microwave heat generation and the different dielectric properties of compounds of cell wall lead to a rapid disruption of extracellular polymer network and residue cells of sludge [13]. however the cell liquor and extracellular organic matter within polymeric network can release into the soluble phase, hereby increase the ratio of accessible and biodegradable component. during the intensive microwave heating the odorous compounds of sludge e.g. volatile fatty acids were reduced too. to summarize, by application of microwave treatment could be achieve a higher flock and cells destruction compared to conventional heating, this effect could be manifested by difference ratio of soluble and total cod and the increased rate of biogas production [14]. but it is had to notice that the temperature control of a microwave pre-treatment process causes some practical difficulties because the conventional thermistors cannot provide accurate temperature measurement, since the local superheating effect within the sample due the interaction of thermistor and thermocouple with electromagnetic field [15]. in the microwave technique widely used infrared thermometer can measure only the surface temperature of sample. by the glass fiber instruments can be measured more exact values of temperature distribution of matters but by a sample with a low moisture content and varying, non homogenous structure, the method is less applicable in practice. 13 materials and methods in our experiments two different sewage sludge were used. the municipal sewage sludge was from an urbanwaste water treatment plant (hódmezővásárhely, hungary). the sludge was the residual solid phase of the biological waste water management technology, the average moisture content was 53.4 w/w%. the industrial sewage sludge was originated from the waste water treatment plant of a local dairy works (sole-mizo ltd., szeged, hungary). in the case of dairy sewage sludge a phyico-chemical waster water technology was applied and the water content of sludge was 58.2 w/w%. the microwave pre-treatments were performed in a labotron 500 (buchner-guyer ag, switzerland) professional microwave equipment, at 2.45 ghz frequency, at 100 to 500 w microwave power. the turntable of microwave equipment compensated for the non-uniform heat distribution. the microwave irradiation time was 10 to 40 minutes. the applied specific microwave power level was 1, 2 and 5 w/g, which was adjusted by the ratio of magnetron power and the quantity of treated sludge. the power of magnetron is changeable continuously 100 to 500 w by toroidal-core transformer, the quantity of sludge was constant 100 g. the disk-form sludge samples were placed invariably in 2 cm layer because of penetration depth of microwave radiation. poly-tetrafluor-ethylene (ptfe) vessels (6 cm internal diameter) were used on account of efficient microwave penetration and absorption. cover was applied to prevent the evaporation during the irradiation. the convective heat-treatment was performed in automatic temperature controlled laboratory heater equipment (medline cm 307, uk) at 95 °c. the surface temperature of sludge an infracam (flir infracam-sd, sweden) was determined after microwave irradiation. chemical oxygen demand (cod) was measured according to the dichromate standard method in cod tests with an et 108 digester and a lovibond pc checkit photometer. the biochemical oxygen demand (bod) measurements were carried out in a respirometric bod meter (bod oxidirect, lovibond, germany), at 20 °c. to ensure the consistency of the results bod microbe capsules (cole parmer, usa) were used for measurements. biodegradability during 5 days (bd5%) was characterized by the following expression: %100 cod bod%db 5 5 ×= the cumulative biogas production tests were performed in batch mode under mesophilic conditions, at 40 °c for 30 day, in a temperature controlled anaerobic digester with oxitop control type pressure mode measuring system (wtw gmbh, germany). the digesters were inoculated with an acclimated anaerobic sludge from a biogas reactor of municipal wastewater treatment plant (hódmezővásárhely, hungary) in order to eliminate the possible lag-phase of biological degradation process. after inoculation nitrogen gas was flowed through the reactor to prevent exposure to air. for methane determination the measurements were performed parallel in two vessels: one of them contained co2 absorber, the other measured the total gas pressure. the resulting pressure difference is proportional to the co2 concentration; the remaining overpressure is proportional to the methane concentration. the composition of produced biogas also was measured by gas chromatographic and mass spectrometric method (agilent 6890n-5976 gc-ms). the net energy product (nep) of processes with microwave pre-treatments can be calculated by the equation [16]: τ×−×= mmethanecomb pmqnep where nep is the net energy product [j], qcomb is the combustion heat [j/kg] of methane, mmethane the mass of the produced methane [kg], pm the power of microwave magnetron [w], τ the time of microwave irradiation [s]. results and discussion the surface temperature of samples was measured by infracam, and the average temperature and standard deviation were represented in the following table. table 1: the surface temperature of microwave irradiated sludge after treatments surface temperature [°c] mw power level 10 min. 20 min. 30 min. 40 min. 1 w/g 75,7 ± 2,9 83,5 ± 1,8 89,2 ± 1,6 90,2 ± 1,3 2 w/g 79,3 ± 2,2 86,7 ± 1,4 89,6 ± 1,1 91,7 ± 0,7 5 w/g 83,6 ± 0,8 89,1 ± 0,9 90,8 ± 0,3 92,8 ± 0,4 in the first series of our experiments the effect of microwave irradiation on biodegradability of sewage sludge was investigated at different specific microwave power level. besides the specific power level the effect of irradiation time was studied too. the biodegradability of untreated dairy and municipal sewage sludge was 7% and 12% respectively. it was found that without pretreatment either municipal or dairy industrial sludge was resistant to aerobical biological degradation. 0 10 20 30 40 50 0 10 20 30 40 mw pre-treatment time [min] b d [% ] 1 w/g 2 w/g 5 w/g convectiv (95°c) figure 1: biodegradability (bd%) of dairy sewage sludge after microwave and convective pre-treatments 14 0 10 20 30 40 50 0 10 20 30 40 mw pre-treatment time [min] b d [% ] 1 w/g 2 w/g 5 w/g convectiv (95°c) figure 2: biodegradability (bd%) of municipal sewage sludge after microwaveand convective pre-treatments the low biodegradability of municipal sewage sludge was caused by large-scale degradable organic material removal of previous biological waste water treatment. the residual components, which was concentrated in the sludge, was less degradable or more resistant to microbial or enzymatical degradation. the structure of dairy sludge, formed by interaction of extracellular polymeric substance and applied chemicals, caused less accessible property for biological decomposition. for comparison the convective heat pre-treatment was examined. the convecive treatment at 95 °c caused increasing in biodegradability, but this effect was less effective than pre-treatment at lowest microwave power level. the microwave pre-treatments increased the biodegradability of investigated sludge. microwave irradiation at low power level (1 w/g) had a sligh effect on biodegradability, especially at sludge originated from dairy industry, but the higher microwave power level and enhanced irradiation time seemed to be more efficient. at highest applied power level (5 w/g) a saturation value of biodegradability was observed. in the case of municipal sludge the ratio of biodegradable component was enhanced from 8 % up to 40 % after 30 minutes irradiation at 5 w/g. the same microwave pre-treatment increased the value of bd% to 48 % at dairy sewage sludge. enhancing of biodegradability may be linked to solubilization of organic matter which was indicated by the increased scod/cod ratio, besides the digestion effect of microwave irradiation on cell wall of residual died and alive microorganisms. besides the change of biodegradability the effect of microwave irradiation on anaerobic digestion was investigated, the digestionable was characterized by cumultive methane production, which were depicted on figs 3-4, in the case of pre-treatment at 1 w/g and 5 w/g . similar to aerobical biodegradation the microwave pre-treatment improved the anaerobical decomposation performance and the increased irradiation time enhanced the biogasand methane production of pre-treated sewage sludge related to control. the untreated control samples had very small (15–30 cm3) methane production, but after a 40 minute long, 1 w/g mw pre-treatment enhanced the methane production up to 200 cm3 at municipal sludge and up to 250 cm3 at dairy sludge. the convectie heat-treatment had a substantially smaller effect on anaerobic biodegradation than microwave irradiation since the smaller biogas product. after a 40 minutes heat-treatment at 95 °c a 25% enhancing of biogas product was experienced by both sludge, but these enhancing was significantly smaller than after a 20 minutes microwave irradiation, although the average temperature of microwave iradiated sludge was just about 83 °c. 0 100 200 300 1 4 7 10 13 16 19 22 25 28 digestion time [day] c um ul at iv e m et ha ne p ro du ct io n [m l] 20 min d 40 min d control d 20 min m 40 min m control m figure 3: methane production of sludge after 1 w/g microwave pre-treatment (d-dairy sewage sludge, m-municipal sewage sludge) the applied microwave treatment both given sludge could decreased the lag-phase period of digestioning process. the higher specific microwave power caused higher increasing in the methane production and higher decreasing in the period of lag-phase. 0 100 200 300 400 500 1 4 7 10 13 16 19 22 25 28 digestion time [day] c um ul at iv e m et ha ne p ro du ct io n [m l] 20 min d 40 min d control d 20 min m 40 min m control m figure 4: methane production of sludge after microwave pre-treatment at 5 w/g (d-dairy sewage sludge, m-municipal sewage sludge) enhancing of microwave power level to 5 w/g resulted an increasing in the methane production 500 cm3 by 40 minutes pre-treatment at municipal sludge. approximately the same biogas yield was achieved by 5 w/g specific mw level at 40 minute long treatment at dairy sludge as it was achived with a 20 minute long mw treatment at municipal sludge. to a first approximation a longer process time and a higher microwave power level seemed to be optimal. 15 after all not only the biogas production itself, but the other energetical parameters must be take into consideration. by assessing the energy of extra-methane produced and calculation of energy requirements of microwave pre-treatments the energy balance of mw enhanced treatment was investigated, and the efficiency of process was characterized by net energy prouction (nep). -18000 -15000 -12000 -9000 -6000 -3000 0 3000 6000 control conv ectiv e (95°c, 40 min) 1 w/g 20 min w/g 40 min 2 w/g 10 min 2 w/g 40min 5 w/g 10 min 5 w/g 20 min δ e [j /g ] figure 5: energy balance of pretreatments of dairy sewage sludge -12000 -10000 -8000 -6000 -4000 -2000 0 2000 4000 6000 control conv ectiv e (95°c, 40 min) 1 w/g 20 min w/g 40 min 2 w/g 10 min 2 w/g 40min 5 w/g 10 min 5 w/g 20 min δ e [j /g ] figure 6: energy balance ofpretreatments of municipal sewage sludge in spite of large energy demand of microwave treatments, there is optimal specific microwave power which produce positive energy balance. in comparison with optimal parameters of methane production different results can be obtained by calculate the energy balance of the treatments. with the exception of the highest microwave power level (5 w/g) the invested microwave energy was balanced by extra methane energy and moreover in the case of dairy sewage sludge at a 40 minute long treatment at 1 and 2 w/g specific power level and in the case of municipal sewage sludge also 40 minute long duration of irradiation of 1 w/g specific power level was beneficial compared to control sample and conventional convective heat-treated sample. therefore, at the different born sludge investigated the lower specific microwave power level used were more advantageous regarding the energy efficiency of sludge pre-treatments by microwave irradiation. conclusion the application of microwave irradiation has advantages in sludge treatment processes. the microwave pretreatments can enhance more efficiently the aerobical biodegradability and biogas yield than the convective heat pre-treatments. the efficiency of treatments is dependent on the applied specific microwave power level and the time of irradiation. our results showed that despite of the quantity of produced biogas the lower specific microwave power level usage could be recommended from energetically aspect. acknowledgements this work was supported by the hungarian national office of research and technology (nkth) and the agency for research fund management and research exploitation (kpi) under contract no. ret-07/2005, and gvop 3.2.1.2004-04. 0252/3.0 project. references 1. bougrier c., delgenes j. p., carrere h.: chemical engineering journal 139 (2008) 236-244 2. banik s., bandyopadhay s., ganguly s.: bioresource technology 87 (2003) 155-159 3. gavala h. n., yenal u., skiadas i. v. westerman p., ahring b. k.: water research 37 (2003) 5461-4572 4. watenabe h., kitamure t., ochi s., ortega s., ozaki m.: water science technology 36 (1997) 239-246 5. eskicioglu c., kennedy k. j., droste r. l.: water research 40 (2006) 3725-3736 6. wang q., kuninobu m., kakimoto k., ogawa h., kato y.: bioresource technology 68 (1999) 309-313 7. stasta, p., boran, j., bebar, l., stehlik, p., oral, j.: applied thermal engineering 4 (2005) 241-250 8. bougrier c., delgenes j. p., carrere h.: process safety and environmental protection 84(b4) (2006) 280-284 9. wojciechowska e.: water research 39 (2005) 4749-4754 10. neyens e., baeyens j.: journal of hazardous materials b98 (2003) 51-67 11. gabriel, c., gabriel, s., grant, e., halstead, b., mingos, d.: chemical society reviews 27 (1998) 213-223 12. jones, d. a., lelyveld, t. p., mavrofidis, s. d., kingman, s. w., miles, n. j.: resources, conservation and recycling (2002) 75-90 16 13. eskicioglu c., terzian n., kennedy k. j., droste r. l., hamoda m.: water research 41 (2007) 2457-2466 14. climent m., ferrer i., baeza m., artola a., vazquez f., font.: chemical engineering journal 133 (2007) 335-342 15. veshetti, e., maresca, d., santarsiero, a., ottaviani, m.: microchemical journal 59 (1998) 246-257 16. beszédes s., kertész sz., lászló zs., géczi g., hodúr c., szabó g.: proceedings of 5th international congress on food technology (2007) vol. 3. 441-446 microsoft word a_23_solecki_r.doc hungarian journal of industrial chemistry veszprém vol. 39(1) pp. 31-34 (2011) methods of surfaces quality comparison in mechanical engineering applications l. solecki széchenyi istvan university, department of materialsand vehicle manufacturing engineering 9026 győr, egyetem tér 1. hungary e-mail: solecki@sze.hu the macroand micro-geometric properties featuring the boundary surfaces of machine components are important for quality reasons. the comparison of surfaces is needed if the machined surface is to be matched to preset requirements or the same surface can be manufactured with different manufacturing processes or various measurement and surface testing methods are available, or the time variation of the surface is to be assessed. after the comparison, surface deviations must be numerically evaluated in relation to size, shape, position, and surface irregularity. nowadays, surface irregularity tends to represent not only the unevenness of the surface but also the comparison of the real surface to a favourable microgeometric structure. information on the actual surface is obtained through perception (optical or mechanical), and the nominal surface can be a mathematical model, a sample, or a previous condition of the surface in the form of any previous perception, or a previously made print of the surface (replica). during comparison, similarities and differences must be evaluated in terms of the key properties of the surface related to the operation of the given component. comparison based on visual inspection is a suitable and acceptable method for a quick inspection, for identification of the parts of the component, and for detection of significant deviations. a technically more advanced method is image processing. three dimensional properties of the surfaces can be evaluated with 3d geometric calculation methods and methods developed for surface roughness. the presentation introduces a method for comparing cylinder surfaces of an internal combustion engine and presents an example of the method currently used in automotive engineering applications. keywords: surface comparison, cylinder liner, replica introduction particular points are measured with 1-2 or 3 coordinates in the length measurement technique in mechanical engineering (along a straight line, in plane or space). based on the measurements, dimensional, shape and position accuracies, and the surface irregularities of the parts are concluded. if the distance between two bores on the connecting rod given in fig. 1 is to be determined then, in theory, it is sufficient to measure the outer (o) and inner (i) dimensions of the bores and to calculate the centre distance (d) based on this with the following formula: ( ) 2 oid + = , (1) where: d – centre distance o – outer dimension of the bores i – inner dimension of the bores this formula is valid for two parallel cylinders. in fact, we try to approach parallelism of the cylinders and the axes of the two bores as far as possible in relation to the shapes of the bores, but this is possible only with the accuracy that is allowed by our production processes. figure 1: connecting rod of an internal combustion engine d i o figure 2: theoretical determination of the centre distance on the connecting rod the profile of a real bore surface measured in one section and its approximate circle are presented on fig. 3, its profiles measured in several sections on fig. 4. 32 -30 -20 -10 0 10 20 30 -30 -20 -10 0 10 20 30 figure 3: profile of bore in 1 section and its approximate circle (shape distortion, 100x zoom) figure 4: measured profiles of bore in 5 sections the centre distance between real bores of irregular geometry can be considered a two-dimensional problem in a simple case. the bore profiles in the mid-pane of the connecting rod, and their approximate circles and their distances are determined. if the issue is considered a spatial problem then the profile of each bore is measured in several sections, and then the cylinders approaching the profiles measured for the individual bores are determined. the approximate cylinders are likely not to have parallel axes, and as a result, we could not use their distances in a mathematical sense either. in techniques, the minimum and maximum values of the centre distances are determined for one piece in such cases, and the centre distance is interpreted to be located between these two values. to be able to use the above formula (1), first we have to determine either the approximate circle of the measured profiles of the circles, or the approximate cylinders of the profiles. this means fitting of a circle to the measured profile in plane, and a cylinder to the measured profile in space. this simple example proves that whether a size, or a shape or a position is determined in length measurement technique, surfaces must be compared in space and profiles in plane, and they must be properly fitted to compare the surfaces. perception of surfaces spatial surfaces are perceived by touch or in an optical way. perception by touch is the determination of the spatial position of a finite or a preliminarily defined point or a point in a system (touching along a line or a circle). optical perception is possible from point to point, similarly to mechanical touching, but several points may be taken within one shot. optical perception does not use force (suitable for elastic parts and it is easy to fasten the piece), there is no wear, and generally more points can be taken in a shorter time than in the case of perception by touch. visibility of the surface is required for optical perception. inner surfaces can be also perceived if x-rays are used (ct technique). coordinate measuring machines are used basically for the measuring of regular geometries in the orthogonal coordinate system, circularity testing units are used for the measuring of rotationalsymmetric parts in the cylindrical coordinate system, optical surface digitalisation systems may be used also for the perception of surfaces of regular but free geometry (orthogonal coordinate system), shape testing units make several sections (plane orthogonal coordinate system), surface-roughness testers make plane sections, but the spatial pattern of the measured surface can be given by the parallel sections. [1] principle of surfaces comparison to determine a geometric dimension, distance between nominal surfaces approaching the real surfaces must be determined in accordance with the example given in the introduction. to determine the shape distortion of the surface, the nominal surface most approaching the surface must be determined again, and the shape distortion will be the greatest deviation of the actual surface from the most approaching nominal value. in the example, the shape distortion of the connecting rod bore is the distance of the point perceived at the greatest distance from the cylindrical shell most approaching the bore. to determine the position fault of a surface, determination of the nominal surface most approaching the real surface is the first step again, but then the position of the real surface is identified with the position of the approximate nominal surface. the parallelism fault of the connecting rod bores is the distance differential of the axes of the cylinders most approaching the bores within the volume of the connecting rod. surface irregularity is the deviation between the real surface and the most approaching nominal surface (plane or cylinder), but the difference from shape distortion is that surface irregularity is examined not on the whole surface but on its basic length involved in irregularity. to determine the surface irregularity of the connecting rod, a line and a plane are fitted not onto the whole surface but onto its small so 33 called basic length section, and the distance measured between the measured points is the irregularity. perception is followed by the determination of the nominal surface most approaching the perceived points. the most approaching profile or surface may be situated basically in two ways: delimiting the measured points from a direction (contact plane of spatial points, greatest circle that can be drawn in the bore, or the smallest circle that can be drawn around points of a stud), or passing between the points so that the resulting division is the least (principle of least squares). [din en iso 14660-2 [din en iso 14660-2, din iso 1101, din iso 8015] in case of simple geometries (line, circle, plane, cylinder, sphere) the surface most approaching the measured points can be calculated in a closed form, and in case of complex surfaces (involute, thread profile, fee surface) approximate iteration methods can be used [2]. wear analysis of cylinder surfaces of internal combustion engines on the cylinder surface, the wear is less measurable for the change of the surface dimension or shape than for the change of the micro-geometry (irregularity) of the surface. the starting cylinder surface is of a special pattern to make the surface the smoothest, and thereby to provide a surface less resistant to motion, requiring a thin lubricant film, subject to less wear, having good bearing properties, but allowing lubricant adhesion. the shape of the cylinder surfaces (cylinder) is provided by honing after drilling. the honing pattern is typical for the whole surface, and the bidirectional linear traces including a specific angle to the movement direction of the piston are evenly spaced. since honing is made in several steps using tools with various granulation sizes, therefore deeper and shallower traces alternate in the pattern. in addition to traditional honing, surface treatment procedures, such as surface laser treatment, providing sufficient lubricant film also over minor surface irregularities and – as in the case of laser treatment – making the surface material layer more resistant to wear are also more and more widely used today [3, 4]. silicon prints were taken of the starting cylinder surface [5, 6]. there are special optical measuring instruments (white light interferometer) able to image the cylinder surface without cutting it. though it is indirect and therefore a disadvantageous method from a point of view of measurement technique, surface evaluation made on the basis of the print has the advantage of preservation of the surface as the wear itself will subsequently determine the places relevant for the evaluation. the engine assembled after the print had been taken was operated for 350 hours under various loads on a testbench. after disassembly of the engine, the cylinder block was cut so as to be able to take direct microgeometric and microscopic measurements on the surface, but prints were taken also of the worn cylinder surface so as to be able to evaluate the accuracy of transfer from the surface pattern to the print. figure 5: optical images of the same point: starting condition of the cylinder surface, worn condition on the silicon print, and the worn condition directly on the cylinder surface the left image on fig. 5 shows the silicon print taken in the starting condition of the cylinder surface, the middle image shows the silicon print of the worn condition, the right one shows the cylinder surface, and they are vertically mirrored to show the patterns in the same position as on the prints. the pistons move vertically, the images show 0.5 mm x 0.8 mm surfaces. the images show the honing pattern, the dark spot on the top of the images of the worn surfaces is the spot above the upper dead point of the upper piston ring. in this area, nothing contacts the surface and coke adheres to it in the explosion chamber. on the starting surface, only the deeper and shallower patterns of honing are visible, wear is represented by two phenomena: vertical scratches appear and the depth of the original pattern decreases. this will disappear in the case of fine patterns and surface parts with fine patterns become bright. optical examination is necessary since the whole surface can be examined with 200 times magnification, on 1.2 mm x 0.9 mm images. surface parts to be evaluated for wear can be chosen and their positions can be determined with optical examination. the optical examination is made with coordinate measuring apparatus type mahr pmc800. the examination was based on the worn print, and spots preliminarily chosen on the worn print were searched on the print of the original surface and the worn cylinder surface with the optical examination. the optical examination does not give wear figures. scanning of the chosen surface parts with surfaceroughness tester type talysurf cli2000 is the next step of the examination. the prints were digitalised with confocal optical scanning, and the worn surface with needle scanning. as a result, the surface height was obtained in 0.5 µm x 0.5 µm grid points, in 10 nm resolution. figure 6: illustration of bivariate point distribution after surface scanning 34 the image of bivariate point distribution obtained via spatial scanning of a 0.3 mm x 0.3 mm part of areas shown on the previous images is illustrated on fig. 6. point clusters obtained with surface digitalisation were fitted using the surface digitalisation evaluation system of gom-atos, gom-inspect, in two steps, first in a three point rough fitting procedure then by fine fitting of all points, with the best fit method. fitting the bottom points of the deep honing grooves would have been more favourable from one aspect; since they are not worn, the wear points would have been directly obtained by fitting the point clusters here. the benefit of fitting all points is that if fitting is made to chosen points then the choice of the fitting points must be correct, and the measuring fault of the fitting points may distort the result. results and conclusions fig. 7 shows the silicon print of the original surface and comparison of the silicon print of the worn surface. image colours on the basis of the height difference: green: approximately identical height, blue: the print of the worn surface is deeper, red: the print of the worn surface is higher than the print of the original surface. figure 7: comparison of the prints of the original surface and the worn surface choosing 10 yellow points, their average height is 1.2 μm, this is the height difference of the cylinder surface against the bottom of the honing grooves after wear. fig. 8 shows the comparison of the print of the worn surface and the direct needle scanning of the worn surface. since in this examination only small surface parts can be compared it is very important to be able to find the same maximum 1 mm x 1 mm surface parts in surface spatial perception. another precondition is that the surfaces must definitely fit to each other, which is possible on the basis of the surface pattern, however the approximate position determination is still subjective and only fining is made with the best fit method. figure 8: comparison of the print of the worn surface and the direct needle scanning of the worn surface acknowledgements this research has been made in the frame of project támop 4.2.1/b-09/1/konv-2010-0003. references 1. h. bubaker-isheil, j. serri, j-f. fontaine: 3d displacement field measurement with correlation based on the micro geometrical surface texture, optics and laser in engineering 49, (2011), 793–803 2. y. li, p. gu: free-form surface inspection techniques state of the art review, computer-aided design 36, (2004), 1395–1417 3. z. dimkovski, c. anderberg, r. ohlsson, b-g. rosen: characterisation of worn cylinder liner surfaces by segmentation of honing and wear scratches, wear 271, (2011), 548–552 4. j. michalski, p. wos: the effect of cylinder liner surfaces topography on abrasive wear of pistoncylinder assembly in combustion engine, wear, 271, (2011) 582–589 5. l. nilsson, r. ohlsson: accuracy of replica materials when measuring engineering surfaces, international journal of machine tools & manufacture 41, (2001), 2139–2145 6. j. a. newman, s. a. willard, s. w. smith, r. s. piascik: replica-based crack inspection, engineering fracture mechanics 76, (2009), 898–910 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word contents.doc hungarian journal of industry and chemistry veszprém vol. 40(1) pp. 5–8 (2012) separation methods in the algae technology z. hodai1 , g. horváth, l. hanák, r. bocsi 1university of pannonia, department of chemical engineering science, 10 egyetem str., 8200 veszprém, hungary e-mail: hodaiz@almos.uni-pannon.hu carbon dioxide is the air pollutant emitted in the greatest volume nowadays. capturing and deposition of carbon dioxide require great financial effort. spontaneous processes exist in nature that can be the basis of re-introducing co2 into the biological system. a number of valuable products can be obtained including motor propellants. nowadays petrol companies all over the world invest increasingly more funds into algae technology research, and there are researches going on in the energy, cosmetics, pharmaceutical, and food industry for marketable microalgae components. the viability of the technology is determined by its energy-needs which are mainly affected by the separation of the biomass from the reproduction medium. in this paper, we look into the circumstances as well as the effects of flocculationdensification and ultrafiltration on the algae suspension. keywords: algae, lipides, separation, ultrafiltration, flocculation introduction microalgae used for energy production take up compounds they need to build up their organizations from aqueous solutions. on one hand they need inorganic salts and simple organic compounds from the nutrient solution, on the other hand they need co2 (exhaust gas) that is introduced to the reaction vessel [1]. light available for the culture (a mass of photosynthesizing organisms) is basically a limiting factor, a reason for which special photobioreactors had to be used for guaranteeing the optimal reproduction conditions [2–5]. some of the requirements for these reactors are that they have to let the specific spectrum of sunlight needed for photosynthesis pass, and they have to be weather-resistant. flat-type closed photobioreactor panels are operated in semi-batch mode at the department of chemical engineering of the university of pannonia. the reactors were specifically planned using special construction units in order to maximize the productivity of the biomass in the local microclimate (figure 1). figure 1: algae cellfactory: large-scale laboratory photobioreactor installed outside with natural lighting removal of the algae suspension from the propagation system harvest is the line in time separating the biologically active and inactive phases. in order to make a proper choice, the behavior of the specific algae species and the added nutrient solution and environmental parameters have to be known. propagation phases are well-resolved life-cycles of the alga population in the reproduction curve. figure 2: reproduction phases of microalgae; reproduction curve in certain cases, a fourth cycle can be observed after the plateau phase showing a decreasing tendency. in this cycle, cell death occurs because of viruses or bacteria or because some other vital parameter is affected. according to our experience, such a population becomes inviable; the change can only be reversed at the cost of large amounts of energy. the suspension has to be processed as soon as possible and restarted with a fresh inoculation culture. 6 harvest can be done by microfiltration, centrifugation, flocculation [6], sonochemical processes, or with other techniques currently under development [7]. membrane separation methods were given special attention along with chemical flocculation, clarification, and autoflocculation. experimental flocculation microfiltration was carried out after the settling experiments with g4 glass filters under vacuum (created by a water aspirator). the needed current quantity of the flocculant and the additives can be determined by measuring the parameters of the algae suspension (ph, particle charge, concentration/ floating mass percentage). because of this, only the interval of the added quantities can be given at the description of the experiments. purification addition of naoh to the mixture is advantageous in the later phases of processing (cell wall destruction). naoh also decreases the specific charge density [8–10]. hence, the first experiments consisted of increasing the ph to 10.5. during the experiments, the freshly harvested and still reproducing algae mixtures exhibited excellent flocculation and appropriate (average) speed of sedimentation (6×10-3 m/s). for algae mixtures in the plateau phase (that do not reproduce any more) this method proved ineffective, making a further additive necessary to increase the sedimentation speed. when setting the ph with naoh, an additive was given to the mixtures in order to help the coagulation and settlement of floccules. iron(iii)sulfate (3–6 cm3, depending on the concentration and ph of the suspension; c(fe2(so4)3) = 150 g/dm3 per 1 g of algae mixture) evidently helps the processes of flocculation and sedimentation (1.4×10-2 m/s). after sedimentation, a solid alga layer remains at the bottom of the mixture. in spite of the excellent sedimentation, further experimentation was needed since the added iron makes it difficult to perform subsequent analysis and processing. iron(iii)sulfate was replaced with a cationic flocculant that we also used for the analytical measurements, namely poly(diallyldimethylammonium chloride) (polydadmac; 60–100 cm3 depending on the pcd values; c (polydadmac) = 2.4 g/dm3 per 1 dm3 of algae mixture). this sedimentation method proved effective in most of the experiments, but the speed of sedimentation is significantly lower (7.6×10-3 m/s), which needs improvement. the sedimentation measured in the former experiment can be accelerated by adding less flocculant to the alkalified solution (approximately 35% less in comparison to the previous experiments; 39–65 cm3 polydadmac / 1 dm3 algae mixture) and significantly less iron(iii)sulfate (approx. 60%; 1.2–2.4 cm3 fe2(so4)3 / 1 dm3 algae mixture). the results show excellent flocculation and appropriate speed of sedimentation (2.2×10-2 m/s). after setting the ph to 10.5, sedimentation of the algae mixtures can appropriately be carried out in the concentration intervals given in table 1. table 1: optimal concentration intervals relative to the cationic flocculant and fe3+ ions lower concentration interval (g/dm3) additives upper concentration interval (g/dm3) 9×10-2 p-dadmac 1.5×10-1 5.2×10-1 fe3+ 1 a comparison of the experiments is given in the diagram of figure 3. figure 3: results of the chemical flocculation experiments ultrafiltration there are problems associated with the abovementioned densification processes, namely that (1) they need the addition of chemicals and (2) that problems can arise associated with upscaling (e.g. the continuous dispersion and mixing of the flocculant in the suspension, etc.). for these reasons, membrane separation and ultrafiltering were also added to the examined processes aiming to improve usability. the ultrafiltration membrane divides the original mass current (algae suspension) into two parts. one of them passes the membrane (this is the permeate: filtered nutrient medium), while the other is the concentrate (in our case, the densified alga suspension). for the densification and purification experiments, a plc controlled device at the department of chemical engineering of the university of pannonia was used that is equipped with a zw-10 module. according to the direction of the permeate flow, the device is conducting an outside-in process. the measurements were carried out with a zenon zw-10 immersion module. according to the specification, the 7 membrane is capable of retaining particles under 1 µm, hence capable of the concentration of our micro algae cells [11–13]. the module works as a sub-unit of a plc controlled device. during the operation of the device, the microalgae suspension is introduced in the technical vessel. this is a rectangular cuboid with a volume of 30 dm3. the vessel is equipped with a level sensor, a ph probe and a thermometer. the permeate (filtered nutrient medium) is introduced into a permeate vessel of 10 dm3, from which the permeate requirement of the backwash is provided. periodic removal of the permeate can be carried out at the sampling outlet, whereas continuous removal can be carried out through the overflow pipe. densification with membranes the suspension in the densification vessel was pneumatically mixed by a vaporizer propelled by an air compressor. after this, sample refill was carried out with a 1 dm3 graduated cylinder in order to minimize fluctuation of the liquid level. to gain the maximal data possible from the processing of the available samples, the measurement was divided into a number of sections. the algae suspension for the filtration experiments was sampled in 40 dm3 portions from the photobioreactor. after densification of the 40 dm3 volume to 20 dm3, the suspension was washed with distilled water. the washing was continued until the complete removal of remaining salts and other organic material and metabolites. the extent of cleansing of the permeate was checked by measuring the dry matter content and electrical conduction. the total dry matter content of the suspension was measured (along with remaining salts). this experiment was used for both the analysis of the concentrate and the permeate. the following 40 dm3 of algae suspension was densified according to the procedure given above and coded uf2. these experiments were conducted 7 times (uf1-uf7). for the complex examination of the filtration, the washed concentrate from the previous densification (concentrated algae suspension) was added to the current concentrate. washing makes it possible to exclusively analyze and process the dry matter content of the suspension of microalgae cells in distilled water. further advantageous properties were shown in comparison to the retentate, as e. g. ease of storage (later onset of decay) and faster evaporation. the densification experiments were conducted until reaching the maximum algae production capacity. the cleansing (washing with distilled water) was carried out until the lowest possible conductivity values. the trends of change in dry matter content and the related conductivity of the permeate were identical in most of the cases. figure 4 shows the relationships between the total dry matter content relative to the algae content of the initial suspension and the permeate conductivity. the data were gathered at the initiation of filtering both from the initial suspension and the permeate outlet. the figure shows the definite tendency and connection between the quantities measured at both sides of the membrane. according to the measurements so far, there is an unambiguous connection between algae contents of the total dry content of the algae suspension and the conductivity of the permeate. the higher the algae concentration is, the higher the initial conductivity is. 0 10 20 30 40 50 60 70 0 1 2 3 4 5 6 7 8 uf period c on du ct iv ity o f t he p er m ea te [m s/ cm ] 0 10 20 30 40 50 60 70 80 90 a ec r a c [% ] conductivity of the permeate aecrac figure 4: conductivity of the permeate vs. all extract content of the initial suspension referred alga cell content (aecrac) similar values were obtained for the permeate flux by all measurements. this means that the device is capable of filtering suspensions of different compositions and concentrations in the examined interval. 0 10 20 30 40 50 60 70 80 90 100 1 2 3 4 5 6 7 uf period d ry m at te r c on te nt o f t he h ar ve st ed al ga e su sp en si on s re la tiv e to a lg ae ce lls [% ] other algae cells figure 5: the dry matter content of the harvested algae suspensions relative to algae cells an algae suspension from a photobioreactor unit operated in natural circumstances was processed in the second uf period of figure 5. further correspondences can be brought to light by examining samples from different reactor units at different reproduction stages. additional analysis would allow far-reaching conclusions in regard of cultivation and implementing these conclusions into the technology further increasing the biomass capacity. 8 the initial algae suspension (40 dm3) was densified from 13 g/l (algae cells, metabolites and salts) to 6.1 g/l (20 dm3; only algae cells). the final algae concentrate has a concentration of 30.4 g/l of microalgae in a volume of 20 dm3. results we have defined the components of a flocculant mixture for optimal use (naoh + polydadmac + fe2(so4)3, minimized the chemicals needed for the mixture (naoh until ph = 10.5, 39–76 cm3 polydadmac, 1.2–2.4 cm3 fe2(so4)3 / 1 dm3 algae mixture). with the flocculant, the concentrate can be gained quicker and by using less energy, but the remainders of the chemicals pose problems in further processing. summary with the evaluation of the results of our ultrafiltration experiments it can be concluded that, according to the values of the permeate flux, our device is capable of filtering suspensions of different compositions and concentrations in the examined interval. after ultrafiltration, it is possible to remove the accompanying compounds, which makes the concentrate more stable and manageable. this is advantageous from a research and development point of view because later processing and analysis are not affected or are only affected to a definable extent. if it is an aim to recycle the nutrient medium (re-use of the remaining salts), the highest priority must be given to the membrane separation methods. considering the membrane separation results and the permeate analysis, the presence of a number of metabolites can be assumed in different concentrations. these can all be separated from the valuable microalgae cells. acknowledgements the authors express their gratitude to chemical engineering institute cooperative research centre of the university of pannonia and the támop-4.2.1/b09/1/konv-2010-0003 application for financial support of this research study. references 1. m. olaizola, s. m. masutani, t. nakamura: recovery and sequestration of co2 from stationary combustion systems by photosynthesis of microalgae, final report, u.s. department of energy, office of fossil energy national energy technology laboratory (2005) pp. 21–197 2. g. c. dismukes: algal photosynthesis, princeton university press, princeton (2008) p. 12. 3. j. benemann, j. sheehan, p. roessler, t. dunahay: a look back at the u.s. department of energy’s aquatic species program: biodiesel from algae, nrel report nrel/tp-580-24190 (1998) p. 3. 4. j. burlew: algae culture: from laboratory to pilot plant, pilot plant studies in the production of chlorella, carnegie institute, washington dc (1953) pp. 235–272 5. i. h. jung, s. h. choe: growth inhibition of freshwater algae by ester compounds released from rotted plants, journal of industrial and engineering chemistry (2002) pp. 297–304 6. a. sukenik, g. a. shelef, m. green: microalgae harvesting and processing: a literature review, report, solar energy research institute, golden colorado, seri/str-231-2396 (1984) pp. 6–57 7. b. jeurissen, e. poelman, n. de pauw: potential of electrolytic flocculation for recovery of microalgae, resources conservation and recycling (1997) p. 19. 8. e. becares, h. o. guzman, i de godos, p. a. garcía-encina, r. muñoz, r. soto, v. a. vargas: coagulation/flocculation-based removal of algal-bacterial biomass from piggery wastewater treatment, bioresource thechnology (2011) pp. 923–927 9. a. hoadley, m. k. danquah, n. uduman, y. qi: marine microalgae flocculation and focus beam reflectance measurement, chemical engineering journal 162 (2010) pp. 935–940 10. p. le-clech, t. a. g. fane, v. chen: fouling in membrane bioreactors used in wastewater treatment, journal of membrane science (2006) volume 284, issues 1–2, 1, pp. 17–53 11. a. g. fane, h. c. chua, j. zhang, j. zhou: factors affecting the membrane performance in submerged membrane bioreactors, journal of membrane science (2006) volume 284, issues 1–2, 1, pp. 54–66 12. b. tae-hyun, t. tae-moon: interpretation of fouling characteristics of ultrafiltration membranes during the filtration of membrane bioreactor mixed liquor, journal of membrane science (2005) volume 264, issues 1–2, 1, pp. 151–160 microsoft word b_05_farkas_r.doc hungarian journal of industrial chemistry veszprém vol. 39(2) pp. 177-181 (2011) the attendance of rational energy utilization and of the green energy a. farkas , p. faragó szent istván university, the management and business administration phd school páter károly utca 1., gödöllő, hungary e-mail: fegnisz@gmail.com in the xxi century the most important global problem is the energy crisis. first of all the problems in hungary based on the import dependence. against the effect of the crises the main solution process could be the rationalization of the energy utilization and the increase of the alternative energy types. the crisis managements arrangements are analyzed from different aspects. most of the publications deal with the economic importance of the renewable energy. at the focus of this subject stands the demand of the green energies subvention and also the announced energy types income and their effect on the markets but these publication are dealing with the legaland political background as well. from technological aspect they show the functioning of the indispensable equipments. from environmental aspect they tone the connection between the environmental protection and the propagation of the green energies. the previously mentioned analyzing aspects are indispensable although beside these sights we should take care of the social system and opinions as well. most of the studies mention the importances change of approach, but they do not review the future tendencies. in our study we demonstrate the connection between the appropriate lifestyle, the spread of the biomass and the auspicious hungarian energy balance. we make a sketch of one of the reasons about our countries over-consumption, we delineate the appearance forms of the biomass and also we measure the hungarian producer potential. keywords: energy balance, energy consumption, time balance-examination, renewable energy, biomass introduction at the beginning of the xxi century the reserves of the world are running out, thus now days our biggest challenge is the solution of the energy crisis. the new energetic conception could be examined from different aspects. several studies inform the readers about the new energetic trends. on the field of the crisis solutions possibility the thrift analysis is momentous, which is mostly examining the financial side of the alternative solutions; from the resource to the market effect. after the financial aspect it is important to mention the technological publications, which handle with the development of the modern equipments. on the other hand there are also several studies in the subject of the environment, these disquisitions are dealing with connection between the energy consumption and the protection of the environment. the analysis’s biggest failures are the social studies. most of the publications only concentrate on the goal and the access path is forgotten. there is no hope on the solution of the energy crisis without the social cooperation. according to several studies, the increase of the alternative energy resources should be combined with the approach change, but there is no opinion in these studies about what sort of instruments are crucial to this change. how is the approach look like now days? what could have been the ideal attitude? how is it possible to reach this ideal state? the aim of this study is to complement the failures and to handle with the social, sociological psychological aspects during the crisis management. through the publication we demonstrate two improvable possibilities of the country energy balance. first of all on the field of the social analysis we measure the energy consumption, then we delineate the current changes during the usage of a few alternative energy resources. energy balance of hungary our country – after the temporary decrease in 2010 – uses more and more energy again. in 2011 the energy consumption is going to develop according to the central statistical office, the rate of this increase depends on the weather. [1] the energy balance shows the stock conformation of hungary in a specific year. according to the dates of the energy balance in 2009 it is possible to announce that almost 70% of the hungarian energy consumption comes from the import. the previously mentioned measurement exfoliated even worse in the pass few years before the fiscal year. 178 summa summarum it can be diagnose that hungary mainly needs to fetch in energy. [2] table 1: energy balance of hungary (2009) announce volume (pj) production 458.5 import 733.1 total resources 1191.6 used energy 1055.8 export 106.3 stock changes 29.5 total stock decrease 1191.6 research methodology in our opinion in the field of the energetics there are loads of reasons for the existence of the social research. in the case of several publications, it is announced that one of the most important benefit of the biomass is the population – observer ability, therefore it should be the migration the main topic. beside the former research it is also significant the “action theory of weber”, the “bourdieu – capital” decision from the sight of the individuals and also the time balance examining. within the confines of a questionnaire research we estimated what kind of attitude could be discovered in one group of the hungarian population, precisely the students of the corvinus university. during the research we even made a time balance monitoring. the questionnaire was filled by 296 people. the research is representative, namely it suits the educational institutions genericand qualification rates. we achieved the research at the university with printed questionnaire sheets (papi). the students filled the sheets alone, therefore we did not use interrogator. the enquiry started in the second half of december in 2010 and it finished at the end of the year. the results of the research during the research we were interested that how many hours the asked students spend with their own physiological needs. in average the youth sleep 7 hours/day, which means that they sleep through one third of their university year. most of the questioned ones sleep 6–9 hours a day. there is only just a few repliers, who relax extremely lot or less. the one of the most important questions at the time balance researches case is that how the population is spending their free time. in our case free time is defined as follows: when the responder is not in the university on a lesson. besides of sleeping, the nourishment and the bathing count as physiological needs. the students do not spend a lot of time on these needs. they spend only half an hour on the previously mentioned basic needs, but the main weight belongs to the bathing. the women spend more hours with the bathing, which causes the higher energy usage. figure 1: aggregated time of the following activities: watching television, usage computer and music listening table 2: descriptive statistics of watching television, usage computer and music listening indicator men women together median 6.00 5.50 6.00 mode 6.00 5.00 6.00 mean 6.74 6.09 6.37 minimum 1.50 0.00 0.00 maximum 25.00 17.00 25.00 first quartile 4.00 4.00 4.00 third quartile 8.00 7.75 8.00 above the physiological needs the youths choose such free time activities which use a lot of energies. in average the hungarian population spends extremely lot of time in front of the television. this statement is true to the students as well, although the computer usage belongs to their every day habits much more. the average youth spend more than 3 hours in front of the screen a day. besides they listen to the music almost 2 hours and they watch the tv a little bit more than for one hour. the mentioned three activities mean around six hours a day (though likely they are each others background activities as well, so the amount of the hours could decline), this means that during the day they use six hours of high volume electricity. the women spend 1.5 times more time on the housework than the men. none of these kind of work approached the women dates in the case of the men. the most important difference could be recognized in the case of the washing, when the men spend almost as much time with this activity as the girls. on the whole the youth spends around one hour every day with housework, as washing, cocking or cleaning etc. during the time balance-research we examined also that how many hours the responders spend with studying. we only count those hours of studying when they are not on university lessons, so when they are studying home or anywhere else if they are concerned with the university knowledge. the result showed us that the responders spend almost an hour every day independently from their gender. 179 for the students the travelling is an everyday activity. in the mentioned research we also asked about their travelling attitudes. most of the responders use public transport, considering with the fact that an average student out of its 13 hours of travelling 8 hours includes the use of public transport. in the view of the energy usage the most friendly transport type are the wayfaring and the cycling, which take just out three hours in the case of the responders. we found differences between the two genders in the choice of car or public transport. the men use the public transport far more often than car. in the studied free time activities the sport activities are also mentionable. the repliers practice sports in average three hours a day even so we can separate them in to two categories. many of them do remarkable sport activities (one hour a day), the others hardly even train for an hour a week. very few of the repliers do the average sport rate, the three hours a week. in the two genders case we came to the result that the men do sport 1.5 times more than the women. the conclusions of the research the questionnaire measuring showed us, that the students' lifestyle in the view of the energy is quite wasteful. the luxury services (listening to music, watching the television) make most of their energy usage instead of the basic needs, as cooking or showering. it is also interesting that the active relaxing types as for example sports are not common in the case of the repliers, which could be seen at the chosen travelling types, because most of them do not walk or cycle. this attitude increase their energy needs. the occurrent effect of the optimistic time balance on hungary in the case of the populations time balance advance, hungary’s energy usage would decline with 10% according to our measures. if we take away this 100 pj energy-saving from the utilization and from the import, the import-usage rate would be 2/3 of itself. it could be also appreciate, that the now days 6–7% of renewing energies utilization would increase it share to 8%. alternative energy resources in the alternative energy resource the natural energy (solar, water, geothermic energy and wind power) resources have a significant importance. the energy plants and the biomass are also appropriate instead of the traditional, fossil energy sources. natural energy sources one of the most important possibilities is in the utilization of the solar energy. the sun is available almost without restraint, though we can just use a small amount of it’s capitalize. the importance of the solar energy is improved by the fact that the energy of the sun can assure the worlds energy needs. hungary is in a favorable situation because the sunny hours are between 1500–2000 hour a year. [3] the water energies most significant signature is that it is in a service seasonally. although the wind cannot be mentioned as a premier energy source according to the 2009 dates, though the water energies emission is less than the others. [4] the emission and hungary’s favorable water map give us a significant opportunity on the field of the water energy utilization. with the maximal calculation we could have win more than 20 times as much energy (1 gw) out of it utilization. [4] the wind power in hungary is developing dynamically, which made this energy resource the market leader out of the natural resources. [5] the wind power after the water energy is the second less pollutant energy resource. although the utilization of it has a serious disadvantage, that in our country the average wind strength is quite low (2–3 m/s). [3] in hungary the most popular natural energy is the geothermic one. [6] for our country the heat of the earth could be a springboard, because the lands energy stock is commanding. the exhibit of this statement is our thermal water stock. energy plants there are two big groups of the energy plants, the ligneous and herbaceous plants. the ligneous plants advantage is that their income is quite big (~10mj/kg) and also during their burn the pollutant materials volume is irrelevant. in hungary the wattle and the sallow are use in energetic purpose. the most important disadvantage of the tree utilization is the high innovation costs. [7] from the herbaceous energy plants many type of them are known in hungary. in our country first of all they are dealing with grape, hemp (annuals), energy reed and grass on the fields. in the comparison with the ligneous plants they own that feature, that they are harvested in every year. though their disadvantage is that these plants own a low level of energy density. [8] biomass biomass means the living and in the short past died organism in the land or in water. [9] the biomass gives the biggest opportunity for the exchange of the fossil energy sources. the proof of this statement is the fact that the green energies share is over 90% out of the renewing energies according to the 2008 dates. [6] hungary’s all green energy stock is 1200 pj, which 180 means by table 1 that is the exactly amount of the yearly energy usage. [10] this means that if most of hungary change to biomass energy than the whole import and an important amount of hungarian fossil energy would have been replaced. in a financial sight the change is also favorable, because the biomasses price is 100–2800 huf/gj and the price of the heavy oil is 7500 huf/gj. [11] according to the formation we separate premier, secondary and third biomasses. in the view of the aggregate we can define consistent, liquid and gas aggregates. consistent aggregated biomass in practice the most important consistent biomasses are the cornstalk, the grape and grain straw, the sunflower stalk, the hay, the fruit tree loppings, the grapevine and the various types of wood. in our country out of these resources the grapevine and the tree loppings are common. the vine is from the big grape fields, after the yearly cut. while the treeloppings are the new part of the plants after the cut in fruit or private gardens. according to this study it is useful to utilize these two resources in an energetic sector, because they do have a value on market until they do not become fuel. the capacity of the grapevine and the treeloppings is around 5 pj/year. [12] liquid aggregated biomass in the category of the liquid biomass we separate the bioetanol and the biodiesel. the bioetanol is such an alcohol, which is the result of the vegetal material fermentation. against this the biodiesel is made out of the oil included vegetal parts it is similar to the heavy oil. [13] the importance of the bioetanol is not arguable, but it is ambiguous, how big could the product potential be. the doubt caused by the change in the case of the e85 fuel, which only stays tax free until the end of 2012, possibly its price will increase from next year. now the e85 fuel is cheaper with 80–100 huf than the traditional types. according to this study the importance of the bioetanol based on the assumption that the use of this biomass would decrease hungary’s import dependence and also new jobs would appear. [14] in our country they use grape and sunflower for the biodiesel production. these two plants have a high oil level and it is possible to utilize it. [15] a study had compared the grape with other plants, which could use to the biodiesels production. the result of the research revealed that the highest income belongs to the sugar beet (120–140 gj/hectare). out of the analyzed plants the wheat and the corn have also high purchase. the maximum energy from the grape is 50 gj/ ha. [16] the government does not support the biodiesel as much as the ethanol, because the biodiesels selling is encumbering with 25% of vat. the government is not planning to change this situation because they would fall from a big amount of revenue tariff. [14] the gas biomass now days for the biogas production first of all they use waste (in 50–60%). to the produce the compounds fell apart to carbon dioxide, methane, hydrogen, nitrogen and to sulphur. a study was dealing with the countries maximal biogas capacity. it announced that hungary’s theoretical emission potential combined with efficiency is between 74.7–233 pj. beside the lowest technology level (biogas production where is possible) it could have been possible to generate 74.7 pj biogas instead of the same amount of fossil energy. [17] conclusion in the study it gets proved, that hungary’s energy balance was unfavorable in the past few years. beside the previously mentioned conclusion our study showed us that the society research could have an important roll in the energetic researches. the proof of this statement is the result of the questioner researches result. the conclusion is that the young people live a wasteful life. the daily average 6 hours of listening to music, using the computer or the television watching in our opinion is mostly part of the fancy category and not the basic needs. according to our measurement we think that the lifestyle advance would cause the energy utilization decrease. the non-rational energy utilization could be recognized in the consumption of the country which includes just 6–7% of renewing energy resources. in the study we introduced many type of alternative possibilities. the utilization of these alternatives would decline the fossil energy resources use. our countries favorable geological position gives us the possibility of the successful use of the geothermic and solar energy. beside the natural resources we introduced also the biomasses different typesin the case of the consistent biomass, the biodiesel, the bioethanol and of the biogas we still have unused capacity, which could advance our energy balance. through the increase of importance the green energy and other alternative resources and with the rational energy utilization, we could decline the countries energy dependence. 181 references 1. központi statisztikai hivatal: a gazdaság összes energiafelhasználása (2011), http://portal.ksh.hu/pls/ksh/docs/hun/xstadat/xstadat _evkozi/e_qe001.html 2. központi statisztikai hivatal: energiamérleg (1990-) (2010), http://portal.ksh.hu/pls/ksh/docs/hun/xstadat/xstadat _eves/i_qe001.html 3. k. nagy: az alternatív energiaforrások magyarországi lehetőségei, különös tekintettel a biomassza potenciálra (2010), budapesti corvinus egyetem, mikroökonómia tanszék, szakdolgozat 4. z. hágen, t. marselek: vízenergia potenciál magyarországon (2010), v. csépe, l. dinya, r. solymos: szociális zöldenergia program, 110–115 5. zs. dupcsák, z. kerek, t. marselek: zöldenergia stratégia magyarországon (2010), v. csépe, l. dinya, r. solymos: szociális zöldenergia program, 77–80 6. j. roncz, t. szép: adottságok és lehetőségek a megújuló energia felhasználására (2010), v. csépe, l. dinya, r. solymos: szociális zöldenergia program, 125–129. 7. cs. gyuricza: fás szárú energianövények, magyar mezőgazdaság 63(37), (2008), 16-18 8. s. magda, s. gergely: energiastratégia – lehetőségek, magyar mezőgazdaság 61(36), (2006), 12–13 9. s. lukács gergely: zöldenergia és vidékfejlesztés (2008), szaktudás kiadó ház, jászberény 10. r. magda: megújuló és fosszilis energiahordozók magyarországon, gazdálkodás 55(2), (2011), 153–166 11. g. büki: biomassza-hasznosítás az épületek energiaellátásában, energiagazdálkodás 51(1), (2010), 5–9 12. g. pintér, k. németh, t. kis-simon: a szőlővenyige és a fanyesedék biomassza-erőmüvi beszállításának elemzése, gazdálkodás 53(4), (2009), 358–363 13. k. kővágó: a hazai bioetanol piac a gazdaságosság és versenyképesség tükrében – nemzetközi kitekintéssel – (2010), budapesti corvinus egyetem, mikroökonómia tanszék, szakdolgozat 14. z. pályi: a bioüzemanyagok adózása magyarországon, gazdálkodás 55(2), (2011), 194–198 15. l. komarek: az agrárgazdaság és a megújuló bioenergia kapcsolata, comitatus: önkormányzati szemle 18(11-12), (2008), 122–129 16. l. tóthné heim, z. peterdi, sz. zvekán: biomasszából előállított folyékony üzemanyagok hazai termőföldigénye és gazdaságossága, gazdálkodás 51(5), (2007), 54–59 17. i. szunyog: elméleti biogáz potenciál – egy európai uniós kutatási projekt részeredménye (2008), http://zoldtech.hu/cikkek/20080314-elmeleti-biogazpotencial << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word content.doc 101 hungarian journal of industrial chemistry veszprém vol. 40 (2) pp. 101-105 (2012) study of the properties of a plain cathode grimm-type dc glow discharge source operated in a current-controlled pulse regime o. bánhidi university of miskolc, institute of chemistry, miskolc-egyetemváros, miskolc, h-3515 hungary e-mail: akmbo@uni-miskolc.hu glow discharge sources have been used for analytical purpose for several years. recently the pulsed operation mode has gained an increasing importance. operating the source in current-controlled mode instead of the traditional voltage-feed method may have the advantage of precise control of the source’s state and it provides a convenient way to study the relationship among the emitted line intensity and the key parameters of the plasma such as the pressure of the filling gas, the voltage-drop on the source as well as the current flowing through the device. in the following the brief description of the system, the relationship among the voltage drop on the source, the pressure of the filling gas (ar), the current of the dc pulses as well as the line intensities are presented and discussed. keywords: dc glow discharge, pulsed current-controlled mode, atom-spectrometric source. introduction glow discharge sources have a great importance in the atom spectrometry. main fields of their application are the analysis of bulk materials and examination of surface layers, i. e. the depth-profile analysis. besides that they play an important role in the massspectrometry an ion-sources. beside the devices based upon the direct current glow discharge, radio-frequency operated sources have also been developed, making possible the analysis and study of non-conducting materials [1]. in case of the dc sources a substantial part of the power applied to the device will be dissipated as heat in continuous operating mode, warming up both the equipment and the sample being the cathode. to avoid this warming-up, which may also be harmful to some parts of the source either, a suitable cooling system have to be applied. another way to avoid harmful effect is to operate the device in pulsed mode. depending on the pulse parameters, the average power applied to the device in the later case is only a few percentages of value necessary on continuous dc mode. several studies can be found in the literature dealing with sources operated in pulse regime [2, 3, 4]. in the above-mentioned studies the sources are powered exclusively in the so-called voltage-feed way. it means that the device is connected to the dc power supply directly, or in order to avoid the damage in case of short-circuited condition, through a so-called ballast resistor. as a consequence of that any change in the state of the source causes a change both on the voltage dropped on the source and that of the current flowing through the device. if because of nay reason the impedance of the source might change , so will change again the voltage drop and the current. this might cause the the source to leave either the area of abnormal mode of operation and will enter the area of normal mode or vice versa. on the other hand it is rather difficult, though not at all impossible, to provide precise highvoltage pulses to feed the system in this voltage-fed mode. so that the change of the voltage drop and the current could be avoidedat and a better control of the system could be achieved, we suggest applying a constant pulse current to the system. by using constant current pulses, the state of the system can also be controlled. to provide constant current pulses, a current generator is needed. it has a very high internal impedance, and because of that the change of the source impedance will not have any effect to the value of the current flowing through the source as long as the current generator is able to provide constant current pulses. in this way the voltage drop and the current will remain unchanged, therefore better control can be achieved. to study the current-controlled mode we have developed a high power current-generator power supply and controller, which is able to operate in pulsed regime. the pulsed regime operation does not mean that current flows through the source only in the duty-cycle period. in the course of the development it was targeted that the source should always operate in the so-called abnormal region, or at least it should be at the border of the abnormal mode. therefore there is a low-current period and a high-current one. the later is eventually the duty-cycle period. e.g. at a frequency value of 102 200 hz and 10% duty cycle, the length of the period is 5 ms, and the duration time of the high-current lasts 0.5 ms, while the low-current one is 4.5 ms long. the use of the pulsed regime may provide two advantages. the first one is that high power resulting in dissipating much heat and warming up the equipment is applied just for a very short time, so the average power is just a few percentages of it. this makes unnecessary to apply a cooling system, as much less heat is dissipated by the source. the other advantage is that the short-time high-current pulses the system provides make possible to study and examine thin layers. experimental main components of the system main parts of the system can be seen in figure 1. the light emitted by the discharge is detected and measured by a spedctrometer. the output signal of the detector is processed by a special computer programmed card, usb 4716 manufactured by the advantech co.. the electric dc voltage and current pulses necessary for the operation of the discharge is provided by the power supply and current generator unit. figure 1: main components of the system the source in the course of the experiemnts a grimm-type source (presented in figure 2) was used, it is based upon the design made by wagatsuma and co-workers [5]. the anode is made of brass, its internal diameter is 7 mm. the power supply and current generator this unit was designed and built in our laboratory. it is able to provide a dc voltage as high as 1000 v. it can be operated in the frequency range of 122 hz–5000 hz. the duty cycle can be chosen between 32 µs – 4.1 ms, resulting values ranging from 0.4% up to 50%, depending on the pulse period and frequency. in the experiments reported here the pulse frequency was figure 2: the source used in the experiments. 122 hz and the duty cycle was 2.3%. the value of the low current is 1.5 ma, while 5 preadjusted values (32, 72, 115, 135 and 160 ma) can be selected for the high current pulses. the device has its own microcontroller unit, which has a serial (rs 232c) link to the ibm compatible computer controlling the system. this build-up makes possible to choose all the important parameters (value of the frequency, duty cycle and that of the high current) using a special computer programme. the same programme is responsible to controll the measuring system and store the measured data. the spectrometer to convert the light of the source into an emission spectrum and to convert the light intensity of the selected spectral line to an electric signal an atomic absorption spectrometer (pye unicam sp9-700) was used. only the spectrometer (monochromator) and the detector (pmt) was used during the experiments. the electric signal processed by the external measuring system was taken from the loading resistor of the photomultiplier tube of the instrument. the narrowest slit width (0.2 nm) was choosen for the experimental work. so that spectras could also be recorded, the device was equipped with a wavelength driving circuitry (consisting of a stepper motor and of a control circuit). the signal measuring system the measuring system must be capable to measure signals both in the high-current and in the lowcurrent period. to fulfill this requirement a multifunction module capable to provide fast analogue to digital conversion has been chosen. it is the usb 4716 multifunction module manufactured by advantech co ltd. it has a 16-bit ad converter with a 16-channel 103 multiplexer and its minimum conversion time is 5 µs. it can operate both in an externally triggered mode and in a so-called software triggered mode. the signal taken from the loading resistor of the photo-multiplier tube (pmt) of the spectrometer is led into the first measuring channel of the device. the electric connection betwen the loading resistor of the pmt and the signal input of the spectrometer own measuring electronic system was eliminated so that these circuits could not have any influence on the measurements. so that not only the emitted signal of the source, but the current flowing through on that and the voltage drop could be measured, there is a resistor network in the system. r3 is a resistor of 15 ohm. it is for measuring of the lamp current. resistors r1 and r2 (20,000,000 and 120,000 ohms respectively) form a voltage drivider, making possible the measurement of the voltage drop on the source. the usb 4716 has digital inputs and outputs, therefore it is able to control the stepping motor of the wavelength drive. the unit is controlled by a programme running on an ibm compatible computer. other important details of the experiments in the course of the experiments high purity argon (99,996%) was used as filling gas. a pressure regulator and a vacuum pump made possible to adjust the required value for the pressure of the filling gas. in all the experiments expect for the demonstation of sputtering ability a brass (copper – zinc alloy) probe was applied as the cathode of the source. results as the device operates in pulsed mode, all the signals are eventually pulses. figure 3 shows the relative signals of emitted light, discharge current and that of the voltage-drop on the source as the function of time..the different signals are shifted in time so that they could be better observed. figure 3: signals of the emitted light, current and voltage-drop pulses as the function of time stability of the current generator from the view-point of the operation it is important to know how much the changes in the pressure of the filling gas affect the value of the high current, in other words how stable the current generator is. as it can be seen in figure 4, the value of the high current is eventually not affected in the pressure range of 300– 950 pa, but under 300 pa it is no longer constant, i.e. under the above-written range the current generatror no longer works. figure 4: the high-current pulses as the function of the filling gas pressure the relation among the voltage-drop, the current and that of the filling gas pressure as the device operates in the abnormal working range, it can be expected that the voltage-drop on the source will increase with increasing current. the relation measured is presented in figure 5, where the voltage-drop on the source can be seen as the function of the current at three argon pressure values. it can be stated that according to the expectations the voltagedrop is greater at higher current, but the increasement is higher at lower argon pressure. the relation of the voltage-drop to the filling gas pressure measured at 72 ma high current is shown in figure 6. it can be observed that there is only a moderate increasement in the voltage-drop with decreasing argon pressure in the range of 400–900 pa, while the voltage-drop increases sharply below that range. 104 figure 5: the voltage-drop as the function of the current at 3 different filling gas pressure. figure 6: the voltage-drop as the function of the filling gas pressure at 72 ma. the light intensity emitted by the cathode material from the viewpoint of the possible practical analytical application the emission by the elements building up the cathode sample has the greatest importance. this emission, i. e. the intensity of the figure 7: the emitted light intensity measured on the 324.8 nm cu i. line as the function of the current at 350 pa. 0.0000 0.0400 0.0800 0.1200 0.1600 0.2000 0.2400 0.2800 0.3200 250 300 350 400 450 500 pressure of ar [pa] in te ns ity [a .u 32 ma 135 ma 160 ma figure 8: the emitted light intensity measured on the 324.8 nm cu i. line as the function of the pressure of the filling gas. emitted light is also the function of the current and the pressure of the filling gas. in the course of the experiments the emission on the strongest atomic line of cu (324.8 nm) was measured. the results are presented in figure 7 and figure 8. looking at these figures it can be stated that the emitted line intensity sharply increases with increasing pulse current and decreases with increasing filling gas pressure. the sputtering ability the atoms of the bulk cathode material can get to the plasma by the mean of sputtering, so this process has a key-importance in the proper operation of the source. beside that it makes possible the depths profile analysis. in order to get information on the sputtering efficiency the sputtering speed has to be determined, which will be performed in the future. in these experiments only the demonstration of the sputtering ability is presented. as this source is operated in pulse mode, high power is applied to the source just a few percentages of the pulse duration, therefore rather low sputtering speed can be expected if it is averaged for the whole period. on the other hand it might advantageous in case of thin layers. to present the sputtering ability a steel plate, which had a 2,0 ± 0,2 µm thick zinc coating on its surface was taken as cathode sample and the zinc emission was measured on the 213.85 nm zn i line at 350 pa argon pressure as the function of time. the value of the high current was 72 ma, the pulse frequency was 122 hz and the duty cycle was 2.3%. the measured data are presented in figure 9. it can be observed that after 3000 s time interval, no zinc emission can be measured. 105 figure 9: the line intensity measure on the 213.85 nm zn i. line as the function of time. discussion of the results in the experiments a dc glow discharge source was studied, which was operated in pulse regime, at constant high and low current values. it could be seen that the current generator can be used in a wide range of ar pressure and the constant current makes possible an easier control of the device. from the viewpoint of the operation of the device the voltage-drop has a key importance, namely as long as it does not exceed the capabilities of the current generator, the constant current mode works. when the current generator runs out of the voltage, it stops working, therefore care must always be taken of the voltage-drop, and careful examination is needed to reveal the relation among the high current, the voltage-drop and that of the filling gas pressure. in figure 6 it can be seen that at 72 ma the source can be used in current regulated mode at the range of 300– 950 pa. below 300 pa the voltage-drop sharply increases with decreasing pressure, so it probably will not work at pressure values lower than 260–270 pa. in figure 5 the relationship between the voltagedrop and that of the current is shown. it must be noticed that the first point in the figure is the voltage-drop at the low current value. this also suggests that the device operates in the abnormal operating region within the whole current range. the emission data measured on the 324.8 nm cu i line are presented in figure 7 and figure 8. it is worth mentioning that the emitted light intensity sharply increases with increasing current, it seems to be an exponential function rather than a linear one. the reason for that sharp increasement may be the better sputtering efficiency. on the other hand, the emitted light intensity decreases with increasing filling gas pressure. in figure 9 the sputtering ability is demonstrated. it took about 3000 s to eliminate the 2 µm thick zn layer. if the duty cycle (2.3%) is taken into account, this would mean a sputtering speed of 1.74 µm /minute at continuous dc current. it must be mentioned that the duty cycle the speed depends also on the current and that of the argon pressure beside the duty cycle of the pulses. it also could be seen that the behaviour of the source is similar to the ones operated in voltage-feed mode, except for the fact that its state can always be charactised precisely bevause of the constant-current mode. acknowledgement the described work was carried out as part of the támop-4.2.1.b-10/2/konv-2010-0001 project in the framework of the new hungarian development plan. the realization of this project is supported by the european union, co-financed by the european social fund. references 1. a. boagerts, e. nexts, r. gijbels, j. van der mullen: gas discharge plasmas and their applicaion, spectrochimica acta part b, 57 (2002), pp. 609–658 2. ch. young, k. ingeneri, w. w. harrison: a pulsed grimm glow discharge as an atomic emission source, journal of analytical atomic spectrometry, 14 (1999), pp. 693–698 3. l. n. mishra, k. shibata, h. ito, n. yugami, y. nishida: charatcterization of pulsed discharge plasma at atmospheric pressure, surface & coating technology, 201 (2007), pp. 6101–6104 4. ch. young. w. w. harrison: investigation of a novel hollow cathode configuration for grimmtype glow discharge emission, spectrochimica acta, part b, 56 (2001), pp. 1195–1208 5. k. wagatsuma, k. hirokawa: observation of cu-ni alloy surfaces by low wattage glow discharge emission spectrometry, surface and interface analysis, 6 (1984), pp. 167–170 microsoft word contents.doc hungarian journal of industrial chemistry veszprém vol. 34. pp. 55-62 (2006) influence of counter cation on the thermal stability, the acidity and the catalytic properties in the dehydration of tert-butanol over 12-molybdophosphates laila i. a.*, nashwa s. abed-elshafy chemistry department, faculty of education, roxy 11757, cairo, egypt *: corresponding author the silver, ammonium, copper, and aluminum acidic salts of 12-molybdophosphoric acid have been prepared, monosubstitution, and their catalytic behavior measured for dehydration of tert-butanol. the reaction has been carried out in a flow system at the temperature range of 323-423 k and the reaction product was analyzed chromato-graphically. the effects of pretreatment temperature, time, partial pressure of alcohol, and non-steady-state regimes have been studied. the samples were characterized by tg, dsc, and bet surface areas. these studies have confirmed a correlation between structural stability and the salt cation, with the silver salt of h3pmo12o40 being the most thermally stable. however, the ammonium molybdophosphate is the less stable catalyst due to the catalyst reduction. mono-substitution of protons in h3pmo12o40 with silver and ammonium form high surface area solids, as compared to copper and aluminum salts. the number of weakly or moderately strong acidic sites remains relatively unchanged with pretreatment temperature to 673 k. all catalysts are highly selective to produce isobutene which is predominate product. isobutene formation is zero order reaction independent of the partial pressure of tert-butanol. this revealed that the dehydration reaction proceeded on the surface of solid catalysts (a surface-type reaction). in this case, the catalytic activities were determined by the concentration of protons on the catalyst surface and hence on the surface acidity. keywords: thermal stability, acidity, tert-butanol, heteropoly compounds. introduction isobutene is an alkene precursor in the synthesis of methyl tert-butyl ether. mtbe is widely used as an oxygenate for gasoline(1) not only to enhance the octane number but also to make motor vehicle fuel burn more cleanly, replacing toxic additives like lead, thereby significantly reducing toxic tailpipe pollution(2). heteropoly acids and related compounds have attracted considerable attention owing to their highly promising potential in industrial applications for acidic catalysis and selective oxidation(3-20). these types of compounds display a great potential of specific synthesis reactions for replacing sulfuric acid to satisfy the requirements of environmental protection(21). heteropoly acids are composed of primary, secondary, and tertiary structures. the primary structure is the structure of the heteropoly anions, and the secondary structure is the three dimensional arrangement of the polyanion and counter cation(6d,15,22,23). it was very important to realize that the primary structure is stable, whereas the secondary structure is flexible. the tertiary structure is very influential on the catalytic function of solid heteropoly acids (6d, 15). the tertiary structure is the structure of solid heteropoly acids as assembled. the size of the particles, pore structure, distribution of protons in the particle, surface area, mode of aggregation, etc., are the elements of the tertiary structures(15). counter cations greatly influence the tertiary structure of hpas. for anhydrous sample, each polyanion interacts with three isolated acidic protons. when the water content increases, the water molecules protonated in the pseudo liquid phase to form h3o+ and h5o2 + accompanied by the decrease in the amount of isolated acidic protons(24). one of the remarkable characteristics is that some solid hpas (group a, hydrogen forms included) absorb easily a large quantity of polar or basic molecules such as alcohol and nitrogen bases in the solid bulk(25). the absorption depends on basicity and the size of the molecule to be absorbed and the rigidness of the secondary structure. the rigidness of hpas depends on the counter cation (size, charge, etc) and apparently on the water content(26). group b salts like csxh3xpw12o40(x>2) adsorbed even polar molecules only on the surface(27). it is generally accepted that dehydration of alcohols takes place on either bronsted or lewis acid sites. the reactivity of alcohols is in the order: meoh < etoh < proh, buoh, and etoh < iso-proh < tert-buoh(28,29), which can be interpreted in view of the relative stability of corresponding carbenium ions or affinity of each alcohol to protons. 56 the aim of this study is to examine the influence of mono, diand trivalent cations on the activity, selectivity and stability of the molybdophosphoric acid towards the dehydration of tert-butanol to produce isobutene as a predominate product. experimental catalyst preparation the acidic salts of multivalent cations (mx n +h3-nxp mo12o40, abbreviated as mx, where m = ag, nh4, cu, and al) were prepared by the titration of an aqueous solution of h3pmo12o40 (0.025 mol dm-3) at 323 k with aqueous solutions of the corresponding nitrates (0.025 mol dm-3). the aqueous solution of nitrate was added dropwise at a rate of about 1 ml min-1 with constant stirring for 2h. for cu0.5 and al0.33, precipitates were not obtained by the titration, so that the solution was evaporated at 343 k to give a solid. in cases of nh4 and ag, solutions containing precipitates were obtained. these were also evaporated to dryness in a similar way. all the solid samples were dried at 393 k for 4 hours. catalysts characterization several techniques were employed for the characterization of solids such as: the surface area was determined by nitrogen adsorption-desorption at 77 k. thermal and differential scanning calorimetry analyses were carried out on a thermogravimeter (shimadzu tga-50) at a heating rate of 20 and 10 k min-1, respectively. the ag+, cu2+, and al3+ contents of the salts were determined by atomic absorption spectrophotometry (aas). for the ammonium salt, the cation composition was calculated from the nitrogen content determined by elemental analysis. catalytic reactions synthesis of isobutene from tert-butanol was performed in a flow system at an atmospheric pressure in the temperature range from 323 to 423 k. tert-butanol was fed by bubbling argon through an isothermal saturator kept at a constant temperature. prior to the reaction, the samples were pretreated in situ at 623 k in the argon flow for 3 hours. the pressure of tert-butanol was changed from 13.5 to 300 torr by changing the saturator temperature. gases at the outlet of the reactor were analyzed with a gas chromatograph (perkin elmer autosystem xl having an fid) equipped with a capillary column of 15 m length packed with carbowx 20m). blank runs have been performed without catalyst under the same experimental conditions similar to those measurements. no conversion of tert-butanol was observed in the temperature range investigated. results characterization of catalysts table 1 shows the chemical composition, surface areas and the surface acidity calculated for the investigated catalysts. it can be seen that the acidic salts of silver, copper, and aluminum, the degree of exchange of protons in the parent acid was in good agreement with the expected theoretical value, whereas it was higher for the nh4 + salt. the deviation of the ammonium salt with respect to the expected degree of exchange has also been observed by others(30-32). moffat et al. found that a deficit of ammonium carbonate employed in the preparation produces a substantial change(31). however, an excess of cation was used during the precipitation step in order to obtain the stoichiometric ammonium compounds(30,32). table 1: chemical composition, surface area and surface acidity calculated for acidic salts of molybdophosphoric acid. sample cation/k.u.a sbet b (m2g-1) surfacec acidity (μ mol g-1) chemical formulae h3pmo12o40 agh2pmo12o40 nh4h2pmo12o40 cu0.5h2pmo12o40 al0.33h2pmo12o40 0.93 1.40 0.54 0.31 8.0 60.9 47.5 21.2 19.1 20.7 106.5 66.5 36.9 33.6 h3pmo12o40 agh2pmo12o40 (nh4)1.4h1.6pmo12o40 cu0.5h2pmo12o40 al0.33h2pmo12o40 a : cation content per keggin unit as calculated from chemical analysis b: measured from the nitrogen adsorption measurements. c: calculated from chemical formulae and surface areas bet surface area of hpmo was 8 m2 g-1. for all the salt examined, the surface area is increased when compared to the parent acid. on the other hand, the surface areas increase as the diameters of the substituted cations are increased from group a (cu2+, al3+) to group b(nh4 +, ag+). the surface area is large for silver and ammonium molybdophosphates because very fine particles are formed during titration due to the very low 57 solubility in water(33,34). however, the low surface areas of copper and aluminum salts, as compared to the silver and ammonium salts, can be explained by their high solubility in water and the fine particles did not precipitate(33,35). also, moffat et al. have been explained the larger surface areas for the salts of large monovalent cations by the rotation and translation of the keggin anions, so that the barriers between the interstitial voids presents in the parent acid are partially removed allowing the formation of channels between the anions and the counter cations(36-39). the surface acidity is estimated from bet surface area and the content of h+ in the chemical formulae(15,40,41) (table 1). the surface acidity of the present acid increases with the partial substitution of proton by the cations. this can be attributed to their high surface area (19-61 m2 g-1) compared with 8 m2 g-1 for the parent acid. the number of the crystallization water and the thermal stability of the parent acid and its acidic salts were performed by tg and dsc analyses (figs 1 and 2). fig. 1: tga curves of molybdophosphoric acid and its acidic salts during thermal gravimetric analysis, water of hydration evolved first, leaving anhydrous keggin units with associated protons at temperatures up to 573 k. as the temperature continued to increase, above 673 k "protonic water" usually called "constitutional h2o" evolved. this water is formed by extraction of an oxygen atom from the keggin anion by two protons, thus decomposing the hetropoly anion structure. the decomposition of hpmo is observed at 697 k with δ h = -61 jg-1 (table 2). in agreement with previous findings, the complete dehydration of free and constitutional water from hpmo is mostly achieved by > 673 k. above 703 k the keggin structure of hpmo is completely destroyed(42-44). it is found that the introduction of copper and aluminum cations lead to decrease in the thermal stability of the parent acid. this is consistent with results of previous findings(45). they concluded that biand trivalent metal salts are not stable. fig. 2: dsc curves of molybdophosphoric acid and its acidic salts 58 table 2: tg-dsc data for acidic salts of molybdophosphoric acid. dsc sample abbreviation physisorbed hydration/kua protonic water/kub exo [k] δh j g-1 h3pmo12o40 agh2pmo12o40 (nh4)1.4h1.6pmo12o40 cu0.5h2pmo12o40 al0.33h2pmo12o40 hpmo agpmo (nh4)1.4pmo cu0.5pmo al0.33pmo 12 8 6 10 12 1.5 1.0 …..c 0.95 1.0 697 694 695 675 652 -61 -82 -29 -41 -60 a : water evolved at low temperature (less than 573 k). b: water loss from decomposition of keggin unit. c: decomposition of ammonium molybdophosphate to ammonia, water and nitrogen(52). the higher thermal stability of agpmo is ascribed to the partial substitution of protons by large monovalent cation(16, 46-48). the reason could be that the larger cations are coordinated to more oxygen atoms on the periphery of keggin structure and consequently cause atoms in anions to have small mobility, which means the crystal is more stable(49). however, in case of ammonium molybdophosphate the exothermic peak do not seem to suffer temperature shift, although the enthalpy values is decreased from 61 to 29 jg-1 for the parent acid and ammonium salt, respectively (table 2). this can be explained by the reduction of catalyst leading to formation of the reduced heteropoly anions, due to the possibility of nh4 + cation being a source of hydrogen(50,51). it is known that decomposition of ammonium molybdophosphate is proceed via elimination of ammonia, water, and nitrogen beginning around 673 k(52). catalytic reaction effect of pretreatment temperature for molybdophosphoric acid the effect of pretreatment temperature on tert-butanol dehydra-tion and selectivity towards isobutene formation is shown in fig. 3. as the pretreatment temperature increases from 373 to 673 k, the conversion is relatively increased and then decrease with further increase in temperature up to 723 k, while the selectivity is nearly constant. this can be attributed to slightly increasing the number of acid sites of sufficient strength required to facilitate the reaction as the pretreatment temperature increase to 673 k beyond which it decreases. this is consistent with the results of moffat et al.(53a) who reported that the number of weakly or moderately strong acidic sites relatively little changed with pretreatment temperatures to a maximum value at approximately 673 k and then decreases as pretreatment temperature increased. this result shows that the strongly acidic sites is not necessary for this reaction. the significant decrease in the catalytic activity at 723 k is ascribed to the decomposition of the acid into the corresponding single oxides. this is evident from tg-dsc data (table 2). fig. 3: effect of pretreatment temperature on conversion of tert-butanol (a) and selectivity for isobutene formation (b) over molybdophosphoric acid effect of reaction temperature fig. 4 shows the changes in the conversion for the acidic salts of hpmo upon the variation of the reaction temperature. in these experiments the data were collected after the reaction reached approximately the stationary state at each temperature. the results obtained indicate that the activity increases with reaction temperature up to 373 k, beyond which the activity changes little. the predominate product is isobutene with small amount of isooctene. the isooctene is formed as a result of the dimerization of isobutene(30,53b). the maximum conversion to isooctene, 7%, was obtained over al0.33pmo at 373 k (not shown) which may be attributed to presence of both bronsted and lewis acid sites on aluminum molybdophosphate catalyst(54a&b). this agrees with the results of connor et al.(54c), who found that the aluminum substituted of hpw is a good catalyst for propene oligomerization. the dehydration activity is in the following order: agpmo > cu0.5pmo > al0.33pmo > hpmo > (nh4)1.4pmo 59 the significant enhancement of agpmo can be attributed to: (i) its high surface acidity which arise from its high surface area (table 1). and/or (ii) the rapid migration of protons which participate in the reaction. this is evident from the conductance value obtained in this study, the value is increased from 200.3 to 240.4 ohm-1 cm2 mol-1 for hpmo and agpmo, respectively. this is consistent with results of baba et al.(55,56). they found that the mobility of protons was enhanced by the presence of silver. the partial substitution of protons by copper and aluminum cations enhances the catalytic activity of parent acid. this can be explained by (i) these salts do not form precipitate by the titration, the solution was evaporated to dryness to obtain the solid salts. during this procedure, ph of the solution increased and in consequence the hydrolysis of the polyanion possibly took place to certain extent. the hydrolysis would form weakly acidic h+(33). (ii) the dissociation of coordinated water(6d,14,57) and/or water produced during the reaction(29,58,59) as a function of the electronegativity of the metal cations, which form protons by a following reaction. mn+ + mh2o → [m(h2o)m]n+ → [m(h2o)m-1(oh)](n-1)+ + + h+ and/or (iii) their high surface acidity (table 1). however, the ammonium molybdophosphate although having a high surface acidity is less active as compared to the hpmo. due to the possibility of nh4 + cation being a source of hydrogen, resulting of the catalyst reduction. the catalyst reduced or partially reduced after pretreatment(50,51). the selectivity towards isobutene formation over all investigated samples remains nearly constant with the reaction temperatures in the range 94-98%. this can be attributed to the dimerization activity being little changed with the reaction temperature (not shown). effect of reaction time fig. 5 shows the time courses of tert-butanol dehydration at 373 k catalyzed by molybdophosphates. the conversion decreases with time and reaches a stationary state value at different time-on-stream. it is believed that this decrease in conversion results from the relatively slower rate of regeneration of the bronsted acid sites in comparison with the rate of formation of the olefinic products on a release of protons(37). previous studies(28a,60-62) showed that the decrease in conversion due to the retention of the alcohols and/or their decomposition products on the catalysts. the stability of the catalyst during the reaction was estimated from the value of the activity retained (ar) by the catalyst at the end of the experiment. this value is the ratio of the conversion at 4h to that at initial stage. the results obtained are summarized in table 3. the highest stability of silver molybdophosphate among these salts may be attributable to its highest mobility of protons(55,56). on the other hand, the stability increased from 0.52 for hpmo to about 0.63, and 0.86 for al0.33pmo and cu0.5pmo, respectively. this indicates that the formation of h+ species, as mentioned before, over these catalysts improve also the stability of catalysts(6d, 14, 29,57-59). the selectivity to isobutene was nearly 100% for all investigated catalysts. this indicates that all of the catalysts possess sites of sufficient acidic strength to facilitate the dehydration reaction and are inactive for isobutene dimerization under these conditions. table 3: initial activity (ai), final activity (af), activity retained (ar), and apparent activation energy for tertbutanol dehydration over acidic salts of molybdophosphoric acid. sample (abbreviated) ai. 10-3 mol h-1 g-1 af. 10-3 mol h-1 g-1 ar ea kj mol-1 hpmo agpmo (nh4)1.4pmo cu0.5pmo al0.33pmo 44.6 48.8 42.5 47.8 45.7 23.3 46.0 19.2 41.0 29.0 0.52 0.94 0.45 0.86 0.63 32.8 18.1 42.8 23.2 18.3 60 effect of alcohol partial pressure the pressure dependence for isobutene formation over investigated catalysts is shown in fig. 6. the conversion is independent of the partial pressure of alcohol, whatever the catalyst examined. the zeroth-order dependence for tret-butanol dehydration indicates that the surface is fully covered by alcohol because an adsorbed species of strong tertiary carbenium ion is mostly likely to form on the surface. this data agrees with the results obtained by several authors(28a,61,63). on cessation of the flow of alcohol to the sample after steady state is reached, the rate of isobutene formation gradually decreases and not falls sharply at the onset of purging for 45 minutes (fig. 7). this behavior can be explained by the existence of strongly adsorbed species on the acid sites of catalyst surface(63). for agpmo catalyst, the interaction of tert-butanol on acid sites is stronger than other investigated samples (fig.7). apparent activation energy the apparent activation energy, ea, cab be calculated from the slope of a plot log k versus 1/t by application of arrhenius equation. the values of ea thus obtained are listed in table 3. it is evident that the partial substitution of the protons in hpmo by ag+, cu2+, and al3+ cations decreases the ea value from 32.8 to 18.1, 23.3 and 18.3 kj mol-1, respectively. the decrease in the value of ea is due to enhancement of their catalytic activity, which is the normal case for catalytic promotion. however, the catalyst containing ammonium cation produces an increase in ea than the parent acid. such behavior can be attributed to a decrease of its catalytic activity. mechanism of isobutene formation the dehydration of alcohols over heteropoly compounds proceeds via a carbenium ion mechanism(28,64). the following conclusion can be drawn from the data obtained in this study: 1the activity correlates well with the surface acidity, indicating that the dehydration of tertbutanol over heteropoly compounds belongs to the surface-type reactions. however, the effect of acidity on the selectivity towards isobutene formation is not significant. 2the predominate product was isobutene with small amounts of isooctene. 3isobutene formation took place via a unimolecular mechanism, whereas isooctene via a biomolecular mechanism. 4the dehydration of tert-butanol is a zeroth-order reaction. this indicates that the surface is fully covered by tert-butanol, due to the strong interaction of the alcohol on the acid sites (bronsted sites). from the previous data, the following reaction mechanism is proposed: (ch3)3coh + h+ … oku → (ch3)3coh2 + … oku (1) (ch3)3coh2 + … oku → (ch3)3c+ + h2o + oku (2a) (ch3)3c+ + oku → (ch3)3cok u (2b) (ch3)3c-ok u → (ch3)2-c=ch2 + h+ … oku (3) the process is clearly analogous to that already described for the dehydration of methanol and ethanol(28,29). they suggest that the alkylation of the catalyst may be vital intermediate step in the dehydration of alcohol in general. in step (1), tert-butanol is rapidly bound to the catalyst via a strong h-bonding interaction with the proton, forming the molecular ion 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to test and to pretune advanced controllers to reduce the onsite work of control engineers and to train operators using advanced control solutions. following the proposed approach a simulation framework has been developed where detailed process model realized in matlab which is connected via opc (objectlinking and embedding for process control) to the profit controller of honeywell. with the application of the resulted simulation system the model predictive control (mpc) of a nonlinear crystallizer has been analysed. the case study demonstrates the efficiency of the proposed approach and the illustrative results show that the linear and robust mpc is an adequate controller of nonlinear crystallizers. keywords: process simulator, model predictive controller, opc introduction the interest for the use of dynamic simulation techniques in process industry is growing continuously, new fields of applications appear and become more reliable. areas such as engineer and operator training [1,2], design or test before commissioning of a new control system are only some examples where simulation-based methods are being applied. in particular, process simulators are found in those industries where training is essential for plant security or process operation. the use of simulators facilitates a deeper knowledge of the process and its behaviour in different operating conditions, so that it can be manipulated without risk and minimizing production losses. all these factors have an impact in the global improvement of plant performance. for control applications, fairly simple models obtained by identification from plant data can give good results, but a simulation for operator training should be based on a first-principles model, able to reflect many details of the process and to cover a wide range of operating conditions [3]. process modelling is a powerful technology that enables managers and engineers to link critical business objectives to improve the design, operations and optimization of a plant [4, 5]. in the literature it is possible to find examples where steady state and dynamic modelling have been used to improve unit operation and control scheme design, even in industrial cases [6, 7]. unfortunately, in these papers very limited information is published concerning the applicability of process simulation tools at the plant level. apart from some specific examples related to operator training [8, 9], the advantages of using state-of-the-art commercial simulation tools at the plant level, e.g. for the improvement of process behaviour, are not well presented. however, it should be noted that the process industry has already started to move towards a more direct application of modelling tools and some engineering organizations have set up guidelines for the use of computer software in the design of process plants [10]. according to these experiences, the possible benefits of the simulation based process development are the following: ● maximizing the return on capital employed by predict the future of the plant today ● allowing the usage of what-if scenarios and sensitivity analyses to identify the optimal design, based on operational and business targets [11] ● ensuring that process equipment is properly specified to assure desired product throughput and specifications ● preparing plant assets for profitable, reliable and safe production [12, 13] ● improving profitability by using simulation online for enhanced process control and optimization [14] ● allowing the evaluation of the effect of feed changes, upsets and equipment downtime on process safety, reliability and profitability ● training plant staff to ensure they can react to abnormal situations and run the plant at safe, yet optimal levels of production ● improving the design of regulatory and advanced control strategies for better plant control and operability the goals of the development approach proposed in this paper are mainly the last two; design a simulation framework that is able to test and pretune advanced controllers to reduce the onsite work of control engineers, and to train process operators how to use the controller. 52 in the developed tool a detailed engineering (firstprinciples) process model is implemented in matlab. this model is connected via opc (object-linking and embedding for process control) to a model predictive controller (mpc). since the aim of the tool to pre-test the efficiency of the advanced control solution in industrial environment, the studied controller is the profit controller of honeywell which is widely used in the process industry. in the following section an overview of the structure and the elements of the proposed framework are highlighted, where the model in general, the model predictive controller, and the opc connection between these elements are presented. this section is followed by a case study where the details of the simulator and its implementation are showed through the control of a continuous vacuum crystallizer. structure of the proposed simulation environment the proposed simulation system is based on the synthesis of the process (model) and the controller. components of the combined simulation system are (see fig. 1): ● the detailed engineering model of the technology, realized in matlab (of course other simulation tool could also be used), ● the controller model, which is a real-time, industrially used model based controller (in this study predictive controller (mpc) is used as advanced control solution.), ● and the connection of the two elements above, which is the standardized opc (originally ole-object linking and embedding for process control). as it is shown in fig. 1, the model is considered to act like the real plant, the manipulated variables (mainly the setpoints for the controllers, e.g. temperature controller) are the inputs of the model, while the outputs of the controller are the controlled variables (e.g. delivery). the value of these variables are transferred from the model to the controller via opc. controller controlled variables opc manipulated variables model figure 1: the sheme of the simulator system in the next section the elements of the system are presented. following this overview the details of the implementation are presented in a case study through an example connected to a particular model of a crystallizer and controller. model “modelling means the process of organizing knowledge about a given system” [15]. “a model (m) for a system (s) and an experiment (e) is anything to which e can be applied in order to answer questions about s” [16]. “by performing experiments, we gather knowledge about the system. however, at the beginning of this process, this knowledge is completely unstructured. by understanding what are the causes and what are the effects, by placing observations in a temporal as well as spatial order, we organize the knowledge that we gathered during the experiments” [17]. for different functions in different environments, different models have to be applied. models can be used during the whole lifecycle of a plant, e.g. in the design, the operation and in the optimization phase as well. such simulation lifecycle is presented in fig. 2. figure 2: the simulation lifecycle at honeywell 53 in this paper the model has not only to be able to cover a wide range of operating conditions, but it has to be also adaptable to the process control system via opc. controller model predictive control refers to a class of computer control algorithms that utilize an explicit process model to predict the future response of the plant [18]. the technique was originally developed to meet the specialized control requirements of power plants and petroleum refineries [19]. mpc technology can now be found in a wide variety of application areas including chemicals, food processing, automotive and aerospace applications. in model predictive control, the control action is provided after solving – in real time at each sampling instant – an optimization problem, and the first element in the optimized control sequence is applied to the process (receding horizon control). the “moving horizon” concept of mpc is a key feature that distinguishes it from classical controllers, where a precomputed control law is employed. a major factor in the success of model based predictive control is its’ applicability to problems where analytical control laws are difficult, or even impossible to obtain. a model is used to predict the future plant outputs, based on prior and current values and on the proposed optimal future control actions. these actions are calculated by the optimizer, taking into account the cost function (where future tracking error is considered) as well as the constraints, for the details see [20]. in this paper a real, industrially used mpc, the profit controller was applied. the honeywell’s profit® controller controls the process using the minimum manipulated variable movement necessary to bring all of the process variables within limits or to setpoints. this controller also optimizes the process with the remaining degrees of freedom in order to drive the process to optimum operation. profit controller uses honeywell's patented range control algorithm (rca) [21]. rca minimizes the effects of model uncertainty while determining the smallest process moves required to simultaneously meet control and optimization objectives. the models for the prediction were also identified in honeywell’s software environment. the overall process model is composed of a matrix of dynamic sub-process models, each of which describes the effect of one of the independent variables on one of the controlled variables [22]. integration issues the integration of a process simulator and the controller was performed with opc. this standard specifies the communication of real-time plant data between control devices from different manufacturers. opc was designed to bridge windows-based applications and process control hardware and software applications. during the integration, the variables have certain definite names (e.g.: mv01.activevalue) called tag. the communication can be asynchronous or synchronous, and the sampling time has to be set. ole for process control which stands for objectlinking and embedding for process control, is the original name for an open standard specification developed in 1996 by an industrial automation industry task force (see http://www.opcfoundation.org). the standard specifies the communication of real-time plant data between control devices from different manufacturers. while opc originally stood for “ole for process control”, the official stance of the opc foundation is that opc is no longer an acronym and the technology is simply known as “opc”. one of the reasons behind this is while opc is heavily used within the process industries, it can be, and is, widely used in discrete manufacturing as well. hence, opc is known for more than just its applications within process control. the opc specification was based on the ole, com, and dcom technologies developed by microsoft for the microsoft windows operating system family. the specification defined a standard set of objects, interfaces and methods for use in process control and manufacturing automation applications to facilitate interoperability. case study the proposed simulation framework was tested for the model based control of a vacuum crystallizer. the crystallizer is a non-linear, multi input multi output (mimo) object, with a high degree of interaction between the process variables. the control of this process has many difficulties, e.g. one can do nothing if the crystals grow beyond a certain size, there is no opposite way of change. for all of these problems, a model predictive controller presents a good solution. mpc can handle the mimo object; and it is predictive, so the controller “prevents” oversized crystals. for nonlinearity within a certain range, a robust controller can be adequate. these problems are tested below in the presented simulation environment. simulation details vacuum crystallizers are able to produce crystals of a certain quality as fast as possible using the minimum amount of energy. the description of the studied vacuum crystallizer and its model can be found in [23]. from controlling point of view a crystallizer the main quality criterions are the properties of the produced crystals, the size and the size-distribution. the delivery of the crystallizer can be also controlled. so, the outputs (the controlled variables, called cvs) calculated from the moments are the following: 54 ● mean crystal size ● standard deviation of the crystal size distribution ● delivery of the crystallizer from the process point of view, in a continuous vacuum crystallizer, the pressure, the temperature and the residence time can be changed in practice. in the environment of the model the inputs (the variables to be manipulated, called mvs), are the following: ● pressure; can be controlled with partial pressure by the valve of the vapour outlet ● temperature; can be changed with the inlet suspension temperature ● residence time there is a strong coupling between the inputs and the outputs, for example any change of the residence time in the vacuum crystallizer not only changes the size but the size distribution (and of course the delivery). to summarize, the above presented crystallizer is a non-linear object, with a high degree of interaction between the process variables. the robustness of the controller is tested in the following case study, where a non-linear process is controlled by a linear mpc. this solution is widely applied in the industry, since the non-linearity of the process can often be handled by the linearization of the process model or the process is operated within a relatively narrow range where the process may act linearly. implementation details the first-principle model of the process has been developed in matlab simulation environment. the honeywell environment of the profit controller is also set up as opc server. according to this solution, the opc read and opc write toolboxes of matlab are used to connect the profit controller of the crystallizer (hci.cryst). matlab simulink view of this solution can be seen in fig. 3, where the red boxes are connected to the profit controller. in this platform, some measurement noise is added to the controlled signal to get closer to a real-time environment. during the simulation, this simulink program is sending and getting the data from the controller at every minute. profit viewer is used to supervise the parameters and performance of the profit controller [21], the online model predictive controller of honeywell. this program serves as a windows based graphical user interface, see figs 4 and 5. in the cv summary display the operator can change the limits or the setpoints of cvs. the value comes from the process unit (now from the model), the ss value is the predicted steady state value while status shows whether the cv is controlled by mpc or not. mv summary screen shows the actual inputs (value), how it has changed in the last execution period (move) and the steady state values (ss value). in normal conditions, the operators do not change the limits of mvs. figure 3: matlab simulink view of the process, connected to the controller 55 figure 4: one of the main profit viewer screens, cv summary figure 5: one of the main profit viewer screens, mv summary results the main goal of the model predictive controller was to follow the setpoint that defines the desired size of the crystals. the standard deviation of the size distribution was minimized within a certain range, but the maximization of the volume was set to be a more important priority than this goal. the default control horizon (where the manipulated variables change in the prediction) in the honeywell controller contains 10 movements of the mvs. the prediction horizon (where the prediction is calculated) is identical to the open loop response interval which is about 1.5 hours in this case. weights, rate of change limits, ramping limits and other tuning parameters were set up in the profit controller manually, based on the results of previous simulation experiments. the optimization speed factor was set to three (fast), which resulted in an optimization horizon approximately two times of the cv overall response time. the cv overall response time was defined as the average of the longest cv response time and the average cv response time, 123 minutes in this case. 56 the simulation results are shown in figs 6 and 7. the dashed lines are the setpoint for cv1 and the minimum and the maximum limits of cv3. the limits of cv2 are irrelevant. 0.11 0.12 0.13 0.14 0.15 0.16 0.17 0.18 22:30 23:30 0:30 1:30 2:30 3:30 4:30 5:30 6:30 7:30 8:30 9:30 10:30 11:30 12:30 13:30 0.15 0.17 0.19 0.21 0.23 0.25 0.27 0.29 0.31 0.33 0.35 cv1*10^3 (left axis) cv1 setpoint (left axis) cv2*10^7 (right axis) cv3*10^3 (right axis) cv3 highlimit (right axis) cv3 lowlimit (right axis) figure 6: simulation results for the controller, optimizer, with controlled variables (cv1 = crystal size, cv2 = crystal size-distribution, cv3 = delivery of the crystallizer) 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 22:30 23:30 0:30 1:30 2:30 3:30 4:30 5:30 6:30 7:30 8:30 9:30 10:30 11:30 12:30 13:30 900 1000 1100 1200 1300 1400 1500 1000*mv1 (left axis) mv2 (left axis) mv3 (right axis) figure 7: simulation results for the controller, optimizer, with manipulated variables (mv1 = pressure, mv2 = temperature, mv3 = residence time) in the test run the optimizer was turned on at 23:00, from that time the cv3 (delivery) increased significantly while the cv2 (size distribution) decreased a little to the optimal values. cv1 setpoint change was realized after a little overshoot, the changes of mvs (fig. 7) show that the controller reacted rapidly. when the range of cv3 was changed, the mvs also changed fast, and the control problem was solved. cv1 also changed significantly due to interaction, but it calmed down after a while. the results shows that the controller optimizes and solves the changes in the range, the mvs react rapidly but smoothly, and the controller is robust. the online measurement of size distribution can be difficult. with profit controller, the size distribution can be an inferred variable calculated from measurable variables. it is an often-used technology, for example, to control the cutpoints in the refineries. during a real commissioning, engineers always check the unbiased model cvs, which are calculated from the linear model matrix. these model cvs should change parallel with the real cvs, it is the validation of the models. if the change is too big, then the gain is too big, if the unbiased model cv changes appear later, then the dead time is too big and the dynamics should be also more or less the same. according to these rules, linear models were checked and changed where it was needed. the results are very good, with the final models the unbiased and the read cvs are changing parallel. (see fig. 8.) figure 8: validation of the models, the bold lines are the unbiased model cvs conclusion the paper demonstrated a successful application of a novel simulation framework, where the detailed engineering model of a process unit is connected to a widely used advanced process controller (apc) via opc. the solution system can be used to pretune the controller, test the controller solution or the operating strategy (e.g. grade transition), to train the engineers and the operators and in many other simulation cases. in the case study, it was examined how a continuous vacuum crystallizer can be controlled by mpc using this system. the control of the crystallizer is difficult, because it is a non-linear mimo object with strong coupling between the variables. the results showed that the linear, robust mpc is and adequate controller of a nonlinear crystallizer, it is adaptable in real unit. it was tested in regulatory and servo mode as well. the simulation system has proved to be a very convenient tool to test the controllability in this special case. according to our knowledge this is the first successful integration of the mpc of honeywell and the matlab simulation environment. the experience gathered in this study can be applied in other projects as well. acknowledgement jános abonyi is grateful for the support of the bolyai research fellowship of the hungarian academy of sciences and to dr. nora moldovanyi at honeywell hungary for the implementation of the simulation system and for providing the results of the simulation experiments. the financial support of the támop-4.2.2-08/1/2008-0018 project is gratefully acknowledged. 57 references 1. dede c.: the evolution of constructivist learning environments: immersion in distributed virtual worlds, educational technology, 35, 46 (1995) 2. pantelidis v. s.: virtual reality and engineering education, computer applications in engineering education, 5(1) (1997), 3-12. 3. santos r. a., alves r., normey-rico j. e., gómez a. m., arconada l. f. a., moraga c. p.: distributed continuous process simulation: an industrial case study computers and chemical engineering (2007), cace-3466 4. unisim simulation solutions product information note, br-07-05-eng honeywell, automation & control solutions, phoenix (2007) 5. hangos k. m., cameron i. t.: process modeling and model analysis, elsevier (2001) 6. roat s. d., downs j. j., vogel e. f., doss j. e.: chemical process control—cpciii, morari, m. and mcavoy, t. j. (eds) (cache=elsevier, austin, tx, usa) (1986) 7. lausch h. r., wozny g., wutkewicz m., wendeler h.: plantwide control of an industrial processes, trans icheme, part a, chem eng res des, 76 (1998), 185-192 8. bretelle d., chua e. s., macchietto s.: simulation and on-line scheduling of pvc plant for operator training, comput chem eng, 18 (1994), 547-551 9. bezzo f., bernardi r. g. c., finco m., barolo m.: using process simulators for steady-state and dynamic plant analysis an industrial case study, trans icheme, part a, chem eng res des, 2004, 82(a4), 499-512 10. icheme cape subject group: good practice guidelines—the use of computers by chemical engineers, version 1.0 (icheme, rugby, uk) (1999) 11. lewin d. r., seider w. d., seader j. d.: integrated process design instruction computers and chemical engineering 26 (2002), 295-306 12. ambrose d. h., bartels j. r., kwitowski a. j., gallagher s., battenhouse t. r. jr: computer simulations help determine safe vertical boom speeds for roof bolting in underground coal mines journal of safety research 36 (2005), 387-397 13. eizenberg s., shacham m., brauner n.: combining hazop with dynamic simulation— applications for safety education journal of loss prevention in the process industries 19 (2006), 754-761 14. jung j. y., blau g., pekny j. f., reklaitis g. v., eversdyk d.: a simulation based optimization approach to supply chain management under demand uncertainty computers and chemical engineering 28 (2004), 2087-2106 15. zeigler b.: multifaceted modeling and discrete event simulation, academic press, london, 1984 16. minsky m.: models, minds, machines, proceedings ifip congress (1965), 45-49 17. cellier f. e.: continuous system modeling, springer-verlag, new york (1991) 18. meadows e. s., rawlings j. b.: model predictive control, englewoods cliffs. nj: prentice-hall (1997) 19. qin s. j., badgwell t. a.: a survey of industrial model predictive control technology control engineering practice 11 (2003), 733-764 20. moldoványi n., lakatos b. g.: model predictive control of continuous crystallizer, hungarian journal of industrial chemistry, 33 (2005), 97-104 21. profit suite documentation, identifier user’s guide ap09-200, honeywell international inc. (2007) 22. moldoványi n., abonyi j.: control of a continuous vacuum crystalliser in an industrial environment: a feasibility study – comparision pid to model predictive control solution, hungarian journal of industrial chemistry, (2008) 23. ulbert zs., lakatos b. g.: simulation of cmsmpr vacuum crystallisers. computers and chemical engineering, 23 (1999) s435 microsoft word contents.doc hungarian journal of industry and chemistry veszprém vol. 40(1) pp. 39–44 (2012) ethyl-acetate synthesis in gas phase by immobilised lipase z. csanádi1 , r. kurdi2, k. bélafi-bakó1 1research institute on bioengineering, membrane technology and energetics e-mail: csanadi@almos.uni-pannon.hu 2university of pannonia, institute of environmental engineering, 10 egyetem str., 8200 veszprém, hungary gas-solid phase biocatalytic reactions offer economic and environmentally sound ways to produce ester compounds, which can be used as natural flavour components, and other types of value-added products. therefore, the aim of this work was first to study the continuous gas-solid phase manufacture of ethyl-acetate (etac), which is an important fruit flavour compound, from ethanol (etoh) and acetic acid (acac) applying immobilised candida antarctica lipase b enzyme in a self-constructed bioreactor and then to determine the effects of initial substrate composition, applied temperature, and the amount of used enzyme on the yield. it can be concluded that there was a well-defined connection between the yield of the ethyl-acetate product, the temperature and the amount of used enzyme, while the correlation between the initial substrate composition and the product yield could not be described so easily. the activation energy of the esterification was found to be much lower in our system than that of the same enzymatic reaction carried out in other reaction media, such as organic solvent system, ionic liquid, etc. keywords: solid/gas phase, enzymatic reaction, lipase, ethyl-acetate introduction organic flavour compounds can be defined as natural when they are produced either from natural sources [1] or in natural processes, such as physical treatment, fermentation [2], or enzymatic reaction [3]. although these natural compounds are healthier and more attractive to the consumers [4], their extraction from natural sources, e.g. various plants and fruits, is not only expensive but also results in extensive waste production. therefore, the production of natural aroma compounds, especially esters by fermentation and enzymatic reactions in aqueous [5], organic solvent [6], or novel environmentally friendly solvent media [7] has become a widely-studied field of research in the last few years. solid-gas phase biocatalysis, where biocatalysts are in solid form while the substrates are in gaseous state or can be easily vaporized [8], offers the following advantages over solid-liquid systems and organic liquid medium [9–11]: higher biocatalyst stability thermo-denaturation of the (partially) dehydrated biocatalyst is limited mass transfer of components is more efficient in the gas phase diffusion limitation is reduced due to the low viscosity in the gas phase production of by-products is reduced or avoided very high conversion yields can be achieved products and unconverted substrates can be easily recovered with condensation risk of microbial contamination is lower recently, both enzymes (mainly lipases in esterification reactions [12, 13]) and whole cells (e.g. baker’s yeast) have been studied in solid-gas systems. the experiments were carried out either by immobilized or soluble biocatalyst [14, 15]. barzana [16] studied the gas-phase oxidation of ethanol vapour with molecular oxygen and dehydrated, immobilized alcohol dehydrogenase from pichia pastoris cells and they found that dry alcohol oxidase was more thermostable in gas-phase than in aqueous solution. in the works of mikolajek [17] and spiess [18] immobilized enzyme preparations were used successfully in carboligation reactions, where benzaldehyde was converted to benzoin using thiamine diphosphatedependent enzymes. gas phase ethyl acetate production was studied by hwang and park [19] in a batch bioreactor applying porcine pancreatic lipase in a powder form. in the experiments, effects of reactant concentration, amount of enzyme, and reaction temperature on the performance of the bioreactor were investigated. letisse and co-workers [20] used a continuous gas phase reactor to study the effect of organic molecules on the kinetic parameters of the alcoholysis of methyl propionate by 1-propanol catalyzed by immobilized candida antarctica lipase b. the gas phase continuous production of acetaldehyde from ethanol and the production of hexanal from hexanol using dried baker’s yeast were studied in a continuous operational system and it was found that after 20 hours long experiments the hexanal conversion was as high as 32% without a decrease in enzyme 40 activity [21]. the results suggested that dehydrated enzymes may have potential advantages in solid-gas phase bioreactors. the aim of this work was first to construct a solidgas phase laboratory scale experimental set-up and then to carry out experiments on the continuous esterification of ethyl-acetate from acetic acid and ethanol applying candida antarctica lipase b enzyme in this bioreactor and to determine the effects of initial substrate composition, applied temperature, and amount of used enzyme on the esterification reaction. the synthesis of ethyl acetate is considered to be a quite important process since it can be extended to the gas-solid phase synthesis of other flavour esters, such as isopropyl acetate, isobutyl acetate, ethyl propionate, and butyrate. furthermore, it was planned to determine the activation energy of the reaction and to compare the results to the data in the literature concerning the same esterification reaction carried out in other types of reaction media. material and methods materials the immobilized biocatalyst, novozym 435 candida antarctica lipase b was purchased from novozysmes (bagsvaerd, denmark). acetic acid (≥99.7%), ethanol (≥99.7%), and ethylacetate were of the highest purity and provided by sigma-aldrich, germany. nitrogen (n2) gas was provided by linde, hungary. all other chemicals were analytical grade and purchased from sigma-aldrich, germany. experimental set-up the experimental set-up, shown in figure 1, is composed of three main functional units; i. substrate saturation module, ii. bioreactor, iii. product and remaining substrate recovery module. it is built up of the following parts; two thermostates (1), flow meter (2), substrate separation unit (3), septums for gas sampling (4), bioreactor with the immobilized biocatalyst (5), two vapour condensation units (6,7), condensated sample reservoir (8), n2 gas outlet (9), and a cryostat (10). substrate was continuously fed to the bioreactor via the flow meter by passing n2 carrier gas through the mixed ethanol and acetic acid substrate solution with a rate of 2 dm3(n2)h-1. the carrier gas first was saturated by the substrates in the substrate saturation unit then was passing through the thermostated glass spiral tube bioreactor packed with approximately 11 g of immobilized lipase operating under atmospheric pressure and with a mean residence time of 72 s. after the enzymatic synthesis of ethyl-acetate took place in the bioreactor, the remaining substrates and products were first condensated and trapped into cold ethanol solution (-18°c), then removed from the n2 stream by cooling, while n2 was recycled. figure 1: scheme of the experimental set-up 1. thermostate, 2. flow meter, 3. substrate saturation unit, 4. septum for gaseous sampling, 5. bioreactor, 6.,7. vapour condensation units, 8. condensated sample reservoir, 9. gas outlet, 10. cryostat in the first two functional units the constant temperature (which was lower in the case of unit i than that of unit ii in order to avoid occasional condensation) was maintained by thermostates. gas phase samples were taken both from the substrate separation unit and the bioreactor through the septums. analytical method the gas samples were analysed by gas chromatography using a hp4890 type gas chromatograph equipped with a fid detector and a ffap fused silica capillary column (macherey nagel, germany). the temperature program was the following: 3 min isothermal period at 60°c, then temperature was raised to 250°c at 10°cmin-1, while the injector and detector were maintained at 250°c. optimization of carrier gas amount optimal flow rate, hence optimal amount of the carrier n2 gas which affects the residence time of the gaseous reactant mixture and productivity of the whole system was determined in the experimental set-up by measuring the conversion of the acetic acid substrate and the yield of ethyl-acetate product at various carrier gas flow rates (2, 3, 4, 5 dm3h-1). in all cases the ratio of acetic acid and ethanol was 80:20 cm3cm-3 (3.86 gg-1), the amount of used enzyme was 11 g, and the temperature of the bioreactor and unit i were 50°c and 30°c, respectively. effect of temperature on the esterification reaction selection of the optimal reaction temperature and the investigation of the effect of temperature were realized by the determination of the acetic acid substrate conversion and ethyl-acetate product yield at different bioreactor temperatures (30°c, 40°c, 50°c, and 60°c). 41 the temperature of unit i was always higher than that of unit ii in order to avoid occasional condensation, and the temperature of unit i and iii were continuously detected. the ratio of acetic acid and ethanol was 80:20 cm3cm-3 (3.86 gg-1), the amount of used enzyme was 11 g, the carrier gas flow rate was 2 dm3h-1 and the experiments were 9 hours long, in all cases. effect of initial substrate composition on the esterification reaction effect of initial substrate composition was studied and the optimal substrate composition was selected by measuring the acetic acid conversion and the ethylacetate yield applying various acetic acid and ethanol ratios (80:20, 75:25, 65:35, 50:50, 25:75 in cm3cm-3). the amount of enzyme was 11 g, the carrier gas flow rate was 2 dm3h-1, the bioreactor and the substrate saturation temperatures were 50°c and 30°c, respectively. effect of the amount of enzyme on the esterification reaction experiments were carried out applying different amounts of novozym 435 lipase enzyme (3.7 g, 6.7 g, 11 g) to determine the effect of enzyme quantity on the ethyl-acetate production. temperature of the bioreactor was kept at 50°c, the n2 carrier gas flow rate was 2 dm3h-1, and the acetic acid and ethanol ratio was 80:20 cm3cm-3 (3.86 gg-1). calculation of the activation energy the activation energy of the reaction was calculated from the arrhenius-equation (eq. 1), and the logarithmic arrhenius-equation (eq. 2), where reaction rate is proportional to the activation energy. v = a × exp(-ea/rt), (1) ln v = ln a ea/rt. (2) where: a – arrhenius constant r – 8.314 (jmol-1k-1) ea – activation energy (jmol-1) t – temperature (k) results and discussion optimization of carrier gas amount ethyl-acetate yields and acetic acid conversions as a function of carrier n2 gas flow rate are represented in figure 2 and figure 3, respectively. figure 2: effect of carrier gas flow rate on ethyl-acetate yield as a function of time it can be seen that both higher conversion and yield can be achieved at lower flow rate, hence longer reaction time provided for the production of ethylacetate can be obtained. therefore, 2 dm3h-1 carrier gas flow rate was selected for further experiments. figure 3: effect of carrier gas flow rate on acetic acid conversion effect of temperature results of the experiments concerning the effect of temperature on the enzymatic esterification and the selection of the optimal reaction temperature are shown in figure 4 and figure 5. figure 4: effect of temperature on ethyl-acetate yield as a function of time fig. 3 shows that the amount of produced ethylacetate increases relatively fast at the beginning of the esterification until it reaches equilibrium, hence, the 42 curves follow the trend of enzymatic reactions. the system can be considered continuous after it reaches equilibrium, which happens approximately after 3–6 hours. figure 5: effect of temperature on acetic acid conversion it is reasonable that higher coversion and yield values belong to higher temperatures; the highest values were measured at 50°c, up till 60°c, where the enzyme activity decreased due to the temperature sensitivity of enzyme proteins. at the selected optimal temperature of 50°c quite high conversion was achieved and the yield of ethyl-acetate was higher than 110 mgdm-3h-1. effect of initial substrate composition the values of ethyl-acetate yield and acetic acid conversion in the case of different substrate mixture compositions are shown in figure 6 and figure 7. it is important to mention that due to the difference in the vapour pressure of the two substrate components (b.p. acetic acid = 11.8°c, b.p. ethanol = 78.4°c), higher amount of liquid acetic acid in the mixture would mean lower amount of acetic acid vapour and higher amount of ethanol vapour and vica versa. the exact values for the substrate composition in liquid and gaseous phases are shown in table 1. table 1: comparison of the initial substrate composition in liquid and gaseous phase ratio of substrates in liquid phase acac:etoh (cm3cm-3) ratio of substrates in gaseous phase etoh:acac (gg-1) 80:20 2.0 ± 0.04 75:25 3.5 ± 0.05 65:35 1.0 ± 0.03 50:50 0.9 ± 0.05 25:75 0.2 ± 0.06 figure 6: effect of initial substrate composition on ethyl-acetate yield as a function of time figure 7: effect of initial substrate composition on acetic acid conversion in fig. 6 it can be seen that the enzymatic esterification has reached equilibrium independent of the initial substrate composition. in the case of 25:75 acetic acid and ethanol ratio, there was so small amount of acetic acid vapour in unit i that the reaction started only after one hour reaction time. the highest conversion and yield values were obtained by the experiment in which the acetic acid and ethanol ratio of 75:25 mlml-1 was used, hence this value is considered to be the optimal initial substrate ratio. the highest conversion values are obtained for 75:25 liquid acetic acid and ethanol ratio, while the lowest value belongs to its opposite, the ratio of 25:75. this can be explained by the fact that the substrate mixture has inhibition effect on the enzymatic reaction mainly caused by acetic acid. therefore, the lower is the acetic acid vapour proportion in the bioreactor is, the less significant of inhibition and more efficient the enzymatic reaction will be. effect of the amount of enzyme the effect of the used enzyme quantity on the conversion is shown in figure 8 and on the yield of ethyl-acetate product is represented in figure 9. 43 figure 8: effect of the amount of enzyme on ethylacetate yield as a function of time figure 9: effect of the amount of enzyme on acetic acid conversion although both the conversion and yield results showed an increase with the increase in the amount of enzyme, it is quite surprising to note that there is only a small difference between the conversion values for 3.7 g and 6.7 g of enzymes, while the conversion was more than four times higher when the amount of enzyme was increased from 6.7 g to 11 g. probably, further enzyme addition would further increase the conversion and the product yield but taking the relatively high price of the enzyme into account, further enzyme addition was not studied due economical considerations. calculation of the activation energy the calculated activation energy of the gas-solid phase ethyl-acetate production reaction was ea = 9.2 kjmol-1, which is in good agreement with the value reported by perez [12]. our result and activation energies determined for the same esterification reaction in other reaction media are summarized in table 2. it can be seen that our result is lower than the ones found in the corresponding literature. therefore, it can be stated that the studied enzyme catalyzed esterification reaction can be carried out more easily and efficiently in gas phase than it other reaction media due to the much more effective mass transfer, low viscosities, and high diffusion coefficients in the gas phase. table 2: activation energy of esterification in different reaction media reaction media activation energy (kjmol-1) solid-gas phase 9.2 [bmim][pf6] ionic liquid [22] 21.7 n-hexane [23] 30.6 solvent-free system [23] 52.9 conclusion in this work, first the candida antarctica lipase b enzyme catalyzed esterification of ethyl-acetate from acetic acid and ethanol was investigated in a self-designed and selfconstructed continuous gas-solid phase system. then, the effect of temperature, enzyme quantity, and initial substrate composition on the conversion of acetic acid and on the yield of ethyl-acetate was determined and the activation energy of the biocatalytic reaction was calculated. it was found that both conversion of acetic acid substrate and yield of ethyl-acetate increased with the increase of temperature and the amount of enzyme and that there was no such linear correlation between these values and the initial substrate ratio. the optimal reaction conditions were found to be described by the following parameters: flow rate of n2 carrier gas: 2 dm3h-1, temperature in the bioreactor: 50°c, amount of used enzyme: 11 g, initial acetic acid and ethanol substrate ratio: 75:25 mlml-1. the activation energy was found to be ea = 9.2 kjmol-1, which is much lower than that of the same reaction carried out in other reaction media. therefore, it can be stated that it is easier and much more effective to carry out this type of enzymatic esterification in the gas-solid phase bioreactor constructed and studied by our research group. references 1. r. bigelis: flavor metabolites and enzymes from filamentous fungi, food technology, 46 (1992) pp. 151–158 2. w. bluemke, j. schrader: integrated bioprocess for enhanced production of natural flavors and fragrances by ceratocystis moniliformis. biomolecular engineering, 17 (2001) pp. 137–142 3. m. karra-chaabouni, h. ghamgui, s. bezzine, a. rekik, y. gargouri: production of flavour esters by immobilized staphylococcus simulans lipase in a solvent-free system, process biochemistry, 41 (2006) pp. 1692–1698 44 4. u. krings, r. g. berger: biotechnological production of flavours and fragrances, applied microbiology and biotechnology, 49 (1998) pp. 1–8 5. e. alvarez-macarie, j. baratti: short chain flavour ester synthesis by a new esterase from bacillus licheniformis, journal of molecular catalysis b: enzymatic, 10 (2000) pp. 377–383 6. j. s. dordick: enzymatic catalysis in monophasic organic-solvents. enzyme and microbial technology, 1 (1989) pp. 194–211 7. s. cantone, u. hanefeld, a. basso: biocatalysis in non-conventional media-ionic liquids, supercritical fluids and the gas phase, green chemistry, 9 (2007) pp. 954–971 8. t. debeche, c. marmet, l. kiwi-minsker, a. renken, m. a. juillerat: structured fiber supports for gas phase biocatalysis, enzyme and microbial technology, 36 (2005) pp. 911–916 9. c. ferloni, m. heinemann, w. hummel, t. daussmann, j. buchs: optimization of enzymatic gas-phase reactions by increasing the long-term stability of the catalyst, biotechnology progress, 20 (2004) pp. 975–978 10. s. lamare, m. d. legoy: working at controlled water activity in a continuous process – the gassolid system as a production, biotechnology and bioengineering, 45 (1995) pp. 387–397 11. v. leonard, s. lamare, m. d. legoy, m. graber: enantioselective acylation of r-2pentanol in a solid/gas reactor catalysed by lipase b from candida antarctica, journal of molecular catalysis b: enzymatic, 32 (2004) pp. 53–59 12. b. major, n. nemestóthy, k. bélafi-bakó, l. gubicza,: enzymatic esterification of lactic acid under microwave conditions in ionic liquids, hungarian journal of industrial chemistry 36 (2008) pp. 77–81 13. t. bányai, k. bélafi-bakó, n. nemestóthy, l. gubicza: biolubricant production in ionic liquids by enzymatic esterification, hungarian journal of industrial chemistry 39 (2011) pp. 395–399 14. v. h. perez, e. a. miranda, g. p. valenca: kinetics of gas-phase hydrolysis of ethyl acetate catalyzed by immobilized lipase, applied biochemistry and biotechnology, 136 (2007) pp. 23–37 15. i. goubet, t. maugard, s. lamare, m. d. legoy: role of water activity and temperature on activity and stability of dried whole cells of saccharomyces cerevisiae in a continuous solid-gas bioreactor, enzyme and microbial technology, 31 (2002) pp. 425–430 16. e. barzana, a. m. klibanov, m. karel: enzymecatalyzed, gas-phase reactions, applied biochemistry and biotechnology, 15 (1987) pp. 25–34 17. r. mikolajek, a. c. spiess, j. buchs: feasibility of gas/solid carboligation: conversion of benzaldehyde to benzoin using thiamine diphosphatedependent enzymes, journal of biotechnology, 129 (2007) pp. 723–725 18. a. spiess, r. mikolajek, m. pohl, s. lamare: enantioselective enzymatic carboligation using thiamine diphosphate dependent enzymes in a solid/gas bioreactor, journal of biotechnology, 131 (2007) pp. 92–93 19. s. o. hwang, y. h. park: gas phase ethyl acetate production in a batch bioreactor, bioprocess engineering, 17 (1997) pp. 51–54 20. f. letisse, s. lamare, m. d. legoy, m. graber: solid/gas biocatalysis: an appropriate tool to study the influence of organic components on kinetics of lipase-catalyzed alcoholysis, biochimica et biophysica acta – proteins and proteomics, 1652 (2003) pp. 27–34 21. t. maugard, s. lamare, m. d. legoy: gas phase biotransformation reaction catalysed by baker’s yeast, biotechnology and bioengineering, 73 (2001) pp. 164–168 22. l. gubicza, k. bélafi-bakó, e. fehér, t. frater: waste-free process for continuous flow enzymatic esterification using a double pervaporation system, green chemistry, 10 (2008) pp. 1284–1287 23. k. bélafi-bakó, a. k. badr, n. nemestóthy, u. ehrenstein, l. gubicza: kinetics of ethyl acetate formation by lipase in organic solvent and solventfree system, chemical paper, 57 (2003) pp. 278–281 microsoft word contents.doc hungarian journal of industrial chemistry veszprém vol. 34. pp. 15-20 (2006) quasi-continuous elution chromatographic purification of a steroid active compound k. temesvári1, , a. aranyi1, z. horváth1, m. nagy2, t. szánya2 and l. hanák2 1gedeon richter ltd., h-1475 budapest 10. po box 27. hungary; e-mail: k.temesvari@richter.hu 2university of pannon, department of chemical engineering pob 158, veszprém, h-8201, hungary a pilot-scale preparative batch elution chromatographic separation of a steroid active compound from its impurities was developed and is applied at our company. the process consists of the following steps: (1.) injection of the crude sample solved in the eluent onto the chromatographic column, (2.) elution of the less retained impurities with the eluent, (3.) elution of the pure fraction of the active compound (main fraction) with the eluent, (4.) back-flushing the column with the more polar solvent component of the eluent to remove the strongly retained compounds, (5.) conditioning the column with the eluent to prepare for the next injection. the above mentioned five-step chromatographic process can be realized quasi-continuously by applying the simulated moving bed (smb) instrument. the subsequent steps can be carried out in parallel in the zones of the smb unit, which are independent from each other in this special case. in our present paper the elaborated quasi-continuous elution chromatographic separation is shown using the following instrument set up and experimental conditions: a knauer csep 9116 laboratory-scale smb unit with five knauer k-501 hplc pumps and eight columns (column dimension: 250x16 mm i.d.). the columns were packed in our laboratory by dry-packing method using vibration, the applied packing material was uetikon c-490 15-35 μm si gel. the appropriate eluent was methylene chloride/ethyl acetate mixture and as back-flushing solvent, pure ethyl acetate was used. after the elaboration of quasi-continuous elution chromatographic purification, the intensification of the process was carried out. the specific capacity parameters of the best quasi-continuous experiments were compared with the performance parameters of the current batch pilot-scale separation of the compound. keywords: quasi-continuous, pilot-scale, preparative chromatographic separation, steroid, simulated moving bed (smb) introduction in pharmaceutical industry there is a strict demand on the quality of active compounds. in most cases the amount of all impurities must be under 0.5-1 %, the maximum level of individual impurities had to be under 0.1 %. in many cases these demands can not be fulfil with traditional techniques, such as distillation or crystallization. pilotand process-scale preparative chromatographic processes can solve these difficult separation problems. [1] the preparative chromatographic processes can be divided into batch and continuous methods, depending on the actual separation task. in some cases these techniques can compete with each other. [2-5] the application areas of continuous counter-current separation methods are chiral, isomer, or other twocomponent (or pseudo two-component) separation problems. [6-11] the simulated moving bed (smb) technology is the up-to-date solution for the practical realization of continuous, counter-current preparative chromatographic processes. it was invented and patented in the late 1950’s and was mainly applied in the petrochemical and sugar industries for large-scale separations. smb has been introduced in the pharmaceutical industry since the 1990’s. [12] the principle of the technique has been described in numerous publications [13-15]. the essence of the process is that instead of the continuous transportation of the particulate solid phase, which leads to a lot of difficulties, (bad efficiency because of high hetp and mechanic problems with transportation of the solid phase) the moving of the solid phase in packed columns is simulated. this simulated moving can be solved either by switching the inlets and outlets co-current with the liquid flow direction, or by the real rotation of the packed columns, connected to special distributing valves. (fig. 1.) in the smb process the strong (s, more retained) and weak (w, less retained) components of the feed (f) of concentration cf,s and cf,w are separated into two outlet flows. in the extract (e, ce,s, ce,w) the better adsorbing strong, while in the raffinate (r, cr,s, cr,w) the less adsorbing weak components are enriched, respectively. (fig. 2.) in purification tasks there are usually one (or some more) main compounds in the presence of numerous impurities of small amount. in such cases smb is generally not applicable, mainly preparative batch elution techniques are used. [16-19] 16 fig. 1: conventional four-zone smb unit with eight columns the conventional smb instrument set-up can be utilized to solve a batch elution chromatographic purification task quasi-continuously, if an astute assembling mode of the available unit is applied. in this present study the quasi-continuous implementation of a current pilot-scale batch elution purification of a steroid active compound is shown. the process consists of the following steps: (1.) injection of the crude sample solved in the eluent onto the chromatographic column, (2.) elution of the less retained impurities with the eluent, (3.) elution of the pure fraction of the active compound (main fraction) with the eluent, (4.) back-flushing the column with the more polar solvent component of the eluent to remove the strongly retained compounds, (5.) conditioning the column with the eluent to prepare for the next injection. the subsequent steps can be carried out in parallel in the zones of the smb unit, which are independent from each other in this special case. the implementation of quasi-continuous process starting from usual smb instrument set-up the conventional smb unit has four zones as can be seen in fig.1. and fig.2. fig. 2.: one of the applied practical solutions of the simulated moving bed it is possible to carry out the above-mentioned actual five-step batch elution chromatographic purification procedure quasi-continuously in these zones with the help of the rotating switching valve of the smb instrument. as in our special case the zones are independent from each other, they can be decomposed to six parts and the flow rate can be reversed in zone i, as fig. 3 shows. fig. 3.: quasi-continuous operation with the help of rotating switching valve of the smb unit the minimum number of columns required in the process is eight and in every second position an empty short capillary is inserted in the unit. one column and one empty position move together to the next position in every switching. with the knowledge of the solvent volumes necessary to the subsequent steps of the separation, the switching time of the rotating smb valve and flow rates of the pumps in the zones can be calculated. the main steps of the elaboration of the quasicontinuous process are: (a.) preliminary elution experiment on one of the eight 250x16 mm i.d. columns used in the smb unit for quasi-continuous elution separation, for the determination of the solvent volumes necessary to the steps of the separation. from these data the switching time of the rotating smb valve and the pump flow rates can be calculated. (b.) carrying out a quasi-continuous experiment applying the calculated parameters. (c.) refining the process parameters in experimental way. (d.) improvement the productivity by decreasing the switching time and proportionally increasing the flow rates of the pumps at the same time. experimental the problem under investigation was the solution of quasi-continuous elution chromatographic purification of a steroid active compound, produced by gedeon richter ltd. the starting point of the investigation was the pilot-plant batch elution chromatographic separation of the compound from its impurities, followed by a crystallisation step (not published here). this procedure has been applied successfully for years. the purity of the crude material was 94 % for the active compound. the goal was to produce the active compound with a purity of >99 %, the maximum level of individual impurities had to be under 0.3 %. 17 chemicals uetikon c-490 15-35 μm si gel was used as the stationary phase, it was purchased from zeochem ag (switzerland). the mobile phase was methylene chloride/ethyl acetate mixture. the back-flushing solvent was pure ethyl acetate. solvents were purchased from merck kgaa (darmstadt, germany). instrumentation preliminary elution experiment the applied instrument consisted of a knauer k-501 hplc pump, the volumetric flow rate was set to 5 ml min-1, one of the eight 250x16 mm i.d. columns used in the smb unit for quasi-continuous elution separation, packed with uetikon c-490 15-35 μm si gel packing material in our laboratory by dry-packing method using vibration, and a knauer uv/vis filter photometer. the wavelength of the measurement was 254 nm. for the purpose of recording the chromatogram a radelkis oh-850 potentiometric recorder was applied. the temperature was set to 25 ˚c. quasi-continuous experiments a laboratory-scale smb unit (knauer csep 9116) was used for the quasi-continuous elution experiments with five knauer k-501 hplc pumps and eight columns. the columns were packed in our laboratory by dry-packing method, using vibration, as we described above. (column dimension was 250x16 mm i.d.). the uniformity of columns was tested by elution investigations, injecting pure active compound on the columns and eluting it with the eluent. in the zone of the pure main fraction a knauer uv/vis filter photometer was connected. the wavelength was set to 254 nm. for the purpose of recording the successive chromatograms a radelkis oh-850 potentiometric recorder was applied. the temperature was set to 25 ˚c. (see fig. 4.) fig. 4.: knauer csep 9116 smb unit assembled for quasi-continuous process analytical method applied for the quality control of the separation the quality control of the purified active compound was performed by a validated analytical chromatographic method, which is applied for the time being in the current manufacturing process of the product. preliminary elution experiment before beginning the experiment, the column was equilibrated with the eluent. the injected sample amount was 0.32 g of crude material, which was solved in 5 ml methylene-chloride. after the injection step, the elution of less retained impurities was started and seven fractions were collected, for the purpose of determination of the first cut point of the pure main fraction. the end cut point of the peak was not so critical, because a certain impurity of small amount, eluting in the tail of the active compound peak can be removed by the crystallization step, following the chromatography. that was the reason, why there was no fraction collection there. fig. 5.: chromatogram of the preliminary elution experiment when the elution of the main compound was finished, the back-flushing with ethyl acetate was started and continued until a stable baseline was achieved. at the end of the back-flushing, the column conditioning was carried out with twice of the column volume of the eluent. based on the pump flow rate and speed of the recorder, the solvent volumes, necessary to the subsequent steps of the separation could be calculated. (fig.5.) quasi-continuous elution experiments the switching time of the rotating smb valve was calculated based on the critical data of the preliminary elution experiment, such as the elution volumes of less retained impurities and the pure active compound. (see table 1.) the pump flow rates were set in accordance with the calculated switching time and the solvent volumes, necessary to the steps of the separation. 18 table 1: results of the preliminary elution experiment steps of the separation solvent volumes necessary to the subsequent steps of the separation (ml) elution of less retained impurities ≈105 elution of the pure active compound ≈84 back-flushing with ethyl acetate minimum 65 column conditioning twice of the column volume, minimum 100 the crude sample was solved in methylene-chloride, which was the weaker solvent component of the eluent. the compounds were adsorbed on the surface of packing material from this solution in a narrow band at the beginning of the columns, therefore the injected sample volume could be higher, in most cases exactly 10.5 ml. in this case the sample pump (p1) flow rate was set to 0.5 ml min-1, which was a reasonable value. in the quasi-continuous experiments the sample load was the same as in the preliminary elution experiment, namely 0.32 g of crude material. the exception was only the second experiment, in which the sample load was lower, exactly 0.29 g of crude material. the process parameters of the experiments are summarized in table 2. table 2: process parameters of quasi-continuous elution experiments flow rates of the pumps (ml min-1) experiment switching time (min) sample injection p1 elution of less retained impurities p5 elution of the pure active compound p4 backflushing p2 column conditioning p3 1. 21 0.5 5 4 4 3 2. 19 0.5 5 4 4 3 3. 21 0.5 4.7 4 4 3 4. 21 0.5 4.5 2.5 4 3 5. 21 0.5 4.5 3.2 4 3 6. 21 0.5 4.5 3.5 4 3 7. 21 0.5 4.5 3.5 4 3 8. 14 0.75 6.75 5.2 6 4.5 results and discussion results of the preliminary elution experiment the aim of this experiment was to determine the solvent volumes necessary to the steps of the separation. the received data can be seen in table 1. elaboration and intensification of the quasicontinuous process as we mentioned before, based on the critical data of the preliminary elution experiment, such as the elution volumes of less retained impurities and the pure active compound, (table 1.) the applied switching time was 21 min in the first experiment. in this first run the purity was very good, but the recovery was poor, because a significant part of the main fraction eluted in the zone of the less retained impurities. the reason of the deviation between the preliminary elution experiment and the first quasi-continuous run was the difference of the extra column volumes of the two systems in which the experiments were carried out. to improve the result of the first quasi-continuous run, two possible ways were tried: the first was the reduction of the switching time, but in this case the sample load and volumes of solvents in each zone were also decreased, therefore finding the optimal set of process parameters was difficult. (2. experiment in table 2.) • the other (easier) way was decreasing the flow rate in the zone of the less retained impurities. (3. experiment) fig. 6.: chromatograms of the pure main fractions eluted from successive columns 19 in the 4., 5. and 6. experiments the cut point at the end tail of the main fraction was optimized with varying the flow rate in the zone of the active compound for the purpose of keeping the recovery as high as possible and the level of the above-mentioned impurity under a certain limit, with respect to the cleaning effect of the crystallisation step. with the best process parameters a repetition was carried out. (7. experiment) in the final step (8. experiment) the productivity was increased with decreasing the switching time and proportionally increasing the flow rates at the same time. the last two runs, switching from parameter set of 7. experiment to the ones of 8. experiment, with two transient peaks can be seen in fig. 6. the reason of transients is that, when the experimental parameters were changed, the peak of the main fraction from the actually injected sample eluted after two switching. that is why the new valuable status was possible to see on the recorder after two transient peaks. the specific capacity parameters of 7. and 8. runs, in comparison with the pilot-plant batch elution separation are shown in table 3. table 3: the specific capacity parameters of 7. and 8. runs in comparison with the pilot-plant batch elution separation specific capacity parameters experiment specific solvent consumption methylene chloride (ml g-1) specific solvent consumption ethyl acetate (ml g-1) productivity [g (kg packing hour)-1] recovery (m m-1 %) batch elution pilot-scale 499.51 214.34 10.15 84.26 7. 836.02 409.97 4.11 86.85 8. 761.58 374.30 6.75 95.06 in the 8. experiment a higher recovery resulted a little bit higher level of impurities in the product, but the quality still met the requirements. conclusion the quasi-continuous elution chromatographic purification of a steroid active compound was possible to carry out successfully with the help of the rotating switching valve of a laboratory-scale simulated moving bed (smb) instrument. the quality of the product, gained at optimum operating conditions met the purity requirements (purity > 99 %, maximum level of individual impurities < 0.3 %). the main advantage of applying this quasicontinuous separation method is that the staff need for processing is less, than in case of batch elution chromatographic separation. fraction collector is not needed, because cutting is done automatically by switching the columns and the main fractions coming from successive columns can be pooled in one vessel. comparing the specific capacity parameters of the quasi-continuous process with the batch pilot-scale separation, the specific solvent consumption is higher and the productivity is lower. but mention must be made, that the number of columns applied in the smb instrument were eight instead of the necessary five because of the construction of the smb unit. the columns applied in the smb instrument were shorter than the pilot-scale column, so the theoretical plate number of these columns was considerably lower, therefore the specific sample load also had to be lower. (in case of pilot-scale column the specific sample load was 0.02 [g sample g-1 packing material], while in quasi-continuous process it was only 0.0143 [g sample g-1 packing material].) the robustness of the process demands the uniformity of columns inserted in the smb instrument. the change of temperature has strong impact on the adsorption behaviour of compounds, therefore transients in temperature can detrimentally influence the separation. symbols i.d. internal diameter f feed c concentration of the compounds r raffinate e extract l liquid recycle d fresh solvent p “recycle of the packing”, column switching time indices w less retained compound s more retained compound f feed r raffinate e extract 20 references 1. mann g. (1998) analusis 26 (7): 76-82 2. colin h. (1998) analusis 26 (7): 15-17 3. katti a. m., jagland p. (1998) analusis 26 (7): 38-46 4. a. seidel-morgenstern (1998) analusis 26 (7): 46-55 5. grill c. m., miller l., yan t. q. (2004) j chromatography a 1026: 101-108 6. nicoud r.-m. (1999) pharmaceutical technology europe 11: 36-44 7. charton f., nicoud r.-m. (1995) j chromatography a 702: 97-112 8. khattabi s., cherrak d. e., mihlbachler k., guiochon g. (2000) j chromatography a 893: 307-319 9. pedeferri m., zenoni g., mazzotti m., morbidelli m. (1999) chem eng sci 54: 37353748 10. lee h.-j., xie y., koo y.-m., wang n.-h. l. (2004) biotechnol prog 20: 179-192 11. santos m. a. g., veredas v., silva jr. i. j., correia c. r. d., furlan l. t., santana c. c. (2004) brazilian journal of chemical engineering 21 (1): 127-136 12. temesvári k., aranyi a., csukás b., balogh s. (2004) chromatographia suppl. 60: 189-199 13. nicoud r.-m., bailly m. (1992) proceedings of “prep 92”, nancy (france), 6-8 april, isbn 2905267-18-6: 205-220 14. blehaut j., nicoud r.-m. (1998) analusis 26 (7): 60-70 15. guiochon g. (2002) j chromatography a 965: 129-161 16. himbert f., pennanec r., guillaumet g., lafosse m. (2004) chromatographia 60: 269-274 17. yang x., liu k., xie m. (1998) j chromatography a 813: 201-204 18. zhang x., geoffroy p., miesch m., julien-david d., raul f., aoudé-werner d., marchioni e. (2005) steroids ‘in press’ 19. doi: 10.1016/j.steroids.2005.06.003 20. heitmann d., ziehr h., müthing j. (1998) j chromatography b 710: 1-8 microsoft word 01_r.doc hungarian journal of industrial chemistry veszprém vol. 35. pp. 57-64 (2007) batch analysis f. molnar1, t. chovan2, f. szeifert2, l. nagy2 1batchcontrol ltd, h-1043 budapest, dugonics u. 11., hungary 2university of pannonia, department of process engineering, h-8201 veszprém, p. o. box 158, hungary batch analysis is one of steps in the design and implementation of batch process plants – an s88 based – analysis of batch processes from the control point of view. it is between the conceptual design of the batch process (pfd or p&i) and the start of the design of the control system (design of instrumentation, control hardware and software). its objective is to fill the gap almost always found between the formulation of requirements and the specification of the actual implementation by transforming user requirements into “process-based” detailed functional requirements. it has several advantages when these problems are handled, not by software engineers, rather by batch control analysts who are closer to the plant and has deeper knowledge of the process. in former batch systems this problem was solved instinctively by the engineers developing control software based on their earlier experience. systematic design, however, allows finding an optimal or close to optimal solution in an easier and more manageable way. the method described in the paper is a new approach in batch engineering practice. its exact formulation was made possible by the introduction of the s88. 01 standard. the application of the proposed approach can bring several benefits, like optimal control structure, well-structured and shorter software code, reduced debugging needs, simplified design and implementation as well as increased system reliability. keywords: batch control, systematic approach, s88. 01 models introduction majority of pharmaceutical and fine chemical processes are accomplished in batch or fed-batch operations. batch processing involving the execution of several separate processing operations on a given amount of materials (batch) in a given order provides a great adaptability for rapidly changing market demands. while the control of batch processes carries much more difficulties than continuous processes do, present computer-based control systems and solutions allows efficient and flexible command of the batch production processes. at the same time, the design of batch control systems represents a rather complex problem for the process and control engineers [1-5]. batch analysis is the phase in the design of a batch process control installation that covers the analysis of the control problem, the structuring of the process and equipment, the distribution of tasks between control levels (basic control, procedural control, coordination control) and the design of the recipe operation library including the control of abnormal situations (exception handling) in order to achieve optimal control [6, 7]. in the plant construction process, batch analysis is between definition of the user requirements and the design of instrumentation, hardware, and software. it is aimed at filling the gap found between the definition of requirements and the actual implementation in almost every project. for example the user may define only the following: crystallization must be executed automatically. to implement this into the control software, the programmer has to decide whether unit approach or equipment module approach should be used to solve the problem. it is better if these questions are answered, not by software engineers, rather by batch control analysts who are closer to the plant and know the process better. batch analysis is system independent, which means, that recommendations are defined without any limitations of the actual system. in the following steps such a control system must be chosen that allows implementation of the control strategies elaborated during the batch control analysis. the original name of the method was batch analysis. since nowadays this term is used for the evaluation of executed batches, we introduced an extended name “batch control analysis” in order to emphasize the difference. we feel this name even more clearly reflects the content, i. e. the analysis of the process and production system for developing an optimal control strategy and control system. in the followings both batch analysis and batch control analysis is used in the same sense. design and implementation of batch processes the main steps of the construction of a batch processing system and their relations are represented in a simplified form on fig. 1 [8]. one of the important steps of this construction procedure is the batch analysis. the approach has been known in engineering practice for several years, however in spite of its significance it is 58 less widely applied. the main objective of the approach is to provide a clear pathway between the user requirements and the actual implementation. requirements defined by the user in the process descriptions do not contain the details necessary for configuring the dcs. it is desirable that this missing information be provided by a process expert – the batch analyst – who knows the process much deeper and better then the configuration expert who is more related to the informatics and control aspects. it is even better if the solution can be given in general form that is valid for other equipment as well, i. e. in form of strategies and basic principles, which could provide guidance for the instrumentation engineer as well as the hardware and software designer in other projects as well. figure 1: construction of a batch plant the batch analysis batch control analysis is one of steps in the design of plants executing batch process an s88-based analysis of batch process from the control point of view in order to reach an optimal control structure, decompose the process and equipment, divide the control functions between control levels (basic control, procedural control, coordination control), design the operation library and the operations themselves including the exception handling. it is between the conceptual design of the batch process (pfd or p&i) and the start of the design of the control system (design of instrumentation, control hardware and software). its objective is to fill the gap almost always found between the formulation of requirements and the specification of the actual implementation. it transforms user requirements into “process-based” detailed functional requirements. it has several advantages if these problems are handled, not by software engineers, rather by batch control analysts who are closer to the plant and know the process better. in former batch systems this problem was solved instinctively by the engineers developing control software based on their earlier experience. systematic design, however, allows finding an optimal or close to optimal solution in an easier and manageable way. the method described in the paper is a new approach in batch engineering practice. its exact formulation was made possible by the introduction of the s88. 01 standard [9-11]. a very important feature of batch control analysis is system-independence. it means that the results of batch control analysis are independent of the actual control system. a good control system will not restrict the implementation of the results. batch analysis must be launched in an early phase of construction process by deciding the control strategy to be applied (total automation, automated islands, etc.). in industrial practice, the tasks are allocated to the control experts only after the deciding fundamental process and machinery problems i. e. after fixing the concepts and topology of the plant. naturally, at this phase the benefits of batch analysis are limited. steps of batch analysis the batch control analysis consists of the following steps (see fig. 2): ● analysis of the process – a simplified description of the process for control purposes. ● decomposition of equipment – definition of hierarchy levels to be followed in the system (process and physical models). ● decomposition of tasks: design of elements of procedural control (procedural control model, library of phases and operations). choice of control structure at the basic level. ● list of instrumentation. ● specification of operator requirements. plan for construction requirements p&id batch analysis validation plan construction instrumentation design hardware design software design orders hardware test software module test system sw test commissioning system tests validation reports validation execution validation protocols 59 figure 2: steps of the batch control analysis process analysis the work is started from a general, brief process description. this document should include the followings: ● short description of the technological process, ● description of the most important operations, ● description of the main process units, ● description of the process chemistry, ● summary of the most important requirements for the process (e. g.: the necessity of high-accuracy temperature control), ● safety, health and environmental protection considerations. the role of process safety risk analysis must be emphasized here. it is definitely to be included in this step since it provides information significantly influencing the further design process. it is decisive in this phase that a simplified process diagram has to be available. it should show all the equipment essential from process control point of view (reactors, dryers, tank park, utilities, shared-use equipment). to avoid misunderstanding, a common terminology has to be agreed. nowadays the usage of the s88. 01 standard is a general requirement. structuring well-considered, well-done structuring makes further work significantly easier. bad compromises accepted during structuring will hit back. it is only a question of time and in some phase of the following work the poorly selected hierarchy will become unusable. it is not worthwhile to give up a decomposition justified by system engineering for illusory, short-range advantages. if structuring is too difficult to do or involves lots of compromises, it suggests that there are shortcomings in the previous design phase (e. g.: in the process or equipment concepts). the first step of structuring is the definition of the process model (see fig. 3). the process model as defined by isa s88 is a four-level hierarchical model composed of process/ process stages/ process operations/ process actions. the complete production process is first divided into process stages, then into process operations. this later one is not equivalent to a recipe operation. the only requirement is that process operations must allow describing the complete process. the process model will serve later as a basis for determining the necessary recipe operations. process process action process stage operation figure 3: the process model the practical use of the process model is very obvious. for illustration, fig. 4 depicts the representation and the use of the operations in the process model. process description user requirements control requirements process flow diagram man-machine interface instrument list actuators list operation library process analysis structuring procedural elements basic control structures list generation control strategy physical model process model process units 60 figure 4: the application of the process model the purpose of the application of each previous column is easily conceivable: code for reference (coordination links), process operation these operations will serve later as the basis for recipe operations, process measurement the following groupings: critical (influencing the quality), important for the process, informative and safety provides the requirements for the designer of the instrumentation. considerable cost reduction can be achieved by choosing suitable types of instruments. required manipulated element operations under automatic control require automatic manipulated elements. other special requirements, coordination requirements, etc. the second step is the definition of the physical model (fig. 5). the main function of the physical model is to define the relations of the process equipment unambiguously. the prerequisite for assuring transparency and order is that each element belongs to one and only one higher-level element. later on, the hierarchy of the control system will follow this model. every control module will be responsible for handling its own physical elements, therefore it must know which elements of the physical model are allowed to be manipulated directly and which are not. enterprise site area process cell control module unit equipment module figure 5: the physical model while the decomposition an intuitive procedure, several general rules can be applied. it must be assured in the structuring of the process system, that: ● functions must be clear and separable, ● they do not be tied to one product, ● it is practical that subordinate elements can accomplish their task independently in an asynchronous way in order to allow precise control for the higher level, ● the connections to other elements are minimized, ● its borders are clearly defined, ● in case of units a corresponding recipe should exist [12]. structuring an equipment group requires the basic knowledge of the supplementary operations. several control modules together can build an equipment module or another control module. the physical model has an important role in maintaining a clear naming and tagging convention, as well. the notation: process cell/ unit/ equipment module/ control module identifies any element of a system precisely. during the whole course of the construction of the process system all of the structuring and grouping steps should follow some of these models. for example, the process graphics can be organized according to the process model. the support system for maintenance tasks should follow the physical model, etc. references define recipe operations recipe formula instrumentation list define modes define manipulated elements code process operation parameters process measurement critical important informative safety process mode required manipulating element comments p1_1 acetone charging 111 l acetone fiqsaceton auto p1_2 water charging 222 l demiwater fiqwater auto p1_3 temperature setting 20 – 25 ºc titcareact ntcreactor ttcjack-in ttjack-out ptsjack auto 61 design of procedural elements procedural control is the most characteristic level of batch process control. it involves the execution of equipment-specific operations in a predetermined order to achieve the production objectives of the process. the procedural control applies the elements of the hierarchical procedural control model to accomplish the required control of the batch process. the procedural control model is shown in fig. 6. procedure phase unit procedure operation figure 6: procedural control model the procedure itself defines the strategy of the main process action. the strategy of final processing e. g. can be – solution, crystallization, centrifuging, drying. the unit procedure is an ordered sequence of the operations belonging to the unit. in case of a centrifuge procedure these are the filling, spinning, washing, spinning, and removal operations. the operation is the sequence of the main processing phases. the execution of an operation results in significant chemical or physical changes of the processed material leading to the required production objectives. the phases of the crystallization e. g. – filling, heat up, cooling and removal. the phase is the lowest level of procedural control (according to iec 488 it can be further divided into steps and transitions). the phase executes the process actions by commanding the operation of basic control level or other phases. the data collection is also accomplished during the phase execution. the phase execution provides commands for the control loops, moves the system to new state according to the statetransition diagram, changes the parameters, etc. the recipe operation is an element of isa s88 recipe model (recipe procedure/ unit-procedure/ operation/ phase). the recipe operation is a more generalized form of process operation, which can be used for a number of different processes. the relationship between process and recipe operations is illustrated in table 1. the library of recipe operations and recipe phases has to be developed during the batch control analysis. at this time required recipe procedural elements have to be generated from the elements of the process model in such a way that the procedural elements must be generic allowing the accomplishment of more process elements and thus allowing that the production task be defined by compiling a recipe from these elements. a few points of view for the development a recipe operation are the following: any process operation (phase) can be generated by assembling one or more recipe operations (phases) serially or parallel. functions used more than once have to be identified. the fewer and the simpler recipe operations required to cover the problem, the better the implementation will be. a simple method for reducing the number of operation is shown in fig. 7 and 8. the simpler available recipe operations are the more difficult is to build a recipe; however, the system will be more flexible. an optimum has to be found to reach the necessary flexibility with the most complex operations. the tool for fitting recipe operations to the actual process application is the use of recipe parameters. the more the available parameters there are, the more flexible the system will be, however at the same time, the more difficult it is to build a recipe and understand and explain an operation and its parameters. the recipe operation library is a collection of recipe operations from which the process engineer can build the master recipe. its content is expanding continuously. as new processing tasks emerge the library selection grows. the library contains also the operation descriptions which are used for developing the operations by the control and software engineers as well as when building a recipe by the process engineer. typical problems in the operation development are the following: very few and complex operations result in a less flexible system. operation parameters are used to solve discrete control functions of the basic control. the operation parameters should belong to the process engineer, not to the system integrator. 62 table 1: relationship of process and recipe operations process operation recipe operation ro no quick heat up quick cool down linear heat up linear cool down temperature hold thermal operations 01 refluxing reflux 09 solvent removal evaporation atmospheric distillation 04 solvent removal in vacuum evaporation in vacuum vacuum distillation 05 solvent charging water charging liquid charging 16 solid charging solid charging 17 inertization inertization 10 filling from drum filling 12 discharging into drum discharging to incinerator discharging by pump circulation discharging 13 transfer into other unit transfer 18 figure 7: tank constructions (they are not identical) fig. 7. shows four different tank constructions. none of them is the same. however the similarity of them is striking. instead of developing the individual operations (filling, discharging, homogenization, inertization, etc.) for the four different tank arrangements, one single virtual tank is formed as a superstructure of the four vessels (fig. 8). in the next step one set of operations is developed and the deviations are handled in the software. feed1 tank farm nitrogen feed1 feed2 tank farm nitrogen feed1 tank farm regeneration nitrogen feed1 tank farm regeneration nitrogen 63 feed1 feed2 tank farm regeneration nitrogen figure 8: virtual tank design of the basic control structures the necessary basic control elements are implicitly defined in the procedural control (valve operations, motor operations, etc.). a well-tried practical approach for solving similar problems is developing typical (standard) solutions, then testing them and finally applying them repeatedly. an important phase of the design process is the design of interlocks. these will assure the a basic level of process safety to prevent accident triggered by the errors of the higher level, more complex and therefore less reliable software elements. these interlocks provide the safety functions at lowest level, close to the process equipment. they also support the safe operation in manual-mode in case of operator interventions. the batch operation requires the understanding and implementation of procedural interlocks which operate only in the active state of the corresponding procedural elements. list of instruments and manipulated elements after defining the operations and the basic control requirements for the instrumentation (i. e. what kind of measurements and manipulating elements are necessary from process point of view) and their importance with respect to the process (critical, important, informative, safety, etc.), each instrument can be defined. therefore the necessary elements of the loops can be designed and selected optimally considering functionality and cost aspects. definition of operator requirements at this phase, based on the ratio of automatic and manual modes (given in the mode column of the process model definition), the operator requirements and the corresponding human-machine interface for the field and control-room operations can be designed. the more manual activities are involved the more complex field hmi is required. it must be decided here that how many operators will operate the plant, how many operator stations will be necessary, what is the function of each station (which consol is allocated for each particular process system), who is responsible for a given section of the system. the structure of displays, i. e. the system of operator displays as well as the tree-diagram for the display transitions must be designed. to provide a unified display system, standards are to be developed for colour coding, equipment symbols (equipment library) and for the general layout of the displays (template). the operator messages must be prioritized. they can be: alarm messages – standard functions are usually available, warnings – a typical warning e. g. is a message of exceeding the planned operation time, call for acknowledgement – e. g. for continuing a recipe. summary engineering approaches similar to that of batch control analysis were necessary in the past as well, of course. engineers developing the control system did this work instinctively based on their earlier experience. systematic design – based on the batch control analysis – however, makes the engineering design simpler, more effective and more straightforward to achieve an optimal or close to optimal solution. according to our experience, in many cases the control software of systematically structured systems is shorter by 50 % than that of instinctively structured solutions. the method reduces not only programming efforts but also the number of software errors by the same ratio, and it results in a system which is simpler to start-up and is more reliable with a much lower number of abnormal occurrences coming from software. it is also not negligible that batch control analysis provides control and process engineers with much deeper knowledge of the process. that has an advantageous effect throughout the design and implementation of the new batch processes. references 1. dixon-decleve s.: world refining, 2001, 12(9), 8 2. fisher g. t.: batch control systems: design, application and implementation, isa, north carolina, 1990 3. liptak b. (ed. ): instrument engineer's handbook, process control volume, chilton book company, 1995 4. ravemark d. e. , rippin d. w. t.: optimal design of multi-product batch plant, comp. chem. eng. , 1998, 22, 177-183 5. reaklaitis g. v.: overview of scheduling and planning of batch process operations, proc. natoasi on batch processing systems engineering, 1992 64 6. thomas g. f.: batch control system: design, application, and implementation, isa, 1990 7. molnar f., chovan t.: integration of package units, wbf european conference, brussels, 2000 8. molnar f, chovan t., nagy t.: batch control analysis, wbf european conference, mechelen, 2002 9. molnar f.: batch analysis (in hungarian), magyar elektronika, 1999, 06, 18-12 10. isa-s88. 01-1995 batch control. part 1: models and terminology, internal society for measurement and control, 1995 11. brandl d.: s88. 01 the standard for flexible manufacturing and batch control, white paper, sequencia corporation 12. verwater-lukszo z.: a practical approach to recipe improvement and optimization in the batch processing industry, computers in industry, 1998, 36, 279-300 13. parsall j., lamb l.: applying s88 – batch control from a user’s perspective, isa, 2000 hungarian journal of industry and chemistry vol. 43(2) pp. 55-66 (2015) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2015-0010 some analytic expressions for the capacitance and profiles of the electric double layer formed by ions near an electrode douglas henderson ∗ department of chemistry and biochemistry, brigham young university, provo, utah 84602, usa the electric double layer, which is of practical importance, is described. two theories that yield analytic results, the venerable poisson-boltzmann or gouy-chapman-stern theory and the more recent mean spherical approximation, are discussed. the gouy-chapman-stern theory fails to account for the size of the ions nor for correlations amoung the ions. the mean spherical approximation overcomes, to some extent, these deficiencies but is applicable only for small electrode charge. a hybrid description that overcomes some of these problems is presented. while not perfect, it gives results for the differential capacitance that are typical of those of an ionic liquid. in particular, the differential capacitance can pass from having a double hump at low concentrations to a single hump at high concentrations. keywords: electric double layer, capacitance, gouy-chapman-stern theory, mean spherical approximation, density functional theory, computer simulation 1. introduction a double layer (dl) or an electric double layer (edl) is formed when charged particles are attracted to a charged surface. the most obvious case is an electrolyte near a charged electrode (as in a battery). however, dna can play a role that is analogous to the electrode. ions can be attracted to membranes. a membrane can be thought of as a pseudo electrode. ions are absorbed (often selectively) into physiological channels in membranes. such channels permit the transport of nutrients into the cell and the removal of waste from the cell and are essential to the functioning of cells and life. the reader’s attention is drawn to some recent reviews of edls [1–3]. it is the case of an electrolyte near a charged flat surface that is considered here. this is the simplest case; it is an interesting and important application of statistical mechanical theory. the theory of the dl is important to our understanding of batteries. it can be used in the analysis of experimental electrochemical data and in analytical chemistry. in the model dl that is presented here, the electrode is approximated as a smooth flat charged surface located at x = 0. this surface is impenetrable and the ions are confined to the region x > 0. the charge of the electrode is located on the surface. there is no charge inside the electrode (x < 0). the electric field does not penetrate the surface. the electrode is a classical metal. obviously, this is an approximation but there has been very ∗author for correspondence: doug@chem.byu.edu little work that takes into account the electronic structure of the electrode. the electrode charge is presumed to be uniform; the charge density of the electrode is σ and has the units of c/m2. ions in the electrolyte near an electrode that have a charge opposite to that of the electrode are attracted to the electrode and form a layer whose net charge is equal in magnitude, but opposite in electric sign, to the charge of the electrode. the electrode and the attracted charge are together called an edl. the charge in the edl of the electrolyte can be spread over an extended region, usually called the diffuse layer, and need not consist solely of counterions whose charge is opposite to the electrode charge. the counterions can bring some coions with them. there may be regions of alternating charge where the coions predominate. however, the net charge of the attracted charged region in the electrolyte is equal in magnitude but opposite in sign to that of the electrode. otherwise, the electric field would not vanish far from the electrode. for simplicity, the model electrolyte that is employed here is a fluid of charged hard spheres of diameter d. in this study, the electrolyte is assumed to be binary. for additional simplicity, the ions are assumed in this article to be symmetric both in the magnitude of their charge and diameter. the value of the charge of an ion of species i is zie, where zi is the ion valence and has the sign of the ion charge. the magnitude of the elementary charge is e. because the ions are symmetric, |zi| = z. in the bulk, the density of the ions of species i is ρi = ni/v, where ni is the number of ions of species i in the bulk 56 henderson and v is the volume of the system. electrical neutrality requires that n1 = n2 or ρ1 = ρ2 or ∑ ziρi = 0. the solvent (usually water) of the electrolyte is characterized by a dielectric constant, ε. any change of the dielectric constant with a change of ion concentration is ignored. this model electrolyte is appropriately called the primitive model (pm). in the particular case considered here, where the ions all have the same diameter, this model is called the restricted primitive model (rpm). in this model, the interaction between a pair of ions, whose centers are separated by the distance r, is given by uij(r) =  ∞ for r < d zizje 2 4πε0εr for r ≥ d , (1) where ε0 is the permittivity of free space, and the interaction of an ion with the surface is given by uwi(x) = { ∞ for x < d/2 −σziex ε0ε for x ≥ d/2 , (2) where x is the distance between the center of the ion and the surface. our task is to determine the density profile, ρi(x), of the ions, or equivalently, gi(x) = ρi(x)/ρi. note that ρi(∞) = ρi, so that gi(∞) = 1. once, the gi(x) are known, the charge profile (c/m2), for x > d/2, is given by q(x) = e ∑ i ziρihi(x), (3) where hi(x) = gi(x) − 1. in writing eq. 3, the global charge neutrality condition ∑ ziρi = 0 has been invoked. the charge density on the electrode is given by σ = −e ∑ i ziρi ∫ ∞ d/2 hi(t)dt. (4) there is no point including the region 0 < t < d/2 in the integral since ∑ hi(t) = 0 in this region. the potential profile (in volts) is given by φ(x) = − e εε0 ∑ i ziρi ∫ ∞ x (t− x)hi(t)dt. (5) in particular, the potential (volts) of the electrode is given by v = φ(0) = − e εε0 ∑ i ziρi ∫ ∞ 0 thi(t)dt. (6) note that these equations satisfy poisson’s equation d2φ(x) dx2 = −q(x) εε0 . (7) indeed, eqs. 3 and 5 are obtained by integrating poisson’s equation. an alternative procedure for computing the potential profile has been proposed by boda and gillespie [4] for simulation purposes. it is often convenient to use dimensionless, or reduced, values that are denoted by an asterisk. for a system whose temperature (k) is t , the reduced temperature is t ∗ = 4πεε0dkt/z 2e2. the reduced density is ρ∗i = ρid 3, the reduced electrode charge density is σ∗ = σd2/e, and the reduced potential is φ∗ = βeφ, where β = 1/kt , with k being the boltzmann constant (the gas constant per particle). 2. poisson–boltzmann or gouy–chapman–stern theory: comparison with simulations the classic theory of the edl was developed by gouy [5], chapman [6], and stern [7] (gcs) a century ago. the theory is based on poisson’s equation together with the boltzmann formula, gi(x) = { 0 x < d/2 exp[−βzieφ(x)] x ≥ d/2 . (8) in electrostatics, poisson’s equation is exact and is equivalent to one of maxwell’s equations. the boltzmann formula is approximate and neglects ion size and correlations between the ions. eq. 8 states that gi(x) for the coions is the reciprocal of gi(x) for the counterions. this is not true, in general [8]. equation 8, when inserted into poisson’s equation, yields what may be called the poisson-boltzmann (pb) or gcs approximation. this approximation is also employed in the debye-hückel (dh) theory for bulk electrolytes that was developed some years later. however, because of the three dimensional geometry of the dh theory, the nonlinear pb equation cannot be solved analytically and the pb equations in the dh theory are usually linearized. in the gcs theory, the resultant pb equation is a nonlinear second order differential equation. as has been pointed out, such equations generally do not yield analytic solutions. however, for the one dimensional geometry of the planar dl that is considered here, an analytic solution is possible in the case of the gcs theory. the resulting pb/gcs potential is βzeφ(x) 2 = ln { 1 + b/2 1 + √ 1 + b2/4 exp[−κy] } − ln { 1− b/2 1 + √ 1 + b2/4 exp[−κy] } , (9) where y = x− d/2 > 0 and b = βzeσ εε0κ , (10) where κ is the debye screening parameter that is given by κ = √ βz2e2ρ εε0 (11) hungarian journal of industry and chemistry double layers near an electrode 57 with ρ = ∑ ρi. the parameter b is another dimensionless measure of the electrode charge density. however, it is not as fundamental a quantity as σ∗ since it arises from a theory. the parameter κ is a screening parameter; it is an inverse measure of the distance over which the profiles reach their asymptotic values within the gcs and dh theories. in the gcs theory the relationship between the potential difference and electrode charge density is given by sinh [ βzeφd/2 2 ] = b 2 , (12) where φd/2 = φ(d/2) is often called the diffuse layer potential. some relations that are equivalent to eq. 12 are cosh [ βzeφd/2 2 ] = √ 1 + b2/4, (13) tanh [ βzeφd/2 2 ] = b/2√ 1 + b2/4 , (14) and tanh [ βzeφd/2 4 ] = b/2 1 + √ 1 + b2/4 . (15) the equivalence of eqs. 12–15 is a result of identities among the hyperbolic functions. thus, eq. 9 can be written as βzeφ(x) 2 = ln { 1 + tanh [ βzeφd/2 4 ] exp(−κy) } − ln { 1− tanh [ βzeφd/2 4 ] exp(−κy) } . (16) alternative forms of eqs. 9 and 16 are tanh [ βzeφ(x) 4 ] = tanh [ βzeφd/2 4 ] exp(−κy) (17) or tanh [ βzeφ(x) 4 ] = b/2 1 + √ 1 + b2/4 exp(−κy). (18) in the gcs theory, the potential difference across the edl is v = − ze εε0 ∑ i ρi ∫ ∞ 0 thi(t)dt = σd 2εε0 + φd/2, (19) where φd/2 is given by eq. 12. thus, the capacitance, c = σ/v , of the edl is 1 c = d 2εε0 + 2 sinh−1(b/2) εε0κb (20) and the differential capacitance, cd = ∂σ/∂v , of the edl is given by 1 cd = d 2εε0 + 1 εε0κ √ 1 + b2/4 . (21) equations 20 and 21 are formally identical to a diffuse layer capacitor with capacitance, cdl = εε0κ b/2 sinh−1(b/2) , (22) or differential capacitance cdl d = εε0κ √ 1 + b2/4 (23) in series with an inner–layer parallel plate capacitor with capacitance (or differential capacitance), c il = c il d = 2εε0 d . (24) at contact, gi(d/2) = exp[βzieφd/2] = 1 + b2 2 − zi z b √ 1 + b2 4 , (25) so that gsum(d/2) = 1 2 [g1(d/2)+g2(d/2)] is, in the gcs theory, given by gsum(d/2) = 1 + b2 2 . (26) this is to be compared with the exact result (for the restricted pm) due to henderson and blum [9] and henderson, blum, and lebowitz [10], gsum(d/2) = p ρkt + b2 2 , (27) where p is the osmotic pressure of the electrolyte. the second term in the above equation is just the maxwell electrostatic stress. thus, eq. 27 is just a force balance condition where the momentum transfer to the electrode is equal to the sum of the osmotic term and the maxwell stress. the gcs theory deals with the electrostatic term correctly but replaces the osmotic pressure with the ideal gas result p = ρkt because of the neglect of the ion diameters. for comparison with the mean spherical approximation (msa), which is a linear response theory that will be considered in the next section, it is worthwhile to give the linearized gcs theory results, obtained for the case of small electrode charge. in this case, gi(x) = { 0 for x < d/2 1− βzieφ(x) for x ≥ d/2 , (28) or gi(x) =  0 for x < d/2 1 + βzieσ εε0κ exp (−κy) for x ≥ d/2 . (29) the potential profile in the diffuse layer is given by φ(x) = φd/2 exp(−κy) (30) with φd/2 given by φd/2 = σ εε0κ . (31) 43(2) pp. 55-66 (2015) doi: 10.1515/hjic-2015-0010 58 henderson 0.00 0.01 0.02 0.03 0.04 (c d dl ) -1 [cm 2 /µf] 0.02 0.03 0.04 0.05 0.06 0.07 c d -1 [ c m 2 /µ f ] -8 -4 -2 0 2 4 8 figure 1: experimental values of the inverse differential capacitance,cd, of an aqueous solution of nah2po4 at 25 ◦c near a hanging drop mercury electrode as a function of the inverse diffuse layer capacitance, cdl d , obtained from eq. 23. the points are the experimental results of parsons and zobel. the light straight lines of unit slope give the results of the gcs theory but with the experimental inner layer capacitance obtained empiricially. the numbers at the low concentration end of the lines give the electrode charges in units of µccm−2. the heavy solid curve gives the results of the msa using a dipolar hard sphere model for the solvent together with an estimate of the contribution of the electronic structure of the electrode and is intended only as an aid to the eye. this figure has been reproduced, with permission, from ref. [1]. the potential difference across the edl is v = σd 2εε0 + σ εε0κ (32) and the capacitance (and differential capacitance) of the edl is given by 1 c = d 2εε0 + 1 εε0κ . (33) in the gcs theory, in the limit of large κ (high concentration) or large b (high electrode charge), the diffuse layer capacitance is large and, as a result, the inner layer capacitance dominates, due to the reciprocal or series additivity of eqs. 20 and 21. hence, in the gcs theory,c = 2εε0/d is the limiting (maximum) value of c or cd at large concentrations or large electrode charges. further, the differential capacitance at low concentrations looks something like a parabola but flattens out at large σ. at high concentrations, the differential capacitance is constant. any additional shape in the experimental differential capacitance is added by an empirical fit of the inner layer capacitance to the experimental results. however, the diffuse layer capacitance is presumed to be given adequately by the gcs theory. parsons and zobel (pz) [11] have plotted their experimental results for the inverse of the differential capacitance as a function of the inverse of the diffuse layer differential capacitance, given by eq. 23. such a plot is often called a parsons-zobel plot. if the gcs theory were correct, this should result in a straight line. the extrapolation of the straight line to 1/cdl d = 0 (high concentration and/or high electrode charge density) should, if the gcs theory were correct, yield the reciprocal of the inner layer capacitance. as is seen in fig. 1, at first sight the experimental results of pz (the points) do seem to follow a straight line and, conventionally, are presumed to provide an experimental verification of the gcs theory. in fig. 1, the light straight lines are the gcs results. the solid curve is the result of the msa that has not yet been discussed. for the moment the solid line can be considered to be an aid to the eye in following the trend of the experimental results. in the conventional gcs picture, the inner layer capacitance might not be given by eq. 24 but might differ because of the presumed effect of the presence and nature of the solvent molecules and the electronic structure of the electrode that are beyond the gcs theory. possible solvent effects might be a lower dielectric constant due to the alignment of the solvent molecules because of the strength of the electrode charge. the important point is that, in the gcs theory, such solvent effects are presumed to be confined only to the inner layer. the gcs theory is conventionally considered to provide an adequate description of the diffuse layer where the ions are present. also, it is thought to provide a description of the edl when combined with some treatment of the solvent molecules in the inner layer, or even an empirical fit. indeed, the extrapolation of the straight lines to 1/cdl d = 0 is one method of obtaining presumed “experimental” values of c il d . however, a careful examination of the pz experimental results in fig. 1 indicates that the experimental differential capacitance does not follow eq. 21 at high concentrations (the left side of the figure) but rises above the extrapolated intercept, possibly without limit. until recently, most experimentalists have ignored this point and did not concern themselves with this issue because ions are not soluble in water when their concentration is large and it is difficult to obtain results with other solvents. additionally, experimental results are difficult to obtain at high electrode charges for conventional electrolytes. however, as we shall see, dls in ionic liquids can be formed at high concentrations and the deficiencies of the gcs theory become quite apparent. given that experiments on aqueous systems are difficult in regimes where problems with the gcs theory become apparent, it is useful to consider computer simulations. one simulation technique is the monte carlo (mc) method. until recently, it has been the most common simulation tool in dl studies. in mc simulations the ions undergo a random walk and the profiles and other properties of interest are obtained by averages over this random walk. a simple random walk would take forever before useful results could be obtained. however, meaningful results can be obtained by means of a biased random walk that confines the ions to regions in which they hungarian journal of industry and chemistry double layers near an electrode 59 0 5 10 15 b 0 2 4 6 βe φ( d/ 2) a 0.0 0.1 0.2 σd 2 /e 0 2 4 6 βe φ( d/ 2) b figure 2: diffuse layer potential of a 1:1 electrolyte (d = 3 å) at room temperature as a function of b (part a) and σ (part b). the curves are, from top to bottom, for 0.01, 0.1, and 1 m solutions. the symbols give the simulation results. the solid curve in part a gives the gcs results. the dotted lines connect the mc results for easier visualization. the lines in part b give the gcs results. part a is reproduced, with permission, from ref. [1]. have a high probability of residing. the simulation cell consists of a parallelopiped with a charged wall (the electrode) at x = 0 and another wall (charged or uncharged) at x = l, where l is so large that the two walls do not interfere. periodic boundary conditions are used in the other two directions. the size of the cell is chosen to be large enough that electrostatic screening eliminates the effects of the periodic image cells. the number of ions of each species is chosen so that the system is electroneutral. the first use of mc simulations for the study of the edl was that of torrie and valleau [12, 13]. after their seminal studies, there was a hiatus in simulation studies of the edl. however in recent years, there has been a renewed interest in simulations of the edl that includes the work of bhuiyan et al. [8], boda et al. [14, 15], and lamperski et al. [16, 17]. another simulation technique is the molecular dynamics (md) method in which the equations of motion are solved and the properties of the system of interest are obtained by averaging over the positions and velocities of the ions. a simulation cell that is similar to that used 0 1 2 3 4 5 g i(x ) a 0 1 2 3 4 5 x/d 0 1 2 3 4 5 g i(x ) b figure 3: normalized density profiles, gi(x), of a 1:1 electrolyte (d = 3 å) at 1 m and room temperature for the state for which the mc values are σd2/e = 0.1685 and βeφ(d/2) = 2.6. the points give the simulation results and the curves give the gcs results. the comparison is made at the same charge density (part a) and the same diffuse layer potential (part b). in mc simulations is employed. in recent years, there has been an interest in md simulations of the edl, especially for ionic liquids. some representative studies are those of vatamanu et al. [18, 19], hu et al. [20], and feng [21] et al.. a comparison with simulation gives an unambiguous test of the gcs theory since uncertainties resulting from empirical fits of the diffuse layer capacitance cannot arise. the gcs theory and simulations both use the same model and interaction parameters that are defined in eqs. 1 and 2. additionally, simulations and theory give results for the density profiles, gi(x), that cannot be obtained by present experimental methods. the simulations plotted in figs. 2–5 are those of boda et al. [22]. in fig. 2a, the electrostatic potential βeφ(d/2) for a 1:1 electrolyte is plotted as a function of b for three concentrations (0.01m, 0.1m, and 1m). if the gcs theory were correct, these curves would be identical and independent of concentration. hence, there can be only one gcs curve in fig. 2a. as is seen, φ(d/2) as a function of b actually decreases with increasing concentration. in fig. 2b, φ(d/2) is plotted as a function of σd2/e. the cgs curves are greater than the simulation results, espe43(2) pp. 55-66 (2015) doi: 10.1515/hjic-2015-0010 60 henderson -0.2 -0.1 0.0 0.1 0.2 σd 2 /e -4 -2 0 2 4 6 βe φ( d/ 2) figure 4: diffuse layer potential of a 2:1 electrolyte (d = 3 å) at room temperature as a function of σ. the curves are, from top to bottom, for 0.01, 0.1, and 1 m for positive σ and the reverse for negative σ. the symbols give the simulation results. the curves give the gcs results. cially as the concentration increases. the density profiles for a 1:1 electrolyte are plotted in fig. 3. the comparison is made at the same value of σ in part a and the same value of φ(d/2) in part b. in principle, there is no reason to choose whether the comparison should be made at the same σ, the same φ(d/2), or the same φ(0). it was natural for torrie and valleau to make their comparisons at the same σ because σ is the input variable in their method. however, φ is the natural variable in the gcs theory. in any case, the gcs theory looks best when σ is used as the input variable. torrie and valleau overstated things when they said that the gcs theory was reasonable for a 1:1 electrolyte. their statement is most applicable if the comparison is made at the same value of σ. the value of the counterion profile would be in poor agreement at x = d/2 if φ(d/2) or φ(0) were used as the input variable. a similar comparison is made for a 2:1 electrolyte in figs. 4 and 5. the agreement of the gcs theory with simulations is much poorer. the electrostatic interactions are stronger because of the presence of the divalent ions. when the divalent ions are the counterions, the potential, φ(d/2) has a maximum and then decreases with increasing electrode charge. this is not seen in the gcs results which are monotonic. further, the simulation profiles are not monotonic whereas the gcs results are monotonic. the simulation profiles have oscillations. the edl can consist of regions where counterions or coions predominate. when the coions predominate, this phenomenon is known as charge inversion. of course, the net charge in the diffuse layer is still equal in magnitude, but opposite in sign, to that of the electrode charge. this is required to screen the electrode charge and potential far from the electrode. generally, experimentalists have been content to ignore the discrepancies in the results of the gcs theory and state that these differences are unimportant since they occur at high electrode charges or high concentrations 0 1 2 3 4 5 g i(x ) a 0 1 2 3 4 5 x/d 0 1 2 3 g i(x ) b figure 5: normalized density profiles, gi(x) of a 2:1 electrolyte (d = 3 å) at 1 m and room temperature for the state for which the mc values are σd2/e = −0.1685 and βeφ(d/2) = −0.15. the points give the simulation results and curves give the gcs results. the comparison is made at the same charge density (part a) and the same diffuse layer potential (part b). or for high valence electrolytes or nonaqueous systems, where experimental results are difficult to obtain. however, this is short-sighted. as scientists, one of our goals is to understand what is happening. this cannot be done with an inaccurate theory even with curve fitting. in the remainder of this article, attention is directed to more accurate, but still analytic, theories. 3. mean spherical approximation the mean spherical approximation (msa) is a natural extension of the linearized gcs theory in which the size of the ions is taken into account. it was first applied to the edl by blum [23]. the gcs is usually obtained by means of the solution of a differential equation whereas the msa is obtained from the solution of an integral equation. at first sight, the connection between the gcs and msa theories is unclear. however, henderson and blum [24] demonstrated that the gcs theory could also be obtained from an integral equation. in fact, the linearized gcs integral equation is just the msa integral equation with the effect of ion size ignored. actually, henderson and blum proved a more general result. they showed that the gcs theory followed from the hungarian journal of industry and chemistry double layers near an electrode 61 hypernetted–chain approximation (hnca) when ion size was neglected. the msa can be regarded as a linearized version of the hnca and, because of this, the stated relation of the linearized gcs theory to the msa follows. in this article, the hnca is not considered because it does not yield analytic results and has severe problems when σ is large [25]. also, the emphasis in this article is upon analytic, or at least explicit, results that can be valuable in practical calculations. the msa result that is analogous to eq. 29 is gi(x) =  0 for x < d/2 g0(x)− βzieσ εε0κ f(y) for x ≥ d/2 , (34) where g0(x) is the percus-yevick (py) profile for hard spheres near a hard surface. earlier, henderson, abraham, and barker (hab) [26] obtained an integral equation for g0(x). the second term gives the electrostatic part of the profile for charged hard spheres near a charged hard surface. blum [23] did not obtain a result for f(y) but he did obtain an analytic result for the laplace transform of f(y),∫ ∞ 0 exp(−sy)f(y)dy = = s s2 + 2(γσ)s+ 2(γσ)2(1− exp[−s]) , (35) where 2γ is a renormalized screening parameter that is related to κ by κ = 2γ(1 + γσ) or 2γσ = √ 1 + 2κσ1. note that for small κ (small concentrations), 2γσ = κσ−(κσ)2/2+···. thus, the msa screening parameter is smaller than the gcs screening parameter. this suggests that the msa edl is wider than that of the gcs theory. this agrees with the simulation results. the notation of blum has been followed. however, it might have been preferable if he had incorporated the factor of 2 into the definition of γ so that γ became κ at low concentrations. note that at low concentrations, the laplace transform of f(y) becomes 1/s(1 + κs). this means that f(y) = exp(−κy), (36) in the limit of low concentrations. also, g0(x) = 1 in this limit. thus, at low concentrations, the msa becomes the gcs theory. blum did not invert the laplace transform of f(y). however, he did obtain the contact value of f(y) by examining the laplace transform of f(y) at large s. he showed that f(0) = 1. using the earlier result of hab for g0(d/2), the contact value of gi(x) is gi(d/2) = 1 + 2η (1− η)2 − βzieσ εε0 , (37) where η = πρd3/6. the msa contact value is an improvement over the gcs result that contains only the ideal gas term. however, the osmotic pressure should have both a hard sphere term and an electrostatic term. additionally, the hard sphere term is accurate only for low values of ρ. equation 37 does not contain the quadratic term b2 of eq. 27. this is because the msa is a linearized theory. a better expression for the osmotic term is p ρkt = 1 + η + η2 − η3 (1− η)3 − γ3 3πρ , (38) where γ is the renormalized screening parameter that has been defined above. this result is obtained from the application of the msa to bulk electrolytes. the msa, as is the case for most theories, is not fully self-consistent. henderson et al. [27] have compared this expression with their simulations (see their fig. 1) and found it to be very accurate. despite these problems, the msa contact value given in eq. 37 does represent an advance. by expansion of the laplace transform of f(y), it is easy to show that the msa edl satisfies electroneutrality. that is, the charge in the edl is equal in magnitude, but opposite in sign, to the electrode charge. again, by expanding the laplace transform, the msa expressions for the total and diffuse layer potentials of the edl are found to be v = σ εε0(2γ) (39) and φd/2 = σ εε0κ [1− (γd)2]. (40) thus, in the msa, the capacitance (and differential capacitance) of the edl is 1 c = 1 εε0(2γ) . (41) expanding the expression that defines γ, 2γ = κ− κ2d/2 + κ3d2/2 + · · ·. (42) therefore, 1 c = 1 εε0κ + d 2εε0 − κd2 4εε0 + · · · . (43) the msa capacitance does not reach a maximum at 2εε0/d but continues to increase, as is indicated in fig. 1. the msa (solid) curve in fig. 1 was not calculated from eq. 41 but from a more sophisticated version of the msa, that is not discussed in detail here, which includes the contribution resulting from explicit solvent molecules and the electronic structure of the metal [28–30]. however, the results of eq. 41 are qualitatively similar to the more sophisticated results. in this paper, the solid curve serves to guide the eye. the inner layer capacitance continues to be 2εε0/d but it is simply the electrode charge divided by potential difference across the inner layer and not a ‘catch all’ for the deficiencies of the gcs theory. the diffuse capacitance is the electrode charge divided by the potential difference from the distance of closest approach to the bulk electrolyte and contains correction terms to the gcs theory. this is the reverse of the usual interpretation of the gcs theory where the gcs expressions are assumed to be accurate for the diffuse layer 43(2) pp. 55-66 (2015) doi: 10.1515/hjic-2015-0010 62 henderson 0.14 0.16 0.18 0.2 0.22 0.24 ρ* 1.4 1.6 1.8 2 2.2 2.4 c /f m -2 mc msa gcs figure 6: double layer capacitance, c, as a function of the reduced density, ρ∗ = ρd3, at the reduced temperature t ∗ = 0.08. the circles are the mc data of henderson et al. [27] and the lines are the msa and gcs results. the line through the circles is given as a guide to the eye. because the msa is a linearized theory, the mc, msa, and gcs capacitances are for σ = 0. capacitance and everything else is ‘lumped’ into the inner layer capacitance. in the more sophisticated version msa, the contributions due to the solvent molecules appear in both the diffuse and inner layer potentials. the solvent molecule profile is as diffuse as that of the ions. the effect of the molecular nature of the solvent is not confined to the inner layer. the initial slope of the φ(d/2) vs. σ curves in figs. 2 and 4 is just the inverse of the diffuse portion of the capacitance. it is seen that the initial slope of the mc curves is well described by the gcs theory at low concentrations but increasingly falls below the gcs initial slope (the inverse of the differential capacitance) with increasing concentration as was seen in the experimental results in fig. 1. henderson et al. [27] compared the gcs and msa differential capacitances with their simulation results for a broad range of densities and at a temperature that was meant to be qualitatively representative of an ionic liquid. as is seen in figs. 6 and 7, the msa results are considerably improved over the gcs results. the comparison with the mc results is made for a small value of σ because the msa is a linearized theory that is applicable only for small σ. although an analytic expression for f(y) is not available, henderson and smith [31] were able to obtain a zonal expansion for f(y). they showed that f(x) = ∞∑ n=1 fn(z)u(z), (44) where z = t−n+ 1, t = x/d, u(z) is the heaviside step function that is zero for z < 0 and one for z ≥ 0 and fn(z) = exp(−µ) µn (n− 1)! [jn−2(µ)− jn−1(µ)] (45) with µ = (γd)z. the function jm(µ) is the spherical x / d 0.5 1.0 1.5 2.0 2.5 0 1 2 3 4 g (x /d ) 0 1 2 3 4 5 counterions co-ions counterions co-ions (a) (b) figure 7: the electrode-ion normalized density profiles, gi(x/d), at the reduced density ρ∗ = ρd3 = 0.5 for the reduced temperature t ∗ = 0.8 and surface charge density, σ = 0.05 c/m2, is small enough that the msa is applicable. the circles are the mc results of henderson et al. [26] and the dashed line gives the msa result. the line through the circles is given as a guide to the eye. this figure is reproduced, with permission, from ref. [26]. bessel function that is easily calculated using the recurrence formula for this function. hundreds of jm(µ) can be calculated without difficulty, even with a laptop computer. henderson and smith [31] also obtained a zonal expansion for g0(x). their result is g0(x) = ∞∑ n=1 gn0 (z)u(z), (46) where z is again given by z = t − n + 1 with t = x/d. the expressions for the gn0 (x) are rather complex. however, henderson and smith gave results for n ≤ 5. the formulae for g0(x) and f(x) are not quite analytic since they involve infinite series. however, these results are explicit and easily used. fortran programs to obtain g0(x) and f(x) are given in supplementary material. note that the program for g0(x) consists of two parts. one part calculates those parameters that depend only on the state of the electrolyte and the other subroutine in each code calculates profiles for a given x. the user should resist the temptation to combine the two parts into one. mcquarrie [32] did this in an appendix to his excellent book and produced an inefficient, and probably incorrect, code that he referred to as ‘henderson’s code’. fortunately, his code hungarian journal of industry and chemistry double layers near an electrode 63 is illegible in the later printing of his book. if the reader does combine the codes, the reader is on his/her own and should not refer to the combined, or otherwise modified, code as ‘henderson’s code’. the functions g0(x) and f(x) are oscillatory, in accord with the simulations. they are improvements, qualitative and quantitative, to the monotonic functions of the gcs theory. 4. a useful hybrid description as has been mentioned, the deficiencies of the gcs theory could, until recently, be dismissed as appearing mainly under conditions that are of limited experimental interest. however, there has been considerable recent interest in edls formed by ionic liquids. ionic liquids can be thought of as room–temperature molten salts. because there is no solvent, the ions do not become insoluble in some solvent and experimental results can be obtained at high concentrations. the fact that they exist at room temperature is a great experimental convenience. kornyshev [33] has drawn attention to these electrochemical systems and aptly suggested that they provide a paradigm change in electrochemistry. he modestly ends the title of his important paper with a question mark. an exclamation mark might have been more appropriate. as well as exposing the deficiencies of the gcs theory, edls in ionic liquids are important in green technologies, the design of novel energy storage devices, such as high-tech batteries and super-capacitors [34]. ionic liquid dls have attracted recent experimental [35, 36] and theoretical interest [18–21, 37–39]. the differential capacitance, as determined by mc simulations, of a simple model [38] of an ionic salt in which t ∗ = 0.8 and d = 8 å is given in fig. 8 for ρ∗ = 0.04, 0.14 and 0.24. at low concentrations, the differential capacitance is parabolic-like, as the gcs theory suggests. however, cd does not become flat at large electrode charges. at higher concentrations, cd at small electrode charges continues to increase with increasing concentration. this has been seen in fig. 6. at high electrode charges, the capacitance decreases. the nature of this decrease seems to be independent of the concentration. this is similar to the gcs theory except that the capacitance is not flat at high electrode charges but decreases. the decrease is due to the fact that the ions are not point charges but occupy space and cannot sit on top of each other. the diffuse layer must become thicker and the capacitance decreases as the electrode charge increases. this is not because the distance of closest approach of the ions increases. strong secondary peaks in the counterion profile appear [37]. the beginnings of this trend were first observed by torrie and valleau [12] and seem to be quite universal. the gcs theory satisfies eq. 27 at high electrode charges but fails at low electrode charges whereas the msa gives reasonable results at small electrode charges. this implies that a repair of the gcs so that it gives the msa results in the regime of the low electrode charges -2 -1 0 1 2 σ∗ 3 4 5 6 7 8 9 c df * 0.24 0.04 0.14 figure 8: differential capacitance, c∗ df = cdd/4πε0, obtained from mc simulation for the edl of a model ionic liquid with d = 4 å and t ∗ = 0.8. the curves are, from bottom to top, for ρ∗ = 0.04, 0.14, and 0.24. this figure has been reproduced, with permission, from ref. [40]. but leaves the high electrode charge part unchanged might be useful. likely, there is no way to accomplish this in a fundamental way. additionally, there are probably several semi-empirical ways in which this could be done. henderson and lamperski [40] have presented one procedure. because it is not based on any fundamental ideas, it is not a theory. it would be more appropriate to refer to their procedure as a description. they proposed that the differential capacitance for a symmetric salt could usefully be written as 1 cd = d′ 2εε0 + d′ 2εε0 √ 1 + b2/4 ( 1 γd′ − 1 ) . (47) the parameter d′ is an adjustable parameter and represents the effective thickness of the diffuse layer. at small b (small electrode charge), eq. 47 yields 1 cd = 1 2γεε0 , (48) which is the msa result. at large b (large electrode charge), eq. 47 yields 1 cd = d′ 2εε0 . (49) the results of eq. 47, using d′ = 2d for the system that lamperski et al. simulated, were given by henderson and lamperski. qualitatively, the results are very similar to the simulation results shown in fig. 8. better agreement could be obtained by making d′ increase with electrode charge. figure 2 of henderson and lamperski suggests that cd is proportional to 1/σ∗ at large σ∗ (electrode charge) with the proportionality constant being independent of concentration. this behavior was first predicted by kornyshev [33] on the basis of a lattice theory and seems to be universal. as well as the simulations of henderson and lamperski, it has been seen experimentally 43(2) pp. 55-66 (2015) doi: 10.1515/hjic-2015-0010 64 henderson -1.5 -1 -0.5 0 0.5 1 1.5 σ* 4 6 8 10 c * d 0.24 0.14 0.04 figure 9: differential capacitance, c∗ d = cdd/4πε0, obtained from the hybrid description of the edl of a model ionic liquid with d = 4 å and t ∗ = 0.8. the curves are, from bottom to top, for ρ∗ = 0.04, 0.14, and 0.24. the solid and broken curves give the results of the hybrid approach and gcs theory, respectively. by islam et al. [35]. something of the nature of d′ = d1 + d2|σ∗| (50) would give the desired decrease of cd at large σ∗. equation 50 is sensible because it is consistent with the diffuse layer becoming thicker as the electrode charge increases. the results of this ansatz with d1 = 2d and d2 = d are given in fig. 9. the results are similar to the simulation results in fig. 8. this hybrid approach is capable of yielding a capacitance with a double hump at low concentrations and a single hump at high concentrations. this behavior is predicted by simulations and all the good theories of the dl of ionic liquids. a hybrid treatment of the profiles, gi(x), is possible. one could start with the msa expression for gi(x) and add to this ggcs i (x; b) − ggcs i (x; b = 0). however, it must be realized that the msa expressions for the profiles are less accurate than the msa expressions for the potential and capacitance. the potential and capacitance are integrals and tend to average out any inaccuracies in the profiles. 5. conclusion the study of the electric dl is an important application of statistical mechanics that is of experimental and applied interest. the gcs theory is popular with experimentalists because it is intuitively simple and easy to use in the routine analysis of experiments. however, the gcs theory has deficiencies. its use leads to the idea that any problems with the gcs theory can be ‘swept under the carpet’ by placing all of these problems into an empirical treatment of the inner layer. in reality, the deficiencies of the gcs theory lie with the gcs treatment of the diffuse layer. admittedly, it is difficult to observe this in aqueous systems. however, it is not impossible. the departure from linearity in the parsons-zobel plot (fig. 1) is real and should not be ignored. the important field of ionic liquid electrochemistry requires something more adequate than the gcs theory. the best theories of the edl are the modified poisson-boltzmann theory [41] and the density functional theory [42]. however, both theories are numerical and require an iterative numerical solution of a fairly large set of equations and may not be appealing in an experimental analysis. a hybrid description, such as that explored here, preserves the advantage of an analytic treatment of the capacitance and is no more cumbersome than the gcs theory. supplementary information fortran programs to calculate g0(x) and f(x−d/2) using msa. the codes can be downloaded free of charge from http://tinyurl.com/hjic-2015-0010-suppl. acknowledgement professor dezső boda assisted with the preparation of this paper. professor lutful bari bhuiyan read the manuscript prior to submission and suggested several important modifications. the author is grateful to both colleagues for their continuing wise advice. references [1] henderson, d., boda, d.: insights from theory and simulation on the electrical double layer, phys. chem. chem. phys., 2009 11(20), 3822–3830 10.1039/b815946g [2] cherstvy, 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polyethylene plant to analyse different productions of a given product and to explore the relationships between different operating and product quality variables. keywords: exploratory data analysis, box plot, quintile-quintile plot introduction the major aims of monitoring plant performance are the reduction of off-specification production, the identification of important process disturbances and the early warning of process malfunctions or plant faults [1]. in modern production systems huge amount of process operational data are recorded with distributed control systems (dcs). these data definitely have the potential to provide information for product and process design, monitoring and control [2]. process monitoring based on multivariate statistical analysis of process data has recently been investigated by a number of researchers [3]. the aim of these approaches is to reduce the dimensionality of the correlated process data by projecting them down onto a lower dimensional latent variable space where the operation can be easily visualized. these approaches use the techniques of principal component analysis (pca) or projection to latent structure (pls). beside process performance monitoring, these tools can be used for system identification [3], ensuring consistent production [4] and product design [1]. for these classical data analysis approaches, the collection of the data is followed by the imposition of a model and the analysis, estimation, and testing that follows are focused on the parameters of that model. most of operational process data may be characterised as historical in the sense that is was not collected on the basis of experiments designed to test specific statistical hypothesis. consequently, the resulting databases are likely to contain unexpected features (e.g. outliers from various sources, unexpected correlation between variables, etc.) this observation is important for two reasons: first, these data anomalies can completely negate the results obtained by standard analysis procedures, particularly those based on squared error criteria (a large class includes many spc and chemometrics techniques, like pca). secondly and sometimes more importantly, an understanding of these data anomalies may lead to extremely valuable insights [5]. pearson suggested using exploratory data analysis (eda) tools for both of these reasons [5]. for exploratory data analysis (eda), the data collection is not followed by a model imposition; rather it is followed immediately by analysis with a goal of inferring what model would be appropriate. eda is an approach/philosophy for data analysis that employs a variety of techniques (mostly graphical) to maximize insight into a data set, uncover underlying structure, extract important variables, detect outliers and anomalies, test underlying assumptions, develop parsimonious models, and determine optimal factor settings. the seminal work in eda is written by tukey, [6]. over the years it has benefited from other noteworthy publications such as data analysis and regression by mosteller and tukey [7], and the book of velleman and hoaglin [8]. most eda techniques are graphical in nature with a few quantitative techniques [9]. the reason for the heavy reliance on graphics is that by its very nature the main role of eda is to open-mindedly explore, and graphics gives the analysts unparalleled power to do so, enticing the data to reveal its structural secrets, and being always ready to gain some new, often unsuspected, insight into the data. in combination with the natural patternrecognition capabilities that we all possess, graphics provides, of course, unparalleled power to carry this out. the particular graphical techniques employed in eda are often quite simple, consisting of various techniques of: 1. plotting the raw data (such as data traces and histograms). 2. plotting simple statistics such as mean plots, standard deviation plots and box plots. 86 3. positioning such plots so as to maximize our natural pattern-recognition abilities, such as using multiple plots per page. the aim of this paper is to present an application relevant survey of some of exploratory data analysis procedures that have been found to be particularly useful in the qualitative analysis of historical databases of production systems. the rest of this paper is organised as follows. the next section deals with the description of the problem used through the paper to illustrate the presented exploratory data analysis approach. section 3. deals with the description of the box plot and shows its application in the comparison of different production of a given product. in the third section the application of quantile-quantile plot is proposed for the exploration of the differences of the different productions and for the analysis the relationship among different operating variables. the examples illustrate that the proposed eda based tools are useful to identify the similar behaviour of operating and model quality variables. problem description formulated products (plastics, polymer composites) are generally produced from many ingredients, and large number of the interactions between the components and the processing conditions all have the effect on the final product quality. if these effects are detected, significant economic benefits can be realized. this consideration lead the “optimization of operating processes” project of the vikkk research center at the university of veszprém supported by the largest hungarian polymer production company (tvk ltd., www.tvk.hu). the aim of the project is to work out a methodology for the datadriven improvement of process. hence, in this paper the monitoring of a medium and high-density polyethylene (mdpe, hdpe) plant of the tvk ltd. in hungary is considered. hdpe is versatile plastic used for household goods, packaging, car parts and pipe. a brief explanation of the phillips license based low-pressure catalytic process is provided in the following. fig. 1 represents the phillips petroleum co. suspension ethylene polymerization process. the polymer particles are suspended in an inert hydrocarbon. the melting point of high-density polyethylene is approximately 135 °c. therefore, slurry polymerization takes place at a temperature below 135 °c; the polymer formed is in the solid state. the phillips process takes place at a temperature between 85-110 °c. the catalyst and the inert solvent are introduced into the loop reactor where ethylene and an α-olefin (1-hexene) are circulating. the inert solvent (isobuthane) is used to dissipate heat as the reaction is highly exothermic. a cooling jacket is also used to dissipate heat. the reactor consists of a folded loop containing four long runs of pipe 1 m in diameter, connected by short horizontal lengths of 5 m. the slurry of hdpe and catalyst particles circulate through the loop at a velocity between 5-12 m/s. the reason for the high velocity is because at lower velocities the slurry will deposit on the walls of the reactor causing fouling. the concentration of polymer products in the slurry is 25-40% by weight. ethylene, α-olefin comonomer (if used), an inert solvent, and catalyst components are continuously charged into the reactor at a total pressure of 450 psig. the polymer is concentrated in settling legs to about 60-70% by weight slurry and continuously removed. the solvent is recovered by hot flashing and distillation. the polymer is dried and pelletized. the conversion of ethylene to polyethylene is very high (95%-98%), eliminating ethylene recovery. the molecular weight of high-density polyethylene is mainly determined by the type of the catalyst and the temperature of the catalyst activation [10]. the main properties of polymer products (e.g. melt index (mi) and density) are controlled by the reactor temperature, monomer, comonomer and chain-transfer agent concentration. comonomer feed ethylene feed recycling solvent fresh solvent catalyst catalyst tank loop reactor reactor circulating pump jacket water cooler jacket water tank water bag filter product flash tank steam purge column circulating pump steam reflux pump steam bottom pump nitrogen nitrogen polymer powder olefin free solvent flash gas compressor cooler water water water cooler reflux tank recycling pump recycling solvent distillation column figure 1: scheme of the phillips loop reactor process [10] 87 an interesting problem with the process is that it is required to produce about ten product grades according to market demand. hence, there is a clear need to minimize the time of changeover because offspecification product may be produced during transition. the difficulty of the problem comes from the fact that there are more than ten process variables to consider. measurements are available in every 15 seconds on process variables zk, which are the zk, 1 reactor temperature (t), zk, 2 ethylene concentration (c2) and zk, 3 hexene concentration (c6) in the loop reactor, zk, 4 the ratio of the hexene and ethylene inlet flowrate (c6/c2in), zk, 5 the flowrate of the isobutane solvent (c4), zk, 6 the hydrogen concentration (h2), zk, 7 the density of the slurry in the reactor (roz), zk, 8 polymer production intensity (pe), and zk, 9 the inlet flowrate of the catalyzator (kat). the product quality yk is only determined later, in another process. the interval between the product samples is between half and five hours. the yk, 1 melt index (mi) and the yk, 2 density of the polymer power (ro) are monitored by off-line laboratory analysis after drying of the polymer that causes one hour time-delay. since, it would be useful to know if the product is good before testing it, the monitoring of the process would help in the early detection of poor-quality product. there are other reasons why monitoring the process is advantageous. only a few properties of the product are measured and sometimes these are not sufficient to define entirely the product quality. for example, if only rheological properties of polymer are measured (melt index), any variation in end-use application that arise due to variation of chemical structure (branching, composition, etc.) will not be captured by following only these product properties. in these cases the process data may contain more information about events with special causes that may effect the product quality [11]. the modelling and monitoring of processes from data involve solving the problem of data gathering, preprocessing, model architecture selection, identification or adaptation and model validation. the process data analyzed in this paper have been collected over three months of operation. the data have been extracted from the distributed control system (dcs) of the process. an sql server has been installed to store and merge this data with the product quality database. according to the data warehousing methodology, the application relevant data have been extracted from this sql database. as one of the objectives is to infer the values of product quality from process data obtained at different operating regions, a set of transition-free data is used that covers the whole range of specifications of the quality properties and the process variables over all the possible operating regions. the data were pre-processed by normalization performed on single variables. the aim of the following sections is to present exploratory data analysis tools that can be applied for the previously presented problem. box plot of operating and quality variables suppose that x is a real-valued random variable for the experiment. in our research work, the analysis of process and product quality variables is considered. hence, the variables are x ∈ {zk, yk}. 0 5 10 15 20 25 30 35 40 -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 time [h] te m p. [] figure 2: example of the change of a process variable (t) 88 an example of the behaviour of a process variable is given in fig. 2, where the change of the dimensionless reactor temperature is shown. at our industrial partner's request most of the data shown in this paper are normalized. the (cumulative) distribution function of x is the function f given by f(x) = p(x ≤ x) for x, which is a function giving the probability that the random variable x is less than or equal to x, for every value x. for a discrete random variable, the cumulative distribution function is found by summing up the probabilities. for a continuous random variable, the cumulative distribution function is the integral of its probability density function. suppose that p ∈ [0, 1]. a value of x such that f(x−) = p(x < x) ≤ p and f(x) = p(x ≤ x) ≥ p is called a quantile of order p for the distribution. roughly speaking, a quantile of order p is a value where the cumulative distribution crosses p. hence, by a quantile, we mean the fraction (or percent) of points below the given value. that is, the 0.25 (or 25%) quantile is the point at which 25% percent of the data fall below and 75% fall above that value. note that there is an inverse relation of sorts between the quantiles and the cumulative distribution values. a quantile of order 1/2 is called a median of the distribution. when there is only one median, it is frequently used as a measure of the center of the distribution. a quantile of order 1/4 is called a first quartile and the quantile of order 3/4 is called a third quartile. a median is a second quartile. assuming uniqueness, let q0.25, q0.5, and q0.75 denote the first (lower), second, and third (upper) quartiles of x. note that the interval from q0.25 to q0.75 gives the middle half of the distribution, and thus the interquartile range is defined to be iqr = q0.75 − q0.25, and is sometimes used as a measure of the spread of the distribution with respect to the median. let q0 and q1 denote the minimum and maximum values of x, respectively (assuming that these are finite). the five parameters q0, q0.25, q0.5, q0.75, q1 are often referred to as the five−number summary. together, these parameters give a great deal of information about the distribution in terms of the center, spread, and skewness. an example of a cumulative distribution function and quantile is given in fig. 3, where the distribution of the reactor temperature shown in fig. 2 is depicted. 89.2 89.4 89.6 89.8 90 90.2 90.4 90.6 90.8 91 91.2 0 10 20 30 40 50 60 70 80 90 100 temp. [°c] f( t) =p (t ≤ x ) q0.25 q0.5 q0.75 figure 3: example of a cumulated distribution function of a process variable (t), the q0.25, q0.5, and q0.75 quintiles are also depicted tukey’s five number summary is often displayed as a boxplot. box plots are an excellent tool for conveying location and variation information in data sets, particularly for detecting and illustrating location and variation changes between different groups of data [9,12]. a box plot consists of a line extending from the minimum value q0 to the maximum value q1, with a rectangular box from q0.25 to q0.75, and tick marks at the q0, the median q0.5, and q1 . hence, the lower and upper lines of the “box” are the 25th and 75th percentiles of the sample. the distance between the top and bottom of the box is the interquartile range. the line in the middle of the box is the sample median. if the median is not centered in the box that is an indication of skewness. thus the box represents the body (middle 50%) of the data. there is a useful variation of the box plot that is more specifically identifies outliers. to create this variation: 1. calculate the median and the lower and upper quartiles. 2. plot a symbol at the median and draw a box between the lower and upper quartiles. 3. calculate the interquartile range (the difference between the upper and lower quartile) and call it iq. 4. calculate the following points: l1 = q0 – 1.5 iq l2 = q0 – 3 iq u1 = q1 + 1.5 iq u2 = q1 + 3 iq 5. the line from the lower quartile to the minimum is now drawn from the lower quartile to the 89 smallest point that is greater than l1. likewise, the line from the upper quartile to the maximum is now drawn to the largest point smaller than u1. 6. points between l1 and l2 or between u1 and u2 are drawn. the “whiskers” are lines extending above and below the box. they show the extent of the rest of the sample (unless there are outliers). assuming no outliers, the maximum of the sample is the top of the upper whisker. the minimum of the sample is the bottom of the lower whisker. by default, an outlier is a value that is more than 1.5 times the interquartile range away from the top or bottom of the box. the plotted outlier points may be the result of a data entry error, a poor measurement or a change in the system that generated the data. an example of a box plot is given in fig. 4, where the distribution of the reactor temperature given in fig. 1 is shown. a single box plot can be drawn for one batch of data with no distinct groups. alternatively, multiple box plots can be drawn together to compare multiple data sets or to compare groups in a single data set. such a comparison is given in fig. 5, where the melt index (mi) distribution of five different production of the same product is shown. hence, box plot has a significant effect on the response with respect to either location or variation and the box plot is also an effective tool for summarizing large quantities of information. 89 .2 89 .4 89 .6 89 .8 90 90 .2 90 .4 90 .6 90 .8 91 91 .2 te m p. [° c] figure 4: example of a cumulated distribution function of a process variable (t), the q0.25, q0.5, and q0.75 quintiles are also depicted 0 0 .1 0 .2 0 .3 0 .4 0 .5 0 .6 0 .7 0 .8 0 .9 1 0 0 .1 0 .2 0 .3 0 .4 0 .5 0 .6 0 .7 0 .8 0 .9 1 0 0 .1 0 .2 0 .3 0 .4 0 .5 0 .6 0 .7 0 .8 0 .9 1 0 0 .1 0 .2 0 .3 0 .4 0 .5 0 .6 0 .7 0 .8 0 .9 1 0 0 .1 0 .2 0 .3 0 .4 0 .5 0 .6 0 .7 0 .8 0 .9 1 figure 5: melt index (mi) of five different production of the same product quantile-quantile plot of process and product quality variables when there are two data samples, it is often desirable to know if the assumption of a common distribution is justified. if so, then location and scale estimators can pool both data sets to obtain estimates of the common location and scale. if two samples do differ, it is also useful to gain some understanding of the differences. the quantile-quantile (q-q) plot can provide more insight into the nature of the difference than analytical methods such as the chi-square and kolmogorov-smirnov 2-sample tests [5,9]. a q-q plot is a plot of the quantiles of the first data set against the quantiles of the second data set. both axes are in units of their respective data sets. that is, the actual quantile level is not plotted. for a given point on the q-q plot, we know that the quantile level is the same for both points, but not what that quantile level actually is. if the data sets have the same size, the q-q plot is essentially a plot of sorted data set a against sorted data 90 set b. if the data sets are not of equal size, the quantiles are usually picked to correspond to the sorted values from the smaller data set and then the quantiles for the larger data set are interpolated. a diagonal reference line is also plotted. if the two sets come from a population with the same distribution, the points should fall approximately along this reference line. the greater the departure from this reference line, the greater the evidence for the conclusion that the two data sets have come from populations with different distributions. if the two data sets come from populations whose distributions differ only by a shift in location, the points should lie along a straight line that is displaced either up or down from the diagonal reference line. the q-q plot is similar to a probability plot, where the quantiles for one of the data samples are replaced with the quantiles of a theoretical distribution. the q-q plot can be used to answer the following questions: do two data sets come from populations with a common distribution? do two data sets have common location and scale? do two data sets have similar distributional shapes? do two data sets have similar tail behaviour? these questions arise at the qualitative analysis of historical databases of production systems. firstly, an example for comparison of two production of two different productions of the same product is given in the first column of fig. 6. figure 6: example of a quantile-quantile plots of process variable distributions related to two different productions (first column: same products, second column: different products). this plot shows that the distributions of the temperature are different, while the distributions of the concentrations are much more similar to each other. this difference is much bigger if the temperature related to the production of two different products are compared (see the second column of fig. 6). the difference between the production of the same and different products is much more characteristic if we compare the distributions of the quality properties (see figs 7 and 8). this small application example suggests that quantilequantile plots can be effectively used to compare different productions. another type of application is given in figs 9 and 10, where the similarities between the distributions of different process and quality variables are analysed. this analysis could be extremely useful to detect dependencies between the operating parameters of the process. based on the application of the proposed tools and the analysis of the presented figures several rules have been extracted. most of these rules found to be useful for our industrial partner, since the extracted knowledge and the resulted plots can be effectively used to summarise trends of the process variables and estimate the quality of the products. 91 -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 -1 -0.5 0 0.5 1 1 mi 2 m i -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 -1 -0.5 0 0.5 1 1 ro 2 r o figure 7: example of a quantile-quantile plots of quality (melt index mi polymer density – ro) distributions related to two different productions of the same product -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 -1 -0.5 0 0.5 1 1 mi 2 m i -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 -1 -0.5 0 0.5 1 1 ro 2 r o figure 8: example of a quantile-quantile plots of quality (melt index mi polymer density – ro) distributions related to two productions of different products 92 figure 9: example of a qunatile-qunatile plot of a process and quality variable distributions related to the same production of a product. figure 10: qunatile-qunatile plot of a process variable distributions related to the same production of a product. the behaviour of the control algorithm of the advanced model-based control system can be also identified from the analysis of these plots. e.g. since the density of the slurry in the reactor (roz) is controlled by the hexene concentration (c6), these two variables have similar distributions as it is shown in fig. 10. furthermore, the ratio of c2-c6 is also controlled, which makes the behaviour of these two variables also similar. because of these relations, the c2-roz distributions become also similar. the quantile-quantile plot of the production rate (pe) and ethylene concentration (c2) is also close to a straight line. this is because the highest ethylene concentration results in highest reaction speed. the previously presented rules are only illustrative, but they show that the proposed tools can be effectively used to detect relationships between process and product quality variables and compare different productions conclusions the paper presented a brief survey of simple exploratory data analysis procedures that have been found to be particularly useful in the qualitative analysis of historical databases of production systems. it has been showed that box plot is an important eda tool for determining if a factor has a significant effect on the response with respect to the quality of a given productions. to analyse the relationships between different production, different products, and different operating variables quantilequantile plots are proposed. 93 acknowledgements the authors would like to acknowledge the support of the cooperative research center (vikkk) (project kkk-ii-1a), and founding from the hungarian ministry of education (fkfp-0073/2001). jános abonyi is grateful for the financial support of the jános bolyai research fellowship of the hungarian academy of science and otka (hungarian national research foundation), no. t037600. the support of our industrial partners at tvk ltd., especially miklós németh, lóránt bálint and dr. gábor nagy is gratefully acknowledged. references 1. lakshminarayanan s., fujii h., grosman b., dassau e., lewin d. r.: new product design via analysis of historical databases, computers and chemical engineering 24 (2000) 671-676 2. yamashita y.: supervised learning for the analysis of the process operational data, computers and chemical engineering 24 (2000) 471-474 3. macgregor j. f., kourti t: statistical process control of multivariate processes, control eng. practice, vol.3, no. 3, (1995) 403-414 4. martin e. b., morris a. j., papazoglou m. c., kiparissides c.: batch process monitoring for consistent production, computers chem. eng. vol. 20. (1996), pp. s599-s605 5. pearson r .k.: exploring process data, journal of process control, 11, (2001), 179-194 6. tukey j.: exploratory data analysis, addisonwesley, (1977) 7. mosteller f., tukey j.: data analysis and regression, addison-wesley, (1977) 8. velleman p., hoaglin d.: the abc's of eda: applications, basics, and computing of exploratory data analysis, duxbury, (1981) 9. militký j., meloun m.: some graphical aids for univariate exploratory data analysis, analytica chimica acta, 277(2), (1993), 215-221 10. nagy g.: the polyethylene, magyar kémikusok lapja (mkl), 52(5), (1997) 233-242, in hungarian 11. jeackle c. m., macgregor j. f.: product design through multivariate statistical analysis of process data, american institute of chem. eng. j., 44(5) (1998) 1105-1118 12. chambers j., cleveland w., kleiner b., tukey p.: graphical methods for data analysis, wadsworth, (1983) microsoft word b_40_r.doc hungarian journal of industrial chemistry veszprém vol. 38(2). pp. 223-226 (2010) two special cases of the holonic manufacturing system k. bányai, z. mándy, i. dudás department of production engineering, university of miskolc, hungary e-mail: karoly.banyai@uni-miskolc.hu, mandy.zoltan@freemail.hu, illes.dudas@uni-miskolc.hu the concept of holonics manufacturing systems (with divided intelligence) is the most intelligent, autonomous, elastic, units collaborating with each other. the idea takes as a starting point the fact that the today's environmental circumstances are exceptionally unsettled; there is need for companies with the ability to respond quickly to maintain competitiveness. holonic manufacturing systems (hms) have been recognized as a paradigm to accommodate changes and meet customers’ requirements flexibly based on the notion of the holon, flexible and decentralized manufacturing architecture. koestler proposed the word “holon” to describe a basic unit of organization in biological and social systems. a holon is an autonomous, co-operative and intelligent entity able to collaborate with other holons to process tasks. autonomy and cooperation are two important characteristics of holons. in this study, we investigated a holonic manufacturing systems for dry-working machine group. keywords: holon, autonomy, holarchy, cim, hms introduction firstly, we have to define what the word “holon” means. it is from greek, means whole and part. another name for a holonic manufacturing system is “divided intelligence”. the word “holonics” was introduced by the japanese (the name is from a. koestler), who began worldwide development in this field. they started to co-operate in 1992 to form intelligent and flexible manufacturing systems become and the holonic manufacturing systems (hms) [1, 5]. autonomy allows holons to decide the actions needed to be taken to accomplish the objectives without consulting any supervisory entity. cooperation makes it possible for holons to agree on common plans and mutually execute them. the distributed architecture of multi-agent systems (mas) and the agents’ characteristics of autonomy and cooperation make mas a potential model for the analysis and implementation of hms. however, the aggregation relation of holons allows a holon to be part of another holon in the holonic architecture, which makes holonic systems different from mas and reflects the difficulties of modeling and analysing hms with existing mas theory. to lay a theoretical foundation for the design and analysis of hms, an available approach is to combine mas architecture with suitable models. van brussel proposed the reference architecture prosa for hms and paved the way for further study and design of hms. in existing literature, surveys of multi-agent manufacturing systems can be found in shen and norrie (1999), monostori et al. (2006)) contract net protocol (cnp), is a well known protocol for distributing tasks in multiagent systems [6]. the holonic conception of manufacturing is that of intelligent, autonomous, elastic system capable of cooperating with other units. the concept arises from environmental circumstances, which are extraordinarily changeable, so that we need much more flexible, quicker facilities to maintain competitiveness. to better understand the whole concept here are given briefly a few definitions [1]: holon: autonomous and co-operatable unit in the manufacturing system, that transforms, carries, storing physical objects. a holon can be a part of other holons. holarchy: the system of the holons is able to co-operate, which works in the interest of the achievement of a given aim. the holarchy defines the co-operation from the fundamental rules. holonic manufacturing system: holarchy that coordinates all of the phases of the production processes, because of the order and the planning of actual production through assembly to marketing. holonics characteristics: the band of those characteristics that makes a holon a unit. the minimal requirement is autonomy and the cooperation in one ability [1]. the structures and principles the holonic manufacturing system (hms) is built up from three elemental holons: an order holon, product holon and a source holon. the first holon is responsible for production, the second for the technological planning and the third one for material transport. 224 the elemental holons there are two aspects of the independent principle of the hms: the source aspect is trying to control the machine, with optimal velocity and max. capacity, the requirements of the customers, logistics and marketing. every hms contains the source, product and order holons. the source holon implies the physical part in the manufacturing system and the information from the parts of the process. this product offers the capacity and the functionality for the holons. the source holon is an abstract form for the product. the hms is not separate from the manufacturing system. the product holon manages the process and provide the capability to reach the suitable quality. actually the producer holon is an informational server between the other holons in hms. the product holon includes the functionality which covers the planning, operation planning and quality assurance [3]. the order holon represents the task in the production. it is responsible for ordering the work to happen in time. the order holon organizes the physical processes with all of the logistics paths. it may represent the customers’ claims and the sources of correction. as fig. 1 shows there are three types of the holons with information in the manufacturing system. order holon product holon source holon holonics manufacturing systems figure 1: the elemental holons the central holon can be the bottleneck if it gives up a task. the autonomy can be injured because the hierarchy among the holons becomes stronger with co-operation. the hms is more developed than the computer-integrated manufacturing (cim) structure. contact-autonomy: for a given unit it has characteristics for which it uses plans created by itself. co-operation: important between the holons. the concept is sketched in fig. 2. the example serves the aim to answer the question of how much central holons should be burdened. centre -(computer) holon (int.) thread-grinding machine controlled holon measure unit holon control unit 1. controll unit 2. cnc-discregulator thread-grinding machine measure unit (ccd) with pictureevaluator 3 d-s measuring machine user desk 1 2 3 4 5 6 7 8 9 11 10 12 13 14 15 16 17 18 figure 2: a holonic manufacturing system [5] case 1 here we present how a screw surface can be ground with hms. the hms is built up from the following elements: (1) nct90 ramdisc, a hard drive to contain the input programs, (2) cnc machine with hunor language, which has been connected to the ramdisc, (3) a disc-regulator, (4) a thread-grinding machine, (5) a picture evaluator unit with ccd camera, (6) a 3d measuring machine (dea type), and finally (7) a modern pc. the pc acts as the central holon, meaning that it controls everything. the connection between the pc and the grinding machine is developed by nct technic ltd. these are the hms. the other parts are the subordinated holons. it is very important to use the suitable cooling fluids, which can actually be considered another subordinate holon, but can be used just manually. when we turn on the machine, it is visible in the display that the grinding disc can move foreward or backwards. the setup of the divided intelligence the system gives all of the information that the subordinate holons can endure because of subordinate autonomy. the insurance of co-operation of the subordinate holons is important because we have to help the subordinate holons communicate with the central holon. if the environmental effects change, the system will respond cooperatively. the main parts of the connection of the holons are important to hold the relationship of the static and the dynamic information. this depends on whether the information flow serves the survival of the structure, and whether it follows the environmental effects for the holonic system for the viewpoint of survival. static information can be the transmission of the geometrical parameters. an example of dynamic information can be the handling of transport. 225 case 2 in order not to overcomplicate the structure we wish to present our ideas for a small factory as an example. the first consideration is input substance and energy. the small factory has one dry-working machine group furthermore men who are hand-assembling in a small group (in the holon the men represent the intelligence). the measure unit holon contains a pc with data evaluating ccd camera and a gauge machine with a dea type 3d measuring machine. a portable romer machine can be an arm type gauge machine. the software being used for monitoring may be a holon, for example the software of statistica with evaluating function. the third (subordinate) holon is the measure unit holon and its structure. it consists of four parts: a pc with data-evaluating single ccd camera for the abrasion examinations, cnc disc regulator, and a portable gauge machine. defective products are avoidable using the measure holon which diagnoses and notices mistakes with feedback. although the measure holon is shown as one piece it actually exists at several workplaces physically. the fourth (likewise subordinate) holon is the holon for carrying a load. it is responsible for the transport of the semi-finished products. it is possible to logically handle the distribution of the tasks from the central one and among the subordinate holon(s). there may be some other kind of solutions in this actual production case, naturally, as the process follows changes. the change is an important question in understanding the concept and the priorities in the process. information from outside and from the totality of the informational/material contacts among the holons defines the number of the elements and the structure of the manufacturing system. the aim is the hierarchy and the formation of the cooperation of the autonomy. when there is a change in the input resources, the holons need more autonomy. if the environment changes in other parts, the inner environment reacts by selflearning and with self-organization. this is shown in fig. 4. the strategic features of the holons are important. there is a continuation in the development chain: automation systems → intelligent systems → multi-agent systems. it is necessary to be able to translate the incoming information concerned in order to make changes in the conditions for the system in order to define the autonomy. self-learning resulting, products, informations conditions and sources target energy material dry-working machine group assemly holon humans measure-holon pc (process) data-evaluating pc ccd kamera romer measure machine centre-controll holon feedback feedback energy information information information material material transport holon transport holon measure holon measure holon figure 3: a dry-machining group 226 about the inner environment as an example of a self-regulation measurable physical quantity, we may call it variable, mentioning for example the direction of the velocity, acceleration, and so on. the mechanism of the self-regulation is feedback: ● communication – the system is able to communicate with other systems; ● learning – the holonics system is able to develop its knowledge; ● self-development – the system can develop itself; ● anticipation – the system is able to forecast the changes in the near environment; ● creativity – the system is able to generate new concepts, plans, methods; ● reproduction: the system is able to plan itself again. material energy target conditionals and sources results, products, informations self-learning self-organization figure 4: the self-organization references 1. b. kádár, l. monostori: holonic manufacturing, fractal firms, www.webkorridor.hu. 2. h. sun, p. k. venuvinod: the humanic side of holonic manufacturing systems, technovation, 21, 2007, 353–360. 3. p. valckenaers, h. van brussel, j. wyns, l. bongaerts, p. peters: designing holonic manifacturing systems, robotics and computer integrated manufacturing, 14 (5-6), 1998, 455–464. 4. j. mathews: organizational foundations of intelligent manufacturing systems – the holonic viewpoint, computer integrated manufacturing systems, 8 (4), 1995, 237–243. 5. i. dudás, i. cser: production engineering iv., university of miskolc, 2004. 6. f.-s. hsieh: design of reconfiguration mechanisms for holonic manufacturing systems based on formal models, engineering applications of artificial intelligence, 23 (7), 2010, 1187–1199. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word b_04_r.doc hungarian journal of industrial chemistry veszprém vol. 38(2). pp. 89-94 (2010) designing of smoother hob s. bodzás, i. dudás department of production engineering, university of miskolc, h-3515 miskolc, egyetemváros, hungary e-mail: sandor.bodzas@uni-miskolc.hu, illes.dudas@uni-miskolc.hu it is important to know the main characteristics of production geometry of the hob for the precise and appropriate quality production, since the various cog wheels, worm gears are produced with this tool. the hobs have complicated geometry and are expensive tools so the production is very expensive. keywords: module, hob, production geometry introduction if we give expanded one direction, turning motion for the indented bar shape tool without alternation, plane or chisel motion such we imagine the suitable lengthly indented bar of spreading out of the diameter along wide sloping thread line to spring to a cylinder surface (in production) and the threads defined, equal distance breaking, we create hob edges then the hob creates. in this article the property, geometry of the hobs and production with this tools is introduced. we work with planning of the hob for which we prepared a program. characteristics of hobs for the smoother production of the worm gear a tool is only used, the tiller surface of which is equal to the worm (fig. 1). with suitable kinematical motion this is called direct motion mapping. figure 1: geometrical shaping of hob the advantage of the solution: there is no division from cog to cog, so work is without interruption [1]. the kinematical track of the tool creates the cog profile. during relative motion the side edges of the hobs cover the cog profile. in production with hob the tool and the workpiece turn such the pitch circle of the workpiece has to turn with cog pitch arch, which multiplied by thread number of the hob, while the hob does one turning. the correct production technology has three preconditions: 1. the geometry and dimensions of the hob without head leak and cog leak have to be equal to the geometry and dimensions of the worm gear connection with worm considering the possibility of the resharpening. 2. the production centre distance has to be equal strictly with the centre distance of the worm gear box in tangential method. the cogs of the worm has to be thinned for the assurance of necessary cog leak which compensates the forming capacity changing because of working temperature. the cog thickness of the worm in the reference cylinder is: axjms − ⋅ = 20 π (1) figure 2: cogging with hob 90 3. the symmetry plane of the hob has to equal with the symmetry plane of the worm gear. the strict observation of the lately two requirement is indispensably important in assembly. there are five characteristics of the hobs: dos – the reference cilinder diameter of the tool; max – axial module; αon – normal basic profile angle; zcs – number of teeth; the geometry of the surface. during the repeated application the tip circle diameter of the hob reduces (we can increase with 5%) because of the after grinding, but the face width of the hob reduces with this because of the backward turning, that is why the face width of the worm gear increases and the reduction of the backlash [3]. because of the resharpening the hob has to be produced with greater diameter and two backward turning. during production the resharpened hob is configured with correction. radial milling it is very productive method, but employed till only 8° sloping angle and the quality surface is not sufficient. during production the centre distance is continuously changing (fig. 3). ω ω figure 3: radial milling tangential milling ω ω figure 4: tangential milling it is employed with only machine with slide head or universal milling head, if it has differencial tool. the hob has the part of 10° starting cone. if we just only smooth with tangential milling then the conical hob is suitable. this method is less productive but results geometrical correct cog surface (with under cutting avoidance) and much better quality surface (fig. 4). combine milling we dress with radial method and smooth with tangential method. we give only several tenth mm for smoothing. it is the best worm gear milling methods. surfaces, edges of the hob in production geometry the beater knife is knowing for one cog of the hob so the production surfaces can be written down in equal function. fig. 5 shows a cog of the hob, prepared by pro engineer software. a) head surface view b) back surface view figure 5: one cog of the hob in the practical realization of production of the hob and the beater knife, the deviation is only in the motion area. the most important limiter surfaces of the cog on fig. 6: h – face surface; rb, rj – back surfaces (left and right) fh – back surface of head ribbon h’ – face surface (after sharpening) f – head ribbon the most important limiter cog edges on fig. 6:vb – left side edge as intersection of b tooth and h face surfaces; vj – right side edge as intersection of j tooth and h face surfaces; vf – addendum edge as intersection of f head ribbon and h face surfaces. when forming the rb and rj back surfaces, besides the effect of the chipping process we have to consider mainly the effect of the resharpening of the tool (the ensurance of profile accuracy) [1]. since the hobs have complicated geometry and are expensive tools, it is 91 important to ensure that the tool could be resharpened several times when we elaborate the geometry of the tool. figure 6: the surface elements of the hob classification of cylindrical hobs we can divide the cylindrical hobs for two groups: dressing hobs: the number of teeth is equal to the number of the teeth of the worm. smoother hobs: we can use the final production period of the worm gear, when we produce the cogs of the gear by the prescribed dimensions and tolerances. the geometry of the hobs fig. 7 shows the worm slopping on the reference cylinder. γ figure 7: the worm slopping on the reference cylinder based on this figure we can write these correlations: 0cosγ n ax tt = (2) 0 0sin d mn=γ (3) 0cosγ n ax mm = (4) tn = mn · π (5) hs = zs · tax = zs · max · π (6) where: tax – axial section pitch; tn – normal section pitch; α0 – reference cylindrical slopping angle; d0 – reference cylindrical diameter; mn – normal section module; max – axial section module; zs – number of teeth. diameter quotient: axm dq 0= (7) we regard the diameter quotient to the axial module. its reason is the mn normal module is normed for cylindrical gear hobs, while the max axial module is normed for worm gear hobs. following on fig. 8 the reference cylindrical slopping angle of the hob is: q z mq mz d htg s ax axss = ⋅⋅ ⋅⋅ == π π γ 0 0 (8) γ π π figure 8: reference cylindrical slopping angle of the hob the reference cylindrical slopping angle is an angle which is closed by tangent of the covered worm of the worm and the perpendicular plane to the worm axis. we choose the slopping angle little in technological view. the axial profile angle of the hob is: 0 0 cosγ α α tgtg ax = (9) the axial profile angle of the covered worm in case of evolvent worm is an angle, which is closed by the normal line of the profile and the framer of reference cylinder in axial section of the covered worm in section point of the thread surfaces and the framer of reference cylinder. the basic cylinder is coaxial imagined cylinder with hob, for which detach the evolvents of the head section of the hob. its diameter is not measurable on the hob, only countable: da = d0 · cosα0h (10) where: 0 0 sinγ ns mzd ⋅ = (11) 0 0 sinγ αα tgtg oh = (12) the γa slopping angle on the basic worm is: cosγa = cosγ0 · cosα0 (13) 92 but it is neither measurable on the hob. the hs slopping of the hob is countable from this formula: hs = zs · tax (14) after backward working the slopping of the two cog sides will not be same. the right side edge has hsj, the left side edge has hsb. on right thread hob: hsj > hs > hsb (15) on left thread hob: hsb > hs > hsj (16) the ta basic pitch is perpendicular distance between the two neighbouring, similar falled (left or right) thread surface of the covered worm (fig. 9). ta = tn · cosα0 (17) γ figure 9: definition of the basic pitch designing directions of hobs using hobs for worm gears cogging are individual, complicated geometrical, expensive tools. every worm needs other tools. the first step of production of hob is defining of construction data, based on that we can create the hob and prescribe the technology. the basic profile angle of the covered worm is equal with the prescribed basic profile angle of the worm gear and the cogging tool. the addendum of the hob cog equals with the dedendum of the worm gear [3]. since the correct rolling down need head leak and the head part of the hob cog will cut that, that is why we added this value to the addendum. we can define the dedendum of the hob cog dimension between outside diameter of the workpiece and the bottom ribbon cog ditch of the hob with consideration of the necessary leak. the value of the whole depth of thread will be defined by the sum of the addendum and the dedendum (fig. 10). the tooth thickness of the hob has to be given on the reference cylinder (fig. 10). the thread pitch of the hob has to equal with the thread pitch of the worm gear and worm. α γ υ α figure 10: main dimensions of the hob the outside diameter of the hob extremely influences the punctual production of the worm gear. we can define the hobs diameter based on the quality requirement of the production worm gear and worm. the hob length has to be defined from starting length of working part. the length of working part has to be defined by length of contact. the numbers of the sliver flute is defined by function of module and surface quality. thick cogging hob is often produced for reducing of surface roughness. the specific sliver force increases with cog number increasing that is why the dressing hobs is prepared with rare cogs and the smoother hobs is prepared with thick cogs. 93 the back angle value is function of the backward turning and material quality. the back angle of the hob is different on the head ribbon and the side surfaces. the diameter of the reference cylinder always changes at resharpening of the hob. during counting this change has to be considered with defining of a middle diameter. the slopping angle of the thread line has to be measured in the reference cylinder. the middle slopping angle could be defined by the perimeter of the middle reference cylinder and the thread slopping of the worm [2]. in practice the flute angle is 22°…30°. the program representation we work out a program for designing of smoother hob and counting reduction in c programming language. the program asks 5 input data and defines the other geometrical dimensions of the hob from these. fig. 11 shows the theoretical processes of program working. we could save the received calculation results in txt file format because of the later utilization. based on table the program gives the flute number (zh) [3]. table 1: the data of the designed hob m 5 mm α0 20° d 90 mm df 27 mm zh 9 tn 15,708 mm sns 7,854 mm fs 6,25 mm ls 6,25 mm hs 12, 50 mm rf 1, 25 mm rl 1,5 mm sf 3,304 mm h 5,5 mm dok 76,125 αd 3° 24' h 20,5 mm l1 65 mm vmp 5 mm l 75 mm γok 3° 45' 6" hcs 3698,5 mm tax 15,708 α1 10° ν 25° z 1 figure 11: the process of program working input data: m – module; z – number of teeth; αax – basic profile angle; d – outside diameter of hob; df – hole diameter. start giving file name output data: zs flute number; tn normal section pitch; sns reference cylindrical tooth thickness; fs addendum; ls dedendum; hs whole depth of thread; rf addendum of tooth rounding radius; rl cog radix rounding radius; sf addendum of tooth width; α1 back angle; h theoretical value of back grinding; dok calculated middle diameter of the hob; α d back angle of side edges; h depth of the sliver flute; ν flute angle; l1 hob working length; vmp hob collar width; l total hob length; γok middle slopping angle, which equals sliver flute arcuation angle; hcs sliver flute slopping; tax hob axial pitch. calculation completion are the results correct? (y/n) stop y n 94 summary we introduced the characteristics, surfaces, edges of the hob. we could see the hobs have complicated geometry, expensive tools that is why the punctual designing and production of hob is very important. repeated resharpening of the hob has to be ensured. we wrote a program for designing of smoother hob and we designed a hob and this geometrical characteristics were introduced by us. acknowledgements this work was supported by otka project k 63377. entitled “complex analysis of the features of production geometry and meshing in case of up-to-date application” (2006-2010). research leader: dr. illés dudás, dsc professor references 1. i. dudás: the theory and practice of worm gear drives, penton press, london, 2000. (isbn 1 8571 8027 5) 2. f. l. litvin, a. fuentes: gear geometry and applied theory, cambridge university press, 2004. (isbn 978 0 521 81517 8) 3. d. maros, v. killman, v. rohonyi: csigahajtások, műszaki könyvkiadó, budapest, 1970. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 /colorconversionstrategy /cmyk /dothumbnails false /embedallfonts true /embedopentype false /parseiccprofilesincomments true /embedjoboptions true /dscreportinglevel 0 /emitdscwarnings false /endpage -1 /imagememory 1048576 /lockdistillerparams false /maxsubsetpct 100 /optimize true /opm 1 /parsedsccomments true /parsedsccommentsfordocinfo true /preservecopypage true 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word contents.doc hungarian journal of industry and chemistry veszprém vol. 40(1) pp. 9–13 (2012) determination of phosphorous, suplhur, and silicon content of low-alloyed and unalloyed steel by icp-aes after a unified wet chemical sample preparation procedure o. bánhidi university of miskolc, institute of chemistry, miskolc-egyetemváros, 3515 miskolc, hungary e-mail: akmbo@uni-miskolc.hu phosphorous, sulphur, and silicon have a great effect on the mechanical characteristics and metallurgical properties of steel. therefore, it always has been important to know their concentration either in the unalloyed or in the alloyed metal. using only wet chemical methods their analysis takes much time and labour. the modern instrumental methods make it possible to carry out their determination in a very short time, but the special equipment necessary for that is rather expensive and can be operated efficiently only if there are a lot of samples to be analysed. inductively coupled plasmaatomic emission spectrometry (icp-aes) needs liquid samples, so solid samples must be dissolved prior the analysis. using this technique, however, one can analyze almost any substance that can be taken into solution provided that there is a suitable sample preparation procedure at the user’s disposal. in this paper, a wet chemical sample preparation procedure is presented, which seems to be suitable for the determination of these important constituents of the steel. keywords: wet chemical sample preparation procedure, icp-aes analysis, determination of p, s and si content of steel introduction phosphorous, sulphur, and silicon are rather important constituents of steel, because they have a strong influence on its properties. as a consequence of that fact, it has always been important to know their concentration in the alloy. before the advent of the powerful instrumental methods, their analysis was performed by gravimetric and volumetric wet analytical procedures, which took a lot of time and labour [1, 2]. because of the development of instrumental analysis and that of the equipments, new instrumental methods based upon mostly spectrochemistry have been developed, which can produce almost complete elementary analysis of metals and metal alloys. as they need solid samples and as a consequence of that, the sample preparation is simple and fast: the analytical results are at the disposal of the user in a very short time. their only disadvantage is the need of special instrument, i. e. usually an optical emission spectrometer using spark or arc excitation, which is normally specially designed for the analysis of a given group of metals or alloys. therefore, their economic use demands large load of the same or similar type of samples. the laboratories meeting general analytical demands cannot operate such special equipment in an economic way because of the insufficient number of samples to be analyzed. instead of the methods requiring solid samples, they prefer the application of analytical techniques that need liquid-type samples. solid samples need to be taken into dissolution prior the analysis. although the methods based on dissolution of the solid samples may have several drawbacks – such as much time may be necessary to dissolve the sample, sample losses may occur, or the sample may be contaminated either from the dishware or from the chemicals, etc. –, the methods using wet chemical sample preparation have some definite advantages: almost any kind of sample can be used and normally there is no need to have many special certified reference materials to perform the calibration. if a flexible emission spectrometric instrument, such as an inductively coupled plasma (icp) spectrometer is used for the analysis, by the use of wet sample preparation procedures the overhelming part of elementary analytical tasks can be performed. therefore, this might be an ideal solution for laboratories performing general analytical tasks. in case of the inductively coupled plasma-atomic emission spectrometry (icp-aes) analysis of steel, the analytical parameters are well-known. for most of the components, the spectral lines, where no or only very little spectral interferences can be observed, are at the user’s disposal and by performing the calibration with the help of the so-called matrix-matching technique most of the chemical interferences can be eliminated. regarding the sample preparation methods, most procedures suggested for sample preparation dissolve the steel sample in hydrochloric acid [3]. this acid is able to dissolve almost all kinds of steel and most metallic constituents will be dissolved and will remain in solution, but regarding p, s, and si its use has some drawbacks. in the course of the dissolution in 10 hydrochloride acid, h2s and ph3 may form. these components are volatile, which may lead to s and p losses. silicon may form sio2 during the process and it may be partially dehydrated, especially when the solution is heated up to its boiling point. the dehydrated silicon-oxide will be no longer soluble in the solution, which also causes analyte losses. using nitric acid instead of hydrochloride acid [4], s will form so2, which produces h2so3 with water, while p will form h3po3. si will form sio2, but it will not tend to deposit in the nitric acid solution. based upon this dissolution procedure, we developed a unified sample preparation method, which is suitable for the determination of p, s, and si. in the following, the details of the sample preparation procedure, the conditions of the icp analysis, and the analytical results with some performance characteristics are reported. experimental the sample preparation procedure because of the above-written properties nitric acid was chosen as dissolving agent. so that many types of steel could be dissolved, dilute (1:3) nitric acid was used. according to our experiences, it is able to dissolve unalloyed steel and most of the low-alloyed steels. after the dissolution, 2 m/m% kmno4 solution was added to the liquid to oxidize p. the excess of the oxidizing agent was decomposed by adding 2 m/m% nano2 solution. when the clean solution cooled down, it was taken into a plastic volumetric flask and 0.5 cm3 hf was added to the sample. the hf will dissolve sio2, no matter whether it is in solution or it is deposited. care should be taken that no free hf should remain in the solution, because it may damage the torch and the spray chamber if they are made of silicon-based material. therefore, 5 cm3 4 m/m% h3bo3 is added to the solution. the icp instrument in the course of the analysis, the varian-make 720 es instrument, an axially-viewed simultaneous multielement icp spectrometer was used. this instrument has a specially designed “echelle” optical system, equipped with a two-dimensional ccd detector. the optical system is able to process the wavelength-range of 160-780 nm. it has a free-running high frequency generator operating at 40 mhz. its power applied to the torch can be adjusted from 800 w up to 1500 w in 50 w steps by the controlling software. because of the properties of the optical system, it is possible to choose several lines for the elements to be measured, which can be especially advantageous in the case of unexpected spectral interferences (e. g., when samples with unknown composition are to be analyzed). the measuring conditions the spectral lines chosen for analysis can be seen in table 1. in the course of the measurement, 1050 w high-frequency power was applied to the torch. the integration time was 8 s and the intensity values were obtained by averaging three consequent readings for each sample. as for the sample introduction, k-type glass-made pneumatic nebulizer and cyclone-type spray chamber were used. table 1: the measured spectral lines p 177.43 nm 178.22 nm 213.62 nm s 180.67 nm 181.97 nm si 212.41 nm 251.61 nm 288.16 nm the samples for calibration and obtaining the performance characteristics to perform calibration of the analytical programme and to obtain some performance characteristics, certified reference material samples (crms) were used, which were prepared using the above-written procedure. so that one could judge how well the method, especially the sample preparation procedure meets the requirements, several certified reference material samples were chosen so that different types of low-alloyed steel could be represented among the samples. the chemical compositions of the selected crms are presented in table 2. table 2: chemical compositions of the crms chosen for calibration and determination of some performance characteristics* identifier c s si p mn asnw nr 177 0.036 0.003 0.223 0.014 0.18 asmw nr59/2 0.40 0.033 1.61 0.039 0.65 asmw nr 162 0.37 0.020 1.40 0.031 1.27 asmw nr 174 0.43 0.024 0.39 0.032 1.78 asmw nr 103 0.176 0.010 0.50 0.013 0.46 asmw nr 159 0.127 0.042 0.30 0.086 0.521 asmw nr98/1 0.16 0.016 0.32 0.011 0.40 identifier cr ni cu mo v asmw nr 177 0.117 0.167 0.058 0.068 0.061 asmw nr59/2 0.14 asmw nr 162 asmw nr 174 0.143 0.008 asmw nr 103 1.29 0.11 1.08 0.300 asmw nr 159 0.76 0.13 0.36 0.047 asmw nr98/1 1.36 3.53 *all the data in table 2 are given in m/m% 11 results in the course of the experiments and measurements, the determination of the detection limits representing the detection power was carried out, which was followed by obtaining the calibration curves. following that, the repeatability of the method was tested using reference materials. determination of the detection limits the determination was carried out using the crm nr 174. 0.4 g sample was taken into solution with the help of the above-written sample preparation procedure. the volume of the solution was made up to 0.1 dm3, so the resulting concentration of p, s and si were 1.28 mg/dm3, 0.96 mg/dm3 and 15.6 mg/dm3, respectively. the details are in table 3. table 3: the detection limits obtained for the three elements with the help of the developed method element wavelength dl, mg/dm3 dl, m/m%* 177.43 nm 0.024 0.0006 178.22 nm 0.034 0.0008 p 213.62 nm 0.025 0.0006 180.67 nm 0.011 0.0003 s 181.97 nm 0.018 0.0005 212.41 nm 0.059 0.0015 251.61 nm 0.039 0.0010 si 288.16 nm 0.041 0.0010 *sample mass is 0.4 g; volume of the solution is 0.1 dm3 calibration calibration is a key question of each analytical method, as it will ensure the traceability of the measurements. in the case of a method that requires liquid samples – and the results are referred to a solid state sample –, calibration can be carried out either by using calibration solution series composed of monoor multi-element certified reference material solutions or with the help of solid crms prepared in the same way as the samples. the first way is easier as it will not need special solid steel crms, but the effect of sample preparation procedure might not be taken into account during calibration and it also may be that the chemical form of some elements present in the sample is not the same in the calibration solutions. so that this problem could be avoided, the calibration was carried out by using solid crm samples prepared in the same way as the samples were. the list of the calibration standards can be seen in table 2. looking at table 3, it can be seen that there is hardly any difference concerning the detection power on all lines chosen, therefore, it seemed to be interesting whether there would be any difference regarding the calibration. the calibration curves are presented in figure 1, figure 2, and figure 3. the most important characteristics of the calibration curves can be found in table 4. y = 60225x + 166,13 r2 = 0,982 p, 213.62 nm y = 22932x + 36,248 r2 = 0,9983 p, 177.43 nm y = 9836,5x + 22,517 r2 = 0,9989 p, 178.22 nm 0 1500 3000 4500 6000 0 0,02 0,04 0,06 0,08 0,1 p, m/m % in te ns ity , a .u . figure 1: calibration curves obtained on p lines y = 32594x + 323,06 r2 = 0,9374 s, 181,97 nm y = 19566x + 181,58 r2 = 0,959 s, 180,67 nm 0 200 400 600 800 1000 1200 1400 1600 1800 0 0,009 0,018 0,027 0,036 0,045 s, m/m % in te ns ity , a .u . figure 2: calibration curves obtained on s lines y = 372107x + 13090 r2 = 0,9995 si, 288.16 nm y = 75265x + 2721,5 r2 = 0,9989 si, 212.41 nm 0 100000 200000 300000 400000 500000 600000 700000 0 0,4375 0,875 1,3125 1,75 si, m/m % in te ns ity , a .u . figure 3: calibration curves obtained on 2 si lines determination of the repeatability in order to determine the repeatability of the method, 2 crms, which were not used in the course of calibration, were chosen and 5 parallel samples from each standard were prepared using the above-written sample preparation procedure. 12 table 4: important parameters of the calibration curves element wavelength r (corr. coeff.) sdcal p 177.43 nm 0.99915 0.00127 178.22 nm 0.99945 0.00102 213.62 nm 0.99096 0.00423 s 180.67 nm 0,97929 0.00242 181.97 nm 0,96819 0.00248 si 212.41 nm 0.99942 0.0210 251.61 nm 0.99910 0.0172 288.16 nm 0.99975 0.0134 the chemical composition of these samples concerning the 5 base elements is presented in table 5. for both standard samples the averages and the standard deviations (sd), as well as the relative standard deviations (rsd%) were calculated from the results obtained for the 5 parallel samples and they can be found in table 6. table 5: the chemical composition concerning the 5 base elements of the standard samples used for the determination of the repeatability* identifier c s si p mn a 12 0.04 0.065 1.20 0.019 0.31 a 17 0.78 0.023 0.37 0.038 1.79 *all the data in table 5 are given in m/m% table 6 : the repeatability determined from 5 parallel measurements sample element, line caverage m/m% rsd% a 12 p, 177.43 nm 0.0182 0.83 p, 178.22 nm 0.0171 2.05 p, 213.62 nm 0.0176 1.14 s, 180.67 nm 0.0661 6.97 s, 181.97 nm 0.0629 6.47 si, 212.41 nm 1.18 1.53 si, 251.61 nm 1.18 1.55 si, 288.16 nm 1.17 1.60 a 17 p, 177.43 nm 0.0415 2.01 p, 178.22 nm 0.0407 1.89 p, 213.62 nm 0.0411 2.77 s, 180.67 nm 0.0262 2.59 s, 181,97 nm 0.0257 2.25 si, 212.41 nm 0.361 8.71 si, 251.61 nm 0.371 9.01 si, 288.16 nm 0.368 8.83 discussion of the results steel is usually regarded as a difficult matrix from the viewpoint of chemical analysis. this is because this material often contains elements with different chemical properties and behaviour. as for the atom-spectroscopy, the main constituent of steel, i. e. iron, is very rich in spectral lines, therefore, the possible spectral interferences always have to be encountered in the course of method development. if wet chemical sample preparation has to be applied, further difficulties may be encountered because it is difficult to develop a sample preparation procedure (that is suitable for all constituents) due to the large differences in the properties of the components. in the case of phosphorous, sulphur, and silicon, the main difficulty is that the usual method, i. e. dissolution of the sample in hydrochloric acid, cannot be used because volatile compounds may form, which can cause analyte losses. on the other hand, silicon is partially dehydrated in hydrochloric acid, therefore, again, analyte losses may occur. using nitric acid as a dissolving agent, care must be taken to avoid metal passivity. that is why dilute nitric acid is used in our method. it is also very important that the elements to be determined should be in proper oxidation state. the role of kmno4 is to meet this requirement. from the chemical composition data, it is obvious that this procedure is suitable for most unalloyed and low-alloyed steels. for highly-alloyed steels, e.g. stainless steels, it is not suitable as the occurrence of the passive state cannot be avoided because of the high chromium content. although there is a substantial dilution because of the dissolution, the detection power reached is suitable for the determination of all the three elements, even at low (0.005%) phosphorous and sulphur concentration. the calibration resulted in linear curves for all elements, and the standard deviation of the curves is rather low, so they can be used down to 0.005% for p and s and about 0.05% for si. the only exception may be the 213.62 nm phosphorous line, as its standard deviation reaches 0.004%, therefore, its lower limit of the analytical working range is 0.01%. the repeatability values were determined by preparing and measuring 5 standard samples. the obtained data prove that the method is suitable to determine these three elements in a wide concentration range. comparing the repeatability values of s to those obtained by using combustion methods with nondispersive ir detection, it can be stated that both methods have approximately the same repeatability. finally, one may ask when this method is worth using by the analyst. regarding the fact that much time is necessary for the wet chemical preparation, this method cannot compete with fast methods, which must be used when there is only little time at the analyst’s disposal. on the other hand, if the analysis time is not of key-importance, this method may be applied, especially when the special equipment necessary for the spark or arc optical emission spectrometry or x-ray fluorescence is not available. 13 acknowledgement the described work was carried out as part of the támop-4.2.1.b-10/2/konv-2010-0001 project in the framework of the new hungarian development plan. the realization of this project is supported by the european union, co-financed by the european social fund. references 1. j. mika: kohászati elemzések, műszaki könyvkiadó, budapest (1958) 2. j. bognár: elemző kémia, tankönyvkiadó, budapest (1977) 3. w. j. price: analytical atomic absorption spectrometry, heyden & son ltd. london (1975) 4. o. bánhidi, l. papp: indirect determination of phosphorous content of steel by organic solvent extraction and icp-oes with minitorch, euromat 94, 30 may – 1 june 1994, conference proceedings iii, p. 975 microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 49-53 (2008) examination of medium supplementation for lactic acid fermentation k. hetényi, á. németh, b. sevella budapest university of technology and economics, department of applied biotechnology and food science h-1111 műegyetem rkp. 3., hungary e-mail: bsevella@mail.bme.hu batch fermentation experiments were performed to evaluate the potentials of different fractions of wheat as alternative carbon and nitrogen source during the economical production of lactic acid by a homofermentative mesophilic bacterium. hydrolysing the starch content of wheat results in well consumable glucose solution, and simultaneously hydrolysing the insoluble protein content (gluten) of wheat the nitrogen source can be assured as well. the necessary yeast extract concentration was 30 g l-1 on hydrolysed wheat starch solution without gluten fraction, and it resulted in 2.01 g l-1 h-1 volumetric lactic acid productivity. other possible (and usually applied) supplementations (corn steep liquor, yeast autolysate) are neither available in hungary nor they are economically considerable alternatives. using the gluten fraction can substitute the major part of the added yeast extract as nitrogen source, but since there is a need for other microcomponents (vitamins, amino acids etc.) of yeast extract, thus a minimal amount of yeast extract is necessary for lactic acid fermentation. the optimized gluten containing medium resulted 2.31 g l-1 h-1 productivity which is an industrially acceptable result, showing to be an effective and alternative nitrogen source. keywords: lactic acid; wheat; hydrolysis; yeast extract; gluten. introduction in our days a significantly increased interest became noticeable in the recovery of fermentation products, such as organic acids, feed or food additives and industrial chemicals. fermentation moves into lowervalue higher-volume chemicals, so it becomes necessary to maximize efficiency and minimize costs and waste by-products to compete against traditional alternatives [1]. the use of excess biomass or wastes from agriculture to produce energy, feed or food, and other useful products can be the solution of many economical and ecological problems. lactic acid can be easily produced by fermentation from different raw materials, applying various technological ways and it can be an appropriate starting-point for several compounds. the agro-industrial residues (such as the residues of corn, wheat, sweet sorghum or whey etc.) can all be suitable raw materials in the production of lactic acid, and with a well-chosen technology they can satisfy every need of lactic acid bacteria without any or with minimal amount of supplementation. in hungary has shown up a claim to use surplus grain capacity (corn, wheat) in green-industrial technologies, and in parallel with oil-processing a new concept was born called “bio-refinery” [2]. the target of this theory is to produce lactic acid from wheat utilizing the whole wheat grain. while the starch content of the wheat serves as carbon source for lactic acid bacteria (after starch hydrolysis forming glucose), the other components (gluten, bran etc.) are also usable byproducts of the technology. they can be used for either in production of bio-gas or for direct commercialization. the lactic acid as main product then can be converted in some simple synthetic steps to other chemicals such as poly-lactate (pla), butyl-lactate, ethyl-lactate, propyleneglycol etc. lactic acid bacteria can utilize the hydrolysate of wheat starch [3-6], but these bacteria require a high level of nutrient supplementation including nitrogen source, amino acids, vitamins and microelements [3, 7-15]. to cover these needs generally yeast extract is added to the media as best nutrient source. however the use of yeast extract as only nitrogen and additional nutrient source makes the technology extremely costly. corn steep liquor (csl) as supplementation suits to the “bio-refinery concept” and applying it in a previously optimized medium with glucose carbon source and a minimal yeast extract supplementation we achieved an industrially reasonable lactic acid productivity (3.86 g l-1 h-1 ) [16]. while yeast autolysate, peptone, trypton etc. may also come into question as alternative organic nitrogen sources, ammonium-sulphate, ammonium-phosphate can be used as inorganic compounds. after a proteolytic digestion the protein fraction (gluten) of wheat can also 50 be utilized for fermentation purposes. the proteolysis of gluten can be carried out either separately or simultaneously with the starch hydrolysis [1], depending on the type and the ph optimum of the protease (neutral or alkaline protease). wheat gluten hydrolysis results in peptide mixtures with high solubility [17-18] helping the microbes to utilize gluten fraction and ameliorating the rheological properties of the medium. the role of vitamin supplementation in lactic acid fermentation is described widespread but it is specific for the producer strain [19-20]. since the vitamin need of our bacteria was not described yet, we performed some experiments to test several vitamins. in this study we report some medium optimization steps for the replacement of expensive nutrient supplementations. utilization of starch content of wheat as carbon source and the protein content as nitrogen source is reported earlier [3-6] and it may prove a great advantage toward a more economical lactic acid production process. materials and methods 1. microorganism lactobacillus sp. mkt-lc878, a facultative anaerobic homofermentative l-lactic acid producer, was obtained from an earlier strain selection program in our research group. the strain was stored on mrs medium agar slants (difco, usa) at 4 °c. 2. culture conditions precultures for experiments in fermentors were prepared by transferring a stock culture onto two or four slants of mrs agar and incubated at 37 °c for 24 h. cells were harvested in sterile water and the cell suspension was transferred by a sterile syringe into the bioreactor. for shaking flask experiments inoculation was done by loop. these experiments were carried out in 250-ml flasks containing 100 ml medium. a 2 liter (b. braun biostat® m 1800/2000 ml) and four 1 liter (b. braun biostat® q 800/1000 ml) were employed for fermenter operations. in shaking flask experiments agitation speed and culture temperature were controlled at 200 rpm and 37 °c (medicor bri-1 rotatory shaker), and ph was maintained by addition of caco3 (stoechiometrically). in the fermentors agitation speed and culture temperature were controlled at 500 rpm and 37 °c respectively, the ph was regulated at 5.8 by 25 % h2so4 and 25 % nh4oh. the flasks, the buffering caco3 and the supplementing media-components were sterilized in an autoclave at 121 °c for 20 min. the wheat hydrolysate did not need sterilization (because of the applied high hydrolysis temperature) while the vitamin solutions were sterilefiltered. 3. media and hydrolysis basic wheat flour medium i. (without gluten): after adding 83 ml tap water to 100 g wheat flour (type 550), 1 hour kneading and addition of 104 ml tap water and 8.2 μl shearzyme® 500l enzyme (novozymes, denmark) was carried out for the agglomeration process. gluten fraction was separated by centrifugation (30 min, 3000 rpm, janetzky k70 d centrifuge), followed by washing with water, and diluting the starch suspension up to 500 ml. the liquefaction of starch was carried out for 40 min by 28 μl termamyl® sc (α-amylase by novozymes), at 85 °c and ph 5.5. for the saccharification (separately and prior to fermentation) 80 μl san® super 240 l (glucoamylase and protease by novozymes), for 46 hours, at 55 °c and ph 5.5 was used. hydrolysis was performed in a 2 liter b. braun biostat® m fermentor. basic wheat flour medium ii. (with gluten): 100 g wheat flour (type 550, protein content 11% [21], wet gluten content 27%) was suspended in tap water to a final volume of 500 ml. the liquefaction and saccharification steps corresponded to the above mentioned process. since the san® super 240 l product of novozyme contains proteases as well, the hydrolysis of gluten was done in line with saccharification. the additional supplements, i.e. yeast extract (reanal budapest, hungary), corn steep liquor (hungrana, szabadegyháza, hungary), yeast autolysate were added to the basic media before sterilization in shaking flask experiments or before hydrolysis in case of bioreactors. whey permeate (friesland-danone, nagybánhegyes, hungary) was used in place of tap water. yeast autolysate was made from 50 g baker’s yeast (lesaffre, budapest, hungary) by adding one drop of toluene, which helps the disintegration of cell wall and the auto-proteolitic activity of yeast cells. the vitamins (biotin, choline, cyanocobalamine, folic acid, inositol, nicotinic acid, paba, panthothenic acid, pyridoxine, riboflavin, thiamine and thymidine) were purchased from sigma-aldrich. 4. analyses substrates and products were analyzed by hplc (waters breeze hplc system, biorad aminex hpx87h column on 65 °c, mobile phase: 5 mm h2so4 at flow rate of 0.5 ml min-1). cell growth was measured as optical density (pharmacia lkb-ultrospec plus spektrophotometer) at a wavelength of 600 nm. in the case of shaking flasks the samples had to be acidified to dissolve caco3 but it resulted precipitation of wheat proteins which disturbed the optical density measurements. 51 results 1. fermentation on wheat starch hydrolysate without gluten and supplementations after the hydrolysis of the starch content of wheat flour the carbon source was the glucose content, the nitrogen source was only the water soluble protein content (in case of wheat flour type 550 the water soluble protein content is ~2.5% [21]). there was no further supplementation, the necessary minerals supposed to be stemmed from wheat and from tap water. the conversion was slow (fig. 1) and after one week cultivation the broth still contained 60 g l-1 residual glucose. this indicated the need of more supplementation for the growth of bacteria. obviously the obtained lactate yield of 64% and the volumetric productivity of 0.22 g l-1 h-1 can not be considered as industrially acceptable. 0 20 40 60 80 100 120 140 0 50 100 150 200 time (h) la ct at e, g lu co se (g l -1 ) 0 2 4 6 8 10 12 o d (6 00 n m ) figure 1: lactic acid fermentation on wheat starch hydrolysate without gluten and other supplements: (●) glucose; (▲) lactic acid; (■) optical (biomass)density 2. optimization of wheat starch hydrolysate based medium to ameliorate the efficiency of fermentation we had to improve the medium with some additional compounds. as a first step the nitrogen supplementation need was examined with three different nitrogen sources: yeast extract (ye), corn step liquor (csl) and yeast autolysate (y/t). the use of yeast extract (rich in vitamins, minerals, amino acids and other easily consumable nitrogen sources) in larger scale makes the process very costly. corn steep liquor, the by-product of corn starch producing technology which contains several vitamins and divers nitrogen sources has much lower price, since it is an agro-industrial by-product, thus it has no significant effect on process cost. yeast autolysate is made from toluene treated baker’s yeast and contains the same nutrient sources as yeast extract, but its prime cost is much lower. the main goal of these experiments was to find the appropriate amount of every single nitrogen source, applying them with equivalent total nitrogen amount and the results are shown in table 1. table 1: the effect of nitrogen-supplementation quality and quantity on lactic acid productivity nsupplementation amount of supplementation (g l-1) total ncontent (g l-1) productivity (48 h) (g l-1 h-1) 10 1 1.71 20 2 1.86 yeast extract 30 3 2.01 26 1 1.71 52 2 1.97 corn steep liquor 78 3 1.91 48 1 1.13 96 2 1.69 yeast autolysate 144 3 1.47 no suppl. (control) 0 0 0.01 as shown by the results the yeast extract and the corn steep liquor proved to be the most appropriate. however, the yeast extract in this amount (in a minimal amount of 20 g l-1) makes the lactic acid production significantly uneconomical, while the corn steep liquor is nowadays not available in hungary. the required total nitrogen amount is 2 g l-1 in the case of yeast autolysate, i.e. 96 g l-1 yeast autolysate is necessary for the fermentation. lab fermentation results with this optimized (yeast autolysate containing) medium (fig. 2) are convincing (lactic acid yield of 93%, productivity of 1.48 g l-1 h-1). nevertheless the enormous (96 g l-1) amount of the required yeast and the complicated previously necessary yeast cell inactivation and for their alcohol producing enzyme system remains partly active even after the inactivation, makes this supplementation inconvenient for a feasible technology. 0 10 20 30 40 50 60 70 80 90 0 10 20 30 40 50 time (h) la ct at e, g lu co se (g l -1 ) 0 5 10 15 20 25 30 35 40 o d (6 00 n m ) figure 2: lactic acid fermentation on optimized wheat starch hydrolysate without gluten: (●) glucose; (▲) lactic acid; (■) optical density 3. fermentation on wheat flour hydrolysate with gluten in the question of supplementations the necessity of finding cheap alternatives for yeast extract available in large amounts led to use the whole protein content of wheat (11% [21]). the gluten is the insoluble protein mixture of wheat, thus is not directly usable as medium component. after a proteolytic digestion it can be made water soluble and assimilable for the lactic acid bacteria as nitrogen source. 52 the proteolysis can be performed simultaneously with the starch hydrolysis and thus the whole flour suspension become usable as fermentation medium. the considerably long fermentation time beside of significant residual glucose concentration (fig. 3) posed the lack or limitation of nitrogen source or some other nutrients (amino acids, vitamins), which can be overcome by yeast extract. 0 20 40 60 80 100 120 0 50 100 150 time (h) la ct at e, g lu co se (g l -1 ) 0 2 4 6 8 10 12 14 16 o d (6 00 n m ) figure 3: lactic acid fermentation on wheat flour hydrolysate with gluten: (●) glucose; (▲) lactic acid; (■) optical density 4. further experiments to supply the wheat flour based medium to find an appropriate supplementation supporting lactic acid fermentation on wheat flour based medium ii. we tried to replace tap water by whey permeate, the byproduct of cheese manufacturing. since it contains lactose and milk proteins, whey can play the role of carbon and nitrogen source simultaneously. however the fermentation results showed that the whey protein was not sufficient to consume the whole glucose and the lactose content of the medium. nevertheless the combined lactic acid yield for both carbon sources was 96%, while the half of the lactose content remained in the system and the lactic acid productivity was as low as 0.52 g l-1 h-1. because the total nitrogen content of wheat flour should cover the nitrogen need of our bacteria, the bottleneck of the fermentation is not the amount of nitrogen source. since the best proven supplementation yeast extract contains a lot of vitamins beside its proteins as nitrogen source, we performed shaking flask experiments to determine the essential vitamins. table 2 contains the applied vitamins and their amounts equivalent to the vitamin content of 20 g l-1 yeast extract. in the first step a medium containing the listed 12 vitamins with no other supplementation was applied but the resulted 0.67 g l-1 h-1 productivity suggested the need of further supplementations. applying 12 vitamins in a flask together with 2 g l-1 yeast extract and the same without vitamins did not show significant difference resulting in 1.19 g l-1 h-1 and 1.16 g l-1 h-1 productivity respectively. however these results were convincing that only a minimal yeast extract supplementation could be sufficient to complete sugar-lactic acid bioconversion. table 2: vitamin content of shaking flasks vitamin amount of vitamin (μg/100 ml) biotin 6.6 choline 60 cyanocobalamine 0.2 folic acid 3 inositol 2800 nicotinic acid 1195.8 paba 1526 panthothenic acid 574.4 pyridoxine 86.4 riboflavin 233 thiamine 1059.8 thymidin 35 5. optimization of wheat flour hydrolysate based medium (with gluten) to find the above mentioned minimum amount of yeast extract (as the source of nitrogen or another necessary component) needed to the complete bioconversion of the glucose, the medium was supplemented by ye in different concentrations (table 3). table 3: the effect of yeast extract supplementation on lactic acid productivity* nsupplementation amount of supplementation (g l-1) total ncontent (g l-1) productivity (48 h) (g l-1 h-1) 0 0 0.80 1 0.1 2.23 2 0.2 2.45 3 0.3 2.47 4 0.4 2.29 5 0.5 2.48 10 1 2.63 15 1.5 2.49 yeast extract 20 2 2.41 *productivity results were calculated at zero residual sugar concentration according to the results shown in table 3 even the use of 1 g l-1 yeast extract can be sufficient to complete lactic acid fermentation with the gluten content of the wheat flour. the lab scale fermentation experiment on this optimized wheat flour based medium (with 1 g l-1 ye) reproduced the convincing results of shaking flask experiment with a yield of 90% and a productivity of 2.31 g l-1 h-1 (fig. 4). 53 0 20 40 60 80 100 120 140 160 0 10 20 30 40 50 time (h) la ct at e, g lu co se (g l -1 ) 0 2 4 6 8 10 12 14 16 18 o d (6 00 n m ) figure 4: lactic acid fermentation on optimized wheat flour hydrolysate with gluten: (●) glucose; (▲) lactic acid; (■) optical density conclusion the wheat contains carbon and nitrogen source in sufficient amount for lactic acid bacteria but in the form of heterogeneous mixture of various starch and protein macromolecules. the hydrolysis of starch and wheat proteins by commercial enzyme products obviously covers the nutrient needs of bacteria. the use of wheat gluten as nitrogen source significantly reduces the need of yeast extract which otherwise would make the lactic acid fermentation very costly. on the basis of a systematic culture medium optimization the initial 20 g l-1 yeast extract demand successfully decreased to as low as 1 g l-1 and by this process the volumetric productivity of lactic acid increased from 1.86 g l-1 h-1 to 2.31 g l-1 h-1 respectively. hereby we approached the lactic acid fementation efficiency had been reached with a previously optimized medium (3.86 g l-1 h-1). acknowledgement we wish to thank hunest biorefinery ltd. for financial support of this work and of our research group. references 1. rojan p. j., madhavan nampoothiri, ashok pandey: biotechnol. lett. 28 (2006) 1823-1826 2. the budapest times, www.budapesttimes.hu, 15 november 2007 3. hofvendhal, hahn-hagerdal: enzyme and microbial technology 20 (1997) 301-307 4. åkerberg, hofvendahl, zacchi, hahn-hagerdal: appl. microbiol. biotechnol. 49 (1998) 682-690 5. hofvendhal, akerberg, zacchi, hahn-hagerdal: appl. microbial biotechnol. 52 (1999) 163-169 6. akerberg, zacchi: bioresource technology 75 (2000) 119-126 7. olmos-dichara, ampe f., uribelarrea j.-l., pareilleux a., goma a.: biotechnology letters 19 (1997) 709-714 8. amrane, prigent, world journal of microbiology & biotechnology 14 (1998) 529-534 9. nancib a., nancib n., meziane-cherif d., abdelhafid boubendir, fick m., boudrant j.: bioresource technology 96 (2005) 63-67 10. krishnan s., prapulla s. g., rajalakshmi d., misra m. c., karanth n. g.: bioprocess engineering 19 (1998) 61-65 11. demirci, pometto, byungtae lee, hinz, j.: agric. food chem. 46 (1998) 4771-4774 12. hofvendahl, hahn–hagerdal: enzyme and microbial technology 26 (2000) 87-107 13. hurok oh, young-jung wee, jong-sun yun, seung ho han, sangwon jung, hwa-won ryu: bioresource technology 96 (2005) 1492-1498 14. rivas, moldes, dominguez, parajo: international journal of food microbiology 97 (2004) 93-98 15. nancib, nancib, boudjelal, benslimane, blanchard, boudrant: bioresources technology 78 (2001) 149-153 16. hetényi k., németh á., sevella b.: conference of chemical engineering ’07 17. kong, zhou, qian: food chemistry 101 (2007) 615-620 18. kong, zhou, qian: food chemistry 102 (2007) 759-763 19. kwon, lee, lee, chang, chang: 26 (2000) 209215 20. shankman, camien, block, merrifield, dunn: the journal of biological chemistry 168 (1947) 2331 21. university of oregon, eric hoffmann laugenbrötle, www.uoregon.edu, 12 november 2006 22. első pesti malomés sütőipari rt., www.epmsrt.hu, 18 october 2008 microsoft word a_04_r.doc hungarian journal of industrial chemistry veszprém vol. 38. pp. 15-19 (2010) study of traffic-related urban pm pollution at different locations v. csom1 , t. szentmarjay2, j. kovács1, e. domokos1 1university of pannonia, institute of environmental engineering, 10 egyetem street, veszprém, hungary 2national inspectorate for environment, nature and water, 4 patak square, veszprém, hungary e-mail: csomv@almos.vein.hu the overall purpose of this study was to determine the ratio of pm2.5 in pm10. measurements of suspended particulate matter were continuous and carried out at four sampling points in veszprém with two high volume samplers. the primary point of view in choosing the site of samplings was the investigation of the effect of the road traffic on the pm2.5 and pm10 concentrations. results show that the pm2.5/pm10 mass fraction mainly depends on the effect of vehicular traffic. furthermore it was also found that the daytime concentrations differ from the overnight ones. taking the pm2.5/pm10 ratios and calculating the pm2.5 concentrations from the pm10 data measured by the hungarian air quality network it can be concluded that many steps must be taken by the local governments in hungary to fulfil the limits and target values for pm2.5 laid down in the directive 2008/50/ec of the european parliament. keywords: dha-80 high volume sampler, suspended particulate matter, limit value, target vlaue, pm2.5, pm10, pm2.5/pm10 mass ratio. introduction among air pollutants particulate matter (pm10 coarse fraction and pm2.5 fine particles) plays an important role in causing serious health effects so the european union deals with them as special importance. in the last decade studies of the short-term effects of pm – based on association between daily changes in pm10 concentrations and various health outcomes – were conducted all over europe. in general, results indicate that pm increases the risk of respiratory death in infants under 1 year, affects the rate of lung function development, aggravates asthma and causes other respiratory symptoms such as cough and bronchitis in children. pm2.5 seriously affects health, increasing deaths from cardiovascular and respiratory diseases and lung cancer. increased pm2.5 concentrations increase the risk of emergency hospital admissions for cardiovascular and respiratory causes; and pm10 affects respiratory morbidity, as indicated by hospital admissions for respiratory illness. [1] air quality control is one of those fields where many steps were taken by the european union recently. the committee amis to establish a comprehensive strategy through which the air quality might be preserved for a long time. a new directive was established out of turn in favour of the reduction of particulate matter concentration. directive 2008/50/ec – on ambient air quality and cleaner air for europe – was released on 21 may 2008. limit value for pm10 has already been known from previous directive (96/62/ec) but pm2.5 was never before controlled. by now new air quality objectives are set for pm2.5 including the limit value and exposure related objectives – exposure concentration obligation and exposure reduction target. member nations got patience time while they have to make arrangements for staying under these limit values. [2, 3] figure 1: number of people suffering from asthma in budapest (1980–2006) experiences during air quality control definitely show that changing social-economical circumstances have modified the significance of some air pollutants in the last decades. traffic originating components are coming 16 to the front where particulate matter plays an important role for its chemical composition, pollution extent and health effect (fig. 1) [4]. we have quite a few pm2.5 measuring data in hungary. continuous fine particulate measuring occurs only at four places therefore for arrangement plans only the pm10 concentrations can be used. our aim was in the course of work to make us able to estimate the pm2.5 fraction from the available pm10 concentrations. materials and methods measurements for determining the fractions of pm10 and pm2.5 were carried out in harmony with the msz en 12341:2000 and msz en 14907:2006 standards that are the hungarian versions of those ones that were worked out by cen, european committee for standardization. two dha-80 high volume samplers of the same kind (fig. 2) were used simultaneously. one of them was operating with a pm10 pre-separator, the other one was equipped with a pm2.5 pre-separator. both appliances correspond to the reference requirements. figure 2: dha-80 high volume sampler (hvs) fig. 2 shows the operating system of a hvs. the air is sampled via a sampling probe (1), using a sampling tube, vertically from the top to the bottom through the filter (3) placed in the flowing chamber (2). with dha-80, changing of filters is done automatically. after the filter, the transported air quantity is measured using a flow meter with a floater (5). its double photo-sensor (5a) optically senses the floater position. in connection with the control electronics (5b, 5c), the capacity of the blower (6) is adapted to the rpm control, so that the air quantity keeps the set-point value. air pressure and temperature are measured upstream the flow meter and continuously averaged by the controller. a real-time protocol states sampling volumes yielding from the sampling time and controlled volume flow as the core information. the air is released from the instrument with reduced noise through the noise baffle (7). air-borne dust particles in the sampled air are separated on to ø 150 mm filters. the flown filter diameter is 140 mm. sequent gravimetric and analytical analysis could be conducted depending upon the pollutants of interest. the filter conditioning is very important in order to achieve reproducible results. dha-80 has a container of 15 filters stretched in filter holders. they were changed automatically to the flow position at the pre-set time. the selected air flow rate is controlled by a flow meter. this value should be calibrated first at the beginning of a measurement, using a gas meter or a secondary standard, e.g. an additional flow meter. during air sampling, the pump flow rate is dynamically controlled, so that this limit value is kept at good reproducibility and at long-term stability despite the deposited filter flow resistance and the sampled ambient air pressure/temperature variation. an integrated microprocessor unit controls the filter changes at the exact pre-set time and collects all relevant data and events. hereby the air quantity flowing through the filter is defined with high accuracy. [5] results and discussion continuous measurements of suspended particulate matter were carried out at four sampling points in veszprém with two high volume samplers. the overall purpose of this study was to determine the ratio of pm2.5 in pm10. the primary point of view in selecting the site of samplings was the investigation of road traffic effect on pm2.5 and pm10 concentrations. among these sites (fig. 3, table 1) we can find such places where the effects of traffic have low importance and places where effects are remarkable in point of air quality. figure 3: sampling sites 17 before the series of measurements we carried out parallel measuring with the two samplers (with the same pre-separators, pm10 pm10, pm2.5 pm2.5) to see whether data we measure matches with the accuracy criteria or not. table 1: sampling sites in veszprém places eov laboratory of central-transdanubian inspectorate for environment, nature and water 4 patak square 563035e 195511n bárczi gusztáv elementary school 12 batthyány street 564798e 196206n hospital 5 mártírok street 563771e 194645n balaton shopping centre 20-28 budapest street 564298e 195187n from the statistical examination results (table 2) it can be concluded that measuring data fulfil the instructions related to the accuracy that is k95 ≤ 5 µg/m3. table 2: comparison of the two hvs samplers (equipped with the same pre-samplers) di (µg/m3) di 2 /2n ∑di 2 /2n sa k95 0.7 0.082 pm10 0.7 0.082 0.6 0.060 0.223 0.47 2.03 0.6 0.060 pm2.5 0.1 0.002 0.3 0.015 0.077 0.28 1.20 measurements were carried out for two days for 12-12 hours (concentrations of a whole day can be determined from the half-day data) after this for another three days for 24 hours at each places. the half-day measurements were started at 1800 and 0600. the aim of this division was to control how pm pollution changes at night time when traffic is low and in the daytime when traffic is heavy. 4 patak square (laboratory of central-transdanubian inspectorate for environment, nature and water) ratio of pm2.5 in fraction pm10 changed between 60 and 70% (fig. 4). probably the higher ratio of pm2.5/pm10 (table 3) is due to the rain whilst sedimentation of coarse particles (pm10) occurs. concentration of pm10 was lower on this day as well. effect of traffic has no importance on this site. table 3: pm2.5 and pm10 concentrations during 24-hour measuring [µg/m3] date pm10 (µg/m3) pm2.5 (µg/m3) pm2.5/pm10 (%) 11-12 sept. 27.9 20.1 72.0 14-15 oct. 34.6 22.9 66.2 15-16 oct. 45.3 28.0 61.8 figure 4: ratio of pm2.5 in pm10 [%] 12 batthyány street (bárczi gusztáv elementary school) this place cannot be regarded obviously to be a so called “background station”. traffic is not determinant but we should not leave it out of consideration. from the 24-hour-data it emerges that the ratio of fine particles increases above 70% (fig. 5) that is ca. 10% higher than values on patak square. difference may be due to the vehicular traffic that is not far from this measuring point. considering fig. 6 it can be stated that ratios of pm2.5 in pm10 are higher at night time (18:00–06:00) than in daytime. we can conclude that a bigger part of the coarse fraction settles out in the late evening hours when traffic and air motion decrease. figure 5: ratio of pm2.5 in pm10 [%] figure 6: ratio of pm2.5 in pm10 [%] 18 5 mártírok street (next to hospital) ratio of pm2.5/pm10 was around 70% during the whole week we measured. weather was not the same on every day and these changes appear in the concentrations as well (table 4). weather was rainy on the last days, during this time around both type of concentrations decreased. half-day values (fig. 7) vary on the same way as in the previous case (fig. 6). table 4: pm2.5 and pm10 concentrations during 24-hour measuring [µg/m3] date pm10 (µg/m3) pm2.5 (µg/m3) pm2.5/pm10 (%) 29-30 sept. 21.3 14.9 70.0 30 sept. – 1 oct. 24.3 16.2 66.7 1-2 oct. 22.1 15.1 68.3 2-3 oct. 19.2 12.5 65.1 3-4 oct. 9.0 6.2 68.9 figure 7: ratio of pm2.5 in pm10 [%] 20-28 budapest street (balaton shopping centre) almost all week was wet. first day of the week was the rainiest, next days there was just drizzling. fig. 8 shows that rain has stopped for a while in the middle of the week and as a result of it concentrations started to increase. as rain appeared again values started to decrease. it is evident that particulate matter is settled out from the ambient air. figure 8: pm2.5 and pm10 concentrations during 24-hour measuring [µg/m3] it can be explained at first with heavy traffic because budapest street has the biggest vehicular traffic among the four selected sites. dust can be derived from exhaust pipes, from abrasion of rubber tyre and mountings of motor vehicle. these particles are continuously stirring so they stay in the ambient air. another fact is that exhaust gases can be characterized primarily by the pm1 and pm2.5 fractions therefore these ranges will be the most significant part in pm10. settling out of coarse fraction can be observed as well (fig. 9) such like in the previous cases. we must mention one more possible explanation for the high amount of pm2.5 in pm10. it may happen that the non-wetting agglomerated particles fall apart to finer particles under the influence of rainy days. figure 9: ratio of pm2.5 in pm10 [%] summary pm2.5-pm10 measurements on different kind of places show that the mass ratios of pm2.5 in pm10 are broadly speaking similar at those places where the effects of traffic are not remarkable. as we can see it below (in table 5) places that are hardly influenced by vehicular traffic have a pm2.5/pm10 ratio of 69%, but where this effect is significant the pm2.5/pm10 ratio increases up to 85% (fig. 10). difference is conspicuous. these facts confirm our aspect that traffic might be the most important reason for pm1-pm2.5 (fine particle) pollution. table 5: confidence interval determined from the pm2.5/pm10 scatterings apart from the measuring sites we experienced that the pm2.5 ratio was always higher at night time (1800–0600) than in the day time (0600–1800). because of the measurements’ short time the calculated ratios are just estimations. to have more exact values many more measurements are needed. 19 figure 10: pm2.5 and pm10 concentrations during 24-hour measuring [µg/m3] the ministry of environment and water accomplished a nationwide measuring together with the inspectorates for environment, nature and water in 2005 and 2008 through the whole year. the type of their measuring sites in veszprém were similar to our ones. one of them was the same (budapest street) and the other one was like patak street that is a kind of “background” station. average of their measuring data in 2005 is 37.8 µg/m3 and it was 21.0 µg/m3 in 2008. if i take our ratios as a norm we have to realise that the pm2.5 concentration would be at the former one 32.0 µg/m3 and in the latter case it would be around 14.0 µg/m3. we must see that pm2.5 concentrations increase above the target value (20 µg/m3) without doubt at those places where traffic is remarkable. serious arrangements are needed everywhere to be able to fulfil limit values set in the directive 2008/50/ec. [6, 7] acknowledgement we acknowledge the financial support of this work by the hungarian state and the european union under the tamop-4.2.1/b-09/1/konv-2010-0003 project. references 1. b. vaskövi: tendency of dust pollution, evaluation of measuring strategy after the changes of rules. study: on behalf of the ministry of environment and water, 2004. 2. council directive 96/62/ec of 27 september 1996 on ambient air quality assessment and management. (directive 1996/62/ec) 3. directive on ambient air quality and cleaner air for europe. (directive 2008/50/ec) 4. h. christos: integrated exposure management tool characterizing air pollution relevant human exposure in urban environment. literature review on urban exposure, 2002. 5. dha-80 high volume sampler (hvs) operating handbook. 6. v. csom: determination of pm2.5 and pm10 concentrations simultaneously in the ambient air, estimating their ratio. diploma work, pannon university, faculty of engineering, institute of environmental engineering, 2008. 7. e. kulcsár: examination of dust pollution in veszprém. diploma work, pannon university, faculty of engineering, institute of environmental engineering, 2006. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 65-69 (2008) modelling of multi-step microfiltration process for solvent exchange z. kovacs1 , m. discacciati2 1johannes kepler university linz, institute of process engineering, welser st 42 a-4060 leonding, austria e-mail: zoltan.kovacs@jku.at 2ecole polytechinque fédérale de lausanne, iacs chair of modeling and scientific computing (cmcs) ch-1015, lausanne, switzerland industrial-scale microfiltration (mf) separation is applied to process a dispersed ternary system containing an organic solvent, water and fine particles. the objective of the separation is to exchange the organic solvent with water and concentrate the water-particle dispersion. the mf separation is carried out in a multi-step batch operation including preconcentration, dilution mode, and post-concentration process steps. in this study, we present a practical computational algorithm which can be used as a basis for process simulations of both concentration and dilution modes. the numerical method is based on mass balance processing and on empirical relations of the rejection and the permeate flux to the feed composition. these empirical relations are obtained from the experimental data of a single test-run with the process liquid. we discuss the input data of the code and the respective experimental design with the necessary sampling. finally, we provide optimum-search techniques considering economical aspects and technological demands. keywords: microfiltration, modelling, solvent exchange, diafiltration, optimization introduction one of the major solvent consuming processes in the chemical and the pharmaceutical manufacturing is solvent exchange. organic solvents are widely used as reaction media for chemical synthesis, raw materials, and as cleaning agents [1]. membrane technology has a great potential to improve the performance of many liquid phase synthesis reactions by reducing the need for complex solvent handling operations. membrane separation can provide a cheaper solution over the conventional solvent exchange via distillation, when the solvent to be removed has a lower boiling point than the replacing solvent [2]. in batch membrane system design, a common separation strategy for selective removal of components with low retentions is to employ a multi-step membrane process. a multi-step batch process is a chain of operations of a defined number and order that are carried out consecutively using the same membrane module. there are two basic operation modes: the concentration and the dilution mode. in a general case, a multi-step process consists of three steps (e.g. operations): preconcentration, dilution mode and post-concentration steps. this concept is one of the conventional process techniques to achieve high purification of macro-solutes with an economically acceptable flux [3]. batch membrane separation has been presented in a number of different forms in the past, which is, and continues to be an active area of interest both academically and industrially. the classical mathematical modelling [4,5] uses the concentration factor as a basis for the calculations, while numerical techniques [6,7] handle the permeate flux and the component rejections as (time-dependent) state functions of the feed composition. in this study, we present a practical computational algorithm which can be used for the simulation of batch operations. the numerical method is based on mass balance processing and on empirical relations of the rejection and the permeate flux to the feed composition. these empirical relations are obtained from experimental data that were obtained from a test-run with the process liquid. we discuss the input data of the computational algorithm and the respective experimental design with the necessary sampling. finally, we provide optimumsearch techniques considering economical aspects and technological demands. although real-life experimental data are used in this study, the latter strictly focuses on the mathematical programming approach, and it does not aim to give a detailed insight into the properties of the applied colloidal system and the confidential technological specifications of the industrial settings. problem statement industrial-scale mf separation is applied to process a ternary dispersed system containing an organic solvent, water and fine particles. the objective of the separation 66 is to exchange the organic solvent with water, and concentrate the water-particle dispersion. the schematic configuration of the industrial membrane filtration plant is shown in fig. 1. figure 1: schematic representation of the batch configuration two basic modes of batch operation are considered: the concentration and the dilution mode. in the concentration mode, the retentate stream is completely recycled into the feed tank, and the permeate stream is collected separately, that results in a continuous volume decrease in the feed tank. in the dilution mode, a diluant is added into the feed tank at a rate equal to the permeation rate. a level sensor is activated in the feed tank, which keeps the adjusted level of the feed volume constant by continuous addition of the wash water. the total weight of the particle in the feed tank remains constant due to the complete rejection, but the solvent passes through the membrane. since the permeate stream is replaced with wash water, there is a continuous decrease of solvent concentration in the feed tank during the dilution mode. the colloidal dispersion is produced batch-wise via chemical synthesis. this ca. 250 kg dispersion is the initial feed for the mf process, and it contains ca. 10 w/w% fine particles and ca. 30 w/w% solvent. the mf separation is carried out in a multi-step batch operation including pre-concentration, dilution mode, and post-concentration process steps. due to technical requirements, the solvent concentration has to be reduced to 0.05 w/w%, and the dispersion concentrated to 100 kg. as far as the membrane separation performance is concerned, the water and solvent permeation rates through the mf membrane are equal, and the dispersed particles are completely rejected by the membrane. the stability of the colloidal system can also affect the mf process performance. at certain feed composition range, the dispersion becomes unstable. this phenomenon can lead to sludge formation which can completely plug the membrane. thus, extra care is needed in the process design. the objective of this study is to define the mathematical basis of the chemical engineering problem by building a model based on real-life experimental data. the problem is attacked with suitable mathematical programming techniques that gives quantitative prediction for the unit operation steps, and provides the optimum operational settings for the overall multi-step separation process. modelling concept the multi-step process is carried out at constant pressure and temperature, and the same hydrodynamic conditions are maintained during the operation. thus, at any time and at any step of the process, the permeate flux can be described solely as a non-linear function of the actual feed composition. the computational technique summarized in the scheme of fig. 2 was developed in order to predict the changes of the feed tank volume and the feed composition during the membrane filtration process. figure 2: uml activity diagram of the process simulation it is assumed that the initial feed concentration of both particle cf p and solvent cf s are known. for simulation purpose, we prior define a sufficiently small time interval δt. if the relationship between permeate flux and feed composition is known, than the permeate flux can be calculated for the initial feed dispersion at the beginning of the process. therefore, the small volume of the permeate δv, which passes through the membrane in the small time-interval, can be quantified. the relationship between flux and feed composition, e.g. j = j(cf p, cf s), can be obtained from theoretical membrane transport models. however, in this study, we use a practical approach based on experimental data. this approach ensures the derivation of a reliable relation from a limited number of experimental data without prior approximations. the function j = j(cf p, cf s) was empirically determined during a test-run with the process stream. complete particle retention is proved with analytical measurements, and the water and solvent permeation rates through the membrane are found to be equal. thus, the mass of each component in the very small permeated volume δv can be estimated. 67 thereafter, mass and component balances for both permeate and feed tank can be used to determine the new compositions and total masses. then, the above described procedure can be repeated with the new values. obviously, in dilution mode operation, we assume a wash-water volume inlet into the feed tank, which is equal to the δv permeated volume. the exit condition of the cycle is the prior defined volume, which is collected in the permeate tank, or alternatively, the solvent concentration in the feed tank. during the computational cycle, the feed composition is checked to determine whether the dispersion is stable and separation can be continued. this code can be run either in concentration or in dilution mode and multi-step process can be built up from individual blocks by defining the input arguments of a latter step as the output arguments of the previous step. the number and the order of the individual steps can be freely chosen by the user. this practical computational technique is not restricted to mf applications, and one can simulate diverse modes of operations. in a recent study [7], a similar numerical approach is presented for the simulation of the separation of inorganic salts from organic molecules with multi-step batch nanofiltration. process simulation the permeate flux was experimentally determined for different feed compositions during one test-run of the industrial-scale membrane plant on place at the chemical company. the initial ca. 250 kg feed was concentrated to ca. 160 kg, and thereafter, 90 kg water was added into the feed tank. then this procedure was repeated several times. although membrane cleaning was not performed in between the concentration mode operations during the test-run, an increased permeate flux was always observed after each concentration step. this may indicate that fouling has minor importance during the process. during this test-run, the permeate flux was measured periodically, and at the same time, samples were taken from the permeate stream for solvent concentration analysis. the solvent/water ratio in the permeate stream was always equal to the actual solvent/water ratio of the feed tank. the total particle mass in the feed tank was 28 kg, and it remained constant during the operation due to complete rejection. the particle concentration in the feed tank was determined by monitoring the total feed volume at the time of sampling. the experimental data of the permeate flux as function of particle and solvent feed concentrations are shown in fig. 3. both particle and solvent feed concentrations have significant contributions to the observed permeate flux. the unstable composition regime, that is where no permeate flux can be measured, is well visible in fig. 3. based on the experimental data, this regime is empirically defined by the set of feed concentrations which satisfy 0.142 ≤ cf p ≤ 0.17 and 0.018 ≤ cf s ≤ 0.092, where cf p and cf s are the particle and the solvent concentration in the feed tank, respectively. figure 3: experimental data of permeate flux (illustrated with x) in the function of particle and solvent concentration (lines are to guide eyes.) it is important to understand that the pronounced flux decline in the above defined region is provoked by the physical-chemical changes in the colloidal system, and the membrane permeation decline is a response to these radical dispersion-based changes. the experimental values of permeate flux follow a uniform trend which is broken only in the unstable regime. thus, it seems reasonable to determine the overall trend for the permeate flux, and to handle the instable regime separately. the permeate flux can be expressed in terms of cf p and cf s by fitting the non-zero experimental results using an equation like: ( ) ( ) ( )f s f s f s cxf p cxf p cx excexcexj 642 53 2 1 −−− ++= , where xi, i = 1, 2, … 6 are the fitting parameters. the estimated empirical plane and the set of coefficients are shown in fig. 4. figure 4: estimated (solid lines) and experimental data (*) of permeate flux in the function of solvent and particle concentration (curve-fitting is based on non-zero flux data.) 68 the changes in the permeate flux and in the concentrations in feed tank are calculated through the computational procedure using the actual (timedependent) feed concentrations. this dynamic method differs from the conventional calculation procedures that are based on volume concentration factors. the currently applied process has three operational steps. first, the initial feed is pre-concentrated. this step is characterized with the pre-concentration grade mpre, which is defined as the total mass of the dispersion in the feed tank when the second step, the dilution mode, starts. thus, for example a pre-concentration grade mpre=200 kg means that the initial 250 kg dispersion is concentrated to 200 kg before the dilution mode starts. fig. 5 shows the complete simulation of a 3-step process. the feed was first concentrated to 200 kg, then dilution mode operation was carried out by applying 1100 l wash-water, and finally the dispersion was concentrated to 100 kg. the permeate flux and the solvent concentration in the feed tank can be predicted over the operation time as shown in fig. 5. figure 5: simulation example for a three-step process including pre-concentration, dilution mode, and post-concentration steps during the pre-concentration step, the increasing feed concentration causes a decreasing flux. it is a conventional wisdom that the amount of wash-water is minimized if it is added where the feed concentration is high [8]. however, as shown in fig. 4, high feed concentrations lead to lower solvent fluxes through the membrane. thus, an optimum pre-concentration grade exists for performing the dilution mode. process optimization the aim of the optimization is to find the set of operation parameters that result in the most economical process, and satisfy the given technological demands of the final product. thus, the total processing cost is the objective function that has to be minimized; the operational parameters of pre-concentration grade mpre and xdiluant volume vd are the decision variables, and the given technological requirements are the constraints of the optimization. we define a product quality and a product mass constraint, e.g. the final solvent concentration has to be reduced under a limit value of climit=0.05 w/w% and the final product mass mfinal of 100 kg has to be obtained. the objective function can be defined as the total cost per unit of product produced. the total cost is a sum of two terms, which are the operational cost of the pump and the cost of the utilized dilution water. the mathematical problem can be described as follows: minimize f(mpre,vd) = k1t + k2vd subject to the constraints mfinal =100 kg and cs final ≤ climit where f(mpre,vd) is the objective function, t is the total operation time, vd is the dilution water consumption, while k1 and k2 are constants. the constant k1 is a product of the power consumption of the pump and the electricity price, and k2 is the unit price of the utilized dilution water. computer simulation of 3-step processes was performed for sets of mpre and vd input parameters. thus, in the first process step, the dispersion was concentrated to a pre-concentration grade mpre, then the diluant volume of vd was applied to wash out the solvent, and finally the dispersion was concentrated to 100 kg in the last step. during these 3-step processes, membrane plugging caused by sludge formation can occur when the composition in the feed tank becomes instable. fig. 6 shows the instable area for the applied operational parameters. figure 6: instable dispersion area illustrated for the applied operational parameters a flux decline can also occur due to high feed concentration as shown in fig. 4. with other words, the dispersion can not be concentrated to a too high extend, because in that case no permeate flux can be gained. obviously, the location of the optimum is affected, not only by the pre-concentrated grade, but also by the extent to which the solvent concentration is reduced in the dilution mode step. the applied diluant volume vd has to be sufficiently big in order to exchange the 69 solvent in the feed tank. if vd is too low, the final solvent concentration can not be reduced to the desired limit value. these issues all contribute to a reduced feasible region in the (mpre,vd) matrix. fig. 6 shows the calculated objective function values in the feasible range. figure 7: objective function in the feasible range as function of pre-concentration grade and diluant volume as shown in fig. 6, for each pre-concentration grade mpre can be found a diluant volume vd, where the quality demand for the final solvent content is satisfied. the optimum operational parameters (mpre,vd) are given by the minimum value of the half-plane of the calculated objective function in the feasible range, and it can be directly read from the graph. it should be noted that the outcome of the optimization is not generally valid. a change in the constants k1 and k2 of the objective function, or the utilization of an other type of membrane would result in a different set of optimum operational parameters. summary a numerical technique is presented to simulate and optimize multi-step batch membrane processes for solvent exchange. this technique can be also used to simulate membrane filtration processes where not only the flux, but also the rejections of the components are dependent on the feed composition. the approach followed in this work did not use the volume concentration factor as a basis for the calculations, but rather the flux as a state function of the feed concentrations. references 1. hellweg s., fischer u., scheringer m., hungerbuhler k.: green chem. 6 (2004) 418 2. lin j. c., livingston a. g.: chem. eng. sci. 62 (2007) 2728-2736 3. blatt w., robinson s.: anal. biochem. 26 (1968) 151-173 4. baker: membrane technology and applications, wiley, west sussex, (2004) 5. mulder m.: basic principles of membrane technology, kluwer academic publishers, dordrecht, (2000) 6. discroll k.: development of a process simulator for the ultrafiltration/diafiltration process. ph.d. thesis, university of arkansas, fayetteville, us (2004) 7. kovacs z., discacciati m., samhaber w.: j. memb. sci. 324 (2008) 50-58 8. morison k. r., she x.: j. memb. sci. 211 (2003) 59-70 microsoft word contents_2.doc hungarian journal of industrial chemistry veszprém vol. 31. pp. 71-75 (2003) solid-phase tryptophan synthase biocatalysts and their application in integrated bioconversion system cs. sisak, á. kovács1, b. szajáni2, l. boross and l. orosz2 (university of veszprém, research institute of chemical and process engineering, p.o.b. 158, h-8201 veszprém, hungary; sisak@mukki.richem.hu 1university of veszprém, department of chemical engineering p.o.b. 158, h-8201 veszprém, hungary 2eötvös loránd university, department of genetics p.o.b. 120 h-1518 budapest, hungary) a trpab gene cloned e. coli strain of high tryptophan-synthase activity was cultivated then the separated biomass was permeabilized [1]. agglomeration of the cells, entrapment into ca-alginate gel and adsorption onto celite-560 beads were investigated to get solid-phase biocatalysts. biotransformation experiments for production of tryptophan and its 5-hydroxy derivative via coupling l-serine with indole/5-hydroxy indole were carried out in aqueous /organic system. productivity has been found to the highest in case of using agglomerated biomass and celite-560 adsorbed biomass but the reusability of the former catalyst was not acceptable. setting-up possibilities of an integrated system consisting of the tryptophan biosynthesis step and of a product separation step have been studied. the aim was to increase the productivity of the bioprocess through reducing the effect of product inhibition. adsorption of the product onto xad-4 neutral resin has proved to be selective enough [2] for its separation from the substrates. the system with alternate operation of the catalytic bioconversion step and the product adsorption step seems to be applicable for production of tryptophan but enhancement of the working stability needs further investigations. introduction solid-phase biocatalysts play an important role in enzyme catalytic production of numerous amino acids and their derivatives. if it follows from the character of the process that non-conventional reaction medium should be chosen, the significance of application of immobilized enzymes increases because they are considerably more stable than native enzymes [3] in such conditions. on the other hand, if the efficiency of bioconversion can be enhanced by simultaneous product removal the reusability of the biocatalyst can be improved by its immobilization [2,4]. according to the literature [2,4,5], and to our previous results [6,7], the use of non-aqueous medium and the application of integrated system both have importance in the biocatalytic synthesis of tryptophan and its derivatives: on one hand, indole substrate can be hardly dissolved in aqueous medium, on the other hand, the in situ removal of the formed amino acid is reasonable to decrease the product inhibition. the aim of this article is to show our results in the matter of the biosynthesis carried out by solidphase biocatalysts produced in different ways as well as concerning the studies on the integrated system including the biocatalysis step and the product removal step. experimental part microorganism: escherichia coli strain with cloned trpab gene was constructed at the agricultural biotechnology center, gödöllő, hungary. 72 maintenance: the e. coli culture was maintained on solid substrate containing 1 % tryptone, 1 % nacl, 5% yeast extract, 2-3 % agar, 20 µg/10 cm3 ampicillin. fermentation and harvesting: tubes were washed into 50 cm3 medium in 300 cm3 e. flask, shaken at 37 oc, 190 rpm for 24 h. (medium: 0.1 mole phosphate buffer ph=7.8 supplemented with 5 g nacl, 1 g yeast extract, 10 g tryptone, 5 mg ampicillin in 1 dm3). then 5 cm3 broth was transferred to 200 cm3 medium and was shaken again for 24 h. a mechanically stirred fermenter (br-97/inel) of 5 dm3 was inoculated with 500 cm3 broth, using the aforesaid medium. cells were harvested by centrifugation then permeabilized by freezing at -20 oc [1]. preparation of solid-phase biocatalysts: biocatalyst a: agglomeration of the cells: the wet, permeabilized biomass was dried on air [6] at room temperature and was stored in refrigerator at 5 oc. biocatalyst b: entrapment into ca-alginate gel: 0.5 g cell mass was suspended in 5.5 cm3 dist. water and the suspension was mixed with 10 cm3 na-alginate solution of 4 w/w% then it was dropped into 0.5 m cacl2. biocatalyst c and biocatalyst d: adsorption onto celite-560 beads: the autoclaved celite-560 (fluka) particles (5 g) were added to 200 cm3 fermentation broth at the 15th (c) and the 48th (d) hour of the fermentation, respectively. the separated particles were dried on air [6] at room temperature and were stored in refrigerator at 5 oc. efficiency of immobilization was evaluated via productivity measurements. the productivity was given in mg trp / mg fixed protein /h and mg trp / mg catalyst /h, respectively. biotransformation conditions: 10 µmol/dm3 pyridoxal-5-phosphate, 0.38 mol/dm3 l-serine, 5 mg/dm3 ampicillin were solved in dist. water and mixed with cyclohexane containing 0.25 mol/dm3 indol or with 2-etil-hexanol containing 0.25 mol/dm3 5-hidroxy-indole. the volume ratio of aqueous and organic phases was changed between 1:4 and 1:9. solid-phase biocatalysts (a),(b),(c) or (d) were added with concentration of 0.15-10 mg biomass / cm3 reaction mixture and were shaken in 50-100 cm3 e. flasks at 37 oc for 72-96 h. concentration of indole or 5-hidroxyindole in the aqueous phase was 0.05-0.1 m. adsorption studies: amberlite xad-4 neutral resin (rohm and haas) [2] was used as adsorbent. l-tryptophan or 5-hidroxy-l-tryptophan were dissolved in 0.1 m phosphate buffer and shaken in flasks with the adsorbent at 37 oc and 175 rpm for 1 hour. studies on parallel adsorption of the substrates and products were carried out in a mixture consisted of 90 % phosphate buffer and 10 % cyclohexane or 2etil-hexanol. analytics: tryptophan and indole content of samples were analyzed by hplc (hp-1050) uv detector at 254 nm. (column hypersil 10 µm (250 x 4 mm), eluent: 20:20:60 mixture of acetonitrile, methanol and phosphate buffer (0.0175 m kh2po4-h3po4), eluent flow rate 0.7 cm3/min.) integrated biotransformation – product adsorption system: the equipment for testing the operation of the integrated system (fig. 1) consisted of 2 parts applied unit 1 unit 2 figure 1: equipment for testing the operation of the integrated biotransformation product adsorption system 73 alternately to perform the catalytic bioconversion step and the product adsorption step. biotransformation was carried out in a 500 cm3 e. flask (unit 1) with 200 cm3 reaction mixture consisted of 20 % organic phase with 0.1 m indole and 80 % aqueous phase with 0.15-0.3 m l-serine. the mixture containing 10 and 5 g biocatalyst b and d, respectively was shaken at 37 oc and 175 rpm. after achieving a sufficiently high amino acid level the reaction mixture was settled then the aqueous phase was transferred into unit 2 where the product adsorption was performed. the adsorbent, amberlite xad-4 neutral resin was mixed with the liquid phase at 37 oc, 175 rpm for 1 hour. then the cyclic functioning of the system carried on and the two-step process was repeated several times in succession. results comparison of different types of immobilized biocatalyst: table 1: specific tryptophan production of different solid phase biocatalysts of different type during 72 hours reaction type of immobilized biocatalyst tryptophan production in72 hours (mg ttrp /mg protein) agglomerated permeabilized biomass (biocatalyst a) 0.157 ca-alginate entrapped biomass (biocatalyst b) 0.004 adsorbed cells onto celite-560 beads in the 15th hour of fermentation (biocatalyst c) 0.223 adsorbed cells onto celite-560 beads in the 48th hour of fermentation (biocatalyst d) 0.417 among the solid-phase biocatalysts, the agglomerated permeabilized biomass showed the best productivity expressed in mg trp / mg catalyst /h but its reuse was very difficult because – due to the small particle size – the loss was high. using caalginate entrapped biocatalyst the productivity was low because of the internal diffusional resistance. cell adsorption onto celite-560 beads has resulted in sufficient productivity and recycling properties. on the basis of the above presented results, the third type immobilized catalysts were chosen to examine its stability properties, accordingly cells were adsorbed onto celite-560 beads by method ‘c’ and ‘d’. 0 1 2 3 4 5 6 7 1 2 3 4 5 6 number of synthesis cycles pr od uc ed l -tr yp to ph an (g /d m 3 ) immobilization in the 15th hour immobilization in the 48 th hour figure 2: catalytic stability of celite-560 supported e. coli cells during tryptophan production cycles the results of stability studies show that the time of addition of the support particles to the fermentation broth influences the catalytic stability of the immobilized cells. if celite-560 was added in the 15th hour (biocatalyst c), the initial activity was significantly lower than in the case of the support addition in the 48th hour (biocatalyst d). on the other hand, the residual activity of biocatalyst c, left after the 6th cycle was almost two times higher than that of biocatalyst d. comparison of formation of tryptophan and 5hydroxy-tryptophan: as it can be seen in fig. 3 the kinetics and the productivity of the amino acid formation catalyzed by biocatalyst a are very similar both in case of production of tryptophan and its 5-hydroxy derivative. 74 0 5 10 15 20 25 0 25 50 75 100 125 reaction time (h) a m in o ac id p ro du ct iv ity (g /c m 3 / g ka t) trp (g/dm3/gkat) 5-oh-trp (g/dm3/gkat) figure 3: formation of tryptophan and 5-hydroxy-tryptophan as functions of reaction time, using agglomerated biomass as catalyst adsorption experiments to develop the adsorption effectiveness we considered the previous results [2] and our selectivity and capacity measurements [7] in aqueous / organic two-phase system as a model of the reaction mixture, which contains the substrates and the product, too. it was found that the capacity of xad-4 resin adsorbent was considerably lower for tryptophan in the presence of indole than without it. the capacity reducing effect was more pronounced in case of adsorption of 5-hydroxy derivatives (fig. 4). the presence of l-serine moderated the indole effect in case of the tryptophan [7]. 0 0,5 1 1,5 2 2,5 3 3,5 4 4,5 0 1 2 3 4 5 6 initial amino acid concentration (mol/dm3×102) a ds or be d am in o ac id (m ol /g ×1 04 ) trp trp+ind 5-oh-trp 5-oh-trp+5oh-ind figure 4: adsorbed l-tryptophan and 5-hydroxy tryptophan quantities on xad-4 neutral resin as functions of composition of the aqueous liquid phase it was concluded from the adsorption results that the effective tryptophan separation is not possible from the two-phase reaction mixture system. therefore after settling of the phases adsorption experiments were carried out in the aqueous phase saturated with indole. in point of all the facts, the reduced capacity seemed to be high enough to use the adsorbent for on-line tryptophan removal. l-tryptophan production experiments in integrated system the integrated biotransformation product adsorption system was carried out with alginate entrapped (biocatalyst a) and celite-560 adsorbed (biocatalyst d) cells. the latter catalyst proved to be more applicable because of its higher productivity and better stability. the productivities of the simple biotransformation system and the integrated biotransformation / product adsorption system were compared. the data are summarized in table 2. it can be seen that efficiency enhancement of 30 % can be achieved using the cyclic integrated system. table 2: comparison of the tryptophan productivity of the simple biotransformation system and the integrated biotransformation product adsorption system type of solid phase biocatalyst 72 hours tryptophan production in simple biotransforma tion process (g ttrp / cm3) 72 hours tryptophan production in integrated biotransforma tion / adsorption process (g ttrp / cm3) ratio of efficiencies of simple biotransforma tion and integrated systems ca-alginate entrapped biomass (biocatalyst b) 0.89 1.12 1.26 adsorbed cells onto celite-560 beads in the 15th hour of fermentation (biocatalyst b) 7.2 9.5 1.32 conclusion comparing different methods to produce solid– phase biocatalysts from genetically manipulated e. coli k-12 cells of tryptophan synthase activity it was found that the catalyst immobilized by adsorption on celite-560 showed the best catalytic character considering both its productivity and stability. 75 carrying out the bioconversion of indole or 5hydroxy indole and serine in aqueous/organic reaction mixture it was stated that the kinetics and productivity were very similar both in case of tryptophan and in case of 5-hydroxy-tryptophan formation. an integrated system constructed as a combination of the alternately working bioconversion and product adsorption steps has been proved to be applicable for tryptophan production and showed about 30 % higher productivity than the simple biotransformation system. xad-4 neutral resin operated quite efficiently to remove tryptophan from indole and serine containing aqueous phase. further developments are necessary to increase the working stability and productivity of the system. acknowledgement the support of hungarian foundation for fundamental research (through grant no t-28980) is gratefully acknowledged. references 1. terasawa m., fukushima m., kurusu y. and yukawa h.: process biochem. int., 1990, 25, 172-175 2. ribeiro m. h. l., prazeres d. m. f. cabral j. m. s. and da fonseca m. m. r.: bioprocess eng., 1995, 12, 95-102 3. langrene s., sicsic s. and le goffic f.: enzyme microb. technol., 1984, 6, 81-84 4. da fonseca m. m. r., mateus d. m. r. and alves s. s.: performance of a liquid-impelled loop reactor with immobilized cells. progress in biotechnol. vol. 11., int. conf. immobilized cells: basics and applications, noordwijkerhout, the netherlands, elsevier sci. publ. amsterdam, pp. 511-517, 1996 5. fernandes p., cabral j. m. s. and pinheiro h. m.: j. molec. catal. b: enzymatic, 1998, 5, 307–310 6. sisak cs., boross l., orosz l. and szajáni b.: configuration studies on immobilized-cell fluidized-bed reactor system for bioconversion of tryptophan and its hydroxy derivative, int. congress chisa'2000 cd-rom full texts. magicware ltd. chisa'2000/1003, 2000 7. kovács á., lővitusz é., szajáni, b., boross l. and sisak cs.: application possibilities of selective product adsorption in case of ltryptophan production by biotransformation, conf. “chemical engineering days 2001”. pp. 216-221, 2001 (in hungarian) 8. wood w. a., gunsalus i. c. and umblreit w. w.: j. biol. chem. 1947, 170, 313-321 9. zaffaroni p., vitobello v., cecere f., giacomozzi e. and morisi f.: agric. biol. chem., 38 1335-1342 1974 microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 35-38 (2008) application of nir spectroscopy by determination of quality properties of vegetable oils and their derivatives a. fülöp , m. krár, j. hancsók department of hydrocarbon and coal processing, university of pannonia, p. o. box 158., h-8201 veszprém, hungary phone: +3688624414, fax:+3688624520 e-mail: fulopa@almos.uni-pannon.hu this study shows that near-infrared spectroscopy is a reliable technique to determine the concentration of the key fatty acid (fa) components (oleic, linoleic, linolenic acid), the acid number, the iodine value and the kinematic viscosity at 40 and 100 °c in sunflower and rapeseed oils. to establish the chemometric model, a calibration set of 36 rapeseed oil samples and 47 sunflower oil samples were used and 51 oil samples were used for external validation. all samples were measured on a bruker-mpa spectrometer in transmittance mode. the samples were scanned in a wave number range of 12000–4000 cm-1 with a resolution of 2 cm-1. the sample scan time was 32 scans. to develop and optimize the calibration models partial least squares (pls) method was used with cross validation. the result of the experiment showed that this technique is sufficiently accurate for estimating the fa composition, the acid number, the iodine value and the kinematic viscosity at 40 and 100 °c in sunflower and rapeseed oil. the calibration results had root mean square error of cross validation (rmsecv) for oleic acid, linoleic acid, linolenic acid, acid number, iodine value, viscosity at 40 °c, viscosity at 100 °c of 0.395, 0.451, 0.0932, 0.208, 0.418, 0.12, 0.0237 respectively and determination coefficient (r2) (%) for the same properties of 99.96, 99.97, 99.95, 99.47, 99.88, 99.7, 99.22 respectively. keywords: near infrared spectroscopy, sunflower oil, rapeseed oil introduction the rising population and thus, the increasing amount of motor vehicles on the world cause higher and higher fuel consumption. besides this, the amount of the fossil fuels is decreasing in the world. that’s why the research of possibilities how the use of fossil fuels can be reduced is a very important challenge nowadays. vegetable oils and their derivatives are one of the most important sources to substitute fossil fuels. besides, the use of vegetable oils and their derivatives as fuel reduces the amount of carbon-dioxide in the air, because the emitted carbon-dioxide will be used for photosynthesis by the growing oil plants. for that reason the determination of the quality of vegetable oils and their derivatives became important not only for the use as edible oil but also for the use as fuel. the near-infrared spectroscopy (nir) is a wellestablished analytical technique based on the absorption of electromagnetic energy in the region of 12000–4000 cm−1. this type of technique allows the determination of physical and chemical properties of multi-component systems (gasoline, diesel oil, vegetable oil, etc.) in a fast and non-destructive way, without requiring complex sample pre-treatments [1-2]. in the nir region, a component typically absorbs at more than one wavelength. on the other hand, absorbance at a given wavelength may have contributions from more than one property. therefore, a wellestablished tool like partial least square (pls) was used for the determination of the vegetable oil properties. the correlation between the absorption of nir radiation and the analytical reference data can be improved through the use of specific spectra pre-processing methods. preprocessing of spectra reduces variations that not directly related to the given property, such as random noise, baseline drift, etc [3-4]. in respect of using vegetable oils and their derivatives as fuel there are many significant quality properties that we have to measure such as fatty acid composition, acid number, iodine value etc. in this study we dealt with the determination of the concentration of the key fatty acid (fa) components (oleic, linoleic, linolenic acid), the acid number, the iodine value and the kinematic viscosity at 40 and 100 °c in sunflower and rapeseed oils. materials and methods oil samples the 134 different types of rapeseed and sunflower oil samples were obtained from various locations of hungary. the sample set was split in to two parts: 83 samples were used to establish and develop the 36 chemometric models and 51 samples were used for external validation. the properties of the samples were determined by the appropriate en iso standard methods. spectra collection and data pre-treatment to perform the nir spectroscopic analysis a brukermpa near-infrared spectrometer was used that works with the opus controller software. all samples were measured in transmittance mode in a wave number range of 12000–4000 cm-1 with a resolution of 2 cm-1. the sample scan time was 32 scans. the spectral data of the oil samples were collected as absorbance spectra. the raw nir spectrums are shown in fig. 1. for data pre-processing two manipulation methods were applied: the base line correction and the smoothing with smoothing points of 25. the manipulated spectrums are shown in fig. 2. the opus software applied further data treatment methods during the optimization process if it is necessary. a bs or ba nc e un it wavenumber, cm-1 figure 1: the raw spectrums of the samples a bs or ba nc e un it wavenumber, cm-1 figure 2: the manipulated spectrums of the samples calibration in our experiment 36 rapeseed and 47 sunflower oil samples were used for calibration. for the better accuracy all samples were measured two times. to create the chemometric models opus software used the partial least-square (pls) regression in cross validation mode. the advantage of this technique is that a stable, robust and accurate chemometric model could be created even if the calibration set contains fewer number of calibration samples. the goodness of a model could be expressed by the root mean square error of cross validation (rmsecv) and with the determination coefficient (r2). 37 the better the model is the rmsecv more converges to zero and the r2 more converges to 100%. the chemometric models can be improved by model optimization. in the optimization process the software applies variations of many different mathematical data treatment method in different wavelength range (that we can set) to select the best approximation. the selection is based on the value of the rmsecv. results calibration results after model optimization, the results of the best approximations are shown in figs 3-9. these figures are the diagrammatic representation of the calibration results, where the true values of the vegetable oil properties were plotted as a function of the predicted values. the true values are the values that were determined by the appropriate en iso standard methods, the predicted values are estimated by nir. in the figures the straight line represents the true, the dots represent the predicted values of the given property. figure 3: the true concentration vs. predicted concentration values of oleic acid figure 4: the true concentration vs. predicted concentration values of linoleic acid figure 5: the true concentration vs. predicted concentration values of linolenic acid figure 6: the true vs. predicted values of acid number true value of iodine number , gi2/100gpr ed ic te d va lu e of io di ne n um be r, gi 2/1 00 g figure 7: the true vs. predicted values of iodine number true value of kinematic viscosity at 40°c, mm2/s pr ed ic te d va lu e of k in em at ic v is co si ty a t 4 0° c , m m 2 /s figure 8: the true vs. predicted values of kinematic viscosity at 40 °c rmsecv=0.395 r2=99.96 rmsecv=0.451 r2=99.97 rmsecv=0.093 r2=99.95 rmsecv=0.208 r2=99.47 rmsecv=0.418 r2=99.88 rmsecv=0.120 r2=99.71 38 true value of kinematic viscosity at 100°c, mm2/s pr ed ic te d va lu e of k in em at ic vi sc os ity a t 1 00 °c , m m 2 /s figure 9: the true vs. predicted values of kinematic viscosity at 100 °c the figures indicate that the dots match the straight line well enough, so the predicted values are very close to the true values in respect of all properties. the numerical forms of the results are summarized in table 1. in this table the rmsecv and r2 values are shown for each property. table 1: the results of the calibration property rmsecv r2, % oleic acid concentration 0.395 99.96 linoleic acid concentration 0.451 99.97 linolenic acid concentration 0.093 99.95 acid number 0.208 99.47 iodine value 0.418 99.88 kinematic viscosity (40 °c) 0.120 99.71 kinematic viscosity (100 °c) 0.024 99.22 table 1 shows that the r2 values are above 99% and the rmsecv values are under one in all cases. according to the calibration results we found that the created calibration models are suitable for the determination of vegetable oil properties. external validation results in the course of external validation the established calibration models were tested with samples that properties are quantitatively known, and were excluded from the calibration set. as a result of this experiment the efficiency of the models could be concluded by the root mean squared error of prediction (rmsep) and the determination coefficient (r2). the better the prediction is the rmsep more converges to zero and the r2 more converges to 100%. the external validation was executed with 51 different types of rapeseed and sunflower oil samples which spectrums were acquired with the same conditions that were applied at the calibration. the results of the experiment are shown in table 2. table 2: the results of the external validation property rmsep r2, % oleic acid concentration 1.092 99. 89 linoleic acid concentration 1.194 99.86 linolenic acid concentration 0.234 99.88 acid number 0.639 91.47 iodine value 1.494 99.57 kinematic viscosity (40 °c) 0.239 99.59 kinematic viscosity (100 °c) 0.028 99.40 apart from the acid number the r2 values are higher than 99% in all cases and the rmsep values are adequately small as well. conclusions according to the results it may be concluded that the nir technique is applicable for the determination of vegetable oil properties. the advantages of this method are the short analysis time, the non-destructive nature, no complex sample pre-treatment is needed and physical properties can also be determined. the difficulty of the technique is that calibration models must be created for the determinations with the help of a carefully collected calibration set. references 1. kim k. s., park s. h., choung m. g., jang y. s.: journal of crop science and biotechnology, (2007) 15. 2. baptistap., felizardo p., menezes j. c., neiva correia j.: analytica chimica acta, (2008) 153. 3. felizardo p., baptista p., menezes j. c., neiva correia j.: analytica chimica acta, (2007) 107. 4. fülöp a., magyar sz., krár m., hancsók j.: proceedings of 43rd international petroleum conference, (2007) 7. rmsecv=0.024 r2=99.22 microsoft word b_17_r.doc hungarian journal of industrial chemistry veszprém vol. 38(2). pp. 137-141 (2010) development of cfd based mathematical models to study heterocatalytic systems gy. rádi , t. varga, t. chován department of process engineering, university of pannonia, 10 egyetem str, hungary e-mail: radigy@fmt.uni-pannon.hu nowadays mathematical models are applied in almost every field of our life to predict how real systems behave. computational fluid dynamics (cfd) has become a standard tool for analyzing various situations where fluid flow has a significant effect on the studied processes. complex models can be implemented and solved in commercial cfd packages (e.g. comsol multiphysics). the goal of this paper is to model a catalytic bed based on the model of individual catalyst pellets. the proposed model takes into account the mass, heat and momentum transport as well as the reactions in a catalytic pellet of an industrial fixed-bed tube reactor. different ways for aggregating pellet models were compared and evaluated applying comsol multiphysics [1]. the catalytic pellet model was exported using matlab-comsol connection, and the catalytic bed model was implemented and tested using matlab. keywords: cfd, heterocatalytic system, pellet model, reactor bed model. introduction characteristics of flow field in process equipments are key issues in design of process units. with a well designed flow field the overall process performance and the safety of operation can be increased at the same time. to support this step, different modelling software packages and flow sheet simulators have been developed in last decades. as computational capacity of computers has being increased the role of computational fluid dynamics (cfd) among the applied modelling techniques and a method has significantly grown since the first computer was switched on [1]. cfd can be considered as a collection of numerical solvers for partial differential equations. with applying cfd codes more complicated problems in more complex structures can be investigated in details than with other modelling techniques. in recent years many papers applying cfd techniques to analyze the processes or to design reactors have been published. the most frequently investigated topics are the pressure drop, flow profile [2,3], heat transfer and mass transfer [4,5,6] for a reactor, the same for a catalytic pellet [8] as well as intra-particle diffusion effects [9]. these examples show that cfd is capable to simulate transport processes and it can be applied as a part of complex mathematical models. our purpose was to study heterocatalytic systems. the model development process will be introduced in case of an industrial heterocatalytic reactor with highly exothermic reaction. comsol multiphysics can give an effective support since it can be applied to solve models which consist of higher order partial differential equations with finite elements method. in this article comsol multiphysics is applied to calculate the development of state variables in a packed bed tube reactor. case study the simplest reactor models studied here were the onedimensional quasi-single phase steady-state and dynamical models. it was followed by a two-phase dynamical model since heterocatalytic processes can be more adequately described by applying separate solid and gas phases. these models can be applied in the analysis of any possible situation in the system, such as reactor runaway. in 1d model the state-variables are calculated along the catalyst bed. however the radial diffusion cannot be considered without expanding dimensions. 2d axial symmetry models take into consideration the geometry and the evolved flow field in the system while requiring only moderate calculation cost during the solution of models. the analysis shows the significant heat sources (hot spots) and the unusual flow fields (back mixing, turbulent waves). these types of results can be suitable in increasing the reactor efficiency [5, 6]. the most complex model studied here was the 2d axial symmetry, twophase model. in this model both solid and gas phases are considered. the detailed mathematical description of the pellet was implemented in comsol multiphysics. it can be applied to investigate the influence of diffusion and the velocity field on the reactor temperature and the rate of transport processes between the considered phases. 138 figure 1: hierarchy of the reactor modelling the pellet model can be applied to design the shape and size distribution of catalyst pellets, to get a closer look to specific locations of the catalyst bed, to analyze the possible development of runaway in a single catalyst pellet, and to build a catalytic bed from them. unfortunately, for solving of this type of complex reactor model requires horrible hardware capacity. pellet model in our previous works, a quasi-single phase mathematical description of the reactor, and 2d models, which takes into consideration the geometry and the evolved flow field in the system were, introduced [4, 7, 10]. the investigated, vertically positioned reactor contains a large number of tubes filled with catalyst. our concept is the integration of a catalyst pellet model, implemented in comsol multiphysics, into the catalytic bed using a pellet by pellet building technique developed in matlab. the first step to accomplish our objective is the implementation of pellet model in the applied cfd code. the reaction taking place is the reaction is an exothermic, equilibrium reaction with changing number of moles.  a + b ≡ c all component mass balances in the gas phase contain terms to calculate convective and conductive transport processes and naturally the mass transport process between the solid and gas phase: caur)cad( a ∇⋅−=∇⋅−∇ (1) cbur)cbd( b ∇⋅−=∇⋅−∇ (2) ccur)ccd( c ∇⋅−=∇⋅−∇ (3) where u – flow rate of gas phase; i = {a; b; c}; ci – concentration of ith-component in gas phase; di – diffusion coefficient of ith-component in gas phase; r – the component source (chemical reaction). tr e 0 a ekr ⋅ − ⋅= (4) where: k0 – preexponential factor; ea – activation energy; r – ideal gas constant; t – temperature of solid phase. terms in both equations are the same as those considered in component balances: tucq)tk( p ∇⋅⋅⋅ρ−=∇−∇ (5) where: ρ – average density of gas phase; cp – average heat capacity of gas phase; tg – temperature of gas phase k – heat conduction coefficient in gas phase finally the momentum balance: dzdydx ∂ + ∂ + ∂ =∇ (6) f)])u(u(ip[ uu t +∇+∇⋅η+⋅⋅∇= =∇⋅⋅ρ (7) 0u =∇ (8) where: η – viscosity p – pressure u – velocity. figure 2: the visualization of the implemented pellet structure this is just a short description of model equations to illustrate the structure of pellet model. all physical properties are calculated as the function of temperature. these equations have been applied to implement a pellet model in comsol. 139 catalytic bed model in the following the pellet model implemented in comsol was used to build the model of the catalyst bed. using the high-level connection between matlab and comsol, the implemented pellet model can be exported to matlab as a function. the user interface of matlab lets you to modify the pellet model, and to build up a structure from them. as [12] shown, the first pellet outlet properties are boundary averages, and these results become the next pellet inlet parameters. finally, a linear catalytic bed was built and the first investigations were conducted on it. now, as fig. 2 shows, the concept of the examination is to make the same size model in two different ways, and to investigate the differences. the classical method was used as a reference; where diameters of the pellets were the same, and these pellets were taken into one domain, which domain’s size was equal the aggregated domains of the built bed. the pellet by pellet model was compared to this model. the pellet by pellet model is working as a network of pellet models. the output parameter profiles of the first pellet models are the second pellets inlet parameters. it makes the model more accurate; because the pellet effect of the velocity field can be appear in the next pellet domain. a pellet and its surroundings were defined, and the scale was fixed during the examinations. when the pellet diameter was increased, the surrounding size was increase too. the differences between the data were examined in the end of every pellet element (the red doted line on the fig. 2). the difference was calculated as a relative square error: 2 2 )value_minvalue_max( )profil_sultreprofil_ference(re − − (9) results and discussions for the comsol multiphysics pellet model the value of state variables entering the reactor were given as boundary conditions in the solution of the pellet model. obtained results of the pellet model are plotted in fig 3. in fig. 3a the temperature surface can be seen and as it was expected the highly exothermic reaction taking place in catalyst increases the temperature of the pellet and it warms up the flowing gas. a) temperature in the catalyst pellet and b) velocity field in the catalyst pellet and in its surroundings in its surroundings c) concentration of raw material a in d) concentration of product component in the catalyst pellet and in its surroundings the catalyst pellet and in its surroundings figure 3: state-variables along the investigated part of reactor in steady-state 140 due to the diffusion in the catalyst pellet the concentration of reagents decreases in the direction to the centre of the pellet (see fig. 3c); while the concentration of the product changes in the opposite direction as shown in fig. 3d. in this model all components can be connected to the same active sites on the catalyst, however in practice there is a competition between components and the reaction rate and the equilibrium of the adsorption determine the concentration in the catalyst. since only the temperature profile and properties of inlet and outlet flows are measured during the reactor operation, the catalyst pellet model cannot be validated without being integrated into the reactor simulator. as it can be seen in fig. 3d the outlet concentration of the product is very low. this suggests that the parameters applied to calculate the rate of adsorption must be modified. still the tendencies of changes in case of all the calculated state variables are the same as we expected. this pellet model have been exported to matlab, and used as a function. the matlab software ensures wide freedom for its users, and with its built-in function it makes possible to implement a catalytic bed pellet by pellet. the effect of the catalyst volume distribution on the conversion was analyzed [12]. this time five pellet in six different diameter were examined. the difference of the “classical” and the network models a component concentration surfaces with 7e-4 m pellet diameter was shown by fig. 5. the diameters of the modelled pellets were 7e-4m-12e-4 m. figure 4: raw material (a) component concentration surfaces of the different modelled bed (pellets diameter: 7e-4 m) figure 5: difference between the velocity profiles the differences were examined at the end of every pellet. the difference was calculated as a relative square error. the relative square differences of each parameter were shown on fig. 5-8. as fig. 5 shows, the highest values of velocity difference are regularly near the wall. the component profile differences are shown on fig. 6-7. when the flow leaves the pellet, the convective effect depends on the flow and it is a good reason why the profiles differ. as you can see on the fig. 4, the wags of the pellets show noticeable difference. figure 6: difference between the concentration of raw material (a,b) profiles (pellets diameter: 7e-4 m) figure 7: difference between the concentration of the product (c) profile (pellets diameter: 7e-4 m) figure 8: difference between the temperature profile (pellets diameter: 7e-4 m) the temperature difference profile has significantly higher relative values, because there were very little differences between the max and min values. by the theory, different concentration results in different reaction rate, and in case of a significantly exothermic reaction this difference appears in the temperature values. 141 1,8e+07 1,8e+07 1,8e+07 1,8e+07 1,8e+07 1,8e+07 1,9e+07 1,9e+07 0 20 40 60 80 100 120 0,0007 0,0008 0,0009 0,001 0,0011 0,0012 pellet size (m) a gg re ga te  re la ti ve  s qu ar e  er ro r particle size dependence of the aggregate  relative square error of the reference and the  built catalyst bed parameters ca cb cc v t_sec_axis figure 9: particle size dependence of the aggregate relative square error of the reference and the built catalyst bed parameters 6 different pellet diameters were examined. as fig. 9 shows, the aggregated error of the components is increasing with the pellet size, and aggregated error of the velocity and the temperature is decreasing with growing pellet size. conclusions to monitor an operation of a tube reactor the process operators usually do not have much information, just some temperature measurements along the reactor and composition of inlet and outlet flows. hence, a reactor simulator can be very useful to follow the operation and to help process operators, e.g. to avoid development of reactor runaways or to optimize reactor operation. the two dimensional model of catalyst pellet with its close surroundings was implemented into comsol multiphysics. this pellet model can be utilized to design the shape and diameter distribution of catalyst pellets, to get a closer look to specific locations of the catalyst bed, and to build a catalytic bed from them. the catalytic bed was implemented pellet by pellet and the validation of results has been started. our vision is a flexible, pellet by pellet catalytic bed model, which can be used for the design, study and development of catalytic pellets and beds with reduced calculation cost. if we find the solution of the difference reduction, this network modelling system would be applicable for modelling tube systems with complex elements, for example flow meters, heaters etc. on a pc. acknowledgements the financial support from the tamop-4.2.2-08/1/20080018 (élhetőbb környezet, egészségesebb ember – bioinnováció és zöldtechnológiák kutatása a pannon egyetemen, mk/2) project is gratefully acknowledged. references 1. v. v. ranade: computational flow modelling for chemical reactor engineering, 0-120 academic press, 2002. 2. a. jafari, p. zamankhan, s. m. mousavi, k. pietarinen: modelling and cfd simulation of flow behavior and dispersivity through randomly packed bed reactors, chemical engineering journal, 144, 2008, 476–482. 3. h. p. a. calis, j. nijenhuis, b. c. paikert, f. m. dautzenberg, c. m. van den bleek: cfd modelling and experimental validation of pressure drop and flow profile in a novel structured catalytic reactor packing, chemical engineering science 56, 2001, 1713–1720. 4. t. varga, j. abonyi, t. chován, l. nagy, f. szeifert, j. réti: proceedings conference of chemical engineering ’06, 2006, 45–48. 5. t. m. moustafa, m. abou-elreesh, seifeddeen k. fateen: modelling, simulation, and optimization of the catalytic reactor for methanol oxidative dehydrogenation, comsol conference 2007, boston, 2007. 6. m. ghadrdan, h. mehdizadeh: mathematical investigation and cfd simulation of monolith reactors: catalytic combustion of methane, comsol conference hannover, 2008. 7. gy. rádi, t. varga, t. chován: conference of chemical engineering ’09, proceedings, 2009, 234– 238. 8. a. nagaraj, p. l. mills: analysis of heat, mass transport, and momentum transport effects in complex catalyst shapes for gas-phase heterogeneous reactions using comsol multiphysics, comsol conference boston, 2008. 9. a. guardo, m. casanovas, e. ramírez, f. recasens, i. magańa, d. martínez, m. a. larrayoz: cfd modelling on external mass transfer and intra-particle diffusional effectson the supercritical hydrogenation of sunflower oil, chemical engineering science, 62, 2007, 5054–5061. 10. t. varga, f. szeifert, t. chován, j. réti: conference of chemical engineering ’07, proceedings, 2007, 113–117. 11. j. m. berty: experiments in catalytic reaction engineering, studies in surface science and catalysis, 124, elsevier, 1999. 12. gy. rádi, t. varga, t. chován: analysis of heterocatalytic reactor bed based on catalytic pellet models, iii international interdisciplinary technical conference of young scientists proceeding, 2010, 476–480. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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<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> /enu (use these settings to create adobe pdf documents best suited for high-quality prepress printing. created pdf documents can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word b_15_r.doc hungarian journal of industrial chemistry veszprém vol. 38(2). pp. 127-132 (2010) developement of new technical solution for starter motors for passenger cars l. nagy, e. jakab rober bosch department of mechatronics, university of miskolc, miskolc-egyetemváros, hungary e-mail: nagy.lajos@uni-miskolc.hu, jakab.endre@uni-miksolc.hu this paper discusses an industrial project which can be solved by “classical” design methods. many theories and methods were and have been developed during the last few decades. methods to support product development cover well-known paradigmatic approaches and models. they are partly built upon experiences from practice, and a lot of them haven't changed much during the last 20 to 30 years. in a product development process or design process, conceptual design is one of the most important phases in which customer needs and technical requirements are translated into design solutions. conceptual design is a component part of a design process during which designers first create new ideas and then translate them into a design structure by synthesis [15]. first of all we defined the formulation of the task and determined the basic functions. after we are looked for solution variants and used to explore the theoretically possible solutions at principle impact level. it was found that the solution field obtained could be divided into three large groups, such as starters controlled by hydraulic, pneumatic, and electric energy sources. we also determined the development direction and finally designed a new possible solutions. keywords: design methodology, starter motors, pinion-engaging mechanism introduction today international competition in the market, accelerating engineering technological development and increasing purchaser requirements have made it crucial for companies to develop competitive products. steadily increasing demands have led to the emergence of the science of methodical design, which encompasses a great number of established and proven principles and methods widely applied in industrial practice as well. so this design theories and methodologies such as systematic design methodology so-called „classical” design theories [1, 2, 3, 10, 11]. theory of inventive problem-solving [12], autogenetic design theory, [5], axiomatic design theory [4], general design theory [yoshikawa], etc. have been developed for the last fifty years. „classical” development and design methods are based on the paradigm that a complete description of requirements and boundary conditions will lead (at the very end) to exactly one solution (the so-called funnel approach) [5]. the german vdi guidelines 2221, 2222 and 2225 describe an integrated model of product development. there are based on the respective design theories developed mainly by pahl, beitz, hubka, koller, franke, and roth. all these design processes have in common that they arrive at the solution in every case by dividing a complex task or problem into sub-tasks and sub-problems and elaborating those separately. they also have in common that they divide the individual processes into three stages which cannot separated from each other markedly and which are the stages of formulating the task, the functional and the construction (design) stage. the objective of this paper is to present the solution of a particular industrial task by means of ‘classical’ design methodology. the project was born in 2006 from an industrial commission, with the objective of developing and constructing a new, state-of-the-art starter for passenger cars. the contents of the paper are related to this objective. the foundation of the task was provided by these classical design methods. here the process plan elaborated in [3, 14, 15] and the franke search matrix [14] were taken as the starting point for solving the problem at hand. in order to obtain a transparent view of starters, it is expedient to do a comprehensive literature and patent research as a first step. the various papers on vehicular electricity [17, 18] discuss the structural analysis and operation of starters for passenger cars, heavy duty and two-stage starters for trucks. the internet search engines of the hungarian, us and european patent offices were used to find several hundred patents in this field. in the course of the research no new development based on scientific foundations was found, therefore the patent specifications found were analysed and catalogued according to the solution applied. 128 towards solving the problem internal combustion engines emerged at the end of the 19th century and were used for driving vehicles. the vehicles ran on petrol and were started using an external, mechanical source of energy (pushing, acceleration on an incline, use of a manual starting handle). the ’tradition’ of manual starting was to be found in vehicles for nearly a century to a decreasing extent, until the 1980s. later, with the use of electrical energy supply units, electrical starter units, called starters (fig. 1), came to the foreground. the task of a starter is to accelerate the main axle of an internal combustion engine from its stationary state to the ignition revolution number nc. the operation of the internal combustion engine becomes self-propelled when the revolution number of its main axle is greater than the ignition revolution number, [17, 18]. the first step of the design is an abstraction of the task. it is expedient to formulate the task so that it will include only the objective to be performed by the technical device created in the design process. accordingly, the task was defined as followed: “designing a device of a new technical principle suitable for starting the internal combustion engines of passenger cars”. it is of utmost importance that the fundamental requirements (table 1), providing the starting point for the further unfolding of the task set, are formulated in this stage. the requirements can be divided into four large groups on the basis of [16]. table 1: requirement list requirements set for the task starting an internal combustion engine functional requirements new technical solution a great number of connections, short connection time building block principle, modular design general requirements low level of noise rapid repair, service or replacement in case of faults easy fit in many different engines operability also in extreme weather conditions priority requirements reliability compactness and small weight long life manufacturing requirements industrial law requirements requirements typical of all machines other (e.g. servicing) requirements on the basis of the research of the literature and the patents, starting an internal combustion engine requires the generation of an impact that can be brought about via the main axle. after the internal combustion engine gets started, it may force the device generating the impact to perform such a great revolution number that exceeds the speed limit and the may endanger the integrity of the construction. therefore the objective is to design a device that drives the main axle of the internal combustion engine with the necessary revolution number and moment, and then the starter returns to normal after the fuel has been ignited in order to prevent possible damage. in the next stage of the design process, it is possible to determine the fundamental theoretical solutions by setting up the structure of functions, finding and combining solution principles. [14, 16] the task formulated is called the overall task, which it is expedient to reduce to simple sub-tasks for which there already exist well-established solutions, and to so many parts that their number can still be followed. these sub-tasks may appear as wellestablished solutions in a great number of other technical devices. next the sub-tasks are to be divided into subfunctions and the sub-functions into the impacts and impact carriers embodying them. the collection of verbs containing 220 words and expressing actions in engineering practice provides considerable help for the accurate description of function definitions [7]. these can be used to give simple definitions for the particular sub-tasks and subfunctions. fig. 8 shows the sub-tasks and sub-functions performing the task total and the impacts achieving them. in the individual blocks of the structure of functions underlining highlights the verbs expressing the actions. in the following the individual sub-tasks and sub-functions are written in bold. in the blocks where there are four dashed lines, they represent connections to mechanical, hydraulic, pneumatic and electric blocks. account must be taken of what sources of energy are there, and which of them are suitable for solving the overall task. on the basis of fig. 8, the sub-task use energy source in vehicles is a supply unit housed in vehicles, which is necessary not only for starting the internal combustion engine, but also performs other functions not belonging to the task. each impact carrier, creating sub-tasks and subfunctions, can be grouped by the energy sources, e.g. mechanical (rigid and flexible bodies), hydraulic (fluids), pneumatic (air) and electric (electrons) supply units can be distinguished. flywheel energy sources are most often used as mechanical energy sources. in the present state of technology, there also exist supra-conducting flywheel energy sources, with an efficiency of 96%. mechanical, hydraulic and pneumatic supply units have to provide the appropriate primary energy source, which are usually electric supply units. starters applied today receive the necessary energy from batteries. sub-task connect device to the crankshaft includes two sub-functions. sub-function create a connection refers to the type of connection (e.g. flywheel gear rim gearwheel connection), which may be direct and indirect transfer of energy. sub-function operate connection refers to the method of creating the connection (e.g. operation in the axial direction). sub-task drive crankshaft includes as its sub-function the bringing about of rotary motion. for devices suitable for generating rotary motions there exist well-established design catalogues [12]. these catalogues have the 129 advantage that they include existing part solutions and one only has to select the one best suited for the task. there exist solutions in practice, which, in addition to the existing main-axle-device connection, also include a separate moment-strengthening unit (e.g. epicyclic gear, or counterdrive). therefore the sub-task change moment – which is a sub-function at the same time – has the objective to impart the greatest possible moment to the main axle, and to reduce the dimensions of the device. after starting the internal combustion engine, the device is to be controlled (set in the starting position) in some way. on the one hand that the process can be repeated at the next starting, and, on the other, in order to prevent damage. a device is set in the starting position when it is in some positive connection with another component (the main axle in this case). the sub-function change function can be closely linked to direct drive. in this case the device cannot be stopped. on the basis of function analysis, it is possible to build a graph hierarchy (structure of functions) between the sub-functions implementing the individual sub-tasks. in order to obtain a solution meeting the requirements of the task set, it is practical to place the individual impacts into a morphology box (matrix) (table 2). in the matrix the fields belonging to the individual rows are connected with the elements of the next row. assigning the individual energy carriers to each sub-function and connecting them gives the possible combinations of the chain of impacts. table 2: morphology matrix sfa a1 a2 a3 a4 sfb11 b11.1 b11.2 b11.3 b11.4 sfb12 b12.1 b12.2 b12.3 b12.4 sfb21 b21.1 b21.2 b21.3 b21.4 sfb sfb22 b22.1 b22.2 b22.3 b22.4 sfc c1 c2 c3 c4 sfd d1 d2 d3 d4 sfe11 e11.1 e11.2 e11.3 e11.4 sfe sfe12 e12.1 e12.2 e12.3 e12.4 notations sfa, …, sfe are interpreted by fig. 3 and the list of notations. the last figures in the notations – from 1 to 4 – refer to the mechanical, hydraulic, pneumatic and electric energy carriers, respectively. in this way e.g. sfb21.1 means: ensure axial connection by mechanical energy transfer. the number of possible theoretical solutions is given according to the following relation: 2621444ssssssssst 9 12fe11fefdfc22fb21fb12fb11fbfas ==⋅⋅⋅⋅⋅⋅⋅⋅= it is easy to see that between the sub-functions sfb11 and sfb12, sfb21 and sfb22, and sfe11 and sfe12 there exists an or connection, therefore the number of theoretical solutions according to (2) is ( ) 32768 8 ssssssssst 12fe11fefdfc22fb21fb12fb11fbfa s = ⋅⋅⋅⋅⋅⋅⋅⋅ = in the functional design stage the characteristics of the solution principles at a low level of concretisation in general are not known to the extent that combination and optimisation can be performed by mathematical methods. in order to develop the solution concepts, it is often not sufficient to have the physical relations, for geometrical (production engineering, assembly, incompatibility, etc.) relations may also set limits and exclude compatibility in a particular case. in more complex systems, the designers have to decide between the variants in this stage of the design process by means of the reduction selection process, which can be described by the activities of selection and prioritising. the impact carrying part solution of the mechanical energy source a1 may be a spring, a flywheel or human force. this solution can be immediately discarded, for it does not meet the requirements of the age or technology. accordingly, the sub-functions sfb21 and sfb22, i.e. the method of bringing about the device – internal combustion engine connection is omitted in this stage, the impacts not achieving particular sub-functions (b12.4, c1, d4, e1.1) are removed from the morphology matrix in table 2. thus the number of theoretical solutions is: ( ) ( ) 8642443332ssssst 2fe12fbfdfcfasm =⋅⋅⋅⋅⋅=⋅⋅⋅⋅⋅= it is purpose to limit the theoretically possible solution field to the feasible solutions. placing the solution possibilities of two compatible impact carriers in the head column and head row of a matrix, and filling the description of the combination (impossible or unfeasible, possible combination) in the field, compatibility can be easily checked in sequence. figure 1: compatibility matrix on the basis of the compatibility matrix (fig. 1), the possible theoretical solutions of the task total can be arranged in a tree diagram sub-functions sfb21 and sfb22 were removed in working with the solution principles, however, they are necessary in the analysis, therefore the number of possible theoretical solutions is 130 2242842tsm =⋅⋅= , which can be divided into three different groups: ● device controlled from a hydraulic supply unit (a2 branch): 961242t 2sma =⋅⋅= theoretical solutions. ● device controlled from a pneumatic electric supply unit (a3 branch): 961242t 3sma =⋅⋅= theoretical solutions. ● device controlled from an electric supply unit (a4 branch): 32442t 4sma =⋅⋅= theoretical solutions. in hydraulic and pneumatic supply units the appropriate primary energy source, usually an electric supply unit, is to be provided. starters used today obtain the necessary energy from batteries. since this is a wellestablished solution, it is not worthwhile deviating from this sub-function. the idea, however, is not discarded immediately, we may return to it later on. since internal combustion engines cannot be altered, i.e. neither the flywheel, nor the crankshaft can be modified, the number of theoretical solutions of branch a4 is consequently reduced from 64 to 2. the methods applied for selecting the appropriate solution variants were the use value analysis (uva) of system technology and the evaluation according to the guidelines vdi 2225 [8]. it follows from the analyses that the most sensitive point of the device is the mechanism ensuring the axial connection, i.e. pinionengaging mechanism (pem). 1 2 3 figure 2: block scheme of the pem modelling and simulation of the pem the basis of developing variants is how the pem can be replaced by other solutions, since the solenoid switch is one of the most sensitive parts of the starter. the length of the path covered by the iron core is an important characteristic, for this determines the axial displacement of the engaging gearwheel. if the path of the displacement is shorter than necessary, the gearwheel connection is not appropriate, and if it is longer, the gearwheel will butt on. moreover, the closing contact of the main circuit must make contact in the appropriate displacement position. the contacts must have burningup spare, for in operation, when the circuit is closed, and particularly when it is broken, there is intense sparking due to the high amperages, which leads to a reduction of the contacts. to sum up, new structural solutions have to perform with reliability the two main functions of the magnetic switch, which are: ● establishing the engagement of the gearwheel and its disconnection, by means of an intermediary device ● closing the main circuit and its disconnection as fast as possible. the two functions are in close connection with each other, therefore variants meeting these requirements were developed. the switch mechanism has to be placed on the starter with the shortest possible leads to be used. the mechanism used so far (figure 2) consists of an iron core coil (1) (electro-magnet), a translation to translation motion transducer (lever) (2) and the driving gear (3). the driving gear performs both linear and rotary movements, through a helical involute profile spline shaft – boss connection. fig. 3 shows that the solenoid switch has 3 pretensioned springs. the armature return spring (10) ensures that the switch opens again when the solenoid is switched off and the armature returns to its resting position. when the solenoid armature hits the armature shaft (9), the movable switch contact (8) moves against the force of the armature shaft spring (it is not numbered in fig. 3). when the switch contacts (6, 8) are closed, the main circuit (the hold-in winding activated at this time) is also closed and the contact spring (5) ensures the best possible surface contact. [18] figure 3: solenoid switch the function of the pem can be divided into five phases. the electromagnetic force has to overcome the force of the pre-tensioned return spring in the first phase. phase 2 is what is called the free travel phase when the solenoid retracts, but does not operate the pinion-engaging lever. this is significant when the power supply to the solenoid is switched off, because there must be sufficient free travel to allow opening the primary circuit switch. if this were not the case, the pinion-engaging lever would hold the armature in place. the other three phases cover the operation of the three springs (fig. 4). the simulation of pem was performed by matlab. the simulation investigations resulted in obtaining time curves of the pem current (fig. 5), the solenoid armature and the pinion displacement (fig. 6) and velocity, the force of the pinion engaging mechanism. the individual curves represent the individual phases, 131 and the resultant curve shows the joint conditions. the simulation results are compared with the measurement results (dot line in fig 5 and solid line in fig 6). figure 4: mechanical model of the pem figure 5: simulation and measurement results of the pem current figure 6: the pinion displacement each curve seems to be the same. naturally, the values of the each curve show some difference. the reason for this difference is that the battery can be modelled by a constant, and we neglect the mass of the spring, the pinionengaging lever, the armature shaft and the switch contacts, and the form of the solenoid armature, the frictional losses, the electric losses (eddy current losses, switch contact losses, air gap losses, etc.), and the magnetic losses. validation of the new solution proposal the aim was set that the new switch mechanism should be coaxially placed with the axle of the electric motor so that the axial increase in dimension should be as small as possible. the operation of the switch mechanism (fig. 7) is performed by an electric motor (4) and a rotary-linear motion transformer drive (2). in the course of the fatigue testing of the experimental device more than 300,000 switchings were simulated. m 4 2 3 figure 7: block scheme of the new pem summary the primary objective in the development project was to design and construct a state-of-the-art device. classical design methodology was used to explore the theoretically possible solutions at the principle impact level. it was found that the solution field obtained could be divided into three large groups, such as starters controlled by hydraulic, pneumatic, and electric energy sources. our findings were proved by the registration of the patent claim no. 2,845,916 by l. j. pihel on 5 august 1958 called hydraulic starting system for internal combustion engine, and the publication of the patent by massami tanaka of a starting device with air motor for internal combustion engine (patent no.: 4,694,791) on 22 september 1987. various decision preparation methods were used to select and determine the viable solutions. determination of the development direction – the decision – was always prepared in cooperation with the engineers of the project partner. design catalogues were prepared and used for each sub-function of the theoretical solutions. these were used to establish that design and development did not each cases mean the conception of something new, but it is much more logical to select the most suitable one of the already existing similar products, and to improve its weak points to fit the modified requirements and boundary conditions. -0.01 -0.005 0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0 2 4 6 8 10 12 14 16 18 time [s] d is pl ac em en t [m m ] ritzel displacement measured phase 2 phase 3 phase 4 0 0.005 0.01 0.015 0.02 0.025 0 5 10 15 20 25 30 35 time [s] c ur re nt [ a ] phase 2 measured phase 1 phase 3 phase 4 phase 5 132 figure 8: structure of functions references 1. k. roth: tervezés katalógussal, műszaki 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word a_07_r.doc hungarian journal of industrial chemistry veszprém vol. 38(1). pp. 35-39 (2010) a nonlinear dielectric measurement method for the study of complex liquids b. horváth , i. szalai institute of physics and mechatronics, university of pannonia, p.o. box 158, h-8201 veszprém, hungary e-mail: bhorvath@almos.uni-pannon.hu a measurement system for the study of nonlinear dielectric effect (nde) of complex liquids is constructed. the method is based on the determination of a change in frequency of an lc oscillator. the fluid is contained in a dielectric cell, which is the capacitive component of the oscillator. a rectangular electric pulse with variable amplitude and width is applied to the liquid, and the frequency of the oscillator is continuously sampled under the duration of the pulse with a modulation domain analyzer. the magnitude of nde for diethyl ether and carbon tetrachloride was measured with the apparatus and compared to corresponding reference data. the nde value of silicone oil used as a carrier liquid of electrorheological (er) fluids was also determined. keywords: nonlinear dielectric effect, dielectric permittivity, electrorheological fluids introduction in many cases the dielectric permittivity of molecular and complex fluids (electrorheological liquids) depends on the electric field strength, e inside the dielectric [1]: k++= 2 20 ee εεε , (1) where ε0 is the linear dielectric permittivity. the change in dielectric permittivity caused by a strong electric field is called the nonlinear dielectric effect (nde). the magnitude of this effect can be described by the ε2 coefficient in eq. (1) [1]: 202 0 02 limlim ee e e e e εεε ε δ = − = →→ . (2) only the ε0 linear dielectric permittivity can be measured by the conventional linear measurement techniques. the nonlinear measurement methods are suitable to determine the ε2 parameter. in the study of electrorheological (er) fluids, the complementary linear and nonlinear dielectric measurements yield valuable information about chain formation induced by the external electric field. the nonlinear dielectric measurement system fig. 1 illustrates the schematic block diagram of the nde apparatus. the concept [3, 5, 6] of the measurement setup is based on the determination of the frequency change of an lc oscillator. the sample under investigation is contained in a dielectric cell, which acts as a parallel plate capacitor. this capacitance cc combined with the inductance l forms the lc oscillator, which has a resonance frequency f. a high voltage power supply and a high voltage switch makes up the pulse generator system, which is used to impose rectangular pulses to the cell. a high voltage decoupling capacitor (cb) connected in series with the dielectric cell blocks the pulse from the active elements of the oscillator. the applied high voltage creates a strong electrical field between the plates of the measuring cell. figure 1: block diagram of the nonlinear dielectric equipment the dielectric permittivity of the fluid changes under the influence of the electric field, which causes a change in capacitance of the dielectric cell. because the value of cc is the decisive capacitive element of the lc oscillator, the nonlinear dielectric effect manifests as a change in frequency (δf). a modulation domain analyzer is 36 responsible for the accurate measurement of this frequency change. the trigger signal initiating the frequency measurement is supplied by the counter unit of a data acquisition (daq) card. the same card is responsible for the generation of the rectangular ttl level pulses controlling the system switching the high voltage pulse. the analogue input of this daq system is used for registering the divided output of the high voltage pulse generator. the control software is developed in labview programming environment. the most important functions of the software are the programming of the daq system and the communication with the modulation domain analyzer. the program is used to set up the temperaturecontrolling equipment. after the measurement is complete, the control software processes the raw measurement data. dielectric cell the construction of the measuring cell is critical, because large forces can act between the plates when a strong electric field is switched on. the schematic structure of the cell is shown in fig. 2. the cylindrical electrodes are made of stainless steel and have diameters of 43 mm. each electrode has a vertically oriented inlet for the convenient, bubble free filling of the cell. in order to avoid measuring errors, the exclusion of air bubbles is crucial. between the two electrodes a quartz ring ensures the fixed distance. the height of this ring is 10 mm, which sets the distance between the electrodes to 0.3 mm. in this configuration the empty cell has a capacitance of 41.71 pf. the quartz spacer can be replaced by rings with different height, so the electrode gap is variable. to prevent leakage, teflon gaskets provide proper sealing on both side of the quartz ring. figure 2: schematic cross section view of the dielectric cell each of the two electrodes is surrounded by a hollow copper mantle through which a water flow is passed. the temperature of the water is controlled by a medingen e20b6 thermostat. the mantle is electrically insulated from the electrode by a teflon disk. one of the electrodes has a bore containing a resistance thermometer (pt100). the whole structure of the cell is held together by four brass screws firmly. oscillator the extremely small magnitude of δεe results in a small frequency change, typically in ppm order. the detection of such small changes in frequency requires a high stability oscillator. a double triode oscillator of type ecc88 valve was chosen. this type has been used previously by various authors [3, 6]. fig. 3 shows the circuit diagram of the used lc oscillator. figure 3: circuit layout of the oscillator an advantage of the valve oscillator is its ability to oscillate even when the cell is filled with moderately conducting liquid. in order to maximize the frequency stability of the oscillator, the anode voltage and the cathode heating current are carefully chosen. the source of the heating current is a custom built power supply unit, while a voltcraft pps-12008 psu provides the anode voltage for the valve. the printed circuit board is designed so that different inductors can be inserted into the circuit. three air core solenoids were made of enamelled copper wires of various sizes wind around ceramic cylinders. the inductances of the coils are: l1 = 19.57 μh, l2 = 10.58 μh, and l3 = 3.53 μh. when the dielectric cell is empty, the resonant frequency of the oscillator is around f1 = 3.48 mhz, f2 = 4.70 mhz, and f3 = 8.32 mhz for the three solenoids. the blocking capacitor is another critical component of the oscillator. its function is to decouple the highvoltage pulse from the active elements of the circuit. it is connected in series with the measuring cell, so it has to have a high capacitance giving small contribution to the capacitance of the cell. another requirement for the cb bypass capacitor is the ability to withstand the peak amplitude of the high voltage pulse. besides these demands, its capacitance must be stable as voltage changes. to meet all these requirements, a cluster of four silvered mica capacitor is used as the decoupling capacitor. the total capacitance of the cluster is 1500 pf, and the rated peak voltage is 2000 v. 37 the high voltage pulse generator is connected to the oscillator through a decoupling resistor, whose resistance is 21 kω. the function of this element is to surpass the change in ohmic resistance connected to the oscillator circuit when the pulse generator system is active. because the valve is sensitive to mechanical vibrations, which can cause unwanted changes in frequency of the oscillator, the whole circuit board and the dielectric cell is rigidly mounted on an aluminium plate. further precaution is taken to minimize the transmission of vibration to the aluminium mounting plate. modulation domain analyzer a hewlett-packard 53310a modulation domain analyzer is used to measure the change in frequency of the oscillator before, during, and after the high voltage pulse. the time interval of the frequency measurement before and after the pulse equals to forty percent of the pulse width. the typical total duration of the measurement is in the range of 5–100 ms. the main time base is set according to the total measurement time. the analyzer has the option to adjust the time base between 10 μs and 10 s. the signal from the oscillator is routed to the analyzer, which has a measurement range of 10 hz to 200 mhz. the sampling rate of the input frequency is managed automatically by the instrument, based on the time base setting. under a typical measurement lasting for 20 ms the sampling interval is 0.1 ms. the internal trigger system of the analyzer is switched off, so it is operating in a triggered mode instead of auto one. an external ttl level signal is connected to the external arm input. the measurement is initiated at the falling edge of the trigger signal, so the occurrence of the trigger is assigned to the zero position of the horizontal time axis. all measurement data is collected after this reference point. before the frequency measurement commences, the analyzer searches for the input signal, and determines the base frequency. the centre of the vertical axis is adjusted to this frequency value, and the span value is given manually. the gpib (ieee-488) port of the instrument is used for communication purposes. all the above mentioned parameters and settings are sent through this interface. the analyzer is armed by a software command after which it is ready to take measurements. the instrument is waiting in this armed state for the trigger to initiate the sampling of the input signal. the results are queried by the control computer, and the raw measurement data is sent through the gpib port. the raw data is composed of ascii characters of screen coordinates. the actual frequency-time point pairs can be computed according to the scale and offset values read from the instrument. the accuracy of the δf measurement is improved by repeating the data acquisition n times, and averaging the results. the n parameter is adjustable: typically an n = 5 value is sufficient. high voltage pulse generator a ps350 dc high voltage power supply made by stanford research system serves as the base of the pulse generator. the output voltage of this programmable precision power supply ranges from 50 v to 5000 v. the maximum output current is 5 ma. the output voltage can be set with a resolution of 1 v, and the voltage set accuracy is 0.01%. the instrument has a gpib port, which is connected to the ieee-488 communication bus. so both the output voltage value and the state of the output are under computer control. a custom built high voltage switch is responsible for the generation of the rectangular high voltage pulses. the device is switched by a ttl level rectangular signal, which is generated by the counter unit of a data acquisition card. the high voltage is reduced 5000-fold and routed to the monitor output of the switch. solid polyethylene insulated rg-59 type coaxial cables lead the voltage to the switch and to the dielectric cell. the cables are fitted with shv connectors. trigger and rectangular pulse generator two signals need to be generated. this function is handled by a pci-6052e multifunction data acquisition card made by national instruments. the daq card occupies a pci slot inside the control computer. the device has two counter units which are used to generate the signals. one trigger is necessary for the modulation domain analyzer to initiate the frequency measurement. this signal is outputted by counter0 and has ttl voltage level, and a logical high idle state. counter1 is the source of the rectangular pulse, which is controlling the high voltage pulse generator. the voltage level of this signal is also ttl, with a logical low idle state. the pulse width and the delay before the rising edge of the pulse are settable by the program. the initial delay is forty percent of the pulse width, so the start of the frequency measurement is synchronized to the generation of the rectangular pulse. the signal generated by counter0 is internally routed to counter1 and initiates it with the pre-programmed parameters. an additional function of the daq card is the registration of the divided voltage monitor output. for this purpose the analogue input of the card is used. the analogue input channel has 16 bit resolution. the maximum sampling rate of the card is 333 ks/s. the actual sampling rate is set to 100 ks/s. the daq device is configured in differential input mode. the data acquisition is triggered by the internally routed signal generated by counter0. this ensures that all functions of the card are started at the same time. a national instruments bnc-2090a shielded rack mountable terminal block connects the daq card to the high voltage pulse generator and to the modulation domain analyzer. 38 temperature control system the temperature of the water circulating in the outer mantle of the dielectric cell is controlled by a medingen e20b6 thermostat. heat losses of the cell are reduced by insulating the tubes connecting the cell to the thermostat. the thermostat controls the temperature of the dielectric cell by the external pt100 resistance thermometer placed inside a hole bored into one of the electrodes. through an rs-232 serial interface the thermostat is communicating with the control pc. this enables the setting of the desired cell temperature by software, and, on the other hand, the actual cell temperature can be monitored. the accuracy of the temperature control system is 0.01 °c control software the labview program provides a graphical user interface, with controls to set the essential parameters of the nonlinear measurement apparatus. the desired cell temperature can be adjusted, and the actual temperature is also shown and updated once per second. additional adjustable parameters are the following: the amplitude and the width of the rectangular high voltage pulse, the span of the vertical display in hertz, and the number of frequency measurements to average. the first task of the software is to switch on the high voltage power supply, and wait until the voltage output is stabilized. the initialization command string sent to the analyzer leaves the instrument in an armed state. the following step programs the two counter units of the data acquisition device and configures the analogue input. after counter0 generates the signal, all the events mentioned in the description of the trigger and pulse generator system are timed by hardware. the control software reads out the raw frequency vs. time data, and the scaling and offset factors from the analyzer. at the same time the voltage values measured on the analogue input channel are requested from the daq device. the aforementioned events are repeated n times and the averaged and scaled frequency vs. time and high voltage vs. time results are displayed as stacked plots with a common horizontal time axis. calibration to calculate the ε2 magnitude of the nonlinear dielectric effect defined by eq. (2) the value of δεe has to be calculated from the measured δf/f ratio. the two values are related through the following equation [4]: ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ + δ =δ 0 0 2 c c f f s e εε , (3) where c0 is the capacitance of the empty dielectric cell and cs is the total stray capacitance. using two materials of relative permittivity (ε0)1 and (ε0)2 and measuring the corresponding f1 and f2 oscillator base frequencies the cs/c0 value can be determined from the equation [4]: ( ) ( ) 1 2 2 1 2 2 1 1020 0 −⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ − = f f f f c cs εε . (4) for the calibration measurements, diethyl ether and carbon tetrachloride was used. the linear dielectric permittivity of both materials was measured with the linear measurement method outlined in the following section. the linear dielectric measurement system for the determination of the linear dielectric permittivity an agilent measurement apparatus is employed. the components of the system are the 16452a dielectric cell for liquids and the 4284a precision lcr meter. the apparatus has a 20 hz to 1 mhz measurement frequency range and a 0.05% basic accuracy. the equipment is controlled over gpib with a custom developed labview program. the dielectric cell employs the parallel plate method, similar to the method used by the nonlinear measurements. the liquid under test is between two circular shaped electrodes, separated by a spacer to form a capacitor. the 4284a lcr meter is used to measure the capacitance of the cell. on the basis of the measured capacitance value and the known geometry (area of the electrode and electrode separation) of the cell the linear dielectric permittivity is easily calculated. to control the temperature of the dielectric cell it is immersed in a silicone oil bath which is placed inside the tank of a medingen e20b12 thermostat. the temperature of the cell is controlled with an accuracy of 0.01 °c. results the nonlinear measurement apparatus was tested with diethyl ether and carbon tetrachloride at 25.0 °c. these two materials were chosen because nonlinear measurement data have been published by various authors for both dielectrics. fig. 4 shows the measured δεe values for diethyl ether as a function of the electric field strength for 25.0 °c. the plot shows that δεe is a quadratic function of e. the width of the rectangular pulse was 20 ms and the base frequency of the oscillator was 2.58 mhz. table 1 summarizes our nde measurement results for diethyl ether and carbon tetrachloride in comparison with reference data. the results are in good agreement with values published by other authors [2, 4]. the nonlinear dielectric effect of silicone oil (polydimethylsiloxane) which is used as a carrier liquid in the preparation of electrorheological fluids was also measured. the kinematic viscosity of the silicone oil 39 was 350 mm2s-1. the material was supplied by sigmaaldrich. for the measurement a 30 ms wide rectangular pulse was applied, and the base frequency of the oscillator equalled to 2.89 mhz. the measured nde value for silicone oil is also shown in table 1. figure 4: the change in relative permittivity of diethyl ether as a function of electric field at 25.0 °c. table 1: nde measurement results compared to reference data. δεe/e2 (10-19 m2v-2) material our result reference diethyl ether -26.46±1.11 -(20–36.5)a carbon tetrachloride 1.93±0.08 1.61–1.93b silicone oil 3.56±0.15 – a [2]. b [4]. conclusions an lc oscillator based measurement equipment for the study of nonlinear dielectric effect of liquids is proposed. the system is tested by the measurement of ε2 for carbon tetrachloride and diethyl ether. in the next future we are going to use the equipment to measure the nonlinear dielectric effect of electrorheological fluids. the chain-formation of er fluids can be described by the linear and nonlinear dielectric measurements using an association theory[7]. acknowledgment we acknowledge the financial support of this work by the hungarian state and the european union under the tamop-4.2.1/b-09/1/konv-2010-0003 project. references 1. i. szalai, s. nagy, s. dietrich: j. chem. phys., 131, 2009, 154905. 2. m. górny, j. ziolo, s. rzoska: j., rev. sci. instrum., 67, 1996, 4290–4293. 3. p. a. bradley, g. p. jones: j. phys. e: sci. instrum., 7, 1974, 449–452. 4. t. krupkowski, g. p. jones, m. davies: j. chem. soc., faraday trans., 2 70, 1974, 1348–1355. 5. g. schwarz, p. walther: ber. bunsenges. phys. chem., 89, 1985, 491–500. 6. b. l. brown, g. p. jones, m. davies: j. phys. d: appl. phys., 7, 1974, 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word b_11_07_r.doc hungarian journal of industrial chemistry veszprém vol. 38(2). pp. 113-116 (2010) designing and manufacturing a goalie mask t. horváth , a. tamásová department of machining and assembly, faculty of materials science and technology, university of technology paulínska 16. 91724 trnava, slovakia e-mail: tibor.horvath.tibor@gmail.com at the present time the composite materials are used in many areas of industry. the main utilizations are in the aircraft industry and the sports equipment manufacturing. the first part of the work offers on overwiew of composite materials, their properties and utilize. the next part introduces the evolution of goalie masks. in the main part, we used the knowledge from the previous chapters, and designed a new shape of the mask and produced a prototype model. the backplate was designed by 3d cad software and the form was produced on nc milling machine. for the production of the mask i used technology of laminating and remark two possible solutions as production forms and prototype models. keywords: composite materials, hockey goalie mask, cnc milling, laminating introduction it´s very hard to find any group from the section of polymeric materials which offers such a wide range of possibilities as fiber reinforced plastics materials. these materials meet the requirements of technical applications from the simplest solutions to extremely complicated structures. the composite materials price became available in the last few years. they offer such a usage, which can not any other material. the use of composite materials has increased dramatically in the last few years. currently they are mostly used in aircraft and automotive industry and in manufacturing of sports equipments. review of composite materials the main advantage of composite materials is their extreme strength at relatively low weight. as a composite can be understood such a material that meets following conditions: were made artificially. the materials consist of at least two chemically different components. the components have homogenous distribution throughout the volume. consequential properties of composite are different from the properties of the individual components. [1] the most common fabric is shown on following figures: figure 1: glass fiber, kevlar, carbon fiber, carbon-kevlar evolution of goalie mask it is hard to believe that ice hockey goalies haven’t used a head protector for many decades. last year goalie mask celebrated its 50th birthday. officially the first goalkeeper, who used some kind of face protector (the first goalie mask) was jacques plante, the goalie of montreal canadiens. his mask was made from fiberglass (gfrp). figure 2: the first goalie mask 114 nowadays, only the specialized technologies and materials are used for the production of goalie masks. composite materials are used for their very good properties. currently all high-quality goalie masks are made of them. of course every producer keep in a secret the “know-how”, how to made a high quality goalie mask which is solid but also very light. the modern hockey goalie mask is composed of two parts. the first is the front part of the mask and the second is the backplate, which is the backside of the goalie mask. the backplate is attached to the mask by rubber bands, which are regulable so we can set the mask to the required size. the backplate was designed in a 3d cam software. figure 3: the modern goalie mask and its parts designing the new shapes we were inspired by goalies masks used in nhl. a material called plasticine was fixed to the original mask. there are many reasons why plasticine was chosen as a suitable material. it is easily formable relatively cheap and popular material which can be simply removed after the lamination. figure 4: the new design of: a) chin b) forehead the chin was formed in symmetrical way. it is important to have a flat surface, because it makes the work easier after the lamination. after applying the necessary amount of separator on the surface of the mask the lamination started. firstly, a bigger glass fabric was used for the inner surface of the prototype form. then smaller pieces of glass fabric were applied because it´s easier to work with. the basic form is composed of three or four layers of fabric. the thickness of the mask depends on the usage because some parts of the mask have to absorb more power than others. after lamination the prototype form was left outside on the open air for a few hours for better solidification. after that process the base mask was taken out from the form. figure 5: the base mask and the prototype form the lamination was followed by sanding the inner surface of the mask. this treatment was repeated twice to get a relatively smooth surface. producting the prototype model before lamination the form had to be separated. a liquid separator called frewax was used for that purpose. frewax – liquid separator, mainly used at form making. [2] for the lamination was used mgs-scheufler l 285 epoxy resin with epoxy hardener no. 285. epoxy resin l 285 – is a liquid resembling honey with its colour and fluidity. [2] ordinary plastic filler was used for that purpose. two different types of fillers were applied, one for the rougher and one for the smoother filling. the filling was always followed by surface grinding. figure 6: separating the prototype form and filling the prototype model the prototype form was separated by frewax. firstly, a thin layer of frewax was brushed on the surface of the prototype model and after the dry up the layer was polished by a dry towel. altogether six layers of separator were brushed on the surface of the prototype form. the effectiveness was verified by using a tape. prototype model became ready by this complicated way. this process was followed by making the final form of the goalie mask for the serial production. this process was very similar to making the prototype model. 115 making the production form the next part of goalie mask producing was the preparation of the surface of the prototype model. a liquid substance called gelcoat was brushed on the internal surface in black colour. figure 7: brushing the gelcoat and laminating the production form gelcoat – is a liquid and thick meld used as an inner layer in the form manufacturing. the gelcoats main advantage is that it could be polished to “mirror” and create a completely smooth surface of the form. [32] the lamination of the form began by brushing the resin on the surface. after that was completed the glass cloth was continuously treated on the surface of the prototype model. after applying about 8-10 layers of glass fabric on the surface of prototype model the form of the goalie mask was ready. the prototype model was taken out from the production form. making the mask the form was cut around the roughness’s were filled up and polished. the edges and vents of the mask were drawn on the form too. for the outer layer of masks were used a carbon cloth because of possible to adjust the surface. if we use kevlar eventually. carbon-kevlar, we couldn´t sand the surface. the forehead and the chin are the most critical parts of the goalie masks and have to maintain the biggest potential impacts of the head. after two layers of carbon cloth there was a need of three more reinforcement layers of hybrid fabric (carbon-kevlar) on forehead and on chin. carbon fiber reinforced with aluminium wires was used for the next few layers and to add more strength to the mask. three more layers of that material were used and the final layer was a carbon fabric again. the vents and holes which attach the cage and the backplate holders were drilled to the mask. after the drilling the mask was prepared for painting. of course the surface of the mask has not been perfectly smooth, so it was necessary to brush the surface again and spread it with resin. figure 8: reinforced chin and forehead with carbon-kevlar and the last layer of resin making the backplate model ice hockey goalie mask consists of two parts. after the first part was ready a solution was proposed for the second part in 3d software. this solution is a 3d model of the backplate. milling of this form was produce on vmc eagle 1000 milling machine. polyurethane (pur) in green colour was chosen for a base product. consequently, the boundaries of the cutting tool were defined. for the roughing was used a monolith milling cutter of diameter 16 mm. the designing was started by defining the main points and drawing the line that intersected the curve of the backplate. the basic form was illustrated in three planes. the three planes were defined by an existing model and by our measurements. after it both curves of the masks were drawn. they were immediately connected together and the surface was ready. figure 9: designing the backplate in 3d for the making of the backplate we milled a production form. as a base we used the previously prepared 3d model. boundary line width was defined previously. the line makes easier the removal of the finished product from the form. 116 the next point we had to select a strategy for milling. for the purpose was chosen roughing by offset. for finishing was used a ø10 mm monolith milling cutter with marking 95102 mega. for completing our work we have select strategy of the optimized constant z. a) b) c) figure 10: milling of backplate form (roughing/finishing): a) tool selection b) way of the tool c) the milling process simulation/real this form will serve us for the further production of the backplate from glass, carbon, kevlar and hybrid fabrics. figure 11: the finished backplate form simulated and real conclusion the main aim of the work was to produce a goalie mask that will be suitable for playing ice hockey. of course, it was necessary to read thoroughly the available literature before the production. the starting point for the work was a goalie mask designed for street hockey. a new design was proposed based on this street hockey mask from composite materials. as a first step we made a prototype form then a prototype model and finally the form for the manufacturing of the mask. by assistance of that form a goalkeeper mask with carbon fabrics was produced. this mask is suitable for playing ice hockey. from the available resources and experiences we found that the most stressed parts of the mask (chin and forehead) need more reinforcement, so on these sites were used more flexible fabric, carbon – kevlar. the blackplate of the mask was designed in the 3d cad software, then that part was milled by powermill software to the polyurethane. the polyurethane milled form of the backplate will be used to produce the back of goalie masks from composite materials. our goal has been achieved because the carbon-kevlar mask stands for a better quality than the street hockey mask. our work helped us to uncover the characteristics, applications, manufacturing technologies and processes for the production from composite materials. references 1. r. moravcik, m. hazlinger: náuka o materiáloch ii(2009)stu isbn 978-80-8096-081-0. 2. company prospectus comp-let s.r.o.: základy výroby laminátových dielov. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word b_36_kohlrusz_r.doc hungarian journal of industrial chemistry veszprém vol. 39(2) pp. 265-270 (2011) comparison of scalar and vector control strategies of induction motors g. kohlrusz , d. fodor university of pannonia, faculty of engineering, institute of mechanical engineering, automotive systems engineering group, h-8200, veszprem, egyetem str. 10., hungary e-mail: kohlrusz.gabor@chello.hu currently the use of three-phase induction machines is widespread in industrial applications due to several methods available to control the speed and torque of the motor. many applications require that the same torque be available at all revolutions up to the nominal value. in this paper two control methods are compared: scalar control and vector control. scalar control is a relatively simple method. the purpose of the technique is to control the magnitude of the chosen control quantities. at the induction motor the technique is used as volts/hertz constant control. vector control is a more complex control technique, the evolution of which was inevitable, too, since scalar control cannot be applied for controlling systems with dynamic behaviour. the vector control technique works with vector quantities, controlling the desired values by using space phasors which contain all the three phase quantities in one phasor. it is also known as field-oriented control because in the course of implementation the identification of the field flux of the motor is required. this paper reports on the changing possibilities of the revolution – torque characteristic curve, and demonstrates the results of the two control methods with simulations. the simulations and the applied equivalent circuit parameters are based on real measurements done with no load, with direct current and with locked-rotor. keywords: speed-torque characteristics, scalar control, vector control, volts/hertz constant control, field-oriented control. introduction the control methods for induction motors can be divided into two parts: vector control and scalar control strategies. in this research on three phase squirrel-cage induction motors the closed loop volts/hertz voltage-fed inverter drive as scalar control technique and the rotor flux oriented control with voltage-fed inverter drive as vector control technique were compared. speed changing opportunities of induction motors many applications require that the speed of the motor be variable without changing the torque. the speed of induction motors can be changed in three different ways [1]: – changing the number of pole pairs, – vary the magnitude of supplied voltage or – vary the frequency of the supplied voltage. changing the number of pole pairs causes huge curve shifting, and varying the magnitude of supplied voltage gives solution only in a small range. the most promising possibility to change the speed of the motor is the varying of the frequency (fig. 1). however, this is not the best solution, because the impedances increase and the currents decrease with growing frequency. figure 1: speed vs. torque curves as functions of frequency current can also be controlled by voltage. this offers a possibility of control through both the voltage and the frequency changing. this idea was the basis of the evolution of a control method which is capable of controlling both speed and torque of induction motors, the so-called volts/hertz constant method. 266 basics of scalar control the scalar control method is based on varying two parameters simultaneously. the speed can be varied by increasing or decreasing the supply frequency, but this results in change of impedances. the change of impedances eventuates the increase or decrease of current. if the current is small, the torque of motor decreases. if the frequency decreases or the voltage increases, the coils can be burned or saturation can occur in the iron of coils. to avoid these problems, it is necessary to vary the frequency and the voltage at the same time. in this way, the occurring disadvantages of changing frequency and voltage can be compensated. according to the equation of induced voltage the v/hz constant control gives constant flux in the stator (eq. 1). ξ⋅ψ⋅⋅= s rms,e n f v 4.44 (1) where ve,rms – the induced voltage in the stator, f – the frequency of the supplied voltage, n – the number of turns, ψs – magnetic flux-linkage in the stator, ξ – constant of coil. the torque–speed equation of induction motors (eq. 2) can be used to determine the voltage–torque and frequency–torque functions [2]. s rit r r m gapair 2 2 3 ω =− (2) where tair-gap – the torque of the motor in the air-gap, ωm – the mechanical angular speed, ir – the rotor current, rr – the resistance of rotor, s – the slip. it can be seen from equation (2) that the relationship between torque and frequency is inverse, while voltage is directly proportional to torque. torque–speed control can be solved by the linear variaton of the two parameters (eq. 3). f v f vt ~ 2 ~ 2 2 ⋅πω (3) with this control method the torque is accessible in all operating points up to the nominal value of speed and the motor can operate over the nominal speed (fig. 2). in the overspeed range, the torque of the motor will decrease in inverse proportion to the increasing frequency because voltage cannot be higher than the value at which the driver electronics is able to operate [3]. figure 2: torque-speed curves with v/hz constant control open-loop scalar control the open-loop volts/hertz control of induction motors is widely used in industry (fig. 3). for this strategy, feedback signals are not required. this type of motor control has some advantages: – low cost, – simplicity and – immunity to errors of feedback signals. figure 3: open-loop v/hz constant control closed-loop scalar control the closed-loop method offers a more precise solution to controlling the speed than the open-loop method. furthermore, the closed-loop technique controls the torque, too. a major disadvantage of the open-loop control method is that this technique does not control the torque, so the desired torque is only accessible at the nominal operating point. if the load torque changes, the speed of the motor will change, too [4]. the closed-loop method contains a slip control loop, because the slip is proportional to the torque. the speed feedback signal from the tachogenerator is compared to the desired speed value. the difference is decreased to zero by the pi controller, so the motor will reach the desired speed. 267 typical applications of this method are in the winder drives [5]. a disadvantage of the method is uncontrolled magnetic flux. figure 4: closed-loop v/hz constant control there are some methods which use current control. current controlling solves the problem of uncontrolled flux, but these methods are more complex, e.g. in the case of current regulated voltage-fed inverter drive. vector control method field oriented control is one of the vector control methods. there are other well-known methods like direct torque control and direct self-control that work with vectors, as well. the field oriented control ensures good and robust control in case of transients. field oriented control is based on a mathematical abstraction. this results in an easier model conformation which corresponds the structure of well-controllable dc machine. the principle of field oriented control works with rotating vectors (or phasors) in a complex coordinate system. the magnitude and the phase of the controlled current change. with this technique, it is possible to uncouple the field components. uncoupling establishes two independent and single controlled currents: the fluxproducing current and the torque-producing current. using these currents, the flux and torque can be independently controlled. moreover, a 90° electric angle is ensured between the uncoupled control currents. as a result, the model of the induction motor loses its complexity, and a highperformance drive can be realized [6]. field oriented control can be carried out by system and coordinate transformations of the basic equations of the motor. after applying the transformations the alternating and sinusoidal quantities become nonalternating quantities. due to uncoupling, the currents can be controlled, and then, after back-transformation it is possible to modify the output of the inverter with three-phase quantities. in this way the magnitude and phase of supplied voltage or current can be modified. the quantities of the motor are described with a space phasor or a park-vector (eq. 4) in a three-phase coordinate system [7]. ( )cba ua+ua+u=u 2 3 2 (4) the equations which are valid instantenously can be described from the general voltage and flux phasors of the motor (eqs. 5 ,6 ,7, 8). it is possible to divide the equations into two parts. the stator equations are valid in the coordinate system fixed to the stator, and the rotor equations are valid in the coordinate system fixed to the rotor [8, 9]. dt ψd +ri=v s ss ⋅ (5) dt ψd +ri=v r rr ⋅ (6) m j rsss leili ⋅⋅+⋅= θψ (7) m j srrr leili ⋅⋅+⋅= − θψ (8) where vr, vs – the supplied voltage in rotor and in stator, ir, is – the current in rotor and in stator, r – resistance of stator and rotor coils, ψr, ψs – magnetic flux-linkage in rotor and in stator, lr, ls, lm – inductance of stator coil, of rotor coil and of the air-gap. it is necessary to determine the electromagnetic torque to get the equation-of-motion of the motor (eq. 9) [7]. rrrre iit ×−== ψϕψ 2 3sin 2 3 (9) where te – the electromagnetic torque of motor, ψr – the magnetic flux-linkage in rotor, ir – the current in rotor. the purpose is the conversion into a two-phase coordinate system. after this, both the stator and rotor quantities need to be transformed into a common coordinate system. then, calculations become executable and so the control signals (e.g. currents) are generated (fig. 5). the system transformation can be performed by the transformation matrix. this calculation results in a real and an imaginary part of the space-phasor. after transformation the equations (5)-(8) become two-phase quantities and need to be handled in a two-phase, complex α-β coordinate system [9, 10]. ⋅=⎥ ⎦ ⎤ ⎢ ⎣ ⎡ 3 2 β α u u ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ − −− 2 3 2 30 2 1 2 11 ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ ⋅ c b a u u u it is expedient to transform the complex, two-phase quantities into a common coordinate system, which is expediently the synchronously rotating d-q coordinate system. as a result of this transformation, the sinusoidal quantities become non-alternating quantities. =⎥ ⎦ ⎤ ⎢ ⎣ ⎡ q d u u ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ − ρρ ρρ cossin sincos ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ ⋅ β α u u 268 after transformations the quantities have to be handled uncoupled to their d and q components. it is desirable to control the torque and speed. to achieve rotor flux orientation it is necessary to orient the rotor flux vector to the d axis of the d-q synchronous rotating coordinate system (fig. 5). then the d directional component of current can control the rotor flux, while the q directional component controls the torque. figure 5: system and coordinate transformation the equation of torque gets also transformed (eq. 10). sqrd ipt ⋅⋅⋅= ψ 2 3 (10) the reduction of the rotor quantities to the stator gives a simpler model, which is the gamma-model (fig. 6). due to this model, the equivalent circuit diagram of the motor can be created [11]. figure 6: gamma-model with reducted values from the uncoupling to d-q components of equations (5)-(8) and from the equation of torque (eq. 10) it is possible to describe the equations of the motor based on the gamma-model (eqs. 11-15). sqk rd ssdsd s sd i dt d riu ldt di ⋅+⎟ ⎠ ⎞ ⎜ ⎝ ⎛ −⋅−= ω ψ σ 1 (11) ( ) sdkrdkssqsq s sq iriu ldt di ⋅−⋅−⋅−= ωψω σ 1 (12) sdm rd rd il dt d ⋅=+ ψ τψ (13) rd sq srk ir ψ ωωω ⋅ ==− (14) j b j m i j p dt d l sqrd r ωψ ω ⋅ −−⋅= 2 3 (15) where isd, isq – d and q components of stator current, lσs – inductance of stator without mutual inductance, usd, usq – d and q components of stator voltage, ωk, ωr – the synchronous and the rotor angular velocity, ψrd – d component of rotor magnetic flux-linkage, r, rs – resistance of rotor and stator, τ – rotor time constant, j – inertia of rotor, p – pole pairs of motor, tl – shaft load of motor, b – friction constant. the block diagram of rotor flux-oriented control can be seen in fig. 7. figure 7: rotor flux-oriented control without flux calculation (indirect field-oriented control) self-commissioning to create the motor model it is necessary to determine the unknown parameters of the motor by measuring the phase currents and phase voltages. moreover, it is necessary to measure the phase difference between voltage and current. for determining the parameters, three different measurements are needed (tables 1-3) [12] : – direct current test, – no-load test, – locked-rotor test. the reactances can be calculated from the impedances which are known if the phase difference between the voltage and the current or the power is known. table 1: results of the measurement with direct current vdc [v] idc [a] 5 0.075 15 0.22 25 0.36 35 0.505 269 from the measured data the stator resistance can be determined. in case of measuring with direct current the reactances are zero, so the measurement of two phase gives only the resistance of the two phase. ω= ⋅ 34 2 , , 1 avgdc avgdc i v =r table 2: results of the no-load test vrms [v] irms [a] p [w] cosθ 220 1.49 93.54 73.39 in case of no-load test the slip is very small, hence the resistance of the rotor is huge. the results are referring to the stator because of the small input current into the rotor. m rms rms nl xx i v =z += 1 = 147.65 ω table 3: results of the locked-rotor test vrms [v] irms [a] p [w] cosθ 60.1 0.851 37.08 43.54 61.1 0.895 40.87 41.65 60 0.855 37.42 43.17 the locked-rotor test was implemented by locking the rotor, which is allowed for a short time, only. in this case the slip is equal to one. the impedances and resistances can be measured both for the stator and the rotor. if the phase difference is known, the remaining parameters can also be determined. avg,rms avg,rms lr i v =z = 69.67 ω ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ ⋅⋅ =θ lt iv parccos 3 = 42.75° xlr = zlr · sinθ = 47.29 ω 221 lrx =xx = = 23.64 ω xm = znl – x1 = 124.01 ω rlr = zlr · cosθ = 51.16 ω r2 = rlr – r1 = 17.16 ω the unknown inductances can be determined from the parameters calculated for modelling. lm = xm · ω = 0.3947 lr = ls = x1 · ω = 0.0753 modelling and simulations the models of the closed-loop v/hz and the rotor fluxoriented control were implemented in matlab/simulink. during the simulations the models were tested with changing speed and torque references. the responses can be seen below. the results in case of speed change are the following: figure 8: closed-loop v/f=constant control figure 9: rotor flux-oriented control from the results it can be seen that volts/hertz control is a sluggish method because it is based on controlling the amplitude of voltage and frequency, instead of current. the rotor flux-oriented method controls the amplitude and phase of current and frequency. moreover, the controlled currents are decoupled, as it was mentioned earlier. in this way, control can be rapid and very robust. the results in case of torque changing are shown in figs. 10-11. figure 10: closed-loop v/f=constant control 270 figure 11: rotor flux-oriented control the response of the model to changing the torque is similar to that in the case of changing the speed reference. the v/hz constant model controls the torque slowly. the field-oriented control provides constant torque response. conclusions both control methods have advantages and disadvantages. scalar control is a cheap, well-implementable method. because of these advantages and its simplicity, many applications operate with this control technique in the industry. on the other hand, it is not satisfactory for the control of drives with dynamic behaviour, since it gives slow response to transients. this is because the v/hz constant method controls the magnitude of voltages and frequency instead of controlling the phase and magnitude of currents. it is a low-performance, but stable control technique. the field oriented control method controls the currents so it operates with fast responses. this method satisfies the requirements of dynamic drives, where fast response is necessary. it is an excellent control method to handle transients. its disadvantage is complexity, and the high price of the driver circuit. nevertheless, it is a high-performance control technique. both techniques are applicable over the nominal speed at the expense of torque. acknowledgement the financial and infrastructural support of the state of hungary and the european union in the frame of the tamop-4.2.1/b-09/1/konv-2010-0003 (mobility and environment) project is gratefully acknowledged. references 1. z. hámori: villamos gépek, tankönyvmester kiadó, (2001), pp. 79–83 2. s. halász: villamos hajtások, bme egyetemi tankönyv, (1993) , pp. 183–184 3. m. a. laughton, d. f. warne: electrical engineer’s reference book, newnes, (2003) , p. 19/6 4. a. hughes: electric motors and drives: fundamentals, types, and applications, newnes, (2005), pp. 286– 289 5. a. m. trzynadlowski: control of induction motors, academic press, (2001), pp. 101–102 6. j. m. d. murphy, f. g. turnbull: power electronic control of ac motors, pergamon press, (1988), pp. 313–314 7. k. p. kovács, i. rácz: váltakozóáramú gépek tranziens folyamatai, akadémiai kiadó, (1954), pp. 40–42, 207–210 8. á. kelemen, m. imecs: vector control of ac drives, volume 1: vector control of induction machine drives, omikk publisher, (1991), pp. 48–62 9. gy. retter: villamosenergia-átalakítók, 2. kötet, aszimmetrikus és tranziens üzem, műszaki könyvkiadó, (1987), pp. 64–78 10. g. j. retter, k. németh: matrix and space-phasor theory of electrical machines, akadémiai kiadó, (1987), pp. 199–204 11. i. schmidt, gy.-né vincze, k. veszprémi: villamos szervoés robothajtások, műegyetemi kiadó, (1999), p. 174 12. s. j. chapman: electric machinery fundamentals, mcgraw-hill, (1998), pp. 430–436 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjdffile 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(adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word szolcs_eloszo.doc hungarian journal of industrial chemistry veszprém vol. 32. pp. 33-39 (2004) starch citrate as an ion exchange material – preparation and investigation e. fajd and g. marton university of veszprém, department of chemical engineering science h-8201 veszprém, egyetem u. 10. p.o.box 158., hungary phone/fax.: +36 88 421 905, email: efajd@almos.vein.hu, martongy@almos.vein.hu waxy starch was allowed to react thermochemically with citric acid to yield starch citrate of high ion binding capacity. purpose of the work was to prepare biodegradable ion exchange material of highest ion binding capacity. reaction variables studied were: reaction time (15min–24h), reaction temperature (135-160 ºc), citric acid/starch ratio (0.3/1-5/1). optimal reaction time vs. reaction temperature and optimal citric acid/starch ratio were determined. best ion binding capacities were around 5 meqv/g (155-160 mg cu2+/g). preparation of starchcitric acid granules proved to be possible in a batch mixer when saturated aqueous citric acid solution was sprayed on the stirred starch. the desired citric acid content was reached gradually. samples were evaluated by ion binding capacity at ph 4.5 in aqueous cu2+ solution. in further experiments the effect of bead size and the effect of the ph of solution on ion binding capacity was examined and preliminary column experiments were carried out to see how binding and regeneration steps work out in a glass column. finally some tests were made to prove and investigate the biodegradability of starch citrate. keywords: ion exchange resin, environmental friendly chemicals, biodegradability introduction ion exchange resins of petrochemical origin have been used for the last few decades to remove heavy metal ions from industrial effluents. these resins are expensive, nonbiodegradable and produced from nonrenewable raw materials. using renewable resources is gaining ever greater importance in the european community as well as in most countries of the world. starch and citric acid are both produced in large quantity, they are inexpensive, environmental friendly, biodegradable and renewable. obtained by their thermochemical reaction, starch citrate, the subject material of present study, is inexpensive and biodegradable, too. agriculturally produced materials can be derivatized to yield ion exchange resins [1,2]. these materials can be used for binding bivalent heavy metal ions like cd, cu, pb, ni, zn.[4]. among these modified materials starch citrate attracts attention with its high ion exchange capacities. several types of starch (waxy, corn, potato, wheat) were investigated from the aspect of ion binding capacity and durability against regeneration and starch citrate prepared from waxy corn starch proved to be of best properties among them [5]. the purpose of the present work was to prepare a biodegradable ion exchange material through modification of waxy starch by citric acid and investigate its properties as for further use in ion exchange columns. experimental materials waxy starch was supplied by hungrana ltd., hungary, citric acid (ca) was supplied by interkémia, hungary. all other chemicals were reagent grade. 34 reaction procedure laboratory scale: 200g of powdered ca was thoroughly mixed with 100g of waxy starch, then water was added and the mixture was rubbed till earth-damp. pilot scale: 1000g of waxy starch was placed in a batch mixer. while stirred, saturated aqueous ca solution was sprayed on it. when water content blocked mixing the product was dried and smashed through a 16 mesh screen; then it was put again into the mixer for further spraying. this process was repeated till desired ca content was reached. both the samples prepared by laboratory scale and pilot scale method were placed in forced air oven to dehydrate at 60 ºc for 24h. that way all surface moisture has been removed and the starch particles were sheathed with ca. oven temperature was adjusted to 135-160 ºc and the mixtures were allowed to react for the reaction predetermined time. the resulting material was slurried in water for 10 min, then filtered, washed and air dried overnight. determination of copper binding capacity 1.000 g of each sample was slurried in 100 ml water containing 190 mg of cu2+. the cu2+ solution was prepared from cu(so4). the ph was adjusted to 4.5 with 0.5 n naoh and maintained at that level till the end of binding procedure. after filtration, copper was removed from the matrix with 50 m/m % hno3, and after filtration it was diluted for analysis with gbc integra xm icp spectrophotometer. at laboratory scale experiments time of copper binding was 24h, while at the pilot scale experiment only 1h binding time was applied. this shorter time allowed faster determination of copper binding capacity and better control of factors (e.g. ph level) of the ion binding procedure. determination of biodegradability 10 g of each sample was put on a clock glass and exposed to the experimental conditions (kept wet; kept in a humid atmosphere). after about three months (101 days) the samples were investigated and the found results were evaluated. results and discussion the purpose of the present study was to examine that at which values of the reaction variables (reaction time, reaction temperature, citric acid/starch ratio) will the thermochemical reaction of starch and ca result in starch citrate of possibly best ion binding capacity and to examine some features of the product in the light of further use in ion exchange columns. when ca is heated it dehydrates and yields citric acid anhydride which can react with starch forming starch citrate adduct: h2c c h2c c cooh cooh ho ost o h2c c h2c cooh cooh cooh ho -h2o h2c c h2c c c cooh ho o o o st-oh citric acid citric acid anhydride starch citrate ∆ figure 1 thermochemical reaction of citric acid with starch resulting in starch citrate if heated beyond an optimal reaction time, starch citrate dehydrates again and crosslinking can take place which results in drop of the ion exchange capacity of the matrix. h2c c h2c c cooh cooh ho ost o -h2o c c o o o st-oh h2c c h2c c coohho ost o c ost o starch citrate anhydride starch citrate crosslinked starch citrate ∆ h2c c h2c c ho ost o figure 2 further thermochemical reaction of starch citrate with starch: cross-linking so determining the optimal reaction times at relevant reaction temperatures is essential. the reaction variables studied were: • reaction temperature: 135-160 ºc • reaction time: 15 min-24 h • citric acid/starch ratio: 0.3/1-5/1 laboratory scale experiments at the first set of experiments the temperature range examined was 135-150 ºc by 5 ºc steps and at a range of reaction times 30-120 min by 30 min steps (fig. 3). 35 cu2+ ion binding capacity of starch citrate at reaction temperatures 135-150 ºc 100 105 110 115 120 125 130 135 140 145 150 0 30 60 90 120 150 reaction time (min) c u2+ io n bi nd in g ca pa ci ty (m g/ g) 150ºc 145ºc 140ºc 135ºc figure 3 results of experiment no.1. examining the curves the conclusions can be drawn that the optimal reaction time at 135 ºc is >120 min, at 140 ºc about 90 min, at 150 ºc approx. 60 min, while at 145 ºc it can be found between 60 and 90 min. data in table i. sums up these findings. table i optimal reaction times at reaction temperatures 135-150 ºc reaction temperature (°c) optimal reaction time (min) 150 60 145 75 140 90 135 >120 at the second set of experiments the temperature range examined was 150-160 ºc by 5 ºc steps and at a range of reaction times 30-90 min by 15 min steps (fig. 4.) and at 135 ºc the reaction times were 120 min, 360 min, 540 min, 720 min and 1440 min (fig. 5). cu2+ ion binding capacity of starch citrate at reaction temperatures 150-160 ºc 120 125 130 135 140 145 150 155 160 165 0 15 30 45 60 75 90 reaction time (min) c u2+ io n bi nd in g ca pa ci ty (m g/ g) 160 ºc 155 ºc 150 ºc figure 4: results of experiment no.2. cu2+ ion binding capacity of starch citrate at reaction temperature 135 ºc 108 110 112 114 116 118 120 122 124 0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560 reaction time (min) c u2+ io n bi nd in g ca pa ci ty (m g/ g) figure 5 results of experiment no.2. from the figures it can be seen that the optimal reaction time at 135 ºc is around 540 min, at 150 ºc 75 min, at 155 ºc 60 min and at 160 ºc 45 min (table ii). table ii: optimal reaction times at reaction temperatures 135 ºc and 150-160 ºc reaction temperature (°c) optimal reaction time (min) 160 45 155 60 150 75 135 540 the above results can be summarized in a graph showing the dependence of optimal reaction times on reaction temperature: figure 6: optimal reaction times at reaction temperatures 135-160 ºc pilot scale experiments pilot scale experiments were carried out to examine the possibility of preparation of starchcitric acid granules in a batch mixer, the ion 36 binding capacity of the starch citrate made out of the granules and at the same time the optimal citric acid-starch ratio. the batch mixer used in the experiments has the dimensions shown in fig. 7. figure 7 the dimensions of the batch mixer (mm) figure 8 the batch mixer used at the experiments the main impeller (100-350 rpm) of the mixer imparts a 3 dimensional tumbling action to the mixture and the side mounted breaker impeller (1800-2300 rpm) chops the larger granules into smaller ones. into one of the openings on the top of the mixer a spraying head is fitted while the other opening mounted with a filter bag is for the outlet air. the mix was prepared as described before. the samples taken out at each step were allowed to react at 140 ºc for 90 min. the ion binding capacities were determined at 1h exposition time in cu2+ solution (fig. 9). figure 9 cu2+ binding vs. ca/starch ratio it can be made out from the graph that approx. 2/1 ca/starch ratio can be considered as an optimal mix composition beyond which no increase in ion binding capacity was experienced. ion binding vs. particle size the particle size of an ion exchange resin influences the time required to establish equilibrium conditions. there are two types of diffusion that must be considered in an ion exchange equilibrium. the first is called film diffusion or the movement of ions from a surrounding solution to the surface of an ion exchange particle. the second is called internal diffusion and is the movement of ions from the surface to the interior of an ion exchange particle. the particle size of an ion exchange resin affects both film diffusion and internal diffusion. a small particle presents more surface area for film diffusion and also contains less internal volume through which an ion must diffuse. a decrease in particle size thus shortens the time required for equilibration. ion exchange processes are usually carried out in columns with resins filled in a column. the spherical particles of ion exchange resins resist the flowing of a liquid through or around them. the smaller the particle size, the greater will be this resistance and thus the pressure drop in the column. this resistance goes up very rapidly when particles smaller than ø ~0.15 mm are used. the starch-citrate granules were fractionated by sieves to <0.2 mm, 0.2-0.4 mm, 0.4-0.63 mm, 0.63-0.8 mm, 0.8-1.0 mm and 1.0-1.6 mm 37 fractions. we have examined the amount of cu2+ ions bound after 1h binding time. cu2+ binding vs. average particle size of starch citrate 0 20 40 60 80 100 120 140 160 0 0,2 0,4 0,6 0,8 1 1,2 1,4 average particle size (mm) c u2+ b in di ng (m g/ g) figure 10 cu2+ binding vs. average particle size of starch-citrate (reaction temperature: 140 ºc, reaction time: 1,5h, cu2+ binding time:1h) the figure shows well that fractions with smaller particle size can bind greater amount of cu2+ ions within a short exposition time. when using the material in an ion exchange column the pressure drop of the package is of much importance. according to the measurement results the diffusion at 0.2-0.4 mm particle diameter is still quick enough and pressure drop is expected to fall also into an acceptable range. ion binding vs. ph being a weakly acidic cation exchange material, ion binding capacity of starch citrate is greatly depending on the ph of the liquid processed. the tipical performance of a weakly acidic cation exchange resin is as seen on figure 11. exchange capacity of weakly acidic cation exchange resins as a function of ph of liquid processed 0 0,5 1 1,5 2 2,5 3 3,5 3 4 5 6 7 8 9 10 11 ph io n ex ch an ge c ap ac ity (e q/ dm 3 ) figure 11 exchange capacity of a weakly acidic cation exchange resin as a function of the solution ph if the ph is by 2 values less then the pka value of the carboxilic group then the ion exchange capacity practically becomes zero, while a maximum capacity is reached when the ph value is at least by 2 values higher than the pka value. as in the case of starch citrate there are two carboxilic groups out of three that are still free and the corresponding pka values are close to each other, the two exchange curves are overlapping and thus no such a characteristic curve can be detected. the pka values of the citric acid are: 3.1, 4.75 and 5.4 but in case of the starch-citrate we have to consider only the two greater value as the third carboxilic group is engaged in building the connection to the starch molecule. ph<2,75 (=4,75-2) → ‘zero’ exchange capacity ph>7,4 (=5,4+2) → maximal exchange capacity cu2+ binding capacity as a function of solution ph 0 20 40 60 80 100 120 140 160 180 200 1,5 2 2,5 3 3,5 4 4,5 5 5,5 6 6,5 ph c u2+ b ou nd (m g/ g) figure 12 ion exchange capacity as a function of the solution ph (starch citrate reaction temperature: 140 ºc, reaction time: 1.5h, binding time:1h) as the measurements were carried out with cu2+ solutions, at ph values higher than 6.0 the cu(oh)2 precipitation hindered the measurements. ion exchange in a column ion exchange processes are usually carried out with ion exchange resins filled into columns. so we made some preliminary experiments to see how starch citrate behaves when used in this way. a glass column of 15 mm diameter was filled with 120 mm high starch citrate packing. cu(so4) solution of 10 g/dm3 concentration was let to flow through the column by force of gravity. after the binding step the column was regenerated with 3 % m/m hno3. 38 figure 13 ion exchange process in a laboratory size glass column. (a: ion exchange in process; b: starch citrate packing reached equilibrium; c: regeneration in process; d: fully regenerated) when binding the cu2+ ions the ion exchange front could be seen well, and while regeneration a sharp front could be detected by sight also. after the regeneration step was complete, no cu2+ ion residue was left on the packing. both hno3 and hcl of 2-3 % m/m concentration was good regenerating agent for the starch citrate packing. using hcl beyond 7 % m/m, cucl2 formation occured that can be seen from the yellowish green color appearance. some phisical properties of the packing: particle size: 0.2-0.4 mm (adjusted by mashing through sieves and screening) swelling (dry to wet): 2.2x wet density: 1.08 kg/dm3 dry density: 0.473 kg/dm3 measurements of further property values are in progress. investigation of biodegradability one great advantage of starch citrate is its biodegradability. some experiments were made to test this quality also. samples were kept in a wet condition for about three months. to quicken the degradation yeast infection was applied. results can be seen on figure 14. figure 14 samples of starch citrate kept in a wet condition for three months (a: before; b: after) other samples of starch citrate were kept in an atmosphere of high relative humidity for three months. the ones of h+ form started to degrade properly while the ones of cu2+ form kept their original condition even after this long exposition time. figure 15 samples of starch citrate kept in a humid atmosphere for three months (a: h+ form; b: cu2+ form) on figure 15.a can be seen the well-developed microbial fundaments, while the cu2+ content of the material impeded the degradation of the matrix. conclusions the thermochemical reaction of starch-citric acid mix yielded starch citrate of high ion binding capacity. above 135 ºc optimal reaction times were found beyond which reaction times the ion binding capacity decreased, probably due to additional cross-linking. an optimal citric acid/starch ratio was found (approx. 2/1 ca/starch) beyond which no increase in ion binding capacity was experienced. with the pilot scale experiments using onspraying technique we could prepare starch citrate of high ion binding capacity comparable to that of synthetic weakly acidic ion exchange resins. the best samples performed ~5 meqv/g (155-160 mg cu2+/g) ion binding capacity. starch citrate like traditional ion exchange 39 resins can be used as packing in columns. it responses to the ph of the solution like other weakly acidic cation exchange resins, and the bead size of starch citrate can be adjusted to the desired average size by mashing through sieves and screening. both binding and regeneration steps can be carried out in the usual way. for regeneration either hno3 or hcl of 1-3 % m/m concentration can be used properly. the exhausted matrix after being regenerated can be deposed to an open field and the material will degrade in some months. degradation can be quickened with application of degrading microbial infection. if heavy metal (e.g. cu2+) ions are bound on the matrix no considerable degradation could be detected. its low raw material and production costs together with its outstanding environmental friendly properties can make starch citrate a competitive alternative for traditional ion exchange resins. acknowledgement the authors wish to thank the cooperative research centre (vikkk, hungary) for its support. references 1. robert e. wing: starch citrate: preparation and ion exchange properties; stärke/starch 48 (1996) nr.7/8, s. 275-279. 2. robert e. wing: corn fiber citrate: preparation and ion exchange properties; industrial crops and products; 5 (1996) 301305. 3. filho n. c., winkler-hechenleitner a. a. and gómez-pineda e. a.: copper (ii) adsorption onto sugar cane bagasse; intern. j. polymeric mater. 34 (1996) pp. 211-218. 4. vaughan t., seo ch. w. and marshall w. e.: removal of selected metal ions from aqueous solution using modified corncobs; bioresource technology 78 (2001) pp. 133-139. 5. svéger h.: preparation of starch citrate ion exchange material from different types of starch; diploma thesis, university of veszprém, 2004. 6. fajd e. and marton g.: starch citrate as an environmental friendly ion exchange material; proceedings of 2nd world conference on biomass for energy, industry and climate protection, rome, italy, 1-14. may 2004. microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 37(2) pp. 139-143 (2009) differences between optimum flow sheet solutions obtained by different economic objective functions m. kasaš, z. kravanja, z. novak pintarič university of maribor, faculty of chemistry and chemical engineering smetanova 17, si 2000 maribor, slovenia e-mail: zorka.novak@uni-mb.si this paper discusses the shapes of cash flow functions obtained by modelling chemical processes at different levels of complexity, and the influence of these shapes on optimal solutions obtained by different economic objective functions. cash flow functions can be unimodal (with maximum) or monotonically increasing (concave) with respect to capital investment. this depends on the quality of major trade-offs established in the model. unimodal shape is common for modelling with simple and aggregated models, where increasing the investment above certain level causes loss to a project, which indicates improper or insufficient trade-offs in the model. monotonically increasing concave cash flow functions are usually obtained by using more detailed models. this implies better trade-offs in the model as increasing the investment always brings some benefit (higher or lower). example of methanol process synthesis presented in the paper indicate that models with monotonic cash flow functions produce significantly different optimal solutions when optimizing different economic criteria, e. g. the net present value, the profit and the internal rate of return. on the other side, the optimal solutions of models with unimodal functions are similar. these results suggest that models should be formulated at the level of complexity which produces monotonically increasing cash flow functions. keywords: cash flow, investment, unimodal, concave function, trade-off, optimization, mathematical programming, objective function, chemical process, flow sheet introduction the engineering community uses different measures for assessing the economic attractiveness of investment projects. the most common are the total annual cost, annual profit before taxes, the payback time, the net present value and the internal rate of return. buskies [1] established that optimal values of process parameters obtained during the optimization of chemical processes depend on the objective function used in the optimization. novak pintarič and kravanja [2] discussed the differences between optimal process designs obtained by means of qualitative, quantitative and compromise economic criteria. faria and bagajewicz [3] performed minlp design of water utilization systems by maximizing the net present value and internal rate of return and also observed different optimal solutions. the origin and characteristics of these differences have not been explained sufficiently in the open literature. the main intention of this paper is to discuss the characteristics of optimal process flow sheets obtained by synthesis and optimization with different economic criteria. it was observed that in some cases, significantly different optimal designs are obtained, while in other cases, differences are negligible. it will be shown in this paper that differences between optimal solutions depend on the slope of the cash flow derivative function, while its slope depends on the shape of the cash flow function with respect to capital investment. unimodal shapes (with maximum) are obtained by using simple, aggregated models. more detailed models produce monotonically increasing concave functions of cash flow. the example in our paper shows that different economic criteria lead to optimal solutions that are significantly different in the term of conversion, level of heat integration, investment, cash flow, and even in the term of topology. the important simplification in this paper is that investment costs are represented as simple continuous nonlinear functions of process size. in general, complex cost functions are discontinuous in terms of size and other factors, e.g. pressure and temperature, and require special modelling techniques in order to be included in optimization models, as shown by turkay and grossmann [4]. optimality conditions optimality conditions for different economic criteria are well known. maximum net present value (npv) is obtained at the investment level where the marginal (incremental) npv is equal to zero and marginal internal rate of return (irr) equals to discount rate used for 140 npv maximization. in practice this means that process units should be enlarged only as long as the incremental increase has positive marginal npv and the incremental irr is greater than the minimum acceptable rate of return (marr). maximum profit before taxes (pb) and irr are obtained at the investment levels where the marginal profit and irr, respectively, equalize to 0. it could therefore be expected that applying different criteria in the objective function by designing, optimizing and synthesizing process flow sheets would not lead to the same optimal results. in our previous work [2] it was shown, that optimization of qualitative criteria, such as payback time and internal rate of return, stimulate smaller process designs and fast (re)investment of capital which results in high profitable solutions. quantitative criteria, such as profit or total costs, produce large processes and higher cash flows, but also require higher capital investments, and achieve lower profitabilities. criteria, such as the net present value and equivalent annual cost, result in intermediate size of the process. these are compromise criteria as they establish a compromise between the investment costs, profitability of invested money, and dynamics of investing [5]. cash flow functions cash flow, fc, is defined by the following equation: c t t d (1 )( ) if r r e r t = − − + (1) where rt represents the tax rate, r the revenues or incomes, e the expenditures, i the investment and td the depreciation period. the term (r – e) in the right-hand side of eq. (1) is the surplus of the revenues over the expenses and actually represents a benefit resulting from invested money. the second part is a tax credit of depreciation originating directly from investment. two shapes of cash flow function with respect to the level of capital investment are mostly obtained when optimizing process flow sheet models: unimodal function with maximum, and monotonically increasing concave function (fig. 1). convex functions of cash flow vs. investment are very rare in the flow sheet optimization. cf a) 0 i 0 10 20 30 40 50 60 70 80 b) 0 cf i figure 1: cash flow functions, a) unimodal, b) concave unimodal cash flow functions unimodal cash flow function is common for flow sheet modeling with simple and aggregated models at early stages of process development, e.g. by stoichiometric reactor with fixed conversion per pass or simple component splitter. in such models, the trade-offs between the revenues, operating costs and investment are often established only through the recycle flow rate. in the case of unimodal cash flow function a mode (maximum) exists and derivative thus changes the sign (fig. 2a). stationary point for maximum cash flow is obtained at: c t t d d d( )(1 ) 0 d d f rr er i i t − = − + = (2) dt t )1(d )(d tr r i er ⋅− −= − (3) from the upper equation it follows, that maximum cash flow of unimodal function occurs at the level where increasing the investment would reduce benefit to a project, as the right hand side of eq. (3) is a constant negative value. this result leads to the assumption that flow sheet optimization model with unimodal cash flow function indicates improper or insufficient trade-offs. in practice, increased investment should result in increased benefit. the benefit growth rate is lower and lower as investment grows, but should not change to a loss, as in the case of unimodal cash flow function, though there are some exceptions in engineering applications. e.g. adding insulation (increasing investment) to circular tubes whose outside radius is smaller than the critical radius increases heat losses up to the value of critical thickness [6]. note that the shape of the benefit function (r – e) vs. investment i would be very similar to the shape of the unimodal cash flow function shown in fig. 1a. -3 -2 -1 0 1 2 3 4 5 0 0 1 /5 2/ 7 2/ 5 1/ 2 3 /5 5 /7 4 /5 a) 0 i cd d f i 1 b) i cd d f i t d r t 1 figure 2: derivative of unimodal (a) and concave (b) cash flow function concave monotonic cash flow functions monotonic concave cash flow functions are obtained by more detailed modeling, where more precise tradeoffs are present, e.g. by kinetic reactor or distillation column. these trade-offs reflect as direct benefit resulting from 141 invested money, e.g. longer catalyst bed in the reactor enables higher conversion of reactants per pass, larger exchanger area enables more heat transferred between process streams and thus lower utility costs etc. in the case of concave monotonic cash flow functions, the slope of the cash flow curve is always positive and decreases monotonically (fig. 2b). the term (r – e) in eq. (1) becomes constant at high investment values and its derivative approaches to zero. the shape of the (r – e) function vs. investment i would be similar to that shown in fig. 1b, with the exception that (r – e) curve would remain constant at higher values of investment while cash flow curve increases linearly due to depreciation term in eq. (1). cash flow derivative thus approaches asymptotically to a constant nonnegative value as investment approaches infinity: c t d d lim di f r i t→∞ = (4) from the above equation, it can be seen that asymptotic constant value depends only on the tax rate, and depreciation period. cash flow at high investment values increases linearly only because of depreciation term in eq. (1). further increase of investment does not increase benefit, but at least does not cause any loss. differences in optimal solutions it could be shown by deriving stationary conditions for optimum economic criteria that the investment levels of optimal solutions increase in the direction from irr over npv to pb criterion [7]. the magnitude of these differences depends on the steepness of cash flow derivative function. the steeper this function is, more similar are the optimal solutions. the derivative function of monotonic cash flow is more flat because it approaches asymptotically to a constant positive value (fig. 2b). optimum npv and pb solutions are thus more apart. besides, models with monotonic cash flow functions comprise more precise trade-offs that enable to find the solutions with higher profitabilities. this forces investment level of optimum irr solution below investment levels of the other two optimum solutions. models with unimodal functions comprise only rough trade-offs which do not allow high profitable solutions. optimization of such models often results in similar optimal solutions. methanol process synthesis minlp synthesis of methanol process flow sheet from synthesis gas is considered in this section. the example was taken from the literature [8] and the prices were updated. superstructure of the process involves four topological selections: 1) two feed streams from which the first one (feed-1) is cheaper as it contains less hydrogen, 2) one-stage or two-stage compression of the feed stream, 3) two reactors from which the second one (rct-2) is more expensive and allows higher conversion, and 4) one-stage or two-stage compression of the recycle stream. kinetic model is used for both reactors. flow sheet comprises 4 hot streams and 2 cold streams. minlp model for heat integration [9] with 4 stages is added to the mathematical model of superstructure for simultaneous heat integration and heat exchanger network (hen) synthesis. design variables for assessment of capital investment are the reactor’s volume, compressors power, and heat exchangers area. the composed minlp model comprises about 600 constraints and 600 variables from which 46 are binary (8 for process topology and 38 for heat matches). the minlp synthesis is performed by means of automated minlp process synthesizer mipsyn [10]. three economic objective functions are optimized: irr, npv and pb. the second feed stream is selected in all optimal solutions together with the two-stage compression of feed stream, and one-stage compression of recycle stream (fig. 3). the cheaper reactor (rct-1) with lower conversion is selected by maximizing irr and npv, while more expensive reactor (rct-2) with higher conversion is obtained by maximizing pb (dotted line on fig. 3). optimal heat integration scheme is equal in all three cases. figure 3: optimal structures of methanol synthesis 142 the solution with highest capital investment and cash flow is obtained in the case of pb maximization (table 1), while the lowest values are observed in the case of maximum irr solution. table 1: optimal solutions of methanol synthesis max rirr max wnp max pb i (meur) 82.63 85.24 89.12 fc (meur/yr) 34.63 35.13 35.50 fc/i 0.419 0.412 0.398 r (meur/yr) 83.98 83.80 83.69 crm (meur/yr) 28.59 28.17 27.90 cut (meur/yr) 11.04 10.68 10.43 wnp (meur) 180.80 181.98 180.92 pb (meur/yr) 38.83 39.26 39.41 rirr (%) 41.69 40.97 39.57 xrct (%) 16.20 18.19 19.56 x o (%) 79.93 80.31 80.54 ahen (m2) 2769 3285 3783 vrct (m3) 24.60* 31.70* 29.37** pcomp (mw) 40.30 38.78 37.87 i (ahen) (meur) 10.77 12.71 14.57 i (vrct) (meur) 16.72 19.38 22.60 i (pcomp) (meur) 55.14 53.15 51.95 * rct-1, ** rct-2 although some economic figures do not differentiate substantially, the optimal designs are significantly different. the cheaper reactor (rct-1) is selected by irr and npv criteria and, as expected, the reactor is significantly larger in the case of max npv. the reactor of pb solution is medium-sized because more expensive option (rct-2) with higher conversion and capital investment is selected. the total area of heat exchanger network (ahen) is significantly different in all three cases. the investment levels of reactor and hen increase from irr to pb, while on the contrary, the total power of compressors (pcomp) decreases and is the smallest in the case of pb solution. this is because the highest conversion is obtained by pb criterion, and consequently, the amounts of feed and recycle streams are the smallest. the largest revenue is achieved in the case of optimum irr solution, however, the consumptions of raw materials and utilities are also the highest. high profitability is achieved on the account of higher input of reactants and utilities, but not with increased level of heat integration and conversion of reactants. the latter increases from irr over npv to pb optimum solution. fig. 4 represents the concave shape of cash flow functions of both optimal process structures obtained by irr and npv criteria, as well as by pb criterion. increased investment is used for increasing the reactor volume and the conversion, as well as for increasing heat exchangers area and thus heat transfer between process streams. fig. 5 represents the derivative functions of both optimal structures. 34.2 34.4 34.6 34.8 35 35.2 35.4 35.6 35.8 82 84 86 88 90 92 max irr and npv max pb (meur)i c (meur)f figure 4: cash flow functions of optimal methanol structures 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 82 83 84 85 86 87 88 89 90 cd d f i (meur)i max irr max npv max pb figure 5: cash flow derivative functions of optimal methanol processes conclusion the differences between optimal solutions obtained by using different economic criteria depend on the slope of cash flow derivative function. the derivative curve of concave cash flow function often has a gentle slope as it asymptotically approaches positive constant value. for this reason, different economic criteria lead to optimal solutions that are significantly different in the term of design variables, and/or economic figures or even in the term of topology if process synthesis is performed. on the other side, the derivative of unimodal cash flow function is very steep leading to similar optimal designs. it was shown that optimum irr solution is obtained at the lowest investment level, optimum npv solution at intermediate level, and optimum pb solution at the highest investment level. conversion of reactants increases from irr to pb, while raw material and utility consumptions decrease. qualitative criteria, like irr and payback time, produce highly profitable optimal solutions with low capital investment. quick return on investment is of top priority, while the effective resource utilization is less important. quantitative criteria, like 143 pb and total annual cost, foster the generation of more efficient solutions with lower operating costs which are achieved by e.g. higher conversion, better separation and/or higher level of heat integration. these solutions are, despite of higher investment level, oriented towards long-term, more sustainable flow sheets. the return to investors is slower, however, this is compensated with higher cash flows. compromise criteria, like npv and equivalent annual cost, establish a balance between quick return on investment and long-term steady generation of benefit. it could be concluded that flow sheet models should be formulated at the level of complexity which produces monotonically increasing cash flow functions. references 1. buskies u.: economic process optimization strategies. chemical engineering & technology (1997) 20, 63–70 2. novak pintarič z., kravanja z.: selection of the economic objective function for the optimization of process flow sheets. industrial & engineering chemistry research (2006) 45, 4222–4232 3. faria d. c., bagajewicz m. j.: profit-based grassroots design, retrofit of water networks in process plants. computers & chemical engineering (2009) 33, 436–453 4. turkay m., grossmann i. e.: structural flowsheet optimization with complex investment cost functions. computers & chemical engineering (1998) 22, 673–686 5. novak pintarič z., kravanja z.: multiperiod investment models for the gradual reconstruction of chemical processes. chemical engineering & technology (2007) 30, 1622–1632 6. eckert e. r. g., drake r. m. j.: analysis of heat and mass transfer. 1972, new york: mcgraw-hill. 7. kasaš m., kravanja z. in novak pintarič z.: cash flow functions and optimal solutions of flow sheet models at different levels of complexity. cape forum (2009) limerick. 8. kravanja z., grossmann i. e.: prosyn an minlp process synthesizer. computers & chemical engineering (1990) 14, 1363–1378 9. yee t. f., grossmann i. e.: simultaneous optimization models for heat integration-ii. heat exchanger network synthesis. computers & chemical engineering (1990) 14, 1165–1184 10. kravanja z., grossmann i. e.: new developments and capabilities in prosyn-an automated topology and parameter process synthesizer. computers & chemical engineering (1994) 18, 1097–1114 microsoft word contents.doc hungarian journal of industrial chemistry veszprém vol. 34. pp. 41-49 (2006) solid dispersions of oxeglitazar in pvp k17 and poloxamer 407 by supercritical antisolvent and coevaporation methods v. majerik1 , g. horváth1, g. charbit2, e. badens2, l. szokonya1, n. bosc3 and e. teillaud3 1department of chemical engineering science, university of pannonia, veszprém egyetem u. 10 po box 158, h-8201, hungary e-mail: majerikv@almos.vein.hu 2laboratoire de procédés propres et environnement, umr6181 université paul cézanne aix-marseille 3, europôle de l'arbois bp 80 13545 aix en provence cedex 4, france 3 merck santé sas, 37 rue st romain 69379 lyon cedex 08, france the objective of this work was to improve the dissolution rate and aqueous solubility of oxeglitazar. solid dispersions of oxeglitazar in pvp k17 (polyvinilpyrrolidone) and poloxamer 407 (polyoxyethylene-polyoxypropylene block copolymer) were prepared by supercritical antisolvent (sas) and coevaporation (coe) methods. drug-carrier formulations were characterized by powder x-ray diffraction, fourier transform infrared spectroscopy, scanning electron microscopy, gas chromatography, uv/vis spectroscopy and in vitro dissolution tests. the highest dissolution rate (nearly 3-fold higher than raw drug) was achieved by preparation of drug/pvp k17 coevaporate. oxeglitazar/pvp k17 solid dispersions were stabilized by hydrogen bonding but contained higher amount of residual dcm than poloxamer 407 formulations regardless of the method of preparation. sas prepared oxeglitazar/poloxamer 407 dissolved more than two times faster than raw drug. however, unlike pvp k17, poloxamer 407 did not form a single phase amorphous solid solution with oxeglitazar which has been manifested in higher degrees of crystallinity, too. among the two techniques, evaluated in this work, conventional coevaporation resulted in higher amorphous content but sas reduced residual solvent content more efficiently. keywords: solid dispersion, poorly water soluble drug, oxeglitazar, supercritical antisolvent, coevaporation, introduction oxeglitazar belongs to a new class of diabetes drugs, the dual peroxisome proliferative activator receptor (ppar) agonists, collectively known as the glitazars (fig. 1) [1]. as an orally administered active pharmaceutical ingredient (api) the bioavailability of oxeglitazar depends on its solubility and permeability in the gastrointestinal (gi) tract [2]. initial studies found that the absorption of oxeglitazar is limited by its poor solubility and dissolution rate. the api has to dissolve in the gi fluid prior to absorption but such drugs remain in suspension and cannot cross the membranes of the epithelial cells in the gi tract. solubility enhancement of hydrophobic active substances is an important area of drug delivery science because one out of four orally administered apis is concerned [3]. to overcome these difficulties, new formulation techniques were developed comprising micronization, surface modification, formation of complexes, solvates, solid solutions and solid dispersions. micronization is an attractive method because no additional excipient is needed but it improves only the dissolution rate by increasing the specific surface area and has no effect on the solubility. in contrast, excipients were shown to increase both dissolution rate and solubility of poorly water-soluble apis. cyclodextrines were successfully used to form inclusion complexes with drug molecules of appropriate size [4-6]. beside cyclodextrins non-ionic surfactants are also widely used foremost in the precipitation of surface-modified drug-carrier systems [7,8], solid solutions and solid dispersions[9]. in solid solutions and solid dispersions drug molecules or very fine drug crystals are dispersed in a biologically inert and biocompatible matrix. the therapeutic use of solid dispersions has been the focus of many recent studies [9-12]. although, the medical benefits associated with solid dispersions are known for long time, they are not widely used because of the manufacturing difficulties encountered with conventional techniques. spray-drying was proved to be efficient in the preparation of micrometer sized solid solution powders but particle collection is still a challenging task [13]. formulations prepared by solvent evaporation and hot melt method may contain impurities coming from solvent residues or thermal decomposition of the api. additionally, if the active substance exists in several polymorphic forms it is recommended that formulation contains the thermodynamically most stable form [14]. metastable forms may convert to a more stable one which in turn may have different bioavailability or, in extreme cases, catastrophic health effects [15]. however, most of these drug-carrier systems contain the active substance in amorphous form which is known to be thermodynamically 42 unstable with respect to its crystalline counterpart above the glass transition temperature. although, pharmaceutical products are supposed to contain only the most stable polymorph, the use of stabilized amorphous form can be justified by medical benefits if there is no provable risk to the patient [14]. several medical benefits have been reported in the literature including better wettability, enhanced dissolution rate and solubility [10,11,16]. however, conventional methods i.e. spray-drying, solvent evaporation and hot melt method are known to have inherent limitations, like poor particle recovery yield, high residual solvent content or thermal degradation of the api. residual solvent traces and degradation products might be highly toxic to the patient and should comply with very low recommended levels. in spite of the tendency to replace toxic solvents or limit their application in the pharmaceutical industry these solvents are not always avoidable. fig. 1. the chemical structure of oxeglitazar. in the late 80’s, supercritical fluid (scf) processes appeared in drug formulation as an alternative to conventional processes [17-21]. the most common scf is carbon dioxide (scco2) which is non toxic, non flammable, cost efficient and available in large quantities. owing to its mild critical temperature (31.06 °c) and critical pressure (73.8 bar), co2 is suitable to precipitate heat-sensitive apis. additionally, these techniques were proved to reduce particle size and residual solvent content in one step and, in some cases, crystal habit, morphology and polymorphic form of the processed drug could be controlled as well [21-26]. unlike liquid solvents, scco2 is easy to separate from solid products and it causes no adverse health effect. furthermore, if the scf plays the role of antisolvent, residual solvent traces can be efficiently removed with scf extraction [22,27]. more than ten different techniques were published and/or patented in the field of particle formation using scfs. the most important are: rapid expansion from supercritical solution (ress) [11,28]; gas antisolvent (gas) [11,29-31], supercritical antisolvent (sas) [28,32-36], aerosol solvent extraction sysytem (ases) [13,22], solution enhanced dispersion by supercritical fluids (seds) [16,37,38] and particles from gassaturated solution (pgss) [39]. in this study, supercritical antisolvent and conventional coevaporation was compared using pvp k17 and poloxamer 407 as excipient and oxeglitazar as model drug. oxeglitazar is one of the newly developed dual ppar alpha/gamma agonists, of which the oral bioavailability is limited by its low aqueous solubility. in addition to potentially low absorption in patients, conventionally crystallized oxeglitazar is difficult to handle because of its needle-like habit. thus, we aimed to improve both bioavailability and manufacturability of the model drug. solid dispersions were characterized by powder x-ray diffraction (xrd), fourier transform infrared spectroscopy (ftir), scanning electron microscopy (sem), gas chromatography (gc), uv/vis spectroscopy and in vitro dissolution tests. experimental oxeglitazar was obtained from merck santé, france; carbon dioxide (99.7 %) was supplied by air liquide, france; ethanol (99.8 %) was purchased from carlo erba, italy; dichloromethane (99.95 %) was purchased from sds, france; dimethylsulfoxide (99.8 %) was supplied by 3d-spektrum, hungary; potassium phosphate monobasic, sodium phosphate dibasic dodecahydrate and sodium chloride were obtained from reanal, hungary. supercritical antisolvent process the schematic diagram of the sas apparatus is shown in fig. 2. feed solutions containing 2 wt. % api and 2 wt. % excipient were prepared by dissolving the calculated amount of pharmaceutical ingredients in 50 ml dcm. feed solution (6) was dispersed through a capillary nozzle (125 μm id) (8) in a cocurrent scco2 stream. feed solution was delivered by a reciprocating hplc pump (gilson 307, france) (7) at a flow rate of 3 ml/min, co2 was compressed to 80 bar in a watercooled membrane pump (dosapro milton roy, france) (3) at a flow rate of 10 g/min. compressed co2 and solution were both heated (5) to 35 ± 0.5 °c before entering the precipitation vessel (top industrie s.a., france) (9). fig. 2. schematic diagram of sas apparatus. 1. co2 source, 2. cooler, 3. co2 metering pump, 4. bursting disc, 5. heat exchanger, 6. solution source, 7. solution metering pump, 8. capillary nozzle, 9. precipitation vessel, 10. frit filter, 11. expansion valve, 12. cold trap, 13. gas flow meter. particles formed by the antisolvent effect were collected on 0.1 μm metal frit filter (10) and washed with pure scco2 for 30 min to remove residual solvents. a cold trap (12) was installed between the heated expansion 43 valve (11) and the flow meter (13) to condense the organic solvents. pressure and co2 flow rate were manually controlled. solid dispersions were dried in a vacuum oven at 40 °c for 24 h so that residual solvent contents are comparable to those of coevaporates. coevaporation process coevaporates were prepared by dissolving oxeglitazar and pvp k17 or poloxamer 407 in a minimum amount (~20 ml) of dcm. the solvent was rapidly removed under reduced pressure in a rotary evaporator at 40 °c. solid dispersions were ground and dried in a vacuum oven at 40 °c for 24 h. physical mixture physical mixtures of oxeglitazar and pvp k17 or poloxamer 407 used in the dissolution studies and ftir analysis were prepared by mixing the appropriate amounts of pharmaceutical ingredients in a mortal until a homogenous mixture was obtained. incorporated oxeglitazar (raw drug) contained exclusively the higher melting polymorph (form a). scanning electron microscopy (sem) sem micrographs were taken using philips xl30 esem environmental scanning electron microscope (philips analytical inc., the netherlands). samples were coated with gold before examination (cathode dispersion). powder x-ray diffraction (xrd) xrd patterns of sas powders were obtained using a philips analytical x-ray diffractometer mpd3710 (philips analytical inc., the netherlands). ground powders were placed in the cavity of an aluminum sample holder and flattened with a glass slide. samples were scanned over the range of 4.0-47.0° 2θ with a step size of 0.020° 2 θ and a count time of 2 s per step using co kα source with a wavelength of 1.78896 å. coevaporates were analyzed on philips analytical x-ray diffractometer b.v. pw3710 (philips analytical inc., the netherlands) over the range of 4.0-40.0° 2 θ with a step size of 0.020° 2 θ and a count time of 1 s per step using cu source (λ = 1. 54056 å). fourier transform infrared spectroscopy (ftir) ftir analysis was carried out on a shimadzu ftir8300 spectrometer (shimadzu corp., japan) equipped with a dlatgs detector. kbr pellets were prepared (2 mg sample in 200 mg kbr) and scanned over a range of 400–3200 cm–1 with a resolution of 2 cm-1. spectra were obtained by coadding 100 scans in transmission mode. the software used for the data analysis was hyper-ir (shimadzu corp., japan). gas chromatography (gc) residual dcm in solid dispersions was assessed using hp 8590 gas chromatograph (hewlet packard, germany) with flame ionization (fid) detector. powders were dissolved in dmso and directly injected in triplicate (2.0 μl) on a chrompack fused silica column (25 m x 0.53 mm) with poraplot q coating (chrompack international, the netherlands). samples were analyzed using ar carrier gas at a constant oven temperature of 210 °c while the injector and detector temperatures were maintained at 260 °c. the method of external standardization was used to calculate the residual solvent content. uv/vis spectroscopy the drug content of formulations was determined using metertech uv/vis sp8001 spectrophotometer (metertech inc., taiwan). formulations were dissolved in ethanol and analyzed at 292.0 nm in duplicate after appropriate dilution. solubility measurement an excess amount (50 mg) of oxeglitazar was added to 20 ml of ph 7.4 phosphate buffer medium (6.4 g na2hpo4·12 h2o; 0.6 g kh2po4 and 5.85 g nacl dissolved in 1000 ml distilled water) having different concentrations of pvp k17 or poloxamer 407. solutions were rotated in water-jacketed flasks at constant temperature (37 ± 0.5 °c). after 24 h, suspensions were filtered through a disposable syringe filter (0.22 μm) and diluted with the dissolution media. the amount of dissolved oxeglitazar was quantified using metertech uv/vis sp8001 spectrophotometer (metertech inc., taiwan). solubility measurements were carried out in triplicate. dissolution studies dissolution tests were performed in triplicate in ph 7.4 phosphate buffer medium. about 100 mg of powder equivalent to ~ 50 mg oxeglitazar were added to 1000 ml dissolution medium. bath temperature and paddle speed were set at 37 ± 0.5 °c and 75 rpm. aliquots of 10 ml were withdrawn through a filtering rod (2 μm) at 5, 10, 15, 30, 45, 60 and 120 min. properly diluted solutions were analyzed on metertech uv/vis sp8001 spectrophotometer (metertech inc., taiwan) at λ = 292.0 nm. error bars represent the standard error of the mean. 44 results particle morphology sem micrograph of the raw drug prepared by cooling crystallization showed thin needle-like crystals (fig. 3a). computer simulation (genmol software) revealed a potential hydrogen bonding between carboxylic oh and the methoxy oxygen (internal rapport). owing to this hydrogen bonding effect, the crystal growth of oxeglitazar is preferred in one crystallographic direction resulting in acicular crystals. this habit was found undesirable because of its poor flow properties. sas prepared coprecipitates formed a thick cottony layer on vessel wall. oxeglitazar/poloxamer 407 powder consisted of aggregated acicular particles ranging from 0.5 to 1.5 mm in length (fig. 3b). in contrast, coprecipitation of drug and pvp k17 resulted in aggregated tabular particles with a mean diameter of less than 200 μm and a thickness of a few micrometers (fig. 3c). aggregates of rod-like crystals and irregular particles were observed for oxeglitazar/poloxamer 407 coevaporate (fig. 3d). unlike the above mentioned formulations, pvp has precipitated as a film rather than particulate powder (fig. 3e). fig. 3. scanning electron micrographs of raw oxeglitazar (a), sas oxeglitazar/poloxamer 407 (b), sas oxeglitazar/pvp k17 (c), coe oxeglitazar/ poloxamer 407 (d), coe oxeglitazar/pvp k17 (e). 45 crystallinity and polymorphic purity xrd patterns of raw drug, excipients, coprecipitates and coevaporates are shown in fig. 4 and fig. 5. oxeglitazar and poloxamer 407 are crystalline compounds with well-defined peaks while pvp k17 is amorphous and shows no diffraction peak. although crystalline drug was detectable in all formulations, considerably lower peak intensities were observed suggesting that semi-crystalline solid dispersions were obtained in both techniques. the highest amorphous content was measured in coe oxeglitazar/pvp k17 followed by sas oxeglitazar/pvp k17, coe oxeglitazar/poloxamer 407 and sas oxeglitazar/poloxamer 407. preliminary xrd and differential scanning calorimetric studies (data not shown) revealed that oxeglitazar has two polymorphic forms of which the higher melting form (a) is the thermodynamically stable one at all temperatures (monotropic system). however, the metastable form was not detectable in any formulation. fig. 4. xrd patterns of raw drug (a), sas oxeglitazar/poloxamer 407 (b), poloxamer 407 (c), sas oxeglitazar/pvp k17 (d), pvp k17 (e). fig. 5. xrd patterns of raw drug (a), coe oxeglitazar/poloxamer 407 (b), poloxamer 407 (c), coe oxeglitazar/pvp k17 (d), pvp k17 (e). hydrogen bonding interactions ftir is probably the most widely used analytical method to detect hydrogen bonding in drug-carrier solid dispersions. it is known, that absorption bands of the groups, involved in hydrogen bonding, shift to lower wave numbers [11]. however, the new band appears only when the ratio of bonded to non-bonded group is high enough. when non-bonded groups dominate over hydrogen-bonded ones, only a slight broadening is observed due to the superposition of the two bands. oxeglitazar contains one hydrogen donor (-oh) and three hydrogen acceptor groups (-c=o, aryl-o-ch3 and aryl-o-r). the characteristic absorption bands of these groups are νc=o at 1681 cm-1, νo-h in the range of 2500-3700 cm-1 (carboxylic group), νasc-o at 12711212 cm-1 and νsc-o at 1047-1029 cm-1 of methoxy and cyclic ether group (fig. 6a). although the stretching vibration of oh gives a broad and intense band it was not considered because of the water residues [40]. the position of νc=o band was below 1700 cm-1 due to the conjugation with double bounds and aromatic ring [41]. likewise, a broad well defined band was observed in the spectrum of pvp k17 at 1672 cm-1 assigned to the carbonyl stretching vibration (fig. 6b). each pyrrole ring of the pvp polymer contains two hydrogen acceptor groups: a carbonyl group and a tertiary amine. however, this latter is not favored in hydrogen bonding due to a steric hindrance [11,42]. the ftir spectrum of the physical mixture revealed no considerable interaction between the pharmaceutical ingredients. the spectrum shown in fig. 6c was a simple summation of those of pure compounds. in contrast, ftir spectra of oxeglitazar/pvp k17 coprecipitate and coevaporate display different absorption bands in the carbonyl region (fig. 6d-e). a new band seems to appear at about 1650 cm-1 beneath the superposed νc=o bands which can be attributed to the carbonyl group of pvp k17 engaged in intermolecular hydrogen bonds with the carboxylic oh of oxeglitazar. ftir spectra of oxeglitazar/poloxamer 407 solid dispersions are shown in fig. 7. the position and intensity of the corresponding bands were similar in the spectra of physical mixture, coprecipitate and coevaporate, suggesting that poloxamer 407 did not form any hydrogen bonding with oxeglitazar. fig. 6. ftir spectra of solid dispersions of oxeglitazar and pvp k17: (a) raw drug, (b) pvp k17, (c) physical mixture, (d) sas oxeglitazar/pvp k17, (e) coe oxeglitazar/pvp k17. 46 fig. 7. ftir spectra of solid dispersions of oxeglitazar and poloxamer 407: raw drug (a), poloxamer 407 (b), physical mixture (c), sas oxeglitazar/poloxamer 407 (d), coe oxeglitazar/poloxamer 407 (e). residual solvent the residual solvent content was determined with gc analysis. dcm is a class 2 solvent with a permitted daily exposure (pde) of 6 mg [43]. two options are available when setting limits of class 2 solvents: option 1 may be applied if the daily dose is not known or fixed. this option assumes a high dose (10 g/day) that is rarely exceeded. option 2 takes into account the daily dose or the maximum daily dose if the drug is not regularly administered. assuming a maximum daily dose of 400 mg, recommended limits of dcm under option 1 and option 2 are 600 and 7500 ppm, respectively. results of gc analysis are shown in table 1. all oxeglitazar/poloxamer 407 formulations met ich requirements under option 2. residual dcm content was even lower than the stricter option 1 limit after vacuum drying (sas-vd and coe-vd). the oxeglitazar/pvp formulations have retained much more solvent. vacuum dried coprecipitate and coevaporate met option 2 limit but exceeded option 1 limit. table 1 residual dcm content (ppm). method poloxamer 407 pvp k17 sas 804 ± 189 13500 ± 248 sas-vd 87 ± 3 618 ± 23 coe 1294 ± 97 18770 ± 817 coe-vd 111 ± 4 668 ± 29 drug content drug contents are listed in table 2. both sas prepared powders contained more oxeglitazar than the nominal value (50 wt. %) suggesting that the dcm-co2 mixture dissolved and washed out more excipient than active substance. in contrast, drug contents in coevaporates were marginally below the nominal value. this deviation has to be taken into account in the preparation of solid oral dosage forms with high content uniformity. table 2 oxeglitazar content (wt. %). method poloxamer 407 pvp k17 sas 53.5 ± 0.4 57.9 ± 0.3 coe 47.0 ± 0.9 47.8 ± 0.7 solubility studies oxeglitazar solubility as a function of excipient concentration is shown in fig. 8. solubility was measured in ph 7.4 phosphate buffer medium at 37 °c. the increase in solubility was linear with respect to the weight fraction of both polymers but the curve of poloxamer 407 was much more steeper. the increase in oxeglitazar solubility was 8.7and 3.9-fold in dissolution media with 10 % w/v poloxamer 407 and pvp k17, respectively. thus, poloxamer 407 solubilized more than twice as much drug as pvp k17. fig. 8. phase solubility diagram of oxeglitazar in ph 7.4 phosphate buffer media with various poloxamer 407 and pvp k17 concentrations. dissolution studies dissolution profiles in fig. 9 and fig. 10 illustrate the dissolution kinetics of drug-carrier solid dispersions, physical mixtures and raw drug in ph 7.4 phosphate buffer medium. coprecipitates and coevaporates exhibited significantly higher dissolution rates compared to conventionally crystallized oxeglitazar and physical mixtures. at 5 min, dissolved oxeglitazar from pvp k17 coevaporate and coprecipitate attained 85.6 and 64.3 %, while only 30.5 % of the raw drug were dissolved. remarkable improvements were achieved with poloxamer 407 as well. 61.9 and 57.9 % of the incorporated oxeglitazar were dissolved from the sas prepared solid dispersion and the coevaporate, respectively. 47 fig. 9. dissolution profiles of oxeglitazar/poloxamer 407 solid dispersions, physical mixture and raw drug. fig. 10. dissolution profiles of oxeglitazar/pvp k17 solid dispersions, physical mixture and raw drug. discussion formulations were shown to have very different morphology depending on the method of preparation and the excipient involved. oxeglitazar/poloxamer 407 coprecipitate consisted of aggregated acicular particles similar to those observed for the raw drug. unusually large particle size was observed in comparison with other scf processed products [13,33,34]. one possible explanation is that poloxamer 407 could not inhibit the growth of oxeglitazar crystals which in turn have kept on growing throughout the whole precipitation process. this theory seems to be consistent with the observations of bristow et al. who found that mean particle size of seds prepared paracetamol increased linearly with the time of precipitation process [44]. large particle size implies low saturation ratio but this theory can not be verified in the lack of data on equilibrium solubility. acicular particles were seen in oxeglitazar/poloxamer 407 coevaporate as well suggesting that poloxamer 407 did not form a single phase solid solution in either process. primary particle size of sas prepared oxeglitazar/pvp k17 was still very large but needle-like shape was successfully changed into tabular one. sem micrographs showed aggregated platelets with a thickness of a few micrometers. in contrast, when solvent was removed by evaporation pvp gave a film-like precipitate wherein dispersed drug was not distinguishable from the excipient matrix in sem micrographs. the physical state of each drug-carrier formulation was investigated by xrd measurements. the highintensity diffraction peaks of oxeglitazar (form a) at d values of 15.26, 8.45, 5.39 and 4.23 å were hardly detectable in solid dispersions. consistently with previous studies pvp has successfully inhibited the crystal growth of the active substance [10,11,45,46] while, poloxamer 407 remained crystalline after the formulation process too, and hence semi-crystalline solid dispersions were obtained instead of solid solutions. a comparison was made between the drug-carrier formulations prepared by the two methods. characteristic peaks were much smaller for coevaporates than for coprecipitates using the same polymer. thus, coevaporation seems to be more efficient in the preparation of oxeglitazar/excipient solid solutions. xrd was also used to assess the polymorphic purity of formulations. only the form a (thermodynamically stable one) was present (data not shown) satisfying current requirements for stable polymorph. in fact, the amorphous form that predominantly constitutes the solid dispersions is also metastable above or near the glass transition temperature. the amorphous to crystalline phase transition is even faster if micro or nano-crystals are present in the formulation. the use of pharmaceutical excipients is often sufficient to inhibit crystallization and improve long-term stability. an amorphous polymer matrix may reduce considerably the molecular mobility of the incorporated api which is in most cases linked by weak interactions such as hydrogen bonding to the polymer [47,48]. ftir studies were performed in order to detect possible hydrogen bonding interactions. such interaction was not found in either physical mixture according to our expectations. absorption bands have simply superposed when pharmaceutical ingredients were mixed dry. in the ftir spectra of oxeglitazar/pvp k17 solid dispersions the νc=o band is split into two frequencies. a new band seems to appear at about 1650 cm-1 beneath the broad absorption band of physical mixture at 1680 cm-1. the shift of carbonyl stretching band to higher frequency implies its engagement in hydrogen bonding with the only hydrogen donor group, the carboxylic oh of oxeglitazar. such interactions between the carbonyl group of pvp and the carboxylic oh of another molecule was previously reported [11,40,46]. in the case of poloxamer 407, possible hydrogen bonding could be expected between the carboxylic oh of the drug and the ether oxygen of the polymer, or between the terminal oh of poloxamer and one hydrogen acceptor group of oxeglitazar. however, ftir studies showed no evidence of such interactions. the spectra of oxeglitazar/poloxamer 407 solid dispersions were virtually identical to that of physical mixture. gc analysis revealed that residual dcm content in oxeglitazar/poloxamer 407 formulations met recommended limits under option 2 and it can be easily reduced below option 1 limit by vacuum drying [43]. unlike the crystalline poloxamer 407, the oxeglitazar/pvp k17 coprecipitate and coevaporate exceeded the higher option 2 limit and formulations did not meet option 1 limit even after drying for 24 h. the main drawback of 48 coevaporation is that solvent traces get trapped in the amorphous solid dispersion and further drying process is needed. coevaporates were left in the rota-dest apparatus for 2 h, the time that a typical sas process has taken, even though dcm had evaporated within a few minutes. thus residual solvent contents in coprecipitate and coevaporate are comparable. residual dcm contents were consistent with published works on scf processed pharmaceutical products. bitz and doelker compared spray-drying, solvent evaporation and ases processes [13]. residual dcm concentrations in l-poly(lactic acid) (l-pla) and l-pla/tetracosactide powders after 4 hours of solvent stripping were 5283 and 758.3 ppm, respectively. powders were further dried under reduced pressure for 3 day after which residual dcm contents decreased below 6 ppm. ruchatz et al. studied the effect of spraying rate and co2 flow rate on the residual solvent content, particle size, yield and morphology of ases prepared l-pla particles [22]. the authors achieved low residual concentrations of dcm (71.5 – 449.9 ppm) after 5 hours of solvent stripping by varying the co2 flow rate in the range of 2 – 11 kg/h. experiments, carried out at constant spraying rate and drying time revealed that residual solvent level and co2 flow rate were inversely proportional. thus, residual solvent level can be reduced by increasing the co2 flow rate or extending the solvent stripping. among the two techniques, assessed in this work, sas was more favorable in terms of residual solvent content, while among the excipients, poloxamer 407 was proved to be easier to dry. owing to its amorphous state pvp has a high tendency to retain solvent residues during the drying or solvent stripping process. all drug-carrier formulations exhibited improved dissolution properties that allow more of the drug to be absorbed. dissolved oxeglitazar from poloxamer 407 coprecipitate and coevaporate at 5 min was 61.9 and 57.9 %, respectively. the increase in dissolution rate was roughly two-fold in both formulations. surprisingly, oxeglitazar/pvp k17 solid dispersions showed even higher dissolution rates: 64.3 and 85.6 % of the active substance prepared by sas and coevaporation process were dissolved within 5 min. this seems to be contradictory to the results of solubility studies. the increase in oxeglitazar solubility was more than two times higher for poloxamer 407 compared to pvp k17. poloxamers are highly water soluble amphiphilic polymers that form micelles in aqueous media and stabilize dissolved molecules or nanoparticles of hydrophobic apis. however, xrd measurements and sem micrographs confirmed that poloxamer 407 did not form a single phase solution with oxeglitazar in either process. in contrast, pvp was proved to be suitable to prepare molecularly dispersed drug-carrier systems. the dissolution of oxeglitazar/pvp solid dispersion is governed by the disintegration of the polymer matrix which was found to be very fast. although, poloxamer 407 exhibited better drug solubilizing properties, the absorption of an orally administered drug is governed by kinetic rather than thermodynamic factors. in addition to better dissolution kinetics, oxeglitazar/pvp k17 solid dispersions are expected to be more stable due to the hydrogen bonding revealed by ftir studies. on the other hand, residual solvent contents were much lower in oxeglitazar/poloxamer 407 formulations. the concentration of dcm was below the option 1 limit after 24 h drying. among the two techniques sas was found to be more efficient in residual solvent removal. dcm concentrations were 38 % lower for oxeglitazar/poloxamer 407 coprecipitate and 28 % lower for oxeglitazar/pvp k17 coprecipitate than for corresponding coevaporates. conclusions supercritical antisolvent and coevaporation techniques were evaluated for their potential use in the preparation of immediate release solid oral dosage forms. solid dispersions of oxeglitazar in poloxamer 407 and pvp k17 were prepared and characterized by powder x-ray diffraction, fourier transform infrared spectroscopy, scanning electron microscopy, gas chromatography, uv/vis spectroscopy and in vitro dissolution tests. solid dispersions obtained in both techniques were poorly crystalline and dissolved quickly in ph 7.4 phosphate buffer solution. the amorphous oxeglitazar dispersed in pvp k17 was stabilized by hydrogen bonding and dissolved faster but contained higher amount of residual dcm than poloxamer 407 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spectra, a practical approach. in: meyers r.a.: encyclopedia of analytical chemistry, john wiley & sons ltd., chichester, pp. 10815-10837, 2000 42. forster a., hempenstall j., rades t.: int. j. vib. spec., [www.ijvs.com] 2001, 5, 6 43. fda, 1997. international conference on harmonisation, ich guidance on impurities: residual solvents, federal register. 62(247), 67377-67388 44. bristow s., shekunov t., shekunov b. y., york p.: j. supercrit. fluids, 2001, 21, 257-271 45. delneuville i., dechesne j. p., delattre l.: int. j. pharm., 1998, 168, 109-118 46. van den mooter g., augustijns p., blaton n., kinget r.: int. j. pharma., 1998, 164, 67-80 47. khougaz k., clas s.-d.: j. pharm. sci., 2000, 89, 1325-1334 48. matsumoto t., zografi g.: pharm. res., 1999, 16, 1722-1728 microsoft word 1_r.doc hungarian journal of industrial chemistry veszprém vol 37(1). pp. 11-20 (2009) examination of crystallization coupled to the smb-lc process g. gál 1 , l. hanák1, t. szánya1, j. argyelán1, a. strbka1 , t. marcinkóová1 a. aranyi2, k. temesvári2 1university of pannonia, department of chemical engineering processes e-mail: gaborgal@freemail.hu 2gedeon richter ltd., 1475 budapest p.o.box. 27, hungary the simulated moving bed preparative liquid chromatography (smb-lc) technique is a highly promising method for optical isomer separation. optimal coupling of smb-lc to crystallization respectfully increases the effect of enantioseparation. extract and raffinate products enriched by smb-lc are suitable for further process by evaporation, cooling crystallization. chromatographic packing and eluent system selection being the best for the separation and determination of optimal working parameters of smb-lc coupled with crystallization can be found in our previous publications. the goal of this paper was the detailed study of crystallization process, investigation of crystallization kinetics, such as sample concentration, composition, cooling speed and end-cooling temperature, application of pure seeding crystals with particular influence on the mass and composition of crystals. keywords: enantioseparation, crystallization, smb-lc, conglomerates, racemic compounds. introduction there are several cases in pharmaceutical industry, when one of the two enantiomers has got good biological activity, while the other is inefficient or human health destroying, toxic. therefore there is high interest in the production of pure enantiomers [1]. the chemical synthesis in most cases results racemic mixture, thus efficient separation methods are required. chromatography is one of the most effective separation technique in this field. in the last years were invented the applications of simulated moving bed liquid chromatography (smblc) and high performance chiral stationary phases to increase separation productivity [2]. this type of separation has got growing importance in chemical engineering practice in the field of industrial chromatography. unfortunately the method is expensive, thus there is a growing interest in coupling the cheapest traditional separation technology with chromatography [3-7], for example coupling crystallization with smblc chromatography seems to be a cheap alternative. since pasteur’s famous separation [8] invention (sodium-ammonium-tartarate enantiomer direct crystallization) numerous researchers have dealt with crystallization process to produce pure enantiomers. selective crystallization can be realized on the bases of solid-liquid equilibrium [9]. our model racemic ethyl-ester mixture in n-hexane liquid belongs to the conglomerate type racemates, when enantiomers crystallize separately [7, 10, 11]. in this case enantioseparation with crystallization can be done directly from the liquid, if composition is significantly different from that of the racemic. this method is efficient if there are only few amounts from one of the enantiomers in the mixture. enrichment of an enantiomer can be realized by smb-lc equipment followed by enantiomer purification with evaporation, cooling crystallization. selection of the best chromatographic packing and eluent system for smb-lc separation and determination of the optimal working parameters of smb-lc coupled with crystallization can be found in our previous publications [7, 10, 11]. crystallization the goal of crystallization is the recovery from auxiliary materials, separation from other compounds, purification, formation to get new crystal morphology, etc. crystallization can be realized from gas, liquid or melting phase. further we focus on the crystallization from liquid phase. in case of crystallization from liquid the driving force is the over saturated condition of the liquid can be achieved by cooling or evaporation. fig. 1 provides equilibrium saturation curve, over saturated curve and three ranges (stable, metastable, unstable). while planning and optimizing of crystallization process the area of metastable range is important can be determined experimentally [12, 13]. 12 t stable unstable metastable saturated solubility curveoversaturated solubility curve c figure 1 on fig. 1 liquid concentration versus temperature diagram shows, that the working point of the liquid to be crystallized can be placed in three areas, namely stable, metastable, unstable areas. stable area (unsaturated liquid area) is under the equilibrium saturation curve, where no crystal forming and increase exist. in the metastable area (limited by the saturated and over saturated solubility curves) there is low crystal seed formation, but the existing crystal particle can increase. there is spontaneous crystal forming in the unstable area and the speed of crystal seed forming quickly rises. if over saturation is high enough, the crystal seed forming is extremely rapid. over-saturation curve and saturation curve seems nearly parallel bordering the metastable area. wideness of metastable area depends on different parameters (cooling speed, mixing conditions, concentration, etc.) and can definitely be determined experimentally. the kinetics of crystallization [12, 13] theoretically the kinetics of crystallization is simplified as a two-step process. in the first step crystal seeds are forming, in the second step they are growing. these two steps go on simultaneously in practice. crystal seed forming are homogenous or heterogeneous. generally crystal seed forming is started by crystal seed injection into the over saturated liquid. the injected crystal seed may be the fine grinded crystal powder product itself. crystal growth starts around the crystal seeds. the kinetics of crystallization is influenced mainly by the degree of over saturation. in case of high over saturation degree crystal products are small in size, while at low over saturation crystals are big in size. kinetic resolution is a novel chemical engineering process in the field of crystallization which is detailed in chapter kinetic resolution with crystal seed injection in case of conglomerate type racemic system. phase diagrams [14] solid-liquid equilibrium phase data are presented on the so called phase diagrams. it is important to have detailed phase diagram, if enantiomer separation or purification with crystallization is planned. biner melting point diagrams can be seen on fig. 2, showing the melting behaviour of the two enantiomers. by roozeboom [9] there are three basic types of enantiomer systems, as follows: conglomerate (a), racemic (b), pseudoracemate (c). 5–10 % of racemates belong to most easily separable conglomerates, 90–95 % belong to the true racemate. the rest is called pseudoracemate. solubility data in a solvent are figured in triangle diagram. fig. 3 shows theoretically our conglomerate type triangle diagram. [7, 10, 11]. figure 2 h s r x 1 2 tc 3 4 0.5 a c b figure 3: (s) and (r) enantiomer, h solvent ternary solubility diagram at t = const. pure components are placed at the triangle peaks: s and r enantiomers are on the lower left and right peaks, h solvent is at the top. the triangle sidelines represent binary system in mol fraction or mass fraction units as s enantiomer/solvent, r enantiomer/solvent, s/r enantiomer systems. 0.5 is the point, where both enantiomers are present in 50-50 %. each inner point of the triangle represents a ternary mixture containing all the three (s, r, h) components. a-b-c-h borders the unsaturated one-phase area, a-b-s and c-b-r are twophase areas, which contain pure enantiomer solid phase and a saturated liquid phase. pure enantiomer solubility at a given t temperature in solvent is represented by a and c points, while racemic mixture is signed by b point. the solubility curve of the terner system is represented by the a-b-c lines. unsaturated liquid area is above this line, while the multi-phase areas are under it. within the area of triangles a-b-s or c-b-r the solid phase containing one of the enantiomers is in equilibrium with the saturated liquid above. s-b-r is a three phase area, where the 13 liquid concentration is racemic in case of equilibrium while the solid phase is enriched only in one of the enantiomers. let see points 1, 2, 3 and 4 on fig. 3 in point 1 there is a solvent enriched in s enantiomer, which is evaporated (te temperature) thus getting to point 2 liquid in point 2 is cooled down to tc temperature, when saturated liquid in point 3 and pure s crystal in point 4 is received. it means that pure s enantiomer can be produced with crystallization coupled to smb-lc, when point 1 is the concentration of raffinate coming out of the smb-lc unit. point 2 is the evaporated liquid concentration inside the a-b-s triangle. point 3 is the concentration of crystallization mother liquor. point 4 is the concentration of pure crystal s. kinetic resolution with crystal seed injection in case of conglomerate type racemic system [1, 15-17] crystal seed injection method can be applied in case of conglomerate type racemic system to produce pure enantiomers. (fig. 4). h s r tc 0.5 b te d e f metastable zone figure 4: theory of kinetic resolution with crystallizaton let the enantiomer containing racemic mixture saturated at te temperature (point d) and cool it down to point e resulting over saturation in metastable area. then add small amount of pure s crystal seed and continue cooling solution to tc temperature. then concentration of liquid does not move directly to point b, but follows the e-f-b trajectory because of the homo chiral crystal surface phenomena. the consequence is, that we receive s enriched crystal fraction on e-f section and naturally the liquid gets concentrated in r component. on f-b section r concentration of crystal mother liquor decreases to the racemic concentration b. in f-b section crystal is richer in r enantiomer. looking at the full e-f-b trajectory the resulted integral crystal concentration is racemic. according to the above mentioned theory the so called “butterfly crystallization” was invented being able to be used for pure enantiomer production from conglomerate type racemic mixtures with kinetic crystal seed injection method. the method is well described in publication of h. lorenz and a. seidel-morgenstern [1]. the main point of the method is that non racemic mixture is cooled while r enantiomer crystal seed is injected. r crystals are filtered out of the liquid. racemic mixture is added to the crystallization mother liquid while heating it. later on s enantiomer crystal seed is added to the liquid while cooling it. crystal s is filtered, and liquid is heated while racemic mixture is added. then we get back to the starting point, the first cycle of the cyclic process is finished and can be repeated according to the above described method. crystallization coupled to the smb-lc process there are several cases in pharmaceutical industry, when one of the two enantiomers has got good biological activity, while the other is inefficient or human health destroying, toxic. therefore there is high interest in the production of pure enantiomers [1]. the chemical synthesis in most cases results racemic mixture, thus efficient separation methods are required. chromatography is the most effective separation technique in this field. in the last years were invented the applications of simulated moving bed liquid chromatography (smb-lc) and high performance chiral stationary phases to increase separation productivity [2]. this type of separation has got growing importance in chemical engineering practice in the field of industrial chromatography. unfortunately the method is expensive, thus there is a growing interest in coupling the cheapest traditional separation technology with chromatography [3-7], for example coupling crystallization with smblc chromatography seems to be a cheap alternative. iv. fresh solvent iii. ii. i. evaporator evaporator crystallizer crystallizer solvent so lv e n t feed extr. raff. fresh feed s crystals r crystals lr out mother liquor mother liquor figure 5: smb with crystallizaton 14 system examined by gál et al. [7] can be seen on fig. 5, which is evaporation, cooling crystallization with crystallization mother liquor and solvent recirculation coupled to smb-lc equipment. the laboratory scale smb-lc equipment can be seen on fig. 6. the end product, the s enantiomer enriched in raffinate is planned to be produced in 99% w/w purity in crystal form in at least 99% yield while minimizing solvent consumption. raffinate from smb-lc is evaporated, then we crystallized with cooling it, crystal s is filtered and dried. crystallization mother liquor is recirculated to the smb-lc feed. extract from smb-lc after full evaporation results >99% w/w crystal. solvents after evaporation are recirculated to the smb-lc when ipa concentration is adjusted in n-hexane. the productivity of smb-lc with coupled crystallization can significantly be increased. details can be found in 7, 10, 11 publications. figure 6: the laboratory scale smb-lc experiments determination of solubility data during the measurement pure s enantiomer or sr racemic mixture (produced by richter gedeon ltd.) was solved in n-hexane (merck extra pure) at 20 °c till solid phase appeared in the solvent. the saturated liquid was kept during 8 hours at given temperature. after that liquid sample was filtered by millex gn type 0.2 μm filter and analyzed by merck-hitachi la chrom type hplc equipment using chiralcel od-h packing and n-hexane:ipa = 95:5% v/v eluent. solubility-temperature function is given by profir et al. [15] equation. t bax +=ln where: x is the mol fraction t is the absolute temperature [k] a, b constants measurements and calculated data can be seen in table 1, 2 and figs 5 and 7. table 1: solubility of s enantiomer in n-hexane t 1000/t c x lnx [°c] [1/k] [g/dm³] [mol/σmol] 20 3.413 28.5 1.538·10⎯² -4.175 -17.5 3.914 1.7515 9.589·10⎯4 -6.95 -19 3.937 1.4948 8.185·10⎯4 -7.108 -20 3.953 1.20 9.417·10⎯4 -6.968 -27 4.065 0.920 5.039·10⎯4 -7.593 table 2: solubility of sr racemic mixture in n-hexane t 1000/t c x lnx [°c] [1/k] [g/dm³] [mol/σmol] 20 3.413 50.9 2.714·10⎯² -3.607 -20 3.953 2.71 1.483·10⎯3 -6.514 -27 4.065 1.47 8.049·10⎯4 -7.125 15 solubility -9.0 -8.0 -7.0 -6.0 -5.0 -4.0 -3.0 3.4 3.5 3.6 3.7 3.8 3.9 4.0 4.1 103/t [k-1] ln x "s" isomer "sr" racemic 806.141000395.5ln +−= t x 957.13100032.5ln +−= t x figure 7: solubility of s and sr, ln mol fraction versus 1000/t solubility -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 3.4 3.5 3.6 3.7 3.8 3.9 4.0 4.1 103/t [k-1] ln c [g /d m 3 ] "s" isomer "sr" racemic 482.2210004359.5ln +−= t c 567.2110003453.5ln +−= t c figure 8: solubility of s and sr, ln concentration versus 1000/t solubility data presentation in a triangle diagram solubility measurements were also carried out, where different s:r mixtures (77.4:22.6, 80:20, 85:15, 87.2:12.8, 90:10, 92.8:7.2, 95:5, 96.7:3.3, 98:2) were prepared from pure s enantiomer and pure r enantiomer (s+r about 5 g/dm³) at 20 °c in n-hexane similarly to the previous chapter. these mixtures were cooled down and kept through 8 hours at -10 °c, -15 °c, -20 °c and -27 °c temperatures. liquid and crystal phase was analyzed. results of solubility measurements in mass fraction measure unit are described in fig. 10 assuming 660 mg/cm³ n-hexane density at 20 °c. the photos of crystals can be seen on fig. 9. by fig. 10 the s-r-h system is a conglomerate type one. s:r=80:20 s:r=85:15 s:r=90:10 s:r=95:5 s:r=98:2 figure 9: the crystals h s r 1 .10 -3 2 .10 -3 3 .10 -3 4 .10 -3 5 .10 -3 6 .10 -3 7 .10 -3 8 .10 -3 9 .10 -3 10 -2 0.999 0.998 0.997 0.995 0.996 0.994 0.993 0.992 0.991 0.99 0.00 1.00 0. 00 1. 1 03 2. 1 03 3. 1 03 4. 1 03 5. 10 -3 6. 1 03 7. 10 -3 8. 1 03 9. 10 -3 10 -2 s : r 98 : 2 96.7 : 3.3 95 : 5 92.8 : 7.2 90 :10 87.2 : 12.8 85 : 15 80 : 20 77.4 : 22.6 x x -27°c, 0.92 [g/dm3] -20°c, 1.2 [g/dm3] -15°c, 2.33 [g/dm3] -10°c, 3.46 [g/dm3] solubility of pure s and r m as s fra ct io n m ass fraction mass fraction initial concentration of mixtures at 20°c ~5g(s+r)/dm3 s[%m/m] in crystals: >99.9 99.33 >99.9 >99.9 >99.9 92.44 >99.9 >99.9 83.29 -10°c -15°c -20°c -27°c figure 10: results of solubility measurements 16 solubility model calculation results our calculation was based on calculations of profir et al. [15] being an ideal model for conglomerate systems. by this model sr solubility is twice as much as s or r solubility. for example solubility of s at -20 °c is 1.2 g/dm³, solubility of r at -20 °c is 1.2 g/dm³. thus solubility of sr is 2.4 g/dm³. be the total concentration of solution for cooling 5 g/dm³ for s+r enantiomers. cool down to -20 °c different s:r (80:20, 85:15, 90:10, 95:5, 98:2, 100:0) solutions. 1.2 g/dm³ s remains in the liquid and the originally present max. 1.2 g/dm³ r. the rest precipitates as pure s crystal from the yield (ηs) of s can be calculated. results can be seen in table 3 and fig. 11. table 3: solubility model calculation results s r s r s [g/dm³] [g/dm³] [g/dm³] [g/dm³] [g] 4 1 80:20 1.2 1 2.8 70 4.25 0.75 85:15 1.2 0.75 3.05 71.8 4.5 0.5 90:10 1.2 0.5 3.3 73.3 4.75 0.25 95:5 1.2 0.25 3.55 74.7 4.9 0.1 98.2 1.2 0.1 3.7 75.5 5 0 100 1.2 0 3.8 76 crystal ηs s :r [%] solute +20 °c, 5 g/dm³ concentration solute -20 °c h s r 1 .10 -3 2 .10 -3 3 .10 -3 4 .10 -3 5 .10 -3 6 .10 -3 7 .10 -3 8 .10 -3 9 .10 -3 10 -2 0.999 0.998 0.997 0.995 0.996 0.994 0.993 0.992 0.991 0.99 0.00 1.00 0. 00 1. 1 03 2. 10 -3 3. 1 03 4. 1 03 5. 10 -3 6. 1 03 7. 1 03 8. 1 03 9. 10 -3 10 -2 s:r 80:20 85:15 90:10 95: 5 98: 2 100:0 x x x x solubility at -20°c 1.2-1.2 g/dm3 s and r at -27°c 0.92-0.92 g/dm3 s and r borderline of pure s according to fig. 3. bs line b s figure 11: solubility model calculation results results of calculations after the profir et al. [15] model can be seen on the previous fig. 10 using different signs as differently coloured continuous and dotted lines. determination of metastable areas in n-hexane with cooling crystallization in case of sr racemic mixture solution concentrated in s enantiomer experimental equipment the cooling system was mlw mk70 type cryostate containing 16 dm³ antifreeze ethylene-glycol, diethyleneglycol solution circulated. 100 cm³ volume jacketed glassware was used for the four experiments and antifreeze solution was circulated in the jacket. the sample to be cooled and the mixture of crystal mother liquor were mixed by metrohm-e 349 type magnetic mixer. the system was thermo-isolated. starting the experiment 50 cm³ solution was prepared with 5 g(s+r)/dm³ n-hexane concentration. after starting the cooling and mixing the experiment lasted for 150–180 minutes while solution temperature was changed from +20 °c to -28 °c. temperature was measured by mercury-in-glass thermometer fixed in crystallization glassware. during the experiment 1 cm³ liquid sample taken out of the crystallization glassware at given times was filtered by millex gn type 0.2 μm nylon filter (id = 13 mm). the filtered liquid was collected separately while the crystals remained on the filter was washed off with 1 cm³ 20 °c n-hexane into separate sample holders. both the filtered liquid and crystal containing liquid were analyzed by merckhitachi la chrom type hplc equipment using chiralcel od-h packing and n-hexane:ipa = 95:5% v/v eluent. according to fig. 3 the kr4 measurement was done with initial concentration 85.84% w/w s and 14.16% w/w r to carry out crystallization in a-b-s area. during kr1, kr2 and kr3 measurements crystallization happened in s-b-r area. in case of kr1 the measurement started with racemic mixture, of kr2 s crystal seeds were additionally used, of kr3 solution slightly differing from racemic mixture was cooled (52.7% w/w s and 47.3%w/w r). the cooling speed initially was 50 °c/h decreasing to 10 °c/h after 60 minutes. after 2 hours it was 5 °c/h. measuring results are summarized in table 4. 17 table 4: measuring results time t s r s r s r s r s r s r s r s r [min] [°c] c [g/dm3] c [g/dm3] [%w/w] [%w/w] c [g/dm3] c [g/dm3] [%w/w] [%w/w] c [g/dm3] c [g/dm3] [%w/w] [%w/w] c [g/dm3] c [g/dm3] [%w/w] [%w/w] 0 22 10 12 15 8.7 2.85 2.86 49.89 50.11 3.25 0.18 94.84 5.16 30 0 2.77 2.76 50.12 49.88 0.13 0.28 32.55 67.45 45 -7.85 2.72 2.72 50.00 50.00 0.17 0.29 36.58 63.42 55 -11.5 2.67 2.68 49.94 50.06 0.17 0.28 38.43 61.57 65 -13.75 2.54 2.54 49.99 50.01 0.05 0.14 26.17 73.83 75 -16.25 1.92 1.73 52.67 47.33 0.22 0.28 44.54 55.46 80 -17.5 1.75 0.00 100.00 0.00 0.59 0.00 100.00 0.00 85 -18.25 1.29 1.13 53.25 46.75 0.13 0.19 40.22 59.78 90 -19 1.49 0.00 99.80 0.20 0.77 0.00 100.00 0.00 95 -20 1.10 0.94 53.74 46.26 0.25 0.30 45.65 54.35 105 -21.4 0.98 0.83 54.19 45.81 0.21 0.25 45.54 54.46 115 -22.5 0.94 0.78 54.59 45.41 0.10 0.09 52.93 47.07 125 -23.5 0.79 0.69 53.36 46.64 0.11 0.15 42.21 57.79 135 -24.2 0.22 0.18 55.47 44.53 0.03 0.04 41.90 58.10 145 -25 0.26 0.21 55.84 44.16 0.05 0.05 48.62 51.38 155 -25.5 0.61 0.47 56.54 43.46 0.04 0.08 31.34 68.66 165 -26 0.58 0.44 56.88 43.12 0.03 0.08 31.02 68.98 kr2 sr racemic s isomer mother liquor crystals mother liquor crystals time t s r s r s r s r [min] [°c] c [g/dm3] c [g/dm3] [%w/w] [%w/w] c [g/dm3] c [g/dm3] [%w/w] [%w/w] 0 20 4.43 0.73 85.84 14.16 30 0 4.40 0.70 86.23 13.77 0.38 0.06 87.09 12.91 45 -6 4.44 0.73 85.90 14.10 0.37 0.06 86.23 13.77 60 -10.5 4.37 0.71 86.10 13.90 0.39 0.06 87.30 12.70 85 -15.5 2.58 0.68 79.08 20.92 3.08 0.12 96.28 3.72 100 -17.5 2.64 0.99 72.69 27.31 2.36 0.10 96.05 3.95 115 -19 2.15 0.83 72.08 27.92 2.73 0.09 96.80 3.20 130 -20 1.87 0.74 71.59 28.41 2.77 0.10 96.49 3.51 145 -21 1.68 0.64 72.36 27.64 2.98 0.12 96.11 3.89 170 -22 1.35 0.47 74.18 25.82 2.59 0.12 95.55 4.45 200 -23 1.22 0.34 78.38 21.62 3.61 0.14 96.31 3.69 time t s r s r s r s r [min] [°c] c [g/dm3] c [g/dm3] [%w/w] [%w/w] c [g/dm3] c [g/dm3] [%w/w] [%w/w] 0 19.5 2.67 2.40 52.70 47.30 30 -1.6 2.65 2.37 52.78 47.22 0.19 0.17 52.97 47.03 45 -8.2 2.65 2.37 52.79 47.21 0.27 0.28 49.23 50.77 60 -13.6 2.58 2.31 52.80 47.20 0.27 0.20 57.30 42.70 75 -17.2 2.53 2.26 52.77 47.23 0.27 0.15 64.22 35.78 90 -20 1.39 1.19 53.86 46.14 0.93 0.78 54.35 45.65 105 -22 1.10 0.90 55.00 45.00 1.28 1.12 53.37 46.63 120 -23.5 1.00 0.80 55.56 45.89 1.50 1.33 53.00 47.00 kr4 sr racemic mother liquor crystals kr3 sr racemic mother liquor crystals time t s r s r s r s r [min] [°c] c [g/dm3] c [g/dm3] [%w/w] [%w/w] c [g/dm3] c [g/dm3] [%w/w] [%w/w] 0 17 2.83 2.82 50.10 49.90 0.00 0.00 0.00 0.00 30 -3 2.87 2.72 51.35 48.65 0.27 0.26 50.93 49.07 45 -10 2.64 2.63 50.09 49.91 0.29 0.28 50.10 49.90 60 -15 2.47 2.46 50.06 49.94 0.21 0.22 48.88 51.12 75 -17 0.15 0.15 50.05 49.95 90 -19.3 2.39 2.38 50.10 49.90 0.18 0.16 53.81 46.19 105 -22.2 0.99 0.97 50.52 49.48 0.58 0.53 51.89 48.11 120 -24.6 0.79 0.75 51.03 48.97 0.42 0.39 51.99 48.01 135 -26 0.66 0.64 50.91 49.09 0.36 0.34 51.25 48.75 150 -27.4 0.58 0.56 50.83 49.17 0.23 0.26 47.28 52.72 155 -28 0.48 0.17 74.39 25.61 0.94 0.97 49.36 50.64 0.62 0.64 49.15 50.85 kr1 sr racemic mother liquor crystals results of kr4 measurements starting the experiment 50 cm³ solution was prepared with 4.4263 g s/dm³ n-hexane and 0.7301 g r/ dm³ nhexane concentration (s 85.84% w/w and r 14.16% w/w). the solution was cooled down during 170 minutes from 20 °c to -23 °c beside 300 1/min mixing speed. the metastable area is expanding from -7 °c to -23 °c or from 30 min to 160 min. examining the concentration data slight concentration wave was found indicating kinetic resolution in function of temperature and cooling time (fig. 12 and fig. 13). about 97% w/w s concentration crystal precipitates from the initially 86% w/w s concentration liquid (s yield 70.65%). it should be noted, that on the basis of the previously described experimental data (see chapter solubility data presentation in a triangle diagram) with slow cooling without mixing >99% w/w s pure crystal could be prepared with better than 70% s yield. results of kr3 measurements 50 cm³ n-hexane solution was cooled. its initial concentrations were as follows: 2.6419 g s/dm³, 52.7% w/w s and 2.3986 g r/ dm³, 47.3% w/w r. solution was cooled down within 165 minutes from 19.6 °c to -26.4 °c with 300 1/min mixing speed. on fig. 14 can be seen s+r concentration of liquid phase in function of temperature and time. sr solubility curve was reached at about -17 °c temperature and at 55 min cooling time. metastable area ranges to -20 °c, and 90 minutes. s concentrations in liquid phase varied between 52.7 and 54.23% w/w s values. concentration of s crystal was between 49.23 and 64.22% w/w s. considering the concentration data slight concentration wave was found indicating kinetic resolution in function of temperature and cooling time (table 4). results of kr1 measurements sr racemic mixture was solved in 50 cm³ n-hexane (2.8311 g s/dm³ and 2.8199 g r/dm³, then the liquid was cooled from 17 °c to -28 °c temperature during 160 min with slow mixing (60 1/min). results of measurement can be seen on fig. 15 and table 4) metastable area ranges from -10 °c to -22 °c temperature or from 45 to 105 min. observation of kinetic resolution phenomena is expected within this area. s concentration of liquid changes by data in table 4 between 50.06–51.35% w/w s values, while s concentration of crystal changes between 50.1–53.81% w/w s. concentration data show slight kinetic resolution effect (table 4). 18 kr 4. 0 1 2 3 4 5 6 -30 -20 -10 0 10 20 t [°c] 0 25 50 75 100 125 150 175 200 solubility of s isomer solubility of sr racemic concentration of sr racemic cooling curve t[°c] c [g(s+r)/dm3] time [min] figure 12: kr4 measurement liquid (s+r) concentration, temperature, time diagram with s and sr solubility curves kr 4. 0 10 20 30 40 50 60 70 80 90 100 -30 -20 -10 0 10 20 t [°c] time [min] 0 20 40 60 80 100 120 140 160 180 200 s% in mother liquid r% in mother liquid s% in crystals r% in crystals t [°c] [%] figure 13: kr4 measurement: crystallization, mother liquid and crystal concentration (s and r % w/w) temperature-time diagram results of kr2 measurements kr1 measurement was repeated using crystal seed injection. sr racemic mixture was solved in one of crystallization glassware in 50 cm³ n-hexane (2.8467 g s/dm³ and 2.8594 g r/dm³), in the other s enantiomer was solved in 12.5 cm³ n-hexane (3.2539 g s/dm³, 40.67 mg s and 0.1771 g r/dm³, 2.21 mg r). then both crystallization glasswares were cooled down to -26 °c during 150 min beside slow mixing speeds (60 1/min). during measurement 5 cm³ liquid (2.1 mg s/cm³, 10.5 mg s and 0.1771 mg r/cm³, 0.8855 mg r) and crystal (5.76 mg s) was taken out at -15 °c from the s enantiomer containing glassware and was injected as crystal seed to the sr racemic mixture containing crystallization glassware. measurement data can be found in fig. 16 and table 4). metastable area ranges from -10 °c to -16 °c and 50–75 min. s concentration of liquid changes initially between 49.89-50.00 % w/w s, then after crystal seed injection 52.67-56.88 % w/w s. kr 3. 0 1 2 3 4 5 6 -30 -20 -10 0 10 20 t [°c] 0 25 50 75 100 125 150 solubility of s isomer solubility of sr racemic concentration of sr racemic cooling curve t[°c] c [g(s+r)/dm3] time [min] figure 14: kr3 measurement liquid (s+r) concentration, temperature, time diagram with s and sr solubility curves kr 1. 0 1 2 3 4 5 6 -30 -20 -10 0 10 20 t [°c] 0 25 50 75 100 125 150 solubility of s isomer solubility of sr racemic concentration of sr cooling curve t[°c] time [min]c [g(s+r)/dm3] figure 15: kr1 measurement liquid (s+r) concentration, temperature, time diagram with s and sr solubility curves kr 2. 0 1 2 3 4 5 6 -30 -20 -10 0 10 20 t [°c] 0 25 50 75 100 125 150 s isomer tank concentration of sr solubility of sr racemic cooling curve t[°c] solubility of s isomer c [g(s+r)/dm3] time [min] seeding figure 16: kr2 measurement liquid (s+r) concentration, temperature, time diagram with s and sr solubility curves results within the frame of this work we examined the crystallization coupled to the smb-lc process. for this purpose we determined the solubility data of a chiral ethyl ester, as s and r, and sr racemic mixture in 19 n-hexane (h) at different temperatures. solubility data were represented on ternary s-r-h diagram. profir et al. [15] solubility equation for ideal crystallization mixtures was used for describing solubility data and concluded, that s-r-h system is conglomerate type from crystallization point of view. during crystallization kinetic investigation we examined cooling of mixtures enriched in s enantiomer and racemic sr mixture in n-hexane between +20 °c and -28 °c temperatures with and without s crystal seed injection. during 0–200 minutes cooling time significant metastable areas were observed (see kr1, kr2, kr3, kr4 measurements, fig. 12, fig. 14, fig. 15, fig. 16, fig. 17). the observation of kinetic resolution phenomena is expected in the above mentioned metastable areas. 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 3.70 3.75 3.80 3.85 3.90 3.95 4.00 103/t [k-1]ln cs+r [g/dm3] kr 1. s+r kr 2. s+r kr 3. s+r kr 4. s+r sol. of s isomer sol. of sr racemic s sr figure 17 cooling speed data can be seen on fig. 18. the cooling speed initially was 50 °c/h and decreased to 10 °c/h after 60 minutes. after 2 hours it was 5 °c/h. according to fig. 3 the kr4 measurement was done with initial concentration 85.84% w/w s and 14.16% w/w r to carry out crystallization in a-b-s area. during kr1, kr2 and kr3 measurements crystallization happened in s-b-r area. in case of kr1 the measurement started with racemic mixture, of kr2 s crystal seeds were additionally used, of kr3 solution slightly differing from racemic mixture was cooled (52.7 % w/w s and 47.3 w/w r). the above measurement liquid concentration data are described in fig. 19, table 4 liquid concentration and crystal concentration data show slight kinetic resolution. this liquid concentration change based on concentration data of table 4 can be seen on fig. 19 show small concentration fluctuation. looking at the composition of crystals from measurements kr1…kr4 it can be concluded, that in case of kr4 measurement 97% w/w s crystal was given in about 70.65% yield. it should be noted, that on the basis of the data written in chapter solubility data presentation in a triangle diagram, namely with slow cooling during 8 hours, from 20 °c to -20 °c without mixing >99% w/w s pure crystal could be prepared with better than 70–76% s yield. see solubility measurement data carried out with different s:r mixtures (80:20, 85:15, 90:10, 95:5, 98:2, s+r about 5 g/dm³) and cooled down the solution from 20 °c in n-hexane through 8 hours to -20 °c temperatures (table 3). -30 -20 -10 0 10 20 30 40 50 60 0 25 50 75 100 125 150 175 t [min] t [° c ], δ t/ δ t [ °c /h ] kr 1. t [°c] kr 1. t/ t [°c/h] kr 2. t [°c] kr 2. t/ t [°c/h] kr 3. t [°c] kr 3. t/ t [°c/h] kr 4. t [°c] kr 4. t/ t [°c/h] . δ δ δ δ δ δ δ δ figure 18 4 h s r 1 .10 -3 2 .10 -3 3 .10 -3 4 .10 -3 5 .10 -3 6 .10 -3 7 .10 -3 8 .10 -3 9 .10 -3 10 -2 0.999 0.998 0.997 0.995 0.996 0.994 0.993 0.992 0.991 0.99 0.00 1.00 0. 00 1. 1 03 2. 10 -3 3. 1 03 4. 1 03 5. 10 -3 6. 1 03 7. 1 03 8. 1 03 9. 10 -3 10 -2 s:r 80:20 85:15 90:10 95: 5 98: 2 100:0 kr4 kr3 kr1 kr2 x x x x b s solubility at -20°c 1.2-1.2 g/dm3 s and r at -27°c 0.92-0.92 g/dm3 s and r borderline of pure s initial concentration σ = 5 g/dm3 at 20°c 4 4 4 4 4 4 4 33 3 33 3 2 2 2 2 2 2 2 2 2 2 2 22 1 1 1 1 1 1 1 1 1 1 4 3 1 2 figure 19 acknowledgements the authors express their gratitude to chemical engineering institute cooperative research center of the university of pannonia and the gedeon richter ltd. for financial support of this research study. references 1. lorenz h. et al.: crystallization of enantiomers, chem. eng. proc., 2006, 45, 863-873 2. cox g. b.: preparative enantioselective chromatography; blackwell publishing, uk, 2005. 3. kaspereit m. et al.: shortcut method for evaluation and design of a hybrid process for enantioseparations, j. chrom. a., 2005, 1092, 43-54 4. lorenz h. et al.: coupling of simulated moving bed chromatography and fractional crystallisation for efficient enantioseparation, j. chrom. a., 2001, 908, 201-214 5. amanullah m., mazzotti m.: optimization of a hybrid chromatography-crystallization process for the separation of tröger’s base enantiomers, j. chrom. a., 2006, 1107, 36-45 6. dingenen j.: scaling-up of preparative chromatographic enantiomer separations, geoffrey b. 20 cox, preparative enantioselective chromatography; blackwell publishing, uk, 2005. 7. gál g. et al.: simulated moving bed liquid chromatography (smb-lc) separation of pharmaceutical enantiomers coupling with crystallization, prep 2006 conference, baltimore, md, usa 8. pasteur l.: recherches sur les relation qui peuvent exister entre la forme crystalline e al composition chimique, et le sens de la polarisation rotatoire, ann. chim. phys. 1848, 3, 442-459 9. roozeboom h. w. b.: löslichkeit und schmelzpunkt als kriterien für racemische verbindungen, pseudoracemische mischkristalle und inaktive konglomerate, z. phys. chem. 1899, 28, 494. 10. gál g. et al.: simulated moving bed (smb) separation of pharmaceutical enantiomers, hung. j. of ind. chem., 2005, 23, 33 11. gal g. et al.: simulated moving bed (smb) separation of pharmaceutical enantiomers and crystallization, hung. j. of ind. chem., 2006, 34, 1-14 12. mersmann a.: crystallization technology handbook; marcel dekker, new york 2001 13. mullin j. w.: crystallization; butterworthheinemann, oxford 1993 14. lorenz h., seidel-morgenstern a.: binary and ternary phase diagrams of two enantiomers in solvent systems, thermochim. acta 2002, 382, 129-142 15. profir v. m., masakuni matsuoka: coll. surf. a. phys.chem.eng.asp. 2000, 164, 315-324 16. jacques j. et al.: enantiomers, in: racemates and resolutions, krieger, malabar, 1994. 17. collet a.: separation and purification of enantiomers by crystallization methods, enantiomer, 1999, 4, 157-172 microsoft word contents.doc hungarian journal of industry and chemistry veszprém vol. 40(1) pp. 19–24 (2012) pvd coating and up-to-date wear test of hot-forming tools f. táncsics1,2 , e. halbritter1 1széchenyi istván university, department of material science and applied technology 1 egyetem square, 9026 győr, hungary 2rába axle ltd, 1 martin str., 9029 győr, hungary e-mail: ferenc.tancsics@raba.hu recently, the requirements for decreasing the tool costs have been increased in forging technologies. these costs could be decreased by increasing the lifetime of the tools. in hot-forming there is a new possibility to increase the lifetime, namely: physical vapour deposition (pvd) coating of the tools. participants in testing the effects of coating were the employees of the universtiy széchenyi istván, rába axle ltd., fraunhofer institut für schichtund oberflächentechnik braunschweig and westsächsische hochschule zwickau. lately, pre-upsetting used in production lines served by robots – as upsetting made between parallel pressure plates used frequently in die-forging – was used to make wear tests. in the wear tests, the friction work according to the energetic model was calculated by applying a kinematically admissible velocity field, which takes into account the friction coefficient and the local displacements. expectable friction coefficient – using the results of previous researches – has been determined based on geometrical data of the pre-upset work-piece. keywords: pvd coating, tool, upsetting, mathematical modeling of material flow, wear introduction the first experiments with physical vapour deposition (pvd) coated tools were made in the forging plant of rába axle ltd. when hot-extrusion tools were coated in 2008. these extrusion tools were made to produce spindle in large series (figure 1). figure 1: steps and tools in forming the spindle before the experiments, it has been determined what data and methods are required (1) to fix the starting condition of the tools and the technological parameters, (2) to provide consistency of hot-extrusion conditions, and (3) to judge that the test tools cannot be used anymore. it has been determined, furthermore, what methods, measurements, and observations are needed to detect wear-out of the tools. experimental production lasted until surface errors appeared on the tools, which inevitably required intervention. at the first intervention point, the experiment was finished. after the extrusion tools were reground, production was continued. two pre-extrusion and two extrusion tools were coated in the institute of fraunhofer institut für schichtund oberflächentechnik umformwerkzeuge in braunschweig (pvd: chrome-vanadium-nitride-layer in ~5 µm thickness) [1] (figure 2). figure 2: photo taken by electron microscope on crvn coating conditions of the extrusion tools before and after the experiments were compared in optical digitalization. in the geometrical change, some wear and some residual deformation – upsetting – could be detected (figure 3). 20 figure 3: change in geometry of the coated extrusion tool coating made regrinding of the tools unnecessary and clearly increased lifetime of the tools. increase in lifetime was nearly four times of the lifetime without coating [1]. then, a new research target was set: how the coating will change the friction conditions, the material flow, and optimal shape of the extrusion tool – where are the force or performance required to forming minimal. when friction conditions were investigated, there was no difference in composition of pvd coatings as preparation of the surface necessary for applying the coating was considered to be determinant [2, 5, 11]. comparison test of friction conditions it seemed to be simpler to inspect the change of friction conditions during pre-upsetting. according to the current technology, during pre-upsetting between parallel pressure plates the work-piece is taken and moved to the next workplace by a robot. due to the good positiontaking accuracy of the robot, the work-piece was always placed onto the same location on the pressure plates, so it was simple to inspect wear of the pressure plate. test was carried out after 26.000 pre-upsetting were made on pressure plates coated and without coating [3]. wear cavities are readily detectable on the pressure plates coated and without coating (figure 4). figure 4: wear mark of pressure plates coated and without coating after 26.000 pre-upsetting cycles were completed on each [5] the nacro® nano-composite platit pvd coating, which is alcrn coating embedded in 5–6 µm thick αsi3n4 matrix was prepared at the plant of pannon platit in hungary. boundary line of the wear cavity is located between the boundary line without friction and the starting boundary line (figure 5). figure 5: illustration of boundary line of wear cavity and of theoretical boundaries geometry of the boundary line was interpreted proportionally with area, according to this volume consistency. when the two pressure plates were compared, we could establish that on the coated plate the boundary line of the cavity covered larger area. this implies lower friction, as the lower the friction coefficient is, the less the work-piece is getting barreled during upsetting and the larger the contact surface of the work-piece to the pressure plate will become [11]. according to this logic, different projection values of the wear cavity can lead to to differences in friction conditions. if coordinates of the points in the boundary line are as closely defined as necessary, by means of cad software – with a spline curve on these points – the closed projection curve can easily be drawn and the area bounded by the curve can be measured. area of the projection, which is closed by boundary line of the wear cavity presented in the fig. 5 is 10225.8 mm2. such a measurement (estimation) can produce numeric data about different friction conditions. of course, it does not mean that the friction coefficient is known. figure 6 shows wear curves of the pressure plates shown in fig. 4, in perpendicular direction to the billet plate. figure 6: wear mark of the pressure plates coated and without coating after 26.000 pre-upsetting cycles were completed on each [5] a conclusion can be drawn on different friction conditions if there is no wear cavity occurring, as during upsetting the hot work-piece causes discoloration on the 21 newly machined surface of the pressure plate [2]. the discolored area (mark) can be determined as described above. based on the wear curves, the effect of coating can be judged to a certain extent [2, 3, 11]. in order to get more exact knowledge, an actual forming has been chosen where the starting material is a cut cylindrical rod. during upsetting the cylindrical work-piece between parallel pressure plates, deformation was mathematically modeled. on the basis of the largest diameter of the barreling work-piece, the approximating value of friction coefficient was determined and wear depth was numerically calculated. experimental determination of friction coefficient during actual forming, in rába’s forging plant, under production conditions 10 cylindrical specimens were upset between newly machined parallel pressure plates with surface roughness of ra = 0.25. experimental specimens are presented in figure 7. figure 7: forgings made in experimental upsetting typical parameters and geometrical data at room temperature: cut mass: m’ = 12.48 ± 0.2 kg, cut length: h0 = 167 mm, heating temperature: theating = 1213–1226°c t(average) = 1219°c, starting diameter: d0 = 110 ± 0.2 mm, upset height: hn(cold dim.) = 142.32–142.91 mm hn(average) = 142.6 mm, upset upper diameter: d1(upper – cold dim.) = 114.2–114.5 mm d1(average) = 114.3 mm, upset lower diameter: d2(lower – cold dim.) = 112.4–113.7 mm d2(average) = 113.0 mm, upset largest diameter: dk(cold dim.) = 121.6–122.3 mm dk(average) = 122.1 mm, lubrication: less lube, forming machine: 10 mn lasco hydraulic press, hardness of tool surfaces: 48 ± 2 hrc, measured surface temperature of tools: tlower – max = 302°c; tupper – max. = 239°c. temperature conditions during upsetting are special. at the contact area of the work-piece to the pressure plate – with some simplification – temperature of the work-piece is 1100°c. the temperature of the pressure plate is 300°c. at the same time, the measured values are mainly at room temperature. dimensions were recalculated, as necessary, according to the law of linear heat expansion. in numerical calculations, a kinematically admissible material flow model was used [7, 9]. by means of the applied material flow model, the approximate value of the kudo friction coefficient was determined at the same time [9], so when the wear depth was numerically calculated, the work-piece got barreled according to the given friction coefficient. the applied material flow velocity field for the cylindrical work-piece – with some simplification – can be specified with two components: axial velocity component: ( ) ( ) ( ) ( ) 3 2 000 0 2 0 2 z h hvm1hzv3hvm1z3 vz2vm1z2 z zw ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ −−−− ++−− = , (1) radial velocity component: ( ) ( ) ( ) ( ) 3 2 000 0 2 0 2 r h hvm1hzv6hvm1z6 vz6vm1z6 r 2 1z,rw ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ −−−− ++−− −= , (2) where: wz(z) – velocity component in height direction[ms-1], wr(r,z) – velocity component in radial direction [ms-1], m – kudo friction coefficient [-], v0 – velocity of the upper pressure plate [ms-1], h – instantaneous height of the upset work-piece [mm]. if we want to expand the relations (1, 2) to the total pre-upsetting, the forming process should be divided into superposed stages. within a stage, the upper pressure plate moves ∆h = v0∆t = 0.1 mm and in each stage the calculation should be made with a new height h. the actual height is obtained if the value δh is deducted from the previous height [3]. after upsetting is simulated in the superposed stages, upset shape and velocity field of a work-piece can be studied in the figure 8. figure 8: instantaneous geometry and velocity field of the upset work-piece (m = 0.8) 22 when simulations are made with dimensions converted to the forming temperature of nominal geometrical data of the experimental parts, changes in the largest and the smallest diameters (radii) can be detected. average of the largest upset diameters is dk(average) = 122.1 mm. taking the forming temperature into account, the largest radius is rmax(1100) = 61.86 mm. when this value is used, the approximate value of the kudo friction coefficient is m = 0.7 on the basis of figure 9. figure 9: changes in the values of rmin and rmax as a function of the kudo friction coefficient at forming temperature earlier, the expectable range of the friction coefficient was determined with the burgdorf ring upsetting. a new set of curves had to be applied to the geometry proper to hot forming [9] (figure 10). figure 10: determination of expectable friction coefficient with burgdorf ring upsetting based on the measurements, in the case of dry friction, the coulomb friction coefficient is actually µ ≈ (0.4–0.45). converted to kudo friction coefficient, it is m ≈ (0.7–0.8). it conforms to the previous value. in numerical calculation of the wear depth, the work-piece gets barreled according to the specified friction coefficient. the friction coefficient defines the field of displacement of the work-piece on the pressure plate. determination of wear depth by using an energetic wear model based on a kinematically admissible displacement field from the point of view of forging, determination of the expectable highest wear depth is important as the wear cavity has sensible effect on material flow. it is a potential hazard point to the surface folds occurring on the work-piece. in the wear test, at the contact of the pressure plate to the upset work-piece – at the location z = 0 – only the radial velocity (displacement) should be taken into account, which is as follows based on the relation (2): ( ) ( ) ( ) h hm1r 2 1t0,rw0,ru rr δδ − == . (3) the archard model, in extreme cases – when friction coefficient is zero or when the displacement is zero typically to whole sticking – has produced some results, which will have to be clarified yet. that’s why the relation between the friction coefficient and the wear depth is investigated by applying the energetic wear model. the energetic wear model assumes proportionality between the volume of the worn material and the friction work causing the wear [4]. based on the energetic wear model, wear depth can be defined as [4] t)t,r(v)t,r(cz m 1i s δτ∑ = = , (4) where: z – wear depth [mm], c – constant typical to material combination [mm3j-1], m – number of discretized time increments [-], τs – friction stress [pa], v – relative sliding speed between friction surfaces [mms-1], ∆t – time increment [s]. using the simplification frequently used in plastic forming, namely 3 k mk f fns =≅= μμστ . (5) in the kudo friction the friction stress τs can be interpreted as proportional to the direct shear yield point m. in the frictionless condition m = 0, in sticking m = 1. in hot forming, the deformation strength kf of the material can be considered constant during upsetting, so local distribution of the wear is determined by the superposed radial (3) displacements defined at the contact of the pressure plate to the upset work-piece. 23 from the point of view of wear, the displacements in each stage should be added. taking the above into account, the wear depth is as follows: ( )∑ = − = n 1i f h hm1r 2 1 3 k m cz δ , (6) where: n – number of superposed stages [piece]. using the relation (5), taking the temperature conditions and initial surface hardness of the tool into account [6, 10, 12], a mathcad program was prepared [3] to define the wear depth. using the friction coefficient m obtained from the experiment, the approximate value of the energetic wear factor c was determined on the basis of literature references [3, 8, 10]. while the wear factor was constant, the depth of wear was inspected to a single upset cycle as a function of the work-piece radius r and the friction coefficient m (figure 11). figure 11: change in depth of wear as a function of the work-piece radius and the friction coefficient fig. 11 illustrates that wear is zero at the location r = 0, it is continuously increasing within the constant contact range along the radius, and it is zero again at the largest radius of the upset work-piece. the constant contact range is up to initial radius r0 of the work-piece [3]. during upsetting the contact surface of the work-piece to the pressure plate is increasing. the radial displacement size of the new surface and, thus, the wear are influenced by the friction coefficient too. in the frictionless case (m = 0), the radial displacements are the largest, however, the tool does not wear. in total sticking (m = 1), the surface of the workpiece does not change at the tool contact. there is no displacement, that’s why the tool does not wear. as per the applied model, at the highest wear the kudo friction coefficient is 0.5. besides the expectable values of friction coefficient (m = 0.7–0.8), the wear curve was taken separately, too (figure 12). figure 12: wear curves in a single upset cycle at various friction coefficients change of wear along the radius is similar to the actual wear shown in fig. 6. we wanted to determine the energetic wear factor c with an experiment. in the experiment, the wear of the pressure plates was inspected after 10 cylindrical workpieces were pre-upset (fig. 7). due to some reasons of measuring technique, the experiment has not produced clear results yet. it can be explained by that after 10 upsetting cycles the average surface roughness of the test tools did not decrease below the value, which is critical for an occurring wear cavity. similar results are obtained on the basis of the friction work occurring on a surface within the constant contact range. during pre-upsetting, friction work occurring on the surface a is as follows: da u 3 k mw a rel f s ∫= , (7) ( ) h9 hm1 m k r 3 4 w f 3 s δπ − = . (8) the above friction work is zero if m = 0 and m = 1, so the extreme cases mentioned previously are properly described by the selected model. the highest friction work occurs if m = 0.5. in calculating both the depth of wear and the wear work, the simplified relation (5) was used. it certainly affects the results, however, in our opinion, based on the work performed it can be declared that during upsetting there is a friction coefficient at which the friction work and the maximal depth of wear are the highest. summary, conclusions based on our experiments, it has been detected that coating has decreased the friction coefficient, the depth of wear and thus the lifetime of the tool have clearly improved. reduction of friction coefficient could be measured from numerical data with projection area of the wear cavities. 24 by using the energetic wear model, we have supported our opinion that during upsetting, in the limits of kudo friction coefficient /m = 0 and m = 1/ there is a friction coefficient at which the wear is maximal. a task for the future could be more exact determination of energetic wear factor c based on a larger experimental sample. references 1. k. kardos, m. kolbe, l. solecki, f. táncsics: inspection of tool wearing at hot extrusion, fraunhofer workshop (2008) (in german) 2. w. tillmann, e. vogli, i. baumann, f. hoffmann: functional wear resistant tool surfaces for hot metal forming processes, steel grips 6 (2008), pp. 133–143 3. f. táncsics, e. halbritter: wear inspection of hot forging dies, a jövő járműve (2012) 01/02, pp. 29–35 (in hungarian) 4. a. m. zamani, f. r. biglari: finite-element investigation of wear in hot forging, tehran international congress on manufacturing engineering (ticme2005), tehran (2005) pp. 1–9 5. l. solecki, e. halbritter: macro-and microgeometrical comparison of the surfaces of forming dies, 13th international conference on tools (ict-2012), miskolc (2012) pp. 245–250 6. e. doege, b. a. behrens, f. shäfer: simulation of phase transformation in hot forging dies during a precision forging process by means of finiteelement-analysis, materials processing and design, cp712, modeling, simulation and application (2004) pp. 572–576 7. e. halbritter: modeling of material flow during upsetting between parallel pressure plates, hungarian electronic journal of sciences (1999) p. 11. 8. t. balogh: érintkező felületek száraz súrlódáskor lejátszódó folyamatok numerikus és kísérleti vizsgálata, ph.d. értekezés, bme közlekedésmérnöki kar (2007) p. 100. 9. f. táncsics, e. halbritter: an original determination and application of friction coefficient by using pro/engineer and mathcad softwares, gép lxi/7 (2010) pp. 34–42 10. s. abachi: wear analysis of hot forging dies, thesis for degree of master of science, the middle east technical university, department of mechanical engineering (2004) p. 94. 11. k. kató: wear in relation to friction – a review, wear 241 (2000) pp. 151–157 12. b. a. behrens, f. shäfer, a. hundertmark, a. bouguecha: numerical analysis of tool failure in hot forging processes, obróbka plastyczna metali t. xix nr 4 (2008) pp. 11–17 editorial hungarian journal of industry and chemistry veszprém vol. 42(1) pp. 13–18 (2014) application of online and laboratory methods for the investigation of surface waters janka bobek,1! zsófia kovács,1 and zoltán zsilák2 1 institute of environmental engineering, university of pannonia, egyetem str. 10, veszprém h-8200, hungary 2 department of general and inorganic chemistry, university of pannonia, egyetem str. 10, veszprém h-8200, hungary !e-mail: bobek.janka@gmail.com pollutions in surface waters run down quickly, so the pollution waves cannot be detected by traditional point sampling. remote controlled online monitoring methods can make the tracking of pollutants possible. these solutions ensure that we can immediately access up-to-date information. the goal of our paper was to compare online monitoring and laboratory measurement techniques. during our work, we investigated the chemical and physical properties of the séd creek in veszprém with two different online monitoring systems. furthermore, we made parallel laboratory measurements of samples taken weekly to evaluate the measurement results of online methods. we discuss the difficulties of installation and operation of online systems and problems arising during emergencies caused by weather. keywords: séd creek, on-line monitoring systems, comparing measurement techniques introduction the 2000/60/ec eu water framework directive (wfd) prescribes that by 2015 all surface water bodies have to reach a good ecological and chemical status. to ensure this, we need to have information about the status of water quality. a desirable feature would be the possibility of continuously track the status of our water bodies with a cost effective monitoring system. the goal of our work was to introduce online monitoring systems and laboratory methods used to measure the physical-chemical parameters of the séd creek in veszprém. in order to continuously monitor water quality, two online monitoring systems were installed, which operate on different principles. the majority of our work was to test the mobile monitoring station (no. 1), which was developed at the environmental engineering institute of the university of pannonia. in addition, we had the opportunity to follow up the operation of a more complex mobile monitoring station (no. 2), which was manufactured by combit it ltd. the two monitoring stations were placed strategically that the effect of the town of veszprém on the stream could be measured. with the help of measurements made online and control measurements made in the laboratory, we mapped the loads effecting the séd creek and to detect pollutant waves travelling down the stream. materials and methods the investigated water body is the middle section of séd creek. the water body belongs to the danube catchment and in it to the northern-mezőföld and eastern-bakony subunit. the séd originates in the bakony, then flows through the city of veszprém, and joins nádor canal at ősi. the total length of sédsárvíz-mill canal is 71.82 km. point pollutions are caused on the territory by communal and industrial wastewater inlets. intensive agriculture and husbandry are characteristic. because of the side-point sources, we also have to focus on the investigation of diffuse pollutions [4]. description of installed online monitoring stations two online water quality mobile monitoring stations were installed on the middle section of séd creek. the evaluated period of continuous measurement was between the august 4, 2013 and october 11, 2013. the two stations were different with respect of place of installation, power source, size, security, sampling, measured physical-chemical parameters, as summarized in table 1. mobile monitoring station 1 (fig.1) was located at the section of séd creek, where it enters veszprém, while mobile monitoring station 2 is at the exit point from the city (fig.1). 14 results and discussion online measurements during the period of august 4, 2013 and october 11, 2013, a tendency was observed for every measured parameter. in fig.3, the ph measured at the examined section of séd was between 7.3–8.0. the average value of conductivity is 720 µs cm-1, the value of turbidity is 30 ntu. differences and jumps compared to the baseline indicate pollution, heavy rain or malfunction. owing to the placing of the mobile monitoring stations changes could be detected in the ph values between the two sampling points. at mobile monitoring station 1 ph value was in average 0.4–0.5 points higher (7.85) than at mobile monitoring station 2 (7.45) (fig.4). there are numerous karst water inflows into the séd as it flows through the city, which causes the lowering of ph. possible acidic pollutants from roadways, rainwater inlets and industrial areas can also add to the mild acidification of the water body. in the case of measured ionic concentrations (fig.5) it was observed that all components have a background baseline with a well-defined average concentration. the differences from the baseline appear as peaks that can indicate pollutants or rainy weather. the baseline concentrations are 0.09, 0.03, 0.02, and 4.5 mg dm-3 for po4 3--p, nh4 +-n, no2 --n, and no3 --n, respectively from their average values. when evaluating the timecourse of all chemical parameters, salient values can be identified and associated with some kind of an event. if we compare figs.3 and 5 carefully, we can see that peaks appear at the same time for all components. during the evaluation of data, we identified pollutants, which were washed into the creek due to precipitation. table 1: properties of mobile monitoring stations monitoring station no.1 monitoring station no.2 location of installation entry point into veszprém in inner defense area of the waterworks exit point from veszprém on an industrial area size 85×85×85 cm outer size monitoring station made of hardened plastic 2.4×2.4 m base area, 2.5 m height monitoring station transportation car truck with crane power source 2 pcs of 12 volt lead battery line power (220v) measured parameters ph [11] turbidity [9] conductivity [8] water temperature [11] dissolved oxygen concentration [10] polyaromatic hydrocarbon concentration [17] ph [12] turbidity [3] conductivity [2] nh4 +-n concentration [13] po4 3--p concentration [16] no3 ±-n concentration [14] no2 --n concentration [15] sampling every 15 minutes every hour maintenance weekly battery replacement cleaning of the probes changing reagents and blind reagent calibration (biweekly) supplying distilled water (biweekly) cleaning of sample dispenser vessel sampling tubes figure 1: location of installed mobile monitoring stations figure 2: structure of mobile monitoring station 1 and 2 15 in addition, we detected pollution waves in two occasions. as can be expected, point sampling cannot give detailed information about the status of a water body. the advantage of online methods is clear due to their continuous monitoring, even if they are only operated for a short period of time. thus, we will get a more holistic picture about the status of a water body toward implementing efficient measures for water quality protection. pollutant leaching from precipitation to identify events, we used data from measurement station 2. in addition, water level data were downloaded from the water management web page of the ministry of interior, hungary. the water level of séd is at an average of 20 cm. from the time points in figs.3–5, we select an event occurred on september 30, 2013. around the time of the event, the water level started rising, the concentrations of physical-chemical parameters have also started to change. the pollutant downwash was detected between 04:00 and 06:00 according to the results; the concentration peak appeared at 05:00. viewing physical parameters (fig.6) the value of turbidity has risen, and after reaching the positive peak (14.6 ntu) it started to decrease. other physical parameters were seen as negative troughs. in the falloff phase all parameters moved back to the average value. looking at the chemical components (fig.6) as an effect of the rising water level, nh4 +-n, po4 3--n and no2 --n concentrations have risen, while no3 --n concentration appeared as a negative trough. outstanding physical-chemical parameters (e.g. po4 3--p at 0.15 mg dm-3 level) measured as an effect of pollutants washed in during precipitation. afterwards, the po4 3--p level moved back to its near average range of 50 µg dm-3. detecting pollutants pollutant waves were identified as events, when water level rise did not support the deviations of data points from their expected average values. alternatively, as a result of precipitation, water level of séd doubled relative to its average value without the presence of in pollutant waves. as an example, we analyze here the effect of a pollution wave appeared on september 26, 2013. the pollution was detected between 17:00 and 19:00 with reaching its peak at 18:00. looking at physical parameters (fig.7) turbidity values doubled relative to the average of 60 ntu. conductivity decreased significantly from 700 µs cm-1 to 640 µs cm-1. the ph decreased by 0.1 unit to 7.3. when we look at ion concentrations in fig.7, nh4 +-n concentration rose fourfold compared to the baseline (0.19 mg dm-3). po4 3-p and no2 --n concentrations also showed significant rise (30–180 µg dm-3). no3 --n displayed a negative trough at 40 µg dm-3, but this component was the least sensitive to the change. measurement of polyaromatic hydrocarbons based on the data points taken every 15 minutes by the polyaromatic hydrocarbon (pah) probe (trios) at measuring station 1 (fig.8) a pah pollutant wave was not detected during the investigated period. the baseline of pah compounds was measured to be 6–7 µg dm-3 and 13–15 µg dm-3. values significantly differing from figure 3: results of physical parameters measured (blue: station1, red: station 2) figure 4: variation of ph value as a result of discharge from the city (blue: station1, red: station 2) figure 5: change of concentration of measured ions figure 6: effect of precipitation on the physico-chemical components 16 the baseline (35 µg dm-3) can be counted as measurement errors. evaluation of laboratory measurement results in the duration of the investigation, we have taken point samples at the two measurement sites 13 times. the samples were always taken according to standard msz iso 5667–1:2007 [6] in the same time when the monitoring stations recorded data. the samples were transported in a cooler according to standard msz en iso 5667–3:2004 [7], and were analyzed on the day of sampling. table 2 summarized the type of instruments used for measurements. we compared the data obtained at measurement station 2 with the results of laboratory measurements (fig.9). correlation can be found for the outliers measured at the monitoring station (250 µg dm-3 po4 3-p) and in the laboratory (310 µg dm-3 po4 3--p). however, difference was found in the no3 --n concentrations between the laboratory and measurement station results showing around half values for the laboratory measurements than those from the measurement stations. based on these observations we proposed that the analyzer at the mobile monitoring station measures higher concentration than the real concentration. the effect of the city of veszprém on séd using laboratory measurements, the effect of the city of veszprém on the creek’s water quality was measured. the results obtained for averages of 13 samples are shown in fig.10. it can be seen that there was no significant change in the concentration of nh4 +-n (26.4–27.3 mg dm-3) between the entry and exit points of the creek with respect of the city. jumps in the concentration of nh4 +-n are characteristic during pollutant waves and precipitation. decrease in concentration of po4 3--p is notable (131–100 µg dm-3) at the exit section. at the entry section, séd flows near to agricultural areas, backyard gardens. we correlate the decrease of phosphate concentration within city limits with the presence of pure karst water inflows resulting in significant dilution effect. in the case of no3 --n and no2 --n concentrations (fig.10) an obvious increase can be seen (1.3–2.6 mg dm-3; 4.3–5.6 mg dm-3), which is related to the high nitrate content of the incoming karst water. the discharges from rainwater drains, backyard gardens, the canal of the zoo, and inflow from roads add to the increase of these concentrations. figure 7: effects of a pollutant wave on the physical-chemical parameters components figure 8: change in pah concentration in the investigated timeframe figure 9: comparing mobile monitoring station 2 and laboratory results 17 measurement of polyaromatic hydrocarbon concentrations the two goals of the measurements were the testing the reliability of the results by enviroflu and evaluating whether the probe can detect other pah compounds that are not fluorescent. to check reliability, we used the addition method with epa tcl polynuclear hydrocarbons mix chemical from sigma-aldrich. furthermore, we also used naphtaline-disulphonate compound for inducing disturbing effect. we measured three solutions as shown in table 3 with probe and we have taken emission spectra. laboratory control measurements (msz 1484-6) [5] were done by elgoscar 2000. comparison of the laboratory and probe results showed significant difference (table 3). if we deduct the values obtained for the sample from séd creek as base values, we get similar results. the reliability of results obtained this way was confirmed by spectra taken by a perkin elmer ls50b type fluorimeter (fig.11) [1]. the enviroflu probe detects fluorescent light at 360 nm. when looking at the curves at 360 nm, we can see that the proportions of intensity differences between the spectra of a sample from séd and artificially polluted samples correspond to the concentration differences. the significant difference between the laboratory and probe results comes from the fact that the probe senses all compounds giving fluorescence at a given wavelength. this was further elaborated by the significant concentration difference when the sample contained naphtaline-disulphonate. water quality according to water framework directive the middle section of séd belongs to type 3, or alpine, calcic-rough bed material, medium catchment water flow according to water management plan [18] on the basis of water framework plan [19.] we have prepared table 2: devices used to measure physical and chemical properties of water samples mobile monitoring station 1 mobile monitoring station 2 laboratory ph neotekponsel, pheht sentek pi11 consort c902 conductivity neotekponsel, c4e endress+hauser indumaxp cls 50 consort c902 turbidity neotekponsel, ntu sensor endress+hauser turbimax w cus41/cus41w po4 3--p µmac c lovibond pc spectro nh4 +-n no3 --n no2 --n pah trios, evirofluhc figure 10: the effect of the city of veszprém on the investigated section of séd creek table 3: comparison of laboratory and online measurement results enviroflu (µg dm-3) laboratory (µg dm-3) sample form séd 13.01 0.13 séd + 20 µg dm-3 pah mix 25.27 13.7 séd +100 µg dm-3 naphtaline-disulphonate 21.03 0.15 figure 11: emission spectra taken with fluorimeter table 4: monthly average values for water quality parameters august september october ph 7.64 7.45 7.43 conductivity, µs cm-1 711.22 707.16 720.74 oxygen saturation, % 84.15 93.4 77.32 dissolved oxygen, mg dm-3 9.39 10.28 8.73 nh4 +-n, µg dm-3 33 31 26 no2 --n, µg dm-3 31 17 15 no3 --n, mg dm-3 5.12 4.02 4.14 po4 3--p, µg dm-3 113.79 96.58 92.04 18 water qualification in the observed timeframe in monthly divisions. for dissolved oxygen and oxygen saturation values we used the results of mobile monitoring station 1 and for other components the results of mobile monitoring station 2. we have calculated monthly average values of water quality parameters (table 4). in addition, we classified each component on a five-level scale and then made class averages. the class minimums provided classifications for each month. the minimum of class average for august, september, and october were 2.5, 3, and 3, respectively; which resulted in water quality that did not reach a good status. conclusions the advantage of online measurement methods was demonstrated due to the possibility of continuously monitoring the quality of the examined creek. with online devices events can be detected that can be missed by point sampling, such as daily fluctuations, pollution waves in extreme time points. another advantage of online methods is the remote controllability, which does not require personnel except for maintenance. a drawback of the larger and more complex mobile monitoring station 2 compared to more portable mobile monitoring station 1 is the need for significant chemical, distilled water and maintenance time. the measurement stations can reveal trends, the results provided by them are in the same magnitude, but it cannot compete with the accuracy of an accredited laboratory. the goal of online measurements is to detect pollutant waves and extreme values. in order to enhance the accuracy of online measurements follow up laboratory control measurements is needed. in addition to the entry and the exit sections of the séd creek, the catchment management plan requires monitoring the physical and chemical parameters of the middle section of séd that are missing. the results presented in the given paper may help in the drafting of the measurement plans. acknowledgements this work was supported by the european union and co-financed by the european social fund in the frame of the támop-4.2.2/b-10/1-2010-0025. references [1] kristóf j.: chemical analysis ii. (instrumental analysis), ve 13/2000. veszprém, pannon egyetemi kiadó, 2000 (in hungarian) [2] endress+hauser conductivity sensor indumaxp cls 50: technical information (ti 182c/07,en, no 51517565), endress+hauser in germany, 2007 [3] endress+hauser solids content sensor turbimax w cus 41/cus 41-w: technical information (ti 177c/07,en, no 51517577), endress+hauser in germany, 2007 [4] water management of central transdanubia: significant water management issues 1–13; northern and eastern bakony field land planning sub-unit, székesfehérvár, 2007 (in hungarian) [5] msz 1484-6:2003: testing of waters. determination of policyclic aromatic hydrocarbons (pah) content gas chromatographic-mass spectrometry, hungarian standards institution standards bulletin, 2003 (in hungarian) [6] msz iso 5667-1:2007: water quality. sampling; part 1: guidance on the design of sampling programmes and sampling techniques, hungarian standards institution standards bulletin, 2007 (in hungarian) [7] msz en iso 5667-3:2004: water quality. sampling; part 3: guidance on preservation and handling of water samples, hungarian standards institution standards bulletin, 2004 (in hungarian) [8] neotek-ponsel digital sensorc4e: conductivity/salinity datasheet, neotek-ponsel in france, 2009 [9] neotek-ponsel digital sensor nephelometric turbidity datasheet, neotek-ponsel in france, 2009 [10] neotek-ponsel digital sensor odot: optical dissolved oxygen datasheet, neotek-ponsel in france, 2009 [11] neotek-ponsel digital sensor pheht: ph, redox, temperature datasheet, neotek-ponsel in france, 2009 [12] sentek electrochemical sensor specialists pi 11 ph elektrode manual, sentek in uk, 2008 [13] systea s.p.a: ammonia in water 0–0.4 ppm n-nh3 (lfa-nh3-05 rev.1 common.609) , systea s.p.a., italy, 2000 [14] systea s.p.a: nitrate in water dtpa uv reduction 0–100 mg dm-3 n-no3 -+n-no2 (lfa-no3dtpa-02 rev.1 comm. 896) systea s.p.a., italy, 2000 [15] systea s.p.a: nitrite in water and seawater 0–5 ppm n-no2 (lfa-no2-01 rev2.comm. 896) systea s.p.a., italy, 2000 [16] systea s.p.a: orthophosphate in water and seawater 0–20 ppm (lfa-po4-02 rev.1 comm.896) systea s.p.a., italy, 2000 [17] trios gmbh: trios optical sensors enviroflu-hc manual submersible fluorimeter for the detection of polycyclic aromatic hydrocarbons (pahs) in water, trios gmbh in germany, 2004 [18] directorate for water and environmental protection: water management plan for the danube river basin in hungary, 2009 (in hungarian) [19] eu water framework directive: the european parliament and of the council, water framework directive (2000/60/ec), ojl 327, 22 december 2000, 1–73 microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 37(2) pp. 113-117 (2009) product composition control of a new batch pressure swing rectifying system á. kopasz, g. modla, p. láng bute department of building services and process engineering 1111 budapest, műegyetem rkp. 3. d. ép. 105, hungary e-mail: lang@mail.bme.hu when operating the double column batch stripper (dcbs) configuration the liquid composition of the common vessel of the two columns must be kept between the two azeotropic compositions by affecting the flow rates of the two products. these can be varied by changing the reboil ratio and/or ratio of division of the liquid flow leaving the common vessel. the goals of this paper: to propose and study a simple control scheme with pid parameters (providing good quality of control) for the new configuration, investigation of the influence of the liquid division ratio, determination of optimal value of liquid division ratio (providing the prescribed separation with minimal specific energy consumption). the calculations were made for a minimum (n-pentane – acetone) azeotropic mixture by using a professional dynamic simulator (ccdcolumn). by the aid of a pid controller we modified the flow rate of the bottom products (affecting the reboil ratios of the columns). we investigated the action of the control loops and the system for two different set points. in the first case the composition of the bottom products, in the second one – most common in the industry – the bottom temperatures were kept constant. keywords: batch rectification, pressure swing, minimum azeotrope, composition control introduction binary pressure sensitive azeotropes can be separated by pressure swing distillation (psd). continuous psd was first applied in the industry in 1928. phimister and seider (2000) studied first the batch (stripping) and semicontinuous application of psd by simulation. first repke et al. (2007) investigated experimentally the batch psd (psbd, pilot-plant experiments for the separation of a minimum azeotrope in a batch rectifier (br) and stripper (bs)). modla and lang (2008) studied different batch configurations (br, bs, combination of br and bs and middle vessel column (mvc)) by feasibility studies and rigorous simulation for the separation binary (maximum and minimum) homoazeotropes. the different pressures can be separated: in time → one column section (e.g. br, bs) in place → two column sections (e.g. mvc) by modifying the mvc, which has not been proven suitable for the psbd, they suggested two new double column batch configurations: rectifier (dcbr) and stripper (dcbs, fig. 1). figure 1: the scheme of a dcbs they compared the different configurations for a given set of operational parameters without optimisation and control. 114 for minimum azeotropes the best results (minimal specific energy consumption for the same quality products) were obtained with the dcbs and for maximum azeotropes with the dcbr, respectively. the columns of these configurations can be operated practically in steady state. modla et al. (2010) studied the feasibility of batch psd separation of most frequent types of ternary homoazeotropic mixtures. when operating these new configurations the liquid composition of the common vessel of the two columns must be kept between the two azeotropic compositions. the ratio of two product flow rates of a dcbs can be changed by varying the /reboil ratios and/or the ratio of division of the liquid flow leaving the common vessel. the goals of this paper are: to investigate the operation of the dcbs for the separation of a minimum azeotrope, to study a simple scheme for the control of product compositions (directly the composition or temperatures of bottoms product are controlled and their flow rates are manipulated), to investigate the effects and to determine the optimal value of the liquid division ratio. the calculations were made for the mixture npentane-acetone by using a professional dynamic simulator (ccdcolumn). the temperature-composition (t–x,y) diagrams and azeotropic data of the mixture studied are shown for the two different pressures in fig. 2 and table 1, respectively. figure 2: t–x,y diagrams of n-pentane-acetone table 1: azeotropic data (uniquac parameters: 571.98 and 95.033 cal/mol) component pentane(a) acetone(b) p [bar] 1.01 10.0 xaz 0.754 0.668 taz [°c] 32.5 116.9 tbp,a [°c] 36.0 124.7 tbp,b [°c] 56.2 142.9 figure 3: chemcad model of the double column batch stripper with control loops 115 simulation method the following simplifying assumptions were applied theoretical stages, negligible vapour hold-up, constant volumetric liquid plate hold-up. the model equations to be solved are well known: a non-linear differential equations (material balances, heat balances), b algebraic equations (vapour-liquid equilibrium (vle) relationships, summation equations, holdup equivalence, physical property models). for solving the above model equations we used the ccdcolumn dynamic flow-sheet simulator of chemcad 6.0 (chemstations 2006, ). for the simulation of columns simultaneous correction method was applied. the following modules were used: dyncolumn (column sections), dynamic vessel (top vessel and product tanks), heat exchanger, pump, valve, mixer, divider, controller, control valve. the chemcad model of the double column batch stripper with control of product compositions is shown in fig. 3. simulation results the number of theoretical stages for each column sections is 40. (the total condenser and total reboiler do not provide a theoretical stage.) the liquid hold-up is 2 dm3/plate. the pressure of the columns: plp = 1.013 bar and php = 10 bar. the total flow rate of liquid leaving the common vessel: l0,total = l0 lp + l0 hp = 6 m3/h. at the start of the distillation plates of the columns are wet (they are filled with charge at its boiling point at the given pressure, “wet start-up”). the quantity of charge containing 30 mol% pentane filled into the common vessel is 4.022 kmol (0.471 m3). the prescribed purity is 98 mol% for both products. the reboil ratios rs lp and rs hp are changed by pid controllers manipulating (with linear control valves) the product flow rates wlp and whp, respectively. the whole process is finished when the amount of liquid in the vessel decreases to 12.5% of the charge. tuning of pid controllers our aim is to determine a set of parameters (ap, ti and td) of the pid controllers which provide good quality control of product compositions in the whole region of the liquid division ratio (φ = l0 lp/l0,total) by taking into consideration the usual criterions (maximal overshoot, control time, number of oscillations). the controllers are calculated by the standard pid algorithm, which is the base setting in the chemcad. (the error definition is reverse which means: error = xset – x.) the quality of control is determined by the evolution of not the controlled variables (composition or temperature of the two bottoms products) but the position of the two control valves (varying the flow rate of the two bottoms product). this was made because the valve position (%) varies much more rapidly than the controlled variable. the following criteria of quality of control are given concerning the two control valves: maximal overshoot: 33%, maximum number of oscillations during the settling time ts (within an error band of ± 5%): 3. we investigated the control schemes with two methods from the point of view of the setpoint parameter. in our fist calculations we gave into the program bottomcomposition-setpoint, and tried to maintain the purity of the bottom product around 98 mol% with the pid controllers. then we gave as setpoints the temperatures, belonging to the purities of 98 mol% (fig. 2). (the relation between the composition and the temperature is non-linear.) table 2 contains the parameters of pid controllers and sensors. the control quality data for the two different cases are shown in tables 3 and 4. table 2: set of parameters for composition and temperature control composition temperature control mode column i column ii column i column ii pb, % 80 50 45 120 ti, min 2.5 10 13 3 td, min 0 1 0.5 1 setpoint 0.982 0.98 52.7 123 variable minimum 0.8 0.6 50 117.1 variable maximum 1 1 56.15 124.74 ctrl input minimum 4 4 4 4 ctrl input maximum 20 20 20 20 116 table 3: control quality data for composition control column i column ii maximal overshoot, % 8 11 ts, min 20.5 15.0 no. of oscillations within ts 2 1 table 4: control quality data for temperature control column i column ii maximal overshoot, % 33 32 ts, min 6.75 7.75 no. of oscillations within ts 1 1 influence of the liquid division ratio after tuning the pid controllers we investigated the effect of the liquid division ratio (φ) on the process. the optimal value of φ was determined according to the minimal overall specific energy consumption (sqlp+ sqhp)/(swlp+ swhp). we consider sqlp és sqhp as the summation of the absolute value of the heating input energy in the reboiler and the cooling output energy in the condenser. the power-supply of the pumps was disregarded, because it’s order of magnitude is much more smaller than the heating energy. the liquid division ratio was varied in the region 0.3–0.9. the specific energy consumption is minimal at φ = 0.55 (fig. 4) in both cases of control mode (composition control, temperature control). 1038 1048 1051 1000 1200 1400 1600 1800 2000 2200 2400 2600 0,3 0,4 0,5 0,6 0,7 0,8 0,9f m j/ km ol figure 4: the influence of the liquid division ratio on the specific heat energy consumption (sq/(swa+ swb) prescribed purity products are obtained with acceptable recoveries (table 5). this table contains also the most important results for the process, such as the total and specific heat energy consumptions of the production. it’s worthy of note that the recoveries can be increased by the reduction of the amount (12,5% of the starting value) remaining in the common vessel. during our investigations we were able to empty the common vessel totally ensuring the prescribed product purities, however under 12% the operation of the controllers became unstable (oscillations). fig. 5 shows the evolution of control valve positions and bottom temperatures, bottoms compositions, reboil ratios at the liquid division ratio of φ = 0.55. table 5: most important results of the production for the optimal liquid division ratio control mode composition temperature n-pentane recovery* % 86.50 75.32 acetone recovery* % 79.50 67.54 n-pentane purity mol% 98.65 98.20 acetone purity mol% 97.96 98.03 total calorific energy (sq) mj 3517 3106 specific calorific energy: sq/(swa+ swb) mj/mol 1019 1038 production time min 62.5 54.0 * related to the amount filled into the comon vessel at the start conclusion we investigated the separation of a maximal boiling point azeotrope n-pentane-water in the double column batch stripper (dcbs) with rigorous simulation by applying the dynamic module of a professional flowsheet simulator chemcad (ccdcolumn). a potential set of pid parameters was determined, wherewith both the prescribed purities and the prescribed criteria of control quality were satisfied. we investigated the influence of the liquid division ratio on the performance of the process, and determined its optimum value (looking for the minimal overall specific heat energy consumption). we got simlar results for the value of the minimal overall specific energy consumption in both cases (composition control, temperature control, which is applied most commonly in the industry). 117 0 10 20 30 40 50 60 70 80 90 100 0 5 10 15 20 25 30 35 40 45 50 55 t [min] va lv e po si tio n [% ] 30 35 40 45 50 55 60 65 70 75 80 t [°c ] valve position temperature 0 10 20 30 40 50 60 70 80 90 100 0 5 10 15 20 25 30 35 40 45 50 55 t [min] va lv e po si tio n [% ] 80 85 90 95 100 105 110 115 120 125 130 t [°c ] valve position temperature 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 0 5 10 15 20 25 30 35 40 45 50 55 t [min] m ol e fra ct io n acetone n-pentane 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 0 5 10 15 20 25 30 35 40 45 50 55 t [min] m ol e fr ac tio n n-pentane acetone 0 10 20 30 40 50 60 70 80 90 100 0 5 10 15 20 25 30 35 40 45 50 55 t [min] r s 1 0 10 20 30 40 50 60 70 80 90 100 0 5 10 15 20 25 30 35 40 45 50 55 t [min] r s 2 column i (lp) column ii (hp) figure 5: the evolution of valve positions and bottom temperatures, bottom compositions, reboil ratios at φ = 0.55 acknowledgement this paper was supported by the janos bolyai research scholarship of the hungarian academy of sciences and the hungarian research funds (otka) (no: k-82070). references 1. chemstations: “chemcad user guide” (2006). 2. lewis w. k.: “dehydrating alcohol and the like”, u.s. patent, 1,676,700, july 10, (1928). 3. modla g., lang p.: feasibility of new pressure swing batch distillation methods, chem. eng. sci, 63(11), 2856–2874 (2008). 4. modla g., lang p. denes f.: feasibility of separation of ternary mixtures by pressure swing batch distillation, chem. eng. sci, 65(1), 870–881 (2010). 5. perry r. h., green d. w., maloney j. o.: “perry’s chemical engineer’s handbook” 5th edition, mcgraw hill, new york, (1998) 6. repke j. u., klein a., bogle d., wozny g.: “pressure swing batch distillation for homogenous azeotropic separation”, proceedings of distillation and absorption 2006, london, 709–718. 7. phimister j. r., seider w. d.:, semicontinuous pressure swing distillation, ind. eng.chem. res., 39, 122–130 (2000). microsoft word 01_r.doc hungarian journal of industrial chemistry veszprém vol. 35. pp. 39-45 (2007) thermal cracking of recycled hydrocarbon gas-mixtures with high olefins concentrations in the feed: operational analysis of industrial furnaces 1t. gál, 2b. g. lakatos 1mol-tisza chemical works co. ltd (tvk), tiszaújváros, hungary 2university of pannonia, institute of chemical and process engineering, department of process engineering, veszprém, hungary simulation studies of thermal cracking of recycled hydrocarbon gas mixtures are presented. due to their relatively high unsaturated content these types of mixtures show behaviour in cracking furnaces different from that of their saturated homologues. the detailed mathematical and kinetic model developed was validated by using the process control laboratory cracked gas analysis of an industrially operated cracking furnace. the effects of different feed compositions and those of operating parameters are also examined. it is shown that the radiant coil temperature profile, online operation period of the furnace, and the yield of the main products are different at various unsaturated concentrations in the feed. the influence of the radiant section residence time is also presented. simulation results compared with the experimentally measured data of an industrially operated cracking furnace show good agreements. keywords: pyrolysis, hydrocarbons, gas-mixtures, olefins, modelling, simulation introduction thermal decomposition of hydrocarbons has been studied for more than 70 years. nevertheless, less attention has been paid on cracking behaviour of olefins since recycling of certain cracked gas-fractions has become important only in past one-two decades. while repyrolysis of formed ethane and propane has been applied for long, recycling of c4 and/or c5 fractions has only been introduced into industrial experience parallel with decreased market demand for plastics produced from butadiene and isoprene. sundaram and froment [1-3] developed kinetic models for thermal decomposition of gaseous hydrocarbons and their mixtures. kinetic parameters presented in these schemes are still applicable for thermal cracking of individual hydrocarbons and mixtures up to c4. van damme et al. [4] and froment et al. [5] compared the results given by their kinetic model with those obtained from industrial applications. ranzi et al. [6], froment et al. [7] and dente et al. [8, 9] presented the initial product distribution when cracking light hydrocarbons and prepared the first fundamental pyrolysis simulation model, the spyro. willems and froment [10] presented a method of calculation of frequency factors and activeation energies, while dente and ranzi [11] prepared a mathematical model for hydrocarbon pyrolysis reactions. more recently, poutsma [12], savage [13], sadrameli and green [14] presented the system of fundamental free radical reaction relevant to pyrolysis and mechanisms and kinetic modelling systems for hydrocarbon pyrolysis, respectively. zou et al., [15], pleiers et al. [16] and kopinke et al. [17,18] studied and presented coke formation rates that influence the online operation period of cracking furnaces. the mentioned c4/c5 fractions are hydrogenated upstream the cracking furnaces. olefin content of hydrogenation reactor effluent mainly depends on its catalyst performance and can vary between 3 and 30%. yet, unsaturated ratio of the furnace feed can also be reduced by mixing fresh, saturated hydrocarbons into reactor effluent. these are mainly butanes and/or pentanes in practice but, according to our simulation results, mixing of ethane also looks to be a promising alternative. this paper examines the effects of unsaturated components in the feed on product yields and online operation period of the furnace aiming the opportunities of harmonizing the operating parameters at different feed compositions. results obtained by numerical experimentation using a computer model are compared with experimentally measured data of an industrially operated cracking furnace. 40 mathematical model the kinetic model starting from the detailed composition of fed hydrocarbons and cracked gases a reaction network was built up with participation of all theoretically supposed ones in the first step of modelling, number of which was closely five hundred. as the second step, kinetic parameters were assigned to each reaction, source of which was the large amount of published literature data. if the published system was found to have been similar to the one examined by us, these parameters could be directly adopted [2, 3, 7]. in cases different from that, parameters were collected from other sources then interpolated or extrapolated on basis of analogy rules between the reactions in the same group [1, 4-6, 8, 9-15]. of course, a comparison was made in the first case as well. the aim of these two steps was to build up a ‘first generation’ kinetic model that could reproduce measured yield data as accurate as possible. validation of the model was performed by comparing the results with those obtained experimentally from cracked gas analysis of an industrially operated furnace. this means that a set of multiply verified data, among stabilized operational circumstances, were collected in concert with the sampling schedule and procedure. received yield data were not averaged but those in coincidence were taken as reference. secondly, influence of each reaction to the yield-structure was examined. effect of those to the yield structure was negligible could be deleted from the system with simplification purposes and for the reasons mentioned earlier. having performed these procedures, 239 reactions remained in the examined system, kinetic parameters of which were fitted to the measured yield data in case of each reaction, except those leading to coke formation (coke ‘yield’ could not be measured). the fitting was performed in such a way that the trend of a product yield or consumption of a feed component was drawn as a function of modification of parameters (a or e). table 1 presents a part of arrangement of frequency factors from different sources together with the adopted ones in the first phase of modelling and with the ones fitted during validation of the model. fig. 1 shows an example of fitting the activation energies to experimentally measured yields at reactions of the prepared network. table 1: assigning frequency factors (a, sec-1 or cm3*mol-1*sec-1) to reactions in the system reaction literature data sources adopted fitted c3h8 → ch3* + c2h5* 7.1·1016c 2·1016 h 1.3·1016j --3·1016 2.2·1016 n-c4h10 → 2 c2h5* 5·1016 c 1.5·1016h ----2·1016 2.5·1016 c3h8 + ch3* → ch4 + 1(2)-c3h7* 1.5·109c 3.4·1010 (4·109) h 108 i 4.9·109 (1.5·109)j 1.5·109 (3·109) 2.2·109 (4.2·109) 1-c3h7* → c2h4 + ch3* 5·1013 c 4·1013 h 5·1013 k 1014 i 5·1013 4.4·1013 ch3* + c2h5* → c3h8 1010 c 3.2·109h ----5·109 3.2·1010 sources in table 1 are indicated as follows: c – dente and ranzi (1983); d – zdenek et al. (2003); h – sundaram and froment (1978); i – ranzi et al. (1997), j – willems and froment (1988); k – ranzi et al. (1983) 10 12 14 16 18 20 22 8,4 25,1 39,8 53,6 62,8 75,4 87,9 125,6 e (kj/mol) m et ha ne y ie ld (w t% ) 18.43% figure 1: variation of methane yield as a function of activation energy in case of reaction: c2h4 + ch3* = c2h3* + ch4 the reactor model the geometry of the furnace coil and high reynoldsnumbers used in thermal decomposition process enable tubular reactor and plug-flow assumptions. as a consequence, mass, energy and momentum balances can be written as follows [19]. mass balance: rc n k i kki i nkni x txcvtr t txc r →=→= ∂ ∂ −= ∂ ∂ ∑ = 1,1 ),(),(),( 1 cα (1) where ci is the concentration of reactant i, x is the axial distance along the reactor, v denotes the cracked gas convective velocity, rk is the rate of the reaction k, and αki stands for the stoichiometric coefficient of component i in the reaction k. nc denotes the number of species, while nr stands for the number of reactions. 41 enthalpy balance: [ ]),(),( ),()(),( 1 11 txttu x txtccv trh t txtcc fb n i ipi n k kk n i ipi c rc −+ ∂ ∂ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ − −−= ∂ ∂ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ ∑ ∑∑ = == cδ (2) where t is the cracked gas temperature, cpi is the heat capacity of species i, δhk denotes the heat of reaction k, u denotes the overall heat transfer coefficient from the fire box to the cracked gas, dt is the inner diameter of the reactor tube, and tfb stands for the temperature of fire box. the pressure drop along the radiant pipe: 2 )( 144 2vx gd lf dx dp t t ρξ ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ += (3) where p denotes the pressure, ρ is the density of gas mixture, lt the equivalent pipe length, g is acceleration due to gravity, ξ(x) is the local resistance coefficient of reactor tube junctions or bends, and f denotes the friction factor which is calculated using the expression for smooth pipes: 25.0 3164.0 re f = (4) the balance equations are solved subject to boundary and initial conditions: )0()0,(,1)()0,( 00 txtnixcxc cii =→== (5) )(),0(,1)(),0( . ttttnitctc incinii =→== (6) the computer model the reference furnace consists of a radiant and a conection section, as well as of six transfer line exchangers (tle) with one steam drum. firing in radiant section is performed by sidewall and floor burners where natural gas is burnt which is also mixed with the methane fraction formed in cracking process. preheating of feed and dilution steam as well as preheating and super-eating of high-pressure steam takes place in convection section. between the feed preheater and steam super-heater a boiler-feed-water preheater is placed. the furnace was designed to assure uniform distribution and ‘drive’ of different streams to convection-section heat-exchanger bundles. furnace feed streams are collected in two places and distributed into 96 radiant coils by laval-nozzles. after a certain length two small-diameter (39 mm) coils unify in a bigger one (57 mm). according to this, the furnace contains 48 radiant coils connected to one tle by eight as it shown in fig. 2. the residence time of reaction mixture in the radiant section is very short (0.3 sec.). having identified the kinetic parameters, simulations were performed by chemcad computer simulator that was chosen for its large thermochemical database as well as for the fact that not only molecules but radicals can also be created and handled. as a further part of its implementation, geometrical data were given according to the technical drawings of the examined industrial furnace. data input of parameters and process-variables were also performed on basis of industrial circumstances. figure 2: radiant coil arrangement so as to determine composition of cracked gases at the furnace outlet the following input data are needed: a.) feed composition by component and its flow-rate b.) inlet and outlet temperatures (cot) of the furnace c.) pressures at inlet and outlet (to calculate pressuredrop along the coil) d.) hydrocarbon/dilution steam ratio and steam flow-rate e.) coil geometry, i.e. the lengths and internal diameters of segments f.) temperature-profile along the coil or heat-transfer coefficient (u), with tube metal temperature (tmt) g.) each chemical reaction taking place in the system with their kinetic parameters (activation energies and frequency-factors, respectively) operating parameters of the furnace (points a – d), such as temperatures, pressures, flow rates are monitored by an advanced process control system (apc) and they can be registered in accordance with feedand cracked gas analysis [20]. the factor of losses depends on convectional circumstances dominant in the pipe (re-number) and its shape. according to this, the total pipe length (point e) is the sum of straight segments and the equivalent pipe length. table 2 presents comparison of measured and simulated yield data with fitted kinetic parameters. 42 experimental: application and presentation of simulated results having validated the model, series of simulations were performed with the purpose of examining the effect of different feed components on product yields. some typical feed compositions are shown in table 3. the influence of the n-butane concentration is shown in table 4. as it is seen, 28% higher n-butane concentration is needed to achieve 4% increased ethylene yield but the relative coke formation rate was decreased by almost 25%. this decline is also due to the lower relative concentration of olefins in the feed, i.e. because of less coke precursors. neither the yield of methane nor that of propylene varies significantly but less aromatic compounds (bt) are produced. in conclusion, when increased olefin content occurs in the feed adding more butane into it appears to be economically reasonable since higher furnace run-length can be reached in parallel with the possible decreased hydrogenation reactor load that also leads to depression of olefin content in the feed. table 2: comparison of the measured and simulated product yields with fitted kinetic parameters component/ yields (wt %) measured 1 fitted 1 measured 2 fitted 2 measured 3 fitted 3 hydrogen 1.06 0.98 1.05 0.98 0.98 0.96 co 0.10 0.11 0.06 0.07 0.05 0.07 methane 18.72 18.67 18.53 18.64 18.27 18.52 ethane 3.39 3.34 3.56 3.51 3.63 3.53 ethylene 30.64 30.58 31.13 31.08 32.30 32.17 propylene 19.51 19.64 19.54 19.61 19.26 19.37 n-butane 8.50 8.58 8.57 8.63 10.08 9.87 acetylene 0.51 0.55 0.51 0.56 0.50 0.49 benzene 1.34 1.36 1.34 1.36 1.33 1.30 toluene 0.22 0.25 0.22 0.25 0.22 0.25 table 3: some typical compositions of the furnace feed component (wt%) sample 1 sample 2 sample 3 sample 4 sample 5 propane 0,8937 0,3251 0,1462 0,4315 0,0880 propylene 0,7019 0,9518 0,1881 0,9308 0,3292 i-butane 12,5453 8,6917 6,5118 6,9339 5,2723 1-butene 0,8193 0,0716 0,1484 0,0891 0,0891 n-butane 61,9166 69,5411 67,6253 72,1629 63,9667 2-butene 2,4412 0,3452 0,3934 0,3899 0,4321 i-pentane 4,9792 6,4142 8,4320 5,9221 9,4355 2m-butene-1 0,2211 0 0,0655 0,0473 0,0843 n-pentane 5,8455 7,0751 8,2326 6,3494 10,8684 2-pentene 0,2306 0 0 0 0 2m-butene-2 1,7299 0,4041 0,5704 0,4425 0,7475 cyclopentene 0,0874 0 0 0 0,0735 cyclopentane 5,9247 5,4214 6,7055 5,7778 7,7222 2m-pentane 0,5752 0,6778 0,6036 0,4434 0,8912 ∑ other c6 1,0885 0,0808 0,3773 0,0794 0 table 4: variation of product yields as a function of n-butane concentration in the feed n-butane conc., wt%→ product yields, wt% ↓ 65.95 simulated 65.95 measured 72.35 simulated 72.35 measured 79.55 simulated 79.55 measured 86.71 simulated 93.89 simulated hydrogen 0.88 0.92 0.89 0.94 0.91 0.99 0.95 0.98 methane 18.54 18.71 18.14 19.32 18.11 19.18 18.02 17.96 ethylene 30.58 30.61 31.02 31.21 32.21 32.42 33.43 34.43 propylene 19.34 19.74 19.28 19.53 19.16 19.34 19.09 19.01 n-butane (residual) 8.92 8.77 9.28 9.17 9.75 9.68 10.07 10.38 benzene + toluene 1.78 1.73 1.61 1.58 1.41 1.37 1.28 1.19 coke (theoretical) 0.0087 -----0.0084 -----0.0081 -----0.0075 0.0069 further simulations were carried out at five different unsaturated concentrations in such a way that concentration of each component in the feed was varied proportionally. rest of independent variables (cot, st/hc) was kept constant. simulated results are presented in fig. 3. as fig. 3 shows, trend of methane yield and that of propylene shows a linear decline with a rising unsaturated rate. rising conversion of n-butane is only ‘virtual’ since its relative concentration in the feed also declines when the unsaturated concentration is higher. nevertheless, variation of ethylene yield shows a slightly rising trend which, for the first sight, looks to 43 be surprising. to find the explication, it was examined how the concentration of some key unsaturated feed components vary along the radiant coil. parallel with this, their kinetic route was also followed. variation of three feed components concentration, that are present in the highest amount in the feed, is shown in fig. 4. concentrations of 2m-butene-2, butane-1 and butane-2 are the most elevated in the feed so their kinetic routes were examined. all of them take part in chain-initiation, hydrogen-abstraction, chain-forwarding and recombination reactions [3] 0 5 10 15 20 25 30 35 0 2,83 5,51 10,51 15,27 olefins in the feed, w/w% pr od uc t y ie ld s, w /w % methane ethylene propylene n-butane coke*1000 figure 3: variation of product yields as a function of olefin concentration in the feed 0 0,01 0,02 0,03 0,04 0,05 0,06 0 2,8 26 5 5,6 52 9 8,4 79 4 11 ,30 6 14 ,13 2 16 ,95 9 19 ,78 5 22 ,61 2 25 ,43 8 28 ,26 5 31 ,09 1 33 ,91 7 36 ,74 4 39 ,57 42 ,39 7 reactor volume, liter m as s fr ac tio n 2m-burene-2 butene-1 butene-2 figure 4: variation of some olefins concentration along the radiant coil fig. 5 shows the temperature profiles in the first part of the radiant coil revealing the differences between those in case of cracking a c3-c6 mixture in a furnace with short residence time (0.3 sec) when the feed is free of olefins and when it contains 15% unsaturated components. this examination was initiated by some operational experiences observed in industrial plants according to which higher coke deposits were realized in the first part of radiant coil, causing a very short online operation time as well as cracking of coils in certain cases. the theoretical explication of this phenomenon is that unlike saturated hydrocarbons, all the olefins and diolefins contribute more to coke deposits in the first part of cracking coil. this is more pronounced the higher the reactivity of the component is. it is a question of profitability to operate the furnace at the lowest possible steam/hydrocarbon ratio since a lower steam rate reduces specific energy consumption of the production unit. basically, one thing has to be decided: up to what extent this ratio can be reduced without having a significant negative effect on product yields and on furnace online period. table 5 shows that reducing the ratio by 20% practically has no influence on product yields but a shorter runtime can be expected because of higher coke formation rate. 0 0,002 0,004 0,006 0,008 0,01 0,012 0,014 0,016 0,018 0,02 0 3,5 33 1 7,0 66 1 10 ,59 9 14 ,13 2 17 ,66 5 21 ,19 8 24 ,73 2 28 ,26 5 31 ,79 8 35 ,33 1 38 ,86 4 42 ,39 7 reactor volume, liter c ok e, w t% 0% unsaturated 15% unsaturated figure 5: formation rate of coke along the radiant coil fig. 6 shows the variation of formation rates of some undesired products, such as co, coke and acetylenes along the radiant coil. as it is seen, formation of mapd starts first and rate of coke formation increases exponentially at the last part of reactor pipe. 0 0,001 0,002 0,003 0,004 0,005 0,006 0 2,4 1 9,2 7,2 4 18 ,8 12 ,1 28 ,6 16 ,9 37 ,4 21 ,7 42 ,4 reactor volume, liter yi el ds o f s ec on da ry pr od uc ts , w /w % co coke acetylene mapd figure 6: variation of formation rates of some undesired products along the radiant coil it should be noted that the effects of the dilution steam reduction cannot be simulated with high accuracy since catalytic effect of tube metals are not described by any known kinetics. though the literature survey [1518] shows a clear classification of coke precursors (such as olefins, acetylenes and aromatics) but there are no detailed discussions on dilution steam effect. nevertheless, practical experience also confirms the data shown in table 5. 44 table 5: simulation at different steam/hydrocarbon ratios steam reduced by...% temperature (cot), ºc → product yields, wt% 5 835 5 840 10 835 10 840 15 835 15 840 20 835 20 840 methane 18.22 18.75 18.32 18.72 18.43 18.83 18.53 19.06 ethylene 32.22 33.73 32.07 33.18 31.92 33.07 31.78 33.25 propylene 20.63 20.15 20.68 20.34 20.74 20.38 20.79 20.32 butadiene 3.97 3.85 3.97 3.89 3.98 3.89 3.98 3.86 n-butane (residual) 8.74 7.58 8.72 7.88 8.70 7.82 8.68 7.56 benzene + toluene 1.61 1.63 1.71 1.64 1.75 1.66 1.81 1.69 coke 0.016 0.019 0.017 0.018 0.017 0.018 0.018 0.019 according to the daily operational experience, for the relatively high unsaturated-content of the feed, online operation period of the furnace became shorter than the designed value, especially at the end of radiant coil lifetime. this is mainly due to the higher coke formation rate, which is caused by the elevated olefin content (coke precursors) in the feed and by those formed during the decomposition process. for these reasons, further alternatives were searched for to process the mixture in question more efficiently. simulations with variation of radiant coil geometry, i.e. alteration of residence time were carried out to compare yield data and coke formation rate. geometrical data of two existing furnaces (cf2 and cf3) were taken as reference so that the calculated residence times could be in real domain, i.e. 0.65 sec and 1.1 sec, respectively. it was supposed that a higher key-conversion and a higher ethylene yield could be reached, parallel with a reduced coke formation rate, when cracking these mixtures in furnaces with longer residence time. simulations at similar feed compositions, total olefin content of which was 15.27%, were carried out with three values of cot and yield data were compared with those obtained from reference furnace. st/hc ratio was adjusted similarly in all three furnaces. results are shown in fig. 7. as it was expected, a higher conversion of n-butane could be achieved both in cf2 and cf3 furnace than in the reference (cf1) furnace. yield of ethylene is by 7% higher in cf2 and by 11.1% in cf3 at same cot. though the coke formation rate is much bigger in both furnaces, by 21% and 32% respectively, this quantity of coke will be deposed on a five times higher surface in cf2 and on a ten times higher one in cf3. taking into consideration the differences in residence times as well, it can be concluded that a 35-40% longer online operation period is expectable in case of both cf2 and cf3. 0 10 20 30 40 50 60 pr od uc t y ie ld s, m /m % cf1 cf2 cf3 cf1 cf2 cf3 cf1 cf2 cf3 n-butane propylene ethylene cot=83 cot=840 cot=845 figure 7: yield comparison at furnaces with different residence time conclusions when thermal cracking of recycled hydrocarbon gas mixtures occurs in industrial furnaces, the feedstock contains a relatively large amount of unsaturated components such as olefins and diolefins, a special attention has to be paid on coke formation since these compounds are coke precursors. the simulation study, carried out by means a computer model developed for examining thermal cracking of recycled gas mixtures, confirmed that variation opportunities originating from very different feed compositions can be harmonized well with operating parameters of the furnaces, with the purpose of achieving a maximum profitability. as it was shown, coke formation rate can significantly be reduced by decreasing olefin content of the feed. this can be done by mixing fresh hydrocarbons into the recycled streams like ethane and/or n-butane. according to industrial practice, recycled ethane is always available and n-butane is also worth to be purchased for this purpose. in conclusion, recycled streams cracking in 45 furnaces with longer residence time looks to be a good alternative for olefin producers. of course, the hydrogenation reactor upstream the cracking furnace as well as its catalyst has a main role in this complex process. nomenclature δhk – heat of reaction k [j/mol] a – surface area per unit axial distance [m2] ci – concentration of reactant i [mol/m3] cpi – heat capacity of species i [j/kg/k] d – diameter of pipe/fitting [m] ƒ – friction factor [-] gc – acceleration of gravity [m/s2] l – equivalent pipe length [m] nc – number of species nr – number of reactions rk – rate of the reaction k [mol/m3/s] t – temperature of cracked gas [k] t – time [s] t – mean residence time [s] tfb – temperature of firebox [k] u – overall heat transfer coefficient from the firebox to cracked gases [w/m2/k] v – convective velocity of cracked gas [m/s] x – axial distance along the reactor [m] αki – stoichiometric coefficient of component i in the reaction k δp – pressure drop [mpa] ρ – density of cracked gas [kg/m3] acknowledgement support provided by tvk olefin unit operational and laboratory staff is gratefully acknowledged. references 1. sundaram k. m., froment g. f.: chemical engineering science, 1977, 32, 601-608 2. sundaram k. m., froment g. f.: chemical engineering science, 1977, 32, 609-617 3. sundaram k. m., froment g. f.: industrial engineering chemistry fundam., 1978, 17, 174-182 4. van damme p. s., narayanan s., froment g. f.: aiche journal, 1975, 21 1065-1072 5. froment g. f., van de steene b. o., van damme p. s., narayanan s., goossens a. g.: industrial engineering chemistry proc. des. dev. 1976, 15, 495-504 6. ranzi e., dente m., pierucci s., biardi g.: industrial engineering chemistry fundam., 1983, 22, 132-139 7. froment g. f., van de steene b. o., vanden berghe p. j.? aiche journal, 1977, 23, 93-105 8. dente m. e., ranzi e. m., barendregt s., goossens a. g.: radical reaction mechanisms in the pyrolysis of light hydrocarbons. aiche-meeting 1979 9. dente m. e., ranzi e. m., goossens a. g.: computers chemical engineering, 1979, 3, 61-75 10. willems p. a., froment g. f.: industrial engineering chemistry research, 1988, 27, 19591971 11. dente m. e., ranzi e. m.: mathematical modelling of hydrocarbon pyrolysis reactions. academic press, 1983 12. poutsma m. l.: journal of analytical and applied pyrolysis, 2000, 54, 5-35 13. savage p. e. journal of analytical and applied pyrolysis, 2000, 54, 109-126 14. sadrameli s. m., green a. e. s.: journal of analytical and applied pyrolysis, 2005, 73, 305-313 15. zou renjun, lou qiangkun, liu huicai, niu fenghui: industrial engineering chemistry research, 1987, 26, 2528-2532 16. plehiers p. m., reyniers g. c., froment g. f.: industrial engineering chemistry research, 1990, 29, 636-641 17. kopinke f-d., zimmermann g., reyniers g. c., froment, g. f.: industrial engineering chemistry research, 1993, 32, 56-61 18. kopinke f-d., zimmermann g., reyniers g. c., froment, g. f.: industrial engineering chemistry research, 1993, 32, 2620-2625 19. gál t., lakatos b. g.: applied thermal engineering, 2008, 28, 218-225 20. gál t., lakatos b. g.: chemical engineering and processing: process intensification, 2008, 47, 603612 microsoft word b_10_r.doc hungarian journal of industrial chemistry veszprém vol. 38(2). pp. 107-111 (2010) state of process developments and trends in hard gear finishing m. lukács department of production engineering, university of miskolc, 3515 miskolc pf.: 15, hungary lukacs_miklos@freemail.hu this paper summarises and presents the dominant processes with a geometrically non-defined cutting edge. the review reflects on the methods of generating and profile gear grinding applied in these days industry. the analyses of the machine tools applied in several processes include functionality, machining quality, productivity and economy. i summarize the most important innovations linked to the elements of the manufacturing system, highlighting the economical application of galvanic bonded cbn grinding wheels trough the combination of processes. i display the processes and tools fexibility, productivity and it’s field of application. keywords: gear finishing, combined process introduction the constantly developing automotive industry demands the production of gearboxes to become faster, more economical and precise. the requirements set up against modern gears pose new challenges to the constructors and the technologists. to reach the lowest possible weight, the top layer of the gearing must be hard and wear-resistant, while the gear core and the gear shaft must be high-strenght to endure the dinamic effects and resist the fatigue. to compensate the load-depending deformation of the gearing and guarantee the undisturbed tooth engagement at the same time, geometric modification of the gearing geometry, as well as form and position modifications are applied. at the beginning of the process chain of gear manufacturing, we shape up the gear geometry before the part gets heat treated. the geometry of the wheel body and the gearing can be made by either forming processes like forging in dies or sintering or cutting processes. pre-machining is usually in conjuction with the subsequent heat treatment, generally case hardening. due to the heat treatment, the material characteristics of the gear are modified and the gearing geometry becomes distorted, which necessitates hard finishing of the wheelbody and the tooth flanks. the major problem of the treatment is the unpredictable nature of these distorsions. thus gear hard machining is the necessary final process step to achieve the most important goals: maximum load capacity and minimum running noise. the hard fine machining of the gears can be achieved applying processes either with geometrically well defined or with non-defined cutting edges. regarding the wheel body, a strong competition can be observed between hard turning cylindrical and face grinding because environmental awareness receives increasing emphasis besides productivity. the hard fine machining of the tooth flanks is mostly performed with geometrocally non-defined cutting edges due to its maximum achievable gear quality. the following section is focusing on the most productive processes of gear grinding [1]. the comparison of gear grinding processes heat treatment is the core step of the high quality production of high-speed and high-loadability gears. these gears are case hardened to maximize the strenght of the tooth flank and tooth dedendum, in addition to minimising their dimensions and weight at the same time. figure 1: abrasive processes for hard gear finishing [4] the hard fine macining of gears is unaviodable due to the fact that the parts are deformed during heat treatment. the most economical way of machining the parts with 50hrc or harder surface is by grinding, where only a layer of about 0.1–0.15 mm is ground off the tooth flank. in the following section, i classify the gear grinding processes after fig. 1 [4]. 108 discontinuous profile grinding with discontinuous profile grinding, the tooth flanks of a gear can be either ground separately or jointly depending on the number and set up of the grinding wheels. the profile of the grinding wheel is usually identical to the profile of the workpiece in normal section. the wheel must always be set up with the helix angle β to the normal section of the workpiece. in order to reduce the deformation of the grinding wheel occurring due to grinding, the axial forces must be reduced and their occurence avoided. there are several variations in the set up of the grinding wheels to avoid these effects. discontinuous profile grinding is currently applied for modules of 1–35 (40) mm for internal and external spur gear manufacturing [3, 4]. continuous profile grinding continuous profile grinding of tooth flanks is an attempt to increase productivity by using a globoid worm-shaped grinding wheel. the tool surrounds a determined part of the workpiece. the globoid worm grinding wheel can only be used for one specific workpiece geometry. therefore, this process is recommended for serial or mass production. this process was developed to the level where it was suitable for serial production around 1980. due to the microscopic grinding structure, which often causes a wheezing noise in the gearbox, gear honing is usually applied after continuous profile grinding. in 1997 a special machine tool was introduced on the market which included continuous profile grinding and the honing process in one setting. a noticable increase in productivity could be reached compared to the high technology of the time. further advantages of this process are high precision and the repeatability of the gearing quality. in spite of the improvements the process is no longer competitive compared to the continuous generating grinding [3, 4]. discontinuous generating grinding during discontinuos generating grinding the tooth flank of the spur gear will be shaped stroke by stroke with a double conical grinding wheel by poligonical small cuts. this process was industrially applied for the first time around 1930. within the technology of discontinuous generating, single flank and double flank grinding can be distinguished. single flank grinding generates better grinding accuracy compared to double flank grinding because the tool can be optimally adjusted to the machining task. this flexible process is able to machine workpieces with a module of 35 mm and a diameter of approximately 4000 mm. combining the advantages of the two precesses, it is possible to perform the roughing operation by double flank grinding and the finishing process by single flank grinding on modern machine tools [4]. continuous generating grinding during the countinuous generating grinding process a single pass or multi pass worm-shaped grinding wheel is continuosly moving along the gear like a hob. the shape of the grinding worm corresponds with the profile of a straight gear rack. the geometry of the worm grinding wheel only depends on the workpiece geometry, i.e. module and penetration angle. during the process the machine tool has a multi point contact with the workpiece, which is responsible for the high productivity due to the fact that more than two flanks can be ground. becouse of the limited width of the grinding worm, this process cannot be used for the machining of large-size gearings. it is currently limited to small and medium sized modules of 8 (10) mm and a diameter of 1000 mm. several process options are distinguished. during pendulum grinding, the worm grinding wheel is fed for a constant small amount at the upper and lower dead centres. in between it is shifted in axial direction to make use of unworn abrasive grains. this process version is called diagonal generating grinding. during shift grinding new areas of the grinding worm are screwed in the cutting zone to compensate wheel wear [3, 4]. process developments and trends in the following section, i am presenting the main process developments applied in the hard finishing of case hardened gears at gearbox manufacturing. developments regarding the work piece during the manufacturing process a kind of heat treatment follows pre-machining, which results in the distorsion of product geometry. the major problem of the heat treatment is the unpredictable nature of these distorsions. experiments were made to eliminate this effect by applying the fem analisys on the process. in recent years, attempts have been made to replaace gear hobbing with precision forging in the gear process chain. the high costs of die making and complicated optimisation qualify this concept exclusively for large batch production. this results in new challenges for the grinding processes. the most critical area to be dealt with is the control of the stock allowance. thermal distortions especially for helical gears might result in unacceptable high allowance on individual tooth flanks bearing the danger of grinding burn [4]. developments of the clamping system in recent years radical canges have been applied both in the machine tool and the workpiece clamping system due to the variable demands. naturally, machine tools possess extremely stiff clamping devices to hold the tool-set containing two or four grinding tools in the right position. 109 for example, one specific tool set is applied for the roughing and finishing of gearing in case two different tools are assembled on the grinding spindle. for the concentric clamping of gears shafts and gears, hydro expansion clamping mandrel or collet are applied, witch is part of the gear grinding monitoring system due to the sensors built in [6, 7]. development of the machine tool trendsetting is the construction of special machine tools for particular applications, which can be offered at very reasonable prices. on the other hand, the target has been set to grind high precision gears in any claimed size and geometrical modification. this goal is achievedby by applying machine tools in varying sizes but with identical kinematics. all in all the time of universal machine tools is gone in mass production. current high-tech is the use of thermally stabilized machine tool structures with integrated dressing units with their own nc-controlled axes. to absorb harmful vibrations polymeric concrete is applied in the frame structure. to reach high precision workpiece movement, linear movelemt drives are built in the machine tool, fitted with measurement and sensor technology. in order to fulfill the “first part good part” philosophy, gearing measurement technology is applied with grinding, measuring, grinding [6]. developments of the tool set for the sake of larger productivity, single-layer electroplated cbn grinding wheels gain ground in the area of mass production. cbn grinding wheels are usually fabricated with a single layer of abrasives that are applied to a steel core using a layer of electroplated nickel. the plating thickness on these wheels is maintained at 50% to 70% of the nominal crystal size. the size of the cbn crystals and the topographical characteristics of the wheel can influence the surface roughness and the grinding texture. in case of wheel selection, the most important factors are cbn crystal toughness and nickel plating thickness. the best performance is obtained with a combination of higher toughness crystals and thinner plating layers. the useful life of these wheels is restricted by the single abrasive layer that exists and the limited amount of crystal exposure above the nickel plating [2, 5]. because of the high tool costs of non-dressable cbn worm grinding wheels, the use of dressable cbn worm grinding wheels is considered. experimental investigations of the dressing of vitreous bonded cbn worm grinding wheels reveal the possibility of grinding gearings. contrary to single layer electroplated cbn worm grinding wheels, vitreous bonded dressable cbn grinding worms have an essential advantage regarding their flexibility during dressing and topography generation. these dressable tools are very common in the industry because the costs of procurement and maintenance make the tools very economical for small batch production. nowadays it is an important requirement against machine tools and tool sets to have the possibility of applying high level process combination. this means that two workpeaces can be ground simultaneously or more than one tool applied in the same tool set [4, 6, 7]. developments of the control and diagnostic systems from the aspect of production stability, it is essential to follow the grinding process through a monitoring system. the most common machine tool control system applied in generating grinding machines is the siemens 840d, which includes its own complex generating grinding software, which can significantly ease machine tool programming. the requirements against control systems are higher and higher in the acpect of both measuring cycle between roughing and finishing, and the adequate monitoring of the grinding process. for example in case of machine tools capable of performing discontinuous profile grinding as well as part generating grinding, it is not rare to have 12 controlled axes. to avoid or detect grinding burn, the grinding process is observed by sensors and the control system maintains the process characteristics under a limit value. this can be done by power monitoring, when the power portion used for material removal is monitored. in case of acustic emission systems, the harmful vibrations are detected, which are generated along with inappropriate technical parameters and lead to grinding burn. in case of micromagnetic measurement technologies, the changes in the physical characteristics of workpiece surfaces are observed [4]. the examination of process combination the main goal is to increase productivity and benefit from the advantages of the two specific hard finishing processes, while avoiding their disacvantages; for this end, several types of process combinations are applied in the industry. roughing and finishing with different tools utilising the same process is considered the lowest level of process combinations. this is the case with continuous generating grinding and profile grinding. advantages can be seen in the optimized specification of the grinding wheel. the next level of process combinations is seen in the simultaneous use of different hard finishing processes in one machine tool. a great example for this solution is the process combination of discontinuous profile grinding and continuous generating grinding. it is possible to grind two gearings on one shaft. this solution is viable for gears shafts because all of the gearings can be completed in one clamp. one specific tool set is applied for each of the two gears, thus four different tools are assembled on the grinding spindle. in this case the machine tool can control the four grinding tools. the combination of processes is of course always combined with the increasing purchase costs of the machine tool, especially if the integrated processes have different kinematics. but a reduction of the manufacturing time 110 can be achieved, especially if otherwise the machining has to be done on different machines after each other. nowadays the highest level of process combination in the field of hard finishing processes is seen in the complete machining of a whole wheel body. this includes the inner diameter bore and/or ground bearing shoulders and plane surfaces and the tooth flanks [2, 4]. tehnical conditions of the experiments this investigation was undertaken to evaluate the effect of different process combinations on gearing quality. during the experiment i measured every tenth workpiece of the batch of 300 pieces applying the method described below. high gearing quality and process safety can be achieved with the combination of discontionuous profile grinding and continuous generating grinding. the use of the worm-shaped grinding wheel results in high productivity and the low occurence of grinding burn instead of higher stock allowance, while the profile grinding disc warrants high gearing quality. during the experiment three versions of process combinations were investigated. the first version is the roughing and finishing of tooth flanks by profile grinding disc. the second version is roughing by grinding worm and finishing by profile grinding disc. the third version is roughing and finishing by grinding worm, which is a new field of application. the comparison of process combinations is demonstrated through the grinding of the long gearing of a layshaft. the conditions of the experiment can be seen below. the machine tool is a kapp kx1 gear grinding center. tool data: roughing grain size: b252 finishing grain size: b64 gringind with worm-shaped grinding wheel: number of threads: 4 tip diameter of worm: dm1 = 161.511 mm mean skew angle: β = 83.8160° machined pressure angle: α = 22° axial distance: ab = 128.999 mm spindle revolution: nc = 5900 min-1 spindle inclination: b = 15.319° grinding with profile grinding disc: tool diameter: d = 109.981 mm cutting speed: vc = 35 m/s spindle revolution: nc = 6078 min-1 measuring was done using a klingelnberg p26 type automatic cnc controlled gear measuring center. the technical data of the machined gear are as follows: number of teeth: z = 18 normal module: mn = 4.7 transverse modul: mt = 5.0691 pressure angle: α = 20° lead angle: β = 22°, right pitch circle dimaeter: d = 91.244 mm addendum circle dia.: da = 106,5 mm root circle diameter: df = 82.1 mm profile displacement: x = 0.55462 face width: b = 36 mm base tangent lenght: wk = 51.765 mm number of teeth: k = 4 analisys of experimental results the measured parameters are as follows: base tangent lenght profile and lead pitch error composite pitch error radial runout table 1: results of the measurements process combination profileprofile wormprofile wormworm pitch error left + 2.2 2 3 pitch error left 2 2 3 pitch error right + 3.2 2 3 pitch error right 4.8 2 3 composite pitch error left 6 5.1 10 composite pitch error right 20 6.9 11 radial runout 14 2.5 10 the figures in the first table represent the average of the measured deviations expressed in micrometers. the second column shows the first process combination, i.e. roughing and finishing using profile grinding discs. due to its low productivity, this combination is only used when the other combinations fail. as it can be seen, the pitch error value on the left tooth flanks alternate between -2 µm and 2.2 µm. however, on the right tooth flanks, this value increased to +3.2 µm and -4.8 µm. the profile disc was deformed by the axial forces, which were produced by the irregular stock allowance on the tooth flanks. the composite pitch error follows this trend as it shown in the chart. the radial runout value is 14 µm, thus excentricity is 7 µm. the second process combination is roughing applying grinding worm and finishing by profile grinding disc. the profiles of the right and the left tooth flank follow the same trend as roughing by the grinding worm had already resulted in even stock allowance. the worm has higher stiffness than the profile disc and the grinding forces cannot deform it. the quality of the profile and lead is ensured by the profile grinding disc during finishing. the values represent this high process stability and the low values of the deviations. finally, the process of roughing and finishing using the grinding worm is analysed. the profile and the lead are similar to the results of the previuos process combination. the trend of the pitch errors is not as regular as seen at roughing and finishing by profile discs. on the left tooth flanks the pitch error alternate between +3 μm and -3 μm. on the right tooth flanks the same values seen. the radial runout value 10 μm means 5 μm excentricity. 111 0 5 10 15 20 25 pitch error left + pitch error left pitch error right + pitch error right composite pitch error left composite pitch error right radial runout μm error comparation of combined processes prof ile-profile worm -profile worm-worm figure 2: conclusions conclusions summing up the above described findings, we can say the application of grinding worms represents a significant improvement compared to the use of profile discs. the set of individual errors is the same in case of all the three processes but the trend of composite pitch error is more favorable when roughing is done by grinding worm and the finishing by profile disc. the best results can be achieved by combining the advantages of the two processes. roughing by the gringing worm is very productive and the possibility of grinding burn is minimal. the profile disc ensures the quality of the tooth flank but the discontinuous process increases the primary processing time. this disadvantage can be eliminated with the application of grinding worms both during roughing and finishing but the increasing productivity is at the expense of gearing quality to a certain extent. all in all developement points towards the application of grinding worms because of their high productivity and the low wear due to the increased grain number on the tool surface. the application of superabrasives like cbn revealed considerable cost advantage due to the number of gears that can be ground by one a tool with a single layer of electroplating . references 1. j. kundrak, b. karpuschewski, k. gyani, et al.: accuracy of hard turning, journal of materials processing technology, 202 (1-3), 2008, 328–338. 2. j. gégény: precíziós megmunkálások gyémánt és köbös bórnitrid szerszámokkal, nyíregyháza, biomed center bt., 2006, 85-164. 3. liebherr: gear cutting technology practise handbook, 94–107. 4. b. karpuschewski, h.-j. knoche, m. hipke: gear finishing by abrasive processes, cirp annals manufacturing technology, 57, 2008, 621–640. 5. r. p. upadhyaya, j. h. fiecoat: factors affecting grinding performance with electroplated cbn wheel, cirp annals – manufacturing technology, 56, 2007, 339–342. 6. www.kapp-coburg.de 7. kapp-verzahnungszentrum kx1 betriebsanleitung. user manual p. 213. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 /colorconversionstrategy /cmyk /dothumbnails false /embedallfonts true /embedopentype false /parseiccprofilesincomments true /embedjoboptions true /dscreportinglevel 0 /emitdscwarnings false /endpage -1 /imagememory 1048576 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word b_22_r.doc hungarian journal of industrial chemistry veszprém vol. 38(2). pp. 163-167 (2010) research of the mechanism of plastic strain in case of tempered steel in hard turning g. szabó department of production engineering, university of miskolc, 3515 miskolc, egyetemváros, hungary e-mail: gergely.szabo@uni-miskolc.hu the paper deals with the strains of removed chip and the root of the chip occurring in hard turning as finish manufacturing procedure, in case of orthogonal cutting. it examines the connections of thermal occurrence and plastic strains by the means of finite element method simulation. for the simulation the data of experiments done previously were used. in the paper the change of the morphology of chip formation is compared depending on the cutting speed. keywords: hard turning, plastic strain, chip morphology introduction nowadays, because of the increased loads, engineering industrial products require better and better accuracy, quality (e.g. wear resistance, etc.). one fulfilment method of this requirement can be solved by the increase of the number of hard, hardened surfaces (>45 hrc) on the components. as conventional finish machining, grinding has a tested, well established technology, although it can be noted that the material removal rate and the possibility of concentration of operations are relatively low. the appearance and spread of super hard tool materials (e.g. pcbn) opened way to finish machining (e.g. hard turning) of hardened steels by cutting tools having single point cutting edges. because of the physical and mechanical characteristic of hardened steels and the pcbn tool material and also the needed edge formation and the applied cutting conditions, the process of chip removal differs from the traditional turning. by the finite element (fem) simulation we wish to prove, on the base of scientific literature [1, 2, 3], the special shape of the chip and the mechanism of chip removal. chip removal in case hard turning in the case of hard turning the removed chip leaves with special mechanism usually [3]. the shape of the chip removed, according to the scientific literature, can be seen in fig. 1 [2]. the negative tool rake angle creates high compressive stresses both on the cutting edge and in the material. as a result, the material is parted by cracking and plasticisation and chips are formed (fig. 2). it removes from the chip root as a chip segment. figure 1: shape of chip can be removed at hard turning [2] owing to the brittleness of the material, the high compressive stress initially leads not to a material flow but to formation of a crack. this crack releases the stored energy and thus acts as a sliding surface for the material segment, allowing the segment to be forced out between the parting surfaces [4]. tool workpiece b' a b e f d d' d' ap d c ? ? 'y ’ y figure 2: a supposed mechanism of chip formation in hard turning [3] 164 while the tool reaches point a from b’, there is a thermal tempering for a while in interval bd, later this interval gets back to its original strength and along the be interval it bonds into the direction of the flank of the tool. the extent of the bulge of the tooth shape depends on the values of ψ [3]. as the ψ changes periodically, according to the designation in fig. 2, in case of ψ < ψ’ point c is situated on interval dd’, while in case of ψ > ψ’ it remains on bd interval once the chip segment has slid away, renewed cutting pressure results in formation of a fresh crack and chip segment. the heat created in the cutting process supplies the temperature increase needed for plastification of a small section of the chip material [3]. modelling of chip formation with fem-simulation in case of hard turning nowadays one of the most effective analysing, simulation procedures of physical processes is the finite element method (fem). for investigation of plastic strain rates at the root of the chip we have the 2d version of the third wave advantedgetm 5.3 program package, which is optimised for cutting processes. by this program package we can examine the process characteristics in orthogonal cutting, that is why the input data have to satisfy these requirements. that is, the geometrical data of the cutting tool need to be defined in the toolorthogonal plane. the program starts from the johnsoncook equation for calculation of the strain and strain rate [5, 6, 7, 10]. ( ) m roomm roomn red tt tt ceba ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ − − −⋅⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ +⋅⋅+= 1ln1 0ε εσ & where σred is the reduced, ε is the plastic strain, ε& is the plastic strain rate, 0ε& is the reference plastic strain rate, t is the temperature of workpiece, tm is the melting temperature of workpiece material, troom is the room temperature, coefficient a is the yield strength, b is the hardening modulus, and c is the strain rate sensitivity coefficient, n is the hardening coefficient, and m is the thermal softening coefficient. for the definitions of designations showed above, and their interpretation we cannot give more details because of lack of space, they can be found in the quoted literature [5]. the johnsoncook parameters of the material quality of the workpiece are the following: σred = 400 mpa; a = 588 mpa; b = 680 mpa; c = 0.057; n = 0,4; m = 0.7 [6]. during the finite element simulation we intended to prove chip formation mechanism described in paragraph 2, for steels with hardened inserts. it was examined how the change of the vc cutting conditions affects the frequency chip segment to be forced out. besides the segment formation and the characteristic of the emerging force components (passive force and main cutting force) were compared. experimental condition the input parameters (for the simulation) of the machining operation can be found in table 1. table 1: research input parameters workpiece workpiece length 5 mm workpiece height 3 mm workpiece material cubic boron nitrid tool rake angle -6° rake face length 3.0 mm relief angle 6° relief face length 3.0 mm cutting edge radius 0.01 mm material 20mncr5 simulation max. number of nodes 24 000 max. element size 0.1 mm min. element size 0.01 mm process depth of cut (ap) 0.1…0.2 mm length of cut 3 mm feed 0.05…0.2 mm/rev cutting speed 90…240 m/min friction coefficient 0.35 coolant not used results of the fem-simulation having completed fem runs the size of plastic deformation connected to different cutting conditions (figs. 3, 4, 5) and the morphology of the related cutting force (fc) as well as passive force (fp) were examined. (because of the simpler demonstration, the change of the cutting forces will be presented only after the temperatures that become stable, therefore the initial stages cannot be seen). 165 fp [n] fc [n] time [10-4s] f [n] 1 2 3 40 60 80 100 120   a  time [10-4s] f [n] 1 2 3 40 60 80 100 120 fp [n] fc [n]   b  fp [n] fc [n] time [10-4s] f [n] 1 2 3 40 60 80 100 120   c figure 3: the size of plastic strain, the morphology of chip formation and cutting force components in the case of vc = 120 m/min. a, ap = 0.10 mm, f = 0.1mm/ford; b, ap = 0.15 mm, f = 0.1 mm/ford; c, ap = 0.2 mm, f = 0.1 mm/ford time [10-4s]1 2 3 40 60 80 100 120 fp [n] fc [n] f [n]   a time [10-4s]1 2 3 40 60 80 100 120 fp [n] fc [n] f [n]   b  time [10-4s] f [n] 1 2 3 40 60 80 100 120 fp [n] fc [n]   c figure 4: the size of plastic strain, the morphology of chip formation and cutting force components in the case of vc = 150 m/min. a, ap = 0.10 mm, f = 0.1mm/ford; b, ap = 0.15 mm, f = 0.1 mm/ford; c, ap = 0.2 mm, f = 0.1 mm/ford 166 fp [n] fc [n] time [10-4s] f [n] 1 2 3 40 60 80 100 120   a  fp [n] fc [n] time [10-4s] f [n] 1 2 3 40 60 80 100 120   b  time [10-4s] f [n] 1 2 3 40 60 80 fp [n] fc [n]100 120 c figure 5: the size of plastic strain, the morphology of chip formation and cutting force components in the case of vc = 240 m/min. a, ap = 0.10 mm, f = 0.1mm/ford; b, ap = 0.15 mm, f = 0.1 mm/ford; c, ap = 0.2 mm, f = 0.1 mm/ford the chip shapes seen in figs. 3, 4, 5 are shown under different cutting speeds. one speed goes with three combinations of the cutting parameters. it can be observed that with the increase of the cutting speed the number of bulges of the removed chip also increases. however, with the increase of the depth of cut, the size of the bulges increases. the effect of the cutting parameters on the bulges of the chip can be examined by the spacing length of the bulges. the frequencies of the bulge of chip segments are characterized by the length of spacing belonging to the different adjusted parameters. their values can be approximately calculated from the coordinates of the rectangular triangles, expressed in mm-s, being in fig. 6. the changing of shape of the chip having almost regular periodicity and the chip formation mechanism allow to conclude that cutting forces have to emerge with similar periodicity during chip removal (figs. 3, 4, and 5.) the connections between cutting speed and the spacing length of bulge originating from the shear can be seen in fig. 7. coordinates of points given in mm-s figure 6: the calculation of the length of spacing between the originating „saw-teeth” of the developing chip 167 figure 7: connection between chip bulge and cutting speed conclusion fem simulation for case hardened steel was carried out to examine the mechanism of chip formation. as a consequence of the simulation it can be stated that the „saw-tooth” structure forming in chip removal depends on the cutting parameters. in the case of high enough cutting speed (vc = 240 m/min), however, it decreases to its minimum, or even disappears. this morphology of formation can be related to the heat formation characteristic of removal process, thus may affect the state of the surface layer of the workpiece. the research of these relationship needs furtherexperiments. acknowledgement the work was presented by the support of the hungarian scientific research fund (number of agreement: otka k 78482), which the authors greatly appreciate. references 1. z. pálmai: fémek forgácsolhatósága, műszaki könyvkiadó, budapest, 1980, 61–69. 2. i. al-zkeri: finite element modeling of hard turning. vdm verlag dr. müller. saarbrücken, 2008, isbn: 978-3-639-110340. 3. m. a. davies, c. j. evans, y. chou: on chip morphology, tool wear and cutting mechanics in finish hard turning. annals of the cirp vol. 45/1, 1996, 77–82. 4. w. könig, r. klinger, r. link: machining hard materials with geometrically defined cutting edgesfield of applications and limitations. annals of the cirp vol. 39/1/1990, 61–65. 5. third wave advantedgetm user’s manual, version 5.1. 6. čsn 41 4220/iso 683/11-70. 7. a. g. mamalis, j. kundrak, a. markopoulos et al.: on the finite element modelling of high speed hard turning, international journal of advanced manufactoring technology, 38/5-6, 2008, 441–446. 8. w. zebala: simulation of cutting with the defined tool geometry, journal of machine engineering (issn 1642-6568), 5/3-4, 2005, 109–119. 9. j. kundrak, a. g. mamalis, a. markopoulos: finishing of hardened boreholes: grinding or hard cutting? materials and manufactoring processes, 19 (6), 2004, 979–993. 10. j. kundrak, w. zebala, v. bana: examination of cutting zone deformation occurring in hard turning by fem simulation. manufacturing technology, journal for science, research and production, 3, 2003, 3–7. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word a_19_r.doc hungarian journal of industrial chemistry veszprém vol. 38(1). pp. 67-70 (2010) mechanical properties of polypropylene/multi walled carbon nanotube composites a. szentes1 , g. horváth1, cs. varga2 1institutional department of chemical engineering, university of pannonia h-8200 veszprém, egyetem u. 10., hungary, e-mail: szentesa@almos.uni-pannon.hu 2institutional department of hydrocarbon and coal processing, university of pannonia h-8200 veszprém, egyetem u. 10., hungary carbon nanotubes (cnts) are promising additives for polymer composites due to their excellent special mechanical, electrical, and thermal properties. polypropylene/multi walled carbon nanotube (pp/mwcnt) composites were produced in single and double screw extruders. the composites contained 0.5, 2, 3 and 5 wt% multi walled carbon nanotubes (mwctn). for comparison, composites with carbon black as an additive instead of mwcnt have been made. the melt flow rate (mfr), flexural modulus, yield strength, tensile strength and heat deflection temperature (hdt) of the composites have been examined. keywords: carbon nanotubes, polypropilene, composites, mechanical properties introduction carbon nanotubes (cnts) were discovered in the soot of arch discharge by sumio iijima in 1991 [1]. carbon nanotubes are allotropes of carbon and members of the fullerene structural family. carbon nanotubes are categorized as single-walled nanotubes (swcnts) and multi-walled nanotubes (mwcnts) [2]. mwcnts consist in a variable number of graphene sheets rolled coaxially into a cylinder of nanometric diameter [3]. the interlayer distance in multi-walled nanotubes is close to the distance between graphene layers in graphite, approximately 0.34 nm. typical diameter of mwcnts are 10–20 nm, their typical length is above 20 μm. several production methods have been developed aiming at the production of carbon nanotubes in large scale, such as laser vaporization [4], electric arc discharge [5] and catalytic chemical vapor deposition of hydrocarbons over metal catalysts (ccvd technique) [6]. the first two methods are high temperature processes and can produce high quality nanotubes. however, the yields are poor and hence not adaptable for large-scale production. in contrast the ccvd technique is a very efficient method to produce multi-walled carbon nanotubes (mwcnts) because this way could be a possibility to produce nanotubes at relatively low temperatures on a large scale at relatively low cost. this method is the most promising method to commercialize the carbon nanotubes growth. in ccvd method transition metals (fe, co or ni) supported on oxides, zeolite or silica are used as catalyst precursor [7]. the combinations of transition metals and supports can be changed depending on the characteristics required, for example the size of the tubes. bimetallic combinations of these transition metals are used for the synthesis of cnts and the relatively high yield and quality have been explained by the characteristic behaviour of this alloy phase [8]. a very effective catalyst is a binary mixture of co-fe. catalysts have been prepared by impregnation method using salts of fe and co. cnts are promising additives for polymer composites due to their excellent special mechanical, electrical, and thermal properties. the special mechanical properties are due to the strong bonding between the carbon atoms that form the carbene plane. the bond length is 0.142 nm which is lower than that in diamond (0.154 nm). the tensile strength of carbon nanotubes is high, 75-times higher than of steel filaments of the same size, and even 15-times higher than of carbon fibers. on the other hand, the density of carbon nanotubes is one sixth of steel. their densities can be as low as 1.3 g/cm3. these facts give excellent opprotunities to produce very strong materials with are light at the same time. plastics enhanced with carbon nanotubes might be the new family of light and strong composites. [9] extrusion is the most effective and most important technology in polymer processing. this makes the thermoplastic polymer plastic, homogenizes its viscous melt, and degasifies it, if necessary. after this, the polymer is compressed, extruded in an open instrument of constant diamater and cooled down. thus, polymer products of constant diameter can be produced in the desired legth, in continous run. [10] 68 experimental for the experiments, mwcnt products prepared by the institutional department of chemical engineering of the university of pannonia were used. the mwcnt is unpurified, it contains the catalyst and the catalyst carrier in 10 wt%. according to transmission electron microscope (tem) images, the diameter of the tubes is between 10 and 20 nm (fig. 1). the length of the tubes cannot be precisely measured. according to the scanning electron microscope (sem) images, the length of the tubes is greater than 50 μm (fig. 2). figure 1: tem images of multi walled carbon nanotubes figure 2: sem images of multi walled carbon nanotubes polypropylene-based (pp) composites were prepared with a brabender-type single screw extruder (sse, zone temperatures: 1: 195 °c, 2: 200 °c, 3: 205 °c, 4: 210 °c, revolutions per minute: 40), and with a werner & pfleiderer-type double screw extruder (dse, zone temperatures: 1: 195 °c, 2: 205 °c, 3: 210 °c, 4: 210 °c, 5: 210 °c, 6: 210 °c revolutions per minute: 100), to decide which method gives better results. the composites contain mwcnt or carbon black (c) in different quantities (0.5 2 3 and 5 wt%). the composites were also prepared with carbon black to make sure that the change in properties is because of the cnts. the composites with the carbon black additive were prepared with the double screw extruder. the content of the composites is summarized in table 1. the normalized specimens with dimensions of 10 mm x 4 mm x 80 mm were produced with injection moulding (temperature: 180 °c, injection melt rate: 0.011 m/s, cooling time: 30 s) for the normalized examinations. the melt flow rate (mfr, patent: iso 1133, 230 °c, 2,16 kg), the flexural modulus (patent: iso 178), the yield strength (patent: iso 527), the tensile strength (patent: iso 527) and the heat deflection temperature (hdt, patent: iso 75) have been measured. table 1: the content of the composites sample code pp (wt%) mwcnt (wt%) c (wt%) pp 100 pp/cnt/sse/0.5 99.5 0.5 pp/cnt/sse/2 98 2 pp/cnt/sse/3 97 3 pp/cnt/sse/5 95 5 pp/cnt/dse/0.5 99.5 0.5 pp/cnt/dse/2 98 2 pp/cnt/dse/3 97 3 pp/cnt/dse/5 95 5 pp/c/dse/0.5 99.5 0.5 pp/c/dse/2 98 2 pp/c/dse/3 97 3 pp/c/dse/5 95 5 results fig 3 shows the effect of different additive contents on the mfr of pp/mwcnt and pp/carbon black melts. the mfr decreased with increasing cnt-content for pp/mwcnt composites prepared with both extruders. the value of mfr decreased more for samples prepared with the double screw extruder (pp/cnt/dse) than for samples prepared with the single screw extruder (pp/cnt/sse). this might be explained by the fact that a better homogeneity can be reached with the double screw extruder, than with the single screw extruder. the mfr values of samples containing carbon black did not change significantly. figure 3: effects of different additive contents on the mfr of pp/mwcnt and pp/carbon black melts the value of the flexural modulus is indicative of the sample’s flexibility. fig 4 shows the effect of different additive contents on the felexular modulus of pp/mwcnt and pp/carbon black composites. by increasing the mwcnt-content, one expects the flexural modulus to increase, too. as shown in fig. 4, in the case of pp/mwcnt composites produced with the double screw extruder (pp/cnt/dse), the value of the flexural modulus inreased significantly. as compared to polypropylene, the flexural modulus of the composite produced with the double screw extruder and which contains 5 wt% 69 mwcnt (pp/cnt/dse/5) increased by 64%. an 18% increase is measured in the case of the composite produced with the single screw extruder. by increasing the concentration, the values are significantly better with the double screw extruder, compared to the single screw extruder. in the case of the carbon black additive (pp/c/dse), the flexural modulus increased by approx. 30%, irrespective of the amount of additive. figure 4: effects of different additive contents on the felexular modulus of pp/mwcnt and pp/carbon black composites the yield strength is the highest tensile stress that the sample is able to withstand during the tensile measurement. for certain materials, such as polypropylene, the value of the yield strength is different from the value of the tensile strength. fig 5 shows the effect of different additive contents on the yield strength of pp/mwcnt and pp/carbon black composites. for the mwcnt composites produced with the double screw extruder (pp/cnt/dse), the yield strength increases with the cnt content, whereas this value decreases above 0.5 wt% mwcnt content for the composites produced with the single screw extruder (pp/cnt/sse). the value of the yield strengtjh is 36.3 mpa for the sample containing 5 wt% mwcnt produced with the single screw extruder (pp/cnt/sse/5), which is identical to the sample’s tensile strength. in the case of the carbon black additive (pp/c/dse), the tensile strength increases with 10%, irrespective of the amount of the additive. figure 5: effects of different additive contents on the yield strength of pp/mwcnt and pp/carbon black composites fig 6 shows the effect of different additive contents on the tensile strength of pp/mwcnt and pp/carbon black composites. the tensile strength is the stress under which the sample is torn. the tensile strength increases with the increasing percentage of the additive. the composite produced with the double screw extruder that contains 0.5 wt% mwcnt (pp/cnt/dse/0.5) has an outstanding tensile strength of 36.7 mpa which means an increase of 36% as compared to the blank polymer (pp). the tensile strength values increased slightly for the composites containing carbon black, but this increase is significantly small compared ot the mwcnt composites. the composite containing 5 wt% carbon black has the same tensile strength as the 0.5 wt% mwcnt composite produced with the single screw extruder (pp/cnt/sse/0.5), which is 30.7 mpa. figure 6: effects of different additive contents on the the tensile strength of pp/mwcnt and pp/carbon black composites the ability of the materials to withstand heat can be measured by hdt (heat-deflection) measurements. fig 7 shows the effect of different additive contents on the heat deflection temperature of pp/mwcnt and pp/carbon black composites. figure 7: effects of different additive contents on the the heat deflection temperature of pp/mwcnt and pp/carbon black composites the blank polypropylene sample (pp) has an hdt temperature of 104 °c, which is significantly lower than for the composites containing additives. the value of the hdt temperature increases with increasing the mwcnt contents. the hdt temperature is 118 °c at 0.5 wt% 70 mwcnt (pp/cnt/sse/0.5 and pp/cnt/dse/0.5). the hdt temperature is 4 °c higher for the mwcnt composites produced with the double screw extruder (pp/cnt/dse/2, pp/cnt/dse/3 and pp/cnt/dse/5) than for the composites of the same content produced with the single screw extruder (pp/cnt/sse/2, pp/cnt/sse/3 and pp/cnt/sse/5). it can be concluded, that the properties of the composites produced with the single and the double screw extruder with 0.5 wt% mwcnt content are nearly the same in the most cases, but with increasing mwcnt content, the composites made with the double screw extruder have better properties. the same mechanical value can be reached with lower mwcnt content with the double screw extruder, than with the single screw extruder. the reason for this is the double screw extruder’s better homogenizing ability. according to the measurement results it can be concluded, that the double screw extruder is more appropriate for the production of the pp/mwcnt composites. the composites are more homogeneous, the dispersion of the cnt in the polymer matrix is significantly better than in the case of the single screw extruder. the composites containing carbon black were prepared with the double screw extruder. it can be seen that the amount of carbon black does not affect significantly the mechanical properties of the composite. conclusions polypropylene/multi walled carbon nanotube composites were produced in single and double screw extruders. the composites contained 0.5, 2, 3 and 5 wt% multiwalled carbon nanotube. for comparison, composites with carbon black as an additive instead of mwcnt have been made. the melt flow rate (mfr), flexural modulus, yield strength, tensile strength and heat deflection temperature (hdt) of the composites have been examined. it can be concluded, that the properties of the composites produced with the single and the double screw extruder with 0.5 wt% mwcnt content are nearly the same in the most cases, but with increasing mwcnt content, the composites made with the double screw extruder have better properties. the same mechanical value can be reached with lower mwcnt content with the double screw extruder, than with the single screw extruder. the reason for this is the double screw extruder’s better homogenizing ability. according to the measurement results it can be concluded, that the double screw extruder is more appropriate for the production of the pp/mwcnt composites. the composites containing carbon black were prepared with the double screw extruder. it can be seen that the amount of carbon black does not affect significantly the mechanical properties of the composite. acknowledgment we acknowledge the financial support of this work by the hungarian state and the european union under the tamop-4.2.1/b-09/1/konv-2010-0003 project. references 1. s. ijima: nature, 354, 1991, 56. 2. s. ijima, t. ichihashi: nature, 360, 1993, 603. 3. l. p. biró, j. gyulai, ph. lambin, j. b. nagy, s. lazarescu, g. i. márk, a. fonseca, p. r. surján, zs. szekeres, p. a. thiry, a. a. lucas: carbon, 36, 1998, 689. 4. y. saito, m. okuda, m. tomita, t. hayashi: chem. phys. lett., 236, 1995, 419. 5. t. w. ebbesen, p. m. ajayan: nature, 358, 1992, 220. 6. w. z. li, s. s. xie, l. x. qian et al.: science, 274, 1996, 1701. 7. k. hernadi, z. kónya, a. siska, j. kiss, a. oszkó, j. b. nagy, i. kiricsi: materials chemistry and physics, 77, 2003, 536–541. 8. z. kónya, j. kiss, a. oszkó, a. siska, i. kiricsi: phys. chem. chem. phys., 3, 2001, 155. 9. j. n. coleman, u. khan, w. j. blau, y. k. gun’ko: carbon, 44, 2006, 1624. 10. z. spitalsky, d. tasis, k. papagelis, c. galiotis: progress in polymer science, 35, 2010, 357. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 /colorconversionstrategy /cmyk /dothumbnails false /embedallfonts true /embedopentype false 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word a_12_r.doc hungarian journal of industrial chemistry veszprém vol. 38(1). pp. 59-62 (2010) nonlinear dielectric effect of two-component dipolar fluids s. nagy , i. szalai institute of physics and mechatronics, university of pannonia, h-8200 veszprém, egyetem u. 10., hungary e-mail: nagys@almos.vein.hu we studied the linear and nonlinear dielectric effects in two-component dipolar hard sphere mixtures. in our approach the hard spheres differ by their dipole moments but their diameters are the same. within the framework of the mean spherical approximation we extended the results of our previous work and realized that the formulas which apply to one-component case are readily applicable to mixtures. we performed canonical monte carlo (mc) simulations for three different binary mixtures for various compositions of the components. the theoretical results are in good agreement with the corresponding mc simulation data. the linear and the nonlinear dielectric permittivities obtained from mc simulations are determined from the fluctuation formulas of the total dipole moment of the system in the absence of an applied electric field. keywords: nonlinear dielectric permittivity, linear dielectric permittivity, two-component dipolar mixture, mean spherical approximation, fluctuation formula, monte carlo simulation, dipolar hard sphere introduction the nonlinear dielectric effect (nde) is extremely sensitive to intermolecular (interparticle) interactions, therefore, it is widely used to study the structure of simple (e.g. dipolar molecular) and comlex (e.g. electrorheological) fluids [1, 2, 3, 4]. as shown in our previous paper [5], the nde of one-component dipolar fluids can be described by the mean spherical approximation (msa). in this paper we extend our theory to two-component dipolar-dipolar and dipolar-apolar mixtures. the dielectric permittivity of simple and complex fluids is a function of the internal electric field: εe = ε0 + ε2e2 + ..., (1) where εe – field dependent dielectric permittivity; ε0 – linear dielectric permittivity; ε2 – nonlinear dielectric permittivity; e – internal electric or maxwell field. the relation between the polarization p and the maxwell field e [1] is 4πp = (εe – 1)e. (2) for simple liquids, the assumption that the dielectric is linear is usually reasonable for small electric fields [1]. from eqs. (1) and (2) we obtain that 0 0 41 = ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ ∂ ∂ += ee pπε . (3) in strong electric fields, we have to take into account the second term in eq. (1). substituting eq. (1) into eq. (2) the third order derivative yields 0 3 3 2 !3 4 = ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ∂ ∂ = e e pπε . (4) wertheim [6] reported the msa solution for the linear dielectric permittivity of the dipolar hard sphere (dhs) fluid. within this approximation the linear dielectric constant of the dhs fluid is ( )( ) ( )( ) ,2 0 yq yq ξ ξε − = (5) where ξ(y) is a parameter without any physical meaning. this parameter is determined by the following equations: 3y = q(2ξ) – q(–ξ), (6) ( ) ( ) ( )4 2 1 21 x xxq − + = , (7) where y is the dipole strength function defined as tk my b ρπ 2 9 4 = , (8) where m – dipole moment of particles; kb – boltzmann constant; t – temperature; ρ – density; q(x) – reduced inverse compressibility factor of the hard sphere fluid. 60 the msa has been extended [7] to finite external fields on the basis of a density functional theory (dft). the field dependence of the polarization can be given as ( )( ) ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎣ ⎡ ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −− += p y qemlmp 3 14 ξπβρ , (9) where: langevin function l(x) = coth(x) – 1/x; β – 1/kbt. in our previous work [5] we proposed a formula for the nonlinear dielectric permittivity on the basis of eq. (9): ( ) ( ) ρ ξ βπ ξ βε 4 4 3 4 22 2 45 4 5 m qq ym − −= − −= . (10) it has been found that eq. (10) is in good agreement with the corresponding simulation data. in this paper, we extend our theory to the nonlinear dielectric constant of dhs mixtures. adelman and deutch [8] have given the solution of the msa for the linear dielectric constant of this system. in their theory, the particles differ by their dipole moments, while their diameters are the same. in this restricted case, the same equations apply (eqs. (6-7)), but using the dipole strength function of the mixture defined as ∑ = =′ 2 1 2 9 4 i ii b m tk y ρ , (11) where mi – dipole moment of component i, ρi – density of component i. similarly, the resulting quantity ξ' for the mixture is introduced and denoted by prime. theory microscopic model we examine the linear and nonlinear dielectric effects in binary mixtures that consist of dipolar hard spheres characterized by parameters σ, m1 and m2 interacting via a dipolar interaction between point dipoles embedded at the centers of the particles: ⎪ ⎩ ⎪ ⎨ ⎧ <∞ ≥− = σ σ 12 123 12 21 , , r rd r mm udhs , (12) ( )( ) ( )21122121 ˆˆˆˆˆˆ3 mmrmrm ⋅−⋅⋅=d , (13) where σ – diameter of particles; r12 – distance between the centers; r12 – difference vector between the centers; 12r̂ – unit vector along r12 vector; im̂ – unit vector of dipole moments. linear dielectric permittivity of binary mixtures in order to obtain the dielectric permittivities of the dhs fluids, the field dependence of the polarization has to be known. this function can be obtained from dft methods [9] using the msa results of adelman and deutch [8]: ( )( )∑ = ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎣ ⎡ ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ′ ′−− += 2 1 3 14 i iii p y qemlmp ξπβρ . (14) to calculate the permittivities, we need to know the derivatives of the langevin function up to the third order: ( ) ( ) ( ) 15 2,0, 3 1 0 3 3 0 2 2 0 −=== === xxx dx xld dx xld dx xdl . (15) from the first order derivative of the implicit polarization function (eq. (14)) one obtains ( )ξπ ′− ′ =⎟ ⎠ ⎞ ⎜ ⎝ ⎛ ∂ ∂ = q y e p e 3 4 1 0 . (16) equations (3) and (16) lead to ( ) ( )ξ ξ ξ ε ′− ′ = ′− ′ += q q q y 2 )( 310 , (17) where the relation between the dipole strength function y' and the inverse compressibility q(x) (eq. (6)) was used. nonlinear dielectric permittivity of binary mixtures in order to obtain ε2, we have to calculate the third order derivative of the polarization (eq. (4)). from eqs. (14) and (15) we obtain: ( ) ( )( ) .1 15 2 0 3 3 2 1 4 3 0 3 3 ξ ρ ξ β ′−−⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ∂ ∂ + ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ′− −=⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ∂ ∂ ∑ = q e p m qe p i ii (18) after further rearrangement on the basis of eq. (4) one finds ( ) i i im q ρ ξ βπε ∑ = ′− −= 2 1 4 4 3 2 45 4 . (19) we note that if we reduce the number of components to one, eqs. (17) and (19) reproduce the corresponding pure fluid results, eqs. (5) and (10). monte carlo simulations we have performed canonical (nvt) ensemble monte carlo (mc) simulations to verify our theoretical results. we used n = 512 particles, and the simulations were started from a simple cubic lattice configuration with randomly oriented dipoles. boltzmann sampling, periodic 61 boundary conditions, and the minimum image convention [10] were applied. in order to take into account the longranged part of the dipolar interaction the reaction field method was used. we used the following formulas to calculate the linear and nonlinear dielectric permittivities, respectively, according to [5] and [11]: 2 0 3 41 m v πβε += , (20) ⎟ ⎠ ⎞⎜ ⎝ ⎛ −= 224 3 2 53 90 4 mm v πβε , (21) where ∑ = = n j i 1 mm – the total dipole moment of the system; v – volume of the simulation box. the advantage of the application of these fluctuation formulas is that we didn’t need to apply any external field during the simulation. the triangular bracket denote the ensemble averages of the corresponding total dipole moments in zero external field. the statistical uncertainty of eq. (21) is quite large due to the fourth exponent. therefore we performed 107 – 2·107 production cycles (after 105 equilibration cycles) to obtain resonable results. the statistical errors were calculated from the standard deviations of subaverages containing one million cycles. results and discussion in the following we shall use reduced quantities: ρ* = ρσ3 is the reduced density and (mi *)2 = mi 2/(ktσ3) is the reduced dipole moment of component i. figs. 1a and 1b show the linear and nonlinear dielectric permittivities as functions of the mole fraction of the first component (x = n1/(n1 + n2)) for (m1 *)2 = 0.5 and (m2 *)2 = 1. (the various curves and symbols correspond to reduced densities ρ* = 0.2; 0.4; 0.6 and 0.8 from bottom to top.) the msa results (lines) are in good agreement with the simulation data (symbols). for the linear dielectric constant the statistical errors are smaller than the size of the symbols. figs. 2a and 2b show the results for mixtures where the first component is non-polar (hard spheres): the dipole moments are (m1 *)2 = 0 and (m2 *)2 = 1. the linear dielectric permittivity, therefore, converges to 1 and the nonlinear dielectric permittivity converges to 0 at x = 1. the values for x = 0 in figs. 2a and 2b are the same as the x = 0 values in figs. 1a and 1b. figs. 3a and 3b show the results for a dipolar – nonpolar mixture with a smaller dipole moment of the dipolar component ((m2 *)2 = 0.5). now, the x = 0 values in figs. 3a and 3b agree with the x = 1 values of figs. 1a and 1b. the msa theoretical data are in very good agreement with the corresponding simulation data. these results show that for moderate dipole moments ((m2 *)2 ≤ 1) our msa based theory is valid for two component mixtures as well. in a subsequent publication we extend the present theory to the investigation of chain formation in electrorheological fluids. figure 1a: linear dielectric permittivities of a two-component dhs fluid mixture with (m1 *)2 = 0.5 and (m2 *) = 1 reduced dipole moments at various densities figure 1b: nonlinear dielectric permittivities with (m1 *)2 = 0.5 and (m2 *) = 1 figure 2a: linear dielectric permittivities with (m1 *)2 = 0 and (m2 *)2 = 1 62 figure 2b: nonlinear dielectric permittivities with (m1 *)2 = 0 and (m2 *)2 = 1 figure 3a: linear dielectric permittivities with (m1 *)2 = 0 and (m2 *)2 = 0.5 figure 3b: nonlinear dielectric permittivities with (m1 *)2 = 0 and (m2 *)2 = 0.5 summary in the present study of the nde for dhs mixtures, the following main results have been obtained: 1) from the electric field dependence of the polarization analytical equations have been obtained for the linear and the nonlinear dielectric constants of twocomponent dhs fluids. our results for the linear dielectric permittivity reproduce the corresponding results of adelman and deutch [8]. 2) nvt ensemble monte carlo simulations have been performed to determine the linear and nonlinear dielectric permittivities for various two-component dhs mixtures. 3) we have compared our theoretical results with the corresponding simulation data and obtained very good agreement verifying the validity of our theoretical approximations. acknowledgement we acknowledge the financial support of this work by the hungarian state and the european union under the tamop-4.2.1/b-09/1/konv-2010-0003 project. references 1. c. j. f. böttcher, p. bordewijk: theory of electric polarization, vol. 1, elsevier, new york, 1978. 2. b. groh, s. dietrich: phys. rev. e, 53, 1996, 2509. 3. s. j. rzoska, v. p. zhelezny: nonlinear dielectric phenomena in complex liquids, nato science series ii: mathematics, physics and chemistry vol. 157, kluwer, dordrecht, 2004. 4. r. tao, g. roy: electrorheological fluids, world scientific, singapore, 1994. 5. i. szalai, s. nagy, s. dietrich: j. chem. phys., 131, 2009, 154905. 6. m. s. wertheim: j. chem. phys., 55, 1971, 4291. 7. i. szalai, s. dietrich: j. phys. condens. matter, 20, 2008 204122. 8. s. a. adelman, j. m. deutch: j. chem. phys., 59, 1973, 3971. 9. i. szalai, s. dietrich: j. phys. condens. matter, to be published (2010). 10. m. p. allen, d. j. tildesley: computer simulation of liquids, clarendon, oxford, 2001. 11. p. g. kusalik: mol. phys., 81, 1994, 199. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word content.doc hungarian journal of industrial chemistry veszprém vol. 40 (2) pp. 107–111 (2012) effects of pan bread making on zearalenone levels in artificial contaminated wheat flour t.a. el-desouky , m. may amer, k. naguib food toxicology & contaminants dept. national research center, dokki, cairo, egypt e-mail: eldesoukyt@yahoo.com the ability of saccharomyces cerevisiae (baker's yeast) in reduces of zearalenone during fermenting dough at 25°c and 30°c for 30 and 45 min was studied. the results indicate that content of zearalenone was reduced to 9.44, 19.22, 37.6 and 63.16µg/kg in dough made from flour artificially contaminated with 25, 50, 75 and 100 µg/kg, respectively when the fermentation process at 25°c for 45 min. on the other hand, during fermentation at 30°c the decrease in the content of zearalenone is greater than ever, particularly with increasing duration or time of fermentation to 45 min. the content of zearalenone after fermentation at 30°c for 45 min was 7.52, 17.14, 34.19 and 60.38µg/kg in dough made from flour artificially contaminated with 25, 50, 75 and 100µg/kg, respectively. the reduction percentage of zearalenone after baking pan bread at 180°c for 25 min was 55.98, 62.78, 62.5 and 60.52%.these results indicate that fermentation and baking are effective in reducing zearalenone. key words: zearalenone, saccharomyces cerevisiae, fermentation and baking introduction zearalenone (zea) is a mycotoxin mainly produced by fusarium graminearum and fusarium culmorum, which are common soil fungi in temperate and warm countries, and are regular contaminants of cereal crops worldwide [1, 2]. zea is mainly with corn and wheat but it occurs also in barley and sorghum amongst other commodities frequently used in human and animal diets. the international agency for research on cancer (iarc) has categorized zea as a class 2a carcinogen [3]. zea produces estrogenic effects in humans and animals leading hyperestrogenism. hyperestrogenism may be manifested enlargement of the reproductive organs. zea can cause severe reproductive and infertility problems in farm animals, particularly in swine [4]. specifically, zea can act as an estrogen analog and cause alterations in the uterus of the reproductive tract of swine and affect follicular and embryo development [5]. the function of zea as an estrogen analog is important because swine are monogastric animals with responses similar to humans in many respects [6]. even though most african countries have a climate characterized by high humidity and high temperature which favor growth of moulds, little information is available on the occurrence of fusarium toxins particularly zea in foods and feeds. high contaminations of the raw materials are an ongoing problem. regulatory issues are not available in the field of food exhibition and retailing, and mycotoxin problems have already been associated with some food contamination in some areas in africa [2]. in egypt, several commodities were reported to contain zea especially corn, wheat and rice and walnut [7, 8]. corn from egypt was also found contaminated with high levels of zea that ranged from 9.8 to 38.4 mg/kg [9]. according to fao [10], zea was regulated in 1996 by 6 countries, but by the year 2003 the toxin zea was regulated in foods and animal feeds by 16 countries. limits for zea in maize and other cereals, currently vary from 50 to 1000 µg/kg. although various prevention strategies have been implemented in many countries, they were not enough to manage the problem efficiently in the developing world. in the recent years, many dietary strategies involving microorganisms have been under investigation. many species of bacteria and fungi have been shown to enzymatically degrade mycotoxins [11]. however, the question still remains on the toxicity of the degradation products. saccharomyces cerevisiae has been utilized in food fermentation for several centuries. in the african and asian countries, fermentation is used as a predominant mode of food processing and preservation. many yeast species, especially saccharomyces cerevisiae, play a predominant role in food fermentation along with lactic acid bacteria [12]. in the african fermented foods such as fermented maize dough (kenkey) as well as sorghum beer (pito), saccharomyces cerevisiae constitutes a predominant component of fermentation microflora and the biodiversity of yeast microflora in these foods has been well documented [13]. mycotoxin binding by saccharomyces cerevisiae and lactic acid bacteria have been reviewed recently [14]. the aim of this work was to study the ability of saccharomyces cerevisiae in reduce of zea during fermenting dough at 25°c and 30°c for 30 and 45 min, also study effect of baking pan bread at 180°c on content of zea. 108 materials and method: materials wheat flours (72% extraction) were obtained from the north cairo mills company, egypt. saccharomyces cerevisiae (baker's yeast) was obtained from alhawamdia company fresh comprised yeast according to the egyptian standard (191/2005). methods preparation of artificial contaminated wheat flour one milligram of zea was purchased from sigma, chemical co. (st. louis, mo, u.s.a). zea was dissolved in 1 ml methanol. then taken appropriate size of focus and complemented the larger size makes it easier to control added to wheat flour. four wheat flour samples (1kg each) were aged in various concentrations (25, 50, 75 and 100µg/kg). each of the contaminated wheat flour samples was used for preparation of pan bread. this mixture was stirred until the solvent had evaporated. pan bread making pan bread was prepared by mixing 100g of wheat flour (72% extraction) with 5 g of baker's yeast, 1.5 g of sodium chloride and 75–80 ml of water and hand blended for about 6 min to form the dough. the dough was lift to rest for 30 min at 25°c & 30°c and 85% relative humidity and was then divided into 150g pieces. the pieces were booted in metal pans that had been left to ferment for about 45 min at the same temperatures and relative humidity according to aacc [15]. and then were baked at 180°c for 25 min the resulted pan bread was allowed to cool at room temperature for 2 h before being packed in polyethylene bags and stored at room temperature for determination of zea. extraction procedure twenty grams of sample was weighted into a 250ml blender jar with 2 g nacl and extracted with 50ml of extraction solution (acetonitrile: water 90:10 v/v). the mixture was blended for 2 min and centrifuged for 3 min at 3,000 rpm. the extract was filtered through filter paper (whatman no.1). 10 ml filtrate was mixed with 40 ml water, followed by filtration through a glass microfibre filter. immunoaffinity clean-up ten milliliter of filtrate was passed through zearalatesttm immunoaffinity columns at about 1-2 drops/s. 10ml water was used to wash the loaded immunoaffinity column at a steady flow rate. zea was eluted with 1 ml of methanol. the methanol elute was filtered through a 0.45μm micro filter and collected in a clean vial for the following hplc. hplc/fluorescence analysis the hplc system consisted of waters binary pump model 1525, a model waters 1500 rheodyne manual injector, a watres 2475 multiwavelength fluorescence detector. the fluorescence detector was operated at wavelength of 274 nm for excision and 440 nm for emission, and a data workstation with software breeze 2. a phenomenex c18 (250 x 4.6 mm i.d.), 5 μm from waters corporation (usa). the mobile phase consisted of a mixture of acetonitrile: water: methanol (48:50:3, v/v/v). a 20 µl of the reconstituted extract was injected onto the column at a flow rate of 1.0 ml/min. zea content in samples was calculated from chromatographic peak areas using the standard curve. statistical analysis the statistical analysis was performed using the spss software program (spss institute, 2011, version 19.0) and the differences in zen concentrations between time and temperatures dough fermentation were analyzed by anova test. p ≤ 0.05 was considered to be statistically significant. results and discussion influence of manufacture process of pan bread on content of zea: effect of dough fermentation the effect of using saccharomyces cerevisiae (baker's yeast)on content of zea during fermentation of artificially contaminated wheat flour dough at 25°c and 30°c for 30 and 45 min was presented in table 1 and 2. the content of zea was reduced to 13.71, 24.18, 43.88 and 71.43µg/kg in dough made from flour artificially contaminated with 25, 50, 75 and 100 µg/kg, respectively when the fermentation process at 25°c for 30 min. while decreased the content of zea more with more time fermenting dough to 45 min. on the other hand, during fermentation at 30°c the decrease in the content of zea is greater than ever, particularly with increasing duration or time of fermentation to 45 min. the content of zea after fermentation at 30°c for 45 min was 7.52, 17.14, 34.19 and 60.38µg/kg in dough made from flour artificially contaminated with 25, 50, 75 and 100µg/kg, respectively. low incubation temperature (25°c) during the growth of the cells seems to adversely affect the binding and the optimal and above-optimal growth temperature did not affect the binding. temperature is known to affect the cell wall composition with lower temperature resulting in reduced cell growth, cell wall dry mass, mannan and β-glucan levels [16]. culture conditions including ph, temperature, oxygenation rate, nature of the medium, and concentration or nature of the carbon 109 source strongly modulate the quantity and structural properties of β-d-glucans, mannans and chitin in cell walls. moreover, the cell cycle stage also interacts with the cell wall composition. for example, budding induces strong changes in the distribution of the structural components of the cell wall such as chitin. changes in the cell wall components at low growth temperatures might have resulted in reduced binding molecules on the cell surface. cell wall of saccharomyces cerevisiae consists of network of β-1,3 glucan back bone with β-1,6 glucan side chains, which is in turn attached to highly glycosylated mannoproteins which make the external layer [17]. the proteins and glucans provide numerous easily accessible binding sites with different binding mechanisms such as hydrogen bonding, ionic or hydrophobic interactions [18]. binding of different mycotoxins such as aflatoxin, ochratoxin and zea to yeast cell surface has been reported earlier and the binding has been attributed to cell wall glucans in case of ochratoxin and zea [19]. β-d-glucans are the yeast component responsible for the complexation of zea, and that the reticular organization of β-d-glucans and the distribution between β-(1, 3)-d-glucans and β-(1, 6)-d-glucans play a major role in the efficacy and add at weak hydrogen and van der waals bonds are involved in the chemical complex formation between zen and β-d-glucans. thus, the chemical interaction is more of “adsorption type” than “binding type”. molecular modeling was performed to validate the concept on other mycotoxins such as aflatoxin b1, deoxynivalenol and patulin [20]. the reduction percentage of zea after fermentation dough at 30°c for 30 min was only 58.8, 55.1, 46.98 and 34.42%, while it was 69.9, 65.72, 54.41 and 39.62% after fermentation dough for 45 min from flour artificially contaminated with 25, 50, 75 and 100µg/g, respectively. the percentage of zea reduction increased with time of fermentation dough shown in (figure 1). there was observed relationship between the degree of reduction and the initial level of zea contamination during fermentation dough . and, as it was expected, a positive relationship was observed between the increase of fermentation time and that of the percentage of reduction on zea-contaminated wheat flour table 1: concentrations of zea determine in artificially contaminated wheat flour after dough fermentation at 25°c (n=3) spiking level of zea (µg/kg) time of fermentation dough (min) 25 50 75 100 after mixed directly 23.26 ±0.34 46.98 ±0.4 73.71 ±0.12 96.45 ±0.17 30 13.71 ±0.46 24.18 ±0.25 43.88 ±0.52 71.43 ±0.39 45 9.44 ±0.18 19.22 ±0.44 37.6 ±0.41 63.16 ±0.51 table 2: concentrations of zea determine in artificially contaminated wheat flour after dough fermentation at 30°c (n=3) spiking level of zea (µg/kg) time of fermentation dough(min) 25 50 75 100 after mixed directly 23.26 ±0.34 46.98± 0.4 73.71 ±0.12 96.45± 0.17 30 10.3 ±0.26 22.45± 0.28 39.76 ±0.71 65.58± 0.73 45 7.52 ±0.1 17.14± 0.19 34.19 ±0.38 60.38± 0.92 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 25 50 75 100 concentration of zea in artificially wheat flour (µg/kg) r ed uc tio n of z e a (% ) fermentation at 30ºc for 30min fermentation at 30ºc for 45min fermentation at 25ºc for 30min fermentation at 25ºc for 45min figure 1: the percentages of zea reduction during fermented dough effect of baking zea concentration as affected by baking of artificially contaminated flour dough during pan bread making is shown in table 3 and figure 2. the residual amount of zea was 3.31, 6.38, 12.82 and 23.84µg/kg after baking dough artificially contaminated with different concentration of zea i,e 25, 50,75 and 100µg/g, respectively. the reduction percentage of zea after baking pan bread at 180°c for 25 min was 55.98, 62.78, 62.5 and 60.52%.the results showed a positive correlation between the initial contamination level and the reduction of zea after baking. the levels of zea in cereal-based foods were reduced significantly by extrusion processing, and reduction of 83% of zea in corn-based foods was obtained with this process [21]. however, there remains a need to demonstrate that the toxicity or biological activity of zea has been reduced or completely eliminated in cereal-based foods using extrusion processing [22]. figure 3a showed the hplc chromatogram of zea standard where fig. 3b showed the sample with zearalenone level of 25µg/kg after fermentation at 30 °c for 30 min. while fig. 3c hplc chromatogram of zearalenone in sample pan bread. 110 table 3: concentrations of zea in pan bread after baking at 180 °c for 25 min. (n=3) spiking level of zea (µg/kg) treatment 25 50 75 100 fermentation dough at 30°c for 45 min 7.52 ±0.1 17.14 ±0.19 34.19 ±0.38 60.38 ±0.92 baking at 180 °c for 25 min 3.3.1 ±0.15 6.38 ±0.29 12.82 ±0.76 23.84 ±1.6 reduction (%) 55.98 62.78 62.5 60.52 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 25 50 75 100 concentrations of zea in artificially wheat flour(µg/kg) r ed uc tio n of z e a ( % ) figure 2: effect of baking at 180 °c for 25 min on content of zea in dough after fermentation at 30°c for 45 min figure 3 a: hplc chromatogram of zearalenone standard figure 3 b: hplc chromatogram of sample with 30°c for 45min figure 3c: hplc chromatogram of zearalenone in sample pan bread conclusion it could be concluded that the fermentation of dough at 30°c for 45 min was best into reduce the content of zea, because this could be a good growth of yeast cells in the dough and is doing and its perfect. so attention must be paid to the process of fermentation and conditions of particular temperature that would influence the activity of yeast cells used. it also shows the importance of yeast cells to reduce the levels of zea. also the results of the study show that the residual of the zea in the bread was within allowable limits internationally. references 1. j. p. f. d’mello, c. m .placinta, a. m. c. macdonald: fusarium mycotoxins: a review of global implications for animal health, welfare and productivity, anim feed sci technol., 80 (1999), pp. 183–205 2. a. zinedinea, j. m .sorianob, j. c. molto, j. manes: review on the toxicity, occurrence, 111 metabolism, detoxification, regulations and intake of zearalenone: an oestrogenic mycotoxin, food chem toxicol., 45 (2007), pp. 1–18 3. international agency for research on cancer (iarc): in. iarc monographs on the evaluation of carcinogenic risks to humans: heterocyclic amines and mycotoxins, 56 (1993), pp. 397 4. council for agricultural science and technology (cast): task force report, 139, council for agricultural science and technology (2003) 5. u. tiemann, s. danicke: in vivo and in vitro effects of the mycotoxins zearalenone and deoxynivalenol on different non-reproductive and reproductive organs in female pigs: a review, food additives and contaminants, 24 (3) (2007) 306–314 6. h. takemura, j. y.shim, k. sayama, a. tsubura, b. t. zhu, k. shimoi: characterization of the estrogenic activities of zearalenone and zeranol in vivo and in vitro. journal of steroid biochemistry and molecular biology, 103 (2007), pp. 170–177 7. e. s. abd alla: zearalenone: toxigenic fungi and chemical decontamination in egyptian cereals, nahrung, 41 (1997), pp. 362–365 8. a. i. abdel-hafez, s. m. saber: mycoflora and mycotoxin ofhazelnut (corylus avellana l.) and walnut (juglans regia l.) seeds in egypt, zentralbl mikrobiol., 148 (1993), pp. 137–147 9. o. m. el-maghraby, i. a. el-kady, s. soliman: mycoflora and fusarium toxins of three types of corn grains in egypt with special reference to production of trichothecene-toxins, microbiol. res., 150 (1995), pp. 225–232 10. fao: worldwide regulations for mycotoxins in food and feed in 2003, fao food and nutrition paper, 81, food and agriculture organization of the united nations, rome, italy 11. a. bata, r. lasztity: detoxification of mycotoxin contaminated food and feed by microorganisms, trends in food science and technology, 10 (1999), pp. 223–228 12. l. jespersen: occurrence and taxonomic characteristics of strains of saccharomyces cerevisiae predominant in african indigenous fermented foods and beverages, fems yeast research, 3 (2003), pp. 191–200 13. r. l. k. glover, r.c. abaidoo, m. jakobsen, l. jespersen: biodiversity of saccharomyces cerevisiae isolated from a survey of pito production sites in various parts of ghana, systematic and applied microbiology, 28 (2005), pp. 755–761 14. p. h. shetty, l. jespersen: saccharomyces cerevisiae and lactic acid bacteria as potential mycotoxin decontaminating agents. trends in food science and technology, 17 (2006), pp. 48–55. 15. aacc: approved method of the american association of cereal chemists, 11th ed (2005), inc. st. paulminnesota, usa 16. b. aguilar-uscanga, j. m. francois: a study of the yeast cell wall composition and structure in response to growth conditions and mode of cultivation, letters in applied microbiology, 37 (2003), pp. 268–274 17. r. kollar, b. b. reinhold, e. petrakova, h. j, yeh, g. ashwell, j. drgonova, j. c. kapteyn, f. m. klis, e. cabib: architecture of the yeast cell wall beta 1,6-glucan interconnects mannoprotein, beta 1,3-glucan, and chitin journal of biological chemistry, 272 (1997), pp. 17762– 17775. 18. a. huwig, s. freimund, o. kappeli, h. dutler: mycotoxin detoxication of animal feed by different adsorbents, toxicology letters, 122 (2001), pp. 179–188 19. a. yiannikouris, j. françois, l. poughon, c. g. dussap, g. bertin, g. jeminet, j. p. jouany: adsorption of zearalenone by b-d-glucans in the saccharomyces cerevisiae cell wall, j. food prot. 67 (2004), pp. 1195–1200 20. j. p. jouany, a. yiannikouris, g. bertin: the chemical bonds between mycotoxins and cell wall components of saccharomyces cerevisiae have been identified archiva zootechnica, 8 (2005), pp. 26–50 21. d. ryu, m. a. hanna, l. b. bullerman: stability of zearalenone during extrusion of corn grins, j. food. prot, 62 (1999), pp. 1482–1484 22. y. cetin, l.b. bullerman: evaluation of reduced toxicity of zearalenone by extrusion processing as measured by the mtt cell proliferation assay, j. agric. food chem., 16 (2005), pp. 6558–6563 microsoft word b_24_r.doc hungarian journal of industrial chemistry veszprém vol. 38(2). pp. 175-179 (2010) the production and investigation of starch based slow released encapsulating agents m. meiczinger , gy. marton† research institute of chemical and process engineering, university of pannonia, pob 158, veszprém, h8201, hungary e-mail: moni@meiczinger.hu nowadays the protection of environmentally aware has important part in the agriculture. the growth of the plants need fill the gap of soil’s nutrient. his manner included for this the fertilizing. the most developed fertilizers contain the essential microelements (b, mn, zn, cu, co, mo), which are needed for plants, and provide their slow releasing. the native starch is a natural biopolymer that can be gained from renewable raw materials. its good property is that the native starch able to slow the releasing of the micro components. this effect can be improved if the starch gets ionic functional groups that are able to bind cations. different starch-phosphates were produced in solid-phase modification with changing the conditions, than we investigated the quality of these starch-phosphates (molecular weight distribution, charge density, solubility). we added copper and zinc microelements to these products using ion exchange method, and examined the dissolution of the micro components. in this paper we present our experiences about dissolution of the zinc and copper in different ph. keywords: slow release, encapsulating agent, starch derivatives introduction for many years our research group deals with the improvement of starch derivatives, which are able to slow release of micro components as fertilizers. the plants use the microelements in a minimal quantity, but their presence is essential to their growth. starch based encapsulating agents are organic or inorganic esters that have the capability of controlled water-repellency. with the use of them, we can reduce the speed of bioactive chemicals’ release from the products. the fertilizers, which have these starch based encapsulating agents, are safe. they do not harm the health neither in the production, nor in the use phase. in addition, since active agents are better utilized, they would reduce the amount of fertilizers’ production. native starch, in itself too, is able to decrease the speed of releasing, but if we build ionic function groups into the starch polymers, which are able to bind cations, we can improve the effect. through the modification of starch, we replaced some of its oh groups in the anhydroglucose monomer unit by the ionic groups of phosphate with chemical reaction. material and methods the production of starch-phosphates the diammonium hydrogen phosphate (cp = 0.1 g phosphate/ 1 g starch) and the urea were dissolved in water. the ph of this solution (ph of phosphorilation = 9.6) was alkalized with sodium hydroxide, which was later sprayed to the starch. after that this mixture was heattreated in oven (t = 145 °c; t = 1.5 h). the effect of this treatment was that phosphate groups replaced some of the starch’s oh groups in the anhydroglucose monomer unit. because of the alkalinity of the solution, two starch polymers could link through the phosphate group, and therefore we could see their polymerization. also, because of the heat treatment, some of the molecules’ degradation could be observed as well. the qualification of starch-phosphates on the quality of starch derivates, the molecular weight distribution (mw), solubility (sol.), and charge density (ch.d.) were determined. for the analysis, a dilute solution was made from starch derivates. the molecular weight distribution was determined by using size exclusion chromatography (hpsec) and malls laser detector. hpsec uses a refractive index detector and its signal proportional with the samples’ solubility (ri-area). charge density was determined by mütek pcd 02, with a particle charge analysator, through colloid titration. this equipment neutralizes the oppositely charged polyelectrolyte solution through titrating the ionic polymer sample. binding the microelements binding the microelements to the starch derivatives was performed after the heat treatment. the zinc was added 176 in solid form, the copper in solution form to the starchphosphate (the starch-phosphate’s temperature was 70 °c). the saturated solution of copper sulphate was sprayed to the starch derivatives during treatment. the solid/solution weight ratio was 1:1–1:0,5. when we added the cuso4’s solution and the solid znso4*7h2o together, at first we sprayed the cuso4’s solutions to the 140–145 °c starch-phosphate, than we mixed the solid znso4*7h2o with this compound. the investigation of the microelements’ release the effectiveness of produced fertilizer additives were characterized by the rate of the microelements’ release. the samples were put in bags made from filter cloth, and were dip them into distillated water (1:80 solid/solution). the dissolution was examined at 3 different ph values (ph1 = 5.5; ph2 = 6.5; ph3 = 7.5). it was made 2 measurement series, firstly the ph of distillated water was adjusted just before the dissolutions, than was measured day by day what happened with the ph. in the second series the 3 different ph were adjusted before dissolutions as well, but were maintained in these level every day. the ph levels were controlled with sodium hydroxide and nitric acid solution. in given periods, after stirring the solution, samples were taken, which cubic content was not more than the solution’s 1/100th part. then the solution samples’ microelements content was analyzed through the complexometric titration and atomic absorption spectrophotometer. results the parameters of the production and the quality of fertilizers additives are shown in tables 1 and 2. the micro components were added to the starchphosphate on the strength of delineated method, than were examined their dissolution in different ph. it is important to compare the micro components dissolution in different ph, because the soil has big buffer capacity in this manner the releasing fertilizer additives affect the ph of the soils less, than the ph of the distillated water which we used in the dissolution tests. the dissolution processes are shown in figs. 1–8. table 1: the parameters of the production and the quality of ready fertilizers additives quality of ready fertilizers additives the parameters of fertilizers production (binding the microelements) before binding the microelements after binding the microelements sample t (°c) cuso4 solution solid znso4*7h2o mw (106da) sol. (mv-ml) ch.d. (meq/g) ch.d. (meq/g) zn/5,5/b 70 x 11.5 2.84 0.63 0.48 zn/6,5/b 70 x 11.5 2.84 0.63 0.48 zn/7,5/b 70 x 11.5 2.84 0.63 0.48 cu/5,5/b 70 x 11.5 2.84 0.63 0.53 cu/6,5/b 70 x 11.5 2.84 0.63 0.53 cu/7,5/b 70 x 11.5 2.84 0.63 0.53 cuzn/5,5/b 70 x x 11.5 2.84 0.63 0.45 cuzn/6,5/b 70 x x 11.5 2.84 0.63 0.45 cuzn/7,5/b 70 x x 11.5 2.84 0.63 0.45 zn/5,5/d 70 x 11.5 2.84 0.63 0.48 zn/6,5/d 70 x 11.5 2.84 0.63 0.48 zn/7,5/d 70 x 11.5 2.84 0.63 0.48 cu/5,5/d 70 x 11.5 2.84 0.63 0.53 cu/6,5/d 70 x 11.5 2.84 0.63 0.53 cu/7,5/d 70 x 11.5 2.84 0.63 0.53 cuzn/5,5/d 70 x x 11.5 2.84 0.63 0.45 cuzn/6,5/d 70 x x 11.5 2.84 0.63 0.45 cuzn/7,5/d 70 x x 11.5 2.84 0.63 0.45 177 table 2: the parameters of the dissolution of ready fertilizers additives dissolution sample ph ph maintaining zn/5,5/b 5.5 before dissolution(b) zn/6,5/b 6.5 before dissolution(b) zn/7,5/b 7.5 before dissolution(b) cu/5,5/b 5.5 before dissolution(b) cu/6,5/b 6.5 before dissolution(b) cu/7,5/b 7.5 before dissolution(b) cuzn/5,5/b 5.5 before dissolution(b) cuzn/6,5/b 6.5 before dissolution(b) cuzn/7,5/b 7.5 before dissolution(b) zn/5,5/d 5.5 day by day (d) zn/6,5/d 6.5 day by day (d) zn/7,5/d 7.5 day by day (d) cu/5,5/d 5.5 day by day (d) cu/6,5/d 6.5 day by day (d) cu/7,5/d 7.5 day by day (d) cuzn/5,5/d 5.5 day by day (d) cuzn/6,5/d 6.5 day by day (d) cuzn/7,5/d 7.5 day by day (d) 0 10 20 30 40 50 60 70 80 90 100 0 50 100 150 200 250 300 time of dissolution (h) z n 2 + d iss ol ut io n (% ) 0 1,4 2,8 4,2 5,6 7 8,4 9,8 11,2 12,6 14 c ha ng e of p h zn/5.5/b zn/6.5/b zn/7.5/b ph (5.5) ph (6.5) ph (7.5) figure 1: the zn2+ dissolution from starch-phosphate, which contain zn2+ micro component, in different ph and the change of ph 0 10 20 30 40 50 60 70 80 90 100 0 100 200 300 400 500 time of dissolution (h) c u 2+ d iss ol ut in (% ) 0 1,4 2,8 4,2 5,6 7 8,4 9,8 11,2 12,6 14 c ha ng e of p h cu/5.5/b cu/6.5/b cu/7.5/b ph (5.5) ph (6.5) ph (7.5) figure 3: the cu2+ dissolution from starch-phosphate, which contain cu2+ micro component, in different ph and the change of ph 0 10 20 30 40 50 60 70 80 90 100 0 50 100 150 200 250 300 350 time of dissolution (h) z n 2+ d iss ol ut io n (% ) 0 1,4 2,8 4,2 5,6 7 8,4 9,8 11,2 12,6 14 c ha ng e of p h zn/5.5/d zn/6.5/d zn/7.5/d ph (5.5) ph (6.5) ph (7.5) figure 2: the zn2+ dissolution from starch-phosphate, which contain zn2+ micro component, in different, but maintained ph and the change of ph 0 10 20 30 40 50 60 70 80 90 100 0 50 100 150 200 250 300 350 time of dissolution (h) c u 2+ d iss ol ut io n (% ) 0 1,4 2,8 4,2 5,6 7 8,4 9,8 11,2 12,6 14 c ha ng e of p h cu/5.5/d cu/6.5/d cu/7.5/d ph (5.5) ph (6.5) ph (7.5) figure 4: the cu2+ dissolution from starch-phosphate, which contain cu2+ micro component, in different, but maintained ph and the change of ph 178 0 10 20 30 40 50 60 70 80 90 100 0 200 400 600 800 1000 time of dissolution (h) z n 2 + d iss ol ut io n (% ) 0 1,4 2,8 4,2 5,6 7 8,4 9,8 11,2 12,6 14 c ha ng e of p h cuzn-zn/5.5/b cuzn-zn/6.5/b cuzn-zn/7.5/b ph (5.5) ph (6.5) ph (7.5) figure 5: the zn2+ dissolution from starch-phosphate, which contain cu2+ and zn2+ micro components, in different ph and the change of ph 0 10 20 30 40 50 60 70 80 90 100 0 200 400 600 800 1000 time of dissolution (h) z n 2+ d iss ol ut io n (% ) 0 1,4 2,8 4,2 5,6 7 8,4 9,8 11,2 12,6 14 c ha ng e of p h cuzn-zn/5.5/d cuzn-zn/6.5/d cuzn-zn/7.5/d ph (5.5) ph (6.5) ph (7.5) figure 7: the zn2+ dissolution from starch-phosphate, which contain cu2+ and zn2+ micro components, in different, but maintained ph and the change of ph discussion the results showed, that: ● the value of the solutions ph set in about ph = 4.5, irrespective of the solutions initial ph value. ● if we maintained the ph day by day in the original value, then we can see same phenomena by next day, but when the rate of releasing decreased, the change of ph was not significant. ● the difference of the releasing value in the three different phs were not considerable, however the difference of the releasing value of the two different micro components was large. ● the dissolution of the zinc was faster either the micro components were separate or together. the stable ph retarded the dissolution, therefore the chance are that the value of the dissolution is more favorable in the soil, comparing to the distillated water what we used in the laboratory tests. 0 10 20 30 40 50 60 70 80 90 100 0 200 400 600 800 1000 time of dissolution (h) c u2+ d iss ol ut io n (% ) 0 1,4 2,8 4,2 5,6 7 8,4 9,8 11,2 12,6 14 c ha ng e of p h cuzn-cu/5.5/d cuzn-cu/6.5/d cuzn-cu/7.5/d ph (5.5) ph (6.5) ph (7.5) figure 8: the cu2+ dissolution from starch-phosphate, which contain cu2+ and zn2+ micro components, in different, but maintained ph and the change of ph 0 10 20 30 40 50 60 70 80 90 100 0 200 400 600 800 1000 time of dissolution (h) c u 2 + d iss ol ut io n (% ) 0 1,4 2,8 4,2 5,6 7 8,4 9,8 11,2 12,6 14 c ha ng e of p h cuzn-cu/5.5/b cuzn-cu/6.5/b cuzn-cu/7.5/b ph (5.5) ph (6.5) ph (7.5) figure 6: the cu2+ dissolution from starch-phosphate, which contain cu2+ and zn2+ micro components, in different ph and the change of ph symbols cp: g phosphate salt/ in 1g starch t/t: temperature of heat treatment/ duration t: temperature of the microelement’s bonding mw: molecular weight distribution sol.: solubility ch.d.: charge density references 1. j. dencs, g. nos, b. dencs, g. marton: proceedings of the 1st world conference on biomass for energy and industry, vol. ii 1024 (2001). 2. m. meiczinger, g. marton, j. dencs, b. dencs: investigation of reaction occurring at starch phosphorylation – industrial and engineering chemistry research. 45, 2005, 9581–9585. 179 3. t. a. tari, r. s. singhal: starch-based spherical aggregates: stability of a model flavouring compound, vanillin entrapped therein – carbohydrate polymers, 50, 2002, 417–421. 4. a. r. kulkarni, k. s. soppimath,. t. m. aminabhavi, a. m. dave, m. h. mehta: ureaformaldehyde crosslinked-starch and guar gum matrices for encapsulation of natural liquid pesticide [azadirachta indica a. juss. (neem) seed oil]: swelling and release kinetics – journal of applied polymer science, 73, 1999, 2437–2446. 5. b. lenaerst, i. moussa, y. dumoulin, f. mebsout, f. chouinard, p. szabo, m. a. mateescu, l. cartilier, r. marchessault: cross-linked high amylose starch for controlled release of drugs: recent advances – journal of controlled release, 53, 1998, 225–234. 6. c. f. williams, s. d. nelson, t. j. gish: release rate and leaching of starch-encapsulated atrazine in a calcareous soil – soil science society of america journal, 63, 1999, 425–432. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice hungarian journal of industrial chemistry veszprém vol. 33(1-2). pp. 11-21. (2005) numerical method-independent structural solvability analysis of dae models* a. leitold1 and k. m. hangos2 1department of mathematics, university of veszprém h-8201 veszprém, p.o.box 158, hungary 2systems and control research laboratory, computer and automation institute, has h-1518, budapest, p.o.box 63, hungary a graph-theoretical method [1,2] for the structural analysis of dynamic lumped process models described by differential and algebraic equations (daes) is applied in this paper in order to determine the most important solvability properties of these models by using the so-called dynamic representation graph. the construction of the dynamic representation graphs that was originally proposed [2] for the most simple, single-step, explicit numerical methods, has been extended in this paper to higher order explicit and implicit solution methods, that are used more frequently and efficiently for numerical solution of dae-systems. it is shown here that the representation graph for both higher order explicit and implicit solution methods has similar properties to the case of explicit numerical solution procedures both for index one and higher index models. thus it is proven that the important properties of the representation graph including the differential index of the models are independent of the assumption whether a single-step, explicit or implicit numerical method is used for the solution of the differential equations. keywords: process models, dae-models, differential index, solvability, structural analysis * an extended version of the lecture presented in 4th mathmod symposium, vienna, austria, february 5-7, 2003 introduction the structural analysis of dynamic lumped process models forms an important step in the model building procedure [3] and it is used for the determination of the solvability properties of the model, too. this analysis includes the determination of the degree of freedom, structural solvability, differential index and the dynamic degrees of freedom. as a result of the analysis, the decomposition of the model is obtained and the calculation path can be determined. this way the appropriate numerical method for solving the model can be chosen efficiently. moreover, advice on how to improve the computational properties of the model by modifying its form or its specification can also be given. effective graph-theoretical methods have been proposed in the literature [2,4] based on the analysis tools developed by murota, et al [1], for the determination of the most important solvability property of lumped dynamic models: the differential index. the properties of the dynamic representation graph of process models described by semi-explicit dae-systems have also been analysed there in case of index 1 and higher index models. besides of the algorithm of determining the differential index by using the representation graph, a model modification method has also been proposed in the literature, which results in a structurally solvable model even in the case of higher index models [5,2]. 12 basic notions structural solvability as a first step, we consider a system of linear or non-linear algebraic equations in its so called standard form [1] : yi = fi (x, u), i = 1, …, m uk = gk (x, u), k = 1, …, k where xj (j = 1,…, n) and uk (k = 1,…,k) are unknowns, yi (i = 1,…,m) are known parameters, fi (i = 1,…,m) and gk (k = 1,…,k) are assumed to be sufficiently smooth real-valued functions. the system of equations above is structurally solvable, if the jacobian matrix j(x, u) referring to the above model is non-singular. consider a system of equations in standard form. we construct a directed graph to represent the structure of the set of equations in the following way. the vertex-set corresponding to unknowns and parameters is partitioned as x∪u∪y, where x = {x1, …, xn}, u = {u1, …, uk} and y = {y1, …, ym}. the functional dependence described by an equation is expressed by arcs coming into yi or uk respectively from those xj and ul, which appear on its right-hand side. this graph is called the representation graph of the system of equations. a menger-type linking from x to y is a set of pair-wise vertex-disjoint directed paths from a vertex in x to a vertex in y. the size of a linking is the number of directed paths from x to y contained in the linking. in case ⏐x⏐ = ⏐y⏐, (m = n), a linking of size ⏐x⏐ is called a complete linking. the graphical condition of the structural solvability is then the following [1] : linkage theorem: assume that the nonvanishing elements of partial derivatives fi and gk in the standard form model are algebraically independent over the rational number field q. then the model is structurally solvable if and only if there exists a menger-type complete linking from x to y on the representation graph. we can adapt the graphical techniques to daesystems, as well. an ordinary differential equation of a dae-system can be described by the following equation: x’ = f(x1,…, xn) here x denotes an arbitrary variable depending on time, x’ denotes the derivative of x with respect to time and x1, …, xn are those variables which have effect on variable x’ according to the differential equation. in dae-systems there are two types of variables. differential variables are the variables with their time derivative present in the model. variables, which do not have their time derivative present, are called algebraic variables. the derivative x’ is called derivative (velocity) variable. dynamic representation graph the value of differential variables is usually computed by using a numerical integration method. so a system of equations including also differential equations, can be represented by a dynamic graph. a dynamic graph is a sequence of static graphs corresponding to each time step of integration. on a dynamic graph there are directed arcs attached from the previous static graph to the succeeding static graph that are determined by the method applied for solving the ordinary differential equations. in case of a single step explicit method, the value of a differential variable at time t+h is computed using the corresponding differential value and its value at a previous time t. for example, when the explicit euler method is used: x(t+h) = x(t) + h⋅x’(t) where h denotes the step length during the numerical integration. the structure of a dynamic graph assuming explicit euler method for solving differential equations can be seen in fig. 1. the structural analysis based on graph theoretical technique is carried out in steps performed sequentially. the first step is to rewrite the model into its standard form. the second step is the assignment of types to vertices in the representation graph. the important types of vertices determined by the model specification are the following [6,2] : • <s>(set)-type variables: these represent variables, which are assigned to the specified given values. in the case of a dynamic representation graph assuming explicit method for solving the differential equations, the differential variables will be labelled by type <s*> because their initial value can be obtained from the initial values, and then their values can be calculated step by step by numerical integration. labels <s> and <s*> are treated the same way during the analysis. • <g>(given)-type variables: a variable assigned to a specific value of a left hand side is a <g>type variable. unlike the <s>-type variables, the values of the right hand side variables will be suitably adjusted so as to preserve the equality of the two sides. 13 x x1 x2 xn x' t x x1 x2 xn x' t+h fig.1 dynamic representation graph assuming first order explicit solution method according to the representation graph, the value of every variable which has incoming arcs only from vertices labelled by type <s> can be calculated by simple substitution into the corresponding equation. these variables become secondarily labelled by type <s>, and this process can be repeated if necessary. omitting all vertices labelled primarily, secondarily, etc. by type <s> and all arcs starting from them from the representation graph we obtain the reduced graph. the classification of vertices of a reduced graph is as follows: • all initial vertices form the unknown variable set x, • all terminal vertices labelled by type <g> constitute the known variable (parameter) set y, • all other vertices constitute the unknown variable set u. the algebraic subgraph belonging to any static graph in the dynamic representation graph can be obtained by considering the algebraic part of the model and taking its induced subgraph. the vertex set of the algebraic subgraph contains the variables that appear in the algebraic equations and the arc set that corresponds to the algebraic equations. differential index dynamic process models can be described by semiexplicit daes as follows: z1 ‘’= f(z1, z2, t), z1(t0) = z10 0 = g(z1, z2, t) the most important structural computational property of dae models is the differential index. by definition [7], the differential index of the above semi-explicit dae is one if one differentiation is sufficient to express z2 ‘’ as a continuous function of z1, z2 and t. one differentiation is sufficient if and only if the jacobian matrix gz2 is non-singular. in our earlier work we have proved that the differential index of the models investigated in [5,2] is equal to 1 if and only if there exists a menger-type complete linking on the reduced graph at any time step t. an equivalent condition [5] of the above is that the differential index of a semi-explicit dae model m is equal to one if and only if there exists a menger-type complete linking on the reduced graph of the algebraic subgraph belonging to model m. we have also proposed an algorithm using the structure of the representation graph for determination of the differential index of the underlying model. the following two examples described in details in [5,2] are used throughout the paper to illustrate the notions and algorithms. example 1: consider a liquid tank system with one inlet stream f and one exit stream l. let the vessel be perfectly stirred. heat is transferred to the liquid using a heater. the standard form of the model of the liquid tank system (m1) is the following: m = ∫ m’ u = ∫ u’ m’ = –l + f u’ = –l⋅hl + f⋅hf + q hl = u ⁄ m hl* = f1(tl, p) hf = f2(tf, pf) s = hl – h l*, s = 0 l = f3(m) here m denotes the mass, u the internal energy, q the heat transfer rate, hl and hl the specific internal enthalpy of inlet and outlet flow, respectively, tf the temperature of inlet flow, pf the pressure of inlet flow, tl the temperature in the vessel, p the atmospheric pressure and f1 and f2 are given functions. 14 let us consider the following two model specifications. specification 1.: the variables f, tf, pf and q are given as functions of time, the initial values m0, u0 and the pressure p are constants. the variables m, u, tl, and l are to be calculated as functions of time. m t t+h f u tl p tf <s> pf <s> q <s*> <s> l hl hl * hf u' m' s <g> <s> <s*> <s> m f u tl p tf <s> pf <s> q <s*> <s> l hl hl * hf u' m' s <g> <s> <s*> <s> fig.2 representation graph of model m1 with specification 1 assuming first order explicit method the representation graph of the liquid tank system and the assignment types of variables corresponding to the above specification are shown in fig.2, while the reduced graph can be seen in fig.3. it can be seen, that there exists a mengertype complete linking on the reduced graph, which indicates that the differential index of the above model is equal to one. tl s <g> hl * fig.3 reduced graph of model m1 with specification 1 next let us consider the following specification. specification 2.: the variables f, tf, pf and tl, are given as functions of time, the initial values m0, u0 and the pressure p are constants. the variables m, u, q and l are to be calculated as functions of time. representation graph of model m1 with the assignment of vertices corresponding to specification 2 are shown in fig.4. it can be seen that there is no menger-type complete linking on the graph, hence the standard form model is not structurally solvable. there is an overspecified part on the graph, which indicates the fact that the initial values of the model can not be chosen independently. the underspecified part q →u indicates that q cannot be calculated from the algebraic equations. this structure of the representation graph shows that the differential index of the model m1 with specification 2 is greater than 1. in our earlier work [2] we suggested an algorithm, which determines the differential index of the model using the structure of the representation graph and transform the model into a structurally solvable modified form. 15 m t t + h f u tl p <s> tf <s> pf <s> q <s*> <s> <s*> l hl hl * hf u' m' s <g> <s> underspecified overspecified m f u tl p <s> tf <s> pf <s> q <s*> <s> <s*> l hl hl * hf u' m' s <g> <s> overspecified underspecified fig.4 representation graph of model m1 with specification 2 assuming first order explicit solution method example 2: consider a simple tank system shown in fig.5. the model (m2) describing change of the level of liquid in the tank in standard form is the following [5]: l = ∫ l’ l’ = 1/a•(f1f2) f1 = cv• (p1p2)1/2 f2 = cv• (p2 p3) 1/2 s = p2 p0 ρ g l, s = 0 here l denotes the level of the liquid in the tank, f1 and f2 the inlet and outlet flow rate respectively. p0, p1, p2 and p3 are pressures corresponding to fig.5. the cross-section of the tank a, the valve parameter cv, the density of the liquid ρ and the gravitational constant g are constant parameters. p1 f1 p2 p0 p3 f2 l fig.5 a simple tank system the variables p0, p1, and p3 are given as functions of time, the initial value l0 is constant. the variables p2, f1, f2 and l are to be calculated as functions of time. the representation graph corresponding to above model and the variable type specifications are shown in fig.6, while the reduced graph is shown in fig.7. it can be seen that there exists a menger-type complete linking on the reduced graph, which indicates that the differential index of the model is equal to one. representation of dae-s assuming a higher-order explicit solution method higher order explicit solution methods, such as runge-kutta methods, are widely used for numerical solution of ordinary differential equations. as a characteristic example of such methods, let us consider a fourth order explicit runge-kutta method, where the value of the differential variable x at time t+h is computed as k1 = f (t, x(t)) k2 = f (t + h/2, x(t)+h/2• k1) k3 = f (t + h/2, x(t)+h/2• k2) k4 = f (t + h, x(t) + h• k3) x(t + h) = x(t) + h/6• (k1+2 k2 +2 k3 + k4) from the known value x(t) at time t and from the right-hand side function f. 16 p3 p2 p1 p0 <s> l <s> l' f2 s <g> <s*> <s> f1 p3 p2 p1 p0 <s> l <s> l' f2 s <g> <s*> <s> f1 fig.6 representation graph of model m2 assuming first order explicit solution method p2 l' s <g> f2 f1 fig.7 reduced graph of model m2 in order to construct the dynamic representation graph for this case, we construct three additional auxiliary graphs in between a pair of static graphs (main graphs) corresponding to an integration step from t to t+h. the internal structure of the auxiliary graphs is similar to that of the main graphs with the exception, that they do not contain the vertices associated to the differential variables and the arcs originating therefrom. the arcs between the main and auxiliary graphs are determined by the numerical solution method, in the above fourth order runge-kutta method case the above set of equation generates the arcs shown in fig.8. if there is an arc from the vertex of the differential variable x to another vertex of another variable xk on the main graph corresponding to time t, then we direct further arcs from vertex x towards every auxiliary graph ending at their vertex xk. the type labels of the vertices on the auxiliary graphs should be identical to that of the corresponding vertex on the main graphs. futrhermore, we associate type <s*> labels to the vertices which have incoming arcs from only main or auxiliary graphs corresponding to previous time instances. as an example, fig.9 shows the representation graph of model m2 assuming a fourth order explicit runge-kutta method as its solution procedure. because of the way of the representation, the main graphs of a representation graph with higher order explicit solution method are identical with the static graphs of the earlier dynamic representation graph belonging to the euler method. only the connecting arcs between the main and the auxiliary graphs become more complicated as a consequence of the more complex numerical solution method. at the same time, the algebraic subgraphs of the main and auxiliary graphs are identical to the earlier algebraic subgraphs belonging to the euler method. therefore we can state the following propositions. proposition 1. the differential index of a semiexplicit dae model m is equal to one if and only if there exists a menger-type complete linking on the reduced algebraic subgraph of its dynamic representation graph independently of the fact if a first or higher order one-step explicit method is applied for the numerical solution. the reduction of the main and auxiliary graphs can be performed following the same rules as we have seen earlier in the case of applying the explicit euler method for the numerical solution. then the following statement is valid. 17 x x1 xn x' = k1 t x x1 xn x' = k1 t + h x1 xn x' = k2 t + h/2 x1 xn x' = k3 t + h/2 x1 xn x' = k4 t + h main graphs auxiliary graphs fig.8 dynamic representation graph assuming fourth order explicit runge-kutta method proposition 2. by performing the reduction of any of the main or auxiliary graphs, the same reduced graph is obtained, and it is identical to the reduced graph of the model when assuming the explicit euler method as a numerical solution procedure. proof. the statement follows from the structure of the dynamic representation graph and from the way the type-labels are associated to the vertices on the main and auxiliary graphs. in agreement of the above proposition, the reduced graphs of the main and auxiliary graphs of model m2 shown in fig.9 are identical to the reduced graph seen in fig.7. it is important to note that there will be overspecified and underspecified subgraphs on each of the main and auxiliary graphs in the case of higher index models assuming higher order explicit numerical solution methods, similarly to the case when the simple explicit euler method was assumed. representation of dae-s assuming an implicit solution method if we consider a single-step implicit solution method (for example the implicit euler method) for the numerical solution procedure of the differential equations, then the value of differential variable x at time t+h is calculated as follows: x(t+h) = x(t) + h⋅x’(t+h) where h is the step length. in this case the modified structure of the dynamic representation graph is depicted in fig.10. it can be seen that the algebraic part of the representation graph does not change compared to the case when an explicit solution method was assumed, hence the following proposition holds. proposition 3: the differential index of model m is equal to 1 if and only if, there is a mengertype complete linking on the reduced graph of the algebraic part of the dynamic representation graph belonging to model m, independently of either an explicit or an implicit single step numerical solution procedure is applied for the solution of the differential equations. assume that the values of all derivative variables x’ directly or indirectly depend on the corresponding differential variable x in the model. this assumption holds for stable models. as a result of this assumption a so called circle of calculation is obtained in the representation graph belonging to the differential variables according to the following definition. 18 p3 p2 p1 p0 <s> l <s> l' = k1 f2 s <g> <s*> <s> f1 p3 p2 p1 p0 <s> l <s> l' f2 s <g> <s*> <s> f1 p3 p2 p1 p0 <s> <s> l' = k2 f2 s <g> <s> f1 p3 p2 p1 p0 <s> <s> l' = k3 f2 s <g> <s> f1 p3 p2 p1 p0 <s> <s> l' = k4 f2 s <g> <s> f1 t + h/2 t + h/2 t + h t + ht fig.9 representation graph of model m2 assuming fourth order explicit runge-kutta method definition: the circle of calculation belonging to the differential variable x is a directed circle path, which contains the vertices x and x’ and this directed circle is either 1. present on the representation graph (type 1 circle of calculation), or 2. if it is absent, then the basic undirected circle (when directions of arcs are not to be considered) can be found on the representation graph and the circle of calculation can be obtained by changing the direction of some arcs (type 2 circle of calculation). the direction of arc x1→x2 can be changed, if there exists a menger type complete linking on the reduced algebraic subgraph, which contains it. x x1 xn x' t x x1 xn x' t+h fig.10 dynamic representation graph assuming single implicit solution method 19 m t t+h f u tl p tf <s> pf <s> q <c> <s> l hl hl * hf u' m' s <g> <s> <c> <s> m f u tl p tf <s> pf <s> q <s*> <s> l hl hf u' m' s <g> <s> <c> <s> hl * fig.11 representation graph of model m1 with specification 1 assuming an implicit solution method ( circle of calculation) the representation graphs of models in examples 1. and 2. assuming implicit method for the numerical solution of differential equations can be seen in figs.11 and 12. type 1 circles of calculation can be seen in fig.11, where the directed circles containing m and m’ or u and u’ are present in the representation graph. a type 2 circle of calculation can be found in fig.12, where the directed circle belonging to variable l can be obtained by changing the direction of arc p2→s. according to the directed circle of calculation the values of some variables (for example x and x’) can be calculated at any time t by iteration. therefore we propose a new type of assignment for all differential variables: p3 p2 p1 p0 <s> l <s> l' f2 s <g> <c> <s> f1 p3 p2 p1 p0 <s> l <s> l' f2 s <g> <c> <s> f1 t t+h fig.12 representation graph of model m2 assuming an implicit solution method • <c> circle-type variables: let <c> be the label of all differential variables in the representation graph, which indicates that the values of these variables can be calculated by iteration only. these labels can be seen in figs.11 and 12. 20 reduction of representation graphs assuming an implicit solution method the reduction of representation graphs can be performed in this case in two steps: the primary reduction is the same as in the case of explicit solution methods: the primary reduced graph can be obtained by omitting all vertices labelled primarily, secondarily, etc., by type <s> and all arcs starting from them. the primary reduced graphs of the investigated models can be seen in figs.13 and 14. the primary reduction is directed both to the implicit part of the model and to the iterations belonging to the differential variables. in the first case (fig.13) iterations can be calculated independently of the implicit calculation and the sequence of the calculation steps can be seen, too. in the second case (fig.14) the implicit calculation of the algebraic variable p2 is a part of the iteration, hence the value of p2 can be obtained iteratively, too. l m' hl u' tl hl * s <g> m <c> u <c> fig.13 primary reduced graph of model m1 with specification 1 the iterations belonging to differential variables come from the implicit numerical solution method and not from the structure of the models. if we do not want to consider these iterations, a secondary reduction can be constructed: the secondary reduced graph can be obtained if we omit the arcs x’→x belonging to all differential variables and the labels <c> are treated similarly to the labels <s> during the reduction. the secondary reduction is directed to the implicit part of the model, only. l' s <g> l <c> f2 f1p2 fig.14 primary reduced graph of model m2 proposition 4: the secondary reduction yields the same reduced graph as it can be obtained by assuming a single step explicit numerical solution procedure. proof: it follows directly from the structure of dynamic representation graphs and from the procedure of reduction. in the case of higher index models with a single step implicit solution method, the representation graph contains an overspecified and underspecified subgraph, in the same way, as in the case of explicit solution methods. the algorithm for determination of the differential index can be performed similarly, too. conclusion the effect of the numerical solution procedure on the structural analysis of dynamic lumped models described by semi-explicit differential and algebraic equations was investigated in this paper. the most important solvability properties of models were determined by graph-theoretical methods using the dynamic representation graph of the models. we compared the structure of dynamic representation graphs in the case of explicit and implicit solution methods for solving the differential equations. it was shown that the representation graph with both higher order explicit and implicit solution methods has similar properties both in case of index 1 and higher index models as compared to first order explicit single-step numerical solution procedures. hence the properties of representation graph including the differential index of the models are independent of the assumption whether a singlestep, explicit or implicit numerical method is used for the solution of the differential equations. 21 references 1. murota k.: systems analysis by graphs and matroids, springer-verlag, berlin, 1987 2. leitold a. and hangos k.m.: computers and chemical engineering, 2001, 25, 16331646 3. hangos k.m. and cameron i.t.: process modelling and model analysis, academic press, new york, london 2001 4. leitold a. and hangos k.m.: hungarian journal of industrial chemistry, 2002, 30(1), 61-71 5. leitold a.: analysis of dynamic process models using computer science methods, phd dissertation, university of eötvös lóránd, budapest, 2002 6. iri m., tsunekawa j. and yajima k.: information processing, 1972, 71. vol. 2. 1150-1155 7. brenan k.e., campbell s.l. and petzold l.r.: numerical solution of initial value problems in differential – algebraic equations, north-holland, new york, 1989 microsoft word 01_r.doc hungarian journal of industrial chemistry veszprém vol. 35. pp. 7-17 (2007) population balance modelling of crystallisation processes b. g. lakatos university of pannonia, institute of chemical and process engineering, department of process engineering, h-8201 veszprém, p.o. box 158, hungary the work presents and discusses the basics of the population balance approach and multi-dimensional population balance models for describing different aspects of solution crystallisation. a two dimensional model is presented for describing evolution of needle-shape crystals characterised by two size dimensions in cooling crystallisation, and a two-population model is developed for describing micromixing of solution, and its effects on the size distribution of crystals and their aggregates in reaction crystallization. moment equation reductions for joint moments of internal variables are developed in both cases which are closed by means of cumulant neglect closure models. the properties and behaviour of crystallization processes described by the models are investigated by simulation. keywords: cooling and reaction crystallisation, multivariable population balance, needle-form crystals, micromixing introduction in model-driven chemical engineering which refers to the systematic use of models as primary engineering artefacts throughout the engineering lifecycle models are considered as first class entities, and due to their cognitive and methodological values serve as fundamental tools of understanding, analysis, design, operation, control and managing of real engineering processes and processing systems. this technique states that any specification should be expressed by models, which are both human and machine understandable. the department of process engineering attempts to organize new efforts in these directions by proposing a framework (1) to clearly define methodologies, (2) to develop models at any level of abstraction, and (3) to organize and automate the testing and validation activities. models, depending on what they represent, can reside at any level of abstraction, and can be restricted to address only certain aspects of the system. well defined, adequate mathematical models usually are of great predictive power and together with the corresponding computer models have become efficient and useful aspects of engineering, especially treating complex engineering processes and processing systems. in chemical and process engineering such complex systems are, among others, those multiphase processes in which at least one of the phases take part in dispersed state, i.e. in form of solid particles, liquid drops or gas bubbles. these systems can not be modelled adequately by means of the classical state variables only since the characteristic properties of the dispersed elements, among others their size, size distribution, habit, shape, structure, or configuration in continuous phase, have to be taken into consideration as well. for these reasons, population balance models in which population balance equations describe the properties and behaviour of dispersed elements, appear to be adequate mathematical models of disperse systems. in chemical engineering, hulburt and katz [1] formulated the population balance equation using the ideas of statistical mechanics, while randolph and larson [2] based their formulation on continuous mechanics aiming to describe crystallization processes. these formulations have found a lot of applications in modelling particulate systems [2-5], systems containing liquid drops [6-8], as well as gas bubbles [9]. ramkrishna [10] presented an excellent state of the art of this research field. while taking part in technological processes disperse elements interact intensively with the continuous phases, and also with the counterparts of the dispersed one. as regards the dispersed phase, here two types of interactions can be distinguished: 1) interactions causing changes of the dispersed elements themselves, and 2) interactions inducing changes of entities carried by the dispersed elements. continuous growth and shrinkage, breakage and aggregation-agglomeration or coalescence of dispersed elements can be mentioned in the first group, while exchange of momentum, mass exchange of chemical species, exchange of heat and electrical charge may be included into the second group. in effective modelling of disperse systems, these interactions and processes induced by those should to be taken into consideration. when modelling solid dispersed phase, i.e. particulate systems, in most part only those inter-particle interactions have been accounted for which cause changes of the particles themselves, i.e. their breakage, aggregation 8 and agglomeration. recently, developing a new, markov process-based formulation of the population balance equation [11, 12], direct inter-particle heat exchange processes [13-16] and, mostly for modelling direct interactions between fluid particles, also mass exchange processes [17-20] have been included into the population balance models, extending in this way the range of effect of the population balance modelling approach. the aim of the present work is to present and discuss the basics of the population balance approach and multidimensional population balance models for describing different aspects of crystallisation from solution. a two dimensional model is developed for describing evolution of needle-form crystals characterised by two size dimensions in cooling crystallisation, and a twopopulation model is presented for describing the mixing effects of solution on the size distribution of crystals and their aggregates in reaction crystallization. moment equation reductions for joint moments of internal variables are developed in both cases which, when the sets of equations are unclosed, are closed by means of cumulant neglect closure models. the properties and behaviour of the systems described by the models are investigated by simulation. two-dimensional population balance models population balance model of a cooling crystallizer for needle-shaped crystals for describing crystallization from solution, which is a widely used cleaning, separation and particle producing technique in the chemical, petrochemical and pharmaceutical industry, population balance models have been proved adequate modelling tools. in this enormously important unit operation, the crystal population is the main product thus the goal of operating crystallizers is to produce crystals of prescribed form, habit, size, and size distribution. the task of describing this process is to predict the properties and behaviour of the whole crystal population from the behaviour of single crystals interacting with the solution and crystals environment. the population is modelled by the density of suitable chosen variables as models of crystals’ characteristic properties variation of which is described by the population balance equation. most of the modelling studies of crystallisation use one-dimensional characterisation of crystals. however, crystalline particles often, especially in the pharmaceutical industry, exhibit much more complex habit, as it is illustrated in fig. 1. crystals in fig. 1b and 1c can be described adequately only by multi-dimensional models, characterising the crystal and crystal growth separately for the main crystallographic faces. here we consider needle-shaped crystals, produced in a cooling crystallizer shown schematically in fig. 2. such needle-shaped crystals can be characterised by two size dimensions l1 and l2, while the crystal population is described by the population density function n(., ., t) by means of which n(l1, l2, t)dl1dl2 expresses the number of crystals from the size domain (l1, l1 + dl1) × (l2, l2 + dl2) in a unit volume of suspension at time t. since the volume of crystals is an important property a volumetric shape factor kv is also defined by means of which the crystal volume can be expressed using only these two size dimensions even in case of different shapes as it is shown in fig. 1c. figure 1: three different crystal systems figure 2: continuous cooling crystallizer let us now assume that: the working volume of the crystallizer is constant; all new crystals are formed at a nominal size l1, n ≅ l2, n ≅ ln ≥ 0, so that we can assume: ln ≈ 0; crystal breakage and agglomeration are negligible; the overall linear growth rates of the two habit faces g1 and g2 are size independent, and have the form of power law expressions: g1 = kg1(c – cs)g1 (1) and g2 = kg2(c – cs)g2 (2) the primary nucleation rate bp is described by volmer’s model feed product vapour cooling water out cooling water in q, cin, csv,in,tin q, c, csv t, n qh, th,in qh, th l1 l3 l2 l1=l2=l3 l3 l1 l2 l1≠l2>>l3 l3 l1 l2 l1=l2<l3 l1 l2 l1<l2 a) b) c) 9 ⎟ ⎟ ⎟ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎜ ⎜ ⎜ ⎝ ⎛ ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −= s e pp c c kkb 2ln expε (3) where ε is the voidage of suspension, expressed as ε(t) = 1 – kv μ1, 2(t) (4) and μ1, 2 is one of the third order joint moments of the crystal sizes l1 and l2. here, the joint moments of variables l1 and l2 are defined as ,...3,2,1,0, ),,()( 0 0 212121, = = ∫ ∫ ∞∞ mk dldltllnllt mk mkμ (5) while the volume of crystals is expressed by means of the moment μ1, 2 as ∫ ∞ == 0 2121 2 212,1 ),,()()( dldltllnllktktv vvc μ (6) the secondary nucleation rate bb is described by the power law relation ( ) jb sbb cckb 2,1μ−= (7) in the kinetic expressions (1)-(3) and (7) coefficients kg1, kg2, kp and kb and are functions of the temperature, expressed as bpgg rt ekk ,,,,exp 210 =⎟ ⎠ ⎞ ⎜ ⎝ ⎛−= ιι ιι (8) under such assumptions the population balance model of the crystallizer consists of the following balance equations. the population balance equation governing the crystal size dynamics becomes ( ) 02,1,0 )()( 2 2 1 1 >=∞<< −=++ til nn v q l ng l ng t n i in∂ ∂ ∂ ∂ ∂ ∂ (9) subject to the initial and boundary conditions: n(l, 0) = n0(l), l ≥ ln (10a) 0,),(),,(lim ≥+= → tbebetlnlccg bbppsll n (10b) 0,0),(lim ≥= ∞→ ttln l (10c) where ep and eb are binary existence variables of the nucleation rates, by means of which the alternative variations of nucleation can be controlled. naturally we have the constraint ep + eb ≥ 1 (11) mass balance of solvent: ( ) ( )svsvinin sv cc v q dt cd εε ε −= (12) with the initial condition csv(0) = csv0. the mass balance equation of solute: ])1([ ])1([])1([ c cininin c c v q c v q dt cd ρεε ρεερεε −+− −−+= −+ (13) subject to the initial condition c(0) = c0. the energy balance equation for the crystal suspension takes form [ ] tccccc rh q tccccc v q rhttua dt tcccccd ccsvsvc mcc inccinsvinsvincin mcch cccsvsv ])1()([ )( ])1()([ )()( )1()( ρεε ρεε ρεε −++ − − −+++ +−+−−= = −++ δ δ (14) subject to the initial condition t(0) = t0. here, rmc denotes the global rate of production of crystal mass in a unit volume of suspension. energy balance for the cooling medium: ( ) ( ) )( hhhin h h hh hh ttuavtt v qc dt tcd −+−= ρ ρ (15) subject to the initial condition th(0) = th0. the dependence of saturation concentration on the temperature is described by the expression: cs(t) = a0 + a1t + a2t2. (16) often, it is useful to complete the set of balance equations (9)-(15) by the equation for the equilibrium saturation concentration given as ( ) dt dttaa dt dt dt dc dt dc ss 21 2+== (17) subject to the initial condition cs(t0) = a0 + a1t0 + a2t0 2. therefore, the state of the crystallizer is given by the quintuple [c(t),csv(t),t(t),th(t),n(.,t)], and its dynamics is described by the population balance model formed by the mixed set of partial and ordinary differential equations (9)-(15). the time evolution of this system occurs in the state space r4×n that is the descartes product of the vector space r4 of concentrations and temperatures, as well as the function space n of population density functions. in the present study, we concentrate on a reduced case, approximating the distributed parameter system of eqs (9)-(15) by a finitedimensional state space model using the six leading joint moments of crystal sizes. 10 moment equation reduction and scaling the moment equation reduction of the population balance model (9)-(15) can be written for the joint moments of crystal sizes (5) by means of which the mean values of sizes are given as )( )( )( 0,0 0,1 1 t t tl μ μ = and )( )( )( 0,0 1,0 2 t t tl μ μ = (18) the infinite hierarchy of the moment equations corresponding to eq. (9) takes the following form ( ) bbppin bebe v q dt d ++−= 0,0,0,0 0,0 μμ μ (19) ( ) ...3,2,1,,1,2 ,11,,, , =+ ++−= − − mkmg kg v q dt d mk mkmkinmk mk μ μμμ μ (20) this infinite set of equations can be closed at any order but natural closing occurs at the third order joint moment μ1, 2 since, because of eq. (6), this moment is required for the mass balance of solute (13). to do that equations for moments μ0,0 μ1,0 μ0,1 μ0,2 μ1,1 are also required. since the system of moment equations often become stiff it is advisable to perform scaling that by defining useful scale parameters and dimensionless scaled variables to allow controlling conditioning of the system. introducing the scale parameters s1, 2 = kv, s0, 2 = kvψ1, s1, 1 = 2kvψ2, s1, 0 = s1, 1ψ2 = 2kvψ2ψ2, s0, 1 = s1, 1ψ1 = 2kvψ2ψ2 s0, 0 = 2kv ψ1ψ2ψ2, sc = 1/cin, st = 1/tin and st, where 1 1 1 0,1 g ctg ssk −−=ψ , 2 2 1 0,2 g ctg ssk −−=ψ , the dimensionless scaled variables xk, m = sk, m μk, m, k, m = 0, 1, 2, 3, ysv = sc csv, y = sc c, ys = sc cs, z = stt, zh = st th, ξ = st t and scaled parameters ccsρα =: , 2 21 1 02: ψψ−= tpvap skkd , 2 21 1 0 12: ψψbctb j vab sskkd −−−= , gbp r se t ,,,: == ιβ ι ι ht c cs uas:=κ , )(: c h t h c s δγ −= 00 : asb c= , t c s asb 1 1 := 2 2 2 : t c s asb = . the closed set of moment equations takes the form ( ) bbppin eexx d dx θθ ξξ ++−= 0,0,0,0 0,0 1 (21) ( ) 0,00,1,0,1 0,1 1 1 xxx d dx gin θ ξξ +−= (22) ( ) 0,01,0,1,0 1,0 2 1 xxx d dx gin θ ξξ +−= (23) ( ) 0,11,01,1,1,1 1,1 21 1 xxxx d dx ggin θθ ξξ ++−= (24) ( ) 1,02,0,2,0 2,0 2 1 xxx d dx gin θ ξξ +−= (25) ( ) 2,12,1,2,1 2,1 1 ψ ξξ +−= xx d dx in (26) ( ) ( ) ( ) 2,1 33 ,3 )1( )( 1 11 ψα ξξ x yyy x x d dy in in − − −− − − = (27) ( ) ( ) ( ) 2,1 3 , 3 3 )1()1 11 ψ ξξ x yyy x x d dy sv svinsv insv − +− − − = (28) ( ) 2,1)(1 ψ φ αγ φ κ φ φ ξξ +−−−= hin in zzzz d dz (29) ( ) )(1 , h hh hinh h h zz v vzz d dz −+−= α κ ξξ (30) subject to the initial conditions xk, m(0) = xk, m0, k, m = 0,0; 0,1; 1,0; 1,1; 0,2; 1,2 ysv(0) = ysv0, y(0) = y0, z(0) = z0, zh(0) = zh0. in eqs (21-30) ( ) 1,12,01,12,02,1 21 , xxxx gg θθψ += (31) ( ) 2,12,11 x c cy c cy c cx h c h c sv h sv αφ +⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ +−= (32) ( ) in h c in h c insv h sv inin x c cy c cy c cx ,2,1,,2,11 αφ +⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ +−= (33) ( ) 2,1,exp =⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −−= i z yy ii i gg sg β θ (34) ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ − ⎟ ⎟ ⎟ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎜ ⎜ ⎜ ⎝ ⎛ ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −−= z y y kxd p s e app β θ exp ln exp)1( 2 3 (35) and ( ) ⎟ ⎠ ⎞ ⎜ ⎝ ⎛−−= z xyyd bjb sabb βθ exp3 . (36) according to eq. (17), the set of eqs (21-30) can be completed using the equation describing the variation of the dimensionless saturation concentration 11 ( ) ( ) ( ) ( )1,12,02,121 21 ,2 )(12 xxzbb zzzzzbb d dy hin ins ψ φ αγ φ κ φ φ ξξ ++ +⎥ ⎦ ⎤ ⎢ ⎣ ⎡ −−−+= (37) note that when l1 = l2 = l, we can write μk,m = μk+m, k, m = 0, 1, 2, 3, ..., and the set of equations (20)-(30) reduces to the one dimensional moment equation model of cooling crystallizers. simulation results and discussion the system of odes (21)-(30) was solved in matlab environment using the process and kinetic parameters presented in table 1. kinetic parameters were chosen followed the works by ma et al. [27] and briesen [28]. simulation runs have been carried out to investigate the influence of nucleation on the crystal shape under the same crystal growth and operation conditions. table 1: process and kinetic parameters used in simulation of cooling crystallizer v = 10 m3 kp0 = 1.6·1030 g1 = 1.48 qin = 10-3 m3 s-1 ke = 2.1 eb = 9.0·104 cin = 350 kg m3 ep = 5.0·104 mol kg1 = 12.2·10-6 m s-1 tin =90 °c kb0 = 1.0·1016 g2 = 1.75 th = 20 °c b = 3.0 j = 1.5 kg2 = 10.08·10-7 m s-1 a0 = 0.2087 a1 = –9.76·10-5 a2 = –9.30·10-5 fig. 3 presents the effects of parameter ke of primary nucleation on the steady state mean size values 〈l1〉 and 〈l2〉. the crystallizer produced practically the same mass of crystals in each run, i.e. about 90 kg m-3 of suspension. figure 3: effects of parameter ke of primary nucleation on the steady state mean size of the crystallographic faces significantly different diagrams were obtained when secondary nucleation was the dominant crystal producing process. as it is shown in fig. 4, in this case crystals were able to achieve size about 1 mm in length while producing almost the same amount of crystalline mass as in the case of primary nucleation. naturally, the differences between the numbers of crystals took some orders of magnitude. the operation mode used in simulation assured good cooling conditions as it is illustrated in figs 5 and 6. projections of trajectories of crystallizer into the 3-d figure 4: effects of parameter b of secondary nucleation on the steady state mean size of the crystallographic faces t–c–μ0 subspace are presented in fig. 5 for primary nucleation and in fig. 6 for secondary one. it is seen well that the transients differ significantly depending on the nature of nucleation. figure 5: trajectories of the crystallizer in the 3-d t-cμ0, 0 subspace in the case of primary nucleation b 1l 1l 2l 2l ke 1l 2l 1l 2l c t 12 figure 6: trajectories of the crystallizer in the 3-d t-cμ0,0 subspace in the case of secondary nucleation two population models generalized coalescence/redispersion model for micromixing the physical phenomena occurring in solution crystallizers are very complex, involving the interactions between large-scale fluid mixing, fine-scale micromixing and complex crystallization kinetics as well as, in reaction crystallizers, chemical reaction kinetics. the macroscopic models of the fluid elements adequately describe macromixing but a quantitative description of the influence of micromixing presents a more challenging problem. most of the works dealing with the influence of micromixing on crystallisation processes was focused on reaction precipitation [21-24]. in crystallisation, however, fine-scale fluid mixing may also affect the crystal size distribution because of the mixing of fresh feed stream with the bulk solution of crystallizer. then, direct interactions between the supersaturation inhomogeneities coupled with highly nonlinear nucleation and crystal growth kinetics may influence the process significantly, as it was demonstrated by means of a probability density function model [25], and, recently, by developing twopopulation models with the usage of coalescenceredispersion micromixing closures [17-19,26]. here, an improved two-population model is presented in which the generalised coalescence-redispersion micromixing model [20] is utilized for describing micromixing of solution. let us now assume the in a continuous crystallizer the supersaturation is generated by a chemical reaction according to the scheme ↑⎯→⎯+ cba k . further, we assume that the fluid phase in the crystallizer can be visualised as consisting of a large number of fluid ele ments in which concentrations and supersaturation can be treated as deterministic quantities. the fluid elements, moving stochastically in the crystallizer, interact intensively with the counterparts and the existing crystals. fluid elements exhibiting different concentrations of species a, b and c change some amounts of mass between each other during their coalescence-redispersion interactions, inducing in this way equalization of concentration differences. the population of fluid elements is characterised by the density function p(.,.), where p(c, t)dc expresses the number of fluid elements having concentration in domain (c, c+dc) in a unit volume of suspension at time t. here, c = (ca, cb, cc) denotes the concentration vector of species a, b and c. the density function p(.,.) describes, in essence, the distribution of concentrations of species in the fluid elements so that the average concentration observable on macrolevel is expressed as ∫ == m cbakdtpc t tc kk c cc 00 ,,,),( )( 1)( π (38) where ∫= m dtpt c cc 0 0 ),()(π (39) provides the total number of fluid elements in a unit volume of suspension. in eq. (38) expression cc d t tpt )( ),()( 0π =prob (40) is interpreted as the probability of there exists a fluid element having concentration in domain (c, c+dc) in a unit volume of suspension at time t. in the crystallizer, between the stochastically moving fluid elements and crystals the following interactions are assumed to occur: 1) fluid-fluid element, 2) fluid element-crystal, 3) crystal-crystal interactions. interactions between the fluid elements are manifest as micromixing of solution that is described by the generalized coalescence-redispersion model [20]: [ ] ( ) ( ) ∫ ∫ ∫∏ ∫ ∫ ∫∏ = = ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎣ ⎡ −⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ + − + + ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎣ ⎡ −⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ + − −= x x x x im 1 00 1 00 "'),"(),'()("')'(212 "'),"(),'()(")'(212 3 1 3 3 1 3 ccccω ccccω ω ω ddtptpdfccccts ddtptpdfcccctsp k kk k kk c k col k kk k kk c k col k k ω δ ωπ ω δ ωπ (41) here, ωk ∈ [0,1] is a random parameter with distribution function fωk, characterizing the exchange process of the kth, k = a, b, c component of c between the fluid elements, while scol stands for the frequency of binary collisions. when fωk = 1(ωk), i.e. the mean value of ωk is zero, then no mixing of the kth species occurs on microlevel, but fωk = 1(ωk – 1), i.e. the mean value of ωk equals 1, denotes maximal micromixing under the given macrolevel conditions. μ 0,0c t 13 as a consequence, beside the crystal population the solution in crystallizer is treated as a second population of the fluid elements, forming in this way a twopopulation system of interacting populations of two different dispersed elements. crystallization kinetics of under non-perfect micromixing conditions in the crystallizer, simultaneously with the chemical reaction of species a and b producing the precipitating species c, nucleation of crystals and their subsequent growth occur, due to the direct fluid element-fluid element and fluid element-crystal interactions, whilst the possible crystal-crystal collision interactions may induce also aggregation of crystals. under such conditions, it seems to be better to characterise crystals on the volume coordinate v, and the population of crystals by the population density function n(., t) by means of which n(v, t)dv expresses the number of crystals from the crystal volume interval (v, v+dv) in a unit volume of suspension at time t. as a consequence, now the motion of the two populations occur in a four-dimensional space of internal properties from which the first one is the volume coordinate of crystals, while the remaining three internal properties are formed by the concentration coordinates of fluid elements. assuming that all new crystals are formed with a nominal volume vn ≈ 0 and vn > 0, then the kinetic expressions for nucleation, growth and aggregation of crystals are as follows. primary nucleation is considered as a result of fluid element interactions while secondary nucleation is a result of those between the fluid elements and crystals. if the intrinsic rate of nucleation is given by expression bt(cc, cs, v) its macrolevel rate is expressed as ( ) ( ) bpdvdtvntp vccbtb nv sc ,,),(),( ,,1 0 =× ×= ∫ ∫ ∞ ι μπ ιι cc mc 00 (42) in similar way, since crystals moving stochastically in the vessel are surrounded and suffer contacts with fluid elements of different composition, the macrolevel crystal growth rate is also expressed as ( ) ( )∫== mc cc 00 dtpvccg t tg dt dv sc ),(,, )( 1 π (43) finally, the rate of aggregation of crystals by means of the frequency of collisions and the aggregation efficiency is given as ( ) ( ) ( ) ( )∫ ∫ ∫ ∫ −−+ +−−−= ∞ m m v asceff asceffa dtpdvtvntvvnvvvsccs dtpdvtvvntvnvvvsccstb c c cc cc 0 00 0 00 ),('),'(),'(,',', 2 1 ),('),'(),(,',,1)( ε πμ ε πμ 0 0 (44) two-population model of reaction crystallization if the reaction crystallizer 1) is operated under isothermal conditions, 2) the frequency of coalescence-redispersion events is constant, and 3) the reaction between species a and b is quasi-linear the rate of which is given as ra = –kcacb, rc = kcacb, then the population balance equation for the fluid elements takes the form [ ] [ ] ( )[ ] ( ) ( ) ∫ ∫ ∫∏ = ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎣ ⎡ −⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ + − +−= ⎥⎦ ⎤ ⎢⎣ ⎡ −=− ∂ ∂ + ∂ ∂ + ∂ ∂ + ∂ ∂ x x 1 00 "'),"(),'()("')'(212),( ),(),(),(),(),(),( 3 1 3 ccccωc cccccc ω ddtptpdfcccc t tstps tptp v qtprr c tpr c tpr ct tp k kk k kk c k col col in in c c b b a a k ω δ ωπ ε ε (45) in eq. (45), expression 〈r〉 represents the rate of decrease of concentration of solute in a fluid element due to crystallization which, because of the rate expressions (42) and (43), can be expressed as an average over all crystals being in its environment: n ccc vb c g c r dt cd ιε ρ μ ε ρ − − − −== 0 (46) boundary conditions for concentration variables specify closed system along the concentration coordinates except the input where any combination of feasible conconcentration values can appear in the inlet density function. this means that for any k ∈ {a, b, c} and any values of the remaining concentration variables 0),()( 0 ==kck tpr cc and 0),()( , = = mkk cck tpr cc . the second population balance equation of the model describes the crystals is formulated here as 14 ( ) ( ) ( )[ ] [ ] ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( )∫ ∫ ∫ ∫ −−+ +−− −−+−=+ ∞ m n m n v v sceffa v sceffa nin ddvtptvntvvnccsvvvs tt ddvtptvnccsvvvs tt tvn vvtbtvntvn v q v tvnvtg t tvn c 0 c 0 cc cc 00 00 '),(,',',',' 2 1 '),(,',,', ),(),( ,,, πμ πμ δ ∂ ∂ ∂ ∂ (47) the boundary and initial conditions to eq. (47) can be written, respectively, as follows: ( ) ( ) 0,,lim = +→ tvnvtg nvv and ( ) 0,lim = ∞→ tvn v (48) and p(c, 0) = p0(c) and n(v, 0) = n0(v) (49) writing eq. (47) it was assumed that the volume vn of nuclei is small but vn > 0, thus the nucleation rate here arises in eq. (47) as a source term inside the support interval [0, ∞) of crystal volumes. the second consequence of this assumption is the first of the boundary conditions (48). moment equation model the two-population model of the reaction crystallizer is formed by the population balance equations (45) and (47), respectively, for the fluid elements and crystals. eq. (45), however, is a three-dimensional equation by itself so that a moment equation reduction requires the joint moments of concentrations, defined as ....2,1,0,,,),()(,, == ∫ nlmdtpccct m n c l b m anlm c cc 0 π (50) the infinite hierarchy of the moment equations corresponding to eq. (45) takes the form ...2,1,0,,,)()(1)()( )()()()()()( )( 0 0 0 ,,,,,,, 0,0,0 ,,,, ,,,1,,1,1,11,,11,1,1 ,, =⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ −− −=+−++ ∂ ∂ ∑∑∑ = = = −−− −−++++ nlmttcbatst v q t v qttrntnktlktmk t t n k l j m i knjlimkjinkljminlmcolnlm innlm in nlmnlmnlmnlm nlm ππ π ππ π ε ε ππππ π (51) where the coefficients of micromixing terms are expressed as ∫ − ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ −⎟ ⎠ ⎞⎜ ⎝ ⎛= 1 0 ,, )( 22 1 aa im a i a mi dfi ma ωωω ω (52a) ∫ − ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ −⎟ ⎠ ⎞⎜ ⎝ ⎛= 1 0 ,, )( 22 1 bb jl b j b lj dfj lb ωωω ω (52b) ∫ − ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ −⎟ ⎠ ⎞⎜ ⎝ ⎛= 1 0 ,, )( 22 1 cc kn cc mi dfkk nc ωωω ω (52c) eqs (51) and (52) show that the micromixing terms are always closed so that the joint moment equations may be unclosed only due to the reaction terms as it seen in eq. (51). as a consequence, the mean values of concentrations (38) are written as π1, 0, 0/π0, π0, 1, 0/π0 and π0, 0, 1/π0. the second part of the moment equation reduction of the two-population model of reaction crystallizer is based on the moments of the crystal volume, given as ( ) ( ) ...2,1,0, == ∫ ∞ kdvtvnvt nv k kμ (53) assuming now hat aggregation of crystals is characterised by sum kernel in which the efficiency is equal 1, then sa(v, v')seff(cc, cs) = sa·(v + v') (54) and the resulting hierarchy of moment equations takes the form ( ) ( ) [ ] ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ...2,1,0, 1 2 )()()( 1 0 1 0 0 101 ,1 =⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ + + + − −+−=− ∑ += = −+ + − ktt j k t s t tttts vtbtt v qtgk t t kj j jkj a kk a k nkinkk k μμ μ μ μμμμ μμμ ∂ ∂μ (55) note that the zero order moment of the set (53) provides the total number of crystals, the first order moment expresses the total volume of crystals in a unit volume of suspension, while the second order one makes possible of predicting the dispersion of the crystal population. in this case the first three moments seem to be sufficient to characterise the crystal population. as a consequence, taking into account eq. (51), the order of moment equations necessary to have a closed system depends on the kinetics of nucleation and crystal growth. for studying the properties and behaviour of the system a second order moment equation reduction is used in simulation. 15 simulation results and discussion applying the power law forms of kinetic expressions, we assume that the exponents are: g=1, b=2 and j=1. then ( ) ( ) ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −⎟ ⎠ ⎞⎜ ⎝ ⎛= − = = ∑ k k s k k kb b cktktb 2,0,0 2 0 1 12)( πμ π 0 (56) i.e. nucleation describes also the possible dependence on the crystalline magma. as regards the crystal growth we have ( ) ( ) ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ −⎟ ⎠ ⎞⎜ ⎝ ⎛= − = = ∑ j j s j j jg cj gk tg 1,0,0 1 00 1 π π (57) while the expressions are give nin eq. (55). since the support of random parameters ωk is the compact interval [0,1] the micromixing parameters is characterised by the beta distribution ⎪⎩ ⎪ ⎨ ⎧ ≥≤ <<− = −− 1ifand0if,0 10if,)1( ),( 1 )( 11 kk k q k p k k qpf k ωω ωωω βωω k = a, b, c (58) including the limiting degenerate distributions given by dirac-delta density functions as well. note that, since we focus our attention on the effects of micromixing, in the model (47) crystals and agglomerates are treated as similar particles what is, in principle, a simplification. the mixing state of the feed consisting of species a and b can also be described by the beta distribution. we assume that the feed contains also species c having uniform concentration cc, in = cs where cs denotes the solubility of c. if species a and b in the feed are totally segregated with concentrations ca, in and cb, in and volumetric ratio φ, then the inlet population density function takes the form ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( )inccinbbain inccbinaaincbain ccccc ccccctcccp ,,, ,,, 1 ,,, −−−+ +−−= δδδπφ δδδφπ 0 0 (59) so that the inlet joint moments are given as π1, 0, 0, in = π0, inφca, in, π0, 1, 0, in = (1 – φ)π0, incb, in π0, 0, 1, in = π0, incc, in, 2 ,,,0,0,2 inainin cφππ 0= ( ) 2 ,,,0,2,0 1 inbinin cφππ −= 0 , 2 ,,,2,0,0 incinin c0ππ = π1, 1, 0, in = 0, π1, 0, 1, in = π0, inφca, in cc, in π0, 1, 1, in = (1 – φ)π0, incb, in cc, in. the system of odes of the second order model equation reduction was solved in matlab environment using the process and kinetic parameters presented in table 2. simulation runs have been carried out to investigate the influence of micromixing and the interactions of micromixing and chemical reaction on the properties of crystal population produced. table 2: process and kinetic parameters used in simulation of reaction crystallizer 10=t s kb=1.0·108 scol=10 s-1 kg=5.0·10-11 cain=2.2 mol dm-3 ρ=1500 g dm-3 cbin=2.2 mol dm-3 g=1.0 ccin=0.5 mol dm-3 b=2.0 cs=0.1mol dm-3 j=1.0 sa=106 s-1 kr=4.0 101 mol dm-3 s-1 vf=1.0·10-15 vn=1.0·10-15 effects of micromixing on the number of particles and the total mass produced in the crystallizer for three different reaction rates are presented in figs 7 and 8. here, the mixing state on microlevel is characterised by the expected values of parameters ωa, ωb and ωc defined as ∫ == 1 0 ,,,)( cbakdfm kkk kk ωωω ωω (60) increasing rate of mixing on microlevel induces increased number of particles, crystals and aggregates, but at the same time the amount of solid mass is also increased. under such circumstances the mean size of particles becomes 10-6-10-5 m of orders of magnitude. the diagrams in figs 7 and 8 indicate also that the sensitivity of variation is increased with increasing rate of the chemical reaction. indeed, these trends are justified by figs 9 and 10 showing variations of the number of particles, as well as of the total volume of solid phase as a function of the rate of chemical reaction at different levels of micromixing. in these simulation runs the expected values of the micromixing parameters were constant mωa = mωb = mωc = 0.5. figure 7: influence of the expected value of micromixing parameters on the number of particles produced kr=1.0 kr=40 kr=0.4 μ 0 ( ) cba mmm ωωω == 16 figure 8: influence of the expected value of micromixing parameters on the mass of particles produced figure 9: influence of the rate of chemical reaction on the number of particles produced figs 9 and 10 show that interactions between the chemical reaction and micromixing appear to be significant in the interval kr ∈ [10-2, 102]. when kr > 102 then micromixing is the rate limiting process while in the case of kr < 102 the chemical reaction turns to be the rate limiting process. conclusions the population balance approach provides a good framework for modelling crystallization systems. in extended form [12, 15, 20], it takes into consideration not only changes of the particles themselves, i.e. nucleation, growth, breakage and aggregation, but also changes of different entities carried by the particles, i.e. mass of chemical species and heat, induced by direct interparticle interactions. this extension often requires formulating multi-dimensional population balance models, and allows to model also interactive multipopulations involving different kinds of disperse elements. figure 10: influence of the rate of chemical reaction on the mass of particles produced the method of moments that seems to be an adventageous tool of handling one-dimensional population balance models can be applied also for multi-dimensional models defining the joint moments of variables describing simultaneously more internal properties of the dispersed elements. for the sake of illustration, a two-dimensional model was presented for describing a cooling crystallizer producing needle-shape crystals, and a two-population model was developed for describing micromixing of solution in reaction crystallisation. in the latter case, the population balance equation of fluid elements turned to be three-dimensional by itself. the second order moment equation reductions for joint moments of internal variables, which were closed by means of cumulant neglect closures, proved to be very useful in handling the rather complex models. notation 〈c〉 mean (macrolevel) concentration, kg/m3 〈g〉 mean crystal growth rate, m/s 〈l〉 mean crystal size, m 〈b〉 mean nucleation rate, no/m3s t mean residence time, s a heat transfer surface in a unit volume of suspension ak coefficients of solubility (k = 0,1,2) b exponent of nucleation rate b nucleation rate, no/m3h c concentration, kg/m3, kmol/m3 dab dimensionless parameter for secondary dap dimensionless parameter for primary nucleation g crystal growth rate, m/s g exponent of crystal growth rate j exponent of nucleation rate kb coefficient of nucleation rate, (no/m3s)⋅(m3/kg)-b kg coefficient of crystal growth rate, (m/s)⋅(m3/kg)-g kr reaction rate coefficient, l/mol s kv volumetric shape factor l crystal size, m n population density function of crystals nucleation kr=40 kr=0.4 kr=1.0 μ 0 μ 1 μ 1 ( ) cba mmm ωωω == 5.0=== cba mmm ωωω 5.0=== cba mmm ωωω kr kr 17 p population density function of fluid elements r rate of chemical reaction, kmol/m3s s scale factor u heat transfer coefficient, w/m2k t temperature, c, k t time, s v volume, m3 vf volume of fluid elements, m3 x dimensionless moments y dimensionless concentration greek letters α dimensionless parameter ρ density of crystals [kgm-3] θ dimensionless nucleation rate ξ dimensionless time ε void fraction μm,k (m,k)th joint moment of crystal sizes πm,k m,k)th joint moment of concntrations indices a,b,c chemical species a,b,c b secondary nucleation in input out output p primary nucleation s equilibrium saturation concentration references 1. hulburt h. m., katz s.: chemical engineering science, 1964, 19, 555-574 2. randolph a. d., larson m. a.: theory of particulate processes (second ed.), academic press, new york, 1988 3. kafarov v. v., dorokhov i. n, kolcova e. m.: sistemnyj analiz processov khimicheskoj technologii. processy massovoj kristallizacji iz rastvorov i gazovoj fazy. nauka, moskva, 1983 4. tavare n. s.: industrial crystallization. process simulation, analysis and design. plenum press, new york, 1995 5. blickle t., lakatos b. g, mihálykó cs.: szemcsés rendszerek matematikai modelljei. a kémia újabb eredményei 89. akadémiai kiadó, budapest, 2001 6. hidy g. m., brock j. r.: the dynamics of aerocolloidal systems. pergamon press, new york, 1970 7. pandis s. n., seinfeld j. h.: atmospheric chemistry and physics: from air pollution to climate change, wiley, new york, 1998 8. friedlander s. k.: smoke, dust, and haze: fundamentals of aerosol dynamics (2nd ed.), oxford university press, oxford, 2000 9. gidaspow d.: multiphase flow and fluidization: continuum and kinetic theory descriptions. academic press, boston, 1994 10. ramkrishna d.: population balances. theory and applications to particulate 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symposium of industrial crystallization. cambridge, uk, 1999 18. lakatos b. g., ulbert zs.: population balance model for micromixing in msmpr reaction crystallizers. proceedings 3rd ecce, dechema, nuremberg, germany, paper 374, 2001 19. ulbert zs., lakatos b. g.: chemical engineering science, 2005, 60, 3525-3538 20. lakatos b. g.: chemical engineering science, 2008, 63, 404-423 21. pohorecki r., baldyga j.: chemical engineering science, 1983, 38, 79-83 22. tavare n. s.: chemical engineering science, 1994, 49, 5193-5201 23. tavare n. s.: aiche journal, 1995, 41, 2537-2548 24. falk l., schaer e.: chemical engineering science, 2001, 56, 2445-2457 25. lakatos b. g., nagy g.: probability function based micromixing model of crystallizers. industrial crystallization’87. (ed. by nyvlt j., zacek s.), praha: academia, 325-328, 1987 26. ulbert zs., phd thesis. university of veszprém, veszprém, hungary, 2003 27. ma h., tafti d., braatz r.: industrial and engineering chemistry research, 2002, 41, 62176223 28. briesen h., chemical engineering science, 2006, 61, 104-112 microsoft word a_08_r.doc hungarian journal of industrial chemistry veszprém vol. 38(1). pp. 41-45 (2010) production of depressed freezing point bio gas oil from slaughter house waste lard t. kasza , j. hancsók department of hydrocarbon and coal processing, institute of chemical and process engineering university of pannonia, h-8201 veszprém, p.o.box. 158, hungary e-mail: kaszatamas@gmail.com besides the second generation bio fuels the bio gas oil, which is a high iso-paraffin containing fuel in the boiling range of the diesel gasoil could be produced by the catalytic hydrogenation of different triglycerides. in this paper to improve the cold flow properties the isomerization of a normal paraffin rich mixture which was produced by the catalytic hydrogenation of slaughter house’s wastes lard was investigated over a pt/sapo-11 catalyst at the temperature of 320–380 °c, pressure of 30–60 bar, space velocity of 1.0–3.0 h-1 and h2/feedsock volume ratio of 400 nm3/m3. at the favourable process parameters excellent diesel fuel blending components (cetane number: 76–88; cold filter plugging point: between -7 and-13) were obtained, which were practically free of heteroatoms and had high isoparaffin content. keywords: biogasoil, waste fat, catalytic hydroisomerisation, sapo-11 catalyst introduction the importance of bio-fuels produced from agrarian products and wastes is higher and higher because of the forecast depletion of crude oil reserves, the increasing crude oil price, the efforts to reduce the dependence on crude oil import, the increasing demands of quantity, the environmental regulations, furthermore the expectations of the european union, and this tendency will continue in the near future [1, 2, 3, 4, 5, 6]. the different vegetable oils and their esters furthermore the products obtained from these by catalytic hydrogenation belong to the bio-fuels. as the utilisation of unconverted vegetable oils as diesel fuel do not work properly, the chemical conversion of the vegetable oils to fuels or fuel blending components having proper quality is necessary [7, 8]. the biodiesels used currently in the highest degree are produced by the transesterification of vegetable oils. these have numerous disadvantage e.g. poor oxidation and heat stability, hydrolysis sensitivity (corrosion), low energy content, poor cold flow properties, high viscosity, etc. [7, 8]. because of these disadvantages the quantity of fatty acid methyl esters which could be blended to the diesel fuels was limited to 7.0 v/v% in the en 590:2009 standard according to the suggestion of the car manufacturers. to satisfy the bio component demand in the near future the so called bio gas oil could be a good solution, which could be produced by the catalytic hydrogenation of different triglycedes and which have high isoparaffin content and are in the diesel boiling range [8, 9, 10, 11, 12]. the feedstock of the bio gas oil could be conventional and ennobled vegetable oils (e.g. rape, sunflower, soy and coconut oils) grown in high quantity for biodiesel production, furthermore fats from the alimentary industry (used cooking oils and fats) and meat and leather industry, furthermore from trap fats of sewage farms, etc. having a lower price. such kinds of feedstocks could be used as well which could be grown in invaluable lands (like jathropa oils) or could be extracted from algaes. in the reactions taking place during the catalytic hydrogenation of triglycerides mainly normal paraffins, propane, carbon dioxide and monoxide, water and oxygenic compounds generate according the following reaction scheme [8, 9, 10, 11, 12, 13, 14, 15]: t i li id k ch2 o c r1 o ch o c r2 o ch2 o c r3 o n-paraffinok i-paraffinok+ + katalizátorok h2, t, p (oxigéntartalmú vegyületek) co +co2+ ch4+c3h8+h2omelléktermékek: the regulations of diesel fuels could be satisfied in the highest degree by that gasoil which has high nand i-paraffin content and is practically free of sulphur and nitrogen and has low aromatic content. but the high content of normal paraffins having high carbon number is unfavourable in the arctic zone and in winter in the temperate zone regarding the cold flow properties. these affect unfavourably the freezing point, pour point and cold filter plugging point (cfpp) [12, 13, 14, 15]. the products obtained from triglycerides by catalytic hydrogenation contain mainly c15-c18 normal paraffins. accordingly the catalytic conversion of the paraffins has high importance, as their cold flow properties do not 42 satisfy the specified values (e.g. cold filter plugging point) of the standard. formerly the isomerisation of smaller carbon number paraffins (c8-c12) was investigated; industrially just the isomerisation of c5-c7 hydrocarbons is practised now. the reason of this is that the catalytic transformation of these paraffins could be realised over a high isomerisation activity catalyst to reach favourable yield and high isomer content contrary to the earlier used mainly hydrocracking catalysts. such highly selective catalysts are the different noblemetal containing zeolites (zsm-5, zsm-22, zsm-23), silica-alumina-phosphates (sapo-11, sapo-31, sapo-41) and mesoporous materials (mcm-41, al-mcm-41) [5]. the freezing points of the isoparaffins are significantly better than that of the normal paraffins. it decreases by decreasing the carbon number and by shifting of the branch toward the centre of the molecule. (fig. 1). furthermore the increase of the number of the branching improves the cold flow properties as well. -100 -80 -60 -40 -20 0 20 40 60 carbon number m el tin g po in t, °c no 2-methyl 5-methyl 1312 16 18 20 branches figure 1: freezing points of the paraffins as a function of the carbon number because of the abovementioned, the aim of our research work was the production of fuel blending components having favourable cold flow properties over a sapo-11 catalyst found to have high isomerisation activity [12]. the feedstock was a high normal paraffin containing mixture produced from slaughter house waste fat, which has lower value than that of the vegetable oils. besides our aim was the investigation of the effects of the process parameters (temperature, pressure, liquid hourly space velocity, hydrogen/ hydrocarbon volume ratio) on the product yield and quality and based on these the determination of the favourable process parameters. experimental during our experiments the ranges of the process parameters were the following: temperature: 300–360 °c; pressure: 20–40 bar; liquid space hourly velocity 1.0–3.0 h-1. the h2/feedstock volume ratio was constant 400 nm3/m3, as during our pre-experiments it was found that the utilisation of lower amount of hydrogen causes the increase of the cracking reactions which led to the decrease of the isoparaffin content of the product. the utilisation of higher amount of hydrogen to feedstock ratio – higher than 400 nm3/m3 – is unfavourable regarding economical aspects; moreover it could roll back the degree of the isomerization. apparatus the experiments were carried out in an apparatus containing a tubular down-flow reactor of 100 cm3 effective volume. it contains all the equipment and devices applied in the reactor system of an industrial heterogeneous catalytic plant [9]. the experiments were carried out in continuous operation with steady-state activity catalyst. materials and methods table 1 contains the main properties of the feedstock of the isomerization. the applied catalyst was a pt/sapo-11 [10]. the properties of the feedstock and the products were determined according to the test methods specified in the en 590:2009 standard and were calculated by other methods (table 2). table 1: the main properties of the feedstock having high normal paraffin content property value density at 40°c, g/cm3 0.7689 cold filter plugging point, °c 23 cetane number 101 sulphur content, mg/kg 6.4 nitrogen content, mg/kg 5.2 i-c15 0.06 n-c15 11.94 i-c16 0.06 n-c16 13.23 i-c17 0.31 n-c17 35.47 i-c18 0.43 paraffin content, % n-c18 33.35 total isoparaffin content, % 0.89 aromatic and cycloparaffon content, % 0.3 table 2: applied test methods property method density en iso 12185:1998 cold filter plugging point msz en 116:1999 sulphur content en iso 20846:2004 nitrogen content astm-d 6366-99 hydrocarbon composition gas chromatography (trace gc 2000) distillation characteristics en iso 3405:2000 43 results and discussion during our experiments the catalytic conversion of a high paraffin containing mixture produced from slaughter house waste (lard) by catalytic hydrogenation was investigated over a pt/sapo-11 catalyst at the temperature of 300–360 °c, pressure of 20–40 bar, liquid hourly space velocity of 1.0–3.0 h-1 and h2/feedstock ratio of 400 nm3/m3. in this paper the most important results of this experiment are presented. the yields of products the yield of the product mixtures decreased by increasing the temperature and by decreasing the pressure and the lhsv (fig. 2 and 3). the reason of this was that the carbeniumions generated on the surface of the catalyst during the isomerization, having lower stability than that of the saturated hydrocarbons, could be cracked more easily at higher temperature and at lower pressure. in the investigated process parameter range, the yield of the product exceeded 90% in every case. 92 93 94 95 96 97 98 99 100 310 320 330 340 350 360 370 380 390 temperature, °c pr od uc t y ie ld , % lshv = 1.0 1/h lshv = 2.0 1/h lshv = 3.0 1/h figure 2: product yields as a function of temperature and lhsv (p = 40 bar) 86 88 90 92 94 96 98 100 20 30 40 50 60 70 pressure, bar pr od uc t y ie ld , % t = 320°c t = 340°c t = 360°c t = 380°c figure 3: product yields as a function of temperature and pressure (lhsv = 1,0 h-1) product composition the isoparaffin concentration of the products increased significantly by increasing the temperature above 340 °c, namely the degree of isomerization become greater. the degree of increase started to decrease at 360–370 °c partially because of by the thermodynamic inhibition (namely the isomerization reactions are exothermic) and partially because of the increase of the cracking. this tendency rose with decreasing the lhsv (fig. 4), because of this the contact time increased, so the reaction could take place in higher degree. 0 10 20 30 40 50 60 70 310 320 330 340 350 360 370 380 390 temperature, °c is om er c on te nt , % lshv = 1.0 1/h lshv = 2.0 1/h lshv = 3.0 1/h feedstock figure 4: the paraffin content of the products as a function of temperature and lhsv (p = 40 bar, h2/hydrocarbon ratio: 400 nm3/m3) besides the obtained isomers mainly (85–90%) mono branching isomers were generated up to 360°c. the freezing point of these is significantly lower than that of the normal paraffins (e.g. 2-methyl-heptadecane: +5.5 °c; 5-methyl-tetradecane: -34.4 °c) and their cetane number is moderately lower than that of the corresponding normal paraffin (e.g. 9-methyl-heptadecane: 66) [16]. but higher amount of multi branched paraffins (15–35%) was generated above this temperature, which have better cold flow properties, however their cetane number is significantly lower (e.g. 2,2,4,4,6,8,8-heptamethylnonane: 15; 5,6-dibutyldecane: 30) [16]. the decrease of the pressure unequivocally increased the degree of isomerization up to 340 °c, as the first step of the isomerization, namely the dehydrogenation of the saturated paraffins to olefins could take place more easily on the active sites of the catalyst by decreasing the partial pressure of the hydrogen. at 360 °c the concentration of isoparaffins had maxima as a function of the pressure, while at 380 °c the decrease of the pressure caused the decrease of the isomer content (fig. 5). the reason of this was that the hydrocracking reactions taking place at higher degree at higher temperature decreased the concentration of the isoparaffins. these reactions were rolled back by the 44 increase of the partial pressure of the hydrogen, because the rate of hydrogenation of the instable carbenium ions generating on the surface of the catalyst increased. 0 10 20 30 40 50 60 70 80 10 20 30 40 50 60 70 pressure, bar is om er c on te nt , % 320°c 340°c 360°c 380°c figure 5: total iso-paraffin content of the products as a function of pressure and temperature performance properties the cold filter plugging point (cfpp) is an important performance property during the utilisation of the diesel fuels, as the paraffin crystals precipitated by the decrease of the temperature could cause operational disorder or unserviceability of the fuel supply system. the cfpp values of the products decreased by increasing the temperature, decreasing the pressure and the lhsv (fig. 6). the reason of this was the increase of the concentration of the isoparaffins, while the freezing point of the isoparaffins is lower than that of the n-paraffins (see fig. 1). the lighter hydrocarbons having low freezing point could decrease the cfpp values as well, which were generated in the hydrocracking reactions. 320 330 340 350 360 370 380 30 40 50 60 -15 -10 -5 0 5 10 15 20 c fp p. ° c hőmérséklet, °c nyomás, b ar 15-20 10-15 5-10 0-5 -5-0 -10--5 -15--10 figure 6: cffp values of the products as a function of temperature, pressure and lhsv the concentration of the multi-branched paraffins increased by increasing the temperature. the reason of this was that at higher temperature the structural transformation of the mono-branched paraffins increased, so in consecutive reactions the possibility of the formation of multi-branching was higher. these compounds affect favourably the cold flow properties, but another important performance property, their cetane number is low. consequently the cetane number of the products decreased by increasing the rate of conversion relative to that of the normal paraffin rich feedstock (101 unit). the cetane numbers of the product were 76–88 unit at the favourable process parameters (determined by a compromise as a function of the yield and the ratio of the mono and multi-branched isoparaffins), which were higher than the specified value of the diesel fuel standard (51 unit). summary the production possibility of bio gas oil having good cold flow properties was investigated over a pt/sapo-11 catalyst. the feedstock was a mixture of mainly normal paraffins which were produced from slaughter house waste lard to broaden the feedstock of the bio gas oil. it was concluded that in the investigated parameter range higher temperature, lower pressure and lsh are favourable for the conversion of isoparaffins. regarding the values of the yield, cfpp and cetane number, the most favourable process parameter combinations were the following: temperature of 360–370 °c, pressure of 40–50 bar and lhsv of 1.0 h-1. at these parameters the products had high yield (95–96 %) and high isomer content (60–62 %). the cfpp values of the products were between -7 °c and -13 °c, which could satisfy the requirement of the summer grade fuel without addition, and the winter grade specification could be fulfilled with some addition as well. these excellent gas oil blending components are practically free of sulphur and have cetane number of 76–88 unit, which is significantly higher than that is specified in the en 590:2009 standard (51 unit). acknowledgement we acknowledge the financial support of this work by the hungarian state and the european union under the tamop-4.2.1/b-09/1/konv-2010-0003 project. references 1. official journal of the eu, 31, 2003 188–192. 2. commission of the european communities, com(2006) 845 final, 2007. 3. anon., world ethanol and biofuels report 4, 2006, 365. 4. graff g., purchasing magazine, june 15. 2006. 5. k. s. tyson, r. l. mccormick: nrel/tp-54038836 report (2006). 6. m. s. graboski, r. l. mccormick: prog. energy and comb. science, 24, 1998, 125–164. 45 7. j. hancsók: modern motor and jet fuels ii. diesel fuels, 1999, university press, veszprém. 8. j. hancsók: modern motor and jet fuels iii. alternative fuels, 2004, university press, veszprém. 9. m. krár, s. kovács, l. boda, l. leveles, a. thernesz, j. hancsók: fuels purpose hydrogenation of vegetable oils over nimo/γ-al2o3 catalyst, műszaki kémiai napok’09, veszprém, april 21-23. 2009. 10. j. gergely, j. petro, j. baladincz, g. szalmásné pécsvári, h. beyer, j. hancsók et al.: hung. pat. 225 912 (2001). 11. j. hancsók, m. 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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page 427 page 428 page 429 page 430 page 431 page 432 page 433 page 434 page 435 page 436 page 437 page 438 page 439 page 440 page 441 page 442 page 443 page 444 page 445 page 446 page 447 page 448 page 449 page 450 page 451 page 452 page 453 page 454 page 455 page 456 page 457 page 458 page 459 page 460 page 461 page 462 page 463 page 464 page 465 page 466 page 467 page 468 page 469 page 470 page 471 page 472 page 473 page 474 page 475 page 476 page 477 page 478 page 479 page 480 page 481 page 482 page 483 page 484 page 485 page 486 page 487 page 488 page 489 page 490 page 491 page 492 page 493 page 494 page 495 page 496 page 497 page 498 page 499 page 500 page 501 page 502 page 503 page 504 page 505 page 506 page 507 page 508 page 509 page 510 page 511 page 512 page 513 page 514 page 515 page 516 page 517 page 518 page 519 page 520 page 521 page 522 page 523 page 524 page 525 page 526 page 527 page 528 page 529 page 530 page 531 page 532 page 533 page 534 page 535 page 536 page 537 page 538 page 539 page 540 page 541 page 542 page 543 page 544 page 545 page 546 page 547 page 548 page 549 page 550 page 551 page 552 page 553 page 554 page 555 page 556 page 557 page 558 page 559 page 560 page 561 page 562 page 563 page 564 page 565 page 566 page 567 page 568 page 569 page 570 page 571 page 572 page 573 page 574 page 575 page 576 page 577 page 578 page 579 page 580 page 581 page 582 page 583 page 584 microsoft word 01_r.doc hungarian journal of industrial chemistry veszprém vol. 35. pp. 1-5 (2007) process engineering research and education at the department of process engineering – – past, present and future j. abonyi university of pannonia, institute of chemical and process engineering, department of process engineering, h-8201 veszprém, p.o. box 158, hungary the aim of this paper and this special issue is to overview the latest developments in process modelling, simulation, control, and process monitoring. the special issue of the hungarian journal of industrial chemistry will be devoted to 30th anniversary of the department of process engineering. it is meant primarily to contain papers written by the colleagues working closely with us. their papers and this overview will illustrate that process engineering covers all the necessary knowledge required for defining, designing, implementing and optimizing any process where physical, chemical and/or biological transformation of materials occur. nowadays, the task of process engineers is to design, construct and operate complete systems. these tasks are very complex and according to that diversity, the papers of this special issue are grouped to five parts: 1) modelling and model analysis, 2) data analysis and data driven techniques, 3) control, 4) optimization, and 5) numerical methods. the aim of this paper is to give a brief overview about how process engineering research and education is effected by the needs of industrial process development, and to highlight how the department of process engineering of the university of pannonia (former university of veszprém) adapts to these challenges. keywords: process engineering, engineering education, research and design needs of industrial process development the term ‘process systems engineering’ may be traced back at least as far as the early 1960s. process engineering covers all the necessary knowledge required for defining, designing, implementing and optimizing any process where physical, chemical and/or biological transformation of materials occurs. it is a crossdisciplinary science organized around fundamental subjects (mass and heat transfer, fluid mechanics, chemical reactors theory, mass and heat balances, distillation, filtration and other separation methods). but it is also concerned with the development of specific methods (coupled transport phenomena, modelling, process control, systemic approach). initially developed in response to the needs of oil industry, the process engineering is concerned with a diversity of other branches today: ● fine chemistry and related activities, ● agri-food, biology, pharmacy and cosmetics industries, ● specialized materials (glass, cement, paper) and materials for microelectronics, ● protection of the environment and water treatment. nowadays, the task of process engineers is to design, construct and operate complete systems. by complete systems we mean both processes and plants that produce products that fully meet the customer’s needs. both the needs of customers as well as the society as a whole have an important effect on the process industry and these needs largely determine what products are produced and how they are produced. these needs determine the challenges that chemical and process engineering have to face and the know-how process engineers need to have [1]. in the words of p. v. danckwerts in 1966: ‘it will be a great mistake to think of the content of chemical engineering science as permanently fixed. it is likely to alter greatly over the years in response to the changing requirements of industry and to new scientific discoveries and ideas for their application.’ as an engineering discipline based on scientific principles the chemical (and process) engineering has two main tasks [1]: a) to model subsystems using the theoretical and methodological scientific knowledge. in this respect, chemical engineering is not different from the natural sciences. b) to develop methods and procedures which allow real systems in all their complexity to be designed and constructed even if not all of the subsystems have been precisely modelled due to a lack of a thorough knowledge of the underlying physics and chemistry. 2 nowadays there is a need for further development both in the descriptions of subsystems and also in the methods and tools for designing overall systems. it is not the purpose of this paper to trace the history and future trends of the development of process systems engineering. the readers interested in these topics should consult the excellent overview papers [1, 2, 3, 4]. our goal will be to seek to map changes in the education of students of process engineering. education in process systems engineering trends in the paper of john perkins [5] a personal view of the history of the development of the process engineering education is given. two complementary approaches have been distinguished. 1. on the one hand, pedagogical materials have been developed and courses delivered covering important advances in process systems engineering as they have emerged from the research community. as a result, the teaching of design and control methodologies, techniques and tools has become more systematic and comprehensive in the past four decades (see task a) presented in the previous session). 2. the second strand of educational development concerns curricula and courses designed to help students to acquire and adopt a ‘systems approach’ to engineering problem solving. while there are much broader questions involved in pursuing the educational objectives associated with this strand, and the issues extend well beyond the boundaries of process systems engineering, nevertheless process systems engineers have made pioneering developments here also. indeed, there is some evidence that the desire to help students to develop the skills needed to tackle complex engineering problems partly motivated the early research in process systems engineering. such courses and methodologies are also described in the literature. e.g. in [6] an advanced process control course to undergraduates, in [7] an introductory course in computer aided process engineering, in [8] an integrated process design instruction are presented, while in [9] the integration of knowledge management tools is discussed. the role of the industry the successful further development of the body of knowledge available to the process engineer will in future only be possible if the needs of industry are addressed, and to do this engineers in universities and in companies have their respective roles to play in extending the scientific foundations necessary to meet these needs [1]: 1. the universities must train highly qualified engineers who will then be able to go into industry and address the problems awaiting them by using the tools and methods of science. these chemical engineers – when necessary – must be able to work closely together with their colleagues at universities and research institutes. 2. the second prerequisite is that although university research and education is guided by the problems encountered in industry, university scientists should not focus narrowly on meeting the needs of industry rather on extending our fundamental knowledge. such a research and training network requires an understanding on the part of industry that the source of many innovation processes lies in fundamental research. furthermore, research and development departments within companies have to recognize that the goal of developing progressive and competitive technologies can be reached only by being fully aware of the pioneering research being carried out elsewhere. brief description of the department historical background since the beginning of sixties, teaching of chemical technology, based on a unified treatment of technological knowledge segmented in accordance to the branches of industry, as well as teaching of unit operations with an integrative foundation of the fundamental principles has gone on parallel in chemical engineering education. at our university, the former were taught by the technological departments founded simultaneously with the university, while the latter was represented by the department of chemical engineering science, founded by professor antal lászló in 1963. professor pál benedek and professor antal lászló worked out the first course of unit operations at the university. professor rezső mohilla completed the course of unit operations by introducing process dynamics, clearing a way also for teaching automation becoming more and more important in the chemical industry. owing to the development of computers and computing methods, however, decomposition of chemical technologies has not been the stopped on the level of operational units, what has been indicated also by appearance of a new department. on 1 july 1977, the autonomous departmental group of chemical cybernetics was founded by professor péter árva, which was developed into the department of chemical engineering cybernetics in 1990. since 1993, the department, together with the department of chemical engineering science and with the department of hydrocarbon and coal processing, has formed the institute of chemical engineering, which has become responsible for the education of students in chemical engineering. since 1995, professor ferenc szeifert has served in the capacity of the head of the department. 3 research and development strategy in hungary, chemical engineering field represented by the department was born around the end of sixties and the beginning of the seventies and it is being fulfilled these days as the technical environment including microelectronics enables the direct application of the theory in real working processes. parallel with the advance of the field in hungary, key researchers of the department always studied the typical problems: mathematical modelling and simulation of unit operations, simulation of the entire process system, complete description of the chemical processes (from the molecules to the production), coordination-level control of processes, application of chemical engineering models in the design, control (model-based control) and development (model-based process development) of technological systems; along with these the solution of problems of numerical methods, computer techniques, information technology, artificial intelligence; techniques of computer process control and the employment of application software. the department provides an ideal background for establishing the harmony of theoretical and practical problems by connecting closely the academic projects and the application ones. the primary function of the basic research in field of chemical engineering cybernetics (systems engineering) and process engineering is the development of methods and tools for the selection and integration of the necessary knowledge from natural sciences (description of transport processes, complex reaction mechanism and kinetics, description of biochemical processes, determination of phase structures, etc.) and economics (profit, market limitations, etc.) in order to analyze (modelling), design and control chemical processes operating at economic optimum. the department is open for the quick introduction and application of the newest methods (fuzzy techniques, artificial neural networks and other artificial intelligence tools, etc.) and engineering tools (mainly software packages). e.g. at the 90’s our most important otka (national scientific research fund) basic research topics of the past and present periods were the following: ● design and control of chemical processes using crisp and fuzzy information (supervisor: péter árva) ● hierarchical modelling and control of chemical processes (supervisor: péter árva) ● evolutionary structures and learning logic programs (supervisor: béla csukás) ● model-based control of crystallizers (supervisor: béla lakatos) ● design and control of flexible chemical processes (supervisor: ferenc szeifert) all of the basic research topics are associated with r&d projects. researchers of the department in the sixties developed simulators of an ammonia plant and of the bayer process. the direct application of these simulators in the process development and control was quite new in that time. the department was among the firsts applying artificial intelligence methods in solving chemical engineering problems (fuzzy algorithms and neural networks in process control). the fundamental principle of the departmental research is that in case of every basic research topic the possibility of application is sought after, while in case of development projects the possibility of generalization is looked for too. by now, the teaching and research activities of the department of process engineering cover mainly the topics of process system engineering, including: ● modelling and simulation of chemical processes, ● process control of chemical processes and computer controlled systems, ● computer-aided design, development and operation of process systems, ● analysis of historical process and business data (data mining). co-operation with industry and academics the information requirement of process engineering methods and tools used in process analysis, control and development is very high and it is almost impossible to be satisfied inside the limits of a university department. therefore the close working relationships to the industrial firms have an important role both in the educational and the research activities of the department. at the end of the seventies, in cooperation with the companies of hungarian trust of aluminium industry (mat) a simulation system for the bayer cycle was developed at the department. based on this simulator a coordination-level control strategy, which is still in use, was formulated. the cooperation with tvk rt. and borsodchem rt. has been going on for several decades and is mainly related to the polymerization plants. the development is based on the hierarchical models of polymerization developed at the department. there is a continuous cooperation in the development of the control structure of flexible chemical plants and in the formulation of the closed information loop of process development including scale-up with chinoin rt. since 1990. the quality assurance (validation) of process control systems was studied in cooperation with richter rt. joint projects in the development of process control of batch systems are going on in cooperation with batch control kft. and comforth kft. important parts of different projects were elaborated for the invitation of bvm rt., dunastyr rt., nitroil rt., nitrokémia rt. and paks nuclear power plant. cooperation is maintained with several academics departments of mukki and budapest technical university among the hungarian institutes. inside the university of veszprém there are working relationships with the following departments: chemical engineering science, physical chemistry, environmental engineering and chemical technologies, earth and environmental sciences, computer science. of course, we also work 4 with institutes, like, umist (uk), bulgarian academy of sciences (bu), university of bradford (uk), babesbólyai university (ro), katholieke universiteit, leuven, (be), universitat politechnica de catalunya (es), berty reaction engineers, ltd. (usa), delft university of technology (ne). process engineering education at the department of process engineering courses taught by our department in teaching, the department covers the whole range of process engineering, while, regarding its research activity, the main research areas include modelling, model-based process control, design and development as well as process informatics. the department is linked strongly to the training of chemical engineers. a significant part of the topics taught by the staff of the department, however, is invariant under the engineering fields; therefore the department participates also in teaching programs of the environmental engineering, engineering management and material engineering courses. since the chemical industry is one of the most important fields of applications of information systems, and the implementation of information systems are attached strongly to the process control, we expect that the subjects taught by the department will also be included into the program of information technology, and the department will have opportunity of teaching these subjects as well. the department plays important role in the phd education as well. professor péter árva is the leader of the che-2 process engineering phd program, while professor béla lakatos and professor ferenc szeifert and dr. jános abonyi participate in that program as project supervisors. so far, 9 students have finished or have been carrying out their phd research projects at the department in the framework of this program. the department also teaches a number of courses in the framework of other programs. infrastructure used in education in education, the department, besides laying intensive theoretical foundation of engineering knowledge, also emphasizes the practical applications of that knowledge. a continuously improved process engineering laboratory has been developed for that purpose, which includes some operational units and technological systems of smaller size, operated and controlled by means of computers. the departmental local network of some 50 computers connected to the worldwide network through the network of the university assures efficient utilization of the modern hardware and software tools. the system make possible also work of the staff at home. this integrated system of teaching tools involves software packages for simulation, control, design and documentation of technological systems. figure 1: (left) batch process unit at our laboratory (right) computer room at our department our philosophy the above presented system plays a key role in our education, since the courses focus to the application of methods and tools of information technology for solution of process engineering problems, – process analysis and modelling, process design and process control –, where ● wide selection of software packages are available, ● general solution is not available, ● tools cannot be simply integrated, ● application requires good engineering background. hence, our main educational objectives are to: ● prepare students to accept and use these tools, ● develop the necessary skill for the application of computer aided process engineering (cape), ● understand the background and operation of the methods, ● be able to learn the new and appropriate software packages, ● critically evaluate the results obtained, ● have some experience in real application. as can be seen, in our philosophy, cape is not a single subject rather a set of carrier ones which contains more or less foundation and application. the curriculum the chemical engineering curriculum is accredited by the icheme (the institution of chemical engineers which is the leading professional body for chemical and process engineers with an international membership across more than 80 countries.) lecturing and research activities are co-ordinated by a coherent team highly concerned with industrial applications. this lecturing – research – application approach implies that students are in closer contact with industry (internships and projects) during their studies. 5 graduates in chemical engineering become aware of the technical, economic, social and human dimensions of companies and jobs. their training leads to: ● acquiring a solid scientific and technical knowledge and learning to adapt to the constant evolution in process engineering, ● knowing how to apply these concepts to real professional situations, ● developing contacts with industry, with foreign cultures and languages, ● developing individual personalities and personal projects and becoming proficient communicators, ● being more and more autonomous. students are trained to deal with area of process engineering, are prepared to adapt to a diversity of life and work patterns and are prepared to work within a team. they easily take part in the following activities: ● defining and designing production units (choosing processes, studying and optimizing mass and energy balances, implementing environmental impact studies, clean technologies and recycling wastes), ● calculating these units and their dimensions, ● monitoring the setting up and operation of these units. the laboratory exercises made in the last two years at our department, the compulsory one month practical engineering summer training following the 8th term (semester), the design project in semesters 8-9, and the accompanied consultations with industrial and academic experts, are considered as the first steps of the students’ engineering practical career. during these studies students are required to solve various engineering problems, use procedures, collect data and write reports. in addition they can undertake scientific activities, solving independent research exercises in preparation for their research career. conclusions (computer aided) process engineering (cape) tools are widely applied in industry. the department of process engineering at the university of veszprém is active in the research and development of new cape tools and it often contributes to the technological development of local firms in need of technical aid. our services include consulting, analyses, diagnoses, design, and software development. according to our lecturingresearch-application approach the results of these projects are directly used in the education as casestudies, illustrative examples, or as problems for design projects. the up-to-date course materials and internships and design projects ensure that our students are in close contact with industry during their studies. acknowledgements the editor wish to thank professor dr. g. horváth (editor-in-chief) for providing the opportunity to edit this special issue on recent advances in computer aided process engineering. i would like to thank the referees who have critically evaluated the papers within the short stipulated time. finally i hope the reader will share our joy and find this special issue very useful. it is also planned to publish another special issue about the end of the year. the web page www.fmt.vein.hu/racape will contain the latest information about that and about the current special issue. the financial support of the “ipar a veszprémi mérnökképzésért” foundation is gratefully acknowledged. references 1. wintermantel k.: process and product engineering – achievements, present and future challenges, chemical engineering science, 54 (1999) 1601-1620 2. grossmann i. e.: challenges in the new millennium: product discovery and design, enterprise and supply chain optimization, global life cycle assessment, computers and chemical engineering, 29, (2004) 29-39 3. ponton j.: process systems engineering: halfway through the first century, chemical engineering science, volume 50, issue 24, december 1995, pages 4045-4059 4. sargent r. w. h.: introduction: 25 years of progress in process systems engineering, computers and chemical engineering, 28 (2004) 437-439 5. perkins j.: education in process systems engineering: past, present and future, computers and chemical engineering, 26 (2002) 283-293 6. lewin d. r., rockman j., lavie r.: teaching advanced process control to undergraduates, computers and chemical engineering, 20, s.13471352, 1996 7. david i., bogle l.: an introductory course in computer aided process engineering (cape), computers and chemical engineering, 20, s.13231327, 1996 8. lewin d. r., seider w. d., seader j. d.: integrated process design instruction, computers and chemical engineering, 26 (2002) 295-306 9. weijnen m. p. c., herder p. m.: process systems knowledge sharing between higher education and industrial practice, computers and chemical engineering, 24 (2000) 1467-1472 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 17-22 (2008) nickel and zinc removal by complexation-ultrafiltration method g. borbély, e. nagy university of pannonia, fit, research institute of chemical and process engineering h-8201 veszprém, p. o. box 158., hungary e-mail: nagy@mukki.richem.hu, nagye@mik.vein.hu there are a lot of toxic materials in several industrial wastewater streams, for example heavy metals (i.e. zn2+ and ni2+) in the wastes of electroplating industries, which should be removed before recycling or discharging these aqueous solutions into surface water. one of the methods for removing toxic metals is the complexation enhanced ultrafiltration process that might be an effective membrane technique. this method was tested 2 types of polyether-sulphone – pes – membranes with different cut-off and several complexation agents (polyethylene-imine – pei –, polyethylene-glycol – peg –, and 2 types of polyamido-amin dendrimers – pamam) for removal these heavy metals from model solutions by a membrane filtration method, which worked in cross-flow mode. keywords: heavy metal removal, complexation, ultrafiltration, membrane separation introduction in the 21st century, water has been rising into a key position for many industries and also of course for many peoples because of the global environmental trends and problems that started in last few decades of the 20th century. the main parts of heavy metals, which are going out to the environment caused by human activity, are or will be in aqueous solution. there are a lot of heavy metals (i.e. zn2+ and ni2+, etc.) or their oxyanions in up to few hundred mg/dm3 concentration in many industrial wastewaters, for example in the wastes of electroplating industries, which should be removed before recycling or discharging them into a surface water. these metal ions are also toxic, similarly to several other heavy metals. impact of nickel can be manifested in allergic reactions, chronic toxicity (dermatitis nausea, chronic asthma, coughing, abdominal cramps, diarrhea, vertigo and lassitude), but acute toxicity is not typical. it is known that nickel is human carcinogen. zinc is biological essential, but the overdose can lead to depression, lethargy, neurological signs such as seizures and ataxia, and increased thirst [schäfer et al, 1999; kurniawan et al., 2006]. both metals can inhibit or kill the microorganisms in a biological wastewater treatment plant [illés et al., 1983]. the conventional processes to treat this kind of wastewater are e.g. chemical precipitation, ion exchange, adsorption or biosorption – and nowadays membrane separations, like electrodialysis (ed), and pressure-driven methods (nanofiltration (nf) and reverse osmosis (ro)) [kurniawan et al., 2006]. the main disadvantages of these processes are e.g. inadequate selectivity, high residual metal concentration, not high enough concentrated metal concentrates for its reuse, periodical batch processes, etc. one of the pressure driven membrane separation method is the ultrafiltration (uf) that is not suitable directly to remove dissolved metal ions because of the pore size of these membranes are too large (about 201000 å). but in some hybrid processes, i.e. micellar [yurlova et al., 2002] or complexation enhanced uf [smith et al, 1995], metal ions could be removed more than 90% efficiency. theoretically, this process does not have any by-products that could not be reused in industries due to the re-winning of complexation agent and the more quintessential metal solution. the regeneration of the complexation agent can be carried out e.g. by electrodialysis with bipolar membrane system [schlichter et al., 2004]. a lot of parameters influence this separation process, the most important are the following: ● properties of the complexation agent [smith et al., 1995], ● ph of the metal solution [smith et al., 1995; rether & schuster, 2003], ● complexation agent/metal ratio [korus et al., 1999], ● properties of membrane [lee & walker, 2006]. one of the most important problems is to find a nearoptimal bounding agent. there are some requirements for which it should be managed. the most important ones are the following [frenay, 2003]: ● high metal fixation capacity, ● fast reaction rate of metal fixation, 18 ● possibility of regeneration, ● desired chemical and physical stabilities. materials and methods in this paper, complexationor polymer-enhanced ultrafiltration (peuf) of zn2+ and ni2+ was studied, where the tested complexation agents are water soluble polymers. in the first step, a high molecular weight polymer compounds as complexation or bounding agent is added to the metal solution. the produced bounding agent/metal complex by a reversible reaction is removed from the solution by ultrafiltration. in the last step of the process, as it can be seen in fig. 1, the concentrated polymer-metal complex in the retentate phase should be split for its regeneration and the two components should be separated from each other, e.g. by means of conventional membrane process as electrodialysis by bipolar membranes. an important aim of the process is that at the end of this separation step, the metal concentration of the outlet stream needs to be concentrated at about 10-fold higher than in the inlet stream for the economical operation. the applied polymers for the complexation were polyethylene-imine – pei, polyethylene-glycol – peg, and 2 types of polyamido-amin dendrimers – pamam. the main parameters of the polymers were listed in table 1. peis are the most currently applied polymers for complexation-uf, i. e. according to smith & robinson [1998]. it could not be found any data in the literature where metals were removed by pure peg, only when peg is in aggregates with sodium dodecyl sulphate [xiarchos et al., 2008]. pamam dendrimers are a relative new group of polymers. these polymers could be applied in a very wide range of bioand nanochemistry [klajnert & bryszewska, 2001], but they are also excellent for example in this kind of wastewater treatment [diallo et al., 2005]. figure 1: the flowchart of the process table 1: the main parameters of the applied polymers sign function group molecular weight [g/mol] made by pei-25 -nh2 25000 aldrich pei-70 -nh2 70000 polysciences inc. peg -oh 10000 sigma-aldrich pamam g4.5 -cooh 23441 res. inst. of chem. and proc. eng., univ. of pannonia pamam g5.0 -nh2 28825 res. inst. of chem. and proc. eng., univ. of pannonia it was tested 2 types of membranes, both of them were in poly(ether-sulphone), but they had different cutoff, namely 10 and 20 kda, pes-10 and pes-20, respectively. both of them were provided by alfalaval. results were expressed in retention (r [%]) that means the following: 1001[%] 0 ∗⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −= c c r p where cp is the metal concentration of the permeate, and c0 is the metal concentration of the feedstock at t0 = 0 time. (c0 can be changed during separation, but it could be negligible.) tests with peis and peg were carried out in laboratory scale equipment made by beroplan. tests with pamams were carried out only in small scale equipment. the main parameters of the applied membrane filtration equipments showed in the table 2. based on schlichter et al. [11], the regeneration of complexation agents were tested by electrodialysis with bipolar membrane system (edbm). the construction of the module showed in fig. 2. the areas of membranes are 100 cm2 one by one, the applied current was constant 36 v. the applied electrolyte solution was 0.05 m na2so4 and there was in the base cycle 2 g/l nacl. 19 results and discussion it was investigated of the effect of ph, mwco of membrane, polymer/metal molar ratio, feed concentration, temperature and pressure. it was experienced that the membrane with 10 kda pore size was more favourable than with 20 kda. the retention was similar but the flux was higher so the process was faster. thus, majority of the measurements were carried out by membrane with cut-off of 10 kda. temperature in the range investigated (table 2) does not affect significantly the separation. (it can cause only a few percent differences). thus, we could work at room temperature without thermostating the solution. there was a slight increase of temperature during the measurement, because the pump and pipes are heating due to the stream (and the higher viscosity of the feed solution due to the presence of the polymer). figure 2: construction of the module of electrodialysis with bipolar membrane system table 2: the main parameters of the membrane filtration equipments peg peis pamams type of membrane pes-10 pes-10 pes-20 pes-10 method of filtration cross-flow cross-flow dead-end amembrane [cm2] 63.62 63.62 19.63 vfeed [cm3] 1000 1000 50 p [bar] 0.5-5 0.5-5 5 t [°c] 15-25 15-25 ~ 20 (room temp.) ph of polymer ~5 >11 ~11 ph of metal solution 2.1 (zn2+)* 5.5 (ni2+)* 2-9 2; 7; 9 polymer/metal [mol/mol] 0.1; 1 0.001-5 (pei-25) 0.001-0.1 (pei-70) 0.1; 1 *: ph of 0.01 m zncl2 and nicl2 according to some researchers [i.e. korus et al. 1999], ph has a significant effect on the retention. in our measurements, these results could not be obviously reproduced in case of pei, but could be it in case of pamam, as it can be seen in fig. 3 and 4. the ph of feed solution is determined by that of polymer solution and not by the ph of the metal solution, because of polymer solution had a very high buffer capacity. retention was calculated from our measered data. an example for the calculation is the following: vfeedstock = 500 ml (=250 ml 0.001 m nicl2 + 250 ml 0.001 m pei-25) so, c0 = 0.0005 m = 29.345 mg/l, and pei/me2+ = 1. the ph was 7, temperature was about 20 °c. permeatum volume was 40 ml/h, what is an average quantity from 3 measurements. flux can be described by the following equation: hm l29.6 h1m1036173.6 1000/ml40 ta v 223 permeatemembrane permeate = ∗∗ = ∗ =φ − . retention was calculated about the equation what could be seen above: %64.98100 l/mg345.29 l/mg4.01100 c c 1r 0 p =∗⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −=∗⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −= , where cp was determined by atomic absorption spectrophotometry. 50 60 70 80 90 100 r [% ] 2 7 8 9 ph of metal solution ni zn figure 3: retention of ni2+ and zn2+ binding by pei-25 versus ph of metal solution pei/me2+ = 1 mol/mol, pes-10 membrane 20 0 10 20 30 40 50 60 r [% ] 2 7 8 9 ph of metal solution zn-pamam g4.5 zn-pamam g5.0 ni-pamam g4.5 ni-pamam g5.0 figure 4: capacity of metal bounding of pamam dendrimers versus ph of metal solution pamam/me2+ = 1 mol/mol, pes-10 membrane according to müslehiddinoğlu et. al. [8], the complexation is affected more by the ratio of complexation agent/metal ion than by the initial concentration of metal or complexation agent polymer. this statement was supported also by our measurements. the effect of the molar ratio of the polymer and metal is plotted in fig. 5 and 6. let us look at first the ni2+ separation (fig. 5). retention obtained more than 90 % (in some cases close up to 100 %). it is surprising that retention is high at very low value of the molar ratio of polymer and metal ion, even in the case when it is far below 1. this behaviour needs explanation. further measurements should be carried out for it. the change of retention has similar tendency in the case of zn2+. e.g. at molar ratio of 0.01, the zinc retention reaches about 100 %. increasing the molar ratio upto 5, slight decrease of retention could be observed in both cases. retention is somewhat lower in the case of the pamam dendrimer. it should be known that only in cases of pamams were ph adjusted, in the other cases it was kept at ph of metal solution. (see for it fig. 3 and 4.) the effect of the feed metal ion concentration was investigated at few concentrations. the results are listed in table 3. its effect is not significant on retention. 0 20 40 60 80 100 0 0,001 0,01 0,1 1 5 polymer/metal [mol/mol] r [% ] pei-25 pei-70 peg pamam g4.5 pamam g5.0 0 20 40 60 80 100 0 0,001 0,01 0,1 1 5 polymer/metal [mol/mol] r [% ] membrane: pes-10; cfeed of polymers: 0.001 m; p: 5 bar figure 5: effect of the complexation agent for the figure 6: effect of the complexation agent for the metal removal in case of ni2+ metal removal in case of zn2+ table 3: the effect of the metal ion concentration in the feed solution for the retention (t = 20 °c, without ph adjustment) me2+ polymer membrane polymer/me2+ [mol/mol] p [bar] cfeed [m] r [%] 3 93.35 5 0.01 81.77 3 93.18 ni2+ pei-25 pes-20 1 5 0.001 95.47 3 59.00 5 0.01 60.23 3 82.10 zn2+ pei-25 pes-20 1 5 0.001 83.79 3 5 0.01 99.97 3 zn2+ pei-70 pes-10 0.01 5 0.001 99.69 the effect of pressure was dual: first, it is well known that on higher pressure the flux is also higher. however, the process will be faster, but it will expectedly be less effective. in our cases, it is difficult to explain the effect of pressure. there is a minimum point in all the pressure-retention curves, as it can be seen in case of ni2+ with pei-25 in fig. 7. this could mean that the separation equipment could be operated at 21 lower pressure range. but it should also be taken into account, that the permeation rate will be higher at higher pressure range. the achieved maximal enrichment in cases of polymers with the necessary operating parameters showed in table 4. regeneration of complexation agents is the basic problem of these kinds of systems. there are only a few data about this step of the process in the literature, i.e. one of the work of schlichter et. al. [11]. we have carried out preliminary experiments in this respect, but results obtained (table 5) should improved by further experiments. 90 92 94 96 98 100 0 1 2 3 4 5 p [bar] r [% ] t = 15 c t = 20 c t = 25 c figure 7: effect of transmembrane pressure on removal of ni2+ with pes-10 membrane at different temperature. pei-25/ni2+ = 1 mol/mol table 4: the achieved maximal retention by complexation polymers membrane t [°c] p [bar] polymer/me2+ [mol/mol] cfeed [m] r [%] ph of me2+* ni2+ pei-25 pes-20 20 1 0.01 0.1 99.87 pei-70 pes-10 20 0.5 0.001 0.001 99.66 peg pes-10 20 0.5 0.01 0.001 99.78 pamam g4.5 pes-10 20 5 1 0.001 56.38 9 pamam g5.0 pes-10 20 5 1 0.001 39.00 9 zn2+ pei-25 pes-10 20 0.5 0.001 0.1 99.96 pei-70 pes-10 20 0.5 0.01 0.01 99.97 peg pes-10 20 1 0.01 0.01 99.53 pamam g4.5 pes-10 20 5 0.1 0.001 48.61 9 pamam g5.0 pes-10 20 5 0.1 0.001 69.81 9 *: free cell means there was not ph adjustment table 5: regenerated portion of bounding agent polymers from metal complex by electrodialysis pei-25 pei-70 peg pamam g.4.5 pamam g5.0 ni2+ 21.4 % 23.7 % 47.4 % 69.0 % 19.4 % zn2+ 19.5 % 30.3 % 45.5 % 33.6 % 75.3 % conclusions the complexation-ultrafiltration method can applied appropriate for heavy metal removal. in this paper, there are different types of water soluble polymer with high molecular weight, which could be applied for this kind of separation process, well. as it was shown, for removal of nickel and zinc ion with complexationultrafiltration method, both of the bounding agents with hydroxyl, carboxyl and amin groups were quiet effective. temperature, ph, feed concentration of metals did not affect the process significantly, but pressure and polymer/metal ratio could be very important operating parameters, which should be the highest priority in this type of metal removal. by the integration of the complexation-ultrafiltration and the electrodialysis steps, it gave a semi-continuous process for the removal. the bottle-neck of the process is the regeneration of the complexation agents. this problem should be solved in order to obtain economic and environmentally friendly separation process. acknowledgements we kindly acknowledge pál halmos (dept. of the analytical chemistry, univ. of pannonia) for the analytical measurements and the hungarian scientific research fund under grants otka 63615/2006 for supported this work. references 1. diallo, m. s., christie, s., swaminathan, p., johnson, j. h. jr., goddard, w. a.: dendrimer enhanced ulrafiltration. 1. recovery of cu(ii) from aqueous solutions using pamam dendrimers with ethylene diamine core and terminal nh2 groups, environmental science & technology 39 (2005) 1366-1377 2. frenay, j.: permea 2003 proceedings of the membrane science and technology conference of the visegrad countries with wider international 22 participation, tatranské matliare, slovakia, 7-11 september, 2003, p. 38 3. illés, i., kelemen, l., öllős, g.: industrial water management, vízdok, budapest, 1983, pp. 231 (in hungarian) 4. klajnert, b., bryszewska, m.: dendrimers: properties and applications, acta biochimica polonica 48 (2001) 199-208 5. korus, i., bodzek, m., loska, k.: removal of zinc and nickel ions from aqueous solutions by means of the hybrid complexation–ultrafiltration process, separation and purification technology 17 (1999) 111-116. 6. kurniawan, t. a., chan, g. y. s., lo, w. h., babel, s.: physico–chemical treatment techniques for wastewater laden with heavy metals, chemical engineering journal 118 (2006) 83-98. 7. lee, j., walker h. w.: effect of process variables and natural organic matter on removal of microcystin-lr by pac – uf, environmental science & technology 40 (2006) 7336-7342 8. müslehiddinoğlu, j., uludağ, y., özbelge, h. ö., yilmaz, l.: determination of heavy metal concentration in feed and permeate streams of polymer enhanced ultrafiltration process, talanta 46 (1998) 1557-1565 9. rether, a., schuster, m.: selective separation and recovery of heavy metal ions using water-soluble n-benzoylthiourea modified pamam polymers, reactive & functional polymers 57 (2003) 13-21. 10. schäfer, s. g., dawes, r. l. f., elsenhans, b., forth, w.: metals, in: marquardt, h., schäfer, s. g., mcclellan, r. o., welsch, f. (eds.): toxicology, academic press, 1999, pp. 755-804. 11. schlichter, b., mavrov, v., erwe, t., chmiel, h.: regeneration of bonding agents loaded with heavy metals by electrodialysis with bipolar membranes, journal of membrane science 232 (2004) 99-105 12. smith, b. f., robison, t. w., cournoyer, m. e., wilson, k. v., sauer, n. n., mullen, k. i., lu, m. t., jarvien, j. j.: polymer filtration: a new technology for selective metals recovery, sur/fin ’95: american electroplaters and surface finishers society meeting and exhibition, baltimore, md (united states), 25-28 jun 1995 13. smith, b. f., robison, t. w.: water-soluble polymers for recovery of metal ions from aqueous streams, united states patent, patent number: 5766478, 1998 14. xiarchos, i., jaworska, a., zakrzewskatrznadel, g.: response surface methodology for the modelling of copper removal from aqueous solutions using micellar-enhanced ultrafiltration, journal of membrane science (2008), article in press 15. yurlova, l., kryvoruchko, a., kornilovich, b.: removal of ni(ii) ions from wastewater by micellar-enhanced ultrafiltration, desalination 144 (2002) 255-260 page 1 page 2 page 3 page 4 page 5 page 6 page 7 page 8 page 9 page 10 page 11 page 12 page 13 page 14 page 15 page 16 page 17 page 18 page 19 page 20 page 21 page 22 page 23 page 24 page 25 page 26 page 27 page 28 page 29 page 30 page 31 page 32 page 33 page 34 page 35 page 36 page 37 page 38 page 39 page 40 page 41 page 42 page 43 page 44 page 45 page 46 page 47 page 48 page 49 page 50 page 51 page 52 page 53 page 54 page 55 page 56 page 57 page 58 page 59 page 60 page 61 page 62 page 63 page 64 page 65 page 66 page 67 page 68 page 69 page 70 page 71 page 72 page 73 page 74 page 75 page 76 page 77 page 78 page 79 page 80 page 81 page 82 page 83 page 84 page 85 page 86 page 87 page 88 page 89 page 90 page 91 page 92 page 93 page 94 page 95 page 96 page 97 page 98 page 99 page 100 page 101 page 102 page 103 page 104 page 105 page 106 page 107 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page 441 page 442 page 443 page 444 page 445 page 446 page 447 page 448 page 449 page 450 page 451 page 452 page 453 page 454 page 455 page 456 page 457 page 458 page 459 page 460 page 461 page 462 page 463 page 464 page 465 page 466 page 467 page 468 page 469 page 470 page 471 page 472 page 473 page 474 page 475 page 476 page 477 page 478 page 479 page 480 page 481 page 482 page 483 page 484 page 485 page 486 page 487 page 488 page 489 page 490 page 491 page 492 page 493 page 494 page 495 page 496 page 497 page 498 page 499 page 500 page 501 page 502 page 503 page 504 page 505 page 506 page 507 page 508 page 509 page 510 page 511 page 512 page 513 page 514 page 515 page 516 page 517 page 518 page 519 page 520 page 521 page 522 page 523 page 524 page 525 page 526 page 527 page 528 page 529 page 530 page 531 page 532 page 533 page 534 page 535 page 536 page 537 page 538 page 539 page 540 page 541 page 542 page 543 page 544 page 545 page 546 page 547 page 548 page 549 page 550 page 551 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objective now is to produce, store, transport and use fuels with lower emission levels. until the last couple of years the vegetable oils were mostly transesterified catalytically to biodiesel to produce fuels. because of the numerous disadvantages of biodiesel production and application the alternative chemical transformations of triglycerides were started to be studied intensively. one of the best alternative is to convert the vegetable oils (or other materials containing triglycerides) and/or their blends with gas oil to hydrocarbons rich in paraffins. these compounds can be applied in diesel-engines directly or blended with petroleum-based gas oil. in our experimental work we examined the heterogeneous catalytic conversion of light gas oil fraction containing 10% sunflower oil on transition metal/al2o3 catalyst. our objective was to study the effect of the operating parameters to the yield of liquid organic products, to the yield of the fraction of gas oil boiling point range and to the product properties. based on our results it can be concluded that with the catalytic hydrogenation of the feedstock containing 10% sunflower oil products with excellent properties can be produced with high yield. the product gas oil had <10 mg/kg sulphur and nitrogen content, lower than 10% total aromatic content and <-5°c cold filter plugging point. the cetane number of the products was significantly higher than the limit (51) of the en 590:2004 standard. keywords: sunflower oil, vegetable oil-gas oil mixtures, biogasoil, heterogenous hydrogenation. introduction the applicability of vegetable oils (tryglycerides) and their derivates is well-known for a long time. the main goal (to produce fuels from non-fossil based energy source) has been extended with the global aims of reducing the environmental pollution, thus to produce, store, transport and use fuels with lower emission levels (carbon-monoxide, hydrocarbons, sulphurand nitrogenoxides, particulates, carbon-dioxide). this could contribute to reduce the chances of acidic rains and the emergence of greenhouse effect. it is well-known that vegetable oils and their derivatives are biodegradable fuels. the aim to use biofuels is significant mostly in the countries of european union. the main reason for this is the deliberate energy policy of the european union, which would like to decrease its dependence on import crude oil due to the unequal distribution of the world’s crude oil reserves. to help this aim, the european council and the european parliament made the 2003/30/ec directive which commited the countries to raise their biofuel share to 2.0% (until 2005) and 5.75% (until 2010) according to the energy content of the transportation-use gasoline and gas oil [1]. as a result in the eu the share of biofuels was only 1.4% in 2005 [2]. according to the newest aims in the eu countries this value has to be raised to a minimum average of 10% until 2020 [3]. one of the solution could be the conversion of vegetable oils and other triglycerides to different fuels, primarily to gas oil boiling range products. until the last couple of years the most commonly applied conversion of triglycerides containing vegetable oils was their catalytic transesterification to biodiesel fuel (vegetable oil fatty acid methyl esters) [4]. this technology and the biodiesel itself have numerous disadvantages which have adverse effect on the applicability and the economics. one main problem is the high amount of glycerol by-product, which caused overproduction in the world market and reduced the price of the glycerol (fig. 1). the glycerol can be unmerchantable in the near future [5]. the alternative chemical transformations of triglycerides were started to be studied intensively due to the numerous disadvantages of biodiesel production and application [6-10] (e.g. high iodine value, high water content, higher cfpp (cold filter plugging point), higher viscosity, hydrolysis sensitivity, storage problems, phosphorous content, methanol content, lower energy content, lower heating value, higher cost). 72 0 500 1000 1500 2000 2500 19 95 19 96 19 97 19 98 19 99 20 00 20 01 20 02 20 03 20 04 20 05 20 06 pr ic e of r ef in ed g ly ce ro l, u sd /t .. . trend actual price figure 1: changing of the price of refined glycerol one of the best alternative is to convert the vegetable oils (or other materials containing triglycerides) and/or their blends with gas oil to hydrocarbons rich in paraffins. these compounds can be applied in diesel-engines directly or blended with petroleum-based gas oil. through the reactions of catalytic hydrogenation of triglycerides primarily normal and isoparaffins, propane, carbon-oxides (co2, co), water and oxygenate compounds are formed according to the next gross equation: ch2 ch o o ch2 c o c o o c r1 o r2 r3 triglycerides catalysts h2, t, p n-paraffins +i-paraffins+ oxygen containing compounds by-products: co + co2 + ch4 + c3h8 + h2o through this process the adequately pretreated triglycerid molecules transform simultaneously or consecutively according to the following reactions [11,12]: – saturation (hydrogenation) of double bonds, – heteroatom removal, o hydrodeoxygenation (dehydration, hdo reaction), o decarboxylation, o decarbonization, – (hydro)cracking of fatty acid chains. through the catalytic hydrodeoxygenation (dehydration, hdo reaction) 1 mol triglycerid molecule is converted to 3 mol n-paraffins having the same chain length as the fatty acid and furthermore, to propane and water (for example in the case of a triglycerid which contains three oleic acid chain) according to the followings: c ch2 o och2 ch c o och2 c o o ch2 ch3ch2 ch ch 76 ch2 ch2 ch3ch2 ch ch 76 ch2 ch2 ch3ch2 ch ch 76 + 15 h2 cat., t, p 3 n-c18h38 + c3h8 + 6 h2o during decarboxylation reaction the deoxygenation produce co2 beside the saturation (hydrogenation) of the double bonds in the fatty acid chain. in this case carbon number of the emerging hydrocarbons is lower by one compared to the triglycerid chains. (for example in the case of a triglycerid which contains three oleic acid chain): c ch2 o och2 ch c o och2 c o o ch2 ch3ch2 ch ch 76 ch2 ch2 ch3ch2 ch ch 76 ch2 ch2 ch3ch2 ch ch 76 + 6 h2 cat., t, p 3 n-c17h36 + c3h8 + 3 co2 during decarbonization reaction 1 mol triglycerid is converted to 3 mol n-paraffins which have lower carbon number by one compared to the fatty acid chains. propane, carbon-monoxide and water are also produced. c ch2 o och2 ch c o och2 c o o ch2 ch3ch2 ch ch 76 ch2 ch2 ch3ch2 ch ch 76 ch2 ch2 ch3ch2 ch ch 76 + 9 h2 cat., t, p 3 n-c17h36 + c3h8 + 3 co + 3h2o the probability of these deoxygenation reactions depends on the catalyst, the temperature, the pressure and the liquid hourly space velocity. according to our experience, usually all three reactions take place simultaneously. the heterogeneous catalytic transformation of vegetable oil triglycerides in the presence of hydrogen can be performed in different ways (fig. 2). in the first alternative process the vegetable oil (or/and other triglycerid) is deoxygenated after adequate pretreatment, and the produced high n-paraffin containing mixture is isomerized (if necessary and after separation). the product, which has high cetane number and good cold flow properties, is called biogasoil [10, 13, 14]. in the second alternative process the vegetable oil are deoxygenated after the pretreatment and the produced high n-paraffin containing mixture (very high cetane number, but bad cold flow properties) is blended into ultra low sulphur gas oil [15]. in the third alternative process the pretreated vegetable oil is blended into a refinery gas oil stream and the mixture is converted in an existing (or slightly modified) desulphurization unit [16]. pretreatment hdo isomerizationvo biogasoil pretreatment hdovo hdsgas oil blend of biogasoil and petroleumderived gas oil pretreatmentvo gas oil hds gas oil containing biogasoil figure 2: alternatives for the production of biogasoil (vo: vegetable oil; hdo:hydrodeoxygenation; hds: hydrodesulfurization) 73 in case of every technology pretreatment of vegetable oils is necessary with proper severity. this should be fitted to the other technology steps and should be made in a reactor containing protection catalyst and in continous operation. in the protection reactor the metal(ca, k, mg), phosphorous and solid contaminant content of the vegetable oil (and/or other triglycerides) are eliminated with proper operating conditions and catalyst. currently a lot of companies and research institues are intensively studying the realization of the alternative processes and their setting to the local equipments. [1017]. the goal of our experimental work was to examine a chemical conversion option to enhance the quality of gas oil fraction containing 10% sunflower oil to produce diesel fuel and/or blending component with excellent properties. one of the major objectives was to find the advantageous process parameters (temperature, pressure, liquid hourly space velocity, hydrogen/hydrocarbon ratio) on the applied transition metal/al2o3 catalyst for the conversion of this feedstock. experimental work in the experimental work we examined the heterogeneous catalytic conversion of light gas oil fraction containing 10% sunflower oil on transition metal/al2o3 catalyst. our objective was to study the effect of the operating parameters on the yield of liquid organic products, on the yield of the gas oil boiling range fraction and on the product properties. the obtained results were compared to the results of the conversion of 100% gas oil and of 100% vegetable oil. the selection of the operating parameters was based on the results of our previous experiments and took into consideration the physical and chemical properties of the gas oil and the vegetable oil. apparatus the experiments were carried out in an apparatus containing a tubular down-flow reactor of 100 cm3 effective volume, and all the equipments and devices applied in the reactor system of an industrial heterogeneous catalytic plant. the experiments were carried out in continuous operation [18]. materials the feedstock was a gas oil – vegetable oil mixture which contained 10% properly pretreated hungarian sunflower oil. the main properties of the feedstock are presented in table 1. the catalyst was an expediently chosen transition metal/al2o3 catalyst. table 1: the main properties of the gas oil and the gas oil-vegetable oil mixture properties gas oil gas oil – vegetable oil mixture density at 15 °c, g/cm3 0.7997 0.8091 kinematic viscosity, 40°c, mm2/s 1.66 2.06 cetane number 51.0 50.7 sulphur-/ nitrogencontent, mg/kg 540/11 499/9 aromatic content, % mono 10.1 9.2 di 4.2 3.9 total 14.3 13.1 analytical and calculation methods the properties of the feedstock and the products were measured and calculated according to the methods of the en 590:2004 standard. these methods are summarized in table 2. table 2: the applied analytical methods properties method/device density en iso 12185:1996 viscosity, 40°c en iso 3104:1996 cold filter plugging point en 116:1997 sulphur content en iso 20846:2004 (multi ea 3100 /greenlab) nitrogen content astm-d 6366-99 (multi ea 3100 /greenlab) hydrocarbon composition gas chromatography (trace gc 2000) distillation characteristic en iso 3405:2000 aromatic content en 12916:2000 results and discussion from the experiments carried out on multiple catalyst systems in wide range of parameters (t: 200–400°c; p: 20–100 bar; lhsv: 0.5–5.0 h-1; h2/feedstock volume ratio: 200–1000 nm3/m3) in this paper the results of the heterogeneous catalytic experiments with gas oil of 10% sunflower oil content are presented between the following parameter range: 300–380°c; 80 bar; 1.0–3.0 h-1; 600 nm3/m3. product yields the products were fractionated to three main fractions: gaseous-, waterand liquid organic fractions. the gaseous phase contained the carbon-monoxide, carbon 74 dioxide, the propane formed from the triglycerid molecule and other light hydrocarbons (from the cracking reactions). the main components of the liquid organic fraction (c5-c20+ fraction) were the light liquid hydrocarbons (c5-c10 paraffins), the gas oil boiling range hydrocarbons (c11-c20 paraffins) and the residue (c20+). based on our results it can be concluded that with increasing the pressure and the temperature and decreasing the lhsv the yield of total liquid organic product decreased. (fig. 3 and 4). the reason of the previous is that the hydrocracking reactions became dominant higher vegetable oil conversion and causing gas oil component cracking. in the tested parameter range the liquid organic product yield was higher than 93% in every case related to the weight of the feedstock. 92.0 93.0 94.0 95.0 96.0 97.0 98.0 99.0 100.0 300 320 340 360 380 temperature, °c y ie ld o f o rg an ic li qu id p ha se , % ... 80bar/lhsv=1.0 1/h 80bar/lhsv=2.0 1/h 80bar/lhsv=3.0 1/h figure 3: organic liquid product yields as a function of temperature and lhsv 90.0 91.0 92.0 93.0 94.0 95.0 96.0 97.0 98.0 99.0 100.0 300 320 340 360 380 temperature, °c y ie ld o f o rg an ic li qu id p ha se , % . 60bar/lhsv=1.0 1/h 70bar/lhsv=1.0 1/h 80bar/lhsv=1.0 1/h figure 4: organic liquid product yields as a function of temperature and pressure the main objective of this experimental work was to convert the triglycerid molecules to gas oil boiling range product. so it is important to know how the amount of this target fraction (c11-c20 hydrocarbons) changed as a function of different operating parameters. from the results it can be concluded that the amount of gas oil boiling range product increased with the decrease of temperature and increase of lhsv (fig. 5). the reason is that the cracking reactions take place less frequently at lower temperatures and higher lhsv than at higher temperatures and lower lhsv. the amount of residues were in every case under 0.4%, which indicates the nearly total conversion of triglycerides. 77.0 78.0 79.0 80.0 81.0 82.0 83.0 84.0 300 320 340 360 380 temperature, °c y ie ld o f g as o il bo lin g ra ng e fr ac tio ns . (c 11 -c 20 h yd ro ca rb on s) , % 80bar/lhsv=1.0 1/h 80bar/lhsv=2.0 1/h 80bar/lhsv=3.0 1/h figure 5. yield of gas oil boling range fractions (c11-c20 hydrocarbons) as a function of temperature and lhsv we examined the effect of sunflower oil blending on the yield of the produced hydrocarbons at advantageous process parameters. the results are compared to the results of processing 100% sunflower oil. on the examined catalyst and at the applied parameter combinations (fig. 6) the yield of light hydrocarbons (c5-c10) decreased by 2–3%, however the gaseous product yield practically did not change (~ 6%) with the blending of 10% sunflower oil to the feedstock. during the experiments carried out with the 100% sunflower oil the yield of light hydrocarbons decreased significantly (12–17 absolut%). 0.0 5.0 10.0 15.0 20.0 25.0 300 320 340 360 380 temperature, °c y ie ld o f l ig ht h yd ro ca rb on s . (c 5c 10 p ar af fin s) , % 0% sunflower oil 10% sunflower oil 100% sunflower oil figure 6: yield of light hydrocarbons (c5-c10 paraffins) as a function of the temperature and the sunflower oil content of the feedstock (80 bar, 1.0 h-1) the yield of gas oil boiling range products (c11-c20 hydrocarbons) decreased with increasing temperature because of the cracking reactions. the 10% sunflower oil content has good effect to the yield of this fraction (fig. 7). that is because through the heterogeneous catalytic transformation mainly gas oil boiling range compounds (c11-c20) are produced from the triglycerides, as we presented in the introduction of this paper. the yield of c15-c18 paraffins increased with the sunflower oil blending (approximately 3%) of course (fig. 8), but it was far from the thoretically available 8.1–8.6%. that is because at the examined severe operating conditions light hydrocarbons were produced in relatively high amount (12–17%) from the 10% sunflower oil content gas oil. 75 74.0 75.0 76.0 77.0 78.0 79.0 80.0 81.0 82.0 83.0 84.0 85.0 300 320 340 360 380 temperature, °c y ie ld o f g as o il bo lin g ra ng e fr ac tio ns . (c 11 -c 20 h yd ro ca rb on s) , % 0% sunflower oil 10% sunflower oil 100% sunflower oil figure 7: yield of gas oil boling range fractions as a function of the temperature and the sunflower oil content of the feedstock (80 bar, 1.0 h-1) 0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 300 320 340 360 380 temperature, °c y ie ld o f c 15 -c 18 p ar af fin s , % . 0% sunflower oil 10% sunflower oil 100% sunflower oil figure 8: yield of c15-c18 paraffins as a function of the temperature and the sunflower oil content of the feedstock (80 bar, 1.0 h-1) main properties of gas oil boiling range fractions out of the properties of gas oil boiling range products (c11-c20) the changes in the sulphurand aromatic content, the cfpp and the cetane number are presented in this paper. the cold filter plugging points of gas oil boiling range fractions obtained from the 10% sunflower oil containing gas oil decreased with increasing temperature and decreasing lhsv (fig. 9). that is because through the cracking reactions lower carbon number products are formed with better cfpp. increasing the sunflower oil content had an increasing effect to the cfpp of the products (fig. 10), because the vegetable oil triglycerides were converted to mainly n-paraffins (c15-c18), which have disadvantageous cold flow properties (melting point: +10 – +28°c), but high cetane number (90–110). that is why the cetane number of gas oil boiling range products increased with 2,5–4,0 at these advantageous parameters and this value is higher than the value in the en 590:2004 standard (51). the sulphur contents of gas oil boiling point fractions made from the 10% sunflower oil content gas oil decreased with increasing temperature and decreasing lhsv (fig. 11). it can be concluded, that already at 340 °c, 60 bar and 3.0 h-1 we produced products with sulphur content lower than 10 mg/kg. applying feedstock with higher sunflower oil content (with lower sulphur content) at same operating conditions the sulphur contents of the products were lower, of course. -18.0 -16.0 -14.0 -12.0 -10.0 -8.0 -6.0 -4.0 -2.0 0.0 300 320 340 360 380 temperature °c c fp p, ° c 60bar/lhsv=1,0 1/h 60bar/lhsv=2,0 1/h 60bar/lhsv=3,0 1/h figure 9: the cfpp of gas oil boiling range fractions (c11-c20 paraffins) as a function of temperature and lhsv -40.0 -30.0 -20.0 -10.0 0.0 10.0 20.0 30.0 300 320 340 360 380 temperature, °c c fp p, °c 0% sunflower oil 10% sunflower oil 100% sunflower oil figure 10: the cfpp of gas oil boiling range fractions (c11-c20 paraffins) as a function of temperature and the sunflower oil content of the feedstock (80 bar, 1.0 h-1) 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 24.0 26.0 28.0 30.0 300 320 340 360 380 temperature, °c su lp hu r co nt en t, m g/ kg . 60bar/lhsv=1.0 1/h 60bar/lhsv=2.0 1/h 60bar/lhsv=3.0 1/h figure 11: sulphur content of gas oil boiling range fractions (c11-c20 paraffins) as a function of temperature and lhsv the aromatic contents of gas oil boiling range fractions obtained from the 10% sunflower oil containing gas oil changed according to minimum curve as a function of temperature (fig. 12). the reason is that below the advantageous temperature the kinetic inhibition, over the advantageous temperature the termodynamic inhibition suppresses the aromatic saturation. since the sunflower 76 oil do not contain aromatics, the higher blending ratio decreases the total aromatic content of the product, of course. 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 300 320 340 360 380 temperature, °c t ot al a ro m at ic c on te nt , % . 60bar/lhsv=1.0 1/h 60bar/lhsv=2.0 1/h 60bar/lhsv=3.0 1/h figure 12. total aromatic content of gas oil boiling range fractions (c11-c20 paraffins) as a function of temperature and lhsv summary based on the results it can be concluded that with the hydrogenation of 10% sunflower oil containing gas oil products having excellent properties with high yield can be produced. we found the process parameters (t: 340–360 °c; p: 60-80 bar; lhsv: 1.0–3.0 h-1; h2/feed volume ratio: 600 nm3/m3) where the produced gas oil boiling range products had sulphurand nitrogen content lower than 10 mg/kg, total aromatic content lower than 10%, cfpp lower than -5°c and cetane number significantly higher than the value in the en 590:2004 standard (≥51). this is due to the high paraffin content of the products which mainly derived from the conversion of the vegetable oil part of the feedstock. references 1. official journal of the european union, 142, (2003) 42-46 2. commission of the european communities, com(2006) 845 final, (2007) 3. commission of the european communities, com(2006) 848 final, (2006) 4. anon.: world ethanol and biofuels report 4 (2006) 365. 5. graff g.: purchasing magazine, 2006.06.15. 6. tyson, k. s., mccormick r. l.: nrel/tp-54038836 report (2006) 7. mittelbach, m., remschmidt, c.: biodiesel: the comprehensive handbook, martin mittelbach, graz, 332 pp (2004) 8. knothe, g. van gerpen, j. krahl, j.: the biodiesel handbook, the american oil chemists' society, champaign, il usa, 303 pp (2005) 9. graboski, m. s. mccormick r. l.: prog. energy and comb. science 24, (1998) 125-164 10. hancsók j., krár m., magyar sz., boda l., holló a., kalló d.: microporous and mesoporous materials, 101, (2007) 148-152 11. corma a., huber, g. w.: angew. chem. int. ed. 46, (2007) 7184-7201 12. krár m., magyar sz., thernesz a., holló, a. boda l., hancsók j.: in of 15th european biomass conference proceedings (2007) 1988-1992 13. leiveld b.: catalysts courier, 65, (2006) 8-9 14. marinangeli r., mccall m., marker t., holmgren j.: alche symp., chicago, 11.10.06. 15. stumborg m., wong a., hogan e.: bioresource technology 56, (1996) 13-18 16. costa p. r.: ptq biofuels (2007) 32-33 17. hancsók j., krár m., magyar sz. boda l., holló a., kalló d.: studies in surface science and catalysis 170 b, (2007) 1605-1610 18. nagy g. hancsók j., varga z., pölczmann gy., kalló d.: topics in catalysis 45, (2007) 195-201 microsoft word content.doc hungarian journal of industry and chemistry veszprém vol. 40 (2) pp. 77–82 (2012) application of the remote earth potential in cathodic protection measurements z. lukacs indexon ltd., 8 veres acs str., 6725 szeged, hungary e-mail: lukacs.zoltan@indexon.hu the conventional potential measurements and evaluation methods of cathodic protection diagnostics do not give reliable results in some practically important cases: in systems where the whole amount of cathodic protection current cannot be interrupted for any reason or the equalizing currents affect the protection to a significant level or interference with other cathodic protection systems is encountered. the paper discusses a model and its practical application dealing with these difficult cases. the test measurement evaluation results justify the theoretical model. on the basis of the theory a very simple measurement method is proposed for the determination of the coating defects ir-free potentials. keywords: cathodic protection, ir-free potential, pipeline corrosion, coating defect 1. introduction the cathodic protection is a widely used, robust and reliable method of corrosion protection of underground pipelines, tank bottoms and underwater parts of immersed structures, e.g. ships and drilling platforms. in the past eight decades a lot of experience has been accumulated concerning the applicability and limitations of cathodic protection. in the most widespread type of cathodic protection, the impressed current systems, the structure to be protected is connected to the negative output of a dc current source („cp station”) and the positive output is connected to a so-called earthing anode which serves for the closing of the electrical circuit (see a typical arrangement for a cathodically protected pipeline in figure 1). the output of the dc source is variable and, in modern devices, can be regulated, either for constant potential or for constant current. if no cathodic protection is applied to a structure corroding in water or soil and no net current is flowing through the structure, then the sum of the anodic (corrosion) and cathodic currents is zero. the ultimate criterion of the effectiveness of cathodic protection is the level of suppression of the anodic current. this can be achieved with the cathodic polarization of the structure. the decrease of the anodic current cannot be measured directly. however, if the applied potential is sufficiently negative (cathodic) then the anodic current (and the corrosion rate) is suppressed, with increasing cathodic polarization theoretically beyond any limit; practically a decrease of 1–2 orders of magnitude can be implemented, which is satisfactory for the practical requirements in most cases. in conclusion, the negative polarization of the structure results in the suppression of the anodic current (this was the goal) and in the increase of the cathodic current, which is an unavoidable consequence of the potential shift, sometimes with unfavourable side effects. during the past decades a lot of empirical experience has been accumulated concerning the optimal operation conditions of cathodic protection. it has been assumed for a long time that cathodic protection has the best performance in typical applications in soils if the electrode potential of the structure is more negative than -850 mv, measured against a saturated copper/copper sulphate electrode [1] (its standard potential at 25°c is 320 mv; all potential data will be given against this type of reference electrode unless specified otherwise). the lower limit of the potential varies for different applications but it is typically assumed to be between 1100 and 1300 mv1. the electrode potential, as discussed above, is the potential that can be measured with a reference electrode placed to the direct vicinity of the electrode, i.e. which does not include any component from the ohmic potential drop through the electrolyte2. this potential, called as ir-free potential, is a central concept in cathodic protection. 1 at more negative potential the excessive rate of cathodic current may have adverse effects on the structure or on the coating. 2 there is another source of the ohmic potential drop, namely, the drop in the electric conductor, which can also be significantly high in the case of pipelines, but this source will not be dealt here; in this paper the ohmic drop is understood as the ohmic potential drop through the electrolyte between the anode and the cathode. 78 figure 1: schematic arrangement of cathodic protection and potential measurement circuitry the determination of the exact value of the ir-free potential is practically impossible in case of buried structures and with conventional methods. this paper is dealing with the mathematical properties of the electric field of the cathodic protection system and provides a simple method to give a good approximation of the irfree potential, with significant practical advantages that are facilitated by making use of the remote earth potential. the discussion below is dealing specifically with the case of coated, buried and cathodically protected steel pipelines. however, the situation with tanks bottoms and other buried structures is quite similar. for offshore and underwater structures the theory also applies but the application technology is slightly different – these cases will be dealt with in separate communications. 2. discussion 2.1. review of the conventional ways of determination of the ir-free potential in the first times of application of cathodic protection the cathodic protection was assumed as effective if the polarized potential was more negative to the opencircuit potential. it was realized very soon that the measured potential value was dependent on the location where the reference electrode was placed (owing to the location-dependent ohmic potential drop) and the need of a criterion of effectiveness was also recognized. the determination of the ir-free potential was carried out by the switching off the current source. this technique is routinely used in the laboratory electrochemical measurements, too. the determination of the ohmic drop compensated corrosion potential of a cathodically protected structure has an enormous literature. a short but concise general overview on the topic was given by bushmann and rizzo [2]. in the standard practice of cathodic protection nowadays the determination of the ir-free potential is carried out by periodically switching the current source off and on. typically a pattern of 2–4 seconds switched on and 0.5–1 second switched off is implemented (the time values may also vary in a wider range). the potential measurements are carried out after a delay of at least 0.1 second, in order to eliminate the effect of the inductive transients (these appear in case of long pipelines and large currents only). the potentials measured with cp stations turned on and off are generally named as on potential and off potential respectively. under field conditions in many cases it is nearly impossible or at least very cumbersome, expensive and time-consuming to switch all the cp stations that are effective in a certain area. if some of the current sources remain switched on while measuring the off potential that results in a major bias in assessing the ir-free potential. this bias may be up to a few hundreds of millivolts in extreme cases, and often leads to erroneous conclusions with respect to the level of protection of structures, sometimes with serious consequences. in spite of these obvious deficiencies, in the industrial practice in most cases the measured off potentials are identified with the ir-free potentials. another source of the uncertainties in assessing the ir-free potential via the off potentials is the ohmic potential drop generated by the equalizing currents flowing between the more and less polarized parts of the structure. stray current sources can also falsify the conventional ir-free potential determinations via the measured off potentials. nowadays typically gps-driven, high precision clock operated interrupters are applied in cp measurements, which facilitate an increased measurement precision and reliability. some manufacturers also provide cp stations with built-in interrupters and remote control options. 2.2. an alternative way of calculation of the ir-free potential from measurement data in spite of the enormous progress in measurement technique and the apparent inadequacy of the determination of the ir-free potential via the off-potential, no much progress has been achieved in the theory and in the evaluation of the measurement data. let us assume a cathodic protection system with an anode and a single coating defect at some part of the protected structure. the potential profile as a function of the distance between the coating defect and the anode is shown in figure 2. the potential field of the coating defect is defined as the domain where the potential is more negative than the remote earth potential and the potential gradients are directed towards the coating defect. figure 2: potential relations in the area of the anode and the coating defect surface equipotential lines coating defect test point potential meter reference electrode protected pipeline cp station anode interrupter with timer current flux vectors 79 let us mark two points in the potential field of the coating defect as p1 and p2. these two points determine two equipotential surfaces that surround the coating defect. also, these equipotential surfaces mark a domain of the space with a definite and constant (i.e. independent from the current flux) electrical resistance. let r1 and r2 be the ohmic resistance between the coating defect and the points p1 and p2 respectively. further on, let us assume that some perturbation is applied to the cp system, i.e. the current is interrupted (completely or partially – it is indifferent from the point of the model). from ohm’s law it follows that off off x x i eer 0− = , offon off x on x x ii eer − − = , (1a, b) where x=1.2 refers to any of the two surfaces and the on and off superscripts refer to the potential or current in the respective states. e0 is the ir-free potential of the coating defect3. expressing rx and rearranging the equation, the irfree potential can be expressed as: ( ) offon off on x off x off x ii ieeee − −+=0 . (2) if ioff=0, i.e. all the current is switched, then eq. 2 is simplified to e0=eoff, that is, the measured off potential is equal to the ir-free potential. however, if ioff≠0 then the determination of eo from eq. 2 is impossible, because the current values are indeterminable. let ioff and ion be expressed from the rearrangement of eq. 1a (for the determination of ion the off superscripts have to be changed to on, but this is allowed because the equation is valid also in the on state of the system). from ohm’s law it is obtained that 2,1 21 r eei offoff off − = , (3a) 2,1 21 r eei onon on − = , (3b) where r1,2 is the resistance between the two distinct equipotential surfaces. substituting eq. 3a and eq. 3b into eq. 2 it follows that ( )( ) ( )offoffonon offoff on x off x off x eeee eeee ee 2121 21 0 −−− − − += , (4) where x=1.2. 3 throughout in this paper it is assumed that the polarization resistance is negligible to the ohmic resistance of the soil between the coating defect and the point of the reference electrode. in most practical cases of buried structures in soil this assumption is valid. effects of the transient decay of the charge/discharge of the electrochemical double layer and other transients related to the inductivity of the pipelines will be dealt with in a separate paper. by means of eq. 4 the ir-free potential is obtained from measurable potential data also in the case if the current, flowing to the coating defect, is interrupted only partially or perturbated in any other way. let us introduce the following notation: )()( 2121 21 offoffonon offoff eeee ee −−− − =ρ , (5) and note that ρ is the quotient of the “not switched” and “switched” currents, flowing to the coating defect, and thus is invariant within the potential field of a certain coating defect. ρ is named foreign current ratio hence because it denotes the ratio of the foreign (i.e. not switched) and switched current. using eq. 5, eq. 4 can be rewritten as ρ)( onoffoff eeee −+=0 , (6) where the x subscripts are no more needed because the equation is valid for potentials measured at any point in the potential field of the coating defect. by means of this calculation the value of the ir-free potential, which is not directly measurable if any current is flowing in the off state, can be determined by means of measurable potential data. an equation formally analogous to eq. 6 had earlier been reported by baeckmann and schwenk [3], but the evaluation presented in their work is started from a quite different approach and also their conclusions are very different. the practical implementation of their measurement method is published in [4]. an important consequence of eq. 6 is that e0 and ρ are linearly dependent if eoff and eon are substituted with the constant values of the remote earth potentials: ρ)(0 onoffoff eeee ∞∞∞ −+= , (7) taking into consideration that for the determination of ρ it is not necessary to connect to the structure with a measurement cable because it is calculated from the differences of potentials at two different places in the on and off state (cf. eq. 5 and fig. 1), eq. 7 provides a simple and fast method to determine the ir-free potential of coating defects where there is no test post in the vicinity. this method is a powerful alternative of the widely used cips (close interval potential survey) or intensive surveys [4]: the coating defect ir-free potentials are practically calculated from potential gradient data and the remote earth potentials recorded with a static data logger. further, by fitting the data received on different coating defects in a cathodic protection system using eq. 7, it is possible to provide data quality control facility: those data which are not fitting on the linear relationship and deviate over a threshold value are to be discarded. this is a unique feature in the practice of cathodic protection. 80 2.3. a practically important case: more coating defects in a system the calculation in section 2.2 is strictly valid if the cathodic protection system includes one anode and one coating defect. obviously, real systems are more complicated. further difficulty is that in real systems the potential of the coating defects is varying; small coating defects with less ohmic potential drop4 can be polarized to a more negative potential than the larger coating defects. this potential difference between the coating defects generates equalizing currents superimposed on the cathodic protection current and, consequently, on changing of the shape of the cathodic protection current vector space, the shape of the equipotential surfaces will be also changed. therefore the resistance between two equipotential surfaces, denoted as r1,2 above, will not be the same quantity for the on and the off state in eq. 3a and eq. 3b. this problem can be diminished by selecting the optimal measurement points for which the equipotential surfaces have the possible smallest distortion caused by the equalizing currents of vicinal coating defects. obviously, the closer the measurement point is to the coating defect the less the shape of the equipotential surface varies on changing of the equalizing current flowing to/from the vicinal coating defect. on the other hand, the remote earth potential is also invariant to the local changes in the vicinity of any coating defect. in conclusion the point nearest to the coating defect (where the measured potential has an extreme as a function of the surface coordinates) and the remote earth potential are to be chosen to maximize the precision of the determination of the ir-free potential. 3. experimental verification 3.1. conditions in order to verify the above conclusions, a test measurement was conducted on a pipeline. the pipeline was a dn 300 gas transfer line with polyethylene coating which was known to be in a bad condition. the measurement was a modified cips carried out with a cpm 401 universal cathodic protection diagnostic measurement system. unlike conventional cips measurements, here the two reference electrodes of the mobile data logger measured different potentials: one reference electrode (electrode no. 2) was measuring the potential above the pipeline and the other electrode (electrode no. 1) was measuring the potential some 3 m apart from the pipeline (cf. fig. 1). in this way the potential gradient, perpendicular to the axis of the 4 a smaller coating defect has a higher resistance. however, the resistance of a coating defect decreases (approximately) linearly with the diameter of the coating defect, while the electrode surface increases with second order. therefore a larger coating defect will always give larger ohmic potential drop in case of a similar geometry. pipeline, was determined both for the on and off states from the data of the mobile data logger. the switching time was 3 second on and 1 second off, the delay time after the switching was 0.1 second and the sampling time was also 0.1 second. the remote potentials were measured with a static data logger. 3.2. results the on and off potential data for the two mobile reference electrodes and the remote potentials are shown in function of the distance in figure 3, which also includes the ir-free potentials calculated for the localized coating defects determined by means eq. 4 and eq. 7. the ir-free potential as a function of the foreign current ratio (both determined from the data of the mobile data logger, based on eq. 4 and eq. 5) are shown in figure 4, with the best fitting line. as follows from eq. 7, the slope of this linear relationship gives the difference of the remote earth on and off potentials and the intercept gives the remote earth off potential. the obtained data, compared to the average of the experimentally measured ones are included in table 1. the “calibration curve” of the ir-free potentials obtained from eq. 4 and from eq. 7, using the remote earth potential data and the foreign current ratio obtained from the mobile logger data are shown in figure 5 (the line is the y=x calibration line) and the numerical values, with the absolute value of the differences are shown in table 2. 3.3. evaluation in fig. 3 six well developed coating defects are localized. the coating defects at 24 and 40 meters are very large, most likely they are more or less continuous series of coating defects of different sizes and positions. they are assumed to be “open” coating defects, where the damaged coating does not cover the exposed pipe area and the larger the coating defect the more positive the ir-free potential. the coating defect at 68 meter is presumably a blistering, because the apparent size is very small but the ir-free potential is very positive which is the sign of high ohmic potential drop due to the “coverage” by the damaged coating. the coating defects at 95, 125 and 130 meters are decreasing in apparent size but shifting to positive direction in ir-free potential and from this tendency it is assumed that their “coverage” is increasing. in conclusion, coating defects of different sizes and types are detected on the selected relatively short pipe section. 81 figure 3: measured and calculated potential data of the test measurement vs. distance figure 4: ir-free potential data, calculated via eq. 4, vs. foreign current ratio figure 5: calibration of ir-free potential data calculated via eq. 7 vs. ir-free potential data calculated via eq. 7 fig. 4 justifies the assumptions of eq. 7. the linear relationship between the foreign current ratio and the ir-free potential has a “double nine” (0.993) correlation coefficient. this data has to be qualified considering the extreme differences in type and size among the coating defects. this relatively good result has to be considered also in the light of the fact that the first two defects are actually a series of defects, which decreases the applicability of the theory of the equipotential surfaces. in short, these circumstances can be considered as a near-worst-case scenario. according to eq. 7, the remote potentials can be determined from the ir-free potential vs. foreign current ratio plot. from tab. 1 a moderate difference of a few tens of millivolts is concluded which justifies the theoretical expectations. table 1: comparison of measured and calculated values of remote earth potentials parameter measured /v calculated from eq. 7/v absolute value of difference/v slope ( )onoff ee ∞∞ − 0.284 0.262 0.022 intercept ( )offe∞ -1.269 -1.229 0.04 table 2: values of ir-free potential at the coating defects, calculated from eq. 4 and eq. 7 distance/m calculated from eq. 4/v calculated from eq. 7/v absolute value of difference/v 24 0.748 0.746 0.002 40 0.780 0.804 0.023 68 0.780 0.776 0.004 95 1.010 1.034 0.025 126 0.940 0.956 0.016 131 0.871 0.863 0.008 average 0.013 from eq. 7 it is also concluded that the ir-free potential of a coating defect can be determined from the potential differences measured with the two reference electrodes of the mobile data logger (i.e. it is not necessary to apply a contact to the pipeline (cf. fig. 1)). in tab. 2 it is shown that the error of the determination of the ir-free potentials using eq. 7, compared to the data using eq. 4, are an average of 13 mv which is far below the practically required precision limit. summary it has been shown that based on the concept of the equipotential surfaces and ohm’s law a linear formula can be provided for the determination of the ir-free potential. the precision of the formula is the highest if the points used for the determination of the foreign current ratio are the points nearest to the coating defect (i.e. where the measured potential data have an extreme) and the remote earth. the theory also provides the value of the foreign current ratio. it was pointed out that the foreign current ratio and the ir-free potential are in a linear relationship where the coefficients of the linear relationship are related to the remote earth on and off potentials. this relationship establishes the connection between the “global” remote 82 and the locally, above the pipeline measured potentials. also this relationship provides an alternative method for the assessment of the ir-free potential, which does not require a measuring cable to be pulled alongside the pipeline. all these theoretical results were confirmed with a test measurement made on a section of pipeline with coating defects of different size and type. the evaluation of the test measurements justified the theoretical assumptions and proved that the determination of the ir-free potential, based on the measurement of the overthe-line potential gradients and the remote on and off potential, is applicable and accurate enough for the practical requirements. references 1. r. j. kuhn: bureau of standards, 73b75 (1928) 2. j. b. bushmann, f. e. rizo: materials performance, july, 1978 3. w. von baeckmann, w. schwenk and w. prinz (editors): handbook of cathodic protection, gulf professional publishing (1997), pp. 88–96 4. w. von baeckmann, h. hildebrand et al.: werkstoffe und korrosion, 34 (1983), 230–235 microsoft word contents.doc hungarian journal of industrial chemistry veszprém vol. 34. pp. 27-33 (2006) a study on the rate and mechanism of thermal degradation of starch in production of flocculants j. gyenis1, j. dencs2, g. nős2 and g. marton2 1research institute of chemical and process engineering, university of pannonia, h-8201 veszprém, po box 158, hungary 2department of chemical engineering, university of pannonia, h-8201 veszprém, po box 158, hungary experiments and theoretical study were carried out to investigate the degradation rate and mechanism of starch molecules to establish suitable conditions of producing biodegradable flocculants by phosphorylation at elevated temperatures. the whole molecular weight range of original starch and the possible starch derivatives was divided into five intervals using an exponential scale. a markov-chain stochastic model with transition probabilities from the higher molecular weight categories to the lower ones was proposed to analyze and explain the experimental findings. by fitting the model to the experimental data the transition probability values were determined for the studied process conditions. from these conclusions were drawn for the kinetics and possible degradation mechanism. it was concluded that the degradation of the molecules took place by splitting the molecules to several pieces, but no end-chain-scission mechanism was present under the studied conditions. keywords: starch, thermal degradation, stochastic model, flocculants. introduction during chemical modification of starch to produce environmentally friendly flocculants, elevated temperature with chemical agents are applied to achieve appropriate product. heat and chemical agents together cause essential modification and degradation of the chemical structure of the original molecules. besides the formation of anionic groups on the resultant molecule fragments, a suitable decrease in their molecular weight is necessary to make the product soluble in water. however, excessive degradation may influence disadvantageously the quality of the product. in order to prepare high quality flocculants, we have to obtain a relatively high molecular weight with narrow distribution which is still soluble. in order to fulfill these requirements, the conditions of treatment, especially the ph, the temperature and the processing time should be optimized. in addition to experimental investigation theoretical study and modeling of the process can help to achieve this objective. the mechanism of degradation highly influences the molecular weight distribution during the treatment. therefore, research works to elucidate the possible ways or mechanisms of molecule splitting have come into the limelight in a lot of recent studies dealing with the degradation of various polymeric materials in different treatments. studying the thermal degradation of linear polymers, staggs [1] has developed a mathematical model for the random scission at different positions of the polymeric chains in the form of a set of ordinary differential equations. this model proved to be suitable to describe the evolution of molecular weight distribution as a function of the fraction of bonds broken. in another work of this author a mathematical model has been constructed to analyze the evolution of the population of molecules in case of simultaneous end-chain scission and their recombination [2]. model predictions on the evolution of the molecular weight distribution well agreed with numerical monte-carlo simulations and experiments. as regards monte-carlo simulations, a molecule was selected at random from a distribution of molecules and allowed to undergo endchain scission, generating a monomer and a new molecule with one fewer repeat units. madras et al. [3] investigated the rate of degradation of pmma polymer, dissolved in toluene, at different temperatures in tubular flow reactor. a discrete model for the first-order rate of polymer degradation was derived and compared to the continuous kinetics approach. in another work madras et al. [4] studied the effect of the molecular weight on the dynamics of polystyrene degradation. it was supposed that the dynamics of polymer decomposition by random-chain scission depend on the molecular weight of the degrading polymer molecules. measurements were carried out with monodisperse polystyrene changing the initial molecular weight from 12 mda to 930 mda. based on the results relating to the time evolution of the molecular weight distribution equations were proposed to determine the rate of degradation. as a result of this investigation the rate coefficients proved to be a second-degree polynomial function of the initial molecular weight. besides the widely studied random 28 scission type degradation of polymers kostoglou [5] emphasized the importance of the chain-end scission mechanism. considering that the breakage population balance equation provides effective and simple means to analyze the change of the molecular weight distribution during the degradation processes various models (continuous, discrete-continuous and corrected continuous models) were developed to analyze the evolution of the product molecular weight distribution. ziff and mcgrady [6] have found that the rate of bond scission depended on the total chain length as well as on the position of the bond within the chain. a model was proposed and solved where the chain bonds break preferentially in the center with a parabolic probability distribution. a monte carlo study of the degradation of highly branched polymer molecules was published by galina and lechowicz [7]. the aim was to verify whether a bond scission led to a split of molecule into two smaller ones or just to reduction in the number of monomer units in the original molecule. the splitting probability of a bond was supposed to be increasing with the substitution degree of the given unit in the molecule. it was pointed out that under the given conditions each degradation step for acyclic molecules led to a split of molecules into smaller components and the average size of molecules decreased rapidly from the very beginning of the process. an interesting work was reported by emsley and heywood [8] too, on computer modeling of the degradation of linear polymers. they used pseudorandom number generator to carry out monte carlo simulation of the process. randomly chosen bonds were split either at random positions along a molecule or breaking the molecule in half or slicing off a fixed number or percentage of units. the resulting molecular weight distributions were compared to experimental measurements relating to the degradation of cellulose in water. it was found that totally random processes did not explain the experimental findings, especially related to the new peaks in the resulted molecular weight distribution and their movements in function of time toward lower molecular weights. a supposed mechanism simulated by systematic scission of polymer chain has led to much better agreement. peak movement was explained by preferential scission of the longest molecules. as regards modeling, the most of the studies in polymer science done till now preferably applied deterministic models based on exact chemical reaction equations or on momentum equations used for the molecular weight distribution. only a few works were there proposing random models with monte-carlo simulation. nassar et al. [9] applied markov-chain approach for stochastic analysis of stepwise enzymatic cellulose degradation. the model has predicted the change of the number or concentration distribution of cellulose chains according to their lengths obtained by hydrolysis after different times. however, several markov-chain models have been developed in other fields of chemical engineering such as to investigate the mixing of particles [10] or particle attrition or breakage [11, 12]. from respect of modeling principles particle breakage is very similar to the degradation of molecules. during this processes it can be supposed that the splitting of a molecule, similarly to the breakage of particles, can not be considered as deterministic one. therefore, stochastic models have a great potential in the analysis and understanding of the degradation of large molecules of natural origin, such as in a complex mixture of starch molecules, because their exact structures and molecular weight distribution is not known in depth. experiments in order to produce environmentally friendly i.e. biodegradable anionic flocculants, corn waxy starch was modified by partial substitution of the oh groups in the anhydroglucose monomer units with phosphate groups in laboratory experiments [13, 14]. the chemical modification was carried out in the solid phase at elevated temperatures, where the phosphorylation and heat degradation of the starch took place simultaneously. during this process, the original molecular weight range of 50-100 mda of the native starch samples has decreased to a range of 2-20 mda. as regards the raw material of these experiments meritena 300 corn waxy starch supplied by hungrana ltd. (hungary) was used. all reactants used for the experiments were of analytical grade bought from merck ag. to carry out the modification the original starch samples were impregnated with the aqueous solution of diammonium hydrogen phosphate and n-containing catalysts in a mortar. then the samples were dried and put into a block thermostat at various temperatures for different periods. the applied temperatures and processing times were changed between 135 and 150 oc, and from 5 to 270 minutes, respectively. the progress of the phosphorylation reaction was monitored by determining the chemically bound phosphorous content in the samples taken from the reaction products. after extracting the free phosphate, the analysis was carried out by biochrom 4060 spectrophotometer from the ash obtained by heating the samples in a furnace. the change of the molecular weight distribution was monitored by size exclusion chromatography. the molecular weight distributions of the resulted starch phosphate products were determined as follows: samples of identical weights were dissolved in distilled water at 95 oc for 24 h (0.05 g starch in 5 ml water) and were analyzed by hpsec/malls/ri as was described in detail by meiczinger et al. [14]. the relative quantities of the soluble part of the samples, i.e. the outputs of phosphorylation /degradation process were determined from the area below the ri chromatograms. the molecular weight distributions were calculated from the chromatograms by discovery 32 software. the mean molecular weights of the products used in this paper were calculated on weight averaging. 29 mathematical model because the breakage of individual molecules and the position of splitting within the molecule has to be supposed accidental, and the degradation process as a whole is influenced by local variables within the reaction mixture that are also random in certain extent, a markov-chain stochastic model was proposed for this study described in more detail in another paper by gyenis et al. [15]. the principle of the applied method is shown in figure 1, where the nodes of the graph (the square boxes) denote discrete molecular weight intervals or categories changing from m5 to m1, where m5 is the highest and m1 is the lowest molecular weight range. in these boxes different weight fractions of the whole reaction mixture are present at a given moment of the process. the edges of the graph (the arrows between the boxes) represent the weight fraction transitions between the boxes, i.e. from given molecular weight categories to the other ones that can happen with certain probabilities. as is seen from the direction of the arrows, only degradation is considered here, i.e. transitions from higher molecular weight intervals to the lower ones can take place only. if, simultaneously with the degradation, polymerization or coupling of certain molecules would also take place, this does not affect this model essentially, because the arrows represent net transitions, and in this case the rate of degradation is always higher then that of the polymerization. fig.1. principle of the applied mathematical model. as was explained in another paper [15], the division of whole molecular weight range to smaller intervals can be done arbitrarily, i.e. the spans of these intervals should not be necessarily identical. because, during the experiments the molecular weight axis of the measured chromatograms had an exponential scale whose linearization could cause some uncertainty in the molecular weight distribution data, we used exponential scale in the model, too, with the following molecular weight intervals decreasing from m5 to m1: m5 > 32 mda > m4 > 16 mda > m3 > 8 mda > m2 > 4 mda > m1 > 2 mda (1) this scale was obtained by stepwise halving of the lower limits of the previous molecular weight intervals. the transition probabilities between the various molecular weight intervals during a given time interval are summarized in a matrix shown in eqn.1, where a matrix element pj,i refers probability of material transition from interval i to interval j. 1 0 00 000 0000 1,23,14,15,1 2,23,24,25,2 3,34,35,3 4,45,4 5,5 pppp pppp ppp pp p p = (2) the quantities of material being in the molecular weight intervals or categories are accounted in mass or weight fraction units. if all the material is present only in one of these intervals (say in the ith interval), it means that the weight fraction being in this interval is 1 (unity), and the weight fractions in all other intervals are zero, because their sum in all intervals should be unity. in case of an arbitrary distribution between the intervals, the expected weight fraction transition during a δt time step from interval i to interval j is txpx iijij δ⋅⋅=δ ,, (3) supposing an initial molecular weight distribution between five molecular weight intervals in the initial state at time t0 (t=0): [ ])()()()()()( 01020304050 tptptptptptp = (4) the probable molecular weight distribution after the nth time step (t=tn) is [ ])()()()()()( 12345 nnnnnn tptptptptptp = (5) that can be estimated by the equation proposed by inoue and yamaguchi [16] in a stochastic model of solids mixing: n n ptptp ×= )()( 0 (6) the probability of the degradation of the molecules being in the ith molecular weigh category is the sum of the transitions probabilities from that category to all other molecular weight intervals: ∑= j iji pp , (7) the details of application of this model are discussed in [15]. m4 m1 m2 m3 m5 p2,4 p3,4 p1,4 p2,3 p1,2 p1,3 p4,5 p2,5 p1,5 p3,5 30 results and discussion as a result of laboratory scale experiments figure 2 shows the variation of the relative yields of the watersoluble degradation products as a function of time at various reaction temperatures compared to their maximal achievable amount measured during this investigation, which was almost 100 per cent of the treated starch sample. the total amounts of these soluble fractions were determined from the ri areas of the chromatograms. from figure 2 it can be seen that the total yields have increased with the duration of the treatment, and were also increasing with rising the reaction temperature from 135 oc to 150 oc. time, min 0 25 50 75 100 125 150 175 200 225 250 275 r el at iv e y ie ld , % 0 20 40 60 80 100 135 o c 138 o c 140 o c 143 o c 145 o c 148 o c 150 o c fig.2. variation of the water soluble product yield in function of time at various temperatures beside the well recognizable tendencies certain irregularities can also be observed in this diagram, due to unexplored effects that could come from the stochastic nature of degradation of the molecules, but most likely from the possible irregular variation of the local conditions during the process that may be distributed not homogeneously within the reactor. figure 3 shows the changes of the mean molecular weights of the samples during the process, calculated from the measured molecular weight distributions in function of the reaction time at various treatment temperatures. from this, it is seen that the mean molecular weight decreases continuously with increasing time. the temperature of the treatment had also crucial influence, because elevated temperatures caused considerable stronger degradation which resulted in lower molecular weights in the product. certain accidental variations in these curves also refer to unidentified influences during this treatment mentioned above. another difficulty during the measurements came from the very low solubility of samples at the very beginning of the process, which can cause reduced reliability of the results gained by the analysis after short reaction times. the samples at the very beginning e.g. below 25 min contained only a negligible quantity of soluble components with relatively high ratios of small molecule debris of not identified origin. therefore these data was disregarded and not shown in this diagram. time, min 0 25 50 75 100 125 150 175 200 225 250 275 m ea n m w , m d a 4 6 8 10 12 14 16 18 135 o c 138 o c 140 o c 143 o c 145 o c 148 o c 150 o c fig.3. change of the mean molecular weight of the obtained water soluble starch derivatives from the samples obtained after longer treatment times the time evolution of the weight ratios in the five fractions m5-m1 was determined for all reaction temperatures. for this, the weight fractions in m4-m1 were obtained from the chromatograms, while the weight fraction of the insoluble starch above 32 mda i.e. in m5 category was determined from the material balance. it should be noticed that the amount of molecule fraction below 2 mda was negligible small for all the temperatures and reaction times studied, therefore a possible sixth category between 0 and 2 mda was disregarded. for all reaction temperatures, the weight fraction above 32 mda, i.e. in the highest molecular weight category rapidly decreased in function of time that is shown in figure 4 as an example for the experiments carried out at 145 oc. reaction product between 2 and 4 mda i.e. in category m1 was observable after a relatively long time at almost all reaction temperatures. at 145 oc e.g. this time delay was more than 100 min. the only exception was observed at 150 oc, the highest reaction temperature studied where this molecular weight fraction appeared just at the very beginning of the process. the amounts of the intermediate fractions m4-m2 showed a relatively rapid rise in the first period of treatment at almost all the studied reaction temperatures, then going through a maximum. at higher temperatures, at 143 oc and above, fraction m4 between 32 and 16 mda practically did not appeared because it was bypassed or too rapidly transformed to lower molecular weight fractions. as it will be shown later, modeling gave a help to elucidate the reason of this observation. although figure 4 referring to 145 oc reaction temperature gives a representative example of these experimental data, more experimental results were shown and discussed in details in an earlier publication [17]. 31 fig.4. evolution of weight fractions of the treated material in different molecular weight categories at 145 oc. to elucidate the mechanism dominating during the studied degradation process simulations were carried out by using the stochastic model shown above. by changing the values of transition probabilities pj,i it was possible to study their effect onto the time evolution of the relative quantities of the studied molecular weight fractions in the reaction products. in this study various suppositions were made regarding the distribution of the splitting probabilities along chains of the starch molecules for different molecular weight fractions [15]. fig.5. comparison of the measured and calculated weight fractions obtained by fitting the model using a trial and error fitting method, a series of parameter identification were carried out by minimizing the standard deviation between the measured and calculated data. by this, the transition probability values that gave the best fit were determined for each experimental condition [17]. figure 5 gives a comparison between the measured and calculated weigh fractions of the five molecular weight categories (m5-m1) for all reaction times and temperatures studied here. the mean deviation between the measured and calculated weight fractions was 0.047 w/w. this seems to be reasonable for such a complex reaction system, considering the stochastic nature of the studied system, and the difficulties of the analysis at the beginning of the process. analyzing the obtained transition probabilities deductions were made regarding the possible mechanism of the degradation process. figure 6 gives an example for the pj,i values for the reaction temperature of 145 oc. a column in this diagram gives the probability of mass fraction transition from given initial molecular weight range to another one during unit time. fig.6. example for the transition probabilities between different molecular weight categories determined by model fitting for 145 oc reaction temperature from this figure the following information can be read out: the transition of the material from the highest original molecular weight range above 32 mda is most probable to the category with molecular weight limits of 8-16 mda. because during the simulation made by a differential equation solver (modelmaker®) very small time steps were used, it can rightly be supposed that the initial molecules split into at least 2-3 fragments of similar lengths in one reaction. transitions to molecular weight ranges of 16-32 and 4-8 mda occur with much less probabilities. this latter transition means that splitting into 4 or more pieces (e.g. from 32 to 8 mda) is also possible. the occurrence of transitions from the >32 mda category into the 2-4 mda is negligible small, therefore splitting off small molecule fragments from the original molecule chains e.g. by end-scission mechanism is not very probable. from these probability data it seems that splitting take place mainly along the inner regions of the molecules, meaning that endscission mechanism is not dominant under the studied reaction conditions. from these data it can also be supposed that there should be certain degradation inside the highest 0,000 0,005 0,010 0,015 0,020 0,025 0,030 2-4 4-8 8-16 16-32 4-8 8-16 16-32 >32 tr an si tio n pr ob ab ilit ie s, w /w /m in resultant mw ranges ini tia l m w ra ng es 145 oc145 oc 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 measured weight fractions, w/w c al cu la te d w ei gh t f ra ct io ns , w /w 0,0 0,2 0,4 0,6 0,8 1,0 0 50 100 150 200 250 2-4 4-8 8-16 16-32 >32 w ei gh t f ra ct io ns , w /w tim e, min mw fractions, mda 145 oc 32 molecular weight category (above 32 mda) whose products still remain within this category (when e.g. a molecule of 100 mda splits into two fragments with 60 and 40 mda molecular weights). unfortunately, the available analytical methods have not allowed us to explore the molecular weight distribution and its changes inside this >32 mda range. but, during selftransitions within this category similar mechanism can be supposed, i.e. by splitting about the inner regions of the molecules without significant end-chain-scission, because practically no direct transitions were found from the >32 mda category into the lowest molecular weight ranges of 2-4 mda or below. as regards the fragmentation of the molecules being in molecular weight range 16-32 mda, similar mechanism can be supposed, because transition into the category of 4-8 mda looks dominant (by splitting the molecules to minimum 2 and maximum 8 fragments) together with certain transition into the range of 8-16 mda (by splitting to minimum 2 and maximum 4 pieces). the probability of transition to the smallest 2-4 mda category is negligible here. end-scission mechanism is therefore not likely in this 16-32 mda molecular weight fraction. the situation is similar for the 8-16 mda category because, most probably, the molecules split here to 2-4 pieces, i.e. the majority of fragments are transferred to the range of 4-8 mda. the transition probability values in this category are much lower than those in higher molecular weight categories. it is also true for the molecules in category of 4-8 mda that are tending to split with relatively low probability to 2 pieces only. due to this decaying transformation rate tendency, the product molecules accumulate within the two or three smallest molecule weight ranges below 16 mda towards the end of the process, as is seen in figure 4 after 150 min treatment. for that time the resultant product belongs to a rather narrow molecular weight range with almost uniform occurrence between 16 and 2 mda. smaller fragments are not present, which is favorable to use this product as high quality flocculants. stopping the process earlier, e.g. somewhere between 50 and 100 min the molecular weight distribution of the product will have even narrow, between 16 and 4 mda under the studied conditions. the proposed mechanism was similar for the other reaction temperatures, too. as regards the kinetics of the process, figure 7 shows the dependence of the degradation probabilities, determined according to eqn. 6, in function of reaction temperature and molecular weights. from this data it is clear that the largest molecules belonging to the >32 mda category degrade most probably thus resulting a very high transformation rate to smaller fragments. this primacy was observed especially at lower temperatures. the data referring to the category of 16-32 mda show some extra high values especially at the high temperatures, but the breakage probability were not so high at lower temperatures. in case of lower initial molecular weights, namely in the range of 8-16 and 4-8 mda the molecules showed more stability, their transformation toward lower mw categories are much lower. this situation does not change much with the increase of the temperature. molecules in the range of 2-4 mda proved to be very stabile and have no degradation tendency at all. 0,00 0,01 0,02 0,03 0,04 2-4 4-8 8-16 16-32 >32 132134136138140142144146148150 d eg ra da tio n pr ob ab ilit y, w /w /m in in itia l m w fr ac tio n. m da temperature, oc fig.7. degradation probabilities of different molecular weight fractions at various treatment temperatures as a whole, it is concluded that the probability of degradation decreases significantly with decreasing molecular weight and treatment temperature. these results helped us to optimize the process conditions to produce flocculants from starch with appropriate molecular weight distribution. temperatures 143-145 oc provided quite high degradation rate resulting in high product quality suitable for flocculants within reasonable treating time. at higher temperatures such as at 148 oc or above, lower molecular weight starch derivatives can be produced which can be utilized for natural-based anti-scale agents. conclusions experiments and simulations were carried out to investigate the rate and mechanism of the degradation of starch molecules in order to find out suitable conditions to produce biodegradable flocculants by simultaneous heat treatment and phosphorylation. for this study a markov-chain stochastic model was proposed to explain the experimental data. the whole molecular weight range between the original >32 mda and the lowest 2 mda was divided into five intervals decreasing their widths or limiting mw values exponentially. by fitting the model to the experimental data the transition probability values were determined for the studied process conditions. from these latter, conclusions were drawn for the kinetics and possible degradation mechanism. the degradation probability of the molecules being in a given molecular weight interval were increasing with rising treatment temperature and reduced significantly with decreasing molecular weight. as regards the possible mechanism, it was concluded that the transformation of the original starch molecules and 33 its intermediate products took place by splitting the molecules to several pieces, and no end-chain-scission mechanism was detected under the studied conditions. as a result of this study it was possible to optimize the conditions to obtain high quality flocculants with relatively narrow molecular weight distribution with mean values around10 mda. acknowledgement the authors gratefully acknowledge the financial support provided by the hungarian national research and development programme in carrying out the project on production and application of environmental-friendly starch derivatives (grant no. nkfp 2001-3/072) symbols mi = molecular weight interval or category, characterized by their lower and upper molecular weight limits in mda, p = mass transition probability matrix defined by eqn.1 pj,i = mass fraction transition probability from molecular weight interval i to interval j, on weight basis, w/w/min pi = degradation probability of the molecules being in the ith molecular weight interval, on weight basis, w/w/min p(tn) = state probability vector describing the expectable distribution of the material between different molecular intervals at time tn,, w/w pi(tn) = probability that the unit weight fraction of the material is in the ith molecular weight interval at time tn , w/w xi = expected weight fraction being in the ith molecular weight interval at a time, w/w δxi,j = expected weight fraction transition from the ith to the jth molecular weight interval during a δt time step, w/w δt = time step, min indices i = index of the initial molecular weight category of a molecule before the degradation j = index of the target molecular weight category of the fragment formed by degradation n = the number of time steps from the beginning of the degradation process where the whole reaction time span is divided into n discrete time interval references 1. staggs, j. e. j. modelling random scission of linear polymers. polym. degrad. stab. 2002, 76, 37–44. 2. staggs, j. e. j. modelling end-chain scission and recombination of linear polymers. polym. degrad. stab. 2004, 85 (2), 759-767. 3. madras, g.; smith, j. m.; mccoy, b. j. degradation of poly(methyl methacrylate) in solution. ind. eng. chem. res. 1996, 35 (6), 1795-1800. 4. madras, g.; chung, g. y.; smith, j. m.; mccoy, b. j. molecular weight effect on the dynamics of polystyrene degradation. ind. eng. chem. res. 1997, 36 (6), 2019–2024. 5. kostoglou, m. mathematical analysis of polymer degradation with chain-end scission. chem. eng. sci. 2000, 55 (13), 2507-2513. 6. ziff, r. m.; mcgrady, e. d. kinetics of polymer degradation. macromolecules 1986, 19, 2513–2519. 7. galina, h.; lechowicz j. b. an algorithm for monte carlo modeling of degradation of polymer networks. computers chem. 1998, 22 (1), 39-41. 8. emsley, a. m.; heywood, r. j. computer modelling of the degradation of linear polymers. polym. degrad. stab. 1995, 49 (1), 145-149. 9. nassar, r.; chou, s. t.; fan, l. t. stochastic analysis of stepwise cellulose degradation. chem. eng. sci. 1991,46 (7), 1651-1657. 10. gyenis, j.; and kátai, f. determination and randomness in mixing of particulate solids. chem. eng. sci., 1990, 45 (9), 2843-2855. 11. duggirala, s. k.; fan, l. t. stochastic analysis of attrition — a general cell model. powder technol. 1989, 57 (1), 1-20. 12. berthiaux, h. analysis of grinding processes by markov chains. chem. eng. sci. 2000, 55 (19), 4117-4127. 13. dencs, j.; nos, g.; dencs, b.; marton, g. investigation of solid-phase starch modification reactions. trans icheme (part a), 2003, 81 1-5. 14. meiczinger, m.; dencs, j .; marton, g. ; dencs, b. investigation of reactions occurring at starch phosphorylation. ind. eng. chem. res., 2005; 44 (25) 9581-9585. 15. gyenis, j., dencs, j., nős, g., marton, gy.: thermal degradation of starch in producing environmentally benign flocculants, part i. stochastic modeling of degradation process. paper submitted to. ind. eng. chem. res., 2007. 16. inoue i., and yamaguchi, k., 1970, particle motion in a mixer. mixing in a two dimensional v-type mixer, int. chem. engng., 10(3), 490-497. 17. gyenis, j., dencs, j., nős, g., marton, gy.: thermal degradation of starch in producing environmentally benign flocculants, part ii. experiments and process identification, paper submitted to. ind. eng. chem. res., 2007. microsoft word a_08_fischer_r2.doc hungarian journal of industrial chemistry veszprém vol. 39(1) pp. 101-106 (2011) superstructure stabilization of ballast bedded railway tracks with geogrids sz. fischer, f. horvát széchenyi istván university, department of transport infrastructure and municipal engineering h-9026 győr, egyetem tér 1., hungary e-mail: fischersz@sze.hu e-mail: horvat@sze.hu the paper deals with the research and development of the authors related to investigation of geogrid railway ballast reinforcement. it summarizes the theory of the geometrical deterioration of railway tracks, as well as the advantages of the use of geogrid reinforced ballast in railway superstructure. this article summarizes the results of the field tests with five different geogrid types on a hungarian main railway line and laboratory multi-level shear box tests. it points out to future research possibilities, for example the modelling of laboratory multi-level shear box tests with discrete element method that may certify their results. keywords: railway, superstructure, stabilization of track geometry, geogrid-reinforced ballast introduction the geometrical deterioration process of ballasted railway tracks geometrically and structurally perfect railway tracks cannot be constructed because of the tolerances and quality differences of constructional elements as well as inaccuracy of geodetic alignment and technology during construction and maintenance works. however the railway tracks’ geometry and quality differ from the accurate conditions, but if the tolerances and quality differences are below their permissible limits, the tracks can be opened to traffic for the speed limit in accordance with the appropriate acceptance requirements. the train traffic and its damaging effects generate harmful changes in the railway track; this is actually the geometrical deterioration process. this geometrical deterioration takes place according to strict physical laws and it is an irreversible process. its speed can be influenced as well as decreased by maintenance works, but it can be never stopped. the function of the geometrical deterioration process in explicit form is the following: 2 0 vmecc ⋅⋅⋅= α (1) in (eq. 1) “c” means the geometrical quality of the railway track, “c0” is a parameter related to the initial track condition and it shows the quality of the maintenance, “m” is the through-rolled mass, “v” is the equivalent speed, and “α” is a superstructure dependent parameter. in the exponent of “e” in (1) there is an expression related to the energy of motion [1]. improvement (i.e. reduction of “c”) can only be reached with maintenance works (e.g. tamping work). “c” value can be decreased more in a track with worse geometrical quality but the result will be characterized with more and more “c” value. function and deterioration of railway ballast the railway ballast has to support the track soundly and flexibly and it has to distribute the load from the sleepers’ lower faces to the substructure (embankment and supplemental layer). the ballast material should have adequate resistance in longitudinal and transversal directions which are necessary for the track’s bedding and structural stability. the direction, the settlement and plane distortion values have to be ensured in respect to relative geometry. the good quality ballast material is an aggregation of non-cohesive, graduated and cubic shaped, angular particles. in this particle aggregation the vertical load of vehicles is distributed through the ‘stone-skeleton’ to the lower layers, while the horizontal loads are balanced by friction between sleepers and ballast particles and by passive earth pressure. in both load-distributions the interlocking effect between particles is very important. external effects (mainly the repetitive through-rolled axles, as well as the weather) change the behaviour of particle aggregation; therefore the actual geometry of 102 the track will be worse and worse. the ballast particles can be pushed into lower layers especially in the case of weak embankment or supplemental layer; therefore large vertical plastic deformations (settlements) can arise. because of the reasons above, a structural modification seems to be practical for prevention to ensure that particles of the aggregate act together. using geogrid reinforcement under the ballast bed can be a good solution for this problem. effect of geogrid reinforcement under railway ballast geosynthethics have been used for soil reinforcement for more decades. they can compensate some weak soil parameters: e.g. they ensure additional tensile and shear strength for soil structures. in this way soils with unsuitable geotechnical parameters can be used for construction of steep slopes, with these types of soils very quick consolidation can also be achieved on bad quality subgrade, and for example geosynthetic-reinforced soils are also suitable for construction of very good isolation and separation layers at waste-dumps by the help of decreasing of water permeability of soils [2]. geogrids ensure additional tensile and shear strength for both granular and cohesive soils. using this soil reinforcement, soils can bear not only pressure but tensile force too, due to the longitudinal and transversal ribs and junctions of geogrid if there is an adequate soil-geogrid interaction. this reinforced structure works similar to the reinforced concrete in which concrete bears pressure and reinforcing steel bars take up tensile forces. geogrids can be used for counterforcing shear forces, but their use is limited because of the shear strength of geogrids. laboratory tests have been made related to such use of geogrids in railway constructions where not the subgrade/subsoil was reinforced but the bed-ballasted railway superstructure [3-19]. besides the laboratory tests field tests [5, 7, 9, 13, 17, 20, 21] and fem [22-24] as well as dem modeling [25-31] were also carried out. these papers certify that geogrids reinforce the granular media the following way. interaction between the granular and angular ballast material particles and the geogrid is the basis of the increase of the internal shear resistance of the layerstructure. it is called interlocking effect of geogrids (fig. 1). the particles can penetrate into the geogrid layer’s apertures, and grapple on to ribs. the other particles bear up onto this composite (particle and geogrid) layer. its face structure is advantageous for the higher internal shear resistance. the re-arrangement of particles is hindered by the composite layer in vertical and horizontal planes too. stresses arise in the ribs and junctions of the geogrid due to vehicle load, the geogrid can offer resistance against these stresses with tensile strength and low strain. tensile strength should be adequate high, but failure strain should be acceptable low, because of the load bearing with small strain. the aim of the following chapters is to summarize the results of the research team at the in this research field. figure 1: interlocking effect and load bearing of a reinforced ballast (modified from konietzky, et al., 2004) goal of the research work the research team investigates the stabilization effect of geogrid layers under railway ballast using three methods: – constructing trial field track sections where the track geometry position and its changes are regularly measured, – setting up laboratory tests which are adequate for determining parameters related to ballast materialgeogrid interaction, – computer-aided modelling for improving and generalizing the relationships. at the trial field track sections, geometric levelling are completed on the rail-heads, therefore the track’s geometry changes can be measured and determined. if the measuring points on the rail-heads are close enough to each other and the measurements are often repeated, there will be a large database which can be processed. values below and their changes can be determined as a function of through-rolled axle tons as well as of the elapsed time from the first tamping work after the geogrid’s built-in: – cross settlement difference between the two railheads, – settlement (can be calculated with different chord lengths on one rail), – plane distortion (twist) (can be calculated with different base lengths), – settlement on individual sleepers. the laboratory tests can help to better understand the behaviour of geogrid-reinforced railway ballast. a great deal of parameters influences this behaviour (e.g. geogrid type, properties and density of ballast material, depth of ballast layer, elasticity of support layer, etc.). the changing of interlocking effect in the ballast material as a function of vertical distance from geogrid layer is a key-role for the conformability of evaluation of geogrid 103 reinforcement’s use. the research team would like to get much information from the test of interlocking effect in order to evaluate the expedience geogrid-reinforced ballast. computer-aided modelling is needed for numerous reasons. consideration of all variable parameters will unfeasibly extend the number of laboratory tests. if an acceptable number of tests have been implemented, models can be constructed whose behaviour can be confirmed and certified by the measured parameters. using this model in computer-aided modelling is conformable for more detailed analysis of various parameters’ effect, as well as for universalizing of statements which are needed for determining correct general laws about the behaviour of geogrid-reinforced railway ballast. this paper doesn’t deal with computer-aided modelling of geogrid-reinforced railway ballast material in detail. tests and results the research team had an opportunity to create a 700 m long trial field track section with uniform soil properties at a hungarian main railway line in may, 2010. this section of railway line contains substructure faults, e.g. water pockets. three different subsections had been constructed in this section and finally five geogrid types had been built-in during ballast cleaning: – sections without ballast cleaning just tamped, – sections with ballast cleaning without geogrid reinforcement then tamped, – sections with ballast cleaning with geogrid reinforcement then tamped. geogrid types 1, 3 and 4 contain geotextile layers too, types 2 and 5 are single geogrids. all tested geogrid types are made of polypropylene. the geogrid and geotextile properties are contained in tables 1 and 2. the last two subsections contain blocks with and without water pockets which water pockets are local faults. fig. 2 shows the setting in work of geogrid type 2 during ballast cleaning technology in railway line lebenymosonszentmiklos (hungary) on 25th of may in 2010. after the final tamping work of the construction (17th of june, 2010) several geometric leveling has been done and their data have been processed. figs 3 and 4 show the mean and standard deviation of plane distortion as a function of elapsed days from 17th of june, 2010. on the 124th day there was a tamping work again, before and after it geometric levelling has been accomplished. table 1: properties of geogrid types used in trial field tests geogrid properties ultimate strength strength at 2 % elongation ultimate elongation geogrid types material uniaxial/ biaxial md (kn/m) xmd (kn/m) md (kn/m) xmd (kn/m) md (%) xmd (%) geogrid type 1 pp biaxial 30 30 11 12 n.a. n.a. geogrid type 2 pp biaxial 30 30 11 12 n.a. n.a. geogrid type 3 pp biaxial 30 30 12 12 n.a. n.a. geogrid type 4 pp biaxial 30 30 12 12 n.a. n.a. geogrid type 5 pp biaxial 30 30 n.a. n.a. 12±3 12±3 table 2: properties of geotextiles in geocomposits used in trial field tests geotextile properties ultimate strength ultimate elongation geocomposits puncture resistance (n) md (kn/m) xmd (kn/m) md (%) xmd (%) permeability (m/s) permeability (l/sm2) unit weight (kg/m2) effective opening size (mm) geogrid type 2 >1500 n.a. n.a. n.a. n.a. 0.135 135 0.16 0.125 geogrid type 3 1670 6 11 60 40 0.11 110 0.15 0.13 geogrid type 4 1670 6 11 50 30 0.09 90 0.15 0.08 figure 2: construction geogrid-reinforced trial railway track on line lebeny-mosonszentmiklos (hungary) on 25th of may in 2010 with geogrid type 2 104 figure 3: mean of plane distortion (twist) (3.6 m base length) as a function of elapsed days from final tamping work after geogrid setting-in figure 4: standard deviation of plane distortion (twist) (3.6 m base length) as a function of elapsed days from final tamping work after geogrid setting-in in fig. 3 and 4 it can be seen that sections without geogrid reinforcement are characterized with higher mean and standard deviation values than several geogrid types, e.g. geogrid type 1 and 2, but other types do not improve the track’s geometric stability in this controlled short time period. sections without ballast cleaning just tamped do not show low values in the mean diagram because of the relatively dense ballast superstructure, but in the standard deviation diagram this section seems to be the worst. the reference time before (123 days) and after (195 days) the 2nd tamping were not long enough, the results will be more precise with extended inspection time, so the measurements have to be continued in the future. for the laboratory tests the research team planned and constructed a multi-level shear box with which the change of the interlocking effect in the railway ballast material was investigated as a function of vertical distance from the geogrid layer. this function in the above form has not been determined by anyone with lab test; international researchers reached such kind of results using of dem modelling of geogrid pullout test (konietzky, et al., 2004; mcdowell, et al., 2006) but not with a multi-level shear box. the 1.0×1.0×1.0 m multi-level shear box mentioned above (fig. 5) contains max. ten 10 cm high horizontal frames filled with max. 50 cm high elastic layer, thereon 10 cm height sand, thereon geogrid layer with or without geotextile as well as thereon four times 10 cm height railway ballast material. horizontal shear resistance can 105 be measured at each frame connection. the tests up to now are related to only one geogrid type (geogrid type 2 in the field test) and to only new loose and dense ballast material. tests were conducted with and without geogrid reinforcement too. fig. 6 shows the horizontal shear resistance of railway ballast aggregate. figure 5: multi-level shear box for laboratory tests dense specimens had higher shear resistance than loose ones; the geogrid reinforcement increased these values especially in the near region of geogrid layer same like in konietzky, et al. 2004 and mcdowell, et al. 2006. conclusion it can be clearly stated that with adequate geogrid type the ballasted railway superstructure can be strengthened. this kind of geosynthetics can guarantee additional shear strength for ballast bed. consequently, the settlements as well as disadvantageous cross settlements, direction faults, twist faults are less likely to occur in these tracks and the interval between maintenance works (for example tamping works) can be extended. this is very important in the aspect of maintenance costs. having processed the measured data, it has to be stated that more measurements are required in field trial and in laboratory tests too, and then the computer-aided modelling will be needed to check the results in laboratory multi-level shearing tests. figure 6: horizontal shear resistance as a function of distance from geogrid layer acknowledgements this paper is supported by tamop-4.2.1/b-09/1/konv2010-0003: mobility and environment. the project is supported by the eu and co-financed by the european social fund. references 1. hungarian railways: modern railway–modern railway technique. railway construction and maintenance, vol. 2. budapest, mav rt., (1999), 157–160 2. r. szepesházi: geotechnika (geotechnics), university course book, szechenyi istvan university, győr (2008), 187 (in hungarian) 3. m. matharu: geogrids cut ballast settlement rate on soft substructures, railway gazette international, 3, (1994), 165–166 4. r. j. bathurst, g. p. raymond: geogrid reinforcement of ballasted track, transportation research record no. 1153, (1987), 8–14 5. g. p. raymond: reinforced ballast bahaviour subjected to repeated load, geotextiles and geomembranes, 20, (2002), 39–61 6. e. c. shin, d. h. kim, b. m. das: geogrid-reinforced railroad bed 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<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> /enu (use these settings to create adobe pdf documents best suited for high-quality prepress printing. created pdf documents can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word 01_r.doc hungarian journal of industrial chemistry veszprém vol. 35. pp. 19-30 (2007) runaway of chemical reactors: parametric sensitivity and stability f. szeifert, t. chován, l. nagy, j. abonyi, p. árva university of pannonia, department of process engineering, h-8201 veszprém, p. o. box 158, hungary although the runaway phenomenon is well known, an exact consistently used definition does not exist. present paper is focused on the relation of reactor runaway and parametric sensitivity to stability. the relationship between criteria for reactor runaway and for thermal stability is also pointed out. based on this critical review new methods based on parametric sensitivity and stability analysis for reactor runaway analysis are proposed in the paper. general runaway criteria based on the application of ljapunov’s indirect method in the geometric and phase space have been developed. to illustrate the relation of the proposed reactor stability analysis to the commonly used runaway criteria a first order reaction was chosen. the application of the suggested method is also presented on a more complex problem, the uckron-i test problem. keywords: runaway, reaction engineering, stability, safety, chemical reactors introduction today process control systems allow more and more extensive utilisation of the potential capacity of chemical processes. optimal operating conditions are pushed to the constraints determined by the laws of physics and chemistry. the most critical safety limit is the runaway condition for reactors with exothermic chemical reactions. since semenov’s pioneer work [1] most of the research in reactor analysis is related directly or indirectly to reactor stability and/or reactor runaway. initially the question was whether reactor runaway is related to reactor stability or it is something completely else. bilous and amundson were the first who treat the problem as parametric sensitivity and thermal runaway distinguishing it from classical reactor stability [2]. schmitz (1975) explained in his review [3] that sensitivity is less precisely defined than stability and the two phenomena might be connected. the first runaway criterion based on the empirical analysis of the temperature profile was suggested by barkelew [4]. dente and collina considered the appearance of an inflection point preceding the temperature maximum (ie. where the second derivative of the temperature with respect to the length of the tubular reactor becomes negative) as a runaway criterion [5]. the same criterion was applied to an industrial problem by berty et al. four years later [6, 26]. hlavacek et al. employed an analogous criterion (second time derivative) in the heat explosion theory. adler and enig suggested that instead of the length or time domain the analysis be conducted in phase space (temperature versus conversion) and the criterion be the point where the second derivative of the temperature with respect to the conversion becomes negative [7]. van welsenaere and froment called this latter one as “the first criterion” and the previous one as “the second criterion” [8], and found that they are close to each other while the second criterion is a bit more conservative. applying the method of isoclines morbidelli and varma gave the necessary and sufficient conditions [9]. to “measure” the sensitivity bilous and amundson introduced the derivative of the maximum temperature along the length (or time) with respect to semenov’s number [2]. this approach was applied first by lacey [10] as well as by boddington et al [11] to determine a runaway criterion. this sensitivity measure gives a maximum curve with respect to the parameter (semenov’s number). if the parameter is less than the critical value belonging to the maximum then runaway does not occur. runaway may take place if the parameter is higher. the idea was generalized by morbidelli and varma [12]. introducing the sensitivity φ * φ ∂ ∂ ts = and the relative sensitivity φ * *φ ∂ ∂ t t s φ = , where t* stands for the maximum temperature and φ for an arbitrary input parameter, they defined the runaway criterion based on the maxima of the sφ – φ and the sφ – φ functions respectively. their numerical calculations 20 demonstrated that for systems “susceptible to runaway” these maxima practically coincide independently from the selection of φ and correspond to the value calculated by adler and enig’s criterion. at the same time in case of systems less “susceptible to runaway” the maxima can be significantly different or even they can be present when runaway does not occur at all. this observation rises questions about the theoretical soundness of the application of the maxima as runaway criterion in spite of the fact that the authors consider the criteria based on the maxima of sensitivity as important intrinsic attributes of runaway (intrinsic criterion) [12]. methods for the mainly approximate calculation of various criteria for different reactions and reactors are discussed in several papers, e. g. by balakotaiah and kodra [13] as well as morbidelli and varma [14]. asymptotic expressions are often used for the approximation. methods of catastrophe and singularity theories are more and more often used for studying complex reacting systems. excellent reviews of these approaches were published by razón and schmitz [15], as well as by doherty and ottino [16]. two important sources of the researchers’ motivations are the following: ● foundation of the solution of important industrial problems is expected (reactor design, operation and safety). e.g. in the paper of luo et al [17] critical ignition, extinction, and transition temperatures and the stable criteria of temperature ● a large variety of processes (with different reactions and different types of reactors) are studied (zaldivar et al [18]) and they are inherently (very) nonlinear (methods of system analysis can be applied with limitations only). avoiding runaway is requested from industrial considerations for the sake of “controllability” and for the protection of the catalyst (high amount of heat is released in a short section). the application of runaway criteria in reactor control for building a model-based control strategy is discussed by szeifert et al [19]. although the runaway phenomenon is well known, an exact consistently used definition does not exist. present paper is focused on the relation of reactor runaway and parametric sensitivity to stability. the relationship between criteria for reactor runaway and for thermal stability is also pointed out. in this study ljapunov’s indirect method that is well known and widely used for dynamic system analysis is applied (perlmutter, [20]); and it is shown that the commonly used runaway criterion can be justified based on this approach. to allow the comparison of different criteria and to illustrate the application of stability analysis a simple process, a model of a homogenous tubular reactor (or an analogous continuous stirred tank reactor) was chosen. the application of the suggested method is also presented on a more complex problem, known as uckron-i test problem (bashir et al, [21]). problem definition a commonly used reactor model can be given in the following form: r d cd −= τ (1) ( ) [ ]1,0, ∈−−= ταβ τ wttr d td ; (2) where the initial conditions are: τ = 0, c = c0, t = t0 (3) and τ stands for the independent variable which is expressed by the dimensionless length (ℓ · v/f) in case of a steady state tubular reactor or by the time itself in case of a batch reactor. the constitutive equation completing model (1-3) is the following for the rate of reaction: ( ) ( )c t tcr ϕδγ ⋅⎟ ⎠ ⎞ ⎜ ⎝ ⎛ −= exp, . (4) instead of the reactant concentration c the conversion x(τ) = 1 – c(τ)/c(0) can be used too: ( ) .00 0,= ,0 = = x r d xdc τ τ (5) the explanation of the model parameters is given in the notation list. the runaway phenomenon occurs only in case of exothermic reactions, that is defined by β > 0. both model (1-4) and model (2-5) describe the concentration (or conversion) and temperature profiles versus the reactor length in case of tubular reactors or versus time in case of batch reactors. a part of the analysis is conducted in the so called phase space. the transformation into the phase space is accomplished by eliminating the independent variable τ (eq. (2) is divided by eq. (5)): ( ) ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ − −≡ −− = r tt r ttr xd td c ww αβαβ 0 1 (6) the initial condition is: x = 0, t(x) = t0. the runaway phenomenon is illustrated by fig. 1. a first order chemical reaction, φ(c) = c was chosen as an example and the following parameters were used: α = 5 l/h, β = 180 m3 k/kmol, γ = 20, δ = 6000 k, c0 = 1 kmol/m3, t0 = 300 k. (7) (parameters were chosen on the basis of practical experience). fig. 1 shows that the temperature profile in the steady state tubular reactor (or in a batch reactor) changes significantly for small changes in the operating conditions (eg. changing the value of tw). 21 260 300 340 380 420 0.0 0.2 0.4 0.6 0.8 1.0 τ [-] t [k ] 270 275 280 285 tw=290 k 282.4 figure 1: parametric sensitivity of a tubular reactor it is well known that model (1-4) gives a unique solution for fixed parameters. that is why bilous and amundson distinguished the reactor runaway problem from the multiplicity and classical stability analysis of the continuous tank reactor and interpreted it as parameter sensitivity. for this reason it is practical to determine the parametric sensitivity form of the above model. one among the operating parameters of the model, the tw external temperature is considered in the further studies. this step does not lessen the generality of the method since the procedure is the same in case of any other parameter. accordingly the following sensitivities are defined: ( ) , wt cu ∂ ∂τ = (8) ( ) wt tv ∂ ∂τ = . (9) differentiating eq. (1-2) with respect to tw the following sensitivity model is obtained: ( )vrur d ud tc ⋅+⋅−= τ (10) ( ) ( )1−−⋅+⋅= vvrur d vd tc αβ τ ,0 00 = == v uτ (11) where rc and rt are the partial derivatives of the reaction rate with respect to the concentration and the temperature respectively. eqs (10-11) can be completed with the differential eqs (1-2) and must be integrated together with those. a differential equation for the calculation of the w(x) = ∂t/∂tw sensitivity measure in the phase space can be obtained by differentiating eq. (6) with respect to tw: ( ) w r td xdrrttr rxd wd c xtw 2 0 1 ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ⋅+−− −= αα τ = 0, w = 0, (12) where rx stands for the partial derivative of the reaction rate with respect to the conversion ( cx rr c −= 0 1 ). eq. 12 and eq. 6 together form a closed system. stability approach to runaway let us consider the following system of nonlinear differential equations of the state variables, x(τ): ( )xf d xd = τ . (13) applying ljapunov’s indirect method the stability analysis of eq. (13) is reduced to an eigenvalue analysis of the jacobian ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ = x f j ∂ ∂ for function f(x): │j – λi │ = 0. (14) if the λ1, λ2, … λn roots of eq. (14) are negative (in case of real roots) or their real components are negative (in case of complex roots) then eq. (13) is stable at x(τ) [16]. applying the method on the set of differential eqs (1-2) the following jacobian and eigenvalues are obtained respectively: ( ) ( ) ,⎥⎦ ⎤ ⎢⎣ ⎡ − −− = αββ τ tc tc rr rrj ( ) ( ) 2 42 2,1 ctctc rrrrr αβαβα λ −−+±−+− = . (15) 22 then the conditions for stability can be expressed as: rc + α ≥ β rt (16) if condition (16) is not satisfied then differential eqs (1-2) are unstable in ljapunov’s sense. it means also that terms of eλτ, / re(λ) > 0 appear in the solution of c(τ) and t(τ) instead of eλτ, / re(λ) < 0 which is the case in the stable region. the jacobian of the sensitivity model (10-11) is eq. (15) as well. it means that if eq. (16) is not satisfied then terms of eλτ, / re(λ) > 0 are present in the approximate solution for the u and v sensitivities causing significant changes in the profile. criterion (16) can be “explained” qualitatively too. as exothermic reactions progress, the rate of reaction is generally decreased by the cooling (α) and the “dependence” of the reaction rate on the concentration (these two together form the l. h. s. of eq. (16)) while it is increased by the “dependence” on the temperature. if the l. h. s of eq. (16) is the larger then positive feedback is not present; however if the r. h. s is the larger then a positive feedback is formed through the rate of reaction causing instability. let us apply the stability analysis for model (6) expressed in the phase plane. the stability analysis becomes simpler since the number of state variables is only one. ( ) ( ) .02 < ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ +−− −≡ ≡⎟ ⎠ ⎞ ⎜ ⎝ ⎛ − −≡⎟ ⎠ ⎞ ⎜ ⎝ ⎛ −− r td xdrrttr r tt td d r ttr td d xtw ww α ααβ (17) after the substitution and rearrangement the following criterion is obtained: ( ) t ww c r tt r ttr rr ββ αβ β ≥ − + −− . (18) obviously this one is different from criterion (16) that is the spatial (length for a tubular reactor, time for a batch reactor) stability criterion and the one expressed in the phase space are not the same. the relation of the two different criteria can be easily determined. for increasing temperature (see balance (2)): βr > α(t – tw) considering the above the relationship between the two l. h. s terms of eq. (16) and eq. (18): ( ) cc w rr ttr r > −−αβ β αβ > − wtt r . (19) consequently eq. (16) is always more conservative i. e. the stability in phase space always follows from the spatial stability while inversely does not! comparing eq. (12) and eq. (17) it can be concluded that the relation between sensitivity and stability in the phase space is the same as it is in the spatial analysis. comparison of runaway criteria the criterion suggested first by adler and enig (criterion 1 van welsenaere, froment) can be obtained by differentiating eq. (6) with respect to x: ( ) 01 2 2 0 =⎟ ⎠ ⎞ ⎜ ⎝ ⎛ − −≡⎟ ⎠ ⎞ ⎜ ⎝ ⎛ −− = dx dt r tt dt d r ttr dx d dx td c ww α αβ (20) since 0≠ dx dt , eq. (20) is the same as the result of the stability analysis in the phase space, eq. (18). it also means that criterion 1, which mainly relies on intuitive bases according to morbidelli and varma [12], can be justified theoretically by ljapunov’s stability analysis. the criterion suggested first by dente and collina (criterion 2 van welsenaere, froment) can be obtained by differentiating eq. (2) with respect to τ: 02 2 =−⎟ ⎠ ⎞ ⎜ ⎝ ⎛ += τ α ττ β τ d dt d dtr d dcr d td tc . after the substitutions the criterion for avoiding runaway is: ( ) t w c r ttr rr βα αβ β ≥+ −− . (21) this criterion gives the same result as the “slope condition”, dt qd dt qd genrem > (berty, 1982), which is related to the generated and transferred heat flows, does. applying the slope condition on the system of eqs (1-2) the following equivalencies are obtained: ( ) ., ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ −− −→→ w ct genrem ttr rrr dt qd dt qd αβ βα showing that the slope condition differs from the above criterion only in a multiplication with a constant. berty et al. [22] showed that the criterion, called “dynamic condition” by gilles and hoffmann [23], can be expressed in the following form, using the original notation: tc genrem c m t q dt qd ∂ ∂ ∂ ∂ +〉 . applying the appropriate notation for the system (1-2) the following substitutions are obtained: .,, c t t c genrem r c mr t q dt qd −→→→ ∂ ∂β ∂ ∂ α eq. (16) differs from the above criterion only in a multiplication with the same constant value concerning every terms; that is the two criteria is the same! 23 the criterion used at the maximum temperature in the practical design is also included in the study for a more complete comparison: ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ≡≤− t w r rttt δ 2 . bashir et al. [21] suggested that this criterion be evaluated at the inflection point instead of the maximum temperature. the above criteria are summarized in table 1. criteria 1 and 3 have been compared in the previous section. if the conditions are the same, criterion 2 obviously indicates the runaway always between criteria 1 and 3, i. e. it is more conservative than the first criterion and less conservative than the third one. criterion 4 used in practical design is especially conservative if the second right hand term is the dominant in criterion 1. table 1: runaway criteria for model (1-2) id criterion stability mathematical form 1 first criterion: inflection in phase space [7] ljapunov in phase space, eq. (18) ( )w c w t ttr rr tt rr −− ⋅ + − ≤ αβ 2 second criterion: inflection in geometric space [7], eq. (21), “slope condition” [22] ( )w c t ttr rrr −− ⋅ +≤ αββ α 3 “dynamic condition” [23] ljapunov in geometric space (or time), eq. (16) ββ α c t rr +≤ 4 practical design (at the hot spot temperature) [21] w t tt rr − ≤ the relation between the different criteria and the parametric sensitivity measures was also studied. using the (1-3, 10-11) sensitivity model and assuming that a first order reaction takes place, the u(τ), v(τ) parametric sensitivities can be determined numerically along τ (length or time) and shown on fig. 2. naturally the character of the functions changes with the tw parameter. for the sake of obtaining a simpler relationship morbidelli and varma evaluated the above sensitivities at the maximum temperature (st). this sensitivity is shown as a function of tw by the dotted line on fig. 3. in the literature almost exclusively the hot spot temperature, t* is used for characterizing the reactor operation in relation with thermal runaway. the question is whether the t* value has a distinguished role indeed or some other value, which characterizes the complete reactor regarding runaway and can be measured or calculated easily, can be used too? -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0.0 0.1 0 0.2 0.4 0.6 0.8 1 τ (length, time) [-] u [k m ol /m 3. k ] -40 -20 0 20 40 60 80 100 120 v [-] 280285tw=290 k u v 290 285 280 tmax (tw=290 k) . . . . tmax (tw=285 k) figure 2: sensitivity values versus τ. 24 0 20 40 60 80 100 120 276 278 280 282 284 286 288 tw [k] s 0 5 10 15 20 25 30 s tljapunov in geometric space (278.4 k) s st inflection in geometric space (281 k) ljapunov in phase space (282.4 k) . . figure 3: parametric sensitivities versus operational parameter let us express the average rate of reaction in the reactor: ( ) ( )( )∫= 1 0 , τττ dtcry (22) based on eq. (5) the relationship between y and the conversion can be given as: ( ) y c x 0 11 = . (23) then a characteristic sensitivity measure can be expressed in the following relative form: w w t y y ts ∂ ∂ ⋅= . (24) applying the (1, 8, 24) relationships s can be calculated from the u(τ) sensitivity: ( ) ( )1 10 u cc ts w ⋅ − −= (25) the solid line on fig. 3 is the s versus tw function. comparing the two sensitivity measures the following conclusions can be drawn: ● the tendency of the two sensitivity measures are similar i. e. the t* value does not have a distinguished role considering runaway; ● the calculation of s value is simpler than that of st (large numerical error in calculation of t*); ● the maxima of the two functions are close to each other (the higher the inclination for runaway is the closer they are); the difference is theoretically important since it proves that the location of the maximum depends on the choice of the sensitivity measure. to show how the sensitivity measures change for the different criteria summarized in table 1, the tw values where the criteria give warning are marked on fig. 3. the very conservative character of criteria 4 can be noticed here too. in fact the sensitivities start to increase significantly at criterion 3; their values are considerably high at criterion 2; and they reach their maximum values in the narrow neighborhood of criterion 1. the c – t relationships of criteria 1-3 are shown on fig. 4 for a first order reaction. from table 1 it is clear that tw is a parameter for criteria 1 and 2; i. e. each criterion provides a set of curves. on fig. 4 these curves are given at the critical values of tw (the operating curves just intersect the criterion curve at the runaway point). tw is not involved in criterion 3 therefore it gives only a single curve. the operating curve at tw = 278.4 k does not intersect even the most strict criterion curve 3 so it is considered as runaway less operation. at tw = 281 k positive exponent components appear in the solution for the state variables along the length (or time), i. e. in ljapunov’s terms the solution is unstable in space. at the operating point tw = 282.4 k an inflection is present along the length (or time), however the system is still just stable in phase space. at operating points tw > 282.4 k the system is in runaway state according to all of the criteria. fig. 5 shows the same on the t – x plane. from the c – t functions it can be seen that if the c0 initial concentration is less than a critical value, ccr runaway does not occur at all. fig. 4 and 5 reflect well the relationship between criterion 1-3 too. as it was shown criterion 3 is independent from the tw value; at the same time as tw increases, criterion curve 2 approaches curve 3 while curve 1 moves away from it. the very conservative character of criterion 4 has been criticized by several researchers. from criteria 1-3 the third one can be suggested for practical design since 25 it is only slightly more conservative than criteria 1 and 2 and at the same time its preventive character assures reasonable safety. based on the above example the following conclusions can be drawn: ● explaining reactor runaway as parametric sensitivity leads to theoretical uncertainty. although their practical useness is indisputable the criteria obtained this way depend on the selected variable therefore the runaway can not be exactly defined ● the best way is to define the runaway as a stability problem (not in the sense of classical reactor stability). the sudden change in the state variables is then only a consequence of the stability problem. the reason is reaching the stability limits and the result is the change of the shape of functions of state variables with different time delays. (in the case study the stability criterion coincides with the inflection one. this occurs in the case of one independent variable only. in case of more independent variables the criteria do not coincide.) ● the stability analysis must be conducted in the original geometric (or time) space. the indication of runaway may be delayed in transformed spaces. 0.0 0.2 0.4 0.6 0.8 1.0 1.2 270 290 310 330 350 370 t [k] c [k m ol e/ m 3] tw=277 k 278.4 280 ljapunov in phase space (282.4) 282.4ljapunov in geometric space (278.4) 284 inflexion in geometric space (281) 281 282 figure 4: criteria in the c – t plane 260 300 340 380 0.0 0.2 0.4 0.6 0.8 1.0 x (conversion)] [-] t [k ] tw=277 278.4 280 ljapunov in phase space (282.4) 282.4 284 ljapunov in geometric space (278.4) inflexion in geometric space (281) 281 282 figure 5: criteria in the t – x plane 26 application for a complex system the primary limitation of different runaway criteria published in the literature is that they are generally derived only for simple or considerably simplified (reaction) systems. at the same time the stability analysis described in section 2 requires only differentiation and calculation of the eigen values. the application of the method therefore does not raise mathematical difficulties. this fact is illustrated using a reactor modeling test problem known as uckron-i in the literature (berty [24]). the uckron-i test problem was developed by berty, lee, and szeifert at the chemical engineering department of the university of akron and by cropley at the research and development of union carbide corporation. uckron-i is aimed at the computer simulation of a catalytic reaction system for a number of groups to gain experience in chemical reaction engineering. the applied model illustrates some of the complexities of a real system and yet the mathematics involved can be easily handled. the net chemical reaction taking place in the specified industrial methanol synthesis reactor is the following: 2h2 + co ch3oh . (26) the homogenous one-dimensional axial-mixing-free reactor model for the total mole mass, the components, the enthalpy and the momentum is the following (berty et al [24]): ( ) rv d cfd 2−= l (27) ( ) { }mchirv d cfd i i ,,, ∈⋅=ν l (28) ( ) ( )wrp ttaurvh d tdccf −−−= δ l (29) c p f ad ff d pd 2 2 2 ⋅ −= ρ l (30) where ( ) 2.0 3 2.118.6 − ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ⋅ ⋅− = a fd f p νε ε is the hicks’ correlation, while ℓ ∈ [0,1]. the rate equation (26) of the net reaction is determined by analysing of the constituent processes and fitting to the data relevant to those processes (szeifert et al [25]): m c m h pk p pkp kr ⋅+ − = 3 2 1 1 , (31) 3,2,1,exp =⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −= i tr eak i ii . the model equations (27-31) can be completed with a suitable state equation (for the sake of simplicity the ideal gas law is applied here). the initial conditions of the system of differential equations are specified at ℓ = 0 in the problem statements (berty et al [24]): ℓ = 0, f0, ci, 0, t0, p0 are given. (32) since the number of net reactions is only one the number of state variables f, ch, cc, cm, t, p can be reduced. since h2 is in excess in the mixture entering the reactor the following form of conversion is introduced: 0,0 0,0 c cc cf cfcf x − = . (33) based on the (27-28) balance equations and the initial conditions the other state variables can be calculated as functions of the x, p, t state variables: { }mchic cxc cxc c c cii i ,,, 2 0,0 0,0, ∈ − + = ν (34) . 2 0,0 0 c cxc f f c− = (35) an alternative form of eq. (34) can be expressed with partial pressures: rt cpp cxc cxc p c cii i = − + = /, 2 0,0 0,0, ν . (36) differential eqs (27-29) can be substituted by the following differential equations applying to x and t: r d dxcc = l 0, (37) ( )[ ], 2 1 wttr xd dt −− − = αβ κl (38) ℓ = 0, x(0) = 0, t(0) = t0 initial conditions, where ( ) 0, 0 0,0, ,, cpc r pc c c cc h ccv au = δ− = ⋅ = κβα . from eqs (37-38) the differential equation in phase space can be derived: ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ − −⋅ − = r tt xdx dt c w c αβ κ 2 11 0, . (39) model (37-39) differs formally in the factor ( ) ( ) ( )w cx wc t ttr crr x tt r c rr −− − −+ −⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ −≤ αβ κ α 0, 0, / 221 from model (2-5) of the simple system. this factor expresses the distortion effect due to the change in number of moles in the chemical reaction. according to ljapunov’s indirect stability criterion the derivative of r. h. s. of eq. (39) with respect to t must be less than zero. after rearrangement the corresponding runaway criterion is the following: 27 ( ) ( ) ( )w cx wc t ttr crr x tt r c rr −− − −+ −⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ −≤ αβ κ α 0, 0, / 221 . (40) comparing the (40) relationship to the first criterion in table 1 the distortion effect due to the change in number of moles can be described by the following inequalities: 121 0, <− cc r α (41) 0 2 112 > − <>− κκ xifx . consequently one of the two positive terms of r. h. s of eq. (40) decreases however the other term can increase therefore the relationship between the two terms determines whether the change in number of moles increases or decreases the risk of runaway. the rt and rx derivatives required for the calculation of the criteria can be obtained by differentiating the rate equation of the reaction: 2tr errt ⋅= , (42) where the “apparent” energy of activation is: , 1 23 3 3 1 e p pbp p pb e pk pkee c m h c m m m ⋅ − −⋅ + −= ( ) ( ) ⎪⎩ ⎪ ⎨ ⎧ +⎥ ⎦ ⎤ ⎢ ⎣ ⎡ ++− − −= mhx ppk k rpp x r 22 2 1 3 1κ ( ) mc m m c pk k p p p pk x 3 1 2 112 1 +⎪⎭ ⎪ ⎬ ⎫ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ + − + (43) according to eqs (42-43) the (40) criterial equation determines a set of curves with respect to parameter tw. any of the curves divides the plane into two regions; one of them is the region where runaway does not occur the other is the runaway region. fig. 6 shows the criterial curves with respect to parameter tw in the t – x plane. it can be seen that under a critical value of the conversion the runaway zone for a given conversion is an intermediate temperature region. both the lower and higher temperatures are outside of the zone. the reason for this is that the reaction is an exothermic reversible one. the criterial curve at tw = 485.95 k and several operating curves at different values of parameter tw are given in the cc – t plane on fig. 7. the criterial curve at tw = 485.95 k and several operating curves at different values of parameter tw are given in the cc – t plane on fig. 7. it can be seen that the operating curve and the criterial curve intersect at tw = 485.95 k. if tw is less than this value then the reactor operates without runaway; if tw is larger then – according to the first criterion – the reactor operates in the runaway region. in case of this system a change of a few tenths k in tw results in a tremendous change in the reactor temperature (see fig. 8). the inflection point of the temperature along the length is found at tw = 485.3 k (criterion 2); positive exponent roots are obtained at tw = 485.1 k (criterion 3). the specified system is “apt” to runaway that is indicated by the fact that the three criteria give signal in 1 k range. the criterial curves indicating runaways are very important in reactor design. as explained in the discussion of a simple reaction the application of the third criterion is suggested for design since it is only slightly more conservative and with the appearance of the positive exponent roots it practically predicts the imminent changes. 500 520 540 560 580 0.0 0.1 0.2 0.3 0.4 x (conversion) [-] t [k ] runaway zone tw=475 k 480 485 490 figure 6: criterial curves in the t – x plane 28 0.4 0.5 0.6 0.7 0.8 470 490 510 530 550 570 t [k] c c [k m ol /m 3] x=0 criterion (tw=485.95 k) tw=473 k 483 485 485.8 485.9 486 figure 7: runaway of the specified reactor in the cc – t plane reaction (26) is a reversible exothermic one. in reactor design for this type of reactions the determination of the state variables corresponding to the maximum rate of reaction plays an important role too. the rate of reaction for a given composition is between zero (equilibrium) and its maximum value depending on the current value of the temperature. the two extrema can be determined the following way: r = 0 (equilibrium) (44) rt = 0 (max. reaction rate necessary condition). (45) eqs (44) and (45) give the corresponding relationships in the t – x and ci – t planes according to eqs (41) and (42) respectively. each curve can be constructed by solving the corresponding nonlinear equation. fig. 9 shows the runaway curve corresponding to the third criterion as well as the equilibrium and maximum curves of the rate of reaction in cc – t diagram. it designates the main limits for the design. in case of low conversion the temperature providing higher rate of reaction is restricted by the risk of runaway. over a critical xcr conversion runaway does not occur therefore the temperature can be increased to approach the one corresponding to the maximum rate of reaction. the approximation of the “ideal operating curve” shown on fig. 9 is a part of the design process and it is outside of the scope of present study. 460 500 540 580 620 0 2 4 6 8 10 12 14 length [m] t [k ] tw=503 k 486 485.9 483 473 figure 8: temperature gradients along the reactor length 29 0.3 0.4 0.5 0.6 0.7 0.8 490 510 530 550 570 t [k] c c [k m ol /m 3] runaway r=0 rmax x=xcr x=0 x=0 figure 9: design diagram conclusions the most important criteria for reactor runaway are summarized in the paper. it is proved that reactor runaway approached as parametric sensitivity can be interpreted as a consequence of stability problems. after the reactor gets into the unstable region of the geometric (length) space (criterion 3) – as a consequence – a convex temperature profile appears soon (criterion 2). “going on” into the unstable region the phase space instability criterion (criterion 1) is reached shortly. the absolute values of the different parametric sensitivities reach their maximum values in this narrow range; however from the fact itself that the parametric sensitivity is at its maximum reactor runaway does not follow. the correspondence and relations of reactor runaway, stability and thermal stability criteria are illustrated on the example of a simple reactor. it is proved that the maximum temperature (hot spot) does not have a distinguished role in the analysis of runaway. this also comes from the fact that the component and enthalpy balances form a mutually linked system. the application of ljapunov’s stability criteria for reactor runaway is demonstrated also on a more complex problem showing that complexity does not restrict the use of the method. to avoid runaway the application of the third criterion is suggested for reactor design or control since it is only slightly conservative (compared to the first and second criteria) and it is the first among criteria 1-3 to predict the appearance of dangerous operating conditions. notation a heat transfer area, m2 a cross section, m2 c concentration, kmol/m3 cp specific heat, kj/m3k dp particle diameter, m e energy of activation, kj/kmol f volumetric flow rate, m3/h fc friction factor (–δhr) heat of reaction, kj/kmol j jacobian matrix k kinetic parameters ℓ dimensionless length, (-) m mass balance function, kmol/m3h p pressure, bar genq generated heat flow, kj/h remq transferred heat flow, kj/h r gas constant, kj/kmol k r rate of reaction, kmol/m3h rc, rt, rx derivative of reaction rate with respect to c, t and x respectively s, st relative sensitivity s absolute sensitivity t temperature, k t* hot spot temperature, k tw wall temperature, k u,v parametric sensitivities x conversion y average rate of reaction, kmol/m3h ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ = pcv ua ρ α parameter, 1/h ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ − = p r c h ρ β δ parameter, m3k/kmol γ kinetic parameter, (-) ⎟ ⎠ ⎞ ⎜ ⎝ ⎛= r eδ kinetic parameter, k ε void fraction, m3/m3 ϕ(c) concentration function of the rate of reaction, kmol/m3h ν dynamic viscosity, kg/m s 30 νi stochiometric coefficient ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ = 0, 0 cc cκ initial ratio of concentrations, (-) ρ density, kg/m3 subscripts c co h h2 m ch3oh 0 inlet cr critical references 1. semenov n. n.: zur theorie des verbreennungsprozesses, z. phys., 1928, 48, 571-581 2. bilous o., amundson n. r.: chemical 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veszprém, hungary e-mail: szentgyorgyi@almos.uni-pannon.hu the aim of this work was to give a general overview on the type and behaviour of anaerobic membrane bioreactors, which are intensively studied for waste water treatment processes. the role of the membrane, the possible design, structures of the bioreactors, the effect of environment are presented here. keywords: wastewater treatment, biogas, membranes, anaerobic conditions introduction the process of wastewater treatment in general includes various steps, where biological degradation and separation techniques play important roles. recently membranes are often applied for the separations. to intensify the processes, biodegradation and separation can be integrated, thus membrane bioreactors (mbrs) are introduced in the particular field. membrane bioreactors may work under aerobic as well as anaerobic conditions. this paper focuses on the anaerobic membrane bioreactors. anaerobic waste water treatment low biomass yields and low growth rates represent one of the important advantages of anaerobic biotechnology, since they translate into the generation of low amounts of waste sludge, up to ten times less than during aerobic treatment. however, during the first developments of anaerobic processes this feature represented a major drawback when trying to increase the biomass concentration in anaerobic reactors [1]. since the installation of the first full scale upflow anaerobic sludge blanket (uasb) reactor, three decades ago [2], anaerobic process has been successfully used for the treatment of many kinds of industrial wastewaters as well as sewage. nowadays, it can be considered an established technology that offers the possibility of an efficient treatment with low capital and operational cost [2]. the success of anaerobic wastewater treatment can be attributed to an efficient uncoupling of the solids retention time from the hydraulic retention time through biomass retention, which is usually accomplished through biofilm or granule formation. with this strategy, a high concentration of biocatalyst is obtained, leading to high volumetric treatment capacities [1]. from the available anaerobic technologies, sludge bed reactors are by far the most applied. at present close to 80% of all full-scale anaerobic installations are sludge bed reactors in which biomass retention is attained by the formation of sludge granules. biomass retention can also be accomplished by biofilm formation, which greatly facilitates biomass-liquid separation. biofilms are very useful in environmental biotechnology since they ensure an effective uncoupling of sludge retention time from liquid retention time, enabling the treatment of large volumes of diluted aqueous solutions, at short liquid retention time [3]. the role of membranes in anaerobic waste water treatments in situations where biofilm or granule formation cannot be guaranteed, such as extreme salinity and high temperatures, or when complete biomass retention must be ensured, membrane assisted physical separation can be used to achieve the required sludge retention [2]. membrane bioreactors (mbr) ensure biomass retention by the application of micro or ultra filtration processes. furthermore, since the permeate is free of solids or cells, water would eventually require les post-treatment steps if reuse or recycle is of interest, in comparison with sludge bed technologies. regarding the structure of the membrane bioreactor systems, two mbr process configurations can be identified: side-stream (or external-loop) and submerged. in side-stream (external) mbrs membrane modules are placed outside the reactor (fig. 1), and the reactor mixed liquor circulates over a recirculation loop that contains the membrane. 182 figure 1: external-loop membrane bioreactor in submerged mbrs, the membranes are placed inside the reactor, submerged in the mixed liquor fig. 2). side-stream mbrs involve much higher energy requirements, due to higher operational trans-membrane pressure and the elevated volumetric flow required to achieve the desired cross-flow velocity. however, sidestream reactors have the advantage that the cleaning operation of membrane modules can be performed more easily in comparison with submerged technology, since membrane extraction from the reactor is needed in the later case. submerged mbrs involve lower energy needs, but they operate at lower permeate fluxes, since they provide lower levels of membrane surface shear. the latter means higher membrane surface requirements. nowadays, most of the commercial applications are based on the submerged configuration, due to lower associated energy requirements [4]. figure 2: submerged membrane bioreactor most of the reported research done with anaerobic membrane bioreactors has been performed with sidestream configuration [5]. so far the drawback of mbr systems is related with membrane costs, energy requirements and membrane fouling [6, 7, 8]. however, important advances have been made in the development of new types of membranes, of which the costs have been significantly reduced [4]. in addition, research is being conducted in order to find reactor configurations and operational procedures that reduce fouling and energy consumption. membrane fouling is definitively the main drawback of the application of mbrs for wastewater treatment [9]. membrane themselves represent a relevant capital cost, so everything that can reduce their lifetime or the applied flux will directly affect the economic feasibility of the process. moreover, membranes cleaning activities directly affect reactor operation due to the need for process interruptions. the flux reduction phenomenon is usually analysed in terms of filtration resistances. three categories of factors affecting applicable flux can be identified: membrane material and pore size, suspension properties, and operational conditions. membrane hydrophobicity has shown in some studies to play a significant role [1, 7, 10]. hydrophobic proteins residues can form strong attachments by hydrophobic membranes resulting in strong fouling [1, 11]. indeed, surface modification of hydrophobic polymeric membranes by grafting more hydrophilic polymers can reduce fouling and improve flux [7, 11, 12]. membrane material can also determine the applicable fluxes [13, 14, 15]. membrane pore sizes used in wastewater treatment applications are in the range of 0.02–0.5 µm [1]. increasing the suspended solid concentration usually produces a decrease in the attainable flux [16, 17]. particle size distribution can also strongly influence solid deposition over the membrane surface. membrane fouling is usually prevented applying shear over the membrane surface. in side-stream mbrs this is accomplished by applying high cross-flow velocities. an increase in the cross-flow velocity usually results in an increase of the applicable flux [18, 19, 20]. gas sparging is the most common way to provide high shear conditions in submerged mbrs. in anaerobic mbrs biogas can be recirculated in order to achieve a similar effect. the applied gas flow represents an important operational parameter for controlling cake layer development, but will affect energy requirements for the applied system. several operational procedures have been reported in order to reduce membrane fouling in mbrs: flux stoppage and permeate back-flush are the most common strategies [1]. the critical flux concept was introduced over 10 years ago, and has proven useful to characterize membrane fouling in membrane applications, especially in mbrs [21]. the critical flux is defined as the flux over which the relation between flux and tmp becomes non-linear [22]. different methods have been used to determine the critical flux, such as direct membrane observation [23], mass balance [24] and tmp observation in flux step or cycling experiment [22, 25, 26]. mass balance and microscopic observation are unlikely to be used in fullscale installations or in submerged mbrs. however, pressure increase at constant flux operation can be easily applied for critical flux determination in any type of membrane process, both at lab and full scale. the membrane resistance of the thermophilic reactor is clearly lower than that of the mesophilic reactor [1]. results show that the change in diffuser type (fine diffuser, coarse diffuser) is as effective in decreasing cake formation rate, as an increase in gas superficial velocity of close to 300% (gas volume from 18 to 54 m/h) [26]. in mesophilic anaerobic smbr sludge concentration is the main operational parameter for cake layer formation. operation over critical flux inevitably implies cake formation (fig. 3). biomass concentration showed to be an important factor determining cake formation in mesophilic mbrs. under mesophilic conditions, biomass concentration affects linearly critical flux. an increase from 25 to 50 g tss/l reduces critical flux from 21 l/m2h to 9 l/m2h 183 [24]. even though gas sparging level also influences critical flux, its effect is much smaller than biomass concentration. figure 3: cake layer formation on membranes thermophilic operation reduces drastically the effect of biomass concentration and gas sparging on cake layer formation, in comparison with mesophilic conditions. biomass concentration and gas superficial velocity presented a value, below and over which no further effect on critical flux was found. thermophilic mbr requires much lower levels of gas sparging in comparison with mesophilic mbr [27]. for achieving similar levels of effluent flux at a fixed biomass concentration, gas requirements under thermophilic conditions were below 50% of those required for mesophilic conditions. even though cake formation is mainly reversible in short term experiment, particle deposition proceeds fast once critical flux has been exceeded. at 50 g tss/l, a flux increase of only 3 l/m2h over the critical flux results in a tmp increase rate of over 1 and a 5 bar/h for the mesophilic and thermophilic reactors, respectively [27]. the operational flux is, therefore, likely to be restricted to values close to the critical flux for both temperatures. since reversible cake formation was identified as the limiting factor for the operational flux, increasing surface shear should result in higher fluxes. preliminary test showed that cross-flow operation may be a feasible alternative to reduce particle deposition [1, 24]. this will be the case only if the high shear stress does not negatively affect the physical properties of the sludge, i.e. including a decrease in particle size. thermophilic anaerobic wastewater treatment offers several potential advantages in comparison with mesophilic processes, such as higher loading potentials, effective removal of pathogenic microorganisms and the elimination of cooling needs when wastewater is already discharges at high temperature [27, 28]. granulation and biofilm formation seems to be more difficult to achieve under thermophilic conditions, in comparison with mesophilic conditions. moreover, lower net biomass yield are expected under thermophilic conditions, in the range of 50% of those possible under mesophilic temperatures, as the result of higher maintenance requirements and higher decay rates [1, 27]. in membrane bioreactor, biomass is retained independently of its capacity of forming flocks or biofilms, and irrespective of its growth rate or yield. in principle, operation at high temperatures should be beneficial for membrane filtration due to the effect of temperature on sludge and permeate rheological behaviours. temperature affects the relation between shear stress and shear rate, which in newtonian fluids is represented by the viscosity [28]. during the operation of an anaerobic submerged mbr, attained fluxes showed to be determined by the development of fraction of small particles. under these conditions, temperature showed little effect on the attainable fluxes, indicating that the physiological effects of temperature on the properties and composition of the sludge can be much more of importance for membrane filtration than the physical effect of temperature on sludge or permeate rheology [28]. the wastewater organic matter concentration determines to a high extent the applied hydraulic retention time, which in turn defines the flow of permeate that has to be achieved. for a given flux, the latter value will determine the membrane requirements, influencing capital and operational costs [2]. therefore, even though the application of anaerobic mbr technology to low strength wastewaters may become technically feasible, its economical feasibility will be strongly determined by the prevailing membrane prices and flux levels that can be achieved. low pore fouling may attribute to cake layer formation. if the membrane is covered by cake layer, it is no longer exposed to the suspension, and pore blocking and other fouling mechanisms are less likely to occur. cake formation also implies that the membrane material and exact pore size may not play a significant role in determining the flux. once the membrane surface is covered by sludge, its properties do not play anymore a role in the further deposition of particles. under these conditions only the suspension properties and operational conditions will determine the relation between backtransport and convective transport. two types of cake formation were identified: short-term, mainly reversible cake formation and a long term consolidated cake formation. the short term cake formation is the main responsible phenomenon determining the critical flux. the long term formation slowly increases the membrane resistance, until a point when the tmp may be too high and a physical cleaning procedure is required. cake formation can be controlled by increasing the surface shear. surface shear is an efficient way of controlling particle deposition, as long as it does not affect suspension properties. however, usually this is not the case, since high shear rates will most likely reduce particle size, increasing particle deposition. high temperature operation positively affects membrane filtration, due to the temperature effect on the rheology of both permeate and sludge. a lower sludge viscosity means that lower shear rates will suffice for providing the same shear stress, resulting in lower energy requirements. a lower permeate viscosity increases membrane permeability, decreasing the trans-membrane pressure. these properties result a better filtration performance for the thermophilic mbr compared to the mesophilic mbr. for aerobic mbrs, submerged configurations are favoured, owing to the relative low energy requirement compared to the side-stream configuration. due to the low bacterial growth rates, anaerobic mbrs need to be operated at higher biomass concentration in order to provide an efficient treatment at high organic loading 184 rates. under these conditions, 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clech, b. jefferson, i. s. chang, s. j. judd: critical flux determination by the flux-step method in a submerged membrane bioreactor, journal of membrane science, 227, 2003, 81–93. 27. j. b. van lier: thermophilic anaerobic wastewater treatment; temperature aspects and process stability, phd thesis, wageningen university, wageningen, the netherlands (2003). 28. m. h. gerardi: microbiology of anaerobic digesters, wiley-interscience, hoboken, nj (2003). << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 /colorconversionstrategy 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word 2012_dr_bodor_endre_hjic.doc hungarian journal of industrial chemistry veszprém vol. 39(3) pp. 335-339 (2011) application of models with different complexity for a stirred tank reactor a. egedy , t. varga, t. chován university of pannonia, department of process engineering, egyetem st. 10. h-8200 veszprém, hungary e-mail: egedya@fmt.uni-pannon.hu engineering problem solving such as process design, process optimization, safety analysis, etc.; relies widely on mathematical models of the process. to solve various engineering problems various models with different complexity are needed. a stirred tank reactor with a highly exothermic reaction is studied in this work, because in the modern chemical technologies mixing is one of the most important operations, and stirred reactors are widely used in industrial applications. the stirring system of a mixed tank is always an important aspect of the design, because the involved processes (such as reactions, heat and component transport) usually require proper contact and homogeneity of the existing phases. for the suitable homogeneity the design and the size of the moving parts are also important problems. in certain situations attachment of static parts to a stirred tank (such as baffles) may have an important effect too. the primary goal of this study is to create models with different level of complexity and determine which model is the best suited for solving different engineering tasks such as process design, scale-up, or optimisation. etc. to determine which model fits best for a problem, mathematical models were created and compared to find out, how the information can be extracted from these models and be applied to solve engineering problems. three types of models have been developed: perfectly mixed reactor model, compartment model, and computational fluid dynamics (cfd) models with different dimensions. the reaction of hydrogen peroxide with sodium thiosulphate in a continuously stirred tank reactor is analysed as a case study. the perfectly mixed vessel models and compartment models were solved in matlab/simulink program package. the cfd models were implemented in comsol multiphysics. keywords: computational fluid dynamics, stirred tank, hydrogen peroxide, model complexity introduction in modern technologies mixing is one of the most important operations. the stirring system of a mixed tank is always an important aspect of the design, because the involved processes (such as reactions, heat or component transport process) require proper contact and homogeneity of the existing phases [1]. nowadays there are an increasing number of applications of model based methods in the industry too. with a correctly built model there is a possibility to examine the dynamic behaviour of the system as well as the mass, heat and momentum transport processes. in this study a kinetic model of the reactions of hydrogen-peroxide and sodium thiosulphate from an earlier case-study is analysed [2]. for developing suitable reactor models we followed a sort of hierarchical modelling concept [3]. three types of models with different complexities have been developed: perfectly mixed reactor model, compartment model, and computational fluid dynamics (cfd) models. since the examined reaction is highly exothermic the thermal runaway problem must have been investigated thoroughly. for achieving different goals different models might be required. to solve the simplest problems such as preliminary design and control, engineers can use simple models to describe a dynamical system, such as perfectly mixed vessel model, or ideal plug flow reactor model. in the case of a perfectly mixed model the whole vessel is homogenous, and models with concentrated parameters can be used. on the other hand the plug flow reactor models can be applied to calculate the inhomogeneity in a tube reactor in axial direction; in this case the distributed model parameters need to be defined [4]. if a simple model is not detailed enough to solve a problem more complex model have to be created, such as operation fermentation reactor with multiple impellers. the second level of models which is discussed in this paper is the compartment models. these models generally contain two or more well defined compartments, built from perfectly mixed reactor or ideal plug flow reactor models. the most important thing at this level of modelling is to find the proper parameters describing the connections between these models [5]. for example to create a compartment model for a stirred vessel in the basic cases the vessel has to be separated at least two different compartments. the impeller and the region near the impeller can be described by using a perfectly mixed reactor model, and at least one other region must be defined, called circulation loops, or circulation region [6]. to model the connections between these models the 336 following parameters need to be determined: the exact volume of the compartments, and circulation rates, or other pre-defined parameters [7]. the more difficult the problem is, the more complex model must be created. in the last few years researchers have been trying to create even hybrid cfd-compartment models that are capable of handling more than 100 compartments [8]. the cfd models are the most complex models examined in this work. the cfd models can be applied to determine the entire hydrodynamics of the system, to define flow patterns, or concentration distributions, or thermal hotspots. with validated cfd models the system can be examined at a completely new level, and engineers can model anomalies such as thermal runaway, and prevent hazardous situations [9]. cfd models can also serve as excellent design tools [10]. in this paper we have created models with different complexities in order to determine how these models can be used to solve various engineering problems in the field of design and control of chemical processes. the perfectly mixed vessel models and compartment models were solved in matlab/simulink program package. the cfd models were implemented in comsol multiphysics. modelling approach at every level of modelling the same exothermic reaction with a well-known kinetics is used [2]. this is the reaction of hydrogen-peroxide with sodium thiosulphate. ohsonaosnaohosna 24264222322 4242 ++→+ (1) the analysed highly exothermic reaction is the oxidation of sodium thiosulphate with hydrogen peroxide. the kinetic parameters of the analysed reaction were determined in an earlier case-study [2]. table 1 contains the model parameters. table 1: model parameters revolution speed 20 [1/min] density 1000 [kg/m3] volume 0.375 [m3] feed 2e-4 [m3/s] viscosity 0.001 [pas] component diffusion ca sodium thiosulfate, cb hydrogen-peroxide, cc sodium trithionate 10-5 [m2/s] the examined stirred vessel is a continuous tank reactor. all the implemented models have the same model parameters for describing reactor geometry (apart from the parameters of the impeller, since the impeller was implemented only in the cfd simulations). because of the exothermic reaction the temperature dependence of the reaction is high, thus it is necessary to define heat balance equations too. in every model component and heat balances was implemented. figure 1: scheme of the reactor component balances { }ohsonaosnaohosnai rcc v b dt dc iibei i 24264222322 , ,,,, )( = ⋅+−⋅= υ (2) heat balance )()(1 tt v bhr cdt dt in p −⋅+δ−⋅⋅= ρ (3) in cfd models a momentum balance was also added besides component and heat balances. momentum balance fpiuu t u ++−∇=⋅∇⋅+ ∂ ∂ ][)( τρρ (4) results and discussion perfectly mixed reactor model in the perfectly mixed reactor model a mathematical formulation based on the modified dahmköhler-equations is applied to describe material and heat balances. the model was implemented and solved in matlab. fig. 2 shows the results of the dynamic simulation of the perfectly mixed reactor model with the previously mentioned reaction implemented. the perfectly mixed reactor model can be used to: ● calculate the maximum productivity and conversion; ● support optimization and design of the reactor; ● study control functions; ● examine runaway situations in the system level; ● etc. the figure shows, that the product concentration reaches a stationary value within a short time, but, the temperature rises 45 k, therefore it is important to control the reaction temperature to avoid hazardous situations. 337 figure 2: results of the perfectly mixed reactor model compartment model at this stage of the work four types of compartment are applied to model macro mixing conditions. the following compartments are applied: ● perfectly mixed reactor; ● mixer; ● distributor; ● dead zone. the first cell is identical to the previously discussed perfectly stirred reactor model. the mixer and the distributor have zero volume, and these compartments are capable of modelling circulation loops. the distributor distribute the flow directly, and the mixer use mixing equation to calculate the outlet variables. the output variables were computed from the input variables using algebraic equations. the dead zone cell represents a cell with real volume; however there is no flow in it. the circulation numbers – describe the ratio of distribution – have constant values at this time and describe the rate of circulation between impeller zone and circulation zones. fig. 3 represents the compartment approach and fig. 4 shows the structure of the compartment model. eight compartments have been used: one dead zone, three perfectly mixed reactor models for impeller top and bottom circulation zones, two mixers and two distributors. the volume of the dead zone is 15 % of the total volume, and each reactor cell has the same volume. figure 3: compartment model for a stirred tank reactor the compartment model can be used to: ● support advanced control and design; ● examine macro mixing and model complex reaction systems; ● examine heat transfer at a more complex level; ● etc. dead zone top circulation zone impeller zone bottom circulation zone mixer mixer distributor distributor feed outlet figure 4: compartment model structure twoand three-dimension cfd models to simulate the behaviour of the system in a cfd environment comsol multiphysics program package was applied. the investigated impeller is a standard six bladed ruston turbine in the 3d simulations and a simple blade in the 2d analysis. the revolution of the impeller is 20 rpm in the first investigation. the revolution of the impeller is low, because a laminar model was used in this case, and laminar models can only work at low impeller revolution. in the future a turbulent model will be implemented to examine higher revolution speed. in case of the 2d analysis the same continuous system cannot be simulated, since the investigated geometry is a slice of the 3d geometry, i.e. the slice in the centre of impeller zone. in the 3d simulations the same continuous reactor is investigated as in the two dimensional simulations. the results of the cfd simulation are shown in fig. 5 and fig. 6. the velocity field are calculated in 2 and 3d. the cfd models can be used for: ● examining of runaway reactions in three dimension; ● studying different impeller geometries; ● testing of new vessel constructions; ● applying multi-level optimisation; ● etc. 338 figure 5: results of the 2d cfd model figure 6: results of the 3d cfd model comparison of the models in the final step of our investigation the simulation results of the developed three models are compared. the results are shown in fig. 7. the concentration refers to the concentration of the product. the results of the cfd model are much more different than the other two, because in this model the real geometry of the reactor has been implemented, and this makes the system more inhomogeneous. because the lack of the validation the question which model is the best is hard to answer. to obtain validated models hydrodynamic measurements will be taken in a glass reactor at our department. figure 7: comparison of the models conclusion the predefined goal – to create models with different complexity – has been achieved. the developed models can be applied in a wide range of industrial purposes, from the design of a reactor to control or solving optimisation problems. at every level of modelling some of the possible applications have been discussed. this approach is expected to be used to determine which level of hierarchical modelling have to be applied to solve a given engineering problem, and to implement the simplest model suitable to work at this level. it is important that all the simulation results need to be validated based on experimental data from real systems. the physical experiments will be the next step in our work. acknowledgement the financial support from the tamop-4.2.208/1/2008-0018 (liveable environment and healthier people – bioinnovation and green technology research at the university of pannonia) project is gratefully acknowledged. appendix appendix 1: the construction parameters of the reactor impeller length 0.6 [m] impeller width 0.1 [m] impeller height 0.01 [m] inner diameter 1 [m] outer diameter 1.2 [m] vessel height 1 [m] feed diameter 0.02 [m] 339 notation name description unit ca hydrogen-peroxide concentration [kmol/m3] cb sodium thiosulfate concentration [kmol/m3] cc sodium trithionate concentration [kmol/m3] cin inlet concentration [kmol/m3] v reactor volume m3 b feed [m3/h] k reaction rate 1/s ρ density [kg/m3] cp heat capacity [j/mol/k] tin feed temperature [k] t reactor temperature [k] u velocity vector [m/s] t time [s] τ shear force tensor g grav. acceleration [m/s2] differentialoperator f force vector n ∇ references 1. e. l. paul, v. a atiemo-obeng, s. m. kresta: handbook of industrial mixing science and practice, wiley-interscience, (2004) 2. p. árva, j. havas: folyamatos üstreaktor vizsgálata, veszprémi egyetem, veszprém, (1974) 3. k. hangos: process modelling and analysis, elsevier science & technology books, (2001) 4. r. h. perry: perry’s chemichal engineer’s handbook (7th edition), mcgraw-hill (1997) 5. p. vrábel, r. g. j. m. van der lans, y. q. cui, k. ch. a. m. luyben: compartment model approach: mixing in large scale aerated reactors with multiple impellers, trans icheme, 77 part a (1999) 310–315 6. a. h. alexopoulos, d. maggioris, c. kiparissides: cfd analysis of turbulence non homogeneity in mixing vessel: a two compartment model, chemical engineering science, 57 (2002) 1735–1752 7. s. s. alves, j. m. t. vascolenos, j. barata: alternative compartment models of mixing in tall tanks agitated by multi-rushton turbines, icheme, (1997) 335–338 8. a. delafosse: stochastic modelling of microorganism displacements in a stirred-tank bioreactor, poster, (2010) 9. a. milewska, e. j. molga: cfd simulation of accidents in industrial batch stirred tank reactors, chemical engineering science, 62 (2007) 4920–4925 10. h. wei: computer-aided design and scale up of crystallization processes: integrating approaches and case studies, chemical engineering research and design, 88 (2010) 1377–1380 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word b_29_r.doc hungarian journal of industrial chemistry veszprém vol. 38(2). pp. 201-206 (2010) examination the interaction between the composition of a theoretical ecosystem and the increase in the atmospherical co2 level á. drégelyi-kiss1, l. gimesi2, r. homoródi3, l. hufnagel4 1bánki donát faculty of mechanical and safety engineering, óbuda university h-1081 budapest, népszínház u. 8., hungary 2department of informatics, faculty of natural sciences, university of pécs h-7624, pécs, ifjúság út 6, hungary 3alöki applied ecological research and forensic institution ltd. h-1118 budapest, kassa utca 118, hungary 4“adaptation to climate change” research group of the hungarian academy of sciences h-1118 budapest, villányi út 29-33, hungary e-mail: leventehufnagel@gmail.com the development of automotive industries and energetics has a large impact on the carbon-dioxide level in the atmosphere and therefore on the climate change process. there is a continuous cycle and flow of inorganic compounds between the atmosphere and the ecosystems, therefore the anthropogenic affects (such as co2 emission) strongly modify the activities of ecosystems. the modified activities are as follows: fluxes of the photosynthesis, co2 emission of the soil or the quantity of dissolved organic compounds in the ocean. these activities could have a feedback on the climate controlling the compounds of the atmosphere and therefore on the temperature of the earth. the most important anthropogenic green-house gas (ghg) is the carbon-dioxide. the global co2-level has an increase from 280 ppm (before industrial era) to 380 ppm (by 2008). the annual fossil co2-emission was 6.0–6.8 pg c in the 1990s, and 6.9–7.5 pg c in 2000–2005. there is positive correlation between the amount of green house gases in the atmosphere and the temperature, so the larger the increase in the ghg-level the higher the global temperature in the earth. the ecosystems could control the climate (precipitation, temperature) in a way that an increase in the atmosphere component (e.g. co2 concentration) induces the processes in biosphere to decrease the amount of that component through biogeochemical cycles. these feedbacks could affect the climate either on positive or negative ways. in our research the answers of a theoretical freshwater ecosystem are examined on the change in the value and the fluctuation of the temperature. our aim is to show a simple ecological model related to this feedback mechanism, and to examine the feedback ability of the theoretical ecosystem to the temperature of the atmosphere. keywords: theoretical ecosystem, feedback, climate modelling, climate change, control introduction and aims the latest ipcc report [8] points out that a rise of 1.5–2.5 °c in global average temperature makes important changes in the structure and the working of ecosystems, primarily with negative consequences towards the biodiversity and goods and services of the ecological systems (e.g. [1, 3, 13, 17]). the ecosystems could control the climate (precipitation, temperature) in a way that an increase in the atmosphere component (e.g. co2 concentration) induces the processes in biosphere to decrease the amount of that component through biogeochemical cycles. paleoclimate researches have proved this controlmechanism for more than 100,000 years. the surplus co2 content has most likely been absorbed by the ocean, thus controlling the temperature of the earth through the green house effect. this feedback is negative therefore the equilibrium is stable. during the climate control there may be not only negative but positive feedbacks. one of the most important factors affected the temperature of the earth is the albedo of the poles. while the average temperature on the earth is increasing the amount of the arctic ice is decreasing. therefore the amount of the sunlight reflected back decreases, which warms the surface of the earth with increasing intensity. this is not the only positive feedback during the control, another good example is the melting of frozen methane hydrate in the tundra. the environment, the local and the global climate are affected by the ecosystems through the climate-ecosystem feedbacks. there is a great amount of carbon in the living vegetation and the soil like organic substance which could be formed to atmospheric co2 or methane hereby affecting the climate. co2 is taken up by terrestrial ecosystems during the photosynthesis and is lost during 202 the respiration process, but carbon could be emitted like methane, volatile organic compound and solved carbon. the feedback of the climate-carbon cycle is hard to determine because of the difficulties of the biological processes [4, 9]. the biological simplification is essential during the modelling of vegetation processes [14, 18, 20]. it is important to consider more feedbacks to the climate system to decrease the uncertainty of the estimations. materials and methods an algae community consisting of 33 species in a freshwater ecosystem is modelled [5, 6, 11, 19]. during the examinations the behaviour of a theoretical ecosystem is studied by changing the temperature systematically. the conceptual diagram of the tegm model summarizes the build-up of the model (fig. 1). theoretical algae species are characterized by the temperature interval in which they are able to reproduce. the daily reproductive rate of the species can be seen on the vertical axis, which means by how many times the number of specimens can increase at a given temperature. this corresponds to the reproductive ability of freshwater algae in the temperate zone [7]. since the reproductive ability is given, the daily number of specimens related to the daily average temperature is definitely determinable. figure 1: conceptual diagram of the tegm model (rr: reproduction rate, rf: restriction function related to the accessibility of the sunlight, n(xi): the number of the ith algae species, r: the velocity parameter) the theoretical ecosystem is imagined that the amount of the biomass (a part of the carbon stored by the ecosystem) participates in the build-up of the plants or affects the carbon-content of the atmosphere. it is supposed that the plants alter into atmospherical co2 at the moment of their ruination. the net primer production (npp) is considered as biomass production of plants, because these data are available instead of net ecosystem production (nep). let be equal the amount of the plant biomass with the production of the temperate freshwater ecosystem. the area of the freshwater lakes, rivers and wetlands is 10.3 million km2 in the earth [16], the average net primer production value of these ecosystems is 0.36 c/m2/year. it is supposed, that the freshwater splits into equal parts in the surface of the earth, so the temperate freshwater ecosystems have 5.15 million km2 area and annual 1.854 pg c net primer production. keeling et al. [12] have found from the measuring of the atmospherical co2-level and the global average temperature in the earth that 6 pg c increase in the atmosphere is analogous with 1 k increase in global average temperature. during the simulation it is important to calculate with the anthropogenic effect. canadell et al. [2] have found that there is 4.1 pg c increase annually in the atmosphere, which is 0.123 pg c related to the temperate freshwater zone (this is the 3% of the surface of the earth). therefore the temperature increases 0.123 pg c/6 = 0.0205 k in every year. to take into account the anthropogenic effect there is 0.0205 k/365 = 6.616·10-5 k increase daily from the start of the simulation study. during this study the base temperature data series is the existing historical daily average temperature from 1960 to 1990 in budapest. this series consist of large number of examinations: 30*365 values. in order to simplify the description of the climate and to ignore the fluctuation between years a function has been fitted to averages and dispersion of the 30 years’ data according to the least squares method. this fitted curve is the base of our simulations, as later can be seen in fig. 2, the t(1) data series. considering the historical daily temperature data series from 1960 to 1990 in budapest it is stated that the daily average total number of specimens (productivity) is 1.17·106 in case of r = 1, and let this number of specimens be equal to the 8.924 pg c net primer production. (hence the specimens of the theoretical ecosystem live for one day, the daily average production is get for the production of the ecosystem.) the control effect of the theoretical ecosystem on the climate has been modelled as can be seen in fig. 2. figure 2: the block diagram of simulation study during the simulation there are some used temperature data series. these are as follows: t(0): the data series where there is no feedback of the ecosystem on the climate, and there is not any anthropogenic effect. t(1): the data series where there is feedback of the ecosystem on the climate, this is related to the measured, historical temperature data. 203 t(2): the data series where there is no feedback between the ecosystem and the climate, but the anthropogenic effect exists. t(3): the data series where there are both the feedback and anthropogenic effects. the equilibrium comes into evidence while a specimen springs carbon passes out from the atmosphere in order to participate in the build-up of the plant. in the proportion of the leaving co2 amount the temperature of the air decreases according to the following equations: j)0(6j)1(j)0( n ]k/pgc[6 1 1017.1 ]yr/pgc[854.1tt ⋅⋅ ⋅ += (1) ]k[n10641.2tt j)0( 7 j)1(j)0( ⋅⋅+= − (2) ]k[j10616.6tt 5 j)0(j)2( ⋅⋅+= − (3) ]k[n10641.2tt j)2( 7 j)2(j)3( ⋅⋅−= − (4) where n means the number of specimens and the indexes are as follows: 0 is related to the case without the plants, 1 is related to the historical data series, 2 is related to the case with anthropogenic effect and without the plants, 3 is related to the case with anthropogenic effect and plants, j means the number of data. so in case of without-plants the temperature would be higher. the simulations were run with two-type temperature inputs. in the first case the temperature input is the fitted data series of the existing daily average temperature of budapest from 1960–1990, and the simulation was run for 120 years to answer the question, what would be if there is no anthropogenic effect. in the other case the anthropogenic effect is considered, and simulation was run from 2010 to 2130. in every temperature interval there are dominant species which win the competition. the output parameters of the experiments are the determination of daily productivity, the diversity (shannon diversity value) and the change in temperature caused by the ecosystem. results during the simulation study the working of a theoretical algae ecosystem were examined for the future. in case of t(0), when there is no anthropogenic effect, the larger number of specimens could be found in summer and fall, in july, august and september. considering the anthropogenic effect (t(2)) there is a decrease in the total number of specimens, the largest productivity values can be found in september and in march, sometimes in june. to compare the two case, the nearly maximum total number of specimen values do not exist in the second case as it appears in the first case. the daily diversity values can be seen in fig. 3a and 3b for the two temperature inputs. the values change between 0 (dark colour) to 1.7 (white). it can be seen in fig. 3a that the maximum diversity exists in may and at the beginning of november, the dispersion of the species is medium in summer and winter [10]. figure 3a: the shannon diversity values from 1990 to 2130 when there is no anthropogenic effect (t(0)-case) figure 3b: the shannon diversity values from 1990 to 2130 where there is anthropogenic effect (t(2)-case) 204 considering the anthropogenic effect (t(2), fig. 3b) the places of the diversity maximums within a year shifts during the consecutive years. at the end of the examined period the diversity maximums can be found in april and at the end of november. because of the high summer temperature and the extinction of the species the diversity decreases in summer. to study the seasonal diversity values it is stated that there is a decrease in the diversity in summer and winter. the composition of the ecosystem determines the feedback effect, the effect of temperature control. in the first case (t(0)) the evolving ecosystem causes 1.5–2.5 k decrease in the temperature in july, august and september (fig. 4a). so the theoretical ecosystem could have cooling effect in summer until 3 k temperature, in fall until 2 k temperature; while in winter and spring there is less amount of biotic feedback. to take into account the anthropogenic effect it can be seen in fig. 4b that the feedback, the ‘cooling effect’ of the ecosystem is less realized, the maximum difference is (t(2)–t(3)) 1.3 k temperature difference. in fall some shifts can be seen, the temperature can decrease in february and in march. discussion the ecosystems are important parts of the biosphere, they have an important role in the development and maintenance of the ecological equilibrium. the environment, the local and the global climate are affected by the ecosystems through the climateecosystem feedbacks. during our simulation study it is investigated how the tegm theoretical freshwater ecosystem model developed by us [5, 6] could affect the climate and the environment. it is found that the productivity of the ecosystem has changed annually and daily when the anthropogenic effect was taken into account. the productivity correlates with the amount of the atmospherical co2, the growing greenery binds carbon from the air. in case where there is no anthropogenic effect the ‘cooling’ effect of the plants is up to 2.5 k dependent upon the seasons, months. considering the amount of the anthropogenic carbon and the global warming it is stated that the ‘cooling’ effect of the living earth, the plants decreases up to 1.3 k temperature after 100 years. this means that there will be maximum 1.2 k increase in temperature except for the anthropogenic warming due to the control ability of the plants for the climate. this result hangs together the issue investigated by friedlingstein et al. [8]. they found that there is additional 0.1–1.5 °c warming by 2100 due to the feedback effect. in the course of ecological modelling and biosphere research it is important to unravel much more the feedbacks and control processes to describe the function of the whole earth. figure 4a: the cooling effect (t(0)–t(1)) of the theoretical ecosystem 1990-2130 without anthropogenic effect figure 4b: the cooling effect (t(2)–t(3)) of the theoretical ecosystem from 1990 to 2130 with anthropogenic effect 205 acknowledgements this investigation was supported by the project támop 4.2.1/b-09/1/kmr/-2010-0005, the “bolyai jános” research fellowship (hungarian academy of sciences), the research assistant fellowship (corvinus university of budapest), adaptation to climate change research group of hungarian academy of sciences and the ‘alöki’ applied ecological research and forensic institute ltd. references 1. a. anda, t. kocsis: applied ecology and environmental research, 6, 2008, 85–94. 2. j. g. canadell, c. le quéré, m. r. raupach, c. b. field, e. t. buitenhuis, p. ciais, t. j. conway, n. p. gillett, r. a. houghton, g. marland: proceedings of the national academy of sciences of the united states of america, 104 (47), 2007, 18866–18870. 3. n. diós, k. szenteleki, a. ferenczy, g. petrányi, l. hufnagel: applied ecology and environmental research, 7(3), 2009, 199–214. 4. á. drégelyi-kiss, g. drégelyi-kiss, l. hufnagel: applied ecology and environmental research, 6, 2008, 111–135. 5. á. drégelyi-kiss, l. hufnagel: applied ecology and environmental research, 7, 2009, 71–78. 6. á. drégelyi-kiss, l. hufnagel: environmental modeling & assessment (2010). doi:10.1007/s10666-009-9216-4 7. l. felföldy: a vizek környezettana. általános hidrobiológia, mezőgazdasági kiadó, budapest (1981). 8. a. fischlin, g. f. midgley, j. t. price, r. leemans, b. gopal, c. turley, m. d. a. rounsevell, o. p. dube, j. tarazona, a. a. velichko: ecosystems, their properties, goods, and services. in climate change 2007: impacts, adaptation and vulnerability, cambridge university press, cambridge, (2007) 211–272. 9. p. friedlingstein, p. m. cox, r. a. betts, l. bopp, w. von bloh, v. brovkin, p. cadule, s. doney, m. eby, i. fung, g. bala, j. john, c. d. jones, f. joos, t. kato, m. kawamiya, w. knorr, k. lindsay, h. d. matthews, t. raddatz, p. rayner, c. reick, e. roeckner, k. g. schnitzler, r. schnur, k. strassmann, a. j. weaver, c. yoshikawa, n. zeng: journal of climate, 19, 2006, 3337–3353. 10. l. gimesi: applied ecology and environmental research, 6(1), 2008, 165–176. 11. l. hufnagel, á. drégelyi-kiss, g. drégelyi-kiss: applied ecology and environmental research, 8(2), 2010, 119–131. 12. c. d. keeling, r. b. bacastow, a. f. carter, s. c. piper, t. p. whorf, m. heimann, w. g. mook, h. roeloffzen: a three-dimensional model of atmospheric co2 transport based on observed winds: 1. analysis of observational data 165–236. in peterson, d. h. (ed.), aspects of climate variability in the pacific and the western americas, geophysical monograph 55, american geophysical union, washington, d.c. (1989). 13. e. kipp: applied ecology and environmental research, 6(4), 2008, 1–14. 14. m. ladányi, l. horváth, m. gaál, l. hufnagel: applied ecology and environmental research, 1(1-2), 2003, 47–74. 15. m. ladányi: applied ecology and environmental research, 6(1), 2008, 147–164. 16. mea (millennium ecosystem assessment, 2005): ecosystems and human well-being: synthesis, island press, washington, dc. 17. a. révész: applied ecology and environmental research, 6(4), 2008, 85–100. 18. cs. sipkay, k. t. kiss, cs. vadadi-fülöp, l. hufnagel: applied ecology and environmental research, 7(2), 2009, 171–198. 19. cs. sipkay, á. drégelyi-kiss, l. horváth, á. garamvölgyi, k. t. kiss, l. hufnagel: community ecological effects of climate change. in climate change and variability, sciyo books, www.sciyo.com, isbn 978-953-7619-x-x (2010). 20. cs. vadadi-fülöp, l. hufnagel, cs. sipkay, cs. verasztó: applied ecology and environmental research, 6(1), 2008. 1–28. << /ascii85encodepages false 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/pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice page 1 page 2 page 3 page 4 page 5 page 6 page 7 page 8 page 9 page 10 page 11 page 12 page 13 page 14 page 15 page 16 page 17 page 18 page 19 page 20 page 21 page 22 page 23 page 24 page 25 page 26 page 27 page 28 page 29 page 30 page 31 page 32 page 33 page 34 page 35 page 36 page 37 page 38 page 39 page 40 page 41 page 42 page 43 page 44 page 45 page 46 page 47 page 48 page 49 page 50 page 51 page 52 page 53 page 54 page 55 page 56 page 57 page 58 page 59 page 60 page 61 page 62 page 63 page 64 page 65 page 66 page 67 page 68 page 69 page 70 page 71 page 72 page 73 page 74 page 75 page 76 page 77 page 78 page 79 page 80 page 81 page 82 page 83 page 84 page 85 page 86 page 87 page 88 page 89 page 90 page 91 page 92 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(2005) stability and bifurcation of continuous cooling crystallizers b.g. lakatos1and n. moldoványi2 1department of process engineering, university of veszprém, h-8201 veszprém, p.o. box 158, hungary 2honeywell process solutions, h-1139 budapest petneházy u. 2-4, hungary stability properties and dynamic behaviour of continuous cooling crystallizers are analysed using a detailed moment equation model. a causal loop diagram between the variables reveals that the roots of instabilities lay in the interactions of the autoinhibition generated negative feedback, a positive feedback between the four leading moments of crystal size and a varying polarity feedback between the temperature and the moments. the stability of steady states is analysed by eigenanalysis of the jacobian matrix and using the mikhailov criterion. stability maps and bifurcation diagrams are presented in the planes of different pairs of system parameters. keywords: cooling crystallizer, moment equation model, causal loop diagram, stability, bifurcation introduction non-isothermal continuous crystallizers, extensively used in the chemical industry, usually are very sensitive to both the external and internal (parameter) disturb-ances. this is because of the highly nonlinear kinetics, many temperature-dependent parameters, which are, in turn, also nonlinear, and different feedbacks between the variables and elementary processes taking place in crystallization processes. all these properties, as well as the interactions between the kinetics, fluid dynamics and crystal size distribution may give rise to different complexities in both the steady state and dynamic beha-viour of continuous crystallizers, a deeper understand-ing of which is important in relation to both the crystallization process itself, and to the operation, control, and design of industrial crystallizers. since the observations by miller and seaman [1] on composition and crystal size distribution oscillations in industrial crystallizers, a number of works have dealt with their stability and dynamic behaviour under iso-thermal conditions [1-16], but less attention has been paid to the problem of taking into account the thermal effects. tavare et al. [17] studied the temperature mul-tiplicity and stability of cooling msmpr crystallizers using linear temperaturedependence of the solubility. melikhov et al. [18] shown that in a circulation vacuum crystallizer the dissolving zone may exhibit two steady states. both works presented also stability criteria but used simplified models, and no primary nucleation and size-dependent growth were taken into account. the present study addresses the stability and bifurcation phenomena of continuous cooling msmpr crystallizers by means of a detailed moment equation model. the stability is examined using the mikhailov criterion, and the effects of primary and magma-dependent secondary nucleation are analysed. bifurcation diagrams and simulation results concerning the dynamic behaviour of crystallizers, as well as the causal loop diagram revealing the important negative and positive feedback loops of the system, responsible for the complex behaviour of crystal-lizers are presented. 50 mathematical model population balance model consider a continuous crystallizer the schematic repre-sentation of which is presented in fig.1. let us assume that the following conditions are satis fied: the crystallizer may be seeded; fig.1. schematic representation of a continuous cooling crystallizer the crystals can be characterized by a linear dimen-sion l; all new crystals are formed at a nominal size so that we assume ; 0≥nl 0≈nl crystal breakage and agglomeration are negligible; no growth rate fluctuations occur; the overall linear growth rate of crystals g is sizedependent and has the form of power law expression: (1) ( ) ( alcckg g sg +−= 1 ) the primary nucleation rate bp is described by the volmer model: ⎟ ⎟ ⎟ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎜ ⎜ ⎜ ⎝ ⎛ ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −= s e pp c c kkb 2ln expε (2) where ε is the voidage of suspension expressed as (3) 31 µε vk−= and µ3 is the third of the ordinary moments of the population density function ,which are defined as (4) ∫ ∞ == 0 ,...3,2,1,0,),()( mdltlnlt m mµ the secondary nucleation rate bb is described by the power law relation ( ) jb sbb cckb 3µ−= (5) where the coefficients kg, kp and kb are functions of temperature expressed as gpg rt ekk ,,,exp0 =⎟ ⎠ ⎞ ⎜ ⎝ ⎛−= ιι ιι . (6) under such assumptions the population balance model of the crystallizer consists of the following balance equations. vapour volume balance of the crystal suspension qq dt dv in −= (7) feed subject to the initial condition (7a) 0)0( vv = cooling water out population balance equation governing the crystal size dynamics 0,0,)()( >∞<<−=+ tlqnnq l gnv t vn inin∂ ∂ ∂ ∂ (8) subject to the initial and boundary conditions: (8a) nlllnln ≥= ),()0,( 0product 0,),(),,(lim ≥+= → tbebetlnlccg bbppsll n (8b) cooling water in 0,0),(lim ≥= ∞→ ttln l (8c) where n(l,t)dl expresses the number of crystals having size in the range l to dl at time t, while ep and eb are binary existence variables of the nucleation rates, by means of which the alternative variations of nucleation can be controlled. naturally we have the constraint 1≥+ bp ee (9) mass balance of solvent ( ) svsvininin sv cqcq dt cvd εε ε −= (10) with the initial condition (10a) 0)0( svsv cc = mass balance of solute ])1([ ])1([])1([ c cinininin c cq cq dt vcvd ρεε ρεε ρεε −+− −−+= −+ (11) with the initial condition (11a) 0)0( cc = energy balance for the crystal suspension takes form [ ] mccccsvsvc inccinsvinsvincinin h cccsvsv vrhtcccccq tcccq dt ()(ε cc ttuavtcvccccvd )(])1()([ ])1[ )()1()( ∆ρεε ρε ρεε −+−++− −− +−−= −++ +++ (12) 51 with the initial condition (12a) 0)0( tt = where rmc denotes the global rate of production of crystal mass in a unit volume of suspension: ( ) ( )[ ]32)1( 3 3 )(])1[( µµρρ ρµρε ε acckkr dt kd dt dr g sgvcc batch cv batch c mc +−== == − = − (13) energy balance for the cooling medium ( ) ( ) )( hhhhinhinhh hhh ttuavtqtqc dt tcvd −+−= ρ ρ (14) subject to the initial condition . (14a) 0)0( hh tt = the dependence of saturation concentration on the temperature is described by the expressions: ⎟ ⎠ ⎞ ⎜ ⎝ ⎛−= t aatcs 1 0 exp)( (15a) or . (15b) 2 210)( tataatcs ++= often, it is useful to complete the set of balance equations (7)-(14) by the equation for the equilibrium saturation concentration given as dt dt dt dc dt dc ss = (16) subject to the initial condition . (16a) 00 )( ss ctc = therefore, the state of the continuous cooling crys-tallizer at time t≥0 is given by the sextuple [v(t),c(t), csv(t),t(t),th(t),n(.,t)], and its dynamics is described by the population balance model formed by the mixed set of partial and ordinary differential equations (7)-(14). the time evolution of this system occurs in the state space r5×n that is the descartes product of the vector space r5 of volume, concentrations and temperatures, and the function space n of population density func-tions. consideration of dynamical problems of crystal-lizers in this product space, however, seems to be quite complex so that hitherto only a few works have studied dynamic problems in this space directly. controllability analysis was carried out by semino and ray [21], while lakatos and sapundzhiev [22] studied the global sta-bility of crystallizers via lyapunov's direct method. in the present study, we concentrate on a reduced case, applying a finitedimensional state space model based on the four leading moments of the crystal size instead of the distributed parameter system of eqs (7)-(14). moment equation model since the overall crystal growth rate (1) is a linear function of size l, the population balance equation (8) can be converted into an infinite set of recursive ordinary differential equations for the moments (4) of the population density function which take the form ( ) bbppin in bebe v q dt d ++−= 0,0 0 µµµ (17) ( ) )()( 1, mm g sgminm inm accmk v q dt d µµµµ µ +−+−= − m=0,1,2,3... (18) subject to the initial conditions .0)0( mm µµ = since the set of eqs (7)-(16) can be closed by means of the first four leading moments, we reduce the infinite set of eqs (17)-(18) to the set of equations governing these moments. in this way, expressing the first derivatives of all the state variables, taking into account the tem-perature dependence of the parameters, and applying the scale factors g ctgv sskks 333 00 6: −−= , , , s , g ctgv sskks 222 01 6: −−= g ctgv sskks −−= 1 02 3: vk=:3 }max{ 1: in c c s = , { }in t t s max 1:= , t v q s ss =: where st and sv can be chosen arbitrary, we introduce the following set of dimensionless variables csycsymsxvsv csvcsvmmmv ===== ,,3,2,1,0,, µ qsftstsztszcsy qththtscs ===== ,,,, ξ and scaled parameters ccsρα = g c − vap kd 6= abd , , , , assk tg −= 1 0β g ctgp sskk 343 00 −− bg ctgb j v sskkk −−−−= 343 00 16 r se tg=gβ , r se tp=pβ , r se tb b =β , ht c cs uas =κ , h ct c hs ∆γ −= , , 00 asb c= t c s asb 1 1 = or , 11 asb t= 2 2 2 t c s asb = . then, the dimensionless scaled equations in the state space form are given as: ff d dv in −= ξ (19) ( ) bbppin in eexx v f d dx θθ ξ ++−= 00 0 (20) ( ) ( ) ( )101,1 1 exp xx z yyxx v f d dx gg sin in β β ξ +⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −−+−= ( ) ( ) ( )212,2 2 2exp xx z yyxx v f d dx gg sin in β β ξ +⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −−+−= (22) ( ) ( ) ( )323,3 3 3exp xx z yyxx v f d dx gg sin in β β ξ +⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −−+−= 52 (23) ( ) ( ) ( ) ( ) ( 32 3 3 ,3 3exp )1( )( 1 1 xxyy zx y yy xv xf d dy g s g in inin β βα ξ +−⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ − − − − −− − − = ) (24) ( ) ( ) ( ) ( ) ( 32 3 , 3 3 3exp )1( )1 1 xxyy zx y yy xv xf d dy g s gsv svinsv ininsv β β ξ +−⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ − − + +− − − = ) (25) ( ) ( ) ( 32 3exp )( xxyy z zzzz v f d dz g s g hin inin β β φ αγ φ κ φ φ ξ +−⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −+ +−−−= ) (26) ( ) )(, h hh hinh h hh zz v vzz v f d dz −+−= α κ ξ (27) ( ) ( ) ( ⎥ ⎥ ⎦ ⎤ +−⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −+ ⎢ ⎣ ⎡ −−−= 32 3exp )( xxyy z zzzz v f dz dy d dy g s g hin ininss β β φ αγ φ κ φ φ ξ ) (28) ( ) 331 x c cy c cy c cx h c h c sv h sv αφ +⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ +−= and ( ) in h c in h c insv h sv inin x c cy c cy c cx ,3,,31 αφ +⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ +−= (29) subject to the initial conditions 00 0000 )0(,)0( )0(,)0(,)0(,)0( hh svsvmm zzzz yyyyxxvv == ==== where ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ − ⎟ ⎟ ⎟ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎜ ⎜ ⎜ ⎝ ⎛ ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −−= z y y kxd p s e app β θ exp ln exp)1( 2 3 (31 a) and ( ) ⎟ ⎠ ⎞ ⎜ ⎝ ⎛−−= z xyyd bjb sabb βθ exp3 . (31b) 3. 3) the causal loop diagram in fig.2 exhibits an important positive feedback between the four leading moments x the moment equation model (19)-(29) of the continuous cooling crystallizer is, in principle, a finite dimensional dynamical system, generated by reducing the infinite dimensional population balance model without any simplifying assumptions. the reduced state is formed by the ninetuple ( 9 3210 ,,,,,,,, r∈= hsv zzyyxxxxvx ) of scaled, dimensionless variables and the time evolution of this system occurs in a bounded region of the state space, defined in the following manner 9rω ⊂ ⎪ ⎪ ⎩ ⎪ ⎪ ⎨ ⎧ <≤< <≤≤≤≤ ≤≤≤≤ ≤≤≤≤≤≤ = max,min,max max33 67.0 max022 67.0 max011max00 max ,0 ,0.10,0 ,0,0 ,0,0,0 hhh svcsvin zzzzz xxxax xaxxx syyyvv ρ xω thus the feasible region of solutions of the dynamical system (19)-(29) is formed by the compact domain (32) of the state space r9. qualitative feedback analysis since any instability problem can be viewed as a feedback of properly phased signals, this difference can be explained qualitatively analysing the causal loop diagram, used extensively in system dynamics [23,24]. since a positive feedback destabilizes, while negative feedbacks stabilize the systems, in principle, their interactions turn to be decisive for the dynamics of crystallizer. because of the nonlinearities of crystallizer, the dominance of the negative and positive feedbacks may change in time during the course of the process what can generate diverse patterns of behaviour of the system. let us consider the causal loop diagram of the moment equation model in the basic size-independent case, presented in fig.2, similarly to that derived by lakatos [14] for an isothermal msmpr crystallizer. here, we show only the main negative and positive causal links between the variables of eqs (19)-(28). from the point of view of dynamics, the following feedback loops are the most interesting parts of this causal loop diagram: 1. 1) there is a negative feedback in each of eqs (19)(28) due to the draw off of crystals and solution. these effects arise in all continuous flow systems naturally, and under certain conditions those by themselves are capable of stabilizing the crystallizer. 2. 2) there exists an important negative feedback loop y→x2→y generated by autoinhibition of the supersaturation: nucleation and growth of crystals relieves supersaturation and inhibits further crystallization process. 0→x1→x2→x3→x0 that is closed through the nucleation rate. 4. 4) depending on if the crystallization process is exothermic or endothermic there exists also a positive or negative feedback between the temperature and the second moment of crystal size z→x2→z. in any case, however, increasing temperature affects the supersaturation negatively. note that the concentration of solvent depends on a number of other variables but there is no feedback from ysv into the remaining variables, i.e. the concentration of solvent has no essential influence on the dynamic behaviour of crystallizer while the volume of the suspension has no effect on the dynamics at all. 53 the dynamic behaviour of crystallizers differs sig-nificantly on if the primary or secondary nucleation is the dominant mechanism of producing the new crystals [10, 11]. the main reason of this difference lays in the di-verse nature of positive feedbacks caused by the different forms of the nucleation rates. namely, derivating both sides of eq.(20) with respect to x3 we obtain inequality 00 3 <⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ξd dx dx d (33) for primary nucleation, i.e. in this case the positive feedback is rate-decreasing. similarly, for secondary nucleation the inequality 00 3 >⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ξd dx dx d (34) holds, i.e. in this case the positive feedback is rateincreasing, forming a feedback of autocatalytic nature. fig.2. causal loop diagram of the basic size-independent case showing only the main feedback loops stability and dynamic behaviour the qualitative analysis has shown that the variables v and ysv does not influence the dynamic behaviour sig-nificantly, while zh, being, in principle, a control var-iable affects the system only through modulating the temperature z. the behaviour of the crystallizer in the neighbour-hood of a steady state may be deduced by eigenanalysis of the jacobian matrix of eqs (19)-(28) at this state. the structure of the jacobian matrix is shown in fig.3 that supports the conclusions of the quality analysis. determining the eigenvalues of the jacobian matrix the characteristic polynomial of the system can be built up by means of which the mikhailov plot is constructed and the mikhailov stability criterion [25] can be applied. this criterion seems to be useful for analysing the stability of crystallizers, since it provides a simple gra-phical means for testing the stability of polynomials, al-lows a deep understanding and visual presentation of the phenomenon and can be formulated also in algebraic terms. ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ = xxxxxxxx xx xxxxxxxx xxxxxxx xxxxxx xxxxxx xxxxxx xxxxxx xxxxxx 00 00000000 00 000 0000 0000 0000 0000 0000 0000000000 j fig.3. the structure of the jacobian matrix of system (19)-(28) the mikhailov plots of the system (19)-(28) are shown in fig.4 as a function of parameter ke in the case of primary nucleation, i.e. for eb=0. since the mikhailov stability criterion says that an nth order real polynomial is asymptotically stable if and only if the mikhailov plot, starting at ω=0 from the positive real axis of the complex plane goes through n quadrants in turn, the plots in fig.4 for ke=1.0 and ke=3.0 indicate stable states, while for ke=5.0 and ke=10.0 we have unstable states. the basic negative feedback: autoinhibition positive feedback: interaction of the moments varying polarity feedback: exotermic-endotermic crystallization negative feedback: withdrawal x1 x2 x3 y x0 + + + + + z if γ>0, then + if γ<0, then + + if γ>0, then + if γ<0, then 54 values of the parameters in all simulation runs were: dap=5000, dab=2000, v=1, fin=f=1, g=1, b=3, j=0.4, α=35, β=0, βg=1.1, βb=2.6, βp=3.45, b0=6, b1=3, b2=0.0,, φin=8.8, αh=30, vh=1, fh=1. fig.4. mikhailov plots of crystallizer for primary nucleation as a function of nucleation parameter ke these curves are shown only for smaller values of ω, since for large ω values the polynomial constructed on the basis of eigenvalues of the jacobian matrix (19)-(28) behaves like (jω)9. therefore, the behaviour at small ω values entirely determines the stability of the system. the mikhailov plot can also be used to count the number of unstable zeroes, i.e. if it goes through only (n-k) quadrants in turn, then the polynomial has k unstable zeros. plots ke=5.0 and ke=10.0 go through quad-rants 1-2-3-2-3-4-1 in turn, what means that it goes through only 7 quadrants in turn thus these plots repre-sent unstable states showing two eigenvalues with pos-itive real parts. as a consequence, these eigenvalues are conjugate pairs so that these instabilities mean limit cycle oscillations. indeed, fig.5 shows the projection of development of the limit cycle oscillations for ke=10.0 into the r3 subspace of variables (x0,y,z). 1 2 3 0.750.760.770.780.790.80.81 0.94 0.96 0.98 1 1.02 fig.5. development of the limit cycle oscillations for ke=10.0 in the r3 subspace of variables (x0,y,z). fig.6 presents the bifurcation diagram ke–ys in which two hopf bifurcations are seen at ke≈3.3 and ke≈15.9. between these points the crystallizer generates limit cycle oscillations with varying amplitudes while outside this interval the crystallizer exhibits stable steady states. fig.6. bifurcation diagram ke-ys for primary nucleation with amplitudes of limit-cycle oscillations when the secondary nucleation becomes the dominant mechanism of forming the new crystals, i.e. when ep=0, then the crystallizer exhibits steady state multiplicity and may have one, two, or even three steady states depending on the values of parameters. the detailed multiplicity analysis of nonisothermal crystallizers will be presented elsewhere, but it can be proved easily that for j>0 the system (19)-(28) always has a trivial boundary (washout) steady state. under such conditions the crystallizer can not be ignited because of the small nucleation rate so that the washout steady states are always stable. fig.7 presents the bifurcation diagram j-ys in the case of magma-dependent secondary nucleation where two regions are set by a boundary bifurcation point at j≈0.8. in the first region the crystallizer has two stable steady states, while in the second region only a unique washout steady state exists. fig.7. bifurcation diagram j-ys for secondary nucleation with boundary bifurcation of the washout steady state the bifurcation diagram dab-ys of similar form is shown in fig.8 in the case of magma-dependent secondary nucleation where two regions are set by a boundary bifurcation point at dab≈460. here, the first region exhibits a unique washout steady state while two stable steady states exist in the second region. ys im re ke=1.0 ke=3.0 ke=5.0 ke=10.0 ω=0 ke=3 ke=15 ke boundary bifurcation x0 y z ke=10 two steady states unique washout steady state ys j 55 fig.8. bifurcation diagram dab-ys for secondary nucleation with boundary bifurcation of the washout steady state in the case of magma-dependent secondary nuclea-tion limit cycle oscillations have not been observed in the feasible region of parameters. fig.9 presents some tran-sients of dimensionless concentration as a function of parameter dab. increasing dab increases the willingness of crystallizer to generate damped oscillations in the tran sient behaviour but next the crystallizer achieves stable stationary states. this phenomenon is important when designing the controlling system for s crystallizer. fig.9. damped oscillations of transients of crystallizer in the case of magma-dependent secondary nucleation conclusions the stability and bifurcation analysis of continuous cooling crystallizers, carried out by means of a detailed moment equation model, has shown that there is a signi-ficant difference between the dynamic behaviour of crystallizers with primary and secondary nucleation. continuous cooling crystallizers may exhibit limit cycle oscillations and multiple steady states. in the case of magmadependent nucleation there exists always a washout steady state where the crystallizer is not ig-nited. the mikhailov plots and criterion, constructed on the basis of eigenanalysis of the jacobian matrix al-lowed a very useful visual form of stability analysis in the frequency domain. the causal loop diagram showing the negative and positive causal links between the model variables of crystallizer revealed that a positive feedback loop exists between the four leading moments of crystal size distribution closed through the nucleation rate. the autoinhibition generated negative feedback is closed mainly through the crystal growth rate although during the onset of crystallization the nucleation rate proves to be the dominant factor also in this feedback loop. the temperature with the second moment and solute concentration forms feedbacks of positive or negative polarity depending on if the crystallization process is exothermic or endothermic. interactions of these feedbacks bet-ween the variables with the kinetic nonlinearities appear to be decisive for the instabilities of crystallizers. simulation studies concerned with the steady state multiplicity and stability patterns, as well as with the dynamic behaviour of cooling crystallizers allow us to conclude that continuous crystallizers have a broad range of complex behaviour in both the steady and dy-namic states. a further examination of these phenomena seems to be useful for both a better understanding of the crystallization process itself, and for improving the operation, control, and design methods of industrial crystallizers. acknowledgement this work was supported by the hungarian research foundation under grant t034406. notation a constant of the crystal growth rate [m-1] b exponent of secondary nucleation rate bp primary nucleation rate [no m-3s-1] bb secondary nucleation rate [no m-3s-1] c concentration of solute [kgm-3] cs equilibrium saturation concentration [kgm-3] dap dimensionless parameter for primary nucleation dab dimensionless parameter for secondary nucleation g exponent of crystal growth rate g crystal growth rate [ms-1] im imaginary part of a complex number j exponent of secondary nucleation rate ke parameter of primary nucleation rate kg rate coefficient of crystal growth [m3g+1 kg-g s-1] kp rate coefficient of primary nucleation [no m-3s-1] kb rate coefficient of secondary nucleation [no m3b-3 kg-b s-1] kv volume shape factor l linear size of crystals [m] n population density function [no m-4] re real part of a complex number sc scale factor of the concentration [kg-1m3] boundary bifurcation ys two steady states unique washout steady state dab y dab 500 1000 5000 10000 ξ 56 sm scale factor of the mth order moment of n (m=0,1,2,...) xm mth order dimensionless moment (m=0,1,2,...) y dimensionless concentration of solute greek letters α dimensionless parameter ß dimensionless parameter γ dimensionles crystal growth rate ε viodage of suspension µm mth order moment of n [mm-3] θ dimensionless nucleation rate ρc density of crystals [kgm-3] ξ dimensionless time subscripts 0 initial value in inlet value p primary nucleation b secondary nucleation s steady state references 1. miller, p. and saeman, w.c.: chemical eng neering progress, 1947, 43, 667-675. 2. randolph, a.d. and larson, m.a.: aiche journal, 1962, 8, 639-645 3. nyvlt, j. and mullin, j.w.: chemical engineer ing science, 1970, 25, 131-147. 4. yu, k.m. and douglas, j.m.: aiche journal, 1975, 21, 917-923. 5. song, y.h. and douglas, j.m.: aiche journal, 1975, 21, 924-925. 6. jerauld, g.r., vasatis, y. and doherty, m.f.: chemical 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e-mail: foa@almos.uni-pannon.hu 2computer and automation research institute has, process control research group, budapest, hungary a previously developed simple dynamic model of an industrial size synchronous generator is analyzed in this paper. the constructed state-space model consists of a nonlinear state equation and a bilinear output equation. it has been shown that the model is locally asymptotically stable with parameters obtained from the literature for a similar generator. the effect of load disturbances on the partially controlled generator has been analyzed by simulation using a pi controller. it has been found that the controlled system is stable and can follow the set-point changes in the effective power well. the sensitivity of the model for its parameters has also been investigated and parameter groups have been identified according to the system’s degree of sensitivity to them. this groups form the different candidates of parameters for subsequent parameter estimation. the ways of applying the developed methods to other generators used in the automotive industry are also outlined. keywords: synchronous machine, dynamic state space model, parameter sensitivity introduction synchronous generators are popular and widely used electrical power sources in a wide range of applications including power plants and the automotive industry, too. whatever size and application area, these generators share the most important dynamic properties, and their dynamic models have a similar structure. in almost all power plants, both the effective and reactive components of the generated power depend on the need of the consumers and on their own operability criteria. this consumer generated time-varying load is the major disturbance that should be taken care of by the generator controller. therefore the final aim of our study is to design a controller that can control the reactive power such that its generation is minimized in such a way that the quality of the control of the effective power remains (nearly) unchanged. because of the specialties and great practical importance of the synchronous generators in power plants, their modelling for control purposes is well investigated in the literature. besides of the basic textbooks (see e.g. [1] and [2]), there are papers that describe the modelling and use the developed models for the design of various controllers [3, 4]. these papers, however, do not take the special circumstances found in nuclear power plants into account that may result in special generator models. the aim of this paper is to perform model verification and parameter sensitivity analysis of a simple dynamic model of a synchronous generator (sg) proposed in [5] and [6]. the result of this analysis will be the basis of a subsequent parameter estimation step. the model of the synchronous generator in this section the bilinear state-space model for a synchronous generator is presented based largely on [5] that will be used for local stability and parameter sensitivity analysis in later sections. modelling assumptions for constructing the synchronous generator model, let us make the following assumptions: ● a symmetrical tri-phase stator winding system is assumed, ● one field winding is considered to be in the machine, ● there are two amortisseur or damper windings in the machine, ● all of the windings are magnetically coupled, ● the flux linkage of the windings is a function of the rotor position, ● the copper losses and the slots in the machine are neglected, ● the spatial distribution of the stator fluxes and apertures wave are considered to be sinusoidal, ● the stator and rotor permeability are assumed to be infinite. 22 it is also assumed that all the losses due to wiring, saturation and slots can be neglected. the six windings (three stators, one rotor and two dampers) are magnetically coupled. since the magnetic coupling between the windings is a function of the rotor position, the flux linking of the windings is also a function of the rotor position. the actual terminal voltage v of the windings can be written in the form ,)()(= =1=1 j j j jj j j irv λ&∑∑ ±⋅± where ij are the currents, rj are the winding resistances, and λj are the flux linkages. the positive directions of the stator currents point out of the synchronous generator terminals. thereafter, the two stator electromagnetic fields, both travelling at rotor speed, were identified by decomposing each stator phase current under steady state into two components, one in phase with the electromagnetic field and another phase shifted by 90°. with the above, one can construct an air-gap field with its maximal aligned to the rotor poles (d axis), while the other is aligned to the q axis (between poles). this method is called the park's transformation.[4, 5] as a result of the derivation in [5] the vector voltage equation is as follows: vdfdqq = –rrsω·idfdqq – li˙dfdqq (1) with idfdqq = [id if id iq iq]t and vdfdqq = [vd –vf vd = 0 vq vq = 0]t, where vd and vq are the direct and the quadratic components of the stator voltage of the sg, vd and vq are the direct and the quadratic components of the rotor voltage of the sg, id and iq are the direct and the quadratic components of the stator current, id and iq are the direct and the quadratic components of the rotor current, while vf and if are the exciter voltage and current. furthermore, rrsω and l are the following matrices ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ +ω−ω−ω− ωω+ ω q edfd d f qqe rs r0000 0rrkmkml 00r00 000r0 kml00rr =r ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ + + = qq qeq drd rff dfed lkm000 kmll000 00lmkm 00mlkm 00kmkmll l where r is the stator resistance of the sg, rf is the exciter resistance, rd and rq are the direct and the quadratic part of the rotor resistance of the sg, ld, lq, ld and lq are the direct and the quadratic part of the stator and rotor inductance, ω is the angular velocity, and mf, md and mr are linkage inductances (see later). the resistance re and inductance le represent the output transformer of the synchronous generator and the transmission-line. the state-space model for the currents is obtained by expressing i˙dfdqq from (1), i.e. i˙dfdqq = –l–1·rrsω·idfdqq – l–1·vdfdqq (2) the motion equation is the following jj dq j dq j qd j qf j qd d 3 ikm 3 il 3 ikm 3 ikm 3 il = • ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎣ ⎡ τ − τττ − τ − τ −ω& • (3) • [id if id iq iq ω] altogether, there are 6 state variables: id, if, id, iq, iq and ω. the input variables (i.e. manipulatable inputs and disturbances) are: tmech, vf, vd and vq. observe, that the state equations are bilinear in the state variables because matrix rrsω depends linearly on ω. note, that (3) can be used as an additional state equation for state space model (2). the loading angle (δ) of the synchronous generator is dt)(= r t 0t0 ω−ω+δδ ∫ that we can differentiate to obtain the time derivative of the δ in per unit notation δ˙ = ω – 1 (4) the output active power equation can be written in the following form: pout = vdid + vqiq, (5) and the reactive power is qout = vdiq – vqid. (6) note, that output equations are bi-linear in the state and input variables. model analysis the above model has been verified by simulation against engineering intuition using parameter values of a similar generator taken from the literature [1]. after the basic dynamical analysis, the set of model parameters is partitioned based on the model's sensitivity on them. generator parameters because the above developed model uses pseudoparameters that are composed from the original physical ones, mathematical expressions are needed to describe how these parameters depend on the physical ones. the parameters are described only for a single phase “a” since the machine is assumed to have symmetrical tri-phase stator windings system. the stator mutual inductances for phase a are )) 6 (2(coslm=l=l msbaab π −θ−− 23 where ms is a given constant. the rotor mutual inductances are lfd = ldf = mr, lfq = lqf = 0 and ldq = lqd = 0. the phase a stator to rotor mutual inductances (from phase windings to the field windings) are given by: laf = lfa = mf cos(θ) where the parameter mf is also a given constant. the stator to rotor mutual inductance for phase a (from phase windings to the direct axis of the damper windings) is lad = lda = md cos(θ) with a given parameter md. the phase a stator to rotor mutual inductances (from phase windings to the damper quadratic direct axis) are given by: laq = lqa = mq cos(θ) the parameters ld , lq , mf , md and mr used by the state space model (2 3, 5, 6) and by the above inductance equations are defined as aqqadr adfadd mssdmssd lmlm lmlm lmlllmll 2 3 2 3 2 3 2 3 2 3 == == ++=++= using the initial assumption of symmetrical tri-phase stator windings we get the resistance of stator windings of the generator, where rf denotes the resistance of the rotor windings, and rd and rq represent the resistance of the d and q axis circuit. in order to avoid working with numerical values that are in order of magnitude different, the equations have been normalized to a base value. we choose the base for rotor quantities and normalize the voltage and the torque accordingly. the variables in the normalized equations are then in „per units”. the parameters of the synchronous generator were obtained from the literature [1]. the stator base quantities, the rated power, output voltage, output current and the angular frequency base values are: s/rad f2= a 6158=i kv 8.66=3/kv 15=v mva 53.333=/3mva 160=s e b b b πω the physical parameters of the synchronous machine and the external network in dimensionless values are: ld = 1.700 ld = 0.150 lmd =0.02838 lq = 1.640 lq =0.150 lmq = 0.2836 ld = 1.605 lf = 0.101 r = 0.001096 lq = 1.526 ld = 0.055 rf = 0.00074 lad = 1.550 lq = 0.036 rd = 0.0131 laq = 1.490 rq = 0.054 re = 0.2 v∞ = 0.828 le = 1.640 d = 2.004 local stability analysis the steady-state values of the state variables can be obtained from the steady-state version of state equations (2, 3) using the above parameters. equation (1) implies that the expected value to id and iq are 0, that coincide with the engineering intuition. the equilibrium point of the system is: 10 q 9 d f q d 105.3334899=i 108.6242856=i 2.97899982=i 0.66750001=i 1.9132609=i 0.9990691= − − ⋅− ⋅− − ω the state matrix a of the locally linearized state-space model x˙ = ax + bu has the following numerical value in this equilibrium: ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ −−−−−⋅− −−−−− − − − −−−− − 0.00110.00050.00080.00020.0002108 1.00050.12340.03522.58392.58393.5009 1.02470.09010.03612.64642.64643.5855 1.47371.61102.20570.09640.00440.0228 0.80250.87731.20110.07720.00490.0124 2.32852.54553.48510.01420.00040.0361 6 the eigenvalues of the state matrix are: 0.123426=104.724291= 101.67235=0.100024= 0.997704103.619088= 6 4 5 3 43 2 1,2 −⋅− ⋅−− ±⋅− − − − λλ λλ λ e j it is apparent that the real parts of the eigenvalues are negative but their magnitudes are small, thus the system is on the boundary of the stability domain. pi controller the control scheme of the synchronous machine is a classical pi controller that ensures stability of the equilibrium point under small perturbations [4]. the controlled output is the speed (ω), the manipulated input is the mechanical torque tmech. the proportional parameter of the pi controller of the speed is 0.05 and the integrator time is 0.1 in per units. model validation the dynamic properties of the generator have been investigated in such a way that a single synchronous machine was connected to an infinite bus that models the electrical network. the response of the speed controlled generator has been tested under step-like changes of the exciter voltage. the simulation results are shown in fig. 1, where the exciter voltage vf and the torque angle δ are shown. 24 when the exciter voltage is increased the loading angle must be decreased as it can be seen in the fig. 1. figure 1: response to the exciter voltage step change of the controlled generator (δ means the deviation form the steady-state value) sensitivity analysis the aim of this sub-section is to define parameter groups according to the system's sensitivity on them. linkage inductances ld, lq, ld, lq, lmd and lmq are not used by the current model, only by the flux model [5]. it is not expected that the output and the state variables of system change when these parameters are perturbed, see fig. 2. as it was expected, the model is not sensitive to these parameters. note, that the linkage inductance parameters are only used for determining the fluxes of the generator. sensitivity of the model to the controller parameters p and i and the dumping constant d has also been investigated. since the pi controller controls ω by modifying the value of tmech , the controller keeps ω at synchronous speed. this is why the output and the steady state value of the system variables do not change (as it is apparent in fig. 3) even for a considerably large change of d. sensitivity analysis of the resistance of the stator and the resistance of the transmission line led to the same result. a ±20% perturbation in them resulted in a small change in currents id, iq and if. this causes the change of the effective and the reactive power of the generator, as shown in fig. 4. the analysis of the effect of the rotor resistance rf showed, that the ±20% perturbation of rf kept the quadratic component of the stator current (iq) constant, but currents id and if were changed. the output of the generator also changed, as it is shown in fig. 5. figure 2: the model states and outputs for a ±20% change of ld figure 3: the model states and outputs for a ±90% change of d 25 figure 4: the model states and outputs for a ±20% change of rresist figure 5: the model states and outputs for a ±20% change of rf the sensitivity of the model states and outputs to the inductance of the rotor (lf) and the inductance of the direct axis (ld) has also been analyzed. the results show only a moderate reaction in id and if to the parameter perturbations, and the equilibrium state of the system kept unchanged. however, decreasing the value of the parameters to the 90 percent of their nominal value destabilized the system. the results of a ±9% perturbation in lf are shown in fig. 6. a small perturbation of the outputs is noticeable. figure 6: the model states and outputs for a ±9% change of lf finally, the sensitivity of the model (2, 3, 5, 6) to the linkage inductance lad has been examined. when the parameter has been changed ±5%, currents id and if changed only a little. on the other hand, the steady-state of the system has shifted as it can be seen in fig. 7. a parameter variation of more than 5% destabilized the system. as a result of the sensitivity analysis, it is possible to define the following groups of parameters: ● not sensitive inductances ld, lq, ld, lq, lmd, lmq, laq, lq damping constant d and the controller parameters p and i. since the state space model of interest is insensitive for them, the values of these parameters cannot be determined from measurement data using any parameter estimation method. ● less sensitive: resistances of the stator r and the transmission-line re. ● more sensitive: resistance rf of the rotor and the inductance of transmission-line le. these parameters are candidates for parameter estimation. 26 ● critically sensitive: linkage inductance lad, inductances ld and lf. these parameters can be estimated very well. figure 7: the model states and outputs for a ±4% change of lad conclusion and further work the simple bilinear dynamic model of an industrial size synchronous generator described in [5] and [6] has been investigated in this paper. it has been shown that the model is locally asymptotically stable around a physically meaningful equilibrium state with parameters obtained from the literature for a similar generator. the effect of load disturbances on the partially controlled generator has been analyzed by simulation by using a traditional pi controller. it has been found that the controlled system is stable and can follow the setpoint changes in the effective power well. eighteen parameters of the system have been selected for sensitivity analysis, and the sensitivity of the state variables and outputs has been investigated for all of them. as a result, the parameters have been partitioned to four groups. based on the results presented here, the further aim of the authors is to estimate the parameters of the model for a real system from measurements. the sensitivity analysis enables us to select the candidates for estimation that are rf, le, lad, ld and lf. it is important to emphasize that this model can be and will be used as a starting point for the model development of a permanent magnet synchronous motor (pmsm) which board spectrum, that is widely used in the automotive industry. this becomes possible by changing the exciter coil of the classical synchronous machine to a permanent magnet: this way the model of the pmsm is obtained, which is one variant of the brushless direct current motors (bldc motor). acknowledgement we acknowledge the financial support of this work for the hungarian state and the european union under the tamop-4.2.1/b-09/1/konv-2010-0003 project. this work was also supported in part by the hungarian research fund through grant k67625. references 1. p. m. anderson, a. a. fouad: power-systemscontrol and stability, the iowa state university press, ames iowa, 1977. 2. p. m. anderson, b. l. agrawal, j. e. van ness: subsynchronous resonance in power systems, ieee press, new york, 1990. 3. a. loukianov, j. m. canedo, v. i. utkin, j. cabrera-vazquez: discontinuous controller for power systems: sliding-mode bock control approach, ieee trans. on industrial electronics, 51, 2004, 340–353. 4. f. p. de mello, c. concordia: concepts of synchronous machine stability as affected by excitation control, ieee trans. power application systems, pas-88:316–329, 1969. 5. a. fodor, a. magyar, k. m. hangos: dynamic modelling and model analysis of a large industrial synchronous generator proc. of applied electronics 2010, plzen, czech republic. 6. a. fodor, a. magyar, k. m. hangos: parameter sensitivity analysis of an industrial synchronous generator proc. of phd workshop 2010, veszprém, hungary. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 /colorconversionstrategy /cmyk /dothumbnails false /embedallfonts true /embedopentype false /parseiccprofilesincomments true /embedjoboptions true /dscreportinglevel 0 /emitdscwarnings false /endpage -1 /imagememory 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word a_60_szentes_r.doc hungarian journal of industrial chemistry veszprém vol. 39(1) pp. 113-116 (2011) effect of multi-walled carbon nanotube content on dynamic mechanical properties and crystallinity of polypropilene composites a. szentes1 , g. horváth1, cs. varga1, g. harrach2 1university of pannonia, institute of chemical and process engineering, 8200 veszprém, egyetem u. 10., hungary e-mail: szentesa@almos.uni-pannon.hu 2university of pannonia, institute of chemistry, 8200 veszprém, egyetem u. 10., hungary this study investigates the effect of multi-walled carbon nanotube (mwcnt) content on the dynamic mechanical properties and crystallinity of polypropylene (pp). carbon nanotubes are promising additives for polymer composites due to their excellent mechanical, electrical, and thermal properties. polypropylene/multi-walled carbon nanotube (pp/mwcnt) composites were produced in single and double screw extruders. the composites contained 0.5, 2, 3 and 5 wt% multi walled carbon nanotubes. the effect of mwcnt addition on the thermal transitions of the pp was investigated by differential scanning calorimetry (dsc) measurements. dynamic mechanical analysis (dma) studies revealed an enhancement of the storage modulus. keywords: carbon nanotubes, polypropylene, composites, dynamic mechanical analysis, crystallization introduction the reinforcement of polymers with nano-scaled fillers developed a new class of advanced multifunctional materials with improved properties, used in many fields ranging from microelectronics to aerospace engineering [1,2]. among nanofillers, carbon nanotubes (cnts) are an especially attractive class of additives because of their exceptional mechanical, thermal and electrical properties. polyolefins are, on the other hand, among the most versatile polymer matrices such as polypropylene, because of their good balance between properties and cost, low density and ease in processability [3]. polypropylene (pp) is one of the most commonly used thermoplastic polymers which has been utilized in automobiles, appliances, construction, household goods, etc. carbon nanotubes were discovered in the soot of arch discharge by sumio iijima in 1991 [4]. carbon nanotubes are allotropes of carbon and members of the fullerene structural family. cnts are promising additives for polymer composites due to their excellent mechanical, electrical and thermal properties. the special mechanical properties are due to the strong bonding between the carbon atoms that form the carbene plane. the tensile strength of carbon nanotubes is high, 75-times higher than of steel filaments of the same size, and even 15-times higher than of carbon fibers. on the other hand, the density of carbon nanotubes is one sixth of steel. their densities can be as low as 1.3 g/cm3. these facts give excellent opportunities to produce very strong materials which are light at the same time. several processing methods are available for the production of polymer/cnt composites, such as melt mixing, solution casting and in situ polymerization [6]. among them, melt mixing is particularly desirable as it combines speed with simplicity. furthermore, it is free of solvents and contaminants and the required equipment is already available in the plastic industry. in all the techniques mentioned above, a homogeneous dispersion and good interfacial adhesion are crucial for the successful preparation of nanocomposites [7,8]. extrusion is the most effective and most important technology in polymer processing. this makes the thermoplastic polymer plastic, homogenizes its viscous melt, and degasifies it, if necessary. after this, the polymer is compressed, extruded in an open instrument of constant diameter and cooled down. thus, polymer products of constant diameter can be produced in the desired length, in continuous run. [6] in this work, the dynamic mechanical properties and the thermal transitions of polypropylene blended with various contents of mwcnt were investigated. similar research was carried out by logakis et al. [9] and teng et al. [10]. experimental multi-walled carbon nanotubes (mwcnt) were produced at 700 °c by chemical vapor deposition (cvd) process over fe-co bimetallic catalyst at the institutional department of chemical engineering (institute of chemical and process engineering, university of 114 pannonia). the purity of mwcnt was ~90 wt%. according to transmission electron microscope (tem) images, the diameter of the tubes is between 10 and 20 nm (fig. 1). the length of the tubes cannot be precisely measured. according to the scanning electron microscope (sem) images, the length of the tubes is greater than 50 μm (fig. 2). polypropylene (pp) homopolymer (h116f, melt flow rate 28.0 g/10 min at 190 °c, 2.16 kg) was used as polymer matrix. figure 1: tem images of multi-walled carbon nanotubes figure 2: sem images of multi-walled carbon nanotubes polypropylene-based composites were prepared with a brabender-type single screw extruder (sse, zone temperatures: 1: 195 °c, 2: 200 °c, 3: 205 °c, 4: 210 °c, revolutions per minute: 40), and with a werner & pfleiderer-type double screw extruder (dse, zone temperatures: 1: 195 °c, 2: 205 °c, 3: 210 °c, 4: 210 °c, 5: 210 °c, 6: 210 °c revolutions per minute: 100), to decide which method gives better results. the composites contained mwcnt in different quantities (0.5, 2, 3 and 5 wt%). the content of the composites is summarized in table 1. table 1: the content of the composites sample pp (wt%) mwcnt (wt%) pp 100 sse/0.5 99.5 0.5 sse/2 98 2 sse/3 97 3 sse/5 95 5 dse/0.5 99.5 0.5 dse/2 98 2 dse/3 97 3 dse/5 95 5 specimens for dynamic mechanical analysis (dma) testing were compression molded under a pressure of 15 mpa for 5 min, at 170 °c. slabs were prepared with a thickness of 2 mm. differential scanning calorimetry (dsc) measurements were carried out in the temperature range of 30 to 200 °c. the sample was heated in two stages in nitrogen environment. in the first run, the sample was heated from 30 to 200 °c at a heating rate of 10 °c/min and held at 200 °c for 1 minute. then the sample was cooled to 30 °c at a cooling rate of 10 °c/min to release the internal stress of the sample. in the second run, the first run procedure was repeated. dynamic mechanical analysis (dma) was performed in the two-point bend mode. the thickness of the specimens was 2 mm. the temperature scan ranged from -155 to 100 °c, at a heating rate of 2 °c/min, the frequency was 1 hz, under a constant nitrogen gas flow rate of 20 cm3/min. results the effect of mwcnt addition on the thermal transitions of the pp was investigated by differential scanning calorimetry (dsc) measurements. table 2 summarizes the peak melting point, the final melting points and the heats of melting of the composites. table 2: peak melting points, final melting points and heats of melting of the composites sample peak melting point (°c) final melting point (°c) heat of melting (j/g) pp 163.9 170.9 120.2 sse/0.5 165.7 170.7 130.1 sse/2 165.7 169.9 127.1 sse/3 166.1 171.0 126.8 sse/5 165.3 169.4 115.0 dse/0.5 165.8 170.4 124.7 dse/2 167.0 172.4 127.1 dse/3 168.0 172.5 129.7 dse/5 168.4 174.3 129.9 as it can be seen clearly, the composites do not differ significantly in their melting properties when using a single screw extruder. when using a twin screw extruder to prepare the composites, the peak and final melting points were rising with the rising carbon nanotube content. the same are true of the heats of melting of the composites. table 3 gives the initial and peak temperatures of crystallization of the composites. as it can also be seen, there is no significant change in the crystallization properties of the composites in the case of the single screw extruder. when using a twin screw extruder to prepare the composites, the initial and peak crystallization temperatures were rising with the rising carbon nanotube content. the extent of rise is illustrated in fig. 3. the rise in melting and crystallization temperatures of the composites is due to the nucleating effect of the mwcnts. the effect is realized in the case of the single screw extruder, but not consequently because there is no relationship with the mwcnt concentration. this is probably due to the low homogeneity of the carbon nanotubes in the matrix. for composites prepared with the twin screw extruder, on the other hand, the nucleating effect is increasing with the increasing carbon nanotube 115 content which can be attributed to the more homogenic dispersion of the tubes in the matrix. table 3: initial and peak temperatures of crystallization of the composites sample initial temperature of crystallization (°c) peak temperature of crystallization (°c) pp 122.6 116.5 sse/0.5 128.4 123.7 sse/2 137.7 124.0 sse/3 132.0 124.3 sse/5 136.0 124.9 dse/0.5 129.6 125.7 dse/2 133.2 128.6 dse/3 135.9 131.0 dse/5 138.1 132.2 figure 3: peak melting and peak crystallization temperatures of the composites dynamic storage modulus (e’) and and tangent delta (tan δ) of the composites were analyzed with dynamic mechanical analysis (dma). e’ of the composites increases in the glassy state and the rubbery state on addition of carbon nanotubes (table 4). the increase of the value of the storage modulus in the glassy phase (e’) is small in the case of the composites produced with the single screw extruder. the value of the storage modulus in the glassy phase increases significantly with the increasing carbon nanotubes content in the case of the composites produced with the single screw extruder. the increase is 45% at 2wt% cnt, and 75% at 5wt% cnt. similar results were obtained for the value of e’ in the elastic phase. the value of e’ did almost not change when using the single screw extruder, while it increased when using the twin screw extruder. the increase is 110% at 3wt% nanotubes content. table 4 shows the glass temperature (tg) of the composites. the peaks which appear in the tangent delta (tan δ) correspond to tg values. the glass transition temperatures of the composites produced with the single screw extruder did not change significantly. a clear-cut tendency with changing the carbon nanotubes content cannot be determined. the temperature of glass transition of the composites produced with the twin screw extruder decreased. table 4: dynamic storage modulus (e’) in the glassy and in the rubbery state for the pure pp matrix and pp/mwcnt composites. sample e’ in the glassy state (at –40°c) (gpa) e’ in the rubbery state (at 60°c) (gpa) tg (°c) pp 3.1 0.9 5.9 sse/0.5 3.4 1.0 5.5 sse/2 3.5 1.1 6.2 sse/3 3.7 1.2 5.1 sse/5 3.8 1.2 5.4 dse/0.5 3.6 1.2 5.0 dse/2 4.5 1.3 4.1 dse/3 5.1 1.9 3.0 dse/5 5.4 2.2 2.4 conclusions polypropylene/multi walled carbon nanotube composites were produced in single and double screw extruders. the composites contained 0.5, 2, 3 and 5 wt% multiwalled carbon nanotube. the melting points, the temperatures of crystallization and the heats of melting of the composites were investigated by differential scanning calorimetry (dsc) measurements. the composites do not differ significantly in their melting and crystallization properties when using a single screw extruder. when using a twin screw extruder to prepare the composites, the melting points and the temperature of crystallization were rising with the rising carbon nanotube content. the same are true of the heats of melting of the composites. the dynamic storage modulus and the glass temperature of the composites were investigated with dynamic mechanical analysis (dma). the e’ and tg values of the composites produced with the single screw extruder changed almost unnoticeably. the e’ value of the composites produced with the twin screw extruder rose significantly with the rising carbon nanotubes content while the temperature of glass transition decreased. acknowledgment the financial support of this work by the hungarian state and the european union under the tamop-4.2.1/b09/1/konv-2010-0003 project is kindly acknowledged. references 1. e. t. thostenson, c. li, t. w. chou: nanocomposites in context, compos. sci. technol., 65, (2005), 491–516 2. f. hussain, m. hojati, m. okamoto, r. e. gorga: polymer–matrix nanocomposites, processing, manufacturing, and application: an overview. j. compos. mater., 40, (2006), 1511–1565 116 3. m. mihaela, a. olaru: handbook of polyolefins. marcel dekker inc. (1993), 267–290 4. s. iijima: helical microtubes of graphitic carbon, nature, 354, (1991), 56–58 5. j. n. coleman, u. khan, w. j. blau, y. k. gun’ko: small but strong: a review of the mechanical properties of carbon nanotube–polymer composites, carbon, 44, (2006), 1624–1652 6. z. spitalsky, d. tasis, k. papagelis, c. galiotis: carbon nanotube–polymer composites: chemistry, processing, mechanical and electrical properties, progress in polymer science, 35, (2010), 357–401 7. n. grossiord, j. loos, o. regev, c. e. koning: toolbox for dispersing carbon nanotubes into polymers to get conductive nanocomposites, chem. mater, 18, (2006), 1089–1099 8. r. andrews, d. jacques, m. minot, t. rantell: fabrication of carbon multiwall nanotube/polymer composites by shear mixing, macromol. mater. eng., 287, (2002), 395–403 9. e. logakis, e. pollatos, c. h. pandis, v. peoglos, i. zuburtikudis, c. g. delides, a. vatalis, m. gjoka, e. syskakis, k. viras, p. pissis: structure–property relationships in isotactic polypropylene/multi-walled carbon nanotubes nanocomposites, composites science and technology, 70, (2010), 328–335 10. c. c. teng, c. c. m. ma, y. w. huang, s. m. yuen, c. c. weng, c. h. chen, s. f. su: effect of mwcnt content on rheological and dynamic mechanical properties of multiwalled carbon nanotube/polypropylene composites, composites: part a, 39, (2008), 1869–1875 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 /colorconversionstrategy /cmyk /dothumbnails false /embedallfonts true /embedopentype false 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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<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> /enu (use these settings to create adobe pdf documents best suited for high-quality prepress printing. created pdf documents can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word 1_r.doc hungarian journal of industrial chemistry veszprém vol. 37(1). pp. 59-67 (2009) pca driven similarity for segmented univariate time series z. bankó, j. abonyi university of pannonia, department of process engineering, p.o. box 158. veszprém h-8200, hungary e-mail: abonyij@fmt.uni-pannon.hu selection of the proper similarity measure is the cornerstone of all time series data mining task. in the recent years, many similarity measures have been introduced to fulfill the needs of chemical process engineering. these measures have been guided by data reduction methods due to the large amount of data. this data reduction can be done explicitly (by segmentation) as well as implicitly (by utilizing the latent variable space). usually, the original multivariate data is projected into a single dimension with principal component analysis (pca) and segmentation is executed. however, the similarity measures which have been used to compare univariate, segmented representations of the original processes do not consider that the main information carried by the univariate representations is the correlation of the original variables. this paper introduces a pca inspired similarity measure for these univariate segments. finally, it is shown that the presented method can be considered as the logical extension of the correlation based dynamic time warping (cbdtw) to univariate time series. keywords: segmentation, dynamic time warping, principal component analysis, piecewise linear approximation introduction a time series is a sequence of values measured as a function of time. these kinds of data are widely used in the field of chemical process engineering, namely for process control, fault detection and analysis of process transitions. the increasing popularity of knowledge discovery and data mining tasks for discrete data has indicated the growing need for similarly efficient methods for time series data. these tasks share a common requirement: a similarity measure has to be defined between the elements of a given database. moreover, the results of the data mining methods from simple clustering (partitioning the data into coherent but not predefined subsets) and classification (placing the data into predefined, labelled groups) to complex decision-making systems used for process control are highly dependent on the applied similarity measure. related work the similarity of multivariate time series can be approached from two different perspectives. the first way is the application of metrics based warping measures such as dynamic time warping (dtw) and longest common subsequence (lcss). these techniques are perfectly suitable for univariate tasks like speech recognition, where the analyzed process is represented by only one variable. in most cases, these methods can be easily generalized for the needs of the multivariate time series where the process depends on two or more variables. however, their application for correlated multivariate time series is often not as effective as it is expected. the direct comparison of the variables used by these approaches ignores the hidden process, i.e. the correlation between the process variables and this hidden process carries the real information in most process control task [1]. hence, principal component analysis (pca) based similarity measures are used to overcome this problem. krzanowski [2] defined the pca similarity factor to measure the similarity between different data by comparing the hyperplanes (the dimensionality reduced latent variable spaces): p uuuutr yxs px t pypy t px nnpca nnnn )( ),( ,,,,= where: xn – the first n-variable multivariate time series yn – the second n-variable multivariate time series uxn,p and uyn,p – the matrices of eigenvectors which belong to the most important p ≤ n eigenvalues of covariance matrices of xn and yn, i.e. the two hyperplanes. the similarity factor has a geometrical explanation, because it measures the similarity between the two hyperplanes by computing the squared cosine values between all the combinations of the first p principal components from xn and yn: ∑∑ = = = p i p j jinnpca p yxs 1 1 , 2cos1),( θ 60 where: θi,j – the angle between the ith principal component of xn and the jth principal component of yn. the main advantage of krzanowski's similarity factor is its optimal variable reduction property (from variance point of view) which makes it ideal for tasks with high number of variables. pca similarity factor has also gained in popularity because of its outstanding feature which makes possible to recognize the direction of the changes in the distance between the variables, i.e. the rotation of the hyperplanes. on the other hand, pca similarity factor weights all principal components equally, hence it may not capture well enough the degree of similarity between the sequences when only a few principal components explain most of the variance. thus, it was natural to define a modified pca similarity factor that weights each principal component by its explained variance. m. c. johannesmeyer [3] defined this modified pca similarity factor by weighting each principal component with its eigenvalue: ∑ ∑∑ = = == p i y i x i ji p i p j y j x i nnpca nn nn yxs 1 , 2 1 1 )( θcos)( ),( λλ λλ λ where: λi xn and λi yn – the corresponding eigenvalues of the ith and jth principal component of xn and yn. this principle was developed by k. yang [4] who presented the logical extension of pca similarity factor and sλpca called eros (extended frobenius norm): ∑∑ == == n i ii n i t yxinneros wiuiuwyxs nn 11 θcos)()(),( where: θi – the angle between the two corresponding principal components wi – the weighting vector based on the eigenvalues of the sequences in the data set. figure 1: two corresponding principal components generally speaking, the eros measures the similarity of two multivariate time series by comparing the angle between the corresponding principal components and using the aggregated eigenvalues as weights, hence it takes into account the variance of each principal component. it has to be noted that eros always computes the acute angle between the two principal components (eigenvectors). therefore, as it is illustrated in fig. 1, when the angle (α) between the two corresponding eigenvectors is not acute, the absolute value of it is taken and the similarity between the two corresponding eigenvectors is computed by using the acute angle (β). more specifically, the inner product of two normal vectors, a and b in fig. 1, yields cos(α), while cos(β) = cos(π-α) = –cos(α) is needed. therefore, the absolute value of cosine of the angle between the eigenvectors is taken, so that cos(α) is computed when α ≤ π/2, while -cos(α) is computed when α > π/2. the previously mentioned methods greatly improved the simple pca similarity factor both in speed and in accuracy; however, they have not dealt with the biggest problem of every pca related technique, i.e. pca considers the time series as a whole but does not take into account the alterations of the correlation structure. this alternation affects the hyperplanes, therefore segmentation is required in most real-life applications to create homogeneous segments from correlation structure point of view. however, the segmentation raises another problem: although in many real-life applications a lot of variables must be simultaneously tracked and monitored, most of the segmentation algorithms are used for the analysis of only one time-variant variable [5]. hence, dimensionality reduction techniques are used, most likely pca, to project the multivariate time series into the one dimensional space where any suitable univariate segmentation method such as piecewise aggregate approximation (paa) or piecewise linear approximation (pla) is executed. finally, the segments are compared with a suitable similarity measure. finding this suitable similarity measure is a difficult task. besides the obvious euclidean distance other, more advanced measures can be used such as dtw. it proved its adaptability and superiority over other similarity measures in wide range of time series applications from speech recognition [6] to fingerprint verification [7] and as final proof of this yanikoglu won the signature verification conference with a dtw based algorithm in 2004 [8]. keogh and pazzani presented modifications on dtw algorithm to handle paa [9] and pla [10] representations of univariate time series. although these new algorithms can provide noticeably better results than euclidean distance and speeds up the computationally expensive general dtw algorithm, they do not take the drift of the segments into account. thus, the segmentation has to be framed in another way. instead of compressing the multivariate data to a univariate time series applying pla or paa, the segmentation can be done in the multivariate space while the correlation is still considered. the authors introduced [11] two homogeneity measures as cost function for segmentation which are corresponding to the two typical applications of pca models. the q reconstruction error can be used to segment the time series according to the direct change of the correlation among the variables, while the hotelling's t2 statistics can be utilized to segment the time series based on the drift of the center of the operating region. a α β b 61 based on these new segmentation methods a novel similarity measure, called correlation based dynamic time warping was created [12]. it was proven that it outperforms all of the previously introduced correlation based similarity measures when the multivariate time series are highly correlated. this paper introduces the univariate version of cbdtw which can be used for pca projected univariate time series. the rest of the paper is organized as follows. section background details the theoretical background of the proposed similarity measure, i.e. segmentation and dtw. in the next section the problems of the current dtw algorithms used for segmented representations are pointed out and the new similarity measure is presented. it is also discussed how it was derived from cbdtw. section 4 conducts a detailed empirical comparison of the introduced pca based method with currently used measures on verification databases widely used by the time series data mining community. finally, validation is performed by clustering of temperature data from a sophisticated model of an industrial catalytic fixed bed tube reactor. background an n-variable, m-element time series, xn = [x1,x2,…,xn], is an m-by-n element matrix, where xi = [xi(1),xi(2),…,xi(n)]t is the ith variable and xi(j) its jth element. xn(j) = [x1(j),x2(j),…,xn(j)] is the jth sample of xn. the similarity between xn and yn is denoted by s(xn, yn), where 0 ≤ s(xn, yn) ≤ 1, s(xn, yn) = s(yn, xn), and s(xn, xn) = 1. obviously, the similarity is nothing more than a real number between zero and one which expresses the tightness of connection between the processes behind the time series. the closer the number is to one, the processes are treated more similar. in practice, the term distance or dissimilarity (d) is used instead of similarity. the value of the distance is given by a number ranged from zero to one. this can be associated with similarity: d(xn, yn) = 1 – s(xn, yn). segmentation the ith segment of xn is a set of consecutive time points, si(a,b) = [xn(a), xn(a+1),…, xn(b)]. the c-segmentation of time series xn is a partition of xn to c non-overlapping segments, sc xn = [s1(1,a),s2(a+1,b),…,sc(k+1,m)]. in other words, a c-segmentation splits xn to c disjoint time intervals, where 1 ≤ a and k ≤ m. the simplest but yet powerful segmentation technique for univariate time series is paa. in this case, to reduce the m-length data from n, the time series are simply divided into n similar sized frames and each frame is represented by its mean value. assuming that n is a factor of m, we get: ∑ +−= = i n m i n mj jx m nix 1)1( 11 )()( besides filtering noise, paa can compensate phase shifts of time axis and difference sampling rates of time series and the distance between two paa representations can be chosen almost freely; however, it cannot handle “locally elastic” shifts of the time axis and it is not enough tight representation for most time series as it is shown in fig. 2. figure 2: the original signal (top) and its paa (middle) and pla representation (bottom) using 10 segments to correct these faults, more sophisticated methods are applied such as pla which, however, arise the „segmentation problem”, i.e. how to segment a times series quickly and how to represent each segment tight enough. segmentation can be framed in several ways [13], but its main goal is always the same: finding homogenous segments by the definition of a cost function, cost(si(a,b)). this function can be any arbitrary function which projects from the space of the time series to the space of the non-negative real numbers. usually, cost(si(a,b)) is based on the distances between the actual values of the time series and the values given by a simple function f (constant or linear function, a polynomial of a higher but limited degree) fitted to the data of each segment: ∑ =+− = b al nni lxflxd ab bas )))((),((( 1 1)),((cost thus, the segmentation algorithms simultaneously determine the parameters of the models and the borders of the segments by minimizing the sum of the costs of the individual segments: ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ = ∑ = c i i c x bass n 1 ))),((cost(min)(cost this segmentation cost of a time series can be minimized by dynamic programming, which is 62 computationally intractable for many real datasets. consequently, heuristic optimization techniques such as greedy top-down or bottom-up techniques are frequently used to find good but suboptimal c-segmentations: bottom-up: every element of xn is handled as a segment. the costs of the adjacent elements are calculated and two elements with the minimum cost are merged. the merging cost calculation of adjacent elements and the merging are continued until some goal is reached. top-down: the whole xn is handled as a segment. the costs of every possible split are calculated and the one with the minimum cost is executed. the splitting cost calculation and splitting is continued recursively until some goal is reached. sliding window: the first segment is started with the first element of xn. this segment is grown until its cost exceeds a predefined value. the next segment is started at the next element. the process is repeated until the whole time series is segmented. all of these segmentation methods have their own specific advantages and drawbacks. accordingly, the sliding window method is not able to divide up a sequence into predefined number of segments but this is the fastest method. the applied method depends on the acutal task. these heuristic optimization techniques were examined in detail through the application of piecewise linear approximation [13]. it can be stated if real-time (on-line) segmentation is not required, the best result will be reached by bottom-up segmentation. while paa represents an equal sized segment with only one value, pla replaces the original data with not equally sized segments of straight lines, i.e. a pla segment of x1 is a 4-taple: [ ]iiii ylxylxxrxxlxix )(,)(,)(,)()( 11111 = where: x1(xl)i and x1(xr)i – left and right time coordinates of the ith segment of x1 x1(yl)i and x1(yr)i – the values of x1 in x1(xl)i and x1(xr)i. finding the optimal pla a of time series and a suitable distance for this representation is a difficult task, that usually depends on the application. however, precison of the mostly used, traditional euclidean distance (or any other lp norm) can be significantly increased with the application of dtw. dynamic time warping the traditional comparision approaches are rarely precise enough for the most applications. this is caused by the brittleness of the conventional similarity measures such as euclidean distance. they are unable to handle the distortions in time axis, so these distortions almost randomly affect the distance between time series. the solution for this problem is the application of dtw which can “warp” the original time series (nonlinearly dilate or compress their time axes) to be similar in shape to the query series as much as possible. to align two univariate sequences (x1 and y1) with dtw, firstly a grid d have to be defined with size of the two time series (mx x my). each cell of this matrix represents the actual distance between the appropriate indices of the two time series. in this step, any application-dependent distance like l1 and l∞ norms can be used but generally euclidean distance is suggested because it allows of the efficient indexing of dtw. considering this we have: 2 2 11 ))()((),( jyixjid −= using grid d, many arbitrary mappings – called warping paths – can be created between x1 and y1. however, the construction of a warping path [p(1),p(2),…,p(l)] has to be restricted with the following constraints: boundary condition: the path has to start in d(1,1) and end in d(mx,my). monotonicity: the path has to be monotonous, i.e. always heading from d(1,1) to d(mx,my). if p(k) = d(i,j) and p(k+1) = d(i’,j’) then i’–i ≥ 0 and j’–j ≥ 0 . continuity: the path has to be continuous. if p(k) = d(i,j) and p(k+1) = d(i’,j’) then i’–i ≤ 1 and j’–j ≤ 1. to find the optimal warping path (the dtw distance of the two time series), every warping path has an assigned cost which is the sum of values of the affected cells divided by normalization constant k: ⎟ ⎟ ⎟ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎜ ⎜ ⎜ ⎝ ⎛ = ∑ = k ip yxd l i dtw 1 11 )( min),( the value of k depends on the application and in most cases this is the length of the path, but it can also be omitted. more information about the method of defining k and its significance can be found in [14]. note that the euclidean distance is a special case of dtw, i.e. we choose the path that is located on the diagonal of grid d and k = 1. figure 3: cumulative distance matrix d and the optimal warping path on it 63 obviously, the number of paths exponentially grows by the size of time series. fortunately, the optimal path can be found in o(mxmy) time with the help of dynamic programming using cumulative distance matrix d. a cell of the cumulative matrix contains the sum of the appropriate cell value in matrix d and the minimum of the three cells from where the cell can be reached: ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ +−− +− +− = ),(d)1,1(d ),(d)1,(d ),(d),1(d min),(d jiji jiji jiji ji the dtw distance between the two time series can be found in d(mx,my). warping the representations dtw can be applied easily on the paa representations of univariate time series. each segment is represented by its mean, thus the dtw algorithm is the same as for the original time series but the computational time is lowered to o((m/n)2). warping the pla representation is much more difficult. vullings et al. [15] were the first to use pla based dtw on ecg data while keogh and pazzani [10] gave a generalized distance between pla segments which can be used to fill matrix d: 2 11 2 )()( 2 )()())(),(( ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ + − + = iiii yryylyyrxylxjyixd as it can be seen this distance arises from paa: it compares the means of the corresponding segments but it utilizes the tighter pla representation. however, this tighter representation, i.e. the different length of the segments, introduces a new problem. the normalization constant k usually based on the length of the warping path but pla, contrary to paa, does not generate equidistant segments. thus, keogh and pazzani suggested to recursively sum an additional variable on the warping path which stores the lengths of the visited segments. pca driven similarity of pla representation as it was mentioned before many problems arise when one would like to use data mining alogrithms on highly correlated mutivariate time series data. the high amount of data requires some reduction techniques. in chemical process engineering, usually pca is used to create univariate time series from the multivariate data because pca preserves the correlation of the original time series which is definitely an important factor to consider. the generated univariate time series make it possible to use traditional segmentation techniques which are often required for two reasons: first, the highly appreciated dtw algorithm computational extensive thus further data compression is advised and second, process transitions and frauds can be revealed by segmentation. considering the previously mentioned, paa is not suitable for our purposes because the segments are equidistant and they are represented by their means, hence paa representation lost the direction of the latent variable in each segment. pla generates a much tighter representation and it can preserve the direction information. in addition, it can be seen as the one dimensional version of pca based segmentation presented in [12,13]. the authors used the q reconstruction error, i.e. the goal of the segmentation was to minimize the sum of the squared euclidean distances between the original and the reconstructed variables in each segment. pla does the same, it minimizes the squared euclidean distance between the original data point and their reconstructed pair (the closest point on the pla segment). this reconstruction error is shown in case of pla segmentation in fig. 4. x1(t) time q figure 4: time series x1 (black dots) and its reconstruction using the pla representation (gray dots) unfortunately, the currently used dtw based measures do not take into consideration that the pla created straight line is the latent variable of each segment while the mean of each segment are used. in [12], it is suggested to use any of the pca based similarity measures to compare the hyperplanes of two segments when the segmentation was driven by pca. this leads to represent each pla segment with its angle of slope: ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ − − = ii ii xlxxrx ylxyrxix )()( )()(atan)(1 please note, none of the segments can be perpendicular to the time axis, hence no further restrictions are required. now, any of the above presented pca based similarity measures can be used to compare the segments based on the slope information. the interested reader might notice that the only difference between the reviewed pca based similarity measures how they weights the angles between the hyperplanes. in the one dimensional space all of them can be reduced to the same equation: ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ + − = )()(1 )()( atancos))(),(( 11 11 11 iyix iyix iyixd where |cos(…)| – can be replaced by cos2(…). 64 this would be a perfect measure for hyperplanes of a pca projection, where the hyperplanes are the coordinates of the projected space, thus their signs are not only meaningless but considering them would destroy the precision. however, the pla representation of a segment of a univariate time series (i.e., its latent variable) is also represents the original time series in the same space, thus the sign information cannot be neglected. for example, if one compares x1(i) = 57 (~89°) and y1(i) = –57 (~91°) as hyperplanes they are almost the same (only 2° is the difference); however, they are completely different from the time series point of view (increasing and decreasing trends). so, the basis distance of dtw should be a function which can measure the difference between the signed slopes. for this paper, the simple squared euclidean distance was chosen: 2 1111 ))()(())(),(( jyixjyixd −= the last thing to handle is the k constant. if it can be treated that preprocessing steps are properly executed (i.e. data is filtered and it is proved that no additional noise is added to it), the role of the k constant is changed. the proper preprocessing ensures that all of the segments are detected due to the underlying process and they are not detected due to the noise; moreover, the minimum number of elements of a segment can also be defined. thus, an additional warping is achieved if the weights of the segments are not considered and the length of the warping path can be used as the value of k or it can be omitted as it is done in this paper. validation according to [16], the presented similarity measure was compared to other methods using the free and widely used datasets and classification algorithm of the ucr time series classification/clustering homepage [17]. the datasets were kindly provided by mr. keogh on march 7, 2007. please note, for easier reconstruction of the results, the algorihms were not executed on the four biggest dataset: face (all), two patterns, wafer, yoga. in this test, the suggested 1-nn classification algorithm was executed on the databases and the error rate (proportion of the faulty classified time series) of each database for every measure was recorded in table 1 and table 2. as a reference, the non-segmented time series was also compared with euclidean distance and dtw, their results can be found in the third and fourth columns. the first four colored columns contain the results of the currently used similarity measures. the time series were segmented with paa and pla to 30 pieces using bottom-up technique and euclidean or the reviewed dtw distance was applied. please note, this means that the mean of the segments were used to compare two segments irrespectively of the applied segmentation method. a ng le 3 0 se gm en ts d tw 0. 37 0. 64 0. 63 0. 59 0. 11 0. 19 0. 39 0. 15 a ng le 3 0 se gm en ts eu cl id ea n 0. 46 0. 71 0. 67 0. 64 0. 32 0. 23 0. 72 0. 46 pl a 3 0 se gm en ts d tw 0. 40 0. 66 0. 50 0. 04 0. 29 0. 20 0. 30 0. 38 pl a 3 0 se gm en ts eu cl id ea n 0. 35 0. 76 0. 53 0. 13 0. 18 0. 20 0. 39 0. 51 pa a 3 0 se gm en ts d tw 0. 36 0. 43 0. 53 0. 02 0. 25 0. 21 0. 23 0. 22 pa a 3 0 se gm en ts eu cl id ea n 0. 36 0. 41 0. 50 0. 07 0. 25 0. 13 0. 17 0. 21 n o w ar pi ng w in do w d tw 0. 31 0. 40 0. 50 0. 00 0. 18 0. 23 0. 17 0. 17 eu cl id ea n d is ta nc e 0. 37 0. 39 0. 47 0. 15 0. 25 0. 12 0. 22 0. 22 ti m e se rie s le ng th 27 0 17 6 47 0 12 8 28 6 96 35 0 46 3 n um be r o f cl as se s 50 37 5 3 2 2 4 7 n am e 50 w or ds a di ac b ee f c b f c of fe e ec g fa ce (f ou r) fi sh ta bl e 1: r es ul ts o f th e u c r ti m e se rie s cl as si fic at io n al go rit hm o n th e fir st e ig ht 65 a ng le 3 0 se gm en ts d tw 0. 05 0. 44 0. 67 0. 37 0. 29 0. 22 0. 67 0. 01 a ng le 3 0 se gm en ts eu cl id ea n 0. 05 0. 39 0. 78 0. 40 0. 70 0. 51 0. 67 0. 17 pl a 3 0 se gm en ts d tw 0. 07 0. 20 0. 44 0. 30 0. 44 0. 28 0. 01 0. 03 pl a 3 0 se gm en ts eu cl id ea n 0. 07 0. 31 0. 47 0. 33 0. 52 0. 44 0. 01 0. 19 pa a 3 0 se gm en ts d tw 0. 07 0. 26 0. 30 0. 13 0. 42 0. 21 0. 04 0. 10 pa a 3 0 se gm en ts eu cl id ea n 0. 09 0. 25 0. 34 0. 13 0. 47 0. 21 0. 01 0. 29 n o w ar pi ng w in do w d tw 0. 09 0. 13 0. 27 0. 13 0. 41 0. 21 0. 01 0. 00 eu cl id ea n d is ta nc e 0. 09 0. 25 0. 43 0. 13 0. 48 0. 21 0. 12 0. 24 ti m e se rie s le ng th 15 0 63 7 31 9 57 0 42 7 12 8 60 27 5 n um be r o f cl as se s 2 2 7 4 6 15 6 4 n am e g un -p oi nt li gh tn in g2 li gh tn in g7 o liv eo il o su l ea f sw ed is h le af sy nt he tic c on tro l tr ac e ‘angle’ denotes the presented similarity measure. the time series were segmented to 30 pieces again but now the slope of each segment was considered. the provided representations were also compared with euclidean distance and dtw. the best results are marked with dark grey for each database. as it can be seen the newly presented method kept up with the expectations. however, some notes have to be made on the results. one can realize that the reduction obtained by the segmentation was only about one order of magnitude which ensures the tight representation even with paa and 30 segments is too much for most databases when pla is used. moreover, all of the databases require different number of segments to get the best results. the aim of this test was to show that it really makes sense to use the slope of a segment instead of its mean when the segment is provided by pla. obviously, the best paa and pla representation can be found for all distance measure but the idea behind the creation of such a test is to provide a unified test environment for all measures and to prevent the researcher from “over optimization”. validation on an industrial fixed bed tube reactor the proposed pca driven similaity measure has also been applied for clustering of temperature data from a sophisticated model of an industrial catalytic fixed bed tube reactor. coolant in coolant out reagents product x = 0 x = l ( )wout,w b,t ( )win,w b,t ( )out,gout,g i out,gout,g p,c,b,t ( )in,gin,g i in,gin,g p,c,b,t figure 5: the simplified scheme of the studied reactor the studied vertically built up reactor contains a great number of tubes with catalyst. highly exothermic reaction occurs as the reactants rising up the tubes pass the fixed bed of catalyst particles and the heat generated ta bl e 2: r es ul ts o f t he u c r ti m e se rie s c la ss ifi ca tio n al go rit hm o n th e se co nd e ig ht d at as et s 66 by the reaction escapes through the tube walls into the cooling water. due to this highly exothermic reaction which takes place in the catalyst bed the reactor very sensitive for the development of reactor runaway. reactor runaway means a sudden and considerable change in the process variables. the development of runaway is in very close relationship with the stability of reactor/model. runaway has two main important aspects. in one hand runaway forecast has a safety aspect, since it is important for avoiding the damage the constructional material or in the worst case scenario the explosion of reactor. on the other hand, runaway has a technology aspect, since the forecast of the runaway can be used for avoiding the development of hot spots in catalytic bed. the selection of operation conditions is important to avoid the development of reactor runaway and to increase the lifetime of catalyst at same time. the worked out mathematical model of the studied reactor has been presented in [5]. the model has been implemented in matlab and solved with a low order runge-kutta method. 0 1 2 3 4 250 300 350 400 reactor length [m] t em pe ra tu re [k ] 0 1 2 3 4 200 400 600 800 reactor length [m] t em pe ra tu re [k ] figure 6: normal (upper graph) and runaway (lower graph) profiles of the studied reactor the obtained simulator was applied to calculate two kinds of profiles. the inlet conditions were set to provide five profiles which correspond to the normal working conditions and other five profiles which describe the development of reactor runaway. the presented similarity measure has been used to classify these profiles. the result of clustering can be seen in the dendogram of fig. 7. 1 3 5 2 4 6 7 10 9 8 d is ta nc e normal runaway figure 7: clustering result of the five normal (number 1-5) and five runaway (number 6-10) profiles conclusion we presented a new similarity measure for segmented univariate time series by considering the pla representation of a segment as the latent variable. the proposed similarity was validated on many real world dataset used by data mining community and on the temperature profiles generated by a sophisticated model of an industrial reactor. both evaluations show that it is worth to consider representing the segments by their slopes instead of their means and using this feature for the comparison. however, there is no decided difference between the two methods, thus we intend to combine these approaches in the future. acknowledgement jános abonyi is grateful for the support of the bolyai research fellowship of the hungarian academy of sciences. the financial support of the támop-4.2.208/1/2008-0018 project is gratefully acknowledged. references 1. kourti t.: application of latent variable methods to process control and multivariate statistical process control in industry, international journal of adaptive control and signal processing 19 (2005), 213-246 2. krzanowski w.: between-groups comparison of principal components, journal of the american statistical society 74 (1979), 703-707 3. johannesmeyer m. c.: abnormal situation analysis using pattern recognition techniques and historical data, m.sc. thesis, university of california, santa barbara, ca (1999) 67 4. yang k., shahabi c.: a pca-based similarity measure for multivariate time series, proceedings of the 2nd acm international workshop on multimedia databases (2004), 65-74 5. kivikunnas s.: overview of process trend analysis methods and applications, erudit workshop on applications in pulp and paper industry (1998), erudit 6. sakoe h., chiba s.: dynamic programming algorithm optimization for spoken word recognition, ieee transactions on acoustics, speech, and signal processing (1978) 7. vajna z. m. k.: a fingerprint verification system based on triangular matching and dynamic time warping, ieee trans. pattern anal. mach. intell. 22 (2000), 1266-1276 8. kholmatov a., yanikoglu b. a.: biometric authentication using online signatures, iscis (2004) 9. keogh e. j., pazzani m. j.: scaling up dynamic time warping for datamining applications, knowledge discovery and data mining (2000) 10. keogh e. j., pazzani m.: scaling up dynamic time warping to massive datasets, 3rd european conference on principles and practice of knowledge discovery in databases (1999) vol. 1704 11. abonyi j., feil b., németh s., árva p.: principal component analysis based time series segmentation, ieee international conference on computational cybernetics (2005) 12. bankó z., abonyi j.: correlation based dynamic time warping of multivariate time series, computational statistics & data analysis (in press) 13. keogh e. j., chu s., hart d., pazzani m. j.: an online algorithm for segmenting time series, icdm (2001) 14. sakoe h., chiba s.: dynamic programming algorithm optimization for spoken word recognition, ieee transactions on acoustics, speech, and signal processing (1978) 15. vullings h. j. l. m., verhaegen m. h. g., verbruggen h. b.: ecg segmentation using time-warping, proceedings of the second international symposium on advances in intelligent data analysis, reasoning about data (1997) 16. keogh e. j., kasetty s.: on the need for time series data mining benchmarks: a survey and empirical demonstration, proceedings of the 8th acm sigkdd international conference on knowledge discovery and data mining (2002) 17. keogh e. j., xi x., wei l., ratanamahatana c. a.: the ucr time series classification/clustering homepage, http://www.cs.ucr.edu/~eamonn/time_series_data/, riverside ca. university of california computer science and engineering department (2006) 18. varga t., szeifert f., réti j., abonyi j.: analysis of the runaway in an industrial heterocatalytic reactor, computer-aided chemical engineering 24, (2007), 751-756 microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 37(2) pp. 83-88 (2009) immobilized enzymes availability for glycerol – 1,3 propanediol bioconversion a. balassy , á. nemeth, b. sevella budapest university of technology and economics, department of applied biotechnology and food science faculty of chemical technology and biotechnology, h-1111 budafoki street 6-8, budapest, hungary e-mail: lyra1111a@gmail.com the increasing abundance of glycerol, its renewability, and attractive pricing make it an appealing platform chemical. glycerol can be utilized in various ways of biological transformation to industrially valuable products. there are some important derivatives among these such as 3-hydroxypropionaldehyde ((3-hpa) commercial name: reuterin), dihydroxyacetone (dha), and 1,3-propanediol (pdo). pdo has the largest potential need. several bacteria are able to ferment glycerol to pdo under anaerobic conditions. a new recombinant technology was worked out with the leadership of dupont and genecor in the last decade, in which a recombinant escherichia coli converts glucose directly to pdo. microbiological production of a molecule has always lower yield than an enzymatic method and usually produces a lot of by-products that can be avoided using enzymatic bioconversion. for years we have been working on a new enzymatic process in order to produce pdo and dha simultaneously from glycerol. for this enzymatic way three key enzymes are needed: glycerol-dehydratase (gdht), 1,3-propanediol-oxydoreductase (pdor), glycerol-dehydrogenase (gdh). these enzymes must be produced by microbial fermentation. we would like to present the results of developing the fermentation media in economic aspect. our pleriminary results (not publicated) indicated that the 2xyt medium is perfect for our clostridium strain. however in economic aspect the concentrations of yeast extract and bactotryptone are too high to scale-up this fermentation procedure. the first purpose of this study was to optimize the fermentation media. optimized media concentrations are yeast extract, 6 g·l-1 and bactotryptone, 2 g·l-1 (instead of 10 and 16 g·l-1 respectively). the other aim of our work was to develop immobilized enzymes suitable for glycerol to propanediol bioconversion and develop a method to measure the immobilized enzymes activity. we tried a covalent method applying chitosan matrix activated with glutaraldehyde. chitosan – a natural polyaminosaccharide obtained from chitin – was chosen as support material to bind the three key enzymes from the crude enzyme solution. we could detect that pdor and gdh enzyme bind to chitosan beads. immobilized enzymes activity was higher than of the soluble enzymes. keywords: glycerol; 1,3-propanediol; enzyme activities; immobilization introduction as glycerol is a nontoxic, edible, biodegradable compound, it will provide important environmental benefits to platform products. glycerol can be converted into industrially valuable derivatives through various ways of biological transformation. there are some important derivatives among these such as 3-hydroxypropionaldehyde (3-hpa), dihydroxyacetone (dha) and 1,3-propanediol (pdo). pdo has the largest potential with more than 100 000 t/yr world production capacity. two examples of large scale applications of 1,3-propanediol are sorona made by dupont applying biopdo produced via biological way and corterra [1], trade mark of shell utilising terephtalic acid (pta) and pdo produced by chemical synthesis (fig. 1). a new recombinant technology [2] was worked out with the leadership of dupont and genencor in the last decade, in wich a recombinant escherichia coli converts glucose directly to pdo. although the fermentative pdo production of dupont is much more environmental friendly than the chemical way, an enzymatic process would be more advantageous. it would not have an upper limit of product yield (which is also decreased by the biomass formation), and would not produce any unwanted metabolites. that is why industrial enzymatic process is usually called “clean technology”. figure 1: basic unit of corterra 84 our research group has been working for several years on a process [3], where glycerol is converted into pdo and dha simultaneously by the enzymes of clostridium butyricum. for this enzymatic way three key enzymes are needed [4]. glycerol-dehydratase (gdht; e.c.4.2.1.30) that produces 3-hpa from glycerol with or without b12 as coenzyme (our clostridium butyricum origin enzyme is b12-independent); 1,3-propanediol-oxydoreductase (pdor; e.c.1.1.1.202) that converts hpa into 1,3-pd using nadh2. in our process the nad+ produced by pdor can be regenerated by a series of oxydoreductases (alcoholdehydrogenase, formate dehydrogenase etc.), but we usually use glycerol-dehydrogenase (gdh, e.c. 1.1.1.6) which produces dha (as the third key enzyme). anaerobic conditions (biebl et al. 1999). clostridium butyricum is to our knowledge the best natural 1,3producer from glycerol [6] and the only microorganism identified so far to use a coenzyme b12-independent glycerol dehydratase. our pleriminary results (not publicated) indicated that the 2xyt medium described by reynauld et al [7] is perfect for the clostridium strain and suitable for enzyme production. however from economic aspect the concentrations of yeast extract and bactotryptone are too high to scale-up this fermentation. one of the purposes of this study was to optimize the fermentation media. immobilization has been revealed as a very powerful tool to improve almost all enzyme properties, if properly designed, like stability, activity, specificity and selectivity, reduction of inhibition effects. immobilized biocatalysts offer some further advantages, like the reusability of the enzymes, the availability of the product in higher purity. chitosan is known as an ideal support material for enzyme immobilization because it is non-toxic, and not harmful to the enzymes. in addition to these, chitosan appears economically attractive since chitin is the second most abundant biopolymer in nature beside cellulose. to carry out enzymatic bioconversions, we have already used successfully a membrane reactor system retaining the enzymes [8-9]. to compare it to other immobilization technics we tried a covalent immobilization method with chitosan matrix. the other aim of our work was to develop immobilized enzymes suitable for glycerol to propanediol bioconversion. materials and methods organism and medium clostridium butyricum ncimb 8082 (the same as vpi 1718) was used as enzyme source. the strain were stored at 4 °c on petri dish on modified reinfored clostridial medium (difco, agar: 12.5 g). batch cultures of c. butyricum were grown anaerobically at 37 °c in 2xyt medium (yeast extract, 10 g·l-1; bactotryptone, 16 g·l-1; nacl, 5 g·l-1), supplemented with 20 g·l-1 glycerol or glucose as carbon source [5]. however, as described under “results”, the concentrations of yeast extract, bactotryptone, glycerol and glucose were varied. analytical methods the cell concentrations were estimated as cell dry weight using a predetermined correlation factor (k: 1.496 g·l-1) between optical density at 600 nm (pharmacia lkbultrospec plus spectrophotometer, pharmacia co., usa) and cell dry weight. substrates and products concentrations were determined by waters breeze hplc system described previously [10]. fermentation experiments batch cultivations are described previously [10, 12] (shown in table 1). samplings (in the cases of test tubes) were realized from different parallel test tubes at the corresponding timepoint, because the need of anaerobic cultivation performed in a closed anaerostat system (merck). the growth temperature was 37 °c, the agitation speed was 200 rpm. preparation of cell-free extracts fermentation broths (from 1-l bioreactor (b. braun biostat® q dcu) and 2-l bioreactor (b. braun biostat® m)) were centrifuged at 6000 rpm for 40 min. for resuspending the harvested cells, hepes buffer ph = 7.4 was applied. this centrifugation/resuspendation cycle was repeated twice. cells were disrupted by ultrasonic desintegration (labsonic-p, 300w; sartorius) [10]. the enzyme activity of supernatant was determined. enzyme assays 1,3-propanediol-oxydoreductase (pdor), glyceroldehydratase (gdh) and glycerol-dehydratase (gdht) activity was determined photometrically using the method described previously [13]. immobilization method chitosan was chosen as support material and enzyme solution including the three enzymes was applied as enzyme mixture. support was prepared by dropping aqueous chitosan solution into 1 n naoh solution containing 25% ethanol. cross linking was carried out with 5% glutaraldehyde in k-phosphate buffer ph 7 (shaked in room temperature, 4 hours). 85 immobilization of the enzymes was performed by shaking the activated chitosan beads with enzyme solution at 10 °c (ph 7.4; support/enzyme solution = 1:2). however, as described under “results”, the time of immobilization were varied. at first chitosan beads are white, after cross-linking green and in the end of immobilization yellow. results fermentation process development to carry out enzymatic bioconversions a large amount of enzyme solution and high enzyme activity is needed. for this, it was neccessary to eliminate the economical bottleneck (costly media) of the scale up process and to select sufficient carbon source and ph regulation. the concentrations of yeast extract and bactotryptone are too high to scale-up this fermentation procedure. at first fermentation experiments were made in shaked test tubes and shaking flasks to determine the optimal concentrations (data shown at chempor2008 [10]). carbon source was glucose or glycerol, ph regulated with k-phosphates or caco3. beside the maximum level of bactotryptone (bt; 16 g·l-1) and two types of substrates we analyzed the effect of yeast extract (ye) concentration (fig. 2a). biomass production decreased significantly below 6 g·l-1 ye. while bt concentration was reduced to 4 g·l-1 at constant ye (10 g·l-1), the biomass was not fallen remarkably (fig. 2b). 0 2 4 6 8 10 0 2 4 6 8 10 yeast extract (g/l) x (g/l) figure 2a: −x− substrate: 20 g/l glucose ··x·· substrate: 20 g/l glycerol 0 2 4 6 8 10 0 4 8 12 16 bactotryptone (g/l) x (g/l) figure 2b: −x− substrate: 20 g/l glucose ···x·· substrate: 20 g/l glycerol further fermentation experiments resulted that the bt concentration can be reduced to 2 g·l-1 beside ph regulation with caco3 [13]. optimized media concentrations are yeast extract, 6 g·l-1 and bactotryptone, 2 g·l-1 with glycerol as carbon source and ph regulation with caco3. for enzyme production we carried out several fermentations in lab scale bioreactor. 1,3-propanediol fermentation scale-up procedure results obtained on glycerol batch cultivation with optimized ye and bt are shown in table 2. table 1:fermentation experiments scale-up (reference) runs test type ye (g·l-1) bt (g·l-1) glu (g·l-1) gly (g·l-1) ferm.1 bq (1 l) 10 16 20 20 ferm. 2 bq (1 l) 10 16 20 runs x (g·l-1) ypd (mol·mol-1) ybp (g·g-1) j (g·l-1·h-1) ferm.1 6.87 0.57 0.24 0.3 ferm. 2 7.94 0.61 0.28 0.4 ph regulation: 20% nh4oh and 25% h2so4 bq (1 l): 1 l bioreactor (b. braun biostat® q dcu) ye: yeast extract; bt: bactotryptone; glu: glucose; gly: glycerol pd: 1,3-propanediol; bp: by products table 2:fermentation experiments scale-up (optimized) runs test type ye (g·l-1) bt (g·l-1) gly (g·l-1) 1 sf(400) 6 2 20 2 bq (1 l) 6 2 20 3 bm (2 l) 6 2 20 runs x (g·l-1) ypd (mol·mol-1) ybp (g·g-1) j (g·l-1·h-1) 1 4.99 0.90 0.42 0.7 2 7.08 0.99 0.34 0.5 3 8.99 0.96 0.28 0.9 ph regulation: caco3, 15.489 g·l-1 sf: shaking flask bq (1 l):bioreactor (b. braun biostat® q dcu) bm (2 l): 2 l bioreactor (b. braun biostat® m) ye: yeast extract; bt: bactotryptone; gly: glycerol pd: 1,3-propanediol; bp: by products all the features of optimized fermentations are better than results of reference fermentations shown in table 1. reference enzyme activities from ferm. 1. and ferm. 2. are shown in table 3. enzyme activities and protein concentrations from run 3 are shown in fig. 3. table 3: enzymes from reference fermentation reference ferm 1. ferm 2. c, protein (mg/ml) 1,16 1.62 pdor (u/ml enzyme sol.) 0.25 0.26 gdh (u/ml enzyme sol.) 0.33 0.026 gdht (u/ml enzyme sol.) 0.63 0.31 sol.: solution 86 pdor activity was 10-times higher than the reference (2.64 u·ml-1 enzyme solution; and 0.25–0.26 u·ml-1 enzyme solution, respectively). gdh activity was not detected from the optimized fermentation broth (reference: 0.33 and 0.026 u·ml-1 enzyme solution; carbon source glucose and glycerol or only glycerol). however gdh is of commercial trade, thus it can be a supplement for the crude enzyme solution. 1,85 2,64 0 0,14 0 0,5 1 1,5 2 2,5 3 c, protein (mg/ml) pdor (u/ml enzyme sol.) gdh (u/ml enzyme sol.) gdht (u/ml enzyme sol.) figure 3: enzyme activities and protein concentration from optimized fermentation enzymes immobilization to carry out enzymatic bioconversions, we already used a membrane reactor system retaining the enzymes [8]. to compare it to other immobilization technics we tried a covalent immobilization method with chitosan matrix. chitosan was chosen as support material and crude enzyme solution from optimized fermentation broth including pdor and gdht enzymes supplemented with commercial gdh was applied as enzyme source. immobilization was carried out as described in “materials and methods”. the enzyme activity measurement method we developed for immobilized enzyme preparations was reported at younghem2008 conference [11]. at first nad+-dependent glucose dehydrogenase (glcdh, e. c. 1.1.1.47) from bacillus megaterium was used as a test enzyme (it has commercial trade). after the process was successfully adapted, the enzyme was changed to the two key enzymes of glycerol metabolism (nad+-dependent pdor and gdh). the production of nadh was monitored by the increase of absorbance at 340 nm and 25 °c. firstly we used one bead in a cuvette (without shaking). in this case we couldn’t detect enzyme activity (data shown fig. 4). as a next step we used not one but ten chitosan beads (with shaking), and measured the absorbance during the reaction in discrete points from given portion of reaction mixture (data shown fig. 5). after volumetric correction the line gradient determined the nadh production rate and the immobilized enzyme activity (data shown fig 6). -0,15 -0,1 -0,05 0 0,05 0,1 0,15 0,2 0 200 400 600 time (s) a340 figure 4: immobilized enzyme activity (one bead) x -: background absorbance ♦ -: nadh absorbance 0 0,4 0,8 1,2 1,6 0 5 10 15 20 25 30 time (min) a340 figure 5: immobilized enzyme activity (ten beads) x -: background absorbance ♦ -: nadh absorbance y = 5,6895x 59,402 r2 = 0,9719 0 40 80 120 160 0 5 10 15 20 25 30 time (min) a340,mod figure 6: immobilized enzyme activity (after volumetric correction) ♦ -: nadh absorbance soluble enzyme activity (u·ml-1) was measured before and after immobilization. enzyme activity on chitosan beads (u·gl-1) was measured in the end of immobilization. the effect of immobilization time was determined. relative activity (%) of immobilized pdor was measured at various immobilization time (1.5; 3; 4.5 and 24 hours; data shown fig. 7). after 24 hours the relative pdor enzyme activity decreased to 25 % of the original activity. 1.5 hours semms to be enough for immobilization. after 1.5 hours imobilization we realised that the immobilized pdor enzyme activity was 100 times higher and gdh enzyme activity was 160 times higher than the soluble enzyme activity (primary activity; data shown fig. 8). 87 relative immobilized pdor activity (%) 0 25 50 75 100 1,5 3 4,5 24 time (hour) figure 7: effect of immobilization time 0,07 10,49 0,113 12,218 0 4 8 12 16 primary activity (u/ml) immobilized enzyme activity (u/g) pdor gdh figure 8: pdor and gdh enzyme activity binding of the third enzyme, gdht to chitosan beads applying the conditions mentioned above has not been proven, yet. only the activity of the soluble enzyme was detectable after the immobilization procedure (data shown fig. 9 and 10).this shows that in case of gdht the applied immobilization process did not assured a certain binding, the process needed further optimization. 0 20 40 60 80 100 0 1,5time (hour) relative gdht activity (%) gdht controll gdht residual figure 9: gdht enzyme activity (experiment 1) 0 20 40 60 80 100 0 1,5time (hour) relative gdht activity (%) gdht controll gdht residual figure 10: gdht enzyme activity (experiment 2) conclusion using clostridium butyricum as an enzyme source our preliminary results indicated that the 2xyt medium is perfect for the cultivation of the bacterium. however from economic aspects the concentrations of organic components are too high to scale-up this fermentation process. examining the culture medium resulted in an optimal composition: 6 g·l-1 yeast extract and 2 g·l-1 bactotryptone with glycerol as carbon source and ph regulation with caco3. to carry out enzymatic bioconversions a large amount of enzyme solution and high enzyme activity is needed. optimized pdor activity was 10-times higher than the reference (2.64 u·ml-1 enzyme solution; and 0.25–0.26 u·ml-1 enzyme solution, respectively). immobilization has been revealed as a very powerful tool to improve almost all enzyme properties. the effect of immobilization time was determined. too long immobilization time caused significant activity lost, 1.5 hours seemed to be enough for immobilization of the pdor enzyme. applying the the 1.5 hour imobilization process the immobilized pdor enzyme activity was 100 times higher and gdh enzyme activity was 160 times higher than that of the soluble enzyme. binding the third enzyme, gdht to chitosan beads has not been proven, yet. references 1. biebl h., menzel k., zeng a. p., deckwer w. d.: microbial production of 1,3-propanediol. applied microbiology and biotechnology (1999) 52, 289– 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(2007) doi: 10. 1016/s1351-4210(07)70046-x focus on surfactants, 2, 4-5 3. sevella b., kupcsulik b., németh á., novák l., poppe l., dukai j., nagy f.: p 05 00961 (2005) 4. papanikolaou s., ruiz-sanchez p., pariset b., blanchard f., fick m.: high production of 1,3propanediol from industrial glycerol by a newly isolated clostridium butyricum strain. journal of biotechnology (2000) 77, 191–208 5. saint-amans s., perlot p., goma g., soucaille p.: high production of 1,3-propanediol from glycerol by clostridium butyricum vpi 3266 in a simply controlled fed-batch system. biotechnology letters (1994) 16, 831–836. 6. biebl h., menzel k., zeng a. p., deckwer w. d.: microbial production of 1,3-propanediol. applied microbiology and biotechnology (1999) 52, 289–297 88 7. reynaud c., sarc. p., meynial-salles i., croux c., soucaille p.: molecular characterization of the 1,3-propanediol (1,3-pd) operon of clostridium butyricum. applied biological sciences (2003) 100(9), 5010–5015 8. németh á., sevella b.: development of a new bioprocess for 1,3-propandiol production i.: modeling of glycerol bioconversion to 1,3propanediol with klebsiella pneumoniae enzymes. applied biochemistry and biotechnology (2008) 144(1), 47–58. 9. németh á., balássy a., sevella b.: difficulties and solutions for the assays of the key enzymes of a new enzymatic glycerol bioconversion. periodica polytechnica chemical engineering (2008) 52, (1), 1–6. 10. balássy a., németh á., sevella b.: a new enzymatical process for glycerol utilization 10th international chemical and biological engineering conference (chempor2008), 2008 11. balássy a., németh á., sevella b.: enzyme immobilization for utilization of biodiesel byproduct glycerol 6th international congress of young chemists (youngchem2008) 12. balássy a., németh á., sevella b.: enzyme production with clostridium butyricum iet biosysbio (synthetic biology, systems biology and bioinformatics) conference cambridge, 2009 13. németh á., kupcsulik b., sevella b.: 1,3propanediol oxidoreductase production with klebsiella pneumoniae dsm2026. world journal of microbiology and biotechnology (2003) 19, 659–663. microsoft word b_18_r.doc hungarian journal of industrial chemistry veszprém vol. 38(2). pp. 143-147 (2010) the examination of the boundary layer formed on the nickel electrode/solution interface in the boundary layer separation method in plastic industrial wastewaters d. pethő-rippel , g. horváth institute of chemical and process engineering, university of pannonia, h-8201 veszprém, hungary e-mail: pethod@almos.vein.hu strict environmental laws limit the emission of wastewaters formed in the manufacturing of plastics. we have developed a new method for the treatment of alkaline wastewaters, which we have given the name boundary layer separation method (blsm). we have utilized the phenomenon that on the surface of an electrically charged electrode, ions can be enriched in the boundary layer, as compared to the liquid phase. the essence of the method is that – with an appropriately chosen velocity – the boundary layer can be removed from the wastewater, and the boundary layer, which is rich in ions, can be recycled. electrosorption is a surface phenomenon, thus the formation of the boundary layer requires appropriate electrodes. nickel pastille electrodes prepared with powder metallurgical methods and nickelized nickel electrodes prepared with electrolysis were used for the experiments. the phenomena on the electorde/solution interface were examined in flowing systems. the discharge of the diffuse part of the boundary layer was examined as the function of the flow rate. it is concluded that it is pointless to exceed the relative velocity of 25 cm/s in the case of nickel pastille electrodes and 10 cm/s in the case of nickelized nickel electrodes. lastly, the ion transport with blsm and the experimental device is presented. electrochemical methods, such as blsm have the advantage of not utilizing dangerous chemicals, only inert electrodes. an additional advantage is that they do not generate further pollutants. keywords: electrosorption, electrochemical double layer, diffuse layer, ion transport introduction the plastic industry in inevitable for the automobile industry. however, during the manufacturing of plastics various gaseous and liquid waste materials are formed, which are regulated by strict environmental laws. the gases are usually cleaned with absorption methods which produces additional industrial wastewaters. alkaline industrial wastewater is formed during the absorption in alkaline absorber towers of pirolysis gases which emerge in the production of olefins. sodium hydroxide is constantly added to the system and the sludge is constantly being removed. the “traditional” wastewater treatment is only capable of removing the organic contents, not the alkaline compounds. the latter poses a considerable threat to the environment. the alkali can be neutralized only to form salt, the emission of which is also strictly regulated by laws of environmental protection. recycling is the most effective technological solution for the treatment of the emerging waste. our aim is to devise a technology that is not only capable of reducing the na+ ion concentration but also of enriching the waste material in another system and reintroducing it into the technology. the pollutants emitted to the environment can be significantly reduced by this method. we have developed a new method for the treatment of industrial wastewaters and given it the name boundary layer separation method (blsm). the method is based on the phenomenon of electrosorption. electrosorption is the absorption process that takes place on the surface of charged electrodes [1]. the electric polarization can be carried out galvanostatically or potentiostatically [2]. generally, the galvanostatic method is favoured in practice [3, 4]. the electrosorption of cations takes place on a cathodically polarized (negative) electrode. this electrosorption is superposed onto the physical adsorption which takes place without charge. if the polarity is reversed, the cations undergo desorption [5, 6, 7, 8]. this phenomenon can be used to produce ion transport with a cyclic method. during electrosorption, an electrical double-layer forms on the electrode-solution interface. the electrical double-layer has two main parts: the helmholtz-layer and the diffuse layer. if the electrode is moved, the diffuse layer might be torn apart, producing a zetapotential between the stationary and the moving parts. the essence of blsm is that – with an appropriately chosen velocity – the boundary layer can be removed from the wastewater, and the boundary layer, which is rich in ions, can be recycled. electrochemical methods such as blsm have the obvious advantage of not utilizing additional hazardous chemicals, only inert electrodes. they also do not 144 generate pollutants. the electrochemical parameters can be measured and adjusted readily. electrosorption is a surface phenomenon. it can only be utilized with good efficiency if the surface area of the electrode is high. mostly, porous carbon electrodes with high specific surface areas are used [9, 10, 11, 12, 13, 14, 15]. electrodes of high surface area can also be made of metals. with the reduction of nio, co3o4 and fe2o3 with hydrogen, macroporous ni, co and fe can be produced [16]. porous ni, cu, ag, pt and au can be produced by precipitating the metal onto colloidal silicic acid [17]. silicon-dioxide is removed with hf after calcination. among electrochemical methods, the production of platinized platinum is well-known. high specific surface area “black” or “gray” nickel electrodes can be made by the same method [18, 19]. the high surface area is not always an advantage because if the pore size distribution is not adequate, parts of the surface might become electrochemically inaccessible. with the use of electrosorption, inorganic [20] and organic ions, such as thiocyanate [1], pyridine [2], aniline and bipyridines [3] can be removed from aqueous solutions. among the practical applications wastewater cleaning [22] and water desalination [23, 24, 25] are remarkable. experimental porous nickel working electrodes, which were produced by powder metallurgical methods, and nickelized nickel electrodes, which were produced electrochemically, were used for the experiments [26]. the experiments were carried out with 0.2% (m/m) naoh model solutions. the phenomena were also proven with 2% (m/m) naoh solutions and actual industrial wastewater. the na+ ion concentration was determined with an aa-6601f type atomic absorption flame emission spectrophotometer (shimadzu corporation, analytical instrument division, kyoto, japan) in emission mode. the samples for analysis were prepared with the mixture of nitric acid:distilled water (1:5). the examination of the diffuse part of the electrochemical double layer if the electrode and the solution move relative to each other, the diffuse part of the double layer is torn and a zeta-potential emerges. the value of the zeta-potential is a function of the velocity of the shift in space, i.e. how fast the electrode is taken out of the solution, or how fast the liquid flows around the electrode. we examined, how the zeta-potential (and thus the place where the double layer is torn) changes as the function of the flow rate of the liquid. the experiments were conducted with nickelized nickel and then also with nickel pastille electrodes. for the measurement of the zeta-potential, we constructed the device illustrated in fig. 1. figure 1: measurement of the zeta-potential, where: r = 15 mm, x = 15 mm, l = 40 mm, 1. cathode, 2. anode, 3. auxiliary electrode the nickel electrodes were mounted in a plastic (pvc) pipe (r = 15 mm) equidistant from the centerline, so that the distance between them is x = 15 mm. a continuous potential difference was introduced between the cathode (1) and the anode (2). the cations are in excess in the diffuse layer of the cathode, whereas the anions are in excess in the diffuse layer of the anode. 0.05 m naoh solution was being flowed in the system at all measurements in the direction given by the arrow. the flow rate was constantly being increased. the stripping of the diffusion layer was followed by putting (plane platinum) auxiliary electrodes before and behind the examined electrodes. the potential difference, the so-called space potential was measured between the auxiliary electrodes (3) as the function of the liquid’s laminar flow rate at different polarization potentials. since a potential difference can be measured between the auxiliary electrodes, the diffusion layer must be able to be gradually swept off with the flowing liquid. the measured space potential is in proportion with the amount of ions that were swept off. fig. 2 illustrates the experiments conducted with the nickel pastille electrodes. 0 20 40 60 80 100 120 140 0 10 20 30 40 50 60 70 80 90 100 v (cm s-1 ) z et a po te nt ia l ( m v ) 1000 mv 1200 mv 1600 mv 2000 mvl 2400 mv figure 2: zeta-potential as the function of the flow rate of the liquid, with porous nickel pastille electrodes the results show that at low flow rates and polarization potentials between 1000 and 2000 mv, the measured zeta-potential values increased rapidly. this leads to the conclusion that most of the ions are swept off. the zetapotential is however, a linear function of the flow rate at 2400 mv polarization potential. a firmly adhering diffusion layer is formed which is harder to be swept off. the zeta-potential does not change significantly below 2400 mv above 25 cm/s linear velocity. it is pointless to use a higher relative velocity in the given system. 145 fig. 3 illustrates the experiments conducted with the nickelized nickel electrodes. 0 20 40 60 80 100 120 140 160 0 10 20 30 40 50 60 70 80 90 100 v (cm s-1) z et a po te nt ia l (m v ) 1000 mv 1200 mv 1600 mv 2000 mv 2400 mv figure 3: zeta-potential as the function of the liquid’s flow rate with nickelized nickel electrodes compared to the nickel pastille electrodes it can be concluded, that most of the ions tear off even at low flow rates, irrespective of the polarization potential. it is thus unadvantageous to have a relative velocity of higher than 10 cm/s in systems using nickelized nickel electrodes. by examining fig. 2 and 3, it can be observed that the steepness of all the diagrams turn to negative at 70–80 cm/s flow rates, that is to say the end of the diagram breaks. before examining this phenomenon, one has to make sure that it is really the because of the behavior of the diagram and not because of a systematic error. for proving the formers, the device was modified as follows: first the anode then the cathode in the pipe (fig. 1) were changed to nickel plate electrodes that have minimal surfaces. this way the discharge velocity of both the anions and the cations could be measured separately at a given potential (1200 mv). no other parameters of the measurement were changed. fig. 4 illustrates the anodic and cathodic polarization diagrams gained in the measurement with nickel pastille and nickelized nickel electrodes. the experimental results show well the difference between the discharge of the cations and the anions. the tendencies are the same for both electrodes. according to the cathodic polarization diagram, the cations can be swept off of the surface easily even at low flow rates. by increasing the flow rate, the curve becomes constant, indicative of the total discharge of the diffusion layer. by examining the anodic polarization diagram, we experienced that a bigger force is needed to sweep off the anions. the discharge process also commences rapidly, but its extent is significantly lower. the potential difference as the function of the flow rate does not become steady between the measuring limits. in the interval, where the cathodic diagram becomes constant, the anodic diagram is linear. this is because the anions do not have hydration shells, which would make a tighter fit possible in the diffusion layer. also, the anions can get closer to the surface of the adsorbent because they lack the hydration shell. this experiment proves the phenomenon of specific adsorption: the anions bond to the surface not only by electric attraction, but also by specific adsorption (e.g. van der waals-bonding). -150 -100 -50 0 50 100 150 200 250 300 350 0 20 40 60 80 100 v (cm s-1) ze ta p ot en tia l ( m v) nickel pastille electrode cathodic polarization nickel pastille electrode anodic polarization nickelized nickel electrode cathodic polarization nickelized nickel electrode anodic polarization figure 4: the anodic and cathodic polarization potentials as the funcion of the flow rate since the experimental setup was the same for the measurement of the anion and cation discharge potentials, the points in the curves were added. the expected tendency can be seen on fig. 5. 0 20 40 60 80 100 120 140 0 20 40 60 80 100 v (cm s-1) ze ta p ot en tia l (m v ) nickel pastille electrode nickelized nickel electrode figure 5: the sum diagram of the anodic and cathodic polarization potentials the difference in potentials decreases at higher flow rates in the sum diagrams. the steepness of the diagrams however, becomes negative at lower flow rates than in the previous measurements, the diagrams of which are in fig. 2 and 3. the reason for this is that electrodes were placed differently in the two measurements which caused different flow circumstances. with experiments we confirmed that the break in the diagrams is not due to measurement error, but to the different nature of anions and cations. experiments in flowing systems the experimental setup is illustrated on fig. 6 [27], where 1. is anode compartment, 2. is cathode compartment, 3. is graphite counter-electrodes, 4. is mobile working electrodes, 5. is lever, 6. is driven axle, 7. is program dial, 8. is electric motor, 9. is microswitches. the two compartments form the chemical cell below. the compartment, where the fix counter electrode is switched as the anode is called the anode compartment, whereas the moving working electrode is switched as the cathode. the compartment, where the fix counter electrode is switched as the cathode and the moving 146 working electrode is the anode, is called the anode compartment. figure 6: the automatic electrosorption device the operation is cyclic, one cycle is composed of the following sub-operations. the high area nickel electrodes are immersed into the solution of the anode compartment, between the graphite counter electrodes. the cell which is thus formed, is given a polarization potential so that the working electrode is the negative (cathode) and the counter electrode is the positive (anode). the positively charged ions then move to the working electrode and absorb on it surface. this is the electroadsportion phase. the saturation of the working electrode can be followed by measuring the current that flows through the cell. when the electrosorption process concludes, the working electrode is taken out of the anode compartment together with the boundary layer rich in ions, and the polarization potential is switched off. the electrode is then immersed into the other solution (the cathode compartment), where the polarity is reversed. the working electrode becomes the positive, the counter electrodes in the other cell the positive ones. the ions are desorbed from the surface of the working electrode because of the electrical repulsion and get into the solution. this process can also be monitored by measuring the current that flows trough the cell. the working electrode is taken out of the solution, the potential switched off, and the electrode immersed into the anode compartment once again. by using the appropriate cycle, a concentration difference can be achieved between the anode and the cathode compartments. by mass transfer, the amount of ions transferred from the anode to the cathode compartment at the given parameters is understood. at the cyclic procedure, the values can be given in units of mg/(m2×cycle). the experimental device is capable of measuring flowing systems. in the experiments the liquids in both the anode and the cathode compartments were recycled with the help of peristaltic pumps. during this, the working electrodes were being displaced from one compartment into the other in the given operational time. the extent of the ion transport was examined as the function of the flow rate. fig. 7 illustrates the experimental results. the mass transfer significantly decreases with both electrodes by increasing the flow rate. 0 50 100 150 200 250 300 350 400 450 0 10 20 30 40 50 60 v (cm s-1) m as s tra ns fe r ( m g n a+ m -2 c yc le -1 ) nickelized nickel electrode nickel pastille electrode figure 7: the extent of mass transferas the function of flow rate in the case of nickelized nickel and nickel pastille electrodes in the case of nickelized nickel electrodes, linear speeds of some centimeters per second were enough to sweep off all the excess ions of the surface of the electrode. a similar phenomenon can be observed in the case of pastille electrodes, but, as previously observed, its extent is smaller. we got a similar diagram when the decrease in the reduced transfer was plotted as the function of the flow rate (fig. 8). for this we defined the mass transport at the flow rate v = 0, and the deviation from this was calculated as percentage giving the decrease in the reduced transfer at the measured velocities. 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 v (cm s-1) r ed uc ed tr an sf er d ec re as e (% ) nickelized nickel electrode nickel pastille elctrode figure 8: reduced transfer decrease with nickelized nickel and nickel pastille electrodes the experiments prove that the decrease in reduced transport increases with the increasing flow rates, its extent reaching 100% with nickelized nickel electrodes at 10 cm/s; and at 30 cm/s with nickel pastille electrodes. after this, the ion transfer is zero, the flowing liquid sweeps all the excess ions off of the surface of the electrode. it was concluded that for the sake of higher mass transfer, the lowest possible flow rate should be used for the liquid. 147 summary a new method has been devised for the treatment of industrial wastewaters which we have given the name boundary layer separation method (blsm). we have utilized the phenomenon that on the surface of an electrically charged electrode, ions can be enriched in the boundary layer, as compared to the liquid phase. the electrodes are removed from the wastewater with an appropriately chosen velocity in a way that the ionrich boundary layer remains on its surface. by placing this boundary layer into another phase, separation is realized. nickel pastille electrodes prepared with powder metallurgical methods and nickelized nickel electrodes prepared with electrolysis were used for the experiments. by measuring the zeta-potential, we proved that if the electrode and the solution move relative to each other, the diffuse part of the double layer is torn, affecting the efficiency of the separation. we concluded that it is pointless to exceed the relative velocity (between the solution and the electrode) of 25 cm/s in the case of nickel pastille electrodes and 10 cm/s in the case of nickelized nickel electrodes. ion transport can be realized with the boundary layer separation method, for which we constructed a device. the device is capable of measuring flowing systems as well. the ion transport changed as the function of the flow rate in accord with the results gained in the measurements of the zetapotential. the ion transfer is approximately zero beyond the limit velocities given. the method, called blsm by us, is novel from a technical point of view. we have already applied for a patent at the hungarian patent office [27]. acknowledgement the authors express their gratitude to the institute of chemical engineering cooperative research center of the university of pannonia for the financial support of this research. references 1. c. rong, h. xien: j. colloid interf. sci., 290, 2005, 190–195. 2. j. niu, b. e. conway: j. electroanal. chem., 521, 2002, 16–28. 3. j. niu, b. e. conway: j. electroanal. chem., 536, 2002, 83–92. 4. a. vaškelis, e. norkus, j. stalnioniene, g. stalnionis: electrochim. acta, 49, 2004, 1613–1621. 5. a. afkhauni, b. e. conway: j. colloid interf. sci., 251, 2002, 248–255. 6. y. xu, j. w. zondlo, h. o. finklea, a. brennsteiner: fuel process. technol., 68, 2000, 189–208. 7. j. c. farmer, d. v. fix, g. v. mack, r. w. pekala, j. f. poco: j. electrochem. soc., 143, 1996, 159–169. 8. e. ayranci, b. e. conway: anal. chem., 73, 2001, 1181–1189. 9. e. bayram, n. hoda, e. ayaranci: j. hazard. mater., 168, 2009, 1459–1466. 10. l. pan, x. wang, y. gao, y. zhang, y. chen, s. zhuo: desalination, 244, 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word b_07_felho_r.doc hungarian journal of industrial chemistry veszprém vol. 39(2) pp. 189-193 (2011) method for determination of the expected roughness of cut surfaces c. felho , j. kundrak university of miskolc, department of production engineering, h-3515 miskolc, egyetemvaros, hungary e-mail: csaba.felho@uni-miskolc.hu nowadays the manufacturing companies create stricter and stricter demands on quality requirements of surfaces machined by cutting. the fulfilment of these requirements is often not an easy task, and in addition technologists should deal with the economic aspects too. surface roughness indexes are important parameters in characterization of the quality of parts, especially in case of engaging and sliding one another machine elements influences remarkably their tribological properties and lifespan. therefore it is indispensably important to completely satisfy the surface roughness requirements. it can mean a great help, if the prospective value of roughness indexes can be predicted in advance for the actual machining environment, since the selection of the optimal tool-geometrical and technological parameters become possible. such a method will be introduced in the paper, by the help of which theoretical values of surface roughness can be determined for single point cutting by the help of an analytical model. a general mathematical model is introduced, by the help of which edge geometry of every realistically evolving tool can be described. theoretical values of the relevant roughness indexes used in practice can be calculated by the application of this model. the connection with the real roughness data gained by experiments can be written down after this, hereby the surface roughness can be predicted, and thus the planning of technology can be faster and more efficient. keywords: surface roughness, theoretical roughness. introduction the accelerated technological evolution, the higher and higher quality requirements demanded for machine parts are provoked increased claims also against manufacturing technologies. this fact is especially prevalent in the automotive industry. more and more tasks are automated, and increasing number of characteristics is described by theoretical and computer models. one important factor for the characterization of surface quality is the microgeometry of the surface profile. the microgeometry can be quantified by practically selected roughness indexes. the determination of theoretical values of surface roughness in different metal cutting processes has been in focus since about a half century. a variety of theories were created, and the problem was examined by many kinds of aspects. the determination of theoretical roughness is important for technologists, since the expectable value of real roughness can be predicted for a given procedure, and thus it can provide help for the computer aided planning of manufacturing processes. benardos and vosniakos [1] have made a good review about the research works created in this field. they have classified the papers to four categories: analitical, based on designed experiment, experimental and ai-based works. based on their work, main research groups dealing with surface roughness are shown in table 1 as it can be seen from the table, there are several different solutions to this problem, and each has its own advantages and drawbacks [2]. the set of parameters that are thought by benardos and vosniakos in [1] to influence surface roughness and thus have been investigated by researchers is diagrammatically represented in fig. 1. a theoretical model is introduced in the article by the help of which the theoretical value of roughness indexes used in practice can be determined for every realistically feasible cutting tool design. through the examination of theoretical roughness it is assumed, that the imprint (negative) of the part of the tool which is near to the nose will remain in the machined surface, and that will form the surface roughness profile, and this geometry can be calculated from the tool-geometrical and technological parameters. 190 surface roughness cutting tool properties machining parameters workpiece properties cutting phenomena workpiece length workpiece hardness workpiece daimeter cutting force variation friction in the cutting zone chip formation vibrations accelerat ions nose radius runout errors tool material tool shape process kinematics cooling fluid stepover depth of cut tool angle feed rate cutting speed figure 1: fishbone diagram with the parameters that affect surface roughness [1] table 1: main research groups dealing with modelling of surface roughness according to benardos&vosniakos [1] modelling procedures and techniques currently active research groups summary of the present status main disadvantages of the method analytical models or computer algorithms grzesik; lin and chan; baek et al.; chen et al.; ehmann and hong; kim and chu; lee et al. ● these ones simulate the cutting process in terms of kinematics and cutting tool properties. ● often includes other parameters (e.g.. vibration) ● the obtained results are fairly good. a lot of other factors that contribute to the roughness formation mechanism are not considered (wear and deflection of the cutting tool or certain thermal phenomena). based on experiments abouelatta and madl; ghani and choudhury; jang et al.; beggan et al.; dhar et al.; munozescalona and cassier; thielle and melkote; baptista and antune simoes; coker and shin; diniz and filho; heisel ● this is the most conventional approach adopted. ● it is not difficult to implement and depending on the level of understanding of the participating phenomena, it can produce very good results. the obtained conclusions have little or no general applicability. based on designed experiments davim; choudhury and elbaradie; feng and wang; kopac and bahor; thomas and beauchamp; alauddin et al.; fuh and wu ● the response surface methodology (rsm) and the taguchi techniques for design of experiments (doe) are the mostly used methods. the obtained relation has no general applicability. based on artificial intelligence (ai) azouzi and guillot; varghese and radhakrishnan; chien and chou; suresh et al.; lee et al.; li et al.; oxley; lin et al.; matsumura et al.; benardos and vosniakos; tsai et al.; lou and chen; ho et al. ● generally the artificial neural network (ann) models or genetic algorithms (ga) are used. ● these can produce very good results and simultaneously offer the possibility for online monitoring and/or control of the process. ● it is very demanding on computational power. ● there is no guarantee for their resulting performance in an application. 191 model for the calculation of theoretical roughness indexes in single point cutting a new mathematical model was developed for the analytical calculation of theoretical roughness indexes in turning operations [3]. the examined roughness parameters were rmax, rz, ra and the tp bearing ratio, however, one great advantage of this model is, that it is possible to calculate virtually all roughness parameters used in practice. the calculation method is introduced for turning cylindrical surfaces, but the model can be easily transformed for cutting other types of surfaces and for other processes, e.g. to face milling. as it was observed from the literature overview, all of these analytical models were created with several simplifications, since there are too much factors affecting the real roughness profile [4]. the most important simplifications which were applied to our model are: ● the workpiece material is un-deformable in the machined surface; ● the cutting system is fully rigid; ● the cutting edge of the tool is a defined geometrical line. figure 2: the overview of the applied method the effect of these parameters can be built into the model by modifier factors. series of experiments has to be performed for this, and the effect of the actual parameter can be measured and quantified. an overview of the applied calculation method is depicted in fig. 2. the essence of this calculation method is to create the general mathematical model of the single point cutting tools which have all of the possible edge sections a practically feasible tool can have. by putting this imaginary tool to an x-y coordinate system with the intersection point of the main and the auxiliary edge (the tool peak point) in the origin, the respective edge sections of the tool can be described by coordinates and emplacement angles (fig. 3). the general cutter profile can be described with the following equation: ( )1 1 1l f , , , , ,′ ′′ ′ ′′= l l l l l l (1) where: ℓ, ℓ´, ℓ˝ – sections of the main edge; ℓ1, ℓ1´, ℓ1˝ – sections of the auxiliary edge. x y 1 2 3 4 5 6 7 r " ' 1 1' 1" κ r2 κ r1 κr 1´ κr 2´ x3 x5 x2 x6 x1=h1 x7=h2 y1 = h 3 y7 = h 4 y6 y5y3 y2 figure 3: the general tool in the coordinate system edge sections of the main edge can be described with the following equations: 2 2 4 3 r 1 3 2 r 2 2 2 1 r r x ; x x x tg x b ; x x x tg x b ; x x x = − − ≤ < ′ = κ ⋅ + ≤ < ′′ = κ ⋅ + ≤ < l l l (2) edge sections of the auxiliary edge can be written as: 2 2 1 5 4 1 r 1 1 6 5 1 r 2 3 7 6 r r x x x x tg ' x b ; x x x tg ' x b ; x x x ; κ κ = − − ≤ < ′ = + ≤ < ′′ = + ≤ < l l l (3) the geometry of the actual tool can be deducted from this general model by the appropriate substitution of function parameters. the roughness profile can be calculated by making a profile shift in the feed direction by the feed rate value (fig. 4). as it can be seen from the picture, the auxiliary edge sections of the forwarded tool (yaux1, yaux2 and yaux3, depending on the feed value) and the main edges of the tool in the origin (ymain1, ymain2, ymain3) are forming the 192 roughness profile. the presented model assumed that a cylindrical surface will be generated. in case of conical turning, the profile shift has to follow the taper edge. x y f 1' 2' 3' 4' 5' 6' 7' p 1 2 3 4 5 6 7 ymain1 ymain2 ymain3 yaux1 yaux2 yaux3 figure 4: typical points of the idealized roughness profile, main and auxiliary edges the next step is to calculate the intersection point p of the main and auxiliary edges. this can be performed by calculating the x,y coordinates, where the equations of the respective edge sections have equal values: yaux n = ymain m. the yp ordinate of this p point gives the maximal height of roughness profile (rmax) if the depth of cut (ap) is greater than the ordinate of this point, or if ap > yp, then rmax = ap. in conical turning, the distance of the rz value (ten-point height of the profile) is equal to this calculated rmax value in the theoretical profile, since there are no deviations. the calculation of the mean line of the profile, which has equal areas below and above is needed for the determination of ra and tp values. this can be done by the least-square approximation method. the ra value can be calculated from the generalized equation ( ) l 0 a 1 r y x dx l = ⋅ ∫ (4) the material ratio tp can be calculated from the following equation: ( )pm pf p x x t 100 [%] f − = ⋅ (5) where: xpm, xpf – intersection points of the profile sectioning level p with the main and the auxiliary edges respectively. the actual surface micro-profile is significantly different from the theoretical value, and it loses its regular character. this can be accounted by the following [5]: ● the material is plastically flows in the near of the peaks of the profile, the bigger is the plastic strain, the greater is the surface roughness; ● the workpiece and the tool are in mutual vibration during the cutting; ● the flank surface of the tool is rubbing against the machined surface; ● the tool edge is differing from the geometrical line which was taken as basis, and it has its own irregularities, and the tool wear is just amplifies this effect; ● in case of built-up-edge the quality of the surface is usually deteriorating. the real (expected) value of the surface roughness can be calculated (forecasted) from the theoretical value [6]. the method for this forecasting is the following: ● perform experiments with the tool geometries and technological data according to our needs, and then measure the generated profile by surface tester equipment. ● the connection between the measured and the calculated roughness data can be calculated by regression analysis. the most accurate approximation can be made by power functions in the form [7]: b real theoreticalr a r= ⋅ (6) where: rreal – the dependent variable; rtheoretical – the independent variable; a, b – coefficients. it can be seen from the introduced method, that this is a very computing-demanded task, and therefore it is advisable to make a computer program for the calculation of theoretical values. thus the calculation can be automated. the software is still under development, and at the time of writing this article, it is able to calculate the theoretical values in turning cylindrical surfaces. it is important to verify the theoretical calculations by experiments; therefore the accuracy of the prediction can be determined. the experimental validation of the introduced model will be the next step of this research work. conslusions the theoretical value of surface roughness in single point cutting can be determined by the method introduced in the article for turning cylindrical surfaces, and for turning conical surfaces with little modifications. the experimental validation can confirm the accuracy of the model. the method can be also improved for multi-point cutting procedures. the calculated theoretical roughness values can be used to predict the real roughness values for a given procedure, and for the tool/material pairs which were experimentally investigated. 193 acknowledgements the described work was carried out as part of the támop-4.2.1.b-10/2/konv-2010-0001 project in the framework of the new hungarian development plan. the realization of this project is supported by the european union, co-financed by the european social fund. the work was presented by the support of the hungarian scientific research fund (number of agreement: otka k 78482 and otka 84177), which the authors greatly appreciate. references 1. p. g. benardos, g.-c. vosniakos: predicting surface roughness in machining: a review, international journal of machine tools and manufacture 43, (2003), 833–844 2. c. lu: study on prediction of surface quality in machining process, journal of materials processing technology 205, (2008), 439–450 3. j. kundrak: increasing the effectiveness of machining by application of composite tools in boring of cylindrical and polygon surfaces (in russian). csc dissertation, tula 1986, p. 315 4. m. c. shaw: metal cutting principles, oxford university press, new york, usa, 1984, p. 256 5. j. bali: forgácsolás, budapest, tankönyvkiadó, 1988, p. 538 6. v. bana: manufacturing of high precision bores, phd dissertation, delft, 2006, p. 149 7. j. kundrak, c. felho: roughness designeability of surfaces machined by cutting, icpm2009, september 15-19, 2009, stara lesna, slovakia, 107–112 editorial hungarian journal of industry and chemistry veszprém vol. 42(1) pp. 1–5 (2014) comparative assessment of the mussel micronucleus test versus bacterial bioassays for genotoxicity testing of benzo[a]pyrene bettina eck-varanka,1! eszter horváth,1 árpád ferincz,1 gábor paulovits,2 and nóra kováts1 1 department of limnology, university of pannonia, egyetem str. 10, veszprém, h-8200, hungary 2centre for ecological research, hungarian academy of sciences, balaton limnological institute, klebelsberg k. str. 3., tihany, h-8237, hungary !e-mail: kovats@almos.vein.hu polycyclic aromatic hydrocarbons are hazardous compounds to the environment and human health, thus their detection is an important task. in this study the genotoxic effect of benzo[a]pyrene (b[a]p) was examined on a freshwater mussel unio pictorum and results were compared to bacterial tests, such as the ames test and sos chromotest. the aim of the study was to calibrate the sensitivity of the mussel micronucleus test to that of the two bacterial tests using b[a]p as a reference chemical. the ames and the micronucleus tests gave similar response both in sensitivity and in concentrationresponse pattern. these two tests are proposed to be applied in a battery for genotoxicity testing. keywords: micronucleus test, ames fluctuation test, sos chromotest, pah introduction polycyclic aromatic hydrocarbons (pahs) are ubiquitous widespread contaminants. the us environmental protection agency (epa) created a list of priority pollutants that have the greatest concern due to potential exposure and adverse health effects on humans. there are 16 pahs on this list, of which the most hazardous are acenaphthene, fluoranthene, naphthalene, benzo[a]anthracene and benzo[a]pyrene [1]. these compounds have proven to have carcinogenic and mutagenic effects on animals and humans, hence their regulation is very important [2]. major sources of pahs are internal combustion engines, residential heating, incineration, and coke production. there are also natural sources, such as forest fires or volcanoes. pahs are present in the atmosphere as gas and/or particulate phases and might be transported to other environmental compartments such as soil, sediment, and water via dry or wet deposition. heavier pahs, such as benzo[a]pyrene (b[a]p), are almost totally adsorbed onto particles. their further environmental fate in solid compartments is mostly influenced by their low water solubility. however, once taken up by the organism, the detoxification mechanism converts these compounds into more soluble molecules. it was shown that the seawater bivalve, mytilus sp. can activate b[a]p to mutagenic compounds and produce reactive oxygen species (ros) [3]. for assessing environmental exposure, benzo[a]pyrene seems to be a good indicator, due to the strong correlation between b[a]p and other pahs [4]. in iarc monograph volume 3 it was concluded that benzo[a]pyrene produced tumours in a wide range of animals tested, following exposure by many different routes (oral, dermal, inhalation, intratracheal, intrabronchial, subcutaneous, intraperitoneal, intravenous). it had both a local and a systemic carcinogenic effect [5]. there are various reasons why the genotoxicity of pahs as well as of other mutagenic compounds is tested on mussels. first of all, bivalves are sedentary creatures, being exposed to both water and sediment contamination. secondly, their ability to bioaccumulate contaminants is well known and widely used in biomonitoring studies. actually, the fact that they can not only bioaccumulate waterborne mutagens, but also metabolise them into active forms, on one hand increase their usefulness in these studies but on the other hand may enhance the potential risk to consumers [6]. of genotoxicity markers, the micronucleus test (mn) is the most widely established, relatively easy-toperform test. micronuclei formation indicates chromosomal dna damage occurring as a result of either chromosome breakage or chromosome missegregation during mitosis [7]. banni et al. used digestive gland cells of the marine mussel mytilus galloprovincialis in an acute test. in this assay, mussels were exposed to 75 nm b[a]p for different exposure time. micronucleus frequency started to show significant response after 24 hours exposure, reaching the maximum after 72 hours [8]. woznicki et al. also tested b[a]p genotoxicity using the mn test, but 2 on another species, the freshwater sinanodonta woodiana (referred to anodonta woodiana in the original article) [9] in which the time-dependency of ecological effect was demonstrated. maximum micronucleus formation was experienced after 4 days of exposure, but after it started to decrease, most possibly due to adaptive mechanisms. the mussel micronucleus (mn) test has also been used in real-world environments, especially for detecting contamination from oil spills. bolognesi et al. demonstrated that even 10 years after the wreck of the tanker haven at the ligurian coast of italy, micronucleus frequency in caged oysters was a reliable way to detect the release of genotoxic compounds [10]. martins et al. assessed genotoxicity of sediment containing pahs and metals after dredging operations. the sediment previously was classified as ’trace contaminated’, but dredging modified the mobility of pollutants, which was clearly visible in the mussel mn test [11]. in addition to the mn test for eukaryotic organisms, which results in chromosomal damage, several bacterial tests are also available for screening purposes due to their rapid response and short exposure time. the sos chromotest is a short-term, enzymatic colorimetric assay for the detection of the presence of genotoxic compounds using escherichia coli pq 37 strain as described by quillardet et al. [12]. the sos system is a complex, dna-damage activated response under the regulation of the sos promoter. in e. coli pq 37 the only functioning β-galactosidase gene (lacz) is fused to the bacterial sfia sos operon. thus, sos response initiates lacz transcription, and β-galactosidase activity is detected spectrophotometrically by the addition of x-gal (5-bromo-4-chloro-3-indolyl-β-dgalactopyranoside) [13, 14]. the ames bacterial reverse mutation assay applies genetically engineered strains of salmonella typhimurium. the method is based on the chemical triggered reversion of histidine producing ability of the strains, enabling them to grow on histidine free medium. several different methods have been developed, including the plate incorporation assay, the preincubation method, and the fluctuation test [15–17]. the ames fluctuation test is a microplate adapted version of the salmonella reverse mutation assay with a ph change indicated colorimetric endpoint. this method is suitable for the screening of large numbers of samples, and because of its sensitivity it is ideal for water sample testing [18]. the ability of both the sos chromotest and the ames test to detect genotoxicity of b[a]p has been long established [19, 20]. b[a]p was also used as a reference chemical for calibrating the newt micronucleus test or jaylet test [21]. the correlation between the genotoxic substances and the number of micronuclei in an organism has been used in water toxicological tests since the 1980’s [22]. the micronuclei are small bodies containing dna parts that appear near the nucleus as a result of chromosome breakage or mitotic spindle dysfunction. this process can occur without external factors as well, but the effect of genotoxic substances made a far greater number of micronuclei than normal. therefore the micronuclei frequency may characterise the extent of genetic damage that accumulate over the life of the individual [23]. the mn test, performed on freshwater mussel species, is widely distributed for assessing genotoxic effects triggered by environmental pollutants [24, 25]. still, the micronucleus test has gained relatively low attention in hungary, therefore a native freshwater mussel, unio pictorum was introduced as test organism. main aim of the study was to calibrate this test also using b[a]p as reference chemical, by comparing its sensitivity to that of the bacterial assays. materials and methods test organisms unio pictorum specimens were collected from lake balaton and were kept in a flow-through aquarium. water source was lake balaton water, therefore not only proper oxygenation was ensured, but a constant food supply as well. animals were acclimatized for 4 weeks prior to testing. test conditions and treatment the assay was performed based on the protocol described by wozniczki et al. with some modifications. a b[a]p stock solution was prepared in acetonitrile in 1 mg cm-3 concentration for the following series: 70 µg dm-3, 175 µg dm-3, 350 µg dm-3 and 700 µg dm-3. for solvent control 0.07% acetonitrile was used, and solvent quantity was adjusted to 0.07% in each treatment. u. pictorum specimens with length of 5–8 cm were used. treatments were performed in triplicates. for each concentration and for the controls, the volumes of the aquaria were 3 l. they were aerated during the experiment and temperature was set at 22 oc. exposure time was 4 days. micronucleus test after 4 days, haemolymph was taken from the posterior adductor using the non-lethal technique described by gustafson et al. [26]. a 1 ml aliquot of haemolymph was mixed with 0.3 ml, 10% acetic acid in methanol as a fixative and centrifuged at 1000 rpm for 5 minutes. the supernatant was discarded and the rest was fixed in 1 ml 80 % ethanol. in this way the sample can be kept refrigerated for several weeks. for processing the samples, refrigerated samples were centrifuged again at 1000 rpm for 5 minutes. the supernatant was discarded and the pellet containing the cells was smeared onto a microscope slide and allowed to dry. after that the slides were fixed in 80 % methanol, dried and stained with 5 % giemsa in distilled water for 20 minutes. photos were taken by a zeiss axioscope a1 microscope with an axiocam icc1 camera and zen 2011 program at 400x magnification. micronuclei were 3 identified according to fenech [27]. for each animal 250 cells were counted. one-way anova with tukey post hoc test was used to compare the mean mn numbers between the treatments. for sos chromotest the sos chromotest tm kit (ebpi – environmental bio-detection products inc.) was used according to the manufacturer’s instructions, and in compliance with the oecd guidelines no 471:1977 [28]. b[a]p concentrations were 1400 µg dm3, 700 µg dm-3, 350 µg dm-3, 175 µg dm-3, 87.5 µg dm-3, 43.75 µg dm-3, 21.88 µg dm-3, 10.9 µg dm-3, 0 µg dm-3. acetonitrile concentration was adjusted to 0.07% in each sample, and an additional dmso solvent control was also used. the absorbance of samples was detected on 615 and 405 nm with diareaderelx800 elisa device. the sos repair system induction was measured by the calculation of induction factor (if) and induction potential (sosip) according to krifaton [29]. samples with 1.5 or higher if were considered genotoxic. ames test the fluctuation ames test was performed according to hubbard with slight modification. in short, salmonella typhimurium ta100 cells were pre-cultured overnight in nutrient broth (oxoid) on 37 ºc. cells were washed twice in davis minimal medium (67.4 mm po4 3-, 8.38 mm so4 2-, 15.1 mm nh4 +, 5.1 mm na+, 98.1 mm k+, 0.83 mm mg2+, 1.7 mm citrate, 139 µm glucose 10 µg cm-3 histidine, 0.1 mg cm-3 d-biotin) and cell number was adjusted to 106 cells cm-3. b[a]p was added to the samples in 700 µg dm-3, 350 µg dm-3, 175 µg dm-3, 70 µg dm-3 and 0 µg dm-3 and acetonitrile concentration was adjusted to 0.07%. samples were distributed in 200 µl volumes to 96 well microplates. cell free control, a solvent free negative control, and a positive control with 0.5 µg cm-3 concentration nan3 were also applied. plates were incubated in humid chamber for 72 hours in 37 ºc. on the day of evaluation 20 µl of 2 mg cm-3 aqueous solution of bromcresolpurple was added to each sample. purple colour signified negative, yellow positive (cell growth) result. intermediate shades were regarded positive. the experiment was also performed with s9 activation, in which case 10 ml suspension contained 2.5 ml s9 mix (ebpi) assembled according to the producer’s guide (s9 activation simulates metabolic processes in the liver of higher organisms). for positive control 2-amino-antracene was used in 100 µg cm-3 concentration. for the evaluation of mutagenic effect the χ2-test was applied with 95% confidence level [30]. results and discussions genotoxic response is expressed as number of micronuclei/250 cells in case of the mussel micronucleus test, percentage of positive wells in case of the ames test and if value in case of the sos chromotest. significant difference between the control and all treatments was observed in case of micronucleus numbers (anova: f = 12.015; df = 5; p < 0.00001, tukey post hoc: p < 0.002); however, only the highest concentration treatment differed from the acn-control (tukey post hoc p = 0.02). the difference between the lowest (70 µg dm-3) and highest (700 µg dm-3) concentrations was also indicated (fig.1). χ2-square tests indicated significant differences between the control and all treatments in case of ratios of ames fluctuations test (p < 0.0017) (fig.2). the results of sos chromotest are shown in fig.3. to date no assessment has been published for comparing the sensitivity of the mussel micronucleus test and bacterial genotoxicity assays. there are a few comparative works; however, those are based on amphibian micronucleus tests. one protocol uses xenopus laevis embryos and the end-point of the test is number of micronucleated erythrocytes per thousand. the test is standardised, international and some national figure 1: result of the mn test with b[a]p showing significant difference compared to control (a), to acn control (b) and to 70 µg dm-3 b[a]p (c) figure 3: result of the s9 supplemented sos chromotest with b[a]p figure 2: result of the s9 supplemented fluctuation ames test with b[a]p (significant difference compared to control (a)) 4 test protocols apply, e.g. the afnor nft 90-325 procedure [31]. mouchet et al. tested genotoxicity of pah-contaminated soil leachates on the amphibian mn test and two bacterial tests (ames and mutatox) [30]. the latter test developed by the microbics company (now azur environmental) uses dark mutants of the luminescent bacterium vibrio fischeri. in the presence of mutagenic compounds, these mutants can revert and recover their luminescence, which is easily measurable by a luminometer. it was found that the mn test was able to detect genotoxicity, while the ames test was not. sensitivity of the mutatox test was intermediate. it should be noted that chemical analysis of both soil and leachate samples revealed much lower individual pah concentration in leachates than in the soil samples. le curieux et al. used the sos chromotest, the ames fluctuation test and another amphibian, the newt pleurodeles waltl for a comparative assessment of 7 chemicals, including b[a]p. in their study, the newt micronucleus test was the most sensitive, the fluctuation test and the sos chromotest gave practically similar but lower response [33]. in our study all three tests gave positive response, but analysis of the concentration-response graphs shows somewhat different patterns. bacterial tests gave positive response only with s9 activation. ideal concentration-response graphs were found for the mn test and the s9 supplemented ames test. ideal concentration-response curve is observed when the response steadily increases for each higher effluent concentration [34]. main difference is the response given in the acn control, which elucidated micronucleus formation but the ames test gave practically the same response for both controls. notably, wozniczki et al. did not find concentration-response relationship when tested b[a]p on sinanodonta woodiana. in the sos chromotest after s9 activation, positive response was given for the lowest concentration, but no clear concentration-response relationship could be established. in general, sensitivity of the sos chromotest is considered lower than that of the ames test. for example, there are mutagenic compounds that do not induce the sos response, such as benzidine, cyclophosphamide, acridines, and ethidiumbromide [13]. conclusions the very similar response of the ames test and the micronucleus test (considering both sensitivity and concentration-response pattern) indicate that b[a]p elucidates both chromosomal aberrations and point mutation, and is genotoxic for prokaryotes and eukaryotes as well; however, this is not necessarily the case for all potentially genotoxic chemicals. as such, for testing genotoxicity of either individual compounds or environmental samples, application of both tests can be advised, defining the minimum necessary battery as the mn and ames tests. acknowledgements this work was supported by the támop-4.2.2.a11/1/konv-2012-0064 research program. this project is supported by the european union and co-financed by the european social fund. references [1] usepa: priority pollutants list (appendix a to 40 cfr part 423). u.s. environmental protection agency, office of water, 2000 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jourdain m.j., ferrier v., triffault g., devauxe a.: biomonitoring of the genotoxic potential of aqueous extracts of soils and bottom ash resulting from municipal solid waste incineration, using the comet and micronucleus tests on amphibian (xenopus laevis) larvae and bacterial assays (mutatox® and ames tests), sci. total environ., 2006, 355, 232–246 [33] le curieux f., marzin d., françoise e.: comparison of three short-term assays: results on seven chemicals. potential contribution to the control of water genotoxicity, mutation res., 1993, 319, 223–236 [34] usepa: method guidance and recommendations for whole effluent toxicity (wet) testing (40 cfr part 136). epa 821-b-00-004, u.s. environmental protection agency, office of water, 2000 microsoft word content.doc hungarian journal of industrial chemistry veszprém vol. 40 (2) pp. 93–99 (2012) optimal design of high-temperature thermal energy store filled with ceramic balls t. borbély1 1university of pannonia, institute of mechanical engineering, 10 egyetem street, h-8201 veszprém, hungary e-mail: borbelyt@almos.vein.hu the momentary amount of the available solar energy and the demand usually are not equal during the usage of solar energy for heating and electric power supply. so it is necessary to store the heat energy. this article shows optimal design of a new construction, sensible heat store filled with solid heat storage material. the planned heat store has cascade system formed a spiral flow-path layout. this is a conceptual model, worked out in case of packed bed with ceramic balls. the aim of the special layout is to realize better overall efficiency than regular sensible heat stores have. the new construction would like to get higher overall efficiency by long flow-way, powerful thermal stratification and spiral flow-path layout which can ensure lower heat loss. the article shows the calculation method of the simulation of the charge and discharge and the calculation method of the overall efficiency using the results of the simulations. the geometric sizes and operating parameters of the thermal energy store with the best overall efficiency were calculated using genetic algorithm (ga). the results of the calculation tasks show that a thermal energy store with long flow-way, with cascade system formed spiral flow-path layout has higher overall efficiency than an one-duct, short flow-way thermal energy store which has equal mass of solid heat storage material as the long flow-way one, mentioned before. keywords: solar energy, heat storage, solid charge, sensible heat, optimization introduction the possible thermal energy storing methods are: sensible heat storage, latent heat storage, sorption heat storage and chemical energy storage [1–8]. the simplest way is the storage of sensible heat, by heating a heat storage material without phase changing. the energy density of the sensible heat storage will be high if the specific heat and the density of the heat storage material are great as well [9]. out of the materials which can be found in the environment in large quantity, the water has the greatest volumetric heat capacity (~4.18 mj/m3k), but water can be applied at atmospheric pressure up to 100ºc only. the heat transport media of the concentrated solar power systems can be used as heat storage liquids as well. the melt of the solar salt (60% nano3 + 40% kno3) is used out of these materials in concentrated solar power plants as heat storage material (operating temperature range 260–550ºc, volumetric heat capacity ~2.84 mj/m3k [11]). it is not flammable, not toxic, and not too expensive. the volumetric heat capacity of some solid materials (magnesite, corundum) – because of their higher density – come near to the volumetric heat capacity of the water with much higher upper temperature limits (magnesite 3.77 mj/m3k, corundum 3.3 mj/m3k, cast iron 4.1 mj/m3k [10]). screened pebble stone, cracked stone (1.5– 2.5 mj/m3k), concrete (0.8–1.8 mj/m3k), wet soil (3.56 mj/m3k) [10] are used as sensible heat storage materials, because they are inexpensive. the sensible heat stores are typical regenerative heat-exchangers. these are instationary thermal state heat-exchangers. the regenerators are long ago applied, great heat capacity heat stores with solid fill and with short charge-discharge cycle time (10–7200 s). my aims were to study the possible interior structure of the long-term heat stores, the charge-discharge process, to calculate the optimal geometric sizes and operating parameters of those. comparison of short (l/d<10) and long (10<l/d) heat stores the temperature-place function of the heat transport medium is similar to the temperature-place function of the solid heat storage material at a moment (the temperature of the heat transport medium tf is higher at charge, lower at discharge than the ts temperature of the solid heat storage material), so it is enough to show the temperature-place functions of the solid heat storage material. charge the hot heat transport medium gives a part of its heat content to the solid heat storage material by flowing 94 through the heat store, which is cold at the beginning of the charge period. in case of short heat store the outlet temperature of the heat transport medium and the solid heat storage material are increasing soon after the beginning of the charging (figure 1), in case of long heat store they start to increase only at the end of the charge period (figure 2). figure 1: the temperature-place functions of the solid heat storage material during charge, in case of short heat store figure 2: the temperature-place functions of the solid heat storage material during charge, in case of long heat store discharge in the discharge period the cold heat transport medium flows through the hot heat store in opposite flow direction of the charge. in case of short heat store the outlet temperatures of the heat transport medium and the solid heat storage material are decreasing soon after the beginning of the discharging (figure 3), in case of long heat store they start to decrease only at the end of the discharge period (figure 4). figure 3: the temperature-place functions of the solid heat storage material during discharge, in case of short heat store figure 4: the temperature-place functions of the solid heat storage material during discharge, in case of long heat store basic idea of the cascade system heat store during the charging and discharging of the long heat store the thermocline zone is located only in a part of the length of the heat store. it is plausible solution to divide to sections the heat store and allow knocking-off the sections from the flow-path of the heat transport medium. let’s call these sections as ducts. in case of the cascade system heat store the heat transport medium must flow through only the ducts where the thermocline zone is going along. the transport power demand of the heat transport medium can be reduced by this solution. the heat-loss of the heat store into the environment will be small if the heat store has small specific surface. from the prismatic bodies the cylinder with h/d=1 ratio has the smallest specific surface, followed by the regular n-sided prism with h/s=1 ratio (assuming that the heat-loss flux is approximately equal in all sides of the body). the higher heat-loss of the long heat store (because of its greater specific surface) can be reduced by using cascade system of the ducts formed a spiral flow-path layout (see later on figure 5). out of the regular n-sided prisms the six-sided can be built from cylinders with the best space utilization. 95 the geometry and operating of the heat store filled with ball particles the ducts of the heat store filled with ball particles are cylinders made of metal sheet with outer thermal insulation (fig. 5). the metal shell holds the bed of the particles, and the heat transport medium. the thermal insulation supports the thermal stratification in radial direction. to choose cylindrical shape for the ducts is necessary – because of the pressure of the packed bed of bulk particles. the outer geometry of the heat store is regular hexagonal prism with h/st≈1 ratio and cascade system of the ducts formed a spiral flow-path layout. figure 5: the construction layout of the heat store filled with ball particles and arrangement in the cascade system with spiral connection st – side distance of the heat store, h – bed height of a duct, δi – thickness of the outer thermal insulation the number of ducts nj is an odd one in case of full filling, but leaving out the last duct we get an even number, so it is possible to lock out or join in the heat transport medium flow into any duct-pairs (duct-pair means a pair of ducts, one downwards and another upwards). this way the place of the last duct could be used e.g. for service purpose. the hot heat transport medium is put in at the top of the middle duct at the beginning of charge and it flows downwards, it turns in the return band flows into the next duct (the lower connecting of the ducts is signed with dashed arrow) and flows trough that upwards. the heat transport medium coming out from the second duct can be led to the next pair of ducts. the heat transport medium must flow through only the ducts where the thermocline zone is going along. in the discharge period the cold heat transport medium flows through the hot heat store opposite to the flow-direction of the charge (from outside to middle). the main sizes of a duct of the heat store can be seen in figure 6. figure 6: top view of a duct dsj – outside diameter of the insulated duct, dj – inside diameter of the duct, ds – whole thickness of the thermal insulation between two ducts basic differential equations of the heat transport in the heat store filled with ball particles k. a. r. ismail, and r. stuginsky jr. [126] have reported an excellent comparative analysis of several models for description of the heat transfer in the heat transport medium and the solid heat storage material. for both media i have chosen a bit simpler model than the general, one-dimensional model. the heat-loss boundary condition is not included in the differential equations, because it takes effect only at the outer ducts, the effect of it will be calculated separately from the calculation of the temperature-place functions. the differential equation for the description of the heat transfer in the heat transport medium is )tt(a x twtc fspf f f f ff −α=⎟ ⎠ ⎞ ⎜ ⎝ ⎛ ∂ ∂ + τ∂ ∂ ρε , (1) where: tf – temperature of the flowing heat transport medium, ts – temperature of the solid heat storage material, ρf – density of the heat transport medium, cf – specific heat of the heat transport medium, wf –average velocity of the heat transport medium in the flow-channels, ap – superficial particle area per unit bed volume, αf – heat transfer coefficient between the flowing heat transport medium and the solid heat storage material, ε –void fraction of the bed. the superficial ball particle area per unit bed volume ap is )1( d 6a b p ε−= , (2) where: db – diameter of the ball particle. 96 the differential equation of the heat transfer in the heat transport medium was discretized by applying explicit forward difference scheme in time and upwind difference scheme in space [13, 14]. the differential equation for the description of the heat transfer in the solid heat storage material is )tt(a x ttc)1( sfpf2 s 2 seffx s ss −α+ ∂ ∂ λ= τ∂ ∂ ρε− , (3) where: ρs – density of the solid heat storage material, cs – specific heat of the solid heat storage material, λseffx – effective axial thermal conductivity of the solid heat storage material. the effective axial thermal conductivity of the solid heat storage material λseffx is sf seffx )1( 1 λ ε− + λ ε λ , (4) where: λf – thermal conductivity of the heat transport medium, λs – thermal conductivity of the solid heat storage material. the differential equation of the heat transfer in the solid heat storage material was discretized by applying explicit forward difference scheme in time and centred difference scheme in space (ftcs) [13, 14]. the heat transfer coefficient between the flowing heat transport medium and the solid heat storage material was calculated according to [15]. the design variable it is practical to choose the diameter of the ball particle db for optimization design variable: x1=db. the flow velocity of the heat transport medium wf has the greatest influence on the charging of the heat store, but it depends on the void fraction ε only (at given inside diameter of the duct dj). in case of the bed filled with uniform ball particles the void fraction ε is independent from the diameter of the particle db. definition of the restrictions geometric restrictions the lower limit of the diameter of the ball particle db is restricted by the manufacturing technology and the pressure drop, and the upper limit is also restricted by the minimal way-length of the heat transfer in the heat storage material. limits for x1 design variable are m1.0m01.0 ≤≤ 1x . (5) for the minimal specific surface the best value of the geometric ratio could be 1 s h t ≈ . (6) pressure drop restriction the pressure drop of the heat transport medium flowing through the packed bed in case of incompressible medium, according to [16] is ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎣ ⎡ ρ ε ε− + νρ ε ε− =δ 2 f b f f2 b ff 2 2 w d 175,1w d )1(150l'p , (7) where: νf – kinematic viscosity of the heat transport medium. the pressure drop of the heat transport medium must be restricted in order not to be necessary to install pressure resistant shell, not to get high transport work demand, can be negligible the compressibility of the gas and may be sufficient to use ventilator instead of blower or compressor in case of gas heat transport medium. the upper pressure drop limit for l=2h flow-way length according to the previous requirements is bar1.0pa10000'p h2 =≤δ . (8) composition of the objective function the objective function is the overall efficiency of the heat storage, which is suitable to compare the variants of the heat stores. the optimal sizes and operating parameters could be got from the maximum-point of the objective function. in the calculation of the overall efficiency i relate the part of the extractable heat quantity which can be used for heating and electric power production to the sensible heat storage capacity of the heat store as it is here: cap trlhid o q qqq −− =η , (9) where: qhid – extractable heat quantity from the heat store during a charge-discharge cycle without heat-loss, ql – heat-loss to the environment through the boundary surfaces during a charge-discharge cycle, qtr – heat-equivalent of the transport work demand during a charge-discharge cycle, qcap – sensible heat storage capacity of the heat store between the inlet and outlet temperature of the heat transport medium at the charge. the optimal value of the design variable can be searched by optimization using the calculation of the 97 temperature-place functions during the whole length of the charge-discharge cycle. the heat quantity qhid the heat quantity qhid is the difference between the heat-content of the heat store after charge and after discharge without heat-loss. it is necessary to know the temperature-place functions of the heat store at the end of the charge and at the end of the discharge. the heat quantity qhid is ( )∫ τ+τ−τ π ε−ρ= hn 0 dcscs 2 j sshid j dx),x(t),x(t 4 d )1(cq , (10) where: τc – term of charge, τd – term of discharge. the final temperature-place function of the charge of the heat store is the initial condition of the discharge. in the discharge period the heat transport medium flows through the heat store in opposite flow direction of the charge. the heat quantity ql the heat quantity ql is the heat-loss into the environment through the boundary surfaces during a chargedischarge cycle is lblslrl qqqq ++= , (11) where: qlr – heat-loss to the environment through the roof surface, qls – heat-loss to the environment through the side surfaces, qlb – heat-loss to the environment through the bottom and the ambient ground. the calculation of the heat-loss has taken into account the temperature of the heat store changing in place and time. the heat quantity qtr the heat quantity qtr is the heat-equivalent of the transport work demand during a charge-discharge cycle. the heat quantity qtr is approximated oh h2ff . dhd2jchc2j tr 'pm)nn( q η δρτ+τ = , (12) where: nj2hc – average number of duct-pairs which are simultaneously used during the charge, nj2hd – average number of duct-pairs which are simultaneously used during the discharge, f . m – mass flow rate of the heat transport medium, δp’2h – pressure drop of the heat transport medium on l=2h flow-way length, ηoh – overall efficiency of the electric power production in a heat power station. the heat quantity qcap the heat quantity qcap is the sensible heat storage capacity of the heat store between the inlet and outlet temperature of the heat transport medium at the charge: )tt(cm)tt(cmqq cs,sce,ssscco,fci,fff . cf . cap −=τ−=τ= ,(13) where: f . q – heat current during the charge, tf,ci – inlet temperature of the heat transport medium at charge, tf,co – outlet temperature of the heat transport medium at charge, ms – mass of the heat storage material, ts,cs – (homogeneous) temperature of the solid heat storage material at the start of the charging, ts,ce – (homogeneous) temperature of the solid heat storage material at the end of the charging. basic data of the optimization task i have made the calculations during the optimization with the following main data: τc=63 day=1512 h=5 443 200 s, f . q =2 mw, tf,ci=400°c, ts,cs=100 oc, ds=0.2 m. τd=58 day=1392 h=5 011 200 s. the solid heat storage material is magnesite, its physical properties are at ts,mid [10]: ts,mid=(ts,cs+ts,ce)/2=(100°c+400°c)/2=250°c λs=23.26 w/mk, ρs=3500 kg/m3, cs=1077.5 j/kgk. the required mass of the heat storage material for an ideal heat store: ms=33 678 t, ε=0.3. the heat transport medium is nearly ambient pressure air, its physical properties are at tf,mid [10]: tf,mid=(tf,ci+tf,co)/2=(400°c+100°c)/2=250°c λf=0.0425 w/mk, ρf=0.6715 kg/m3, cf=1038.5 j/kgk, νf=4.1525·10-5 m2/s. the final temperature-place function of the charge of the heat store is the initial condition of the discharge. the mass flow rate of the heat transport medium is constant during the charge-discharge process. the inlet temperature of the heat transport medium during discharge is: tf,di=100°c. data of the outer thermal insulation: λi=0.0468 w/mk, δi=1 m. ηoh=0.3. 98 i have applied the genetic optimization algorithm of the matlab software in order to find the optimal geometric sizes and operating parameters of the thermal energy store with the best overall efficiency. optimal sizes and operating parameters of the thermal energy store with the best overall efficiency the optimization process has been executed with number of ducts nj=1, 6, 18. the results are summarized in table 1 and figure 7. table 1: optimal sizes and overall efficiencies with several number of ducts nj [-] 1 6 18 x1 [m] 0.045 0.1 0.1 h [m] 27.5 29.6 28.8 l [m] 27.5 177.6 518.4 dsj [m] 25.5 10.1 6.0 st [m] 27.5 29.6 28.8 db [mm] 45 100 100 wf [m/s] 0.064 0.412 1.203 qcap [pj] 10.89 10.89 10.89 qhid [pj] 8.45 9.38 9.98 ql [pj] 0.92 1.11 1.01 qtr [pj] 0.01 0.25 2.87 ηo [-] 0.6908 0.7363 0.5601 figure 7: the optimal overall efficiency against the number of ducts main results the best overall efficiency can be reached with six ducts. it is better than the overall efficiency of one-duct type and eighteen-duct type. the expected significant increasing of the overall efficiency was ruined by the increasing transport work demand of the heat transport medium and the increasing heat-loss. the advantage of the six-duct type against the oneduct type is the smaller inside diameter of a duct dj. it is easier to distribute the stream of the heat transport medium along a smaller flowing cross-section than along a larger one. the overall efficiency decreases with increasing of the number of ducts, the main reason of it is the powerful increasing of the transport work demand. in case of liquid heat transport medium the transport work demand would be much smaller, so better overall efficiency could be reached with greater number of ducts. the upper limit of the overall efficiency would be restricted by the heat-loss. the void fraction of a packed bed, filled with uniform balls, in case of exact space-filling ε=0.26 is, in practice ε≈0.3 is! the void fraction of the volume of the heat store would have to fill with heat transport liquid. this large liquid volume brings up the idea of the establishment of a heat store with liquid heat storage medium, built from cylindrical tanks, in cascade system formed a spiral flow-path layout. the thermal stratification of the heat store with liquid heat storage material would be sharper, the overall efficiency would be higher than with solid heat storage material. conclusions i have worked out the constructional and the mathematical model of the long flow-way, sensible heat store with cascade system. the temperature-place functions and the overall efficiency can be calculated by using the mathematical model. i have used genetic optimization algorithm in order to find the optimal variant of the thermal energy store with the best overall efficiency. the chargeable and the dischargeable heat quantity of the multi-duct, long flow-way heat store is more than of the one-duct, short flow-way thermal energy store with equal mass of solid heat storage material. the temperature level of the outgoing heat transport medium is more advantageous in case of the multi-duct heat store than in case of the one-duct type during the whole charge-discharge cycle. the heat-loss can be reduced by using heat store with small specific surface and by allowing charge from middle to outside and discharge from outside to middle. the transport power demand of the heat transport medium can be reduced by making the flow of the transport medium only through the ducts where the thermocline zone is going along. according to the results of the optimization higher overall efficiency can be reached in case of six-duct type heat store than in case of one-duct type, filled with ceramic balls. the overall efficiency decreases with increasing of the number of ducts – because of the strong increasing of the transport work demand. 99 acknowledgements this work was supported by the research project támop-4.1.1.c-12/1/konv-2012-0017. references 1. p. muthukumar: thermal energy storage systems for solar thermal power plants: methods and materials, indo-spain joint work on renewable energy, sevilla, spain (2011), p. 34 2. r. dunn: a global review of concentrated solar power storage, proceedings of solar 2010, 48th auses conference, canberra, australia (2010), p. 10 3. a. h. abedin, m. a. rosen: a critical review of thermochemical energy storage systems, the open renewable energy journal, 4 (2011), pp. 42–46 4. y. demirel: energy production, conversion, storage, conservation, and coupling, springer (2012), p. 503 5. t. schmidt, d. mangold, h. müllersteinhagen: seasonal thermal energy storage in germany, ises solar world congress, göteborg (2003), p. 7 6. d. laing: thermal energy storage for concentrated solar power: state of the art and current cevelopments, ises annual meeting tel aviv university (2011), p. 25 7. d. laing: solar thermal energy storage technologies, energy forum, 10 000 solar gw, hannover (2008), p. 25 8. d. laing, d. lehmann: concrete storage for solar thermal power plants and industrial process heat, ires iii, 3rd international renewable energy storage conference, berlin (2008), p. 6 9. i. árpád: investigation of sensible heat storage and heat insulation in the exploitation of concentrated solar energy, hungarian journal of industrial chemistry, 39, 2 (2011), pp. 163–167 10. k. raznjevic: hőtechnikai táblázatok, műszaki könyvkiadó, budapest (1964), p. 336 11. d. kearney, u. herrmann, p. nava, b. kelly, r. mahoney, j. pacheco, r. cable, d. blake, h. price, n. potrovitza: overview on use of a molten salt htf in a trough solar field, nrel parabolic trough thermal energy storage workshop golden, co, usa (2003), p. 27 12. k. a. r. ismail, r. stuginsky jr.: a parametric study on possible fixed bed models for pcm and sensible heat storage, applied thermal engineering, 19 (1999), pp. 757–788 13. g. tóth: számítógépes modellezés, elte ttk, atomfizika tanszék, egyetemi jegyzet, budapest (2001), p. 118 14. i. faragó, r. horváth: numerikus módszerek, elte ttk – bme ttk egyetemi jegyzet, budapest (2011), pp. 341–391 15. verein deutscher ingenieure vdi-gesellschaft verfahrenstechnik und chemieingenieurwesen (gvc): vdi heat atlas, second edition, springerverlag berlin heidelberg (2010), pp. 743–744, 1423–1433 16. g. fejes, g.tarján: vegyipari gépek és műveletek, tankönyvkiadó, budapest (1979), pp. 36–45 microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 89-94 (2008) separation of a ternary homoazeotropic mixture by pressure swing batch distillation g. modla, p. lang bute department of building services and process engineering, h-1521 budapest, muegyetem rkp. 3-5, hungary e-mail: lang@mail.bme.hu the separation of a ternary mixture (n-pentane-acetone-cyclo-hexane) with two binary minimum azeotropes is studied by feasibility studies and rigorous simulation calculations. by the feasibility studies based on the analysis of the vessel paths in the residue curve maps at the two different pressures (pi, pii) the separation steps are determined for the two configurations studied (batch stripper (bs), double column batch stripper (dcbs)). the rigorous calculations are performed by the ccdcolumn professional dynamic flow-sheet simulator. for the dcbs two operational policies are compared. keywords: batch distillation, separation of azeotropes, pressure swing distillation, batch column configurations, feasibility study, rigorous process simulation introduction distillation is the separation method most frequently applied in the chemical industry, which is based on the difference of volatility of the components of a liquid mixture. for the separation of the two components (a and b) forming an azeotrope a special distillation method must be applied such as the pressure swing distillation (psd), extractive or heteroazeotropic distillation. the pressure swing distillation is the least studied from these three methods. batch distillation (bd) has always been an important part of seasonal, uncertain or low capacity and high-purity chemicals’ production. it is a process of key importance in the pharmaceutical and several other industries and in the regeneration of waste solvent mixtures. many mixtures form an azeotrope, whose position can be shifted substantially by changing system pressure, that is, a pressure sensitive azeotrope. (at some pressure the azeotrope may even disappear.) this effect can be exploited to separate azeotropic mixtures without the application of a separating agent by the so-called pressure swing distillation. lewis (1928) was the first, who suggested distilling the azeotropic mixtures by pressure swing distillation. this process has been suggested to separate azeotropic mixtures by e.g. black (1980), abu-eishah and luyben (1985), chang and shis (1989). more details about the pressure swing continuous distillation can be found in books of van winkle (1967) and wankat (1988). knapp et al. (1992) developed a new process, in which pressure swing continuous distillation was combined with entrainer addition. the possibility of the application of an entrainer for the separation of binary azeotropic mixtures increases to a large extent the number of mixtures separable by this process. on the other hand the separation of the original components from the entrainer means an additional task. phimister and seider (2000) studied the separation of a minimum azeotrope (thf-water) by semicontinuous psd and reverse-batch operation (batch stripping). in the semicontinuous column better performance was achieved than in the batch stripper. they also investigated the control and other practical aspects of these configurations, and their performance was compared with that of a continuous system, as well. wasylkiewicz et al. (2003) developed an algorithm which allows the variation of compositions of azeotropes with pressure to be tracked, and all new azeotropes that appear within specified pressure range to be found. to our knowledge repke et al. (2006) were the first, who investigated experimentally the application the pressure swing distillation in batch. they studied the separation of a minimum boiling, homoazeotropic mixture (acetonitrile-water) by pressure swing distillation in a batch rectifier and in a stripper with pilot-plant experiments and rigorous simulations. the aim of these authors was rather the experimental study of the pressure swing batch distillation than the exhausting theoretical study of the feasibility of the process. the above authors have not studied either the separation of ternary mixtures. the aim of our work is to study the separation of a ternary mixture (n-pentane-acetone-cyclo-hexane) forming two binary minimum azeotropes by feasibility studies and rigorous simulation calculations. by the feasibility studies based on the analysis of the vessel paths in the residue curve maps at the two 90 different pressures (pi, pii) the separation steps are determined for the two configurations studied (batch stripper (bs), double column batch stripper (dcbs)). the rigorous calculations are performed by the ccdcolumn professional dynamic flow-sheet simulator. feasibility method first the method applied for the assessment of feasibility is briefly presented, then the feasibility of different column configurations will be investigated. when making feasibility studies we suppose that maximal (perfect) separation can be produced. this involves the following assumptions: infinite number of stages, very high reflux/reboil ratio, negligible liquid plate hold-up, negligible vapour hold-up. the method is based on the determination of the feasible compositions of products (continuously withdrawn) and those of residues (remaining in the vessel). since we consider ternary mixtures for the feasibility analysis, we study the residue curve maps. classification of residue curve maps the concept of a residue curve map was first introduced by schreinemakers (1901). a residue curve map is a triangular diagram (with the pure components at each vertex) which shows the locus of the liquid-phase composition as it varies with time during a simple distillation process. the trajectories of the various residue curves have a directional character which is represented by arrows (pointing toward increasing temperatures, and also increasing time during the simple distillation process). a mathematical description is given by doherty and perkins (1978), who developed a set of nonlinear ordinary differential equations, which model the liquid composition profiles as a function of time. the most recently applied tools for the studing of the separation of ternary mixtures is the residue curve map analysis. gurikov (1958) was actually the first to derive the rule of azeotropy and propose a thermodynamic topological classification of ternary mixtures. later, serafimov (1970) defined the topological classification of ternary mixtures into 26 diagrams. an even more detailed classification is proposed by matsuyama and nishimura (1977), who also rank the components in the order of their boiling temperatures light(l), intermediate(i), and heavy(h). this classification includes 113 diagram classes of which 87 are graphically presented by doherty and caldarola (1985). nowadays these two methods are applied for the classification of ternary mixtures. neither of these two classification methods takes into consideration that with the variation of pressure: the azeotropic composition can considerably vary, the azeotrope may even disappear, the volatility order of components may change. first modla et al. (2008) recognised the necessity of modifying these methods in the case of mixtures whose components form pressure sensitive azeotrope(s). the classification of residue curve maps by matsuyama and nishimura is as follows: the three digits signify the type of binary azeotropes on the l-i, i-h, and h-l edges of the triangle, respectively. the numbers are assigned by the following rules: 0: no ateotropes, 1: binary minimum-boiling azeotrope, node (must be unstable) 2: binary minimum-boiling azeotrope, saddle, 3: binary maximum-boiling azeotrope, node (must be stable) 4: binary maximum-boiling azeotrope, saddle the single letter after the first three digits signifies the type of ternary azeotrope. m: minimum-boiling ternary azeotrope (must be an unstable node) m: maximum-boiling ternary azeotrope (must be a stable node) s: intermediate boiling ternary azeotrope (must be a saddle) for the psbd the classification of the rcm (eg by matsuyama and nishimura (1977, m&n) by serafimov (1970, s)) must be extended. the pressure sensitivity of an azeotrope must be always indicated even if there is no change in the type of rcm since it has influence on the separation method to be applied. (we write ‘p’ after the number of m&n if it is pressure sensitive). if the type of rcm varies it must be given for both pressures. feasibility region of the separation (fr) is defined as follows: all feed compositions, from where all components can be purely recovered by maximal separation at the given pressure or by applying pressure swing. the regions outside the fr can be conditionally feasible: from where fr can be reached by a preparatory step (distillation/stripping or addition of e) infeasible: from where a fr can not be reached. column configurations the pressure swing batch distillation (psbd) can be realised in configurations with either one or two column section(s). because of the occurrence of the azeotrope the two pure components must be produced at two different pressures. the different pressures can be applied at different times (in the same column section) or in different column sections (at the same time). 91 configurations with one column section in this case the pressure swing can be performed only in time. hence there must be at least two sequential production steps at different pressures in one cycle. the pressure swing batch distillation (psbd) can be realised in batch rectifier(br) or batch stripper(bs). the feed is charged into the bottom (rectifier, fig. 1a), or top vessel (stripper, fig. 1b). (in fig. 1a for the sake of better comparability the two functions of the reboiler (storage(vessel) and evaporation(total reboiler)) are separated.) continuous product withdrawal is performed from the top (rectifier) or the bottom (stripper). depending on the feed composition and the type of the azeotrope in the case of a binary mixture a-b the first (and the following) product withdrawn can be pure a, pure b or the azeotropic mixture (modla and lang, 2008). a) batch rectifier b) batch stripper figure 1: single column configurations a) double column batch rectifier b) double column batch stripper figure 2: double column configurations double column configurations the two different pressures are applied in different column sections. in the case of a ternary mixture it is theoretically possible to produce three pure components in a single production step. (two components are withdrawn continuously and the third remains in the vessel.) feasibility studies the vapour-liquid equilibrium data of the ternary mixture (n-pentane-acetone-c-hexane) studied are given in tables 1 and 2. the components of this mixture form two minimal boiling point binary azeotropes. one of them (acetone-n-pentane) is pressure sensitive, whilst the other one (c-hexane-acetone) is not. the c-hexane (h) and acetone (i) vertices are stable nodes, while the n-pentane (l) vertex is a saddle. (fig. 3a). the azeotrope i-h (azih), which is not pressure sensitive, is a saddle. the azeotrope l-i (azli), is the unstable node, its location considerably depends on the pressure (fig. 3b). the (extended) m&n class of the mixture: 1p-2-0. table 1: boiling points of the pure components at the two different pressures pi=1.01 bar pii=10 bar n-pentane (l) 36.07 °c 124.74 °c acetone (i) 56.25 °c 142.98 °c c-hexane (h) 80.72 °c 182.31 °c table 2: azeotropic data (temperature, composition) at the two different pressures 1.01 bar 10 bar n-pentane acetone 32.75 °c 0.75-0.25 116.99 °c 0.67-0.33 acetone c-hexane 53.95 °c 0.77-0.23 140,27 °c 0.79-0.21 92 figure 3: sketch of the residue curve map (a) and psbd regions (b) separation steps for the one column configuration a. charge composition in the region h: 1. removal of component h from the mixture with a batch stripper (the residue is mixture l-i). 2. separation l/i with pressure swing batch stripping. b. charge composition outside the region h: in this case pressure swing must be applied already in the ternary area, as well: 0. preparation step: the vessel composition is brought into the area of the triangle azi li-azii li-azih. 1. in the first production series we get alternately pure components h and i as bottoms, until the vessel composition reaches the edge l-i. 2. in the second production series we get alternately pure components i and l as bottoms. separation steps for the double column configuration a. charge composition in the region h: 1. removal of component h from the mixture by operating one of the two columns (the residue is mixture l-i). b. charge composition outside the region h: 0. preparation step: the vessel composition is brought into the area of the triangle azi li-azii li-azih by operating only one of the columns. 1. production of components h and i as bottom products of the two columns (the vessel residue is mixture l-i). 2. production of components l and i as bottom products of the two columns. a) one column b) double column figure 4: vessel path (---) and x-profiles (…) we investigate with rigorous simulation only the double column configuration since in the case of the one column configuration if the composition of the charge is located: in region h, the ternary separation can be reduced to a binary one, outside region h, sufficient recoveries can be only produced with a lot of separation steps beginning with pressure change. rigorous simulation results the amount of charge: 1 m3 (13.42 kmol). its composition is shown in table 3. table 3: the composition of the charge n-pentane (l) acetone (i) c-hexane (h) mol% 19.3 64.5 16.2 vol% 25.6 54.3 20.1 the prescribed purity for both products: 98 mol%. both columns of the dcbs contains 40 theoretical plates (ni= nii=40). the pressures: pi=1 bar, pii=10 bar, the liquid hold-up: 2 dm3/plate. the liquid flow rate leaving the common top vessel, which is divided between the two columns: ltotal = 10 m3/h (cca. 11.6 kmol/h). (the reboil ratios are not fixed.) at different liquid division ratios (η = li/ltotal) the optimal operation conditions (where the energy consumption is minimal) are determined. two different operational policies are studied and compared: 1. the production is begun in each column immediately when the bottoms reaches its prescribed purity (policy 1). 2. the production is begun in both columns at the same time when both bottoms have already reached the prescribed purity (policy 2). in both cases two production steps can be performed: 1. production of h and i 2. production of l and i in our case (at the given charge composition) at the end of step 1 the amount of residue is so small, that this residue can not be separated in the given (industrial size) installation therefore only step 1 is performed. the evolution of the composition of vessel and two product tanks in step 1 is shown for policy 1 (η = 0.6) in figs. 5 and 6a-b, respectively. depending on the value of the bottoms composition the values of reboil ratios were varied with a pid controller whose parameters (ap i = 0.1, ti i = 0.9 s, td i = 13 s, ap ii = 0.1, ti ii = 0.9 s, td ii = 13 s) were selected by trials. 0 0.2 0.4 0.6 0.8 1 0 100 200 acetone c-hexane n-pentane min mol/mol figure 5: the evolution of the vessel liquid composition i h l az ih az ii li az i li i h l az ih az ii li az i li i h l az ih azii li az i li i h l az ih az li h 93 0 0.2 0.4 0.6 0.8 1 0 50 100 150 200 250 acetone c-hexane n-pentane min mol/mol 0 0.2 0.4 0.6 0.8 1 0 50 100 150 200 250 acetone c-hexane n-pentane min mol/mol figure 6: the evolution of the two product compositions at the end of step 1 the whole amount of c-hexane is recovered. the vessel liquid of low quantity contains a binary mixture of n-pentane-acetone. the production is begun earlier in column i (fig. 6a) than in column ii (fig. 6b). the purity of acetone in product tank i remained at the prescribed value (0.98). the purity of the c-hexane slightly decreased in time but at the end it was near to its prescribed value (0.981). policy 1 step 1: production of h and i on the increase of the liquid division ratio the recovery of product h increases and that of product i decreases (fig. 7a). the average recovery slightly increases. the average energy consumption has a minimum at η = 0.55 (fig. 7b). figure 7: the effect of the liquid division ratio η on the a) recoveries b) energy consumptions (policy 1) policy 2 step 1: production of h and i on the increase of the liquid division ratio the recovery of product h increases and that of product i decreases (fig. 8a). the average recovery slightly increases. the average energy consumption has a minimum at η = 0.65 (fig. 8b). it must be still noted that for liquid division ratios smaller than 0.6 the prescribed product purity was not reached at all. figure 8: the effect of the liquid division ratio, η on the a) recoveries b) energy consumptions (policy 2) comparison of the different operational policies by the two operational policies similar recoveries were produced but the energy consumption was lower by the operational policy 1 (fig. 9). figure 9: comparison of the two operational policies a further advantage of this operational policy is that it can be applied in a wider liquid division ratio which is favourable from the point of view of the control of the process. the location of the minimum of the average energy consumption is different at the two operational policies. conclusion the separation of a ternary mixture (n-pentane-acetonecyclo-hexane) with pressure swing batch distillation was investigated by feasibility studies and rigorous simulation calculations. by the feasibility studies based on the analysis of the vessel paths in the residue curve maps at the two different pressures (pi, pii) the separation steps are determined for the two configurations studied (batch stripper (bs), double column batch stripper (dcbs)). we stated that it depends on the charge composition that the application of the one or the double column configuration is more favourable. η η η η η η 94 the rigorous simulation calculations were performed with the ccdcolumn program of the ccdcolumn professional dynamic flow-sheet simulator package for a given separation problem. for the double column batch stripper two different operational policies were compared. by the two policies similar recoveries were reached. however the operational policy by which in the column whose bottoms has already reached the prescribed purity we begin the production immediately (before reaching the prescribed purity in the other column) provided more favourable results from the point of view of energy consumption. a further advantage of this operational policy is that it can be applied in a wider liquid division ratio. acknowledgement this work was financially supported by the hungarian scientific research fund (otka) (no:t-049184) and by the janos bolyai research scholarship of the has. appendix a. antoine constants : ct baln(p) + −= where p vapour pressure [torr], t temperature [k] component a b c n-pentane (l) 15.993 2554.6 -36.25 acetone (i) 16.732 2975.9 -34.52 c-hexane (h) 15.802 2797.6 -49.10 b. uniquac parameters i,j uij-ujj, cal/mol uji-uii , cal/mol l,i 571.98 -95.033 l,h -48.806 71.682 i,h -77.536 543.590 references 1. abu-eishah s. i., luyben w. l.: „design and control of two-column azeotropic column azeotropic distillation system”, ind. eng. chem. process. des. dev., 24, 132-140 (1985). 2. black c.: „distillation modelling of ethanol recovery and dehydration processes for ethanol and gasahol”, chem. eng. prog., 76, 78-85 (1980). 3. chang t., shih t. t.: „development of an azeotropic distillation scheme for purification of tetrahydrofuran”, fluid phase equilib., 52, 161168 (1989). 4. doherty m. f., caldarola g. a.: "design and synthesis of homogeneous azeotropic distillations. 3. the sequencing of columns for azeotropic and extractive distillation", 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(1928). 12. phimister j. r., seider, w. d.: „semi-continuous, pressure swing distillation”, ind. eng. chem. res., 39, 122-130 (2000). 13. repke j. u., klein a., bogle d., wozny g.: „pressure swing batch distillation for homogenous azeotropic separation”, icheme symposium series, no. 152, 709-718 (2006). 14. schreinemakers f. a. h.: „dampfdrucke ternarer gemische. theoretischer teil: dritte abhandlung”, z. phys. chem., 36, 710-740 (1901). 15. serafimov l. a.: „the azeotropic rule and the classification of multicomponent mixtures vii. diagrams for ternary mixtures”. russ. j. phys. chem. 44(4), 567-571 (1970). 16. van winkle: „distillation”, mcgraw-hill, new york (1967). 17. wankat: (1988). „equilibrium-staged separations”, elsevier, new york. 18. wasylkiewicz s. k., kobylka l. c., castillo f. j. l., „pressure sensitivity analysis of azeotropes”, ind. eng. chem. res., 42, 207-213 (2003). microsoft word hjic 2015 43(2) 55-101.docx hungarian journal of industry and chemistry vol. 43(2) pp. 85–89 (2015) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2015-0014 application of ionic liquids in the utilization of the agricultural wastes: towards the one-step pre-treatment and cellulose hydrolysis gábor megyeri,1 nándor nemestóthy,1 milan polakovic,2 katalin bélafi-bakó,1 lászló gubicza1,* 1 membrane technology and energetics, research institute of bioengineering, faculty of engineering, university of pannonia, egyetem u. 10., veszprém, 8200, hungary 2 department of chemical and biochemical engineering, institute of chemical and environmental engineering, faculty of chemical and food technology, slovak university of technology, radlinského 9., bratislava, 81237, slovakia cheap, renewable lignocellulosic materials are relevant to the future of biofuel production. wood and agricultural wastes (e.g. straw, corn stover) provide a raw material source that cannot be used for human consumption, thus biofuels from such sources do not threaten the food supply. the aim of the work was to carry out the pre-treatment and hydrolysis of lignocellulosic material in the same ionic liquid solvent (1-n-butyl-3methyl-imidazolium-chloride, [bmim]cl), using ground wheat straw and a mixture of corn (zea mays) leaf and stover, as substrates. our measurements show that it is possible to achieve an acceptable glucose content from the cellulose by applying cellic® ctec2 and cellic® htec2 enzyme complexes. keywords: ionic liquid, enzyme, hydrolysis, glucose, agricultural waste, lignocellulose 1. introduction nowadays, lignocellulosic plant biomass is considered as a renewable and cheap natural source of energy for second-generation alcohol production and a source of other platform compounds [1]. the main components of plant biomass are cellulose, hemicellulose, and lignin, which form a quite complex molecular structure [2]. among these substances, the glucose content of cellulose is desirable, which can be obtained in an enzymatic hydrolysis process. however, it is a difficult process, since cellulose is barely soluble in water [3] and thus various pre-treatment methods are required. physical, chemical, physic-chemical, and biological pretreatments can be used [4], such as steam explosion [5], dilute and concentrated acids [6], etc. these techniques may liberate certain inhibitory compounds that are not desirable, because they can significantly hinder enzymatic hydrolysis. some ionic liquids, on the other hand, are able to dissolve cellulose selectively making it accessible to the enzymes while unwanted components are not formed. ionic liquids are salts with low melting points [7, 8]. they are considered as green solvents [9] due to their negligible surface tension. a large number of anions and cations are available in countless variations for forming ionic liquids [10]. the asymmetric organic *correspondence: gubiczal@almos.uni-pannon.hu cation causes the low melting point, because it reduces the lattice energy in 1-alkyl-3-methyl-imidazolium salts [11]. according to literature examples [12, 13], the ionic liquid (il) formed from 1-butyl-3-methyl-imidazolium chloride salt ([bmim]cl) was used to dissolve cellulose. this is the most effective ionic liquid in cellulose pretreatment, but some have found that it could cause the deactivation of the enzymes. hydrolysis cellulase enzyme complexes can be used including endocellulases, (ec 3.2.1.4), exo-cellulases (ec 3.2.1.91) and cellobiases or β-glucosidases (ec 3.2.1.21). the aims of this work were i) to study these two key steps (pre-treatment and enzymatic hydrolysis) using pure cellulose, ii) to decide if it is possible to carry out the two steps in the same il solvent, and iii) to study the processes by using real agricultural waste materials. 2. materials and methods the ionic liquid 1-butyl-3-methyl-imidazolium chloride ([bmim]cl) was provided by io-li-tec (heilbronn, germany). the enzymes celluclast 1.5l, cellic htec2, and cellic ctec2 were supplied by novozymes (bagsvaerd, denmark). a description of the enzyme (mixtures) can be found on the websites of the producers as in the case of the chemicals. cellic ctec2 is a brown liquid with a density of 1.15 g cm-3 and a slightly fermented odour that contains cellulase (iub: megyeri, nemestóthy, polakovic, bélafi-bakó, gubicza hungarian journal of industry and chemistry 86 3.2.1.4) and xylanase. cellic htec2 is a yellow liquid with a density of 1.09 g cm-3 and lightly fermented odour that contains xilanase (endo-1,4 derivative, iub: 3.2.1.8). the optimal temperature and ph for both enzymes are 45–50 ºc and 5.0–5.5, respectively. the enzymatic reaction was followed by measuring either the glucose content using a god glucose kit (sigma-aldrich, budapest, hungary) or the reducing sugar concentration by the ortho-toluidine (sigma-aldrich) spectrophotometric method (hacklange dr 3800 spectrophotometer). sodium acetate buffer (ph = 5) was used in the hydrolysis experiments with a mixture of acetic acid from scharlau (debrecen, hungary) and naoh from spektrum 3d (debrecen, hungary). purified cellulose powder (macherey-nagel, düren, germany), grounded corn leaf and stover (cls), and wheat straw from local (veszprém) farmers were used as substrates. the ash contents of the cls and wheat straw were 7.7% and 7.3%, respectively, while the maximum obtained reducing sugar yield (rdmax) was 44.9% and 29.6% in the cases of cls and wheat straw, respectively. for the pre-treatment, a specified amount of lignocellulosic substance was dissolved in 0.5 g of ionic liquid in a glass reactor then mixed slowly (50 rpm) for 10 minutes in a 100 ºc oil bath. afterwards some buffer and 0.015 cm-3 enzyme preparation were added to the mixture. then hydrolysis was carried out for 2 hours in a 50 ºc water bath with vigorous mixing (650 rpm). when the hydrolysis finished, the samples were centrifuged in eppendorf tubes. after that the reducing sugar content was measured using ortho-toluidine. 3. results and discussion the first set of experiments was carried out using pure cellulose to study the effectiveness of the pre-treatment as well as enzymatic hydrolysis. then ground corn stover and leaf, and finally wheat straw were used as substrates. 3.1. pure cellulose for the pre-treatment, 25 mg of cellulose (5%) was added into 0.5 cm3 of ionic liquid. following the description of sample preparation in ref. [14], the highly viscous mixture was incubated at 100 ºc for 10 min, and stirred slowly. pictures were taken under a microscope to follow changes during the pre-treatment. the pictures of the pure cellulose particles dispersed in il before and after the 10 min pre-treatment are shown in figs.1-2. on the basis of these photos, it seems that a 10 min pre-treatment time is enough for the cellulose to dissolve into the il. for the hydrolysis acetate buffer (ph = 5) and enzyme were added to the mixture. on the basis of our preliminary experiments 3.5 cm3 of buffer and 0.015 cm3 of cellic ctec2 enzyme seemed to be suitable amounts for the reaction. since the total amount of the mixture is still quite small, the glucose concentration of only the final sample was determined by using the god glucose kit. a reaction time of 2 hours was selected on the basis of preliminary measurements. the glucose content was measured in the reaction mixture right after the pre-treatment as well. no glucose was found in the pre-treated mixture, but 9.6 mg of glucose was detected in the reaction mixture after the enzymatic hydrolysis, which corresponds to approximately 35% conversion. this indicates that the enzyme was able to function in il inspite of literature data [15-17] suggesting that il may inhibit enzymatic function. thus, our experiment confirmed that it was possible to carry out the pretreatment and enzymatic hydrolysis in the same il without needing to separate il from the reaction mixture before the degradation of cellulose. figure 1. cellulose in il before pre-treatment (scale in mm is shown below the picture). figure 2. cellulose in il after pre-treatment. table 1. the glucose content after 2 hr of hydrolysis of pure cellulose. enzyme glucose content (mg) celluclast 1.5 l 0.7 cellic htec2 8.4 cellic ctec2 9.6 application of ionic liquids in cellulose hydrolysis 43(2) pp. 85–89 (2015) doi: 10.1515/hjic-2015-0014 87 as follow-up measurements, similar conditions were applied, but the other two enzymes were employed. the glucose content was determined by using the simpler ortho-toluidine reducing sugar method rather than the expensive god glucose kit. the results are shown in table 1. it can be seen from table 1 that the celluclast 1.5l enzyme was practically ineffective, while the performance of cellic ctec2 was similar to the cellic htec2 enzyme. hence, it was decided to use the two cellic enzymes in our further experiments. in the next set of measurements, a higher substrate concentration of at least 20% was applied, although, according to the literature [10], the solubility of cellulose in a similar il is only 5%. however, in industry it is not practical to use excessively diluted cellulose solutions. cellulose of 0.1 g was added to 0.5 cm3 of il (20%) and the mixture was treated as described above. the higher initial substrate concentration caused difficulties in stirring the mixture. its viscosity was extremely high and the texture was rather tacky. elevated stirring was necessary for complete mixing. after the pre-treatment, the mixtures were treated using buffers and enzymes for the hydrolysis. firstly, the same conditions were applied as earlier, then the amount of buffer was varied from 1 to 7 cm3. the corresponding results are shown in table 2. on the basis of data in table 2, it was concluded that 1 cm3 of buffer seems to be insufficient for the hydrolysis. a larger buffer amount, however, does not necessarily result in a higher conversion rate; rather it dilutes the samples considerably. therefore the 3.5 cm3 buffer amount was used in further experiments, which corresponds to a 1:7 ratio of il solution to buffer. this ratio is similar to the literature data found beneficial for the hydrolysis [17]. the conversion rates of the hydrolysis seem quite high especially in the case of the cellic ctec2 enzyme (64.5–76.2%), but these results can be attributed to the usage of pure cellulose and the higher activity enzymes developed lately. 3.2. corn leaf and stover after the successful experiments using the model substrate: pure cellulose, measurements using ground corn leaf and stover were carried out applying the conditions found suitable earlier: 0.5 cm3 il, 100 ºc, and 10 min pre-treatment time. the initial amounts of the substrate were chosen to be 0.750, 0.100, and 0.125 g corresponding to 15, 20, and 25%, respectively. the process was followed again by taking pictures under a microscope (figs.3-4). the higher initial substrate concentration (25%) also caused difficulties in stirring the mixture, but finally the increased stirring applied was enough to achieve complete mixing. it seems, however, that 25% of substrate poses a physical limit for the process. the pictures proved that the biomass dissolved in the il during the pre-treatment. enzymatic hydrolysis was carried out in the pretreated cls by adding buffer (3.5 cm3) and either enzymes cellic ctec2 or cellic htec2 (0.015 cm3). after the degradation (2 hours of reaction time) sufficiently high amounts of glucose were found in the figure 4. corn leaf and stover in il after pretreatment (scale in mm is shown below the picture). table 3. amount of reducing sugar (mg) in the corn leaf and stover samples. amount of substrate (mg) cellic htec2 cellic ctec2 0.075 6.99 10.06 0.100 13.82 11.61 0.125 9.11 11.14 table 2. the amount of reducing sugar (mg) in the various samples. amount of buffer (cm3) cellic htec2 cellic ctec2 1.0 3.5 7.0 7.16 9.36 33.10 64.48 32.84 76.19 figure 3. corn leaf and stover in il before pretreatment (scale in mm is shown below the picture). megyeri, nemestóthy, polakovic, bélafi-bakó, gubicza hungarian journal of industry and chemistry 88 mixture (table 3), though these values are lower than the ones in the case of pure cellulose. from the data in table 3, it can be seen that both enzymes were able to degrade the cellulose content of the biomass, and a quite high amount of glucose was produced. it seems that the differences between the glucose concentrations obtained are not too high, which means that we are approaching the substrate saturation limit, where increased substrate content does not result in a higher amount of glucose production. the conversion data obtained in the range of 7.2– 14% indicate that the cellulose content of this biomass is rather difficult for the enzyme to access, thus the hydrolysis is less effective than in the case of pure cellulose. the hydrolytic effectiveness of the enzyme cellic ctec2 was similar to that of cellic htec2. 3.3. wheat straw in the final set of experiments, wheat straw was ground and processed in a similar way to other sources used as a substrate in the experiments by applying similar conditions as mentioned earlier. the initial substrate concentration was 25%, which means that 0.125 g of wheat straw was added to 0.5 cm3 of il. the results are summarized in table 4. it can be seen that it is possible to carry out the bioconversion processes using wheat straw as a substrate, but the conversion rate is even lower than for in the case of cls. 4. conclusion it can be stated that the pre-treatment and enzymatic hydrolysis of the cellulose content of various types of plant biomass can be carried out using the same ionic liquid, 1-butyl-3-methyl-imidazolium-chloride. our experiments have proven that acceptable conversion rates could be achieved. thus, this technique is considered as a chemically feasible approach for the utilisation of the cellulose content of agricultural waste materials for energetic and other purposes. acknowledgement this work was supported by the projects támop4.2.2.b-15/1/konv-2015-0004 and slovakianhungarian cooperation sk-hu-2013-0008. references [1] abels, c.; thimm, k.; wulfhorst, h.; spiess, a.c.; wessling, m.: membrane-based recovery of glucose from enzymatic hydrolysis of ionic liquid pretreated cellulose, biores. technol., 2013, 149, 58–64 doi: 10.1016/j.biortech.2013.09.012 [2] ha, s.h.; mai, n.l.; an, g.; koo, y.m.: microwave-assisted pre-treatment of cellulose in ionic liquid for accelerated enzymatic hydrolysis, biores. technol., 2011, 102(2), 1214–1219 doi: 10.1016/j.biortech.2010.07.108 [3] iguchi, m.; aida, t.m.; watanabe, m.; smith, r.l.: dissolution and recovery of cellulose from 1butyl-3-methylimidazolium chloride in presence of water, carbohydrate polymers, 2013, 92(1), 651– 658 doi: 10.1016/j.carbpol.2012.09.021 [4] chandra, r.; bura, r.; mabee, w.; berlin, a.; pan, x.; saddler, j.: substrate pre-treatment: the key to effective enzymatic hydrolysis of lignocellulosic, adv. biochem. engng./biotechnol., 2007, 108, 67– 93 doi: 10.1007/10_2007_064 [5] van eylen, d.; van dongen, f.; kabel, m.; de bont, j.: corn fiber, cobs and stover: enzymeaided saccharification and co-fermentation after dilute acid pre-treatment, biores. technol., 2011, 102(10), 5995–6004 doi: 10.1016/j.biortech.2011.02.049 [6] lozano, p.; bernal, b.; jara, a.g.; belleville, m.p.: enzymatic membrane reactor for full saccharification of ionic liquid-pretreated microcrystalline cellulose, biores. technol., 2014, 151, 159–165 doi: 10.1016/j.biortech.2013.10.067 [7] wang, y.; radosevich, m.; hayes, d.; labbé, n.: compatible ionic liquid-cellulase system for hydrolysis of lignocellulosic biomass, biotechnol. bioengng., 2010, 108(10), 1042–1048 doi: 10.1002/ bit.23045 [8] pinkert, a.; marsh, k.n.; pang, s.; strainger, m.p.: ionic liquids and their interaction with cellulose, chem. rev., 2009, 109(12), 6712–6728 doi: 10.1021/ cr9001947 [9] zhu, s.; wu, y.; chen, q.; yu, z.; wang, c.; jin, s.: dissolution of cellulose with ionic liquids and its application: a mini-review, green chem., 2006, 84(4), 325–327 doi: 10.1039/b601395c [10] fehér, e.; major, b.; bélafi-bakó, k.; gubicza, l.: on the background of enhanced stability and reusability of enzymes in ionic liquids, biochem. soc. trans., 2007, 35(6), 1624–1627 doi: 10.1042/ bst0351624 [11] łuczak, j.; hupka, j.; thöming, j.; jungnickel c.: self-organization of imidazolium ionic liquids in aqueous solution, colloids surf. a: physicochem. engng. aspects, 2008, 329(3), 125–133 doi: 10.1016/ j.colsurfa.2008.07.012 [12] swatloski, r.p.; spear, s.k.; holbrey, j.d.; rogers, r.d.: dissolution of cellulose with ionic liquids, j. am. chem. soc., 2002, 124(18), 4974– 4975 doi: 10.1021/ja025790m table 4. amount of reducing sugar (mg) in the hydrolysed wheat straw samples. enzyme amount of reducing sugar (mg) cellic htec2 7.07 cellic ctec2 8.89 application of ionic liquids in cellulose hydrolysis 43(2) pp. 85–89 (2015) doi: 10.1515/hjic-2015-0014 89 [13] lozano, p.; bernal, b.; bernal, j.m.; pucheault, m.; vaultier, m.: stabilizing immobilized cellulase by ionic liquids for saccharification of cellulose solutions in 1-butyl-3-methylimidazolium chloride, green chem., 2011, 13(6), 1406–1410 doi: 10.1039/ c1gc15294g [14] auxenfans, t.; buchoux, s.; djellab, k.; avondo, c.; husson, e.; sarazin, c.: mild pre-treatment and enzymatic saccharification of cellulose with recycled ionic liquids towards one-batch process, carbohydrate polymers, 2012, 90(2), 805–813 doi: 10.1016/j.carbpol.2012.05.101 [15] turner, m.b.; spear, s.k.; huddleston, j.g.; holbrey, j.d.; rogers, r.d.: ionic liquid saltinduced inactivation and unfolding of cellulase from trichoderma reesei, green chem., 2003, 5(4), 443–447 doi: 10.1039/b302570e [16] salvador, â.c.; santos, m. da c.; saraiva, j.a.: effect of the ionic liquid [bmim]cl and high pressure on the activity of cellulase, green chem., 2010, 12(4), 632–635 doi: 10.1039/b918879g [17] kamiya, n.; matsushita, y.; hanaki, m.; nakashima, k.; narita, m.; goto, m.; takahashi, h.: enzymatic in situ saccharification of cellulose in aqueous-ionic liquid media, biotechnol. lett., 2008, 30(6), 1037–1040 doi: 10.1007/s10529-008-9638-0 hungarian journal of industrial chemistry veszprém vol. 33(1-2). pp. 89-96 (2005) robust model predictive control with state estimation for an industrial pressurizer system p. tamás, i. varga, g. szederkényi and j. bokor systems and control laboratory, computer and automation research institute, has, h-1518 budapest, p.o. box 63, hungary robust model predictive control of an industrial pressurizer is presented in this paper. the physical model of the system is based on first engineering principles and the model parameters have been previously identified from measured data. to satisfy the hard constraints on the state variables and the input even in the presence of disturbances, the so-called single policy robust model predictive control method is applied. the maximal admissible level set, the disturbance invariant set and the terminal sets are determined for the system. simulation results show that the proposed controller satisfies all the requirements and shows good timedomain behavior. keywords: process control, robust model predictive control, constrained control introduction recently, there has been a growing need for automation of increasingly complex plants in different branches of industry. fortunately, the improving quantity and quality of measurements and actuators allows us to apply an increasing variety of techniques in systems and control theory developed in the last few decades. this paper presents a robust model predictive control for an industrial pressurizer system used mainly for pressure control in a nuclear power plant. in [9] an advanced dynamic inversion-based pressure controller has been designed for the systems of this type. although this controller performs very well in practice, our aim is to further develop control performance. for this, a robust model predictive control approach is proposed in this paper that is able to handle the strict input and state constraints even if disturbance affects on the system. the dynamic model of the system system description the system discussed is a pressurized water reactor, which means that in the primary circuit high pressure ensures that the coolant is not boiling. the task of the pressurizer is to keep the pressure within a predefined range. from a modeling point of view, the pressurizer is a vertical tank and inside this tank there is hot water at a temperature of about 326°c and steam above. if the primary circuit pressure decreases, water might start to boil. in order to prevent this, electric heaters switch on automatically in the pressurizer. due to the heating there will be intense boiling, more steam will be generated and this leads to a pressure increase. if the increasing pressure in the pressurizer reaches a certain limit, firstly the heaters are turned off and then cold water is injected into the tank (if needed) to reduce the pressure down to the predefined range [7]. the heating power of the electric heaters can be set continuously. the measured outputs of the system are the pressure in the pressurizer and the temperature of the tank wall. the 90 controlled output is the pressure in the tank. the simplified flowsheet of the pressurizer is shown in fig. 1. yp10 s kg m s kgm .constm = 1χ 4χ3χ2χ [ ]kt i [ ]kt figure 1: simplified flowsheet of the pressurizer the physical model of the plant modeling of industrial systems depends heavily on the modelling goal. most of the commercially available dynamic models are implemented in simulators (see e.g. [1]) and are used for equipment design and retrofitting purposes. the models used in this area are typically in the form of partial differential equations that are discretized in space to have a lumped version. this way a high dimensional (with 10-100 state variables) complicated dynamic model is obtained that is unnecessarily complex for control applications. instead, a simplified lumped dynamic model is constructed for control design purposes based on first engineering principles [2] that captures the most important dynamics of the tank. for this purpose, the following assumptions were used: 1. there are two perfectly stirred balance volumes, one for the water and another for the wall. 2. there is a single component in each of the balance volumes (water and metal, respectively). 3. constant overall mass in both balance volumes. 4. constant physico-chemical properties. 5. vapour-liquid equilibrium in the tank. the simplified model consists of two energy balances: one for the water and and another one for the wall of the tank as balance volumes. water energy balance ( )= − + − +p i p w w he du c mt c mt k t t w dt ⋅ χ (1) wall energy balance ( ) =w w w lo du k t t w dt ss (2) the following constitutive equations, describing the relationship between the internal energies and the corresponding temperatures, complete the model. = = p w pw u c mt u c tw (3-4) the variables and parameters of the above model and their units of measure are the following t water temperature °c wt tank wall temperature °c pc specific heat of water j kg°c u internal energy of water j wu internal energy of the wall j m mass flow rate of water kg s it inlet water temperature °c m mass of water kg pwc heat capacity of the wall j °c hew total heating power of one electric heater w χ portion of total heating power turned on wk wall heat transfer coefficient w °c lossw heat loss of the system w the manipulable input to the system is the external heating, all the other input variables are regarded as disturbances. then we can list the disturbances with physical meaning as follows. • cold water infiltration. this effect is taken into account with the in-convection term in the water energy conservation balance (1), where the in and outlet mass flowrate m is controlled to be equal (but might change in time) and the inlet temperature can also be time-varying. p ic mt it • energy loss towards the environment. this effect is modelled as a loss term in the wall energy balance (2). lossw the pressure of saturated vapor in the gas phase of the tank depends strongly on the water temperature in an exponential (nonlinear way). the experimental measured data found in the literature [7] have been 91 used to create an approximate analytic function to describe the dependence. the function has the form ( ) 2 3 0 1 2 3 ( ) 100 ( ) = = = + + + tep h t t c c t c t c t ϕ ϕ (5) for the parameters of ϕ , the following values were obtained 1 0 1 5 2 3 6.5358 10 4.8902 10 9.2658 10 7.6835 10 − 2 8 − − − = ⋅ = ⋅ = − ⋅ = ⋅ c c c c (6) the validity range of the model is the usual operating domain of the pressurizer, i.e. 315°c ≤ t ≤ 350°c. in pressure terms, this means 105.65 bar ≤ p ≤ 137.09 bar. state space description based on eqs (1)-(2) and (3)-(4) we can write the system model in the following standard state-space form = + +& c c cx a x b u e d (7) where the state vector [= t wx t t ] , the manipulable input u is directly proportional to the heating power, and the disturbance input vector [ ]= t i lossd t w . furthermore, the matrices in (7) are the following 0 , 100 w w p p c w w pw pw he pc c pw k km m c m c m a k k c c mw mc mb e c ⎡ ⎤− −⎢ ⎥ ⎢ ⎥= ⎢ ⎥ −⎢ ⎥ ⎢⎣ ⎡ ⎤⎡ ⎤ ⎢ ⎥⎢ ⎥ ⎢ ⎥= =⎢ ⎥ ⎢ ⎥⎢ ⎥ ⎢ ⎥⎣ ⎦ ⎣ ⎦ ⎥⎦ (8-9) the real physical measured variable in the system is the pressure. since (according to our assumptions) the temperature in the tank is a monotonous and invertible function of the pressure, we can write a linear output equation in the form [ ]1 0y = x (10) this means that we can express the performance requirements (bounds) for the pressure in terms of the temperature in the tank. the unknown parameters of the continuous-time model have been estimated from input-output measurement data. the model structure together with the estimated parameter values have been successfully validated. the detailed system identification procedure is described in [11]. for the controller design, it is convenient to center the state, input and disturbance variables as follows: , ,x x x u u u d d d∗ ∗ ∗= − = − = − (11) where x∗ is the required steady state to be kept by the controller, d∗ is the nominal (mean) value of the disturbances and u∗ is the constant input necessary to keep the prescribed steady state x∗ . using the centered coordinates, the system model (7)-(9) can be rewritten as c c cx a x b u e d= + +& (12) for the controller design, we need a discrete-time state space model of the system (12). the discretization was performed assuming zero order hold on the input with a sampling interval of 10s. the centered discrete-time model is given by the equations 1k k k kx ax bu w+ = + + (13) where the effect of the disturbance term is expressed in discrete-time by the state disturbance . ce d kw robust model predictive control design control problem formulation the aim of the control is the robust stabilization of a prescribed operating point in case of additive disturbance, while the state and the control are subject to hard constraints. to solve this problem we apply the single policy robust model predictive control proposed by langson et al. in [5]. since this method requires the knowledge of the entire state, in our case it has to be completed with an appropriate state estimator. the control design procedure will then consist of three steps: first, assuming that the full state is available for measurement and no disturbance affects on the system, a nominal mpc controller is designed. then the robustification of the nominal controller comes making the nominal mpc applicable in the presence of external disturbances. the last step is the design of a state estimator and its integration into the mpc control framework. before starting the procedure the following assumptions have to be made: • the disturbance is bounded and there exists a convex polytope w containing the origin in its interior s.t. kw w k∈ ∀ • the constraints on the state and the control input are convex, i.e. there are given convex, polytopic sets x 92 and u containing the origin in their interior s.t. , ku u∈ kx x∈ have to be hold . for simplicity we moreover assume that u is rectangular i.e. k∀ 1 1 2 2 [ , ] [ , ], [ , ] p pl l l l l lu u u u u u u= − × − × × −l . nominal mpc following the steps of control design procedure in [5] we have to first formulate and solve the model predictive control problem for the disturbance free case. this means the determination of an admissible receding horizon policy ( )kxµ , which steers the centered system from initial state 0x x∈ to the origin. the solution to this problem can be derived from the result of the following optimization problem: 1 0 0 1 0 1 1 0 0 arg min ( ) ( ) ( ( ), ) , [ , , ], [ , , ] , , v n n t t n n i i i i n n i i i i i k n f v v v v v v x v v x qx v rv v v v x x x x ax bv x x x x v u x x ∗ − = − − + + = = = + = = = + = ∈ ∈ ∈ ∑ k k i (14) where n is the length of the horizon and fx x⊂ is a terminal set having the following properties: there existsan admissible static state feedback control , which keeps the system trajectories in ( )u x fκ= = x fx i.e. for all ( ) , ( )f fx x x u ax b x xκ κ∈ ∈ + ∈ (15) and asymptotically stabilizes the system i.e. 1 0lim 0 if ( ) and k k k k k fx x ax b x x xκ→∞ += = + ∈ (16) in possession of the optimal control input vector v∗ we can formulate the single policy mpc controller in the following way: nom if( ) if i i i v ix n fx i µ ∗⎧ ≤⎪= ⎨ >⎪⎩ n (17) i.e by means of single policy approach we determine v∗ only in the beginning (and later only if the prescribed operating point changes), and after depleting the entire control sequence, we switch to the linear feedback fx (dual-mode control). it can be easily proved [5], [6] that the control policy (17) asymptotically stabilizes the plant in the disturbance free case and both the state and the input will satisfy the constraints. the lyapunov function for the closed loop dynamics can be derived from the quadratic cost . nv to implement the formulated mpc algorithm on a particular system we need to determine the feedback gain f and the associated terminal set fx . it is straightforward to choose f as an unconstrained lq controller minimizing the infinite horizon cost function defined as: 0 1 ( ) ( , ) , , , 0 t t i i i i k k k k k v v v x v x q x v r v v fx x ax bv x x q r ∞ ∞ ∞ ∞ ∞ = + ∞ ∞ = = + = = + > ∑ 0 0 i = k (18) the solution f and the quadratic lyapunov function of the closed loop dynamics ( ) tw x x px= 1 ( )kx a bf x+ = + can be obtained as a solution of a discrete algebraic ricatti equation: (19) 1( ) ( ), ( )( )( ) t t t t t t t f b pb r b pa p a pa a pb b pb r a pb q − ∞ ∞ ∞ = + = − + + since the terminal set fx has to be invariant for the dynamics 1 ( )k kx a bf x+ = + it can be constructed from an appropriate level set of w(x). let fx be the maximal level set, which satisfies the input constraints, i.e. , { | } max , { | max }t i t f t i lx x px x x x px f x u iγ γ γ γ γ γ ∗ ∗ ∈γ ≤ = ≤ = γ = ≤ ∀ (20) where t if is the ith row of f. notice that is a support function of the set ,( ) max t t i x x pxh f f xγ≤= i { | }tx x px γ≤ , which can be calculated as 1( ) t i ih f f p fγ −= i ([4],[3]). consequently in single input case 2 1 , tl t u f f f p f γ ∗ − = = (21) since fx may be larger than x, let f fx x x= ∩ . (the numerical calculation of the intersection can be greatly simplified if the polytopic approximation of x and fx is used.) robust mpc the next step of the controller design is the "robustification" of the nominal control policy. this can be performed by tightening the constraints of the nominal mpc and completing the nominal control input nom ( )ixµ with an appropriate error feedback term, i.e. more precisely: 93 nom( ) ( ) ( )i i i ix x k x xµ µ= + − (22) where ix is the nominal state value – calculated by iterating 1 nom ( )k k kx ax b xµ+ = + i, x is the true state (measured / estimated), and k is a stabilizing feedback for the disturbance-free dynamics 1k k kx ax bu+ = + . (it is possible to choose k f= . in order to formalize the new, tighter constraints for the robust mpc problem, we have to determine the following disturbance invariant set: 0 ( )i i z a bk w ∞ = = +∑ (23) because of the infinite summation the equation above can not be applied directly. there are two possibilities: we can use an approximation for z ([8]), or we can apply (23) till the difference between two consecutive sets becomes smaller than the numerical accuracy of the computing software. the first approach is mathematically precise, but we used the second one, since it is easier to implement and the convergence of (23) is fast enough to make this procedure practically applicable. using z the stringent sets of constraints can be calculated as follows: , f fx x u u kz x x= ∼ ζ = ∼ , = ∼ z } (24) where ~ denotes the pontryagin difference of two sets, defined as: ~ { |a b x x b a= + ⊂ (25) at this point we can formulate the robust mpc procedure: 1 0 0 1 0 1 1 0 0 arg min ( ) ( ) ( ( ), ) , [ , , ], [ , , ] , , v n n t t n n i i i i n n i i i i i k n f v v v v v v x v v x qx v rv v v v x x x x ax bv x x x x v u x x ∗ − = − − + + = = = + = = = + = ∈ ∈ ∈ ∑ k k i (26) i.e. we follow the same procedure as (14), but – instead of , , fx u x – we use the tightened constraint sets , , fx u x . according to (22) the control policy is defined as: ( ) if( ) ( ) if i i i i i i i v k x x i nx fx k x x i n µ ∗⎧ + − ≤⎪= ⎨ + − >⎪⎩ (27) state estimation as we have mentioned in the first section the state 2x of the pressurizer can not be measured directly. for this, we apply discrete-time state estimator to approximate it on-line from the input u and the measured output 1y x= . the robust mpc controller will then work with this estimated state. the estimator applied is given in the following wellknown form: 1| 1 1| 1 1| 1| | ˆ ˆ ( ) ˆ ˆ k k k k e k k k k k k k k x x k y cx x ax bu + + + + + + = + − = + (28) where |k kx denotes the estimated state at time instant k. substituting (13) into (28) the following error dynamics can be derived: 1 1 1| 1 | ˆ ( )( ) ( ( ) ( ) k k k k e k k k e e k e k e x x ) ka k ca x x i k c w a k ca e i k c w + + + += − = − − + − = − + − (29) where ek is chosen so that the matrix ea k ca− will be stable. before applying the estimator we have to examine the effect of the estimation error on the stability of the controlled system and on the prescribed constraints. we examine the system behaviour after the disappearence of the initial transients of (29), i.e. we assume that the estimation error is caused only by the disturbance , and not the initial difference between the estimated and the true states. by iterating (29) we can easily see that after some steps kw |ˆk k k ex x z k∈ + ∀ , where ez is a disturbance invariant set constructed in the following way: 0 ( ) (i e e e i )z a k ca i k c w ∞ = = − −∑ (30) since by (13) 1k k kx ax bu w+ ∈ + + holds and ez is symmetric to the origin, for the estimated state a following relation can be derived: 1| 1 | | 1| 1 | ˆ ˆ ˆ ˆ ˆ , k k k k k e e k k k e k k k k k k k e x ax bu w az z ax bu w x ax bu w w w + + + + ∈ + + + + = + + ⇓ = + + ∈ (31) thus, if we perform the same controller synthesis as before with instead of w we get a control policy ew ˆ( )kxµ which guarantees the stability of (31) while keeping the state ˆkx and the input in the predefined range. since the difference between the true and the 94 estimated state is considered in the real state will also satisfy these constraints. since is generally larger than w the sets ew ew , , fx u x constructed from prescribe much tighter constraints than those which are constructed from w . ew simulation results to demonstrate and examine the performance of the controller designed above an identified model of the pressurizer was used [10]. after discretization the following state space model was obtained: 0.6651 0. 0.1035 , 0.0355 0. 0.0024 a b ⎡ ⎤ ⎡ ⎤ = =⎢ ⎥ ⎢ ⎥ ⎣ ⎦ ⎣ ⎦ 91 21 = 3341 9645 (32) for the simulation two reference values were chosen: (33) 327.166, 326.166a b r ry y= = the corresponding operating points are as follows: (34) 327.1660 , 1.71 326.7760 326.1660 , 1.71 325.7760 a a ss ss b b ss ss x u x u ⎡ ⎤ = =⎢ ⎥ ⎣ ⎦ ⎡ ⎤ = =⎢ ⎥ ⎣ ⎦ the lq controller was designed by using the following weighting matrices: (35) 210 , 20q i r∞ ∞= the resulted feedback gain is [ ]0.1439 0.8392f = . the following constraints for state and input were chosen by considering the physical limitations of the system: (36) 1 21.5 1.5, 3 3, 1.71 1.71x x u− ≤ ≤ − ≤ ≤ − ≤ ≤ the cause why the constraint on the control input was constructed in the form above is the following: in the true system the control input has to be between 0 and 4, which is equivalent to constraints 4ss su u u− ≤ ≤ − s for the centered model. but it is more convenient to handle constraints, which are independent from the operating point and symmetric to the origin, so we restrict the bounds to [ ]1.71 1.71− where 1.71 min( , )a b ss ssu u≤ by examining the system behavior, it was seen that the difference between the nominal and the true d∗ d disturbance is at most 15%, which means that w in the centered, discrete model is inside the rectangle defined as: [ ] [ ]0.05 0.05 0.005 0.005w w∈ = − × − (37) we used kalman filter as a state estimator, which was designed according to the measurement noise conditions. the obtained filter gain was [ ]0.7712 0.5982ek = . setting the stabilizing k controller equal to f the sets needed for the mpc algorithm can be calculated. figure 4. 5. shows the results in the case when full-state measurement is assumed and figure 3. 4. shows the obtained constraint sets in the case of state estimation. it can be seen that the constraints to be satisfied by the input and states are much more tighter if state estimator is applied. in the simulation the horizon was n=50, the system started from and the weighting matrices in the mpc optimization were chosen to be [0 327.5 327 tx = ] 0i 2 ,iq i i r= ⋅ = s (38) the system had to track first, and this reference was changed to at time a ry b ry 24000t = . to illustrate the robustness of the controllers designed the maximal 15%± persistent disturbance was added to the original plant. figure 6 shows the factors by which the nominal disturbance was multiplied. the simulation results in the cases of full state measurement and state estimation the can be found in figures 7. and 9. figure 8. shows the state estimation error. it can be seen that in all cases the output remains in the 1.5-wide neighborhood of the prescribed value while the control input also satisfies the constraints. it is also seen that from reference tracking point of view there is no significant difference between the cases of full state measurement and state estimation. although the controller using estimated states has to satisfy more stringent constraints to achieve the same result. examining the settling performance it can be stated that the overshoot is negligible and the setting time is acceptable small. the time-consuming optimization procedure was executed only twice: first, in the beginning and later at 24000t s= , when the change of reference took place. conclusions and further work a single policy robust model predictive control was successfully applied to a pressurizer model. it was shown that the states and the stabilizing control input designed by this approach remain in the given range even if additive disturbance is present. by using single policy approach the computation time needed for the control input has been drastically reduced. 95 acknowledgements this research was partially supported by the grants no. otka t042710 and f046223. figure 2 : constraint sets in the case of state estimation , , ,f ex z x x figure 3 : constraint sets in the case of state estimation , , ,f fz x x u figure 4: constraint set in the case of full state measurement , ,fx x x figure 5 : constraint set in the case of full state measurement , , ,f fz x x u 96 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 x 10 4 0 0.5 1 1.5 2 2.5 u 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 x 10 4 325.5 326 326.5 327 327.5 328 y yr figure 9 : reference signal (solid), system output (dashed) and control input in the case of state estimation 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 x 10 4 0.8 0.85 0.9 0.95 1 1.05 1.1 1.15 1.2 1.25 d1 d2 figure 6 : disturbance scaling factors used in simulation. references 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 x 10 4 325.5 326 326.5 327 327.5 328 y yr 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 x 10 4 0 0.5 1 1.5 2 2.5 u 1. apros. apros – the advanced process simulation environment, vtt industrial systems, 2005. http://www.vtt.fi/tuo/63/apros/. 2. k.m.hangos and i. t. cameron: process modelling and model analysis. academic press, london, 2001. 3. i. kolmanovsky and e. g. gilbert.: maximal output admissible sets for discrete-time systems with disturbance inputs. american control conference, 1995. 4. i. kolmanovsky and e. g. gilbert.: theory and computation of dysturbance invariant sets for discrete-time linear systems. mathematical problems in engineering, 4:317-367, 1998. 5. w. langson, i chryssochoos, s. v. rakovic and d. q. mayne: robust model predictive control using tubes. automatica, 40:125-133, 2004. figure 7 : reference signal (solid), system output (dashed) and control input in the case of full state measurement 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 x 10 4 −0.1 −0.05 0 0.05 0.1 0.15 0.2 0.25 x1−x1e x2−x2e 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 x 10 4 325 325.5 326 326.5 327 327.5 328 x1e x1 x2e x2 6. d. q. mayne, j. b. rawlings, c. v. rao and p. o. m. scoakert: constrained model predictive control: stability and optimality. automatica, 36(3):789-814, 2000. 7. r. h. perry and d. w. green: perry’s chemical engineers’s handbook (7th edition). mc graw hill, new york, 1999. 8. s. v. rakovic, e. c. kerrigan, k. kouramas and d. q. mayne.: approximationof the minimal robustly positively invariant set for discrete-time lti systems with persistent state disturbances. 42th conference on decision and control, 2003. 9. z. szabó, p. gáspár and j. bokor: reference tracking of wiener systems using dynamic inversion. in 2005 international symposium on intelligent control, limassol, cyprus, pages on cd, paper id: wea06.5. 2005. 10. i. varga, g. szederkényi, k. m. hangos and j. bokor: modelling and model identification of a pressurizer at the paks nuclear power plant. in 14th ifac symposium on system identification. (submitted), 2006. figure 8 : true (solid) and estimated (dashed) states and estimation error. http://www.vtt.fi/tuo/63/apros/ microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 37(2) pp. 119-122 (2009) comparison of calibration models based on near infrared spectroscopy data for the determination of plant oil properties a. fülöp, j. hancsók university of pannonia, department of hydrocarbon and coal processing p. o. box 158., h-8201 veszprém, hungary, phone: +3688624414, fax:+3688624520 the aim of this study was to compare the prediction efficiency of different type of linear calibration models using near infrared (nir) absorbance spectral data of vegetable oils. the applied model types were the pca-mlr (principal component analysis-multiple linear regression), the pls (partial least squares regression), the pca-ann (principal component analysis-artificial neural network) and the ga-ann (genetic algorithm-artificial neural network). the calibrations were executed on the models for the determination of the concentration of oleic acid of vegetable oils and the performances of the different models were determined using external validation. during external validation the built models were tested with vegetable oil samples of which oleic acid content was known and was not included in the calibration sample set. the comparison of the models was executed on the basis of the accuracy of the prediction. keywords: near infrared spectroscopy, sunflower oil, rapeseed oil introduction the near infrared spectroscopy (nir) is a wellestablished analytical technique based on the absorption of electromagnetic energy in the region of 12000– 4000 cm-1. this type of technique allows the determination of physical and chemical properties of multi-component systems (gasoline, diesel oil, vegetable oil, etc.) in a fast and non-destructive way, without requiring complex sample pre-treatment and sample preparation [1]. the difficulty of the technique is that in the nir region a component typically absorbs at more than one wavelength and the absorbance at a given wavelength may have contributions from more than one property. therefore, extracting relevant information from the nir spectra and modelling the relationship between the spectral data and the component concentration is a big challenge. to extract the relevant information from the nir spectra pca (principal component analysis) and ga (genetic algorithm) wavelength selection methods were used, and for prediction mlr (multiple linear regression) and ann (artificial neural network) linear model types were applied. besides, the pls (partial least squares regression) method, the most popular linear calibration method in near infrared spectroscopy was applied as well. materials and methods oil samples a total of 144 rapeseed and sunflower oil samples were obtained from various locations of hungary. the sample set consisted of three types of vegetable oil: sunflower oil with low oleic acid content (around 25%), rapeseed oil with oleic acid content of around 65% and sunflower oil with high oleic acid content (around 85%). the sample set was split in to two parts: 102 samples were used for calibration and 42 samples were used for external validation. the fatty acid compositions of the samples were determined using gaschromatography by the appropriate en 14103 standard method [1]. spectra collection to perform the nir spectroscopic analysis a brukermpa near infrared spectrometer was used that works with the opus controller software. all samples were measured in transmittance mode in a wave number range of 12000–4000 cm-1 with a resolution of 2 cm-1. 120 to produce suitable signal/noise ratio 32 scans were accumulated. the spectral data of the oil samples were collected as absorbance spectra using a sample thickness of 0.5 cm. the raw nir spectra are shown in fig. 1 [3]. figure 1: the raw spectra of the samples at the optimisation process we found that better approximation can be achieved by using a restricted wavenumber range instead of the full range, therefore the experiments were carried out on a range of 5730– 4570 cm-1. calibration and optimisation for calibration 102 oil samples were used. the calibration of each model type was carried out using leave-one-outcross-validation method. thus, the accuracy of a given model could be expressed by the value of the root mean squared error of cross validation (rmsecv). this value was the basis of the determination of the optimal model parameters [1, 5]. there are several model parameters that effect the performance of a given model type. to achieve the best approximation we had to find the optimal model parameter combination for each model. this procedure is the model optimisation that was conducted using leaveone-out-cross-validation method. the model parameters that were varied during the optimisation process in respect of each model type are shown in table 1. table 1: the varied parameters in optimisation process model type parameter value pca-mlr number of principal components 1-20 pls number of latent variables 1-20 pca-ann number of principal components 1-20 number of variables 1-20 number of individuals in the population 1-30 ga-ann number of generations 1-10 beside these parameters, spectral preprocessing methods were also varied along the optimisation processes. these methods were the mean-centering, the autoscaling, and the range-scaling [2]. external validation in the course of the external validation the calibration models were tested with vegetable oil samples of which oleic acid content was known and was not included in the calibration sample set. for the experiment 42 oil samples were used. as the result of this experiment the prediction efficiency of the models could be concluded by the value of the root mean squared error of the prediction (rmsep). results and discussion pca-mlr model the pca-mlr technique is the simplest approach of the linear calibration model that is also called principal component regression (pcr). the pca is widely used in statistics to reduce the number of the variables of a data matrix. in the nir spectroscopy the pca algorithm replaces the original spectra data matrix with some orthogonal vectors (principal components) such that the first vector (first principal component) represents the greatest variance of the data set, the second vector (second principal component) represents the second greatest variance of the data set, and so on. thus, roughly say, the pca selects those wavenumber regions where the absorbance of the given component is the most plausible. in pcr the principal components are used as the independent variables of the multiple linear regression, thus it could be applied to estimate the concentration of the given component [2]. figure 2: the result of the external validation in respect of pca-mlr model the result of the external validation of pca-mlr model can be seen in fig. 2. in the figure the true concentration values of oleic acid were plotted as a 121 function of the predicted values, therefore the straight line represents the true, the dots represent the predicted values. the rmsep value that could be achieved with this model type at the optimal model parameters was 3.89. pls model this approach is the most popular chemometric method for calibration model creation. the pls regression is a generalisation of the pca-mlr method and that simultaneously executes the dimension reduction of the spectra data matrix and the regression. the main advantage of this technique in contrast to pcr is that the pls takes into account the correlation between the spectral data and the component concentration as well, while extracting the latent variables from the original data matrix, thus the latent variables refer to the given component directly [2]. the result of the external validation of pls model can be seen in fig. 3. the rmsep value of the external validation of pls method was 1.65. figure 3: the result of the external validation in respect of pls model pca-ann model this approach is the combination of the pca wavenumber selection method and the ann model type. the artificial neural networks can be found in application of different areas of sciences and techniques but occurred in chemometric only recently. this method can be used for the interpolation and extrapolation of multiple-input multiple-output (mimo) linear and nonlinear systems. in our experiments an mlp (multilayer perceptron) feed forward neural network was used that worked with the basic levenberg-marquard training algorithm. the structure of the network consists of one hidden layer where the number of neurons was 5 in all cases, because we found that this parameter did not affect the model performance significantly. at the algorithm the number of training iteration was 200 and the activation function of all neurons at the hidden and output layers were linear transfer functions, because we assumed that linear relation exists between the absorbance data and the component concentrations. in the input layer transfer function was not used [2, 4]. the result of the external validation of pca-ann model can be seen in fig. 4. as the result of the external validation an rmsep value of 1.15 could be achieved. figure 4: the result of the external validation in respect of pca-ann model ga-ann model this method combines the ga wavenumber selection technique and the ann model type. the genetic algorithm is a multivariable adaptive optimum search procedure based on the mechanics of natural genetics and natural selection and could be used for a variety of search problems. among the genetic operations the selection (elite individuals: 3) and the crossover (crossover fraction: 100%) were used and mutation function was not used. in the process the ga selects the wavenumbers where the performance of the ann model is the best [4, 6]. the result of the external validation of ga-ann model can be seen in fig. 5. among the four methods the ga-ann provided the best prediction efficiency with an rmsep value of 0.89. 122 figure 5: the result of the external validation in respect of ga-mlr model conclusions comparing the different methods according to the rmsep values at the optimal parameter combinations the ga-ann approach offered the best prediction efficiency and the pca-mlr provided the worst one (table 2). table 2: the rmsep values of the models model type rmsep pca-mlr 3.89 pls 1.65 pca-ann 1.15 ga-ann 0.89 although the best performance was given using gaann method, we have to mention that this technique was the most complex and time consuming and there were a lot of model parameters that had to be varied in the optimisation process. therefore the calibration and optimisation took a very long time. references 1 baptista p., felizardo p., menezes j. c., neiva correia m. j.: analytica chimica acta (2007) 153 2 balabin r. m., safieva r. z., lomakina e. i.: chemometrics and intelligent laboratory systems 88 (2007), 183–188 3 fülöp a., magyar sz., krár m., hancsók j.: proceedings of 43rd international petroleum conference (2007) 7 4 nan q., lihua w., mingchao z., ying d., yulin r.: chemometrics and intelligent laboratory systems 90 (2008), 145–152 5 kim k. s., park s. h., choung m. g., jang y. s.: journal of crop science and biotechnology 10 (2007), 15–20 6 yibin y., yande l.: journal of food engineering 84 (2008), 206–213 microsoft word 1_r.doc hungarian journal of industrial chemistry veszprém vol 37(1). pp. 21-25 (2009) synthesis and evaluation of modified polyethylene wax applied as dispersant in rubber bitumen composites a. angyal , n. miskolczi, l. bartha, p. gergó university of pannonia, department of hydrocarbon and coal processing, h-8201 veszprém, p. o. box 158, hungary e-mail: angyala@almos.uni-pannon.hu grain rubber obtained from waste tyre has become one of the most important bitumen modifiers nowadays, but rubber precipitation from bitumen can cause problems during utilization. in our experimental work additives were synthesised as dispersant for rubber bitumen composites. raw material was polyethylene wax (pew) obtained from mild thermal cracking of polyethylene waste. the synthesis was a copolymerisation of olefins and maleic-anhydride. during the products evaluation the main analytical method was fourier transform infra-red (ft-ir) spectroscopy. there were significant differences between the characteristic of raw material and synthesised products. the dispersant effect of the additives was studied in rubber-bitumen composites. all additives increased the stability of rubber-bitumen composites. from the results of the experiments it was stated that the modified polyethylene wax obtained from polyethylene waste can solve the instability problem of rubber-bitumen composites. keywords: polyethylene wax, rubber-bitumen, dispersant additive introduction the free-radical grafting of maleic anhydride (ma) onto polyolefins in presence of initiator was the topic of several researches in the last decades. these investigations resulted that the chemically modified polyolefins can be used in polymer blends and composites to improve the chemical and mechanical properties [1-4]. several successful polyolefin grafting methods have been developed, the functionalization of polyolefins can be achieved either in a melt process or in a solution process [5-7]. in a solution process the polyolefins are dissolved in a suitable solvent at reaction temperature (100–200°c), than ma and an initiator (usually peroxide) are added into the reaction mixture. this method is relatively complex, but it is advantageous because the individual molecular structures of grafted polyolefins can be achieved easier with different feeding order of reactants. there are methods which can increase the rate of grafting by adding another co-monomer into the reaction mixture [8-9]. ying et al. studied the grafting of ma onto polypropylene in the presence of styrene. they investigated the graft degree of ma at different rate of monomers. it was established that styrene reacts with ma to form styrene-maleic-anhydride copolymer during the grafting process and it leads to improving the graft degree of ma [10]. in most experiments the grafting of ma onto polyethylene and polypropylene have been studied and there are studies about modifying of polystyrene [11] and polyolefin copolymers [12], too. however, the grafting of polyethylene wax (pew) was not reported. aliphatic waxes can be produced with mild, thermal cracking of plastic wastes (polyethylene, polypropylene). lots of researches suggest that the best utilisation way of the cracking products is the energetic application, so the aim of these investigations is to achieve the biggest yield of liquid product (light oils). however the yield of c30+ hydrocarbons can be considerable at mild reaction parameters [13-14]. the utilisation of this heavier fraction is less described in the literature (e.g. incineration). an alternative way for utilisation of residue obtained from waste plastic cracking is blending into bitumen. it is well known that polymers have been used as bitumen modifiers to increase mechanical properties [15-17]. there are lots of studies about bitumen modification with various polymers. elastomers, plastomers and moreover waste plastics and rubbers were used in these experiments. grain rubber obtained from waste tyre has become one of the most important bitumen modifiers nowadays. however the inhomogeneity of rubberbitumen composites is a considerable problem during the utilisation [18]. the precipitation of rubber from bitumen can affect the product quality, to avoid precipitation stirred storage tanks were used. an other solution of this problem that functionalised poliolefin wax by maleic-anhydride is added into rubber-bitumen composite. therethrough the modified pew works in the rubber-bitumen composites as dispersant additives. the aim of this paper was to synthesize such modified polyethylene wax which can be used in rubber-bitumen 22 composites as dispersant additives. raw material of the synthesis was c30+ hydrocarbon fraction obtained from thermal cracking of polyethylene waste. a further aim of this study was to analyse the grafted products and to evaluate the dispersant effect of the additives in rubberbitumen composites. experimental materials polyethylene wax was produced by thermal cracking of polyethylene waste derived from package industry. the thermal cracking carried out in a horizontal tube reactor system at 530 °c reaction temperature. the produced pew was analysed and following results were given: i/br number 45.9 g i/ 100 g pew; olefin content 42.8%; mw 990 g/mol. the used reagents for the grafting reaction are monomers (maleic-anhydride (ma), ndecene, styrene), initiator (di-tertiary-butyl-peroxide (dtbp)) and solvent (xylene). main properties of these materials are shown in table 1. the synthesized additives were evaluated in rubber bitumen composite. the composites were prepared by mixing of grain rubber with two types of bitumen in appropriate amount. table 2 shows the properties of these bitumens, while the grain rubber has the following properties: grain size <2 mm; moisture 0.5 w/w%; free from metal contamination and it was grained by water jet system. table 1: properties of the used materials properties ma n-decene styrene dtbp 20 4d g/cm3 − 0.745 0.909 0.796 refraction index − 1.4230 1.5463 1.3891 molecular weight, g/mol 98.0 140.0 104.1 146.2 boiling point, °c 200 170 145 − table 2: properties of the used bitumens bitumen b160/200 b50/70 softening point, °c 40 48 penetration, 0.1 mm 190 51 fraass breaking-point, °c -15 -12 dynamic viscosity 135°c, mpas 194 495 dynamic viscosity 180°c, mpas 41 90 synthesis a commercial solution grafting process was used to graft ma onto pew. the reaction recipe was typically as follows: in a sealed vessel 420 g pew was dissolved in xylene at 140 °c under stirring. after complete dissolution of pew ma and dtbp were added and moreover in some cases styrene and n-decene were added as co-monomers. the xylene was removed from the grafted pew by vacuum distillation. the product was washed with boiling acetone and dried in vacuum at 80 °c for 12 h. three types of dispersant additives (modified polyethylene wax) were synthesized with this reaction recipe. in one case only ma was grafted onto the wax pew/ma/dtbp (pe/1). in other cases besides of ma n-decene or styrene was used to increase the graft degree of ma on pew. these co-monomers were added pew/ma/dtbp/n-decene (pe/2) or pew/ma/dtbp/ styrene (pe/3). the effect of dispersant additives was evaluated in rubber bitumen composites. these composites were prepared with a so called multistage method. this method means that the chemical dispersion of rubber and other additives in bitumen is followed by a mechanical shearing. in all cases the samples contained 15 w/w% grain rubber and the preparation parameters were fixed. six different composition were produced: a commercial rubber-bitumen without any additives (rb), a composite with a reference additives (rb+r), three composite with the synthesized additives (rb+pe/1, rb+pe/2, rb+pe/3) and the non modified pew was investigated in rubber-bitumen (rb+pew). the reference additive was a styrene-butadiene-styrene copolymer, which was tested in a previous work [19]. analysis procedures the molecular structure of the additives were determined by a fourier transform-infrared (ftir) technique with a tensor 27 type spectrometer (resolution: 4 cm-1, illumination: sic globar light, monochromator: kbr prism, detector: rt-dlatgs type detector) in the 4000–400 cm-1 wave number range. opus5.5 software was used for the spectrometer control and the data processing. utilization properties of the prepared rubber-bitumen composites were tested by the following examinations: penetration (astm d 597), softening point (astm d 3695), elastic recovery (astm d 6084-04), brookfield viscosity at 180°c (astm d 4402), storage stability (en 13399). results and discussion infrared spectroscopy the ftir spectra of the pure pew and the modified polyethylene waxes are shown in fig. 1. peaks in 3000– 2800 cm-1 wave number range are typical of the bond vibrations of saturated hydrocarbons. moreover other typical groups of paraffin infrared bands can be seen in fig. 1. the wax obtained from the thermal cracking of polyethylene consisted paraffinic and olefinic hydrocarbons, these olefinic molecules were mostly α-olefins. the α-olefins molecules are more reactive than the other olefins or paraffin hydrocarbons, therefore 23 these molecules are advantageous in the ma grafting. the c–h deformation bond vibrations at region 1000– 850 cm-1 are typical of unsaturated hydrocarbons (fig. 1). the band par of vinyl group (rhc=ch2) appeared at 990 and 910 cm-l wavenumber, where the later band has double intensity. in case of vinylidene group (r1hc=chr2) two bands could be seen at 980 and 960 cm-1. the comparison of the infrared spectrums of synthesized additives and the raw material showed significant differences. these differences confirm the reaction of pew and ma, because new adsorption bands at 1795–1775 cm-1 and at 1870–1850 cm-1 can be assigned to grafted anhydride, which are due to symmetric (υsc=o) (strong) and asymmetric (υasc=o) (weak) stretching vibration of five members cyclic anhydrides [12], respectively. appearing of peaks between 1140 and 1000 cm-1 are the consequences of anhydride υasc–o–c vibrations, moreover other typical anhydride bands can be seen at range 1300–1180 cm-1 and 1050–900 cm-1. an other evidence shows the successful pew grafting, because in case of the using styrene co-monomer vibration bands can be observed, at 780–690 cm-1 which are typical of aromatic hydrocarbons. fig. 2 shows the enlarged infrared spectrum of product and pew at 1600–1900 cm-1 wave number range. in the spectrum of additives at 1870–1850 cm-1 and 1795–1775 cm-1 the grafted ma content can be observed on the pew. intensity of both peaks show that the grafting rate increased with the using of comonomers. in case of pour ma grafting the grafting rate was the lowest and styrene makes the largest improvement in the grafting ration. in the literature it was presented that the co-monomer enhanced the ma grafting on to polymers [10]. the maximum intensity at 1775 cm-1 indicates that the ma attached to the styrene monomers to form short oligomers and after that this oligomers grafted onto the pew. li et al. [10] reported that the ftir spectrum has maximum intensity at 1770 cm-1 than single ma grafting occurred, in case of the maximum intensity at 1790 cm-1 the polymeric ma grafting was the main reaction. in our ftir spectra the maximum intensity of vibration bands appeared between 1790 and 1770 cm-1 wave number. figure 1: ftir spectra of pew and the grafted pew figure 2: ftir spectra of additives at region 1900–1650 cm-1 24 analysis of rubber bitumen composites softening point fig. 3 shows the softening point data of the rubber bitumen samples. in all cases the dispersant additives decreased the softening point of the composites, although this effect was not significant. the softener effect of the pew and the additives can be advantageous property, because adding small amount from them can modify the rubber bitumen composition. 56 58 60 62 64 66 rb rb+r rb+pew rb+pe/1 rb+pe/2 rb+pe/3 s of te ni ng p oi nt , ° c figure 3: softening points of rubber bitumen composites penetration it can be seen in fig. 4 that the additives and the pew increased the penetration of the rubber bitumen samples. the properties of rubber bitumen can be modified with the synthesized additives. usually the penetration data are in connection with the softening point, but in this case the additives did not affect significantly the softening point of the rubber bitumen composites, however the penetration was increased with the modification. 40 45 50 55 60 65 rb rb+r rb+pew rb+pe/1 rb+pe/2 rb+pe/3 p en et ra tio n, 0 ,1 m m figure 4: penetration data of rubber bitumen composites storage stability the best way to evaluate the efficiency of the dispersant additives is the studding of the storage stability properties of the samples. in all cases the additives improved the storage stability. quality requirements of the rubber bitumens consist the storage stability and the maximum limit is 5 °c differences between upper and lower layer softening point. in case of pew the precipitation of rubber from the bitumen was occurred, that can be seen in fig. 5. however it is considerable that the storage stability of pew modified rubber bitumen was the same as the original rubber bitumen, so the pew did not decreased this property. all of the additives had similar increasing affect as the reference additive, therefore the 5 °c limit could be maintained. 0 2 4 6 8 10 rb rb+r rb+pew rb+pe/1 rb+pe/2 rb+pe/3 ∆t , ° c figure 5: storage stability of rubber bitumen composites temperature dependence of viscosity it is beneficial to determine the temperature dependence of viscosity of rubber bitumens, because it is important for the further utilisation of the products. fig. 6 shows the temperature-viscosity characteristics of the rubber bitumen samples. according to practical experiences 500 mpas viscosity is suitable for the bitumen mixing in the industry at 180 °c. the softening affect of pew and the additives appeared at this property too, because the original rubber bitumen sample has 1020 mpas viscosity than after modification this decreased to 520–610 mpas. figure 6: temperature-viscosity characteristic of rubber bitumen samples elastic recovery elastic recovery shows the flexibility properties of rubber bitumens, the most flexible composite has the bigest relaxation time. fig. 7 shows the elastic recovery results of the samples. according to fig. 7 it can be established 25 that the rubber gives the flexibility of the composite, because the behaviour of the curves are similar. figure 7: elastic recovery of the rubber bitumen composites conclusion in our experimental work additives were synthesised as dispersant for rubber bitumen composites with copolymerisation of olefins and maleic-anhydride. raw material was polyethylene wax (pew) obtained from mild thermal cracking of polyethylene waste. the infrared spectrum of pew and the synthesised additives was determined at 600–4000 cm-1 wavenumber range and it was stated that there were significant differences between the characteristic of polymers, so the grafting of ma onto pew was successful. the dispersant effect of the additives was studied in rubber-bitumen composites. all additives increased the stability of rubber-bitumen composites and other properties were increased. advantageous softening points and viscosity data could be achieved with the using of additives. the pew increased these properties too. from the results of the experiments it was stated that the modified polyethylene wax obtained from polyethylene waste can solve the instability problem of rubber-bitumen composites. references 1. boucher e., folkers j. p., hervet h., leger l., creton c.: effects of the formation of copolymer on the interfacial adhesion between semicrystalline polymers. macromolecules (1996) 29, 774-782. 2. kudva r. a., keskkula h., paul d. r.: morphology and mechanical properties of compatibilized nylon 6/polyethylene blends. polymer (1999) 40, 6003-6021. 3. qiu w. l., zhang f. r., endo t., hirotsu t.: preparation 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(2000) 36, 1419-1429 13. predel m., kaminsky w.: polym degrad stab 70 (2000) 373-385 14. angyal a., miskolczi n., bartha l.: j. anal. appl. pyrolysis 79 (2007) 409–414 15. becker y., méndez m. p., rodrígez y.: polymer modified asphalt, vision technologica, 9, 1, 2001 16. xiaohu lu, isacsson u.: low-temperature properties of styrene]butadiene]styrene polymer modified bitumens construction and building materials 12 (1998) 405-414 17. hinislioglu s., agar: use of waste high density polyethylene as e. bitumen modifier in asphalt concrete mix materials letters 58 (2004) 267– 271 18. navarro f. j., partal p., martínez-boza f., gallegos c.: thermo-rheological behaviour and storage stability of ground tire rubber-modified bitumensfuel 83 (2004) 2041–2049 19. bíró sz., geiger a., bartha l., deák gy., miskolczi n.: crumb rubber as active bitumen modifying agent, wastetech-2005 congress, 31 may microsoft word contents_2.doc hungarian journal of industrial chemistry veszprém vol. 31. pp. 13-21 (2003) application of fourier transformation for waste minimization in batch plants. 2. process-units assignment n. g. vaklieva-bancheva*, e. g. shopova, b. b. ivanov institute of chemical engineering – bulgarian academy of sciences “acad. g. bontchev” street, bl.103 1113 sofia, bulgaria the problem for determining the minimum environmental impact for compatible products manufacturing in multipurpose batch plants is considered in this study. it is based on the use of the fourier transformation for mathematical descriptions of the waste emissions from routine sources appearing into the horizon cyclically an approach which has been proposed in its first part [4]. the problem takes into accounts both the used materials compositions and the constructed production routes. the formulated sets of constraints follow for feasibility and compatibility of the chosen production routes and justify the accomplishment of the production demands into the determined horizon. global or local environmental impact assessments are used as the objective function. an example concerning simultaneous manufacturing in a dairy of two types of curds is used to illustrate the considered problem. the aim is to determine the milkfat content in the skimmed milk used as a raw material for both products, and plant units assignment for the respective processing tasks, at which the bod generated from the process is minimal for accomplishment of some production requirements in a given horizon. both the bod generated due to the amount and composition of the processed milk and the one due to inherent losses are taken into account in the formulated problem. keywords: waste minimization, fourier transformation, multipurpose batch plants, bod, dairy processing * to whom correspondence should be addressed: e-mail vaklieva@bas.bg introduction following contemporary trends to reduce the environmental impact by developing systematic methodologies for waste minimization in sources, pistikopoulos at al. have created the minimum environmental impact methodology for continuous and batch plants [1-3]. they have embedded the life cycle analysis principles within a design and optimization framework and introduced appropriate quantitative environmental impact assessments. the latter are defined on the basis of the introduced environmental impact indices, such as ctam, ctwm, smd, gwi, poi, sodi, etc., and determine the environmental impact of the whole system or of a particular pollutant over the time horizon. later, in the first part of the current study [4], an approach describing the wasting from the batch routine sources has been proposed. it is based on the transformation of the periodic discontinuous function of the waste mass rate of pollutants w in the fourier series into the time horizon and allows for the relevant pollutant to be followed within the horizon. the obtained continuous time function presents a mathematical model of the waste producing from the routine source, which appears cyclically into the horizon during batch product manufacturing. the model involves the general characteristics of the batch product, such as batch size, cycle time, and processing times as well as accounts for the raw materials composition. it can 14 be propagated readily not only to all the routine sources of pollutant w at a current manufacture, but also to those, appearing at the compatible processing of a group and campaign of batch products in the definite horizon. its integration over the time allows for the determination of the produced waste w from the relevant routine sources. this permits the use of the environmental impact assessments introduced in [1-3]. as an illustration, the proposed approach has been applied for production recipes analysis of examples from dairy industry (curds processing). the aim was to determine the raw material composition at which the environmental impact, assessed by bod, for manufacturing of 1-kilogram target product was minimal. in order to reduce the waste from the multipurpose batch plant, at accomplishing the production demands for a group of compatible products, both the raw materials compositions and the process/units assignments must be taken into account. they affect not only the production characteristics, such as batch size and the number of processed batches, but also the environmental impact through the amount of the waste produced. usually, production and environmental requirements are in conflict. the objective of this study will be to find the best tradeoff between them. it will be based on the application of the approach for mathematical modeling of the wasting from appearing cyclically routine sources proposed in the first part. the aim will be reached through simultaneously determining the used materials compositions and the process/units assignments at which the production demands will be fulfilled into the given horizon with minimum environmental impact. the paper is structured as follows: a description of the problem is presented in next part. a mathematical formulation of the waste minimization problem is laid out in part 3. an application of the proposed approach on an example from the dairy industry – simultaneous processing of two types of curds into a given plant is presented in part 4, while the concluding remarks are in part 5. problem description let us consider a multipurpose batch plant comprising p units pp∈ of different types. each unit has a volume pv , pp∈ and could be connected with others in the plant. the plant provides an opportunity for a compatible manufacturing of i different products, ii∈ within a given time horizon h . iq [kg] is the production demand for the respective products i . each product i comprises ,li processing tasks, ill ∈ . a set of in key components inn∈ is used for product manufacturing. the key components are introduced into the process by the raw and/or other supporting materials. only one material source for any particular key component n is allowed. the composition of the key components could be changed within the technologically defined boundaries nn )imax(x,)imin(x . physical, chemical or biochemical transformation takes place in each task until the target product is obtained. the tasks processing times ilt are supposed to be constant. the cycle time depends on the chosen operational mode. for the overlapping case it is { }ili tmaxtc = , while for the non-overlapping ∑= l ili ttc . each processing task could be performed in one or more appropriate plant units. a variety of process/unit assignments exists, which results in multiple routes for product manufacturing. binary matrices lp)i(id are introduced to identify the appropriate plant units for products i as follows: 1)i(id lp = , for units p suitable to process task l , and 0)i(id lp = , for the others. the volumes of the involved plant units and the size factors for the respective tasks determine the batch size of a structured production route. usually, the size factors are taken to be constant. but in fact they depend on the used materials composition. the effect of the key components composition on batch size will be taken into account in the problem. manufacturing the products is accompanied by producing different waste types. the standard limit values www s,w,a µµµ , for air, water and soil are 15 given for the processed pollutants w , ww∈ . in principle, each task ill ∈ of the products i could be a potential routine source of effluent with pollutants w . the amount of the wastes produced over the time horizon also depends on both the key components composition and the respective batch sizes. the above description brings the waste minimization problem to determining the composition of raw materials, solvents and other components used in the process and the respective production routes for each product i so that the demands iq could be accomplished into the horizon h at minimum environmental impact. mathematical formulation of the optimization problem variables and constraints variables a set of continuous variables n)i(x is introduced for each product i to account for the change of composition of the key components n in the relevant material sources. a set of binary variables p)i(ζ is used to structure the different production routes for each product i , as follows: 1)i( p =ζ if unit p is used for product i manufacturing, and 0)i( p =ζ , otherwise. constraints structural constraints. the objective of this set of constraints is to structure feasible and compatible production routes for products i . manufacturing each product i is feasible, if at least one of the plant units, suitable for tasks l , is assigned in the structured production route: ∏ ∑ = = ∈∀≥     il 1l p 1p plp ii,i1)i()i(id ζ . (1) the structured production routes for all i products are compatible if there are not any common shared units. pp,p1)i( i 1i p ∈∀≤∑ = ζ . (2) production constraints. this group of constraints is introduced to account for the demands iq to be accomplished within the time horizon h . taking into account that the composition of the key components in the used materials affects both, batch size and environmental impact, admissible vectors )n,i(x of the independent variable values n)i(x should be formed for each product i , { } inn1 )i(x,...,)i(x,...,)i(x)n,i(x = . ii,inn,n i ∈∀∈∀ , (3) subject to: iiinnnixixix innn ∈∀∈∀≤≤ , , ,)max()()min( . (4) the sizes of batches that are determined by the plant units assigned to the processing task of product i are: , ))n,i(x(s )i(.)i(id.v ))i(),n,i(x(b l p plpp l ∑ = ζ ζ inn,n ∈∀ ii,ill,l i ∈∀∈∀ , . (5) the size factors l))n,i(x(s in equations (5) are functions of the key components composition and can be calculated from the mass balances, according to the production recipes: ))n,i(x(y )i(v ))n,i(x(s lj j l ∑ ∈= , { } ii,i,ll,l,llllj ii ∈∀∈∀∈∈ , inn,n ∈∀ (6) where: )i(v is the volume of the input flow j in the processing task l of product i )),(( nixy is the yield of the target product i presented as a function of the key components compositions. the batch size for each product i is limited by the processing task with the minimum batch size: { } ,))i(),n,i(x(bmin))i(),n,i(x(b lζζ = inn,n ∈∀ , ii,ill,l i ∈∀∈∀ , . (7) 16 the number of batches being carried out in order to manufacture the planned amounts iq for the products i is:       = ))i(),n,i(x(b q ))i(),n,i(x(nb i ζ ζ , inn,n ∈∀ ii,i ∈∀ . (8) finally, the time required to manufacture the demand iq for the products i : itc)).i(),n,i(x(nb))i(),n,i(x( ζζ =θ , inn,n ∈∀ , ii,i ∈∀ , (9) must be within the time horizon h : h))i(),n,i(x( ≤ζθ , inn,n ∈∀ , ii,i ∈∀ . (10) mathematical models of the wasting from batch routine source accounting for the composition of the key components and production routes the mathematical description of the waste w produced from the cycle batch routine source is analogous to that proposed in [4]. the fourier transformation is used. however, here it must account for the structured particular production routes done through the respective batch sizes, (see equation (5)), and for the key components composition done through both the batch size and the mass wl))n,i(x(m of the pollutant w , generated in the task l for processing of 1 kg. target product: ( ) ( )( ) ( ) ( )[ ] ( )[ ( ) ( )( ) ( ) ( )[ ] ( )]]           +−+ ++−+ = ∑ tktktsktktsk tktktsktktsk tk tc nixminixb tinixf ilililil k ilililil il i wl wl ϕϕϕϕϕ ϕϕϕϕϕ ϕζ ζ cossincos1cossin sinsinsincos1cos1 2 1 . )),(()).(),,((2 )),(),,(( tct0 ≤≤ ll,l,ww,w,nn,n ∈∀∈∀∈∀ , ii,i ∈∀ , (11) where ϕπ = tc 2 . the mass wl))n,i(x(m of the pollutant w , for products i , can be determined from the pollutants mass balance of the production recipes as it is proposed in [5, 6]: ,)i(c.)i(mo))n,i(x(r)i(c.)i(mi ))n,i(x(y 1))n,i(x(m lj l'j wjjwlwjjwl       −+= ∑ ∑ ∈ ∈ ii,i,ll,l,ww,w,nn,n ii ∈∀∈∀∈∀∈∀ (12) where: )i(mi and )i(mo note the amount of materials input into processing task l of product i by the flows j and output by the flows; )i(c is the composition of pollutant )i(c w is the relevant flow; ))n,i(x(r is the waste produced in the task l . objective function the local and global environmental impact assessments introduced in [1-3] are used for the objective function definition. the need for the purpose relevant environmental impact indices such as stam, wtam, sdm etc. can be presented by means of the mathematical models (11) introduced above firstly as time dependent functions. thus, they will account for the used materials composition and process-unit assignment: ∑= l wl w w tinixf a tinixctam )),(),,((1)),(),,(( ζ µ ζ , ∑= l wl w w tinixf w tinixwtam )),(),,((1)),(),,(( ζ µ ζ , ∑= l wl w w tinixf с tinixsmd )),(),,((1)),(),,(( ζ µ ζ , ww,w ∈∀ , ,lll,nn,n ∈∀∈∀ ii,i ∈∀ , tct0 ≤≤ . (13) the environmental impact indices are obtained after the integration of the equations (13) over the 17 cycle time duration and multiplying by the number of batches (equations (8)), that can be performed to produce the planned amounts iq for products i : ∑ ∫= =θ l tc wl w inix w dttinixf a inixnb inixctam 0 ))(),,(( )),(),,((1)).(),,(( ))(),,(( ζ µ ζ ζ ζ ∑ ∫= =θ l tc wl w inix w dttinixf w inixnb inixwtam 0 ))(),,(( )),(),,((11))(),,(( ))(),,(( ζ µ ζ ζ ζ ∑ ∫= =θ l tc wl w inix w dttinixf s inixnb inixsdm 0 ))(),,(( )),(),,((1))(),,(( ))(),,(( ζ µ ζ ζ ζ , ww,w ∈∀ , ,lll,nn,n ∈∀∈∀ ii,i ∈∀ , tct0 ≤≤ . (14) it follows, the relevant local environmental impact assessments with regard to the particular pollutant w and respectively global environmental impact assessment, for all produced pollutants are obtained as:         = = θ θθ θ ))(),,(( ))(),,(())(),,(( ))(),,(( ))(),,(( ))(),,(())(),,(( ))(),,(( inix w inix w inix w inix w inixsdm inixctwminixctam inixei ζ ζζ ζ ζ ζζ ζ ww,w ∈∀ , ii,i ∈∀ , tct0 ≤≤ , (15) ∑ θ θ = = w inix w inix inixei inixgei ))(),,(( ))(),,(( ))(),,(( ))(),,(( ζ ζ ζ ζ . ww,w ∈∀ , ii,i ∈∀ , tct0 ≤≤ . (16) depending on the particular problem, the local environmental impact assessments or the global one could be used as the objective functions in the problems for minimization of the environmental impact of the multipurpose batch plants at the simultaneous production of a group of products. ))i(),n,i(x( w)i(),n,i(x ))i(),n,i(x(eimin ζ ζ ζ θ , (17) ))i(),n,i(x( )i(),n,i(x ))i(),n,i(x(geimin ζ ζ ζ θ . (18) as a result, the optimal composition of the used raw and other supporting materials and necessary process-units assignment for the production tasks will be obtained. the non-linear–objective functions (17) or (18), equations (14), (15) (and (16) at the objective function (18)), the mathematical models of the wasting from routine batch sources (11) and eqs. (12), and as well as constraints (1)-(3) and (5)(10) represent the problem for environmental impact minimization on the process/unit level. the problem comprises the sets of the two types of independent variables continuos )i(x , forming the vectors )n,i(x equ. (3), the key components compositions in raw materials, and binary )i(ζ structuring the production routes for products i , and constraints in the form of equalities and nonequalities. its result is the mixed integer non-linear programming (minlp) problem. environmental impact minimization in curds processing wastewater is a common factor in the dairy industry that generates a considerable treatment cost. the biological oxygen demand (bod) measures the effluent strength of the wastewater in terms of the amount of dissolved oxygen utilized by microorganisms to oxide the organic components. the bod load depends not only on the composition and amount of processed whole and/or skimmed milk, but also on the inherent losses due to spilled whey, milk coagulated and glued on the unit’s walls, products and by-products lost etc. since the latter could not be avoided, it is accepted to regulate them to the inherent levels, which are accounted by bod “produced” in the relevant processes. the example under consideration concerns simultaneous manufacturing in a dairy of two types of curds ( 2i = ), one with a low fat content 0.3%, called product a; and the other with a high fat content1%, product b. the aim is to determine the milkfat content in the skimmed milk used as a raw material for both products, and plant units assignment for the respective processing tasks, in which the bod generated from the process is minimal for the accomplishment of the posed production requirements in a given horizon. 18 curds manufacture is a typical cyclic batch process. for it, processing standard milk skimmed into the boundaries %05.0)imin(x = and %4.1)imax(x = is used. the key component for both products is the milkfat content ii),i(x ∈∀ . the composition of standard whole milk is given in the first part of the current study [4]. a detailed report of the curds processing is proposed in [4], too. the description of the processing tasks is presented in table 1. the composition of the target products and values of the respective recovery factors are presented in table 2. table 1 processing tasks description. cy1(x)* is the yield of curds by-product and x is milkfat content in skimmed milk production tasks task duration input/output fractions task 1 pasteurization 30 min. in. skim-milk out. pasteurized skim-milk 1 1 task 2 acidification 240 min. in. skim-milk in. culture out. curds by product out. whey 0.88 0.12 cy1(x)* 1-cy1(x) task 3 draining 30 min. in. curds by-product out. curds target product out. drained whey 1 0.9 0.1 table 2 the product compositions and values of the recovery factors composition of the curds target products values of the recovery factors moisture% fc% cc% sc% rs rc rf a 80 0.3 11.3 20 1.724 0.96 0.075 b 81.58 1.009 12.28 18.42 1.386 0.96 0.231 the van slyke equation is used for yield calculation [7]: [ ] %sc rs.))i(x%(mc.rc)i(x.rf))i(x(cy + = , ii∈∀ (19) where: ))i(x%(mc is the casein content in the standardized skimmilk; rs,rf,rc are the recovery factors for casein, milkfat and other solids different from them; %sc is the solids content in the target products. since both products involve identical processing tasks, identical relationships determined on the base of the information given in table 1 are used for relating them to size factors l))i(x(s :                   = 1.1 ))i(x(cy 1 ))i(x(cy 88.0 ))i(x(s ii,i ∈∀ . (20) the manufacture of products a and b is carried out simultaneously in a plant comprising the apparatuses listed in table 3. the suitable plant units for the processing tasks of both products are identified by the introduction of the following binary matrices: table 3 plant data type pasteurizator vat reactor drainer no 1 2 3 4 5 6 7 8 9 10 11 [m3] 300 250 150 100 300 400 250 80 60 60 100 2,1 ' 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 1 1 1 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 )( =           = iiid . (21) the cycle overlapping operational mode is applied for the products manufacturing, where [h] 4tmaxtc li == . two types of production demands named q-i and q-ii are considered for performing in two different horizons h-i and h-ii, see table 4: table 4 production demands products q-i [kg] q-ii [kg] h-i [h] q-i [kg] q-ii [kg]i h-ii [h] a 5500 7000 5500 7000 b 6000 7000 360 6000 7000 400 each cessing task from the curds production generates the bod due to: i) the amount and composition of the used skimmed milk. the bod load of 1 kilogram skimmed standard whole milk is determined as follows: ))(%(.69.0 ))(%(.031.1)(.89.0))(( ixml ixmpixixbodm + ++= , (22) where: ))i(x%(mp and ))i(x%(ml are casein and lactose contents presented as a function of the milkfat content; and 19 ii) associated to the tasks inherent losses [8, 9]: task 1 – pasteurization. the pollutant processed is due to the milk coagulated and glued on the pasteurizer’s walls. the “generated” bod depends on the amount of the pasteurized milk. the bod load of 1-kilogram pasteurized milk is: milkdpasteurizekg okg10.5.1bod 23 p −= . (23) task 2 – acidification. the pollution results entirely from spilled whey. the inherent leaks are wl%=1.6% from the processed whey mass. the bod load of 1-kilogram acid whey is: wheyacidkg okg10.32bod 23 w −= . (24) task 3 – draining. the polluting is due to: i) draining and discharging of the whey remained in the curds. the bod load of 1kilogram acid whey is the same as in task 2; and ii) inherent losses of target product gluing on the drainer’s wall. they depend on the curds fat content (fc%) %fc.0017.0%cl = , the bod load of 1-kilogram curds depends on the yield and the bod of used skimmilk: cheesekg okg ))i(x(bod)).i(x(cy))i(x(bod 2 mc = . (25) the mass wl))n,i(x(m of the pollutant w , for both products i , is determined from the pollutants mass balance by using the data presented in table 1 and equations (23)-(25): i,l,w, %cl.100 9.0 1.0%wl. ))i(x(cy 9.0 1.01))i(x(cy1 0 00 ))i(x(cy 88.0 ))i(x(m l,w ∀∀∀                           +− = . (26) the above data and the obtained relations, equations (20) and (26), are completely sufficient to formulate the posed optimization problem, according to equations (1)-(12). as an optimization criterion the “generated” global bod in the simultaneous manufacturing of the products a and b is used. it is obtained on the base of the local bods of the pollutants due to the milk processed, whey spilled and curds lost, from the respective processing tasks – pasteurization, acidification and draining: ∑ ∫ = θ = = 3 1 0 ))(),(( )),(())(()).(),(( ))(),(( l tc wlw iix w dttixfixbodiixn iixbod ζ ζ ζ , ii,i ∈∀ , 3,2,1w = . (27) where:           = ))i(x(bod bod bod ))i(x(bod c w p w . taking into account equation (27) the objective function global biological oxygen demand gbod, presented as a function of milkfat content )i(x for products a and b and structured production routes for them by means of vectors )i(ζ is: ∑∑ = = = 3 1w 2 1i ))i(),i(x( w)i(),i(x ))i(),i(x(bodgbodmin ζ ζ ζ θ .(28) the problem formulated above in the optimization criteria (28) is the environmental impact model for the simultaneous manufacturing of products a and b in the dairy. a– an outcome of its solution the values of the independent variables milkfat in the skimmilk used for both products and the assigned plant units for the respective tasks are obtained in a way to minimize the gbod for the plant. these data are listed in the table 5. table 5 optimal values of gbod and the values of the variables at which they are obtained pro duction demands h, [h] gbod , kg o2 pro ducts x(i), % b(i), [kg] nb(i) units assigned q-i h-i 146.943 a 0.633 61.798 89 1, 7, 11 b 1.071 68.966 87 2, 3, 4, 5, 8 q-ii h-i 178.096 a 0.93 112.904 62 2, 3, 5, 7, 8, 9 b 1.131 78.683 89 1, 6, 10, 11 q-i h-ii 146.943 a 0.633 61.798 89 1, 7, 11 b 1.071 68.966 87 2, 3, 4, 5, 8 q-ii h-ii 178.058 a 1.055 70.707 99 2, 5, 9, 11 b 1.079 104.482 67 1, 4, 6, 7, 8, 10 the batch sizes and number of batches subject to processing into the horizons h-i and h-ii are shown in the same table. in table 5 it could be seen that for the production demands q-i in both horizons, equal values of gbod are obtained, while for the demands q-ii, which are more strained, the optimal values of gbod are diverse and are reached at different values of the independent variables. in real practice, the 20 different milkfat content effects on the raw material consumption are what could be taken into account. but in the case considered here it is not accounted. for illustration this affect is shown in table 6. table 6 raw material consumption for processing demand qii in horizons h-i and h-ii pro duction demand pro ducts amount , [kg] x(i), % skimmed milk con sumption in h-i [kg] x(i), % skimmed milk con sumption in h-ii [kg] q-ii, a 7000 0.93 2.818.104 1.055 2.812.104 b 7000 1.131 3.034.104 1.069 3.046.104 finally, the local bod values for the processed pollutants are listed in table 7 to illustrate the weight of the inherent losses into the “generated” gbod. they constitute approximately 28.7% ofod generated in accomplishing production demands q-i and q-ii. table 7 values of local bods for the pollutants from the tasks for demands q-i, and qii accomplished in horizons h-i and h-ii products a and b, kg routine source bod [kg o2] pasteurized milk whey curds q-i, h-i and h-ii xà=0.633 % xâ=1.071 % task 1 63.822 task 2 18.213 task 3 40.889 24.019 q-ii, h-i [h] xà =0.93 % xâ =1.131 % task 1 77.251 task 2 21.998 task 3 49.788 29.059 q-ii, h-ii [h] xà =1.055 % xâ =1.079 % task 1 77.326 task 2 22.028 task 3 49.783 28.925 conclusions the general problem for determining the minimum environmental impact for compatible products manufacturing in multipurpose batch plants is considered in this study. it presents an evolving of the process/units assignment level, proposed in the first part [4] approach, based on the fourier transformation use, for mathematical descriptions of the waste emissions from routine sources appearing into the horizon cyclically. the problem takes into accounts both the used materials compositions and the constructed production routes, which are set as independent variables. the formulated sets of constraints follow for feasibility and compatibility of the chosen production routes and justify the accomplishment of the production demands into the determined horizon. global or local environmental impact assessments are used as the objective function, and for their definition the mathematical descriptions of pollutants from cyclic batch routine sources are used. an example from the dairy industry is considered to illustrate the possibilities of the proposed system oriented approach for modeling the environmental impact of the multipurpose batch plants. simultaneous processing of two types of curds low fat and high fat is regarded. the biological oxygen demand is used to assess the dairy environmental impact. both the bod generated due to the amount and composition of the processed milk and the one due to inherent losses, are taken into account in the formulated problem. the most appropriate milkfat content of the skimmed milk used in products manufacturing and respective process-units assignments (production routes) is determined to result in minimum values of the “processed” global bod from the entire plant. the considerable contribution of inherent losses into the gbod is illustrated too. acknowledgement this study is conducted with the financial support of the bulgarian national science fund under the contract x-1108/01. 21 symbols b – batch sizes [kg]; c – waste mass concentration [kg/kg] %,cc – casein content in the curds; cl% – inherent loss of curds; %fc – fat content in the curds; h – time horizon [h] ; h-i, h-ii – names of horizons used in the example; i – number of products; id – units/tasks identification matrix l – number of production tasks; %mc – casein content in the skim-milk; mi – amount of material input to the task [kg]; %ml –lactose content in the skim-milk; mo – amount of material output from the task [kg]; %mp –protein content in the skim-milk; n – number of key components in used materials nb – number of batches; p – number of plant units q – production demand [kg]; q-i, q-ii – names of production demands used in the example; r – waste processed in the task [kg]; rc – recovery factor for casein; rf – recovery factor for milkfat; rs – solids recovery factor; %sc – solids content in curds; t – processing time [h]; tc – cycle time [h]; ts – starting time of task with regard to the cycle beginning; v – apparatus volume [m3]; wl% – inherent loss of whey; x – vector of the key components; m – mass of waste processed from the production task per 1 kilogram target product [kg/kg]; s – size factor [m3/kg]; t – time [h]; x –particular key component composition in used materials continuos variables, (milkfat content for the example) subscripts i – product; j j, j’ – input output flows of the task; k – a series order; l – production task; n – key component; p – plant unit; w – waste greek letters µ – the standard limit value for the pollutant; ν – volume of input to the task flow [m3]; ζ – binary variables presenting the process-units assignments references 1. pistikopoulos e. n., stefanis s. k. and livingston a. g.: aiche symposium series, pollution prevention via process and product modification, , 1994 90 (303), 139-150. 2. stefanis s. k., livingston a. g. and pistikopoulos e. n.: computers&chem. eng., 1995, 19, s39-s44. 3. stefanis s. k., livingston a. g. and pistikopoulos e. n.: computers&chem. eng., 1997, 21, 1073-1094. 4. vaklieva-bancheva n., shopova e. g. and ivanov b.: hungarian journal of industrial chemistry, 2002, 30, 199-206. 5. hilaly a. k. and sikdar s. k.: j. air waste manage. assoc., 1994, 44, 1303-1308. 6. hilaly a. k. and sikdar s. k.: ind. eng. chem. res., 1995, 34, 2051-2059. 7. johnson m.: curd clinic, wisconsin center for dairy research, dairy pipeline, 2000,12, no 2 (july), 9-11. 8. carawan r. e., chambers j. v. and zall r. r.: spinoff on dairy processing water management, extension special report no am-18.b, january 1979, published by the north carolina agricultural extension service. 9. overview of dairy processing, cleaner production assessment in dairy processing, prepared by cowi consulting engineers and planners as, denmark, for unep and danish epa, pp. 7-11, 2000. microsoft word a_28_bocsi_r.doc hungarian journal of industrial chemistry veszprém vol. 39(1) pp. 45-49 (2011) extraction examinations of microalgae propagated for biodiesel additives r. bocsi , g. horvath, l. hanak, z. hodai university of pannonia, department of chemical engineering science 8200 veszprém, egyetem u. 10, hungary e-mail: bocsirobert@almos.uni-pannon.hu because of the growing energy consumption of the world co2 emission is also growing. a part of this carbon emission can be captured by microalgae. these creatures like any other photosynthetizing organisms consumes it as carbon source. they set up their cells and makes lots of valuable compounds of it. some of these compounds can be transformed into biodiesel or blending components. we have studied the whole range of algae cultivation and processing is at the department of chemical engineering at the university of pannonia. the utilization of algacultures in experimental photobioreactors is examined, together with the optimization of the operational conditions both for artificial and natural light and different fertilizers. we made extraction experiments of dried algae. keywords: algae, biodiesel, lipides, lipid exraction introduction driven by the rising need for biofuels and by the necessity to capture carbon dioxide, autotroph organisms got into the spotlight of energetic research. with cultivation of these organisms we can feed back the carbon content of co2 into biological systems and we can get numbers of valuable organic compounds, among others biofuel, to reach ecological and economical benefits. algae production is the most promising solution amongst the alternatives because of its specific area necessity and high reproduction rate. additional benefits are that there is no need to use growing fields and some wastewater may be used with nutrient supplementation. the algae-based technology algae based fuel technology was mentioned in the beginning of the 1950’s. some pilot plant to cultivate algae as energy source was built in 1970’s. algae oil production for fuel technology was mentioned at first in the 1980’s which lives its renessaince in 21st century [1, 2]. algae species are applicable for energetic purposes wich produce lipids as more as it possible in their whole growing period. some of these species’ lypide content may be more than 40 percent of their own weight. these lypides mostly contents glycerine esthers of various c16-c20 fatty acides. these compounds are applicable for biodiesel production [4]. cultivation parameters of algae autotrophic organisms synthetizes complicated organic compounds which need them to build up their own cells. these organisms can be monocytae (microalgae) or other differentiated autotrophics (e.g. corn, soy beans). algae are a large goup of simple, typically autotrophic organisms. they are eucaryotic, autotrophic, unicellular or multicellular form. algae get nutrients and other compounds from aqueous solution (see fig. 1) figure 1: algae cellfactory lipids byproducts npk +micro light co2 alga 46 co2 capture on one hand they consume inorganic compounds and simple organic compounds, on the other hand they feed co2 in the form of hydrogencarbonate from dissolved gas mixture. we use co2 as a fetilizer to reach higher biomass productivity than the average [3]. generally, we feed as a gas mixture about 5–30 vol% co2 and air is the rest. it is possible to grow algae in gas mixtures without air, but their oxygen content for the dark period is an essence. the applicable co2 concentration depends on the temperature and liquid fertilizer contents and concentration too. light source light has a special function since it supplies the energetic background of the biochemical reactions in the light period. autotrophic organisms use only a part of total sunlight spectrum (400–700 nm) for photosynthesis. this range is 42.3% of the total spectrum. this is called photosynthetic active radiation (par). the average energy of the photones is 218 kj/mol in this interval. the maximum theoretical photosynthetic energy efficience (pe) can be determined from these data given above. pe is 9% for the total spectrum of sunligh and it is 21.4% for the range of par. for laboratory use we can applicate of several types of light sources. it is important to use that type of source wich spectra meets the needs of algaculture. inorganic nutrients there are significant differences in nutrient requirement among species of the same alga genus. accordingly, an optimal nutrient composition for a specified alga might not be applicable for another species in the same genus. commonly an optimized medium composition is only valid and applicable in the same circumstances as observed. it is an important to mention that in these systems single nutrient composition changes do not have effets of the same intensity than in combination with another nutrient(s). there are multilateral effects between nutient component concentrations, these connections might be a relevant information. there are a lot of media recipes accessible. there are recommendations for the most algae species. generally nitrogen (as nitrate), phosphate and potassium addditon to the media arean instance. there are other macro nutrients are also important: calcium, magnesium, suplphur. there are micronutrients which must be added in small amount of concentration (above the effective and below the toxic amount). generally applicated micronutrients are shown in fig. 2. these compounds are in the media is essence to reach high alga biomass concentration in a good condition. figure 2: generally applicated micronutrients for microalgae culturing the first is getting acclimatized. it can lasts from a few hours to 1-2 days. it is probably affected by the change of environmental parameters. the second is the quick growth or exponentional phase when significant biomass multiplication is shown. in this phase batch harvesting is too early. after this, a maximum is reached in biomass concentration. the next phase is the decrease of biomass comcentration. in this phase algae should be harvested. at the end of this phase there are a few algae in population and the chances are that other harmful microorganisms have been proliferated. figure 3: population vs. age of population we use quasi-continious systems. in this case part of the culture is harvested and restored with fresh medium. its advantage is the ability of simple automation system but the disatvantage is the need of a proper harvesting schedule. it is important to avoid the proliferation of harmful microbes and important to monitor the accumulation of metabolites. photobioreactors we use special photobioreactors (pbr) to keep specified cultivation parameters. common expectations are specified below. it is important that as much par type light as possible be accesible for the algae. input and output streams must be safely and well built because the toxic co2 content of the gas mixture. these reactors must be designed to be resistant against environmental effects (wind, rain, sunlight, insects etc.). these algae suspensions must be well stirred, because degradation might be started in subsided algae conglomerate. stirring is also important to keep algae cells at the side of absorbance wall for the optimal resistance time in the applicated light conditions. these reactors must be designed for local microclimate and mostly mounted with cooling system. the planned cultivating volume affects the reactor geometry. micronutrients fe b co zn mn zn mo ni potentially harvest time 47 the largest volume can be reached in open pond systems. in this case we can keep those type of algae which are resistant against local microbes and environmetal effects. to avoid invasive species proliferation parameters must be well monitored. generally, mechanical stirring is applied to maintain aeriation and stirring. another open type cultivation is the raceway system. in this case algae suspension flows in a canal. the thickness of the layer is between 100–500 mm. another type of cultivation can be in closed photobioreactors. these reactors have a well-defined area of light trasmitting wall. this is critical to the design. we should reckon with shadows of statically necessary elements on the light side. inner or outer contaminations of walls must be regularly eliminated. source of outer contaminations origin can be technical (eg. scratches) or other environmental (eg. dust). important is the choice of optimal thickness of layer to reach sufficient mixing. a thoughtful reactor design and monitored inputs can assure a well balanced algae cultivating system with low risk of unwanted external effects. closed photobioreactors are built in two designs. the first is the pipe system, with the advantages of simple geometry and few shading element but it has the disadvantage of low area by volumetric unit. the second type is the panel with the advantage of high area of volumetric unit and the disadvantage of evolving idle spaces. algae culturing conditions we used flat type pbrs (see fig. 3). some of them were in natural light and others were in artificial light (special fluorescent tubes). we mixed the 5–8 vol% co2 content gas mixture outside the reactor. then this gas mixture were dispensed in the alga culture. this suspension contains the algae cells, and also the nutrients (modified bg-11 type medium). figure 3: algae pbr. panel and its supplies we let these cultures to grow up their biomass concentration to maximum 6 g/l (dried content). generally we don’t let them to reach the declension phase in pbrs because it is easier to concentrate the suspension and avoid the quality loss. pretreatment of harvested suspension the harvested suspensions are concentrated and dried. the concentration method consist generally two steps. first is the flocculation and the second is filtration. we are test the applicability of membrane separation processes which may be promising solutions of this problem. next step is drying. we dry the algae cake 65 °c to avoid of the cells boiling. in occurrence of boiling, the cells are destrtoyed. this can causes easyer attack of microbes and other (mainly separational) problems in the following procedures. milling of dry alga can be also an important step if the algae cake were dried in blocks. extraction extraction can be carried out in two startegies. one of them is to extract oil from dry or moist material. the other is cell degradation come before extraction. the latter can be made by ultrasonic, microwave radiation, chilling shock, cell blast, enzymatic process. the aim of these methods that let intracellular compounds achievable for extracting material. but they can causes solventseparation problems. in table 1 we present some common used solvent systems. in complex solvent systems, the polarity order is kept. table 1: common solvent systems for algae extraction use of supercritical extraction is not so competitive but there are researches to get the optimal fluid-cosolvent pair. there are more and more new algal oil extraction can be reached. some of these keeps to solvent free technologies [19] others lead to new solvent base ones [20-22]. extraction solvent1 solvent2 solvent3 chloroform methanol water hexane i-propanol water hexane ethanol water ethanol 1buthanol water solid-liquid acetone hexane supercritical fluid co2, water, methanol, buthane, penthane novel techniques ultrasonic, microwave, ase, cell-milking, liquid dimethyl-ether 48 these solvent systems are not applcable right now beacause its high costs. by the way these solutions shouldn’t be neglected. on table 2 there are the possibly application timeline of these procedures. experimental data when we inspect measured data, we should count on with crosseffects. at first the growing method effects to both of algae culture and cell composition. when we have a good conditioned suspension, we try to concentrate it. different flocculating and filtering methods effects differently to the amount of achiavable dry biomass and the latter technology parameters. when a concentrated, well dried, well milled alga is available we can start its extraction. after the specific extraction method and time we should separate the residue from the new, organic suspension. this can be usually made by simple filtration. on the other hand we must evaporate the solvent from extract. if we make several processes on algae suspension from concentrating to drying, we should extract the widest range of compounds of biomass. then we extracted chloroform methanol mixture which solved several other compounds than glycerol aldehydes of fatty acids such as colurs, eicosanol etc. these latter compounds may gives other benefits than energetic use of algae extract. table 2: alga extraction with chloroform-methanol mixture algae grow id extraction id e operating conditions extraction time (h) lipide content (%) t1 58 natural 3 37.00 t2 59 natural 3 21.10 t3 90 natural 20 28.10 t4 88 natural 20 21.10 t5 62 natural 3 17.60 t6 63 natural 3 18.80 t7 117 natural 42 8.30 t8 65 natural 3 11.40 tv602bm 75 laboratory 3 10.20 tv605bm 78 laboratory 3 10.40 tv6312bm 76 laboratory 3 22.90 the rest of the samples had different lipide content considering their growing conditions.. natural operating conditions means: natural light conditions o t1-t2: july-august, chlorella v. o t5-t6: july-august: scenedesmus a. o t3-t4: october-november chlorella v. o t7-t8: october-november scenedesmus a. laboratory artificial light o e75, e78 fluorescent tube, scenedesmus a. o e76 fluorescent tube, chlorella v. in this experiment the chlorella v. had higher growing potential and also higher lipide content in each type of growing conditions. but we must be careful beacause the starter culture was stronger chlorella than scenedesmus. we found at later inspections that these suspensions was probably about to change. conclusion algae technology is lives its renessaince in the 21th century. we use flat panel pbrs to test the effects of parameters on algae growing, ang alga suspension processing at the whole technolgy line. several parameters have influence on the quality and quantity of the algae extract. at first we must keep our eyes on growing parameters to get strong and high concentration of biomass. we must make the necessary changes on suspension to get dry and easily processable biomass. we must extract a wide spectra of compounds from algae to get several valuable of it. extraction is a very important in algae technology but cross effects between growing and processing parameters are cannot neglible. there are still a lots of challenge in algae technology. some of them limited by well known parameters but others have some latent parameters which is before discover. acknowledgement we acknowledge the financial support of this work by the hungarian state and the european union under the tamop-4.2.1/b-09/1/konv-2010-0003 project. references 1. n. g. carr, b. a. whitton: the biology of bluegreen algae university of california press (1973), isbn 0520023447 2. nabors, w. murray: introduction to botany. san francisco, ca: pearson 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 143-147 (2008) improving the mathematical model of a heterocatalytic tube reactor t. varga , g. rádi, t. chován university of pannonia, department of process engineering, h-8200 veszprém egyetem u. 10., hungary e-mail: vargat@fmt.uni-pannon.hu in recent decades the applicability and usefulness of mathematical models in the solution of many industrial problems have been shown. there are many cases when the correct answer can not be given because of the complexity of the problem however cfd approaches can be applied to dig deeper and improve the reliability of results. in this work the improvement of the first-principle model of a tubular fixed-bed reactor is shown applying comsol multiphysics. mathematical models of tubular fixed bed catalytic reactors to simulate their operation are well known and the formulation of such models is well documented. in most cases the aim of modeling is the development of the simpliest model which can be applied to solve the modeling task. however, nowadays these modeling problems can be more complicated and require more accurate models, e.g. in case of model based diagnostic systems, early detection systems. after the model with the adequate complexity was developed it must be solved with the necessary accuracy. in general, as the complexity of the model increases, so does the chance of encountering numerical difficulties. our purpose is to apply the most appropriate software methodology to solve problems at each level of the model hierarchy, therefore a proccess model of an industrial heterocatalytic reactor has been extended with integrating transport processes on micro level. the idea is the integration of a model of a single catalyst pellet implemented in comsol multiphysics into the steady-state process simulator of the reactor developed in matlab. the proposed approach makes possible to develop the model of a whole catalyst bed from the particle models. the first step to accomplish our purpose is the implementation of the pellet model in the applied cfd code. then the pellet model can be integrated into the process simulator at the higher model hierarchy level. keywords: heterocatalytic tube reactor, mechanistic modeling, computational fluid dynamics, catalyst pellet introduction the aim of all production technologies is formation of a more valuable material through some chemical reactions. the reactor is a place where reactions generally take place. hence, a reactor must be able to convert the necessary amount of raw materials into products with desired quality in given amount of time. a chemical technology can not be imagined without a reactor consequently the design process of a reactor has a really important role in generating a well profitable technology. furthermore the planing of instrumentation and optimization of operating variables is also crucial. main steps in development of a well functioning reactor are the following: ● defining desired performance of reactor operation; ● collecting all a prior information and physical constraints; ● determining and/or investigating velocity field in the reactor; ● assigning all operating variables. nowadays development of flow field in process equipments is a key issue in planning of process unit. with a well designed flow field the overall process performance and safety of operation can be increased at the same time. to support this step, different modeling softwares and flow sheet simulators have been developed in last decades. as computational capacity of computers has being increased the role of computational fluid dynamics (cfd) in applied modeling technics and methods has significantly grown since the first computer was switched on [1]. cfd is a collection of numerical solvers for partial differential equations. with applying cfd codes more complicated problems in more complex structures can be investigated in details than with other modeling technics. coupling of mathematical models of different physical and chemical processes with efficient numerical solvers makes possible to analyze chemical engineering and other kind of engineering problems in much more details. of course, as in other modeling technics, cfd models must be validated before it can be used to predict the behavior of invesigated system. validation of models is based on comparing simulation results with measured variables, i.e. developing an adequate cfd model, because of the complexity of model, needs welldesigned and precisely carried out experiments. 144 in recent years many papers applying cfd technics to analyze some phenomenon or to design a reactor have been published. the most frequently investigated phenomenon are the transport processes between a stationary and a moving phase, or two moving phases, such as heat transfer [2] and mass transfer [3] in a fluidized bed. another interesting field of application of cfd models is the modeling of bubble columns [4-8]. cfd models can be applied not only in reactor and column design but in solving other kind of engineering problems, e.g. designing a protective suit [9]. these examples show that cfd is capable to simulate transport processes and it can be applied as a part of complex mathematical model. in this paper the concept of a detailed mathematical model of an industrial used heterocatalytic reactor will be introduced. the former version of reactor model was applied in a operator support system [10] to support process operators in choosing appropriate values of important operating variables to keep the production in safe and efficient regime. to improve the accuracy of our reactor model mass and heat transfer processes between solid catalyst pellets and moving gas are considered. in previous investigations a small difference was noticed between the characteristic of measured and calculated temperature profiles but model relability couldn’t be furher improved without increasing model complexity. however, to improve our quasi-single phase model solid phase and all coupled transport processes are considered. our idea is the integration of the model of a single catalyst pellet implemented in comsol multiphysics into the steady-state process simulator of the reactor developed in matlab. the proposed approach makes possible to build up catalyst bed from particles which have different size. the first step to accomplish our purpose is the implementation of the pellet model in the applied cfd code. then pellet model can be integrated into the process simulator at the higher model hierarchy level. after short introduction regarding the most frequently applied cfd codes and some cfd application examples in model development the investigated case study is presented, than simulation results obtained at this level of work are evaluated and finally conclusions are drawn and future steps are outlined. case study our approach is to apply the most appropriate software to solve problems at each level of model hierarchy, therefore a mathematical model of an industrial heterocatalytic reactor was developed with integrating processes at the level of thermodynamic phases. reactor model the investigated, vertically positioned reactor contains a large number of tubes filled with catalyst as shown in fig. 1. a highly exothermic reaction takes place as reactants are rising up in tubes passing through the fixed bed of catalyst particles while generated heat by reaction is removed through tube walls by cooling media. the reaction has equalibrium and since temperature is increasing in reactor more and more product decomposed. due to the highly exothermic reaction it has a great chance to develop hot spots somewhere in catalyst bed which increase the rate of catalyst ageing. direction of the flow of cooling media is not important in this process because there is only 7-8 k difference between the inlet and outlet temperature of cooling media. selection of appropriate operating conditions is important to avoid the development of reactor runaway and to increase lifetime of catalyst. the investigated reactor is a heterocatalytic tube reactor where gas phase is the moving phase while catalyst is the stationary phase. in our previous work a quasi-single phase mathematical description of the reactor was introduced [10]. since model accuracy couldn’t be improved without increasing model complexity the quasi-single phase must be divided into solid and gas phases as it shown in fig. 2. state variables are calculated in both phases which are coupled by mass and heat transport processes. as it can be seen at components level in fig. 2 the reaction is considered only in solid phase so the produced heat by the highly exothermic reaction is removed by cooling media in jacket. coolant in coolant out reagents product x = 0 x = l ( )wout,w b,t ( )win,w b,t ( )out,gout,g i out,gout,g p,c,b,t ( )in,gin,g i in,gin,g p,c,b,t figure 1: simplified scheme of reactor as it can be seen in the model structure in fig. 2 process variables calculated in two phases in the tubes. thermodynamic phases are coupled by mass and heat transport processes. steps of the assumed overal process are summarized in fig. 3. first steps, the adsorption of reagents take place simultanously and it is called competitive adsorption because two components are competing to get to the same active sites on the surface 145 of the catalyst. after both reagents adsorb a second order reaction takes place and generates the product which leaves the surface of catalyst by desorption process. developed model calculates changes only along the reactor, i.e. model is one dimensional and it doesn’t consider the diffusivity along the radius of catalyst bed. before the introduction of model equations some simplifications must be considered to simplify the real problem. these simplifications are summarized as follows: ● gas and solid phases are considered in tubes, which are connected by the mass and heat transport processes; ● highly exothermic, second order reaction takes place in solid phase; ● diffusivity along radius of the reactor is neglected; ● all catalyst pellets have the same size and spherical shape; ● to calculate pressure drop in catalyst bed a modified ergun-equation is applied. a steady-state model based on the overall rate of all mass transport processes and reaction with detailed description of applied simplifications can be found in [10]. that model was solved in matlab and calculated temperature profiles were compared to measured ones in order to determine missing model parameters. it was concluded that accuracy of developed model was appropriate, although some minor differences could be experienced between characteristics of calculated and measured profiles. to further improve model accuracy, overall rate was substituted for by a cfd model of a catalyst pellet to simulate basic steps introduced in fig. 3. steady-state reactor model is not introduced in this paper, a detailed description can be found in [10]. reactor tube(s) jacket solid phase a b c x a b c mass&heat transport reaction(s) heat transport liquid phase w gas phase figure 2: structure of two phases model our concept is the integration of a catalyst pellet model implemented in comsol multiphysics into the reactor simulator developed in matlab. the first step to accomplish our objective is the implementation of pellet model in the applied cfd code. as it can be seen in fig. 2 processes at the micro level can be simulated and developed cfd model can be integrated into higher hierarchy level. comsol is more than just a software which uses a cfd code because mathematical models of many processes in different area of science are collected and classified; consequently the necessary time to solve an engineering problem is less than with applying other cfd software. comsol applies the finite element method [1] to discretize the investigated object and to solve model. figure 3: basic steps of the assumed overall process catalyt pellet model in comsol multiphysics the first step of model building in comsol is the selection of the necessary correlations from the model collection. of course there is a possibility to introduce new correlations. to investigate complex geometries an interactive graphical interface helps the user to define it or the user can import it from a cad software. our comsol model contains only one catalyst pellet with the narrow surroundings of the particle. the surrounding is flowing around the pellet and the transport processes make the connection between two phases. matlab simulator runs this simulator and builds the whole catalyst bed. difference between each pellet is considered by changing boundary conditions before solving the pellet model. to describe the whole catalyst bed the matlab simulator of the reactor evaluates boundary conditions based on the position of the acual pellet in the catalyst bed. because of the axial symmetry of tubes and the spherical symmetry of the catalyst pellet the comsol model is two dimensional. based on the introduced simplifications and the introduced pellet model the following equations were applied to calculate the state variables in both phase. all component mass balances in the gas phase contain terms to calculate convective and conductive transport processes and naturally the mass transport process between the solid and gas phase: ( ) ( ) ,cca dx cdd dx cbd g i s i gs i gs 2 g i 2 g i g i g −⋅β⋅+−= ⋅ where bg – flow rate of gas phase; ci g – concentration of i-component in gas phase; i = {a; b; c}; x – reactor length; di g – diffusion coefficient of i-component in gas phase; ags – interface area between the gas and solid phase; βi gs – mass transfer coefficient between the gas and solid phase of i-component; ci s – concentration of i-component in solid phase. 146 of course the convective term in solid phase is missing: ( ) ,rvcca dx cd d i sg i s i gs i gs 2 s i 2 s i ⋅ν⋅+−⋅β⋅−= where di s – diffusion coefficient of i-component in solid phase; vs – the volume of solid phase; νi – the stoichiometric coefficient of i-component; r – reaction rate which is calculated by the following correlation: , k cc ccekr s x s cs b s a tr e 0 s a ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ⋅ −⋅⋅⋅= ⋅ − where k0 – preexponential factor; ea – activation energy; r – ideal gas constant; ts – temperature of solid phase; cx s – concentration of active sites on catalyst; k – reaction eqaulibrium constant which is a function of the temperature. as it can be seen in the last equation the effect of temperature on reaction rate is considered therefore changes of temperature of gas and solid phase are calculated too. terms in both equations are the same as those considered in component balances: ( ) ,tta dx td dx dtbc gsgsgs 2 g2 g g gg p g −⋅α⋅+ +⋅λ−=⋅⋅⋅ρ where ρg – density of gas phase; cg g – heat capacity of gas phase; tg – temperature of gas phase; λg – heat conduction coefficient in gas phase; αgs – heat transfer coefficent between the gas and solid phase. a) temperature in catalyst pellet and in surroundings b) the concentration of a component in catalyst pellet and in surroundings c) concentration of b component in catalyst pellet and in surroundings d) concentration of c component in catalyst pellet and in surroundings figure 4: changes in the value of state-variables along the investigated part of reactor in steady-state 147 and finally the heat balance of solid phase: ( ) ( ) ,r sgsgsgs 2 s2 s δhrvttαa dx tdλ −⋅⋅+−⋅⋅−=⋅ where λs – heat conduction coefficient in solid phase; ∆hr – reaction heat. this is just a short description of model equations to show the structure of pellet model. all physical properties are calculated as the function of temperature. these eqautions were implemented in comsol to develop a pellet model which replaces the reaction rate of overall catalyst processes of earlier developed reactor simulator. integration of reactor simulator made in matlab and the pellet model implemented in comsol is just a vision yet, still as it can be seen in next chapter that pellet model gives good results. results and discussions to check the applicability of the developed comsol multiphysics pellet model in our modeling approach, the value of state variables in front of reactor were given as boundary conditions in the solution of the pellet model. generated results are plotted in fig. 4. in fig 4a temperature surface can be seen and as it was expected the highly exothermic reaction taking place in catalyst increases the temperature of pellet and it warms up the flowing gas. due to the diffusion in catalyst pellet the concentration of reagents decrease in the direction to the centre of the pellet (check fig. 4b and fig. 4c.) while the concentration of the product changes in the opposite direction as shown in fig. 4d. in this model all components can be connected to the same active sites on the catalyst but in reality there is a competition between components and the rate and the equalibrium of the adsorption determine the concentration in the catalyst. since the temperature profile and properties of inlet and outlet flow are measured during the reactor operation the catalyst pellet model can not be validated without integrating it into the reactor simulator. as it can be seen in fig. 4d the outlet concentration of product from the investigated part of the reactor is very low and it suggests that the parameters applied to calculate the rate of adsorption must be modified. still the characteristic of changes in case of all the calculated state variables are the same as we expected. conclusions and future work to follow an operation of a tube reactor usually process operators do not have any more information but some temperature measurements along the reactor and composition of inlet and outle flow. hence, a reactor simulator can be very useful to follow the operation and to help process operators, e.g. to avoid development of reactor runaway or to optimize reactor operation. to achieve this aim an adequate reactor model with correct model parameters is needed. the paper proposed a possible way to improve a former developed mathematical model of a heterocatalytic tube reactor applied in the process industry to detect reactor runaway. at this phase of our work applicability of comsol multiphysics in modeling a catalyst pellet and its narrow surroundings is investigated. the developed model and the applied software can be applied to generate and simulate state variables in the whole catalyst bed. integration of pellet model into an earlier developed reactor simulator is our next step. after the success integration a model validation must be performed comparing the calculated temperature profiles with the measured ones. finally the accurate model can be built into an operator support system to improve reliablility of runaway detection. references 1. ranade v. v.: computational flow modelling for chemical reactor engineering, academic press (2002) 2. behjat y., shahhosseini s., hashemabadi s. h.: international communications in heat and mass transfer 25 (2008) 357-368 3. jung j., gamwo i. k.: powder technology 183 (2008) 401-409 4. bhole m. r., joshi j. b., ramkrishna d.: chemical engineering science 63 (2008) 22672282 5. klusener p. a. a., jonkers g., during f., hollander e. d., schellekens c. j., ploemen i. h. j., othman a., bos a. n. r.: chemical engineering science 63 (2007) 5495-5502 6. zhang d., deen n. g., kuipers j. a. m.: chemical engineering science 61 (2006) 7593-7608 7. darmana d., deen n. g., kuipers j. a. m.: chemical engineering science 60 (2005) 33833404 8. chen p., sanyal j., dudukovic m. p.: chemical engineering science 59 (2004) 5201-5207 9. tesch k., collins m. w., karayiannis t. g., atherton m. a., edwards p.: applied thermal engineering, (2008) in press 10. varga t., szeifert f., chován t., réti j.: műszaki kémiai napok ’07, konferencia kiadvány, (2007) 113-117 microsoft word b_14_kun_bodnar_r.doc hungarian journal of industrial chemistry veszprém vol. 39(2) pp. 211-214 (2011) cutting of aluminium alloy by abrasive waterjet k. kun-bodnár, zs. maros university of miskolc, department of production engineering, h-3515 miskolc – egyetemváros, hungary e-mail: krisztina.bodnar@uni-miskolc.hu e-mail: zsolt.maros@uni-miskolc.hu aluminium sheets are cut several times by abrasive waterjet cutting. the article summarizes the experimental results accomplished for determination of connection between the technological parameters and the depth of kerf. so we defined, how the depths of kerf depends on parameters (f, m, p) investigated during the research. beyond the graphical representation of the results, we defined mathematical connection in the paper, with which the depth of kerf can be determined at given cutting parameters, before the machining process. keywords: abrasive waterjet, aluminium alloy, efficiency introduction ultra high-pressure abrasive water jet cutting has for the last few years become a competitor to various procedures that generate heat. the new technique has become popular because the heat of cutting does not deform the material and the cut surface is of high quality. the fact that almost every type of material (both soft and hard) may be cut by the method and that the thickness of the cut is less limited, are two of the several important advantages of the abrasive water jet technology. aluminium alloys are widely used in the fields of industry like aerospace and automotive industry. abrasive waterjet cutting is one of the first operations when machining from sheet metal blanks. investigation of depth of kerf is widely used for research of efficiency of abrasive waterjet cutting. the end-users can influence the depth of kerf mostly by the feedrate (f), the abrasive mass flow rate (m), and the water pressure. efficiency of the waterjet cutting essence of the abrasive waterjet cutting is not an abrasive machining, but a so-called solid erosion process. solid erosion is a material loss occurred because of the collision of liquid and solid particles. the process is concentrated both in the space and in the time, so the erosion speeds up, which results machining process. during the collision of the solid particles in the liquid and the workpiece different processes can be occurred [1]: shear deformation, plastic deformation, crack formation and growth, hardening, brittle fracture and local melting of the material, (fig. 1). extent of erosion material removal – and with this the efficiency of the cut – depends on many parameters. velocity and mass of particles, loading angle, rate of hardness of the workpiece and the abrasive grains, form of the particles and the material characteristics are the parameters which have significant effect on the machining process. all these defined the characteristics of the material removal. figure 1: material removal processes in course of solid particle erosion when making kerfing test, we do not cut through the material, only make cuts and examine what kind of depth can be achieved with changing technological parameters. when measuring the depth of kerf (fig. 2), more measurements should be made along the cut and average of these values gives the depth of kerf (hmax). figure 2: kerfing in glass 212 from technological parameters affecting on the efficiency we investigated the effect of the feed rate, pressure, and abrasive mass flow (mass of the abrasive grains given to the waterjet during unit time). other parameters such as nozzle diameter and diameter of focusing tube, length of focusing tube and type of abrasive material were constant. their values were chosen on base of prior experience and professional literature. cutting experiments target of the cutting experiments was to define a method for the end users, with which the choice of technological parameters can be supported. tested material was almgsi0,5 aluminium alloy. the almgsi0,5 aluminium alloy widely used in different industrial fields, mainly where the strength does not has important role. in the circle of researchers investigating the abrasive waterjet cutting is accepted that the efficiency can be graphically and easy characterised by the so called depth of kerf (h). kerfing tests (fig. 3) were accomplished on the given aluminium alloy for the investigation of the efficiency. figure 3: kerfing tests in almgsi0,5 aluminium alloy the technological parameters were ranked in two groups in the course of cutting experiments, so called group of constant and changing parameters. the values of constant parameters were determined on base of facility of the machine, the changing parameters were chosen by preliminary tests. table 1 shows the applied parameters for the experiments. table 1: parameters of cutting experiments in aluminium alloy constant parameters material almgsi0,5 nozzle diameter 0.25 mm diameter of focusing tube 0.8 mm length of focusing tube 70 mm stand of distance 2 mm abrasive garnet #80 changing parameters pressure, mpa 200; 250; 300 abrasive mass flow, g/min (100); 200; 400 feedrate, mm/min 100; 300; 500; 700; (800) experimental results the average of depth of kerf was measured after the cutting experiments (h). like it can be seen on the fig. 4, increase of the feedrate results decreasing of the depth of kerf, mainly at small feedrates, the curves are hyperbolic. feedrate cause the most characteristic effect on the extent of the depth of kerf. feedrate has great effect on the machining costs as well. because of this the feedrate should be chosen always the maximal extent with which the prescribed accuracy and surface quality till can be assured. figure 4: effect of the feedrate on the depth of kerf at different pressures and abrasive mass flow rates, on almgsi0,5 aluminium alloy on the basis of fig. 5 we can say that the effect of changing of the pressure is linear. interesting to recognise that at 100 mm/min feedrate, role of change of the pressure is significant while at higher pressures (at 800 mm/min) this effect is not so significant. (inaccuracies of the curves is decreasing at higher feedrates). this phenomenon can be explained with the extent of the so called loading time. increasing the federate the loading time is decreasing, so the higher speed of the abrasive grains, originating from the higher pressure, is not able to effect significantly on the efficiency. extent of the abrasive mass flow rate increases the depth of kerf (fig. 6) particularly at increase of small abrasive flow rates. in the investigated interval the depth of kerf increased on double. if the mass flow rate exceeds a given value, there are too much abrasive grains will banged up from the machined surface, which results the decreasing of the depth of kerf. this can be observed only at kerfing tests, but will not appear at real cut through process. 213 figure 5: effect of the pressure on the depth of kerf at different feedrates and abrasive mass flow rates, on almgsi0,5 aluminium alloy figure 6: effect of the abrasive mass flow rate on the depth of kerf at different feedrates and pressures, on almgsi0,5 aluminium alloy summarised effect of the parameters common investigation of the cutting parameters can be accomplished with help of mathematical models. in this case at optional technological parameters preliminarly can be defined the extent of the depth of kerf. in the young history of abrasive water jets many scientists have described the effect of material removal by theoretical modelling. the models stretch from simple to complicated terms to describe the influence of different process parameters. the most important predictive models, that have been proposed in the literature. [2] they can be subdivided as classic (tikhomirov, hashish, zeng and kim), partly empirical (oweinah, blickwedel, matsui) and empirical (chung, kovacevic, brandt c.) models. on base of results of figs 4-6, mathematical model of the cutting process can be written up as follows [3]: d cb f mpah &⋅ ⋅= (1) where: a − constant of the function defined by multivariable regression, b, c, d – exponents of the function defined by multivariable regression, h – estimated depth of cut, mm p – pressure, mpa m& – abrasive mass flow, g/min f – traverse feedrate, mm/min on base of the experimental results, constants of the model and their statistical characteristics can be determined (table 2). regression analysis of results of cutting experiments was accomplished by the minitab software. applying the monno model for the regression we have got a multivariable regression analysis, solution of which needs a linearization. [4] table 2: regression constants of the monno model material a b c d r2 almgsi0,5 0.046 1.270 0.706 0.947 95.30% 214 extent of the defined constants is proportional to the effect intensity of the given technological parameter on the depth of kerf. with help of this correlation cut through depth can be defined at a given technological parameter combination before the real machining process. the industrial employers of the waterjet cutting do not optimise the technological parameters. setting of those machines is happened by test cutting, in practical way/method. special nomograms can be compiled from fulfilled results of experiments to help to user in choice of technological data. with help of the minitab software we are also able to generate special nomograms for end users of waterjet technology. conclusions in the course of examination the feedrate, pressure and the abrasive mass flow rate was investigated from the several technological parameters effecting on the efficiency at an aluminium alloy. based on achieved examination the following statements can be composed: effect of the feedrate is very characteristic. by increasing the feedrate the depth of kerf decreases decreasing acclivously mainly at slow speeds. pressure of the water increases the depth of kerf. while at small federates the pressure has important role, at higher federates effect of the change of the pressure decreases. this can be explained with the extent of the loading time. by increasing the feedrate the loading time is decreasing, so the higher grain speed – originating from the higher pressure – cannot effect considerably on the depth of kerf. the extent of the abrasive mass flow rate increases the depth of cut. at small abrasive mass flow rates the depth of kerf increases linearly. if the extent of the abrasive mass flow rate is higher then a given value then the depth of kerf will decrease because of the very high amount of returned grains from the cut surface. this phenomenon does not occur at cut through processes. machining of aluminium alloys with abrasive waterjet cutting is accomplished by solid erosion, because of this there is no need long time for the cut. this means that by increasing the pressure the abrasive grains will have high speeds and high energy, which results good material removal. results of this phenomenon the pressure will the dominant technological parameter instead of the federate. acknowledgement the described work was carried out as part of the támop-4.2.1.b-10/2/konv-2010-0001 project in the framework of the new hungarian development plan. the realization of this project is supported by the european union, co-financed by the european social fund. references 1. h. c. meng, k. c. ludema: wear models and prediction equations: their form and content, wear 181-183 part ii., (1995), 443–457 2. s. brandt, zs. maros, m. monno: awj parameters selection – a technicaland economical evaluation, 15th international conference on jetting technology, ronneby, sweden, 6-8 september 2000., 353–366 3. m. monno: selection of process parameters for abrasive water jet (awj) cutting, international conference on cutting technology, icct, march 5-6, 1997, hannover, 109–114 4. k. bodnár, zs. maros: mathematical estimation of depth of kerf at waterjet cutting, ict-2007, international conference on tools, miskolc, 2007, 333–338 5. r. kovacevic: monitoring the depth of abrasive waterjet penetration. international journal of machining and tools manufacturing, 32, (1992), 725–736 microsoft word 1_r.doc hungarian journal of industrial chemistry veszprém vol 37(1). pp. 5-9 (2009) novel n removal with some industrial realisation in hungary p. thury1 , b. fazekas1, i. pasztor1, v. pitas1, l. balasko2, a. karpati1 1university of pannonia, institution of environmental engineering, h-8200 veszprém, egyetem street 10., hungary e-mail: thuryp@almos.vein.hu 2atevszolg co., h-1097 budapest, illatos street 23, hungary continuous decrease of discharge limits of purified wastewater and the demand for minimization of investment and treatment costs resulted in new discoveries and technological developments in nitrogen removal from sewages and industrial wastewaters. almost all the newly recognised processes are based on the no2 – route of the nitrogen removal. the sharon process comprises an autotrophic and a following heterotrophic nitrogen transformation step. the anammox process however requires around 1:1 nh4 +:no2 – ratio in its influent. besides the n2 gas production in the process, a small portion of the nitrogen turns into no3 –. nowadays the practical importance of the aforementioned processes is unfortunately limited to some special wastewater streams, but the utilization of this shortcut of the nitrogen removal in municipal sewage treatment would also be highly beneficial. it appears that according to our practical data collected in specially designed treatment plants for the purification of the wastewater of some animal waste rendering plant and two-stage activated sludge municipal sewage treatment plants the new technologies can easily be realized. the two-stage systems contain two separate sludge cycles in series. both cycles comprise an aerobic bioreactor and a following mainly rectangular clarifier. the first stage is specially designed for cod removal while the second for autotrophic nitrification. the highly overloaded first stage can remove of the main portion of the influent cod. this way the sludge of the second stage contains 5-10 times more autotrophic microorganisms than the conventional a2/o systems. this results in similar increase in the specific nitrification capacity, while significant simultaneous denitrification can occure. keywords: nitrogen removal, nitrit route, two sludge cycle, animal waste rendering industry introduction nowadays wastewater treatment is the essential part of the environmental infrastructure. as a result of the centralization, the wastewater treatment has become an inevitable task since the middle of the last century. one of the biggest challenge of the future in this field is to increase the specific efficiency, besides the cut of the usage of the external energy sources. the issue of this paper is to point out the collected national and international experiences, and to introduce one possible way of the future development to remove the nitrogen from domestic and special industrial wastewater streams in a cost-effective way. the realization of the nitrogen removal in the past the recognition of the special ways of nitrogen elimination in the wastewater treatment and the experimental results in the same field have resulted in the development of new wastewater treatment strategies. one of the most important results of the last 2-3 decades was the discovery of the nitrit route [1] in nitrogen removal. international research groups have identified the fully autotrophic way of nitrogen removal besides the autotrophic/heterotropic nitrate route [2, 3]. it came to the light that nitrogen removal over nitrite can take place in treatment plants that operate with special, concentrated (tkn), warm (>35 °c), wastewater streams [4, 5]. the aforementioned process was implemented mainly for the treatment of the sludge liquor of the anaerobic sludge digestion [6], however some publications are existing concerning similar processes for the treatment of special wastewater streams [6]. the researchers and the engineers have implemented some full scale technologies for the side stream of the communal wastewater treatment starting out from the laboratory scale [7, 8]. at first these plants were able to convert the ammonium to nitrite autotrophically and in a subsequent heterotrophic reaction into nitrogen gas (with external carbon source addition) (sharon). the stoichiometry of the first step is presented in equation 1 [9]. at the beginning of the operation of the sharonanammox technology the operators could stop the oxidation of the ammonium at nitrite but the autotrophic reduction of the nitrite wasn’t carried out in the second anoxic reactor [10]. the second step of the process (anammox, equation 2 [11]) was successfully developed in the year of 2006. as a result of their success the autotrophic conversation of the nitrite and the ammonium of the effluent of the sharon reactor were realised [8]. 6 55 nh4 ++76 o2+109 hco3 – → c5h7no2 biomassza + + 54 no2 –+57 h2o+104 h2co3 (1) nh4 + + 1,31 no2 – + 0,066 hco3 – + 0,13 h+ → 1,02 n2 + + 0,26 no3 – + 0,0066 ch2o0,5n0,15 + 2,03 h2o (2) the advantages of the nitrogen removal over nitrite have been mentioned several times [12, 13] but the remained nitrogen (nitrate) compounds of the treated wastewater haven’t been emphasized. it is known that about 10% of the influent ammonium is remained in the effluent as nitrate. the unconverted ammonium is added to the total effluent nitrogen based on the practical experiences, consequently the effluent of the anammox reactor always contains ammonium and nitrate as well [8]. it is easily countable that with the typical concentration of the reduced nitrogen form in the raw communal wastewater and without post-denitrification or the recycle of the treated wastewater, the nitrate content of the effluent couldn’t be lower than 5–7 mg no3-n/l. that characteristic of the process can limit the application or it requires another treatment step that can convert the above mentioned pollutants into gas or solid phase. as a consequence of the slow growing and the specific environmental inquiries of the anammox bacteria it seems as if these species could exclusively be suitable in the practice only for the treatment of the side streams of the communal wastewater treatment or for special industrial wastewaters. the supernatant of the anaerobic sludge treatment contains about the 15–25% of the total nitrogen load of the communal treatment plants [14] and these surplus of the load arises only at those plants where anaerobic sludge treatment is operated. thus the practicable realization of the similar system configuration and its output are limited (>50 000 population equivalent). moreover the total nitrogen load of these plants could be reduced by more simply controllable, more competitive methods as well [15]. in case of these specifications of the reactions one should find a suitable combination of the conventional and the novel conversation routes of nitrogen. in our opinion the real question is how to combine the above mentioned processes so as to be suitable for the treatment of the mainstream of the wastewater treatment plant. the development of the wastewater technologies yielded numerous results in the operation of the nonactivated sludge processes like granular sludge technologies (anaerobic [8], aerobic [16]), and technologies containing artificial or natural biofilm carriers [17, 18]. in this respect the most important advantage of these technologies in contrast to the activated sludge (as) processes is that these provide suitable selection for the slow growing micro-organisms. this way simultaneous processes (for example: nitrification/denitrification) can take place in the different layers of the granule or the biofilm [18]. under suitable process control nitrification and denitrification can occur in the same bioreactor simultaneously. it is interesting to see the duplicate role of the aerated bioreactors nowadays: the carbon and the ammonium oxidation. as the carbon oxidation is a heterotrophic, the ammonium oxidation is an autotrophic process, the control of the sludge retention time has an important function in the treatment. to achieve a suitable nitrification rate the sludge residence time must be around 14–15 days in the as systems in winter time. from the personal equivalent and the specific sludge yield of the above mentioned two biochemical processes it is easily countable that the ratio of the autotrophs in the activated sludge is around 3–5%. based on the ratio of the nitrifiers in these as systems assuming the usual sludge concentrations (3–6 g mlss/l) the expected maximal volumetric nitrification rate could be around 0,06–0,12 kg nh4-n/m3d. consequently it is unambiguous that the volumetric capacity can be increased with the increase of the sludge concentration (uf membrane, improvement of the sludge settling) [19], but in our opinion there is another option to improve the volumetric nitrification capacity. this solution could be the well-known spatial separation of the heterotrophic carbon and the autotrphic ammonium oxidation in the treatment of communal wastewater streams (two sludge cycles) (fig. 1). the disadvantages of these technologies are easily solvable. the chemical phosphorus removal and the reduction of the oxidised nitrogen with the recirculation of a certain amount of the effluent can result in effective treatment technologies. the adoption of the experiences of the past decades in the sphere of special nitrogen removal ways and the combination with other newly applied devices could result in an effective solution in small reactor volume treating the mainstream of communal wastewater. the two sludge cycle systems contain continuously aerated as tanks with rectangular clarifiers and sludge recycle. the two activated sludge culture formed are not mixed with each other (just in the first stage) so the efficient carbon oxidation in the first stage provides favourable conditions for the selection of the autotrophs in the second stage [19]. figure 1: the scheme of the 2ab system after the collection and evaluation of the operational data of such treatment plants in hungary [19] it can be concluded that the 2ab systems operate with a high loaded first stage to oxidise the maximal portion of the organic carbon in the raw wastewater. due to the short hydraulic retention time (hrt), law dissolved oxygen concentration (do), and the high sludge concentration, small srt is formed. under these circumstances only the organic carbon oxidation can take place in this step resulting in high sludge yield so that the decrease of the nitrogen and phosphorous concentration of the wastewater is the effect of the growing of micro-organisms [19]. it is noticeable that in one hungarian treatment plant (2ab configuration) the specific sludge yield of the organic carbon removal (in the 1st stage) is around 0,4–0,5 kg mlss/kg bod5 due to the high organic 7 load, low do level and the over-designed intermediate clarifier. so in this plant such specific sludge yield is formed as in the fixed film systems [20]. typically the effluent of the first stage contains small amount of biodegradable cod and nearly the total tkn. in consequence of the small cod/tkn ratio of the influent wastewater of the second stage the ratio of the autotrophs could be higher than in the conventional a2/o treatment plants. it is easily countable that the ratio of the autotrophs could be around 20–25% if the intermediate clarification and the first aerobic stage work properly. so no wonder that the nitrification rate of this stage can reach the 1 kg nh4-n/m3d in summer with 3–4 mg/l do level, and 3–4 g mlss/l sludge concentration at the same time [19]. this is clearly due to the increase of the ratio of autotrophs in the sludge. more surprising is that besides the above mentioned nitrification capacity around 0,6 kg nox-n/m3d denitrification rate can be observed in the second as stage. from the small cod/tkn ratio it is indirectly suspectable that the nitrogen removal must happen via nitrite heterotrophically or only autotrophically [13]. in our opinion the nearly forgot 2ab technology in combination with the research experiences of the past decades could be one direction of the further development to purify the main communal and industrial wastewater streams. an opportunity presents itself to recycle a certain portion of the treated wastewater to be denitrified. so in the first step due to the low do level the denitrification of the remaining nox-n can occur as well. moreover the combination of the 2ab system with the biofilm processes could result in more efficient technologies to treat the also communal and industrial wastewater. one possible way for the purification of the liquid waste of the rendering industry one can find some of the above mentioned 2ab or similar treatment technology in the rendering industry treating the 1-3rd. class animal waste in hungary. in hungary the atev co. carries out the elimination of the animal waste ranked into 3 classes: ● specified risk material (srm) based on the hungarian regulations (1st class), ● fatty sludges, manure, dead domestic/farm animals (2nd class), ● slaughterhouse waste that is not used for foodproduction (3rd class), the various elimination strategies result in different amount of wastewater with different quality. the widespread strategies for the elimination of the animal waste are the wet and the dry technologies. the decision between the two technologies is based mainly on the type of the animal waste. the product of the dry technology is the meat flour that can be used as a fodder or it can be burned up. the product and the by-product of the wet technology could be used in the biogas and compost production. in the so-called wet fat extraction technology the fat is extracted from the wet meet paste. the heatconsuming drying and the pressing or the grinding and classification of the meat flour and the packaging do not happen in this technology. in the classical meat flour production (dry technology) after the boiling of the raw material the pasta is transported to the dryer and the fat is extracted with pressing from the dried material. the subsequent step is the grinding (in a mill), where the dried material is grinded into flour, and packed into sacks (50 kg) or into big-bags. the biggest amount of the wastewater is produced during the pressure compensation of the boiled (sterilized) meat paste. the boiler operates at 3 bar pressure, 135 °c temperature minimum 20 minutes long. the wastewater has high tkn concentration that is produced during the pressure compensation (condensation). the average parameters of the condensate are the following: ● high temperature (40–60°c), ● high ph (8–9,5), ● high cod concentration (~3–6 g/l), ● high tkn concentration (depending on quality of the raw material 1–3 g/l). the other considerable wastewater stream is the water leakage of the raw material terminal station that has varying composition (greasy, fatty). the average parameters of the leakage are the follows ● high cod concentration (depending on quality of the raw material ~10–30 g/l), ● high suspended solid content (1–2 g/l) , ● high tkn concentration (depending on quality of the raw material 0,5–2 g/l). most often the mentioned wastewater streams are treated together. this mixed wastewater is pumped through an oil and fat separator, and the next step is usually the air flotation with chemicals. in case of efficient flotation the physically and chemically treated water’s cod/tkn ratio is about 1–4 (~2,5–4 g/l cod/1–2 g/l tkn). the ph and the temperature of the pre-treated water remains high after the physical and chemical treatment, too. the treatment plants with different configurations built in the 90’s are operated properly with these wastewaters, due to the regular reconstruction and careful operation. almost all of them were built in 2ab or similar configuration. for example one of them operates with a high loaded trickling filter in combination with an as second stage (bőny), an other one is a modified 2ab as configuration (debrecen). in table 1 one can see the nitrification rates are close to the well-known design data for the communal wastewater, but significant denitrification activity with low cod/tn ratio can be observed. the high denitrification activity can prove the nitrit route under these circumstances (high temperature even in winter, high nh4-n concentration, small cod/tn ratio). 8 ta bl e 1: o pe ra tio na l d at a of so m e h un ga ria n a te v c o. w as te w at er tr ea tm en t p la nt s tr ea tm en t p la nt w as te w at er o pe ra tio na l p ar am et er pl an t pr et re at m en t b io lo gy q m 3 /d c o d g/ l n h 4n g/ l b o d 5 g/ l c o d /t n ls p k o i kg /m 3 *d ls p b o i5 , kg /m 3 *d ls p n h 4n kg /m 3 *d ηk o i % ηn h 4n % ηt n % v ox (a no x) m 3 x gs s/ l b o o il a nd gr ea se se pa ra tio n tr ic kl in g fil te r/ a s (c yc lic ae ra tio n) 60 -8 0 0, 50, 7* 0, 40, 5* n. a. 1, 31, 8 0, 40, 6* n. d. 0, 30, 4* 90 -9 5 60 -7 0 70 -7 5 60 / ~6 d eb o il a nd gr ea se se pa ra tio n, fl ot at io n 2a b a s 12 015 0 ~6 /~ 4* * ~1 /~ 0, 7* * ~4 /~ 2* * ~6 /~ 2* * 1, 5/ 0, 75 ** 1, 1/ 0, 4* * 0, 3/ 0, 13 ** 35 /8 5* * 25 /3 0* * 40 /9 0* * 52 5/ 72 0* * 3/ 5* * m d fl ot at io n a /o 15 0 ~4 ~1 ,2 ~2 ~3 0, 3 0, 15 0, 09 98 -9 9 95 -9 9 85 -9 5 16 00 (4 00 )* ** 45 h m v h f lo ta tio n 25 0 ~6 ~0 ,8 ~3 ~7 ,5 1, 1 0, 55 0, 19 98 -9 9 95 -9 9 90 -9 5 10 00 (4 00 ) 6, 5 n. d. : n o da ta b o : w as te w at er tr ea tm en t p la nt o f b őn y d eb : w as te w at er tr ea tm en t p la nt o f d eb re ce n m d : w as te w at er tr ea tm en t p la nt o f m át yá sd om b h m v h : w as te w at er tr ea tm en t p la nt o f h ód m ez őv ás ár he ly * w as te w at er th at g oe s i n to th e a s st ag e ** fi rs t s ta ge /s ec on d st ag e (e ff ic ie nc y is c al cu la te d fr om th e in flu en t a nd th e ef flu en t c on ce nt ra tio n of th e gi ve n st ag e) ** * cy cl ic a er at io n in th e ae ro bi c ba si n (1 ,5 h ou rs a er at io n 1 h ou r m ix in g) 9 summary based on our practical experiences it is clear that there is significant simultaneous denitrification in all of the observed industrial wastewater treatment plants (bőny, debrecen, sárvár, mátyásdomb). the no3 – concentration in the effluent is lower than it should be in no3 – route (stochiometrically). without detailed researches the data support that the simultaneous nitrit route can take place in these industrial wastewater treatment plants. references 1. hellinga c., schellen a. a. j. c., mulder j. w., van loosdrecht m. c. m., heijnen j. j.: the sharon process: an innovative method for nitrogen removal from ammonium-rich waste water, wat. sci. tech. (1998) 37(9), 135-142 2. kuai l., verstraete w.: ammonium removal by the oxygen-limited autotrophic nitrificationdenitrification system. applied and environmental microbiology (1998) vol. 64, no.11, 4500-4506 3. schmidt i., sliekers o., schmid m., bock e., fuerst j., kuenen g., jetten m. s. m., strous m.: new concepts of microbial treatment processes for the nitrogen removal in wastewater, fems microbiology reviews (2003) 27, 481-492 4. mulder a., van de graaf a. a., robertson l. a., kuenen j. g.: anaerobic ammonium oxidation discovered in a denitrifying fluidized bed reactor, fems microbiol. ecol. (1995) 16, 177-183 5. sliekers a. o., derworth n., gomez j. l. c., strous m., kuenen j. g., jetten m. s. m.: copletely autotrophic nitrogen removal over nitrite in one single reactor, water res. (2002) 36, 24752482 6. egli k. r.: on the use of anammox in treating ammonium-rich wastewater, universität zürich, doctoral dissertation (2003) 7. mulder j. w., van loosdrecht m. c. m., hellinga c., van kempen r.: full scale application of the sharon process for treatment of rejection water of digested sludge dewatering, water sci technol (2001) 43, 127-134 8. abman w. r., schultz c. e., mulder j. w., van loosdrecht m. c. m., van der star w. r. l., strous m.: full scale granular sludge anammox process, biofilm systems vi. conference amsterdam rai, (2006) 24-27 september 9. sorensen b. h., jorgensen s. e.: the removal ot nitrogen compounds from wastewater, elsevier (1993) 10. van dongen u., jetten m. s. m., van loosdrecht m. c. m.: the sharon-anammox process for treatment of ammonium rich wastewater, water sci technol (2001) 44, 153-160 11. strous m., heijnen j. j., kuenen j. g., jetten m. s. m.: the sequencing batch reactor as a powerful tool for the study of slowly growing anaerobic ammonium-oxidizing microorganisms, appl microbiol biotechnol (1998) 50, 589-596 12. thury p., kárpáti á.: újabb n-eltávolítási lehetőségek a szennyvíztisztításban. környezetvédelem, környezetvédelem 21-22, (2005) 47-61 13. thury p., fodor m., karpati a.: unique nremoval in the wastewater treatment, iceem/ 03 conference, iasi, romania, szeptember 21-24., issn:1582-9596, vol. 5, no3. (2006) 359-366 14. fazekas b., thury p., kárpáti á.: a vízből történő ammónium eltávolítás múltja, jelene és távlatai, maszesz hírcsatorna, január-február, (2008) 3-9 15. thury p., kárpáti á.: autotróf nitrogéneltávolítás lehetőségei az iszaprothasztás vízéből, valamint a szennyvíztisztítás főáramából, környezetvédelem 9-10, (2005) 55-72 16. scheffer r., thury p., kárpáti á.: aerob szennyvíztisztítás iszapgranulációval, xxiv. országos hidrológiai vándorgyűlés, pécs, (2006) július 5-6. 17. chung li: dynamic variations of carbonceous and nitrifying activities is hybrid reactors with different operating conditions, phd thesis, (2004) the hong kong university of science and technology, hong kong 18. thury p., pascik i.: eleveniszapos szennyvíztisztás hatásfokának javítása új típusú, adszorbeáló, ioncserélő felületre biofilm beépítéssel – hibrid rendszerként –, “10 éves a maszesz” jubileumi konferencia, lajosmizse, (2007) május 22-23., poszter 19. thury p.: iszaphozam és deammonifikáció a hódmezővásárhelyi két-iszapkörös szennyvíztisztítóban, pannon egyetem, (2007) k+f szakmérnöki dolgozat 20. thury p., szentgyörgyi e., pasztor i., pulai j., fazekas b., kárpáti á.: the unique specific excess sludge yield in a highly overloaded two stage as plant, european water association, ewater electronic journal, under referation, www.ewaonline.de/journal/online.htm (2007) microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 77-81 (2008) enzymatic esterification of lactic acid under microwave conditions in ionic liquids b. major , n. nemestóthy, k. bélafi-bakó, l. gubicza university of pannonia, research institute of chemical and process engineering 8200 veszprém, egyetem u. 10, hungary e-mail: majorb@mukki.richem.hu ethyl lactate is a natural flavouring compound and can be used as an environmentally friendly solvent, as well. lactic acid production requires costly downstream processes, which increases the price of the products. one of the latest purification methods is the extraction of the lactic acid from the fermentation broth by phosphonium type ionic liquids. this method gives the possibility to synthetise lactates in the extracting agent avoiding an expensive separation process. microwave heating is widely used in organic chemistry because it usually shortens the reaction time and enhances the reaction rate, but its effect on enzymatic esterification reactions in ionic liquid media was hardly investigated. for comparison of the ethyl lactate synthesis in different media two organic solvents and 20 ionic liquids were tested. eight suitable media were found: toluene and 7 ionic liquids. the reaction conditions of the enzymatic synthesis were optimised in toluene and in cyphos 104. using toluene the highest yield (80%) was achieved in a reaction mixture consisting of 1 mmol lactic acid, 5 mmol ethanol and 4.5 w/w% initial water content diluted by organic solvent to 5 cm3. the enzyme amount needed was 250 mg. in cyphos 104 medium 0.8 mmol ionic liquid, 2 mmol lactic acid, 7 times ethanol excess, 2 w% initial water content and 25 mg immobilised candida antarctica lipase b was enough to carry out the reaction up to 95% yield in 24 hour on 40 °c. the obtained yields and reaction parameters were compared using the two previous media and enzyme reusability tests were done. this experiment gave the result that smaller enzyme amount is enough in ionic liquid than in toluene and the enzyme stability is also much better in it. the synthesis was studied under microwave conditions as well, and the following effects were observed: the optimal initial water content was shifted from 3.7 w/w% to 3 w/w% but the same yield was achieved. microwave heating accelerated the hydrolysis of lactoyllactic acid providing the mixture with fresh lactic acid and enhancing the reaction rate. keywords: ethyl lactate, cyphos type ionic liquid, candida antarctica lipase b, microwave introduction in recent years, there is increasing demand on using renewable materials instead of petroleum-based feedstocks because of the rising crude oil prices and the increasing necessity reducing dependence on petroleum. an important bio renewable building block is lactic acid (la) (2-hydroxypropionic acid), an α-hydroxy acid containing both a hydroxyl and carboxylic acid functional group, which results its wide application field [1]. la is mainly consumed by the food industry as an additive or preservative, but it is also used as a pharmaceutical intermediate and as the basic compound of poly-lactic acid, a biodegradable polymer. its esters are alternative “green” solvents to glycol ether. additionally, ethyl lactate is a natural flavouring compound, so a valuable food and perfumery additive [2, 3]. although la can easily be produced either via fermentation or via a chemical route and has several applications, this potential can only be realised if the cost of production is competitive. the main problem is that fermentation-derived la requires extensive and costly purification processes because it is not volatile. several downstream processes have been developed such as reactive distillation, reactive extraction, electrodialysis, adsorption and esterification [4] and one of the newest methods is the extraction by phosphonium type ionic liquids (ils), because they form complexes with la, so they are proper extracting agents for them [5]. enzymes are normally used in water. however, one of their most interesting properties is their ability to possess excellent catalytic activity in non-aqueous media (e.g. organic solvents, ils or supercritical fluids) if they contain trace amounts of water [6]. a major reason for applying enzymes (e.g.: lipases) under such conditions is to avoid hydrolysis when performing non-hydrolytic transformations, such as esterification. since ils can be perfect media for enzymatic reactions because of their negligible vapour pressure, reusability and enzyme stabilization effect [7-9] our first aim was to test if there is a possibility to produce lactates in the extracting agent avoiding an expensive separation process. traditionally organic syntheses are carried out using external heat source, although it is not a really efficient way of energy transport because its velocity depends on 78 the heat conductivity of the vessel and the reaction mixture. in contrast to conventional heating microwave is independent of these factors. the result is a localized heating by dipole rotation or ionic conduction, which are the two fundamental mechanisms for transferring energy from microwaves to the reaction mass being heated. microwaves transfer energy in 10−9 s with each cycle of electromagnetic energy. the kinetic molecular relaxation from this energy is approximately 10−5 s. this means that the energy transfers faster than the molecules can relax, which results non-equilibrium conditions and a greater number of energetic collisions. this leads to enhancement in reaction rates and product yields [10]. moreover using microwave conditions enhances the reaction rate not only in chemical but in enzymatic reactions [11-13]. although both microwave and ils present several advantages only one article describes an enzymatic acylation reaction using the two special conditions simultaneously [14]. so our second aim was to test the influence of the microwave energy on the enzymatic synthesis of ethyl lactate in ils. experimental chemicals enzyme: novozym 435 (immobilised candida antarctica lipase b) was received from novozymes, denmark as a gift. ionic liquids: all the utilized ils, trihexyl-tetradecylphosphonium-bis(2,4,4-trimethylpentyl)-phosphinate (cyphos 104), trihexyl-tetradecyl-phosphonium-bromide (cyphos 102), trihexyl-tetradecyl-phosphonium-dodecylbenzene-sulfonate (cyphos-202), trihexyl-tetradecylphosphonium-hexafluorophosphate (cyphos 110), tetrabutyl-phosphonium-bromide (cyphos 163), tetraoktyl phosphonium-bromide (cyphos 166), ,triisobutyl-methyl-phosphonium-tosylate (cyphos-106) were bought from iolitec gmbh, germany other chemicals: ethanol (absolute) and lactic acid (90 w/w% solution) were purchased from spektrum 3d, hungary. toluene, acetonitrile and hexane were received from scharlau, spain. methods and instrumentation to avoid the inhibition effect of the water concentrated la solution (90 w/w%) was used as a substrate which resulted the presence of la dimers in the reaction mixture [1]. by acid-base titration the accurate monomer concentration of the acid solution was determined and the yields were correlated to this amount. its composition was: 53 w/w% la, 26 w/w% lactoyllactic acid, 7 w/w% lactide and 14 w/w% water. a typical reaction mixture in organic solvents contained la, ethanol in equimolar amounts or an excess of the ethanol, 0.5–5.5 w/w% water and organic solvent to get a total volume of 5 cm3. to this mixture 100–500 mg enzyme was added. in a typical reaction using il media the reaction mixture contained 2 mmol la, 4–16 mmol ethanol, 0,3–1,3 mmol il, 1–4 w/w% water and 25–100 mg enzyme. sample preparation: samples from organic media needed no extra preparation. using il 50 μl samples were taken and they were extracted with 4*80 μl hexane before gc analysis. as a preparation for hplc analysis the samples were diluted in 5 ml phosphate buffer (ph: 2.3, 6% acetonitrile content). instrumentation: the reactions using conventional heating were carried out in a gfl 3031 shaking incubator at 150 rpm and on 40 °c. tests under microwave conditions were performed in a commercial microwave equipment (fig. 1) (discover series, benchmate model, cem corporation, usa) with a capacity of 4 ml. it was provided with magnetic stirrer and a non-contact infrared temperature sensor to monitore the temperature, which was kept constant (±1°c) by altering the microwave power. for the esterification reactions of la maximal energy was 10 w to maintain 40 °c. figure 1: cem discover microwave equipment analytical methods: water content of the substrates was measured by a mettler toledo dl31 type karl fisher titrator. the samples were analysed by hp 5890 a gas chromatograph, with hp-ffap column, and fid detector. to test the enantioselectivity of the reaction an fp lipodex e column was necessary. 79 the hplc analyses were done by a merck type equipment with zorbax sb-aq 76 column, and l-7450 detector. the monitoring wave-length was 215 nm. results and discussion experiments using organic solvents for comparison of the results in ils reactions were carried out in organic solvents. according to the literature data [15-16] toluene and hexane are the most appropriate solvents for the enzymatic esterification of la. as mentioned by parida et al. [16] straight-chain 2-hydroxy acids are highly reactive in esterification reactions with 1-butanol using 5000 mg candida rugosa enzyme/mmol la, while according to from et al. [15] esterification of one mmol la in hexane needs 10 mg immobilised candida antarctica lipase b. in our experiments ethyl lactate was produced with high yield in toluene, while in hexane the conversion remained under 15%. the needed enzyme amount was quite high (fig. 2), at least 250 mg immobilised candida antarctica lipase b was necessary for a measurable conversion of one mmol la. increasing the initial water content from 2.5 w/w% to 4.5 w/w% the yield was increased up to 80% using 250 mg enzyme. the best result was achieved at 1:5 la-ethanol molar ratio. 0 10 20 30 40 50 60 70 80 90 100 0 100 250 400 500 enzyme amount (mg) et hy l l ac ta te y ie ld (% ) figure 2: ethyl lactate yield obtained after 24 h vs. enzyme amount used (la 1 mmol, ethanol 5 mmol, initial water content 2.5 w/w% diluted with toluene to 5 cm3) reusability of the enzyme was also tested in toluene where ethyl lactate yield was decreased completely after four cycles, which shows the fast deactivation of the enzyme. experiments using ils under conventional heating as a second step 20 different ils were tested, but reaction could be carried out with considerable yield only in 7 media (table 1). these media could be divided into 3 groups. to the first one belonged cyphos 104, where only the enzyme had catalytic effect on the reaction. there were some media (cyphos 163, cyphos 166, cyphos 102, cyphos 106 and cyphos 110) where the reaction was catalysed by the il as well, and similar ester yield was observed without enzyme. finally, cyphos 202 was situated between the two previous groups, because it slightly catalysed the reaction itself. table 1: comparison of the ester yields in different ils (40 °c, 25 mg enzyme, 3 w/w% initial water content) ionic liquid yield (%) catalyst cyphos 104 80 enzyme cyphos 202 95 enzyme + slightly il il + slightly enzyme il + slightly enzyme il + slightly enzyme il + slightly enzyme cyphos 163 cyphos 166 cyphos 106 cyphos 102 cyphos 110 104 90 74 60 36 il + slightly enzyme all the listed ils formed one phase system with the substrates and products, except cyphos 110, which gave an emulsion. this two phase system was the reason for the obtained lowest product yield (36%). increasing the reaction temperature the yield was growing, and this enhancement was the highest between 50 and 60 °c, where the reaction mixture became one phase. the enantioselectivity of the reaction was tested as well, and cyphos 104 was the only medium where a slight excess of ethyl l-lactate (e.e. 19%) was observed. in the next step ethyl lactate production was optimized in cyphos 104, because marták et al. [5] it gave the best result as the extracting agent of la. it was important to investigate the minimal amount of solvent necessary for the reaction. in the range from 200 mg (0.3 mmol) to 1000 mg (1.3 mmol) il, the following effect was observed: increasing of the amount of the il to 600 mg the yield was increased extensively but its further addition had no influence on the ester yield. based on these results for the further reactions 600 mg (0.8 mol) il was used. to investigate the effect of initial water content the la was dehydrated using zeolite 3a, and different amounts of water were added to the reaction mixture. in the range from 1 to 2 w/w% water had positive effect on the enzyme activity providing the monomolecular water layer to the enzyme. more water shifted the thermodynamic equilibrium of the reaction towards hydrolysis. the best la : ethanol molar ratio was found at 1:7 unlike to toluene, where 1:5 was found optimal. the amount of immobilised enzyme was varied between 12.5–50 mg/mmol la depending on the required reaction time, but using the smallest amount the reaction was completed in 24 hours. the reusability of the enzyme was also tested and compared with the results in toluene (fig. 3). in this experiment reactions were carried out using the optimal parameters. after 24 hour reaction time and sample analysis the enzyme was filtrated, washed, dried and a new reaction was started with it. all the yields were correlated to the yield of the first cycle. it was found that in cyphos 104 the ethyl lactate yield decreased only 20% after 6 cycles, while in toluene it dropped completely in four cycles. 80 from these experiments we can conclude: the reaction was carried out in an il which can be used for the extraction of la as well. in il media smaller amount candida antarctica lipase b was enough than in toluene, and the reusability of the enzyme was also much better. 0 10 20 30 40 50 60 70 80 90 100 1 2 3 4 5 6 cycles re la tiv e yi el d (% ) ionic liquid organic solvent figure 3: reusability of the enzyme in toluene and cyphos 104 il experiments using ils under microwave heating reactions were carried out under microwave heating in the 7 suitable il media, but positive effect was observed only in four cases (cyphos 202, 166, 163 and 102) where the reaction time decreased. in cyphos 202 it was 7 h instead of 24h. in the other ils the results did not change compared to conventional conditions, except cyphos 104 where the yield decreased. however, there are reports which describe that novozym 435 weakly interacts with the microwave [12] and microwave can be used for example with imidasolium and pyridinium-based ils [14], control reactions were carried out to clarify our results in cyphos 104. in our experiments different systems (il, enzyme, il with enzyme and il with enzyme and ethanol) were irradiated by microwave energy for 2 hours. after this treatment, reactions were started with them in shaking incubator, and the obtained yields were compared (fig. 4). the first column in fig. 4 shows the control reaction carried out in shaking incubator without any previous incubation of the compounds. by the second column microwave irradiation had no effect on cyphos 104, but after the incubation of the pure enzyme it reached only the 72% of the expected yield. its reason was probably not the microwave, but the fact that enzymes are not really stable without a solvent, although they are immobilised. using il as a solvent for the enzyme the reaction was not successful, because the high viscosity hindered the mixing and local overheating caused denaturation of the enzyme. so this was the reason for the decreased yield under microwave conditions. after solving this problem by previously homogenised reaction mixture the reaction reached the same yield using microwave irradiation as in shaking incubator. to maintain the effect of microwave irradiation on candida antarctica lipase b the viscosity of the il was decreased by additional ethanol although it slightly damages the enzyme. the result was compared to the obtained yield in the same solution incubated in shaking incubator (control 2). by the fifth and sixth column of fig. 4 they are equal, therefore microwave has no effect on immobilised candida antarctica lipase b. 0 10 20 30 40 50 60 70 80 90 100 control 1 il enz il+enz il+enz+etoh control 2 incubated systems re la tiv e yi el d (% ) figure 4: enzyme and il stability under microwave conditions further experiments were carried out in cyphos 202, because it was the only media where the reaction was catalysed by enzyme and microwave had positive effect on it. since the influence of the initial water content is very important in esterification reactions [17] and the polar water molecules can influence the energy conduction under microwave conditions [13], the most significant parameter was the optimal initial water content. in our experiments with both methods (conventional and microwave heating) small (2 w/w%) initial water content decreased the yield dramatically (38% and 45% respectively). under conventional conditions the highest ethyl lactate content was achieved at 3.7 w/w% while under microwave conditions at 3 w/w% initial water content with identical yield (105%). as table 1 and the experiments using microwave conditions show, in some cases ester yield exceeded the monomer la content of the reaction mixture, which can be only possible if the dimers are able to decompose to monomers and form ethyl lactate. engin et al. describes [18] neither temperature change, nor catalyst addition alters the dynamic equilibrium between la, lactoyllactic acid and water, but in an esterification reaction the formation of water causes the hydrolysis of the dimer. they have found that lactoyllactic acid hydrolysis is a very slow reaction and may be a rate-limiting step in ethyl lactate formation. by our experiments an advantage of the microwave heating is that it accelerates the hydrolysis of the dimer (fig 5). by the results of hplc analysis presented in fig. 5 not only the amount of la but the amount of lactoyllactic acid decreased in the esterification reaction, while their ratio did not changed (about 47% la, 43% lactoyllactic acid and 10% lactide). so the dimer can decompose fast enough, and the rate of hydrolysis is not a limiting step any longer. this effect results in faster reaction using microwave irradiation than under conventional conditions. 81 48.6 45.8 45.9 47.4 44.5 42.9 43.5 42.3 8.5 9.6 10.6 10.3 0 10 20 30 40 50 60 70 80 90 100 0 2 4 7 time (h) co m po si tio n (w /w % ) lactide lactoyllactic acid lactic acid figure 5: composition of the la solution in the reaction mixture vs. reaction time and the ratio of the compounds after certain reaction times (0.7 mmol cyphos 202 il, 2 mmol la, 14 mmol ethanol, 3 w/w% initial water content) conclusion for the esterification of la different media were tested. the reaction was successful in toluene (yield 80%) and in 7 ils. after the optimisation of the parameters and the comparison of the two media ils were found better solvents because of the needed smaller enzyme amount (12.5 mg enzyme/mmol la instead of 250 mg) and its enhanced reusability. in toluene the enzyme could be recycled only 3 times, while in cyphos 104 the yield remained 80% after 6 cycles. it was determined that microwave heating harms neither candida antarctica lipase b, nor cyphos type ils and it promotes the ethyl lactate production accelerating the hydrolysis of lactoyllactic acid. as a result the reaction time was shortened from 24 h to 7 h. acknowledgements this work was partly supported by the croatianhungarian science and technology cooperation (project no. cro-28/06). we gratefully acknowledge novo nordisk a/s (bagsvaerd, denmark) for the gift of novozyme 435 lipase enzyme. references 1. vu d. t., kolah a. k., asthana n. s., peereboom l., lira c. t., miller d. j.: fluid phase equilibr., 236, (2005), 125-135 2. lipinsky e. s., sinclair r. g.: chem. eng. process, 82, (1986), 26-32 3. datta r., henry m.: j. chem. technol. biot., 81, (2006), 1119-1129 4. joglekar h. g., rahman i., babu s., kulkarni b. d., joshi a.: sep. purif. technol., 52, (2006), 1-17 5. marták j., schlosser š.: sep purif technol, 57, (2007), 438-494, 6. cantone s., hanefeld u., basso a.: green chem., 9, (2007), 945-971 7. yang z., pan w.: enzyme microb. technol., 37, (2005), 19-28 8. lau r. m., sorgedrager m. j., carrea g., van rantwijk f., secundo f., sheldon a.: green chem., 6, (2004), 483-487 9. ulbert o., fráter t., bélafi-bakó k., gubicza l.: j. mol. catal. b-enzym., 31, (2004), 39-45 10. yadav g. d., lathi p. s.: enzyme microb. technol., 38, (2006), 814-820, 11. roy i., gupta m. n.: curr. sci., 85 (2003), 16851693 12. yu d., wang z., chen p., jin l., cheng y., zhou j., cao s.: j. mol. catal. b-enzym., 48, (2007), 51-57, 13. huang w., xia y.-m., gao h., fang y.-j, wang y., fang y.: j. mol. catal. b-enzym., 35, (2005), 113-116, 14. lundell k., kurki t., lindroos m., kanerva l. t.: adv. synth. catal., 347, (2005) 1110-1118 15. from m., adlercreutz p., mattisson b.: biotechnol. lett., 19, (1997), 315-317 16. parida s., dordick j. s.: j. am. chem. soc., 133, (1991), 2253-2259 17. romero m. d., calvo l., alba c., daneshfar a., ghaziaskar h. s.: enzyme microb. technol., 37, (2005) 42-48 18. engin a., haluk h., gurkan k.: green chem., 5, (2003), 460-466 microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 37(2) pp. 95-99 (2009) production of bio-isoparaffins by hydroisomerisation of bioparaffins t. kasza , p. baladincz, j. hancsók university of pannonia, institute of chemical and process engineering, department of hydrocarbon and coal processing h-8201 veszprém, p.o.box.: 158, hungary e-mail: kaszatamas@almos.uni-pannon.hu the importance of biofuels becomes more acute, especially in the european union. beside them, those second generation products are spreading increasingly which have better product and performance properties relative to the first generation biofuels. the bio gas oil is a promising product that is a fuel with high isoparaffin content in the gas oil boiling range, which can be produced by the catalytic hydrogenation of different triglycerides. in this paper the isomerisation of an intermediate product with high n-paraffin content was studied on sapo-11 catalyst at 300–360 °c temperature, 20–40 bar pressure, 1.0–3.0 liquid space velocity and 400 nm3/m3 h2/feed ratio. during the experiments we succeeded to produce an excellent quality diesel gas oil blending component with high i-paraffin content which is practically free of heteroatom content. this product satisfies with some addition all the requirements of the european diesel fuel standard. keywords: bio gas oil, catalytic hydroisomerisation, sapo-11 catalyst. introduction the continually increasing quantity demand, the efforts to decrease the crude oil dependency of several countries all over the world, the prediction exhaust of crude oil reserves, the increasing crude oil price, the environmental regulations and the requirements of the european union induce the increasing importance of biofuels which can be produced from agricultural products and wastes, and this tendency will go on in the close future [1-6]. the different vegetable oils, and the different esters of them, furthermore the products obtained from the previous ones by catalytic hydrogenation belong to biofuels. as unconverted vegetable oils did not come up to the expectations as diesel fuel, the chemical conversion of these vegetable oils is necessary in order to produce proper quality fuels and fuel blending components [7-8]. nowadays among biofuels the biodiesel has been used in the highest degree which is produced by the transesterification of vegetable oils. it has numerous disadvantages, for example: poor heat and oxidation stability, hydrolysis sensitivity (corrosion), low energy content, unfavourable cold start properties, high viscosity, etc [7-8]. in the near future the bio gas oil which is biofuel with high isoparaffin content in the gas oil boiling range produced by the catalytic hydrogenation of different triglycerides (conventional and ennobled vegetable oils, used cooking oils and fats, greases from meat-packing and leather-work, “trap grease” from sewage farm, etc.) [8-12] provides a good solution to satisfy the bio component demand in gas oil. during the reactions of catalytic hydrogenation of triglycerides mainly normal and isoparaffins, propane, carbon-oxides (co2, co), water and other oxygen containing compounds are generated according to next gross reaction equation [8-15]: t i li id k ch2 o c r1 o ch o c r2 o ch2 o c r3 o n-paraffinok i-paraffinok+ + katalizátorok h2, t, p (oxigéntartalmú vegyületek) co +co2+ ch4+c3h8+h2omelléktermékek: catalysts n-paraffins i-paraffins oxygen containing compounds triglycerides by-products: the diesel fuel requirements can be satisfied by high nand i-paraffin containing blending components with reduced aromatic content (which are practically free of sulphur and nitrogen). at arctic climate and at winter time in the temperate zone the normal paraffins with high carbon number in the diesel fuel are unfavourable regarding the cold flow properties, which affect unfavourably the freezing point, cloud point and cold filter plugging point (cfpp). consequently, to improve the cold properties, the catalytic paraffin conversion technologies are becoming more and more important [12-15]. during the production of bio gas oils by catalytic hydrogenation the products have generally high nparaffin content. so the catalytic paraffin conversion has high significance, because the cold properties (for example the cold filter plugging point) could not satisfy 96 the specifications of diesel fuel quality standard. with the newest improved high activity catalyst high isoparaffin containing products can also be produced, by this way the cfpp values are more favourable, because of the lower freezing point of isoparaffins relative to normal paraffins [12-15]. experimental work the aim of our experimental work was the investigation of production possibilities of bio gas oil with good flow properties by catalytic paraffin conversion from high nparaffin containing mixture produced from sunflower oil by catalytic hydrogenation. besides, our objective was to determine the effects of the favourable operational parameters (temperature, pressure, space velocity, hydrogen/feed ratio) on the yield and quality of the products on the used pt/sapo-11 catalyst. apparatus the experiments were carried out in an apparatus containing a tubular down-flow reactor of 100 cm3 effective volume. it contains all the equipment and devices applied in the reactor system of an industrial heterogeneous catalytic plant. the experiments were carried out in continuous operation [9]. materials the main properties of feedstock used in these heterogen catalytic experiments are presented in table 1. the catalyst was an expediently chosen pt/sapo-11 catalyst [10]. table 1: the main properties of the high n-paraffin containing feedstock properties value density at 40°c, g/cm3 0.7697 kinematical viscosity, 40°c, mm2/s 3.714 cold filter plugging point, °c +23 flash point, °c 50 sulphur content, mg/kg 3.4 nitrogen content, mg/kg 2.3 acid number, mg koh/g 1.9 iodine number, g i2/g <1 c177.0 n-c17 46.8 i-c17 0.8 n-c18 42.9 i-c18 0.9 paraffin content, % c18+ 1.7 analytical and calculation methods the properties of the feedstock and the products were measured according to the methods of the en 590:2004 standard and those were calculated according to the standard methods. these methods and the standard deviations of these analytical methods are summarized in table 2. table 2: the applied analytical methods and theirs standard deviations properties method/device standard deviations* density, g/cm3 en iso 12185:1998 ± 0.0015 viscosity, at 40°c, mm2/s en iso 3104:1996 ± 0.03 cold filter plugging point, °c en 116:1999 ± 1 sulphur content, mg/kg en iso 20846:2004 (multi ea 3100 /greenlab) ± 1.5 nitrogen content, mg/kg astm-d 6366-99 (multi ea 3100 /greenlab) ± 1.5 hydrocarbon composition gas chromatography (trace gc 2000) ± 1 % rel * in the investigated parameter range results and discussion during our experiments we investigated the catalytic transformability of the high n-paraffin containing mixture produced by catalytic hydrogenation of hungarian sunflower oil on pt/sapo-11 catalyst at 300–360 °c temperature, at 20–40 bar pressure, at 1.0–3.0 h-1 liquid space velocity and at 400 nm3/m3 h2/feed ratio. in this paper we present the major results of this experiment. product yields during the experiments using this catalyst the yields of the products decreased by increasing the temperature and by decreasing the pressure and the liquid space velocity (fig. 1 and 2) which was caused by the hydrocracking reactions which took place in an increasing degree beside the isomerisation reactions. in the ranges of the operational parameters the product yields were higher than 80% in all cases. 97 88% 90% 92% 94% 96% 98% 100% 290 300 310 320 330 340 350 360 370 temperature, °c pr od uc t y ie ld s, % . lshv = 1.0 1/h lshv = 2.0 1/h lshv = 3.0 1/h figure 1: product yields as a function of the temperature and the lhsv (p = 40 bar) 75% 80% 85% 90% 95% 100% 15 20 25 30 35 40 45 pressure, bar pr od uc t y ie ld s, % . lshv = 1.0 1/h lshv = 2.0 1/h lshv = 3.0 1/h figure 2: product yields as a function of the pressure and the lhsv (t = 360 °c) the composition of the products the composition of the products was determined by gas chromatography. the products contained c17 and c18 hydrocarbons in the highest amount (85–92%) furthermore other compounds with lower (c17-) and higher (c18+) boiling point in minor amount. in the c18 fraction by increasing the temperature the quantity of isoparaffins increased significantly above 340 °c. this effect was intensified by decreasing the liquid space velocity (fig. 3). this figure also shows that the quantity of c18 hydrocarbons in the product decreased by increasing the temperature, which was caused by the hydrocracking reactions as it was mentioned earlier. 0 5 10 15 20 25 30 35 40 45 50 290 300 310 320 330 340 350 360 370 temperature, °c c om po si tio n, % ic18 (lshv = 1.0 1/h) ic18 (lshv = 2.0 1/h) ic18 (lshv = 3.0 1/h) σc18 (lshv = 1.0 1/h) σc18 (lshv = 2.0 1/h) σc18 (lshv = 3.0 1/h) figure 3: composition of the c18 fraction as a function of the temperature and the lhsv (p = 40 bar) in this fraction the quantity of isoparaffins increased by reducing the pressure, as well. the reason of why the decreasing pressure increased the rate of the formation of isomers and of lower components in the product is that the lower partial pressure of hydrogen the higher partial pressure of hydrocarbons, accordingly the rate of reactions increased, so the cracking reactions could become conspicuous, consequently the quantity of nparaffins decreased. in the c17 fraction (like in the c18 fraction) by increasing the temperature the quantity of isoparaffins increased significantly above 340 °c, which effect was intensified by decreasing the liquid space velocity (fig. 4). this figure also illustrates that the quantity of c17 hydrocarbons in the product decreased by increasing the temperature. in the c17 fraction the quantity of isoparaffins increased by reducing the pressure. by lowering the liquid space velocity the degree of the conversion increased in this case, as well. according to these effects the total isomer content increased by increasing the temperature and by reducing the pressure and the liquid space velocity (fig. 5). 0 5 10 15 20 25 30 35 40 45 50 290 300 310 320 330 340 350 360 370 temperature, °c c om po si tio n, % ic17 (lshv = 1.0 1/h) ic17 (lshv = 2.0 1/h) ic17 (lshv = 3.0 1/h) σc17 (lshv = 1.0 1/h) σc17 (lshv = 2.0 1/h) σc17 (lshv = 3.0 1/h) figure 4: composition of the c17 fraction as a function of the temperature and the lhsv (p = 40 bar) 300 310320 330340350360 20 25 30 35 40 0 10 20 30 40 50 60 70 to ta l i so pa ra ff in c on te nt , % 60-70 50-60 40-50 30-40 20-30 10-20 0-10 figure 5: total isoparaffin content of the products as a function of the temperature and the pressure (lhsv = 1.0 1/h) 98 the cold filter plugging point the cold filter plugging point (cfpp) is an important performance parameter during the application of diesel fuels, namely the precipitation of paraffin crystals caused by decreasing the temperature leads to derangements or could cause unserviceability in the fuel supply system. we found that the cfpp values of the products decreased by increasing the temperature and by decreasing the pressure and the liquid space velocity (fig. 6). the reason of this fact was the increase of the isoparaffin content, namely the isoparaffins have a lower freezing point than n-paraffins do. in fig. 7 the correlation between the quantity of isoparaffins and the cfpp values can be seen. the cfpp values were also improved by the formation of lighter hydrocarbons generated in the hydrocracking reactions beside the isomerisation of paraffins. 300 310 320 330 340 350 355 360 20 30 40 0 5 10 15 20 25 c ol d fil te r pl ug gi ng p oi nt , ° c . 20-25 15-20 10-15 5-10 0-5 figure 6: cffp values of the products as a function of the temperature and the pressure (lhsv = 1.0 1/h) 0 5 10 15 20 25 300 310 320 330 340 350 360 temperature, °c c fp p, °c 0 10 20 30 40 50 60 t ot al is om er c on te nt , % . cfpp (lshv = 1.0 1/h) cfpp (lshv = 2.0 1/h) cfpp (lshv = 3.0 1/h) isomer content (lshv = 1.0 1/h) isomer content (lshv = 2.0 1/h) isomer content (lshv = 3.0 1/h) cfpp of the feedstock = 23°c figure 7: total isoparaffin content and the cffp value of the products as a function of the temperature and the lhsv (p = 40 bar) other product parameters the removal of sulphur and nitrogen content from the fuels has numerous advantages. the most significant ones are that the storage stability of the products increase, the risk of corrosion decreases, the oil change interval is undiminished and the poisoning of the threeway catalyst is avoidable. besides, the removal of heteroatoms is important from environmental and human biological considerations, because by this way the quantity of the harmful materials (sulphur-dioxide, nitrogen-oxides, etc.) generated during the combustion in the engine could be reduced, furthermore the medical risk caused by the carcinogenic heterocyclic nitrogen compounds could be decreased. the sulphur content of the feedstock and consequently that of the products was lower than 10 mg/kg in all cases, which satisfied the requirements of the valid standard. all products had lower than 3 mg/kg sulphur content and lower than 2.5 mg/kg nitrogen content, and these values were several times close to the lower limit of the detection (it is about 0.5 mg/kg). the values of the flash point were 35–45 °c in every case, because the flash point of the hydrogenated vegetable oil used as feedstock was also low, in addition the light component generated during the hydrocracking reactions had low flash point as well. this quality parameter could be easily set by a simple product distillation to the specified value of 55 °c of the standard. during the investigation of the kinematical viscosity of the product at 40 °c, we found that the viscosity of the products decreased by increasing the reaction temperature and by decreasing the pressure and the space velocity, but these values satisfied the requirements of the standard in all cases. summary during the experiments the production possibilities of bio gas oil with good flow properties from high n-paraffin containing mixture produced from sunflower oil by catalytic hydrogenation on sapo-11 catalyst were investigated. it was concluded that in the investigated process parameter range the higher temperature, the lower pressure and the lower space velocity are favourable for the isomerisation of the n-paraffins and for the decrease of cfpp values. at 360 °c temperature, 30–40 bar pressure and 1.0 h-1 liquid space velocity the products had high yield (86–89 %) and high isoparaffin content (50–58 %). at these operational parameters the cfpp values of the products were favourable (between +8 °c and +3 °c). these values satisfy without addition the summer grade requirements of the standard and with some addition the further grade could be fulfilled as well. by the stabilisation of the product the flashpoint values agree with the regulation of the standard. the viscosity and the sulphur content of the products meet the specifications of the standard. summarizing, an excellent quality diesel gas oil blending component with high i-paraffin content was produced which was practically free of heteroatom content which satisfied with some addition all the requirements of the european diesel fuel standard. 99 references 1. official journal of the european union (2003) 123, 42–46. 2. commission of the european communities, com(2006) 845 final, (2007) 3. anon., world ethanol and biofuels report 4 (2006), 365. 4. graff g.: glycerin glut sends prices plummeting, purchasing magazine, 2006.06.15. 5. tyson k. s., mccormick r. l.: nrel/tp-54038836 report (2006) 6. graboski m. s., mccormick r. l.: combustion of fat and vegetable oil derived fuels in diesel engines, prog. energy and comb. science 24 (1998) 125–164. 7. hancsók j.: modern motor and jet fuels ii. diesel fuels, veszprém university press, veszprém, 1999, (in hungarian) 8. hancsók j.: modern motor and jet fuels iii. alternative fuels, veszprém university press, veszprém, 2004, (in hungarian) 9. krár m., kovács s., boda l., leveles l., thernesz a., hancsók j.: hydrogenation of vegetable oils over nimo/γ-al2o3 catalyst, days of chemical engineering’09, veszprém, 21-23. april 2009., (isbn 978-963-9696-68-6), 220–227., (in hungarian) 10. 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(in hungarian) microsoft word b_15_mihaly_r.doc hungarian journal of industrial chemistry veszprém vol. 39(2) pp. 215-218 (2011) using graphical processing units in scheduling problems k. mihály , o. hornyák university of miskolc, department of information engineering, 3535 miskolc egyetemváros, hungary e-mail: krisztian.mihaly@sap.com scheduling problems exist everywhere in the so-called “real world”. they are there in manufacturing, transportation and logistics as well. the main object of these problems is to find an optimal sequence of tasks to be able to fulfil predefined objectives. there are efficient methods to solve complex scheduling problems in science and industry, which methods can be divided into several classes, like heuristic algorithms, genetic algorithms, etc. even if these methods allow reducing significantly the computational time of the solution search space exploration, this latter cost remains exorbitant when very large problem instances are to be solved. some of these methods are not designed for parallel computing; they are using a cpu as an arithmetical unit. from this point of view the bottleneck is the number of processed commands. meanwhile the capabilities of specialized graphical processing units (gpus) have been extremely increased and they can provide an efficient platform for developing graphical algorithms. nowadays there are new programming languages and platforms, where these gpus can be used for more generic problems, using its hardwired parallel processing resources. our goal is to use this specialized graphical platform for solving scheduling problems. this paper is an initial research of the existing platforms and solutions in general and describes the existing solutions in fact of scheduling problems. keywords: gpu; cuda; scheduling introduction this paper goes to give a short overview about the history of the age of parallel processing on graphical processing units and the available hardware and development platforms. this paper investigates the platform of main architecture and the feasibility of algorithms in general for parallel processing and special in area of scheduling problems. finally the future researching areas will be outlined and some conclusions of the justification of this new approach will be given. short history of graphical processing units (gpu) before the review of gpuperformance and computing capacity we have to point out the improvement problems with the currently used central processing units (cpu). over the last decades the main interest for improving the performance of a personal computer device was to increase the speed at the processor’s clock operated. the best example is that the early 1980s, the consumer cpu ran with internal clock operating near 1 mhz. in 2010 most desktop processors have clock speeds between 1 ghz and 4 ghz. it means ~1000 times better solution in the same chip. so what is the problem?! this method hits the power and heat restrictions as a rapidly approaching physical limit of the transistor size. it is no longer feasible to rely on upward-spiralling processor clock speeds. the hardware manufactures changed their approach of creation of new cpus and in the year 2005 they started to ship multicore central processors. this process is sometimes referred as multicore revolution. “in the meantime the state of graphics processing underwent a dramatic revolution. in the late 1980s and 1990s, the growth in popularity of graphically driven operating systems such as microsoft windows helped create a market for a new type of processors. in the early 1990s, users began purchasing 2d display accelerators for their personal computer. these display accelerators offered hardware-assisted bitmap operations to assist in the display and usability of graphical operating systems” [1]. around the same time another approach was developed for three-dimensional graphics. in 1992, the silicon graphics opened the programming interface to its hardware by releasing the opengl library. it was a standardized, platform-independent method for developing 3d applications. in this time the computing of rendering was running in the cpu. because the success of first-person shooting games, as doom, duke nukem 3d and quake the market has created hardware support to create better, more-realistic applications with 3d display. the main companies were the nvidia, ati technologies and 3dfx interactive. first the graphical hardware took care of transform and lighting computations, so these operations could run in the hard-wired graphical processors and the cpu could use for other tasks. the next breakthrough in parallelcomputing point of view was the first graphic card, which supported the microsoft’s directx 8.0 standard. this standard introduced the programmable vertex 216 and pixel shaders. this was the first point, when the developers were able to influence the control of gpus program. figure 1: the difference between the cpu and gpu in measurement of gflop/s [2] early gpu programming; pain-points the directx apis was designed to use gpu to execute special graphical tasks. they were designed to get some data from “input colors” with some additional “color” or “texture” information. the programmer could use this information during the computation. the “color” can mean any number. a clever, but simple trick was to use these containers to put data into the gpu, do some calculations and get back the data. it is quite simple to see, the pain points of this approach. the apis were designed to support graphical apis and the programmers needed very deep knowledge from the graphical platform. there were resource constraints; data could be loaded as picture and texture and retrieved data was another picture. so if the algorithm required accessing a memory area to write, it cannot run on gpu. it was nearly impossible to predict how your particular gpu can deal with floating-point data. they didn’t exist any good method to debug implementations in gpu. new gpu programming approach;opencl; cuda and stream as platforms graphical hardware manufacturer companies came out a new generation of gpus, where the partitioned resources as vertex and pixel shaders where changed and a unified shader pipeline has been introduced. this new generation allows each and every arithmetic logical units (alu) to be controlled by program intending to perform generalpurpose computations. usually, like in case of nvidia’s solution, these alus were built to comply with ieee requirements. near ieee these alus are able to read and write memory as well in software-managed ways. unlike, each main supplier introduced their own architecture or standard. the nvidia has the “computing unified device architecture” (cuda), the ati has the stream. near the industry standards there are open standards as well, the main one is the opencl standard [3]. cuda architecture the cuda architecture has two main parts, one is the hardware which supports the cuda programming and it can be called as device and the programming language to be able create programs using the device capacity. the programming language is based on industry standard c and adds relatively small number of keywords in order to harness some of the special features of cuda architecture. there is a public compiler for this language, the cuda c. we are going to give a short overview about the architecture, but further information you can refer the cuda programming guide by nvidia [4]. as mentioned before cuda is an extension of c language and hides gpu relevant apis and interfaces. there are 3 main tasks, which is the task of the developers, as thread hierarchy, memory access and synchronisation [5]. thread hierarchy to perform computation with cuda, programmers have to define a special c function, the so-called kernel. this is function can be run in a thread using a specified number of lightweight threads in gpu. the kernel is loaded to the device from the host, where the “normal” code is running. threads are grouped into blocks, and blocks forms a so-called grid. threads can communicate through the memory area assigned to the block. the blocks are running independently and their behaviour cannot be affected by the programmer. figure 2: cuda thread hiearchy [6] 217 memory hierarchy there are a lot of types of memory areas, as global memory, shared memory, constant memory, registers and local memory. the differences between the memory types are the size, the accessing time, the caching property. you can read more details in [4] or in [5]. figure 3: basic organization of the geforce 8800 [7] synchronisation it could be needed to force a central point in the kernel, where the threads within the same block are waiting for each other. for example when the shared memory is used by the threads, it could be necessary to have a consistent state in case after writing of a thread. the cuda language provides mechanism, a __synctrheads( ) method, which defines a waiting point in the kernel code. each thread executes his code and stops the processing, while other treads are executed this statement as well. show-cases of cuda applications cuda has many areas, where it could be used, from the astrophysics or physical modelling of fluids, through medical imaging or representing mathematical sets. it cannot be our goal to describe each one; you can read more in [8]. as an example one show-case is described here, from the medical imaging [1]. there are a lot of people, who have been affected by breast cancer in the past 20 years. ultimately, every case of breast cancer should be caught early to prevent the ravaging side effects of chemotherapy and radiation. to achieve this, an effective, fast and minimally invasive way has to be developed. there is the mammogram for early detection, but it has limitations. during the process two or more image need to be taken and the images have to be analysed by skilled doctors. there is another technique, the ultrasound imaging, which is safer, then x-ray image made by mammogram, but it is not used in practice because of the computation limitations. with the gpu capacity this limitations are eliminated. in practice 35 gb of data can be generated by a scan. with tesla c1060 a doctor can manipulate a highly detailed, three-dimensional image of the woman’s breast within 20 minutes. scheduling algorithms in general generally, the purpose of scheduling is to find an optimal processing order of tasks (also called activities, operations or jobs) on a set of processors (machines) subject to several constraints imposed on the tasks, machines and their mutual relationships. in the literature there are a lot of types of scheduling models, like shop scheduling model, real-time scheduling, monoprocessor/dedicated processor/parallel process models, cyclic scheduling, etc. [9, 10, 11] show-cases of cuda applications and a scheduling algorithm parallel computing is considered as it is capable providing solutions for various complex optimization problems. [12] solves the traveling sales man problem by means of gpu. they also used generic operators, and tabu list. in a hybrid cpu-gpu environment the memory handling is also important. [13] applied a two level metaheuristic to solve the flexible job shop problem. the machine selection layer and the operation scheduling module are executed parallel. they implemented a code in c language (cuda) for gpu. also a tabu list was used. [14] suggested the scheduling problem to solve in aheterogeneouscpugpu environment. the cpu and gpu behave differently but both can execute the same task. so they implemented an appropriate load balancing algorithm between cpu and gpu. they achieved 30–40% speedup. [14] investigates a flowshop problem to solve by gpu computing. they focused on an efficient memory mapping model in order to implement a multiobjective local searchtask on gpu. they described their speedup as promising. [15] describes two approaches to parallel flowshop evaluation on cuda platform. according to their measure the gpu based algorithmis faster up to 5%. conclusion as the result of our first project task we get overview about the existing solutions and the main power of parallel computing on the gpu device. the show-cases have a very wide focus, from the medical to the abstract mathematic world. in this huge area the scheduling in manufacturing systems is a little stone. after the literature research we are going to implement the existing solutions in our new hardware, when it will be purchased and installed. we are going to do speed up implementations 218 in direction of floor-shop and job-shop models when the purchasing process of the new hardware will be finished. acknowledgements this research was carried out as part of the tamop4.2.1.b-10/2/konv-2010-0001 project with support by the european union, co-financed by the european social fund. references 1. j. sanders, e. kandrot: cuda by example, addison-wesley,(2010), p. 3 2. j. masood: nvidia cuda http://www.hardwareinsight.com/nvidia-cuda/ (2011. 08. 25) 3. opencl standard, kronosgroup: http://www.khronos.org/registry/cl/specs/opencl1.0.29.pdf (2011. 08. 25) 4. nvidia programming guide 4.0, nvidia developer zone: http://developer.download.nvidia.com/compute/cuda/ 4_0_rc2/toolkit/docs/cuda_c_programming_gui de.pdf (2011. 08. 25) 5. m. czapisnky, s. barnes: tabu search with two approaches to parallel flowshop evaluation on cuda platform, j. parallel distrib. comput. 71(6), (2011), 802–811 6. http://mohamedfahmed.wordpress.com/2010/05/03/ cuda-computer-unified-device-architecture/ (2011. 08. 25) 7. s. ryoo, c. i. rodriges, s. s. baghsorkhi, s. s. stone: optimization princiles and application performance evaulation of multithread gpu using cuda 8. cuda showcases, nvidia webpage: http://www.nvidia.com/object/cuda_showcase_stage. html 9. j. blazevicz, k. h. ecker, e. pesch, g. schmidt, j. weglarz: scheduling computer and manufacturing processes, springer, (2001), isbn 3-540-41931-4 10. p. bruckner, s. knust: complex scheduling, springer, (2006), isbn 978-3-540-29545-7 11. b. chen, c. n. potts, g. j. woeginer: a review of machine scheduling: complexity, algorithms and approximability, handbook of combinatorial optimization (volume 3), (1998), 21–169. 12. j. zhao. q. liu, w. wang, z. wei, p. shi: a parallel immune algorithm for traveling salesman problem and its application on cold rolling scheduling. information scienced 181, (2011), 1212–1223 13. w. bozejko, m. uchronski, m. wodecki: parallel hybrid metaheuristics for the flexible job shop problem. computers and industrial engineering 59, (2010), 323–333 14. t. v luong, n. melab, e. g. talbi: gpu-based approaches for multiobjective local search algorithms. a case study: the flowshop scheduling problem. evocop 2011, 155–166 15. m. czapinski, s barnes: tabu search with two approaches to parallel flowshop evaluation on cuda platform. journal of parallel and distributed computing archive, 71(6, june), 2011, 802–811 16. c. j. jimenez, k. vilanova, i. gelado, m. gil: predictive runtime code scheduling for heterogeneous architectures. hipeac 2009, 19–33 microsoft word b_09_fuleki_r.doc hungarian journal of industrial chemistry veszprém vol. 39(2) pp. 195-199 (2011) performance evaluation of bitumens at high temperature with multiple stress creep recovery test k. adorjányi, p. füleki istván széchenyi university, department of transport infrastructure and municipal engineering 9026 győr egyetem tér 1, hungary e-mail: adorjany@sze.hu e-mail: fulekip@sze.hu the paper evaluates performance properties of paving grade, hard and modified binders with multiple stress creep and recovery tests (mscr) at +60 °c. the dynamic shear rheometer measurements were made on rolling thin film oven test aged samples at three stress levels. the delayed viscoelastic response was evaluated with recoverable strain and the resistance to permanent deformation with non-recovered compliance. close relationship presented between average recoverable strain and non-recoverable compliance at different stress levels. the performance parameters have been compared with specified requirements. keywords: bitumen, creep and recovery, dynamic shear rheometer, multiple stress creep and recovery test introduction in the frame of strategic highway research program (shrp) superpave (superior performing asphalt pavements) which was started in usa in 1987 new performance related properties were defined and related test method were introduced among others for bitumen. the performance behaviour of bitumen was defined with viscoelastic properties measured with dynamic shear rheometer. the resistance to permanent deformation at high temperatures was specified with parameter g*/sinδ (complex shear modulus/sin (phase angle)). later it has been shown by several authors that this parameter was not always adequate with performance in the road pavement especially in case of modified bitumen. during revision of binder superpave specification for replacing this parameter the multiple stress creep recovery test (mscr) has been developed by d’angelo at al [2]. this test method has been introduced as aashto tp 70-2 test method, and the mscr parameters were used for binder m 320-09 binder specification [1, 3]. the paper discusses the application of mscr measurements for evaluation of typical binders used in road pavement construction in hungary and compares the obtained parameters with aashto performance-graded binder specification. laboratory test method the mscr tests were performed according to aashto tp 70-07 specification, with dsr at 0.1 kpa, 3.2 kpa and 6.4 kpa stress levels on 25 mm diameter specimen and 1 mm gap at temperature of +60°c on rtfot aged samples. at each stress level 10 cycles were applied with 1 s creep phase and 9 s recovery phase. the strain was measured at 0.1 s steps, and there was no relaxation time between stress levels. the samples were tested through 3x10 cycles at three stress levels the time (t), shear stress (τ) and shear strain (γ), were recorded and the non-recoverable creep compliance (jnr) was calculated. the delayed viscoelastic response of the binder was evaluated with recoverable strain and the permanent deformation with non-recoverable compliance [1, 2]. the adjusted strain at the end of creep phase of each cycle: γ1 = γc – γ0, (1) where: γ1 – the adjusted strain value at the end of creep phase of each cycle, (t=1 s), γ0 – the strain value at the start of creep phase of each cycle, (t=0 s), γc – the strain value at the end of creep phase of each cycle, (t=1 s). 196 the recoverable strain at each cycle is: γrec = 100·(γ1 – γ10)/γ1, (2) where: γrec – the recoverable strain at each cycle, γ10 – the adjusted unrecovered strain value at the end of recovery phase of each cycle (t=10 s) can be given as: γ10 = γr – γ0, (3) where: γr – the strain value at the end of recovery phase of each cycle (t=10 s). substituting (1) and (3) into (2) the percent recovery at each cycle can be expressed as γrec = 100·(γc – γr)/(γc – γ0). (4) the average percent recovery for ten cycles at stress level of τ is ( ) ( )τγ⋅=τγ ∑ 10 1 recrec 10 1 . (5) where: γrec(τ) – the recoverable strain at each cycle at τ stress level. the percent difference in recovery between two given stress levels (τ1<τ2) is ( ) ( ) ( )[ ]2rec1rec 1rec rec τγτγ τγ 100%γδ −⋅= (6) fig. 1 illustrates the definitions of strains at each cycle. 0.0 0.5 1.0 1.5 2.0 2.5 4 14 24 st ra in [% ] time [s] γ1 γ0 γc γ10 γr γ1-γ10 figure 1: strain diagram of creep and recovery the assessment of permanent deformation was made with average non-recoverable compliance, at stress levels of τ=0.1 kpa, 3.2 kpa and 6.4 kpa as follows: ( ) ( ) τ/τγτj 10nr = . (7) percent differences in average non-recoverable compliance between 0.1 kpa and 6.4 kpa, 0.1 kpa and 3.2 kpa, 3.2 kpa and 6.4 kpa were calculated as ( ) ( ) ( ) )τ(j/]τjτj[100ττ%jδ 1nr2nr1nr21nr −⋅=− . (8) tested binders for performing mscr tests 6 different types of bitumens were used which are typically applied in hungary in hot asphalt mix production. the bitumen types as well as values of needle penetration, ring and ball (r&b) softening point measured on pure samples are given in table 1. the number in brackets after the bitumen type sign refers to sample number of bitumen. table 1: types, penetration and softening point values of tested bitumens bitumen type penetration at 25°c, 0.1 mm r&b softening point, °c hard b 15 (3) 17 70.5 polymer modified pmb 10/40-65 24 67.0 polymer modified pmb 25/55-65 48 66.2 paving grade b 35/50 (2) 35 56.0 paving grade b 50/70 (3) 56 51.0 paving grade b 50/70 (4) 60 48.8 discussion of test results for each of three stress levels the average percent of recovery of ten cycles was determined according to aashto tp 70-07. fig. 2 demonstrates that the paving grade bitumen shows considerable larger creep strain and lower recovery than the modified bitumen. 0 1 2 3 4 5 6 7 8 9 10 4 9 14 st ra in [% ] time [s] pmb 10/40-65 b 50/70 (3) figure 2: plot of creep and recovery phase of paving grade bitumen b 50/70 (3) and modified bitumen pmb 10/40-65 at 1st cycle of 0.1 kpa stress level the rate of strain value increases and shows change at the start of each stress level. for paving grade bitumen b 50/70 (4) most part of the strain (13500%) was developed at the largest stress level (6.4 kpa) over 315 s test duration (see fig. 3). 197 0 2000 4000 6000 8000 10000 12000 14000 0 100 200 300 st ra in [% ] time [s] figure 3: strain value versus time for bitumen b 50/70 (4) during whole test while the average recoverable strain of pmb 10/40-65 modified bitumen and of hard b 15 (3) bitumen doesn’t depend on the stress level, binders with higher penetration show lower recoverable strains. the distinction between two b 50/70 binders can also be detected here where the differences in recoverable strains are 40–50% depending on stress levels (fig. 4). the plot of average unrecovered strain determined from ten cycles for each stress level is illustrated on fig. 5. the lowest values of average unrecovered strains have the hard bitumen b 15 (3) and the pmb 10/40-65, while b 35/50 (2) and pmb 25/55-65 binders show almost the same values. despite the same penetration grade the two b 50/70 binders coming from different distilleries show difference in average unrecovered strains. percent difference in recovery was calculated by (6) between three stress levels as: δγ̄rec' – percent difference recovery at 0.1 kpa and 3.2 kpa stress levels, δγ̄rec'' – percent difference recovery at 0.1 kpa and 6.4 kpa stress levels, δγ̄rec''' – percent difference recovery at 3.2 kpa and 6.4 kpa stress levels (table 1). table 2 and table 3 summarize the percent differences in recoveries and the non-recoverable compliances for different stress levels. 0 10 20 30 40 50 60 70 0.1 3.2 6.4 a ve ra ge re co ve ra bl e st ra in [% ] stress [kpa] pmb 10/40-65 b 15 (3) b 35/50 (2) pmb 25/55-65 b 50/70 (3) b 50/70 (4) figure 4: average recoverable strains of different binders depending on stress levels 0. 5 0. 1 2. 7 3. 1 7. 3 11 .8 17 .1 4. 7 97 .1 11 1. 9 26 3. 7 42 4. 2 36 .3 9. 2 21 7. 2 25 6. 0 58 7. 0 91 4. 0 0 200 400 600 800 1000 pmb 10/40-65 b 15 (3) b 35/50 (2) pmb 25/55-65 b 50/70(3) b 50/70 (4) a ve ra ge a dj us te d un re co ve re d st ra in [% ] γ10 (0.1 kpa) γ10 (3.2 kpa) γ10 (6.4 kpa) figure 5: adjusted average unrecovered strains at 0.1-3.2-6.4 kpa stress levels of different binders the non-recoverable compliance depicted on fig. 6 shows very well the sensitivity of binders to permanent deformation under repeated loads. the diagram on fig. 6 illustrates that binders with lower penetration (b 15 (3), pmb 10/40-65) have lower values of non-recoverable compliance irrespectively of being polymer modified or not. low values of differences in recoveries of pmb 25/55-65 and b 15 (3) indicate the low stress sensitivity of these binders having lower penetration (fig. 7). the pmb 25/55-65 shows almost the same parameter values as paving grade b 35/50 (2) bitumen. percents difference in non-recoverable compliance illustrated on fig. 8. the calculated differences with stress combinations τ1=0.1 kpa and τ2=3.2 kpa or τ1=3.2 kpa and τ2=6.4 kpa don’t show significant deviation between hard bitumen and modified bitumens. percent difference of hard bitumen b 15 (3) presented negative values which needs further investigation. 198 table 2: percent difference in recovery and nonrecoverable compliance [1/kpa] of hard bitumen and modified binders sample pmb 10/40-65 b 15 (3) pmb 25/55-65 δγrec ' 2.22 0.37 22.36 δγrec '' 4.23 -0.46 43.53 δγrec ''' 2.05 -0.83 27.27 jnr(0.1) 0.051 0.015 0.306 jnr(3.2) 0.053 0.015 0.350 jnr(6.4) 0.057 0.014 0.400 table 3: percent difference in recovery and nonrecoverable compliance [1/kpa] of paving grade binders sample b 35/50 (2) b 50/70 (3) b 50/70 (4) δγrec ' 22.38 46.99 65.97 δγrec '' 49.90 77.46 83.42 δγrec ''' 35.45 57.48 51.29 jnr(0.1) 0.274 0.730 1.180 jnr(3.2) 0.303 0.824 1.326 jnr(6.4) 0.339 0.917 1.428 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 n on -r ec ov er ab le c om pl ia nc e [1 /k pa ] jnr0.1 jnr3.2 jnr6.4 figure 6: diagram of non-recoverable compliance for different binders depending on stress levels 2. 2 0. 4 22 .4 22 .4 47 .0 66 .0 4. 2 -0 .5 49 .9 43 .5 77 .5 83 .4 2. 1 -0 .8 35 .5 27 .3 57 .5 51 .3 -10 0 10 20 30 40 50 60 70 80 90 pmb 10/40-65 b 15 (3) b 35/50 (2) pmb 25/55-65 b 50/70 (3) b 50/70 (4) δγrec' δγrec'' δγrec''' figure 7: percent difference in recoveries of different binders depending on stress levels -10 -5 0 5 10 15 20 25 30 35 δj nr [% ] δjnr(6.4-0.1) δjnr(3.2-0.1) δjnr(6.4-3.2) figure 8: percent difference in non-recoverable compliance of different binders depending on stress level 0 10 20 30 40 50 60 70 80 0.0 0.5 1.0 1.5 γrec (0.1) γrec (3.2) γrec (6.4) log. (γrec (0.1)) log. (γrec (3.2)) log. (γrec (6.4)) (τ ) [ % ] (τ) [1/kpa] figure 9: average recoverable strains versus average non-recoverable compliance for different binders 199 fig. 9 shows the close relationship between average recoverable strain and average non-recoverable compliance for three stress levels of 0.1 kpa, 3.2 kpa and 6.4 kpa. the regression equations with good correlation coefficients for stress level of 0.1 kpa (r2=0.934) are as the following: )jln(.. .nrrec _ 107761352414 ⋅−=γ , (9) for stress level of 3.2 kpa (r2=0.941): )jln(.. .nrrec _ 23371159857 ⋅−=γ , (10) for stress level of 6.4 kpa (r2=0.935): )jln(.. .nrrec _ 46102163014 ⋅−=γ . (11) comparison with aashto standard specification the performance of binders is evaluated in this section obtained with mscr test data. in aashto (american association of state highway and transportation officials) “standard specification for performance – graded asphalt binder m 320-09” the non-recoverable compliance and percent difference in compliance are specified as performance parameters. the comparison was made for very heavy traffic level. the stress sensitivity parameter was determined as: ( ) ( ) ( ) )1.0(j/]1.0j2.3j[1001.02.3%j nrnrnrnr −⋅=−δ .(12) table 4: conformity of different binders for heavy traffic with aashto m320-09 specification traffic level very heavy specified jnr (3.2) <1.0 specified percent difference δjnr(3.2-0.1), % 75 type of binder jnr(3.2) at 60°c 50/70 (3) 0.303 50/70 (4) 0.824 pmb 25/55-65 0.35 pmb 10/40-65 0.053 b 35/50 0.303 b 15(3) 0.015 type of binder δjnr(3.2-0.1) at 60°c 50/70 (3) 11.4 50/70 (4) 11.0 pmb 25/55-65 12.5 pmb 10/40-65 5.5 b 35/50 9.66 b 15(3) -0.72 if this ratio is greater than 75% then the bitumen is considered stress sensitive and doesn’t satisfy the requirement. the non-recoverable compliance jnr(3.2), shall be below 1.0 [1/kpa]. table 4 contains the specified values and the derived parameters of binders from mscr test. the cited specified values were taken for pg 64 grade bitumen. however the tests were performed at +60°c because this temperature is specified for wheel tracking test of hot asphalt mixes in hungary. being aware of this difference it can be regarded that the tested binders meet the specification requirements. conclusions the mscr test is appropriate for evaluation of elastic and unrecoverable response of paving grade and polymer modified binders. six different binders were selected in penetration range 10–70 and the mscr test was performed on rtfot residues using dynamic shear rheometer at +60 °c. the mscr test can reveal distinction between same penetration grade binders coming from different producers. among six tested binders the b15 (3) hard bitumen has the best mscr performance. percent difference of non-recoverable compliance for stress combinations (3.2-0.1) kpa and (6.4-3.2) kpa show no significant deviation for hard bitumen and polymer modified bitumens. there is a significant deviation between non-recoverable compliance differences at different stress combinations for 50/70 paving grade binders. close regression relationship has been found between average recoverable strain and non-recoverable compliance with good correlation coefficients r2=0.934–0.941. the tested binder parameters meet the aashto m320-09 specification requirements for pg 64 grade binder. references 1. multiple stress creep recovery (mscr) test of asphalt binder using a dynamic shear rheometer (dsr), aashto designation: tp 70-07 2. j. d’angelo, r. kluttz, r. dongré, k. stephens, l. zanzotto: revision of the superpave high temperature binder specification: the multiple stress creep recovery test. journal of aapt 76, (2007), 123–162 3. standard specification for performance-graded asphalt binder, aashto designation: m320-09 microsoft word b_01_r.doc hungarian journal of industrial chemistry veszprém vol. 38(2). pp. 77-81 (2010) motion simulation of a path controlled vehicle d. antal robert bosch department of mechatronics, university of miskolc, miskolc-egyetemváros, hungary e-mail: antal.daniel@uni-miskolc.hu the dynamical modelling of a path controlled vehicle is analyzed in this paper. in addition to the discussion to determine the orientation and location of a vehicle the problems of redesigning a commercial mini car are also discussed. special emphasize has been laid on the dynamical analysis of the model in the starting transient period. a simple controlling were also attached to the model the velocity, current flow and the roamed path have been obtained. keywords: path control, motion simulation, dynamical analysis, dynamical model introduction the number of application of automated guided vehicles is increased in logistics during the last decades [1]. by the use of such vehicles, one can decrease the expenditure of the production cost and increase the operational efficiency and its reliability. in this paper the designing aspects of a path controlled vehicle is discussed. it is essential to solve the navigational problem, i.e., the vehicle should be moved from the initial position to the final one through a predefined path. the path can be defined by fixed methods e.g., painted paths, inductive loops, and by flexible methods, i.e., mathematical definition of the path which can be combined by gps or other navigation systems. in this paper the later approach will be preferred, since the modification of a path can be carried out easily by changing the mathematical definition in the software. the advantage of this method is the arbitrary path definition, but its disadvantage is lower accuracy. the accuracy can be improved by feedbacks. in addition to logistics wide range of applications of such vehicles can be found e.g., scanning on a minefield or mowing the lawn automatically. the design and dynamical modelling of a path controlled vehicle are detailed, its accuracy is less than 0.1 m. the first part of the paper deals with the problem of the sensing and correction of the vehicle position. in the second part the vehicle will be redesigned to follow paths. in the third part the electro-dynamical model of the vehicle is analyzed. methods determining orientations and locations according to the introduction, guiding on a flexible path requires a position and orientation sensing methods, whereby the moving of the vehicle is controlled. these methods are based on different types of sensors, which provide feedbacks for the calculations. the orientation and position sensing methods can be divided into three groups [4, 5]: odometrical method is based on step counting and is carried out by summarizing the relative motion information, absolute method is based on distance measuring from objects at known positions and other methods. the odometrical distance measuring gives indirect information about the movement, which can be: ● angular position sensing with rotary encoder by an absolute or an incremental one depending on the specific construction. the two methods can be distinguished by the applied rotating disc and the assigned signal processing. these encoders are mounted on the shaft. ● measuring the revolution of the motor in the drive train with optical, inductive, capacitive or hall sensor, e.g., teeth of a metal gear passing by an inductive sensor, or sensing the symmetrically placed magnets on the side of a gear with hall sensors. ● motor independent movement sensing system with a measuring wheel or a measuring ball, e.g., mechanical computer mouse. the odometrical distance measuring methods may have regular and irregular errors. the measuring error is 78 incremental so the calculated position should be refined regularly by absolute distance measuring methods. during absolute distance measuring the position is calculated by known position objects which are called marker points. these points can be active or passive, and natural or artificial depending on the construction. absolute distance measuring methods: ● optical marker technique. setting or using visually distinguishable points in the area. ● laser and ultrasonic technique. instruments based on triangulation method are using the beam to set the direction. instruments based on phase modulation or radar principle the beam as an electro-magnetic wave to determine the distance between the measuring equipment and the signal point can be used. ● radio principle positioning system. the positioning requires to set up a radio based local positioning system or an existing system, e.g., gps can be utilized for it. comparing the odometrical distance measuring with the absolute distance measuring one can state that the later has only a regular error which is constant. the absolute technique is a time consuming method, therefore it is used rarely. it means that the less expensive odometrical position determination can be refined by an expensive one. there are also other location and orientation determining methods, e.g., doppler sensor or a system provided by accelerometers, gyroscopes or their combinations. redesigning of a commercial car for path controlling in order to study path controlling, a commercial tyco rebound radio controlled mini car has been redesigned. the redesigned vehicle contains the following functional parts: ● the controller electronics is a dspicdem mc1 motor control development board, which contains a dspic30f6010a microcontroller. the software is written in c programming language. ● the sensors (tle4905l) are creating digital ttl voltage level signal for the controller electronics, when one of the 4 neodymium magnets on the side of the gear is passing by. ● the power pcb (printed circuit board) is containing the socket for the motor, optical coupling to the controller board and the power supply of the hall sensors. the power pcb physically contains an integrated full h-bridge (l298n), +5 v supply for the ttl logic (ka7805) and the optical coupler integrated circuit (cny74-2h). the position is determined by the wheel revolutions on different sides (by odometrical method), the principle is shown in fig. 1. it is clearly visible, how the vehicle is moving along the arc δα if only one of the sides is driven with one increment. figure 1: calculation of the rotation belonging to one increment from geometrical considerations, the coordinates of the vehicle could be calculated increment by increment: ( )1 sin / 2n n nx x k α α+ ≅ + + δ , (1) ( )1 cos / 2n n ny y k α α+ ≅ + + δ , (2) where δα = ±k / h depends on the directions, i.e., in case of +/the movement is forward/backward, the value of k is the arc length associated with one increment and h is the radius of the path. during the calculations of the coordinates the angle should be increased by π. learning mode of the vehicle operation has been developed, while data of the whole path are saved by the software. afterwards the path data is accessible on a personal computer via rs-232 communication. furthermore a preprogrammed mode is accessible, when the vehicle is controlled by itself performing a preprogrammed path. the motors are controlled via the power pcb by pwm (pulse width modulation) signals. during the test of the redesigned vehicle two important vehicle attributes have been determined for the software: h = 3.625 m and k = 42.25 mm. dynamical analysis of the vehicle the wheels on the two sides of the vehicle are controlled independently by two dc motors. the characteristics of the lre260-18130a type dc motor are given as: operating range 1.5–4.5 v, nominal 3 v, (at no load: speed 6900 r/min, current 0.095 a), (at maximum efficiency: revoultion 5000 r/min, current 0.37 a, torque 9.5 gcm), (at stall: torque 48 gcm, current 1.4 a). the gear transmission between the wheels and the motor is im,w = 1:28.3451. the dynamical model of the vehicle [6] can be formulated by measuring the electrical and dynamical parameters, and using the catalogue values of the motors. during the straightforward motion of the vehicle, the complex mechanism can be modelled by a one degree of freedom system, where the general coordinate is the angular rotation of the motor shaft (q = φ). the electro-dynamical equations are written as: 2 t t dj b k i m dt ω ω+ = ⋅ − , (3) 79 2e b dil ri k v v dt ω+ + = − , (4) where j is the reduced inertia moment, ω = φ̇ is the angular velocity of the motor shaft, b is the damping coefficient, 2·kt is the motor constant for two motors, mt is the reduced loading torque, i is the current, v is the applied armature voltage, l is the armature inductance, r is the armature resistance and ke back emf constant (kt ≅ ke). the reduced inertia moment j is derived by the inertia moments with respect to point a of the four wheels 4·jk (see fig. 2), and the inertia moment due to the rest of the vehicle mass mv. the inertia moment of a wheel is determined by the period t of a pendulum and using the formula 2 24 k k m g r j t π = . figure 2: the wheel as a pendulum the mechanical parameters of the model are given as: mv = 0.686 kg, mk = 0.091 kg, t = 0.59 s, r = 0.051 m, j = 1.731·10-5 kgm2. the loading torque is changing in relation of the angular acceleration, until a certain value. the inductance of the armature is l = 3.28·10-4 h. at the three working conditions stall, maximum efficiency and idle. one can obtain the brush voltages 2vbs = 0 v, 2vbm = 0.446 v and 2vbn = 0.5493 v, respectively. the brush voltage loss is approximated by a quadratic function 2vb = aω2 + bω, where a = -4.615·10-7 vs2 and b = 1.094·10-3 vs (see fig. 3). figure 3: approximation of the brush voltage loss the systems of equations (3, 4) have been solved for homogenous initial conditions by matlab simulink program system. the controlling software is developed in c language, to shorten the calculation time. the simulated path during the path controlling is shown in the fig. 4. three points are programmed to reach, which are a tolerance is used for passing the points. after reaching the last programmed point [500;1000], the control switches to zero, when the motors are working as generators until the vehicle stops. figure 4: the roamed path two of the four output parameters, i.e., currents, angular velocity, angular acceleration, velocity of the vehicle, are shown as a function of time in fig. 5 and 6. in fig. 6 the lighter line represents the current for the right motor, and the darker for the left one. due to the loading torque, the vehicle reaches the maximum value of velocity after ~10 seconds. when the control is turned off, the vehicle slows until the back emf value reaches zero. one can see how the control is changing rapidly, when the vehicle is moving on a “zig-zag” path. in this case the control changes in almost every calculation cycle, hence the motors are alternating between motor and generator state. 80 figure 5: the velocity of the vehicle during the controlling figure 6:the currents of the motors 81 figure 7: the digital control signals of the left motor in fig. 7 one can see, how the control is changing throughout the simulation for the left motor. before reaching the last point, the motors are fed alternatively, so the control for the right motor is the opposite of the left one. summary the dynamical modelling of a path controlled vehicle is analyzed in this paper. in addition to the discussion to determine the orientation and location of a vehicle the problems of redesigning a commercial mini car are also discussed. special emphasize has been laid on the dynamical analysis of the model in the starting transient period. a simple controlling were also attached to the model the velocity, current flow and the roamed path have been obtained. references 1. j. borenstein, l. feng: measurement and correction of systematic odometry errors in mobile robots, robotics and automation, 12(6), 1996, 869–880. 2. m. vogel: ipari robotjárművek helymeghatározó rendszerei, műszerügyi és méréstechnikai közlemények, 37(68), 2001, (in hungarian). 3. b. koleszár: szárazföldi robottechnikai eszközök tervezésének és alkalmazásának biztonsági szempontjai, (in hungarian), www.zmne.hu/tanszeke/ehc/konferencia/prezrw8/ koleszar_bela.pdf. 4. balluff elektronika kft, online catalogue, http://www.balluff.hu. 5. plc és folyamatirányítás, (in hungarian), http://szirty.uw.hu/alapfokon/encoder/encoder.html. 6. prof. dr. i. h. altas: dynamic model of a permanent magnet dc motor, neuro fauzzy systems, projects for students, 08.11.2007 http://www.ihaltas.com/courses/fbe_elk5320/eng/pro jects/project_37.pdf. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word b_35_horvath_r.doc hungarian journal of industrial chemistry veszprém vol. 39(2) pp. 257-263 (2011) optimal tool selection for environmental-friendly turning operation of aluminium r. horvath, b. palásti-kovács, s. sipos óbuda university, donát bánki faculty of mechanical and safety engineering, 1081. népszínház str. 8., hungary e-mail: horvath.richard@bgk.uni-obuda.hu e-mail: palasti@bgk.uni-obuda.hu e-mail: sipos.sandor@bgk.uni-obuda.hu in case of machining of automotive parts in large series it is necessary to change to machining operations, sparing the environment. the paper summarises the experiences of the authors, gathered in turning operation. with the help of experiments, planned, carried out and documented systematically, determine the conditions, considered to be the most favourable for the fine turning operations of high silicon-content aluminium cast parts in order to achieve the most advantageous surface roughness parameters. they deal with the topographic examination of surfaces, describing the working characteristics of the machined parts; furthermore, the topological maps of the surfaces, machined with diamond, will be introduced as well. the most favourable parameters were determined not only in the case of tool material and optimal edge construction in case of selection of cutting conditions. keywords: machinability, aluminium castings, finish turning, carbide inserts, polycrystalline diamond turning, environmental-friendly machining introduction in the case of production of automotive parts in a large series it is necessary to pay a special attention to all factors, improving the quality and effectiveness of production. at the same time, operations, sparing the environment, should not be ignored: there is an increasing demand to completely change to application of any environmental-friendly flushing-lubricating-cooling medium in order to avoid use of cooling method, carried out with flood-type application of emulsion. although machining operations, carried out with emulsion, mean only a few ten forints pro part [1], but in case of a component, produced in a few millions of items this amount causes not only increase of production costs, but unnecessary burdens to the environment as well. in case of machining high silicon-content aluminium cast parts, dry turning operation is one of the alternatives to avoid the difficulties. the following papers deal with this subject [1-3]. it is reasonable to select such items from the tools with different shapes and design, which are able to produce the most favourable surface roughness profile with the smallest possible expenditure of time. in the present lecture we are going to introduce some from the results, gained by us during fine turning operations, carried out with carbide and diamond inserts. in our article we are going to determine machining operations as well, recommended by us to be followed. description of the goals and circumstances of the tests the aim of the tests was to get a clear picture of how the tools of different materials and with different edge geometry can meet the extremely strict roughness standards, applied in the automobile industry. the test was designed to research the disturbing phenomena that arise during turning operations of difficult-to-machine base material. the difficulties have been increased further by the fact that we had to carry out the tests without the use of cooling-lubricating liquid. surface roughness values, made with different compositions polycrystalline diamond tools, were compared, where the dry turning operations were performed with tools with different point angles and nose radii; (the cutting speed was varied in a very wide range (vc = 630–2000 m/min)). the depth of cut – due to reason of saving materials – were kept on a constant value (a = 0.5 mm), other testing conditions can be seen in table 1. 258 table 1: machine and materials used in the test machine tool type: euroturn 12b (nct kft.) control: nct2000 workpiece material: as17 (rencast reyrieux) contents: si 16.8%, cu 4.1%, zn 1%, fe 0.8%, mg 0.5%, mn 0.2%, other components: pb, sn, ni, ti (<0.08%) applied carbide and diamond inserts carbide inserts, made by wnt gmbh.: dcgt 11t304-al h210t (wnt) dcgt 11t308-25q h210t (wnt) polycrystalline diamond, made by hoffmann group gmbh.: dcgw 11t304 fn (without chipbreaker) dcgt 11t304 fn twf (chipbreaker) dcgt 11t304 fn twm (chipbreaker) testing circumstances a= 0.5 mm (constant) vc= 630 …2000 m/min (varied) f= 0.05 – 0.063 – 0.08 – 0.1 mm measuring devices surftest sj301 (mitutoyo, japan) perthometer concept 3d (perthen-mahr, germany) electron microscope jsm-5310 (jeol co., japan) handycam, dcr-sr290e (sony, japan) test results description below contains the surface roughness values, measured along three different measuring lines, at setting every single of the test values. machinability of hypereutectic aluminum alloys one of the circumstances, making the machining difficult, is that aluminium is an easy-to-machine material, soft and ductile; but by increasing the silicon-content, the abrasive effect of the alloys increases and the difficulties, arising during the machining. because of the primary silicon crystalls, embedded in the aluminium matrix, the chips become easy-to-break; however, the presence of these hard particles lead to the quick wear of the insert, due to their strong adhesion and chemical reactions as well as low abrasive resistance with al-si alloys. when the primary si-particles contact the tool edge in the cutting zone, they wear it intensive; furthermore, due to their hardness they hinder the formation of surface of good quality. in our previous paper [1, 3-5] we have introduced the machinability of alloys with aluminium content of 16%. in our present research we have paid a special attention to two undesirable disturbing phenomena (built-up edge and deceptive chip formation), developing during chip formation. briefly about the well-known phenomenon of builtup edge: it develops on the rake face of the tool from the material of workpiece and in the majority of cases it deteriorates the roughness of the machined surface. there are less articles in the topic of phenomenon „deceptive chip formation”, published in the specialised technical literature: its development and effects are less known; we can gather more information on it with research of slow-motion video records. depending on the edge quality and wear conditions of the tool and as a result of intensive cutting conditions, in the chip formation zone increasing force and temperature can be observed. if the developed temperature reaches the melting point, as a result of the three-sided stress state a chip-like formation (a so-called deceptive chip, dch or flank build-up, fbu), having only few μm thickness, will be extruded from the zone between the flank land of tool and the contacting surface of workpiece, being machined at the given moment. the material particles, having been extruded, adhere to the flank land of insert: the intensity of this process depends on the cutting conditions (mainly on vc and f values), settled by us. all the factors, like cooling the zone, variing of material and friction properties of the tool, appropriate shape and condition of the tool edge and application of less intensive cutting parameter, affect the development of deceptive chip formation. the phenomena, observed during our tests, can be seen in fig. 1. a) built up edge (observed only on the rake face) b) deceptive chip formation (observed only on the flank land) figure 1: the disturbing phenomena of chip development, in case of turning of hypereutectic aluminum alloys with carbide inserts; cutting conditions: carbide insert; rε=0.4 mm; vc=1000 m/min; f=0.05 mm application of carbide inserts at increased cutting speed values (quasi hsc machining) the basic goal of the tests was to find out in what kind of degree the carbide inserts, recommended expressly for this purpose, can be applied to environmentallyfriendly cutting under hsc conditions. for these test we have selected tools, recommended by the manufacturer, expressly to application in factory due to their design. the characteristics of the tools are: ● optimal edge quality, its determinant properties are: ● very low surface roughness values on the rake face and flank land, ● resulting in very low edge roughness, ● minimum value of edge radii; ● the material quality of carbide meets the specification: it belongs to the k group, according to iso, 259 ● in order to support the optimal chip flow we have selected d insert shape, ● nose radius of different sizes have been selected, ● on one of the types, chipbreaker has been placed. due to the reasons, mentioned earlier, the tests were proved to be carried out in a significantly increased range of cutting speed values, compared to our previous tests [5]. the insert, coded dcgt11t304-al, expressly suitable for cutting operations of aluminium: it had an average edge fillet off rn=17 μm, the edge roughness is rzedge=10 μm, the other one type, coded dcgt11t30825q, with chipbreaker and wiper edge form, had an average edge rounding off rn=10 μm, the edge roughness is rzedge=10 μm. both types had a finely polished rake face and flank land (raγ≈raα=0.05–0.08 μm), it is a very important precondition to the cutting operation of aluminium. due to space limitations it is not possible to introduce other data, concerning the tool edge, or any other diagrams. the design of carbide inserts, tested by us, can be seen in fig. 2. a) rε=0.4 mm (iso shape) b) rε=0.8 mm (wiper edge form) figure 2: the most popular carbide inserts for aluminum turning applications a) dcgt11t304-al (left, magnification: 35x) b) dcgt11t308-25q (right, magnification: 35x) manufacturer: wnt deutschland gmbh, germany [6] in fig. 3 the maximum height of profile roughness (rz) and the well-known bauer-formula (rthbau) of theoretical surface roughness is introduced. the tests had really surprising results and they can be summarised as follows: the measured surface roughness values – due to the disturbing phenomena, mentioned earlier – had a constant or even a mildly decreasing tendency in case of increase of the feed rate. in case of inserts, having small nose radius it can be explained by the fact that as a result of a relatively great edge rounding off, the minimum detachable layer (hmin) is great, the built-up edge and deceptive chip formation have unfavourable effect on surface roughness of the machined surface. in case of insert with greater nose radius we have measured much lower edge rounding off value, and the occurrence frequency of disturbing phenomena was lower. a) rε=0.4 mm (iso); chipbreaker: al b) rε=0.8 mm (wiper); chipbreaker: 25q figure 3: the development of maximum height of profile (rz) and theoretical surface roughness (rthbau) in case of carbide inserts the iso shaped insert with nose radius of 0.4 mm (fig. 2a) has produced just a bit worse surface roughness, compared to the surface, produced by insert with masterfinish edge construction and wiper edge section, having nose radius of 0.8 mm. it can be explained by the fact that both carbide inserts have been applied at the same conditions (dry hsc cutting operation); therefore it was not possible to observe in full measure the development of the more favourable surface finish producing capability of the wiper edge form. in case of insert with small nose radius, the increase of the cutting speed has a clearly unfavourable effect from the point of view of surface roughness. the low cutting speed values, enabling favourable surface roughness, affects unfavourably the main times (tg, min) and the reachable level of productivity (q, pcs/h) in the tested range of cutting speed values. in case of insert with wiper edge form (fig. 2b) we have succeeded to find out an optimal cutting data range, as regards surface roughness (rzopt=2–3 μm), it is as follows: vcopt=630–1000 m/min and 260 fopt=0.08–0.1 mm. furthermore, in this range of set values the productivity can be evaluated as excellent. during comparison of the performance of these two inserts, we have to consider, that the insert, having small nose radius – excepting one case – has worked with development of built-up edge or deceptive chip formation, while working with tool with masterfinish geometry no disturbing phenomena could be noticed in the majority of cases (mainly at cutting speed value of vc=1250 m/min and in case of feed rate of f=0.05–0.063 mm). during our research – continuing our previous works – we have striven to determinate the topological map of surfaces, machined with fine turning and carbide inserts. the topological map contains the distribution of skewness (rsk) and the kurtosis (rku) of amplitude parameters. the first one is the measure of the symmetry of realised profile about the mean line, while the last one can detect if measure profile „spikes” or „bumps” are evenly distributed above and below the mean line. the surfaces, having reliable working properties, like rsk<0 and rku<3, mean that the surface roughness profile indicates a predominance of valleys, or bumpy surfaces have a low kurtosis values. fig. 4 shows the average of skewness (rsk) and kurtosis (rku) values, determined by three individual measurements, under conditions of our examination. (the value of rku=3, showing the gauss-distribution, has been indicated separately on the double-diagrams.) a) iso shaped b) masterfinish edge figure 4: topological maps of different carbide inserts with varied rake face designs cutting conditions: vc=630–1250 m/min; f=0.05–0.1 mm; dry turning from the above diagram it can be noticed that in the range of values, settled during the examinations, the carbide inserts with different edge constructions, have produced a quite favourable surface roughness profile as regards working conditions: the rku-values were mainly below 3.5, while rsk values have reached a maximum value of approx. 0.8. the surface, machined with iso-shaped insert, has shown negative rsk-values in this case of certain data combination and it means – considering the low rku-value, achieved by us – working surfaces of quite durable and long-lasting parts. it has been noticed in case of surfaces, machined with low feed rate. the results, gained by us, refer to the fact that 32 surface profiles, produced with both types of tools, contain details, reminding of valleys and blunt outstanding peaks. this type of surface textures means excellent load bearing capacity, appropriate wearing properties and contain cavities, being favourable for lubricating oil film. application of polycrystalline diamond inserts at increased cutting speed values (quasi hsc machining) as we have already introduced in our previous studies [1-4], tools with plane rake face are absolutely appropriate to fine turning operations of high silicon-content aluminium: the si-content guarantees the favourable break of the chip, occurred by itself. the versions with chipbreaker have come onto the market only in the past few years: these special constructions can be produced only by few companies, machining with laser operation [6]. we have already introduced some of the results, gained during fine turning operation tests with diamond inserts [2]. in this process our goal was to test different types of chipbreakers, produced by other company. on fig. 5 three edge types of polycrystalline diamond inserts, received from the producing company, can be observed and compared – the inserts have the same code (dcgt 11t304 fn). as it can be seen well on fig. 5a, the type (fn), produced with plane rake face (and without of chipbreaker), has an edge rounding off value rn=1.5 μm and edge roughness of rzedge=2.7 μm. the fig. 5b shows the twf coded insert: it has a chipbreaker. this type has the characteristic feature that the dividing ridge of the chipbreaker has a direct connection with the main and minor edges, therefore we can observe a narrow groove with small depth and width: it has been developed exclusively to use with low depth of cut and feed rate values. this type has an edge rounding off 2 μm and edge roughness value of 1.6 μm respectively. the twm coded chipbreaker (it can be seen on fig. 5c) can be characterised by relatively great width, the dividing ridge of the chipbreaker is relatively far from the edges, therefore it is customary to apply this type to chips with greater cross section. this version has been produced with the following parameters: rn=2 μm and rzedge=1.9 μm. to sum up the results of the preliminary researches, it can be established that in case of all the three insert types the flank land and the rake face of the inserts have been 261 finely polished raγ ≈ raα=0.04–0.05 μm; therefore we have measured unusually low values of edge rounding off. due to space limitations we refrain from introducing further data and diagrams, concerning edges. we have taken photos on all the three insert types after machining operation, in this way the aluminium material particles, adhered to the tool and the wear marks, developed on the inserts, can be understood well. b) twf-type, with breaker c) twm-type, with breaker a) fn-type, without breaker figure 5: the tested polycrystalline diamond inserts with various rake face constructions (sem photograph, magnification: 150x) fig. 6 shows average results of three measurements: the tests have been carried out with the same depth of cut value (a=0.5 mm) and similar feed rate values (f=0.05–0.1 mm) and in the range of cutting speed values (vc=1250–2000 m/min), settled for diamond tools. based on the measured average surface roughness values the followings conclusions can be drawn: in that case of machining with insert, produced without chipbreaker, the settled feed rate powerfully influences the measured surface roughness values, while the applied cutting speed value has a lower influencing affect on it; therefore the surface finish producing capability of this insert can be evaluated as moderate. the insert with twf chipbreaker reacts to the settled cutting data really sensible: at low cutting speed values the settled feed rate causes really great deterioration in the surface roughness, while in case of cutting speed values of vc ≥1600 m/min the feed rate almost does not influence (!) the roughness of the machined surface. the twm chipbreaker has excelled in its surface finish producing capability: it was the best, the cutting speed values have not influenced the surface roughness, the feed rate had only small influence on it. during the evaluation of the results we have to consider the fact that the final profile of the machined surface is mainly determined by the feed rate values, settled by us (this is the so-called kinematic or theoretical roughness), but the undesirable phenomena, like undetachable chiplayer (hmin), built-up edge (bue), formed on the rake face or deceptive chip formation (dch), developed on the flank land, have a great effect on it. the last-mentioned phenomena have played a significant role on the surface roughness, determined with measurements, and in case of fn geometry we have observed the development of these phenomena in 12 cases from 16 data combinations. in this case of inserts with chipbreaker the disturbing phenomena, stated earlier, have played smaller role: in case of tests, carried out with twf, we have observed the development of bue and/or dch in 9 cases, while in case of twm-type only in 3 cases. c) chipbreaker type: twm b) chipbreaker type: twf a) without chipbreaker figure 6: the development of average surface roughness parameters in function of examination data, at finish turning with polycrystalline diamond inserts cutting conditions: vc = 1250–2000 m/min; f=0.05–0.1 mm; dry turning 262 summing up the results of the researches, carried out by us, we can establish that in case of dry machining the disturbing phenomena are surely limiting factors from the point of view of the minimum produceable surface roughness. if these phenomena do not develop too often, then – considering the point of view of process security – the same surface roughness values as in case of use of flushing-cooling-lubricating liquids can be reached even in case of working surfaces of parts, produced under conditions of environmental-friendly machining [1, 2]. the rsk-rku diagrams (i.e. the topological map) of the polycrystalline diamond inserts have shown an interesting result (fig. 7) – the diagrams have been made based on average values from three measurements. in case of fn-type insert with plane rake face (and without chipbreaker), the rsk-rku values, measured at the same time and in case of machining with different data combinations, have been depicted in diagrams: the values are distributed in a very wide range, as regards skewness and kurtosis values, and their tendency has shown a surprising great correlation. the rku and rsk-values of the insert with twm chipbreaker, having achieved a better performance, have distributed in a much narrower range, but it is much more difficult to determine any trend. figure 7: topological maps of different pcd inserts with various rake face constructions cutting conditions: vc=1250–2000 m/min; f=0.05–0.1 mm; dry turning the correlation of the surface roughness and the cutting data from the tests, carried out by us, it become clear that the arithmetical height roughness parameters (like rz, ra etc.) significantly depend on the cutting conditions. in the previous parts of the present study we have separately analysed the effect of feed rates and cutting speed values on the surface profile, developed during machining. the results of several surface roughness measurements, carried out by us, show promise for us to use the formula, developed by us, to the calculation of theoretical surface roughness values in the following form: relm = c1·hmin + c2·fc 3 + c4·hmin·fc 5 (1) where hmin – minimum detachable layer thickness, μm, f – settled feed, mm, c1, c2, c4 – constants, determined with regression, c3, c5 – exponents, determined with regression. the feed rate (vf = f·n, mm/min) is a complex, characteristic mark of the turning operation, combing two cutting data, (feed rate, f and cutting speed, vc) and through the main machining times it significantly influences the important objective functions of the process – and in this way the optimal conditions of the machining as well. based on the results of our tests, the rsk and rku values, describing the statistical distribution of the outstanding peaks of the machined profile, have a provable correlation with the feed rate. according to our experiences, in all cases, examined by us, the rku parameter, compared to the rsk, show a tighter correlation with the settled vf values. fig. 8 shows the comparison of two polycrystalline diamond inserts, having different rake face constructions. analysing the diagrams, the conclusion can be drawn that rku values have shown a clearly decreasing tendency in case of increase of the feed rate. the insert with a plane rake face construction has shown correlation of relatively greater tightness, while in case of the insert with twm chipbreaker correlation with smaller tightness can be observed. from the examinations it has become clear that the most favourable rku values have been observed above the cutting speed value of vf≥360. figure 8: kurtosis vs feed rate of polycrystalline diamond inserts with varied rake face constructions cutting conditions: vc=1250–2000 m/min; f=0.05–0.1 mm; dry turning 263 in both cases the number of the optimal settlements amounts to 6, they belong to the following values: fopt=0.08–0.1 and vcopt=1600–2000 m/min. we would like to remark that the correlation between rsk and vf, published in our previous articles [1-5], has shown a similar characteristic mark, and it was possible to determine it either with function, locating minimum extreme value or with monotonous decreasing function. summary during our short term tests, carried out to examine the cutting performance of applied inserts, we can get a picture about the roughness parameters of surfaces, machined with tools, having different materials, shapes, constructions and produced by different manufacturers. the most important conclusions are the following: 1. one of the important conclusion of our researches is that in case of diamond insert, with appropriate tool material design and edge geometry, it is possible to meet the requirement of the average surface roughness ra≈0.3 μm, even under conditions of environmentalfriendly machining. 2. the carbide as tool material may be used in case of dry machining only in case if the insert has a shape, being similar to the one, published in the present article (point angle εr=55°), has a wiper-like edge construction (so-called masterfinish) and the operation is carried out with similar conditions, as mentioned in our present study. 3. we have shown a clear correlation between the surface finish producing capability of the inserts, and the topological map. the rsk and rku diagrams can play an important role during the selection of the optimal insert and generating data as well. for the last one there was a demonstrative example: the data search, carried out based on fig. 8. it is recommended to carry out preliminary tests in case of preparation works, prior to production in large series. we are going to conduct further research on other environmentally-friendly methods of cutting operations and in our next paper we are going to introduce the results of the process, carried out with compressed, cold air and with minimum quantity of lubrication (mql/mmks). acknowledgments authors wish to thank mr. laszlo nagy, working at delphi thermal hungary kft. in balassagyarmat, for their valuable comments and for the company as well, supplying the casting components. the work of mr. laszlo lang and gabor nagy is greatly acknowledged. references 1. r. horvath, b. palasti-kovacs, s. sipos: environmental-friendly cutting of automative parts, made of aluminium castings (hu issn: 0133-0276) hungarian journal of industrial chemistry (hjic), 38(2), (2010), 99–105 2. r. horvath, b. palasti-kovacs, s. sipos: new results in fields of aluminium automotive parts, machined by cutting operation nemzetközi gépész, mechatronikai és biztonságtechnikai szimpózium, budapest, 2010. november 10-11. cd-n szereplő kiadvány, isbn 978-615-5018-10-7 3. r. horvath, s. sipos: nagy szilíciumtartalmú alumíniumötvözetek forgácsolhatósága xv. fmtü, kolozsvár, 2010. március 25-26., p. 135–138. issn 2067-6 808 4. s. sipos, r. horváth: újabb eredmények gyémántszerszámmal esztergált felületek topológiájában xvi. fmtü, kolozsvár, 2011. március 24-25. p. 283–286. issn 2067–6808 5. r. horvath, s. sipos: nagy szilíciumtartalmú alumíniumötvözetek forgácsolhatósága gyártóeszközök, szerszámok, szerszámgépek, műszaki kiadványok, xv. évf., 2010. p. 44–48. issn 1587-9267 6. http://www.tirotool.com << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error 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model can provide a better approach and can give more realistic picture of the complex situation. in this article the authors introduce an interactive, configurable simulator to analyze stock levels in a complex supply chain. this new modeling approach (simware) is capable to simulate complex multi-echelon supply chains where the frequency of stock transfer between the individual levels of the supply chain can be optimized. the authors evaluate different optimization strategies and methods. the introduced simware method can be used to minimize the environmental impact of the supply chain by minimizing the transportation between the nodes of the supply chain hierarchy. the model provides an optimization methodology where the objective function is the total cost of the supply chain. keywords: supply chain, simulation, safety stock, optimization. introduction supply chains present a complex decision situation for management. supply chain performance impacts the financial performance of the company therefore it is important to find a way to optimize the performance of the supply chain. simulation provides a way to get closer to real life situations and use less simplifications and assumptions than you need with analytical solutions. our objective is to build a simulator that can use simple building blocks to construct models of complex supply chain networks. supply chains processes can be simulated using these models, where parameters of key performance indicators are analyzed by sensitivity analysis. the result is a decision support tool flexible enough to handle complex situations and straightforward and simple to use enough for management purposes. literature review the research of inventory management or the investigation of supply chain is widespread in the scientific literature. it is a seriously researched area since the fifties; simpson [6] was the first one who formulated the serial-line inventory problem. graves and willems extend simpsons work to spanning trees in [2], while in [3] they give a comprehensive review of the previous approaches for safety stock placement, the same as they propose two general approaches and introduce the supply chain configuration problem. there exist good overviews in the literature for supply chain and inventory management, like in [11], where authors give an overview of different approaches of supply chain modeling, and outline future opportunities. in [9] lau et al. give an overview of various average inventory level (ail) expressions and presents two novel expressions which are simpler and more accurate than previous ones. a comprehensive overview can be found in [13], where a simulation model for a real problem with lost sales is presented, where authors consider several types of inventory policies. the determination of safety stock in an inventory model is one of the key actions in the management, miranda and garrido include both cycle and safety stock in the inventory model in [12], and the resulting model in this article has a non-linear objective function. authors in [4] gives a model for positioning safety stock in a supply chain subject to non-stationary demand, and they show how to extend their former model to find the optimal placement safety stocks under constant time service (cst) policy. prékopa in [16] gives an improved model for the so called hungarian inventory control model to find the minimal safety stock level that ensures the continuous production, without disruption. the bullwhip effect is an important phenomenon in supply chains, authors in [10] show how a supply chain can be modeled and analyzed by colored petri nets (cpn) and cpn tools and they evaluate the bullwhip effect, the surplus of inventory goods, etc. using the beer game as demonstration. more recent research can be found in [1], which shows that an order policy applied to a serial single-product supply chain with four echelons can reduce or amplify the bullwhip effect and inventory oscillation. 108 miranda et al. investigate the modeling of a two echelon supply chain system and optimization in two steps [15], while a massive multi-echelon inventory model is presented by seo [19], where an order risk policy for general multi-echelon system is given, which minimizes the system operation cost. a really complex system is examined in [20], where it is necessary to apply some clustering for similar items, because detailed analysis could become impossible considering each item individually. the simulation-based approach was published only in the last decade. jung et al. [7] make a monte carlo based sampling from real data, and apply a simulation– optimization framework while looking for managing uncertainty. they use a gradient-based search algorithm, while authors in [8] discuss how to use simulation to describe a five-level inventory system, and optimize this model by genetic algorithm. schwartz et al. [18] demonstrate the internal model control (imc) and model predictive control (mpc) algorithms to manage inventory in uncertain production inventory and multiechelon supply/demand networks. the stability of the supply chain is also a seriously researched area recently, [14] shows that a linear supply chain can be stabilized by the anticipation of the own future inventory and by taking into account the inventories of other suppliers, and vaughan in [21] presents a linear order point/lot size model that with its robustness can contribute to business process modeling. a complex instance of inventory model can be found in [5], where orders cross in time considering various distributions for the lead time. sakaguchi in [17] investigates the dynamic inventory model in which demands are discrete and varying period by period. the author gives an algorithm to solve several examples. based on the previous review it is clear that most of the multi-echelon supply chain optimization and analysis are based on analytical approach. simulation however provides a very good alternative, because it can model real life situations with accuracy, more flexible in terms of input parameters and therefore it is more easy to use in decision support. the simulation results can be analyzed with various statistical methods and numerical optimization algorithms. to analyze complex, especially multi-echelon systems, multi-level simulation models can be used, where the results of optimized high level model feeds into the lower level more detailed models. the structure of the paper is the following: section 2 is a general introduction to the problem describing the multi-echelon supply chain and the relevant cost structure. section 3 introduces the flexible modeling tool to build complex multi-echelon supply chain models using simple, easy to understand modules. section 4 represents the main results through a case study, while section 5 concludes our work. the reader can follow the solution of a problem and we demonstrate the use of sensitivity analysis as a decision support tool. finally we talk about the integration of this methodology to a complex decision support system which is part of the company management information system. the proposed method our intent was to create a monte-carlo simulator which uses probability distributions based on material usage data posted in the logistic module of an erp system. this new methodology has two main objectives. simware can be used as a verification tool to analyze and evaluate inventory control strategies pinpoint problems due to mrp parameter determinations. the simulation of “actual” inventory controlling strategies provides the most important kpi-s of these strategies. on the other hand we can use the simulator as part of optimization and determine the optimal values of the key inventory control parameters. simware provides a framework to analyze the cost structure and optimize inventory control parameters based on cost objectives. we are in the process to finalize the costing model therefore we used a simple cost function at this point. we have minimized the inventory holding cost by changing the parameters of our operational space while keeping the service level at the required value. simple warehouse model figure 1: the classic model of inventory control. in fig. 1, q is the theoretical demand over cycle time t and this is the order quantity; r is the reorder point, which is the maximum demand can be satisfied during the replenishment lead time (l). s is the safety stock; this is needed if the demand is higher than the expected (line d). we have a special type of safety stock in our example. utility companies use this stock to cover demand due to system failures. now we give a summary of the most important parameters of inventory control and their relevance and connection to our model. lead time l is the time between the purchase order and the goods receipt. d̄ l denotes the average demand during the replenishment lead time. d̄ l = d̄ ·l, where d̄ is the daily average demand. using the same logic dl is a special case; it yields consumption if the service level is 100%. we will use dl to denote the consumption during the manuscript. a cycle time (t) is the time between two purchase orders. the order quantity is q where q = d¯·t. this is the ordered quantity in a purchase order. ld zs lσ= q tout outt l lll t l d zdesdr −+=−+= σ d out l t l de = 109 q is equal to the expected demand and the maximum stock level. maximum stock level is the stock level necessary to cover the expected demand in period t; therefore it has to be the quantity we order. reorder point is the stock level when the next purchase order has to be issued. it is used for materials where the inventory control is based on actual stock levels. in an ideal case r equals to total of safety stock and average demand over lead time: ( sdr l += ). s is the safety stock which is to cover the stochastic demand changes and for a given service level this is the maximum demand can be satisfied over the lead time. assuming constant demand pattern over the cycle time, average stock (k) can be calculated as follows. sqk += 2 (1) it is calculated as a weighted average of stock levels over the cycle time. service level (sl) is the ratio of the satisfied and the total demand (in general this is the mean of a probability distribution), or in other words it is the difference between the 100% and the ration of unsatisfied demand: q rdsl l )(100100 − −= (2) we assume that all demand is satisfied from stock until stock exists. when we reach stock level r the demand over the lead time (dl) will be satisfied up to r. consequently if dl > r, we are getting a stock out situation and there will be unsatisfied demand therefore the service level will be lower than 100%. dl is not known and it is a random variable. the probability of a certain demand level is p(dl). based on this, the service level is formed as shown in the next equation. q drddp sl d d lll l ∫ − −= max ))(( 100100 , (3) where dl is continuous random variable, and dmax is the maximum demand over lead time. stochastic model based on our experience in analyzing actual supply chain systems we discovered that the probability functions of material flow and demand are different from the theoretical functions. as fig. 3 shows the distribution function of an actual material consumption is significantly different from the theoretical one (fig. 2). this makes us believe that there is a difference between the theoretical (calculated) and the actual inventory movements, therefore it makes sense using an approach based on “actual” distribution function. we will demonstrate the results of the simulation using this approach. figure 2: theoretical cumulative distribution function figure 3: actual cumulative distribution function for a raw material based on its consumption data inventory movements can be modeled much better using stochastic differential equations than modeling based on the theoretical assumption that movements are following normal distribution. we propose the following model: ),,( 1 uill tropxuwxx ii +−= + , (4) where xi is stock level on the ith week, wi is a stochastic process to represent consumption. this stochastic process is based on the empirical cumulative distribution function we described in the previous section. u is the quantity of material received on week i, based on purchase orders. purchase orders are calculated based on the actual inventory level (x), and reorder point (rop), and the replenishment lead-time (tu). optimization of the system optimization process is changing the reorder point while keeping the service level at the required value. as a result we find the optimal reorder point for the given service level. this determines an optimal inventory level to minimize our current cost objective function. in the first phase we created the simulator using the sequential quadratic programming (sqp) functionality of matlab’s optimization toolbox. during the optimization we calculate the minimum value of a restricted non-linear multi-variable function. in our case we use the reorder point as optimization variable (parameter), we are seeking for the minimum of the average days of inventory. our restriction is the required value of the service level. 110 in the basic case we use one set random consumption data for the optimization therefore the optimum is related to this dataset. we applied the monte-carlo process to overcome this problem. this is a robust methodology which generates empirical distribution functions of consumption. we use these data sets as input for the simulation model to simulate the stock movements. we use many random paths like this in every optimization step. based on the proven convergence of the monte-carlo process the calculated stock movements, stock turnover and service level are good estimations of the actual process at a given reorder point. in the current example the optimization process executes 100 simulation runs for each parameter set and uses the average of the results as objective function or constraint. we use the reorder point as optimization variable (parameter), we are seeking for the minimum of the average days of inventory. our restriction is the required value of the service level. we demonstrate the results in the next section. results in this chapter we show a complete process for the optimization of a 2-echelon supply chain, as well as we demonstrate how to solve a more complex problem by the help of our proposed simware program. analysis of a 2-level system in this demonstrated example we used the simulator to analyze a system with two connected warehouses. the simulator is capable to optimize the two warehouses in the same time and calculate the optimum for the supply chain as a whole. the following diagram shows the supply chain, i.e. the structure of the analyzed 2-level system. figure 4: the analyzed 2-level system where the objective function is: f(z) = mean(h1) + 1.3*mean(h2), (5) i.e. the holding cost in the second warehouse is 30% higher than in the first warehouse. in fig. 5, the values of the objective function (i.e. cost) is presented as a function of the reorder point of the two warehouses. fig. 6 shows the service level of warehouse 1 in the 2-level system. the constraint for the service levels is 95% in this case. cost reorder point – storage 2  reorder point – storage 1 co st     reorder point – warehouse 1reorder point –warehouse 2 figure 5: the values of the objective function for the 2-level system   se rv ic e  le ve l  service level –warehouse 1  reorder point –warehouse 1 reorder point – warehouse 2  figure 6: the values of service level for warehouse 1. the figure above shows only the service level for the first warehouse, but in the optimization problem both service level has to take into consideration as well as the constraints. in the next picture, we investigate all of these. figure 7: the result of the optimization. fig. 7 shows the result of the optimization using the sqp method. the optimal solution is highlighted with the green square. it satisfies the 95% constraints and ensures the minimal holding cost in the warehouses. the cost function can be seen in fig. 5. the result of the simulation run is presented in the next figure. the diagram shows weekly inventory levels in the warehouses at the optimal case. 111   weeks  y figure 8: inventory levels in the 2-level system. in the rest of this section, we present a more complex, 3-level inventory model for illustration. this model can be seen in the next figure, which contains 9 warehouses in a 3-echelon structure. in the simware program, users have to define the structure of the problem, i.e. the connection between the warehouses. the parameters of each warehouse has to be defined also, e. g. the lead time or the average demand for a product as well as the cost values, like the holding cost. fig. 10 represents the results of the simulation for a 3-level inventory model, where each inventory level is depicted by lines with different style.   wh1  wh2   wh3   wh4  wh43wh42   wh41   wh31 wh21  figure 9: the analyzed 3-level system. weeks  in ve nt or y  le ve l  figure 10: the inventory levels in the 3 level multiechelon system. note that we have used separate distribution functions for the central warehouse and the other regional warehouses to simulate the consumption. we constructed these distribution functions based on actual data. the central warehouse consumption figures are calculated as a total of the downstream warehouse consumptions. using different distribution functions in a multiechelon supply chain, or using different consumption values for each warehouse is not a trivial, but necessary task if we want to construct a more realistic model or simulator. the simware program offers an easy-to-use interface to build even complex supply chains, and propose a novel component based structure. using this program, users can easily optimize the supply chain, for example by an sqp method, but the proposed methodology gives a chance to use more effective optimization algorithms. conclusions a framework for modeling a multi-echelon supply chain has been defined. the mm and wm modules of sap system provide data for the model for the whole supply chain. in our project we simulated a central purchasing scenario. in this supply chain the central warehouse supplies the other companies in the group. our methodology can be used to calculate stock turnover ratio and safety stock based on the agreed service level of the warehouses. our methodology can handle the stochastic behavior of the replenishment lead time. we used monte-carlo based simulation to evaluate the results and also were able to evaluate the mrp parameters used in the erp system. extended the model to analyze and optimize the inventory levels at the other companies in the group as well. the matlab simulation model can be used to determine the optimal parameters for a required service level. the simware model is available at the following website: www.folyamatmernok.hu acknowledgement this work was supported by the tamop-4.2.1/b09/1/konv-2010-0003 and tamop-4.2.2/b-10/1-20100025 projects and the e.on business services kft. references 1. g. caloiero, f. strozzi, j. m. z. comenges: a supply chain as a series of filters or amplifiers of the bullwhip effect, international journal of production economics, 114(2), (2008), 631–645 2. s. c. graves, s. p. willems: optimizing strategic safety stock placement in supply chains, manufacturing & service operations management, 2(1), (2000), 68–83 3. s. c. graves, s. p. willems: supply chain design: safety stock placement and supply chain configuration. handbooks in operations research and management science, 11, (2003), 95–132 112 4. s. c. graves, s. p. willems: strategic inventory placement in supply chains: nonstationary demand, 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word 2012_dr_bodor_endre_hjic.doc hungarian journal of industrial chemistry veszprém vol. 39(3) pp. 349-352 (2011) properties of diesel-alcohol blends l. hajba1 , z. eller2, e. nagy1, j. hancsok2 1university of pannonia, faculty of information technology, research institute of chemical and process engineering h-8200 veszprém, egyetem u. 10., hungary e-mail: hajba@mukki.chemres.hu 2 university of pannonia, department of mol hydrocarbon and coal processing h-8200 veszprém, egyetem u. 10., hungary fuels from renewable sources such as biodiesel or bioalchohols are getting more attention also as blending components to fossil fuels and because of their less environmental impact. stability and physico-chemical properties of different dieselalcohol blends were investigated by different composition. the solubility properties of the alcohols are mainly dependent on the carbon chain length of the alcohol, their water content, additives, temperature and also on the hydrocarbon composition of the diesel fuel. bio-butanol has better physic-chemical properties than bio-ethanol and its blends with diesel fuel have proper parameters, like cold filter plugging point and high frequency reciprocating rig lubricity are close to those of the base diesel fuel. keywords: bioalcohol, diesel-ethanol blend, diesel-butanol blend, cold filter plugging point, high frequency reciprocating rig introduction diesel fuels from fossil source are widely used in automobiles and transportation vehicles because of its drivability and thermal efficiency. the strict governmental regulation on exhaust emissions and the fast depletion of worldwide petroleum reserves provide a strong encouragement to the research for alternative fuels. so fuels from renewable sources such as biodiesel or bioalchohols are getting more attention because of their less environmental impact. mixtures of fossil fuel and biofuels are also promising. our current investigation is focusing on the use of alcohol as a blending component in diesel fuels. the high oxygen content of the alcohols can improve the burning efficiency of the fuel blend and also can reduce emissions of the particulate matter (pm), carbon monoxide (co), hydrocarbon (hc) and nitrogen oxides (nox) [1-3]. the solubility of the alcohols depends on the temperature and also on the hydrocarbon chain length (non-polar part). also crucial the water content of the alcohols. especially phase separation can occur in the fuel blend if ethanol has higher water content than 1 v/v % [4, 5]. important physical-chemical properties such as cetane number and heating value are reduced in the diesel-alcohol blends. these values can be improved by additives. properties of diesel-ethanol blends the solubility of ethanol in diesel fuel mainly depends on the following factors: – water content; – temperature; – hydrocarbon composition of the diesel fuel; – additives. the presence of ethanol causes physico-chemical changes in diesel fuel. it can significantly reduce the cetane number, heat content, viscosity, flashpoint, etc. for example the heat content of the diesel fuel is reducing by ca. 2% if 5 v/v% ethanol is added to it. table 1 shows the decreasing tendency in the heat content with increasing ethanol content. table 1: heat content of ternary mixtures [6] mixtures gross heat content (mj/kg) diesel 42.35 diesel + 10% ethanol + 1% a1 + 1% a2 40.98 diesel + 15% ethanol + 1% a1 + 1% a2 40.75 diesel + 20% ethanol + 1% a1 + 1% a2 39.59 a1, a2 emulsifier additives 350 the cetane number of the diesel-ethanol blend fuel reduces significantly, because the cetane number of ethanol is extremely low. each 5 v/v% ethanol added to the diesel fuel, the cetane number reduced ca. 4-6 units in the diesel-ethanol blend [5]. fig. 1 shows the decreasing order of cetan number in the function of ethanol content. figure 1: the change of diesel fuel cetane number in the function of ethanol content. therefore it is preferable to add ignition improver in order to raise the cetane number of diesel-ethanol blends. with organic nitrates (alkyl nitrates, triethilene glycol dinitrate etc.) as prefered ignition improvers the cetane number can be increased up to the level of the normal diesel fuel [7]. the hydrocarbon composition of the diesel fuel especially the aromatic content greatly affects the ethanol solubility. reducing aromatic content of diesel fuels influences the miscibility of ethanol in diesel fuel and it affects the amount of additive required to achieve a stable blend. with the use of emulsifiers one can avoid phase separation even in case of higher ethanol concentration (≥15v/v%). experimetal the diesel-butanol blends were produced by the base gas oils summarised in table 2, by butanol. the concentrations of the emulsifiers and butanol were changed between the following ranges: emulsifiers: 0.5–2 v/v% butanol: 5–20 v/v% the water content of the butanol was varied between 0 and 2 v/v%. preparation of the blends was carried out in vials of 150 cm3 volume. emulsions were stirred in a laboratory shaker for 24 h. stability of the emulsions was investigated in the temperature range (–20)–(+25) °c. table 2: “a”: hydrotreated gas oil with low sulphur content, “b”: light gas oil from paraffinic crude oil (algyő, hungary) properties “a” “b” density at 15 °c, g/cm3 0.8364 0.7971 sulphur content, mg/kg 8 600 nitrogen content, mg/kg 30 5 total aromatic content (hplc), % 32.7 13.8 kinematic viscosity at 40 °c, mm2/s 2.75 2.86 cfpp (cold filter plugging point), °c -3 ca. -24 flash point (pensky-martens), °c 72 52 destillation range, °c 176–361 169–291 cetane number 50.3 54.8 hfrr, µm 556 749 properties of diesel-butanol blends using butanol instead of ethanol as a blending component in diesel-alcohol blends has several advantages. butanol has higher heat content and higher miscibility in diesel fuel than ethanol. in diesel-butanol blends it is less susceptible to separation in the presence of water than diesel-ethanol blends because of the lower solubilities of butanol in water and water in butanol. since its vapor pressure is much lower than of ethanol the dieselbutanol blends are potentially suitable for transport in the existing piplines and one can avoid the need for additional transportation and storage infrastructure and so extra costs. butanol has different isomers, based on the location of the hydroxyl group (–oh) and carbon chain structure. butanol production from biomass tends to yield mainly straight chain molecules. therefore in our experiments synthetic grade n-butanol was used. in our investigation the butanol concentration was changed between the range of 5–20 v/v%. butanol with 1 v/v% and 2 v/v% water content was also used as blending components. to avoid phase separation because of the water content emulsifier (tween 85, tween 80, epilan kcl 3. epilan kcl 11/90, epilan kp 7/90) were added in the concentration range of 1–2 v/v%. results of our investigation can be summarised as follows: – synthetic grade butanol greatly dissolves in diesel fuel at any ratio (5–20 v/v%). – to avoid phase separation emulsifier must be added to the blends with water containing butanol to get stable blends. – the homogenous blends have stayed stable without any phase separation by changing the temperature in the range 5–25 °c. 351 – in the case of winter grade diesel fuel paraffin precipitate has appeared below the temperature -15 °c, probably because butanol reduced the efficiency of the paraffin dispersant additive. – other not polysorbate and not fatty alcohol etoxilate based surfactants also should be tested. the following selected stable blends were tested for the cold filter plugging point (cfpp) and high frequency reciprocating rig (hfrr) lubricity parameter (table 3). the results of the measurements are summarised in table 4. table 3: composition of the selected stable blends sample composition 15 85 v/v% diesel „a” + 15 v/v% butanol with 2 v/v% water 16 80 v/v% diesel „a” + 20 v/v% butanol with 2 v/v% water 33 89.33 v/v% diesel „a” + 10 v/v% butanol with 2 v/v% water + 0.67 v/v% span 80 34 86.33 v/v% diesel „a” + 13 v/v% butanol with 2 v/v% water + 0.67 v/v% span 80 35 84.33 v/v% diesel „a” + 15 v/v% butanol with 2 v/v% water + 0.67 v/v% span 80 36 79.33 v/v% diesel „a” + 20 v/v% butanol with 2 v/v% water + 0.67 v/v% span 80 43 95 v/v% diesel „b” + 3 v/v% butanol with 2 v/v% water + 2 v/v% empilan kcl 3 44 93 v/v% diesel „b” + 5 v/v% butanol with 2 v/v% water + 2 v/v% empilan kcl 3 45 90 v/v% diesel „b” + 8 v/v% butanol with 2 v/v% water + 2 v/v% empilan kcl 3 46 88 v/v% diesel „b” + 10 v/v% butanol with 2 v/v% water + 2 v/v% empilan kcl 3 table 4: the cold filter plugging point (cfpp) and high frequency reciprocating rig (hfrr) value of selected stable blends sample cfpp, °c hfrr, µm diesel “a” -3 556 15 0 364 16 1 351 33 -1 232 34 0 279 35 0 263 diesel „a” 36 0 300 diesel “b” -24 749 43 -32 266 44 -33 289 45 -33 311 diesel „b” 46 -33 281 one of the low-temperature properties the cold filter plugging point (cfpp) has changed slightly compared to the base diesel fuels, so even higher concentration of butanol has relatively minor effect on that parameter. in case of diesel “b”, cfpp values decreased definitely. the lubricity properties of diesel fuels are generally evaluated by the use of a bench test described as the high frequency reciprocating rig (hfrr). the test measures the wear scar of a test specimen that is subjected to wear, using only the test fuel as lubricant. based on the european norm en 590:2009 (test method iso 12156-1) for diesel fuels all of the blends fulfill the maximum 460 μm of the hfrr value. the use of the diesel-butanol blends in diesel engines is very promising as has already reported in the literature [8]. conclusions the diesel-bioalcohol fuel blends are very promising fuel alternative. the solubility of diesel-alcohol blends is mostly dependent on carbon chain length of the primary alcohol and its water content. therefore butanol seems to be more suitable for a mixing component, because it hardly dissolves in or adsorbs water. the other physico-chemical parameters (heating value, cetane number, kinematic viscosity etc.) of butanol are also much better than that of ethanol. the cfpp and hfrr values of the produced diesel-butanol blends are really promising and close to the values of a base diesel fuel. we should also investigate the possibility to use biodiesel as the third mixing component in the fuel blends [9, 10]. acknowledgement the project támop 4.2.1/b-09/1/ konv-2010-0003 “mobility and environment: researches in the fields of motor vehicle industry, energetics and environment in the middle-and west-transdanubian regions of hungary.” greatly acknowledged for the financial support. references 1. e. a. ajava, b. singh, t. k. bhattacharya: experimental study of some performance parameters of a constant speed stationary diesel engine using ethanol–diesel blends as fuel, biomass and bioenergy 17 (1999) 357–365 2. b. q. he, s. j. shuai, j. x. wang, h. he: the effect of ethanol blended diesel fuels on emissions from a diesel engine, atmos. environ. 37 (2003) 4965–4971 3. a. c. hansen, q. zhang, p. w. l. lyne: ethanol– diesel fuel blends – a review, biores. technol. 96 (2005) 277–285 4. r. l. mccormick, r. parish: advanced petroleum based fuels program and renewable diesel program, milestone report: technical barriers to the use of ethanol in diesel fuel, national renewable energy laboratory, 2001 5. k. r. gerdes, g. j. suppes: miscibility of ethanol in diesel fuels, ind. eng. chem. res. 40 (2001) 949–956 352 6. p. satgé de caro, z. mouloungui, g. vaitilingomb, j. ch. berge: interest of combining an additive with diesel–ethanol blends for use in diesel engines, fuel 80 (2001) 565–574 7. n. m. ribeiro, a. c. pinto, c. m. quintella, g. o. da rocha, l. s. g. teixeira, l. l. n. guarieiro, m. c. rangel, m. c. c. veloso, m. j. c. rezende, r. s. da cruz, a. m. de oliveira, e. a. torres, j. b. de andrade: the role of additives for diesel and diesel blended (ethanol or biodiesel) fuels: a review, energy and fuels 21 (2007) 2433–2445 8. d. c. rakopoulos, c. d. rakopoulos, e. g. giakoumis, a. m. dimaratos, d. c. kyritsis: effects of butanol–diesel fuel blends on the performance and emissions of a high-speed di diesel engine, energy conversion and management 51 (2010) 1989–1997 9. a. chotwichien, a. luengnaruemitchai, s. jai-in: utilization of palm oil alkyl esters as an additive in ethanol–diesel and butanol–diesel blends, fuel 88 (2009) 1618–1624 10. m. zöldy, a. holló, a. thernesz: butanol as a diesel extender option for internal combustion engines, sae international (2010) 01. << 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word b_31_r.doc hungarian journal of industrial chemistry veszprém vol. 38(2). pp. 211-214 (2010) power spectral density (psd) analysis of machined surfaces i. barányi donát bánki faculty of mechanical engineering and safety technology, óbuda university 1081 budapest, népszínház u. 8., hungary e-mail: baranyi.istvan@bgk.uni-obuda.hu in the first half of the 90s, computers of adequate speed of operation and processing softwares became increasingly available, made it possible to realize 3d surface characterisation. in the literature different directives can be found none of them has become widely used. beside the extension of 2d parameter based technique to 3d many other methods have been developed. one is the power spectral density (psd) technique when “global” surface characterisation is carried out using complex mathematical tools. nowadays one of the most important tasks in tribology to design the surfaces optimised to the operation. in the present study topographical measurements and psd characterizations were performed to study the engineering surfaces produced by turning and to analyse the effectiveness of 2d and 3d psd. keywords: power spectral density, topography, fractal dimension introduction efficient research in the course of the past decades has provided experts involved in surface microtopography research with a number of tools and methods to design an operationally optimized surface. at the same time, this knowledge is utilized only to a small degree in the analysis and control of tribological processes. characteristically, designers continue to content themselves by requiring few roughness parameters [1]. in the first half of the 90s a lot of surface characterisation method has been developed. one is the power spectral density (psd) technique when “global” surface characterisation is carried out using complex mathematical tools. psd provides full length scale analysis, which takes into consideration not only the dominant topographic elements but also the submicro features, in contrast with traditionally surface characterisation methods. the fractal dimension derived from psd topography seems to be an efficient tool for characterization. in the present study topographical measurements and psd characterizations were performed to study the orientated engineering surface two and three dimensional fractal analysis. in my experience, these methods are associated with in point of view of fractal dimension. mathematical background of characterisation to characterize the measured topographies an algorithm was developed in cooperation with department of machine and industrial product design, budapest university of technology and economics and interpreted as psd analysis software. the theoretical base of 3d psd analysis was [2] and [5]. discrete fourier transformation (dft) of 3d topography can be written as follows: ∑∑ = = +−δ⋅δ= n d m c qyqxi dcyx ydxceyxzxyqqf 1 1 )(2),(),( π (1) where: qx – frequencies in x direction, qy – frequencies in y direction, z(xc, yd) – height coordinate located in xc, yd, m – number of points in profile, n – number of profiles, δx– sampling distance in x direction, δy – sampling distance in y direction. dft gives complex results: )),(im()),(re(),( yxyxyx qqfiqqfqqf ⋅+= (2) the psd “amplitude” is calculated (fig. 1): yxmn ffapsd δδ + = 22 imre (3) where: apsd – psd amplitude, re f – real part of the fourier transformation, im f – imaginary part of the fourier transformation. 212 lgapsd lgql lgpk figure 1: psd surface psd topography can be reduced to psd curve using (4). it means 2d representation, which can be easy handled, but contains 3d information about topography (fig. 2). 22 yx qqq += (4) figure 2: psd curve from the reduction of the psd surface there are two possibilities of showing results. one is to represent the amplitude of psd in the function of wavelength. the other prevalent method is logarithmic scale frequency-psd amplitude visualization. the practical gain of the first method is that dominant wavelength components appear as a maximum point of the psd curve. in the second method the height frequency range of the curve can be approximated by a line. the slope of the line is in correlation with the fractal dimension of surface. in the latter case, wavelengths smaller than the highest dominant wavelength play a considerable role. psd amplitude becomes constant – the self-affinity character of the surface disappears – in a lower wavelength range. the slope of fitted line (s) to psd curve has correlation with fractal dimension of surface according to (5). 2 4 sdf += (5) where: df – fractal dimension. psd analysis of the theoretical surface in this part i solve the fractal dimension of the theoretical surface. this analysis gives a chance to investigate the surface psd profondly. in this part i generate a topography which is constans in every direction. the psd surface and psd curve of this surface summarised in fig. 3 and fig. 4. figure 3: theoretical surface psd analysis figure 4: approximating straight line the calculated fractal dimension from the slope of the straight line is df = 2,51. we can see in fig. 3, the applied program use calculating in logarithmical scale. in fig. 4 felharmoincal points are farther position of the straight line. two and three dimensional psd analysis of the turned surfaces the turned surfaces have two orientation: one is perpendicular, and the other is paralell with the machining direction. the profiles of these directions are different (fig. 5 and 6). in this part i choosed a surface, which average surface roughness war sa = 3,02 μm. in this part of investigation was the fractal dimension in direction of paralell and perpendicular direction with machining direction. fig. 5 shows the profile with characteristic wavelenghts. fig. 7 representes this profile main wavelenghts. parallel in the machining direction (fig. 6) can’t find characteristic wavelenghts (fig. 8). 213 figure 5: profile in perpendicular with machining direction figure 6: profile in parallel in the machining direction figure 7: profile 2d psd analisys in machining direction figure 8: profile 2d psd analisys in perpendicular with machining direction the calculated fractal dimension of the profile is df = 1.36 in machining direction and the turned topography fractal dimension is df = 2.33. in this case the persson equation associate the profile and the surface fractal dimension. the affection of small psd amplitudes (in parallel direction of the machinining direction) isn’t considerable in the calculation of 3d fractal dimension (the 2d farctal dimension is in 1 and 2, and the 3d fractal dimension is 2 and 3). the 3d fractal dimension is one more than 2d fractal dimension. analisation of turned surface with various roughness in this part of investigation i generated profiles with various average roughness from the original profile (fig. 5). the profiles can be solved with constants multiplication. this generation algorythm can be warranted to waves are same in the profiles and the average roughness is more or less than the original profile’s. table 1 summarizes the average roughness, the two dimensional and three dimensional fractal dimension and the vertical axis intersection of the generated profile. fig. 9 shows the modification of the vertixal axis intersection. based on these results it can be supposed that fractal dimension didn’t modify, when the profile is increased in vertical direction. this increasing modify the psd amplitude and offset the persson line up. table 1: characterestic data of the profile 2d analysis 3d analysis ra [μm] intersect. with vertical axis df intersect. with vertical axis df 0.6 -7.1066 1.36 -7.0378 2.33 0.75 -6.9127 1.36 -6.8631 2.33 1.51 -6.3107 1.36 -6.2931 2.33 3.02 -5.7086 1.36 -5.7114 2.33 6.03 -5.1066 1.36 -5.1487 2.33 9.05 -4.7544 1.36 -4.8218 2.33 12.06 -4.5045 1.36 -4.5895 2.33 15.08 -4.3107 1.36 -4.4379 2.33 -7,5 -7 -6,5 -6 -5,5 -5 -4,5 -4 0 5 10 15 20 ra in te rs ec tio n 2d analysis intersection 3d analysis intersection figure 9: the modification of the vertixal axis intersection 214 conclusion the turned surfaces farctal dimension is different in dirrection of perpendicular and parrellel direction. the characteristic direction is parallel with the machining direction. the 3d fractal dimension is one more than the parallel profile fractal dimension. the profiles fractal dimension isn’t change, when the profile is blown up or reduced. the persson line intersection with the vertical axis is modify in blown up or reduced profile. references 1. b. palásti kovács: forgácsolással megmunkált felületek mikrogeometriájának értékelése, kandidátusi értekezés, budapest, 1983. 2. s. horváth: a felületi hullámosság jelentősége, a hullámosság 3d-s értelmezése, gép 2005/9-10, 2005, 82–85, 3. vda 2006: oberflächenbeschaffenheit, regeln und verfahren zur beurteilung der oberflächenbeschaffenheit, 2002. 4. b. n. j. persson, o. albohr, u. trataglino, a. i. volokitin, e. tosatti: on the nature of surface roughness with application to contact mechanics, sealing, rubber friction and adhesion, j. phys, condens. matter, 17, r1-r62, 2005. 5. á. czifra: sensitivity of power spectral density (psd) analysis for measuring conditions, rudas i. j., fodor j., kacprzyk j. (eds.): towards intelligent engineering and information technology, 2009, 505–517. 6. k. j. stout, l. blunt, p. j. sullivan, w. p. dong, e. mainsah, n. luo, t. mathia, h. zahouani: the development of methods for characterisation of roughness in three dimensions, printing section, university of birmingham edgbuston, birmingham, 1993. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 /colorconversionstrategy /cmyk /dothumbnails false /embedallfonts true /embedopentype false /parseiccprofilesincomments true /embedjoboptions true 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word 2012_dr_bodor_endre_hjic.doc hungarian journal of industrial chemistry veszprém vol. 39(3) pp. 375-379 (2011) investigation of catalytic conversion of fischer-tropsch wax on pt/alsba-15 and pt/beta zeolite catalysts gy. pölczmann1, j. valyon2, j. hancsók1 1university of pannonia, mol department of hydrocarbon and coal processing h-8200 veszprém, egyetem u. 10., hungary e-mail: hancsokj@almos.uni-pannon.hu 2hungarian academy of sciences, chemical research center, h-1025 budapest, pusztaszeri u. 59-67., hungary because of the more serious problems with the environment (e.g. greenhouse effect) and the crude oil supply (e.g. import dependence) the use of fuels and lubricants produced from renewable feedstocks have come to the front nowadays. the fischer-tropsch wax (60–80% of the fischer-tropsch products) which is produced on synthesis gas from different sources (biological or waste), is a mixture of high molecular weight (c20-c60) n-paraffins, which are in solid state (high pour point) at normal conditions. the products (fuels and base oils) which can be produced from this paraffin mixture have high quality and have fewer negative effects on the environment (practically zero sulphurand nitrogen content, low aromatic content, excellent application properties) thus they do not demand changes in the fuel supply infrastructure and in the engine constructions. the isomerization of high molecular weight n-paraffins can be effectively carried out on bifunctional catalysts. there are only a few indications about the application of metal catalysts on mesoporous carrier in the literature. consequently our objective was to investigate some pt/alsba-15 (sba: santa barbara amorphous) catalysts which have not been investigated in detail in this reaction system yet, and compare its properties with a pt/beta zeolite catalyst which has been recommended for this reaction earlier. the applicability and catalytic activity of pt/alsba-15 and pt/beta zeolite catalysts of 0.5% platinum content for the selective isomerization of fischer-tropsch wax was investigated in the present experiment. the experiments were carried out in a high-pressure microreactor system in continuous operation and on a catalyst with steady-state activity. the main properties of the feedstock which was a mixture of paraffin produced by fischer-tropsch synthesis (the synthesis gas was produced from biomass) were: n-paraffin content (c18-c57): 97.4%, sulphur content: <5 mg/kg, pour point: 72 °c. in the experiment the following process parameters were applied: t = 275–375 °c, p = 40–80 bar, lhsv = 1.0–3.0 h-1, h2/hydrocarbon ratio: 400–800 nm3/m3. the composition of the products was determined by gas chromatography. from the catalysts with different support the best results were gained on the catalysts with alsba-15 support, and with increasing temperature the yield of liquid products (c5+) decreased, but until 325 °c this value was above 93% in every case. in case of the beta zeolite high amount of cracking took place. increasing the pressure shifted back the hydrocracking reactions (with the increasing number of moles) so it had a decreasing effect on the volume of the gas products and the lower contact time (higher liquid hour space velocity) had the same effect. in the gas products mainly branched isobutane was identified, which indicated that the cracking enacted partly after the isomerization reactions. the isoparaffin contents of the liquid products in the function of process parameters increased with increasing temperature and decreased with increasing pressure and lhsv in every case while other parameters were kept constant. based on the isoparaffin contents of the different fractions it can be concluded that on pt/alsba-15 catalyst at advantageous process parameter combinations (t = 300–325 °c (c11-c20)/ 275–300 °c (c21-c30), p = 40–80 bar, lhsv = 1.0–2.0 h-1) the catalyst was applicable to produce c11-c20 and c21-c30 fractions with high isoparaffin content (63.5–85.6% and 34.1–58.7%) with adequate yields (29.9–36.6% and 46.2–58.8%). we experienced that the gas oil fractions having the lowest pour point were obtained in the case of high concentrations of 5-methyl isomers. the c21-c30 fraction is a high viscosity index (vi ≥ 125) base oil. the selectivity of the target product fractions was high, and based on these facts the selective isomerization of the fischer-tropsch wax can be a new application area of the pt/alsba-15 catalyst. keywords: fischer-tropsch wax, pt/alsba-15, hydroisomerization, hydrocracking 376 introduction nowadays, the application of fuels and lubricants produced from renewable feedstocks has come to the front because of serious environmental problems (e.g. greenhouse effect) and ambiguity of crude oil supply (e.g. import dependence). in the integrated fischer-tropsch synthesis (fig. 1) liquid hydrocarbons („synthetic crude”) and subsequently fuels, base oils, paraffins and other special products are produced from natural gas, coal, crude oil derivates, biomass and wastes through synthesis gas in three main steps. the base process is the fischer-tropsch synthesis which forms the hydrocarbon molecules – significantly simplified – from –ch2– units. the fischertropsch wax (60–80% of the fischer-tropsch products) produced of synthesis gas of different sources is a mixture of high molecular weight (c20-c60) n-paraffins, which is practically free of sulphur, nitrogen and aromatics, but which is a solid at ambient conditions (high pour point). these paraffin mixtures can be excellent feedstocks of catalytic processes which can produce high quality products (fuels and base oils), less harmful to the environment (practically zero sulphurand nitrogen content, low aromatic content), with excellent application properties and their use does not call for changes in the fuel supply infrastructure and in the engine constructions [1-6]. the final step of the integrated fischer-tropsch technology is product upgrading and separation to get fractions having required compositions and quality. the fischer-tropsch paraffin mixture is upgraded by hydrocracking or hydroisomerization to get lower pour point product. the product comprises of lower and/or branched hydrocarbons (fig. 2). the volume of the gaseous and naphta products formed over conventional hydrocracking catalysts is significant (6–8% and 10–20%), however, the selectivity for the target fraction (middle distillate) is relatively low. therefore, it is very important to develop new catalytic systems for selective isomerization (skeletal arrangement) (reactor, feedstock, reaction mixture, process parameters) that can produce the appropriate mixture of gas oils and base oils (target product mixture) with high iso-paraffin content, and also to develop the suitable catalysts and application parameters [7-11]. the isomerization of high molecular weight n-paraffins can be effectively carried out over bifunctional catalysts. the metal component is responsible for the hydrogenationdehydrogenation activity. the activation of c–c and c–h bonds proceeds on the acidic active sites of the support that is usually zeolite or mesoporous alumino-silicate. there are only a few data in the literature about the application of noble metal on mesoporous support for the hydroisomerization of high molecular weight paraffins [12, 13]. consequently, our objective was to investigate mesoporous aluminosilicate pt/alsba-15 catalyst which has not been studied in details in the above reaction yet, and to compare with a pt/beta catalyst which was highly recommended earlier for the same purpose [4, 14]. figure 1: the integrated fischer-tropsch synthesis 0 1 2 3 4 5 6 7 c15 c18 c21 c24 c27 c30 c33 c36 c39 c42 c45 c48 c51 c54 c57 carbon number c om p os it io n , % isoparaffins n-paraffins total paraffin figure 2: the paraffin composition of the feedstock 377 experimental objectives the aim of our experiments was to investigate 0.5% pt containing alsba-15 and beta zeolite catalysts catalyst applicable for hydroisomerization and hydrocracking of fischer-tropsch wax to produce high quality gas oil and base oil fractions. the catalysts having 0.5% platinum were investigated because they were found based on our pre-experiments advantageous in the view of activity and economics for the selective isomerization of fischer-tropsch wax. the activity and selectivity of the catalysts and the effect of the process parameters (pressure, temperature, liquid hour space velocity, h2/hydrocarbon volume ratio) on the yield and on the product compositions were also studied. feedstock the feedstock of our experiments was a paraffin mixture produced from biomass-based synthesis gas with fischertropsch synthesis. the main properties and the paraffin composition of the feedstock are shown in table 1 and fig. 2. table 1: the main characteristics of the feedstock properties value n-paraffin content (c18-c57), % 99.6 sulphur content, mg/kg 2.5 nitrogen content, mg/kg 12 pour point, °c 72 catalysts we used as catalyst alsba-15 and beta zeolite carrier materials prepared by us. beta zeolite was prepared from 1 sio2 : 0.028 al2o3 : 0.89 na2o : 0.38 tetra-ethyl ammonium hydroxide : 36.2 h2o synthesis mixture by hydrothermal synthesis at 135 °c for 5 days. alsba-15 catalyst were synthesized according to the procedure of vinu et al. [15] with reaction mixture composition of 1 sio2 : 0.04 al2o3 : 0.016 p123 : 0.46 hcl : 127 h2o, and aluminum isopropoxide as al source. 0.5 wt.% of pt was loaded by incipient wetness impregnation method on both supports in the form of tetraammineplatinum(ii) hydroxide hydrate precursor. the catalysts were loaded into the reactor after forming. in order to assure the appropriate liquid distribution the reactant and the hydrogen was fed on a bed of quartz beads placed above the catalyst bed in the reactor tube. catalysts were activated by reduction at 450 °c in hydrogen flow. main properties of the catalysts are presented in table 2. table 2: main properties of the applied catalysts properties β zeolite alsba-15 pt content, % 0.5 0.5 brønsted acidity, mmol nh3/g 0.83 0.6–0.65 bet area, m2/g 280 470 average pore diameter, nm 0.76 x 0.64 3.6 si/al ratio 19.2 17.8 experimental equipment catalytic experiments were carried out in a high-pressure microreactor system (fig. 3) at continuous operation and on steady-state catalyst. minimum 80 °c temperature was maintained in the reactor system to avoid condensation (the feedstock was solid at room temperature). process parameters the process parameters of the experiments were determined by our pre-experiments, which were the followings: temperature: 275–375 °c, pressure: 40–80 bar, liquid hour space velocity: 1.0–3.0 h-1, h2/hydrocarbon volume ratio: 400–800 nm3/m3 analytical methods the composition of the gas and liquid products was analyzed on-line gas chromatograph (gc) with fid detector. the main properties and the analytical parameters are shown in table 3. table 3: main properties of the gas chromatographs properties liquid(solid) analysis gas analysis type of column agilent tech db-1ht supelco equity-1 detector flame ionization flame ionization results and discussion our catalytic result showed that on the pt/alsba-15 catalyst higher liquid product (c5+) yield could be reached compared to pt/beta. with increasing temperature the yield of the liquid products (c5+) decreased, but until 325 °c this value remained above 93% in case of the pt/alsba-15 catalyst (fig. 4). on the pt/beta zeolite catalyst the c5product yield increased significantly above 300 °c. with increasing h2 pressure the hydrocracking reactions were suppressed, the volume of the gas products decreased. lower contact times had the same effect. 378 the yield of the c4fractions as a function of different process parameters is shown in fig. 5. the produced amount of methane and ethane was very small or zero on both catalysts suggesting that hydrogenolysis did not proceed. increasing temperature resulted in an increased yield of propane and higher molecular weight compounds. in the c5fractions on both catalysts mainly branched iso-butane could be identified which is probably formed by the β-scission of the branched carbenium ion intermediate. the iso-paraffin content of the c5+ products increased with increasing temperature and decreased with increasing h2 pressure and lhsv while other parameters were kept constant. it is important to be noted that the isomer content of the liquid products was significantly higher on the pt/alsba-15 catalyst than on the other catalyst (fig. 6). based on the iso-paraffin content of the different fractions produced on the pt/alsba-15 catalyst it can be concluded that at advantageous parameters (t = 300–325 °c, p = 40–80 bar, lhsv = 1.0–2.0 h-1, and t = 275–300 °c, p = 40–80 bar, lhsv = 1.0–2.0 h-1) the catalyst produce c11-c20 and c21-c30 fractions with high iso-paraffin content (63.5–85.6% and 34.1–58.7%) with reasonable yields (29.9–36.6% and 46.2–58.8%). it was found that the gas oil fractions having the lowest pour point were obtained with high concentrations of 5-methyl isomers. these gas oil boiling point range mixtures are excellent blending components having practically zero sulphur-, nitrogenand aromatic content and can be used alone too. the c21-c30 fraction can be used as environmentally friendly, high viscosity index (vi ≥ 125) base oil (table 4). it was also found that, the activity and isomerization selectivity of the alsba-15 catalyst having 0.5 wt.% of platinum did not change during the 240 hours time on stream experiment. table 4: the main characteristics of produced base oils and gas oils at the optimum process parameters properties gas oils (c11-c19) base oils (c21-c29) yield, % 29.9–36.6 46.2–58.8 cetane number >65 viscosity index 125–135 pour point, °c (-16)–(-21)* (-16)–(-10) sulphur content, mg/kg <2 <3 * cold filter plugging point hydrogen valve bypass valve pumpfeedstock (with filter) reactor and ceramic jacket separator to gas cromatograph gas products product valve pressure regulator valve to flow meter valves heated part figure 3: scheme of the catalytic system 0 10 20 30 40 50 60 70 80 90 100 250 275 300 325 350 375 temperature, °c c 5+ p ro du ct y ie ld , % pt/beta, 40 bar pt/alsba-15, 40 bar pt/beta, 60 bar pt/alsba-15, 60 bar pt/beta, 80 bar pt/alsba-15, 80 bar figure 4: changes in the yield of liquid product yield (c5+) as a function of process parameters (lhsv = 1.0 h-1) 0,0 5,0 10,0 15,0 20,0 25,0 methane ethane propane i-butane n-butane i-pentane n-pentane y ie ld o f c 5 p ro du ct s, % pt/beta, 40 bar pt/beta, 60 bar pt/beta, 80 bar pt/alsba-15, 40 bar pt/alsba-15, 60 bar pt/alsba-15, 80 bar figure 5: the composition of c5products as a function of process parameters (325 °c, lhsv = 1.0 h-1) 379 0 10 20 30 40 50 60 70 80 250 275 300 325 350 375 temperature, °c is om er c on te nt , % pt/beta, 40 bar pt/alsba-15, 40 bar pt/beta, 60 bar pt/alsba-15, 60 bar pt/beta, 80 bar pt/alsba-15, 80 bar figure 6: the effect of process parameters on the total isomer content of the products (lhsv = 1.0 h-1). conclusions in summary, the pt/alsba-15 catalyst showed better results in the production of gas oil and base oil fractions with high isoparaffin content from fischer-tropsch wax than the pt/beta catalyst. the main cause of this is the higher isomerization and lower cracking activity of the previous catalyst. the yields of the target fractions (29.9–36.6% and 46.2–58.8%) adequately high. our result supported that the mesoporous pt/alsba-15 materials can be suitable catalyst for the selective hydroisomerization of the fischer-tropsch waxes. acknowledgement “tamop-4.2.1/b-09/1/konv-2010-0003: mobility and environment: researches in the fields of motor vehicle industry, energetics and environment in the middleand west-transdanubian regions of hungary the project is supported by the european union and co-financed by the european regional development fund” references 1. c. perego, r. bortolo, r. zennaro: gas to liquids technologies for natural gas reserves valorization: the eni experience, catalysis today, 142 (1-2) (2009) 9–16 2. e. f. sousa-aguiar, l. g. appel, c. mota: natural gas chemical transformations: the path to refining in the future, catalysis today, 101 (2005) 3–7 3. j. hancsók: „modern engine and jet fuels iii. alternative fuels”, veszprém university press, (isbn 963 9495 33 6), veszprém, (2004), 438 p. 4. s. gamba, l. a. pellegrini, v. calemma, c. gambaro: liquid fuels from fischer–tropsch wax hydrocracking: isomer distribution, catalysis today, 156(1-2) (2010) 58–64 5. m. kobayashi, m. saitoh, s. togawa, k. ishida: branching structure of diesel and lubricant base oils prepared by isomerization/hydrocracking of fischer-tropsch waxes and α-olefins, energy & fuels, 23 (2009) 513–518 6. g. ondrey: gas-to-liquid projects get the green light, chem. eng., 111 (2004) 23–27 7. z. zhou, y. zhang, j. w. tierney, i. wender: producing fuels from fischer-tropsch waxes, ptq, 9(1) (2004) 137–143 8. a. c. vosloo: fischer-tropsch: a futuristic view, fuel processing technology, 71 (2001) 149–155 9. c. bouchy, g. hastoy, e. guillon, j. a. martens: fischer-tropsch waxes upgrading via hydrocracking and selective hydroisomerization, oil & gas science and technology, 64 (2009) 91–112 10. a. abu-jrai, a. tsolakis, k. theinnoi, r. cracknell, a. megaritis, m. l. wyszynski, s. e. golunski: effect of gas-to-liqiud diesel fuels on combustion characteristics, engine emissions, and exhaust gas fuel reforming. comparative study, energy & fuels, 20 (2006) 2377–2384 11. m. kobayashi, m. saitoh, k. ishida, h. yachi: viscosity properties and molecular structure of lube base oil prepared from fischer-tropsch waxes, j. of japanese petroleum institute, 48 (2005) 365–372 12. h. deldari: suitable catalysts for hydroisomerization of long-chain normal paraffins, applied catalysis a: general, 293 (2005) 1–10 13. i. rosetti, c. gambaro, v. calemma: hydrocracking of long chain linear paraffins”, chemical engineering journal, 154(1-3) (2009) 295–301 14. a. soualah, j. l. lemberton, l. pinard, m. chater, p. magnoux, k. moljord: hydroisomerization of long-chain n-alkanes on bifunctional pt/zeolite catalysts: effect of the zeolite structure on the product selectivity and on the reaction mechanism, appl. catal. a: general, 336 (2008) 23–28 15. a. vinu, v. murugesan, w. böhlmann, m. hartmann: an optimized procedure for the synthesis of alsba-15 with large pore diameter and high aluminum content, j. phys. chem. b, 108 (2004) 11496–11505 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 /colorconversionstrategy /cmyk /dothumbnails false /embedallfonts true /embedopentype false /parseiccprofilesincomments true /embedjoboptions true /dscreportinglevel 0 /emitdscwarnings false /endpage -1 /imagememory 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word content.doc hung. j. ind. & chem. 2012, vol. 40(2) pp. 65–119 table of contents comparative study on electrodialysis systems for galacturonic acid recovery .......... 65–67 k. bélafi-bakó, e. molnár, z. csanádi, n. nemestóthy effect of a new type of coupling agent on the mechanical properties of various multiwalled carbon nanotube/rubber composites .................................................................. 69–75 cs. varga, b. tóth, p. gergó, l. bartha application of the remote earth potential in cathodic protection measurements ....... 77–82 z. lukacs study on analysis of antibiotic compounds from enthomopathogenic bacteria by ft-ir ................................................................................................................................. 83–86 d. vozik, j. madarász, z. csanádi, a. fodor, k. dublecz, k. bélafi-bakó biocatalytic hydrogen sulphide removal from gaseous streams................................... 87–91 g. tóth , é. lövitusz, n. nemestóthy, k. bélafi-bakó optimal design of high-temperature thermal energy store filled with ceramic balls ..... 93–99 t. borbély study of the properties of a plain cathode grimm-type dc glow discharge source operated in a current-controlled pulse regime........................................................... 101–105 o. bánhidi effects of pan bread making on zearalenone levels in artifical contaimnated wheat flour ....................................................................................................................... 107–111 t. a. el-desouky, m. may amer, k. naguib magnetorheological fluid brake basic performances testing with magnetic field efficiency improvement proposal ................................................................................... 113–119 a. poznić, a. zelić, l.szabó 700 materials from characterization to industrial application – renewable feedstock and waste recycling a new research project at the university of pannonia the industrial mass production generates an ever growing volume of volume of waste production and discarded goods that have a significant impact on the environment. the costs of disposing these wastes are high. in the same time, the demand of industry for raw materials is increasing rapidly and certain raw materials become more and more expensive as their availability becomes limited. waste recycling and waste prevention are possible solutions for these problems. the implementation of these approaches requires new chemical processes. due to the variability of composition of wastes as raw materials, the development of these technologies is a large challenge for chemical engineering, too. the sustainability of our society and the environment, however, depends largely on the success of these r&d activities. the development of greener processes are investment into the future. in order to achieve these goals, the university of pannonia together with the college of dunaujváros applied for a támop-4.2.2.a-11/1/konv grant called for the funding of implementation of basic research projects with international cooperation in the framework of the social renewal operational program (támop) of the new széchenyi plan. the goal of the project entitled “materials from characterization to industrial application – renewable feedstock and waste recycling” was to start an r&d activity in order to establish new tools and procedures that support the integrated development of products and technologies. the guiding principle and concept of the project is the development of green processes and technologies considering simultaneously the interests of industries of strategic importance and the different aspects of sustainable development. the research activities taking place in the project cover different levels of time and space from molecular modeling to design of technological procedures. the control and supervision of these activities require the application of an integrated multilevel approach that manages the whole project effectively. further information on the project can be found at the project’s website (http://mkweb.unipannon.hu/hulladek/) and in the relevant papers of hungarian journal of industry and chemistry. 700 hungarian journal of industrial chemistry veszprém vol. 40 (2) pp. 65–67 (2012) comparative study on electrodialysis systems for galacturonic acid recovery k. bélafi-bakó , e. molnár, z. csanádi, n. nemestóthy university of pannonia, research institute on bioengineering, membrane technology and energetics, 10 egyetem str., 8200 veszprém, hungary e-mail: bako@almos.uni-pannon.hu electrodialysis (ed) is an electromembrane separation process suitable for recovery of organic acids. in this work galacturonic acid (ga) obtained by enzymatic hydrolysis of pectins from various sources was separated by a laboratory scale, two-step ed stack and a scaled-up, complex ed system. the experimental results from the two systems were compared. keywords: electrodialysis, pectin, galacturonic acid introduction galacturonic acid is the monomer of pectin, a polysaccharide [1] often occurred in agro-wastes, like sugar beet pulp, apple pomace, press cakes of fruits... etc. pectin can be hydrolyzed by enzymes and the process results a galacturonate (gat) solution. since it is an acidic (charged) compound, its recovery and separation can be carried out by electrodialysis (ed). electrodialysis is an electro membrane process, where charged components move in the direction of the oppositely charged electrode under electrical potential difference [2, 3]. ed has already been applied to separate various organic acids like citric acid, lactic acid, acetic acid, propionic adic, gluconic acid, maleic acid [4–8]. in case of pectin hydrolysates ed can be used for recovery and desalination of galacturonate ions (the counter ion is usually na). a laboratory scale, two step ed stack and a fumatech ft-ed-4-100-10 scaled-up complex module were applied in our laboratory to recover ga ([9 ,10]. in this work the stacks are compared from the aspects of yield, operation parameters, energy requirement and average current efficiency. material and methods galacturonic acid (ga) applied in the model solutions was purchased from sigma-aldrich, while sodium sulphate from spectrum (hungary). cation(fumasep fkb), anion-selective (fumasep fab) and bipolar (bp) membranes were purchased from fumatech. hydrolysis of pectin solutions from sugar beet pulp and citrus was carried out by pectinase enzymes (pectinex 100l enzyme preparation) in a shaking incubator. the process was followed by acid titration (0.5 m naoh). the laboratory scale ed set up consisted of two stacks (one conventional and the other contains bipolar membrane) was constructed in our workshop. the first stack was an symmetric ed cell (described in [9]), with 0.0225 m2 membrane surface area. here the galacturonate ions from the hydrolysate moved toward the anode and passed through the anion selective membrane, while sodium ions are transported in the other way. thus a concentrate stream containing mainly na-galacturonate was formed. then its desalination was carried out in the second ed cell, where 2 cation selective and a bipolar membrane were built in (figure 1) altogether with 0.0135 m2 membrane surface area. separation of sodium and galacturonate ions was possible: galacturonate anions remained in the feed solution forming an acid solution, while na ions passed through the cation selective membrane into the alkali solution forming naoh. figure 1: set-up of the second laboratory scale ed module 66 the scaled-up complex module containing cation, anion selective and bipolar membranes was described in [10], its membrane surface area was 0.31 m2. both ed stacks were operated by recirculation, using na2so4 solution (electrode solution). the experiments were followed by measuring the concentration of ga (dns test [11]) in various streams, conductivity, ph, electric current and voltage, the data were collected by a data acquisition device (national instruments usb6008/6009) and recorded by the program labview. the important stack and operation parameters for the laboratory scale stacks and the scaled-up complex ed module were summarized in tables 1 and 2, respectively. table 1: parameters of the two-step ed system for galacturonic acid recovery and desalination features of the modules conventional asymmetric ed combined with bp membrane membranes 3 cation selective, 2 anion selective 2 cation selective, 1 bipolar membrane surface area 0.0225 m2 0.0135 m2 volumes of solutions feed (diluate): 100 ml, concentrate: 150 ml feed (acid): 100 ml, alkali: 150 ml recirculation rate 32 ml/min 32 ml/min electrode solution 200 ml 0.5 mol/l na2so4 200 ml 0.5 mol/l na2so4 recirculation rate 60 ml/min 60 ml/min applied voltage 5 v 5 v processes galacturonate anions and na cations pass through the membranes to accumulate in the concentrate galacturonate anions remain, bp provides h+, acid formation na cations pass through the membranes, form alkali solution final results concentrate rich in na-galacturonate formation of galacturonic acid and naoh solutions table 2: parameters of the scaled-up complex ed system features of the module scaled-up complex module membranes 10 anion selective, 11 cation selective, 10 bipolar membrane surface area 0.31 m2 volumes of solutions feed (diluate): 400 ml, acid: 400 ml, alkali: 450 ml recirculation rate 380 ml/min electrode solution 500 ml 0.1 mol/l na2so4 recirculation rate 500 ml/min applied voltage 36 v processes both galacturonic anions and na cations pass through the membrane, formation of acid and alkali solutions final results recovery and desalination of galacturonic acid in one step results pectin hydrolysates from sugar beet pulp and citrus were studied by using the two ed systems. the experimental results are compared in table 3. from the table it can be seen, that higher initial concentration feed was applied in case of the two-step laboratory module, since in the second step we had to use the result of the first step: the na-galacturonate solution (recovered from the hydrolysate). it was desalinated in the bp module. in the scaled-up complex system the separation process (recovery and desalination) was achieved in one single step. though the energy consumptions were much higher in the scaled-up system and the current efficiencies were lower (than in the laboratory scale stack), but larger amount of product solutions (pure galacturonic acid) were manufactured. if the product acid obtained were related to the energy consumption, we found that – in case of ed separation of sugar beet pectin hydrolysate – 1 wh energy resulted in 0.09 g and 0.13 g ga production by the two-step, laboratory and the scaled-up, complex system, respectively. the scaled-up system worked with higher effectiveness, moreover it should be taken into account that its operation can be further optimised, and the energy consumption might be reduced even more. 67 table 3: comparison of the two ed systems two-step laboratory ed system hydrolysate asymmetric ed bp module scaled-up complex ed system from sugar beet pulp pectin feed volume feed conc. yield current eff. energy final result 100 ml 36.5g/l 63% 56% 9.2 wh 150 ml 15.4 g/l nagat solution 100 ml 15.4 g/l desalination – 4.6 wh 100 ml 12.1 g/l desalinated ga solution 400 ml 15 g/l 65% 41% 31 wh 400 ml 9.8 g/l desalinated ga solution from citrus pectin feed volume feed conc. yield current eff. energy final results 100 ml 48.9 g/l 78% 63% 8.9 wh 150 ml 25.4 g/l nagat solution no data 400 ml 39 g/l 86% 54% 39 wh 400 ml 33.5 g/l desalinated ga solution the yield, current effectiveness values are better for citrus pectin hydrolysate than for sugar beet pulp pectin hydrolysate, which may be explained by the higher purity of the citrus pectin preparation. as a summary, we concluded that electrodialysis is a suitable method for recovery, desalination and purification of galacturonic acid from hydrolysates of various pectins. the complex module was able to separate the product in one step and it seems that the scaled-up system worked more efficiently: higher yield was achieved by less energy consumption. therefore the complex ed system is suggested to apply for further experiments, aiming to study the possibilities of industrial applications. acknowledgement this work was partly supported by the támop4.2.1/b-09/1/konv-201-0003 and támop-4.2.2/b10/1-2010-0025. references 1. z. i., kertész: the pectic substances, interscience publishers, new york (1951) 2. h. strathmann: ion-exchange membrane separation processes, elsevier, amsterdam (2004) 3. s. beszdes, zs. lászló, g. szabó, c. hodúr: enhancing of biodegradability of sewage sludge by microwave irradiation, hungarian journal industrial chemistry, 36 (2008), pp. 11–16 4. s. novalic, j. okwor, k. d. kulbe: the characteristics of citric acid separation using electrodialysis with bipolar membranes, desalination, 105 (1996), pp. 277–283 5. m. cytko, k. ishi, k. kawai: continuous glucose fermentation for lactic acid production: recovery of acid by electrodialysis, chemie ingenieur technik, 59 (1987), pp. 952–954 6. n. yoshiyuki, i. masayoshi, h. motoyoshi: acetic acid production by an electrodialysis fermentation method with a computerized control system. applied environmental microbiology, 54 (1988), pp. 137–142 7. s. novalic, t. kongbangkerd, k. d. kulbe: recovery of organic acids with high molecular weight using a combined electrodialytic process, journal of membrane science, 166 (2000), pp. 99–104 8. k. bélafi-bakó, n. nemestóthy, l. gubicza: study on application of membrane techniques in bioconversion of fumaric acid to l-malic acid, desalination, 162 (2004), pp. 301–306 9. e. molnár, m. eszterle, k. kiss, n. nemestóthy, j. fekete, k. bélafi-bakó: utilisation of electrodialysis for galacturonic acid recovery, desalination, 241 (2009), pp. 81–85 10. e. molnár, n. nemestóthy, k. bélafi-bakó: utilisation of bipolar electrodialysis for recovery of galacturonic acid, desalination, 250 (2010), pp. 1128–1131 11. g. l. miller: use of dinitro-salicylic acid reagent for determination of reducing sugar, analytical chemistry, 31 (1959), pp. 426–428 700 hungarian journal of industrial chemistry veszprém vol. 40 (2) pp. 69–75 (2012) effect of a new type of coupling agent on the mechanical properties of various multi-walled carbon nanotube/rubber composites cs. varga1 , b. tóth1, p. gergó1, l. bartha1 1university of pannonia, institutional department of mol hydrocarbon and coal processing, 10 egyetem str., 8200 veszprém, hungary e-mail: vcsilla@almos.uni-pannon.hu in our experimental work application of carbon nanotubes in rubbers have been investigated. the effects of the type of the rubber matrix, the concentration of the carbon nanotubes and the effects of a coupling agent on the mechanical properties of the composites have been studied. the strength of the rubber matrix had great influence on the strengthening behaviour of the carbon nanotubes. by application of surface treated carbon nanotubes the strength of the composites made from a rubber matrix having the tensile strength under 10 mpa could be improved by 35%. however, the composites from the rubber with higher tensile strength contained treated carbon nanotubes afforded balanced performance against fatigue stresses probably due to the effect of the coupling agent and the homogenous distribution of the carbon nanotubes. introduction rubbers reinforced with carbon black (cb) are used for numerous industrial applications, such as vibrationresistant structures, electromagnetic interface (emi) shielding materials, antistatic devices, etc. [1–4]. cb improves the mechanical properties (modulus and strength) of the rubber due to the interactions among the fillers and the fillers and the other components of the rubber. the cb particles were proven to form aggregates because of the strong bonding effects to each other. a part of the rubber is encapsulated in those aggregates because of the branched structures of the latter one and is shielded from macroscopic deformations [1]. small domain size is required for effective reinforcement. on the one hand only branched structures small enough (< 50 nm) can be trapped and thereby achieved a strongly bonded system, and on the other hand only the adequately small domains have high surface activity [1, 2]. in the last two decades researches focused on to substitute cb with another fillers (eg. caolin, sepiolite, sio2, zinc-disorbate, titania) also having reinforcing effects [4–6] and also on to reduce the particle size of the cb to improve their dispersion in the rubber matrix [2]. in the former step modification of the surface of the fillers had to be also solved because they are incompatible with the most organic matrices, therefore, coupling agents were being used [5, 7]. the fillers for substitution of cb like sio2 have been spread in the recent years especially due to the higher demand for non-black applications [7–11]. several solutions have been developed in the cb/rubber research area: as two step grinding technology, application of dispersants or coupling agents, pre-treatment of the carbon surface or chemical modification of the elastomer chains, moreover distribution of the cb in a latex solution instead of solid mixing [2]. not much significant improvements were achieved by the first three solutions. in case of the latter one the modification of the cb surface represented the largest difficulty in order to disperse them homogeneously in the water solution of latex [4, 12]. application of cb has been still significant because besides it can increase the strength of the vulcanized rubber; it also has a positive effect on the optical and electrical properties, and reduces production cost [3]. application of carbon nanotubes (cnt) may represent a breakthrough in rubber matrices either but only small quantities have been introduced because of their relatively high price. furthermore, by dispersion of the cnt arisen the same problems like the cb due to the high surface charge [13,114]. a lot of papers were published about cnt/epoxy and cnt/thermoplastic composites but only a very few about cnt/elastomers [4, 8, 15–18]. the most exciting challenge in the area of cnt containing composites was to solve the proportional dispersion of the cnt because absence of a well-homogenized morphology the distinguished mechanical improvements of the reinforcement can not be achieved in elastomers either. e.g. das and co-workers [19] used untreated and modified multi-walled carbon nanotubes (mwcnt) in a blend of styrene-butadiene rubber (sbr) and butadiene rubber (br) with 50/50 ratio. hydroxyl-groups were enacted to the surface of the modified mwcnt (nanocyl®3153), and bis(triethoxy-silylpropyl)tetrasulfone was applied as the coupling agent for bonding to the rubber. composites were manufactured by a two-roller mill and a stabilized non-ionic surfactant/ethanol solution was 70 used for mwcnt-treating. the coupling agent was applied in 2.5% related to the mass of the rubber. strength of composites containing 5% mwcnt could be enhanced from 1mpa to 4.5 mpa. the new process with the ethanol solution was more effective then other traditional methods in the given concentration range. similar properties were obtained by mwcnts having hydroxyl-groups. application of a silane type coupling agent did not significantly affect the mechanical properties. our research has been directed to the application of mwcnt in rubbers. the mwcnt has the same favourable effect in the point of view of the mechanical properties [20–22] as cb, and moreover by introduction of a proper coupling agent strong interaction can be established between the mwcnts and the rubber. as mwcnts have excellent mechanical properties they should have better strengthening effect than cb has. if mechanical properties of rubber composites can be improved to a large extent enough then the cost reduction can become less important. for the surface treatment of mwcnt an olefinmaleic-anhydride copolymer based coupling agent has been applied [24]. not only the possible effects of the coupling agent but also effects of the mechanical properties of the initial rubber matrix as raw material have also been investigated in mwcnt/rubber composites. 2. experimental 2.1. materials multi-walled carbon nanotubes (mwcnt) were produced at 700°c by chemical vapor deposition (cvd) process over fe-co bimetallic catalyst at the institutional department of chemical engineering (institute of chemical and process engineering, university of pannonia). purity of mwcnt was higher than 90 wt%, the diameter was between 10 nm and 20 nm, the average length was above 30 μm. natural rubber (nr) and styrene-butadiene rubber (sbr) based (r-i and rii) and nitrile-butadiene rubber (nbr) (acn content: 45%, mooney viscosity, 100°c: 60) based blends (riii) were used as matrix material. h n ch2 o o ch r2 o o ch2 ch3 ch3 n o ch2 o o r1 ch r2 o o ch2 ch3 ch3 k l m ch2 ch3 oh o ch2 ch3 o ch2 ch3 nh ch2 ch3 a a b b figure 1: structure of the ester-amide-imide derivative of the experimental olefin-maleic-anhydride copolymer (r1: alkyl group with length of the olefinic monomer (c16-c18); r2: alkyl group with r1-2 carbon number; a: 3-40, b: 3-32; k: 0,2-2; l: 1-7; m: 1-7 and n: 0,3-2) the coupling agent was produced at the institutional department of mol hydrocarbon and coal processing (institute of chemical and process engineering, university of pannonia) that was an ester-amide derivative of an experimental olefin-maleic-anhydride copolymer (figure 1). 2.2. preparation of composites compounds were prepared by a milling process. a tworoller mill was applied also for mixing the carbon nanotubes into the basic mixture of rubber. sheets of the mixtures were compression moulded at 180°c for 5 minutes vulcanization time. dog-bone samples for mechanical testing were cut from the sheets. compositions of the samples were given in table 1. table 1: composition of the different mwcnt/rubber composites sample rubber matrix type mwcnt content, wt% coupling agent, wt% c-1 r-i 0 c-2 r-i 1.0 c-3 r-i 1.0 0.2 c-4 r-ii 0 c-5 r-ii 1.0 c-6 r-ii 1.0 0.2 c-7 r-iii 0 c-8 r-iii 1.0 c-9 r-iii 1.0 0.2 c-10 r-iii 1.5 c-11 r-iii 2.4 c-12 r-iii 2.4 0.5 effects of the coupling agent were also studied by application with an experimental treating method developed for surface treating of mwcnts for pp [24]. surface of mwcnt was covered by the coupling agent from the hydrocarbon solution of the additive with stirring the mixture for 1 hour at 60°c then the solvent was distilled out. treated mwcnts were then dried at 110°c for 2 hours and were mixed into the basic mixture of rubber by a two-roller mill. r-i and r-ii matrices were nr and sbr based blends with lower and medium mechanical strength, riii matrix was an nbr based one with high mechanical strength. thus effects of the type of the rubber were also studied on the properties of the composites. mwcnts were applied in untreated and in treated form in order to investigate the influence of the coupling agent either. 2.3. measurement of tensile properties to determine the tensile and fatigue tensile properties (mainly stress, modulus and extension) (msz en iso 527-1-4:1999) an instron 3345 universal tensile 71 testing machine was used. the temperature in the laboratory was 23°c and the relative humidity was 50% during the mechanical tests which were carried out at 90 mm/min crosshead-speed both in case of tensile and fatigue tensile tests. structural information about the developed coupling agent was obtained by infrared technique with a tensor 27 type ftir1, illumination: sic globar light, detector: rt-dlatgs type) in the 400-4000 cm-1 wavenumber range. scanning electron microscopy (sem) was used to study the structure of fractured faces of the specimens and to follow the possible interaction between the reinforcements and the matrices. the applied apparatus was a phillips xl30 esem instrument. 3. results and discussion discussion of the results was divided into three parts. on the first hand effects of the type of the rubber matrix were detailed then on the second hand effects of the mwcnt concentration and finally the effects of the coupling agent were demonstrated. 3.1. effect of the change in the rubber matrix on the tensile properties in the present work effects of multi-walled carbon nanotubes (mwcnt) in three rubber matrices (signed as r-i, r-ii, r-iii) with different tensile strengths were investigated. different effects were measured for the rubber matrices (figure 2). introduction of mwcnts into the rubber either in treated or in untreated form resulted in both increase and in decrease of the tensile strengths. 0,0 4,0 8,0 12,0 16,0 20,0 r‐i r‐ii r‐iii te ns ile  s tr en gh t,  m pa sign of the rubber matrix rubber matrix untreated mwcnt treated mwcnt figure 2: effects of type of the rubber matrix on tensile properties (1wt% mwcnt-content) different effects were measured for the samples where treated mwcnts were incorporated. tensile strength enhanced from 8.6 mpa to 11.6 mpa meaning a 35% increase for the r-i matrix. meanwhile in the case of r-ii signed rubber the tensile strength reduced by 26% in the presence of untreated mwcnt. application of the coupling agent improved the tensile strength by 12% but tensile strength of the original matrix could not be achieved. tensile strengths of the mwcnt containing composites did not differ to that of the r-iii matrix having the highest tensile strength (19.2 mpa). 0,0 4,0 8,0 12,0 16,0 20,0 r‐i r‐ii r‐iii te ns ile  s tr en gh t,  m pa sign of the rubber matrix rubber matrix untreated mwcnt treated mwcnt figure 3: effects of type of the rubber matrix on fatigue tensile properties (1 wt% mwcnt, fatigue conditions: 100 cycles and 10 n) resistance of the samples against fatigue tensile stresses of 100 cycles and 10 n as loading force were also studied (figure 3). comparing the results of the fatigue tensile tests to those of the static tensile tests two important outcomes could be stated. first of all mwcnts in the rubber blends could either improve or deteriorate the mechanical properties depending on the type of the rubber matrices. on the second hand composites made from basic mixture of r-ii showed different behaviour than the others. fatigue tensile strength was found to have been deteriorated by 6.5% if the mwcnt was incorporated in untreated form. the opposite behaviour was experienced by mwcnts treated by the coupling agent since a 5% increase was measured. standard deviation (sd) was calculated to be 0.8 mpa for unteated and 1.0 mpa for surface treated mwcnt containing samples. elongation at break was also represented for both types of tensile tests (figures 4, 5). 0 50 100 150 200 250 300 350 400 r‐i r‐ii r‐iii el on ga ti on  a t  br ea k,  % sign of the rubber matrix rubber matrix untreated mwcnt treated mwcnt figure 4: effects of type of the rubber matrix on elongation at break (1 wt% mwcnt content) 72 considerations for the elongation at break were established similar to the tensile strength. type of the rubber was determinative in the evolution of the elongation at break (fig. 4) either. reinforcing rubber r-i with mwcnts the value of 250% of elongation at break significantly decreased due to the pristine mwcnts. changing the reinforcement to surface treated mwcnts an 18% improvement could be measured as the property increased to 290%. mwcnts even in coupling agent treated form deteriorated the elongation at break of r-ii rubber. 0 50 100 150 200 250 300 350 400 r‐i r‐ii r‐iii el on ga ti on  a t  br ea k,  % sign of the rubber matrix rubber matrix untreated mwcnt treated mwcnt figure 5: effects of type of the rubber matrix on elongation at break for fatigue tensile tests (fatigue conditions: 100 cycles and 10 n, 1 wt% mwcnt) elongation at break did not change if the matrix with the highest elongation was reinforced with mwcnts either in untreated or in surface treated form. regarding to the results for elongation at break after the fatigue tensile tests a more balanced picture could be drawn. approximately a 20% decrease was measured for r-i and r-ii matrices in the elongation at breaks for fatigue tensile testing compared to static tensile testing. but mwcnt containing composites had the same values for elongation at break both for r-i and for r-ii based samples even for fatigue tensile tests. there were not any significant effects of the coupling agent on the elongation at break of all the rubber matrices. 3.2. effect of carbon nanotube concentration in that chapter changes in tensile strength, tensile modulus and elongation at break of r-iii based composites was discussed in function of the concentration of the mwcnt. lower tensile strength was measured for r-iii matrix after fatigue tensile tests (figure 6). regarding to the static tensile strength approximately 1.5 wt% mwcnt was required for a slight increase. the fatigue tensile results were represented for the same fatigue load (10 n) with two different cycles: 100 and 1500 cycles (fig. 6). resistance of the rubber (riii) deteriorated with the duration of the fatigue test. the same trends were observed for carbon nanotube containing samples either. 2.4 wt% mwcnt was needed to exceed the tensile strength of r-iii after long time fatigue stresses. with lower concentration of mwcnts in the rubber there was no difference among the property at the same fatigue conditions. 14 16 18 20 r‐iii 1.0wt% mwcnt 1.5wt% mwcnt 2.4wt% mwcnt te ns ile  s tr en gh t,  m pa without fatigue 100 cycles 1500 cycles figure 6: effects of carbon nanotube concentration on the fatigue tensile strength (fatigue load: 10 n for both 100 cycles and 1500 cycles) figure 7 represented the effects of filler concentration on the tensile modulus. on the first hand, values of modulus by the static tensile test increased with the mwcnt content. the modulus of the samples containing 1 wt% mwcnt have been enhanced by 13% related to the reference. the same extent of improvement was measured for the other two mwcnt/rubber composites. fig. 7 showed the results for fatigue tensile test either. depending on the duration of the fatigue tests positive changes were getting lower with increasing mwcnt contents. in that case moduli for the fatigue conditions were compared to the results of the simple tensile test. all the reinforced samples performed higher tensile modulus than that of the rubber matrix, so toughness of the composites enhanced by incorporation of mwcnts. the modulus of the sample with 2.4 wt% mwcnt depended the less on the duration of fatigue stresses. that phenomenon could be related to orientation of the mwcnts into the direction of the periodic stresses based on previous experiments with carbon fibres. 0 2 4 6 8 r‐iii 1.0wt% mwcnt 1.5wt% mwcnt 2.4wt% mwcnt m od ul us , m pa without fatigue 100 cycles 1500 cycles figure 7: effects of carbon nanotube concentration on fatigue tensile modulus (fatigue load 10n) figure 8 reperesented changes in the elongation at break in the function of the mwcnt content. elasticity of the samples had been expected to decrease with the mwcnt content. thus, a reduction in elongation at 73 break was observed above 1 wt% mwcnts in the rubber. not a significant change was calculated for 1 wt% mwcnt/rubber samples. samples containing 2.4 wt% mwcnt had a value of 300% for elongation at break meanwhile the same property was 345% for the basic rubber. 0 50 100 150 200 250 300 350 400 r‐iii 1.0wt% mwcnt 1.5wt% mwcnt 2.4wt% mwcnt el on ga ti on  a t  br ea k,  % without fatigue 100 cycles 1500 cycles figure 8: effects of carbon nanotube concentration on fatigue elongation at break (fatigue load 10 n) 3.3. effect of surface treatment in that part of the paper effects of surface treatment were discussed on tensile and fatigue tensile properties. in figures either results of the unreinforced rubber matrix with composition r-iii or results of the composites containing 2.44 wt% mwcnt reinforcement were demonstrated. during the fatigue tensile tests a fatigue force of 10 n was applied with different duration times (100 and 1500 cycles). figure 9 represented the effects of untreated and coupling agent treated mwcnts on tensile strength and fatigue tensile strength of the unfilled rubber. changes for simple tensile test could be not significant both for untreated and treated mwcnt/rubber samples containing the same concentration of mwcnt. change was calculated to be below 5%. 14 16 18 20 r‐iii mwcnt 2.4% mwcnt 2.4% (treated) te ns ile  s tr en gh t,  m pa without fatigue 100 cycles 1500 cycles figure 9: effects of surface treatment on fatigue tensile properties (fatigue load: 10 n) the same trend was observed for the fatigue tensile tests. as fig. 9 clearly showed, values of fatigue tensile strength slightly decreased for the rubber matrix and the pristine mwcnt/rubber composites with the increasing number of fatigue cycles. however, the composite containing surface treated mwcnts afforded more balanced performance even for a long period of fatigue stress (1500 cycles) in the given range of concentration and the coupling agent has a higher stabilizing effect in the composite. 0 2 4 6 8 r‐iii mwcnt 2.4% mwcnt 2.4% (treated) m od ul us , m pa without fatigue 100 cycles 1500 cycles figure 10: effects of surface treatment on fatigue tensile properties of the composites (fatigue load: 10 n) in figure 10 the effects of the surface treated mwcnts were demonstrated on the tensile moduli in function of number of fatigue cycles. due to application of mwcnts in the rubber matrix the values of modulus enhanced compared to the rubber since the aforementioned reinforcing material can increase toughness of plastics, elastomers and rubbers. resistance against fatigue stresses were also showed in fig. 10. the values of modulus have been increased both for untreated and treated mwcnt containing samples compared to the initial rubber matrix independently from duration of the fatigue stress. almost the same moduli were determined for both mwcnt/rubber composites at the same level of fatigue conditions. surface treatment was concluded not to have significant effects on tensile modulus but more balanced behaviour was experienced for treated mwcnt/rubber samples. 0 50 100 150 200 250 300 350 400 r‐iii mwcnt 2.4% mwcnt 2.4% (treated) el on ga ti on  a t  br ea k,  % without fatigue 100 cycles 1500 cycles figure 11: effects of surface treatment on fatigue tensile properties of the composites (fatigue load: 10 n) figure 11 demonstrated the effects of both forms of mwcnts on the elongation at break for distinct fatigue duration. values of elongation at break for mwcnt/ rubber composites were measured to be below the value of the rubber matrix. the trends were the same both for simple and for fatigue tensile tests. results were observed to be more balanced for coupling agent treated mwcnt reinforced rubber in that point of view too. although elongation at break for the original rubber matrix was the highest among all the 74 samples regarding the tensile test but after a longer fatigue tensile test significant (13%) deterioration was obtained and the value of the treated mwcnt/rubber was less sensitive against fatigue stresses. 3.4. sem homogeneity of the samples based on r-i rubber was studied on the sem graphs of the broken surface of the composites (figure 12–14). figure 12: sem graph of the broken surface of the original rubber matrix figure 13: sem graph of the broken surface of the pristine cnt containing rubber composite figure 14: sem graph of the broken surface of the coupling agent treated cnt containing rubber composite components of the rubber formula were clearly remarked (white spots) on sem graph of all the samples. difference was observed between the carbon nanotube containing samples. composites with untreated cnts showed a less smooth surface after tensile test than samples with surface treated reinforcements. narrower and more homogeneous particle size distribution was experienced on the surface of coupling agent treated carbon nanotube/rubber samples indicating higher degree of compatibility of the components which could probably result the improvement of the mechanical properties. conclusion our research has been directed to the application of mwcnt in rubbers in which effects of an olefinmaleic-anhydride based coupling agent was also studied. the results were summarized as follows: application of carbon nanotubes in a rubber matrix could both enhance and deteriorate the mechanical properties of the composites depending on the types and strength of the original rubber mixture. difference in the behaviour in mwcnt containing composites could be experienced during the fatigue tensile test, which could be important especially for rubber products. at least 2.4 wt% mwcnt was required to achieve better performance during long time fatigue than the rubber matrix with the highest tensile strength (r-iii). acknowledgement we acknowledge the financial support of the work by the hungarian state and the european union under the támop-4.2.2/b-10/1-2010-0025 project. authors are also grateful to the project of baross gábor program (reg_kd_09_2-2009-0026) for the financial support. references 1. b. omnes, s. thuillier, p. pilvin, y. grohens, s. gillet: compos part a, 39 (2008), pp. 1141–1149 2. x. he, z. peng, n. yu, j. han, c. wu: compos sci technol, 68 (2008), pp. 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application dealing with these difficult cases. the test measurement evaluation results justify the theoretical model. on the basis of the theory a very simple measurement method is proposed for the determination of the coating defects ir-free potentials. keywords: cathodic protection, ir-free potential, pipeline corrosion, coating defect 1. introduction the cathodic protection is a widely used, robust and reliable method of corrosion protection of underground pipelines, tank bottoms and underwater parts of immersed structures, e.g. ships and drilling platforms. in the past eight decades a lot of experience has been accumulated concerning the applicability and limitations of cathodic protection. in the most widespread type of cathodic protection, the impressed current systems, the structure to be protected is connected to the negative output of a dc current source („cp station”) and the positive output is connected to a so-called earthing anode which serves for the closing of the electrical circuit (see a typical arrangement for a cathodically protected pipeline in figure 1). the output of the dc source is variable and, in modern devices, can be regulated, either for constant potential or for constant current. if no cathodic protection is applied to a structure corroding in water or soil and no net current is flowing through the structure, then the sum of the anodic (corrosion) and cathodic currents is zero. the ultimate criterion of the effectiveness of cathodic protection is the level of suppression of the anodic current. this can be achieved with the cathodic polarization of the structure. the decrease of the anodic current cannot be measured directly. however, if the applied potential is sufficiently negative (cathodic) then the anodic current (and the corrosion rate) is suppressed, with increasing cathodic polarization theoretically beyond any limit; practically a decrease of 1–2 orders of magnitude can be implemented, which is satisfactory for the practical requirements in most cases. in conclusion, the negative polarization of the structure results in the suppression of the anodic current (this was the goal) and in the increase of the cathodic current, which is an unavoidable consequence of the potential shift, sometimes with unfavourable side effects. during the past decades a lot of empirical experience has been accumulated concerning the optimal operation conditions of cathodic protection. it has been assumed for a long time that cathodic protection has the best performance in typical applications in soils if the electrode potential of the structure is more negative than -850 mv, measured against a saturated copper/copper sulphate electrode [1] (its standard potential at 25°c is 320 mv; all potential data will be given against this type of reference electrode unless specified otherwise). the lower limit of the potential varies for different applications but it is typically assumed to be between 1100 and 1300 mv1. the electrode potential, as discussed above, is the potential that can be measured with a reference electrode placed to the direct vicinity of the electrode, i.e. which does not include any component from the ohmic potential drop through the electrolyte2. this potential, called as ir-free potential, is a central concept in cathodic protection. 1 at more negative potential the excessive rate of cathodic current may have adverse effects on the structure or on the coating. 2 there is another source of the ohmic potential drop, namely, the drop in the electric conductor, which can also be significantly high in the case of pipelines, but this source will not be dealt here; in this paper the ohmic drop is understood as the ohmic potential drop through the electrolyte between the anode and the cathode. 78 figure 1: schematic arrangement of cathodic protection and potential measurement circuitry the determination of the exact value of the ir-free potential is practically impossible in case of buried structures and with conventional methods. this paper is dealing with the mathematical properties of the electric field of the cathodic protection system and provides a simple method to give a good approximation of the irfree potential, with significant practical advantages that are facilitated by making use of the remote earth potential. the discussion below is dealing specifically with the case of coated, buried and cathodically protected steel pipelines. however, the situation with tanks bottoms and other buried structures is quite similar. for offshore and underwater structures the theory also applies but the application technology is slightly different – these cases will be dealt with in separate communications. 2. discussion 2.1. review of the conventional ways of determination of the ir-free potential in the first times of application of cathodic protection the cathodic protection was assumed as effective if the polarized potential was more negative to the opencircuit potential. it was realized very soon that the measured potential value was dependent on the location where the reference electrode was placed (owing to the location-dependent ohmic potential drop) and the need of a criterion of effectiveness was also recognized. the determination of the ir-free potential was carried out by the switching off the current source. this technique is routinely used in the laboratory electrochemical measurements, too. the determination of the ohmic drop compensated corrosion potential of a cathodically protected structure has an enormous literature. a short but concise general overview on the topic was given by bushmann and rizzo [2]. in the standard practice of cathodic protection nowadays the determination of the ir-free potential is carried out by periodically switching the current source off and on. typically a pattern of 2–4 seconds switched on and 0.5–1 second switched off is implemented (the time values may also vary in a wider range). the potential measurements are carried out after a delay of at least 0.1 second, in order to eliminate the effect of the inductive transients (these appear in case of long pipelines and large currents only). the potentials measured with cp stations turned on and off are generally named as on potential and off potential respectively. under field conditions in many cases it is nearly impossible or at least very cumbersome, expensive and time-consuming to switch all the cp stations that are effective in a certain area. if some of the current sources remain switched on while measuring the off potential that results in a major bias in assessing the ir-free potential. this bias may be up to a few hundreds of millivolts in extreme cases, and often leads to erroneous conclusions with respect to the level of protection of structures, sometimes with serious consequences. in spite of these obvious deficiencies, in the industrial practice in most cases the measured off potentials are identified with the ir-free potentials. another source of the uncertainties in assessing the ir-free potential via the off potentials is the ohmic potential drop generated by the equalizing currents flowing between the more and less polarized parts of the structure. stray current sources can also falsify the conventional ir-free potential determinations via the measured off potentials. nowadays typically gps-driven, high precision clock operated interrupters are applied in cp measurements, which facilitate an increased measurement precision and reliability. some manufacturers also provide cp stations with built-in interrupters and remote control options. 2.2. an alternative way of calculation of the ir-free potential from measurement data in spite of the enormous progress in measurement technique and the apparent inadequacy of the determination of the ir-free potential via the off-potential, no much progress has been achieved in the theory and in the evaluation of the measurement data. let us assume a cathodic protection system with an anode and a single coating defect at some part of the protected structure. the potential profile as a function of the distance between the coating defect and the anode is shown in figure 2. the potential field of the coating defect is defined as the domain where the potential is more negative than the remote earth potential and the potential gradients are directed towards the coating defect. figure 2: potential relations in the area of the anode and the coating defect surface equipotential lines coating defect test point potential meter reference electrode protected pipeline cp station anode interrupter with timer current flux vectors 79 let us mark two points in the potential field of the coating defect as p1 and p2. these two points determine two equipotential surfaces that surround the coating defect. also, these equipotential surfaces mark a domain of the space with a definite and constant (i.e. independent from the current flux) electrical resistance. let r1 and r2 be the ohmic resistance between the coating defect and the points p1 and p2 respectively. further on, let us assume that some perturbation is applied to the cp system, i.e. the current is interrupted (completely or partially – it is indifferent from the point of the model). from ohm’s law it follows that off off x x i eer 0− = , offon off x on x x ii eer − − = , (1a, b) where x=1.2 refers to any of the two surfaces and the on and off superscripts refer to the potential or current in the respective states. e0 is the ir-free potential of the coating defect3. expressing rx and rearranging the equation, the irfree potential can be expressed as: ( ) offon off on x off x off x ii ieeee − −+=0 . (2) if ioff=0, i.e. all the current is switched, then eq. 2 is simplified to e0=eoff, that is, the measured off potential is equal to the ir-free potential. however, if ioff≠0 then the determination of eo from eq. 2 is impossible, because the current values are indeterminable. let ioff and ion be expressed from the rearrangement of eq. 1a (for the determination of ion the off superscripts have to be changed to on, but this is allowed because the equation is valid also in the on state of the system). from ohm’s law it is obtained that 2,1 21 r eei offoff off − = , (3a) 2,1 21 r eei onon on − = , (3b) where r1,2 is the resistance between the two distinct equipotential surfaces. substituting eq. 3a and eq. 3b into eq. 2 it follows that ( )( ) ( )offoffonon offoff on x off x off x eeee eeee ee 2121 21 0 −−− − − += , (4) where x=1.2. 3 throughout in this paper it is assumed that the polarization resistance is negligible to the ohmic resistance of the soil between the coating defect and the point of the reference electrode. in most practical cases of buried structures in soil this assumption is valid. effects of the transient decay of the charge/discharge of the electrochemical double layer and other transients related to the inductivity of the pipelines will be dealt with in a separate paper. by means of eq. 4 the ir-free potential is obtained from measurable potential data also in the case if the current, flowing to the coating defect, is interrupted only partially or perturbated in any other way. let us introduce the following notation: )()( 2121 21 offoffonon offoff eeee ee −−− − =ρ , (5) and note that ρ is the quotient of the “not switched” and “switched” currents, flowing to the coating defect, and thus is invariant within the potential field of a certain coating defect. ρ is named foreign current ratio hence because it denotes the ratio of the foreign (i.e. not switched) and switched current. using eq. 5, eq. 4 can be rewritten as ρ)( onoffoff eeee −+=0 , (6) where the x subscripts are no more needed because the equation is valid for potentials measured at any point in the potential field of the coating defect. by means of this calculation the value of the ir-free potential, which is not directly measurable if any current is flowing in the off state, can be determined by means of measurable potential data. an equation formally analogous to eq. 6 had earlier been reported by baeckmann and schwenk [3], but the evaluation presented in their work is started from a quite different approach and also their conclusions are very different. the practical implementation of their measurement method is published in [4]. an important consequence of eq. 6 is that e0 and ρ are linearly dependent if eoff and eon are substituted with the constant values of the remote earth potentials: ρ)(0 onoffoff eeee ∞∞∞ −+= , (7) taking into consideration that for the determination of ρ it is not necessary to connect to the structure with a measurement cable because it is calculated from the differences of potentials at two different places in the on and off state (cf. eq. 5 and fig. 1), eq. 7 provides a simple and fast method to determine the ir-free potential of coating defects where there is no test post in the vicinity. this method is a powerful alternative of the widely used cips (close interval potential survey) or intensive surveys [4]: the coating defect ir-free potentials are practically calculated from potential gradient data and the remote earth potentials recorded with a static data logger. further, by fitting the data received on different coating defects in a cathodic protection system using eq. 7, it is possible to provide data quality control facility: those data which are not fitting on the linear relationship and deviate over a threshold value are to be discarded. this is a unique feature in the practice of cathodic protection. 80 2.3. a practically important case: more coating defects in a system the calculation in section 2.2 is strictly valid if the cathodic protection system includes one anode and one coating defect. obviously, real systems are more complicated. further difficulty is that in real systems the potential of the coating defects is varying; small coating defects with less ohmic potential drop4 can be polarized to a more negative potential than the larger coating defects. this potential difference between the coating defects generates equalizing currents superimposed on the cathodic protection current and, consequently, on changing of the shape of the cathodic protection current vector space, the shape of the equipotential surfaces will be also changed. therefore the resistance between two equipotential surfaces, denoted as r1,2 above, will not be the same quantity for the on and the off state in eq. 3a and eq. 3b. this problem can be diminished by selecting the optimal measurement points for which the equipotential surfaces have the possible smallest distortion caused by the equalizing currents of vicinal coating defects. obviously, the closer the measurement point is to the coating defect the less the shape of the equipotential surface varies on changing of the equalizing current flowing to/from the vicinal coating defect. on the other hand, the remote earth potential is also invariant to the local changes in the vicinity of any coating defect. in conclusion the point nearest to the coating defect (where the measured potential has an extreme as a function of the surface coordinates) and the remote earth potential are to be chosen to maximize the precision of the determination of the ir-free potential. 3. experimental verification 3.1. conditions in order to verify the above conclusions, a test measurement was conducted on a pipeline. the pipeline was a dn 300 gas transfer line with polyethylene coating which was known to be in a bad condition. the measurement was a modified cips carried out with a cpm 401 universal cathodic protection diagnostic measurement system. unlike conventional cips measurements, here the two reference electrodes of the mobile data logger measured different potentials: one reference electrode (electrode no. 2) was measuring the potential above the pipeline and the other electrode (electrode no. 1) was measuring the potential some 3 m apart from the pipeline (cf. fig. 1). in this way the potential gradient, perpendicular to the axis of the 4 a smaller coating defect has a higher resistance. however, the resistance of a coating defect decreases (approximately) linearly with the diameter of the coating defect, while the electrode surface increases with second order. therefore a larger coating defect will always give larger ohmic potential drop in case of a similar geometry. pipeline, was determined both for the on and off states from the data of the mobile data logger. the switching time was 3 second on and 1 second off, the delay time after the switching was 0.1 second and the sampling time was also 0.1 second. the remote potentials were measured with a static data logger. 3.2. results the on and off potential data for the two mobile reference electrodes and the remote potentials are shown in function of the distance in figure 3, which also includes the ir-free potentials calculated for the localized coating defects determined by means eq. 4 and eq. 7. the ir-free potential as a function of the foreign current ratio (both determined from the data of the mobile data logger, based on eq. 4 and eq. 5) are shown in figure 4, with the best fitting line. as follows from eq. 7, the slope of this linear relationship gives the difference of the remote earth on and off potentials and the intercept gives the remote earth off potential. the obtained data, compared to the average of the experimentally measured ones are included in table 1. the “calibration curve” of the ir-free potentials obtained from eq. 4 and from eq. 7, using the remote earth potential data and the foreign current ratio obtained from the mobile logger data are shown in figure 5 (the line is the y=x calibration line) and the numerical values, with the absolute value of the differences are shown in table 2. 3.3. evaluation in fig. 3 six well developed coating defects are localized. the coating defects at 24 and 40 meters are very large, most likely they are more or less continuous series of coating defects of different sizes and positions. they are assumed to be “open” coating defects, where the damaged coating does not cover the exposed pipe area and the larger the coating defect the more positive the ir-free potential. the coating defect at 68 meter is presumably a blistering, because the apparent size is very small but the ir-free potential is very positive which is the sign of high ohmic potential drop due to the “coverage” by the damaged coating. the coating defects at 95, 125 and 130 meters are decreasing in apparent size but shifting to positive direction in ir-free potential and from this tendency it is assumed that their “coverage” is increasing. in conclusion, coating defects of different sizes and types are detected on the selected relatively short pipe section. 81 figure 3: measured and calculated potential data of the test measurement vs. distance figure 4: ir-free potential data, calculated via eq. 4, vs. foreign current ratio figure 5: calibration of ir-free potential data calculated via eq. 7 vs. ir-free potential data calculated via eq. 7 fig. 4 justifies the assumptions of eq. 7. the linear relationship between the foreign current ratio and the ir-free potential has a “double nine” (0.993) correlation coefficient. this data has to be qualified considering the extreme differences in type and size among the coating defects. this relatively good result has to be considered also in the light of the fact that the first two defects are actually a series of defects, which decreases the applicability of the theory of the equipotential surfaces. in short, these circumstances can be considered as a near-worst-case scenario. according to eq. 7, the remote potentials can be determined from the ir-free potential vs. foreign current ratio plot. from tab. 1 a moderate difference of a few tens of millivolts is concluded which justifies the theoretical expectations. table 1: comparison of measured and calculated values of remote earth potentials parameter measured /v calculated from eq. 7/v absolute value of difference/v slope ( )onoff ee ∞∞ − 0.284 0.262 0.022 intercept ( )offe∞ -1.269 -1.229 0.04 table 2: values of ir-free potential at the coating defects, calculated from eq. 4 and eq. 7 distance/m calculated from eq. 4/v calculated from eq. 7/v absolute value of difference/v 24 0.748 0.746 0.002 40 0.780 0.804 0.023 68 0.780 0.776 0.004 95 1.010 1.034 0.025 126 0.940 0.956 0.016 131 0.871 0.863 0.008 average 0.013 from eq. 7 it is also concluded that the ir-free potential of a coating defect can be determined from the potential differences measured with the two reference electrodes of the mobile data logger (i.e. it is not necessary to apply a contact to the pipeline (cf. fig. 1)). in tab. 2 it is shown that the error of the determination of the ir-free potentials using eq. 7, compared to the data using eq. 4, are an average of 13 mv which is far below the practically required precision limit. summary it has been shown that based on the concept of the equipotential surfaces and ohm’s law a linear formula can be provided for the determination of the ir-free potential. the precision of the formula is the highest if the points used for the determination of the foreign current ratio are the points nearest to the coating defect (i.e. where the measured potential data have an extreme) and the remote earth. the theory also provides the value of the foreign current ratio. it was pointed out that the foreign current ratio and the ir-free potential are in a linear relationship where the coefficients of the linear relationship are related to the remote earth on and off potentials. this relationship establishes the connection between the “global” remote 82 and the locally, above the pipeline measured potentials. also this relationship provides an alternative method for the assessment of the ir-free potential, which does not require a measuring cable to be pulled alongside the pipeline. all these theoretical results were confirmed with a test measurement made on a section of pipeline with coating defects of different size and type. the evaluation of the test measurements justified the theoretical assumptions and proved that the determination of the ir-free potential, based on the measurement of the overthe-line potential gradients and the remote on and off potential, is applicable and accurate enough for the practical requirements. references 1. r. j. kuhn: bureau of standards, 73b75 (1928) 2. j. b. bushmann, f. e. rizo: materials performance, july, 1978 3. w. von baeckmann, w. schwenk and w. prinz (editors): handbook of cathodic protection, gulf professional publishing (1997), pp. 88–96 4. w. von baeckmann, h. hildebrand et al.: werkstoffe und korrosion, 34 (1983), 230–235 hungarian journal of industrial chemistry veszprém vol. 40 (2) pp. 83–86 (2012) study on analysis of antibiotic compounds from enthomopathogenic bacteria by ft-ir d. vozik1, j. madarász2, z. csanádi1 , a. fodor3,4, k. dublecz4, k. bélafi-bakó1 1university of pannonia, faculty of engineering, research institute on bioengineering, membrane technology and energetics, 10 egyetem str., 8200 veszprém, hungary 2university of pannonia, faculty of engineering, department of organic chemistry, 10 egyetem str., 8200 veszprém, hungary 3university of pannonia, georgikon faculty, institute of plant protection, 16 deák f. str., 8360 keszthely, hungary 4university of pannonia, georgikon faculty, department of animal sciences, cepo group, 16 deák f. str., 8360 keszthely, hungary e-mail: csanadi@almos.uni-pannon.hu entomopathogenic bacteria produce antibiotic molecules effective against plant, animal and human plant pathogenic bacteria. they produce broad-spectrum antibiotics, which can be applied in several different fields where suppression of microbes is needed. these antibiotic molecules have different chemical structure such as peptides. analysis and identification of these molecules provide useful ways in the research and development of drugs and agrochemicals. keywords: entomopathogenic bacteria, antimicrobial activity, peptides, analysis introduction insect pathogenic or entomopathogenic nematodes (epn) and their symbiotic entomopathogenic bacteria (epb) can be used as microbial control agents against agricultural insect pests [1]. these nematodes of heterorhabditis and steinernema species are symbiotically associated with the members of the bacteria family enterobacteriaceae as photorhabdus and xenorhabdus species, respectively [2–3]. the epb have several special functions in this symbiotic relationship. one of them is the production ability of broad-spectrum antibiotics, which keep monoxenic conditions in insect cadavers in soil [4]. antibacterial resistance is increasing worldwide. the compounds produced by epn symbiotic bacteria have showed a wide range of bioactivities of medicinal and agricultural interest, such as antibiotic, antimycotic and insecticidal effects [5]. these antimicrobial peptides have been successfully applied in pharmaceutics, plant disease control and many other fields [6]. antimicrobial peptides have many beneficial characteristics, such as broad-spectrum antibiotic activity, thermal stability, and low molecular weight, and most significantly, compared with most antibiotics, they are not easy to lead to the development of resistance in the target [7]. these compounds were reported as showing in vitro activity against gram-positive bacteria, including for example the multi-drug resistant strain of staphylococcus aureus. they have diverse chemical structures including peptides as well [5]. analytical study of these molecules can be achieved in different ways. edman degradation, developed by pehr edman [8], is a method of sequencing amino acids in a peptide. in this method, the amino-terminal residue is labeled and cleaved from the peptide without disrupting the peptide bonds between other amino acid residues. a major drawback to this technique is that the peptides being sequenced in this manner cannot have more than 50 to 60 residues (and in practice, under 30). the peptide length is limited due to the cyclical derivatization not always going to completion. the infrared spectrum of a protein provides a wealth of information on structure and environment of the protein backbone and the amino acid side chains [9]. this makes infrared spectroscopy an extremely useful tool for the investigation of protein structure. the absorption of a side chain in a protein may deviate significantly from their absorption in solution or in crystal. the special environment provided by a protein is able to modulate the electron density and the polarity of bonds, thus changing the vibrational frequency and the absorption coefficient. therefore, the band positions given in reviews should be regarded only as guidelines for interpretation of spectra [10]. in this study, we aimed the isolation and analysis of some peptide-type antibiotic compounds from two epb strains. 84 material and methods antibacterial peptide-producing entomopathogenic bacteria were xenorhabdus budapestensis (ema) and xenorhabdus szentirmaii (emc). they were cultured in luria broth (lb and lba) liquid and solid media as previously described [11]. cell-free culture media (cfcm) were prepared as follows: aliquots of the stock culture were added separately into 900 ml sterile medium. the flasks were incubated in a shaker at 200 rpm and 30ºc for 24 h and centrifuged at 13 000 rpm (10 000 g for 30’). after centrifugation the supernatant was filtrated through express plus filter (0.22 µm) (merck millipore). purification of antimicrobial compounds: 1000 ml of cfcm was mixed with activated amberlite xad polymeric adsorbent in a 1:20 ratio and incubated for 24 h. the resin-cfcm mixture was filtered through millipore express plus filter of 0.22 µm pore-size and washed subsequently with 200 ml of distilled water, 200-200 ml of 25 v/v%, 50 v/v% and 80 v/v% methanol (meoh), removing all inactive compounds by this way. after this the resin was washed with 200 ml cc. meoh:hcl (99:1) and 200 ml i-propanol (iproh) to eluate biologically active compounds. these samples were evaporated by vacuum distillation and resulted samples with meoh and iproh, respectively. for the analysis of the purified antimicrobial compounds a thermo nicolet avatar ft-ir-330 ftir apparatus was used to determine ft-ir spectra and a hitachi u-2910 uv-vis spectrophotometer was used to form the uv spectra. solid samples were prepared for the ir: some quantity of samples were ground with purified kbr and this mixtures were pressed in a mechanical press to form a transparent pellet through which the beam of the spectrometer can pass. resolution: 2.000 cm-1, scans: 16. results and discussion the most precise method for the protein and peptide identification after their separation by high-performance liquid chromatography (hplc) is mass spectrometry [12]. however, this method is quite expensive. absorbance at low wavelength (<220 nm) detects peptide bonds and amino acid residues with detection limits between nanomoles and picomoles. peptides having aromatic residues (phenylalanine (phe), tyrosine (tyr), and trypthophan (trp)) can be detected at 254 or/and 280 nm. for this reason we made a uv spectra of the purified antibiotic activity compounds. results of these measurements are shown in table 1. table 1: uv absorbance (nm) of the antibiotic compounds ema emc iproh meoh iproh meoh 201 203 200 202 213 218 217 ir spectra were made with the above described method. results of these measurements are shown in figures 1–4. figure 1: antibiotic compounds purified with iproh from ema figure 2: antibiotic compounds purified with meoh from ema in the case of amino acids only two side chain moieties absorb in spectral regions that are free from overlapping absorption by other groups and thus allow the spectroscopists an unambiguous assignment without further experiments. these are the sh group of cysteine (2550–2600 cm-1) and the carbonyl group of protonated carboxyl groups (1710–1790 cm-1). these groups were obtained in none of the ir spectra. figure 3: antibiotic compounds purified with iproh form emc 85 all other side chain absorption overlap with the absorption of other side chains or of the polypeptide backbone and further experiments are needed to assign an absorption band to a specific side chain moiety. figure 4: antibiotic compounds purified with meoh from emc the ν(c=o) vibration of glutamine side chains near 1680 cm-1 is a relative strong infrared absorber, the bands are sensitive to h-bonding and the band position is lower the stronger the h-bond is (table 2, 3). the ν(c=o) vibration of the deprotonated carboxylate group of the glutamate shows two strong bands near 1400 and 1570 cm-1 for symmetric and antisymmetric stretching vibration, respectively (tab. 2, 3). the ν(cn) vibration of histidine is a useful band near 1100 cm-1 (tab. 2, 3). tyrosine is a relatively strong infrared absorber due to its polar character. the most intense bands originate from ν(cc), the ν(c-o) and the δ(coh) mode near 1517, at 1235–1270 and at 1169–1260 cm-1 (tab. 2, 3). table 2: the ir spectra of ema antibiotic compounds with different eluents band position in cm-1 assignment iproh meoh 1659 1654 glutamine (ν(co) in proteins 1659–1696 cm-1) 1634 1638 histidine (ν(c=c) in proteins 1617 cm-1) 1605 tyrosine (ν(cc) ring in proteins 1615 cm-1) 1548 1556 glutamine (νas(coo-) in proteins 1553–1575 cm-1) 1520 tyrosine (ν(cc) ring, δ(ch) in proteins 1516–1518 cm-1) 1446 lysine (δ(ch2) in proteins 1445 cm-1) 1409 1405 glutamine (νs(coo-) in proteins 1397–1424 cm-1) 1246 1234 tyrosine (δ(coh) in proteins 1228–1250 cm-1) 1108 1082 histidine (ν(cn), δ(ch) in proteins 1094–1114 cm-1) while the δas(ch3), the δ(ch2) and the δs(ch3) vibration near 1465, 1450 and 1375 cm-1 are relatively good group frequencies, the δ(ch) and γ(ch2) vibrations are often coupled to other modes (tab. 2, 3). the only tryptophan bands with considerable infrared intensity seem to be those at 1334 and 1455 cm-1 (tab. 2, 3). table 3: the ir spectra of emc antibiotic compounds with different eluents band position in cm-1 assignment iproh meoh 1653 glutamine (ν(co) in proteins 1659–1696 cm-1) 1640 histidine (ν(c=c) in proteins 1617 cm-1) 1548 1542 glutamine (νas(coo-) in proteins 1553–1575 cm-1) 1446 1452 tryptophane (ν(chb)a, ν(ccb)a, ν(cn) in proteins 1455 cm-1) / lysine (δ(ch2) in proteins 1445 cm-1) 1403 1406 glutamine (νs(coo-) in proteins 1397–1424 cm-1 1336 tryptophane (ν(ccp)a, ν(cn) in proteins 1334 cm-1)/ lysine (γ(ch2), γ(ch2) in proteins 1345 cm-1 1246 1245 tyrosine (δ(coh) in proteins 1228–1250 cm-1 1201 tryptophane (ν(cc) 1203 cm-1 1152 proline (γ(ch2), 1168 cm-1 1085 1084 histidine (ν(cn), δ(ch) in proteins 1094–1114 cm-1) “b” and “p” indicate vibrations of the benzene or pyrole moieties, respectively. acknowledgement this work was partly supported by cepo, the austrianhungarian cooperation project for poultry excellence centre, working within the frame of erfa between 2007–2013 and támop-4.2.2/b-10/1-2010-0025. references 1. g. c. smart: entomopathogenic nematodes for the biological control of insects, journal of nematology, 27 (1995), pp. 529–534 2. g. m. thomas, g. o. poinar: xenorhabdus gen. nov., a genus of entornopathogenic, nematophilic bacteria of the family enterobacteriaceae, international journal of systematic bacteriology, 29 (1979), pp. 352–360 86 3. n. e. boemare, r. j. akhurst, r. g. mourant: dna relatedness between xenorhabdus spp. (enterobacteriaceae), symbiotic bacteria of entomopathogenic nematodes, and a proposal to transfer xenorhabdus luminescens to a new genus, photorhabdus gen. nov.. international journal of systematic bacteriology, 43 (1993), pp. 249–255 4. r. j. akhurst: antibiotic activity of xenorhabdus species, bacteria symbiotically associated with insect pathogenic nematodes of the families heterorhabditidae and steinernematidae, journal of general microbiology, 128 (1982), pp. 3061–3065 5. j. m. webster, g. chen, k. hu, j. li: bacterial metabolites, in: entomopathogenic nematology, cabi publishing, usa (2002), pp. 99–115 6. y. j. gordon, e. g. romanowski, a. m. mcdermott: a review of antimicrobial peptides and their therapeutic potential as anti-infective drugs, current eye research, 30 (2005), pp. 505–515 7. y. xiao, f. meng, d. qiu, x. yang: two novel antimicrobial peptides purified from the symbiotic bacteria xenorhabdus budapestensis nmc-10, peptides, 35 (2012), pp. 253–260 8. p. edman, e. högfeldt, l. g. sillén, p. o. kinell: method for determination of the amino acid sequence in peptides, acta chemica scandinavica, 4 (1950), pp. 283–293 9. a. barth: the infrared absorption of amino acid side chains, progress in biophysics & molecular biology, 74 (2000), pp. 141–173 10. b. hernandez-ledesma, l. amigo, m. ramos, i. recio: application of high-performance liquid chromatography-tandem mass spectrometry to the identification of biologically active peptides produced by milk fermentation and simulated gastrointestinal digestion, journal of chromatography a., 1049 (2004), pp. 107–114 11. e. m. motitu: evaluating antibacterial potential of entomopathogenic bacterium strains on agriculturally important plant pathogenic bacteria. master thesis, university of pannonia, georgikon faculty, institute of plant protection, keszthely, hungary (2011) 12. t. herraiz: sample preparation and reversed phase-high performance liquid chromatography analysis of food-derived peptides, analytica chimica acta, 352 (1997), pp. 119–139 hungarian journal of industrial chemistry veszprém vol. 40 (2) pp. 87–91 (2012) biocatalytic hydrogen sulphide removal from gaseous streams g. tóth , é. lövitusz, n. nemestóthy, k. bélafi-bakó university of pannonia, research institute on bioengineering, membrane technologies and energetics, 10 egyetem str., 8200 veszprém, hungary e-mail: tothgabor2@gmail.com hydrogen sulphide is one of the most important substances responsible for unpleasant odour emissions in gas phase. it is often formed in higher concentration beyond other sulphur containing volatile compounds like methane thiol (mt), dimethyl sulphide (dms) and dimethyl disulphide (dmds). removal of hydrogen sulphide is usually carried out by physical-chemical methods (e.g. adsorption), but nowadays some bio-processes may be considered as promising alternatives. certain sulphur oxidising thiobacteria can be successfully applied for hydrogen sulphide conversion from gaseous streams like biogas. various strains have been applied so far for degradation of hydrogen sulphide, they belong mostly to the group of thiobacillus, which are autotrophic microorganisms. these autotrophic bacteria have the drawback in application that they grow slower than the heterotrophic ones and it is more difficult to control their growth. a number of chemotrophs are suitable for the biodegradation of h2s. these bacteria grow and produce new cell material by using inorganic carbon (co2) as a carbon source and chemical energy from the oxidation of reduced inorganic compounds such as h2s.the objective of the work described here was to study the ability of elimination of hydrogen sulphide by two chemotrophic microorganisms (thiomonas intermedia, thiobacillus thioparus) in a batch bioreactor. the other aim was the study of the immobilization of these bacteria to different supports. keywords: hydrogen sulphide, chemotrophic, biological oxidation thiomonas intermedia, thiobacillus thioparus, batch reactor, support introduction volatile sulphuric compounds like methane thiol (mt), dimethyl sulphide (dms), dimethyl disulphide (dmds) are harmful, corrosive components, and present in various gas streams, e.g. biogas [1, 2], among them hydrogen sulphide can be found in relatively high concentration. the concentration of hydrogen sulphide varies between 0,1 és 2% and depends on the quality of feed substance [3]. utilisation of biogas is mainly hindered by its hydrogen sulphide content, therefore its removal is essential. the current technologies based on chemical removal are quite expensive, thus usage of biogas in power plants is not supported [4]. yet, in most cases physico-chemical methods are used. recently biological processes received some attention due to their effectiveness and low operational and maintenance costs [2], [4]. biological removal of hydrogen sulphide can be carried out by autotrophic and heterotrophic ways. from the operation point of view heterotrophic strains are more beneficial, but mos chemoautotrophic bacteria seem suitable for degradation of the compound. these bacteria can live using inorganic carbon (e.g. co2) as carbon source, while energy is obtained by oxidation of reduced compounds (e.g. h2s) [5]. the aim of this work was to study a suspended batch bioreactor, where chemoautotrophic aerob bacteria (thiomonas intermedia, thiobacillus thioparus) are able to use carbon dioxide present as carbon source, while hydrogen sulphide is converted into sulphur powder or oxidised sulphur compounds. the investigations were conducted in liquid phase by using free and immobilised cells. materials and methods microorganisms thiomonas intermedia is an aerobic, chemoautotrophic bacterium, purchased in lyophilised state from the national collection of agricultural and industrial microorganisms (ncaim budapest, hungary). for its growing thiomonas intermedia broth elaborated by dsmz (deutsche sammlung von mikroorganismen und zellkulturen gmbh, germany) was used [6]. its composition is (g/l): nh4cl 0.1, kh2po4 3.0, mgcl2*6 h2o 0.1, cacl2 0.1, na2s2o3*5 h2o 5.0, yeast extract 1.0, 1000 ml distilled water. during the growing period ph was adjusted to 5.5–6.0, then it was incubated at 33°c temperature and 120 rpm. 88 the other, also chemoautotrophic aerobic bacterium is thiobacillus thioparus, which was purchased from dsmz (germany) strain collection. its growing parameters are the same as given in thiomonas intermedia. the features of microorganisms are summarized in table 1. table 1: the features of thiomonas intermedia és a thiobacillus thioparus thiobacillus thioparus thiomonas intermedia optimal ph 5–9 5–7.5 optimal temperature [°c] 33–35 30–35 cell type gram negative gram negative shape, size rod, 0.9–1.8 μm trophity obligate chemoautotrophic facultative chemoautotroph energy source thiosulphate, sulphide thiosulphate, sulphide oxygen demand aerob aerob source [7] [8] analysis to follow the concentration of hydrogen sulphide in the liquid phase a photometric method was applied. the principle of the measurement is that the sulphide in acidic environment gives a colourful reaction with n,n dimethyl-p-phenilene diamin resulting in methylene blue, which can be measured by photometer in 670 nm after 20 min reaction time, using 5 cm cuvette (hachlange dr 3800) [9]. the advantages of the method are that easily applicable, having good reproducibility and the measuring range is wide: between 0.1 and 1.2 mg s2-/l. the composition of the gas phase was determined by dräger x-am 7000, which is a mobile electrochemical device, able to detect hydrogen sulphide and carbon dioxide. the experiments were carried out in 250 ml, jacketed, thermostated reactor (figure 1), where the total volume of the liquid phase was 200 ml. its composition was: 10% inoculum, 5%, water containing 2500 mg/l hydrogen sulphide and 85% broth. the optical density of the samples were measured by a photometer (hachlange dr 3800), in 620 nm. the biochemical reactions in the reactor resulted in a decrease of sulphide content in the liquid phase. the water vapour in the gas phase disturbs the optimal operation of the gas analysis equipment, therefore the vapour had to be condensed before. samples were taken every half an hour during the exponential growing period of the bacterium, otherwise it was taken every hour, and dissolved sulphide concentration and optical density were determined. figure 1: set-up of the batch reactor immobilization the strains were immobilised in three types of supports and the process was checked in a serial of measurements. mavicell-b cellulose beads, alginate beads and granulated activated carbon were used in the experiments. mavicell-b (table 2) is cellulose beads, widely used for immobilization of various microbes, having large adsorption surface area, thus a highly suitable support, moreover it can withstand to the corrosive effect of hydrogen sulphide. the cells can be bound on the surface of the support by adsorption. table 2: features of mavicell-b feature regenerated cellulose content 45–55% ash 35–40% particle size 2–3.5 mm aggregate thickness 250–300 g/dm3 water uptake at 25ºc 150–200% special pore volume 1.5–2 cm3/g special pore surface area 8–10 m2/g swelling increase in diameter 1.5 fold increase in volume 3 fold the other support used was alginate beads, widely used in biotechnology for immobilization of cells and enzyme, (figure 2) by the so called entrapment technique. during jellification small hollows are formed in alginate where biocatalysts (enzymes and cells) can be entrapped. the structure of the gel is compatible with the biocatalysts, thus no chemical modification is needed [10]. finally the granulated activated carbon (gac) support was purchased from airwatec s.a. (belgium). 89 figure 2: alginate beads containing cells due to its high surface area it seems also a promising support material for immobilisation of microorganisms. the features are listed in table 3. table 3: features of activated carbon parameter value total surface area (bet) (m2/g) 1080 ph 7.0 water content (%) 1,1 ash content (%) 8.6 granules diameter (mm) 1.0 during the experiments immobilised strains were kept in two vessels (for the two strains) and a blind one was used as a control, for all the three types of immobilization. samples were taken from all vessels regularly, and sulphide contents were determined. then fresh broth was given to the strains. in the end of the experiments the amount of immobilised cells (on the surface of mavicell and activated carbon particles, as well as in the alginate beads) – or more precisely the protein content – was measured by the modified folin-method. results firstly 24 h long batch fermentations were carried out by free thiomonas intermedia and thiobacillus thioparus microbes. the results are shown in figure 3 and figure 4. as it can be seen from figure 3 and figure 4 after a 8–12 h lag phase bacteria started to grow, the exponential growing period was found from around 10th h till 15-16th h, then a the rate of growing was slower. all the four parameters measured confirmed that the maximal growing rate of both bacteria was at the 12–13th h of the fermentations. a b figure 3: concentration of hydrogen sulphide and carbon dioxide (a), dissolved sulphide and optical density of thiomonas intermedia (b) as a function of time moreover it can be established that both thiomonas intermedia and thiobacillus thioparus reduced the concentration of hydrogen sulphide in the reaction mixture, i.e. they mostly obtained energy from degradation of hydrogen sulphide (dissolved sulphide) during the metabolisms. in both figures 3/b and 4/b dissolved sulphide concentration as a function of time shows some discrepancy, which is difficult to explain. we think that the analytical method (by photometer) may be disturbed by some nutrient compound present in the liquid phase, therefore another method should be found in future. another reason of the strange behaviour might be that certain metabolic products were formed during the fermentation which resulted it in the second half of the experiments. 90 a b figure 4: concentration of hydrogen sulphide and carbon dioxide (a), dissolved sulphide and optical density of thiobacillus thioparus (b) as a function of time operational stability in the liquid phase the bacteria were immobilised in three different support: mavicell-b cellulose beads, alginate beads and granulated activated carbon. to check their work they were kept in reaction mixtures, containing nutrients and hydrogen sulphide, and samples were taken regularly. figure 5 presents the experimental results: the variation of hydrogen sulphide concentration [mg s2-/l] compared to the control (bind) one as a function of reaction time in cases of mavicell-b cellulose beads (fig. 5/a), alginate beads (5/b) and granulated activated carbon (5/c). it can be observed that a decrease in hydrogen sulphide concentration compared to the blind was measured, due to the activity of the bacteria immobilised on the support. to check this phenomenon protein content of the supports (measured in the end of the experiments by washing out the microbes from the surface of the support, or – in case of alginate – destroying the gel structure) was determined. the results are summarized in table 4. a b c figure 5: operational stability of bacteria immobilised in mavicell-b (a), ca-alginate (b) and activated carbon granulates (c) from the table 4 it can be seen that the protein measurement confirmed our experimental results: considerable amount of microbes were immobilised on all of the supports. since bacteria were entrapped in 91 alginate (not only adsorbed on the surface), much higher protein content was found in that case. table 4: the amount of protein (microbes) measured in the various support mavicell-b caalginate ga c thiomonas intermedia [mg dm/g carrier] 0.12 6.3 0.15 thiobacillus thioparus [mg dm/g carrier] 1.83 7.1 2.05 it can be stated that the bioconversion processes can be followed by measuring the hydrogen sulphide concentration in the liquid phase, but the photometric determination of the total sulphide content can not be applied here. based on the protein determination it is obvious that the microbes were able to immobilise in the supports and worked properly to reduce hydrogen sulphide concentration in the liquid phase. evaluation as a summary it can be stated that our experiments proved: the two microbes investigated are suitable for the biological degradation, removal of hydrogen sulphide. however, the analytical method to follow the bioconversions should be improved and we should continue the experiments in gas phase. based on the successful immobilisation and measurements in liquid phase, the bioreactor system should be redesigned to be able to operate in gas phase and to determine exactly the ability and effectiveness of the bacteria. acknowledgement the research work was partly supported by the „social renewal operational programme” (new széchenyi plan) in the frame of támop-4.2.2.a-11/1/konv2012-0038 project, entitled „complex multidisciplinary investigation of the effects of human activity and the related social conflicts on a sensitive geographical area pertaining to a shallow lake (the water body of lake balaton and its southern catchment area). the project is supported by the european union and co-financed by the european social fund. references 1. k. s. cho, m. hirai and m. shoda: degradation of hydrogen sulfide by xanthomonas sp. strain dy44 isolated from peat, appl. environ. microbiol., 58 (1992), pp. 1183–1189 2. e. szentgyörgyi, n. nemestóthy, k. bélafibakó: application of membranes in biogas production, desalination and water treatment, 14 (2010), pp. 112–115 3. g. lastella, c. testa, g. cornacchia, m. notornicola, f. voltasio, v. k. sharma: anaerobic digestion of semi-solid organic waste: biogas production and its purification, energy conversion and management, 43 (2002), pp. 63–75 4. g. tchobanoglous, f. l. burton, h. d. stensel: wastewater engineering. treatment and reuse, 4th edition mcgraw-hill companies, new york (2003), cap. 14., 1505–1532 5. m. l. prescott, p. j. harley, a. d. klein: microbiology, 5th edition. mcgraw-hill companies, new york (2003) 6. www.dsmz.de 7. l. vlasceanu, r. popa, k. b. kinkle: characterization of thiobacillus thioparus lv43 and its distribution in a chemoautotrophically based groundwater ecosystem, applied and environmental microbiology 63(8) (1997), pp.3123–3127 8. s. k. panda,v. jyoti, b. bhadra, k. c. nayak, s. shivaji, f. a. rainey, s. k. das: thiomonas bhubaneswarensis sp. nov., an obligately mixotrophic, moderately thermophilic, thiosulfateoxidizing bacterium int. j. syst. evol. microbiol., 59 (2009), pp. 2171–2175 9. j. d. cline: spectrophotometric deter-mination of hydrogen sulfide in natural waters, department of oceanography, university of washington seattle, 14 (1969), pp. 454–458 10. l. boross, cs. sisak, b. szajáni: szilárd fázisú biokatalizátorok – előállításuk, tulajdonságaik és gyakorlati alkalmazásuk, akadémiai kiadó, budapest (2008), pp. 53–54 700 hungarian journal of industrial chemistry veszprém vol. 40 (2) pp. 93–99 (2012) optimal design of high-temperature thermal energy store filled with ceramic balls t. borbély1 1university of pannonia, institute of mechanical engineering, 10 egyetem street, h-8201 veszprém, hungary e-mail: borbelyt@almos.vein.hu the momentary amount of the available solar energy and the demand usually are not equal during the usage of solar energy for heating and electric power supply. so it is necessary to store the heat energy. this article shows optimal design of a new construction, sensible heat store filled with solid heat storage material. the planned heat store has cascade system formed a spiral flow-path layout. this is a conceptual model, worked out in case of packed bed with ceramic balls. the aim of the special layout is to realize better overall efficiency than regular sensible heat stores have. the new construction would like to get higher overall efficiency by long flow-way, powerful thermal stratification and spiral flow-path layout which can ensure lower heat loss. the article shows the calculation method of the simulation of the charge and discharge and the calculation method of the overall efficiency using the results of the simulations. the geometric sizes and operating parameters of the thermal energy store with the best overall efficiency were calculated using genetic algorithm (ga). the results of the calculation tasks show that a thermal energy store with long flow-way, with cascade system formed spiral flow-path layout has higher overall efficiency than an one-duct, short flow-way thermal energy store which has equal mass of solid heat storage material as the long flow-way one, mentioned before. keywords: solar energy, heat storage, solid charge, sensible heat, optimization introduction the possible thermal energy storing methods are: sensible heat storage, latent heat storage, sorption heat storage and chemical energy storage [1–8]. the simplest way is the storage of sensible heat, by heating a heat storage material without phase changing. the energy density of the sensible heat storage will be high if the specific heat and the density of the heat storage material are great as well [9]. out of the materials which can be found in the environment in large quantity, the water has the greatest volumetric heat capacity (~4.18 mj/m3k), but water can be applied at atmospheric pressure up to 100ºc only. the heat transport media of the concentrated solar power systems can be used as heat storage liquids as well. the melt of the solar salt (60% nano3 + 40% kno3) is used out of these materials in concentrated solar power plants as heat storage material (operating temperature range 260–550ºc, volumetric heat capacity ~2.84 mj/m3k [11]). it is not flammable, not toxic, and not too expensive. the volumetric heat capacity of some solid materials (magnesite, corundum) – because of their higher density – come near to the volumetric heat capacity of the water with much higher upper temperature limits (magnesite 3.77 mj/m3k, corundum 3.3 mj/m3k, cast iron 4.1 mj/m3k [10]). screened pebble stone, cracked stone (1.5– 2.5 mj/m3k), concrete (0.8–1.8 mj/m3k), wet soil (3.56 mj/m3k) [10] are used as sensible heat storage materials, because they are inexpensive. the sensible heat stores are typical regenerative heat-exchangers. these are instationary thermal state heat-exchangers. the regenerators are long ago applied, great heat capacity heat stores with solid fill and with short charge-discharge cycle time (10–7200 s). my aims were to study the possible interior structure of the long-term heat stores, the charge-discharge process, to calculate the optimal geometric sizes and operating parameters of those. comparison of short (l/d<10) and long (10<l/d) heat stores the temperature-place function of the heat transport medium is similar to the temperature-place function of the solid heat storage material at a moment (the temperature of the heat transport medium tf is higher at charge, lower at discharge than the ts temperature of the solid heat storage material), so it is enough to show the temperature-place functions of the solid heat storage material. charge the hot heat transport medium gives a part of its heat content to the solid heat storage material by flowing 94 through the heat store, which is cold at the beginning of the charge period. in case of short heat store the outlet temperature of the heat transport medium and the solid heat storage material are increasing soon after the beginning of the charging (figure 1), in case of long heat store they start to increase only at the end of the charge period (figure 2). figure 1: the temperature-place functions of the solid heat storage material during charge, in case of short heat store figure 2: the temperature-place functions of the solid heat storage material during charge, in case of long heat store discharge in the discharge period the cold heat transport medium flows through the hot heat store in opposite flow direction of the charge. in case of short heat store the outlet temperatures of the heat transport medium and the solid heat storage material are decreasing soon after the beginning of the discharging (figure 3), in case of long heat store they start to decrease only at the end of the discharge period (figure 4). figure 3: the temperature-place functions of the solid heat storage material during discharge, in case of short heat store figure 4: the temperature-place functions of the solid heat storage material during discharge, in case of long heat store basic idea of the cascade system heat store during the charging and discharging of the long heat store the thermocline zone is located only in a part of the length of the heat store. it is plausible solution to divide to sections the heat store and allow knocking-off the sections from the flow-path of the heat transport medium. let’s call these sections as ducts. in case of the cascade system heat store the heat transport medium must flow through only the ducts where the thermocline zone is going along. the transport power demand of the heat transport medium can be reduced by this solution. the heat-loss of the heat store into the environment will be small if the heat store has small specific surface. from the prismatic bodies the cylinder with h/d=1 ratio has the smallest specific surface, followed by the regular n-sided prism with h/s=1 ratio (assuming that the heat-loss flux is approximately equal in all sides of the body). the higher heat-loss of the long heat store (because of its greater specific surface) can be reduced by using cascade system of the ducts formed a spiral flow-path layout (see later on figure 5). out of the regular n-sided prisms the six-sided can be built from cylinders with the best space utilization. 95 the geometry and operating of the heat store filled with ball particles the ducts of the heat store filled with ball particles are cylinders made of metal sheet with outer thermal insulation (fig. 5). the metal shell holds the bed of the particles, and the heat transport medium. the thermal insulation supports the thermal stratification in radial direction. to choose cylindrical shape for the ducts is necessary – because of the pressure of the packed bed of bulk particles. the outer geometry of the heat store is regular hexagonal prism with h/st≈1 ratio and cascade system of the ducts formed a spiral flow-path layout. figure 5: the construction layout of the heat store filled with ball particles and arrangement in the cascade system with spiral connection st – side distance of the heat store, h – bed height of a duct, δi – thickness of the outer thermal insulation the number of ducts nj is an odd one in case of full filling, but leaving out the last duct we get an even number, so it is possible to lock out or join in the heat transport medium flow into any duct-pairs (duct-pair means a pair of ducts, one downwards and another upwards). this way the place of the last duct could be used e.g. for service purpose. the hot heat transport medium is put in at the top of the middle duct at the beginning of charge and it flows downwards, it turns in the return band flows into the next duct (the lower connecting of the ducts is signed with dashed arrow) and flows trough that upwards. the heat transport medium coming out from the second duct can be led to the next pair of ducts. the heat transport medium must flow through only the ducts where the thermocline zone is going along. in the discharge period the cold heat transport medium flows through the hot heat store opposite to the flow-direction of the charge (from outside to middle). the main sizes of a duct of the heat store can be seen in figure 6. figure 6: top view of a duct dsj – outside diameter of the insulated duct, dj – inside diameter of the duct, ds – whole thickness of the thermal insulation between two ducts basic differential equations of the heat transport in the heat store filled with ball particles k. a. r. ismail, and r. stuginsky jr. [126] have reported an excellent comparative analysis of several models for description of the heat transfer in the heat transport medium and the solid heat storage material. for both media i have chosen a bit simpler model than the general, one-dimensional model. the heat-loss boundary condition is not included in the differential equations, because it takes effect only at the outer ducts, the effect of it will be calculated separately from the calculation of the temperature-place functions. the differential equation for the description of the heat transfer in the heat transport medium is )tt(a x twtc fspf f f f ff −α=⎟ ⎠ ⎞ ⎜ ⎝ ⎛ ∂ ∂ + τ∂ ∂ ρε , (1) where: tf – temperature of the flowing heat transport medium, ts – temperature of the solid heat storage material, ρf – density of the heat transport medium, cf – specific heat of the heat transport medium, wf –average velocity of the heat transport medium in the flow-channels, ap – superficial particle area per unit bed volume, αf – heat transfer coefficient between the flowing heat transport medium and the solid heat storage material, ε –void fraction of the bed. the superficial ball particle area per unit bed volume ap is )1( d 6a b p ε−= , (2) where: db – diameter of the ball particle. 96 the differential equation of the heat transfer in the heat transport medium was discretized by applying explicit forward difference scheme in time and upwind difference scheme in space [13, 14]. the differential equation for the description of the heat transfer in the solid heat storage material is )tt(a x ttc)1( sfpf2 s 2 seffx s ss −α+ ∂ ∂ λ= τ∂ ∂ ρε− , (3) where: ρs – density of the solid heat storage material, cs – specific heat of the solid heat storage material, λseffx – effective axial thermal conductivity of the solid heat storage material. the effective axial thermal conductivity of the solid heat storage material λseffx is sf seffx )1( 1 λ ε− + λ ε λ , (4) where: λf – thermal conductivity of the heat transport medium, λs – thermal conductivity of the solid heat storage material. the differential equation of the heat transfer in the solid heat storage material was discretized by applying explicit forward difference scheme in time and centred difference scheme in space (ftcs) [13, 14]. the heat transfer coefficient between the flowing heat transport medium and the solid heat storage material was calculated according to [15]. the design variable it is practical to choose the diameter of the ball particle db for optimization design variable: x1=db. the flow velocity of the heat transport medium wf has the greatest influence on the charging of the heat store, but it depends on the void fraction ε only (at given inside diameter of the duct dj). in case of the bed filled with uniform ball particles the void fraction ε is independent from the diameter of the particle db. definition of the restrictions geometric restrictions the lower limit of the diameter of the ball particle db is restricted by the manufacturing technology and the pressure drop, and the upper limit is also restricted by the minimal way-length of the heat transfer in the heat storage material. limits for x1 design variable are m1.0m01.0 ≤≤ 1x . (5) for the minimal specific surface the best value of the geometric ratio could be 1 s h t ≈ . (6) pressure drop restriction the pressure drop of the heat transport medium flowing through the packed bed in case of incompressible medium, according to [16] is ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎣ ⎡ ρ ε ε− + νρ ε ε− =δ 2 f b f f2 b ff 2 2 w d 175,1w d )1(150l'p , (7) where: νf – kinematic viscosity of the heat transport medium. the pressure drop of the heat transport medium must be restricted in order not to be necessary to install pressure resistant shell, not to get high transport work demand, can be negligible the compressibility of the gas and may be sufficient to use ventilator instead of blower or compressor in case of gas heat transport medium. the upper pressure drop limit for l=2h flow-way length according to the previous requirements is bar1.0pa10000'p h2 =≤δ . (8) composition of the objective function the objective function is the overall efficiency of the heat storage, which is suitable to compare the variants of the heat stores. the optimal sizes and operating parameters could be got from the maximum-point of the objective function. in the calculation of the overall efficiency i relate the part of the extractable heat quantity which can be used for heating and electric power production to the sensible heat storage capacity of the heat store as it is here: cap trlhid o q qqq −− =η , (9) where: qhid – extractable heat quantity from the heat store during a charge-discharge cycle without heat-loss, ql – heat-loss to the environment through the boundary surfaces during a charge-discharge cycle, qtr – heat-equivalent of the transport work demand during a charge-discharge cycle, qcap – sensible heat storage capacity of the heat store between the inlet and outlet temperature of the heat transport medium at the charge. the optimal value of the design variable can be searched by optimization using the calculation of the 97 temperature-place functions during the whole length of the charge-discharge cycle. the heat quantity qhid the heat quantity qhid is the difference between the heat-content of the heat store after charge and after discharge without heat-loss. it is necessary to know the temperature-place functions of the heat store at the end of the charge and at the end of the discharge. the heat quantity qhid is ( )∫ τ+τ−τ π ε−ρ= hn 0 dcscs 2 j sshid j dx),x(t),x(t 4 d )1(cq , (10) where: τc – term of charge, τd – term of discharge. the final temperature-place function of the charge of the heat store is the initial condition of the discharge. in the discharge period the heat transport medium flows through the heat store in opposite flow direction of the charge. the heat quantity ql the heat quantity ql is the heat-loss into the environment through the boundary surfaces during a chargedischarge cycle is lblslrl qqqq ++= , (11) where: qlr – heat-loss to the environment through the roof surface, qls – heat-loss to the environment through the side surfaces, qlb – heat-loss to the environment through the bottom and the ambient ground. the calculation of the heat-loss has taken into account the temperature of the heat store changing in place and time. the heat quantity qtr the heat quantity qtr is the heat-equivalent of the transport work demand during a charge-discharge cycle. the heat quantity qtr is approximated oh h2ff . dhd2jchc2j tr 'pm)nn( q η δρτ+τ = , (12) where: nj2hc – average number of duct-pairs which are simultaneously used during the charge, nj2hd – average number of duct-pairs which are simultaneously used during the discharge, f . m – mass flow rate of the heat transport medium, δp’2h – pressure drop of the heat transport medium on l=2h flow-way length, ηoh – overall efficiency of the electric power production in a heat power station. the heat quantity qcap the heat quantity qcap is the sensible heat storage capacity of the heat store between the inlet and outlet temperature of the heat transport medium at the charge: )tt(cm)tt(cmqq cs,sce,ssscco,fci,fff . cf . cap −=τ−=τ= ,(13) where: f . q – heat current during the charge, tf,ci – inlet temperature of the heat transport medium at charge, tf,co – outlet temperature of the heat transport medium at charge, ms – mass of the heat storage material, ts,cs – (homogeneous) temperature of the solid heat storage material at the start of the charging, ts,ce – (homogeneous) temperature of the solid heat storage material at the end of the charging. basic data of the optimization task i have made the calculations during the optimization with the following main data: τc=63 day=1512 h=5 443 200 s, f . q =2 mw, tf,ci=400°c, ts,cs=100 oc, ds=0.2 m. τd=58 day=1392 h=5 011 200 s. the solid heat storage material is magnesite, its physical properties are at ts,mid [10]: ts,mid=(ts,cs+ts,ce)/2=(100°c+400°c)/2=250°c λs=23.26 w/mk, ρs=3500 kg/m3, cs=1077.5 j/kgk. the required mass of the heat storage material for an ideal heat store: ms=33 678 t, ε=0.3. the heat transport medium is nearly ambient pressure air, its physical properties are at tf,mid [10]: tf,mid=(tf,ci+tf,co)/2=(400°c+100°c)/2=250°c λf=0.0425 w/mk, ρf=0.6715 kg/m3, cf=1038.5 j/kgk, νf=4.1525·10-5 m2/s. the final temperature-place function of the charge of the heat store is the initial condition of the discharge. the mass flow rate of the heat transport medium is constant during the charge-discharge process. the inlet temperature of the heat transport medium during discharge is: tf,di=100°c. data of the outer thermal insulation: λi=0.0468 w/mk, δi=1 m. ηoh=0.3. 98 i have applied the genetic optimization algorithm of the matlab software in order to find the optimal geometric sizes and operating parameters of the thermal energy store with the best overall efficiency. optimal sizes and operating parameters of the thermal energy store with the best overall efficiency the optimization process has been executed with number of ducts nj=1, 6, 18. the results are summarized in table 1 and figure 7. table 1: optimal sizes and overall efficiencies with several number of ducts nj [-] 1 6 18 x1 [m] 0.045 0.1 0.1 h [m] 27.5 29.6 28.8 l [m] 27.5 177.6 518.4 dsj [m] 25.5 10.1 6.0 st [m] 27.5 29.6 28.8 db [mm] 45 100 100 wf [m/s] 0.064 0.412 1.203 qcap [pj] 10.89 10.89 10.89 qhid [pj] 8.45 9.38 9.98 ql [pj] 0.92 1.11 1.01 qtr [pj] 0.01 0.25 2.87 ηo [-] 0.6908 0.7363 0.5601 figure 7: the optimal overall efficiency against the number of ducts main results the best overall efficiency can be reached with six ducts. it is better than the overall efficiency of one-duct type and eighteen-duct type. the expected significant increasing of the overall efficiency was ruined by the increasing transport work demand of the heat transport medium and the increasing heat-loss. the advantage of the six-duct type against the oneduct type is the smaller inside diameter of a duct dj. it is easier to distribute the stream of the heat transport medium along a smaller flowing cross-section than along a larger one. the overall efficiency decreases with increasing of the number of ducts, the main reason of it is the powerful increasing of the transport work demand. in case of liquid heat transport medium the transport work demand would be much smaller, so better overall efficiency could be reached with greater number of ducts. the upper limit of the overall efficiency would be restricted by the heat-loss. the void fraction of a packed bed, filled with uniform balls, in case of exact space-filling ε=0.26 is, in practice ε≈0.3 is! the void fraction of the volume of the heat store would have to fill with heat transport liquid. this large liquid volume brings up the idea of the establishment of a heat store with liquid heat storage medium, built from cylindrical tanks, in cascade system formed a spiral flow-path layout. the thermal stratification of the heat store with liquid heat storage material would be sharper, the overall efficiency would be higher than with solid heat storage material. conclusions i have worked out the constructional and the mathematical model of the long flow-way, sensible heat store with cascade system. the temperature-place functions and the overall efficiency can be calculated by using the mathematical model. i have used genetic optimization algorithm in order to find the optimal variant of the thermal energy store with the best overall efficiency. the chargeable and the dischargeable heat quantity of the multi-duct, long flow-way heat store is more than of the one-duct, short flow-way thermal energy store with equal mass of solid heat storage material. the temperature level of the outgoing heat transport medium is more advantageous in case of the multi-duct heat store than in case of the one-duct type during the whole charge-discharge cycle. the heat-loss can be reduced by using heat store with small specific surface and by allowing charge from middle to outside and discharge from outside to middle. the transport power demand of the heat transport medium can be reduced by making the flow of the transport medium only through the ducts where the thermocline zone is going along. according to the results of the optimization higher overall efficiency can be reached in case of six-duct type heat store than in case of one-duct type, filled with ceramic balls. the overall efficiency decreases with increasing of the number of ducts – because of the strong increasing of the transport work demand. 99 acknowledgements this work was supported by the research project támop-4.1.1.c-12/1/konv-2012-0017. references 1. p. muthukumar: thermal energy storage systems for solar thermal power plants: methods and materials, indo-spain joint work on renewable energy, sevilla, spain (2011), p. 34 2. r. dunn: a global review of concentrated solar power storage, proceedings of solar 2010, 48th auses conference, canberra, australia (2010), p. 10 3. a. h. abedin, m. a. rosen: a critical review of thermochemical energy storage systems, the open renewable energy journal, 4 (2011), pp. 42–46 4. y. demirel: energy production, conversion, storage, conservation, and coupling, springer (2012), p. 503 5. t. schmidt, d. mangold, h. müllersteinhagen: seasonal thermal energy storage in germany, ises solar world congress, göteborg (2003), p. 7 6. d. laing: thermal energy storage for concentrated solar power: state of the art and current cevelopments, ises annual meeting tel aviv university (2011), p. 25 7. d. laing: solar thermal energy storage technologies, energy forum, 10 000 solar gw, hannover (2008), p. 25 8. d. laing, d. lehmann: concrete storage for solar thermal power plants and industrial process heat, ires iii, 3rd international renewable energy storage conference, berlin (2008), p. 6 9. i. árpád: investigation of sensible heat storage and heat insulation in the exploitation of concentrated solar energy, hungarian journal of industrial chemistry, 39, 2 (2011), pp. 163–167 10. k. raznjevic: hőtechnikai táblázatok, műszaki könyvkiadó, budapest (1964), p. 336 11. d. kearney, u. herrmann, p. nava, b. kelly, r. mahoney, j. pacheco, r. cable, d. blake, h. price, n. potrovitza: overview on use of a molten salt htf in a trough solar field, nrel parabolic trough thermal energy storage workshop golden, co, usa (2003), p. 27 12. k. a. r. ismail, r. stuginsky jr.: a parametric study on possible fixed bed models for pcm and sensible heat storage, applied thermal engineering, 19 (1999), pp. 757–788 13. g. tóth: számítógépes modellezés, elte ttk, atomfizika tanszék, egyetemi jegyzet, budapest (2001), p. 118 14. i. faragó, r. horváth: numerikus módszerek, elte ttk – bme ttk egyetemi jegyzet, budapest (2011), pp. 341–391 15. verein deutscher ingenieure vdi-gesellschaft verfahrenstechnik und chemieingenieurwesen (gvc): vdi heat atlas, second edition, springerverlag berlin heidelberg (2010), pp. 743–744, 1423–1433 16. g. fejes, g.tarján: vegyipari gépek és műveletek, tankönyvkiadó, budapest (1979), pp. 36–45 700 101 hungarian journal of industrial chemistry veszprém vol. 40 (2) pp. 101-105 (2012) study of the properties of a plain cathode grimm-type dc glow discharge source operated in a current-controlled pulse regime o. bánhidi university of miskolc, institute of chemistry, miskolc-egyetemváros, miskolc, h-3515 hungary e-mail: akmbo@uni-miskolc.hu glow discharge sources have been used for analytical purpose for several years. recently the pulsed operation mode has gained an increasing importance. operating the source in current-controlled mode instead of the traditional voltage-feed method may have the advantage of precise control of the source’s state and it provides a convenient way to study the relationship among the emitted line intensity and the key parameters of the plasma such as the pressure of the filling gas, the voltage-drop on the source as well as the current flowing through the device. in the following the brief description of the system, the relationship among the voltage drop on the source, the pressure of the filling gas (ar), the current of the dc pulses as well as the line intensities are presented and discussed. keywords: dc glow discharge, pulsed current-controlled mode, atom-spectrometric source. introduction glow discharge sources have a great importance in the atom spectrometry. main fields of their application are the analysis of bulk materials and examination of surface layers, i. e. the depth-profile analysis. besides that they play an important role in the massspectrometry an ion-sources. beside the devices based upon the direct current glow discharge, radio-frequency operated sources have also been developed, making possible the analysis and study of non-conducting materials [1]. in case of the dc sources a substantial part of the power applied to the device will be dissipated as heat in continuous operating mode, warming up both the equipment and the sample being the cathode. to avoid this warming-up, which may also be harmful to some parts of the source either, a suitable cooling system have to be applied. another way to avoid harmful effect is to operate the device in pulsed mode. depending on the pulse parameters, the average power applied to the device in the later case is only a few percentages of value necessary on continuous dc mode. several studies can be found in the literature dealing with sources operated in pulse regime [2, 3, 4]. in the above-mentioned studies the sources are powered exclusively in the so-called voltage-feed way. it means that the device is connected to the dc power supply directly, or in order to avoid the damage in case of short-circuited condition, through a so-called ballast resistor. as a consequence of that any change in the state of the source causes a change both on the voltage dropped on the source and that of the current flowing through the device. if because of nay reason the impedance of the source might change , so will change again the voltage drop and the current. this might cause the the source to leave either the area of abnormal mode of operation and will enter the area of normal mode or vice versa. on the other hand it is rather difficult, though not at all impossible, to provide precise highvoltage pulses to feed the system in this voltage-fed mode. so that the change of the voltage drop and the current could be avoidedat and a better control of the system could be achieved, we suggest applying a constant pulse current to the system. by using constant current pulses, the state of the system can also be controlled. to provide constant current pulses, a current generator is needed. it has a very high internal impedance, and because of that the change of the source impedance will not have any effect to the value of the current flowing through the source as long as the current generator is able to provide constant current pulses. in this way the voltage drop and the current will remain unchanged, therefore better control can be achieved. to study the current-controlled mode we have developed a high power current-generator power supply and controller, which is able to operate in pulsed regime. the pulsed regime operation does not mean that current flows through the source only in the duty-cycle period. in the course of the development it was targeted that the source should always operate in the so-called abnormal region, or at least it should be at the border of the abnormal mode. therefore there is a low-current period and a high-current one. the later is eventually the duty-cycle period. e.g. at a frequency value of 102 200 hz and 10% duty cycle, the length of the period is 5 ms, and the duration time of the high-current lasts 0.5 ms, while the low-current one is 4.5 ms long. the use of the pulsed regime may provide two advantages. the first one is that high power resulting in dissipating much heat and warming up the equipment is applied just for a very short time, so the average power is just a few percentages of it. this makes unnecessary to apply a cooling system, as much less heat is dissipated by the source. the other advantage is that the short-time high-current pulses the system provides make possible to study and examine thin layers. experimental main components of the system main parts of the system can be seen in figure 1. the light emitted by the discharge is detected and measured by a spedctrometer. the output signal of the detector is processed by a special computer programmed card, usb 4716 manufactured by the advantech co.. the electric dc voltage and current pulses necessary for the operation of the discharge is provided by the power supply and current generator unit. figure 1: main components of the system the source in the course of the experiemnts a grimm-type source (presented in figure 2) was used, it is based upon the design made by wagatsuma and co-workers [5]. the anode is made of brass, its internal diameter is 7 mm. the power supply and current generator this unit was designed and built in our laboratory. it is able to provide a dc voltage as high as 1000 v. it can be operated in the frequency range of 122 hz–5000 hz. the duty cycle can be chosen between 32 µs – 4.1 ms, resulting values ranging from 0.4% up to 50%, depending on the pulse period and frequency. in the experiments reported here the pulse frequency was figure 2: the source used in the experiments. 122 hz and the duty cycle was 2.3%. the value of the low current is 1.5 ma, while 5 preadjusted values (32, 72, 115, 135 and 160 ma) can be selected for the high current pulses. the device has its own microcontroller unit, which has a serial (rs 232c) link to the ibm compatible computer controlling the system. this build-up makes possible to choose all the important parameters (value of the frequency, duty cycle and that of the high current) using a special computer programme. the same programme is responsible to controll the measuring system and store the measured data. the spectrometer to convert the light of the source into an emission spectrum and to convert the light intensity of the selected spectral line to an electric signal an atomic absorption spectrometer (pye unicam sp9-700) was used. only the spectrometer (monochromator) and the detector (pmt) was used during the experiments. the electric signal processed by the external measuring system was taken from the loading resistor of the photomultiplier tube of the instrument. the narrowest slit width (0.2 nm) was choosen for the experimental work. so that spectras could also be recorded, the device was equipped with a wavelength driving circuitry (consisting of a stepper motor and of a control circuit). the signal measuring system the measuring system must be capable to measure signals both in the high-current and in the lowcurrent period. to fulfill this requirement a multifunction module capable to provide fast analogue to digital conversion has been chosen. it is the usb 4716 multifunction module manufactured by advantech co ltd. it has a 16-bit ad converter with a 16-channel 103 multiplexer and its minimum conversion time is 5 µs. it can operate both in an externally triggered mode and in a so-called software triggered mode. the signal taken from the loading resistor of the photo-multiplier tube (pmt) of the spectrometer is led into the first measuring channel of the device. the electric connection betwen the loading resistor of the pmt and the signal input of the spectrometer own measuring electronic system was eliminated so that these circuits could not have any influence on the measurements. so that not only the emitted signal of the source, but the current flowing through on that and the voltage drop could be measured, there is a resistor network in the system. r3 is a resistor of 15 ohm. it is for measuring of the lamp current. resistors r1 and r2 (20,000,000 and 120,000 ohms respectively) form a voltage drivider, making possible the measurement of the voltage drop on the source. the usb 4716 has digital inputs and outputs, therefore it is able to control the stepping motor of the wavelength drive. the unit is controlled by a programme running on an ibm compatible computer. other important details of the experiments in the course of the experiments high purity argon (99,996%) was used as filling gas. a pressure regulator and a vacuum pump made possible to adjust the required value for the pressure of the filling gas. in all the experiments expect for the demonstation of sputtering ability a brass (copper – zinc alloy) probe was applied as the cathode of the source. results as the device operates in pulsed mode, all the signals are eventually pulses. figure 3 shows the relative signals of emitted light, discharge current and that of the voltage-drop on the source as the function of time..the different signals are shifted in time so that they could be better observed. figure 3: signals of the emitted light, current and voltage-drop pulses as the function of time stability of the current generator from the view-point of the operation it is important to know how much the changes in the pressure of the filling gas affect the value of the high current, in other words how stable the current generator is. as it can be seen in figure 4, the value of the high current is eventually not affected in the pressure range of 300– 950 pa, but under 300 pa it is no longer constant, i.e. under the above-written range the current generatror no longer works. figure 4: the high-current pulses as the function of the filling gas pressure the relation among the voltage-drop, the current and that of the filling gas pressure as the device operates in the abnormal working range, it can be expected that the voltage-drop on the source will increase with increasing current. the relation measured is presented in figure 5, where the voltage-drop on the source can be seen as the function of the current at three argon pressure values. it can be stated that according to the expectations the voltagedrop is greater at higher current, but the increasement is higher at lower argon pressure. the relation of the voltage-drop to the filling gas pressure measured at 72 ma high current is shown in figure 6. it can be observed that there is only a moderate increasement in the voltage-drop with decreasing argon pressure in the range of 400–900 pa, while the voltage-drop increases sharply below that range. 104 figure 5: the voltage-drop as the function of the current at 3 different filling gas pressure. figure 6: the voltage-drop as the function of the filling gas pressure at 72 ma. the light intensity emitted by the cathode material from the viewpoint of the possible practical analytical application the emission by the elements building up the cathode sample has the greatest importance. this emission, i. e. the intensity of the figure 7: the emitted light intensity measured on the 324.8 nm cu i. line as the function of the current at 350 pa. 0.0000 0.0400 0.0800 0.1200 0.1600 0.2000 0.2400 0.2800 0.3200 250 300 350 400 450 500 pressure of ar [pa] in te ns ity [a .u 32 ma 135 ma 160 ma figure 8: the emitted light intensity measured on the 324.8 nm cu i. line as the function of the pressure of the filling gas. emitted light is also the function of the current and the pressure of the filling gas. in the course of the experiments the emission on the strongest atomic line of cu (324.8 nm) was measured. the results are presented in figure 7 and figure 8. looking at these figures it can be stated that the emitted line intensity sharply increases with increasing pulse current and decreases with increasing filling gas pressure. the sputtering ability the atoms of the bulk cathode material can get to the plasma by the mean of sputtering, so this process has a key-importance in the proper operation of the source. beside that it makes possible the depths profile analysis. in order to get information on the sputtering efficiency the sputtering speed has to be determined, which will be performed in the future. in these experiments only the demonstration of the sputtering ability is presented. as this source is operated in pulse mode, high power is applied to the source just a few percentages of the pulse duration, therefore rather low sputtering speed can be expected if it is averaged for the whole period. on the other hand it might advantageous in case of thin layers. to present the sputtering ability a steel plate, which had a 2,0 ± 0,2 µm thick zinc coating on its surface was taken as cathode sample and the zinc emission was measured on the 213.85 nm zn i line at 350 pa argon pressure as the function of time. the value of the high current was 72 ma, the pulse frequency was 122 hz and the duty cycle was 2.3%. the measured data are presented in figure 9. it can be observed that after 3000 s time interval, no zinc emission can be measured. 105 figure 9: the line intensity measure on the 213.85 nm zn i. line as the function of time. discussion of the results in the experiments a dc glow discharge source was studied, which was operated in pulse regime, at constant high and low current values. it could be seen that the current generator can be used in a wide range of ar pressure and the constant current makes possible an easier control of the device. from the viewpoint of the operation of the device the voltage-drop has a key importance, namely as long as it does not exceed the capabilities of the current generator, the constant current mode works. when the current generator runs out of the voltage, it stops working, therefore care must always be taken of the voltage-drop, and careful examination is needed to reveal the relation among the high current, the voltage-drop and that of the filling gas pressure. in figure 6 it can be seen that at 72 ma the source can be used in current regulated mode at the range of 300– 950 pa. below 300 pa the voltage-drop sharply increases with decreasing pressure, so it probably will not work at pressure values lower than 260–270 pa. in figure 5 the relationship between the voltagedrop and that of the current is shown. it must be noticed that the first point in the figure is the voltage-drop at the low current value. this also suggests that the device operates in the abnormal operating region within the whole current range. the emission data measured on the 324.8 nm cu i line are presented in figure 7 and figure 8. it is worth mentioning that the emitted light intensity sharply increases with increasing current, it seems to be an exponential function rather than a linear one. the reason for that sharp increasement may be the better sputtering efficiency. on the other hand, the emitted light intensity decreases with increasing filling gas pressure. in figure 9 the sputtering ability is demonstrated. it took about 3000 s to eliminate the 2 µm thick zn layer. if the duty cycle (2.3%) is taken into account, this would mean a sputtering speed of 1.74 µm /minute at continuous dc current. it must be mentioned that the duty cycle the speed depends also on the current and that of the argon pressure beside the duty cycle of the pulses. it also could be seen that the behaviour of the source is similar to the ones operated in voltage-feed mode, except for the fact that its state can always be charactised precisely bevause of the constant-current mode. acknowledgement the described work was carried out as part of the támop-4.2.1.b-10/2/konv-2010-0001 project in the framework of the new hungarian development plan. the realization of this project is supported by the european union, co-financed by the european social fund. references 1. a. boagerts, e. nexts, r. gijbels, j. van der mullen: gas discharge plasmas and their applicaion, spectrochimica acta part b, 57 (2002), pp. 609–658 2. ch. young, k. ingeneri, w. w. harrison: a pulsed grimm glow discharge as an atomic emission source, journal of analytical atomic spectrometry, 14 (1999), pp. 693–698 3. l. n. mishra, k. shibata, h. ito, n. yugami, y. nishida: charatcterization of pulsed discharge plasma at atmospheric pressure, surface & coating technology, 201 (2007), pp. 6101–6104 4. ch. young. w. w. harrison: investigation of a novel hollow cathode configuration for grimmtype glow discharge emission, spectrochimica acta, part b, 56 (2001), pp. 1195–1208 5. k. wagatsuma, k. hirokawa: observation of cu-ni alloy surfaces by low wattage glow discharge emission spectrometry, surface and interface analysis, 6 (1984), pp. 167–170 700 hungarian journal of industrial chemistry veszprém vol. 40 (2) pp. 107–111 (2012) effects of pan bread making on zearalenone levels in artificial contaminated wheat flour t.a. el-desouky , m. may amer, k. naguib food toxicology & contaminants dept. national research center, dokki, cairo, egypt e-mail: eldesoukyt@yahoo.com the ability of saccharomyces cerevisiae (baker's yeast) in reduces of zearalenone during fermenting dough at 25°c and 30°c for 30 and 45 min was studied. the results indicate that content of zearalenone was reduced to 9.44, 19.22, 37.6 and 63.16µg/kg in dough made from flour artificially contaminated with 25, 50, 75 and 100 µg/kg, respectively when the fermentation process at 25°c for 45 min. on the other hand, during fermentation at 30°c the decrease in the content of zearalenone is greater than ever, particularly with increasing duration or time of fermentation to 45 min. the content of zearalenone after fermentation at 30°c for 45 min was 7.52, 17.14, 34.19 and 60.38µg/kg in dough made from flour artificially contaminated with 25, 50, 75 and 100µg/kg, respectively. the reduction percentage of zearalenone after baking pan bread at 180°c for 25 min was 55.98, 62.78, 62.5 and 60.52%.these results indicate that fermentation and baking are effective in reducing zearalenone. key words: zearalenone, saccharomyces cerevisiae, fermentation and baking introduction zearalenone (zea) is a mycotoxin mainly produced by fusarium graminearum and fusarium culmorum, which are common soil fungi in temperate and warm countries, and are regular contaminants of cereal crops worldwide [1, 2]. zea is mainly with corn and wheat but it occurs also in barley and sorghum amongst other commodities frequently used in human and animal diets. the international agency for research on cancer (iarc) has categorized zea as a class 2a carcinogen [3]. zea produces estrogenic effects in humans and animals leading hyperestrogenism. hyperestrogenism may be manifested enlargement of the reproductive organs. zea can cause severe reproductive and infertility problems in farm animals, particularly in swine [4]. specifically, zea can act as an estrogen analog and cause alterations in the uterus of the reproductive tract of swine and affect follicular and embryo development [5]. the function of zea as an estrogen analog is important because swine are monogastric animals with responses similar to humans in many respects [6]. even though most african countries have a climate characterized by high humidity and high temperature which favor growth of moulds, little information is available on the occurrence of fusarium toxins particularly zea in foods and feeds. high contaminations of the raw materials are an ongoing problem. regulatory issues are not available in the field of food exhibition and retailing, and mycotoxin problems have already been associated with some food contamination in some areas in africa [2]. in egypt, several commodities were reported to contain zea especially corn, wheat and rice and walnut [7, 8]. corn from egypt was also found contaminated with high levels of zea that ranged from 9.8 to 38.4 mg/kg [9]. according to fao [10], zea was regulated in 1996 by 6 countries, but by the year 2003 the toxin zea was regulated in foods and animal feeds by 16 countries. limits for zea in maize and other cereals, currently vary from 50 to 1000 µg/kg. although various prevention strategies have been implemented in many countries, they were not enough to manage the problem efficiently in the developing world. in the recent years, many dietary strategies involving microorganisms have been under investigation. many species of bacteria and fungi have been shown to enzymatically degrade mycotoxins [11]. however, the question still remains on the toxicity of the degradation products. saccharomyces cerevisiae has been utilized in food fermentation for several centuries. in the african and asian countries, fermentation is used as a predominant mode of food processing and preservation. many yeast species, especially saccharomyces cerevisiae, play a predominant role in food fermentation along with lactic acid bacteria [12]. in the african fermented foods such as fermented maize dough (kenkey) as well as sorghum beer (pito), saccharomyces cerevisiae constitutes a predominant component of fermentation microflora and the biodiversity of yeast microflora in these foods has been well documented [13]. mycotoxin binding by saccharomyces cerevisiae and lactic acid bacteria have been reviewed recently [14]. the aim of this work was to study the ability of saccharomyces cerevisiae in reduce of zea during fermenting dough at 25°c and 30°c for 30 and 45 min, also study effect of baking pan bread at 180°c on content of zea. 108 materials and method: materials wheat flours (72% extraction) were obtained from the north cairo mills company, egypt. saccharomyces cerevisiae (baker's yeast) was obtained from alhawamdia company fresh comprised yeast according to the egyptian standard (191/2005). methods preparation of artificial contaminated wheat flour one milligram of zea was purchased from sigma, chemical co. (st. louis, mo, u.s.a). zea was dissolved in 1 ml methanol. then taken appropriate size of focus and complemented the larger size makes it easier to control added to wheat flour. four wheat flour samples (1kg each) were aged in various concentrations (25, 50, 75 and 100µg/kg). each of the contaminated wheat flour samples was used for preparation of pan bread. this mixture was stirred until the solvent had evaporated. pan bread making pan bread was prepared by mixing 100g of wheat flour (72% extraction) with 5 g of baker's yeast, 1.5 g of sodium chloride and 75–80 ml of water and hand blended for about 6 min to form the dough. the dough was lift to rest for 30 min at 25°c & 30°c and 85% relative humidity and was then divided into 150g pieces. the pieces were booted in metal pans that had been left to ferment for about 45 min at the same temperatures and relative humidity according to aacc [15]. and then were baked at 180°c for 25 min the resulted pan bread was allowed to cool at room temperature for 2 h before being packed in polyethylene bags and stored at room temperature for determination of zea. extraction procedure twenty grams of sample was weighted into a 250ml blender jar with 2 g nacl and extracted with 50ml of extraction solution (acetonitrile: water 90:10 v/v). the mixture was blended for 2 min and centrifuged for 3 min at 3,000 rpm. the extract was filtered through filter paper (whatman no.1). 10 ml filtrate was mixed with 40 ml water, followed by filtration through a glass microfibre filter. immunoaffinity clean-up ten milliliter of filtrate was passed through zearalatesttm immunoaffinity columns at about 1-2 drops/s. 10ml water was used to wash the loaded immunoaffinity column at a steady flow rate. zea was eluted with 1 ml of methanol. the methanol elute was filtered through a 0.45μm micro filter and collected in a clean vial for the following hplc. hplc/fluorescence analysis the hplc system consisted of waters binary pump model 1525, a model waters 1500 rheodyne manual injector, a watres 2475 multiwavelength fluorescence detector. the fluorescence detector was operated at wavelength of 274 nm for excision and 440 nm for emission, and a data workstation with software breeze 2. a phenomenex c18 (250 x 4.6 mm i.d.), 5 μm from waters corporation (usa). the mobile phase consisted of a mixture of acetonitrile: water: methanol (48:50:3, v/v/v). a 20 µl of the reconstituted extract was injected onto the column at a flow rate of 1.0 ml/min. zea content in samples was calculated from chromatographic peak areas using the standard curve. statistical analysis the statistical analysis was performed using the spss software program (spss institute, 2011, version 19.0) and the differences in zen concentrations between time and temperatures dough fermentation were analyzed by anova test. p ≤ 0.05 was considered to be statistically significant. results and discussion influence of manufacture process of pan bread on content of zea: effect of dough fermentation the effect of using saccharomyces cerevisiae (baker's yeast)on content of zea during fermentation of artificially contaminated wheat flour dough at 25°c and 30°c for 30 and 45 min was presented in table 1 and 2. the content of zea was reduced to 13.71, 24.18, 43.88 and 71.43µg/kg in dough made from flour artificially contaminated with 25, 50, 75 and 100 µg/kg, respectively when the fermentation process at 25°c for 30 min. while decreased the content of zea more with more time fermenting dough to 45 min. on the other hand, during fermentation at 30°c the decrease in the content of zea is greater than ever, particularly with increasing duration or time of fermentation to 45 min. the content of zea after fermentation at 30°c for 45 min was 7.52, 17.14, 34.19 and 60.38µg/kg in dough made from flour artificially contaminated with 25, 50, 75 and 100µg/kg, respectively. low incubation temperature (25°c) during the growth of the cells seems to adversely affect the binding and the optimal and above-optimal growth temperature did not affect the binding. temperature is known to affect the cell wall composition with lower temperature resulting in reduced cell growth, cell wall dry mass, mannan and β-glucan levels [16]. culture conditions including ph, temperature, oxygenation rate, nature of the medium, and concentration or nature of the carbon 109 source strongly modulate the quantity and structural properties of β-d-glucans, mannans and chitin in cell walls. moreover, the cell cycle stage also interacts with the cell wall composition. for example, budding induces strong changes in the distribution of the structural components of the cell wall such as chitin. changes in the cell wall components at low growth temperatures might have resulted in reduced binding molecules on the cell surface. cell wall of saccharomyces cerevisiae consists of network of β-1,3 glucan back bone with β-1,6 glucan side chains, which is in turn attached to highly glycosylated mannoproteins which make the external layer [17]. the proteins and glucans provide numerous easily accessible binding sites with different binding mechanisms such as hydrogen bonding, ionic or hydrophobic interactions [18]. binding of different mycotoxins such as aflatoxin, ochratoxin and zea to yeast cell surface has been reported earlier and the binding has been attributed to cell wall glucans in case of ochratoxin and zea [19]. β-d-glucans are the yeast component responsible for the complexation of zea, and that the reticular organization of β-d-glucans and the distribution between β-(1, 3)-d-glucans and β-(1, 6)-d-glucans play a major role in the efficacy and add at weak hydrogen and van der waals bonds are involved in the chemical complex formation between zen and β-d-glucans. thus, the chemical interaction is more of “adsorption type” than “binding type”. molecular modeling was performed to validate the concept on other mycotoxins such as aflatoxin b1, deoxynivalenol and patulin [20]. the reduction percentage of zea after fermentation dough at 30°c for 30 min was only 58.8, 55.1, 46.98 and 34.42%, while it was 69.9, 65.72, 54.41 and 39.62% after fermentation dough for 45 min from flour artificially contaminated with 25, 50, 75 and 100µg/g, respectively. the percentage of zea reduction increased with time of fermentation dough shown in (figure 1). there was observed relationship between the degree of reduction and the initial level of zea contamination during fermentation dough . and, as it was expected, a positive relationship was observed between the increase of fermentation time and that of the percentage of reduction on zea-contaminated wheat flour table 1: concentrations of zea determine in artificially contaminated wheat flour after dough fermentation at 25°c (n=3) spiking level of zea (µg/kg) time of fermentation dough (min) 25 50 75 100 after mixed directly 23.26 ±0.34 46.98 ±0.4 73.71 ±0.12 96.45 ±0.17 30 13.71 ±0.46 24.18 ±0.25 43.88 ±0.52 71.43 ±0.39 45 9.44 ±0.18 19.22 ±0.44 37.6 ±0.41 63.16 ±0.51 table 2: concentrations of zea determine in artificially contaminated wheat flour after dough fermentation at 30°c (n=3) spiking level of zea (µg/kg) time of fermentation dough(min) 25 50 75 100 after mixed directly 23.26 ±0.34 46.98± 0.4 73.71 ±0.12 96.45± 0.17 30 10.3 ±0.26 22.45± 0.28 39.76 ±0.71 65.58± 0.73 45 7.52 ±0.1 17.14± 0.19 34.19 ±0.38 60.38± 0.92 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 25 50 75 100 concentration of zea in artificially wheat flour (µg/kg) r ed uc tio n of z e a (% ) fermentation at 30ºc for 30min fermentation at 30ºc for 45min fermentation at 25ºc for 30min fermentation at 25ºc for 45min figure 1: the percentages of zea reduction during fermented dough effect of baking zea concentration as affected by baking of artificially contaminated flour dough during pan bread making is shown in table 3 and figure 2. the residual amount of zea was 3.31, 6.38, 12.82 and 23.84µg/kg after baking dough artificially contaminated with different concentration of zea i,e 25, 50,75 and 100µg/g, respectively. the reduction percentage of zea after baking pan bread at 180°c for 25 min was 55.98, 62.78, 62.5 and 60.52%.the results showed a positive correlation between the initial contamination level and the reduction of zea after baking. the levels of zea in cereal-based foods were reduced significantly by extrusion processing, and reduction of 83% of zea in corn-based foods was obtained with this process [21]. however, there remains a need to demonstrate that the toxicity or biological activity of zea has been reduced or completely eliminated in cereal-based foods using extrusion processing [22]. figure 3a showed the hplc chromatogram of zea standard where fig. 3b showed the sample with zearalenone level of 25µg/kg after fermentation at 30 °c for 30 min. while fig. 3c hplc chromatogram of zearalenone in sample pan bread. 110 table 3: concentrations of zea in pan bread after baking at 180 °c for 25 min. (n=3) spiking level of zea (µg/kg) treatment 25 50 75 100 fermentation dough at 30°c for 45 min 7.52 ±0.1 17.14 ±0.19 34.19 ±0.38 60.38 ±0.92 baking at 180 °c for 25 min 3.3.1 ±0.15 6.38 ±0.29 12.82 ±0.76 23.84 ±1.6 reduction (%) 55.98 62.78 62.5 60.52 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 25 50 75 100 concentrations of zea in artificially wheat flour(µg/kg) r ed uc tio n of z e a ( % ) figure 2: effect of baking at 180 °c for 25 min on content of zea in dough after fermentation at 30°c for 45 min figure 3 a: hplc chromatogram of zearalenone standard figure 3 b: hplc chromatogram of sample with 30°c for 45min figure 3c: hplc chromatogram of zearalenone in sample pan bread conclusion it could be concluded that the fermentation of dough at 30°c for 45 min was best into reduce the content of zea, because this could be a good growth of yeast cells in the dough and is doing and its perfect. so attention must be paid to the process of fermentation and conditions of particular temperature that would influence the activity of yeast cells used. it also shows the importance of yeast cells to reduce the levels of zea. also the results of the study show that the residual of the zea in the bread was within allowable limits internationally. references 1. j. p. f. d’mello, c. m .placinta, a. m. c. macdonald: fusarium mycotoxins: a review of global implications for animal health, welfare and productivity, anim feed sci technol., 80 (1999), pp. 183–205 2. a. zinedinea, j. m .sorianob, j. c. molto, j. manes: review on the toxicity, occurrence, 111 metabolism, detoxification, regulations and intake of zearalenone: an oestrogenic mycotoxin, food chem toxicol., 45 (2007), pp. 1–18 3. international agency for research on cancer (iarc): in. iarc monographs on the evaluation of carcinogenic risks to humans: heterocyclic amines and mycotoxins, 56 (1993), pp. 397 4. council for agricultural science and technology (cast): task force report, 139, council for agricultural science 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prot. 67 (2004), pp. 1195–1200 20. j. p. jouany, a. yiannikouris, g. bertin: the chemical bonds between mycotoxins and cell wall components of saccharomyces cerevisiae have been identified archiva zootechnica, 8 (2005), pp. 26–50 21. d. ryu, m. a. hanna, l. b. bullerman: stability of zearalenone during extrusion of corn grins, j. food. prot, 62 (1999), pp. 1482–1484 22. y. cetin, l.b. bullerman: evaluation of reduced toxicity of zearalenone by extrusion processing as measured by the mtt cell proliferation assay, j. agric. food chem., 16 (2005), pp. 6558–6563 700 hungarian journal of industry and chemistry veszprém vol. 40 (2) pp. 113-119 (2012) magnetorheological fluid brake – basic performances testing with magnetic field efficiency improvement proposal a. poznić1 , a. zelić1, l. szabó2 1university of novi sad, 6 trg dositeja obradovića, 21 000 novi sad, serbia e-mail: alpoznic@uns.ac.rs 2university of pannonia, 18 zrínyi str., 8800 nagykanizsa, hungary a review of all magnetorheological brake types was presented. based on overall braking torque analytical comparison for all magnetorheological brake types and other relevant parameters, the most promising design was selected. a test rig, utilizing selected brake type filled with magnetorheological fluid – basonetic 5030 was manufactured and then tested. to analyze the effect produced by magnetic field on magnetorheological fluid and hence at overall braking torque, the authors used amplification factor. results were discussed and the magnetic field efficiency improvements were proposed. keywords: magnetorheological brake, basonetic 5030, test rig, amplification factor, efficiency improvements introduction the convectional friction brake (fb) is the most commonly used brake type in almost any mechanical system today. however, it is characterized by drawbacks such as periodic replacement due to wear, large mechanical time-delay, bulky size etc. [13, 29], partially altered. electromechanical brakes (embs) have potential to overcome some of these drawbacks and are a suitable fb replacement. today embs are applicable in almost any mechanical system. application of intelligent materials is the next step in the development of emb. magnetorheological (mr) fluids belong to a class of intelligent materials that respond to applied magnetic field with fast, continuous, and reversible change in its rheological behaviour [3, 7, 28], partially altered. mr fluids are a type of suspensions, with carrier fluid usually mineral or synthetic oil, water, kerosene and micro size magnetizable particles dispersed in it. when exposed to external magnetic field particles form a chain-like structures thus changing the viscosity of the fluid. in this study, authors used basf’s magnetorheological fluid, basonetic 5030. mr fluids have attracted extensive research interest in recent years since they can provide simple, quiet and fast response interface between electronic control and mechanical system [11, 20, 22]. a lot of work was done on mr fluid brakes modelling, properties investigation and control [3, 6, 11]. a wide range of mr fluid devices have also been investigated for their potential applications in different systems, such as: clutch system, vibration control, seismic response reduction, etc. [9, 10, 26]. mr fluid brakes have also been used in actuators due to their distinguished force control and power transmission features [5, 15]. by applying a proper control effort, viscosity with large varying range is achievable with the mr fluid brake. currently, there are many solutions for mr fluid brake design. some mr fluid brakes with attractive properties, such as high yield stress and stable behavior, have been developed and commercialized [4, 16]. the objective of this work was to compare overall braking torque analytical expressions and design complexity for all mr fluid brake types. based on results obtained from these comparisons, mr fluid brake type with the most promising properties was manufactured and tested on a specially designed test rig. results were discussed and a proposal for new mr brake design with higher magnetic efficiency was presented. magnetorheological effect mr fluids are suspensions composed out of three major components: carrier fluid usually mineral or synthetic oil, magnetizable particles carbonyl iron powder and set of additives [2, 17], partially altered. when exposed to an external magnetic field (on state), change in mr fluid’s viscosity occurs. in the absence of an external magnetic field (off state), mr fluid acts as newtonian fluid [7, 11] and can be described as: τ η γ= ⋅ & (1) in (1) τ represents shear stress, η the viscosity of the fluid and γ& shear rate. often, for mr fluid brakes, 114 denoted as r / gγ ω= ⋅& , where r is rotor radius, ω and g are angular speed and mr fluid gap length, respectively. when in on state, mr the rheological properties of mr fluid change. magnetizable particles induce polarization and form chain-like structures in magnetic flux path direction, thus changing apparent viscosity of the fluid. on state behavior of mr fluid is often represented as a non-newtonian [1, 3, 5], having a variable yield strength. the usage of bingham’s model (2), in this situation, gives reasonably good results, [1, 11, 20, 22]: bτ τ η γ= + ⋅ & , (2) where τb is the yield stress, developed in response to the applied magnetic field. its value is a function of the magnetic field induction b. when used in a device, mr fluid can be in one of four modes: shear, flow (pressure), squeeze and pinch, [8, 18, 28]. in brake i.e. torque transfer applications, mr fluid operates in shear mode [1]. braking torque values are adjusted continuously by changing the external magnetic field strength. magnetorheological brakes mr brake consists out of four main parts: rotor, housing i.e. stator, coil and mr fluid, figure 1. the shape of the rotor is what differentiates mr brake types from each other. one needs the quantitative parameters of mr brake, to be able to determine its specific application suitability. mr brake types, mechanical model, quantitative parameters comparison for all mr brake types are presented in next section. magnetorheological brake types through literature research [9, 14, 22, 23, 24], authors of this paper have identified five major mr fluid brake designs: drum brake, inverted drum brake, disk brake, t-shape rotor brake and multiple disks brake, fig. 1. drum brake along with the disk brake is the easiest designs to manufacture. however, large inertia is its major drawback compared to disk brake design [1]. the disk brake design is the most common mr brake design found in literature today and was the first one to be investigated [25]. it is the easiest one to manufacture and gives reasonably good results in terms of weight and compactness [14]. there are some variations in mr disk brake design such as: the use of two coils instead of one in order to increase the magnetic pole area and/or relocation of the coil on top of the disk in order to reduce its external diameter [22], but the basics remain the same. it is also interesting to note that the mr disk brake design is currently the only one commercially available as a standard product, manufactured by lord corporation [16] and that it was used in several studies [7, 19, 21]. in order to increase compactness of the mr disk brake design, several disk-shape rotors can be used instead of one, with segments of stator located in between each rotor disk, fig. 1.d. this multiple disk design is very popular in literature and was used in several applications that required high torque in limited space and weight [13, 22, 23]. the equations describing this particular design are very similar to those of the single disk brake, presented paper’s sequel. the t-shape rotor brake design (fig. 1.e), is more compact than all other designs but is also more complex to manufacture. despite its advantages, this design is not so common in literature [22]. figure 1: types of mr brakes: a) drum, b) inverted drum, c) disk, d) multiple disks, e) t-shaped rotor, [28] for all aforementioned mr brake types, the rotor has a cylindrical shape and the magnetic flux lines run in the radial direction, fig. 1. to author’s knowledge, an in-depth comparison of all these architectures is not yet available. mechanical model the key objective in mr fluid brake design is to establish the relationship between the overall braking torque, magnetic field strength and design parameters. interaction of mr fluid and inner surfaces of the brake will generate the braking torque. based on eq. (2) and the specific geometrical configuration of mr brake, for all mr brake types, it applies: 2d 2 dt n r rπ τ= , (3) where: n – number of surfaces of the rotor, perpendicular to the magnetic flux lines and in contact with mr fluid, r – the radius of the rotor. the overall braking torque toverall, consists of three components: the magnetic field induced component tb, due to the field-dependent yield stress, the fluid viscosity dependent component tvis and the friction induced component tfric.. thus, the overall brake torque: 115 overall b vis frict t t t= + + (4) the sum of the first two components tb and tvis i.e. the braking torque can be obtained by the following integral: 22 d o i r b vis r t t n r rπ τ+ = ∫ , (5) where ro and ri are the brake’s rotor outer and inner radii respectively. considering practical conditions, for all mr brake types, the value of the ri can be ignored because the ro is several order of magnitude of the ri (figure 2). figure 2: mr fluid disk brake simplified representation based on eq. (5), the authors formed the final analytical expressions for all five mr brake designs. expressions were adopted from several different literature sources [1, 6, 12, 13, 21, 27, 29] and were partially altered in order to make the comparison easier. the last part of torque, tfric can be precisely obtained only by torque gauge. 3 44( ) 3overall o o frict r r t g ωπ τ η= + + , (6) 3 44( ) 3overall o o frict n r r t g ωπ τ η= + + , (7) 2 34 ( )overall o o frict h r r t g ωπ τ η= + + , (8) 2 38 ( )overall o o frict h r r t g ωπ τ η= + + . (9) variable h is the height of the rotor. it is now easy to distinguish components of overall braking torque in eq. (6–9), for disk, multiple disks, drums and t-shaped rotor, respectively. the yield stress τb given in eq. (2), varies with magnetic induction, but can reasonably be fitted with the third-order polynomial [12], as follows: 2 3 1 2 3b k b k b k bτ = + + , (10) where ki represents coefficients of regression. performances comparison mr brakes can be compared on several different aspects e.g. overall braking torque, dynamic range, mechanical simplicity, inertia, electric power consumption, torque to volume ratio, compactness, etc. authors of this paper compared level of mechanical simplicity for all five mr brake types and the overall braking torque based on analytical expressions, given in eq. (6–9), table 1. in addition, the dynamic range and inertia were consider and presented in the same table. table 1: characteristics of various mr brake designs b ra ke ty pe t o ve ra ll le ve l o f m ec ha ni ca l si m pl ic ity d yn am ic ra ng e t b /t vi s in er tia (1) m h b i g r τ ηγ ⋅ & 21 2 omr * (2) m l 4 3 b o g r τ ηγ ⋅ ⋅ & 21 2 omr (3) h l 4 3 b o g r τ ηγ ⋅ ⋅ & 21 2 o dmr n (4) h h b o g r τ ηγ ⋅ & 2 2 2 i i o m r mr − explanations: brake types: (1)drum and inverted drum, (2) disk, (3) multiple disks, (4) t-shaped rotor. level of mech. simplicity: h – high, m medium, l – low. * for inverted drum brake design, expression is the same as for the t-shape rotor design. nd – the number of rotor disks, mi – missing inner mass of the disk. dynamic range represents ratio of field induced component tb and viscous component tvis (friction torque component not considered). t-shaped rotor brake performs best dynamic and can offer biggest overall braking torque, however it has a large inertia, and is considered difficult to manufacture. the other four designs are globally less compact than the t-shaped rotor design. the two drum based designs have comparable performances but are burdened with even larger inertia for same rotor radius. finally, the disk and multiple disks designs offer a good alternative, being mechanically the simplest, with smaller inertia and giving reasonable dynamic range and the overall braking torque. test rig based on test rigs literature research [10, 15, 20, 27] and mr brake properties comparison (eq. (6–9) and tab. 1), 116 the authors of this paper selected the most promising mr brake design and manufactured it. with lowest inertia, good dynamic range and the highest mechanical simplicity, the disk type promised the biggest potential. for performance evaluating of the selected mr brake type a rig was set up. the test rig was designed and manufactured at faculty of technical sciences, novi sad – serbia, and is presently at its laboratory for engines and vehicles. the test rig with its parts is depict in figure 3 and 4, and consists of four main parts: drive, power supply, mr brake and measuring and data acquisition equipment. an 8-pole ac squirrel cage motor with 0.75 kw and nominal speed of 700 rpm, model 5 az 100 la – 8 (končar) was placed at one end of the support-frame, of the test rig. the inverter micro master (siemens), fig. 4, position 2, controls the direction and variablespeed of the ac motor. speed range was from 150 rpm to 750 rpm with 50 rpm increment. these two elements form a drive part of the test rig. the flexible coupling connects ac motor and the shaft of the mr brake. mr brake rests on two self-aligning ball bearings into housings p203 (fk bearing group). to avoid leakage of mr fluid, nitrile rubber lip seals, suitable for mr type application, have been used. torque transfer from the mr brake to a measurement device was done indirectly. a load arm, connected to the mr brake housing at one end, rests on top of the load cell on the other end, fig. 3. thus, by measuring the force on the load cell, the value of transmitted torque was obtained. load cell was internally calibrated by calibration weights. the capacity of the load cell, 1030 (tedea), was 15 kg. figure 3: demonstrating the test rig for mr brake 1. drive, 2. coupling, 3. self-aligning ball bearing, 4. mr fluid brake, 5. self-aligning ball bearing, 6. optical encoder, 7. load arm, 8. load cell, 9. data acquisition card the optical encoder, model amt102-v-rev-c (cui inc.), was connected to the shaft of the mr brake, at the opposite side of the ac motor and rotated at the same speed sample rate was 2048 per rotation. the signals were processed by universal amplifier, kws 673.a2 (hbm), fig. 4, position 3. the dc power supply, ea ps 2016-100 (elektro-automatik), was connected to the leads of the coil to provide flux generation. this was the control current, with range of 0 a to 2 a and 0.2 a increment. the coil, made of copper wire with diameter of 1 mm (18 gauges) has been coiled on outer radius of the mr brake housing. the mr fluid used in this experiment was basonetic® 5030, from basf® [17]. it is a carbonyl iron powder based mr fluid. figure 4: measurement and data acquisition equipment: 1. stabilized power supply, 2. inverter, 3. universal amplifier a typical testing procedure was as follows. first, the mr brakes shaft was set to a certain speed for 1 min as an initial condition, which stirred the mr fluid in the brake to distribute it uniformly. the desired magnetic field was then applied by setting the coil current i.e. control current and waiting for 1 min. this ensured stable structure forming of the mr fluid. the load cell detected transmitted torque. finally, the signal from the load cell was processed and recorded. experimental results and improvement proposal the goal of this experiment was to determine overall braking torque capabilities of selected mr brake design. the experiment was conducted on a specially designed test rig, with different control currents and speed sets. to eliminate the effects of previous observations, different combinations of control current and rotational speed were set for each reading. to bring repeatability in the reading, every speed set was carried out twice at different instance of time. for every reading, approximately 1 min time, before torque data recording, has been allotted to distribute the carbonyl iron particles uniformly in the mr fluid and form a stable structure. experimental results the experiment itself consisted out of tree parts. the first part was to determine the influence of the supporting ball bearings and seals, without mr fluid inside the brake and no control current applied. this was a friction braking torque component. second part of the experiment had the same setup but it included mr fluid inside the brake. viscous torque data was then 117 recorded, assuming that bearings and seals did not change their friction characteristics in time. aforementioned recordings were needed in order to get clear and precise information about field induced component. this was the third part of the experiment and it included mr fluid inside the brake and application of the control current. the same speed sets were used for the friction and the viscous torque component measurements were repeated. for each speed set, a 2 minute recording time was used. some field induced component results are depict in figure 5. magnetic field influence is apparent. a) b) figure 5: samples of overall braking torque results: a) 0,2 a at 150 rpm, b) 1,6 a at 300 rpm because of the large number of data obtained in this experiment, authors decided to use amplification factor to determine the effect produced by magnetic field. amplification factor (af) represents relation between overall braking torque and sum of friction and viscous torque, i.e. relation between the on and off state of the mr fluid. at current at zero current overall overall t i af t = (11) amplification factor curves for all 13 speed sets are plotted in figure 6. this figure shows linearity in amplification factor with increase in control current. this was expected, since the higher the current, the higher the field induced torque should be. results are presented with rotational speed variation as well. figure 6 indicates that the amplification factors for speeds 150, 200, 250, 300 and 350 were much larger than the ones for 450, 500, 550, 600, 650, 700 and 750 rpm. transition rpm value for this mr brake was 400 rpm. this was somewhat opposite to the torque predicted by eq. (6) where the toverall should increase with angular speed. this was not the case here. however, other authors have also reported the same trend – reduction of amplification factor with increment of speed [20, 27]. this may be due to the possible shear thinning effect of the mr fluid at high shear rates. this reduces the effectiveness of mr brake at higher speeds. therefore, to make mr brake effective at higher speed operation, one needs to think of „shear stable mr fluid“. figure 6: variation in amplification factor with control current mr brake improvement proposal in order to increase the overall braking torque of any mr brake type its geometry needs to be optimized [14]. state of the art mr brake designs base their torque generation on the inner section of the coil [4, 10, 13]. these designs are rather inefficient, because the magnetic field is not used to its full potential and active mr area is small. flux mostly travels through the housing of the mr brake. in this configuration, magnetic field is concentrated on small area of the mr fluid. figure 7: novel mr brake design with enhanced magnetic field efficiency by altering earlier mr brake designs, it is possible to concentrate magnetic field effect. one such design has been presented in figure 7. compared to the dimensions of the tested mr disk brake, radius of the coil was reduced so that it could be placed in a more suitable position inside new mr brake design. new coil position allows for magnetic flux to be 118 used more efficiently. now, the magnetic flux inside mr brake passes through mr fluid several times. based on analytical comparison, presented in eq. (6–9) and tab. 1, new design features two disks in order to create more mr fluid active area. greater number of disks creates more mr fluid gaps thus the volume of mr fluid can be increased. conclusion authors compared all mr brake types on several different aspects. based on this information, the most promising mr brake type was selected, manufactured and tested on a specially designed test rig. the mr brake produced desirable results, which coincide with literature sources. approximately linear relation between the overall braking torque and the control current intensity was observed. to present results in more readable manner, the amplification factor was introduced. the experiment showed that the tested mr brake has potential for practical applications due to easiness and accuracy of control. however, the value of the overall braking torque is still small. to increase it, better utilization of the existing magnetic field is needed. the authors suggested different approach in comparison to the conventional mr brake design that would increase the overall braking torque by increasing the magnetic field efficiency and the contact area of the mr brake fluid. by multiplying the number of the disks in contact with mr fluid, value of the overall braking torque will multiply as well, eq. (7). in order to maximize the potential of the proposed mr brake, further investigations on magnetic field propagation is needed as well as design optimization. finite element method model of the novel mr brake is the next step in this process. acknowledgments this research was done as a part of project tr31046 “improvement of the quality of tractors and mobile systems with the aim of increasing competitiveness and preserving soil and environment”, supported by serbian ministry of science and technological development. mr fluid used in this experiment was provided by basf® company, under commercial name basonetic® 5030. the authors of this paper would like to express their sincere gratitude to basf company as well as to the project manager dr. christoffer kieburg for all the supports. references 1. t. m. avraam: mr-fluid brake design and its application to a portable muscular rehabilitation device, phd thesis, active structures laboratory, department of mechanical engineering and robotics, universit´e libre de bruxelles, bruxelles (2009) 2. g. bossis, s. lacis, a. meunier, o. volkova: magnetorheological fluids, journal of magnetism and magnetic materials, 252 (2002), pp. 224–228 3. j. d. carlson, m. r. jolly: mr fluid, foam and elastomer devices, mechatronics, 10 (2000), pp. 555–569 4. j. d. carlson, d. m. catanzarite, k. a. clair: commercial magnetorheological fluid devices, in proceedings of the 5th international conference on er fluids, mr suspensions and associated technology (ed. w. a. bullogh), singapore (1996), pp. 20–28 5. e. d. ericksen, f. gordaninejad: a magnetorheological fluid shock absorber for an off-road motorcycle, international j. vehicle design, 33 no 1-3 (2003), pp. 139–152 6. a. farjoud, n. vahdati, y. f. fah: mathematical model of drum-type mr brake using hershelbulkley shear model, journal of intelligent material systems and structures (2007), pp. 1–8 7. d. g. fernando: characterizing the behavior of magnetorheological fluids at high velocities and high shear rates, phd thesis, faculty of the virginia polytechnic institute and state university, blacksburg,virginia (2005) 8. f. d. goncalves, j. d. carlson: an alternate operation mode for mr fluids – magnetic gradient pinch, journal of physics: conference series, 149 (2009), pp. 1–4 9. k. h. gudnundsson, f. jonsdottir, f. thorsteinsson: a geometrical optimization of a magneto-rheological rotary brake in a prosthetic knee, smart materials and structures, 19 (2010) pp. 1–11 10. z. herold, d. libl, j. deur: design and testing of an experimental magnetorheological fluid clutch, strojarstvo, 52 no. 3 (2010), pp. 601–614 11. j. huang, j. q. yhang, y. yang, y. q. wei: analysis and design of a cylindrical magnetorheological fluid brake, journal of material processing technology, 129 (2002) pp. 559–562 12. a. jinung, k. dong-soo: modelling of magnetorheological actuator including magnetic hysteresis, journal of intelligent material systems and structures, 14 (2003) pp. 541–550 13. k. karakoc, j. e. park, a. suleman: design considerations for an automotive magnetorheological brake, mechatronics, 18, no. 8 (2008), pp. 434–447 14. k. karakoc: design of a magnetorheological brake system based on magnetic circuit optimization, phd thesis, department of mechanical engineering, university of victoria, victoria, canada (2007) 15. b. m. kavlicoglu, f. gordaninejad, c. a. evrensel, n. cobanoglu, y. lui, a. fuchs, g. korol: a high-torque magneto-rheological fluid clutch, proceedings of spie conference on smart 119 materials and structures, march 2002, san diego, pp. 1–8 16. k. kayler: lord corporation expands production of steer-by-wire tfd brakes to meet demand, available from: http://www.lord.com/newscenter/press-releases/lord-corporation-expandsproduction-of-steer-by-wire-tfd-brakes-to-meetdemand-.xml. (accessed on 6. 20. 2013.) 17. c. kieburg: mr-fluid basonetic 5030, technical information, basf se metall systems, ludwingshafen, germany (2010) 18. u. lange, l. richter, l. zipser: flow of magnetorheological fluids, journal of intelligent material systems and structures, 12 (2001), pp. 161–164 19. d. lampe, r. grundmann: transitional and solid state behaviour of a magnetorheological clutch. in proceedings of actuator 2000, bremen (2000) 20. w. h. li, h. du: design and experimental evaluation of a magnetorheological brake, the international journal of advanced manufacturing technology, 21 (2003), pp. 508–515 21. b. liu, w. h. li, p.b. kosasih, x. z. zhang: development of an mr-brake-based haptic device, smart materials and structures, 15 (2003), pp. 1960–1966 22. q. n. nguyen, s. b. choi: selection of magnetorheological brake types via optimal design considering maximum torque and constrained volume, smart materials and structures, 21 (2012), pp. 1–12 23. e. j. park, d. stoikov, l. f. da luz, a. suleman: a performance evaluation of an automotive magnetorheological brake design with a sliding mode controller, mechatronics, 16 (2006), pp. 405–416 24. n. phuong-bac, c. seung-bok: a new approach to magnetic circuit analysis and its application to the optimal design of a bi-directional magnetorheological brake, smart materials and structures, 20 (2011), pp. 1–12 25. j. rabinow: magnetic fluid torque and force transmitting device, us patent 2,575,360, 1951. 26. b. f. spencer, s. j. dyke, m. k. sain, j. d. carlson: phenomenological model of a magnetorheological damper, asce journal of engineering mechanics, 123, no. 3 (1996), pp. 1– 23 27. v. k. sukhwani, h. hirani: design, development, and performance evaluation of high-speed magnetorheological brakes, proceedings of the institution of mechanical engineers, part l: journal of materials design and applications, 222 (2008), pp. 73–82 28. j. wang, g. meng: magnetorheological fluid devices: principles, characteristics and applications in mechanical engineering, proceedings of institution of mechanical engineers – part l – journal of materials: design and application, 215 (2001), pp. 165-174 29. z. a. zainordin, a. m. abdullah, k. hudha: experimental evaluations on braking responses of magnetorheological brake, international journal of mining, metallurgy & mechanical engineering, 1, no. 3 (2013), pp. 195–199 700 content dokumentum1 eleje dokumentum1 elso dokumentum1 masodik dokumentum1 harmadik negyedik otodik dokumentum1 hatodik dokumentum1 másolat 7_bo_hijc_article_0804_vs1a3 dokumentum1 nyolcadik dokumentum1 kilencedik dokumentum1 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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page 427 page 428 page 429 page 430 page 431 page 432 page 433 page 434 page 435 page 436 page 437 page 438 page 439 page 440 page 441 page 442 page 443 page 444 page 445 page 446 page 447 page 448 page 449 page 450 page 451 page 452 page 453 page 454 page 455 page 456 page 457 page 458 page 459 page 460 page 461 page 462 page 463 page 464 page 465 page 466 page 467 page 468 page 469 page 470 page 471 page 472 page 473 page 474 page 475 page 476 page 477 page 478 page 479 page 480 page 481 page 482 page 483 page 484 page 485 page 486 page 487 page 488 page 489 page 490 page 491 page 492 page 493 page 494 page 495 page 496 page 497 page 498 page 499 page 500 page 501 page 502 page 503 page 504 page 505 page 506 page 507 page 508 page 509 page 510 page 511 page 512 page 513 page 514 page 515 page 516 page 517 page 518 page 519 page 520 page 521 page 522 page 523 page 524 page 525 page 526 page 527 page 528 page 529 page 530 page 531 page 532 page 533 page 534 page 535 page 536 page 537 page 538 page 539 page 540 page 541 page 542 page 543 page 544 page 545 page 546 page 547 page 548 page 549 page 550 page 551 page 552 page 553 page 554 page 555 page 556 page 557 page 558 page 559 page 560 page 561 page 562 page 563 page 564 page 565 page 566 page 567 page 568 page 569 page 570 page 571 page 572 page 573 page 574 page 575 page 576 page 577 page 578 page 579 page 580 page 581 page 582 page 583 page 584 microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 37(2) pp. 145-151 (2009) structural analysis of process models using their representation graph a. leitold1 , m. gerzson2 university of pannonia, department of mathematics, p.o.b. 158, veszprém, h-8201, hungary e-mail: leitolda@almos.vein.hu university of pannonia, department of electrical engineering and information systems, p.o.b. 158, veszprém, h-8201, hungary a graph-theoretical method for the structural analysis of dynamic lumped process models described by differential and algebraic equations (daes) is applied in this paper in order to determine the most important solvability properties (degree of freedom, structural solvability, model decomposition, dynamic degree of freedom, differential index, e.g.) of these models by using the so-called dynamic representation graph. the structure of the dynamic representation graph is suitable for the determination of the mentioned solvability properties. the most common methods in the modelling practice for the construction of models of complex systems are the union of submodels and hierarchical modelling. our goal is to investigate the effect of the model union to the solvability properties, especially to the differential index. we show how the representation graph of a complex model can be built up from the representation graphs of submodels. the effect of the structure of submodels and their joining points to the structure of the complex graph and the conclusions drawn from the complex graph structure to the solvability properties are also investigated. the representation graph of the complex model can be easily built up from the representation graphs of the simple models according to the linking of the technological subsystems. if one of the submodels has greater than one differential index then the under and overspecified subgraphs referring to this higher index can be found in the representation graph of the complex model, too. the change in the relative position of the underspecified and the overspecified subgraphs has an effect to the value of differential index. if these subgraphs move further from their original positions the value of the differential index increases. if their relative positions do not change during the built up process then the value of the differential index of the complex system is equal to the value of the differential index of the subsystem having the higher value. keywords: process models, model composition, dae-models, differential index, solvability, structural analysis introduction the structural analysis of dynamic lumped process models forms an important step in the model building procedure [1] and it is used for the determination of the solvability properties of the model, too. this analysis includes the determination of the degree of freedom, structural solvability, differential index and the dynamic degrees of freedom. as a result of the analysis, the decomposition of the model is obtained and the calculation path can be determined. this way the appropriate numerical method for solving the model can be chosen efficiently. moreover, advice on how to improve the computational properties of the model by modifying its form or its specification can also be given. effective graph-theoretical methods have been proposed in the literature [2, 3] based on the analysis tools developed by [4], for the determination of the most important solvability property of lumped dynamic models: the differential index. the properties of the dynamic representation graph of process models described by semi-explicit dae-systems have also been analysed there in case of index 1 and higher index models. beside the algorithm of determining the differential index by using the representation graph, a model modification method has also been proposed in the literature, which results in a structurally solvable model even in the case of higher index models [2]. basic notions structural solvability as a first step, we consider a system of linear or nonlinear algebraic equations in its so called standard form [4]: yi = fi (x, u), i = 1, …, m uk = gk (x, u), k = 1, …, k where xj (j = 1,…, n) and uk (k = 1,…, k) are unknowns, yi (i = 1,…, m) are known parameters, fi (i = 1,…, m) and gk (k = 1,…, k) are assumed to be sufficiently smooth real-valued functions. the system of equations 146 above is structurally solvable, if the jacobian matrix j(x, u) referring to the above model is non-singular. consider a system of equations in standard form. we construct a directed graph to represent the structure of the set of equations in the following way. the vertex-set corresponding to unknowns and parameters is partitioned as x ∪ u ∪ y, where x = {x1, …, xn}, u = {u1, …, uk} and y = {y1, …, ym}. the functional dependence described by an equation is expressed by arcs coming into yi or uk respectively from those xj and ul, which appear on its right-hand side. this graph is called the representation graph of the system of equations. a menger-type linking from x to y is a set of pairwise vertex-disjoint directed paths from a vertex in x to a vertex in y. the size of a linking is the number of directed paths from x to y contained in the linking. in case ⏐x⏐ = ⏐y⏐, (m = n), a linking of size ⏐x⏐ is called a complete linking. the graphical condition of the structural solvability is then the following [4]: linkage theorem: assume that the non-vanishing elements of partial derivatives fi and gk in the standard form model are algebraically independent over the rational number field q. then the model is structurally solvable if and only if there exists a menger-type complete linking from x to y on the representation graph. we can adapt the graphical techniques to daesystems, as well. an ordinary differential equation of a dae-system can be described by the following equation: x’ = f(x1,…, xn) here x denotes an arbitrary variable depending on time, x’ denotes the derivative of x with respect to time and x1, …, xn are those variables which have effect on variable x’ according to the differential equation. in dae-systems there are two types of variables. differential variables are the variables with their time derivative present in the model. variables, which do not have their time derivative present, are called algebraic variables. the derivative x’ is called derivative (velocity) variable. dynamic representation graph the value of differential variables is usually computed by using a numerical integration method. therefore a system of equations including also differential equations can be represented by a dynamic graph. a dynamic graph is a sequence of static graphs corresponding to each time step of the integration. on a dynamic graph there are directed arcs attached from the previous static graph to the succeeding static graph that are determined by the method applied for solving the ordinary differential equations. in case of a single step explicit method, the value of a differential variable at time t+h is computed using the corresponding differential value and its value at a previous time t. for example, when the explicit euler method is used: x(t+h) = x(t) + h⋅x’(t) where h denotes the step length during the numerical integration. the structure of a dynamic graph assuming explicit euler method for solving differential equations is shown in fig. 1. figure 1: dynamic representation graph assuming first order explicit solution method the structural analysis based on graph theoretical technique is carried out in steps performed sequentially. the first step is to rewrite the model into its standard form. the second step is the assignment of types to vertices in the representation graph. the important types of vertices determined by the model specification are the following [2, 5]: • <s>(set)-type variables: these represent variables, which are assigned to the specified given values. in the case of a dynamic representation graph assuming explicit method for solving the differential equations, the differential variables will be labelled by type <s*> because their initial value can be obtained from the initial values, and then their values can be calculated step by step by numerical integration. labels <s> and <s*> are treated the same way during the analysis. • <g>(given)-type variables: a variable assigned to a specific value of a left hand side is a <g>-type variable. unlike the <s>-type variables, the values of the right hand side variables will be suitably adjusted so as to preserve the equality of the two sides. according to the representation graph, the value of every variable which has incoming arcs only from vertices labelled by type <s> can be calculated by simple substitution into the corresponding equation. these variables become secondarily labelled by type <s>, and this process can be repeated if necessary. omitting all vertices labelled primarily, secondarily, etc. by type <s> and all arcs starting from them from the representation graph we obtain the reduced graph. the classification of vertices of a reduced graph is as follows: • all initial vertices form the unknown variable set x, • all terminal vertices labelled by type <g> constitute the known variable (parameter) set y, • all other vertices constitute the unkown variable set u. 147 differential index dynamic process models can be described by semiexplicit daes as follows: z1 ‘’= f(z1, z2, t), z1(t0) = z10 (1) 0 = g(z1, z2, t) (2) the most important structural computational property of dae models is the differential index [6]. by definition [7] the differential index of the semi-explicit dae (equations (1)-(2)) is one if one differentiation is sufficient to express z2 ‘’ as a continuous function of z1, z2 and t. one differentiation is sufficient if and only if the jacobian matrix gz2 is non-singular. in our earlier work we have proved that the differential index of the models investigated in [2] is equal to 1 if and only if there exists a menger-type complete linking on the reduced graph at any time step t. if the differential index of the investigated model is greater than 1 then there is no menger-type complete linking on the static graph at any time step t. the properties of a static graph of a dynamic model, which has differential index >1 are as follows. 1. the fact that the initial values of differential variables cannot be chosen independently results in an overspecified part on the graph. this situation can be easy shown by assignment of types to vertices corresponding to the model specification. there is an overspecified part on the graph if a vertex labelled by type <s*> or <g> can also be labelled preliminary, secondarily, tertiarily or etc. by type <s>. 2. non-singularity of gz2 results in an underspecified part on the graph. in this part those algebraic variables appear, which cannot be calculated from algebraic equations and those derivative variables, which we want to calculate from them. we have also proposed an algorithm using the structure of the representation graph for determination of the differential index of the underlying model. the main steps of this algorithm are the following: 1. let us form the following variable sets. i0 is the set of the differential variables belonging to the overspecified subgraph, d0 is the set of the derivative variables referring to the differential variables of set i0, i1 is the set of differential variables from which directed paths lead to the derivative variables in the set d0, d1 is the set of derivative variables referring to the differential variables of set i1, … , ik is the set of differential variables from which directed paths lead to the derivative variables in the set dk-1, dk is the set of derivative variables referring to the differential variables of set ik, … 2. let n be the smallest natural number for which the set dn contains some derivative variables of the underspecified subgraph. then the differential index of the model is νd = n+2 if there is no such number n then the model is not structurally solvable. in our earlier work we have shown that the important properties of the representation graph including the differential index of the models are independent of the assumption whether a single-step, explicit or implicit numerical method is used for the solution of the differential equations [8]. structural analysis of simple models using their representation graphs in this section, simple, small sized, dynamic models are investigated using their representation graphs. we show the influence of the change of the modelling goal (and so the model specification) and the modelling conditions to the differential index. the examples used in this and next sections are based on examples of [9]. example 1 – perfectly stirred tank reactor suppose a perfectly stirred tank reactor and let the concentration of its inlet flow be denoted by c0. the change of concentration in the tank can be described by the following equation: ( )cc v qc −=′ 0 (3) where c is the concentration in the tank, q is the outlet flow rate and v is the volume of the tank. case a) let us assume that we know the concentration of the inlet flow in the function of time: c0 = c(t), and we want to determine the concentration of the outlet flow. the standard form model consists of the following equations: c = ∫ c’ ( )cc v qc −=′ 0 c0 = c0(t) given: c(t0), c0(t); constant: q, v; to be calculated: c as a function of time. since the structural properties of the model described by representation graph can be investigated based on the structure of the static graphs, and these properties are independent from the arcs connecting individual static graphs to each other, we illustrate only one static graph as a representation graph of models for the sake of simplicity. the representation graph of this simple model is shown in fig. 2a. the reduced graph is an empty graph in this case indicating the differential index is equal to 1. we remark that the substitution of the condition c0 = c0(t) into the equation (3) results in a model of 148 technological system with only one differential equation, so the differential index would be equal to 0. case b) let us assume now that the modelling goal is the dynamic design of the same system, i.e. the determination of the necessary inlet flow concentration in order to ensure the required outlet concentration c = c(t). the standard form model is the following: a) b) figure 2: the representation graphs of the example 1 c = ∫ c’ ( )cc v qc −=′ 0 c = c(t) given: c(t0), c(t); constant: q, v; to be calculated:c0 as a function of time. in this case, there are an underspecified and an overspecified subgraphs on the representation graph (see fig. 2b) referring to the differential index greater than 1 value. the differential index can be calculated based on the structure of the representation graph: i0 = {c} d0 = {c’} since the vertex referring to the derivative variable c’ can be found in the underspecified subgraph, therefore n = 0 and νd = n + 2 = 2. example 2a – liquid mixer model suppose a liquid mixer tank having one inlet and one outlet flow (see fig. 3) the inlet flow consists of two components a and b. the two components have different density. there is a certain amount of liquid in tank at t = t0. the feed is perfectly mixed with the tank liquid. the density of the liquid in tank, the flow rates and the mol fractions of the components are functions of time. the number of moles (ni) of components a and b can be described by the following equation: ni ’ = f0xi0 – fxi where i = {a, b} where f0 and f are the inlet and outlet flow rate, and xi0 and xi are the mol fraction of the component i in the inlet and outlet flows, resp. let pl denote the pressure of the liquid at the bottom of the tank, a the area of the tank and mwi the molar weight of the component i. the outlet flow rate depends on the liquid pressure (pl) and the valve constant (k). figure 3: liquid mixer tank with variable volume the modelling goal is to calculate the liquid composition in the tank. the standard form model consists of the following equations: na = ∫ na’ nb = ∫ nb’ na ’ = f0xa0 – fxa nb ’ = f0xb0 – fxb n = na + nb xa = na/n xb = nb/n mw = mwaxa + mwbxb pl = p0 +(mw ⋅ n)/a f = k⋅(pl – p0)1/2 given: na(t0), nb(t0), xa0, xb0, f0; constant: mwa, mwb, a, k, p0; to be calculated: na, nb, f as functions of time. the representation graph of the model is shown in fig. 4. the reduced graph is an empty graph because there is no implicit equation in the model, therefore the differential index (νd) is equal to 1. figure 4: the representation graph of the example 2a example 2b – liquid mixer model with constant tank volume suppose a liquid mixer tank as in example 2a but let the volume of the liquid in the tank v be constant in this case (fig. 5). let va and vb be the molar specific volumes of components a and b, resp. the other assumptions are the same as in example 2a. the modelling goal is to calculate the liquid composition in the tank, again, but the modified volume condition must be taken into account. the standard form model consists of the following equations: na = ∫ na’ nb = ∫ nb’ na’ = f0xa0 – fxa nb’ = f0xb0 – fxb 149 n = na + nb xa = na/n xb = nb/n v = vaxa + vbxb v = n⋅v given: na(t0), nb(t0), xa0, xb0, f0, v; constant: va, vb; to be calculated: na, nb, f as functions of time. figure 5: liquid mixer tank with constant volume an overspecified and an underspecified subgraph can be found on the representation graph (see fig. 6) and the differential index can be determined based on their structures: i0 = {na, nb } d0 = {na’, nb’} since the vertices referring to derivative variables na’, nb’ can be found in the underspecified subgraph, n = 0 and νd = n + 2 = 2. figure 6: the representation graph of the example 2b structural analysis of composite models in this section, more complex composite models are built from the simple dynamic models of the previous section. the goal is to investigate the effect of this “build up process” of simple, small sized models, i.e the effect of the model composition to the structural properties of the composite models. example 3 – cascade of perfectly stirred tank reactors suppose a system consists of k perfectly stirred tank reactors. a feed of concentration c0 is fed into the first tank. the concentrations in the tanks are described by the following equation: ( ) k,,,icc v qc ii i i k211 =−=′ − where ci is the concentration in the tank i, q is the flow rates from tank to tank and vi is the volume of the tank i. two different specifications can be added to these equations according to modelling goal: a) in dynamic simulation studies the feed concentration c0 is given by c0 = c0(t); b) in dynamic design the product concentration ck is given by ck = ck(t). the representation graphs referring to these specifications can be seen in figs 7a and b. these graphs can be considered as multiplications of the representation graphs in figs 2a and b. in the first case, the reduced graph is an empty graph, therefore the differential index is equal to 1. in the second case, there are under and overspecified subgraphs on the representation graph and based on their structures: i0 = {ck} d0 = {ck’} i1 = {ck-1} d1 = {c’k-1} � ik-1 = {c1} dk-1 = {c1’} since the vertex referring to the derivative variable c1’ can be found in the underspecified subgraph, n = k – 1 and νd = n + 2 = k + 1. a) b) figure 7: the representation graphs of the example 3 the effect of the increasing differential index of the cascade model can be followed on the representation graph: the underspecified and the overspecified subgraphs move increasingly further from each other as the cascade elements are inserted. the path between the derivative variable c1’ of the underspecified subgraph and the differential variable ck of the overspecified subgraph is increasingly longer (the direction is not taken into account) and along this path the differential and derivative variables are located alternately. 150 example 4 – sequence of mixing tanks suppose that a system consist of a sequence of k mixer tanks (see fig. 8). let the volume of liquid in the tank j be constant while in the other tanks the liquid volumes are variables. the model of the constant volume tank is described in example 2b, while the models of the other tanks are the same as the model in example 2a. the following assumptions are held: a liquid feed stream is fed into the first tank. the feed consists of two components a and b. the liquid flows from the first tank through the system. the other assumptions are the same as in example 2a and 2b. the model of this cascade system using the models of example 2. is the following: nai = ∫ nai’ nbi = ∫ nbi’ nai’ = fi-1xai-1 – fixai nbi’ = fi-1xbi-1 – fixbi ni = nai + nbi where i = 1, …, k xai = nai/ni xbi = nbi/ni mwi = mwaxai + mwbxbi pli = p0 +(mwi ⋅ n)/a fi = k (pli – p0)1/2 where i = 1, …, k, i ≠ j figure 8: sequence of liquid tanks vj = vaxaj + vbxbj vj = nj⋅vj given: nai(t0), nbi (t0), i = 1, …, k xa0, xb0, f0, vj; constant: mwa, mwb, a, k, p0, va, vb; to be calculated: nai, nbi, fk as functions of time. this model is built up from k–1 differential index 1 models and one differential index 2 model according to the liquid mixing system. the representation graph of the whole system can be constructed easily from the representation graphs of the simple models (see figs 4 and 6). the resulted graph can be seen in fig. 9. an overspecified and an underspecified subgraph can be found on the representation graph and the differential index can be determined based on their structures: figure 9: the representation graph of the example 4 i0 = {naj, nbj} d0 = {naj’, nbj’} since the vertices referring to differential variables naj’, nbj’ can be found in the underspecified subgraph, n = 0 and νd = n + 2 = 2. in this example the union of the representation graphs of submodels has been created in such a way that the position of the underspecified and overspecified subgraphs referring to the higher differential index in the extended graph is unvaried to their original position, therefore the differential index of the complex model is the same as of the model of example 3b. conclusion in this paper we investigated the solvability properties of complex dynamic systems when they are built up from simple models. we have shown that the representation graph can be used efficiently for the investigation of the differential index during the model composition process, 151 too. the representation graph of the complex model can be easily built up from the representation graphs of the simple models according to the linking of the technological subsystems. if one of the submodels has greater than one differential index then the under and overspecified subgraphs referring to this higher index can be found in the representation graph of the complex model, too. the change in the relative position of the underspecified and the overspecified subgraphs has an effect to the value of differential index. references 1. hangos k. m., cameron i. t.: process modelling and model analysis. academic press, london (2001) 2. leitold a., hangos k. m.: structural solvability analysis of dynamic process models, computers chem. engng 25, (2001), 1633–1646 3. leitold a., hangos k. m.: effect of steady state assumption on the structural solvability of dynamic process models, hung. j. of ind. chem. 30 1 (2002), 61–71 4. murota k.: systems analysis by graphs and matroids. springer verlag, berlin (1987) 5. iri m., tsunekawa j., yajima k.: the graphical techniques used for a chemical process simulator ‘juse gifs’, information processing, 71. (1972) vol. 2, 1150–1155 6. gear c. w., petzold l. r.: ode methods for the solution of differential/algebraic systems, siam j. numer. anal. (1984) vol. 21, no. 4, 716–728 7. brenan k. e., campbell s. l., petzold l. r.: numerical solution of initial value problems in differential – algebraic equations. north-holland, new york (1989) 8. leitold a., hangos k. m.: numerical methodindependent structural solvability analysis of dae models, hung. j. of ind. chem. 33 (2005) 1-2, 11–21 9. moe h. i.: dynamic process simulation. phd thesis university of trondheim, dept. of chemical eng. (1995) microsoft word a_55_tothp_r.doc hungarian journal of industrial chemistry veszprém vol. 39(1) pp. 153-156 (2011) tyre pressure monitoring with wavelet-transform p. tóth , k. enisz, d. fodor university of pannonia, faculty of engineering, institute of mechanical engineering 10 egyetem street, veszprém 8200, hungary e-mail: petertoth.19810809@gmail.com the tire pressure monitoring system (tpms) is considered to be a widespread system in automotive industry. it has two basic aspects of view – direct and indirect. the first one uses pressure sensors while the second one uses the wheel speed signals of the esp system on board to make an estimation of the pressure levels of the tyres. the aim of this study is to find an indirect method which can be the competitor in digital signal processing of the most common and currently used fourier-transform, and can be a match for the classic solution in complexity, necessary runtime and efficiency. another part of this research is to find an appropriate model to generate wheel speed signals that contain the additional information to detect the pressure change, moreover to develop a function library for the research to support the measurements and to analyze the results. keywords: tyre, pressure, dsp, indirect, wavelet, fourier, complexity introduction nowadays the tyre pressure monitoring systems (tpms) are almost a standard equipment of mid-size passenger cars and this solution will be a mandatory feature for new cars in europe starting 2012. the reason is simple. due to some difference between the ideal and current pressure the traction and the stability can decrease dramatically and it can easily lead to an accident. methods there are two methods to measure the pressure in the tyres. the simplest one is to place intelligent pressure sensors in the tyres. their radio signals are acquired and the pressure levels can either be displayed in the cockpit or be used by the driving stability system on board. this solution, called direct monitoring, is simple and reliable as long as the batteries of the sensors and the sensors themselves last. if the signals of the wheel speed sensors (fig. 1) of an esp system contained some information about the actual pressure levels, this attribute could be used. the second method, called indirect monitoring, is based on this additional information in the speed signals. moreover using sensors already available in the vehicle instead of new ones would reduce the costs. figure 1 : a wheels speed sensor of a stability system once the tyre is on the wheel and it’s blown to a pressure level its circumference – apart from extreme driving manoeuvres and situations – can be considered to be constant. the only variant in this equation would be the tyre pressure. if it changes, the circumference changes as well. since the wheel speed sensors measure the rotational speed (ω) of the wheel and that value is multiplied by a constant radius (r) parameter (v = ω·r) the real circumferential speeds of wheels with different pneumatic pressures and equal rotational speeds may be diverse. the wheel with the smallest circumference runs the most, the one with the highest runs the least. this behaviour can be observed and after a few calculations quite a good tyre pressure feedback can be given. the weakness of this solution is that it’s less reliable as the vehicle speed increases. still in the indirect method the wheel speed signals can be observed from another point of view. the wheel can be considered as a spring-mass system. the spring is the flexible tyre the mass is the wheel base and some amount of the suspension. it starts oscillating while running on the road and as all such systems this one has 154 an eigenfrequency which appears in the wheel speed signal too (fig. 2). figure 2: the wheel speed signal used in the experiments this frequency depends on the amount of mass and the spring coefficient. the mass is usually constant so the only variant in this system is the tyre, mostly its pressure. the less pressure the tyre has the lower frequency appears and vice versa. current solution to gather the eigenfrequency of the mentioned system some kind of frequency analysis must be performed. the effective and obvious solution for this has been the fourier-transform so far. it decomposes the signal to its constituent frequencies and returns the amplitudes of them. its equivalent in digital world is the fast fouriertransform (fft). its result can easily be transformed to an exact form to find the most dominant components. figure 3: partial result of a fft once the transform has been performed the only work to do is to find the tyre’s eigenfrequency in it which is usually in the range of 40–60 hz. the example in fig. 3 has been calculated from 32 samples so as in the case of a fft the result will have 32 values. the fft is symmetric so only the half of the resulting array contains real information. therefore there are only 16 values available in the image (0...15). the sampling frequency (fs) is 200 hz so the highest detected frequency component at this sampling frequency is fs / 2 = 100 hz. the range of 0–15 in the result means a frequency range from 0 to 100 hz. the peak at 7 in the image means f = (100 hz/16)·7 = 43.75 hz. (1) however there are only 16 values for 100 hz which means there is 6.25 hz for each segment. therefore the actual eigenfrequency has to be calculated from all values instead of simply searching the maximal one. of course for higher accuracy more samples are necessary. development in this study the mentioned fourier-transform has been replaced by the wavelet-transform. more specifically by the haar-transform which is one of the simplest variants of the wavelet-transforms. it still contains the frequency information, but has time information in the result as well. to perform the haar-transform the haar-functions have to be calculated first. there always are as many haar-functions as many samples. the exact form to describe all these functions is as follows: ( ) n th 1 0 = (2) ( ) ( ) ( ) ( ) otherwise qtq qtq n th pp pp p p k 2/2/5.0 2/5.02/1 | | | 0 2 2 1 2/ 2/ <≤− −<≤− ⎪ ⎩ ⎪ ⎨ ⎧ −= (3) where k = 1...n; p = [log2k]; q = k – 2p + 1, the time is transformed to a [0 ; 1]interval, so 0 ≤ t ≤ 1. a possible output for the haar-transfom can be seen in fig. 4. if performed on a noiseless signal, the domains in it are easy to see (fig. 5). all of them belong to different frequency components but the different values within them contain the time information. figure 4: partial result of the haar-transform figure 5: domains in the haar-transform 155 table 1: domains in the haar-transform interval f tperiod 0 dc component ∞ 1 6.25 hz 160 ms 2-3 12.5 hz 80 ms 4-7 25 hz 40 ms 8-15 50 hz 20 ms 16-31 100 hz 10 ms the time information isn’t important at this point due to the narrow time interval of the 32 samples. fs = 200 hz → ts = 5 ms → t32samples = 160 ms (4) therefore only a mean value is calculated for each domain and the time information is cancelled. this way the disturbing noise effects can be damped a bit with a minimal loss of (unused) information. figure 6: mean values for each domain after the curve of the mean values is available (fig. 6) the different frequency values can be paired with their corresponding curves. the actual eigenfrequency can be found based on a frequency-curve table and some interpolation. the mean value of the domains described in table 1 can be seen in fig. 7 along the frequency range between 40 and 60 hz. the correlation of the mean values and the different frequency values is obvious, but the highest frequency domains have to be used in the calculations to get a definite result. figure 7: mean values of domains for different frequencies benefits the benefits of using the wavelet-transform can be measured in miliseconds. there is a comparison of the necessary running times in the following charts. the running times of a basic discrete fourier-transform (dft) and a discrete haar-transform (dht) were compared. figure 8: runtime with 32 samples; red: dht, blue: dft the experiment was performed on an average pc so the transforms had to be run 400 times to get quite an accurate measurement. this way the necessary time with 32 samples for dft was ~10.5 ms, for dht just above 4 ms. the new solution is 2,5 times faster already but let’s see what would happen if the amount of samples was increased to 64: 156 figure 9: runtime with 64 samples; red: dht, blue: dft the haar-transform got about 4 times faster. let’s see the same situation with 128 samples: figure 10: runtime with 128 samples; red: dht, blue: dft for this amount of samples the dht is at least 7 times faster than the dft. the complexity of the dft is considered to be o(n·log n). the complexity of the dht can be reduced to o(n) with a minimal optimization: its generator functions – mostly at higher frequencies – contain intervals full of zeroes. these parts can be ignored due to the pointlessness of multiplications with zero. otherwise the runtime would be similar to the runtime of the dft. this comparison may seem useless but the stability controller ecus in vehicles are usually equipped with low-end cpus. therefore every reduced µs matters. figure 11: runtime with 32, 64, 128 and 256 samples acknowledgement we acknowledge the financial support of this work by the hungarian state and the european union under the tamop-4.2.1/b-09/1/konv-2010-0003 project. references 1. f. gustafsson: virtual sensors of tire pressure and road friction, society of automotive engineers. warrendale, pn: 2001-01-0796 2. c. jaideva, a. goswami, k. chan: fundamentals of wavelets, john wiley and sons 3. n. persson: event based sampling with application to vibraton analysis in pneumatic tires. in: proceedings of ieee int conf on acoustics, speech, and sig proc 2001 in salt lake city, usa 6, 3885–3888 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word b_41_polak_r.doc hungarian journal of industrial chemistry veszprém vol. 39(2) pp. 317-320 (2011) efficiency and mass optimization of electric permanent magnet motor driven vehicle j. polák széchenyi istván university, department of automotive and railway engineering h9026 győr, egyetem square 1, hungary e-mail: polakj@sze.hu the propulsion system of road vehicles could be realized with the use of electric motor and a transmission system. complex analysis of these systems has been the topic of many recent researches, so an existing drive train has been chosen. the systems in this paper consist a permanent magnet 3 phase synchronous motor and switchable, continuously variable as well a constant ratio propulsion system. the most important variables in this study are the torque, rpm and power of motor, the combined efficiency dimensions and mass of drive train, vehicle mass, speed levels, mode and way of vehicle use. our target is to create such a drive train, which has the best efficiency and lowest weight at a defined power level. keywords: efficiency, mass, optimization, vehicle introduction the solution is an optimized selection, based on the analysis of different construction variants and gear ratios. from construction point of view, the most simple solution is the direct drive electric motor, what requires high size and expensive motor. gearbox applied in order to extend the rpm range will change dimensions, efficiency and makes the system more expensive. our goal is to find the ideal combination for the given vehicle. dynamic investigation of vehicle drive trains in case of internal combustion engine and electric motor the combined operation of internal combustion engine and vehicle can be described graphically on a torquerpm diagram, where we plot the torque of the crankshaft of the engine in the function of rpm, the constant power curves, the different resistances of the vehicle at different gear ratios and the specific consumption at different load and rpm levels. the torque of elevation and rolling resistance at the engine crankshaft can be described by the following equation: mψ = ψ·g·rg·ihm / ηhm the torque of drag projected as a resistance on the engine crankshaft can be calculated by the following equation (see on fig. 1): ml = 2·ρl·rg·a·cv·π2·ihm 3 / ηhm figure 1: the torque of drag projected as a resistance on the engine crankshaft figure 2: the torque of drag projected as a resistance on the electric motor shaft 318 based on the method above, the combined operation of electric motor and vehicle can be described on a fig. 2. in the diagram, you can see the efficiency of the electric motor instead of specific consumption. the correspondences above gives possibility of stationary study of different motor and transmission combinations, what makes the foundation of further and deeper analysis. electric motors applicable for vehicle drive the heart of all electric driven vehicle is the electric motor. they are existing in many variations, and belongs to the most efficient drive units. compared to the ic engines, electric motors crates zero emission. technically there are 3 moving parts on a motor, and estimated lifecycle is definitely longer then ic engines. the applicable electric motors for vehicle drive are the following: ● external excitation motors (coil or permanent magnet) ● ac motors a) reluctance motors (switched reluctance motor, srm), b) mcdc motors c) 3 phase electronic commutation direct current (ecdc) motors d) 5 phase ecdc motors e) bldc motors different type of electric motors may be classified based on the most important properties (table 1). current state of the art vehicle drives uses 3 phase pm synchronous motors, so we are going to study in this paper this type only. in our environment we have engineering know-how in design as well manufacturing ability. table 1: different type of electric motors bdc bldc/pms ac cont. excitat. ext. excitation reluctance crossfield power high small medium high good good high mass heavy light light light medium medium medium dimension big small medium small medium medium big rpm low high high medium medium high low cost medium expensive cheap very expensive medium cheap very expansive transmissions applicable for vehicle drive the following transmission types may be used for electric motors constant ratio transmissions ● chain drive ● cogged belt drive ● gear box type ● v-belt drive variable ratio transmissions ● gear type ● continuously variable transmission ● planetary gear transmission efficiency of transmissions may vary between 20–95% the value of efficiency of drive defined by technical literature, but these facts concern general situation. in this instance the correct choose of drive is with testing bench. studying the transmissions, there are two main types among them: constant ratio and variable ratio. when selecting a transmission type, two factors are taken into consideration: mass and efficiency. among this two parameters, also important factors are the complexity of transmission, what defines the manufacturing cost and feasibility for the certain application, as well the necessary auxiliary equipment parameters what has affect on overall mass and efficiency of the unit. studying the transmission types for electric driven vehicles available on the market, we may state that there are 3 main types of transmissions: chain drive – most of the case on two wheel vehicles cogged belt transmissions – commonly used on two wheeled vehicles and smaller four wheel vehicles planetary gear transmissions – medium and big sized four wheel vehicles small mass, low weight, simple construction, easy and fast repair are the advantages of the chain and cogged belt drives. meanwhile, because of the constant ratio, it is hard to optimize the transmission for the ideal conditions matching to the electric motor’s parameters. the advantage of applying planetary gear drives are the ability of changing gear ratios. this allows to operate the electric motor on the best efficiency range among different operation environment. although considering the switching mechanism, it makes a more complex and heavier transmission. weight and efficiency optimization of transmission motor: by studying weight/power ratio of electric motors, we can state, that the weight increase compared to power increase is smaller. see on fig. 3. for the mass optimization of a drive train, we can select dependent and independent variables. independent variables are: rpm of motor (n), diameter of motor (ǿ), mass of motor (mm), efficiency of motor (ηm) gear ratio (zh), mass of transmission (mh), efficiency of transmission (ηhm). dependent variables are the mass (mhl) and efficiency (ηhl) of drivetrain. 319 figure 3: the weight/power ratio of electric motors mass of drivetrain depends on the weight of motor and transmission: mhl = f(mm, mh) efficiency of drivetrain depends ont the efficiency of motor and transmission ηhl = f(ηm, ηhm) mhl = mm + mh weight reduction of pmsm motors can be performed on the following components: o weight reduction of copper (mcopper), o iron rotor mass reduction (miron), o magnet mass reduction (mmagnet). other components int he motor (front and rear cover, shaft, bearing etc) mass (mconst.) may considered as constant elements. mass of motor consist the mass of these components, so the weigh of the motors equals to: mpms = mcopper + miron + mmagnet + mconst changing the mass and proportions of the above mentioned components have effect on the pmsm motor characteristics, operational properties and efficiency. by applying transmission, beside the mass of the motor the mass of transmission will count as well: mhl = mpms + mh by increasing motor diameter, the torque derived by the motor also can be increased, but this way the inertia moment of motor will increase too, therefore the acceleration to the set point of motor will be slower. the torque is proportional to the dn/dt value of acceleration. πθ m dt dn dt dnπθm 2 2 =⇒⋅= by studying moment of inertia of the rotor, we can state that the moment of inertia is proportional to the square of the distance measured from the center of rotation. θ = m·r by application of hub motors, the motor and wheel common moment of inertia needs to be examined. by installing transmission unit, an additional rotating mass gets into the system, where the moments of inertia are cumulated. ∑ = ⋅= n i ii rmθ 1 2 therefore by increasing diameter of the motor, such motors can be designed, where the increasing torque and reduced rpm (max. 200–1200 rmp) by appropriate optimization the application of transmission unit may be omitted. by decreasing the diameter of the motor, the maximum torque output will be reduced as well, but the rpm of the motor can be increased (max. 4000–7500 rpm). although by reaching such rpm range, application of transmission system will be necessary. efficiency of drivetrain depends on the transmission and motor efficiency: ηhl = f (ηm, ηhm) drivetrain efficiency in case of hub motor: ηhl = ηm by applying transmission in the drivetrain, we have to take into consideration the transmission efficiency: ηhl = ηm·ηhm visible that the analysis of vehicle drives and motor, the work up convenient transmission system is a complicated mathematical analysis. the first step we make the adequate mathematical relation after we can test the convenient transmission on testing bench. we can get some results and these compare results with results of testing bench. summary goal of the study, is to develop and create the most efficient and lightest drivetrain and transmission to a given parametric system, (weight, speed, application area, etc.) vehicle. it is not possible to define the optimal drivetrain to a certain vehicle type. analyzing drivetrain parameters based on the vehicle input data can be chosen the most suitable drivetrain. for drivetrain analysis, mathematic modeling can be used, which leads to the most suitable drivetrain selection based on the dependent and independent variables considered in the system. by the use of math software, one can simulate and analyze the drivetrains. by studying the results, the drivetrain can be selected and built and tested on test bench. results of testing can be compared against modeling. this comparison gives feedback for further model creation, also it makes the optimization process examinable and analyzable. ef fic ie nc y de ns ity (k w /k g) 320 symbols mψ torque of elevation and rolling resistance on engine shaft ml torque of drag on engine shaft ψ rolling friction resistance g mass force of vehicle rg rolling radius ihm total transmission ratio ηhm transmission efficiency ρl air density a vehicle surface perpendicular to driving direction cv drag coefficient θ inertia moment n rpm of motor m mass r distance measured from shaft mhl mass of drivetrain ηhl efficiency of drivetrain ǿ motor diameter mm motor mass zh gear ratio mh mass of transmission mcopper copper (coil) mass miron iron rotor mass mmagnet magnet mass mconst. motor component mass ηm motor efficiency ηhm transmission efficiency acknowledgements tamop-4.2.1/b-09/1/konv-2010-0003: mobility and environment: research in the fields of motor vehicle industry, energetics and environment in the centraland western-transdanubian regions of hungary the project is supported by the european union and co-financed by the european social fund” references 1. l. guzzella, a. sciarretta: vehicle propulsion systems, springer-verlag, berlin heidelberg, 2005, isbn 978-3-540-25195-8 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word a_39_medve_r.doc hungarian journal of industrial chemistry veszprém vol. 39(1) pp. 141-146 (2011) analysis and modeling of slotless permanent magnet synchronous motors i. szalay1 , h. medve, d. fodor2 university of pannonia, institute of mechanical engineering, automotive system engineering group 8200 veszprém, egyetem u. 10, hungary 1 e-mail: ifj.szalay.istvan@gmail.com 2 e-mail: fodor@almos.uni-pannon.hu in the automotive industry, where reliability and cost efficiency are especially important, applications based on permanent magnet synchronous motors are gaining more and more ground. the slotless pmsms have high power and torque density, but they are much more difficult to model than iron cored ones and their sensorless control has not yet been completely solved. the main aims of this study are to better understand the physical phenomena in a slotless pmsm caused by the high frequency injection at standstill, to present an automated measurement environment and measurement results, and to suggest a partial position detection method for slotless pmsms at standstill. keywords: slotless permanent magnet synchronous motor, air core winding, modelling, sensorless position detection, initial position detection, high frequency injection, digital signal processing. introduction sensorless control of permanent magnet synchronous motors is a low cost and reliable alternative to traditional sensor based pmsm control and therefore is becoming widely accepted by the industry. during the latest decades various sensorless methods has been developed, which can be used successfully in the control of conventional variants of pmsms. the control of pmsms is based on the rotor position feedback, which is essential to perform correctly the electronic commutation. to start the motor without any unwanted vibration and reverse rotation, as it is required in many applications, and to do precise position control, it is necessary to know the initial rotor position. however, there are some types of pmsms, such as slotless ones, on which the standard sensorless position detection methods fail at low and zero speed or behave in unpredictable ways at any speed, making it impossible to detect the initial rotor position. the most promising sensorless method for precise initial position detection is high frequency signal injection, which is able to transform the effect of anisotropic characteristics of nd2fe14b permanent magnet rotor into angle dependent electrical quantities. this means that the (current, induced voltage, etc.) response of the pmsm for a given sinusoidal excitation voltage will vary, depending on the rotor position. the high frequency signal injection can be used with slotless air-core winding motors too, because the success of the measurement depends on the anisotropic properties of the permanent magnet instead iron saturation. in this study, the analysis of slotless pmsms is presented including mathematical and physical modelling of the rotor permanent magnet and a differential measurement method of the induced voltages at zero speed. measurement result, signal plots, a national instruments labview1 based automated measurement environment, the discovered motor characteristics and based on these motor characteristics, a partial sensorless rotor position detection method for slotless pmsms are also presented with explanations and comments on them. mathematical modelling electric drives are complex electromechanical systems. their power supply and their control is usually electrical and their output is usually mechanical. therefore usually their modeling is interested in only the electrical and mechanical phenomena. however, if the magnetic structure of the motor is important (because the existence of anisotropies, saturation, hysteresis, and the combination of them are not negligible) then it should be taken into consideration thoroughly. most of sensorless position detection methods are based on the anisotropic magnetic phenomena, so the analysis of the magnetic structure and its effect on the electrical signal is very important from both theoretical and experimental view. 1 labview is a trademark of national instruments corporation 142 geometric model the modeled pmsms are cylindrically designed ones, they have 3 phase slotless windings on their stator and a cylindrical permanent magnet on their rotor (see fig. 1). the motor parts are considered to be perfectly cylindrical shaped. figure 1: the tructure of a slotless pmsm electrical model the voltage equations of the phases (the voltage reference point is the star point): i i i ri dt du + φ = (1) where: ui, ii – voltage and current of phase i φi – magnetic flux in phase i r – resistance of one phase winding the flux in phase i can be dissolved into flux components that are produced by the windings and the permanent magnet: ( ) imiicibiai ri dt du +φ+φ+φ+φ= (2) where: φij – magnetic flux component in phase i produced by phase j φmi – magnetic flux component in phase i produced by the permanent magnet rotor the phase flux can be dissolved into products of inductances and current derivatives: micicbibaiai ililil φ+++=φ (3) where: lia, lib, lic – inductances corresponding to phase i the change of the phase flux component from the permanent magnet induces the following voltage component, which can be considered proportional to the actual rotor angular speed, so the flux of the permanent magnet is constant, only rotation can cause changes. equation (3) defines three flux equations for a three phase motor. the vectorial flux equation, which describes the relation between the phase fluxes and phase currents: ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ φ φ φ + ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ = ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ φ φ φ mc mb ma c b a cccbca bcbbba acabaa c b a i i i lll lll lll n 1 (4) mil n φ+=φ 1 (5) where: φ, φm – total and permanent magnet flux vectors l – inductance matrix n – number of turns of a phase winding in the development of the sensorless method’s mathematical background it is an important task to determine the l inductance matrix, and its dependencies on the other physical quantities, especially the rotor’s angular position. in the magnetic modeling one of the main goals will be to write the inductance matrix into a form, which uses the magnetic properties of the motor. the inductance matrix is important also because it is the mathematical object which describes the relationship between the electric and magnetic parts of the model. magnetic model the most important physical phenomena were the followings during the mathematical modeling of the motor’s magnetic structure: saturation: the rotor permanent magnets reluctance is flux dependent. hysteresis: b-h curve of a permanent magnet is a hysteresis loop. anisotropies: the rotor permanent magnets reluctance and probably the saturation and the hysteresis are anisotropic quantities. another phenomenon, that should be considered, is the eddy current on the rotor permanent magnet surface. for geometrical reason the motor model should be divided into two parts: stator and air gap model, rotor model. stator and air gap: stator contains the air core windings, the air gap between the windings and the rotor, and the external iron cylinder. the air gap and the air core can be discussed together as a simple reluctance. the external iron cylinder, the air core and the air gap can be modeled as constant reluctances. the stator windings are magnetomotive forces in the magnetic circuit. rotor: the rotor is a permanent magnet, which is a cylinder-shaped object. the permanent magnet can be modeled as a magnetic circuit, which contains reluctances and magnetomotive forces. first it is practical to model separately the reluctances and the magnetomotive forces, to create a reluctance model and a magnetomotive model, and then connect them. suppose the rotor is cylindrical perfectly, the magnetic field of the rotor permanent magnet is symmetrical to the plane defined by the d axis and motor shaft. 143 the field lines of the magnetic field go through the rotor surface only on the cylinder-cover. the flux flowing through the cylinder base of the rotor is zero. the field lines don’t close inside the rotor permanent magnet, so the leakage flux is 0 wb. reluctance model hypothesis: the reluctance between two circumferential points opposite each other depends on the point pair and the flux flowing from one to the other. in other words, using the symbols of fig. 2, the reluctance ℜab depends on the angle φ1 and ℜcd depends on φ3 and both reluctances depend on the actual φ flux flowing through the permanent-magnet. φ1 φ3 d q s n a b c d θ d q α β mc mb ma figure 2: illustration of reluctancies between arbitrary circumferential points (left) and the equivalent star connected reluctances (right) so any φ angle and φ flux define an ℜ(φ, φ) “passing through” reluctance value, which can be divided into two radial reluctance components: ( ) ( ) ( )φ−+ℜ+φℜ=φℜ ,,, 111 πϕϕϕ mm (6) where ℜm(φ, φ) is the “radial” reluctance function of the rotor magnet, which defines the “radial” reluctance between the center and the surface point in the direction of the φ angle, when the flux flowing through is φ. the reluctance between non-opposite surface points can be divided into two “radial” reluctances. for example, the reluctance between the points a and c, when φ flux flowing through from point a to point c, is computed in the following way using the ℜm(φ, φ) function: ( ) ( )φ−ℜ+φℜ=ℜ ,, 31 ϕϕ mmac (7) where: φ1, φ3 – see fig. 2. the above method has some error, which is greater when the difference of the two angles (in the above example the difference of φ1 and φ2) is smaller. if the difference is large enough (for example 120°, as it is between the center lines of the phase windings), then the error can be acceptable. the whole rotor magnet can be modeled as reluctances connected in a star using the ℜm(φ, φ) function, see fig. 2 (right). the phase reluctances and their pins are fixed in the standing coordinate system. because the rotor can rotate, the value of the phase reluctances will change, and will depend on the rotor position θ. describing the phase reluctances with the ℜm(φ, φ) function yields with indexed quantities: ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ φ+−ℜ=ℜ immi i , 3 2πθ (8) where ℜmi is the reluctance component of phase i at θ angular rotor position. magnetomotive model the flux density by the circumference is supposed to be sinusoidal. fig. 3 shows flux density is plotted against the φ angle in the (d – q) coordinate system. φ90° 180° 270° 360° b φ b0 ­b0 b0cos φ figure 3: flux density by the circumference the flux density by the circumference is supposed to be sinusoidal. suppose the flux density is parallel to the surface normal in every point of the surface. φ d q α=a β c b a3, k3 a1, k1 a2, k2 φma φmc φmb φma φmc φmb figure 4: the magnetomotive forces, reduced into three parts and three pins the rotor’s model should have three pins for connect them to the three phases through the air gaps. these pins are surface third parts contracted into single points. the pins are on the centers of the third parts which are 120° parts of the cylinder-cover. the fluxes flowing through the surface third parts, which are attached to the fixed (α – β) system, depends on the θ angular rotor position. 144 measurement conception in the focus of the performed measurements was the data acquisition for developing the high frequency injection based sensorless rotor position detection method of the pmsms at zero speed. the analysis of the rotor position’s effect on the induction, induced voltages, and current response requires measurement data. the examined motors were a maxon ec 118890 with two pole rotor magnet and a maxon 252463 type motor with four pole rotor magnet. excitation process on the examined motors one phase excitation method has been applied using the star points of them. in the automated process the stepper motor (48 steps per rotations) rotates the rotor of the pmsm to the desired position. the connection of the non-excited windings to the oscilloscope and the excited winding to the amplified function generator output is provided by the control strategy of relay network. this procedure is repeated for all three phases of the motor, so this method results in three measurements at a specified angular position. the three phase voltages are treated as excitation voltage (ue), “positive” induced voltage (up) and “negative” induced voltage (un). the “positive” and “negative” denominations are for clearing the sign of the δu difference. in the performed measurements the amplitude of the excitation voltage was 5 v, the frequency was 1 khz. figure 5: the measurement configuration and the measured signals. the star point of the stator winding has been made accessible for measurement purposes table 1: excitation and measurement pattern ue (excited) up (meas.) un (meas.) δu=up-un 1 2 3 2-3 2 3 1 3-1 3 1 2 1-2 table 1 defines the roles of the phase windings during the three steps of the measurement at a specified position, and the definition of the induced voltage difference, δu. measurement environment the measurement environment includes a tektronix® mso4154b oscilloscope, a tektronix® afg3022b arbitrary function generator, and a control card for isolation, switching and stepper driving purposes. data acquisition and high level control is performed by national instruments labview (see fig. 6). the measurable physical quantities: ● excitation voltage before or after amplifying, ● current response in the excited phase winding, ● induced voltages in the non-excited phase windings, ● difference of the induced voltages, amplified by an instrumentation amplifier the measurements have been done by 1 µs sample time, which was enough to sample 1 khz frequency signals without aliasing. the waveform, amplitude and frequency of the excitation voltage are automatically adjustable. the simplest way of high frequency current measurement was the use of a precision current shunt. measurement results measurements from 0° to 360° with 48 step resolution has been performed to get the entire angular characteristics of the induced voltage difference. the results of the measurements can be seen on fig. 7 and fig. 8. figure 6: structure of the measurement automation environment 145 figure 7: the characteristics of the measured induced voltage difference on the maxon ec 118890 while phase 1 was excited (coloured 3d surface, z(x, y) = δu(θ, t)), the scaled excitation voltage (black line, for phase illustration) and the extreme values of the difference signal (red lines). figure 8: the induced voltage difference characteristics for all the three phases. continuous lines show the extreme values of differences closer to the maximum of the corresponding excitation voltage, dashed lines show the closer to the minimum characteristic curves shown on fig. 7 and fig. 8 prove the existence of measurable anisotropic effect of the permanent magnet on the electrical signal, in the case of slotless maxon pmsms. in the case of 5 v excitation voltages, the difference between the induced voltages reaches the 100–180 mv interval, depending on the excited phase. the weakness of the discovered phenomenon has a periodicity of 180° (all the curves on fig. 8 have a periodicity of 180°), which isn’t enough to clearly determine the rotor position; the number of possible rotor position values can be reduced to two opposite angular position (0 – π ambiguity problem). 146 data analysis the primary goal of the data analysis is to find the anisotropic characteristics – angular dependencies of electric parameters and signals – of the maxon slotless pmsms. simplest way of anisotropy analysis is the construction of the characteristics of a measured or computed quantity versus angular position. mathworks® matlab®2 has been chosen as development environment for signal analysis and data visualization. a processing program has been developed, which visualize the excitation voltage and current, the induced voltages and their difference, the phase shift between any of the chosen signals, amplitude characteristics, phase characteristics, inductivity changes. the processing program reads the signals from the text files generated by the selected measurement, and performs some preprocessing and signal conditioning task, like filtering, amplification and scaling. induced voltage difference analysis fig. 9 and fig. 10 show the most significant parameters, amplitude and phase of the induced voltage difference. figure 9: the amplitudes of the induced voltage differencies on the maxon ec 118890 (red line: phase 1 excited, green line: phase 2 excited, blue line: phase 3 excited) figure 10: the phases of the induced voltage differencies on the maxon ec 118890 (red line: ph. 1 excited, green line: ph. 2 exc., blue line: ph. 3 exc.) 2 mathworks® and matlab® are registered trademarks of the mathworks, inc. partial position detection method the phases (πi) of the three induced voltage difference signals can be used to coarse position detection. according to fig. 10, each πi has two possible discrete value with π rad difference, and there is six combination of πi-s. that makes possible to reduce the rotor position value into two 30° size, opposite sector. conclusions an automated mesurement environment has been implemented for support the development of a sensorless initial position detection method for slotless pmsms. the analysis of the measured signals discovered measurable anisotropic effect, which depends on the rotor position, but the detected phenomenon has a periodicity of 180°. so an other method is needed to distinguish between the magnet poles to solve the 0 – π ambiguity problem. in the theoretical part of the work the ℜm(φ, φ) radial reluctance function for the rotor magnet should be determined. acknowledgement we acknowledge the financial support of this work by the hungarian state and the european union under the támop-4.2.1/b-09/1/konv-2010-0003 project. references 1. j. persson: innovative standstill position detection combined with sensorless control of synchronous motors, (2005) 2. m. linke, r. kennel, j. holtz: sensorless position control of permanent magnet synchronous machines without limitation at zero speed. ieee 2002, 28th annual conference of the industrial electronics society, vol. 1, (2002) 674–679 3. d. c. hamill: lumped equivalent circuits of magnetic components: the gyrator-capacitor approach. ieee transactions on power electronics, 8(2), april, (1993), 97–103 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word szolcs_eloszo.doc hungarian journal of industrial chemistry veszprém vol. 32. pp. 41-56 (2004) novel particle engineering techniques in drug delivery: review of coformulations using supercritical fluids and liquefied gases v. majerik1, g. horváth1, g. charbit2, e. badens2, l. szokonya1, n. bosc3 and e. teillaud3 1department of chemical engineering science, university of veszprém, p.o. box 158, h-8201, hungary 2laboratoire de procédés propres et environnement (lppe), europôle de l’arbois, domaine du petit arbois, rd 543, 13545 aix-en-provence cedex 04, france 3merck santé, 37 rue st romain 69379 lyon cedex 08, france contact information: majerikv@almos.vein.hu this paper aimed to survey the numerous publications and patents issued in the fields of supercritical fluid assisted and cryogenic formulation techniques with special regard to coformulations of active substrate – excipient composites. these methods open new possibilities in formulation of drug carrier composites with targeted physical properties including particle size, morphology, crystallinity, polymorphism and residual solvent content both methods were proved to be viable alternatives to conventional formulation techniques. introduction lately, coformulations of active pharmaceutical ingredients (api) with biodegradable polymers draw more and more attention. composites of drugexcipinet systems are widely used in controlled delivery systems and formulation of water insoluble apis. in controlled drug delivery the release of the api may be constant or cyclic over a long period, or it may be triggered by the environment (ph, enzymes, temperature, ion strength, chemical species, etc.). the main goal of controlled drug delivery is to achieve more effective therapies with fewer administrations and avoid both underand overdosing. depending on the route of administration (oral, transdermal, parenteral, intranasal, intravenous, intramuscular, subcutaneous or intraocular) drug formulation techniques must meet additional requirements concerning the physical properties of dry powder or emulsion. one of these properties is the particle size. for instant, only nanoparticles can be injected intravenously while particles in the range of 1-5 µm are suitable for pulmonary delivery, particles ranging from 5 to 100 µm are subcutaneously injectable. conventional techniques for the production of drug-loaded microparticles including emulsion and double-emulsion solvent extraction, spray and freeze drying, liquid antisolvent and solvent evaporation are generally associated with high residual solvent contents, low encapsulation efficiencies and thermal degradations. apart from spray-drying all of these techniques are multi-stage processes. in certain cases dry powder must undergo a micronisation step – usually by milling – to generate the required particle size and size distribution. micronization techniques like air jet milling have several disadvantages (cohesive, electrostatically charged product with occasional crystallographic defects). researches of recent years pointed out that supercritical fluid processes offer alternative single-step methods to prepare micronized dry powder of apis with controllable physical properties including particle size, morphology, crystallinity, residual solvent content, etc [1]. 42 coprecipitations of drug-excipient systems are also widely used in formulation of poorly water soluble apis [2]. the most important methods of drug solubilization are (1) formulation of solid dispersion (or solid solution), (2) preparation of surface modified nano and microparticles and (3) complexation of api in water soluble cyclodextrin derivates. solid dispersions of drug-excipient systems are composites containing nanosized particles of crystalline or amorphous api homogenously dispersed in the carrier particles. the solid dispersion that contains api dispersed on molecular level is referred to as solid solution. formulations containing amorphous forms are generally more soluble than their crystalline counterparts but for the same reason they are less stable and may tend to crystallize during the product shelf life. these materials are often sensitive to water sorption, mechanical and thermal stresses. surface modification techniques aim to hide the hydrophobic nature of the surface of drugparticles either by forming an adsorbed layer of surfactants or by coating with hydrophilic polymers. this approach requires smaller amount of excipient compared to solid dispersion [3]. the third method is forming inclusion complexes of apis and water soluble cyclodextrin (cd) derivates. in addition to conventional techniques – hot melt extrusion, spraydrying and solvent evaporation – amorphous composites can be obtained by cryogenic formulation techniques discussed in the second chapter. coformulations using supercritical fluids since the first experiences of hannay et al. in 1879 [4], application of dense gases in crystallization processes has made a long way [1,5]. this chapter reviews the different techniques published and patented so far in the field of particle design with supercritical fluids with special regard to coprecipitation of active substrate-carrier matrix composites. beside the most important techniques such as the rapid expansion from supercritical solution (ress), particles from gas-saturated solution (pgss), gas antisolvent (gas), supercritical antisolvent (sas), solution enhanced dispersion by supercritical fluids (seds), precipitation with a compressed fluid antisolvent (pca) and the aerosol solvent extraction system (ases), some other less known methods were as well discussed like rapid expansion from supercritical solution with a non-solvent (ressn), rapid expansion from supercritical to aqueous solution (resas), rapid expansion of liquefied gas solution (relgs), rapid expansion of liquefied-gas solution and homogenization (relgs-h) and polymer liquefaction using supercritical solvating (pluss) (see fig. 1). these methods use supercritical fluids (scf) either as solvent (ress) or antisolvent (gas, sas, ases, seds) and/or dispersing fluid (gas, seds, pgss). as applied scfs (usually co2) are gases at ambient temperature and pressure, they are easy to separate from both organic cosolvent and solid product, therefor supercritical technology is considered as clean, recyclable and “green” technology. in addition, carbon dioxide – the most commonly used fluid – is chemically inert, nontoxic, non-flammable and inexpensive. having mild critical temperature (31,1 °c) and a critical pressure of 73,8 bar, co2 is suitable to treat heat-sensitive materials – even explosives – without any thermal degradation with relatively low energy costs. rapid expansion of supercritical solution (ress) ress consists in depressurising the solution of the solid substrate solvated in supercritical fluid through a heated nozzle (10-50 µm, i.d.), causing an extremely rapid nucleation of the substrat in question [4]. this process is attractive due to the absence of organic solvent, but efficiency and/or feasibility depends on the solubility of the treated substrate in scf at the operating temperature and pressure. to overcome the difficulties associated with scco2-insoluble polar compounds and high molecular weight polymers, mishima et al. have invented a new method called rapid expansion from supercritical solution with a non-solvent (ress-n). this process involves a second solvent which solubilizes the solid substrates in supercritical conditions but doesn’t dissolve them at atmospheric pressure. this cosolvent is homogenized in the pure scf before the extraxtion unit, the modified scf is saturated in the solid substrates and expanded through a nozzle to atmospheric pressure [6]. this method was afterwards used for encapsulation of proteins (lysozyme, lipase) as well as flavone and 3-hdroxyflavone in biodegradable polymers like: polyethylene glycol (peg), poly(methyl methacrilate) (pmma), poly(lactic acid) (pla), poly(lactic-co-glycolic acid) (plga); poloxamer and eudragit e100 [7-9]. the concentrations of cosolvents must be at least 27 % (w/w) to achieve enough high solubility of polymer in scco2/cosolvent system and the active principle must be insoluble in the chosen cosolvent. 43 in 1994, frederiksen et al. patented a method suitable to prepare liposomes containing at least one phospholipid, an excipient and a water soluble api [10,11]. phospholipids and excipients were dissolved in an appropriate polar solvent and homogenized in scco2, this solution was afterwards expanded to atmospheric pressure and simultaneously dispersed in the aqueous solution of api. residual organic solvent can be removed by evaporation, dialysis or gel filtration. five years later, ma shuxian patented another process for preparation of liposomes by (1) dissolving a phospholipid, an excipient and a lipophilic api in compressed or supercritical co2 (2) releasing the co2 until the density of co2 is lower than that of lipophilic api (3) quickly depressurizing the vessel (4) loading a dispersing liquid and stirring in order to form api-coated liposomes [12]. to obtain sub-micron particles of water-insoluble solids henriksen et al. submerged the nozzle of ress process in an aqueous solution containing surfactants, typically phospholipids [13] . in another embodiment of the invention api is precipitated by compressed gas antisolvent method and stabilized in the aqueous solution. stabilized suspensions of cyclosporine, indomethacin and tetracaine hi nanoparticles were prepared. young et al. detailed the precipitation of cyclosporine sprayed in a solution of tween-80 polymer. the mean particle size was between 400 and 700 nm and the solubility of cyclosporine increased significantly [14]. resas (rapid expansion from supercritical to aqueous solution) is a viable method to enhance the solubility of actives principles that are insoluble in water but soluble in scco2. godinas et al. invented a process wherein an active principle together with a surface modifier is dissolved in a dense gas which is afterwards expanded in an aqueous solution containing a second – optionally, identical to the first – surface modifier and other additives [15]. this technique was patented by the name of rapid expansion of liquefied gas solution (relgs) or rapid expansion of liquefied gas solution and homogenization (relgs-h). suspensions of fenofibrate and cyclosporine were prepared with mean particle sizes of 200 and 23 nm, respectively. the surface modifiers were lipoid-80 and tween-80 dissolved in scco2 in the case of fenofibrate and tween-80 in fluid phase with egg phospholipid and mannitol in aqueous phase for cyclosporine. obviously, the latter three inventions – resas, relgs and relgs-h – are applicable only in the case of water-insoluble compounds. also, in 1999, bausch et al. patented a method wherein a biologically active substrate is dissolved in a compressed gas, liquid or scf containing a surface modifier, and is either expanded to lower pressure or dispersed in an anti-solvent phase [16]. table 1. summary of drug-carrier systems precipitated by ress and related methods. substrate excipient observation references lovastatin pla needles of substrate in polymer microspheres [17] pyrene pla solid dispersion [18] znpc(so3h)4 a fitc-dextranb popc c cholesetrol liposomes, 200 nm [10,11] naproxen pla microcapsules [19] cyclosporine tween 80 phospholipid suspension, 28 – 80,9 nm [10] flavone 3-hydroxyflavone peg mean particle size: 10 µm [7] fenofibrate lipoid e80 tween 80 suspension, 0,2 µm cyclosporine tween 80 mean particle size: 23 nm [15] tetrahydrolipstatin brij 96 mean particle size: 1,4 – 2,1 µm aerosol ot mean particle size: 0,8 – 3,8 µm saquinavir brij 96 mean particle size: 1,4 µm [16] cyclosporine tween 80 suspension, 0,5-0,7 µm [14] 3-hydroxyflavone eudragit e100 microcapsules [8] lipase lysosyme peg pla plga pmma poloxamer microcapsules, 6 62 µm [9] lidocaine peg 8000 solid dispersion [20] a zinc-phthalocyanine tetrasulfonate; b fluorescein isothiocyanate-dextran; c 1-palmitoyl-2-oleoylphosphatidylcholine; 44 particles from gas-saturated solution (pgss) pgss consists in dissolving a compressed gas – supercritical fluid – in a molten solid or in a solution or suspension of solid substance followed by a rapid expansion to lower – atmospheric – pressure [21]. the very first application of the pgss concept related mostly to paint and polymer industry particularly to powder coating [22]. since the solubilities of compressed gases in liquids and solids like polymers are usually much higher then those of such liquids and solids in the compressed gas this method is proved to be more advantageous over ress. active ingredients can be micronized from aqueous solution as well according to the patent of sievers et al. [23]. since co2 is one of the most soluble gases in water, depressurization of the ternary mixture – solid-water-co2 – produce extremely high expansion. water can be evaporated from the aerosol in high temperature furnace to obtain dry powder. in 1998 shine et al. patented a method called polymer liquefaction using supercritical solvating (pluss) whereby pgss method is applicable below the melting point of the processed material [24]. as polymers in high pressure co2 atmosphere swell or melt at lower temperature, active substrates can be dispersed and encapsulated without any thermal degradation. shakeseff and coworkers from the university of nottingham have successfully applied scco2 as dispersing and plasticizing fluid to prepare composites of biologically active materials and polymers [25-28]. kerc et al. described the micronization of three pure drugs (nifedipine, felodipine and fenofibrate) as well as their composites with peg 4000 polymer by pgss process [29]. the addition of polymer to the solid substance avoids agglomeration, enhances the solubility of treated drug in water and decreases considerably the process temperature [30]. table 2 summary of drug-carrier systems precipitated by pgss and related methods. substrate excipient observation references ibdv vaccinea polycaprolactone agglomeration of fine particles [24] nifedipine peg 4000 non-regular porous particles [30] nifedipine felodipine fenofibrate peg 4000 mean particle size: 16 30 µm [29] avidin pla solid solution [28] avidin pla-peg-biotin protein-loaded particles [26] rhbmp-2b pla porous scaffolds [25] ribonuclease a lysozyme pla protein-loaded particles, 10 300 µm [27] theophylline hpoc microcapsules, 2,5 3 µm [31] a infectious bursal disease virus; b growth factor recombinant human bonemorphogenetic protein-2; c hydrogenated palm oil; gas antisolvent (gas) when a gas is absorbed in a solution this latter gradually expands and losses its solvent strength. this sudden drop in solvent strength leads to the precipitation of dissolved substrates from the supersaturated solution. gas process claims a precipitator, which is partially filled with the solution of api (and excipient). the supercritical fluid is preferably introduced at the bottom to achieve a better mixing. unlike the other antisolvent processes described later, in that case the liquid phase is the continuous one and the antisolvent constitutes the dispersed phase. when precipitation is complete particles are washed in pure scf. among the related patents the one of krukonis et al. represents the most what we call gas process [32]. authors described crystallization of two difficult to handle explosives (rdx and nq), an inorganic salt (cobalt chloride) and a pharmaceutical precursor (saligenin). two years latter pallado et al. patented a gas application whereby microcapsules of apis and biocompatible polysaccharides can be obtained [33]. recently, moneghini and kikic achieved a remarkable enhancement of carbamazepine 45 dissolution rate using peg 4000 polymer in gas technology [34]. drug and peg 4000 particles were still distinguishable at d/p = 1:1,5. at d/p = 1:11 they precipitated together, but crystalline drug remained detectable. corrigan et al. compared three formulation methods including solvent evaporation, spray drying and gas recrystallization [3]. hydrocortisone and polyvinylpyrrolidone (pvp) were coprecipitated in different d/p ratios. it was found that spray drying was the most effective process for eliminating hydrocortisone crystallinity, followed by gas and solvent evaporation. however, the highest dissolution rate was observed in the case of solvent evaporation, followed by spray drying. the dissolution rates of particles from gas recrystallisation were almost the same as those of physical mixture of drug and polymer. bertucco et al. described the encapsulation of potassium chloride and phenylpropanolamine in various polymers, including hydroxypropyl methylcellulose phthalate (hp-55), eudragit e and ethylcellulose (ec) [35]. authors used a stirred precipitator in batch mode. polymer concentration was found to have strong influence on particle morphology: at low concentration only partial encapsulation was observed, at high polymer concentration particles were aggregated. in a previous study bertucco et al. prepared controlled release particles of two steroids and a protein embedded in hyaff-11 (hyaluronic acid benzylic ester) polymer [36]. although, the authors called their process supercritical anti-solvent, it corresponds much more to gas, in our nomenclature. they obtained particles with an average diameter of around 4 µm. however, yields were rather poor for steroids due to their nonnegligible solubilities in scco2. table 3 summary of drug-carrier systems precipitated by gas and related methods. substrate excipient observation references insulin calcitonin gmscfd hyaff-7a hyaff-11b hyaff-11-p75c mean particle size: 0,1 1 µm [33] steroids hyaff-11 [36] kcl phenylpropanol-amine hp-55 eudragit e100 ec mean particle size: 500 nm [35] carbamazepine peg 4000 heterogeneous precipitate [34] hydrocortisone pvp particles with crystalline substrate [3] carbamazepine peg 4000 theophylline hpmc solid dispersion [37] carbamazepine peg 8000 gelucire 44/14 vitamin e tpgs e solid dispersion [38] carbamazepine pvp k30 gelucire 44/14 vitamin e tpgs solid dispersion [39] a ethyl ester of hyaluronic acid; b benzyl ester of hyaluronic acid; c partial benzyl ester of hyaluronic acid; d granulocyte macrophage colony stimulating factor; e d-α-tocopheryl polyethylene glycol 1000 succinate supercritical antisolvent (sas) aerosol solvent extraction system (ases) precipitation with a compressed fluid antisolvent (pca) sas (ases, pca) involves a capillary through which the solution of api is dispersed in a continuous scf flow. the nomenclature is not consistent at this point; certain authors use the name of sas as a synonym of gas. in this work sas (ases, pca) signifies the process wherein the solution is dispersed in the supercritical fluid or compressed gas by spraying through a capillary nozzle in a co-current gas anti-solvent flow. the main advantage of sas over gas is the faster expansion in steady state conditions, which results in higher nucleation rate, and hence smaller mean particle size and narrower size distribution. in addition, physical properties of processed powder 46 can be easily optimized by controlling the operating parameters like scf flow rate, solution flow rate, nozzle diameter, pressure and temperature. fisher and müller patented a coprecipitation process wherein a solution containing an active substrate, an excipient or both is dispersed in a scf flow optionally containing the excipient, active substrate or both [40]. authors used both single and multi-nozzle injection device and disclosed a number of ways in which the fluids can be contacted with one another. sterilizing capacity of the invented method was proved by treating eight microorganisms – including bacterias, fungis and yeasts – mixed with pla. samples were totally sterile due to the treatment at 140 bar 50 °c. in another example, clonidin-hcl was coprecipitated with pla from dichloromethane (dcm). in 1998 william j. schmitt patented a similar process. his method consists in dissolving a solid in an appropriate organic solvent and injecting the solution in supercritical fluid anti-solvent [41]. triamcinolone acetonide particles were precipitated from terahydrofuran (thf) both in static scco2 and continuous flow with particle diameters ranging from 10 to 30 mµ and from 5 to 10 mµ, respectively. also, in 1998, manning et al. patented a method, which extends sas over hydrophilic pharmaceutical substrates by using an amphifilic additive [42]. this additive – preferably a surfactant – forms a hydrophobic ion pair (hip) complex and solubilizes the active substrate. the resulting solution can already be subjected to any supercritical anti-solvent method. falk et al. prepared pla micro-spheres with embedded apis: gentamycin, naltrexone and rifampin by pca process [43]. the solution containing both the api and the polymer was dispersed through an ultrasonic spray nozzle instead of a capillary tube. gentamycin and naltrexone were solubilised in dcm by hydrophobic ion-pairing method; the chosen surfactant was sodium bis-2-ethylexyl sulfosuccinate. particles ranged from 0,2 to 1,0 µm in size, drug loading was higher for ion-paired pharmaceuticals due to their lower solubilities in scco2/dcm. in a subsequent study the authors focused on influence of process parameters on residual solvent level in pla coated gentamycin particles [44]. residual dcm content was found to decrease, when scco2 flow rate was higher during the precipitation. taki et al. used sas method to prepare controlled release system for the herbicide, diuron [45]. authors studied the effect of pressure, flow rate and composition on the solid dispersion of diuron in pla. it was confirmed that the morphology of coprecipitated particles depends heavily on the concentrations of drug and polymer. spherical particles of pla entrapping diuron with mean particle size between 1 and 5 µm were successfully precipitated when the concentrations of diuron and pla were below 0,1 and 3 % (wt.), respectively. sze tu et al. studied the effect of the main process parameters, like: pressure, temperature, spraying velocity, solution concentration and solvent strength on ases-precipitated pla particles loaded with para-hydroxybenzoic acid (phba) and lysosyme [46,47]. authors used a multiple nozzle (three-passages) with a capillary tube of 180 µm i.d. in the middle. initially, api and polymer were delivered in the same solution through the inner capillary tube. in a second stage, solution of active substrate was delivered in the inner nozzle and the polymer in the intermediate passage. the encapsulation efficiency – using the multiple nozzle – of p-hba and lysosyme was 8,2 % and 12,4 %, respectively. average drug loading was between 3 and 8 % (wt.) while theoretical drug loading was typically between 60 and 84 % (wt.). solution enhanced dispersion by supercritical fluids (seds) seds was described in sequential patents associated with the name of the university of bradford and recently bradford particle design plc [63-68]. this method claims a coaxial nozzle to co-introduce the scf and the solution of api in the precipitation vessel. due to the high velocity of scf – driven preferably in the inner passage – a jet is forming at the outlet of the nozzle wherein the scf brakes up the solution into small droplets and extracts the solvent. the high dispersion that characterises the jet leads to almost instantaneous precipitation of micron and sub-micron sized uniform particles. the main advantage of seds over other supercritical fluid based techniques is the fact that scf plays both the role of dispersing fluid and antisolvent which allows better control over mean size and size-distribution of the product. 47 table 4 summary of drug-carrier systems precipitated by sas, ases, pca and related methods. substrate excipient observation references clonidin-hcl pla agglomerated spheres, 10 – 100 µm [40] hyoscine butyl-bromide pla agglomerated particles, < 20 µm [48] hyoscine butylbromide, indomethacin, piroxicam, thymopentin pla microcapsules [49] thymopentine plga lecithin microcapsules [50] naproxen pla mean particle size: 5 µm [51] steroidsa pcb mean particle size: 2 9 µm [52] gentamycin, naltrexone, rifampin aotc pla spherical particles, 0,2 1 µm [42,43] tetracosactide pla microcapsules, 5,9 µm [53,54] pla fibrous network p-hba plga microcapsules [46] α-chymotrypsin aot pla spherical particles, 2 3 µm insulin sds spherical and irregular particles 1 5 µm ribonuclease peg sds fiber-like and spherical particles 0,5 1 µm cytochrome c sds collapsed spherical particles, 5 µm pentamidine sds spherical particles, 0,1 – 1 µm streptomicin aot spherical particles, 0,4 – 1 µm [42] albumin estriol plga agglomerated spherical particles, 10 – 130 µm [55] chimotrypsin-aot insulin-lauric acid conjugate insulin lysozyme pla mean particle size: 1 – 5 µm [56] diuron d pla microcapsules, 1 5 µm [45] insulin peg pla drug-loaded spheres, 0,4 – 0,6 µm [57] insulin pla drug-loaded spheres, 0,5 – 2 µm [58] p-hba lysosyme pla agglomerated irregular particles [47] budesonide pla spherical particles, 1 – 2 µm [59] rhdnase e lysosyme lactose amorphous agglomerated spheres [60] copper indomethacin pvp solid dispersion, 0,05 – 4 µm [61] insulin peg pla agglomerated spherical particles, 360 – 720 nm [62] a beclomethasone-17,21-dipropionate, betamethasone-17-valerate, budesonide, dexamethasone-21-acetate, flunisolide, fluticasone-17-propionate, prednisolone and triamcinolone acetonide; b phosphatidylcholine; c bis-(2-ethylhexyl) sodium sulfosuccinate; d herbicide; e recombinant human deoxyribonuclease; in their first seds patent york et al. reported the coprecipitation of salmeterol xinafoate with hydroxypropylcellulose from acetone using both twoand three-passage nozzles [63]. in both cases peaks of salmeterol xinafoate were weaker in xray diffraction patterns due to the amorphous fraction of the incorporated drug. since water is hardly miscible with scco2, hydrophilic compounds like sugars can not be processed directly. for this reason york et al. have completed their previous patent by describing a 48 process in which sugars are precipitated from aqueous solution by mixing it with a cosolvent (ethanol or methanol) which make water miscible with scco2 in a restricted concentration range [64]. as amorphous phase drugs are generally considered to be meta-stable, their stability over the storage period at ambient temperature is a crucial point. to demonstrate the viability of seds york et al. has devoted a whole patent to coprecipitating drug-carrier systems [67]. the drugs were chosen to cover a broad range of polarities including the highly apolar ketoprofen and in ascending order of polarity, indomethacin, carbamazepine, paracetamol, theophylline and ascorbic acid. the coformulation of these drugs with hydrophilic hydroxypropylmethylcellulose (hpmc), pvp and hydrophobic ec polymers revealed that the more they are alike in polar and hydrogen bonding characteristics the higher concentration of amorphous phase can be achieved. the amorphous phase of indomethacin coformulated with all three excipient was the most dominant in pvp (60 %) followed by hpmc (35 %) and ec (25 %). furthermore, york et al. have coprecipitated two cyclo-oxygenase-2 (cox-2) inhibitors with hydroxypropylcellulose (hpc) and poloxamer 237 as well as an anti-diabetic drug with 75/25 dl-lactide-co-caprolactone. the reduction of crystallinity level was linear in the whole concentration range for poloxamer 237 and above 20 % for hpc. all these drug-carrier systems proved to be stable for at least three months stored between 0 and 25 °c. juppo et al. studied the formation of solid dispersion of the model drug 2,6-dimethyl-8-(2-ethyl6-methylbenzylamino)-3-hydroxymethylimidazo[1,2-a]pyridine mesylate and two excipients: eudragit e and mannitol [69]. although mannitol gave no true one-phase dispersion (solid solution) it improves the solubility of the model drug. eudragit e is known to inhibit crystallisation but due to its low glass transition temperature it gives no well-defined particles in seds and can dissolve in scco2/solvent mixture reducing significantly the yield of this method. indeed, eudragit e was found to form amorphous dispersion, but with extremely low yield (< 20%). ghaderi et al. used a combination of supercritical n2 and co2 to incorporate hydrocortisone in plga matrix. microparticles with hydrocortisone were more irregular in shape, but differed slightly in size from pure plga particles [70]. table 5 summary of drug-carrier systems precipitated by seds and related methods. substrate excipient observation references salmeterol xinafoate hpc cristalline drug enbedded in polymer matrix [63] hydrocortisone plga microcapsules, 9 13 µm [70] ec ascorbi acid hpmc aggragated particles, 0,5 µm ec carbamazepine hpmc aggragated acicular particles, 0,5 µm hpmc amorphous aggragates and fibers, 0,05 1 µm ec amorphous particles, 100 µm indomethacin pvp amorphous particles, 10 250 µm hpmc amorphous aggragates, 0,1 – 0,3 µm ketoprofen ec aggregates hpmc amorphous spheres, 3 – 200 µm paracetamol ec fine powder hpmc amorphous aggragates, 0,1 – 50 µm theophyline ec amorphous aggragates, 1 – 70 µm hpc model druga poloxamer 237 clusters and agglomerates of spheres, 2 – 32 µm model drugb hpc clusters and irregular agglomerates, 4 – 47 µm [67] plasmid-dna mannitol dna-loaded particles [71] chlorpheniramine maleate eudragit rl drug crystals incorporated in swelled polymer [72] mannitol mixture of drug particles and polymer fibers, 1 20 µm model drugc eudragit e solid solution [69] a ((z)-3-[1-(4-chlorophenyl)-1-(4-methansulfonyl)methylene]-dihydrofuran-2-one); b ((z)-3-[1-(4-bromophenyl)-1-(4-methansulfonyl)methylene]-dihydrofuran-2-one); c 2,6-dimethyl-8-(2-ethyl-6-methylbenzylamino)-3-hydroxymethylimidazo-[1,2-a]pyridine mesylate; 49 fig. 1 schematic diagram of supercritical particle engineering technologies. particle design using liquefied gases cryogenic particle design is present in particle engineering for some 30 years [73]. during this period several invention were published and patented. all of these methods take advantage of instantaneous freezing of a solution or suspension dispersed in cryogenic fluid. inventions can be classified by the type of injection device: type of nozzle (capillary, rotary, pneumatic, ultrasonic), location of nozzle (above or under the liquid level); and the composition of cryogenic liquid (hydrofluoroalkanes, n2(l), ar(l), o2(l), organic solvents). first we considered the techniques where the orifice is located above the liquid surface, afterwards those of immersed nozzle. briggs and maxwell invented the first process of spray freezing onto cryogenic fluid. their first patent dates back to 1973 wherein the authors described a process of blending a solid biological product with solid sugar [74]. the chosen api together with the carrier sugar (mannitol, maltose, lactose, inositol or dextran) were dissolved in water and atomized above the surface of a boiling agitated fluorocarbon refrigerant. to enhance the dispersion of the aqueous solution authors placed a sonication probe in the stirred refrigerant. solid particles were collected with a sieve and lyphilized. freon 12 (dichlorodifluoromethane) was found suitable for this purpose because its boiling point (tb= -30 °c) is sufficiently low to cause instantaneous freezing, but not enough low to form an extensive "vapor barrier" around the droplets which would hinder fast freezing. several apis were blended by this method including proteins, pharmaceuticals and enzymes (luciferase, hexokinase, glucose-6-phosphate dehydrogenase (g-6-pdh), lactate dehydrogenase (ldh), pyruvate kinase; luciferin, bovine albumin, morpholinopropane sulfonic acid (mops), 2,6dichlorophenol indophenol (dip), nicotinamideadeninine-dinucleotide (nad) and its reduced derivative (nadh). in the following two patents, the authors completed the above list of apis with blood serum, red blood cells, bacitracin, polymyxin b, tetracycline, chlorpromazine, maltase enzyme, testosterone, vitamin c, cholesterol and gelatin [75,76]. processed materials were characterized by high biological activity, homogeneity and stability. in 1980 adams et al. patented a method similar to the one of briggs and maxwell with the slight difference that they used needle (capillary) nozzles to disperse the solution or suspension onto the surface of stirred halocarbon refrigerant [77,78] (see fig. 2). blood plasma particles processed in freon 12 ranged from 0.84 to 1.68 mm in diameter. fig. 2 schematic diagram of the apparatus invented by adams et al. 1. refrigerant; 2. rotated vessel; 3. nozzles; 4. wire screen; 5. condenser hebert et al. prepared microparticles of controlled release device by spraying the solution containing an api and a biodegradable polymer into cold nitrogen gas [79] (see fig. 3). particles 50 were frozen partially in the gaseous phase and collected in the liquid phase at the bottom of the vessel where they solidified completely. in a second vessel liquid nitrogen was evaporated and residual organic solvent is removed by extraction. fig. 3 schematic diagram of the apparatus invented by hebert et al. 1. freezing vessel; 2. extraction vessel; 3. nozzle; 4.liquified gas inlet; 5. mixing means gombotz et al. patented a similar process to prepare microparticles of biodegradable polymers wherein the solution of api is atomized directly into liquid non-solvent or in liquified gas containing frozen non-solvent at a temperature below the melting point of the solution [80]. the solvent in the microspheres then thaws and is slowly extracted by the non-solvent. however, it can be difficult to find a good solvent, which extracts exclusively the organic solvent, and residual organic traces are generally hard to remove by extraction. previously, gombotz et al. published another process, which consists in atomizing the solution or suspension of api into a liquefied gas and lyophilizing the frozen particles [81]. their method aimed to prepare microspheres of apis including zinc insulin, catalase, heparin, hemoglobin, dextran, superoxide dismutase (sod), horse radish peroxidase (hrp), bovin serum albumin (bsa), glycine and testosterone. particles ranged from 10 to 90 µm in diameter and kept 70 – 95 % of their initial biological activity. to achieve a mean diameter smaller than 10 µm – which is desirable in the case of injectable polymeric microspheres of controlled drug delivery system – the lyophilized product was suspended in a nonsolvent and exposed to ultrasonic energy. owing to the porous structure and the great specific surface area that characterize the lyophilized product, particles were easy to disintegrate, leading to a mean diameter between 0,1 and 10 µm. lyophilization is a widespread process in pharmaceutical and food industry but rather expensive and time-consuming. mumenthaler and oyler used recirculated dry gas instead of vacuum to remove residual solvent from particles previously sprayed into cryogenic air [82,83] (see fig. 4). during spray-freezing cold gas is supplied on the top of the vessel around the spray nozzle. when spray freezing is over, frozen particles are fluidized by passing the gas through the bed. solvent vapors are continuously condensed in a heat exchanger. the temperature of dry gas must be carefully controlled to supply the heat of sublimation without melting the frozen droplets. fig. 4 schematic diagram of the apparatus invented by oyler. 1. freezing and drying vessel; 2.cyclone; 3. turbine; 4.heat exchanger; 5.three-way valve; 6. nozzle more intense atomization can be achieved by submerging the nozzle into the cryogenic substance. due to the liquid-liquid collision, atomization beneath the surface of cryogen results in smaller droplets which freeze much faster. in 1969, harold a sauer patented the first method using submerged atomization device [84] (see fig. 5). solution was injected in liquid refrigerant through a heated nozzle at the bottom of the vessel. at the end of the atomization process, frozen droplets floating on the surface were collected in a spherical screen and dried in cold air or nitrogen gas. residual moisture was removed by successively reducing the pressure in the chamber. the method developed by dunn involves two immiscible halocarbon refrigerants. the boiling point of the denser refrigerant must be slightly above the melting point of the solvent while that of the lighter one is lower. solution is dispersed through a heated nozzle in the denser phase from 51 fig. 5 schematic diagram of the apparatus invented by harold a sauer. 1. freezing and drying vessel; 2. nozzle; 3. screen hemisphere; 4 .mixer paddle; which rising solution droplets step in the lighter refrigerant and solidify [85] (see fig. 6). the frozen particles floating on the surface of the upper refrigerant are collected and lyophilized. authors described the precipitation of aluminum sulfate in various freon–based cryogenic systems. fig. 6 schematic diagram of the apparatus invented by dunn et al. 1. denser refrigerant (injection zone) ; 2. lighter refrigerant (freezing zone); 3. atomization device; 4 heating coil; 5. cooling coil recently, williams et al. invented a method called spray-freezing into liquid (sfl) which, due to an insulating nozzle, allows injection into extremely cold liquids – i.e. liquefied gases – without any nozzle blockage [86] (see fig. 7). the authors recommended nozzles made of molded tip (polyetheretherketone, polyether block amide or polyurethane elastomers). fig. 7 schematic diagram of the apparatus invented by williams et al. 1. liquified gas; 2. insulating nozzle; 3. propeller stirrer physical properties of the lyophilized solid particles were found advantageous in many respects foremost in the case of poorly water soluble apis: • mean particle size: 0,68 – 16 µm • amorphous solid dispersion • great specific surface area: 3-117 m2/g • porous structure • enhanced rate of dissolution • improved wettability • low residual solvent content. 52 table 6 summary of drug-carrier systems precipitated by cryogenic formulation techniques. drug excipient solvent observation references nad, nadh, luciferase, luciferin, hexokinase, g-6-pdh, ldh, pyruvate kinase, bovine albumin, mops, dip mannitol, maltose, lactose, inositol, peg water (kcl, nahco3) embedded substrates with high biological activities [74] blood serum citric acid maltase enzyme inositol, mannitol testosteron sodium monoglutamate vitamin c inositol water cholesterol sds water/ethanol embedded substrates with high biological activities [75,76] sod, hrp, mitomycin c, etoposide, hemoglobin pla plga dcm microspheres mps b = 30 50 [80] carbamazepine sds danazol pva (22000) poloxamer 407 pvp k15 water/thf insulin tyloxapol lactose trehalose water solid solution mps = 5,06 7,11 ssa c = 12,81 44,44 [86,87,90] danazol hp-β-cd water/thf solid solution mps = 7; ssa = 113,5 [86,88] danazol pva (22000) poloxamer 407 pvp k15 water/thf water/ethyl acetatea water/dcma solid solution mps = 6,52 16,75 ssa = 8,9 83,06 [86,89] carbamazepine poloxamer 407 pvp k15 water/thf acetonitrile solid solution mps = 0,68 7,06 ssa = 3,88 13,3 [86,91] salmon calcitonin, tyloxapol lactose water danazol poloxamer 407 triamcinolone acetonide poloxamer 407 pvp k15 thf solid solution mps = 5,06 10,49 ssa = 11,04 19,16 [86] danazol pvp k15 acetonitrile dcm solid solution ssa = 28,50 -117,50 [92] a emulsion.; b mean particle size (µm); c specific surface area (m2/g) conclusion this paper aimed to survey the numerous publications and patents issued to date in the fields of supercritical fluid assisted and cryogenic particle design with special regard to coprecipitation of active substrate-excipient composites. all of these techniques have their own advantages and drawbacks. to choose the right method and the optimal working conditions preliminary experiments have to be carried out for each api and/or excipient. lipophilic molecules are usually soluble in scfs thus they can be processed by ress technique. however, applicability of ress is not restricted to lipophilic apis, low yield associated with polar apis and polymers can be increased by adding cosolvents to the scf (ress-n). owing to the rapid expansion nucleation is more important than crystal growth 53 hence the sub-micron particles. to prevent particle agglomeration – one of the main drawbacks of ress – supercritical solution can be expanded into an aqueous solution containing a stabilizer (resas, relgs-h). additional stabilizers can minimize particle aggregation and reduce the mean particle size by orders of magnitude [14]. unlike the ress, pgss is applicable whether the apiexcipient is soluble in scf or not. this tecnique was developed in paint and polymer industry to prepare coated micro-particles. as most polymers swell and melt at lower temperature when placed in high pressure co2, thermolabil apis (peptides, enzymes, viruses) can be as well encapsulated without considerable decrease of their biological activity (pluss). in contrast to pgss, supercritical antisolvent techniques (gas, sas, seds, ases, and pca) require a solvent wherein the api and excipient are dissolved and which is miscible with the scf at working conditions. the fact that these techniques use scfs as antisolvents make them available for a wide range of apis and excipients and allow milder working conditions compared to ress. furthermore they provide additional operating variables i.e. flow rates, concentrations, nozzle diameter and solvent, some of which proved to be critical in terms of particle size, morphology, polymorphism and crystallinity [93]. aqueous solutions can be processed as well with cosolvents (ethanol or methanol) mixed in a three-passage nozzle [64]. scf assisted precipitation techniques are successful candidates for drug-excipient coformulation for controlled release dosage forms. however amorphous solid solutions are great challenge for scf assisted particle design, as it’s not always possible to reduce product crystallinity to zero [67,69]. pharmaceutical formulations using cryogenic fluids were originally developed to blend thermolabil biological substances (peptides, enzymes, cells) preserving their biological activities [74-76]. in recent years, williams and co workers pointed out that formulation processes using liquefied gases can be successfully applied to enhance the solubility of poorly water soluble or insoluble apis. apart from applied solvent (organic solvent, 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university of pannonia, department of mol hydrocarbon and coal processing 8200 veszprém, egyetem u. 10. hungary e-mail: borsodinikolett@almos.uni-pannon.hu pyrolysis of contaminated waste plastics was carried out in a laboratory scale batch reactor at 450 °c under nitrogen atmosphere. raw materials were original high density polyethylene (hdpe) and waste motor oil flasks from industrial sector. volatile products were passed through a fixed catalyst bed with temperature of 350 °c. in the experiments y-zeolite, β-zeolite, hzsm-5, co/mo and ni/mo catalysts were used. three product fractions were obtained: gas, liquid and heavy oil. catalysts had mainly effect on the gas and liquid yields, the amount of the residue did not show significant differences in the case of the same raw material. by pyrolysis of contaminated raw material higher volatile product yield could be observed compared to pyrolysis of the original raw material. catalysts increased gas yields and had influence on the composition of products. most significant effect could be observed in the case of y-zeolite and β-zeolite catalysts. contaminant level of liquid products could be decreased in case of thermo-catalytic pyrolysis, which is a key property for further application of the pyrolysis products. keywords: pyrolysis, contaminated plastic waste, heteroatom removal, catalyst introduction in the last decades both the amount of polymer materials and the wastes from them has shown a rapidly increasing tendency. disposal of plastic wastes is very important because the degradation of these materials takes a very long time. moreover plastics have very high hidden energy content. there are many possibilities for recycling plastic wastes, one of them is pyrolysis. during pyrolysis the long polymer chains of plastics are degrading into smaller hydrocarbon molecules in absence of oxygen and in the temperature range of 400–900 °c. pyrolysis products are similar to the hydrocarbonfractions generated in an oil refinery, therefore they can be used as fuels or petrochemical feedstock [1-4]. by pyrolysis of plastic wastes the saving of crude and energy and reduction of co2 emission is possible. plastic wastes usually have heteroatom as contamination (e.g. sulphur, nitrogen or chlorine containing substances) on their surface or in their own material. chemical recycling of contaminated plastic wastes is possible, but contaminants present problem because they appear in the products. many researchers have investigated the composition of products derived from pyrolysis of different contaminated plastic materials [5-8]. in most of the studies were used raw materials, which had contamination in their own material (heteroatom containing plastics or additives) but pyrolysis of plastic wastes, which contain heteroatom containing substances on their surface was slightly studied. in terms of further energetic utilization there are limits for heteroatom containing substances in the products. therefore reduction the amount of the contaminants in the products is very important because by that procedure the range of raw materials could be widened (e.g. contaminated plastic wastes could be also recycled this way). the catalyst application is one possible way for decreasing the heteroatom content in the products. catalysts are capable both to absorb heteroatom containing substances and change the composition of the products by taking over the heteroatoms in the gas phase. many researches were carried out to examine the efficiency of different catalysts [9-13]. in many works there were used catalysts in vapour phase contact with the products. it means that only volatile products are getting to the catalyst bed therefore catalysts affect only the composition of the volatile products. the applied catalysts decreased the chlorine and nitrogen content of pyrolysis oils even by 90% or more. in this work pyrolysis of contaminated plastic waste was carried out at 450 °c. volatile products were driven trough different catalysts in order to decrease the concentration of heteroatom containing substances in the liquid products. the applied catalysts are widely used in the industry, too. 52 nitrogen residue waste plastic 1 11 2 3 6 75 gas 4 8 figure 1: the layout of the process: 1. raw material, 2. shredding and grinding, 3. nitrogen bottle, 4. reactor, 5. catalyst bed, 6. cooler, 7. liquid product receiver, 8. water trap experimental raw materials motor oil flasks were obtained from design kft. the flasks were shredded and grinded into particles up to 3 mm diameter. composition of the raw material was followed by fourier-transformed infrared spectroscopy. it was found that the main component of that was hdpe (88.6 wt%). in addition the raw material contained significant amount of motor oil contamination (7.2 wt%) and adsorbed water (0.6 wt%). the rest (3.6 wt%) was foil of the motor oil flasks, which had the following composition: 53.3 wt% pp, 40.0 wt% pvc and 6.7 wt% hdpe. for comparison experiments were done also with original, off-grade hdpe, obtained from tvk co. catalysts five different catalysts were applied in order to improve the product qualities: y-zeolite, hzsm-5, β-zeolite, co-mo, and ni-mo. table 1: properties of the applied catalysts bet surface, m2/g si/al microporous surface, m2/g acidity, meq. of nh3/g y-zeolite 205 45 127 0.61 hzsm-5 322 31 198 0.55 β-zeolite 446 33 384 0.47 co-mo cat. 196 12 99 0.28 ni-mo cat. 177 14 74 0.26 the first two are commonly used cracking catalysts having isomerization function and the last two are bifunctional catalysts with hydrogenization/dehydrogenization function. properties of the catalyst are shown in table 1. before the experiments catalysts were heated at 500 °c in nitrogen atmosphere for 4 hours. pyrolysis process pyrolysis was carried out in a batch reactor with 2.0 dm3 volume. the layout of the process is shown in fig. 1. the raw material was first shredded and grinded after that it was fed into the reactor. in every experiment 400 g of raw material was pyrolized in nitrogen atmosphere. the reactor temperature was 450 °c in every case. above the reactor a fix catalyst bed was placed. the temperature of the catalyst bed was 350 °c. volatile products generated during pyrolysis were passed over the catalyst bed after that they were cooled and condensed in a vessel. the non-condensable products (gases) were blown through a water trap to collect the inorganic substances. all of the experiments were taken 150 minutes, after that the reactor was cooled and residue (heavy oil) was taken off at the bottom of the reactor. the reactor and the catalyst bed were electrically heated, measurement of temperature occurred with thermocouples. analysis of pyrolysis products a dani gas-chromatograph fitted with a 30 m x 0.53 mm rtx-1 column was used for hydrocarbon analysis of pyrolytic oils. composition of the raw material was analyzed by a tensor 27 type fourier transformed infrared spectrometer in the 4000–400 cm-1 wave number ranges. for chlorine determination a mitsubishi tox-100 type instrument was used. the temperature was 900 °c, and argon was used as inert gas. determination of nitrogen and sulphur content of fractions were performed by using standardized methods: astmd 6428 99 and astmd 6366 99, respectively. 53 results and discussion product yields during pyrolysis three different products were obtained: gas, liquid and heavy oil. product yields are shown in figs 2 and 3. 0 10 20 30 40 50 60 70 80 90 100 thermal yzeolite hzsm-5 co-mo ni-mo betazeolite pr od uc t y ie ld , % heavy oil liquid gas figure 2: product yields obtained during pyrolysis of the original raw material 0 10 20 30 40 50 60 70 80 90 100 thermal yzeolite hzsm-5 co-mo ni-mo betazeolite pr od uc t y ie ld , % heavy oil liquid gas figure 3: product yields obtained during pyrolysis of the motor oil flasks in the case of the different raw materials different product yields were observed. from the contaminated raw material more volatile products were obtained (gas yield changed between 12.0 and 33.5 wt% and yield of liquid product was between 17.2 and 45.7 wt% in the case of the motor oil flask raw material, while in the case of the original raw material those values were only 7.5–28.2 wt% and 16.0–36.5 wt%).it is important to remark that the difference between the volatile product yields from the two raw materials was more then the amount of volatile contaminations (water and oil) on the surface of the motor oil flasks. the reason of that could be explained by the theory that the contaminations have initiated the decomposition of other polymers at lower temperatures, because they were able to given free radicals at lower temperature. this way the activation energy of the pyrolysis decreased in the case of the contaminated raw material. in other words at the same temperature more volatile products could be obtained. if the yields in the thermal and thermo-catalytic cases are compared it could be seen that the volatile product yields are higher in almost every times in the thermal cases than in the thermo-catalytic cases. it is similar result with the works of others [14] but the cause of the phenomena was not explained in the mentioned reference. probably it might be because of the changed flow conditions but to clarify that needs more investigations. yields of the gases are higher in the thermo-catalytic cases compared to the thermal cases. it is due to the secondary cracking on the catalyst bed. the strongest effect had the y-zeolite in the case of the same raw material because this catalyst has the largest microporous surface. 0 10 20 30 40 50 60 70 80 90 100 thermal yzeolite hzsm-5 co-mo ni-mo betazeolite pr od uc t y ie ld , % n-alkanes n-alkenes branched figure 4: composition of gases obtained from original raw material 0 10 20 30 40 50 60 70 80 90 100 thermal yzeolite hzsm-5 co-mo ni-mo betazeolite pr od uc t y ie ld , % n-alkanes n-alkenes branched figure 5: composition of gases obtained from motor oil flasks the molecules of the liquid fraction can fit only in the micropores where secondary cracking reactions are taking place therefore micro-porous surface has a strong effect on the yields. composition of gases carbon number distribution analysis of gases showed that gas products were in the carbon number range c1-c6. the gas phase contained c6 hydrocarbons because the not complete condensation. most of the gases (65–80 wt%) was in the c3-c4 fraction. composition of gases was analyzed by gas-chromatography and the results are shown in figs 4 and 5. in all of the cases nalkanes, n-alkenes and branched hydrocarbons were detected. in the figures it could be clearly seen that composition of gases obtained from the different raw materials do not show significant differences. thus, the composition of the raw material has not effect on the composition of the gas product but the applied catalysts 54 affected it. namely the amount of branched hydrocarbons in the gas phase increased in the thermo-catalytic cases that could be explained by the isomerization effect of the used catalysts. isomerization was the strongest in the case of the co-mo and ni-mo catalysts, the increase of the branched substances was 16.3 and 23.9% in the case of the original raw material and 11.7 and 17.0% in the case of the motor oil flasks compared to the gases obtained from the thermal pyrolysis. 0 10 20 30 40 50 60 70 80 90 100 thermal yzeolite hzsm-5 co-mo ni-mo betazeolite pr od uc t y ie ld , % n-alkanes n-alkenes branched + aromatic figure 6: composition of liquid products obtained from original raw material 0 10 20 30 40 50 60 70 80 90 100 thermal yzeolite hzsm-5 co-mo ni-mo betazeolite pr od uc t y ie ld , % n-alkanes n-alkenes branched + aromatic figure 7: composition of liquid products obtained from motor oil flasks composition of liquid products composition and carbon number distribution of liquid products are shown in figs 6-7 and figs 8-9, respectively. in all of the cases n-alkanes, n-alkenes, branched and aromatic hydrocarbon groups were detected. the figures clearly show that composition of the liquid products do not changes significantly with the composition of the raw material. except of the liquid products obtained by using y-zeolite catalyst the samples contained around 50% n-alkanes. when y-zeolite was used, most of the liquid product was unsaturated. the amount of branched and aromatic compounds increased in the thermocatalytic cases. this could be explained by the isomerization effect of the catalysts. the strongest isomerization could be observed in the case of the co-mo and β-zeolite catalysts. they caused 9.9 and 16.3% or 20.2 and 14.6% differences in the amount of branched and aromatic hydrocarbons in the case of the original and motor oil flask raw materials compared to the thermal cases. 0 5 10 15 20 25 30 35 5 9 13 17 21 25 29 carbon number c om po si tio n, % thermal y-zeolite hzsm-5 co-mo ni-mo beta-zeolite figure 8: carbon number distribution of liquid products obtained from original raw material 0 5 10 15 20 25 30 5 9 13 17 21 25 29 carbon number c om po si tio n, % thermal y-zeolite hzsm-5 co-mo ni-mo beta-zeolite figure 9: carbon number distribution of liquid products obtained from motor oil flasks liquid products were in the carbon number range c5-c29. if catalysts with cracking function were applied, the average carbon number of the liquid product decreased. it means that the amount of the lighter compounds increased and the amount of the heavier hydrocarbons decreased in the oil. this was slightly more apparent in the case of original raw material than in the case of motor oil flasks because the contaminants decreased the activity of the catalysts. the reason of the decrease in the average molecular weight is the secondary cracking of the liquid product on the catalyst bed. the greatest effect had the y-zeolite catalyst that enlarged mainly the c8-c9 fraction (more than 50 wt% of the samples were c8-c9 hydrocarbons). this could be explained by the large macro-porous surface of the y-zeolite. contaminant level of liquid products chlorine and nitrogen content of liquid product was measured. reduction in contaminant level of the liquid products by catalysts in the case of liquids obtained from contaminated raw material is shown in fig. 10. chlorine and nitrogen content of liquid products derived from pyrolysis of original raw material was negligible therefore it is not included in the diagram. reduction in contaminant level was calculated from the contaminant level of the liquid products obtained from thermo-catalytic pyrolysis compared to the liquid from 55 the thermal case. it is clear that significant reduction could be reached both in chlorine and nitrogen content using catalysts. in chlorine content there was 45–84% and in nitrogen content 20–60% decrease. the co-mo catalyst had the most significant effect in case of both heteroatoms. however, it is important to note that in all of the experiments there were used fresh catalysts and the decrease in the activity and the regenerability of these catalysts was not studied, it is the aim of our future work. 0 30 60 90 y-zeolite hzsm-5 co-mo ni-mo betazeolite r ed uc tio n, % chlorine content nitrogen content figure 10: reduction in chlorine and nitrogen content of liquid products by catalysts conclusion in this work thermal and thermo-catalytic pyrolysis of contaminated raw materials was investigated. the ability of five different catalysts for improving the quality of the liquid products and decrease the contaminant level of them was examined. between the volatile products and the catalyst it was a vapour phase contact. the product yields did not show significant differences in thermo-catalytic cases compared to the thermal cases but the applied catalysts had favourable effect on product qualities. the amount of branched hydrocarbons in gas and liquid products increased in the thermo-catalytic cases and the catalysts with cracking function decreased the average molecular weight of the liquid products. these changes are advantageous in terms of energetic utilization. contaminant level of liquid products could be decreased significantly by catalysts but further investigation is needed in view of changes in activity of catalysts in time. acknowledgements the research was funded by the tamop-4.2.1/b09/1/konv-2010-0003 project (financial support by the hungarian state and the european union) whose support the authors gratefully acknowledge. the authors are grateful to the institute of chemical engineering cooperative research centre of the university of pannonia and hungarian academy of sciences, jános bolyai researching foundation for financial support received for this work. references 1. n. miskolczi, l. bartha, g. deák, b. jóver, d. kalló: thermal and thermo-catalytic degradation of high-density polyethylene waste, j. anal. appl. pyrolysis, 72, (2004), 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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page 427 page 428 page 429 page 430 page 431 page 432 page 433 page 434 page 435 page 436 page 437 page 438 page 439 page 440 page 441 page 442 page 443 page 444 page 445 page 446 page 447 page 448 page 449 page 450 page 451 page 452 page 453 page 454 page 455 page 456 page 457 page 458 page 459 page 460 page 461 page 462 page 463 page 464 page 465 page 466 page 467 page 468 page 469 page 470 page 471 page 472 page 473 page 474 page 475 page 476 page 477 page 478 page 479 page 480 page 481 page 482 page 483 page 484 page 485 page 486 page 487 page 488 page 489 page 490 page 491 page 492 page 493 page 494 page 495 page 496 page 497 page 498 page 499 page 500 page 501 page 502 page 503 page 504 page 505 page 506 page 507 page 508 page 509 page 510 page 511 page 512 page 513 page 514 page 515 page 516 page 517 page 518 page 519 page 520 page 521 page 522 page 523 page 524 page 525 page 526 page 527 page 528 page 529 page 530 page 531 page 532 page 533 page 534 page 535 page 536 page 537 page 538 page 539 page 540 page 541 page 542 page 543 page 544 page 545 page 546 page 547 page 548 page 549 page 550 page 551 page 552 page 553 page 554 page 555 page 556 page 557 page 558 page 559 page 560 page 561 page 562 page 563 page 564 page 565 page 566 page 567 page 568 page 569 page 570 page 571 page 572 page 573 page 574 page 575 page 576 page 577 page 578 page 579 page 580 page 581 page 582 page 583 page 584 microsoft word a_31_enisz_r.doc hungarian journal of industrial chemistry veszprém vol. 39(1) pp. 57-62 (2011) vehicle dynamics based abs ecu testing on a real-time hil simulator k. enisz , p. tóth, d. fodor, t. kulcsár university of pannonia, institute of mechanical engineering, faculty of engineering 8200 veszprém, egyetem u. 10., hungary e-mail: krisztian.enisz@gmail.com satisfying the ever increasing needs for safety and environmental issues the electronic control units (ecu) of today vehicles become more and more complex [1, 2]. regarding the controllability and safety requirements posed against automotive industry, the cost efficient ecu testing and the development of the software sensors becomes an important issue. the aim of this paper is to present the setup a hil (hardware-in-the-loop) simulation environment which makes the functional testing and development of ecus possible, and test the realized hardware and software environment with the integration of a general motors anti-lock braking system ecu. keywords: hil simulation environment, abs, ecu introduction the cost efficient ecu testing becomes an important issue. the development of new algorithms and new ecus are necessary because the safety requirements are ever increasing. the testing of the new methods with real vehicle on a test track is very important but very expensive and it takes too much time. to help the proof of concepts developments it is necessary to implement a test and simulation environment which makes easier to create and validate new algorithm for different types of vehicles and ecus. the aim of the research was to create a software and hardware environment which is easily reconfigurable and its training time for new users is relatively short. the functions of the system will be introduced with the hardware and software integration of abs ecu. the architecture of the simulation environment the simulator has got modular architecture (fig. 1 and fig. 2) which makes it easily reconfigurable. the first part is a standard high performance pc with windows 7 operation system. it can be used as standalone system without the other part of the simulator and makes it possible to test new algorithm without any ecus of the vehicle. the core of the system is a vehicle dynamics based simulation software, the tesis vedyna 3.10.4. this software is based on matlab/simulink and the new algorithms can be implemented under simulink environment, and capable to create new maneuvers, parameterize different vehicle models and the environment like road surface etc. the interface for the real time hardware is the national instruments veristand 2010. it can handle the models which were built by the vedyna, and can make the connection between input and outputs of the model and the hardware devices. the signal modification or override is one of the most important feature of the veristand. it can prepare the signals for the model or device inputs by the modification of the signals by simple mathematical algorithms or more complex labview models. figure 1: the anatomy of the hil simulation environment 58 the second part is national instruments based pxi real-time system. it has modular inputs and outputs and can be extended by national instruments pxi and compact rio cards, like can, flexray, digital and analog io cards. the pxi system has external interfaces like vector most and ttech flexray interface which can be used without the pxi system, with a standard pc. figure 2: the physical appearance of the simulation environment the third part is an electric motor emulator, which can emulate different types of electric motors used by electric cars driving systems. the integration of an ecu after the realization of the simulation system, the very important step was the integration of an ecu (fig. 3). figure 3: the hardware integration of the abs ecu the hardware integration the ecu was extended with simple and small electric circuits to emulate the wheel speed sensors (fig. 4), the valves (fig. 5) and the motor (fig. 6). the motor and the valves are controlled by the ecu, the real-time system only measured the states of these components. the wheel speed sensors are controlled by the simulator and a digital output switching the voltage on/off according to the provided wheel speed to generate the pulses with the correct frequency for the abs. figure 4: the emulation of the wheel speed sensors figure 5: the emulation of the valves figure 6: the emulation of the motor the software integration into the tesis vedyna the brake system part of the original vedyna simulink model was modified to handle the incoming valve states, and modify the brake pressure at the wheels according to the valves position (fig. 7), independently for each wheel. 59 figure 7: the software integration of the abs ecu into the tesis vedyna the main equation of the pressure modification algorithm is (eq. 1): τ )( arg ))(()()( nt diffett enpnpnp − −= , (1) where: n – the current simulation step p(n) – the modified brake pressure for the wheel. ptarget(n) – the target brake pressure pdiff(n) – the difference between the current and the target brake pressure t(n) – the current time of the cycle τ – the time constant the algorithm has six different part as can be seen on the matlab / simulink chart (fig. 8): ● state selection (fig. 9) ● main pressure change check (fig. 10) ● cycle interval calculation (fig. 11) ● target pressure calculation (fig. 12) ● pressure difference calculation (fig. 13) ● brake pressure calculation (fig. 14). the state selection part sets the current state corresponding to the valves position and sign that the valves states is different from the previous valves state (fig. 9). figure 9: the calculation of the state(n) and state changed(n) parameters figure 8: the pressure modification model for one wheel 60 the main pressure change check is necessary because if the driver increase or decrease the brake pressure the model cannot follow correctly this linear change. the problem was solved with a small modification to build up the linear pressure with small steps (where the step size is pmax change and the pmain is the unmodified brake pressure for the wheel) (fig. 10). figure 10: the calculation of the pmain start(n) and pmain changed(n) parameters the cycle interval calculation module gives values of the current cycle interval, where the tstep is the simulation step length (fig. 11). figure 11: the calculation of the t(n) and t’(n) parameters the target pressure calculation part selects the target pressure (fig. 12). figure 12: the calculation of the ptarget(n) the pressure difference calculation part calculates the difference between the current and the target brake pressure (fig. 13). figure 13: the calculation of the pdiff(n) the pressure calculation part calculates the modified brake pressure (fig. 14). figure 14: the calculation of the p(n) 61 after the modification of the vedyna model the next step was the creation of veristand project. the compiled model is compatible with the veristand so the input and output signals can be connected to the devices inputs and outputs. the conversion of wheel speed signals is necessary because the model provides the wheel speeds in km/h but the abs ecu expect it frequency modulated pulses (eq. 2) (switch on and off the voltage with a frequency). teethn k v f 6.3= , (2) where: v – the vehicle velocity k – the circumference of the wheel nteeth – the numbers of the teeth of the speed measure disc another important setting is the emulation of the ecu starter can frames. the final step was to create a veristand user interface for the simulation to observe and change the parameters (fig. 15). figure 15: the speeds and pressure page of the user interface results based on the developments a real-time vehicle simulator was realized to create an integrated hardware in the loop (hil) simulation environment in which new theoretical research results can be easily validated. figure 16: the vehicle velocity (km/h) and wheel speeds (km/h) without the abs ecu (emergency braking from 115 km/h) figure 17: the brake pressures (pa) without the abs ecu (emergency braking from 115 km/h) figure 18: the vehicle velocity (km/h) and wheel speeds (km/h) with the abs ecu (emergency braking from 115 km/h) figure 19: the brake pressures (pa) with the abs ecu (emergency braking from 115 km/h) the behavior of the abs ecu based test system was in concordance with expectations (fig. 16., fig. 17., fig. 18. and fig. 19.) but some small further development needed to refining the simulation. another improvement should be on the pressure model taking into consideration of the motor state of the abs. acknowledgment we acknowledge the financial support of this work by the hungarian state and the european union under the tamop-4.2.1/b-09/1/konv-2010-0003 project and the intensive technical support of continental teves veszprem and national instruments budapest. 62 references 1. p. e. rieth, s. a. drumm, m. harnishfeger: electronic stability program: the brake that steers, verlag moderne industrie, 2002, 16–26 2. f. gustafsson: automotive safety systems, replacing costly sensors with software algorithms, ieee signal processing magazine, 26(4), 2009, 32–47 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word 1425 dobos 104.docx hungarian journal of industry and chemistry veszprém vol. 42(2) pp. 79–84 (2014) challenges of enterprise policy compliance with smartphone enablement or an alternative solution based on behaviour-based user identification sándor dobos* and attila kovács department of information technology, elte university budapest, budapest, 1117, hungary *email: sandor.dobos@hu.ibm.com current trends show the intense growth in the role and importance of mobile technology (smartphones, tablets, etc.) in business due to economic, social and technological reasons. the social element drives a powerful convenience expectation called “bring your own device” (byod) for taking notes and accessing internal and external network resources. apparently, the future is leading toward a more extensive enablement of smartphones and tablets with their enterprise applications. internal security standards along with applicable regulatory ones to achieve ‘policy enforcement’ as types of solutions and controls; however, this allows for merely one aspect of compliance. an alternative solution could be behaviour-based analysis to identify the user, attacker or even a malicious program accessing resources on phone or internal networks. complex networks can be defined by graphs, such as connections to resources on smartphones and serve as a blueprint. in case the motif is different from the user’s actual behaviour, the company can initiate specific actions to avoid potential security violations. this document reviews the it security challenges related to smartphones as well as the concept of graph-based user identification. the challenges of the latter are the identification of motif, selection of search algorithm and defining rules for what is considered a good or bad behaviour. keywords: mobile device security, “bring your own device” (byod) management, secure data communication, behaviour-based identification of threat, graph-based user identification introduction enterprise policy enforcement with current mobile technology management tools (mobile device management (mdm), virus detection, and other necessary modules) ensure only the compliance of piece of equipment. within enterprise, mdm servers initiate the compliant actions, if the smartphone client fails the access privilege is taken away; however, this has an immediate impact on revenue through operational efficiency affecting the business. the enterprise compliance of the smartphone device is only a validated response, which can be altered by understanding the mobile technology, such as the application structures or the way mdm technology works. hackers are heavily attacking smart devices with malicious software (malware). these can be viruses, spyware, adware, and other types of attacks. a specific example is the “obad.a trojan”, which is now being distributed via mobile botnets. the trojans are occupying a larger space and becoming more complex, which shows the need for it security to find new ways to detect them. the secure enterprise environment is crucial for organizations to ensure the business strategy and continuity of operation, irrespective of its environment being production, service delivery, or customer support related. companies are following the trend to ensure efficiency and simplify service accessibility for their customers, business partners or employees. it is an essential element of the it security strategy to be aligned with the business strategy due to (i) the intense growth of mobile technology and (ii) pressure from enterprise that has transformed business operations. forrester research from the q2 foresights security survey shows (fig.1) that mobile security is of primary concern amongst enterprise leaders. ceos are concerned about the risk of data loss, particularly due to device loss or theft. another worry regards data protection or data leak prevention usually in connection with data related to finance and innovation. figure 1: degree of concern of ceos from forrester research, foresights security survey 80 current challenges within today’s economic environment, profit-driven organizations are challenged from revenue, growth or profit target perspectives. in order to meet such expectations, organizations are under high pressure to offer innovative products (services) within newly identified channels and more accessible yet-to-bepenetrated markets to a demanding customer base, especially in the area of providing smartphone solutions. on the other hand, regulatory bodies are alarmed at mobile enablement and organizations in general striving to protect critical financial systems better, in particular via identity and access management. at the same time, organizations need to maintain operational resiliency and perform risk management assessments as an integrated part of day-to-day operations. the cost perspective is an important factor for customers facing the task of achieving a lower total cost of ownership (tco) although, by this shift in paradigm, they move from reactive protection to proactive value creation mode. the alignment of the current it strategy to business strategy is a challenge for corporations as it is a service provider within an enterprise also offering business enablement leads. companies need to manage security policy at the corporate level, assess the security health of the heterogeneous it environment, monitor the security weakness(es) in processes and systems and, of course, meet the plethora of banking laws, regulations and standards including sox, basel iii, glba, and pci compliance. with the adaptation of the byod concept in business practices, mobile technology itself contributes to additional and more complex challenges. enterprises are not the owners of those smart devices with access to enterprise networks and their data. fig.2 illustrates how smartphones with applications developed by unknown sources could be a threat to enterprise’s sensitive data. business drivers for change as introduced above an active need is emerging for more effective mobile solutions. it is not only a reflection of the compliance requirements but a real protective solution against mobile threats without any restrictions on financial growth or cutbacks on efficiency initiatives. there are compelling reasons to act and change now including data potentially at risk, pressure from regulatory bodies and audit firms to be compliant with the applicable data handling regulations, and the implementation of mobile security into an existing security structure. highlights of a political-economic-social-technology (pest) analysis politicians are setting high standards for data management regardless of platforms, even if they are related to mobile devices or mobile applications. these regulations mostly focus on the handling of financial data such as the sarbanes–oxley act of 2002 (sox). there are new developments regarding data (pictures, text, etc.) ownership such as the stop online privacy act (sopa). the preventing real online threats to economic creativity and theft of intellectual property act or in short protect ip act (pipa) will have an even more rigorous norm for enterprises who need to meet these regulations in order to obtain permission to operate in a certain field or market (market player). the economic situation puts more pressure on businesses as the trend still shows stagnancy on a macro level while in some segments it is still in decline. firms have high demands for business achievements measured by revenue and profit perspectives to meet shareholder expectations. one way to do so is to improve cost structures with mobile enablement (particularly byod). society wants to live more comfortably by searching for easily accessible services, such as online mobileenabled bank transfers or online mobile retail orders. companies aim to reach their customers via mobile applications that are more easily accessible through user-friendly interfaces, such as social network platforms. as usual, this trend is typical for major market areas, such as north america or, western europe; however, other regions are expected to follow. the trend in technology continues to be more vivid from a computing power and portability perspective. internet service providers are granting access to higher bandwidth networks for new applications and online content. policy enforcement and its weaknesses to manage the various types of mobile devices in an enterprise, a solution was introduced in 2008 by stricklen, mchale, caminetsky and reddy based on pattern definition for mobile device management (mdm). mdm is the most common approach how mobile devices (including smartphones, tablets) are managed within the enterprise as a management tool for monitoring and policy enforcement. even though this technology is available and wide-spread, according to abi research, mobile threats grew by 261% just in the figure 2: graphical illustration of mobile phone technology security threats 81 last quarter of 2012; however, mdm technology is not growing at a comparable rate to the number of vulnerabilities and attacks. one of the components of mdm is the registration module, which is responsible for identifying mobile devices within the enterprise network, where the identifier indicates the platform of each mobile device, e.g. smartphone and tablet. the other significant element is the management module. its job is to receive a management function definition performed on mobile devices using identifiers from mobile devices. the management module is responsible for instructions for the first platform to perform the management tasks and provides instructions for the other modules specific to the second platform to perform the management task on at least the second device. however, mdm is not the ultimate solution for mobile device security within the enterprise environment due to some concerns regarding the verifiable device integrity. there are attempts at identifying mdm solutions to detect modifications of the underlying platform, but since the mdm agent has limited privileges and was susceptible to compromise by malicious privileged software, these stand little chance of detecting a targeted attack. the us national security agency (nsa) describes an immutable cryptography, as the ‘root of trust’ on a specific platform, to be available for leveraging by mdm or other software, providing a means of countering this type of threats. encryption enables devices to attest their integrity on an enterprise and carry out any local policy decisions. the availability of this ‘root of trust’ to other software can vigorously complement a chain of trust that begins when booting and extends into the system runtime. an additional benefit of an immutable root of trust is that it allows a company to bind the unique identifier of that device together with other credentials to restrict company access to only those devices. in effect, the device itself can become one of the factors of a multi-factor access. in summary, mdm’s current capabilities support the byod and enterprise-owned use of mobile devices with certain gaps for high-security issues. management capabilities are limited to those provided for mdm products by the underlying mobile os (ios, android, and other platforms), and therefore, these capability gaps cannot be closed by mdm providers alone. ongoing cooperation between enterprise customers, os vendors, and mdm vendors is critical to the continued advancement of enterprise-level security for mobile devices. closing stated holes will enable the deployment of commercially available mobile devices to tackle high-security use issues common in sensitive industrial and governmental environments. secure data networks need to guarantee integrity, confidentiality and availability; this is when security is fulfilled. policy enforcement with the mdm can be too liberal, but then there is no real need for mdm or strictly constraining users thus limiting the value-add. the proposed solution is to identify the user based on behaviour and compare behaviour changes. behaviour analysis and challenges growing recognition drove the importance of network science related to the behaviour of sophisticated systems that is shaped by relations among their constituent elements. the rising availability and tractability of large and high quality data sets on a wide range of complex systems [1-3] have led to a primary insight: substantially diverse complex systems often share core key organizational principles. these can be quantitatively characterized by the same parameters, which means that they show remarkably similar macroscopic behaviour despite reflective differences in the low-level details of the components of each system or their mechanisms of interaction. the behaviour as described above can be modelled by mathematical graphs, where the graphs are defined simply as a set of nodes called vertices linked together in direct or indirect ways by connections (edges). from a mathematical point of view, g(v, e) are canonical graphs as the vertices and edges are labelled. in network science, methodological advances permit research to quantify other topological properties of complex systems, such as modularity [4], hierarchy [5], centrality [6] and the distribution of network hubs [7,8]. there have also been significant efforts to form the development or evolution of complex networks [9], to link network topology to network dynamics, and to explore network robustness and vulnerability. these topics are likely to become more relevant in relation to behavioural studies. structural and functional behaviour maps can be created using graph theory through the following four steps: 1. define the network nodes. 2. estimate a continuous measure of association between nodes. 3. generate an association model by compiling all pairs of associations between nodes and usually apply a threshold to each element of this model to produce a binary adjacency matrix or undirected graph. 4. calculate the network parameters of interest in this graphical model of the behaviour network and evaluate them against the equivalent parameters of a population of random networks. the elements such as defined network nodes, relationship of nodes, generated association matrix and network parameters give the basis of the behaviour type of “blueprint” of a user. a mobile user can be defined as an identity based on certain features of this behavioural “blueprint” as the key points of a fingerprint within the enterprise company. in fig.3 the darker highlighted edges could be the essential elements for the identifier. access to resource driven networks is defined in the graph theory as a set of nodes or vertices and the edges or lines, plus the connections between them. the graph topology can be quantitatively captured by a wide variety of measures used to generate the key points of the blueprint. the most important measurement is the node degree. the degree of a node is the number of 82 connections it links to the rest of the network. based on this definition, it is the most elementary network measure, and most other measures are ultimately linked to the node degree. the degrees of all the network’s nodes identified form a degree distribution [10]. in randomly selected networks all of the connections are equally probable, i.e. the result is a gaussian distribution. however, complex networks in general have non-gaussian distributions, often with a long tail towards higher degrees. the degree distributions of the scale-free networks follow a power law [11]. this landmark study [11] was the first to describe the scalefree organization of many complex networks and proposed a simple growth rule for their formation. the number of connections could give a large graph network that could be used for usability needs to define clustering, coefficients, and motifs. if the nearest neighbours of a node are also directly linked to each other, they form a cluster, and the clustering coefficient quantifies the number of connections that subsist between the nearest neighbours of a node as a quantity of the maximum number of possible connections [12]. the randomly selected networks exhibit low average clustering, whereas compound networks displays high clustering. interactions between neighbouring nodes can also be counted by counting the occurrence of small motifs of interconnected nodes [13]. the distribution of different motif classes (nodes efl and kmj in fig.3) in a network provides information about the types of local interactions that the network can support [14]. the numbers of reachable nodes and hops needed for connectivity are defined by the path length and efficiency. the path length is the minimum number of edges that must be passed through to start moving from one node to another. random, complex networks have short mean path lengths; they exhibit high global efficiency of parallel information transfer, whereas regular patterns exhibit long mean path lengths. efficiency is inversely related to path length. nevertheless it is numerically easier to estimate topological distances between elements of disconnected graphs. moreover, the link density or cost of the route provides further description. the connection density is the actual number of the network edges in the graph as a proportion of the total number of possible edges and is the simplest estimator of the physical cost of the network. hubs are nodes of high degree, where the centrality of a node measures how many of the shortest paths exist between all other node pairs in the network passing through it. it can be asserted that nodes with high centrality are thus crucial to efficient communication [15]. the importance of an individual node to network effectiveness can be assessed by deleting it and estimating the efficiency of the severed network. the robustness property refers either to the structural integrity of the network following the deletion of nodes, edges or effects of perturbations on local or global network states. finally, modularity is the property that has significant influence on the “blueprint” of the behaviour. there are algorithms that estimate the modularity of the network on the basis of hierarchical clustering [16]. each module contains several densely interconnected nodes, and there are relatively few connections between these nodes in different modules. airline hubs described this as a function of their roles in community structure [17]. provincial hubs are connected mainly to nodes in their modules where the connector hubs are connected to nodes in other modules. graph based analysis of smartphone usage previously, the challenges of using mobile devices in the enterprise environment were discussed. it is important to identify the activities on the device in order to take either preventive or corrective actions. g(v, e) used for the behaviour identification and description graphs. vertices are defined as applications, more precisely, vertices within the device or network addresses and sites. edges are the connections between the vertices applications called websites, network addresses, useror process-initiated connections. • network nodes can be defined as the resource access, i.e. applications, programs, and device elements access initiated by the user or application calls. • association between network nodes could be defined as the connections of the applications (calls, connections, as web access), usually resources are connecting together. • based on the above elements, network nodes and associations provide the details to calculate the association matrix. • the following steps include network parameter analysis calculated from the above. the question is not whether mobile activity can be defined as a complex network and describable by graph, but whether the process identies a user by a motif. however, before this question can be answered certain challenges need to be faced: • identify motifs as maximum independent set, • search motif in the complex network, • define „approved behaviours” according to the identification of user behaviour. figure 3: an example of a mobile user’s identity on the basis of a “blueprint” network 83 identification of the motif in the graph the task is to find the maximum independent set (mis) of a particular graph as was defined by garey and johnson [18] as np-complete and remains so even for bounded degree graphs. according to feige et al. [19] mis cannot be approximated even within a factor of |v|1 − o(1) in polynomial time. the greedy algorithm (gmis) can provide a solution for the identification of the maximum independence set. the algorithm selects a vertex of minimum degree, deletes that vertex and all of its neighbours from the graph, and repeats this process until the graph becomes empty. a recent detailed analysis of the gmis algorithm has shown that it produces reasonably good approximations of the mis for boundedand lowdegree graphs defined by halldorsson and radhakrishnan [20]. in particular, for a graph g with a maximum degree δ and an average degree 𝑑, the size |i| of the mis satisfies eq.(1). |𝐼| ≤ min   ∆!! ! |gmis 𝐺 |, !!! ! |gmis 𝐺 | (1) where |gmis(g)| is the size of the approximate mis found by the gmis algorithm. eq.(1) provides an upper-bound of the number of edge-disjoint embeddings of a particular sub-graph, and will use this bound to obtain a computationally tractable problem formulation that is guaranteed not to miss any sub-graphs that can potentially be frequent. searching for a discover motif in the graph the grochow-kellis method [21] can be used to find all examples of sub-graphs of a given size, similar to exhaustive methods. in the background, all nonisomorphic graphs are generated of a particular size using mckay’s tools [22]. then for each graph, the method evaluates its significance. due to symmetries, a set sub-graph of g may be mapped to a set query graph h multiple times. therefore, a simple mapping-based search for a query graph will locate every case of the query graph as many times as the graph has symmetries. to avoid this, the method computes and enforces several symmetry-breaking conditions, which ensure that there is an exclusive map from the query graph h for each case of h in g, so that the search only spends time finding each instance once isomorphicextensions (f,h,g[,c(h)]: finds all isomorphic extensions of partial map f : h → g [satisfying c(h)] start with an empty list of isomorphism. let d be the domain of f. if d=h, return a list consisting solely of f. (or write to disk.) let m be the most constrained neighbour of any d ∈ d (constrained by degree, neighbours mapped) for each neighbour n of f (d) if there is a neighbour d ∈ d of m such that n is not neighbours with f(d), or if there is a non-neighbour d ∈ d of m such that n is neighbours with f(d) [or if assigning f (m)=n would violate a symmetrybreaking condition in c (h)], then continue with the next n. otherwise, let f=f on d, and f (m)=n. find all isomorphic extensions of f. append these maps to the list of isomorphism. return the list of isomorphism the symmetries of a graph h equals automorphism (self-isomorphism). the collection of automorphism of h is indicated by aut(h). for a set a of automorphism, two nodes are stated to be “a-equivalent” if there is some automorphism in a which maps one to the other, or just “equivalent” if a =aut(h). given a set of conditions c, α preserves the conditions c if, given a labelling l1 of h which satisfies c, the corresponding labelling l2: h → z given by l2(n) = l1(α(n)) also satisfies c. we are thus searching for setting c, such that the only automorphism preserving c is the identity. this ensures exactly one map from h onto each of its instances in g to satisfy the conditions. to find these conditions, an aut(h)-equivalence class {n0, ..., nk} of nodes of h, and the condition l(n0) < min (l(n1), ..., l(nk)) imposed. any automorphism must send n0 to one of the ni, since these are all of the nodes equivalent to n0. however to preserve this state, an automorphism must send n0 to itself. then the process continues recursively, replacing aut(h) with set a of automorphisms that send n0 to itself. because findsubgraphinstances starts with a particular node that node can be considered already fixed. the main reasons for the selection of the grochow and kellis method are summarized as follows: • capable of finding more significant motifs by enabling exhaustive discovery of motifs up to seven nodes. to find even larger motifs, the method samples a connected subgraph, and then finds all its occurrences and assesses their significance using this method. this practice has enabled the algorithm to find motifs of up to fifteen nodes and examine subgraphs of up to thirty-one nodes; • capable of quering a particular subgraph by querying whether a particular subgraph is significant; • capable exploring motif clustering; because the algorithm finds all occurrences of a given subgraph, it can be used to examine how these cases cluster together to form larger structures; • time and space applied to all subgraphs of a set size, takes exponentially a smaller amount of time than previous methods, even when implementing the previous method with the hashing scheme. conclusions apparently the current policy enforcement solutions are not sufficient because they mainly focus on policy compliance based on the response of the device. the installation of malicious applications could alter the mobile devices response (jailbreak on ios or android 84 and software imitating a response to the mdm server) taking to more serious security issues. similarly to the recently identified malware oldboot.b, which can install malicious applications in the background, it can inject malicious modules into the system process that prevents malware applications from uninstalling. oldboot.b can change the browser setup (set a new and unwanted home page), and it also can uninstall or disable installed mobile antivirus software, and even steal data such as credit card information or any other critical data. this malware is especially dangerous as it implements evasion techniques to stay undetected. in order to optimize current threat detection, which is also in line with business requirements, additional and different methodologies are required such as user identification based on the blueprint of the behaviour of the user. to create a working model of the graph-based user identification, several tasks await completion. the running tasks are the edges started by the system or user defined as the connections between them. once the complex network and graph are set up the motif can be identified with a greedy algorithm and search of the global graph with the grochow-kellis algorithm. in order to have a behaviour-based decision making system, all of the above algorithms will be tested to further develop the behaviour-based system. references [1] amaral l.a.n., scala a., barthelemy m., stanley h.e.: classes of small-world networks, proc. natl acad. sci. usa 2000, 97, 11149–11152 [2] amaral l.a.n., ottino j.m.: complex networks. augmenting the framework for the study of complex systems, eur. phys. j. b 2004, 38, 147– 162 [3] barabási a.l., oltvai z.n.: network biology: understanding the cell’s functional organization, nature rev. genet. 2004, 5, 101–113 [4] girvan m., newman m.e.j.: community structure in social and biological networks. proc. natl acad. sci. usa 2002, 99, 7821–7826 [5] ravasz e., barabási a.l.: hierarchical organization in complex networks, phys. rev. e stat. nonlin. soft matter phys. 2003, 67, 026112 [6] barthélemy m.: betweenness centrality in large complex networks, eur. phys. j. b 2004, 38, 163– 168 [7] guimera r., amaral l.a.n.: functional cartography of complex metabolic networks, nature 2005, 433, 895–900 [8] guimera r., mossa s., turtschi a., amaral l.a.: the worldwide air transportation network: anomalous centrality, community structure and cities’ global roles, proc. natl acad. sci. usa 2005, 102, 7794–7799 [9] kashtan n., alon u.: spontaneous evolution of modularity and network motifs, proc. natl acad. sci. usa 2005, 102, 13773–13778 [10] amaral l.a.n., scala a., barthelemy m., stanley h.e.: classes of small-world networks, proc. natl acad. sci. usa 2000, 97, 11149–11152 [11] barabási a.l., albert r.: emergence of scaling in random networks, science 1999, 286, 509–512 [12] watts d.j., strogatz s.h.: collective dynamics of “small-world” networks, nature 1998, 393, 440–442 [13] amaral l.a.n., ottino j.m.: complex networks. augmenting the framework for the study of complex systems, eur. phys. j. b 2004, 38, 147– 162 [14] barabási a.l., oltvai z.n.: network biology: understanding the cell’s functional organization. nature rev. genet. 2004, 5, 101–113 [15] freeman l.c.: a set of measures of centrality based on betweenness, sociometry 1977, 40, 35– 41 [16] girvan m., newman m.e.j.: community structure in social and biological networks. proc. natl acad. sci. usa 2002, 99, 7821–7826 [17] guimerà r., mossa s., turtschi a., amaral l.a.: the worldwide air transportation network: anomalous centrality, community structure and cities’ global roles. proc. natl acad. sci. usa 2005, 102, 7794–7799 [18] garey m.r., johnson d.s.: computers and intractability: a guide to the theory of npcompleteness. new york: w. h. freeman and company, 1979 [19] feige u., goldwasser s., lovasz l., safra s., szegedy m.: approximating clique is almost np complete, proc. 32nd ieee symposium on foundations of computer science (focs), 1991, 2–12 [20] halldorsson m.m., radhakrishnan j.: greed is good: approximating independent sets in sparse and bounded-degree graphs, algorithmica, 1997, 18(1), 145–163 [21] grochow j.a., kellis m.: network motif discovery using subgraph enumeration and symmetry-breaking, computer science and ai laboratory, m.i.t. broad institute of m.i.t. and harvard, 2007 [22] mckay b.d.: isomorph-free exhaustive generation, j. algorithms, 1998, 26, 306–324 microsoft word b_25_tancsics_r.doc hungarian journal of industrial chemistry veszprém vol. 39(2) pp. 243-249 (2011) ‘by’ treating of micro-alloyed steels supported by integrated ‘it’ technology in the forging factory of raba f. tancsics1, 2 1university of széchenyi istván, department of material and vehicle technology 9026, győr, egyetem tér 1, hungary 2rába axle ltd, 9029, győr, martin út 1, hungary e-mail: ferenc.tancsics@raba.hu in the forging industry typical in the 21st century, economical production requires environment-friendly manufacturing of integrated and complicated products of larger and larger masses. difficulties to be solved require effective researches, technological developments and cost analyses. most frequently, cost analyses call the attention to energy demand of forging, to tool costs and to the efficiency of raw material usage. preservation and enhancement of competitiveness based on environment-friendly technological solutions are one of the most important challenges for the forging industry in the 21st century. our case study presents by (the best yield) treatment technology of a planetary carrier developed in the rába forging plant. development of the basic technology required integrated application of cad (computer aided design) – cae (computer aided engineering) and a test method using thermographic camera. integration of it (information technology) systems created a new design method, which enables relatively precise determination of cooling technology for by treated products even in the design stage. the properly micro-alloyed basic material and cooling technology made it possible to omit the quench and temper heat treatment and to adopt an energy-saving forging process. keywords: by, cooling, micro-alloying, simulation, thermographic camera. introduction micro-alloyed steels, at controlled cooling, are able to get the same mechanical properties as the heat treated steels. it means that a forging – that meets the same requirements – can be produced with significantly less energy and other additional costs. the most important micro-alloying materials are vanadium, niobium and titan [1, 2]. affinity of these elements to carbon and nitrogen is higher than that of iron. they are more stable even at higher temperature than iron carbide, that’s why at the temperature of hotforming they are forming carbides, nitrides and carbonitrides with carbon and nitrogen contents of steel. in the english literature, these steels are called as hsla (high strength low alloy) steels, while in the german region they are called as afp (ausscheidungshartenden ferritisch-perlitischen – hardening by segregation, ferritic-pearlitic). nowadays, the micro-alloyed steels have higher toughness (accompanied by increase of ferrite content in the microstructure) as a result of decreased carbon content, and have higher strength as a result of increased silicon and manganese contents [1, 2]. an important factor in increasing the strength is grain refining, which increases not only the strength, but at the same time the toughness, too. strength increasing effect of grain refining is caused by the property of crystallite limits eliminating movement of dislocations. fineness of secondary microstructure depends on primary microstructure, so grain size of ferrite depends on grain size of transforming austenite. grain size of austenite is influenced by initial temperature of forging, degree of forming and kind of re-crystallization. transformation following forming is also affected by final temperature of forging, as overheating of austenite increases the number of ferrite crystal nucleuses, which results in finer microstructure. strength increasing effect of grain size can be determined by hall-petch equation. the other mechanism for increasing strength is performed by dispersive segregations, when a relatively small volume of alloys provides significant results. strength is largely increased by segregations, which occur at lower temperature, partly in the austenite and then during the transformation γ → α. effect of these segregations is primarily expressed by decreasing the grain size of ferrite. the most effective micro-alloys are those that dissolve properly in austenite, segregate by making compound with carbon and nitrogen contents of ferrite, so they improve the strength in the following sequence: vanadium, titan, niobium [2]. the evenly distributed, spherical segregations eliminate movement of dislocations. dislocations intersect the obstacles, depending on their size and kind, or go around them by leaving dislocation circuits. strength increase caused by particles of incoherent boundary means hardening by segregation. in the material containing the dispersive second phase, the moving 246 dislocations are not able to go through the second phase, they go around. this process is the orowan-mechanism. each micro-alloy is segregating at different temperatures in steel. in case of vanadium and titan, nitrides and carbides are forming not in parallel, i.e.: formation of one beside the other can be neglected (fig. 1). figure 1: example for segregation of micro-alloys zf steels are a certain group of steels micro-alloyed with vanadium. these steels have got their names from the german firm zf friedrichshafen ag, who produces carriers for various vehicles. basic material of the planetary carrier is steel zf59, whose conformity criteria (composition, hardenability, strength) are specified and stipulated in standards by this german company [3]. by treatment of planetary carrier as for its function, a planetary carrier has to meet high requirements for strength and toughness so that the dynamic loadings developed in the axle should perfectly be withstood. when the mechanical and microstructure properties to be achieved with zf59 micro-alloyed steel as per the standard en 10083 were adjusted, the precisely controlled cooling has got a very important role. basic material was continuously cast, which was important during the technological designing, because reduction ratio is a factor, which affects the forged microstructure. (fig. 2). based on the above, the most important task was set: to elaborate the bases for by treatment technology of micro-alloyed steels. figure 2: locations of taking samples to qualification a strict requirement for the forging process of the micro-alloyed basic material is scheduled production when stable temperature range is assigned to each phase. in our case, use of cooling equipment was necessary, which stabilized the production capability. when the cooling technology was elaborated, cad (pro/engineer), cae (simufact.forming) design systems were applied for modeling the cooling process virtually. the following simplifying assumptions were set for simulation inspections: the work piece is homogenous and isotropic heat distribution of the heated work piece is even in the whole volume, namely (using fourier-kirchoff relation): 0)t(gradq =−= λ&r (1) where: q& r vector of heat flow density (w/m2) λ thermal conductivity (w/mk) t temperature distribution (k) during the operations, distribution of heat flow is inhomogeneous, which is generated by forming work and cooling conditions: )t(gradq λ−=& r (2) basically, cooling is a function of heat energy lost by heat radiation (using stefan-boltzmann law): 4 0 100 te ⎟ ⎠ ⎞ ⎜ ⎝ ⎛= εσ (3) where: e heat energy lost by radiation (w/m2) σ0 heat radiation factor of absolute blackbody (w/m2k4) ε blackness (w/o dimensional unit) t absolute temperature of radiating body (k). modeling was necessary so that later, during the experiments we could test the process in a well-defined way, primarily for cycle times and surface temperatures belonging to the critical process elements. the following marginal conditions were stipulated: virtual temperature of the basic material (1) 1240 °c final temperature of forging on each surface element of the forged geometry is above ac3 [1] the surface assigned for practical measurements is always the surface element of the highest temperature. according to the simulation, total duration of by treatment is 3148 seconds [4]. determinant process elements are finishing of finish-forging in the 59th second and start of intensive cooling in the 148th second. duration of intensive cooling stage is 1200 seconds with controllable air flow, which has separate parameters. temperature of the virtually finish-forged planetary carrier was calibrated on a plain surface, which could be properly measured, in an inspection using thermographic camera. (fig. 3). 247 figure 3: surface temperature is 1133 °c at a properly measurable location after practical testing, a more precise simulation was made in thermographic camera inspections (high resolution variocam thermographic camera). with the thermographic camera, the highest surface temperature was 1130.21 °c at the location selected for control measurement and 1080 °c at the sample taking location (fig. 4). figure 4: photo taken with thermographic camera. emission factor: 0.95 after validating the simulation, cooling – grain refining experiments as well as tests of internal temperature distribution were carried out [4]. above 900 °c the effect of tic grain refiner can be utilized in the finish-forging temperature range of 1000–1070 °c [5]. vn and vc are segregating at or below ac3 transformation limit [2]. as forming of the planetary carrier requires high energy, our possibilities were limited in terms of the possible lowest temperature that finishes forming. cooling – grain refining experiments: 1. with limited austenite overcooling from normal (designed) heating temperature (~1240 °c) in air flow, in defined loading order (designed) (fig. 5) without air flow, in defined order (fig. 6) from higher heating temperature (~1290 °c) in air flow, in defined loading order without air flow, in defined order. figure 5: planetary carriers cooled in cooling equipment, in air flow figure 6: planetary carriers cooled in quiet air, without air flow 2. with limited austenite overcooling and minimal increase of ti alloying (ti 0.033% instead of max. 0.025%) [5] from normal (designed) heating temperature (~1240 °c) in air flow (designed) without air flow from higher heating temperature (~1290 °c) in air flow without air flow. based on the laboratory test results of the experiments we could supplement the determinant process elements of by treatment with the temperature limits assigned to cycle times. process is started in the 0th second of the heated basic material from 1205–1255 °c. finish-forging is completed in the 59th second, 1040–1080 °c is measured at the sample taking locations (location can easily be measured with manual pyrometer) and intensive cooling is started in the 148th second 1020–1060 °c. in the intensive cooling stage the forging is cooling to 530–570 °c on the measured surface. speed of cooling equipment was set to 150 mm/min, air blow speed was set to 10 m/sec. intensive cooling stage works only in the length corresponding to 1200 seconds (fig. 7). we should mention that the experiment with increased ti content, with the volume indicated, did not provide any result. 248 figure 7: photo taken by thermographic camera on start of intensive cooling stage. emission factor: 0.95 higher ti content did not increase significantly the number of tic crystal nucleuses, however, increased the danger of formation of primary segregation tin lumps. the electron-microscopic fracture and point analyzing inspections could not detect tin lumps, however their effect was sensible through nearly 50% decrease of the contraction (z%) (fig. 8). the experiments made at increased temperature (~1290 °c) proved the danger of grain coarsening near the surface and the presence of duplex microstructure in the core. the inspections of the internal temperature distribution were primarily aimed at detecting the relationship between hardness distribution, grain size and internal heat distribution. samples of cooling providing the best result were used in the inspections as the number of tic crystal nucleuses was very important due to even and fine texture of the microstructure [5]. the inspection has detected that within the planetary carrier there is a heat distribution zone. in this range the microstructure can be made satisfactory to the expectations (fig. 9). figure 8: electron-microscopic photo taken on the fracture figure 9: relationship between the internal heat distribution and the microstructure figure 10: cooling diagram of planetary carrier 249 in order to stabilize the microstructure it is practical to widen and optimize this zone in a simulation-directed way [6]. possible and real means for widening are further grain refining, which is a slight increase (some thousandths) of al alloying [1, 4], increasing the reduction ratio, introduction of v/ti > 5 proportion. until this zone is widened, the elaborated cooling technology shall strictly be kept (fig. 10). when the technology shown in the diagram is applied, the temperature measured at the sample taking location meets the expectation. temperatures measured with manual pyrometer were in the range of 1015–1067 °c. cooling in air flow provides the possible highest degree of vc and vn segregations through an intensive cooling stage [2]. monitoring indexes of the process are process capabilities (pp, ppk) calculated from the results measured in sample taking hardness inspection. the process capability meets the requirement of ±4σ (67 ppm). summary, conclusions the trimmed forging had to be cooled on the cooling equipment, loaded in a defined loading order, in air flow provided by a vent, within a specified period of time. during the controlled cooling a defined temperature time program was run [6] (fig. 11). figure 11: planetary carriers on by equipment the essence of the process is: after forging is finished to cool the planetary carrier still in austenitic condition with a cooling speed, which allows the ferritepearlite microstructure and the specified hardness, that corresponds to hardening and tempering by the end of the process. by controlling the speed and the volume of the blown air, the ferrite-pearlite proportion as well as hardness, tensile strength of the microstructure can be varied and adjusted near a value specified within a dimensional range. in case of larger forgings (due to their sizes), this method cannot be utilized with safety, as due to the high cooling speed as well as the large cross-section some deviations can be detected in the microstructure, near the surface and in the core. deviations in the cross-section and their degrees can only be proven in destructive material inspections. the regular surface hardness measurements – in the presence of several disturbing factors (e.g.: surface decarburization) – can only indirectly provide information about the internal microstructure of the forging. references 1. j. m. chilton, m. j. roberts: micro-alloying effects in hot-rolled lowcarbon steels finished at high temperatures, metallurgical transactions, 11a, (1980), 1711–1721 2. r. j. golodowski: a review of vanadium micro alloying in hot rolled steel sheet products, international seminar 2005 on application technologies on vanadium in flat-rolled steels, pp. 43–51 3. zf friedrichshafen ag: zf59 material specification, (2009) 4. a. molnár: introduction of micro-alloyed steels in raba forging plant, study of master’s degree (2010), (in hungarian) 5. m. r. toroghinejad, g. dini: effect of ti-microalloy addition on the formability and mechanical properties of a low carbon (st14) steel, international journal of issi, 3(2), (2006), 1–6 6. b. k. panigrahi: processing of low carbon steel plate and hot strip an overview, bull. mater. sci. 24(4), (2001), 361–371 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjdffile false /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 /colorconversionstrategy /cmyk /dothumbnails false /embedallfonts true /embedopentype false /parseiccprofilesincomments true /embedjoboptions true /dscreportinglevel 0 /emitdscwarnings false /endpage -1 /imagememory 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(adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word b_44_rippelne_r.doc hungarian journal of industrial chemistry veszprém vol. 39(2) pp. 283-287 (2011) removal of hydrogen sulfide from natural gas, a motor vehicle fuel á. vágó1, d. rippel-pethő2 , g. horváth2, i. tóth2, k. oláh1 1mol hungarian oil and gas company plc., 1117 budapest október 23. utca, hungary e-mail: pethod@almos.uni-pannon.hu 2university of pannonia, institute of chemical and process engineering, 8200 veszprém egyetem u. 10., hungary compressed natural gas (cng) is one of the fossil fuels, and is nothing other than the compressed version of the natural gas extracted by mining. cng is mostly used for heating and the production of electricity. if used as a fuel for motor vehicles, it entails less emission of co2 than does the use of gasoline or diesel. irrespective of usage, the contents of commercial natural gas are strictly regulated by laws. besides energy density, hydrogen sulfide content for example is a critical quality parameter of natural gas, hence it is strictly regulated. hydrogen sulfide is extremely corrosive for the pipes. when burning such gases, hydrogen sulfide is converted to sulfur dioxide (so2) which is harmful for the environment. we have devised a procedure for the replacement of solid adsorbents and amine-containing chemicals in hydrogen sulfide removal that can also be used with gases containing carbon dioxide. the essence of the method is that the natural gas is brought into contact with a dilute solution of naoh in contact time of less than 1 second. at the beginning of chemisorption, hydrogen sulfide is absorbed 1-2 orders of magnitude faster than carbon dioxide. for the experiments, a laboratory jet reactor was planned. the efficiency of purification was examined with different hydrogen sulfide containing model gas mixtures with respect to the following parameters: gas volume flow, alkali volume flow and alkali concentration. keywords: compressed gas, motor vehicle fuel, hydrogen sulfide, chemisortpion, selective extraction introduction natural gas is a primary raw material. the typical contents of natural gas are given in table 1, but they can be different for every gas field. the natural gas consumption of hungary exceeds 14 billion m3 per annum, which is 70% of the total energy consumption [1]. table 1: typical contents of natural gas component percentage methane (ch4) 97% ethane (c2h6) 0.919% propane (c3h8) 0.363% butane (c4h10) 0.162% carbon dioxide (co2) 0.527% oxygen (o2) 0–0.08% nitrogen (n2) 0.936% noble gases (ar, he, ne) trace other (e.g..:h2s) 0–0.001% there are 210 welland/or research sites of natural gas. most of the wellsites are in the western transdanubia and in eastern hungary. domestic resources do not satisfy the consumption, making the country dependent on a significant import, the extent of which is nowadays 80%. most of the import is arriving from russia. fig. 1 illustrates the distribution of natural gas use. the major part of it (45%) is the residential consumption with district heating (more than 6 billion cubic meters per annum). electricity production (21%) requires 3 billion cubic meters of natural gas per annum. industrial consumers constitute 33%, while other uses are less than 1%. industrial consumers 33 % 21 % electricity production other 1 % residential consumption 45 % figure 1: the distribution of natural gas use other uses include use as motor vehicle fuel. however, it is important do differentiate between lpg and cng fuelled vehicles [2]. lpg (liquefied petroleum gas) is a by-product of petroleum oil drilling [3]. formerly it was usually burned off; nowadays it is sold on the market. as for its contents, it consists of a mixture of 40% propane (c3h8) and 60% butane (c4h10). it is used in fuel tanks at a 284 pressure of 6 bar in a liquefied form. there are approximately 260 lpg tank stations in hungary. cng (compressed natural gas) is not a by-product, but the extracted fossil gas. cng contains 90–92% methane and is in the gaseous state even when densified. the main problem with its use can be caused by imperfect burning, causing the release of greenhouse gases into the atmosphere. this however, is not a threat with a well-set cng motor vehicle in a good condition. when burning pure methane, one part carbon dioxide (co2) and two parts water (h2o) in the form of vapor are formed. compared to traditional fuels, the amount of carbon monoxide (co) is lower by 60–90%, while the amount of hydrocarbons (chx) by 40–60%. cng burns at a lower temperature than gasoline, reducing the amount of nitrous oxides (nox) by 20–40% in the exhaust gas. in contrast to diesel motor vehicles, there is no release of carcinogenic solid particles. its advantage compared to lpg is that it is a volatile gas that does not set close to the ground [4]. several car manufacturers have their own cng models in hungary, e.g. opel (zafira and combo), ford (focus) and volvo (s60, s80 and v70). the only setback for cng fueled vehicles to become widespread is the scarcity of the tank stations. irrespective of usage, the contents of commercial natural gas are strictly regulated by laws. besides energy density, hydrogen sulfide content for example is a critical quality parameter of natural gas, hence it is strictly regulated. the amount of hydrogen sulfide can be different for different wellsites, in hungarian wells, it ranges from 50 to 3000 ppm. the amount of hydrogen sulfide in commercial natural gas, however, cannot exceed 5 ppm. removal of hydrogen sulfide from natural gases there are several indications for the removal of hydrogen sulfide. the most important is environmental protection, because by burning hydrogen sulfide, sulfur dioxide (so2) is formed, which is harmful for the environment. the operational indication is that hydrogen sulfide is extremely corrosive for pipes. since pure natural gas has a higher price, there is also an economical reason. there are several methods for the removal of hydrogen sulfide, such as adsorption, absorption, membrane technology and biological removal. these methods are compared in the followings. for the adsorption methods, the following adsorbents can be used: activated carbon [5, 6], zeolite [7, 8], metal-based (fe, ti, cr, zn, al) adsorbents [9, 10] and composites [11, 12]. these adsorbents are efficient at absorbing sulfur, but they have to be regenerated. most adsorbents can only be regenerated 2 or 3 times consecutively, after this the packing needs to be replaced and disposed of. membrane separation methods are characterized by ease of installation and use. membranes are used for hydrogen sulfide removal [13] but their efficiency is not good enough on their own. because of this, they are used in combined methods [14]. hydrogen sulfide can be selectively removed by biological ways. however, these systems are hard to control [15]. the absorption techniques use for example alkanolamines [16, 17]. their advantage is that they have a high yield and they are regenerable; their disadvantage is that they foam and they are not environmentally friendly. sodium hydroxide is also used as an absorbent. these techniques can be utilized for the removal of hydrogen sulfide with good efficiency in traditional chemisorption devices [18]. however, with the use of naoh solution, the selective removal of hydrogen sulfide can be realized for gases containing carbon dioxide as well. the technique based on competitive chemisorption has been known for 55 years now [19]. there are different techniques for the realization of chemisorption. the essence of all of them is that the contact time has to be very short (below 1 sec) and the contact has to be very intensive. this is because (depending on pressure) hydrogen sulfide is absorbed orders of magnitudes faster than carbon dioxide at the beginning of chemisorption [20]. the reaction is exothermic and strongly ph dependent [21]. the above cannot be realized with chemisorbers of classical construction. for alkali consumption, the range of hsformation is the optimal. for efficiency, a higher, 12-13 ph range is better. optimization is required of course to determine whether an excess of alkali or several steps are required for the best separation [22, 23]. the intensive contact can be realized by parallel static mixing reactors [24] or by counterflow vaporization [22]. experimental the natural gas that had to be purified contained 20–100 ppm hydrogen sulfide and 10 (v/v)% carbon dioxide. the aim of the research is the selective removal of hydrogen sulfide. the chosen method is chemisorption with an aqueous solution of sodium hydroxide. quick and intensive contact is provided by vaporization in the already known process; while the construction enables efficient and fast phase separation to take place. experimental device fig. 2 illustrates the experimental device built at the department of chemical engineering at the university of pannonia. for the experiments, a model gas mixture (1) was produced in a acid-proof gas mixing bridge. the alkali was fed from the alkali vessel (3) with a feeder pump (4), whose volume flow can be regulated. the alkali is vaporized into the reaction space by the gas to be purified (6) through a nozzle (7). the intensively contacted gas and liquid get from the reactor space to the separation space (8). the wastewater (9) can be removed from the 285 separation space, and, after a drop catcher (10), the purified gas (11).there is sampling at both the gas inlet and outlet (12). the hydrogen sulfide and carbon dioxide percentage of the gas is measured by a dräger x-am 7000 gas analyzer (13). a computer can be attached to the device. with the help of a program, the alkali and gas volume flows can be precisely set. the measured data (temperature, pressure, pressure drop, gas velocity, alkali velocity, gas concentration) can be recorded. figure 2: experimental device. 1. gas cylinder, 2. gas inlet, 3. alkali vessel, 4. chemical feeder pump, 5. alkali inlet, 6. reactor space, 7. nozzle, 8. separation space, 9. wastewater removal, 10. drop catcher, 11. outlet of purified gas, 12. gas sampling, 13. gas analyzer the effect of parameters on the efficiency of purification the carbon dioxide concentration of the natural gas was a constant 10 (v/v)% for all experiments, as was the operational pressure of 30 bar. the aim of the experiments is to determine if the incidental fluctuation of the amount of gas or its concentration has any effect on the efficiency of the purification. this is important, because the gas parameters can change when opening or closing a well at a wellsite. the aim is to prove that the procedure can be operated stably, safely and with a near constant efficiency in a given range. the efficiency of the gas purification was examined by changing the following parameters: gas velocity, alkali velocity and alkali concentration. figs 3 and 4 show the effect of the change of the amount of the gas to be purified. the experiments were carried out with two nozzles: one marked with “a” (fig. 3) and one marked with “b” (fig. 4). the velocity of the gas changes in accord with the amount of gas, thus affecting the efficiency of vaporization. because of this, the nozzles can only be loaded in a given interval without significant changes in efficiency. nozzle “a” is most efficient at 1100 nm3/h. 0 10 20 30 40 50 60 70 80 90 100 0 50 100 150 200 250 300 350 400 450 alkali volume flow (cm3/h) ef fic ie nc y (% ) 1.1 nm3/h 1.5 nm3/h 1.8 nm3/h 2.2 nm3/h 2.8 nm3/h figure 3: change in efficiency as a function of the amount of alkali and gas with nozzle “a”. fig. 4 illustrates the experiments with nozzle “b”. nozzle “b” is most efficient at 2200 nm3/h. as for the experiments of figures 3 and 4, it can be stated that the decrease of efficiency can be compensated by properly adjusting the velocity of the alkali. with a proper alkali velocity in the range of 1000–3000 nm3/h, the efficiency of purification changes by ±10%. the adjustment of the amount of alkali to the actual amount of gas can be solved easily. 0 10 20 30 40 50 60 70 80 90 100 0 50 100 150 200 250 300 350 400 450 alkali volume flow (cm3/h) ef fic ie nc y (% ) 1.1 nm3/h 1.5 nm3/h 1.8 nm3/h 2.2 nm3/h 2.8 nm3/h figure 4: change in efficiency as a function of the amount of alkali and gas with nozzle “b”. figs 3 and 4 also show the effect of the volume flow of the alkali on the purification efficiencies. as it can be seen, increasing the amount of alkali only increases the efficiency to a certain level. by increasing the amount of the inlet alkali even further, the efficiency is affected negatively. this is due to factors in vaporization. for a given gas velocity, an increasing amount of liquid decreases the efficiency of vaporization. because of this no intensive contact takes place, also causing the efficiency of purification to decrease. in order to get good efficiency, it is important to choose the appropriate size of nozzles for the given volume flow of the gas, and to set the appropriate alkali velocity as well. fig. 5 shows the effect of alkali concentration on the efficiency of purification. only little improvement of efficiency can be achieved by increasing the concentration of the alkali. as long as ph favors the formation of hs, the rate of reaction is minimally dependent on concentration. 286 0 10 20 30 40 50 60 70 80 90 100 0 50 100 150 200 250 300 350 400 450 alkali volume flow (cm3/h) ef fic ie nc y (% ) 1.5 % naoh 2.5 % naoh 5 % naoh figure 5: change of efficiency as a function of alkali concentration fig. 6 illustrates the effect of the concentration of hydrogen sulfide on efficiency. as it can be clearly seen, the concentration of hydrogen sulfide between 20 and 100 ppm does not have an effect on the efficiency of purification (gas volume flow: 1800 nm3/h). this is of practical importance. if the hydrogen sulfide content of the gas at a given wellsite is fluctuating between the given limits, there is no need to change the technological parameters. the procedure operates with practically the same efficiency throughout. 0 10 20 30 40 50 60 70 80 90 100 0 50 100 150 200 250 300 350 alkali volume flow (cm3/h) ef fic ie nc y (% ) 20 ppm 50 ppm 100 ppm figure 6: change of efficiency as a function of the hydrogen sulfide content of the gas the value of specific alkali concentration in addition to the efficiency of purification, the value of the specific alkali concentration (alkali/h2s) is also important. the specific alkali concentration is the proportion of the used alkali and the removed hydrogen sulfide. it gives information about how much more alkali has been used compared to the amount that is required by the chemical reaction. the specific alkali concentration can be decisive when determining the volume flow and concentration of the alkali. fig. 7 illustrates the values of the specific alkali concentration (with the same gas velocity and 20 ppm hydrogen sulfide content) at different alkali concentrations. as it can be seen, increasing the concentration of the alkali only minimally increases the efficiency. this, however, is enough for the specific alkali concentration to be lower at higher concentrations. the difference is insignificant at lower alkali velocities. at higher alkali velocities, the efficiency decreases, significantly increasing the specific alkali concentration. 0 20 40 60 80 100 120 140 160 0 50 100 150 200 250 300 350 alkali volume flow (cm3/h) al ka li/ h 2s (m ol /m ol ) 1.5 % naoh 2.5 % naoh 5 % naoh figure 7: change of specific alkali concentration as a function of alkali concentration fig. 8 illustrates the effect of hydrogen sulfide concentration on the specific alkali concentration (using the same amount of gas and 2.5 (m/m)% alkali). as we have already seen, the concentration of hydrogen sulfide between 20 and 100 ppm does not have an effect on the efficiency of the purification. however, the specific alkali concentration contains the amount of removed hydrogen sulfide. hence, the higher the hydrogen sulfide concentration of the gas (in the given range), the lower the specific alkali concentration will be. 0 20 40 60 80 100 120 140 160 180 200 0 50 100 150 200 250 300 350 alkali volume flow (cm3/h) al ka li/ h 2s (m ol /m ol ) 20 ppm h2s 50 ppm h2s 100 ppm h2s figure 8: change of specific alkaly concentration as a function of the hydrogen sulfide content of the gas summary we have devised a procedure for the replacement of solid adsorbents and amine-containing chemicals in hydrogen sulfide removal that can also be used with gases containing carbon dioxide. the essence of the method is that the natural gas is brought into contact with a dilute solution of naoh in a contact time of less than 1 second. for the experiments, a laboratory jet reactor was planned. the efficiency of purification was examined by changing the following parameters: gas volume flow, alkali volume flow and alkali concentration. it has been concluded, that for a good efficiency, a nozzle of proper size has to be selected for the given gas volume flow. also, a proper alkali flow has to be set. the efficiency of purification changes between ±10% at the proper 287 alkali velocity (in the range of 1000–3000 nm3/h). the concentration of the hydrogen sulfide gas has no effect on the efficiency of the purification between 20 and 100 ppm. only minimal improvement in efficiency can be achieved by increasing the concentration of the alkali. these observations are of great practical value. the procedure can be operated stably and safely with almost the same efficiency if the parameters fluctuate in the above ranges. acknowledgement the authors express their gratitude to the institute of chemical engineering of the university of pannonia for the financial 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meeting, (1997) 38273-ms 24. c. j. wels, process for removing sulphide from sour gas stream, u.s. patent no. 4,395,385 (1983) << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjdffile false /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 /colorconversionstrategy /cmyk /dothumbnails false /embedallfonts true /embedopentype false /parseiccprofilesincomments true /embedjoboptions true /dscreportinglevel 0 /emitdscwarnings false /endpage -1 /imagememory 1048576 /lockdistillerparams false /maxsubsetpct 100 /optimize true /opm 1 /parsedsccomments true 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(adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word contents.doc hungarian journal of industry and chemistry veszprém vol. 40(1) pp. 25–31 (2012) application of improved bio-paraffins in diesel fuels t. kasza1, cs. tóth2, j. hancsók2 1mol hungarian oil and gas plc., százhalombatta, hungary 2university of pannonia, mol department of hydrocarbon and coal processing, 10 egyetem str., veszprém, hungary e-mail: hancsokj@almos.uni-pannon.hu bio-paraffin containing mixtures produced from different natural triglycerides (conventional and improved vegetable oils, used cooking oils and fats, etc.) have high cetane number (95-105 units), but their freezing points are high (between +15 and +32°c). this property can be improved by catalytic hydroisomerization. products obtained over 0.5% pt/sapo-11 catalysts (t = 280–380°c; p = 20–80 bar; lhsv = 0.25–4.0 h-1; apparent contact time: between 1/3 and 4.0 h (at lhsv = 3.0 h-1; h2/feedstock = 400 nm3/m3) had cfpp values of +5°c; -20°c and -32°c. at the same time, there was decreased cetane number of the isomerates (87, 70 and 65 unit, respectively) relative to the feedstock. these biogasoils are suitable for bio-components of premium quality diesel fuel or for the improvement of cetane number. they can also reduce the density of low grade components providing some economic savings and some flexibility to refineries. keywords: biogasoils, biofuels, cetane number, cold flow properties introduction the energy demand of the world is continuously increasing because of the industrial development and the population growth. because of these and the environmental advantages, the importance of different bio fuels is significant nowadays [1–3] through the energy policy of the european union. its aim is to decrease the energy and oil dependency. to inspire the utilization of bio fuels 2003/30/ec, and then 2009/28/ec directives were created specifying the recommended and compulsory share of bio-components in the transportation fuels. currently, mainly the biodiesels (mixtures of methyl esters) are used as diesel fuel blending components, which have numerous performance disadvantages; for example, their oxidation and heat stability is poor because of the great number of olefinic bonds [3–10]. water content and the hydrolysis of ester bonds brings about corrosion problems [3, 7, 8] resulting in poor storage stability [3–6]. in addition, because of the good conductivity, corrosion may damage the metallic parts. furthermore, the solving nature may cause compatibility problems with plastic construction materials [7–12]. due to these disadvantages, the maintenance costs are higher, and the lifetime of the engine is shorter [10]. because of the lower energy content the fuel consumption is higher [9–13]. the combustion characteristics differ from those of diesel fuels (ignition delay, adiabatic flame temperature, radiation heat loss, etc.), the nox emission is higher [9, 13–16], and the aldehyde emission is also higher [13]. in addition, the cold filter plugging point is higher [10, 15]. they have inadequate compatibility with lubricating oils [10]. the after-treatment catalysts may be damaged by alkali and/or alkaline earth metals and phosphorus present in fatty oils [7]. the production costs are also higher than for diesel fuels [6, 17, 18]. for these reasons, car manufacturers recommend the blending concentration of the fatty acid methyl esters by 7.0 v/v% in the european union in accordance with the en 590:2009 standard. at the same time, up to 2020 the european union prescribed to use 10% of bio origin components in fuels. accordingly, the production of fuels having a preferable chemical structure from different triglyceride containing feedstocks (e.g. oils of conventional and ennobled plants, used frying oils and animal fats, algae oils, fats from meat and leather industry, so called brown grease from the sewage farms, etc.) has an important role in reaching the purposes of the mentioned directives [19]. a promising solution is the fuel purpose catalytic hydrogenation of these triglycerides. the utilization of these products is already supported by the cwa 15940:2009 standard. for this mainly sulfided transition metal(s) (ni, co, mo, w) containing catalysts having high heteroatom removal activity are suggested [19–24]. during the catalytic hydrogenation of triglycerides, mainly normal paraffins and some iso-paraffins generate beside the formation of propane, carbon oxides (co2, co), water, and oxygenic compounds according to figure 1 [19]. there are two main approaches to the hydrogenation of triglycerides: co-processing or stand-alone catalytic conversion. the co-processing systems require only slight changes in the existing hds units, which cost only a few percent of refinery installation costs. 26 ch c o o r2 c o ch2 o r1 ch2 c o o r3 catalyst h2, t, p n-paraffins i-paraffins+ by-products: co + co2 + ch4 + c3h8 + h2o + oxygen containing products figure 1: general reaction scheme of the hydrogenation of triglycerides during the co-processing of gasoil – triglyceride mixtures in a two-step process biogasoil containing gasoils can be produced with improved cetane number and suitable cold flow properties [20]. in the case of stand-alone systems the investment costs are higher compared to co-processing systems, but there is higher control on the process and higher product quality can be realized [21]. in this study biogasoils produced in such a stand-alone system are considered. the stand-alone produced, stabilized biogasoils have good heat and storage stability and outstanding cetane number (95-105). but their freezing points are high (between +15 and +32°c); accordingly to their cold filter plugging points (cfpp), they cannot satisfy either the summer grade specification of the temperate zone (at most +5°c) or the winter grade specifications (at most – 20°c). therefore their molecular structure has to be modified in order to that the cfpp value fulfill the standard specification. for this purpose, the most suitable technology is the isomerization as the freezing point of the branching paraffins is lower by 20–40°c than that of the normal paraffins having the same carbon number. to reach favourable yields, high activity and selectivity catalysts should be used. these kinds of catalysts can be the 10member-ring zeolites (e.g. zsm-22, zsm-23) and zeolite analogues (sapo-11, sapo-31, sapo-41) containing different noble metals (pt, pd) [25–27]. during the hydroisomerization, the convenient selection of the operational parameters is very important because of the favourable yield and composition, as wel as because of the disadvantageous effects on the catalyst activity. accordingly, the goal of our experiments was the investigation of the effects of the process parameters (temperature: 280–400°c, pressure: 5–80 bar, liquid hourly space velocity (lhsv): 0.5-4.0 h-1, h2/ hydrocarbon ratio: 200–800 nm3/m3) on the yield and product quality during the isomerization of normal paraffin mixture produced from sunflower oil. furthermore, we compared the performance properties of the produced biogasoils with those of fossil gasoils. experimental section apparatus the experiments were carried out in an apparatus containing a tubular down-flow reactor of 100 cm3 effective volume. it contains all the equipment and devices applied in the reactor system of an industrial heterogeneous catalytic plant [3]. the experiments were carried out in continuous operation with steady-state activity catalyst. materials during our heterogenic catalytic experiments, a normal paraffin mixture (cfpp = 23°c; hydrocarbons: c17-: 6.3%, i-c17: 0.3%, n-c17: 46.7%, i-c18: 0.4%, n-c18: 43.3%, c19+: 2.0%, content of oxygenic compounds: 0.06%, oxygen content : 68 mg/kg) produced with high yield (84.8%; which is relatively high regarding the theoretically highest yield, which is about 86.2% in the case of sunflower oil, which could change as a function of the oleic acid composition of the used triglyceride) from hungarian sunflower oil over commercial hydrotreating nimo/al2o3 catalysts was used as a base feedstock. the 0.5% pt/sapo-11 catalyst was prepared as described and characterized according to hu 225 912 patent. methods the properties of the feedstock and the products were analyzed according to eu and astm standards and gc (shimadzu 2010 gc) and gc-ms (hp 6980a). the oxygen content of the feedstock and products was determined by chns/o analysis. the crystal structure of the catalyst and its change during the experiments were determined by x-ray diffraction (xrd). xrd data were collected by siemens d500 equipment, philips pw 1730/10 (pw 1050/70 goniometer) diffractometer, cukα (40 kv, 35 ma) ray were applied. the xrd characterization of the obtained powder confirmed that it was sapo-11. the synthesized sapo-11 microporous molecular sieve was impregnated with pt(nh3)4cl2 solution. the platinum content was determined according to the uop274 standard. the platinum dispersion was determined by h2 chemisorption [29], which was 91%. the surface properties of the catalyst were determined by asap 2000 equipment (micromeritics) (pore range of 1.7–300 nm) and mercury penetration method using carlo-erba equipment (pore range 7.5–15000 nm). the specific surface area of the catalyst was 100.1 m2/g. the acidity was determined by ammonium adsorption, which was 0.66 mmol nh3/g. prior to the activity measurements the catalysts were pre-treated in situ, as described in our earlier publication [3]. results and discussion the experiments were carried out in a wide range of process parameters (t = 280–380°c; p = 20–80 bar; lhsv = 0.25–4.0 h-1; apparent contact time: between 1/3 and 4.0 h (at lhsv = 3.0 h-1). our aim was to find a combination where the liquid yield is at least 90% similarly to the industrially required yield. it is 27 necessary to avoid the fast deactivation because of the significant cracking and industrially at least 90–95% liquid yield is required. according to our preexperiments using practically heteroatom free (lower than 10 mgs/kg) feedstocks, it was concluded that the increase of the platinum content increased the isoparaffin content of the products significantly up to 0.5%. it was because the increase of the number of the hydrogenationdehydrogenation active sites promoted the isomerization reactions and the prompt hydrogenation of the intermediate carbenium ions as a consequence inhibited their cracking. the further increase of the platinum content had only insignificant effects [30, 31]. consequently, the platinum content of the applied pt/sapo-11 was 0.5%. product yield and composition during the systematic isomerization of the practically heteroatom-free normal paraffin mixture, the products were separated to gas and liquid phases. the gas products taken from the top of the separator contained mainly hydrogen and light hydrocarbons generated in the hydrocracking reactions. these hydrocarbons were mainly normal and isobutane (higher than 40% of the light hydrocarbons) which could be used in the oil industry for several purposes (e.g. lpg production, alkylation of i-c4 with olefins, dehydrogenation of i-c4 to isobutylene, etc.) [32]. the target product contained the c11 and heavier hydrocarbons beside which c5-c10 valuable side products were also generated in a small quantity. the yield of the target products decreased by increasing the temperature; this effect was intensified by decreasing the lhsv (figure 2). the reason of this was that the chain breaking of the unstable carbenium ions could happen easily at higher temperature on the catalyst surface; furthermore, the lower the flow rate of the molecule was the higher the contact time was and the higher the possibility of the cracking was. 84 86 88 90 92 94 96 98 100 270 290 310 330 350 370 390 410 pr od uc t y ie ld , % temperature, °c lshv = 0.5 1/h lshv = 0.75 1/h lshv = 1.0 1/h lshv = 2.0 1/h lshv = 4.0 1/h figure 2: product yields as a function of the temperature and the lhsv (p = 40 bar, h2/feedstock ratio = 400 nm3/m3) the yield of the products decreased by decreasing the pressure in the investigated pressure range (20–80 bar) because the partial pressure of the hydrocarbons increased resulting in a lower degree of hydrogenation of the instable carbenium ions, thus increasing the possibility of the cracking. the product yield also decreased by decreasing the hydrogen/ hydrocarbon ratio similarly to the decrease of the total pressure, because of the rising cracking. it was especially dominant below 400 nm3/m3. increasing the contact time by reacting again and again the paraffin rich mixture at 360°c, 40 bar, and lhsv of 3.0 h-1, (where the cracking selectivity is relatively low) the yield continuously decreased, since more and more polybranched paraffins were generated (see figure 6), which are more susceptible to cracking than normal and monobranched paraffins. the isoparaffin content of the product increased significantly above 300°c by increasing the temperature, but it started to decrease at about 360°c partly because of the thermodynamic inhibition (as the isomerization reactions are exothermic), partly because of the better approach of the thermodynamic equilibrium, and partly because of the cracking reactions (figure 3). 0 10 20 30 40 50 60 70 80 90 270 290 310 330 350 370 390 410 is op ar af fin c on te nt , % temperature, °c lshv = 0.5 1/h lshv = 0.75 1/h lshv = 1.0 1/h lshv = 2.0 1/h lshv = 4.0 1/h figure 3: the isoparaffin content of the products as a function of the temperature and lshv (p = 40 bars, h2/feedstock ratio = 400 nm3/m3) up to about 360°c, mainly (>85%) mono branched paraffins were generated, whose significant part (>98%) was mono-methyl-paraffins. it was because, in the case of the 10-member ring zeolites, only a small amount of isoparaffins having alkyl chain of more than one carbon number can form due to the steric inhibition [33]. their freezing points are more favourable than those of the normal paraffins, and their cetane number is high enough (figure 4). 0 20 40 60 80 100 120 4 6 8 10 12 14 16 18 20 22 24 c et an e nu m be r carbon number n-paraffins mono-branched paraffins multi-branched paraffins figure 4: cetane number of the paraffins as a function of the carbon number [34] however, above 360°c a significant amount (15–35%) of multi-branched paraffins formed, which also have favourable cold flow properties, but their cetane number 28 is low (e.g. 2,2,4,4,6,8,8-heptamethylnonane: freezing point: 0°c, cetane number: 15 unit). this effect was increased by decreasing the lhsv (fig. 3). up to 340°c, the concentration of isoparaffins increased by decreasing the pressure to 20 bar, because by decreasing the hydrogen pressure the conversion of hydrocarbons could be increased. but above 360°c the increase of the pressure to 50 bar was favourable, because the partial pressure of the hydrogen could roll back the cracking reactions (figure 5). 0 10 20 30 40 50 60 70 80 0 10 20 30 40 50 60 70 80 90 is op ar af fin c on te nt , % pressure, bar 320°c 340°c 360°c 380°c 400°c figure 5: the isoparaffin content of the products as a function of the pressure and the temperature (lhsv = 1.0 h-1, h2/feedstock ratio = 400 nm3/m3) at 360°c, which was favourable regarding both the yield and the isoparaffins content, at least 400 nm3/m3 h2/feedstock volume ratio was necessary to reach a high isoparaffin content. in the case of lower values, the concentration of the isoparaffins was decreased by the hydrocracking reactions. increasing the apparent contact time (number of runs multiplied by 1/lhsv), the isoparaffin content of the product continuously increased by reacting again and again the paraffin rich mixture in the reactor (at 360°c, 40 bar and lhsv of 3.0 h-1). at the apparent contact time of 2.0 h [= 6 x 1/(3.0 h-1)] the isoparaffin content exceeded 90%. further increase of the conversion increased only the concentration of polybranched paraffins (fig. 6). 9.77 7.10 4.25 3.18 2.64 2.38 2.06 1.85 1.56 1.41 1.29 1.21 0 10 20 30 40 50 60 70 80 90 100 0.33 0.67 1.00 1.33 1.67 2.00 2.33 2.67 3.00 3.33 3.67 4.00 is op ar af fin c on te nt o f t he p ro du ct , % apparent contact time, h concentration of monobranched paraffins, % concentration fo polybranched paraffins, % ratio of mono/polybranched paraffins figure 6: the monoand polybranched isoparaffin in the products as a function of the apparent contact time performance properties the cold filter plugging point (cfpp) of the products having gasoil boiling range decreased by increasing the concentration of the isoparaffins. at relatively low conversion of n-paraffins (<30%), the cfpp decreased only some units (figure 7). it was because the resolvent effect of isoparaffins could not inhibit the formation and growing of n-paraffin crystals. at higher conversion, not only the higher isoparaffin concentration improved the value of cfpp, but the formation of lower carbon number molecules generating mainly at higher than 70% of conversion by the cracking of polybranched paraffins. accordingly, the cfpp value of the products can satisfy not only the winter specification of the temperature zone, but the specification valid in the arctic zone (-20°c; -26°c; -32°c and -38°c) as well. -50 -40 -30 -20 -10 0 10 20 30 40 20 30 40 50 60 70 80 90 100 110 0 10 20 30 40 50 60 70 80 90 100 c ol d fil te r p lu gg in g po in t, °c c et an e n um be r conversion of n-paraffins, % cetane number cold filter plugging point, °c figure 7: the cold filter plugging point and the cetane number of the products as a function of the n-paraffin conversion (t = 360°c; p = 40 bar; h2/feedstock ratio = 400 nm3/m3) the cetane number of the products decreased as a function of the conversion (fig. 7) relative to that of the feedstock (101 unit), as the mono-methyl paraffins and polybranched paraffins have lower cetane numbers (60–75 and 40–65 unit, respectively) than those of the normal paraffins (90–110 unit) [34]. the cetane numbers of the products having improved cold flow properties (satisfying at least the summer grade specification) were between 65-86 unit, which is significantly higher than the specified value (51 unit) of the current diesel fuel standard (en 590:2009 + a1:2010). while the viscosity of the obtained biogasoils was in the range of 2.5–3.5 mm2/s meeting the specification, the density could not provide direct blending as it was in the range of 0.772–0.782 g/cm3 underachieving the expected 0.820 g/cm3 (figure 8). 0,764 0,766 0,768 0,770 0,772 0,774 0,776 0,778 0,780 0,782 0,784 2,0 2,5 3,0 3,5 4,0 4,5 0 20 40 60 80 100 d en sit y, g /c m 3 k in em at ic v isc os ity , m m 2 /s conversion of n-paraffins, % viscosity (40°c) density (40°c) figure 8: the viscosity and density of the products as a function of the n-paraffin conversion (t = 360°c; p = 40 bar; h2/feedstock ratio = 400 nm3/m3) 29 utilization possibilities of biogasoils since biogasoils consist of purely normal and isoparaffins, they have more preferable chemical structures than biodiesels. accordingly, they can eliminate the above disadvantages having an important role in reaching the purposes of the mentioned directives. furthermore, these products are excellent diesel fuel blending components, as they are practically free of sulfur and aromatic compounds, and burn exceptionally clearly. accordingly, biogasoils can be used for premium quality diesel fuels or using these low density products could provide some economic savings and some flexibility for crude refineries in case of blending of gasoils having high aromatic content and low cetane number. we note that during the production of these improved products the yield decreases. furthermore, the usability of isoparaffin rich jet and gasoline fractions has to be considered as well. biogasoils as blending components of premium quality diesel fuels regarding the production costs, the feedstock price (figure 9) of biogasoils, which is the most significant cost of bio-fuels, can be lower than that of biodiesels since (as it was mentioned) they can be produced from a broader base of feedstock. on the other hand, the installation cost of a biogasoil plant can be higher than that of a biodiesel plant because of the relatively high price of the hydrogenation catalysts and the pressurized equipment. regarding the operational costs, the hydrogen consumption represents one of the highest items in the case of biogasoils. however, because of the high exothermic nature of the hydrogenation reactions, biogasoil production has a net steam production capability, which can be utilized effectively in a refinery. to sum it up, biogasoils can be competitive with biodiesels regarding only the costs, while they excel those performance properties. 0 200 400 600 800 1000 1200 1400 1600 1800 2000 m on fly p ri ce o f v eg et ab le o ils , $ /m 3 sunflower oil rapeseed oil palm oil soybean oil figure 9: the monthly price of vegetable oils [35] comparing only the current product price of biogasoils with that of low sulphur diesel gasoils (950-1050 $/t), biogasoils can hardly compete because of the high feedstock price (800–1400 $/m3 ≈ 850–1450 $/t). considering the performance properties as well, the competitiveness of biogasoils seems to be more favorable, since the production of gasoils with cfpp value of -20°c or lower can be realized with some yield loss and significant extra costs. in addition to the production of gasoils with biodiesel content, the cfpp value can be a further challenge (cfpp of biodiesels is in the range of -5°c and +5°c depending on the feedstock) [6]. consequently, a high amount of additives has to be used. on the other hand, biogasoils having low density and excellent cold flow properties may have a positive effect on the cold flow properties of gasoils, therefore, they might improve the economy of premium gasoil production. biogasoils used for quality improvement of gasoils having low cetane number and high density in order to increase the profitability refineries try to increase the distillate yield, especially the diesel yield. some of the easier options are that the refineries can consider crude selection, cut points, operating modes, and catalysts. for further distillate yield improvement, such technologies should be used that break or crack larger, higher boiling point components into smaller, lower boiling point components. these options require capital investment and higher operating costs [36, 37]. as an alternative option, many european refineries try to change the fcc unit for increased distillate production using new catalyst formulations with better cracking capabilities [37]. however, the blending of light cycle oil (lco) having gasoil boiling range into diesel pool requires further processing as it generally has a high aromatic content (65–75%), low cetane number (15–25), and a relatively high sulfur content (100–1000 mg/kg). during the processing of relatively low value (650–700 $/t) lco, the hydrogen consumption is significant (20–25 kg/t); the cetane number can be improved reasonably up to about 30–35 unit. in the case of biogasoil production, hydrogen consumption is similar, approximately 20–25 kg/t as a function of the feedstock composition, but the cetane number is in the range of 65–86 unit. experiments showed that during the blending of biogasoils into gasoils the physical-chemical properties and the cetane number change almost linearly as a function of the biogasoil content in the gasoil [38]. these data correlated well with our results. we used an obtained biogasoil product (cfpp = -12°c; cetane number: 74.3) and a conventional light cyclic oil. the main properties of the blended mixture are summarized in table 1. as the data of table 1 show different blends obtained by the admixture of a low density, high cetane number biogasoil and a high density, low cetane number light cyclic oil meets the specification of the diesel standard. 30 table. 1. main properties and the estimated production cost of mixtures of a biogasoil and a light cyclic oil biogasoil and light cyclic oil mixtures property biogasoil 80:20 60:40 50:50 40:60 20:80 hydrotreated lco density, g/cm3 0.777 0.808 0.838 0.854 0.869 0.899 0.930 cetane number 74.3 65.8 57.3 53.1 48.9 40.4 32.0 cfpp, °c -12 -9 -6 -4 -3 0 3 production cost, $/t 1500 1350 1200 1125 1050 900 750 the cfpp value of the obtained mixture was more favourable than that of the lco. accordingly, the quality of the lco improved with biogasoil can be a suitable gasoil blending component. mixtures containing 40-60% biogasoil as a blending component have a production cost – depending on the price of the feedstock – competitive with the production cost of diesel fuels. 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bioparaffins over pt/sapo-11. chemical engineering transactions, 21 (2010) pp. 1225–1230 31. j. hancsók, m. krár, sz. magyar, l. boda, a. holló, d. kalló: investigation of the production of high quality biogasoil from prehydrogenated vegetable oils over pt/sapo11/al2o3, studies in surface science and catalysis, 170 (2007) pp. 1605–1610 32. t. kasza, j. hancsók: investigation of fuel components produced by the isomerization of bioparaffin mixtures, hungarian journal of industrial chemistry, 39(1) (2011) pp. 121–126 33. j. a. martens, m. tielen, p. a. jacobs, j. weitkamp: estimation of the void structure and pore dimensions of molecular sieve zeolites using the hydroconversion of n-decane, zeolites, 4 (1984) pp. 98–107 34. m. j. murphy, j. d. taylor, r. l. mccormick: compendium of experimental cetane number data, subcontractor report, national renewable energy laboratory, nrel/sr-540-36805, 2004. 35. http://www.indexmundi.com/, october, 2012 36. d. gibbons: naphtha to diesel via novel routes – an unconventional, synthetic approach to converting lpg and naphtha components could boost diesel production, petroleum technology quarterly (2011) q3, pp. 27–33 37. r. karlin, a. macris, r. adarme, k. wu: flexible solution for increased diesel production, petroleum technology quarterly (2009) q4, pp. 27–42 38. m. lapuerta, m. villajos, j. r. agudelo, a. l. boehman: key properties and blending strategies of hydrotreated vegetable oil as biofuel for diesel engines, fuel processing technology, 92 (2011) pp. 2406–2411 microsoft word b_50_szalkay_r.doc hungarian journal of industrial chemistry veszprém vol. 39(2) pp. 301-303 (2011) the region of sebes-körös and holt-sebes-körös as sample areas of the water framework directive cs. szalkay szent istván university, department of landscape ecology, h-2103 gödöllő, 1 páter street, hungary e-mail: szalkay.csilla@chello.hu water is an essential element of life and therefore must be protected and managed. the water policy and main aims in water economy of the european union is summarized in the water framework directive (wfd), which has operated in hungary since 2002. wfd concerns to the maintenance and improvements of the freshwater ecosystems. therefore the protection and long term conservation of the freshwaters and wetlands in consideration of the water requirements of these lands is first of the objectives. the competent authority according to the instructions of the wfd in hungary marked out for reference areas: the area of sebes-körös and holt-sebes-körös, because they have special ecological significance therefore the areas are important objects of the conservation. in 1997 then in 2002 the hungarian authorities made a study of the water state of the territory. the monitoring of the water’s conditions is started in 2004 with the examination of the values of ecosystems. the primary aim of my research to the selected reference points of measurement determines the main physical and chemical water parameters and a comparison with the previous measurement data and observe the changes in evolution. keywords: water framework directive, physical and chemical parameters of sebes-körös and holt-sebes-körös, water classification introduction water framework directive provides the solutions and one of the most significant manifestations of water management [1]. wfd additionally gives clear shoots on how to achieve good ecological conditions till 2015 [2, 3]. it is obviously necessary to know the qualitative and quantitative parameters of the freshwater, to know the ecosystem of the freshwater and wetlands in order to protect the waters and maintenance of good conditions. the competent hungarian authorities started to examine the exact factors of the balanced ecological systems of the wetlands and the freshwater ecosystems and they according to the instructions of the wdf in hungary marked out for a reference areas just as körös. examination units have been defined in the water management plan. according to this hungary has been divided into 42 units [4]. holt-sebes-körös and sebeskörös is included within category 2–14 [5] (fig. 1). the region of körös is found in the south-east border of hungary (fig. 1). the körös that came from the transylvanian mountains has formed the surface of the area for thousands years. the infilling could not balanced everywhere the sinking of lithosphere, therefore we can find marshlands in a huge territory. the area of the marshlands that is covered by water increased in the years when there was more precipitation and shrank those years that had less precipitation. those areas that did not have permanent water cover but effected by the change in the level of groundwater went through a salinization process because of the leaching of sodium ions. in addition these days the effects of the human impacts also influence the ecosystem. the biggest environmental change – because of the spread of agriculture – started with the water regulation of the körös in the 18-19th centuries. figure 1: catchment area of sebes-körös and holt-sebes-körös 302 materials and methods my measures started with the help of water specialist. i marked two townships (okány and mágor) at part of holt-sebes-körös and three townships (körösszakál, komádi, körösladány) at part of sebes-körös (fig. 2), where i did some important physical, chemical measurements minimum four times per year from 2007. figure 2: sampling sites calibrated and portable devices were applied to take outside measurements like temperature, ph-value, conductivity. alkaline and codps; co3 2-; hco3 were analyzed by titrimetry. the so4 2-, po4 3-; nh4 +; no3 -; no2 -; cl were analyzed by spectrophotometer. na+; k+; ca2+; mg2+ concentrations were defined using aas methods [6]. so far on the base of the results of field and laboratory measurements surface water has been qualified according to msz 12749:1993 standards (excellent, good, tolerable, polluted, extremely polluted) [7]. result and discussion to describe the physical and chemical parameters of the sebes-körös and holt-sebes-körös i did my measures in 2009. during my work on the characterization of water status of the water board and the körös-maros national park directorate made by experts (in 2004) of the physical and chemical analysis of the results i wanted to use [8, 9, 10]. the classification of the water samples, were based on the physical and chemical parameters defined in the 6/2002. (xi. 5.) ministry of environment and water regulation. on-site measurements fig. 3 represents clearly the seasonal changeability of temperature. the measurement points are approximately the same temperature. along downstream ph-level is between 7.5–9 so the water is defined as smoothly alkaline. the ph of the water flow at higher speed (at körösszakál, komádi and körösladány), more balanced (the year varies only 1-2 decimal places). mágor and okány has a ph measurements in april projecting the times (fig. 4). figure 3: temperature values in körös figure 4: ph-level in körös tendency of conductivity in körös was also permanent (400–600 µs cm-1). the highest values (1000 µs cm-1) was measured in mágor. in general, the conductivity is the highest in spring (fig. 5). the values of conductivity is due to the bed material (salinated). figure 5: conductivity in körös laboratory measurements the nitrate concentration is somewhat higher in winter than in summer, but the difference is striking in mágor (about three times higher than elsewhere), which indicates probable contamination of the town (fig. 6). the nitrate concentration in contrast to the ammonia concentration is higher in summer primarily for the direct pollution (livestock, fertilizer, liquid manure). fig. 7 shows the highest concentration values measured in mágor. 303 figure 6: nitrate concentration in körös figure 7: ammonium ion concentration in körös level of the orthophosphate concentration in körös was changed always between 150–650 µg l-1 (fig. 8), except for two villages (körösszakál and körösladány), where the measured concentration was twice as much because of human fertilizer. figure 8: orthophosphate concentration in körös results of the measured 8 main ions have supported that körös runs through in salinated area because of high concentration of na+, hco3 2and clwas measured. conclusion categorization of körös was performed according hungarian standards. in point of conductivity the tested part of körös can be classified as moderate water except at mágor which has been ranked as polluted backwater. ammonium ion, orthophosphate and nitrate concentration has been changed between good and polluted categories. water quality in mágor has been considered as polluted and it refers to contamination caused by local husbandry. in körösszakál and körösladány the measured concentration of orthophosphate is higher than the average value in the sampling point because of sewage of the townships transmitted into freshwater. the nitrite and nitrate concentration of the water is lower than the average values of the measurements in 1970. that is because of the area is pronounced to be protected by the law, thus the farm production is limited. references 1. d. zsikos, k. bithas: the case of a “weak water” governance model, proceedings of the 2006 iasme/wseas int. conf. on water resources, chalkida, greece, may 11-13 2006 pp. 161–166 2. directive 2000/60/ec of the european parlament and of the council 3. z. simonffy: object of water framework directive. hungarian academy of sciences, water management researcher team 4. schedule of water management plan 2006-2009 5. execution of wdf in hungary 2-14 sebes-körös subcategory 2010 6. b. welz, m. sperling: atomic absorption spectrometry, wiley-vch, weinheim, germany 1999 7. msz 12749:1993 standards water classification 8. nagyminta kísérlet: a holt-sebes-körös ökológiai vízigényének meghatározása – ökológiai szakvélemény. körös-vidéki vízügyi igazgatóság, 2003 9. nagyminta kísérlet: a holt-sebes-körös ökológiai vízigényének meghatározása – a 2004. évi ütem előkészítése. körös-vidéki vízügyi igazgatóság, 2003 10. wwf tanulmány: az ökológiai vízmennyiség létesítményüzemeltetési szempontból történő meghatározása és figyelembevétele a térségi vízpótlásban, 2002 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb 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(adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word 2012_dr_bodor_endre_hjic.doc hungarian journal of industrial chemistry veszprém vol. 39(3) pp. 407-411 (2011) study on sorption characteristics of citric acid modified rape-seed pellet considering the chemical pre-treatment processes d. németh1 , z. barta2, j. labidi3, l. gubicza1, k. bélafi-bakó1 1university of pannonia, research institute on bioengineering, membrane technologies and energetics egyetem street 10, veszprém, h-8200, hungary 2budapest university of technology and economics, department of applied biotechnology and food science 3university of the basque country, department of chemical and environmental engineering e-mail: nemethd@almos.uni-pannon.hu the ground rape-seed pellet was pre-treated then reacted with citric acid which resulted in a rape-seed citrate having ion exchange capacity. the effects of pre-treatment steps (including extraction of fatty substances by organic solvent, moreover acidic and alkali treatment of the rape-seed pellet) on the ion binding capacity of the materials were investigated. the capacity was determined for three cations (copper, zinc and nickel) separately, from aqueous solutions in batch mode of operation. based on the experimental results it was found that the highest ion exchange capacity for all the cations was obtained by the process involved the pre-treatment combining of extraction and alkali treatment followed by the reaction with the citric acid. keywords: ionic liquid, organic synthesis introduction the removal and recovery of heavy metals, which are the main source of water pollution, are important in protecting the environment and human health. that is why strict environmetal protection legislation, public environmental concerns and express of conventional disposal methods provide incentives for developing novel techniques for heavy metal wastewater treatment. several kinds of agricultural waste have natural deionising property [1]. the possibility of producing low cost adsorbents gained from agricultural waste enhanced many researchers’ interest. in the last few years, several products with deionising characteristics were prepared from agricultural materials. including sawdust [2], sugar-cane bagasse [3], wheat-husk [4], the corn-cob [5], rice husk [2], soya husk [6], tobacco [7], peanut husk pellet [8], orange wastage [9], banana peel [10], etc. these papers showed that different chemical treatments could be used successfully for improving the sorption capacity or the chemical characteristics of biological polymers – like the fibres containing starch or cellulose. however, because the combination of the wastage has various composition, the optimal producing methods and features (capacity, , stability, etc.) might be very different. their inadaptability is caused by the lack of this information. unlike the deionising synthetic resins which have petrol-chemical origins and used in water treatment, these wastage are biodegradable and more affordable. searching for the possible raw materials, then turning them into value-added products and investigating the product-characteristics is a very significant field of research nowadays. in this research we used the rape-seed pellet as a new possible adsorbent material. the rape-seed pellet is pressing wastage proceeded from the production of biodiesel. this lignocellulose based remainder is originated from the 65% of the rape-seed used for the production. currently, they are used for energetic and foraging purposes. the ground rape-seed pellet is submitted to a proceeding process containing combined pretreatment and citric acid modification, and it resulted in a rapeseed citrate with ion exchange characteristics. the effects of the dissolvent extraction and the acidic and alkali pretreatments for the formation of the adsorption efficiency of citric acid modified rape-seed is studied. the adsorbents produced in different combinations were classified according to their adsorption efficiency showed with three metal ions (copper, zinc and nickel), typically found in sewage-water. 408 materials the rape-seed pellet is provided by the öko-line hungary ltd. (hungary). the ingredients of the rape-seed pellet is presented in table 1. the pellet has been ground to 0–1 mm particle size of the powder. the humidity of the raw material is 7 (w/w)% in average. the citric acid and any other chemicals were supplied by spektum 3d ltd and scharlab hungary ltd (hungary). table 1: the ingredients of rape-seed pellet, based on the weight of the total solid substance (tss) components (w/w)% glucan 6.0 xilan 3.4 arabinan, galactan, mannan 4.4 cellulose 6.0 hemicellulose 7.8 lignin 9.7 protein 32.5 ash 5.8 hexane extractives 17.2 treatments solvent extraction solvent extraction with hexane was carried out in a soxhlet extractor. keeping the 21.5 ml/g hexane: dry rape-seed ratio, the extraction filter is filled with rapeseed and measured the needed amount of hexane into the extractor’s test-tube. a spherical condenser is put on and heating is started. the extraction treatment has been carried out for an hour and it has been completed by this time. the extracted fibre was dried room at temperature for having the rest of the hexane evaporated, than we dried it to constant weight on 105 °c. we suspended the dry fibre half an hour for in distilled water (sugars) setting the dry-substance content on 10%, than we filtrated and washed it in triple amount of water. we dried it to constant weight and stored it in a desiccator. acidic and alkaline treatment one (w/w)% naoh and h2so4 solution was poured into a screw topped bottle setting the dry-substance content on 10%, in which we put the dry material and kept it at room temperature for a week, shaking it once a day. by the end of the treatment period we filtrated the substance, than washed it in distilled water to make it free from acid and alkali. the fibre we gained was dried at 105 °c and stored in a desiccator. modification with citric acid in laboratory scale citric acid solution was mixed with powdered rape-seed pellet using 10 ml/g citric acid solution/rape-seed ratio. the mixture was dried at 60 °c until the weight became constant, resulting a hard, bulky material. the product was then ground and sieved to provide the suitable particle size, which means greater contact surface area for the thermochemical reaction. then the sample was placed in an oven to dehydrate at 60 °c for 24 h. that way all surface moisture was removed. then the temperature is increased to 120 °c and kept 120 minutes, while the thermochemical reaction is completed (fig. 1), [12-13]. in the end of the process the not reacted citric acid is removed from the surface of the particles by washing with water and then the rape-seed citrate is dried. the applied reaction parameters are determined with utilizing full factorial experimental plans. figure 1: thermochemical reaction of polysaccharide and citric acid determination of sorption efficiency the evaluation of produced sorbent samples is based on their binding capability of cu(ii), zn(ii), ni(ii). 1 g sample with 200–400 μm particle size was put into 100 ml 30 mm cuso4 or znso4 or nicl2 solution, where the ph=4.5 was adjusted by acetic acid – sodium acetate puffer. the mixture was stirred for 24 h, at 130 rpm and 25±3 °c with a magnetic stirrer. when the contact time was over, the solid material was filtered, the cu, zn, ni content of the filtrate has been determined with icp. the sorption capacity was determined as follows: m )cc(vq e0 −= (1) where: v – the volume of the solution (l) m – weight of the sorbent sample (g) c0 – initial concentration of the solution (mg/l) ce – final concentration of the solution (mg/l) q – the binded mg cu (ii)/zn(ii)/ni(ii) / g sorbent 409 the sorption capacity can be expressed in the following form: 100 vc q% q 0 = (2) where: q% – the binded cu(ii)/zn(ii)/ni(ii) content in % of its initial quantity / g sorbent results it can be seen in fig. 2 that the modification of untreated rape-seed with citric acid had a positive effect on the binding of the metal ions.   figure 2: adsorption effectiveness of the untreated (rp) and citric acid modified rape-seed (rp/m) in the case of metal ions in fig. 3, the inclination of the pre-treated samples (without citric acid modification) can be observed against copper, zinc and nickel ions. figure 3: the adsorption effectiveness of the pre-treated rape-seed in the case of metal ions (rp – rape-seed without pre-treatment; rpe – extracted rape-seed; rpe/s – extracted and acidic treated rape-seed; rpe/l – extracted and alkaline treated rape-seed) although the dissolvent extraction improved the fibre’s ability to bond in the case of copper and nickel, we did not observed significant changes with zinc. after the pressing procedure in the production of bio-diesel, there were some triglycerides left in the pellet (table 1). this material (table 1) was supposed the features of the lignocellulotic structure. with its extraction, the active surface can be increased. because of the significant improvement of the quality that was gained by extraction, the acidic and alkaline treatment was not performed as a separate treatment, but connected to the previous one. these washes damaged our results in hexane extraction. it is to be mentioned though, that the adsorption results received through acidic treatment were higher than in the case of untreated rape-seed. the combination of extraction-alkaline can be classified as an unsuccessful treatment, as its results did not even reach the results of the untreated base material. concluding these results it can be proved that, among all the pre-treatments we made, the extraction performed with hexane was only significant, while the treatments widened the procedure and the time of the adsorbent production unnecessarily. the materials gained by this procedure were further modified by citric acid. so the previously produced materials can be considered as the core of the ion changing substance on which we built the ion changing function group. because these cores had already had adsorption capacity and they were very different, fig. 4 only shows the ability to bond the metal ions gained with citric acid, to avoid any misunderstanding. figure 4: the effect of citric acid modification for the adsorption efficiency of the properly pre-treated rape-seed in the case of copper, zinc and nickel ions (rp/m – rape-seed modified with citric acid; rpe/m – extracted and citric acid modified rape-seed; rpe/sm – extracted and acidified, citric acid modified rape-seed; rpe/lm – extracted and lixiviated, citric acid modified rape-seed) in the case of all the three examined ions we experienced that the effect of the modification was almost the same at the extracted (rpe/m) and extracted and acidified (rpe/sm) samples, as at the citric acid modified samples (rp/m). this is very interesting concerning the extracted material, because its core had previously showed better results than the untreated one. on the basis of this research, the citric acid reaction is less effective with the extracted core than with the untreated rape-seed. presumably, the specific surface increases thanks to the extraction but the number of the reactive groups decreased. the failure of the acidic pretreatment and modification can be explained with the fact that in the presence of acid, the number of the negative charged places decreased remarkably [2]. this restricts the natural sorption characteristics and the 410 number of the reactive places that are able to make ester bonds. in the case of alkaline treated samples, the modification was significantly efficient (~50 % cu). at the previous analysis (fig. 3) its core showed the worst results. on the basis of these, the reactivity of the extracted and alkaline treated and prepared core was the the highest. its metal ion bonding capability gained by the modification was always higher than in the case of untreated core (with cooper ions appr. +23%, with zinc ions appr. +14%, with nickel ions appr. +11%). the extraction and the naoh treatment contributed to the formation of the reactive construction, therefore a large number of carboxyl group was built in with citric acid modification. summarizing the results of the pre-treatments and modifications, under the given circumstances, the best values of the metal ion bond can be reached by the extracted, alkaline pre-treated citric acid modified rapeseed (table 2). in fig. 5 the results of all the modifications can be seen together. table 2: amount of the metal ion bond by extracted, alkaline treated, citric acid modified rape-seed in the given research circumstances rpe/lm q q % cu2+ 101.9 mg/g 53.9% zn2+ 42.3 mg/g 20.0% ni2+ 47.5 mg/g 27.1% figure 5: the adsorption efficiency of the pre-treated and modified rape-seed in the case of copper, zinc and nickel ions (see explanation of the symbols at fig. 4) the efficiency of the naoh treatment had been discussed in many studies [2, 5, 6, 10, 11]. the experiences are rather dissimilar as they depend on the different raw materials and treatment circumstances. in the case of smaller capacity enhancement it is not recommended to apply the pre-treatments as it increases the time of production and the costs. apart from the quantity data it is worth considering the changes in quality. for instance, the un-extracted fibres leaked some brown pigments into the solutions during the 24 hours bound, which changed the solutions’ colour significantly. the same problem occurred during the treatment of soya husk [6]. so the extraction of the unwanted ions was done, however some other organic contamination appeared in the solution. this did not occurred in the case of the treated fibres. summary the ground rape-seed pellet was extracted by hexan and pre-treated by naoh and h2so4 in order to improve the natural adsorption characteristics of the rape-seed. from these procedures, the best metal ion bond was gained with the extracted rape-seed. in the case of the citric acid modification of the pretreated substances the number of the sorbent bound metal ions enlarged, regardless the type of the pre-treatment. the degree of the efficiency of the modification was the highest in the case of extracted, citric acid modified alkaline treated core. considering the results of the pre-treatments and the modification, the best metal ion bounds results can be reached by the extracted, citric acid modified alkaline pre-treated rape-seed, under the given circumstances. acknowledgement the research work was supported by the project tamop-4.2.2. entitled „livable environment and healthier people – bioinnovation and green technology research at the university of pannonia” and by the hungarian fundamental research fund, grant otka 72710. present article was published in the frame of the projects támop-4.2.1/b-09/1/konv-2010-0003 and támop-4.2.2/b-10/1-2010-0025. the projects are relaized with the support of the hungarian government and the european union, with the co-funding of the european social fund. references 1. 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marshall, l. h. wartelle, d. e. boler, m. m. johns, c. a. toles: enhanced metal adsorption by soybean hulls modified with citric acid, bioresource technology, 69 (1999) 263–268 7. m. a. k. hanafiah, w. s. w. ngah, h. zakaria, s. c. ibrahim: batch study of liquid-phase adsorption of lead ions using lalang leaf powder, journal of biological sciences, 7 (2007) 222–230 8. w. wafwoyo, c. w. seo, w. e. marshall: utilization of peanut shells as adsorbents for selected metals, journal of chemical technology and biotechnology, 74 (1999) 1117–1121 9. x. li, y. tang, z. xuan, y. liu, f. luo: study on the preparation of orange peel cellulose adsorbents and biosorption of cd2+ from aqueous solution, separation and purification technology, 55 (2006b) 69–75 10. k. s. low, c. k. lee, a. c. leo: removal of metals from electroplating wastes using banana pith, bioresource technology, 51 (1995) 227–231 11. w. s. ngah, m. a. k. m. hanafiah: removal of heavy metal ions from wastewater by chemically modified plant wastes as adsorbents: a review, bioresource technology, 99 (2008) 3935–3948 12. j. mcsweeny, r. m. rowell, s.-h. min: effect of citric acid modification of aspen wood on sorption of copper ion, journal of natural fibers, 3(1) (2006) 43–58 13. d. j. sessa, r. e. wing: thermochemical derivatization of soybean and corn protein with citric acid to enhance metal binding properties, paradigm for succesful utilization of renewable resources, aocs press, champaign, il, pp. 232–246 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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<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> /enu (use these settings to create adobe pdf documents best suited for high-quality prepress printing. created pdf documents can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word contents.doc hungarian journal of industry and chemistry veszprém vol. 40(1) pp. 1–4 (2012) improvement of biofilm carriers for the treatment of automotive industry wastewater p. thury1 , l. bartha2, g. gulyás1, v. pitás1, b. fazekas1, a. kárpáti1 1university of pannonia, institute of environmental engineering, 10 egyetem str., 8200 veszprém, hungary e-mail: thuryp@almos.vein.hu 2university of pannonia, institutional department of mol hydrocarbon and coal processing 10 egyetem str., 8200 veszprém, hungary the efficient biological treatment of the wastewater of the automotive industry is difficult, mainly because of the low biological oxygen demand/chemical oxygen demand (bod/cod) ratio. moreover, wastewater of the automobile industry contains heavy metals and other chemical substances that may have toxic effects. biofilm and hybrid technologies could be optimal solutions for the treatment of such heavily biodegradable wastewater streams. this paper presents the experimental results of the examination of modified biofilm carriers developed for the treatment of the wastewater of the automotive industry. three modified biofilm carriers were examined: a high-density polyetyilene (hdpe), an hdpe modified with 50% carbon nanotube (cnt) content, and an hdpe modified with 75% cnt content. they were compared to a patented biofilm carrier having similar morphological properties (control). the examination consisted of two parts: (1) studying the colonisation of biofilm on each carrier, and (2) studying the biological cod removal efficiency of biofilm reactors filled with the four different biofilm carriers in 25% volumetric ratio each with an influent industrial emulsion sewage. the obtained results demonstrated that neither the rate of biofilm colonisation, nor the cod removal efficiency show any significant difference comparing the four biofilm carriers. the colonisation of biofilm was appropriate on each carrier and this ensured proper efficiency of cod removal in each biofilm reactor. based on the results, it can be stated that the suggested advantageous characteristics of cnts do not appear as it is mixed in the plastic raw material during the production of biofilm carriers. the absence of the significant difference observed between the examined carriers suggests that the production of biofilm carriers from recycled plastic could carry financial advantages compared to the control carrier. further experiments could specify differences by various hydraulic loads or toxic effects. keywords: automotive industry wastewater, biofilm carrier, cnt, cod removal, emulsion sewage introduction during biological wastewater treatment processes, bacteria utilize various forms of c, n and p present in wastewater [1]. the biological treatment processes can be characterized according to the presence of the microbiological forms. the microbes are aggregated into flocks in the activated sludge (as) processes or fixed on the surface of biofilm carriers (biofilm technologies). the processes, where both flocks and biofilm carriers are present are called hybrid systems. the history of conventional activated sludge treatment dates back to hundreds of years. in the past fifty years, several experiments have been made with biofilm or hybrid technologies due to the advantages these technologies hold compared to the conventional as systems [2]. the main points of it are the better achievable nutrient removal, the possibility of higher applied specific nutrient load, and the reduced sensitivity of the biofilm towards the toxic compounds of wastewater [2]. the efficient biological treatment of the wastewater of the automotive industry is difficult, mainly because of the low biological oxygen demand/chemical oxygen demand (bod/cod) ratio. moreover, wastewater of the automobile industry contains heavy metals and other chemical substances that may have toxic effects [3]. the advantages of biofilm or hybrid technolgies, therefore, can be exploited in the treatment of automotive industry astewater. this paper presents the experimental results of the examination of modified biofilm carriers developed for the treatment of the wastewater of the automotive industry. methods according to several studies, the relatively fast colonisation of biofilm has been observed on the surface of activated carbon [4–7] compared to the conventional plastic carriers. the examined biofim carriers in this study have been modified with the addition of carbon nanotubes (cnt) to the plastic raw material during the production of carriers. the raw plastic was high-density polyetyilene (hdpe). 2 three biofilm carriers have been produced and examined: 1. 100% hdpe 2. hdpe modified with 50% cnt 3. hdpe modified with 75% cnt. these three biofilm carriers have been compared to a patented biofilm carrier [8] having similar morphological properties (control). the first part of the examination was mainly morphological: some properties of the three modified carriers have been investigated and compared to the control one. in the second part of the experiment, biofilm carriers have been examined during biological wastewater treatment. this part of the experiment consisted of two stages: 1. studying the colonisation of biofilm on each carrier, 2. studying the biological cod removal efficiency of biofilm reactors, filled with the four different biofilm carriers, in 25% volumetric ratio each, with an influent industrial emulsion sewage. first, the colonisation of the biofilm on the carriers was carried out in four sequencing batch reactors reactors (sbr) of the same kind, having a useful volume of 4 litres, with 25% carrier filling ratio. the reactors were inoculated with municipal sewage sludge and were fed with municipal sewage. the biological wastewater treatment took place within aerobic conditions (since the focus of the experiment was solely cod removal). after 3 weeks of operation, the mixed liquid suspended solid (mlss ) concentration was reduced to 0.5 g/l to allow faster colonisation of the biofilm. the colonisation of the biofilm took about 6 weeks. after the first 6 weeks of operation, the amount of colonised biofilm on the carriers was determined in every 3 weeks by a method developed in the institute of environmental engineering, university of pannonia, veszprém. after the visible colonisation of the biofilm on the carriers, the feedstock of the reactors was changed to an emulsion sewage. the focus of the experiment was the examination of cod removal in the reactors. the applied reactor configuration can be seen in figure 1. figure 1: 4 parallel reactors the inlet of the reactors can be characterized with the following parameters: codtotal 1000–1700 mg/l; codfiltered 800–1600 mg/l; bod5/cod ratio 0.4–0.5; nh4-n 15–25 mg/l; orto-p 5–160 mg/l. the hydraulic retention time in the reactors was 4 days in the first 8 weeks, after that it was reduced to 3 days until the end of the experiment. the mlss concentration was controlled between 0.5–1.5 g/l. results and discussion morphological examinations showed that the weight of the modified biofilm carriers is about 30% more than the weight of the control carrier, independent of the amount of cnt added. it resulted in a different bulk density of the modified biofilm carriers, but no difference has been observed in hydrodynamics compared to the control carrier. the modified biofilm carriers showed more roughness on their surface compared to the control carrier, and some dimensions of the modified carriers also differed slightly from the control carrier. biofilm colonisation has been examined on the biofilm carriers after it became visible (after about the first 6 weeks of operation). the results of the determination of the amount of biofilm colonised on the carriers is depicted in figure 2. the figure shows the biofilm concentration in g/l, which is an excess mlss concentration in the reactors, calculated from the measured amount of biofilm per carrier and the filling ratio. according to fig. 2 no significant difference can be observed either between the three moified carriers, or compared them to the control carrier. 0 0,2 0,4 0,6 0,8 1 1,2 1,4 1,6 1 8 11 15 weeks b io fil m (g /l re ac to r) control 100 % hdpe 50 % cnt 75 % cnt figure 2: the results of the determination of the amount of biofilm in the last experimental period, the biological cod removal was studied in the 4 reactors, filled in 25% with the 4 different biofilm carriers. results are shown in figures 3–6. continuous vertical lines show the change in the influent wastewater, while broken lines show the date of excess sludge removal from the reactors. according to fig. 3–6, no significant difference can be seen either between the cod removal of the reactors filled with the modified biofilm carriers, or compared them to the reactor filled with the control carrier. the effluent from each reactor contained 130–140 mg/l codtotal (100–110 mg/l codfiltered). the difference between codtotal and codfiltered is indicated by the difficulty of decantation in the sbr reactors. the 3 examined four biofilm carriers flow up to the surface during sedimentation, and some sludge is removed this way during decantation. the excess sludge removal caused a slight increase in the effluent cod each time in each reactor (broken vertical lines in fig. 3–6). the reason is the sudden increase in the specific organic load of the sludge remaining in the reactors when excess sludge is removed. figure 3: cod removal in the control reactor figure 4: cod removal in the 100% hdpe reactor figure 5: cod removal in the 50% cnt reactor figure 6: cod removal in the 75% cnt reactor conclusions the obtained results demonstrated that neither the rate of biofilm colonisation, nor the cod removal efficiency show any significant difference either comparing the three modified biofilm carriers, or comparing them to the control carrier. the colonisation of biofilm was appropriate on each carrier and this ensured proper efficiency of cod removal in each biofilm reactor. based on the results, it can be stated that the suggested advantegous characteristics of carbon nanotubes do not reveal as it is mixed in the plastic raw material of the biofilm carriers. the absence of the significant difference observed between the examined carriers suggests that the production of biofilm carriers from recycled plastic could have financial advantages compared to the control carrier. further experiments could specify differences by various hydraulic loads or toxic effects. acknowledgements this research was funded by támop-4.2.1/b-09/1/ konv-2010-0003 tender, mobility and environment, research of automotive industry, energetics and environment in the middleand western-danubian region nr. 1. course, in the frames of the sub-topic called pe/1.1.5. (production of admixtures for the improvement of the compatibility of plastic components). this research was also supported by the european union and co-financed by the european social fund in the frame of the támop-4.2.2/b-10/1-2010-0025 project. references 1. m. henze, p. harremoes, j. c. jansen, e. arvin: wastewater treatment, biological and chemical processes (1995), springer-verlag, berlin 2. v. pitás, g. németh, k. reich, b. fazekas, dr. á. kárpáti: biofilm hordozó hatása biofilmes/ hibrid reaktorok működésére, műszaki információ, környezetvédelem (2009) 6. szám, pp. 63–74 3. m. salehi, s. a. m. mirbagheri: determination of kinetic constants and biological treatment of automobile industries wastewater, international journal of environmental research (2010) vol. 4, no. 1, pp. 131–136 4. d. hadijev, d. dimitrov, m. martinov, o. sire: enhancement of the biofilm formation on polymeric supports by surface conditioning, enzyme and microbial technology (2007) vol. 40, pp. 840–848 5. d. dimitrov, d. hadijev, i. nikov: optimisation of support medium for particle-based biofilm reactors, biochemical engineering journal (2007) vol. 37, pp. 238–245 6. j. bolton, a. tummara, c. kapadia, m. dandamudi, j. m. belovich: procedure to quantify biofilm activity on carriers used in wastewater 4 treatment systems, journal of environmental engineering (2006) vol. 132, pp. 1422–1430 7. i. apilánez, a. gutiérrez, m. díaz: effect of surface materials on initial biofilm development, bioresource technology (1998) vol. 66, pp. 225–230 8. ep 1 884 282 b1 patent disclosure microsoft word a_37_kovacs_r.doc hungarian journal of industrial chemistry veszprém vol. 39(1) pp. 73-78 (2011) estimation of the maximum applicable voltage level of aluminium electrolytic capacitors by automated spark-detection measurement l. kovács1, d. fodor2 1electronic parts and components ltd., csaba st. 30., 9700 szombathely, hungary e-mail: laszlo.kovacs@epcos.com 2university of pannonia, faculty of engineering, institute of mechanical engineering egyetem str. 10., 8200 veszprém hungary e-mail:fodor@almos.uni-pannon.hu the paper deals with the presentation of a complete measurement automation system (mas) implemented in an aluminium electrolytic capacitor development laboratory at epcos hungary. the main function of the mas is to facilitate electrolyte and capacitor research and development by automation of the related measurement tasks and to provide a powerful database system background for data retrieval and decision support. the presentation focuses on the architecture of the spark-detection measurement system and introduces a reliable estimation procedure for determining the maximum level of the voltage which can be applied to the capacitor without damage. for the design engineers it is often impossible to determine the exact maximum voltage which will never be exceeded in the application. with the presented spark detection measurement a good estimation of the allowable maximum voltage can be given. keywords: measurement automation, test automation, passive electronic components, electrolytic capacitor introduction there are many different kinds of capacitors (ceramic, foil, electrolytic and tantalum capacitors). the most widely used type is the aluminium electrolytic capacitor which can be found in many electrical systems like energy storage, power conditioning in power supply, power factor correction in electric power distribution, etc. the lifetime of electronic systems depend significantly on the lifetime of the capacitor, so they use this type of capacitors because reliability is very important in these systems. the aluminium electrolytic capacitor has many really important properties: capacity (1 µf – 3 f), operational voltage (from a few volts up to 700 v), operational temperature (from -55 °c to 125 °c), loss factor, size and shape. the design engineer must determine the exact maximum operating voltage. it is not an easy task, in contrast with the other parameters, because the capacity of the capacitor is specified by the surface capacitance of the anode foil. the spark-detection measurement system presents a good estimation procedure for determining the maximum level of the voltage which can be applied to the capacitor without damage. in addition to that, the paper deals with the basic construction of the wet aluminium electrolytic capacitor and introduces a measurement automation system (mas) of an electrolytic capacitor development laboratory at an international company in hungary. aluminium electrolytic capacitor the winding of aluminium electrolytic capacitors contains two foils (anode and cathode foil) with an impregnated paper. they are rolled together tightly into a winding [1] as shown in fig. 1. the positive foil is made from pure aluminium (the purity is higher than 99.9 %). the foil has been etched to increase the effective surface area (and the capacitance of the capacitor). it is typically 30–100 times larger than the plain area of the foil. on the etched surface of the foil an aluminium oxide layer has been formed electrochemically. the voltage of the etched foil is 30–40 % higher than the rated voltage [2] of the capacitor. the cathode foil is made from pure aluminium, too, and it has a thin oxide film (only a few volts, regardless of rated voltage). it is typically etched to increase the surface area slightly. the function of the aluminium cathode foil is to reduce the series resistance of the capacitor by making contact with the paper over a wide area. the positive pole of the capacitor is the anode foil. the other pole is a combination of high-absorption paper impregnated with an electrolyte, in contact with the cathode foil. the electrolyte is there to make good contact with the anode, by permeating its etched structure, and also to repair any flaws in the oxide layer when the capacitor is polarized. the anode and the cathode foils are contacted by aluminium tabs which are extended from the winding 74 and are riveted to the aluminium terminals of the cover disk. the tab foils are not etched but they also feature an oxide film made by electrochemical oxidization. figure 1: winding of aluminium electrolytic capacitor before being housed in a suitable container, the complete winding is impregnated with electrolyte. after housing the edges of the can are curled back. before being sleeved and packed, capacitors are first aged. the purpose of this stage is to repair any damage in the oxide layer and thus reduce the leakage current to very low levels. leakage current of capacitors the leakage current is the most important parameter of capacitors. real capacitors have failure places on the oxide layer of the anode foil. damage to the layer can occur due to the failure of the oxide layer’s structure or mechanical breakdown, e.g. slitting of the anode foil (foil manufacturers produce the anode foil in rolls), riveting the tabs to the anode foil, or minor mechanical damage caused during winding. numerous effects depend on the magnitude of the leakage current, for example the time, the ambient temperature and the voltage of the capacitor. the time-function of the leakage current [3] is shown by fig. 2. at the initial stage, the current has a peak, and then decreases by time until it reaches a low, almost constant value (irb). figure 2: characteristic of leakage current according to fig. 2, decreasing of the leakage current is exponential. the decreasing can be written down by a simple relation: a t tii ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ = 2 1 12 or a t tii ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ = 1 2 21 (1) where: i1 – the leakage current value at the t1 time i2 – the leakage current value at the t2 time t1 and t2 – time of the leakage current’s measurement a – constant. a well-operating capacitor's a index value is equal to 0.5. as a result of a = 0.5, the previous figure changes to: 2 1 12 t tii = or 1 2 21 t tii = (2) for the calculation of the leakage current, t1 and i1 assets are needed. however, the value of the leakage current is affected not only by the time but the ambient temperature, too. its characteristic can be seen on fig. 3. figure 3: ratio of leakage current increasing dependence on ambient temperature the figure above shows the ratio of the increasing current caused by the ambient temperature and the irb value at 20 °c. the higher the ambient temperature the higher the leakage current. moreover, the capacitor’s leakage current depends on the operating voltage, too, shown by fig. 4. figure 4: leakage current dependence on voltage of aluminium electrolytic capacitors it can be seen that the irb leakage current increases by ub operating voltage. after reaching the un rated voltage, the gradation of the current curve increases. the closer the voltage level to the uf forming voltage, the bigger the gradation of the current curve becomes. between us surge voltage and uf forming voltage the leakage current does not regenerate the capacitor's oxide 75 layer but starts damaging procedures, e.g. heating of the capacitor, gas emission, electrolyte decay, formation of imperfect oxide layer. when devising the capacitor's construction, design engineers must set the optimal operating voltage. it is important not to cause too high current during operation because that can lead to the breakdown of the capacitor. developing process of capacitor development of aluminium electrolyte capacitors is a complex process. the ideal flow-chart is shown by fig. 5. figure 5: flowchart of capacitor development the flowchart shown on fig. 5 consists of two parts: the first part is electrolyte development, and the second part is capacitor construction development. both sections include measurements and experiments. measurements of and experiments on electrolyte last for a short time while measurements of and experiments on capacitor construction can last for thousands of hours. the stages of development are determined by the purpose of the development project: there are cases when the only object is developing a new construction so measurements of and experiments on electrolyte are irrelevant. regarding measurements of electrolyte, this article only deals with spark measurement which helps design engineers in determining the optimal operation voltage. the automation of multi-operating, data-registering, mid-long and long measurements and experiments was optimal, increasing the efficiency and speed of capacitor development. the automation has been realized by creating an information technological system which studies every aspect of capacitor development. measurement automation system (mas) the main purpose of mas [4] is to help capacitor development, which is a time-consuming and really complicated task. the base of the whole software system is a framework originally designed to provide a common user interface for different measurements and registry programs. the measurement system includes at least 30 different measurements and software modules. the whole system can not be presented here we only focus on the software modules related to the estimation of the maximum voltage level. the main structure has two different parts. the first one contains the measurements, while the second one contains the data evaluation modules, concluding data management and data visualization modules that can display all the results of measurements, tests and experiments. the “class” of measurements has two subgroups involving the electrolyte and the capacitor measurements. the electrolyte experiments are controlled by a ni-pxi which is connected to the database. the structure of the measurements is shown by fig. 6. the graphical interfaces of electrolyte measurements have two pages. the first one contains the settings of the measurements and equipments (e.g. number of serial port, cell voltage of conductivity equipment, file path of saved data, etc.). this page is used before the measurement. the second one shows the status of the experiment. it displays the measurement results with numeric indicators and graph, the elapsed and remaining time, etc. the software can store the results into a file and the global database. figure 6: structure of the electrolyte measurements the most important electrolyte measurements are the following: ● “conductivity(t)”: measuring temperature dependence of conductivity. in this experiment the temperature of the solution is regulated and after the stabilization time the conductivity value is measured with the controlled equipment. ● “ph(t)”: measuring ph value as a function of temperature. the structure of the program is the same as that of the above-mentioned one, with the only difference that a ph meter is used instead of conductivity meter. the measurement is important because the ph value of the electrolyte used in the electrolytic-capacitor must be within a specified range. 76 ● “mixing(ph with single temperature)”: measuring ph value as a function of the concentration of an electrolyte composition at a specified temperature. as a matter of fact, we use this measurement in order to set up the ph value of the electrolyte. ● “spark detector”: measuring the breakdown potential of the electrolyte. this measurement is one of the most important tasks, and will be presented in detail in the next section. the second subgroup contains the capacitance management modules which simplify the electrical measurements and data registration. in addition, it includes the registration interface of the capacitor experiments for qualification approval. the most important measurements in this group are the following: ● capacitor registration: this module simplifies the registration of the properties (anode, cathode foil, type of can, cover disk, etc.) of the capacitor. ● “esr (equivalent serial resistance) matrix”: this measurement is mostly used in order to determine the resistance of the capacitor at different frequencies and temperatures. ● “gas pressure”: measuring the internal gas pressure of the capacitor in various operating conditions. ● electrical measurement: measuring the electrical parameters (capacitance, impedance, esr) of the capacitor by an agilent lcr equipment at different frequencies. ● leakage measurement: the oxide layer of the capacitor's anode foil is not flawless, so dc current is flowing through the capacitor if voltage is applied to it. this current is the leakage current. its value depends on the applied voltage, the duration of the charging period and the capacitor's temperature. the last part of the system has been developed for data management. this software module contains really useful tools, which facilitate the representation and evaluation of the stored data. for example: the report generate module can make a standard report in less than one minute. this module contains the following software: ● report generate: for composing a standard report about the specified experiment (e.g. endurance, surge test, etc.) ● search: for constructing several sql commands that can build "ad hoc" queries. ● documentation library: for handling the reports on experiments. the software package facilitates electrolyte and capacitor development because these tools accelerate the experiments and make work easier. the most important measurement is the “spark detector” experiment, which helps estimate the maximum applicable voltage of aluminium electrolytic capacitors. spark measurement during a spark measurement the breakdown voltage of the tab foil's oxide layer is measured. breakdown voltage is the voltage where the dielectric starts to conduct. a spark can occur because of the electric field. this phenomenon happens by growing of the polarization bias. the field strength is increasing. if the increase is adequate, the neutral corpuscles become polarized and the insulator starts to conduct. such spark phenomenon occurs too if the dielectric loss heats up the insulator. above a specified heat level the insulating attribute no longer exists. a spark is featured by its time interval, which can extend from a few nanoseconds to seconds. spark is affected by the pressure, the humidity, the temperature and the material purity. because of the spark phenomenon's sensitive nature, small voltage changes in short time intervals must be detected. the equipment built for this purpose detects spark the following way: damages of the dipped tab are repaired by the current. the oxide layer becomes thicker, so voltage is increasing. during etching a limited oxide layer with limited sturdiness can be produced. above this critical voltage level spark happens, accompanied by a hissing and crackling sound. the current of the circuit is momentarily increasing. instead of voltage generator mode, the system's power supply works in current generator mode. by this method a sufficient layer of insulating material can be produced on the freshly cut edges on the influence of the electrolyte's limited current level. after reaching a critical voltage level, the voltage is no longer increasing and spark happens. the oxide layer starts to conduct and the power supply's voltage falls. this voltage can easily be detected. the complete measurement system can be seen on fig. 7. the system includes the power supply, the thermostat, the thermostated beaker and the spark detector. figure 7: the spark measurement system for collecting, registering and handling measurement results a suitable software has been developed. the user's interface of the software is shown in fig. 8. 77 figure 8: graphical interface of spark measurement the equipment and the measuring pxi communicate through an rs-232 port. the software can set the properties of the equipment and control the entire experiment. the users just have to start the experiment. there are two graphs on fig. 8. the upper one shows the number of sparks while the lower one shows the voltage level. after the experiment, the measured results can be saved into the database or exported into ms excel. results many experiments were performed with the equipment and the data on voltage and sparking density of the electrolytes were stored. the spark phenomenon was measured at the maximum temperature of the climatic category of capacitors (as previously discussed, breakdown voltage is influenced by the temperature). the results showed (fig. 9) that the peak of the gausscurve of spark density specifies a voltage, which is approximately the maximum voltage level of the electrolyte. the applicable voltage is determined by the paper construction of the capacitor: spark voltage of the electrolyte has grown by about 5 to 10 percent. by this method, the capacitor's maximum applicable voltage can be approximately evaluated. this voltage level is not used during the usage of the capacitor. the actual voltage levels in practice are 400 v, 450 v, 500 v, etc. international standards determine certain experiments to be performed for qualification approval. the capacitor's selected rated voltage must withstand a defined voltage level. for example, a capacitor with a 450 v rated voltage must withstand a 495 v voltage level, which is determined by the surge test. in practice, first the spark voltage of the capacitor must be measured (the experimental electrolyte's spark voltage is 479 v), and after that a ramp test is recommended. figure 9: spark voltage of the electrolyte in the ramp test the voltage level is continuously increased until the failure of the capacitor. the experimental electrolyte was tested with capacitors of different paper construction. (with a thinner paper during the first, and with a thicker paper during the second test). the first test's current curves can be seen on fig. 10 and the second test's current curves can be seen of fig. 11. figure 10: the current, with the first paper construction figure 11: the current, with the second paper construction 78 the breakdown voltage of the capacitor is 516 v and 525 v. the first one is 107.7 % while the second one is 109.6 % of spark voltage. this proves that the paper's thickness influences the spark voltage. the capacitor's rated voltage is 450 v. the cecc standard defines a surge test, where the capacitor must endure 110 % of the rated voltage, in this case 495 v. conclusion this paper presents the measurement automation system of an electrolytic capacitor development laboratory at epcos hungary that contains more than 30 modules, including measurements on electrolytes and capacitors and data visualization software. all measurements have been implemented in a similar manner. first, the user initializes the measurement, sets the measurement parameters, launches the execution and leaves the program to run on its own, sending the results of the measurements to a database system, from where the data can be retrieved in a predefined or non-predefined way. the data acquisition system increases the efficiency of work (by decreasing the possibility of failures and assisting the developer engineer), and accelerates the process of development. these advantages are due to the automation of the measurements and the effective data visualization tools. the paper presents in detail an important and very useful method, the spark measurement which helps determining the maximum applicable capacitor voltage level by measuring the electrolyte's breakdown voltage. this voltage level is 90–95 % of the capacitor's operating voltage. for defining the maximum voltage level, a ramp test must be executed after the spark measurement where the voltage of the capacitor is continuously increasing. the voltage measured this way is the capacitor's maximum voltage. the executed tests prove the accuracy and adaptability of the measurement. acknowledgments the authors express their gratitude for the auspices of the project „tamop-4.2.1/b-09/1/konv-2010-0003: mobility and environment: researches in the fields of motor vehicle industry, energetics and environment in the middleand west-transdanubian regions of hungary”, supported by the european union and cofinanced by the european regional development fund”, and to their colleagues at the epcos company. references 1. online postgraduate courses for the electronics industry homepage, http://www.ami.ac.uk/courses/topics/0136_ec/index. html 2. o. klug, a. bellavia: high voltage aluminium electrolytic capacitors: where is the limit (2001) 3. k. theisbürger: “der elektrolyt-kondensator”, frako kondensatorenund apparatbauen gmbh. teningen, (internal material) 4. d. fodor, l. kovács: aluminium electrolytic capacitor 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page 410 page 411 page 412 page 413 page 414 page 415 page 416 page 417 page 418 page 419 page 420 page 421 page 422 page 423 page 424 page 425 page 426 page 427 page 428 page 429 page 430 page 431 page 432 page 433 page 434 page 435 page 436 page 437 page 438 page 439 page 440 page 441 page 442 page 443 page 444 page 445 page 446 page 447 page 448 page 449 page 450 page 451 page 452 page 453 page 454 page 455 page 456 page 457 page 458 page 459 page 460 page 461 page 462 page 463 page 464 page 465 page 466 page 467 page 468 page 469 page 470 page 471 page 472 page 473 page 474 page 475 page 476 page 477 page 478 page 479 page 480 page 481 page 482 page 483 page 484 page 485 page 486 page 487 page 488 page 489 page 490 page 491 page 492 page 493 page 494 page 495 page 496 page 497 page 498 page 499 page 500 page 501 page 502 page 503 page 504 page 505 page 506 page 507 page 508 page 509 page 510 page 511 page 512 page 513 page 514 page 515 page 516 page 517 page 518 page 519 page 520 page 521 page 522 page 523 page 524 page 525 page 526 page 527 page 528 page 529 page 530 page 531 page 532 page 533 page 534 page 535 page 536 page 537 page 538 page 539 page 540 page 541 page 542 page 543 page 544 page 545 page 546 page 547 page 548 page 549 page 550 page 551 page 552 page 553 page 554 page 555 page 556 page 557 page 558 page 559 page 560 page 561 page 562 page 563 page 564 page 565 page 566 page 567 page 568 page 569 page 570 page 571 page 572 page 573 page 574 page 575 page 576 page 577 page 578 page 579 page 580 page 581 page 582 page 583 page 584 microsoft word b_42_popita_r.doc hungarian journal of industrial chemistry veszprém vol. 39(2) pp. 271-278 (2011) heavy metal contamination assessment and its environmental impact in the area of rural waste disposals in cluj county, romania g. popiţa1, , i. varga1, c. modoi1, r. haţegan1, a. popovici2 1babes bolyai university, faculty of environmental science, department of environmental science, 30 fântânele street, 400294, cluj-napoca, romania e-mail: gabi.popita@yahoo.com 2regional environmental protection agency, 99 dorobanţilor street, 400609, cluj-napoca, romania this study aims at to investigate the environmental impact caused by heavy metal contamination from the waste disposal facilities in rural areas and depending on soil pollution, the possible future uses of these lands. in addition, we have studied the heavy metal contamination of the surface waters from the vicinity of these disposal facilities. the heavy metals influence was investigated by analyzing various water and soil samples collected from two county areas where more rural disposal facilities were functioned. zeenit 700 atomic absorption spectrometer was used for the analysis of metals and the collected soil samples were mineralized according to iso 11466, by extraction with aqua regia (3 parts hcl: 1 part hno3). the evaluation of the soil analysis results from the area no. 1 proves that there is no potential impact, because the studied metals concentrations are below the alert threshold. water analysis results from area no. 1, shows a quality class v for lead and nickel, which indicate a high pollution originating from these metals. in the area no. 2, lead has exceeded the intervention thresholds for sensitive and less sensitive use of land and it is considered that there is an environmental impact on the soil. regarding the water quality, it can be concluded that the area no. 2 exhibits the greatest pollution impact stemming from heavy metals. keywords: heavy metals, soil pollution, water pollution, waste. introduction recently, in romania, the closure of legally noncomplying municipal landfills is on increase. this action was implemented also in the rural areas, with the final objective: land rehabilitation (july 16, 2009) by cleaning up and rehabilitation/re-entry into the natural ecocycles or by closure. in the past, approximately 80 storage facilities were in operation in cluj county and the most of them were declared to be closed, cleaned and/or rehabilitated. for further utilization/use of these waste disposal sites the assessment of the soil pollution and underground waters were taken into consideration depending on the use and classification of the land (sensitive or less sensitive use) and the contamination levels/classification under the threshold regarding the type of use. in terms of the legislation, the sensitive use of land is considered in case of residential, recreational, agricultural utilization/purposes, as protected areas or sanitary areas with restriction regime, while less sensitive use of land includes all industrial and commercial uses. the heavy metals content was investigated by analyzing various water and soil samples collected from two county areas (fig. 1), where several rural disposal facilities were functioned: area no. 1 is situated in the nw of the cluj county with six waste disposal facilities: tog site from turea village, cariera site from corneşti village and four waste storage facilities in: ticu village, ticu colonie village, arghişu village and dâncu village (fig. 2); area no. 2 is situated in the e of the cluj county with four waste disposal facilities: sojba site from mociu village, sub deal site from chesău village, ciscut site from aruncuta village and dâmburile site from dâmburile village (fig. 3). the soil samples were taken from the surface of the waste disposal facilities and the surface water samples were taken from the immediate vicinity of these facilities, because the most of them were located at the sides of different streams. 272 figure 1: the location of the sampling points in the areas no. 1 and no. 2, cluj county, romania – drinking water sampling point, – surface water sampling points, – soil sampling points figure 2: waste disposal facility in rural area no. 1 figure 3: waste disposal facility in rural area no. 2 materials and methods the soil is a rich and fragile ecosystem which can be found on the surface of the earth crust with a thickness of about 1.5 m. it is a dynamic layer in which several complex physical, chemical and biological processes are taken place continuously. the soil pollutions stems from human activity that causes an imbalance in the normal functioning of the soil as an element of the environment. it is manifested in physical, chemical or biological degradation. the analyses that can be carried out to assess the soil pollution are as follows: physical methods: resistance of penetration, conductivity, etc. chemical methods: ph, humus content, total n, mobile p, mobile k, soluble salts, heavy metals, pesticides, etc. [1]. the soil sampling was carried out in plastic bags with a plastic spatula. before sampling, the vegetal top layer was removed on an area of 15x20 cm. the samples were taken from a depth of 10–15 cm. 273 figure 4: atomic absorption spectrometer zeenit 700 in order to determine the concentration of heavy metals, the atomic absorption spectrometer zeenit 700. was used (fig. 4). the collected soil samples were mineralized according to iso 11466, by extraction with aqua regia (3 parts hcl : 1 part hno3). water samples collected for heavy metal analysis were acidified with hno3 65%, at site, to a ph of about 2-3 to prevent the precipitation of the heavy metal ions and the retention of these on the vessel wall. results and discussions soil samples the metals from the soil can be strongly bounded or complexed. the sum of total forms represents the total metal content in the soil. the forms under which the metal can be founded depends on the nature of the soil, ph and on the presence of the humic matter content [2]. the soil is characterized by the existing heavy metals, which depends on soil type and its composition and by soil contamination with these metals provided by human activity [3]. table 1: the heavy metals concentration in the soil samples from area no. 1 mg/kg sample cd cr cu fe ni pb zn ss1 0.043 0 7.78 1340.60 6.08 21.80* 22.64 ss2 0.073 4.73 6.93 1477.27 7.58 20.47* 33.49 ss3 0.089 4.73 7.85 1422.27 24.82* 19.80 37.79 ss4 0.093 13.79 8.83 1456.93 24.92* 22.80* 29.29 ss5 0.080 15.26 11.30 1436.93 24.52* 24.13* 39.82 ss6 0.086 12.56 9.26 1381.93 14.20 21.80* 28.42 ss7 0.090 5.11 3.36 1147.93 4.57 11.80 9.13 ss8 0.006 10.61 12.38 1296.27 20.33* 35.80* 40.49 note nv 1 30 20 20 20 100 at 3 100 100 75 50 300 it 5 300 200 150 100 600 ss – soil sample, nv – normal value, at – alert threshold, it – intervention threshold, according to the decree no 756 of the government of november 3 of 1997, *the heavy metals concentrations that are higher than nv the household waste contains heavy metals, especially stemming from: batteries, metal alloys, plastic, paper, cardboard and glass. in table 1 the heavy metals concentrations from the analyzed soil samples are given from the area no. 1. for the area no. 1, samples were taken from two sites from the waste disposals: ticu colonie village and dâncu village (fig. 5). the soil samples were taken from all the waste disposal sites including surface, from both areas, and the sampling points were fixed as shown in fig. 6. for the area no. 2, samples were taken from two sites from the waste disposals: sojba site from mociu village, sub deal site from chesău village, ciscut site from aruncuta village and dâmburile site from dâmburile village (fig. 7). figure 5: selection of the soil sampling points in area no. 1 – soil sample point 274 figure 6: selection of the sampling points figure 7: selection of the soil sampling points in area no. 2 – soil sample points after sampling, the samples were good homogenized and the final soil samples obtained were numbered from ss1 to ss8. for area no. 1 the homogenous soil samples belongs to each waste disposal as follows: ss1 – waste disposal ticu colonie; ss2 – waste disposal ticu colonie; ss3 – waste disposal ticu sat; ss4 – waste disposal dâncu; ss5 – waste disposal dâncu; ss6 – waste disposal arghisu; ss7 – waste disposal cornesti; ss8 – waste disposal turea. for area no. 2 the homogenous soil samples belongs to each waste disposal as follows: ss1 – waste disposal sojba, mociu; ss2 – waste disposal sojba, mociu; ss3 – waste disposal sub deal, mociu; ss4 – waste disposal sub deal, mociu; ss5 – waste disposal ciscut, aruncuta; ss6 – waste disposal ciscut, aruncuta; ss7 – waste disposal dâmburile; ss8 – waste disposal dâmburile. the disposed waste, from both areas, comes from the village houses: plastic, paper, glass, hazardous waste, metals, weee, construction waste, demolition waste, etc, but unfortunately there is no inventory on the quantities of the disposed waste. fig. 8 shows the cumulative results of the heavy metals concentrations from the soil samples from the area no. 1. figure 8: cumulative results of the heavy metals concentrations in the area no. 1 the heavy metals concentrations in the soil of the area no. 1, are as follows: cd, zn, fe, cu, cr – the samples concentrations are lower than the normal values ni – the concentrations of the samples no. 3, 4, 5 and 8 are higher than the normal values pb – the concentrations of the samples no. 1, 2, 4, 5, 6 and 8 are higher than the normal values the results proved that in the soil from the area no. 1, the lead and nickel exhibit the highest concentrations, more than the normal values specified in the national legislation but those are under the alert threshold, compared with cadmium, copper, zinc and chromium, whose concentrations are below the normal values. in table 2 the heavy metals concentrations are given from the analyzed soil samples from area no. 2. fig. 9 shows the cumulative results of the heavy metals concentrations from the soil samples taken from area no. 2. the heavy metals concentrations in the soil of the area no. 2, are as follows: cu – the concentration of the sample no. 4 is higher than the normal values, but under the alert threshold cd, zn, fe, cr – the concentrations of the samples are below than the normal values ni – the concentrations of the sample no 1 is higher than the normal values but under the alert threshold pb – the concentrations of the samples no 1, 3, 5, 6, 7 and 8 are higher than the normal values; the concentration of the sample no. 4 is higher than the alert threshold and the concentration of the sample no. 2 is higher than the intervention threshold. in the soil of area no. 2, lead has exceeded the intervention threshold set forth by the legislation and nickel and copper have exceeded the normal values comparing with cadmium, zinc, iron and chromium whose concentrations are below the normal values. 275 table 2: the heavy metals concentration in the soil samples from area no. 2 mg/kg sample cd cr cu fe ni pb zn ss1 0.006 16.83 16.67 4553.33 20.93* 40.33** 31.13 ss2 0.006 12.82 13.15 4493.33 18.40 154.67+ 22.98 ss3 0.006 14.93 13.38 4436.67 18.70 28.00** 19.64 ss4 0.032 21.94 29.07* 4253.33 16.08 60.00+ 38.37 ss5 0.006 8.11 15.17 3923.33 17.06 39.00** 27.13 ss6 0.006 11.68 14.54 3823.33 15.55 41.67** 29.87 ss7 0.006 6.97 14.30 3780.00 17.35 34.33** 19.47 ss8 0.006 6.94 14.10 3563.33 17.81 35.33** 19.91 note nv 1 30 20 20 20 100 at 3 100 100 75 50 300 it 5 300 200 150 100 600 ss – soil sample, nv – normal value, at – alert threshold, it – intervention threshold, according to the decree no 756 of the government of november 3 of 1997, *the heavy metals concentrations that are higher than nv **the heavy metals concentrations that are higher than at +the heavy metals concentrations that are higher than it figure 9: cumulative results of the heavy metals concentrations in the area no 2 water samples the following physical and chemical parameters: ph, conductivity, salinity, total dissolved solids, redox potential and temperature were determined using wtw multiparameter inolab 720 series at site (fig. 10). figure 10: the wtw multiparameter inolab 720 series according to the results for tds, high conductivity and salinity, indicates a high load of dissolved salts. the national law doesn’t provide normative figures for the conductivity, tds and salinity in wastewater and natural waters, although an increase in the growth of the tds level may indicate higher water pollution. the main sources of the water pollution with heavy metals are as follows: geological sources (natural), mining and metal processing; industrial use of the heavy metal salts (chromium from tanneries, manganese from paints, dyes, batteries, fertilizers, herbicides, cadmium from electroplating process, ni-cd/pb batteries, pigments, mercury from fungicides, the salt water electrolysis, lead from the ore processing); the infiltration from the waste disposal sites [4]. among the analyzed metals, the most frequently identified water pollutants are as follows: iron, cadmium and mercury. the heavy metals are toxic in different valence states, except mercury which is toxic in the elemental form [5]. regarding the classification of the land use, the transfer of heavy metal pollution was studied into the surface water. it can be given that the water quality classes are as follows: i – very good, ii – good, iii – moderate, iv – weak, v – bad, according to the decree no 161 of the government of february 16 of 2006. it is used for the assessment and classification of the surface waters to determine the ecological status of the water. from the streams of the area no. 1 samples were taken and analyzed at the follow points: sw1, sw2, sw3, sw4 and sw5 (fig. 11). table 3 presents the metals concentrations in the surface water from the streams in the area no. 1. table 4 presents the water quality classes according to the decree no 161 of the government of february 16 of 2006. table 5 presents the clasification of the streams from the area no. 1 regarding the ecological status, from the point of view of the metal contaminations. 276 figure 11: selection of the surface water sampling points in the area no. 1 – surface water sample points table 3: the metals concentration in the surface water from the streams in the area no. 1 sample cd μg/l cr μg/l cu μg/l fe mg/l ni μg/l zn μg/l pb μg/l sw1 0.03 110.0 35.5 0.1949 307.5 21.7 96.0 sw2 0.03 116.0 26.0 0.1449 311.6 90.5 108.0 sw3 0.03 112.0 49.8 0.1278 317.2 0 103.0 sw4 0.05 0 44.6 0.2231 317.9 0 109.0 sw5 0.03 0 50.1 0.1872 314.7 0 98.0 sw– water sample table 4: the water quality classes according to the decree no. 161/2006 quality class (conc. µg/l) metal class i very good class ii good class iii moderate class iv weak class v bad cr 25 50 100 250 >250 cu 20 30 50 100 >100 zn 100 200 500 1000 >1000 pb 5 10 25 50 >50 cd 0.5 1 2 5 >5 ni 10 25 50 100 >100 mg/l fe 0.3 0.5 1 2 >2 table 5: clasification of the streams from the area no. 1 regarding the ecological status, according to the the analyzed metal content, sw1 (*), sw2 (+), sw3 (◊), sw4 (○), sw5 (□) no. metal class i very good class ii good class iii moderate class iv weak class v bad 1 cd *+◊○□ 2 cr ○□ *+◊ 3 cu + *◊○ □ 4 fe *+◊○□ 5 ni *+◊○□ 6 zn *+◊○□ 7 pb *+◊○□ 277 water analysis results from area no. 1, shows a quality class v for nickel and lead, which indicate a high pollution of these metals, and a quality class iv for chromium. for cadmium, iron and zinc the results support a quality class i. from the streams of the area no. 2 were taken and analyzed samples from the following points: sw1 and sw2 (fig. 12). table 6 presents the metals concentration in the surface water from the streams in the area no. 2. table 7 presents the clasification of the streams from the area no. 2 regarding the ecological status, from the point of view of the analyzed metals. for the area no. 2, the water analysis results show a v quality classes for lead and nickel regarding the pollution. for cadmium, copper, iron and zinc, the results support a quality class i. also samples were taken from the groundwater from wells situated in area no 2, in the villages, near to the waste disposal facilities. the concentration of the heavy metals is presented in the table 8. figure 12: selection of the surface water sampling points in area no. 2 – surface water sample points table 6: the metal concentrations in the surface water from the streams in the area no. 2 sample cd μg/l cr μg/l cu μg/l fe mg/l ni μg/l zn μg/l pb μg/l sw1 0.04 41.7 5.9 0.2000 253.1 30.5 118.0 sw2 0.01 31.8 4.6 0.2200 244.5 16.9 116.0 sw– water sample table 7: classification of the streams from the area no. 2 regarding the ecological status according to the analyzed metal contents, sw1 (■), sw2 (●) no. metal class i very good class ii good class iii moderate class iv weak class v bad 1 cd ■● 2 cr ■● 3 cu ■● 4 fe ■● 5 ni ■● 6 zn ■● 7 pb ■● table 8: the concentration of the heavy metals from the water of wells, in the area no 2 sample cd μg/l cr μg/l cu μg/l fe mg/l ni μg/l zn μg/l pb μg/l sdw1 0.03 34.4 7.0 0.230 244.2 20.6 103.0 sdw2 0.02 33.6 6.6 0.190 238.0 22.8 122.0 sdw3 0.01 34.5 6.8 0.249 260.3 18.9 116.0 sdw – drinking water sample 278 figure 13: selection of the drinking water sampling points in the area no. 2 – drinking water sample points the analysis show similarities between the heavy metal concentrations of the water samples taken from wells and from the surface water. conclusions the waste disposal facilities in rural areas had been declared to be closed down in 2009, but those failed to be cleaned and rehabilitated. this study was made in order to establish, depending on soil pollution, the possible future utilization/uses of these lands. the evaluation of the soil analysis results from the area no. 1 proves that there is no potential impact, because the studied metal concentrations are below the alert threshold, however, higher than normal values. however, the ecological measures are necessary to be implemented in order to fit the sensitive use of the land. in the area no. 2 due to the lead concentration which exceeds the intervention thresholds for sensitive and less sensitive use of land, it is to be noted that there is a significant environmental impact on the soil. according to the decree no 756 of the government, when the concentrations of one or more pollutants in soils exceed the intervention threshold, the competent authorities should enforce a risk assessment study and mitigation measures should be done to reduce the concentration of the pollutants in discharges. additionally, analyses were made on the surface water from the streams situated near to the waste disposal areas, and for the area no. 2, water samples were taken from wells situated in the villages near to the waste disposal areas. water analysis results from area no. 1 and 2 shows a quality class v for nickel and lead, which indicate a high pollution with these metals. regarding the water quality, it was found, as in the case of soil pollution with heavy metals, that the surface waters, in both areas have exhibited serious impact of heavy metal pollution. the results of the analyses of the wells in area no. 2, shows that the concentrations of the heavy metals are similar to that of the surface water streams. acknowledgements this work was carried out with financial support of the project eurodoc “doctoral scholarship for performance in european research”, funded by the european social fund and the romanian government. references 1. v. ciobotaru, a. m. socolescu: priorities of the environmental management, publishing house meteor press, 2006 bucharest 2. c. roşu: the basis of the environmental chemistry, theoretical elements and practical applications, publishing house casa cărţii de ştiinţă, 2006 cluj-napoca 3. c. drăghici, d. perniu: the pollution and the environmental monitoring, publishing house universităţii transilvania, 2002 braşov 4. g. burtică, d. micu, a. negrea, c. orha: the pollutants and the environment, publishing house politehnica, 2005 timişoara 5. a. x. lupea, a. gharibeh branic, a. ardelean, d. ardelean: the basis of the environmental chemistry, publishing house didactică şi pedagogică, 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/leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word b_21_nagy_r.doc hungarian journal of industrial chemistry veszprém vol. 39(2) pp. 233-235 (2011) determination of the inductance of starter relays l. nagy, j. lénárt, e. jakab university of miskolc, robert bosch department of mechatronics, miskolc-egyetemváros, hungary e-mail: nagy.lajos@uni-miskolc.hu e-mail: lenart.jozsef@uni-miksolc.hu e-mail: jakab.endre@uni-miksolc.hu this paper deals with the determination of the inductance of starter relays. the article proposes a method for the electromechanical determination of the self-inductance of the electromagnet and its derivative for various positions of the iron core. the results obtained at different current levels are given in tables and figures. keywords: starter relay, electromechanical model, inductance measurement introduction the actuator of the pinion-engaging mechanism of the starter motor consists of concentric iron core coils [1]. the coils are excited by relatively high currents. the electro-dynamic modelling of the mechanism requires inductance of the relay and its derivative depending on the position of the iron core. the electromagnet has selfinductance, electrical resistance and mechanical force acting on the iron core. the inductance of an electromagnet is generally determined by purely electrical measurements, e.g. by current-voltage methods or bridge methods, by the resonance method, etc. [2, 3]. relatively few methods are available for dc excited inductance measurements [4]. the inductance of a coil without an iron core can be determined by measurement or also by calculation with sufficient accuracy. it is particularly difficult to determine the inductance of a coil in the case of movable iron cores. the iron core has in general nonlinear magnetic properties, i.e. b-h characteristic curves are nonlinear or hysteresis also may occur [5]. in this work, the inductance function is determined in an indirect way, by measuring the electromagnetic force in the case of direct current excitation. it is assumed that the inductance depends on the position of the iron core and on the current. the time dependency and hysteresis are neglected. the measurement provides the derivative of the inductance function directly. the induction function sought is produced by integration when the inductance of the air core coil and the derived function of the iron core coil are known. the measurement is repeated for three current values. the final objective of the measurement is to model electro-dynamically the pinion-engaging mechanism of the starter motor, which includes both the inductance function and its derivative. the electromechanical model fig. 1 shows the cross-section of a typical starter relay [1]. the relay consists of a moving iron core – 1, a pullin winding – 2 and a hold-in winding – 3, a fixed iron core – 4, a contact spring – 5, a switch contacts – 6, an electrical connection – 7, a switch contact – 8, an armature shaft – 9, and a return spring – 10. figure 1: cross-section of a starter relay an experiment is designed to measure the inductance electromechanically, without springs. the electromagnetic force is measured by a compact load cell in discrete positions of the iron core. positioning is registered by a laser interferometer. the experiment is performed using a supply unit integrated into the measurement circuit. apart from the phenomenon of switching on, the measurement is done with a constant current i. the electromechanical model of the measurement relies on the following coupled differential equation system: 234 ( ) ( ) 0,, uirixixl dt diixl =+′+ & , (1) ( ) ( )txfiixlxm , 2 , 2 =′−&& , (2) where l(x,i) is the equivalent self-inductance of the relay depending on position x and current i, l'(x,i) is the partial derivative of the self-inductance function by location, ẋ, ẋ̇ are the velocity and acceleration of the iron core, respectively, r is the equivalent resistance of the relay, u0 is the terminal voltage of the battery, m is the mass of the iron core and f(x,t) is the force acting on the compact load cell. equations (1)-(2) are also suitable for describing the switch-on phenomenon. in a steady-state condition the time-derivative of the current as well as the velocity and acceleration of the iron core are zero. in this static state the following equations hold: 0uir = , (3) ( ) ( )txfiixl , 2 , 2 =′− , (4) in the examination the current i and the force acting on the iron core are measured and equation (4) is used to determine the derivative inductance function: ( ) ( ) 2 2,, i txfixl −=′ , (5) the self-inductance factor of an air core coil can be calculated using the parameters of the coil: j jj j l an l 2μ = , j=1, 2, ... (6) where μ is air permeability, n is the number of turns of the coil, a is the coil diameter and l is coil length. mutual inductance is: 21 llkm = , (7) where k is coupling factor. the self-inductance of the air core coil can also be determined using an inductance meter. in the present case the parallel connected two coils and the mutual inductance arising between the coils produce the equivalent inductance. the equivalent inductance is obtained by the following relation: ( )( ) m mll mlmll + −+ −− = 221 21 0 , (8) the inductance function sought can be produced by integration when the inductance of the air core coil and the derivative function of the iron core coil are known: ( ) ( )∫ ′+= x dsisllixl 0 0 ,, , (9) measuring the inductance of the relay in order to design the measurements firstly the original relay with springs mechanism is tested during normal operation. the measured current of the operating relay versus time function is shown in fig. 2. it can be seen that during the whole period (t=0–0.025 s) the current is varying between 0 to 35 amperes. the measurements are planned to perform at three different current levels, i.e. i = 8 a, 26 a, 32 a. the set-up of the measurement is shown in fig. 3. the instruments used for the measurements are given in table 1. 0 0.005 0.01 0.015 0.02 0.025 0.03 0 5 10 15 20 25 30 35 time [s] c ur re nt : i [a ] figure 2: the exciting current of an operating relay figure 3: the measurement circuit used table 1: elements of the measurement circuit nr. title type 1 ac power supply ea-stt 2000 b-4.5 a 0–260 v ac 2 laser interferometer renishaw xl-80 3 data acquisition device spider 8 4,8 khz/dc 4a relay vs440-22 220–230 v ac 4b timer crm-91h 5 dc power supply matrix mps-3005l-3 0–30 v 6 battery 12v 544 402 440a (en) 44 ah 7 laptop 8a iron core actuator with compact load cell gefran tu-k1c (0–100 kg) 8b the analyzed relay 31 4a, 4b2 5 6 7 8a, 8b 235 the measurements were done using a variety of supply units. in the first case a controlled unit supplies exciting current i < 10 a. in the second case the supply unit is a starter battery, supplying current typical of operating conditions. in the latter case a magnetic switch and timer were built in the measurement circle as protection against heating. table 2 sums up the function values l'i(x,i), l'ii(x,i) and l'iii(x,i), obtained in the measurement series. table 2: measurement results xi [mm] l'i(x,i) xii [mm] l'ii(x,i) xiii [mm] l'iii(x,i) 0.00 0.0044 0.00 0.0596 0.00 0.07505 1.00 0.078 1.49 0.0894 1.68 0.0998 5.00 0.2343 4.39 0.1639 4.016 0.1628 7.1 0.2959 6.99 0.3309 5.95 0.2514 9.1 0.7078 8.5 0.4710 8.00 0.3913 9.95 1.1031 9.49 0.6255 10.00 0.5526 10.70 3.0653 10.44 0.7811 10.47 0.6039 10.95 5.025 11.01 0.9332 11.01 0.7583 the derivative functions are numerically integrated by the trapeze method. the inductance functions obtained at i = 8 a is approximated by an exponential function and the rest of them by five-degree polynomials. the coefficients of the functions are: x.x. i e.e.l 5151716430 10528159230 ⋅⋅+⋅= − , (10) 673800792100054050 003742000034660102 2 3455 .x.x. x.x.xlii +⋅+⋅− −⋅+⋅−⋅⋅= − , (11) 67420091940 00594200031920 00018260103387 23 455 .x. x.x. x.x.liii +⋅+ +⋅−⋅+ +⋅−⋅⋅= − , (12) figs 4 and 5 show the inductance functions and their derivatives obtained in the three measurement series. on the basis of the results of the measurement series it can be established that if the displacement of the iron core is more than 8 mm, i.e. the iron core is located deep in the coils, dependence on current appears to be significant. this non-linear characteristic can be explained by the saturation of the iron core. 0 10 20 30 40 0 5 10 15 0 2 4 6 8 10 i [a]s [mm] l( s, i) [m h ] figure 4: inductance functions 0 10 20 30 40 0 5 10 15 0 2 4 6 8 10 i [a]s [mm] dl (s ,i) figure 5: derivative inductance we note that the exciting current of the relay falls in the interval i = 25–35 a, where the inductance slightly depends on the variation of current. conclusion the paper recommends an electro-mechanical method for determining the inductance function of starter relays. the inductance depends on the position of the iron core and on the current. the time dependency and hysteresis are neglected. the method is based on the direct measurement of the inductance derivative with respect to the iron core position. the inductance is obtained by numerical integration. it is assumed that the inductance of the air core coil is given. the current dependency is significant when the whole geometry of the iron core is situated in coils. acknowledgements the described work was carried out as part of the támop-4.2.1.b-10/2/konv-2010-0001 project in the framework of the new hungarian development plan. the realization of this project is supported by the european union, co-financed by the european social found. references 1. r. meyer, h. braun, r. rehage, h. weinmann: alternators and starter motors, robert bosch gmbh, 2003 2. s.-y. mak: the rcl circuit and the determination of inductance, phys. educ. 29, (1994), 94–97 3. s.-y. mak: six ways to measure inductance, phys. educ. 37(5), (2002), 439–445 4. a. stankovic, e. r. benedict, v. john, t. a. lipo: a novel method for measuring induction machine magnetizing inductance, ieee transactions on industry applications, 39(5), 2003, 1257–1263 5. j. elbaum: electromagnets (in hungarian), műszaki könyvkiadó, budapest, 1968 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjdffile false /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 /colorconversionstrategy /cmyk 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/leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice editorial hungarian journal of industry and chemistry veszprém vol. 42(1) pp. 19–23 (2014) adsorption and intercalation of small molecules on kaolinite from molecular modelling studies attila táborosi,1! róbert kurdi,1 and róbert k. szilágyi2 1 surfaces and nanostructures laboratory, institute of environmental engineering, university of pannonia, veszprém, h-8201, hungary 2 department of chemistry and biochemistry, montana state university, bozeman, mt 59717, u.s.a. !e-mail: taborosia@almos.uni-pannon.hu kaolinite is an abundant natural material with considerable industrial potential. despite its simple composition (al2si2o5(oh)4 and layered structure being a phyllosilicate), it is notable that only little known about the interaction of kaolinite sheets with small organic reagents at the molecular level. these assumed to govern intercalation, delamination, and then the complete exfoliation processes. a common methodology to model the molecular structure of kaolinite is the employment of periodic boundary conditions. the application of molecular cluster models gained importance nowadays by capitalizing on the availability of wide range of theoretical tools for describing structural features and reaction mechanisms. in this study, we present our results using theoretical methodologies and modelling strategies from literature that are applied for adsorption and intercalation of urea, ethylene glycol, and potassium acetate. keywords: kaolinite, intercalation, adsorption, hydrogen bonding, molecular cluster model introduction a significant hindrance in the design, optimization, and execution of experimental research involving clay minerals is the lack of our understanding of molecular level processes occurring at the outer (adsorption) or at the inner surface (intercalation) of layers of clay. molecular modelling approaches have the potential to aid experimental design, mitigating cost of chemicals used, rationalizing unsuccessful trial-and-error experiments, and thus contributing to tailored utilization of clay minerals as industrial raw materials. given the periodic nature of the crystalline clay minerals, a common approach in modelling is the use of periodic boundary conditions [1–4]. a competitive approach is based on molecular cluster models [5–9]. an advantage of using the latter is the availability of a broad range of quantum chemical tools for studying the local chemical environment of the site(s) of adsorption and/or intercalation. in the given study, we have utilized kaolinite, which is a member of the 1:1 class of clay minerals. this implies that the layers of this simplest phyllosilicate are composed of octahedral (o) and tetrahedral (t) sheets. the o-sheet contains hexacoordinate al3+ ions, while the t-sheet has tetracoordinate si4+ ions. the oand tsheets are connected via tricoordinate oxide anions, while the separate ot or 1:1 layers are connected through hydrogen bonds (h-bonds) (fig.1). computational methods the computational models were created from the unit cell of the experimental x-ray diffraction structure of crystalline kaolinite [10]. we will discuss results here for models for separate oand t-sheets with figure 1: schematic presentation of adjacent ot layers of delaminated kaolinite 20 stoichiometry of al6o24h30 and si6o18h12, respectively (figs.2a and c). these are the smallest possible cluster models for the hexagonal, honeycomb like units of the oand t-sheets. in addition, two larger models of al10o38h46 and si10o29h18 were also considered (figs.2b and d) for the larger intercalating agents (ethylene glycol, potassium acetate). the unit cell of kaolinite was multiplied in all crystal dimensions to create a super-cell. this was then truncated to the cluster models presented above. the charge neutrality was achieved by terminating dangling bonds with protons at the periphery of the models. the initial positions of the adsorbent reagents were set at the centre of the hexagonal honeycomb-like unit of both oand tsheets and it was allowed to fully relax during optimizations. given that the computational models shown in fig.2 are simplifications of the experimental crystal structure environment, structural constrains were applied during geometry optimizations. in all calculations, the atoms of the organic reagents, the surface hydroxide groups (sho-) of the o-sheet, and the bridging oxide groups (bo2-) of the t-sheets were allowed to move, while the positions of the rest of the atoms were kept fixed. after structural optimizations, the positions and relative arrangements of the organic reagents with respect of the outer and inner surfaces, the shortest distances of possible ion/dipole interactions or h-bonds were noted. for computational models of t…reagent…o intercalation, the basal spacing was set at the beginning of calculations to the experimental values of 10.7, 9.5, 11.5 å, and 14.2 å for urea [11], ethylene glycol [12], and potassium acetate in the absence or in the presence of water [13], respectively. the calculations were carried out using the b3lyp hybrid density functional [14,15] with lanl2dz basis set [16] as implemented in gaussian09 [17]. the interaction energies were not considered in this work due to the modest level of theory and lack of consideration of explicit or implicit solvation shell. the main focus of the given work is to establish initial structural models for rationalizing experimental observations and prepare for more advanced computational modeling. the optimized structures presented in this work were made available at computational.chemistry.montana.edu/si. results and discussions kaolinite-urea interactions the lowest energy, optimized structure for the adsorbed urea on o-sheet can be characterized by two short o(urea)…s-hodistances of 1.92 and 1.95 å, while one of the amide groups approaches the opposite s-ho group within 1.73 å as shown in fig.3a. the presence of both donor and acceptor interactions for the same reagent molecule result in a tilted orientation of the urea. an alternative orientation in which only the carbonyl group is interacting with three s-hogroups (see below for intercalation model) was not found to be a stationary structure at this level of theory. figs.3b and c illustrate the two different orientations of the urea at the t-sheet, where the amide groups are h-bonded to the b-o2groups of the same si4+ ion (geminal) with nh…b-o2distances of 2.03 and 2.12 å or two different si4+ ions (vicinal) with 2.02 and 2.08 å figure 2: computational models for the hexagonal honeycomb-like units of [6al] (a) and [10al] (b) octahedral, [6si] (c) and [10si] (d) tetrahedral cluster models for oand t-sheets of kaolinite, respectively 21 distances. the energetic difference between the germinal and vicinal coordination is not significant (less than 10 kj mol-1) at this level of theory. when the adsorption of urea considered simultaneously at both the oand t-sheets, a model can be obtained for a plausible structure of the urea intercalated between two ot-layers (fig.4). in this computational model, the carbonyl group of urea forms three h-bonds at 1.74, 1.78, and 1.83 å distances with three s-hogroups of the hexagonal o-sheet cross from each other. at the same time, the intercalated urea forms two h-bonds with the geminal b-o2groups at 1.94 and 2.62 å distances. the tilted orientation of the urea is the consequence of the experimental basal spacing of 10.7 å, which was kept fixed during the structural optimizations. it is important to recognize that according to our computational model, there is not enough room between the expanded layers of kaolinite to accommodate urea perpendicular to the basal planes or with parallel carbonyl groups to the crystallographic ‘c’ axis. kaolinite-ethylene glycol interactions ethylene glycol is generally used in exchangeintercalation as a step followed by initial dimethyl sulfoxide or potassium acetate intercalation. as shown in fig.5a, the donor interaction between the reagent hydroxyl group and the al3+ bound s-hois much shorter (1.66 å) than those seen for urea adsorption (1.73 å), while the acceptor interaction is slightly longer (1.99 å). given that the b-o2groups of the tsheet can only act as h-bond acceptors with ethylene glycol, the reagent spans the entire hexagonal honeycomb-like unit of the t-sheet by forming longer (2.05 and 1.94 å), thus weaker h-bond interactions than with the o-sheet. the complementarity of the oand t-sheets with respect of being h-bond donor and acceptor, respectively, allows for an ideal orientation of the functional groups of ethylene glycol for maximizing the strength of h-bond interactions. the o-sheet forms a short (1.61 and 1.79 å) interaction between the o(glycol)…s-hogroups. the t-sheet accepts the ho groups of the ethylene glycol at 1.73 and 1.88 å distances. comparison of the urea (fig.5) and ethylene figure 3: computational models for urea absorption at o(a) and t-layers in geminal (b) and vicinal (c) arrangements figure 5: computational models for the adsorption of ethylene glycol at the (a) oand (b) t-sheets figure 4: computational model for intercalation of urea in kaolinite 22 glycol (fig.6) intercalated models, the network of interactions between the layers and reagents parallel well the different experimental basal spacing (10.7 vs. 9.5 å, respectively). while the urea opens the interlayer space more; however, it anchors the two layers with a stronger set of interactions than ethylene glycol. this can be correlated with the limited reactivity of urea/kaolinite complex in exchange intercalation; while ethylene glycol often provides the last step before complete delamination and exfoliation of clays. kaolinite-potassium acetate interactions a limitation of the in vacuo models used in this study greatly hinders the dissociation of the potassium ion from acetate and thus in both adsorption models the cation remained at the centre of the hexagonal honeycomb-like model for the oand the t-sheets in the vicinity of the anion acetate. in addition, the ionized carboxylic group of the reagent form two short and thus strong h-bonding interactions at 1.65 and 1.89 å distances with two germinal s-hogroups of the osheet. the shortest acetate c-h…b-o2distance in fig.7b is 2.95 å, which indicates the presence of weak interactions between the methyl group and the b-o2 groups. in the adsorption model for the t-sheet, the acetate appears to be held in place by the cation at about 2.66 and 2.68 å. some of the plausible structures for the intercalation of potassium acetate were obtained from simulations in the absence (fig.8a) and presence (fig.8b) of solvent water. similarly to the other models the values of basal spacing were set to their corresponding experimental values of 11.5 and 14.2 å, respectively. the 2.7 å difference allows for the accommodation of a water molecule as shown in fig.8b. in agreement with the absorption models in fig.7, we found short h-bond distances between the carboxylate group and the s-ho of the o-sheet at 1.59 and 1.83 å distances. when water figure 7: computational models for the adsorption of potassium acetate on (a) oand (b) t-sheets figure 6: computational model for ethylene glycol intercalation in kaolinite figure 8: computational models for potassium acetate intercalation in the (a) absence and (b) presence of solvent water 23 is present, it is likely to solvate the negatively charged end of the acetate ion with a characteristic -coo-…hoh distance of 1.63 å. the interaction of the water and the o-sheet is asymmetrical with 1.77 and 2.08 å o(water)…s-hodistances. given the energetic preference of the o-h…ohhbonding interaction, the methyl group of the acetate will only interact with anionic groups of the t-sheet with representation c-h…b-o2distances of 3.15 and 3.25 å. the lack of a representative solvent environment is of less importance for the position of the potassium ion in the intercalation models, since the inner environment of this model will likely be only exposed to bulk solvent only to a limited extent. conclusions we have started with a few notable preliminary results the establishment of a structural database for reference models related to the adsorption and intercalation of small molecules and kaolinite. we found that even a modest level of theory with respect of the basis set can provide reasonable structures. these results allow us for visualizing molecular structures in order to rationalize experimental observables and generate new ideas for research directions. furthermore, these models can be considered as initial structures for higher-level calculations that are currently in progress in our laboratory. acknowledgement this research was supported by the european union and the state of hungary, co-financed by the european social fund in the framework of támop 4.2.4.a/2-111-2012-0001 ‘national excellence program’ (rks and at) and támop-4.2.2.a-11/1/konv-2012-0071 (rk). the authors acknowledge the helpful discussions with prof. jános kristóf and prof. erzsébet horváth. we acknowledge the use of the computational facilities at montana state university, bozeman, mt. references [1] smrcok l., tunega d., ramirez-cuesta a.j., ivanov a., valuchova j.: the combined inelastic neutron scattering and solid-state dft study of hydrogen-atoms dynamics in kaolinitedimethylsulfoxide intercalate, clays clay minerals, 2010, 58(1), 52–61 [2] mercier p.h.j., le page y.: rational ab initio modeling for low energy hydrogen-bonded phyllosilicate polytypes, eu. j. mineral., 2011, 23(3), 401–407 [3] geatches d.l., jacquet a., clark s.j., greenwell h.c.: monomer adsorption on kaolinite: modeling the essential ingredients, j. phys. chem. c, 2012, 116(42), 22365–22374 [4] tunega d., bucko t., zaoui a.: assessment of ten dft methods in predicting structure of sheet silicates: importance of dispersion corrections, j. chem. phys., 2012, 137(11), 114105 [5] ható z., makó é., kristóf t.: water-mediated potassium acetate intercalation in kaolinite as revealed by molecular simulation, j. mol. mod. 2014, 20(3), 1–10 [6] michalkova a., robinson t.l., leszczynski j.: adsorption of thymine and uracil on 1:1 clay mineral surfaces: comprehensive ab initio study on influence of sodium cation and water, pccp, 2011, 13(17), 7862–7881 [7] dawley m.m., scott a.m., hill f.c., leszczynski j., orlando t.m.: adsorption of formamide on kaolinite surfaces: a combined infrared experimental and theoretical study, j. phys. chem. c, 2012, 116(45), 23981–23991 [8] scott a.m., dawley m.m., orlando t.m., hill f.c., leszczynski j.: theoretical study of the roles of na+ and water on the adsorption of formamide on kaolinite surfaces, j. phys. chem. c, 2012, 116(45), 23992–24005 [9] song k.h., wang x., qian p., zhang c., zhang q.: theoretical study of interaction of formamide with kaolinite, comp. theor. chem., 2013, 102, 72–80 [10] bish d. l.: rietveld refinement of the kaolinite structure at 1.5-k, clays clay minerals, 1993, 41(6), 738–744 [11] makó é., kristóf j., horváth e., vágvölgyi v.: kaolinite-urea complexes obtained by mechanochemical and aqueous suspension technics-a comparative study. j. colloid inter. sci., 2009, 330(2), 367–373 [12] gardolinski j.e.f.c., lagaly g.: grafted organic derivatives of kaolinite: i. synthesis, chemical and rheological characterization, clay minerals, 2005, 40(4), 537–546 [13] frost r.l., kristóf j., kloprogge j.t., horváth e.: rehydration of potassium acetateintercalated kaolinite at 298 k. langmuir, 2000, 16(12), 5402–5408 [14] lee c.t., yang w.t., parr r.g.: development of the colle-salvetti correlation energy formula into a functional of the electron-density, phys. rev. b, 1988, 37(2), 785–789 [15] becke a.d.: density-functional thermochemistry 3 the role of exact exchange, j. chem. phys. 1993, 98(7), 5648–5652 [16] dunning jr. t.h., hay p.j., (ed.: schaefer iii h.f.): modern theoretical chemistry: methods of electronic structure theory, plenum, new york 1976, vol. 3, pp. 1–28 [17] frisch m.j.t., trucks g.w., schlegel h.b., scuseria g.e., robb m.a., cheeseman j.r.; et alas: revision d.01 ed., gaussian, inc., wallingford ct, 2009 microsoft word 1422 max 101.docx hungarian journal of industry and chemistry veszprém vol. 42(2) pp. 57–64 (2014) a comparison of advanced non-linear state estimation techniques for ground vehicles györgy max! and béla lantos 1 department of control engineering and informatics, budapest university of technology and economics, magyar tudósok körútja 2, budapest, 1117, hungary !email: max@iit.bme.hu this paper presents a comparative examination of state-of-the-art non-linear state estimation techniques. first, the sigmapoint (spkf) stochastic estimators are investigated on the basis of the unscented transformation. this is followed by the technique of non-linear symmetry-preserving observers for non-linear dynamics on the basis of symmetrical lie groups. the variety of the deterministic and stochastic state estimation algorithms is studied the kinematics of ground vehicles. two cases are described that deal with the reliability of path tracking, the convergence and speed of off-line calibration. keywords: state estimation, invariant observers, unscented kalman filter, vehicle kinematics introduction vehicles are indispensable in modern society, and vehicle safety is consequently of importance in everyday life. a lack of information about the state of vehicle and parameters presents a major obstacle for the development of vehicle control systems. the effectiveness of vehicle stability control largely depends on the accuracy of the vehicle state parameters that are measured by appropriate sensors. unfortunately, measurements from these sensors contain bias, as well as electrical noise, and can drift with temperature changes. however, the state estimation method is also able to dramatically reduce errors introduced by measurement and process noise contained in the signal. the focus of this work is the non-linear state estimation techniques. firstly, the ‘sigma-point kalman filter family’ (spkf) is discussed on the basis of the ‘unscented transformation’ (ut) and sterling’s interpolation [3, 5, 6]. secondly, the symmetry-preserving observer is presented [15, 16, 18], which is based on lie-transformation of invariant frames. the various state estimation procedures are then examined and compared through an illustrative nonlinear example of vehicle kinematics. sigma-point kalman filters sigma-point kalman filter [2, 4, 7] is a collective name for derivativeless kalman filters that employs the deterministic sampling based sigma-point approach to calculate the optimal terms of the state estimation. common methods use the scaled unscented transformation [4] and sterling’s polynomial interpolation. the former replaces the original set of sigma-points with a transformed set in order to minimize the errors of higher order terms, the latter approximates the derivation of the divided difference filter [10, 11] and central difference filter in [12]. the scaled unscented transformation the scaled unscented transformation (sut) has two steps. first, a fixed number of sigma points is chosen to capture the desired moments (at least mean and covariance) of the original distribution. then the sigma points are propagated through the non-linear function and the moments of the transformed variables are estimated. the advantage of sut over the taylor series based approximation is that sut is better at capturing the higher order moments caused by the non-linear transformation, as discussed in [1, 8-10]. consider a non-linear function y = g(x) and assume x has mean x and covariance xp . the first two moments of y are calculated by the following two steps: 1) weighted sigma-point selection: x0 = x xi = x + (l +λ)px( )i=1…l xi = x − (l +λ)px( )i=l+1…2l (1) with weights w0 m = λ l+λ w0 c = λ l+λ + (1−α2 +β ) wi m = wi c = λ 2(l+λ ) (2) 58 where wi m, and wi c are associated with the ith sigmapoint such that 1 2 0 =∑ = l i iw . symbols λ, α, and β denote scaling parameters and ( ) ixpl )( λ+ is the ith column of the matrix square root of the weighted xpl )( λ+ covariance matrix. 2) propagation: )( ii xgy = y ≈ wi myi i=0 2l ∑ py ≈ wi c(yi − y )(yi − y )t i=0 2l ∑ pxy ≈ wi c(xi − x )(yi − y )t i=0 2l ∑ (3) where y , yp , and xyp are the approximated mean, covariance and cross-covariance respectively. the unscented kalman filter (ukf) the algorithm of the ukf according to refs. [3, 7, 8] consists of the following steps: 1) initialization: x̂0 = e x0[ ] , px0 = e (x0 − x0 )(x0 − x0 ) t" # $ % (4) x̂0 a = e x̂0 a! " # $= x̂0 t v0 t n0 t! "% # $& t (5) p0 a = px0 0 0 0 rv 0 0 0 rn ! " # # # # $ % & & & & (6) 2) state estimation for ∞= …1k : a) calculate sigma-points: xk−1 a = x̂k−1 a x̂k−1 a +γ pk−1 a x̂k−1 a −γ pk−1 a" # $ % & ' (7) b) time-update: xi,k|k−1 x = f (xi,k−1 x ,xk−1 v ,uk−1), i = 0,…, 2l x̂k − = wi mxi,k|k−1 x i=0 2l ∑ pxk − = wi c(xi,k|k−1 x − x̂k −)(xi,k|k−1 x − x̂k −)t i=0 2l ∑ (8) c) measurement-update: yi,k|k−1 = h(xi,k|k−1 x ,xk−1 n ), i = 0,…, 2l ŷk − = wi myi,k|k−1 i=0 2l ∑ pŷk = wi c(yi,k|k−1 − ŷk −)(yi,k|k−1 − ŷk −)t i=0 2l ∑ pxkyk = wi c(xi,k|k−1 x − x̂k −)(yi,k|k−1 − ŷk −) i=0 2l ∑ (9) kk = pxkyk pŷk −1 x̂k = x̂k − +kk (yk − ŷk −) pxk = pxk − −kkpŷkkk t (10) where xk a = xk t vk t nk t! "# $ %& t and xk a = (xk x )t (xk v )t (xk n )t! "# $ %& t are the l dimension vectors of the augmented states and sigma-points respectively, vr and nr are the covariances of the process and measurement noise respectively, λγ += l , λ = α2(l+κ)+l, α = 10-3, κ = 0, β = 2, and wi is the weighting parameter defined in eq.(2). the central-difference kalman filter this approach is based on sterling’s polynomial interpolation, which was used in the derivations of divided difference filter [10, 11] and central difference filter in ref. [12]. the result of this approximation can be used for sigma-point approach as in the case of sut. the algorithm consists of the following steps: 1) weighted sigma-point selection: x0 = x xi = x + h px( )i=1…l xi = x − h px( )i=l+1…2l (11) with weights w0 m = h2−l h2 , wi m = 1 2h2 , wi c1 = 1 4h2 , wi c2 = h2−1 4h2 , (12) where wi m, and wi c are associated with i = 1, …, 2l sigma-point. 2) initialization: the same as defined in eqs.(4-6) 3) state estimation for k = 1, …, ∞: a) sigma-points for time-update: x̂k−1 av = x̂k−1 v" # $ % , pk−1 av = pxk−1 0 0 rv " # $ $ % & ' ' (13) xk−1 av = x̂k−1 av x̂k−1 av + h pk−1 av x̂k−1 av − h pk−1 av " # $ % & ' (14) b) time-update: xi,k|k−1 x = f (xi,k−1 x ,xk−1 v ,uk−1), i = 0,…, 2l x̂k − = wi mxi,k|k−1 x i=0 2l ∑ pxk − = wi c1 (xi,k|k−1 x − xl+i,k|k−1 x )2 + i=1 l ∑ wi c2 (xi,k|k−1 x + xl+i,k|k−1 x − 2x0,k|k−1 x )2 i=1 l ∑ (15) 59 c) sigma-points for measurement-update: x̂k−1 an = x̂k − n" #$ % &' , pk|k−1 an = pxk − 0 0 rn " # $ $ % & ' ' (16) xk|k−1 an = x̂k|k−1 an x̂k|k−1 an + h pk|k−1 an x̂k|k−1 an − h pk|k−1 an " # $ % & ' (17) d) measurement-update: yi,k|k−1 = h(xi,k|k−1 x ,xk|k−1 n ), i = 0,…, 2l ŷk − = wi myi,k|k−1 i=0 2l ∑ pŷk = wi c1 (yi,k|k−1 −yl+i,k|k−1)2 i=0 2l ∑ + wi c2 (yi,k|k−1 +yl+i,k|k−1 − 2y0,k|k−1)2 i=0 2l ∑ pxkyk = w1 c1pxk − (y1:l,k|k−1 −yl+1:2l,k|k−1)t kk = pxkyk pŷk −1 x̂k = x̂k − +kk (yk − ŷk −) pxk = pxk − −kkpŷkkk t (18) symmetry-preserving observers among many problems in control theory, the symmetric nature of the system can be utilized, such as in the case of optimal control for feedback or regulations. the symmetry properties can also be used in the design of observers. symmetry-preserving observers are also known as invariant observers that are based on the differential geometric background of abstract liegroups [15, 16, 18]. the constructive algorithm can be defined for designing invariant observers, which is based on the group transformation of symmetry. the aim is to produce invariant frames and invariant output errors to transform a locally asymptotically convergent observer around an equilibrium point into an invariant one, retaining its first-order approximation. the method in refs. [16, 18] benefits from the fact that the error equations and the first-order approximation can be calculated explicitly and the relationships can be defined globally. in addition, the invariant error equations make stability issues easier to deal with [1921]. assumptions suppose g is a lie-group with identity e on manifold σ. the group transformation (ϕg )g∈g on σ is a smooth mapping (g,ξ )∈g ×σ→ϕg(ξ )∈ σ (19) such that ϕe(ξ ) = ξ and ϕg2 (ϕg1 (ξ )) =ϕg2g1 (ξ ) for ζ, g1, and g2. the transformation group is local if ϕg(ξ ) is defined only when g lies sufficiently near to e. we consider only local transformations. invariant observers are designed for the smooth nonlinear system d dt x = f (x,u) , y = h(x,u) (20) where x, u, and y belong to the open subsets x ⊂ ℝn, ⊂u ℝm, and ⊂y ℝp respectively and p ≤ n . let r ≤ n be the dimension of the lie-group. we assume that for each x the mapping x→φg(x) is full rank. time functions u(t) and y(t) are known. invariant pre-observer for the differential geometric description of the symmetric observers [14], the following definitions and theorems should be introduced: definition 1. the group of local transformation on manifold ux× is expressed by (x,u) = (φg(x),ψg(u)) (21) where φg(x),ψg(u) is local diffeomorphism and g ∈g definition 2. system d dt x = f (x,u) is g-invariant, if f (φg(x),ψg(u)) = dφg(x) ⋅ f (x,u) for g, x, u. thus, the system remains unchanged for the local transformation, !x = f (x,u) . definition 3. the output y = h(x,u) is g-equivariant, if there exists ρg transformation on y, such that g ∈g and h(φg(x),ψg(u)) = ρg(h(x,u)) for g, x, u. thus, the output remains unchanged for the local transformation, y = h(x,u) . definition 4. the vector field w is g-invariant on manifold x, if d dt x = w(x) is invariant to the transformation, i.e. w(φg(x)) = dφg(x) ⋅w(x) for g, x. definition 5. an invariant frame (w1, w2, …, w3) consists of n linearly point-wise independent ginvariant vector fields on x thus (w1(x),w2(x),…,wn (x)) is a basis of the tangent space tx(x) . lemma 1. the invariant frame can be constructed from the canonical basis of x. the vector field defined by wi(x) = (dφγ (x) ) −1 ⋅ ∂∂xi (22) for i = 1, …, n forms an invariant frame. definition 6. the system d dt x̂ = f(x̂,u, y) is a preobserver, if f(x,u,h(x,u)) = f (x,u) is satisfied for x and u. furthermore, if lim x̂(t) = x(t) as t→∞ , then the pre-observer is asymptotic. 60 definition 7. the pre-observer is g-invariant, if ),,ˆ()ˆ())(),(),ˆ(( yuxfxdyuxf gggg ⋅= ϕρψϕ (23) is satisfied for g, x̂ , u, and y i.e. the observer remains unchanged for the group transformation on yu,,x . thus, x = φg(x) , u =ψg(u) , y = ρg(y) , and d dt x̂ = f(x̂,u,y ) . an invariant observer is an asymptotic g-invariant pre-observer. moreover, if the pre-observer is ginvariant and rank (f) = dim y , then the output map y is g-equivariant. definition 8. smooth map (x̂,u, y)→ e(x̂,u, y)∈ ℝp is an invariant output error if a) y→ e(x̂,u, y) is invertible for x̂ , u, and y b) e(x̂,u,h(x̂,u)) = 0 for x̂ and u c) e(φg(x̂),ψg(u),ρg(y)) = e(x̂,u, y) for x̂ , u, and y. the first two properties mean e is an output error, the third expresses the invariance. the introduction of the invariant error is necessary, because the output error ŷ− y does not usually preserve the geometry of the system [21]. the following three theorems [15, 16] support the construction of the symmetry-preserving observers. theorem 1. the observer d dt x̂ = f(x̂,u, y) is a ginvariant pre-observer for the g-invariant non-linear eq.(20) with a g-equivariant output if and only if f(x̂,u, y) = f (x̂,u)+ li(i(x̂,u),e(x,u, y)) i=1 n ∑ wi(x̂) (24) where e is an invariant output error, (x̂,u)→ i(x̂,u)∈ ℝn+m&r is a full rank function, li is a smooth function, such that li(i(x̂,u), 0) = 0 and (w1,w2,…,wn ) is an invariant frame. since li(i,e) = li(i,e)e li(i,e)wi i=1 n ∑ = wi(li(i,e) i=1 n ∑ e) = w1 … wn( ) l1(i,e) ! ln (i,e) " # $ $ $ $ % & ' ' ' ' e (25) the observer can be written as follows f(x̂,u, y) = f (x̂,u)+w (x̂)l(i(x̂,u),e(x̂,u, y))e(x̂,u, y). (26) theorem 2. the following statements are valid: • (x̂,u, y)→ e(x̂,u, y) invariant output error exists, • there is a (x̂,u)→ i(x̂,u)∈ℝn+m&r invariant function, • every other invariant output error has the form of !e(x̂,u, y) = l(i(x̂,u),e(x̂,u, y)) (27) where l is a smooth function such that l(i, 0) = 0 and e →l(i,e) is invertible. theorem 3. consider the equilibrium of a non-linear system f (x,u ) = 0 and y = h(x,u ) assume that the linearized system a,b,c,d around this equilibrium is observable, where a = ∂f ∂x (x,u ) , b = ∂f ∂u (x,u ) ,c = ∂h ∂x (x,u ) , a = ∂h ∂u (x,u ) and let l be such that a+ lc is a stable matrix. from the locally asymptotically convergent observer d dt x̂ = f (x̂,u)+ l(ŷ− y) , ŷ = h(x̂,u) (28) an invariant observer can be constructed by the same linear approximation d dt x̂ = f (x̂,u)+w (x̂)l(i(x̂,u),e(x̂,u, y))e(x̂,u, y) (29) where l = −w (x)−1lv−1 and v = ∂e ∂y(x,u,y ) is an invertible matrix of pp× dimensions. there is no general algorithm for designing the li gain functions of theorem 1. however, if we consider the following invariant state error η(x, x̂) = φγ (x)(x̂)−φγ (x)(x) (30) instead of the xx −ˆ state error, where )(xγ is the solution of φg a (x) = c (31) with respect to g, then the invariant error will only depend on the i(x,u) trajectories. constructive algorithm consider an invariant system, i.e. unchanged by transformation eq.(21) with an equivariant output (definition 3). the non-linear observer design for nonlinear dynamic systems [10, 11] can be divided into the following steps: a) choose a g lie-group and a group transformation taking into account the symmetrical properties of the system. b) solve the normalization eq.(31). build an invariant error e and the complete set of scalar invariants i. c) construct the invariant frame eq.(22). d) determine the pre-observer eq.(25). e) linearize the system f (x,u ) = 0 around the equilibrium and obtain a,b,c,d matrices. check the observability and design an invariant observer from the chosen linear observer by using theorem 3. choose an appropriate l . f) choose the parameters of the linearized error equations, based on the invariant state-errors η, such that the invariant system will be asymptotically stable. 61 then the non-linear symmetry-preserving observer is asymptotically stable, and converges locally and exponentially along all system trajectories. case study: a non-holonomic vehicle in this section, the previously introduced state estimation procedures are employed for an example of a non-holonomic vehicle tracking control. the wellknown model in the robotics of the simplified vehicle kinematics is considered. the tracking is maintained by satisfying the kinematic constraints with the appropriate choice of reference signals. kinematic model the simplified kinematic model of the vehicle can be written in the following form !x !y !θ ! " # # # $ % & & & = ucosθ usinθ uv ! " # # # $ % & & & , h(x, y,θ ) = (x, y) (32) where u is the velocity, v is the curvature, i.e. a function of the steering angle and h is the measured output. all signals contain additive gaussian noise. the model assumes that the contact point of the wheel and the ground does not slip. notice, that the linearized system is not observable. tracking for path tracking the control signals are set to satisfy the kinematic constraints, thus u and v are calculated as follows: u(t) = !xr 2(t)+ !yr 2(t) and v(t) = !!yr (t) !xr (t)− !xr (t)!!yr (t) u3(t) (33) where xr(t) and yr(t) are time functions of the reference signal. the initial conditions for tracking control is θr (0) = tan −1 !yr (0) !xr (0) " # $ % & ' . (34) hence, the reference signals for the vehicle velocity and steering function can be calculated. in the simulations, sinusoidal path tracking is implemented using the reference signals xr (t) = t, and yr (t) = asin(ωt). invariant observer design group transformation eq.(32) is independent of the origin and of the orientation of the frame chosen, i.e. it is invariant with regards to the group of rotations and translations. we chose the lie-group g = se(2) and defined the group transformation as follows: φ(xg,yg,θg )(x, y,θ ) = xg yg θg ! " # # # # $ % & & & & ⋅ x y θ ! " # # # $ % & & & = = x cosθg − ysinθg + xg xsinθg + ycosθg + yg θ +θg ! " # # # # $ % & & & & (35) ψ(xg,yg,θg )(u,v) = u v ! " # $ % & ρ(xg,yg,θg )(x, y) = x cosθg − ysinθg + xg xsinθg + ycosθg + yg ! " # # $ % & & one can check that eq.(32) is invariant to the transformations ϕ, and ψ in terms of definition 1 and the output is equivariant to transformation ρ in terms of definition 3. invariant output errors the normalization eq.(31) for :0=c 0 = x cosθγ − ysinθγ + xγ 0 = xsinθγ + ycosθγ + yγ 0 =θ +θγ (36) the solution of eq.(36), the scalar invariants and output errors can be written as follows respectively xγ yγ θγ ! " # # # # $ % & & & & = x y θ ! " # # # $ % & & & −1 = −x cosθ − ysinθ xsinθ − ycosθ −θ ! " # # ## $ % & & && = γ x y θ ! " # # # $ % & & & (37) i(x, y,θ,u,v) =ψγ (x,y,θ )(u,v) = u v ! " # $ % & (38) e = ρ(xγ ,yγ ,θγ )(x̂, ŷ)− ρ(xγ ,yγ ,θγ )(x, y) = cosθ̂ sinθ̂ −sinθ̂ cosθ̂ " # $ $ % & ' ' x̂ − x ŷ− y " # $$ % & '' (39) invariant frame w = (dφγ (x,y,θ )(x, y,θ )) −1 ∂ ∂(x,y,θ ) = = dφγ (x,y,θ )(x, y,θ ) = cosθ −sinθ 0 sinθ cosθ 0 0 0 1 # $ % % % & ' ( ( ( . (40) 62 invariant pre-observer d dt x̂ ŷ θ̂ ! " # # # $ % & & & = ucosθ̂ usinθ̂ uv ! " # # # # $ % & & & & + cosθ̂ −sinθ̂ 0 sinθ̂ cosθ̂ 0 0 0 1 ! " # # # # $ % & & & & l × cosθ̂ sinθ̂ −sinθ̂ cosθ̂ ! " # # $ % & & x̂ − x ŷ− y ! " ## $ % && (41) where l is a smooth 23× gain matrix, whose elements depend on the invariant error e and the invariants i. error equations and error dynamics η = ηx ηy ηθ ! " # # # # $ % & & & & = γ (x̂, ŷ,θ̂ ) x̂ ŷ θ̂ ! " # # # $ % & & & −γ (x̂, ŷ,θ̂ ) x y θ ! " # # # $ % & & & = = (x̂ − x)cosθ̂ + (ŷ− y)sinθ̂ −(x̂ − x)sinθ̂ + (ŷ− y)cosθ̂ (θ̂ −θ ) ! " # # # # $ % & & & & (42) !ηx !ηy !ηθ ! " # # # # $ % & & & & = u(1− cosηθ )+ (uv+ l31ηx + l32ηy )ηy usinηθ − (uv+ l31ηx + l32ηy )ηx 0 ! " # # # # $ % & & & & + +l ηx ηy ! " # # $ % & & (43) it can be seen that the invariant error equations are independent of the trajectory and only depend on the relative quantities ηx, ηy, and ηθ and the i invariants. stability and convergence the weighting matrix is defined as follows l = − |u | a ubey −uv uv−ubey − |u | c 0 −ub " # $ $ $ $ % & ' ' ' ' , (44) where a and b are care positive scalars and ey = ηy. the invariant error dynamics can be made locally asymptotically stable. furthermore, the resulting symmetry-preserving observer is almost globally asymptotically convergent, i.e. it converges any initial condition except for one as described in refs. [15-16]. simulation results the state estimation techniques are illustrated in two tracking examples. for comparative purposes, the following algorithms have been implemented: extended kalman filter (ekf), central difference and unscented kalman filter (ckf, ukf) and the symmetry preserving observer (sym) discretized by the sample time of the sigma-point estimators. the reference paths are xr (t) = t, and yr (t) = asin(ωt) , where a = 3 m and ω = π/5 rad s-1. zero mean additive gaussian noise is assumed with standard deviations of 0.01 and 0.005 for the process noise and 0.02 for the measurement noise. the sampling time is ts = 0.1 s. the initial values are x0 est = y0 est =θ0 est =1 , and x0 = y0 = 0 . example 1 the vehicle starts from the origin of the xy-plane with large initial estimation error and tracks a sinusoidal path. fig.1 shows the estimated output positions of the vehicle using sigma-point kalman filters and symmetry-preserving observers. the estimation errors of different algorithms can be seen in figs.2 and 3. the errors are smaller and show smoother signals in the case of the spkf estimators, which was expected, since the sym observer is deterministic. large errors appear at the peak values of the reference signals; however, both estimation techniques achieved the same satisfactory results in spite of the relatively small sampling frequency. figure 2: estimation errors of the sigma-point and extended kalman filters from example 1 63 root-mean-square errors can be seen in table 1. we can conclude that among the processes of state estimation techniques the sym observer is competitive with spkf estimators. example 2 in this example the vehicle performs an off-line estimation before movement starts, followed by an online estimation along a sinusoidal path. it is notable that in the stationary state the velocity is zero and at the beginning of movement the velocity changes to a nonzero value abruptly, see eq.(33). figs.4-7 illustrate the estimated output positions and the measurement errors for the sigma-point estimators and the invariant observers respectively the error signals show a quick convergence in the case of the symmetry-preserving observer. the speed of convergence depends on the parameters set in the l matrix; however, high gains can cause the observer to be divergent and make larger errors. since there are no u and δ signals in the stationary position and the orientation is not directly measured, the orientation can only be estimated after the vehicle starts moving. the error signal oscillates around zero in a similar way to example 1. due to calibration, smaller errors appear. the invariant observer and sigma-point estimators have the same magnitude of error components. the root-mean-square errors of the simulation can be seen in table 2. figure 3: estimation errors of the symmetry-preserving observer (sym) from example 1 figure 6: estimation errors of the sigma-point and the extended kalman filters from example 2 figure 4: estimated output position of the vehicle using sigma-point state estimation (ukf, ckf) and extended kalman filter (ekf) from example 2 figure 5: estimated output position of the vehicle using symmetry-preserving observer (sym) from example 2 figure 7: estimation errors of the symmetrypreserving observer (sym) from example 2 table 1: root-mean-squared errors of the estimated signals from example 1 rmse x, m y, m θ, rad ukf 0.1368 0.1587 0.0338 ckf 0.1366 0.1577 0.0336 ekf 0.1371 0.1551 0.0352 sym 0.1371 0.1628 0.0455 table 2: root-mean-square errors of the estimated signals from example 2 rmse x, m y, m θ, rad ukf 0.0998 0.1180 0.0627 ckf 0.0993 0.1175 0.0628 ekf 0.1013 0.1165 0.0648 sym 0.1264 0.1453 0.0760 64 conclusion in this paper we presented a comparison of two different recently developed state estimation techniques. the sigma-point (spkf) stochastic estimator is based on the unscented transformation and the non-linear symmetry-preserving observers are based on the group transformation of symmetrical lie groups and invariant frames. two examples are considered for the estimation of vehicle kinematics: the first example deals with the path tracking reliability of the vehicle; the second example examines the convergence and the speed of the off-line calibration followed by path tracking. the examples illustrate that for non-linear systems in noisy environments the use of stochastic stateestimators is needed. moreover the sigma-point approach provides more accurate estimation results than the commonly used non-linear ekf state estimators. the symmetry preserving observers for non-linear systems benefit from their constructive design method, which provides local asymptotic convergence. this method can be utilized by non-linear applications in which the physical and mechanical symmetry properties of the system can be exploited. references [1] bar-shalom y., li x.-r., kirubarajan t.: estimation with applications to tracking and navigationm, wiley interscience, new york, ny, u.s.a., 2001 [2] särkkä s.: recursive bayesian inference on stochastic differential equations, phd thesis, helsinki university of technology, helsinki, finland, 2006 [3] julier s.j., uhlmann j.k.: unscented filtering and nonlinear estimation, proc. ieee, 2004, 92(3), 401–422 [4] van der merwe r., wan e.a., julier s.: sigma-point kalman filters for nonlinear estimation and sensorfusion: applications to integrated navigation, proc. aiaa guidance, navigation & control conference (gnc), providence, ri, u.s.a. 2004 [5] van der merwe r.: sigma-point kalman filters for probabilistic inference in dynamic state-space models, phd thesis, oregon health & science university, eugene, or, u.s.a., 2004 [6] julier s.j., uhlmann j.k.: corrections to unscented filtering and non-linear estimation, proc. ieee, 2004, 92(12), 1958–1958 [7] julier s.j., uhlmann j.k.: unscented filtering and nonlinear estimation, proc. ieee, 2004, 92(3), 401–422 [8] wan e.a., van der merwe r.: the unscented kalman filter, in kalman filtering and neural networks, ed.: haykin s., john wiley and sons, new york, ny, u.s.a., 2001, chapter 7 [9] norgaard m., poulsen n., ravn o.: advances in derivative-free state estimation for non-linear systems tech. rep. imm-rep-1998-15, dept. math. modelling, technical university of denmark, lyngby, denmark, 2000 [10] norgaard m., poulsen n., ravn o.: new developments in state estimation for nonlinear systems, automatica 2000, 36(11), 1627–1638 [11] ito k., xiong k.: gaussian filters for nonlinear filtering problems, ieee trans. automatic control 2000, 45(5), 910–927 [12] van der merwe r., wan e.: efficient derivative-free kalman filters for online learning, proc. 9th eur. symp. artificial neural networks (esann) bruges, belgium, 2001, 205–210 [13] van der merwe r., wan e.: the square-root unscented kalman filter for stateand parameterestimation, proc. ieee int. conf. acoustics, speech, and signal processing (icassp), salt lake city, ut, 2001, 6, 3461–3464 [14] salam eran: filtering algorithms and avionics systems for unmanned aerial vehicles, phd thesis, mines paristech, paris, france, 2010 [15] bonnabel s., martin p., rouchon p.: non-linear symmetry preserving observers on lie-groups, ieee transactions on automatic control, 2009, 54(7), 17091713 [16] bonnabel s., martin p., rouchon p.: symmetrypreserving observers, ieee transactions on automatic control, 2008, 53(11), 2514–2526 [17] bonnabel s., martin p., rouchon p.: a non-linear symmetry-preserving observer for velocity aided inertial navigation, proc. 2006 american control conference, minneapolis, mn, u.s.a., 2006 [18] ayhanman n., rouchon p.: on invariant asymptotic observers, cdc, 2002 [19] rouchon p., guillaume d.: observation and control of simplified car, ifac, 1998 [20] bonnabel s.: symmetries in observer design: review of some recent results and application to ekf-based slam, robot motion and control 2011, lecture notes in control and information sciences 2012, 422, 3–15 [21] collon c., rudolph j., woittennek f.: invariant feedback design for control systems with liesymmetries – a kinematic car example, discrete cont. dyn. sys. 2011, 2(11), 312–321 hungarian journal of industry and chemistry vol. 45(2) pp. 1–7 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0012 methyl-tert-butyl-ether synthesis reactor modelling and optimization using an aspen custom modeler zeeshan nawaz sabic technology & innovation, po box 42503, saudi basic industries corporation (sabic), riyadh, 11551, saudi arabia a pseudo-homogeneous model of methyl-tert-butyl-ether (mtbe) synthesis in a multi-tubular packed-bed reactor has been developed using an aspen custom modeler (acm) for selecting optimum operating strategies, for the maximization and enhancement of mtbe production, and isobutylene consumption, respectively. the model accounts for mass, energy and momentum balances; and the effectiveness factor is evaluated in a onedimensional pseudo-homogeneous model. the kinetic investigation contains kinetic rate expressions as given by the effectiveness factor for accounting the resistance of pellets in terms of mass and heat transfer. an activity coefficient can be used in order to systematically obtain a new steady-state solution. the model used literature-based correlations for the estimation of heat transfer coefficients. the value of the coefficient for gascoolant heat transfer can be adjusted by using a tuning coefficient in order to enrich the process data. reasonable agreement was found between model predictions and data under similar conditions. the studies concerning model sensitivity compute the optimum temperature, pressure, feed flow rate, methanol/isobutylene ratio, heat removal rate, etc. of the reactor and suggest optimum operating conditions of the reactor. keywords: methyl-tert-butyl-ether (mtbe) synthesis, lead reactor, multi-tubular packed-bed, aspen custom modeler (acm), isobutylene 1. introduction methyl-tert-butyl-ether (mtbe) is of importance among petrochemicals due to its physicochemical properties and as an additive in gasoline. it contributes to the gradual elimination of lead-based additives, increasing the octane number (as an octane booster) and serves as a volume extender [1]. it is formed by the etherification reaction of an alcohol with a tertiary olefin. ethers are preferable over alcohols due to their lower sensitivity values, i.e. the difference between the ron (research octane number) and mon (motor octane number) [2]. today, standard (huls ag) and ethermax are the known processes commercialized by snamprogetti, cdtech, universal oil products (uop), axens, fortum, arco, phillips, bp-intevep, sinopec, sumitomo, etc. these are similar processes to each other. in this study a snamprogetti-lead reactor is modelled to maximize its productivity. 2. experimental conditions considered 2.1. reaction chemistry the following five reactions (eqs.(1-5)) are involved in mtbe synthesis when isobutylene reacts with methanol *correspondence: zeeshan@sabic.com (meoh). mtbe synthesis is an exothermic liquidphase reversible reaction catalysed by a cationic ionexchange resin (sulphonated macroporous polystyrene). for each mole of isobutylene converted, ~37.7 kj of heat is released and the thermodynamic equilibrium determines the extent of conversion [1-2]. mtbe: ch3oh + (ch3)2c=ch2  (ch3)3coch3 (1) however, undesirable side reactions may take place such as the dimerization of isobutylene to diisobutenes (dib), 2,4,4-trimethyl-1-pentene (tmp-1) and 2,4,4trimethyl-2-pentene (tmp-2); and the formation of methyl sec-butyl ether (msbe), dimethyl ether (dme) and tert-butyl alcohol (tba). the water produced during the formation of dme may react with isobutylene to form tert-butyl alcohol (tba) and its blending octane number is lower than that of mtbe. on the other hand, the presence of water reduces the acidity of the catalyst (reducing activity) and therefore a higher reaction temperature is required. dib: 2 (ch3)2c=ch2  (ch3)3ch2(ch3)c=ch2 + (ch3)3c(h)c=c(ch3)2 (2) msbe: ch3oh + (c2h5)ch=ch2  ch3ch(och3)(ch2ch3) (3) dme: 2 ch3oh  ch3och3 + h2o (4) tba: (ch3)2c=ch2 + h2o  (ch3)3coh (5) nawaz hungarian journal of industry and chemistry 2 2.2. thermodynamics etherification is an exothermic equilibrium reaction between a primary alcohol and an iso-olefin containing a double bond on a tertiary carbon atom (such as isobutene (ibu) under the operating temperature and pressure. owing to the non-ideality of liquid mixtures due to their disparate polarities and equilibria, the kinetic rate expressions for the synthesis of mtbe are generally given in terms of component activities. equilibrium and rate equations based on activities were first proposed by rehfinger et al. [3] and kinetic (including the effectiveness factor) and equilibrium data from an isothermal packed-bed reactor using the catalyst amberlyst-15 were discussed by zhang et al. [4]. the activity-based equilibrium constant is expressed as: �a = � �mtbe �ibu∙�meoh � eq. = � �mtbe �ibu∙�meoh ∙ �mtbe �ibu∙�meoh � eq. (6) where ameoh, aibu, and amtbe are the activities of methanol, isobutene, and mtbe, respectively, while γ and x are the activity coefficients and mole fractions of these components, respectively. the values of the equilibrium constant (ka) published in the literature vary significantly (fig.1) as a function of temperature [3-10]. deviations may stem from the different bases used for the evaluation of the activity coefficient as well as from the operating temperature of the reactor, for example, employing primary reactors or reactive distillation columns. 2.3. catalysis and kinetics the acidic cation exchange macroporous resin catalysts used commercially for the synthesis of mtbe are provided by bayer, dow chemical (rohm & haas), purolite, kairui, etc. the resins are prepared by the suspension of styrene in the presence of an appropriate cross-linking agent (divinylbenzene (dvb)) for polymerization functionalized by means of sulphonation with sulphuric or chlorosulphonic acid [11]. a reduction in volume of ~20-30% is observed because of the shift of the resin from the hydrated form (as it is generally charged in water) to a more contracted form due to a much less polar-reacting medium (a hydrocarbon/methanol mixture). the usability of the catalyst largely depends upon the process conditions, namely the type of reactor, e.g. a reactor receiving thermal support is better than adiabatic and thermal degradation with breakage of the carbon-sulphur bond (therefore, temperatures below 130 °c are recommended) and feed impurities (cations, e.g. na, ca, fe, al, cr, si, etc., strong n-bases like ammonia and amines, weak n-bases like acetonitrile and propionitrile, and dienes). the rate expressions, essential kinetic parameters and thermodynamic data such as the activation energy, effectiveness of the catalyst, heat of reaction, equilibrium constant and so forth have been selected from the literature [3-14]. the rate of reaction depends substantially on two parameters: acidity (type and number of acidic sites) and accessibility (porosity, content, particle diameter and treating medium). in the homogeneous model (in the absence of the diffusion phenomena), the reaction rate can be described in terms of confined catalyst pores, where the reactant concentration is in a partition equilibrium with the corresponding concentrations in the external solution. the rate-determining step was estimated to be the surface reaction between protonated adsorbed methanol and isobutylene [3-13]. this simplifies the rate of consumption for isobutylene after assuming that polar methanol molecules are preferentially adsorbed onto the ion-exchange resin catalyst (table 1) and the fraction of unoccupied sites over the catalyst surface was small as follows [4]: aibu mtbe ibu 0 2 meoh a meoh 1            e rt a a r a e a k a (7) where ibur is the rate constant of the reaction, r is the universal gas constant, ae is the activation energy of 85.4 kj mol-1 (for amberlyst-15 this value varies between 71 and 93 kj mol-1 and is influenced by not figure 1. values of the equilibrium constant ka as a function of temperature. table 1. properties of the catalyst amberlyst-15. properties specifications porosity of catalyst (ɛp) 0.31-0.39 tortuosity of catalyst (t) 0.7-1.7 density of catalyst (kg m-3) ~2000 physical shape spherical beads ionic form hydrogen moisture content (g/g %) ~50 particle size (mm) 0.3-1.5 functional group rso3h surface area (m2 g-1) ~45 pore diameter (å) ~250 acid sites (eq(h+) kg-1) 4.6-5.2 mtbe synthesis reactor modelling 45(1) pp. 1–7 (2017) 3 only the type of catalyst but also by the composition of the reaction mixture); and a0 = 6.3 x 1012 mol h-1 g-1. the effective diffusion coefficient and activation energy of methanol over amberlyst-15 at 60 oc was estimated to be 2.3·10-9 m2 s-1 and ~35.4 kj mol-1, respectively [4]. the given value of the effective diffusion coefficient is slightly lower than the one rehfinger and hoffmann reported (3.5·10-9 m2 s-1) [3]. the catalysts kastel cs 381 and amberlyst csp used in the synthesis of mtbe possess similar rate constants to amberlyst-15, whereas amberlyst xe 307 and duolite es 276 have significantly higher; and duolite c16p and duolite c26 have substantially lower values for their rate constants [3-15]. every resin undergoes deactivation, if sodium ions are exchanged for their protons. due to the acidic nature of resins, the activity is strongly reduced by the presence of basic substances and/or salts in the reaction mixture. the heat of reaction, ∆hº(mtbe), in the liquid phase at 25 ºc was reviewed by iborra et al. and found to be within the range of -34 to -40 kj mol-1 [5]. the rate for dimerization of isobutene (dib formation) [4, 10] can be calculated as follows: -66.7kj/mol 1 1 2333 ibu dib 0 ad meoh ibu           r t a r k e k a a (8) where the unit of rdib is mmol s-1 eq-1, kad is the ratio of adsorption equilibrium constants, and k0 is the frequency factor of the kinetic constant. 2.4. reactor and process generally, the multi-tubular packed-bed reactor is used exclusively as a front-end for the reactor performing the synthesis of mtbe, where the catalyst is lodged in the tubes (~10,000 tubes of diameter ~30 mm, length ~6 m, ɛ = 0.4). the cooling water flows in the shell side and can either flow coor counter-current. the reactor column is used solely for finishing and exploits the principle of catalytic distillation possessing the normal fractionation trays with reactive trays (where the catalyst is packed) [2, 16]. therefore, the maximum degree of isobutene conversion was achieved and reactants were separated from the product simultaneously, as mtbe has a much higher boiling temperature. reactor parameters used for the modelling are given in table 2. almost all the commercial etherification technologies use similar sections with regard to operation and separation, but are different in terms of type of reactors, numbers and process schemes [16-17]. the mtbe plant consists of a multi-tubular packed-bed reactor, and reactive distillation and methanol recovery sections. there are two separation towers after each reactor that recover the c4/methanol azeotrope from the top and mtbe from the bottom, followed by the washing tower where water removes the methanol from the c4, and then a distillation tower to separate water and methanol. 3. reactor modelling classical models of multi-tubular packed-bed reactors (pseudo-homogeneous one-dimensional) have been extensively discussed in the literature [1, 3-5]. in this study, a custom model of an mtbe water-cooled multitubular packed-bed reactor was built using an aspenbased platform (acm) with the ultimate objective of developing a complete process flow-sheet using the same method as in refs. [18-19]. model equations have been developed based on the following assumptions:  steady-state operation;  plug flow with no axial mixing;  one dimensional as no temperature and composition gradients exist in a radial direction (perfect radial mixing);  pseudo-homogeneous conditions for fluid solid phase interactions: transport limitations in terms of catalyst particles are taken into account by using the concept of an effectiveness factor;  heat transfer coefficient of the liquid phase to coolant (constant value along the reactor axis) is implemented as a sub-model. the heat transfer coefficient was evaluated under various changeable process parameters as defined the coolant inlet temperature, inlet flow rate, inlet pressure and inlet composition;  pressure drops according to the ergun equation in the model. 3.1. mass and energy balance the steady-state material balance in the liquid phase expressed in terms of vectors of the molar flow rates of the components in z direction is d d  a z f r and t b kef   r s r (9) where r is the vector of the rate of production or consumption per unit volume of a component, s is the stoichiometric matrix, rkef is the vector of effective reaction rates, a is the cross-sectional area of the reactor, f is a molar flow rate vector of the component, and b the bulk density of the catalyst. the liquid side of the heat balance equation under steady-state conditions is as follows: table 2. specifications of the reactor system. specification units value reactor length m ~8 reactor diameter m ~3.5 lhsv h-1 ~2-9 porosity ~0.35 feed inlet temperature oc ~40 i-c4/meoh ratio molar ~1.1 pressure bar ~10 recycling ratio % ~15 nawaz hungarian journal of industry and chemistry 4    t r kef f t c t p        ca h d t tdt dz h f c r (10) where δhr is the vector concerning the heat of reaction, cp is the vector concerning the molar specific heat of a component, t and tc are the liquid phase and coolant absolute temperatures, respectively, hfc is the liquid-tocoolant heat transfer coefficient, and dt is the diameter of the reactor tube. the shell side of the heat balance equation under steady-state conditions is as follows:  fc t cc vcool cool s,cool         h d t tdt dz f c (11) where fvcool is the volumetric flow rate of the coolant, cool is the density of the coolant, and cs,cool is the specific heat capacity of the coolant. in terms of modelling, the negative sign stands for the countercurrent and the positive sign for the co-current. the boundary conditions at the inlet of the reactor in terms of the material and energy balance differential equations are z = 0, fi(0) = f0,i , t(0) = t0, tc(0) = tcool,in and tc(rl) = tcool,in. 3.2. effectiveness factor the effectiveness factor for the synthesis of mtbe has been evaluated on the basis of data concerning the generalized thiele modulus (φg) [3]:  = tanh(g) / g . (12) in terms of the pseudo-homogeneous model, the effectiveness factor is expressed as a function of temperature and conversion: 2 3x 1 4 1 conversion % 1.1 100                x rtx e x . (13) the parameters x1 – x4 have been evaluated by minimizing the absolute error between evaluations by zhang et al. [4] and the values predicted by eq. 13. the accuracy of the prediction is shown in fig.2. 3.3. overall heat transfer coefficient the overall heat transfer coefficient, taking into account the small value of the wall thickness, is evaluated as follows: fc te ti fouling fw pipe shell 1 1 1 2           h d d r h h (14) where dti and dte are the internal and external diameters of the reactor tube, respectively, λpipe is the thermal conductivity of the reactor tube, hfw is the fluid-to-wall heat transfer coefficient, hshell is the shell side (wall-tocooling water) heat transfer coefficient, and rfouling is the fouling factor. the evaluation of the fluid-to-wall heat transfer coefficient was conducted on the basis of a newly proposed correlation for the estimation of the total (wall and effective thermal conductivity effects) heat transfer coefficient [16]: 0.643 0.333 f f f ti p 1.37 nu 3.87 3.77 exp re pr                      d d .(15) in this case, both nuf and ref are expressed based on particle diameters. the heat transfer coefficient of the shell side is expressed as a function of nu and re and are both based on the external diameter of the tube, where ɛφ stands for a correction factor accounting for the angle between the coolant stream and reactor tubes: nu s  0.4 e  re s 0.6pr s 0.333 . (16) 3.4. acm property estimations the physical properties of components and mixtures like viscosity, density and specific heat, were estimated by aspen properties (using unifac dortmund property package). the “.appdf” file prepared by aspen properties is the one called in acm for seamless transfer of properties. the kinetic sub-model helps in terms of the calculation of reaction heats using the aspen properties database. figure 2. effectiveness factor for the mtbe synthesis reaction based on data from ref. [4]. mtbe synthesis reactor modelling 45(1) pp. 1–7 (2017) 5 3.5. performance parameters reactor performance is evaluated by the following equations: key_reactant key_reactant 0 z key_reactant 0 conversion( )   f f z f (17) key_product key_product z 0 key_reactant key_reactant 0 z selectivity( )    f f z f f (18) yield( ) conversion( ) selectivity( ) z z z (19) where z stands for the axial coordinate. 4. model predictions and analysis acm is the preferred choice for robust reactor modelling. its equation-oriented modelling platform can be easily exported to aspen plus process flow-sheets. the coding of a multi-tubular packed-bed reactor in terms of the synthesis of mtbe was conducted in a modular form. the main reactor model defines the constitutive equations in the bulk phase and sub-models in terms of the reaction kinetics, the estimation of the heat transfer coefficient, and the development of the pellet design. the normal operating conditions for the primary reactor were selected as the base case in terms of modelling (table 3), where mtbe productivity is ~50 t h-1. the molar concentration profile of the reactants and product along the axis of the reactor is shown in fig.3. the full length of the reactor is used for the synthesis of mtbe. fig.4 shows the temperature profiles of the reactor and coolant. the temperature sensitivity is controlled by keeping the temperature difference between the coolant and feed temperatures constant (fig.5). it was observed that due to the exothermic nature of the reaction, the maximum temperature increased significantly with the table 3. typical base-case operating conditions and results for the primary reactor. specification units value tube length m 6 tube diameter (id) mm 21 number of tubes 10,000 porosity 0.33 feed inlet temperature ºc 50 isobutene/meoh ratio molar 1.1 pressure bar 8 coolant inlet temperature ºc 45 feed flow rate kmol h-1 2,000 isobutene mole fraction 0.35 ∆p bar 0.723 conversion % 84.7 mtbe selectivity % 97.86 figure 3. molar concentration profile along the length of the reactor. figure 4. temperature profiles of the reactor and coolant. figure 5. temperature sensitivity by varying the feed temperature and keeping constant the temperature difference between the coolant and feed temperatures. nawaz hungarian journal of industry and chemistry 6 increase in reaction temperature. at a constant pressure and feed flow rate, the increase in the reaction temperature led to an outer mass transfer limitation that strongly affects the rate of conversion. at the same time the selectivity also decreased due to a significant increase in the maximum temperature of the reactor (product degradation) and the maximum rate of conversion was achieved in almost ~30% of the reactor. the isobutylene/methanol molar ratio is one of the key operating parameters and is always kept higher than its stoichiometric value. table 4 shows that by deviating from the stoichiometric ratio the effect on the rate of conversion and selectivity also decreases with the increase in the isobutylene/methanol molar ratio. the predictions according to reactor modelling were found to be in good agreement with data from the literature. the reaction must reach an equilibrium at the rear end of the lead reactor. the estimated effectiveness factor is 0.75 which was also used in the model. the possible explanation for the occurrence of minor discrepancies could be the use of a different catalyst or errors in terms of experimental measurements. it was observed that the maximum degree of productivity corresponded to an isobutene/meoh molar ratio of close to 1 and a feed inlet temperature of between 50 and 55 ºc. however, it is necessary to synchronize this with the secondary reactor and other unit operations. 5. conclusion an acm-based pseudo-homogeneous model with regard to the synthesis of mtbe using an industrial multi-tubular packed-bed (methyl-tert-butyl-ether) reactor has been developed for enhancing operation strategies. the unifac dortmund property package was used for reactor modelling. the effectiveness factor was implemented as a function of the reaction temperature. the model was validated using data from the literature. various sensitivity evaluations were conducted to determine the operational optimization and maximization of mtbe production under different operating parameters. the model was able to predict reaction behaviour and produce temperature and concentration profiles along the length of the reactor. sensitivity studies were able to calculate the optimum temperature, feed flow rate, methanol/isobutylene ratio as well as heat removal rate of the reactor and thus provide insights into a reasonable operational strategy. symbols a cross-sectional area of the reactor a activity ameoh, aibu, amtbe, ainert activities of methanol, isobutene, mtbe and inert isobutane, respectively a0 6.3 x 1012 mol h-1 g-1 cp molar specific heat vector of a component cs,cool specific heat capacity of the coolant dt diameter of the reactor tube dti, dte internal and external diameters of the reactor tube, respectively ea activation energy in kj mol-1 fvcool volumetric flow rate of the coolant f molar flow rate vector of a component hfc liquid-to-coolant heat transfer coefficient hfw fluid-to-wall heat transfer coefficient hshell shell side (wall-to-cooling water) heat transfer coefficient δhr heat of reaction vector γ activity coefficient ka equilibrium constant (based on activities) kad ratio of adsorption equilibrium constants kmeoh, kibu, kmtbe, kinert adsorption equilibrium constants for methanol, isobutene, mtbe and inert isobutane, respectively k0 frequency factor of the kinetic constant kr reaction rate constant λpipe thermal conductivity of the reactor tube r universal gas constant r vector of the rate of production or consumption per unit volume of a component rkef vector of effective reaction rates rfouling fouling factor b bulk density of the catalyst cool density of the coolant s stoichiometric matrix t , tc absolute temperatures of the liquid phase and coolant, respectively x mole fraction acknowledgement the author gratefully acknowledges the technical support of prof. dr. ing. teodor todinca at the university politechenica timisoara in romania. references [1] nawaz, z.: light alkane dehydrogenation to light olefin technologies: a comprehensive review, rev. chem. engng., 2015 31(5), 413–436 doi 10.1515/revce-2015-0012 table 4. dependence of conversion (%), selectivity (%) and the maximum temperature of the reactor (tmax) on the isobutene/methanol molar ratio (ibu/meoh). ibu/meoh 0.8 0.9 1.0 1.1 1.2 1.3 conversion 84.7 85.4 85.5 84.6 80.7 76.7 selectivity 98.1 98.1 98.1 97.9 97.1 95.4 tmax, ºc 56.1 56.5 56.9 57.7 59.5 62.0 mtbe synthesis reactor modelling 45(1) pp. 1–7 (2017) 7 [2] digirolamo, m.; sanfilippo, d.: etherification: process to improve the quality of distillates, in beccari m.; romano, u.; eds. encyclopaedia of hydrocarbons (eni s.p.a and istituto della enciclopedia italiana fondata da giovanni treccani s.p.a, roma, italy) 2006 vol. ii. pp. 193–209 [3] rehfinger, a.; hoffmann, u.: kinetics of mtbe liquid phase synthesis catalyzed by ion-exchange resin. i. intrinsic rate expression in liquid phase activities, chem. eng. sci., 1990 45(6), 1605–1617 doi 10.1016/0009-2509(90)80014-6 [4] zhang, t.; datta, r.: integral analysis of mtbe synthesis kinetics, ind. eng. chem. res., 1995 34, 730–740 doi 10.1021/ie00042a004 [5] iborra, m.; tejero, j.; ben el-fassi, m.; cunill, f.; izquierdo, j.f.; fite, c.: experimental study of the liquid phase simultaneous synthesis of mtbe and tba, ind. eng. chem. res., 2002 41, 5359–5365 doi 10.1021/ie010640q [6] chen, f.; huss, r.s.; doherty, m.f.; malone, m.f.: multiple steady-states in reactive distillation: kinetic effects, comp. chem. engng., 2002 26, 81– 93 doi 10.1016/s0098-1354(01)00750-5 [7] lisal, m.; smith, w.r.; nezbeda, i.: molecular simulation of 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doi 10.1016/0255-2701(95)04122-2 [18] nawaz, z.: dynamic modeling of catofin® packed-bed isobutane dehydrogenation reactor for operational optimization, int. j. chem. reactor engng., 2016 14(1), 491–515 doi 10.1515/ijcre-20150087 [19] nawaz, z.: heterogeneous reactor modeling of an industrial multitubular packed-bed ethylene oxide reactor, chem. engng. technol., 2016 39(10), 1845–1857 doi 10.1002/ceat.201500603 microsoft word a_47_jakab_r.doc hungarian journal of industrial chemistry veszprém vol. 39(1) pp. 91-94 (2011) bycicle abs prototype development r. jakab1, k. enisz1, v. hauptmann2, f. speiser1 , d. fodor1 1university of pannonia, faculty of engineering, institute of mechanical engineering h-8200 veszprém, egyetem str. 10., hungary e-mail: ferenc.speiser@gmail.com 2continental teves kft., h-8200 veszprém, hungary the passive and also the active safety systems of the vehicles were developed in the last decades. beside the safety system of cars and trucks the smaller vehicles (like the motorbikes, scooters, e-bikes and bicycles) were developed as well. by emergency or persistent braking the wheel can lock making it impossible to steer the vehicle. [1, 2]. the aim of the project was to create and develop a prototype bicycle that uses a hydraulic type anti-lock braking system called abs. keywords: abs, hydraulic brake system, bicycle introduction nowadays more and more efforts are taken to make the road traffic safer. on the traffic side not even for the cars and trucks, but also for the motorbikes and bicycles there are extra safety products as well to avoid or at least to reduce the harms and injuries. car manufacturers have already developed several built-in safety functions such as pedestrian and bicyclist recognizer camera system or distance estimation with radar system. for motorbikes there are also active protective systems such as airbag, abs (anti-lock braking system), rear wheel lift off protection, hill start assist and so on. if the wheel of bicycle is locked, then the motor bicycle became uncontrollable and it can slip off the road. this can be handled by abs, since the system does not let the wheel lock. there is no need to have a driving license for a bicycle therefore it is reachable for everyone as means of traffic. in the last years more and more people choose to use bicycle and thus the number of accidents caused by bicyclist and suffered by bicyclist raised in hungary. a lot of people use it without the minimum protection, for example helmet, kneeand elbow-protector. by a simple fall serious injuries can happen. the only solution to protect the rider is to have the safety function on the bicycle itself. this is the reason why continental teves started the project together with the university of pannonia as a pilot project for developing hydraulic abs for a bicycle. the primary aims were to: – develop a new control algorithm for low weight vehicles with two wheels, and optimize this algorithm for use only the data from the wheel speed sensors as input parameters – create a prototype from existing components and a test environment which is suitable for testing new algorithms. existing methods results of the market and research survey in the bicycle abs field shows that there is no widespread active safety product for bicycles nowadays. for electric motor aided or hybrid bicycles are already present, but regular bicycles are still not supported. there are some simple solutions by modifying the brake-pad shape, using springs in the brake wires and also exist more complex methods such as brake force distribution or balancing. although could not be found any ready to buy product that uses some kind of intelligence, there are a few proof of concepts. the idea to apply some intelligent decision aiding mechanism is relatively new. the following methods are used: – mechanical brake force distribution, – pneumatic aided abs, – abs realization with electronic stepper motor, – hydraulic abs, only one controlled wheel. structure of the system the difference between the previously mentioned methods and this pilot project is the concept. the abs control algorithm is able to run on a separate sbc (single board computer) and not only on the ecu (electronic control unit), the bicycle has hydraulic brake system and the algorithm is able to actuate both of the wheels independently but in synchronized manner. the system consists of three main parts (fig. 1): – a pc to observe and modify the parameters of the bicycle and the control algorithm – a sbc to run the control algorithm and make log from the internal parameters of the algorithm and the data from the sensors – the control units and the sensors 92 figure 1: structure of the system (where v1 and v2 are the wheel speed sensors, the p1,2,3,4 are the pressure sensors) the pc and the monitoring software an external laptop was utilized to continuously monitor the abs, download measurement data, monitoring the operation (fig. 2) and upload matlab/simulink control model. the external pc connects to the sbc with standard wireless communication. figure 2: bicycle monitoring client software the sbc and the control algorithm the sbc is a small pc with an intel atom processor (z530p) and with the standard interfaces. on this small computer runs the control algorithm and collects the data from the ecu. the single board computer on the sbc an embedded windows xp is running as an operating system with limited functions, optimized for running the matlab/simulink program and enabled network connections. as there is no direct connection to the sbc an application is used, that is able to function as a diagnostic, control and file transfer tool. on the sbc the module shall run as a server application independently. this module shall observe the status of the control model, such as running, activating the valves, in failure. this should be able to communicate with the external computer (client side), to send new control commands to the sbc, and to receive the log files and monitoring information back to the client side to display them during tests. the sbc does not have any peripheral device such as display, keyboard, pointer device when it is on the bicycle. there is only a feedback led that is indicating the sbc is powered up and the os is running. the connection and control to the sbc is made over a wireless connection. analogue to digital converter beside the sbc there is an a/d converter for the logging of the pressure values. the converter reads the data from the pressure sensors and forwards it to the single board computer. communication for onboard communication system the controller area network system was chosen. the main reason for using this system was that the ecu and the sensors support this kind of communication system, and other components of the system can be adapted to be able to communicate on can. defined can nodes in the onboard network (fig. 1): – hydraulic and electronic control unit (hecu) – single board computer (sbc) via converter – pressure signal adapter (p1,2,3,4) 93 the control algorithm the control algorithm was implemented in matlab/ simulink. the algorithm is based on the comparison of the wheel speed and a calculated ideal speed. false true measured data abs data calculation of ideal speed abs data = release release wheel ideal k v v ≥ hold wheel ideal k v v ≥ abs data = hold abs data = increase false true figure 3: abs control flowchart the calculation of the ideal speed value is based on a linear function defined by a speed slope value and the initial speed value. startideal vsnv +∗= (1) where: videal – ideal speed value defined by linear function n – elapsed time from measurement of initial speed (the number of steps) s – defined speed slope vstart – initial speed (offset, the last valid speed value, before the actuation) the comparison of speed and the calculated ideal speed is based on the eq. 2 and eq. 3. 1−=absdata if dif wheel ideal k v v max≥ and itideal vv lim> (2) 1=absdata if dif wheel ideal k v v max< or itideal vv lim< (3) where: absdata – is the actuation request (normally the -1 is the release, the +1 is the increase state of the abs) vwheel – actual speed value of the wheel kmax dif – is a defined maximum “difference” vlimit –speed limit for abs actuation the algorithm calculates the vstart value in every loop (eq. 4, eq. 5) wheelstart vv = if wheelideal vv ≤ (4) startstart vv = if wheelideal vv > (5) the current algorithm has only two states (the release and the increase state), because it is the simplest and the fastest version of the actuation, but in the control part there is a third state, the hold, which will be used in the future for the more effective braking. the hecu / ecu and the sensors the hecu is a modified motorbike hecu, which currently works as a dummy ecu without a control algorithm, thus an external controller has to send the control messages for valves and pump states. figure 4: speed and pressure sensors on the bicycle to create the connection between the hydraulic system of the motorbike abs and the brake system of the bicycle was hard, because these parts were designed for different pressure intervals and were designed for different filling methods. for monitoring the different parameters of the bicycle, some sensors were mounted. the pressure sensors were connected to the inlet and outlet lines of the abs, and four different wheel speed sensors (fig. 4) were mounted to test which one is the most suitable for this application. test and measurements the first test was made on dry asphalt with the manoeuvre of emergency braking from 15 km/h speed and the results are promising. the diagram on fig. 5 shows the data for the rear wheel. when the difference between the ideal and filtered wheel speed were increasing the abs decreased the brake pressures and the wheel was accelerated near to the ideal speed. 94 figure 5: braking maneuvre (rear wheel) conclusions in many countries all around the world a lot of people use bicycle not just for spare-time activity but also as part of their everyday life to commute to the workplace. during these times accidents can happen to anybody, so it is important to prevent the bicycle riders from injuries. with this prototype the aim of the project team is to show that the abs technology is also a solution for bicycles. after testing and further improvements of the software should be realized that can help the riders in dangerous situations to mitigate collision or just to stop in a safe way. for car industry it started the same way and now it is a compulsory supplement in every produced car in europe and america also. though the anti-lock braking system theory is the same for cars and bicycles the circumstances are really different. the point of later development shall be to keep the focus on the helping the rider to run in a safe way. in the future if the development of the bicycle brake assist system evolves as the brake systems for the car, in some-ten years the abs for high-end bicycles or mopeds may be compulsory also. the first concept of electrical and hydraulic components are mounted on the bicycle (fig. 6), the control model can be tested and tuned now on. in automotive industry the abs system tuning for a vehicle is a long process based on the experience of the drivers and engineers. for the bicycle it is even more specific because there is no previous test result. in a later development phase beside abs other safety and comfort control functions can be added to the system (e.g.: lift-off protection, hold-and-go function, brake-by-wire). figure 6: the bicycle acknowledgement we acknowledge the financial support of this work by the hungarian state and the european union under the tamop-4.2.1/b-09/1/konv-2010-0003 project. references 1. v. cerone, d. andreo, m. larsson, d. regruto: stabilization of a riderless bicycle a linearparameter-varying approach, ieee control systems magazine, october (2010) 2. k. j. åström, r. e. klein, a. lennartsson: adapted bicycles for education and research, ieee control systems magazine, august (2005) << /ascii85encodepages false 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page 538 page 539 page 540 page 541 page 542 page 543 page 544 page 545 page 546 page 547 page 548 page 549 page 550 page 551 page 552 page 553 page 554 page 555 page 556 page 557 page 558 page 559 page 560 page 561 page 562 page 563 page 564 page 565 page 566 page 567 page 568 page 569 page 570 page 571 page 572 page 573 page 574 page 575 page 576 page 577 page 578 page 579 page 580 page 581 page 582 page 583 page 584 microsoft word inner cover.docx hungarian journal of industry and chemistry veszprém vol. 41(2) pp. 115–118 (2013) the energy balance of separation opportunities in microalgae technologies zoltán hodai, ! dóra rippel-pethő, géza horváth, lászló hanák, and róbert bocsi department of chemical engineering science, university of pannonia, veszprém, egyetem u. 10., 8200, hungary !email: hodaiz@almos.uni-pannon.hu algae technology is at the focus of international research and development, since it is a green technology that reduces emissions of harmful chemicals and can be considered as a renewable energy source. carbon dioxide from stack gases and the nitrogen content of wastewater can be considered as food sources for plants and algae. the utilisation of carbon dioxide by algae technologies depends on the technical environment and logistics of teamwork. this technology is a new opportunity in hungary for decreasing emissions. we grew algae populations to utilise the carbon dioxide from a refinery’s stack gas in the continental climate of hungary. critical parameters of the technology are the concentration of the algae suspension and extract, because of high investment and operating costs as well as the long operation time, which determines the feasibility of the algae technology. our specific aim was to separate the algae mass faster and more efficiently from the starting solution. the optimisation of separation operations and technologies took into consideration environmental and economic aspects. keywords: microalgae technology, separation, filtration, renewable energy source introduction the utilisation of microalgae carbon dioxide fixation is an important area of international research and development. the absorption of certain technological exhaust gases is possible on the basis of the photosynthesis of microalgae. the absorption of carbon dioxide can reach a magnitude of hundred ton per hectare. c16-c22 esters are formed in certain algae cells that can be used for the production of biodiesels. this method is thus capable of producing fuels from renewable sources [1-4]. algae production is a promising solution amongst the alternative fuel production processes, because it requires of low specific area for growth and high reproduction rate [5-8]. algae are considered to be one of the most efficient organisms on earth due to their outstanding reproduction rate, and generally high lipid content. for example, they can double their biomass in 24 hours [9-12]. their lipid content on average is 20%, but it can be up to 60-80% for certain species [7, 9, 13, 14]. research into oil production from algae is primarily based on microalgae. these are photosynthesising organisms with a cell size of no greater than 0.5 mm. they can be utilised for carbon dioxide and nitrogen oxide fixation, because they convert these compounds in a photosynthetic energy conversion [15]. the end product of these processes contains a significant amount of solar energy stored as chemical energy. furthermore, considerable amounts of biodiesel can be obtained [16-19]. the composition of a microalgae cell depends on cultivation parameters. we tested the available and applicable species under local climatic conditions. afterwards microalgae that passed the local environmental tests can be considered useable for production. research is being carried out into carbon dioxide fixation from technological flows at our institute [15]. the absorption of carbon dioxide and reduction of the release of other pollutants in wastewater using microalgae are being studied. algae technology utilises waste gases and some environmentally harmful components from wastewaters as nutrients, and thus purifies the growth media. these specific pollutants provide excessive amount of nutrients for the algae, which results in the algae’s exponential growth. in addition to the above-mentioned method of energy extraction, a number of research efforts [4, 5, 8, 10-12, 18, 19 25] are currently dealing with the alternative use of biomass produced in this way, and biomass residue that remains after processing. in addition to the abovementioned advantages, the operating costs can be a limiting factor. the most critical steps in the production of algaebased biofuels are the harvesting of algae (harvesting, dewatering, and drying), and lipid extraction, because of the high level of investment and operating costs. the main challenge of the technology is to reduce costs, which by in large originate from the separation steps that need to be minimised. 116 results and discussions our research focuses on carbon dioxide fixation from technological flows. we designed and built various grower systems at the department of chemical engineering of the university of pannonia (fig.1), as well as at a refinery (figs.2 and 3). by utilising these technological solutions we conducted research into the production of biomass and algae-based products as possible renewable fuels. the propagation and environmental tolerance parameters were examined along with the possibilities of developing the technology. during the experiments, the whole technological chain was examined providing the possibility to optimise the entire chain of operational steps. the utilisation of algae cultures in experimental photobioreactors is examined, together with the optimisation of the operational conditions both for both artificial and natural light with different substrate solutions. the various parameters for algae processing are also determined. the foci of our work were the processing and separation operations. critical points of the technology are the processing steps, such as concentrating the algae suspension and extracting valuable components (lipids). the extraction technologies are of importance because of the high costs of investment and long operation periods. from the literature [5, 10, 12, 15, 17, 22, 23], biodiesel is not yet comparable to fuel produced from petroleum, however the cost of algae technology is dropping. furthermore, algae technology could become viable if we consider the cost of wastewater purification and flue gas adsorption, and the price of products obtained from microalgae. we need to consider separating possibilities and beyond by analysing gains and losses simultaneously. our specific aim was to devise densification and separation processes, which have low energy requirements and advantageous operation times. furthermore, we defined useful components from algae and their optimised extraction, based on the optimisation of extraction techniques and other economical and environmental aspects. separation opportunities harvesting can be carried out by microfiltration, ultra filtration, centrifugation, flocculation, sonochemical techniques, or some new techniques that are under development [21, 22]. in addition to chemical flocculation, clarification, and membrane separation procedures, special attention was paid to auto flocculation phenomena. forms of technology pay more and more attention to convert disposed waste into useful materials. the photosynthesising microorganisms, such as microalgae, utilise solar energy, rapidly reproduce, and do not require any soil to grow in. the biomass product contains solar energy stored in chemical bonds. to process the final product, the suspension, concentration, and extraction of the biomass are the most problematic parts of the methods of algae-based energy production. the main techniques for separation are mechanical operations (filtration, centrifugation, and settling), mechanical operations with admixture (flocculation and defecation), membrane operations (microfiltration and ultrafiltration), and other notable operations (sonochemical techniques, electroflocculation, and flotation). according to examples from the literature [9, 11, 15, 18], there are still only limited generally applicable and proven methods that can be used for biomass production with specific energetic goals. energetic considerations increasingly diluted suspensions were examined during separation operations (fig.4). data from the literature [23-37] need to be brought to a common denominator for carrying out comparisons. for example, our results show that if we want to gradually treat more dilute suspensions using flotation, the energetic considerations can change by orders of magnitude. figure 1: closed grower systems at the university of pannonia figure 2: closed grower systems at a refinery figure 3: open grower systems at a refinery 117 according to fig.4, cross-flow membrane separation, electroflocculation, centrifugation known as “spiral plate”, immersion membrane separation, the flocculation, foam flotation and operation of the flotation by dispersed air are positioned favourably with respect to energetic rating (smaller demand of energy as the energy amount from the separated biomass). the energy balances of chemical flocculation and electroflocculation do not include the costs of the procurement of chemicals and post-treatment, which would complicate the determination of its energy status. the amounts of chemicals used according to the quality of the suspension were between such wide intervals that they could not be considered using simple factors. by energetic rating, we should note the concentration of the kind of algae suspension in the chosen operation. the increase in volume and decrease in concentration of the suspension may require a review of the cost, materials and energy needs of the separation, and thus change its energetic status. for example, we can conduct a thought-experiment for flotation to see whether the treatment of a dilute suspension needs a device with a different energetic rating. because of the fixed size of the flotation’s device, we cannot decrease the amount of gas flow and the dilute suspension could start to foam, which may make it more difficult to handle than the stability and volume of the foam from a more concentrated suspension. due to foaming, it will be more difficult for the algae layer to become thicker in the foam unless we use more chemicals and surfaceactive agents, which result in more parameters to consider. apart from the above, an important question is how we consider the time domain of the technology (periodic, half-continuous, or continuous). the kind of growing system determines how to connect the separation operation. half-continuous or continuous (or almost that) operation is beneficial for industrial biomass production to maximise the capacity of biomass. by running the reactor at the maximum rate of reproduction, we can maximise its capacity. according to the latter, the immersion membrane separation operation would be preferable. conclusions according to our investigations, the usable operations for extraction and concentration in algae cultivation with regards to energetic causes vary greatly with respect to energy demands. for dilute suspensions, flotation and foam flotation are the most useful separation processes. we can use flocculation as well, but we have to consider the costs of and environmental damage caused by waste chemicals. acknowledgements this research was supported by the european union and the state of hungary, and co-financed by the european social fund in the framework of támop 4.2.4. a/211-1-2012-0001 ‘national excellence programme’. references [1] straka f., doucha j., lívansky k.: utilisation of flue gas for cultivation of microalgae (chlorella sp.) in an outdoor open thin-layer photobioreactor, j. appl. phycology, 2005, 17(5), 403-412 [2] olaizola m.: microalgal removal of co2 from flue gases: changes in medium ph and flue gas composition do not appear to affect the photochemical yield of microalgal cultures, biotechn. bioproc. engng., 2003, 8(6), 360-367 [3] lamenti g., prosperi g., ritorto l., scolla g., capuano f., pedroni p.m., valdiserri m.: enitecnologie r&d project on microalgae biofixation of co2: outdoor comparative tests of biomass productivity using flue gas co2 from a ngcc power plant, proc. 7th int. conf. greenhouse gas control technologies, 2005, 2(1), 1037-1042 [4] carlsson a.s., bilen j.b., möller r., clayton d.: mircroand macroalgae: utility for industrial applications, ed.: bowles d., outputs from the epobio project. cpl press, berks, uk, 2008 [5] briggs m., vasudevan p.t.: biodiesel production-current state of the art and challenges, j. ind. microbiol. biotechnol., 2008, 35, 421-430 [6] hwang e.j., shin h.s., chae s.r.: single cell protein production of euglena gracilis and carbon dioxide fixation in an innovative photobioreactor, bioresource technol., 2006, 97(2), 322-329 [7] becker e.w., baddiley j.: microalgae: biotechnology and microbiology, cambridge univ. press, new york, usa, 1994, p. 178 [8] posewitz m.c., jinkerson r.e., subramanian v.: improving biofuel production in phototrophic microorganisms with systems biology tools, biofuels, 2011, 2(2), 125-144 figure 4: the energetic consideration of selected separation processes (the dashed line shows the energy content of algae suspensions on average of 25 mj m-3) 118 [9] kojima e., zhang k.: growth and hydrocarbon production of microalgae botryococcus braunii in bubble column photobioreactors, j. biosci. bioengng., 1999, 87(6), 811-815 [10] briggs m.: wide-scale biodiesel production from algae, ph.d. dissertation, university of new hampshire, 2004 [11] hwang e.j., shin h.s., chae s.r.: single cell protein production of euglena gracilis and carbon dioxide fixation in an innovative photobioreactor bioresource technol., 2006, 97(2), 322-331 [12] chisti y.: biodiesel from microalgae, biotechnol. adv., 2007, 25(3) 294–306 [13] dismukes g.c.: algal photosynthesis, princeton university press, princeton, nj, usa 2008 [14] shi d., song d., fu j.: construction of a shuttle vector for heterologous gene expression in escherichia coli and microalgae anabaena, chin. j. biotechnol., 2008, 24(3), 341-348 [15] bocsi r., horváth g., hanák l.,: microalgae production in service of fuel production, hung. j. ind. chem., 2010, 38(1), 9-13 [16] olaizola m., masutani s.m., nakamura t.: recovery and sequestration of co2 from stationary combustion systems by photosynthesis of microalgae, u.s. department of energy, office of fossil energy national energy technology laboratory, pittsburgh, pa, usa, 2006 [17] benemann j., sheehan j., roessler p., dunahay t.: biodiesel from algae, a look back at the u.s. doe’s aquatic species program, nrel report nrel/tp-580-24190, 1998 [18] burlew j.: algae culture: from laboratory to pilot plant, carnegie institute, washington dc, usa 1953 [19] jung i.h., choe s.h.: growth inhibition of freshwater algae by ester compounds released from rotten plants, j. ind. engng. chem., 2002, 8(4), 297-304 [20] shelef g.a., sukenik a., green m.: microalgae harvesting and processing: a literature review, techn. rep., solar energy research institute, 1984 [21] poelman e., pauw n.d., jeurissen b.: potential of electrolytic flocculation for the recovery of micro-algae, res. conserv. recyc., 1997, 19(1), 110 [22] leite g.b., abdelaziz a.e.m., hallenbeck p.c.: algal biofuels: challenges and opportunities, bioresource technol., 2013, 145, 134-141 [23] rawat i., ranjith kumar r., mutanda t., bux f.: biodiesel from microalgae: a critical evaluation from laboratory to large-scale production, appl. energy, 2013, 103, 444-467 [24] dassey a.j., theegala c.s.: harvesting economics and strategies using centrifugation for cost-effective separation of microalgae cells for biodiesel applications, bioresource technol., 2013, 128(2), 241-245 [25] udom i., zaribaf b.h., halfhide t., gillie b., dalrymple o., zhang q., ergas s.j.: harvesting microalgae grown on waste water, bioresource technol., 2013, 150, 513-522 [26] uduman n., bourniquel v., danquah m.k., hoadley a.f.a.: a parametric study of electrocoagulation as a recovery process of marine microalgae for biodiesel production, chem. eng. j., 2011, 174(1), 249-257 [27] beach e.s., eckelman m.j., cui z., brentner l., zimmerman j.b.: preferential technological and life cycle environmental performance of chitosan flocculation for harvesting of the green algae neochloris oleoabundans, bioresour. technol., 2012, 121, 445–449 [28] banerjee c., ghosh s., sen g., mishra s., shukla p., bandopadhyay r.: study of algal biomass harvesting using cationic guar gum from the natural plant source as flocculent, carbohydrate polymers, 2013, 92(1), 675-681 [29] schlesinger a., eisenstadt d., bar-gil a., carmely h., einbinder s., gressel j.: inexpensive non-toxic flocculation of microalgae contradicts theories; overcoming a major hurdle of bulk algal production. biotechnol. adv., 2012, 30(5), 1023–1030 [30] jungmin k., byung-gon r., kyochan k., bokyong k., jong-in h., ji-won y.: continuous microalgae recovery using electrolysis: effect of different electrode pairs and timing of polarity exchange, bioresource technol., 2012, 123(2), 164-170 [31] mascia m., vacca a., palmas s.: electrochemical treatment as a pre-oxidative step for algae removal using chlorella vulgaris as a model organism and bdd anodes, chem. enging. j., 2013, 219(5), 512-519 [32] lee a.k., lewis d.m., ashman p.j.: harvesting of marine microalgae by electroflocculation: the energetics, plant design, and economics, appl. energy, 2013, 108(3), 45-53 [33] amer l., adhikari b., pellegrino j.: technoeconomic analysis of five microalgae-to-biofuels processes of varying complexity, bioresource technol., 2011, 102(20), 9350–9359 [34] edzwald j.k.: algae, bubbles, coagulants, and dissolved air flotation, water sci. technol., 1993, 27(10), 67–81 [35] nurdogan y., oswald w.j.: tube settling of high-rate pond algae, water sci. technol., 1996, 33(7), 229–241 [36] collet p., hélias a., lardon l., ras m., goy r.a., steyer j.p.: life-cycle assessment of a microalgae culture coupled to biogas production, bioresoure technol., 2011, 102(1), 207–214 [37] cowarda t., leea j.g., caldwellb g.s.: development of a foam flotation system for harvesting microalgae biomass, algal research 2013, 2(2), 135-144 microsoft word a_56_baladincz_r.doc hungarian journal of industrial chemistry veszprém vol. 39(1) pp. 7-13 (2011) investigation of the hydroconversion of lard and lard-gas oil mixture on ptpd/usy catalyst p. baladincz , cs. tóth, s. kovács, j. hancsók university of pannonia, department of mol hydrocarbon and coal processing h-8201 veszprém egyetem str. 10, hungary e-mail: baladinczp@almos.uni-pannon.hu the necessity to maintain mobility and the increasing energyand environmentally sound demands necessitated the research, development and utilization of engine fuels from renewable resources. because of the negative features of the already and generally applied bio-derived diesel fuel, the biodiesel, it was necessary to research and develop other chemical processes that convert triglycerides through different reaction ways. these second generation bio-fuels are the bio gas oils, which are mixtures of nand i-paraffins. otherwise these hydrocarbons are the choice components of the fossil derived diesel fuels. during the experimental work our aim was to investigate the heterogeneous catalytic hydrogenation of waste lard – as a renewable agro-derived feedstock – and by mixing it to deep desulphurized gas oil stream, respectively on ptpd/usy catalyst. in the course of it, we studied the effects of the process parameters (temperature: 300–380 °c, pressure 40-60-80 bar, lhsv: 0.75–1.25 h-1, h2/feedstock rate: 600 nm3/m3) on the quality and quantity of the products. we determined that during the co-processing of lard and desulphurized gas oil, the saturation of the aromatic content and the deoxygenation of the triglyceride part of the feedstock -isoparaffins formed took place, respectively and at process temperatures (360–380 °c) found to be favourable by us, excellent, bio-component containing and significantly dearomatized diesel fuel blending components could be obtained. these products meet the valid diesel gas oil standard en 590:2009+a1:2010, except for their cold flow properties. keywords: lard, hydrogenation, ptpd/usy, zeolite, coprocessing, renewable. introduction mobility is a keystone of great importance in the modern human society. it is essential for maintaining and developing the economy and thus the standard of living, and for meeting the social demands. the material equipment of mobility is the vehicles, nowadays almost every one of them (>95%) operates with fossil derived fuels. the limited amount and the unequal distribution of the available oil reserves is a source of international tensions, therewith to ensure the life standard of their citizens, most countries rely on import. besides, there are more and more vehicles, so to ensure the mobility means more and more intense environmental pollution. for this reason, on the whole world research has started for the development and utilization of cleaner and more available energy sources. among these alternative fuels, there are the renewable, agricultural-derived fuels from biomass and amongst them the bio-derived motor fuels (agro-motor fuels). bio-derived motor fuels in the european union because of environmental consideration and its intense rely on import energy sources (>55%) the european union treats the research of agriculture-derived, renewable energy sources with great attention and urges their utilization in greater volumes [1–3], besides attending the agricultural production too. the 2003/30/ec directive is the first where the european union literally declared the necessity of the production of bio motor fuels and their extensive utilization [1]. as an effect of this, the diesel fuel standards validated from 2004 allow the blending of bio-components (biodiesel maximum 5 v/v%, then 7 v/v% from 2009). the european council in the com(2006) 34 strategy of the union announced seven political keystones and one of them is the effort to expand the feedstock supplies of bio motor fuels [5]. besides this, the european union in the com(2006)845 report specified those steps which must be taken in the interest to increase the 1% share of bio-derived automotive fuels to 10% till 2020. in this report it was determined that the research and development of the second generation bio motor fuels could help to boost the innovation and to preserve the competitiveness of the european union in the renewable energy sector, and 8 also, with the partial utilization of the second generation bio motor fuels the goal becomes achievable [3]. in the 2009/28/ec (ren – renewable energy directive) directive of the european union, the european council confirmed the content of the com(2006)845 report, namely that the average share of the renewable energy sources must be raised to 20% until 2020, and in it the average content of renewable fuels must be raised to 10% in all automotive fuels in the european market until 2020. besides, it affirms that the suggested blending amount of bio fuels must be set at minimum 5.75% until 2010 calculated on the basis of the energy content [3]. the valid 2009/30/ec (fqd – fuel quality directive) directive specifies to decrease the ghg emission of the transportation sector with 6%, and to suit it, the valid diesel fuel standard got the supplement a1 [4]. therefore in the currently valid en 590:2009+a1:2010 diesel gas oil standard the blendable amount of biodiesel was increased from 5 v/v% to 7 v/v%. thus the suggested blending amount – 5.75% until 2010 – urged by the european committee became achievable. among the motor fuels, the use of diesel-fuels decreased at present as a consequence of the worldwide economic crisis, but the long-distance tendency shows increase such as the total use of motor fuels increases and within it the share of the middle distillates increases. before the worldwide economic crisis, the tendency of the automotive fuel market in the european union showed a probable increase in the demand [8] for diesel fuels and this tendency will restore in contempt of the feasible spread of hybrid vehicles. therefore the research and development of the agriculture-derived bio motor fuels is coming to the front. triglycerides and their derivatives the main constituents of the vegetable oils and animal fats are the triglycerides, which are esters of a polyvalent alcohol, the glycerine, and fatty acids with different carbon number (fig. 1). since they are natural triglycerides, their carbon number of the chain is always paired and they contain unsaturated bonds in different measure. for the sake of satisfying the continuously increasing gas oil demand, vegetable oils and their different percentage mixtures with gas oil are attempted to be utilized. however the differences between the physical and utilization properties of the vegetable oils and the conventional diesel fuels do not permit to simply replace the conventional gas oils with vegetable oils [6]. therefore it is necessary to convert them with different conversion pathways. these conversion pathways can be: ● thermal and ● catalytic pathway. in practice, the more important is the latter one. from these types of conversions the most important ones are the esterification (specifically esterification with alcohols) and the hydrogenating with motor fuel purpose. biodiesel nowadays, the agriculture-derived bio motor fuel and bio blending component that is produced and utilized in the greatest volume is the fame (fatty-acid-methylester) or biodiesel from the first generation biofuels. this is made by the catalytic esterification of vegetable oils and other fats. however the technologies producing biodiesel and the product itself also have numerous disadvantages [7]: ● high unsaturated content (causing bad thermal-, oxidation-, and thus storage stability), ● high water content (corrosion problems) ● sensitivity to hydrolysis (poor storage stability), ● methanol content (toxic), ● reactive oh-group (corrosion of coloured metals), ● low energy content that results in greater fuel consumption (~10–15%), ● unfavourable cold properties (cold-start and pulverizing, cfpp). ● high production costs compared to the applicational value, etc. bio gas oil the most suitable for the utilization in diesel engines and the most valuable compounds of the fossil derived gas oils are the normaland iso-paraffins with high cetane number and with good cold flow properties. [7–11], therefore intense research has started to produce products with similar chemical structure on triglyceride (as a renewable agriculture-derived feedstock) base. one of the alternatives to produce such a product rich in iso-paraffins on triglyceride base is the catalytic hydrogenation and if necessary, their isomerization. then the conversion of triglycerides to a product rich in iso-paraffins is recommended by multistage catalytic process (fig. 1). catalyst hydrogen, t, p n-parraffins i-parraffins oxygen containing compounds byproducts:vegetable oil (triglycerides) co + co2 + ch4 + c3h8 + h2o figure 1: the reaction pathway of the bio gas oil production (r1,r2,r3: carbon chains with c11-c23 carbon number) through the reaction pathway, in the first step the hydrogenating of the unsaturated bonds of the triglycerides takes place. then deoxygenating reaction occurs. in this reaction, monoglycerides and carboxylic acids form and then these intermediates are converted to paraffins by three different pathways: decarboxylation, decarbonylation and hydrodeoxigenation (reduction, hdo). as the next possible step in the process isomerization reactions can occur, of which measure depends on the applied catalyst 9 and process parameters. cracking reactions may occur in the course of the whole process [8–12]. the product of the reaction is the so called bio gas oil, of which concept was introduced by the mol department of hydrocarbon and coal processing of the university of pannonia [13–14]. according to its definition, the bio gas oil is a mixture of nand i-paraffins in the gas oil boiling point range, made with specific catalytic hydrogenating process of raw materials with high triglyceride content (vegetable oils, animal fats, used frying oils, brown greases of sewage works etc.). to produce bio gas oil and products containing it, there are different technological methods according to our experiments and the literature data. it is possible to pre-treat the triglyceride containing feedstock in a pretreater reactor and then hydrodeoxygenate it, in other words convert it in a second hdo reactor. the obtained product in this technology is rich in normal-paraffins, has very high cetane number (90–105) but besides it, the product needs to be isomerized after the separation to improve its poor cold flow properties (18–26 °c). the bio gas oil obtained with such technology can be blended to deeply desulphurized gas oil stream and thus gas oil with bio-component content can be made. beyond that, through blending the pre-treated triglyceride containing feedstock to a straight run gas oil stream and process this feedstock mixture in an existing (or slightly modified) desulphurization plant, bio-component containing gas oil can be obtained (fig. 2) [9–13]. figure 2: possible technological solutions to produce bio gas oil as we aforementioned, a wide range of publications engage in the examination of the conversion of triglycerides per se, or the so called co-processing. however these articles deal mostly with the applicability of desulphurization catalysts (nimo/al2o3, como/al2o3). the applicability of ptpd/usy catalyst examined in this paper, as we know, have never been published so far. because of its strongly acidic support, this catalyst may be favourable of the skeletal isomerization of the forming n-paraffins, namely for the oxygen removal in one step and for the cfpp improvement via isomerization, too. experimental during our experimental work our aim was to investigate the possibility of converting properly prepared lard as an agriculture-derived, triglyceride containing renewable feedstock, to bio gas oil on ptpd/usy catalyst. in the course of it, the possibility of processing lard was investigated to make a product which can be utilized in diesel-engines by itself or as a bio-blending component to conventional gas oils. therefore we investigated the possibilities of heterogeneous catalytic conversion of pure (100%) lard and 50% lard containing deep desulphurized gas oil feedstocks, respectively, on ptpd/usy catalyst. the process parameters were chosen on the basis of our previous experimental results considering the physical and chemical properties of the feedstocks experimental equipment the experiments were carried out on experimental equipment with a tubular reactor of 100 cm3 active volume capacity (fig. 3). the experimental work was carried out in continuous mode. the equipment contains all of the main apparatus of a heterogeneous catalytic hydrogenation plant [12]. liquid product purge gas raw material hydrogen to the gaschromatograph figure 3: experimental equipment applied feedstocks and catalyst as the base stock of the heterogeneous catalytic hydrogenating experiments we used lard (fatty acid composition is in table 1) of hungarian origin and a deep desulphurized gas oil stream (properties in table 2) – derived by mol plc. – obtained from russian crude. as feedstocks we used pure lard, pure gas oil and their mixtures of 50%. as catalyst we applied ptpd/usy catalyst. this catalyst sensible for sulphur containing compounds, that is why we used already deep desulphurized gas oil fraction as our gas oil feedstock. 10 table 1: the typical fatty acid composition of the applied lard feedstock fatty acid lard c14:0 1.19 c16:0 21.35 c16:1 2.04 c18:0 11.54 c18:1 45.40 c18:2 12.50 c18:3 0.78 c20:1 1.06 c22:2 0.67 *cx:y, where x: carbon number of the fatty acid, y: number of the unsaturated bonds in the fatty acids. **other – fatty acids with higher carbon number than c22 table 2: the heteroatom and aromatic content of the feedstocks properties gas oil lard sulphur content, mg/kg 5 20 nitrogen content, mg/kg <1 61 aromatic content, % 22.5 polyaromatic content, % 2.4 0.0 process parameters the series of experiments were carried out at process parameters based on previous experimental results: t: 300–380 °c, p: 40-60-80 bar, lhsv: 0.75-1.25-2.0 h-1, h2/feedstock ratio: 600 nm3/m3. analytical methods the properties of the feedstocks and the products were specified according to the specifications of the valid en 590:2009+a1:2010 diesel fuel standard, and with standardised calculation methods. the obtained liquid organic product’s composition was identified by gas chromatography. obtaining the main product fraction the fractionating of the product mixture was carried out as it can be seen in fig. 4. in the course of the experiments, the product mixture was separated into gaseous and liquid phase in the separator unit of the experimental equipment. after separating the water from the obtained liquid product mixture, we separated the light, c5-c9 hydrocarbon products by distillation up to 180 °c from the organic liquid phase. the fraction above the boiling point of 180 °c was separated to gas oil boiling point range main product (c10-c22 hydrocarbons up to the boiling point of 360 °c) and to residual fraction by vacuum-distillation. all product yields are based on the amount of the feedstock. product mixtures gas phase (co, co2, c3h8, c3h6, c1-c4 hydrocarbons h2s, nh3) water phase organic phase (c5+) light hydrocarbons (c5-c10) gas oil fraction (180-360°c) residue (triglycerides , diglycerides, monoglycerides , hydrocarbons with higher carbon number, carboxylic acids , esters) figure 4: the method of the product fractionating results and discussion the gaseous phase besides hydrogen, contained carbonoxides formed during the deoxygenation, propane originated from the triglyceride molecule, hydrogen sulphide and ammonia formed in the course of heteroatom removal and a very small amount of lighter hydrocarbons (c4-) originated from the hydrocracking reactions. the increasing amount of the lighter hydrocarbons (c4-) in the gaseous phase and mainly the amount of the fraction below boiling point of 180 °c (c5-c10) shows (fig. 5) that the hydrocracking activity of the applied catalyst increased with the temperature. 0 5 10 15 20 25 270 280 290 300 310 320 330 340 350 360 370 380 390 temperature, °c y ie ld o f t he li gh t l iq ui d hy dr oc ar bo n pr od uc ts , % 50% lard gas oil figure 5: yield of the light liquid hydrocarbons (boiling point <180 °c) as function of the temperature (40 bar, 1.25 h-1) 0 5 10 15 20 25 30 35 40 45 270 280 290 300 310 320 330 340 350 360 370 380 390 temperature, °c y ie ld o f t he r es id ua l p ro du ct , % figure 6: yield of the residual fraction as a function of the temperature (40 bar, 1.25 h-1, 50% lard) the decreasing yield of the residual fraction with increasing the temperature (fig. 6) as well as the increasing 11 yield of the main product fraction with increasing the temperature (fig. 7) inform us about the increasing conversion of the triglyceride part of the feedstock. 40 50 60 70 80 90 100 270 280 290 300 310 320 330 340 350 360 370 380 390 temperature, °c y ie ld o f t he m ai n pr od uc t f ra ct io n, % 50% lard gas oil figure 7: the yield of the gas oil boiling point range (180–360 °c) main product as a function of the temperature (40 bar, 1.25 h-1) fig. 8 provides information about how the different deoxygenating reactions take place and about the relationship between them. in the course of the deoxygenation of the natural – and so its is containing fatty acids with conjugated carbon numbers in their carbon chains – triglycerides, during the hydrodeoxygenation (hdo) reaction pathway paraffins with the same carbon numbers as the fatty acids are forming next to water, while in the course of decarboxylation-decarbonylation (dcx) reaction pathways, paraffins with one less carbon numbers as the fatty acids are forming next to carbon oxides.. as it can be seen on fig. 8, the dcx reaction pathway come to the front with increasing the temperature, at the expense of the hdo reaction pathway. 0 0,2 0,4 0,6 0,8 1 1,2 1,4 270 280 290 300 310 320 330 340 350 360 370 380 390 temperature, °c (c 15 +c 17 )/( c 16 +c 18 ) r at io figure 8: the ratio of dcx/hdo reaction pathways as a fiunction of the temperature (40 bar, 1.25 h-1, 50% lard) by increasing the pressure as a process parameter, it can be seen that the yield of the main product fraction decreased in the case of each feedstock (fig. 9). fig. 9 suggests that in the case of pure lard feedstock the conversion is lower than 50% and in the case of the most favourable process parameters only a maximum conversion of about 60% has been achieved nevertheless that the maximum theoretical conversion is about 80.7–85.5%, in the case of dcx-hdo reaction pathway, respectively. based on this, it can be stated, that the applied catalyst is not suitable for the hydrodeoxygenation of pure triglyceride feedstock or at least not at the examined process parameters. however, in the case, of 50% triglyceride containing feedstock, higher conversion of the triglyceride part can be achieved and at process parameters of 380 °c, 40–60 bar and 0.75 h-1 full conversion of the triglyceride part occurs. on fig. 10, it can be seen, that with increasing the pressure, the hdo reaction pathway come to the front, while the dcx reaction pathway declined. 30 40 50 60 70 80 90 30 40 50 60 70 80 90 pressure, bar y ie ld o f t he m ai n pr od uc t f ra ct io n, % 50% lard 100% lard gas oil figure 9: yield of the main product fraction as a function of the pressure (360 °c, 1.25 h-1) 0 0,2 0,4 0,6 0,8 1 1,2 1,4 1,6 1,8 2 30 40 50 60 70 80 90 pressure, bar (c 15 +c 17 )/( c 16 +c 18 ) r at io 50% lard 100% lard figure 10: the ratio of dcx/hdo reaction pathways as a function of the pressure (360 °c, 1.25 h-1) on fig. 11, the yield of the gas oil boiling point range main product fraction can be seen as a function of the liquid hourly space velocity. it can be seen, that with increasing liquid hourly space velocity, the yield of the main product fraction increases in the case of pure gas oil feedstock, while it is decreases in the case of triglyceride or triglyceride containing feedstock, because of the lowering retention time with the increasing liquid hourly space velocity. in the first place, crack reactions decline, and in the case of triglyceride containing feedstocks, the triglyceride conversion decreases. by increasing the liquid hourly space velocity, in the case of pure lard feedstock, the dcx reaction pathway come to the front (fig. 12), while in the case of 50% lard containing feedstock, opposing trend can be seen, namely, the hdo reaction pathway come to the front while the dcx 12 reaction pathway declined. this occurs, because of the different heteroatom content of the feedstocks, as in the case of pure lard, the oxygen content of the feedstock is about 11.6% without detectable aromatic content, while in the case of 50% lard containing feedstock means 5.8% oxygen heteroatom with nearly 12.5% aromatic content from the gas oil part of the feedstock. so, with increasing pressure, different reaction pathways come to the front in the case of different feedstocks. 30 40 50 60 70 80 90 100 0,6 0,8 1,0 1,2 1,4 1,6 1,8 2,0 2,2 lhsv, h-1 y ie ld o f t he m ai n pr od uc t f ra ct io n, % 50% lard 100% lard gas oil figure 11: yield of the main product fraction as a function of the liquid hourly space velocity (360 °c, 60 bar) 0 0,2 0,4 0,6 0,8 1 1,2 1,4 1,6 0,6 0,8 1 1,2 1,4 1,6 1,8 2 2,2 lhsv, h-1 (c 15 +c 17 )/( c 16 +c 18 ) r at io 50% lard 100% lard figure 12: the ration of dcx/hdo reaction pathways as a function of the liquid hourly space velocity (360 °c, 60 bar) to produce up to date diesel gas oils the dearomatization of the feedstocks is necessary too. the decrease of the aromatic content of the gas oils are essential not only because the regulations of the valid standards. with decreasing the aromatic content the cetane number of the gas oil increasing and thus the emission. in the case of a two step desulphurizating and dearomatizating process, the ptpd/usy catalyst examined in this paper can be applied for the second, dearomatizing step. on fig. 13 it can be seen, that at the temperature of 320 °c and above the quantity of the aromatic compounds decreased significantly (fig. 7). this effect shows the increasing hydrogenating activity of the catalyst with increasing temperature. as an affect of the increasing temperature, above 330–340 °c the dearomatization efficiency – on account of the thermodynamical inhibition caused by the exothermal dearomatization reactions – decreased. by applying the most favourable process parameters for dearomatization (340 °c, 40 bar, 0.75–1.25 h-1) a dearomatization efficiency of about 70% is achieved. on fig. 13, it can be seen that in the case of 50% triglyceride containing feedstock, compared with what can be experienced in the case of pure gas oil feedstock, it is turned up, that the most favourable process temperature for achieve the maximum dearomatizing efficiency slightly higher, thanks to the high heteroatom content of the feedstock originated from its triglyceride part. 5 7 9 11 13 15 17 280 300 320 340 360 380 400 temperature, °c a ro m at ic c on te nt o f t he m ai n pr od uc t f ra ct io n, % 50% lard gas oil figure 13: the aromatic content of the main product fractions as a function of the temperature (40 bar, 1.25 h-1, 50% lard) conclusions in this paper we shortly introduced the necessity for the research and development of the bio-derived motor-fuels, the already known bio-derived fuels of diesel-engines and the bio gas oil or bio gas oil containing gas oil producing technologies, respectively. during our experimental work we investigated the heterogenous catalytic hydrogenation of lard, as a renewable agriculture-derived feedstock, deep desulphurized gas oil fraction and their 50% mixture on ptpd/usy catalyst. the properties of the feedstocks and the products were specified according to the specifications of the valid en 590:2009+a1:2010 diesel fuel standard, and with standardised calculation methods. we found that with the applied catalyst, in the case of pure lard feedstock even at the most favourable process parameters (380 °c, 40 bar, 0.75 h-1) only about a conversion of 60% can be achieved. in the case of 50% lard containing feedstock, by applying these favourable process parameters (380 °c, 40 bar, 0.75 h-1) full conversion of the triglyceride part can be achieved, however in the case of this process temperature, the dearomatization efficiency (38.7%) of the gas oil part declined because of thermodynamical inhibition and because of the high oxygen content (5.8%) originated from the triglyceride part of the feedstock. in the case of these process parameters, the cracking activity of the applied catalyst significantly increased too, since the yield of the light liquid hydrocarbons (c5-c10) was about 20%. meanwhile, the yield of the gaseous product did not increase significantly. the cold filter plugging point 13 of the obtained main product fractions at the most favourable process parameters did not decrease below +15°c in the case of 50% lard containing feedstock, because of the high amount of n-paraffins formed during the conversion of the triglyceride part. in the case of 50% lard containing feedstock, at process parameters of 340–360 °c, 40–60 bar and 0.75–1.25 h-1 a main product yield of about 85% can be achieved on the basis of the feedstock and in addition, the aromatic content of the products also decreased significantly. the properties of the main product fractions obtained at these process parameter combinations and in the case of 50% lard containing feedstock meet the valid diesel gas oil standard en 590:2009+a1:2010, besides their cold flow properties (15–17 °c). however these products could be excellent diesel gas oil blending components because their low sulphur-, nitrogen-, and aromatic content, and because their high cetane number (about 75 unit) ensured by the n-paraffins forming during the triglyceride conversion. the cold flow properties of the products are improvable by catalytic hydroisomerization of the nparaffins then with additives. hereby high quality biomotor fuel or bio-derived blending component containing diesel motor fuel could have been obtained which meet the valid diesel gas oil standard en 590:2009+a1:2010. in short, we determined, that by the application of ptpd/usy catalyst in the case of pure lard feedstock, full hydrodeoxygenating conversion of the triglyceride is not achievable, however in the case of mixture feedstock of 50% lard and 50% deep desulphurized gas oil fraction, by applying the favourable process parameters (340–360 °c, 40–60 bar), nearly full conversion of the triglyceride part can be achieved, while the dearomatizing of the gas oil part occurs substantially also. acknowledgement we acknowledge the financial support of this work by the hungarian state and the europen union under the tamop-4.2.1/b-09/1/konv-2010-0003 project. references 1. 2003/30/ec directive „the promotion of the use of biofuels or other renewable fuels for transport”, official journal of the 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kovács, l. boda, l. leveles, a. thernesz, i. wáhlné horváth, j. hancsók: fuel purpose hydrotreating of vegetable oil on nimo/γal2o3 catalyst, hungarian journal of industrial chemistry, 37(2), 2009, 107–111 15. z. varga, j. hancsók, g. nagy, gy. pölczmann: quality improvement of heavy gas oils on nimo and como catalysts, 7th international symposium motor fuels 2006, slovakia, tatranské matliare, june 19-22., 2006, in proceedings (isbn 80-968011-3-9), 328–339 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word a_33_hatos_r.doc hungarian journal of industrial chemistry veszprém vol. 39(1) pp. 157-161 (2011) parameter sensitivity analysis of an induction motor p. hatos, a. fodor , a. magyar university of pannonia, department of electrical engineering and information systems, veszprém, hungary e-mail: foa@almos.uni-pannon.hu a simple dynamic model of an induction motor is presented in this paper based on engineering principles that describe the mechanical phenomena together with the electrical model. the investigated state space model consists of nonlinear state equations and linear output equations. the model has been verified under the usual controlled operating conditions when the speed is controlled. the effect of load on the controlled induction motor has been analyzed by simulation. the sensitivity analysis of the induction motor and the bridge of the inverter have been applied to determine the model parameters to be estimated. keywords: induction machine, dynamic state space model, parameter sensitivity analysis introduction the induction motors are the most commonly used electrical rotating machines in several industrial applications including the automotive industry, too. in the modern adjustable speed induction motor drives inverters are used to drive the three-phase motor as variable frequency voltage or current sources. whatever the size and the application area, these motors share the most important dynamic properties, and their dynamic models have a similar structure. therefore the final aim of our study is to design a controller that can control the speed and the torque of the induction motor. because of the specialties and great practical importance of the induction motor in industrial applications, their modelling for control purposes is well investigated in the literature. besides of the basic textbooks (see e.g. [1-3]), there are several papers that describe the modelling and use the developed models for the design of different types of controllers: vector control [1] and [4], sensor less vector control [5] and direct torque control (dtc) [6]. the aim of this paper is to build a simple dynamical model of the induction motor together with the threephase inverter and analyze the models sensitivity of its parameters. the result of this analysis will be the basis of a subsequent parameter estimation step. the state space model has been implemented in matlab/simulink environment which enables us to analyze the parametric sensitivity based on simulation experiments. the model of the induction motor in this section the statespace model for an induction motor is developed. modelling assumptions for constructing the induction motor model the following assumptions are made: ● symmetrical three phase windings, ● the slotting effect and the copper losses are neglected, ● the permeability of the iron parts is assumed to be infinite with linear magnetic properties, ● flux density is radial in the air gap, ● the spatial distribution of fluxes and apertures wave are considered to be sinusoidal, ● the spatial distribution of the stator fluxes and apertures wave are considered to be sinusoidal. according to the above modeling conditions the mathematical description of the induction motor is developed through the space vector theory. if the voltage of the stator is presumed to be the input excitation of the machine, then the spatial distribution along the stator of the x phase voltage can be described by the complex vector usx(t). we can determine the orientation of the voltage vector us the direction of the respective phase axis and the voltage polarity. (2.1) (2.2) 158 (2.3) , (2.4) where a = ej120° in equation (2.1) 2/3 is a normalizing factor. the flux density distribution can be obtained by integrating the current density wave along the cylinder of the stator. the flux linkage wave as a system variable, because it contains detailed information about the winding geometry. the rotating flux density wave induces voltages in the individual stator windings. thus stator voltage us(t) can be represented in the overall distributed voltages in all phase windings: (2.5) (2.6) (2.7) (2.8) considering the stator of the induction machine as the primer side of the transformer, then using the kirchoff’s voltage law the following equation can be written: (2.9) figure 1: the equivalent circuit of the induction motor as for the secondary side of the transformer, it can be deduced that the same relationship is true for the rotor side space vectors: (2.10) equations (2.9) and (2.10) describe the electromagnetic interaction as the connection of first order dynamical subsystems. since four complex variables (is(t), ir(t), ψs(t), ψr(t)) are presented in these two equations, (2.1) and (2.5) flux equations are needed to complete the relationship between them. (2.11) (2.12) where angle ρ(t) defines the position of the rotor compared to the axis of the stator, while and are the three-phase inductances and ls, lr are the inductances of a stator and a rotor phase winding, lm = 3/2*lm is the mutual inductance between the stator and the rotor. by applying the following substitutions: (2.13) (2.14) then the following equations are obtained with the flux connections in the model: (2.15) (2.16) the mechanical energy pmech(t) of the system can be defined as: (2.17) where the mechanical energy wmech(t) in case of rotating motor can be given by: (2.18) on the other hand, there is another expression for the mechanical energy: (2.19) where is the input electric power, is the resistive power loss, and is the air gap power. using the above equations it can be concluded that: (2.20) the transformer can be decomposed into d-axis and q-axis. park’s transformation converts the equations to a simplified and more tractable form. figure 2: the equivalent circuit of the d axis of the induction motor figure 3: the equivalent circuit of the q axis of the induction motor the actual terminal voltage v of the windings can be written in the following form 159 (2.21) where ij are the currents, rj are the winding resistances, and ψj are the flux linkages. assume, that the positive directions of the stator currents point out of the induction motor terminals. by considering the d-axis and the q-axis of the induction motor, the following equations can be written: (2.22) (2.23) (2.24) (2.25) , (2.26) where ω is the reference frame angular velocity and ωr is the electrical angular velocity. (2.27) (2.28) (2.28) (2.29) the above model can be summarized in a statespace model by expressing the fluxes from the voltage equations. parameter sensitivity analysis thirteen parameters of the state space model of the induction motor and the bridge have been selected for sensitivity analysis (collected in table 1), and the sensitivity of the state variables: voltage, phase a current, speed, electric torque, and outputs has been investigated for all of them by means of matlab/simulink dynamical simulation. some simulation results are shown in figs 4-7. the blue signal represents the simulation result with the nominal parameter values and the red signal represents the simulation result with the modified parameter values. fig. 4 shows the model responses for changing a critically sensitive parameter (stator self inductance ls). it is apparent, that the speed diverges even for a 10% change of the parameter value. it can be seen that the speed of the motor becomes minus infinity and the electronic torque is zero. the case of a sensitive parameter (stator resistance rs) can be seen on fig. 6. table 1: the parameters of the induction motor and the bridge parameter initial value dimension name of the parameter rs 0.435 ohm stator resistance lls 0.002 h stator leakage inductance rr 0.816 ohm rotor resistance llr 0.002 h rotor leakage inductance m 0.0693 h mutual inductance p 2 number of pole pairs in 0.089 kg·m2 inertia of the motor ed 1000 v voltage of the inverter rsn 105 ohm resistance of the snubber circuit csn 1010 f capacitor of the snubber circuit rbr 10-3 ohm resistance of the bridge ls m+lls h stator self inductance lr m+llr h rotor self inductance 160 figure 4: the -10% changing of parameter ls figure 5: the +50% changing of parameter m figure 6: the -90% changing of parameter rs figure 7: the -90% changing of the resistance of the snubber circuit 161 as a result, the model parameters have been partitioned to four groups: ● critically sensitive: the self inductance of the rotor widings (lr) and the self inductance of the stator widings (ls) ● sensitive: the inertia (in) and the resistance of the stator (rs) ● less sensitive: the stator leakage inductance (lls) and the resistance of the rotor (rr), the rotor leakage inductance (llr) and the mutual inductance (m) ● not sensitive: the resistance of the bridge (rbr ), the capacitor of the snubber circuit (csn) and the resistance of the snubber circuit (rsn). conclusions and future works based on the results presented here, it is possible to select the candidate parameters for model parameter estimation based on real data that is a further aim of the authors, the four parameters are rotor self inductance (lr), stator self inductance (ls), inertia and rotor resistance (rs). the final aim of is to develop a simple yet detailed state space model of the induction motor for control purposes which gives us the possibility to develop and analyze different control strategies for the induction motor. acknowledgement we acknowledge the financial support of this work for the hungarian state and the european union under the tamop-4.2.1/b-09/1/konv-2010-0003 project. references 1. p. vas: artifical-intelligence-based electrical machines and drives, oxford university press, (1999) 2. p. vas: sensorless vector and direct torque control, oxford university press, (1998) 3. l. zheng, j. e. fletcher, b. w. williams, x. he: dual-plane vector control of a five-phase induction machine for an improved flux pattern, ieee transaction on industrial electronics, 55(5), (2008), 1996–2005 4. e. levi: impact of iron loss on behavior of vector controlled induction machines, ieee transaction on industry applications, 31(6), (1995), 1287–1296 5. m. hasegawa, k. matsui: robust adaptive fullorder observer design with novel adaptive scheme for speed sensorless vector controlled induction motors, ieee-iecon, (2002) 6. t. geyer, g. papafotiu, m. morari: model predictive direct torque control—part i: concept, algorithm and analysis, ieee transaction on industrial electronics, 56(6), (2009), 1894–1905 7. h. m. emara, w. elshamy, a. bahgat: parameter identification of induction motor using modified particle swarm optimization algorithm, ieee international symposium on industrial electronics 2008, 841–847 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 /colorconversionstrategy /cmyk /dothumbnails false /embedallfonts true /embedopentype false /parseiccprofilesincomments true /embedjoboptions true /dscreportinglevel 0 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice hungarian journal of industry and chemistry vol. 45(2) pp. 9–12 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0013 modelling the partial demineralization process of cow milk by superpro designer attila csighy,* andrás koris, and gyula vatai department of food engineering, szent istván university, ménesi út 44, budapest, 1118, hungary milk and dairy products contain a number of biologically active compounds (proteins, lipids, vitamins and minerals) that are essential for human nutrition. the most common procedures for demineralization are based on ion exchange-, nanofiltrationand electrodialysis-based technologies. in this study, the application of membrane filtration-based partial demineralization of cow milk was investigated and the process modelled. using design equations, the partial demineralization process was designed and the economy of the process calculated. the modelling and simulation of the partial demineralization process was carried out by the superpro designer programme. as the first step the unit operations of the demineralization technology were defined using the tools of the programme. the superpro designer possesses industrial tools with reactor models, chemical components, a database of mixtures, and price estimations. by analysing the influence of the operation parameters, the feasibility of the proposed process was investigated. from the results of the modelling it can be concluded that the partial demineralization process can be successfully implemented, achieving the expected demineralization rates with a relatively good payback time of two years. keywords: partial demineralization, superpro designer, modelling, economic analysis 1. introduction dairy products play an important role in the health of humans as milk contains a number of biologically active compounds (proteins, lipids, vitamins and minerals). therefore, the consumption of milk and dairy products is highly recommended [1-2]. milk is the main raw material in the cheese and casein industry. the disposal of whey creates a major environmental problem for the cheese industry due to the high amount of organic compounds it contains. in the cheese industry to manufacture 1 kg of cheese, 9 kg of whey is produced as a by-product. whey possesses a large ‘biochemical oxygen demand’ (bod) value, therefore, treatment is required before it is released into the environment or recycled. suárez [3] observed that the nanofiltration membrane is an effective medium for the demineralization of whey. the demineralization efficiency depends on the transmembrane pressure and the volume concentration ratio (vcr). experimentally, monovalent ions exhibit the highest degree of permeation. [3] whey is a watery, dilute liquid, which generally contains 0.8-1.0% total protein, 4.5-5.0% lactose, 0.50.7% minerals and 93-94% water. whey can be divided into two different compositions, namely sweet and acid whey [4]. another process as part of the treatment of whey is demineralization. upon demineralization, whey *correspondence: csighy.attila@gmail.com can be used for manufacturing drinks, desserts or icecream products. a novel alternative process for demineralization is nanofiltration. nanofiltration is a membrane separation method that lies between ultrafiltration and reverse osmosis. nanofiltration membranes can maintain monovalent ions (nacl) and also organic compounds between 300 and 100 in the dalton range. nanofiltration is an effective technique to remove salts, while preserving valuable components [5]. in order to examine the feasibility of the process, technological and economic experiments were carried out by the superpro designer software [6]. this programme is widely used in the pharmaceutical, biotechnology and food industries. the superpro designer is capable of preparing technological and economic documentations and reports about the modelled process. the programme possesses an industrial tool, where the unit operations (reactions, solid/liquid separation, tanks) can be prepared [7]. the purpose of this study is to model the demineralization process using the superpro designer programme and by analyzing the influence of the operation parameters, the feasibility of the proposed process was investigated. 2. experimental 2.1. materials and methods in this study, one ultrafiltration (uf) and two nanofiltration (nf) membranes were used. the first step was the pre-concentration of milk using the uf csighy, koris, and vatai hungarian journal of industry and chemistry 10 membrane. a schumasiv type 100 nm pore size membrane was used for the pre-concentration phase, a schumasiv type 5 nm pore size membrane for nanofiltration of the ultrafiltration retentate, and a membralox type 5 kda membrane for nanofiltration of the ultrafiltration permeate. the experiments were carried out using ultraand nanofiltration units in a laboratory unit designed by the department of food engineering. the effective area of the membranes was 0.005 m2. the milk sample was circulated at a constant temperature (21±1 ºc) maintained by a thermostat. the optimal working parameters were measured during an experimental design in both the uf and nf processes. during the uf process the transmembrane pressure was 1.5 bars and the recirculation flow rate was 150 dm3 h-1. in both nf processes, the transmembrane pressure was 2 bars and the recirculation flow rate was 200 dm3 h-1. the transmembrane pressure and the recirculation flow rate were controlled by regulating valves. 2.2. process simulation the partial demineralization process was modelled using superpro designer software version 8.5 by intelligen, inc. the main target task was partial demineralization. the superpro designer software possesses an industrial tools section, where models of reactors, chemical components, a database of mixtures, price estimations and economic evaluations can be used. the parameters used were calculated from laboratory experiments as shown in table 1. firstly, the superpro designer tool was used to install the unit operations. the first unit is the ultrafiltration system. the raw milk enters the system and is separated into its permeate and retentate. in the next step, the two fractions are transferred to each diafiltration unit. another major step is the definition of essential material streams for milk, the addition of distilled water to the diafiltration unit and the provision of electricity. the diafiltrated, partially demineralized milk and whey components are then sent to the storage tank. the last part of the process is the packaging system, where the products are completed. the demineralized whey is finally loaded into a truck. the mass of the filled entity is 40 metric tons (mt). the basic process flow diagram of the combined partial demineralization of cow milk is shown in fig. 1. the composition of the milk was defined as illustrated in table 2. in the next step, the transmembrane pressure, flow rate and flux as operating parameters were set and the cost of purchase assigned to each operating unit. the annual operating time is 300 days for this process. the cost of purchase of the ultrafiltration system was set at $100k, the two diafiltration units at $75k, the storage table 1. the characteristics of the membranes used. membrane type process parameters pressure, bar flow rate, dm3 h-1 uf (100 nm) 1.5 150 nf (5 kda) 2.0 200 nf (5 nm) 2.0 200 figure 1. process flow diagram of the demineralization of cow milk. table 2. the composition of the cow milk considered ingredient’s name mass (%) casein 3.4 fats 3.4 lactose 5.2 sodium chloride 1.0 water 87 modelling the partial demineralization process of cow milk 45(2) pp. 9–12 (2017) 11 tanks at $75k, and the packaging unit at $50k. in addition, the cost of raw materials was set at $1/kg, of packaging material at $0.1/piece (100g), and of water at $0.1/kg. the product must be sold at a price that is in line with the market conditions (est. $2.2/kg). each unit operation needs a minimum of one operator, thus the cost of labour was set at a basic rate of $10 per hour. the electricity, cooling and heating energy demands were estimated by the programme (table 3). 3. results and analysis upon the establishment of costs, technological and economic simulations were executed. the summary of the run simulations for the partial demineralization process yielded the relevant costs, revenue and payback time as shown in table 4. according to the simulation results, the annual total revenue is higher than the operating costs. the production costs are given with and without amortization. table 5 summarizes the indices of the project. the ‘payback time’ or ‘return on investment’ (roi) for the partial demineralization process in this case was calculated for four years. the roi is defined by eq. (1): roi (%) = annual net profit capital cost ·100 (1) other important parameters were the ‘internal rate of return’ (irr) before and after tax. the irr is a discount value when the ‘net present value’ (npv) is zero. the npv is determined by calculating the costs and benefits of the technological investment. the npv is defined by eq. (2): npv (usd) = ∑ �t (���)t − �� (2) where ct is the cash flow, t is the lifetime in years, d is the discount rate, and c0 is the initial investment. if the npv remains positive, the process will be economically viable [8]. the costs of materials and supplies are shown in table 6 with the most expensive item being the raw material (cow milk) while the cost of packaging materials is far less. table 7 presents the total cost of the plant for the demineralization process. in addition to purchasing the equipment, other costs were the piping, instrumentation, and electrical, building and construction fees. according to the simulated revenues of the partial demineralization process, the production of milk and lactose solution cost $2.2 and $0.3 per kg, respectively. assuming that the demineralized whey is transferred into a truck, it can be sold to food industries for $40 per metric ton. the composition of the demineralised whey in the form of lactose solution is 4.3% lactose, 0.8% nacl and 95% water, which is suitable for the production of candy, yoghurt and ice cream. it is also important to consider the cost of waste treatment. the superpro designer generated two different costs, namely those of utilities ($25k) and transportation ($874k). 4. conclusion this study examined the feasibility of the partial demineralization process which was successfully table 5. summary of project indices (irr = internal rate of return, npv = net present value). gross margin, % 6.78 return on investment, % 24.90 payback time, years 4.02 irr before tax, % 28.36 irr after tax, % 18.20 npv (at 7.00%) 5,381,025 table 6. summary of the costs of materials (in usd per kg annually). raw materials unit amount cost milk $1.00 21,766,316 21,766,316 water $0.10 10,879,641 1,087,964 packaging material $0.20 10,800,661 2,160,132 total 25,014,412 table 7. total cost of the plant (in thousands of usd). equipment purchase $563k installation $266k process piping $197k instrumentation $225k insulation $17k electrical $56k buildings $253k yard improvements $84k auxiliary facilities $225k engineering $472k construction $66k table 3. cost estimates for energy supplies energy supplies price steam (high p) [242 ℃] $10/mt steam [152 ℃] $6/mt chilled water [5 ℃ 10 ℃] $0.4/mt cooling water [25 ℃ 30 ℃] $0.05/mt std. power $0.1/kwh table 4. summary of economy indices (mp stands for “flow of discrete entity”). total investment $6,279,438 total annual revenue $30,315,042 annual operating cost $28,258,168 annual unit production reference rate (mp entity) $10,800,660 unit product cost (per mp entity) including depreciation $2.62 excluding depreciation $2.59 csighy, koris, and vatai hungarian journal of industry and chemistry 12 modelled by the superpro designer software. according to an economic evaluation, the net present value, return on investment, and internal rate of return were $5.3million for four years, 28% and 18%, respectively. the revenues of the products were $2.2 per unit and $0.3 per kg (or $40 per metric ton) for the milk and lactose solution, respectively. future research will focus on the optimization of costs and exploration of alternative ways of recycling whey. acknowledgement the research was supported by the doctoral school of food sciences at szent istván university. references [1] csapo, j.; csapone, k.zs.: milk and dairy products in food consumption (mezőgazdasági kiadó, budapest) 2002 (in hungarian) isbn 963 9358 68 1 [2] mass, s.; lucot, e.; gimbert, f.; crini, n.; badot, p.m.: trace metals in raw cow’s milk and assessment of transfer to comté cheese, food chem., 2011 129(1), 7–12 doi: 10. 1016/j.foodchem.2010.09.034 [3] suárez, e.; lobo, a.; álvarez, s.; riera, f.a.; álvarez, r.: partial demineralization of whey and milk ultrafiltration permeate by nanofiltration at pilot-plant scale, desalination, 2006 198(1-3), 274–281 doi 10.1016/j.desal.2005.12.028 [4] tsakali, e.; petrotos, k.; alessandro, a.d.; goulas, p.: a review on whey composition and methods used for its utilization for food and pharmaceutical products, proc. 6th int. conf. simul. modelling food bioind., 2010 (cimo research centre, bragança, portugal) pp. 195-201 [5] pan, k.; song, q.; wang, l.; cao, b.: a study of demineralization of whey by nanofiltration membrane, desalination, 2011 267(2-3), 217–221 doi 10.1016/j.desal.2010.09.029 [6] mel, m.; yong, a.s.h.; avicenna; ihsan, s.i.; setyobudi, r.h.: simulation study for economic analysis of biogas production from agricultural biomass, energy procedia, 2015 65, 204-214 doi 10.1016/j.egypro.2015.01.026 [7] flora, j.r.v.; mcanally, s.a.; petrides, d.: treatment plant instructional modules based on superpro designer® v.2.7, environ. model. software, 1998 14(1), 69–80 doi 10.1016/s13648152(98)00059-0 [8] kwan, t.h.; pleissner, d.; lau, k.y.; venus, j.; pommeret, a.; lin, c.s.: techno-economic analysis of a food waste valorization process via microalgae cultivation and co-production of plasticizer, lactic acid and animal feed from algal biomass and food waste, biores. technol., 2015 198, 292–299 doi 10.1016/j.biortech.2015.09.003 microsoft word 00.00 inner cover.docx hungarian journal of industry and chemistry vol. 43(1) pp. 19–23 (2015) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2015-0004 evaluation of the heavy metal content of the upper tisza river floodplain soils over the last decade zoltán győri,1* norbert boros,2 péter sipos,2 emese bertáné szabó,2 katalin kovács,3 márk horváth,3 anita takács,3 and györgy heltai3 1 institute of regional economics and rural development, szent istván university, páter k. u. 1, gödöllő, 2100, hungary 2 institute of food science, university of debrecen, böszörményi u. 138, debrecen, 4032, hungary 3 department of biochemistry and chemistry, szent istván university, páter k. u. 1, gödöllő, 2100, hungary in early 2000, two contamination events at baia mare first and baia borsa second involving large amounts of toxic elements impacted the hungarian section of the river tisza with disastrous ecological and economical impacts. we evaluated the sortand long-term effects of this pollution by determining the total and bioavailable concentrations of potentially toxic metals from soil samples collected along the tisza (tivadar, vásárosnamény, rakamaz, and tiszacsege) in 2000 and between 2011 and 2013. the current and previous results were compared in respect of copper and lead contents. keywords: river tisza, floodplain soils, heavy metal pollution, lakanen-erviö extraction, nitric acid/peroxide extraction 1. introduction there were intensive cu, zn, pb, au, and ag mining activities during early 2000 in the catchment area of the river tisza [1]. in the last two decades of the previous century, the processing of tailings pond using cyanide was popular as a recovery technology. the resulting wastewaters contain fine-grained sediments with heavy metal contents [2]. in early 2000, two contamination events (at baia mare first and baia borsa second) involved the release of large amounts of toxic elements that impacted the hungarian section of the river tisza with disastrous ecological and economical consequences. the first one released 100,000 m3 wastewater that contaminated with cyanide and heavy metals the river tisza via its tributary lápos-szamos. the second disaster sent about 20,000 tons of mud containing heavy metals into the river lápos-tisza along with a simultaneous flood settling, forming a layer of approximately 5-10 cm in depth on the pre-existing soil [3-8]. metals were primarily bound to floating material and deposited in floodplain areas. the metal pollution of the floodplains was also observable [9, 10]. the environmental risk of this type of soil contamination is that the buffer capacity of new layer is smaller than the previously and the potential *correspondence: gyori.zoltan@gtk.szie.hu decreases in ph enhance metal bioavailability and toxicity. the mobility and phytoavailability of metals depend on their chemical forms [11]. the speciation justifies the use of sequential extraction method (sep) for analyzing these soil samples. considering the above information, it is likely that the residual heavy metal load may entail economic effects that cannot be envisaged at the moment as the valley of river tisza is under agricultural use (pastures, meadows, orchards, and arable land). this is the reason why intensive research has aimed at testing and monitoring the ecological systems of both water and floodplains. this paper presents only the vertical distribution and forms of heavy metals in polluted areas, although plant relations were also examined [6]. the aim of this study was to evaluate the effects of these sources of pollution on the total and bioavailable metal contents of soil samples collected in 2000 and between 2011 and 2013 from floodplains and pastures along the tisza (tivadar, vásárosnamény, rakamaz, and tiszacsege) and compare these results to earlier ones. 2. materials and methods soil samples were collected in 2000 after the flood and in april 2011 and september 2013 by deep drilling using a nordmeyer drill (nordmeyer holland, overveen, the netherlands). we sampled the 3 m-deep soil layer in triplicates. sampling sites are represented in table 1. győri, boros, sipos, bertáné-szabó, kovács, horváth, takács, heltai hungarian journal of industry and chemistry 20 soil samples were air dried and sieved (< 2 mm) for further analysis. the chemical analysis was carried out in accordance with a hungarian standard [12], using hno3h2o2 digestion, which yields total elemental contents. the extraction of the easily available metal contents was conducted according to lakanen and erviö [13]. sequential extractions were performed to determine the concentration of metals associated with different operationally defined soil fractions, in the course of which, stronger and stronger extractants are used to remove metals from the sample. in this case the mcgrath method [14] was used, which uses 0.1 m cacl2 to determine water soluble and exchangeable metal fractions, 0.5 m naoh to determine the fraction of metals bound to organic matter; 0.05 m na2edta to determine metals bound to carbon and finally, destruction using aqua regia determines the residual fraction. in order to obtain the standard data we used a merck-made (e. merck, darmstadt, germany) analytical grade hno3 (65%) solution. merck and bdh standard solutions were used to prepare the stock solutions, and reanal (budapest, hungary) solid chemicals were used. ultrapure water was used to prepare the solutions (millipore, paris, france). samples were analysed using an inductively coupled plasma optical emission spectrometer (icpoes) to determine cu content (perkin-elmer optima 3300 dv; perkin-elmer ltd., shelton, usa). the pb content was measured by a qz 939 gf-aas (unicam) in 2000 and by an x7 icp-ms (thermo fischer scientific) between 2011 and 2013. target analytics were al, ba, ca, cd, co, cr, cu, fe, k, la, li, mg, mn, mo, na, ni, p, pb, s, and zn. in this study, we focused on cu and pb, because these elements were connected to the contamination on the floodplain. certified standard materials used in qa/qc were bcr crm 141r: calcareous loam soil [15]; bcr crm 142r: light sandy soil [16], and bcr crm 143r: sewage sludge amended soil [17]. we assumed that the investigation of the upper 30 cm soil layer every five years using sequential extraction could give accurate information about the changes in the bioavailability of heavy metals and the rearrangement among fractions. all statistical analyses were performed using spss (version 22.0). 3. results and discussion figs.1 and 2 show the total elemental composition for the four sampling sites. although replicate cores and sampling locations differ, they show an overall trend. the cu content of the topsoil was higher than that of the lower layers formed earlier. data indicates that the cu and pb contents of the topsoil are greater in vásárosnamény compared to in tivadar, possibly due to the combined effects of the two contamination incidents convening at the confluence of the rivers tisza and szamos. the 70 to 170 cm soil layers at vásárosnamény show high lead content. the lakanen-erviö soluble element content is shown in figs.3 and 4. data indicate that the heavy metal content of the floodplain soils is greater in vásárosnamény compared to in tivadar. from this point downstream, the level of contamination appears to decrease with distance, with the lowest value (data not shown) in the topsoil of the arboretum at tiszakürt (275 river km) where atmospheric deposition may be the table 1. summary of sampling sites. sampling sites geographical coordinates river km types of samples additional information tivadar n 48o 04' 00.6'' e 22o 31' 04.8'' 709 active floodplain affected by the second pollution event vásárosnamény n 48o 07' 46.5'' e 22o 19' 39.5'' 683 pasture affected by the first and second pollution events rakamaz n 48o 07' 43.8'' e 21o 26' 28.7'' 543 pasture affected by the first and second pollution events tiszacsege n 47o 42' 59.9'' e 20o 57' 08.7'' 455 active floodplain affected by the first and second pollution events 8 years ago the area was refilled with soil ! figure 1. hno3-h2o2-extractable copper concentration of different layers of soils (blue: tivadar; burgundy: vásárosnamény; yellow: rakamaz; and light green: tiszacsege). figure 2. hno3-h2o2-extractable lead concentration of different layers of soils (blue: tivadar; burgundy: vásárosnamény; and yellow: rakamaz; light green: tiszacsege). evaluation of heavy metal content 43(1) pp. 19–23 (2015) doi: 10.1515/hjic-2015-0004 21 source of pollution. the cu content of the upper 10 cm soil layer is nearly twice as high as levels measured in the other layers. the bioavailable cu and pb contents at vásárosnamény exceeded the temporary limit values of lakanen-erviö extractable metal contents for soil contamination [18], while the upper soil layer of the tivadar floodplain appeared to be uncontaminated. the mcgrath method of sequential extraction can be used for assessing the contents of toxic and potentially toxic elements in soil, and their biological effects, i.e. for the determination of the amounts bound to various forms of compounds in soils. the proportion of the water soluble and exchangeable fractions (cacl2 extraction fraction) is negligible as regards cu and pb. the ratio of metals bound to organic matter (naoh extraction) is low, according to the expectations, as metals bound to carbonates (na2edta extraction) is higher in the vásárosnamény and tiszacsege soils, but lower at the other sites. the residual fraction of metals (aqua regia extraction) is the largest amongst the samples (figs.5 and 6). we determined the cu and pd content of the floodplain soils after ten years of the previous waves of contamination. figs.7 and 8 illustrate the vertical distribution of hno3/h2o2 extractable cu and pb contents. there is no statistically proven difference between the results of the samples taken at two different times. figs.9–12 show the lakanen-erviö soluble element contents of the same core. there is no statistically significant difference between the results of the samples taken at the two different times. the effect of the second source of pollution (baia borsa, march 2000) on the available metal contents of the tivadar floodplain was not detectable, which is in accordance with the results of szabó et al. [19]. figure 5. proportions of the different cu fractions in the topsoil (solid: cacl2 soluble, hollow: naoh soluble, small dotted: na2edta soluble, checked:aqua regia soluble). figure 6. proportions of the different pb fractions in the topsoil (solid: cacl2 soluble, hollow: naoh soluble, small dotted: na2edta soluble, checked:aqua regia soluble). figure 7. total cu concentration (hno3/h2o2 soluble) at vásárosnamény (dark: 2002, light: 2013). figure 8. total pb concentration (hno3/h2o2 soluble) at vásárosnamény (dark: 2002, light: 2013). figure 3. ammonium-acetate-edta (lakanenerviö)-extractable cu concentration of different layers of soils (blue: tivadar; burgundy: vásárosnamény; yellow: rakamaz; and light green: tiszacsege). figure 4. ammonium-acetate-edta (lakanenerviö)-extractable pb concentration of different layers of soils (blue: tivadar; burgundy: vásárosnamény; yellow: rakamaz; and light green: tiszacsege). győri, boros, sipos, bertáné-szabó, kovács, horváth, takács, heltai hungarian journal of industry and chemistry 22 4. conclusion the cu and pb contents of the topsoil were found to be the highest in the upper 10 cm layer as a result of the latest sources of contamination. the degree of this effect varies according to the sampling sites. the lowest element content was measured at tivadar, while samples from vásárosnamény showed a maximum for many elements because of the first coincidence of the two pollution waves. according to the core samples, higher element contents could be found in some of the deeper layers as marks of former sources of pollution. the investigation of the upper 30 cm soil layer in the coming years using sequential extraction could give accurate information about the changes in the bioavailability of heavy metals and the rearrangement among fractions in addition to laboratory experiments of the effects on soil acidity. acknowledgement this work was supported by köm 811, nsf-mtaotka, ktia_aik_12-1-2012-0012, and otka 108558 projects. references [1] nguyen, h.l.; braun, m.; szaloki, i.; baeyens, w.; grieken, r.; van leermakers, m.: tracing the metal pollution history of the tisza river through the analysis of a sediment depth profile, water air soil pollut., 2009 200, 119—132 10.1007/a11270-0131525-1 [2] macklin, m.g.; brewer, p.a.; balteanu, d.; coulthard, t.j.; driga, b.; howard, a.j.; zaharia, s.: the long term fate and environmental significance of contaminant metals released by the january and march 2000 mining tailings dam failures in maramures county, upper tisza basin, romania, appl. geochem., 2003 18, 241–257 10.1016j/apgeochem.2013.04.013 [3] unep/ocha: spill of liquid and suspended waste at the aurul s. a. retreatment plant in baia mare assessment mission report, geneva, 2000 [4] bird, g.; brewer, p.a.; macklin, m.g.; balteanu, d.; driga, b.; serban, m.; zaharia, s.: the solid state partitioning of contaminant metals and as in river channel sediments of the mining affected tisza drainage basin, northwestern romania and eastern hungary, appl. geochem., 2003 18, 1583– 1595 10.1016/j.apgeochem.2013.04.013 figure 10. soluble cu contents of the 110 cm deep soil profile at tivadar (dark: 2002, light: 2013). figure 9. soluble pb contents of the 110 cm deep soil profile at tivadar (dark: 2002, light: 2013). figure 11. soluble pb contents of the 110 cm deep soil profile at vásárosnamény (dark: 2002, light: 2013). figure 12. soluble cu contents of the 110 cm deep soil profile at vásárosnamény (dark: 2002, light: 2013). evaluation of heavy metal content 43(1) pp. 19–23 (2015) doi: 10.1515/hjic-2015-0004 23 [5] brewer, p.a.; macklin, m.g.; balteanu, d.; coulthard, t.j.; driga, b.; howard, a.j.; bird, g.; zaharia, s.; serban, m.: the tailings dam failures in maramures county, romania and their transboundary impacts on the river system, nato sci. ser.: iv: earth environ. sci., 2003 20, 73–83 issn: 1568-1238 [6] győri, z.; alapi, k.; sipos, p.; zubor, á.: effects of heavy metals on floodplain soils and pastures of the river tisza, hungary ii. examination of soil and herbaceous plants in the upper tisza. in natural attenuation of metals along the tisza river–floodplain wetlands continuum, eds.: adriano, d.; németh, t.; győri, z., (university of debrecen, debrecen, hungary) 2003, pp. 161–173 isbn: 963-472-726-3 [7] osán, j.; kurunczi, s.; török, s.; van grieken, r.: x–ray analysis of riverbank sediment of the tisza (hungary): identification of particles from a mine pollution event, spectrochim. acta part b atomic spec., 2002 57, 413–422 issn: 0584-8547 [8] wehland, f.; panaiotu, c.; appel, e.; hoffmann, v.; jordanova, d.; jordanova, n.; denut, i.: the dam breakage of baia mare – a pilot study of magnetic screening, phys. chem. earth, 2002 27, 1371–1376 issn: 1474-7065 [9] kraft, c.; tümpling, w.; zachmann, d.w.: the effect of mining in northern romania on the heavy metal distribution in sediments of the rivers szamos and tisza (hungary), acta hydrochim. hyrdobiol., 2005 34(3), 257–264 10.1002/aheh.200400622 [10] győri, z.; alapi, k.; prokisch, j.; németh, t.; adriano, d.; sipos, p.: cd, cu, pb and zn content of the riparian zone of the tisza river (hungary) after heavy metal pollution, agrochem. soil sci., 2010 59, 117–124 10.1556/agrokem.59.2010.1.14 [11] kabata-pendias, a.; pendias, h.: trace elements in soils and plants, 3rd ed. (crc press, ltd. boca raton, fl usa) 2001 isbn: 978-1-4200-9368-1 [12] msz 21470-50: environment protection. testing of soils. determination of total and soluble toxic element, heavy metal and chromium(vi) content. hungarian standard, 1998 (in hungarian with english summary) [13] lakanen, e.; erviö, r.: a comparison of eight extractants for the determination of plant available micronutrients in soil, acta agr. fenn., 1971 123, 223-232 [14] mcgrath, s.p.; cegarra, j.: chemical extractability of heavy metals during and after long-term applications of sewage sludge to soil, j. soil sci., 1992 43, 313–321 10.1111/j1365-2389.1992.tb00139.x [15] quevauviller, ph.; muntau, h.; fortunati, u.; vercoutere, k.: the certification of the total contents (mass fractions) of cd, co, cr, cu, hg, mn, ni, pb and zn and aqua regia soluble contents (mass fractions) of cd, co, cr, cu, hg, mn, ni, pb and zn in a calcareous loam soil. (crm 141r). bcr information. commission of the european communities, 1996 isbn 92-827-7412-0 [16] maier, e.a.; griepink, b.; muntau, h.; vercoutere, k.: certification of the total contents (mass fractions) of cd, co, cu, pb, mn, hg and ni and the aqua regia soluble contents (mass fractions) of cd, pb, ni and zn in a light sandy soil. (crm 142r). bcr information. commission of the european communities, 1994 cd-na-15284-en-c [17] maier, e.a.; griepink, b.; muntau, h.; vercoutere, k.: certification of the total contents (mass fractions) of cd, co, cu, pb, mn, hg and zn and the aqua regia soluble contents (mass fractions) of cd, cr, pb, mn, ni and zn in a sewage sludge amended soil. (crm 143r). bcr information. commission of the european communities, 1994 cd-na-15284-en-c [18] kádár, i.: about the examination of contaminated soils. handbook for rehabilitation 2. (ministry of environmental protection, budapest, hungary) 1998 [19] szabó, sz.; posta, j.; gosztonyi, gy.; mészáros, i.; prokisch, j.: heavy metal content of flood sediments and plants near the river tisza, agd landscape environ., 2008 2, 120–131 issn 17897556 microsoft word b_03_r.doc hungarian journal of industrial chemistry veszprém vol. 38(2). pp. 83-88 (2010) modelling of polymer particle formation using population balance model á. bárkányi , b. g. lakatos, s. németh department of process engineering, university of pannonia, 8200 veszprém, egyetem str. 10., hungary e-mail: barkanyi.agnes@gmail.com the paper presents a study of formation of the primary particle size distribution in suspension “powder” polymerization of vinyl chloride. the process is modelled by means of a population balance model, and the primary particle size distribution inside the polymerizing monomer droplets is determined by analysing the population balance equation, governing the nucleation, growth, and aggregation of the primary particles, using the moment method. the infinite set of moment equations obtained by moment transformation was closed using a sum aggregation kernel, and for numerical experimentation a second order moment equation model was used. the results show how important are to choose the correct parameters in production of poly(vinyl chloride) by suspension polymerization. changing the parameters a bit the quality of product may change significantly. the results presented in the paper illustrate well that the population balance model can be used for describing the process and a number its properties with sufficient accuracy. keywords: suspension polymerization, vinyl chloride, population balance equation, moment equation, simulation. introduction plastics are major industrial goods used in the building, construction, packaging, transportation, electronic , etc., idustries. plastics can be in general classified into thermoplastics, thermosetting resins and engineering plastics. commodity thermoplastics are manufactured in large volumes and comprise polymers such as polyvinil chloride, polyethylene (low and high density), isostatic polypropylene, polystyrene. the main basic material of the plastics manufacturing is the polyvinyl chloride. due to its unique morphological characteristics, pvc can be combined with a number of additives resulting in materials exhibiting a broad range of end-use properties. the morphological properties of the pvc grains are determined by the following process variables: polymerization temperature, quality of agitation, type and concentration of the surface active agents, so it is needed to studying the effects of these variables. the quality of pvc is primarily characterized by the morphology of the polymer grains. the morphology of pvc grains, produced by the suspension polymerization process, is determined by the grain shape, and grain size distribution, the average grain porosity and pore size distribution as well the accessibility of the grain’s internal pores. it should be noted that pvc morphology greatly affects its handling, processing and application characteristics. grain porosity largely influences the removal of unreacted vcm and plasticizer uptake by the pvc grains during processing. the morphology of the pvc grains is depended on the properties of primary particles. the primary particle size distribution influences the porosity of the final grains to a large degree. so, the first goal is modelling the primary particle size distribution in suspension polymerization. the population balance approach has proved to be an adequate tool for model-based investigation of suspension polymerization by tracking the time evolution of polymer particles [1, 2, 3]. this approach was applied also by bárkányi [4] and bárkányi et al. [5] to study formation of the primary particle size distribution in suspension polymerization of vinyl chloride. the aim of the paper is to present the population balance equation and its second order moment equation reduction used in analysing formation of the primary particle size distribution in suspension polymerization of vinyl chloride. the infinite set of moment equations obtained by moment transformation is closed using an approximate sum aggregation kernel. results obtained by numerical experimentation by a second order moment equation model illustrate well that the population balance approach can be used for describing the process. 84 the mechanism of the suspension pvc process the suspension polymerization of vinyl chloride monomer (vcm) proceeds in two phases: the first one is the monomer-rich phase and the other one is the polymerrich phase. so, the model includes the polymerization processes in the two phases and the describing of the component transfer between the phases. [6, 7, 8]. previously published papers [9, 10, 11, 12, 13, 14, 15] on the morphology of pvc grains have postulated the following five-stage kinetic-physical mechanism, shown in fig. 1, to describe the nucleation, stabilization, growth, ad aggregation of pvc primary particles. figure 1: evolution of primary pvc particles during the first polymerization stage (vcm conversion range: 0 < x < 0.01%), primary radicals, formed via thermal decomposition of initiator molecules, rapidly react with monomer to produce polymer chains that almost instantaneously become insoluble in the monomer phase. the polymer chains precipitate out of the continuous vcm phase when they reach a specific chain length. it has been postulated that approximately 10–50 polymer chains are subsequently combined together to form nano-domains also called basic particles. the nanodomains are swollen with monomer and have an initial diameter of about 10–20 nm. in stage two (vcm conversion range: 0.01 < x < 1%), the formation of pvc domains, also called primary particle nuclei, takes place. because of the limited stability of the domains, they rapidly undergo coagulation leading to the nucleation of the primary particle nuclei. the initial size of these primary particle nuclei has been found to be in the range of 80–100 nm. typically, a primary particle nucleus may contain about 1000 nanodomains. the primary particle nuclei carry sufficient negative electrostatic charges to form stable colloidal dispersions in the monomer phase. in stage three (vcm conversion range: 1 < x < 20%), growth and aggregation of the primary particles occur. the size and the number of the primary particles depend on the growth rate and the electrostatic-steric stability of the primary particles. the latter attribute decreases as the monomer conversion increases. massive aggregation of the primary particles results in the formation of a continuous three-dimensional primary particle network within the vcm droplet. the three-dimensional primary particle network structure, i.e. its initial porosity and mechanical strength depend on the size and the number of primary particles, the electrostatic and steric forces between the primary particles, the polymerization temperature and the polymer viscoelastic properties. in stage four (vcm conversion range: 20<x<70-75%), the growth and fusion of the primary particles continues. that is, the primary particles increase in size due to polymerization and also undergo substantial fusion. both processes result in a continuous decrease in particle porosity. the primary particles continue to grow until the disappearance of the separate monomer phase. finally, in stage five (vcm conversion range: 70-75<x<90-95%), polymerization continues only in the monomer swollen polymer phase, however, at a lower rate, until the monomer has been depleted. at the final vc conversion, the size of the individual primary particles is in the range of 1–1.5 μm while the size of the primary particle aggregates is about 3–10 μm. the model despite the importance of the primary particle size distribution (ppsd) on the development of pvc grain morphology, there is only a limited number of quantitative models dealing with the dynamic evolution of the primary particles in terms of process variables. [7] in general, the dynamic evolution of the particles size distribution in a particulate process can be obtained from the solution of a population balance equation (pbe). the population of the primary particles can be expressed in terms of a number density function, n(v, t) that represents the number of particles per unit volume of monomer droplet phase in the differential size interval (v, v+dv). for a dynamic system under-going particle nucleation, aggregation, and growth, the evolution of the particle size distribution is described by the following non-linear integral-differential pbe: ∫ ∫ ∞ − −−+ −= ∂ ∂ + ∂ ∂ 0 2/ 0 00 ),(),(),( ),(),(),( )()()),(),((),( dutuntvnuv dutuntuvnuuv tsvv v tvntvg t tvn v β β δ (1) where g(v, t) is the particle growth rate due to polymerization in the polymer-rich phase, s0(t) is the 85 nucleation rate of primary particles of volume v0 in the monomer-rich phase, and β(v, u) is the aggregation rate kernel for particles of volume u and v. eq. (1) satisfies the following initial and boundary conditions: n(v, 0) = 0, at t = 0, and n(0, t) = 0, at v = 0. in order to solve eq. (1), the functional forms of g(v, t) and s0(t) need to be first determined. according to kiparissides [3] the primary particle nucleation and growth rates is given by v x rm tvg m ppw ρ =),( (2) 0 0 )1( )( v mr ts mp wpm ϕρ − = (3) where x is the monomer conversion, φm is the volume fraction of monomer in the polymer-rich phase, mw is the molecular weight of vcm, ρm and ρp are the corresponding monomer and polymer densities, rpm and rpp denote the respective polymerization rates in the monomer and polymer-rich phase. note that the growth rate is linear with respect to the particle volume, typical of bulk polymerization systems and depends on rpp and, thus, on time. the polymerization rates in the monomer and polymer-rich phase, rpm and rpp can be calculated from a kinetic model [10, 16, 17]. in the present study, a simplified kinetic model was applied [18]: )1( )()1( ]][[ 2/1 xx xx x bx imkr f f f f dpm − −− = (4) )1( )1( ]][[ 2/1 xx xx pimkr f f ppp − − = (5) where kd is the rate constant for initiator decomposition, [m] is the monomer concentration, [i] is the initiator concentration, and xf is the vcm conversion at which the separate monomer-phase disappears. calculation of conversion x depends on if x is smaller or larger than the critical conversion xf. calculation of x is provided by the following equations: if x < xf: )2/exp(][ )1( 1 2/1 02/1 tkik bx qx dt dx d−× − + = (6) if x > xf: [ ] )2/exp( )1( )1( 1 2/1 2 2/1 0 tk bx xi x pk dt dx d f −× − − − = (7) where k = kp (fkd / kt)1/2 and f is the initial factor, and q = ap – a +1. the dimensionless coefficients of the kinetic model: a = (1 – xf) / xf (8) b = (ρp – ρm) / ρm (9) ( ) ( ) )273(14,027 /2 /2 −−≈= t mtkdfk ptkdfk p (10) for determination of the primary particle size distribution can we used the gamma distribution function: b x eax aab baxfy − ⋅−⋅ γ == 1 )( 1),( (11) where a and b parameters which can be determined from the moment equations, and γ is the gamma function. solution and results the numerical solution of eq. (1) is very difficult while analytic solution is not known. thus we solved it by using moment transformation. it was assumed that b(v, u) = b0(v + u), where π γ& =0b and )/1(8 21 μμ πγ + = v rd δ & , where rd is the radius of the monomer droplets, δv is the relative velocity of the droplets, μ1 and μ2 are the viscosity of waterand polymer phases. the moment equations are: equation for the zero order moment: ( ))()()( 010 0 txstb t t +⋅−= ∂ ∂ μ μ (12) where: μ0 is the zero order moment of volume v: ∫ ∞ = 0 0 ),( dvtvnμ (13) eq. (12) provides the time evolution of the total number of particles. equation for the first order moment: ( ) ( ))()()()( 0010 1 txsvttxg t t ⋅=⋅− ∂ ∂ μμ (14) where: μ1 the first order moment of volume, v: ∫ ∞ ⋅= 0 1 ),( dvtvnvμ (15) eq. (14) gives the total volume of particles. equation for the second order moment: ( ) ( ))( )( )()(2)()(2)( 0 2 0 0 21 020 2 txsv t ttbttxg t t ⋅+ ⋅ =⋅− ∂ ∂ μ μμμμ (16) μ2 has not got any physical meaning but the knowledge of these properties is needed for characterizing the system. the initial conditions of moment equations are: μ0(0) = μ1(0) = μ2(0) = 0; t = 0. the set of moment equations were solved in matlab environment, and the parameter values used were obtained from the literature. as the model provided adequate results we examined how the results regarding the 86 moments varied changing the parameters. in this case, examination of process was focused on the analysis of the b0’s effect. this parameter influences the rate of aggregation in the process. we varied parameters rd and δv since, because the kinetic parameters were constant it did not influence the conversion and the time variation of the concentration of initiator. but changing these parameters influenced the moments significantly. 0 0.5 1 1.5 2 2.5 3 x 104 0 1 2 3 4 5 x 1012 0. moment time (sec) m u0 rd=5e-4,du=5e7 rd=5e-5,du=5e7 rd=5e-4,du=5e4 rd=5e-4,du=5e6 rd=5e-5,du=5e4 rd=5e-5,du=5e6 rd=5e-6,du=5e4 rd=5e-6,du=5e6 figure 2: evolution in time of the zero order moment fig. 2 shows the time evolution of the zero order moment in function of changing of parameters. the differences between the running down of curves are on account of the changing of the rate of aggregation. the bigger the rate of aggregation the fewer particles there are in the system, because they cohere. 0 0.5 1 1.5 2 2.5 x 104 0 0.5 1 1.5 2 2.5 x 10-3 1. moment time (sec) m u1 rd=5e-4,du=5e7 rd=5e-5,du=5e7 rd=5e-6,du=5e7 rd=5e-4,du=5e4 rd=5e-4,du=5e6 rd=5e-5,du=5e4 rd=5e-5,du=5e6 rd=5e-6,du=5e4 rd=5e-6,du=5e6 figure 3: evolution in time of the first order moment in fig. 3 one can see that changing the parameters in question do not influence the first order moment. because the first order moment denotes the total volume of particles it is not a surprising fact since the total volume of particles is independent on aggregation. in fig. 4 we see two different types of curves. if the rate of aggregation is able to neglectful compared to the rate of nucleation, the curve monotonously increases, otherwise it goes through a maximum, and after it starts decreasing. after that we studied the dependence of behaviour of the process as a function of the parameter b0. in figs 5 and 6 it can be seen that changing the parameter b0 influence only the zero and second order moments so we studied these two moments. 0 0.5 1 1.5 2 2.5 x 104 0 1 2 3 4 5 6x 104 2. moment time (sec) m u2 rd=5e-4,du=5e7 rd=5e-5,du=5e7 rd=5e-4,du=5e4 rd=5e-4,du=5e6 rd=5e-5,du=5e4 rd=5e-5,du=5e6 rd=5e-6,du=5e4 rd=5e-6,du=5e6 figure 4: evolution in time of the second order moment 0 0.5 1 1.5 2 2.5 3 3.5 x 104 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5x 1012 time (sec) b0=1e9 b0=1e10 b0=0 b0=1e11 b0=5e10 b0=1.1e11 figure 5: evolution in time of the zero order moment 0 0.5 1 1.5 2 2.5 3 3.5 x 104 0 1 2 3 4 5 6x 104 time (sec) b0=1e9 b0=1e10 b0=0 b0=1e11 b0=5e10 b0=1.1e11 figure 6: evolution in time of the second order moment figs 5 and 6 show that evolution of the process depends strongly on the ratio of growth and aggregation rates. with increasing aggregation rate the number of particles in the system decreases significantly. as the aggregation rate passes a critical value the process likely exhibits gelation phenomenon what would be the subject of a future interesting study. 87 0.5 1 1.5 2 2.5 3 3.5 4 x 10-4 0 1 2 3 4 5 6 7 8 x 10-17 diameter of particle (m) fu nc tio n va lu e t=1e-21 sec t=1.3e3 sec t=3.8e3 sec t=7e3 sec t=1.1e4 sec t=1.5e4 sec t=1.8e4 sec t=1.9e4 sec t=2.1e4 sec t=2.3e4 sec figure 7: primary particle size distribution 0 1 2 x 10-40 1 2 x 104 0 2 4 6 8 x 10-17 diameter of particle (m) time (s) fu nc tio n va lu e figure 8: primary particle size distribution (3d) figs 7 and 8 show the primary particle size distribution. it can be seen when the polymerization is going, the diameter of particles continually grows. conclusions a population balance model and a second order moment equation system was presented for analysing formation of the primary particle size distribution in suspension “powder” polymerization of vinyl chloride. the model involves nucleation, growth and aggregation of primary particles having significant influence on the properties of polymer grains. the infinite set of moment equations obtained by moment transformation was closed using an approximate sum aggregation kernel, and for numerical experimentation a second order moment equation model was used. the results revealed that it is very important to choose the correct parameters in production of poly(vinyl chloride) by suspension polymerization since changing the parameters a bit the quality of product may change significantly. the results presented in the paper illustrate well that the population balance model can be used for describing the process and a number its properties with sufficient accuracy. acknowledgements this work was supported by the hungarian scientific research fund under grant k77955. the financial support from the tamop-4.2.208/1/2008-0018 (livable environment and healthier people – bioinnovation and green technology research at the university of pannonia) project is gratefully acknowledged. symbols a, b constants a, b parameters of gamma-distribution d diameter of particle, m f iniciator factor g growth rate in volume-scale, m3/s i0 initial value of iniciator concentration, kmol/ m3 k constant kd the rate constant for initiator decomposition constant, 1/s kp monomer phase propagation constant, 1/s kt termination rate constant, 1/s m weight, kg m monomer concentration, kmol/ m3 n number density function, db/m6 p, q constants r radius of particle, m rd radius of vcm droplet, m rpm polymerization rate in the monomer phase, mol/s/m3 rpp polymerization rate in the polymer phase, mol/s/m3 s0 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice hungarian journal of industrial chemistry veszprem vol. 30. pp. 47-52 (2002) characterizationofgelconcentrationinultrafiltration of oil-in-water emulsion . x. hu, e. bekassy-molnar.1 and g. vatai1 (institute oftribology, hefei university of technology, hefei 230009, pr china 1faculty of food science and engineering, szent istvan university, h-1118 budapest, hungary) received: july 13,2001 processing of oil-in-water emulsions with conventional ultrafiltration membranes leads to rapid membrane fouling and flux decline and it is generally uneconomic because of this problem. the major hurdles to be overcome in the development of a practical industrial unit are concentration polarization and fouling. this paper presented a new model for the calculation of the gel concentration at the membrane surface. the model includes the following influence factors: transmembrane pressure, feed concentration, mass transfer coefficient, membrane resistance and so on. in the present experimental conditions, the gel concentration for fp 055a ultrafiltration membrane is about 30 vol. %. keywords: ultrafiltration, oil-in-water emulsion, gel concentration, concentration polarization introduction ultrafiltration has been accepted versatile membrane separation process for water 'purification and wastewater treatment in the last years. its industrial applicat~on is so wide that it is presently regarded as a well established unit process. using ultrafiltration membrane to separate oil-in-water emulsions many articles have been reported [1-3]. the water removal from wastewater by ultrafiltration is influenced by the membrane material, the physical performance itself and the operation conditions. for a selected membrane it is necessary to choose the best operation parameters in order to assure the membrane works under optimal conditions. as a fundamental study, in our former researches, it was studied that the effects of several kinds of. ultrafiltration membranes with different nominal molecular weight cut off (mwco) and pore size on the treatment efficiency of the oil-in-water emulsions with different oil concentrations [4, 5]. the results show that the tested membranes can be applied to remove water from oil-in­ water emulsions with different permeate flux, oil rejection and cod in the permeated fluid. however, there are two significant problems which are always found dwing the ultrafiltration membrane operation of oily emulsion [6]. (1) concentration polarization, which is the build-up of a concentrated layer on the membrane surface. the permeate resistance of water increased greatly, and the permeate flux declined. (2) membrane fouling, which results from the adsorption of solute in the membrane structure and mainly causes changes in surface chemistry. these effects lead to a decrease in permeate flux with time and limit the separation efficiency. many authors have introduced and enucleated the concentration polarization and the ultrafiltration model of gel layer [7-10]. two typical models, hydraulic resistance model and osmotic pressure model, are widely acceptably [11, 12]. the coefficient of mass transfer at the membrane surface has been studied according to reynolds number and schmidt number. however the relationship between models of the concentration polarization and gel layer has been less referred. this research introduces the calculation expression of gel concentration on the basis of understanding concentration polarization and gel layer for the ultrafiltration separation of oil-in~water emulsion. theoretical fundamentals the permeate flux, j w'j is an important parameter in the design and analysis of the economic feasibility of the ultrafiltration separation process. hydro-dynamics of membrane modules have an important effect on the mass transfer, separation, and fouling behavior of .membrane systems. during ultrafiltration the solutes are 48 bulk solution r x=o boundary layer membrane j s fig.! concentration profile in the boundary layer of uf carried and accumulated at the membrane surface, and formed a concentration difference between the membrane surface and bulk solution. it leads to the solutes diffusing into the bulk solution backward till a balance situation of concentration is attained. as shown in fig.] [10]. the permeate flux can been shown as follows: j =din em -ct w o eb-er (1) where jm is the permeate flux (llm2h); cb is the solute concentration in the bulk solution of feed (gil); em is the solute concentration at the membrane surface (gil); e1 is the solute concentration in the permeate (gil); d is the diffusion coefficient of solute (m2/s); o is the thickness of the boundary layer (polarization layer) (m). if the ultrafiltration effect is prefect~ there is no any solute in the permeate, e1 can be ignored. so eq.( 1) can be simplified: (2) where k = ~ , coefficient of mass transfur. ahhough eq.(2) does not present the relation between the pressure and other factors. increasing pressure can improve permeate flux of water~ and the so1ute concentration at the membrane surface is also increased. the concentration polarization becomes more severe. which causes the flux of the solute diffusion backward to be increased. as uf process became stable at a specified pressure. the.logarithm functional relation between j..,.. and cm was keeping with eq.(2). in addition, the thickness of boundary layer in eq~(2). o. depends on the hydraulic dynamic conditions. such as, the water flow velocity parallel to the membrane surface. the diffusion coefficient d is related with the solute property and feed temperature. if the treated object is a macromolecular solution. the solute concentration at the membrane surface. c"'. increased greatly because of the smaller d. and the backward­ diffusion flux of solute is lower as well. it results in increasing the ratio of cn/eb. when the pressure reached the critical pressure, the gel layer was produced. the solute concentration at the membrane surface ( cm) is named of gel concentration (c8). so eq.(2) can be changed into: n eg j =-lnw o cr (3) for a selected solute: the gel concentration can be regarded as a stable value under certain conditions. the gel concentration is related with the solubility of the solute in water. so lw can also be considered as a determined value. if increasing the transmembrane pressure continually, the backward-diffusion flux of the solute cannot be enhanced. in a short time, the permeate flux might be increased, the enhanced pressure, however, is balanced by the gel layer resistance quickly with increasing the thickness of the gel layer. the permeate flux of water returned to the previous level so, according to eq.(3), it can be drawn the following opinions: (1) once the gel layer is formed the permeate flux of water does not increase with the pressure; (2) the permeate flux of water decreased linearly with the logarithm relation of the solute concentration, cb.; (3) the permeate flux of water still depends on the hydraulic dynamic conditions which defined the thickness of the boundary layer. on the other hand, there is a polarization layer resistance besides the intrinsic membrane resistance if the polarization layer cannot be ignored. darcy's law (also known as the resistance-in-series theory) is widely used to relate the permeate flux to the applied pressure and the fouling resistance [1013]: (4) here, fl. is the solution viscosity (pa s). .t1p is transmembrane pressure (pa). rm · is the intrinsic membrane resistance (1/m). rp is the polarization layer resistance (1/m). the intrinsic membrane resistance is unaffected by operating parameters whereas the polarization layer resistance is a function of applied pressure. as the gel layer is formed, the resistance of uf includes still the gel layer resistance, r8 (1/m), so the permeate flux of water can be expressed: j == llp w jl.(rm + rp + r 8 ) (5) because r8 >> rp, when rp is negligible, the filtrate flux is given by the following eq.(6) (6) under certain transmembrane pressure it can he seen that the resistance of gel layer is proportional directly to the solute amounts retentated which is proportional directly to the accumulative water volume, v, permeated according to the general filtration principle,. provided :c s ;:. >< :l ;;:: cl) 'tii cl) e cl) ll.. 450 400 350 300 250 200 150 100 50 • 20 40 60 80 100 120 140 160 180 200 time, [min.] e ff502-04 • 08·100 4 fs40pp t fssopp fig.2 permeate flux as a function of time for different membranes at feed oil concentration 0.5 vol. % the gel layer cannot be compressed. so the relation between rg and v can be expressed to rg oc v. in addition, the pure sol vent transport through porous uf membranes is directly proportional to the applied transmembrane pressure, ap. models that can be used to describe the convective flow, lw0 , are the kozeny-carman and hagen-poiseuille equations [14]: 10=~ w jl.orm (7) where f-lo is the solvent viscosity (pa s). taking eqs.(6) and (7) together the following equation can be given if the solvent viscosity is nearly equal to solution one. _1 =-1 +}!_v = j.lorm + ly jw j; m m m (8) where {3 is coefficient is to be determined. if taking a plot of mllw with v at a specified pressure, a line can be presented and its intercept is equal to (j.lrm) value. according to the slope of the line, the coefficient {3 can also be attained, and the rg can be calculated as well (rg = {3v). if pressure is variable, the increased pressure can enhance the permeate flux in a shorter time and forces more solute to the membrane surface. both the thickness and the resistance of gel layer are also increased. so it can be seen that rg is directly proportion to l!p at that time, then eq.(6) can be modified: p(rm +a•m) (9) where a is the coefficient to be determined. the equation above shows the relation between lw and &>. comparing eq.(9) with eq.(2), it can be seen eq.(9) cannot present the influences of flow velocity of bulk solution and feed oil concentration, and eq.(2) cannot 49 0.0048 0.0048 0.0044 • ff502-04 0.5% 0.0042 ~ 1 0.0040 ";t ~ 0.0038 0.0038 0.0034 0.0032 100 200 300 400 500 600 700 800 900 v,(lfm2] fig.3 the relation diagram of l!jwv for uf membrane ff 502-04 at the feed concentration of 0.5 vol. % show directly the effects of the pressure and resistance. however they erect the relations of lw -l!p and jw­ cm respectively under the concentration polarization and gel layer. if letting them equal, a novel equation can be obtained. (10) subsequently: c =c •exp{..!_( ___ m' ___ )} m b k j.l(rm +ct•m') (11) with respect to the above equation, it can calculate approximately the solute concentration withm concentration polarization region under different pressures and the gel concentration under critical pressure at the membrane surface, respectively. evaluation of experimental results calculations of membrane resistance and gel layer resistance as an example, fig.2, which plotted the flux with time for different uf membranes f 4 ], was selected to characterize the relationship between lijw and v. the operating pressure is 3 bar, the oil-in-water emulsion concentration is 0.5 vol. %. the viscosity of emulsion jl. = 1.147 cp = 1.1245 x 10"3 pas. at the beginning of operation the flux declines rapidly. and becomes stable gradually. according to the experimental data, the fig.3 plotted lllw with v was presented for ff 502-04 uf membrane. according to eq.(8) the relation of lllwv for ff 502-04 membrane can be expressed: iijw = 0.00325 + l73xl0-6v as treating an emulsion with a feed oil concentration of 0.5 vol. %. the intercept of the line is 0.00325, the item of (j..t r,/!jp) is equal to 0.00325 m2h/l. so after conversion rm = 3.12x10 12 lim. 50 450 400 -5%experimental results ····•··· 5%calculation resuhs 350 -0.5% -experimental results i 300 .... .,. ... 0.5% -calculation resuhs x 250 :::> :;:: 200 s i!) € 150 q) 0.. 100 so a 4 pressure, [bar} fig.4 permeate flux as a function of transmembrane pressure for fp 055a membrane at different emulsion concentration in addition, another item of (j.l/yap) is 1.73 h/m2 according to the slope of the line. f3 = 1.73 hlm2 x 3x105 p.a /1.1245xlo-3 pa s = 1.6615x1012 11m2 • rg = f3v = 1.6615xl012v. with the same methods above, for the other uf membran~ ds-100, fs 40pp and fs sopp plotted in fig.2, their expressions between lllwv and their resistances can be shown as follows, respectively: ds-100: lllw= 0.00088 + 2.1x10-6v (rm= 8.452x1011 ; rg= 2.017x1012v) fs 40pp: lllw = 0.0043 + 10.5x10-6v (rm = 4.130 xl 0 12 ; r8 = 1.008 x1013v) fs 50pp: lllw = 0.0077 + 3.12xl0-5v (rm= 7.395x101~; rg= 2.996x1013v) from these expressions, it can be seyn that the resistance of gel layer increases with the accumulative volume of the permeate water under a specified pressure. both of the gel resistance and the membrane resistance of ds-100 ultrafiltration membrane are the least among the membranes measured. jw--ap expression the relationship between flux and transmembrane pressure was discussed elsewhere [ 15]. to increase transmembrane pressure can improve the permeate flux. at lower emulsion concentration (0.5 voi. % ), the concentration polarization is not obvioust the permeate flux is almost increased linearly with the transmembrane pressure. at higher emulsion concentration (5 vot %) the effect of pressure on the permeate flux depends on the magnitude of pressure. under a lower pressure tbe flux is also increased with pressure. the flux~ however~ is controlled by the gel layer at higher pressure~ not by transmembrane pressure. so the membrane has a critical flux at higher feed concentration. fig.4 showed the permeate flux as a function of operating pressure for fp 055a membrane at 3(fc under different emulsion concentrations. the eq.(9} can be expressed: ~ e ~ ";~: a: <l ~ ~ m b ·:~: :::; a. <l 0.(l24 • 0.020 • 0.5o/o--fp 055a o.q16 0.012 0.008 0.004 5 ap, [bar] fig.5 a diagram of mllw -t1p at oil concentration of0.5 vol.% 0.06 0.05 0.04 o.ro 0.02 0.01 0.00 2 4 li.p,{bar] fig.6 a diagram of mllw -t1p at oil concentration of 5 vol.% m> -=j..l(r +a•ap)=j.lr +j.la•ap (12) jw m m . taking a diagram of apijw with ap at 0.5 vol. %, as shown in fig.5,.in which the intercept, j.!rm = 0.0059 (bar m2hll), the slope, pa = 0.0026 (m2hll). so for the emulsion with a feed concentration of 0.5 vol.%, 0.0059 + 0.0026ap (13) using the same methods, another plot of apilw with dp at 5 vol. % is shown in fig.6, in which j.!rm = 0.0075 (bar m2hfl), pa = 0.0069 {m2hll). so, for the emulsion with a feed concentration of 5 vol. %: 0.0075+0.0069ap (14) both eqs. of (13) and (14) show the expressions of lw--tlp for fp 055a ultrafiltration membrane under different feed concentrations, respectively. in fig.4, the square points symbols the experimental values; the up­ triangle points stands for 30 --fp055a 15 ap, [bar] fig.7 a relation of cm --!j.p for fp 055a membrane treated oil-in-water emulsion by calculation the calculation values at feed concentration of 5 vol. %. the cycle points are the experimental values; the down­ triangle points are the calculated values at feed concentration of 0.5 vol. %. from these results, it is seen that the experimental and calculated values are approximately near to each other. the equation above can be used to express the relation of lw-jp for oil-in­ water emulsion. expression ofcm--& according to data in fig.4, the critical flux lcritl = 276 llm2h as ch1 = 0.5 vol. % at a steady state; the critical flux lcnt2 = 120 llm2h as cb2 = 5 vol. %. since the cross­ flow velocity was constant throughout, it can be assumed that the mass transfer coefficient (k) was also constant under different feed concentrations and therefore the plot appears linear for the theory to hold true. according to eq.(2) j j ~2 5 cnt!critz =kln-= kln-=276-120=156 cbl o.s so k= 67.75 mlh. then taking k into eq.(2). the relationship between the critical flux and the gel concentration can be expressed: cg jcritl =67.75ln0.5 (15) then, cg can be solved as about 29.4 vol. %. the variation of flux with the concentration at membrane surface can be expressed: c j w = 67.75jn_!!!_ 0.5 for the feed oil concentration of 0.5 vol. % c jw =67.75jn_!!!_ 5 for the feed oil concentration of 5 vol. % (16) (17) 51 according to eq.( 11) the oil concentration, cm, at the membrane surface can be calculated by the following eq.( 18) or eq.(19): c =0.5eex -1 {1( d.p )} m p 67.75 0.0059+0.0026ap ( s) c =5•ex -19 { 1 ( tup j} m p 67.75 0.0075 + 0.0069a.p ( ) taking different operating pressures into the eq.( 18) or eq.( 19) above, the oil concentration, cm, at the membrane surface can be calculated approximately. fig. 7 shows that the oil concentration at the membrane surface varied with pressure. as the operating pressure increases, the cm is also approaching to cg (about 30 vol. %). 4. conclusions a relation between the permeate flux and transmembrane pressure can be drawn: jw = !::..p j.l (rm +a· b.p) at the same time, it can approximately be calculated the solute concentration within concentration polarization region under different pressures and the gel · concentration under critical pressure at the membrane surface with respect to the following equation: c c • exp{_!_( ___ ap ___ ]} mb kl }.l(rm +a•ap) under our present experimental conditions, the gel concentration for fp 055a membrane treated oil-in­ water emulsion is about 30 vol. %. acknowledgments the authors are grateful to the support of the following companies: zoltek magyar viscosa corporation, hungary for mavibran membranes and hoechst corporation for the hoechst membrane. fruitful discussions with professor x. l. wang and technical assistance from dr. h. fen at nanjing university of chemical technology are gratefully acknowledged. financial supports from the foundation for exchange scholars between hungary and china, and chemitechnik pharma corporation budapest are also gratefully acknowledged. references 1. mahdi s. m. and skold r. 0.: tribology international, 1991, 24, 389 52 2. dick r. m.: lubrication engineering, 1982, 38, 219 • 3. perkins t. w., saksena s. and van rbis r.: j.: membr. sci., 1999, 158, 243 4. hu x., bbkassy-molnar e., vatai g., meiszel l. and olah j.: hung. j. ind. chern., 1996, 24, 241 5. hu x., bekassy-molnar. e., vatai g., meiszel l. and olah j.: chern. technik, 1998,50, 119 6. cheryan m. and rajagopalan n.: j. membr. sci., 1998, 151, 13 7. pradanos p., abajo j., campa j. g. and hernandez a.: j. membr. sci., 1995, 108, 129 8. bouchard c. r., carreau p. j., matsuura t. and sourirajan s.: j. membr. sci.,1994, 97,215 9. song l.: j. membr. sci., 1998, 144, 173 10. wang n.: tech. water treat., 1984, 10 (6), 51 11. porter m. c.: ind. eng. chern. prod. res. dev., 1972, 11,234 12. vander berg g. b. and smolders c. a.: j. membr. sci., 1989,40, 149 . 13. belfort g., davis r. h. and zydney a. l.: j. membr. sci., 1994,96, 1 14. marchese j., ochoa n. a., pagliero c. and al.mandoz c.: environ. sci. techno!., 2000, 34, 2990 15. hu x., bekassy-molnar e. and vatai g.: experimental pressure and temperature profiles for ultrafiltration behaviours of emulsified oily water, chern. technik, (to be published) page 45 page 46 page 47 page 48 page 49 page 50 microsoft word 00.00 inner cover.docx hungarian journal of industry and chemistry vol. 43(1) pp. 7–13 (2015) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2015-0002 multi-elemental inductively coupled plasma-optical emission spectroscopic calibration problems of the sequential extraction procedure for the fractionation of the heavy metal content from aquatic sediments györgy heltai,1* ilona fekete,1 gábor halász,1,2 katalin kovács,1 márk horváth,1,2 anita takács,1 norbert boros,3 and zoltán győri2 1 department of chemistry and biochemistry, szent istván university, pater k. u. 1., gödöllő, 2100, hungary 2 regional knowledge centre, szent istván university, pater k. u. 1., gödöllő, 2100, hungary 3 department of environmental and chemical engineering, university of debrecen, ótemető u. 2-4., debrecen, 4028, hungary for the characterisation of the environmental mobility of heavy metal contamination in aquatic sediments, the eu bureau of reference has proposed a fractionation by sequential extraction procedure. for its validation, the crm-701 sample is available containing cd, cr, cu, ni, pb, and zn. in this paper, the matrix-matched calibration problems are presented. a multi-elemental inductively coupled plasma-optical emission technique is employed for the detection of heavy metals in the extracts. it was established that the sensitivities are strongly influenced by the extractants, which causes significant matrix effects: the sensitivities are strongly influenced by the solvents applied in extraction steps; the summarised recoveries show an acceptable agreement with the certified values; however, in the individual extraction steps for certain elements significant differences may occur due to the neglected interferences. therefore, further optimisation is required utilising the flexible line selection possibility offered by the horiba jobin yvon activa-m instrument. keywords: fractionation, sequential extraction, multi-elemental icp-oes, matrix-matched calibration, heavy metal contamination, sediments 1. introduction environmentally toxic elements, such as heavy metals, are the most significant inorganic pollutants. the role of different chemical elements in food production has been an important question of agrochemical research since the middle of the nineteenth century. numerous extraction methods have been developed for determining biologically available fractions of nutritionally relevant elements in soils. environmental researchers have confronted similar problems over the last few decades of the twentieth century in characterising the humanand eco-toxicological impacts of increasing heavy metal pollution. this challenge has created new requirements for analytical methodology and contributed to the development of speciation analytical chemistry. this scientific discipline provides the foundation for the evaluation of toxicological impacts of chemical elemental species detectable in environmental systems [1,2]. in such procedures, the original physico-chemical structural forms of chemical elements present in the system must be preserved during sampling and sample preparation. then, appropriate separation methods must be applied before element specific analytical detection (fig.1). *correspondence: heltai.gyorgy@mkk.szie.hu the european union established the european virtual institute for speciation analysis in 2002 for promoting cooperation, collection, reviewing, and discussion of information and knowledge related to chemical speciation analysis (www.speciation.net). attention was drawn to the mobility and biological impact of heavy metals in environmental systems influenced by their chemical speciation. biological risk assessment of contaminated areas therefore requires the total speciation of all chemical elements present in the system. however, due to the complex structure of solid environmental samples (e.g. soils, sediments, gravitation dust, mining waste, etc.), these analytical tasks in practice cannot be fully completed. as a compromise, the fractionation of the heavy metal content according to environmental mobility and estimation of biological availability by sequential extraction procedures have become the main research approaches. papers published in this area and their citations exponentially increased in the period of 1995 figure 1. scheme of the speciation analysis procedure. sampling preservation of the intact species preparation extraction separation analysis detection of the elemental species heltai, fekete, halász, kovács, horváth, takács, boros, and győri hungarian journal of industry and chemistry 8 and 2013: from 200/year to 700/year; according to related citations from 1000/year to 19,000/year based on thomson reuters, web of science database. a primary risk assessment of heavy metal contamination in the soil/water/atmosphere system was based on the fractionation of metallic element content of environmental samples according to their environmental mobility. the term “fractionation” was recommended by the iupac in 2000 [2]. the mobility of an element according to the different solubilities of different binding classes can be estimated by solvents sequentially applied containing physico-chemically increasingly aggressive reagents [3,4]. in agricultural chemistry, the serial single step strategy (fig.2), in environmental chemistry the strategy of sequential extraction has become dominant (fig.3). the first sequential extraction procedure for the characterisation of the mobility of heavy metals in aquatic sediments was developed by tessier et al. [5], who classified the metal content of sediments according to the solubility and binding forms of metallic species as presented in scheme 1. based on this essential work [5], numerous 5-8step sequential extraction schemes have been developed by which the original chemical structures (binding forms) are gradually dissolved and/or decomposed [9]. the complete duration of these procedures is 5–6 days, while the duration of the batch leaching steps is determined by a long setup time of solubility and heterogeneous chemical equilibria. the proposal for a 3(+1)-step sequential extraction procedure issued by bcr in 1993 is a simplified version of the above-mentioned schemes [6], but it is still time-consuming and labourintensive. as shown in scheme 1, the water soluble, weakly adsorbed, and carbonate-associated metal fractions are extracted simultaneously by acetic acid in the first leaching step. in the second step, the metal fractions associated with reducible fe and mn oxides are produced after reduction by hydroxylamine. a fraction of metals coordinated to organic molecules and associated with sulphides is extracted after oxidation by h2o2 in the third step. in the extra step, the residual fraction can be obtained by means of digestion with aqua regia or hno3/h2o2. re-adsorption of extracted metals during phase separation can lead to analyte losses. in the extracts, the high concentration of the reagent may cause strong matrix effects during spectrochemical element detection. the crm 601 sediment reference material issued in 1997 has been certified for this procedure only for cd, cr, ni, pb, and zn [7,8]. during the analysis of the bcr 701 sediment materials, the original bcr procedure was modified to avoid analyte loss during the second leaching step due to ph instability [10–13]. however, this modification in bcr procedure may cause significant differences relative to previously obtained data. the bcr procedures in their original and modified versions were successfully applied to aquatic sediments and soils; however, soil crm has not been issued for this procedure up to now [14–21]. it can be concluded that the tessier-based fractionation procedures [5] are widely used for heavy metal contamination assessments in soils and aquatic sediments, but the realistic interpretation of these data requires standardisation. however, this has been hindered due to methodological problems of measurements and analysis [22–23]. these problems limiting the application of the bcr sequential figure 2. strategy of serial single-step extractions. figure 3. strategy of sequential extractions (s(r) stands for solvent(reagent)). scheme 1. element fractions in aquatic sediment as classified by kersten and förstner [4], caroli [3], and tessier [5] (left-hand side) and the original bcr sequential extraction steps [6-8] (right-hand side) icp-oes multi-elemental calibration problems 43(1) pp. 7–13 (2015) doi: 10.1515/hjic-2015-0002 9 extraction procedure have initiated a cooperative research project between szent istván university gödöllő and the technical university košice as summarised in table 1. the aim of the given study was the evaluation of changes in the environmental mobility of heavy metals at two polluted areas (upper tisza/2000–2001 and gödöllőisaszeg lake system/1995–1998) by means of the repeated bcr fractionation of heavy metals in the sediments and soils [31–34]. a flexible, multi-elemental inductively coupled plasma-optical emission (icpoes) technique with a charge-coupled device (ccd)detection system was employed instead of the formerly applied flame atomic absorption spectroscopy (faas). the latter had to be optimised for each analyte element individually. hereby, the problems of the matrix-matched multi-elemental calibration of the icp-oes method are described using different solvent applied from the bcr procedure. the validation of the calibration was controlled by the fractionation of the crm 701 sample. 2. experimental 2.1. elemental analysis and instrumentation for element detection in different extractant matrices, the horiba jobin yvon activa-m icp-oe spectrometer was employed, which is able to record the entire uv-vis spectrum range by rapid scanning ccddetection. it also makes possible the flexible analytical line selection for 75 elements. the wavelength scale calibration of recorded spectra is based on a reference line position set by the user. the c 193.026 nm line is proposed by the manufacturer in routine analytical applications. the instrument’s scheme and technical parameters are presented in fig.4. introduction of the sample can be performed by a concentric glass nebuliser and glass cyclone spray chamber fed by a 3-channel peristaltic pump. 2.2. icp-oes operation parameters the operation parameters of icp-oes were selected on the basis of the manufacturer’s manual proposed for multi-elemental analysis as follows: • incident power: 1000 w, • plasma gas flow: 13.14 dm3 min-1, • sheath gas flow: 0.32 dm3 min-1, • nebuliser gas flow: 0.28 dm3 min-1, • nebuliser gas pressure: 2.86 bar, and • nebuliser sample flow uptake: 0.85 cm3 min-1. 2.3. matrix matched calibration solutions amounts of 1 mg dm-3 (in cc hno3) mono-elemental cd, co, cr, cu, fe, mn, ni, pb, v, and zn (précis certified standards for icp spectroscopy, horiba scientific, france) standard solutions corresponding to 0, 5, and 20 mg dm-3 concentrations were pipetted into a 50 cm3 volumetric flask and then diluted by solvents applied in the bcr sequential extraction procedure: • 1st step: 0.11 m acetic acid. • 2nd step: 0.1 m hydroxylamine-hydrochloride. • 3rd step: 1 m ammonium acetate. • extra step: 13 g/g nitric acid. 2.4. analytical lines the following analytical lines were selected according to the manufacturer’s proposal for multi-elemental analysis: • cd 214.441 nm • co 230.785 nm • cr 205.571 nm • cu 324.754 nm • fe 259.940 nm and 240.489 nm • mn 257.610 nm • ni 222.296 nm (instead of 221.650 nm!) • pb 220.353 nm • v 309.311 nm • zn 213.857 nm in the first, second, and extra step, the wavelength readout started from the c 193.026 nm reference line. in the third step, the correct wavelength readout was only figure 4. scheme of the horiba jobin yvon activa-m icp-oe spectrometer and relevant technical parameters table 1. overview of the cooperative research projects between szent istván university gödöllő and the technical university košice limitations of the bcr scheme achievements by szie and tu košice research groups does not match the natural mobilisation pathways → better modelling of environmental mobility by the application of h2o and h2o/co2 solvents [24]. does not preserve the intact species of the sample → application of aqueous extractions for the elaboration of biological tests [25]. time consuming (4-5 days) → acceleration of batch leaching by means of sonification [26]. → development of continuous flow operation in the supercritical fluid extractor for co2, h2o and h2o/co2 solvents [24] cross-contamination during operation and applied reagent ↗ → reduction of operations and reagents limited applicability and validation: validation and available crm only for sediments → extension of the application to other matrices: soils, gravitation dusts, biofilms, red mud, and composts [26-30]. validation of the procedure for cd, cr, cu, ni, pb, zn → multi-elemental calibration and validation for different matrices and extracts [27]. high reagent and organic content of the extracts ↗ focal length = 0.64 m dual back-to-back gratings: optical resolution < 10 pm for 120–430 nm and < 18 pm for 430–800 nm nebuliser 2048×512 pixels (13.5×13.5 µm) peltier cooling (-20 ºc) heltai, fekete, halász, kovács, horváth, takács, boros, and győri hungarian journal of industry and chemistry 10 possible when the readout started from the ar 404.442 nm reference line due to the use of 1 m ammonium acetate solution. 2.5. validation for validation of the crm 701 sediment, the reference sample was applied. the fractionation of its element content was performed according to the modified bcr proposal [10–13] in triplicates. for the extraction of the residual fraction in the extra step and for the determination of the pseudo total element content microwave supported cc hno3/h2o2 digestion was applied. table 2. the calibration lines (y = mx+b, at wave length λ in nm), correlation r2 values, residual standard deviations (rsd), background equivalent concentrations (bec in µg dm-3), and detection limits (cl(3σ) in µg dm-3) obtained by a 0.11 m acetic acid matrix. λ cl(3σ) bec m b r2 rsd cd 214.441 0.5 65 43778 2867 0.9999 1.1% co 230.785 0.8 145 41860 6064.7 0.9997 2.5% cr 205.571 1.5 174 18298 3184.2 0.9996 2.9% cu 324.754 0.2 121 159951 19374 0.9998 2.0% fe 259.940 0.5 72 205720 14716 0.9999 1.2% mn 257.610 0.2 105 902188 94673 0.9999 1.8% ni 222.296 2.0 115 7154 823.38 0.9998 2.0% pb 220.353 3.5 17 4087.4 68.946 1.0000 0.3% v 309.311 0.6 34 259817 8897 1.0000 0.5% zn 213.857 0.6 148 60540 8951 0.9998 2.2% table 3. the calibration lines (y = mx+b, at wave length λ in nm), correlation r2 values, residual standard deviations (rsd), background equivalent concentrations (bec in µg dm-3), and detection limits (cl(3σ) in µg dm-3) obtained by a 0.10 m hydroxylamine-hydrochloride matrix. λ cl(3σ) bec m b r2 rsd cd 214.441 0.9 87 47809 -4145.2 0.9999 1.5% co 230.785 1.4 19 44538 -856.49 1.0000 0.3% cr 205.571 1.4 14 18911 -258.4 1.0000 0.2% cu 324.754 0.9 72 163871 11765 1.0000 1.0% fe 259.940 0.3 1 204879 236.82 1.0000 0.2% mn 257.610 0.2 63 911472 57160 0.9999 1.1% ni 222.296 3.7 63 7505.8 471.04 1.0000 1.0% pb 220.353 3.9 4 4375.2 -17.636 1.0000 0.2% v 309.311 0.2 58 260057 -15164 1.0000 1.0% zn 213.857 1.5 45 63846 2845.5 1.0000 0.5% table 4. the calibration lines (y = mx+b, at wave length λ in nm), correlation r2 values, residual standard deviations (rsd), background equivalent concentrations (bec in µg dm-3), and detection limits (cl(3σ) in µg dm-3) obtained by a 1.00 m ammoniumacetate matrix. λ cl(3σ) bec m b r2 rsd cd 214.441 0.6 57 70051 -4008.3 1.0000 1.0% co 230.785 1.4 2 54840 -119.26 1.0000 0.03% cr 205.571 1.2 21 25579 546.52 1.0000 0.3% cu 324.754 2.5 213 151053 32156 0.9994 3.5% fe 259.940 15.8 160 258243 41379 1.0000 0.6% mn 257.610 0.4 2 1291505 2013 1.0000 0.02% ni 222.296 2.3 17 9902 -170.25 1.0000 0.3% pb 220.353 3.5 148 5905.2 -874.08 0.9997 2.6% v 309.311 1.4 85 312207 26636 0.9999 1.4% zn 213.857 14.5 33 79775 2643.2 0.9968 1.9% table 5. the calibration lines (y = mx+b, at wave length λ in nm), correlation r2 values, residual standard deviations (rsd), background equivalent concentrations (bec in µg dm-3), and detection limits (cl(3σ) in µg dm-3) obtained by a 13 g/g nitric acid and hydrogen peroxide matrix. λ cl(3σ) bec m b r2 rsd cd 214.441 0.4 392 74770 29293 0.9980 6.6% co 230.785 3.5 319 50151 16009 0.9986 5.4% cr 205.571 1.7 328 23088 7580.7 0.9986 5.5% cu 324.754 0.9 343 104399 35859 0.9985 5.6% fe 259.940 0.7 219 216961 47594 0.9995 3.2% mn 257.610 0.5 211 1056725 222941 1.0000 3.6% ni 222.296 0.5 320 9282.3 2974.7 0.9987 5.4% pb 220.353 8.7 265 6483.7 1717.4 0.9991 4.4% v 309.311 0.7 54 256488 13775 1.0000 0.9% zn 213.857 17.3 517 87624 45308 0.9968 8.3% table 6. results for the bcr-fractionation of element content (in µg dm-3) of the crm 701 sample. steps measured certified recovery 1st cd 6.45 ± 0.07 7.34 ± 0.35 88% co 1.68 ± 0.06 cr 1.88 ± 0.08 2.26 ± 0.16 83% cu 44.93 ± 0.25 49.3 ± 1.7 91% fe 57.74 ± 2.53 mn 133.17 ± 6.52 ni 12.52 ± 0.34 15.4 ± 0.9 81% pb 1.92 ± 0.19 3.18 ± 0.21 60% v 0.06 ± 0.23 zn 160.07 ± 4.22 205 ± 6 78% 2nd cd 3.96 ± 0.08 3.77 ± 0.28 105% co 2.71 ± 0.03 cr 26.53 ± 0.78 45.7 ± 2 58% cu 87.61 ± 0.81 124 ± 3 71% fe 5648 ± 50 mn 106.99 ± 2.90 ni 19.55 ± 0.35 26.6 ± 1.3 73% pb 92.17 ± 2.24 126 ± 3 73% v 8.50 ± 0.09 zn 98.77 ± 2.27 114 ± 5 87% 3rd cd 1.17 ± 0.01 0.27 ± 0.06 435% co 1.80 ± 0.08 cr 196.4 ± 8.24 143 ± 7 137% cu 63.59 ± 2.92 55.2 ± 4 115% fe 4652 ± 133 mn 43.65 ± 1.25 ni 24.49 ± 0.35 15.3 ± 0.9 160% pb 60.14 ± 0.82 9.3 ± 2 647% v 5.86 ± 0.21 zn 66.44 ± 0.62 45.7 ± 4 145% extra cd 1.38 ± 0.01 co 7.63 ± 0.18 cr 101.12 ± 4.79 cu 49.48 ± 1.92 fe 24988 ± 805 mn 302.9 ± 3.7 ni 44.50 ± 1.36 pb 12.77 ± 0.30 v 40.30 ± 0.67 zn 127.12 ± 1.36 icp-oes multi-elemental calibration problems 43(1) pp. 7–13 (2015) doi: 10.1515/hjic-2015-0002 11 3. results and analysis the parameters of analytical calibration lines, background equivalent concentrations (bec) and detection limits (cl(3σ)) obtained by different extraction matrices are summarised in tables 2–5. it can be established that the extraction matrix solvents significantly influence the sensitivity (b) values for all elements in the order of b(3rd) > b(extra) > b(2nd) > b(1st) as a function of steps taken. with the exception of some outliers, the residual standard deviation values are in the range of 1–2% and the detection limits are in the range of 0.5–2 µg dm-3. the outliers for pb, zn and fe in certain matrices refer to neglected spectral interferences. the results of the fractionation of the element content of the crm 701 sample by applying the matrix matched calibration for determining the element contents in the extracts are summarised and compared with the certified and pseudo-total values in tables 6–8. it can be seen that the metal content in bcr steps 1–3 shows an acceptable agreement (< mg dm-3) with certified values. in the individual steps, there are larger differences for elements than are acceptable: 1st step: pb; 2nd step: cr, cu, and pb; 3rd step: cd, ni, pb, and zn. 4. conclusion based on the results presented here, it can be concluded that the extractants applied in the bcr sequential extraction procedure cause significant matrix effects even in the case of matrix-matched multi-elemental calibration of the icp-oes determination of element content. the sensitivities were strongly influenced by the extractant media, therefore, a much higher incident power was required to eliminate these differences to ensure conditions that are more robust. the recoveries of certified values of the crm 701 sample were within the acceptable range when the summary of extracted amounts in the bcr steps 1–3 was compared. significant differences occurring in individual extraction steps between the measured and certified values refer to neglected spectral interferences. this requires a detailed study utilising the flexible line selection possibility offered by the horiba jobin yvon activa-m instrument. acknowledgement this work was supported by the hungarian scientific research fund (otka 108558), ktia aik-12-1-20120012 and the research centre of excellence 85265/2014/tudpol. references [1] gunn, a.m.; winnard, d.a.; hunt, d.t.e. : trace metal speciation in sediment and soils, in metal speciation: theory, analysis and application, eds.: kramer, j.r.; allen, h.e. (lewis publications, boca raton, fl, usa) 1988 isbn 0873711408 9780873711401 [2] templeton, d.m.; ariese, f.; cornelis, r.; danielsson, l.g.; muntau, h.; van leeuwen, h.p.; lobinski, r.: guidelines for terms related to chemical speciation and fractionation of elements. definitions, structural aspects, and methodological approaches, pure appl. chem., 2000 72, 1453–1470 10.1351/pac200072081453 [3] caroli, s.: element speciation in bioorganic chemistry (wiley, new york, usa) 1996 isbn 0471-57641-7 [4] kersten, m.; förstner, m.: speciation of trace metals in sediments and combustion waste. in chemical speciation in the environment, eds.: ure, a.m.; davidson, c.m. (blackie academic and professional, london, u.k.) 1995, pp. 237275 [5] tessier, a.; campbell, p.g.c.; bisson, m.: sequential extraction procedure for the speciation of particulate trace metals, anal. chem., 1979, 51, 844–851 10.1021/ac50043a017 [6] ure, a.m.; quevauviller, ph.; muntau, h.; griepink, b.: speciation of heavy-metals in soils and sediments an account of the improvement and harmonization of extraction techniques undertaken under the auspices of the bcr of the commission of the european communities, int. j. envir. anal. chem., 1993 51, 135–151 10.1080/0306731908027619 table 7. comparison of the summarised element content (in mg kg-1) extracted in bcr steps 1-3 using certified values for the crm 701 sample. steps 1-3 certified recovery cd 11.58 11.38 102% co 6.19 cr 224.8 191.0 118% cu 196.1 228.5 86% fe 10358 mn 283.8 ni 56.6 57.3 99% pb 154.2 138.5 111% v 14.42 zn 325.3 364.7 89% table 8. comparison of the summarised element content (in mg kg-1) extracted in bcr steps 1-3 using pseudo-total values. steps 1-3+extra pseudo-total recovery cd 12.96 9.63 135% co 13.81 10.68 129% cr 325.9 290.5 112% cu 245.6 257.7 95% fe 35323 31285 113% mn 586.4 567.7 103% ni 101.0 77.2 131% pb 167.0 158.2 106% v 54.68 39.20 140% zn 452.3 417.7 108% heltai, fekete, halász, kovács, horváth, takács, boros, and győri hungarian journal of industry and chemistry 12 [7] quevauviller, p.; rauret, g.; lópez-sánchez, j.f.; rubio, r.; ure, a.; muntau, h.: certification of trace metal extractable contents in a sediment reference material (crm 601) following a threestep sequential extraction procedure, sci. total environ., 1997 205, 223–234 10.1016/s00489697(97)00205-2 [8] lópez-sánchez, j.f.; sahuquillo, a.; fiedler, h.d.; rubio, r.; rauret, g.; muntau, h.; quevauviller, ph.: crm 601, a stable material for its extractable content of heavy metals, analyst, 1998 123, 1675– 1677 10.1039/a8022720j [9] gleyzes, c.; tellier, s.; astruc, m.: fractionation studies of trace elements in 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tested and optimised three-step sequential extraction procedure, j. envir. monit., 2001 3, 243–250 10.1039/b01025k [13] rauret, g.; lópez-sánchez, j.f.; lück, d.; ylihalla, m.; muntau, h.; quevauviller, ph.: certification of the extractable contents of cd, cr, cu, ni, pb and zn in a freshwater sediment following a collaboratively tested and optimised three-step sequential extraction procedure, european commission bcr information reference materials bcr 701, 2001 isbn 92-894-0755-7 [14] sahuquillo, a.; rigol, a.; rauret, g.: overview of the use of leaching/extraction tests for risk assessment of trace metals in contaminated soils and sediments, trends anal. chem., 2003 22, 152– 159 10.1016./s0165-9936(03)00303-0 [15] žemberyová, m.; barteková, j.; hagarová, i.: the utilization of modified bcr three-step sequential extraction procedure for the fractionation of cd, cr, cu, ni, pb and zn in soil reference materials of different origins, talanta, 2006 70, 973–978 10.1016/j.talanta.2006.05.057 [16] kubová, j.; streško, v.; bujdoš, m.; matúš, p.; medved, j.: fractionation of various elements in crms and in polluted soils, anal. bioanal. chem., 2004 379, 108–114 10.1007/s00214-004-2505-5 [17] kubová, j.; matúš, p.; hagarová, i.; bujdoš, m.; medved, j.: utilization of optimised bcr threestep sequential and dilute hcl single extraction procedures for soil–plant metal transfer predictions in contaminated lands, talanta, 2008 75, 1110– 1122 10.1016/j.talanta.2008.01.002 [18] konradi, e.a.; frentiu, t.; ponta, m.; cordos, e.: use of sequential extraction to assess metal fractionation in soils from bozanta mare, romania, acta univers. cibiniensis ser. f chemia, 2005 8(2), 5–12 http://saiapm.ulbsibiu.ro/rom/cercetare/art/art2.pdf [19] okoro, h.k.; fatoki, o.s.; adekola, f.a.; ximba, b.j.; snyman, r.g.: a review of sequential extraction procedures for heavy metals speciation in soil and sediments, open access sci. rep., 2012 1(3): 181 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heltai, gy.; fehér, b.; percsich, k.; barabás, b.; fekete, i.: application of sequential extraction with supercritical co2, subcritical h2o, and an h2o/co2 mixture for estimation of environmentally mobile heavy metal fractions in sediments, anal. bioanal. chem., 2002 373(8), 863–866 10.1007/s00216-0021388-6 [25] heltai, gy.: chemical interpretation of a new sequential extraction scheme based on supercritical co2 and subcritical h2o solvents, bull. szent istván university, 2005, 107–122 [26] rusnák, r.; halász, g.; horváth, m.; remeteiová, d.: preliminary results on the intensification of the bcr sequential extraction with sonication for sediments, soils, and gravitation dust sediment samples, toxicol. environment. chem., 2010 92(3), 443–452 10.1080/02772240903300139 [27] horváth, m.; halász, g.; kucanová, e.; kuciková, b.; fekete, i.; remeteiová, d.; heltai, gy.; flórián, k.: sequential extraction studies on aquatic sediment and biofilm samples for the assessment of heavy metal mobility, microchem. j., 2013 107(3), 121–125 10.1016/j.microc.2012.05.024 icp-oes multi-elemental calibration problems 43(1) pp. 7–13 (2015) doi: 10.1515/hjic-2015-0002 13 [28] flórián, k.; matherny, m.; nickel, h.; pliešovská, n.; uhrinová, k.: environmental characteristics of the atmosphere of residential agglomerations i. dustiness of the agglomerations, chem. pap., 2003 57(5), 369–373 [29] flórián, k.; matherny, m.; nickel, h.; pliešovská, n.; uhrinová, k.: environmental characteristics of the atmosphere of residential agglomerations ii. main, minor, and trace elements in the gravitation dust sediments, chem. pap., 2003 57(5), 374–381 [30] remeteiová, d.; sminčáková, e.; flórián, k.: study of the chemical properties of gravitation dust sediments, microchim. acta, 2007 156(1-2), 109– 113 10.1007/s00604-006-0603-0 [31] shiowatana, j.; tantidanai, n.; noobkaew, s.; nacapricha, d.: a novel continuous–flow sequential extraction procedure for metal speciation in solids, j. environ. qual., 2001 30, 1195–1205 10.2134/jeq2001.3041195x [32] heltai, gy.; fekete, i.; gémesi, z.; percsich, k.; flórián, k.; tarr, zs. : environmental evaluation of a local lake chain affected by wastewater by means of spectrochemical analytical methods, microchem. j., 1998 59, 125–135 10.1006/mchj.1998.1574 [33] győri, z.; alapi, k.; szilágyi, sz.: effects of heavy metal on floodplain soils and pastures of the river tisza, hungary i. in natural attenuation of metals along the tisza river–floodplain–wetlands continuum (university of debrecen, debrecen, hungary) 2003, pp. 146–160 isbn: 963 472 726 3 [34] győri, z.; alapi, k.; sipos, p.; zubor, á.: effects of heavy metal on floodplain soils and pastures of the river tisza, hungary ii. in natural attenuation of metals along the tisza river–floodplain– wetlands continuum (university of debrecen, debrecen, hungary) 2003, pp. 161–163 isbn: 963 472 726 3 microsoft word inner cover.docx editorial preface systems and control theory is a constantly evolving scientific area and the dominant driving force in key industries and engineering fields e.g. process engineering, automotive engineering, bioengineering, and the energy industry. the aim of the current issue (volume 42, number 2) is to provide an overview of research topics pursued by selected phd students. the papers presented here were selected from contributions at the 13th international phd workshop on systems and control conference held on august 25, 2014 (virt.uni-pannon.hu/phdws2014). the objective of the conference was to establish an international forum for young researchers. the meeting provided opportunities for the participants to present and discuss the latest results and up-to-date applications in systems and control. this issue represents the entire spectrum of systems and control engineering as follows: • process modelling and analysis • control (traditional, intelligent, adaptive, etc.) • process monitoring and supervision • system identification and signal processing • bioengineering • traffic control • reaction kinetic networks • modelling of complex systems (classical, hierarchical, bayesian, fuzzy, networks) • image processing and pattern recognition • artificial intelligence • soft computing (neural, genetic, fuzzy algorithms, etc.) • software (parallel computing, distributed and network computing, data visualization) • decision making (decision support, data mining) • applications of systems and control theory the organizers are grateful for the contributions of the authors. the tradition of the international phd workshop continues. you are invited to participate at the 14th international phd workshop in veszprém in 2015! attila magyar university of pannonia, veszprém, hungary guest editor page 1 page 2 page 3 page 4 page 5 page 6 page 7 page 8 page 9 page 10 page 11 page 12 page 13 page 14 page 15 page 16 page 17 page 18 page 19 page 20 page 21 page 22 page 23 page 24 page 25 page 26 page 27 page 28 page 29 page 30 page 31 page 32 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450 page 451 page 452 page 453 page 454 page 455 page 456 page 457 page 458 page 459 page 460 page 461 page 462 page 463 page 464 page 465 page 466 page 467 page 468 page 469 page 470 page 471 page 472 page 473 page 474 page 475 page 476 page 477 page 478 page 479 page 480 page 481 page 482 page 483 page 484 page 485 page 486 page 487 page 488 page 489 page 490 page 491 page 492 page 493 page 494 page 495 page 496 page 497 page 498 page 499 page 500 page 501 page 502 page 503 page 504 page 505 page 506 page 507 page 508 page 509 page 510 page 511 page 512 page 513 page 514 page 515 page 516 page 517 page 518 page 519 page 520 page 521 page 522 page 523 page 524 page 525 page 526 page 527 page 528 page 529 page 530 page 531 page 532 page 533 page 534 page 535 page 536 page 537 page 538 page 539 page 540 page 541 page 542 page 543 page 544 page 545 page 546 page 547 page 548 page 549 page 550 page 551 page 552 page 553 page 554 page 555 page 556 page 557 page 558 page 559 page 560 page 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complex they can’t be exactly defined with simple measurement-technique. to define these geometries a computer tomography and methods with limited-element have been used. in the lecture we are introducing some interesting examples. keywords: gt suite, model, intake pipe, valve lift, computer tomography, straight pipe, bent pipe, y-connector introduction the research and development project set target to build the vehicle power train. the first important step is to build the internal combustion engine model. to build this model important data of the chosen engine are required. there are only a few of these as base data available. therefore most of the geometrical sizes have to be defined by measurements. the engine chosen for modelling is a 1.6-liter 8-valve gasoline engine. table 1: the main dates of chosen engines are as it follows: construction 4-cylinder line engine engine capacity 1595 cm3 bore ø81.0 mm stroke 77.4 mm compression ratio 10.3:1 max. power 75 kw, 5600 min-1 max. torque 148 nm, 3800 min-1 the characteristic curves are shown on fig. 1 and fig. 2. figure 1: engine torque figure 2: engine power 36 data validation for the model for the modelling it is necessary to know the elements of the intake and exhausting system details. hereinafter we show the method of the measuring process. defining the valve-lift chart we measured the valve moving chart with disassembled cylinder head. for this measuring we use inductive way and angle signaller. with this measuring technique we get the chart which is based on camshaft rotation. figure 3: measuring the valve movement chart (movement measure) figure 4: measuring the valve movement chart (angle signaller) figure 5: the valve movement chart from the measure definition of the mass data of the crank gear as an example, measurements of the mass of the piston are presented: table 2: results of the measurements connecting-rod mass 539.63 g mass without pin 286.6 g mass with pin 348.7 g piston + pin + connecting rod mass 886.86 g figure 6: measuring the piston mass definition of geometrical data of the crank gear we present the measurements of the data of the piston and combustion chamber measured on the components of the given engine. figure 7: piston geometrical dimensions ● piston cup diameter ø 62.4 mm ● maximum piston cup depth 2.5 mm ● piston cup diameter (edge) ø 62.4 mm ● piston cup centre depth 2.5 mm ● piston height 51 mm ● deck thickness 9.7 mm ● average ring thickness 3 mm 37 figure 8: piston and combustion chamber dimensions ● head region diameter (max.) ø80.6 mm ● head region diameter (edge) ø 80.6 mm ● head region height 8 mm data of the intake system with the computer tomography we can control the outside and inside geometries with high accuracy. the external profile can be measured with atos optical measuring system, and the 3d digitalizing system is creating a polygon-mesh with high resolution. the system converts these data to cad data using reverse engineering method. the steps of this process are: ● cloud-model ● stl file(*.stl) only the surface is described with the help of 923.196 triangle elements ● making the 3d model using the computer tomography geometries of lower part of the intake system ● fitting the guideline to intake system and defining the length of the axis and the angle between the two connecting surfaces ● using the section guideline we can measure the diameter of the intake system shown on fig. 10 figure 9: lower intake system figure 10: dimensions of the lower intake system data of exhaust system the geometric measures of the exhaust system have to be defined exactly. according to this the exhaust system pipes can be set up from the following model elements: 1. straight d=ø45.4 mm l=40 mm 2. bent d=ø45.4 mm 38°45’ r=45.4 mm 3. straight d=ø45.4 mm l=530 mm 4. y connector with 90° angle 5. straight d=ø45.4 mm l=80 mm 6. d=ø45.4 mm → ø130 mm l=47 mm 7. straight d=ø130 mm l=158 mm 8. d=ø130 mm → ø 54.4 mm l=47 mm 9. straight d=ø54.4 mm l=960 mm 10. bent d=ø54.4 mm 10° r=54.4 mm 11. straight d=ø54.4 mm l=230 mm 12. bent d=ø54.4 mm 55° r=54.4 mm 13. straight d=ø54.4 mm l=210 mm 14. bent d=ø54.4 mm 55° r=54.4 mm 15. straight d=ø54.4 mm l=40 mm 16. catalyst 17. straight d=ø54.4 mm l=40 mm 18. bent d=ø54.4 mm 30° r=54.4 mm 19. straight d=ø54.4 mm l=150 mm 20. bent d=ø54.4 mm 45° r=54.4 mm 21. straight d=ø54.4 mm l=260 mm 22. bent d=ø54.4 mm 45° r=54.4 mm 23. muffler 24. exhaust pipe end 38 figure 11: dimensions of the exhaust system it is quite simple to model the straight sections if we know the geometric data. the bent pipe length can be defined with the measured angle (length of arc): 360 r2i α ⋅π⋅⋅= (1) where: i – pipe length (mm) r – radius (mm) α – angle [°] to model the y-connector we have to give the dimensions precisely. beside this the volume has to be given according to changing size of the blue sphere on the model shown on fig. 12. we have to measure the following dimensions to define the catalytic system: ● the section of the catalytic system (11959 mm2) ● flow section (flow factor) from gt suite, value 70% ● we choose the following parameters for cell density which is 400 cpsi (cells per square inch) = 62 cells/cm2 (this value is used for passenger car) for modelling the silencer we use the gt suite sample model because we cannot disassembly the exhaust system. the silencer has a lot of parts like pipe and t connector, etc. which is shown on fig. 14. figure 12: modelling the y connector 39 figure 13: model of the catalytic system figure 14: model of the silencer summary to carry out the model of the chosen four-cylinder, 8valved, four stroke engine we have to get the rest of the dimensions. in this presentation we highlighted only some significant elements. acknowledgment the financial support of this work by the hungarian state and the european union under the tamop-4.2.1/b09/1/konv-2010-0003 project is kindly acknowledged. references 1. a. rahamn, m. dzaidin: optimal design of automobile exhaust system using gt-power, international journal of mechanical and materials engineering (ijmme), 2(1), (2007), 40–47 2. u. kramer: potentialanalyse des direktstarts für den einsatz in einem stopp-start-system an einem ottomotor mit strahlgeführter benzindirekteinspritzung unter besonderer berücksichtigung des motorauslaufvorgangs, dissertation, universität duisburg – essen, 2005 3. m. bos: validation gt-power model cyclops heavy duty diesel engine, msc. thesis, 2007 4. dr. i. lakatos ph.d.: gépjármű hajtáslánc modellezése és szimulációja, hajtáslánc optimális irányítása, mobilitás és környezet: járműipari, energetikai és környezeti kutatások a középés nyugat-dunántúli régióban támop 4.2.1/b09/1/konv-2010-0003 workshop, győr, 2011.06.27. 5. dr. i. lakatos: töltetcsere-időzítés hatása a négyütemű feltöltetlen otto-motorok üzemére, ph.d. disszertáció, bme, 2002, 112 p. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word 2012_dr_bodor_endre_hjic.doc hungarian journal of industrial chemistry veszprém vol. 39(3) pp. 331-333 (2011) feasibility study of gas separation membranes for biohydrogen separation p. bakonyi1, , n. nemestóthy1, j. ramirez2, g. ruiz-filippi2, k. bélafi-bakó1 1university of pannonia, research institute on bioengineering, membrane technology and energetics egyetem út 10, 8200 veszprém, hungary e-mail: bakonyip@almos.uni-pannon.hu 2pontificia universidad católica de valparaíso, escuela de ingeniería bioquimica, general cruz 34, valparaíso, chile hydrogen is considered as a promising clean energy carrier that could replace fossil fuels. it can be produced by several ways including biological processes which are definitely environmental-safe methods. unfortunately, the concentration of hydrogen in the gas mixture obtained during the fermentation process is not high enough for direct utilization (e.g. in fuel cells) since there are other gases (mainly carbon-dioxide) present as a result of the microbial activity. in this work concentration of biohydrogen by gas separation membranes were aimed to study. two different membrane modules were tested in order to obtain pure hydrogen. the permeabilities and selectivities for both membranes were determined by single gas experiments and the feasibility of the membranes for biohydrogen separation was discussed. keywords: separation, membranes, biohydrogen introduction in most cases removal of hydrogen from the headspace of the bioreactor is required in continuous hydrogen producing biosystems [1], mainly due to the high partial pressure of hydrogen formed during the fermentation since it could significantly reduce gas production rates and yields [2]. therefore, separation and enrichment of biohydrogen is desirable in order to ensure optimal conditions for sustainable microbial hydrogen production and the appropriate concentration of hydrogen for its end-use e.g. in fuel cells [3, 4]. biohydrogen producing processes are carried out in gas tight bioreactors where anaerobic circumstances are always essential [5]. usually, anaerobic conditions at start-up phase are provided by inert gas sparging (e.g. nitrogen) in the liquid and gas phase within the fermenter [6]. the elimination of the redundant impurities from hydrogen is obviously needed. there are different methods for hydrogen separation and concentration including the membrane processes such as membrane gas separation [7, 8] which is considered extremely attractive from environmental point of view [9]. gas separation is one of the most widely applied membrane techniques which is basically a pressure driven procedure where the initial gas mixture is divided into two fractions (the permeate and the retentate) by the membrane [10]. these membranes can be characterized by different parameters but permeability and selectivity are considered the most important. among available polymers, membranes made of aromatic polysulfones [11], polycarbonates [12], polyarylates [13], polyaryl ketones [14], polyarylene ethers [15] and polyimides [16-18] have demonstrated appropriate potential for gas separation due to their favorable properties. in addition, porous membranes could also be used for gas separation (based on knudsen-diffusion) when the permeabilities and selectivities are determined by molecular weights of the gas compounds [10]. during gas separation the pressure issue is one of the most crucial limiting factors, therefore pressure difference must be maintained between the feed and the permeate side of the membrane in order to achieve high permeabilities and selectivities. at laboratory scale, high pressure ratio is generally provided by using compressors at the primary side (high feed pressure) while vacuum pumps are often used at the permeate side (low pressure) [10]. in present work two different gas separation membrane modules were aimed to study. single gas experiments with pure h2, co2, n2 were carried out to determine the permeabilities and theoretical selectivities (the ratios of the fluxes). afterwards, the feasibility of the membranes for hydrogen separation were performed based on the obtained experimental result. our final goal is to construct a continuous integrated system where biohydrogen fermentation and membrane gas separation could be coupled in order to produce purified hydrogen to be used in fuel cells. 332 materials and methods both membranes (me1 and me2) tested in dead-end experiments were non porous, hollow fibre, composite polymers which were manufactured at the university of twente. the me1 hollow fibres were made of matrimid 5218 polyimid. the polyimid is consisted of 3,3’,4,4’benzophenon tetracarboxyl-dianhydrid and diaminophenilidene, while me2 was a ppo (poly(2,6-dimethyl1,4-phenilene oxide)) supported hollow fibre membrane which were dipped and two times coated with pebax 1657 (polyether-polyamide or polyether block amide) 1% wt. the membranes were built in a high pressure stainless steel tube (fig. 1). the active transfer surface area of me1 and me2 were 12 cm2 and 25 cm2, respectively. the hydrogen, nitrogen and carbon-dioxide gases in cylinders were the products of messer hungarogas (hungary) with a purity higher than 99.9 vol%. the membrane modules were tested using single gases, and the permeation rates were determined. the feed gases were delivered on the shell side of the modules at ~2 bar pressure from a buffer vessel (approx. 2.4 l), while permeate was collected from the inner side of the fibres. the temperature was maintained at 40 °c. figure 1: the capillary membrane module results and discussion gas separation measurements were performed using pure, single gases: hydrogen, nitrogen and carbon dioxide where the decreasing pressure of the feed gas with time was followed. the measured and evaluated data for me1 and me2 membranes are demonstrated in fig. 2 and fig. 3, respectively. 2.05 2.1 2.15 2.2 2.25 2.3 2.35 0 4 8 12 16 20 0 20 40 60 80 100 fe ed p re ss ur e ( ba r) pe rm ea tio n ra te (g pu ) time (min) co2 permeation rate h2 permeation rate n2 permeation rate co2 pressure h2 pressure n2 pressure figure 2: the permeation data for me1 1.94 1.96 1.98 2 2.02 2.04 2.06 2.08 0 10 20 30 40 50 60 70 80 90 0 10 20 30 40 50 60 fe ed p re ss ur e ( ba r) pe rm et io n ra te (g pu ) time (min) h2 permeation rate co2 permeation rate n2 permeation rate h2 pressure co2 pressure n2 pressure figure 3: the permeation data for me2 it seems that pressure decreased rather quickly due to the high gas permeation through the membrane thus the experiments were conducted in a narrow range of pressure. the permeabilities were determined when steady-state occurred. based on the determined permeabilities the theoretical selectivities were calculated as a ratio of the permeation rates of the various gases and the results for me1 and me2 modules are listed in table 1. table 1: the theoretical selectivities for me1and me2 me1 me2 h2/n2 21.2 9.8 h2/co2 4.5 0.5 co2/n2 4.7 18.1 selectivity (40 oc) experimental results indicated that me1 and me2 gas separation membranes have advantageous properties regarding the selectivities and permeabilities (not shown). the h2/n2 selectivity is remarkably high for both membranes, while the h2/co2 selectivity of me1 and co2/n2 of me2 would appear to meet the requirements of carbon-dioxide separation. it can be pointed out that membranes tested are attractive for h2 recovery and these membrane materials have high potential for practical applications but it is important to consider that the industrial applicability of the modules requires extended research with binary and ternary model gas mixtures and long-term experiments using raw gas directly from the fermenter are particularly important, as well. acknowledgement this work was financially supported by the european union and co-financed by the european social fund in the frame of the tamop-4.2.1/b-09/1/konv-20100003 and tamop-4.2.2/b-10/1-2010-0025 projects and fondecyt project 1090482 from conicyt. the authors would like to acknowledge kitty nijmeijer et al. (university of twente) for the gas separation membranes. 333 references 1. d. h. kim, s. k. han, s. h. kim, h. s. shin: effect of gas sparging on continuous fermentative hydrogen production. int j hydrogen energy 2006, 31, 2158–2169 2. k. bélafi-bakó, d. búcsú, z. pientka, b. bálint, z. herbel, k. l. kovács, m. wessling: integration of biohydrogen fermentation and gas separation processes to recover and enrich hydrogen. int j hydrogen energy 2006, 31, 1490–1495 3. p. c. hallenbeck: fermentative hydrogen production: principles, progress, and prognosis. int j hydrogen energy 2009, 34, 7379–7389 4. t. m. liang, s. c. cheng, k. l. wu: behavioral study on biohydrogen fermentaion reactor installed with silicone rubber membrane. int j hydrogen energy 2002, 27, 1157–1165 5. d. das, t. n. veiroğlu: hydrogen production by biological processes: a survey of literature. int. j. hydrogen energy 2001, 26, 13–28 6. d. b. levin, l. pitt, m. love: biohydrogen production: prospects and limitations to practical application. int. j. hydrogen energy 2004, 29, 173–185 7. m. harasimowicz, p. orluk, g. zakrzewskatrznadel, a. g. chmielewski: application of polyimide membranes for biogas purification and enrichment. j haz mat 2007, 144, 698–702 8. p. pandey, r. s. chauhan: membranes for gas separation. prog polymeric sci 2001, 26, 853–893 9. e. szentgyorgyi, n. nemestothy, k. belafibako: biomethane production by gas separation membranes. des water treat 2010,14, 112–115 10. m. h. v. mulder: basic principles of membrane technology. kluwer academic publishers, dordrecht, 1996 11. j. j. mchattie, w. j. koros, d. r. paul: gas transport properties of polysulfones. part ii. effect of bisphenol connector groups. polymer 1991, 32, 2618–2625 12. m. w. hellums, w. j. koros, g. r. husk, d. r. paul: gas transport in halogencontaining aromatic polycarbonates. j appl polym sci 1991, 43, 1977– 1986 13. m. r. pixton, d. r. paul: gas transport properties of polyarylates. part i. connector and pendant group effects. j polym sci part b: polym phys 1995, 33, 1135–1149 14. j. m. mohr, d. r. paul, g. l. tullos, p. e. cassidy: gas transport properties of a series of poly(ether ketone) polymers. polymer 1991, 32, 2387–2394 15. m. aquilar-vega, d. r. paul: gas transport properties of polyphenylene ethers. j polym sci part b: polym phys 1993, 31, 1577–1589 16. t. s. chung, e. r. kafchinski, p. foley: development of asymmetric hollow fibers from polyimides for air separation. j membr sci 1995, 75, 181–195 17. a. y. alentiev, k. a. loza, y. p. yampolskii: development of the methods for prediction of gas permeation parameters of glassy polymers: polyimides as alternating copolymers. j membr sci 2000, 167, 91–106 18. s. r. reijerkerk, k. nijmeijer, p. r. cláudio, b. d. freeman, m. wessling: on the effects of plasticization in co2/light gas separation using polymeric solubility selective membranes. j membr sci 2011, 367(1-2), 33–44 hungaria journal of industrial chemistry./ veszprém vol. 14. pp. 22;'-236 (1986) computer drawing of enthalpy-humidity charts z. pakowski (institute of chemical engineering, lodz technical university, lodz, poland) received: september 3, 1985 enthajpy-humidity charta for a gas-vllpour mixture still provide a fast and easy tool for use in process culculations in drying, solvent recovery and related procesees. they have to be individualjy constructed for each new system encountered. the computer graphplotting method provides a fast and reliuble way of enthalpy-humidity chart production. theoretical principles of computerized i-y chart plotting are provided. exemplary char ts for systema of nitrogen and benzene, n-heptane, and cyclohexane are given. introduction traditionally parametere of a humid gas were presented on a psychrometric chart made in rectangular linear coordinates: temperature v.8. absolute humidity y. such charta containing lines of constant relative humidity, and constant wet-bulb temperature are still in use in psychrometry, le. humidity measuring by wet and dry-bulb ternperature read-outs, in 1923, r. mollier [1] introduced an enthalpy-humidity chart (i-y chart) allowing for simultaneous humidity, temperature and enthalpy read-outs. the chart was initially constructed in rectangular enthalpy-humidity coordinates. ral\izin modified the chart by introducing oblique axes, which allow for better resolution of rh lines in low humidity area. figure 1 presenta a comparison of both types of charta, i.e. psychrometric versus enthalpy-humidity chart. the relationships on which both charta are made can be directly used in a computer programme [2], however, the graphical form of a chart is handy in practical use and visually appealíng when used for presentation of the computed resulta. there are many industrial processes (e.g. drying) in which mixtures of vapour and inert gas other than water and air are dealt with. enthalpyhumidity charta for such systems are only occaaionallyencountered in literature (e.g. [3]-tricworoethylene-air and [4]-n2-methanol; n2-toluene). on the other hand, a fully computerized production of enthalpy-humidity charta 16 226 z. pakowski y )4-",ir / '-l -:v ./ -:;;... vol. 14' .....y "fig.l two typ es of charta for humid gasea a paychrornetric, b enthalpy-humidity (mollier chart) is feasible and has already been irnplemented by the leading dríer manufacturers [5]. this paper presents the principles of the computerized drawing of iy charta, together with ex mplary charta produced in this way. p rp=p. summary of thermodynamic relationships for a gas-vapour mixture absolute humidity y is a number of kilograms of vapour per kilogram of dry gas. relative humidily ep is a ratio of actnal partial pressure of vapour to that of saturated vapour at the same temperature: (1) on the basis of dalton's law, there is a following relationship between the two humidites: y=d rpp. p-q,p. (2) where d=maimij. (3) dew point temperaiure to is the temperature at which the vapour in gas becomes saturated. by cooling gas below this temperature, fog is formed. enthalpy of humid qae i is calculated additively aceording to the simplified formula: i=(cr+cay)t+.óh.oy (4) where specifíc heats cb and ca are averaged values. a veraging is perforrned between the reference ternperature and temperature t. for substances whose melting point is below o ° ,the reference temperature is taken as o oc. the latént heat of vaporization l1hvo is taken at the same temperature. temperature of adiabatic saturation tas corresporrds to the equilibrium between gas and liquíd, and can be calculated aceording to the following equation: 1986 computer drawing of enthalpy-humidity charta 227 . .. t -1.as y-y:' (5) wel bulb temperalure twb is reached by a small amount of liquid exposed to a large quantity of gas. contrary to the la. it is controlled by kinetics of heat and mass transfer, and therefore depends on the lewis number le=sc/pr. theoretical (thermodynamical) wet bulb temperature can be calculated from the following formula [4]: (6) where: (7) the coefficient {3is a correcting factor usually close to 1. geometry of the enthalpy-humidity chart an enthalpy-humidity chart is made in an oblique coordinate system. the vertical axis contains an enthalpy scale and the oblique axis an absolute humidity scale. both scales are linear. in practice the projection of the oblique y axis on a horizontalone is used, since the range of parameters between these two is of little intere t in indu trial applications. finally on a rectangular chart we have a grid of vertical constant y lines and oblique constant i lines (ísoenthalps). the angle between them i arbitrarily chosen as 1350 for an air-water system, although it can be selected otherwise. as each point in the chart simultaneou ly gives enthalpy, humidity and temperature, a grid of isotherms is also placed in the chart. on top of that, lines of constant relative humidity y are superimposed with the most important one for ip= 100%the saturation line. for fúrther information, lines of constant adiabatic saturation temperature and constant wet bulb temperature are added. au these elements of i-y chart geometry are shown in fig. 2. y yci ,, y ~ x yct 16· fig.2 elements of enthalpy-hwnidity chart geometry 228 z. pakowski vol. 14. when using a computerized graph-plotter, all these lines must be converted into x, y coordinates of the plotter. therefore equations of all basic lines of i-y chart must be first derived. for that purpose we assume that at the origin of graph-plotter coordinates (x = o and y = o) we also have i= o and y = o. additionally, scaling factors for enthalpy and humidity scales 81 and 8y are set in such a way that: y=byl (8) (9) where l is a certaln distance from the origin in unita of the plotter (mm or inches). lsoenthalp equation isoenthalp as a straight line has the following equation: (10) the intercept yci on the basis of (8) is given by: yc1=i/bl (ll) the slope al can be calculated from both intercepts xli and ycl' usually the slope is selected in such a way that: ycibl = llhvoxc!by (12) it is equivalent with an assumption that t = 0° isotherm coincides with the horizental axis x (as will be proven later). ome authars select other forms of condition (12), which leads to a different location of the isotherm 0°0. oombining (io), (ll) and (12) we have: al= llhvo(by/bi) (13) and therefore the isoenthalp equation has the following form: y= llhvo(by/bt}x+i/bi (14) constant y line equation as vertical lines they have a trivial form of: 8yx=const (15) isotherm equation local slope at of an isotherrn is given by the ratio lly / llx as can be seen in fig. 3. the value of lly can be found from isoenthaips as: lly = alllx + !li/bi (16) on the other hand, from (14) it follows that: (17) hence: lly at=llx (18) 1986 computer drawing of enthalpy-humidity charta 229 fig.3 auxiliary diagram for evaluation of slope of isotherm which on the basis of (13) is equal to: at = catby/81 (19) as can easily be seen from (19) the slope is constant for given t (but changes with temperature). therefore, the isotherma are straight lines. the full isotherm equation has the form: y=at.x+yct (20) where yct can be easily found from the enthalpy scale (on the vertical axis y =0) as: (21) finally we have: 8y y =cat x +cbf,/81 81 (22) it is worth noticing that for t= o y= o so the isotherm o oc is identical with the x axis, in the fog area, isotherma follow a different equation (that of an adiabatic saturation line), which is explained in most textbooks. this area is of littie industrial interest and will be omitted here. other lines the remaining lines are not straight (in principle it amo concerns tas and twb lines). deriving a detaíled equation for these lines is not always simple or feasíble, taking into consideration changes of specific heats and other parameters with temperature, other plotting procedures are then employed. the scale factora 8y and 81 are selected on the basis of the required dimensions of the chart áx and áy (in graph-plotter unita) and maximum values of temperature and humidity to be covered by the chart. they are given by the formulas: ymax 8y=-ax cntmax 81=-áy (23, 24) plotting of the individual elements of the enthalpy-humidity charta is performed by procedures described below. 230 z. pakowski vol. 14. procedure: isoenthalp draws subsequent isoenthalp for agiven increment lli. line drawing subroutine of graph plotter is used. each time end points of an isoenthalp are calculated prior to plotting. the end points correspond to an intersection of the isoenthalp and chart frame. procedure: isohu mid-y using the line plotting subroutine of graph-plotter plots vertical lines for a given increment lly. procedure: isotherm using the line plotting subroutine plots isotherms for agiven increment llt. the left end of eaoh isotherm corresponds to the left side of the frame, the right end oorresponds to the saturation line or the frame side (right or upper). the intersection point of an isotherm with saturation line is computed using eq. (2). additionally a boiling point isotherm (dashed line in figs. 4-6) is drawn. procedure: isohu mid-rh draws ep = const lines for given values of ep tarting with ep = 1. they are indicated on the right-hand side of the chart frame. it employs a three-point parabole fitting procedure of the plotter. for a given ep the following prooedure is performed: three values of temperature are taken (starting with t= o) corresponding values of yare computed from eq. (2) coordinates of these three points are converted into the x, y coordinates of the plotter a ourve is drawn through these points and the procedure repeated with the next three values of t unti! t = tb or unti! y:> ymax' procedure: ast line a function plotting subroutine of the plotter is used in general to aooommodate ohanges of speoific heats with temperature. if high aoouraoy can be saorificed, then a straight line procedure may be used. procedure: wbt line beoause of the implicit form of the relationship (6), a similar procedure as for relative humidity lines was employed. for agiven twb three subsequent values of t are taken, starting with a point on the saturation line. then by a numerical method eq. (6) is solved to find corresponding values of y. after conversion of ooordinates, a curve is drawn through these points and new values of temperature taken. this procedure was not employed in figs. 4-6.-: 1986 computer drawing of enthalpy-humidity charta 231 m~llier chart f~r benzene-nitr~gen pre s s u r_~ 1 o 1325. o .p a 5 c als rhy. s. 10. 20. 30. 40. 50. 60. 70. 60. 90. 100. \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \\ \ \ "\ \ <t\ \ '''.' \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ ,.. \ \ \ \ tn \ \ \ \ \ :< \ \ \ \ '"\ >< \ \ \ \ \ \ \ a. \ \ \ \ \ \ .. \ \ \~ \ \ \ \ \ n\ \ \ \ \ \ \ \ \ \\ \ \ \ \ \ \ \ \ \ \\ \ \ \ \ \ \ o \ \ cb. o 200.0 400.0 600.0 600.0 humioit'r. g/kg fig.4 enthalpy-humidity chart for nitrogen-benzene 232 z. pakowski vol. 14. m~llier pressure chrrt f~r 101.~25. o n-heptrne-nitr~gen prscrls rh~ 5. 10. 20. 30: 40. 50. 60. 70. 80. 90. 100.': n ci> '"•• '"'":ii: d x a: el ••• .l \ \ \ 200.0 \ \ lod.o ~co.o 8 hum 10 1tt. g/ kg fig.5 ,/ enthalpy-humidity chart for nitrogen-n-heptane 1~00_0 \200.0 1986 computer drawing of enthalpy-humidity charta 233 mollier chrrt for pressur~101325. o cyclohexrne-nitrogen prscrls t!>~ <,-, ~ )c, -'ci: :r: lz: lll rmi 5. 10. 20. 30. 40. 50. 60. 70. 80. 90. 100. gl~~t~'~~\11~~í~~t~1~~1~1~~ís)t~~=jf\~\{t~~~~i\~\i\t~it\~~t~j~~f~~~\~\t~jt~f~~~~f;j\ \ \ \ \ \ \ \ \ \ \ \ o \ \ \ \ ~. o 200_ ji 400. o 600. o800. a 1000. ahumioity.g/kg n., a> 7 '"\ •.. \ "\ o \ '"a:... n. fig.6 enthalpyhumidity chart for nitrogen-cyclohexane 234 z. pakowski vol. 14. a uxiliary procedurea these procedures draw picture frame, temperature, enthalpy and humidity scales and print the chart's title. closure the above described procedure were used in the programme grafite written in fortra for a zeta 3653 c plotter. a series of charta for most common systems were dawn [6j. eiqures 4-6 contain three charta for selected systems. data used for plotting th ee charts are given in the appendix. the method is highly efficient and can be used for chart production in the design of elosed cycle dryers for pharmaceutical and other industries. appendix data used for plotting the enclosed charts 1. specific heat of gas and vapour was calculated from the following equation: el=a+ bx lo-2t+ c x lo-at2+ a»: lo-gts with coefficients: b o d ben zene -0.4716 6.2177 -4.079 1.013 n-hept.mo q. 24 5 6.0392 2.739 0.4144 cyclohexane -0.71171 8.0170 -4.4361 0.91344 nitrogen 1.05679 0.1973 0.4948 0.18834 a b o d 2. specific heat of liquid was ealcula ted from the following equation: cl=a+ sx lo-2t+ex 1o-4t2+dx lo-7t3 with coefficients: ben zene -6.2007 6.472 -1.8296 1. 459 n-heptane 0.12796 1.651 -0.4262 0.46061 cyclohexane 5.3759 5.6061 -1.4695 1.3510 3. saturated vapour pressure was oalculated from the following equation: /' iogio (p./133.322}=a-b/(e+t) 1986 computer drawing of enthalpy-humidity charta with coefficients: 235 a b c ben zene n-heptane cyclobexane 6. 9272 6.90253 6.84941 1203.531 1267.82 1206.001 219.888 216.823 223.148 4. molar masses and latent heat of vaporization at ooc were as follows: axay ll:! at ca cb cal ca d l1hv l1hvo i le l ma. mb p p p. 81 8y t t tms" x yymax ~ ffj m ben zene n-heptane cyclohexane nitrogen 78.11 100.20 86.17 28.01 446 381 406 ymbols dimension of chart in x-direction, mrn dim nsion of chart in y-dlrection, mrn slope of the isoenthalp, slope of the isotherm, specific heat of vapour (moisture), kj/kgk specific heab of gas (inert), kj /kgk specifío heat of liquid (moisture), kj/kgk humid heat eq. (7), kj /kgk rnolar mass ratio, latent heat of vaporízation, kj /kg lo.tent heat of vaporization at standard temperature (o oc),kj /kg enthalpy of humid gas, kj/kg dry gas levls number, distance from the origin of chart, mm molar mass of moisture, kmol/kg molar mass of gas, kmol/kg ambient pressure, pa vapour pressure, pa saturated vapolll' pressure, pa scaling factor for enthalpy, kj/kg mm scaling factor for humidlty, kg/kg mm temperature, k temperature, oc maximum temperacure on the chart, oc horizental coordinte of graph-plotter, mm absolute humidity, kg/kg dry gas maximum absolute humidity on the chart, kg/kg dry gas vertical coordinate of graph-plotter, mm correction factor in eq. (6), relative humidity (rh), 236 z. pakowski vol. 14. subscripts and superscripts as wb * adiabatic saturation point wet bulb point saturated averaged between standard and given temparature references 1. mollier,r.: zeits. vdi, 1923, 67, 869. 2. brooker,d. b.: trans. of the asme, 1967, 558. 3. mrowieo,m., ciesielozyk,w.: inz. iap. chem., 1976, 1, 22. 4. keey, r. b.: iriteoductíon to industrial drying operutions, pergamon press, 1978. 5. moller,j. t., hansen, o.: proc. eng., 1972, 53, 84. 6. pakowski, z.: enthalpy-humidity charts. in: handbook of industriul drying, ed. a. s. mujumdar, marcel dekker, 1986. pe3iome .llharpammbi nma sararmax-arraroconepscaaae raaoao-napossrx cmecea oka3bibaetciisecswa rrone3hblm hhctpymehtom b pacxérax npoueccos cynrxa h h3bne'fehhll pactbophtenej:!.3th nnarpassmbl .nonlkhbl 6bitb cocraanensr b cootbetctbidfmy'lehhoj:! chctemblb ka)l(.nomkohkpethomcnyxae. bblphcobbib31u1e.nharpamm aaransnaa-anaroconepseaaae c nomoiubl<j3bm llbjllietcii 6blctpblm ii ha.ne:>kh:bimmeto.nom. b nacroamea ctati! o6cy)i(.zj.elfbireoperasecsae npennocsrrnor coctabnehhll .d.harpamm iy. b xasecrae rrpasrepoa nposeneusi .d.liarpammhi cbctem33ot-6eh30n, -rerrraa -uaxnorexcaa nony'1ehhl>ieha 3bm. microsoft word 1423 mario 102.docx hungarian journal of industry and chemistry veszprém vol. 42(2) pp. 65–70 (2014) telemedical heart rate measurements for lifestyle counselling mario salai,* gergely tuboly, istván vassányi, and istván kósa faculty of information technology, university of pannonia, egyetem u. 10.,veszprém, 8200, hungary *email: mario.salai@gmail.com in this paper we analyse a low-cost commercial chest belt to be integrated into a lifestyle counselling system as a source of heart rate data. we compared data from a schiller ecg holter device, which serves as a reference to a cardiosport device. due to missing data in the cardiosport device caused by loss of contact with the body, the creation of special algorithms was necessary for synchronization and data validation. the results show that when using our synchronization algorithms the average absolute percentage error between the two signals was 2% with correlation of more than 99%. using a data validation algorithm, we were able to get on average more than 70% of the signal with an absolute percentage error of 3% and a high average correlation of 99%. the mean rr interval values and standard deviation of rr intervals are very close to those of the reference device using both the synchronization and data validation algorithms. when using the data validation algorithm, the reference measurements produced only slightly better results with regard to false detections of atrial defibrillation than the cardiosport device. in conclusion, we found that with a simple preprocessing algorithm, cardiosport as a low-cost device can be safely integrated into a lifestyle support system as a telemedical solution. keywords: telemedicine, lifestyle counselling, heart rate monitor introduction low-cost telemedical sensors are often used in modern ambient assisted living (aal) telemonitoring and selfmanagement systems for providing inputs to medical intelligence algorithms [1]. such systems extend the scope of traditional health care that is based purely on data measurement. however, the proper interpretation and reliability of the results depends on the reliability of the measured data and the sensor itself. nevertheless, there are still surprisingly few reviews reported in the literature to date on the validation of the information content of such low-cost sensors compared to the clinically accepted reference device. an example of a device that was tested for validity is the sensewear hr armband [2]. in this study, they used the reference device simultaneously with the tested device as a way of validating data. however, most of the compared devices are expensive high-end devices, which present an obstacle for their wide use in telemedicine. in this proof-of-concept paper, we analyse a simple commercial chest belt chosen to be integrated into the lavinia lifestyle mirror system [3] as a source of heart rate (hr) data. in the lavinia system, the hr signal of the patient will be used to (i) estimate the calories burnt by physical activity, (ii) calculate the heart rate variability (hrv) in order to detect periods of mental or emotional stress, and (iii) analyse arrhythmia patterns (poincare plots) for atrial fibrillation detection. our approach involves the comparison of the hrv and poincare plots computed from the filtered chest belt signal, with those parameters computed from a reference holter device. methods measurements two devices were used simultaneously by a healthy volunteer over a 24 hour period. a schiller mt101/mt-200 holter device was our reference device designed for clinical use. the chest belt was a cardiosport tp3 heart rate transmitter device. since this device does not have its own memory for storing data, we used a nexus 7 tablet with android version 4.4.2 to connect the device via the bluetooth 4.0 protocol and store the measured data on the tablet. although both devices were worn by volunteers for 24 hours, only 12 hours of the overall signal were used for analysis due to frequent detachments of the device from the body during nighttime. the measurements of 12 hours were repeated on 4 additional healthy male subjects. signal analysis the direct comparison of measured data was not possible due to the different designs of the reference and the telemedical devices. however, we wanted to 66 compare signals directly in terms of time and also to develop a data validation algorithm for removing the noisy parts of the cardiosport device measurements reliably without using the reference data. the problem was that the chest belt was not firmly attached to the body and sudden movements of the device caused signal loss. therefore, we needed to create a software module for synchronization and data validation before any analysis. data validation means removing obviously bad data (artefacts) and keeping only ‘good’ data segments of sufficient length, because, as a rule of thumb, both hrv and poincare plot computations require data chunks of at least 5 minutes. even though the data validation algorithm removed a considerable amount of data from the original signal, we still had enough useful data for analysis from the daytime. the synchronization algorithm our simple algorithm for signal synchronization uses a sliding window that passes from the beginning of the chest belt signal to the end and calculates the absolute error between the two signals. when sliding finishes, the location of the sliding window with the minimum absolute error is considered as the point where the two signals should be synchronized. this applies only if the correlation of the data in the sliding window and the same amount of data from the reference device are higher than a minimum set by the user. if these conditions are met, the algorithm copies data from the sliding window into a newly generated third signal, which represents the chest belt signal fully synchronized with the reference signal. if conditions are not met, the third signal is filled with zeros. finally, the algorithm extracts all the highly correlated segments from the third signal ignoring zero values. also, a file with all the merged segments is generated for general analysis. the algorithm uses the following 5 main parameters that can be set up by the user: 1. window size: amount of data copied from the signal into the sliding window (default: 200), 2. window shift step: the number of samples by which we shift the sliding window in each iteration (default: 50), 3. absolute error window: amount of data used for calculating the minimum absolute error (default: 200), 4. maximum error distance: the number of samples by which we shift the absolute error window in order to find the minimum absolute error (default: 1000), 5. minimum correlation: minimum correlation, expressed as a percentage, required for the two signals to consider data in the chest belt signal as accurate (default: 97%). each parameter’s default value was determined empirically. after running the synchronization process, we obtained segments of highly correlated data. fig.1 shows the distribution of the lengths of signal segments. we can see that most segments are 3 to 18 minutes long. the longest highly correlated segment with the reference data is 110 minutes long. the default parameter settings minimize the number of overly short (< 5 min) segments. most of the bad segments (fig.2) are shorter than one minute, and only one bad segment was 60 minutes long. data validation algorithm another type of algorithm was used in the real telemedical scenario for finding good parts of the signal without relying on reference data. this implies finding gaps and abnormal values and omitting them. first, we compared the timestamp of each data point with the timestamp of the previous one. if the difference between the timestamps was longer than 3 seconds, we marked this as a ‘gap’. the 3-second gap detection was enabled by the chest belt’s buffering system that can tolerate short detachments of the device from the body. in the second step we identified abnormal values in the signal that were treated as gaps. the abnormal values are identified by observing the mean value of 20 neighbouring data points (10 before and 10 after a given point). if the mean value differs from the value of the figure 1: the distribution of strongly correlated segment lengths for all subjects figure 2: the distribution of weakly correlated segment lengths for all subjects 67 current sample by more than 300 units, we consider it invalid and mark it as a gap/error in the signal. finally, we extract the good segments from the signal with a length of more than 5 minutes. we implemented the above algorithm in a simple software tool (fig.3). on the left-hand side we can load the two signals and set the parameter values as well as the amount of data to be analysed. the graph shows two signals after the synchronization process was completed. the user can examine signals by clicking the previous and next buttons. general statistics are shown in the middle part of the screen, while in the lower part, we can see the histogram, and save the histogram and results as a file. two tabs in the top left-hand corner allow the user to switch between synchronization and data validation algorithms. statistical analysis time and frequency domain analyses, correlation comparisons, mean absolute percentage errors, and the slopes of scatter plot diagrams were compared between two measurements for hrv analysis. the specificities of a self-developed atrial fibrillation detector algorithm were compared for atrial fibrillation analysis. the latter algorithm is based on the k-means clustering of poincaré plots (consisting of rr intervals) the time and frequency domain analyses for hrv were performed using kubios hrv analysis software, while the rest of the analysis for hrv and atrial fibrillation was performed in microsoft excel. atrial fibrillation detection was done using the matlab environment and the results were saved as microsoft excel workbooks. results and analysis heart rate variability after the synchronization process, we got strongly correlated (greater than 97%) synchronized data segments of various durations. table 1 summarizes the duration of signals analysed. table 2 shows results in the time domain for schiller and cardiosport devices after using the algorithm for the synchronization of signals. time domain analysis shows similar values for mean rr values and standard deviation (std rr in eq.(1)). the average mean rr values for the schiller and cardiosport devices are 851 and 871 respectively. the average std rr for the schiller device is 108 and 110 for the cardiosport device. figure 3: synchronization and data validation software table 1: signal duration after the synchronization process subject duration (h:m:s) #1 10:53:28 #2 8:45:40 #3 10:30:17 #4 7:46:56 68 𝑆𝑇𝐷  𝑅𝑅 = ! !!! (𝑅𝑅! − 𝑅𝑅)!! !!! (1) the frequency domain analysis for the synchronization process is presented in table 3. the absolute power was compared for very low frequencies (vlf: 0-0.04 hz), low frequencies (lf: 0.04-0.15 hz), high frequencies (hf: 0.15-0.4 hz) and ratios between low frequencies and high frequencies (lf/hf). results show no significant difference between schiller and cardiosport device values. the average mean absolute percentage error (mape) between two signals is 2% with a high average correlation of close to 100%. using the data validation algorithm, we extracted data points from the collected signals. the duration of the resulting signal is shown in table 4. it is important to note that due to the noise on schiller device recordings, we had to remove noisy parts from the original signal. therefore, even though the signal was recorded continuously for 12 hours, overall duration is much less. calculations show that in the worst scenario only 45% of the signal can be used for analysis using this data validation method, while in the best scenario this number reaches 95%. this leads to a conclusion that results are rather subject dependent. the results of data analysis in the time domain after the removal of bad parts using the validation algorithm can be seen in table 5. the mean rr intervals for schiller and cardiosport devices are 851 and 871 and standard deviations are 104 and 106, respectively. the cardiosport device has slightly greater values, but these are practically identical. the frequency domain analysis for the data validation process is presented in table 6. the absolute power was compared for very low frequencies (vlf: 00.04 hz), low frequencies (lf: 0.04-0.15 hz), high frequencies (hf: 0.15-0.4 hz), and ratios between low frequencies and high frequencies (lf/hf). as in the synchronization process, the results show no significant difference between the schiller and cardiosport device values. the minimum, maximum and average percentage errors on whole signals were calculated using 5 minute long sliding windows with one minute long shift steps (table 7). only one subject had a high maximum error value of 34%. by visual examination, it was determined that the cause of such a high error was the artefact of the schiller device. in spite of that, the average error remained low (2%). table 2: time domain analysis after synchronization mean rr (ms) a std rr (ms) b subject schiller cardiosport schiller cardiosport #1 738 755 123 125 #2 704 720 91 93 #3 908 929 90 93 #4 855 875 145 148 #5 937 959 107 109 average 851 871 108 111 a with 2% error, b with 1-3% error table 3: frequency domain analysis after synchronization schiller cardiosport error subject absolute power (ms2) absolute power (ms2) % % % % vlf lf hf lf/hf vlf lf hf lf/hf vlf lf hf lf/hf #1 7937.6 3086 1578 1.956 8444 3224 1330 2.4235 6 4 19 19 #2 5431.5 626.6 245 2.557 5723 659.3 250.9 2.6281 5 5 2 3 #3 4251.2 1927 494.4 3.898 4543 2055 538.8 3.8146 6 6 8 2 #4 12682 1790 636.5 2.813 13514 1869 621.5 3.0077 6 4 2 6 #5 6139.8 1212 476.7 2.542 6465 1274 481.4 2.6459 5 5 1 4 table 4: signal duration after data validation subject duration (h:m:s) #1 1:28:10 #2 11:20:03 #3 6:15:38 #4 9:27:07 #5 4:29:44 table 5: time-domain analysis after data validation mean rr (ms) a std rr (ms) b subject schiller cardiosport schiller cardiosport #1 701 724 136 139 #2 700 717 91 93 #3 899 921 100 100 #4 846 866 139 142 #5 958 981 88 90 average 851 871 105 106 a with 2% error, b with 0-2% error table 6: frequency domain analysis after data validation schiller cardiosport error subject absolute power (ms2) absolute power (ms2) % % % % vlf lf hf lf/hf vlf lf hf lf/hf vlf lf hf lf/hf #1 10414 2297 1171 1.96 10847 2442 1004 2.43 4 6 17 19 #2 5446 631 245 2.57 5718 654 245 2.67 5 3 1 4 #3 5163 1990 523 3.80 5424 2054 540 3.80 5 3 3 0 #4 11683 1769 616 2.87 12149 1831 594 3.08 4 3 4 7 #5 4356 1235 317 3.89 4522 1303 330 3.95 4 5 4 1 69 fig.4 represents a typical relationship between cardiosport and schiller devices. all gradient values are close to 1. the lowest slope value is 0.98 while the highest value is 1.02. the average mean absolute percentage error (mape) between two signals was 3% with a strong average correlation of 99%. atrial fibrillation we carried out the detection of atrial fibrillation (afib) by analysing poincaré plots consisting of 30 rr intervals. we considered 30 rr intervals per iteration and in each iteration after constructing the poincaré plot we calculated the dispersion around the diagonal line and used k-means based cluster analysis to determine the number of the clusters. if the dispersion was too high (greater than 0.06) and the number of clusters was 1, or the number of clusters was more than 9; we assigned “afib” to that series of rr intervals, otherwise to “non-afib”. the details of the algorithm can be seen in our previous study [16]. since our data set did not contain real afib cases, only specificity could be calculated with regard to the efficiency of detection. the evaluation of atrial fibrillation detection results for synchronized data validation can be seen in tables 8 and 9. conclusion even though the cardiosport device may suffer from signal loss due to its design, we managed to determine that it can be safely used for telemedical purposes of measuring hrv and atrial fibrillation. we found only a few usable data segments that were less than 5 minutes long. with our algorithm that detects gaps and errors in table 7: the minimum, maximum and average percentage errors subject minimum error maximum error average error #1 0.1% 3.5% 1.5% #2 0.0% 7.7% 2.1% #3 0.0% 33.9% 3.2% #4 0.1% 6.7% 1.9% #5 0.1% 5.1% 2.2% average 0.1% 13.4% 2.4% figure 4: comparison of the cardiosport and schiller devices after data validation table 8: results from the synchronized data related to atrial fibrillation detection subject number of iterations schiller mt-101/mt-200 system cardiosport tp3 heart rate transmitter afib cases non-afib cases afib cases non-afib cases #1 331 26 8% 305 92% 31 9% 300 91% #2 1796 9 1% 1787 99% 3 >1% 1793 ~100% #3 1120 7 1% 1113 99% 5 1% 1115 99% #4 1427 11 1% 1416 99% 16 1% 1411 99% #5 964 46 5% 918 95% 45 5 919 95% min 1% 92% >1% 91% max 8% 99% 9% ~100% mean 3% 97% 3% 97% std 3% 3% 4% 4% table 9: results from the data validation process related to atrial fibrillation detection patient number of iterations schiller mt-101/mt-200 system cardiosport tp3 heart rate transmitter afib cases non-afib cases afib cases non-afib cases #1 241 3 1% 238 99% 8 3% 233 97% #2 1879 29 2% 1850 98% 2 >1% 1877 ~100% #3 808 15 2% 793 98% 3 >1% 805 ~100% #4 1296 10 1% 1286 99% 20 2% 1276 98% #5 544 6 1% 538 99% 7 1% 537 99% min 1% 99% >1% 97% max 2% 99% 3% ~100% mean 1% 99% 1% 99% std >1% >1% 1% 11% 70 the signal and removes them with an average effectiveness of more than 70%, which translates into having enough data to calculate hrv and atrial fibrillation from daytime measurements. regarding atrial fibrillation detection, we can conclude that by using the developed data validation algorithm the reference schiller mt-101/mt-200 measurements produced only slightly better results with regard to false detections than the cardiosport tp3 heart rate transmitter. in two cases the cardiosport measurements proved to be even better than schiller records, which implies that some relatively simple heart rate recorders are equivalent to some holter devices after signal processing using the data validation algorithm. we have to emphasize; however, that we have not performed any measurements on actual atrial fibrillating patients yet. therefore, the investigation of the sensitivity of our atrial fibrillation detection algorithm under the presented circumstances could be the subject of further studies. in summary, the cardiosport as a low-cost device can easily be integrated into a lifestyle support system as a telemedical solution. acknowledgments this research was supported by the european union and co-funded by the european social fund “telemedicinefocused research activities in the field of mathematics, informatics and medical sciences” támop-4.2.2.a11/1/konv-2012-0073. references [1] patel s., park h., bonato p., chan l., rodgers m.: a review of wearable sensors and systems with application in rehabilitation, j. neuroengng. rehab., 2012, 9(21), 1–17 [2] kristiansen j., korshøj m., skotte j.h., jespersen t., søgaard k., mortensen o.s., holtermann a.: comparison of two systems for long-term heart rate variability monitoring in freeliving conditions a pilot study, biomed eng. online, 2011, 10(27), 1–14 [3] kósa i., vassányi i., nemes m., kálmánné k.h., pintér b., kohut l.: a fast, android based dietary logging application to support the lifestyle change of cardio-metabolic patients, global telemedicine and ehealth updates: knowledge resources, eds.: m. jordanova, f. lievens, 2014, 7, 553–556 [4] salai m., tuboly g., vassanyi i., kosa i.: reliability of telemedical heart rate meters, ime j., 2014, 8(5), 49–55 microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 125-130 (2008) towards sustainable water usage in a beverage plant h. tokos , z. novak-pintarič university of maribor, faculty of chemistry and chemical engineering smetanova 17, si-2000 maribor, slovenia e-mail: hella.tokos@uni-mb.si the current drive towards environmental sustainability and the rising costs of freshwater and effluent treatment have forced the process industry to reduce freshwater consumption and wastewater generation, which can be achieved inter alia by water re-use. the mathematical models presented in the literature need to be modified in order to match industrial circumstances. this paper presents a mathematical model for water re-use in batch processes in the presence of continuous streams with acceptable purity. the model is based on a design method developed by kim and smith [7], modified to properly balance continuous streams. continuous streams are treated as limited freshwater sources. two cases were analysed: 1) re-use of continuous streams within those time intervals where the continuous streams exist, 2) re-use of continuous streams in later time intervals with intermediate storage of unused continuous streams. the opportunities of water re-use by the developed model were analysed in a brewery plant. by using the identified re-use connections, the brewery could save about 18% of its current freshwater demand. keywords: water minimisation; batch processes; continuous process; water re-use; industrial application. introduction waste minimisation and pollution prevention have become everyday terms in the process industry, as strict environmental regulations have induced producers to find new ways of reducing the environmental impact of their production. water is one of the most important natural resources used in process industries. excluding process changes, there are three approaches to reducing freshwater demand: re-use, regeneration-reuse, and regeneration-recycling. in the literature, studies on the design of water reuse and wastewater treatment networks in industry have been mainly concerned with continuous processes [1, 2], while little attention has been directed towards the development of water conservation strategies for batch operations. the complexities of batch process industries lie in the fact that the production processes consist of elementary tasks with operating conditions and resource demand varying over time. two main approaches are generally used to address the issue of freshwater demand minimisation, i.e. the graphical approach, and the mathematically based optimization approach. wang and smith [3] initiated a graphical design method based on water pinch analysis, where they combined time constraint with concentration driving force constraint. foo et al. [4] have developed a twostage graphical procedure for synthesizing the maximum water recovery network for a batch process system. majozi et al. [5] presented a graphical method where, in the first instance, the time dimension was taken as a primary constraint, and concentration as a secondary one. subsequently, the priority of constraints was reversed. almato et al. [6] developed an optimization framework for water use in batch processes based on the superstructure approach. kim and smith [7] developed a design method where water recovery was limited through time constraints. this model allows minimization of freshwater cost, storage tank costs and piping costs. majozi [8] presented a continuous-time mathematical formulation for freshwater minimisation with and without central reusable water storage. cheng and chang [9] incorporated three optimisation problems, the batch scheduling, the water re-use network, and the wastewater treatment network, in a single minlp model, to generate an integrated water network in batch processes. this paper presents a mathematical model for water re-use in batch processes in the presence of continuous streams with acceptable purity. the continuous streams are treated as limited freshwater sources, which can be integrated with batch water-using operations. this model is based on the design method developed by kim and smith [7], modified to properly balance the continuous streams. the opportunities for water re-use were analysed in a brewery plant where several continuous waste streams with low contaminant concentrations are available for re-use in batch operations with lower purity requirements. 126 extended mathematical model the water mass balance for an overall water-using system is defined by equation: 0lossgain outw , w , =−+ +−+ ∑∑ ∑ ∑∑∑∑ n n n n ww n n n nww fw n nfw mm mmm (1) where: w fw,nm – water mass from freshwater source fw to operation n, t w ww,nm – wastewater mass from continuous operation ww to batch operation n, t out nm – wastewater mass from operation n to discharge, t gain nm – mass of water gain in operation n, t loss nm – water mass loss in operation n, t. in comparison with the original model, the mass balance is extended with additional variable, w n,wwm , which represents the integration of continuous streams with batch operations. the contaminant mass load balance for each waterusing operation is: ( ) ( ) ( ) ( ) ( ) ( ) 0loss , lossgain , gain ml , out , opout , pp , w , w , w , w , =⋅−⋅+ ++⋅−⋅+ +⋅+⋅ ∑ ∑∑ ncnncn ncncn nc nccnnc ww wwcnww fw fwcnfw cmcm mcmcm cmcm (2) where: pp nc ,nm – re-use water mass from operation nc to operation n, t op nm – water mass inside operation n, t ml c ,nm – mass load of contaminant c removed by water in operation n, g w c , fwc – mass concentration of freshwater source, g/m³ w c ,wwc – mass concentration of continuous water source, g/m³ out c ,nc – outlet water mass concentration of operation n, g/m³ gain c ,nc – mass concentration of water gain in operation n, g/m³ loss c ,nc – mass concentration of water loss in operation n, g/m³. the water mass balance for each operation is obtained by equation: 0lossgainoutpp , pp , w , w , =−+−− −++ ∑ ∑∑∑ nnn nc ncn nc nnc ww nww fw nfw mmmm mmm (3) total water mass of the water-using operations is defined by: lossgain pp , w , w , op nn nc nnc ww nww fw nfwn mm mmmm −+ +++= ∑∑∑ (4) feasibility constraints on the inlet and outlet concentrations are: ( ) ( ) ( ) 0maxin, , op out , pp , w , w , w , w , ≤⋅− −⋅+⋅+⋅ ∑∑∑ ncn nc nccnnc ww wwcnww fw fwcnfw cm cmcmcm (5) 0maxout, , out , ≤− ncnc cc (6) where: in, max c ,nc – maximum inlet mass concentration of operation n, g/m³ out, max c ,nc – maximum outlet mass concentration of operation n, g/m³. upper and lower bounds for the water flows of each stream in the superstructure are: 0w , wub, , w , ≤⋅− nfwnfwnfw ymm (7) 0w , wlb, , w , ≥⋅− nfwnfwnfw ymm (8) 0w , wub, , w , ≤⋅− nwwnwwnww ymm (9) 0w , wlb, , w , ≥⋅− nwwnwwnww ymm (10) 0pp , pp ub, , pp , ≤⋅− ncnncnncn ymm (11) 0pp , pp lb, , pp , ≥⋅− ncnncnncn ymm (12) 0outout ub,out ≤⋅− nnn ymm (13) 0outout lb,out ≥⋅− nnn ymm (14) where: ub, w lb, w fw,n fw,nm , m – upper and lower bounds for water mass from freshwater source fw to operation n, t ub, w lb, w ww,n ww,nm , m – upper and lower bounds for water mass from continuous water source ww to operation n, t ub, pp lb, pp n,nc n,ncm , m – upper and lower bounds for re-used water mass from operation n to operation nc, t ub, out lb, out n nm , m – upper and lower bounds for wastewater mass from operation n to discharge, t w fw,ny – binary variable for the existence or non existence of water mass from freshwater source fw to operation n w ww,ny – binary variable for the existence or non existence of water mass from continuous water source ww to operation n 127 pp n,ncy – binary variable for re-used water mass from operation n to operation nc out ny – binary variable for wastewater mass from operation n to discharge. a logic constraint is used to identify the existence or non-existence of a storage tank within a network: esstpp , ,0 nncnncn ttnyy ≥∀≤− (15) where: st ny – binary variable for storage tank to operation n s nt – starting time of operation n, h e nt – terminal time of operation n, h. eq. 15 implies that water re-use between operations over different time interval is only allowed through a storage tank, however, operations within the same time intervals can be connected directly. the capacity of a storage tank is obtained by equation: espp , st , nnc nc ncnn ttnmm ≥∀= ∑ (16) where: st nm – capacity of a storage tank, t. storage tank investment cost: stst nnn ysmrct ⋅+⋅= (17) where: nct – storage tank investment cost of operation n, £ r – variable investment cost of storage tank s – fixed investment cost of storage tank. additional equations for water re-use from continuous operations in batch operations are given in the continuation. the overall water mass balance of the continuous stream is defined by equation: ( ) ∑∑ +=−⋅ j jww n nwwjww mmttq out , w , s 1 e (18) where: wwq – mass flow rate of the continuous stream, t/h e jt – finishing time of the continuous stream in the last time interval j, h, s 1t – starting time of the continuous stream, h out ww, jm – water mass from continuous process to discharge in the interval j, t. the water mass balance for each time interval, j, is: ( ) eess , seout , , jnjn n w nwwjjwwjww ttttn mttqm =∧=∀ −−⋅= ∑ (19) time intervals, j, for the continuous operations are defined according to the starting and ending times of batch processes. the objective function is the overall cost of the water network that involves the freshwater cost and annual investment cost of storage tank installation. ( ) ( )( ) anall ohy wseww ,obj fct t pttqpmf n n ww j wwjjww fw n fwnfw ⋅⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ + ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎣ ⎡ ⋅−⋅+⋅= ∑ ∑∑∑∑ δ λ (20) where: fobj – objective function, £/a w fwp – price of freshwater source fw, £/t w wwp – price of continuous water source ww, £/t λohy – annual operating time, h/a alltδ – overall time interval, h fan – annualization factor. mathematical model extended with a storage tank the model presented in the previous section allows for water re-use between batch process streams and continuous ones, only over those time intervals where wastewater streams exist. the unused wastewater is discharged. collecting the unused wastewater in a storage tank would enable water re-use over the following time intervals. the contaminant mass load balance for each waterusing operation is: ( ) ( ) ( ) ( ) ( ) ( ) ( ) 0loss , lossgain , gain ml , out , opout , pp , w , st , w , w , w , w , =⋅−⋅+ ++⋅−⋅+ +⋅+⋅+⋅ ∑ ∑∑∑ ncnncn ncncn nc nccnnc ww wwcnww ww wwcnww fw fwcnfw cmcm mcmcm cmcmcm (21) where: st ww,nm – re-use water mass from storage tank of water source ww to operation n, t. the additional expression in equation (21), ( )∑ ⋅ ww wwcnww cm w , st , , makes possible the incorporation of a storage tank for unused wastewater into the water-using system. the water mass balance for each operation is obtained by equation: 0lossgainoutpp , pp , st , w , w , =−+−− −+++ ∑ ∑∑∑∑ nnn nc ncn nc nnc ww nww ww nww fw nfw mmmm mmmm (22) total water flow through the water-using operation is defined by: lossgainpp , st , w , w , op nn nc nnc ww nww ww nww fw nfwn mmm mmmm −++ +++= ∑ ∑∑∑ (23) the feasibility constraint on the inlet concentration is: 128 ( ) ( ) ( ) ( ) 0maxin, , op out , pp , w , st , w , w , w , w , ≤⋅− −⋅+⋅+ +⋅+⋅ ∑∑ ∑∑ ncn nc nccnnc ww wwcnww ww fwcnww fw fwcnfw cm cmcm cmcm (24) upper and lower bounds for water mass from a storage tank are defined by equation: 0st , st ub, , st , ≤⋅− nwwnwwnww ymm (25) 0st , st lb, , st , ≥⋅− nwwnwwnww ymm (26) where: ub, st lb, st ww,n ww,nm , m – upper and lower bounds for water mass from storage tank of continuous water source ww to operation n, t st ww,ny – binary variable for water mass from storage tank of water source ww to operation n. the storage tank capacity for continuous source is obtained by summation of the re-used continuous wastewater stream, after the last time interval j: esst , stc, , jn n nwwww ttnmm ≥∀= ∑ (27) where: c, st wwm – storage tank capacity for the continuous stream ww, t. the sum of the re-used continuous streams can not exceed the available water mass from those time intervals before the last time interval j, where the continuous stream exists: esout . st , , jn j jww n nww ttnmm ≥∀≤ ∑∑ (28) storage tank investment cost: st , stc, nwwwwww ysmrct ⋅+⋅= (29) where: wwct – storage tank cost for water source ww, £. the objective function is: ( ) ( )( ) anall ohy wseww ,obj fctct t pttqpmf ww ww n n ww j wwjjww fw n fwnfw ⋅⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ++ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎣ ⎡ ⋅−⋅+⋅= ∑∑ ∑∑∑∑ δ λ (30) equations (6)–(18) remain unchanged. illustrative example the model described in the previous section is illustrated by the first example from kim and smith [7], extended by one continuous stream, fig. 1. the limiting conditions and timing for the batch processes are shown in table 1. table 1: limiting water data for batch processes limiting mass concentration (g/m³) time (h) process cin cout limiting water mass (t) ts tf p1 0 200 40 0 0,5 p2 100 200 25 0,5 1,0 p3 100 400 50 0,5 1,0 p4 100 400 50 1,0 1,5 the average flow rate of the continuous process stream is 100 t/h, the contaminant concentration is 50 g/m³. the continuous stream is available within the time interval 0–1 h. in the case of no water re-use, the freshwater consumption per batch is 227,5 t. water re-use opportunities for batch processes without integration of the continuous stream, are shown in fig. 1. water re-use between batch operations enables a reduction in freshwater consumption per batch from 227,5 t to 202,5 t. according to the network design, a storage tank needs to be installed, with a capacity of 37,5 t. the overall cost for the freshwater and storage tank installation is 1 080,6 k£/a. figure 1: water network design for batch processes further reduction in freshwater consumption per batch can be achieved by integrating the continuous stream in the water network. the optimal network design is shown in fig. 2. 129 figure 2: water network design – extended model processes p2 and p3 use wastewater from the continuous process instead of freshwater, which reduces the freshwater consumption per batch to 165 t. the continuous water source can not be used in process p1 as the concentration of continuous stream is higher than the maximum inlet concentration of p1. the storage tank capacity is reduced to 25 t. the overall cost for the freshwater and storage tank installation is estimated to be 885,7 k£/a. as the continuous stream is absent during the last time period, an extended model was applied which included a storage tank for wastewater collection from the continuous process. the final network design is shown in fig. 3. the freshwater consumption per batch is reduced to 140 t. all processes, except the process p1, use wastewater from the continuous process. the capacity of the storage tank increases to 50 t, but the overall cost decreases to 753,7 k£/a because of higher water re-use. figure 3: final network design case study in the case of the brewery studied in this paper, the volume ratio of water consumption to beer sold was 6.04 l/l or 653 300 m3/a. compared with the ratio specified by the reference document on best available techniques in the food, drink and milk industries [10], the fresh water consumption exceeded the upper limit by 144 900 m3/a. in the first stage, the water balance was obtained and the most critical processes were identified by comparing their water consumption with those values given in bref [10], and the european brewery convention [11]. when comparing the results, the cellar with filters and the packing area were marked as the critical points in the brewery. in order to estimate any possibilities of water re-use, the maximal inlet values of contaminants (cod, ph and conductivity) were determined for each water consumer, and its flow rate measured. the water re-use opportunities were analysed in the packaging area. the freshwater consumption per batch is 5 503 t. the continues streams are: 1) the outlet stream of the rinser for non returnable glass bottles (k1), and 2) the wastewater from the rinser for cans (k2). the average water flows for the continuous processes are 48,37 t/h and 9,68 t/h, the average outlet concentrations are 34 g/m³ and 23 g/m³. the final water network design is shown in fig. 4. the wastewater from continuous process, k2, can be re-used in the pasteurisation processes p23–p31. based on the cod, the outlet stream of the rinser for non returnable glass bottles, k1, could be connected by the tunnel pasteurizer, however, this is forbidden because of the high quality requirements of pasteurisation. the wastewater from pasteurizers can be reused in the bottle washer for returnable bottles, processes p1–p5 and p20–p22. in case of the packing line for returnable glass bottles, filling line a and b, water consumption could be reduced by reusing the outlet stream of the bottle washer in the crate washer, processes p6–p19. the freshwater consumption per batch is reduced from 5 503 t to 4 498 t. no storage tank installation is needed. conclusion a mathematical model for water re-use in batch processes in the presence of continuous streams was developed by modifying the model by kim and smith [7]. in the first case, the model allows for re-use of the continuous wastewater stream over time intervals, where this stream exists. in the second case, the re-use in later time intervals is possible with the collection of an unused continuous wastewater stream. the results of examples and the case study show that incorporating continuous steams in the analysis of dominant batch processes, can contribute to the reduction of freshwater consumption, as well as the total cost of the network. 130 figure 4: water network design for the packaging area references 1. karuppiah r., grossmann i. e.: comp. chem. eng. (2006) 650-673 2. bagajewicz m.: comp. chem. eng. (2000) 20932113 3. wang y. p., smith r.: trans icheme (1995) 905-910 4. foo c. y., manan z. a., tan y. l.: journal of cleaner production (2005) 1381-1394 5. majozi t.: journal of environmental management (2006) 317-329 6. almato m., espuňa a., puigjaner l.: comp. chem. eng. (1999) 1427-1437 7. kim j. k., smith r.: trans icheme (2004) 238-248 8. majozi t.: comp. chem. eng. (2005) 1631-1646 9. cheng k. f., chang c. t.: ind. eng. chem. res. (2007) 1241-1253 10. bref, reference document on best available techniques in the food, drink and milk industries, european commission, seville, pp. 202-203, 2006 11. ebc, manual of good practice: water in brewing, european brewery convention, nürnberg, pp. 5, 1990 hungarian journal of industry and chemistry veszprém vol. 42(2) pp. 103–107 (2014) on the parametric uncertainty of weakly reversible realizations of kinetic systems györgy lipták b1, gábor szederkényi1,2 and katalin m. hangos1,3 1process control research group, mta sztaki, kende u. 13-17, budapest, 1111, hungary 2faculty of information technology, péter pázmány catholic university, práter u. 50/a, budapest, 1083, hungary 3department of electrical engineering and information systems, university of pannonia, egyetem u. 10, veszprém, 8200, hungary be-mail: lipgyorgy@gmail.com the existence of weakly reversible realizations within a given convex domain is investigated. it is shown that the domain of weakly reversible realizations is convex in the parameter space. a lp-based method of testing if every element of a convex domain admits weakly reversible realizations is proposed. a linear programming method is also presented to compute a stabilizing kinetic feedback controller for polynomial systems with parametric uncertainty. the proposed methods are illustrated using simple examples. keywords: parametric uncertainty; computational methods; optimization; kinetic systems introduction the notion of parametric robustness is well-known and central in linear and nonlinear systems and control theory [1]. it is used for ensuring a desirable property, such as stability, in a given domain in the parameter space around a nominal realization having the desired property. the aim of the paper is to extend the notions and tools of parametric robustness for a class of positive polynomial systems, namely a class of kinetic systems. only the very first steps are reported here that offer a computationally efficient method for checking one of the many important properties of kinetic systems, their weak reversibility. basic notions and methods the basic notions and tools related to reaction kinetic systems and their realizations are briefly summarized in this section. kinetic systems, their dynamics and structure deterministic kinetic systems with mass action kinetics or simply chemical reaction networks (crns) form a wide class of non-negative polynomial systems, that are able to produce all the important qualitative phenomena (e.g. stable/unstable equilibria, oscillations, limit cycles, multiplicity of equilibrium points and even chaotic behaviour) present in the dynamics of nonlinear processes [2]. the general form of dynamic models studied in this paper is the following ẋ =m · ψ(x), (1) where x ∈ rn is the state variable and m ∈ rn×m. the monomial vector function ψ : rn → rm is defined as ψj(x) = n∏ i=1 x yij i , j = 1, . . . ,m (2) where y ∈ nn×m 0 . the system eq.(1) is kinetic if and only if the matrix m has a factorization m = y ·ak. (3) the kirchhoff-matrix ak has non-positive diagonal and non-negative off-diagonal elements and zero column sums. the matrix pair (y,ak) is called the realization of the system eq.(1). the chemically originated notions: the chemically originated notions of kinetic systems are as follows: the species of the system are denoted by x1, . . . , xn, and the concentrations of the species are the state variables of eq.(1), i.e. xi = [xi] ≥ 0 for i = 1, . . . , n. the structure of kinetic systems is given in terms of its complexes ci, i = 1, . . . ,m that are non-negative linear combinations of the species i.e. ci = ∑n j=1[y ]jixj for i = 1, . . . ,m, and therefore y is also called the complex composition matrix. the reaction graph: the weighted directed graph (or reaction graph) of kinetic systems is g = (v,e), where 104 v = {c1, c2, . . . , cm} and e denote the set of vertices and directed edges, respectively. the directed edge (ci, cj) (also denoted by ci → cj) belongs to the reaction graph if and only if [ak]j,i > 0. in this case, the weight assigned to the directed edge is ci → cj is [ak]j,i. stoichiometric subspace: stoichiometric subspace s is given by the span of the reaction vectors s = {[y ]·i − [y ]·j | [ak]ij > 0}. (4) the stoichiometric compatibility classes of a kinetic system are the affine translations of the stoichiometric subspace: (x0 + s) ∩ rn ≥0. structural properties and dynamical behaviour it is possible to utilize certain structural properties of kinetic systems that enable us to effectively analyze the stability of the system. deficiency: there are several equivalent ways to define deficiency. we will use the following definition δ = dim(ker(y ) ∩ im(bg)), (5) where bg is the incidence matrix of the reaction graph. it is easy to see that deficiency is zero if ker(y ) = {0} or equivalently rank(y ) = m. weak reversibility: a crn is called weakly reversible if whenever there exists a directed path from ci to cj in its reaction graph, then there exists a directed path from cj to ci. in graph theoretic terms, this means that all components of the reaction graph are strongly connected components. deficiency zero theorem: a weakly reversible kinetic system with zero deficiency has precisely one equilibrium point in each positive stoichiometric compatibility class that is locally asymptotically stable (conjecture: globally asymptotically stable). computing weakly reversible realizations formulated as an optimization problem in this section, first a method for computing weakly reversible realization based on ref.[3] is briefly presented. we assume that we have a kinetic polynomial system of the form eq.(1). we use the fact known from the literature that a realization of a crn is weakly reversible if and only if there exists a vector with strictly positive elements in the kernel of ak, i.e. there exists b ∈ rn + such that ak · b = 0 [4]. since b is unknown, too, this condition in this form is not linear. therefore, we introduce a scaled matrix ãk ãk = ak · diag(b) (6) where diag(b) is a diagonal matrix with elements of b. it is clear from eq.(6) that ãk is also a kirchhoff matrix and that 1 ∈ rm (the m-dimensional vector containing only ones) lies in kernel of ãk. moreover, it is easy to see that ãk defines a weakly reversible network if and only if ak corresponds to a weakly reversible network. then, the weak reversibility and the kirchhoff property of ãk can be expressed using the following linear constraints m∑ i=1 [ ãk ] ij = 0, j = 1, . . . ,m m∑ i=1 [ ãk ] ji = 0, j = 1, . . . ,m[ ãk ] ij ≥ 0, i, j = 1, . . . ,m, i 6= j[ ãk ] ii ≤ 0, i = 1, . . . ,m. (7) moreover, the equation eq.(3) is transformed by diag(b) (we can do this, because diag(b) is invertible): m · diag(b) = y ·ak · diag(b)︸ ︷︷ ︸ ãk (8) finally, by choosing an arbitrary linear objective function of the decision variables ãk and b, weakly reversible realizations of the studied kinetic system can be computed (if any exist) in a lp framework using the linear constraints eq.(7) and (8). weakly reversible crn realizations in this section, first the convexity of the weakly reversible kirchhoff matrix will be shown. after that the practical benefits of this property will be demonstrated in the field of system analysis and robust feedback design. convexity of the weak reversibility in the parameter space theorem 1. let a(1) k and a (2) k be m × m weakly reversible kirchhoff matrices. then the convex combination of the two matrices remains weakly reversible. proof. the idea behind the proof is based on ref.[5]. a kirchhoff matrix is weakly reversible if and only if there is a strictly positive vector in its kernel. therefore strictly positive vectors p1, p2 exist such as a(1) k · p1 = 0 and a (2) k · p2 = 0. let us define the following scaled kirchhoff matrix: â(1) k = a (1) k · diag(p1) and â(2) k = a (2) k · diag(p2). these scaled matrices have identical structures to the original ones. moreover, â(1) k ·1(m) = 0 and â(2) k ·1(m) = 0 where the vector 1(m) denotes the m dimensional column vector composed of ones. for that (λâ (1) k + (1− λ)â(2) k ) · 1(m) = 0. (9) for any λ ∈ [0, 1]. therefore the convex combination of the original two realizations has to be weakly reversible. 105 (a) (b) (c) figure 1: a weakly reversible reaction graphs of the three realizations (y,a(1) k ), (y,a(2) k ) and (y,a (3) k ) weak reversibility of crn realizations with parametric uncertainty we assume that a crn with parametric uncertainty is given as ẋ =m · ψ(x), (10) where x ∈ rn is the state variable, ψ ∈ rn → rm contains the monomials and the matrix m ∈ rn×m is an element of the following set m = { l∑ i=1 αimi | (∀i : αi ≥ 0) ∧ l∑ i=1 αi = 1 } . (11) the goal is to find a method for checking the weak reversibility of the system eq.(10) for all matricesm ∈m. when all vertices mi have a weakly reversible realization (y,a (i) k ) then any element of the setm has a realization (y,ak) such that ak is the convex combination of the kirchhoff matrices a(i) k . the obtained realization ak will be weakly reversible due to theorem 1. therefore, it is enough to compute a weakly reversible realization for each matrixmi by using the previously presented lp-based method. a simple example let us consider the following polynomial system[ ẋ1 ẋ2 ] =m ·  x1 x2 x1x2  , (12) where m is an arbitrary convex combination of the following three matrices m1 = [ 0 1 −1 1 −1 0 ] , m2 = [ −1 1 0 1 −1 0 ] , and m3 = [ 0 1 −1 0 0 0 ] . figure 2: a weakly reversible realization of the convex combination m = 0.2m1 + 0.4m2 + 0.4m3 in order to show weak reversibility for all possible convex combinations, we have to find a weakly reversible realization for each matrix m1, m2 and m3. the resulting weakly reversible reaction graphs are depicted in fig.1, while fig.2 illustrates an inner point realization which is weakly reversible too. computing kinetic feedback for a polynomial system with parametric uncertainty besides the possible application of the above described lp-based method for robust stability analysis, it can also be used for stabilizing feedback controller design. for this purpose, a generalized version of our preliminary work on kinetic feedback computation for polynomial systems to achieve weak reversibility and minimal deficiency [6] is used here. the feedback design problem we assume that the equation of the open-loop polynomial system with linear constant parameter input structure is given as ẋ =m · ψ(x) +bu, (13) where x ∈ rn is the state vector, u ∈ rp is the input and ψ ∈ rn → rm contains the monomials of the open-loop system. the input matrix is b ∈ rn×p, the corresponding complex composition matrix is y with rank m, and m ∈ rn×m is an element of the following set m = { l∑ i=1 αimi | (∀i : αi ≥ 0) ∧ l∑ i=1 αi = 1 } . (14) moreover, a positive vector x ∈ rn >0 being the desired equilibrium point is given as a design parameter. note that the above polynomial system is not necessarily kinetic, i.e. not necessarily positive, and may not have a positive equilibrium point at all. 106 the aim of the feedback is to set a region in the state space r ⊆ rn ≥0 where x is (at least) a locally asymptotically stable equilibrium point of the closed-loop system for all m ∈m. for this purpose we are looking for a feedback in the form u = kψ(x) (15) which transforms the open-loop system into a weakly reversible kinetic system with zero deficiency for all m ∈ m with the given equilibrium point x. feedback computation similarly to the realization computation, the matrix k will be determined by solving an lp problem. the convexity result shows that it is enough to compute one weakly reversible realization (y,a (r) k ) in each vertex mr to ensure weak reversibility for all possible closed-loop systems. all realizations will have zero deficiency, because of the rank condition rank(y ) = m [7]. first we note, that the realization (y,a (r) k ) that corresponds to the closed-loop system is mr +b ·k = y ·a(r) k . (16) where the matrix a(r) k should be kirchhoff m∑ i=1 [ãk]ij = 0, j = 1, . . . ,m [ãk]ij ≥ 0, i, j = 1, . . . ,m, i 6= j [ãk]ii ≤ 0, i = 1, . . . ,m. (17) in order to obtain a weakly reversible closed-loop system with an equilibrium point x, the matrix a(r) k should be weakly reversible and has to have the vector ψ(x) in its right kernel, i.e. a (r) k · ψ(x) = 0. (18) finally, by choosing an arbitrary linear objective function of the decision variables a(1) k , . . . , a (l) k and k, the feedback gain k can be computed (if it exists) in a lp framework using the linear constraints eqs.(16-18). with the resulting feedback gain k, the point x will be an equilibrium point of all possible closed-loop systems, and x will be locally asymptotically stable in the region s = (x+s)∩rn ≥0, where s is the stoichiometric subspace of the closed-loop system. example let the open-loop system be given as ẋ =m  x1x2 x2x3 x1 +  0 1 0 u (19) figure 3: weakly reversible realization of the closed-loop system, where m = 0.6m1 + 0.2m2 + 0.2m3 where m is an arbitrary convex combination of the following three matrices: m1 =  −1 1 0 2 1 2 1 −1 0  , m2 =  0 0 0 1 1 3 0 0 0  , and m3 =  0 1 −1 2 0 3 0 −1 1  . the desired equilibrium point x = [1 1 1] t . we are looking for a feedback law with gaink which transforms the matricesmi into weakly reversible kinetic systems with the given equilibrium point. by solving the feedback design lp optimization problem using the linear constraints eqs.(16-18), the computed feedback is in the following form: u = [ 2 1 2 ] ψ(x). (20) fig.3 depicts a weakly reversible realization of the closed-loop system. the obtained closed-loop system in an inner point of the convex setm has the following stoichiometric subspace: s = span  1 1 0 −  0 1 1  ,  1 1 0 −  1 0 0  . (21) therefore, the equilibrium point x will be asymptotically stable with the region s = (x+s)∩rn ≥0. note, that one should choose the initial value of the state variables from s. fig.4 shows the time dependent behaviour of the closed-loop solutions started from different initial points in s. 107 figure 4: time-domain simulation of the closed-loop system conclusion it is shown in this paper that the domain of weakly reversible realizations is convex in the parameter space. this property is utilized for developing methods in system analysis and robust control design. an lp-based optimization method is proposed for testing if every element of a convex domain given by its extremal matrices admits a weakly reversible realization. an lp-based feedback design method is also proposed that guarantees stability with a desired equilibrium point. the proposed methods are illustrated with simple examples. references [1] siljak d.: parameter space methods for robust control design: a guided tour, aut. contr., ieee transactions on, 1989, 34(7), 674–688 [2] angeli d.: a tutorial on chemical network dynamics, eur. j. contr., 2009, 15, 398–406 [3] szederkényi g., hangos k. m., tuza z.: finding weakly reversible realizations of chemical reaction networks using optimization, match commun. math. comp. chem., 2012, 67, 193–212 [4] feinberg m., horn f.: chemical mechanism structure and the coincidence of the stoichiometric and kinetic subspaces, arch. rational mechanics and analysis, 1977, 66(1), 83–97 [5] rudan j., szederkényi g., hangos k.m., péni t.: polynomial time algorithms to determine weakly reversible realizations of chemical reaction networks, j. math. chem., 2014, 52(5), 1386–1404 [6] lipták g., szederkényi g., hangos k.m.: kinetic feedback computation for polynomial systems to achieve weak reversibility and minimal deficiency, 13th eur. control conf. ecc, strasbourg, france, 2014, 2691–2696 [7] angeli d., lenhee, p.d., sontag e.d.: on the structural monotonicity of chemical reaction networks, proc. 45th ieee conf. decision and control, 2006, 7–12 hungarian journal of industry and chemistry vol. 45(2) pp. 13–18 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0014 investigations of the tlinp2se6–in4(p2se6)3 system and its optical properties valeria tovt, 1 igor barchiy, 1 * michal piasecki, 2 iwan kityk, 3 and anatolii fedorchuk 4 1 department of chemistry, uzhgorod national university, pidgirna st. 46, 88000 uzhgorod, ukraine 2 institute of physics, jan dlugosz university, armii krajowej 13/15, 42-200 częstochowa, poland 3 faculty of electrical engineering, częstochowa university of technology, dabrowskiego 69, 42201 częstochowa, poland 4 department of inorganic and organic chemistry, lviv national university of veterinary medicine and biotechnologies, pekarska st. 50, 79010 lviv, ukraine the equilibrium phases were investigated and the corresponding phase diagram constructed for the tlinp2se6– in4(p2se6)3 system from physical and chemical analyses, namely differential thermal analysis (dta), x-ray diffraction (xrd), and microstructural analysis (msa). it was established that this system belongs to the eutectic type and is characterized by the formation of boundary solid phases containing complex compounds. single crystals of the compounds tlinp2se6 and in4(p2se6)3 were grown using the bridgman method. both crystals were found to exhibit diffuse reflection spectra and photoinduced dependence of birefringence at various ir wavelengths generated by co2 laser irradiation. birefringence properties were investigated using the senarmont method. keywords: phase diagram, solid solution, crystal structure, optical properties, direct-gap semiconductor, indirect-gap semiconductor, photoinduced birefringence 1. introduction compounds with the formula m2p2se6 possess promising magneto-electric, piezoelectric, electro-optical, and thermoelectric properties that indicate their suitability as functional materials in optoelectronics [1-2]. due to their crystal structure, they exhibit anisotropy in terms of their physical properties. in a multilevel structure of m2p2se6 compounds, metal cations and pairs of phosphorous atoms occupy the octahedral positions between planes of selenium atoms. this structure is characterized by its layered arrangement of atoms, which contributes to the formation of a dipole moment between the layers of cationic and anionic groups. the replacement of the metal cation м2+ by other metal cations (м+, м3+ or м4+) leads to the deformation of the structure [3-4], changes the magnitude of the dipole moment and, consequently, its physical properties. the tl2se–in2se3–“p2se4” ternary system is composed of binary tl2se–in2se3, tl2se–“p2se4” and in2se3–“p2se4” systems. the tl2se–in2se3 system is characterized by the formation of two intermediate ternary compounds: tlinse2 melts congruently at 1023 k and tlin5se8 is formed according to the peritectic reaction l + in2se3  tlin5se8 at 1029 k [5-6]. in the sys *correspondence: i_barchiy@ukr.net tem tl2se–“p2se4” with a ratio of 2 to 1, interoperable components form the compound tl4p2se6 which possesses a congruent nature of melting at 758 k [7]. the in2se3–“p2se4” system is characterized by the formation of the compound in4(p2se6)3 in a syntectic reaction of l1 + l2  in4(p2se6)3 at 880 k [8]. in the tl2se– in2se3–“p2se4” system at the intersection of incisions, the phases tl4p2se6–in4(p2se6)3 and tlinse2–“p2se4” form the complex compound tlinp2se6 [9]. 2. experimental ternary tl4p2se6 and in4(p2se6)3 compounds were prepared by melting stoichiometric quantities of binary tl2se with elementary indium, phosphorous and selenium under a vacuum of 0.13 pa in quartz ampoules using a single temperature method. in all syntheses, components were used that possess a purity greater than 99.999 %. the maximum temperatures of synthesis were 993 and 893 k for in4(p2se6)3 and tlinp2se6, respectively. the rate of heating up to the maximum temperature was 50 k h-1. the melts were maintained at the maximum temperature for 72 hours. cooling was performed at a rate of 50 k h-1 down to an annealing temperature of 573 k. the linearity of the heating and cooling processes was achieved by a rif-101 temperature controller. the homogenization process occurred over 120 hours. identification of the complex compounds and alloys was conducted by differential thermal analy tovt, barchiy, piasecki, kityk, and fedorchuk hungarian journal of industry and chemistry 14 sis (dta) (pra-01, chrome-alumina thermocouple 5 k), x-ray diffraction (xrd) (dron-3 diffractometer, cukα radiation, ni filter) and microstructural analysis (msa) (metallurgical microscope lomo metam r-1). crystal structural calculations were conducted using the software package wincsd [10]. optical properties were investigated using an sf-18 spectrophotometer within the wavelength range of 400 – 750 nm. a co2 laser was used for photoinduced electrons in samples employing 200 ns pulses with a pulse repetition frequency of about 10 hz, a fundamental frequency of 10.6 μm and a frequency doubling of 5.3 μm beams. the birefringence was measured using a er:glass cw laser at 1540 nm by application of the senarmont method. 3. results and analysis 3.1. phase diagram of the tlinp2se6– in4(p2se6)3 system the tlinp2se6–in4(p2se6)3 system is a quasi-binary section of the tl2se–in2se3–“p2se4” ternary system (figs.1 and 2). it belongs to the eutectic type (v-type diagram by rozeboom). the complex compounds tlinp2se6 and in4(p2se6)3 melt congruently at 875 k and 963 k, respectively. tlinp2se6 is characterized by two polymorphic transformations lttlinp2se6  mttlinp2se6 at 680 k and mttlinp2se6  httlinp2se6 at 711 k. the prefixes lt–, mt– and ht– represent low–, medium–, and high–temperature modifications, respectively. in4(p2se6)3 is also characterized by two polymorphic transformations ltin4(p2se6)3  mtin4(p2se6)3 at 665 k and mtin4(p2se6)3  htin4(p2se6)3 at 903 k. when the temperature rises above 791 k, an invariant eutectic process is observed l  httlinp2se6 + mtin4(p2se6)3 (in the presence of 15 mol% in4(p2se6)3). the system is described by the sequence of the efficient peritectic processes httlinp2se6 + mtin4(p2se6)3  mttlinp2se6 (714 k) and mttlinp2se6 + mtin4(p2se6)3  lttlinp2se6 (689 k) based on the polymorphic transformation of tlinp2se6. the polymorphism of in4(p2se6)3 produces metatectic htin4(p2se6)3  l + mtin4(p2se6)3 (884 k) and eutectic mtin4(p2se6)3  lttlinp2se6 + ltin4(p2se6)3 (652 k) processes. regions of homogeneity in solid solutions, based on the batched complex selenides during annealing at a temperature of 573 k, do not exceed 10 mol%. 3.2. crystal structure of the compounds in4(p2se6)3 and tlinp2se6 the crystal structures of the compounds tlinp2se6 and in4(p2se6)3 were solved using the rietveld method. as an initial model for tlinp2se6 [2], the parameters of in4(p2se6)3 were used [8]. analysis of the crystalline structures of the investigated compounds (table 1) showed that it is possible to define the structural group of the anionic group [p2se6] 4–, which is formed by two single tetrahedra (fig.3). cationic atoms occupy positions between the anionic groups and none are located between the layers. figure 1. results of the xrd analysis of the tlinp2se6–in4(p2se6)3 system. (i rel – intensity, 2 theta angle of reflection) figure 2. phase diagram of the tlinp2se6–in4(p2se6)3 system. (1–l, 2–l+htin4(p2se6)3, 3–htin4(p2se6)3, 4–httlinp2se6, 5–l+mtin4(p2se6)3, 6–htin4(p2se6)3+mtin4(p2se6)3, 7–httlinp2se6, 8–httlinp2se6+mtin4(p2se6)3, 9–mtin4(p2se6)3, 10–httlinp2se6+mttlinp2se6, 11–mttlinp2se6, 12–mttlinp2se6+mtin4(p2se6)3, 13–mttlinp2se6+lttlinp2se6, 14–lttlinp2se6+mtin4(p2se6)3, 15–mtin4(p2se6)3+ltin4(p2se6)3, 16–lttlinp2se6, 17–lttlinp2se6+ltin4(p2se6)3, 18–ltin4(p2se6)3). table 1. crystal data of tlinp2se6 and in4(p2se6)3 compounds. compound crystal system space group lattice constant in4(p2se6)3 [8] trigonal r3 h (146) a = 6.362(3), c = 19.929(6) å in4(p2se6)3 trigonal r3 h (146) a = 6.3808(8), c = 20.014(4) å tlinp2se6 [2] triclinic p-1 (2) a = 6.4310, b = 7.5002, c = 12.124 å, tlinp2se6 triclinic p-1 (2) α = 100.553, β = 93.735, γ = 113.451 investigations of the tlinp2se6–in4(p2se6)3 system 45(2) pp. 13–18 (2017) 15 the structure of in4(p2se6)3 can be derived from the structure of sn2p2se6 [11]. it is composed of multiple substitutions of the isovalent cations according to 2m2+  m4+. the crystal structure of the compound in4(p2se6)3 can be presented based on the composition of the anionic group [p2se6] 4– (fig.4), in which the indium atoms occupy the space between the anionic groups. the second coordination environment (sce) [12] is of cuboctahedron form. indium cations are surrounded by a triangular environment of anionic atoms of the group [p2se6] 4–and within the frames of its environment bonding exists with six atoms of selenium while the coordination form is octahedral (fig.5). the structural and chemical properties of the меімеііір2se6 compositions are related to the important role concerning the dimension of the cation on its location between the layers of the anionic [p2se6] 4–groups. crystallographic analysis showed that smaller cations occupy a position in the plane perpendicular to the main axis. atoms located in a second coordination environment of anionic groups in the structure of tlinp2se6 compounds can be presented as a strongly distorted hexagonal-equivalent cuboctahedron (fig.6). the atoms of metallic cations, located in the cavities between the atoms of the anionic groups, are within an asymmetric environment (fig.7). in3+ cations move toward tetrahedral cavities on the boundary between tetrahedral and octahedral cavities, and tl+ cations move in the direction of the octahedral cavities. moreover the in3+ cations are located in the same plane together with the centres of the anionic [p2se6] 4– groups (fig.8) and some tl+ cations are shifted relative to the plane. therefore, this arrangement is a source of the interesting electro-physical and optical properties of materials based on compounds of this type. 3.3. optical response of single crystals of tlinp2se6 and in4(p2se6)3 the most important parameter of the energy spectra of semiconductors is the width of the band gap, eg, which is defined by the difference in energy between the bottom of the conduction band, ec, and the top of the valence band, ev. all semiconductors can be divided into two groups. in the first group, the minimum of the conduction band and the maximum of the valence band occupy the same point in the brillouin zone, i.e. at an identical location in the space of quasi-moments. in this case, the optical transitions of electrons from the valence band to the conduction band (with the absorption of a quantum of light) and from the conduction band to the valence band (with the emission of a quantum of light) occur so that the electrons practically do not change their quasi-moments. such transitions are characteristic of direct-gap semiconductors. for the second group, the absolute minimum of the conduction band and the absolute maximum of the valence band are at different points in the brillouin zone, and optical inter figure 3. structure of the anionic group [p2se6] 4–. figure 4. arrangement of the polyhedra anionic group [p2se6] 4– in in4(p2se6)3. figure 5. coordination environment of the indium atoms in the structure of in4(p2se6)3. figure 6. second (sce) and nearest (nce) coordination environments of atoms in the [p2se6] 4– anionic groups in the structure of tlinp2se6. tovt, barchiy, piasecki, kityk, and fedorchuk hungarian journal of industry and chemistry 16 band transitions must be accompanied by a large change in the electron quasi-moment. these are characteristic of indirect-gap semiconductors. since the photon moment is negligibly small compared with the electron quasi-moment, the latter case is possible only when the electron interacts with the phonon. according to the phase diagram, the single crystals of tlinp2se6 and in4(p2se6)3 were grown using the bridgman method in two vertical zone furnaces. experimental studies of optical spectra in the absorption region yielded information on the energy spectrum of electrons near the edges of the conduction band and band gap. studies concerning the dependence of diffuse reflection on wavelength (r = f(λ)) have shown that the compound tlinp2se6 refers to indirect-gap semiconductors. on the graph there are two rectilinear sections, one of which (for small wavelengths, , and large values of e) characterizes the interband transitions of electrons with phonon emission, and the other (for large  and small e) describes the processes of phonon absorption (fig.9). the intersection of the first section with the wavelength axis, , yields the value of eg + ephonon ( = 560 nm, e = 2.21 ev), and the intersection of the second characterizes eg – ephonon ( = 605 nm and e = 2.05 ev). the length of the segment between the points of intersection of both straight lines with the wavelength axis, , is equal to the doubled energy of the phonons, 2ephonon (0.16 ev), interacting with the electron. the middle of this segment corresponds to the photon energy equal to the width of the band gap of the indirect-gap semiconductor, eg. experimental calculations in terms of the compound tlinp2se6 have shown that eg = 2.13 ev and ephonon = 0.08 ev. the compound in4(p2se6)3 refers to direct-gap semiconductors, which characterizes the interband transitions of electrons in terms of photon absorption (fig.10). the intersection of the line with the wavelength axis,  ( = 651 nm), yields the value of eg = 1.91 ev. the crystals of in4(p2se6)3 and tlinp2se6 were illuminated by 10.6 μm and (its second harmonic) frequency doubling of 5.3 μm beams. each channel of the beam was split by 200-ns co2 laser pulses with a pulse repetition frequency of about 10 hz. the angle between these two laser beams was changed from 18º to 22º. figs.11 and 12 present these dependences. treatment with a 10.6 μm beam achieved a smaller maximum birefringence (about 1.5510-2) in comparison to the 5.2 μm beam. this indicates a different photoinduced anisotropy for the in4(p2se6)3 and tlinp2se6 crystals. because a) b) . figure 7. coordination environments of the thallium (a) and indium (b) atoms in the structure of tlinp2se6. figure 8. arrangement of the polyhedra anionic group [p2se6] 4– in the structure of tlinp2se6. figure 9. dependence of the diffuse reflection r on the wavelength  for the compound tlinp2se6. figure 10. dependence of the diffuse reflection r on the wavelength  for the compound in4(p2se6)3. investigations of the tlinp2se6–in4(p2se6)3 system 45(2) pp. 13–18 (2017) 17 these crystals contain chalcogenide anions that contribute to the anharmonicity of the phonon, they play a crucial role in terms of the second harmonic generation [13-14]. the maximum changes in the birefringence achieved were less than 210-2 and 6.310-2 for co2 laser wavelengths of 10.6 μm and 5.3 μm, respectively. 4. conclusion differential thermal analysis, x-ray diffraction and microstructural analysis were used to construct a phase diagram for the tlinp2se6–in4(p2se6)3 system, which can be characterized by a eutectic-type interaction. the invariant eutectic process l  httlinp2se6 + mtin4(p2se6)3 (15 mol% in4(p2se6)3) occurs at 791 k. two polymorphic transformations were identified for tlinp2se6 at 680 k and 711 k and for in4(p2se6)3 at 665 k and 903 k. new compounds were not detected in the binary system. the regions of solid phases of the complex compounds tlinp2se6 and in4(p2se6)3 do not exceed 10 mol%. single crystals of both test compounds were achieved by the bridgman method. investigations concerning the dependence of the diffuse reflection spectrum showed that the compound tlinp2se6 is characteristic of indirect-gap semiconductors (eg = 2.13 ev, ephonon = 0.08 ev), while the compound in4(p2se6)3 is characteristic of direct-gap semiconductors (eg = 1.91 ev, ephonon = 0.08 ev). the dependence of the birefringence was photoinduced by wavelengths of 5.3 μm and 10.6 μm, which is indicative of different photoinduced anisotropy. acknowledgement we are grateful for the financial support of this work by the ministry of education and science of ukraine under the project db874p_0117u000380. symbols ht high–temperature modification mt middle–temperature modification lt low–temperature modification sce second coordination environment nce nearest coordination environment eg band gap, ev ephonon phonon energy, ev r diffuse reflection  wavelength, nm references galdamez, a., manriquez, v., kasaneva, j., avila, [1] r.e.: synthesis, characterization and electrical properties of quaternary selenodiphosphates: amp2se6 with a – cu, ag and m – bi, sb, mat. res. bull., 2003 38, 1063-1072 doi: 10.1016/s00255408(03)00068-0 mcguire, m.a.; reynolds, t.k.; di salvo, f.j.: [2] exploring thallium compounds as thermoelectric materials: seventeen new thallium chalcogenides, chem. mater., 2005 17, 2875-2884 doi: 10.1021/cm050412c gave, m.a.; bilc, d.; mahanti, s.d.; breshears, [3] j.d.; kanatzidis, m.g.: on the lamellar compounds cubip2se6, agbip2se6 and agbip2s6. antiferroelectric phase transitions due to cooperative cu+ and bi3+ ion motion, inorg. chem., 2005 44, 5293-5303 doi: 10.1021/ic050357 pfeiff, r.; kniep, r.: 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in sb2te3–baf2–pbcl2 glasses, j. phys. chem. b, 2003 107, 10083-10087 doi: 10.1021/jp030058a hungarian journal of industry and chemistry vol. 48(1) pp. 87–93 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-14 examination of fuel consumption factors, basics of precision and on-board diagnostic measurements tibor busznyák∗1 and istván lakatos1 1department of road and rail vehicles, széchenyi istván university, egyetem tér 1, győr, 9026, hungary in this paper, different factors of fuel consumption are examined. driveload equitation is used as a basis and the parts that handle energy consumption in particular are analyzed. for the purposes of visibility, it was implemented using matlab. in statistical works, fuel consumption data require that the energy consumption of vehicles be analyzed correctly. variables which affect fuel consumption during a given drive are defined. research is analyzed in the second part of the paper where vehicle diagnostics are combined with global positioning. examinations are necessary to create on-board diagnostics-based positioning. keywords: gps, obd, correlation, drive, assistance 1. introduction nowadays, innovation is a key. economical, safetycentred or traffic optimization tasks are increasingly regulated. these criteria require developers to actuate and consequently upgrade their conceptions. new technologies are rapidly emerging so industries have to keep up to date. drive options, including alternative drive solutions, are continuously being updated, the number of driverassistance features is ever-increasing towards a possible fully autonomous level [1]. the role of development focusing on smart city concepts and sustainable traffic is becoming more important. critical aspects of it are efficient energy use (the central question of the present paper), range of online communication systems, autonomous transport systems and conceptions of autonomous vehicles. reliable operation requires cooperation between different participants, e.g. the information technology, urban development and automotive industries. these aspects are interrelated, therefore, a more efficient intelligent transportation system (its) could be realized [2–4]. information technologies between different units of traffic are elementary in terms of automated traffic. the stability of dataflow is unavoidable. communication channels play a key role in everyday life as information is accessed from the internet. as information content defines the quality of data, the demands of traffic quality have recently been increasing. the number of automobiles in hungary has almost doubled over the past twenty years. safety issues and ∗correspondence: busznyaktibor@gmail.com accidents are increasingly commonplace. besides accidents, traffic jams have also become more frequent. as a result, driving has become harder. rush-hour traffic that slowly inches forward, searching for a parking space or simply parking itself put drivers to the test under crowded, metropolitan conditions. the need to avoid similar situations has led to the emergence of driverassistance systems. the quality of data transmissions as well as trouble loggerand indicator systems, which evaluate inputs from sensors or on-board diagnostics, are closely connected to vehicle information. the aforementioned technologies help driver-assistance systems to function. due to information technology and automatization, it is possible to create a vehicle network. one of these networks is the vehicle-to-everything (v2x) communication platform where vehicles communicate with each other along with the infrastructure provider to share information about the locations of traffic jams and avoid congestion. vehicle communication and driver-assistance systems help to improve road traffic safety and make more accurate predictions [5–7]. an important task is to define databases based on the optimization of traffic. several methods, e.g. based on vehicles or infrastructure, are available in order to build a database. if the vehicle investigated predominantly drives in well-maintained, intelligent infrastructure, then the number and complexity of built-in vehicle systems can be reduced. in this case, information is supplied to the vehicle by an uninterrupted connection with external systems. this could also be true of the drive of a vehicle on predefined routes, e.g. buses. it is easier to build infrastructure for https://doi.org/10.33927/hjic-2020-14 mailto:busznyaktibor@gmail.com 88 busznyák és lakatos public transport vehicles because their routes are predefined. on the other hand, a vehicle can be defined as a separate unit. without infrastructure, vehicles rely on built-in sensors and can drive anywhere, external infrastructure is unnecessary. how could the complexity of a given vehicle’s sensor system be reduced? would it be possible to use built-in on-board diagnostics for positioning tasks. basic ideas originate from simple experiences. if people drive uphill in cruise control, the amount of data concerning fuel consumption that appears on the dashboard increases. the core of this research is the possible connection between elevation and fuel consumption: 1. can a connection between elevation data from global positioning and fuel consumption data from on-board diagnostics at a constant or various speeds be identified? 2. is it possible to create a topographic elevation model from fuel consumption data? 3. if it is possible, then the fuel consumption can be predicted from road conditions. 4. by integrating on-board diagnostics into conventional or intelligent transportation systems using the presented relations, a vehicle can be located. connections between data from global positioning systems and fuel consumption are sought. it is necessary to define important variables that affect the fuel consumption of a vehicle. the relevant equations and propulsion power requirements are analyzed. 2. experiment 2.1 propulsion power requirements and fuel consumption – defining variables internal combustion engines function by burning fuel which is blended with air in line with energy requirements. propulsion power is necessary for a vehicle to move but its movement is restricted by various internal and external driving resistances. external driving resistances rolling resistance is fg = µmg (1) the rolling force resists motion when tires are rotating on a given surface. internal and external factors are included in the equation. the external factor is the rolling resistance coefficient which depends on contacting surfaces. the internal factor is the deformation of the tires which is dependent on the load of the vehicle. a loss in power results. power against rolling resistance is pg = fgv (2) aerodynamic drag is fl = cwρav 2/2 (3) drag acts in the opposite direction to which the vehicle is moving. it plays a major role in terms of vehicle dynamics and efficiency. at higher speeds, it is more significant because drag increases with the square of the velocity. power against drag is pl = flv (4) climbing resistance is fe = mg sin(α) (5) climbing resistance depends on the elevation of the route, mass of the vehicle and road gradient. power against climbing resistance is pe = fev (6) internal driving resistances acceleration resistance is fgy = (1 + θ)ma, (7) where θ is a coefficient of rotating components (table 1). energy is required to accelerate. the acceleration resistance can be calculated from the masses of the rotating components and vehicle. power against acceleration resistance is pgy = fgyv (8) other internal resistances, e.g. transmission resistance, are peff = (1− η)ph (9) another internal resistance arises when the transmission system moves and depends on the efficiency of its parts, moreover, it is used to calculate power. this internal resistance is constant and includes the efficiency of the differential (0.93), efficiency of the clutch (0.99), efficiency of the drive shaft (0.99), efficiency of the gearbox (0.97) and efficiency of the bearings (0.98): η = ηtk ηdiff ηkt ηcs ηny (10) finally, energy produced by the combustion of fuel is translated into the energy requirements of given resistances. at constant velocities, the acceleration resistance is zero and transmission resistance constant as well as calculable, as is shown in table 2. thus, the traction force or driveload equitation can be written in the following wellknown form: fv = fe + fg + fl (11) pv = fvv (12) hungarian journal of industry and chemistry examination of fuel consumption factors 89 table 1: values of θ gear [ith] θ 1 0.4 2 0.3 3 0.2 4 0.1 5 0.08 table 2: defined variables known values a, m, g, µ, cw, ρ variables v, α 2.2 matlab implementation the analysis of traction force components was conducted in the matlab development environment to try and define how variations in velocity and road gradient can explain power requirements. an analysis was conducted based on theoretical elements and data were defined by given measurements. vehicle: ford b-max (2014) • empty mass (m) = 1275 kg; • maximum power (pmax, peff ) = 74 kw; • drag coefficient (cw) = 0.32; • frontal area (a) = 2.8 m2; • rolling coefficient (µ) = 0.007 velocity codomain: • v = [0, 140 km/h] road gradient codomain: • α = [0, 30 ◦] figs. 1-3 show the effects of different resistances. the rolling resistance diagram (fig. 1) exhibits a linear trend. the power demand increases as the velocity and road gradient increase. the climbing resistance diagram (fig. 2) also exhibits a linear trend. according to real data, it is necessary to define a power limit, in this case 74 kw, which is the maximum power of the vehicle. analysis above this limit in not required since the engine is incapable of providing more power. on the contrary, the vehicle would decelerate or remain stationary beyond this limit. the air resistance diagram (fig. 3) exhibits a square trend between the velocity and power demand of the vehicle. the power demands of external resistances are presented in fig. 4. important values were compiled in tables 3–5. in the first part of this chapter, constant, discrete velocities were assumed. the next step is the parameterization of acceleration. for this task, values of theta are required (table 1). acceleration codomain figure 1: diagram of the power demand of rolling resistance as a function of velocity and road gradient figure 2: diagram of the power demand of climbing resistance as a function of velocity and road gradient figure 3: diagram of the power demand of air resistance as a function of velocity and road gradient • a = [0, 5 m/s2] gravitational acceleration [g] is a dimensionless, unofficial and descriptive measure. g codomain can be derived from a codomain. the effects of acceleration are shown in fig. 5. it is visible that at predefined shifts, diagram flow refracts and represents real cases. important values are compiled in tables 6–8. 3. results and analyses at high velocities and on steep road gradients, the power demand is also higher. the declaration of variables is necessary as a result of precise planning to follow on-board diagnostics (obd) measurements, especially routes. two independent measurement systems, obd and gps, are 48(1) pp. 87–93 (2020) 90 busznyák és lakatos figure 4: diagram of the power demand of external resistances as a function of velocity and road gradient comparable to connect the concept [8]. precision positioning is widely used and consists of numerous important boundary conditions. this paper examines the obd side of the concept, details of precise gps and gnss measurements are presented in previous papers of ours. a statistical analysis of the fuel consumption database is given from the equation of motion. for this database, work was used, that is the product of the force and displacement in the direction of the force. table 3: notations of v and α variables v(↓) low velocities v(←) medium velocities v(↑) high velocities α(↓) shallow road gradients α(←) medium road gradients α(↑) steep road gradients table 4: values for p [v, α] calculated in the matlab environment v(↓) = 3.6 [km/h] α (↓) = 0◦ p= 0.3064 [kw] α(←) = 5◦ p = 1.178 [kw] α(↑) = 30◦ p = 6.342 [kw] v(←) = 50 [km/h] α (↓) = 0◦ p= 2.824 [kw] α(←)) = 5◦ p = 18.09 [kw] α(↑) = 30◦ p = 74 [kw] v(↑) = 140 [km/h] α (↓) = 0◦ p = 40.78 [kw] αmax (140) = 4◦ p = 74 [kw] α (↑) = α (←) = αmax table 5: p [v, α] matrix p [v, α] v(↓) v(←) v(↑) α(↓) p (↓) p (↓) p (←) α(←) p (↓) p (←) p (↑) α(↑) p (←) p (↑) p (↑) figure 5: diagram of the power demand of acceleration as a function of velocity and g lifting work is wem = fem∆s = mg∆h (13) lifting work is the work that is done by lifting an object over a given period of time. it is proportional to its mass and change in height. friction (or rolling) work is ws = µmg∆s (14) table 6: notation of v and g variables v(↓) low velocities v(←) medium velocities v(↑) high velocities g(↓) low accelerations g(←) medium accelerations g(↑) high accelerations table 7: values for p [v,g] calculated in the matlab environment v(↓)=3.6 [km/h] g(↓)=0.01 p=0.1785 [kw] g(←)=0.1 p=1.185 [kw] g(↑) = 0.3 p = 5.93 [kw] v(←)=50 [km/h] g(↓)=0.01 p=2.142 [kw] g(←)=0.1 p=21.42 [kw] g(↑)=0.3 p=64.26 [kw] v(↑)=140 [km/h] g(↓)=0.01 p=5.508 [kw] gmax(140)=0.1424 p=74 [kw] g(↑)=g(←)=gmax table 8: p [v,g] matrix p [v,g] v(↓) v(←) v(↑) g(↓) p (↓) p (↓) p (←) g(←) p (↓) p (←) p (↑) g(↑) p (←) p (↑) p (↑) hungarian journal of industry and chemistry examination of fuel consumption factors 91 table 9: proportionalities over the period of time wem v, ∆h ws v wgy v2 wk v2 table 10: determination of coefficients constant velocity [km/h] coefficient of determination [r2] 30 0.9549 40 0.9160 50 0.8370 friction work is proportional to its mass and displacement. acceleration work is wgy = 1 2 m∆v2 (15) acceleration work is proportional to its displacement, mass and the square of its velocity. work done by air resistance is wk = 1 2 acwρv 2∆s (16) work done by air resistance is proportional to its displacement, drag coefficient (cw), frontal area (a), density (ρ) and square of its velocity. for the purpose of statistical analysis, proportionalities were compiled in table 9. now the statistical analysis can be conducted. in the first step, a single variable analysis is carried out. previously, a given route was measured, thus gps and obd databases were available. a connection between elevation and fuel consumption data was sought. table 10 shows that the concept is highly usable at low velocities, but when the range of velocities increases, the coefficient of determination becomes less efficient. multivariate analysis provides a solution to this problem. in this case, experienced variables, as summarized in table 9, were used. a route comprised of different road gradients and velocities was examined. a visual check is recommended to summarize the regression model, with which it is possible to forecast correlations according to different predictors (r2). range of velocity = [20, 70 km/h] 1. examination with ∆(v2) • r2 = 57.2% • where ∆(v2) = variation in the square of the velocity. 2. examination with ∆(v2) and ∆h figure 6: results of the multivariate analysis • r2 = 86.4% • where ∆h = change in height. 3. examination with ∆(v2), ∆h and v • r2 = 87.1% • where v = actual velocity. fig. 6 respresents the regression equation with the coefficient of determination. the regression equation can be rewritten in the following form: con = a∆(v2) +b∆h+ cv +d (17) con is an abbreviation of fuel consumption and appears constant. it reflects other possible predictors that have not been examined, for example, losses of the internal combustion engine. 3.1 obd-based positioning a drawback of precision positioning devices on the market are their prices, but the obd connectors are basic, standardized accessories of vehicles. the presented structure, when a connection is made between the positioning and on-board diagnostics, can be used for driver assistance tasks [9]. a matlab implementation of obd-based positioning has been proposed that is connected to the aims of this paper and will be presented shortly. dataflow and the stability of the system with regard to a precision positioning measurement are crucial. its boundary conditions are the following: • connection to 5 gnss satellites simultaneously; • dataflow stability in terms of the satellites and the base; • online connection with the base, from where the correction of data originates. 48(1) pp. 87–93 (2020) 92 busznyák és lakatos figure 7: operation of the matlab algorithm for obdbased positioning while weighing up the risks of two independent measurement methods, it is clear that the precision positioning technique is riskier. a significant safety risk can be reduced if it can be substituted for other alternatives. an alternative to the elevation database of the routes and obd data, which is accessible to every vehicle, may exist. to summarize our matlab implementation, continuously incoming obd data are compared to a reference database which consists of a map with coordinates. by searching for the minima of the squared differences of the two databases, an algorithm was derived that is capable of defining position based on changing trends. fig. 7 presents the operation of the developed algorithm at a constant velocity of 30 km/h. few incorrect obd data points were obtained, for example, at a horizontal displacement of 125 m. as the database of fuel consumption is continuously expanding, the significance of this imprecision is decreasing. 4. conclusion in this article, the driveload equitation was examined and special care taken with regard to its power demands. in the matlab environment, characteristics of different resistances were shown. moreover, the fixing of dependent variables was the main exercise in this research besides understanding the basic connections between onboard diagnostics and precision positioning. obd-based positioning is a possible method to determine the actual position of a vehicle without constantly being connected to gps or gnss. it could be useful as part of v2x or other intelligent transportation systems. in order to extend the concept to electric vehicles, the velocity and road gradient are the main variables, the power demands of both are comparable, and optimal charging points on a given route can be calculated. this could form the basis for a future paper. symbols µ rolling resistance coefficient m mass of moving object g gravitational acceleration v velocity cw drag coefficient ρ density a front surface α road gradient θ coefficient of rotating object a acceleration g gravitational constant η efficiency ηtk efficiency of gearbox ηdiff efficiency of the differential ηkt efficiency of cardan-shaft ηcs efficiency of bearings ηny efficiency of the clutch h altitude s displacement acknowledgements this research was carried out as part of the efop3.6.2-16-2017-00016 project within 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227–232 doi: 10.5176/2010-2283_1.2.65 [8] sun, q.; xia, j.; foster, j.; falkmer, t.; lee, h.: pursuing precise vehicle movement trajectory in urban residential area using multi-gnss rtk tracking, transportation research procedia, 2017, 25, 2356– 2372 doi: 10.1016/j.trpro.2017.05.255 [9] busznyák, t.; pálfi, g.; lakatos, i.: on-board diagnostic-based positioning as an additional information source of driver assistant systems, acta polytechnica hungarica, 2019, 16(5), 217–234 issn: 1785-8860 48(1) pp. 87–93 (2020) https://doi.org/10.5176/2010-2283_1.2.65 https://doi.org/10.1016/j.trpro.2017.05.255 introduction experiment propulsion power requirements and fuel consumption – defining variables matlab implementation results and analyses obd-based positioning conclusion editorial hungarian journal of industry and chemistry veszprém vol. 42(1) pp. 51–56 (2014) development of a reaction structure identification algorithm jános kontos,1! lászló richárd tóth,2 and tamás varga2 1 department of physical chemistry, university of pannonia, egyetem st. 10, veszprém, h-8200, hungary 2 department of process engineering, university of pannonia, egyetem st. 10, veszprém, h-8200, hungary !e-mail: kontosjan@gmail.com the most important step in the design procedure of a chemical reactor is the understanding the chemical reaction network (crn), which will take place in that reactor. the structure of a crn as representation of the reaction mechanism contains all the elementary reaction steps that are required to convert the reagents into products. the aim of the reaction mechanism analysis is the identification of the route how the system goes from its initial to the end state. in order to do this, a lot of knowledge is required about chemistry supplemented with some analytical measurements. in this work, we focus on the development of an algorithm, which requires a few data inputs to reveal all the reaction steps that are important in the reactor design point of view. it is trivial that the structure of a dynamic system cannot be determined without the identification of the model parameters that belong to that structure. hence, the algorithm reported here can be used to obtain the parameters of the reaction rate equations for each identified chemical reaction. first, the structure is identified followed by its parameters. in this study the processed data are obtained by a crn generator, which is applied to generate random crns based on some specified parameters to reach maximal reaction order. concentration profiles, which characterize each crn at a specific reaction rate constants combination, are obtained as a result of simulations based on the randomly generated crns. the developed algorithm for reaction mechanism identification is based on a modified type of linear least-squares method (llsm) in which the searching variables must be higher than zero, since the reaction rate constants cannot have negative values. the developed algorithm is tested in different cases to check the applicability of llsm in reaction structure identification procedure and the obtained results show that with some further improvements the proposed algorithm can be applied solving more complex identification tasks. keywords: chemical reaction network, structure identification, non-negative least-squares method, crn generator introduction one of the most important tasks during the design procedure of any chemical technology is the engineering design of the conversion subsystem and to ensure the optimal and safe operation. hence, before starting the design of a technology phenomena with impact on the dynamic behaviour of the subsystem must be identified. the most crucial part of the conversion subsystem is the chemical reactor in which we try to control the processes that was identified on the basis of laboratory experiments. in this work we proposed a method to support the identification of the individual reaction steps and their rates in a chemical reaction network (crn). numerous literature examples can be found that describe different methodologies to generate the structure of crns, as representations for reaction mechanisms [1, 2]. the reaction mechanism of a reaction system represents all the elementary reaction steps, which are required to convert the reagents into products. hence, the aim of reaction mechanism identification is the determination of the intermediate steps, which take the starting materials to the final products. trivially, it is challenging to follow and model the movements of all the molecules in a system in full detail. however, we can describe a reaction system on the basis of the cumulative effects of great number of molecules in specific states. such specific states are the formation of stable intermediates. the intermediates are chemical species produced in the elementary reaction steps. often, it is possible to detect them by experimental methods. the produced amount of these intermediates is sometimes very low and they react very fast to produce another intermediate or final product. hence, the identification of the latter components and the measurement of their concentrations can be challenging. most of the reactions take place through multiple intermediate steps. these scenarios are called multi-step reactions. in a single reaction step, the sign of stoichiometric coefficients represent that a given molecule is a reagent (-) or product (+), and the absolute value of these coefficients give how many moles are consumed/formed. the transient states of a reaction system and the intermediates can be investigated with two kinds of methods on the basis of whether a priori knowledge of reaction kinetics is available or not [3]. the foundation of the reaction mechanism analysis is the precise identification of all intermediates and their 52 concentration. with the lack of this information the stoichiometry of the reaction cannot be revealed reliably. the nature and the amount of the products can contain as much information as a well-qualified chemist requires identifying the reaction mechanism of an unknown reaction system. the proposed algorithm can support this process in case we have lack of experience in the identification of the structure of a crn and parameters of kinetic expressions, which describe the rate of the reaction steps considered in the crn. the essence of the parameter identification process is the solution of a constrained minimization problem in which the objective function can be the sum of squared error between the measured and the calculated component concentration profiles. the searching variables are the unknown parameters in the kinetic expressions (i.e. pre-exponential factor, activation energy, reaction order). the role of the structure identification is the definition of correlated variables and their mathematical formalization. in our case, the identification means the selection of reaction steps that can take place in the reactor. the identification tasks can be solved by the application of linear least-squares method (llsm) [4]. the main challenges using this method are the definition of the correct initial conditions for the applied searching algorithm and the speed up of the identification procedure. one of the most important simultaneous methods is the incremental approach, which applies a hierarchical modelling methodology to decompose the complex identification problem into simpler sub-problems [5]. the method applies target factor analysis to identify the suitable structure of the unknown crn. this method has been successfully applied in reaction mechanism identification process in a multi-phase system based on concentration and calorimetric measurements [6]. correlation metric method was developed to analyse the strength of the connections between the components in the system, which is based on the qualitative analysis of the measured data [7]. qualitative trend analysis was also applied in reaction mechanism identification algorithms to divide the entire experimental time into shorter periods in which the correlations are analysed between the concentrations of components [8]. in this work, our aim is to develop a simple, but reliable method for structure identification of crns, which need as few data as possible. in our case the input of the algorithm is only the list of components and concentration profiles, which are the result of the simulation based on randomly generated crns. these crns were generated based on user specified parameters, such as maximal reaction order. on the basis of the randomly generated crns, the concentration profiles for each crn at a specific reaction rate constants combination are determined. the algorithm developed for reaction mechanism identification is based on a modified llsm method, in which the searching variables must be higher than zero, since the reaction rate constants cannot have negative values. development of simulation methods since our aim is to develop a generally applicable algorithm to support the identification process of crns with unknown structure, we developed a crn generator, which can be applied to randomly generate crns based on some structural parameters, such as the maximum number of components or reactions in crn. there are many examples in literature for developing a crn generator that analyses the affinity of molecules taking part in reactions [9], applies mixed integer programming to build up reaction networks [10], or using group contribution method to generate the structure of the crn and the kinetic parameters of the reaction steps in that network [11]. in this work we developed a simple crn generator that randomly generates a crn from randomly generated components. in this generator, we define probabilities in situations for building different kinds of crns. for example, if we would like to have more decomposition reactions in the crn then the probability of this type of reaction is increased. the scheme of the developed crn generator can be seen in fig.1. the first step of the algorithm of the crn generator is the definition of the parameters of the desired crn, such as the probabilities of the different types of reactions. in this step the maximal number of building block types in a component and the maximal number of specific building blocks in a component are defined. figure 1: the scheme of the proposed crn generator 53 the next step is the development of the first reaction step in which we define a new component next to the components that are already in the component list. the stoichiometric coefficients of the reaction are randomly generated based on the user-defined parameters. the composition and the chemical formula of the added component are determined based on the material balance of the reaction. with the first reaction step, it is checked whether the numbers of components and reactions in the generated crn are enough. if the user defined value of these parameters are higher than the current values the crn generator starts to build a new reaction with selecting the reaction type, the components. based on the crn parameters it randomly generates stoichiometric factors for that new reaction and checks the material balance. components that are involved in more reactions have a smaller chance to be chosen for the next new reaction building iteration. if there are enough components or reactions in the generated crn, the algorithm steps to the next phase in which it randomly generates the reaction kinetic constants for reactions in the crn. in this phase, the algorithm randomly generate kinetic parameters, while maintaining the same order of magnitude of the reaction rates, to make it harder to find out the structure of the generated crn. particle swarm optimization method has been applied to solve this constrained optimization problem, where the objective function is defined as the difference of the integral of reaction rates over the time [12]. general reactor model the kinetic experiments are usually performed in a tempered flask that can be modelled as an isothermal batch reactor. all the reagents are added to the unit with or without catalyst and samples are taken from the reaction mixture in specific times. as mentioned earlier the simplest case is considered as we have only concentration measurements from a batch reactor. however, the developed algorithm can be improved and the processability of data can be widened with the application of mathematical models of other reactor types. hence, at this point of the development of the proposed algorithm, we consider that the unit in which the kinetic experiments are performed is a well-mixed, isothermal batch reactor. the model of a batch reactor should be developed first to contain component mass balance equations. applying the well-mixed assumption the component mass balances can be simplified and we obtain the equations: { } ,;...c;b;air dt dc i i == (1) where i identifies the components in the system in which we have nc components; ci is the concentration of the ith component [mol m-3]; ri is the component source of the ith component [mol m-3 s-1], which can be calculated as: ri = υ ji ⋅ rj j=1 nr ∑ , (2) where j identifies the reaction in the system; nr gives the number of reactions considered; νji is the stoichiometric coefficient of the ith component in the jth reaction; rj is the reaction rate of the jth reaction [mol m3 s-1], which is calculated with following expression: rj = k j ci n ji i= a;b;c;...{ } ∏ , (3) where nji denotes the order of ith component in jth reaction [1], kj is the reaction rate constant of the jth reaction [the unit is dependent on the order of the reaction, [mol1-n m3n-1 s-1], where n is the summarized reaction order in jth reaction: n = nji i= a;b;c;...{ } ∑ . (4) this summarized reaction order is equal to the absolute value of the stoichiometric coefficient of the ith component in the jth reaction, if the given component is a reagent in a given reaction, otherwise it is 0. the developed general reactor model has been implemented in matlab. proposed algorithm for structure identification of crn our primary aim is to develop an algorithm, which can be efficiently applied in reaction mechanism identification tasks on the basis of concentration profiles. in this phase, we considered that the concentration profiles are known for all the components in the system. it is a simplification with respect of practical problems; however, in this work we aim to evaluate if a simple method of llsm is suitable for a complex task. llsm is based on the minimization of a special model error, which is based on comparing the measured to the calculated time series. in our case, the time series are the numerical derivatives of the concentration profiles. based on the measured concentration profiles the change in concentration during two sampling steps can be calculated as a numerical derivative with respect to length of that time step. if we have nk samples, the difference in kth sample can be defined as follows: δĉ i δt k( ) = ĉ i k( )− ĉ i k −1( ) , (5) where k is the current sample; δĉ i is the difference of the measured concentration of ith component in between k and k-1 sampling steps; tδ is the time difference between k and k-1 sampling steps. if we calculate this difference for all the components and in every sampling steps we get a matrix which has k-1 rows and as many columns as many components we assume in the system. based on the calculated concentration profiles another matrix can be built with the calculated variables. in our case the sum of the 54 squared differences between these two matrices is defined as the model error, which should be minimized during the identification process: e = δĉ i δt k( )− δci δt k( ) # $ % & ' ( 2 k=1 nk ∑ i= a;b;c;...{ } ∑ , (6) where e is the calculated model error, which is basically the difference of the measured and calculated component sources defined with eq.(2); δci is the calculated changes in concentrations of ith component from eq.(1), but the steps is equal with the sample times of measurement. to make it easier to follow the process we define eq.(6) using vectors instead of sums: e = δĉ ___ − δc ___# $ % & ' ( t δĉ ___ − δc ___# $ % & ' ( , (7) where the length of vectors are nc(nk-1) (i.e. the change in concentrations of components should be calculated in every sample time except in the initial phase) and defined with the following structures: δĉ ___ = δĉa 1( ) δĉb 1( ) ! δĉa 2( ) δĉb 2( ) ! δĉa k( ) δĉb k( ) ! " # $ $ $ $ $ $ $ $ $ $ $ $ $ $ % & ' ' ' ' ' ' ' ' ' ' ' ' ' ' , δc ___ = δca 1( ) δcb 1( ) ! δca 2( ) δcb 2( ) ! δca k( ) δcb k( ) ! " # $ $ $ $ $ $ $ $ $ $ $ $ $ $ % & ' ' ' ' ' ' ' ' ' ' ' ' ' ' . (8) the task in llsm is the minimization of the model error defined in eq.(7) by manipulating the model parameters, such as the reaction rate constants of all the possible reaction steps, which are the building blocks of the unknown crns. hence, to use llsm in reaction mechanism identification process first we need to collect all the possible reaction steps, which can take place in the system based on the defined component list. to get the necessary reaction steps, we generate all the possible combination of reactions, which satisfy the material balances. a given reaction step has to be further processed, since some reaction steps can be produced from each other with linear combinations. thus, only the independent reactions should be kept in the reaction set. the resulted reaction set is represented in a matrix (i.e. in stoichiometric matrix): =υrs , ba ba ba ! ! ! " # $ $ $ % & υυ υυ !"" # # " # 22 11 2 1 (9) which has the same number of rows and columns as the number independent reactions and components are considered in the system, respectively. after the possible reaction steps have been automatically collected, all the reaction steps of the set are considered as the part of the unknown crns. based on the reaction set the mathematical model of the system is automatically generated based on eqs.(1)-(3). the unknown parameters in this model are the reaction rate constants for all reactions in the reaction set. the calculated concentration differences in eq.(7) can be obtained using eq.(10) on the basis of the general reactor model (eqs.(1-3)): ,ckc ___ υ=δ (10) where c denotes a special matrix in which a diagonal matrix is repeated from sample time to sample time and in the diagonal matrices we calculate the concentration product term in eq.(3) in every sample time. the following general matrix shows the structure of the resulting diagonal matrix in this step if we have nr reactions in the reaction set: =c ci 0( )( )n1i i= a;b;c;...{ } ∏ 0 ! 0 ci 0( )( )n2i i= a;b;c;...{ } ∏ ! " " # ci 1( )( )n1i i= a;b;c;...{ } ∏ 0 ! 0 ci 1( )( )n2i i= a;b;c;...{ } ∏ ! " " # ci k −1( )( )n1i i= a;b;c;...{ } ∏ 0 ! 0 ci k −1( )( )n2i i= a;b;c;...{ } ∏ ! " " # # $ % % % % % % % % % % % % % % % % % % % % % % % % & ' ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( (11) υ denotes a special matrix in which the stoichiometric matrix representing the reaction set (eq.(9)) is repeated as many times as the sample times minus one: =υ υrs υrs ! ! " # # # # # $ % & & & & & (12) k indicates reaction rate constant vector for all the reactions in the reaction set. by applying llsm, the structure of the unknown crn can be identified since the reaction rate constants that can be the part of the unknown crn will have different values than zero at the end of the identification process and all the other reactions in reaction set get zero value. based on eqs.(7) and (10) we can solve the minimization problem and the following expression is the result for the calculation of reaction rate constants for all reactions in the generated reaction set: 55 ___''''' ĉccck δ×## $ % && ' ( ×# $ %& ' (υ× * * + , . / ## $ % && ' ( ×# $ %& ' (υ×## $ % && ' ( ×# $ %& ' (υ= −1 (13) reactions with zero reaction rate constants indicate that they cannot be part of the unknown crn. this means that at the end of the identification process we get the reaction rate constants as well, next to the structure of the crn. results and discussion since we do not have measurements from a real system in this work the developed crn generator has been applied to randomly generate some crns. table 1 shows two reaction steps in the unknown crn. we have defined five components (a-e) in the system. a and b components are reagents in the first reaction step (r01), in which c and d components are produced. however, in the second reaction (r02) only e is consumed while 2 moles of a and 1 mole of d are produced. the last column of table 1 shows the exact values of reaction rate constants. the unit of reaction rate constants can be determined for the jth reaction based on the sum of the reaction orders of each component in that reaction: mol m3 ! " # $ % & 1− nji i= a;b;c;...{ } ∑ ! " # # $ % & & ⋅ 1 s (14) table 2 shows the five components (a-e) that are built from nine (a-j) building elements. these building elements can be imagined as atoms or groups. the numbers in the matrix represents the stoichiometric coefficients of composition. the last row shows a fictitious molecular mass of the components in the system. based on the molecular mass and the number of building elements in the components all the independent reaction steps were generated as shown in table 3. the 22 possible reaction steps can be found for the five components from table 2. the unknown reaction mechanism should be built from these reaction steps. in table 1 we saw that we need only two of these steps and as it can be seen in the last column of table 3 with the proposed algorithm we can find these two reactions of rs01 and rs16. however, the algorithm identifies a third possible reaction step, rs13, which can be the part of the unknown crn. as can be seen in the last column of table 3, the reaction rate constant corresponding to this reaction step is very low. this means rs13 should not be considered as the part of the unknown crn. after the above simple task, we tested our method in nine other cases. we defined a quantitative measure to check the correctness of the identified kinetic parameters as the mean average difference between the known and the identified reaction rate constants: mae = 1 ndr k̂l − kl l=1 ndr ∑ (15) where ndr is the number of reactions in unknown crn; l identifies the current reaction rate constant; k̂ is the reaction rate constant value what we are looking for, such as the last column in table 1 for crn01. table 4 presents the number of reaction steps in the unknown crn (ndr), the number of components (nc) in the system, the number of the possible reaction steps (nr) as a representation of the size of the reaction set, if the algorithm can find the perfect reaction steps or not, and mae values when available from eq.(15). table 1: a randomly generated crn with crn generator a b c d e k [-] r01 -1 -1 1 1 0 1.5590 r02 2 0 0 1 -1 1.0184 table 2: the generated compound matrix a b c d e a 9 0 1 8 26 b 10 0 8 2 22 c 7 1 1 7 21 d 2 10 7 5 9 e 4 12 13 3 11 f 12 0 1 11 35 g 8 0 6 2 18 h 11 5 7 9 31 j 6 1 3 4 16 m [mass mol-1] 359 195 252 302 1020 table 3: the resulted reaction step matrix with the identified reaction rate constant rs id a b c d e k [-] rs01 -1 -1 1 1 0 1.626 rs02 -3 -1 1 0 1 0 rs03 -2 0 0 -1 1 0 rs04 -2 6 3 -4 0 0 rs05 -3 5 4 -3 0 0 rs06 -4 4 5 -2 0 0 rs07 -5 3 6 -1 0 0 rs08 0 4 5 0 -2 0 rs09 -3 3 6 0 -1 0 rs10 5 -3 -6 1 0 0 rs11 3 -3 -6 0 1 0 rs12 4 -4 -5 2 0 0 rs13 0 -4 -5 0 2 0.004 rs14 3 -5 -4 3 0 0 rs15 2 -6 -3 4 0 0 rs16 0 -6 -3 3 1 0 rs17 2 0 0 1 -1 1.051 rs18 0 -2 2 3 -1 0 rs19 1 1 -1 -1 0 0 rs20 0 2 -2 -3 1 0 rs21 3 1 -1 0 -1 0 rs22 0 6 3 -3 -1 0 56 based on the results in table 4 it can be seen that the proposed algorithm has some limitations in this phase. however, if the size of the reaction set is relatively small it gives very good agreement with the desired parameters. this means that we should improve this method to make possible the analysis of more complex problems with it. if the algorithm cannot find the perfect match for the unknown crn a ratio is given which shows how many of the reaction steps are correctly identified from the unknown mechanism. conclusions the structure of a crn represents all the elementary reaction steps that are required to convert the reagents into products. hence, the aim of reaction mechanism identification is to discover the intermediate steps, which connect starting materials with the final product. the proposed algorithm can support this process even in the case, when we lack knowledge about the reaction mechanism and/or kinetic parameters. the applied structure identification method is based on linear least-square method. the measured and calculated concentration profiles are compared and the difference between these profiles is minimized during the identification process. the proposed algorithm for reaction mechanism identification was implemented in matlab. the results of initial testing showed promising results for this simple method being applicable for a complex task; however, the proposed algorithm should be improved toward processing reaction sets. the given implementation of the algorithm for batch reactor models can be easily extended to other reactor models, which enables to employ our method to realistic problems from chemical industry. acknowledgements this research was supported by the european union and the state of hungary, co-financed by the european social fund in the framework of támop 4.2.4.a/2-111-2012-0001 ‘national excellence program’. references [1] delvin s.: organic reaction mechanism, sarup & sons, new delhi, 2002 [2] grossman r.b.: the art of writing reasonable organic reaction mechanisms, springer, new york, 2003 [3] friess s.l., lewis e.s.: investigation of rates and mechanisms of reactions, john wiley & sons, new york, 1963 [4] walter e.: identification of parametric models from experimental data, springer-verlag, berlin 1997 [5] bendel m.l., bonvin d., marquardt w.: incremental identification of kinetic models for homogeneous reaction systems, chem. eng. sci., 2006, 61, 5404–5420 [6] srinivasan s., billeter j., bonvin d.: extentbased incremental identification of reaction systems using concentration and calorimetric measurements, chem. eng. j., 2012, 207–208, 785–793 [7] samoilov m., arkin a., ross j.: on the deduction of chemical reaction pathways from measurements of time series of concentrations, chaos, 2001, 11, 108–114 [8] varga t.: qualitative analysis based reaction mechanism identification, chem. eng. trans., 2013, 35, 769–774 [9] ratkiewicz a., truong t.n.: application of chemical graph theory for automated mechanism generation, j. chem. inf. comput. sci., 2003, 43, 36–44 [10] first e.l., gounaris c.e., flouda c.a.s: stereochemically consistent reaction mapping and identification of multiple reaction mechanisms through integer linear optimization, j. chem. inf. model, 2012, 52, 84–92 [11] west r.h., allen j.w., green w.h.: automatic reaction mechanism generation with group additive kinetics, cheminform., 2012, 43, 36–258 [12] kennedy j., eberhart r.: particle swarm optimization in neural networks, proc. ieee international conference on neural networks, perth, australia, 1995, 4, 1942–1948 table 4: testing the developed algorithm in case of 10 crns crn id ndr nc nr match mae [-] crn01 2 5 22 y 0.0498 crn02 3 5 40 n (1/3) crn03 3 5 11 y 0.0983 crn04 2 5 17 y 0.0268 crn05 4 5 26 y 0.1197 crn06 2 5 13 y 0.0146 crn07 3 5 10 y 0.0216 crn08 4 5 119 n (0/4) crn09 3 5 85 n (0/3) crn10 4 5 19 y 0.0748 microsoft word a_40_neukirchner_r.doc hungarian journal of industrial chemistry veszprém vol. 39(1) pp. 147-152 (2011) modeling and parameter sensitivity analysis of a synchronous motor l. neukirchner, a. fodor , a. magyar university of pannonia, department of electrical engineering and information systems, veszprém, hungary e-mail: foa@almos.uni-pannon.hu a simple dynamic model of a synchronous motor is developed in this paper based on first engineering principles that describe the mechanical phenomena together with the electrical model. the constructed state space model consists of nonlinear state equations and bi-linear output equations. the developed model has been verified under the usual regulated operating conditions when the speed and the torque are controlled, the manipulated input is the network voltage and the exciter voltage. the effect of load on the controlled synchronous motor has been analyzed by simulation using pi controllers. model parameter sensitivity analysis has been applied to determine the model parameters to be estimated. keywords: synchronous machine, dynamic state space model, sensitivity analysis, parameter estimation introduction classical synchronous motors are widely used machines when constant speed is necessary. the speed control of synchronous machines is a difficult problem since the motor speed is a linear function of the network frequency. for the control of the synchronous motor (sm) we have to use an inverter which generates the three phase sinusoidal electrical network and a dc power supply which provides the exciter voltage. the final aim of our study is to design a controller that regulates the speed and the torque of the synchronous motor. because of the specialties and great practical importance of synchronous machines in industry, their modeling for control purposes is well investigated in the literature. besides of the basic textbooks (see e.g. [1, 2]), there are papers that describe the modelling and use the developed models for the design of various controllers. the aim of this paper is to perform the parameter sensitivity analysis of a simple dynamic model of a synchronous motor. the result of this analysis will be the next step of the parameter estimation. the model of the synchronous motor modelling assumptions for constructing the synchronous motor model, let us make the following assumptions: ● a symmetrical tri-phase stator winding system is assumed, ● one field winding is considered to be in the machine, ● all the windings are magnetically coupled, ● the flux linkage of the windings is a function of rotor position, ● the copper losses and the slots in the machine are neglected, ● the spatial distribution of stator fluxes and apertures wave are considered to be sinusoidal, ● the stator and rotor permeability are assumed to be infinite. ● it is also assumed that all the losses due to wiring, saturation and slots can be neglected. the four windings (three stators and one rotor) are magnetically coupled. since the magnetic coupling between the windings is a function of the rotor position, the flux linkage of the windings is also a function of the rotor position. the actual terminal voltage v of the windings can be written in the form )()ir(=v j j 1=j jj j 1=j λ±⋅± ∑∑ & (1) where ij are the currents, rj are the winding resistances, and λj are the flux linkages. the positive directions of the stator currents point in the synchronous motor terminals. thereafter, the two stator electromagnetic fields, both travelling at rotor speed, were identified by decomposing each stator phase current under steady state into two components, one in phase with the electromagnetic field and another phase shifted by 90°. with the above, one can construct an air-gap field with its maximal aligned to the rotor poles (d axis), while the other is aligned to the q axis (between poles). this method is called the park's transformation [3, 4]. 148 figure 1: the equivalent circuit of the sm as a result, the vector voltage equation is: dfqddqrsdfq ilir=v &+ω (2) with [ ]tqfddfq iiii = [ ]tqfddfq vvvv = where vd and vq are the direct and the quadratic components of the stator voltage of the synchronous motor, id and iq are the direct and the quadratic components of the stator current, while vf and if are the exciter voltage and current. flux linkage equations the synchronous motor consists of six coupled coils referred to with indices a, b and c are the stator phases coils, f is the filed coil. the linkage equations can be written in the following form: ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ = ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ λ λ λ λ ff i i i i llll llll llll llll c b a fffcfbfa cfcccbca bfbcbbba afacabaa c b a (3) where lxx are the strator and rotor mutual inductances. after applying park’s transformation, the following linkage equations are obtained: ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ = ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ λ λ λ λ f q d 0 ff q fd 0 f q d 0 i i i i l0km0 0l00 km0l0 000l (4) voltage equations we can write kirchoff’s voltage laws in the following form: nvriv ++= λ& (5) abcnmabcnn ilirv &−−= (6) ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ +⎥ ⎦ ⎤ ⎢ ⎣ ⎡ +⎥ ⎦ ⎤ ⎢ ⎣ ⎡ ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ =⎥ ⎦ ⎤ ⎢ ⎣ ⎡ 00 0 n abc abc f abc f abc f abc v i i r r v v λ λ & & (7) ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ = c b a abc r r r r 00 00 00 ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ = nnn nnn nnn nm lll lll lll l ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ = nnn nnn nnn n rrr rrr rrr r where vn is the neutral voltage and rf = rf. using park’s transformation is replaced with the equations for the d-q voltage components: ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ + ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ −− = ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ q f d q ff fd q f d qfd f qd q f d i i i l lkm kml i i i rkml r lr v v v & & & 00 0 0 00 0 ωω ω (8) the voltage equation in matrix form (8) is: dfqdfqrsdfq ilirv &+= ω (9) the state space model for the currents is obtained by expressing dfqi& from (11), i.e. dfq 1 dfqrs 1 dfq vlirli ⋅−⋅⋅−= − ω −& (10) power and torque equations the electrical energy of the sm is a sum of the following mechanical equations. dwelectr = dwmech + dwfield + dwω (11) time derivate of the energy equation is the power equation, which represents the energy change: pmech = pelectr – pfield – pω (12) 149 torque is obtained from dividing power by angular velocity. tmech = λdiq – λqid (13) dt dθ =ω (14) the torque from field enegy is given by the torque equation: ) d i d i d i(t q q d d 0 0field θ λ + θ λ + θ λ = (15) afterwards the torque is: tmech = telectr – tfield – tdump (16) from newton’s law of motion we can write the speed and torque equation: ω−−=ω dtth2 mechelectr& (17) where d is a damping constant. we can write the input power in the following equation: 2 0n 2 q 2 d 2 0 q q d d 0 0dqqdelectr ir3)iii(r ) d i d i d i()ii(p −++− θ λ + θ λ + θ λ −λ−λω= (18) (in balanced condition i0 = 0.) after we can compute the accelerating torque: dumpmechelectr dumpmech 3electr acc ttt tt 3 tt −− =−−= to compute eletrical torque we sould write the direct and quadratic part of the stator flux from equation (12): qqq ffddd il ikmil = += λ λ (19) after it the write eletrical torque can be expressed: [ ] ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ −= q f d dqqfqd3eletr i i i ilikmilt (20) using dt tacc=ω& it is possible compute the speed of the synchronous machine. the motion equation is as follows: [ ] j mecht qfd jj dq j qf j qd tiii d 3 il 3 ikm 3 il = τ −ω ⋅ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎣ ⎡ τ − τ − ττ ω& (21) the loading angle (δ) of the synchronous motor is dtr t t )(= 0 0 ωωδδ −+ ∫ (22) that can be differentiated to obtain the time derivative of δ rωωδ −=& (23) altogether, there are five state variables: id , if , iq , ω and δ. the input variables (i.e. manipulable inputs and disturbances) are tmech, vf, vd and vq. observe that the state equations are bilinear in the state variables. the outputs of the model are the speed (ω) of the motor and the loading angle (δ) of the sm. model analysis the state space model (10, 21, 23) has been verified by simulation against engineering intuition using parameter values of a similar machine [5]. after the basic dynamical analysis, eleven parameters have been selected for sensitivity analysis. motor parameters the parameters are described only for phase a since the machine is assumed to have symmetrical tri-phase stator windings system. the stator mutual inductances for phase a are: )) 6 5(2(lmll )) 2 (2(lmll )) 6 (2(lmll msacca mscbbc msbaab π +θ−−== π −θ−−== π −θ−−== (24) where ms is a given constant. the phase a stator to rotor mutual inductances are given by (from phase windings to the field windings): ) 3 2cos(mll ) 3 2cos(mll )cos(mll ffccf ffbbf ffaaf π +θ== π −θ== θ== (25) where mf is a given constant. parameters ld, ld, l0 and mf used by the state space model (10, 21, 23) are defined as: 3 2 2 2 3 2 3 0 = = −= −+= ++= k k lm mll lmll lmll af f ss mssq mssd (26) 150 using the initial assumption of symmetrical tri-phase stator windings (i.e. ra = rb = rc = r) the resistance of stator windings of the machine we denoted by r. resistance of the rotor exciter is represented by rf. parameters ld and lq are the direct and quadratic stator inductances, lf is the stator exciter inductance. dconst presents the damping constant, p is the proportional, i is the integrator parameter of the torque pi controller. the parameter values were obtained from the literature [1]: h00849.0l h0126.0l h0126.0l h138.0l h171.0l h176.0l f q d f q d = = = = = = 05.0p 1.0i 004.2d 0195.0r 5577.0r h1302.0l f af = = = ω= ω= = (27) stability analysis eleven parameters of the synchronous motor have been selected for sensitivity analysis, and the sensitivity of the state variables has been investigated by matlab dynamical simulation. the equilibrium point of the state space model can be obtained from the steady-state version of state equations (10, 21, 23) using the above parameter values. the equilibrium point of the system is: 2.912249p 0.375484i -2.046594i 2.978999i 779712.1 in q d f = = = = =ω (28) the state matrix of the state space model (28) has the following numerical value in this equilibrium: ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ ⋅−⋅−− ⋅⋅⋅ ⋅⋅−⋅ −−⋅⋅− −− −−− −−− −− 12 133 132 42 103330.5105201.36031.42364.6 104654.21685.1102970.1107901.6 101782.93503.4104983.2105277.2 2242.18023.5108667.8103714.3 (29) figure 2: the matlab simulink model of the synchronous motor the eigenvalues of the state matrix are: 3 4 3 3 2 2,1 103064115.1 100820501.4 068256.4j10399932.3 − − − ⋅−=λ ⋅−=λ ±⋅−=λ (30) the real parts of the eigenvalues are negative but their magnitudes are small, thus the system is on the boundary of the stability domain. parameter sensitivity analysis pi controller the applied control method of the synchronous machine is a classical pi controller (fig. 2) that ensures stability of the equilibrium point under small perturbations. the controlled output is the mechanical torque, the manipulated 151 input is the voltage. the proportional parameter of the pi controller of the torque is 0.05 and the integrator time is 0.1 in per units. model validation the dynamical properties of the motor have been investigated. the response of the torque controlled motor has been tested under step-like changes of the exciter voltage. the simulation results are shown in figs. 3, 4, 5 and 6 where the quadratic linkage inductance lq the damping constant d, the stator exciter resistance rf and the stator resistance r are shown. figure 3: model responses for the +90% changing of parameter lq sensitivity analysis the aim of this section is to define parameter groups according to the system’s sensitivity on them. linkage inductances ld, lq, lf are not used by the current model, only by the flux model. as it was expected, the model is insensitive for these parameters. note, that the linkage inductance parameters are only used for calculating the fluxes of the machine (fig. 3). response to the exciter voltage step change of the controlled motor (means the deviation form the steady-state value) sensitivity of the model to the controller parameters p (proportional) and i (integrator) and the damping constant d has also been investigated. this is why the output and the steady state value of the system variables do not change even for a considerably large change of d (fig. 4). figure 4: model responses for the +90% changing of parameter d figure 5: model responses for the +90% changing of parameter r stator resistance not sensitive: these are the linkage inductances ld, lq, lf and damping constant d. the state space model is insensitive for them, the parameter values cannot be determined from measurement data using any parameter estimation method. sensitive: the stator resistance r, the proportional controller parameter p, the integrator controller parameter i and the stator inductances ld and lq. critically sensitive: the rotor exciter resistance rf and the rotor exciter inductance lf. 152 figure 6: model responses for the +10% changing of parameter rf rotor exciter resistance conclusions and future works based on the results presented here, it is possible to select the candidate parameters for model parameter estimation based on real data that is a further aim of the authors. the four parameters to be estimated in a later work are p (proportional parameter of the controller), lf (rotor exciter inductance), rf (rotor exciter resistance), and r (stator resistance). the final aim of is to develop a simple yet detailed state space model of the induction motor for control purposes which gives us the possibility to develop and analyze different control strategies for the synchronous motor. acknowledgement we acknowledge the financial support of this work for the hungarian state and the european union under the tamop-4.2.1/b-09/1/konv-2010-0003 project. references 1. p. vas: artifical-intelligence-based electrical machines and drives, oxford university press, (1999) 2. t. w. mon, m. m. aung: simulation of synchronous machine in stability study for power system, international journal of electrical systems science and engineering, (2008), 49–54 3. p. m. anderson, a. a. fouad: power-systemscontrol and stability, iowa state university press, ames iowa, (1977) 4. a. fodor, a. magyar, k . m . hangos: parameter sensitivity analysis of a synchronous generator, hungarian journal of industrial chemistry, (2010) 5. a. fodor, a. magyar, k . m . hangos: dynamic modelling and model analysis of a large industrial synchronous generator, proc. of applied electronics 2010, pilsen, czech republic, (2010), 91–96 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 /colorconversionstrategy /cmyk /dothumbnails false /embedallfonts true /embedopentype false /parseiccprofilesincomments true /embedjoboptions true /dscreportinglevel 0 /emitdscwarnings false /endpage 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<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> /enu (use these settings to create adobe pdf documents best suited for high-quality prepress printing. created pdf documents can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word b_17_molnar_r.doc hungarian journal of industrial chemistry veszprém vol. 39(2) pp. 219-224 (2011) comparison of hard machining procedures on material removal rate v. molnar , j. kundrak university of miskolc, department of production engineering, h-3515 miskolc-egyetemvaros, hungary, e-mail: viktor.molnar@uni-miskolc.hu the economic efficiency of machining plays an important role in the comparison of alternative procedures in the field of precision manufacturing too. it is not easy to performthe comparison because of the dissimilarities of material removal processes and/or procedures. however, there are some indicators that facilitate the analysis. the paper focuses on the economic comparison of the different finish procedures: grinding, hard turning and combined procedures. we analysed the practical material removal rate and the consumption of the used up coolant and lubricant (cl) as the basis of the operation time of the machining. compared with grinding, hard turning and combined procedures showed lower operation time and higher material removal rate besides lower environmental load. keywords: 9 hard machining, operation time, material removal rate introduction the increasing customer needs referring to the quality determine the change of functional properties of the products. to achieve it, the increase of tenacity of the components is important. it can be reached with the hardening of the surfaces too. the hardening is a procedure which is also applied to simplify the production chain in some groups of components. the abovementioned also facilitate the increase of hard surfaces on the components. hardening is generally followed by finishing which results the final geometry of the component. for a long time, grinding was the most often used finish procedure but today hard turning and the combination of these procedures play an important role in this field. however, it is not easy to outline the application fields where grinding may be substituted by hard turning [1, 2]. the application of hard cutting and combined procedures requires different machine tools and new production organizing methods. these changes affect the costs of production and other fields of the enterprise. that is why decision makers have to solve an optimization task extending to the whole production chain to compare the possible machining versions. to compare the procedures, the machined components have to be produced by the same accuracy and quality requirements. grinding and hard turning are basically different procedures referring to material removal. if the specified accuracy and quality requirements can be assured by two or more procedures, those can be considered as the alternatives of one another. besides ignoring or supposing the constancy of the costs of investments, human resources and other management processes, the practical material removal indicators can be useful to compare the alternative procedures by economic aspect [3, 4, 5, 6]. a special aspect of the investigation is the extent of environmental load. the environment pollution of machining includes several components but we focus only on the consumption of coolant and lubricant. the applied procedures and environmental load characterising the procedures the most often analysed hard machining procedures are grinding, hard turning and the combined procedure. grinding had a distinguished importance in finishing of hardened surfaces referring to machining of engineering industrial components because the machining of hardened surfaces with high accuracy and low roughness was possible to be provided in most cases by this procedure only. besides its several advantages, one of its disadvantages is that it particularly loads the environment. grinding, because of the large amount of cl, pollutes the environment in large measure, damages the workers’ health and even the process costs are higher. grinding requires expensive auxiliary materials, and among the remaining materials the mud and the used up lubricant are considered dangerous waste. the second hard machining procedure which spreads more and more nowadays is the hard turning. the rapid increase of the procedure can be observed particularly in disc-featured components and by the machining of different bore-holes. hard turning loads the environment less. hard turning shows a much more favourable picture than grinding from the point of view of environment 220 protection, too, as those unfavourable effects do not occur. the machining can be completed without using cl. the chips are the same as the workpiece material, thus they can be recycled. hard turning provides an entirely environment friendly, clear and hygienic machining of the workpieces while they have the same quality as by grinding [7, 8]. the third procedure is the combined procedure. roughing is done by hard turning and smoothing is by grinding. to compare that with the traditional procedures, the major difference is, that the machining is carried out on the same machine tool in one clamping in one operation. that is why the smoothing allowance can be smaller. it is important because the environmental load caused by the operation is in proportion with the machining time of the two procedures. experiments on disc-feature components, internal cylindrical surfaces were with different geometry machined. the sizes of the components machined at the plant and the technological data applied there in grinding were considered as basis. hard surfaces are often internal cylindrical surfaces, which, in producing parts, are often to be formed. the machining of bore-holes in most cases is a more difficult and more expensive procedure than the machining of external surfaces. earlier grinding was the major procedure for machining hardened internal cylindrical surfaces too. bore-hole grinding is an often used, wide-spread procedure. boring can also be done under more difficult conditions compared to external turning. that is why the machining with adequate efficiency of bore-holes and the surfaces being in connection with them is a particularly important task e.g. in the machining of gearwheels. the aim of the experiments was to establish an order among the procedures. conditions of the experiments the experiments were performed on workpieces (workpiece: wp) with the same diameter but different lengths and also on workpieces with the same length but different diameters (table 1). the data of the workpiece were as follows. − material: 16mncr5 − hardness: 61..63 hrc − accuracy: it5..6 − ℓ/d relationship: 0.41..1.04 − allowance: 0.15 mm − sequence size: 200 0.1 mm of allowance was removed by roughing and 0.05 mm by smoothing. the major technological data (machine tool, tool, allowance, feed, cutting speeds etc.) and the drafts of procedures are detailed in table 2. table 1: geometric data of the workpieces sign: wp1 wp2 wp3 wp4 diameter, d [mm] 37±1 48 66 length, l [mm] 29.85 38.45 27.35 table 2: technological conditions of the machining experiments technological conditions procedure tool and machine tool roughing smoothing vf,l=2.2 m/min ae=0.02 mm nw=90 1/min vf,l=2.0 m/min ae=0.001 mm nw=90 1/min sign vc [m/s] sign vc [m/s] wp1 25 wp1 25 wp2 25 wp2 25 wp3 29 wp3 29 grinding vf,l .   .   . .   .   . .      . .   .  . .     . .. . . . . . . ... .. .. . . . ... vw b l ae vc roughing and smoothing: 40x20x16-9a80-k7v22 machine tool: si-4/a wp4 29 wp4 29 vc=180 m/min ap=0.1 mm insert standard wiper f [mm/rev.] 0.15 0.24 combined procedure vc b l ap f vf,r .   .   . .   .   . .      . .   .  . .     . .. . . . .. . ... .. . .. . . ... vw vc . . . . . ... .. . . . . oscillation roughing: cnga 120408s-lo cbn smoothing: 40x40x16-9a80-k7v22 machine tool: emag vsc 400 ds vf,r,la=0.108 m/min vf,r,n=0.005 m/min nw=90 1/min vc=45 m/s vf,r,s1=0.0033 m/min vf,r,s2=0.0016 m/min nw=90 1/min vc=180 m/min ap=0.1 mm vc=180 m/min ap=0.05 mm insert standard wiper insert standard wiper hard turning vc b l ap f roughing: cnga 120408s-lo cbn smoothing: cnga 120408 7020 machine tool: pittler pvsl-2 f [mm/rev.] 0.15 0.24 f [mm/rev.] 0.08 0.12 221 the three different machining procedures (pr) were performed on different machine tools in five different versions. − pr1: grinding (roughing and smoothing) − pr2: combined procedure (roughing by standard insert, smoothing by corundum wheel) − pr3: combined procedure (roughing by wiper insert, smoothing by corundum wheel) − pr4: hard turning (roughing and smoothing by standard insert) − pr5: hard turning (roughing by wiper insert and smoothing by standard insert) the roughing grade of the combined procedure included a grinding process too. the internal traverse grinding (sign a) was performed by two cutting speeds. the workpiece revolution was constant by the grinding procedures.the number of sparking out strokes was ik=16 by all gear-wheels. in case of hard turning an l’ length has to be defined, which is the sum of the borehole length and the running on and running off lengths of the tool. calculation method operation time is in close relation with the changing costs of the production. it includes e.g. the preparation, replacement or piece times besides the machining time, therefore it gives a clear picture about the connection between the economic and technical aspects. some parameters are calculated by the technological data and others include empirical values resulted by the concrete production. in the industry these empirical values have a major importance. in case of large sequence size the values can be well estimated as a result of a process monitoring. in differing cases the analysis is difficult because there are no acceptable, exact calculation methods. the empirical values were taken from the process documentation of the company where the production was performed. the machining time is the sum of machining time of roughing and smoothing. the details of the calculation are showed by equations 2, 3 and 4. , ,m m r m st t t= + , [min] (1) − grinding: , , , , , , 2 2 sr m sp f l r e r f l s e s zzl lt i v a v a ⎛ ⎞⋅ ⋅ = ⋅ + ⋅ +⎜ ⎟⎜ ⎟ ⎝ ⎠ , [min] (2) − combined procedure: , , , , , , 0.27 a sr m sp f r l f r n f r s zz t t v v v = + + + + ' w r l n f + ⋅ , [min] (3) where: isp – the number of sparking out strokes tsp – the time of sparking out − hard turning: ' ' m r w s w l lt f n f n = + ⋅ ⋅ , [min] (4) the replacement time is taken from the technological documentation. − grinding: trepl = 0.4 min − hard turning: trepl = 0.2 min base time is the sum of machining and replacement times. tb = tm + trepl, [min] (5) the supplement time is given. when 1.5 < tm < 8, value of tsupp is the following. − grinding: tsupp = 0.15tm, [min] − hard turning: tsupp = 0.2tm, [min] the piece time is the sum of base and preparation times. tpiece = tb + tsupp, [min] (6) − grinding: tpiece = 1.15tb, [min] − hard turning: tpiece = 1.2tb, [min] the preparation time is given from the data of technological documentation. − grinding: tprep = 180 min − hard turning: tprep = 20 min the operation time is calculated by the following equation: prep op piece t t t n = + , [min] (7) the theoretical value of the material removal rate (mrr) is a widely used indicator, which gives information about the efficiency of machining. it is defined as the amount of the removed material per second (equation 8 in internal traverse grinding, 9 in grinding and equation 10 in turning). qw = ae·f·vw, [mm3/s] (8) qw = l·vf,r·d·π, [mm3/s] (9) qw = ap·f·vc, [mm3/s] (10) this indicator ignores the factors of the machining included in one procedure and not included in an other. to resolve this hiatus a practical value of the mrr was introduced (eq. 11). the essence of the conception is, that the theoretical mrr is corrected by a properly chosen datum of time which is suitable for the actual investigation. therefore the gained value will fit to the machining times and costs. , ' 60wp op x d l zq t π⋅ ⋅ ⋅ = ⋅ , [mm3/s] (11) where: d – bore-hole diameter l’ – sum of bore-hole length and running on and off z – allowance tx – relevant time of investigation (in present investigation: tx=top) 222 to get information about the environmental load, the percentage of the used up of coolant and lubricant was determined depending on the operation time by a simple proportioning. results of experiments and evaluation the machining experiments were separated by the machined bore-hole geometry. in the first step we chose two components with different bore-hole lengths (l) besides the same bore-hole diameters (d). in case of the other two gear-wheels the lengths were the same. we performed a detailed calculation referring to the machining times, material removal rate and environmental load. by traverse grinding, the machining times (tm,r and tm,s) was depended on the bore-hole length (table 2, pr1). the reason for that was the type of the procedure: the bore-hole is longer than the width of the grind wheel having an alternating motion in axial direction. therefore, the operation times besides the same bore-hole lengths were equal. bin internal traverse grinding the operation time increases with the bore-hole length. in a combined procedure, the machining time of roughing (hard turning) increases with the bore-hole length (table 2 pr2 and pr3) by 21–22 percent as well as with the diameter of the bore-hole (table 3, pr2 and pr3) by 40–43 percent in case of both standard and wiper insert. but the roughing time with wiper insert shows 35–40 percent reduction (tables 2 and 3, pr2 and pr3). the applied workpiece speeds were different by each part, id. est. wp3 and wp4 were machined at higher speeds. this is the reason for the smoothing machining time reducing with the increase if the bore-hole diameter. other times were approximately equal by each workpiece. in hard turning, the machining times of smoothing are smaller than in the other procedures, which corresponds with the expectations. by the increase of the length or the diameter, these times increase too. in the first case this value is 16–23 percent, depending on which insert is used (table 2, pr4 and pr5) and in the second the value is 36–40 percent (table 3, pr4 and pr5). table 3: contents of operation time and cl quantity (by constant bore-hole diameters) sign of workpiece procedure wp1 wp2 operation time, top [min] tr av er se gr in di ng pr1 0.14 1.97 1.68 3.78 0.17 2.54 1.77 4.48 3.78 4.48 0 1 2 3 4 5 6 7 wp1 wp2 pr2 0.14 0.330.43 0.27 0.63 0.17 0.41 0.44 0.3 0.72 0.90 1.01 0 1 2 3 4 5 6 7 wp1 wp2 c om bi ne d pr oc ed ur e pr3 0.09 0.330.43 0.18 0.66 0.11 0.41 0.43 0.19 0.75 0.84 0.95 0 1 2 3 4 5 6 7 wp1 wp2 pr4 0.14 0.260.42 0.83 0.17 0.32 0.44 0.92 0.83 0.92 0 1 2 3 4 5 6 7 wp1 wp2 h ar d tu rn in g pr5 0.09 0.180.39 0.66 0.11 0.210.40 0.72 0.66 0.72 0 1 2 3 4 5 6 7 wp1 wp2 machining time (roughing), tm,r machining time (smoothing) tm,s other times (top-tm) consumption of coolant and lubricant dry machining 223 table 4: contents of operation time and cl quantity (by constant bore-hole lengths) sign of workpiece procedure wp3 wp4 operation time, top [min] tr av er se gr in di ng pr1 0.12 1.81 1.65 3.58 0.12 1.81 1.65 3.58 3.58 3.58 0 1 2 3 4 5 6 7 wp3 wp4 pr2 0.16 0.38 0.43 0.3 0.68 0.23 0.33 0.43 0.4 0.58 0.98 0.98 0 1 2 3 4 5 6 7 wp3 wp4 c om bi ne d pr oc ed ur e pr3 0.10 0.38 0.43 0.19 0.72 0.14 0.330.43 0.27 0.63 0.91 0.90 0 1 2 3 4 5 6 7 wp3 wp4 pr4 0.16 0.31 0.43 0.91 0.23 0.42 0.47 1.12 0.91 1.12 0 1 2 3 4 5 6 7 wp3 wp4 h ar d tu rn in g pr5 0.10 0.200.40 0.71 0.14 0.280.42 0.85 0.71 0.85 0 1 2 3 4 5 6 7 wp3 wp4 machining time (roughing), tm,r machining time (smoothing) tm,s other times (top-tm) consumption of coolant and lubricant dry machining in the investigation of operation times, it is observable that they increase with the bore-hole length because more material has to be removed. the traverse grinding showed the largest values and the hard turning the smallest. it seems, that this result allows the expectation that hard turning can be the most efficient procedure considering economic aspects but this simple indicator is not enough to enunciate it with absolute certainty. using wiper inserts results lower operation times in both cases (combined procedure and hard turning). with the increase of bore-hole diameter, operation times are similar regarding grinding and the combined procedure but the wiper insert results lower values here too. in hard turning these times increase. we compared the environmental load of the different procedures. the extent of it was calculated by the operation times. because of the above mentioned reason, hard turning is the most environmental friendly procedure. the lower circle diagrams in the table 2 and 3 show the results referring to the used cl. the practical values of material removal rate are summarized in figs 1 and 2. they include the concrete values of the five investigated procedure versions. generally it can be stated that the values of the mrr indicator corrected by the operation times are lower besides smaller bore-hole diameter or shorter length. one exception is the internal traverse grinding. with the same diameter, the value of practical mrr is independent of the bore-hole length. besides different bore-hole lengths or diameters, the practical mrr values are in proportion with the change of these parameters in hard turning. furthermore, it is observable that the values are significantly higher by using wiper insert. in combined procedure the effect of the insert type determines these values only to a small extent (7–10 percent). by increasing the bore-hole diameter, the values of combined procedure are sharply different. the reason for that is the higher workpiece speed. besides the material removal rate the other widely used indicator is the surface rate. we defined the practical value of that too. but because of the different allowances 224 and thus the different d.o.c’s, this parameter gives not such exact information about the econimic efficiency as the practical mrr. 2,4 9,9 10,610,8 13,6 2,4 10,7 11,511,8 15,1 0 4 8 12 16 pr1 pr2 pr3pr4 pr5 l = 29.85 mm l = 38.45 mm qwp,op [mm3/s] d=37±1 mm figure 1: practical values of material removal rate based on the operation time by the same bore-hole diameter 2,9 10,6 11,311,4 14,5 4,0 14,4 15,812,7 16,7 0 6 12 18 pr1 pr2 pr3pr4 pr5 d = 48 mm d = 66 mm qwp,op [mm3/s] l=27.35 mm figure 2: practical values of material removal rate based on the operation time by the same bore-hole length conclusion focusing on industrial demands, the applicability of hard machining procedures and the determination of their fields of application have been invariably a key research topic. the required workpiece characteristics (e.g. formand dimension accuracy and surface roughness), can be provided by the high level reliability of the production processes in these types of machining. several decisive advantages and disadvantages of hard cutting and grinding procedures are known, but further research is needed to reduce for example the process time or the environmental load. to reduce the whole process-chain in the hard machining of more and more parts (components) is possible for example by using only one machine tool for the whole process. further task: within one process as big part of the allowance should be removed by hard turning as possible. the experiments proved that the application of hard turning in the finish operation involves both economic and environmental benefits. the comparison of hard turning and grinding in machining bore-holes showed the significant advantage of hard turning referring to economic efficiency. the existing differences were revealed by all investigated parameters, like operating time and the practical values of material removal rate. the combined (hybrid) machining provides economic efficiency similar to hard turning. acknowledgement the work was presented by the support of the hungarian scientific research fund (number of agreement: otka k 78482), which the authors greatly appreciate. the described work was carried out as part of the támop-4.2.1.b-10/2/konv-2010-0001 project. references 1. f. klocke, e. brinksmeier, k. weinert: capability profile of hard cutting and grinding process. annals of the cirp 54(2), (2005), 22–45 2. h. k. tönshoff, c. arendt, r. ben amor: cutting of hardened steel, annals of the cirp, 49(2), (2000), 547–566 3. t. tóth, j kundrák, k. gyáni: the material removal rate and the surface rate as two new parameters of qualification for hard turning and grinding, tmce, 2004 4. j. kundrák, b. karpuschewski, k. gyáni: accuracy of hard turning, jmpt 202(1-3), (2008) 328–338 5. j. kundrák, t. tóth, k. gyáni: how to make a choice of machining methods on the basis of economy: comparison between hard turning and grinding the eleventh international conference on machine design and production, antalya, 2004, 31–45 6. j. kundrak, i. deszpoth: material removal rate and surface rate in turning and grinding boreholes, microcad 2007, kharkov, 110–121, (isbn978-966-8944-35-2) 7. j. kundrak, a. g. mamalis, a. markopoulos: finishing of hardened boreholes: grinding or hard cutting? materials and manufacturing processes 19(6), (2004), 979–993 8. j. kundrak, k. gyani, v. bana: roughness of ground and hard-turned surfaces on the basis of 3d parameters, international journal of advanced manufacturing technology, 38(1-2), (2008), 110 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice hungarian journal of industry and chemistry vol. 47(1) pp. 65–70 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-10 aggregation of heterogeneous flexibility resources providing services for system operators and the market participants istván balázs *1, attila fodor1, and attila magyar1 1department of electrical engineering and information systems, faculty of information technology, university of pannonia, egyetem u. 10, veszprém, 8200, hungary power systems characterized by large, centralized generation sources and the typical flow of energy from the transmission grid to the distribution grid towards consumers are evolving. the increasing penetration of intermittent and distributed renewable energy generation is forcing system operators to increase the volume of balancing capabilities and procure flexibility services at the distribution grid level that must be supported by the aggregation of small-scale resources connected at the distribution grid. this paper suggests an aggregator framework that provides services for both operators of transmission and distribution systems while optimizes its portfolio to perform on wholesale energy trading markets too. overlaying phases of multi-period optimization runs are proposed that incorporate stochastic renewable energy generation as well as load forecasts and, moreover, the continuously changing business context while enabling cooperation between optimization phases throughout the business process. keywords: generation aggregator, optimization, distributed energy resources, tso-dso coordination, smart grid 1. introduction conventional power systems are characterized by large generation sources that inject power into the transmission grid, which is transported to distribution networks before being delivered to the end users. power flows one way from the high-voltage transmission grid to the end user at low-voltage networks. centralized, dispatchable and predictable generation provides flexibility at the transmission level to the electricity system to balance generation and demand. the increasing amount of distributed and renewable generation (from around 21% of total net electricity generation in 2010 to 44% in 2030 [1]) has transformed generation into a more variable and intermittent source of energy. demand has become more active, emphasizing the engagement of consumers. distributed generation (dg), demand response (dr) and storage facilities will become important components of power systems in the future. these resources are connected to lowand medium-voltage networks, thus, making the distribution grid a crucial element of the electricity sector. the increasing penetration of intermittent generation and distributed energy resources has already forced tsos (transmission system operator) to increase the volume of balancing capabilities and start procuring services for *correspondence: balazsistvan08@protonmail.com system balancing not only from the transmission grids but also from distribution grids. an important concept is flexibility, that is the modification of generation injection and/or consumption patterns in reaction to an external signal (price signal or activation), in order to provide a service within the energy system [2]. it is the active management of an asset that can impact the balance of a system or power flows to the grid on a short-term basis. the proper management of available flexibility, both in terms of generation and demand, can help to compensate for the lack of certainty with regard to renewable sources. on the other hand, dsos (distribution system operator) have started to manage congestion actively in their distribution grids and consider procurement of flexibility services to redispatch the system at the distribution level. as a result, the same flexibility resources could also be potentially used for congestion management and voltage control by the tso and dso [3]. conflicts of interest may arise between the tso and dso that must be managed by suitable coordination schemes [4], but this also provides an opportunity for players on the distribution grids to offer flexibility capabilities to multiple customers resulting in higher demand. an aggregator, that is a new market agent, will play a central role in collecting resources on the distribution grid and involving them in markets that are unavailable for them individually. usef (universal smart energy mailto:balazsistvan08@protonmail.com 66 balázs, fodor, and magyar framework) foundation’s aggregator workstream analyzed the different topics related to the role of the aggregator whilst paying particular attention to demandresponse aggregation as well as the relationship between an aggregator and the brp (balance responsible party)/supplier. seven different models to implement aggregation were identified, and advantages as well as limitations evaluated [5]. flexibility resources were investigated in detail and an information model set up by smartnet d1.2 [6] that contains a mathematical description of the dynamic behaviour of the resource, its constraints in terms of flexibility provision, and a formulation of the different components of costs needed to provide flexibility. the research project bestres (best practices and implementation of innovative business models for renewable energies aggregators) [7] explored different ways in which an aggregator can create value, and categorized services that are provided into internal (own balancing) as well as external reasons (wholesale, retail, reserve capacity mechanisms). an aggregation function manages distributed energy resources, the optimization of dispatch by taking into consideration the states of a time-variant system is a core capability. with regard to isolated microgrids, olivares et al. [8] proposes a stochastic-predictive control approach. the uncertainty of an isolated grid for a single purpose (generation and load balancing) is addressed, a two-stage stochastic receding horizon approach is presented that can be generalized to develop formulations for marketconnected multi-purpose optimization scenarios. the objective of this study is to develop a framework for an aggregator that implements the aggregator role of heterogeneous distributed energy resource management, complies with the typical electricity market model, follows its business processes, and operates in both wholesale energy and electricity balancing markets. the present paper provides novelties in terms of aggregator roles. it is based on a centralized approach where a new market agent, the aggregator, manages the flexibilities of a portfolio and offers services to tso, dso and external brps. in addition, it participates in wholesale energy trading activities and co-optimizes resource portfolios for both energy trading as well as flexibility services. the building blocks of such an aggregator have been determined: 3 phases of an overlaying optimization process are recommended, optimization requirements are defined and input/output parameters determined to enable cooperation between optimization phases throughout the business process. section 1 introduced challenges that concern the energy sector, defined a problem statement and presented current research as well as implementations. section 2 describes the architecture of an aggregator extending the virtual power plant concept with heterogeneous resources of flexibility and the optimization module. differences between typical aggregator definitions and functions proposed in this paper are highlighted. an architecture is planned where optimization is separated from the generator control module as it has to solve a much more complex problem than regular, built-in dispatch functions face. the business context is presented that assumes a complex optimization approach as introduced in section 3. here optimization requirements are collected to fulfil the objectives of previous sections and to optimize process phases, data exchange between phases is determined. 2. aggregator framework the flexibility center (fc) is introduced in this paper as an entity that implements the role of the aggregator. it is a framework of tools and functions that enable the aggregation of distributed, heterogeneous flexibility resources and provide services in wholesale markets. components of the fc will be presented as well as its operating environment in order to provide a framework for optimization of heterogeneous energy resources. 2.1 aggregator role according to the definition derived from the universal smart energy framework (usef) [9], an aggregator is responsible for acquiring flexibility from prosumers, aggregating it into a portfolio, creating services that draw on the accumulated flexibility, and offering these flexibility services to different markets that serve various market players. in return, the aggregator receives the value it creates on these markets and shares it with the prosumer as an incentive to shift its load. in the definition above, usef only restricts the scope of the aggregator for prosumers by limiting the activities of the aggregator with regard to demand response aggregation. the eu commission proposal for the recast of the e-directive [2] defines the aggregator as a market participant that combines multiple customer loads or generated electricity for sale, purchase or auction in any organised energy market. in this study the commission’s definition is used that incorporates aggregation of all types of decentralized energy resources. the objective of the research is to identify optimization use cases of an aggregator, so assumptions have to be made to simplify the market environment the aggregator operates in. to be able to ignore challenges concerning the dissociation of energy supply / wholesale energy trading and flexibility activation, which is a significant change to current market models, the fc implements the role of the aggregator using an integrated aggregator model [5]. following the integrated model, the roles of the supplier/trader and aggregator are combined into one market party, both of which are part of the same balancing group, contracted by the same brp. since compensation for imbalances and the open supply position are unnecessary, portfolio optimization efforts rather than market issues remain the primary focus. definitions and implementations of an aggregator, as referenced in section 1, outline a model aggregator as a hungarian journal of industry and chemistry aggregation of heterogeneous flexibility resources 67 service provider that responds to external requirements. in this study, the role of the aggregator is extended to operate on the wholesale energy markets as well, in cooperation with its brp/energy trader. it is proposed that the flexibility center should both fulfil external requests and participate in energy trading to optimize economic gain. 2.2 architecture the proposed flexibility center contains individual modules that cooperate to implement the roles of aggregation. the scada (supervisory control and data acquisition) system is responsible for data acquisition and control. it can be considered as a low-level interface to the controlled resources. standard building block. the aglc (automatic generator loading control) module controls power levels concerning elements of the portfolio using scada services based on the expected optimized dispatch. standard building block. the forecast module provides forecasts with regard to generation, consumption volumes and market prices. generation and consumption is forecast as a standard function for any implementations that control intermittent resources. however, price forecasting is an additional function required by the trading responsibility of the flexibility center. the proposed architecture of the aggregator defines optimization as an individual module. according to the proposed architecture, it has an extended responsibility, enabling the flexibility center to control a diverse portfolio of distributed resources and optimize their capacities in order to both participate in wholesale energy markets and fulfil external requests for flexibility activation. 2.3 services offered and customers the flexibility center provides services for its customers in terms of aggregating the flexibility capabilities of distributed resources. in terms of the fc, the reason why a customer requested flexibility is irrelevant. however, to prepare high-quality services that meet the technical requirements of the customer and are profitable for the fc, a set of offered services has to be defined. fig. 1 presents connections between flexibility providers, the flexibility center and customers. the flexibility center provides services to potential customers: internal brp: fc provides optimal dispatch of the portfolio and trading recommendations to maximize profit on the day-ahead and intraday energy markets. fc can use the portfolio of its own balancing group to minimize imbalance costs of providing such a service for the balance responsible party (brp) of the balancing group near the delivery time. tso: tso procures balancing reserves to ensure resources for load-frequency control. fc can bid on both balancing capacity and balancing the energy market by offering frequency restoration reserves (frr). tso dso internal brp external brp scada flexibility center optimization forecast aglc distributed generation demand response energy strorage c u st o m e rs fl ex ib ili ty p ro vi d e rs a gg re ga to r 1 2 4 3 nondispatchable load figure 1: flexibility center services and operational context dso: dso’s will be empowered to actively purchase local flexibility capabilities to mitigate voltage and grid congestion problems due to the increasing penetration of intermittent and distributed energy resources in the distribution system. fc can bid on future local flexibility markets by offering services for congestion management in the distribution network [9]. voltage / reactive power controls may also be a positive use case, but these are not considered in this study. external brp: similarly to the internal brp service, it is also economically worthwhile to balance an external brp portfolio [10]. 2.4 flexibility resources distributed generation refers to power generation facilities connected to the distribution grid. it may consist of predictable, dispatchable and intermittent generation. demand response is defined as the changes in energy use by end users (domestic and industrial) from their current/normal consumption patterns in response to market signals. energy storage can be used to store an excess of energy during high generation periods and transform it back into electricity during periods of high demand or to balance the power system. a non-dispatchable load is the consumption of an end user that does not participate in demand response programs. 3. optimization phases markets, in which the fc operates, change over time during the same delivery period. information on the market, assets of the portfolio, contractual commitments and weather conditions all change over time and the fc optimization function has to reflect such changes. an optimization approach is proposed that takes into consideration the changing objectives and status of the optimization phases. 47(1) pp. 65–70 (2019) 68 balázs, fodor, and magyar 0 3 6 9 12 15 18 21 0 3 6 9 12 15 18 21 day: d-1 day: d da: d d ay ah ea d in tr ad ay id: d / h 00:00 id: d / h 01:00 id: d-1 / h 23:00 id: d-1 / h 10:00 id: d-1 / h 09:00 … … id: d / h 18:00 id: d / h 18:00 period 1 results period 2 results 18:00 18:10 18:20 18:30 18:40 18:50 19:00 20:0019:10 19:20 19:30 19:40 19:50 g&l 18:00 g&l 18:05 g en er at io n & lo ad d is p at ch … g&l 18:40 g&l 19:20 … … figure 2: examples of optimization phases and look-ahead windows 3 phases are identified that are built upon each other. each phase shares the same primary objective to maximize profit, but the objective function, set of variables, parameters and constraints may differ as the time of delivery approaches and former calculations/forecasts become reality. in order to prepare a consistent optimization framework for the fc, optimization phases are identified and descriptions provided. fig. 2 depicts an example of overlaying optimization runs. day-ahead planning is run once a day, intraday planning is initiated every hour, and generation and load dispatch is executed every 5 minutes. once initiated, all optimization runs have to update optimization parameters so they can provide progressively more precise results. 3.1 requirements of optimization requirements of wholesale energy and flexibility activation call for a complex optimization approach. in this paper, common optimization requirements are identified, however, detailed formulations will be developed as part of future research. the flexibility center as an aggregator manages distributed resources that use the grid but does not operate the grid. it is not responsible for nor able to perform network monitoring and control, thus, the grid is not modeled, rather an economic dispatch problem is solved by fc optimization. due to uncertainties concerning consumption and intermittent renewable generation, a stochastic optimization function has to manage multiple, probability-weighted load and generation scenarios. energy storage, ramping and unit commitment considerations require a multi-period planning horizon. objective functions are formulated to maximize profit and optimization phases share execution results, but they all solve a different optimization problem. variables, parameters, cost functions and constraints must be aligned accordingly. contractual commitments have no cancellation value, these are obligatory constraints. orders from contracted customers (tso, dso, brp) must be superposed to fulfil expectations and incorporated into the portfolio optimization model. 3.2 day-ahead planning the goal of the day-ahead planning phase is to provide portfolio dispatch for schedule nominations containing make-or-buy recommendations based on market price forecasts. since this is performed on a daily basis, the run time is not critical. multi-stage stochastic unit commitment and economic dispatch optimization are recommended to mitigate generation and load uncertainties. periods of 15 minutes in duration are necessary to meet the requirements of the nomination process. input parameters for day-ahead planning are reserved flexibility capacities, contractual commitments (e.g. reserved capacities, commercial contracts), the state of the system at the beginning of day d according to the previous intraday run, technical and price parameters with regard to the assets of the portfolio, the generation forecast of intermittent resources, the consumption forecast of loads, and the day-ahead spot price forecast. the outhungarian journal of industry and chemistry aggregation of heterogeneous flexibility resources 69 table 1: timeframes of phases phase interval number of runs periods da 1 calendar day 1 / day 96× 15 min periods id 24 hours 24 / day 96× 15 min periods g&l 60−5 mins 12 / hour 12−1× 5 min periods put contains the power dispatch of the portfolio including binary unit commitment decisions and day-ahead trading recommendations. table 1 summarizes optimization intervals and the duration of each phase. the results of day-ahead optimization are inputted into schedule nominations and dayahead trading so a calendar day is covered but executed according to nomination schedules from the middle of the previous day. 3.3 intraday operation the primary objective of the intraday run is to determine the system state at the end of the first hour which is then used by generation and load dispatch as a target state (19:00 according to the example in fig. 2). it can also be used to fine-tune day-ahead results and produce inputs for intraday trading and schedule modifications. intraday optimization takes into consideration unit commitment decisions, nominated day-ahead as well as intraday schedules, reserved capacities, more precise weather as well as price forecasts, portfolio parameters and the current state of the system provided by the scada module, price parameters of the assets from the portfolio, and activation orders from customers. it is executed hourly by applying a 24-hour look-ahead window. the run-time is critical and the unit commitment is not revised, but probability-weighted generation and load scenarios still need to be generated for stochastic optimization. multi-period stochastic optimization is recommended. the duration of periods is 15 minutes to support intraday trading. 3.4 direct generation and load dispatch intraday optimization performs a 24-hour run and determines a target system state for a direct generation and load dispatch run to calculate optimized dispatch for the automatic generator loading control module. here the optimization interval is 1 hour and the duration of calculations is 5 minutes. the result of the first period is used by the aglc to directly control the assets of the portfolio. the initial parameter set is the actual system state provided by the scada module, the target state is determined by the intraday run. it also follows the shrinking horizon model by being executed every 5 minutes and performing calculations up until the hourly target. results must be sent to aglc to control assets since the run-time is extremely critical. a deterministic optimization linear programming formulation is proposed. 4. conclusion in this paper, an aggregator framework was presented that aims to manage distributed energy resources, provide services for system operators, support brps to minimize imbalances in the balancing group, and determine energy trading volumes in day-ahead and intraday markets. 3 phases of overlaying process optimization were recommended in line with a regular marketing process. a. appendix: acronyms abbr. description aglc automatic generator loading control brp balance responsible party bsp balancing service provider dg distributed generation dr demand response dso distribution system operator fc flexibility center scada supervisory control and data acquisition tso transmission system operator b. appendix: definitions balancing group: a group of market participants (consumers, producers, traders) who optimize costs by netting deviations (imbalances) and reduce overall deviations between the projected and reported electricity usage. balance responsible party: a chosen representative of a balancing group who is responsible for the imbalance of the group. balancing service provider: a market participant providing balancing services to the tso. balancing services: (1) balancing energy is energy used by tso to perform balancing and (2) balancing capacity, namely a volume of capacity that a bsp has agreed to hold to and in respect of to which the bsp has agreed to submit bids for a corresponding volume of balancing energy to the tso. balancing: balancing encompasses all actions and processes through which tso ensures the system frequency is within a predefined stability range and complies with the amount of reserves needed with respect to the required quality. 47(1) pp. 65–70 (2019) 70 balázs, fodor, and magyar distribution system operator: responsible for providing and operating low-, mediumand high-voltage networks for the regional distribution of electricity as well as for the supply of lower-level distribution systems and directly connected customers. transmission system operator: responsible for providing and operating highand extra high-voltage networks for the long-distance transmission of electricity as well as for the supply of lower-level regional distribution systems and directly connected customers. prosumer / active customer: customers who consume, store or sell electricity generated on their premises, or participate in demand response or energy efficiency schemes provided that these activities do not constitute their primary commercial or professional activity. demand response: the change of electricity load by final customers from their normal or current consumption patterns in response to market signals, including timevariable electricity prices or incentive payments, or in response to acceptance of the final customer’s bid. references [1] merino, j.; gómez, i.; turienzo, e.; madina, c.: ancillary service provision by res and dsm connected at distribution level in the future power system, tech. rep., smartnet project d, 2016, http://smartnet-project.eu/wp-content/ uploads/2016/12/d1-1_20161220_v1.0.pdf [2] european commission: proposal for a directive of the european parliament and of the council on common rules for the internal market in electricity, 2017 [3] de jong, g.; franz, o.; hermans, p.; lallemand, m.: tso-dso data management report, tech. rep., cedec, edso, entso-e, eurelectric, geode, 2016 [4] gerard, h.; rivero, e.; six, d.: basic schemes for tso-dso coordination and ancillary services provision, tech. rep., smartnet project d, 2016, http://smartnet-project.eu/wp-content/ uploads/2016/12/d1.3_20161202_v1.0.pdf [5] de heer, h.; van der laan, m.: recommended practices and key considerations for a regulatory framework and market design on explicit demand response, tech. rep., universal smart energy framework, 2017 [6] le baut, j.; leclerq, g.; viganò, g.; degefa, m.z.: characterization of flexibility resources and distribution networks, tech. rep., smartnet project d, 2017, http://smartnet-project.eu/wp-content/ uploads/2017/05/d1.2_20170522_v1.1.pdf [7] verhaegen, r.; dierckxsens, c.: existing business models for renewable energy aggregators, 2016 , 2689723 http: //bestres.eu/wp-content/uploads/2016/08/bestres_ existing-business-models-for-re-aggregators.pdf [8] olivares, d.e.; lara, j.d.; cañizares, c.a.; kazerani, m.: stochastic-predictive energy management system for isolated microgrids, ieee transactions on smart grid, 2015 6(6), 2681–2693, doi: 10.1109/tsg.2015.2469631 [9] framework, u.s.e.: usef: the framework explained, tech. rep., universal smart energy framework, 2015 [10] olivella-rosell, p.; lloret-gallego, p.; munnécollado, i.; villafafila-robles, r.; sumper, a.; ottessen, s.ø.; rajasekharan, j.; bremdal, b.a.: local flexibility market design for aggregators providing multiple flexibility services at distribution network level, energies, 2018 11(4), 822, doi: 10.3390/en11040822 hungarian journal of industry and chemistry http://smartnet-project.eu/wp-content/uploads/2016/12/d1-1_20161220_v1.0.pdf http://smartnet-project.eu/wp-content/uploads/2016/12/d1-1_20161220_v1.0.pdf http://smartnet-project.eu/wp-content/uploads/2016/12/d1.3_20161202_v1.0.pdf http://smartnet-project.eu/wp-content/uploads/2016/12/d1.3_20161202_v1.0.pdf http://smartnet-project.eu/wp-content/uploads/2017/05/d1.2_20170522_v1.1.pdf http://smartnet-project.eu/wp-content/uploads/2017/05/d1.2_20170522_v1.1.pdf http://bestres.eu/wp-content/uploads/2016/08/bestres_existing-business-models-for-re-aggregators.pdf http://bestres.eu/wp-content/uploads/2016/08/bestres_existing-business-models-for-re-aggregators.pdf http://bestres.eu/wp-content/uploads/2016/08/bestres_existing-business-models-for-re-aggregators.pdf https://doi.org/10.1109/tsg.2015.2469631 https://doi.org/10.1109/tsg.2015.2469631 https://doi.org/10.3390/en11040822 https://doi.org/10.3390/en11040822 introduction aggregator framework aggregator role architecture services offered and customers flexibility resources optimization phases requirements of optimization day-ahead planning intraday operation direct generation and load dispatch conclusion appendix: acronyms appendix: definitions microsoft word b_24_szoke_r_irod.doc hungarian journal of industrial chemistry veszprém vol. 39(2) pp. 237-242 (2011) prototype of a multi-robot system for autonomous gas mapping in polluted environments d. lupea , i. szőke, a. majdik, gh. lazea technical university of cluj-napoca, department of automation, c. daicoviciu 15 cluj-napoca, romania, e-mail: diana.lupea@aut.utcluj.ro the need of environmental monitoring robots is imposed by nowadays trends related to sustainability – towards protecting the environment and the human factor. this research received a great amount of focus in the past years. the directions of study in this area of research will be overviewed in the next lines. they are varied and range from robots designed to monitor ammonia pollution near animal farms to robots which search for unexploded ordinance, or sources of leaks from pipes and tanks, and even to a collecting and segregating garbage robot which also monitors pollution while performing its other tasks. this paper describes a novel system that aims to explore dangerous sites (old mines, chemical plants, etc), where an autonomous ground robot and a micro unmanned aerial vehicle (uav) are sent together to map the area in order to detect toxic gases. the new approach proposes a multi-robot architecture which uses a multi-sensor gas detection measurement unit which uses a simultaneous localization and mapping (slam) algorithm for 3d autonomous gas mapping. current research is trying to shift the use of robots for gas detection from indoor environments towards the outdoors. there can be found several research directions with applications based on ecological robots. keywords: autonomous multi-robot system, mapping, navigation, polluted enviromnets, multi-sensor. introduction the interest on using chemical sensors in robotic systems began in early nineties focusing mainly on the development of two typologies of robots: the first one is able to follow odour trails marked on the ground like in the case of ants following a pheromone trail [1]; the second one was for tracking odour trails formed in fluid media to find a chemical spill source [2, 3, 4]. other robots for monitoring gas pollution in areas of interest have been proposed in literature. there are robots designed to monitor ammonia pollution near animal farms [5], robots designed to go into old mines and detect dangers of gas intoxication and so on [6]. in case of the underground search finding unexploded ordinance, land mines, and sources of leaks from pipes and tanks are some examples. dustcart [7] was developed by numerous european companies and universities; the project aims to build a collecting and segregating garbage robot. to top it all off, it can also act as a mobile pollution monitor by recording atmospheric pollution levels. another proposal is the artificial clouds proposed by profesor abdul ghani from the qatar university. he proposed a system of robots mimicing clouds for the 2022 world cup spectators, in order for them to be shed from the scourching sun of the area. the robots are supposed to be from lightweight carbon, mimic the shape of clouds and they will contain gas and helium. the robots will be solar powered and controlable remotelly in order to protect spectators and athletes. another example is the one of e.on ruhrgas ag to develop infrared laser light-based remote sensing system called charm® (ch4 airborne remote monitoring) which – when installed onboard helicopters used for routine aerial surveys (fig. 1) – can be utilized to check natural gas pipelines for tightness and detect very small traces of methane [8]. figure 1: system setup inside the charm helicopter in the field of chemical sensor research there were numerous scientific work dealing with the detection of the chemically toxic gases. real-time information on the composition of combustion gases is important for improving efficiency and reducing emissions. one approach for monitoring gas composition is to collect a sample gas, which then can be analyzed either by spectroscopic techniques or by room temperature gas sensors. however, the gas composition could change 238 during cooling to room temperature, so analysis of the gas at high temperatures is preferred. such analysis can be performed using optical techniques based on infrared radiation or laser spectroscopy. placement of a sensor directly in the high temperature gas would avoid such interferences, so sensors for in situ monitoring of combustion gas components, including oxygen (o2), hydrogen sulfide (h2s), sulfur oxide (sox), methane (ch4) and hydrocarbons, at the high temperatures typical of combustion processes have been developed. among the various approaches used, solid electrolyte based sensors are particularly well suited to high temperature aggressive environments. nowadays this research field of finding places where chemical sources are present or in the air or on the ground surface or underground, has been widely spread. system description our system proposal aims to develop a multi-sensor gas detection measurement unit specially designed for mobile robotic platforms. the novel system aims to explore dangerous sites (old mine, chemical plant, etc), where autonomous ground robot and a micro unmanned aerial vehicle (uav) are sent together to map the area in order to detect toxic gases. the developed, novel multi-robot architecture will be equipped, among the novel gas detection measurement unit with sensors that allow a precise localization of the robots and complex perception of the surroundings, such as: stereo camera system, laser unit, kinect sensor, 3d compass, and gps module (fig. 2). the team is creating a topological map and a gas distribution map of the environment, which is explored at exact intervals. in case of pollution detection a warning signal is sent to the server by wireless network. the warning message contains the position of the gas spill and the quantity of pollutant. using all this information the rescue team can be sent to avoid more tragic events, explosions which can harm the workers. in the following sections the a description of the systems components and of the used methods will be made. figure 2: plant scene with the proposed system theoretical background chemical sensors there are two electrochemical types of gas detection sensor (i) amperometric cell known as clark electrode and (ii) a solid-state electrochemical cell based on metal oxides or semiconductor electrodes. (i) for the first type the galvanic detection principle is based on the diffusion of the gas molecules through the membrane, following the partial pressure gradient between water and detector room, according to the law of henry. hence, the concentration in the detector space is directly correlated to the concentration in the outside water. the correlation is expressed by the calibration formula [9]. (ii) the simplest and most direct use of a solid electrolyte in a chemical sensor is to measure the concentration of the ion that is mobile in the electrolyte. however, the number of available solid electrolytes is limited, so electrolytes that conduct the desired species are often not available. in such cases, however, an additional phase, referred to as an auxiliary electrode, can be used to provide an equilibrium reaction between the target species and the ion that is mobile in the solid electrolyte, so that the voltage generated by the electrochemical cell is related to the concentration of the target species. while increasing the number of components complicates the design, fabrication and operation of the sensor, such complications are often necessary to achieve satisfactory performance [10]. to test the developed measurement unit the gases proposed for study will be generated. in the generated conditions experiments and tests will be performed to determine the concentrations of toxic gases. the obtained results with the new measurement unit will be analyzed in comparison with measurements obtained by commercial, standard sensors or other type of determination. in the case of toxic gases the security and safety rules will be respected. sulfur oxides (sox), mainly produced from the burning of substances containing sulfur, are one of the typical air pollutant gas species causing acid precipitants, and the suppression of sox gas emissions into the atmosphere is an urgent issue. in order to reduce sox gas emission, it is essential to develop the sox gas sensing tool which can detect the sox gas concentration rapidly and exactly at every emitting site. for this purpose, compact sox gas sensors with semiconductors, liquid electrolytes and solid electrolytes having rapid and accurate sensing are required. the detection of so2 using solid electrolytes such as li2so4–ag2so4, β-al2o3, zro2 and nasicon (sodium super ionic conductor); al3+ ion conducting (al0.2zr0.8)20-19nb(po4)3; by solid state electrochemistry techniques has been reported [11, 12]. methane (ch4), which is the main component of city gas, is highly explosive even at low concentrations. therefore, methane detection has become an important issue with increasing urbanization. ch4 sensor using, lagao3-based electrolyte was successfully fabricated [13]. oxygen consumption is one of the most important indexes of biological activity during cell culture and 239 microbial development. in the past two decades, owing to the progress in semiconductor and micromachining techniques, various types of miniature clark-type oxygen sensors have been proposed, like bafe0.8ta0.2o3 solid electrolyte [14]. theoretical background of the vision and laser system proposed algorithm in fig. 3 the diagram of the proposed algorithm is shown. in the first step the algorithm needs a prior map of the environment. the offline, prior map is a 3d feature map containing all the 3d image features collected by the robot while it navigates throughout the environment. for the visual perception of the mobile robot we used the surf image feature detector and descriptor. by detecting identical features on both of the images of the stereo pairs 3d features can be computed. details about the surf features and the stereo geometry of the visual system are given later on. at every position the online 3d feature point cloud is searched based on the surf descriptor in the saved map. for the features found a point clouds is selected from the offline map. to estimate the displacement between these two feature clouds a variant of the ransac algorithm is used. the features that are considered to be outliers are excluded from the online point cloud. the algorithm is repeated iteratively. figure 3: the flow diagram of the proposed algorithm surf for interest point detection to solve the localization problem the recognition of the landmarks in the environment is a key issue. our algorithm uses image features detector and descriptor called surf. surf is an abbreviation from speeded up robust features; it is a method, known in the field of computer vision to detect interest points on images. surf has the advantage of the computational speed compared to other image feature detectors like scaleinvariant feature transform (sift) presented by [15], maintaining approximately the same or even better performances regarding: repeatability, distinctiveness and robustness. in [16] is concluded that surf is one of the most suitable descriptor for visual simultaneous localization and mapping applications. the algorithm and the performances are largely discussed in [17] and [18], whereas hereby only a short overview is presented. the main reason why the algorithm decreases the computational time is because surf uses integral images [19] as intermediate representation, in this way the sum of intensities over any upright, rectangular region is calculated with only four additions. the surf algorithm is based on the fast-hessian detector, which computes the determinant of the hessian matrix: ( ) ( ) ( ) ( ) ( ) xx xy xy yy l , l , h , l , l , p p p p p σ σ σ σ σ = ⎡ ⎤ ⎢ ⎥ ⎣ ⎦ , (1) where with lxx(p,σ) is denoted the convolution of the second order gaussian derivative ∂2g(σ)/∂x2 of the image at point p(x,y) and scale σ in the x direction. lxy(p,σ) and lyy(p,σ) are calculated similarly, these derivatives are known as laplacian of gaussian. another reason why the surf algorithm performs fast is that it approximates the laplacian of gaussian with a box filter representation. the box filter allows a performance increase in time when they are computed on integral images. simultaneous localization and mapping simultaneous localization and mapping (slam) is a technique used for autonomous vehicles to build up a map of an unknown environment (without a priori knowledge), or to update a map of a known environment (with a priori knowledge from a given map), while at the same time keeping track of the vehicle’s current location. slam consists of multiple parts: landmark extraction, data association, state estimation, state update and landmark update. there are many ways to solve each of the smaller parts. the critical problems for large scale implementations [20] will be described next. first, data association-finding correspondences between map landmarks and robot sensor measurements-becomes difficult in complex, cluttered environments, especially if the robot location is uncertain. second, the information required to maintain a consistent map using traditional methods imposes a prohibitive computational burden as the map increases in size. and third, the mathematics for slam relies on assumptions of small errors and near-linearity, and these become invalid for larger maps. in outdoor environments, the problems of scale are exacerbated by complex structure and rugged terrain. this can impede the detection of stable discrete landmarks, and can degrade the utility of motion estimates derived from wheel-encoder odometry [21]. the main scope of a slam system is to obtain an estimate of the probability distribution, at time t, over all possible robot states x and over all maps of the environment θ, by means of the previous sensor measurements zt and navigation commands ut. 240 p(x, θ|zt,ut), (2) this distribution is called the slam posterior. considering the general state space model with the hidden variables ht = {h0, h1,..., ht} and the observed variables ot = {o0, o1,..., ot}, the goal is to perform inference on the hidden variables. if we consider the known observations, the bayesian inference relies on the joint posterior distribution p(ht | ot). if the hidden variables have an initial distribution p0(h0) and a transition model p(ht | ht–1), then if the observations are conditionally independent, there exists the following recursive expression for the posterior, which can be updated using only the observations and transition models: ( ) ( ) ( ) ( ) ( ) 1 1 1 1 | | | | | t t t t t t t t t p o h p h h p h o p h o p o o − − − − = , (3) particle filters are mathematical models that represent the probability distribution as a set of discrete particles which occupy the state space. in the update step a new particle distribution given motion model and controls applied is generated. in our case the particle filters are a sequential monte carlo approximation to the recursive bayesian filter. particle filters provide a good implementation of bayesian filtering for systems whose belief state, process noise, and sensor noise are modelled by non-parametric probability density functions [22]. here, the particle filter is set to keep a discrete approximation for the slam posterior by means of using a large set of particles, which are including the state space for the algorithm: s = {xt,θ}. so we obtain a weighted approximation of the bayes filter: ( ) ( ) ( ) 1 | , no of samples i i t t t t i p s z u w s = ≈ ∑ , (4) the particles are updated taking samples: ( ) ( )( )1~ |i i t t ts q s s − , (5) where the last term in the equation is a term from which samples can easily be extracted. so the weights’ update is: ( ) ( ) ( )( ) ( ) ( )( ) ( ) ( )( ) 1 1 1 | | | , i i i t t t ti i t t i i t t t p z s p s s w w q s s z − − − ∝ , (6) usually the motion model is used p(xt | xt–1), because is a normal distribution and allows us to simplify the weight update equation to: ( )( )( ) ( ) 1 |i i i t t t tw w p z s − ∝ , (7) a problem depicted by the use of st to wrap the state space is that particle filters sample over the entire state space of the robot. as long as this state space doesn’t have big dimensions, as in the case of estimating the position of a vehicle, a few hundred samples will adequately represent the true distribution. but for slam, the state space of the robot consists of the robot position and the map, so it becomes pretty large. each particle is a sample from all possible maps and all possible positions within that map, in order to solve this problem, a solution would be the rao-blackwellized particle filters [23] which keeps the map portion of the state in a computationally efficient closed form. ellipse fitting in this in this paper the used form of the quadratic curve has the following form: ax2 + 2bxy + cy2 + 2dx + 2fy + g = 0, (8) coefficients a, b, c, d, f, g are giving little input to the shape of the ellipse, they are not unique solutions to this equation, and even if they are multiplied by a number δ ≠ 0 the shape of the ellipse will not change. despite this issue, calculating the coefficients of the algebraic equation it is possible to extract the parameters of the ellipse. the five ellipse parameters are: the coordinates of its center x0 and y0, the lengths of the semi-major axis a and of the semi-minor axis b, and the angle θ between the axis and the major axis. defining a b d b c f d f g δ = , (9) , a b j i a c b c = = + , (10) the curve is an ellipse if the following conditions are true 0, 0 0j and i δ ≠ > < δ , (11) assuming that the ellipse is nondegenerate, if it is not a circle a ≠ c and we know that is not a point, since j = ac – b2 ≠ 0, (12) after obtaining the coefficients of the algebraic equation the parameters of the ellipse can be calculated: the center of the ellipse: 0 02 2 , cd bf af bd x y b ac b ac − − = = − − , (13) the semi-axis lengths: ( ) ( ) ( ) ( ) 2 2 2 ' 22 2 2 2 4 af cd gb bdf acg a b ac a c b a c + + − − = − − + − +⎡ ⎤ ⎣ ⎦ ,(14) 2 2 2 ' 2 2 2 2( 2 ) ( ) ( ) 4 ( ) af cd gb bdf acg b b ac a c b a c + + − − = − − − + − +⎡ ⎤ ⎣ ⎦ ,(15) 241 the counterclockwise angle of rotation: ( )( )( ) ( ) 1 1 1 | 0 0 1 0 2 1 / 2 cot 0 2 1 0 2 2 cot 2 i i i t t t tw w p z s for b and a c for b and a c a c for b and a c b for b and a c a c b ∅ π π − − − ∝ = = < = > − ≠ < + ≠ > − ⎧ ⎪ ⎪ ⎪ ⎪ ⎛ ⎞⎨ ⎜ ⎟ ⎝ ⎠⎪ ⎪ ⎪ ⎛ ⎞⎪ ⎜ ⎟ ⎩ ⎝ ⎠ , (16) the ellipse’s parametric equation is: 0 0 0 2 xx cos sin acost t yy sin cos bsint θ θ π θ θ − = + ≤ ≤ ⎡ ⎤⎡ ⎤ ⎡ ⎤ ⎡ ⎤ ⎢ ⎥⎢ ⎥ ⎢ ⎥ ⎢ ⎥⎣ ⎦ ⎣ ⎦ ⎣ ⎦⎣ ⎦ , (17) the objective is to calculate the ellipse’s parameters using the coefficients from the algebraic equation (8). experimental results the experimented algorithms are based on mixture gaussian models, expectation-maximization algorithm and the formulas presented in chapter ellipse fitting. the acquired data set is clustered into groups which are representing the same object. as can be seen in fig. 4 the environment is presenting the office and the detected obstacles which are the desks shown with different colour. to each obstacle an ellipse is fitted and a trajectory is built from the set of the waypoints obtained after the connection of the neighbour ellipses. this path planning method is combined with the localization algorithm based on surf. the objective is to gain an efficient localization which allows the tracking of the calculated trajectory (fig. 5). figure 4: the optimal trajectory obtained after applying the algorithm figure 5: result of the proposed algorithm after four steps (top view) future work our future work is aimed at obtaining a multi-robot system capable of performing active large scale area simultaneous localization and mapping. to accomplish this goal in an efficient data management manner the bag of words representations will be used. the laser system will be combined with the markovian properties. for the active slam a submapping technique which uses conditionally independent graphs will be used. acknowledgement this paper was supported by the project “doctoral studies in engineering sciences for developing the knowledge based society-sidoc” contract no. posdru/88/1.5/s/60078, project co-funded from european social fund through sectorial operational program human resources 2007–2013. references 1. h. ishida, t. morizumi: machine olfaction for mobile robots, s. s. schifman, h. t. nagle, j. w. weinheim t. c. pearce [eds.]: handbook of machine olfaction: electronic nose technology, 2006 weinheim: wiley-vch 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word b_51_szauter_r.doc hungarian journal of industrial chemistry veszprém vol. 39(2) pp. 305-308 (2011) development of a vehicle-dynamic measurement and information system f. szauter , j. á. székely, e. horváth széchenyi istván university, department of automotive and railway engineering h9026 győr, egyetem square 1, hungary e-mail: szauter@gmail.com the aim was to develop vehicle-dynamic measurement and data collection tools in case of electric-drive vehicles. the system gives more detail oriented view of the driving stability of the alternative vehicles via the record of complex data. keywords: development, measurement, devices, can-bus, automotive, unique system development, arduino, labview introduction the first aim of the developing vehicle-dynamic measurement and data collection system is to produce two devices, one of these is capable to examine an internal combustion engine powered vehicles and the other is for examine alternative vehicles. during the development process we were able to produce two prototypes that meets these conditions. we call these two systems mobile dynamic measurement (or short: mob dymes) and canbus dynamic measurement. mobile dynamic measurement application area a mobile dynamic measurement can be applied mainly for scooters and for vehicles which do not support can protocol. the system was developed according to test and inspection purposes of alternative and electric-powered vehicles, so the most important from the measured signals were the following: the driving electrical characteristics (voltage, current, power) and the battery current status characteristics of the bms (battery management system) monitoring. structure the device has gps module rtc module, microsd card slot, three-dimensional acceleration sensor, temperature sensor and ics to measure current and voltage. the display and input device is with an oled touch screen realized. it can display the battery status and the bms system, temperature, current speed, distance travelled gps coordinates, time, vehicle steering angle and the date of this form (this feature is a measurement of tracks of vehicles used). on the display there are menu “command-keys” displayed as well. there is also an audio warning through a piezo-speaker. figure 1: the touch screen the unit works with an individually programmed operating system. the data-processing is done through a microprocessor. the measured signal conditioning takes place within the device. the resulting data represents the actual decimal parameters, so there is no need for decoding programs. gps on of the main component of the system is a 66-channel 10 hz gps. since the program we have built calculates the speed and distance according to the the gps data, we needed a really accurate unit. the results are more accurate with the help of different positioning algorithms calculated from the acceleration sensor. 306 figure 2: a 66-channel gps module rtc module today many applications need the date and time information. the rtc module (real time clock module) can store time and date parameters. of course, they can be obtained from the gps data, but it would narrow down the gps data stream communication. the ds1307 rtc has calendar-circuit and a lithium battery, which is not discharged for 17 years. figure 3: real time clock module three-dimensional acceleration sensor the built in three-axis analogue accelerometer sensor can measure acceleration in range +/3 g. as the matter of proper use of our intentions, this interval is enough and the sampling rate can be increased up to 1600 hz. figure 4: three-dimensional acceleration sensor programming the system the chosen microcontroller was arduino uno, which is programmable with the arduino ide environment. arduino hardware is programmed using a wiring-based language, similar to c++ with some simplifications and modifications, and a processing-based ide. the arduino ide comes with a c/c++ library called “wiring”, which makes many common input/output operations much easier. arduino programs are written in c/c++, although users only need define two functions to make a runnable program: ● setup() – a function run once at the start of a program that can initialize settings ● loop() – a function called repeatedly until the board powers off in the program we are free to use any normal control structures (if, else, for, while, etc.), arithmetic operators (+, -, % etc.), data types (void, byte, integer, float, etc.), not to mention the ide’s build in functions, which allows us to perform digital and analogue i/o operations, timing operations (milis(), delaymicroseconds(), etc.), mathematical operations (sin(), cos(), etc.), and also interrupt operations. in case of learning the programming there is a relatively well documented literature available on the internet and plenty source codes are also obtainable. canbus dynamic measurement the structure of the system the second developed tool is capable to communicate with can-bus (controller area network bus) system too, completely independent from vehicle platforms. it also records gps coordinates and three-dimensional acceleration data with a time stamp to a memory card, like the mob dymes. this means vehicle at any given moment can be determined by the gps coordinates, motor vehicle data and acceleration values calculated from dynamical parameters. the system allows us to accurately reconstruct the vehicle movement in vehicle dynamics software. one area of application can be the internal combustion engine vehicles which can be later electric driven redeveloped. the system could be used to compare the two states of these vehicles with precise driving dynamics simulation. furthermore it can be applied for the determination and examination of alternative-powered vehicles parameters. the display device is an lcd and has 2 rows, each row can display 16 characters, input device is a joystick, which has four directions and also has a button function in the central position. with the help of the joystick it is possible to navigate in the menu system. when left and right directions pressed we can move between menu options. we can select a menu by pressing the button and exit from a menu by moving down. the system can only collect data with variable sampling rate. this sampling rate depends on the amount of parameters to collect. at maximum data recording speed it can record data in every 0.1 seconds, but if we want to collect every parameter it can only record in every 0.5 seconds. 307 figure 5: the prototype on can area network in a vehicle gps the positioning system of canbus dynamic measurement is a 20-channel, 10 hz gps module. the accuracy is 1 meter. canbus dynamic measurement of global positioning system, a 20-channel, 10 hz gps module. accuracy can be up to 1 meter. figure 6: 20 channel gps module the rtc and the three-dimensional accelerometer modules are the same as used in mob dymes. the initialization and the menu of the program after the initialization of the system it shows a welcome screen. if we move the joystick left or right we can select one of the menus. there are 7 menus to be selected. these are the followings: record to sd card: start/stop recording to the sd card sd settings: there can be selected which data to record and also the output format of the file sd content: a limited access to the file’s content and also a directory listing accelerator monitor: gives us the possibility to see the current acceleration values or the angle can monitor: gives us the possibility to see the current engine data provided by the vehicle’s can system gps monitor: gives us the possibility to see the current gps values time monitor: gives us the possibility to see the current time and date values output file entering tot the device’s sd settings (sd beállítások) menu gives us the possibility to choose which data (parameters) to record into the output file. the system records the collected data to an output file on the micro-sd card. the possible data (parameter) can be the following: time stamp engine speed engine temperature vehicle speed maf sensor lamda probe voltage torque x-axis acceleration y-axis acceleration z axis acceleration gps coordinates (lat, long) the short review on the source code #define labview; this definition is only necessary if the device is connected to a computer and there is a need to stream live data (such as acceleration, gps coordinates etc.). it can be processed with our self-developed labview program. the type of the connection is basically a serial connection but it is realised in the usb port. if there is no need for live streaming the definition can be commented. in this case the commands between #ifdef labview and #endif won’t be executed. it is also a possibility for better and faster debug of the program. menumegjelenites(); this function displays the menu according to the joystick state. void sdrogzit(); this function saves all the data (parameters) which have been selected before. void ketorles(); this function provides a possibility to clean the lcd. void poz(byte s, byte o); this function provides the possibility to put the cursor to the s row and o column. after that we can write to that point. void beallit(); this function provides a possibility to select which data can be stored on the sd card. void sdolvas(); this function provides a limited access to the output file (because of the limitation of the 16x2 lcd screen) gyorsulaskijelzes(); this function provides live acceleration values. it can be displayed on the lcd screen. cankijelzes(); this function provides current engine data from the vehicle’s can system. gpskijelzes(); this function provides current gps values. it can be displayed on the lcd screen. 308 orakijelzes(); this function provides the current date/time values. void setup(); this is a necessary function of all arduino programs. it contains functions and operations that run once at the start of a program and who can initialize settings. void loop(); this is also a necessary function of all arduino programs. it contains functions and operations which are called repeatedly until the board powers off. further goals during the development of system we already started to write labview programs, which help in data processing and simulation. one of the program is capable to analyse and display data from the output file the other can stream and display live data when the device is connected to the computer. there is a need for further develop of the algorithm, to get practiser driving dynamics, and engine data. the device has diagnostic functions also, and there is a possibility of further integration with avl simulation environment. summary our researcher group is developing a new vehicle dynamics measurement and information systems which are vehicle platform-independent. these mobile systems have self-developed programs and have touch screen for controlling and displaying data. there are different signals to be measured which are conditioned within the unit. the system was developed according to test and inspection purposes of alternative and electric-powered vehicles, so the most important from the measured signals were the following: the driving electrical characteristics (voltage, current, power) and the battery current status characteristics of the bms (battery management system) monitoring. the system is prepared to the connection to the can-bus (controller area network bus) system and also to measure these kinds of signals. acknowledgements tamop-4.2.1/b-09/1/konv-2010-0003: mobility and environment: research in the fields of motor vehicle industry, energetics and environment in the centraland western-transdanubian regions of hungary the project is supported by the european union and co-financed by the european social fund” references 1. a. r. de souza, a. c. paixao, d. d. uzeda, m. a. dias, s. duarte: the arduino board: a low cost option for physics experiments assisted by pc (revista brasileira de ensino de fisica, 2011) 2. http://arduino.cc/ 3. http://en.wikipedia.org/wiki/arduino 4. a. thomas: computer hardware and low level machine language programming, integrated graphic and computer modelling, 2008, 177–222 5. m. zhou, x. ao, j. wang: fault diagnosis of automobile based on can bus, information and automation, communications in computer and information science, 86, (2011), 317–323 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) 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/leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice . lászló rácz hungarian journal of industry and chemistry vol. 45(1) editorial preface hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0021 in memoriam jános liszi this issue is dedicated to professor jános liszi who was the rector of the university of veszprém in 1989-1995. the university acquired this name during his term in an era of severe political and economic challenges (today: university of pannonia). under his leadership the university took on these challenges and has been modernized to become an institution with a wider scope. he was the head of the department of physical chemistry for many years. the department was also reshaped during this period. his early death was unexpected and mourned. he influenced the life of many and left his mark on his alma mater in veszprém, but he also had an impact on other institutions as the commemoration of lászló rácz below indicates. lászló rácz was the head of the chemistry department in eger when professor liszi joined to teach physical chemistry there. it was an honor to organize and edit this issue to salute my respected supervisor. veszprém, 10 october 2017. dezső boda issue editor the eger-connection of professor liszi he was a tough and righteous man towards himself just as towards his colleagues in veszprém. i can say that the same was true regarding his relationship with the colleagues and students of the chemistry department at the eszterházy károly college in eger. that is why we got to like him so much. when a position for teaching physical chemistry became available in our department, it was not easy to find the right person to fill the boots left by an excellent colleague who had held this position for 30 years. according to the urgent need to yield the proper knowledge to our students, our director indicated to professor liszi that there was a problem to be solved in eger. he did not hesitate and drove 230 km to eger right away. he assisted with our teaching work for many years. a fruitful professional relationship had been established between veszprém and eger. we gladly accepted the support offered by professor liszi. beyond his physical chemistry courses in the curriculum, he regularly gave seminars about various topics not only to our students but also to colleagues and students from other departments. an example that i witnessed characterizes his professional work. after a class, a student from the physics programme approached him and said, “i will enter the chemistry programme because this was so beautiful and logical”. and he did. he became a physics-chemistry teacher and now works in the physics department. since 2015, our college has functioned as a university. i am sure that the support of professor liszi has contributed to the development of our institution considerably. he has also contributed to my personal development because he encouraged me to defend my habilitation thesis. he also contributed to the education of our team beyond the field of physical chemistry. during excursions to tihany and at the benedictine order he acted as a guide and demonstrated his vast knowledge of history and classical culture. the expertise of our department, making wine, also belongs to classical culture. it was a pleasure to host him and his wife for wine tastings on several occasions. at such times, we discussed the science of wine-making. time flew and we got onto the subject of the thermodynamics of multicomponent homogeneous systems after a few glasses of wine. sadly the blessing of st. john had to come early because he had an early start the following morning. the minimum 1000 m session in the swimming pool could not be left unperformed. together with him we profess that technical details can only come after the firm scientific basics have been laid down. he achieved a lot for higher education and research in eger. we are grateful for his efforts we respected and loved him not only for his knowledge, but also for his humanity. eger, 12 october 2017 microsoft word 2012_dr_bodor_endre_hjic.doc hungarian journal of industrial chemistry veszprém vol. 39(3) pp. 391-394 (2011) manufacture of acid urease by lactobacillus fermentum fermentation zs. varga , é. lövitusz, zs. csanádi, k. bélafi-bakó university of pannonia, research institute on bioengineering, membrane technology & energetics egyetem street 10, veszprém, h-8200, hungary e-mail: vargazs@almos.uni-pannon.hu ethyl carbamate can be found in fermented foods and alcoholic beverages, such as sake, beer and wine. it is considered as a carcinogenic compound for some animals, and probably carcinogenic to humans, as well. ethyl carbamate is formed by a chemical reaction of ethanol and urea. the urea content should be reduced to less than 1 mg/l to prevent the formation of ethyl carbamate. urease is an enzyme, which hydrolyzes urea into ammonia and carbon dioxide. the acidic condition of fermented beverages is optimal for these types of ureases, which show high activity at low ph. acid urease is an intracellular enzyme produced by gram positive bacteria like lactobacillus fermentum. it is commercially not easily available, hence it has to be produced by fermentation, extracted from the bacteria and purified properly. keywords: acid urease, lactobacillus fermentum, fermentation introduction ethyl carbamate (urethane, ec) is a naturally occuring component in all fermented foods (soy sauce, yoghurt, bread) and alcoholic beverages (sake, wine, beer, brandy), being spontaneously produced by the reaction between urea and ethanol. 35225222 nhhcoocnhohhcconhnh +→+ ec has been known to be carcinogenic, teratogenic and mutagenic. therefore, removal of urethane or prevention of its formation from alcoholic beverages is an emerging problem all over the world [1]. as large amounts of ethyl carbamate were found in brandy, sake and distilled spirits, some governments established guidelines limiting the amount of ec in alcoholic beverages (table 1). table 1: survey of ethyl carbamate levels (µg/l) in alcoholic beverages product range beer 0–5 grape wine 0–10 distilled spirits 10–6000 sake 10–380 fruit brandy 10–22000 in hungary the maximum concentration of ec is 1 mg/l. the most important precursor of ethyl carbamate in alcoholic beverages is assumed to be the urea produced during the metabolism of arginine by yeast. ethanol is produced during the beverages fermentation, it reacts with urea and ethyl carbamate is formed [2]. other precursors to the formation of ethyl carbamate are citrulline and carbamyl phosphate [3]. a lot of methods for decreasing urea level, hence preventing ethyl carbamate were tried by many scientists [4-6]. possible methods of preventing ethyl carbamate formation in alcoholic beverages are shown in table 2 [7]. in our work the opportunities of enzymatic removal of urea by urease was studied. table 2: possible way for preventing ethyl carbamate formation in alcoholic beverages decreasing urea selection or breeding of yeast control of fermentation process utilization of urease utilization of artificial urease adsorption site: chain of polyoxyethylene active site: imidazole – cooh-ni control of pasteurization and storage of alcoholic beverages utilization of urethanase: citrobacter sp. acid urease urease enzyme (fig. 1) is mainly found in the jack bean (canavalia ensiformis). its maximum activity is at ph 6.5–7.5. therefore, urease with an optimum ph on the acid side (acid urease) was developed, because the ph of alcoholic beverages is low (about ph 4.4 and 3.2, respectively). 392 figure 1: urease enzyme it has been known that urease hydrolyses urea into carbon dioxide and ammonia: 23222 22)( conhohnhco +→+ urease with an optimum ph was first found in lactobacillus sp. from the rat gastrointestinal tract, lactobacillus fermentum isolated from intestinal anaerobes in rat [9]. urease from lactobacillus fermentum was partially purified, characterized, and named acid urease by takebe and kobashi [10]. acid urease was found in several lactobacillus, streptococcus, escherichia, staphylococcus, morganella, bifidobacterium, arthrobacter and zoogloea species [9], and their optimal ph values are shown in table 3. table 3: optimal ph of several types of acid urease [8] optimal ph type of acid urease ph=3 acid urease from lactobacillus reuteri ph=3 acid urease from lactobacillus fermentum ph=5 acid urease from streptococcus bovis ph=4 acid urease from streptococcus mitior ph=4 acid urease from streptococcus salivarius ph=5 acid urease from lactobacillus ruminis bacteria and cultivation lactobacillus fermentum (fig. 2) belongs to gram-positive species of bacteria in the genus lactobacillus. it is an acid urease producer strain [11]. figure 2: lactobacillus fermentum l. fermentum was grown at 26 °c for 48 hours in a medium comprising 2% glucose, 0.5% yeast extract, 1% meat extract, 1% peptone, 0.1% tween 80, 0.5% sodium acetate, 0.2% sodium citrate, 0.2% k2hpo4, 0.02% mgso4·7h2o, 0.005% mnso4·7h2o. methods for cell crushing cell crushing can be carried out from either the whole broth or the mass separated by filtration or centrifuge. lactobacillus fermentum has thick periplast (15–50 nm), consists of peptidoglucan, polysaccharide and teichoic acid (fig. 3). figure 3: periplast of gram-positive bacterium [12] ultrasonic waves, extraction with surfactant solutions, salts and enzyme solutions can be applied for the cell crushing [12]. the cell crushing method has an optimal time course, the yield is getting worse after a certain time period (fig. 4). figure 4: relationship between cell crushing and enzyme activity enzyme solutions researchers have identified numerous enzymes that are able to crush periplast compound and the chemical bond (table 4). table 4: specific enzymes for cell crushing microorganism enzyme bacteria lysozyme yeasts mannanase mildews chitinase, cellulase algas cellulase during the enzymatic lysis not only the proper enzyme should be found, but its application method should be optimized, as well. better results generally can be achieved by multi-enzyme. the advantage of the enzyme treatment is specificity, other compounds, bonds are not degraded. the lytic acting enzymes are expensive thus their applications are limited [12]. 393 determination of urea concentration the methods for the determination of urea can be classified into three categories, based on colour-forming reactions, enzymatic hydrolysis and chromatographic separations. colour-forming reactions these are non-enzymatic spectrophotometric analysis methods, where the spectrophotometric agent reacts with samples and generates a colourful compound. p-dimethylamino-benzaldehyde (fig. 5), butane-2,3-dione and 1-phenyl-1,2-propanedione-2-oxime are applied as reagents [13]. figure 5: para-dimethylamino-benzaldehyde enzyme catalysed hydrolysis the enzymatic methods include hydrolysis of urea by urease then ammonia formed is measured. test kit is available and used by numerous researchers. the ammonia measurement method is based on the reaction between ammonia and 2-oxoglutarate. nadh is reduced by ammonia and the decrease of it – monitored by absorbance at 340 nm – is proportional to the amount of ammonia therefore the urea concentration can be determined in the original sample [13]. chromatographic separation high-performance liquid chromatography (hplc) and gas chromatography (gc) are used to separate and quantify many components in alcoholic beverages. hplc with fluorescence detection and gc with capillary column are applied for the determination [13-15]. determination of acid urease activity during the determination of acid urease activity 100 µl 0.6% urea solution was added to the mixture of 0.5 ml of enzyme solution and 2.5 ml of 0.1 m ph 4.0 citrate buffer containing 20% ethanol, and it was mixed. after exactly 30 minutes at 37 °c 4 ml of 10% tca solution was added to stop the reaction. under these conditions, 1 unit is defined as the activity which liberates 1 µmole of ammonia per minute at an initial reaction [16]. colour-forming reaction was applied for the determination of urea concentration. the reagent was pdimethylamino-benzaldehyde. in this method 5 ml of urea solution and 5 ml of p-dimethylamino-benzaldehyde solution were mixed. after 10 minutes at room temperature the samples were measured at 440 wavelength in the spectrophotometer. [17] method of the cell crushing one liter of cultured medium (culture broth) was centrifuged to obtain 7.0 g of wet cells, which were suspended in 10 mm phosphate buffer (ph 7.0) to make 10 ml suspension. to this suspension 10 mm phosphate buffer (ph 7.0) containing 0.02 g of triton x-100 and 2 mg of lysozyme were added. after agitation the mixture was allowed to stand for 3 days at 30 °c. cell residue was removed by centrifugal separation to obtain a crude enzyme solution. after it the supernatant was precipitated by ice-cooled ethanol to adjust final ethanol concentration to 60%, and the mixture was subjected to centrifugal separation. the resulting filter cake was dissolved in 10 mm phosphate buffer (ph 7.0) and the solution was dried [18]. results and discussion ethyl carbamate is a carcinogenic, teratogenic and mutagenic component in alcoholic beverages and is chemically produced from urea and ethyl alcohol. acid urease was developed for removal of ec or prevention of its formation in beverages, and it was found in several bacteria. in this work acid urease was manufactured from lactobacillus fermentum. our aim was to prepare acid urease with higher quantity and activity. 0.223 g 7 u/g crude dried enzyme was possible to prepare by cell crushing using lysozyme and triton x-100 then precipitation of the supernatant by ethanol. references 1. m. esti, m fidaleo, m. moresi, p. tamborra: modeling of urea degradation in white and rosé wines by acid urease, j. agric food chem., 55 (2007) 2590–2596 2. c. s. ough, e. a. crowell, l. a. mooney: formation of ethyl carbamate precursors during grape juice (chardonnay) fermentation. i. addition of amino acids, urea, and ammonia effects of fortification on intracellular and extracellular precursors, am. j. enol. vitic, 39 (1988) 243–249 3. k. c. fugelsang, c. g. edwards: wine microbiology, practical applications and procedures, springer (2007) 170–171 394 4. k. yoshizawa, k. takahashi: utilization of urease for decomposition of urea in sake, j. brew. soc. jpn. 83(2) (1988) 142 5. c. s. ough, g. trioli: urea removal from wine by an acid urease, am. j. enol. vitic. 39(4) (1988) 303–307 6. k. kobashi: ethyl carbamate in alcoholic beverage, eisei kagaku, 35(2) (1989) 110 7. k. matsumoto: removal of urea from alcoholic beverages by immobilized acid urease, bioprocess technology 16 (1993) 255–273 8. s. kakimoto, y. sumino, y., t. suzuki: acid urease and production thereof, united states patent, patent number: 5,093,255 (1992) 9. m. fidaleo, m. esti, m. moresi: assessment of urea degradation rate in model wine solutions by acid urease from lactobacillus fermentum, j agric food chem., 54 (2006) 6226–6235 10. s. takebe, k. kobashi: acid urease from lactobacillus of rat intestine, chem. pharm. bull., 36(2) (1988) 693–699 11. s. kakimoto, y. sumino, k. kawahara, e. yamazaki, i. nakatsui: purification and characterization of acid urease from lactobacillus fermeutm, appl. microbiol biotechnol 32 (1990) 358–543 12. m. pécs: separation processes in biological industry, budapest university of technology and economics 2011 (manuscript) 13. p. s. francis: the determination of urea in wine – a review, australian journal of grape and wine research, 12 (2006) 97–106 14. a. bertrand, m. c. ingargiola, j. delas: effects of nitrogen fertilization and grafting ont he composition of must and wine from merlot grapes, particularly ont he presence of ethyl carbamate, international symposium on nitrogen in grapes and wine, seattle, washington, usa (1991) 215–220 15. s. clark, p. s. francis, x. a. conlan, n. w. barnett: determination of urea using highperformance liquid chromatography with fluorescence detection after automated derivatisation with xanthydrol, journal of chromatography a, 1161 (2007) 207–213 16. nagase chemtex corporation (japan): technical support e305-0508 17. fodders-nutrition value assessment, determination of the urea content msz 6830/13-78 18. k. kobashi, s. takebe, t. kobayashi, 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice editorial hungarian journal of industry and chemistry veszprém vol. 42(1) pp. 31–37 (2014) effects of washing of raw material on properties of carbon nanotube containing poly(ethylene-terephthalate) composites tímea molnár,1 csilla varga,1! and lászló bartha1 1 department of mol hydrocarbon & coal processing, university of pannonia, egyetem str.10, veszprém, h-8200, hungary !e-mail: vcsilla@almos.uni-pannon.hu our interest has been focused on mechanical recycling of poly(ethylene-terephthalate) (pet) bottle waste, because recycling of plastic waste has crucial importance nowadays. the present article deals with the effects of washing of the secondary raw materials on properties of carbon nanotube (cnt) reinforced composites. in the first step advantageous washing compounds and their concentration were determined. after selecting the proper washing method extrusion moulding characteristics of pet granulates were investigated, and effects of carbon nanotubes as reinforcing additives and also application of coupling agents on the mechanical and rheological properties of composites were studied. keywords: carbon nanotubes, coupling agent, poly(ethylene-terephthalate), bottle waste recycling introduction almost all human activities result in waste generation either directly or indirectly. satisfying the daily needs for growing amounts of products results in higher consumption of raw materials, higher quantities of processing waste, and also higher amounts of wastes after the end of product life [1–4]. selectively collected pet bottles derived from municipal solid waste considered as waste plastics of a specific type, but the liquid stored in them contaminates their surfaces. fig.1 shows the typical treatment cycle and possible recycling methods for plastic wastes, especially for the pet bottles collected selectively. washing the surface of the waste materials is an important issue as biofilm can be formed. therefore, this raw material will be contaminated with some biological content. removing biofilm can be carried out in water, acidic or alkaline solvents. effectiveness of the method is measured by using reactions with folin reagent. pet has excellent mechanical and chemical properties, therefore, its resistance against chemicals and irradiation is outstanding; however, it can also have serious impact on the environment, because the biodegradation requires a long time, and expensive pretreatment methods are needed in order to bring them within reach of decomposing enzymes [3–8]. carbon nanotubes (cnt) are members of the family of fullerenes with cylindrical shapes, where carbon atoms are located at the surface of a cylinder. typical diameter is between the 1–50 nm regime, length can exceed even the 10 µm scale. carbon nanotubes have non-polar character. their surface contains only a few functional groups, which can react with polymers. in order to enhance the interaction between nanotubes and polymer matrices, the nanotube surface needs to be modified by application of coupling agents [7–11]. the given study deals with mechanical recycling of pet bottle wastes by applying secondary raw material for polymer matrix of cnt reinforced composites. after selecting the proper washing method, extrusion moulding characteristics of pet granulates were investigated. furthermore, the effects of carbon nanotubes as reinforcing additives, and application of coupling agents on the mechanical and rheological properties of composites were studied. experimental materials selectively collected pet bottles waste was used as the polymer matrix in the composites in washed and figure 1: pre-treatment and recycling of plastic wastes 32 unwashed form. mfi values of the pet granulates were measured, and changed in the interval of 10–14 g (10 min)-1 (255 °c, 2.16 kg). multi-walled carbon nanotubes (mwcnt) were produced at 700 °c by chemical vapour deposition (cvd) process over fe-co bimetallic catalyst at the department of chemical engineering, institute of chemical and process engineering, university of pannonia. purity of mwcnt was higher than 90 wt%, diameter was between 10 nm and 20 nm, the average length was above 30 µm and the betsurface was 200 m2 g-1. carbon nanotubes were applied in pet matrix in pristine and surface treated form. for treating surface of the carbon nanotubes experimental olefin-maleic-anhydride copolymer based coupling agents (fig.2) were used with the properties summarized in table 1. the ratios of the functional groups in coupling agents were determined by measuring acid value and saponification number by classical analytical methods and on the second hand the ratios were estimated by a previously developed ft-ir method [12]. production of composite samples cnt/pet composites were produced by a laboratory twin/screw extruder (lte 20-44, labtech engineering, fig.3). temperature profiles and screw rotation speed for production were previously determined [13]. washing of the waste material after the washing process, raw materials from selectively collected pet and pet derived directly from waste deposit were compared. the solutions with 0.05 m concentration were used for both acidic and alkaline washing method. citric acid and potassium hydroxide were chosen for the acidic and the alkaline wash. measurements to determine the tensile properties of the extruded strings (namely strength, modulus, and extension) an instron 3345 universal tensile testing machine was used. the temperature in the laboratory was 23 °c, while relative humidity was 37% during the mechanical tests that were carried out at 90 mm min-1 crossheadspeed. rheological measurements were carried out in a ceast smart rheo 2000 capillary rheometer at 265 °c. before measurements, 180 second preheating was applied to all samples. structural information about the developed coupling agent was obtained by ir technique using a tensor 27 ftir spectrometer (resolution: 3 cm-1, illumination: sicglobar light, detector: rt-dlatgs type) in the 400–4000 cm-1 spectral range. scanning electron microscopy (sem) was used to study the morphology of fractured faces of specimens and to follow possible interaction between the reinforcements and matrices on a phillips xl30 esem instrument. results and discussion surface treating effects of surface treatment were studied in two applications. firstly, the coupling agents on the cnt surface was investigated, thereby properties of pristine cnt were compared to properties of two different coupling agent treated cnts. bet-surface was measured and surface energy measurements were conducted. secondly, the effects of concentration of the coupling agent applied on the cnt surface were studied with additive concentration to be 15% and 20%. by the surface treatment the bet surface of pristine cnt reduced at least by 35–40% (table 2). on the basis of mesopore volume distribution results (fig.4), it was determined that coupling agents mainly attached to pores with diameters below 10 nm, because numbers of that pore size decreased the most. structure table 1: main properties of coupling agents property ca-1 ca-2 acid value, mg koh (g sample)-1 12.8 33.1 saponification number, mg koh (g sample)-1 95.3 126.5 molecular weight (mw)*, g mol-1 3520 3660 polydispersity factor 1.10 1.40 ratio of functional group, % anhydride 7.9 12.0 semi-ester 2.7 37.6 ester-amide 44.7 25.2 imide 44.7 25.2 * related to ps standard figure 2: structure of the ester-amide-imide derivative of the experimental olefin-maleic-anhydride copolymer (r1: alkyl group with length of the olefinic monomer (c16-c18); r2: alkyl group with r1-2 carbon number; a: 3-40, b: 3-32; k: 0,2-2; l: 1-7; m: 1-7 and n: 0,3-2) figure 3: production of pet composites in a twin-screw extruder table 2: bet-surface of different carbon nanotubes samples surface area pristine 191.1 m2 g-1 20% ca-1 coupling agent 125.5 m2 g-1 15% ca-2 coupling agent 172.3 m2 g-1 20% ca-2 coupling agent 102.1 m2 g-1 33 of the coupling agent had considerable impact on the distribution since different ratios of decrease were measured in the mesopore volumes, therefore surface interactions with different strength may were evolved between the coupling agent and the cnt. concentration of the coupling agent on the cnt surface also influenced the results (fig.5). decreasing the concentration from 20% to 15% resulted in an increase in the mesopore volumes to such an extent that almost the values for pristine cnts were achieved. properties of heterogeneous polymer systems are influenced by interfacial interactions and structure; however, no direct method is available to determine strength of interactions. therefore, models are used generally for their estimation. inverse gas chromatography measurements can be a useful tool for measuring the surface properties of different fillers and thus, the strength of interactions can be estimated. the dispersive component of surface energy describes london-interactions that can be used for estimation of the non-polar character, while other types of interactions (hydrogen-bond, polar, acid-base, etc.…) are included in the specific component (fig.6). we found that the dispersive surface energy of the coupling agent treated cnt was half of the pristine one at 70 °c (fig.6). this is indicative of the surface treated carbon nanotubes likely having lower tendency for agglomeration than pristine cnts. constant for the acid-base interactions were calculated based on the gutmann equation [14] as summarized in table 3. on the basis of these results it can be stated that acid character of the pristine cnts do not change significantly after surface treatment but the basic character improved. on the surface of the treated cnt-s weak basic active centres were predominant over acidic ones. effects of washing both acidic and alkaline washing were shown to be effective by which biofilm had been removed from surface of pet granulates with 100% efficiency. since biofilm cannot stick to the surface of pet due to its crystalline structure biofilm can be removed by application of weak acid or lye. ft-ir spectra of the granules before and after washing gave the opportunity to study the changes in functional groups of the plastic. it is important to highlight that no significant differences were observed between ft-ir spectra of acidic and alkaline washed samples. therefore, none of the compounds during washing deteriorated structure of pet (fig.7). effect of screw rotational speed pet samples were produced at various screw rotational speeds to study their rheological behaviour and also their mechanical properties. screw rotational speed during processing caused significant differences in viscosities in the low shear rate regime (beyond 500 s-1) (fig.8). figure 4: changes in mesopore volume distribution due to surface treatment (20% coupling agent) figure 5: changes in mesopore volume distribution due to surface treatment with various coupling agent (ca-2) concentrations figure 6: dispersive surface energy based on schultz-method (temperature: 70 °c) table 3: acid-base constants calculated by gutmann equation [14] at 70 ºc sample r2 pristine cnt ka 0.086 0.928 kb 0.000 15% coupling agent treated cnt (ca-1) ka 0.086 0.806 kb 0.253 20% coupling agent treated cnt (ca-1) ka 0.090 0.849 kb 0.213 34 in the medium shear rate region (500-5000 s-1) differences among the viscosities of the samples continuously disappeared. no differences were observed at higher shear rates, above 5000 s-1 dedicated to shear rates characteristic for injection moulding. that indicated that all the samples could probably be injection moulded at the same parameters. all the tensile properties (yield strength, modulus) improved by increasing screw rotational speed during processing (figs.9 and 10). the highest values for the tensile properties were measured for samples produced at the highest screw rotational speed. sample produced at the lowest rotational speed had values nearly identical to literature data [15]. however, samples processed at the highest rotational speed had 35–40% higher yield strength than the original material used for bottle production. it is important to note that washed pet granulates with the lowest rotational speed could not be produced at the same temperature profile as the plastic melted. pet composites containing pristine cnt washing the raw material caused 15% deterioration in yield strength, but the modulus did not change. untreated cnt could be introduced into the polymer melts at 2 wt% level both into washed and unwashed pet raw materials by the same side feeder screw rotational speeds. application of pristine cnt did not influence yield strength of the composites (figs.11 and 12), so yield strength of cnt/pet samples did not depend on the previous washing of the raw material. the pet raw materials had ca. 2000 mpa tensile modulus either for washed and unwashed plastic, so rigidity of the samples was stated to be the same. figure 8: effect of screw rotational speed on rheological behaviour of pet raw material figure 7: ft-ir spectra of pet sample in the 4000-600 cm-1 wavenumber range (purple: potassium-hydroxide; green: citric acid; blue: without washing) figure 10: effect of screw rotational speed on tensile modulus of pet raw material figure 9: effect of screw rotational speed on yield strength of pet raw material figure 11: effects of cnt application on yield strength of pet figure 12: effects of cnt application modulus of pet 35 pristine cnt containing washed pet had 20% lower modulus than unwashed pet based samples had, thereby; the property of the pet raw material was achieved. adding pristine cnt to washed pet plastic no difference was measured in the modulus compared to the washed pet without any reinforcing. effects of type and concentration of coupling agent two different, previously successfully applied coupling agents [13] were used on the surface of cnts. concentration of the coupling agents varied from 15% (conc-1) to 20% (conc-2) related to the weight of the pristine cnt. with respect of processing, surface treated cnts were much easier to introduce into the polymer melt. cnt concentration could be elevated up to 2.7–2.9 wt% in the polymer matrix at the same processing parameters using coupling agent treated cnts instead of pristine type. yield strengths of washed pet based composites increased with increasing concentration in the presence of both coupling agents compared to the pristine cnt containing pet sample (figs.13 and 14). improvement of 78% for ca-1, and 30% for ca-2 was realized in the presence of coupling agents at the higher concentration (20%). using unwashed pet, as raw material also resulted in enhancement of yield strength, but to a different extent, such as ca-1 resulting in 55%, while ca-2 causing 16% increase. based on the above results, the ca-1 additive was worth applying in higher (20%) concentration due to the achieved more than 50% higher yield strength relative to the pristine cnt containing pet composite. raw material is worth washing before processing if cost of washing could be balanced by the advantage of the 10 mpa increase in yield strength applying ca-1 coupling agent in 20% concentration. in case of ca-2 additive washing did not influence the properties at the lower (conc-1) concentration level, but with higher additive concentration (conc-2) a 14% difference was measured between the composites made from the two raw materials. comparing the samples with various additive concentrations an increase was observed in the modulus with increasing concentration for both raw materials and coupling agents. applying unwashed raw material 34% improvement was realized with ca-1 coupling agent and 32% with ca-2 additive if the concentration increased from 15% to 20%. a lower degree of improvements were measured for washed pet based samples making the same comparison. comparison of pristine and surface treated cnt containing samples showed that coupling agent was advantageous to be applied in higher concentration from the point of view of the modulus either. for unwashed pet based composites application of coupling agents resulted in 10–15% decrease in modulus related to the pristine cnt containing sample. for washed pet based samples making the same comparison changes were calculated to be +45% in case of ca-1, and +20% for ca-2 additive. the most advantageous observation based on the results is the lack of an effect on the mechanical properties in the investigated interval of raw material quality with respect of washing pet bottle waste, when used as polymer matrix for cnt reinforced composites. this could be realized in easier handling and pretreating of the raw material before recycling. sem graphs broken surfaces of samples were studied by scanning electron microscopy. cnts concentrated at one side of the extruded string in pristine cnt containing samples (fig.15a). diameter of the probable carbon nanotube nucleation centres varied (figs.15b and c). there were agglomerates with diameter of 30–40 µm and also with 5-10 µm number of the latter seemed to be higher. in addition, there were only a few nucleation centres both for washed and unwashed pet based composites. on the cross section of the extruded strings a crystalline part was rendered likely in larger areas in coupling agent treated cnt containing samples than in pristine cnt/pet samples. in pet containing 15% ca2 coupling agent a likely crystalline part was found at the middle of the extruded sample (fig.16). more nucleation centres and more homogeneous structure were observed (fig.16) than in pristine cnt containing sample from the same pet raw material. it is in accordance with the 15% lower cnt content of the pristine cnt/pet composite than the treated cnt containing one. the diameters of the nucleation parts were in the range of 20–30 µm. area related to the probable crystalline structure was higher in washed pet based sample on the sem graphs of the extruded strings (fig.17a). nucleation parts were figure 13: tensile properties of surface treated cnt containing pet composites figure 14: tensile properties of surface treated cnt containing pet composites 36 located in the middle of the sample and connected to each other diameters were identical to the former sample that was treated (fig.17b). based on the sem graphs it was concluded that carbon nanotubes were easier to handle and distribute more homogeneously due to surface treating both for washed and unwashed pet raw material, and on the other hand numbers of the nucleation parts and sizes could be influenced. conclusions the present article gave a brief insight into mechanical recycling of pet bottle wastes by applying that secondary raw material for polymer matrix of cnt reinforced composites. after selecting the proper washing method extrusion moulding characteristics of pet granulates were investigated and it was concluded that tensile properties improved by increasing screw rotational speed. effects of washing in carbon nanotubes containing pet composites were also investigated where carbon a b c figure 15: sem graphs of pet sample containing pristine cnt a b figure 16: sem graphs of unwashed pet based sample containing 15% ca-2 coupling agent treated carbon nanotube a b figure 17: sem graphs of washed pet based sample containing 20% ca-1 coupling agent treated carbon nanotube 37 nanotubes were applied either in pristine or surface treated form. washing of the waste plastic did not affected yield strength in case of pristine carbon nanotubes containing samples but for coupling agent containing composites mechanical properties significantly changed. if the proper coupling agent was applied in higher concentration, 20% e.g. yield strength improved by higher than 60% while modulus increased at least 20%. acknowledgements this research was supported by the european union and the state of hungary, co-financed by the european social fund in the framework of támop-4.2.4.a/211/1-2012-0001 ‘national excellence program’. the authors are also grateful for the financial support of this work by the hungarian state and the european union under the támop-4.2.2.a-11/1/konv/2012-0071 project. references [1] la mantia f.: handbook of plastic recycling, shrewsbury, rapra technology, 2002 [2] wégner k.: towards more efficient waste management, yearbook of hungarian plastic and rubber industry, 2013, 27–32 (in hungarian) [3] wu g., li j., xu z.: triboelectrostatic separation for granular plastic waste recycling: a review, waste mngnt., 2013, 33, 585–597 [4] fortelny i., michalková d., krulis z.: an efficient method of material recycling of municipal plastic waste, polym. degrad. stabil., 2004, 85, 975–979 [5] aksa w., medles k., rezoug m., boukhoulda m.f., bilici m., dascalescu l.: two stage electrostatics separator for the recycling of plastic from waste electrical and electronic equipment, j electrost., 2013, 71, 681–688 [6] sánchez a.c., collinson s.r.: the selective recycling of mixed plastic waste of polylactic acid and polyethylene terephthalate by control of process conditions, eu. polym. j., 2011, 47, 1970–1976 [7] wang y., gao j., ma y., agarwal u.s.: study on mechanical properties, thermal stability and crystallization behavior of pet/mmt nanocomposites, composites part b, 2006, 37, 399–407 [8] logakis e., pissis p., pospiech d., korwitz a., krause b., reuter u., pötschke p.: low electrical percolation threshold in poly(ethylene terephthalate)/multi-walled carbon nanotube nanocomposites, eu. polym. j., 2010, 46, 928–936 [9] li z., luo g., wei f., huang y.: microstructure of carbon nanotubes/pet conductive composites fibers and their properties, composites sci. techn., 2006, 66, 1022–1029 [10] fiedler b., gojny f.h., wichmann m.h.g., nolte m.c.m., schulte k.: fundamental aspects of nano-reinforced composites, composites sci. techn., 2006, 66, 3115–3125 [11] borrell a., rocha v.g., torrecillas r., fernández a.: surface coating on carbon nanofibers with alumina precursor by different synthesis routes, composites sci. tehn., 2011, 71, 18–22 [12] varga cs.: production and investigation of compatibilizing additives for polymer composites, phd thesis, university of pannonia, veszprém, 2010 (in hungarian) [13] molnár t.: effects of carbon nanotubes and coupling agents in poly(ethylene-terephthalate) polymer, itdk report, university of pannonia, veszprém, 2011 (in hungarian) [14] gutmann v.: the donor-acceptor approach to molecular interactions, plenum press, new york, 1978 [15] pál k.: recycling of plastics wastes as secondary raw material, műanyagipari szemle, 2006/2 microsoft word b_03_bodzas_r.doc hungarian journal of industrial chemistry veszprém vol. 39(2) pp. 173-176 (2011) connection theory of conical worm gear drives s. bodzás1, i. dudás2 1,2college of nyíregyháza, department of technical preparatory and production engineering h-4400 nyíregyháza, sóstói u. 9-11., hungary 1,2university of miskolc, department of production engineering, h-3515 miskolc, egyetemváros, hungary e-mail: bodzassandor@nyf.hu e-mail: illes.dudas@uni-miskolc.hu we worked out a mathematical modell for the production geometry and mathematical analysis of spiroid worm gear drives. this modell is adapted for analysis of spiroid worm gear drives with random profile. using this modell it could be possible for defining of the equations of cog surfaces, the surface normal vector, contact curves and connection surface in one concrete case. keywords: spiroid, transformation matrix, normal vector introduction in technical practice conical worm surfaces, which can be used in many ways, are most widely applied as a function surface of conical worms. the conical worm – crown wheel pairs spiroid drive, can be used for example as jointless drives of robots and tool machines [1]. the jointless drives are attained by simply shifting (setting) the worm in an axial direction. the cog surface of the conical worm of the spiroid drives (fig. 1) can be attained the same way as that of the cylindrical worm, but besides the axial shift of the hob, a tangential shift must be done depending on the conicity of the worm. different – evolvent, archimedean and convolute – helical surfaces can be defined in case of spiroid worm surface similar to the line surface cylindrical worm. figure 1: spiroid worm gear drive the dentation of crown wheel is produced with hob which tiler surface is similar to conical worm surface. this is called direct motion mapping. with these modern drive pairs, which are characterized by favourable hidrodinamic conditions, great strength and high efficiency, the energy loss in the gear can be reduced significantly [1]. in power dissipation it is important to apply those cog geometrical characteristics which result in good connection terms. defining of the spatial coordination systems ϕ1 ϕ1 ϕ2 ϕ2 figure 2: evading rotation axis coordinate system for defining of cog surfaces 174 we worked out this model based on the general mathematical model of dr. illés dudás [1, 2]. defining of minimum four coordinate systems are needed for analysing of motion transmission between evading axis and defining of cog surface describing spatial coordinates: two fixed rotation coordinate systems for the first part k1f (x1f, y1f, z1f) and the second part k2f (x2f, y2f, z2f) and two standing coordinate systems for the first part k1 (x1, y1, z1) and the second part k2 (x2, y2, z2), where the positions of the rotating coordinate systems can be defined (fig. 2). the rotation axis of the elements are z1 and z2, the turning direction is positive watching from the directions of the axis (opposite for the clock working), the turning angles, the motion parameters are φ1 and φ2. the transformation matrixes between the rotation coordinate system k1f (x1f, y1f, z1f) for the first part and the standing coordinate system k1 (x1, y1, z1) for the first part are: ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ − = 1000 0100 00cossin 00sincos 11 11 1,1 ϕϕ ϕϕ fm (1) ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ − = 1000 0100 00cossin 00sincos 11 11 1,1 ϕϕ ϕϕ fm (2) the transformation matrixes between the standing coordinate system k1 (x1, y1, z1) for the first part and the standing coordinate system k2 (x2, y2, z2) for the second part are: figure 3: connection between the k1 (x1, y1, z1) and the k2 (x2, y2, z2) standing coordinate systems ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ −− = 1000 010 100 001 1,2 c b a m (3) ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ − − −− = 1000 010 100 001 2,1 b c a m (4) the transformation matrixes between the standing coordinate system k2 (x2, y2, z2) for the second part and the rotation coordinate system k2f (x2f, y2f, z2f) for the second part are: ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ − = 1000 0100 00cossin 00sincos 22 22 2,2 ϕϕ ϕϕ fm (5) ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ − = 1000 0100 00cossin 00sincos 22 22 2,2 ϕϕ ϕϕ fm (6) the transformation matrixes between the rotation coordinate system k1f (x1f, y1f, z1f) for the first part and the rotation coordinate system k2f (x2f, y2f, z2f) for the second part are: =⋅⋅= ffff mmmm 1,11,22,21,2 ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ ⋅+⋅⋅−⋅ ⋅+⋅−⋅⋅− = 1000 0cossin cossincossinsincossin sincossinsincoscoscos 11 2222112 2221212 c ba ba ϕϕ ϕϕϕϕϕϕϕ ϕϕϕϕϕϕϕ (7) =⋅⋅= ffff mmmm 2,22,11,12,1 ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ − ⋅−⋅⋅−⋅ ⋅−⋅−⋅⋅− = 1000 0cossin cossincossinsinsincos sincossinsincoscoscos 22 1111212 1112112 b ca ca ϕϕ ϕϕϕϕϕϕϕ ϕϕϕϕϕϕϕ (8) the equations of conical thread surface the grr leading curve is given in the k0 ( , , ) tool coordinate system and its equation of the η coordinate function. that is: )(ηgg rr rr = (9) since we consider the coordinate an independent variable, the equation of the leading curve is: kjirg rrrr ⋅+⋅+⋅= )()( ηζηηξ (10) carrying out a pa axial and pr radial helical motion of the k0 ( , , ) coordinate system – which includes the grr leading curve – along the z axis and the y axis alternatively includes, the leading curve touches a conical helical surface in the k1f (x1f, y1f, z1f) an independent position and equals k0 coordinate system before the helical motion (fig. 4). 175 ϕ1 ϕ1 ϕ ζ η ξ υ υ figure 4: touched thread surface by leading curve the helical surface touched by grr curve in the k1f (x1f, y1f, z1f) coordinate system is: gff rmr rr ⋅= 0,11 (11) the transformation matrix between the two coordinate systems is: ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ ⋅ ⋅ − = 1000 100 0cossin 00sincos 0,1 ϑ ϑϑϑ ϑϑ a r f p p m (12) that is: ϑηϑηξ sincos)(1 ⋅−⋅=fx ϑϑηϑηξ ⋅+⋅+⋅= rf py cossin)(1 (13) ϑηζ ⋅+= af pz )(1 we gave the equations of the helical surface in the k1f (x1f, y1f, z1f) rotation coordinate system (13). the given describing thread surface ),(11 ϑηff rr rr = two parameters vector – scalar function can be transformed from the k1f coordinate system to the k2f coordinate system: ffff rmr 11,22 rr ⋅= (14) 1212 ϕϕ ⋅= i direct case the ),(11 ϑηff rr rr = is given, the two parametric vectorscalar function in the coordinate system k1f (x1f, y1f, z1f) for the surface to be generated. in the difference geometry for the independence of the η and θ parameters are essential condition: 011 ≠ ∂ ∂ × ∂ ∂ ϑη ff rr rr (15) the η and θ parameters are the curve line coordinates of the surface. υ=υ3 υ=υ2 υ=υ1 η=η1 η=η2 η=η3 υ η figure 5: definition of the surface normal vector we suppose the surface is continuous on the working parts of cogs, it is continuous function of η and θ parameters; two coordinate lines have to be crossed throught on every m point of the surface: a) η = const, b) θ = const the tangents of this lines do not coincide in this point. the working parts of the cog surfaces could contain only general points. the normal vector belong to the surface and the tangent plane will be decided only in the general point. the plane defined by the tangents of the η∂ ∂ fr1 r and ϑ∂ ∂ fr1 r parameter lines is the tangent plane of the surface in the given point. the surface normal vector fn1 v is perpendicular for the tangent plane and it can be defined: ϑη ∂ ∂ × ∂ ∂ = ff f rrn 11 1 rr v (16) the normal vector in the k1f coordinate system is: ϑϑϑ ηηηϑη ∂ ∂ ∂ ∂ ∂ ∂ ∂ ∂ ∂ ∂ ∂ ∂ = ∂ ∂ × ∂ ∂ = fff fffff f zyx zyx kji rr n 111 11111 1 rrr rr v (17) the relative velocity of the two surfaces can be determined in coordinate system k2f using the transformation between k1f (x1f, y1f, z1f) coordinate system for worm and the k2f (x2f, y2f, z2f) coordinate system for worm gear: ( ) fffff rm dt dr dt dv 11,22 )12( 2 rrr ⋅=⋅= (18) the vector )12( 2fvr should be transformed into coordinate system k1f (x1f, y1f, z1f) to determine the necessary connection surface, so: ( ) ffffffffff rprm dt dmvmv 1111,22,1 )12( 22,1 )12( 1 rrrr ⋅=⋅⋅=⋅= (19) where: ( )ffff m dt dmp 1,22,11 ⋅= (20) the matrix for kinematic generation. 176 ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ ⋅⋅−⋅ ⋅⋅⋅ ⋅⋅−⋅−− = 0000 0sincos sinsin01 coscos10 11 11 11 1 iaii ibi ibi p ϕϕ ϕϕ ϕϕ (21) on the connecting cog surfaces of elements, as on tiler each other surfaces the contact curve can be defined by the concomitant solving of expression of connection i. statement 0)12()12( 22 )12( 11 =⋅=⋅=⋅ vnvnvn ffff rrrvrv (22) contact equation and describing cog surfaces vector – scalar function. the connection equation expresses the correlation between the η and θ surface parameters and the φ1 motion parameter, that is ( ) 0,, 11 =ϕϑηff (23) defining of the contact curves of the ∑1 and ∑2 cog surfaces in the k1f coordinate system is: ( ) 0,, 11 =ϕϑηff ),(11 ϑηff rr rr = (24) the tiler surfaces of contact curves forming the equations of cog surface of the second part are in the k2f coordinate system: ( ) 0,, 11 =ϕϑηff ),(11 ϑηff rr rr = (25) ffff rmr 11,22 rr ⋅= the connection equation is in the k1f coordination system: 0)12( 11 =⋅ ff vn rv (26) the relative velocity is: =⋅= ff rpv 11 )12( 1 rr ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ ⋅+⋅⋅−⋅⋅ ⋅⋅+⋅⋅+ ⋅⋅−⋅⋅−− = 0 sincos sinsin coscos 1111 1111 1111 iaiyix ibizx ibizy ff ff ff ϕϕ ϕϕ ϕϕ (27) with which the connection equation in the k1f coordinate system is: ( ) ( ) ( ) 0sincos sinsin coscos 11111 11111 11111 =⋅+⋅⋅−⋅⋅⋅ +⋅⋅+⋅⋅+⋅ +⋅⋅−⋅⋅−−⋅ iaiyixn ibizxn ibizyn fffz fffy fffx ϕϕ ϕϕ ϕϕ (28) the application of the model we designed a conical worm of which we carried out the virtual model and using the mathematical model (fig. 6) we carried out the virtual model of the connecting worm gear (fig. 7). ϕ ϕ ϕ ϕ figure 6: defining of the coordinate systems figure 7: our designed worm gear drive model summary we worked out a mathematical model for production geometry and mathematical analysis of spiroid worm. this modell is appropriate for every spiroid worm gear drives with random profile. we designed a spiroid worm gear drive and using this model we carried out the virtual model of this drive pair. references 1. i. dudás: the theory and practice of worm gear drives. penton press, london, 2000. (isbn 1 8571 8027 5) 2. i. dudás: gépgyártástechnológia iii., miskolci egyetemi kiadó 2005. (isbn 963 661 572 1) 3. h. józsef: untersuchugen zur anwendung von spiroidgetrieben. diss. a. tu. desden, 1988 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 /colorconversionstrategy /cmyk /dothumbnails false /embedallfonts true /embedopentype false /parseiccprofilesincomments true /embedjoboptions true /dscreportinglevel 0 /emitdscwarnings false /endpage -1 /imagememory 1048576 /lockdistillerparams false /maxsubsetpct 100 /optimize true /opm 1 /parsedsccomments true /parsedsccommentsfordocinfo true /preservecopypage true 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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page 427 page 428 page 429 page 430 page 431 page 432 page 433 page 434 page 435 page 436 page 437 page 438 page 439 page 440 page 441 page 442 page 443 page 444 page 445 page 446 page 447 page 448 page 449 page 450 page 451 page 452 page 453 page 454 page 455 page 456 page 457 page 458 page 459 page 460 page 461 page 462 page 463 page 464 page 465 page 466 page 467 page 468 page 469 page 470 page 471 page 472 page 473 page 474 page 475 page 476 page 477 page 478 page 479 page 480 page 481 page 482 page 483 page 484 page 485 page 486 page 487 page 488 page 489 page 490 page 491 page 492 page 493 page 494 page 495 page 496 page 497 page 498 page 499 page 500 page 501 page 502 page 503 page 504 page 505 page 506 page 507 page 508 page 509 page 510 page 511 page 512 page 513 page 514 page 515 page 516 page 517 page 518 page 519 page 520 page 521 page 522 page 523 page 524 page 525 page 526 page 527 page 528 page 529 page 530 page 531 page 532 page 533 page 534 page 535 page 536 page 537 page 538 page 539 page 540 page 541 page 542 page 543 page 544 page 545 page 546 page 547 page 548 page 549 page 550 page 551 page 552 page 553 page 554 page 555 page 556 page 557 page 558 page 559 page 560 page 561 page 562 page 563 page 564 page 565 page 566 page 567 page 568 page 569 page 570 page 571 page 572 page 573 page 574 page 575 page 576 page 577 page 578 page 579 page 580 page 581 page 582 page 583 page 584 microsoft word 2012_dr_bodor_endre_hjic.doc hungarian journal of industrial chemistry veszprém vol. 39(3) pp. 363-368 (2011) isomerization of paraffin mixtures produced from sunflower oil t. kasza, j. hancsók university of pannonia, mol department of hydrocarbon and coal processing, hungary e-mail: hancsokj@almos.uni-pannon.hu the importance of biofuels becomes more acute, especially in the european union. beside them, the bio gas oil is a promising product that is a fuel with high isoparaffin content in the gas oil boiling range, which can be produced by the catalytic hydrogenation of different triglycerides. in this paper the isomerization of different intermediate products obtained over different hydrogenation catalysts and having high n-paraffin content was studied on sapo-11 catalyst at 300–380 °c temperature, 20–80 bar pressure, 0.5–3.0 h-1 of liquid space velocity and 400 nm3/m3 of h2/feed ratio. it was found that the oxygen containing intermediate products significantly changed the degree of isomerization, but the hydrocarbon composition and the aromatic content of the n-paraffin mixtures had no noticeable effect on the conversion. during the experiments excellent quality diesel gas oil blending components were produced with high i-paraffin content and they were practically free of heteroatom content. keywords: bio gas oil, isomerization, pt/sapo-11, oxygen containing compounds, hydrocarbon composition, aromatics introduction biofuels and bio blending components have higher and higher importance because of their economical and environmental advantages both in europe and on the other parts of the world [1-2]. mainly the second generation ones have very favourable composition, since they are practically free of sulphur and nitrogen, and their olefin and aromatic content is close to zero. they contain mainly iso and normal paraffins which have very favourable performance properties. consequently during their combustion environmentally and toxicologically harmful compounds (sox and nox) do not form, their combustion is clear (low particle emission), furthermore the greenhouse gas emission is significantly lower relative to the whole life cycle [3]. nowadays mainly the mixture of fatty acid methyl esters (biodiesels) are used as biocomponents of diesel fuels which are produced from different vegetable oils and used cooking oils by transesterification with generally methanol. but these have numerous disadvantages such as they form deposits in the fuel supply system and the combustion chamber, they have poor storage (heat and oxidation) stability because of the olefinic double bonds of the molecules, they tend to water uptake, the esters bond tend to be hydrolysed resulting corrosive acids, they shorten the oil change interval, etc. [4]. consequently in the european union the maximum blending quantity of fatty acid methyl esters into diesel fuels was limited to 7.0 v/v% by the en 590:2009 standard based on the proposition of the vehicle manufacturers. at the same time the use of at least 10% of bio origin component is a target up to 2020 in the eu. because of these disadvantages and of the quantity of bio-origin fuels can be increased from the natural triglycerides (conventional and improved vegetable oils, used cooking oils and fats, greases from meat and leather processing industry, “brown grease” of sewage farms, etc.) such kind of fuel components have to be produced which molecular structure differs from that of the fatty acid methyl esters. this kind of compounds are hydrocarbons produced by heterogeneous catalytic hydrogenation of triglycerides, consisting mainly from mixtures of normal paraffins, consequently they have not possess with the disadvantageous properties of biodiesels [4]. however the cold flow properties of these mixtures rich (>95%) in normal paraffins (mainly n-c12-n-c20) are unfavourable (the freezing point of normal paraffins is high, e.g. n-c18: +28 °c). this characteristic generally can be improved by additivation and/or isomerization. but the currently used flow improver additives were not effective enough in case of these products of new composition [5]. accordingly the isomerization seems to be the suitable finishing process step to produce mixtures with good cold flow properties and high cetane number [4, 6-7]. the composition of the mainly n-c12-n-c20 mixtures obtained by the fuel purpose hydrogenation of triglycerides can be significantly different depending on the used feedstock and catalytic system (catalyst, process parameters) [4, 8-12]. the oxygen removing reactions change as a function of the catalyst and process parameters. for example at elevated temperature and on higher acidity catalyst the decarboxylation reaction 364 became dominant resulting shorter hydrocarbon chain by one carbon number than that of the fatty acid. side reactions also take place during the oxygen removal. for example by increasing the severity of operational parameters the cracking reactions become dominant, furthermore the aromatization may also take place over high activity catalysts or at high temperature. accordingly the aim of present paper was the investigation of the effect of feedstock on the hydroisomerization of normal paraffin rich (>95%) mixtures (produced from sunflower oil) over 0.5% pt/sapo-11 catalyst. experimental part experiment were carried out at the operational parameter combinations found to be favourable in our pre-experiments over 0.5% pt/sapo-11 catalyst [6, 7], which were the following: temperature = 300–380 °c, pressure = 20–80 bar, liquid hourly space velocity (lhsv) = 0.5–3.0 h-1. the value of the h2/feedstock ratio was unchanged; it was 400 nm3/m3. apparatus the experiments were carried out in an apparatus containing a tubular down-flow reactor of 100 cm3 effective volume. it contains all the equipment and devices applied in the reactor system of an industrial heterogeneous catalytic plant. the experiments were carried out in continuous operation with steady-state activity catalyst. materials and methods during our heterogenic catalytic experiments paraffin mixtures produced from two different sunflower oil (“a”: palmitic acid 4.5%, stearic acid: 2.1%, oleic acid: 63.2%, linoleic acid: 20.6%, linolenic: 6.8%, other carbon acids: 2.8%; “b”: palmitic acid: 6.6%, stearic acid: 3.7%, oleic acid: 26.4%, linolic acid: 62.2%, other fatty acids: 1.1%) were used, which main properties are summarized in table 1. feedstock “a1” was produced from sunflower “a” over sulphided nimo/al2o3 catalyst (nickel content: 3.2%, molybdenum content 13.4%; bet specific surface area: 214 m2/g; acidity: 0.489 mmol nh3/g) having high activity, so it practically contained only paraffins. feedstock “a2” was blended from “a1” and 0.5% oleic acid to investigate the effect of oxygen content. feedstock “b1” was produced from sunflower “b” over raneynikkel catalyst (nickel content: 65.3%, aluminium content: 34.4%; bet surface area: 68 m2/g) having very high activity; however beside the cracking reaction the aromatization took also place because of the high reaction heat. feedstock “b2” was obtained by the distillation of “b1” at 330 °c, while the most of the c18 fatty acids which were the most dominant oxygen containing compounds were removed. as catalyst we used pt/sapo-11, which contained micro and mesopores as well (platinum content: 0.5%; pt-dispersity: 69%; bet surface area: 105 m2/g; acidity: 0.661 mmol nh3/g). it was prepared according to hu 225 912 patent [13]. prior to the activity measurements the sapo-11 catalyst were pre-treated in situ, as described in our earlier publication [13]. table 1: the main properties of the used paraffin mixtures (the type of the used hydrogenation catalyst) sign of the feedstock, (hydrogenation catalyst) property “a1” (sulphided nimo) “a2” (sulphided nimo) “b1” (raney nickel) “b2” (raney nickel) analytical method composition, % i-c15 0.05 0.05 0.09 0.10 n-c15 3.10 3.10 6.00 6.70 i-c16 0.04 0.04 0.22 0.24 n-c16 3.15 3.15 4.40 4.90 i-c17 0.26 0.26 2.45 2.70 n-c17 47.30 47.10 64.70 72.00 i-c18 0.33 0.33 1.05 1.10 n-c18 43.90 43.70 13.60 9.10 total isoparaffin content,% 0.75 0.75 4.30 4.75 oxygen containing intermediate products, % 0.06 0.55 4.95 0.60 shimadzu 2010 gc cfpp, °c 23 23 22 21 en 116:1997 aromatic and naphthenic content, % <0.1 <0.1 2.3 2.1 en 12916 cfpp: cold filter plugging point 365 test and calculation methods the characteristics of the feedstock and the products of gas oil boiling range were determined according to test methods specified in en 590:2009 diesel fuel standard, while the hydrocarbon composition was measured by shimadzu 2010 gc using zebron db-1 high temperature (30 m x 0.32 mm x 0.1 μm) column. the repeatability of measurements for determination of hydrocarbon composition was the following: hydrocarbon concentration range, % repeatability*, abs% relative error**, rel% ≥30 0.3 ≤1 ≥5–30 0.2 1–4 ≥2–5 0.15 4–7.5 ≥0.5–2.0 0.1 7.5–20 ≥0.1–0.5 0.03 20–30 * maximum deviation of two parallel gc test results ** maximum relative deviation of two parallel gc test results the crystal structure and the purity of the sapo-11 catalyst were determined by x-ray diffraction (xrd). xrd characterization of the obtained powder confirmed that it was sapo-11. the platinum content of the catalyst was determined according to uop-274 standard. the platinum dispersion was determined by h2 chemisorption. the surface properties of the catalyst were determined by asap 2000 equipment (micromeritics) and mercury penetration method using carlo-erba equipment. the acidity of the sapo-11 catalyst was measured by nh3 adsorption. results and discussion during the heterogeneous catalytic experiments we investigated the effect of the composition of paraffin mixture, namely the indirect effect of process parameters and the used catalyst of the hydrogenation on the activity, selectivity and performance of the 0.5% pt/sapo-11-al2o3 isomerization catalyst. the products obtained during the isomerization of the paraffin rich feedstocks were the mixtures of liquid and gas phase hydrocarbons at every investigated operational parameter. the gas products generated by the hydrocracking side reactions contained mainly butane and isobutane (>40% in the gas phase). these could be used for several purposes in a refinery e.g. lpg production, alkylation of i-c4 with olefins, dehydrogenation of i-c4 to isobutylene, etc. the feedstocks of the isomerization contained in the highest concentration (91–98%) c15 and c18 hydrocarbons and gasoil boiling range, smaller molecule mass hydrocarbons (c11-c14) in different concentration, furthermore higher molecule mass compounds (c19+) in a small quantity (<2.0%; which were mainly c19-c22 paraffins and different oxygenic compounds). in the c10-c18 fractions the alteration of the concentration of the normal and isoparaffins could be detected exactly by the used gas chromatography method, so the degree of the structure conversion could be observed as a function of the operational parameters. the yield of the products the yields of the products decreased by increasing the temperature and decreasing the lhsv (fig. 1), furthermore by decreasing the pressure (fig. 2) in case of every feedstock. this was because of the increasing rate of cracking reactions took place beside the isomerization and because of the longer contact time of hydrocarbons. 91 92 93 94 95 96 97 98 99 100 310 320 330 340 350 360 370 380 390 pr od uc t y ie ld ,% temperature, °c "b1" "b1" "b2" "b2" "a2" "a2" "a1" "a1" figure 1: the product yields as a function of the temperature (p = 40 bar; continuous line: lhsv = 1.0 h-1; broken line: lhsv= 3.0 h-1) 90 91 92 93 94 95 96 97 98 99 100 10 20 30 40 50 60 70 80 90 pr od uc t y ie ld ,% pressure, bar "b1" "b1" "b2" "b2" "a2" "a2" "a1" "a1" figure 2: the product yields as a function of the pressure (lhsv = 1.0 h-1; continuous line: t = 360°c; broken line: t = 320°c) by decreasing the lhsv the flow rate of the molecules slowed down on the surface of the catalyst particles resulting increased degree of cracking. by decreasing the pressure the partial pressure of the hydrogen decreased, accordingly the hydrogenation rate of the unstable iso-carbenium ions formed during isomerization decreased. consequently they could be cracked easier. the yields of the products decreased in the order of “b1” >> “b2” ≈ “a2” > “a1” as a function of the feedstock. it was because the more oxygen containing intermediate was in the feedstock the higher inhibition of the cracking reactions was manifested by these components and the forming water [14, 15]. 366 the composition of the products by increasing the temperature the isoparaffin content of the products increased significantly above 320 °c in case of all feedstock, namely the degree of isomerization increased. however, at about 360–380 °c it reached a maxima and then started to decrease. it was partly because of the thermodynamic inhibition (namely the isomerization is an exothermic reaction) and partly because of the increase of the cracking reactions. this effect was intensified by the decrease of the liquid space velocity (fig. 3). 0 10 20 30 40 50 60 70 80 90 310 320 330 340 350 360 370 380 390 is op ar af fin c on te nt ,% temperature, °c lshv = 0.5 1/h lshv = 1.0 1/h lshv = 2.0 1/h lshv = 3.0 1/h figure 3: isoparaffin content of the product as a function of the temperature (feedstock „a1”; p = 40 bar) the isoparaffin content of the products obtained from feedstock “b1” was significantly lower than the other feedstock. (fig. 4). it was because feedstock “b1” contained relatively high amount of oxygen containing intermediate products (mainly fatty acids). these compounds partly cover the active sites of isomerization; the water formed from them can react with the brønsted acidic sites of the catalyst resulting irreversible structure damage [4, 16] and decreased acidity; the forming co can adsorb on the surface of the platinum [17, 18], which decrease the hydrogenation activity, so thus induce cracking or coking, as well. 0 10 20 30 40 50 60 70 80 90 310 320 330 340 350 360 370 380 390 is op ar af fin c on te nt ,% temperature, bar "b1" "b2" "a2" "a1" figure 4: isoparaffin content of the product as a function of the feedstock (lhsv = 1.0 h-1, p = 40 bar) these harmful reactions decreased the degree of isomerization. consequently, by the decrease of the intermediate concentration of the feedstock the isoparaffin concentration of the product (“a1” > “a2” ≈ “b2” >> “b1”) increased. it was also concluded, that the carbon number change of the hydrocarbons caused by the different degree of decarboxylation/decarbonylation and hydrodeoxygenation reactions took place on different hydrogenation catalysts had no demonstrable effect on the isomerization, namely in case of “a2” and “b2” feedstock the isoparaffin content of the product was practically the same. furthermore, in the investigated concentration range (0.1–2.3%) the aromatic compounds did not inhibit the isomerization reactions in higher degree than the limit of the measure. this and that the aromatic content of feedstock “b1” and “b2” significantly decreased during the isomerization proved the high hydrogenation activity of the platinum containing catalyst [19]. the performance properties of the products as by the increase of the temperature and decrease of lhsv the isoparaffin content of the product increased the cold filter plugging point (cfpp) of the products decreased. it was because the freezing point of the isoparaffins is lower than that of the normal paraffins and the lighter gas oil boiling range compounds (b.p. > 180 °c) formed by cracking in small quantity (<10%) also improved the cfpp value. above 360–380 °c the cfpp values were not decreased further (between -15 and -5 °c), because the isoparaffins were decomposed by the intensive cracking. in case of the investigated mixtures the hydrocarbon composition and the aromatic content of the feedstock did not influenced noticeably the cfpp value. but the oxygen containing intermediate products remarkably hindered the improvement of cold flow properties. the cetane number of the products decreased as a function of the conversion relative to the feedstock (97–101). anyway the derived cetane number of the products (determined with a cid 510 derived cetane number analyzer according to astm d7668 standard) with favourable cold flow properties was about 71–83 unit (the shorter or branched hydrocarbons have lower cetane number [20]). these values were significantly higher than the specified values of at least 51 (en 590 diesel standard). conclusion it was concluded that the oxygen containing intermediate products had significant effect on the isomerization of different paraffin mixtures (produced from sunflower oil) over 0.5%pt/sapo-11 catalyst. because of the good hydrogenation activity of the platinum containing catalyst the aromatic compounds did not inhibit the isomerization reactions. due to the difference in the reactivity of long alkanes (c15-c18) is relatively small 367 the hydrocarbon composition had no notable effect on the degree of conversion. the main product having gas oil oiling range reached had the highest isoparaffin content at 360 °c and lhsv of 0.5–1.0 h-1 (65–70%) (table 2). at higher temperature the degree of cracking was significant. the cold filter plugging point of the products decreased with the increase of the isoparaffin content. these isoparaffin rich products satisfy the summer grade regulation of cfpp value (at most +5°c; en 590:2009 diesel fuel standard) and are above just a few the winter grade specification (cfpp at most -20 °c). table 2: the main properties of the product obtained from feedstock “a1” over pt/sapo-11 at 360 °c, p = 40 bar; lhsv = 1.0 h-1, h2/hc ratio: 400 nm3/m3 property value hydrocarbon composition, % i-c15 1.73 n-c15 1.42 i-c16 2.45 n-c16 2.10 i-c17 34.00 n-c17 19.50 i-c18 24.80 n-c18 9.40 total isoparaffin content,% 67.80 oxygen content, % <0.05 cfpp, °c -11 derived cetane number 78 aromatic and naphthenic content, % <0.1 to sum it up over the selected 0.5% pt/sapo-11 catalyst and at the favourable process parameters (t = 360 °c, p = 40–60 bar; lhsv = 1.0 h-1, h2/hc ratio: 400 nm3/m3) excellent quality (cetane number: 71–83), environmentally sound (sulphur and nitrogen content below 10 mg/kg, aromatic content <1%) gas oil blending component was produced from natural feedstock. acknowledgement we acknowledge the financial support of this work by the hungarian 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word 2012_dr_bodor_endre_hjic.doc hungarian journal of industrial chemistry veszprém vol. 39(3) pp. 433-436 (2011) effects of supercritical carbon dioxide on rocks having carbon dioxide storage potential gy. lévai1, m. berta2, cs. király2, gy. falus3, i. gresits1, e. székely1 , cs. szabó2 1budapest university of technology and economics, department of chemical and environmental process engineering budafoki street 8. f ii 1. em. 1111 budapest, hungary e-mail: sz-edit@mail.bme.hu 2eötvös university, budapest, department of petrology and geochemistry, lithosphere fluid research lab pázmány péter street 1/c. 1117 budapest, hungary 3eötvös loránd geophysical institue, columbus street 17-23. 1145 budapest, hungary one of the most important problems of our society is the rising co2 concentration of the atmosphere supposed to be a reason of the climate change. the carbon capture and sequestration (ccs) may be a temporary solution for this problem. ccs is the technology when the co2 is separated from the local co2 sources, and is injected at least 800–1000 m deep where, because of the high pressure and higher than ambient temperature, it will be supercritical (scco2). we need to study what are the geochemical changes induced by scco2 to use safely this technology. this was the main motive why we started to make experimental and analytical methods on real core samples from exploration drilling. we added scco2 to sandstone core samples in brine and very high purity calcite samples in 5 w/w% nacl solution in 70–220 bar pressure interval and in 55–65 °c temperature interval in a high pressure resistant bomb and autoclave. after experiments the brine and solution samples were analyzed by icp-ms and the core samples by xrf and sem. the results indicated significant alteration in the concentration of na, ca, mg, k, fe and sr ions concentration before and after the addition of scco2. after adding scco2 the concentration of ca grew in the brine and was reduced on the surface of the sandstone. the xrf results indicated a very high dispersion of the elements on the surface of the samples. the sem images show ca soluble-cuts and solution of the surface. keywords: carbon-dioxide capture and storage; ccs; reactions in co2; long-term co2 storage; calcite dissolution introduction europe's efforts to cut green house gas (ghg) emissions, as well as the eu directives are major policy drivers in all the countries of the eu. the final solution of the increased co2 emission will be the use of the renewable energy sources. today these technologies are not economical, thus we should use temporary solutions to avoid the continuous accumulation of co2 in the atmosphere. in hungary carbon capture and sequestration (ccs) is considered to be a viable possibility to reduce co2 emissions mostly in the energy sector. the major storage potential of hungary is in deep saline aquifers (2000 mt) and hydrocarbon reservoirs (400 mt), therefore a potential site for co2 storage can be a regional saline aquifer in the northeastern part of the great hungarian plain [1]. the main concept, behind the technological process, co2 is separated from the flue gas of local sources like energy power plants. the separated co2 is compressed and transported to the injection site, where it is injected to at least in 800 m deep in to an adequate storage volume. here the co2 becomes supercritical (scco2), because of the elevated pressure and temperature. one part of the scco2 injected in the reservoir dissolves in the pore water and converts to h2co3. the h2co3 dissociates, therefore lowers the ph of the brine. the acidic ph changes the geochemical equilibrium between the pore water and rocks. finally, the result may be a change in porosity and permeability of the co2 storing lithologies. also, it may influence the stability of the storage and cap rocks, meanwhile the efficiency and safety of the co2 storing itself. for millennial timescale must be assured that the injected co2 can be stored in the deep reservoir without any harmful effects, or leaking back to the surface. this can only be achieved through multiscale studies involving laboratory tests, real time field experiments and use of natural analogues to inform models that can robustly predict the fate of co2 once injected into the ground [2]. in this paper we present the results obtained contacting model brine with rock samples from potential storage formations in scco2 and with pure calcite formations, and monitoring the changes in the system by scco2. 434 materials and methods geological background preceding studies (e.g., eu geocapacity 2006–2008) suggested that the lower pannonian stratigraphic system is the most suitable for storage because of generally better reservoir geological parameters than the upper pannonian unit. moreover, the depth of the lower pannonian sedimentary sequences corresponds to pressures high enough to maintain the supercritical state of co2. the thickness of the algyő formation at some points of the pannonian basin can reach 900 m and it provides a regional cover for the szolnok formation (fig. 1). it is an association of sublitoral and slope facieses of the delta, containing mainly siltstone and clay marl, but there are some bodies of sandstone (fig. 1). from the aspect of the storage process algyő formation is considered to be the sealing formation. figure 1: macroscopic view of characteristic sedimentary rock samples from the jászság subbasin of a drilling core: a) clayey algyő formation, b) sandy szolnok formation the thickness of the szolnok formation in the study area can reach 1000 m (fig. 2), it is composed mainly by sandstone and rarely siltstone. this formation is a thin-layered, turbiditic series, in which the layers are sharply separated from each other and sometimes contain charred plant pieces [3]. for sequestration purposes it is considered to be used for storage (fig. 1/b). figure 2: theoretical cross section of the studied area showing the jászság subbasin. the colors show the different formations deposited in sequential periods the red rectangle shows the interval the samples were taken from the clayey algyő formation and the sandy szolnok formation. the samples from the szolnok formation were the target of the current study (fig 2). the mineral composition of the rock determined by polarization microscopy corrected by determination of pore volume by water saturation: quartz (40%), calcite (28%), feldspar (7%) and mica (5%), pores (11%), cement (9%). in analytical quantity: rutile, tourmaline, pyrite was also found. the average grain measure 30–90 μm, the porosity is 11%. high pressure equilibrium experiments first the rocks were saturated under vacuum with brine (similar in composition to that observed on the field: 5% nacl eq.). autoclave experiments were run to react carbon dioxide with sandstone samples from szolnok formation immersed in brine. the experimental time varied within 5–37 days, the temperature was set between 55–65 °c and the pressure range studied was 70–220 bar. two pieces of core samples were placed in a glass boat and model brine was added. two boats were placed into the autoclave tube and after setting the temperature it was pressurized with co2 (99.7% purity) by an isco 260 d syringe pump. the glass boats are necessary to avoid chloride corrosion of the stainless steel autoclave. before the slow depressurization the autoclave was cooled to room temperature. liquid samples were taken directly from the residue in the boat, whereas the stone samples were immersed in distilled water prior to surface analysis. high pressure kinetic experiments a set of experiments with pure calcite samples was run by sampling the liquid phase of the solid – liquid – fluid heterogeneous reaction system. the designed reactor setup allows us to take sample from the bottom of the reactor at constant pressure and temperature (fig. 3). co2 pump c o 2 cy lin de r 2 magnetic mixer 2 tp 1 liquid sample thermostating fluid figure 3: high pressure reactor setup for isobar and isotherm sampling of the liquid phase. 1: stir bar, 2: valves, p: pressure transducer, t: thermocouple 435 the constant pressure was maintained by co2. in the kinetic experiments calcite samples of 0.2–0.3 mm diameter size were mixed in 5 w/w% nacl solution as model brine. analytical methods the surface analysis of the core samples were made by scanning electron microscopy (sem) and x-ray fluorescence (xrf). the average surface concentration of the following elements was possible to be detected by xrf: br, ca, cl, co, cr, cu, f, fe, k, mn, mo, nb, ni, p, rb, s, si, sr, te, ti, v, y, zn, zr. the concentration of ba, ca, co, fe, k, mg, mn, na, ni, sr, zn in the liquid samples were analyzed by inductively coupled plasma – mass spectroscopy (icp-ms), and flame emission analysis. results and discussion the sandstone samples showed significant changes even at short contact time (several days). result of surface analytics (sem, xrf) and analysis of liquid samples are in good agreement. concentrations of ca and mg in the liquid samples increase with reaction time. quantification of minor elements suggests also dissolution from the pores (fig. 4, where the a and b samples are parallel experiments; note that the diagram is in logarithmic scale). large standard deviation was observed by xrf measurements on sandstone samples. sem images confirmed that there is a significant increase of the specific surface for the xrf during the scco2 reaction. it is noticeable in fig. 5, where the dissolution of the calcite created deep lanes in the originally smooth surface. 1 10 100 1000 10000 100000 na mg k ca mn fe sr co ni zn c on ce n tr at io n [m g/ l] elem en ts figure 4: minor cations of the liquid samples. the 1st columns show the composition of the model pore fluid, the 2nd columns the concentration values of pore fluid which is in equilibrium with the core samples in atmospheric pressure. the 3rd and 4th columns show the composition of the pore fluid after reacting the sample with co2 (a and b indicate parallel samples): 163 bar, 55 °c, 14 days to analyze the time scale of the dissolution of calcite in order to reach a new equilibrium, pure calcite samples of controlled particle size were immersed in brine and reacted with co2. the surface of the calcite grains showed again erosion like picture (fig. 6). the erosion phenomenon was dependent on the reaction time of the scco2 exposure (fig. 6 and fig. 7). the most reactive minerals are the calcite and feldspar. there is no visible change on the surface of the quartz as expected (fig. 5). calcite quartz figure 5: “erosion lanes” on the surface of calcite observed after 14 days long reaction with scco2 figure 6: calcite erosion by the scco2 contacting (contacting time: 4 days) on figs. 6 and 7 we can also observe that the evolving calcite peaks show a trend in either way. figure 7: strong calcite erosion at longer reaction time (15 days) 436 the surface of the sample remained intact (unchanged) if it was only contacted with the co2 phase without brine being present (this case is relevant for rock close to the injection site). on fig. 8 there is a drop of solution on the surface of the calcite sample. one may notice the calcite erosion and solubility within the borders of the brine drop, but there is no dissolution visible outside. figure 8: a former nacl-water solution drop on the calcite surface time-dependent liquid phase ca concentration is shown in fig. 9. the samples were taken from one batch and analyzed by icp-ms. the heterogeneous system, even with mixing to reduce the mass transfer limitations (250 rpm), did not reach the equilibrium in 4 days. ca concentrations in the liquid phase increased with more than 3 orders of magnitude during the experiment, high above the atmospheric saturation concentrations. figure 9: calcite dissolution curve at 89 °c, 150 bar. conclusions hungary has significant regional saline aquifers, mainly those that were formed in the middle to late miocene. among these the most adequate for co2 storage purposes is the szolnok formation as the main limit for the safe and economical storage is the adequate reservoir rock. it is highly important to understand the geochemical reactions (e.g., dissolution, alteration, crystallization) occurring in the minerals composing the potential future reservoir rock. our results show that there are significant changes already in short experimental times (i.e., few days or weeks). these changes may affect the long term safe storage potential even by increasing safety or by rising concerns. among the major constituents of the studied sandstone samples the most reactive mineral is calcite but feldspar is also slightly affected. short experiments offer preliminary results however, this field needs further research to achieve the required accuracy of experimental results for reliable modeling of the time scale of geological times. acknowledgements we gratefully thank of: juhász györgyi, bendő zsolt, záray gyula, óváry mihály, simándi béla. the acquiring of sections and details helped in part by otka number: t-060861. references 1. t. fancsik, k. török, m. törökné, cs. szabó, l. lenkey: possibilities of long-term storage of co2 from industrial sources. (in hungarian) in: magyar tudományos akadémia-miniszterelnöki hivatal: stratégiai kutatások (in hungarian). budapest, meh-mta (2006) pp. 89–118 2. c. j. ballentine, b. s. lollar: noble gas isotope insights into the geological storage of carbon, ima 2010. budapest, 21-27. 09. 2010. 3. gy. juhász: lithostratigraphy of the pannonian s.l. formations of hungarian neogene deep basins in hungary. in: i. bérczi, á. jámbor: stratigrahpy of hungarian geological formations (in hungarian) magyar olajipari részvénytársaság és a magyar állami földtani intézet kiadása, budapest, (1998) pp. 469–484 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word b_43_raczkovi_r.doc hungarian journal of industrial chemistry veszprém vol. 39(2) pp. 279-282 (2011) cbn tool life prediction by artifical neural network l. raczkovi university of miskolc, department of production engineering, 3515 miskolc-egyetemváros, hungary e-mail: laszlo.raczkovi@uni-miskolc.hu for economic application of cbn tools it is important to know how the tool life changes as a function of the most important technological parameters (cutting speed, feed rate, depth of cut and work piece diameter). these technological parameters have significant effects on the productivity of machining. the extended taylor equation takes the effects of feed rate, depth of cut into account besides the cutting speed, but this equation is not valid in the whole range of cutting speed. beyond the publicated tool life equations in the professional articles, the tool life can be determined by artificial neural network (ann). anns have huge flexibility and can handle different number of inputs thus they are suitable for determining tool life as a function of several cutting parameters. keywords: tool life, artifical neural network introduction cubic boron-nitride was synthesized by r. h. wentorf in 1957. it was first produced in industrial sizes in 1968. cbn tools with definite tool edge geometry have been produced since 1970’s. due to coating processes (pvd, cvd) have appeared later the various (tin, tialn, ticn) coated cutting tools. cbn is the second hardness material after diamond. due to its great hardness and heat resistance, cbn is suitable for machining hardened steel (>55 hrc). nowadays the hard turning is used more widely in finish machining instead of/besides grinding. hard turning has several benefits over grinding: higher flexibility, machining complex work pieces in one clamping, no need for coolant liquid, easy automation and better material removal rate [1]. the providing of required strict dimensionaland shape accuracy of the work piece demand high quality in cutting tools. it is a basic demand from these cutting tools to provide the quality and accuracy expectations of work piece beside long tool life. nowadays the numerical methods are widely used to solve several different problems in engineering science. one of these numerical methods is that of the least squares, which is used to function approximation. due to the available mathematical softwares the artificial neural networks (anns) can be applied to approximate different types of functions using the method of least squares. the bases of anns were laid down by mcculloch and pitts in 1943 [2]. nowadays anns are widely used to evaluate various experimental results. in this study, ann was created and simulated to determine tool life in case of different cutting speeds, work piece diameters, constant feed rate and depth of cut. artificial neural network a model of a neuron anns consist of a set of hierarchically organised neurons. the neurons do the same operations parallel. each neuron in a network is connected to a certain number of neurons, and this is usually a one-way relationship. fig. 1 shows the structure of a neuron [3]. figure 1: the architecture of a neuron the p1, p2, p3,…,pn inputs are connected to the neuron by w1n weights. furthermore there is an additive part b which is called bias. eq. (1) shows how a neuron works. n 1,n n i 1 a f ( w p b) = = +∑ (1) the function f is the activation function of neuron. usually it is a sigmoid type function such as tangent sigmoid, which is shown by eq. (2). 280 2 ( x ) 2f(x) 1 1 e− ⋅= − + (2) multi-layered anns a neural network consists of three different layers at least. the first is called the input layer. this layer contains those neurons which transfer the input signal to the network. the second is the hidden layer. the neurons which carry out the real processing belong to this layer. a network has one or more hidden layers. the third (or last) layer is the output layer. the neurons in this layer transfer the information to the outside. the tasks of these neurons are same as that of the neurons in the hidden layer. the structure of a multi-layered feed-forward neural network is shown by fig. 2 [3]. figure 2: structure of a multi-layered neural network multi-layered feed forward neural networks can be used for function fitting. these networks are using backpropagation training algorithm. during the training, the network changes the values of weights and biases according to the error function. the aim of ann training is to minimize the error function e, which is shown by eq. (3) [4]. n 2 i i i 1 1e a t 2 = = −∑ (3) where: ai – the i-th output value, ti – the i-th target value, n – number of outputs, e – the mean square error. the i-th net input of k+1-th layer can be calculated by eq. (4) ∑ = +++ += s j k i k j k ji k i bawn 1 11 , 1 (4) where: ni k+1 – the i-th net input of k+1-th layer, wij k+1 – the weight between the j-th neuron of previous layer and the i-th neuron of subsequent layer, aj k – the j-th output of k-th layer, bi k+1 – the i-th bias of k+1-th layer. the i-th output of k+1-th layer can be calculated by eq. (5). )( 111 +++ = k i kk i nfa (5) where: fk+1 – the activation function of k+1-th layer. before training the network is initialized by random weights and biases. each weights and biases are updated during training using eq. (6) which is known as the back-propagation delta rule [4]. 1 1 1 + + + −= ∂ ∂ −=δ k j k ik ij k a w ewij δαα (6) where: α – the learning rate, which defines the step length of each iteration in the negative gradient direction, δj k+1 – the backpropagated error at the j-th neuron in the k+1-th layer, ai k – the i-th output of k+1 layer. the value of δj k+1 is different, depending on that, whether the k+1-th layers is an output layer or a hidden layer. if the k+1-th layer is an output layer [4]: ))(1( 1111 j k j k j k j k j taaa −−= ++++δ (7) if the k+1-th layer is a hidden layer [4]: ∑= +++++ −= m i k i k ij k j k j k j waa 1 22111 )1( δδ (8) determining tool life by artifical neural network in this paper the experimental data set given in [5,6] is used to design a neural network model which predicts tool life according to given range of feed rate, depth of cut, workpiece diameter and cutting speed. the applied technological parameters, which were used for training is shown in table 1. the ann used for modelling tool life is a two layered feed-forward network with 35 neurons in the hidden layer and 1 neuron in the output layer. the network was made using matlab r2009 software. the activation function in hidden layer is a sigmoid type and in the output layer it is linear. the network was trained with 108 data points according to table 1 and simulated with 27 data points. a data point contains the feed rate, the depth of cut, the workpiece diameter and the cutting speed. the applied cutting parameters to simulate ann were the following: depth of cut ap=0.15 mm, feed rate f= 0.05 mm/rev., cutting speed vc=11–120 m/min, workpiece diameter d= 45, 75, 100 mm. 281 table 1: technological parameters for training the network feed rate f mm/rev. depth of cut ap mm workpiece diameter d mm cutting speed vc m/min 0.025 0.125 0.050 0.250 0.10 0.10 0.15 0.25 45 0.025 0.125 0.050 0.250 0.10 0.10 0.15 0.25 75 0.025 0.125 0.050 0.250 0.10 0.10 0.15 0.25 100 11,20,29,40,50,68,92,105,120 the back-propagation learning algorithm has been used with ‘trainlm’ training function. this training function is based on levenberg-marquardt nonlinear least squares method. as a result of the simulation the calculated tool life and the deviations between measured and calculated tool life are summarized in table 2. it can be seen, the maximal deviation between measured and calculated tool life is 58%, but it occurs at very small value thus it is not significant. fig. 3 shows the results of simulation. the correlation r between the outputs of ann and the measured tool life values can be seen in fig. 3a. the simulated data set is different in feed rate and depth of cut from the data set of training. the value of correlation r=0.99029 is very close to 1 which means a good fitting of calculated values to measured values. fig. 3b shows the tool life curves at different workpiece diameters and constant feed rate and depth of cut. table 2: the calculated tool life values and deviations between measured and calculated tool life values workpiece diameter, mm 45 75 100 f, mm/rev. a, mm f, mm/rev. a, mm f, mm/rev. a, mm 0.05 0.15 0.05 0.15 0.05 0.15 vc m/min tm tann e e% tm tann e e% tm tann e e% 11 258 270.93 -12.93 5.0 314 331.59 -17.59 5.6 325 388.56 -63.56 19,5 20 194 219.61 -25.61 13.2 236 234.51 1.48 0.6 245 257.66 -12.66 5,1 29 203 215.17 -12.17 6.0 215 225.07 -10.07 4.6 224 237.51 -13.51 6,0 40 216 210.20 5.79 2.6 227 222.42 4.57 2.0 231 234.70 -3.70 1,6 50 216 196.57 19.42 8.9 229 217.37 11.62 5.0 241 231.89 9.10 3,7 68 93 114.99 -21.99 23.6 154 176.66 -22.66 14.7 198 212.98 -14.98 7,5 92 25 25.43 -0.43 1.7 54 50.57 3.42 6.3 77 94.14 -17.14 22,2 105 14 17.80 -3.80 27.1 31 27.89 3.10 10,0 43 46.66 -3.66 8,5 120 10 15.80 -5.80 58,0 18 21.77 -3.77 20.9 26 31.49 -5.49 21,1 tm – measured tool life tann – ann predicted tool life e – deviation between measured and ann predicted tool life e% – deviation in % 282 a) the correlation between ann results and b) the measured and simulated tool life values at measured tool life values different workpiece diameters (f=0.05 mm/rev, ap=0.15 mm) figure 3: the results of ann simulation it can be seen on fig. 3b that the characteristics of tool life curves predicted by ann are similar to curves by specified in [6]. in [7, 8] professional articles kundrak et al. was a new generalized tool life equation used [5].this equation is valid in the whole range of the cutting speed. the effect of changing of the workpiece diameter on tool life was published kundrak et al. in [6]. according to this at small workpiece diameter the changing of the direction of chip flow vector is steeper than in case of greater diameters. therefore the tool life is decreased at small workpiece diameters. summary the aim of this paper was to determine the tool life of cbn cutting tools using artifical neural network. the inputs of ann were feed rate, depth of cut, workpiece diameter and cutting speed. these parameters have huge influence on tool life of cbn cutting tool. the predicted tool life by ann shows good agreement with experimental results of [6]. acknowledgements “the described work was carried out as part of the támop-4.2.1.b-10/2/konv-2010-0001 project in the framework of the new hungarian development plan. the realization of this project is supported by the european union, co-financed by the european social fund.” references 1. h. k. tönshoff, c. arendt, r. ben amor: cutting of hardened steel. cirp annals manufacturing technology, 49(2), (2000), 547–566 2. w. s. mcculloch, w. pitts, a logical calculus of the ideas immanent in nervous activity, bull. math. biophys. 5, (1943), 115–133 3. m. hudson, m. beale, t. hagan, h. demuth: neural network toolbox™ user’s guide copyright 1992-2010 by the mathworks, inc. 4. r. rojas: neural networks, springer-verlag, berlin 1996 5. j. kundrák: determination of tool life in cutting, proc. of the tenth international conference on tools, ict-2000, september 6-8, 2000. miskolc, hungary, pp. 205–210. (isbn 963 661 434 2) 6. j. kundrák, v. zubar: vlijanie diametra rastchivanija na osobennosti processa rezanija, cutting and tools in manufacturing systems, 59, 2001, 143–148 7. a. g. mamalis, j. kundrak, m. horvath: wear and tool life of cbn cutting tools, international journal of advanced manufacturing technology 20(7), (2002), 475–479 doi: 10.1007/s001700200180 8. a. g. mamalis, j. kundrak, m. horvath: on a novel tool life relation for precision cutting tools, journal of manufacturing science and engineering transactions of the asme, 127(2), (2005), 328–332 doi: 10.1115/1.1794158 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true 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(adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice hungarian journal of industry and chemistry vol. 45(2) pp. 19–21 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0015 examination of innovative high-throughput fermentations áron németh* department of applied biotechnology and food science, budapest university of technology and economics, műegyetem rkp. 3, budapest, 1111, hungary during the investigation of fermentations, issues such as the need for numerous parallel experiments with regard to strain improvement or screening were often met, or in the case of media optimization the need for online measurements to avoid a lack of night-samples was also required. therefore, several new instruments were introduced to solve one or more of these problems: impedimetricand reverse-spin-technologies (rst) were compared via fermentation of a well-known species of yeast, saccharomyces cerevisiae, under both aerobic and anaerobic conditions, resulting in a diauxic growth curve. to identify the most accurate method, a wellknown mathematical description was fitted to the measured data. since the initial parameters were considered reliable as they originated from real experiments, during model fitting, the parameters were further fine-tuned, and the less modifications reported the better the system since it produces a growth curve that is more similar to standard bioreactors. according to our study, the impedimetric equipment was more efficient, and could run 40 parallel experiments, but the rst was more flexible. keywords: fermentation, high-throughput, scale-down, online measurement, mathematical modelling 1. introduction developments in fermentations face numerous challenges which may require expensive analytics, media components or special tools to facilitate aseptic work and sampling. furthermore, these biological processes vary significantly. to overcome these difficulties, the process should be scaled-down in combination with high-throughput methods, resulting in many parallel, small-scale experiments. such experiments are used in terms of strain and technological improvements as well as media optimization. a good solution may be the consideration of micro-bioreactors. however, because of their high investment and operational costs, they have not become widespread in hungary. while each can provide almost every service required for bioreactors, for example, aeration, agitation and sampling in addition to ph and temperature control, they possess considerable limitations, namely non-standard conformations resulting in scaleup difficulties, or special measurement techniques that are incompatible with standard methods. a readily available alternative, to be more precise, microtiter-plates (mtp), for microscale highthroughput fermentations has already been presented and reported [1]. the basic principle is to use sterile ’96-well’ microtiter plates with a special “sandwich cover” that facilitate sufficient aeration but reduce the likelihood of cross-infection. this system requires an *correspondence: naron@f-labor.mkt.bme.hu adapter to be able to mount microtiter plates into a commercial rotary incubator shaker. the next issue is to analyse and follow the processes in the wells since their volumes are so small (ca. 100 l) that sampling is impossible. therefore, either a microplate reader is required or a simple office scanner to produce a greyscale photo taken from the bottom of the plate. the colour of high cell-densities is close to white, but empty broths have a black background. in the case of species that produce high levels of acid, like lactobacillus, even a ph indicator can be applied and besides a greyscale photo a coloured one has to be taken as well; alternatively, caco3 should be added at the start but this can disturb the scanner-based “photometry”. our partner (enzyscreen.com) even offers microtiter plates for fed-batch fermentations. to achieve this, the feed components are adsorbed onto the material of the mtp, and are programmed to slowly release the fresh substrate during cultivation. however, another innovative solution has been developed for small-scale fermentations using online monitoring: biosan ltd. (lithuania) applies reverse-spin technology in the equipment of their personal bioreactor (rts-1). this cost-effective equipment rotates a standard falcon tube, filled with ca. 10 ml of fermentation media, at different rotation speeds in several directions at various controlled temperatures using a variety of aeration holes on the cap. this instrument also involves a photometer to facilitate the programming of measuring frequencies at a given wavelength (= 850 nm). for calibrated and reproducible measurements, a constant film layer is necessary, therefore, the instruments increase the rate of németh hungarian journal of industry and chemistry 20 rotation until 2000 rpm. the changes in parameters effect shear forces as well as levels of aeration. finally, this comparative study used an impedimetric system by sy-lab (austria) which is called bactrac 4100 [2]. this equipment possesses a block thermostat composed of 40 measurement cells, each containing 4 electrodes. one pair of them follows the changes in the impedance of the media, m%, caused by the secreted acids and metabolites. in the case of microorganisms that exhibit high levels of ionic strength in the media, it is hard to detect m%, therefore, with the application of a different frequency the changes in impedance on the other electrode surface (e%) can be followed. in direct measurements, these electrodes are immersed directly into the culture, but in the case of indirect measurements, they are rinsed with koh which can adsorb the formed co2 released by the culture. while this system does not possess mixer/aerator solutions, this result can be transferred carefully to the known systems, namely benchtop fermenters or shaking flasks. however, it is able to follow forty different cultures. in this study, a well-known model organism (s. cerevisiae) was chosen that exhibits special biochemical behaviour. it was used to test the compare the ability of the three systems introduced above. what is special about s. cerevisiae is that it can change from aerobic to anaerobic cultivation according to pasteur and crabtree effects; i.e. under lack of oxygen or excess to sugar, respectively. after changing to anaerobic metabolism, it produces mostly alcohol but later this can be consumed by yeast as well resulting in a stepwise growth curve, also referred to as a diauxic growth profile. thus, the question was whether such a system could show and follow this diauxic growth. 2. experimental commercial s. cerevisiae, i.e. baking yeast produced by lesaffre, was cultured on a media of molasses that were diluted by a factor of 10 resulting in a saccharose concentration of ca. 75 g dm-3 and a 20:1 volume of molasses to nh4oh ratio at 34°c. the 100 l of inoculum possessed a cell-dry-weight (cdw) content of 10 g/dm3. rts-1 collected the data in a microsoft excel database. bactrac only provided the data collected on screen plots, but with the help of digitizelt v.2.3 software the measurement data was transported into microsoft excel. to compare the data in microsoft excel, the structured model of blanch et al. [3] was adopted and programmed in berkeley madonna for windows 8.1. this model can describe both anaerobic cell growth on excess sugar with the formation of alcohol and aerobic cell growth on alcohol as a substrate. it divides cells into two main compartments, i.e. substructures: one is responsible for metabolism (both aerobic and anaerobic), and the other is responsible for cell division. the parameters, for example reciprocal yields and stoichiometric coefficients of the model, were partly determined experimentally, but others were determined by nonlinear model fitting, i.e. model calibration on real samples. 3. results and analysis 3.1. reverse-spin technology vs. personal bioreactor (rts-1) fig.1 presents the results of rts-1. while optical density (od), i.e. turbidity at = 850nm, changed slowly, the specific growth rate calculated online only reflected the uncertainty of the od measurements, but the temperature remained constant as expected. additionally diauxic growth was also detected but over a very long period of time. the model fitting was quite difficult because a satisfactory fit was only achieved after remarkable changes to basic constants, for example maximum specific growth rates on both substrates, etc., had been applied. 3.2. impedimetric system: bactrac in the case of the impedimetric experiments, three different arrangements were tested: an anaerobic cell with (a) (b) figure 1. the measured parameters (temperature, , od850) and calculated data (cdw from od850) along with the data of the predicted (i.e. fitted) model. (a) green line: temperature; blue line: measured turbidity at 850nm; brown line: measured specific growth rate. (b) green line: temperature; red crosses: calculated cell dry weight from the measured turbidity at 850nm; purple line: fitted model-based prediction for cdw. 0 5 10 15 20 25 30 35 40 -2 -1 0 1 2 3 4 0 50 100 150 200 250 300 350 t(°c)od (850nm) fermentation time (h) od(850nm) µ (h ̄ ¹) t °c growth on sugar growth on ethanol d i a u x i c g r o w t h 0 5 10 15 20 25 30 35 40 0 2 4 6 8 10 12 14 16 18 0 50 100 150 200 250 300 350 t(°c)cdw fermentation time (h) cdw predicted cdw t °c examination of innovative high-throughput fermentations 45(2) pp. 19–21 (2017) 21 an incorporated valve for gas release, an aerobic one, and an indirect one (fig.2). only m% values yielded explainable curves. indirect measurements yielded an inverse growth curve (decreasing) as expected, but did not exhibit a two-step decrease, i.e. diauxic growth, therefore, m% values of direct measurements were evaluated. the two curves of aerobic and anaerobic m% values were very similar to each other, but perhaps the anaerobic example is more relevant as in the case of high sugar content, the metabolism of yeast shifted in the anaerobic direction. fig.3 shows the fits of the model in which less constants had to be changed and diauxic growth was detected. 4. conclusion both tested systems – personal bioreactor (rts-1, biosan) and bactrac (sy-lab) – detected diauxic cell growth of baking yeast. rts-1 seemed to be a little bit more flexible, but bactrac gave faster results, was able to make 40 measurements at the same time and offered three options in terms of evaluation. maybe in the near future a solution to regular automatic sampling from larger-scale fermenters will be found and then the results can be compared with the ones presented here. acknowledgement we are sincerely grateful to sy-lab for the support provided with regard to bactrac, and to biocenter kft. for importing rts-1. references [1] németh, á.; kiss, á.; sevella, b.: experiments for d-lactic acid production with fermentation, hung. j. ind. chem., 2011 39(3), 359–362 [2] bankovsky, v.; bankovsky, i.; bankovsky, p.; isakova, j.; djackova, i.; sharipo, a.; eskin, j.; dišlers, a.; rozenstein, r.; saricev, v.; djacenko, s.; makarenko, v.; balodis, u.: reverse–spin® technology innovative principle of microbial cultivation, manufacturer's online leaflet: https://biosan.lv/images/uploads/content/files/reverse_spinner.pdf [3] blanch, h.w.; clark, d.s.: biochemical engineering (marcel dekker, ny, usa), 1996, pp. 231–236 isbn 9780824700997 (a) (b) (c) figure 2. the results of three bactrac measurements: relative changes in impedancy in the m% of media vs. time (h) (a) indirect-; (b) aerobic-direct-; (c) anaerobic-direct measurements. figure 3. model fitting to the anaerobic bactrac curve (m%): red crosses: measured data; purple line: modelpredicted values; green line: temperature (°c). 0 5 10 15 20 25 30 35 40 0 2 4 6 8 10 12 0 20 40 60 80 100 120 t(°c) measured (m%) and predicted impedancy fermentation time (h) m(%) predicted impedancy t °c d i a u x i c g r o w t h growth on ethanol growth on sugar page 1 page 2 page 3 page 4 page 5 page 6 page 7 page 8 page 9 page 10 page 11 page 12 page 13 page 14 page 15 page 16 page 17 page 18 page 19 page 20 page 21 page 22 page 23 page 24 page 25 page 26 page 27 page 28 page 29 page 30 page 31 page 32 page 33 page 34 page 35 page 36 page 37 page 38 page 39 page 40 page 41 page 42 page 43 page 44 page 45 page 46 page 47 page 48 page 49 page 50 page 51 page 52 page 53 page 54 page 55 page 56 page 57 page 58 page 59 page 60 page 61 page 62 page 63 page 64 page 65 page 66 page 67 page 68 page 69 page 70 page 71 page 72 page 73 page 74 page 75 page 76 page 77 page 78 page 79 page 80 page 81 page 82 page 83 page 84 page 85 page 86 page 87 page 88 page 89 page 90 page 91 page 92 page 93 page 94 page 95 page 96 page 97 page 98 page 99 page 100 page 101 page 102 page 103 page 104 page 105 page 106 page 107 page 108 page 109 page 110 page 111 page 112 page 113 page 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447 page 448 page 449 page 450 page 451 page 452 page 453 page 454 page 455 page 456 page 457 page 458 page 459 page 460 page 461 page 462 page 463 page 464 page 465 page 466 page 467 page 468 page 469 page 470 page 471 page 472 page 473 page 474 page 475 page 476 page 477 page 478 page 479 page 480 page 481 page 482 page 483 page 484 page 485 page 486 page 487 page 488 page 489 page 490 page 491 page 492 page 493 page 494 page 495 page 496 page 497 page 498 page 499 page 500 page 501 page 502 page 503 page 504 page 505 page 506 page 507 page 508 page 509 page 510 page 511 page 512 page 513 page 514 page 515 page 516 page 517 page 518 page 519 page 520 page 521 page 522 page 523 page 524 page 525 page 526 page 527 page 528 page 529 page 530 page 531 page 532 page 533 page 534 page 535 page 536 page 537 page 538 page 539 page 540 page 541 page 542 page 543 page 544 page 545 page 546 page 547 page 548 page 549 page 550 page 551 page 552 page 553 page 554 page 555 page 556 page 557 page 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studied. samples were taken from the wastewater arriving to the secondary settler at different times in order to determine the settling profiles belonging to different concentrations. the vesilind function and the maximum practical settling velocity were derived base on these data. using three sets of measurement data the takács model was fitted by modifying certain parameters. the simulation results gave an overestimation on the concentrations of the effluent in all three cases and there were differences of a few percents in the lowest layer as well. taking the changes in the order of magnitude of the suspended solids concentration into consideration in the process of sedimentation i.e. it had to be decreased from 4000–6000 g/m3 to 8–12 g/m3 the higher values in the effluent layer are acceptable until they are below the permissible limit. key-words: settling velocity, takács-model, wastewater, vesilind-function introduction the phase separation units of wastewater treatment plants, the settlers share the same importance as the activated sludge reactors [12]. this feature appears in modelling wastewater treatment sytems, too. of the many models developed in order to describe the processes of sedimentation, the one dimensional settler models with given number of layers are popular [5, 6, 13]. these models while adequately predicting the main functionalities of the settlers do not add significant computational load to the process model of the wastewater treatment plant [3]. even when such a model is used, proper calibration of parameters is vital. beside modifying the effluent quality the settler influences the results of the biological model through the returned sludge concentration. false settler values deteriorate the results of the whole model of the wastewater treatment plant. the one-dimensional models are based on the simplifying assumption that the horisontal velocity profiles are uniform and that the horizontal concentration gradients are negligible [4, 6, 8]. this concludes that only vertical solids movement is modeled. the settler cylinder is taken as a continuous flow reactor. at the inlet section, the inflow together with the introduced suspension are homogeneously spread over the horizontal cross section. the mixed liquor concentration is modified by convection and other transport processes. the flow is divided into a downward flow towards the underflow exit at the bottom, and an upward flow towards the effluent exit at the top [7]. at the bottom of the reactor the solids flux due to gravitation is taken zero. the premise of the research was supplied by the dissertation of holenda [4]. he examined six different one-dimensional settler models based on literature data. the results were not validated on a real settler but it became clear that the different models gave different output values using the same input. other works [2, 13] highlighted that the model parameters depend on the given systems and have to be altered according to the actual load. in this paper the parameter dependency of the most wide-spread model of wastewater treatment simulation practice, the takács-model [13] was examined by modeling the secondary settler of a regional municipal wastewater treatment plant. there are several parameters in the applied equation that can not be measured directly and even if they can be, the measurement results are burdened with observational errors. the focus of the research was on how the parameters affect the effluent and returned sludge suspended solids concentration and whether and to what extent can one set of parameters be used for different sets of input values with similar incoming concentrations. 160 materials and methods the double exponential velocity function of takács [13] was used for modelling but the maximum practical velocity was determined with the vesilind function [14]. sampling from the mixed liquor arriving to the secondary settler of the examined wastewater treatment plant was repeated for several different times. the multiple samples resulted in sedimentation curves for different suspended solids concentrations. settler models there are four different types of sedimentation characteristics depending on the quality and the concentration of the suspended solids [13]: 1. discrete particle settling: it is characterized by solids which settle individually without any significant interaction. 2. flocculent particle settling: it is characterized by the flocculation of solid particles while they settle through the water column. 3. hindered settling: the mass of particles settles as a unit, the interaction between the particles hinder the settling process. 4. compression settling: the decrease of the interface level is achieved by the compression of the mass of particles. the most widespread model that is used to describe the ongoing processes in a settler unit is the takácsmodel. the used equation is based on the model of vesilind [14]. beside the hindered settling described by the function developed by vesilind, takács et al. [13] added a second term to implement the effect of the flocculent particle settling as well. they hoped to create a function that is able to give a more realistic estimate on the effluent suspended solids concentration. the double exponential equation settling velocity of takács is as follows [13]: ( ) ( )( )[ ]{ }minmin 0 ' 0 ,min,0max xxrxxr s ph eevvv −−−− −= where v0 practical maximum (vesilind) settling velocity (m/d), v0’ theoretical maximum settling velocity (m/d), rh hindered zone settling parameter (m3/g), rp flocculent zone settling parameter (m3/g), xmin minimum attainable suspended solids concentration (g/m3) xmin = fnsxf where fns non-settleable fraction (-) and xf mixed liquor suspended solids concentration entering the settler (g/m3). while the vesilind function is [14]: xp s hinevv −= 0 where vs actual settling velocity (m/d), v0 starting settling velocity at 0 g/m3 theoretical suspended solids concentration (m/d), phin hindered zone settling parameter x suspended solids concentration (g/m3) in cases of small (0–1500 g/m3) concentrations the vesilind function can be interpreted only mathematically. the settling velocity in this range is either immeasurable or the results show great uncertainty. features of the wastewater treatment plant the capacity of the examined wastewater treatment plant is 21,000 m3/day. there are two parallel biological lines capable of enhanced biological phosphorous removal. each train ends in a dorr-type secondary settler having 5100 m3 volume, a diameter of 40 m and 2.8 m depth. the samples were taken from line i. at the time period examined the weather was dry therefore the effect of rainfall did not have to be taken into consideration. since the typical sludge age of the plant is around 20 days it can be assumed that the quality and so the settling characteristics of the sludge did not change significantly therefore the samples taken at different times and the results derived from them can be compared to each other. the data used for the research are shown in table 1. table 1: sets of measurement data used for the experiment sludge concentration aerobic tank top of the settler bottom of the settler flow excess sludge removal g/m3 g/m3 g/m3 m3/day m3/day 1. set 4316 8 9000 7030 200 2. set 5039 12 7900 6954 250 3. set 3892 8 6600 6993 250 preparation for modeling samples from the last section of the aerated tank were taken for three different occasions in order to receive different suspended solids concentrations. the sedimentation curves of the three homogenized samples were measured by registering the height of the sludgewater interface in a 1000 cm3 cylinder in the function of time. each sample was diluted to approximately half of the original concentration and the measurement process was repeated. the results are shown in fig. 1. in order to determine the settling velocity belonging to each ss concentration the linear section of the curves had to be specified. fig. 2 shows a general sedimentation curve where each section is numbered (the linear section is labelled as no.2). 161 0 50 100 150 200 250 300 350 0 50 100 150 200 250 le ve l o f i nt er fa ce  (m m ) time (minute) 5039 4316 3892 2784 2618 2309 suspended solids  concentration  (g/m3) figure 1: sedimentation curves of samples with different suspended solids concentrations 50 40 30 20 10 0 0 10 20 30 40 50 60 70 linear section 1 2 3 4 time (minute) le ve l o f i nt er fa ce (c m ) figure 2: sedimentation curve [3, 9] 1 – flocculation zone, 2 – hindered settling zone, 3 – transitional zone, 4 – compression zone the linear section which is the phase of the hindered sedimentation provides the constant settling velocity that can be coupled with a certain concentration. the precision of the examination relies on the recognisability of this phase on the real sedimentation curves. beside the uncertainty of the measurement a great hindrance can be when the interface is not well determinable, for example if the sludge is subject to bulking or foaming. after determining the linear sections the settling velocities of the different samples could be calculated. the settling velocities plotted in function of the suspended solids concentration are shown in fig. 3. the exponential curve fitted on these values is described with an equation identical to the vesilind equation therefore it provides the maximum practical settling velocity (v0 = 15.101 m/d). this value was used in the takács-model but other parameters were estimated in the course of modelling. vs = 15.101e‐0.403 mlss r² = 0.9826 0 2 4 6 8 10 12 14 16 0 2 4 6 8 v s (m /d ) mlss (kg/m3) calculated values fitted curve figure 3: determining the vesilind curve based on the measured linear settling velocities results the measurement results of the three samples without dilution and the calculated vesilind settling velocity was used for fitting the takács-model by adjusting the other parameters. the model development was done using matlab/ simulink r2007b program package. the program package offers the utilization of graphical interfaces beside the freedom of creating codes in several languages [10, 11]. the combination of these features makes the matlab/simulink environment favourable among researchers from other fields than computer science (see for example [1]). three parameters were altered in an iterating process to converge modeling results to the suspended solids concentration of the treated water (top layer) and the returned sludge (bottom layer). these were as follows: non-settleable fraction (fns), the hindered zone settling parameter (rh) and flocculent zone settling parameter (rp). the beginning values were: fns = 2.28·10-3; rh = 5.76·10-4; rp = 2.86·10-3. the following values were found satisfactory for fitting measurement results: fns =1.00·10-4; rh =3.10·10-5; rp =8.00·10-2. the suspended solids concentration values for the top and bottom layer and the difference between calculated and measured results after parameter estimation are shown in table 2. the iterative process was stopped when further improvement in converging to the three sets of goal results could not be achieved. the main focus was on to receive such parameters that can used for estimation in all three cases. if the scenarios were looked at separately better fitting could have been achieved but the aim was to use one set of parameters for all three cases. table 2: result of the highlighted layers after parameter fitting top layer difference bottom layer difference g/m3 % g/m3 % 1. measurement 13.58 69.78 7242.26 -19.53 2. measurement 14.39 19.93 8412.36 6.49 3. measurement 12.02 50.26 6497.79 -1.55 the simulation with the applied parameters overestimated the suspended solids concentration in all three cases. the greatest difference was received in the first measurement scenario. the values in percentage are somewhat deceptive since the measured concentration was 8 g/m3 which a very good quality but the same could be said if it was 14 g/m3 as the simulation calculated. a difference of 6 g/m3 in case of suspended solids concentration should not be considered as a significant 162 calculation error taking into consideration the input value was three orders of magnitude greater. it has to be mentioned the the strictest limit value allows 35 g/m3 suspended solids concentration in the effluent. the difference in case of the bottom layer concentration of the first scenario (20% lower than measured) proved to be a greater error. this and the fact that in the other cases the differences were within the margin of error shows that one set of parameters cannot be applied to all cases. it also has to be mentioned that the samples taken from the end of the aerated tank to determine the suspended solids concentration entering the settler and to calculate the settling velocity were point samples while the other data, i.e. effluent and returned sludge flow ss concentration and the flow rates were provided by the plant management and were daily average values. this fact could contribute to the errors discussed above. nonetheless the inaccuracy of the takács-model is underpinned by the results shown in fig. 4. it is clearly visible that the concentrations calculated in layers 6–9 are equal to each other. this situation could not occur in reality as the concentration would increase in function of depth due to the effect of compression. the concentration in the bottom layer was higher in the model only because the gravitational settling velocity was taken zero by definition. 1 10 100 1000 10000 1 2 3 4 5 6 7 8 9 10su sp en de d  so lid s  co nc en tr at io n  (g /m 3 )   layers figure 4: calculated suspended solids concentration in different layer of the model settler conclusions as the results of the simulation show the takács-model may be adequate after parameter estimation but it must be noted that one set of parameter that is capable to describe one situation may not be appropriate for another. according to the results presented in this paper other one-dimensional models will be examined and compared to each other from the aspect of accuracy based on averaged measurement results. references 1. v. galvanauskas, r. simutis: wseas transactions on biology and biomedicine, 4, 2007, 136–144. 2. k. grijspeerdt, p. vanrolleghem, w. verstraete: water science technology, 31, 1995, 193–204. 3. m. henze, m. c. m. van loosdrecht, g. a. ekama, d. brdjanovic (eds.): biological wastewater treatment, principles, modelling and design iwa publishing (2008). 4. b. holenda: development of modelling, control and optimization tools for the activated sludge process, thesis, 2007, 85–102. 5. u. jeppson, s. diehl: water science technology, 34, 1996, 19–26. 6. u. jeppson, s. diehl: water science technology, 34, 1996, 85–92. 7. p. krebs: water science technology, 23, 1991, 1037–1046. 8. p. krebs: water science technology, 31, 1995, 181–191. 9. l. lázár: maszesz hírcsatorna, 2004, 15–18. www.maszesz.hu/hircsatorna/hcs_2004_2.pdf 10. j. c. martínez: benchmarking the star controller using matlab, msc. dipl., 2006, 101–110. 11. mathworks: simulink® 7 writing s-functions (2007) 12. takács: ülepítés in biotechnológia a környezetvédelemben, ed. p. benedek, műszaki könyvkiadó, budapest, 1990, 270–272. 13. takács, g. g. patry, d. nolasco: water research, 25, 1991, 1263–1271. 14. p. a. vesilind: water and sewage works, 115, 1968, 302–307. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 /colorconversionstrategy /cmyk 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice 40 moravcová and planeta figure 1: hilic separation of four purine bases in a bare silica monolithic capillary column. mobile phase: 95% (v/v) acn, 5% (v/v) 100 mm ammonium acetate ph=4.5; flow rate 500 nl/min; uv detection at 210 nm. peak identification: 1 – toluene (unretained compound), 2 – xanthine, 3 – caffeine, 4 – theobromine, and 5 – hypoxanthine. silica capillary 0.025 mm × 150 mm in length). the inlet section of the monolithic column was inserted through the body of the splitter into the injection valve to minimize extra-column dispersion. the outlet of the monolithic column was connected to a spectra 100 uv/vis detector (thermo separation products, waltham, massachusetts, usa) via a 0.035 mm × 120 mm-long fused silica capillary (with an optical bubble cell window inner diameter (id) 0.110 mm) using a polytetrafluoroethylene (ptfe) sleeve. uv detection was performed at 210 nm. the detector signal was processed by the chromatography station software clarity (dataapex, prague, czech republic). 3. results and discussion 3.1 chromatographic properties of the bare silica monolith the prepared bare silica monolithic capillary columns were evaluated under hilic conditions by employing a mixture containing toluene as an unretained compound and four purine bases, namely xanthine, caffeine, theobromine and hypoxanthine. the obtained chromatogram table 1: the retention factor (k), the height equivalent to the theoretical plate (h), the number of theoretical plates per meter (n ), and peak asymmetry (as) obtained on the silica monolithic column. see fig. 1 for separation conditions. compound k h/µm n as toluene – 7.4 135,185 0.67 xanthine 0.03 4.5 222,547 0.88 caffeine 0.13 5.8 172,795 1.00 theobromine 0.19 5.2 192,528 1.13 hypoxanthine 0.87 4.8 209,601 1.33 table 2: the retention factor (k), number of theoretical plates per meter (n ), and peak asymmetry (as) obtained on the mepc column. see fig. 2 for the separation conditions. compound k n as toluene – 138,955 1.0 adenosine 0.16 201,048 1.0 uridine 0.25 289,537 1.1 cytidine 0.41 244,314 0.9 amp 1.24 206,697 1.3 ump 1.66 183,465 1.5 cmp 2.50 157,760 1.4 adp 3.98 122,169 2.0 udp 5.34 112,389 2.4 cdp 7.58 81,476 2.8 atp 9.73 61,462 2.1 where all purine bases are baseline separated and have narrow symmetrical peaks is presented in fig. 1. the prepared column exhibits a high degree of separation efficiency reaching values of between 135,000 and 220,000 theoretical plates/m which corresponds to the minimum plate height within the range of 4.5–7.4 µm, as outlined in table 1. 3.2 hilic separation of nucleosides and nucleotides the commercially available methacrylate-based monomers medsa and mepc were selected for the preparation of zwitterionic stationary phases. the bare silica monolith prepared in a 0.1 mm id fused silica capillary was modified by 3-(trimethoxysilyl)propyl methacrylate and a polymer layer, with the appropriate zwitterion grafted onto it. the suitability of these columns for the isocratic hilic separation of nucleosides and nucleotides was studied. chromatograms for selected compounds obtained on medsa (fig. 2a) and mepc (fig. 2b) capillary columns are presented in fig. 2. an enhanced degree of separation was obtained on the mepc column (fig. 2b) where all 11 compounds present in a sample mixture were well separated within 25 mins. the value of peak asymmetry (as) reflects the change in the molecular shape of the analyte and increases slightly as the number of phosphate groups increases in the relevant nucleotide, as presented in table 2. on the other hand, the separation efficiency decreases along with the number of phosphate groups in the molecule of nucleotide exhibit lower values of n compared to nucleosides. a similar trend was also observed on the medsa-modified monolithic capillary column. the medsa-modified monolithic column exhibits a poorer separation efficiency than the mepc column for all nucleosides and nucleotides, even the number of theoretical plates per meter for toluene is comparable, as illustrated in table 3. the medsa column also exhibits hungarian journal of industry and chemistry silica monolithic capillary columns for hilic separations 41 figure 2: separation of nucleosides and nucleotides on prepared medsa (a), mepc (b) and bare silica (c) monolithic columns. mobile phase: 70% (v/v) acn/30% (v/v) 50 mm ammonium acetate ph = 4.5; flow rate 500 nl/min; uv detection at 210 nm. a lower retention factor for selected compounds, especially for diand triphosphates of the relevant nucleosides. this can be explained by the fact that monomers used for column modification differ in terms of their terminal groups, which affects the selectivity of the prepared stationary phases. the medsa monolithic capillary column contains negatively charged terminal sulfo groups which decrease the retention factor of negatively charged nucleotides. on the other hand, the mepc monomer provides the stationary phase with a slightly positive charge originating from the phosphorylcholine functional group which improves the retention factor of negatively charged table 3: the retention factor (k), number of theoretical plates per meter (n ), and peak asymmetry (as) obtained on the medsa column. see fig. 2 for the separation conditions. compound k n as toluene – 131,000 1.2 adenosine 0.12 135,641 1.1 uridine 0.19 129,895 1.2 cytidine 0.28 130,754 1.2 amp 0.46 101,991 1.5 ump 0.66 89,032 1.0 cmp 0.91 90,838 1.1 adp 0.97 71,440 1.7 udp 1.40 48,371 5.1 cdp 1.78 49,250 3.1 atp 1.78 59,378 3.5 nucleotides under the hilic separation conditions, e.g. the retention factor k for atp is approximately 5 times higher on the mepc column compared to the medsa column. the separation of nucleosides and nucleotides on a bare silica monolithic capillary column is shown in fig. 2c. the bare silica monolith does not exhibit a sufficient degree of selectivity to compounds of the target. all compounds are eluted from the column within 1 min and accompanied with the coelution of most compounds. 4. conclusion a silica-based monolith in a capillary format coated with zwitterionic polymer layers is a good alternative for the analysis of complex mixtures containing highly polar compounds such as nucleosides and nucleotides. in particular, the mepc stationary phase containing positively charged terminal groups enables the highly selective hilic separation of nucleosides and nucleotides to be achieved. the utilization of such a stationary phase with regard to the analysis of real samples, where usually other highly polar-interfering species originating from complex matrices are present and complicate the analysis, should be evaluated in the future. acknowledgement this research was supported by the czech science foundation (project no. 16-03749s), the ministry of the interior of the czech republic (project no. vi20172020069), and by the czech academy of sciences (institutional support rvo:68081715). references [1] nakanishi, k., soga, n.: phase separation in silica sol-gel system containing polyacrylic acid i. gel formation behavior and effect of solvent composition, j. non-cryst. solids, 1992 139 1–13 doi: 10.1016/s0022-3093(05)80800-2 46(1) pp. 39-42 (2018) 42 moravcová and planeta [2] minakuchi, h., nakanishi, k., soga, n., ishizuka, n., tanaka, n.: octadecylsilylated porous silica rods as separation media for reversed-phase liquid chromatography, anal. chem., 1996 68(19) 3498–3501 doi: 10.1021/ac960281m [3] ikegami, t., tanaka, n.: recent progress in monolithic silica columns for high-speed and highselectivity separations, annu. rev. anal. chem., 2016 9, 317–342 doi: 10.1146/annurev-anchem-071114040102 [4] moravcová, d., planeta, j., kahle, v., roth, m.: zwitterionic silica-based monolithic capillary columns for isocratic and gradient hydrophilic interaction liquid chromatography, j. chromatogr. a, 2012 1270, 178–185 doi: 10.1016/j.chroma.2012.11.005 hungarian journal of industry and chemistry introduction experimental material and instrumentation results and discussion chromatographic properties of the bare silica monolith hilic separation of nucleosides and nucleotides conclusion microsoft word b_06_farkas_r.doc hungarian journal of industrial chemistry veszprém vol. 39(2) pp. 325-330 (2011) thoughts about the clear energy a. farkas , p. faragó szent istván university, the management and business administration phd school páter károly utca 1., gödöllő, hungary e-mail: fegnisz@gmail.com the life of humanity has become faster in the 20th century. due to globalization technology has improved a great deal, every decade had its own revolutionary invention. however, globalization has its drawbacks as well, which have an impact on every field of life. these challenges must be met by humanity. one of these global challenges is the energy crisis and energy dependency. in the last decade a research involving experts was carried out which ranked the challenges humanity faces. the problems analysed involved such key fields as education or discrimination. according to the findings the highest ranked issue is energy supply, which means, according to experts, this is the most crucial problem for what we need a solution. in this research we introduce how university students look at alternative energy sources. the findings are compared to the results of two previously carried out researches. providing information about alternative energy sources is an excellent solution to change attitudes and such a change is absolutely necessary since the students of one of our most reputable universities, the corvinus university of budapest, have much less knowledge of the topic than the desireable level. making up for the shortcomings is an extremely important task as it is required for a social cooperation which is needed in order to solve humanity’s most important problem in the 21st century, the energy crisis. keywords: association, attitudes, energy sources, knowledge the aim of the survey if we want every layer of society to cooperate for success we need society to believe in alternative energy sources and acquire the basic knowledge related to it. a longitudinal study was carried out in 2006 and 2009, the topic of which was residential attitude to alternative energy sources. the two surveys touched upon basic knowledge of these sources as well. the findings of the 2006 study can be found in the 4th edition, 2006 of marketing & management (henceforth the 2006 research) , while the results of the 2009 study were published in the 1st edition, 2010 of gazdálkodás (henceforth the 2009 research). analysing these results we have come to the conclusion that it would be important to carry out a residential attitude survey in 2010 [1]. in this study we present the findings of a research whose topics match those of the aforementioned two researches. our main aim was to compare the longitudinal study to our findings, which is the reason why we put similar questions similar to the mentioned study. research methodology the residential attitude research was carried out in the form of a survey. we used the papi method. no interviewer was used in the process, the interviewees worked individually. the target group involved day students of the corvinus university of budapest who attended the 2010/2011 autumn term. the research was carried out from the 20th december to the 23rd in 2010 and also during the last five days of the year. the forms were filled in two buildings of the pest campus which belongs to the university. 296 of the 314 handed out forms were processed for the research. the students’ willingness to answer were variant, but all things considered three out of five perople agreed to fill in the forms. the sample of approximately 300 people is larger than the sample of the 2009 research. let's suppose that the population can be divided into three groups concerning their knowledge. we believe we can assume that the students of the corvinus university of budapest are better informed than the average since a proportion of these students already have a degree of higher education, which makes them more well-informed and gives them better accessibility to information. this better situation is important because if we categorise the interviewees of the 2009 attitude research based on their own information about the subject and we suppose that the distribution of the participants of this research in north hungary is uniform, we get about the same proportion of interviewees who are better informed than the average as in my research (~267 people). during the planning stage we found it important to represent the sex ratio as well as we can in the sample. we acquired the student list of the campus that contains 326 their sex distribution and we used it as a pattern to be followed during the analysis of my research. the data were collected in october, 2010, so they were relevant to our research. the data base contains the sex distribution in every faculty. this two dimensional data base made it possible for us to carry out a survey which is representative regarding qualification also since the ratios of the total population and the sample differed by a maximum of 7%. the findings of the research „association” one of the methods of attitude research is “free association” in the survey we were interested in the interviewed young adults’ associations with the term “alternative energy sources”. the 2009 research contained an association-related question and the findings were published by the authors. this question is the same as in the 2010 research, with the exception of a methodological difference. we asked the interviewees to write down the first maximum three words that come into their minds when they hear the words “alternative energy sources”. the question was open, there were no predefined answers were given, but for the sake of simplicity and better comparability we coded these answers as numeric values and not as strings in the data base. during the coding phase the “mentioned it” category was treated loosely (e.g. economization ~ cheap). we put every category that was present in the 2009 research in our database and we broadened the scale with expressions frequently mentioned by the students. the first ten variables were crucially important because they made findings of the two researches comparable. the following diagram shows the proportion of the answers the interviewees mentioned in both researches. association based analysis of alternative energy sources 0 10 20 30 40 50 60 70 80 90 100 inv es tm en t sup po rt che ap tec hno log y la nd us ag e lo ca l e ne rgy poli tic s sup po rt o f a gri cu ltu re emplo ym en t env iro nm en tal prot ecti on m en tio ne d (% ) the f indings of the 2009 research the f indings of the 2010 research figure 1: association based analysis of alternative energy sources the diagram clearly shows that the 2009 research in north hungary has different findings from ours. every category of the x-axis is a motivation factor (cheap) or an expression that makes the alternative energy source well-known (agricultural support). investment is the only category where my findings are near the 2009 data. the findings for the rest of the categories are shown in the following diagram. association based analysis of alternative energy sources 0,0 10,0 20,0 30,0 40,0 50,0 60,0 70,0 80,0 90,0 100,0 solar water wind "g reen" misc ellaneo us m en tio ne d (% ) the findings of the 2010 research figure 2: association based analysis of alternative energy sources the interviewees mentioned the words or expressions in fig. 2 apart from the categories in fig. 1. it is clear that the most frequently mentioned expressions are types of alternative energy sources. the most frequently mentioned alternative energy sources in the “miscellaneous” category are geothermic energy and biomass. the conclusion we can draw based on the above mentioned is that the interviewees associate the term with different types of sources rather than factors that promote their more widespread use. factors promoting the widespread use of alternative energy sources in order to make alternative energy sources more widespread several conditions, which we tried to analyse, have to be met. we took ten factors to be analysed, which can be categorised into three groups: factors related to the environment ● economic environment ● legal background ● political background ● financial support system factors related to the economy ● willingness to invest ● sense of responsibility ● lack of profit orientation factors related to society ● trust among members of the society ● conventional practices of the individuals ● cultural standards of the individuals we believe that the above mentioned ten factors are not enough for a complex attitude analysis, so we also analysed how the youth look at the present hungarian situation considering factors, which are important for them. both of the questions could be answered on a scale of five. in terms of importance meant that the interviewee did not consider the factor important at all while 5 meant „very important”. the more important the 327 factor was considered, the higher number the interviewee chose. the results are shown in the following chart. table 1: the opinion of university students considering a few factors and the present hungarian situation as the chart shows we managed to choose factors that most of the interviewees considered important. however, taking the deviation into account we could define that there is a big difference in opinion among the interviewees. based on the answers some factors have primary importance, while others are considered secondary. in order to make the following results more illustrative we have created a deviation diagram as well. figure 3: the attitudes of students it is clear that there is no factor in the upper right quadrant, which means that none of them are considered important or that they are not satisfied with them. it is essential to recognise the most important factors required to make renewable energy sources more widespread. with this knowledge the given factor should move from the bottom left quadrant to the upper right. it is also clear that, with the exception of a few factors, three groups of these factors move together. the interviewees have already realised the importance of the global environmentrelated factors, namely the economic environment, the financial support system and the political background, but they feel that the present situation is unsatisfactory. the legal background is considered an exception in this group since most of the interviewees found it satisfactory. the enterprise-related factors are in the bottom right, while the environment-related factors are in the bottom left quadrant. the only factor that the interviewees have not found important, is the companies’ lack of profit orientation. the less positive image we got was in the case of society-related factors – the only factor the interviewees found important was the sense of responsibility. however it is possible that many considered this factor to belong to the group of enterprise-related factors and that is the reason why they attached great importance to it. the purely society-related factors are presently not considered important, although they are not negligible since both enterprises and the state consist of individuals. the demographic variables used during the analysis had no significant effect on the results. there was only one difference in terms of classification based on sex and location. with respect to sex, men generally place politics into the bottom right quadrant while women place it into the bottom left. the position of the legal background in the diagram is much more diverse in the case of men – it falls closer to the bottom left quadrant. in terms of location the greatest difference was caused by the fact that the “financial support system” factor was close to the optimal top right quadrant in the case of countryside residents. however, budapest residents are not so optimistic about presently available financial support. in terms of “legal background” the answers of budapest residents are much more diverse – the results based on the answers are close to every quadrant, while in the case of countryside residents the results fall into the upper left quadrant. all things considered we’ve come to the conclusion that according to the students’ opinion the state is the only macro-economic actor that promotes the spread of alternative energy sources. the administration tries to discourage the private sector (households and enterprises) from using fossil energy sources. the enterprises are adapting business characteristics that support the spread of alternative energy sources, but this change of attitude is yet to come in households. setting up plants producing alternative energy sources in our research we were also interested in the attitude of corvinus university students towards the setting up a plant that produces alternative energy sources. 70% of the respondents thought that setting up such a plant would be beneficial both from a financial and an environmental point of view. another quarter of the respondents believed that their settlement would benefit either financially or environmentally from the setting up of such a plant. a mere five percent found the setting-up indifferent or harmful. based on the distribution of the answers we can claim that the interviewees find it beneficial to set up plants using renewable energy sources. however, a positive attitude is not enough to carry out such a project since its operation is expensive and it requires a lot of work. as a consequence it was necessary to put the following question concerning attitudes. the question concerned whether the interviewee would support the setting up of a plant producing alternative energy. almost fifty percent of the respondents would support the setting up of a plant only if it required no contribution 328 from them. almost 70% of these students admitted the financial and environmental importance of such a plant in one of the previous questions. 30% of the respondents recognise the importance of the plant but they are not willing or able to contribute either by offering labour or financial support. one out of four students would support the setting up of the plant with a further 25% contributing their own work. only 2% declared their unwillingness to contribute to the setting up in any way. comparing the two researches we concluded that the respondents of the 2006 research had more negative attitudes since the rate of those who didn't support the setting up of the plant was higher. degree of support for the setting up of a local plant producing alternative energy 62 5.6 19.9 23.8 1.0 33.8 33.1 38.2 0 10 20 30 40 50 60 70 no, i w ould not supoort it. yes, f inancially. yes, by ow n labour. yes, unless it requires financial contribution. mentioned (%) the finding of the 2010 research the finding of the 2006 research figure 4: degree of setting up of a local plant producing alternative energy fossil nuclear renewable energy sources beside an attitude analysis the well-informedness of the respondents is also an important factor. we asked the students of the pest campus what they thought of the proportion of nuclear, fossil and renewable energy in hungary in 2009. with the evaluation of the answers we took into account the publication called ksh statisztikai tükör (the statistical mirror) [2] and a register provided by éva richter (the information manager of energia központ nonprofit kft.). [3] based on the two sources we came to the conclusion that the mentioned three types are in the following distribution: fossil energy sources: ~80%, nuclear energy sources: ~14% and renewable energy sources: ~6%. of all the 296 interviewed students only a single one knew, or guessed correctly, the correct distribution. the average of the estimations was 52.15% with fossil energy sources, 36.66% with nuclear energy sources, while 11.21% with renewable energy sources. this means that the respondents greatly underestimated the proportion of traditional energy sources while “overpositioning” nuclear energy sources. all things considered we believe that this question has properly shown the students' lack of information even though we supposed that university students are more well-informed than the average. knowledge of alternative energy sources during the survey we were also interested in the wellinformedness of students regarding different types of alternative energy sources. these questions in my research regarding well-informedness were also present in the 2006 and 2009 research. we'll compare the findings published in 2010 to the findings of our results. we asked the respondents to name alternative energy sources that they had heard of. no alternatives were provided here, it was an open question. when evaluating the answers we only took those answers into account which were present in the 2009 research in order to ensure comparability. the following diagram shows the results of the mentioned categories in the 2009 and our research. general knowledge of energy sources 10.0 15.4 25.3 36.638.0 50.5 55.3 61.9 69.5 92.8 96.798.4 0.3 1.4 2.4 0.3 6.4 33.8 4.7 43.9 5.1 68.9 85.1 86.8 0 20 40 60 80 100 120 sola r p ow er wind po wer hidrop ower biod iese l geo the rm al en erg y biog as biom as s bioe tan ol coa l-b ric k ene rgy gr as s ene rgy fo res t pho toe lec tro nic en erg y m en tio ne d (% ) the finding of the 2009 research the finding of the 2010 research figure 5: general knowledge of energy sources the results of the two researches clearly differ. the rate of references in the case of all alternative energy sources was higher in the 2009 research. the smallest difference can be seen in the case of solar power and wind power (~10–15%). with regards to biomass and geothermic energy this difference is medium (~30–35%). the energy sources we have not put into any of these groups show great difference in terms of how wellknown they are. the findings of the two researches differ so much that the t-test of the two samples showed significant difference in both cases, which means that the difference is not coincidental. we also performed an analysis with using several divisions (male-female, secondary qualification higher education qualification, pest-countryside), but found no significant difference. the other question regarding knowledge aims to show how well the respondents know the respective energy sources. during the research we also wanted to know those energy sources that the students have some basic knowledge of. since the previous question was an open question, the respondents could only choose from the answers they had given to the previous question. the following diagram shows the rate of how well the respondents knew the energy sources during the 2009 and the 2010 survey. 329 percentage of people with general knowledge of alternative energy sources 89.7 82.5 71.7 35.6 36.8 21.6 21.1 15.5 20.0 15.8 8.7 4.8 57.4 51.0 37.5 1.7 20.9 1.4 9.5 1.4 0.0 0.3 0.3 0.3 0 10 20 30 40 50 60 70 80 90 100 sola r p ow er wind po wer hidrop ower biod iese l geo the rm al en erg y biog as biom as s bioe tan ol coa l-b ric k ene rgy gr as s ene rgy fo res t pho toe lec tro nic en erg y m en tio ne d (% ) the finding of the 2009 research the finding of the 2010 research figure 6: percentage of people with general knowledge of alternative energy sources the diagram above shows similarly big differences. the most extreme figure is represented by the coalbrick, where the difference between the two studies is 100%. the smallest difference -30% is represented by those energy sources which showed similar results in the previous diagram. conclusions during the research the main aim was to give a comprehensive overview of the knowledge and attitude of budapest corvinus university students concerning alternative energy sources. the findings of researches show significant differences. the 2006 and 2009 research assumes a higher knowledge and more positive attitude. in terms of attitude fewer than expected respondents claimed that they would only support the setting up of a plant if they didn't have to contribute but this answer was still the most common. we believe that, during the year that passed between the two researches, the respondents' attitude could have changed enough to explain most of the differences between the findings. based on our research however, the attitude towards alternative energy sources is rather neutral than positive. this claim is supported by those two questions that showed that the respondents recognise the advantages of such plants but they are unwilling to support its setting up either financially or by offering labour. according to the students' views the spread of alternative energy sources nowadays is supported by the state. the social factors are the furthest behind, which leads me to the conclusion that society is not yet motivated enough to promote the spread of alternative energy sources and not open enough to tolerate the attitude, which required for them. if we accept the condition that university students are more informed than the average, a question arises: is it possible that an information-wise homogenous group, the students of corvinus university, do not reach the level of well-informed group, that the information-wise heterogeneous residents of north hungary do? another question is: is such a difference in knowledge between regions plausible? possible explanations to the differences this research has shown that the findings published by domán fodor tamus and our research differ greatly. there is more than one reason for these differences. one of the most important differences is the total population of the two researches, which might have caused this contrast. the 2009 and the 2006 research samples were taken from the residents of seven different counties (heves, jász-nagykun-szolnok, borsod-abaújzemplén, nógrád, pest, szabolcs-szatmár-bereg and hajdú-bihar counties) while in our research the samples were taken from the relatively small group of students attending the corvinus university of budapest. another reason might be the fact that the authors of the 2009 research interviewed 0.02% of the total population [4, 5], while in our research 296 people represented 10 000, which means that we interviewed a greater proportion of the total population. the fact that neither of the samples were bigger than 1000 people might be another reason for the differences. the size of the sample is important because in smaller samples people with more radical views get more emphasis (outliers) than in samples of over 1000 people. another source of the contrasts can drive from differences in methodology. according to the authors the interviews were oral and took place in the homes of the respondents, while in our research the interview was written and voluntary at corvinus university. the authors of the 2009 research did not indicate the methodology used by the research assistants, which can also explain some of the differences. if we read the questions related to association or knowledge the explanation is even more relevant. it is assumable that fewer people would mention energy sources when open questions are used than with predefined answers. if the 2009 research had used open questions we can't explain the differences by a difference in methodology. we have mentioned the homogeneity of the respondents as the third option. it is possible that a proportion of corvinus university students are not more well-informed than the average or interviewees with higher knowledge were overrepresented in the 2009 research. both explanation can be valid, they do not exclude each other. finally, the most obvious cause of the difference can be caused by the fact that the contrasts regarding attitudes and knowledge are real. in this case we have to draw the conclusion that a part of the higher layer of our future society do not have as much knowledge concerning alternative energy sources as an average resident of north hungary. 330 references 1. sz. domán, m. fodor, a. tamus: alternatív energiaforrások lakossági megítélésében bekövetkezett változások, gazdálkodás, 54(1), (2010), 92–98 2. központi statisztikai hivatal: fosszilis és nem fosszilis energiaforrások statisztikai tükör, 3(107), (2009): http://portal.ksh.hu/pls/ksh/docs/hun/xftp/gyor/jel/je l309052.pdf – data collected: 30/12/2010 3. energia központ nonprofit kft: energiagazdálkodási statisztikai évkönyv 2009, (2010) 4. l. dinya, sz. domán, m. fodor, a. tamus: alternatív energiaforrások lakossági megítélése, marketing & menedzsment 40(4), (2006), 49–54 5. központi statisztikai hivatal: a lakónépesség területi egységek és főbb korcsoportok szerint, 1990, 2009. january 1 (2010): http://portal.ksh.hu/pls/ksh/docs/hun/xtabla/oregedes/ tablto09_04.html – data collected: 05/01/2011 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 /colorconversionstrategy /cmyk /dothumbnails false 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word a_32_feher_r.doc hungarian journal of industrial chemistry veszprém vol. 39(1) pp. 63-66 (2011) oligomerization of izobutene in the presence of ionic liquid – based catalysts c. fehér1, r. skoda-földes1 , e. kriván2, j. hancsók2 1university of pannonia, institute of chemistry, department of organic chemistry h-8201 veszprém, p. o. box 158, hungary e-mail: skodane@almos.uni-pannon.hu 2university of pannonia, department of mol hydrocarbon and coal processing h-8201 veszprém, p. o. box 158, hungary in the petrochemical industry, the c4 stream including isobutene is an important raw material that can be upgraded. oligomerization of isobutene is a very promising reaction, as the hydrogenation products of dimers and trimers, obtained from isobutene, can be used as gasoline and diesel additives, respectively. in the present paper, our results concerning the use of brønsted acidic ionic liquids as oligomerization catalysts are presented. the ionic liquids were supported on silica. most of the solid catalysts were reused several times without loss of activity. by the proper choice of the ionic liquid and reaction conditions, good selectivity towards either c8 or c12+ products could be achieved. keywords: oligomerization, isobutene, ionic liquid introduction the oligomerization of light olefins is an important alternative for the production of higher molecular weight hydrocarbon mixtures useful as fuels (e.g. gasoline or diesel). both brønsted and lewis acids have been used as oligomerization catalysts in either homogeneous (h2so4, organometallic complexes, etc.) or heterogeneous (mixed oxides, zeolites, clays, ion exchange resins etc.) phase. [1] the main challenges in the design of catalysts for this reaction are focused to reach high conversion and high selectivity. consequently, several solid acid catalysts of different types have been developed for the oligomerization of lower alkenes, such as isobutene. [2] at the same time, ni-based catalysts containing phosphine ligands can be used efficiently in the homogeneous phase in the presence of various additives. [3, 4] however, a great drawback of homogeneous catalytic reactions is the problem of catalyst recovery and recycling. the use of a two-phase solvent system, together with a transition metal complex, is an attractive alternative, as it enables catalyst separation and reuse. this methodology was found to be very efficient in alkene oligomerization by cationic nickel complexes in chloroaluminate [5-8] or hexafluorophosphate [9] ionic liquids as solvents. chloroaluminate ionic liquids with lewis acidic character were shown to catalyze oligomerization themselves, without the addition of transition metal complexes or salts. [10] these catalysts were applied in the oligomerization of linear 1-olefins. [11] imidazolium ionic liquids with so3h functionalized side chains were also found to be excellent and reusable catalysts in oligomerization of various alkenes. [12] generally, ionic liquids (ils) have gained increasing attention with multiple applications in synthesis and catalysis. [13] despite their advantages, there are also some drawbacks, including the difficulties in product purification or il recycling and the problems for application in fixed bed reactors. also, biphasic ionic liquid-organic systems require large amounts of the expensive ils, which hinders industrial applications. these difficulties can be overcome by the use of supported ionic liquid phases (silps) prepared by the immobilization of ionic liquids on solid supports. [14] based on these findings, we decided to explore the possibility of the use of silica-supported so3hfunctionalised ils as catalysts in the oligomerization of isobutene. in this paper, we report on our results concerning the effects of the changes in the reaction conditions on the outcome of the oligomerization reaction. experimental materials the ionic liquids (il-1 — il-4) were synthesized by methods analogous to literature procedures. [15, 16] the supported catalysts (silp-1 — silp-4) were obtained by reacting the ionic liquid (il-1, il-2, il-3 or il-4) (10 mmol) and silica gel (kieselgel 60 (0.040–0.063 mm), pre-heated at 250 °c for 5 h) (10 g) in 25 ml meoh at 64 room temperature for 24 h. meoh was removed in vacuo and the catalyst was dried at 60 °c in vacuo for 1 h. oligomerization experiments the reactions were carried out in an autoclave under argon. the autoclave was cooled to -15 °c and isobutene (5 ml, 57.5 mmol) was charged into the reactor, which contained the catalyst (10 mmol of il-1 or il-2 or 1 g of the supported ionic liquids silp-1 — silp-4). the autoclave was pressurised with argon (22 bar, room temperature). in a typical reaction the mixture was stirred at 100 °c for 5 h. the autoclave was cooled to -15 °c, the organic phase was separated and analysed by gas chromatography. the silp catalysts were washed with pentane (3x5 ml), dried in vacuo and reused. analytical methods reaction mixtures were analyzed by gas chromatography using a hewlett packard 4890d instrument equipped with a fid detector and a 30 m hp-1 column. gc-ms measurements were carried out with a hewlett packard 5971a gc-msd. results and discussion four brønsted acidic ionic liquids (il-1 — il-4) were prepared and were immobilized on silica gel by adsorption to give catalysts silp-1 — silp-4 (scheme 1). n nr so3 n nr so3h cf3so3h cf3so3 -150 oc, 5 h il-1 r= ch3 il-2 r= (ch2)3ch3 n nr so3h hso4 il-3 r= ch3 il-4 r= (ch2)3ch3 h2so4 150 oc, 5 h silp-1 silp-2 silica meoh rt, 24 h silp-3 silp-4 silica meoh rt, 24 h scheme 1: synthesis of ionic liquids il-1 and il-2 and supported ionic liquids silp-1 — silp-4 to compare the activity and selectivity of immobilized and non-immobilized ionic liquids, oligomerization was carried out first in il-1 and il-2 under the standard conditions (100 °c, 5 h). in these reactions, the isobutene/catalyst ratio was 57.5/10. almost total conversion was obtained in both cases and the ratio of c12 products was higher in il-2 than in il-1 (table 1, entries 1, 2). this phenomenon can be explained by the higher solubility of c8 in the ionic liquid with the longer side chain. similar change in the selectivity of oligomerization with increasing alkyl chain length of the ionic liquid catalysts had been observed by deng et al. before [12]. the supported ionic liquid catalysts (silp-1 — silp-4) were also found to be active in the oligomerization (table 1, entries 3-6). immobilization of the ionic liquids resulted in a change in the selectivity of the reaction (compare entries 1, 3 and 2, 4). in the presence of il-1, the dimers were obtained as the main products (entry 1). at the same time, good c12+ selectivity was observed using the immobilized version of the same catalyst (silp-1, entry 3). on the contrary, immobilization of il-2 led to an increase in c8 selectivity (entry 4), compared to the results obtained with il-2 (entry 2). it should be mentioned, that in the case of the reactions carried out with the immobilized catalysts, the substrate/ionic liquid ratio was much lower (57.5/1 instead of 57.5/10). despite this, the conversion of isobutene was similar, or even a little higher under the same reaction conditions. table 1: oligomerization of isobutene in the presence of ionic liquid based catalystsa entry catalyst conv. [%]b ratio of products [%]b c8 c12 c16 c20 1 il-1 98 75 24 1 2 il-2 99 33 60 7 3 silp-1 100 16 54 29 1 4 silp-2 100 54 35 10 1 5 silp-3 85 83 17 6 silp-4 92 82 18 a reaction conditions:100 °c, 5 h b determined by gc the catalysts containing ionic liquids with hydrogensulfate anion showed the best selectivity toward the dimers but their activity was found to be somewhat lower (entries 5, 6) compared to the other two supported catalysts. the possibility of the reuse of the supported catalysts was also investigated. silp-1 (fig. 1) and silp-2 (fig. 2) 65 were reused several times without loss of activity or considerable change in selectivity. 0 10 20 30 40 50 60 70 80 90 100 run 1 run 2 run 3 run 4 run 5 run 6 run 7 run 8 % conv. c8 c12 c16 c20 figure 1: oligomerization of isobutene in the presence of silp-1 (100 °c, 5 h) 0 10 20 30 40 50 60 70 80 90 100 run 1 run 2 run 3 run 4 run 5 run 6 run 7 run 8 % conv. c8 c12 c16 c20 figure 2: oligomerization of isobutene in the presence of silp-2 (100 °c, 5 h) silp-1 showed good selectivity toward c12+c16 products, resulting in oligomeric mixtures with c12 as the main components (fig. 1). on the contrary, in the presence of silp-2, dimers were obtained in yields higher than 50 % and the ratio of c16 products was only around 10 % (fig. 2). the supported catalysts obtained with ils with hydrogensulfate anion (silp-3 and silp-4) showed lower activity than silp-1 or silp-2, similarly to the non-immobilized versions of these catalysts (see table 1). besides, a great drop of activity was observed even in the second run when silp-3 or silp-4 was recycled (fig. 3). that means that in spite of the excellent selectivity that can be achieved with these catalysts, their use is unfavourable from an economic point of view. the effect of the change in the temperature on the outcome of oligomerization was explored with supported catalysts silp-1 (fig. 4) and silp-2 (fig. 5). 0 10 20 30 40 50 60 70 80 90 100 run 1 run 2 run 1 run 2 run 3 % conv. c8 c12 c16 (a) (b) figure 3: oligomerization of isobutene in the presence of (a) silp-3 and (b) silp-4 (100 °c, 5 h) as it was expected, an increase in the temperature led to an increase in the conversion. with silp-1, total conversion of isobutene (in 5 h) was observed only at 100 °c or above, but in the presence of silp-2, the conversion was higher than 90 % even at 60 °c. an increase in the temperature led to a decrease in the c8 selectivity of the reaction with both of the catalysts. the best selectivity for c8 and c12 products can be reached by using silp-2 at 60 °c and silp-1 at 100 °c, respectively. 0 10 20 30 40 50 60 70 80 90 100 60°c 80°c 100°c 120°c r. temp. % conv . c8 c12 c16 c20 figure 4: oligomerization of isobutene in the presence of silp-1 at different temperatures 0 10 20 30 40 50 60 70 80 90 100 60°c 80°c 100°c 120°c r. temp. % conv. c8 c12 c16 c20 figure 5: oligomerization of isobutene in the presence of silp-2 at different temperatures 66 conclusions supported brønsted acidic ionic liquids were proved to be efficient catalysts in isobutene oligomerizaton. the solid catalysts are easier to handle than the ionic liquids themselves, so separation and recovery of even small amounts of catalysts are simple. although immobilization of ionic liquids affects slightly the selectivity of oligomerization, the catalysts with the trifluoromethanesulfonate anion can efficiently be used and recycled. by the proper choice of the ionic liquid and reaction temperature, either c8 or c12+ products can be obtained with good selectivity. these results clearly show that this type of supported catalysts can be applied flexibly to follow the changing demands of fuel production. acknowledgment the authors thank tamop-4.2.1/b-09/1/konv-20100003 ( mobility and environment: research in the fields of motor vehicle industry, energetics and environment in the centraland western-transdanubian regions of hungary.) for the financial support. the project is supported 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice hungarian journal of industry and chemistry vol. 46(2) pp. 73–77 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0022 effect of algae treatment on stevia rebaudiana growth réka czinkóczky1 and áron németh *1 1department of applied biotechnology and food science, budapest university of technology and economics, műegyetem rkp. 3, budapest, 1111, hungary stevia rebaudiana bertoni is a small, perennial and herbaceous shrub which originated in paraguay (south america). stevia rebaudiana is not native to hungary but its cultivation and consumption may have many benefits, e.g. to reduce blood pressure and as a non-caloric sweetener. steviol glycosides, mostly stevioside and rebaudioside a, located in the leaves are about 200–300 times sweeter than sucrose. s. rebaudina cultivation in hungary would offer many opportunities in healthcare and the sweet industry. with the aim of achieving good green biomass yields, the effect of macc4 autotrophic and heterotrophic algae strains was investigated by testing them as both leaf and soil fertilizers in the soil of stevia rebaudiana seedlings and in its aqueous rooting experiments. in one of the later set up, the formation of roots was improved by combining the application of red light and algae treatment. keywords: stevia rebaudiana, steviol glycosides, algae treatment, chlorella vulgaris 1. introduction stevia rebaudiana bertoni (fig. 1) is a perennial shrub and a member of the asteraceae family. stevia originated in brazil and paraguay (south america). this plant is widely used by the guaraní indians of south america to sweeten tea [1, 2]. s. rebaudiana was botanically classified in 1899 by moisés santiago bertoni, who described it in more detail. initially called eupatorium rebaudianum, its name changed to s. rebaudiana (bertoni) in 1905. the sweet principle was first isolated in 1909 and only in 1931 was the extract purified to produce stevioside, its chemical structure was established in 1952 as a diterpene glycoside. stevioside (fig. 2) is described as a glycoside comprised of three glucose molecules attached to an aglycone referred to as steviol moiety [3, 4]. s. rebaudiana also has other names like sweet leaf, sweet herb of paraguay, sweet honey leaf and candyleaf. the sweetening components of the plant, i.e. steviol glycosides, were described in 1931 [5]. s. rebaudiana and its extracts have been used for a long time in asia, south america and several countries in europe. s. rebaudiana leaves and highly refined extracts are used as low-calorie sweeteners in korea, japan and brazil [6]. stevioside, one of the steviol glycosides, has been reported to lower the postprandial blood glucose concentration of type ii diabetics and the blood pressure of mildly hypertensive patients [7]. s. rebaudiana is used by diabetics as a diet therapy, and its extracts exhibit pharmacological effects such as anti-insulin resistance, the promotion of insulin secretion, as well as antihypertensive and anti-obesity proper*correspondence: naron@f-labor.mkt.bme.hu figure 1: stevia rebaudiana ties [8]. nowadays, the utilization of alternative sweeteners has become a viable option for producing lowor zero-calorie foods due to the development of the healthy food industry which intends to reduce the sucrose content of food products by the total or partial replacement of sucrose with alternative sweeteners. steviol glycosides are mainly produced in the leaves of the plant. the major components are steviol, stevioside and rebaudioside a. the typical proportions of the major components of the leaves are stevioside (5–10 % of the mailto:naron@f-labor.mkt.bme.hu 74 czinkóczky and németh figure 2: structure of stevioside total dry weight of the leaves), reb a (2–4 %), reb c (1–2 %) and dulcoside a (0.4–0.7 %) [9]. the leaves ofs. rebaudiana are sessile, 3-4 cm in length, elongate-lanceolate or spatulate in shape with blunt-tipped laminae in addition to serrated margins from the middle to the tip and on the entire underside. the upper surface of the leaves is slightly glandular-pubescent. the stem is weak-pubescent at its base and woody. the rhizome has slightly branching roots. flowers are composite surrounded by an involucre of epicalyx. the capitula are in loose, irregular, sympodial cymes. the flowers (fig. 3) are white and pentamerous [5]. this plant can grow up to 1 m tall if it is exposed to sufficient light and receives enough nutrients as well as water. therefore, it is worth considering the examination of crop production due to its wide range of applications. chlorella vulgaris is a eukaryotic unicellular green algae which is one of the fastest growing microalgae. this algae can be used in biodiesel processing following cell cultivation. the economic feasibility of algal biodiesel production highly depends on the biomass productivity and lipid yield [10]. green algae (like chlorella vulgaris) may produce phytohormones which can influence the growth of plants. odgerel et al. used chlorella vulgaris as a biofertilizer on barley and wheat. faheed et al. used c. vulgaris as a biofertilizer on lettuce plants. these results showed that algae treatment yields longer roots and shoots of wheat compared to control [11, 12]. the aim of our work was to test chlorella vulgaris figure 3: stevia rebaudiana flowers figure 4: plant cells macc4 autotrophic and heterotrophic cultures of microalgae to enhance the roots, biomass and stems of s. rebaudiana. 2. materials and methods in our work, the effects of hormones produced by algae on s. rebaudiana were tested. phytohormones may improve its development. the plants were in a phytotron (25±1 ◦c) where they received 16 hours of light per day. each plant was placed in a 4.5 cm × 5.0 cm planting cell (fig. 4). in table 1, the blue background denotes the rootgrowing experiments where seedlings were placed into water as a control and into an aqueous algal suspension for trials. furthermore, the green background indicates the modeling of experiments in land: while seedlings in samples of commercial potting soil were sprinkled with water as a control and an algal suspension as to test changes in biomass, the growth of roots and stems was recorded in terms of weight and length, respectively. cells were replicated three times for each setting. as algal suspensions, chlorella vulgaris macc4 heterotrophic and autotrophic cultivated strains were used. the cell suspension was diluted by up to 300 times with water to achieve a concentration of 5 × 107 colonyforming units (cfu)/ml. from this solution, 2 ml was sprinkled onto each cell every 2 to 3 days. the duration of the experiments was about five weeks. at the end of the fifth week (fig. 5), the mass of the total green biomass and the length of the stem and roots in both water and soil were measured. for the results a statistical evaluation was conducted with minitab 17 statistical software. the statistical analysis consisted of a two-sample table 1: planting cells (h: heterotrophic, a: autotrophic, c: control, green: seedlings in soil, blue: seedlings in water, white: empty cells) hungarian journal of industry and chemistry effect of algae treatment on stevia rebaudiana growth 75 figure 5: s. rebaudiana plants at the end of the experiment t-test where the algae-treatment samples were compared against the controls and each other. 3. results and discussion the two-sample t-test in terms of the growth in biomass observed in the seedlings planted in soil is presented in fig. 6. the p-value shows whether or not the treatment had an effect on biomass growth. the comparison between heterotrophic algae treatment and the control samples is presented in fig. 6a. the p-value was 0.653, i.e. no significant difference exists between the two groups of results that were examined. a figure 6: box plots of two-sample t-tests: biomass growth in soil (a: heterotrophic algae vs. control, b: heterotrophic vs. autotrophic algae, c: autotrophic algae vs. control). iiuv()luv comparison between the heterotrophic and autrotrophic algae cultures is presented in fig. 6b. the p-value was 0.511, i.e. no significant difference exists between them. a contrast is made between the autotrophic algae treatment and the control samples in fig. 6c. the p-value was 0.316, i.e. no significant difference exists between these groups either. from the results it can be seen that algae treatment does not have a positive effect on the growth of the green biomass of s. rebaudiana with regard to model experiments in soil. the two-sample t-tests in terms of stem growth are presented in fig. 7. a comparison between the heterotrophic algae treatment and the control samples is presented in fig. 7a. the p-value was 0.642, i.e. no significant difference exists between them. the results of heterotrophic versus autotrophic algae treatment cultures are shown in fig. 7b. the p-value was 0.055, i.e. once more no significant difference exists between them. a contrast between autotrophic algae treatment and control samples is presented in fig. 7c. the p-value was 0.147, i.e. yet again no significant difference exists between both groups. from these results it can be concluded that no significant improvements were observed in terms of the yield of plant biomass of algae treatments applied to seedlings planted in soil. however, the autotrophic alfigure 7: box plots of two-sample t-tests in terms of stem growth in soil: (a: heterotrophic algae vs. control, b: heterotrophic vs. autotrophic algae, c: autotrophic algae vs. control) 46(2) pp. 73–77 (2018) 76 czinkóczky and németh figure 8: box plots of two-sample t-tests in terms of root growth in land (a: heterotrophic algae vs. control, b: heterotrophic vs. autotrophic algae, c: autotrophic algae vs. control) gae treatment seemed to be the most significant which suggests a weak positive effect in terms of the plant development of s. rebaudiana in soil may occur. the two-sample t-tests in terms of the root growth observed in soil are presented in fig.8. a comparison between heterotrophic algae treatment and the control samples is presented in fig. 8a. the p-value was 0.503, i.e. no significant difference exists between them. a contrast between the heterotrophic and autotrophic algae treatments is shown in fig. 8b. the p-value was 0.357, i.e. no significant difference exists between them either. the difference between autotrophic algae treatment and the control samples is presented in fig. 8c. the p-value was 0.811, i.e. once again no significant difference exists between the examined two groups of results. these results suggest (without significance) that heterotrophic algae cultures maybe preferred for the root development of s. rebaudiana seedlings in soil. the two-sample t-tests in terms of the root growth in water are presented in fig. 9. a comparison between heterotrophic algae treatment and the control samples is shown in fig. 9a. the p-value was 0.012, i.e. a significant difference exists between them and heterotrophic treatment is beneficial. a contrast between heterotrophic figure 9: box plots of two-sample t-tests in terms of root growth in water (a: heterotrophic algae vs. control, b: heterotrophic vs. autotrophic algae, c: autotrophic algae vs. control) and autotrophic algae treatments is presented in fig. 9b. the p-value was 0.003, i.e. a significant difference exists between them and heterotrophic algae treatment is also beneficial. the difference between autotrophic algae treatment and the control samples is shown in fig. 9c. the p-value was 0.128, i.e. no significant difference exists between them. from these results it can be concluded that while heterotrophic algae treatment was found to be significantly advantageous for the root development of s. rebaudiana in water, the effect of autotrophic cultures did not significantly differ from that of the control samples. in soil a lateral-like root was formed, while in water the formation of a thicker root was observed. just like when the root fibers were grown in land, not all the soil could be washed out without damaging the root. therefore, a comparison between the biomass yield in water and soil was not conducted. 4. conclusion the following conclusions can be drawn from the experiments with regard to the growth of s. rebaudiana. neither heterotrophic nor autotrophic algae treatments had any positive effect on the biomass growth in soil. by examining the stem growth, the autotrophic culture seemed hungarian journal of industry and chemistry effect of algae treatment on stevia rebaudiana growth 77 to have a slightly positive effect but was not significant. in terms of root growth in soil, none of the treatments had any significant effect, but heterotrophic cultures seemed to have a slightly positive effect. root growth in water supplemented regularly with heterotrophic algae cultures had a significant positive effect in comparison to the other treatments. probably the positive effect of algae treatment in the case of the experiments on s. rebaudiana seedlings in water can be attributed to the fact that the applied algae provided complex nutrients unlike the pure tap water, while in the case of the experiments on seedlings in soil the additional nutrients provided by the algae treatment was practically negligible in comparison to those offered by the soil. therefore, further studies will be done to separate the effect of algae as a provider of nutrients and as a source of plant hormones. further studies would be necessary to prove whether changes in algae cell concentrations have an effect on the growth of stevia rebaudiana or not, i.e. in soil, experiments on biomass growth should be applied differently in diluted algae suspensions with and without any additional nitrogen sources. moreover, different types of light, e.g. red, blue and white, will be tested. these additional plant studies will be implemented using larger numbers of samples. references [1] geuns, j. m. c.: stevioside. phytochemistry, 2003 64(5), 913–921 doi: 10.1016/s0031-9422(03)00426-6 [2] kaur, g.; pandhair, v.; cheema, g. s.: extraction and characterization of steviol glycosides from stevia rebaudiana bertoni leaves. j. med. plants. stud., 2014 2(5), 41–45 issn: 2320-3862 [3] lemus-mondaca, r.; vega-gálvez, a.; zura-bravo, l.; kong, a. h.: stevia rebaudiana bertoni, source of a high-potency natural sweetener: a comprehensive review on the biochemical, nutritional and functional aspects. food chem., 2012 132(3) 1121– 1132 doi: 10.1016/j.foodchem.2011.11.140 [4] barriocanal, l. a.; palacios, m.; benitez, g.; benitez, s.; jimenez, j. t.; jimenez, n.; rojas, v.: apparent lack of pharmacological effect of steviol glycosides used as sweeteners in humans. a pilot study of repeated exposures in some normotensive and hypotensive individuals and in type 1 and type 2 diabetics. regul. toxicol. pharmacol., 2008 51(1), 37–41 doi: 10.1016/j.yrtph.2008.02.006 [5] madan, s.; ahmad, s.; singh, g. n.; kohli, k.; kumar, y.; singh, r.; garg, m.: stevia rebaudiana (bert.) bertoni – a review. indian j. nat. prod. resour., 2010 1(3), 267–286 isbn: 3216321509, issn: 09760504 [6] kinghorn, a. d. (ed.): stevia the genus stevia in: hardman, r. (ed.) medicinal and aromatic plants – industrial profiles series vol. 19, crc press, taylor & francis, london uk, 2003. isbn: 0-203-16594-2 [7] gregersen, s.; jeppesen, p. b.; holst, j. j.; hermansen, k.: antihyperglycemic effects of stevioside in type 2 diabetic subjects. metabolism, 2004 53(1), 73–76 doi: 10.1016/j.metabol.2003.07.013 [8] dyrskog, s. e. u.; jeppesen, p. b.; colombo, m.; abudula, r.; hermansen, k: preventive effects of a soy-based diet supplemented with stevioside on the development of the metabolic syndrome and type 2 diabetes in zucker diabetic fatty rats. metabolism, 2005 54(9), 1181–1188 doi: 10.1016/j.metabol.2005.03.026 [9] puri, m.; sharma, d.; tiwari, a. k.: downstream processing of stevioside and its potential applications. biotechnol. adv., 2011 29(6), 781–791 doi: 10.1016/j.biotechadv.2011.06.006 [10] kim, j.; lee, j-y.: growth kinetic study of chlorella vulgaris (august 2016), pp. 2–7. 2009. isbn: 9781615679140 [11] odgerel, b.; tserendulam, d.: effect of chlorella as a biofertilizer on germination of wheat and barley grains proc. mong. acad. sci., 2017 56(4) 26 doi: 10.5564/pmas.v56i4.839 [12] faheed, f. a.: effect of chlorella vulgaris as biofertilizer on growth parameters and metabolic aspects of lettuce plant. j. agri. soc. sci., 2008 4(4) 165-169 issn: 1813-2235 46(2) pp. 73–77 (2018) https://doi.org/10.1016/s0031-9422(03)00426-6 https://doi.org/10.1016/j.foodchem.2011.11.140 https://doi.org/10.1016/j.yrtph.2008.02.006 https://doi.org/10.1016/j.metabol.2003.07.013 https://doi.org/10.1016/j.metabol.2005.03.026 https://doi.org/10.1016/j.metabol.2005.03.026 https://doi.org/10.1016/j.biotechadv.2011.06.006 https://doi.org/10.1016/j.biotechadv.2011.06.006 https://doi.org/10.5564/pmas.v56i4.839 https://doi.org/10.5564/pmas.v56i4.839 introduction materials and methods results and discussion conclusion microsoft word a_38_marczi_r.doc hungarian journal of industrial chemistry veszprém vol. 39(1) pp. 133-139 (2011) diagnostic investigations based on the petri net model generated from the process information b. márczi1, m. gerzson1 , a. leitold2 1university of pannonia, department of electrical engineering and information systems, veszprém, hungary e-mail: gerzson@almos.vein.hu 2university of pannonia, department of mathematics, veszprém, hungary a novel structure comparison procedure for discrete event systems described by petri nets are proposed in this paper for model-based diagnosis that utilizes the graph distance metric method. the model of the investigated system was defined in hierarchical colored cp-net form. both normal reference model describing the faultless operation and the extended model containing the different faults were developed. for the fault simulation we used the arc and transition inscriptions. in order to visualize the model in different faulty modes a converter program were developed. the proposed procedure was illustrated on a simple manufacturing process with different faulty modes. keywords: discrete event systems, structure identification, graph representation, petri nets, fault isolation. introduction model-based techniques [1] are widely used and are very popular in control and diagnostic applications because of their efficiency and good performance both for systems with continuous and discrete range spaces. the appropriate models in the discrete range space case are built using the tools and techniques of discrete event systems [2], and these are mainly in the form of petri nets. when used for model-based fault detection and isolation, one not only needs a model for the normal operation of the system, but also other models are required that describe the considered faulty modes. this gives the possibility to isolate the actual faulty mode from measured data and the structurally different faulty models the comparison of which is the subject of the present paper. the idea of using model structure identification and comparison of discrete event systems models [3] is not new, but the field has matured only recently by a review paper [4] that focuses on petri net models used for model-based diagnosis. as a first step, the distance of the describing petri net models should be defined that may characterize the severity of the fault if its model is compared to the normal model. as a next step, the actual model of the real operating system determined by process mining [5] from the measured data are compared to the models of the different faulty modes in order to achieve fault isolation. this paper has two aims. the first is to elaborate on the method for transforming data resulting from technological system into suitable form for process mining. the second aim is to propose and analyze a graph distance based on the maximal common subgraph for the above purpose, and illustrate its use on a simple manufacturing process with different faulty modes. basic notions petri net model of a process petri nets enable both the mathematical and the graph representation of a discrete event system to be modeled, where the signals of the system have discrete range space and time is also discrete [4]. petri nets can be used for describing a controlled or open-loop system, for modeling the events occurring in it and for analyzing the resulted model. during the modeling and analysis process we can get information about the structure and dynamic behavior of the modeled system. for the different application purposes various modifications of the original petri net were developed, and several types of nets were introduced by researchers from all over the world since the first application of petri nets by c. a. petri. the aim of these modifications is to improve the modeling capabilities of this method. one of them is the colored petri nets (cp-nets). in our paper we use the cp-nets for diagnosis purposes, i.e. for the determination of faulty operational modes of the investigated system. 134 cp-nets the cp-nets combine the modeling advantages coming from petri nets and compactness of the functional programming language standard ml [11]. a petri net is bipartite graph having circles and rectangles as nodes. circles refer to the places in the net and rectangles to the transitions. places represents the state of elements of the modeled system while transitions the actions taken place in it. there are arcs between places and transitions referring to logical relations of the system. if an arc directs from a place to a transition then the place acts as a precondition of the given transition while the arcs in the opposite direction represent consequences of transitions. each place can be marked with one or more tokens representing the state of the modeled element. here we emphasize two important novelties of cpnets only. the tokens describing the state of the system have data value attached to them. this data value is called token color and it refers to the value of the measured signal or to the value of data sets. places, transitions and arcs can have inscriptions. an inscription of a place determines the set of color that a token on the place can have. another place inscription gives the actual number of the tokens on the place, i.e. the current marking of that place. the inscriptions of transitions can contain different types of functions. these functions determine the type of the color set of the incoming and outgoing tokens and the operation performed on them. the arc inscriptions can be used for evaluating of the result of the performed action at the previous transition. these conditional expressions define the color of the token on the following place. one of the main advantages of modeling with petri nets is the ability of describing sequences of discrete events. in a real system the events occur both in a serial and in a parallel way. in case of parallelism we can distinguish two different situations. in the first case the two or more series of events can take place independently from each other. in the other case only one of the event sequences can take place because these events exclude mutually each other. usually it means these events have the same precondition, and the occurrence of any of them makes this precondition invalid. this kind of parallelism is called conflict situation. in the petri net the conflict can be recognized when a place is the precondition of two or more transitions. in this case it is random which transition takes place. while the real parallelism can occur in normal operational circumstances, the conflicts mean fault situations in general. although faults also have their preconditions, but these are frequently invisible for the operator and it seems to be the effect of randomness which event takes place. hierarchical petri nets form a special class of cpnets. as one can use subroutines in a main program or submodels in a complex modeling process, so subnets can be used during the model construction of a technological system in cp-net form. there is a possibility to define subnets for separate technological subprocesses at the lower level, thereafter build them together defining their relation at the higher level. this way of modeling improves the readability of the model on the main level and allows the investigation of the subnets separately. logs and traces an event log is a set of finite event sequences, whereas each event sequence corresponds to a particular materialization of the process. we refer to an event sequence as a trace hereafter. we assume that it is possible to record events in a way that each event refers to an activity (i.e. a well defined step in the process), and each event belongs to a case (i.e. a process instance). in addition, each event can have a performer also referred to as originator (the person who executes or initiates the activity), and events have a time stamp, while they are totally ordered. having an event log, well established procedures of process mining [5] can be used for fitting the actions taken place in the modeled system to the transitions of a cp-net. it is important to emphasize that an event log contains a set of event sequences that each corresponds to a particular behavior, and the events recorded in a log may have ”measurement errors”, that is, some of them may be omitted or have a perturbed time stamp, for example. graph distance metric based on the maximal common subgraph algorithms for graph matching include the detection of graph and subgraph isomorphism. a possible method to cope with errors and distortions is based on the maximal common subgraph of two graphs [6]. let g = (v, e, µ) be a graph, where v is a set of finite vertices, e ⊆ v × v is a set of edges, and µ : v → lv is a function assigning labels to the vertices. the graph s = (vs, es, µs) is a subgraph of g, if vs ⊂ v and es = e ∩ (vs × vs)  and µs is the restriction of µ to vs. the notation s ⊆ g is used to indicate that s is a subgraph of g. a bijective function f : v → v ’ is a graph isomorphism from a graph g = (v, e,  µ) to a graph g’ =(v ’, e ’, µ’) if (v1, v2) ∈ e ⇔ (f (v1),  f (v2)) ∈ e ’ and µ(v) = µ’(f(v)) for all v ∈ v. an injective function f : v → v’ is a subgraph isomorphism from g to g’ if there exists a subgraph s ⊆ g’ such that f is a graph isomorphism from g to s.  let g, g1 and g2 be graphs. g is a common subgraph of g1 and g2 if there exist subgraph isomorphism from g to g1 and from g to g2. a common subgraph g of g1 and g2 is maximal if there exists no other common subgraph g of g1 and g2 that has more nodes than g. the maximal common subgraph of two graphs g1 and g2 will be denoted by mcs(g1, g2). notice that mcs(g1, g2) is not necessarily unique for two given graphs g1 and g2. let us denote the number of nodes of a graph g = (v, e) by |g|. 135 the distance of two non-empty graphs g1 and g2 is defined according to eq. (1). ( ) ( ) ( )21 21 21 1 g,gmax g,gmcs g,gd −= (1) it can be proved that the above distance measure d fulfills the properties of metric [6]. classical algorithms for computing the maximal common subgraph of two graphs is based on maximal clique detection [8] or backtracking [9]. fault diagnosis using cp-net models petri net models of a manufacturing process can be constructed from the a priori engineering knowledge and from measured real data. taking the data set of real process executions, i.e. the event logs, process mining techniques can be used for process discovery [5]. this section deals with the latter way of construction and with the comparison of the constructed petri net models. during the planning process one can define the set of operation leading to the technological goal of the system. also the relation of the steps to each other and their timing is determined. one of the most important questions of the plan is to define which actions can take place in parallel way and which are the mutually exclusive events. another important part of the planning procedure is the exploration of possible faults. one can prepare for some of the faults but the fault diagnosis during the operation of the system has also great significance. as a result of fault handling one can avoid them or their frequency can be reduced. normal reference model as a first step the model of investigated manufacturing system has to be defined in cp-net form and be implemented in the cpntools. cpntools is a software tool which allows the modeling of discrete event system in the form of colored and hierarchical petri nets. it was developed in aarhus, denmark [11]. if we want to investigate the operation of the system with no fault, i.e. we simulate the work of the normal reference model, then a token can be interpreted as a piece of product, and the arc and transition inscriptions have no significance. describing fault modes using petri nets let us assume that we have the petri net of the normal operational course in the form of cp-net, the so called normal reference model. if we know the possible faulty cases then we can integrate them into the cp-net of the system either as faulty places or using the transition and arc inscriptions. the normal reference model completed with faults is called extended model. having an event log we can establish the fired transitions in the cp-net. if we know all the steps of normal operational mode and the faulty cases then this reconstructed net should be a subnet of the extended net of the system. comparing the reconstructed net and the net of normal operational mode the difference between them refers to the deviation from the normal operational course. comparing the reconstructed net and the extended net of the modeled system we can establish the most likely operational course and in case of fault the most feasible reason of it can be diagnosed. occurring of faults can be forced with arc and transition inscriptions. the transition inscriptions contain special check functions which return fault or no fault value with a user defined probability. the arc inscriptions are conditional statements. they interpret the result of the check function of the previous transition, i.e. the color of the token and deliver the token to the next place. in case of faults causing immediate shutdown of the process separate arcs ensure the break of this simulation course and the return back to the initial state. if we use this way of fault modeling, then there is no need for separate fault places in the net. the occurrence of the fault happens automatically and the probability function in the arc inscription controls it with a user defined probability. this solution results in a smaller, compact net but it makes its readability more difficult. interpretation of log files during the simulation the cpntools can record the important events in a trace file, where it is the modeler’s responsibility to select the registered transitions belonging to those events. an entry of the registration contains the identifier of the transition and its originator, the type of the event (normal or fault), in case of fault its identifier and the time stamp. one course of the process generates one trace file. performing the simulation several times, separate trace files are generated and traces can be collected in one log file. our aim is to analyze these trace and log files in order to determine the diagnostic situation of the system, i.e. whether it works under normal conditions, and determine the type and number of occurring faults. for this analysis a set of software tools was used. the cpntools creates the trace files with *.cpnxml extension. these trace files can be collected into a log file with *.mxml extension with the software promimport. the final evaluation of the logs is done with prom data mining software [13]. the cpntools stores the cp-net of the modeled system in a file having *.cpn extension. for the evaluation we have to input both the structure of the cp-net and the log file to prom in appropriate format. to achieve this we have to convert the original cpn file into standard pnml file. we developed an appropriate software tool to perform this conversion. the main task of our converter is to handle the inscriptions present in the original cp-net model. as it was mentioned before, we modeled the occurrence of 136 faults by special transition and arc inscriptions. these inscriptions can be interpreted in cp-net environment only but not in prom. our converter program interprets these inscriptions and generates distinct fault transitions to resolve this problem. another task of this converter is to build in the subnets into the main net. as a result of the conversion the prom tool is able to visualize the structure of the extended net. there are different possibilities to process the log files and net structure describing files. 1) for the visualization of the structure of the reference model of the normal operation the following steps are needed: a) convert the cpn file describing the structure of a cp-net without any log file to pnml file using our converter software. b) input the resulted pnml file into the prom. the prom visualizes the structure of the reference net referring to normal operation. 2) for the visualization of the structure of extended model the following steps are needed: a) collect into one log file the trace files of different simulation courses generated by cpntools using the promimport [13] software. b) convert the cpn file describing the structure of a cp-net with the log file to pnml file using our converter software. c) input the resulted pnml file into the prom. the prom visualizes the structure of the extended net containing all transitions referring to both normal operation steps and faults. 3) the following steps are necessary for the visualization of the model and logs. a) define the probability of possible errors and do the simulation predefined times. convert the trace files into one log file using the promimport. b) convert the structure of a cp-net using our converter software but take into account the log file during the conversion. before the conversion we then have to declare what faults have to be considered from the faults found in the logs. c) input the resulted pnml file to prom. in this case the visualized net contains the transitions referring to the selected faults together with the transitions referring to the normal operation steps. 4) there is a possibility to visualize one trace file, i.e. one course of simulation. a) define the probability of errors and do the simulation only once. b) convert the resulted trace file into a log file using the promimport. c) convert the net structure also into pnml format with our converter program. d) input these files to prom. in this case we have to match the events found in the log file to the transitions of the extended net manually. if a transition has no pair in the log it should be declared as an invisible transition. as a result of this process the prom visualize the extended net but the transitions referring to the events found in the log have their name tag while the invisible transitions appear as a black box. 5) the software prom provides analysis of log files, too. for this create the log file from trace files using promimport and input it to prom. we can get several data about the events and originators, such as classes and types of events, the absolute and relative frequency of occurrence of events and the number of operations performed by the different originators. performance and structural analysis can be made, too. comparison of the reference model and the reconstructed models 1. comparison in the space of events here the comparison is performed by comparing the event log generated by the reconstructed model with the one generated by the reference model using some signal norm. as the event sequences (without the timing information but with their labels as symbols) can be seen as strings, the efficient algorithms of string comparison (see e.g. [10]) can be applied. 2. comparison in the space of petri net models here one compares the structure of the two models by using some general graph comparison methods and related graph distance [6, 7] based thereon. suppose we have a model of the process in the form of a cp-net n1. this model is based on our original concepts about the system and on the experiences resulted from the logs of many executions of the process. note that this model may describe both normal (i.e. non-faulty) operation courses and operation courses belonging to the known faulty modes. based on the workflow log of the actual operational courses and using some mining algorithm we construct another cp-net n2. the question is whether n2 is a subgraph of n1. if it is true then we can determine whether the system works under normal operational conditions or we can isolate the fault. if it is not true then probably a new fault has been detected. simple case study the aim of this section is to show the modeling process, the steps of log processing and the graph comparison and distance determination method using a simple illustrative case study. the investigated system is manufacturing process containing serial and parallel actions and has different faulty possibilities. the manufacturing system and its operating procedure our hypothetic manufacturing system contains four processes. each process is set of coherent actions. process 1 and process 2 can take place simultaneously while processes 3 and 4 are sequential, they can start if the previous process or processes are ready. the actions of a process take place in sequential way. we assume that one operational course of the system refer to manufacturing of the product. 137 according to the description of the system the events of the manufacturing operation are organized into processes. these processes were described in separate subnets. in this way we get a hierarchical petri net. the upper level of cp-net model consists of these processes and some other auxiliary nodes which are necessary for the simulation and error handling. the lower levels describe the structure of processes. each subnets contain set of actions and their perquisites and consequences. transitions of the net refer to the actions of the process while places refer to their pre and post conditions. three types of faults are to be considered. the faults belonging to the first group are the most serious cases, if they occur the course of operation is immediately over. in this case the system gets back into its initial state and a new course can start. in this simple model we do not handle the pieces of the stopped course. in the second case the effect of the fault is less, all the process steps take place but the product may have quality problem. in the third case the fault has minor effect only. the main net of cp-net model of the system can be seen in fig. 1 while the net of normal operational way (i.e. operation without any fault) visualized in prom is depicted in the fig. 2. figure 1: the main net of the model figure 2: the normal reference model visualized in prom fault diagnosis investigations as it was mentioned earlier, different types of fault possibilities have been built into the model. our aim was to investigate the diagnosability of these faults using the described graph distance metric method. for this we generated trace files containing one or two predefined faults. three different cases have been investigated: ● operation containing stop error in earlier phase of the course; ● operation containing a minor fault; ● operation containing two faults, a minor and a stop error close to end of the course. the certain occurring of faults was forced by giving the maximal probability value to each fault. the resulted petri nets belonging to the different cases can be seen in figs 3-5. in the first case the stop error faults occur in process 2. in this situation – although process 1 could terminate in normal way – but process 2 and thus the complete operation ended immediately after fault f2 has occurred. the distance between the graph of normal operation (fig. 2) and the graph of this faulty situation (fig. 3) can be determined based on eq. 1: ( ) 690 42 1311 .g,gd n =−= (2) 138 in the second case a minor fault occurs during the operation only. instead of transition t8 the fault f3 takes place. because this fault modifies slightly the quality of the product the operation can go further, and it terminates in a normal way. comparing fig. 2 and fig. 4, the difference between the two graphs is minimal that is reflected in the calculated distance value, too: d(g2, gn) = 0.024. it is easy to show that we get the same result in case of any other minor faults. in the third case a minor fault (f4) occurs during and operation and after that, as a consequence of a stop error (f6) the operation ends immediately. the graph of this situation can be seen in fig. 5. the calculated distance value is not too high, d(g3, gn) = 0.143, because the fault f6 occurs close to the normal termination of the operation. from the above one can see, that it is possible to characterize the effect and seriousness of the fault with the calculated graph distance value. figure 3: a visualized trace when there is a stop error in the beginning of the process figure 4: a visualized trace when there is a small error in the process figure 5: a visualized trace when there is a stop error in the end of the process conclusion a novel structure comparison procedure for discrete event systems described by petri nets are proposed in this paper for model-based diagnostic purposes that utilize the notions and tools of graph distances. the model of the investigated system was defined in hierarchical colored cp-net form. both normal reference model describing the faultless operation and the extended model containing the different faults were developed. for the fault simulation we used the arc and transition inscriptions. the visualization of net was performed by prom. in order to get the files having the appropriate form and extension we developed a converter program. the proposed procedure was illustrated on a simple manufacturing process with three faulty modes. it was concluded that a characterization of the severity of a fault can be performed by using the graph distance between the cp-net models of the normal and faulty operation. acknowledgement authors acknowledge the financial support of this work by the hungarian state and the european union under the tamop-4.2.1/b-09/1/ konv-2010-0003 project “mobility and environment: researches in the fields of motor vehicle industry, energetic and environment in the middleand west-transdanubian region”. part of the work is also supported by the hungarian national research fund through project k83440. 139 references 1. m. blanke, m. kinnaert, j. lunze, m. staroswiecki: diagnosis and fault-tolerant control, springer-verlag, 2006, isbn 3-540-01056-4 2. c. g. cassandras, s. lafortune: introduction to discrete event systems, kluwer academic publishers, 1999, isbn 0-7923-8609-4 3. m. e. meda, a. ramirez, a. malo: identification in discrete event systems, ieee international conference on systems, man, and cybernetics, 1998, 740–745 4. m. p. fanti, c. seatzu: fault diagnosis and identification of discrete event systems using petri nets, 9th international workshop on discrete event systems, wodes 2008, 2008, 432–435 5. w. m. p. van der aalst, k. m. van hee: workflow management: models, methods and systems, mit press, cambridge, ma, 2002 6. h. bunke, k. shearer: a graph distance metric based on the maximal common subgraph, pattern recognition letters 19, 1998, 255–259 7. h. bunke: on a relation between graphs edit distance and maximum common subgraph, pattern recognition letters 18, 1997, 689–694 8. g. levi: a note on derivation of maximal common subgraphs of two directed or undirected graph, calcols, 9, 1972, 341–354 9. j. j. mcgergor: backtrack search algorithms and maximal common subgraph problem, software practice and experience, 12, 1982, 23–34 10. w. cohen, p. ravikumar, s. fienberg: a comparison of string distance metrics for namematching tasks, proceeding of the ijcai, 2003 11. k. jensen, l. m: kristensen, l. wells: coloured petri nets and cpn tools for modelling and validation of concurrent systems, int. j. of software tools for technology transfer, 9(3-4), (2007), 213–254 12. cpn group, university of aarhus, denmark: cpntools 2.2.0 http://wiki.daimi.au.dk/cpntools/ 13. process mining group, eindhoven technical university, the netherlands: prom 5.2. and promimport, http://www.promtools.org/prom5/ and http://www.promtools.org/promimport/ << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word hjic 2015 43(2) 55-101.docx hungarian journal of industry and chemistry vol. 43(2) pp. 79–83 (2015) hjic.mk.uni-pannon.hu doi: 10.1515//hjic-2015-0013 a study of the adsorption characteristics of cobalt and caesium from a solution by using vietnamese bentonite le phuoc cuong,1 pham hoang giang,2 bui dang hanh,3 and gergő bátor4* 1 the university of danang-university of science and technology, danang, vietnam 2 vnu university of science, hanoi, vietnam 3 vietnam atomic energy institute (vinatom), hanoi, vietnam 4 institute of radiochemistry and radioecology, university of pannonia, veszprém, h-8201, hungary the radioactive waste produced from the construction of a nuclear power plant is a controversial topic. the resulting radioactive waste contains 60co and 137cs isotopes that are the most difficult to remove. bentonite is widely used as an adsorbent for heavy metals. an important factor is the safe operation of waste management at a nuclear power plant to be built in vietnam. therefore, a method of degrading complexes of radionuclides and the adsorption of radionuclides onto vietnamese bentonite was implemented in this study. in current literature, uv radiation and heating with oxidising substances are used in general for degrading complexes of radionuclides. the experimental results for the adsorption of co(ii) and cs+ onto vnb suggest that vnb can be used in the future for large-scale liquid waste treatment due to its low cost, high efficiency, and environmentally friendliness. keywords: radionuclides; vietnamese bentonite; adsorption; uv radiation; hydrogen peroxide 1. introduction during operation, a nuclear power plant (npp) releases a large quantity of liquid waste containing radionuclides. the sources of liquid waste include contaminated boric acid solutions, liquid that has leaked from the primary circuit, a solution used to decontaminate the equipment of the primary circuit, and other waste sources. radionuclides that exist in liquid waste include 137cs, 60co, 59fe, 51cr, 54mn, etc. [1–4]. in all types of nuclear reactors, the solutions that are used to decontaminate equipment containing chemicals are for example, alkalis, kmno4, edta, etc. [4] in order to oxidise or to form complexes with radionuclides. these complexes are highly soluble in reactor solutions. liquid waste containing radionuclides has to be stored for a certain period of time to decay. radionuclides with short half-lives decay during this storage time. the longer-lasting radionuclides such as 60co and 137cs are still present in concentrations above the discharge limit of 1 kbq dm-3. thus, they are not allowed to be discharged into the environment even after several years of storage [5–10]. one of the most effective methods for the treatment of radioactive waste is on the basis of ion exchange and adsorption processes using inorganic ion exchangers. the desirable characteristics of high *correspondence: kt@almos.uni-pannon.hu exchange capacity and favourable selectivity for some radioisotopes made certain zeolites useful in the treatment of radioactive waste. natural zeolites considered for radioactive waste treatment include mordenite, erionite, chabazite, clinoptilolite, and bentonite. among these, bentonite has received much attention due to its widespread usage, large surface area, and high selectivity for some radiotoxic metals [4, 11]. bentonite consists predominantly of the mineral montmorillonite, an aluminium hydrosilicate. its crystal structure shows distinct layers forming a lattice (fig.1). the term “bentonite” was first used by knight in 1889 following the discovery of highly colloidal plastic clay near fort benton in the cretaceous bed of wyoming. bentonite is a naturally occurring cationic clay, which can be processed or modified to tailor its properties, so it is suitable for various applications and uses. in its pure form or with some chemical additives or modifications, bentonite can be used as a rotary mud, an anticaking agent for certain granular fertilisers, a binding agent in the agglomeration of cattle feed, in pesticides or mineral oil, for filling, oil deodrising, palletising or bleaching, and in civil construction, foundries, and the alkylation of phenols [4, 6–8]. the aim of this study was the identification of degrading and mineralising complex compounds of co(ii) and cs+ by using uv radiation and heating with oxidation substances. in addition, we also determined the adsorption efficiency of these radioactive isotopes onto vnb. phuoc cuong, hoang giang, dang hanh, and bátor hungarian journal of industry and chemistry 80 2. experimental 2.1. objectives in order to extract 60co and 137cs from radioactive liquid waste, a combined treatment method was used. this method includes two stages. in the first stage, the edta complexed radionuclides were degraded and mineralised by uv radiation and heating with oxidising substances and then in the second stage radionuclides ions were removed by adsorption using vnb. in order to prepare the model solutions for this study, the activity concentrations of the radioactive isotopes of 137cs and 60co in a typical liquid radioactive waste sample were determined by standard γ spectrometry using a gamma műszaki zrt scintillation (nai) detector. table 1 shows measurements taken from the liquid waste radioactive sample. 2.2. research methodology the concentrations of radioactive elements were determined by using an ice 3000 atomic absorption spectrometer (aas, thermo scientific, usa) with an air-c2h2 flame at a flow rate of 0.9 dm3 min-1. the chemicals used as analytical standards were all reagent grade or better. ethylenediaminetetraacetic acid (edta), h3bo3, naoh, h2o2, coso4, and cscl were purchased from merck (germany). all glassware and polyethylene bottles were thoroughly washed and then rinsed using ultrapure water before use. 2.2.1. degradation of complex compounds by heating with an oxidant in the heated system (fig.2), the degradation of complex edta, coso4, and h3bo3 was investigated under two sets of conditions at 60 and 70 ºc both with and without h2o2 in 30 mg dm-3 concentration. each experiment lasted 1 hr for three solutions with various concentrations of coso4 (10, 20, and 40 mg dm-3). aliqots of samples were taken at regular intervals, such as 10, 30, and 60 min. these solutions were centrifuged and stirred with vnb for 1 hr. after that, the solution samples, with and without vnb, were analysed to determine the co(ii) concentration. 2.2.2. degradation of complexes by uv radiation and oxidizers aspects of photocatalytic degradation of complexes with edta, coso4, and h3bo3 were investigated. degradation efficiencies were studied in detail using a uv radiation system within the range of 280–315 nm and at 0.15 w m-2 (fig.3) under the following conditions: 1. only with uv light; 2. uv and o2 with flow rate of 70 dm3 h-1); 3. uv, o2, and h2o2 in 3 mg dm-3 concentration; 4. uv, o2, and tio2; 5. uv, o2, tio2 and h2o2. figure 1. structure of bentonite [6]. figure 2. the experimental set-up of the heating system. table 1. typical radioactive liquid waste sample (3/2/2015 measurements). radionuclides activity concentration, bq dm-3 ph dry matter, g dm-3 boric acid, g dm-3 edta, g dm-3 60co 1.23×104 12.5 85.23 120 4 137cs 2.51×105 figure 3. the experimental set-up for uv radation system. adsorption characteristics of cobalt and caesium 43(2) pp. 79–83 (2015) doi: 10.1515/hjic-2015-0013 81 each experiment lasted for 2 hr for the three solutions using various concentrations of coso4 (10, 20, and 40 mg dm-3). samples were taken at regular intervals of 10, 30, 60, and 120 min. the solutions were centrifuged and stirred with vnb for 1 hr. after that, the solution samples, with and without vnb, were analysed to determine the co(ii) concentration. 2.2.3. adsorption of radioactive elements onto vnb experiments on the adsorption of co(ii) and cs+ onto bentonite were performed in batches to determine their adsorption time and equilibrium isotherms. a volume of 30 cm3 of radioactive solution at various initial concentrations for coso4 (10, 20, and 40 mg dm-3); and cscl (60 and 120 mg dm-3) was stirred with bentonite for 1 hr within a ph range of 12 to 13, depending on the initial concentrations of edta and h3bo3 in the model solution. samples were taken at regular intervals, centrifuged, and the concentration of co(ii) and cs+ ions were measured. 2.2.4. adsorption isotherms to evaluate the adsorption ability of ions onto bentonite, the langmuir and freundlich isotherm models were employed. on the basis of experimental data, the typical parameters of the adsorption process were determined by using the linear regression method. the langmuir equation is given by: qe = qmkace/(1+kace) . (1) its linear form is ce/qe = (1/qm)ce + 1/(kaqm) (2) where qe is the amount of ions adsorbed (mg g-1) at equilibrium; ce is the equilibrium concentration (mg dm-3); qm is the maximum adsorption capacity (mg g-1); and ka is the adsorption equilibrium constant. a plot of ce/qe against ce expected to give a straight line with a gradient of 1/qm and an intercept of 1/(kaqm). the freundlich equation is given by: qe = kfce 1/n . (3) its linear form is: ln qe = ln kf + (1/n) ln ce (4) where kf and n are constants. 3. results and discussion 3.1. efficiency of the adsorption of radioactive elements onto vnb for the estimation of the adsorption ability of co(ii) onto vnb, 0.1 g of vnb was stirred with 50 cm3 of co(ii) solution (8–200 mg dm-3). after equilibrium was achieved, the residual concentration of co(ii) was measured using an ice 3000 aas (atomic absorption spectrometer). the effect of initial concentrations on the adsorption of co(ii) by vnb can be seen in fig.4. when the initial co(ii) concentration was increased from 8 to 200 mg dm-3 the absolute amount of co(ii) adsorbed per unit weight of vnb increased from 2.31 mg g-1 (96.5%) to 6.95 mg g-1 (11.8%). however, the percentage adsorption decreased with increasing initial concentration. the results showed that at higher initial concentrations, the number of available adsorption sites decreased and hence, the removal of co(ii) ions depends upon the initial concentration. to determine the optimal reaction time in order to achieve an equilibrium state, flasks containing a mix of solutions (cscl, naoh, h3bo3) with vnb were stirred for different periods of time (10, 30, 60, and 120 min). the concentrations of cs+ ions in the solutions were measured using an atomic absorption spectrometer. the reaction time required to achieve an equilibrium state was defined between the start of stirring and when the analyte concentration remained constant. fig.5 describes the cs+ content in the solution after different periods of time. according to fig.5, a period of 100 min can be considered optimal reaction time to achieve equilibrium. this optimal time was implemented for the experiments on the adsorption of cs+ ions onto vnb. 3.2. study of the kinetics of the adsorption of radionuclides onto bentonite 3.2.1. adsorption isotherms of co(ii) fig.6 shows the adsorption isotherms of co(ii) onto vnb, which can be described by the langmuir model with a correlation coefficient (r2) of 0.9791 and a maximum adsorption capacity of 8.15 mg g-1. the equilibrium data also corresponded to the freundlich isotherm with a correlation coefficient (r2) of 0.9640. figure 4. the effect of the initial concentration on the adsorption of co(ii) onto vnb. figure 5. cs+ content in the solution after different periods of time. phuoc cuong, hoang giang, dang hanh, and bátor hungarian journal of industry and chemistry 82 regarding the four experiments with heating, only exp. 4 with reaction at 90 ºc and 30 mg dm-3 of h2o2 could reduce the concentration of co(ii) otherwise the co(ii) concentration remained unchanged or showed no significant change. fig.7 shows that the concentration of co(ii) decreased as time increased within 30 minutes, but after that, it practically remained constant. moreover, initial concentrations also affected the efficiency of removing co(ii) with initial concentrations of 10, 20, and 40 mg dm-3. the corresponding efficiency values for removing co(ii) were 22.2%, 31.5% and 61.7%, respectively for samples that were not stirred with vnb, and 22.7%, 43.3%, and 67.7% for samples that were stirred with vnb. thus, the experimental adsorption capacity of vnb indicate that it can adsorb co(ii) at the highest value of adsorption capacity of 8.15 mg g-1, but in the four experiments with heating, the efficiency of removing co(ii) with vnb did not show significant differences without vnb. previous research [2, 4, 6] showed that bentonite exhibits good adsorption capacities toward organic matter. however, these results showed that the adsorption ability of edta onto bentonite is low, and co(ii) still remains complexed with edta. it is removed only when edta is completely degraded. with regard to the uv system, the results from all experiments show that the outcome of this method was not affected by decreasing co(ii) concentration. rekab et al. showed [2] that the efficiencies of uv/tio2 and uv/h2o2 treatments are 67% and 42%, respectively at low ph. on the other hand, the degradation efficiency was greater under acidic ph conditions, likely due to the dissociation of h2o2 into ho2 at alkaline ph, and the photolytic generation of oh• radicals is therefore hindered. the amine functional groups in edta is dominantly converted to ammonia, which forms a complex compound with co(ii) [2]. 3.3. adsorption isotherms of cs fig.8 shows that the adsorption isotherm of cs+ onto vnb could be described by both the langmuir and freundlich models with correlation coefficients (r2) of 0.98 for both respectively. on the basis of both of these models, the highest value of adsorption capacity was 1.15 mg g-1 showing that vnb can adsorb cs. 4. conclusion vnb was tested as an adsorbent material for the removal of cobalt and caesium ions from sulphate and chloride waste solutions. the adsorption of co(ii) ions figure 6. adsorption isotherms of co(ii) onto vnb. figure 7. degradation of co(ii) over different time periods (ex. 4) using solution 1: 40 mg dm-3 co(ii); solution 2: 20 mg dm-3 co(ii); and solution 3: 10 mg dm-3 co(ii). figure 8. adsorption isotherms of cs+ onto vnb. adsorption characteristics of cobalt and caesium 43(2) pp. 79–83 (2015) doi: 10.1515/hjic-2015-0013 83 onto vnb followed the pseudo-second order rate model. the adsorption isotherm of co(ii) was described by the langmuir and freundlich models. these show that radioactive isotopes can be highly efficiently adsorbed onto vnb. the adsorption isotherm of cs+ corresponded to both the freundlich and langmuir models with high correlation coefficients. in the presence of edta in radioactive waste solution, radioactive isotopes could not be adsorbed onto vnb due to forming stronger complexes with edta therefore, in this study two pre-treatment systems were implemented to remove edta from the liquid waste. heating achieves an efficiency of 67% while the uv radiation did not exhibit satisfactory improvement of treatment efficiency. we are planntng to scale up the uv system to include the optimisation of ph values and the effect of ammonium converted from edta in order to apply these findings to radioactive solution waste on a large scale. acknowledgement the authors would like to thank the ministry of education and training, vietnam for funding this research, and the institute of radiochemistry and radioecology at the university of pannonia for providing the experimental conditions. references [1] manohar, d.; noeline, b.; anirudhan, t.: adsorption performance of al-pillared bentonite clay for the removal of cobalt(ii) from aqueous phase, applied clay science, 2006, 31(3-4), 194– 206 doi: 10.1016/j.clay.2005.08.008 [2] rekab, k.; lepeytre, c.; dunand, m.: h2o2 and/or photocatalysis under uv-c irradiation for the removal of edta, a chelating agent present in nuclear waste waters, appl. cat. a: general, 2014, 488(11), 103–110 doi: 10.1016/j.apcata.2014.09.036 [3] omar, h.; arida, h.; daifullah, a.: adsorption of 60co radionuclides from aqueous solution by raw and modified bentonite, appl. clay sci., 2009, 44(1), 21–26 doi: 10.1016/j.clay.2008.12.013 [4] egamediev, s.kh.; nurbaeva, d.a.; tashtemirova, n.g.: modified bentonite as adsorbents for radionuclides: adsorption of carrier-free radiocobalt-57 on acid modified and calcined bentonite, proc. int. conf. “nuclear science and its application”, samarkand, uzbekistan, september 25-28, 2012, pp. 345–346 inis: rn:44129011 [5] iaea: modified combined methods for liquid radioactive waste treatment, final report (int. atomic energy agency, tecdoc-1336) 1997– 2001 issn: 1011–4289 [6] dale ortego, j.; kowalska, m.; cocke, d.: interactions of montmorillonite with organic compounds adsorptive and catalytic properties, chemosphere, 1991, 22(8), 769–798 doi: 10.1016/0045-6535(91)90052-f [7] milyuin, v.v.; kononenko, o.a.: sorption of caesium on finely dispersed composite ferrocyanide sorbents, radiochem., 2010, 52(3), 281–283 doi: 10.1134/s1066362210030100 [8] tofalvi, r.; sepsey, a.; horvath, k.; hajos, p.: environmental significance and identification of metal-chelate complexes using ion chromatography, hung. j. ind. chem., 2011, 39(1), 95–99 [9] frerich, j.k., flugge, u.: high performance catalytic tubular membrane reactors owing to forced convective flow operation, hung. j. ind. chem., 2005, 33(1–2), 31–42 [10] varga, k.; hirschberg, g.: accumulation of radioactive corrosion products on steel surface of vver-type nuclear reactors. ii. 60co, j. nucl. mater., 2001, 298(3), 231–238 doi: 10.1016/s00223115(01)00658-4 [11] kolics, a.; varga, k.: study of cobalt sorption on polyethylene, j. colloid interface sci., 1994, 168(2), 451–457 doi: 10.1006/jcis.1994.1441 microsoft word 00.00 inner cover.docx hungarian journal of industry and chemistry vol. 43(1) pp. 49–53 (2015) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2015-0009 study of the interference effects of aluminium on the atomand ion-lines of alkaline earth metals in aqueous solutions using an icp spectrometer with axially viewed plasma olivér bánhidi institute of chemistry, university of miskolc, miskolc-egyetemváros, miskolc, 3515, hungary the main advantage of inductively coupled plasma spectrometers with axially viewed plasma relative to the radially viewed plasma is the better detection power. the detection limits of the former are about 5–10 times lower than the latter. on the other hand, the axially viewed plasma has disadvantages. the most notable is the increased number of interference effects. in this paper, the study of the interference effects of aluminium on the atomand ion-lines of alkaline earth metals are presented by examining different types of sample-introduction devices, such as a simple meinhart-type concentric nebuliser, a v-groove nebuliser using a sturman-masters spray chamber, and an ultrasonic nebuliser. keywords: aluminium interference effects, icp atomand ion-lines, alkaline earth metals, sampleintroduction device, axially viewed plasma 1. introduction inductively coupled plasma-atomic emission spectrometry (icp-aes) is a widely used method for the elementary analysis of different types of material due to its advantageous features. the axial plasma view offers an increased detection power, which is important when the element of interest is present in trace levels. on the other hand, the emitted light is subjected to strong interferences as it reaches the entrance slit of the optical system of the spectrometer. therefore, it is an important task to understand the origin and nature of the interference effects [1–3]. the interference may affect both the sampleintroduction and excitation processes taking place in the plasma. in the first case, they may have different effects on the different types of sample-introduction devices, while they might affect the atomand ionlines of a given element in different ways [4]. icp is commonly used for the analysis of liquid samples, where different types of nebulisers are the most frequently applied devices for sampleintroduction. during nebulisation, the liquids to be analysed are dispersed into small droplets. the difference regarding the different nebulisers lies partially in different processes resulting in small liquid droplets and the nebulisation efficiency. these kinds of effects may be different when different nebulisers are applied, while they appear in the case of both radially and axially viewed plasma. correspondence: akmbo@uni-miskolc.hu the spectral interferences are stronger and more frequent when an axially viewed icp source is used. this is due to the light being emitted from the hot internal part of the plasma that has to travel a long way to reach the entrance slit of the optical system. on its way, the emitted light goes through layers of plasma at a lower temperature. this process may be subjected to strong self-absorption effects. consequently, the intensity of the ionand atom-lines of a given element may change. this change affects the relationship between the emitted line intensity and analyte concentration in the sample, and thus the calibration procedure. the alkaline earth metals may be present from trace up to high concentration levels in different materials, such as surface and groundwater, different types of rocks and minerals, metal alloys, etc. in many cases, these materials may contain aluminium in high concentrations that contributes to the observation of interferences [2,3]. in the present work, we studied the effect of aluminium on the spectral lines of alkaline earth metals present in lowconcentrations in aqueous solutions, as well as the influence of different sample-introduction devices. 2. experimental 2.1. icp spectrometer for the presented experiments, a varian 720 es spectrometer was used, which is an axially viewed, instrument with key parameters summarised in table 1. bánhidi hungarian journal of industry and chemistry 50 due to the layout of the optical system, many (even several hundred) spectral lines can be measured simultaneously, which makes the study of the interferences on several atomand ion-lines of a given element possible. in the course of line selection, care was taken in choosing both more and less sensitive lines, where enough lines were available. the spectral lines examined in this study are summarised in table 2. 2.2. the sample-introduction devices three types of sample-introduction device were used in the given set of experiments: a concentric nebuliser, a v-groove nebuliser, and an ultrasonic nebuliser. the concentric nebuliser is the one that is used most commonly for the icp-aes analysis of liquid samples. its nebulisation efficiency is rather low, but it can be operated easily, and its maintenance demand is low. generally, it is used in combination with a cyclone-type glass spray chamber. the v-groove nebuliser eventually becomes a modified babington-type nebuliser. it is used with a sturman-masters type spray chamber, which has a special plastic surface and is resistant to almost all chemicals including hydrogen fluoride. its detection power is slightly less than that of the concentric nebuliser, but it has an excellent salt-enduring ability. the cetac 5000 type ultrasonic nebuliser boasts a detection power 10 times better than the former two devices. on the other hand, its operation is more difficult and it may be sensitive to higher matrix concentration levels. 2.3. samples used the solution samples contained some acid, the alkaline earth analyte elements and aluminium as a matrix component. the matrix element was diluted from a spectrascan (teknolab) stock solution containing aluminium at a concentration of 10 g dm-3. the aluminium concentration in the sample solutions was 0, 200, 500, 1000, and 5000 mg dm-3. the analyte elements were diluted from a multi-element spectrascan solution of 0.1 g dm-3. the concentrations of the elements studied were in the range of 0.1 and 10 mg dm3. the solutions contained hydrochloric acid in a concentration of 0.5 mol dm-3. 2.4. measurements each of the solutions was measured at a 1050 w output of high frequency power. the recorded signal intensity was averaged from 3–10 s long replicates. the raw intensities were corrected applying the so-called twoside off-peak background correction method. in order to easily evaluate the effects, the net intensities measured using sample solutions containing no aluminium were used as reference values, and the net intensity values measured in the presence of aluminium were divided by these reference values. in other words, the evaluation presented here is based upon the relative intensities. 3. results in the experiments, we studied the intensity changes of several atomand ion-lines of the alkaline earth metals as a function of aluminium concentration, analyte concentration and that of the device used for sampleintroduction. the results measured using a concentric nebuliser are presented in figs.1–10. the net intensities obtained using a v-groove nebuliser (figs.11 and 12) and an ultrasonic nebuliser (figs.13 and 14) are also presented for the case of calcium ions. 4. discussion figs.1–10 show that by using the concentric nebuliser both atomicand ionic-lines of all alkaline earth metals are affected by aluminium. nevertheless, substantial differences can be seen depending on the element, type table 2. the spectral lines (wavelength λ in nm and excitation energy e in ev) studied. element type of the line λ e be be i 234.861 5.30 be be i 249.473 5.01 be be ii 313.042 3.99 be be ii 313.107 3.99 mg mg i 285.213 4.38 mg mg i 383.829 3.23 mg mg ii 279.553 4.47 mg mg ii 280.270 4.59 ca ca i 422.673 2.96 ca ca ii 317.933 3.93 ca ca ii 393.366 3.18 ca ca ii 396.847 3.15 sr sr i 460.780 2.71 sr sr ii 216.596 5.76 sr sr ii 407.771 3.07 sr sr ii 421.552 2.96 ba ba i 705.994 1.77 ba ba ii 233.527 5.36 ba ba ii 455.403 2.75 ba ba ii 493.408 2.53 table 1. characteristics of the icp spectrometer used in the given study. plasma-view: axial the frequency and power of the rf generator: 40 mhz, 900–1500 w adjustable via software the optical system employed: echelle build-up with a double monochromator detector used: two-dimension ccd wavelength range: 160 – 780 nm available sampleintroduction systems: concentric (k-type) nebuliser, v-groove nebuliser, ultrasonic nebuliser controlling software: icp expert ii (microsoft win xp os) study of the interference effects of aluminium 43(1) pp. 49–53 (2015) doi: 10.1515/hjic-2015-0009 51 of spectral line studied, concentration of aluminium, and that of the analyte. at low beryllium concentrations (0.1 mg dm-3) the intensities on all lines are heavily affected even at relatively low aluminium concentration (1 g dm-3) levels. higher aluminium concentrations cause only a moderate reduction in the signal. similar behaviour can be observed in the case of magnesium, strontium, and barium. as for calcium, the greatest decrease was observed also at an aluminium concentration of 1 g dm-3, but higher aluminium concentrations cause a smaller decrease, even some increase can be observed in the ion-lines. it can also be observed that atom-lines are usually more strongly affected than ion-lines. at higher analyte concentrations, the effect of aluminium is greater on all the lines examined and increases with increasing aluminium concentration. the only exception is the intensities measured at an aluminium concentration of 1 g dm-3, where in the case of each analyte the relative intensities are significantly lower than both the values gained at aluminium concentrations of 0.5 and 2 g dm-3 concentration, though the extent of the effect is different. this effect is larger or even larger in the case of beryllium, magnesium, and barium, and it is less profound for calcium and strontium. with respect to the different types of lines, in the case of beryllium, where all the lines studied are sensitive, one of the atom-lines (234.861 nm) is less, while the other (249.473 nm) is more affected than the ion-lines. one of the atom-lines (383.829 nm) of magnesium is a weak line, while the other one (285.213 figure 1. the relative intesities of 0.1 mg dm-3 be as a function of al concentration, using a concentric nebuliser. figure 2. the relative intesities of 10 mg dm-3 be as a function of al concentration, using a concentric nebuliser. figure 3. the relative intesities of 0.1 mg dm-3 mg as a function of al concentration, using a concentric nebuliser. figure 4. the relative intesities of 10 mg dm-3 mg as a function of al concentration, using a concentric nebuliser. figure 5. the relative intesities of 0.1 mg dm-3 ca as a function of al concentration, using a concentric nebuliser. figure 6. the relative intesities of 10 mg dm-3 ca as a function of al concentration, using a concentric nebuliser. bánhidi hungarian journal of industry and chemistry 52 nm) is sensitive. the first is heavily affected by aluminium, while the other lines manifest smaller effects. in the case of calcium and strontium, the atomline is much more affected than the ion-lines, while the reverse can be observed for barium. its atom-line is much less affected than its sensitive ion-lines. the effect of the sample-introduction devices in figs.11–14 in the case of calcium manifests that at low analyte concentrations (0.1 mg dm-3) almost the same type of curve is observed with the help of an ultrasonic nebuliser. using a v-groove type device, only slight effects were detected. at higher analyte concentrations, all the lines are affected using the v-groove nebuliser; while in the case of the ultrasonic device the sensitive ion-lines (393.366 nm and 396.847 nm) are only slightly affected. 5. conclusion using the axially viewed plasma, the light emitted from the high-temperature inner part of the plasma has to pass through the flame to reach the entrance slit of the optical system. as the photons travel, they pass through plasma layers of lower and lower temperatures. in the cooler environment, self-absorption, secondary excitation, and scattering processes can take place. these processes depend on the local temperature, which is also influenced by the high/higher concentration of elements in the sample than the analyte. all these processes make the relationship between line-intensities emitted and analyte concentration rather complicated. figure 7. the relative intesities of 0.1 mg dm-3 sr as a function of al concentration, using a concentric nebuliser. figure 8. the relative intesities of 10 mg dm-3 sr as a function of al concentration, using a concentric nebuliser. figure 9. the relative intesities of 0.1 mg dm-3 ba as a function of al concentration, using a concentric nebuliser. figure 11. the relative intesities of 0.1 mg dm-3 ca as a function of al concentration, using a v-groove nebuliser. figure 12. the relative intesities of 10 mg dm-3 ca as a function of al concentration, using a v-groove nebuliser. figure 10. the relative intesities of 10 mg dm-3 ba as a function of al concentration, using a concentric nebuliser. study of the interference effects of aluminium 43(1) pp. 49–53 (2015) doi: 10.1515/hjic-2015-0009 53 it can be concluded that aluminium exhibits a strong interference effect on the emitted spectral line intensities of all alkaline earth elements studied. it can also be seen that atom-lines are usually more affected than ion-lines. although the relationship between the interferences and line intensities is complicated, in practice it can be eliminated by careful matrixmatching, i.e. the calibration solutions must contain the interfering element (al) possibly at the same concentration level as the analyte in the samples. in addition, calibration curves can be extended, only with care in the presence of al, as it could be observed that the extent of the interference is different at low and high analyte concentrations. acknowledgement this research was supported by the támop-4.2.1.b10/2/konv-2010-0001 project and carried out as part of the támop-4.2.2.a-11/1/konv-2012-0019 project in the framework of the new széchenyi plan. this project was supported by the european union, and cofinanced by the european social fund. references [1] záray, gy.: modern methods of elementary analysis, gas discharge plasmas and their application (university press, budapest, hungary) 2006 (in hungarian) [2] bánhidi, o.: examination of the interference effects in the course of icp-aes determination of strontium content of aluminium alloys, proc. 24th microcad conf. (university of miskolc, miskolc, hungary) 2012, section c [3] dubuissan, c.; pousserl, m.; mermet, j-m.: comparison of axially and radially viewed inductively coupled plasma atomic emission spectrometry in terms of signal to background ratio and matrix effects, j. anal. at. spect., 1997 12(3), 281–286 10.1039/a606445k [4] brenner, i.b.; zander, a.t.: axially and radially viewed inductively coupled plasmas a critical review, spectrochim. acta, part b, 2000 55(8), 1195–1240 10.1016/s0584-8547(00)00243-3 figure 13. the relative intesities of 0.1 mg dm-3 ca as a function of al concentration, using an ultrasonic nebuliser. figure 14. the relative intesities of 10 mg dm-3 calcium as a function of al concentration, using an ultrasonic nebuliser. microsoft word inner cover.docx hungarian journal of industry and chemistry veszprém vol. 41(2) pp. 119–122 (2013) solid-liquid extraction of chlorophyll from microalgae from photoautotroph open-air cultivation éva molnár, ! dóra rippel-pethő, and róbert bocsi department of chemical engineering, institute of chemical and process engineering, university of pannonia, egyetem u. 10., veszprém, 8200, hungary !email: molnare@almos.uni-pannon.hu among industrial pollutants, strict quotas limit the emission of carbon dioxide in the european union. the capturing and deposition of carbon dioxide requires significant expenditures. one of the newer solutions for the reduction of the carbon dioxide emissions is provided by algae technology. in this technology, the absorption of carbon dioxide is achieved by photosynthesis. besides the reduction of pollutants, algae technology has another advantage by supplying valuable products, such as natural pigments, proteins, vitamins and oils from algae biomass. since it has a high reproduction rate, algae cultivation can be a feasible substitute for plants traditionally used in the production of chlorophyll. the viability of the technology is dependent on whether or not the processing can be done economically. an investigation was carried out in order to compare and contrast two extraction methods (soxhlet extraction and leaching) and four solvents (acetone, diethyl ether, ethanol and methanol) to determine the most effective method for the extraction of chlorophylls from dried microalgae (chlorella vulgaris sp.). it was concluded that methanol is the most effective solvent for the extraction of both chlorophylls a and b using both soxhlet extraction and leaching. keywords: microalgae, extraction solvent, extraction, chlorophyll, spectrophotometry introduction energy demand has been rapidly increasing throughout the world, which is mainly met by the combustion of fossil fuels that results in an increase in the concentration of greenhouse gases in the atmosphere. however as a possible remediation strategy, carbon dioxide levels can be reduced with the use of algae technology [1]. algae technology is of significant interest in research and development since it is a ‘green’ technology that is capable of both decreasing the emission of pollutants and serving as a renewable energy source. the algae absorb carbon dioxide for photosynthesis while producing a number of valuable components [2]. microalgae are a collection of various microscopic species capable of photosynthesis and are typically found in water with an exceptionally high reproduction rate. for propagation, they mainly need light, water and co2. some species can even survive in waste water. algae are good alternatives for plants that are traditionally used for the production of chlorophyll. appropriate conditions are required for the successful cultivation of algae (solar energy, temperature, ph, and mixing) [3, 4]. however, the critical point of algae technology is neither cultivation nor processing. the biggest complication concerns the concentration of the microalgae suspension and the subsequent extraction of the valuable components due to the high investment costs and long operational times [5]. there is, however, an increasing demand for microalgae. the reason for this is that their oil content can be as much as 50% of their body mass, making them important in the production of biodiesel. the natural pigments, proteins and vitamins extracted from microalgae are primarily used by the pharmaceutical, cosmetic and food industries [3, 6]. chlorophyll has been used for centuries as a traditional remedy for unpleasant body odours, for the neutralisation of the odours of stool and urine, and detoxification or sterilisation of wounds. nowadays, its use is even more widespread. it is used as a food additive, food colouring, and nutritional supplement, especially because of its detoxifying and excellent basifying effects. it is also a strong antioxidant, which inhibits the harmful oxidative processes in the body and enhances the protection of cells and tissues [7, 8]. however, the processing of algae still needs to be improved with respect to determining the optimal methods, pieces of equipment, solvents, and parameters for the efficient and economic extraction of chlorophyll. extraction is a process that can be carried out in a number of ways. there are also a number of solvents and preparation methods available. also, variables such as pressure, temperature, the efficiency of contact and time all play an important role [9, 10]. chlorophyll is sensitive to extreme light exposure, ph values and temperatures [7-9]. when choosing the solvent, one has to consider the sensitivity of the extracted component. a number of considerations are important, too: density, viscosity, heat of evaporation, price, effect on the environment and health. it is also essential that the 120 solvent does not react with or cause damage to the extracted component and is not corrosive. different methods can be used for different microalgae species [9-10]. experimental in advance of the extraction experiments the algae suspension (chlorella vulgaris sp.) was concentrated, dried at 60 ºc until it reached a constant mass, then ground in a ball mill. chlorophylls a and b products were obtained by the methods detailed in the following sections from this ground algae powder, which contains approximately 4 wt% water. the soxhlet extraction method one of the most well known pieces of equipment for laboratory scale solid-liquid extraction is the soxhlet extractor. in a soxhlet extractor multiple fractional distillations are carried out, the extraction is always done with the pure condensate [10]. the first step of the extraction was to fill a cellulose casing with 1-3 g of algae powder. the filled casing was placed in the middle part of the piece of equipment (fig.1). the lower round-bottom flask was filled with 400 cm3 of solvent. the soxhlet extraction was carried out with methanol, ethanol, and acetone. pumice and a magnetic stirring rod were placed into the lower flask to ensure proper boiling. the cooling water was set to a continuous flow and then the heating was turned on. after the extracting solvents had reached their boiling points and started to evaporate, they condensed in the reflux condenser and dripped back down onto the algae powder at which point the extraction of the chlorophylls started. the liquid level continuously rose in the middle section until it reached the overflow pipe letting the chlorophyll extract pour back into the lower flask. a sample of 4–6 cm3 was taken at the end of every cycle. the extraction continued as long as the absorption spectra measured by the spectrophotometer did not show a significant change. the method of leaching leaching was carried out with so-called ‘cold solvents’ at room temperature. samples of 0.1 g; 0.5 g; and 0.75 g of algae powder were measured into a test tube, then 5– 5 cm3 of solvent was added. the list of solvents was the same as for the soxhlet extraction method with the inclusion of diethyl ether. the weight of the solvent was also measured and recorded in order to have reference data in the later phases of the experiment. the samples were mixed with vortex and centrifuged for 2 minutes at 4000 rpm. a sample was taken from the top layer after centrifuge and its absorbance measured with a spectrophotometer [11, 12]. calculations the chlorophyll contents of the given samples were calculated with empirical formulae according to eqs.(1)-(8). cchlorophyll-a(90% methanol) = 15.65·a666 7.34·a653 (1) cchlorophyll-b(90% methanol) = 27.05·a653 11.21·a665 (2) cchlorophyll-a(96% ethanol) = 13.95·a665 6.88·a649 (3) cchlorophyll-b(96% ethanol) = 24.96·a649 7.32·a665 (4) cchlorophyll-a(100% acetone) = 11.75·a662 2.35·a645 (5) cchlorophyll-b(100% acetone) = 18.61·a645 3.96·a662 (6) cchlorophyll-a(95% diethyl ether) = 10.05·a662 0.76·a644 (7) cchlorophyll-b(95% diethyl ether) = 16.37·a644 3.14·a662 (8) where aλ is the absorbance at λ (in nm) wavelength, and cchlorophyll-a and cchlorophyll-b denote concentrations of chlorophyll a and chlorophyll b in µg cm-3 [12] as a function of solvents. in soxhlet extraction, the mass of the chlorophyll in the extract was calculated by the multiplication of the measured chlorophyll concentration values by the volume of the liquid in the round bottom flask. this also enabled the calculation of efficiency in mg of chlorophyll per g of dry algae units (relative to 100% dry algae powder). in the leaching experiments, the chlorophyll concentration results calculated with the empirical formulae were multiplied by the volume of the solvent that resulted in the relative chlorophyll mass values in the given samples. knowing the mass and water content of the algae, the efficiency of chlorophyll extraction relative to the mass of the dry algae can be calculated. these results were normalised to match the measurements and average values were calculated. figure 1: soxhlet extractor [12] 121 results and discussion soxhlet extraction the chlorophyll concentration measured changed according to a saturation curve as shown in fig.2. it can be concluded that under the given circumstances the solvents reached their maximum efficiency and there was no need for longer extraction times. the ability of the solvents to extract chlorophyll relative to dried algae mass during the soxhlet extraction is given in fig.3. the experiments were carried out using acetone, ethanol and methanol. it can be concluded that under the conditions of soxhlet extraction, methanol is the most potent extracting solvent of chlorophyll a and b from the algae powder, followed by ethanol and acetone respectively. it can also be pointed out that acetone and methanol are more effective for the extraction of chlorophyll b while ethanol is more effective for the extraction of chlorophyll a. the latter experiment was not carried out with diethyl ether due to health and safety considerations. extraction by leaching figs.4 and 5 illustrate the results of leaching. fig.4 depicts the concentration of chlorophyll for different masses of algae powder introduced into the system. the curves approach a saturation point in concentration, but do not reach the maximum. when we added progressively more and more algae powder to the same volume of solvent we observed increasing saturation behaviour. fig.5 presents the chlorophyll extracting ability of the various solvents when mixing 0.1 g of algae powder and 5 cm3 of solvent. as expected, the best result was obtained by utilising at least 0.1 g of algae powder of. the efficiency ranking was similar to that of the soxhlet extraction. methanol proved to be the most efficient solvent, followed by ethanol, acetone and diethyl ether respectively. the results are summarised in table 1, which contains mg of chlorophyll per g of dry algae yields. this comparison enables the different solvents to be ranked and extraction methods, which is as follows according to their efficiency: methanol, ethanol, acetone, and diethyl ether. additionally, significantly more chlorophyll can be extracted from ground algae with soxhlet extraction than with leaching. in the figure 2: changes in chlorophyll concentration during the soxhlet measurements figure 3: the efficiency of chlorophyll extraction of the various solvents during soxhlet extraction figure 4: change in chlorophyll concentration as a function of mass during leaching figure 5: efficiency of leaching using the various solvents 122 experiments conducted with acetone, it was observed that the extraction efficiency of chlorophyll a or chlorophyll b is greatly dependent on the conditions. methanol, the solvent that proved to be the most efficient, could be removed later from the chlorophyll by low temperature evaporation. conclusions from a systematic investigation of solid-phase extraction of chlorophyll a and chlorophyll b using soxhlet extraction and leaching as a function of the employed solvent, it was found that the most efficient solvent is methanol. in both extraction techniques, the extracted amount of chlorophyll using methanol as a solvent is approximately an order of magnitude higher than in acetone and close to three to four times greater than the results of ethanol. references [1] borowitzka m.a.: energy from microalgae: a short history, develop. appl. phycology (springer, the netherlands), 2013, 5, 1-15 [2] najafi g., ghobadian b., yusaf t.f.: algae as a sustainable energy source for biofuel production in iran: a case study, renewable and sustainable energy reviews, 2011, 15 (8), 3870–3876 [3] mata t.m., martins a.a., caetano n.s.: microalgae for biodiesel production and other applications: a review, renewable and sustainable energy reviews, 2010, 14(1), 217– 232 [4] bocsi r., horvath g., hanak l., hodai z.: extraction examinations of microalgae propagated for biodiesel additives, hung. j. ind. chem., 2011, 39(1), 45-49 [5] faizal b.: biotechnological applications of microalgae: biodiesel and value-added products, crc press, bosa roca, fl, united states, 2013, pp. 80 [6] demirbas a., demirbas m.f.: the importance of algae oil as a source of biodiesel, energy conversion and management, 2011, 52(1), 163170 [7] lanfer-marquez u.m., barros r.m.c., sinnecker p.: antioxidant activity of chlorophylls and their derivatives, food res. int., 2005, 38(89), 885–891 [8] hosikian a., lim s., halim r., danquah m.k.: chlorophyll extraction from microalgae: a review of the process engineering aspects, int. j. chem. engng., 2010, article id 391632 [9] simpson n.j.k., wells m.j.m.: introduction to solid-phase extraction, marcel dekker inc, new york, ny, usa, 2000, pp. 1-18 [10] meireles m.a.a.: extracting bioactive compounds for food products, theory and applications contemporary food engineering series, crc press, dublin, ireland 2009, pp. 140159 [11] lan s., wu l., zhang d., hu c., liu y.: ethanol outperforms multiple solvents in the extraction of chlorophyll-a from biological soil crusts, soil biology and biochemistry, 2011, 43(4), 857–861 [12] wellburn a.r., lichtenthaler h.: formulae and program to determine total carotenoids and chlorophylls-a and b of leaf extracts in different solvents, adv. agricul. biotechn., 1984, 2(1), 9-12 table 1: comparison of the chlorophyll (chl.) extraction results soxhlet extraction leaching chl. a chl. b chl. a & b chl. a chl. b chl. a & b acetone 0.164 0.270 0.435 0.183 0.059 0.242 ethanol 1.329 1.290 2.619 0.395 0.259 0.654 methanol 3.206 3.657 6.862 1.109 1.199 2.307 diethyl ether n/a n/a n/a 0.044 0.017 0.062 page 1 page 2 page 3 page 4 page 5 page 6 page 7 page 8 page 9 page 10 page 11 page 12 page 13 page 14 page 15 page 16 page 17 page 18 page 19 page 20 page 21 page 22 page 23 page 24 page 25 page 26 page 27 page 28 page 29 page 30 page 31 page 32 page 33 page 34 page 35 page 36 page 37 page 38 page 39 page 40 page 41 page 42 page 43 page 44 page 45 page 46 page 47 page 48 page 49 page 50 page 51 page 52 page 53 page 54 page 55 page 56 page 57 page 58 page 59 page 60 page 61 page 62 page 63 page 64 page 65 page 66 page 67 page 68 page 69 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dominant factor is the time factor. in the industrialized world a large part of the emission of the primary air pollutants (nox, volatile organic compounds (voc) and co) originates from road traffic. here we present the major source of the air pollutants in the cities caused by the vehicle emissions in hungary. besides the growing number of vehicles and development of reducing the exhaust air pollutants of the ignition motor running conditions, the total emission is growing. the air pollution regulations and law control related to the traffic and some technical evaluations to decrease the motor air pollutants are summarised. some experimental studies were carried out to investigate the activity of used commercial catalysts for cleaning processes of otto engines exhaust gases. the structure of catalyst samples were characterised by morphological properties namely surface area and pore volume. on the based of experimental data we stated that the commercial catalyst activity in nitrogen-oxide reduction and methane combustion reactions decrease correlated to the running period and conditions of them. keywords: gas emissions, vehicle, catalytic converter, nitrogen oxides, hydrocarbons introduction the sustainable development should be taken into consideration in everyday life activities, that is respected behind the process mechanization, automatization the environmental and atmosphere protection problems as well. air pollution and its impact on human health have become issues of increasing public concern during the last decades, since the pollution prevention concept emerged many years ago [1]. after the central european countries jointed to the european union the environmental protection topics got key role. the next laws are regulating the quality protection of human existence insurant ambient air in this area [2]: – government decree no. 306/2010 (xii. 23.), on the protection of air, – ministry of country development decree no. 4/2011 (i. 14.), on the limits of the load level of the air and on the emission limits of the fixed air polluting sources, – ministry of country development decree no. 5/2011 (i. 14.), about modification related to the air protection, – ministry of country development decree no. 6/2011 (i. 14.), on the rules of the examination control and evaluation of the load level of the air and the fixed air polluting sources, – ministry of environment and water decree no. 4/2002. (x. 7.) on the designation of air pollution agglomerations and zones, – ministry of transport, communication and building decree no. 6/1990. (iv.12.) on technical conditions of road vehicles issue and run. numbers of ignition engine vehicles are exceeding the one billion in the world mainly used for transportation purpose. the number of the cars, buses and motorcycles and trucks running on roads exceeded one billion values in 2010, and increase about 40 million per a year. the estimated number of ignition vehicles will increase to 124 million all over the world by 2015. the types and numbers of the vehicle used are varying country by county [3]. table 1 shows the changing of vehicular structure related to hungary. until 1960's the industrial production was the major source of the air pollutants in the cities, but later the air pollution is mainly caused by motor vehicles emissions. more than 85% of traffic-related air pollutions are coming from motor vehicles exhaust emission. in hungary about 35–40% of air pollutants can be originated to the public traffic emission. in urban area it sometimes can reach near 90%. number of cars and trucks were increased during last 25 years period in 2 and 2.6 times respectively in hungary as it can be seen in table 2, at the same time the number of buses decrease by about 30%. the average utilization of motor vehicle increases by year to year as the statistical data show [4]. 80 table 1: number of different type of vehicles in hungary 1985 1990 1995 2000 2005 2010 cars 1 435 937 1 944 553 2 245 395 2 364 706 2 888 735 2 984 063 motorcycles 395 622 168 817 159 091 91 193 122 705 142 251 buses 24 854 26 121 20 223 17 855 17 450 17 641 trucks 157 136 224 061 292 144 342 007 391 731 416 672 lurries 31 392 38 397 32 613 24 426 35 917 48 207 table 2: gasoline and diesel engine exhaust emission and health effect gasoline engine diesel-engine pollutant g emission/ dm3 fuel ratio of gasoline/diesel health effect carbon monoxide 350 20 17.5 non-carcinogenic hydrocarbons 50 39 1.28 carcinogenic nitrogen oxides 17 23 0.74 carcinogenic lead compounds 0.4 0 carcinogenic soot (particle) 1.5 8 0.2 carcinogenic sulphur dioxide 0.2 8 0.03 reduced lung function in spite of improvement for the combustion system of vehicles, the emission of air pollutants increases due to of growing number and age of vehicles [5]. in case of optimal conditions the fuel and air mixture could be burnt completely resulting carbon-dioxide (co2) and steam. for the total combustion of the fuel an optimal air-fuel mass ratio is required, otherwise the combustion results an incomplete process producing air pollutant gases: carbon monoxide (co), hydrocarbons (chx), nitrogen oxides (nox), polyaromatic hydrocarbons (pah), volatile organic compounds (voc), and increasingly growing emission of aerosols as well. otto type and diesel engine have similar air pollutants but different concentration in the exhaust gases [6]. in case of gasolined engine the gas phase pollutant are performed while diesel engines get mainly solid particles and nitrogen oxides (nox) into the air. diesel engined vehicles particlemostly contain cracked products with an order of magnitude higher than the petrol engines. suspended carbon (soot) presents in significant amount in diesel exhaust gases on which polycyclic hydrocarbons (e.g. 3,4-benzpyrene) are able to adsorb. these fine particles have carcinogenic effect and can lodge in lungs and cause respiratory and heart problems. also unburned polycyclic hydrocarbons adsorb on other airborne particles present in air, therefore the environmental impact of hazardous substances depends on efficiency of engine air purification system. the sulphur oxides can be detected in exhaust gases of diesel engines due to the presence of decreasing sulphur in diesel fuel. table 2 shows the difference between gasolineand diesel engines exhaust emission. lead emission is decreased significantly for last decade, because leaded fuel was withdrawn from allowed commercialized fuels since april 1st, 1999. so2 emission is stepwise decreasing, due to constantly development and improvement of fuel processing technology. the main possibilities to reduce the vehicle exhaust gas emission are the follows [7]: ● development of vehicle with lower fuel consumption by: o decrease of rolling friction by 25% causes 4% o decrease of aerodynamic resistance by 25% causes 6% o decrease of mass of vehicle (e.g.: vehicle part made from plastic and aluminium) by 25% leads to decrease consumption of fuel by 17%. ● introduction traffic control measures and arrangements o traffic telemetry o green wave organization, building ring roads, roads with slow lines ● policy and legal arrangements and laws: o prohibit of using vehicle above 3.5 tons from rural area o official emission control document o updating and implementation of new normative (euro normative) ● change the type of fuel (e.g. liquefied petroleum gas, biodiesel) ● development and improvement of engine construction ● exhaust gas purification ● use of alternate fuel (e.g. hydrogen, bioethanol, biodiesel) experimental method the catalytic tail gas purification methods to clean of otto engines exhaust gases are widely applied in the practice. these three-way catalysts are known to suit requirements of euro vi normative during the running period. the aim of experimental studies to get measured data about the activity of the commercial catalysts samples collected after different time of period and running conditions. the catalytic transformation efficiencies of methane and nitrogen oxide were used to characterize the activity of examined catalyst samples. for testing the catalyst samples a measuring system was constructed as it is shown on fig. 1. 81 the main part of the measuring device is a tubular flow reactor with 44 mm in inner diameter. a 44 mm diameter, 50 mm long cylinder-shaped segments was cut out from catalyst samples for the studies. two thermocouples -moveable in axis in wellsare placed into the reactor to determine the radial and axial temperature profile of the catalyst bed. after loading the catalyst samples into the tube, the test reactor body was heated up and operated in controlled conditions (heating rate, gas flow rate and composition) applying different flow rate of natural gas in the inlet gas mixture as a model exhaust gas (these measurements were carried out with gas mixture containing methane; methane and in constant flow rate of steam; methane, constant flow rate of steam and nitrogen oxides). the carbon monoxide-, carbon dioxide-, methane-, oxygenand hydrogen concentration in the outlet gas of catalytic test reactor were determined. the carbon monoxide, carbon dioxide and methane concentration were detected by on-line ndir (non dispersive infrared) analysers (servomex 1490), while the oxygen, hydrogen, over measuring range of methane and carbon monoxide concentration were detected with chromatron gchf-18-3 type gas-chromatograph using 5a type molecular sieve packed column and thermal conductivity detector. the concentration of nitrogen oxides were analysed with chemiluminescence no-nox analyser (thermo environnement inc., type model 42-h). the methane flow rates of the model gas mixture were adjusted according to molar ratios of the oxidant components (the gas flow contained nitrogen oxide were produced by catalytic oxidation of ammonia in controlled conditions). the composition of the inlet gas mixture was characterised by the so called air excess factor [λ] (the ratio of the stoichiometric and applied amount of the reductant medium in practice). origin, properties and main parameters of the catalyst samples used are collected in the table 3. figure 1: for catalyst samples testing analysis constructed measuring system table 3: the used catalysts samples catalyst sample description a almost new (shattered): ~5000 km running, mechanically damaged, taken out from exhaust pipeline b used (shattered): after 30000 km running, mechanically damaged, taken out from exhaust system c used (exchanged): replaced after environmental control, without mechanical damage d used (partly melted): replaced after the engine control, breakage pieces the specific surface area and pore size distribution in the micropore ( 0–2 nm), mesopore ( 2–50 nm), and the macropore ( 50–300 nm) diameter ranges were determined by nitrogen adsorption/desorption isotherms measured with a micromeritics asap 2000-type instrument on samples previously out gassed overnight in vacuum at the temperature of 100 °c. the surface areas of the samples (sbet) were determined by the bet method from the corresponding nitrogen adsorption isotherm [8]. the meso and macropore volume values were calculated from the nitrogen desorption isotherms using the bjh (barret–joyner–halenda) theory [9]. the pore volume of pores have 10–15000 nm in diameter range were determined by mercury penetration method using carlo erba porozimetro’70 device. 1 natural gas inlet 2 pneumatic air flow controller 3 desulphurization unit 4 inlet nox flow control 5 rotameter 6 natural gas flow control valve 7 water measuring cylinder 8 water pump 9 water flow controller 10 water cooler 11 condensate storage 12 wet gas-meter 13 digital temperature reading unit 14, 15 gas cylinders 16, 18 toroid transformator 17 temperature controller 82 results the activity tests of the samples were carried out in laboratory scale equipment introduced in fig. 1. fig. 2 shows the methane conversion over „new” type of a catalyst. nitrogen oxides reduction conversion over this catalyst is showed on fig. 3. the activity of applied catalyst for depollution process significantly depends on operation temperature. fig. 4 display the methane and nitrogen oxides conversion over a type catalyst at 600 and 700 °c temperature and at different stoichiometric ratio, λ. 40 50 60 70 80 90 100 0,50 0,75 1,00 1,25 1,50 1,75 2,00 stochionometric factor, λ c at al yt ic c on ve rs io n of c h 4, % dry inlet with steam steam + nox, t~700 °c steam + nox, t~600 °c figure 2: methane oxidation efficiency 0 20 40 60 80 100 0,50 0,75 1,00 1,25 1,50 1,75 2,00 stochionometric factor, λ co nv er si on o f n o x, % steam + nox, t~700 °c steam + nox, t~600 °c figure 3: nitrogen oxides oxidation efficiency comparison of activity of catalysts used for different periods of time is shown in fig. 5 and 6 it can be observed that activity of methane combustion and nitrogen oxides reduction decreases with increasing of running time period of catalysts, especially for the used catalyst sample d. changes in morphological structures of catalysts used for different circumstances observed are summarized in table 4. (bet surface area: sbet, m2/g, mesopore-volume: v1.7-300 nm, cm3/g, surface macropore, calculated from result of mercury penetration measurements: sbjh m2/g and macropore-volume: v10-15000 nm, cm3/g). 0 20 40 60 80 100 250 350 450 550 650 750 temperature, °c n o x a nd c h 4 c on ve rs io n, % = 1.05; = 1.16; = 1.29; =1.05; =1.16; =1.29; λ λ λ λ λ λ ch4 ch4 ch4 nox nox nox figure 4: methane and nitrogen oxides conversion over a type catalyst 0 20 40 60 80 100 0,50 0,75 1,00 1,25 1,50 1,75 2,00 air excess factor (λ), c on ve rs io n of m et ha ne , % sample a, = 710 °c sample b, =742 °c sample c, =735 °c sample d, =730 °c tmean tmean tmean tmean figure 5: methane conversion over catalysts 0 20 40 60 80 100 0,50 0,75 1,00 1,25 1,50 1,75 2,00 air excess factor (λ), c on ve rs io n of n itr og en o xi de s, % sample a, = 710 °c sample b, =742 °c sample c, =735 °c sample d, =730 °c tmean tmean tmean tmean figure 6: nitrogen oxides reduction over catalysts 83 table 4: morphological structures of catalysts sample sbet, m2/g v1,7-300 nm, cm3/g shg, m2/g v10-15000 nm, cm3/g a 5.47 0.0381 3.41 0.231 b 2.78 0.0202 1.51 0.187 c 1.86 0.0144 0.89 0.151 d 0.14 0.0007 0.77 0.142 conclusions the utilization period of motor vehicle, engine construction and technical conditions of the catalysts significantly influence the exhaust emission level of the internal combustion engine. increasing the operation time of catalysts the catalytic activity of hydrocarbon oxidation and nitrogen-oxide reduction decreased which might be directly associated with changes in catalyst morphological structure. at least the operating temperature and conditions of the catalyst should be continuously controlled during the operation of the catalyst in the engine exhaust gas system. for these reason the tests on the catalyst structure and activity of the new catalysts after thermal shock under controlled conditions are in progress. acknowledgements this work was supported by the european union and co-financed by the european social fund in the frame of the tamop-4.2.1/b-09/1/konv-2010-0003 projects.” references 1. a. n. riga-karrandinos, c. saitnis: comparative assessment of ambient air quality in two typical mediterranean coastal cities in greece. chemosphere 59, (2005), 1125–1136 2. https://kereses.magyarorszag.hu/jogszabalykereso 3. b. ferris, p. widerkehr: technical options for reducing motor vehicle emissions, chemistry and industry, 15, (1995), 597–600 4. http://statinfo.ksh.hu/statinfo/haviewer.jsp 5. m. kousoulidou, l. ntziachristos, g. mellios, z. samaras: road-transport emission projections to 2020 in european urban environments, atmospheric environment, 42, (2008), 7465–7467 6. h. grohe: ottound dieselmotoren, spiegel, verlag bucheverlag, (1992) 7. p. künczel, j. dietiker: luftreinhaltung und verkehr, schweizer ingenieur und architekt, 116(5/6), (1998), 9–10 8. s. brunauer, p. h. emmett, e. teller: adsorption of gases in multimolecular layers, j. am. chem. soc., 60, (1938), 309–319 9. p. barrett, l. g. joyner, p. p. halenda: the determination of pore volume and area distributions in porous substances. i. computations from nitrogen isotherms, j. am. chem. soc., 73, (1951), 373–380 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 /colorconversionstrategy /cmyk /dothumbnails false /embedallfonts true /embedopentype false /parseiccprofilesincomments true /embedjoboptions true /dscreportinglevel 0 /emitdscwarnings false /endpage -1 /imagememory 1048576 /lockdistillerparams false /maxsubsetpct 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/pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word 00.00 inner cover.docx hungarian journal of industry and chemistry vol. 43(1) pp. 25–32 (2015) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2015-0005 toxicology aspects of the decomposition of diuron by advanced oxidation processes tünde alapi,1,2* gergő simon,1,2 gábor veréb,1 krisztina kovács,3 eszter arany,1 krisztina schrantz,1,4 andrás dombi,1 and klára hernádi1,5 1 research group of environmental chemistry, university of szeged, rerrich béla tér 1, szeged, 6720, hungary 2 department of inorganic and analytical chemistry, university of szeged, dóm tér 7, szeged, 6720, hungary 3 institute of isotopes for energy security and environmental safety, centre for energy research, hungarian academy of sciences, p.o. box 49, budapest, 1525, hungary 4 laboratory for high performance ceramics, empa – swiss federal laboratories for materials science & technology, überlandstrasse 129, dübendorf, 8600, switzerland 5 department of applied and environmental chemistry, university of szeged, rerrich béla tér 1, szeged, 6720, hungary diuron is a phenylurea-based residual herbicide with toxic and endocrine disrupting effects. the aims of the present work were the comparison of the efficiency of various advanced oxidation processes, such as direct ultraviolet photolysis, ozonation, their combination, and heterogeneous photocatalysis from the point of view of the transformation rate of diuron, rate of mineralisation and dehalogenation, formation of aromatic intermediates, and ecotoxicological effects of the formed multicomponent solutions during the treatments. the initial rates of transformation of diuron are in the order of ozonation < heterogeneous photocatalysis < uv photolysis < combination of uv photolysis and ozonation. each method provided similar tendencies in the decrease of the concentration of organically bound chlorines (aox) since, until the diuron was completely degraded, the concentration of aox decreased almost to zero in each case. however, only heterogeneous photocatalysis was found to be effective in terms of mineralisation. ecotoxicological results showed that in each case, except for ozonation, the toxicity of the treated solutions changed through a maximum during the transformation of diuron. the maximum value was found to be lower in the case of heterogeneous photocatalysis. thus, the formation and decomposition of by-products of relatively higher toxicity than diuron can be supposed. our results confirmed that the amount of the formed (aromatic) intermediates, their quality and specific toxicity strongly depend on the applied processes. keywords: phenylurea, ozonation, ultraviolet photolysis, heterogeneous photocatalysis, daphnia magna, vibrio fischeri 1. introduction diuron (3-(3,4-dichlorophenyl)-1,1-dimethylurea, fig.1) is a phenylurea-type residual herbicide that is widely used throughout the world. it is registered in the european union’s pesticide database, in the u.s. epa, and the australian apvma. its use is strictly controlled due to its known toxic and presumed endocrine disrupting effects. it has a broad spectrum of uses, mainly as a total herbicide in non-agricultural areas (roads and railways) for the preand post-emergence control of weed-type plants, but it also has plant protection purposes in the case of certain species (e.g. sugar cane and corn) [1]. another application is as an antifouling agent, either in aquariums or in paint, to prevent algal growth on hulls of boats for example [2]. diuron has a relatively low water solubility of 42 mg dm-3 at 25 °c. it is quite *correspondence: alapi@chem.u-szeged.hu persistent in soil with a typical half-life of 75.5 days and in water-sediment of 48 days [3]. based on these data and other investigations [4], it can be concluded that this compound and its metabolites pollute the environment over an extended period of time, by leaching and run-off into ground and surface waters. this causes concerns regarding the ecosystem, mainly for aquatic plants (as the main method of action of the compound is to block photosynthesis), but also lower aquatic animals, and later presumably even more advanced organisms in the wild as well as the human body. therefore, contaminated soils and waters have to be treated in an efficient and environmentally friendly figure 1. schematic chemical structure of diuron (n(3,4-dichlorophenyl)-n,n-dimethylurea). alapi, simon, veréb, kovács, arany, schrantz, dombi, hernádi hungarian journal of industry and chemistry 26 manner. for water treatment purposes advanced oxidation processes (aops) seem to be sensible choices as secondary treatments, as they are effective, environmentally friendly and economical methods for the elimination of pollutants such as pesticides. these treatments are based mainly on the generation of highly reactive hydroxyl radicals that can induce the degradation of organic matter. the transformation of the target substance can be induced by direct photolysis given that the target molecule is able to absorb irradiating light. it can also be induced by ozonation, which is used as an industrial scale supplementary water treatment method. alternatively, heterogeneous photocatalysis, the fenton-reaction or a combination of all the above can also be used [5–9]. benítez et al. [10] investigated the transformation of phenylurea herbicides during the ozonation of natural waters and determined the reaction rate constants of diuron with both ozone (16.5±0.6 mol dm-3 s-1) and the hydroxyl radical (6.6±0.1×105 mol dm-3 s-1). during the oxidative transformation of diuron several aromatic by-products form. the main attack sites for hydroxyl radicals are the aromatic ring and the methyl group, leading to de-chlorinated or demethylated derivatives. in some cases, the reaction with the hydroxyl radical can lead to ring opening byproducts. the most important intermediates are 1-(3,4dichlorophenyl)-3-methylurea, n'-(3-chlorophenyl) n,n-dimethylurea, 1-(3,4-dichlorophenyl)urea and 3,4dichloroaniline [4]. toxicological studies regarding diuron and its metabolites showed that the parent compound is usually less toxic than a multicomponent solution containing its metabolites; however, total toxicity decays with treatment time [4]. the mode of action of diuron is to block the hill reaction during photosynthesis. two of its metabolites, 1-(3,4-dichlorophenyl)-3-methyl-urea) and n'-(3-chlorophenyl)-n,n-dimethylurea, retain this specific effect; however, the demethylation of diuron decreases its ability to bind to photosystem ii [11]. the aim of the present work was the comparison of the efficiencies of various advanced oxidative processes, such as direct ultraviolet (uv) photolysis, ozonation, the combination of these and heterogeneous photocatalysis. this comparison was made regarding the rate of transformation of diuron, the rate of mineralisation and dehalogenation, the formation of aromatic intermediates and the ecotoxicological effects of the multicomponent solutions formed as a result of the treatments. 2. experimental 2.1. the light sources and experimental apparatus for ozonation and its combination treatment, the light source was a low-pressure mercury vapour lamp, which emits 254 nm ultraviolet (uv) and 185 nm vacuum ultraviolet (vuv) light (uv/vuv lamp). this lamp (gcl307t5vh/cell, lighttech, hungary) was covered with a high purity quartz sleeve, which transmits both 185 nm vuv and 254 nm uv light. ozone was generated by the vuv photolysis of pure molecular oxygen in the gas phase. for direct uv photolysis, the sleeve of the same low-pressure mercury vapour lamp made of commercial quartz (gcl307t5/cell, lighttech, hungary), which transmits 254 nm uv light and absorbs 185 nm vuv light (uv lamp). another light source, a specific fluorescent uv lamp (lightech, hungary) emitting between 300 and 400 nm (maximum intensity at 365 nm) was applied during heterogeneous photocatalysis. the electric (15 w electric input) and geometric parameters (227 mm arc length, 307 mm length and 20.5 mm external diameter of the sleeves) of the different light sources corresponded to each other. the emitted photon fluxes were determined by ferrioxalate actinometry [12] and were found to be 8.10±0.65 × 10-6 mol photon(254nm) s-1 for low-pressure mercury vapour lamps (uv/vuv and uv) and 1.20(±0.06) × 10-5 mol photon(300–400nm) s-1 for the specific fluorescent lamp. all experiments were performed in the same photoreactor (fig.2). the light source, surrounded by an envelope was centred in a water-cooled, tubular glass reactor (340 mm length, 46 mm inner diameter). in the course of the measurements, envelopes (320 mm length and 28 mm internal diameter) made of various materials were used. the thermostat controlled (25±0.5 °c) solution of pesticide (500 cm3, c0 = 1.7×10-4 mol dm-3) was circulated (375 cm3 min-1) continuously and stirred with a magnetic stirrer bar in the reservoir. before each experiment, air was bubbled through the solution at least for 10 min. the injection of the air was continued throughout the experiment. the kinetic measurements were initiated by switching on the light source. ozonation, uv photolysis or the combination of these methods could be applied by the careful selection of the light source and apparatus envelope. ozonation figure 2. the experimental apparatus. 1: power supply; 2: teflon packing ring; 3: light source with sleeve; 4: envelope; 5: reactor; 6: reservoir; 7: magnetic stirrer; 8: pump; 9: thermostat; 10: air bottle; 11: flow meter from ref. [13]. toxicology aspects of the decomposition of diuron 43(1) pp. 25–32 (2015) doi: 10.1515/hjic-2015-0005 27 was performed using a uv/vuv lamp and perforated glass envelope. oxygen flowed through the teflon packing ring between the wall of the lamp and envelope, which separates the gas phase and aqueous solution, as shown in fig.2. the ozone was generated by the direct vuv photolysis of molecular oxygen and bubbled through the perforated envelope into the solution. using a uv lamp and non-perforated quartz envelope, uv photolysis at 254 nm could be investigated. in the case of the combination of uv photolysis with ozonation, a perforated quartz envelope was used. when heterogeneous photocatalysis was applied, the specific fluorescent lamp and nonperforated glass envelope were used. thus, the efficiency of these processes could be compared using the same energy consumption. 2.2. analytical methods and materials the concentration of diuron was determined using an hplc system (merck hitachi l-7100 with l-4250 uvvis detector). the separation of aromatic compounds was achieved with an rp-18 column (licrospher 100), using 60 % methanol and 40 % water as eluents, with a flow rate of 0.8 cm3 min-1. the quantification wavelength for uv detection was 210 nm. spectra (200 to 400 nm) of the samples during each degradation measurement were acquired on an agilent 8453 spectrophotometer using 2 mm cuvettes. the concentration of ozone in the gas phase was measured using the same spectrophotometer in a flow cell at 254 nm (ε(254 nm) = 2,952 mol-1 dm3 s-1 [14]), and was found to be 1.37×10-5 m, using oxygen gas. the adsorbable organic halogen (aox) content was recorded using an aox analyser, which consisted of an analytik jena multix 2500 aox sample unit and an apu2 sample preparation unit. samples were adsorbed on active carbon, transferred into the aox furnace and burned at 950 °c under an oxygen flow. chlorine was quantified using a micro-coulometric method. the total organic carbon (toc) content was determined using a multi n/c 3100 analyser (analytik jena). the toxicity towards daphnia magna was determined using daphtoxkit f™ magna (microbiotests inc.) tests according to the iso standard 6341. the ephippia were used after 72–90 h of hatching time at 21 °c, applying 6000 lx bottom illumination and after 2 h of pre-nourishment. the zooplankton containing samples were incubated under the same conditions for 48 h, and 8–10 neonates were added to each sample. the number of the neonates was counted using a 3×/8× table-gooseneck magnifier (vwr). mortality values were given as the percentage of the dead and/or immobilised neonates compared to their initial number. the toxicity towards vibrio fischeri luminescent bacteria was determined by measuring the natural light emission of these microorganisms using a hachlange lumistox 3000 luminometer. the inhibition of the light emission in the presence of the sample was determined against a non-toxic control. nacl was added to each sample to obtain a 2 % solution. the samples were diluted by half with 1.0 mol dm-3 naoh and 1.0 mol dm-3 hcl solutions to achieve a ph value of 7±0.2. samples containing bacteria were incubated at 15 °c for 15 min before the toxicity measurements. samples for the toxicity tests were taken at the same degradation degrees (0, 12, 25, 50, 75, 100, and above 100 %) of diuron for the treatments. the decomposition of diuron, as characterised by the initial rate of transformation, which was obtained from linear regression fits to the actual concentration of pesticide versus the time of irradiation, up to 30 % of the concentration of the transformed target compound. diuron (3-(3,4-dichlorophenyl)-1,1-dimethylurea, purity 98 %) was purchased from sigma-aldrich and used without further purification. ultrapure water obtained from a millipore milli-q system was utilised for the preparation of all stock solutions and hplc eluents. hplc-grade methanol was purchased from hipersolv chromanorm. the degussa p25 photocatalyst (49 m2 g-1 surface area, 90:10 anatase/rutile ratio with 25.4 and 40 nm primary particle sise, respectively) with 0.5 g dm-3 loading was used during the heterogeneous photocatalytic experiments. 3. results and discussion 3.1. the rate of transformation of diuron in the present work, the initial rate (r0) of transformation of diuron was determined using various advanced oxidation processes. these can be ranked as ozonation (r0 = 1.0±0.05 × 10-8 mol dm-3 s-1) < heterogeneous photo catalysis (r0 = 7.9±0.3 × 10-8 mol dm-3 s-1) < uv photolysis (r0 = 13.6 ± 1.2 × 10-8 mol dm-3 s-1) < combination of uv photolysis and ozonation (r0 = 27.3±1.2 × 10-8 mol dm-3 s-1) (fig.3). the rate of direct photolytic transformation is determined by the molar absorbence of the target compound and quantum yield of the photolytic process. the absorption coefficient of diuron at the irradiation wavelength of the lamp (254 nm) was determined by using the beer-lambert law, and was found to be ε = 15,000 mol-1 dm3 cm-1. djebbar et al. [15] determined figure 3. kinetic curves of the transformation of diuron using ozonation (!), heterogeneous photocatalysis (�), direct uv photolysis (") and the combination of uv photolysis with ozonation (#). alapi, simon, veréb, kovács, arany, schrantz, dombi, hernádi hungarian journal of industry and chemistry 28 the quantum yield of the photolysis of diuron at 254 nm to be 0.0125, insensitive to ph within the range 2–8.5. the apparent quantum yield of the photoinitiated transformation of diuron was calculated on the basis of the absorbed photon flow and initial transformation rate of the target molecule. in the present work, this value was found to be 0.008. at the applied initial concentration (c0 = 1.70×10-4 m), the solution of diuron fully absorbed the emitted photons. ozonation was found to be the least effective method (fig.3). in aqueous solutions, the decomposition of ozone yields reactive oxygen containing species such as hydroxyl radicals, which are generally a stronger oxidising agent than molecular ozone. the decomposition of ozone in an aqueous solution is initiated by hydroxide ions. at a neutral ph and/or under acidic conditions, molecular ozone should be the dominant oxidant species. during the ozonation of diuron the ph strongly decreased from 8.3 to 4.1, consequently, ozone reacts with diuron mainly as molecular ozone and the formation of hydroxyl radicals is irrelevant. referring to the reaction mechanisms, molecular ozone can react with organic substrates either through cycloaddition to unsaturated bonds or in electrophilic and nucleophilic reactions [16]. nucleophilic reactions occur at molecular sites exhibiting an electron deficit and, more frequently, on carbons carrying electron-withdrawing groups, such as chlorine. based on the values of the initial rate of decomposition, it can be concluded that, by applying the combination of uv photolysis and ozonation, the synergistic effect occurred. the addition of ozone, although in a relatively low concentration, caused the rate of decomposition to double (r0 (254 nm / o3) / r0 (254 nm) = 2.0) (fig.3). both uv photolysis and ozonation are quite selective methods in the oxidative transformation of organic substances. their combination via uv photolysis of ozone itself can produce reactive species, mainly hydroxyl radicals. consequently, the combination of uv photolysis with ozonation generally results in a less selective and more effective method for the oxidative transformation of organic substances. it has to be mentioned, that the relative contribution of direct photolysis to the transformation probably remains high, because of the high molar absorbence of diuron and the relatively low concentration of ozone. under the employed experimental conditions, light absorption of ozone was negligible compared to that of diuron. in the present work, the light emitted by the fluorescent lamp was suitable for the excitation of tio2. the direct photolysis of the compound was excluded by the chosen experimental conditions. this was controlled during the measurements. upon irradiation in the near uv range, electron hole pairs are formed in the tio2 nanoparticles. these charges may reach the surface of the catalyst particle, and undergo redox reactions with substrates or dissolved molecular oxygen, producing highly reactive species such as hydroxyl radicals and hydroperoxyl or superoxide radicals, which can efficiently oxidise the organic pollutants. besides, contaminants adsorbed on the surface of the catalyst particles can directly react with the photochemically formed holes and electrons, promoting the processes of mineralisation. comparing the efficiency of heterogeneous photocatalysis to direct photolysis, this method is less efficient, but much more efficient than ozonation in the case of the transformation of diuron (fig.3). 3.2. spectrophotometric measurements spectrophotometric measurements were carried out on each treatment experiment. the spectra of solutions show that the absorbence at 277 nm increased during the decomposition of diuron while the absorbence at 248 nm changed according to the maximum curves in uv irradiated solutions (fig.4a). it has to be mentioned, that the absorbence at 277 nm decreased slowly after the decomposition of diuron. this suggests that aromatic figure 4. spectra of the samples treated with uv photolysis (a), ozonation (b), combination of uv photolysis with ozonation (c) and heterogeneous photocatalysis (d) at 0, 25, 50, 75 and 100 % decomposition of diuron (inserted figures show the absorbences at 248 nm (!) and 277 nm ($) versus the decomposed diuron). toxicology aspects of the decomposition of diuron 43(1) pp. 25–32 (2015) doi: 10.1515/hjic-2015-0005 29 intermediates accumulated and probably decomposed during the uv initiated transformation. the maximum value of the absorbence at 277 nm was found to be much higher in uv irradiated solutions (0.145) (fig.4a) than in the case of the combination of ozonation with uv photolysis (0.09) (fig.4c). this suggests that the addition of ozone strongly enhanced the rate of formation and decomposition of these intermediates and consequently, hindered their accumulation, most likely due to radical based reactions. the time dependence of the relative absorption at 277 nm suggests that not only the formation, but also the decomposition of these aromatic intermediates took place. this latter process was partly completed in parallel with the transformation of the parent compound, and partly after its transformation. the colour of the aqueous solution of diuron changed from colourless to intensive yellow-pink when uv photolysis was applied. at the same time, when the combination of uv photolysis with ozonation was applied, the change in colour was less intensive. each solution became colourless after the decomposition of diuron. using ozonation (fig.4b) or heterogeneous photocatalysis (fig.4d) neither the change in colour of the solution, nor increase in absorbence at 277 nm was observed. this suggests that the coloured aromatic intermediates were most probably formed mainly during the direct uv photolysis of diuron. these results and observations also suggest that the amount and quality of the aromatic intermediates strongly depend on the applied process. 3.3. dehalogenation and mineralisation uv photolysis, ozonation, the combination of these and heterogeneous photocatalysis provided similar tendencies with respect to the decrease in concentration of adsorbable organically bound chlorines (aox), since in each case, until the 100 % transformation of diuron was achieved, the concentration of aox decreased by almost 100 % (fig.5a). this means that not only the pesticide itself, but the formed halogenated by-products were also de-chlorinated simultaneously within the timeframe of transformation of the parent substance. it has to be mentioned, that the rate of dechlorination was higher in the case of uv photolysis than heterogeneous photocatalysis, mainly at the beginning of the treatment. direct uv photolysis is a quite selective method for the transformation of organic substances and can be effective for the transformation of compounds, which highly absorb at 254 nm (such as diuron and probably its aromatic intermediates), mainly by the dissociation of the carbon-halogen bond. on the other hand, in the case of heterogeneous photocatalyis, adsorption has an important role. competitive adsorption can occur between the aromatic compounds containing chlorine atom(s) and the formed intermediates, which do not contain chlorine atom, and exhibit better adsorptivity (mainly carboxylic acids). consequently, the formation of these intermediates and their adsorption on the surface of the photocatalyst can cause a relatively slow decrease in the rate of dechlorination (fig.5a). ozonation is a quite selective method for the transformation of organic substances, similar to direct uv photolysis. these methods are generally not effective in terms of mineralisation, as also observed in this work (fig.5b). in the case of the combination of these methods the toc content slightly decreased, most likely because of the hydroxyl radical based reactions. in the case of heterogeneous photocatalysis, the rate of mineralisation was very low at the beginning, but the toc decreased rapidly in the final stage of decomposition of diuron (fig.5b). compared to uv photolysis and ozonation, heterogeneous photocatalysis is a less selective method and generally results in the transformation and, in most cases, the mineralisation of a large variety of organic substances. however, the transformation of compounds takes place on the surface of tio2 particles, thus adsorption has a crucial role in this case, as mentioned previously. it is probable that the superior adsorptivity of aliphatic intermediates (mainly carboxylic acids) is the reason why mineralisation takes place in parallel with the transformation of parent compounds. this explanation is in agreement with the observation that the rate of the change in concentration of aox increased when mineralisation became dominant (fig.5). 3.4. ecotoxicological measurements the results obtained from both daphtoxkit ftm and vibrio fischeri luminescence inhibitory tests showed that the toxicity of the treated solutions changed through a maximum value within the time frame of transformation of diuron in solutions irradiated with 254 nm uv light (figs.6a and 7a). consequently, the figure 5. kinetic curves of the transformation of diuron using ozonation (!), heterogeneous photocatalysis (�), direct uv photolysis (") and the combination of uv photolysis with ozonation (#). alapi, simon, veréb, kovács, arany, schrantz, dombi, hernádi hungarian journal of industry and chemistry 30 formation and decomposition of by-products exhibiting relatively higher toxicities than expected from diuron. during ozonation, both the mortality and inhibitory effect increased, which can be explained by the formation and accumulation of intermediates more toxic than the parent compound (figs.6b and 7b). the tendencies of mortality and the inhibitory effect were similar, although mortality increased slightly, and the inhibitory effect increased strongly during the transformation of diuron. it can be supposed, that vibrio fischeri is more sensitive to the presence of the intermediates formed due to the reaction of molecular ozone with diuron, which can be the reason for this observation. in the case of the combination of uv photolysis with ozonation, the mortality and inhibitory effect changed through maxima (figs.6c and 7c), in a similar way to direct uv photolysis. however, in this case the maxima were reached at 25 % and 50 % decomposition of diuron (figs.6c and 7c), while during uv photolysis the maxima were reached at 50 % and 75 % decomposition of diuron (figs.6a and 7a). using heterogeneous photocatalysis, the mortality and inhibitory effect changed also through maxima (figs.6d and 7d). at the same time, it has to be mentioned, that in this case, the values of the maxima were found to be lower than those determined in the case of uv photolysis and its combination with ozonation, mainly in the case of results obtained using the daphtoxkit ftm test. the mortality using heterogeneous photocatalysis did not reach 40 %, while in the case of uv photolysis and its combination with uv photolysis it exceeded 60 %. this confirms that the amount of the aromatic intermediates was less, and/or their specific toxicity was lower than in the case of uv photolysis and its combination with ozonation. at this point, a correlation can be established between the results of spectrophotometric measurements and ecotoxicological tests. in the case of uv photolysis, the formation and accumulation of aromatic intermediates were supposed, while in the case of the combined method, their amount was likely to be lower. at the same time, in the case of heterogeneous photocatalysis, their formation was less favourable than in the presence of 254 nm uv light. these observations, together with the results of the ecotoxicological tests, suggest that the toxic intermediates are most likely aromatic by-products. 4. conclusion in this work, various advanced oxidation processes, such as uv photolysis at 254 nm, ozonation, their combination and heterogeneous photocatalysis were investigated and compared regarding the oxidative transformation of diuron. the initial rates of transformation were determined at the same electric energy input and exhibited the following order: ozonation < heterogeneous photocatalysis < uv photolysis < combination of uv photolysis and ozonation. the results obtained from spectrophotometric measurements suggested that aromatic intermediates accumulated during the uv initiated transformation of diuron. the addition of ozone of relatively low concentration strongly enhanced the rate of formation and/or decomposition of these intermediates. using ozonation or heterogeneous photocatalysis, the amount figure 6. mortality of daphnia magna after uv photolysis (a), ozonation (b), the combination of uv photolysis with ozonation (c) and heterogeneous photocatalysis (d) at 0, 12, 25, 50, 75, 100 % and above 100 % (samples taken 10 minutes after total decomposition) decomposition of diuron. figure 7. inhibition values for vibrio fischeri after uv photolysis (a), ozonation (b), the combination of uv photolysis with ozonation (c) and heterogeneous photocatalysis (d) at 0, 12, 25, 50, 75, 100 % and above 100 % (samples taken 10 minutes after total decomposition) decomposition of diuron. toxicology aspects of the decomposition of diuron 43(1) pp. 25–32 (2015) doi: 10.1515/hjic-2015-0005 31 of the formed aromatic intermediates was likely to be lower. uv photolysis, ozonation, their combination and heterogeneous photocatalysis provided similar tendencies in the decrease of the concentration of adsorbable organically bound chlorines (aox) since, in each case, until the 100% degradation of diuron was achieved, the concentration of aox decreased by almost 100%. on the other hand, only heterogeneous photocatalysis was found to be effective in terms of mineralisation during the decomposition of diuron. in this case, the rate of mineralisation was low at the beginning, but the total organic carbon content decreased rapidly in the final stage of the decomposition of diuron. ecotoxicological measurements were carried out with both daphtoxkit ftm and vibrio fischeri luminescence inhibitory tests. the results showed that the toxicity of the treated solutions changed through a maximum curve within the time of transformation of diuron in each case, except for with ozonation. thus, the formation and decomposition of by-products, having relatively higher toxicity than diuron, can be supposed. using heterogeneous photocatalysis, the mortality and inhibitory effect also changed through maxima, but the values of the maxima were found to be lower than that determined in the case of uv photolysis and its combination with ozonation. our observations and results confirmed that the aromatic intermediates formed, their quantity, and specific toxicity strongly depend on the applied process. acknowledgement this research was supported by the european union and the state of hungary, co-financed by the european social fund in the framework of támop-4.2.4.a/ 211/1-2012-0001 ‘national excellence program’. the financial help of the “társadalmi megújulás operatív program” (támop-4.2.2.a-11/1/konv-2012-0047) is also highly appreciated. the environmental chemistry research group would like to thank the swiss contribution (sh7/2/20) for its financial support. references [1] holmes, g.: australia’s pesticide environmental risk assessment failure: the case of diuron and sugar cane, marine pollut. bull., 2014, 88(1–2), 7–13 10.1016/j.marpolbul.2014.08.007 [2] yebra, d.m.; kiil, s.; dam-johansen, k.: antifouling 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arany, schrantz, dombi, hernádi hungarian journal of industry and chemistry 32 [14] atkinson, r.; baulch, d.l.; cox, r.a.; crowley, j.n.; hampson, r.f.; hynes, r.g.; jenkin, m.e.; rossi, m.j.; troe, j.: evaluated kinetic and photochemical data for atmospheric chemistry: volume i gas phase reactions of ox, hox, nox and sox species, atmos. chem. phys., 2004 4, 1461-1738 10.5194/acp-4-1461-2004 [15] djebbar, k.; sehili, t.; mazellier, p.; de laat, j.: phototransformation of diuron in aqueous solution by uv irradiation in the absence and in the presence of h2o2, environ. technol., 2003 24, 479–489 10.1080/09593330309385583 [16] hoigné, j.; bader, h.: rate constants of reactions of ozone with organic and inorganic compounds in water i: non-dissociating organic compounds, water res., 1983 17, 173-183 10.1016/00431354(83)90098-2 microsoft word b_48_szabog_r.doc hungarian journal of industrial chemistry veszprém vol. 39(2) pp. 289-294 (2011) investigation on coherencies between residual stresses and tool geometry by hard turning g. szabo , j. kundrak university of miskolc, department of production engineering, h-3515 miskolc, egyetemváros, hungary e-mail: gergely.szabo@uni-miskolc.hu a wide group of scientists are concerned by the studying of chip removal in hard turning even today. the reason for that is that the cutting conditions must be chosen accurately to exploit the benefits provided by hard turning. among the parameters influencing the material removal, the edge geometry of the cutting tool also plays a decisive role since the effective chip removal is ensured by a special edge formation made from a hardened surface of about 60 hrc hardness. in this paper the effect of the tool rake angle on the chip removal process is investigated, examining a relatively wide interval of the rake angle value. keywords: hard turning, residual stresses, rake angle introduction to choose the cutting tool with a proper edge geometry, the research experience gained so far through the examinations of the characteristics of workpieces and tools must be taken into account. when applying pcbn tools generally the negative rake angle is preferred often supplied with facets. the proper smoothness of the cutting edge is reached by honing after grinding and/or coating. the cutting edge geometry significantly affects the physical properties of the workpiece, the status of the tool wear and the residual stress in the surface of the workpiece. the change of the cutting edge has got the highest effect on the change of residual stress in the surface layer of the workpiece. however, there have been researches [1, 2, 3] on how the change of the rake angle concretely influences the stress condition, and that does not necessarily show linearity with the change of the rake angle. there were researchers who proved that a certain decrease of the value of the rake angle increased the compressive residual stresses, but with a further increase a lower compressive stress remained [1, 3]. residual stresses in case of hard turning residual stresses play a very important role in the research of the surface quality. the surface structure characteristics are considered the most important part of the surface quality. the most important technical components of the surface quality can be seen in fig. 1. kloos and kaiser [2] researched residual stresses by various ways of manufacturing. figure 1: the most important areas of surface engineering [1] however, they found residual stresses only in semifinished and readymachined parts. residual stresses are in one respect static triaxial stresses, and stresses emerging from external mechanical effects (cutting force components and/or moments). they always develop in microscopic scale, in the direction of the crosssection of the multilayered surface deformed plastically by external and internal forces [2]. the compressive residual stresses play the most important role in the surface layer. the most important consequence of the compressive residual stresses is their effect on the fatigue life [1, 3]. fig. 2 shows the possible causes of residual stresses. 290 figure 2: the causes of residual stresses [1] byrne et al. [1, 4] examined the behaviour of the residual stresses in case fine of finishing processes with geometrically defined cutting edges of hardened steels. their opinion is that the values of the residual stresses are in dependence of the value of friction between the workpiece and the cutting tool [4]. dahlman et al. [5] researched the influence of the rake angle and cutting parameters on the residual stress of the workpiece surface in case of hard turning. the used material was hardened steel (aisi 52100) with the hardness 62 hrc [1, 4]. they researched the influence of the rake angle from -6° to -61°. in case of application -61°, the maximum values of compressive residual stresses were approximately six times higher than in case of -6° [1, 4]. rech and moisan [6] researched the mechanical stresses in case of hardened steels (27mncr5) with hardness 850 hv (65.7 hrc). they researched the external conical surfaces of gears in mass production. according to their research the residual stresses are determined by the tool material, the tool coatings, the edge geometry and the various machining parameters [1]. the changes of the physical properties of the surface layer are due to the cutting force and the cutting temperature [1, 6]. the typical residual stress profile in the tangential direction can be seen in fig. 3 (vc=110 m/min, ap=0.1mm, f=0.1 mm/rev). figure 3: residual stresses at rake angle of -21° [5] figure 4: the unit cutting force in dependence of the rake angle [7] 291 modelling of residual stresses with fem-simulation in case orthogonal hard turning the research of the residual stresses in case of orthogonal hard turning was executed with the application of finite element method (fem). the investigation of the rake angle change effect on the residual stresses in tangential direction was done by the 2d version of third wave advantedgetm 5.5 program package, which is optimised for cutting process, therefore several researchers [8, 9, 10] use this software to simulate metal cutting. for the material quality 16mncr5 (aisi 5115) used by us, we have to find the proper model of “deformationstress” which has to meet two important requirements: high accuracy and a relative mathematical simplicity, because of quick computation. for the behaviour of the workpiece material used by us, a johnson-cook model was applied. this model is a strain-rate and temperature dependent, visco-plastic material model suitable for problems where strain rates vary over a large range (102–106 s-1), and where the temperature changes due to plastic deformation caused by thermal softening [11]. we used the next form of the johnson-cook equation: ( ) 444 3444 2144 344 21 & & 43421 ..cos 0. 1ln1 termsoftening m roommelt room termityvis termplasticelasto n eq tt ttcba ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ − − −⋅⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ ⋅+⋅⋅+= − ε εεσ (1) where σeq is the equivalent stress, ε is the plastic strain, ε& is the plastic strain rate, 0ε& is the reference plastic strain rate, t is the temperature of workpiece, tmelt is the melting temperature of workpiece material, troom is the room temperature, coefficient a is the yield strength, b is the hardening modulus, and c is the strain rate sensitivity coefficient, n is the hardening coefficient, and m is the thermal softening coefficient. for the definitions of designations showed above, and their interpretation we cannot give more details because of lack of space, they can be found in the quoted literature [1, 2, 3, 4, 6, 8]. the values of the parameters of johnson-cook equation for material 16mncr5 are: σeq=400 mpa; a=588 mpa; b=680 mpa; c=0.057; n=0.4; m=0.7 [11]. the process parameters of the experiment are listed in table 1. table 1: fem-software input parameters workpiece workpiece length 5 mm workpiece height 3 mm workpiece material cubic boron nitrid tool rake angle +15°…-30° rake face length 3.0 mm relief angle 6° relief face length 3.0 mm cutting edge radius 0.01 mm material 20mncr5 simulation max. number of nodes 24 000 max. element size 0.1 mm min. element size 0.01 mm process depth of cut (ap) 0.2 mm length of cut 3 mm feed 0.2 mm/rev cutting speed 180 m/min friction coefficient 0.35 coolant not used the effect of the rake angle on the residual stresses in our investigations the effect of the rake angle was analysed in the interval of 0 – -26° in 5 degree steps. the results of fem-analysis of the tangential residual stresses in the hard turned workpiece surface can be seen in fig. 5. on the left side of the figures (fig. 5, 6, and 7) the processed tangential residual stresses are shown at different values of depth (0–150 µm) of the machined surface layer. on the right side of the figures the colour fem-results of the machining process can be seen. at the value of as γo=0° the effect compressive residual stresses emerge in the surface layer. it is characteristic that starting from a small value of tensile stresses in the surface layer even at a small depth high compressive residual stresses are present. reducing the rake angle, the maximum value of the compressive stress increases. reaching the γo=-25°rake angle the value of the compressive stress increases from 800 mpa to 1200 mpa that is to its half as big again at the examined depth of surface. the presence of the compressive stresses is beneficial since it means the hardening up of the surface layer, which is advantageous for the life of the components built in the structure (fig. 5-6). the compressive stresses are highly important for the hardening of the material surface. therefore it is worth applying a negative rake angle in the researched rake interval (γo = 0 – -25°) in case of hard turning, by all means. having a tool with γo=-20°, the change of the stress condition of the workpiece was examined depending on the distance from tool tip. the change depending on the depth of the surface layer is shown in fig. 5. 292   figure 5: the change depending on the depth of the surface layer (γo=-20°) a) b) c) figure 6: the change of the residual stress depending on the depth of the surface layer (a: γo=0°; b: γo=-5°; c: γo=-10°) 293 a) b) c) figure 7: the change of the residual stress depending on the depth of the surface layer (a: γo=-15°; b: γo=-20°; c: γo=-25°) conclusion this paper presents the comparison of the residual stresses by means of fem simulation, in hard turning, changing the values of rake angles. in cutting generally by all means we strive to choose a cutting technology which supposedly develops the some residual stress. the experiments show that having a value of γo negative rake angle, this expectation can be ensured. the research reveals how significantly the tool edge geometry affects the planned surface creation. in the researched rake interval it is worth applying the biggest negative rake angle, because here the compressive residual stresses are the highest. acknowledgement the described work was carried out as part of the támop-4.2.1.b-10/2/konv-2010-001 project. the work was presented by the support of the hungarian scientific research fund (number of agreement: otka k 78482), which the authors greatly appreciate 294 references 1. j. p. davim: surface integrity in machining. springer verlag, london, 2010. isbn: 978-1-84882-873-2, p. 215 2. k. h. kloos, b. kiser: residual stresses induced by manufacturing, residua stresses measurement, calculation, evaluation. deutsche gesellschaft füt wärmebehandlung und werkstofftechnik. deutsche gesellschaft für metalkunde, 1991, pp. 191–226 3. m. c. shaw: metal cutting principles. oxford university press, new york, 2005 4. g. byrne, d. dornfeld, b. denkena: advancing cutting technology, cirp annals, 2003, manufacturing technology, 52(2), 483–507 5. p. dahlmann, f. gunnberg, m. jacobson: the influence of rake angle, cutting feed and cutting depth on residual stresses in hard turning, journal of materials processing technology 147(2), (2004), 181–184 6. j. rech, a. moisan: surface integrity in finish hard turning of case-hardened steels, international journal of machine tools & manufacture, 43, (2003), 543–550 7. e. pauksch, s. holsten, m. linß, f. tikal: zerspantechnik. vieweg + teubner verlag, wiesbaden, 2008, isbn 978-3-8348-0279-8 8. j. p. davim, c. maramhao: a study of plastic strain and plastic strain rate in machining of steel aisi 1045 using fem analysis. materials and design, 30, (2009), 160–165 9. d. umbrello, s. rizzuti, j. c. outeiro, r. shivpuri, r. m’saoubi: hardness-based flow stress for numerical simulation of hard machining aisi h13 tool steel. journal of materials processing technology, 199, (2008), 64–73 10. w. zębala: simulation of cutting with the defined tool geometry, journal of machine engineering, 5(3-4), (2005), 109–119 11. čsn 41 4220/iso 683/11-70 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjdffile false /createjobticket false /defaultrenderingintent /default 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(adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word 2012_dr_bodor_endre_hjic.doc hungarian journal of industrial chemistry veszprém vol. 39(3) pp. 381-386 (2011) degradation of organic pollutants in photocatalytic reactors a. ujhidy1, e. szabó-bárdos2, o. horváth2 , a. horváth2, k. schmidt2 1university of pannonia, research institute of chemical technology, h-8201 veszprém, p. o. box 158, hungary 2university of pannonia, institute of chemistry, department of general and inorganic chemistry h-8201 veszprém, p. o. box 158, hungary e-mail: otto@vegic.uni-pannon.hu titanium dioxide-mediated photocatalytic mineralization of oxalic acid and formic acid as model compounds were studied in a laboratory-scale reactor and in a pilot equipment to promote the development of procedures for wastewater treatment. experimental results obtained by using various tio2 catalysts indicate that the adsorption of the pollutant substrates on the surface of the semiconductor particles is not directly correlated with the specific surface area of the adsorbent. the initial rate of the photocatalytic degradation of the model compounds is enhanced by increasing the adsorption capability of the titanium dioxide applied, but the overall mineralization efficiency is jointly determined by several factors such as the crystal structure, the mean value and the distribution of the particle size, as well as the number of the hydroxyl groups on the particle surface. the vp p90 tio2 proved to be the most efficient photocatalyst for degradation of both model compounds studied. application of static mixer in the pilot equipment enhanced the rate of the photocatalytic mineralization of formic acid by about 27%. this effect can be attributed to the increased interfacial mass transfer facilitating the movement of photogenerated ho● radicals from the catalyst surface or the boundary layer to the bulk solution. keywords: photocatalysis, degradation, titanium dioxide, adsorption, oxalic acid, formic acid, mineralization, wastewater treatment introduction sustainable development and environmental protection warrant newer and stricter rules regarding the level of pollution. thus, increasing attention should be paid to the viewpoints of environmental chemistry in the industrial production and agricultural activity. the best strategy, of course, is prevention, i.e., the application of environmentally friendly, pollution-free „green” technologies [1]. nevertheless, in several cases, the use of materials having serious environmental impact, being even dangerous, moreover, toxic, cannot be avoided. the photocatalytic detoxification of wastewaters is a typical representative of the advanced oxidation processes (aop) [2]. in the modern environmental protecting procedures, in the past decade, the techniques applying uv light-driven catalytic treatment became widespread. in such a process of degradation the oxidizing agent is oxygen and/or ozone, or solution of hydrogen peroxide, which finally became the part of the simple inorganic end-products of the mineralization (such as h2o or co2). thus, the purified water does not contain any rest or trace of the oxidizing agent. the most reliable and widely used photocatalyst applied for wastewater treatment is nanosized titanium dioxide semiconductor [3, 4]. upon irradiation in the near uv range, electronhole pairs are formed in the tio2 nanoparticles. these opposite charges may recombine or, reaching the surface of the catalyst particle, can undergo redox reactions with h2o, hoor dissolved o2, producing highly reactive species such as ho● and ho2 ●, which efficiently oxidize the organic pollutants in the bulk solution. besides, contaminants adsorbed on the surface of the catalyst particles can directly react with the photochemically formed holes and electrons, promoting the processes of mineralization. currently considerable efforts were made to thoroughly study the photomineralization of a wide range of organic contaminants on various types of tio2 catalysts [5-7]. several procedures have already been applied for practical use [8, 9], thus, one of the most important requirements regarding the catalyst utilized is the highest possible efficiency. beside the crystal structure of tio2 [10-12], the photoactivity of the catalyst is affected by the following parameters: the mean size [13, 14], the size distribution, and the specific surface area of the semiconductor particles [15]. these properties jointly determine the rate of the electron-hole recombination, the adsorption activity of the catalyst, and the numbers of surface hydroxyl groups [16], which significantly influence the efficiency of the degradation processes. the crystal structure of the semiconductor predominantly depends on the preparation technology. for development of a photocatalytic treatment of a wastewater, beside the elucidation of the degradation 382 mechanisms of the pollutants contained, it is extremely important to design the photoreactor and to determine the limits of its applicability. hence, for these purposes, we have studied the degradation of formic and oxalic acids as model compounds in a laboratory-scale photoreactor as well as in a larger pilot equipment, using tio2 photocatalysts of different types. experimental laboratory-scale photoreactor irradiations of the reaction mixtures were carried out in a photoreactor of 3 dm3 net volume (fig. 1). the lightsource was a 40-w light-tube developed for such a photocatalytic purpose. most of its radiation energy is emitted above 300 nm (fig. 2). figure 1: simplified scheme of the laboratory-scale reactor 1. cylinder for compressed air vessel, 2. regulating valve, 3. rotameter, 4. buffer, 5. input stump, 6. light source, 7. glass filter, 8. sampling stump, 9. gas output in this reactor the heterogeneous reaction mixture (tio2 suspension) was circulated by continuously fed air with a flow rate of 40 dm3 h−1. the photon flux of the internal light source was determined by potassium tris(oxalato)ferrate(iii) chemical actinometry. it was estimated to be 4.3·10-6 mol photon dm-3 s-1. the concentration of tio2 was 1 g dm-3 in all photochemical experiments. high purity water used in these experiments was double distilled and then purified with a milli-q system. the initial ph of the reaction mixture was adjusted using h2so4 and naoh solutions prepared by of pure reagent grade acid and hydroxide, respectively. pilot equipment a solardetox ® acadus-2005/2.0 movable reactor developed for investigation of photocatalytic procedures driven by solar radiation has been modified so that it can be operated by artificial light sources, too (fig. 3). for irradiation of the reactor consisting of 24 tubes connected, three 40-w light-tubes were applied, the emission spectrum of which was similar to that used in the laboratory-scale equipment (fig. 2). 0.00 0.05 0.10 0.15 0.20 290 340 390 wavelength / nm ir ra di an ce / w m -2 figure 2: emission spectrum of the light tube applied at 40 w load, uv-b (280–315 nm): 0.15 w m-2 uv-a (315–400 nm): 6.3 wm-2 figure 3: the simplified scheme of the photochemical reactor for promotion of homogeneous energy transfer to the flowing reaction mixture, the stream of the fluid was modified with static mixers. an efficient photocatalytic oxidation needs the titanium dioxide powder kept in homogeneously suspended state. the static mixers in the reactor tubes promote not only the effective energy input, but they prevent the sedimentation of the catalyst powder and its deposition on the glass wall of the reactor. cooler air ho2 2 tio2 solar uv 383 analysis before and during the continuous uv-a irradiation aliquot samples were taken from the reaction mixture through a septum with a syringe. tio2-containing samples were filtered through a millipore millex-lcr ptfe 0.45 μm membrane filter. the ph of the aqueous phase of the reaction mixture was measured by a sen tix 41 electrode. the initial concentration of oxalic acid was adjusted to be 10-3 m and of formic acid was adjusted to be 2·10-3 m. the concentration of the oxalic acid was determined by classical permanganometry using the aliquot of the clear liquid sample. the mineralization of model compounds was followed by measuring the total organic carbon (toc) concentration, utilizing a thermo electron corporation toc-tn 1200 apparatus. results and discussion the adsorption and the efficiency of the photodegradation of the model compounds, formic and oxalic acids, have been studied on catalysts of various compositions and particle sizes. the characteristic data of the individual catalysts are summarized in table 1. table 1: characteristic data of the catalysts applied anatase rutile catalyst anatase (%) particle size (mean diameter) (å) specific surface area (m2 g-1) vp p90 94 278 195 90 aeroxid p25 91 275 435 50 degussa p25 70 278 484 50 mpc 500 100 69 300 adsorption measurements for determination of the adsorption the suspension containing the catalyst was circulated in the photoreactor for 60 minutes without irradiation. the initial concentration of the investigated formic acids was adjusted to 2·10-3 m and oxalic acid 1·10-3 m. aliquot samples were taken from suspensions after various time intervals. the samples were filtered. the measure of the amount of the substrate adsorbed on the surface of the catalyst was determined on the basis of the change in toc in the aqueous phase. it decreased continuously until the equilibrium concentration has been achieved. after 30 minutes stirring the concentration of the model compounds was found to be constant in the homogeneous solutions. as fig. 4 displays, the adsorption of formic acid on the catalyst aeroxid p25 is surprisingly low, while it is about the same on the other semiconductors. also in the case of reaction mixtures containing oxalic acid, the lowest adsorption was observed on aeroxid p25 catalyst, while the highest one on degussa p25 (fig. 5). comparing the values of the adsorption and the specific surface areas of the semiconductor, interesting relations can be noticed. it is unambiguously seen that the measure of adsorption is determined by not only the magnitude of the catalyst’s specific surface area. it is valid for both substrates studied that the highest adsorption is observed not on the catalyst mpc 500 with the largest specific surface area (300 m2 g-1). the adsorption on the particle surface is also affected by the anatase content of the catalyst. the catalysts degussa p25 and aeroxid p25 are of the same specific surface area and very similar mean particle sizes (278 å and 274 å, respectively), but the higher anatase content for the second tio2 sample (70% vs. 91%) resulted in lower adsorption (23% vs. 18.8% for oxalic acid and 19.2% vs. 4.9% for formic acid). 0 5 10 15 20 25 a ds or pt io n (% ) vp p90 ae p25 dp 25 m pc 500 figure 4: the surface adsorption of formic acid, c0(formic acid) = 2·10-3 mol dm-3, 1 g dm-3 tio2 0 5 10 15 20 25 a ds or pt io n (% ) vp p90 ae p25 d p25 m pc 500 figure 5: the surface adsorption of oxalic acid; in the case of the mpc 500 (300 m2 g-1) catalyst consisting of pure anatase, only 19.2% of oxalic acid is absorbed on the surface, this is significantly lower than that observed for degussa p25, c0(oxalic acid) = 10-3 mol dm-3, 1 g dm-3 tio2 384 photodegradation of the model compounds in the laboratory-scale reactor the efficiency of the photocatalytic degradation was followed by measuring the total organic carbon content (toc, before and after the removal of the suspended tio2) and the ph of the reaction mixture (fig. 6). figure 6: photodegradation of formic acid, c0(formic acid) =2·10-3 mol dm-3, 1 g dm-3 tio2; toc measured before (o) and after (•) filtration the decrease of toc indicates that the substrate is mineralized, i.e., hydrogen carbonate or carbon dioxide is formed during the process. although hydrogen carbonate is dissolved, but it is protonated at about ph 5. if the ph of the reaction mixture is ca. 5, bubbling (40 dm3 h-1 air) removes carbon dioxide from the system, thus the total inorganic carbon (carbonate) content (tic) of the photocatalysed samples is practically zero. in solutions of higher ph tic increases to some extent, and the difference between the total carbon content (tc) and tic gives the actual value of toc. on the vp 90 catalyst, 40 min irradiation significantly decreased the toc of the reaction mixture, along with the increase of ph (fig. 6). the initial rate of the photocatalytic degradation was determined by a simple procedure of fitting polynomial on the toc vs. irradiation time plots (fig. 7). the experimental results clearly indicate the strong correlation between the adsorption of the substrate to be mineralized and the initial degradation rate (figs. 4 and 7). both the most efficient absorption and the highest initial degradation rate for formic acid were observed on the vp p90 catalyst. besides, the measurement data suggest that other factors also affects the degradation rate of the substrates studied. the lowest adsorption was measured on the aeroxid p25 catalyst, while the initial mineralization rate on it is significant. the lowest degradation rate was observed in the case of the mpc 500 catalyst consisting of 100% anatase and having the highest specific surface area. apparently pure anatase is not advantageous from the viewpoint of the reaction rate, and there is an optimum for the magnitude of the specific surface area above which an increase is not favourable. 0 0.1 0.2 0.3 0.4 0.5 v 0 t o c / m g dm -3 m in -1 vp p90 ae p25 dp 25 m pc 500 figure 7: the initial degradation rate of formic acid on the catalysts applied the photocatalytic mineralization of oxalic acid was studied in reaction mixtures of 10-3 mol dm-3 concentration. the tendencies in this system were similar to those observed in the case of formic acid. the mineralization was followed by measuring the actual concentration of the oxalic acid and the toc in the reaction mixture. since the value of toc measured in the reaction mixture and that calculated from the actual concentration of the starting material agreed within the measurement error (3–5%), the model compound was mineralized practically without formation of any longer-lived intermediate. fig. 8 displays the results regarding the suspension containing degussa p25 catalyst. fig. 9 shows the comparison of the initial degradation rates measured on different catalysts applied. figure 8: photocatalytic degradation of oxalic acid on degussa p25 catalyst, c0(oxalic acid) = 10-3 mol dm-3, 1 g dm-3 tio2; toc measured before (o) and after (●) filtration similarly to the case of formic acid the most efficient adsorption of oxalic acid was observed on the surface of vp p90 (fig. 5), also the initial mineralization rate of the substrate was the highest in the suspensions containing this catalyst (fig. 9). according to our observations, vp p90 proved to be the most efficient photocatalyst for degradation of both model compounds studied, while the mineralization 385 processes of these substrates were found to be the slowest on m-pc 500. notably, the photoactivities of the degussa p25 and aeroxid p25 catalysts were quite similar despite of their significantly different anatase contents (degussa p25 – 70%, aeroxid p25 – 94%). similarly to our observations, no direct relationship was found between the degradation rate and the specific surface area in the case of photocatalytic oxidation of phenol and 3-nitrobenzenesulfonic acid on various types of tio2 catalysts [17]. 0 0.2 0.4 0.6 0.8 v 0 t o c / m g dm -3 m in -1 vp p90 ae p25 d p25 m pc 500 figure 9: initial degradation rates of oxalic acid on different catalysts photodegradation of formic acid in the pilot equipment in order to investigate the effect of static mixer on the rate of the photocatalytic degradation of pollutants 7·10-3 m solution of formic acid was irradiated in the presence of degussa p25 catalyst (1 g dm-3) in the pilot equipment. as fig. 10 shows, application of static mixer appreciably enhanced the mineralization rate of formic acid in this photoreactor. 40 50 60 70 80 90 0 2 4 6 irradiation time / h t o c / m g dm -3 with static mixer without static mixer figure 10: photocatalytic degradation of formic acid on degussa p25 catalyst in the pilot equipment with and without static mixer, c0(formic acid) = 10-3 mol dm3, 1 g dm3 tio2 the relative increase of the rate, compared to that measured under the same conditions but without static mixer, is 27% (at 16.7 dm3 min-1 flow rate), which is in good agreement with the results quite recently published on the photocatalytic degradation of phenol in a similar system (16.4% at 2.2 dm3 min-1 flow rate) [18]. considering that the flow rate in our case was about one order of magnitude higher than that applied in ref. 18, and the relative effect of the static mixer significantly decreases upon increasing the flow rate, our result is quite promising. the effect of the static mixer enhancing the mineralization rate organic pollutants can be attributed predominantly to the increased interfacial mass transfer as a consequence of the intense mixing [19]. since the reactive radicals playing key roles in the oxidation mechanism are generated mostly on the surface of the catalysts particles, and then diffuse to the boundary layer and also into the bulk solution, intensification of mixing significantly enhances their mobility, promoting the latter steps, and, thus, increasing their overall reaction rate. nevertheless, oxidation of the adsorbed substrate by the photogenerated holes play also considerable role in the mechanism of the photocatalytic degradation, but this type of process can be influenced by the static mixer to a much lesser extent. preliminary experiments were also carried out by utilization of solar radiation. apart from the light source, the experimental conditions (materials, concentrations, flow rate, etc.) were the same as in the case of irradiation with light tubes. the application of static mixer considerably increased the degradation rate of formic acid under these circumstances, too. the magnitude of the relative enhancement was somewhat lower (ca 17%) than for the photocatalysis with artificial light. this difference suggests that the effect of the static mixer may depend on the light intensity. conclusions and outlook the determining steps of a semiconductor-mediated photocatalytic oxidation, beside the primary electrontransfer processes, can be the reactions of the substrate with the superoxide radical anion formed via electron scavenging, and with the hydroxyl radical formed via hole scavenging. the reactivity of a semiconductor photocatalyst, such as tio2, depends on, beside its crystal structure, the mean value and the distribution of the particle size, and the specific surface area. these measurable properties jointly determine the rate of the electron-hole recombination, the number of the hydroxyl groups on the particle surface, and the adsorption capability of the catalyst. the crystal structure as well as the adsorption features of the nanoparticles predominantly depend on the preparation technology. thus, catalysts of different structure and particle size were studied by application of two model compounds from the viewpoints of adsorption and photodegradation. the results of our experiments with various tio2 catalysts support that the adsorption of the model compounds significantly influence 386 their degradation rate, and also confirm that the efficiency of a photocatalyst is collectively determined by several factors. accordingly, for a photochemical treatment the catalyst ought to be chosen by considering the composition of the wastewater to be cleaned. application of a static mixer in the pilot equipment appreciably increased the rate of the photocatalytic mineralization of formic acid. this effect can be explained by the enhanced interfacial mass transfer promoting the movement of photogenerated ho• radicals from the catalyst surface or the boundary layer to the bulk solution. our further investigation, continuing the successful preliminary experiments, is focused on the application of natural light source, i.e., on the utilization of solar energy in the photocatalytic wastewater treatment. acknowledgments this work was supported by the national development agency (támop 4.2.2.-08/1/20080018, livable environment and healthier people – bioinnovation and green technology research at the university of pannonia, the project is being co-financed by the european social fund with the support of the european union). references 1. v. l. budarin, p. s. shuttleworth, j. r. dodson, a. j. hunt, b. lanigan, r. marriott, k. j. milkowski, a. j. wilson, s. w. breeden, j. 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word a_27_torocsik.doc hungarian journal of industrial chemistry veszprém vol. 39(1) pp. 41-44 (2011) some design issues of multi-plate magnetorheological clutches d. törőcsik széchenyi istván university, department of mechatronics and mechanical engineering 9026 győr, egyetem tér 1, hungary e-mail: torocsik@sze.hu magnetorheological (mr) devices gain more and more importance nowadays. it is especially true for mr clutches, whose transmissible torque is now getting close to industrial needs. this paper gives introduction to mr basics and deals with ways how to increase transmissible torque of mr clutches. the survey is based on a simulation process, carried out by comsol package. special aspect of investigation is the calculation of power consumption of mr clutches. as a result, optimal number of plates has been determined. keywords: magnetic flux density, number of plates, magnetic resistance, torque, power consumption introduction in the past mr fluid was mostly applied in shock absorbers of active or semi-active car suspension systems. due to the following beneficial features: easy electronic controllability with short response time and simple mechanical construction without moving parts, mr fluid is gaining importance in mr clutches to. initially, only double plate prototype clutches were built [1, 2]. it has become clear that the transmissible torque is very moderate and unsuitable for direct industrial application. the raise of the transmissible torque can be found in the focus of the further research activities. dratzer et al. at magna [3] prepared a multi-cylindrical mr clutch of 700 nm torque. the construction of a multi-cylindrical mr clutch is complicated. this paper focuses exclusively on the behaviour of a multi-plate clutch. after summarizing mr basics, the influence of both the geometric buildup of the magnetic circuit and the number of the plates on the transmissible torque will be studied. different numbers of plates from 1 to 51 are chosen to each of the three magnetic geometries with different flux-guide thickness (a, b, c) and transmissible torque is calculated with these data. finally, the power consumption of magnetization is studied. magnetorheological fluid (mrf) in magnetorheological clutches torque transmission is produced by a special kind of fluid. the fluid contains carbonyl iron powder, which is suspended in oil with additives. the major role of using additives is to prevent the precipitation of the iron powder in the suspension. the diameters of the iron powder particles are 1–10 µm in size. due to the size and the spheroid shape of the particles, the fluid has low viscosity resulting small idling waste. its shape also indicates that the fluid has a small wear out effect on the surfaces to be joined. in the absence of an applied magnetic field the particles are in a disordered position in the fluid. h figure 1: behaviour of mrf in a magnetic field with the application of such a field in the fluid the iron particles become polarized and form net-like chains in the direction of flux lines (fig. 1). the enhancement of the electro-magnetic excitation modifies the viscosity of the fluid. initially, its density is similar to water's but increasing the excitation parallelly enhances its apparent viscosity up to the point it reaches the required excitation to show the features of solids. this state is appropriate for joining the two plates of a clutch like a solid body. figure 2: shear stress in the mrf τ τ y vr 42 the shear stress occurring in fluids when you put load under magnetization (fig. 2) can be calculated by the following formula: dy dv)b(ττ 0 η+= (1) where: τ0 – shear stress depending on the induction of the mr fluid η – the dynamic viscosity of the fluid dv/dy – the speed gradient in the gap the second part of the formula originates from the behaviour of the newtonian-fluid and its effect is neglectable (torque without magnetization). features of mr-clutches automotive industry is one of the possible applications of magnetorheological clutches. the 700 nm torque of a magna powertrain clutch used for four-wheel drive can even be enhanced up to 1300 nm with using a planetary gearing [3]. during the planning phase certain preliminary directives – such as smallness in size, weight, production costs and large transmittable torque need to be complied. on the ground of the optimal usage of the maximum yield stress, it is the most effective to place the torque transmission provided by the fluid onto the largest possible diameter. magnetic circuits are to be created with the shortest possible magnetic field lines to decrease the magnetic resistance, which results larger inductance and larger transmittable torque. similar effects can be achieved by increasing the cross-section of the magnetic circuit avoiding the impregnation of the material. as for their constructivity, clutches have two types: centrifugal and plate clutches (fig. 3). the basic distinctive feature between the two alternatives lays in the magnitude of the transmittable and idle torque. b b a) b) figure 3: mr-clutch constructions in the case of plate clutches (fig. 3a) the effect of the centrifugal force creates a stream of particles between the inner and the outer part of the fluid. this effect grows with increasing revolution and even 1000 1/min creates a remarkable flux in the fluid. on the effect of the larger viscosity caused by the augmented number of particles on the outer diameter the idling waste of the clutch increases. outer diameters play a big part in transmitting torque while the effect of the inner ones is insignificant. in the case of cylindrical clutches (fig. 3b) there is no significant particle stream which results alike fluid viscosity in the clutch. since the fluid does not congeal even on the larger diameter, the idle waste is low. expanding on a large surface is a very beneficial feature of the mr fluid because it improves the value of the transmittable torque. induction needs inductors which can occur in two possible ways: standing or rotating with the shaft. torque calculation of plate type mr clutches we restricted our research to examine a plate clutch with a fixed inductor. in fig. 6 the design of a one-plate clutch can be seen. the radius of the plate is 45 mm. depending on the induction this construction is able to transmit 10–20 nm. when calculating torque we presuppose a constant induction distribution in the fluid among the disc gaps. this presupposition was also supported by the simulation made in a program called comsol where we used an mr 132 ld type fluid produced by lord corp. the outstanding ferromagnetic material c10 (aisi1010) was used for flux guide parts. figure 4: magnetic flux density in the first gap the yield stress of mr fluid can be calculated from the next formula: [4] 4 ax 3 ax 2 axax 53.55b204.1b 206.1b2.774bτ(b) +−= =+−= (2) having calculated the magnitude of the yield stress in the fluid, the torque can be given by the following formula: (in one gap) ∫ τπ= 2r 1r 2drr))r(b(2m (3) applying more plates, magnetic flux density in the mr fluid gaps differs only slightly from each other. for example, magnetic flux density in gaps of 11-number of plates mr clutch measured at r=32 mm radius can be seen in fig. 5. magnetic flux density can be regarded constant apart from the third plate. the difference is only 0.3%. 43 figure 5: magnetic flux density in the gaps r 1 r 2 1 2 3 4 5 67 8 9 mrf b figure 6: mr-clutch construction the clutch developed consists of three well distinguishable units. the first one: (1) the driving shaft (2) two ferromagnetic flux guide rings (3) copper tube (4) right hand side cap (6) the driven shaft the second one: (7) deep groove ball bearings (5) the ferromagnetic plate the third one: (8) electromagnetic coil (9) ferromagnetic casing with this construction slip rings are not needed to activate the coil. in case of applying a multi-plate clutch, an odd number of plates is required to be disposed in the clutch. every second plate is to be fixed to the external rotating part (copper tube). result of simulation the fixed part of the examined clutches has different magnetic resistance which can be achieved by the increase of the cross-section of the magnetic conductor. better conductance results in larger induction in magnetic fluids increasing the torque to be transmitted. having a small number of discs, this difference is significant. the dimensions of the examined geometries were: table 1: geometry of the magnetic circuit geometry l1=l2 a 8 mm b 10 mm c 20 mm a bn l1 l2 figure 7: geometry of the magnetic circuit figure 8: torque increase at b and c geometry relative to a we can state that the torque difference among the examined geometries was approximately constant after 10-15 discs. figure 9: relative torque increase enhancing l1 and l2 from 8 mm to 10 mm resulted 1.2 nm torque increase per disc, which means nearly an increase of 9%. however, in the case of 51 discs, the excess is only 0.6%. increasing the fixed part from 44 8 mm to 20 mm causes a much larger excess torque per disc. in this case it is 3 nm, which means a 20 % growth. power consumption for magnetization j=2·106 a/m2 (i=1 a) current density was applied to the winding area of width a=13.8 mm and of variable length b. the length of winding is approximately proportional to the number of plates n and consists of n turns. limiting the current of winding to imax=3 a, copper wire of diameter dw=0.8 mm will be sufficient to avoid overheating. if the mean radius of winding is rm=0.07 m, the resistance of a single turn can be calculated as ω== π π ρ= 0157.0 8.0 07.0*8018.0 4 d r2r 2 w 2 m 1 (4) the magnetizing power is then p = i2·nr1. table 2 contains data of magnetization in term of the number of plates (n). table 2: power consumption n b [mm] a [mm2 n p [w] t [nm] 1 25.5 351.9 700 11.1 13.7 3 35.5 489.9 975 15.5 27.0 5 45.5 627.9 1250 19.8 40.2 11 70.5 972.9 1937 30.7 73.3 21 120.5 1662.9 3310 52.5 139.2 31 170.5 2352.9 4683 74.2 205.1 51 275.5 3801.9 7567 120 343.3 it can be concluded that the increasing number of plates results higher transmissible torque, but also higher energy consumption. it is worth considering the limit of an acceptable power consumption as well. a practical point of view may be the specific torque (e.g. transmissible torque divided by power consumption) in term of number of plates that can be seen in fig. 10. the graph tends monotonously to 3 nm/w. figure 10: specific torque conclusion this paper dealt with optimization of geometric buildup of a multi-plate mr clutch. the simulation process showed that the transmissible torque of an mr clutch can be enhanced by reducing the magnetic resistance of flux-guide parts with using only small numbers of plates. increasing the number of plates, the previously mentioned effect is getting negligible because the high magnetic resistance of the several gaps filled with mr fluid. increasing the number of the plates is a more efficient way to enhance the transmissible torque. to conclude, the transmissible torque is approximately proportional to the number of plates, but because of power consumption of magnetization, the number of plates cannot be raised unlimitedly. acknowledgement our research was supported by the project „tamop4.2.1/b-09/1/konv-2010-0003: mobility and environment: research in the fields of motor vehicle industry, energetics and environment in the centraland western-transdanubian regions of hungary”, and project támop-4.2.1-08/1-2008-0005. the project is supported by the european union and co-financed by the european social fund. references 1. e. e. bansbach: torque transfer apparatus using magnetorheological fluids. us patent, no: 5,779,013, 1998. 2. d. lampe: anwendung von magnetorheologischen fluiden in kupplungen, http://www.donnerflug.de/publikationen/antrieb.pdf 3. f. gratzer, h. steinwender, a. kusej: magnetorheologische allradkupplungen. atz, jahrgang 10, 2008, 902–909 4. m. jaindl, a. köstinger, c. magele, w. renhart: optimal design of disk type magnetorheologic fluid clutch, elektrotechnik & informationstechnik 124(7-8), (2007), 266–272. doi: 10.1007/s00502-007-0453-4 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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/pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word 16.06 gergely.docx hungarian journal of industry and chemistry vol. 44(1) pp. 55–70 (2016) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2016-0007 hydrogen sulphide corrosion of carbon and stainless steel alloys immersed in mixtures of renewable fuel sources and tested under co-processing conditions andrás gergely,* 1 roland locskai,1 péter szabó,2 antal krójer,3 and tamás kristóf1 1 department of physical chemistry, institute of chemistry, university of pannonia, egyetem u. 10, veszprém, 8200, hungary 2 department of general and inorganic chemistry, institute of chemistry, university of pannonia, egyetem u. 10, veszprém, 8200, hungary 3 department of inspection and maintenance, mol co., olajmunkás u. 2, százhalombatta, 2443, hungary in accordance with modern regulations and directives, the use of renewable biomass materials as precursors for the production of fuels for transportation purposes is to be strictly followed. even though, there are problems related to processing, storage and handling in wide range of subsequent uses, since there must be a limit to the ratio of biofuels mixed with mineral raw materials. as a key factor with regards to these biomass sources pose a great risk of causing multiple forms of corrosion both to metallic and non-metallic structural materials. to assess the degree of corrosion risk to a variety of engineering alloys like low-carbon and stainless steels widely used as structural metals, this work is dedicated to investigating corrosion rates of economically reasonable engineering steel alloys in mixtures of raw gas oil and renewable biomass fuel sources under typical coprocessing conditions. to model a desulphurising refining process, corrosion tests were carried out with raw mineral gasoline and its mixture with used cooking oil and animal waste lard in relative quantities of 10% (g/g). co-processing was simulated by batch-reactor laboratory experiments. experiments were performed at temperatures between 200 and 300ºc and a pressure in the gas phase of 90 bar containing 2% (m3/m3) hydrogen sulphide. the time span of individual tests were varied between 1 and 21 days so that we can conclude about changes in the reaction rates against time exposure of and extrapolate for longer periods of exposure. initial and integral corrosion rates were defined by a weight loss method on standard size of coupons of all sorts of steel alloys. corrosion rates of carbon steels indicated a linear increase with temperature and little variation with composition of the biomass fuel sources. apparent activation energies over the first 24-hour period remained moderate, varying between 35.5 and 50.3 kj mol-1. scales developed on carbon steels at higher temperatures were less susceptible to spall and detach. nonetheless, moderate deceleration of corrosion rates as a function of time are due to the less coherent, frequently spalling and low compactness, higher porosity of the scales evolved at lower and higher temperatures, respectively. on the surface of high alloy steels, sulphide scales of an enhanced barrier nature formed during the induction periods and the layer formation mechanism was found to be assisted by the increasing temperature as initial reaction rates considerably decreased over time. nevertheless, corrosion-related sulphide conversion of metals and mass loss of the high alloys are strongly affected by the composition of the biomass fuel sources especially animal waste lard. thermal activation in the first 24 hours decreased from 68.9 to 35.2 kj mol-1. a greater degree of failure to develop protective sulphide scales was experienced by changing to composition of the biomass fuel sources than the impact of thermal activation between a narrow temperature range at around 100ºc. in accordance with the literature, high free fatty acid contents lead to high corrosion rates accounted for direct corrosion of high alloy steels and assisted solubilisation of corrosion products. in addition, the pronounced acceleration of sulphide corrosion is connected to the diminishing inhibition effect of the sulphide scales. keywords: hydrogen sulphide corrosion, gas phase corrosion, carbon and high alloy steels, renewable biofuels, used cooking oil, animal waste lard 1. introduction in an increasing power-hungry society coupled with the age of unprecedented global warming, the relevance of the substitution of fossil fuels from mineral sources and their mixtures with materials obtained from renewable biomass sources in the highest possible proportions is *correspondence: gergelyandras432@gmail.com one of the most urgent priorities for current and future generations to observe. sustainable biomass resources, vegetable oils, and waste lard are renewable feedstocks for partial substitution of mineral oils in production of biofuels. although their availability is limited at present, there are clear benefits of biofuel production, namely meeting local consumption demands, reduced emissions of greenhouse gases during transportation over long distances in supply chains. in addition, the lower dependence on fossil fuels unequivocally contributes to increased national security. by 2010, the gergely, locskai, szabó, krójer, and kristóf hungarian journal of industry and chemistry 56 european commission set a goal that eu biofuels must account for 5.75% of transportation fuels. biodiesel as a mono-alkyl ester of vegetable oils and waste lard [1–3] is distinguished from second-generation type renewable feedstocks of inedible oils and algae. using vegetable oils, composed of a majority of natural triacylglycerols in similar to waste lard, biodiesel production involves processing by either trans-esterification with methanol or ethanol besides production of glycerol or catalytic hydrocracking. the latter is an economically more feasible option given the absence of investment costs [4, 5] as no dedicated facility is required [6]. cracking, pyrolysis, catalytic hydrodesulphurisation (hds), deoxygenation [7], and the saturation of olefins and aromatics favour the production of ultra-low sulphur petrodiesel [8, 9]. the fuel derived from lipid feedstock of biological sources emulating the composition of petro-diesel is renewable diesel. several crops such as rapeseed, soybean, palm, sunflower, etc. are excellent renewable oil sources recycled for energy storage and production lines, currently maize is the most frequently used feedstock for biofuel production primarily due to its high profitability. however, when the profit margin is a priority, used cooking oil trumps virgin vegetable oils, since it is around three times cheaper. as for the chemical stability aspects, fossil fuels containing methyl esters of fatty acids are less oxidation-resistant and more hygroscopic, so their long-term storage is not recommended. to process biomass in conventional oil refineries, vegetable oil and vacuum gas oil mixtures are preferred for quality diesel production [10, 11] as hydrotreating the latter along with heavy gas oil results in normal alkanes of c15-c18 [12]. moderate reaction temperatures yield diesel, while higher temperatures lead to gasoline production. technological parameters of hydroprocessing under mild conditions [13] generally mean temperatures of 320–430ºc and pressures of 3.5– 5.5 mpa with a relative quantity of the biomass source of ~5.5%. high isoparaffin content is obtained by catalytic hydrogenation of triglycerides stemming from waste lard [14]. nevertheless, there are vegetable oils (tall oil) that have high fatty acid contents [15–19] similar to waste lard. if they are not processed properly, they will be corrosive in nature in subsequent applications. their conversion to liquid hydrocarbons by catalytic hydrocracking seems a viable option. nevertheless, aside from indispensable processes relating to biomass-based fuel production, all sorts of sources including biofuels are to be refined to decrease heteroatom content, such as sulphur, nitrogen and phosphorous, which might be potential sources of pollutants. to preserve safety and profitability one should consider possible corrosion risks of coprocessing of renewable fuel sources to metallic structures from which equipment of existing petroleum refineries has been built and used for decades. industrial methods and technological means to protect oil production equipment were reviewed in terms of corrosion protection [20]. in relation to highly corrosive effects caused by waste lard, it depends on the quantity and composition of free fatty acids as a way of dissolution of metal-acid complexes coupled with reduction of a depolarisator. some fatty acids, such as stearic, palmitic, myristic and lauric acid, are even used for heat storage systems and their corrosivity is enhanced by thermal cycling [21]. acceptable resistance of the 304l stainless steel (1.4307) and an aluminium alloy with passive oxide layers on their surfaces was pointed out. the kinetics of naphthenic acid and sulphide corrosion and their interactions with q235 and 5cr1/2mo steel alloys were investigated at 270ºc in oil with naphthenic acid and sulphur contents of up to 1.0% (g/g) as synthetic refining media [22]. in the liquid phase with naphthenic acids at 230ºc, the low alloy and carbon steels indicate nearly the same naphthenic corrosion rates but above 230ºc the former gave higher rates. this is attributed to its higher activation energy (63 kj mol-1) compared to that of carbon steel (54 kj mol-1) leading to greater acceleration with increasing temperature. in dimethyl disulphide containing oil, sulphide corrosion follows parabolic kinetics. film growth was faster on carbon steel than on low alloy steel. in oil containing naphthenic acids and dimethyl disulphide, low alloy steel showed lower corrosion rates than carbon steel; thus, sulphide corrosion proved to be rate-governed by pseudo-passive films. different resistance of the alloys was connected to the chromium sulphide (cr5s8) in the pseudo-passive film formed on low alloy steel, in contrast with pyrrhotite (fe7s8) and troilite (fes) films obtained on carbon steel. at oil refineries, especially in the hds streamline part, the rate of metal loss either in the form of general or local corrosion is one of the highest. thus, to achieve an optimal balance between production, inspection and maintenance careful planning is required. aside from works on corrosion risks of biofuels at low temperatures without the presence of hydrogen sulphide rather for the automotive than refining industry, to our best knowledge, there is a rather limited number of studies in the literature to date, giving insights into either the corrosion rates of engineering alloys or the integrity risk assessment of plant equipment regarding the hds co-processing of renewable fuel sources such as used cooking oil and waste lard in low proportion mixtures with raw gas oils in refining plants originally designed to withstand mineral oils. therefore, the aim of this work is to investigate corrosion rates of inexpensive engineering alloys, two types of carbon steels (1.0425 and st35.8) and a low alloy steel sample (1.7335), which are all basic materials of heat-resistant tube and pipe systems. in addition, for the purpose of making a comparison, as structural materials of absorbers, strippers, and overlays in reactors, three high alloy steel samples (1.4541, 1.4571, 1.4401) were selected for hydrogen sulphide corrosion, tested at a pressure of 90 bar and temperatures between 200 and 300ºc. under the aforementioned parameters, hydrogen sulphide and naphthenic acid corrosion of steel alloys are investigated focusing on the dependence of corrosion rates on temperature and time. sulphide corrosion of steel alloys immersed in renewable biomass sources 44(1) pp. 55–70 (2016) doi: 10.1515/hjic-2016-0007 57 2. experimental in processing technology before the hydrotreating reactor is heated to ~420ºc, generally the high proportions of unsaturated and saturated free fatty acids cause the main corrosion problem, after that hydrogen sulphide is usually responsible for most of the corrosion risks. therefore, experiments were planned to satisfy the goals of investigating the corrosion rates of engineering steel alloys representative of materials in hds plants caused by the evolution of hydrogen sulphide during processes, combined with the increased risks exerted by the mixture of used cooking oils and animal fats that should all be co-processed in the same plant altogether under the same conditions. batch type experiments were carried out in two reactors with a wall thickness of 25 mm (manufactured by lampart vegyipari gépgyár zrt) having internal sizes of 2 and 4 litres. the temperature was measured inside the reactors through a stainless steel tube casing leading from the head into the core of the inner volume, with platinum100 resistive thermometers and adjusted with haga kd481dd controllers within ±6ºc after auto-tuning refining with liquidand gas-filled reactors at pressure targets. heating of the reactors was performed with 6 resistance-heating wires, which were evenly distributed around the encasings wrapped in a 4 cm thick thermo-insulation layer of glass wool lined inside steel scaffolds. the apparent effective performance of the heating systems with power consumptions of 3.7 and 6 kw at 3*380 v and drew currents of 4.5 and 7.2 a to the small and large reactors, respectively. heat ramp and cooling down phases of batch-type experiments were carried out as rapidly as possible especially in the cases of the 24and 72-hour tests. fast temperature ramp ups were achieved by providing the highest laboratory temperature and the close location of the nearby working reactor to utilise its dissipated heat (initial pressure was corrected for fillups). during cooling down phases at the end of corrosion tests, reactor encasings were removed from scaffolds. the inside pressure was slowly reduced by letting the gas slowly out of the reactor through pressure valves so that gas phase reactions were frozen within the shortest possible period. the time when the temperature decreased to 200ºc and/or the gas pressure dropped to at least 70% of its initial target was regarded as the end time of reactor experiments. short stainless steel tubes (outerand inner-diameters of 6 and 4 mm) were employed for fill-ups and long ones for the evacuation of reactor gases. for safety reasons, used reactor gases still containing about 2% (m3/m3) hydrogen sulphide werße led over several steps through erlenmeyer flasks containing an aqueous solution of sodium bicarbonate with a moderately high ph to work as alkaline absorbers. coupons of steel alloys of a standard size (32 mm outerand 10.5 mm inner-diameters with a thickness of 2 mm) were used for the experiments. all coupons were grated and polished with silicon carbide emery papers (#400 and #600) soaked in water to remove rust and stain spots. then they were ultrasonicated twice for 5 minutes in isopropanol and acetone. the cleaning process obeyed and adapted principles of the astm g1 standard (‘standard practice for preparing, cleaning, and evaluating corrosion test specimens’). after drying, mass of the coupons was measured with an analytical balance. compositions of the investigated steel alloys are summarised in table 1. with proper engravings, coupons were assembled on glass rods, each with annular glass cylinders (8 mm long) for proper spacing. then glass rods with steel alloys were inserted into large glass tubes holding the media of raw or refined gas oil and its mixture with used cooking oil (uco in 10% (g/g)) or waste lard (wl in 10% (g/g)). the composition of gas oil and renewable sources, supplied by the department of analytics and the institute of biotechnology, and bay zoltán non-profit ltd. for applied research, are summarised in table 2. animal waste lard was one of the most corrosive types available in the region owing to its high free fatty acid content. all materials were supplied by mol co., hungary. glass tubes accommodated five coupons (parallel samples) four times (according to the four different chemical compositions of steel alloys). when integral corrosion rates were defined for a time period by weight loss measurements, the standard deviation was also assessed by the 5 parallel specimens. error bars in figures based on gathered data are directly related to the standard deviation of population samples of the experiments obtained by five coupons in one autoclave test. the level of the fluids was set well above the upper coupons. to minimize loss of the fluids owing to evaporation especially around 300ºc despite the high pressure, inner and outer glass caps were employed for each glass tube. glass caps with an appropriate figure did not hinder efficient gas diffusion into sample holder glass tubes, ensuring good access to the fluids and steel coupons. table 1. chemical compositions of autoclave experiment-tested steel alloys in weight percent (fe in balance). alloys c cu si p s mn cr ni mo n ti 1.0425 ≤0.20 ≤0.30 ≤0.40 ≤0.025 ≤0.015 ≤0.80-1.40 ≤0.30 ≤0.30 ≤0.08 ≤0.012 ≤0.03 st35.8 0.10-0.35 ≤0.04 ≤0.04 0.40-0.80 1.7335 ≤0.08-0.18 ≤0.30 ≤0.35 ≤0.025 ≤0.01 0.4-1.0 0.70-1.15 0.5 0.012 1.4541 ≤0.06 ≤0.75 ≤0.04 ≤0.015 ≤2.0 17.0-19.0 9.0-11.0 5*c-0.70 1.4571 ≤0.08 ≤1.0 ≤0.045 ≤0.015 ≤2.0 16.5-18.5 10.5-13.5 2.5 5*c≤0.70 1.4401 ≤0.07 ≤1.0 ≤0.045 ≤0.03 ≤2.0 16.5-18.5 10.0-13.0 2.5 ≤0.1 gergely, locskai, szabó, krójer, and kristóf hungarian journal of industry and chemistry 58 for the experiments, bottled hydrogen gas (2.5ip, with a purity of 99.5%) with an initial pressure of 150 bar (provided by messer hungarogáz kft.) was used as received to fill up reactors at around room temperature (or the temperature when the experiment started). initial fill-up pressures were calculated according to the pressure of hydrogen refining at the target temperature according to the p-v-t database [23]. there were pressure increments almost in all experiments, which were caused by the varying volatility of raw and refining gas oil phases. hence real pressure of reactor gas phases was recorded during the experiments. the mixtures of gas oil and used cooking oil or animal fats were not so volatile as pure gas oil so pressure increases were less pronounced with those materials. at the time of filling up, the gas pressure inside the reactors was measured both by a reductor (200/200, supplied by messer hungarogáz kft.) and pressure gauges (merrkfm prlt s91, pressure measuring was calibrated before and after experiments) nested in reactor heads. for practical and safety reasons, hydrogen sulphide of stoichiometric quantity was in situ produced from elemental sulphur. the quantity of hydrogen sulphide was calculated to be ~2 percent by volume in all autoclave experiments at the target pressure, but the overall pressure was greater because of the changing volatility of the organic fluid phases. thus, the pressure in autoclave experiments was higher than the hydrogen table 2. basic characteristics of the renewable biomass fuel sources and distillation data of raw gas oil. fuel source distillation data of raw gas oil used cooking oil animal waste lard boiling point of fractions proportion of fractions organic acids (c1-c4, mg kg-1) 136.4 initial citric acid 1.90 187.2 5 lactic acid 32.69 197.3 10 formic acid 8.46 214.1 20 acetic acid 64.43 94.13 227.6 30 isobutyric acid 0.00 30.83 241.8 40 butyric acid 27.69 175.58 258.2 50 organic acids (c8-c20, mg kg-1) 274.2 60 caprylic acid 1 1.5 291.5 70 capric acid 1 310.9 80 lauric acid 2 1 331.9 90 myristic acid 3 11 347.3 95 palmitoleic acid 2.5 18 recovery 96.7 heptadecanoic acid 3.5 residue 1.5 γ-linoleic acid 0.6 5 loss 1.8 arachidic acid 3.5 gondoic acid 7.5 nervonic acid 1 palmitic acid 100 165 stearic acid 25 95 oleic acid 285 310 linoleic acid 190 65 extractable petroleum hydrocarbons (c10-c40, mg kg-1) c36 1.15 0.30 c37 0.10 c38 0.15 0.24 c39 0.12 iodine number (10-2 mg g-1) 96 65 total acid number (koh mg g-1) 6 74 alcohol components (mg kg-1) glycerol 7014.05 methanol 100.33 ethanol 11.12 6.35 water content (mg kg-1) 611 1171 metals & other elements as impurities al 0.02 0.016 fe 0.001 0.004 na 0.005 0.740 p 0.021 s 0.038 k 0.021 ca 0.036 amino acids (in % g/g) -less than 0.3 sulphide corrosion of steel alloys immersed in renewable biomass sources 44(1) pp. 55–70 (2016) doi: 10.1515/hjic-2016-0007 59 sulphide contents would have been lower with a maximum of 15%, but stoichiometric quantities were initially set with an excess of 10% in the experiments so the concentration of 2% (m3/m3) was considered to be assured. before the series of autoclave experiments, blind tests were performed to validate the proportion of hydrogen sulphide of the gas phase (2 volume percent) after an induction time of one hour at a temperature of 250ºc and at least 40 bar of pressure. the reactor gas was diluted by 100 times with a nitrogen stream then the mixture was entrained into a draeger x-am 5600 h2s detector to validate the hydrogen sulphide contents of the reactors. after continuous decompression at the end of the autoclave experiments, reactor heads were removed then glass tube holders (made of stainless steel) with the fluid and steel samples were gathered. depending on the kind of alloy, the heavy oil and greasy residue of steel coupons were removed with paper towels then purification was performed three times for 10 minutes each using ultrasonication to eliminate traces of organic phases. sulphide corrosion scale was removed by careful polishing, while continuously monitoring the surface for intact metallic steel. the use of clark’s solution was attempted to use but it proved to be inefficient in cleaning metal sulphides first rather than attacking some of the remaining metallic parts of steel coupons near the surface. the masses of the coupons were measured on the same analytical balance as before the tests then by relying on the weight loss method corrosion rates were assessed for the measured periods. in almost all experiments, high mass changes were obtained with low relative variance of data. corrosion tested coupons were not investigated for internal penetration forms of corrosion products deep inside the bulk lattice and the corrosion of grain boundaries, only external corrosion scale products were analysed. although the temperature highly impacts the efficiency of hydroprocessing of biomass sources and composition of diesel fuels [24] at the proposed target temperature of 420ºc and pressure of 100 bar to reproduce original conditions, severe limitations were faced because of the rapid coke formation from the mixture of raw gas oil with used cooking oil and animal fat, yield complete conversion within less than 24 hours. this made it impossible to carry out experiments at such a high temperature. therefore, the temperature rage had to be compromised and balanced with the dwelling time of the samples. then, all experiments could be carried out without any noticeable loss of the organic fluid phase caused by evaporation or cock deposition. 2.1. x-ray diffraction after reactor testing, spalled layers were crushed. the powdered and low adhering sulphide scales were scrubbed, gathered, and purified twice over 10 minutes each using ultrasonication in isopropanol. xrd analysis was performed using a philips pw 3710 type powder diffractometer equipped with a pw 3020 vertical goniometer and curved graphite diffracted beam monochromator. the radiation applied was cukα from a broad-focus cu tube, operating at 50 kv and 40 ma. samples were measured in a continuous scan mode with a 0.02° s-1 scanning rate. data collections and evaluations were carried out with x’pert data collector and x’pert high score plus software. 2.2. scanning electron microscopy and energy dispersive spectroscopy at the end of reactor testing, steel coupons containing multiple layers of low-adhering sulphide scales and powders gathered from removed surface scales were purified twice over 10 minutes each using ultrasonication in isopropanol. the morphology of corroded steel coupons was measured with a scanning electron microscope (sem, philips xl31 esem) in the secondary electron mode with an accelerating voltage of 20 kv and recording images produced by back-scattered electrons, as well. for rough elemental analysis, energydispersive x-ray spectroscopy (eds) was also carried out. 2.3. micro-raman spectroscopy after gathering the metal coupons from fuel mixtures and removing the traces of organic phases twice of over 5 minutes each using ultrasonication both in isopropanol and acetone, sulphide scales were probed five times at different spots on the surface. raman measurements were performed at atmospheric pressure and gas composition. a bruker senterra raman microscope was used to analyse samples. the source was a green semiconductor laser with a diameter of 532 nm and a maximum power of 10 mw. for the microscope, a 10x objective was used. raman signals were collected with a thermoelectrically-cooled charge-coupled device detector and recorded for typically 15 scans. the typical integration time to record raman spectra was 15 s on average with a spectral resolution of 4 cm-1. 3. results and analysis 3.1. reactor experiments temperature dependence of the corrosion rates of steel alloys immersed in raw gas oil and its mixtures with renewable biomass sources are presented in fig.1. over a narrow temperature range of 100ºc, the 1.0425 carbon steel indicated saturation of sulphidation rates at 275ºc in all organic fluids. corrosion rates in raw gas oil at 300ºc remained similarly high but in used cooking oil and waste lard mixtures decreased beyond a random scatter of data. the st35.8 carbon steel indicated a similar trend. in case of the 1.7335 carbon steel, the highest corrosion rates were obtained with almost linear relationship between the reaction rate and temperature. reaction rates over the entire temperature range were the least affected by the types of organic fluids. as expected, the 1.4541 high alloy steel gave the lowest gergely, locskai, szabó, krójer, and kristóf hungarian journal of industry and chemistry 60 sulphidation rates in all experiments. the higher corrosion resistance of this alloy is well reflected by the almost levelled rates up to 225ºc, although its markedly different behaviour can be observed by the steeply increasing sulphidation rates above 250ºc. this temperature range is associated with the evolution of adherent sulphide scale in appreciable amounts. the special behaviour of this alloy is also underscored by the high sensitivity to composition of the organic phase, i.e. waste lard, showing various corrosion rates even around 200ºc which remained decisive over the entire temperature range. corrosion rates were heavily dependent on fluid phase composition with biomass sources mixed in 10% (g/g) than on variation of the temperature up to 250ºc. generally, sulphidation rates of metals should be similarly more temperature dependent than hydrotreating and desulphurising conversion of the hydrocarbons [25]. in addition, according to the literature, corrosion rates of the 18/8 stainless steels are 10–50 μm year-1 between 250 and 300ºc in the presence of hydrogen sulphide at 2% (m3/m3). in our case, carbon steels indicated much greater sulphidation rates than the advisable as maximum of 0.25 mm year-1, which should be acceptable up to 390ºc under a pressure of 34 atm with 10% (m3/m3) of hydrogen sulphide [26]. logarithmic corrosion rates as a function of reciprocal absolute temperature were used to evaluate thermodynamic activation. as results over a short timescale characterise thermodynamics of the sulphide corroding alloys immersed in various organic fluid phases, long-term results are much more dependent on inherent kinetic controls such as barrier effect of the scales. therefore, reaction rates were both evaluated over the first 24 h and the entire 504 h periods. estimated activation energies are assumed to be closely related to the overall free energy change of the reactions, as presented in tables 3 and 4. over a short time period, the highest activation energy of the 1.4541 was ascertained to be in raw gas oil and its mixture with used cooking oil. nevertheless, about half of the energy was required for the activation in the waste lard mixture of gas oil. this tendency was found to be reversed over long periods when activation was the lowest in gas oil and the highest in the waste lard mixture. this result might only be interpreted as acid corrosion of the 1.4541 taking place over short time periods and sulphidic corrosion occurring over longer periods in parallel with the hydrodesulphurisation gas oil. adsorption of the fluid phase components and dissolution of the ionized metals are probably inhibited by the firm and adherent sulphide scales. the 1.0425 and st35.8 carbon steels indicated lower activation energies in the short term almost independent of the composition of the organic fluid phase, although the st35.8 might yield some increase with the presence of biomass sources. over longer periods, except for the st35.8 in gas oil, lower activation with regards to sulphide corrosion manifested, which leads to the recognition that corrosion of these alloys is primarily governed by the hydrogen sulphide. furthermore, if activation of the interfacial reactions changes it almost certainly decreases over time, which is anticipated in many metal sulphide forming reactions. the 1.7335 low alloy experienced high reaction rates featuring low thermal activation irrespective of the nature of the organic phase and time exposure. similarly to carbon steels, activation tends to decrease over time, suggesting a catalysed reaction by the scales of precipitating corrosion products, which were porous, susceptible to spalling and semiconductors. this behaviour reveals an insignificant difference between the rates of sulphidic and acidic corrosion, whereas an inefficient barrier effect of the sulphide scale. in short term experiments, figure 1. integral corrosion rates over 504 hours of test period (as a function of temperature) of steel alloys immersed in raw gas oil (go) and its mixtures with used cooking oil (uco) and animal waste lard (awl) at an overall pressure of 90 bar in the presence of 2% (m3/m3) hydrogen sulphide, as well as the integral corrosion rates for test periods of 24 hours for the alloys of (b) 1.0425, (c) st35.8, (d) 1.7335, and (e) 1.4541. table 4. temperature dependence of logarithmic integral corrosion rates (in mm m-2 year-1) expressed in activation energies (δ𝐸! ⋕ in kj mol-1) of steel alloys over 21 days. all other parameters are the same as detailed in table 2. steel alloys in organic fluids raw go go-uco go-wl δ𝐸! ⋕ δ𝐸! ⋕ δ𝐸! ⋕ 1.0425 30.5 41.1 36.7 st35.8 78.8 46.5 43.1 1.7335 30.3 30.3 33.3 1.4541 30.3 41.6 53.3 table 3. temperature dependence of logarithmic corrosion rates of steel alloys (in mol m2 s-1) expressed in activation energies (δ𝐸! ⋕ in kj mol-1) over the first 24 hours tested at a pressure of 90 bar in the presence of 2% (m3/m3) hydrogen sulphide. steel alloys in organic fluids raw go go-uco go-wl δ𝐸! ⋕ δ𝐸! ⋕ δ𝐸! ⋕ 1.0425 50.3 45.8 52.0 st35.8 45.4 53.3 63.1 1.7335 35.5 31.0 45.6 1.4541 68.9 67.8 35.2 sulphide corrosion of steel alloys immersed in renewable biomass sources 44(1) pp. 55–70 (2016) doi: 10.1515/hjic-2016-0007 61 higher activation energy of the 1.4541 for sulphide corrosion is due to the formation of metal sulphides with the chromium and nickel alloying elements. in contrast, over long time exposures the lower activation energy barrier is partly related to the increased thermodynamic preference in complete balance of the reaction between hydrogen sulphide and iron [27]. furthermore, the activation of surface processes such as adsorption and dissociation is more attributed to a less preferable free energy balance increasing with the organic materials of used cooking oil and animal fat having a greater absorption abilities. in this regard, the 1.4541 high alloy steel proved to be more sensitive exhibiting more than 2 orders of magnitude changes depending on composition of the organic phase, rather than that of carbon steel alloys indicating changes within a magnitude of 3 times or less. consequently, the reaction mechanism leading to sulphide corrosion should partly be impacted by adsorption and accelerated by saturated free fatty acids composing a considerable proportion of waste lard. moreover, the increasing temperature is known to play a vital role in governing the mechanism of naphthenic acid corrosion either by chemical or electrochemical mechanisms [28]. the latter is more dependent on thermal activation as a greater rate of dissociation of the weak acids occurs at elevated temperatures [29]. electrochemical acceleration may lead to local corrosion and pit formation, whereas chemical naphthenic acid corrosion at lower temperatures results in general processes. pearlite as an interpenetrating bicrystal phase composed of ferrite and cementite in plain carbon steels is a relatively good cathodic area due to the effective depolarisation for hydrogen ion discharge [23]. in our case, selective corrosion like pitting on specimens of the steel alloys was not observed as a function of temperature between 200 and 300ºc except for the 1.0425 carbon steel exhibiting pitting corrosion of metal lattice regardless of the organic fluid phase. process of the latter must be governed by the hydrogen sulphide which with its increasing concentration after a threshold enhances the rate of local process around metal crystal boundaries and sulphide inclusions. as a blind experiment to probe the effects of an hds plant using a batch reactor experiment, alloys were tested under the same conditions as for temperature dependence at 250ºc and the results are presented in fig.2 and table 5. the corrosion rates of carbon steels (1.0425, st35.8 and 1.7335) were greater with low variances of data compared to the ones measured for the 1.4541, 1.4571 and 1.4401 high alloy steels that exhibited reaction rates an order of magnitude lower with high variances, except for the 1.4541. thus, the firm corrosion resistivity of the 1.4541 alloy was observed, which is primarily connected to its high chromium [30] and moderate nickel contents and the absence of molybdenum. nickel and molybdenum are of high and moderate concentrations in tested steel alloys causing somewhat decreasing sulphation resistance [31, 32]. furthermore, from the results of an independent experiment, a less favourable activation of metal sulphide formation is suspected due to the inefficient adsorption and dissociation of hydrogen sulphide from the gas phase besides the absence of dissolved small molecule acids in the fluid phase. thus, corrosion rates of steel alloys might be the least affected by the adsorption of species from the organic phase only the gaseous phase, such as hydrogen and rather the hydrogen sulphide. the difference between the medium sulphidation resistivity of the 1.4571 and 1.4401 high alloy steels at low temperatures can be explained. on the other hand, by comparing the results of the blind experiment with that obtained in raw gas oil, the corrosion rates were roughly the same or somewhat greater, since the refining of the raw gas oil and the desulphurisation of the raw gas oil content should not have a notable effect on the resistivity of investigated alloys and their observed corrosion rates at least up to 250ºc. the timespan, over which parabolic corrosion rates appear after a short term linear reaction rate decrease in the induction period is related to development of thick sulphide scales. therefore, the time dependence of integral corrosion rates is presented in figs.3a–3d. the 1.0425 and st35.8 carbon steels indicated parabolic or even more intense decay of corrosion rates over time periods above 250ºc in all organic fluids but especially in waste lard mixture (figs.3a and 3b). the only exception was the st35.8 at 275ºc that exhibited a less pronounced decay of sulphidation rates over time. this figure 2. corrosion rate of steel alloys immersed in refined gas oil tested in a blind experiment for 504 hours at a pressure of 90 bar and temperature of 250ºc in the presence of 2% (m3/m3) hydrogen sulphide. table 5. general corrosion rates of steel alloys (in mm year-1) immersed in raw and refined gas oils, tested at 250oc over 21 days under a pressure of 90 bar in the presence of 2% (m3/m3) hydrogen sulphide. steel alloys raw gas oil refined gas oil 1.0425 0.10 – 0.50 0.55 st35.8 0.10 – 0.50 0.60 1.7335 0.30 – 1.00 0.55 1.4541 0.01 – 0.10 0.05 1.4401 0.10 1.4571 0.10 gergely, locskai, szabó, krójer, and kristóf hungarian journal of industry and chemistry 62 may be attributed to the partially incorrect experimental data owing to the lack of a large number of samples and parallel experiments to provide a more reliable prediction of the most probable corrosion rates with the least scattering of the mean values as possible. below 250ºc, a less remarkable decay of reaction rates was ascertained for both metals. the 1.7335 low and 1.4541 high alloys exhibited moderately intense parabolic figure 3. integral sulphide corrosion rates of steel alloys over time at various temperatures: (a) 1.0425, (b) st35.8(a38), (c) 1.7335, (d) 1.4541, parameters as defined in fig.1. figure 4. gradients (in terms of absolute value) of logarithms of integral corrosion rates over 21 days in raw gas oil (go) and its mixtures with used cooking oil (uco) and waste lard (wl) as a function of temperature: (a) 1.0425, (b) st35.8, (c) 1.7335, (d) 1.4541, parameters as defined in fig.1. sulphide corrosion of steel alloys immersed in renewable biomass sources 44(1) pp. 55–70 (2016) doi: 10.1515/hjic-2016-0007 63 decreases of reaction rates over time. nevertheless, the gradients of decay of the reaction rates were lower (greater in absolute value) at higher temperatures than quadratic rate decreases at and under 250ºc as a function of time (figs.3c and 3). the 1.7335 yielded gave almost constant corrosion rates at 250ºc between 3 and 21 days of exposure (fig.3c). its induction period seemed to be restrained to the first 24 h term in the mixture of used cooking oil. the 1.4541 steel experienced the lowest corrosion rates in the used cooking oil mixture over the parameter space (fig.3d), which exhibited a rather linear dependence as a function of temperature. overall, all steel alloys indicated the most severe corrosion-type integrity loss in the waste lard mixture of gas oil. the absolute values of the gradients obtained by linear fitting to the logarithms of the integral corrosion rates measured over 21 days is presented in figs.4a–4d. sulphidation rates of the 1.0425 and st35.8 carbon steels exhibited the highest temperature dependence in the waste lard mixture (a 5 times increase), whereas the lower gradients probably indicate that a less sensitive thermal activation occurs in raw gas oil and the used cooking oil mixture (enhanced by around 3 times, figs.4a and 4b). as for the 1.7335 low and the 1.4541 high alloy steels, the low and the lowest gradients with restrained enhancement of around two times were obtained as a function of temperature (figs.4c and 4d). this signifies a less pivotal role of thermal activation in the interfacial sulphidic corrosion of the latter two alloys but in all cases waste lard was the fluid phase that was proven to be the most susceptible to open thermally-allowed reaction mechanism leading in some cases to the highest corrosion rates by far. among all steels, only the 1.4541 exhibited low thermal rate dependence in used cooking oil compared to the results obtained in other phases. as a general impression, either the most intense dependence of thermal activation on sulphidation or the highest magnitudes of reaction rates occurred in the waste lard mixture of gas oil. thus, not only sulphidation takes place by the hydrogen sulphide, but also acidic corrosion occurs and competes with the former at a rate of the latter becoming higher by increasing temperatures. this finding may also point out that the contributing role of free fatty acids in parts of the corrosion processes could be adsorption of mercapto compounds assisted by possible chelating effect and thermally favoured dissociation of the anchoring functional groups. the greater oxidation ability of the organic compounds than hydrogen sulphide, and their more positive redox potentials are due to their stronger electron withdrawing ability boosted by conjugated electron systems of various extents. the desorption of corrosion products is promoted by the proper dissolution of metal ions with lipophilic complexes, and diffusion through porous, cracked or spalled scales, allowing a less hindered access of the steel surface to the species taking part in subsequent processes. in the case of the exclusive hydrogen sulphide corrosion, effective desorption and diffusion from the surface can only be realised by high porosity, cracking or spalling, and failure of the scales as observed with many of the carbon and low alloy steels but it should not happen to high alloy steels developing quasi-passivating, coherent and adherent sulphide scales. in the latter case, fluid phases with improved wettability based on the closer surface energy of the solid phases and tension of the fluid phases compared to that of the raw gas oil and steel combination is beneficial as less hindered interfacial reactions result. 3.2. x-ray diffraction in fig.5a, diffraction pattern of troilite, a 1:1 stoichiometric ratio of iron sulphide (fes) was identified on the whole in the powder of the spalled scales of the 1.0425 steel tested in raw gas oil at 250ºc. low crystallinity metallic iron fe(0) with high magnetic susceptibility formed the majority of the rest phase. figure 5. xrd patterns of the (a) 1.0425 carbon steel immersed in raw gas oil and (b) refined gas oil tested at 250ºc, (c) 1.7335 low alloy steel immersed in a gas oil mixture with waste lard (10% g/g) tested at 300ºc, all for 21 days at a pressure of 90 bar. gergely, locskai, szabó, krójer, and kristóf hungarian journal of industry and chemistry 64 because typical high intensity reflections at 2θ values of 12º, 15º, and 19º [33] and 40º, 50º, and 59º [34] were not measured, the low intensity reflections gained at 2θ values of 17.5º and 30º might not be connected to mackinawite. the absence of its phase in metal sulphides in the long-term tested samples is attributed to its formation during the early reaction phase and rapid transformation to more stable pyrrhotite, the sub-phase of troilite. the reflections together at 2θ values of 30º and 53º may not be related to greigite as its stability region is above the h+/h2 equilibrium line. troilite is more stable in weakly acidic aqueous solutions under reducing conditions, i.e. below the h+/h2 equilibrium line [35]. the intense reflection at 2θ value of 44º cannot unanimously be attributed to pyrrhotite [36], as it undoubtedly overlaps with one of the main reflections of polycrystalline iron [37]. in fig.7b, a different diffraction pattern of the corrosion scale can be identified by the varied intensity ratios of reflections at 43º and 53º. this is due to a composition change of the scale leading to metallic iron fe0 and crystalline troilite formation (fes) in molar ratio of about a 2:1. thus, a considerable amount of metallic iron segregated over the course of high rates of sulphide corrosion, but its amorphous phase did not result in its conversion to sulphide by either hydrogen sulphide or naphthenic acids in refined gas oil subjected to testing over 21 days at 250ºc and 90 bar. as expected, long-term medium temperature exposure resulted in high sulphide conversion of metallic iron and the formation of iron sulphide crystals in raw gas oil of a high sulphur content. on the other hand, roughly the same reaction rates resulted in the evolution of a similar amount of sulphide scales in refined gas oil, which proved to be more brittle. thus, high proportions of the scale detached and rapid disintegration of the metallic phase occurred, resulting in corrosion products with far lower ratio of the elements than stoichiometry. the lower sulphur content of the refined (hydrodesulphurised) gas oil is accountable for this finding because of the lower plasticity of the more compact sulphide scale. an xrd investigation of the sulphide scale formed on the 1.7335 low alloy steel coupons yielded a similar diffraction pattern (fig.5c) to that of the 1.0425 carbon steel (fig.5b) tested under the same conditions. nevertheless, in this case the massive amount of highly porous corrosion scale formed with a low spalling ability (high coherence and adherence) should mean less frequent occasions of the surface to renew by spalling or detachment resulting in further hydrogen sulphide attack but lower diffusion hindrance to accessing the metallic surface by sulphide species. 3.3. sem and edx analyses morphology of the sulphide scales gathered from the bottom of the glass tubes and removed from the surface of the 1.0425 carbon steel specimens is presented in table 6. sem-eds composition (in atomic %) of the corrosion product of sulphide corrosion scales removed from the surface of carbon steel coupons (1.0425) immersed in raw gas oil tested at a temperature of 250 °c and pressure of 90 bar. elements spot 1 spot 2 c (k) 0.00 6.95 o (k) 6.02 7.42 si (k) 0.00 0.38 s (k) 36.58 35.77 mn (k) 1.06 1.02 fe (k) 56.33 48.00 figure 6. sem image of (a) the powdered form of sulphide scale removed from the surface of the 1.0425 carbon steel coupons immersed in raw gas oil and tested at a temperature of 250ºc and pressure of 90 bar; (b and c) the elemental composition of the scale removed from surface of the coupons obtained by eds analysis of spots 1 and 2 marked by arrows, respectively. sulphide corrosion of steel alloys immersed in renewable biomass sources 44(1) pp. 55–70 (2016) doi: 10.1515/hjic-2016-0007 65 fig.6a. the multiple layers of sulphide scale were moderately easy to detach, brittle, and highly porous. spalled and detached scales were of a lateral size of about 500 μm and a thickness of 40 μm. the spots of 1 and 2 (arrowed in the image) were analysed to identify the elemental composition of the scale and the semeds results (figs.6b and 6c) is presented in table 6. the molar ratios of the iron sulphide (surmised to be 1:1 stoichiometric ratio of fes) and metallic iron (fe0) were 3:1 and 1.8:1 at spots 1 and 2, respectively. this is in acceptable agreement with and supplementary to xrd results. 3.4. micro-raman spectroscopy the raman spectra of the sulphide scales gathered from the surface of the steel coupons (tested at 250ºc over various time exposures) are presented in fig.7. similar spectra were obtained for the st35.8 carbon (b) and 1.7335 low alloy (c) steels. the 1.4541 high alloy steel (d) indicated a strong feature in the wavenumber region of 550–800 cm-1. in the low wavenumber range, a similar raman spectrum was detected to that of the 1.0425 carbon steel (a). because raman spectra depend strongly on the intensity and wavelength of the incident beam, based on the weak feature of the spectra around the main raman characteristic wavenumbers, it is thought that small proportion of troilite in the crystalline phase [38] should probably have formed after the chemical conversion of the initial metal sulphide on the st35.8 and 1.7335 (lines at 289 and 290 cm-1) over a short time period. metal sulphides, detected in a somewhat greater proportion of crystallinity (yielding a relatively low amount of scale) formed on the slower corroding 1.4541, resulting in to the more pronounced features in the wavenumbers between 550 and 800 cm-1. corrosion scales of st35.8, 1.7335, and 1.4541 alloys yielded intense broad and weak features at 1292 and 218 cm-1 as a result of the troilite phase. these characteristic wavenumbers were only found in the spectra in accordance with the literature [40]. this reveals that the low crystallinity of corrosion scales evolved within 24 hours. other raman features of troilite, a weak intensity peak at 456 cm-1 and the sharp ones at 600, 398, and 283 cm-1 [41], and 400 and 295 cm-1 [38] were not found. on the other hand, iron sulphide in a form close to mackinawite [42] might keep evolving in the early stages on 1.0425, st35.8 and 1.4541 as wavenumbers of moderate intensity at 321, 317, and 315 cm-1, respectively, were detected. they usually appear as intense overlapping peaks between 310 and 320 cm-1 depending on the degree of crystallinity [43]. thus, this seems to concur with greater reaction rates leading to a lower proportion of crystallinity in the product as the rate of nucleation overtakes to a level of far beyond orientation and growth. insignificant raman intensities in the regions of 280-360 cm-1 (at 206, 257, and 296 cm-1 and at 256, 312, and 355 cm-1) are generally connected to mackinawite (fe(ii)s1-x and fe(ii)-fe(iii)s1-x) and ironrich mackinawite, and greigite, respectively [44]. in the 1.4541, the very low raman intensity at 240 cm-1 is probably due to the presence of chromium-rich troilite whereas the low intensity features at 255 (290) and 365 cm-1 are partly connected to daubrelite (fecr2s4 and fecr2s3). nonetheless, these phases should have been present in negligible quantity, because none of the supporting xrd results could confirm the presence of such crystals, besides theoretical thermodynamic calculations of stable regions of iron sulphides (see discussion). in all cases, the low crystallinity of the corrosion products is attributed to the short time-scales and low temperatures of the experiments. it should also be noted that amorphous iron sulphide scales, which evolved in the induction periods were far less coherent, more crystalline, and more susceptible to spalling and detaching than the ones formed in slower reactions. thus to explain this phenomenon, lower mechanical stress might have accumulated over time in scales generated by slower and decreasing rates of reactions. as a result, the induction time of sulphide scale formation should be very low at a pressure as low as 20 bar but crystallisation must occur over longer periods. therefore, time constants in terms of spalling, and the failure of the scales to detach might be related to relaxation of accumulated stresses, probably at a rate faster than the crystallisation of iron sulphides. for troilite, it must be longer than 8 hours, but much less than 21 days at 250ºc and a pressure of 90 bar. in fact [45], due to kinetic reasons in connection with the highest reaction rate of scale growing without diffusiontype mass transport control [46], it has been stated that [47] generally mackinawite is expected to form rapidly first almost regardless of reaction conditions. for thermodynamic reasons, if metastable cubic fes formed, it should have also transformed into pyrrhotite and troilite over the weeks the experiment was undertaken at a moderate temperature and pressure both in the presence [48] and absence of chloride [49]. phase transformation of metal sulphides to troilite takes place in days or even hours as was found in our case. the evolution of pyrrhotite might occur over a couple of figure 7. micro-raman survey spectra of steel alloys tested under specified conditions as stated: a) 1.0425 (250ºc/20 bar, 8 h), b) st.35.8 (250ºc/50 bar, 24 h), c) 1.7335 (250ºc/20 bar, 8 h) and d) 1.4541 (250ºc/50 bar, 24 h). gergely, locskai, szabó, krójer, and kristóf hungarian journal of industry and chemistry 66 days so its detection in samples tested over at least 3 days can be anticipated. not exactly in line with the location of the pyrrhotite-troilite transition boundary [50, 51], in our case elevated temperatures favoured the formation of troilite rather than pyrrhotite under less than 2 bar of partial pressure of the hydrogen sulphide. 4. discussion the hypothetical growth in thickness of the sulphide scales over selected time periods based on the mass changes of the coupons is given in figs.8a–8d. the 1.0425 at 225ºc exhibited thicker scale development in biomass mixtures with lower reductions in rate over time than in neat gas oil (fig.8a). at 250ºc, all corrosion rates exhibit proportional growth as time of exposure increases. such linear rates of sulphidation started to decelerate as a function of time above 250ºc. the lowest variation of corrosion rates over time manifested in the used cooking oil mixture. the st35.8 exhibited similar sulphidation resistance behaviour up to 275ºc but at 300ºc a higher drop in corrosion rates was observed in mixed organic environment of the biomass and a smaller reduction in neat gas oil over time (fig.8b). the 1.7335 experienced increasing corrosion rates in all fluids as a function of temperature, without any notable decrease related to barrier effects over longer time periods (fig.9c). depending on the type of the organic phase, moderate drops and increases in the corrosion rates over intermittent periods were observed at 74, 168, and 168 h for 1.0425, st35.8 and 1.7335 steels, respectively. according to our experience, the growth rate in the thickness of stable scales on carbon steels never exceeded 10 µm over the first 3 days. up to 250ºc, the 1.0425 exhibited a higher and the st35.8 a somewhat lower susceptibility of the sulphide layers to spalling and detachment. the 1.7335 manifested the development of more coherent scales that were not susceptible to spalling or failure over time especially at and above 275ºc. a less frequent variation in time of reaction rates along with the observed quantity of detached scales in the form of a sediment at the bottom of the glass tubes led to the conclusion that the about low compactness, and high porosity of the sulphide scales are the primary reasons for the longlasting high sulphidation rate of this alloy. nonprotective scales exhibit linear growth and a mass change over time similar to that of the 1.733. this is typical for porous or cracked films, which facilitate the less hindered transport of reactants and access to the metallic phase at faster rates than at which the chemical reaction proceeds. as far as the 1.0425 and st35.8 carbon steels are concerned, due to the high barrier nature of the sulphide scales at elevated temperatures, variations in the time needed to renew the surface almost to the metallic phase were necessary to maintain the high reaction rates over long periods of time. scale failures should have been caused by the accumulation of high internal stresses along with high growth rates taking place on polycrystalline surfaces. such failures do not occur within scales at the scale/metal interface since it is cohesive in nature due to the high electrostatic forces that exceed the yield strength of the scales [52]. figure 8. hypothetical differential metal-sulphide scale thicknesses developed over time periods based on the mass change of the coupons of steel alloys immersed in refined gas oil (go) and its mixtures with used cooking oil (uco) or waste lard (wl) tested at a pressure of 90 bar in the presence of 2% (m3/m3) hydrogen sulphide. sulphide corrosion of steel alloys immersed in renewable biomass sources 44(1) pp. 55–70 (2016) doi: 10.1515/hjic-2016-0007 67 thus, hypothetically speaking, further scale growth as a solid-state reaction must trigger the breakdown of scales [53]. this is basically in line with the literature [54] as the corrosion resistances of carbon and low alloy steels are approximately equal. the low chromium alloys of up to 5% (g/g) warrant little or no advantages over carbon steels in terms of resistance to reactions with hydrogen sulphide. nonetheless, the 18cr-8ni stainless steels feature acceptable resistances over a wide range of pressures, temperatures, and hydrogen sulphide concentrations, except under severe conditions [55]. in other aspects, the protection potential of sulphide scales for carbon steels is usually questionable when well adsorbing species or compounds are in fluid media. after the first phase of mackinawite growth, corrosion rates can accelerate because the tarnish is not a uniform film, but rather composed of discrete crystallites that are highly permeable [56]. if the electrochemical mechanism of sulphide corrosion occurs and cathodic depolarisation is efficient, pyrrhotite formation becomes anodically controlled by cation diffusion that takes place through sulphides, which are in part limited by maximum reaction rates. thus, as thermodynamic simulations delineated the region of stability of troilite [57], in our experiment the electrode potential of the steel coupons should have been between -0.4 and -0.65 v versus standard hydrogen electrode (she), which is a narrow stability region in neutral media. at 250ºc, the 1.4541 showed slight variations in sulphidation over time regardless of the fluid phase (fig.8d). the scale structure was less compact and easily removable from the surface. at 250ºc, the highest decrease in reaction rate was obverserved over moderate periods of time that could only be accounted for by the greater initial sulphidation rates, increased compactness, and packing of the corrosion film, resulting in the metallic surface becoming more rapidly blocked, thus preventing subsequent reactions leading to less hindered ionic diffusion. as the temperature increased to 275ºc and above, time variations in the reaction rates became less remarkable as a function of time with similar changes in all organic fluids. this may suggested as the factors of utmost importace that determines the type of sulphide scales that could grow on the specimens, which slows down further metal sulphide forming reactions. as recognised first by wagner [58], some metals develop oxide scales exhibiting excellent protection characteristics as a result of the decreasing diffusion rate of ions through compact scales. such quasi-passivating behaviour was found in the sulphide corrosion of the 1.4541 under the experimental conditions, as mass changes obeyed the parabolic law as a function of time. this is in accordance with the nature of chromium, which is considered to be present in relatively high amounts as the most significant alloying element that increases sulphidation resistance. in some instances, the logarithmic rate of sulphide conversion by mass change was also observed in the initial phases of the reactions. the induction periods in the formation of metal sulphides were intense probably because of the lack of mass transport hindrances at the interfaces which evidently evolved to various extents in later phases of the experiments as thermal activation between 200 and 300ºc is inefficient to maintain high ion fluxes through the lattice of scales of moderate thicknesses and compactnesses. thermodynamic calculations based on gibbs free energy changes of the reactions of sulphide corrosion processes do not justify remarkable changes in reaction rates as a function of temperature. therefore, kinetic factors are likely to play a pivotal role in the enhancement of reaction rates in all cases. as a comparison of the protection performances provided by sulphide scales on different sorts of steel alloys, corrosion layers on the 1.4541 and the st35.8 evolved better barrier characteristics at higher temperatures than under 250ºc, which is generally in agreement with the terms of scaling tendency [59]. more coherent and adherent scales of metal sulphides formed at greater rates as corrosion products were not as solubile in go and uco compared to the wl mixture. so precipitates shrank and became more compact, which is partly is accounted to their mediocre thermal activations. in waste lard mixtures, corrosion through both chemical and electrochemical mechanisms assisting each other resulted in a pronounced efficiency of thermal activation was experienced along with the impact of acids relegating protective function of the chromium-, nickel-, and molybdenum-alloying elements. aside from the 1.7335 exhibiting good mechanical protection characteristics independent of temperature, the 1.0425 yielded rapidly increasing sulphidic corrosion with temperature. the former is attributed to high porosity of the sulphide film and the latter is explained by detachment of the layers thereof regularity depends on the corrosion rate and surface structure, orientation of the metallic crystallites, affecting the rate of stress accumulation in the corrosion products. the pronounced sensitivity of corrosion resistance in the 1.4541 regarding composition of the organic fluid phase resulted in high reaction rates especially in waste lard mixtures not only in the short run, but over longer periods, suggests the existence of an altered microstructure, lower compactness and increased solubility of metals and sulphide scales in acid containing fluid than in neat gas oils. this is in agreement with the literature [60] as naphthenic acids are most accountable for the highly corrosive nature oils [61–64]. the high corrosion rate of the st35.8 at low temperatures probably is a result of diffusion along short-circuit paths at grain boundaries or dislocations rather than of lattice diffusion, as thermal activation is high compared to over long periods when kinetic control of barrier effects besides the seldom failure of scales. slow growing scales proved to be more coherent and protective, exerting better mass transport control on during subsequent reactions. the gibbs free energy change of the metal sulphide reactions is inferior to diffusion activation in the solid state. the growth mechanism of metal sulphide scales takes place via outward diffusion of cations which leads to lower rate of stress accumulation in the layer. in carbon steel gergely, locskai, szabó, krójer, and kristóf hungarian journal of industry and chemistry 68 samples, spalling and scale failure were experienced over the first 24 hours as one of the four types of stressrelief mechanisms. in the case of thin scales, maximumstress affects metal/scale interface. the imperfections of the flat surface and the geometry of the coupons is also partially connected to the detachment of sulphide scales [65] especially at the inner and outer edges as flat interfaces are less susceptible to spalling compared to the ones with small radii, high curvatures [66]. low film ductility at low temperatures and high corrosion rates might inevitably lead to spalling, undermining and detachment. 5. conclusion the corrosion rates of carbon steels yielded an almost linear dependence as a function of temperature between 200 and 300ºc regardless of the biomass fuel sources. although carbon steels developed less spalling and detaching sulphide scales with increasing temperature, the porous layers did not contribute to the higher protection of the metallic phase as a result of their enhanced barrier natures. in contrast, on the surface of high alloy steels sulphide scales with excellent protection characteristics evolved during the induction period and the layer formation is assisted by temperature. integrity loss of the high alloys can severely be affected by biomass fuel sources such as animal waste lard when they are used in high proportions along with raw gas oil. free fatty acids play probably a dominant role in the corrosion mechanism. the higher corrosion rates observed than reported in the literature lead us to conclude that the proportion of the biomass sources used, especially those the ones having high free fatty acid contents, should preferably be kept low to prevent rapid losses in integrity of steel alloys, ensuring long and safe life cycles of the equipment used in hds refining plants. acknowledgement the authors are indebted to ferenc molnár, corrosion research group, department of physical chemistry, institute of chemistry, university of pannonia, for his invaluable discussions and advice on planning experiments and evaluating results. bence nagy, mol co., is gratefully acknowledged for his mediation and help in the procurement of precursors for the experiments. the authors are indebted to róbert bocsi, department of chemical processing, institute of chemical and process engineering, university of pannonia, for his 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10.1016/0020-7683(84)90012-x microsoft word hjic 2015 43(2) 55-101.docx hungarian journal of industry and chemistry vol. 43(2) pp. 67–71 (2015) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2015-0011 comparison of two variable interpolation methods for predicting the vapour pressure of aqueous glycerol solutions istván szalkai, 1* attila sebestyén, 2, † biancamaria della-vecchia, 3 tamás kristóf, 4 lászló kótai, 5 and ferenc bódi6 1 department of mathematics, university of pannonia, veszprém, 8201, hungary 2 department of inorganic chemistry, university of pannonia, veszprém, 8201, hungary 3 dipartimento di matematica, istituto g. castelnuovo, universita degli studi di roma ‘la sapienza’, rome, 00185, italy 4 department of physical chemistry, university of pannonia, veszprém, 8201, hungary 5 institute of materials and environmental chemistry, research centre for natural sciences, hungarian academy of sciences, po box 17, budapest, 1525, hungary 6 faculty of engineering, university of pannonia, veszprém, 8201, hungary several general mathematical methods for approximating two variable functions are applied for the study of the relationships between the temperature, concentration, and vapour pressure of aqueous glycerol solutions. the general properties of each of the applied methods are discussed in respect of possible alternative applications. keywords: vapour-pressure approximation, splines, glycerol, aqueous solutions, multi-dimensional interpolation 1. introduction recently, the evaporation of aqueous solutions with low glycerol concentrations from the combined processes of ion-exchange and chemisorption of diluted solutions is preferred instead of the expensive purification of concentrated glycerol solutions. these processes are important in the cosmetic industry [1–3]. during the atmospheric evaporation of highly concentrated glycerol solutions, glycerol molecules condense by losing water and convert into acrolein or polyglycerols. thus, the control of the appropriate temperature and pressure limits is of great importance in industrial processes. in the present work, mathematical relationships with regard to concentration, vapour pressure, boiling point, and temperature data are studied for aqueous glycerol solutions. the possibilities for data interpolation using several two variable splineinterpolation methods are investigated with the aim of calculating low pressure evaporation conditions and upper temperature limits for aqueous glycerol solutions with given concentrations as a continuation of our previous work [4, 5]. *correspondence: szalkai@almos.uni-pannon.hu †deceased in 2001. 2. data and methods we use the data shown in table 1 that were taken from ref. [6]. the dataset is graphically presented in fig.1. approximating a two valued function means that we are given the measured values zi, j ∈ r at the measured points pi, j = (xi, yj) for 1 < i < m, 1 < j < n and we want to construct a smooth function s: r2 → r such that s(xi, yj) = zi, j for 1 < i < m, 1 < j < n. in the present paper we considered the following general approximation methods: • iterated one-dimensional (1d) cubic splines [8], • hermite type, two-dimensional (2d) interpolation, improved by lénárd in three versions [10-12], and • shepard’s generalised method for a scattered dataset with certain parameters in two versions [15, 17]. these methods are general approximation methods that are applicable not only to the present problem. when discussing the errors in computer outputs, we differentiate between general mathematical and chemical (material) specific reasons. in order to test the practical applicability of these methods we used every second column of the original dataset (table 1, pressures of 5.3, 20.2, ..., 101.3 kpa) as inputs, then we computed the approximations for the omitted columns, and finally we compared the computed values to the measured data from table 1 in the omitted columns (13.3, 26.6, ..., 93.3). these szalkai, sebestyén, della-vecchia, kristóf, kótai, and bódi hungarian journal of industry and chemistry 68 approximations and comparisons are shown in table s1 (not included in the paper due to its size) and are graphically summarised in figs.2–6. we did not consider specific semi-empirical relationships such as those in ref. [7]: ln(p) = a(c) ⋅ ta(c), where p, c, and t stand for pressure (mpa), concentration (%), and temperature (ºc), respectively. 2.1. iterated one-dimensional interpolations in refs. [8] and [9], one finds the well-known method of two variable spline interpolations, which repeatedly uses 1d spline interpolations. the details can be found in ref. [2] as well. this method requires that the domain of the function we are approximating is rectangular [a, b] × [c, d]. furthermore, the measured points pi, j lie on lines ℓj parallel to the ordinate axis for 1 < j < n. for calculating s(x, y) at each inner point (x, y) ∈ [a, b] × [c, d] we follow a two-step calculation. first, we use 1d splines sj in each horizontal line ℓj to compute the values ℓj(x, yj) = sj(x) for 1 < j < n. next, we use another 1d spline along the vertical line crossing the point (x, y). then, we calculate the value s(x, y) using the numbers ℓj(x, yj) for 1 < j < n and a 1d spline on them. in practice we can compute all the formulae of the splines sj in advance, so later the values of sj(x) can be obtained by an easy substitution. in our computations, we used cubic splines as described in refs. [2], [8] and [9]. the approximating function s(x, y) for our glycerol data is plotted in fig.2, detailed numeric values can be found in table s1. the similarity between figs.1 and 2 shows the small error of iterated 1d spline interpolation, while magnification can reveal some differences. the advantages of this method include that the 1d approximation is widely known, no equidistance tabulated (measured) points yj or xi are needed, and only the parallel lines ℓj are assumed. the method also gives an approximation at the margins of the closed rectangle [a, b]×[c, d] and it can be easily generalised for higher dimensions. a disadvantage of this method is the repeated use of the final spline approximation (“vertical step”) for getting s(x, y) at each point (x, y), which makes the computation slightly slower. we repeatedly have to build up and solve a tridiagonal n×n size system of linear equations. 2.2. direct two-dimensional interpolations in ref. [10], one can find simple, but general direct 2d methods for constructing directly a 2d spline interpolation of minimal degree of hermite type, invented by lénárd. she investigated 2d and higher dimensional methods as discussed also in refs. [2], [11], and [12]. this method requires that the dataset (measured data points) form a rectangular grid, i.e. each quadruple of table 1. the measured boiling points (in ºc) of aqueous glycerol solutions as a function of pressure (kpa) and concentration (mass percent, g g-1) as in table 44 of ref. [6]. conc. pressure 5.3 13.3 20.2 26.6 33.3 39.9 46.6 53.3 59.9 66.6 73.3 79.9 86.6 93.3 101.3 0% 34.0 51.6 60.1 66.4 71.6 75.9 79.6 82.9 85.9 88.7 91.2 93.5 95.7 97.7 100.0 10% 34.4 52.1 60.7 67.0 72.3 76.6 80.3 83.7 86.7 89.5 92.0 94.3 96.6 98.6 100.9 20% 34.9 52.7 61.3 67.7 73.0 77.3 81.1 84.4 87.5 90.3 92.9 95.2 97.4 99.5 101.8 30% 35.5 53.4 62.1 68.6 73.8 78.2 82.0 85.3 88.4 91.3 93.8 96.2 98.4 100.4 102.8 40% 36.5 54.4 63.1 69.5 74.9 79.3 83.1 86.4 89.5 92.4 95.0 97.3 99.6 101.7 104.0 50% 37.5 55.7 64.5 71.1 76.4 80.9 84.8 88.2 91.3 94.2 96.8 99.2 101.5 103.6 106.0 60% 39.5 58.0 66.9 73.5 79.0 83.5 87.4 90.9 94.1 97.0 99.7 102.1 104.4 106.0 109.0 70% 43.0 61.7 70.8 77.6 83.1 87.7 91.7 95.2 98.4 101.4 104.1 106.6 109.0 111.1 113.6 80% 49.1 68.2 77.4 84.3 90.0 94.6 98.7 102.3 105.6 108.7 111.4 113.9 116.3 118.5 121.0 90% 59.5 80.2 90.3 97.7 103.9 109.1 113.5 117.4 121.0 124.4 127.4 130.2 132.8 135.2 138.0 figure 1. the original dataset from table 1. figure 2. estimated boiling points from iterated 1d splines. interpolation methods for predicting vapour pressure 43(2) pp. 67–71 (2015) doi: 10.1515/hjic-2015-0011 69 { (xi, yj), (xi+1, yj), (xi, yj+1), (xi+1, yj+1) } (1) forms a rectangle, but not necessarily of the same size. ref. [11] requires equidistant grids. the problem associated with this is discussed in ref. [2]. the method we currently use is from ref. [10] that gives us separate formulae for each rectangle in eq.(1) as s(x, y) = si, j(x, y) if (x, y) ∈ [xi, xi+1] × [yj, yj+1] (2) such that finally a) s is twice continuously partially differentiable in both variables on its whole domain [a, b]×[c, d], b) si, j values are polynomials in both variables of minimal degree and their degrees, as two variable polynomials, are minimal, too. moreover, lénárd provided three different formulae for points a) and b) with the details described in eqs.(1,3), (2,3), and (3,3) of ref. [10]. the implementation of each of these three methods with numeric values can be found in table s1. the differences among the approximated results using these methods are not so significant, so we present here the plot only for the results of the first method in fig.3. the similarity between figs.1 and 3 shows the small error of lénárd’s hermite-type interpolation. an advantage of this method is that although the precomputation of the higher dimensional arrays takes some time, s(x, y) can then be computed as a polynomial at any point (x, y), making the computation fast. furthermore, the method can be easily generalised for higher dimensions as described in ref. [12]. one disadvantage of this method is that we ultimately need rectangular tabulated, measured data points, pi, j = (xi, yj). if required, the data points can be transformed to form an equidistant grid, i.e. the rectangles in eq.(1) would become congruent as in ref.[2], for example. furthermore, the method gives no approximation at certain margins of the rectangle [a, b]×[c, d], since we cannot compute the finite partial differences of higher order at the margins. 2.3. shepard’s method in ref.[13], shepard presented a more general method for continuous approximation in any dimension as was also discussed in refs. [14–17]. this method does not require any special assumption on the positions of the data points pi, j∈rn as it works for arbitrary distribution as well. this method can be introduced as follows: let the arbitrary measured data points p1, p2, ..., pm ∈rn and the corresponding values f1, f2, ..., fm ∈r be given. then the formula for each p∈rn u (p) = fi ⋅σ d(p,pi )( ) i=1 m ∑ σ d(p,pi )( ) i=1 m ∑ (3) gives a continuous and exact approximation: u(pi) = fi for any i≤m (4) where d(p, pi) is the euclidean distance of the points p and pi and the positive “weight function” σ:r→r+ satisfies lim d→0+ σ d( ) = +∞ and lim d→+∞ σ d( ) = 0+ . (5) in other words, u(p) is a weighted arithmetic mean of the measured values fi with weights, which are “inverses” of the distances of points pi from point p. the closer pi is to p, the greater weight f has in eq.(3). theoretical and practical considerations in refs. [15] and [17] suggest σ to be chosen as figure 3. estimated boiling points from lénárd’s hermite-type interpolation. figure 4. estimated boiling points from shepard’s method. szalkai, sebestyén, della-vecchia, kristóf, kótai, and bódi hungarian journal of industry and chemistry 70 σ d( ) = d−α ⋅e−λd (6) for some "appropriate" α, λ ≥ 1, usually 1 ≤ α, λ ≤ 2 are satisfactory in practice. this problem is discussed in detail in refs. [14–17]. in our present calculations, we used the values α = λ = 1. the approximating function u(p) of shepard’s method is shown in fig.4, detailed numeric values can be found in table s1. it is worth noting that the wave-like patterns on the surface in fig.4 show the unique property of shepard's interpolation (see references [15] and [17] for details). the main advantage of shepard’s method is the simplicity of eq.(3), which makes both theoretical investigations and practical computations easy. furthermore, the measured points p1, p2, ..., pm ∈ rn can be chosen totally arbitrarily, which may be of great assistance during measurements. however, an important disadvantage of this method is that σ and thus u are sensitive to the measurement units, mpa or kpa in our case. though u is always continuous and eq.(4) is valid for any σ, which satisfies eq.(5), the “shape” of u is the best when the distribution of the data points pi is “nearly” uniform in a region of rn (see ref. [17]). to improve our approximation we used data expressed in kpa in table 1. moreover, larger data sets slow down the processing of eq.(3) greatly, even when m ≈ 150 the computational time can be several minutes. a workaround for managing this problem is to deal only with the data points pi closest to p. in our example with aqueous glycerol solutions, we used 4×4 matrices of data points againts pressure and concentration, respectively, surrounding the requested approximated point. this approximation greatly speeded up the execution times. the continuity property of u in this variant is discussed in refs. [15] and [16]. 3. discussion for an alternative comparison of the methods considered in this paper, we present figs.5 and 6. in fig.5, we displayed the boiling points for different fixed concentrations. in fig.6, the pressure is examined. iterated 1d splines are the dashed-dotted lines, lénárd’s hermite-type 2d spline is the dashed line, and shepard’s method is shown in dotted lines. as can be seen, lénárd’s and iterated splines are practically undistinguishable. it seems that shepard’s method works less well than the other two methods. we can see this from the 3d plot (fig.4) with the effect of the flattening being evident. also it is evident from the 2d plot (fig.6) with constant concentration, where estimation in the middle (supposed missing) points is poor (plotted as squares). the flattening effect is again evident from the 2d plot (fig.5) with constant pressure. 4. conclusion we conclude that although shepard’s method represented by eqs.(3) and (4) is an easy approximating method for the measured data, it is extremely sensitive for the large and small distances among the data points. for data sets situated in a rectangular grid (as in table 1), spline methods are more accurate. symbols zi, j measured values in 2d fi measured values in ‘n’-dimension pi, j measured points in 2d pi measured points in ‘n’-dimension s approximating function in 2d u approximating function in ‘n’-dimension σ weight function in shepard’s method figure 6. boiling point dependence on glycerol vapour pressure as a function of concentration. figure 5. boiling point dependence on glycerol concentration as a function of vapour pressure. interpolation methods for predicting vapour pressure 43(2) pp. 67–71 (2015) doi: 10.1515/hjic-2015-0011 71 acknowledgement the research is supported by the european union and co-funded by the european social fund, “telemedicinefocused research activities in the field of mathematics, informatics and medical sciences”, project number: támop-4.2.2.a-11/1/konv-2012-0073. supporting information table s1 can be downloaded free of charge from math.uni-pannon.hu/~szalkai/hjic-16-table2-150110.xls. references [1] isahak, w.n.r.w.; ramli, z.a.c.; ismail, m.; jahim, j.m.; yarmo, m.a.: recovery and purification of crude glycerol from vegetable oil trans-esterification, sep. purif. rev., 2015, 44(3), 250–267 doi:10.1080/15422119.2013.851696 [2] ardi, m.s.; aroua, m.k.; hashim, n.a.: progress, prospect and challenges in glycerol purification process: a review, renewable sustainable ene. rev., 2015, 42, 1164–1173 doi: 10.1016/j.rser.2014.10.091 [3] hunsom, m.; autthanit, c.: adsorptive purification of crude glycerol by sewage sludge-derived activated carbon prepared by chemical activation with h3po4, k2co3 and koh, chem. eng. j., 2013, 229, 334–343 doi: 10.1016/j.cej.2013.05.120 [4] szalkai, i.; sebestyén, a.; kótai, l.; bódi, f.: comparison of interpolation methods for predicting the vapour pressure of aqueous glycerol solutions, proc. 42nd annual conf. canadian soc. chem. engng., toronto, canada, 1992, pp. 279– 280 math.uni-pannon.hu/~szalkai/szalkai-1992c-konftor.pdf [5] szalkai, i.; sebestyén, a.; kótai, l.; bódi, f.: comparison of interpolation methods for predicting the vapour pressure of aqueous glycerol solutions, preprint no. 036 (university of veszprém, veszprém, hungary) 1995 math.unipannon.hu/~szalkai/szalkai-1995preprint-glic.pdf [6] kiss b.: plants oil industry and household tables (mezőgazdasági kiadó, budapest, hungary) 1988 (in hungarian) [7] saburov, a.g.; vasilienec, i.m.; postolov, j.m.; klibov, n.p.: numerical formulae for thermodynamic properties of aqueous glycerol solutions, mashlo-khim. promusl., 1987, 21–22 (in russian) [8] djuric, m.; ranogajec, j.; marinkov-neducin, r.: predicting of floor tiles behaviour by using twodimensional spline interpolation, hung. j. ind. chem., 1992, 20(1), 39–44 [9] press, w.h.; flannery, b.p.; teukolsky, b.p.; vetterling, w.t.: numerical recipes the art of scientific computing (cambridge univ. press, cambridge, uk) 1985 [10] lénárd m.: on the two-dimensional spline interpolation of hermite-type, colloquia math. soc. j. bolyai, 1985, 49, 531–541 [11] lénárd m.: spline interpolation in two variables, studia sci. math. hung., 1985, 20, 145–154 [12] lénárd m.: on an n-dimensional quadratic spline approximation, j. approx. theory, 1992, 68(2), 113–135 doi: 10.1016/0021-9045(92)90088-6 [13] shepard d.: a two dimensional interpolation function for irregularly spaced data, proc. 23rd acm nat. conf., new york, ny, usa, 1968, pp. 517–524 doi: 10.1145/800186.810616 [14] gordon, w.j.; wixon j.a.: shepard’s method of "metric interpolation" to bivariate and multivariate interpolation, math. comp., 1978, 32(141), 253– 264 doi: 10.1090/s0025-5718-1978-0458027-6 [15] szalkai i. : scattered data interpolation via improved shepard’s method, preprint no. 76. (university of veszprém, veszprém, hungary) 1999 math.unipannon.hu/~szalkai/szalkai-1999preprint-shepard.pdf [16] allasia g.: a class of interpolating positive linear operators: theoretical and computational aspects, in approximation theory, wavelets and approximation, (ed.: singh s.p., kluwer publ., dordrecht, the netherlands) 1995, pp. 1–36 doi: 10.1007/978-94-015-8577-4 [17] della-vecchia, b.; szalkai i.: finding better weight functions for generalised shepard’s operator on infinite intervals, int. j. comp. math., 2011, 88(13), 2838–2851 doi: 10.1080/00207160.2011.559542 microsoft word 96.07 barakat.doc hungarian journal of industrial chemistry veszprém vol. 25. pp. 175 180 (1997) krafft-clear point diagrams for some sodium 1,4 di-nalkylbenzene sulphonates y. barakat, t.s. gendy, v. ibrahim and a.i. mead* (egyptian petroleum research inst., nasr city, cairo, *chemistry department, faculty of education, suez canal university, el-arish, egypt) received: february 5, 1996 the sodium salts of 1,4-di-n-butylbenzene-, 1,4-di-n-pentylbenzene-, 1,4-di-n-hexylbenzeneand 1,4-di-n-octylbenzene sulphonates were prepared and evaluated, on a laboratory scale, for enhanced oil recovery (eor) formulation systems. krafft-clear point diagrams, for the aqueous solutions of these sulphonates, in presence of added electrolyte and/or alcohols, were drawn. the study revealed that the most distinctive property of 1,4-di-n-alkylbenzene sulphonates which sets them apart from the corresponding 1-phenyl-n-alkane sulphonates having the same molecular weight, is their low krafft points in presence of the same electrolyte and/or alcohol concentrations. introduction the adsorption of surfactants onto reservoir rock has been one of the major difficulties and the key factor which governed the economics of surfactants flooding process [1]. this adsorption can hamper the surfactant's ability to give the lowest possible interfacial tension [2], which is the backbone of this process. adsorption onto rock surfaces and poor solubility at high salinity, are the main drawbacks of monoalkylated benzene sulphonates employed for this purpose [3]. the importance of the krafft-clear point diagrams is that the boundaries are defined where clear and cloudy solutions can exist. the krafft-clear point diagram separates the various surfactant phases and defines the boundaries where adsorption can be avoided. based on these diagrams, a laboratory evaluation of any given class of surfactant, for enhanced oil recovery (eor) applications, has to be conducted at a temperature above the krafft point. in some previous investigations [4,5], several equation models have been developed to evaluate the effect of alkyl chain length; added alcohols and/or electrolyte on the krafft points of linear 1-phenylalkane sodium sulphonates. the present study deals with the krafft and clear point diagrams of some sodium 1,4-din-alkylbenzene sulphonates and applies the previously established equations [4] to this group of anionic surfactants. experimental surfactants the sodium salts of isomerically pure 1,4-di-nbutylbenzene-, 1,4-di-n-pentylbenzene-, 1,4-di-nhexylbenzene-, 1,4-di-n-heptylbenzeneand 1,4-di-noctylbenzene sulphonates were prepared according to the synthesis scheme shown in fig.1. details including synthesis steps, mass spectroscopy, nmr and ir that confirmed the structure of the intermediate and the final products, have been reported [6,7]. the critical micelle concentrations (cmc), surface properties and thermodynamic parameters have also been reported [8]. r + cl-c-r o f.c. cs2 r c-r o h 5% pd/c 2 r r r r so h3 h so (15% so ) 2 4 3 naoh r r so na3 1-phenylalkane ketone 1,4-di-n-alkylbenzene sulphonic acidsodium salt where r = c4h9, c5h11, c6h13, c7h15, and c8h17 r’ = c3h7, c4h9, c5h11, c6h13, and c7h15 (r and r’) are linear chains) fig.1 synthesis scheme of monoisomeric 1,4-di-nalkylbenzene sodium sulphonates 176 table 1 physical properties of 1,4-di-n-alkylbenzene sodium sulphonates general structure r r so na3 r abbreviation mol. colour of cmc (µmoles per litre) wt. powder 28 °c 38 °c 48 °c 58 °c c4h9 1,4-di-n-c4-bs 292 white 6348 7432 9502 14341 c5h11 1,4-di-n-c5-bs 320 white 2366 3219 3484 4549 c6h13 1,4-di-n-c6-bs 384 white 906 1091 1521 2114 c7h15 1,4-di-n-c7-bs 376 lightly tan 300 373 527 660 c8h17 1,4-di-n-c8-bs 404 lightly tan ⎯ 198 301 616 krafft and clear point determination krafft point of sulphonate aqueous solution was obtained by observing the temperature at which a solid precipitate disappeared [6,9]. a sulphonate solution of approximately 5000 µmole per litre was prepared. if no precipitate appeared at room temperature, the solution was cooled in an acetone-dry ice bath until a precipitate was observed. the sulphonate solution was then heated slowly (1 to 2 °c min-1) while being stirred by a magnetic stirrer. the temperature at which the precipitate suddenly disappeared was taken as the krafft point [6,10]. the same procedure was used for the determination of clear point. the temperature at which the solution went from turbid to completely clear was taken as the clear point. results and discussion very little work has appeared in literature concerning the utilisation of dialkylated benzene sulphonates for tertiary oil recovery formulation systems [11]. no one has published any results of a systematic study dealing with the structure-performance of these components. in this concern, alkyl ortho-xylene sulphonates are the only trialkyl benzenes which have received a considerable attention [12-14]. the present study deals therefore, with a laboratory-scale evaluation of a homologous series of 1,4-di-n-alkylbenzene sulphonates for tertiary oil recovery formulation systems. the sodium salts of 1,4-di-n-butylbenzene-, 1,4-din-pentylbenzene-, 1,4-di-n-hexylbenzene-, 1,4-di-nheptylbenzene and 1,4-di-n-octylbenzene sulphonates were prepared. the physical properties of the prepared sulphonates and their critical micelle concentrations (cmc) in aqueous solutions are given in table 1. the determined krafft and clear points, in the presence of added electrolyte and/or alcohols, are shown in tables 2 and 3. it is apparent from data in table 2 that for the lower molecular weight members of the investigated sulphonates, the krafft points can be easily determined even at higher electrolyte concentrations. for instance, up to 1.5 wt.% added nacl, the krafft point of 1,4-di-nc4-bs remains at 5 °c or lower. at 1.75, 2.0 and 2.5 wt.% nacl, slightly turbid (st) solutions are obtained and solid sulphonate crystals disappear at their krafft points : 15, 18 and 28 °c, respectively. these slightly turbid solutions turn clear upon heating to their clear points at 48, 56 and 70 °c , respectively. at 3.0 wt.% nacl, the krafft point of 1,4-di-n-c4bs aqueous solution, is found to be 78 °c. it gives a turbid (t) solution in spite of the fact that it contains no solid precipitate, since upon heating to its clear point (87 °c) it turns clear. at 3.25 wt.% nacl, a badly turbid (bt) solution is obtained. consequently, it is difficult to distinguish between a true solution and a fine suspension. at this electrolyte content, the solution does not render clear by increasing temperature since it has a clear point above the boiling point of the solution. the problem seems to be in the krafft point determination of the higher molecular weight 1,4-di-nc8-bs. this sulphonate gives a turbid solution even in absence of an added electrolyte. the turbidity remains up to 1.5 wt.% nacl. at 1.75 wt.% nacl, the sulphonate solution is found to be so badly turbid that it does not permit visual observation to define the table 2 experimental values of krafft and clear points in presence of added sodium chloride (a: 1,4-di-n-c4-bs, b: 1,4-di-n-c5-bs, c: 1,4-di-n-c6-bs, d: 1,4-di-n-c7-bs, e: 1,4di-n-c8-bs; additive =nacl) additive a b c d e wt.% krafft point , °c ≤ 5 ≤ 5 ≤ 5 8 31(t) 0.50% ≤ 5 ≤ 5 ≤ 5 8 31(t) 1.00% ≤ 5 ≤ 5 7 12 33(t) 1.25% ≤ 5 7 10 18(st) 37(t) 1.50% 8 12 23(st) 31(t) 40(t) 1.75% 15(st) 21(st) 28(t) 39(t) *(bt) 2.00% 18(st) 24(st) 32(t) *(bt) 2.50% 28(t) 63(t) *(bt) 3.00% 78(t) *(bt) 3.25% *(bt) clear point , °c ≤ 25 ≤ 25 30 34 38 0.50% ≤ 25 ≤ 25 32 36 51 1.00% ≤ 25 ≤ 25 35 41 72 1.25% ≤ 25 ≤ 25 39 58 90 1.50% ≤ 25 ≤ 25 45 86 96 1.75% 48 52 58 > 100 > 100 2.00% 56 71 83 2.25% 63 79 > 100 2.50% 70 92 3.00% 87 > 100 3.25% > 100 (st) = slightly turbid solution , (t) = turbid solution, (bt) = badly turbid solution and it is difficult to define its solubility 177 solubility of the sulphonate crystals. it becomes difficult to determine the krafft point exactly because many surfactants give cloudy solutions which do not sediment. salager [15] has determined the size of light scattering particles causing the turbidity of sulphonate solutions. it has been suggested that the turbidity is caused by the formation of liquid crystals or swollen micelles. the clear point represents the transition temperature at which these liquid crystals or swollen micelles disperse, perhaps to form smaller micelle structures, which are too small to scatter light. data presented in table 2 indicate that up to 1.5 wt.% nacl addition, the clear points of 1,4-di-n-c4-bs and 1,4-di-n-c5-bs do not exceed 25 °c, i.e. they have clear aqueous solutions at room temperature. however, this is not the case of 1,4-di-n-c6-bs, 1,4-di-n-c7-bs and 1,4-di-n-c8-bs solutions which have clear points at 45, 86 and 96 °c, respectively. at 1.75 wt.% nacl, 1,4di-n-c7-bs and 1,4-di-n-c8-bs have clear points above the boiling points of their solutions. it is also obvious from data in table 2 that the addition of an electrolyte to the surfactant solution has resulted in an increase in their krafft and clear points due to the reduced solubility of surfactants in salt solutions [16,17]. it may be also pointed out that the sulphonates with longer hydrocarbon chains have higher krafft and clear points. this may be attributed to the decrease in the sulphonate solubility as the hydrocarbon chains are increased [18]. it may be interesting, to compare the reported krafft point values of linear 1-phenylalkane sodium sulphonate [4] with the obtained krafft points of the corresponding 1,4-di-n-alkylbenzene sulphonates. for example, at 1.0 wt.% of added nacl, the krafft points of linear 1-phenyldecane-, 1-phenyldodecane-, 1phenyltetradecaneand 1-phenylhexadecane sulphonates have been found to be 58, 67, 73 and 82 °c, respectively. whereas, the determined krafft points of 1,4-di-n-c5-bs, 1,4-di-n-c6-bs, 1,4-di-n-c7-bs and 1,4-di-n-c8-bs have been found to be 5, 7, 12 and 33 °c, respectively, at the same electrolyte concentration. based on this comparison, it may be concluded that the most distinctive property of 1,4-di-n-alkylbenzene sulphonates, and one which sets them apart from the corresponding linear 1-phenylalkane sulphonates having the same molecular weight, is their lower krafft points in presence of the same electrolyte concentrations. aqueous surfactant formulation systems, for eor applications, contain a co-surfactant which is usually an alcohol (or alcohols). this added alcohol affects not only the solubility but also the performance of the surfactant in these systems. moreover a considerable reduction in krafft and clear points, of aqueous sulphonate solutions, is caused by the alcohol addition in the presence or absence of added electrolytes [4,17,18]. the determined values of the krafft and clear points, of 1,4-di-n-alkylbenzene sulphonates in presence of added alcohol and electrolyte, are given in table 3. the effect of added isopropyl alcohol (ipa) on the krafft points of this class of surfactants is presented graphically in fig.2. a regular decrease in krafft point is seen in presence of 2 wt.% nacl. at the same salinity, the effect of alcohol molecular weight, on krafft point, is illustrated in fig.3. it is obvious that 3.0 wt.% of isoamylalcohol (iaa) or iso-butyl alcohol (iba) is sufficient for reducing the krafft points of the investigated sulphonates below 20 °c. addition of the same amount of ipa is found to be insufficient to cause such a reduction in the krafft points of 1,4-di-n-c7-bs and 1,4-di-n-c8-bs. fig.3 illustrates also that the higher molecular weight iaa is more efficient, for reducing krafft point, than iba. the effect of added alcohol structure on the krafft and clear points of 1,4-di-n-alkylbenzene sulphonates, was studied. four butanol isomers, namely; n-butyl-, sec-butyl-, iso-butyland tert-butyl alcohols (nba, sba, iba and tba), were investigated. the krafft and clear points were determined at 3.0 wt.% of butanol isomer in presence of 2.0 wt.% nacl. the data obtained are presented graphically in figs.4 and 5. fig.4 illustrates that the efficiency in the krafft point reduction is in the following order : nba > iba > sba > tba. this sequence may lead to the conclusion that this efficiency is linked, in someway, with the miscibility of these alcohols with water. for example, the least miscible n-butyl alcohol (nba) is the most efficient while the completely miscible tertiary butyl alcohol (tba) is the least efficient for reducing the krafft point. the miscibility of nba, iba and sba with water is 9, 10 and 12.5 g pro 100 g h2o, respectively [19]. table 3 experimental values of krafft and clear points in presence of added nacl and alcohols (b: 1,4-di-n-c5-bs, c: 1,4-di-n-c6-bs, d: 1,4-di-n-c7-bs, e: 1,4-di-n-c8-bs; additive =nacl, alcohol) additive b c d e wt.% krafft point , °c 2.0% nacl, 1.0% ipa 19 26 35 47 2.0% nacl, 2.0% ipa 15 22 29 41 2.0% nacl, 3.0% ipa 11 18 24 36 2.0% nacl, 4.0% ipa 7 15 20 29 2.0% nacl, 5.0% ipa 6 10 16 23 1.5% nacl, 3.0% iba ≤ 5 6 11 19 2.0% nacl, 1.0% iba 9 10 13 23 2.0% nacl, 2.0% iba 7 11 12 20 2.0% nacl, 3.0% iba 6 8 12 18 1.5% nacl, 1.0% iaa ≤ 5 9 17 24 2.0% nacl, 1.0% iaa 6 11 20 27 2.0% nacl, 2.0% iaa ≤ 5 8 15 22 2.0% nacl, 3.0% iaa ≤ 5 6 10 14 clear point , °c 1.0% nacl, 3.0% ipa ≤ 25 ≤ 25 31 45 1.5% nacl, 4.0% ipa ≤ 25 ≤ 25 42 48 1.0% nacl, 2.0% iba ≤ 25 ≤ 25 30 46 1.5% nacl, 3.0% iba ≤ 25 28 48 52 1.0% nacl, 1.0% iaa ≤ 25 ≤ 25 ≤ 25 32 1.5% nacl, 1.0% iaa ≤ 25 27 46 51 178 fig.5 shows a general trend in clear point reduction, by the addition of any butanol isomer. however, an undefined sequence and an insignificant difference in the efficiencies of the four butanol isomers, are observed. based on these results, it seems also reasonable to conclude that water miscibility of the investigated butanol isomers has nothing to do with their efficiencies in clear point reduction. krafft clear point diagrams krafft-clear point diagrams for 1,4-di-n-alkylbenezne sulphonates at 1.25 and 1.5 wt.% nacl are shown in fig.6. at 1.25 wt.% nacl, all the investigated members of this homologous sulphonate series have krafft points below room temperature except 1,4-di-n-c8-bs. at 1.5 wt.% nacl; both 1,4-di-n-c7-bs and 1,4 -di-n-c8-bs have krafft points above room temperature. on the other hand, at these electrolyte concentrations, only 1 ,4-di-n-c4-bs and 1,4-di-n-c5bs give clear aqueous solutions. sulphonates having a krafft point above room temperature, can not be used for surfactant flooding at room temperature because precipitation occurs. adsorption of a cloudy or turbid sulphonate solution has been found to be highly due to physical entrapment by porous media [20]. addition of small amounts of alcohol depresses the krafft and clear points [15,21]. krafft-clear point diagrams for 1,4-di-nalkylbenzene sulphonates at 1.5 wt.% nacl after the addition of 3.0 wt.% isobutanol and 1.0 wt.% isopentanol are shown in fig.7. it is apparent from these diagrams that both the krafft and clear point curves are lowered. this is expected because alcohols tend to increase the solubility of the surfactants. fig.2 effect of added isopropanol on krafft point of 1,4-din-alkylbenzene sodium sulphonates fig.3 effect of alcohol mol. wt. on krafft point of 1,4-di-nalkylbenzene sodium sulphonates fig.4 effect of alcohol structure on krafft point of 1,4-di-nalkylbenzene sodium sulphonates fig.5 effect of alcohol structure on clear point of 1,4-di-nalkylbenzene sodium sulphonates 179 the qualitative appearance of the diagrams obtained is not altered by the molecular weight of the added alcohols. for example, 1.0 wt.% isopentanol addition is found to be more or less effective as the addition of 3.0 wt.% isobutanol in reducing the krafft and clear points of the investigated sulphonates. 1,4-din-c4-bs has a krafft point below 0 °c after the addition of the alcohol. fig.7 shows that the clear points of 1,4-di-n-c7-bs and 1,4-di-n-c8-bs remain in the vicinity of 50 °c after the alcohol addition. some investigators have reported [12,22] that between 18 and 50 °c, the highly turbid aqueous solutions of alkyl ortho-xylene sulphonate gave the same interfacial behaviour. this means that, within this range of temperature, turbidity does not alter the sulphonate performance. taking these results into consideration and provided that the oil field temperatures are from 50 °c upwards [12], it may be predicted that, with these amounts of added alcohols, negligible physical entrapment may take place if any of the investigated sulphonates are run through porous media (reservoir rocks). 250 350 450300 400 20 60 100 0 40 80 120 250 350 450300 400 20 60 100 0 40 80 120 surfactant conc. 5000 mol./dmµ 3 1.25 wt% nacl clear solution turbid solution solid hydrates sulphonate mol. wt. krafft point clear point extrapolated surfactant conc. 5000 mol./dmµ 3 clear solution turbid solution solid hydrates sulphonate mol. wt. krafft point clear point extrapolated 1.5 wt% nacl fig.6 krafft clear point diagrams of 1,4-di-n-alkylbenzene sulphonates at 1.25 and 1.5 wt.% 250 350 450300 400 10 30 50 70 90 0 20 40 60 80 100 250 350 450300 400 10 30 50 70 90 0 20 40 60 80 100 surfactant conc. 5000 mol./dmµ 3 3.0 wt% iba clear solution turbid solution solid hydrates sulphonate mol. wt. surfactant conc. 5000 mol./dmµ 3 clear solution turbid solution solid hydrates sulphonate mol. wt. 1.5 wt% nacl krafft point clear point extrapolated 1.0 wt% iaa 1.5 wt% nacl krafft point clear point extrapolated fig.7 krafft clear point diagrams of 1,4-di-n-alkylbenzene sulphonates at 3.0 wt.% iba and 1.0 wt.% iaa 180 conclusion krafft and clear points of 1,4-di-n-alkylbenzene sulphonates are lower than those of isomeric sulphonates in which the benzene ring is attached to a mid-chain alkyl carbon or to a terminal chain alkyl carbon. acknowledgement the authors are highly indebted to prof. f.m. ebeid, the former director of the egyptian petroleum research institute, for supporting this work through fruitful discussions. references 1. trogus f.j., schechter r.s., pope g.a. and wade w.h.: adsorption of mixed surfactant systems, sre 6845, presented at 52nd annual fall technical conference, october 9 12, 1977 2. trogus f.j.: equilibrium and non equilibrium adsorption of amphiphilic compounds, ph. d. dissertation, the university of texas, austin, texas, usa, 1977 3. wilson p.m., murphy l.c. and foster w.r.: the effects of sulphonate molecular weight and salt concentration on the interfacial tension of oil-brinesurfactant systems, paper spe 5812, presented at the spe symposium on improved oil recovery. march 22 24, 1976 4. gendy t.s., el-mergawy s.a., barakat y. and mead a.i., hung. j. ind. chem., 1994, 22(4), 219 5. barakat y., el-saghir a.m. and el-mergawy s.a., tesce, 1989, 14 (2), 42 6. ibrahim v.: a study on development of some surfactant formulation systems for enhanced oil recovery, m. sc. thesis, cairo university, faculty of science, cairo, egypt, 1992 7. el-zein s., isaac y.a. , ibrahim v. and barakat y.: erdol erdgas kohle, 1993, 109, 1 8. gendy t. s., ibrahim v. and barakat y.: indian j. chem. technol., nov., 1994, 1, 337 9. verezhnikov v.n., germasheva i.i. and backarov v.v.: kolloidn zh., 1981,43(3), 557 10. fernandez m.e.: adsorption of sulphonates from aqueous solution onto mineral surfaces, m. sc. thesis, the university of texas, austin, texas, usa, dec. 1978 11. doe p.h., el-emary m., wade w.h. and schechter r.s.: j. am. oil chem. soc., 1978, 55, 513 12. morgan j.c., schechter r.s. and wade w.h.: recent advances in the study of low interfacial tensions, improved oil recovery by surfactant and polymer flooding, shah d.o. and schechter r.s., eds. academic press. inc., new york, pp. 101-117, 1977 13. bolsman t.a.b.m.: phase behaviour of alkylxylene sulphonate (oil) brine systems, proc. second european symposium for eor, editions technip, paris, 2, 1982 14. bolsman t.a.b.m. and daane g.j.r.: spe reservoir engineering, 1986, jan., 53 15. salager j.l.: physico-chemical properties of surfactant-water-oil mixtures, ph. d. dissertation, the university of texas at austin, texas, usa, 1977 16. nakayama h. and shinoda k.: bull. chem. soc. of japan, 1967, 40, 1797 17. shinoda k. and hirai t.: j. phys. chem., 1977, 81(19), 1842 18. shinoda k. hato m. and hayaski t.: j. phys. chem., 1972, 76(6), 909 19. linstromberg w.w.: organic chemistry a brief course, 3rd ed., d. c. health and company, lexington massachusetts, 1974, pp 182 194 20. trushenski s.p., dauben d.l. and parrish d.r.: micellar flooding-fluid propagation, interaction and mobility. spe 4582 presented at 48th annual fall meeting of spe of aime, sep. 30 oct. 3, 1973 21. nakyama h., shinoda k. and hutchinson e.: j. phys. chem., 1960, 10(11), 3502 22. shechter r.s. and wade w.h.: annual report research on tertiary oil recovery, energy research administration grant, contract ey-76-s-02-0031, the university of texas at austin, texas, usa, 1980 microsoft word 00.00 inner cover.docx hungarian journal of industry and chemistry vol. 43(1) pp. 15–18 (2015) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2015-0003 nitrogen removal controlled by an ammonium-analyser at the north pest wastewater treatment plant zsófia kassai budapest sewage works pte ltd., asztalos sándor u. 4., budapest, 1087, hungary at the north pest wastewater treatment plant, a nutrient removal process has been in operation since 2011. new tanks have been built, which can receive approximately half of the pre-settled wastewater. a predenitrification system has been planned and built both to the old and new lines. due to the relatively small anoxic zones, periodic aeration was initiated first in the new line to achieve the lowest possible effluent total nitrogen concentration. because of its positive impact, the operation of periodic aeration was initiated in the old line as well. ammonium-analysers are used to control the aeration periods. due to this process, the plant can provide a very low total nitrogen effluent value (below 10 mg dm-3 on average) as well as save energy and operational costs. keywords: wastewater treatment, nitrogen removal, nitrification, denitrification, ammoniumanalyser, operation control, periodic aeration 1. introduction in the north pest wastewater treatment plant, the nutrient removal phase has been in operation since 2011. the pre-settled wastewater is divided into two parts: one part is led to the “a” biological line and the other to the “b” line. both biological lines were constructed for pre-denitrification with anoxic selectors. since the volume of these selectors is relatively small, the operation of periodic aeration is carried out in order to provide more time for the denitrifying bacteria to use the slowly biodegradable particulate chemical oxygen demand (cod) as well. the aim of its operation is to keep the effluent total nitrogen (tn) concentration under an annual average value of 10 mg dm-3. therefore, the precise control of periodic aeration is important to fulfil this aim and save energy and costs as well. 1.1. nitrification and denitrification in the case of municipal wastewaters, the hydrolysis of nitrogen containing compounds takes place mainly in the sewage system. therefore, ammonium is the main form of nitrogen present in the influent wastewater. the nitrogen content of the filtration originates from the sludge treatment technology, which could also be significant for wastewater treatment plants. the first step of the biological nitrogen removal process is nitrification, which is the biological oxidation of ammonia or ammonium to nitrite followed by the oxidation of the nitrite to nitrate. the process is performed by autotrophic bacteria as follows: correspondence: kassaizs@fcsm.hu [nh4]+ + o2 + co2 → (moa) → (moa)’ + nox + 2 h+ where (moa) and (moa)’ stand for autotrophic bacteria. the growth rate and specific sludge production of the nitrifying bacteria are lower than for heterotrophic bacteria, thus the growth of the autotrophic bacteria has to be in the appropriate ratio of wastewater quality to amount of sludge production [1, 2]. therefore, appropriate sludge loading can balance out the conditions for the growth of the two groups of bacteria. increasing the sludge retention time and decreasing the organic loading rate of the activated sludge could balance out the disadvantage posed by the nitrifying bacteria [3, 4]. the second step of nitrogen removal is denitrification, when special heterotrophic facultative anaerobic bacteria produce molecular nitrogen (n2) from nitrate as follows: nox + bod5 + h+ → (moh) → (moh)’ + n2 + co2 where bod5, (moh), and (moh)’ stand for biological oxygen demand, and heterotrophic bacteria, respectively. 2. experimental setup during the construction of the nutrient removal phase a pre-denitrification system was built both in the “a” and “b” lines with 2–2 ganged, rectangular, mixed anoxic reactors for each section. both “a” and “b” lines have four parallel sections. in the case of the “a” line, the anoxic selectors were separated from the beginning of kassai hungarian journal of industry and chemistry 16 the existing rectangular aeration tanks (fig.1). as for the “b” line, the new anoxic reactors were built before the new caroussel type aeration tanks (fig.2). the volume of the anoxic tanks is relatively small, since only 18 vol.% of the total activated sludge can be held in both lines. the best available effluent total nitrogen value was chosen for the design of the control system of the nitrogen removal program instead of the smallest ammonium nitrogen value. the standard value for total nitrogen is 35 mg dm-3, but the aim of the plant was to keep the effluent total nitrogen under 10 mg dm-3 as an annual average. the problem was that for the small anoxic volumes there was not enough time for the denitrification to take place completely. the other challenge was that the quality of the incoming wastewater had changed, since the original design of the nutrient removal phase was made. the incoming wastewater was diluted, but the rate of dilution was not the same for each parameter (table 1). 3. results and analysis the organic matter content (cod, bod5) and the total suspended solids (tss) decreased the most, while the decrease in nutrients, especially in the nitrogen forms was only modest. the difference was caused by the filtration water of the sludge dewatering system (table 2). at the wastewater treatment plant, there are two operating mesophilic digesters with a volume of 12,000 m3 each. these digesters receive not only the thickened sludge from the plant, but other wastes containing high quantities of organic matter, such as dried sludge, industrial wastewater, and animal protein. in table 2, it can be seen that the nitrogen content of the filtration is very high so the ratio of the nitrogen in the influent wastewater is higher, too. considering the planned values from table 1, the cod:tn ratio is 11.5:1 while the actual ratio is only 7– 8:1. previous experiments showed that the readily biodegradable soluble cod (ss) content of the wastewater is only about 20% [5], thus the total amount of organic matter isn’t available for the denitrifying bacteria in the anoxic zones. the average hydraulic retention time in the anoxic zones is about 3.5 hours. with periodic aeration (fig.3), the denitrifying bacteria can consume not only the ss, but the slowly biodegradable particulate cod, which becomes available as a result of hydrolysis. table 1: planned and real daily loads in kg. load planned actual deviation in % annual 2013 annual 2014 1st quarter 2013 annual 2014 1st quarter cod 133 406 73 103 74 692 55 56 bod5 72 800 41 390 42 043 57 58 tss 63 336 41 408 37 316 65 59 nh4-n 7 553 6 298 6 357 83 84 tn 11 575 9 137 9 487 79 82 tp 1 984 1164 1279 59 65 loads: cod = chemical oxygen demand, bod5 = biological oxygen demand, tss = total suspended solids, nh4-n = ammonium nitrogen, tn = total nitrogen , tp = total phosphorous figure 2. schematic layout of the “b” line. figure 1. schematic overview of anoxic selectors in the “a” line. table 2. average cod and nitrogen content of the filtration water in mg dm-3. cod n (nh3-nh4) tn cod:tn ratio 2013 847 1,163 1,326 ~1:1.6 2014 1st quarter 815 1,091 1,262 ~1:1.5 figure 3. effluent total nitrogen values between july and december 2010. nitrogen removal controlled by ammonium-analyser 43(1) pp. 15–18 (2015) doi: 10.1515/hjic-2015-0003 17 first, the periodic aeration system was evaluated in the “b” line as shown in fig.3. the blue diagram shows the effluent total nitrogen values from the “b” line, the red from the “a” line. it can be seen that with periodic aeration the effluent values from the “b” line are much lower compared to the “a” line. due to this positive effect, the periodic aeration process has been used in the “a” line since 2011 as well. 3.1. controlling periodic aeration in the case of the “b” line, controlling the system is quite simple, because the treated wastewater coming from four parallel, activated sludge tanks is mixed before the final settling tanks. there is a short channel before the wastewater is divided and led to the eight rectangular secondary sedimentation tanks, where a ‘hach lange amtax sc.’-type ammonium-analyser is set up. aeration is controlled by the measured ammonium-nitrogen value (table 3). due to the carousel race-track type activated sludge tanks, aeration can be switched off even for 3 hours, because the four agitators in each section do not let the sludge settle. controlling the “a” line was much more difficult partly because there are no agitators in the rectangular activated sludge tanks. on the other hand, the wastewater coming from four sections is only mixed after the final settling. thus, the ammonium-nitrogen level has to be measured separately for each section. there are two ‘amtax sc.’-type ammoniumanalysers in dual channel mode for the “a” line for sections 1–2 and separately for sections 3–4. because of the lack of agitators, there is a time limit in order to prevent the sludge from settling. after 60 minutes, the aeration has to be switched on even if the measured ammonium is not over the set value. in the “a” line, all the sections are controlled separately. the hours when aeration is switched on and off can be chosen. there are “manual”, “time control”, and “automatic” modes as shown in fig.4. in “time control” mode the operator can fill in a timetable with aeration periods (green). yellow areas show the hours when the aeration is turned off. in “automatic” mode, the program calculates an average nh4-n for each section from the past hour and compares it to the set values. if the average value is under the minimum in a section then there will be two hours with aeration on and one hour off (fig.4). if the value is between the limits, there will be three aeration hours and one without. if the average value is over the maximum limit, aeration remains on until the value decreases below the limit. the operation of the blowers is also an important parameter. aeration must not be switched off in every section at once. fig.5 shows the effluent total nitrogen levels for the controlled periodic aeration of both lines. in may, the “a” line operated under “time control”, thus the effluent results were much better in the “b” line. automatic control of the “a” line was turned on in the summer of 2014 as shown in fig.5. sometimes the effluent values in the “a” line are better according to the tn than in the “b” line as can be seen from data point 06.2014. due to periodic aeration, the effluent total nitrogen level was under the annual average of 10 mg dm-3 (table 4). 4. conclusion our study indicates that with periodic aeration external carbon sources are not needed at the north pest wastewater treatment plant in order to ensure the requested total nitrogen value. for optimal operation, control by ammonium analysers is essential, while the time-controlled system did not prove to be sufficient. figure 4: aeration control in the “a” line figure 5: effluent total nitrogen levels between april and august 2014. table 4. average effluent values in mg dm-3 between january and august 2014 load effluent standard cod 30 125 bod5 < 10 25 tss 5 35 nh4-n 2.54 10 tn 9.63 35 tp 1.39 5 loads: cod = chemical oxygen demand, bod5 = biological oxygen demand, tss = total suspended solids, nh4-n = ammonium nitrogen, tn = total nitrogen , tp = total phosphorous table 3. control parameters for aeration in the “b” line. nh4-n level (mg dm-3) sections with aeration on [pcs] sections with aeration off [pcs] < 5.0 1 3 5.0 7.0 2 2 7.0 10.0 3 1 > 10.0 4 0 kassai hungarian journal of industry and chemistry 18 acknowledgement this work was supported by the staff of the north pest wastewater treatment plant and the laboratory of budapest sewage works ltd. references [1] kárpáti, á.: ways of development in activated sludge systems – i. bod and nitrogen removal. – 1-14. ii. biological phosphorous removal and optimal utilization of organic carbon sources. 1424. in activated sludge systems and control. no. 2. ed.: kárpáti, á. (university of veszprém, department of environmental engineering and chemical technology, veszprém, hungary) 2002, pp. 97 (in hungarian) [2] kárpáti, á.; pásztor, i.; pulai, j.: current and future perspectives of nitrogen removal in wastewater treatment, vízmű panoráma, 2004 7(2) 17–22 (in hungarian) [3] grady, l.c.p.; lim, h.c.: biological wastewater treatment. theory and applications (marcel dekker, new york, usa) 1980 [4] henze, m.; gujer, w.; mino, t.; matsuo, t.; wentzel, m.c.; marais, g.v.r.: activated sludge model no. 2. (iawq scientific and technical report, london, uk) 1995 [5] kassai, zs.: modeling processes undergoing under anoxic conditions with nur test, proc. mht meeting, sopron, hungary, pp. 1-7 2010 (in hungarian) microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 37(2) pp. 69-75 (2009) investigation of hydrogenation of aromatic hydrocarbons on pt/pd/usy catalyst g. nagy1, z. varga1, d. kalló2, j. hancsók1 1university of pannonia, institute of chemical and process engineering department of mol hydrocarbon and coal processing, veszprém, p.o.box.: 158. h-8201, hungary e-mail: hancsokj@almos.uni-pannon.hu 2hungarian academia of sciences, chemical research centre, budapest, p.o. box 17, h-1525, hungary in this paper the aromatic reduction of gas oils and the conversion of several hydrocarbon groups in the conditions of hydrodearomatization were investigated on pt/pd/usy catalyst. it was concluded that in case of hydrodearomatization of gas oils cycloparaffin hydrocarbons (naphthenes) were key components, i.e. the practical process parameters of hydrodearomatization in case of a defined catalytic system (catalyst, feed, etc.) is that where the concentration of naphthenes have a maximum value. in case of this the deep hydrodearomatization and further deep heteroatom reduction can be carried out with maximum yield of gas oil. it was additionally determined that in the condition of hydrodearomatization mainly isoparaffins are formed via ring opening of naphthenes, the rate of increase of n-paraffin concentration is slower, i.e. the decadence of cold flow properties of reduced aromatic containing products are less beside the high cetane number. therefore the gas oil products can be applied as winter quality diesel fuel blending components. keywords: aromatic reduction, noble metal catalyst, gas oil, cetane number. introduction in the last couple of years the demand for diesel fuel has increased due to the increasing number of diesel fuelled passenger cars and heavy duty vehicles [1]. additionally the decreasing emission level of these vehicles results the continuously tightening specifications of diesel fuels [2] (table 1). since 1st january, 2009 the maximum sulphur content of diesel fuels has been 10 mg/kg, the maximum allowable polycyclic aromatic content has decreased from 11% to 8% (in the future 2–4%) and the maximum level of total aromatic content might be specified (about 15–20%) [3]. the importance of deep heteroatom and aromatic reductions technologies, which is one of the key technologies of the production of modern diesel fuel blending components, has increased beside the quality specifications and demand. in the first step of these technologies the deep heteroatom reduction and partial hydrodearomatization takes place on supported transition metal catalysts (e.g. como/al2o3, nimo/al2o3) [4, 5]. in the second step deep hydrodearomatization and further deep heteroatom reduction occurs on supported noble metal catalysts. nowadays the increasing of heteroatom resistance and hydrodearomatization activity of the above mentioned supported noble metal catalysts is in the focus of research and development activities [6, 7, 8]. the particular reactions of hydrodearomatization are studied in these catalysts as well [9]. the main focus of our research activity was the investigation of hydrodearomatization of aromatic hydrocarbons and the conversion of main hydrocarbon groups in the condition of hydrodearomatization in real gas oil matrix. experimental the hydrodearomatization experiment was carried out in a high pressure reactor system with 100 cm3 efficient volume tube reactor. it contains equipment and devices applied in the reactor system of hydrotreating plants. the range of the applied process parameters – based on the results of preliminary experiments – was the following: t: 260–340 °c, p: 35–60 bar, liquid hourly space velocity (lhsv): 1.0–4.0 h-1, h2/hydrocarbon volume ratio (in further: h2/hc) = 600 nm3/m3. prehydrogenated gas oil fraction derived from russian crude was used for the hydrodearomatization experiments. its important properties are summarized in table 2. the hydrodearomatization experiments were carried out on ptpd/usy zeolite (sio2/al2o3 molar ratio: 33.6, total and mesoporous surface area: 650 m2/g and 51 m2/g, total noble metal content: 0.9%, pd/pt atomic ratio: 3.7:1, metal dispersion: 55%, acidity: 0.20 mmol nh3/g) catalyst in continuous flow operation. 70 table 1: the change of diesel fuel specifications hungary hungary (eu) properties msz 1627 (1973) msz 1627 (1974) msz 1627 (1986) msz 1627 (1993) msz 1627 (1997) msz en 590 (1999) msz en 590 (2000) msz en 590 (2004) msz en 590 (2009) cetane number, minimum 48/45 48/45 42 48 48 49 51 51 51 density (kg/m3) 815-860 815-860 815-860 820-860 820-860 820-860 820-845 820-845 820-845 total aromatic content (%) 15-20* polycyclic aromatic content (%) 11.0 11.0 8.0 (2.0-4.0***) sulphur content (mg/kg) 10000 /5000/ 2000 10000 /5000/ 2000 5000/ 2000 2000/ 500/ 100 500/ 100 500 350 50/ 10** 10 the msz 1627 diesel fuel standard was overruled in 1999 and the msz en 590 standard became operative. i.e. the hungarian and eu standards of diesel fuels have been the same since 1999. * it might be introduced in the near future, no specifications ** the 10 mg/kg maximum sulphur containing diesel fuels have to be available in a regionally balanced manner *** it might be introduced in the near future table 2: main specifications of feed properties value density at 15.6°c (g/cm3) 0.8374 sulphur content (mg/kg) 6 nitrogen content (mg/kg) <1 aromatic content (%) total 25.5 mono 23.1 diand poly 3.4 cetane number 50 distillation range (°c) 184–350 the properties of the feed and products were determined and calculated by standard test methods (table 3). the hydrodearomatization activity of the catalysts was calculated by equation 1. had (%) = 100(af-ap)/af (1) where: hda: hydrodearomatization activity (%), af: aromatic content of feed (%), ap: aromatic content of product (%). table 3: standard test methods properties methods density en iso 3675 sulphur content en iso 20846 nitrogen content astm d 6366 aromatic content en 12916 distillation range en iso 3405 cetane number en iso 5165 the rate of conversion of individual hydrocarbon groups in the condition of hydrodearomatization was determined by the diagram of logarithmic conversion vs. contact time (equation 2). lhsv ktk c c ln f f a 0a == (2) where: ca0 – total aromatic content of feed, ca – total aromatic content of product, kf – pseudo reaction rate of hydrodearomatization, lhsv – liquid-hourly-space-velocity. the pseudo reaction rate constant of hydrodearomatization is calculated by the gradient of this curve. the determination of the composition of feeds and products was carried out by the results of gcxgc method. the equipment was a thermo trace 2dgc instrument containing a fid detector. the conditions were the following: • columns: 0.25 μm rtx (118 m x 0.25 mmid) and 0.1 μm bpx50 (140 cm x 0.1 mmid), • carrier gas: 6.0 purity helium with 0,1 cm3/min flow rate, • temperature programme: 40 °c → 280 °c 4 °c/min heating rate. the liquid products were separated to lighter (<200 °c boiling range) and to gas oil (>200 °c boiling range) fractions and the change of the yield and quality of the products was examined as a function of the process parameters. results and discussion the yield of the gas oil changed according to the projection; it decreased with increasing temperature and total pressure and decreasing lhsv; i.e. the rate of hydrocracking reactions, which produce the lighter hydrocarbons, increased (fig. 1, 2). temperature has the highest effect on the yield of the gas oil. for example it increased from 85% to 94% with decreasing temperature at 45 bar and lhsv = 1.0 h-1 in the investigated temperature range. the gas oil yield changed between 84% and 98% in the overall range of process parameters, therefore the lowest yield of gas oil occurred at the strictest process parameter (t = 340 °c, lhsv = 1.0 h-1, p = 60 bar, h2/hc = 600 nm3/m3). 71 80 84 88 92 96 100 250 270 290 310 330 350 370 temperature (°c) y ie ld o f g as o il (% ) 35 bar 45 bar 60 bar figure 1: the effect of temperature and pressure on the yield of gas oil (lhsv = 1.0 h-1, h2/hc = 600 nm3/m3) 80 84 88 92 96 100 0.5 1.5 2.5 3.5 4.5 lhsv (h-1) y ie ld o f g as o il (% ) 260°c 280°c 300°c 320°c 340°c 360°c figure 2: the effect of lhsv and temperature on the yield of gas oil (p = 45 bar, h2/hc = 600 nm3/m3) the hydrodearomatization activity of the investigated catalyst as a function of process parameters is presented in fig. 3, 4 and 5. the rate of hydrodearomatization increased in the lower temperature range from 240 to 320 °c. after the optimal temperature (320 °c) it decreased, i.e. the optimal temperature of hydrodearomatization of the investigated catalyst was 320 °c. the reason of this was the exothermic reaction profile of aromatic hydrogenation. the change of hydrodearomatization as a function of lhsv and total pressure was according to the projection, i.e. it increased with decreasing lhsv and increasing total pressure. it was concluded that the hydrodearomatization efficiency of the investigated catalysts was relatively high, because the polycyclic aromatic content of the products changed in the reproducibility range of the applied test method (it was maximum 0.1%). consequently the products did not contain polycyclic aromatic hydrocarbons. therefore the hydrodearomatization efficiency was calculated by the monoaromatic content, which was practically the same as the total aromatic content. the hydridearomatization efficiency was between 12% and 88% in the range of the investigated process parameters. the lowest aromatic containing product was produced (~3%, hydrodearomatization efficiency: 88%) at 320 °c, 60 bar and lhsv = 1.0 h-1. 0 20 40 60 80 240 280 320 360 temperature (°c) h d a (% ) 35 bar 45 bar 60 bar figure 3: the change of hydrodearomatization efficiency as a function of temperature and total pressure (lhsv = 2.0 h-1, h2/hc = 600 nm3/m3) 0 20 40 60 80 100 240 280 320 360 temperature (°c) h d a (% ) lhsv=1,0 lhsv=2,0 lhsv=3,0 lhsv=4,0 figure 4: the change of hydrodearomatization efficiency as a function of temperature and lhsv (p = 45 bar, h2/hc = 600 nm3/m3) 0 20 40 60 80 100 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 lhsv (h-1) h d a (% ) p=35 bar p=45 bar p=60 bar figure 5: the change of hydrodearomatization efficiency as a function of total pressure and lhsv (t = 320 °c, h2/hc = 600 nm3/m3) the rate of abatement of hydrodearomatization efficiency after the optimal temperature of aromatic hydrogenation (cause of thermodynamic properties) changed as a function of total pressure. the decrease of hydrodearomatization efficiency was high in case of low total pressure (e.g. 35 bar) and it was significantly lower at 60 bar. the reason of this phenomenon was the fact that in case of higher total pressure the rate of ring opening reactions of naphthenes increased. therefore paraffines formed from naphthenes, which were 72 produced from aromatic hydrocarbons. consequently the equilibrium reaction system of polycyclic aromatic monoaromatic naphthene changed to naphthenes, because the ring opening reactions are irreversible. it can be seen in the change of hydrocarbon composition (fig. 6, 7). 0 20 40 60 80 240 280 320 360 temperature (°c) r at io (% ) cp% ca% cn% figure 6: the change of hydrocarbon composition of the products as a function of temperature (rate of carbon atoms in cp: paraffinic-, ca: aromaticand cn: naphthenic, p = 45 bar, lhsv = 1.0 h-1, h2/hc = 600 nm3/m3) 0 20 40 60 80 30 35 40 45 50 55 60 65 70 pressure (bar) r at io (% ) cp% ca% cn% figure 7: the change of hydrocarbon composition of the products as a function of total pressure (rate of carbon atoms in cp: paraffinic-, ca: aromaticand cn: naphthenic, t = 320 °c, lhsv = 1.0 h-1, h2/hc = 600 nm3/m3) it can be seen that the rate of ring opening and/or hydrocracking reactions increased with temperature (cp was increased). the rate of the increase of carbon atoms in paraffinic bond increased with total pressure. the increase (about 1–2%) of carbon atoms in paraffinic bond was low in the lower temperature range (260 °c → 320 °c), but at higher temperature it was significantly higher (about 10%). i can be seen that the carbon atoms in naphthenic bond changed as a maximum curve. it was concluded based on the yield and hydrocarbon composition of the gas oils that the yield of the gas oil significantly decreased with increasing paraffin content, i.e. in hydrodearomatization conditions the paraffinic hydrocarbons are cracked with the production of lower boiling range hydrocarbons. based on the above mentioned phenomenon the following inference was drawn: the hydrogenation of aromatic hydrocarbons should be done in a range of process parameters where the concentration of naphthenic hydrocarbons has a maximum value (tmax = 320–330 °c). in this situation deep hydrodearomatization can be carried out with high gas oil yield. therefore the naphthenic hydrocarbons become key components in case of hydrodearomatization. the investigation of hydrogenation of individual hydrocarbon groups was carried out with model compounds and their mixtures in the literature. therefore there is just a little information about the experimental results with real gas oil matrix. the reason of this is that the mono-, diand polycyclic aromatic hydrocarbons and naphthenic molecules transform via numerous reactions to each other and to paraffines on the catalyst surface. these reactions take place in serial and parallel succession, therefore in the real gas oil matrix only the transformation of individual hydrocarbon groups can be investigated (e.g. monoaromatics, diaromatics, normal and isoparaffines). therefore the second objective of our experiments was to study the conversion of individual hydrocarbon groups on the condition of aromatic hydrogenation on the investigated catalyst. the change of the concentration of alkyl-diaromatic hydrocarbons as a function of temperature is shown in fig. 8. it can be seen that the optimal temperature of hydrogenation of alkyl-diaromatic compounds was between 280–290 °c. 0.0 0.5 1.0 1.5 2.0 240 260 280 300 320 340 360 temperature (°c) a lk yl -d ia ro m at ic s ( % )... 1,0 2,0 3,0 4,0lhsv, h-1 figure 8: change of the concentration of alkyldiaromatic compounds as a function of temperature (p = 35 bar, h2/hc = 600 nm3/m3) the optimal temperature of hydrogenation of cycloalkyl-aromatics was 300 °c (fig. 9), but the highest optimal hydrogenation temperature was that of the alkyl-benzenes (320 °c) (fig. 10). based on the results it was concluded that the hydrogenation rate of the different aromatic compounds from the slower to the fastest changed in the following order: alkyl-naphthalenes (condensate alkyl-diaromatics) < cycloalkyl-aromatics (decalin containing different carbon number alkyl-groupa) < alkyl-monoaromatics (alkylbenzenes) (fig. 11). 73 0 2 4 6 8 240 260 280 300 320 340 360 temperature (°c) c yc lo al ky l-b en ze ne s ( % ) 1,0 2,0 3,0 4,0lhsv, h-1 figure 9: the change of the concentration of cycloalkyl-benzenes as a function of temperature (p = 35 bar, h2/hc = 600 nm3/m3) 4 6 8 10 12 14 240 260 280 300 320 340 360 temperature (°c) a lk yl -b en ze ne s ( % ) 1,0 2,0 3,0 4,0lhsv, h-1 figure 10: the change of the concentration of alkylbenzenes as a function of temperature (p = 35 bar, h2/hc = 600 nm3/m3) r2 = 0.9943 r2 = 0.9956 r2 = 0.9822 0.0 0.5 1.0 1.5 2.0 2.5 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1/lhsv (h) ln (c a 0/c a ) alkyl-diaromatics cycloalkyl-benzenes alkyl-benzenes figure 11: the hydrogenation rate of different oneand two-ring akly(cyclioalkyl)-aromatic hydrocarbons (t = 300 °c, p = 35 bar, h2/hc = 600 nm3/m3) therefore the hydrogenation rate of the first ring of aromatic compounds increases with the increasing number of rings in the molecules. the reason of this might be the fact that the aromatic electron system of condensate diaromatic is distortional. the change of the concentration of formed oneand two-ring naphthenes produced by hydrogenation of aromatics as a function of temperature is shown in fig. 12 and 13. it can be seen that the concentration of alkyl-dicycliparaffines decreased with increasing temperature. this means that these compounds are transformed to alkyl-monocycloparaffines via ring opening even in case of the mildest process conditions. 4 8 12 16 240 260 280 300 320 340 360 temperature (°c) a lk yl -d ec al in es (% )... 1,0 2,0 3,0 4,0lhsv, h-1 figure 12: the change of the concentration of alkyldicycloparaffines as a function of temperature (p = 35 bar, h2/hc = 600 nm3/m3) 24 28 32 36 40 240 260 280 300 320 340 360 temperature (°c) a lk yl -c yc lo pa ra ffi ne s ( % )... . 1,0 2,0 3,0 4,0lhsv, h-1 figure 13: the change of the concentration of alkylcycloparaffines as a function of temperature (p = 35 bar, h2/hc = 600 nm3/m3) the concentration of alkyl-cycloparaffines changed as a maximum curve, i.e. it first increased with temperature (alkyl-cycloparaffines are formed in the low temperature range via ring opening from alkyldicycloparaffines and via hydrogenation from alkylbenzenes). after the maximum point (300 °c) it decreased with increasing temperature (the reaction rate of ring opening of alky-cycloparaffines increased, therefore the ring opening of alkyl-dicycloparaffines and hydrogenation of alkyl-benzenes could not compensate the quantity of alkyl-cycloparaffines, which were transformed to paraffines via ring opening). the ring opening of alkyl-cycloparaffines can be seen in the increasing concentration of paraffin hydrocarbons with the temperature in the investigated temperature range (fig. 14, 15). 74 22 26 30 34 38 240 260 280 300 320 340 360 temperature (°c) i-p ar af fin es (% ).. . 1.0 2.0 3.0 4.0lhsv, h-1 figure 14: the change of the concentration of i-paraffines as a function of temperature (p = 35 bar, h2/hc = 600 nm3/m3) it can be further concluded from the change of the concentration of nand i-paraffines that i-paraffines are formed via ring opening. the concentration of nparaffines increased with temperature by only a few degrees in the lower temperature range (260–300 °c). after this range it set to a constant value, i.e. the curve became saturation. it means that the reaction rate of ring opening to n-paraffines was low. it was caused by the following two facts. on the one hand the shrinking of the 6-member ring to a 5-member ring branched with one alkyl-group takes place on the strong acidic catalyst. on the other hand the rate of ring opening is lower in the substituted carbon atom [15-18], due to the steric hindrance and the fact that the alkyl-groups have electron-donor properties, which lead to the increasing electron-density of the ortoand para-located carbon atoms. therefore the ring opening reactions take place in these atoms. 16 18 20 22 24 240 260 280 300 320 340 360 temperature (°c) npa ra ffi ne s ( % ).. . 1,0 2,0 3,0 4,0lhsv, h-1 figure 15: the change of the concentration of nparaffines as a function of temperature (p = 35 bar, h2/hc = 600 nm3/m3) the main advantage of the formation of a large amount of isoparaffins in case of the hydrodearomatization is the better cold flow properties of the products than in the case of n-paraffines. therefore these products can be applied as blending components of winter quality diesel fuels. conclusions the objective of our research and development work was to study the hydrogenation of aromatic compounds on ptpd/usy catalysts in case of real gas oil matrix as feedstock, and the determination of conversion of individual hydrocarbon groups in the condition of aromatic hydrogenation, respectively. it was concluded that the cycloparaffines are key components in hydrodearomatization, i.e. the aromatic hydrogenation in extant catalytic system (feed, catalyst) should be done at process parameters where they have a maximum concentration. in case of this the hydrodearomatization can be carried out with maximum yield of gas oils, and the hydrogen consumption can also be decreased. the reason of the latter is the fact that it does not need extra hydrogen consumption without ring opening to produce saturated hydrocarbons. on the investigated catalysts modern diesel fuel blending components can be produced, which satisfy the future requirements (<10 mg/kg sulphur-, <1mg/kg nitrogen content, <15-20% totaland <2.0–4.0 polycyclic aromatics, at t = 320°c, p = 45 bar, lhsv = 1.0–2.0 h-1, h2/hc: 600 nm3/m3 process parameters with high yield (about 90%). it was further concluded that in case of hydrodearomatization condition mainly isoparaffines are formed via ring opening of naphthenes on the investigated catalyst, the increase of the concentration of n-paraffins was lower. therefore the hydrodearomatization can be done with high gas oil yield with the use of appropriate process parameters, and the decadence of cold flow properties of partially aromatic saturated products is lower. references 1. larivé j. f.: “concawe review”, 15 (2006) 2. 2. worldwide fuel charter, sept. 2006. 3. szalkowska u.: proceedings of the 7th international colloquium on fuels, edited by.: bartz, w. j., 2009, 59–62 (isbn: 3-924813-67-1). 4. abu i. i., smith k. j.: applied catalysis a., 328 (2007) 58-67. 5. olivas a., galván, d. h., alonso, g., fuentes, s.: applied catalysis a., 352 (2009), 10–16. 6. varga z., hancsók j., nagy g., kalló d.: stud. surf. sci. catal., 158 (2005), 1891–1898. 7. yoshimura y., toba m., matsui t.: applied catalysis a., 322 (2007), 152–171. 8. yoshimura y., toba m., farag h., sakanishi k.: catalysis surveys from asia, 8(1) (2004), 47–60. 9. yasuda h., kameoka t., sato t., kijima n., yoshimura y.: applied catalysis a., 185 (1999), 199–201. 75 10. wilson m. f., kriz j. f.: fuel, 63 (1984), 190. 11. fujikawa t., idei k., ohki k., mizuguchi h., usui k.: applied catalysis a, 205 (2001), 71–77. 12. yui s. m., sanford e. c.: proc.-refining department, petroleum institute, 64 (1985), 290– 297. 13. corma a., martinez a., martinez-soria v.: journal of catalysis, 169 (1997), 480–489. 14. corma a., martinez a., martinez-soria v.: journal of catalysis, 200 (2001), 259–269. 15. santana r. c., do p. t., santikunaporn m., alvarez w. e., taylor j. d., sughrue e. l., resasco d. e.: fuel, 85 (2006), 643–656. 16. mcvicker g., daage m., touvelle m., hudson c., klein d., baird w.: journal of catalysis, 210(1) (2002), 137–148. 17. kubicka d., kumar n., maki-arvela p., tiitta m., niemi v., karhu h., salmi t., murzin d. y.: journal of catalysis, 227 (2004), 313–327. 18. santikunaporn m., herera j. e., jongpatiwut s., resasco d. e., alvarez w. e., sughure e. l.: journal of catalysis, 228 (2004), 100–113. editorial hungarian journal of industry and chemistry veszprém vol. 42(1) pp. 39–42 (2014) investigation the properties of y-ba-cu-oxide superconductors prepared by hydraulic pressing and molding anna maloveczky,! margit enisz-bódogh, and tamás kulcsár institute of materials engineering, university of pannonia, egyetem str. 10., veszprém, 8200, hungary !e-mail: anna.maloveczky@gmail.com levitation applications of superconductors require the fabrication of bulk ceramic superconductors with special shapes. the conventional hydraulic pressing is not suitable for the production of superconductors with complicated forms, so we have applied slip casting to shape bulk superconductors. superconducting powders with different yba2cu3oy (123) and y2bacuo5 (211) phase content and different (pt, pb, ce) additives were prepared by solid-state reactions. the nonsuperconducting (211) particles can be considered as flux pinning centres; thus the magnetic properties can be influenced by their amount and particle sizes. the addition of a few weight percent of dopant in the nominal composition can modify the particle size and distribution of the (211) grains. we have investigated and compared the phase compositions, morphologies and magnetic levitation forces of bulk superconductors formed by hydraulic pressing and moulding. the shielding abilities of a moulded superconductor were simulated with the comsol multiphysics 4.4 software. keywords: ybco superconductor, moulding, shielding, modelling introduction the use of superconductivity is promoted by the need for stable high magnetic fields. the high-temperature superconductors are attractive for engineering applications, such as contactless superconducting bearings, trapped field magnets, levitation trains, fusion reactors, and nmr spectrometers. an important application of superconducting magnets is the magnetic resonant imaging (mri). superconducting magnetic shielding can be used simultaneously to protect the personnel and other medical equipment from the strong magnetic fields produced by an mri system. the relative magnetic permeability of type i superconductor is theoretically zero, which means when we use it for shielding, it expels the magnetic fluxes from itself. the high-tc superconductors can also be used for shielding sensitive electronic devices from external electromagnetic fields. due to the meissner effect [1,2], it is sufficient to surround the volume to be protected by a thin film. for quasi-monocrystalline films of ybacuo thickness of 1 µm would be sufficient for virtually perfect shielding. a granular ceramic layer would require a larger thickness, but in all cases the thickness and weight of the superconducting shields would be much less than those of magnetic materials providing a comparable effect. for these applications of high-tc superconductors outstanding magnetic properties and special shapes are required. the scientific literature suggests two main ways for improving the magnetic properties of superconductors that are structure damaging or doping [3–9]. both methods work the same way, such as by increasing the amount of pinning centres (such as 211 phase) in the superconducting (123) material and decreasing the size of these centres by addition of different dopants. the damaging method could be done by ion or neutron radiation to destruct the bulk of the material and generate faults. preparation of high-tc superconductors with special, complicated forms is a particular challenge due to their brittle nature. slip casting, namely pouring low viscosity water-containing slurry into moulds is the oldest ceramic forming method for production of special shapes. for superconductors slip casting of shapes is also possible although the use of water as liquid phase is not optimal due to hydrolysis and other reactions. another preparation method for ceramic superconductors is tape casting of viscous slurry containing ceramic particles in organic solvent [10]. materials and methods in this work, y-ba-cu-oxid-based superconductive powders were prepared with different 123/211 phase content and different (pt, pb, ce) additives. shaped bulk superconductors were produced from these powders with hydraulic pressing and moulding. the effects of these parameters were investigated on the phase compositions, morphologies and magnetic levitation forces of the sintered bulk superconductors. for modelling the superconductor as a shield in different geometries, comsol multiphysics 4.4 software was used that provides a simulating and 40 modelling environment using the finite element method. instead of the original ac-dc module of comsol, a module by roberto bambilla was used, which was developed for modelling ybco superconductors. results and discussions samples made by hydraulic pressing the superconducting samples were prepared by using y2o3, ba(oh)2·8h2o and cuo. the latter was obtained by the calcinations of cu(oh)2·cuco3·nh2o with a specific surface area of 18.4 m2 g-1, ptcl4, pbo and ce(no3)3·6h2o starting materials. the 123:211 molecular ratio of the nominal compositions was changed in the range of 1.00:0.15. samples were prepared without additives as well as with 2.0 wt% ce + 0.5 wt% pt, and 2.0 wt% ce + 0.5 wt% pb dopants. for sample preparations, barium-hydroxide was ground in agate mortar, but in some cases the pulverization and grinding was made in the presence of alcohol. the mixture of raw materials was homogenized by thoroughly mixing with alcohol in an agate mortar and compacted into disks of 25 mm × 3mm by hydraulic pressing at 70 mpa. firstly, the samples were prereacted at 960 °c for 4 hours to obtain the desired (123+211) phases by solid-state reaction. the heattreated samples were ground and the powders were pressed into pellets by hydraulic pressing using a pressure of 70 mpa. the relatively dense structure was obtained by liquid state sintering at 1010 °c peak temperature for 6 hours in oxygen atmosphere [11]. the levitation force of the samples after the heat treatments is shown in fig.1. as described in the literature, we also found that the levitation force shows an increasing trend with increasing amount of 211 phases. in the case of ce+pt and ce+pb dopant containing samples higher levitation forces can be obtained after the first heat treatment at 960 °c. it is notable that the samples prepared from barium hydroxide ground in the presence of alcohol showed improved magnetic properties. samples made by moulding part of the pre-reacted at 960°c ground samples were used for shaping superconductors by moulding. previously, superconductive slurries were prepared with different organic liquid additives and those were burnt out during the annealing. from these materials only a few were good enough for further studies. samples providing a proper cohesion and appearing to be homogeneous were selected for future analysis. after heat treatment, x-ray diffraction analysis was used to study the phase composition changes caused by addition of organic materials for deciding if any of the dopants has a negative influence on the superconductor properties. as shown in table 1, the metylan reduces the amount of the superconducting phase (123) and this leads to the tetragonal, non-superconducting structure. polyvinyl formal did not have a negative influence on the formation of 123 phase. thus, the polyvinyl formal binder was chosen with dioxane for further experiments. with respect of ideal concentrations, it was found that 1 wt% of polyvinyl formal/dioxane must be added to the superconducting powders to obtain a slurry with a density of 2.4 g cm-3, which was dense enough, but still can be poured. the second step was to find the appropriate mould form. different types of materials were investigated, such as stainless steel, glass, plastic, gypsum, and silicone rubber. the prepared slurries stuck to most of these materials rendering them useless for moulding with the exception of silicone rubber as sample could be removed perfectly. using this type of moulds we can make superconductors with complex geometry. the moulded samples were heat treated at the same program as used for hydraulic pressed samples. the moulding technique applies no pressing thus provides a porous structure. however, the pores can lead to poor superconductor properties. to decrease the porosity melt-producing dopants were applied. ag and pb with ce proved to be good in the case of hydraulic pressed samples. table 1: the peak intensity of the crystalline phases samples peak intensity, counts binder solvent 123 d=2.72 å 211 d=2.99 å 011 bacuo2 d=3.05 å cuo d=2.52 å baco3 d=3.72 å 1. polyvinyl formal dioxane 4460 1122 562 956 2. metylan dest. water 2952 919 737 725 3. metylan ethanol 1477 765 679 459 figure 1: levitation forces of the heat treated samples 41 it was found that only in the moulded samples prepared from barium hydroxide ground in alcohol provide enough melt for efficiently fill the pores. the use of dopants alone toward this goal was not sufficient. furthermore, with this grinding technique, the peritectic temperature of the superconducting phase (123) decreased, which allowed for a more economical heat treatment. it can be proposed that this grinding resulted in particle size reduction of barium hydroxide and the higher specific surface area leading to higher reactivity. in this case bulk superconductor with higher density can be obtained, which has an oriented, large plate-like 123crystalls containing structure (figs.2 and 3). modelling ybco as magnetic shield ybco can shield from magnetic fluxes due to the meissner effect. it works the opposite way than the commonly used ferromagnetic materials, which means that superconductor expels the magnetic fluxes from itself, while iron collects them. using the comsol multiphysics 4.4 package, the shields of iron and superconductor were compared in figs.4 and 5. the shielding ability of the superconductor is comparable with iron, and even better. it has the advantage that in alternating magnetic field it does not get heated. the ferromagnetic materials shield poorly in too small and too big fields because they have saturation flux density. superconductors are being used as shields in various devices [12–16]. with a geometry shown in fig.6, very sensitive magnetic devices could be fully shielded and vice versa the environment could be protected from a device, which induces strong magnetic field. with the shape in fig.7, for example a skull could be protected in the mri in case of presence of metal implants in the head. theoretically moulding could be used to prepare these shields. it would be cheaper and thin layers could be made, thus more economical wall could be produced by a few thin layers. figure 2: sem micrograph of the moulded sample ground conventionally figure 3: sem micrograph of the molded sample ground in alcohol figure 4: simulation of iron shield figure 5: simulation of superconductor shield figure 6: simulation of shielding for sphell geometry 42 conclusion in the case of the hydraulic pressed pellets, the results confirmed those from the literatures. improved magnetic properties were noticed with the increasing of the 211 phase content. this was further enhanced by the presence dopants. it was found that pb performs as good as pt or even a little bit better, which is preferred due to the price of pt. the grinding of barium-hydroxide in the presence of alcohol provided a denser structure and more melt phase leading to better superconducting properties. furthermore, it seems that this method decreases the peritectic temperature of the superconducting 123 phase. the homogenization needs to take place after grinding in alcohol to be effective. the adequate liquid-to-material ratio to make a slurry with 1 wt% polyvinyl formal in dioxane and the ideal moulding form of silicone rubber were determined. this allowed for making complex shaped superconductors. the melt-producing dopants cannot reduce the porosity enough to sufficiently improve the levitation force. alternative heat treatment programs with slow annealing up to 500 ºc, while all of the organic materials burn out, can avoid the cracks in the structure. application of vacuum during the moulding can also be useful, since it can eliminate trapped air bubbles from the mass. simulations carried out using comsol multiphysics 4.4 software indicated ybco being a good shielding material. utilization of complex geometries, sensitive devices can be protected, such as skull protection during mri measurements. references [1] takash m., tomioka y., miyauchi t., sato s., murai a., ido t., wakita k., terada h., ohkido s., matsubara m.: characterization of a large-scale non-doped yba2cu3o7-x superconductor prepared by plastic forming without high-pressure molding, j. amer. ceram. soc. 2007, 90(7), 2032–2037 [2] evetts j.: concise encyclopaedia of magnetic and superconducting materials, pergamum press, oxford, 1992, pp. 532–533 [3] monot i., leblond c., marinel s.m., desgardin g.: precursor and microstructure control for melt texturing of high-tc superconductive ybco ceramics, development of high-temperature superconducting alternators combining rotating and levitating principles, russian academy of science, saint-petersburg, 2002, pp. 27–45 [4] shlyk l., nenkov k., krabbes g., fuchs g.: melt-processed ybco with pt or ce additions: comparison of pinning behaviour, physica c 2005, 423, 22–28 [5] riches j.d., alarco j.a., barry j.c.: effects of pto2 and ceo2 additives on the microstructures of the quenched melts of y–ba–cu–o materials physica c superconductivity, 2000, 336, 43–56 [6] leblond c., monot i., provost j., desgardin g.: optimization of the texture formation and characterization of large size top-seeded-meltgrown ybco pellets, physica c, 1999, 311, 211–222 [7] hardy v., simon c., provost j., groult d.: pinning forces in bi-2212 single crystals irradiated by 6 gev pb ions, physica c, 1993, 206, 220–226 [8] wesche r.: magnetic relaxation and flux pinning in yba2cu3o7 a high-tc oxide irradiated by 5.3 gev pb ions, physica north-holland c 1992, 190, 289–298 [9] horvat j., wang x.l., dou s.x.: vortex pinning in heavily pb-doped bi2212 crystals physica c 1999, 324, 211–219 [10] grader g.s., johson d.w.: forming methods for high tc superconductors, thermochimica acta, 1991, 174, 239–251 [11] komlai k.: investigation of the the properties of the incongruent melting reaction of yba2cu3o-y superconductor phase, m.sc. thesis, university of pannonia, 2013 (in hungarian) [12] tavernier s.p.k., van den bogaert f., van lancker l.: the design of a magnetic shielding for an array of photomultipliers in a strong external field, nucl. instrum. methods, 1979, 167, 391–398 [13] bitter t., eisert f., el-muzeini p., kessler m., kinkel u., memt e., lippert w., meienburg w., werner r.: a large volume magnetic shielding system for the ill neutron-antineutron oscillation experiment, nucl. instrum. methods phys. res., 1991, a309, 521–529 [14] tripathi a., vedavathy t.s.: electromagnetic shielding using superconductors, pergamon press ltd, oxford,vol. 2, no. i, 1994, pp. l–5 [15] spillantini p.: active shielding for long duration interplanetary manned missions, adv. space res., 2010, 45, 900–916 [16] yusuf s.m., osgood iii r.m., jiang j.s., sowers c.h., bader s.d., fullerton e.e., felcher g.p.: magnetic profile in nb/si superconducting multilayers, j. magnet. magnetic mat., 1999, 198–199, 564–566 figure 7: simulaton of shielding using a semi-sphell geometry page 1 page 2 page 3 page 4 page 5 page 6 page 7 page 8 page 9 page 10 page 11 page 12 page 13 page 14 page 15 page 16 page 17 page 18 page 19 page 20 page 21 page 22 page 23 page 24 page 25 page 26 page 27 page 28 page 29 page 30 page 31 page 32 page 33 page 34 page 35 page 36 page 37 page 38 page 39 page 40 page 41 page 42 page 43 page 44 page 45 page 46 page 47 page 48 page 49 page 50 page 51 page 52 page 53 page 54 page 55 page 56 page 57 page 58 page 59 page 60 page 61 page 62 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crystallization of para-xylene in a batch cooling crystallizer was investigated by means of computer simulation. the mathematical model used in this modelling study consists of the population balance equation for crystals completed with the differential equations governing the mass balance of solute and the heat balance of the crystalline suspension. the population balance equation was reduced to a finite set of ordinary differential equations for moments of the crystal size variable using the standard moment method. the resulted finite system of ordinary differential equations was solved in matlab environment. the simulation results revealed that both the dynamic trajectories of the crystallizer and the final properties of the crystalline product depend strongly on the cooling profiles. using the numerical model presented the batch crystallization system can be optimized by choosing the best temperature profile for producing a crystalline product exhibiting the required properties. keywords: para-xylene, cooling crystallization, population balance model, moment method, optimization, simulation introduction xylenes are widely used materials in industry since the three xylene isomers are important components of diverse paints and varnishes and also of the gasoline and fuel of airplanes. the leather industry consumes xylenes in great amounts too. xylene as a mixture of three isomers, i.e. orto-xylene, meta-xylene and para-xylene is produced mostly from petroleum. these isomers have the same chemical formula c6h4(ch3)2 but different structural configuration. among the xylene isomers para-xylene plays important role since it is the principal precursor to terephthalic acid and dimethyl terephthalate. both monomers are used in the production of polyethylene terephthalate (pet) which is a widely used raw material of polyesters. some modern technologies use pet-based materials to produce vehicle parts as engineering resins often in combination with glass fibre [1]. after the first steps in crude oil separation technology the isomers and other components are in the same phase and that needs a further separation step for producing pure para-xylene. the three xylene isomers exhibit rather close boiling points but taking advantage of differences in the melting points cooling crystallization is a well suited separation technique for producing pure paraxylene product [2]. crystallization is an important, often used unit operation of chemical industry as a separation and purification technique. during the course of process solid particles are formulated from solution. the driving force for crystallization is supersaturation which is, in essence, the difference between the actual and the equilibrium saturation concentration of solute depending on temperature. in crystallization, the crystalline product exhibits size distribution (csd) even under ideal process conditions. this is an important quality parameter in processing. csd depends on the degree of supersaturation that influences the nucleation and growth of crystals significantly. investigation by properly constructed mathematical models is a feasible tool for process design of crystallization. the balance equations which contain process and kinetic parameters as constitutive expressions are coming into view by development of computer science and technology. in the case of crystallization the population balance equation describes the behaviour of the crystal population by means of which the size distribution of crystals and dynamics of crystallizer can be investigated. the population balance equation is often solved by applying the moment method [3-9]. the moment equations of low order moments describe some important properties of crystals such as the number of crystalline particles, the total crystal volume in the solution, the size distribution and the mean size of the crystalline product. a well designed moment equation model beside the properties of crystalline population involves information also on the mass and heat balance and dynamic behaviour of crystallizer [10, 11]. the aim of this paper is to investigate the para-xylene crystallization process by using a controlled cooling 2 profile in a batch crystallizer. the process is described by a suitable population balance model, and the population balance equation is solved by means of the moment method. the properties of the crystalline product and dynamic behaviour of the crystallizer obtained by numerical experimentation in matlab environment are presented and analysed. population balance model consider a stirred batch crystallizer in which supersaturation is generated by cooling as it is illustrated in fig. 1. in this case, the crystallizer is considered as a two phase operational unit having liquid and solid phases. assuming that: crystals are characterized by a linear dimension l; all new crystals are formed at a nominal size ln ≥ 0 so that we take ln ≈ 0; crystal breakage and agglomeration are negligible; no growth rate fluctuations occur, then the set of process equations, termed population balance model consists of the following balance equations. population balance equation: ( ) ( ) ( ) 0,,,, = ∂ ∂ + ∂ ∂ l tlntwwg t tln sc (1) subject to the initial and boundary conditions ( ) ( )lntln 00, == (2) ( ) ( ) ( )twwbtlntwwg scscl ,,,,,lim 0 = → (3) ( ) 0,lim = ∞→ tln l (4) figure 1: schematics of a cooling crystallizer cooled by means of a jacket in eq.(1), b denotes the nucleation rate given by the power law expression ( ) b s scb bsc w ww rt ektwwb ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ − ⎟ ⎠ ⎞ ⎜ ⎝ ⎛−= exp,, 0 (5) where kb0 is the constant kinetic coefficient, eb is the energy of nucleation, t is the temperature of crystalline suspension, wc is the concentration of solute and ws denotes the equilibrium saturation concentration. the growth rate of crystals is calculated by the following equation ( ) g s scg gsc w ww rt e ktwwg ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ − ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −= exp,, 0 (6) where kg0 denotes the constant kinetic coefficient. the equilibrium saturation concentration ws, i.e. the solubility of para-xylene is given by the second order polynomial 2 210)( tbtbbtys ++= (7) obtained by fitting to the measurement data published by de geode [13]. the results of fitting of eq.(7) to the experimental data of equilibrium saturation concentration of para-xylene dissolved in a mixture of xylene isomers is presented in fig. 2. further thermodynamic properties of xylene isomers are listed in table 1. figure 2: equilibrium saturation concentration of para-xylene in solution of xylenes table 1: thermodynamic properties of xylene isomers melting point (°c) boiling point (°c) para-xylene 13.3 138.5 ortho-xylene -25.2 144.0 meta-xylene -47.9 139.3 the mass and energy balance equations are also parts of the mathematical model. these equations are required to complete the population balance equation to obtain a full crystallizer model for computing the cooling profile, crystallization process and the properties of the product. the solute mass balance is given as 23 μρ gmk dt dwm svcv c sv −= (8) where msv denotes the total mass of solvent in the crystallizer, kv is the volumetric shape factor, ρc is the density of crystals and µ2 is the second order moment from the raw moments of the crystal size variable l weighted by the population density function defined as qh, th,in c, msv, t, n qh, th 3 .3,2,1,0,),()( max 0 == ∫ kdltlnlt l k kμ (9) naturally, here the mass msv of solvent is constant. the heat balance equation for the crystalline suspension is expressed as ( ) ( ) ( )ttmua ttvua dt dtmmcc control sv sv v controlsvvsvccsv −= −=+ ρ (10) where cc and csv are the heat capacities of crystals and solvent, tcontrol denotes the controlled temperature of fluid medium in the jacket, u is the overall heat transfer coefficient and av is the heat transfer surface in a unit volume of suspension. in eq.(10), mc denotes the total mass of solute and crystals in a unit volume of suspension 3μρ cvcc kwm += (11) assuming that the heat capacities of crystals and solute are the same value. moment equation model the population balance model (1)-(11) describes the properties of crystalline particles and the behaviour of crystallizer but the numerical solution of the population balance equation (1) is a complex time consuming procedure. the moment method provides an alternative way of handling the problem. this is a widely used method in studying the disperse systems which often provides exact results. the mass and heat balances are formulated by means of the third order moment which can be determined from the set of equations for the first four leading moments in the moment equation hierarchy: ( ) ( )twwb dt td sc ,,0 = μ (12) ( ) ( ) ( )ttwwg dt td sc 0 1 ,, μμ = (13) ( ) ( ) ( )ttwwg dt td sc 1 2 ,,2 μμ = (14) ( ) ( ) ( )ttwwg dt td sc 2 3 ,,3 μμ = (15) as a consequence, the ordinary differential equations for moments μ0, μ1, μ2 and μ3 together with the mass and heat balance equations (8) and (10) provide a closed model consisting of six ordinary differential equations, as well as of the kinetic equations (5) and (6) and the constitutive expression (7) describing the solubility of para-xylene in a xylene solution. simulation results and discussion numerical solution of the set of differential equations (8), (10) and (12)-(15) were solved using the ode solvers in matlab environment. in numerical experiments the temporal temperature profile was simulated by means of the following function ( ) startendstart bn endc bn c control ttt t tt +− ⎟ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎜ ⎝ ⎛ + − = 11 , 1 (16) where fixing the start and end values, the shape of the profile was controlled by changing the parameter bn. fig. 3 presents some possible temperature profiles depending on the value of parameter bn. the thin lines present the evolution of temperature in the suspension while the thick lines show the temperature changes in the jacket. the differences reflect, in principle, the dynamics of the crystalline suspension coupled with the wall of the crystallizer. the process and kinetic parameters used in numerical experimentation are listed in tables 2 and 3. the kinetic parameters were chosen as published by mohameed et al. (2006) table 2: process parameters used in simulation v=10 m3 vh=3 m3 t0=5 °c uav=1,1e3 qh=1 m3 s-1 tend=-18 °c b0=0.6943 b1=0.02 b2=0.0002 table 3: kinetic parameters used in simulation kg0=28.5 ms-1 g=3.95 kv=0.52 b=0.89 kb0=812.6 #m-3s-1 ρh=1000 kg m-3 ρc=1100 kg m-3 ρsv=1000 kg m-3 eg=785. j mol-1 eb=-56.37 j mol-1 figure 3: temperature profiles by eq.(16) 4 a number of numerical experiments have been carried out to choose the so called optimal temperature profile which provide the maximum final mean size of crystals 32l defined as ( ) ( ) ( )end end end t ttl 2 3 32 μ μ = (17) where tend denotes the final moment of time corresponding to the final temperature tend. fig. 4 shows the temporal profiles of solute concentration and the equilibrium saturation concentration corresponding to the temperature profiles in fig. 3. the evolutions of the zero order moment μ0 are presented in fig. 5 for the cooling methods shown in fig. 3. this moment provides, in principle, the total number of crystals in a unit volume of suspension. differences are observed in the final values of the number of crystals as a function of the cooling profiles. the optimal cooling profile produced the lowest value of crystal number. figure 4: solute and saturation concentration figure 5: evolution of the zero order moment μ0 the histories of the third order moment μ3 as a function of time are shown in fig. 6. this moment is related to the total volume of crystals in a unit volume of suspension from which the mass of the crystalline product can be obtained by multiplying that with the density of crystals. there are significant differences in the time profiles but the final volumes of the crystalline product becomes of nearly the same value at the end of the process. temporal evolutions of the mean size of crystals 23l , defined by eq.(15) are presented in fig. 7. the graphs in fig. 7 illustrate well that variation of the mean crystal size exhibit significant differences during the course of the batch process. the optimal cooling profile gives the largest mean crystal size in accordance with the results shown in figs 5 and 6. the other two cooling methods produced nearly the same mean sizes. figure 6: evolution of the third order moment μ3 relating to the total volume of crystals in a unit volume of suspension for different cooling methods figure 7: temporal evolutions of the mean crystal size 32l depending on the cooling methods of fig. 3 5 it should be noted that the temporal evolution of the mean crystal size passes through maximum in each case as it is shown in fig. 7. it is a consequence of that although all the moments increase monotonously in time the rates of their increase differ leading to such an unusual phenomenon. similar phenomena can be observed in fig. 8 comparing the temporal evolutions of the mean crystal size 32l with that of 10l defined as ( ) ( ) ( )t ttl 0 1 10 μ μ = (18) both graphs presented in fig. 8 were computed applying the linear temperature profile. the corresponding evolutions of the first order moment are shown in fig. 9 for the sake of illustration that these moments also increase monotonously in time. figure 8: temporal evolution of the mean sizes 32l and 10l figure 9: evolution of the first order moment μ1 it seems to be interesting to note that the mean crystal size 32l is greater than 10l at each moment of time during the course of the process leading to greater value even at the final moment. mohameed et al. (2006) published kinetic parameters differing to some extent, obtained by fitting their model to experimental data produced by using diverse cooling profiles. a second set of their kinetic parameters is shown in table 4. the differences between the processes of crystal mean sizes obtained by table 4: kinetic parameters used in simulation kg0=16.25 ms-1 g=4.74 kv=0.52 b=0.71 kb0=345.59 #m-3s-1 ρh=1000 kg m-3 ρc=1100 kg m-3 ρsv=1000 kg m-3 eg=370.23 j mol-1 eb=-63.37 j mol-1 using the original parameters listed in table 3 and those in table 4 are shown in fig. 10. fig. 10 illustrates well that the time histories of the mean crystal sizes differ from each other significantly but the final mean sizes of the crystalline product exhibit just about 10% difference. this means that the parameters obtained from different experiments reflect different dynamic behaviour of the batch crystallizer but rather similar final product properties. figure 10: evolution of the mean size 32l by using the kinetic parameters in tables 3 and 4 conclusions a population balance model was developed and applied for simulation of batch cooling crystallization of paraxylene. in order to apply the moment method a moment equation hierarchy was generated from the population balance equation. the set of equations for the first four moments coupled with the mass and energy balance equations proved suitable to investigate the dynamic 6 behaviour of the crystallizer and to predict the product properties of the cooling crystallization process. the applied model allowed simulating the heat transfer through the wall of crystallizer by using a controlled jacket cooling method. in this case, there was negligible difference in the product values from the perfectly controlled crystallizer and that when the controlled jacket temperature model was applied. the results of numerical experimentations revealed that different cooling profiles generate significant differences in the characteristic values of the crystalline product. analysis of the simulation results allows concluding that the product properties can be computed and designed successfully by using a mathematical model and numerical experimentation. by means of the numerical model presented the batch crystallization system can be optimized by choosing the best temperature profile for producing a crystalline product exhibiting the required properties. acknowledgements this work was supported by the hungarian scientific research fund under grant k 77955. also, this work was supported by the european union and co-financed by the european social fund in the frame of the tamop-4.2.1/b-09/1/konv-2010-0003 and tamop4.2.2/b-10/1-2010-0025 projects. symbols av heat transfer surface in a unit volume, m2 m-3 b nucleation rate, # m-3 s-1 b kinetic parameter bn optimization variable, eq.(14) c heat capacity, j kg-1 k-1 e energy, j mol-1 g growth rate, m s-1 k kinetic coefficient l size variable, m n population density function, # m-4 t temperature, k t time, s u heat transfer coefficient, j m-2 s-1 k-1 v volume, m3 w concentration, kg_solute kg_solvent-1 greek symbols ε volumetric ratio of solution μk kth order moment ρ density, kg m-3 indices b nucleation c crystal g growth in inlet s equilibrium saturation concentration sv solvent references 1. h. a. mohameed, b. a. jdayil, k. takrouri: separation of para-xylene mixture via crystallization, chem. eng. proc., 46, (2006), 25–36 2. j. h. perry: chemical engineers handbook (in hungarian); technical press, budapest, hungary (1968) 3. t. bickle, b. lakatos, cs. mihálykó: mathematical models of particulate system. (in hungarian); the new results in chemistry 89, academic press, budapest (2001) 4. b. g. lakatos: population balance modelling of crystallization processes, hungarian journal of industrial chemistry 35, (2007), 7–17 5. b. g. lakatos, cs. mihálykó, t. bickle: modelling of interactive populations of disperse systems, chemical engineering science 61, (2006), 54–62 6. d. ramkrishna: population balances, theory and applications to particulate systems in engineering, academic press, san diego (2000) 7. a. d. randolph, m. a. larson: theory of particulate processes, academic press, new york (1988) 8. n. s. tavare: industrial crystallization. process simulation, analysis and design. plenum press, new york (1995) 9. zs. ulbert: investigation and modelling of dynamic processes of crystallizers (in hungarian). phd thesis, university of veszprém, veszprém (2002) 10. á. borsos, b. g. lakatos: modelling of crystal size distribution in batch cooling crystallizer (in hungarian); proceedings of conference chemical engineering days, veszprém (2011) 11. á. borsos: modelling and optimizing cooling crystallizers (in hungarian), msc thesis, university of pannonia, veszprém (2010) 12. á. borsos, b. g. lakatos: investigation of dynamic processes of cooling crystallizers in case of needle-shape crystals (in hungarian). acta agraria kaposváriensis (in press) (2010) 13. r. de geode: crystallization of para-xylene with scraped surface heat exchangers; ph.d. thesis, delft university of technology, netherlands (1988) << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default 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page 427 page 428 page 429 page 430 page 431 page 432 page 433 page 434 page 435 page 436 page 437 page 438 page 439 page 440 page 441 page 442 page 443 page 444 page 445 page 446 page 447 page 448 page 449 page 450 page 451 page 452 page 453 page 454 page 455 page 456 page 457 page 458 page 459 page 460 page 461 page 462 page 463 page 464 page 465 page 466 page 467 page 468 page 469 page 470 page 471 page 472 page 473 page 474 page 475 page 476 page 477 page 478 page 479 page 480 page 481 page 482 page 483 page 484 page 485 page 486 page 487 page 488 page 489 page 490 page 491 page 492 page 493 page 494 page 495 page 496 page 497 page 498 page 499 page 500 page 501 page 502 page 503 page 504 page 505 page 506 page 507 page 508 page 509 page 510 page 511 page 512 page 513 page 514 page 515 page 516 page 517 page 518 page 519 page 520 page 521 page 522 page 523 page 524 page 525 page 526 page 527 page 528 page 529 page 530 page 531 page 532 page 533 page 534 page 535 page 536 page 537 page 538 page 539 page 540 page 541 page 542 page 543 page 544 page 545 page 546 page 547 page 548 page 549 page 550 page 551 page 552 page 553 page 554 page 555 page 556 page 557 page 558 page 559 page 560 page 561 page 562 page 563 page 564 page 565 page 566 page 567 page 568 page 569 page 570 page 571 page 572 page 573 page 574 page 575 page 576 page 577 page 578 page 579 page 580 page 581 page 582 page 583 page 584 microsoft word b_52_sztankovics_r.doc hungarian journal of industrial chemistry veszprém vol. 39(2) pp. 309-312 (2011) rotational turning in precision finishing i. sztankovics university of miskolc, department of production engineering, h-3515 miskolc egyetemváros, hungary e-mail: istvan.sztankovics@uni-miskolc.hu this paper shortly describes modern hard machining methods and some of the possibilities of rotational turning. the methods of tangential feed turning are grouped by the numbers of cutting edges, the path of the feed rate and the position of the cutting edge. the important geometrical characteristics of rotational turning are summarized to analyse it for simplification. finally, based on the results simpler tool geometry was created and some calculations were made for the preparation of an experiment. keywords: rotational turning, hard turning, tangential feed introduction nowadays the use of hard machining methods in finishing operations plays a crucial role. these operations use super hard cutting tools in the machining of hardened steels (hrc>45). hard turning and hard milling appeared in the industrial environment. earlier the operations used in precision finishing of cylindrical surfaces were the followings: rough and smooth turning before heat treatment for specified hardness, followed by grinding operation. in grinding the tool and the workpiece are in contact in a continuous, long line. the heat development caused by the frictional force is high. therefore we need to use some kind of coolant intensively, which will turn into hazardous waste after the process [1]. the appearance of super hard cutting tools (e.g. pcbn) has enabled to develop appropriate machining methods to fulfil the demands of environmental protection. one of the most important features of cubic boron nitride tools is their great hardness and for this reason these tools can be used in machining of hardened steels. [2, 3] other attributes of these tools are also acceptable for machining operations. it is significant that there is no need to use any kind of coolants contrary to other cutting tool materials. with the use of super hard cutting tools the machining technologies of hardened surfaces have been altered. grinding operations are not necessary to use because hardened surfaces can be machined by pcbn tools, therefore the machining operations will be more environment-friendly unlike older methods [2, 3]. however, like every technology hard turning has some disadvantages. one of this is caused by the path of the tool during turning operations. since the edge of the tool moves one unit in axial direction during one turn of the workpiece, the chip is cut off from the surface helically. the depth of this generated groove depends on the construction of the tool, the used technological parameters and the hardness of the machined surface. the dimension of the depth is around 10 µm. due to this micro-thread on the workpiece the areas of applications of the hard machined surfaces are limited. hard turning cannot be used in some cases, for example on the treads of needle roller bearings and on surfaces below sealings. the easiest solution of this problem is to partially return to grinding operations. to do this we must apply a machine which can make the turning and grinding operations in one place without the movement of the workpiece [2]. this way the punctuality of the operations can be increased. the thickness of the material cut during the process is lower than in regular grinding operations, therefore this combined technology is more environmentfriendly unlike the grinding operations in the past decades [3]. another solution for the micro-thread problem is the application of a new hard machining technology, which does not create helical grooves on the surface. one of the applicable methods is the turning with tangential feed. tangential feed in turning operations tangential feed is a turning method if the direction of the feed is tangent to the machined surface. there is a special form of tangential feed, if the edge of the tool is on a circular path. in that case the direction will be tangent in the cutting zone. tangential feed can be achieved with different tools: it can be executed with standard tools or with designed monolithic prismatic or cylindrical cutting tools. 310 grouping of tangential feeds by the path of the tool edge by the path of the tool edge the tangential feeds can have two groups. these methods can be linear or circular. the operation uses linear tangential feed, if the edge is on a linear path and the path is tangent to the machined surface of the workpiece. the tangential speed of the surface, caused by the rotation of the workpiece, needs to be much higher than the speed of the tool. the other method is the circular tangential feed. in this case the edge of the tool is on a circular path, and this circle will be tangent to the machined surface. the vector of the workpiece’s speed and the cutting tool’s speed will be parallel. during the machining the angular speed of the cutting tool needs to be much lower than the angular speed of the workpiece. grouping of tangential feeds by the number of the cutting edges two groups can be created by the number of the cutting edges in tangential feed turning operations. the cutting tool can be single-edged or multi-edged. in the previous case the design of the tool is very simple. the production is easier and in case of fracture or if the tool wear passes beyond the wear-criteria the replacement is quicker. in multi-edged design the depth of cut splits up in multiple segments. the combined grouping by the number of cutting edges and by the path of the tool edge is shown in table 1. table 1: grouping of tangential feeds by the path of the tool edge and the number of cutting edges path of the tool edge linear circular si ng le -e dg ed n um be r o f e dg es m ul tied ge d grouping of tangential feeds by the spatial position of cutting edge similar to other cutting tools, the cutting tools for methods using tangential feed can have different cutting edge inclination angles. the grouping by the spatial position of cutting edge is presented in table 2. when the cutting edge inclination angle is equal to zero (λ=0°), the design and the production of the tool is simpler. therefore the acquisition cost of the tool is lower and in case of fracture or if the tool wear passes beyond the wear-criteria the replacement is quicker. however, when the cutting edge inclination angle is not equal to zero (λ≠0°) just a part of the edge is in contact with the workpiece at the beginning of the process. during the machining the depth of cut continuously grows to the defined value and it remains constant until the ending phase of the cut. accordingly, from the viewpoint of the load this case is substantially better than the zero inclinational angled case. at the beginning of the cutting the dynamic force is low. in the middle phase the static force does not affect the tool life dramatically. table 2: grouping of tangential feeds by the path of the tool edge and the inclinational angle of the edge path of the tool edge linear circular λ = 0 in cl in at io na l a ng le λ ≠ 0 comparison of tangential feed turning methods according to the observations above the following conclusions can be made: by the direction of the feed it is better to use circular feed operations. in this case the efficiency of the machining will be better. by the design of the tool it is better to favour a single-edged construction. with the simpler design and production some of the tool costs can be spared. by the spatial position of the tool edge it is better to design the tool with some inclination angle. however, the production of the tool will be more difficult, but it is better because there is no significant dynamic force. to sum up we can make the following conclusions: in hard machining methods with tangential feed it is practical to use single-edged tool with non-zero inclination angle and to apply circular feed. the best solution is when the edge is on a helical curve on the superficies of the tool. this way we get the tool for rotational turning [4]. 311 machining with rotational turning henceforth the paper presents one of the recent tangential feed methods of hard machining. in tangential feeds the rotational turning is a method with circular feed, and uses a single-edged tool with non-zero inclination angle. fig. 1 shows the sketch of rotational turning [5]. the symbols in fig. 1 are the following: dwz – blank diameter dw – workpiece diameter ds – tool diameter nw – revolutions per minute of the workpiece ns – revolution per minute of the tool ap – depth of cut fa,v – virtual axial feed figure 1: sketch of rotational turning in fig. 1 we can see that during the cutting the edge of rotating tool generates a hyperboloid-like surface. therefore it is difficult to define the cross-section of the chip. point p is the point of the tool’s edge which touches the workpiece first. the depth of cut continuously grows during the beginning phase of the cut by the rotation of the tool [4]. during the ending phase the edge continuously leaves the workpiece, therefore the depth of cut decreases smoothly. in the middle phase the cross-section of the chip remains constant. the characteristics of the cutting tool rotational turning requires a special tool. the edge is on a helical curve on the superficies of the tool. with this design the relative angular offset of the edge can be guaranteed. the pitch of the helical curve affects the cutting conditions: if the pitch is high the relative angular offset of the edge will be small in the cutting zone; if the pitch is low the tool will be very short. by circular feed the method demands a special machine-tool and tool clamping system so the rotational motion of the tool can be ensured [6]. machinable workpiece length the machinable workpiece length cut by rotational turning depends on the use of axial feed by the circular feed. basically the value of the axial feed is equal to zero. in this case the machinable workpiece length is shorter than the axial length of the tool. in the other case there is an axial feed besides the circular feed. if the values of the circular and axial feed are correctly calculated and set in the machine then longer surfaces can also be machined by rotational turning. in fig. 2 a machining case is shown, where the axial feed of the tool is equal to zero [5]. the symbols of fig. 2 are the following: lw – machinable workpiece length dw – workpiece diameter nw – revolutions per minute of the workpiece vf,t – relative tangential feed speed vf,a – relative axial feed speed p – beginning point on the cutting edge p’ – beginning point on the workpiece v – ending point on the cutting edge u’ – ending point on the workpiece figure 2: explanation of the machinable workpiece length in fig. 2 we can see that at point p of the edge begins the cutting in point p’ of the workpiece and at point v of the edge finishes the cutting in point u’. if the workpiece is longer than the axial length of the cutting tool additional axial feed speed is also applied. its value must be high enough to enable point v of the tool’s edge to reach point u’ of the workpiece. simpler tool edge geometry simpler tool edge geometry was created for further experiments on rotational turning. the basis of the simplification is the following: in the cutting zone the helical curve of the cutting edge is equal to a line with the pitch angle of α. with this method we can use a linear edge instead of the complicated helical curve edge for geometric investigation of the process. 312 for the preparations of the experiments it is necessary to make it clear how long the cutting edge should be for the cutting. to make these calculations we need to create a sketch based on the simplifications. this sketch is presented in fig. 3. the symbols in fig. 3 are the following: l – minimal length of the cutting edge b – projected length of the cutting edge d – diameter of the machined workpiece a – depth of cut α – theoretical pitch angle figure 3: the theoretical sketch of the linear edge the last point of the edge which is involved in the cutting stays at the middle line of the workpiece (there is no cutting above the middle line because the surface is already machined). the depth of the cut can also be seen in fig. 3. however, in this case axial feed is applied, but this model is geometrically a good approximate solution to observe the alterations in the cutting zone during machining. the calculation of the cutting edge’s minimal length the minimal length of the cutting edge can be calculated with the formula based on the sketch; the length is in function of the diameter of the machined workpiece, the depth of cut and the theoretical pitch angle. the projected length of the cutting edge is calculated first with the use of the pythagorean theorem and the result will be the function of the workpiece’s diameter, the depth of cut. the minimal length of the cutting edge will be the function the pitch angle and the projection length of the edge. equation (1) is applied to calculate the minimal length of the cutting edge, which is a function with three variables. ( ) α ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ −− =α cos app ,a,dl 22 24 (1) two of the three variables is locked down to plot the function. the diameter of the machined surface has to be constant; this way the minimal length can be analysed to a given workpiece. the pitch angle is also locked down so the depth of cut will be the variable. the minimal length of the cutting edge is presented in fig. 4. in this graph various cases of the pitch angle are drowned to choose the optimal case for a 100 mm diameter workpiece. figure 4: cutting edge length, dm=100 mm conclusions it has been shown that in tangential feed machining methods rotational turning is a good and productive alternative in hard machining methods. with the examination of the minimal length of the cutting edge we can conclude that there is no need of a long edged tool for the initial experiments of the research. acknowledgement the work was presented by the support of the hungarian scientific research fund (number of agreement: otka k 78482), which the authors greatly appreciate. the described work was carried out as part of the támop-4.2.1.b-10/2/konv-2010-0001 project. references 1. b. karpuschewski, h.-j. knoche, m. hipke: gear finishing by abrasive processes, cirp annals 57, (2008), 621–640 2. j. kundrák, b. karpuschewski, k. gyáni, v. bana: accuracy of hard turning, journal of material processing technology, 202(1-3), (2008), 328–338 3. f. klocke, e. brinksmeier, k. weinert: capability profile of hard cutting and grinding processes, cirp annals 54, (2005), 22–45 4. j. g. weisser: patent von werkzeugmaschinenfabrik, st. georgen, swarzwald, deutschland (2004) 5. j. kundrák, k. gyáni, i. deszpoth: precision hard turning of external cylindrical surfaces by rotation procedure (2011) 6. j. kundrák, o. szabó, k. gyáni, s. szabó, g. szabó: tárcsaszerű alkatrészek megmunkálásának vizsgálata rotációs esztergálással (me gépgyártástechnológiai tanszék, tanulmány) (2009) << /ascii85encodepages false /allowtransparency false 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(adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word 1426 göllei 105.docx hungarian journal of industry and chemistry veszprém vol. 42(2) pp. 85–89 (2014) measurement-based modelling and simulation of a hydrogen generating dry cell for complex domestic renewable energy systems attila göllei,* péter görbe, attila magyar, and lászló neukirchner department of electrical engineering and information systems, university of pannonia, egyetem u. 10., veszprém, 8200, hungary *e-mail: golleia@almos.uni-pannon.hu nowadays, the growing need for energy from renewable sources and growing revulsion towards fossil and nuclear fuels puts sustainable and green energy in the limelight. producing (electrical) energy in domestic power plants from renewable sources (mainly solar and wind) hardly results in difficulties, but the storage of energy not consumed immediately is a great engineering challenge. in the present paper a complex model has been developed by investigating renewable energy sources, the surplus energy not actually consumed and stored in electrical vehicle (ev) batteries, the conversion to hydrogen for storage purposes and how the main grid is fed. a measurement-based model of a hydrogen generating cell developed for the simulation of complex energetic systems. the parameter estimation of the static model was based on the collected measurement data coming from the detailed examination of a built demonstration cell. the novel element of this work is the matlab simulink model for the hydrogen generation cell. using this model, a dynamic simulator of a complex domestic power plant is made available using renewable energy sources and hydrogen generation cells. hydrogen generation enables the lossless long-term storage of surplus electric energy collected, but not consumed or injected into the low voltage grid. the generated hydrogen can be consumed for transportation purposes in suitable vehicles or it can be applied in fuel cells generating direct electrical energy for energy-deficient low voltage network situations. energetic situations potentially occurring in practice were simulated in our complex model. simulations showed that the presented model is suitable for domestic scale low voltage complex energetic systems. keywords: hydrogen generation, renewable energy sources, domestic power plants, modelling and simulation, measurement-based modelling introduction producing hydrogen gas (h2) from excess energy is not a new idea. this is an alternative way to store and convert renewable energy for further utilization. the produced hydrogen can be stored or used in power cells to be converted back to electric energy or in vehicles for hydrogen propulsion [1]. although the described procedure is efficient and able to produce a high quantity of h2 it is not suitable for application in combination with domestic power plants. the most relevant from of h2 production is when the energy consumption and quantity of produced h2 are controlled. when power consumption and generation are continuous (and not necessarily deterministic) functions of time, the h2 production depends solely on the excess energy of the grid. the best solution is the usage of supervisory control and data acquisition systems (scada) of management [2]. the domestic applicability of this technology in the future depends on the cost of scada system installation. producing hydrogen and oxygen gases from water using electricity in a laboratory is a simple electrochemical process that can be performed easily and in a very demonstrative way. producing hydrogen on a large scale or in industrial quantities calls for an optimized or near-optimized cell model. in an energy demanding process only a few percent of variance in efficiency could mean a significant energy surplus or shortage [3]. the electrochemical parameters of a dry cell (fig.1) that are used here are discussed to simulate hydrogen and oxygen gas production. compared to wet oxyhydrogen (hho) cells where the entire unit is underwater, the plates of dry cells are separated with rubber seals. these seals stop the water from leaking from the cell. the electrical connections and edges of figure 1: the theoretical setup of a dry hho block 86 the plates do not touch the electrolyte. these parts of the unit stay dry, thus the name dry cell. to make sure the gas made from the electrolyte gets out of the cell and the solution flows between the plates, there are holes on the top (for the gas) and bottom (for the electrolyte) on the metal slats (fig.1). the application of dry hho units has two main advantages. the surface of the dry cell plates enables one to use smaller amounts of electrolyte compared to with wet cells; therefore, the volume and weight of the cell is smaller. furthermore, the connectors of dry cells remain dry, i.e. they do not corrode unlike to wet cells, where the connectors are underwater therefore their surface slowly corrodes [4]. electrochemical foundations electrochemical cells can be considered as galvanic batteries where the electrochemical reactions are supported by an external current supply. they are composed of two electrodes and a conductive electrolyte fluid. if the electrode material does not participate directly in the electrode reaction, it is called an indifferent electrode (e.g. graphite). during electrolysis, if there is more than one possible type of electrochemical reaction, then a simple anion will detach from the positive anode (e.g. chloride), without this anion, howill be created by water splitting. the dissolution voltage of water is 1.23 v at 25 °c, the temperature coefficient is -0.85 mv/k, which means that at 100 °c this voltage decreases to 1.17 v. therefore, in the light of these data, the specific energy demand to make hydrogen via electrolysis at 25°c can be calculated from eqs.(1–4). the amount of charge needed to evolve 1 kg of h2 gas is q = zfm = 2⋅96487⋅0.5 = 96487 a s mol-1 = = 26801 ah kg-1 (1) wh2 = qemf = 26801⋅1.23 = 32966 wh kg-1 (2) since the volume of 1 kg of standard state h2 is 12474 dm3, the amount of energy required to produce 1 dm3 of h2 gas is: wh2 = 32966 12474 = 2.64 wh dm−3 (3) to generate 1 dm3 of hydrogen gas, 1.5 dm3 of hho gas is needed and thus the energy demand of producing 1 ldm3 of hho gas (0.667 dm3 h2) is: wh2(hho) = 0.667⋅2.64 = 1.76 wh dm-3 (4) the unit has been measured at 10 different electrolyte concentrations, using different currents. at the same time, the voltage on the plates and amount of gas produced by electrolysis has also been measured. the hho cell unit the setup of one block of the unit is shown in fig.2. usually five cells make up one block giving one gasproducing block. the block’s electrical connections are on the ends of two plates (fig.1). four of the six electrode plates are neutral electrodes, as there is no voltage connected to them. the potential is divided between the neutral plates according to voltage division in series connections. it means that the voltage between two electrodes is one fifth of the voltage on one whole block. in the experiment, a unit with three blocks connected in parallel has been used. besides the hho cell, a water reserve tank to infuse the electrolyte into the cell was necessary. a tube between the gas outlet and the tank has also been installed since due to bubbling, electrolyte comes out of the tube that needs to be recycled back into the system. then, as the electrolyte drips back into the tank, the gas can escape into the bottle through another hose. the produced h2 volume and the production speed are measured with this bottle. a power supply (manson sps9600) has been connected to the electrical connections of the hho unit, in this way the input current was controlled (table 1). matlab model of the dry cell the model of the dry cell considered was implemented in matlab simulink using the simpowersystems toolbox. two unknown functional relationships between the generated h2 volume, the cell current and the koh concentration and between cell voltage, cell current and koh concentration were approximated using fourth and third order polynomials, respectively figure 2: the setup of a hho gas generator cell block table 1: experimental results electrolyte concentration, g dm-3 mmwa, cm3 min-1 w-1 gas production, dm3 min-1 power of unit, w 1 2.13 0.20 10.8 2 2.66 0.75 34.4 3 2.66 1.37 55.8 4 2.59 1.51 82.2 5 2.72 1.90 90.6 6 2.63 2.52 119.5 7 2.67 2.96 140.0 8 2.65 2.76 125.0 9 2.46 2.28 105.6 10 1.82 2.15 103.2 a millilitres per minute per watt 87 using the matlab surface fitting tool. as the fitted polynomials do not have a physical connection to the given device, the model is applicable to any similar electrochemical h2 generation device with an electric two-pole system. in the different linear and non-linear physical and chemical models different coefficients become dominant. the voltage relationship is given by eq.(5), where icell denotes the cell current and ckoh stands for the koh concentration. parameters can be found in table 2. ucell(icell,ckoh) = p00 + p10 icell + p01 ckoh + p20 icell 2 + p11 icellckoh + p02ckoh 2 + p30icell 3 + p21icell 2 ckoh (5) the volume of the generated h2 is given by eq.(6). h2 (icell,ckoh ) = p00 + p10 icell + p01 ckoh + p20 icell 2 + p11 icellckoh + p02 ckoh 2 + p30 icell 3 + p21 icell 2 ckoh + p12 icellckoh 2 + p03 ckoh 3 + p40 icell 4 + p31 icell 3 ckoh +p22 icell 2 ckoh 2 + p13 icellckoh 3 (6) table 3 and figs.3-4 show representative results for the model. as expected, the h2 generation speed decreases and the cell finally stops working as the amount of water decreases and the koh concentration increases. a simulink block scheme of the cell model is depicted in fig.5. this simulink model was validated by considering a system with the same parameters as the layout of the experimental cell. in this layout, we ran a simulation for 24 h using this model, decreasing water and increasing koh concentrations. the results of this simulation can be seen in fig.6. it can be seen that the hydrogen gas generated is reduced because of the rising koh concentration. the exact values are in good agreement with our measurements. dry cell model in complex energetic systems the model for h2 generating cells described in the previous section was investigated in the matlab simulink simulation environment that studies the energy flow conditions of a complex energetic system consisting of a renewable source with a gridtable 2: coefficients of the polynomial relationship describing the cell voltage value value value p00 1.429 p10 0.2548 p01 -0.1226 p20 -0.008571 p11 -0.01191 p02 0.008257 p30 0.0001141 p21 -8.76e-05 p12 0.0009697 table 3: coefficients of the polynomial relationship for the generated h2 gas value value value p00 -0.1695 p10 0.1687 p01 -0.01765 p20 -0.007486 p11 -0.03234 p02 0.03446 p30 -0.0001077 p21 0.00412 p12 -0.004094 p03 -0.004061 p40 -4.269e-06 p13 6.169e-05 p22 -0.0005518 p13 0.0009544 figure 3: simulation of the cell model with a constant current of 5 a for 1 day figure 4: generated h2 as a function of koh concentration and dry cell current figure 5: matlab simulink model of the hho cell. the functional blocks implementing eqs.(5) and (6) are denoted by different background colours figure 6: simulation of a cell model with a constant current of 5 a for 1 day 88 synchronized inverter, a low voltage grid, an intermediate voltage controller [3,5] and a lithium ion battery. we replaced the lithium ion battery in this cell model, which reduces the potential energy flow modes, because this cell can only adsorb current for storing energy in hydrogen production. it cannot reverse the electrochemical process for electrical energy generation from hydrogen gas. the structure of the system can be seen in fig.7, where it is apparent that the cell model is connected directly only to the grid-synchronized inverter module of the system. the system depicted in fig.7 operates in different discrete states according to the energy flow direction. four cases can be defined: • normal inverter mode: the energy flows from the renewable source to the grid only (fig.8a). • normal inverter and hydrogen generation mode: the energy flows from the renewable source to both the dry cell and the grid (fig.8b). • hydrogen generation only mode: the energy flows from the grid to the dry cell only (fig.8c). • distortion reduction only mode: the energy flows from the grid into the intermediate capacitance and from the intermediate capacitance into the grid. the energy balance is zero for a period, and the active power is zero (fig.8d). model verification was performed by changing the energy flow modes in subsequent time intervals, and this was implemented by changing the energy balance of the system with outer current loads (iouter load). the different values for the simulations as parameters can be figure 7: simulink model of a complex energetic system with an hho cell model inside figure 8: complex energetic system energy flow modes: a: normal inverter mode, b: inverter and hydrogen generator mode, c: hydrogen generation only mode, d: distortion reduction only mode 89 seen in table 4. the simulation results are shown in fig.9, where uconn is the effective value of the voltage at the connection point, ihho is the current value of the dry cell, vh2 is the volume of generated hydrogen gas, ckoh is the koh concentration of the electrolyte and vwater is the volume of water inside the cell system. these values are plotted as a function of time. the results of the simulation show that the behaviour of the simulated electronic two-pole system is identical to that of the measured database. conclusion we developed a complex model to investigate renewable energy sources, for the conversion of surplus energy to hydrogen gas for storage and to represent how a main grid is fed. we built a measurement-based model of a hydrogen-generating cell for the simulation of complex energy systems in matlab simulink environment. we estimated the parameters of the model based on measurements collected during the detailed examination of a demonstration cell. we carried out a series of experiments on a hho gas producing dry cell to find the optimal electrolyte concentration, current value, etc. or change the setup by altering the distance between the plates with koh electrolyte solution. we monitored the experimental setup in several regards, for example cell voltage, and gas production. the novel element is the temperature and concentration dependent matlab simulink model of the hydrogen generation cell, which was found to be suitable for simulation purposes. we tested it in a simulation of a complex domestic power plant using a renewable energy source and hydrogen generation cell. hydrogen generation enables the long-term storage of surplus electrical energy collected, but not consumed or injected into the low voltage grid. the generated hydrogen can be consumed by vehicles for transportation purposes or it can be applied in fuel cells generating direct electrical energy for energy-deficient low voltage network situations. we simulated all the potential energetic situations in this complex model of an energetic system. the simulations showed that the presented model of a hydrogengenerating cell performed well. acknowledgement we acknowledge the financial support of this work by the hungarian state and the european union under the tamop-4.2.2.a-11/1/ konv-2012-0072 project. references [1] koutsonikolasa d.e., kaldisa, s.p., pantoleontosb, g.t., zaspalisac, v.t., sakellaropoulosc, g.p.: techno-economic assessment of polymeric, ceramic and metallic membranes integration in an advanced igcc process for h2 production and co2 capture, chem. engng. trans. 2013, 35, 715-720 [2] ziogoua c., elmasidesb c., papadopoulouca s., voutetakisa s.: supervisory control and unattended operation of an off-grid hybrid power generation station with hydrogen storage chem. engng. trans. 2013, 35, 529-534 [3] görbe p., magyar a., hangos k.m.: line conditioning with grid synchronized inverter's power injection of renewable sources in nonlinear distorted mains, proc. 10th international phd workshop on systems and control, 2009, 978-980 [4] al-rousan a.a.: reduction of fuel consumption in gasoline engines by introducing hho gas into intake manifold, int. j. hydrogen energy, 2010, 35, 12930-12935 [5] görbe p., magyar a., hangos k.m.: thd reduction with grid synchronized inverter’s power injection of renewable sources, proc. 20th int. symp. power electronics, electrical drives, automation and motion (speedam) 2010, 13811386 figure 9: simulation results of a complex energetic system using a cell model short time range (5 sec) hungarian journal of industry and chemistry veszprém vol. 42(2) pp. 91–95 (2014) quasi-polynomial representation-based control of mechanical systems lászló neukirchnerb and attila magyar department of electrical engineering and information systems, university of pannonia, egyetem u. 10., veszprém, 8200, hungary be-mail: neu.groszber@gmail.com a simple kinematic model of a differential steering mobile robot is investigated using a nonlinear technique based on the quasi-polynomial representation of the dynamical model. dynamical systems can be embedded in the generalized lotka-volterrs (or quasi-polynomial) form under mild conditions. quasi-polynomial systems are good candidates for a general nonlinear system representation, since their global stability analysis is equivalent to the feasibility of a linear matrix inequality. the stabilizing quasi-polynomial state feedback controller design problem is equivalent to the feasibility of a bilinear matrix inequality. the classical stabilizing state feedback problem for quasi-polynomial systems was extended with the ability of tracking time-dependent reference signals. it is shown that the stabilizing quasi-polynomial controller design is equivalent to a bilinear matrix inequality. the results are applied to the model of the differential steering mobile robot. the goal reaching quasi-polynomial controller is shown to be a special kind of proportional state feedback. keywords: quasi-polynomial, robotics, differential drive robot, control systems, kinematics, lotka-volterra system introduction trajectory and goal tracking of mobile robots is an intensively studied field of modern robotics as well as modern control theory. several papers deal with an adaptive output feedback approach [1]. on the other hand some groups try to apply neural network-based methods for the task [2]. another direction is to describe the problem as an optimal control problem and apply optimal control results for it [3]. the class of quasi-polynomial (qp) systems plays an important role in the theory of nonlinear dynamical systems because nonlinear systems with smooth nonlinearities can be transformed into quasipolynomial form ref.[4]. this means, that any applicable method for quasi-polynomial systems can be regarded as a general technique for nonlinear systems [5]. the aim of this work is to widen the applicability of the quasipolynomial representation-based methods to the class of mechanical systems, more precisely to mobile robots. the goal reaching problem of a differential steering mobile robot is reformulated as a globally stabilizing feedback design problem in the quasi-polynomial framework. basic notions differential drive mobile robot kinematics the chosen mechanical system is the kinematic model of a two wheeled differential drive mobile robot eq.(1). the model deals with the geometric relationships that govern the system. it calculates the motion without considering the affecting forces. the system’s states are the cartesian coordinates x, and y and the orientation θ of the mobile robot. the basic kinematic model of the differential drive robot is given by θ̇ = r 2a (ωleft − ωright) ẋ = r 2 cos(θ)(ωleft + ωright) ẏ = r 2 sin(θ)(ωleft + ωright), (1) where a is half the shaft’s diameter, r is the radius of the wheels and ω is the angular velocity of the right or left wheel. to order the robot to reach a specific goal, it is acceptable to design a proportional controller to govern the expected trajectory eq.(2) [6] . in this case, the model is modified to calculate the state errors between the ordered and the present value. the new error model with proportional gain is ẋ = kv(edis cos(θ)− x(t)) ẏ = kv(edis sin(θ)− y(t)) θ̇ = kh(eang − θ(t)) edis = √ (xg − x(t))2 + (yg − y(t))2 eang = arctan ( 2 yg − y(t) xg − x(t) ) , (2) wherekv is the velocity control gain,kh is the rotational velocity control gain, edis is the distance error, eang is the 92 angular error, and xg, yg are the cartesian coordinates to reach. quasi-polynomial representation of nonlinear systems some basic notions of quasi-polynomial and lotkavolterra systems are summarised in this section. generalised lotka-volterra form representing an ode in generalised lotka-volterra (glv) form can increase the structural simplicity in exchange for increasing its dimension. the glv or quasipolynomial (qp) form: ẋi = xi ( λi + m∑ i=1 aij · n∏ k=1 x bij k ) , i = 1, . . . , n, m ≥ n (3) where a and b are n × m, m × n real matrices, and λ ∈ rn is a vector. the set of non-linear odes can be embedded into qp form if it meets two requirements: (i) the non-linear odes should follow this form: ẋs = ∑ is1...isn,js ais1...isn,jsx is1 1 . . . xisnn f(x̄)js , xs(t0) = x0s, s = 1 . . . n (4) where ais1...isn,jsεr, s = 1 . . . n, and f(x̄) is some scalar function which cannot be reduced to quasy-monomial form. (ii) the partial derivatives of the system eq.(4) should fulfil: ∂f ∂xs = ∑ es1...esn,es bes1...esn,esx es1 1 . . . xesnn f(x̄)es , (5) where bes1...esn,esεr, s = 1 . . . n. by embedding, we introduce the new auxiliary variable: y = fq n∏ s=1 xpss. q 6= 0 (6) differentiating the new, substituted equations we get the qp representation of the original equation eq.(4): ẋs = xs  ∑ is1...isn,js ( ais1...isnjsy js/q n∏ k=1 xisk−δsk−jspk/q )] , s = 1 . . . n (7) where δsk = 1 if s = k and 0 otherwise. a new additional dimension appears as the ode of the new variable y: ẏ = y [ ∑ is1...isn,js ( psx −1 s ẋs + + ∑ isα,js esα,es aisα,jsbisα,jsqy (es+js−1)/q × × n∏ k=1 x isk+esk+(1−es−js)pk k )] . α = 1 . . . n (8) it is important to mention that the new ode is not unique because we can choose the parameters ps and q. the quasi-monomial transformation is defined as: xi = n∏ k=1 xcikk , i = 1 . . . n (9) where c is an arbitrary invertible matrix. the matrices of glv can be modified as b̂ = b · c, â = c−1 · a, and λ̂ = c−1 ·λ, and the transformed set is also in glv form. lotka-volterra models the above family of models is split into classes of equivalence according to the values of the products m = ba and n = bl. the lotka-volterra form gives the representative elements of these classes of equivalence. if rank(b) = n, then the set of odes in eq.(3) can be embedded into the following m-dimensional set of equations, the so-called lotka-volterra model: żj = zj ( nj + m∑ i=1 mjizi ) , j = 1, . . . ,m (10) where m = ba, n = bl, and each zj represents a so-called quasi-monomial: zj = n∏ k=1 y bjk k , j = 1, . . . ,m. (11) input-affine qp model the well known input-affine model of nonlinear systems is given in the following state space model: ẋ = f(x) + p∑ j=1 gj(x)uj where f ∈ rn → rn, and gj ∈ rn → rn are qp functions and the input variable u is p-dimensional. in 93 figure 1: membership functions for angular error this case we need a qp form with the matrices from the glv form ode set: ẋi = xi λi + m∑ j=1 a′ij n∏ k=1 x bjk k + + p∑ l=1 xi µli + m∑ j=1 clij n∏ k=1 x bjk k ul. i = 1 . . . n (12) it can be proven that if u = h(x) state feedback is in qp form, the closed-loop system remains in qp form as well, but the quasi-monomials of the system will be greater, than the system’s without the feedback. global stability analysis global equilibrium points can be obtained by finding a lyapunov function v (·). for lv systems there is a well known lyapunov function family: v (z) = m∑ i=1 ci ( zi − z∗i − ln zi z∗i ) , ci ≥ 0, i = 1 . . .m (13) and the time derivative: v̇z = ∂v (z) ∂z · ∂z ∂t = = 1 2 (z − z∗)(cm +mt c)(z − z∗), (14) where z∗ = (z∗1 . . . z ∗ m)t is the unique positive equilibrium point, c = diag(c1, . . . , cm) and m is the invariant coefficient matrix of the lv form. if cmt +m c is negative semi-definite then z∗ is stable and if negative definite then z∗ is asymptotically stable. the global stability analysis is thus equivalent to the linear matrix inequality cmt +m c ≤ 0 c > 0. (15) the presented lyapunov function eq.(13) can be extended to glv systems by embedding the system using the lv coefficient matrix m = ba. it is necessary to solve the lmi system eq.(15) for the stability analysis of the qp and lv system:( c 0 0 −cmt −m c ) > 0 (16) controller design in quasi-polynomial representation the globally stabilizing qp state feedback design problem for qp systems can be formulated as follows [7]. consider arbitrary quasi-polynomial inputs in the form: ul = r∑ i=1 kilq̂i, l = 1 . . . , p (17) where q̂i = q̂i(y1, . . . , yn), i = 1, . . . , r are arbitrary quasi-monomial functions of the state variables of the system and kil is the constant gain of the quasi-monomial function q̂i in the l-th input ul. the closed-loop system will also be a qp system furthermore, the closed-loop lv coefficient matrix m̂ can also be expressed in the form m̂ = b̂ â = m0 + p∑ l=1 r∑ i=1 kilmil. (18) then the global stability analysis of the closed-loop system with unknown feedback gains kil leads to the following bilinear matrix inequality m̂ t c +cm̂ = m0 tc +cm0+ p∑ l=1 r∑ i=1 kil ( mil tc +cmil ) ≤ 0. (19) the variables of the bmi are the p × r kil feedback gain parameters and the cj , j = 1, ..,m parameters of the lyapunov function. if the bmi above is feasible then there exists a globally stabilizing feedback with the selected structure. quasi-polynomial control of a differential drive mobile robot quasi-polynomial representation of the kinematic model with the given differential drive robot model eq.(1) and the explained error model eq.(2) the qp representation can be built. the fist step as mentioned, is to find the new auxiliary variables, that help to eliminate the non-qp expressions. the newly chosen auxiliary variables are: α = cos(θ), β = sin(θ), γ = arctan ( 2 yg − y xg − x ) , δ = (xg − x)2 + (yg − y)2, and ε = √ δ + (xg − x). (20) 94 −2 0 2 4 6 0 2 4 6 start finish x [m] y [m ] pid qp fuzzy figure 2: comparison of different controllers by substituting them into the original system eq.(2) and performing the differentiation of the new equations eq.(20): ẋ = x ( kv √ δα x −kv ) ẏ = y ( kv √ δβ y −kv ) θ̇ = θ ( khγ θ −kh ) α̇ = α ( −β α ) β̇ = β ( α β ) (21) γ̇ = γ· ( − 2kvβ √ δ γε +kvy γε −kvxgβ γε +kvxβ γε + kvxgy γε √ δ −kvxy γε √ δ + kvygα γε −kvyα γε −kvygx γε √ δ +kvxy γε √ δ ) (22) δ̇ = δ ( − 2kvxgα√ δ + 2kvxgx δ + 2kvxα√ δ − 2kvx 2 δ − 2kvygβ√ δ + 2kvygy δ + 2kvyβ√ δ − 2kvy 2 δ ) (23) ε̇ = ε ( −kvxgα ε +kvxα ε + kvxgx ε √ δ −kvx 2 ε √ δ −kvygβ ε +kvyβ ε + kvygy ε √ δ −kvy 2 ε √ δ +kvα ε −kvx ε √ δ ) (24) figure 3: membership functions for distance error the closed-loop qp system eq.(21-24) has 29 quasimonomials. x : α √ δx−1 y : β √ δy−1 θ : γθ−1 α : βα−1 β : αβ−1 γ : β √ δγ−1ε−1, yγ−1ε−1, βγ−1ε−1, xβγ−1ε−1, yγ−1δ−1/2ε−1, αγ−1ε−1, yαγ−1ε−1, xγ−1δ−1/2ε−1 δ : αδ−1/2, xδ−1, xαδ−1/2, x2δ−1, βδ−1/2, yδ−1, yβδ−1/2, y2δ−1 ε : αε−1, xαε−1, xε−1δ−1/2, x2ε−1δ−1/2, βε−1, yβε−1, yε−1δ−1/2, y2ε−1δ−1/2, (25) the qp system eq.(21-24) can obtain the glv form invariants with the help of monomials. these matrices are: a the coefficient matrix, b the exponential matrix and λ the constant’s matrix. the invariant matrix product ba results in the lv coefficient matrix m , which is necessary for the global stability analysis. controller design as the original model eq.(2) already contains the proportional controller parameters kh and kv, they naturally appear in the qp and lotka-volterra forms, respectively. the closed-loop lotka-volterra coefficient matrixm contains the proportional gains in a linear manner eq.(26) [7] m = m0 +khmh +kvmv, (26) where m ∈ r29×29. this means, that the globally stabilizing feedback design bmi can be formulated, and checked for feasibility. the controller design is practically solved as a control-lyapunov function-based state feedback. the prescribed lyapunov function parameters are c1,2,3 = 0.1, c4,5 = 1 and c6−29 = 0. the control gains are obtained by solving an lmi version of the feedback design bmi by substitutingc into eq.(19). the obtained values are kh = 2.78 and kv = 0.8. 95 table 1: rules for the fuzzy controller ∧ ∧ eang edis ωleft ωright zero zero ⇒ zero zero pos zero pos neg zero neg pos zero pos pos pos pos pos pos zero pos zero pos comparison of results for different controller types the first and most basic method was the proportional controller approach. this was explained in the second chapter. this is a more systematic approach, but with the increasing non-linearities it is becoming a more difficult method to solve. fig.3 shows that the robot moves on a significantly wider curve compared to the other two designs. secondly a fuzzy controller was designed to compare the original design to. this is a much more intuitive approach, the physical nonlinearities were easily implementable with the cost of inaccuracy. this can be seen in fig.3, where the robot travels on a much smaller curve. table 1 shows the definition of the rules. the membership functions follow simple triangular shapes according to the acceptable rate of angular and velocity changes. the qp controller performance can be seen in fig.3. where a classical pid controller and a fuzzy logic controller are also shown. it is apparent, that the qp controller performs well by means of the length of the trajectory. conclusions a quasi-polynomial representation-based nonlinear control design method has been applied to the kinematics of a differential steering mobile robot in this work. it has been shown, that the quasi-polynomial model of the mobile robot’s kinematics extended with the tracking error dynamics has 29 quasi-monomials, i.e. the sizes of matrices appearing in the bilinear matrix inequality that should be solved for a globally stabilizing feedback controller acknowledgement this research was supported by the european union and the state of hungary, co-financed by the european social are reasonably great. the resulting controller and the trajectory were compared to the trajectories of a reference pid controller and a fuzzy logic controller. it can be seen that the controller performs satisfactorily. possible future directions include the application of the lmi and /or bmi cost function to introduce some optimality measure to the problem to be minimised. a next step would be the application of a time dependent goal position (i.e. a trajectory). fund in the framework of the támop 4.2.4. a/2-11-12012-0001 ’national excellence programme’. references [1] huang j., wen c., wang w., jiang z.-p.: adaptive output feedback tracking control of a nonholonomic mobile robot, automatica, 2004, 50(3), 821– 831 [2] mohareri o., dhaouadi r., rad a.b.: indirect adaptive tracking control of a nonholonomic mobile robot via neural networks, neurocomputing, 2012, 88, 54–66 [3] li j., guo x., li z., chen w.: stochastic adaptive optimal control of under-actuated robots using neural networks, neurocomputing, 2014, 142, 190-200 [4] hernández-bermejo b., fairén v.: nonpolynomial vector fields under the lotka-volterra normal form, phys. lett. a, 1995, 206, 31–37 [5] magyar a., fodor a.: quasi-polynomial control of a synchronous generator, hung. j. ind. chem., 2013, 41(1), 55–61 [6] tzafestas s.g.: mobile robot control i: the lyapunov-based method, in introduction to mobile robot control (tzafestas s.g., ed.) elsevier, oxford, 2014, 137–183 [7] magyar a., szederkényi g., hangos k. m.: globally stabilizing feedback control of process systems in generalized lotka-volterra form, j. proc. contr., 2008, 18(1), 80–91 microsoft word a_57_kasza_r.doc hungarian journal of industrial chemistry veszprém vol. 39(1) pp. 121-126 (2011) investigation of fuel components produced by the isomerization of bio-paraffin mixtures t. kasza, j. hancsók university of pannonia, mol department of hydrocarbon and coal processing, hungary e-mail: hancsokj@almos.uni-pannon.hu the importance of biofuels becomes more acute, especially in the european union. beside them, the biogasoil is a promising product that is a fuel with high isoparaffin content in the gas oil boiling range, which can be produced by the catalytic hydrogenation of different natural triglycerides. in order to improve the cold flow properties of mixtures consist of mainly normal paraffins they have to be isomerized. in this paper the isomerization of paraffin mixture consists of only normal and iso-paraffin was studied on 0.5% pt/sapo-11 catalyst at 300–380 °c temperature, 40 bar pressure, 0.5–4.0 h-1 of liquid space velocity and 400 nm3/m3 of h2/feed ratio. it was found that cfpp value of the products can be tailored between -7 °c and -15 °c at a gas oil yield of 85–95%. during the conversion 2–5% of bio-jet fuel was obtained with cfpp value of between -55 °c and -45 °c. bio-naphtha also formed with a yield of 2–5.5%, which can be used as a feedstock of naphtha isomerization. all of the products are free of aromatics, sulphur and nitrogen content, so they are environmentally sound blending component. keywords: biogasoil, bio-jet fuel, bio-naphtha, isomerization, pt/sapo-11 introduction in the last decade, the express population growth of the world and the increase of the living standard in the developing countries have increased significantly the energy demand of the world. besides, the demand of fuels has constantly extended. in the developed countries of the world environmental regulations were made to protect the environment and to stimulate the economy. because of these effects and environmental advantages the role of bio-fuels has become more and more important [1-5]. bio-fuels are materials which are suitable for carrying energy and drive engines, and are produced by different ways from different biomass such as agricultural products and/or wastes. because of the several disadvantages of the currently used bio-fuels and those production technologies and of the different demands and incentives the research, development and market introduction of second or new generation bio-fuels came into front in european union [6-8], usa [9] and on other part of the world [10]. accordingly products of different composition have to be produced. because of these in the last few years intensive research-development activity started in the field of production and utilization of diesel fuels produced from natural triglycerides via thermal or mainly catalytic processes. beside these bio-fuels one of the most promising one is the so-called biogasoil, which can be produced from natural triglycerides by catalytic hydrogenation (fig. 1) [11-15]. figure 1: reaction scheme of the biogasoil production during the catalytic hydrogenation – as a function of the catalyst and process parameters – normal paraffins form which carbon number is the same or shorter by one than that of the carbon number of the fatty acid of the triglyceride [13, 16]. the concentration of iso-paraffins – as a function of the catalyst and process parameters – generally do not exceed 30%; often less than 10% [13]. the concentration of the intermediate oxygenic compounds (e.g. mono and diglycerides, carboxyl acids, esters, etc.) is often below 0.5% over the high activity heteroatom removal catalysts [14]. as a feedstock of biogasoils not only soy, palm, coconut, rapeseed and sunflower oils are suitable (which are cultivated currently in large quantities for biodiesel production), but the waste triglycerides such as used cooking oils, waste animal fats, greases from meat and leather processing industry, brown greases of sewage farms, saturated fatty acids of palm oil production, as 122 well. in the last few years, in order to broad the feedstock supply the cultivation of such oil plants started which can subsist on unarable lands or salt water coasts, as well (jatropha, mahua, karanja, neem, jupati [17-19]). furthermore the production of algae and fungal oils are intensively researched, as well [19-23]. the second step of the biogasoil production is the isomerization of paraffin rich mixture to improve the cold flow properties. during this process branched hydrocarbons form from linear paraffins, which freezing point is lower by 20–30 °c than that of the convenient normal paraffins (fig. 2), while their cetane number is still higher than it is specified in the current diesel standard (fig. 3) [24]. -10 -5 18 28 37 -46 -26 -10 6 18 -70 -69 -31 -20 -7 -100 -80 -60 -40 -20 0 20 40 60 carbon number fr ee zi ng p oi nt ,°c normal paraffin 2-methyl-paraffin 5-methyl-paraffin 1312 16 18 20 figure 2: freezing point of some iso and normal paraffin as a function of the carbon number 0 20 40 60 80 100 120 5 10 15 20 25 c et an e nu m be r carbon number paraffins olefins isoparaffins mono-ring aromatics mono-ring naphthenes decalines naphthalines tetralines figure 3: cetane number of different hydrocarbons as a function of carbon number during the catalytic hydroisomerization hydrocracking reactions also take place in different measure as a function of the applied catalyst and process parameters. during these reactions smaller molecule mass hydrocarbons form which have different number of branching. in the research field of isomerization of bioparaffins only a few research paper were published. these have not discussed the yield of the products and those performance properties in detail and with academic depth. accordingly the aim of our present contribution was the conversion of hydrocarbon mixture produced from sunflower oil in order to be suitable to use in diesel engines as fuel or blending component. during this we investigated the change of yield and composition of the product over pt/sapo-11 catalyst found to be favourable in our pre-experiments. experimental during the experiments the process temperature was varied between 300 and 380 °c, while liquid hourly space velocity (lhsv) was changed between 0.5 and 4.0 h-1. the process pressure was 40 bar which was found to be favourable in our experiments over 0.5% pt/sapo-11 catalyst [11, 15]. applying lower pressure resulted loss of yield and catalyst deactivation because of the intensifying cracking reactions, while the use of higher pressure did not have further beneficial effect on the product yield and composition. the value of the h2/feedstock ratio was unchanged; it was 400 nm3/m3. during our pre-experiments it was found that the utilization of lower amount of hydrogen causes the increase of the cracking reactions which led to the decrease of the isoparaffin content of the product. the utilization of higher amount of hydrogen/feedstock ratio – higher than 400 nm3/m3 – is unfavourable regarding economical aspects; moreover it could retard the degree of the isomerization [11, 15]. apparatus the experiments were carried out in an apparatus containing a tubular down-flow reactor of 100 cm3 effective volume. it contains all the equipment and devices applied in the reactor system of an industrial heterogeneous catalytic plant [13]. the experiments were carried out in continuous operation with steady-state activity catalyst. materials and methods table 1 contains the properties of paraffin mixture produced from sunflower oil used as feedstock. the properties of the feedstock and the products were determined according to the test methods specified in en 590:2009 diesel fuel standard. the hydrocarbon composition was measured by shimadzu 2010 gc using zebron db-1ht (30 m x 0.32 mm x 0.1 μm) column. the catalysts were prepared as described and characterized according to hu 225 912 patent. the crystal structure and the purity of the catalyst were determined by x-ray diffraction (xrd). xrd characterization of the obtained powder confirmed that it was sapo-11. the synthesized sapo-11 microporous molecular sieve was impregnated with pt(nh3)4cl2 solution. the platinum content of the catalyst was determined according to uop-274 standard. 123 table 1: the main properties of the feedstock properties value density at 40°c, g/cm3 0.7697 kinematical viscosity, 40°c, mm2/s 3.714 cold filter plugging point, °c +23 flash point, °c 50 sulphur content, mg/kg 3.4 nitrogen content, mg/kg 2.3 acid number, mg koh/g 1.9 iodine number, g i2/g <1 c177.0 n-c17 46.8 i-c17 0.8 n-c18 42.9 i-c18 0.9 paraffin content, % c18+ 1.7 the dispersity of the platinum was determined by h2 chemisorption, which was 91%. the bet surface area of the catalyst was 100.1 m2/g. the acidity of the catalyst determined by nh3 adsorption was 0.66 mmol nh3/g. prior to activity measurements the catalysts were pretreated in situ, as described in our earlier publication [11]. results and discussion the products obtained during the isomerization of the paraffin rich feedstock were the mixtures of liquid and gas phase hydrocarbons. the gas products were generated by the hydrocracking side reactions. they contained mainly butane and isobutane (more than 40% of the gas phase). these can be used for several purposes in a refinery e.g. lpg production, alkylation of i-c4 with olefins, dehydrogenation of i-c4 to isobutylene, etc. the liquid products were the mixtures of iso and normal paraffins. these were separated by distillation to gasoline (c5-c9 hydrocarbons; b.p.: 40–160 °c) and jet fuel fraction (c10-c13 hydrocarbons; b.p.: 160–240 °c) as valuable side product and to the gas oil boiling range (c14-c22 hydrocarbons; b.p.: 240–360 °c) main product. the yields of products the yield of the liquid product mixtures decreased by increase of the level of the conversion (by increasing the temperature and by decreasing the lhsv) (fig. 4). the reason of this was that the carbenium ions generated on the surface of the catalyst during the isomerization, having lower stability than that of the saturated hydrocarbons, could be cracked more easily at higher temperature [25]. in the investigated process parameter range, the yield of the product exceeded 85% in every case. 84 86 88 90 92 94 96 98 100 310 320 330 340 350 360 370 380 390 l iq ui d pr od uc t y ie ld , % temperature, °c lhsv = 0.5 1/h lhsv = 0.75 1/h lhsv = 1.0 1/h lhsv = 2.0 1/h lhsv = 4.0 1/h figure 4: product yields as a function of temperature and lhsv (p = 40 bar; h2/hc ratio = 400 nm3/m3) the composition of the products by increase the temperature up to about 360 °c the isoparaffin content of the products increased significantly, namely the degree of isomerization increased. however, at about 360 °c it reached a maximum, and then started to decrease. it was partly because of the thermodynamic inhibition (namely the isomerization is an exothermic reaction) and partly because of the increase of the cracking reactions (fig. 5). cracking reactions not only decreased the yield of isoparaffins, but caused coke formation, that decreased the activity of catalyst, as well. 0 10 20 30 40 50 60 70 80 90 300 310 320 330 340 350 360 370 380 390 is op ar af fin c on te nt , % temperature, °c lhsv = 0.5 1/h lhsv = 0.75 1/h lhsv = 1.0 1/h lhsv = 2.0 1/h lhsv = 4.0 1/h figure 5: isoparaffin content of the products as a function of temperature and lhsv (p = 40 bar; h2/hc ratio = 400 nm3/m3) the carbon number based fraction distribution and the faction composition of some products are given in fig. 6. it presents well that the share of c14-c19+ fractions decreased while that of c3-c13 fractions increased by the increase of the conversion. methane and ethane were not found in gas products. it suggested that cracking of hydrocarbons occurred by beta cracking, wherein cracked products having at least three carbon number (table 2) [25]. the distribution of cracked products was not similar to that of the theoretical, modal cracked product distribution, it was shifted toward to lighter hydrocarbons. it indicated that the secondary cracking of long chain hydrocarbons took place as well. 124 figure 6: hydrocarbon composition of the feedstock and products obtained at lhsv of 4.0, 2.0 and 0.75 h-1 respectively (upper number in the bubble is isoparaffin content of the given carbon number fraction; while lower value is the ratio of mono and multibranched isoparaffins of the given carbon number fraction; t = 360 °c; p = 40 bar; h2/hc ratio = 400 nm3/m3); * can not be measured, or no such a compound. table 2: five types of β-cracking type ncamin example a ≥8 b1 ≥7 b2 ≥7 c ≥6 d ≥5 ncamin: minimal carbon number of carbenium ion the isoparaffin content and the ratio of mono/multi branched paraffins of the different fractions obtained at lhsv of 0.75 h-1 are presented in fig 6. it can be seen well that concentration of isoparaffins formed from the dominant fractions (n-c15 – n-c18) and the ratio of mono/multi branched paraffins were significantly higher than those of the lower molecule weight hydrocarbons. the reason of these effects was the special pore structure of pt/sapo-11 catalyst. namely, during the isomerization of paraffins over sapo-11 catalyst, mainly mono and multi branched methyl paraffins form. their cracking could happen via c and d type beta cracking (table 2), because between the branchings of these multibranced paraffins have at least 3 or 4 carbon number distance [25]. accordingly during the cracking of monomethyl paraffins two normal paraffins form, while from dibranched paraffins a normal and an isoparaffin generate. investigation of the performance properties the cold filter plugging point (cfpp) of diesel fuels is an importance performance property, because at decreased temperature the precipitated paraffin crystals can cause operational disorders or unserviceability of the fuel supply system. the cfpp values of the products decreased by the increase of the temperature and the decrease of the lhsv. its reason was mainly the increase of the isoparaffin content of the products. the lower molecule weight compound formed in the cracking reactions also improved the cfpp value, as they have lower freezing point. accordingly, at the favourable operational parameters (t = 360 °c, p = 40 bar, lhsv = 0.75–1.0 h-1 and h2/feedstock ratio of 400 nm3/m3) the cfpp value of the products was between -11 and -15 °c. by the increase of the conversion the concentration of the multibranched paraffins increased. it had a positive effect on the cold flow properties of the products. however, another important performance property, the cetane number varied somewhat unfavourably. consequently during the catalytic conversion the cetane number of the products decreased relative to that of the feedstock (101 unit) as a function of the conversion. however, products obtained at the favourable process parameters still had a cetane number of 76–88. these exceed significantly the standard value of 51. 125 investigation of side products during the isomerization about 1–3% of side-product having jet fuel boiling range was formed. in case of this fraction the key characteristics are the crystallization point and the smoke point. the obtained jet fuel fractions had an isoparaffin content of 40–70%, wherein 5–20% was the concentration of multi-branched isoparaffins. consequently these fractions had a crystallization point of between -55 °c and -50 °c, so they could satisfy the standard value of at most -40 °c or -50 °c values. since they are free of aromatics, sulphur and nitrogen they burn cleanly. at the investigated parameter ranges 3–7% of light hydrocarbons having gasoline boiling range also formed in the cracking reactions. in case of this fraction the key characteristics is the octane number. in spite of that this fraction contained about 40–50% of isoparaffins, the octane number was low, because they were mainly mono-branched isoparaffins. we note that the multibranched paraffins having high octane number cannot be formed over sapo-11 catalyst because of the special pore structure. however these fractions were free of sulphur, aromatics, benzene and olefins, so they are good feedstock for naphtha isomerization plants. the obtained propane-butane fraction can be used as heating gas, or might be used in alkylation plants because of its high isobutene content. summary during our experiments the production possibilities of biogasoil with good cold flow properties was investigated using a mixture of n-paraffins over pt/sapo-11 catalyst. based on the results it was found that up to a limit the increase of the temperature and decrease of the lhsv were favourable for the conversion of n-paraffins. regarding the yield, the cfpp value and cetane number of the products the most favourable parameter combination was the temperature of 360 °c, pressure of 40 bar, 1.0 h-1 of lhsv and 400 nm3/m3 h2/feedstock ratio. at the favourable process parameters product had high yield (95.4%) and high iso-paraffin content (68.0%). at this parameter combination the cfpp of the product was favourable (-11 °c), which satisfy the summer grade quality (+5 °c) of diesel standard, and with some addition can satisfy the winter grade specification (-20 °c), as well. the cetane number of this practically heteroatom and aromatic free product was about 77 unit, which is significantly higher than that is specified in the diesel fuel standard (51). the jet fuel boiling range side-products had perfect freezing point (between -55 and -50 °c), and they can satisfy all of the specification of the standard. the gasoline boiling range compounds can be converted to excellent quality gasoline blending compounds by isomerization. acknowledgement we acknowledge the financial support of this work by the hungarian state and the european union under the tamop-4.2.1/b-09/1/konv-2010-0003 and the tamop-4.2.2/b-10/1-2010-0025 projects. references 1. a. demirbas: political, economic and environmental impacts of biofuels: a review, applied energy 86, (2009), s108 2. f. cherubini, n. d. birda, a. cowie, g. jungmeier, b. schlamadinger, s. woess-gallasch: energy and greenhouse gas-based lca of biofuel and bioenergy 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fuels, fuel 85, (2006), 643–656 25. c. bouchy, g. hastoy, e. guillon, j. a. martens: fischer-tropsch waxes upgrading via hydrocracking and selective hydroisomerization, oil & gas science and technology – rev. ifp, 64(1), (2009), 91–112 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 /colorconversionstrategy /cmyk /dothumbnails false /embedallfonts true /embedopentype false /parseiccprofilesincomments true /embedjoboptions true /dscreportinglevel 0 /emitdscwarnings false /endpage -1 /imagememory 1048576 /lockdistillerparams 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/pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice 24 kubáň, ďurč, lačná, greguš, foret, et al. the use of mii-ph is, however, rather unpleasant and up to one third of subjects report discomfort. in this paper, the replacement of the above-mentioned mii-ph method with a significantly less invasive technique for analyzing ebc was attempted. ebc was collected using a specially designed miniature sampler [4, 9, 10] that was previously developed in our laboratory. ebc samples were collected from several healthy volunteers and a group of patients suffering from symptoms attributed to gastroesophageal reflux disease. capillary electrophoresis was used to analyze the ionic content of ebc samples and differences in selected ion concentrations were identified between the groups. 2. experimental 2.1 instrumentation an in-house-built ce instrument was used for all electrophoretic separations at ± 15 kv using a high voltage power supply unit (spellman cze2000r start spellman, pulborough, uk). two pt wires (with an outer diameter (od) of 0.5 mm, 3 cm in length, advent research materials ltd., eynsham, uk) were inserted into the electrolyte vials to serve as electrodes. fused-silica (fs) capillaries (with an inner diameter (id) of 50 µm, od of 375 µm, 39 cm in total length, polymicro technologies, phoenix, az, usa) were used for the separation. all ce experiments were performed at ambient temperature. a custom-made contactless conductometric detector (ccd) (version 5.06, admet s.r.o., prague, czech republic) operating at a frequency of 1.8432 mhz and a voltage of 50 vp−p was used for the detection of the separated analytes. data were collected using an orca 2800 24-bit a/d converter and ecomac software ver. 0.254 (ecom spol s.r.o., prague, czech republic). in all experiments, hydrodynamic injection was applied to the samples, consisting of the elevation of the sample vial to a height of 10 cm for 20 s. the sampler for the collection of ebc has been developed in our group previously [9]. briefly, it was constructed from a 2 ml syringe (b. braun melsungen ag, melsungen, germany) cooled by a 5 cm-long hollow aluminum cylinder with an od of 2.5 cm and an id identical to the od of the syringe (see fig. 1). the cylinder was kept in dry ice at -80 °c prior to the collection of ebc and an insulation sleeve was used during its collection. a straw with an od of 6 mm, and a wall thickness of 0.2 mm (purchased in a local store) was used to exhale the air through the sampler. the end of the syringe was enclosed with a parafilm septum to avoid loss of ebc. 2.2 chemicals all chemicals were of reagent grade (sigma-aldrich, steinheim, germany) and deionized (di) water (purite, figure 1: the photograph and scheme of the ebc sampler used in this work. neptune, watrex, prague, czech republic) was used for the preparation of stock solutions and dilutions. background electrolytes (bges) for ce measurements were prepared daily by diluting 100 mm of stock solutions of 2-(n-morpholino)ethanesulfonic acid (mes), l-histidine (l-his) and 18-crown-6 to the required concentrations. cetyltrimethylammonium bromide (ctab) was prepared as a 10 mm stock solution in 5 % acetonitrile. the separation electrolyte that was used for separation and quantitation of inorganic anions, cations and organic acids consisted of 20 mm mes, 20 mm l-his, 2 mm 18-crown-6 and 30 µm ctab. 2.3 capillary-conditioning procedure prior to its first use, the separation capillary was preconditioned by flushing it with 0.1 m naoh for 30 mins., then with di water for 30 mins. and finally with a solution of bges for 10 mins. between two successive injections, the capillary was flushed with the bge solution for 1 min. at the end of a working day, the capillaries were washed with di water for 15 mins., followed by the application of a vacuum for 5 mins. before being stored dry overnight. 2.4 sample-collection procedure the ebc was collected in the morning, the subjects did not eat or drink beforehand. the ebc was collected using the previously described ebc-sampler. the subject was asked to exhale deeply 3-5 times into the sampler, but depending on the lung capacity of each, the number of exhalations was modified to collect approximately 100 µl of their ebc. after the sampling of ebc was completed, the condensate from the walls of the syringe was forced to the tip of the syringe by the plunger and transferred to the sample vial for ce analysis. part of the ebc sample was also used in another experiment published elsewhere, in which the ph was measured using a microelectrode. hungarian journal of industry and chemistry ce analysis of ebc in gerd diagnosis 25 figure 2: separation of a model mixture consisting of 4 inorganic anions and 4 organic acids. bge: 20 mm mes/lhis, 2 mm 18-crown-6, 30 µm ctab. hv: positive +15 kv, c4d detection. ion concentrations in the parentheses in µm: acetate (200); chloride, nitrate, lactate, propionate, butyrate (25); nitrite, sulfate (10). 2.5 selection of patients and healthy individuals in this initial screening, a group of healthy individuals and a group of patients diagnosed with asthma and pulmonary fibrosis were selected. the healthy individuals had no history of gerd or heartburn and were free from other related symptoms. the healthy individuals selected were from approximately the same age group as the patients, i.e., the average age of healthy subjects was 48 and that of patients was 56. the patients suffered from asthma and pulmonary fibrosis and were from the department of pulmonary diseases and tuberculosis at the faculty hospital brno. 3. results and analysis 3.1 electrolyte selection to separate the ionic content of the ebc, the bges composed of mes and l-his was chosen as this electrolyte allows for the analysis of anions, organic acids, and cations with good degrees of sensitivity. mes and lhis fulfill the criteria for suitable coions and counterions in ce separation using contactless conductivity detection (c4d). the conductance of the respective bge components is low, thus analytes including small organic acids (acetate, lactate, butyrate) will be detected as positive peaks. the addition of 18-crown-6 to the separation electrolyte improves the resolution of k+ and nh+ 4 cations figure 3: separation of a model mixture of 5 inorganic cations. bge: 20 mm mes/l-his, 2 mm 18-crown-6, 30 µm ctab. hv: negative -15 kv, c4d detection. ion concentrations in the parentheses in µm: ammonium (1000); calcium (25); potassium, sodium and magnesium (10). and does not influence the selectivity of other measured cations to a great extent, nor does it influence the separation of anions and organic acids. ctab is added to the separation electrolyte to decrease the electroosmotic flow (eof). it should be noted here that although this separation electrolyte allows for the simultaneous separation of anions and cations using dual-opposite end injection [11], in this work anions and cations were determined separately by switching the high-voltage polarity. the separation of a model mixture consisting of 8 anions in less than 2.5 mins. is shown in fig. 2. the ion concentrations were selected to be similar to those found in ebc samples. the separation of cations using the same conditions but using reverse-polarity voltage is shown in fig. 3. the ammonium cation is usually present at a concentration 100 times greater than other cations in the ebc, its concentration was thus also increased to 1000 µm to reflect the expected concentration. note that even with this significant excess the separation of nh+ 4 from k+ is sufficient and the bge composition can be used for real sample analysis. 3.2 analysis of anions in ebc samples from each subject, the ebc sample was collected as described previously. about 50 µl of the sample was transferred into an eppendorf tube and hydrodynamically injected into the ce system. the ebc samples were analyzed first for anions and organic acids using positive hv polarity and then for cations using negative hv polarity, 46(1) pp. 23-27 (2018) 26 kubáň, ďurč, lačná, greguš, foret, et al. figure 4: separation of anions in ebc samples of healthy persons as well as patients with acid reflux or weakly acid reflux. bge: 20 mm mes/l-his, 2 mm 18-crown-6, 30 µm ctab. hv: positive +15 kv, c4d detection. with the hv electrode placed in the detection vial. the concentrations of all 13 ions in the samples were evaluated using calibration curves measured with standard solutions. the parameters such as the calibration curve, regression coefficient (r2) and concentration range are shown in table 1. in this initial screening the analysis of several samples from the healthy group and patients that were diagnosed as having the acid reflux or weakly acid reflux was attempted and the ions that would be significantly different in these groups identified. a series of electropherograms of anions and organic acids in a healthy individual, patient with acid reflux and patient with weakly acid reflux is shown in fig. 4. one can clearly see that the concentrations of several anions, most notably chloride, nitrate and organic acids, are significantly higher in the group of patients than in that of the healthy volunteers. some small inorganic anions such as nitrite and nitrate are often found in the ebc of patients with respiratory diseases as markers of nitrosative stress. on the other hand, the presence of an increased concentration of chloride and organic acids may be a significant step towards the diagnosis of gerd. 3.3 analysis of cations in ebc samples the analysis of cations in the same samples can be seen in fig. 5. although higher concentrations of the ammonium cation were found in patients compared to healthy individuals, the content was not significantly different from that of healthy individuals, and this applied for other cations (k+, na+, ca2+, mg2+) as well. figure 5: separation of cations in ebc samples of healthy persons as well as those with acid reflux and weakly acid reflux. bge: 20 mm mes/l-his, 2 mm 18-crown-6, 30 µm ctab. hv: negative -15 kv, c4d detection. 4. discussion a limited number of subjects were tested and the determination of whether a simple ebc sample could be used as a surrogate for more invasive, expensive and tedious diagnostic methods attempted. the analysis of anions showed some promising results with regard to the small inorganic anions (chloride and nitrate) collected and the concentration of organic acids that were elevated in the patients table 1: calibration equations of all separated anions, cations and organic acids. bge: 20 mm mes/l-his, 2 mm 18-crown-6, 30 µm ctab. hv: positive +15 kv or negative -15 kv, c4d detection. ion calibration equation r2 range (µm) cl− y = 0.0278x+ 0.0258 0.9957 0.6-25 no− 2 y = 0.0270x+ 0.0023 0.9994 0.6-25 no− 3 y = 0.0315x+ 0.0166 0.9987 0.6-25 so2− 4 y = 0.0656x+ 0.0143 0.9980 0.25-10 acetate y = 0.0156x+ 0.0200 0.9995 1-200 lactate y = 0.0207x+ 0.0097 0.9996 0.6-25 propionate y = 0.0189x+ 0.0024 0.9983 0.6-25 butyrate y = 0.0188x− 0.0001 0.9990 0.6-25 nh+ 4 y = 0.0211x− 0.1437 0.9993 25-1000 k+ y = 0.0347x+ 0.0013 0.9994 0.25-10 ca2+ y = 0.0528x+ 0.0059 0.9995 0.6-25 na+ y = 0.0356x+ 0.0079 0.9996 0.25-10 mg2+ y = 0.0618x− 0.0054 0.9995 0.25-10 hungarian journal of industry and chemistry ce analysis of ebc in gerd diagnosis 27 suffering from gerd symptoms, compared to healthy volunteers. unfortunately, with regard to the analysis of cations, the differences were not significant and cations were deemed unsuitable. 5. conclusion capillary electrophoretic analysis of ebc was used for the first time in an attempt to distinguish the groups of patients with gerd from healthy individuals. ce with c4d was used for the analysis of small inorganic anions, cations and organic acids present in the ebc samples. although it has been shown that selected samples had elevated concentrations of chloride, nitrate, butyrate and propionate, the number of subjects was too small to draw definite conclusions concerning the discriminatory power of these ions. it also seems that although there is a difference between groups of healthy individuals and sufferers of acid reflux/weakly acid reflux, the results with regard to acid reflux and weakly acid reflux are very similar and these two groups cannot be distinguished based on the current data. a larger scale clinical study, in which the ebc of patients and healthy individuals is scrutinized with regard to the ion content, ph and concentration of other biomarkers (for instance pepsin in saliva) to obtain statistically significant results for evaluation is currently being undertaken. nevertheless, the initial data is somewhat promising for ebc as a useful non-invasive alternative for other methods used in gerd diagnostics. symbols bge background electrolyte ce capillary electrophoresis c4d contactless conductivity detection ctab cetyltrimethylammonium bromide di deionized ebc exhaled breath condensate gerd gastroesophageal reflux disease l-his l-histidine id inner diameter mes 2-(n-morpholino)ethanesulfonic acid od outer diameter acknowledgement this research was supported by grant no. 17-31945a from the ministry of health of the czech republic. references [1] sidorenko, g.i.; zborovskii, e.i.; levina, d.i.: surface-active properties of the exhaled air condensates (a new method of studying lung function), ter. arkh., 1980 52, 65–68 [2] kubáň, p.; foret, f.: exhaled breath condensate: determination of non-volatile compounds and their potential for clinical diagnosis and monitoring. a review, anal. chim. acta, 2013 805, 1–18 doi: 10.1016/j.aca.2013.07.049 [3] hayes, s.a.; haefliger, s.; harris, b.; pavlakis, n.; clarke, s.j.; molloy, m.p.; howell, w.m.: exhaled breath condensate for lung cancer protein analysis: a review of methods and biomarkers, j. breath res., 2016 10(3), 034001 doi: 10.1088/1752-7155/10/3/034001 [4] greguš, m.; foret, f.; kindlová, d.; pokojová, e.; plutinskı, m.; doubková, m.; merta, z.; binková, i.; skřičková, j.; kubáň, p.: monitoring the ionic content of exhaled breath condensate in various respiratory diseases by capillary electrophoresis with contactless conductivity detection, j. breath res., 2015 9, 027107 doi: 10.1088/1752-7155/9/2/027107 [5] aldakheel, f.m.; thomas, p.s.; bourke, j.e.; matheson, m.c.; dharmage, s.c.; lowe, a.j.: relationships between adult asthma and oxidative stress markers and ph in exhaled breath condensate: a systematic review, allergy, 2016 71(6), 741–757 doi: 10.1111/all.12865 [6] el-serag, h.b.; sweet, s.; winchester, c.c.; dent, j.: update on the epidemiology of gastro-oesophageal reflux disease: a systematic review, gut., 2014 63(6), 871–880 doi: 10.1136/gutjnl-2012-304269 [7] tutuian, r.; castell, d.o.: review article: complete gastro-oesophageal reflux monitoringcombined ph and impedance, aliment. pharmacol. ther., 2006 2, 27–37 doi: 10.1111/j.1365-2036.2006.03039.x [8] johnson, l.f.; demeester, t.r.: twenty-four-hour ph monitoring of the distal esophagus. a quantitative measure of gastroesophageal reflux, am. j. gastroenterol., 1974 62, 325–332 [9] greguš, m.; foret, f.; kubáň, p.: single-breath analysis using a novel simple sampler and capillary electrophoresis with contactless conductometric detection, electrophoresis, 2015 36(4), 526–533 doi: 10.1002/elps.201400456 [10] greguš, m.; foret, f.; kubáň, p.: portable capillary electrophoresis instrument with contactless conductivity detection for on-site analysis of small volumes of biological fluids, j. chromatogr. a, 2016 14(27), 177–185 doi: 10.1016/j.chroma.2015.11.088 [11] kuban, p.; karlberg, b.; kuban, p.; kuban, v.: application of a contactless conductometric detector for the simultaneous determination of small anions and cations by capillary electrophoresis with dualopposite end injection, j. chromatogr. a, 2002 964, 227–241 doi: 10.1016/s0021-9673(02)00656-8 46(1) pp. 23-27 (2018) introduction experimental instrumentation chemicals capillary-conditioning procedure sample-collection procedure selection of patients and healthy individuals results and analysis electrolyte selection analysis of anions in ebc samples analysis of cations in ebc samples discussion conclusion microsoft word 2012_dr_bodor_endre_hjic.doc hungarian journal of industrial chemistry veszprém vol. 39(3) pp. 413-418 (2011) reduced aromatic jet fuels z. eller , j. hancsók university of pannonia, mol department of hydrocarbon and coal processing h-8200 veszprém, egyetem str 10., pf. 158, hungary e-mail: ellerz@almos.uni-pannon.hu at present time growing demand and more sever quality specifications are observed for the jet fuels. the reasons of these are the growing aviation and the more conscious environmental requirements. the expansion of aviation featured the last two decades, especially the 2% at the beginning of the reviewed period approaches 15%, if we calculate in the point of passenger kilometers the driven passages with vehicles, buses, railroads and jets. it can not be left from focus that aviation generates only 2% of the co2 emission of the world. this value can grow only for 3% to 2050, moreover it generates 12% of the co2 emission of the full transportation section, for comparison the public way transport generates 76% of the co2 emission. one of the greatest problems is the jets that fly at one time more than 1500 kilometers, because aviation produces 80% of the greenhouse gases. but there are no other alternatives for bridging these distances in the transport section. the quality of the jet fuels is improvable with reducing their sulphurand aromatic content. the hydrogenation of the aromatic content of the jet fuels to naphtenic hydrocarbons can produce products that are environment-friendly, they have high energy content, lower density, which contributes to satisfying the growing demands. our aim was to study the possibilities of producing low sulphur and aromatic content jet fuels in a catalytic way. on a transient metal catalyst we studied the possibilities of quality improving of russian crude oil based petroleum fraction depending on the change of the operating parameters (temperature, pressure, liquid hourly space velocity, volume ratio). with 1800 mg/kg sulphur content petroleum on the nimo/γ-al2o3 catalyst we carried out the experiments at 200–340°c, 20–50 bar pressure, 1.0–3.0 cm3/cm3h liquid hourly space velocity and 200-400 nm3/m3 hydrogen/hydrocarbon ratio. based on the quality parameters of the liquid products we found that we made from the russian based petroleum in the adequate technological conditions products which have lower sulphur content than 10 mg/kg and which have reduced aromatic content, so these are excellent jet fuels, and their stack gases damage the environment less. we blended bioparaffins to the products of the catalytic experiments. we reached products with lower aromatic content than 5%. keywords: jet fuel, hydrodesulphurization, bioparaffin, aromatic saturation introduction recent demands for jet fuels have shown significant increase in the last 20 years. (fig. 1) [1]. this was generated by the constant growing of aviation. in addition the quality requirements of jet fuels get more tightened. this was generated by the more severe environmental regulations and the increasing quality requirements. for the production of the jet fuels with good burning properties low aromatic hydrocarbons fractions are mainly suitable [1, 2, 3]. the expansion of aviation featured the last two decades, especially the 2% at the beginning of the reviewed period approaches 15, calculating passenger kilometres the driven passages vehicles, buses, railroads and jets. it can not be left from focus that aviation generates only 2% of the co2 emission of the world [5, 6]. this value can grow only for 3% to 2050, moreover it generates 12% of the co2 emission of the full transportation section, for comparison the public way transport generates 76% of the co2 emission [4, 7, 8]. figure 1: quantity demands of fuels (eu-27) [1] one of the greatest problems is the jets that fly at one time more than 1500 kilometres, because aviation produces 80% of the greenhouse gases. the reason of it the reserve fuel is let in the atmosphere at the end of the flying, so the formation of green house effect is 414 increased. but there are no alternatives for bridging these distances in the transport section [9, 10]. recently the properties of gasolines and diesel gas oils got continuously more severe, so the properties of jet fuels will become more severe, too. so now some people study the possibilities of producing low aromatic and low sulphur content jet fuels in a heterogeneous catalytic way [2, 7, 8]. in our present jet fuels are produced from different origin feedstocks. with the increasing demand more feedstocks must be in the focus. with using these feedstocks environmental friendly (low sulphurand aromatic content) and good performance fuels are productable (fig. 2) [1-6, 11, 12]. role of produce jet fuels from triglycerides on catalytic way will be more important in the near future. during the hydrogenation, the formed normaland isoparaffin hydrocarbons have suitable energetically and low temperature properties near the hydrogenation of triglycerides two other renewable feedstock processing technology can get role in the future; one produces different fuels with transformation and hydrogenation of lignocelluloids, while the other is the fischer-tropsch synthesis, which is applied in our present and processes synthesis gas from biomass. figure 2: classification of jet fuel production possibilities 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. i-2 i-3 13. 14. 15. 16. 17. 18. 19. 20. 21. hydrogen feedstock purge gas liquid product 22. 23. figure 3: the applied experimental apparatus 1: bottle-storage; 2, 4, 6: non-return valves; 3, 5: gas reductors; 7: gas flow controller; 8: feedstock vessel; 10: filter; 11: feedstock pump; 12: throttle valve, 13: flow meter; 14: reactor; 15, 16, 17: thermometers; 18: separator; 19: pneumatic valve; 20: gas-meter; 21: magnetic valve; 22: product receiver; 23: liquid product outlet 415 experimental our aim was to study the possibilities of producing low sulphur and aromatic content jet fuels in a catalytic way with hydrogenation of a petroleum fraction. we studied the effect of the process parameters to the product yield and quality. our further aim was to study kerosene boiling point range paraffin mixture, produced with catalytic hydrogenation of triglycerides, as a possible jet fuel blending component. experimental apparatus the heterogeneous catalytic hydrogenation experiments for aromatic saturation were carried out in a reactor system which contained all of the important apparatus and units that can be found in a reactor loop of an industrial desulphurizer and aromatic hydrogenation plant. the simplified process flow diagram of the apparatus is shown in fig. 3. the effective volume of the reactor was 100 cm3. used materials during the experiments we used a nimo/al2o3 catalyst, which is suitable for the desulphurization of gas oils. before the starting of the experiments we loaded 60 cm3 (56.79 g) catalyst into the middle sector of the reactor. the preparation of the new not activated catalyst we carried out by the activation method, that is made at the department after the loading. we given the properties of the feedstock for the catalytic experiments in table 1. this is produced from russian crude oil with distillation by mol plc. table 1: quality properties of the used petroleum fraction appearance clear, transparent and sediment free aromatic content, % monoaromatic diaromatic 17.9 3.8 mercaptan sulphur content, % 0.01 total sulphur content, mg/kg 1800 density on 15 °c, g/cm3 0.8083 crystallization point, °c -43 heating value, mj/kg 42.37 smoke point, mm 23.4 table 2 contains the main quality properties of the alternate origin blending component (paraffin mixture), that we used at the blending of jet fuel. table 2: main properties of the alternate based jet fuel blending components (c10-c12 paraffin mixture) density, g/cm3 0.7404 sulphur content, mg/kg <1 aromatic content, % <0.1 heating value, mj/kg 43.2 crystallization point, °c -52 process parameters of the catalytic experiments the circumstances of the catalytic experiment are given in table 3. table 3: applied process parameters during the catalytic experiments temperature, °c 200–380 pressure, bar 20–50 h2/hydrocarbon volume ratio, nm3/m3 400 lhsv, cm3/cm3 h 1.0–3.0 methods we determined the quality properties of the feedstock and the liquid products with standards, given in this table. table 4: standard test methods of the feedstock and liquid products property standard number appearance msz 10870:1995 density on 15°c, g/cm3 en 12185:1998 sulphur content en 14596:2007 en 20846:2004 aromatic content en 12916:2000 hydrocarbon-group analysis (ir) msz 09.60134 smoke point msz 970:1984 crystallization point en 2047:1986 distillation properties en 3405:2000 results and discussion the yield of the liquid products were greater than 96%, which is very preferable for the main product (fig. 4). the loss comes from the cracking reactions and from the h2s, that is formed during the desulphurization reactions. based on the measurements with hplc, total aromatic content of products decreased with the rising of the temperature (fig. 5). the quantity of the decreasing, so the effectiveness of the aromatic saturation was the 416 highest at 340 °c and 50 bar pressure. at the same time on temperature 360 °c the aromatic concentration of the products was higher than at 340 °c. the reason is the exothermic aromatic saturation reactions are inhibited by the thermodynamically inhibition. the saturation of monoaromatics comes to the foreground at 280 °c (fig. 6), until this temperature high desulphurization and hydrogenation of diaromatics are typical. above 280 °c the hydrogenation activity of studied nimo/al2o3 is increased very well. 96.0 96.5 97.0 97.5 98.0 98.5 99.0 99.5 100.0 280 300 320 340 360 380 400 temperature, °c l iq ui d pr od uc t yi el d, % lhsv=1.0 1/h; p=50 bar lhsv=2.0 1/h; p=50 bar lhsv=3.0 1/h; p=50 bar lhsv=1.0 1/h; p=20 bar lhsv=2.0 1/h; p=20 bar lhsv=3.0 1/h; p=20 bar figure 4: yield of the liquid products (h2/hc ratio: 400 nm3/m3) 4 6 8 10 12 14 16 18 20 22 24 240 260 280 300 320 340 360 380 temperature, °c t ot al a ro m at ic c on te nt , % . 0 15 30 45 60 75 a ro m at ic s at ur at io n ef fi ci en cy , %p=20 bar p=30 bar p=40 bar p=50 bar p=20 bar p=30 bar p=40 bar p=50 bar total aromatic content of feedstock: 21.7% diaromatic : 3.8 % figure 5: changing of the total aromatic content of products as a function of the temperature (lhsv: 1.0 1/h, h2/hc ratio: 400 nm3/m3) 4 6 8 10 12 14 16 18 240 260 280 300 320 340 360 380 temperature, °c m on oa ro m at ic c on te nt , % . p=20 bar p=30 bar p=40 bar p=50 bar figure 6: changing of the monoaromatic content of products as a function of the temperature (lhsv: 1.0 1/h, h2/hc ratio: 400 nm3/m3) we studied with infrared spectroscopy the hydrocarbongroup composition of the products, to determine what hydrocarbons are formed from the aromatic content of the feedstock. the values of this test method are not equal with the hplc aromatic content values, but they give correct information about the composition of the hydrogenated products. the share of nand isoparaffin hydrocarbon-groups changed a little during the experiments (table 5). oppositely the cycloparaffin content of the products are increased compared to the cycloparaffin content of the feedstock, the rate of this was equal with the decreasing of the aromatic content (fig. 7). based on this we determined the aromatic content of the feedstock is hydrogenated to cycloparaffin hydrocarbons, so ring opening reactions did not work or worked in low rate and resulted linear paraffins. this hydrogenation is very preferable, because cycloparaffins are not just environmental friendly, but the have better energetically properties and lower crystallization point than that aromatics with the same carbon number (table 6). table 5: nand i-paraffin contents of products based on ir test nand i-paraffin content, % lhsv=1.0-2.0 1/h; h2/ch ratio: 400 nm3/m3 t,°c p, bar 280 300 320 340 360 20 51.9 51.2 51.6 51.6 51.9 30 52.2 52.2 51.6 51.6 51.8 40 52.2 52.2 51.6 51.6 51.8 50 52.1 51.6 51.6 51.6 51.8 30 32 34 36 38 40 260 280 300 320 340 360 380 temperature, °c c yc lo pa ra ff in g ro up c on te nt , % 0 2 4 6 8 10 12 14 16 18 20 a ro m at ic g ro up c on te nt , % p=50 bar p=40 bar p=30 bar p=20 bar p=50 bar p=40 bar p=30 bar p=20 bar figure 7: changing of the cycloparaffin-group content of products as a function of the temperature (lhsv: 1.0 1/h, h2/hc ratio: 400 nm3/m3) table 6: heating values and crystallization points of aromatics and cycloparaffins with the same carbon number heating value, mj/kg crystallization point, °c n-penthyl-benzene 34.1 -43 n-penthyl-ciklohexane 36.5 -58 n-hexyl-benzene 34.1 -42 n-hexyl-ciklohexane 36.5 -52 n-hepthyl-benzene 34.2 -40 n-hepthyl-ciklohexane 36.6 -47 the legal sulphur content of jet fuels is maximum 3000 mg/kg. in the near future this value will be decreased. so it composed a part of our experimental work to study the effect of the different process parameters to the sulphur content of the products. at the mildest process parameters (t: 200°c, p: 20 bar, lhsv: 3.0 1/h) sulphur content of the product decreased well compared to the feedstock. with increasing of the temperature and the pressure 417 sulphur content of the products decreased further (fig. 8 and 9). at low lhsv (1.0 1/h) and on 20 bar we approached lower sulphur content than 10 mg/kg, which is the specification for gasolines and diesel gas oils in the european union. on 50 bar pressure and on 280 °c sulphur content of the product decreased under 50 mg/kg, while on 300 °c and 1.0 1/h lhsv it didn’t exceed 10 mg/kg, moreover increased lhsv to 3.0 1/h it didn’t exceed 200 mg/kg. 0 100 200 300 400 500 600 700 800 180 200 220 240 260 280 300 320 340 360 380 400 temperature, °c su lp hu r co nt en t, m g/ kg . p=20 bar p=30 bar p=40 bar p=50 bar figure 8: changing of the sulphur content as a function of the temperature (lhsv: 1.0 1/h, h2/ch ratio: 400 nm3/m3) 0 20 40 60 80 100 120 140 160 180 200 0.5 1.0 1.5 2.0 2.5 3.0 3.5 lhsv, 1/h su lp hu r co nt en t, m g/ kg . t=300°c t=320°c t=340°c t=360°c t=380°c t=280°c figure 9: changing of the sulphur content as a function of the lhsv (p: 50 bar, h2/ch ratio: 400 nm3/m3) we introduced some of the performance properties of the products – smoke point, crystallization point. aromatic hydrocarbon content of the middle distillate influences value of smoke point decisively. aromatics burns smoke flame by their lower hydrogen-carbon ratio, than the cycloparaffins and paraffins with higher hydrogen-carbon ratio. on fig. 10 hydrogenation of aromatic hydrocarbons smoke point value increased well. on 320 °c the some point values of the products exceeded the standardized minimum 25 mm. this is given by the cycloparaffins with better flaming properties, that are formed during the hydrogenation reactions. crystallization point of products decreased continuously compared to the crystallization point of feedstock (-50.5 °c–(-51.5 °c)) by the high hydrogenation of aromatics. decreasing of crystallization point is favourable, the current stand standard prescribes maximum -47 °c (fig. 11). 22 24 26 28 30 32 280 300 320 340 360 380 temperature, °c sm ok e po in t, m m p=50 bar p=40 bar p=30 bar p=20 bar figure 10: changing of the smoke point as a function of the temperature (h2/ch ratio: 400 nm3/m3, lhsv: 1.0 1/h) -52 -51 -50 -49 -48 260 280 300 320 340 360 380 400 temperature, °c c ry st al liz at io n po in t, ° c p=50 bar p=40 bar p=30 bar p=20 bar figure 11: changing of the smoke point as a function of the temperature (p= 50 bar, lhsv: 1.0 1/h) we blended bioparaffin mixture to the products of catalytic experiment to study their effect to the aromatic content and performance properties. we blended 10–30% bioparaffin to the product, that we reached at 340 °c, 50 bar and on 1.0 1/h, than we studied the important properties of these mixtures. as we decreased sulphur content of the products during the catalytic experiments, so sulphur content of product mixtures did not change significantly, moreover the studied performance properties did not change in important quantity, but at the same time aromatic content decreased under 5% (table 7). based on these results we determined, bioparaffin mixture from catalytic hydrogenation of triglycerides (c10-c12) do not worsen the properties of the crude oil based jet fuel. table 7: effect of blending bioparaffin to properties of the products from the catalytic experiments bioparaffin content, % property 0 10 20 30 density, g/cm3 0.7998 0.7938 0.7878 0.7819 sulphur content, mg/kg 9 8 7 6 heating value, mj/kg 43.0 43.1 43.1 43.1 crystallization point, °c -51 -51 -51 -51 aromatic content, % 5.9 5.3 4.7 4.1 418 results and discussion our aim was to produce low aromatic and sulphur content jet fuel, which has better energetically property, lower crystallization point, moreover its burning products damage the environment less by its changed hydrocarbon group composition during the hydrogenation. we studied the effect of the process parameters (t: 200–380 °c, p: 20–50 bar, lhsv: 1.0–3.0 h-1, h2/ch volume ratio: 400 nm3/m3) to the yield and quantity of the products, moreover we determined the preferable process parameters of the aromatic saturation and hydrodesulphurization. we determined, the yield of the products was greater than 96.0%, which is very preferable. increasing of the temperature and the pressure have significant effect to the aromatic saturation, liquid hourly space velocity has effect to the hydrodesulphurization. total aromatic content of the products decreased to 340 °c, than with further temperature increasing hydrogenation of aromatics declined by the thermodynamically inhibition. quantity of hydrodesulphurization did not change. decreasing of aromatic hydrogenation caused by the thermodynamically inhibition by the high temperature. aromatic hydrocarbons formed to cycloparaffins, they have better performance properties than aromatics. based on experimental results, the determined preferable process parameters for desulphurization and aromatic saturation are the following: temperature: 340 °c, pressure: 50 bar, liquid hourly space velocity: 1.0 h-1, h2/hydrocarbon ratio: 400 nm3/m3, with these parameters, aromatic content of product was 5.9%, and the sulphur content was lower than 10 mg/kg. so, we produced successfully product, that has better properties than the prescriptions of the actual jet standard. blended 10–30% bioparaffins to the products that produced at the preferable process parameters, we determined, the aromatic content decreased from the investigated properties, the other properties did not 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word a_34_hodai_r.doc hungarian journal of industrial chemistry veszprém vol. 39(1) pp. 67-71 (2011) densification processes of microalgae bred for biodiesel production z. hodai , g. horváth, l. hanák, r. bocsi university of pannonia, institutional department of chemical engineering science 10 egyetem street, h-8200 veszprém, hungary e-mail: hodaiz@almos.uni-pannon.hu an alga technology system has been developed, built and operated for the absorption of carbon dioxide and the production of biodiesel raw material. the main critical point in the technology is the separation of micro algae from the breeding medium (densification of the alga suspension). this is the most costand time-intensive part of the technology. the success of options in the literature, as well as further applicable phenomena and operations have also been studied. along with flocculation, clarification and autoflocculation phenomena, special attention has been paid to membrane separation operations. our aim is to devise a densification and separation process that has a low energy need and an advantageous operation time. the ultrafilter membrane splits the original mass flow (which consists of homogenized suspensions of different density) into two parts. one part passes the membrane, this is the permeate (deposited feed medium), the other is the concentrate, also called ‘retentate’ (in this case the concentrated alga suspension). this retentate can be easily and quickly cleaned of the accumulated metabolic products and remaining salt which can later cause a significant disturbance (at processing or in the following examinations). according to the assessment of the experimental results, the optimal solution seems to be membrane separation, on different grounds. it has a low energy need and an advantageous operation time and results in an appropriately clean suspension (i.e. void of metabolic products and salt). a plc-controlled device equipped with a zw-10 module was used for the densification experiments. the latter is the property of the department of chemical engineering at the university of pannonia. keywords: micro algae, biodiesel, ultrafiltering, membrane separation, densification introduction algae are considered to be one of the most efficient organisms on earth because of their outstandingly high reproductivity, and generally high lipid content. as for their reproduction, they can double their biomass in 24 hours [1, 2, 3, 4]. their lipid content is 20% on average (60–80% for certain species) [1, 5, 6, 7]. research for oil production from algae is primarily focused on micro algae. these are photosynthesizing organisms, the size of which does not exceed 0.5 mm. they can be, with a good chance, the solution to carbon dioxide and nitrogen oxide absorption, because they convert them with photosynthetic energy conversion [8]. the end product of the process contains a significant amount of solar energy stored as chemical energy. as a result, “high amounts” of biodiesel can be obtained [4, 9, 10, 11, 12]. besides the above mentioned advantages, algae can not only be used for fume gas cleaning, but they also use certain components of wastewaters as nutrient substrates, thus cleaning the wastewaters. the contamination provides an excess of nutrient for the algae which start to grow in an exponential rate. in contrast to the above mentioned advantages, their major disadvantage is the high cost need of production. harvesting of the algae (harvest, dewatering, drying), the extraction of lipids and their conversion are the most critical steps in the production of alga-based biofuels because of the high investment and operation costs. thus the biggest challenge to the technology is cost minimization, which can be done first at the separation step. harvesting can be done by microfiltration, centrifuging, flocculation, sonochemical processes or by other technologies currently under development [13, 14]. in addition to chemical flocculation, clarification and autoflocculation phenomena, special attention has been paid to membrane separation procedures. our aim is to devise a densification and separation process which has a low energy need and an advantageous operation time. experimental ultrafiltration although the operation has “filtration” in its name, there is significant difference between traditional filtration and ultrafiltration. in the former, the liquid medium pressed through the filter moves perpendicular to its surface and 68 at least one of its components is accumulated inside or on the surface of the filtering medium. as opposed to this, the ultrafiltering membrane splits the original mass flow (alga suspension) into two. one of the two parts passes the membrane, this is the permeate (the separated nutrient substrate), the other is the concentrate (in our case: the concentrated alga suspension). the momentary performance of the filter depends on – besides the applied pressure differences – the viscosity of the medium to be filtered, the size distribution of the solid grains, the thickness of the filter cake, its imporosity and rheology. in the case of the membrane module, no filter cake is formed. thus the properties of the filter cake do not have an effect on the actual performance of the filtering; however, the applied driving force and the flow of the medium parallel to the membrane do. the permeability of the membrane is significantly affected by the applied pressure difference, while osmotic pressure in general has only little effect. thus the permeate flow can be described with the following equation: ppj l pkjpgradkj lv δ⋅=⇒ δ −=⇒⋅⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −= μμ )( (1) where jv is the rate of filtration, k is the hydraulic permeability factor that is dependent on the material, l is the thickness of the filtrating layer, and µ is the viscosity. this representation is analogue to the d’arcy law. the gradient is the quotient of the pressure difference between the two sides of the membrane and its thickness. the parameters before this function can be summarized as the liquid permeability constant pl, which is the water rate of the membrane. the water rate gives the maximal filtering performance of the membrane measured with pure water. operational characterization of ultrafiltration when characterizing the operations, it is advisable to use units that supply the most information of the state of the process from the combination of the most easily measurable parameters. the concentration factor (cf) is a generally used descriptor which is defined as follows: r 0 volumeretained volumeinput v v cf == (2) the capacity (rec) is indicative of the amount of the purified solution. 0 p volumeinput permeateofvolume v v rec == (3) with the volume balance equation v0 = vr + vp, the two measures can be expressed as follows: rec cf − = 1 1 (4) the device used for ultrafiltration a plc controlled device, equipped with a zw-10 module was used for the densification and purification experiments (fig. 1). the device is the property of the department of chemical engineering of the university of pannonia. figure 1: the device used for the measurements as regards the permeate flow, the device carries out an outside-in operation. the measurements were done with a zw-10 immersion module supplied by the company zenon. according to its specifications, the membrane is capable of retaining particles as small is 1 µm [15, 16, 17]. the module is of hollow fiber type, its outer diameter is 4.5 mm, and it consists of strings of 0.4 µm pore diameter (fig. 2). figure 2: configuration of the zw-10 membrane module. a: permeate outtake, b: air injection the total surface area of the membrane is 0.9 m2, from which the membrane venting density is 289 m2/m3. according to the manufacturer’s specifications, the pressure difference between the two sides of the membrane (δpm) cannot be outside the ±0.5 interval for a prolonged period. if the value of |δpm| is constantly above 0.6 bar, an irreversible decrease in membrane permeability can be expected. this decrease is due to structural changes and pore collapse. 69 the module functions as part of a plc controlled device. the construction of the device is illustrated in fig. 3. figure 3: the construction of the ultrafiltrator device air is blown into the device immediately next to the membrane fibers which enhances the cleanliness of the surface while also ensuring a steady sludge content due to the mixing effect of the air bubbles. one of the key units in ultra filtration is the permeate pump. this pump is responsible for permeate eduction in uf (ultra filtering) mode, while in bp (back pulse, backwash) it is responsible for the backpumping of the permeate. the frequency switch in the control module ensures the two-way operation of the pump as well as the stepless regulation of the motor speed. a manometer (dp) is installed at the permeate eduction side which gives information about the overpressure on the permeate side of the membrane. the micro alga suspension is introduced to the technical vessel (tk-1). this is a rectangular prism with a volume of 30 dm3, equipped with a level indicator (li), a ph-meter probe (ph-1) and a thermometer (ti). the permeate (separated nutrient substrate) is introduced to the 10 dm3 tk-2 permeate vessel. the permeate need of the backwash is also supported from here. periodic eduction of the permeate is possible through the eduction pipe end, while continuous eduction is possible via the overflow valve. after overall cleaning, a zw-10 membrane module was installed in the device. the previous record of the module is known, experiments were done with it on living sludge wastewater. the required conservation procedures were carried out before storage. before it was put in practice, the regeneration procedures required by the distributor were carried out on the membrane. testing of the used module was done with tap water. this test is informative of the success of conservation and that the membrane is ready for measurement. densification experiments the measurement was done covering the whole operational range with the minimally necessary step interval. the main device parameters are given in table 1. table 1: device parameters ultrafiltration backpulse volume flow [l/h] 20 25 time [sec] 600 60 the suspension in the densifying vessel was pneumatically mixed with an injector fed by the air compressor. sample supply was carried out in the followings with the use of a 1 dm3 graduated cylinder in order to avoid fluctuation in the liquid level. in order to gain the most data possible from the given sample volume, the measurement was divided into several phases. the alga suspension was removed from the photobioreactors in portions of 40 dm3 for filtering. after densifying 40 dm3 to 20 dm3, cleansing with distilled water was used. washing was done until the complete removal of remaining salts, organic material and metabolic products in the suspension. the extent of cleansing was monitored by measuring the extract content and the electrical conductivity of the permeate. the following 40 dm3 of alga suspension was concentrated according to the method described earlier; after this 20 dm3 cleansed concentrate from the previous densification was given to it. this concentrate was then washed with distilled water again. the densification experiments were carried out repetitively until reaching the highest possible concentration factor with the device. cleansing (washing the concentrate with distilled water) was done until reaching the lowest electric conductivity possible as well as reaching an extract content lower than three decimals (fig. 4). the effect of washing the concentrate on the permeate flow 0 10 20 30 40 50 60 70 1 3 5 7 9 11 13 15 17 19 washing period el ec tri c co nd uc tiv ity po ss ib le [m s/ cm ] 0 0,2 0,4 0,6 0,8 1 1,2 ex tra ct c on te nt [% ] electric conductivity possible extract content figure 4: the effect of washing the concentrate on the permeate flow 70 results by using the zw-10 membrane module in 7 densification phases, 280 dm3 of alga suspension feed was concentrated to 20 dm3, the final concentration factor being cffinal = 14. the change in extract content of the concentrate is summarized in fig. 5. figure 5: change in extract content of the concentrate the decrease in extract content in the first phase is due to the washing. as it can be seen, approx. 50% of the alga suspension consist of residual salts and other organic materials. the initial alga suspension (40 dm3) was concentrated for a concentration of 13 g/l to 12.2 g/l (20 dm3). the final alga concentrate has a concentration of 30.4 g/l with respect to algae in a volume of 20 dm3. thus, the extract content was raised from 1.22% to 3.04% during the processes. 3,04 0 1,22 0,97 0 0,5 1 1,5 2 2,5 3 3,5 1 2 ultrafiltration beginning and end ex tra ct c on te nt [% ] concentrate permeate figure 6: the extract content of the concentrate and the permeate at the beginning and end of the experiment summary according to the evaluation of the experimental results, the membrane separation process seems to be the best solution by the following reasons. it has a low energy need, an advantageous operation time and results in a suspension that is appropriately clean (void of metabolites and salts) and is appropriately concentrated. acknowledgements the authors express their gratitude to chemical engineering institute cooperative research centre of the university of pannonia and the támop-4.2.1/b09/1/konv-2010-0003 application for financial support of this research study. references 1. k. zhang, e. kojima: effect of light intensity on colony size of microalga botryococcus braunii in bubble column photobioreactors, journal of bioscience and bioengineering 87, (1999) 2. m. briggs: widescale biodiesel production from algae, university of new hampshire, physics department (2004), 5 3. e. j. hwang, h. s. shin, s. r. chae: single cell protein production of euglena gracilis and carbon dioxide fixation in an innovative photo-bioreactor, bioresource technology (2006), 322–329 4. y. chisti: biodiesel from microalgae beats bioethanol, institute of technology and engineering, massey university, new zealand (2007), 126–131 5. e. w. becker, j. baddiley: microalgae: biotechnology and microbiology, cambridge univ. press, cambridge, inc., new york (1994), 178 6. m. c. posewitz, r. e. jinkerson, v. subramanian: improving biofuel production in phototrophic microorganisms with systems biology tools, biofuels 2, (2011), 125–144 7. d. shi, d. song, j. fu: exploitation of oil-bearing microalgae for biodiesel, chinese journal of biotechnology (2008), 341–348 8. m. olaizola, s. m. masutani, t. nakamura: recovery and sequestration of co2 from stationary combustion systems by photosynthesis of microalgae, final report, u.s. department of energy, office of fossil energy national energy technology laboratory (2005), 21–197 9. j. benemann, j. sheehan, p. roessler, t. dunahay: a look back at the u.s. department of energy’s aquatic species program: biodiesel from algae, nrel report nrel/tp-580-24190 (1998), 3 10. j. burlew: algae culture: from laboratory to pilot plant, pilot plant studies in the production of chlorella, carnegie institute, washington dc (1953), 235–272 11. i. h. jung, s. h. choe: growth inhibition of freshwater algae by ester compounds released from rotted plants, journal of industrial and engineering chemistry (2002), 297–304 12. g. horváth, l. hanák, r. bocsi: microalgae production in service of fuel production, hungarian journal of industrial chemistry, 38(1), (2010), 9–13 71 13. a. sukenik, g. a. shelef, m. green: microalgae harvesting and processing: a literature review, report, solar energy research institute, golden colorado, seri/str-231-2396 (1984), 6–57 14. b. jeurissen, e. poelman, n. de pauw: potential of electrolytic flocculation for recovery of micro-algae, resources conservation and recycling (1997), 19 15. p. le-clech, t. a.g. fane, v. chen: fouling in membrane bioreactors used in wastewater treatment, journal of membrane science, 284(1-2), (2006), 17–53 16. a. g. fane, h. c. chua, j. zhang, j. zhou: factors affecting the membrane performance in submerged membrane bioreactors, journal of membrane science, 284(1-2), 1 (2006), 54–66 17. b. tae-hyun, t. tae-moon: interpretation of fouling characteristics of ultrafiltration membranes during the filtration of membrane bioreactor mixed liquor, journal of membrane science, 264(1-2), (2005), 151–160 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word a_46_solymosi_r.doc hungarian journal of industrial chemistry veszprém vol. 39(1) pp. 85-90 (2011) investigation of hydrogenation of conventional and high oleic acid content rapeseed or sunflower oils p. solymosi, t. kasza, j. hancsók university of pannonia, mol institutional department of hydrocarbon and coal processing 8200 veszprém egyetem út 10., hungary, e-mail: hancsokj@almos.uni-pannon.hu the european union created the 2003/30/ec and later the 2009/28/ec directives to encourage the blending of bio components in the motor fuels. nowadays the second generation or new generation bio fuels researching, improving and market introduction are facilitated. the main reason of this is the demand for better quality and wide raw material basis. all this above-mentioned things make it reasonable to investigate lower cost feedstock or researching of more efficiently processable or raw material basis. for example these special modified hybrids can be rapeseed oil with high euric acid content (bassica napus) , rapeseed oil with high oleic acid (pioneer hi-berd 45a37), or sunflower oil with high oleic acid (saaten union capella). these raw materials can be converted to motor fuels by heterogenic catalytic hydrogenation, thus we can produce outstanding gasoil blending components. further advantages are that the motor fuel purpose crop products can not meet the human health aspects hence genetically modified breeds can be applicable, therefore these raw materials do not endanger the security of food supplement. hence the aim of our research activities was to produce bio gas oil from properly prepared oil with various fatty acid composition vegetable oil. we made the experiment on commercial available aluminium-oxide supported co/mo. the applied process parameters were based on our earlier research: temperature: 300–380 °c, pressure: 20–80 bar, liquid hourly space velocity: 0.5–3.0 h-1, h2/triglycerides ratio: 600 nm3/m3. during the conversion of high oleic acid vegetable oils while applying the favourable process parameter combination the yield was higher and the hydrogen consumption was unequivocally lower. keywords: bio-gasoil, hydrodeoxigenation, sunflower oil, rapeseed oil introduction in the european union the main reason of the consumption of biofuels within the alternative fuels is the insufficient quantities and availability of energy carriers (primarily the crude oil and natural gas) and the effort in the passenger and freight transport to reduce the dependence on fossil fuels which are produced from import crude oil. to achieve these goals, the european union created the 2003/30/ec and 2009/28/ec directives. the main purpose of the directives is to promote the use of biofuels in the engine fuels specifying the recommended or required quantity of biofuels in engine fuels. nowadays the research, development and market introduction of second or next generation biofuels is going on. this is mainly due to the disadvantages of conventional biofuels (biodiesel, bioethanol), the demand for better quality of motor fuels (blending components), the wider base of raw materials (climate, topography, soil conditions) and the support by the european union for the second generation biofuel research and development [com(2006) 34]. from among the biocomponents used as blending components in diesel fuels in short and medium term the bio gas oils will be highlighted. the bio gas oil is a mixture of normal and isoparaffins having a boiling point range similar to diesel fraction which can be produced by oneor more-step catalytic hydrotreating of different natural triglycerides (fatty acid esters, fatty acids, etc.) [2, 3]. regarding the performance properties they contain the best utilization technical components of the crude oil derived gas oils which have improved and ‘‘cleaner” ignition, and it results in lower emissions. to reach all these goals we must define all of these cultivated species which can accomplish the industrials usage specific demands as a consequence of their specific composition. the cost of bio motor fuel production is defined by the applied oilseeds yield and the fatty acid composition from the biological side. in southern regions the sunflower, in the northern regions the rapeseed means the potential source of bio gas oil production. in the hungarian region the sunflower was grown in the biggest volume in 2010, of this snow area was 501 thousand hectares and the average yield was 2.2 t/ha. the rapeseed was grown on 259 hectares and the average yield was 2 t/ha. we investigated the effect of the operation parameters on the product quality, including the type of hydrogenation reactions during processing various fatty acid composition feedstocks. during the conversion of triglyceride molecule to biogasoil the following reactions take place [8-12, 16]: 86 full saturation of double bonds (hydrogenation), heteroatom removal (hydrogenolisis) oxygen removal δ hydrodeoxigenation (hdo reaction, reduction), δ decarboxylation, δ decarbonylation, removing of other heteroatoms (sulphur, nitrogen, phosphorus, metals), different side reactions: hydrocracking of fatty acid chain of triglyceride molecule, water–gas-shift reaction, methanization, cyclization, aromatization, etc isomerization of n-paraffins which are formed during the oxigen removing during the reduction reaction (hdo) normal paraffins form of which carbon number is equal to the triglycerides builder fatty acids. in the case of decarboxylation and decarbonylation reactions (hdc) normal alkanes are produced of which carbon number is lower by one than the carbon number of fatty acids in the original vegetable. (fig. 1) figure 1: possible pathways of vegetable oil oxygen removal (fatty acid component: oleic acid) as fig. 1 shows the yield of the organic products depends on the carbon number of the hydrocarbon chains, the feedstock and the reaction pathways [4, 5]. the reaction pathways were investigated in full details.[e.g. 14, 15] experimental on the basis of the above-mentioned reasons the aim of our experimental work was the investigation of heterogenic catalytic hydrothreating oxygen removal of sunflower and rapeseed oil pressed from expediently grown high oleic acid sunflower and rapeseed of hungarian origin on a commercial available como/al2o3 (mo: 13,5 %, co: 2,9 %, fbet: 193 m2/g) catalyst. in this context we studied the processing options (with this end the conversion and hydrogen consumption) of the conversion of triglycerides, the yield of the organic products and the yield of the target fraction. furthermore the effect of the operation parameters (temperature, pressure, lhsv, h2/ch ratio), the effect of the degree and the type of the deoxygenation reaction were also investigated. feedstocks the feedstock of the hydrotreating experiments was conventional and high oleic acid sunflower and rapeseed oil pressed form hungarian sunflower and rape seed and it was properly pre-treated (filtered). its important properties are summarized in table 1. the catalyst was a commercial available supported bimetallic como/al2o3 catalyst. the catalyst was pre-treated in hydrogen stream. table 1: the main properties and fatty acid composition of the applied sunflower oils properies conventional sunflower high oleic acid sunflower conventional rapeseed high oleic acid rapeseed kinamatic viscosity, (40 °c) mm2/s 37.04 39.6 34.4 39.9 density (15.6 °c), g/cm3 0.9153 0.9132 0.915 0.917 cloud point, °c -1 2 -2 3 iodine number, g i2/100g 134 84 114 90 cetane number 38 37 37 36 fatty acid composition (cx:y*), % c16:0 6.0 2.1 4.5 3.2 c16:1 0 0 0 0.3 c18:0 4.0 1.6 1.9 1.9 c18:1 20.0 91.6 61.5 74.4 c18:2 68.0 1.2 20.8 9.3 c18:3 0 0.1 9.7 7.9 c20:0 0 0.1 0.3 0.7 c20:1 0 0 1.3 1.1 c22:0 0 0 0 0.1 c22:1 0 0 0 1.4 other 2.0 3.2 2.5 0.8 *x: means the fatty acid carbon number; y: means the number of olefinic double bonds 87 experimental apparatus and products separation the experimental tests were carried out in one of the measure sections of a high pressure reactor system containing two flow reactors (isothermal catalyst volume: 100 cm3). the reactor system contained all the equipment and devices applied in the reactor system of a hydrotreating plant [13]. figure 2: simplified schema of the reactor system the product mixtures obtained from the hydrotreating of sunflower oil were separated to gas phase, water and organic phase. the gas phase obtained from the separator of the reactor system contained carbon-monoxide, carbon-dioxide, propane, the hydrogen-sulphide and ammonia which evolved during the heteroatom removal of sunflower oil, furthermore the lighter hydrocarbons (c1-c4 as valuable by-products) which evolved during the hydrocracking reactions. the liquid product mixtures obtained from the separator of the reactor system contained water, hydrocarbons and oxygen containing compounds. after the separation of the water we obtained the light (c5-c9) hydrocarbons (gasoline boiling range) from the organic fraction by distillation up to 180 °c. the residue of the atmospheric distillation was separated by vacuum distillation into the target product (gas oil boiling range fraction, mainly c11-c19 hydrocarbons) and the residue. the residue contained the unconverted triglycerides, the evolved and unconverted diglycerides and monoglycerides, fatty acids, esters, which evolved as intermediate products or were originally in the feedstock. figure 3: the separation of product fraction process parametrs the range of the applied process parameters based on our pre-experimental results were the following: temperature 300–380 °c, total pressure 20–80 bar, liquid hourly space velocity (lhsv): 1.0 h-1 and h2/rapeseed oil volume ratio: 600 nm3/m3. analytical methods the properties of the sunflower oil feedstock were measured according to standard methods (table 2). table 3: standard methods used for characterization of feedstocks properies standard methods kinamatic viscosity en iso 3104:1996 density en iso 3675:2000 acid number en 14104:2004 iodine number en 14111:2004 cfpp en 116:1999 fatty acid comosition en iso 5509:2000 en 14103:2004 the composition of the total organic products obtained from the catalytic conversion of the triglycerides was determined by high temperature gas chromatograph (shimadzu 2010 gc [column: phonomenex zebron inferno db 1ht]). the composition of the gas products was determined by gas chromatograph (trace gc thermo finnigan) with thermal conductivity detector (tcd) [column: supelco carboxen 1006 plot (30 m x 0.32 mm)] results and discussions the aim of our experimental work was the investigation and comparison of conventional and high oleic acid sunflower and rapeseed oil hydrotreating option for motor fuels. in this context we investigated the yield of gasoil boiling point range products and the effects of the operation parameters on the yield and quality of the target products by various fatty acid composition vegetable oil feedstocks. on the basis of our experimental results we obtained that during the processing of sunflower and rapeseed oil the conversion was higher in the case of high oleic acid hybrid feedstocks. its possible cause is that the high oleic acid content vegetable oil has a lower olefinic double bond content (it is shown by the iodine number of the used vegetable oil, the difference of 50 units between the conventional and high oleic acid vegetable oil). furthermore, while using both the conventional and high oleic acid content vegetable oil the conversion increased with the increase of the pressure and temperature (with the increasing severity). it is shown in fig. 4/a, b. 88 conventional and high oleic acid sunflower oil 0 10 20 30 40 50 60 70 80 90 100 20 40 60 80 pressure, bar c on ve rs io n, % conventional sunflower 340°c conventional sunflower 360°c conventional sunflower 380°c high oleic acid sunflower 340°c high oleic acid sunflower 360°c high oleic acid sunflower 380°c figure 4/a. the conversion of conventional and high oleic acid content sunflower oil as the function of the pressure (lhsv: 1.0 h-1; h2/vegetable oil ratio: 600 nm3/m3) conventional and high oleic acid rapeseed oil 0 10 20 30 40 50 60 70 80 90 100 20 40 60 80 pressure, bar c on ve rs io n, % conventional rapeseed 340°c conventional rapeseed 360°c conventional rapeseed 380°c high oleic acid rapeseed 340°c high oleic acid rapeseed 360°c high oleic acid rapeseed 380°c figure 4/b. the bio gasoil yield of conventional and high oleic acid content rapeseed oil as the function of the temperature (lhsv: 1.0 h-1; h2/vegetable oil ratio: 600 nm3/m3) on the basis of our experimental results we obtained that the yield of the target fraction increased with increasing the temperature. at lower temperatures the yield of the main fraction increased significantly with increasing the pressure, but at a higher temperature the yield of the main fraction drew a maximum curve (fig. 5). it can be explained by that that at a higher temperature the hdc reactions took place in a higher degree (due to the formation of co2 the generated products were shorter by one ch2group) and the crack reactions took place in a higher degree and it decreased the yield of the target fraction. conventional and high oleic acid sunflower oil 0 10 20 30 40 50 60 70 80 90 100 20 40 60 80 pressure, bar y ie ld o s b io g as o il, % conventional sunflower 340°c conventional sunflower 360°c conventional sunflower 380°c high oleic acid sunflower 340°c high oleic acid sunflower 360°c high oleic acid sunflower 380°c figure 5/a. the bio gasoil yield of conventional and high oleic acid content sunflower oil as the function of the pressure (lhsv: 1.0 h-1; h2/vegetable oil ratio: 600 nm3/m3) conventional and high oleic acid rapeseed oil 0 10 20 30 40 50 60 70 80 90 100 20 40 60 80 pressure, bar y ie ld o f b io g as o il, % conventional rapeseed 340°c conventional rapeseed 360°c conventional rapeseed 380°c high oleic acid rapeseed 340°c high oleic acid rapeseed 360°c high oleic acid rapeseed 380°c figure 5/b. the bio gasoil yield of conventional and high oleic acid content rapeseed oil as the function of the temperature (lhsv: 1.0 h-1; h2/vegetable oil ratio: 600 nm3/m3) the fatty acids as one acid value even carbon number carboxylic acids have more than 200 known variables. the synthesis of fatty acids starts from acetyl-coa and in consecutive steps it gets longer with 2 carbon number in every step. this is main reason why the various fatty acids only have an even carbon number chain [17]. thus uneven carbon number paraffins in the product fraction only came from hdc (decarboxilation, decarbinilation) and crack reactions. in the case of the mainly c18 carbon number fatty acid containing vegetable oils the c17/c18 paraffin ratio in the main fraction is the outstanding marker to follow the hdo/hdc reaction ratio. we concluded that the c18/c17 ratio in the main fraction decreased with the increasing temperature and it increased with the increasing pressure. consequently at higher pressure the hdc reactions resulting in mole number increase took place in a lower degree, while at a higher temperature the oxygen removal occurred mainly by hdc reactions (fig. 1) on the basis of our experimental 89 results we obtained that in case of hydrogenation of high oleic acid sunflower and rapeseed oil the oxygen removal mainly took place in the hdc reactions resulting lower hydrogen consumption. conventional and high oleic acid sunflower oil 0 5 10 15 20 25 30 20 40 60 80 pressure, bar c 18 /c 17 r at io , % conventional sunflower 340°c conventional sunflower 360°c conventional sunflower 380°c high oleic acid sunflower 340°c high oleic acid sunflower 360°c high oleic acid sunflower 380°c figure 6/a. the c18/c17 ratio of conventional and high oleic acid content sunflower oil as the function of the pressure (lhsv: 1.0 h-1; h2/vegetable oil ratio: 600 nm3/m3) conventional and high oleic acid rapeseed oil 0 5 10 15 20 25 30 20 40 60 80 pressure, bar c 18 /c 17 r at io , % conventional rapeseed 340°c conventional rapeseed 360°c conventional rapeseed 380°c high oleic acid rapeseed 340°c high oleic acid rapeseed 360°c high oleic acid rapeseed 380°c figure 6/b. the c18/c17 ratio of conventional and high oleic acid content rapeseed oil as the function of the pressure (lhsv: 1.0 h-1; h2/vegetable oil ratio: 600 nm3/m3) furthermore our experiments covered the effect of the fatty acid composition on the hydrogen consumption. on the basis of the gas phase analysis we concluded that during the hydrogenation of high oleic acid vegetable oils the hydrogen consumption was significantly lower than during the processing of conventional vegetable oils. it can be explained by the high oleic acid hybrids’ lower olefinic double bound content. on the basis of experimental results we obtained that at a higher temperature and pressure the oxygen removal took place by hdo reactions resulting higher hydrogen consumption. conventional and high oleic acid sunflower oil 13 14 15 16 17 18 19 20 40 60 80 pressure, bar h yd ro ge n c on su pt io n, m ol t ry gi ce ri d in ta ke /m ol h yd ro ge n conventional sunflower 340°c conventional sunflower 360°c conventional sunflower 380°c high oleic acid sunflower 340°c high oleic acid sunflower 360°c high oleic acid sunflower 380°c figure 7/a. the hydrogen consumption of conventional and high oleic acid content sunflower oil as the function of the pressure (lhsv: 1.0 h-1; h2/vegetable oil ratio: 600 nm3/m3) conventional and high oleic acid rapeseed oil 13 14 15 16 17 18 19 20 40 60 80 pressure, bar h yd ro ge n c on su pt io n, m ol t ry gi ce ri d in ta ke /m ol h yd ro ge n conventional rapeseed 340°c conventional rapeseed 360°c conventional rapeseed 380°c high oleic acid rapeseed 340°c high oleic acid rapeseed 360°c high oleic acid rapeseed 380°c figure 7/b. the hydrogen consumption of conventional and high oleic acid content rapeseed oil as the function of the pressure (lhsv: 1.0 h-1; h2/vegetable oil ratio: 600 nm3/m3) summary we investigated the motor fuel purpose hydrogenation of conventional and high oleic acid content sunflower and rapeseed oil on a como/al2o3 catalyst while applying various operation parameters. we concluded that the triglyceride conversion was close to 100 %, the bio gas oil yield was near 80 % in case of both conventional and high oleic acid content sunflower and rapeseed while applying a como/al2o3 catalyst in the favourable operation parameter range, 380 °c, 40–60 bar, 600 nm3/m3 h2/vegetableoil ratio, lhsv: 1.0 h-1. during processing high oleic acid sunflower and rapeseed oil the hydrogen consumption was 5–12 relative percent lower than in case of the conventional sunflower or rapeseed oil. 90 acknowledgement this work was supported by the european union and co-financed by the european social fund in the frame of the tamop-4.2.1/b-09/1/konv-2010-0003 and tamop-4.2.2/b-10/1-2010-0025 projects. references 1. b. kavalov: report eur 21012 en, (2004) 2. j hancsók, m. krár, sz. magyar, l. boda, a. holló, d. kalló: investigation of the production of high quality biogasoil from prehydrogenated vegetable oils over pt/sapo-11/al2o3, studies in surface science and catalysis 170(2), (2007), 1605–1610 3. j hancsók, m. krár, sz. magyar, l. boda, a. holló, d. kalló: investigation of the production of high cetane number bio gas oil from prehydrogenated vegetable oils over pt/hzsm-22/al2o3, microporous and mesoporous materials 101(1-2), (2007), 148–152 4. s.lestari, i. simakova, a. tokarev, p. maukiarvela, k. eranen, d.y murzin: synthesis of biodiesel via deoxygenation of stearic acid over supported pd/c catalyst, catalysis letters, 122(3-4), (2008), 247–251 5. p. mäki-arvela, m. snåre, k. eränen, j. myllyoja, d. yu. murzin: continuous decarboxylation of lauric acid over pd/c catalyst, fuel, 87(17-18), (2008), 3543–3549 6. j. gusmao, d. brodzki, g. djéga-mariadassou, r. frety: utilization of vegetable oils as an alternative source for diesel-type fuel: hydrocracking on reduced ni/sio2 and sulphided ni-mo/γ-al2o3, catalysis today, 5(4), (1989), 533–544 7. m. krár, a. thernesz, cs. tóth, t. kasza, j. hancsók: investigation of catalytic conversion of vegetable oil/gas oil mixtures silica and silicates in modern catalysis. transworld research network, kerala, india (2010), 435–455 8. b. donnis, r. g. egeberg, p. blom, k. g. knudsen: hydroprocessing of bio-oils and oxygenates to hydrocarbons. understanding the reaction routes, topics in catalysis 52(3), (2009), 229–240 9. y. liu, r. sotelo-boyás, k. murata, t. minowa, k. sakanishi: hydrotreatment of jatropha oil to produce green diesel over trifunctional ni-mo/sio2-al2o3 catalyst, chemistry letters 38(6), (2009), 552–558 10. k. w. craig, w. d. sorevan: us 4,992,605. 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word hjic 2015 43(2) 55-101.docx hungarian journal of industry and chemistry vol. 43(2) pp. 97–101 (2015) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2015-0016 comparative study of advanced oxidation processes to treat petroleum wastewater dheeaa al deen atallah aljubourya,1* puganeshwary palaniandy,1 hamidi bin abdul aziz,1 and shaik feroz2 1 school of civil engineering, universiti sains malaysia, nibong tebal, seberang perai selatan, pulau pinang, 14300, malaysia 2 caledonian center for creativity & innovation (ccci), caledonian college of engineering, p.o.box 2322, cpo seeb 111, muscat, oman this study was carried out to compare the performance of different oxidation processes, such as solar photo-fenton reaction, solar photocatalysis by tio2, and the combination of the two for the treatment of petroleum wastewater from sohar oil refinery by a central composite design with response surface methodology. the degradation efficiency was evaluated in terms of chemical oxygen demand (cod) and total organic carbon (toc) reductions. solar photocatalysis by the tio2/fenton method improved the performance of the photocatalyst at neutral ph for petroleum wastewater without the need to adjust the ph during this treatment. under acidic conditions, the solar photo-fenton process is more efficient than solar tio2 photocatalysis while it is less efficient under alkaline conditions. the tio2 dosage and ph are the two main factors that improved the toc and cod reductions in the solar photocatalysis using combined tio2/fenton and the solar tio2 photocatalysis processes while the ph and h2o2 concentration are the two key factors that affect the solar photo-fenton process. keywords: solar photo-fenton process, solar photocatalysis by tio2, petroleum wastewater, chemical oxygen demand, total organic carbon 1. introduction a major problem facing industrialised nations is contamination of the environment by hazardous chemicals. a wide range of pollutants have been detected in petroleum wastewater at sohar oil refinery (sor). therefore, the elimination of these chemicals from petroleum wastewater is presently one of the most important aspects of pollution control in oman. advanced oxidation processes (aops) have the capability of rapid degradation of recalcitrant pollutants in aquatic environments. remediation of hazardous substances is linked to the hydroxyl radical since it has the potential to degrade organic pollutants [1]. the advantages of aops are that these processes can occur at very low concentrations and do not form environmentally hazardous byproducts [2]. during the solar photocatalysis by tio2, upon exposure to sunlight an electron hole is created in the valence band of tio2 and concomitantly an electron is injected into the conduction band in response to light absorption. this electron hole causes the oxidation of hydroxyl anions and produces the hydroxyl radicals at the tio2 surface. during the photo-fenton process the hydroxyl radicals are formed from the reaction of fe2+ with h2o2 under *correspondence: msc.dheeaa@yahoo.com sunlight irradiation. in the treatment of nonbiodegradable and toxic compounds, the photocatalytic processes have shown promising results [3]. previous studies have reported the enhanced oxidation of contaminants by tio2 photocatalysis in the presence of fenton reactivity. kim et al. [4] reported that the combination of tio2 photocatalysis and the fenton-like reaction synergistically increased the degradation of organic compounds at around neutral ph (6.5–7.5) by the increased production of reactive oxidants and their improved reactivity. however, it has not been clearly addressed whether the integration of the uv/tio2 and fe2+/h2o2 systems exhibits synergistic results with respect to the degradation of contaminants. little data are available on the role of fe2+ ions in the uv/fe2+/tio2 system at neutral ph, where the fe2+/h2o2 or uv/fe2+/h2o2 system alone is not effective for oxidant production and pollutant oxidation due to the low aqueous iron solubility and h2o2 decomposition via a non-radical mechanism without hydroxyl radical generation [1,4,5]. zarei et al. [6] showed that the removal efficiency of phenol was 69% after 150 min using photoelectro-fenton (pef)/mn2+/tio2 nanoparticles for the removal of phenol from aqueous solutions. nogueira [7] showed that the role of fe2+ ions and h2o2 are much more important than that of tio2 in the photodegradation of both 4-chloro-phenol (4cp) and dichloro-acetic acid (dca) under solar irradiation [7]. aljubourya, palaniandy, aziz, and feroz hungarian journal of industry and chemistry 98 the aims of the given study are as follows: (i) comparison of the homogenous (solar photo-fenton) and heterogeneous photocatalytic systems (solar photocatalysis by tio2 and solar photocatalysis using combined tio2/fenton processes) by central composite design (ccd) with response surface methodology (rsm) on the basis of their performances with regard to the chemical oxygen demand (cod) and total organic carbon (toc) in petroleum wastewater and (ii) assessment of treatment efficiencies and the main factors with regard to these methods by ccd and rsm. to our knowledge there are no reports in the literature of a similar comparison by a central composite design (ccd) with response surface methodology (rsm) applied to the homogeneous and heterogeneous photocatalytic systems for treatment of petroleum wastewater as shown in table 1. 2. materials and methods 2.1. wastewater characterisation the physicochemical characteristics of the petroleum wastewater from sor are summarised in table 2. samples of the petroleum wastewater were collected on different days. samples were transferred to the laboratory and stored in a refrigerator at 4 ºc until use. samples were characterised before the analysis for their chemical and physical properties. the petroleum wastewater was characterised by the quantification of ph and chemical oxygen demand (cod) according to the standard methods for the examination of wastewater methodology [12]. 2.2. materials the catalyst used was tio2 aeroxide p-25 manufactured by evonik industries co., germany. hydrogen peroxide (h2o2) (35% dm3 dm-3) and iron sulphate hydrate (feso4⋅xh2o) were supplied by emprove exp. (usa). sulphuric acid and sodium hydroxide were used to set the desired ph values. 2.3. analytical procedures a shimadzu toc analyser (lcsh/csn) was used to measure the total organic content (toc). chemical oxygen demand (cod) was measured by a cod photometer (manufactured by chemetrics). the ph levels were monitored by using a digital ph meter. toc and cod were determined before and after treatment. before each analysis, samples were filtered by using a 0.22 µm millipore durapore membrane (40 ashless, diameter 150 mm) filter paper. 2.4. experimental procedure the solar photocatalytic equipment used is shown schematically in fig.1 consisting of a stirred glass recirculation tank (1.5 dm3). the tubular solar reactor contained four tubes 50 cm in length × 2 cm in inner diameter × 0.1 cm in thickness. the solution was recirculated through the reactor at a flow rate of 1.5 dm3 min-1 using a peristaltic pump. natural sunlight was used as a light source. the added materials and their concentrations such as tio2, h2o2, and fe2+ were varied according to a central composite design (ccd) with response surface methodology (rsm) to determine the cod and toc removal efficiencies under the optimum operational conditions. table 1. overview of research done in the area of fenton/tio2 processes in recent years. no. wastewater method material removed ref. 1 aqueous imidacloprid photocatalysis by tio2 photo-fenton imidacloprid [1] 2 milli-q water tio2/fenton-like/solar 2,4-dinitrophenyl hydrazine (dnph) [4] 3 aqueous solutions tio2/photoelectro-fenton/mn2+/uv phenol [6] 4 aqueous media tio2/fenton-like/solar 4-chloro-phenol (4cp) and dichloroacetic acid (dca) [7] 5 oil-water emulsions tio2/h2o2/fe2+/uv tio2/h2o2/fe2+/uv/air zno/h2o2/fe2+/uv organics measured by reduction in cod value [9] 6 dye polluted water tio2/h2o2/fe2+/uv tio2/h2o2/fe2+/solar azo dye basic blue 4 [11] 7 petroleum wastewater tio2/h2o2/fe2+/solar solar photocatalysis by tio2 solar photo-fenton organics measured by reduction in cod and toc values this study table 2. characteristics of petroleum wastewater from sohar oil refinery (sor). parameters units ranges of concentration in petroleum wastewater average concentration standard discharge limit ph 6–8 7 6–9 conductivity µs cm-1 2600–3950 3275 2000–2700 tds ppm(mg dm-3) 1200–1500 1350 1500–2000 toc ppm (mg dm-3) 220–265 243 50–75 cod ppm(mg dm-3) 550–1600 1075 150–200 comparative study of advanced oxidation processes 43(2) pp. 97–101 (2015) doi: 10.1515/hjic-2015-0016 99 3. results and analysis 3.1. effect of ph there are two types of advanced oxidation processes (aops) depending on the reaction medium: a homogeneous process such as the solar photo-fenton process, a heterogeneous process such as solar tio2 photocatalysis, and their combined processes. according to previous results [13], the solar photofenton process is more efficient for petroleum wastewater treatment than solar tio2 photocatalysis under acidic conditions. by comparing solar photocatalysis using combined tio2/fenton processes with the solar photo-fenton process under the same ph values, the toc and cod removal efficiencies improved from 16% to 23% and from 27% to 38%, respectively at ph 7 as shown in table 3. this enhancement is attributed to increased hydroxyl radical (•oh) production by the presence of tio2. as shown in fig.2, solar photocatalysis using combined tio2/fenton processes improves performance at neutral ph for petroleum wastewater. therefore, there is no need to adjust the ph during this treatment. by comparing these results with previous studies, the results of this work are in agreement with some studies. ardhendu et al. [2] reported that the greatest toc reduction took place under photo-fenton process (pfp). it was found to be more efficient than uv/tio2 photocatalysis (uvpc) under acidic conditions. gbandi et al. [3] found that photocatalysis of tio2 was independent of the ph of the solution, while under fenton photocatalysis, the degradation rate of orange ii increases as the ph decreases. duran et al. [8] found that the tio2 concentration and ph were the main factors for the tio2/fenton/sunlight method for the degradation of the “blue 4” dye. kim et al. [4] showed that the synergistic removal of benzoic acid by the uv/tio2/fe3+/h2o2 system was very efficient between the ph values of 4 and 7. but, at higher ph values (ph>7), the addition of fe3+ and h2o2 to the uv/tio2 system caused negative effects. however, tony et al. [9] reported that the neutral ph of the oil-water solution was the optimum ph value for the degradation of cod by the fenton/tio2/uv system. 3.2. effect of fenton reagent and tio2 concentration the degradation of organic matter monitored by toc and cod for solar tio2 photocatalysis is significantly improved by using a fenton reagent in combination with solar photocatalysis as shown in fig.2 for the tio2/fenton system. the excess iron has a negative effect because it reacts with hydroxyl radicals reducing the degradation rate of the pollutant [6]. also, the excess amount of hydrogen peroxide can cause the auto decomposition of h2o2 to oxygen and water, and the recombination of hydroxyl radicals. therefore, decreasing the concentration of hydroxyl radicals and table 3. comparing the removal efficiencies (%) for three degradation processes expressed by toc and cod under acidic ph range between 5.5 and 7 of petroleum wastewater. removal (%) ph tio2/ solara fenton/ solarb tio2/fenton/ solarc toc 5.5 9 17 26 7.0 15 16 23 cod 5.5 6 39 61 7.0 24 27 38 experimental conditions: a1 g dm-3 tio2 and 180 min (rt); b1 g dm-3 h2o2, 0.04 g dm-3 fe2+ and 180 min (rt); c1 g dm-3 tio2, 1 g dm-3 h2o2, 0.02 g dm-3 fe2+ and 180 min (rt). figure 2. the three processess of toc (a) and cod (b) under different ph figure 1. schematic view of the experimental setup for solar photo-fenton, solar tio2 photocatalysis and solar photocatalysis using combined tio2/fenton processes. a b aljubourya, palaniandy, aziz, and feroz hungarian journal of industry and chemistry 100 reagents reduces efficiency [9]. the degradation rate measured by cod and toc increases as the tio2 concentration increases up to the optimum tio2 dosage in solar tio2 photocatalysis and solar photocatalysis using combined tio2/fenton processes, which were l g dm-3 and 0.66 g dm-3, respectively. however, tio2 dosages greater than the maximum value have a negative effect on these processes since the excess tio2 particles increase the turbidity of the solution that decreases the penetration of light into the solution resulting in a reduction in production of hydroxyl radicals (•oh) at the tio2 surface [10]. 3.3. treatment efficiency to assess the interactive relationships between the independent variables and the responses of certain models, 3d surface response plots were created by design expert 6.0.7. as shown in figs.3 and 4, the tio2 dosage and ph were the two main factors that improved the toc and cod values after removal under solar photocatalysis using the combined tio2/fenton and solar tio2 photocatalysis processes, while the ph and h2o2 concentration were the two main factors in the solar photo-fenton method. the greater removal rates from toc and cod values under acidic conditions for solar photocatalysis using the combined tio2/fenton and solar photo-fenton methods were achieved with ph values of 3.6 and 4.2, respectively. however, they were under alkaline conditions (ph 8) for solar tio2 photocatalysis. the fenton ratio and fe2+ concentration were the essential variables for solar photocatalysis using the combined tio2/fenton and solar photo-fenton methods, respectively. figure 4. figure 3. response surface models for toc removal efficiencies for . a a b b c c tio2 tio2 ph ph ph ph ph ph tio2 tio2 h2o2 h2o2 comparative study of advanced oxidation processes 43(2) pp. 97–101 (2015) doi: 10.1515/hjic-2015-0016 101 4. conclusion the given study evaluated the performance of advanced oxidation processes for the treatment of petroleum wastewater by a central composite design with response surface methodology. these processes include solar photo-fenton catalysis, solar tio2 photocatalysis, and solar photocatalysis using the combined tio2/fenton processes. the decomposition of organic matter was monitored by chemical oxygen demand and total organic carbon content. we obtained experimental evidence for the superior performance of solar photocatalysis using the combined tio2/fenton methods over using tio2 only in the case of petroleum wastewater at neutral ph. under acidic conditions, solar photo-fenton process was found to be more efficient than solar tio2 photocatalysis. however, it was less efficient than the solar tio2 photocatalysis under alkaline conditions. the tio2 dosage and ph can be used to improve the toc and cod values for solar photocatalysis using the combined tio2/fenton processes and solar tio2 photocatalysis only. the ph and h2o2 concentration are the two main factors that influence the efficiency of the solar photo-fenton process. references [1] giri, a.s.; golder, a.k.: fenton, photo-fenton, h2o2 photolysis, and tio2 photocatalysis for dipyrone oxidation: drug removal, mineralisation, biodegradability, and degradation mechanism, ind. eng. chem. res., 2014, 53(1), 1351–1358. doi 10.1021/ie402279q [2] durán, a.; monteagudo, j.m.: solar photocatalytic degradation of reactive blue 4 using a fresnel lens, water res., 2007, 41(3), 690–698. doi 10.1016/j.watres.2006.06.042 [3] djaneye-boundjou, g.; amouzou, e.; kodom, t.; tchakala, i.; anodi, k.; bawa, l.m.: photocatalytic degradation of orange ii using mesoporous tio2 (p25) and fenton reactivity, int. j. environ. sci., manage. & eng. res., 2012, 1(2), 91–96. www.ijesmer.com/web_documents/20121_2_006.pdf [4] hermosilla, d.; cortijo, m.; huang, c.p.: optimising the treatment of landfill leachate by conventional fenton and photo-fenton processes, sci. total environ., 2009, 407(11), 3473–3481. doi 10.1016/j.scitotenv.2009.02.009 [5] kim, h.-e.; lee, j.; lee, h.; lee, c.: synergistic effects of tio2 photocatalysis in combination with fenton-like reactions on oxidation of organic compounds at circumneutral ph, appl. catal. b: environ., 2012, 115, 219–224. doi 10.1016/j.apcatb.2011.12.027 [6] lee, h.-s.; hur, t.; kim, s.; kim, j.-h.; lee, h.-i.: effects of ph and surface modification of tio2 with siox on the photocatalytic degradation of a pyrimidine derivative, catal. today, 2003, 84(1) 173–180. doi 10.1016/s0920-5861(03)00271-2 [7] malato, s.; caceres, j.; agüera, a.; mezcua, m.; hernando, d.; vial, j.; fernandez-alba, a.r.: degradation of imidacloprid in water by photofenton and tio2 photocatalysis at a solar pilot plant: a comparative study, environ. sci. technol., 2001, 35(1), 4359–4366. doi 10.1021/es000289k [8] nogueira, r.f.; trovó, a.g.; paterlini, w.c.: evaluation of the combined solar tio2/photofenton process using multivariate analysis, water sci. technol., 2004, 49(4), 195–200. hwst.iwaponline. com/content/49/4/195 [9] bouras, p.; lianos, p.: synergy effect in the combined photo degradation of an azodye by titanium dioxide photocatalysis and photo-fenton oxidation, catal. lett., 2008, 123, 220–225. link.springer.com/article/10.1007%2fs10562-008-9466-9 [10] tony, m.a.; zhao, y.q.; purcell, p.j.; el-sherbiny, m.f.: evaluating the photocatalytic application of fenton's reagent augmented with tio2 and zno for the mineralisation of an oil-water emulsion, j. environ. sci. health a, 2009, 44(5), 488–493. doi 10.1080/10934520902719894 [11] zarei, m.; khataee, a.; fathinia, m.; seyyednajafi, f.; ranjbar, h.: combination of nano photocatalysis with electro-fenton like process in the removal of phenol from aqueous solution: gc analysis and response surface approach, int. j. ind. chem., 2012, 3(1), 27–28. doi 10.1186/2228-5547-3-27 [12] standard methods for the examination of water and wastewater (american public health association (apha), 21th ed., washington, dc) 2005. [13] aljuboury, d.d.a.; palaniandy, p.; abdul aziz, h.b.; feroz, s.: treatment of petroleum wastewater using combination of solar photo-two catalyst tio2 and photo-fenton process, j. environ. chem. engng., 2015, 3(2), 1117–1124 doi 10.1016/j.jece.2015.04.012 microsoft word 2012_dr_bodor_endre_hjic.doc hungarian journal of industrial chemistry veszprém vol. 39(3) pp. 353-358 (2011) profit optimization of batch-continuous production systems under stochastic processing conditions by simulation é. orbán-mihálykó1 , cs. mihálykó1, b.g. lakatos2, t. szabó1, a. papp1 1university of pannonia, department of mathematics, h-8200 veszprém, egyetem u. 10. hungary e-mail: orbane@almos.uni-pannon.hu 2university of pannonia, department of process engineering, h-8200 veszprém, egyetem u. 10. hungary the properties of a production system working under stochastic processing conditions are investigated. the production system consists of batch units of an input subsystem and a continuously operated deterministic output one which are coupled by an intermediate storage system. the randomness of operation is caused by the uncertainties of batch sizes and the time intervals of arrival to the storage. taking into account the expenses and the income arising from the production the expectation of the profit is defined and investigated. an integral equation is presented for the expected profit, and is solved using monte carlo method. the optimal initial amount of material to be processed, storage volume and withdrawing rate are determined by simulation. keywords: processing system, intermediate storage, stochastic operation, profit, expectation introduction intermediate storage plays an important role in improving the operating efficiency of processing systems, and fitting to each other the subsystems with different operational characteristics. its application increases the availability and variability of systems and reduces the process uncertainties. such buffering action requires rational sizing of intermediate storages in the design phase [1, 2, 3]. however, beside the important technical aspects, the economical profitability of the processing system is also important and often the main aspect of the design. the aim of the paper is to discuss this problem. if a processing system consists of batch and continuous subsystems then these parts may be coupled by means of intermediate storage. the batch units form the inputs of the storage system, while at the output the material processed is removed continuously with constant volumetric rate q(t)=c for the continuous subsystem. the removed material is processed and sold, consequently the factory obtains income. moreover, if the material cannot be stored in the storage because of lack of capacity, it seems rational to sell it immediately. then an important question arises: how much profit can be obtained as a function of the volume of storage system, the initial amount of the material in the storage and the output rate. a schematic structure of the processing system is seen in fig. 1. published research has demonstrated that modelling the operation of intermediate storage is rather stochastic than deterministic [4]. in this paper we also consider the random behaviour of the processing system and we deal with the maximization of expectation of the discounted profit. figure 1: schematic structure of the processing system continuous subsystem q(t)=c output intermediate storage yi inputbatch subsystems 1 l 354 the investigated model: basic notations and assumptions the material to be processed is filled into the intermediate storage by the units of the input subsystem. let the starting point of the process be t0 = 0. the time interval between the (i-1)th and the ith filling is given by the random variable ti i = 1,2,... . these random variables are supposed to be nonnegative, identically distributed and independent ones with common distribution function f(t), density function f(t) and expectation μf. the ith filling happens at the random time point ∑ = i j jt 1 . let n(t) be the number of fillings up to time t. the amount of material filled into the storage during the ith filling is also random, its value is given by the random variable yi, i = 1,2,... . these variables are also supposed to be nonnegative, identically distributed and independent with common distribution function g(y), density function g(y), and expectation μg. we suppose also that the filling process n(t) and the random variables yi are independent from each other. the output process is continuous with constant intensity c. let the volume of storage be denoted by y, and the initial amount of material in the storage be x. let the random period of process from the beginning to running out of material be called cycle, and first we consider the temporal change of material during such a cycle only. temporal change of material in the storage is caused by the difference between the material filled into the storage and withdrawn from that. if the volume of the storage would not be a physical bound for the filled material then the function ctyxtv tn i i −+= ∑ = )( 1 * )( (1) could express the amount of material being in the storage as a function of time. since n(t) and yi are random, v*(t) is a stochastic process. moreover, this process is controlled as some of the material might not be filled into the storage because of the overflow. the maximum of the amount of material being in the storage is y thus the extra amount as compared to it is not filled into. the total extra amount to time t is given by the random function r(t). consequently the amount of material being in the storage at time t is )()()( * trtvtv −= . (2) as the inputs arrive at the moments of time ∑ = = i j ji tt 1 and they cause finite jumps in the functions describing the amount of the material, therefore the process proves to be one hand side continuous with finite jumps. we consider it right-hand side continuous. if the amount of the ith filling yi is so much that it would cause overflow, i.e. the inequality yytv ii ≥+− )( (3) holds then the amount yytv ii −+− )( (4) is considered to be extra amount which cannot be filled into the storage. this means that at time ∑ = = i j ji tt 1 we have yytvtrtr iiii −+=− −− )()()( (5) and v(yi) = y. over the remaining time the value of r(t) does not change, and r(0) = 0. this defines the process in terms of intermediate storage. let us now consider the costs of production and the income. let the cost of the filled material per unit volume be denoted by λk. consequently the cost of the material during the ith filling equals λkyi. we get a more realistic model if we take into consideration also the effects of inflation. more precisely, we distinguish the nominal and the real value of income discounted by inflation. as the costs and income are computed on discounted values and this cost has to be paid at the moment of time ∑ = i j jt 1 , its present value is ∑ λ = − i j jt ik ey 1 δ (6) where δ is the discount factor. hence the total cost of the material filled into the storage up to time t is given by the function ⎟ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎜ ⎝ ⎛ ∑ += ∑ = − = )( 1 1),( tn i t ik i j j eyxxtk δ λ (7) if the extra material is sold at price λ1 per unit volume then the discounted income from selling is )(),( 0 1 sdreytb t s∫ −= δλ . (8) if the income from the production per unit volume is denoted by λ2 then the profit from the production up to time t can be given by δ λλ δ δ tt s ecdseccth − − − == ∫ 1),( 2 0 2 . (9) taking into account that the cost of the start is i and the cost of the investment q(y) depends on the storage size then the total profit as a function of time can be expressed as iyqxtkcthytbcyxth −−−+= )(),(),(),(),,,( . (10) the investment cost is computed by the often applied formula q(y) = k·y0.6, where k is a constant depending on the material and operational conditions, mostly on the pressure of the storage [5]. the process is 355 considered while material exists in the storage, i.e. while the inequality v(t) ≥ 0 holds. the endpoint of the cycle is the time when storage runs out of the material. the random time for this occurrence can be given as follows: }{ ⎪ ⎩ ⎪ ⎨ ⎧ ≥≥∞ <≥ <≥ = 0allfor 0)(if, 0)(for which 0such exists thereif,0)(:0inf )( ttv tvt tvt xt where x denotes the initial amount of material in the storage. the total profit in a cycle is h(t(x), x, y, c). since it is a random variable we consider its expectation expressed as )),,),(((),,( cyxxthecyxm = (11) as a function of the initial amount of material x, the volume of the storage y and the withdrawing rate c. to illustrate the profit and the change of the amount of material in the intermediate storage we present fig. 2 and fig. 3. in computation of processes shown in figs. 2 and 3, the time interval and the amount of material filled into the storage were exponentially distributed for which the following parameter values were used: x = 5, y = 8, c = 2, μf = 2, μg = 2.5, λk = 1, λ1 = 0.9, λ2 = 3, δ = 0.1, q(y) = 0, i = 0. figure 2: evolution of the amount of material in the intermediate storage figure 3: evolution of the profit as a function of time fig. 2 illustrates well that in the generated cycle extra amounts of material were obtained four times, which were sold on market. at the same time, fig. 3 shows negative profit at the beginning of the process, naturally, the reasons of that are the expenses of the initial amount of material and, in general case, also the cost of the investment. note that this model was investigated previously by avanzi et al. [6] in insurance mathematics in the special case of λ2 = 0 and λk = 0. they set up an integral equation for the expectation of the profit and they presented an analytical solution for it in the case of exponential distributions. actually, our aim is to set up an integral equation satisfied by the expected profit m(x, y, c) when the case λk = 0 but λ2 ≠ 0 holds. integral equation for the expected profit let c and y be fixed and let we investigate the function m(x, y, c). obviously, if y < x then ),,(),,( cyymyxcyxm +−= (12) on the basis of the renewal theory one can prove that for 0 ≤ x ≤ y m(x, y, c) satisfies the following integral equation: ( ) ( ) ( ) .1 )()(),,()( )()(,,,, 0 2 0 )( 1 0 )( 0 dte c xf dzdttfzgcyymyzctxe dzdttfygcyzctxmecyxm c x t c x ctxy t c x ctxy t ∫ ∫ ∫ ∫ ∫ − ∞ −− − −− − ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ⎟ ⎠ ⎞ ⎜ ⎝ ⎛−+ +−+−+ ++−= δ δ δ λ λ (13) this integral equation is inhomogeneous due to the last two expressions on the right hand side. consequently there is no method to solve it analytically even in special cases. as the upper bound of the integral is infinity, it is difficult to handle it numerically as well. therefore we elaborated a monte carlo simulation method to determine the approximate values of m(x, y, c) in the general case. monte carlo simulation for determination of the expectation of the discounted profit the basic concept of simulation is the fact that although the process parameters are continuous it is enough to investigate the process in discrete moments of time ∑ = i j jt 1 , ,...2,1=i , handling the system as a discrete event. the moments of time are given by ∑ = i j it 1 when finite jumps happen and when extra income arrives. the left hand limits of function v(t) in these points show if material runs out. it is also easy to compute the value of 356 tv(x) as well because of the linearity of function v(t) in the interval ⎟ ⎟ ⎠ ⎞ ⎢ ⎢ ⎣ ⎡ ∑∑ = − = i j j i j j tt 1 1 1 , . indeed, if nitv i j j ,..,3,2,1,0 1 =≥⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ −∑ = (14) and 01 1 1 1 <−⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ =⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ − + = + = ∑∑ n n j j n j j cttvtv (15) then material has run out in the time interval ⎟ ⎟ ⎠ ⎞ ⎢ ⎢ ⎣ ⎡ ∑∑ + == 1 11 , n j j n j j tt and ( ) c tv txt n j jn j jv ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ += ∑ ∑ = = 1 1 (16) generating the random time points tj and the inputs yj to the storage we can check whether overflow would happen or not and how much extra material arises. computing the costs and the income and finally determining the total income from production h(t, x, y, c) can be calculated for any realization. as the average of the sample is the best estimator of the expectation we can compute the profit for every realization and take the average. the probability of running out of material is estimated by the relative frequency of this event. to show the correctness of the simulation we have compared the results getting on the basis of the analytical formula given by avanzi et al. [6] in special case. the results obtained from the analytical solution and by using monte carlo simulation have proved practically identical as it is shown in fig. 4. here, all simulation runs were carried out repeatedly for n=10000 times. figure 4: comparison of the analytical and simulation results simulation results for the general case let us turn to the investigation of the general model. first we consider it in a single cycle. the expectation of the discounted profit is presented in fig. 5. the expectation of the discounted profit is dependent on the storage volume and the initial amount of material. again, the investment cost was computed by the formula q(y) = k·y0.6. the initial amount of material-storage volume-m(x, y, c) surface, shown in fig. 5, was computed using the parameter values: c = 2.5, i = 2, δ = 0.01, k = 3, μf = 0.55, μg = 2.5, λk = 2, λ1 = 1.8, λ2 = 3. figure 5: the expected profit as a function of the initial amount of material and the volume of the intermediate storage if we fix the initial amount of material then the expected profit as a function of the volume of intermediate storage is a single variable function. fig. 6 shows this function as a section of the three-dimensional graph of fig. 5 at x = 9. the other parameters were identical with those used in computing the surface in fig. 5. figure 6: the expected profit as a function of the volume of the intermediate storage we have determined the maximum of the function shown in fig. 6 numerically by applying golden section. the maximal value is equal to 14.8 which is achieved at the storage volume y = 13.3. m(x,y,c) 0 5 10 15 20 0 5 10 15 20 -20 -10 0 10 20 kezdő anyagmennyiségtartályméretvolume of the storage y initial amount of material x 357 avanzi et al. [6] proved that in the model considered by them the optimal size of the storage does not depend on the initial amount of the material. we have carried out some numerical experiments obtaining identical result: if λk = 0 then the optimal size of the storage is approximately constant. consequently, the value of the maximum profit depends on the initial amount of material but the optimal volume of the storage does not. the simulation results on which this conclusion was drawn are presented in fig. 7. figure 7: optimal volume of the intermediate storage as a function of the initial amount of material we also investigated by simulation the case when the production in the system is restarted following run out of the material. the initial amount of material in the cycle is the filled material after running out. the factory does not have income from production between the time of run out of material and that of restart. it is worth to restart the production only in such cases when the expected profit of a cycle exceeds the cost of the restart. in this case the initial expenses are the costs of start i and the cost of filled amount of material but there are no investment costs. in fig. 8, the expected profit is presented as a function of the initial amount of material when modelling the production process with possible restart. in these computations the values of parameters were as follows: λk = 2, λ1 = 1.8, λ2 = 3, t = 100, y = 10, c = 2.5, δ = 0.01, i = 2, μf = 0.55, μg = 2.5, k = 3. figure 8: the expected profit as a function of the initial amount of material it is seen in fig. 8 the function describing the expected profit increases to about x = 7. here it has a maximum and it decreases when the initial amount of the material exceeds 7. this maximum has been determined numerically. when the restart of production in the system is possible then it is an interesting question how much is the optimal withdrawing rate to ensure maximum profit up to a certain moment of time. in fig. 9, the expected discounted profit is presented as a function of the withdrawal intensity for the case when the initial amount of material and the size of the storage are fixed. figure 9: the expectation of the profit as a function of the withdrawal rate in these computations the values of parameters were as follows: δ = 0.01, x = 8, y=15, k = 3, λk = 2, λ1 = 1.8, λ2 = 3, t = 100, μf = 0.55, μg = 2.5. the maximum value was determined again by golden section and it is proved to be 175.8 at c = 5.5. conclusions the properties and behaviour of a production system, consisting of batch units of an input subsystem and a continuously operated deterministic output subsystem, which are coupled by intermediate storage, were investigated. it has appeared that when the uncertainties of batch sizes and the moments of time of filling those to storage are so significant that these cause some randomness of operation then the system can be modelled by means of the tools of discrete event systems. taking into consideration the discounted expenses and income from production the expected value of the total profit was formulated. an integral equation, determining the expected profit as a function of the initial amount of material, the storage volume and the withdrawing rate was presented and solved by simulation using monte carlo method. optimization of the system with the expected profit as the goal function revealed that the maximum profit depends both on the initial amount of the material to be processed by the system and the volume of the intermediate storage. if the production can be restarted when run out of material occurs then the expectation of the profit exhibits optimum also with respect to the withdrawal rate of material for the continuous subsystem. 358 acknowledgement this work was supported partly by the hungarian scientific research fund under grant k77955 for which one of the authors (bgl) gratefully acknowledges. references 1. é. orbán-mihálykó, g. b. lakatos: intermediate storage in batch/continuous processing systems under stochastic operation conditions, computers and chemical engineering, 28 (2004) 2493–2508 2. é. orbán-mihálykó, g. b. lakatos, cs. mihálykó, l. lucz: probability and expected time of emptying of intermediate storages under stochastic operation, hungarian journal of industrial chemistry, 37 (2009) 89–94 3. s. terrazas-moreno, i. grossmann, j. wassick, s. bury: optimal design of reliable integrated chemical production sites, computers and chemical engineering, 34 (2010) 1919–1936 4. e. s. lee, g. v. reklaitis: intermediate storage and operation of batch processes under equipment failure, computers and chemical engineering, 13 (1989) 411–498 5. m. stone: plant design and economics for chemical engineers. mcgraw-hill, new york, (2000) 6. b. m. avanzi, h. u. gerber, e. s. w. shiu: optimal dividends in the dual model, insurance mathematics and economics, 41 (2007) 111–123 << /ascii85encodepages false /allowtransparency false 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of industry and chemistry vol. pp.45(1) pp. 1–3 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0001 dynamical temperature from the phase space trajectory andrás baranyai * department of theoretical chemistry, eötvös loránd university, p. o. box 32, budapest, 1518, hungary in classical statistical mechanics the trajectory in phase space represents the propagation of a classical hamiltonian system. while trajectories play a key role in chaotic system theory, exploitation of a single trajectory has yet to be considered. this work shows that for ergodic dynamical systems the dynamical temperature can be derived using phase space trajectories. keywords: temperature, statistical mechanics a hamiltonian system of n mass points is related to the microcanonical ensemble of statistical mechanics when the volume, v, and the energy, e, of the system are fixed. a microscopic state of the system is a point in phase space represented by a 6n-dimensional vector, ),...,,,...,( 2121 nn pppqqqγ  . the time evolution of this point is described as a trajectory in phase space. in microcanonical ensembles, since the energy is fixed, the evolution of the system is restricted to a 6n-1 dimensional hypersurface. the logarithm of the area of this hypersurface yields the entropy, s, of the system. since the entropy of a stable thermodynamic system is a monotonically increasing function of the internal energy, the accessible phase space increases with energy. this provides the opportunity to determine the thermodynamic derivative, tes nv /1)/( ,  , where t is the absolute temperature. the trajectories within the limit of infinite time perfectly cover the 6n-1 dimensional hypersurface according to the ergodic hypothesis. this means that the length of the trajectory for a period of time,  , is proportional to the microcanonical entropy: .limln 0 2             γdtks (1) eq.(1) is a line integral measuring the length of the path of the moving system in phase space. this equation can be rewritten as: .limlnlimln 00 2                                   γγ h dtk h dtks (2) *correspondence: baranyai@chem.elte.hu let us consider two hamiltonian systems, h and h’, with only a minor difference between their energy parameters, e and e’. the distance covered in phase space by these systems is different because the two energies belong to different areas of the hypersurface to be covered by the trajectories. if the difference in entropies between the two systems is calculated, the quotient in the argument of the logarithm makes it possible to use equality instead of a mere proportionality. . ' ln ' ln lim lim ln)()( 0 0                                                                             τ γ τ γ γ γ h h k h h k h dt h dt keses       (3) in eq.(3) the time integral was replaced with the product of time and the time-average of the integrands. the hamiltonian, h’, can be approximated as .γ γ d h hh    (4) then . 2 2 γ γγγ d hhh         (5) baranyai hungarian journal of industry and chemistry 2 using eq.(5), eq.(3) can be rewritten as . ln)()( 2 2 2 2 γ γ γ γ γ γγ                             h d h k h d hh keses (6) in the second equality of eq.(6), the xx  )1ln( approximation was exploited. to obtain the temperature, division with the energy difference should be included: . 1 )()( 2 2 2 2 2 th h k d h h d h k ee eses                 γ γ γ γ γ γ γ (7) the dynamical temperature was derived first by rugh as a time average of )/( 2 hh  on the energy surface [1]. . 1 2 h h kt    (8) later, butler et al. applied a similar approach and derived eq.(8) only for the configuration part of the phase space and also checked the performance of the method numerically [2]. the essence of both derivations was to transform the phase-space vector, γ , from system e into γ of system e’ by a vector containing the hamiltonian gradient. in this way arelationship was established between the phase-space points of the two systems. our result uses the average speed of evolution of trajectories in phase space, therefore, a hamiltonian gradient is not required to connect the two sets of phasespace points. expansion of the energy in eq.(4) is sufficient to relate the two trajectories. certainly, the results are identical which proves the validity of this alternative approach while, at the same time, it is a nice example of ergodicity: the method which uses the difference in area of hypersurfaces in an ensembleaverage fashion leading to results that are identical to the method that uses relative trajectory propagation in time. the explicit form of eq.(7) can be written as , / /3 1 1 22 2 1        n i i n i m m kt q q p (9) where  is the position-dependent potential in the hamiltonian and m is the mass of a particle. eq.(9) contains two terms that feature both in the numerator and denominator. the quotient of the first terms is the well-known kinetic temperature and the quotient of the second terms is the configurational temperature. in actual calculations these two temperatures can be calculated contrary to the full form of eq.(9) which contains dimensional discrepancies in both the numerator and denominator. the configurational temperature calculation was suggested as an algorithmic check for monte carlo computer simulations where the boltzmann temperature is an input parameter [2]. for completeness, the third, very simple method of deriving the configurational temperature is mentioned [3].the previous derivations did not state whether the two temperatures, the kinetic and configurational, are equal. using a trivial derivation it is shown that the two quotients are equal [3]. a further advantage of this method is that there is no need for the condition of n to accept the validity of a microcanonical result in terms of the canonical ensemble. the temperature from the momenta of the particles is . 3 1 1 2   n i i nkm t p (10) if this temperature remains constant over time: ,0 11    n i ii n i ii cct fppp  (11) where, for the sake of simplicity, the constant factor is denoted in front of the sum as c and  ii qf  / is the newtonian force, it is also possible to write that .0 )( 1 ,, 2 2 1                    n i zyx ii i n i iiii m p fc ct     f fpfp  (12) at equilibrium in isotropic systems the different cartesian directions are equivalent and there is no correlation between velocities and position-dependent quantities. thus, dynamical temperature from the phase space trajectory 45(1) pp. 1–3 (2017) 3 . 3 2 2 2    q q kt p m (13) eq.(13) can be written in this form when t is manipulated. the results would be the same. therefore, if the expectation value of the temperature is constant, the kinetic and configurational temperatures are equivalent. as for the temperature derivation from the phasespace trajectory it is important to note that the  condition is essential. finite segments of trajectories do not cover the hypersurface completely and only contain minimal information about the temperature and force distributions of the system. references [1] rugh, h.h.: dynamical approach to temperature, phys. rev. lett., 1997 78(5), 772-774 doi:10.1103/physrevlett.78.772 [2] butler, b.d.;ayton, g.a.;jepps, o.g.;evans, d.j.: configurational temperature: verification of monte carlo simulations, j. chem. phys., 1998 109, 65196522 doi:10.1063/1.477301 [3] baranyai, a.: on the configurational temperature of simple fluids, j. chem. phys., 2000 112, 39643966 doi:10.1063/1.480995 hungarian journal of industrial chemistry veszprem vol. 30. pp. 61 -71 (2002) effect of steady state assumption on the structural solvability of dynamic process models a. leitold and k. m. hangos1 • 2 (department of mathematics, university ofveszprem, p.o.b. ·158, veszprem, h-8201, hungary 1systems and control research laboratory, computer and automation institute has, p.o.b. 63, budapest, h-1518, hungary 2department of computer science, university ofveszprem, p.o.b. 158, veszprem, h-8201, hungary) received: july 18, 2001; revised: september 24, 2001 the variable structure of dynamic process models is represented by a directed graph termed the representation graph for the purpose of solvability analysis in this paper. structural solvability analysis, the determination of the structural differential index and the structural decomposition of the dae model set can be performed using the representation graph. it is shown that the effect of steady state assumption for a state variable :x can be handled on the representation graph by modifying the assignment of the derivative variable vertex x'. the method enables us to select a suitablr modification of the original specification such that the structural solvability and the differential index of index 1 process models remains unchanged. in the case of index 2 models, a steady state assumption may decrease the differential index of the modified model to i if the derivative variable is on the underspecified subgraph. the notions and methods are illustrated on simple process examples. keywords: process models, dae models, differential index, solvability, structural analysis, steady state assumption introduction lumped process models are in the form of differential­ algebraic equations which are sometimes difficult to solve numerically due to index and stiffness problems. therefore the solvability analysis of differential­ algebraic equations (dab) process models are of primary importance for dynamic simulation. it is an important related question how high index process models arise. the effect of some decisions taken during the modelling process on the structural solvability has already been investigated in detail [8]. it is known that the change in the specification may transform an index 1 model to a higher index one [4j. it is also known that algebraic transformations, that is transformations which only change the algebraic form of a dae model may change its structural solvability properties, namely its decomposition in a rather drastic way [6], but they do not change the differential index of the model. various methods and techniques have been proposed for structural solvability analysis based on both algebraic (see e.g. [11], [2j) and graphical combinatorial ([9], [12], [loj) techniques. marquardt et al. defined a structural approach to the characterization of daes which is derived from symbolical algorithm fllj. in addition to this, two systematically different structural approaches were applied to support the development of low index models. it is intuitively clear, that modelling assumptions may drastically affect the structur:u. solv~bility properties of a process model. therefore 1t is of pnmary importance to analyze the effect of widely used model specification assumptions, for example the steady state assumption on the differential index. in order . to elllighten the importance and significance of analyzmg the solvability properties of process models and the effect of modelling thereon we should recajj ~at modelling is one of the key and most labour..consumm.g activity in process system engineering serving as a b~sts for process flowsheeting, process control, fault detection and diagnosis. modelling assumptions can be seen. as artifacts of process modelling being a seq~enttal­ iterative procedure with the assumptions codmg the decisions of the modeller. in the case of problems with solving the model one is interested in finding the decisions leading to it. 62 static and dynamic flowsheeting packages nowadays are almost all equipped with hpost mortem" solvability analysis tools but these cannot give advice on how to repair a model with solvability problems. therefore there is a growing demand from the users of such packages to have an intelligent front-end advisor to help them. the current paper can be regarded as one of the first steps to achieve this ambitious goal. the graph theoretical method proposed by murota [9] serves as a basis of the analysis, which can effectively be used for large systems with several hundred variables. this solvability analysis of the model equations gives information on the computa~ion order and on the size of nonlinear sub-sets fo equat10ns to be solved iteratively. decompositions of the original dae model are used for detailed solvability analysis. in our earlier work [ 6] we used these graph­ theoretical methods for index analysis of dae process models and we developed index reduction techniques · for high index models based thereon. the graph representation of dae process models offers computationally cheap methods for analysing . t~e differential index and structural solvability decompositions which can effectively be used for large systems. in this paper our aim is to investigate how a steady state assumption for a state variable can be handled on the representation graph and what is the effect of this assumption on the solvability properties of the model in general and on the differential index, in particular. . the paper is organised as follows. we start w1th basic notion on structural solvability analysis and on the graph representation of dae process models in the next section. thereafter the effect of steady state assumption on the differential index is discussed both for index 1 and higher index models. finally conclusions are drawn. basic notions the basic notions on structural solvability are described here for both algebraic and dae models. related questions. such as the representation of dae models and the handling of model specifications are also discussed. from the viewpoint of the solvability. the most important characteristic feature of process models is the differential index which determines the difficulty of their solution. therefore the basic notions on differential index. of dae models are also discussed in this section. the structural solvability of a dae model can be investigated on the so-called representation graph (9]. structural sol\·ability as a first step~ we consider a .system of linear or non­ lin~ar algebraic equations in its so-called standard form [9): y, = ft(:r.u). i = i. .... m (i) (2) wherexj, (j = 1, ... , n) and uh (k = 1, ... , k) ar~ unknown, y· (i = 1, ... , m) are known parameters, fi, (z = 1, ... , m) a~d gh (k = 1, ... , k) are assumed to be sufficiently smooth real-valued functions. we assume that the partial derivatives of functic:ms t and gk are elements of a field j that is an extension of the rational number field .2. the system of equations above is structurally solvable, if the jacobian matrix j(x, u) as a matrix over :j, is non-singular, where [ j(f,x) j(f,u) j j x,u) = ( j(g,x) j(g,u)ik (3) [ at,. j j(f,x) = ax~ ' j(f,u) =-~ [ at,. j ~ aul (4) [ agk j j(g,x) = axj , [agk] j(g,u)= aul (5) and ik is the k x k identity matrix. it is possible to consider the standard form with no loss of generality in such a way that the variables in left­ hand side of equations appear only once [9]. consider a system of equations in the standard form. we construct a directed graph to represent the structure of the set of equations in the following way. the vertex­ set corresponding to unknowns and parameters is partitioned as xu u u y, where x= {xi>···' xn}, u == {ur, ... , uk} and y == {yt.···, ym}. the functional dependence corresponding to the equations is expressed by arcs coming into yi or uk respectively from those xj and u1, which appear on the right-hand side. this graph is called the representation graph of the system of equations. it is denoted by g == (v, a, x, y), where v is the vertex-set, a is the arc-set, x is the entral).ce and yis the exit of the graph. the representation graph satisfies the following properties: 1. each vertex x e x has no in-com~ng arcs. (these are initial vertices.) 2. each vertex y e y has no out-going arcs. (these are terminal vertices.) the representation graph may be regarded as the flow of information in the system as it expresses the existence of functional dependence among variables. example 1. consider the following system of equations: yt = /i(xl"~t•u3) (6) yz == f2(upu3) (7) yj = f3(xz,u3,u4) (8) u1 == g1(x1,u2} (9) "2 = 8z(xl,x2,u3) (10) u3 = g3(u1) (11) ~ arcs of a mengsr-type complete linking fig.l representation of model in example i (12) the representation graph of the system above is shown in fig. i. there is a generality assumption (abbreviated by ga) on the functions.fi, (i = 1, ... , m) and gb (k = 1, ... , k) on which the graphical methods of decomposition are based which is stated as follows: ga: let .j' be the collection of all partial derivatives of .fi and gkthe non-vanishing elements of .j' are algebraically independent over the rational number field .f. this assumption means, that the non-vanishing partial derivatives of.fi and gk are "so general", that they do not satisfy any polynomial relation with integer coefficients. a menger-type linking [9] from x to y is a set of pair-wise vertex-disjoint directed paths from a vertex in x to a vertex in y. the size of a linking is the number of directed paths from x to y contained in the linking. in case !xi = jyj, (m = n), a linking of size lxi is called a complete linking. the graphical condition of the' structural solvability is then the following: linkage theorem [9]: assume ga is true. a system of equations in the standard form is structurally solvable if and only if there exists on the representation graph a menger-type complete linking from x to y. in rigorous mathematical sense, the structural solvability and the existence of the menger-type complete linking are equivalent under the above generality assumption ga. in many cases, however, it is difficult to check the validity of this assumption and/or the assumption does not hold at all, therefore we use the property conditional structural solvability as follows. a system of standard form equations is conditionally structurally solvable if there exists a menger-type complete linking from x to y on the representation graph. here we do not take into account the generality assumption ga. obviously the conditional structural solvability is a necessary condition. of structural solvability. in further examples we investigate the conditional structural solvability of models. example 1 (continued). as shown in fig.l there exists a menger-type complete linking {xi --7ytt x2 ~ u2 ~ ut _,. u3 -t y2, x3 --7u4 --7 y3 } on the representation 63 graph, so the system described in example i is structurally solvable under ga. from the viewpoint of structural solvability two types of model decompositions can be defined and constructed using the representation graph. the goal of these decompositions is to obtain the sub-systems of a model and to determine a successful way for solving the model equations. representation of dynamic process models we can adapt the graphical techniques described above to dab-system, as well [12]. an ordinary differential equation of a dae system can be described by the following equation: (13) here x denotes an arbitrary variable depending on time, x' denotes the derivative of x with respect to time and xj, ... , xn are those variables which have effect on variable x' in the model. the variable x of the above differential equation is usually determined using a numerical integration method: (14) in dab systems there are two types of variables. differential variables are the variables with their time derivative present in the model. variables which do not have their time derivative present are called algebrau variables. the derivative x' is called derivarirt.' (velocity) variable. a system of equations including also differential equations, can be represented by a dynamic graph. a dynamic graph· is a sequence of static graphs corresponding to each time step of integration. on a dynamic graph there are direct arcs attached from the previous static graph to succeeding static graph corresponding to the method for solving ordinary differential equations. in case of an explicit method for solving ordinary differential equations the value of a differential variable at a given time is computed using the corresponding differential value and its value at previous time, for example. therefore if there is an ordinary differe~~~~~ equation x' = f (xt. .... xn) in the model, we can rewnte tt into the following standard fonn: x=jx' (15) (16) the representation graph corresponding to equations (15) and (16) is shown in fig.2. it can be ~n that there are vertices on the static graphs refemng to the differential variable x, the derivative variable x' and the variables xh ... • x11 occurring in eq.( 16). direct arcs attached to static graphs at time step t and t+ 1 correspond to the applied euler or oth~ expli~it one·step method for solving ordinary d1fferenual equations. 64 t+1 --~------------r-~---------~'~ ~/ . ' " ., .. :>:-r t>{/ ... ! fig.2 representation of the structure of an ordinary differential equation by dynamic graph standard form and the reduced graph the form of the representation graph for dae system models suitable for .structural solvability analysis is developed in steps performed sequentially. the first step for investigation of a dynamic process model by the graph theoretical technique is to rewrite ·the model into the standard form (see eqs. (1)-(2) and ( 15)-(16)). the second step is the assignment of types to vertices in the representation graph [5]. the important types of vertices corresponding to the model specification are the following: • < s > ( set)-type variables these represent variables, which are assigned to the specified given values. these variables require no computation and are present in the specification associated to the process model. the type < s > is usually assigned to initial vertices of the representation graph. in case of dynamic representation graph we can assume an explicit euler method (or another one­ step explicit method) for solving the differential equations. therefore the differential variables wm be labeled by type < s > because their initial vaiue can be obtained from the initial conditions then their values can be calculated step by step by numerical integration. in order to distinguish the label < s > assigned to differential variables from the label < s > of other variables with specified given values the label of differential variables is denoted by < s*' >. labels < s > and < s• > are treated the same way in the rest of this paper. • < g > ( gi\·en)-type l'ariables a variable assigneq to a specific value of a left hand side is a < g >·type variable. unlike in case of < s >-type variables the values of the right band side variables wm be suitably adjusted so as to preserve the equality of the two sides. the type < g > is usually assigned to terminal vertices of representation graph. a non~terminal vertex assigned to type < g > can be split into two copies one of which being initial and the other which being terminal vertices. the initial vertex is labeled as type < s > and the terminal as type< g >. as a result, vertices of type< g > form a subset of the terminal vertices. according to the representation graph the value of ev_ery variable which has incoming arcs only from vertices labeled by type < s > can be calculated by simple substitution in~o the corresponding equation. these variables become secondarily labeled by type < s >. after this we can calculate the value of all variables which have incoming arcs only from vertices primarily and secondarily labeled by type < s > by simple substitution. these variables will be tertiarily labeled by type < s > and this process can be repeat~d if necess~y. omitting all vertices labeled primarily, secondanly,_ etc. by type < s > and all arcs starting from them from the representation graph we obtain the reduced gr~ph. the classification of vertices of a reduced graph 1s as follows: • all initial vertices form the unknown variable set x, • all terminal vertices labeled by type < g > constitute the known variable (parameter) set y, • all other vertices constitute the unknown variable set u. differential algebraic equations and the differential index the degree of difficulty to solve a dab-system f(z(t), z'(t), t) = 0 can be characterized by the differential index of the model. the definition of the differential index [1] is as follows. the minimum number of times that all or part of a dab-system f(z(t), z'(t), t) = 0 must be differentiated with respect to time in order to determine z' as a continuous function of z and t is the differential index of the dae-system. numerical solution of daes includes both initialization and integration. to· solve daes successfully the initial values must be consistent. in case of odes the initial values can be chosen independently hence the so called dynamic degree of freedom is equal to the number of differential equations. in contrast to this the initial values of daes can be constrained by the algebraic equations, so the initialization of daes can be cumbersome and the problems related to initialization increase with higher index values. difficulty of numerical integration of daes also increases with higher index values [3]. dynamic process models can be described by semi­ explicit daes as follows [4]: z; = f(z1 ~z2 ,t), z1(t0 ) == zlo (17) 0=g(zpz2 ,t) (18) according to the definition of the differential index a semi~explicit dae has index one if and only if one differentiation is sufficient to express z'2 as a continuous function of z~o z2 and t. one differentiation is sufficient only if the jacobian matrix gz2 is non-singular. p fig.3 a simple liquid system structural non-singularity of gz2 i.e. the full structural rank of gz2 results in a model which is structurally semi­ explicit index 1. the initial values of the differential variables in the semi-explicit index one models may be chosen independently. . if gz2 is singular then the differential index is greater than 1. structural singularity of gz2 is a sufficient conditio~ for differential index being > 1 numerically. i~ pract:ce . most of dynamic process models having differential mdex > 1 are semi-explicit index 2 models, ?ut there are models having arbitrarily large differential mdex [8]. the initial values of the differential variables in the higher index semi-explicit models cannot be chosen independently. hi~h index models c.an either be simulated directly by an mtegrator which tackles high index daes or be transformed to semi-explicit index 1 model and then integrated. investigation of structural solvability of dynamic process models in our earlier work [7] a graphical technique is p:esented which is suitable to compute the structural differential index of lumped dynamic process models. !he characteristic features of the representation graph of mdex 1 and high index semi-explicit dab-models are also described there. . based on the structural solvability properties a novel ~ndex reduction algorithm has been proposed for both mde~ 2 and higher index models. the developed algonthm can also be used for the investigation of the structural differential index and the structural solvability of these models. these results are illustrated on the following example. . example 2. consider a liquid tank system with one mlet stream and one exit stream as is shown in fig.j. let the vessel be perfectly stirred. heat is transferred to the liquid using a heater. the flow rate and the enthalpy of inlet stream as well as the flow rate of the outlet stream and the heat transfer rate are functions of time. 65 th~ model equations of the above system are the followmg: m' =-l+f (19) u =-l·hl +f·hf +q (20) hl = f1 (tl,p) (21) hf = fz(tf,pf) (22) u=m·ul (23) ul = f3(hl,p) (24) l=f4 (m) (25) herem denotes the mass, u the internal energy, q heat transfer rate, f and l inlet and outlet mass flow rate, hf and hl specific enthalpy of inlet and outlet flow~ ul specific internal energy, tftemperature of inlet flow, pf pressure of inlet flow, tl temperature in the vessel, p atmospheric pressure, respectively and fi, f2 and h are given functions. the standard form of this model is as follows: m=fm' (26) u=ju' (27) m' =-l+f (28) u' =-l·hl +f·hf +q (29l hl = f1(tl,p) (30) h f = fz (t f' p f) (31) u (32! ul=m u~ = f3(hl,p) (33) * s=o (34) s =ul -ul, l= / 4 (m) (35} introduction of new variables u; ~ s and the equation s = u l u ~. s = 0 into the original model guarantees that all variables on the left-hand side of the model are different. in eq.(34) the "satellite .. notes = 0 refers to the fact that the value of variable s is set to 0. i.e. the variable vertex s is labeled by type < g >. the representation graph of the liquid tank system is shown in fig.4a. we indicate differential variables on the static graph at time step t+l only. but the structun~ of this graph is the same as the structure of static graph at time step t. 66 p, <s> t • • a, b, m ... -----~ i' i t+1 fig a representation of model with specification i in example 2; a, representation graph; b, reduced graph furthermore, consider the following specification. specification 1. given: the properties of the inlet flow f, tp, pf and the heat transfer rate q as functions of time; the initial values of mass and internal energy m0, u0 and the pressure p are constants; to be calculated:the mass, the internal energy and temperature of the liquid in the vessel and the outlet flow rate m, u~ tl, l as functions of time. it can be shown that the differential index of this semi-explicit dae system is equal to 1. dynamic degree of freedom is 2., so initial values of mass m and internal energy u can be chosen independently. the types of variables assigned corresponding to specification 1 are shown in fig.4a. the reduced graph according to specification 1 is shown in fig.4b. having produced reduced graph, the variable classes related to it can also be given (see the general standard form model ( 1) ~ (2)) as follows: (36) y={s} (37) (38) and the existence of the menger~type complete linking can be investigated. it can be seen that there exists a menger-type complete linking on the reduced graph hence the model is conditionally structurauy solvable. t+1 fig.s representation graph of model with specification 2 in example 2 next let us consider the following specification: specification 2. given: f, tp, pp, tl as a function of time; m0, u0, p constants; to be calculated:the mass, the internal energy of the liquid in the vessel, the heat transfer rate and the outlet flow rate m, u, q, l as functions of time. it is easy to show that the model with specification 2 is a semi-explicit index 2 model, because the unknown variable q is not present in the algebraic equations, so two differentiations are needed to express q '. the dynamic degree of freedom is 1, so initial values of mass and internal energy can not be chosen independently. the types of variables which (}.fe assigned corresponding to specification 2 are shown in fig.5. based on the structure of the representation graph on fig.5 the following structural solvability properties can be determined. l. the standard form model is not structurally solvable. (there is no menger-type complete linking on the graph.) 2. there are an overspecified part and an underspecijied part on the representation graph. the overspecified part indicates the fact that the initial values of the 111odel can not be chosen independently. the underspecified part q ~ u' indicates, that q can not be calculated from the algebraic equations, so the index of the model is >1. the following theorem holds generally [7]. theorem: consider a dynamic process model m in the standard form described by a semi-explicit dae system. assume that the generality assumption ga is true. then the differential index of m is equal to 1 if and only if there exists a menger-type complete linking on the reduced graph at any time step t. consequence: under the assumptions of theorem above the following statement holds. if the differential index of m is greater than 1 then there is no menger­ type complete linking on the static graph at any time step t. the properties of a static graph of a dynamic model which has differential index > 1 are as follows. 1. the fact that the initial values of integral variables can not be chosen independently results in an overspecified part on the graph. this situation can be easily shown by assignment of types to vertices corresponding to the model specification. there is an overspecified part on the graph if a vertex labeled by type < g > can also be labeled secondarily or tertiarily or etc. by type<s>. 2. non-singularity of gz2 results in an underspecified part on the graph. in this part those algebraic variables appear which can not be calculated from algebraic equations and those differential variables which we want to calculate from them. there is a natural method for index reduction suggested by the structure of the representation graph of semi-explicit dab-systems. example 2 (continued). consider example 2 with specification 2. this model has differential index 2. modify the standard form of the model as follows: instead of equation _ u = j u' introduce the following equation: (39) where lf and [j+i denote the value of internal energy u at time step t and t+l, respectively. this equation corresponds to numerical derivation so if we get the derivative u' by numerical derivation we can calculate qfromit. according to the above transformation of the standard form, let the modified standard form of model of example 2 be the following: m' =-l+f s=u· -u·•, s=o (40) {41) (42) (43) (44) (45) (46) (47) 67 t+1 q p~ _j '-'-"""-<$> __ a, b, fig.6 representation of modified model in example 2; a, representation graph; b, reduced graph (48) (49) during the modification the internal energy u turns from a differential variable into an algebraic variable and u' turns from a derivative variable into an algebraic one. an important consequence of the modification is that there is no integration for variable u in the modified model, so it is not necessary to give initial value for the variable u. the representation graph of the modified model can be seen in fig.6a. the static graph at time step t+ 1 shows vertices belonging to variables only, which are necessary to calculate q in time step t. the reduced graph is shown infig.6b. it can be seen that there exists menger~type complete linking on the reduced graph, so the modified model is conditionally structurally solvable. inspired by the above example we generalized the idea of using the "reverse information flow" for computations for a wide class of semi-explicit dae systems and formulated a general index reduction algorithm [7]. the effect of steady state assumption models of complex dynamic systems are often large­ sized and complicated. in order to obtain process models of a reasonable size we most often use model simplification. the most frequently applied model simplification assumption originates ~om the st~a~y state circumstances valid for a state vanable. our a1m is to investigate how the effect of steady state assumption can be described on the representation graph of process models and what is the effect of this assumption on the 68 structural solvability, model specification and differential index. steady state assumption applied for models with differential index 1 consider a dynamic process model described by a semi­ explicit dab-system with differential index 1. a state variable of this model can be considered being in steady state if its change in time is approximately equal to 0, compared to the other terms of the differential equation: ,tfx x =-:=::0 dt (50) this fact can be treated on the representation graph in such a simple way, that the assignment of the derivative variable x 1 becomes type< g >, because the value of x' is equal to zero. the effect of this modification to the structural solvability can be summarized as follows: proposition 1: consider a dynamic process model described by a semi-explicit dae system in standard form. let the differential index of this model be 1. assume that the generality assumption ga is true. assume that the size of menger-type complete linking on the static graphs of the dynamic representation graph of the model is equal to k. assume, that the state variable $x$ is in steady state. let us modify the assignment of the vertex of the derivative variable x' to type< g >. then 1. the static graphs become overspecified at any time step t, hence there are no menger-type complete linking on them, therefore the model is not structurally solvable. 2. modify the model specification as follows. consider that there exists a variable xi on the static graph which is labelled by < s > or < s* and there is a directed path from xi into x, which is vertex-disjoint to paths of a menger-type complete linking on the original graph. drop the label < s > or < s* of variable xj· after this: there is a menger-type complete linking on static graphs at any time step t. so the model is structurally solvable. the size of the menger­ type complete linking is equal to k+ 1. proof: let g be the static graph of the original dynamic model at time step t and let g' be the modified static graph. l. there is a menger-type complete linking on the original static graph g, hence the elements of variable sets x and y are equal to each other: jx1 = jyi = lc. during the modification of the assignment of variable x'. the number of variables labelled by type < g > increases. hence g' becomes overspecified~ so there is no menger­ type complete linking on it. $ <g> fo~· .· .dm <g> . du du tt---.... h~ __ __,,..<~> a, b, u••-----·~-~~l---·-··~···-1 du ~<g> tl ___ .,..... __ ~s h~ <g> o-----------~:~ c, d, fig.7 reduced graph of model in example 2 with specification i; a, assuming steady state for m (mo is considered to be unknown); b, assuming steady state form (f is considered to be unknown); c, assuming steady state for u (u0 is considered to be unknown); d, assuming steady state for u (q is considered to be unknown) 2. changing the model specification the way described above, the following is true on the reduced graph of g': ix'i = iy'i = k+ 1 and there is a directed path from xi into vertex x', which gives a menger-type complete linking on g' with a suitable menger-type complete linking on the reduced graph of g. consequence: changing the variable assignment (and the model specification) according to proposition 1 above, the differential index of the dynamic model does not change. example 2 (continued). consider example 2 with specification 1. 1. assume, that the mass in the tank is in steady state, that is . (51) according to the above, this assumption can be treated on the representation graph by modifying the assignment of vertex m' in such a way that it is labelled by type < g >. after this, all static graphs become overspecified. according to fig.4a there exist two vertices (m and f) on the representati~n graph which are labelled by type < s > or < s > and from which a directed path starts into vertex m'. both of these paths are vertex-disjoint with the menger-type complete linking of the original reduced graph (see fig.4h ). hence there are two possibilities to modify specification according to proposition 1. either the initial value of mass m0 or the inlet mass flow rate f can be unknown, so the original label of one of these vertices can be dropped on the representation graph. with these modifications the new reduced graphs can be seen in figs.7a and lb. b, fig.8 reduced graph of model in example 2 with specification 1 assuming steady state for m and u; a, m0 and u0 are considered to be unknown; b, f and q are considered to be unknown in both cases there is a menger-type complete linking on the reduced graph, so the model is conditionally structurally solvable. the size of menger-type complete linking increases from 1 to 2. 2. consider that the internal energy of liquid in the tank is in steady state, that is u· ~a (52) let the value of the derivative variable u' be equal to zero, so it becomes to be labelled by type< g >.it can be seen in fig.4a that there are six vertices (m, f, u, tl, p f and q) on the static graph which are labelled by < s > or < s* > and from which a directed path starts to vertex u'. dropping the label < s > or < s* > of any of these vertices is suitable to obtain a conditionally structurally solvable model. figs.7c and 7d show the reduced graphs of the modified model. in the first case variable u while in the other case variable q is unknown. 3. assume, that both the mass and the internal energy of liquid are in steady state in the tank: m' ~ 0 and u · = 0 . (53) in this case both vertex m' and vertex u' become labelled by type < g > because of their values are equal to zero. for the appropriate modification of the model specification two vertices must be found on the original representation graph (fig.4a) which are labelled by type< s >or< s* > and from which two directed paths start into m' and u'. these paths must be vertex-disjoint with the original menger-type complete linking (see fig.4b ). let m and u or f and q be the chosen variable pairs. dropping the original label of these vertices means that these variables are considered to be unknown. reduced graphs are shown in figs.ba and bb. assuming steady state for a state variable x, the most usual modification of the specification in the modelling practice is to drop the initial value of variable x from the specification. the above example illustrates that there can be many other modifications of the specification which yield a structurally solvable model. the 69 representation graph is a very suitable tool to find these possible modifications of the original specification. steady state assumption for models with dijferential index 2 consider a dynamic process model described by a semi­ explicit dae system, which has differential index 2. the representation graph corresponding to the standard forni 0f the model contains an underspecifled and an overspecified part. assume that a state variable x being on the underspecified subgraph is in steady state. then the following proposition is true. proposition 2: consider a standard form dynamic model described by a semi-explicit dab-system, which has difierential index 2. assume that the generality assumption ga is true for the algebraic part of the model. consider the dynamic representation graph of the model. assume that there is only one initial vertex without label < s > on the underspecified part of static graphs. let x' be a derivative variable also on the underspecified subgraph. assume that the state variable xis in steady state, so let the value of derivative variable x' be equal to zero. hence let the label of x' be type < g >.then: 1. static graphs at any time step t are overspecifled, hence there are no menger-type complete linking on them. 2. modify the specification of the model as follows: look for a variable vertex xk on the overspedfied part which has label < s > or < s* > and drop this label of xk. then xk becomes an unknown variable. the modified model is then structurally solvable. proof: 1. it follows from the procedure in proposition 2 that the overspecified subgraph is unchanged while the underspecification of the originally underspecified part disappears. 2. variable x' has label < g > therefore there is a directed path from an initial vertex having neither label < s > nor < s* > into vertex x' on the originally underspecified subgraph. furthermore, there is a new directed path from xt into a vertex with label < g > on the originally underspecified subgraph as result of the described modification of specification. these directed paths together with a maximal menger~ type complete linking of the original graph yield a menger-type complete linking on the modified graph. hence the modified model is structurally solvable. consequence: the differential index of modified model corresponding to proposition 2 decreases from 2 to 1. 70 u~~ f ---------ih <~~ q~du <g> a, b, fig.9 reduced graph of model in example 2 with specification 2; a, assuming steady state for u; b, assuming steady state for m example 2 (continued). consider example 2 with specification 2. the differential index of this model is equal to 2. assume that the internal energy of liquid is in steady state in the tank: u· ::::o (54) then the value of derivative variable u' is equal to zero, so let the label of vertex u' be type < g > on all static graphs. hence the underspecification of the originally underspecified subgraph disappears. modify the model specification according to proposition 2. there are 4 vertices with label < s > or < s* > (m, u, tl and p) on ~e overspecified subgraph (see fig.5). drop the label < s > of vertex u for example, i.e. consider the initial value of internal energy of liquid to be unknown variable in the tank. the reduced graph of modified model can be seen in fig. 9a. there is a menger-type complete linking on the reduced graph~ so the standard form of modified model is conditionally structurally solvable. hence the differential index of the modified model is equal to 1. the result is the same if we drop the labels of m, tl or p during the modification of specification. it can be seen, that the differential index of the standard model decreases from 2 to i during the steady state assumption of internal energy of liquid and with the proposed modification of model specification. consider a dynamic process model with differential index 2. assume that the derivative variable x' does not exists on the. underspecified subgraph corresponding to the standard form. assume that the state variable x is in steady state. consider the model modified by the index reduction algorithm and its representation graph for this case. let the value of .r· is equal to zero hence the vertex .r' becomes type < g >. the effect of this modification on the structural solvabilily is similar to the case of inde:( l models as the following example illustrates. e.tample 2 tconti11ued}. consider again example 2 with specificatioll 2. assume that the mass of liquid is in steady state in the tank: .m =0 (55) since the vertex m' does not exist on the underspecified part corresponding to standard fonn (see fig.5) consider the representation graph belonging to the ~el modified by the index reduction algorithm (see f1g.6a). let the value of variable m' be equal to zero. hence the vertex m' has label < g > on all static graphs. look for a \'ertex with label < s > or < s· > from which there is a directed path into m·. this directed graph must be vertex-disjoint to the paths of menger-type complete linking of modified model (see fig.6b). there are two vertices (m and f) which are suitable under the above conditions. choosing the vertex f and dropping its label < s > the inlet flow rate of liquid is to be considered as an unknown variable. the reduced graph corresponding to the modified model can be seen in fig.9b. the size of linking increases from 1 to 2. the modified model is conditionally structurally solvable. it can be seen that the steady state assumption for the mass of liquid in the tank does not change the differential index of the model. conclusion it is shown in this paper that a steady state assumption for a state variable x of a dynamic process model can be handled on the representation graph by modifying the assignment of the derivative variable vertex x'. the value of x' is equal to zero hence vertex x' becomes type <g>. this modification of the original model results in an overspecified model therefore we must change the model specification to obtain structurally solvable model. after this modification of the specification the differential index of originally index 1 model does not change. in case of index 2 models two different cases are considered. if the derivative variable vertex x' is on the underspecified subgraph corresponding to the original standard form model, then the standard form of modified model becomes structurally solvable, i.e. the differential index decreases from 2 to 1. if this is not the case, then the effect of a steady state assumption is the same as for the index 1 case. it was shown that the applied graph theoretical method for structural analysis of dae process models can be used effectively for investigation of the effect of modelling assumptions. further work is directed towards analyzing the effect of other modelling assumptions on the structural solvability properties in general and on the differential index, in particular. such results may guide the modeller on which assumptions have decreasing effect on the differential index and warn him/her about assumptions which can increase the index. acknowledgement this research was supported by the hungarian national research fund through grant no. t -026575 which is gratefully acknowledged. references i. brenan k. e., campbeu. s. l. and pe'fzoi.d l. r.: numerical solution of initial value problems in differentialalgebraic equations north-holland, new york, 1989 2. duff 1.: analysis of sparse systems, d.phil oxford university, 1972 3. hairer e., lubich c. and roche m.: the numerical solution of differential-algebraic systems by runge-kutta methods, springer­ verlag, berlin, heidelberg, 1989 4. hangos k. m. and cameron i. t.: process modelling and model analysis, academic press, new york, london, 2001 5. iri m., tsunekawa j. and yaj.ima k.: information processing, 1972, 71, 1150-1155 (proc. ifip congr. 71, vol. 2., (appl.)) 6. leitold a. and hangos k. m.: on algebraic model transformations. proc. of cmp'98 prague, czech rep. pp. 133-138, 1998 71 7. leitold, a. and hangos k. m.: computers and chemical engineering, 2001, in press. 8. moe h. i.: dynamic process simulation, studies on modeling and index reduction, phd thesis, university of trondheim, 1995 9. murota, k.: systems analysis by graphs and matroids, springer-verlag berlin, 1987 10. sargent, r. w. h. and westerberg a. w.: trans. inst. chern. eng., 1964,42, 190-197 11. unger j., kroner a. and marquardt w.: computers chem. engng, 1995, 19, 8, 867·882 12. yajima k. and tsunekawa j.: graphical techniques used for a dynamic chemical process simulation, proc. loth ifip conf. new york city, 1981 (in eds. r.f. denrick and f. kozin, lecture notes in control and information sciences, 38, springer, berlin, 826-833, 1982) page 58 page 59 page 60 page 61 page 62 page 63 page 64 page 65 page 66 page 67 page 68 microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 43-48 (2008) sweet sorghum juice and bagasse as a possible feedstock for bioethanol production m. gyalai-korpos1 , j. feczák2, k. réczey1 1budapest university of technology and economics, department of applied biotechnology and food science 1111 budapest, szent gellért tér 4. hungary e-mail: miklos_gyalai-korpos@mkt.bme.hu 2agroszemek ltd., seed improvement and distribution, 6800 hódmezővásárhely, makói országút 212/a, hungary the aim of our study was to estimate the overall ethanol potential of a promising hungarian sweet sorghum variety called ‘monori édes’ developed by agroszemek ltd. for ethanol production following parts of the plant can be utilized: the stem juice containing sucrose and the bagasse built up mainly from lignocellulose. as lignocellulosics have to be pretreated and hydrolyzed prior to fermentation, another purpose of our research was to apply weak alkaline pretreatment methods to enhance enzymatic digestibility of bagasse thus, to improve the ethanol yield. in our study the effect of two bases (naoh and koh) in two concentrations (1% and 2%) and at two temperatures (room temperature and 121 °c) was investigated on the efficiency of enzymatic hydrolysis. every pretreatment type affected positively the hydrolysis efficiency but in different degrees. best results were achieved with 2% naoh at 121 °c. however highest ethanol conversion based on the glucan content of pretreated material was reached using 2% naoh at room temperature. summarizing the ethanol potentials of juice and bagasse an overall potential of about 8 300 l/ha was estimated. keywords: sweet sorghum, enzymatic hydrolysis, alkaline pretreatment, ethanol fermentation introduction sorghum is the forth most important forage crop in the world with a cultivation area over 40 million hectares [1]. in the dry zones of tropical and subtropical areas it is used for food purposes too while under the moderate climate the utilization as feed has priority. two different sorts of sorghum are cultivated, the grain sorghum and the sweet sorghum which is a sugar cane-like plant with sucrose-rich juice in the stem. in contrast to sugar cane, sweet sorghum can be cultivated in nearly all temperate climatic areas in europe, also in regions possessing weak arable land conditions. besides using sweet sorghum as animal feed there is anohter possibility to cultivate it as energy crop getting more and more attention. from the extracted juice fuel ethanol can be produced, in asia there are already industrial scale factories based on this technology. in 2007 4.92 billion liters of ethanol were produced from sweet sorghum juice in china and india. the first factory of the usa utilizing sweet sorghum juice alone will be built in florida by renergie which has recently received a 1.5 million dollars grant to start the project [2]. in our study the ethanol potential of a hungarian sweet sorghum variety called ‘monori édes’ developed by agroszemek ltd was estimated. since this variety has been improved in hungary, it has adapted to the climatic conditions and it can produce high green biomass yield, i.e. 80–100 t/ha. it is harvested in september–october when the sugar content of the stem is the highest. the sugar concentration of the juice can reach 14–20%. nowadays, it is mostly used as cattle feed but there is a growing interest to utilize it as ethanol fermentation feedstock. in this case the harvested stems get pressed to extract the juice (40–50 t/ha); the byproduct of the process is the bagasse, the leftover of the stem (40–50 t/ha, 50% dry weight) built up mainly from lignocellulose. although bagasse could be used as raw material for second generation bioethanol production, regularly it is burnt to supply the energy demand in the juice-to-ethanol process. while the technology based on juice is already available on industrial scale, the lignocellulose conversion is still in experimental phase. there are only a few papers available on this alternative utilization. gnansounou et al. [3] studied the theoretical possibility for a sweet sorghum biorefinery under circumstances in north china. the purpose of our work was to analyse and utilize the bagasse of ‘monori édes’ as a possible raw material for ethanol production. before fermentation the lignocellulosic bagasse has to be pretreated and hydrolyzed to liberate glucose molecules. the aim of pretreatment is to break down the complex and resistant structure of lignocellulose and hereby increase the efficiency of subsequent enzymatic hydrolysis. usually after grinding a chemical or physicochemical method is applied. in case of chemical treatment acid, base or organic solvent is used. based on previous 44 results achieved with other agricultural by-products alkaline pretreatment was used in our experiments [4]. their effect on the efficiency of enzymatic hydrolysis was evaluated. the pretreated and hydrolized samples as well as the juice were fermented by baker’s yeast to determine the ethanol potential of the whole plant. materials and methods raw materials both the frozen, with nitric acid acidified juice (ph = 3.0–3.5) and the bagasse were obtained from the site of agroszemek ltd. near to hódmezővásárhely. harvest and pressing were performed during the autumn of 2007. before use the bagasse was chopped, dried and ground. hplc analysis water soluble sugar (cellobiose, glucose, xylose and arabinose) and ethanol content were determined by high-performance liquid chromatography (hplc). samples for hplc analysis were prepared by filtration through a 0.45 μm pore size regenerated cellulose syringe filter (la-pha-pack, profill™, langerwehe, germany). an aminex hpx-87h (biorad, hercules, ca, usa) column was used at 65 °c with 5 mm sulphuric acid mobile phase at 0.5 ml/min flow rate. separated compounds were detected by a shimadzu rid-10a refrective index detector (shimadzu, kyoto, japan). raw material analysis initial sugar content of the juice was determined in triplicate by ’sucrose, d-fructose and d-glucose’ kit (megazym). celluloseand hemicellulose content of bagasse were determined in triplicate before and after pretreatments by a two-step sulfuric acid hydrolysis. the principle of this method was originally described by hägglund [5]. firstly 0.5 g of dry ground bagasse was hydrolysed in 2.5 ml of 72% sulfuric acid for 2 hours at room temperature. after that 77 ml of distilled water was added into it and further hydrolysed for 1 hour at 121 °c. after separation the reaction mixture on a g4 glass filter hplc analysis was carried out from the liquid fraction. the solid fraction was washed with hot distilled water and dried. this residue was defined as the lignin content and was determined gravimetrically. pretreatments bagasse pretreatments were carried out on eight different ways. the effect of three parameters was investigated on two levels: type of base (naoh versus koh), concentration of base (1% versus 2%) and temperature – time combination (25 °c, 3 days versus 121 °c, 1 hour). ground bagasse (0.3–1.4 mm) at 10% dry weight content (40 g dm in 400 g total mass) was suspended into naoh or koh solution in 1000 ml screw-capped bottles and left at room temperature for 3 days or autoclaved at 121 °c for 1 hour. after pretreatments the mixtures were separated and the solid phase was washed with hot distilled water to remove solubles. filter cake was dried at 50 °c and used for raw material analysis and for enzymatic hydrolysis. hydrolysis pretreated bagasse samples were hydrolyzed at 50 °c at 2% dry weight content in 0.05 m acetate buffer (ph 4,8) by commercially available enzymes celluclast 1.5l and novozym 188 (novozymes) at 20 and 40 iu/ g dm, respectively. as control untreated bagasse was also hydrolyzed. process was carried out in 250 ml screw-capped bottles containing 4 g dm pretreated bagasse in 200 g total mass with stirring (250 rpm). 1.8 ml of samples were taken at start of hydrolysis and after 1, 3, 4, 6, 24 and 48 hours. samples were centrifuged in eppendorf tubes at 15 000 rpm for 5 minutes, subsequent reducing sugar determination was carried out from the supernatant. after 48 hours the hydrolisates were cooled down to 30 °c and moved to the fermentation step. reducing sugar determination hydrolysis was tracked by reducing sugar content determination according to miller’s colometric method [6]. a suitable volume (containing reducing sugar inside the applied calibration range) was pipetted from the samples into test tubes and completed to 1.5 ml by adding distilled water. 3 ml of dns (3,5-dinitrosalicylic-acid) reagent was added and the mixture was boiled for 5 minutes. after cooling down to room temperature 16 ml of distilled water was added, mixed and the absorbance was measured at 550 nm against a blank sample. results were obtained due to the calibration of the dns reagent. 45 fermentation batch fermentations were carried out at 30 °c in 250 ml stirred flasks (250 rpm) with measuring co2 production by an online fermentation module device, developed by nonfood group (bme) and stereo vision ltd. baker’s yeast suspension was added to 2 g dry weight per liter. at the end of fermentation when co2 production ceased, flasks were sampled. samples were centrifuged in 50 ml centrifuge tubes at 9 000 rpm for 5 minutes. supernatant was analyzed for sugar and ethanol concentration by hplc. two different carbon sources were investigated: enzymatic hydrolysates of sweet sorghum bagasse pretreated in different ways. sweet sorghum juice (prior to fermentation the ph was adjusted to 5 by 10% naoh solution). results and discussion sweet sorghum juice total sugar content of sweet sorghum juice was 163.8 g/l with a standard deviation of 7.3 g/l. distribution of diand monosaccharide molecules can be seen in table 1. sweet sorghum juice contains primary sucrose but due to acidification and storage sucrose hydrolyzed partially to fructose and glucose. table 1: composition of sweet sorghum juice initial after fermentationcomponent g/l g/l fructose 14.2±0.3 7.6±0.1 glucose 16.5±1.6 sucrose 133.1±5.8 n/a ethanol n/a 68.7±2.1 160 ml of sweet sorghum juice was inoculated with yeast suspension in a volume to correspond to 2 g dm/l. after approximately 20 minutes to inoculation the gas production started. it reached a constant velocity in 70 minutes for a 8 hour interval which was slowly declining and gas formation stopped in the 24th hour of fermentation, fig. 1. tracking was stopped and broths were sampled for hplc analysis; table 1. hplc detected also some remaining fructose which corresponds to the results of phowchinda and strehaiano [7], they have found that sugar remains in low concentration at the end of the fermentation. based on the initial sugar content and final ethanol concentration conversion value of 78.9% was calculated. this high value corroborates that no complementary salt addition and ph regulation are necessary during fermentation to reach good conversion. 0 1000 2000 3000 4000 5000 6000 7000 0 5 10 15 20 25 time (hour) g as v ol um e (m l) . sweet sorghum juice/1 sweet sorghum juice/2 figure 1: ethanol fermentation of the juice tracked by co2 production in online fermentation module device sweet sorghum bagasse prior to pretreatment ground bagasse contained 41.30±0.07% glucan which can be considered as cellulose content, 17.41±0.15% xylan and 17.62±0.11% lignin, on dry weight basis. pretreatment resulted in an enhanced glucan and xylan content of bagasse. the sum of these was the basis for conversion calculations. glucan content increased from 41% to 45–67% on dry weight basis depending on pretreatment. xylan content reached a maximum of 29.37% using 2% koh at elevated temperature. detailed results are summarized in table 2. highest increase of glucan content was caused by bases in 2% concentration at elevated temperature. at room temperature 1% naoh solution had the same effect on glucan content as the 2% koh. generally it can be said that naoh is a more efficient pretreating agent than koh in both concentrations and at both temperatures. 46 table 2: composition of pretreated bagasse samples glucan xylan pretreatment average std dev average std dev 1% naoh 48.24 0.57 25.16 0.35 2% naoh 50.02 0.52 23.34 0.13 1% koh 44.59 1.19 24.25 0.29 25 °c 2% koh 48.63 0.68 24.44 0.30 1% naoh 49.57 0.67 25.75 0.46 2% naoh 66.86 0.39 28.76 0.35 1% koh 45.78 0.59 24.56 0.74 12 1 °c 2% koh 64.85 0.36 29.37 0.16 decrease of the lignin content was observed, which is in line with what had been expected. in case of alkaline pretreatment it is supposed that the lignin fraction get partly solved. lignin content of sweet sorghum bagasse showed 2–7% decrease depending on pretreatment conditions. during hydrolysis of pretreated material in every case the reducing sugar contentration started to increase rapidly and then the velocity decreased depending on substrate availibility. hydrolysis curves of the room temperature pretreated bagasse can be seen on fig. 2 while the hydrolysis data of the pretreatment experiment performed at 121 °c are summarized on fig. 3. 0 5 10 15 20 25 0 10 20 30 40 50 time (hour) re du ci ng su ga r ( g/ l) 1% naoh 2% naoh 1% koh 2% koh control figure 2: reducing sugar concentrations during enzymatic hydrolysis on 25 °c pretreated materials 0 5 10 15 20 25 0 10 20 30 40 50 time (hour) re du ci ng su ga r ( g/ l) 1% naoh 2% naoh 1% koh 2% koh control figure 3: reducing sugar concentrations during enzymatic hydrolysis on 121 °c pretreated materials in pretreatment at room temperature koh was not effective in 1% concentration the reached reducing sugar content was nearly the same as the one for control sample (6.5 g/l). although the pretreatment with 2% naoh gave the highest reducing sugar concentration (17.0 g/l), the pretreatments with 1% naoh (rc = 12.9 g/l) and 2% koh (rc = 15.4 g/l) can be considered also efficient. hydrolysis of the bagasse pretreated at 121 °c resulted in a more diverse pattern where hydrolysis on bagasse pretreated by 2% naoh and 2% koh gave the 47 highest reducing sugar concentrations, 22.9 and 21.3 g/l respectively. for the calculation of conversion the actual reducing sugar content was divided by the monomer equivalent of the xylan and glucan content of pretreated material. since there were differences in the composition of the pretreated bagasse depending on the applied pretreatment, the order of conversion values is not always the same as that of the reducing sugar contents. the final (at 48 hours) conversion values can be seen in table 3. based on conversion results the bagasse pretreated with 2% bases (both koh and naoh) gave the highest values under room temperature pretreated materials. among on elevated temperature pretreated materials the bagasse treated with naoh showed better results than the ones with koh in both concentrations. the highest conversion value (94.6%) was achieved in case of 2% naoh pretreatment performed at elevated temperature. in ethanol fermentation of various hydrolyzates a short lag phase could be observed, the constant gas formation rate was reached in less than an hour. it took only 3–5 hours for the yeast cells to consume the liberated glucose which after no more co2 gas formation could be detected, fig. 4. table 3: conversion values at the end of hydrolysis (48 h) – based on reducing sugar measurements 0 50 100 150 200 250 0 2 4 6 8 10 12 time (hour) g as v ol um e (m l) 2% koh, 25 ºc/1 2% koh, 25 ºc/2 1% naoh, 121 ºc/1 1% naoh, 121 ºc/2 control/1 control/2 figure 4: ethanol fermentation tracked by co2 production in online fermentation module device the curves recorded by the online fermentation module device show a good parity between the duplicates, indicating that measuring the gas volume is an appropriate method to track ethanol fermentation. largest difference between paralels was about 40 ml (data not shown) which corresponds to less than 0.1 g ethanol (calculated according to the ideal gas law and stochiometry of hexose fermentation). according to the final ethanol concentrations measured by hplc combined hydrolysis and fermentation conversion values were calculated based on the glucan content of the pretreated materials, table 4 as saccharomyces cerevisiae used in the experiments was unable to utilize xylose. these conversion values vary in a wide range, but no correspondence could be observed between them and the hydrolysis efficiency (table 4 versus table 3). some acetic acid formation was detected in nearly every sample suggesting by-product formation. table 4: results of ethanol fermentation and combined hydrolysis and fermentation conversion values ethanol conc. conversion pretreatment g/l % 1% naoh 2.777 ± 0.370 48.2 2% naoh 4.158 ± 0.337 69.6 1% koh 1.160 21.8 25 °c 2% koh 2.413 ± 0.047 41.6 1% naoh 3.107 ± 0.556 52.5 2% naoh 3.829 ± 0.199 48.0 1% koh 1.910 ± 0.004 34.9 12 1 °c 2% koh 4.461 ± 0.355 57.6 conversion pretreatment % 1% naoh 68.4 2% naoh 86.8 1% koh 33.1 25 °c 2% koh 83.2 1% naoh 90.5 2% naoh 94.6 1% koh 57.6 12 1 °c 2% koh 89.2 control 20.4 48 ethanol potential sweet sorghum juice has high and directly fermentable carbohydrate content which can be fermented to ethanol without any salt addition effectively. according to the ethanol concentration reached in our fermentation (68.7 g/l) an ethanol yield (l/ha) was calculated equal to 3 729 l/ha assuming 45 t/ha juice yield. based on the results 4 560 l/ha ethanol yield was calculated for bagasse which corresponds to the highest ethanol conversion rate (69.9% – pretreatment: 2% naoh at room temperature) in case of 45 t/ha bagasse yield with 50% dry weight. adding up the ethanol yields of juice and bagasse an overall ethanol potential of 8 289 l/ha can be calculated. summary sweet sorghum juice fermented during our research had an initial sugar concentration of 163.8 g/l and which a conversion value of 78.9% it yielded 68.7 g/l ethanol. in order to improve the degradability of sweet sorghum bagasse eight different alkaline pretreatments were performed. best hydrolysis conversion based on reducing sugar measurement was reached in case of pretreatment at 121 °c in 2% naoh solution, namely 94.6%. enzymatic hydrolyzates were fermented to ethanol using saccharomyces cerevisiae. highest ethanol concentration, 4.461 g/l was reached when bagasse pretreated with 2% koh at 121 °c was used. concerning conversion, based on the glucan content of pretreated material, the highest combined hydrolysis and fermentation conversion was 69.9% by the pretreatment 2% naoh at room temperature. the overall ethanol yield (l/ha) of the whole plant is about 8 300 l/ha. our research demonstrated that the hungarian sweet sorghum variety ‘monori édes’ is promising feedstock for bioethanol production with a high overall ethanol yield. acknowledgement the authors gratefully acknowledge to otka ts 049849 and nkfp3-00006/2005 for their financial support. novozymes (denmark) is kindly thanked for providing enzymes. references 1. faostat – fao statistics division, http://faostat.fao.org/ 2. checkbiotech, biofuels news, march 8, 2008, http://www.checkbiotech.org/ 3. gnansounou e., dauriat a., wyman c. e.: bioresource technology 96 (2005) 985-1002 4. varga e., szengyel zs., réczey k.: applied biochemistry and biotechnology 98-100 (2002) 73-86 5. hägglund e.: chemistry of wood, new york, academic press, 1951 6. miller g.: analytical chemistry 31 (1959) 426-428 7. phowchinda o., strehaiano p.: thammasat international journal of science and technology 4 (1999) 23-31 microsoft word inner cover.docx hungarian journal of industry and chemistry veszprém vol. 41(2) pp. 109–114 (2013) investigations of bio-gasoil production péter solymosi, ! zoltán varga, and jenő hancsók mol department of hydrocarbonand coal processing, university of pannonia, egyetem u. 10., veszprém, 8200, hungary !email: solymosip@almos.uni-pannon.hu liquid engine fuels are the main source of power for transportation in the passenger sector. it is the projection of the european union (eu) to reach 10% utilisation of renewable fuels by 2020. to achieve this goal the eu created the 2003/30/ec and furthermore the 2009/28/ec directives. for example, the feedstocks of these renewable engine fuels can be non-edible oil plant hybrids, such as rapeseed oils with high euric acid content obtained from special hybrids of rape (e.g. brassica napus) waste lards (used cooking oil and slaughterhouse lards). if the preconditions of utilisation are given with respect to the sustainability and technical compatibility of motor engines and vehicle construction, these bio components can be blended with motor fuels in large quantities. considering the properties of currently used first generation biofuels, the maximum amount of bio-component in engine fuels is approximately 7 (v/v)% fatty acidmethylester in diesel fuels. a reliable production technology of second generation biofuels, which can be blended into diesel fuels is the heterogenic catalytic hydrogenation of triglycerides and waste lards. furthermore, isomerisation can improve the quality of a bio-paraffin mixture. in this context, we studied the isomerisation of bio-paraffin mixtures, which were obtained from the hydrodeoxygenation of vegetable oil. the characteristics of these products were favourable, such as their cetane number being higher than 75, for example. the actual en590:2013 standard does not limit the blending ratio of the paraffinic bio-component in diesel fuels. consequently, these products obtained by the catalytic hydrogenation of vegetable oils can be blended into gasoil by up to 10 % or even more to meet the above eu requirements with respect to the utilisation of renewable fuels. keywords: bio gasoil, hydrodeoxygenation, catalytic conversion, biofuels, blending diesel fuels introduction interest in alternative fuels is on the rise due to the unequal presence of the fossil energy carriers, the periodic rise in the price of fossil fuels, the need for decreasing dependence on crude oil, and the regulations of the european union. they can play a significant role in achieving the eu plan to reach a 10% energy ratio of total fuel consumption using alternative fuels by 2020. thus, the application of the biofuels can be increased to a large degree in the longand medium-terms. for example, in some countries the domestic demand on biofuels could increase to 20% by 2030, along with the decrease in the demand for engine fuels that could be up to 70%. the world’s energy production from biomass could reach 5% by 2050 [4, 5]. accordingly, to ensure the availability of this feedstock the production costs could decrease. to achieve these goals, the eu created several directives (1998/70/ec, 2001/77/ec, 2003/17/ec, 2003/30/ec, 2003/87/ec, 2009/28/ce, and 2009/30/ce). natural triglycerides like vegetable oils (edible or non-edible/waste) can be feedstock for biofuels as alternative energy sources [6, 7], such as special breeding non-edible oil plants [8, 9], animal fats or waste cooking oil [10, 11]. during the conversion of natural triglyceride molecules to bio-gasoil the following reactions take place [1, 2, 3]: • full saturation of double bonds (hydrogenation), • heteroatom removal o oxygen removal " hydrodeoxygenation (hdo reaction, and reduction) " decarboxylation, " decarbonylation o removing of other heteroatoms (sulphur, nitrogen, phosphorous, and metals), • isomerisation of n-paraffins that are formed during the removal of oxygen • different side reactions o hydrocracking of the fatty acid chain of triglyceride molecules, o water-gas shift reaction o methanisation, o cyclisation, aromatisation, etc. during the hdo reduction reaction normal paraffins are formed with carbon numbers that are equal to the fatty acids in triglycerides. in the case of decarboxylation and decarbonylation reactions (hdc) normal alkanes are produced, where the carbon number is one less than that of fatty acids of the original vegetable (fig.1). bio-gasoil is a mixture of gasoil with the boiling range of isoand normal-paraffins. it can be obtained by the hydrogenation of vegetable oils and natural triglycerides 110 from other sources. these constitute the second generation biofuel components of diesel engines. they have good quality characteristics, such as high cetane number, good flow properties, unlimited mixability with engine fuels, and the a production line compatible with existing refinery structures [18, 19]. the actual en 590:2013 standard does not limit the blending ratio of second generation bio-components, while the blending of biodiesel is limited to 7 v/v%. all the above mentioned aspects of alternative fuels can rationalise the investigation of the hydrogenation of non-traditional feedstock sources. these are the vegetable oils that can be obtained from non-edible hybrid oil-plants, rapeseed oil from brassica napus with high euric acid content to produce diesel fuel blending components with good flow properties in colder conditions (below +5 °c). the freezing point of iso-paraffins from bio-sources is lower than for equal chain length normal-paraffins (fig.1) [12-15, 17]. thus, products with high iso-paraffin contents have more favourable cold flow properties (cfpp) with cloud points at lower temperatures (fig.2). the aim of our work was the production of diesel gasoil blending components via the isomerisation of paraffin mixtures obtained from the hydrodeoxygenation of rapeseed oil with high euric acid content. experimental in this work, a diesel gasoil bio-blending component production technique was investigated that meets the requirements of the en:590 standard with the possibility of blending it with engine fuels in unlimited quantities. thus, the hydrodeoxygenation of natural triglycerides and further the isomerisation of the obtained bio-paraffin mixture were investigated over the pt-sapo-11 catalyst [16] developed in-house. the effect of the operation parameters, such as temperature, pressure, and liquid hourly space velocity (lhsv) was studied on the yield, composition, and utilisation properties of the products. experimental apparatus and product separation the experimental tests were carried out in one of the measured sections of a high-pressure reactor system containing two tubular reactors with a isothermal catalyst volume of 100 cm3. the reactor system contained all the equipment and devices applied in the reactor system of a hydrotreating plant. the apparatus is suitable for maintaining if not succeeding the industrial precision of main process parameters. analytical methods the main properties of the feedstock materials and products were determined by standard methods. the hydrocarbon composition of the bio-paraffin mixture was determined by high temperature gas chromatography (shimadzu 2010 gc [column: phonomenex zebron mxt]). process parameters the ranges of the applied process parameters in the isomerisation test on the basis of our earlier experimental results [13, 14, 17, 20-23] were as follows: temperature 300–360 °c, total pressure 20–80 bar, liquid hourly space velocity (lhsv) 1.0 h-1, and h2/feed volume ratio of 400 nm3 m-3. feedstock materials the feedstock of the catalytic tests was a bio-paraffin mixture, which was obtained from the hydrodeoxygenation of rapeseed with euric acid produced in hungary. it was properly filtered as a pre-treatment. the main properties of the feedstock material are shown in table 1. the catalyst was pt-sapo-11 (0.5 % pt), the main properties of this can be found in table 2. figure 1: pathways for the removal of oxygen from vegetable oils figure 2: the freezing point of iso-paraffins as a function of the branch position 111 results and analysis the first step was to produce a bio-paraffin mixture with a boiling range of gasoil from rapeseed with a high euric acid content. the properties of the bio-paraffin are summarised in table 1. the commercially available nimo/al2o3 catalyst was utilised for the production of the bio-paraffin mixture. during the catalytic test the employed operation parameters were as follows: 320– 380 °c, 20–80 bar, lhsv = 1.0 h-1, and h2/ch ratio of 600 nm3 m-3 [8]. it was found that the favourable operation parameters are 340 °c, 40 bar, lhsv=1.0 h-1, and h2/ch ratio of 600 nm3 m-3. the tested catalyst is suitable for the production of bio-paraffin mixtures with high yields from natural triglycerides. due to the moderate acidity of this catalyst, the formation of isoparaffins was lower (5 wt%, fig.3). accordingly, the cfpp of the products was found to be high (27 °c). the product fraction produced in this way, in practice, cannot be blended into diesel fuels in low temperate zone countries. it is necessary then for the improvement of cfpp via the catalytic isomerisation of this mixture with high normal-paraffin content [10, 11]. a large amount of bio-paraffin mixture was produced in a thousand hour, long-term catalytic test. the target fraction of the isomerisation tests was the 180–360 °c boiling range, which is the boiling range of gasoil. the yield of the target products was higher than 94 % in all operation parameter combinations (fig.4). the lighter fraction with a boiling range of up to 180 ºc contains mainly iso-paraffins, which can be outstanding gasoline blending components due to their high octane numbers (>85). we found that by adjusting the operation parameters, such as increasing the temperature, and decreasing the lhsv, the yield of the target fraction was decreased due to the higher yield of the cracking reaction. the target fraction obtained between 70% and 80% table 1: selected properties of the feedstock materials properties rapeseed oil bio-paraffin mixture kinematic viscosity at 40 °c, mm2 s-1 46.56 3.493 density at 15 °c, g cm-3 0.9804 0.7923 cloud point, °c 16 32 cetane number 42 104 compositions, % fatty acid paraffin c16:0 2.3 c140.2 c16:1 0.1 c14 0.1 c18:0 1.2 c15 0 c18:1 28.8 c16 2.3 c18:2 12.4 c17 29.5 c18:3 8.3 c18 28.8 c20:0 0 c19 6.1 c20:1 4.8 c20 5.6 c22:0 0.1 c21 14.8 c22:1 41.8 c22 12.5 other 0.2 c22+ 0.1 figure 3: hydrogenation of rapeseed oil with high euric acid content (diamond: residual triglyceride, square: iso-paraffin content, cross c21/c22 ratio) table 2: selected properties of the isomerisation catalyst used properties pt/sapo-11 pt content, w% 0.5 pt dispersity, % 69 bet surface area, m2 g-1 105 average pore size, nm 0.61 micropore volume, cm3 g-1 0.06 macropore volume, cm3 g-1 0.20 total pore volume, cm3 g-1 0.26 acidity, mmol nh3 g-1 0.13 acidity (rel.), mmol nh3 m-2 cat. 0.0012 112 contained c17–c22 hydrocarbons, as well as other (c13– c16) hydrocarbons from the boiling range of gasoil. the iso-paraffin content of the target fraction increased significantly with the operating temperature (fig.5). the increase of the iso-paraffin concentration occurred at 360 °c then at higher temperatures it started to decrease, due to the thermodynamic hindrance of the exothermic reactions, and the higher rate of cracking reactions. up to ca. 320 °c, mainly mono-branched isoparaffins were formed and were by in large mono-ethylparaffins (fig.6). the freezing points of these products are much lower than normal-paraffins and the cetane number is high enough for a fuel additive. the greater formation of mono-methyl-paraffins over the sapo-11 catalyst can be explained by the reduced formation of iso-paraffins due to steric hindrance. at 340 °c or higher, the formation of multi-branched isomers was significant (fig.6). these compounds have better cold flow properties (below -20 °c), but their cetane numbers are high enough (30–45) as shown in fig.2. the favourable operation parameters in terms of biogasoil yield and iso-paraffin concentration were as follows: t = 360 °c; p = 40 bar; and h2/feedstock ratio = 400 nm3 m-3. the cfpp values of the products as a function of temperature and operation pressures are shown in fig.7. these components have low enough cfpp values to blend into diesel gasoil in moderate amounts. on the basis of the experimental results, it was concluded that the production of bio-gasoil meets the standard’s requirements with a cfpp value of max. +5 °c and 70% iso-paraffin content (fig.8) in the case when the raw material contains 8% c17–c22 isoparaffins. conclusions based on our experimental results, it was concluded that the nimo/al2o3 catalyst is suitable for the long-term production of bio-paraffin mixtures from natural triglycerides via catalytic hydrodeoxygenation. furthermore, the investigated pt-sapo-11 catalyst is suitable for improving the quality of a bio-paraffin mixture that was obtained from the hydrodeoxygenation of rapeseed oil with high euric acid content. during the isomerisation with optimised operation parameters, the yield of the target fraction was higher than 94%. at 340 °c or higher the iso-paraffin content is close to 70%. consequently, the cold flow property of the cloud point is lower than +5 °c. therefore, this approach can produce gasoil bio-blending components with good utilisation properties, such as high cetane number, and low temperature values for cold flow properties. overall, the products described here are suitable for blending components of diesel fuels with concentrations of 10% or higher. figure 6: the composition of the products as a function of operation parameters (pressure: 40 bar, liquid hourly space velocity: 1.0 h-1) figure 7: cffp of the products as a function of operation parameters (liquid hourly space velocity: 1.0 h-1, h2/feed ratio: 400 nm3 m-3) figure 4: the yield of the target fraction as a function of operation parameters (pressure: 40 bar, liquid hourly space velocity square: 1.0 h-1, diamond 2.0 h-1, triangle 3.0 h-1) figure 5: the iso-paraffin concentration of the target fraction as a function of operation parameters (pressure: 40 bar, liquid hourly space velocity: square 1.0 h-1, diamond 2.0 h-1, triangle 3.0 h-1) 113 acknowledgements we acknowledge the financial support of the hungarian state and european union under támop-4.2.2.a-11/1/ konv-2012-0071 and támop-4.1.1.c-12/1/konv2012-0017. references [1] huber g.w., o’connor p., corma a.: processing biomass in conventional oil refineries: production of high quality diesel by hydrotreating vegetable oils in heavy vacuum oil mixtures, appl. catal. a:general, 2007, 329,120-129 [2] da rocha filho g.n., brodzki d., djegamariadassou g.: formation of alkanes, alkylcycloalkanes and alkylbenzenes during the catalytic hydrocracking of vegetable oils, fuel, 1993, 72(4), 543-549 [3] simacek p., kubicka d., sebor g., pospisil m.: fuel properties of hydroprocessed rapeseed oil, fuel, 2010, 89(3), 611-615 [4] schollnberger w.e.: between 2020 and 2030 to be re-joined the course for the global energy mix, erdöl erdgas kohle, 2013, 129(12), 2-7 (in german) [5] shell deutschland oil gmbh: shell study sees great potential for biofuels, erdöl 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[22] kasza t., hancsók j.: isomerisation of paraffin mixtures produced from sunflower oil. hung. j. ind. chem., 2011, 39(3), 363–368 [23] kasza t.; tóth cs.; hancsók j.: application of improved bio-paraffins in diesel fuels, hung. j. ind. chem., 2012, 40(1), 25–31 editorial hungarian journal of industry and chemistry veszprém vol. 42(1) pp. 25-29 (2014) impact of size heterogeneity of core-shell packing materials on chromatographic separation of large biomolecules diána lukács and krisztián horváthb department of analytical chemistry, university of pannonia, 8200 veszprém, egyetem st. 10., hungary be-mail: raksi@almos.uni-pannon.hu the effect of particle size heterogeneity of core-shell stationary phases on the efficiency of chromatographic separation of large biomolecules was studied. it was shown that the column efficiency was affected significantly by the breadth of particle size distribution. the chromatographic efficiency decreased as the heterogeneity of particle sizes increased. although the absolute decrease of separation efficiency was affected by the linear velocity, u, of the eluent, the relative change of hetp was independent of u in the practical range of eluent velocities. the results showed that the affect of particle size distribution was the highest in case of fully porous phases, and it decreased as the diameter of the inner core decreased. it was shown that, in the usual range of particle size heterogeneity of core-shell phase, the peak capacities did not change significantly even at high eluent velocities. keywords: high performance liquid chromatography, particle size heterogeneity, separation efficiency, core-shell phases introduction modern analytical applications of liquid chromatography require efficient stationary phases. before the introduction of core-shell particles – particles with a porous layer surrounding a solid core (fig. 1) – the use of monolithic silica rods [1, 2], or of sub-2 µm particles offered today the most satisfactory results. due to their excessive radial heterogeneity, however, the efficiency of monolithic columns currently is lower than that of sub-2 µm particles. columns packed with fine particles, however, have a low permeability [5–7]. thus, efficiency of columns packed with core-shell particles similar to the columns packed with sub-2 µm particles, but can be operated with the same instruments as those used for conventional columns. the use of core-shell phases is particularly advantageous in the separation of large biomolecules [8]. recently, coreshell phases were optimized for the separation of large biomolecules [9, 10]. besides their unique structure, the high efficiency of core-shell phases is in part due to the very narrow particle size distribution, with a relative standard deviation around 5–10% vs. 20–40% for most totally porous particles [7]. in literature, fairly contradictory information can be found about the effect of particle size distribution, psd, on the separation efficiency. some results suggest that the large particle size variance has no influence on the column efficiency, while according to other data the wide psd decreases the efficiency of chromatographic separation. halász and naefe [11] were the first ones who examined the effect of particle size distribution porous shell non-porous core r core r p � shell figure 1: structure of core-shell particles on the column efficiency in case of particles that were larger than 50 µm. in their work, no experimental result was found for the change of chromatographic efficiency even in case of wide psds (⇠ 40%). two years after halász’s work, significantly smaller, 1-10 µm, particles were tested by endele et al. [12]. no change in the permeability and in the chromatographic efficiency were observed as long as the average particle size remained the same. dewaele and verzele prepared columns packed with mixtures of different compositions of reversed phase particles of 3 and 8 µm and investigated the effect of the psd on the column efficiency [13] with similar results. billen et al. found that the breadth of the distribution of the stationary phase particles has no effect on the chromatographic efficiency as long as no fines are present. in the presence of fines, the efficiency decreases significantly [14]. they emphasized that 26 different conclusions can be drawn about the goodness of a chromatographic column depending on the definition used for the particle size distribution. the effect of the psd on the chromatographic efficiency of sub-2 µm particles was studied by cabooter et al. by analyzing kinetic plots of these phases [15]. in their work, they showed that not just the psd is important but also the separation efficiency one wants to achieve. it was concluded that the greater the achievable number of theoretical plates, the more the psd affects the separation efficiency. in their experiments, the authors obtained better results by using columns with a narrower psd than by using columns of the same dimensions but packed with particles with broader psd. recently, gritti et al. found that the chromatographic efficiency of the columns can be optimized if a small amount of greater particles is added to the sub-3µm particles which leads to better bead homogeneity [16]. manufacturers practice matches these, because on their confession they add a small amount of larger particles to the bathes to optimize the pressure drop along the column. experimental study of the effect of psd on chromatographic efficiency is rather complex, because the column packing procedure is hardly reproducible. it is particularly true when we work with stationary phases which have different psds. the quality of column packing also affects the column efficiency significantly. theoretical models can provide more reliable data on this field because it does not affected by the variability of column packing. the goal of this work is to study the effect of particle size heterogeneity on the chromatographic efficiency of separation of large biomolecules on core-shell stationary phases on a theoretical basis. theory in hplc, one of the measure of separation efficiency is the height equivalent to a theoretical plate, hetp [17]. the higher the plate height, the less efficient the separation is. the general rate model of chromatography [18] permits the calculation of hetp of columns packed by core-shell phases [8]: h(d p ) = 2d l u + k2 1 1 + k2 1 ⌦ u d2 p 30fd p + u d p 3fk f ! , (1) where d p is the diameter of particles of packing material, u the linear velocity of the eluent in the interstitial volume, k 1 the interstitial retention factor, f the phase ratio, d l and d p the axial and pores diffusion coefficients, respectively, and k f the external mass transfer coefficient. ⌦ is given by the relationship ⌦ = (1� ⇢) 1 + 3⇢+ 6⇢2 + 5⇢3 (1 + ⇢+ ⇢2) 2 , (2) where ⇢ represents the ratio of the radius of the inner solid core, r core , to the radius of the particle, r p (see fig. 1): ⇢ = r core r p . (3) accordingly, ⇢ is zero for fully porous particle and one for non-porous particle. for a core-shell particle, the interstitial retention factor is k 1 = (1� " e ) (1� ⇢3) " e [k a (1� " p ) + " p ] , (4) where " e is the external bed porosity, " p is the porosity of the porous shell, and k a is the adsorption equilibrium constant (henry constant). the particle size distribution is usually described by log-normal distribution [19]. the psd of a packing material with mean µ and variance �2 is fdp = 1 d p p 2⇡✓ exp 0 b@� ⇣ ln dp µ + 1 2 ✓ ⌘ 2 2✓ 1 ca , (5) where ✓ = ln ✓ �2 µ2 + 1 ◆ . (6) on the basis of the equations above, the probability density function of local hetps, fh , can be derived by applying the change-of-variables rule [20]: fh = ���� d dh d p (h) ���� frp (dp(h)) , (7) where d p (h) is the inverse function of h(d p ) (see eq. (1)). the observable hetp of the column is the first moment of eq. (7): h col = 1z 0 h fh dh. (8) methods of calculations for the calculation of h col (eq. (8)) a software written in c++ language, using the adaptive quadrature routine provided by gnu scientific library (gsl, v. 1.15) [21]. the integration region was divided into subintervals, and on each iteration the subinterval with the largest estimated error was bisected. as a result, the overall error reduced rapidly, as the subintervals became concentrated around local difficulties in the integrand. these subintervals were managed by the gsl library, which handled the memory for the subinterval ranges, results and error estimates too. the relative error of integration was set to 10 �10. the source code of the program was compiled by g++ shipped by gnu 27 0 50 100 150 200 h e t p [ m ] 0 10 20 30 40 50 eluent velocity [cm/min] = 0.8 m = 0.6 m = 0.4 m = 0.2 m = 0.0 m figure 2: van deemter plots of large biomolecules in case of different standard deviations of particle size distributions of 2.6 µm core-shell stationary phases compiler collection ver. 4.7.2 using o1 optimization. the calculations were performed on a pentium iv computer (2.80 ghz) running gnu linux operating system (debian wheezy). the function fh (eq. (7)) for the numerical integration was derived symbolically by mathematica 8.0 (wolfram research, inc.). h (eq. (1)) was calculated as it is described in ref. [8]. the internal (" p ) and external column porosities (" e ), were 0.05 and 0.4, respectively. the distribution coefficient of the compounds were set to 3. the ratio of the molecule size and the average pore diameter were assumed to be 0.68. the molecular diffusivity was 2.5⇥10�5 cm2/min. the value of “eddy” diffusion term, the internal and external obstruction factors were 1.3, 0.31 and 0.6, respectively. the linear velocity of the eluent was varied between 0.1 and 50 cm/min. the average pore size was 80 å. it was assumed that the quality of the column packing remained identical in all cases. results and discussion in fig. 2 the calculated van-deemter curves of large biomolecules separated on 2.6 µm core-shell phases can be seen. the ratio of the radius of the inner solid core to the radius of the particle, ⇢, is 0.7 representing the typical core size of commercial core-shell phases. the standard deviation of particle size distribution is varied between 0.0–0.8µm that corresponds to 0–30% relative standard deviation. close examination of fig. 2 highlights that the hetp values of large biomolecules are approximately directly proportional to the eluent velocity. fig. 2 shows that the heterogeneity of particle sizes has a significant effect on the separation efficiency of large biomolecules. the separation efficiency is the highest when the variance of particle size distribution is zero (solid black line). increasing breadth of particle size distribution decreases the efficiency of separation. the decrease in the efficiency is more significant at higher eluent velocities. at 10 cm/min, the difference between 1.00 1.05 1.10 1.15 1.20 r el at iv e h e t p 0 10 20 30 40 50 eluent velocity [cm/min] = 0.8 m = 0.6 m = 0.4 m = 0.2 m figure 3: relative van deemter plots of large biomolecules in case of different standard deviations of particle size distributions of 2.6 µm core-shell stationary phases the two extremes (� = 0 and � = 0.8) is less than 5 µm that is approximately 15% of the total plate height at this eluent velocity in ideal case (� = 0). in case of 30, 40, and 50 cm/min the differences are significantly larger: ⇠15, ⇠20, and ⇠25µm, respectively. note, however, that the relative increase is ⇠15% in each case suggesting that the relative change of hetp is independent from the eluent velocity. in fig. 3 the relative hetp, h rel , values of large biomolecules can be seen as a function of eluent velocity. h rel were calculated as h rel = h� h 0 , (9) where h� and h 0 are hetp values at �2 and 0 variance of psd. in fig. 3, it can be seen that raising eluent velocity increases the relative hetp. above ⇠8 cm/min, however, a plateau is reached and the change of relative hetp becomes negligible. it suggests that, at low eluent velocities, the interstitial dispersion is the governing effect in band dispersion. as the velocity of eluent increases, the pore diffusion becomes more and more significant. accordingly, in practice (u > 10 cm/min), it is the dominant effect in band dispersion. fig. 4 shows the effect of core size on the chromatographic efficiency at different breadth of coreshell particle distribution. the linear velocity of the eluent was 15 cm/min that is a typical value in chromatographic applications. it can be seen that, as expected from eq. (1), the efficiency of stationary phase increases as the thickness of porous layer decreases. the effect of width of particle size distribution is less significant at larger ⇢ values. while in case of fully porous particles, the difference is almost 17µm between the hetp values of the two extremes (� = 0 and � = 0.8), it is slightly more than 4µm at ⇢= 0.8. the relative hetps calculated as in case of fig. 3 do not change significantly with the diameter of nonporous core until ⇢ = 0.8 (fig. 5). above that value, 28 0 20 40 60 80 100 120 140 h e t p [ m ] 0.0 0.2 0.4 0.6 0.8 1.0 = 0.8 m = 0.6 m = 0.4 m = 0.2 m = 0.0 m figure 4: hetp of columns packed with 2.6 µm core-shell particles 1.00 1.05 1.10 1.15 1.20 re la ti v e h e t p 0.0 0.2 0.4 0.6 0.8 1.0 = 0.2 m = 0.4 m = 0.6 m = 0.8 m figure 5: relative hetps of columns packed with 2.6 µm core-shell particles h rel s decrease abruptly, at ⇢ = 1 there is no difference between the cases. it can be explained by considering that the separation efficiency of large biomolecules is affected mainly by the pore diffusion (second term of eq. (1)). as the thickness of porous layer of core-shell particles decrease, the diffusion paths reduce as well. as a result, the impact of pore diffusion on band broadening is less and less significant. the difference between the distinct particles vanishes. finally, at ⇢ = 1, only the interstitial band spreading (first term of eq. (1)) influences the efficiency of separation. since d l is not affected by the particle size distribution, h rel s become unity. besides the plate heights, the change of peak capacities were also studied. peak capacity, n c , is a practical measure of separation potential in hplc. n c is defined as the maximum number of components that can be resolved completely between the peaks of the least and most retained solutes [22]. several expressions exist for the calculation of peak capacity [23] depending on the mode of chromatography. in case of isocratic mode of separation, nc can be calculated as nc = 1 4 p n (t max � t min ) ln t max t min , (10) where t max and t min are the retention times of the first and last eluting peaks, and n the number of theoretical 0.90 0.92 0.94 0.96 0.98 1.00 r el at iv e p ea k ca p ac it y 0 10 20 30 40 50 eluent velocity [cm/min] = 0.2 m = 0.4 m = 0.6 m = 0.8 m figure 6: relative peak capacities of columns packed by 2.6 µm core-shell particles; l = 10 cm, t 0 = 10/9, t max = 100/9 plates (n = l/h). in fig. 6 the peak capacities of 2.6 µm core-shell phases can be seen as a function of eluent velocity in case of separation of large biomolecules. the calculated peak capacities were normalized for value that belongs to zero variance of psd. the figure shows that the achievable peak capacity of a column packed with core-shell particles is affected by the heterogeneity of particle sizes. the decrease of peak capacities, however, is significantly smaller than the decrease of column efficiencies (fig. 2). that is because n c is proportional to the reciprocal square root of h . accordingly, 15% increase in the plate height results in ⇠7% loss of peak capacity that is not significant in practice. conclusions since their introduction, core-shell stationary phases became very popular for the analysis of large biomolecules. the morphology of these phases results in less band broadening compared to fully porous particles and thus delivers extremely high efficiencies. in this work, the effect of particle size heterogeneity of core-shell stationary phases on the efficiency of chromatographic separation of large biomolecules was studied. the results showed that slopes of van deemter curves were affected by the breadth of particle size distribution. as a result of widening psd the column efficiencies decreased significantly. the analysis of peak capacities showed that the maximum number of large biomolecules that can be resolved by core-shell phases was not affected significantly, even if the psd was wide. considering that the relative standard deviations of pdss of core-shell phases are between 0.2–0.4µm for 2.6 µm particles, it can be concluded that the efficiency of these phases is affected significantly by the size heterogeneity of the particles. further efforts from column manufacturers in order to improve the psd do not give any more advantages and are not profitable. 29 acknowledgements this research was supported by the european union and the state of hungary, co-financed by the european social fund in the framework of támop-4.2.4.a/211/1-2012-0001 ‘national excellence program’. the research infrastructure was supported by the hungarian scientific research fund (otka pd104819) and the hungarian state and the european union under the támop-4.2.2.a-11/1/konv-2012-0071 project. references [1] nakanishi k., soga n.: phase separation in gelling silica–organic polymer solution: systems containing poly(sodium styrenesulfonate), j. am. ceram. soc., 1991, 74, 2518–2530 [2] minakuchi h., nakanishi k., soga n., ishizuka n., tanaka n.: octadecylsilylated porous silica rods as separation media for reversedphase liquid chromatography, anal. chem., 1996, 68, 3498–3051 [3] kirkland j., langlois t., destefano j.: fused core particles for hplc columns, american laboratory, 2007, 39, 18–21 [4] destefano j.j., langlois t.j., kirkland j.j.: characteristics of superficially-porous silica particles for fast hplc: some 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galassi m., davies j., theiler j., gough b., jungman g., alken p., booth m., rossi f.: gnu scientific library reference manual third edition, network theory ltd. 2009 [22] horvath c., lipsky s.r. : peak capacity in chromatography, anal. chem., 1967, 39, 1893– 1893 [23] grushka e.: chromatographic peak capacity and the factors influencing it, anal. chem., 1970, 42, 1142–1147 microsoft word b_02_faluvegi.doc hungarian journal of industrial chemistry veszprém vol. 39(2) pp. 169-172 (2011) control operation and analysis of the spur gears profile e. faluvegi , l. cristea transilvania university of brasov, department of mechanical engineering b-dul eroilor nr.29, 500036 brasov, romania e-mail: faluvegi.erzsebet@gmail.com the theoretic profile of cylindrical gear can be described with an involute curve detected in the front section. the correct formation of the profile assures uniform transmission of the angular velocity from the conducting wheel to the driven one. profile errors result non-uniform gait, noise and pulsation in the teeth and in bearings. the aim of this paper is the determination of the profile errors using the theoretical profile as reference. the experiment was carried out using a coordinate measuring machine. the real profile is constructed by theoretical equations. the errors are determined comparing these two sets of surfaces, the theoretical and the measured profile. these errors are presented in a graphical user interface (gui) made by the authors. this gui is parameterized, so it can be used to evaluate any gear. keywords: cylindrical gear, involute profile, profile error, graphical user interface. introduction the profile measurement of the gears are discussed in many papers. the gear manufacturers opinion is that the measurement of these components decelerates the manufacturing process. however, if a wrong gear, without any control processes is installed into a machine, causes loss of time and it is much more expensive. therefore, the control operations are very important, as the errors are detected before the gears are used. the wrong profile causes unequal meshing, noise and pulsation on the gears teeth and in bearings. the profile measuring consits of the accurate verification of the gear-cutting machines and the gear cutting tools. the measuring instruments used for the gears profile verification are based on the same principle: the probe tip moves through the profile. the deviation from the nominal involute is shown by a dial gauge or is evaluated by graphical representation in 2d, presented in [1-3]. according to the probe tip movements, these measuring instruments can be divided into two groups. these are the fixed and the moving line methods, as presented in [4]. in [2], there is defined a tolerance range where the measured profile has to allocate. in [5], completely different profile verification methods are presented, using models. these can be: verifying models for the tooth profile gaps and for tooth profile. these control methods are simple, even if, they do not offer a numeric value of errors. as the industrial development rapidly accelerated, the coordinate measuring machines appeared. using these machines the profile and the tooth direction can be measured. these control machines allow the topographical representation by two slanted perspective planes which gives a three-dimensional impression of the flank presented in [2, 3, 6]. the objective of this paper is to present the differences, the errors, between the theoretical and the measured tooth surfaces of the spur gear. to achieve this paper's goal, the measurements were made using a coordinate measuring machine, dea global performance. adequate temperature was provided while measuring the gears teeth surfaces. using mathematical equations the theoretical data were well determined. the errors are presented in a graphical user interface made by the authors and they are also parameterized. the theoretical involute curve the involute curve can be created in two ways, which is a relative movement between the base circle of the gear and the tangential line of the base circle, presented in [4]. according to the equation of this curve, which is generated by a given point p fixed on this line, is defined in fig. 1. the path of the point p is represented in (1), where x(φb), y(φb) are the instantaneous coordinates, rb is the radius of the base circle and φb is the involute curve’s running parameter, which is changing all the time. ( ) ( ) ( ) ( )⎩ ⎨ ⎧ ⋅⋅−⋅= ⋅⋅−⋅= bbbbbb bbbbbb rry rrx ϕϕϕϕ ϕϕϕϕ sincos)( cossin)( (1) 170 figure 1: the involute curve of a base circle with rb radius, [4] flank topography combined measurement tasks can be realized with the coordinate measuring machines. using coordinate measuring machines the accuracy of the pitch, the lead and the profile track can be measured, presented in [2]. this paper focuses on profile measurement, which realization was made using a coordinate measuring machine, the dea global performance. all the measuring process begins with the calibration of the probe tip, which is realized with the calibration sphere. after this, a local coordinate system was defined, in which the coordinate points were saved. the origin of the local system is on the gear rotation axis so that the z axis of the local system coincides with the rotation axis (fig. 2). the gear was fixed on the table of the coordinate measuring machine, without using a rotary table. x y z y oo figure 2: schematic draw for illustration the local coordinate system a probe tip with 2 mm diameter was used. taking into account the papers [7, 8], the probe compensation is turned on and the measuring surface was detected in normal direction (fig. 3). with these measuring settings the detected points are not calculated in the center of the probe tip, but on the measured surface. the gear flank measuring was extended in the whole gear width. this measuring process results 671 points on one flank. the measurement was realized in the following way: the coordinate on the z axis was decreased in small steps while in each step the x and y coordinates were travelling on the profile (z – constant for a step while x and y varies). the limits of these two coordinates, x and y, were the root and the tip diameter. finishing the measurement, these coordinates (x, y, z) were saved for post-processing. the measured surface the measuring direction (perpendicular to the measured surface ) probe tip with 1 mm radius figure 3: schematic illustration of the measuring direction, [7, 8] gui for cylindrical gears the post processing of the measured and theoretical data is realized in matlab software. a graphical user interface, presented in fig. 4, was made by the authors for cylindrical gears. the gui bases on the interface presented in [9]. this graphical user interface has three parts: − a part for introducing the theoretical data of the measured cylindrical gear; − a part for selecting the experimental data of the measured cylindrical gear; − a part for presenting the theoretical and measured coordinate points and evaluating the mean error. introducing the theoretical data first step is to generate the theoretical flanks surfaces. the initial parameters of the cylindrical wheel are introduced, which are: − the module; − the pressure angle; − the number of teeth. with these three parameters the theoretical flanks are constructed using (1), (fig. 5). the base circle, rb, is calculated by the well known formula, [10]: )cos( 2 α⋅ ⋅ = zmrb , (2) 171 part iii part i part ii figure 4: the designed gui for cylindrical gears figure 5: the theoretical surfaces of the measured cylindrical gear importing the experimental data the measured gear coordinate points saved previously in a text file, is loaded by the “add file” pushbutton. in an open file window the measured data can be selected. this dataset is presented on the graphical part of the gui (fig. 6). the two sets of data are presented on a common figure in the gui to compare them. the comparison is realized in the background having two steps: overlaying the two sets of data and calculating the errors between the coordinate points. the surface overlaying uses the pitch cylinder of the gear. the program determines the intersection points between the measured surface with the pitch cylinder and the theoretical surface with the pitch cylinder. identifying the intersection points, a supplemental transformation is needed. this is a rotation along the z axes of the gear. the applied rotation angle is determined between the intersection points (fig. 7). figure 6: the measured surfaces of the cylindrical gear figure 7: the rotation angle determination coordinate points representation and error evaluation in this part of the gui are presented the overlapped surfaces and the mean error (fig. 8). the errors, the distances are calculated using the formula of euclidean distance. 172 figure 8: data evaluation having a pop-up menu in the left corner of the gui the user can move the graphical part (in which the coordinate points are presented). this menu contains three possibilities: zoom, rotate, pan. conclusions the objective of this paper is to present the differences, the errors, between the theoretical and the measured tooth's surfaces of the spur gear. the errors are presented in a parameterized graphical user interface which was realized. the advantage of this gui is that it is possible to evaluate every measured cylindrical gears flanks surfaces by introducing the correct initial parameters. it is possible to expand the presented program with angular teething. acknowledgement this paper is supported by the sectoral operational programme human resources development (sop hrd), id59321 financed from the european social fund and by the romanian government. references 1. gy. erney: a fogaskerekek mérése és gyártásellenőrzése, műszaki könyvkiadó, budapest, (1959), 13–47 2. gy. erney: fogaskerekek, műszaki könyvkiadó, budapest, (1983), 394–443 3. g. goch: gear metrology, cirp annals – manufacturing technology, 52(2), (2003), 659–695 4. d. hollanda: bazele aşchierii şi generării suprafeţelor, editura univ. petru maior târgu mureş, (1996), 149–155 5. c. minciu: precizia şi controlul angrenajelor, editura tehnică, bucureşti, (1984), 128–153 6. t. demian, a. pascu, gh. stoica. aparate de măsurat în coordonate, editura tehnică, bucureşti (1991), 145–153 7. m. ristic, i. ainsworth, d. brujic, contact probe radius compensation using computer aided design models, proc instn mech engrs, 215 (2001) b, 819–834 8. hexagon metrology inc, available on: 9. http://www.sheffieldmeasurement.com/applications/ about-iso-standards 10. e. faluvegi, cs. mate, l. cristea: gui to evaluate the precision of the flanks of the bevel gear 3rd international conference on innovations, recent trends and challenges in mechatronics, mechanical engineering and new high-tech products development, bucharest, (2011) 11. l. sauer, et al.: angrenaje vol i. editura tehnică bucureşti, (1970) << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket 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page 427 page 428 page 429 page 430 page 431 page 432 page 433 page 434 page 435 page 436 page 437 page 438 page 439 page 440 page 441 page 442 page 443 page 444 page 445 page 446 page 447 page 448 page 449 page 450 page 451 page 452 page 453 page 454 page 455 page 456 page 457 page 458 page 459 page 460 page 461 page 462 page 463 page 464 page 465 page 466 page 467 page 468 page 469 page 470 page 471 page 472 page 473 page 474 page 475 page 476 page 477 page 478 page 479 page 480 page 481 page 482 page 483 page 484 page 485 page 486 page 487 page 488 page 489 page 490 page 491 page 492 page 493 page 494 page 495 page 496 page 497 page 498 page 499 page 500 page 501 page 502 page 503 page 504 page 505 page 506 page 507 page 508 page 509 page 510 page 511 page 512 page 513 page 514 page 515 page 516 page 517 page 518 page 519 page 520 page 521 page 522 page 523 page 524 page 525 page 526 page 527 page 528 page 529 page 530 page 531 page 532 page 533 page 534 page 535 page 536 page 537 page 538 page 539 page 540 page 541 page 542 page 543 page 544 page 545 page 546 page 547 page 548 page 549 page 550 page 551 page 552 page 553 page 554 page 555 page 556 page 557 page 558 page 559 page 560 page 561 page 562 page 563 page 564 page 565 page 566 page 567 page 568 page 569 page 570 page 571 page 572 page 573 page 574 page 575 page 576 page 577 page 578 page 579 page 580 page 581 page 582 page 583 page 584 microsoft word inner cover.docx hungarian journal of industry and chemistry veszprém vol. 41(2) pp. 83–108 (2013) corrosion protection with ultrathin graphene coatings: a review andrás gergely ! and tamás kristóf department of physical chemistry, institute of chemistry, university of pannonia, egyetem u. 10., veszprém 8200, hungary !email: gergelyandras@almos.uni-pannon.hu developments in surface treatment or finishing, and modification of structural metals have probably never been so dynamic than in recent years due to the need for new approaches to efficient corrosion protection. the application of coatings is a strategy to be followed to physically separate corrosive environments from metal surfaces. the overall protection efficiency depends on the coating’s barrier properties. traditional alternatives to coating suffer from inefficient physical protection in cases of low film thicknesses and at elevated temperatures. one of the most advanced options is to apply ultrathin atomic films to ensure complete separation of the metallic surface from the fluid media. among the numerous materials and methods, exceptional chemical resistance and high domain size make graphene a promising candidate for constituting ultrathin coatings with interfacial atomic layers adherent and homogeneous coverage to feature firm barrier behaviour. this review focuses on the major efforts with notable results and points out some short comings that must be resolved to serve as a basis for further progress in this field. keywords: ultrathin coatings, graphene, metals, corrosion protection introduction nowadays graphene (gr) is undoubtedly of great interest in many fields of science and engineering. the attention is due to its unique structure, electrical properties [1, 2], efficient heat spreading [3], wetting transparency [4], surface wetting tenability [5], and high reflectivity (mirrors for the beams of he and h2) [6]. the gr’s practical impermeability to gases [7-9] is a result of the combination of its strong structure (carbon bond energy and intrinsic strength are 4.9 ev and 43 n m-1, respectively) and its morphology that makes gr to be the thinnest and most impermeable membrane [10]. in addition, because of its chemical inertness [11], especially against oxidation [12, 13], it is highly resistant to corrosion [14] under conditions where other substances would undergo chemical reactions [15, 16]. as a lightweight mono-atomic coating, gr can function as one of the most advanced electronand ion-transfer barriers at the metal-electrolyte interface, without notably altering optical properties and thermal conductivity of the substrates. gr on metal surfaces is expected to afford oxidation resistance [11] based on its airtight balloon behaviour associated with its excellent barrier nature against oxygen diffusion [7]. nevertheless, coherence, and uniformity of gr coatings are apparently vital to achieve good corrosion protection. in accordance with general expectations, electrochemical properties of gr [17, 18] and its coated derivatives were extensively investigated. the main results achieved recently are described in the following sections that are organised from the viewpoint of synthesis techniques and application purposes. pure graphene coatings direct chemical vapour deposition (cvd) on metal surfaces early studies were inspired to synthesise full surface covering gr films of the highest domain (single sheet) size and integrity to exert impermeability over macroscopically large surfaces. later findings proved the viability of this concept as interfacial construction of thin layers is a promising way to provide durable corrosion protection for metallic substrates [19]. generally, coatings play a vital role in improving surface quality and protection of substrates, since much effort has been made to produce films featuring excellent properties. graphene is certainly one of the most prominent representatives of this kind and subsequently has been studied in almost all scientific and engineering fields. this new generation material has been a novel subject to incorporate into the latest corrosion protecting coatings. achievements in utilising gr as a pure and composite coating were first reviewed by tong et al. [20]. the synthesis and functionalisation of gr were briefly discussed and future perspectives suggested. 84 the simplest way is to grow gr directly on metal surfaces, even though this strategy does not provide the most protective coatings due to low adherence of the inorganic layers as consequence of weak interaction. by direct cvd, metals like nickel [21], cobalt [22], iridium [23], ruthenium [24] and copper [21, 25-27] were coated with gr (on large areas in certain cases) [25] using methane or acetylene as a carbon source [28, 29]. deposition kinetics of carbon and the formation of gr layers on copper were thoroughly explored; surface mediation theory was proved when poly-crystalline films were characterised with the domain size of 10 µm2 [30]. except for assessing the influence of grain orientation, the effect of other growth parameters was estimated. the most relevant findings are as follows: 1. the density of gr nuclei decreased, conversely flake domain size increased as temperature increased and partial pressure of the carbon source decreased. 2. when the pressure dropped below a critical threshold then no gr nucleation was observed and film formations terminated before reaching full surface coverage. 3. to achieve complete surface coverage, the partial pressure of methane must have been increased above 500 mtorr then full coverage was reached within 2 to 3 min. only a supersaturated surface relaying on a critical threshold of partial pressure ~285 mtorr was suggested to drive the formation of fully coated copper substrates with a continuous layer of gr flakes. thus, carbon nuclei formed in the first step under a lower pressure followed by a second step of nuclei growth at a higher pressure, promoting full surface coverage. the effects of these parameters coupled with the investigation of the orientation of metal crystals on gr domain size were quantitatively evaluated at low temperatures [31]. the activation energy for gr nucleation under atmospheric pressure was noticeably higher (9 ev) than under low-pressure cvd procedures (4 ev). such a difference was attributed to copper sublimation at low pressure, because copper evaporation probably has a decisive impact on the desorption rate of carbon from the surface. copper evaporation is restricted under atmospheric pressure, so the activation energy is assigned to the desorption of carbon clusters. close to the melting point of copper, large single-crystal gr synthesis was proposed at the highest possible temperature (probably to maintain the highest rate of interfacial mass-transfer, diffusion coefficient of the decomposed and fragmented precursor agents). by following these principles, single gr crystals with a domain size of ~1 mm could be synthesised. the nucleation density was higher on (111) than on (100) and (101) surfaces without any identifiable preference at higher temperatures [32]. under carefully optimised conditions, continuous films of some layers were obtained on polycrystalline nickel without void areas at the flake boundaries [21]. in that case, ambient pressure cvd was to grow gr films of 1-12 layers, with flake sizes of up to 20 µm for singleand bilayers (bls). an ultra high vacuum (uhv) chamber was not needed [33, 34] to finely balance nucleation and growth processes, instead, thermal annealing was employed leading to the emergence of single-crystalline nickel with grain sizes of 1-20 µm. grain surfaces became atomically flat with some terraces and steps similar to single-crystals usually used for epitaxial uhv experiments and gr growth took place probably via the precipitation of carbon in the metal. because metallic grains may independently affect film thickness as a result of the high density of atomic steps at grain boundaries, multi-layer (ml) nucleation occurred mainly at those areas. by using atmospheric pressure cvd, high quality gr was grown on copper, eliminating all the major difficulties associated with the low-pressure method. parameter optimisation involved evaluating the influence of the thickness, purity, morphology and crystallographic orientation of the metal foils on growth rates and the number of gr layers. scanning electron microscopy (sem) images illustrating gr flakes on polished foils besides xrd patterns of annealed foils are presented in fig.1 showing large copper domains on nr foils. the effects of copper impurities on the density of bilayers are signified; complete surface coverage on aa2 (the purest foil (99.999%) without double layers), aa1 and nr. in fig.2, gr quality is presented at various distances along the tube reactor. the methane concentration was higher at the inlet leading to a greater abundance of mls (darker islands in the images). gradual increase of concentration resulted in the formation of single-layer (sl) gr growth over the entire length. a constant methane concentration yielded a high percentage of mls at the inlet, incomplete coverage in the middle and separated single domains (seen as darker islands) at the outlet. as a method of surface pre-treatment, electropolishing [36, 37] in phosphoric acid seemed to be a good choice to achieve an appropriate degree of surface cleaning and minimised roughness. acetic acid was highly efficient at cleaning the copper surface, but only capable of removing oxidised species without any further etching. etching with ferric chloride solution generally gave similar results to electropolishing despite the greater roughness of the fecl3 treated copper foils. this was probably due to the considerable scale of copper recrystallisation during annealing at temperatures close to the melting point of copper before the cvd process, leading to the evolution of a smoother surface with a low density of defects serving as nucleation sites. additionally, the growth rate was estimated depending on the purity and crystallographic orientation of copper but by far not as much as the partial pressure of hydrogen, because the amount of dissolved hydrogen depends less on the thickness of the copper substrate. crystallographic orientation was found to be an important factor, since the growth rate on the surface of substrates characterised by miller indexes (100) was faster than on (111) surface under ambient pressure. in contrast, at low pressure and temperature the (111) surface facilitates the fastest growth rate [38]. furthermore, optimal conditions to achieve full surface covering films with the minimum proportion of mls might greatly vary with purity of the metal specimens. high purity substrates contribute to the formation of sl 85 films, and low purity metals support the evolution of multi-layer (ml) gr coatings. due to the multiple aspects of the reaction mechanism, optimal conditions for long foils are related to low and varied concentrations of carbon sources along the tube reactors, similarly to the application of temperature gradients (furnace dimensions and its relation to foil size) as well. figure 1: sem images illustrate (a) gr growth rate on polished aa1 and polished nr foils. xrd of annealed aa1 shows (100) orientation, the nr foil with the majority of (111) with smaller contributions from (110) and (311); (b) the effect of copper impurities on the density of bilayers [35] (republished by courtesy of the publisher, elsevier) figure 2: gr films at various distances along the cvd reactor used at atmospheric pressure. (a) gradual methane concentration, single-layer gr growth over the tube reactor; (b) multilayers at the inlet, incomplete surface coverage in the middle and separated single domains at the outlet [35] (republished by courtesy of the publisher, elsevier) 86 the gradual increase of methane concentration from 30 to 100 ppm in the mobile phase helps resolve the changing rate of activated carbon production [39]. because methane concentration near the outlet increases slowly as a result of thermal decomposition and deposition, the main purpose of the gradually increasing methane concentration was to minimise bilayer growth at the inlet over the synthesis duration and to ensure full surface coverage near the outlet with the highest concentration of the carbon source. in fact, optimisation in the case of the atmospheric pressure cvd is more complicated than vacuum ones, which process in long tube chambers with small foils. a steady methane concentration at the inlet surely results in an increasing proportion of mls at the inlet and incomplete coverage at the outlet, with visibly separated flake boundaries. the initial methane concentration of less than 30 ppm exclusively led to sl gr at the inlet. high quality gr grows with >99% monolayer coverage and in some cases films consisted of flake sizes of around 100 µm. high temperature etching with oxygen led to the visualisation of inter-domain boundaries as etching started at these boundaries and expanded into domains in a dendritic pattern, leaving diagonal stripes etch-free. efficient corrosion resistive film properties were reported when experiments were made with samples exposed to air at 300 ºc, showing no sign of oxidation (oxygen enrichment in the metallic phase) over gr coated areas in comparison to bare substrates. according to a similar preference, growing gr layers on copper is favourable, because copper does not dissolve carbon as much as nickel at high temperatures. however, it is also possible to grow mls with highly ordered crystalline structures suing atmospheric cvd with controlled film thickness [40]. both pure nickel and copper were covered with cvd grown gr films detected as covering the majority of the metals in a sl form besides some areas of double and fragmented mls (less than 5% of the coating) [41]. an optical micrograph and raman map with the respective raman spectra obtained from the ni–gr and cu–gr surfaces are presented in figs.3 and 4, respectively. electrochemical tests indicated that such coatings substantially reduced the corrosion rate of the substrates. by raman spectroscopy investigation, sl gr showed sharp g (1580 cm-1) and 2d (2650–2700 cm-1) bands with a small g/2d ratio, whereas ml gr with a high g/2d ratio and an altered, less sharp 2d band were detected. hence, 80 and 60% of the copper/nickel surface was covered with gr as a singleor few-layers coating without uniformity on nickel. scanning electron micrographs of the samples showed different thicknesses of the films with various scales of folding, full of wrinkles and edges. thus, the overall conclusion was reached that coherent sl gr is hard to obtain by direct deposition processes. immersion type corrosion tests indicated open circuit potentials (ocps) or free corrosion potentials of copper and nickel shifted towards the positive potential region. the electrochemical test conditions are summarised in table 1. a potential ennoblement of about 0.3 v was measured for the corroding system of nickel/gr and a cathodic shift of ~0.2 v observed with coated copper samples. the cathodic reduction processes were affected, inhibited by the gr layer on copper and the rate of anodic half-reactions was apparently reduced near the steady free corrosion potential. however, during extended linear potential scanning gr/nickel showed higher anodic currents than uncoated substrates opposed to the modified copper that exhibited no changes in the anodic branch after gr deposition. as an oxidation barrier for liquid and liquid–vapour phase-change cooling systems almost the same heat transfer efficiency was reported using bare and gr/copper surfaces in liquid-phase and two-phase thermal performance tests [42]. after thermal treatment, figure 3: optical micrograph, raman map of ~2700 cm–1 peaks and respective raman spectra of the areas on the ni–gr surface [41] (republished by courtesy of the publisher, elsevier) 87 analysis revealed oxide formation on the entire surface of bare copper and limited oxidation at grain boundaries on the coated substrate. in conclusion, few gr layers acted as a protective layer even under vigorous flow conditions near the boiling point of the fluid phase. graphene prepared by microwave (mw) assisted cvd protected substrates from chemical oxidation when samples were heated under atmospheric conditions in a sequential multi-step procedure with dwelling times from 15, or 30 min to 1 h [43]. a very low degree of chemical oxidation of gr over copper was indicated by xps and the presence of cuprous oxide was found on the entire surface of bare specimens. there are special applications such as steering and focusing elements for neutral atomic and molecular beams in de broglie microscopes [44]. these mirrors utilise the quantum reflection of an atomic beam on metal surfaces since interaction volume is strictly limited to an extremely thin atomic layer of the metals. oxidation and any other form of corrosion or adsorption of atmospheric gases might well lead to far lower reflectivity of the metallic surfaces, and the coatings of more than a few atomic layers are unacceptable. thus, there are exceptional requirements of protective coatings and gr films were expected to provide the solution in this matter too. complete and uniform monolayers could be grown on polycrystalline ruthenium of a columnar structure on fused silica, exposing flat surface facets [45]. single-layer gr protects underlying metals with special structures like concave focusing mirrors and non-planar microelectrode arrays from oxidation under ambient gases. ruthenium was recovered by heating the samples under ambient conditions at 250 ºc for half an hour in an ultra-high vacuum, which was indicated by missing peaks in the oxygen (1s) region of the xps spectra. gr on copper provided mediocre protection against electrochemical degradation in chloride environments [46]. impedance measurements showed increased resistance at the metal/solution interface as anodic and cathodic current densities decreased with about hundred times higher charge-transfer resistance besides about thousand times lower double-layer capacitance in comparison to uncoated copper. ennoblement of the free corrosion potential was also observed and related to the good barrier nature of the film. the protection of copper against corrosion by the growing number of gr layers was in part demonstrated [47]. to enable reliable and complete mechanical blockage by the coating exploiting its impermeability and chemical inertness, preparation parameters were balanced to obtain an appropriate film structure. in fig.5, cyclic voltammograms (cvs) of the bare and passivated copper (the latter with 1-3 gr layers) are shown along with the intensity of oxidative currents besides the atomic force microscope image of the cu/gr after etching. fig.6 depicts cvs of gr-coated copper and grcopper post-treated with aluminium oxide (alox) of different thicknesses, along with the comparison of their peak currents. nonetheless, nanometre size structural defects at flake boundaries were the main source of deficiency, decisive in the often-observed limited protection efficacy. to circumvent this problem, a general strategy is to grow ml island-free gr films. selective coverage of defect areas was achieved by atomic layer deposition, resulting in enhanced protection of ~99%. bare copper in an aerated sulphate solution indicated a pitting corrosion rate of ~9 nm s-1 with a density of ~1 µm-2. the estimated diffusion rate of the reactants was above 1 m s-1 limiting the rate of corrosion processes. figure 4: an optical micrograph, raman map of ~2700 cm–1 peaks and respective raman spectra of the areas on the cu–gr surface [41] (republished by courtesy of the publisher, elsevier) 88 interestingly, in the case of the ml gr films, mass transport remained fast across the sheets and parallel along their planes, which was anticipated by the outcome of a water permeation experiment [8]. this may explain the unchanged chemical inertness of the gr coating, owing to the fast mass transport along and across the layers as etchant species permeate through unburied areas in outer layers and diffuse laterally while finding open areas in layers underneath. inertness to electrochemical reactions could only be attained by thin layer deposition of aluminium oxide (within ~5 nm) by the means of an atomic layer deposition technique on gr/copper. only by this way could unburied regions on the copper surface be made void-free. after 160 atomic layer deposition cycles with a ~16 nm thick passivating film inhibition efficiency was ~99%. this was partly confirmed by tafel analysis giving instantaneous general corrosion rates of ~99% to the copper-single layer gr with 16 nm aluminium oxide and 87% to sl gr/cu, in comparison with bare copper. the approach of the direct loading of a precursor, i.e., acetone on copper then annealing it to convert its vapours into gr was investigated [47]. monolayers formed with nearly 100% coverage after rapid thermal annealing. under optimal conditions, acetone derived films with good crystallinity compared to common cvd grown counterparts. the passivity of the metal coated/masked with sl gr was attributed to remarkably inhibited cathodic reduction reactions and barrier action against the diffusion of anions accessing the underlying substrate. so, sl gr/copper exhibited ca. forty times lower corrosion rates compared to the mechanically polished copper, which means an inhibition efficacy of up to 97%. nevertheless, optimal protection performance was proposed to be achieved by the application of four gr layers with their short-term inhibitions of up to 99%. the corrosion current of the gr/copper reduced by ca. sixty times compared to mechanically polished substrates and the ocp shifted towards the negative potential region. electrochemical impedance spectroscopy (eis) indicated ten thousand times lower electrolyte-metal interfacial capacitance (cdl) of the gr/copper samples than those of the mechanically polished specimens. such a notable drop suggests a significant shrinkage of the exposed surface to the electrolyte. cdl of the gr/copper was ca. three times higher in nacl solution (0.6 m) than in its diluted media (0.1 m), but 6.4 times lower than that obtained in 0.1 m na2so4. cdl and constant phase element (cpe) of the gr/copper samples suggest an electrochemically smaller active surface to interfacial charging (discharging) and adsorption (like a non-faradaic helmholtz capacitor) as the density of conductive pathways decreases besides the lower effective surface roughness than that of the mechanically polished substrate. the cpe was 2.7 times higher than that table 1: metallic substrate, type and growth parameters to obtain gr films by direct cvd deposition substrate preparation type & parameters corrosion test parameters surface of the working electrode (cm2) types of electrochemical test ref. cu & ni cvd grown on metal surfaces flat-cell, 0.1 m nacl 0.07 potentiodyn. pol., scan rate: 1 mv s-1, after min at ocp [41] cu cvd grown flow-cell, mass velocity: 38 kg m-2 s-1 for 9 h, t = 59.5±0.5oc 3.06 none [42] cu mw assisted cvd heating at 150oc, in air at 1 atm for 1 h unknown none [43] ru cvd ambient exposure unknown none [45] cu cvd 0.1 m nacl 0.785 potentiodyn. pol., scan rate: 0.5 mv s-1 from ocp, eis after 1 h [46] cu cvd aerated 0.1 m na2so4 0.24 cyclic voltammetry, scan rate: 10 mv s-1 [47] ni cvd treated at 600 ºc in air, then 31 wt.% h2o2 for up to 2 h unknown none [49] cu & ni cvd & mech. transferred by spin-coating with pmma at 4000 rpm for 45 s 0.1 m naso4 0.4 potentiodyn. pol. & cv, scan rate: 0.005 mv s-1, eis [50] cu & si cvd then transfer of layers with pmma cured at 165 ºc ox. at 225 ºc for 60 min and red. of cu at 450 ºc for 90 min under o2 and h2 flow unknown none [60] cu cvd, thiol func.: slg-cu treated with hcl & h2o then 7.5 mm thiol-ethanol treatment for 2 h lymphocyte transformation test & in vivo experiment 1.4 tests: cu conc. by icpoes, cell viability & stimulation index for lymphocyte [80] ni template directed cvd anode in glucose based electrolyte, ni in ferricyanide catholyte 8 cv and eis [116] 89 measured in nacl solution (0.1 m) and over ten times lower than in na2so4 solution (0.1 m). the resistance of coated copper to corrosion (rcorr) was ca. thirty five times higher than those of mechanically polished ones 6×104 and 1.6×103 ω cm2, respectively. rcorr was appreciably lower than that of nacl and higher than with na2so4 solutions. thus, inhibition efficacy was found as follows; >97% in 0.6 m and >71% in 0.1 m nacl. thus, performance was sensitive to the integrity of the gr film as mechanically polished samples indicated rapid protection efficiency losses with increasing chloride concentrations in the test solutions. rigorous corrosion testing of nickel/cvd grown gr films revealed low intensity oxidation of the substrate by heat treatment. oxidation resistance was effective up to 500 ºc for 3 h, and with durable exposure (2 h) to essential hydrogen peroxide (31 wt.%) solution [49]. both nickel and copper were coated with ml gr films [14] by mechanical transfer. cv measurements indicated a remarkable restriction of the evolution of anodic and cathodic current transients, resulting in the effectively decreased electrochemical activity of the metal substrates. fig.7 depicts cvs of bare and grcoated copper samples, and xps spectra of copper under ambient conditions, at 100 mv and sputter cleaning. region (i) and (ii) contains a shoulder and a peak due to cuo and cu2o/cu, respectively. the third part of the figure shows sem images of cu and gr/cu before and after voltammetry scans. based on tafel analysis, corrosion rate assessment (quantification prediction) for bare substrates gave the following results: ca. 6×10-13 and ca. 3×10-14 m s-1 for copper and nickel respectively. graphene/copper indicated lower corrosion rate of ca. 8×10-14 m s-1 up to ca. seven times less than the bare substrate. the gr/nickel showed a reduced rate of ca. twenty times to 2×10-15 m s-1. with two or four folds of gr layers, the corrosion rate of nickel decreased to 2×10-14 and 8×10-15 m s-1 respectively, which is considered as a notable performance improvement. eis measurements suggested an undamaged state of gr, but the metal surface might corrode at high rates around void areas in the film. the most probable electrical network included resistive elements of the solution; rs ≈ 40 (6.5 ω cm2) and charge-transfer at the interface; initial rct ≈ 3±0.5 kω cm2 due to faradaic processes. the mass transport process was modelled with a warburg element (w ≈ 1.0±10-3 ω-1 s0.5 cm-2) as a semi-infinite diffusion component. the inhomogeneity of the surface was handled by incorporating a cpe as a non-ideal capacitance in the circuit due to the impedance dispersity of the electrical double layer component at the metal-liquid interface. double layer capacitance was best achieved with 2.2 µf cm-2 and the cpe was yo ≈ 7.6±10-5 ω-1 s cm-2. increased resistance coupled in series was caused by the electrical surface resistance of gr (≈1 kω) with a double layer capacitance of ~3.8 cm-2. average fitting parameters were changed figure 6: cvs of (a) cu/gr/al samples, (b) peak currents of cu(0) for cu/gr/al with different aluminium thicknesses and in comparison to cu/gr with 1-3 gr layers (adapted with permission from ref. [47] copyright (2014) american chemical society) figure 5: cvs of (a) bare cu and cu passivated by 1-3 layers of gr, (b) intensity of oxidation currents under various passivation conditions, (c) atomic force microscope image of cu/gr after etching (adapted with permission from ref. [47] copyright (2014) american chemical society) 90 accordingly as follows: cdl ≈ 9±5.0 µf cm-2, cpe: yo ≈ 2±10-5 ω-1 s cm-2, w ≈ 3±0.5 ω-1 s0.5 cm-2, and rct ≈ 10±1.2 kω cm-2. the cdl was ca. ten times lower than measured with bare copper, which seemed to be unrealistic. such a difference is thought to originate from the quantum capacitance of the gr film as a contribution in series with the cdl. this is partly due to the small density of states in the gr, which is in good agreement with the reported quantum capacitance of 7– 10 µf cm-2 [50]. the increased rct of the copper samples in comparison with the one measured at the beginning of corrosion test suggested that the minor proportion of the metal substrate was uncoated with gr, participated in corrosion processes. the proportion of this unburied area was estimated to be unexpectedly high (a ≈ 0.3), exceeding the scale impressed by microscopy images (a < 0.05). such a difference was attributed to the access to larger substrate areas by the diffusing depolarisator species and a subsequent greater proportion of helmholtz capacitance then pseudocapacitance based on electrochemical activation of metallic substrates for anodic reactions. nevertheless, the ability of gr to catalyse, and depolarise cathodic reactions such as oxygen reduction [51] by well-coupling micro-galvanic cells in contact with the poly-aromatic sheets [52] either in planar or concentric forms (according to the function of the surface quinone group on carbon electrodes, i.e. garten and weiss’s mechanism) is almost always a concern. thus, protection efficiency depends largely on the deposition technique, quality, and epitaxial pile structure of the gr sheets, affecting ionic and electrical transport through the films. due to low adherence as a result of the lack of direct grafting or anchoring type chemisorption, direct cvd-grown films are classified as fragile coatings liable for potential polarisation and charging of the surface due to their structural alterations [53]. to increase the small domain size of the flakes, high temperature annealing at ~1035 ºc on the metal surface offers a resolution promoting further development of coherency of the films composed of large domains [54]. however, there are many problems with direct cvd deposition on metals like nickel because of the film formation mechanism of polyaromatic carbon materials. the mechanisms of surface catalysis and adsorption during gr growth on copper were determined [13, 55] to be different from film growth on nickel, which is governed by the combination of catalysis and adsorption as well as solubility and rejection. as the cvd technique enables the synthesis of gr on larger metal surfaces [22, 56], carbon sources are thermally decomposed and fragmented into smaller segments, then atoms arrange into 2d honeycomb lattices. the preparation of cvd grown gr films takes place readily on surfaces with face-centred cubic and hexagonal close-packed crystal structures. methane and ethylene, which decompose at a temperature of ~1000 ºc are used as main precursors [24, 25] even though such a high temperature might significantly affect the metallographic state of the substrate, nucleation and deposition kinetics. metals with close to zero solubility of carbon at the reaction temperature, e.g., copper, deposit via a catalytic mechanism and they are more likely to assist the formation of sl gr instead of ml ones owing to the lack of catalytic effect after the first layer is deposited. thus, the metal surface acts as a catalyst facilitating gr growth in the form of a finishing coating, as deposition is restricted to sl [57]. film growth on metals with mediocre carbon solubility at reaction temperatures undergoes via a complicated mechanism in which carbon diffuses into the bulk metal, e.g., nickel, and is rejected during the cooling process because of the decreasing solubility at lower temperatures. the rate of carbon rejection is critical to the development of ml gr coatings. hence, these films form preferentially instead of sls on copper. further complications may arise by the use of thicker metal specimens because thicker substrates dissolve larger amounts of carbon during the cooling phase since they release more carbon to produce larger amounts of carbon soot. although any process that needs to be scaled-up must be optimised for engineering alloys, there are many results of theoretical interests as well. figure 7: cvs of (a) bare cu and gr/cu samples with the blue line corresponds to the measurement with n2 bubbled through the solution; (b) xps spectra of copper under ambient conditions at 100 mv and sputter cleaning with regions (i) and (ii) are due to cuo and cu2o/cu(0), respectively; (c) sem images of cu and gr/cu before and after cv scan (adapted with permission from ref. [14] copyright (2014) american chemical society) 91 a thesis [58] thoroughly investigated the protection efficacy of direct cvd grown gr on copper, depending on flake size and uniformity, duration and temperature of the heat treatment. key factors leading to firm protection performance both in terms of instantaneous and long-term functions are identified as to eliminate defects in the gr sheets, flakes must build up a flawlessly continuous, coherent, and uniform film. low nucleation and high growth rates must be maintained under low pressure to gain a low density of carbon spots (as probability of deposition decreases) and coherent films with the absence of unburied areas at flake boundaries. the films with large flake sizes were tested in a number of experiments to optimise growth parameters in order to reduce the amount of disorders, defects and void areas. a series of chemical oxidation experiments were performed by heating bare and coated copper foils at various temperatures and for various time frames. ellipsometry helped characterise the thickness of oxide layers on the highly reflective copper. heat treatment was carried out at 120 ºc under air for up to 76.5 hours. the growth rate of copper oxide layers, as an inherent indicator of the oxidation rate, almost linearly increased with time and the difference was only ca. a factor of six between the bare and coated copper foils. corrosion deterioration was located at two spots where air leaked through defects in the gr film and around its flake boundaries. following growth time in low pressure cvd experiments, films were grown in a way that their flakes were not connected. therefore, flake growth stopped before expanding sufficiently to connect with one another. then oxidation was performed at 190 ºc for up to 37 h and 26 min. optical microscopy images revealed a remarkable difference between the bare and coated copper samples. then oxidation was repeated with closely spaced gr flakes investigated by optical and sem. the samples with closely spaced flakes gave very good results after a 30 min treatment at 190 ºc. a 13.5 h treatment led to minor deterioration in the substrate exhibiting black oxide patches on the surface but a 23 h and 35 min annealing resulted in corrosion of nearly the entire surface. in a series of experiments, copper substrates coated with continuous gr flakes were treated at 190 ºc for various periods of time. after a 30 min heating, samples exhibited a fine condition with some proportion of the surface composed of dark copper oxide. after a 10 h and 45 min treatment, migration of the corrosion front on the copper surface (cuo formation) proved to be far advancing and the heavily corroded areas showed a homogeneous distribution in the form of tree roots. optical microscope images after 35 hours of heating indicated heavy corrosion, but the surface was not fully covered with oxides. raman spectroscopy quantitatively characterised copper oxidation, which could proceed at flake boundaries as they feature the least hindrance to mass transport of depolarisators and the large sheets did not damage or etch oxidatively inside. apart from growth related issues, electrochemical aspects of the shortfalls may also be relevant. gr films, acting as physical separators, might take part in electron transport, helping interfacial charge-transfer perpendicular to the surface based on good coupling and ballistic electron transport parallel to the basal plane of the sheets. oxygen adsorption and reduction reactions with low activation energies may further complicate the application of this material, which has been recently underlined in a shortand long-term performance test of gr/cu and si substrates [59]. results clarified that the samples heated at 250 ºc for 6 min showed heavy oxidised spots on bare copper, but little oxidation on the gr coated one. therefore, gr served as a sufficient oxidation barrier helping to preserve the metallic state from chemical oxidation over a short time period at high temperatures. nonetheless, long-term annealing of coated copper led to severe oxidation probably because oxygen diffusion proceeded through discontinuities and defects around gr sheets. after 17 h at 250 ºc, coated copper became heavily oxidised in a way indistinguishable from the bare specimens subjected to the same conditions. similarly, a 15 min treatment at 185 ºc resulted in partial oxidisation of bare copper but coated samples remained almost entirely in a pristine state. nevertheless, after 17 h annealing in air at 185 ºc, both bare and monolayer coated substrates became severely corroded and the products were identified as cupric oxide (cuo) in a stoichiometric ratio. the timescale of protection against thermal oxidation by gr on copper was estimated to be ~1 h at 185 oc and ca. ten times faster at 250 ºc. to explore the long-term protection ability under less severe conditions, bare and coated copper specimens were stored under ambient conditions (at 25 ºc) at low but variable humidity levels for up to two years. bare copper showed relatively slow oxidation at room temperature. gr/cu tested after up to eighteen months exhibited oxide-free condition over the first two weeks but within a month the surface started to tarnish non-uniformly (in several hundreds of micrometres in size). within a few months, most of the regions became heavily oxidised with an estimated oxide layer thickness of tens or hundreds of nanometres. alignment between the substrate grains and gr flakes was concluded to have an influence on oxygen and water diffusion along the surface. after eighteen months, the entire surface had become oxidised as edax analysis revealed a predominant percentage of cuprous oxide (cu2o) in the oxide phase. gr/silicon gave similar results as bare and coated samples were compared to each other after one week under atmospheric conditions, indicating an increased oxygen content of silicon as time of exposure increased. according to the outcome of the series of experiments, short-term oxidation testing reflected some degree of protection but long-term propagation unveiled extensive wet corrosion, similar to that seen in the case of bare copper specimens. the high rate of the wet corrosion of copper is due to promoted galvanic cell formation on a micrometre scale at ambient temperature, especially over long-term exposure. as a special field, the majority of medical applications require metals even today, in bone and joint replacements [60, 61], stents [62, 63] dental materials [64, 65], pacemakers and generators [66, 67]. stainless 92 steel, titanium and cobalt alloys are the most common orthopaedic materials for joint prostheses articulated with a plastic bearing surface for many body parts [68, 69]. there are areas that require the use of alloys of mercury, silver, tin, copper along with limited amounts of zinc, palladium, indium, selenium and titanium in dental surgery [70, 71]. despite the numerous successes, the main disadvantage of most of the alloys in medicine is their corrosion and the resulting physical deterioration (disintegration), quantity loss and contingent toxic side effects. the increased concentration of the aforementioned elements as soluble metals surely leads to chemical reactions of altered enzyme functions. it has been proven that soluble metals released because of corrosion processes can induce an innate monocytesmacrophage response and trigger immune responses, causing toxic, inflammatory, allergic or mutagenic reactions to patients [72]. in addition, corrosion leads to the adverse formation of metallic debris; solid particles and inorganic or organometallic compounds, in the periprosthetic soft tissues causing metallosis [73]. furthermore, the corrosion degraded structural integrity leads to the premature failure and loosening of the metal devices [74]. therefore, corrosion protection of metals used in physiological environments is of paramount importance and needs to be properly addressed for the sake of durable successful biomedical applications. currently ceramic coatings are the most widely used to isolate metals from body fluids, e.g., zirconia transited from a zirconium alloy minimises corrosion in knee implants but the implants roughen with time. nano-size diamond coatings and apatite-nano-diamond composites are promising candidates for the protection of metallic implants [75, 76], but they are highly permeable and greater surface roughness notably decreases their performance. nowadays, atomic thin gr films enhance the bioand hemo-compatibility of implants to some extent [77, 78]. interestingly, the outcome of almost all cell viability tests showed the biocompatibility of gr on the nickel-titanium surface with some protection. after considering these facts, studies focused on clarifying the possibility of application of gr as a corrosion protective film on structural metals used for biomedical devices. the most important future application would be the efficient corrosion protection of metallic prosthetics to avoid serious health problems to patients. in an effort to offer an alternative to protect metallic implants, gr was proposed as a biocompatible and protective film as well [79]. copper was the substrate for cell viability tests to reveal any change in immune response (lymphocyte transformation test) and the metal sensitivity test because of its high toxicity [80] making the experiment sensitive to reflect any significant protection. in vivo experiments served to study the protection of copper in live animals to evaluate gr as a biocompatible film in physiological conditions. corrosion inhibition of copper with gr films was studied by the way of release and accumulation of copper ions in biological aqueous environments of phosphate buffered saline, fatal bovine serum and hank’s balanced salt solution. cell culture figure 8: concentration of cu(ii) ions from different biological solutions: in (a) pbs, (b) fbs, (c) hbss solutions, and (d) cell culture media in the presence of sl (black) and bl gr/cu (red), cu (blue) and blank solutions as controls (pink) measured by inductively coupled plasma-mass spectrometry (icp-ms). all results are presented in a mass ratio (ppm) [79] (republished by courtesy of the publisher, nature publishing group) 93 media were monitored with inductively coupled plasma optical emission spectroscopy (icp-oes) for five days. single-layer gr/copper indicated slightly varied but very good conditions on average. the copper ion release rate was found to be at least an order of magnitude lower compared to bare copper that correlates almost linearly with time. the copper concentration in the solutions was higher when bilayer gr/specimens propagated as compared to those of the tests with sl gr obtained in all solutions. this was attributed to the stronger adhesion of sl films to metallic surfaces than bilayer ones, probably because of the better adaption to surface topography with high flexibility [81]. fig.8 shows the concentration of copper ions detected in different biological solutions such as phosphate buffered saline (pbs), fetal bovine serum (fbs), hank's balanced salt solution (hbss) and cell culture media with sl and bl gr films and blank solutions as controls. cell viability tests indicated almost the same results with singleand bilayer gr/copper samples showing ±2.2 and 2.6% differences respectively compared to the control samples after the first day. nonetheless, the results produced by low concentrations of dissolved copper in test solutions do not mean good results overall because the ion concentration could be much higher in a micro-milieu between the cells and coated substrate. the point of such a difference can explain why the cell viability dropped remarkably by more than 90% over the second, third, and fourth days of the test compared to the gr contained samples although the copper concentration in the solutions remained very low (less than 70 ppm). probably interfacial accumulation of metal ions must play a pivotal role in exceeding the toxicity limit, inevitably triggering lower cell viability. to resolve this problem, a further modification of the metal surface was necessary [82, 83]. by self-assembly monolayer treatment with decanethiol, bare and gr/copper was modified with decanethiol, which was obviously assembled on the bare surface around the boundaries of gr flakes. this is because the seemingly proper protection of copper was accompanied by much improved cell viability over three days (fig.9). the thiol modified sl gr/cu indicated that cell viability was ca. 55.8% after an incubation period of three days compared to sl gr/cu (fig.10). thiol modified copper showed an improvement of up to 2% in comparison to the less than 1% viability observed for bare copper. these results suggest that gr on copper is the major factor for protection, which can be appropriately enhanced by thiol modification. the film was also found to reduce immune response to copper in a clinical setting by a lymphocyte transformation test. animal experiments indicated a positive outcome to coated copper samples tested under in vivo conditions. the copper concentration was less than 3 and ~4.5 ppm in blood samples extracted from living rats implanted with sl coated and bare foils, reflecting the potential of thin gr films in biomedical applications. cvd-grown graphene loading on metal surfaces by mechanical and electrical techniques spin-coating there are a number of techniques to obtain high quality thin films. static and dynamic dispense techniques such as dip [84-86], angle-dependent dip [87, 88], and hot dip spin, spin [89-92], spray [93], flow [94, 95], capillary [96, 97], roll [98], and reverse roll coating [99, 100] have developed thin layers on solid surfaces. by careful design, it is also possible to complement one another, offering a way to be tailored to application demands. optimisation of these techniques is mostly dependent on actual parameters of the fluid phases and molecular or colloid solutions such as concentration, temperature, pressure, partial pressure or volatility of substances and solvents, dynamic or kinetic viscosity, and surface tension of fluid phases. the texture (roughness) of the substrate surface has much less influence (except for the surface energy) on the quality and quantity of casting. drying and curing might later take place. from them, the ones featuring well controllable gr growth are detailed in the following. both spin-coating (sc) and kinetic spray (ks) are relatively novel techniques enabling us to form coatings of good quality on any sort of surface texture regardless of the substrates. sc is figure 9: relative cell viability and concentration of cu(ii) ions as a function of time. (a) relative cell viability vs. time for slg/cu, blg/cu and cu; (b) concentration of cu(ii) ions in the cell culture medium after incubation with slg/cu. blg/cu and cu (calculated from icp-ms). a medium taken from a regular cell culture without cu foils was used as the control [79] (republished by courtesy of the publisher, nature publishing group) 94 suitable to work out and implement practical deposition methods for atom-thick films on various metals, although a different approach must be applied for newtonian [101] and non-newtonian fluids [102]. uniform coatings can be obtained over large areas with reproducible thicknesses in a good controllable manner, but only on planar substrates, which is a major limitation of this technique. sc starts by applying a small puddle onto the centre of the substrate, then spinning commences at initially a lower then, within a matter of seconds, at a higher rotational speed (two stages of centrifugation up to ~3000 rpm). the centrifugal force and centripetal acceleration result in excessive spreading of the fluids on the surface (wetting and covering depend on multiple physical-chemical parameters) and an inevitable loss (can be recycled) around the edges of the substrate until the spin-off time is completed. then, a thin film forms releasing solvents and curing takes place, because of chemical reactions. kinetic spray kinetic spray (ks) utilises a laval nozzle to spray gr colloid solutions at a very high speed and the supersonic acceleration leads to the production of very small droplets that evenly disperse then evaporate reducing the tendency of flake aggregation. besides the uniform and smooth layers, defects in the gr flakes were not observed. hence, high quality film production by ks depends on the energy of the impact stretches gr sheets then carbon atoms arrange into flawless hexagons based on plasticity probing of the gr flakes [103]. transmittance of graphene oxide (gro) film spray deposited on soda-lime glass (from a 10 wt.% colloid solution of gro in ethanol) was 73% and sheet resistance was 19 kω sq-1 using incident light at the wavelength of 550 nm. the electrical conductivity of the coatings increased by up to a thousand times after hydrazine reduction and annealing at 400 ºc. additional thermal annealing at 1100 ºc further enhanced conductivity by ca. 10 times. soda-lime glass with a transparency of 80% and electrical conductivity of 209 s cm-1 (or sheet resistance; rs = 2 kx sq-1) as applied to a 14 nm thick gr film [104]. ks is a reliable technique of wide commercial availability and offers a flexible solution to large-scale using according to recently reported corrosion tests [105-107]. electrospinning electrospinning (es) creates polymer fibres with a diameter range of between 40 and 2000 nm. the fibres can be made from solutions or from fused materials, controlling diameter size through the adjustment of figure 10: relative cell viability of (a) bone cells incubated with sl gr and sl gr/cu-sh, cu-sh and bare cu foil for 3 days. control is a regular cell culture without cu foils; (b) relative cell viability of bone cells incubated with tr-sl gr/cu, bare cu, tr-sl gr/cu-sh, and cu-sh for 1 day; (c) concentrations of cu(ii) ions in blood samples extracted from live rats with concentrations of cu(ii) from normal rats before implantation as control (black square), rats with implanted slg/cu foils (blue triangles) and rats with implanted cu foils (red dots) as a function of time [79] (republished by courtesy of the publisher, nature publishing group) 95 surface tension, solution concentration, conductivity and so forth [108-110]. es occurs when the electric force of the surface overcomes the surface tension of the fluid phase triggering an electric spark, results in the solution being expelled from a syringe forming jet flow impacts and deposits. when the expelled material dries out or solidifies, it forms an electrically charged fibre that can be directed or speeded up by electric forces. so, a polymer solution stored in a syringe is charged to a high electrical potential. as the jet stretches and dries, radial electrical forces cause it to splash repeatedly. dried, solidified fibres are collected on an electrically conductive (metal) screen. by es, the composition of nylon 6-6 and gr was prepared and deposited on porous silica then tested under various conditions [111]. oxidation and reduction potentials in acidic, alkaline, and peroxide solutions were assessed by dynamic polarisation. sem observations determined that treatment with acidic and basic solutions led to the formation of solid aggregates and slightly folded gro flakes. thermal treatment at 700 ºc gave samples with a porous structure. after annealing, a subsequent chemical derivatisation with acidic, basic and peroxide solutions assisted with ultrasonication facilitated the separation of gro sheets, leading to a solid composed of lower dimensional flakes, especially in the case of oxidation. oxidation was carried out in koh and the reduction in h2so4 solution. eis data obtained in the immersion test with a na2so4 solution indicated decreasing interfacial capacitance of the es produced samples with the ny-gro coatings. the eis data calculated at 0.8 hz changed between 1.4–4.5×10-5 and 7.5–8.9×10-7 f cm-2 (depending on the concentration of the electrolyte) with the gro content increasing from 0.4 wt.% to 2 wt.%. electrophoresis electrophoretic deposition (epd) is a promising technique to fabricate functionally graded [112-114] and hybrid composites [115, 116], laminated nano-ceramics [117, 118], and functional, nanostructured films and coatings [119-121]. in the last couple of years, numerous epd applications have emerged as industries count on commercial advantages over other fabrication routes. it is a versatile and cost effective technique with acceptable levels of control over microstructure, stoichiometry, and macroscopic-microscopic dimensions and properties [122, 123]. epd is a two-step colloid process in which electrostatically charged particles, suspended in a liquid medium, migrate according to the electric field towards the oppositely charged electrode. then particles deposit, and flocculate on the electrode surface forming a relatively dense, homogeneously packed, bonded layer. increasing the volume fraction of the nanoparticles and their deposition on the surface of any electrically conductive material is relatively easy. usually, a post-treatment is required to increase the density of deposits and eliminate porosity [122]. sometimes special modifications are required to render surfaces with notable properties such as increasing hydrophobicity by silylation. epd is performed in stable colloid solutions in which there are plenty of electrostatically charged particles migrating in response to an impressed dc electric field and deposit either as a loose homogeneous or compact film onto the oppositely charged electrodes. to make deposits denser and eliminate porosity, additional epd or heat treatment is required. oxide particles, conductive polymers [124] and highly dispersed activated carbon [125] of nearly any size in colloidal suspensions [122] were deposited by this method, reflecting its high versatility. furthermore, by electrophoresis uniform thin layers can be made on highly ragged, complex surfaces. moderate electrical conductivity of the resulting substrates is the only requirement. the sample surface is treated as a whole in a uniform manner, whereas dimensions, deposition rate, uniformity and scale up features are also favourable. epd is a preferable alternative to many other methods like slurry dipping, thermal and plasma spraying, sputtering, and physical/chemical vapour deposition. in the course of thick gr layer deposition on copper by epd [126], deoxygenation of carbon was hinted at by bathochromic shifts in the uv spectra because of the electrochemical configuration and reaction mechanism. potentiodynamic scanning showed positively shifted corrosion potentials and lower corrosion currents (icorr), which suggested only mediocre protection by the thick gr films in the initial phase of immersion propagation. the composite coating of reduced gro was prepared by cathodic epd in an aqueous solution in a symmetrical cell-electrode arrangement [127]. optimum conditions for cathodic deposition were found to produce a thickness of ~40 nm by applying 10 v for 30 s. sem observations revealed the size of the gro sheets being 1–2 µm, covering the surface uniformly. the composite coating was shown to protect copper firmly from electrochemical corrosion. potentiodynamic measurements indicated an ennobled free corrosion potential with slightly reduced anodic and cathodic current branches, suggesting a lower corrosion rate of the composite coated copper compared to its bare form during the early phase of propagation. experimental conditions are summarised in table 2. by electrophoresis, gro was uniformly deposited on a permanent magnet, e.g., ndfeb and the coating was subsequently reduced to partially remove functional groups containing oxygen [128]. the epd gro coating showed substantially better adhesion to the substrate compared to the spin-coated ones. the surface of the bare ndfeb was rough and porous but site-dependent topography of the epd-gro modified samples depended on the amount loaded. the relationship between the increasing thickness and decreasing adhesion of the coating with an extension of deposition time was determined. raman, infrared, and x-ray photoelectron spectroscopy (xps) results reflected the strong adhesion of epd films and that was connected to the koble-type decarboxylation mechanism [129, 130] of the surface yielding gro flakes. an unexpected outcome was that several deterioration reactions were observed in gro. the signal of epoxy groups decreased 96 after deposition, which might be explained by the high anodic electrode potential applied to the working electrode and the large potential drop at the interface. the decrease in current density during potentiodynamic scanning and the positive shift in the free corrosion potential of the system reflected efficient initial protection but lower cohesion and adhesion of the thicker coatings, leading to a poorer protection potential. the gro-acrylic polymer composite fully covered the copper substrates, but the sheets were separated far from one another in an island like manner consequently a large percentage of the surface remained unburied [131]. as for the reagents, solution and cell arrangement, epd conditions e.g. voltage (10 v) and deposition time (30 s) proved to be optimal to obtain crack-free films of an average thickness of 45 nm. an electrochemical investigation indicated insignificant protection performance of the composite coating under immersion propagation. a steady corrosion current extrapolated to the ocp region showed slight changes over the anodic and cathodic regions. a current density drop of 38.3–3.5 µa cm-2 was observed in comparison to the bare copper. a polarisation resistance of the composite covered specimen was assessed by eis, assigning an increased charge-transfer resistance of ~25 ω cm-2 (bare copper: ~8 ω cm-2). stainless steel specimens with an exposed geometrical surface of 100 cm2 were almost uniformly deposited with gro in h2so4 solution by coupling the substrate cathodically [132]. for transferring purposes, chemical and electrochemical etching was developed to delaminate the reduced gro film, giving coherent freestanding membranes or deposit them onto other substrates. by optimising electrophoretic parameters, a low voltage of 3 v was found to consolidate reduced gro layers preferentially aligned in an in-plane direction through a cohesive electrophoretic squeezing force in near volume range of the electrode (cathode). the free-standing gr membrane was reduced, annealed at 1000 ºc then a graphite-like architecture evolved with a d-spacing of 3.42 å and c/o ratio of 16.7. electrical conductivity was of high as 5.5×105 s m-1. graphene coated metals in electrochemical cells and batteries because corrosion is a serious problem in energy storage devices like batteries and fuel-cells [133], the application of gro as a barrier coating to inhibit the corrosion of aluminium electrodes in lithium ion batteries is considered to be an innovative solution. spin-coating was employed to coat aluminium with gro and decrease the corrosion rate when the electrode was subjected to the electrolyte of lipf6 (1.0 m) dissolved in ethylene carbonate and dimethylcarbonate (50:50 vol.%) [134]. sem observations with energy dispersive x-ray spectroscopy analysis and atomic force microscopy (afm) scanning suggested increasing surface roughness of aluminium with lower gro quantity, but its greater amount helped reduce the roughness remarkably. the average roughness of the bare substrate was around 350 nm, which changed to 199-154 nm for the gro loaded one. the thickness of the film showed great epitaxial variety even though the coating was relatively thick. cyclic voltammetry showed a decreasing electrochemical current response of the gro coated electrodes with increasing surface loading. this indicated hindered and impeded chargetransfer through the electrode interface without any direct implication of capacitive and adsorption charge loss in the current transients. accordingly, chronoamperometry curves exhibited moderately changing characteristics (as a consequence of altered electrode kinetics) in the early phase of the transients and table 2: metallic substrate, type and growth parameters to obtain gr film by epd and chronoamperometry substrate preparation types and their parameters corrosion test parameters work-electrode surface (cm2) types of potentiodynamic tests ref. cu gro, epd in sol. c = 1.0 mg cm-3, e=1 v / 10 mm-1, 10 min air ox. at 200 ºc for 4 h, in 30 wt.% h2o2 for 2 min, then 0.1 m nacl solution unknown after 1 h at ocp, scan rate: 1 mv s-1 [131] cu red. gro with polyiso-cyanate cured with haa (hydroxyl acrylic acid), epd for 30 s, at e = 10 v 10 mm-1, 0.1 m nabh4 red. for 5 min 3.5 wt.% nacl, at 25 ºc 1 after 2 h at ocp, scan rate: 1 mv s-1 [132] ndfeb gro red., epd in sol. of 1 mg cm−3 gro, ndfeb anode & pt cathodic dep., e=10 v / 10 mm-1, 3.5 wt.% nacl solution at room temperature unknown eis [133] cu gro isocyanate cured with hydroxy acrylic, then silylation, epd on cu at 10-30 v 10 mm-1 3.5 wt.% nacl, at 25 ºc 1 eis [136] cu chronoamperometry of gro at −1.5 v for 10 min in sol. c = 2 g dm-3, in 0.1 m kcl, at −1.5 v for 10 min, then gro red. nabh4 (0.1m) for 5 min ocp 3.5 wt.% nacl sol. after 1 h 1 eis [138] mild steel epd in ni sol. at ph = 3, iρ = 1 a dm-2, at t = 40oc, gr c=100 mg dm-3 3.5 wt.% nacl, at 27 ºc 1 scan rate: 0.01 v s-1, eis [169] 97 decreasing base currents over the complete timescale because of the smaller electroactive surface. eis spectra suggested a somewhat higher resistance against pitting, the lower susceptibility to localised corrosion. thus, gro restricted aluminium oxidation, behaving as a charge-transfer barrier. otherwise, the lower capacity and potential of the cells should have been measured by the set-ups with the gro loaded electrodes during charge–discharge testing. instead, surprisingly the opposite was reported. nevertheless, enhanced cyclelife stability (lower rate of capacity loss) of the modified electrode compared to the cell configuration with bare aluminium is of course self-explanatory. self-discharge was lower as a decreasing rate of open circuit voltage decline was observed to the modified aluminium samples. gro films did not show any corrosion and the underlying native oxide layer remained intact under test conditions. microbiologically induced corrosion (mic) severely limits the structural integrity and lifetime of metallic structures in technological processes and applications because of frequently evolving mechanisms, i.e., crevice and pitting local corrosion phenomena. a microbial fuel cell (mfc) is a galvanic cell producing an electric current that causes bioelectro-chemical oxidation of organic substances on anodes and abiotic reduction on cathodes [135]. mfcs have been used as a galvanic tool to simulate extracellular electron transfer mechanisms of microbes and the bio-electrochemical oxidation of organic substances. in addition, metals are not used as anodes in mfcs due to their fast galvanic corrosion. owing to this, gr films are employed as barrier coatings and the corrosion rate of the working nickel electrode was evaluated by galvanic coupling in the mfc set-up [136]. regarding the experiment, it was determined that the geometrical ratio of the working and counter electrodes was the guarantee to maximise, and concentrate current densities on the working electrode. nevertheless, the cell design did not allow the assessment of adequate kinetic parameters (general corrosion rate) because of the large uncompensated ohmic drop and unfavourable cell geometry. these are all relevant in dc techniques, although inadequate voltammetric data could provide a rough estimation, even though 5 mv s-1 was higher than recommended and might have resulted in the considerable rate of adsorption and pseudo-capacitive current during the measurement. in relation to the impedance measurement and its evaluation, these data are even more sensitive to inappropriate cell design. the protection efficacy of the gr film was assessed under realistic operating conditions, the bare and coated nickel electrodes represented a 3d microporous structure. the overall outcome confirmed a retardation of corrosion processes by the gr film for extended periods. cv scanning showed decreased current transients of coated nickel, which was ca. ten thousand times lower than measured for the bare nickel electrode based mfc after a propagation for 2800 h. nickel dissolution rates of the gr coated anodes were at least ten times lower than the baseline (uncoated) electrode. eis characterisation confirmed impeded mic on the gr/nickel for ca. 40 folds in comparison with uncoated electrodes. the effective masking of nickel from the mixture of microorganisms and their metabolic products was concluded. composite graphene coatings physically mixed and in situ polymerised mixtures chronoamperometry was successfully employed to prepare gr coated copper, starting from an aqueous colloid solution of gro [137]. as a result of the epd process, a seemingly compact and void of area without coating; and polymer film with gr inclusion was obtained. nevertheless, the distribution of gr flakes was highly uneven and inhomogeneous (random), whereas the sheets showed various degrees of folding and overlapping in the polymer matrix. in addition, the fast reduction of gro in the polymer proves the high permeability of the matrix, although it reached a thickness of several micrometres. on the other hand, the coatings with reduced gro provided moderate protection for copper with an initial inhibition rate of 94% drawn from the potentiodynamic polarisation measurement data (at nil impressed potential). the corrosion rate reduced to 0.2 mm yr-1 from the rate for pure copper of ca. 3.65 mm yr-1. this assessment was only made at the beginning of the immersion test (after an hour), whilst waiting for stabilisation of the freshly installed cell set-up. in comparison with the eis investigation, the composite coating provided electrical insulation and ionic diffusion hindrance to the copper surface. so, the protection was related to the increased polarisation resistance of gr loaded coatings of ca. 26 ω cm2 compared to bare copper of 9 ω cm2. intrinsically conducting polymers (icps) like electroactive polyaniline (pani) have been widely used materials for some time providing corrosion protection regardless of the long-standing disagreement over the anodic protection mechanism and the generally less effective barrier nature. pani is a preferable electronconducting polymer with favourable properties over other alternatives. under optimal conditions, the protection mechanism leads to the formation of a passive (dense) metal oxide layer [138-140]. to increase protection performance, many substances such as well dispersed clay [141] with an aspect ratio of ca. 200 was aimed at lengthening mass transport pathways through the composite films for all redox active species. these polymer-clay mixtures exhibited notable protection improvements over neat polymers. besides the several attempts to combine of carbon nanotubes (cnts) with organic [142-156], inorganic, and metal [157-160] matrixes for corrosion protection and resistance, respectively, there are examples from the literature about testing gr-polymer composites for various purposes [160-162]. the main focus of these works was the exploitation of high relative aspect ratio of gr (ca. 500) [163] in comparison to exfoliated clay minerals. hence, gr is a key filler in advanced gas barrier materials, motivating studies to 98 achieve very low oxygen permeability using low filler contents (compared to neat polystyrene and the best polymer-clay mixture known at that time) [164] and underscore the possible obliteration of traditional claypolymer composites [165-169]. thus, a carefully designed and well-prepared pani-gr mixture exhibited outstanding impermeability characteristics against the diffusion of molecular oxygen and water vapour versus neat pani and pani-montmorillonite using a filler content of 0.5 wt.% and the excellent protection performance of steel substrates. potential ennoblement of steel electrodes with coatings of increasing gr content was considerable and an approximately fifteen times lower steady corrosion current was reported. the main reason for the success is mostly related to the high dispersity of gr in the composite of microscopically isolated and macroscopically non-percolating distribution [170]. experimental conditions are summarised in table 3. lower electrical and ionic conductivities always provide better corrosion protection. therefore, metals coated with gr filled composites of electrically less or non-conducting (practically insulating) matrices like epoxy (in the case of high dispersity) can behave as a super-hydrophobic interface [171-176]. these composites are characterised by a water contact angle of at least 150º making them repellent, resistant to water absorption [177] and their exceptionally good antiwetting properties results in good corrosion prevention potentials. the nano-casting prepared epoxy-gr composite featured high hydrophobicity and provided excellent protection for cold-rolled steel (crs) panels [178]. fig.11 shows tafel plots of bare, epoxy, hydrophobic epoxy (he) and hydrophobic epoxy-gr composite (hegc) coated crs panels. the open circuit potential of the immersion tested steel panels coated with epoxygr showed appreciable ennoblement of ca. 0.3 v and ca. ten times lower corrosion currents compared to neat epoxy coated steel. the much higher polarisation resistance was partly attributed to the more hindered mass transport through the gr loaded coating (with less than half the oxygen permeability) and access to its interface on the fluid side as a result of the finely patterned structure of the outer surface. the reproducibility of the data is questionable because parameters were not representative to properly describe the kinetic processes of the system, proceeding at the metal-solution interface. as in other cases, electrochemical techniques gave instantaneous rate assessments (in the first 30 min of the tests). thus, the reported data are not suitable for forecasting long-term corrosion rates. table 3: metallic substrate, type and growth parameters to obtain gr films by spin coating and solution casting. types and settings of corrosion tests and electrodes with the reference number of the article substrate preparation type and parameters corrosion test parameters work-electrode surface (cm2) types of electrochemical tests ref. porous silica electrospin gr-nylon 6-6 in formic acid agitated for 12 h then add. of gro, es at 12 kv, flow rate: 0.2 ml h-1 for hours, electrode: polymer solution 90 wt.% of formic acid with 0.36-2 wt.% gro and ny potentiostatic oxidation in koh (0.5 m) for 3.5 h, reduction in h2so4 at ph = 2 for 8 h, eis in na2so4 in (110-1-10-2-10-3 m) for hours unknown potentiostatic treatment, potentiodynamic polarisation, scan rate: 100 mv min-1, eis [112] alox gro sonication in ethanol then spincoating lipf6 in ethylene carbonate and dimethyl-carbonate (50:50 vol.%); at 1.0 m 100 cyclic voltammetry, chronoamperometry, potentiodynamic polarisation and eis [114] cu spin-coating of gr with acetone (20 cm3 cm-2) then rapid annealing 8001000 ºc for 3 min seawater 3.0–3.5% nacl 0.25 potentiodynamic polarisation, scan rate: 2 mv s-1, eis [136] steel pani-gr comp. (nmp complex and casting) 3.5 wt.% nacl solution unknown potentiodynamic polarisation [153] coldrolled steel gro red. with n2h2, pressing powders then curing (thickness: ~120 µm) 3.5 wt.% nacl, at 25oc 1 potentiodynamic scanning at 10 mv min-1, after 30 min eis [161] low alloy steel 2 wt.% gr/mwcnt/pei & 20 wt.% gr/pei comp.-s, dispersion in paa cured at 150 ºc for 5 min, then 250 ºc for 5 min for imidisation 3.5 wt.% nacl solution 9.62 potentiodynamic polarisation (scan rate: 1.67 mv s-1) [7] figure 11: tafel plots of the (a) bare, (b) epoxy-coated, (c) he coated, and (d) hegc-coated crs electrodes [178] (by courtesy of the publisher, elsevier) 99 a more exotic approach is to develop metal-gr composites for corrosion protection, although this strategy may have more disadvantages than advantages like with the metal-cnts [179-182] because of the cnt activity towards catalytic oxygen reduction reactions [183-185]. electrodeposited thin films of nickel matrix with gr inclusion indicated a slight improvement in general protection performance; ennobled ocps by ~0.1 v and steady corrosion currents reduced by over 50% were observed in comparison with pure nickel coated mild steel [186]. as a result of greatly affected nucleation and growth rate, measurement results are much more related to the highly altered crystalline structure of the nickel host matrix (lower electrical conductivity was unfortunately not characterised) as a consequence of the inclusion of gr sheets, but differences in the texture and hardness of pure nickel and the gr-nickel coatings were reported. similarly to many other works, protection efficacy was not evaluated and reported over long-term immersion testing. on the one hand, the tafel analysis of ni and ni–gr performed in 3.5 wt.% nacl solution (in fig.12) was carried out using high voltage rate scanning without ohmic drop compensation, leading to distorted current legs over both potential regions (from the open-circuit or free corrosion potential of the electrode). a less representative transient is due to the low proportion of faradaic charge-transfer current primarily assigned to the credible corrosion rate assessment. probably due to these reasons, there is not much difference between the given corrosion currents of ni and ni-gr samples. the gr incorporation, cathodic and anodic tafel regions exhibited almost ideal symmetry. this should mean the same scale of activation (expressed as a transfer function) in the cathodic (reduction and deposition) and anodic (oxidation and dissolution and/or deposition) processes. this feature is a kind of ineffectively blocked electrode behaviour, a quite reversible characteristic with less viable hindrance either in the anodic or cathodic processes. this suggestion seems to be confirmed by the reported similar corrosion currents. on the other hand, the adequacy of eis data may also be doubtful as basic requirements of system stability (in the time domain), linearity (immediate response), and causality (the unquestionable relationship between perturbation and type-degree of response) might not be met. the time frame of 5 min to wait for a stationary or a steady-state condition then making measurements is in itself questionable. the large variation in the solution resistance (between the pure and composite ni coating) is surely inadequate. in addition, the highly varied interfacial and coating resistance (swop between them) along with a hundred times difference in the coating capacitance are also unbelievable and can lead only to false interpretation. the depressed semicircle is a result of the complexity of the ni/gr electrode interface. the electrode was a porous electron and ion conductor and such systems need to be carefully handled (modelled with at least two transmission lines) when evaluation of impedance spectra in relation to structure and mechanistic behaviour of a complicated interface comes into the picture. therefore, presented data and the corresponding evaluation are not appropriate and even misleading. an innovative approach is the composite of multiwalled cnts (mwcnts) and exfoliated gr embedded in polyether-imide (pei) serving as a coherent and porefree matrix [187]. this endeavour was made in an attempt to achieve a uniform dispersion of the nano-size additives in the host matrix (without functionalisation of the filler phase) and good adhesion of tailored pei to the substrate, facilitating the maximum attainable corrosion protection performance. the protection mechanism was delineated according to the following: the composite protects steel alloys by a complex, active–passive way, serving as a physical barrier to water permeation against the evolution of ion channels to the metal surface and passivating metal surface by electron depletion at the interface based on the schottky barrier effect [188-190]. figure 12: tafel curves of ni and ni–gr materials [186] (by courtesy of the publisher, elsevier) figure 13: cryo-fractured sem images of (a) and (b), pei, (c) and (d) 2 wt.% nfg/mwcnt/pei, (e) and (f) 20 wt.% unfg/pei [187] (published with permission from the! american ceramic society bulletin) 100 exfoliated but non-functionalised gr was derived from ultrasonication in a solution of n-methyl-pyrrolidone (nmp). pei as a host matrix was selected for its flexibility under a high glass transition temperature (155 ºc), thermal stability, firm resistance against radiation and appropriate interaction with carbon fillers via π–π stacking [191-193]. in situ synthesis and the imidisation protocol yielded coatings with appropriate adhesion properties to the steel surface of a thickness of 15– 20 µm, whereas agglomeration and phase segregation of the fillers were low with the mwcnts. the sem investigation revealed a fairly smooth surface finish without cracks or visible pinholes in the coatings. no phase segregation of the gr and mwcnt fillers was observed in the mixtures around the interface as its clearly seen in fig.13 of the cryo-fractured samples of non-functionalised gr (nfg), carbon nanotubes and pei in 2 wt.% (c and d) and nfg/pei of 20 wt.% (e, f) in comparison with pure pei (a and b). ocps were positively shifted by ~0.6 v, meaning a remarkable ennoblement. this was inferred, although substrates with high resistance coatings showing notable positive potentials must be at least partially attributed to the potential drop through the coatings [194] as a result of masking the real corrosion potential of the metalcoating interface to various extents. a potentiodynamic test indicated current densities of several orders of magnitudes lower (~10-9 a cm-2) for composite coated specimens compared to bare low-alloy and galvanised steel samples with current densities of ~10-5 a cm-2. immersion tested samples were characterised quantitatively with regards to the perspective of corrosion rate or protection of steel substrates by weight-loss measurement (according to the astm-g1 protocol) after 3,144 hours. the substrate coated with 20 wt% gr-pei performed best with ca. thousand times lower corrosion rates (ca. 8.5×10-4 mm year-1) than bare low-alloy steel samples (ca. 1.2×10-1 mm year-1). however, the pei film containing gr and mwcnt (ca. 9.2×10-3 mm year-1) manifested a moderate average corrosion rate of ca. 5.5×10-4 mm year-1 compared to the neat pei film. concluding remarks overall, it is evident that atomic pure graphene films lack uniformity and partly this leads to insufficient instantaneous protection performance. therefore, some sort of physical and/or chemical post-treatment is needed to facilitate long-term protection performance from direct deposition techniques, the broadly and thoroughly investigated cvd technique is undoubtedly a viable alternative when large-scale continuous surface finishing is highly demanded. however, it is far from the best choice when corrosion protection efficiency and durability are the priorities, due to the complexity of growing cohesive films on the surface of metal substrates with preferable orientation of the grains, and weak adherence of gr films sensitive to mechanical and surface charging effects. when performance is an essential preference then spin-coating, kinetic spray, electro-spinning, and electrophoretic deposition should be employed depending on the complexity of the surface, conductivity of the substrate and additional technological aspects in relation to further processes. among them, spin-coating and kinetic spray techniques develop good quality and homogeneous coatings of greatly varied thicknesses. thin and ultra-thin films feature high a dispersity, and an even distribution and sometimes even improved quality of the nanoparticles. when thicker coatings are obtained on electrically conducting substrates with strong adhesion to complex surface geometries without the matter of a certain degree of alteration of the nanoparticles, then electrophoretic deposition must be used. with respect to the 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(eds.): handbook of corrosion protection, theory and practice of electrochemical protection processes, third edition, golf publishing company, houston tx, usa, 1997 page 1 page 2 page 3 page 4 page 5 page 6 page 7 page 8 page 9 page 10 page 11 page 12 page 13 page 14 page 15 page 16 page 17 page 18 page 19 page 20 page 21 page 22 page 23 page 24 page 25 page 26 page 27 page 28 page 29 page 30 page 31 page 32 page 33 page 34 page 35 page 36 page 37 page 38 page 39 page 40 page 41 page 42 page 43 page 44 page 45 page 46 page 47 page 48 page 49 page 50 page 51 page 52 page 53 page 54 page 55 page 56 page 57 page 58 page 59 page 60 page 61 page 62 page 63 page 64 page 65 page 66 page 67 page 68 page 69 page 70 page 71 page 72 page 73 page 74 page 75 page 76 page 77 page 78 page 79 page 80 page 81 page 82 page 83 page 84 page 85 page 86 page 87 page 88 page 89 page 90 page 91 page 92 page 93 page 94 page 95 page 96 page 97 page 98 page 99 page 100 page 101 page 102 page 103 page 104 page 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438 page 439 page 440 page 441 page 442 page 443 page 444 page 445 page 446 page 447 page 448 page 449 page 450 page 451 page 452 page 453 page 454 page 455 page 456 page 457 page 458 page 459 page 460 page 461 page 462 page 463 page 464 page 465 page 466 page 467 page 468 page 469 page 470 page 471 page 472 page 473 page 474 page 475 page 476 page 477 page 478 page 479 page 480 page 481 page 482 page 483 page 484 page 485 page 486 page 487 page 488 page 489 page 490 page 491 page 492 page 493 page 494 page 495 page 496 page 497 page 498 page 499 page 500 page 501 page 502 page 503 page 504 page 505 page 506 page 507 page 508 page 509 page 510 page 511 page 512 page 513 page 514 page 515 page 516 page 517 page 518 page 519 page 520 page 521 page 522 page 523 page 524 page 525 page 526 page 527 page 528 page 529 page 530 page 531 page 532 page 533 page 534 page 535 page 536 page 537 page 538 page 539 page 540 page 541 page 542 page 543 page 544 page 545 page 546 page 547 page 548 page 549 page 550 page 551 page 552 page 553 page 554 page 555 page 556 page 557 page 558 page 559 page 560 page 561 page 562 page 563 page 564 page 565 page 566 page 567 page 568 page 569 page 570 page 571 page 572 page 573 page 574 page 575 page 576 page 577 page 578 page 579 page 580 page 581 page 582 page 583 page 584 microsoft word b_20_nadasi_r.doc hungarian journal of industrial chemistry veszprém vol. 39(2) pp. 229-232 (2011) on-board applicability of mems-based autonomous navigation system on agricultural aircrafts p. nádasi , i. szabó szent istván university, faculty of mechanical engineering, 2103 gödöllő, páter károly u. 1, hungary e-mail: nadasi.peter@gek.szie.hu in practical terms of agricultural flights, the success of the mission has been largely determined by the airmanship, experience and visual reference of the pilot. by using microelectro-mechanical system (mems) devices, a complex onboard system can be designed which increases flight safety and improves the efficiency of pest control. with the help of dead reckoning navigation system using mems accelerometers and gyroscopes, the spatial attitude and geographic location of the aircraft can be obtained. by measuring the surrounding local air pressure and applying the mathematical model of particular aircraft types´ vortex and stream systems and the properties of the pesticides deployed the accuracy of the crop spraying can be improved while the spraying device can be operated automatically in a control loop. with real-time data processing the pesticide coverage is more uniform, the overlap spraying of the fields can be avoided, and the lateral distance limit between fields and urban built-up areas can be better controlled. it follows that the environmental load can be decreased and the usage of chemicals and pesticides can be optimized. keywords: agricultural flight, pest control, on-board systems, dead reckoning navigation, mems devices there are a lot of applications of mems-based devices in automotive and defence industries. now it is about to become common in the commercial aerospace industry, as new perspectives are opening up in general aviation. this paper focuses especially on their deployment onboard agricultural aircrafts, where pest control and crop spraying efficiency can be dramatically improved, thus the environmental load can be minimized. general overview the early commercial deployment of microelectromechanical system (mems)-based accelerometers and gyroscopes were in the automotive industry in the late 1980´s in airbag systems. today they are widely used in active restraint systems, dynamic stability control, suspensions and in several on-board electronic devices. in the aerospace industry the laser-gyros provided the best performance for a very long time but now the mems-based devices can be constructed with the same accuracy yet with better resolution and long term stability. mems-based inertial measurement units (imu) are now certified for primary navigation equipment onboard of general aviation aircrafts. according to yazdi et al. [1] the accuracy of mems devices has doubled every second year since 1991. this could help compete with the accuracy of the navstar gps system which is now used for secondary navigation equipment only. the main reason not to use navstar gps as a primary source is its availability. its operation is not independent (operated by us department of defense), can be jammed, sensitive to interferences and requires continuous view of at least three satellites for a 2d fix. on the other hand the mems-based imu system is a self contained, low cost, easy-to-integrate solution and can be deployed on-board of every vehicle even on those which have no sky view (e.g. subways, trains in tunnel, submarines, etc). the inertial grade mems gyros (table 1) and the navigation grade accelerometers (table 2) are now providing the required accuracy and performance for the construction of a high-end airborne navigation system. the original specification of navigational grade accelerometer in table 2 has been altered from ±1g to ±10g to conform to the general aviation requirements. most utility category aircrafts – like the agricultural aircrafts which are now in our focus – are designed for -1,8g to +4,5g load. for aerobatics or military usage a ±15g range would be a reasonable choice. agricultural aspect a generic agricultural flight profile is executed at 5–30 m above ground level with a 120–160 km/h velocity according to the visual flight rules (vfr). the pilot relies mostly on his perceptions and the senses transmitted by his vestibular system. during the crop spraying fly-bys the standard cockpit instruments are mostly used for crosschecks only. they are the most important contributing factors which influence the efficiency of the crop spraying. that is why the success still depends mostly on the 230 flight experience and airmanship of the pilot. according to the national regulations, crop spraying cannot be executed when the actual wind component exceeds 6 m/s and at least a 500–2500 m boundary strip shall be kept between fields subject to different chemicals and between fields and built-up areas. as a consequence, significant sizes of fields may be left out of treatment and the efficiency of the spraying is not uniform or optimal. that is why the pilot should be supported during his mission. the utilization of the mems devices on-board of agricultural aircrafts is now in an early stage. our main goal in this article is to provide a concept for the deployment of mems-based imu navigation systems which could improve the flight safety as well as the efficiency of the crop spraying and pest control. mems imu on board the aircraft flies relative to the wind which is expressed with the value of the true airspeed (tas). from the actual wind component (wc) and the tas the aircraft’s relative speed over the ground (ground speed, gs) can be obtained. tas ± wc = gs (1) usually the airspeed indicator in the cockpit indicates the so called indicated airspeed (ias) which is subject to position, compression, instrument and density errors. the pilot has mostly inadequate information on the actual wind vector (wind speed and wind direction, wc) which as a matter of fact has the highest impact on the dispersion and coverage of crop spraying. moreover it is an important factor in general navigation, as well. in a mems imu device the accelerometers measure the linear acceleration referred to the inertial reference frame and the gyroscopes measure the angular velocity. the accelerometers provide the direction and the gyroscopes the orientation about the x-y-z axis. by integrating the inertial accelerations with an initial condition set to the original velocity – practically zero, since imu setup in the aircraft shall be performed on ground prior block off – the system yields the inertial velocities which is considered as the ground speed (gs). integrating again yields the system’s inertial position. if the initial inertial position has been entered to the imu then the actual inertial position can be calculated any time and can be provided for other system components for further processing. the kind of determination of the position without external reference is known as deadreckoning. it is useful to enter wgs-84 compatible initial position by latitude and longitude – which can be obtained by a stable gps measurement – to preserve compatibility with icao standards1 and navstar gps. in this way the mems imu can be used to provide ground speed, position, spatial referenced attitude and heading 1 international civil aviation organization (icao) establishes standards which are mandatory for all contracting countries. icao is the organization of the united nations dedicated to increasing the safety and security of international civil aviation. information and g-load. based on those data further key air navigation information can be obtained especially if external sources (map and performance database, magnetometer, air data computer, etc.) are linked. to obtain the tas value it is practical to use a digital air data computer (adc) which provides the static and dynamic air pressure and outside air temperature via standard digital interface (arinc2 421). the sandia aerospace type sac 7-35 adc [2] could be a costeffective choice. some of the pressure-sensing parts of the unit are also mems devices. if the imu is extended with an adc equation 1 can be solved. the wind vector (wc) can be gained by the vector difference of the corresponding heading and track information provided. the angle between the two vectors is called drift angle and it has high importance in navigation as well as in the dispersion-calculation of the pesticide particles. adding a geo-referenced navigational database (navdata) to the system would be beneficial for both purposes, general navigation and pest control, crop spraying. navdata should comprise of the waypoints, airspace fixes, navigational aids, terrain objects, towns, roads and should provide additional space for user defined fixes such as lateral extension of a field to be sprayed. referred to this database and the data obtained from imu+adc; bearing, distance and eta (estimated time to arrival) information can be calculated. in this way, the imu+adc+navdata system provides an optimal and cost-effective solution compared to a simple gps receiver or a high-end laser-gyro based platform. the average refresh rate of this system is about 300 hz, while a precision grade gps is able to give position information maximal 5 times per second. extending the system’s capability by installing an angle-of-attack vane opens more safety feature for the operator. wind shear warning and stall indication can be released to the pilot. this could dramatically improve the situation awareness and therefore the flight safety and absolute necessary for proper dispersion calculations of crop spraying. design concept every component of the designed system is permitted for civil use without restrictions and available in commercial retail stores off-the-shelf. due to the strict certification rules in aviation, the system is designed for experimental, supplementary use only, but it is capable for redundant, airborne usage and ready by design for airworthiness certification. the control display unit (cdu) is located in the cockpit at the dashboard in the pilot’s field of view. the design of the cdu shall accommodate the latest humanmachine interface requirements. it is extremely important to design the cdu in cooperation with the pilots and 2 arinc is a major provider of transport communications and system engineering in aviation industry. in its 400 series standards numerous design foundations and guidelines for databuses and databases has been developed. 231 operators to achieve the best ‘user-experience’ and the highest level of ergonomics on board. the main goal is to support the pilot and not to increase his workload. the central processing unit can be a single board computer (sbc) running real-time linux based operating system. inertial unit based on analog devices adis16405 isensor imu [3], adc is the above introduced sandia sac 7-35 [2]. the adis16405 imu is a triaxial inertial sensor with magnetometer which is capable of autonomous operation and data collection. its gyroscopes are inertial grade and accelerometers are well over the navigation grade. the dynamic range of the angular rate sensor can be reconfigured in-flight which improves the scale factor accuracy during lower roll-rate turns (e.g. enroute flights). the angle of attack vane is optional for inertial navigation purpose, but mandatory for agricultural deployment. the angle of attack value is used among others in the calculation of the drift of the pesticide particles in the slipstream and vortex system of the aircraft in actual atmospheric conditions. figure 1: block diagram of the mems imu based system on-board agricultural aircraft the optional audio warning system and head-up display contributes to situation awareness and flight safety. navdata and performance data are solid-state databases stored in the sbc. the navdata is based on standard airac (aeronautical information regulation and control) circulars and updated in every 28 days. the update can be done through memory cards or usb. the performance data database stores the specific parameters related to the particular aircraft type. these parameters include the local slipstream and vortex system of the aircraft in different speed versus angle of attack ranges, moreover the dispersion and spreading of the pesticide chemicals at different mixture ratio. they come mostly from wind tunnel measurements and mathematical models and field experiments. in the 1980´s significant research [4] was also performed in hungary, where the most frequently used agricultural aircrafts (e.g. an-2, ka-26, z-37) were involved in this experiment. to improve the accuracy and efficiency of the spraying, the location of the field and the aircraft’s position and ground speed must be known as well as the trajectory of the sprayed particles in the air. navdata provides the coordinates of the field to be treated. imu is used to determine the aircraft’s actual position and ground speed. the performance database stores the model of the aircraft and the pesticide chemical’s physical dispersion properties. based on imu and adc data the atmospheric condition with wind vectors, pressure surfaces and temperature lapse rates can be obtained. the calculation of the pesticide particles dispersed over the field can be formulated as a complex ballistic problem; the motion of the particle under the influence of wind, gravity, drag and lift forces while it suffers from elastic form changes and evaporates too. kármánbiot [5] offers a simplified solution for the ballistic problem, derevjanko [6] calculated and proved the motion trajectory for some typical droplet sizes. using them helps to create a computer based model which can be used for real-time calculation of the approximate dispersion of the pesticide particles from the particular aircraft under the actual atmospheric conditions. the cpu is responsible for the soft real-time calculation of the differential equations belonging to the ballistic problem. this way it is possible to calculate the pseudo-waypoints where the pilot shall commence the spraying and where it shall be terminated near the end of each row and the point where the turn for the new fly-by shall be initiated, etc. their representation on the head-up display and cdu device is also the task of the cpu. the visualization can be similar like the bomb sights on military aircrafts however the aiming is more peaceful. if the spray nozzles can be inserted in a control loop then their operation can also be controlled by the signals provided by the cpu or the autopilot. this would highly contribute to the efficiency of the crop spraying, the dispersion could be more uniform and accurate. moreover it would significantly decrease the environmental load caused by over-dosing or unintentional spread off the fields caused by wind and the aircraft’s slipstream. the cabin of the agricultural aircrafts is usually neither pressurized nor hermetically isolated. therefore it has a notable risk of harmful chemicals entering into the cabin which have adverse effects on the health of the pilot. by numerical tracking of the particle cloud sprayed before an aural and/or visual warning could be released to the pilot if his intended track coincides with an earlier sprayed and supposedly not yet properly dispersed pesticide cloud. this threat is very serious on older agricultural aircrafts with open cabins like kamov ka-26 helicopter and zlin z-37 cmelak or piper pawney. according to local regulations, the crop spraying cannot take place in updrafts. with the convective updrafts the pesticide particles are not dispersing on the ground onto the plants but they may rise up to high 232 altitude. if they reach the condensation level then they would be mixed in the precipitation which could affect areas which were not intended to be treated by the pesticide included in the precipitation. usually updrafts build over light colour fields on sunny days which are also typical and ideal for the agricultural mission. with the help of imu and adc the updrafts can be detected or even predicted so if the spraying device is being controlled by the cpu, then the spray nozzles can be closed and the pesticide can be cut off before flying into the updrafts. the track of the flights over the fields can be recorded and with the spraying together a virtual coverage map can be constructed. the areas which were not involved adequately in the crop-spraying can be displayed or visualized on the hud or cdu. this can provide essential information for the pilot for a proper crop spraying technique. the virtual coverage map can be utilized at a later stage for evaluation and further analysis on the efficiency and profitability of the procedure. furthermore the operator of the agricultural aircraft and the pilot will be accountable for the flight time, duty time, fuel and pesticide usage and the treated areas. conclusion the outlined mems-based inertial navigation system can contribute to the improvement of the efficiency of the agricultural crop spraying missions. moreover, it could improve flight safety even in general aviation. it provides a proper platform for further development and deployment on various aircraft types. the feasibility and the economical manufacturing of the designed structure are assured by the cost-effective availability of all necessary components. the later certification of the system may open wider range of further usage. the industrial utilization of this system is open for all countries where aerial agricultural activities are still in progress. the benefit of deploying this advanced solution would be enormous both for environmental protection and from an economical point of view. the possible operators may come from usa, ukraine, russia and china where huge amount of agricultural aircrafts are still in service and the agricultural flights are widely used for pest control over large areas. table 1: performance requirements for different classes of gyroscopes by yazdi et al [1] parameter grade tactical inertial angle random walk, h/° >0.5 0.5–0.05 <0.001 bias drift, °/h 10–1000 0.1–10 <0.01 scale factor accuracy, % 0.1–1 0.01–0.1 <0.001 full scale range, °/sec 50–1000 >500 >400 table 2: typical specifications of accelerometers for automotive and inertial navigation applications by yazdi et al [1] parameter automotive navigation range ±50 g (airbag) ±2 g (stability system) ±10 g resolution <100 mg (airbag) <10 mg (stability sytem) <4 μg off-axis sensitivity <5% <0.1% nonlinearity <2% <0.1% references 1. n. yazdi, f. ayazi, k. najafi: micromachined inertial sensors, proceedings of the ieee 86, (aug. 1998), 1640–1659 2. sandia aerospace sac 7-35 digital air data computer [online]. http://sarasotaavionics.com/product.aspx?id=466 3. analog devices adis16405 high precision tri-axis gyroscope, accelerometer, magnetometer [online]. http://www.analog.com/static/importedfiles/data_sheets/adis16400_16405.pdf 4. á. szász, l. varga: mezőgazdasági repülés (1998) budapest, mezőgazda 5. t. kármán, m. a. biot: mathematical methods in engineering (1940) mcgraw-hill 6. в. с. деревянко: влияние аэродинамических возмущений на процессы авиационного опыливания и опрыскивания (1974) москва, транспорт << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word b_13_kovacsa_r.doc hungarian journal of industrial chemistry veszprém vol. 39(2) pp. 205-210 (2011) experimental results of dry drilling of wear resistant steel a. kovács1 , gy. varga2 1college of nyíregyháza, department of technical preparatory and production engineering h-4400 nyíregyháza, sóstói u. 31/b, hungary e-mail: kovacs.attila@nyf.hu 2university of miskolc, department of production engineering, h-3515 miskolc-egyetemváros, hungary nowadays, adverse human induced impacts on the environment are constantly increasing, which urges engineers to make their production planning activities more environmentally conscious. in addition, during the realization and manufacturing processes of goods, the application of environmentally demanding and polluting materials is expected to be reduced or even eliminated. the application of the increasingly popular minimal lubrication method or even dry cutting could be considered to be efficient methods for reducing adverse environmental impacts. on the other hand, the mentioned methods have drawbacks since they considerably shorten tool life, result in a more significant cutting tool wear and lead to increase in friction. as a result, the tool and the work place temperature rise. this article aims to give an overview of how the feed direction force, the cutting torque, the tool wear, and the surface roughness change during the cutting procedure, if cutting is done under dry conditions while different cutting speed and feed motion parameters are applied. keywords: environmentally friendly metal cutting, dry drilling, drilling force, torque, wear, surface roughness introduction modern technologies have to meet several, in many respects, contradictory requirements. by means of cutting, increasingly sophisticated spare parts have to be manufactured from advanced materials that are more and more difficult to machine. the production of spare parts involves growing productivity and an increasingly accurate sizing. in order to make production operations cost-effective, expensive and multifunctional machine tools and tool equipment (etc) are required [1, 2, 3]. when aiming for a higher productivity, an increase in material flow (cm3/min) is required, which goes out with an increase of main speed and auxiliary motion speeds. increasing of feed motion and especially intensifying cutting speed result in a drastic rise of chip removal zone temperature [4, 5]. cutting fluids (oils, emulsions, synthetic fluids) have not only influenced the reduction of machine time beneficially, but favourably contributed to the reduction of tool wear as well. moreover, the size accuracy and surface roughness attained were appropriate. in the past some experts expressed their doubts regarding operation mediums and claimed that the application, handling (filtering), storage and disposal of cooling and lubricating materials involved huge costs [3, 5]. since the 1990s, there have been mounting doubts regarding the rising costs related to cutting fluids as well as concerning environmental regulations that have been becoming increasingly rigorous. not to mention the psychical effects machine operators have been subjected to: inhaling poisonous steams produced by cutting fluid at cutting temperature and fumes with unpleasant smell, which develop allergy. in the case of long-lasting work even various pulmonary diseases can be suffered. what is more, skin irritation as a bacteriological effect can also be detected. the other factor which enforced the change is of ecological nature: the strict environmental regulations set out in the workers’ interest, as well as obeying these regulations consciously – all this must give a larger scope to a thoroughly new technological approach. in the present article, we give an overview of our experimental results in the field of environmentally conscious cutting. figure 1: the experimental setup in cutting, the most effective (and at the same time most radical) method of mitigating environmental damage is the switch-over to dry machining (fig. 1). at present, 206 this technology change is very much on the agenda and draws a great deal of attention. of course, in order to achieve some success in this area, it is necessary to analyse the factors influencing the success of machining procedures. starting from the geometry, as well as the shape and size accuracy of machined parts, factors like machinability of the work piece, the applied operations and cutting conditions as a whole are to be examined. the main advantages of dry cutting are as follows [6]: this machining method is environmentally friendly, i.e. it does not generate air pollution in the workshop; the machine operator is not subjected to insalubrious effects: no respiratory or skin diseases are experienced; the expenses of chip cleaning (oil, emulsion or chemical relief) can be decreased; there are no coolant and lubricant fluidrelated (purchasing, storing, cleaning, disposal) costs; the structure of machining-related expenses changes (the tool-related increases, but the coolingand lubrication-related expenses do not change), thus, the production expenses decrease. on the other hand, there are some drawbacks of dry cutting. they are as follows [6]: the operation becomes less flexible and less complex (primarily in the case of drilling); cutting data need to be reduced, consequently, the machining time increases and the productivity decreases n; tool life shortens, consequently, tool costs mount; the reliability of the process generally worsens due to the significantly stronger scatter of tool life; in some cases, when turning or milling castings, rusty or scaled pieces at a high productivity level, dry cutting jeopardizes workers’ health; there is a limited accuracy and surface roughness attainable. as a general experience, it can be stated that the application of dry cutting is possible only if the accuracy requirements for the machined parts are not too high. thus, pre-machining rough cutting and/or half-finishing operations can also be performed by dry cutting, however, further steps required for attaining the final shape or position accuracy, can only be achieved by further operations with the application of coolant & lubricant fluid. hardox wear resistant steel sheets must meet strict requirements as steady quality, flatness and surface condition. the unique consistence of qualities like high hardness, high strength and outstanding shock-resistant toughness makes hardox wear resistant steel sheets extremely suitable for a wide range of use. hardox steels have been in the market since the 1970s and are continuously being developed to meet customer preferences (fig. 2). the sheets feature a thickness of 3 mm up to 130 mm. the high hardness and wear resistance significantly increase the useful life of final products. due to their increased toughness, hardox steels are also very resistant to low temperatures. figure 2: heat treatment of hardox steel is unique [7] they are relatively well machinable and make production and renovation easy [7]. the hardness of hardox 450 wear resistant steel comes to 450 brinell; some other characteristics are plotted in table 1. table 1: typical properties of different steels [7] type of steel elastic limit, n/mm2 tensile strength, n/mm2 hardness, hbw s235 (structural steel) 235 400 120 s355 (structural steel) 355 480 170 hardox 450 1200 1400 450 objective the experiment aimed to examine the effects the technological cutting parameters exerted on the cutting procedure during drilling by means of dry machining and minimal lubrication machining hardox 450 wear resistant steel. during the course of this activity, the effect depending on the tool feed and the set cutting speed is being measured: the feed force and the drilling torque demands as well as the average surface roughness of the machined hole vary correspondingly. the evaluation of the results of hole machining experiments is carried out by applying the factorial experiment design in order to determine connections between technological drilling parameters and the average surface roughness measured in the hole. research conditions the type of drill used in the experiment: ø10.2 mm l102/55 d12 marked sirius210 (high productivity, dimension-keeper, safe for drilling) helica (alcrn based) coated drill. the workpiece materials are hardox 450 (rm=1400 mpa) wherein we made 30 mm long holes with the occasion of experiments. the experiments were conducted under the following parameters: cutting speed: vc1 = 28.82 m/min vc2 = 44.83 m/min feed: f1 = 0.08 mm/rev f2 = 0.14 mm/rev length of hole: lw = 30 mm 207 equipment used for measuring feed force and torque the thrust (ff) as well as the torque (mc) were measured by a two-component compact dynamometer of kistler 9271a type, which features a high dynamic strength. therefore, it has a high eigen-frequency that allows measuring smaller dynamic force impulses even during high basic loads measurement of tool wear: the drill wear in the characterization of the corner wear (vbc) and flank wear (vb3.5) were chosen. the flank wear was measured on 3.5 mm radius from the centre line of the twist drill; the flank wear is the width of the wear from the main edge to the flank face. we measured the tool wear after every 30 mm drilling both edge then the measured values are averaged. the drilling distance is the product of the numbers of holes and the thickness of the material (s = zf · lp). we created high quality digital images of drill. images processed with coreldraw software. we issued the image with reference size (fig. 3). the wear value is the difference of the after-edge-image of various drilling distance and the reference line (fig. 4). figure 3: the sharp drill (m=300) figure 4: the worn drill l=1350 mm (m=300) during the measurements, using the same parameter settings, we repeated every measurement three times, and subsequently we processed the measurement results by means of mathematical statistical methods. we plotted the average values measured against drilling distance, then, by regression analysis, we determined the correlation index as well as the equation of the particular graph that follows the measurement points best. measurement of surface roughness in order to determine the average surface roughness of the holes made, sj-201 (mitutoyo) was used. the surface roughness values were measured on 30 mm length specimens, along 5 contour lines per hole. during the measurements, the same parameter settings were used. every measurement was repeated three times. the measurement results were processed by means of mathematical statistical methods. the average values measured against drilling distance was plotted, then, by regression analysis, we determined the equation of the particular graph that follows the measurement points best. experimental results results of drilling with sharp tool the experimental results are summarised in table 2. table 2: experimental results thrust, kn f1 = 0.08 mm/rev f2 = 0.14 mm/rev vc1 = 28.82 m/min 0.784 1.072 vc2 = 44.83 m/min 0.830 1.213 torque, nm vc1 = 28.82 m/min 4.59 4.96 vc2 = 44.83 m/min 6.59 6.97 surface roughness, µm vc1 = 28.82 m/min 2.29 2.95 vc2 = 44.83 m/min 2.45 3.24 by using the entire factorial experiment design, out of the measurement results, we obtained the equations of the surfaces for the case of dry cutting (1) – (3) ( ) fvfvfvf ccc 03851.048.700239.03128.0, −+−= (1) ( ) fvfvfvm ccc 010331.08471.512396.052389.0, +++= (2) ( ) fvfvfvra ccc 13325.01597.700066625.04292.1, −−+= (3) based on the measurement results it can be ascertained (fig. 5) that dry machining and the low feed increase feed direction force by nearly 6% when the cutting speed is accelerated from 28.82m/min to 44.83 m/min. in the case of a higher feed, the increase in feed direction force amounts to 13%. the results show that when dry cutting is applied and the feed is increased, the feed force increases by about 37% in the case of a higher cutting speed; in the case of a lower cutting speed it goes up by over 46%. 208 figure 5: the changes of the thrust in cutting speed and feed rate depending on dry machining with sharp tool figure 6: the changes of the torque in cutting speed and feed rate depending on dry machining with sharp tool figure 7: the changes of the average surface roughness in cutting speed and feed rate depending on dry machining with sharp tool examining the cutting torque values obtained during the drilling experiments (fig. 6) we experienced that when dry drilling is applied, the cutting torque increases more significantly, if the cutting speed is increased from a lower value to a higher one (then, at f=0.14 mm/rev drilling torque increases by 40%; at f=0.08 mm/rev by 43%). by increasing feed and maintaining a steady cutting speed, the increase in drilling torque is significantly lower. when evaluating the measurement results pertaining to the quality of the dry-machined surface (fig. 7) we noticed that, according to our expectations, the surface roughness of the machined hole increased by about 6%, if we increased the cutting speed from 28.82 to 44.83 m/min, using lower feed. in the case of a higher feed, this increase amounted to about 9%. when we adjusted a higher feed value during a steady speed, the increase in surface roughness will be nearly 28% at a speed of 28.82 m/min and it will be 32% at 44.83 m/min. results of drilling with worm tool during the course of the experiments, after each drilling distance of 90 mm, feed direction cutting force, drilling torque, flank wear, corner wear and average surface roughness were measured. the experimental results are summarised in tables 3-6. table 3: experimental results when the cutting speed is 44.83 m/min and the feed rate is 0.14 mm/rev. l, mm mc, nm ff, kn vb3.5, mm vbc, mm ra, µm 0 6.97 1.213 0.000 0.0000 3.2400 90 6.92 1.121 0.0189 0.0365 3.1351 180 7.17 0.992 0.0382 0.0655 3.4628 270 7.42 1.111 0.0542 0.1123 3.2256 360 7.82 1.171 0.0797 0.1452 3.4681 450 7.96 1.148 0.0945 0.1719 3.6814 table 4: experimental results when the cutting speed is 44.83 m/min and the feed rate is 0.08 mm/rev. l, mm mc, nm ff, kn vb3.5, mm vbc, mm ra, µm 0 6.590 0.830 0.0000 0.0000 2.4500 90 6.720 1.004 0.0164 0.0323 2.5450 180 7.114 1.155 0.0277 0.0553 2.6936 270 7.471 1.046 0.0479 0.0933 2.7989 360 7.739 1.185 0.0557 0.1282 2.8808 450 7.830 1.225 0.0695 0.1453 3.0710 table 5: experimental results when the cutting speed is 28.82 m/min and the feed rate is 0.14 mm/rev. l, mm mc, nm ff, kn vb3.5, mm vbc, mm ra, µm 0 4.960 1.072 0.0000 0.0000 2.9500 90 5.144 0.982 0.0089 0.0186 2.7360 180 5.425 1.035 0.0193 0.0366 2.7553 270 5.541 0.994 0.0295 0.0595 3.2106 360 5.831 0.986 0.0382 0.0690 3.1034 450 6.312 1.016 0.0457 0.0958 3.0109 540 6.546 0.951 0.0564 0.1104 3.1530 630 6.930 1.015 0.0704 0.1430 2.9695 720 6.981 1.132 0.0803 0.1530 3.2942 810 7.478 1.178 0.0825 0.1741 3.0846 900 7.489 1.006 0.0969 0.1928 2.9266 990 7.520 1.032 0.0949 0.2082 3.2411 1080 7.990 1.140 0.1077 0.2298 3.2513 209 table 6: experimental result if the cutting speed is 28.82 m/min and the feed rate is 0.08 mm/rev. l, mm mc, nm ff, kn vb3.5, mm vbc, mm ra, µm 0 4.590 0.784 0.0000 0.0000 2.2900 90 4.761 1.024 0.0080 0.0125 3.1655 180 4.734 0.955 0.0184 0.0276 2.2103 270 4.808 1.071 0.0250 0.0378 2.3864 360 5.027 0.959 0.0331 0.0514 2.3235 450 5.265 1.203 0.0430 0.0681 2.2749 540 5.227 1.206 0.0455 0.0728 2.2122 630 5.226 1.013 0.0635 0.0862 2.2139 720 5.685 0.986 0.0718 0.1139 2.3723 810 5.759 0.951 0.0693 0.1254 2.3089 900 5.862 0.980 0.0749 0.1336 2.2073 990 6.060 1.098 0.0894 0.1350 2.0300 1080 5.953 1.003 0.0886 0.1705 2.2230 1170 5.990 1.219 0.1005 0.1791 2.1967 1260 6.305 1.098 0.1105 0.1821 2.2808 1350 6.326 1.185 0.1064 0.2012 2.4134 1440 6.391 1.237 0.1312 0.2231 2.5811 1530 6.817 1.173 0.1326 0.2309 2.2407 1620 6.586 1.120 0.1295 0.2336 2.5526 1710 6.628 1.166 0.1508 0.2745 2.3392 1800 6.840 1.033 0.1611 0.2884 2.5649 1890 7.382 1.180 0.1519 0.2888 2.2708 1980 7.110 0.979 0.1672 0.3002 2.6339 2070 7.604 0.966 0.1824 0.2962 2.5618 2160 7.414 0.979 0.2012 0.3036 2.4164 2250 7.316 1.019 0.1837 0.3495 2.3495 2340 7.656 1.059 0.2112 0.3585 2.6585 2430 7.840 1.221 0.2099 0.3439 2.6018 2520 7.690 1.141 0.2279 0.3538 2.4726 when drilling, a slight increase in the cutting force can be noticed (fig. 8). the values vary mostly between 0.8 and 1.2 kn, i.e. they can be regarded as approximately stable during drilling. from the torque values measured it became apparent (fig. 9) that the torque raised depending on the drilling distance. the highest value (6.97 nm) was measured at a cutting speed of 44.83 m/min and a feed value of 0.14 mm/rev. according to our expectations, the lowest value (4.59 nm) was measured at the lowest cutting speed and feed. the used tool fractured at an average cutting torque of almost 8 nm. after examining the flank wear, we can state (fig. 10) that this value was the highest at parameters of 44.83 m/min and 0.14 mm/rev. the slowest wear was noticed at parameters of 28.82 m/min and 0.08 mm/rev. the highest flank wear also emerged in this case: 0.23 mm at the measurement before tool fracture, however, this did not reach the wear criteria set by us. figure 8: the changes of the thrust in cutting speed and feed rate depending on dry machining figure 9: the changes of the torque in cutting speed and feed rate depending on dry machining figure 10: the changes of the flank wear in cutting speed and feed rate depending on dry machining having examined the corner wear (fig. 11), the same observations could be made as in the case of flank wear results: the highest speed of corner wear was observed at the maximum speed and feed and the corner wear reached its highest speed at the lowest parameters used. however, the highest wear value (0.35mm) was experienced in this case. the change in average surface roughness (fig. 12) shows a slim increase. using a feed parameter of 0.14 mm/rev at a speed of 44.83 m/min, the best average surface roughness is 3.24 µm which spells a deterioration of 13% compared to the original value. we can obtain the best value by using the slowest feed at the slowest speed, thus, the initial value of 2.29 µm shows an increase of 7%. 210 figure 11: the changes of the corner wear in cutting speed and feed rate depending on dry machining figure 12: the changes of the average surface roughness in cutting speed and feed rate depending on dry machining the tool fracture is illustrated in table 7. during the experiment, the maximum tool usability was 2550 mm at parameters more suitably set. table 7: the breaking of the tools under dry cutting max drilled length, mm f1 = 0.08 mm/rev f2 = 0.14 mm/rev vc1 = 28.82 m/min 2550 1080 vc2 = 44.83 m/min 510 480 summary our paper demonstrated how feed direction force, cutting torque, corner wear, flank wear and surface roughness changes during dry-drilling wear resistant steel (hardox 450). the most important conclusions drawn out of our investigations can be summarised as follows: the functions determined by the full factorial experiment design is suitable to determining how the important cutting parameters have effect on average surface roughness, thrust, or torque if a sharp cutting tool is applied. during drilling procedures, there is an increase in thrust, torque, tool wear and hole surface roughness, depending on the drilling distance. acknowledgements “the described work was carried out as part of the támop-4.2.1.b-10/2/konv-2010-0001 project in the framework of the new hungarian development plan. the realization of this project is supported by the european union, co-financed by the european social fund.” references 1. k. weinert: trockenbearbeitung und minimalmengenschmierung. springer verlag 2000 2. i. dudás, gy. varga f. szigeti, l. péter, a. százvai: furatmegmunkálás minimálkenéssel, műszaki tudomány az észak alföldi régióban c. konferencia (dab) , nyíregyháza, 2006. nov. 16. műszaki füzetek, 2. kötet, 77–92 3. r. čep, m. neslušan, b. barišič: chip formation analysis during hard turning. strojarstvo, issn 0562-1887, 50(6), (2008), 337–345 4. j. kundrak, a. g. mamalis, k. gyani, a. markopulos: environmentally friendly precision machining, mater manuf. process 21(1), (2006), 29–37 5. s. suzuki: developments in oil supplying systems for mql cutting, journal of japanese society of tribologists, 47(7), (2002), 538–543 6. i. dudás, f. lierath, gy. varga: környezetbarát technológiák a gépgyártásban, forgácsolás szárazon, minimális hűtéssel-kenéssel, műszaki kiadó, budapest, 2010, p. 308, isbn 987-963-16-6500-0 7. http://www.winfa.sk/pdf/hardox007.pdf (17.05, 2011.) 8. http://www.aemach.com/pdf/b2-allmprodinfo_eng.pdf (07.12, 2010.) 9. http://www.rekord-system.no/html%20sider/ brosjyrer/pdf%20filer/16_hardox.pdf (17.05, 2011.) page 1 page 2 page 3 page 4 page 5 page 6 page 7 page 8 page 9 page 10 page 11 page 12 page 13 page 14 page 15 page 16 page 17 page 18 page 19 page 20 page 21 page 22 page 23 page 24 page 25 page 26 page 27 page 28 page 29 page 30 page 31 page 32 page 33 page 34 page 35 page 36 page 37 page 38 page 39 page 40 page 41 page 42 page 43 page 44 page 45 page 46 page 47 page 48 page 49 page 50 page 51 page 52 page 53 page 54 page 55 page 56 page 57 page 58 page 59 page 60 page 61 page 62 page 63 page 64 page 65 page 66 page 67 page 68 page 69 page 70 page 71 page 72 page 73 page 74 page 75 page 76 page 77 page 78 page 79 page 80 page 81 page 82 page 83 page 84 page 85 page 86 page 87 page 88 page 89 page 90 page 91 page 92 page 93 page 94 page 95 page 96 page 97 page 98 page 99 page 100 page 101 page 102 page 103 page 104 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word 00.00 inner cover.docx hungarian journal of industry and chemistry vol. 43(1) pp. 33–38 (2015) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2015-0006 organisation of the analytical, stoichiometric, and thermodynamic information for water chemistry calculations rita földényi* and aurél marton department of environmental science, university of pannonia, egyetem u. 10., veszprém, 8200, hungary a common feature of the chemical processes of the hydrosphere and water treatment plants is that essentially the same types of chemical equilibrium reactions occur in both fields. these equilibria could be acid/base, complexation, redox, precipitation, and interfacial processes. since these reactions may also occur in combination, the aqueous environments are unavoidably multispecies systems. due to multiple equilibria, the state of aggregation, the state of oxidation, as well as the electric charge of the species may change dramatically. calculation of the equilibrium concentration of the species is facilitated by the availability of analytical, stoichiometric, and thermodynamic information that are consistently organised into an asti matrix. the matrix makes it possible to apply a uniform algebraic treatment for all occurring equilibria even, if later on, further reactions have to be included in the chemical model. the use of the asti matrix enables us to set up the necessary mass balance equations and equilibrium relationships, which together form a non-linear system of equations (nlse). the goal of our paper is to show that the use of the asti matrix approach in cooperation with the powerful engineering calculation software, mathcad14, results in fast and easy handling of the nlse-s and, consequently, the calculations of speciation in aqueous systems. the paper demonstrates the method of application in three examples: the calculation of the ph dependence of the solubility of calcite in closed and open systems, the calculation of the ph and pε in a system where acid/base reactions, complexation equilibria, and redox equilibria occur, and a study of adsorption of lead ions on aluminium oxide. keywords: multiple solution equilibria, asti matrix method, solubility of calcite, redox calculation, adsorption of lead 1. introduction information on the speciation profile of aqueous systems is of primary importance in many fields of chemistry. the usual acid/base, complexation, redox, precipitation, and interfacial reactions may occur simultaneously leading to the formation of a large number of species in both natural and artificial aquatic systems. contemporary numerical and graphical treatments of aqueous equilibria were presented in seminal publications in the fields of environmental engineering [1], natural aquatic systems [2–7] and geochemistry [8, 9]. an important aspect of the recent approaches is the systematic organisation of the analytical, stoichiometric, and thermodynamic information relevant to the studied system. the input of structured information became particularly indispensable in the use of the modern computer programs dedicated to chemical equilibrium modelling: mineql [10], mineql+ [11], minteqa [12], phreeqc [13], and wham [14], to name a few. *correspondence: foldenyi@almos.uni-pannon.hu 2. methods 2.1. organisation of information into the asti matrix in order to collect and organise data for the equilibrium calculations a strict distinction has to be made between the terms: reagent, reactions, species and components. under laboratory conditions, reagents (denoted hereafter by a) are simply those chemicals that are present at the beginning of reactions. each reagent is characterised by its analytical molar concentration (c in mol dm-3 or m). under environmental conditions, we have to assume the presence of a ‘contaminating’ compound of reagents: e.g. acid rain forms as a result of due to the presence of nitric acid in rainwater. when reagents are mixed, several reactions may take place (the total number of reactions is denoted by r). for each reaction, the relevant equilibrium constant (k) refers to the correct stoichiometry of the reaction, such as h2co3 ⇄ hco3 + h+, k1 = 10-6.35 (1) hco3 ⇄ co3 2+ h+, k2 = 10-10.33 (2) földényi and marton hungarian journal of industry and chemistry 34 where the k values are given for a specified temperature (25 ºc), pressure (101.3 kpa), and ionic strength (0.1 m). the considered reactions or chemical models generate a large number of chemical particles with appreciable stabilities. this set of entities is called species (the number of species is denoted by s). the smallest subset of selected species that enable us to describe the formation of all the other species of the system are called components (their number is denoted by c). in order to meet the requirements of the gibbs phase rule [15], the needed number of components has to be calculated from the relationship c = s r. if there are 6 reactions and 10 species then from the list of species four species have to be selected as component c = 4. the concept of this component is the “key and door” to the organisation of the database and, consequently, to equilibrium calculations. in principle, any subset of the species can be selected (promoted) as a component, but chemical considerations dictate some rules that have to be kept in mind: 1. h2o and h+ have to always be selected as components, 2. species with fixed activities whose concentrations do not change during the reactions have to be selected as components too; such species are the solvent (h2o), solid phases (e.g. caco3), and gases of known pressure (e.g. atmospheric co2, p = 10-3.5 atm), and 3. species that are presumably present in dominant concentrations will also be selected as components. after selecting the components, the formation reactions for the rest of the species have to be written up in terms of these components. the equilibrium (formation) constant of the species is calculated by hess’s law using algebraic manipulation of the reactions, in such a way, to obtain the target reaction. the left-hand side of the target reaction only contains components and the right-hand side only displays the species e.g.: if in the studied system co3 2is selected as a component (besides h2o and h+) then by using eqs.(1) and (2), the formation of the hco3 and h2co3 species should be given as: co3 2+ h+ ⇄ hco3 , (k2)-1 (3) co3 2+ 2h+ ⇄ h2co3 . (k1·k2)-1 (4) when the formation of all the (s c) species is expressed in this way then the stoichiometric relationship between the components and species is revealed. in addition to this, the stoichiometric connection between the components and reagents has to be established too. this can be done by synthesising the reagents through the reaction of the components, just like in the case of species, but now only the stoichiometric coefficients are relevant. the above procedure highlights the central role of the component and allows us to arrange the available analytical, stoichiometric and thermodynamic information into a coherent matrix abbreviated hereafter as the asti matrix. the columns and rows of the matrix list the c number of components and all the s number of species, respectively. the elements of the matrix are filled with the respective stoichiometric coefficients (including zeros too). analytical concentrations (c) and the equilibrium constants (k) are introduced into this matrix as shown in the examples discussed below. for the calculation of the unknown concentration of s species, we need the s stoichiometrically independent equation. the main purpose of our effort to develop the asti matrix is to draw up the required s equations. based on the columns and rows matrix two types of equations can be drawn up. the mass balance equations (mb) are based on the columns of the asti matrix and are drawn up usually for all the c components (in exceptional cases, not all the mb equations are needed, see example 1. below). the mb equation is, in fact, an additive relationship showing the weighed concentration sum of all species containing the particular component. the weighing factors are the respective stoichiometric coefficients. the other type of equations, based on the asti matrix, are the equilibrium relationships (er). this multiplicative type of equations are drawn up on the basis of the rows of the species. the er gives the equilibrium concentration of the (s c) species expressed as a product of the concentration of all the c components raised to the power of the stoichiometric coefficients (which could be zeros too). consequently, the er-s expresses the concentration of the species in terms of the concentration of the components. it is worth noting, that a different choice of components yields different mb equations and er (a further indication of the importance of the choice of component in the equilibrium calculation). the application of these principles will be shown in the examples below. the mass balance equations together with the equilibrium relationships form a (usually) non-linear system of equations (nlse) for calculating the concentration of all the s species. 2.2. solving the non-linear system of equations (nlse) using mathcad mathcad 14 (ptc. inc.) is a versatile and powerful engineering calculation software. it works seamlessly with numbers, units, equations, texts, and graphs. after giving the required k, analytical concentration data, and assigning initial values for the unknown variables, the s number of nlse is introduced on the screen between the given and find commands. mathcad then rapidly solves the nlse by using the iterative levenberg marquardt algorithm [16]. for example, the solution of the nlse with ten unknowns takes only a couple of seconds. to assign a good guess for ten variables is rather cumbersome; therefore, the algebraic reduction of the number of unknowns is desirable. this can be done by substituting the equilibrium relationships into the mass balance equations, which reduces the number of variables against the number of components (c < s). in organisation of the analytical, stoichimetric, and thermodynamic information 43(1) pp. 33–38 (2015) doi: 10.1515/hjic-2015-0006 35 this case, the solution of the c number of nlse (instead of the s) returns the equilibrium concentration of the components, which are then substituted into the applicable er to obtain the concentration of the (s c) species. in addition to this algebraic method of the reduction of variables, chemical considerations may also be applied to reduce the number of species. chemical background information often suggests that certain species of the system are present in minor concentrations only. these terms may then be safely omitted from the additive type of mb equations and neglected from the set of er-s. this principle works for the opposite case too. sometimes it is desirable to improve the original chemical model by including further equilibria. this can be done seamlessly if the new equilibria are expressed also in terms of the components and the asti matrix is augmented by the required new data. the above considerations clearly highlight the appreciable advantage of using the asti matrices in association with mathcad. the asti matrix can be decomposed and treated by the well known methods of matrix algebra. here; however, we like to keep chemistry in focus, so the matrix algebraic solution is not treated here explicitly, because its elegant and concise formalism conceals chemical insights. 3. simulation results 3.1. calculation of the ph dependence of the solubility of calcite in open and closed systems (example 1) the solubility of caco3(s) in water is calculated as a function of ph for an open and a closed system. the open system is exposed to the atmosphere where pco2 is 10-3.5 atm, where the exchange of co2 molecules between the solution and gas phases is allowed. considering the similarities between the two systems, and for brevity, the process leading to the asti matrix and the nlse is shown only for the open system, while the results are presented for both systems. in the open system, we have three species whose equilibrium concentrations (activity, a) are known (h2o(l) with a = 1, caco3(s) with a = 1, pco2 = 10-3.5 atm) so, according to rules of selection from above, they have to be selected as components. the details of the procedure are shown below: reagents, a=3: h2o(l) a = 1, caco3(s) a = 1, pco2= 10-3.5 reactions, r = 5: h2o ⇄ h+ + oh kv = 10-14 ca2+ + co3 2⇄ caco3(s) ks = 108.35 co2(g) + h2o ⇄ h2co3 * kh = 10-1.5 co3 2+ h+ ⇄ hco3 k1 = 1010.3 hco3 + h+ ⇄ h2co3 * k2 = 106.3 species, s = 9: h2o, h+, oh-, co3 2-, hco3 -, h2co3 *, co2(g), caco3(s), ca2+ components, c = s – r = 4 h2o, h+, caco3(s), co2(g) asti matrix s/c h2o h+ co2(g) caco3(s) k (logk) h2o 1 h+ 1 co2(g) 1 caco3(s) 1 oh1 -1 kw (-14) ca2+ 2 -1 1 ks -1·kh -1·k1·k2 (9.8) h2co3 * 1 1 kh (-1.5) hco3 1 -1 1 kh·k2 -1 (-7.8) co3 21 -2 1 kh·(k1·k2)-1 (-18.1) a/tot m a(h2o) 1 1 a(caco3(s)) 1 1 pco2(g) 1 10-3.5 mass balance equations, mb toth = [h+] [oh-] + 2[ca2+] [hco3 -] 2[co3 2-] = 0 equilibrium relationships, er [oh-] = kv·[h+]-1 [ca2+] = ks -1·kh -1·k1·k2 ·(pco2)-1·[h+]2 [h2co3*] = kh· pco2 [hco3 -] = kh·k2 -1·pco2·[h+]-1 [co3 2-] = kh·(k1·k2)-1·pco2·[h+]-2 the required six equations (mb + er) are therefore available for the calculation of the six unknown concentrations (h+, oh-, co3 2-, hco3 -, h2co3 *, and ca2+). the nlse was solved by mathcad and the results are shown in table 1. for the closed system, the asti matrix can be obtained by omitting the co2 from the list of reagents, species and components as well as the kh equilibria from the list of reactions. as shown in table 1, the dissimilarity between the ph values is the most remarkable difference between the equilibrium systems. the solubility of the caco3(s) was also calculated for both systems as a function of ph. fig.1 shows that in a closed system the solubility tends to be a limiting value as ph increases. the solubility vs. ph function changes dramatically, if the system is open to the atmosphere, pco2 = 10-3.5 atm, as shown in fig.2. as opposed to the closed system, when the calcium-carbonate-water system is open to the atmosphere (pco2 = 10-3.5 atm), the solubility continuously decreases as ph increases (compare figs.1 and 2). table 1. comparison of speciation in the caco3(s)h2o(l) (closed) and caco3(s)-h2o(l)-co2(g) (open with pco2 = 10-3.5 atm) systems both at 25 ºc. -log c closed system open system ph 9.9 8.3 -logca 3.9 3.3 -logco3 24.4 5.0 -loghco3 4.1 3.0 -logh2co3 7.8 5.0 földényi and marton hungarian journal of industry and chemistry 36 3.2. calculation of speciation in the iron(ii)/iron(iii) system involving complexation (example 2) the ph and pε values are calculated for the ferrous/ferric ion redox system involving the complexation of the metal ion with the oh-, cland f ions starting from a hypothetical solution of fecl2, fecl3, nacl, and naf. two additional questions were also addressed, such as what is the measurable redox potential of the system, and if a trace quantity of arsenic gets into this system, what will be the dominant redox form of the arsenic. the organisation of information follows the same flow as outlined above. reagents, a c(fe2+) = 10-4 m, c(fe3+) = 10-4 m, c(cl-) = 105·10-4 m, c(na+) = 105·10-4 m, c(f-) = 5·10-4 m reactions, r = 6 h2o ⇄ h+ + oh kw = 10-14 fe3+ + e ⇄ fe2+ kr = 1013 pε° = 13 fe3+ + h2o ⇄ fe(oh)2+ + h+ k1 = 10-2.19 fe3+ + 2h2o ⇄!fe(oh)2 + + 2h+ k2 = 10-5.67 fe3+ + f⇄ fef2+ k3 = 106.2 fe3+ + cl⇄ fecl2+ k4 = 101.48 species, s = 13: h2o, h+, oh-, fe3+, fe2+, fe(oh)2+, fe(oh)2 +, f-, fef2+, cl-, fecl2+, na+, e components, c = s – r = 7: h2, h+, fe3+, f-, cl-, na+, e asti matrix s /c h+ fe3+ fclna+ ek h+ 1 fe2+ 1 f 1 cl 1 na+ 1 e 1 oh-1 kw fe(oh)2+ -1 1 k1 fe(oh)2 + -2 1 k2 fef2+ 1 1 k3 fecl2+ 1 1 k4 fe2+ 1 1 kr tot m cfecl2 1 2 1 10-4 cfecl3 3 10-4 cnacl 1 1 10-2 cnaf 1 5·10-4 mass balance equations, mb toth = [h+] [oh-] [fe(oh)2+] – [2fe(oh)2 + ] = 0 totfe = [fe3+] + [fe(oh)2+] + [fe(oh)2 +] + [fef2+] + + [fecl2+] + [fe2+] = 2·10-4 totf = [f-] + [fef2+] = 5·10-4 totcl = [cl-] + [fecl2+] = 3·10-4 + 2·10-4 + 10-2 totna = [na+] = 10-2 + 5·10-4 tote = [e-] + [fe2+] = 10-4 equilibrium relationships, er [oh-] = kw ⋅ [h+]-1 [fe(oh)2 +] = k1 ⋅ [h+]-1⋅[fe3+] [fe(oh)2 +] = k2 ⋅ [h+]-2⋅[fe3+] [fe(f)2+] = k3·[fe3+]·[f-] [fe(cl)2+] = k4·[fe3+]·[cl-] [fe2+] = kr·[fe3+]·[e-] the system of nlse generated by seven mb and six er equations was solved by mathcad and the results are summarised in table 2. since the charge and oxidation state of the introduced arsenic species are controlled by the ph and pε values of the environment, the calculated ph and pε data make it possible to visualise, which oxidation state would dominate the studied redox-complex system. the relevant predominance area (pε vs. ph) diagram is shown in fig.3. according to fig.3, the calculated ph = 4 and pε = 10 values corroborate the existence of the h2aso4 anionic arsenic species in this hypothetical system. figure 2. change in the -log(solubility) = -log[ca2+] of the caco3(s) in an open system as a function of ph (graphs for -log[co3 2-] and -log[hco3 -] are also presented). figure 1. change in the -log(solubility) = -log[ca2+] of the caco3(s) in a closed system as a function of ph (graphs for -log[co3 2-] and -log[hco3 -] are also presented). organisation of the analytical, stoichimetric, and thermodynamic information 43(1) pp. 33–38 (2015) doi: 10.1515/hjic-2015-0006 37 3.3. adsorption of lead(ii) ions on the surface of γ-al2o3 adsorbent (example 3) the asti matrix based approach of the equilibrium calculation makes it possible to include heterogeneous reactions in the calculation like e.g. adsorption and ion exchange. here the adsorption of the pb(ii) ions from pbcl2 on γ-al2o3 is studied as a function of ph and the concentration of chloride ions from excess nacl. the active surface group, -oh of the adsorbent is denoted here by ≡xoh. the mechanism of lead adsorption is interpreted using the surface complexation model [5] leading to the formation of the surface complex defined by the symbol ≡xopb+. reagents: m(γ-al2o3) = 0.3846 g volume of the solution, v = 500 cm3 adsorption capacity, q = 1.3·10-4 mol g-1 concentration of surface sites, c≡x = m·q/v = 10-4 m c(pb2+) = 10-5 m; c(cl-) = 0.1002 m; c(na+) = 0.1 m; ph = 6 reactions, r = 6: h2o ⇄ h+ + oh kw = 10-14 pb2+ + h2o ⇄ pboh+ + h+ k1 = 10-7.7 pb2+ + cl⇄ pbcl+ k2 = 101.6 ≡xo+ h+ ⇄ ≡xoh k3 = 107.7 ≡xoh + h+ ⇄ ≡xoh2 + k4 = 106 ≡xopb+ ⇄ ≡xo+ pb2+ k5 = 10-6.1 species, s = 11: h2o, h+, oh-, pb2+, pboh+, cl-, pbcl+, ≡xo-, ≡xoh, ≡xoh2 +, ≡xopb+ components, c = s – r = 5: h2o, h+, pb2+, cl-, ≡xoh2 + asti matrix: s /c h+ pb2+ ≡xoh2 + clk h+ 1 oh-1 kw pb2+ 1 pboh+ -1 1 1 k1 cl pbcl+ 1 1 k2 ≡xoh2 + 1 ≡xoh -1 1 (k4)-1 ≡xo-2 1 (k3·k4)-1 ≡xopb+ 1 1 (k3·k4·k5)-1 tot m cpb 1 10-5 c≡x 1 1.3·10-4 cnacl 1 0; 0.1; 0.5 mass balance equations, mb: (mb for water is usually omitted, if the ph is fixed then toth is not needed and clis known): totpb =[pb2+] + [pboh+] + [≡xopb+] + [pbcl+] = cpb totxoh2=[≡xoh2 +] + [≡xoh] + [≡xo-] + [≡xopb+]= c≡x equilibrium relationships, er: [pboh+] = k1⋅[pb2+]⋅[h+]-1 [pbcl+] = k2⋅[pb2+]⋅[cl-] [≡xoh] = (k4)-1 ⋅[≡xoh2 +]⋅[h+]-1 [≡xo-] = (k3⋅k4)-1⋅[≡xoh2 +]⋅[h+]-2 [≡xopb+] = (k3⋅k4⋅k5)-1⋅[≡xoh2 +]⋅[pb2+]⋅[h+]-2 the two mb-s and five er-s define the unique value of the concentration of the seven dissolved and surface species. the mathcad solution of the nlse yields the data summarised in table 3. considering that the er equations are valid at all ph values and chloride concentrations, arbitrary useful functions can be defined by using these concentration functions. let this function now be the distribution coefficient widely used in liquid chromatography and defined as the ratio of the total concentrations of the lead (totpb) in the two phases: figure 3. predominance area (pourbaix) diagram of the arsenic showing the existence of the species of various oxidation states (from p.193 of ref [8]). table 2. calculated ph and pε values and the concentration of the species occurring in the fe2+/fe3+ redox system containing the oh-, cland f coordinating ligands. the measurable electromotive force (emf) with respect to a calomel reference is also shown (εref = 0.244 v). ph = 4.13 pε = 9.93 [fe2+] = 1.0·10-4 [fe3+] = 8.5·10-8 [fe(oh)2+]= 7.4·10-6 [fe(oh)2 +] = 3.3·10-5 [fecl2+] = 2.7·10-8 [fef2+] = 5.9·10-5 [f-] = 4.4·10-4 [cl-] = 1.0·10-2 εind = 0.059·pε = 0.59 v; emf = εind εref = 0.35 v table 3. speciation of pb(ii) in the presence of adsorbent (γ-al2o3), in 0.1 m nacl solution at ph = 6. species molarity ≡xoh 6.3·10-5 ≡xoh2 + 6.3·10-5 ≡xopb+ 2.4·10-6 ≡xo1.3·10-6 pb2+ 1.5·10-6 pbcl+ 6.0·10-6 pboh+ 3.0·10-8 földényi and marton hungarian journal of industry and chemistry 38 d = totpb on the ads. totpb in the solutn. = [xopb+ ] [pb2+ ]+[pboh+ ]+[pbcl+ ] (5) after substituting the appropriate er relationship into the above equation the distribution coefficient can be calculated as a function of ph and the chloride ion concentration. the result is shown in fig.4. as shown in fig.4, the adsorption of lead increases sharply with the increase of ph, since the formation of surface complexes is preferred at higher ph values. it is interesting to observe that at ph 6 the adsorption of the positive pb(ii) species is significant despite the fact that the surface species, ≡xoh2 +, is also positively charged at this ph. 4. conclusion in order to solve complex aqueous speciation problems a logical scheme for arranging the available data is needed. this convenience scheme is provided by the tabulated form of the arrangement of analytical, stoichiometric, and thermodynamic information. this matrix of data allows us to set up the necessary mass balance and equilibrium equations of the calculation. this paper presented typical examples of the use of these principles in the field of water chemistry. symbols a number of reagents asti analytical stoichiometric and thermodynamic information c number of components er equilibrium relationship h2co3* h2co3 + co2(aq) k equilibrium constant mb mass balance nlse non-linear system of equations r number of reactions s number of species totx total concentration of species ‘x’ acknowledgement the research was supported by támop-4.1.1.c12/1/konv-2012-0015. references [1] brezonik, p.l.; arnold, w.a.: water chemistry (oxford university press, oxford, uk) 2011 [2] stumm, w.; morgan, j.j.: aquatic chemistry, 3rd ed. (wiley interscience, new york, usa) 1996 [3] snoeyink, v.l.; jenkins, d.: water chemistry (j. wiley and sons, new york, usa) 1980 [4] pankow, j.f.: aquatic chemistry concepts (lewis publ., chelsea, mi, usa) 1991 [5] morel, f.m.m.; hering, j.g.: principles and applications of aquatic chemistry (j. wiley and sons, new york, usa) 1993 [6] benjamin, m.m.: water chemistry (mcgraw-hill, new york, usa) 2002 [7] jensen, j.n.: a problem-solving approach to aquatic chemistry (j. wiley and sons, new york, usa) 2003 [8] drever, j.: geochemistry of natural waters (prentice-hall, englewood cliffs, nj, usa) 1982 [9] zhu, c.; anderson, g.: environmental applications of geochemical modelling (cambridge university press, cambridge, uk) 2002 [10] westall, j.c.; zachary, j.l.; morel, f.m.m.: mineql, a computer program for the calculation of chemical equilibrium of aqueous systems (dept. of civil engineering, mass. inst. technol., cambridge, ma, usa) technical note 18, 1976 [11] mineql+ver.4.6, a chemical equilibrium modeling system (environmental research software, hallowell, mn, usa) 2008 http://mineql.com [12] u.s. epa. 2006. minteqa2 (ver. 4.03) http://www.epa.gov/ceampubl/mmedia/minteq [13] parkhurst, d.; charlton, s.; riggs, a.: reactiontransport modeling in ground-water systems. phreeqc ver.2. a computer program for speciation, batch-reaction, one-dimensional transport, and inverse geochemical calculation (us geol. survey, reston, va, usa) 2008 [14] tipping, e.: humic ion binding model vi: an improved description of the interaction of protons and metal ions with humic substances. aquat. geochem., 1998 4, 3-48 [15] atkins, p.w.: physical chemistry (oxford university press, oxford, uk) 1978 [16] mathcad user’s guide (1995) mathsoft inc. cambridge, mass., usa p. 637 figure 4. change in the distribution of the pb(ii) ions as a function of ph at different chloride ion concentrations. the second index of d refers to the chloride ion concentration (eq.(5)): 0 = no chloride, 1 = 0.1 m, 2 = 0.5 m. hungarian journal of industry and chemistry vol. 46(2) pp. 79–84 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0023 comparison of particle size distribution models for polymer swelling ádám wirnhardt *1 and tamás varga1 1department of process engineering, university of pannonia, egyetem u. 10, veszprém h-8200, hungary in polymer technologies, various particle shapes and size distributions can be found. one of these are heterodisperse polymer beads. the capabilities of polymer swelling can be used in industries, e.g in the production of ion-exchange resins, to intensify specific technological steps such as sulphonation in the manufacturing process of ion-exchange resins. according to the literature different approaches can be used to create models for describing the behavior of disperse systems, of which the simplest models are the particle size distribution models for a given state of the solid phase. the aim of our examination was to compare and evaluate these simple models in terms of modeling polymer swelling. hence, most of these models examine how each of the investigated models can be applied to approximately describe growth in a heterodisperse polymer system and how the identified model parameters in each time step could be interpreted. all the models were fitted to generate particle size distributions based on a swelling rate constant. the swelling of a styrene divinylbenzene-based copolymer was chosen as the basis of our examination. a model is proposed that is capable of describing the changes in the size of beads over time in this system. keywords: polymer swelling, particle size distribution, heterodisperse polymer beads, modeling, ion-exchange resin 1. introduction polymer beads are used as raw materials in a wide range of technologies, e.g. in the production of ion-exchange resins. before the chemical modification of polymer beads, they are often swollen with different types of swelling agents such as dichloroethane, dichloromethane, toluene, etc. monodisperse and heterodisperse types of beads are known in polymer technologies. the process of the swelling of monodisperse beads is easily measurable and easily predictable. the production of monodisperse polymers is a more expensive process than the production of heterodisperse beads, which makes heterodisperse polymer beads a more popular form. heterodisperse polymer beads exhibit a closely normal distribution in terms of particle size. the prediction of the swelling of these particle systems is more difficult because the different beads can swell at significantly different rates due to the change in the specific area of each bead. the swelling of the polymer network system has already been a subject of interest. painter and shenoy[1] considered the chemical properties of polymers. schott [2] described the kinetics of polymer swelling. first order and second order kinetics were founded by him. a *correspondence: wirnhardt.adam@fmt.uni-pannon.hu swelling model was formulated by sweijen et al. [3] according to the diffusion properties of components in the polymer matrix. these models are capable of describing the swelling of polymer networks, but because of its complexity they are hard to apply in any kind of optimization process. hence, the simplest particle size distribution (psd) model, which can describe the swelling of polymers over time using the least number of parameters, can be of interest from a process intensification point of view. bayat et al. collected psd models from the last seventy years [4, 5]. thirty-five models were listed. these models describe the cumulative mass fraction of polymers as a function of the diameter of polymer beads. the models contain one, two, three or four unknown parameters, which can be identified with a specific polymer fraction. a hyperbolic tangent distribution [6, 7] psd model composed of four parameters was added to this list by us. this study is the first step in the process of developing this model which focuses on the investigation of the swelling phenomena of the styrene divinylbenzene copolymer system. therefore, our focus is on identifying a simple psd model which is capable of describing the swelling of heterodisperse polymer beads. hence, all the previously mentioned psd models are investigated and compared. our aim was not only to identify a psd model which is capable of describing the distribution of the investigated polymer system but to find a psd model which mailto:wirnhardt.adam@fmt.uni-pannon.hu 80 wirnhardt and varga exhibits a correlation between changes made to parameters and particle size. 2. experimental for the modelling of heterodisperse polymer systems physical experiments with regard to swelling should be performed to obtain the data necessary to validate the model. in our case, with the lack of experiments, the data were generated from a model implemented and solved in matlab. a code was made in matlab for the generation of these distributions. in the developed model, the swelling of polymer beads with a given theoretical rate of growth was calculated. the volume of each bead increased at the same rate. hence, the diameter of the beads does not influence the rate of growth and the tension caused by the swelling process of the polymer beads is neglected in this investigation. the following simplifications were implemented in the model: 1. the shape of the polymer beads is a perfect sphere. 2. the particles swell until they reach a steady state. 3. the swelling rate of particles is constant until a steady state is achieved. 4. the number of particles is constant. 5. the initial psd of the beads is close to normal. to generate the distributions after different durations of swelling an initial unswollen distribution is required. the initial distribution was calculated by matlab from a picture of heterodispersed particles. the varion ks preform styrene divinylbenzene copolymer was used for the zero-time distribution. the polymer beads were identified by a circle detection algorithm and the size distribution of the detected particles was calculated using a reference particle. from the initial state, the size of the polymer particles starts to increase by applying a swelling agent to the system. the size of the particles increases until a steady state is achieved. the steady state in this case means that the size of the particles grows until a state when the amount of infiltration of the swelling agent is equal to the outcome amount. the size of the particles can increase until a maximum is reached because of the internal tension of the polymer. the data are generated using the parameters of the steady state. these parameters are the swelling rate (p [-]) and time required (t [sec]). psds were generated at different times during the swelling process. the next step was to examine the psd models to determine if they were able to describe the distribution in every instant. 2.1 psd models in this study only psd models that are capable of describing cumulative mass fraction distribution were investigated. altogether five models with one parameter, twelve with two, two with three and four with four were examined. they are collected in table 1. the cumulative mass fraction of particles is denoted by p (d), the maxima and minima of the particle size range are represented by dmax and dmin, respectively, and the particle diameter [mm] is denoted by d. the models were fitted to all the distributions collected over time using extreme value problem solver algorithms in matlab. 2.2 theoretical methodologies two types of extreme value problem-solving methods were applied to fit the psd models. one is a local extreme value problem solver known as the nelder-mead simplex algorithm and its function “fminsearch” to implement it in matlab. the other one is a global extreme value problem solver called “nomad” [8]. they are both components of the matlab toolkit. matlab 2011b was applied in all modelling steps. the minimum difference was sought between the generated distribution data and calculated distributions based on each model. the parameters of psd models were the results of this search. in every case, the goodness of fit was measured. for each model, every sample time was considered and the difference examined using the mean absolute difference. the average of the mean absolute difference of the percentage difference was calculated for every function. the extreme value problem solver attempted to find the minimum of the following equation et = ∣∣p (d) ′ t − p (d)t ∣∣ nd (1) where the mean absolute difference between the generated and calculated distribution is et at instant t. the calculated distribution is denoted by p (d) ′ t and the generated distribution by p (d)t at instant t. the number of items of data is represented by nd. 2.3 model selection a selection could be made according to the average percentage differences. the selection was carried out with a criterion. this criterion was an average percentage difference of five percent because under this value the difference is not considerable but over it an unacceptable fit is shown. three different models, namely the rosin-rammler, the exponential-power_pasikatan and the logarithm-zhuang models fitted to the generated data are shown in fig. 1. the goodness of fit for these three models is 1 %, 5 % and 11 %, respectively. as can be seen the differences of 1 % and 5 % are negligible, and are only noticeable at diameters in excess of 0.7 mm. however, a considerable difference can be observed between the models with fits of 5 % and 11 %. it can be seen that a goodness of fit of under 5 % is appropriate. hungarian journal of industry and chemistry comparison of particle size distribution models for polymer swelling 81 table 1: the investigated psd models name model 1 parameter (k1) 1 gaudy-meloy p (d) = 1− (1− d/dmax) k1 2 nesbitt-breytenbach p (d) = 10[(1/(k1 + 1)](d/2)k1+1 +[0.1− 1/(k1 + 1)](d/2)1/[1/(k1+1)−0.1] 3 rosin-rammler p (d) = 1− exp(−k1d) 4 jaky p (d) = exp { − ( 1/k21 ) [ln(d/dmax)] 2 } 5 schumann p (d) = (d/dmax) k1 2 parameters (k1, k2) 6 power lowpaskikatan p (d) = [k1/(1− k2)]d1−k2 7 van genuchten p (d) = [ 1 + (k1/d) k2 ]1/k2−1 8 rosin-rammler p (d) = 1− exp ( −k1dk2 ) 9 fractal p (d) = exp {ln(k2))+[( 3k21 − 13k1 + 14 ) / ( k21 − 5k1 + 4 ) + 1 ] log(d) } 10 power low gimenez p (d) = k1d k2 11 best p (d) = [ 1 + (k1/d) k2 ]2/k2−1 12 bennet p (d) = k1k2d k1−1 exp ( −k2dk1 ) 13 exponential powerpasikatan p (d) = exp ( −k1dk2 ) 14 logarithm-zhuang p (d) = k1 ln(d) + k2 15 log-exp-kolev p (d) = k1 exp [k2 log(d)] 16 weibull-2par p (d) = 1− exp [ −(d/k1)k2 ] 17 lognormalzobeek p (d) = 1/ { k1(2π) 1/2 exp [ −(log(d)− k2)2/(2k21) ]} 3 parameters (k1, k2, k3) 18 s-curve: vipulanandan ozgurel p (d) = 100 exp { −k1 [ k2 ln(d/0.001) d/k3 ]} 19 weibull-3par p (d) = k1 − exp [ −(d/k2)k3 ] 4 parameters (k1, k2, k3, k4) 20 gompertz p (d) = k1 + k2 exp {− exp [−k3(d− k4)]} 21 weibull-4par p (d) = k3 + (1− k3) [ 1− exp ( −k1kk2 4 )] where k4 = (d− dmin)/(dmax − dmin) 22 fredlund p (d) = { 1/ [ ln ( exp(1) + (k1/k2) k2 )]k3 }{ 1− [ln(1 + k4/d)/ ln(1 + k4/0.001)] 7} 23 tanh if 0<k2+k3d then p (d) = { tanh [ (k2 + k3d) k4 ]}k1 otherwise p (d) = 0 46(2) pp. 79–84 (2018) 82 wirnhardt and varga figure 1: the cumulative distribution of the rosinrammler (1 %), exponential-power pasikatan (5 %) and logarithm-zhuang (11 %) models as well as the generated data. 2.4 parameter correlation the next step in the modelling process was the investigation into how the model parameters of each simple psd model can be fitted into a monotonous series over time. based on this experiment, these simple models can be applied to describe the swelling of specific material systems over time. by depicting the parameters of the distribution functions as a function of time, a statement can be made for the models if they were capable of this task. assuming that the correlation is linear for every model parameter, in each psd model it can be calculated as follows: kx = ax +bxt (2) where the parameter of the psd model is denoted by kx, the parameters of the k parameter are a and b, and the time passed is t. it is obvious that there are twice as many unknown model parameters than in the previous step, i.e. every model parameter in each model is defined by eq. 2, however, only one set of parameters is required to describe the swelling process over time. in this examination, the mean absolute difference was also needed to fit the functions to different time instants. in this case the extreme value problem solver determined the minimum for the average of the mean absolute difference: e = ∑nt t=1 et nt (3) where the average of the mean absolute difference is denoted by e and the number of time instants by nt. 3. results and analysis the zero distribution was evaluated by matlab based on a picture taken from a sample of polymer beads. the sample consisted of approximately five hundred beads within the diameter range of 0.2 to 0.9 mm. the probability distribution with regard to the size of the polymer beads is shown in fig. 2. figure 2: the probability distribution with regard to the size of the polymer beads before swelling within the diameter range of 0.2 to 0.9 mm. the parameters for the generated data were p = 2 and t = 1500 s which means the polymer beads doubled their size in 1500 s and the steady-state size of the beads is this rate of growth. psd was calculated twenty-five times between 0 and 1500 s. three of the twenty-five distributions are shown in fig. 3. all 23 models were fitted to all the distributions generated at every instant. altogether twenty-three times twenty-five curve fittings were performed. the parameters were calculated for all the fitted models. for every fitted value a mean absolute difference (et) was determined, the average of which are shown in table 2 according to the values in table 1 a selection of psd models could be made. those models show good agreement with the generated psd, which yields an average mean absolute difference of less than five percent. a difference can be observed between the two methods to find extreme values. the global finder “nomad” has found a better fit for the two-parameter model known as best. in most cases the two search methods give the same results using the same model parameters. in some models, the global optimizer has found a better solution than was expected. eleven of the twenty-three models were found to be able to describe the distribution at all time instants. from figure 3: cumulative distribution functions at three different time instants during the swelling of the polymer beads. hungarian journal of industry and chemistry comparison of particle size distribution models for polymer swelling 83 table 2: the goodness of fit for the different models. psd model id simplex fitting e [%] nomad fitting e [%] 1 15 15 2 39 39 3 24 24 4 2 2 5 10 10 6 12 8 7 3 3 8 1 1 9 19 13 10 8 9 11 39 2 12 5 5 13 5 5 14 12 12 15 8 8 16 1 1 17 30 30 18 35 13 19 0 0 20 2 1 21 1 1 22 37 34 23 1 1 these, the best model was the weibull-3par which is shown in fig. 4. this result does not mean that the model is able to describe polymer growth. a correlation should be present in terms of changing the parameters. by examining the correlation of model parameters in these eleven models, one model called jaky exhibited a correlation as shown in fig. 5 the other models did not show any kind of correlation over time. the jaky model consists of one parameter and it seems to describe properly the growth of heterodisperse polymer systems. the other models did not show any correlation in terms of the changing of the parameter over time. in most cases one parameter was present which did figure 4: the change in the parameter of the weibull-3par model after various durations of swelling. figure 5: the change in the parameter of the jaky model after various durations of swelling. not show any regularity as is shown in fig. 4. the following examination sought to set a correlation between the change in the parameter and time due to the swelling of beads. with linear criteria (see eq. 2) the goodness of fit will definitely deteriorate. the presumption was to find a model which exhibits a goodness of fit of under five percent after setting the criterion. the results collected in table 3 show that two of the eleven selected models produced a goodness of fit of under 5 %, the others were all in excess of 30 %. therefore, the jaky model consisting of one parameter and the rosin-rammler model of two exhibit a linear correlation for their parameters over time. the other nine models did not exhibit a linear correlation in their parameters over time. it would be worthwhile trying other non-linear functions to describe the parameters. 4. conclusion in polymer technologies, one of the steps is the swelling of the polymer beads. several studies were conducted that deal with the swelling of polymer networks. our aim was to examine the swelling of the polymer beads from a different point of view to find out if a simple psd model exists which may be able to describe changes in size of this system. table 3: the goodness of fit of the linear correlation of parameters over time. psd model id simplex fitting e [%] nomad fitting e [%] 4 2 2 7 33 14 8 1 1 11 − 44 12 44 44 13 53 44 16 44 44 19 35 35 20 35 35 21 30 52 23 44 44 46(2) pp. 79–84 (2018) 84 wirnhardt and varga psd models were examined according to their ability to describe the swelling of polymer beads. the results show that two models were present which could be used to describe and predict the behavior with regard to changes in size of the heterodisperse polymer bead systems. in this examination, the copolymer styrene divinylbenzene was used. two extreme value problem solvers were used to identify and confirm psd models that are able to describe changes in size of the copolymer system. two models, namely the one-parameter jaky model and the two-parameter rosin-rammler model, were able to describe the growth in size over time with an error of less than 2 %. the parameters of these models could be interpreted by a linear correlation over time according to the generated data that was produced in this study. based on these working models a prediction can be made with regard to changes in size of a heterodisperse copolymer system over time. symbols et mean absolute difference e average of mean absolute difference p (d) ′ t calculated distribution p (d)t generated distribution nd number of data nt number of time instants kx parameters of models acknowledgment this research was supported by the széchenyi 2020 project ginop 2.2.1-15-2017-00059. references [1] painter, p.c.; shenoy, s.l.: a simple model for the swelling of polymer networks, j. chem. phys., 1993 99(2), 1409-1418 doi: 10.1063/1.465385 [2] schott, h.: swelling kinetics of polymers, j. macromol. sci., part b: physics, 1992 31(1), 1-9 doi: 10.1080/00222349208215453 [3] sweijen, t.; van duijn, c.j.; hassanizadeh, s.m.: a model for diffusion of water into a swelling particle with a free boundary: application to a super absorbent polymer particle, chem. eng. sci., 2017 172, 407-413 doi: 10.1016/j.ces.2017.06.045 [4] bayat, h.; rastgou, m.; nemes, a.; mansourizadeh, m.; zamani, p.: mathematical models for soil particle-size distribution and their overall and fraction-wise fitting to measurements, eur. j. soil sci., 2017 68(3), 345-364 doi: 10.1111/ejss.12423 [5] bayat, h.; rastgo, m.; zadeh, m.m.; vereecken, h.: particle size distribution models, their characteristics and fitting capability, j. hydrology, 2015 529, 872-889 doi: 10.1016/j.jhydrol.2015.08.067 [6] blickle, t.; lakatos, b.g.; ulbert, zs.; mihálykó, cs.: the hyperbolic tangent distribution and its applications-i. mathematical foundations, hung. j. ind. chem., 1998 26, 89-96 [7] blickle, t.; lakatos, b.g.; mihálykó, cs.; ulbert, zs.: the hyperbolic tangent distribution family, powder technology, 1998 97, 100-108 [8] le digabel, s.: algorithm 909: nomad: nonlinear optimization with the mads algorithm, acm trans. math. softw., 2011 37(4), 1–15 doi: 10.1145/1916461.1916468 hungarian journal of industry and chemistry https://doi.org/10.1063/1.465385 https://doi.org/10.1080/00222349208215453 https://doi.org/10.1080/00222349208215453 https://doi.org/10.1016/j.ces.2017.06.045 https://doi.org/10.1111/ejss.12423 https://doi.org/10.1016/j.jhydrol.2015.08.067 https://doi.org/10.1145/1916461.1916468 https://doi.org/10.1145/1916461.1916468 introduction experimental psd models theoretical methodologies model selection parameter correlation results and analysis conclusion microsoft word inner cover.docx hungarian journal of industry and chemistry (hjic) formerly (until 2012) hungarian journal of industrial chemistry the hjic is an international periodicals that focuses on results of fundamental and applied research in the field of • biotechnology • chemical engineering science • chemical processes • energetics • environmental chemistry • environmental engineering & technology • industrial management • material science • mechanical engineering • mechatronics • process & system engineering • recycling in the form of original papers, reviews, short communications, and conference proceedings written in english. editorial board editor-in chief: róbert k. szilágyi department of chemistry and biochemistry, montana state university, bozeman, mt, u.s.a. honorary senior editor: géza horváth department of chemical engineering science, university of pannonia, veszprém, hungary associate editors: jános abonyi department of process engineering, university of pannonia, veszprém, hungary dezső boda department of physical chemistry, university of pannonia, veszprém, hungary norbert miskolczi mol department of hydrocarbon and coal processing, university of pannonia, veszprém, hungary dóra rippel pethő department of chemical engineering science university of pannonia, veszprém, hungary editors: lászló bartha mol department of hydrocarbon and coal processing, university of pannonia, veszprém, hungary katalin bélafi-bakó research institute of bioengineering, membrane technology and energetics, university of pannonia, veszprém, hungary peter czermak institute of bioprocess engineering and pharmaceutical technology, mittelhessen university of applied sciences, giessen, germany dénes fodor institute of mechanical engineering, university of pannonia, veszprém, hungary maria gavrilescu department of environmental engineering and management, gheorghe asachi technical university of iasi, romania lászló gubicza research institute of bioengineering, membrane technology and energetics, university of pannonia, veszprém, hungary jenő hancsók mol department of hydrocarbon and coal processing, university of pannonia, veszprém, hungary jiří klemeš centre for process integration and intensification, university of pannonia, veszprém, hungary zoltán kovács department of management, university of pannonia, veszprém, hungary jános kristóf department of analytical chemistry, university of pannonia, veszprém, hungary ákos rédey department of environmental engineering and chemical technology, university of pannonia, veszprém, hungary istván szalai institute of physics and mechatronics, university of pannonia, veszprém, hungary ferenc szeifert department of process engineering, university of pannonia, veszprém, hungary jános szépvölgyi research centre for natural sciences, university of pannonia, veszprém, hungary imre tímár institute of mechanical engineering, university of pannonia, veszprém, hungary gyula vatai department of food engineering, corvinus university of budapest, hungary gábor veress federation of technical and scientific societies – mtesz budapest, hungary ibolya zsoldos department of material science and technology, széchenyi istván university, győr, hungary editorial office: university of pannonia, p.o. box 158, veszprém h-8201 (hungary) tel.: +36 (88) 624-298, e-mail: hjic@almos.uni-pannon.hu; web: hjic.mk.uni-pannon.hu felelős szerkesztő: szilágyi róbert károly phd kiadja: pannon egyetem, 8200 veszprém, egyetem u. 10. levélcím: h-8201 veszprém, postafiók 158, tel.: (88) 624-000 felelős kiadó: a pannon egyetem, mérnöki kar dékánja editorial preface process engineering and factory automation became nowadays the dominant driving forces behind key industries, such as oil and gas industry, chemical, pharmaceutical, food, machinery, electronic industry and automobile manufacturing. the aim of the current issue (volume 41, number 1) is to overview the latest developments in industrial process automation and process engineering. the papers presented here were selected from contributions at the factory automation conference held on may 21–22, 2013. the objective of the conference was to establish an international forum for specialists both from the industry and academia. the meeting provided opportunities for the participants to present and discuss the latest developments and up-to-date applications in automation. this issue represents the entire spectrum of process engineering as follows: • automation tools and solutions of manufacturing processes • industrial robots in automation • automation of quality control • industrial communication networks • automation safety • application fields of cad/cam, eda • lifecycle management • production control, production logistics • monitoring and diagnostics of manufacturing processes • production design, optimization and simulation we are grateful for the authors for their contributions. we anticipate that the readership of the hungarian journal of industry and chemistry will be inspired and benefit from the selected good quality papers. we plan to continue the tradition of the former industrial automation conference series. you are welcome to participate at the international automation congress (http://www.iac2014.hu) in budapest, october 29–31, 2014! jános abonyi and rozália pigler-lakner university of pannonia, veszprém, hungary guest editors hung. j. ind. & chem. 2013, vol. 41(1), pp. 1–82 table of contents vehicle routing approach for lean shop-floor logistics david gyulai, lászló monostori ............................................................................................... 1–6 design of a new chemical injection pump system for gas hydrate inhibition csaba vörös, viktor füvesi, ákos pintér ............................................................................... 7–10 ionic liquids in advanced energy storage cells attila göllei, attila magyar ................................................................................................ 11–15 monitoring and diagnosis of manufacturing systems using timed coloured petri nets adrien leitold, brigitta márczi, anna ibolya pózna, miklós gerzson ......................... 17–26 immediate event-aware model and algorithm of a general scheduler tibor dulai, ágnes werner-stark, katalin m. hangos .................................................... 27–34 estimation of parameters of an extremely low fuel consumption internal combustion engine-based megameter-iii vehicle istván pintér, mihály bagány ................................................................................................ 35–40 influence of can flatness on heat dissipation of aluminium electrolytic capacitor lászló kovács, lászló gál, dénes fodor ............................................................................ 41–46 fine tuning of automated assembly machines using video analysis alíz katona, viktor kovács, dóra tasner, zoltán kovács ............................................ 47–50 quasi-polynomial control of a synchronous generator attila magyar, attila fodor ................................................................................................ 51–57 a structured model based diagnosis method for discrete dynamic processes using event sequences attila tóth, katalin m. hangos, ágnes werner-stark .................................................... 59–64 role of steady state data reconciliation in process model development barbara farsang, sándor németh, jános abonyi .............................................................. 65–75 statistical quality control based performance evaluation of online analyzers tibor kulcsár, jános abonyi .................................................................................................. 77–82 hungarian journal of industry and chemistry veszprém vol. 41(1) pp. 1–6 (2013) vehicle routing approach for lean shop-floor logistics david gyulai1,2! and lászló monostori1,2 1 fraunhofer project centre for production management and informatics, computer and automation research institute (sztaki), kende str. 13–17, budapest, h-1111, hungary 2 department of manufacturing science and technology, budapest university of technology and economics, egry j. str. 1, budapest, h-1111 hungary ! e-mail: david.gyulai@sztaki.mta.hu in order to satisfy the material supply needs of large scale shop-floors and production systems, various logistics solutions are applied. in lean manufacturing enterprises, the material supply is pulled by the demands of manufacturing/assembly processes; therefore, a milkrun service is often applied to support the production without glitches. the milkrun logistics planning is a special case for vehicle routing problem (vrp), and requires effective approach to solution in order to satisfy various constraints, and minimize the cost of service. this study gives an overview about lean logistics as well as the most efficient vrp solver algorithms. furthermore, a novel initial solution with generation heuristics is proposed, which is specially focused on flexible milkrun planning. in order to demonstrate the capabilities of the solution, a software environment is developed as a demonstration that focuses on the main industrial requirements of logistics planning like effective layout definition, quick response of the delivery service and effective order handling. keywords: vehicle routing problem, milkrun, local search, factory logistics introduction the material provision of largeand medium-scale production systems requires prudent planning and control, since it influences the performance of the production and affects the order management directly and storage assignment [1]. in order to manage effectively the material provision of the production, practical transport logistics and distribution tasks are usually formulated as vehicle routing problems, whose objective is to obtain a minimum-cost route plan serving a set of customers with known demands [2]. in state-of-the art manufacturing systems, lean processes are successfully applied to eliminate the wastes on all the levels of production, and they raise the overall efficiency of the system by reducing the nonvalue adding activities in the process chain. the shopfloor logistics processes have to be adapted to the production system; therefore the waste reduction in the material provision also has a key role in balancing the workload and ensuring a smooth running of production. a well-operating lean logistics system keeps the inventories and operational costs on the most cost efficient levels, via by providing the materials what that are needed, exactly when they are needed. for satisfying these requirements, concepts of the lean logistics can be applied that are primarily aimed at controlling the transport services duly to the pull strategy. the paper is focused on the ‘milkrun’ service, which is defined as a manually operated, cyclic transport system delivering raw materials (or sub-assemblies) and disposing empties based on consumption using a fixed route and time schedule [3]. according to this characterization, milkrun scheduling is considered as a special vehicle routing problem with time windows, a limited capacity, and number of vehicles. in this paper a novel, multi-level planning approach is proposed, which combines the advantages of existing algorithms as for example local search for vehicle routing. first, an overview of the state-of-the-art factory logistics is given, considering the recent shop-floor characteristics and planning demands. then the main solution approaches and algorithms are introduced, as well as the critical points of milkrun planning. in section 4, the proposed layout representation hierarchy and the novel initial solution generation heuristics method are described. the latter focuses on the real industrial criteria and give a feasible milkrun schedule. in the last section, an industrial case-study and some numerical results present the efficiency of the milkrun planning method developed. shop-floor logistics the shop floor logistics are part of the production logistics in the supply chains of companies. while logistics in general is about supplying a customer with 2 necessary goods in time, with the goal of efficiency, and the lowest possible costs, production logistics is the task of bringing necessary material to workstations and machines and transferring it to the next station. in the realm of logistics planning methodologies the lean approach, originating in the toyota production system, of overall waste reduction has become a major planning paradigm, constituting the lean logistics approach [4]. principles of lean logistics of the seven waste categories, eliminating unnecessary transports, waiting times, superfluous movement and excess inventory are the most relevant in lean logistics. klug identifies the following characteristics of lean logistics [5]: synchronicity and a clocked material flow, flow orientation, standardization, pull principle, stability, integration, as well as perfection. regarding the pull principle, as the most relevant feature, material is only transferred to a workstation if it is about to process the material thus reducing inventory levels by reducing shop floor stock to safety buffers only. beside the above principles of lean logistics, a relatively novel issue in material provision of production is ‘green logistics’ that is generally about establishing an ecologically sustainable transportation system considering factors like energy consumption and airpollution [7]. while in the general external logistics context theses planning principles are reflected in transport concepts such as the just-in-time delivery, there are also corresponding design concepts in production and shop floor logics. for the supplier/source side, establishing zones for decentralized incoming goods and supermarkets in the vicinity of assembly stations is a means of reducing transport lengths. on the receiving side, standardized shelves and reusable containers, replenishment schemes like ‘kanban’ are applied. for the transport system between supply and workstations, ‘tugger trains’ (fig.1) with fixed time intervals, standardized capacity, and transport lot sizes are preferred over forklift transport in the context of lean logistics; the goal of, which is the reduction of inventory and avoiding erratic peaks in production known as the bullwhip effect [8]. this transport concept of scheduled tugger trains in the context of a lean-oriented logistics system is usually combined with the milkrun transport concept that is in the focus of this paper. especially in production environments with a high product complexity, variety amid a complex and changing material flow, planning a system of milkrun transports is a complex planning task. thus, an efficient system of milkruns could significantly in-crease the efficiency of the overall production logistics. milkrun as a vehicle routing problem vehicle routing (vrp) is a challenging combinatorial optimization problem, introduced first by dantzig and ramser in 1959 [9]. the general vrp is known as the capacitated vehicle routing problem (cvrp), were the aim is to satisfy the needs of all the customers at different locations by having a given number of vehicles with capacity constraints [11]. when milkrun is applied as a material providing system, the time constraint of the runs has also to be added to the general problem (vrp with time windows – vrptw). the general objective is to minimize the costs either by minimizing the total distance travelled, or minimizing the number of vehicles applied. a specific type of vrp is the pickup and delivery problem (pdp) where the vehicles not only provide the locations with materials, but also pick up materials at the stations and deliver them to another one. the milkrun problem is also a pdp, with time windows and cyclic service [12]. several approaches from the operations science are used to solve vrps, as for example constraint programming that manages flexibly the various specific constraints of the vrp [14]. local search is one of the fundamental approaches to find solutions for hard computational – including constraint satisfaction – problems. the basic idea behind local search is to start with a randomly or heuristically generated candidate solution, and to iteratively improve that by means of defined functions [15]. generating the initial solution is always a crucial point when applying local search, since it significantly affects the running time of the algorithm. sophisticated heuristics for the vrp are the two-phased ones, which decompose the problem into a clusteringand a routing problem, with possible feedback loops between the two stages. cluster-first route-second (cfrs) algorithms perform a single clustering of the vertex set and then they determine a vehicle route on each cluster. the bestknown cfrs algorithm is the fisher-jaikumar algorithm, which solves the general assignment problem (gap) to form the clusters [17]. the local search starts from the initial solution and subsequently moves from the present solution to a neighbouring solution in the search space where each solution has only a relatively small number of feasible neighbour solutions and each movement is determined by neighbouring operators [20]. when applying local search, the combination of the neighbourhood operators produces the next local optimum solution (fig.1). although the most general forms of the vrp can be solved effectively with the above approaches, the milkrun planning problem is hard to interpret as a simple graph-search problem, and the general initial solution heuristics are difficult to transform for this problem. the mapping process of the factory layout also requires special processing; therefore general solution methods cannot be applied easily for such a special problem. 3 problem formulation hereby, we provide a definition to the milkrun planning problem. consider a layout of the shop-floor, which is defined by a set of routes and stations. the routes can be either oneor two-way ones, and each route endpoint is defined as a “routenode”. along a specific route, there can be more stations (fig.2). the problem also considers demands that belong to the stations and defined by the amount of the transported goods in standard units and the required cycle-times of the transportation. the goods are transported by vehicles (practically by tugger trains), which are defined by their capacity and average speed. in order to plan feasible milkruns, real-world constraints are considered, such as the capacity constraints of the vehicles, which limit the maximum number of the transported goods. another constraint is the time limit of the plan, which means the total time consumption of a milkrun plan cannot exceed the cycletime of the demands. the loading and unloading points can be reached from both sides of the tugger train, and the train can approach the station from both endpoints of the route that the station belongs to. a milkrun plan is built-up by paths, where each path is given as the list of the visited stations and the list of the routes that the vehicle passes along. the plan does not partition the demands, and a visit of a particular station only occurs in a specific path. a milkrun plan is characterized by its total time consumption, which is required by the vehicle(s) to perform the plan. a milkrun plan is considered to be better than the other one only if its total time consumption is smaller, while it satisfies all the demands. the goal of milkrun planning is to minimize the number of the required vehicles via minimizing the time consumption of the plan. the proposed planning process layout representation for vehicle routing as it was mentioned in the previous section, solving the general vrp is not enough to plan feasible milkrun schedule, since most of the routing algorithms does not calculate with the physical constraints determined by the shop-floor. most of the general solution approaches consider the problem as a graph-search, where the stations are represented by vertices and the routes are represented by edges [21]. in many cases, this representation does not support effectively the planning processes with feasible results, unless the application of the following constraints. frequently, when representing a shop-floor by directed graphs, it turns out that the structure of the layout results some direct and indirect routing constraints. a direct case means that the additional equations can be formalized immediately when constructing the graph, such as the asymmetric edge formulas, while the others require further consideration. indirect constraints are usually implied by the narrow and one-way corridors, which limit the abilities of the vehicles from going to a station directly from another, even if a path connects them. these constraints are implied by the moving abilities of the common applied tugger train, since it cannot turn in the middle of an aisle, and in many of the cases it have to take a detour before visiting the next station (fig.2). in order to handle the shop-floor constraints effectively and be able to avoid impossible movements of the vehicle, a novel hierarchical layout representation is proposed. the layout is defined by three main different classes, each having their own specific attributes. this structure can be handled dynamically during the path calculations, and the asymmetric nature of the distance matrix is represented together with the limitations of vehicles movements. fig.3 shows the hierarchy of the layout, defined by “routenodes”, “routes” and “stations”. to calculate the distance matrix of the layout, storing the shortest paths between the stations, dijkstra’s algorithm was applied that solves the single-source shortest path problem in logarithmic running time [22]. in this case, the input of the algorithm is a directed graph where the vertices are the set of the “routenodes” and the edges are the routes. this graph representation is able to handle all the nodes of the layout with their connections, and by applying dijkstra’s algorithm the asymmetric distance matrix can be calculated. figure 2: layout elements and vehicle movement figure 1: interand intra-route relocate operators 4 initial solution generation in order to plan feasible milkrun cycles with the lowest operational costs, the shop-floor constraints have to be taken into consideration. to handle the constraints effectively, the routing algorithm needs to select the stations to be visited dynamically. thus, a so-called triplet solution is applied, which helps to avoid impossible movements of the vehicle. a triplet is consisted of three identical nodes: three current, the previous and the next position of the vehicle. the next position is calculated dynamically when determining a particular path of the vehicle. the milkrun planning method strongly focuses on the industrial requirements of vehicle routing; therefore, a novel initial solution generation heuristics was implemented. the goal is to generate a solution that is as close to the criterion as possible. the proposed heuristics can be classified as a cfrs type rule, and differs from the fisher-jaikumar algorithm by the cluster generation method, since it does not require solving time-consuming gap, but defines the clusters based on practical reasons [18]. to generate a feasible initial solution, the algorithm calculates a path to each station applying dijkstra’s shortest path algorithm. then a greedy search algorithm is applied to calculate the next node, which must be visited by the vehicle before returning to the depot, so as to avoid violating the turnaround constraints of the vehicle. the greedy search iterates forward the nodes applying a best-first search strategy [23], and finds the first node from, which the shortest path to the depot does not contain the previous node. the “roundtrip” planning method is applied for each station, and detects all the feasible tours on the shop floor. in order to determine the set of paths for the initial solution, the paths with most visits are selected one by one while the set of unsatisfied demands is not void. performing the services required by these cycles provides a feasible and acceptable initial solution for the planning algorithm. the pseudo-code of the proposed algorithm is the following: vv∈ set of stations { }vv|v:p ∈= path }p{p set of paths [ ] v)s,r(|dd rs ∈= distance matrix }p{i initial solution iq demands of the ith station }q{q i= set of demands ct cycle time c capacity of the vehicle initialize v, i, q, c{v}, c, tc foreach i in v calculate d0i foreach v in d0i add v to ci calculate di0 foreach v in di0 add v to ci align c [length(ci+1) < length (ci)] while |q| > 0 while time(c1) > tc or load(c1) > c remove rand v from c1 (v≠i) foreach v in c1 delete qv from q add c1 to i delete c1 from c return i local search strategy and neighbourhood functions in order to improve the initially generated solution, neighbourhood functions are applied. to be able to reach all the points of the search space, both intraand inter-route operators are necessary to calculate with, although in this case the effect of the inter-route functions is more significant since the initial solution heuristics could provide paths with stations in a rather good sequence. the algorithm performs the local search to minimize the paths, and the cycle-time of them. then, a simple bin-packing problem is considered, to allocate the paths to a minimal number of vehicles. to solve the problem, first fit heuristics was applied, which is a proven 11/9 opt solution algorithm [24]. case study and test results the milkrun planner software, which includes both the user interface and the solver algorithms were implemented in a .net environment using c++ language. within the performance evaluation of the implemented software, a real production environment was modelled in order to analyse its capabilities. the purpose of the implemented application is to offer userfriendly and efficient milkrun planning environment; therefore a graphical, point-and-click layout definition interface and xml communication have been applied (fig.4). figure 3: hierarchy of the layout representation 5 first the input parameters are processed and stored in the memory, and dijkstra’s algorithm is applied to calculate the shortest path between each station. the distance matrix is built up from vectors, each having two distance elements. this data structure is required by the applied triplet-based path planning method, which selects dynamically the proper distance parameter from the vector, based on the location of the previously visited station. the initial solution generation uses the distance matrix to create the tours, based on the station loops detected on the layout. the initial solution contains only feasible paths that satisfy the time constraints as well as the capacity constraints of the actual vehicle. to avoid overloaded vehicles, a pre-check method is performed: the vehicle is loaded by all the raw materials in the depot, and then all the other loading and unloading processes are calculated station-by-station to simulate the real milkrun process. in order to calculate with time constraints, both the travel-time (with constant average speed) and the loading/unloading time (time/item) are considered. the purpose of the generated initial paths is to satisfy all the demands by the lowest possible number of feasible cycles. the local search algorithm takes the initial paths and reduces their total time consumption by applying neighbourhood functions where it is possible. the algorithm iterates through all the combinations of the stations, and detects the possible insertions from one path to another. as local search iterates through the paths in a random sequence, different test runs can result different milkrun plans. in order to approximate the global optimum solution, the implemented application performs the local search several times and selects the most appropriate schedule from the generated solutions. the capabilities of the algorithm were tested in a real production environment. this was a large-scale automotive production system with 2 factory halls, 67 stations and 96 routenodes. the milkrun plan has to satisfy 193 various demands in 60 minutes cycle-time. the analysed system requires efficient planning process, since the total length of the routes is over 2.5 km that affects critically the total time of the milkrun schedule. the application of inefficient milkrun schedule results low-utilized vehicles and high number of cycles. in this case, the goal of the test was to minimize the number of vehicles required to perform the services via minimizing the time of the cycles. the proposed initial solution heuristically generated eight feasible paths with 20,400 seconds total time. first, the algorithm tries to optimize the plan by applying one vehicle, and increases the number of the vehicles only if the improvement steps cannot decrease the time requirement of the total plan under the cycle-time (3600 seconds). by this way, the test run could optimize the plan for two vehicles in 177 iterations, and generated a schedule, which time requirement is only 57 minutes (fig.5). conclusions after an overview about the state-of-the art shop-floor logistics, and the general formulations of the vehicle routing problem, a solution was proposed that uses a novel layout representation and initial solution generation heuristics to solve the milkrun planning problem. in order to demonstrate the capabilities of the figure 4: the user interface of the milkrun planner application figure 5: test results of the case study 6 solution, a software prototype was developed and tested on real-life industrial data. future work includes the extension of the model with demand partitioning so as to increase capacity utilization of the transportation vehicles. moreover, handling inhomogeneous demand types (physical aspects of material handling) requires further constraints to be included in the model. secondly, future work will be dedicated for making the solution available in practical industrial applications. in an on going research project the milkrun planning algorithm will be implemented in a factoryand a logistics planning application currently under implementation. acknowledgements the research has been partially supported by the national office for research and technology (nkth) grant "digital, real-time enterprises and networks" (omfb-01638/2009). references [1] kovács a.: optimizing the storage assignment in a warehouse served by milkrun logistics, international journal of production economics, 2011, 133, 312–318 [2] lau h., sim m., teo k.: vehicle routing problem with time windows and a limited number of vehicles, european journal of operational research, 2003, 148(3) 559–569 [3] droste m., deuse j.: a planning approach for inplant milk run processes to optimize material provision in assembly systems, proc. 4th cirp international conference on changeable, agile, reconfigurable and virtual production, 2011, 605–610 [4] arnold d.: handbook of logistics, 3rd edition, springer, heidelberg, germany, 2008 (in german) [5] womack j.p., jones d.t.: lean thinking, free press, 2003 [6] klug f.: logistics management in automotive industry, springer, 2010 (in german) [7] lin c.: survey of green vehicle routing problem: past and future trends, expert systems with applications, 2014, 41, 1118–1138. [8] bichler k., krohn r.: gabler kompaktlexikon logistik, 2nd edition, springer, wiesbaden, germany, 2011 (in german) [9] savelsbergh m.w.p., sol m.: the general pickup and delivery problem, transportation science, 1995, 29(1), 17–29 [10] dantzig g.b., ramser j.h.: the truck dispatching problem, management science, 1959, 6(1), 80–91 [11] pillac v.: a review of dynamic vehicle routing problems, european journal of operational research, 2013, 255(1), 1–11 [12] lu q., dessouky m.: an exact algorithm for the multiple vehicle pickup and delivery problem, transportation science, 2012, 38, 503–514 [13] berbeglia g.: feasibility of the pickup and delivery problem with fixed partial routes: a complexity analysis, transportation science, 2012, 46, 359–373 [14] russel r.: a constraint programming approach to designing a newspaper distribution system, international journal of production economics, 2013, 145, 32–138 [15] rossi f., beek van p., walsh t.: handbook of constraint programming, elsevier, 2006 [16] cacchiani v., hemmelamayr v.c., tricoire f.: a set-covering based heuristic algorithm for the periodic vehicle routing problem, discrete applied mathematics, 2014, 163, 53–64 [17] vidal t., crainic t.g., gendreau m., prins c.: heuristics for multi-attribute vehicle routing problems: a survey and synthesis, european journal of operational research, 2013, 231, 1–21 [18] the vrp web: http://neo.lcc.uma.es/vrp, (last accessed: may 25, 2014) [19] hashimoto h.: studies on local search-based approaches for vehicle routing problems, phd thesis, kyoto university, 2008 [20] carić t.: a modelling and optimization framework for real-world vehicle routing problems, vehicle routing problem, hrvoje gold, 2008 [21] matai r., singh s., mittal m.l.: traveling salesman problem: an overview of applications, formulations, and solution approaches, traveling salesman problem, theory and applications, intech, 2010 [22] wilt c.m., thayer j.t., ruml w.: a comparison of greedy search algorithms, proc. 3rd annual symposium on combinatorial search, 2010, 129–136 [23] russell s.j., norvig p.: artificial intelligence: a modern approach, 2nd edition, prentice hall, 2002 [24] yue m.: a simple proof of the inequality ffd (l) ≤ 11/9 opt (l) + 1, ∀l for the ffd bin-packing algorithm, acta mathematicae applicatae sinica, 1991, 7(4), 321–331 hungarian journal of industry and chemistry veszprém vol. 41(1) pp. 7–10 (2013) design of a new chemical injection pump system for gas hydrate inhibition csaba vörös1!, viktor füvesi1, and ákos pintér2 1,2research institute of applied earth sciences, university of miskolc, miskolc-egyetemváros, pob 2, h-3515 hungary 1department of research instrumentation and informatics, miskolc-egyetemváros pob 2, h-3515, hungary 2department of reservoir and mining chemical engineering, miskolc-egyetemváros pob 2, h-3515, hungary !e-mail: voros@afki.hu in this study the main feature of chemical injection systems used in gas industry are detailed. the two main energy sources of these systems are air and electric power source. the general structure and main properties of these injection systems are discussed. examples for a pneumatic commercial and a newly developed, electric system are compared. keywords: chemical injection system, hydrate inhibition, solar energy, pneumatic system introduction during the production of gas, a major problem is the formation of hydrate crystals in the pipeline. a considerable amount of hydrate crystal can cause hydrate plugs in the pipeline. the hydrate plug effect lengthens production outages and results in loss of money for the maintainer [1], because elimination of the plug is a time consuming procedure. one of the most widely used traditional solutions to prevent hydrate formation is addition of methanol to the steaming gas. the methanol helps to dehydrate the gas, thus, the growth of hydrate crystal is limited [2]. the methanol can be transported from the gas separator station or gas collection station to the gas wells via a dedicated pipeline. this traditional solution was the most popular practice for a long time in gas industry. this technology is safe, but has several drawbacks, such as the cost of additional pipe to the gas wells, the cost of the methanol regeneration [3], and methanol contamination of the environment. regardless the methanol technologies are still major solutions for hydrate inhibition for the currently operating gas wells. the modern installations use methanol in low concentrations for newly installed gas wells. these bring the need for injecting methanol locally at the site of the gas wells. thus, an injection unit is needed for this purpose. the production-related aspects such as the consumers expecting increased flexibility from gas provider cannot be neglected, because of the habits of the consumers and the appearance of competitive energy-saving technologies. therefore the different injection systems spread noticeably dynamically in recent years. in the first part of the paper, the main features of the commercial injection systems are detailed followed by the introduction of a newly developed injection system. chemical injection systems in gas industry there are two applications, where chemical injection is required. the first one is the above described gas hydrate inhibition technology. the second one is where usage of corrosion prevention chemicals is needed. new chemical injection technology appeared in sophisticated form using a wide service range as a result of a change in gas production and distribution in the last decade. structure of pneumatic chemical injection pump systems the most commonly used chemical injection units in gas industry employ the energy of gas for dosing. these systems are called “operating without auxiliary power systems”. in details, the energy of gas steam in the pipeline is used as a power source in the dosing of hydrate inhibiting chemical pump systems. this method has the major advantage that the gas is always available, or it is not necessary to provide a separate power source for the equipment to operate. big disadvantage of the technique is that gas is required for operation and this gas is emitted to environment, which is a harmful effect, moreover, the cost of it is also not negligible. there are some solutions to utilize the emitted gases, but these methods raise the price of the pump. 8 fig.1 shows a common structure of chemical injection pump systems, which illustrates how the actuated gas gets into the injection system through a gas preparation unit. this unit is typically a special tank, which is filled with methanol. by using this type of conditioning one can be sure that the gas is sufficiently dry, thus, the water does not disturb the operation of the pump. it is needed to avoid the risk of freezing out various components. the gas bubbles through the methanol, so it loses a significant part its water content. the replacement of the methanol is needed at appropriate intervals of time as a technology management. after the gas leaves the conditioning unit, the gas steams through a two-stage pressure regulator. this unit provides the required pressure to the system for operation. the timer unit is responsible for providing appropriate technological demands of the schedule, i.e. sufficient number of strokes is needed to operate the pump. the chemical is injected with the piston of the injection pump. the injection system includes other components, which are essential for the operation, such as check valves, ball valves and other fittings. the hydrate inhibitor compound can be found in the tank. the main task of the control system is the monitoring of the injection system, so several parameters are required to be measured, e.g. the level of chemical in the tank, the pressure of the after the regulator and the ambient temperature. one of the most substantial information about the injection pump is the entry of the inhibitor to the pipeline. to measure these parameters, transducers are needed, which require some solar energy for the operation. fig.2 shows a wellorganized, modern gas well in hungary. the injection system used employs the gas of the well for its operation. injection system from haskel milton roy the haskel milton roy company develops and manufactures various injection systems for special oil and gas applications for many years. chemical injection pump (cip) series is one of the most widely used equipment for gas wells. a pneumatic version of the device is shown in fig.3, as a typical system. the driving gas or air is fed from the regulator to the gasdrying unit. the air is let into the injection pump, which includes the timer unit. the chemical enters the pump through the appropriate valves and filters. the dosage of chemicals can be adjusted through the rate setting gauge unit (typically it is a burette) at, which the quantity of chemical of one injection is displayed. the strokes can be counted by using the flow meter on the system. the check valve prevents the injection pump from the backpressure of the process fluid. the company can deliver the complete unit in different versions according to the quantity of injection, e.g. the given series can be adjusted from 0.27–25.8 dm3 min-1. the range of operation pressure is also wide, typically 120–600 bar. structure of electric injection systems this category includes systems, where the electricity is the only energy source. in general, the site of the gas figure 1: block scheme of chemical injection system figure 2: chemical injection system on a gas well figure 3: pneumatic injection system from haskel milton roy [4] 9 well is not equipped with electric power because of the relatively large distance from the processor (separator station, collector, etc.). thus, these systems are not commonly employed in the gas well applications. most of the electric chemical injection pump systems are based on the principle of displacement pumps. these high-pressure pumps provide the chemical injection by using speed adjustment in a wide range, or with different piston volumes. as shown in fig.4, the electrical injection pump system contains relatively few units. it cannot be ignored that the electric pump does not only include a motor-driven piston with frequency inverter, the controller electronics is also an important part of the system. solar energy can be applied as energy source of this type of system. this source can feed the control electronic besides the main actuator of the system. in-house designed injection system the development of the injection system was a part of a bigger project with the scada ltd, a company from automation industry. the aim of development was to create an injection system, which can be used mainly at hungarian gas wells. thus, the temperature requirement of the system was in the -40 °c to 60 °c range. the system must be capable of working in ‘ex’ environment with high efficiency. the power source of the actuator is solar energy to reach close to zero emission of the system. in the system, corrosive chemical has to be injected, thus, a corrosive resistant is required at critical parts of the equipment e.g. piston, piston space, etc. the maximal working pressure was 160 bars. a wide range of injection volume was also a fundamental requirement. these requirements were the main parameters at the design phase of the equipment. the block scheme of the developed system can be seen in fig.5. the base of the system is an ex class asynchronous motor (table 1), which is assembled with a helical gear unit from nord manufacturer. the base of injection system is a crank mechanism, which transforms the rotary motion to alternating motion. the pump has two pistons to reach higher injection volume and a wellbalanced load of the motor. the main parameters of the mechanics can be found in table 1. the sealing of the mechanism is a critical design point. the relatively high pressure, corrosive fluids, and high stroke number require special solution for sealing. a single acting, spring energized-seal was selected. the application conditions demanded the tight guiding of neck of piston, to avoid the damage of seals during the operation of pump (fig.6). the electromechanical actuator gives the opportunity to smoothly alter the injected volume in continuous or in periodic operation. table 2 shows the injected volume of the pump at different frequency of the inverter in continuous mode. the power source of the system is an array of solar cells. the power of solar energy system was 2 kw to get extended service and short recharge time. the capacity of the accumulators was 800 ah. the developed equipment has a plc-based control system to monitor the main parameters of the technology and to change the behaviour of the injection system. figure 4: block scheme of electric power injection system figure 5: block scheme of new injection system table 1: main parameters of the injection pump designed asynchronous motor nominal voltage 230 v(y) /400 v (d), 50 hz nominal power 0,12 kw ex class ptb 07 atex 1058 x ii2g ex de iic t4 type dex 63k/4k vendor hew helical gear unit gear ratio 41,58 ex class ex ii 2g c iic t4 x type sk02f-iec63 /26-63 s/4 tf/2g vendor nord crank mechanism length of stroke 20 mm ratio of mechanics 7 injection unit diameter of piston 5 mm vendor of seals trelleborg type of seals turcon® variseal® 10 the measured parameters are the pressure of siphon of well, drill pipe, injection pipe; the temperature of pipe of well, soil, chemicals, controller, temperature of inverter; the level of the chemical in the tank; the current and the voltage of the inverter. the frequency of the inverter can be changed in function of the conditions of the well. the injection system is able to communicate wirelessly with a server. by using modern computer technology, the main parameters of the system can be monitored and changed. fig.7 shows the website of the system, which shows, on one hand, the main actual online parameters of the system, on other hand, the trends and history of the parameters on diagrams. the structure of the website is user friendly, simple. a model technology for an actual gas well was set up at the site of the scada ltd. near to hajdúszoboszló (fig.8). at the test site, main parameters like level of the chemical in the tank, process gas pressure, frequency of the inverter, etc. were monitored and measured. after the successful test of the model technology, the equipment was moved to a real gas well at békásmegyer in october 2012. conclusion a new solar energy-based chemical injection pump system was developed with a modern control and computerized support system at university of miskolc, research institute of applied earth sciences. the equipment meets the modern requirements. it is an efficient injection system; it has wide operation range and has user-friendly high-level computer support. in the process automation field of gas industry, the adaptation of new approaches appear slower in consumer or in industrial environments than in other fields of industry. the new, energy efficient, solar supplied, standalone chemical injection systems hopefully can enter in the field and will be utilized more wells in hungary. acknowledgement this work was partially supported by the framework of the centre of excellence of mechatronics and logistics at the university of miskolc. references [1] berecz e., balla-achs m.: gázhidrátok, akadémiai kiadó, budapest, hungary, 1980 (in hungarian) [2] hammerschmidt e.g.: formation of gas hydrates in natural gas transmission lines, ind. eng. chem. 1934, 26(8), 851 [3] lederhos j.p., long j.p., sum a., christiansen r.l., sloan, e.d. jr.: effective kinetic inhibitors for natural gas hydrates, chemical engineering science, 1996, 51(8), 1221–1229 [4] williams chemical metering pumps: www.willamspump.com (last accessed: may 25, 2014) figure 7: website of pump system figure 6: section of injection unit table 2: injected volume of pump at 150 bars frequency of inverter, hz injected volume, dm3 h-1 30 21.71 50 36.19 70 50.67 90 65.14 figure 8: block scheme of chemical injection system hungarian journal of industry and chemistry veszprém vol. 41(1) pp. 11–15 (2013) ionic liquids in advanced energy storage cells attila göllei ! and attila magyar department of electrical engineering and information technology, university of pannonia, egyetem str. 10, veszprém, h-8200, hungary !e-mail:gollei.attila@virt.uni-pannon.hu the interest in the research and application of ionic liquids has been increased worldwide, especially in petrochemical industry, nuclear industry, oil and gas industry, chemical, and electro-chemical industry. in the field of chemical operations in microwave field with ionic liquids (organic chemical synthesis, catalytic operations, etc.) new horizons opened that were supported by the dramatically increasing number of studies dealing with this question and their impact. due to the high durability of ionic liquids as a function of temperature, a wider temperature range of operations can be accessed. in addition, it offers environmental friendly solution in the replacement of the toxic solvents with generally low volatility. the area of application extends to electrolytes of novel battery cells. the important prerequisite for application of ionic liquids is the knowledge of their physical and chemical properties. our aim was to test the dielectric properties, viscosity, and temperature dependence of the electrical conductivity. considering our measurements, it can be declared that the aforementioned properties show significant temperature dependence in the case of ionic liquids. this knowledge is important for the usability, design and execution of production and related optimization processes. it is particularly important that energy storage cells can be exposed to large temperature fluctuations. this study discusses the sample materials, the usage possibilities of the sample materials and the obtained results. keywords: ionic liquids, energy storage cells, conductivity, temperature dependence, viscosity introduction the key parameters in the modelling of microwave behaviour of ionic liquids are the dielectric constant, dielectric dissipation factors, in addition the parameters characterizing the polarizability and the microwave energy absorption. traditional measurement methods of the static dielectric constant of ionic liquids fail, because they cause intense shortcut due to their high electrical conductivity. according to literature, these contexts have not been studied systematically because of the novelty of this subject. the significance of these results is critically important in the planning and controlling chemical reactions. ionic liquids (il) opened new technological possibilities at the end of the 1990s providing a wide range of applications, especially for areas of chemistry and particularly in green chemistry. ils are beneficial due to their special chemical and physical characteristics. nowadays, the use of energy storage units, particularly mobile phones, electric vehicles, and uninterruptible power supply systems has more and more importance. recently, room temperature ionic liquids (rtils) have been extensively studied as electrolytes of lithium ion batteries from cellular phones to electric vehicles. the unique properties make rtils attractive candidates for the electrolyte base of safe lithium battery [1, 2]. generally, rtils are well known to be thermally stable and non-flammable and their nature can hopefully improve the safety of electrochemical devices with aprotic solvents, such as li batteries and supercapacitors. 1-ethyl-3-methyl-imidazolium tetrafluoroborate (emim-bf4) has a high ionic conductivity, which is comparable to those of organic solvent electrolytes. in addition, the viscosity of emim-bf4 is low. therefore, emim-bf4 is expected to be a good electrolyte candidate for li batteries. we have found that a li/licoo2 cell with rtils as an electrolyte base works reversibly, indicating that qaimide rtils are quite stable even at the li reduction potential. clearly, rtils improve the safety of li-ion batteries with carbon anodes. to date, rtils are the most promising electrolytes for improving the safety of li-metal batteries, which could be important for higher energy densities [3]. a set of four imidazolium ionic liquids (solid at room temperature) and one imidazolium ionic solid were screened for their potentials as electrolytes in manganese dioxide free leclanché batteries, equipped with a zinc anode and graphite cathode [4]. it should be noted that the ionic liquid 1-ethyl-3methylimidazolium hydrogensulphate (emim-hso4) similar to many other ionic liquids, such as those based on nitrate and dihydrogenphosphate anions, have also been found they work well in this battery design. novel 12 batteries are designed using standard cathode materials such as mno2, pbo2, nio and ago, and anode materials such as zn, sn and pb. additionally, by using a solid polymer electrolyte composed of polyvinyl alcohol and anionic liquid, new types of solid state batteries were demonstrated with discharge voltages ranging up to 1.8 v, depending upon the type of cathode and anode used [5]. ionic liquids like 1-butyl-3-methylimidazolium tetrafluoroborate (imim-bf4) or hexafluorophosphate (imim-pf6) and 1-butyl-4-methylpyridinium tetrafluoroborate (pybf4) were mixed with organic solvents such as butyrolactone (bl) and acetonitrile (acn). the specific ionic liquid used in the given study is shown in fig.1. a lithium salt (libf4 or lipf6) was added to these mixtures for possible application in the field of energy storage (batteries or super-capacitors). viscosities, conductivities and electrochemical windows at a pt electrode of these electrolytes were investigated. all the studied electrolytes are stable toward oxidation and exhibit a vitreous phase transition, which has been determined by application of the conductivity measurements. mixtures containing the bf4 anion exhibit the lowest viscosity and highest conductivity [6]. methods the essential precondition for the application of ionic liquids in batteries is a preliminary examination of its properties. therefore, every measurement method available to us was used on a number of ionic liquids examined. we have carried out microwave measurements, such as temperature change, dielectric properties at 2.45 ghz frequency, electrical conductivity according to temperature and viscosity changes depending on the temperature. the velocity of temperature change of ionic liquids was measured in the cem discover unit. this is a wellknown and commercially available apparatus in microwave chemistry. the device has a cylindrical operating space and on the cylindrical peripheral surface there are many slots where microwave energy can enter. this solution provides a special high homogeneity of the microwave field. the temperature was measured at the bottom of the compartment with an infrared thermometer. the amount of the samples used was 0.5 g, which was placed in an inner diameter of 12.5 mm of borosilicate cylindrical glass flask. it is important to know that during microwave treatment the microwave energy interacts with the treated material, and the material converts the electric energy into thermal energy according to its characteristic of dielectric properties. during this conversion process, the macroscopically observable result is the measurable increase of the temperature in the treated material. the rate of the temperature increase depends on the microwave field and the treated material properties, which is described in the following equation: δt /δt = pv / ρcp = ie 2 fε"/ ρcp (1) where, the ∆t/∆t is the velocity of temperature change in kelvin per second, pv is the absorbed power in the sample, ρ is the density of the sample, cp is the specific heat of the sample, e2 is the strength of the electromagnetic field in the sample, f is the frequency of the field and ε” is the dielectric loss, i means this is a complex value [4]. eq.(1) shows that the temperature of the treated material is influenced by a number of factors. the separate testing of their effects is not an easy task, since ρ, ε, cp features themselves are temperature dependent, and this value is difficult to accurately measure inside a material. in case of strictly homogeneous series of examined compounds the situation is more simplified, because some simplifications are allowed. assuming ρ and cp does not change significantly in the function of temperature, the multiplication ρ cp was almost considered to be constant, so that the rate of temperature change is determined by e and ε" only. further simplifications can be made if the device is single-mode with the same volume and shape, and the microwave energy is constant during the investigation. the value of e is determined by ε' and ε' and ε" and the rate of temperature change is essentially determined by ε" value. figure 1: the structure of investigated ionic liquids table 1: the formulas of investigated ionic liquids compound r y 1 ch3 bf4 2 c2h5 bf4 3 c3h7 bf4 4 c4h9 bf4 5 ch3 pf6 6 c2h5 pf6 7 c3h7 pf6 8 c4h9 pf6 9 c2h5 ci 10 c2h5 br 11 c2h5 scn 12 c2h5 n(cn)2 13 c2h5 n(so2cf3)2 13 measurement setup the schematic representation of the in-house designed experimental set-up for automated online measurement of dielectric properties of ionic liquids in a definite temperature range is shown in fig.2. it is composed of the following devices and instruments; cylindrical sample holder unit, thermostat, peristaltic pump, waveguide, temperature sensor, displaceable piston, stepper motor, magnetron, detectors, control unit, and a pc. the il sample, which is placed in the thermostat to be kept at the desired temperature, is passed across the waveguide having a length of about 3λ through the sample holder tube with the help of a peristaltic pump. the electric energy is transformed into microwave energy by the magnetron. the stepper motor is controlled by a microprocessor control unit equipped with an intel 8-bit microcontroller, a 12 bit a/d converters for receiving the four diode-detector signals, a stepping motor driver, and a rs-232 serial interface to connect it to a pc. the control unit collects the detector signals and the temperature data from the temperature sensor and sends them to the pc. furthermore, it controls the position of the short circuit displaceable piston on the basis of algorithm software elaborated for this purpose. the measurement method is based on the compensation of phase change due to the microwave energy absorption of the liquid sample. the short circuit piston situated behind the sample must be actuated for compensation. the energy conditions created by the wave front in the waveguide are measured by four diode-detectors. dielectric constants, dielectric loss factors and the temperature dependence of the dielectric properties of ionic liquids intended to be used in batteries were determined by the above described self-designed microwave dielectrometric apparatus (fig.3) at the frequency of 2.45 ghz and at different temperatures (30°c, 40°c, 50°c, 60°c, 70°c, 80°c, 90°c, 100°c, 110°c and 120°c). the speed of the change in temperature depends on the electrical field strength in the material (e), the absorbed microwave power, (pv) density (ρ), the specific heat capacity (cp) and the dielectric loss factor ε” and can be given by eq.(1) [7]. results and discussions the effects of r groups (table 1) were examined in case of two anions bf4 (1–4) and pf6 (5–8) at 3 to 5 w of microwave energy. the results indicate that the decrease of the number of c atoms in r increases the rate of temperature change. by increasing the microwave power significantly the temperature rapidly converge and sometimes crossing over, but this is not typical in fig.3. overall, the rate of temperature rising follows the order of ε' and ε" suggesting that in a strictly homologous series the temperature change of ionic liquids is determined by ε" [5]. after evaluating the rate of temperature change, we investigated two additional properties of the ionic liquids used in the advanced batteries. these parameters were the viscosity and the electrical conductivity. both of these parameters are the functions of temperature. they were examined between 20 °c and 100–120 °c temperature range. the viscosity was measured up to 95 °c due to the sample material being heated by a waterfilled heat exchanger. the measurements were performed in a sv-10 type of vibration viscometer (a&d ltd. japan). fig.4 shows that the viscosity at room temperature is high, typically several hundred pa·s. it decreases rapidly with the temperature increase similar to a reciprocal curve. at 100 °c, the value of viscosity can be ten times lower then at the initial value as can shown in fig.4. the investigation of the viscosity is important, since it basically correlates with the mobility of ions in the electrolyte, which can affect the conductivity, and thus the internal resistance of the battery cell. by cooling ionic liquids, the viscosity is increasing rapidly. around freezing temperature the ionic liquids were already similar to a “honey density” mass. since the energy storage cells are used in a wide temperature range, it is important to know that the figure 2: scheme of the experimental setup figure 3: temperature profile for 1-butyl-3methylimidazolium tetrafluoroborate at 3w 14 electrical conductivity of the electrolytes is a function of temperature. fig.5 contains five different electrical conductivity plots of ionic liquids in the function of temperature. it can be seen that the above mentioned bmim-bf4 does not have the highest conductivity value, but the depending on the temperature the conductivity value of this material increases with the greatest intensity [6]. a new and surprising result can be seen in fig.6. the dielectric constant value of bmim-bf4 reaches a value of 1 at close to 100 °c, similarly to the value of the vacuum and with the further raising of the temperature this value decreases into the negative range. this fact suggests that by increasing the temperature the electrical conductivity is rising greatly and this compound is no longer an insulating material, but a conductor. therefore it is important to keep the temperature in an adequate range when batteries are used and especially in the charging period. the dielectric constant (e1), dielectric loss factor values of ils built up of the same bf4 anion and six previously described cations containing alkyl chains with different lengths (dietmeim+, dietetim+, dietprim+, and dietbuim+) at different temperatures between 30°c and 120°c are shown in fig.7. at the initial measuring temperature of 30 °c all four of the studied ils have similar dielectric constants around 7. with the increase in temperature the e1 values for dietmeim(bf4), dietetim(bf4) and dietprim(bf4) slightly increase up to 13, while the dielectric constant for dietbuim(bf4) shows a sudden break at 90°c and at 120°c it reaches the value as high as 27. this could be explained with some sudden changes in the structure of the ils or in the physico-chemical interactions between the anion and the cation. excluding the results for dietbuim(bf4) the values at elevated temperature show that the highest e1 value belongs to dietmeim(bf4), followed by dietetim(bf4) and then by the dietprim(bf4), hence the dielectric constant increases with the decrease in the alkyl chain length of the cation. taking into account the dielectric constant, dielectric loss and electrical conductivity results of all the investigated ils it can be concluded that the alkyl chain length of the cation and the structure of the anion strongly influence the dielectric properties of the ils and that the highest g value is exhibited by the dietmeim(bf4) il at 30°c temperature, hence it is the most suitable candidate for battery applications. furthermore it can be stated that implementing the knowledge about the connection between the il structure and the dielectric properties another ils should be studied in order to select the ones most adequate for electrolyte application. figure 4: viscosity of bmim-bf4 as a function of the temperature figure 5: conductivity of five compounds as a function of temperature figure 6: dielectric constant of bmim-bf4 as a function of the temperature figure 7: dielectric constant of ils containing common bf4 anion and different cations 15 conclusion due to the special characteristics of ils, such as wide electrochemical windows, high inherent conductivities, high thermal and electrochemical stability, tuneable physicochemical properties, etc., they are potentially excellent candidates for environmentally sound, green electrolytes in batteries. in order to predict their success in a specific application, it is essential to gain information about their dielectric properties. however, several techniques have already been published about determination of the dielectric properties of ils, so far no experimental methods were introduced due to the fact that such measurements cannot be realized by classical methods because of the high conductivity of ils. summarizing our results, we can conclude that when ionic liquids in the energy storage cells were used, their physical, chemical and electrical parameters are significantly temperature dependent. in any case, when they are applied, we should specify the range of application temperature. stepping out of this range of the energy storage cell may not meet the expected specification values, or in the worst case it may be permanently damaged. acknowledgements we acknowledge the financial support of the hungarian state and the european union under the tamop4.2.2.a-11/1/ konv-2012-0072. references [1] alarco p.j., yaser a.l., ravet n., armand m.: lithium conducting pyrazoliumimides plastic crystals: a new solid state electrolyte matrix. solid state ionics, 2004, 172(1–4), 53–56 [2] schiffmann r.f.: microwave and dielectric drying, in: 2nd handbook of industrial drying, (ed. mujamder a.s.), vol 1, marcel dekker, new york, usa, 1995, pp. 345–372. [3] hikari s., hajime m., kuniaki t.: application of room temperature ionic liquids to li batteries electrochimica acta, 2007, 53, 1048–1054 [4] zhang z., gao x., yang l.: electrochemical properties of room temperature ionic liquids incorporating bf4 and tfsi anions as green electrolytes, chinese science bulletin 2005, 50(18), 2009 [5] gao x.h., zhu m.j., zhang z.x.: research on room temperature molten salts with alkylated imidazolium salt as electrolytes, chemical world (supplement, i), 2004, 45, 156–157 (in chinese) [6] nishida t., tashiro y., yamamoto m.: physical and electrochemical properties of 1-alkyl-3methylimidazolium tetrafluoroborate for electrolyte, j. fluor. chem., 2003, 120, 135–141 [7] göllei a., vass a., pallai e., gerzson m., ludányi l., mink j.: apparatus and method to measure dielectric properties (ε’ and ε”) of ionic liquids. review of scientific instruments, 2009, 80(4), 6734–6748 advertise upcoming meetings, conferences, and workshops; make public announcements; introduce your research laboratory; a new product or a service in the hungarian journal of industry and chemistry please contact us if interested! editorial office: university of pannonia p.o. box 158, veszprém h-8201 (hungary) tel.: +36 (88) 624-298, e-mail: hjic@almos.uni-pannon.hu; web: hjic.mk.uni-pannon.hu felelős szerkesztő: szilágyi róbert, phd kiadja: pannon egyetem, 8200 veszprém, egyetem u. 10. levélcím: h-8201 veszprém, postafiók 158, tel.: (88) 624-000 hungarian journal of industry and chemistry veszprém vol. 41(1) pp. 17–26 (2013) monitoring and diagnosis of manufacturing systems using timed coloured petri nets adrien leitold1, brigitta márczi2, anna ibolya pózna2, and miklós gerzson2! 1 department of mathematics, university of pannonia, egyetem str. 10, hungary 2 department of electrical engineering and information systems, university of pannonia, egyetem str. 10, hungary !e-mail: gerzson@almos.uni-pannon.hu novel fault modelling and integration method were applied in the case when the faultless operation of the system was modelled by a high-level, coloured petri net. in order to achieve realistic investigations, a timed coloured petri net model of the system was constructed, where faults can occur in the manufacturing lines. the faultless and fault containing models were implemented in cpntools both for non-timed and timed cases. the resulted model was investigated both via simulation and using the occurrence graph. for efficient analysis of the occurrence graph a software module called oganalyser was developed. keywords: monitoring and diagnostics of manufacturing processes, coloured timed petri nets, probabilistic models, occurrence graph introduction models are often used for the description and investigation of complex systems even if they cannot perfectly describe the investigated system. the course of a manufacturing system can be split up to distinct steps of serial or parallel technological sub-processes. this enables the description of the system by a discrete event systems model [1] in the form of petri nets. during the design process of a manufacturing system, often only a model of the faultless operation is created. the integration of possible faults into the model could give important information for more complex investigation of the system. in our previous work [2] we have integrated fault events with different occurring possibilities into low-level petri net models of manufacturing systems in such a way that the size of the model remained almost the same. in our recent work, we applied the above fault integration method for the case when the faultless operation of the system was modelled by a high-level, coloured petri net (abbreviated as cp-nets) [3]. in lowlevel petri nets the transitions fire instantaneously, but the events of a real system take place for a certain amount of time influencing the operation of the system. therefore, a timed coloured petri net model of the system is constructed in order to achieve realistic investigations. cpntools [4] offer tools for modelling and analysing of cp-nets. there are two possibilities for the investigation of a manufacturing system in cpntools: the simulation and the analysis of the occurrence graph. in case of fault modelling using different occurring possibilities; however, the standard occurrence graph does not give information about the probability of the different occurring states of the system. therefore, a special software module, called the oganalyzer has been developed for solving this problem. weights can be assigned to the arcs of the occurrence graph and the software calculates the probability of each node in the occurrence graph, i.e. of each operational state of the system. petri net model of a manufacturing process petri nets enable both the mathematical and the graph representation of a discrete event system to be modelled, where the signals of the system have discrete range space and time is also discrete [5]. petri nets can be used for describing a controlled or open loop system for modelling the events occurring in it, and for analysing the resulted model. for the different application purposes, various modifications of the original petri net were developed with the aim of improving the modelling capabilities. one of the approaches is the coloured petri nets (cp-nets). we use here the cp-nets for modelling technological systems and their diagnosis, i.e. for the determination of faulty operational modes of the investigated system. coloured petri nets the cp-nets combine the modelling advantages of petri nets and the compactness of the functional 18 programming language standard ml [6]. a petri net is bipartite graph having circles and rectangles as nodes. circles refer to the ‘places’ in the net and rectangles to the ‘transitions’. places represent the state of the elements in the modelled system, while transitions correspond to the actions taken place in it. there are ‘arcs’ between places and transitions referring to logical relations of the system. if an arc directs from a place to a transition then the place acts as a precondition of the given transition while the arcs in the opposite direction represent consequences of transitions. each place can be marked with one or more coloured tokens representing the state of the modelled element. here we emphasize two important novelties of cpnets only. the tokens describing the state of the system have data value, the so-called token colour attached to them. in this paper these colours are used to identify workpieces and to describe the operation to be performed on them. places, transitions and arcs can have ‘inscriptions’. an inscription of a place determines the set of colours that a token on the place can have. another place inscription gives the actual number of the tokens on the place, i.e. the current marking of that place. the inscriptions of transitions can contain different types of functions. these functions determine the type of the colour set of the incoming and outgoing tokens and the operation performed on them. the arc inscriptions can be used for evaluating the result of the performed action at the previous transition. these conditional expressions define the colour of the token on the following place. the original petri net concept did not contain the time; however, the firing of transition takes place instantaneously. in case of real technological systems the time has a great role during the occurring of events. cp-nets also offer the possibility of adding time to the operation of transitions. the firing rule of a transition in timed petri nets is as follows: a transition is enabled if all of its input places contain sufficient number coloured tokens defined by the arc functions and the allotted time has elapsed. one of the main advantages of modelling with petri nets is the ability of describing sequences of discrete events that occur both in a serial and in a parallel way. in case of parallelism, we can distinguish two different situations. in the first case the two or more series of events can take place independently of each other. this situation occurs when workpieces can be elaborated in different manufacturing lines in parallel way. in the other case only one of the event sequences can take place because these events exclude mutually each other. these events have the same precondition, and the occurrence of any of them makes this precondition invalid. this kind of parallelism is called ‘conflict situation’. in a petri net the conflict can be recognized when a place is the precondition of two or more transitions. in this case it is randomly selected, which transition takes place. the conflict can have two different sources in technological systems. a conflict occurs in a technological sense when two or more processes want to use the same tool or resource e.g. a robot. usually it is worth to assign priority to each conflicting transition in order to define their sequence. when a fault occurs during the operation of the system, it also causes a conflict situation. this can be avoided by adding a special probability function to arc expression functions. by evaluating this function, the occurrence of the fault can be unambiguously determined during execution. analysis of petri nets there are two basic directions for the analysis of a petri net: (i) the structural method, which is independent of the initial state of the net and (ii) the investigations based on a given initial state (the behavioural analysis). in this paper the latter is used for the investigation of technological system behaviour. simulation is our primary tool for the checking the correctness of a model. starting from a given initial state the user can check whether the operation of the system terminates in the appropriate state. it can also be investigated, which transitions become enabled in certain steps, whether there is a conflict among then. simulation investigations do not give unambiguous answers to questions of formal analysis formulating in petri net literature [7] but they complement them well. another petri net analysis method uses the ‘occurrence graph’. the basic idea of the occurrence graph is to construct a graph, which contains all of the reachable markings from a given initial state. these marking are the nodes of the occurrence graph and the arcs connecting the nodes refer to the logical relations realized by the firing transition between two markings. unfortunately, the occurrence graph even of a small petri net may become very large. therefore, several reduction methods were proposed in order to get a relatively small occurrence graph [7]. most of the simulation tools, as the cpntools [4] used by us, are able to construct the occurrence graph. modelling and analysis of technological systems in the following, we wish to demonstrate the use of cpnets and their occurrence graphs for modelling and analysis of technological processes. both for normal faultless and faulty mode operation of the technological system are considered in the non-timed and timed cases. the analysis is performed via simulation and with different investigations of the occurrence graph. the manufacturing system and its operating procedure a simple case study is presented here for a manufacturing system containing two manufacturing lines and a robot. the arrangement of the system can be seen in fig.1. 19 the workpieces to be processed appear on the input place in. the task of the robot is to put them to the appropriate input place of a manufacturing line m1_in or m2_in according to operational instructions. assume that the two manufacturing lines perform different actions on the workpiece of interest. when the manufacturing process is over, the finished workpiece appears at the output end of the line either on m1_out or m2_out depending on the performed action. if the workpiece has to be modified on the other manufacturing line then the robot puts it onto the other input place. if the manufacturing process is over then the robot puts it into the product container out. assume that one workpiece at a time can be on the input and output places of manufacturing lines. it follows that the robot can only transfer a workpiece from place in to the input place of a manufacturing line if this place is empty and the precondition of the start of a manufacturing process is that the output place of this line should be empty. as a general precondition of all transfer processes the robot has to be free. the cp-net model of the normal (faultless) operation of the manufacturing system in the form of a screenshot from cpntools can be seen in fig.2. the process starts with a token at place start. the transition generator generates the prescribed number of tokens representing workpieces at place in. the colour assigned to a token contains an identifier of the workpiece and a code referring to the manufacturing process or processes to be carried out. four kinds of manufacturing mode are possible in this manufacturing system: the workpiece has to be processed on line 1 (denoted by m1) or on line 2 (m2) only, or it has to go through the line 1 and then through line 2 (m12) or in reverse order (m21). as an example, the token (1,m12) refers to the workpiece having identifier '1' and this piece has to be processed first on line 1 then on line 2. the state of input and output of manufacturing lines is modelled with two places. the places tin_empty, tin_full refer to state of inputs and they are mutually exclusive. the colour of tokens referring to the state of these places consists of the identifier of the line only. if the input place of the line 1 is empty then there is a token having colour m1 on the place tin_empty, and there has not to be a token having colour m1 on the place tin_full. the same applies for the places (tout_empty and tout_full) describing the state of the output places of manufacturing lines. figure 2: the cp-net model of the faultless operation of the manufacturing system figure 1: the manufacturing system 20 the transfer processes are disintegrated into three steps: to transitions referring to the (i) start and (ii) end of the transfer and to a place representing the (ii) transfer itself. transitions transfer#_start correspond to the start of transfer processes from in, if # = 1, from tout_full if # = 2 or 3. the places transfer# represent the transfer process 1, 2 or 3. the transitions transfer#_end refer to completing of transfer process to the input place of a line (# = 1), to product container (# = 2) or to the input place to another manufacturing line (# = 3). the place manuf_line refers to two manufacturing lines and the colour of token shows the line being processed. assume that only a single fault can occur in the system during manufacturing: the identification label of the piece can get damaged therefore it cannot be identified. workpieces with damaged label get into a separate container represented by place out_fault. the repairing of the label is not handled in this example. the modified part of the petri net model can be seen in fig.3, where the occurring of fault is taken into account. the occurrence of the fault is forced by a check function built into arc inscriptions in the petri net model randomly. this check function returns with a fault in predefined probability. this probability of the can be set in the definition part of the net and different fault probability values can be assigned to the two manufacturing lines. by comparing figs.2 and 3, it can be stated that a new place out_fault appears as a consequence of fault modelling and integration and the arc expression functions of arcs starting from transition manuf_line are extended with the fault checking. for realistic investigation of a technological system the timed version of the cp-net model is used as a case study. a time point is assigned to the transitions. the transition generator does not belong to the technological system closely, so it fires under zero time, i.e. instantaneously. different time units are assigned to the other transitions. these time values appear as transition inscriptions ‘@+i’$ (where$ i is an integer number defining the amount of time in seconds) on the net as it can be seen in the fig. 3. during the simulation investigations different time values have been applied in order to check the possibility of a deadlock. preliminary analysis by simulation as a first step, simulation is applied for the investigation of the developed petri net model of the manufacturing system. these were carried out assuming both faultless system operation and when fault can occur during the manufacturing. both non-timed and timed operational modes were considered. the short description of the simulation is as follows. the simulation starts with the generation of tokens representing workpieces. the number of these tokens i.e. the number of workpieces to be processed can be modified in the arc expression function belonging to the transition generator. the type of processes to be performed i.e. the label referring to the manufacturing line(s) of the tokens can be set in the definition part of the cp-net. as a result, the colour of generated tokens refers to the identifier and to the process(es) to be carried out. because of the highest priority of transition generator the transition transfer1_start can only fire after the prescribed number of token appears at the place in. as mentioned above, the transition transfer1_end refers to the completion of the transfer of the workpiece to the input place of a manufacturing line. as a next step, the firing of transition manuf_line corresponds to the completion of manufacturing process. the only fault in the system can occur during this process. if it happens then the token gets into the place out_fault, which represents the fault container. if the fault does not occur then the system checks whether the manufacturing process is over or the workpiece has to be also processed on the other line. in the first case the robot puts it to the place out representing the product container, while in other case it transfers the token representing the piece into the input place of another line. the modelling of the other two transfer processes (transfer of a workpiece from the output place of a manufacturing line either to the product container or to the input place of the other line) is similar to the transfer from place in to place tin_full. if the appropriate input place and the robot are free, another transfer process can start. the primary goal of the simulation is to check the correct operation of the model. another aim is the investigation of possible deadlock situations. in case of deadlock, the process stops without completing all the prescribed technological actions. it can happen in case of timed simulation of our investigated system and it refers to the wrong determination of the timing of actions. figure 3: the petri net model after integration of fault 21 simulation cannot ensure the thorough investigation of the modelled system, but it complements well the further analysis. for the detailed investigations we applied the analysis of occurrence graph. analysis based on the occurrence graph the thorough analysis of the behavioural properties of a cp-net can be performed using its occurrence graph. the concept of the occurrence graph was introduced above. the cpntools generates automatically the occurrence graph, but the check functions used for the fault generation have to be removed from the arc expressions otherwise the occurrence graph is generated only for the normal mode or for the faulty mode. for the illustration of generation and analysis of the occurrence graph let us assume that there are two workpieces to be processed, one of them has to go through manufacturing line 2, while the other has to go first through manufacturing line 1 then through line 2. let the operation of the system be faultless and let the firing of all transition be instantaneous, i.e. the net is non-timed. the resulted occurrence graph can be seen in fig.4. the explanation of numbers in the occurrence graph can be seen in fig.5. the frames in the upper part of boxes are the identifiers of system states. the expression x:y in lower part shows the number of preceding and succeeding states. the token distribution belonging to a node can be obtained by selecting the triangle in left low corner. the opening window contains the name of places and the number and colour of tokens. all the branches on the graph are explained by technological reasons, as there is no built in rule for the robot to start the transfer with any particular workpiece. the graph has only one terminal node (highlighted by green) and it refers to the normal termination of the process i.e. all the prescribed manufacturing processes terminated properly. now we can repeat the simulation with the same initial condition relating to workpieces but assuming that faults can occur during manufacturing process. the resulted occurrence graph can be seen in fig.6. figure 4: the occurrence graph no fault, no timing figure 6: the occurrence graph with fault, no timing figure 5: key for the occurrence graph 22 it can be stated that the occurrence graph has become larger and the number of terminal nodes has increased due the effect of the possible faults. the reason of branches on the graph can be either technological (at the nodes 3, 9, 28, 51 and 54) or due to the fault. only one of the terminal nodes refers to the normal termination of the process (highlighted by green, node 62), the others belong to the faulty cases (highlighted by red, nodes 22, 37, 43, 56 and 57). in case of faulty operation the identification tag of at least one workpiece get damaged during the manufacturing process. next we repeat the simulation again but adding the timing information to the net and assuming faultless operation. let the time duration of transfer processes be equal to unit time, and the time of manufacturing processes is equal to 5 time units. the resulted occurrence graph can be seen in fig.7. the resulted occurrence graph is a tree and its two terminal nodes (nodes 28 and 29) differ only in time stamp of the tokens (the time stamp can be seen only in cpntools with a detailed label for each node). comparing this graph with the occurrence graph in fig.4, it can be stated that the number of parallel branches is less and they have different terminal states. adding timing information to the model reduces the number of the possible different technological variants. as the fourth case, let the simulation be performed with both timing and faults. the resulted occurrence graph (see fig.8) is a tree again, the number of nodes is almost the same but the number of terminal nodes has doubled comparing to the occurrence graph in fig.6. it can be stated based on figs.4 and 6–8 that the occurrence graph is relatively simple in case of small number of workpieces and the analysis of nodes can be done manually. thus, it is easily to find the terminal node or nodes referring to normal, faultless termination of the process, and those terminal nodes where the manufacturing of one piece or of both pieces ends with fault. however, the size of the occurrence graph grows figure 8: the occurrence graph with fault and timing figure 9: the node numbers in occurrence graph figure 7: the occurrence graph no fault, with timing 23 exponentially if the number of pieces becomes larger, as it can be seen in the left part of fig.9 assuming faultless or faulty operational mode, and non-timed or timed net. in case of large number of simpler workpieces when the identification is not necessary for each item, the identification tag can be omitted from the colour of the token. assuming this situation all the simulation investigations (with and without fault, with and without timing) is repeated. the size of the resulted occurrence graphs is less than an order of magnitude simpler compared to the equivalent case with identifier as it can be seen in the right part of fig.9. since the workpieces have to be processed on the same manufacturing line, they have the same colour, thus they are indistinguishable. since the robot selects among workpieces having the same colour, there will be no technological branches on the occurrence graph. this results in a much simpler occurrence graph especially when there are large number of workpieces and the processes to be performed is one or two kind of sorts. as an example, let us investigate the structure of occurrence graphs in case when there is no timing in the system, the token colour contains the identification tag and both faultless and faulty operational mode is assumed. according to data in table 1, the size of the occurrence graph depends on the number of workpieces, the number of manufacturing procedures to be processed, and the presence of fault. if fault can occur during the manufacturing process both the number of nodes and the arcs increases dramatically. there are several terminal nodes, too, but only one refers to normal termination of manufacturing processes the others belong to different faulty situations. the labelling of workpieces has also a significant effect on the complexity of the occurrence graph. if there are one or more workpieces, which should be processed on both manufacturing lines then the number of nodes and arcs is doubled as it can be seen in the corresponding rows in table 1. the results of an investigation with timing information can be seen in table 2. if the number of workpieces is less than four or the workpieces have to be processed on only one manufacturing line, then the size of the occurrence graph depends on the number of workpieces and the presence of fault. on the other hand if there are at least four workpieces and at least two of them have to be processed on both manufacturing lines, but in reverse order then a deadlock situation can occur. a further condition of a deadlock that the manufacturing time should be longer than the transfer time but it is true in general. in case of a deadlock, the process stops because the precondition of transfer processes cannot be fulfilled. there are workpieces on input and output places of both manufacturing lines and therefore no further steps are enabled. if all the workpieces have to be processed on both manufacturing lines and there is no fault then all of terminal nodes refer to a deadlock as it can be seen in the rows marked by a footnote in the table 2. the identification tag can be omitted from the colour of token in certain cases. if the number of workpieces is small and they have to be processed in different ways then there is a significant change in the occurrence graph. on the other hand in case of large number of workpieces, the structure of occurrence graph becomes much simpler if the identification tag is removed from the colour. analysis of the occurrence graph using the oganalyzer as mentioned above, cpntools cannot use the information about the probability of faults at the generation of occurrence graph. however, assigning this value to the appropriate edges, the probability of each node of the occurrence graph, i.e. of each system state can be determined. for this purpose, software called table 1: comparing the structure of occurrence graphs – no timing no. of workpieces label (identifier, manufacturing information) faultless operational mode faulty operational mode nodes arcs tna nodes arcs tna 1 (1,m1) 7 6 1 8 7 2 1 (1,m12) 10 9 1 12 11 3 2 (1,m1)++(2,m2) 29 32 1 42 50 4 2 (1,m1)++(2,m12) 37 40 1 60 70 6 2 (1,m2)++(2,m12) 39 41 1 62 72 6 2 (1,m12)++(2,m21) 42 44 1 82 95 9 3 (1,m1)++(2,m2)++(3,m12) 145 173 1 306 409 12 3 (1,m2)++(2,m12)++(3,m21) 165 189 1 414 536 18 3 (1,m1)++(2,m1)++(3,m1) 107 123 1 210 273 8 4 (1,m1)++(2,m2)++(3,m12)++(4,m21) 631 772 1 2063 2900 36 4 (1,m1)++(2,m1)++(3,m1)++(4,m1) 340 404 1 949 1300 16 5 (1,m2)++(2,m12)++(3,m21)++(4,m1)++(5,m2) 2208 2797 1 9813 14420 72 5 (1,m21)++(2,m12)++(3,m21)++(4,m12)++(5,m21) 3259 3839 1 23709 32939 243 5 (1,m2)++(2,m1)++(3,m2)++(4,m1)++(5,m2) 1621 2165 1 5252 8051 32 6 (1,m2)++(2,m12)++(3,m21)++(4,m1)++(5,m2)++(6,m12) 8698 10980 1 62751 93323 216 6 (1,m21)++(2,m12)++(3,m21)++(4,m12)++(5,m21)++(6,m12) 12184 14562 1 146992 208602 729 6 (1,m2)++(2,m1)++(3,m2)++(4,m1)++(5,m2)++(6,m1) 5638 7686 1 21630 38886 64 a terminal nodes 24 oganalyzer has been developed. we assumed that the occurrence graph belonging to a given initial state of a cp-net model is finite and acyclic. the occurrence graphs of petri nets modelling manufacturing systems fulfil this assumption in general. let the probability of faults be known from technological consideration and let the first step of the analysis be the assignment of the arc weights to the edges of occurrence graph as follows. 1. if a node on the occurrence graph has only one outgoing arc, then the next state follows unambiguously, thus the arc weight is equal to 1. 2. if there is more than one outgoing arcs from a given node then it means that different states can follow from it. these states come into existence with different probabilities depending on whether this branch has technological or fault related reason. a. if there is no fault in the system then every branch has a technological reason, because there is no built-in priority rule for the robot to the selection among the workpieces. it means that every selection that is every arc has the same probability so all of the arcs starting form this node have to get the same arc weight, which is equal to the reciprocal value of the number of outgoing arcs. b. the introduction of the fault into the model causes the appearance of another type of branching in the occurrence graph. let us assume that only one type of fault can occur in a given system state. it results in 2 new system states: one for the normal operation and one for the faulty mode. let the probability of fault be equal to pf. then the weight of arc leading to faulty mode is equal to the probability of the fault while the arc leading to the normal operational mode gets the value 1-pf. assigning these arc weights to the edges of the occurrence graph the probability of a given state on the graph can be determined in the following way if the faults occurring one after the other in the system are independent: 1. if the graph is a tree or only one route leads to the given node then the probability of the state representing by this node is equal to the product of arc weights along the route leading from the node representing the initial state to the given node. 2. if there are more than one route leading to the given node from the initial node then the probability value of each route has to be determined with the production of arc weights along the route as in the first step, then to sum these resulted values. 3. if the faults are not independent from each other, then the probability of nodes can be calculated in a similar way but using conditional probability values. as described above, this determination method and the operation of oganalyzer has been illustrated using the example of two workpieces to be processed and one of them has to go through manufacturing line 2, while the other has to go first through line 1 then trough line 2. faults can occur during the manufacturing process and let the fault probability be equal to 0.3 in case of line 1 and 0.1 in case of line 2. as before, we consider the timed case, when the transfer transitions have the same transition time of 1 time unit, while the manufacturing time is equal to 5 for both lines. after the simulation cpntools generates the occurrence graph, the structure of, which is the input of oganalyzer. as a first step oganalyzer reads the structure of the generated occurrence graph from the data file generated by cpntools and visualizes it in its own window as it is shown in fig.10. the user can get the token distribution belonging to nodes as it is shown at node 1 in fig.10. the next step is the identification of branches. the software can distinguish between the two different types of branches on the occurrence graph (that are technological and fault caused branches). for this the user has to define the fault colour for the appropriate branches in a separate window. table 2: comparing the structure of occurrence graphs – with timing no. of workpieces label (identifier, manufacturing information) faultless operational mode faulty operational mode nodes arcs tn/da nodes arcs tn/da 1 (1,m1) 7 6 1/0 8 7 2/0 1 (1,m12) 10 9 1/0 12 11 3/0 2 (1,m1)++(2,m2) 23 22 2/0 41 40 8/0 2 (1,m1)++(2,m12) 29 28 2/0 59 58 12/0 2 (1,m2)++(2,m12) 29 28 2/0 58 57 12/0 2 (1,m12)++(2,m21) 35 34 2/0 87 86 18/0 3 (1,m1)++(2,m2)++(3,m12) 73 74 4/0 264 263 48/0 3 (1,m2)++(2,m12)++(3,m21) 86 85 4/0 392 391 72/0 3 (1,m1)++(2,m1)++(3,m1) 85 84 6/0 262 261 48/0 4 (1,m1)++(2,m2)++(3,m12)++(4,m21) 173 172 8/2 1473 1472 258/2 4 (1,m1)++(2,m1)++(3,m1)++(4,m1) 365 364 24/0 2121 2120 384/0 5 (1,m2)++(2,m12)++(3,m21)++(4,m1)++(5,m2) 574 573 24/4 9320 9375 1582/8 5b (1,m21)++(2,m12)++(3,m21)++(4,m12)++(5,m21) 154 153 24/24 12076 12075 2196/60 5 (1,m2)++(2,m1)++(3,m2)++(4,m1)++(5,m2) 514 513 24/0 5152 5247 780/0 6 (1,m2)++(2,m12)++(3,m21)++(4,m1)++(5,m2)++(6,m12) 1725 1732 80/40 71817 72336 12300/116 6b (1,m21)++(2,m12)++(3,m21)++(4,m12)++(5,m21)++(6,m12) 325 324 72/72 45541 45540 8280/432 6 (1,m2)++(2,m1)++(3,m2)++(4,m1)++(5,m2)++(6,m1) 2341 2412 72/0 39349 41076 5760/0 a terminal nodes/deadlocks, b labels where all terminal nodes refer to deadlocks 25 it is assumed that the technological branches have the same probability, so oganalyzer assigns the reciprocal of the number of branches to these edges. the fault caused branches are collected into a table and the user has to define the probability of faulty and normal modes as it can be seen in fig.11. the occurrence graph with arc weights depicted in oganalyzer can be seen in fig.12. the black numbers attached to the arcs are the arc weights. values equal to 1 were not depicted. using these probability values the oganalyzer calculates automatically the probability of a node by multiplying arc weights along the path leading from the node representing the initial state to that node. if two or more paths lead to the node then the probability values belonging to these paths are summed. the calculated probability values can be also seen in fig.12 as red numbers assigned to nodes. in this manner the probability of all system states in the investigated system can be calculated. for example, the probability of faultless completing of both workpieces is 0.28 + 0.28 = 0.56, which is equal to the sum of the probabilities belonging to the nodes 55 and 57. the probability of that case when the first workpiece is manufactured without fault, but the label of the other piece gets damaged during the second manufacturing process is 0.03 + 0.03 = 0.06 (sum of the probabilities belonging to the nodes 46 and 48). in case of timed nets the occurrence graph is often a tree and the same token distribution belongs to different nodes because of the different time stamp. for the determination of probability of a given system state, the probability values belonging to different nodes have to be summed up. figure 11: defining the probabilities values of faults figure 12: the occurrence graph with arc weights and probability values figure 10: the occurrence graph of the example in the window of oganalyzer 26 conclusion a novel occurrence graph investigation procedure for discrete event systems described by petri nets was proposed in this paper for model-based diagnostic purposes that utilize the knowledge of the occurrence probability of faults. the model of the investigated system was defined in timed coloured petri net form. the colours of tokens representing the workpieces were used to distinguish them and to assign a label of the processes to be carried out. the arc inscriptions and built-in probability functions were used for the fault modelling and integration. the operation of the system was investigated via simulation both in timed and non-timed cases and in faultless and possible fault operational modes with given number pieces and prescribed manufacturing lines. for the behavioural analysis of the model the occurrence graph method was used. a special software module, called oganalyzer has been developed for the handling of the probabilities on the occurrence graph and for calculating the occurrence probability of system states. acknowledgements this research is partially supported by the hungarian research fund through grant no. k-83440. we also acknowledge the financial support of the hungarian state and the european union under the tamop4.2.2.a11/1/ konv-2012-0072. references [1] cassandras c.g., lafortune s.: introduction to discrete event systems, kluwer academic publishers, 1999 [2] gerzson m., márczi b., leitold a.: diagnosis of technological systems based on their coloured petri net model, argesim report no. s38 (eds. troch i., breitenecker f.) 2012, p. 358/1–6 [3] jensen k.: coloured petri nets: basic concepts, analysis methods and practical use, springerverlag, 1997 [4] cpn group, university of aarhus, denmark: cpntools 2.2.0 http://wiki.daimi.au.dk/cpntools/ (last accessed: may 25, 2014) [5] fanti m.p., seatzu c.: fault diagnosis and identification of discrete event systems using petri nets, proc. 9th international workshop on discrete event systems, wodes, 2008, 432–435 [6] jensen k., kristensen l.m., wells l.: coloured petri nets and cpn tools for modelling and validation of concurrent systems, int. j. of software tools for technology transfer, 2007, 9(3–4), 213–254 [7] murata t.: petri nets: properties, analysis and applications, proceedings of the ieee, 1989, 77(4), 541–580 hungarian journal of industry and chemistry veszprém vol. 41(1) pp. 27–34 (2013) immediate event-aware model and algorithm of a general scheduler tibor dulai1!, ágnes werner-stark1, and katalin m. hangos1,2 1 department of electrical engineering and information systems, university of pannonia, egyetem str. 10, veszprém, h-8200, hungary 2 process control research group, computer and automation research institute, kende u. 13-17, budapest, h-1111 hungary !e-mail: dulai.tibor@virt.uni-pannon.hu a stochastic scheduling problem is investigated in this work that considers workpieces to be manufactured according to individual recipes containing manufacturing steps performed by workstations as resources. unexpected stochastic breakdown of a workstation or the faulty termination of a recipe, when a manufacturing failure renders the workpiece out of specifications, forms the set of immediate events. a model and an algorithm are proposed as the basis of a scheduler, which takes into account the possible immediate events, estimates their probability and suggests resource allocations which provide the best overall work-flow even when an immediate event happens. this model includes the possibility of handling alternative resources that can substitute each other in case of an immediate event, like sudden technical failure of a resource. immediate events are not exactly predictable; however, based on previous experiences, their probabilities can be estimated. our model uses the properties of the resources (including how they can substitute other types of resources) and the required sequence of them during the workflow (i.e. the recipes). the proposed scheduling algorithm constructs a solution workflow that reacts in the best way (in average) even for an unexpected event. the proposed model and scheduling algorithm is illustrated on two industrial case studies. keywords: scheduling, resource allocation, alternative resources, immediate event-awareness introduction scheduling is an important and widely used topic of operations research. besides of its theoretical importance, industries can also benefit from optimal schedules and resource allocation. several different algorithms were established for organizing process elements on the time scale [1, 2], related to for example computer networks [3], business processes [4, 5] or industrial processes [6]. the results are usually represented on a gantt chart. there are also differences between these algorithms related to their application times. some of them are applied offline before the scheduled processes starts, others are applied real-time. real time scheduling techniques, and a special adaptive real-time scheduler is introduced in ref. [10]. for improving their results, there are cases when the methods use historical data during the creation of the schedule [11]. the common scheduling methods usually handle the resources individually and do not take into account the relationships, e.g. the similar functionality between them. only few publications investigate the cooperation possibilities that are enabled by the similar functionality of resources in scheduling [7]. in this paper a scheduling method is proposed, where resources may substitute each other and immediate failures of resources may happen. after we introduce the problem and its main building blocks, we present our model and the algorithm developed. its operation and properties are demonstrated on a simple and a more complex problem as case studies. problem specification a general scheduler intends to determine the placement of activities of resources on the time scale. in an advanced case one might consider additional features given in the problem’s model – like substitution possibility of the resources – which help to redefine the classic scheduling problem to be usable in different reallife applications. this substitution may help in achieving a certain fault tolerance property in such a way that a technical failure causes the least possible negative effect. the basic aspects and sub-tasks related to this extended scheduling problem are collected in this section. 28 cooperation in some cases more than one resource is able to carry out a particular activity (usually with different productivity). it means that when the appropriate resource is busy, there can be another resource that is able to take over a particular task if required. we shall term this case a cooperative situation when substitution is possible, in other words, the resources can cooperate with each other. taking the cooperation aspect into account during scheduling the performance may increase [8]. we introduced the so called substitution vector as an element of our model to handle substitution related sub-problems. any scheduler [1, 2] can be applied as a basis of the cooperative extension, which inputs the sequence of resources as input processes and has to arrange them on the time scale taking into account the availability and temporal constraints. all the improvements are done on this basic schedule. improving fault tolerance when a schedule is ready and the workflow starts, an immediate event (e.g. a technical failure of a resource) in a process may influence other processes, too, in a negative way [9]. if the effects of that event are calculated in the schedule, then the solution with the best answer to immediate events can be selected from the set of solutions with the same performance, and the faults’ negative impact on the schedule decreases. our model deals also with this aspect. the model for the above mentioned problem set, we created an universal model and an algorithm to carry out the scheduling. the work intends to be the basis of several different tasks with the goal that the operation time should be minimal. in this section we introduce our model and the scheduler that works on this model. main parameters, notations and functions the model and its parameters are designed in such a way that it can be applied for different kinds of scheduling problems (e.g. scheduling of industrial production processes, test processes, scheduling and managing the resources of electrical networks, etc.). for this reason we collected the necessary parameters that make possible the development of a general framework, which uses different kinds of resources in different processes. it is able to handle different needs. in this sub-section we introduce the main parameters and functions we use in our work. these are as follows: process = {proc1, …, procj}, (1) stands for the set of processes; p = {p1, …, pl}, (2) stands for the set of product types; r = {r1, …, rm}, (3) stands for the set of resources; o(ri) = {oi1, …, oik}, (4) stands for the set of the operation modes of resource i; a = {a1, …, an, pause(t)}, (5) stands for the set of basic activities, where pause(t) is an empty activity with length of t hour; ra : r × a → {0, 1}, (6) defines a function for determining whether a resource is able to perform an activity; rap: r × a × p → {0, 1}, (7) defines a function for determining whether a special activity of a resource can be applied for a product type; t: r × a × p × o → n, (8) provides the suggested operation time of a resource in a given operation mode performing a given activity on a given product type; q: r × a × p × o → [0,100], (9) provides capacity information: how many percent of a resource capacity is occupied by one piece of a given product type in a given operation mode of a resource while performing a given activity; e: r × a × p × o → [0,100], (10) provides the probability of resource failure during performing a given activity on a given product type in a given operation mode; s: r × a × p × o → {0, 1}, (11) results in a binary decision: whether a resource activity in a given operation mode on a given product type can be suspended without restarting it from its beginning; rreq: r × a × p × o × datetime → p(r, n) (12) (power set on pairs of a resource and a natural number), provides the additional resource need of a resource’s given activity on a given product type in a given operation mode in a given hour subst(ri,aj, pk,oil ) = [ hi1 ... him ] , (13) 29 is the substitution vector, where m is the number of resources, hin is a natural numbers for all 1 ≤ n ≤ m, ri is the ith resource, aj is a basic activity, pk is a product type, oil is an operation mode of resource i, hin denotes how many percent of the productivity of resource i is needed in a given activity in a given operation mode on a given product type to substitute totally resource n supposing unchained operation time. the substitution vector is calculated based on the function ra and other functions (e.g. function t in case of time-based optimization). map: r x datetime → n, (14) provides the information on accessibility of resources: how many resource of a given type is accessible in a given hour; f: r → n, (15) provides the expected number of hours how long a given resource is unavailable in case of its failure; tstart: process → datetime, (16) shows the start time of a process; tmaxend: process → datetime, (17) shows the maximum finish time of a process; prev: process × a × n+ → {a, ø}, (18) provides the prior basic activity of the nth occurrence of a given basic activity in a given process; next: process × a × n+ → {a, ø}, (19) provides the following basic activity of the nth occurrence of a given basic activity in a given process; maxdelay: process × a × n+ → n, (20) provides the maximal duration of time out, which is tolerated by the nth occurrence of a given basic activity in a given process; dur: process × a × n+ → q, (21) provides the time scale, which number the default operation time of the of the nth occurrence of a given basic activity in a given process has to be multiplied with, for getting the real operation time of the activity. the proposed algorithm our algorithm was created to take into account the cooperation possibilities of the resources and to have failure-aware behaviour during scheduling. the algorithm can be separated into three main blocks, as it is shown in fig.1. in the first phase, we associate resources for each basic activity of the processes. at the start, processes are described only as a sequence of basic activities. we have to turn it into the “language” of resources. in this task, we use the function ra for determining, which resources are able to carry out the desired basic activity. furthermore, we deal with the minimization of the operation time; we select the resource, which has the operation mode with the minimal operation time, i.e. ri with min(t(ri, a, p, oil )), ∀oil ∈o(ri ), ra(ri,a) =1 (22) is selected. the first step of our algorithm results in a sequence of resources for each process. the second phase of the algorithm is performed by the main scheduler task, taking into account the alternative resources. the first task in this phase is to select the “basic” process, which has the least robustness. we do it by selecting proci with min(tmaxend (proci )− tstart (proci )−tdur) , (23) where tdur is the sum of the durations of all of the basic activities of proci. after the determination of the basic process, the algorithm enters a loop, in which it selects a process from the set of the remaining processes and attempts to place all the basic activities of the selected process element-by-element on the time scale. during this operation the algorithm handles the substitutability of the resources. the insertion of a basic activity starts at the initial activity of the process and each activity is inserted into the earliest possible time point. this assumption is a fundamental point in the method. the insertion of an activity at its earliest time may have two possible outcomes: • successful insertion • unsuccessful insertion, which means that there is not enough amount of the resource to serve the activity which starts at its earliest time point. we call this case a collision. in case of a collision, the algorithm attempts to find an alternative resource using the substitution vector, figure 1: the basic parts of our algorithm 30 which has enough leftover capacity to carry out the activity at the desired earliest time point. if this is not possible, because there is not enough resource at the desired time, the algorithm tries to shift one of the collided activities to solve the problem. the detailed mechanism of the activity-insertion task is illustrated in fig.2. when the activity-shift resulted in no success, the algorithm attempts to repeat the same process with other alternative resources. if there is no success, the whole process will be left from the final solution; otherwise the initial scheduling is ready. in the final, third phase of our algorithm the schedule is tried to be modified in such a way that it should have a higher fault tolerance than the original one. this phase assumes that fault happens at the processing of special activities of the processes and calculates its effect into the schedule. we do not want to hurt the time constraints of the original problem that’s why one of the main parameters of this phase are the maximum finish time values (tmaxend) of the processes. we process the processes starting from their end in the following way: let wp be the process list we work on. at the start wp = process. for each element of wp, we create a pointer, which points at the penultimate activity of the process. the activities pointed by the pointers (let their set be wa) are candidates for assuming them to have fault. starting from this initial state, this phase of the algorithm works as follows: 1. select the aj activity from wa with the highest error probability: max(e(ri, a j, pk, oil )), a j ∈wa (24) 2. if the start of the basic activity which follows ai can be shifted by ai’s duration plus by f(r(ai)), where r(ai) is the resource which carries out ai without causing collision and without exceeding tmaxend(prock), where prock is the process which belongs ai to, then (i) the shift will be done, and (ii) the basic activity, which precedes ai in the process will be added to wa and ai will be taken out from there. it means that the pointer of the process will be set one step backward. else, ai is taken out from wa and its process is taken out from wp, too. it means that the activities of the process are not modified any more. this phase of the algorithm modifies the placement of the basic activities of the processes on the time scale in such a way that there is no need to change the scheduled activities in case of failures with high probability. it means that these failures will not cause delay and exceed of the maximum finish time. case studies in this section, the previously presented algorithm is applied to two hypothetical manufacturing examples: we show how it takes into account the substitutability of the resources and how to make the schedule ready for possible technical failures. a simple problem and its solution let there be four processes with the same start and maximum finish time (tstart = 0 and tmaxend = 65 are identical in each cases). the sequences of the process activities can be seen in fig.3. in this example, we work only with one product type (p), and we intend to minimize the maximum operation time. let’s suppose that in this example there are two pieces of resource r1, while only 1 piece of the others, and ra(ri, aj) = 1 only if i=j, (25) excepting two cases: ra(r2, a3) = 1 (26) and ra(r3, a2) = 1, (27) as well. moreover, the substitution vector of r2 is: subst(r2,a3,p,o) = [ 0 100 125 0 ] , (28a) while the substitution vector of r3 is: subst(r3,a2,p,o) = [ 0 200 100 0 ] , (28b) figure 3: activity sequence of the example processes figure 2: activity insertion onto the time scale 31 which means that r2 can substitute r3, and r3 can substitute r2. however, the substitution results in 125 percent or 200 percent more time, respectively. another assumption is when only r1 has two operation modes: in one of its operation mode its operation time at a1 activity on product p can be reduced with 10%. as our goal is to minimize the necessary time, we will use this operation mode of r1 in each case. moreover, assume that all the resources are unavailable for 2 time units in case of failure. based on this information, the first step of our algorithm creates the sequence of the resources for each process. this sequence completed with the durations of each activity after user-based modification of the default operation times is illustrated in fig. 4. the second phase of the algorithm determines the basic process; in our case it is proc3 with its 63 unit length. its representation on the time scale is shown in fig.5. after this selection a loop is started, choosing the less robust process from the remaining set. the next process is proc1. its first activity can be placed onto the time scale without collision. the placement of the second activity collides with the basic process’s first activity. the first reaction of the algorithm is to search for alternative resource. resource r2 can substitute r3 without collision; however in this case the operation time will increase from 4 to 5 units. the third activity of proc1 can be inserted, since there are two pieces of resource r1. the fourth activity collides again; however substitution solves this problem, and the problem-free placement of the final activity of the process can be seen in fig.6. the third process to handle is proc4. its first activity can be placed easily; however, the second activity has collision and there is no possibility to substitute it without collision either. this case requires the shift of the activity as illustrated by fig.2. the activity that shifts the later start is reason for a pause was defined in proc4. the third and fourth activities have to be also shifted. the difference between the two cases is the resource that is able to substitute gets free earlier. this is why the fourth activity will be carried out by r2 instead of r1, started after a short pause. after the placement of the process’s final activity and all the activities of proc2,, this provided the schedule with some activities of the previously placed processes shifted necessarily twice, as illustrated in fig.7. the final phase of the algorithm is to make the schedule to be fault-aware. as tmaxend = 65 and the length of proc3 is 64, we will not modify this process. similarly, we will not modify proc1 and proc4 either. only proc2 lets the algorithm to prepare it to be faultaware, and the modification can be applied to all of its figure 5: placement of the basic process onto the time scale figure 6: the schedule after handling proc1 figure 7: the schedule after the second phase of the algorithm figure 8: the final schedule figure 4: sequence of the initial resource allocation 32 activities. the result can be seen in fig.8. a more complex problem and its solution in this example we deal with six processes. in contrast with the previous example, they differ in their start and maximum finish time as shown in table 1, where the values are represented in time units. the activitysequences of the processes are illustrated in fig.9. in the example form fig.9, eight different activities are applied. the next question is which resources are able to carry out these activities. in this example, there are six kinds of resources, six resource types (r1 r6). suppose that two pieces of resource type 2, 3 and 5 exist, while all the other resource types have only one representative. the substitution vectors of the resources are as follows: subst(r1,a2,p,o) = [ 100 150 0 0 0 0 ] , (29a) subst(r2,a1,p,o) = 150 100 0 0 0 0! " # $ , (29b) subst(r3,a5,p,o) = 0 0 100 0 300 0! " # $ , (29c) subst(r5,a3,p,o) = 0 0 120 0 100 0! " # $ , (29d) subst(r4,a1,p,o) = 166 0 0 100 0 0! " # $ . (29e) it means that r1 and r2 resources may substitute each other, r3 and r5 resources are able to substitute each other and r4 resource is capable to substitute r1 resource. other substitutions are not possible. these vectors show that ra(r2, a1) = 1, (30) ra(r1, a2) = 1, (31) ra(r3, a5) = 1, (32) ra(r5, a3) = 1 and (33) ra(r4, a1) = 1. (34) moreover, we suppose that ra(ri, aj) = 1, if i = j; (35) ra(r2, a7) = 1 and (36) ra(r5, a8) = 1. (37) this means that a7 activity can be carried out by r2 resource, and a8 activity can be carried out only by r5 resource. in case of failure, the resources are unavailable as much as shown in table 2. we suppose that each resource works only in one operation mode and all of the resources have the same error probability. in the example we work only with one product type (p), and we intend to minimize the maximum operation time. applying the first step of our algorithm, we create the sequence of the resources for each process. this sequence completed with the durations of each activity after user-based modification of the default operation times as illustrated in fig.10. at this phase we apply the second step of our algorithm and determine the robustness of each processes. in the calculation, we use the following computation method, as we mentioned earlier: tmaxend (proci )− tstart (proci )−tdur (38) the values obtained are summarized in table 3. table 1: some properties of the processes of the second case study process start time, tstart max. finish time, tmaxend p1 0 30 p2 15 30 p3 7 30 p4 3 25 p5 0 23 p6 6 29 figure 9: the activities of the second example’s processes figure 10: resource-sequence of the example’s processes table 2: the effect of failure on the second example’s resources resource r1 r2 r3 r4 r5 r6 time of unavailability (f) [time unit] 2 1 3 2 2 1 33 table 3 indicates that the basic process is proc4, which is the least robust process. we place its activities onto the time scale as a chart illustrates this in fig.11. the black line represents the 0 time point and the red one signs the maximal finish time of the process. the second least robust process is proc3. the placement of its activities onto the time scale can be done easily, without any collision as shown in fig.12. the third least robust process is proc2. during its placement there is one collision: its second activity collides with proc4’s fifth activity. however, it doesn’t cause any problem, because there are two pieces of resource r2. the second resource of r2 resource type can carry out the activity in the originally planned time. the result is shown in fig.13. looking for the next least robust process, proc6 is the next. its fourth activity collides, thus the second piece of r3 resource type has to be used for carrying it out. moreover, its final activity also collides. unfortunately, there is only one piece of r1 resource type. however, r2 resource type can substitute an r1 resource. the problem is that both r2 resources are occupied at the desired time. there is another resource type, r4, which is able to substitute an r1 resource with a bit more necessary time than r2. as r4 is free at the desired time, it will take over the task. the time it requires for its task is 1.66 times more than an original r1-type resource would need for that. fig.14 illustrates the results. the second most robust process is proc5. during the placement of its activities onto the time scale, we find that the second activity collides with proc4’s second activity. fortunately, there is a second piece of r3 resource type which can be used freely for the desired time interval. it solves the problem and results a chart as seen in fig.15. at last, three problematic cases happen during process 1: the collision of the third and fourth activities can be solved by the second piece of the desired resource types; however, in case of the final activity only time shift can solve the collision, because there is only one piece of r4 resource type and it can not be substituted by any other resource. the result is shown in fig.16. after placing all activities onto the time scale and solving all collisions, only the fault-tolerance-related improvement need to be done, as the final step of our algorithm. this phase intends to shift the activities of the processes in time, starting from their end by the duration of their preceding activity plus its f value. because of the maximal finish time constraint, proc4 and proc3 (the first two processes on fig.16) cannot be modified. if we look at fig.16’s third process, its last activity requires f(r1) = 2 time units plus its normal operation time in case of failure. if we take into account the maximal finish time of the process, its place cannot be modified. this is the case for the fourth process, as well. the fifth process in in fig.16 ends with r3 resource. in case of a failure, it requires 8 time units until it reaches the maximal finish time of the process. taking this into account, only 3 time units remain, figure 11: placement of the second example’s basic process onto the time scale (proc4) figure 12: placement of the second example’s second process onto the time scale (proc3) figure 13: placement of the 2nd example’s third process onto the time scale (proc2) figure 14: placement of the second example’s fourth process figure 15: placement of the second example’s fifth process onto the time scale (proc5) figure 16: placement of all processes of the second example onto the time scale (proc1) table 3: the robustness values of the example’s processes process proc1 proc2 proc3 proc4 proc5 proc6 robustness 16 4 2 0 11 8 34 which is not enough for the previous activity. that’s why we do not modify this process, either. the final activity of the last process, proc1 is carried out by an r4 resource. in case of a failure, it requires 4 extra time units. in order to avoid collision we shift this activity a bit more forward as shown in fig.17. as f(r2) = 1, and a2 activity requires 3 time units to be carried out by r2 resource, proc1’s fourth activity can also be shifted in time. its previous activity would require 6 time units after itself. its shift would result 1 extra time unit for previous activity, which is not enough for making it ready for tolerating fault. this hinders building in more fault tolerance. the final result of the algorithm is shown in fig.18, in which we have a schedule, which took into account the possible substitutions, the capabilities of the resources; moreover in some places, it tolerates faults of resources without the need of rescheduling. conclusion we presented a model and algorithm for creating schedules, which tolerate some resource-failures and utilize the substitutability possibilities of the resources. our goal was to establish a model, which can be the basis of applications in different segments of scheduling problems and makes it possible to generate schedules with the optimization criteria related to the operation time. we introduced an algorithm, which creates an initial schedule on the basis of the input processes and the substitutability of the resources. this can be improved with preparation for likely failures of resources. the operation of the algorithm was presented on two hypothetical case studies. acknowledgements this research was supported by the european union and hungary and co-financed by the european social fund through the project támop-4.2.2.c-11/1/konv-20120004 and tamop-4.2.2.a-11/1/konv-2012-0072, and in part by the hungarian research fund (otka) grant number k83440. support from the national research centre for development and market introduction of advanced information and communication technologies is also acknowledged. references [1] pinedo m.l.: scheduling: theory, algorithms, and systems, 4th ed., springer, new york, usa, 2012 [2] brucker p.: scheduling algorithms, 5th ed., springer, osnabrück, germany, 2007 [3] brahimi b., aubrun c., rondeau e.: modelling and simulation of scheduling policies implemented in ethernet switch by using coloured petri nets, proc. 11th ieee int. conf. emerging technologies and factory automation, prague, czech republic, 2006, 667–674 [4] barba i., valle c. del: a job-shop scheduling model of software development planning for constraint-based local search, int. journal of software engineering and its applications, 2010, 4(4), 1–16 [5] xu j., liu c., zhao x., yongcareon s.: business process scheduling with resource availability constraints, proc. otm’10, hersonissos, crete, greece, 2010, 1, 419–427 [6] sule d.r.: production planning and industrial scheduling: examples, case studies and applications, 2nd ed., crc press, ruston, la, usa, 2007 [7] murthy s., akkiraju r., rachlin j., wu f.: agent-based cooperative scheduling, proc. aaai workshop on constraints and agents, providence, ri, usa, 1997, 112–117 [8] dulai t., werner-stark á.: immediate eventaware routing based on cooperative agents, proc. factory automation, veszprém, hungary, 2012, 144–148 [9] palombarini j., martinez e.: smartgantt – an intelligent system for real time rescheduling based on relational reinforcement learning, expert systems with applications: an international journal, 2012, 38(11), 10251–10268 [10] nandanwar j., shrawankar u.: an adaptive real time task scheduler, ijcsi international journal of computer science issues, 2012, 9(6/1), 335–340 [11] gregg c., boyer m., hazelwood k., skadron k.: dynamic heterogeneous scheduling decisions using historical runtime data, proc. 2nd workshop on applications for multiand many-core processors, san jose, ca, 2011 figure 17: building fault tolerance into the last process of the second example figure 18: building fault tolerance into the last process of the second example hungarian journal of industry and chemistry veszprém vol. 41(1) pp. 35–40 (2013) estimation of parameters for an extremely low fuel consumption internal combustion engine-based megameter-iii vehicle istván pintér1! and mihály bagány2 1 department of informatics, kecskemét college, izsáki str 10, kecskemét, h-6000, hungary 2 department of natural sciences and engineering, kecskemét college, izsáki str 10, kecskemét, h-6000, hungary !e-mail: pinter.istvan@gamf.kefo.hu megameter-iii is a special vehicle designed and constructed for international competitions by our team. a crucial part of the vehicle is the internal combustion engine, which ought to have extremely low fuel consumption. the experiences of previous competitions confirmed that it is necessary to develop a professional telemetry system, which allows tracking and logging online important parameters of the engine and the vehicle. in this paper, we discuss results for estimating of several parameters of the engine (angular velocity, angular acceleration, the coulomb-morin external friction torque and the damping constant). in our work, injector-pulses and inductive sensor’s signals were monitored. keywords: internal combustion engine, extremely low fuel consumption, angular velocity, angular acceleration, external friction torque, damping constant introduction since 2010, the racing team at kecskemét college participates in international competitions of fuelefficient vehicles. the vehicles were named after 1 megameter being 1000 km. the first result with megameter-i in gasoline category was 1588 km l-1 (2010, lausitz, germany), and the best result of megameter-ii was 2661 km l-1 (2011, nokia, finland). megameter-iii achieved 2696 km l-1 (2012, rotterdam, nederland. the team-photo can be seen in fig.1). the latest model, the megameter-iv has exceeded the 3000 km/litre dream-limit (3082 km l-1; 2013, nokia, finland) [1]. during the development of the megameter series, it became clear that in order to improve the technical parameters of the vehicle it is necessary to establish a telemetry system suitable for measuring, displaying and logging the engine’s and vehicle’s parameters during the race. this paper presents our recent results in this work, which have already been utilized in developing and construction of the megameter-iv. the measurements were taken using the megameteriii engine, which has the following characteristics: • one cylinder, four-stroke, air-cooled • overhead controlled, overhead valve, intake manifold injection • bore/stroke: 31.5/45 mm • displacement volume: 45 cm3 • compression ratio: 14 • power: 700 w • torque: 2.2 n·m • specific fuel consumption 235 g kwh-1 there are different application areas and methods for estimation of engines’ angular velocity. these estimation procedures are based mainly on crankshaft’s rotation angle [2, 3, 4]. in the problem of model-based estimation of mechanical losses, the dependence of instantaneous angular velocity on angular position plays an important role [4]. a second-order splineinterpolation-based method was proposed in [2] for realtime measurement of angular velocity and angular acceleration. our telemetry system is related to this latter work, and our results proved to be useful in further developing our special vehicle. figure 1: student team photo with the megameter-iii vehicle (rotterdam, 2010, second place) 36 the physical model with its approximations and the parameter estimation in order to achieve ever decreasing fuel consumption it is necessary to uncover the sources of energy losses. for this purpose a suitable physical model of internal combustion engine (ice) is needed [5]. moreover, with an appropriate physical model in hand, one can design the measurement for estimating the parameters of the physical model. physical model for estimating the external friction torque and damping constant the instantaneous angular velocity of the crankshaft is changing even during only one crankshaft revolution. it is smaller on the compression stroke and greater in the midst of power stroke. the friction torque affecting the engine, averaged for two crankshaft revolutions depends on the instantaneous angular velocity. by expanding this function up to the second order we get eq.(1): −m ≈ m 0 + m1 ω1 ω + m 2 ω2 2 ω 2 (1) where the indexed quantities are constant and positive, and they have physical meanings as follows: m0 is the coulomb-morin external friction torque, which is independent of the relative speed of frictional surfaces (in this case the relative speed is the angular velocity); m1/ω1⋅ω defines the damping constant (the second term corresponds to torque resulting from newton’s internal friction’s force, it is proportional to the first power of angular velocity); m2/ω2 2⋅ω2 stands for the drag torque characterizing the turbulent flows in pipes; it is in proportion to the square of angular velocity and it is resulting from the flow resistance in the intake and exhausting channels, in the valve-cage and in the airpipe of the crankcase. our task is the estimation of the external torque from the measured data; therefore it is necessary to estimate the angular velocity. the basic equation of rotational motion is shown in eq.(2): −m = −θ dω dt (2) where after substitution of eq.(2) into eq.(1) we get m 0 + m1 ω1 ω + m 2 ω2 2 ω 2 = −θ dω dt (3) let’s assume that the initial value of the angular velocity is ω0. by separating the variables and integrating we get eq.(4): dω m 0 + m1 ω1 ω + m 2 ω2 2 ω 2ω0 ω ∫ = − dt θ0 t ∫ . (4) the result of the integration is shown in eq.(5). t = − 2θ 4ac− b2 atan 2cω + b 4ac− b2 # $ % & ' (+ + 2θ 4ac− b2 atan 2cω0 + b 4ac− b2 # $ % & ' ( , (5) where three new variables were introduced for more readability as shown in eq.(6). a =m 0 , b = m1 ω1 , c = m 2 ω2 2 2 . (6) by solving eq.(5) for ω one can get the final solution. however, instead of doing so, we analysed two approximate solutions of eq.(4). as we will see below, these approximate solutions fit real measurements well. in order to estimate the engine’s friction torque and damping constant long measurement duration (e.g. 20 s) is necessary. the relevant physical quantities can be estimated from the measured injector pulses. approximation 1: the friction torque is independent from angular velocity by assuming that the other two terms are negligible compared to external friction m0 the differential eq.(4) simplifies to: dω m 0ω0 ω ∫ ≈ − dt θ0 t ∫ , (7) and its solution is: ω =ω0 − m 0 θ t , (8) where ω0 is the value of angular velocity at the beginning of deceleration. the angular velocity of the engine’s crankshaft has to be measured as the function of time for parameter estimation. namely, after line-fitting to measured data the intercept and slope can be computed from relationship ω̂ = a− bt , so both the estimation of coulomb-morin external friction torque and the estimation of initial value of angular velocity can be determined: ω0 = a , m 0 = bθ . 37 approximation 2: the friction torque is independent from the squared value of angular velocity when the engine is running with wide open throttle, and the friction torque of pipe-flow losses is negligible comparing to external and internal losses, the differential equation to be solved is the following: dω m 0 + m1 ω1 ωω0 ω ∫ ≈ − dt θ0 t ∫ . (9) the solution of eq.(9) is: ω = ω1 m 0 m1 +ω0 ! " # $ % &e − t τ −ω1 m 0 m1 , (10) where τ = ω1θ/m1 is the time constant characterising the angular deceleration. by measuring the engine’s crankshaft’s angular velocity as the function of time, and after fitting a biased exponential-type curve we get the estimation cae bt −= −ω̂ , from which the estimates of physical quantities are the following: the external friction torque is: m0 = bcθ, the damping constant is: m1/ω1 = bθ, the initial value of angular velocity resulted from curve-fitting is: ω0 = a-c. estimation of the instantaneous torque and the running irregularity the instantaneous angular acceleration as the derivative of the instantaneous angular velocity is needed for estimation of the instantaneous torque. moreover, knowing the instantaneous angular velocity, another important parameter of the engine, the running irregularity can be determined. from the point of view of measurement, the estimation of instantaneous angular velocity requires the duration of two crankshaft revolutions (e.g. 100 ms). for measuring this, an inductive sensor was used. when determining the running irregularity, the engine and the dynamometer were disconnected and the flywheel ring gear teeth together with an inductive sensor served as signal source. the induced voltage from the sensor can be approximated as: u u0 = ω +β t( ) ω0 cos zω t + z β 2 t 2 ! " # $ % & , (11) where u is the output signal of the sensor, u0 is the amplitude of the sensor corresponding to the constant angular velocity of ω0, ω is the angular velocity of the crankshaft, β is the angular acceleration of the latter, z is the number of teeth of ring gear. in case of zero or small values of angular velocity the relationship eq.(11) simplifies to u u0 = ω ω0 cos zω t( ) . (12) by assuming that during the pass-time of one tooth (tooth-time) the angular velocity is not changing significantly, the signal amplitude during the tooth-time can be well approximated by a constant. that is, the approximated sensor signal when passing the zth tooth is given as u/u0k = cos (z ωk t). the running irregularity is defined as a ratio in eq.(13): δ = ωmax −ωmin ωaverage (13) measurements, estimations and evaluations the measurements were accomplished in the student’s workshop of gamf faculty using an agilent dso-x 2002a digital storage oscilloscope. the oscilloscope is two-channel type with upper input cut-off frequency of 70 mhz, maximum sampling frequency of 2 gs/s and with sample storage of 50000 samples. the algorithms used for evaluation of measured data were intentionally different. in one case the data series were not re-sampled and the differentiation was approximated by finite differences, and in the other case both re-sampling and smoothing derivative algorithm were applied. moreover, the computation method of the trend of angular acceleration was also different. estimation of the external friction torque and damping constant in this setup, an extra flywheel was driven by the engine fixed on the test stand. the measurement setup can be seen on fig.2. the reduced resultant moment of inertia of synchronously rotating components with the crankshaft was θ ≈ 0.0534 kg m2. the dynamometer’s friction torque was approximately constant with a value of mdynamometer ≈ 0.2 n m. figure 2: arrangement for measuring the friction torque 38 the engine’s injector was triggered by a signal from the crankshaft, one injection occurred in every two crankshaft revolutions. the oscilloscope was connected to the injector’s solenoid, and the solenoid’s signal was sampled with a sampling frequency of 2.5 khz, that is the sampling interval was ts = 400 µs. the part of measured injector pulse-signal can be seen on fig.3. the crankshaft’s angular velocity ω = ω (t) as a function of time was determined from the stored samples, with duration of 20 seconds. at the beginning of the measurement, the engine was accelerated to 4000–4200 rpm, then the injector was disconnected from the intake manifold, and the engine was allowed to decelerate freely. by defining a suitable trigger level, the elapsed time t between two consecutive rising edges of the impulse can be determined. the instantaneous frequency is two times the reciprocal value of t (finstantaneous = 2 / t), because every two revolution results in one impulse. the instantaneous angular velocity can be computed from this instantaneous frequency value. as the resulting angular velocity value sequence is nonequidistant, it has been re-sampled using cubic spline interpolation. first, a linear model was fitted (fig.4). the results are summarised in table 1. the two methods gave similar parameters, but the resampling resulted in somewhat better goodness-of-fit. the estimation of the physical quantities from parameters shown in table 1 can be seen in table 2. the estimations resulted by the two methods are similar in case of model of eq.(7). in case of model of eq.(9), the fitting has been fulfilled on the resampled data series. the results are demonstrated on fig.5. from the above results the external friction torque is m0 = b⋅c⋅θ ≈ 0.419 n·m; the average braking torque of the engine is mengine = m0 mdynamometer ≈ 0.219 n·m; the damping constant is m1/ω1 = bθ = 6.94⋅10-4 n·m·s. the initial angular velocity and revolution are ω0 = a – c ≈ 352 rad s-1, n0 = 3358 rpm. we can conclude that the two types of models gave similar results, but the biased exponential model fitted somewhat better the measured data than the linear model, thus the former are preferred. furthermore, the presented data indicate that both the average breaking torque of the engine and the damping constant are acceptable small, therefore the engine is acceptable from this point of view. estimation of the instantaneous torque and the running irregularity from measurements when the running irregularity was measured, the engine and the dynamometer were disconnected. the moment of inertia of the parts running synchronously with the crankshaft was θ = 4000 kg·mm2. a ring gear fixed to the crankshaft was used as signal source (number of teeth is z = 66) together with an inductive sensor fitted from the teeth in a distance of 4 mm. an oscilloscope was connected to the sensor and the voltage signal was sampled with 500 khz sampling frequency (fig.6). it is necessary to use such a great sampling rate because of the following. in order to acceptably estimate the instantaneous angular velocity, it is necessary to measure n samples during the tooth-time. in case of nominal revolution of n0, the sampling frequency is fs = figure 3: measured injector pulses using a power mosfet table 1: results of the fitting of data shown in fig.4 resampling a, rad s-1 b, rad s-2 r2 no 353.78 12.103 0.9954 yes 346.75 10.952 0.9981 table 2: estimation of physical quantities resampling n0, rpm m0, n·m mice, n·m no 3378 0.650 0.450 yes 3311 0.585 0.385 figure 4: linear model: the brake torque is independent of angular velocity figure 5: biased exponential model: the braking torque is independent of the square of angular velocity 39 n0⋅n⋅z / 60, that is in case of n0 = 4000 rpm and n = 100 samples, fs = 440000 hz. the nearest possible setting of the dso is 500 khz. the capacity of the sample storage is 50000 samples, so the duration of the measurable signal is 0.1 s. as it is greater than the duration t2 of two crankshaft revolution, the measurement of at least one full engine cycle is feasible using this dso (t2 = 2⋅(60/n0) = 0.03 s). the instantaneous angular velocity is the reciprocal of the time between two falling edge of the sensor’s signal, so the raw signal had to be smoothed before the zero-crossing detection. two different smoothing methods were implemented in this case as well: a 10-point moving average smoothing and savitzky-golay smoothing with tenth order polynomial and 31-point length window (for the latter see fig.7). because the number of teeth is known, the exact value of the crankshaft angle also with the tooth number can be tracked (see fig.8). as the angular velocity values are nonequidistant, cubic spline interpolation-based resampling was applied as in the previous section. due to the fast sampling rate, we can track very short-time changes in angular velocity values during 100 ms. however, our task is to estimate the crankshaft’s instantaneous angular velocity. for this purpose the trend of the angular velocity curve estimated at teeth is necessary. the trend was determined on the one hand by using a 10-point moving average filter, on the other with fft-based filtering (for the latter see fig.9). in the first case the time of averaging was around 2 ms. using this value for the time-constant τ of a low-pass filter for the fft-based computation, for the cut-off frequency of the low-pass filter we get fh = 1 / (2⋅π⋅t) ≈ 80 hz. following its definition, the running irregularity was computed using the maximum, minimum and average values of the angular velocity trend shown in eq.(14). δ = ωmax −ωmin ωaverage = 389.3−379.7 384.7 ≈ 0.02 . (14) the estimation of instantaneous acceleration was computed with differences in case of moving averagebased trend. in case of fft-based trend, the savitzkygolay smoothing derivative algorithm was applied (tenth order polynomial, 31-point length window). fig.10 illustrates the instantaneous acceleration as a function of time. in this measurement the maximum figure 6: setup for measuring the instantaneous torque figure 8: inductive sensor’s signal labelled with the crankshaft’s angle and tooth number (angles are in degrees) figure 7: the raw and smoothed signal of inductive sensor in case of savitzky-golay smoothing figure 9: instantaneous angular velocity values and the fftbased trend figure 10: estimation of instantaneous acceleration as smoothing derivative of the trend of instantaneous angular velocity 40 value of angular acceleration was 1113 rad s-2, so for the corresponding instantaneous torque we get: mmax =θβmax ≈ 0.004 kg ⋅m2 ⋅1113 rad s2 ≈ 4.5n ⋅m. (15) nearby the power stroke instant higher value of angular acceleration can be estimated. in that measurement the corresponding instantaneous torque was of 16 n·m (for details see ref. [6]). the crankshaft’s torque gets to wheel by a drive train with a reduction ratio of 7, so the maximal torque at the wheel is 112 n·m. the wheel’s maximal slipless torque transmission is 40–50 n·m that is during the maximal instantaneous acceleration the wheel will slip on the road, which results in energy loss. this effect ought to be concerned in designing the drive chain of megameter-iv, e.g. torque-damping torsion clutch should be built in. conclusions two methods were elaborated for instantaneous speed and acceleration of an internal combustion engine via on-line measurement. both the injector-pulse-based and the inductive sensor-based methods gave useful data for developing the next engine, namely the megameter-iv. the results presented in this paper are the numerical estimation of the engine’s internal friction, the damping constant, the instantaneous angular velocity, the instantaneous angular acceleration and the estimation of the instantaneous torque of the engine during the power stroke. these results provided the foundation for the design and construction of the on-board electronic control unit, which can be seen on fig.11. acknowledgement this research is supported by támop-4.2.2.c11/1/konv-2012-0012: "smarter transport" it for co-operative transport system and támop-4.2.2.a11/1/konv-2012-0012: basic research for the development of hybrid and electric vehicles, the project is supported by the hungarian government and cofinanced by the european social fund. references [1] www.eco-marathon.eu (last accessed: may 20, 2014) [2] bélanger p.r.: estimation of angular velocity and acceleration from shaft encoder measurements, proc. ieee international conference on robotics and automation, nice, france, 1992, 585–589 [3] stotsky a., forgo a.: recursive spline interpolation method for real time engine control applications, control engineering practice, 2004, 12, 409–416 [4] cruz-peragón f., palomar j.m., díaz f.a., jiménez-espadafor f.j.: fast on-line identification of instantaneous mechanical losses in internal combustion engines, mechanical systems and signal processing, 2010, 24, 267–280 [5] bagány m.: internal combustion engines, kecskemét college, gamf faculty, 2011, 192 (in hungarian) [6] pintér i., bagány m.: algorithm development for the megameter-iii telemetry system to estimate the parameters of extremely low fuel consumption internal combustion engine, proc. factory automation, veszprém, hungary, 2013, 21–22, 94–99 figure 11: ecu is under development for motor control and telemetry hungarian journal of industry and chemistry veszprém vol. 41(1) pp. 41–46 (2013) influence of can flatness on heat dissipation of aluminium electrolytic capacitor lászló kovács1!, lászló gál1, and dénes fodor2 1 department of aluminium electrolytic capacitor development (sz alu pd), epcos llc, szt. lászló str. 6, szombathely, h-9700 hungary 2 automotive mechatronics department, institute of mechanical engineering, faculty of engineering, university of pannonia, egyetem str. 10, veszprem, h-8200 hungary !e-mail: laszlo.kovacs@epcos.com the lifetime of aluminium electrolytic capacitors highly depends on their core temperature. heat dissipation in general applications happens by the extended cathode, which is in contact with the inner side of the can. in the case of heat sink applications, the most important heat transfer phenomenon is the heat conduction through the bottom of the aluminium can. the quantity of the dissipated heat is in direct proportion to the size of the heat transfer surface. the more dissipated heat may increase the lifetime of the capacitor. therefore, the flatness value of the can bottom is critical. this paper presents a flatness measurement method, which can successfully replace the equipment for a more complex and more expensive 3d measurement. it discusses an implementation of a measurement environment, where data acquisition and visualization are automated by a labview-based software. in addition, this study deals briefly with the influence of production processes on the flatness value of the capacitor produced by leading manufacturers. keywords: aluminium electrolytic capacitor, measurement automation, heat dissipation, graphical programming environment, flatness measurement introduction the aluminium electrolytic capacitor is the most commonly applied capacitor type, due to the fact that the capacitance and voltage range of the components is wide. the rated voltages change from 5 v to 550 v, while the capacitance 1 µf to 3 f. these are applied in many fields of industry, such as energetics, power electronics, automotive application, etc. and used for energy storage, smoothing and filtering function. the lifetime of the capacitor highly depends on its core temperature. each decrease of 10 ºc doubles the lifetime [1]. operating temperature is determined by the ambient temperature, by the applied ripple current, by the used voltage, and by the equivalent serial resistance (esr). there are two ways for the reduction of core temperature. the first one is the extended cathode foil and the second one is the cooling of the capacitor can. cooling in general applications is realized by applying a heat sink at the bottom of a capacitor can. this paper presents the basic construction of capacitors and the most important production steps, introduces the heat conduction between the can and the environment and describes the effect of the flatness of the can to heat conductivity. it also presents the entire measurement environment (measurement station, data acquisition and evaluation software), the database behind the measurement system that stores the results. at last, it discusses the effect of production processes to the measured flatness, and presents the flatness of capacitors produced by leading capacitor manufacturer companies. structure and construction of aluminium electrolytic capacitor the winding of an aluminium electrolytic capacitor contains two foils and papers [1]. these are rolled together tightly into a winding. the material of the anode, positive foil is aluminium with purity higher than 99.9%. the foil has been etched [2] to increase the effective surface area (and thus the capacitance of the capacitor). as a result, the effective surface area becomes typically 20–40 times larger than the plain area of the foil. on the etched surface of the foil an aluminiumoxide layer [3] has been generated electrochemically. the forming voltage of the anodized aluminium foil [4] is 30–60% higher than the rated voltage of the capacitor. the material of the cathode foil is also aluminium and itself has a thin oxide film (the forming voltage is only a few volts regardless of the rated voltage). it is typically etched to slightly increase the surface area. the anode and cathode foils are connected to aluminium tabs, which are coming out from the winding and are riveted to the aluminium terminals of the cover disk. the tab foils are not etched but are provided with an oxide layer made by 42 electrochemical oxidization. before being housed in a suitable container, the complete winding is impregnated with electrolyte. after housing the edges of the can are curled down. before being sleeved and packed, capacitors are first aged. the purpose of this stage is to repair any damage in the oxide layer and thus to reduce the leakage current to very low levels. during manufacturing there are two processes (curling and aging processes), which apply mechanical stress to the casing of capacitors. the effect of flatness of aluminium cans on heat conductivity in common applications with usage of extended cathode (the cathode is wider than the anode and exposed to the bottom of the winding) or different kinds of capacitor cooling (for example air or water cooling) are applied to reduce the core temperature that effects its lifetime. earlier investigations showed that there are three types of heat transfer phenomenon between capacitor and the environment [5]: (i) heat conductivity (mostly at the bottom), (ii) radiation (mostly at the side), and (iii) convection. this paper only deals with heat transfer from the bottom of the capacitor to the environment. from the general theory of thermodynamics the heat conduction can be described by eq.(1). p = ka dt dx , (1) where p represents power of the heat flow (w); a is the size of the tangential surface (m2); dt/dx is the temperature gradient (k m-1); and k stands for heat conductivity of the material (w km-1). in our case the linear approximation is acceptable. as already described, the rate of the heat flow depends on the size of the tangential plane. definition of the flatness was adapted from ref. [6]. it is given as the distance between the two closest tangential planes of the bottom of the aluminium electrolytic capacitor can. in the case of capacitors with higher flatness the tangential surface of the aluminium can is lower. the distance between the bottom of the capacitor and the heat sink is filled by air. it is well known that the heat conduction coefficient of the air is much lower than the aluminium. the aspect ratio between the two constants is in the order of magnitude ~104. therefore the flatness of the bottom in the case of regular heat sink applications is an important value. theoretical background of used measurement method there are several different methods for measuring the flatness of a surface [4]: 1. the entire surface is compared with a known reference surface (holistic methods); 2. points on the surface are compared to a reference plane; 3. straightness of the lines in the surface is measured. the holistic methods (e.g. holographic and interferometric methods) are not suitable for large surfaces with more than 90 mm diameter of screw terminal capacitor [7]. the third method is too complex and time-consuming for applying in serial production. therefore, a point-to-point method (second type) was chosen for this investigation. of course, the expensive optical methods may be more precise (in the order of 100 nm deviations) [8], but in our case this high precision is unnecessary. on the other hand, the pointto-point method is very fast, can be used easier and cost-efficient. for point-by-point methods, the grid size is a critical issue, which determines the lowest limit for observable surface irregularities. in our case, approximately 60 cm2 surface area needs to be characterized. the height difference was measured between n points within the bottom. trials were made to find the applicable grid. finally, a 9-point-grid was chosen with circular symmetry, because the measurement time is short enough and the accuracy of the measurement is acceptable. least mean squares (lms) method was used for plane fitting, because the randomly distributed measurement errors have the smallest influence to the results [9]. eq.(2) was used for the lms: xi 2 i=1 n ∑ xiyi i=1 n ∑ xi i=1 n ∑ xiyi i=1 n ∑ yi 2 i=1 n ∑ yi i=1 n ∑ xi i=1 n ∑ yi i=1 n ∑ 1 i=1 n ∑ " # $ $ $ $ $ $ $ $ % & ' ' ' ' ' ' ' ' × a b c " # $ $ $ % & ' ' ' = zixi i=1 n ∑ ziyi i=1 n ∑ zi i=1 n ∑ " # $ $ $ $ $ $ $ $ % & ' ' ' ' ' ' ' ' , (2) where n is the number of the grid points; xi, yi are coordinates within the measured surface [mm]; zi corresponds to the measured height compared to z1 of the ith point (mm), a, b, c are constants for the fitting. the fitted plane is described by eq.(3). z(x, y) = ax+by+c (3) by solving the system of linear equations, for example with gauss-elimination the fitted plane is given. the gauss-elimination is not necessary if the grid points are centrally symmetric. in this case, the input matrix is diagonal, so the solution of the equation system is simple. the distance between the individual points and the fitted plane was calculated. the sign of this distance describes the location of the point respect to the fitted plane. the flatness is the distance between the farthest points above and under the fitted plane. the fig.1 shows an example of measured points and the fitted plane. 43 implemented measurement environment the base of the hardware was a measuring pad made from stainless steel, which has an extremely smooth surface. by the lms method, the error that comes from the tilt of the steel pad was avoided. to stay clear of the effect of the temperature gradient, the measuring equipment was kept under controlled environmental conditions. the data acquisition programme for the flatness measurement was written in labview with contains two major parts. the first one collects the data from the controlled hardware (height meter) and stores them into a local database in ms excel format. this software communicates through an rs-232 port with the measuring equipment. the user sets the actual position, pushes a button and the module registers the results. the graphical user interface developed is shown in fig.2 with hungarian annotations. the software displays the number of actual measurement points and controls the entire process. for example, if the flatness value exceeds a predetermined limit, the software sends a warning to the operator. the second module can extract the results from the database of an examined capacitor(s) or the user can import the measured values from excel. if the results are in the input table, the evaluation module can calculate the flatness of the capacitor can. the graphical user interface of the second module can be seen in fig.3. the implemented automation environment fits into the measurement automation system (mas) [10] being used at the aluminium electrolytic capacitor development department of epcos llc. the system uses two frameworks: a labview based framework for data acquisition and an asp.net based framework for data management. the measurement part contains automated data acquisition measurements, which are connected to the electrolyte (conductivity, ph, viscosity, etc.) and different kind of capacitor tests. (lifetime, surge voltage and storage test, etc.). the experiments on the electrolyte are controlled by an ni-pxi, which is connected to the database (fig.4). pxi stand for pci extensions for instrumentation. these platforms are used as a basis for building of electronic test equipment, automation system, etc. pxi chassis can handle many modules for example plug-in data acquisition (daq) cards, communication cards like rs-232, and different analogue and digital i/o boards. the capacitor measurements are controlled by computers and not by the ni-pxi, because the current implementation measures the low and high voltages separately. the asp.net part of the system was developed for data management and evaluation. this is a software module that contains useful tools that facilitate data handling. data management module simplifies the registration of the constructive properties of the capacitor (like anode foil, cathode foil, type of can, cover disk, etc.) and helps the data storage of applied figure 1: example of the measured points and the fitted plane figure 3: graphical user interface of the evaluation software figure 2: graphical user interface of the data acquisition software figure 4: architecture of the electrolyte measurements 44 voltage and current, ambient temperature, etc. the evaluation part supports the evaluation process by generating a standardized report. the user can tailor the reports according to its needs by the report generation tool. the desired data appear in a representative way and even the trends of the parameters can be shown. the goal of the mas is to automate the previously manual measurements and eliminate paper-based registration. there are many advantages like making the measurements more precise, more reliable and fault tolerant, running multiple measurements in parallel, which all contribute to speed up the research and development of new component and devices. change of flatness value during the manufacturing the flatness of the capacitor can is measured at the incoming inspection and at the final measurement of the production. the initial value of the flatness of the capacitor is determined by the incoming aluminium cans. these parts are produced by cold extrusion of aluminium slugs, so the irregularities of the cans is in the order of magnitude ~10 µm, which is negligible for our purposes. the fig.5 shows the flatness values measured at the incoming inspection of the capacitors. it can be seen that the mean of the measured flatness values is 0.09 mm. as mentioned above, the flatness is mainly affected by two procedures: curling and aging. during curling the can is closed hermetically by curling back the edges of the aluminium can. this curled edge sinks into the rubber ring of the cover disk. as a consequence, the cover disk presses down the winding. it can affect the flatness value, since for example concave shaped aluminium can turn into a convex shape. during aging, the flaws of the anode foil are repaired by applying voltage to the capacitor and placing it in an oven. as a side effect gas is generated. the pressure of the generated gas can change the geometry of the can. from the distribution of the flatness values the effect of epcos production steps (coloured curves in fig.6) can be estimated. the results show that the different production steps do not influence significantly the bottom flatness of the capacitor at the epcos. experimental results regarding to core temperature measurements two experiments were completed for investigating the importance of the flatness value of the capacitor can. sample capacitors were produced with different bottom flatness values. the aluminium cans were made to be convex. these were ordered directly from the supplier and the used parts were sorted out. regular heat sinks were assembled to the bottom of the parts. the tangential planes of the heat sinks were flat (~2 µm) due to their grinded surface. the heat sinks were fixed to the bottom of the samples with the bottom screw of the capacitors. the mechanical stability of the fixation was made with torque wrench. also guaranteed the same fixation level in each case. during the tests, forced aircooling was not used. heat conductive wires were applied to the core of the samples, which allowed us to measure the core temperature of the capacitors directly. the core temperature measurement system is shown in fig.7. in case of the first measurement, sample capacitors with very similar equivalent serial resistance (esr) and leakage current were selected. these parts were taken to 85 °c oven and rated voltage (450 v) was applied to them for 100 h. this preparation is necessary to avoid the different behaviour of the leakage current of the capacitors (isolated from each other to avoid the heat transfer). during the experiment a sinusoidal current figure 5: the measurement results from incoming inspection department figure 6: the effect of the production processes to the flatness of capacitor table 1: results of the ripple current measurement average flatness (mm) average of temperature at equilibrium state (°c) 0.102 90.6 0.259 90.9 0.509 91.5 45 was applied at 50 hz. the current and the temperature (the upper category temperature) of the test are specified by the data sheet of the capacitor. in this case the examined capacitor was b43586a5278q (c = 2700 µf, ur = 450 v, i (85 °c, 100 hz) = 12 a), the applied current (multiplying with the frequency factor) was 10.8 a. the selected samples were placed into an oven at 85 °c and a rated voltage of 450 v was applied. the core temperature was measured during the test. the equilibrium temperature was measured and compared. test was started with the remaining three prepared samples. in case of the second measurement the behaviour of the capacitors was tested against transient heat. the parts were heated up to 85 °c and removed from the oven after 10 hours. the core temperature of the capacitors was measured during cool down time. the recorded core temperature curves (fig.8) show exponential decay. the time-constant of the decay depends on the flatness value of the bottom. as a comparison, the flatness values for screw terminals capacitors from leading manufacturers were inspected. table 2 summarizes the flatness results by leading manufacturers. conclusion it is possible to measure the flatness of a capacitor can with the presented and implemented measurement environment. the expensive 3d measurement equipment can be replaced with this cost-effective method. the measurement and evaluation software was implemented in labview programming environment, which perfectly fits into the previously presented measurement automation system, which is currently being used at the aluminium electrolytic capacitor product development department of epcos. the faults of previously manual measurements have been lowered with the help of automation and data acquisition software. this study discussed the basic construction of a capacitor and highlighted the critical construction steps from the aspect of flatness. in addition, it reveals the flatness values of other capacitor manufacturers’ products. acknowledgments the authors gratefully acknowledge the support of the hungarian state and european union under the "green energy – cooperation of the higher education sector for the development of green economy in the area of energetics” project (támop-4.1.1.c-12/1/konv2012-0017), and the support of the támop-4.2.2.a11/1/konv-2012-0071. references [1] tdk corporation, aluminium electrolytic capacitors, 2013 [2] park d., kim h.: electrochemical etching of aluminium through porous alumina, analytical sciences, 2001, 17(supplement), a73–a76 [3] church h.f.: the dielectric properties of anodic aluminium oxide films, proc. iee – part b: electronic and communication engineering, 1962, 109, 399–403 figure 8: the behaviour of core temperature in case of different bottom flatness values figure 7: core temperature measurement of a capacitor table 2: flatness results for products from leading manufacturers company capacitor series flatness (mm) epcos b43586 0.095±??? hitachi fxr 0.158±??? kemet als 0.225±??? nichicon nt 0.330 46 [4] chen c., mass w., hutchins g.: anodization of aluminium electrolyte capacitor foil, u.s. patent 4,481,084, 1984 [5] parler s.g. jr.: thermal modelling of aluminium electrolytic capacitor, ieee industry applications society conference, 1999 [6] iso/ts 12781–1: geometrical product specifications (gps) – flatness – part 1: vocabulary and parameters of flatness, 2003 [7] de groot p.j.: grating interferometer for flatness testing, optics letters, 1996, 21(3), 228–230 [8] meijer j.: accuracy of surface plate measurements – general purpose software for flatness measurement, annals of the cirp, 1990, 39, 545–548 [9] haitjema h., meijer j.: evaluation of surface plate flatness measurements, european journal of mechanical engineering, 1993, 38(4), 165–172 [10] kovács l., fodor d., klug o., enisz k.: measurement automation system for aluminium electrolyte capacitor development, ieee instrumentation & measurement magazine, 2013, 16(3), 38–43 hungarian journal of industry and chemistry veszprém vol. 41(1) pp. 51-57 (2013) quasi-polynomial control of a synchronous generator attila magyarb1 and attila fodor1 1department of electrical engineering and information systems, university of pannonia, egyetem u. 10., h8200 veszprém, hungary be-mail: magyar.attila@virt.uni-pannon.hu a simple dynamic model of permanent magnet synchronous generator, that is used for electrical energy generation is investigated in this work using a nonlinear technique based on the quasi-polynomial representation of the dynamical model. it is well known that dynamical systems with smooth nonlinearities can be embedded in a quasi-polynomial model. quasipolynomial systems are good candidates for a general nonlinear system representation since their global stability analysis is equivalent to the feasibility of a lmi. moreover, the stabilizing quasi-polynomial state feedback controller design problem is equivalent to the feasibility of a bilinear matrix inequality. the classical stabilizing state feedback problem for quasipolynomial systems has been extended in this work with the ability of tracking time-dependent reference signals. it is shown, that the stabilizing quasi-polynomial servo controller design is equivalent to a bilinear matrix inequality. the results are applied to the model of a synchronous generator. keywords: quasi-polynomial systems, lotka-volterra systems, stability analysis, state feedback control, synchronous generator, wind turbine introduction electrical power systems should operate in an economic way with minimum possible operating cost under normal operating conditions. to ensure this, a preventive controller for power systems has been presented in [1]. it encompasses many types of control actions, including generation rescheduling, load curtailment and network switching reactive compensation. from the viewpoint of the power grid, the electric power generation can be characterized by the operation of the electrical generators, the subject of our study. these power plants should not only be able to follow the timevarying active power demand of the consumers and the central dispatch center, but also keep the quality indicators (frequency, waveform, total harmonic distortion) of the grid on the expected level. this can be achieved by applying proper control methods based on dynamic models of plant (see e.g. [2, 3]) and the involved generators. because of the specialties and great practical importance of the synchronous generators in power plants, their modeling for control purposes is also well investigated in the literature. besides of the basic textbooks (see e.g. [4]) that describe the modeling, specialized papers are also available that use the developed models for the design of various controllers [5]. a wind turbine driving permanent magnet synchronous generator is proposed in [6] with current controlled voltage source inverter, which is the best choice when the output power is small. the current control of the voltage source inverter has bidirectional active and reactive power control ability, avoiding the intricacy of the controller designing. the class of quasi-polynomial (qp) systems plays an important role in the theory of nonlinear dynamical systems because nonlinear systems with smooth nonlinearities can be transformed into a qp form [7]. this means, that any applicable method for qp systems can be regarded as a general technique for nonlinear systems. previous work in the field of qp systems include [8], which proves that the global stability analysis of qp systems is equivalent to the feasibility of a linear matrix inequality (lmi). it has been shown in [9] that the globally stabilizing state feedback design for qp systems is equivalent to a bilinear matrix inequality (bmi). although the solution of a bmi is an np-hard problem, an iterative lmi algorithm could be used. a summary of linear and bilinear matrix inequalities and the available software tools for solving them can be found in [10]. another control synthesis algorithm for polynomial systems is presented in [11]. the goal of this paper is to formulate the servo controller design problem for qp systems based on the results presented in [9] and to design a servo controller for a synchronous generator model using the qp controller synthesis methodology that keeps the active power at the desired level. 52 basic notions in what follows, the basic modeling assumptions and definitions to be used in the sequel are summarized briefly. nonlinear model of a synchronous generator the modeling procedure of the synchronous generator is mainly based on [12] and [13], therefore, only the resulting model is presented here. the model is based on the following simplification assumptions: • a symmetrical tri-phase stator winding system is assumed, • one field winding is considered to be in the machine, • all of the windings are magnetically coupled, • the flux linkage of the winding is a function of rotor position, • the copper loss and the slots in the machine can be neglected, • the spatial distribution of the stator fluxes and apertures wave are considered to be sinusoidal, and • stator and rotor permeability are assumed to be infinite. it is also assumed that all the losses due to wiring, saturation, and slots can be neglected. the four windings (three stators and one rotor) are magnetically coupled. since the magnetic coupling between the windings is a function of the rotor position, the flux linkage of the windings is also a function of the rotor position. the actual terminal voltage v of the windings can be written in the form v = ± jx j=1 (r j i j )± jx j=1 ✓ d' j dt ◆ , (1) where i j are the currents, r j are the winding resistances, and ' j are the flux linkages. the positive directions of the stator currents point out of the synchronous generator terminals. thereafter, the two stator electromagnetic fields, both traveling at rotor speed, can be identified by decomposing each stator phase current under steady state into two components, one in phase with the electromagnetic field and another phase shifted by 90�. with the above, one can construct an air-gap field with its maximal aligned to the rotor poles (d axis), while the other is aligned to the q axis (between poles). this method is called the park’s transformation. as a result of the derivation in [12] the vector voltage equation is as follows v dfq = �ri dfq �l d dt i dfq , (2) with v dfq = ⇥ v d �v f v q ⇤ t i dfq = ⇥ i d i f i q ⇤ t , (3) figure 1: the equivalent circuit of the synchronous generator. where v d , v q and i d , i q are the direct and the quadrature components of the stator voltage and current of the synchronous generator, while v f and i f are the exciter voltage and current of the synchronous generator. furthermore, r and l are the following matrices (see fig.1) rrs! = 2 4 r 0 !l q 0 r f 0 �!l d �! km f r 3 5 l = 2 4 l d km f 0 km f l f 0 0 0 l q 3 5 , (4) where r is the stator resistance, r f is the exciter resistance of the synchronous generator, l d , and l q are the direct and the quadrature part of the stator and rotor inductance, ! is the angular velocity, and m f is linkage inductances. the state-space model for the currents is obtained by expressing d dtidfq from eq. (2), i.e. d dt i dfq = �l�1 r rs! i dfq �l�1 v dfq . (5) the purely electrical model eq. (5) has to be extended with the equation of rotational motion (eq. (6)) that gives the mechanical sub-dynamics, that is d! dt = �l d i q 3⌧ j i d + �km f i q 3⌧ j i f + + l q i d 3⌧ j i q + �d ⌧ j ! + tmech ⌧ j . (6) 2 664 i̇d ˙ if i̇q !̇ 3 775 = 2 6666666664 �lf h kmf h 0 0 kmf h �ld h 0 0 0 0 1 lq 0 0 0 0 1 ⌧j 3 7777777775 2 64 �vd vf �vq tmech 3 75+ 53 2 66666666664 � rlf h kmf rf h �!lf lq h 0 rkmf h � rf ld h !kmf lq h 0 �!ld lq !kmf lq r lq 0 �ld iq 3⌧j �k mf iq 3⌧j lq id 3⌧j �d ⌧j 3 77777777775 2 64 id if iq ! 3 75 (7) where h = k2m2 f � l d l f 2 664 i̇d ˙ if i̇q !̇ 3 775 = 2 64 �1.7100 0.5893 0 0 0.5893 �6.6918 0 0 0 0 �1.7090 0 0 0 0 0.0006 3 75 2 64 �vd vf �vq tmech 3 75+ 2 64 �0.0019 0.0004 �3.4883! 0 0.0006 �0.0042 1.2022! 0 3.5888! 2.6489! �0.0019 0 �0.0004 iq �0.0003 iq 0.0004 id �0.0011 3 75 2 64 id if iq ! 3 75 (8) altogether, the state equations eqs. (5) and (6) have four state variables: i d , i f , i q , and !. the manipulated input vector of the generator is u = ⇥ v f t mech ⇤ t , while the disturbance input vector is d = ⇥ v d d q ⇤ t . realize that the state equations eqs. (5) and (6) are bilinear in the state variables because matrix rrs! depends linearly on !. the obtained model is nonlinear and it has four state variables: i d , i f , i q and ! [14]. output equations of the model: the output active power equation can be written in the following form: p out = v d i d + v q i q (9) and the reactive power is q out = v d i q � v q i d . (10) eqs. (9) and (10) are the output equations of the generator’s state space model. it is important to note, that these equations are bi-linear in the state and input variables. note, that although only the active power is to be controlled in this case, as a possible future extension of the work, reactive power can also be controlled in order to follow an external reference signal. quasi-polynomial representation of nonlinear systems let us denote the element of an arbitrary matrix w with row index i and column index j by w ij . quasipolynomial models are systems of ordinary differential equations (ode) of the following form ẏ i = y i 0 @l i + mx j=1 a ij ny k=1 y bjk k 1 a , i = 1, . . . , n. (11) where y 2 int(rn +), a 2 rn⇥m, b 2 rm⇥n, l i 2 r, i = 1, . . . , n. furthermore, l = [l1 . . . l n ]t . let us denote the equilibrium point of interest of eq. (11) as y⇤ = [y⇤1 y⇤2 . . . y⇤ n ]t . without the loss of generality we can assume that rank(b) = n and m � n (see [15]). lotka-volterra models the above family of models is split into classes of equivalence [16] according to the values of the products m = ba and n = bl. the lotka-volterra form gives the representative elements of these classes of equivalence. if rank(b) = n, then the set of odes in eq. (11) can be embedded into the following mdimensional set of equations, the so called lotkavolterra model: ż j = z j n j + mx i=1 m ji z i ! , j = 1, . . . ,m (12) where m = ba, n = bl, and each z j represents a so called quasi-monomial: z j = ny k=1 y bjk k , j = 1, . . . ,m. (13) stability analysis using linear matrix inequalities henceforth it is assumed that y⇤ is a positive equilibrium point, i.e. y⇤ 2 int(rn +) in the qp case and similarly z⇤ 2 int(rm + ) is a positive equilibrium point in the lotka-volterra case. for lv systems there is a well known candidate lyapunov function family ([8, 17]), which is in the form: v (z) = mx i=1 c i ✓ z i � z⇤ i � z⇤ i ln z i z⇤ i ◆ , (14) c i > 0, i = 1 . . .m, where z⇤ = ⇥ z⇤1 . . . z⇤ m ⇤ t is the equilibrium point corresponding to the equilibrium y⇤ of the original qp system (eq. (11)). the time derivative of the lyapunov function eq. (14) is: v̇ (z) = 1 2 (z � z⇤)(c m +mtc)(z � z⇤), (15) where c = diag(c1, . . . , cm) and m is the invariant characterizing the lotka-volterra form (eq. (12)). therefore, the non-increasing nature of the lyapunov function is equivalent to a feasibility problem over the following set of lmi constraints (see [18] or [19]): c m +mtc  0 c > 0 (16) where the unknown matrix is c, which is diagonal and contains the coefficients of eq. (14). 54 the derivation of global stability analysis for nonautonomous qp systems from the autonomous case is straightforward. the lyapunov function (eq. (15)) also depends on the equilibrium value of the input (u⇤) and has the form ˙̃v (z) = 1 2 (z � z⇤)(c m̃ + m̃ t c)(z � z⇤), (17) where m̃ depends on the coefficient matrices of the input-affine lotka-volterra model (eq. (21)): m̃ = m0 + px l=1 ml u ⇤ l . the corresponding lmi feasibility problem to be solved in order to check global asymptotic stability is c m̃ + m̃ t c  0 c > 0. (18) input-affine qp system models an input-affine nonlinear system model with state vector y, input vector u and output vector ⌘ ẏ = f(y)+ p p i=1 gi(y)ui ⌘ = h(y) (19) is in qp-form if all of the functions f , gi and h are in qp-form. then the general form of the state equation of an input-affine qp system model with p-inputs is: ẏ i = y i 0 @l0i + mx j=1 a0ij ny k=1 y bjk k 1 a+ (20) + px l=1 y i 0 @l li + mx j=1 a lij ny k=1 y bjk k 1 au l where i = 1, . . . , n, a0,al 2 rn⇥m, b 2 rm⇥n, l0,ll 2 rn, l = 1, . . . , p. the corresponding input-affine lotka-volterra model is in the form ż j = z j n0j + mx k=1 m0jkzk ! + (21) + px l=1 z j n lj + mx k=1 m ljk z k ! u l where j = 1, . . . ,m, m0,ml 2 rm⇥m, n0,nl 2 rm, l = 1, . . . , p, and the parameters can be obtained from the input-affine qp system’s ones in the following way m0 = ba0 n0 = bl0 ml = bal nl = bll l = 1, . . . , p. (22) the controller design problem for qp systems globally stabilizing qp state feedback design problem for qp systems can be formulated as follows (for a more detailed desription, see [9]). consider arbitrary qp inputs in the form: u l = rx i=1 k il q̂ i , l = 1 . . . , p, (23) where q̂ i = q̂ i (y1, . . . , yn), i = 1, ..., r are arbitrary quasi-monomial functions of the state variables of eq. (20) and k il is the constant gain of the quasimonomial function q̂ i in the l-th input u l . the closed loop system will also be a qp system with matrices â = a0 + px l=1 rx i=1 k il ail, b̂, l̂ = l0 + px l=1 rx i=1 k il lil. (24) note that the number of quasi-monomials in the closedloop system (i.e. the dimension of the matrices) together with the matrix b̂ may significantly change depending on the choice of the feedback structure, i.e. on the quasimonomial functions q̂ i . furthermore, the closed loop lv coefficient matrix m̂ can also be expressed in the form m̂ = b̂ â = m0 + px l=1 rx i=1 k il mil. (25) then the global stability analysis of the closed loop system with unknown feedback gains k il leads to the following bmi m̂ t c +cm̂ = m0 tc +cm0+ (26) px l=1 rx i=1 k il ⇣ mil tc +cmil ⌘  0. the variables of the bmi are the p⇥ r k il feedback gain parameters and the c j , j = 1, ..,m parameters of the lyapunov function. if the bmi above is feasible, there exists a globally stabilizing feedback with the selected structure. note that (marginal) infeasibility of the bmi (eq. (26)) means only that the closed loop system is not proven to be globally asymptotically stable. however, the solution k il may still guarantee local stability, which is enough in several cases. controller design using bilinear matrix inequalities a bmi is a diagonal block composed of q matrix inequalities of the following form gi 0 + px k=1 x k gi k + px k=1 px j=1 x k x j ki kj  0, i = 1, . . . , q (27) 55 where x 2 rp is the decision variable to be determined and gi k , k = 0, . . . , p, i = 1, . . . , q and ki kj , k, j = 1, . . . , p, i = 1, . . . , q are symmetric, quadratic matrices. the main properties of bmis are that they are nonconvex in x (which makes their solution numerically much more complicated than that of linear matrix inequalities), and their solution is np-hard [10], so the size of the tractable problems is limited. however, there exist practically applicable and effective algorithms for bmi solution [20], [21], or [22]. in matlab environment the tomlab/penbmi solver [23] can be used effectively to solve bmis. quasi-polynomial servo control as in the linear case, the problem statement of the servo, or reference tracking control is as follows. consider a nonlinear system in the form of eq. (20) and an external reference signal r which is to be followed by the system output ⌘. it is possible to define the tracking error signal (eq. (28)) whose time derivative gives the tracking error dynamics which should be stabilized together with the system (eq. (20)). z(t) = z t t0 r(⌧)� ⌘(⌧)d⌧. (28) it is easy to see that the differential equation of the tracking error has the form (eq. (29)). ż(t) = r(t)� ⌘(t), (29) u(t) = �k r z t 0 r(⌧)� ⌘(⌧)d⌧ �k y(t). if the output equation is also in qp form, then the extended closed loop qp system can be written up in lotka-volterra form similar to (eq. (25)) and the bmi for the globally stabilizing controller design can be formulated. quasi-polynomial control of the synchronous generator quasi-polynomial form of the synchronous generator the bilinear nature of the state equations (eq. (8)) enables us to directly apply the qp mechanism without qp embedding [16]. the system has the following set of quasimonomials: ⇢ 1 i d , i f i d , i q ! i d , 1 i f , i d i f , i q ! i f , 1 i q , i d ! i q , i f ! i q , 1 ! , i f i q ! � the qp coefficient matrices of the input-affine system (eq. (20)) are a0 = 2 66666666666666664 �2.323 0 0 0 0.0004 0 0 0 0.5893 0 0 0 �3.4883 0 0 0 0 0.8 0 0 0 0.0006 0 0 0 �6.6918 0 0 0 1.2022 0 0 0 0 �0.7861 0 0 0 3.5888 0 0 0 2.6489 0 3 77777777777777775 t a1 = 2 66666666666666664 0.5893 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 �6.6918 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 3 77777777777777775 t a2 = 2 66666666666666664 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.0006 3 77777777777777775 t feedback structure there is a degree of freedom in the selection of the stabilizing feedback structure. a wise choice of the feedback structure does not increase the number of monomials of the closed loop system. this way the size of the bmi to be solved remains tractable. in our case, a linear full state feedback is applied, i.e. the feedback law is in the form v f = k r1 r t 0 r(⌧)� p out (⌧)d⌧+ +k1 id + k2 if + k3 iq + k4 ! t mech = k r2 r t 0 r(⌧)� p out (⌧)d⌧+ +k5 id + k6 if + k7 iq + k8 !. (30) controller design and verification via simulation using the feedback law (eq. (30)), the closed loop system is also in qp form with 18 quasi-monomials: ⇢ 1 i d , i f i d , i q i d , ! i d , i q ! i d , 1 i f , i d i f , i q i f , ! i f , i q ! i f , 1 i q , i d ! i q , 56 0 10 20 30 40 50 60 70 80 90 100 0 0.5 1 1.5 time pout(t) r(t) figure 2: the controlled output p out of the system (solid line) together with the reference input r (dashed line). i f ! i q , i d ! , i f ! , i q ! , i d i q ! , i f i q ! � . due to the lack of space, the 19⇥19 (the extra dimension comes from the tracking error dynamics) matrices of the bmi and the closed loop lotka-volterra system are not listed here. the bmi (eq. (26)) for the globally stabilizing feedback design case suffers from rank deficiency and the available bmi solvers stop with marginal infeasibility, which means that global stability cannot be proven using the feedback law (eq. (30)). however, simulation results indicate, that the system is locally stable with the controller gain parameters yielded by the globally stabilizing bmi (eq. (26)) formulated for the closed loop generator model extended with the tracking error dynamics. k r1 = 1.0000 k r2 = �0.0002 k1 = �0.2932 k2 = �1.6880 k3 = �1.9609 k4 = 0.2259 k5 = 0.0001 k6 = 0.0000 k7 = �0.0001 k8 = 0.1450 the simulated behavior of the controlled generator can be seen in fig. 2 where the controlled output of the system (i.e. p out ) is shown together with the reference input (r). both of them are dimensionless. the tracking properties of the system are acceptable, moreover, its disturbance rejection is also good (at time 40, a step-like change has been applied to the disturbance input v d ). the simulation has been performed in matlab/simulink environment [24]. conclusions a novel servo control design technique based on the qp representation has been formulated in this work. as an example, an active power tracking controller has been designed for a synchronous generator model. the tracking properties of the closed loop system are satisfactory. further work includes the extension of the method for vector reference signals and use the degree of freedom lying in the bmi problem for formulating a robust/optimal controller design problem. another direction of future research is to apply graph theoretical techniques for controller structure selection that applies the underlying connections between qp systems and chemical reaction networks [25]. acknowledgments this research was supported by the european union and the state of hungary, co-financed by the european social fund in the framework of támop 4.2.4. a/2-11-1-20120001 ’national excellence program’. references [1] verma, k., niazi, k. a coherency based generator rescheduling for preventive control of transient stability in power systems, international journal of electrical power & energy systems, 2013, 45, 10– 18 [2] banavar, r., deshpande, u. robust controller design for a nuclear power plant using h-infinity optimization, in proc. of the 35th conference on decision and control, kobe, japan [3] na, m., jung, d., shin, s., jang, j., lee, k., lee, y.: a model predictive controller for loadfollowing operation of pwr reactors, ieee transactions on nuclear science, 2005, 52,1009–1020 [4] anderson, p., fouad, a. power-systemscontrol and stability (the iowa state university press, ames iowa, usa), 1977 [5] de mello, f., concordia, c. concepts of synchronous machine stability as affected by excitation control, ieee transactions on power apparatus and systems, 1969, pas-88(4), 316–329 [6] muyeen, s., al-durra, a., tamura, j. variable speed wind turbine generator system with current controlled voltage source inverter, energy convers manage, 2011, 52 [7] hernández-bermejo, b., fairén, v. nonpolynomial vector fields under the lotka-volterra normal form, physics letters a, 1995, 206, 31–37 [8] figueiredo, a., gleria, i. m., rocha, t. m. boundedness of solutions and lyapunov functions in quasi-polynomial systems, physics letters a, 2000, 268, 335–341 [9] magyar, a., szederkényi, g., hangos, k. m. globally stabilizing feedback control of process systems in generalized lotka-volterra form, journal of process control, 2008, 18(1), 80–91 [10] vanantwerp, j., braatz, r. a tutorial on linear and bilinear matrix inequalities, journal of process control, 2000, 10, 363–385 [11] tong, c.-f. , zhang, h., sun, y.-x. controller design for polynomial nonlinear systems 57 with affine uncertain parameters, acta automatica sinica, 2007, 33(12), 1321–1325 [12] fodor, a., magyar, a., hangos, k. m. control-oriented modeling of the energyproduction of a synchronous generator in a nuclear power plant, energy, 2012, 39, 135–145 [13] fodor, a., magyar, a., hangos, k. m. parameter sensitivity analysis of a synchronous generator, hungarian journal of industrial chemistry, 2010, 38(1), 21–26 [14] fodor, a., magyar, a., hangos, k. dynamic modeling and model analysis of a large industrial synchronous generator, in applied electronics, pilsen, czech republic, 91–96 [15] hernández-bermejo, b., fairén, v., brenig, l. algebraic recasting of nonlinear odes into universal formats, j. phys. a, math. gen., 1998, 31, 2415– 2430 [16] hernández-bermejo, b., fairén, v. lotkavolterra representation of general nonlinear systems, math. biosci., 1997, 140, 1–32 [17] hernández-bermejo, b. stability conditions and lyapunov functions for quasi-polynomial systems, applied mathematics letters, 2002, 15, 25– 28 [18] boyd, s., ghaoui, l. e. , feron, e., balakrishnan, v. linear matrix inequalities in system and control theory (siam, philadelphia) 1994 [19] scherer, c., weiland, c. linear matrix inequalities in control (disc, http://www.er.ele.tue.nl/sweiland/lmi.pdf), 2000 [20] kocvara, m., stingl, m. a code for convex nonlinear and semidefinite programming, optimization methods and software, 2003, 8, 317–333 [21] tuan, h., apkarian, p., nakashima, y. a new lagrangian dual global optimization algorithm for solving bilinear matrix inequalities, international journal of robust and nonlinear 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[24] i. the mathworks: matlab environment 2007) copyright 1984-2007 the mathworks, inc. http://www.mathworks.com [25] hangos, k. m., szederkényi, g. the underlying linear dynamics of some positive polynomial systems, physics letters a, 2012, 376(45), 3129– 3134 advertise upcoming meetings, conferences, and workshops; make public announcements; introduce your research laboratory; a new product or a service in the hungarian journal of industry and chemistry please contact us if interested! editorial office: university of pannonia p.o. box 158, veszprém h-8201 (hungary) tel.: +36 (88) 624-298, e-mail: hjic@almos.uni-pannon.hu; web: hjic.mk.uni-pannon.hu felelős szerkesztő: szilágyi róbert, phd kiadja: pannon egyetem, 8200 veszprém, egyetem u. 10. levélcím: h-8201 veszprém, postafiók 158, tel.: (88) 624-000 hungarian journal of industry and chemistry veszprém vol. 41(1) pp. 59-64 (2013) a structured model-based diagnosis method for discrete dynamic processes using event sequences attila tóth b1, katalin m. hangos1,2, and ágnes werner-stark1 1department of electrical engineering and information systems, university of pannonia, veszprém h-8200, hungary 2computer and automation research institute, budapest, hungary b e-mail: atezs82@gmail.com a novel model-based fault detection and diagnosis method is proposed that is based on following event sequences measured in a discrete dynamic process. the model of the nominal and faulty operation modes is given in the form of event sequences, that are decomposed according to the components and sub-components present in the process system. the faulty event sequences are defined using extended procedure hazid tables. a diagnostic algorithm is also presented that uses a component-wise decomposed form of the event sequences. the operation of the algorithm is illustrated on a simple example of a process system consisting of three similar tanks. keywords: process monitoring, diagnosis, discrete event systems, qualitative models introduction fault prevention and mitigation in the field of process system management is a task of crucial importance in avoiding serious accidents. thus, numerous hazard identification (hazid) techniques have been developed in the past decades to ensure the safe operation of process systems and to relieve effects of faults (see [1] for a broad presentation of the field). among these techniques, the most important methodologies involve the functiondriven hazop (hazard and operability, see [2]) analysis and the component-driven fmea (fault mode and effects analysis). there have been results in the past decade for automating the creation of hazop analysis ([3] with a concrete application described in [4]). blending the component-driven and function-driven analyses also resulted in a novel hazard identification approach described in [5]. although the information collected in the hazop and fmea studies serve the purpose of hazard identification, these studies can be the basis of diagnostic procedures, too. a model-based diagnostic method based on hazop and fmea information is reported in [6]. it is important to note that the above techniques concentrate on the static case when the deviation from a normal steady-state behaviour is of importance. therefore, the transient case when the plant is controlled by an operational procedure is not addressed in these results. a recent study [7] tries to deal with the diagnostic task by using a specially constructed p-hazid analysis and a diagnostic algorithm. in this paper, this diagnostic idea is extended to be able to handle more complex diagnostic tasks by taking advantage of a possible decomposition of typical process systems along their similar components. basic notions in a complex system the full dynamic model that describes its behaviour under normal and faulty operation models is rarely available, therefore one should base the diagnosis on qualitative information both in terms of the dynamic models and in the measured data. here we briefly summarize the basic notions for qualitative model based diagnosis. qualitative range spaces current values of continuous measurable outputs in process systems can be described using a properly selected qualitative range space. for example, to describe the value of a level sensor in a tank, the following range space can be used: qe = {e�, 0, l,n,h, e+}. (1) here, 0 means an empty tank, l, n and h means low, normal and high fluid level, respectively, while e� and e+ refer to unmeasurably low and high fluid levels (this might mean a failure in the level sensor itself). this range space will be used to describe system outputs during operation. input-output event sequences operational procedures in process systems are detailed list of instructions for the plant operator personnel to 60 perform certain operations on the plant. procedures can be formally described using finite input-output event sequences where a single event describes a change in either the inputs or the outputs of the system at a specific time instant. therefore the syntax of a single input-output event (at time instant t) is the following eventt = (t; input values; output values). the input in an event always refers to a state of an actuator component in the process system (e.g., in the case of a valve it can be open (op) or closed (cl)). on the other hand, the output in an event refers to a value of an output of the process system in the qualitative range space using the qualitative set defined in eq. (1). sequences formed from these events are called traces and defined as t (t1, tn) = eventt1 , ..., eventtn . separate events in a trace contain the same inputs and outputs. note that the discrete event time instances ti are abbreviated by their indexes i in the description, i.e. 2 stands for t2. examples of single events for a two-input single output case include (1; cl, op;n) , (2; cl, op; l) where at time instances t1 and t2 the two valve inputs are held closed and open, respectively, while the level decreases form its normal value to the low level. the trace formed form the above two consecutive events is written as t (1, 2) = ((1; cl, op;n), (2; cl, op; l)) . for every operational procedure there exists a trace (called the nominal trace) which describes its behaviour under fault-free conditions. the diagnostic method compares this trace to other traces which may have been executed under faulty conditions (called characteristic traces), and the differences (called deviations) are later used to find possible malfunctions of components in the system. deviations nominal and characteristic traces can be compared by comparing their corresponding event fragments. the difference between two corresponding event fragments is described by a deviation. deviations are formed from a deviation guideword and the nominal event from which the corresponding characteristic trace event is deviating from. the following deviation types are used during diagnosis: • never-happened: when the particular event never happened in the characteristic trace. • later: when the event happened in the characteristic trace, but at a later time instant. • earlier: when the event happened in the characteristic trace, but at an earlier time instant. • greater: when a particular output’s qualitative value was higher in the characteristic event than that of the nominal trace. • smaller: when a particular output’s qualitative value was lower in the characteristic event than that of the nominal trace. for the detailed description of the greater and smaller qualitative relations, please refer to [7]. procedure hazid as a combination and extension of the widely used fmea and hazop analyses (for details, refer to [7] or [1], and in particular to [5]), the procedure hazid (abbreviated as p-hazid) analysis can be used for fault diagnosis during operational procedures in a given process system. the result of this p-hazid analysis is given in the form of a spreadsheet and it consists of deviations together with their implications and possible (root) causes. a cause is considered to be a root cause if it is a nonmeasurable failure mode of a system component (which is an elementary part of the system). for example, a leak on a tank is considered as a root cause. a simple example of a p-hazid table can be found in table 1. using the initial set of differences (deviations) between the characteristic trace and the nominal trace, the set of possible root causes can be found using simple reasoning. for details, refer to ref. [7]. the diagnostic algorithm uses this technique first to find possible p-hazid row(s) to start from (using the set of initial deviations). then, following the deviation chains defined by these rows, the algorithm proceeds towards a possible root cause by traversing new rows based on the initial set of deviations. using this procedure, it may end up at a root cause or at a row with deviations from which it cannot proceed forward, because they are not contained in the initial set of deviations. the algorithm assumes that the root causes are static and they happened before the execution of the procedure began. component based diagnosis it is widely known that complex systems can often be decomposed in a hierarchical way using simple nondividable elements that are called components. the connection of these components is usually specified in terms of a graph called flowsheet. such a decomposition can be used effectively for the operation of a reasoning-based diagnostic algorithm. component based structural decomposition the above mentioned fault diagnosis based on the phazid analysis is only developed for process systems 61 table 1: a simple example of a p-hazid table. inputs: op=open, cl=closed. outputs: 0=no, l=low, n=normal. deviations: nh=never-happened, lat=later, ear=eariler, sml=smaller and gre=greater. faults: tank-leak is the leak of the tank and pos-bias is the positive bias failure of the tank level sensor. cause deviation implication tank-leak nh(2;op,cl;l) nh(3;op,cl;n) nh(2;op,cl;l) nh(3;op,cl;n) nh(4;op,op;n) tank-leak sml(2;op,cl;l) sml(3;op,cl;n) sml(2;op,cl;l) sml(3;op,cl;n) sml(4;op,op;n) pos-bias gre(1;op,cl;0) gre(2;op,cl;l) gre(1;op,cl;0) gre(2;op,cl;l) gre(3;op,cl;n) gre(2;op,cl;l) gre(3;op,cl;n) nh(4;op,op;n) pos-bias nh(1;op,cl;0) ear(2;op,cl;l) nh(1;op,cl;0) ear(2;op,cl;l) ear(3;op,cl;n) consisting of different individual components in [7]; the possible redundancy of such systems (e.g. multiple components of the same characteristics) were not taken into account. however, complex process systems in practice can be decomposed into a connected network of more simple components. for example, the process system in fig. 1 can be decomposed into three smaller similar components each formed by an input and an output valve and a tank. when developing the decomposed form of a process system it can happen that some elements are part of multiple subsystems as in the case of valves vb and vc in fig. 1. these elements are called boundary components, and are assumed to be error-free during the diagnosis. traces affecting different components can also be decomposed into a chain of trace fragments each referring to a single component of the trace. events in such a trace fragment have only a subset of inputs and outputs of the united trace (only the inputs and outputs of the particular component that is present in them). fragments also have information about the next trace fragment (called the next trace), and there is a starting condition (an event) that is associated with them to help the diagnosis. along with the trace fragment, each component has its own associated p-hazid spreadsheet. the component based diagnostic algorithm applying the diagnostic approach described in [7] on a decomposed process system, the components can be diagnosed separately against faults, treating them as a whole system during diagnosis. after the separate diagnosis, the root causes can be collected and the resulting set of root causes yields to the set of root causes in the united system. using the component decomposition, the size of the hazid information required can be made lower in cases when similar connected subsystems form the process system to be diagnosed. on the other hand, va vb vc vd tc tb ta ta level tb level tc level figure 1: process system consisting of 3 similar tanks system-level deviations need to be converted into component deviations by aligning their time and reducing the inputs and outputs in their associated events to componentlevel inputs and outputs. the diagnosis is then performed by comparing the whole nominal trace with the characteristic trace, and then distributing the deviations (differences) among the components. before distributing, time alignment and reduction of input and output states to component level are performed (including the component’s boundary elements). after the distribution, component-level diagnosis may begin to explore possible (root) causes on the component-level. the diagnosis proceeds along the flow direction by starting from the first component, takes the deviations, generates the set of possible root causes from them, and then tries to proceed to the next component by checking the starting condition of the next trace fragment if there is any. if the start condition is fulfilled, the diagnosis continues, otherwise it halts. for example, in the case of fig. 1 the second fragment might have a start condition containing a statement about the minimum level of fluid in tank ta, and in the case of the congestion of valve va no fluid is coming into a system, therefore, tank ta is not even filling up to the specified minimum level. in this case the diagnosis stops. the result of the diagnostic algorithm is always the union of identified and non-identified root causes created by the consecutive diagnostic algorithm that runs on the components of the consequent nominal trace fragments. for reference, the whole diagnostic algorithm is presented as a pseudo-code in algorithm 1. the algorithm collects all root causes (sets inc and irc) given a component decomposition, a starting component, and a possibly faulty characteristic trace. case study in the case study the diagnosis procedure for the simple process system in fig. 1 containing three sequentially connected tanks is used. the measured output of the tanks 62 algorithm 1 component-based reasoning procedure 1: inc {;} 2: irc {;} 3: actualcomponent startcomponent 4: continue true 5: shift 0 6: while continue do 7: dev generatedeviations(actualcomponent, chrtrace, shift) 8: fdp collectfinaldeviationpairs(dev) 9: for all pair 2 fdp do 10: startdeviation proj1(pair) 11: startimplication proj2(pair) 12: reason(startdeviation, startimplication, actualcomponent.phazid) 13: end for 14: if actualcomponent has successive component and its start condition evaluates to true then 15: shift length(actualcomponent.trace)� 1 + shift 16: actualcomponent getcomponent(actualcomponent.successivecomponent) 17: else 18: continue false 19: end if 20: end while 21: function generatedeviations(component, chrtrace, shift) 22: dev {;} 23: nomtrace component.trace 24: reducedtrace trimtrace(chrtrace, shift, shift+ component.trace.length) 25: locchrtrace converttocomponentlevel(reducedtrace) 26: for t := 1 to length(nomtrace) do 27: for all deviation d of locchrtrace from nomtrace at time t do 28: dev dev s (d) 29: end for 30: end for 31: return dev 32: end function 33: procedure reason(deviation, implication, phazid) 34: if 9r 2 rows(phazid), deviation = devphazid(r), implication = impphazid(r) then 35: for all {r, devphazid(r) = deviation and impphazid(r) = implication} do 36: if causephazid(r) 2 rc then 37: irc irc s causephazid(r) 38: return 39: else if causephazid(r) 2 dev and causephazid(r) � devphazid(r) in dev then 40: reason(causephazid(r), devphazid(r), phazid) 41: else 42: inc inc s causephazid(r) 43: return 44: end if 45: end for 46: else 47: inc inc s causephazid(r) 48: return 49: end if 50: end procedure 63 table 2: tank fill operational procedure. time input values output values va vb vc vd ta tb tc 1 op cl cl cl 0 0 0 2 op cl cl cl l 0 0 3 op op cl cl n 0 0 4 op op cl cl n l 0 5 op op op cl n n 0 6 op op op cl n n l 7 op op op op n n n table 3: normal fill in a single tank with no faults. input valve output valve tank level op cl 0 op cl l op op n is the tank level that takes its values from qe in eq. (1), and the input variables are the valve positions (open (op) or closed (cl)). components, operational procedure, and nominal trace every tank may contain no fluid (the tank level is equal to no (0)), may be low on fluid (level value is low (l)), or might have normal fluid level (level value is normal (n)). in every time instant the level increases by one qualitative magnitude (i.e. from no to low or from low to normal) if fluid is coming through the input valve but the output valve is closed. due to the same size of the valves the effect of fluid flow out of the system is similar, but in the opposite direction (from normal to low or from low to no). the valve positions (open (op) or closed (cl)) can be changed by the operator; they are considered as inputs of the system. leak in the tank is assumed to be equal to the size of an open valve (i.e. a quite substantial leak). the considered operational procedure is the initial filling of all the three tanks with fluid (the fill operational procedure in short), and is described in detail in table 2. the process system can be decomposed into three components, therefore the fill operational procedure can also be partitioned into three identical procedure fragments along the component boundaries (the vb and vc valves). the fragment abstracted from the three identical trace fragments associated to the three tanks can be observed in table 3. it has only the subset of inputs and outputs which are directly related to the particular tank component the input and output valve and the tank level. the corresponding component p-hazid table can be found in table 4 with some of the component faults and deviations associated to them. instances of this p-hazid table are used in the case of all three tanks during diagnosis. table 4: p-hazid table of a single tank component with two valves for a reference trace of table 3. faults: tank-leak is leak of the tank, pos-bias is the positive bias fault of the level sensor and neg-bias is the negative bias failure of the level sensor. cause deviation implication tank-leak nh(2;op,cl;l) nh(3;op,op;n) tank-leak sml(2;op,cl,l) sml(3;op,op;n) neg-bias lat(1;op,cl;0) nh(2;op,cl;l) lat(1;op,cl;0) nh(2;op,cl;l) nh(3;op,op;n) neg-bias sml(1;op,cl;0) sml(2;op,cl;l) sml(1;op,cl;0) sml(2;op,cl;l) sml(3;op,op;n) pos-bias nh(1;op,cl;0) ear(2;op,cl;l) nh(1;op,cl;0) ear(2;op,cl;l) nh(3;op,op;n) pos-bias gre(1;op,cl;0) gre(2;op,cl;l) gre(1;op,cl;0) gre(2;op,cl;l) gre(3;op,op;n) table 5: tank fill operational procedure with a leak in the second tank tb. the leak caused two different events in the operational procedure related to tb (in bold), these differences resulted in the four deviations the diagnosis could start from. time input values output values va vb vc vd ta tb tc 1 op cl cl cl 0 0 0 2 op cl cl cl l 0 0 3 op op cl cl n 0 0 4 op op cl cl n 0 0 5 op op op cl n 0 0 6 op op op cl n 0 0 7 op op op op n 0 0 the operation of the diagnostic algorithm the operation of the diagnostic algorithm is illustrated with the case when a rupture of the second tank is present as a root case (fault). a characteristic trace with the leak of the second tank can be seen in table 5. the size of the leak is assumed to be larger or equal to the size of an outbound pipe, therefore, the tank cannot fill up and no fluid can flow to the third tank tc. the starting condition of the tb and tc tank components is the appropriate “normal” level in the preceding tank. in that way it is ensured that diagnosis is done on the operational components only. the diagnosis of this faulty scenario begins by starting with the first tank component ta. there are no differences (and therefore no deviations) regarding this component. the start condition of the second component is fulfilled, therefore, the diagnosis moves towards the next component tb. however, in the case of tb the following deviations are found after comparing the nominal and characteristic traces (due to that two consequent events did not hap64 pened, instead, two events happened with lower output values at time instant 4 and 5 in the operational procedure): • never-happened(4;open,closed;low) • never-happened(5;open,open;normal) • smaller(4;open,closed;low) • smaller(5;open,open;normal) the time instant of the deviations are shifted back by 2 units because the second component’s first event happens at the third system-level time instant. after that, the diagnosis is initiated on the hazid table. searching for the already found deviations and connecting them to possible root causes (as in the case of the original diagnostic idea in [7]) the leak of the second tank can be found. because of the lack of fluid in the second tank, the start condition of the third component is not fulfilled, therefore, the diagnostic process halts at this step resulting in a single possible root cause being the tankleak. conclusions a novel component based extension of the single component diagnostic algorithm presented in [7] is described in this paper. using the extension, the domain of application can be extended to more complex composite process systems. driven by the decomposition of the overall system into components, the p-hazid tables used for diagnosis are processed at component level by the diagnostic algorithm. the extended method is efficient in the cases when the overall process system consists of similar small components. the component-based diagnostic procedure was described on a formal level, along with its proposed pseudocode. a case study for a process system of multiple components and a simple failure was also provided. the following improvements are planned to extend the component-based diagnostic approach: • the procedure is based on the assumption that the boundary elements between different components are free of failures. as a future work, this limitation might be removed by using a higher level reasoning above the components (as in the form of a systemlevel hazid table, for example). • at the moment, the algorithm is only working for already coded static event information in order to find faults in the system. diagnosis would be more valuable if events could be processed dynamically, thus the diagnostic procedure could be executed realtime along with the operational procedures. • diagnosis would be more accurate if the derivatives of internal states (e.g. the derivative of the tank level) were present in the events. acknowledgements the research was supported by the hungarian research fund through grant k83440. we acknowledge the financial support of the hungarian state and the european union under the tamop-4.2.2.a-11/1/konv2012-0072. references [1] cameron, i. t., raman, r. process systems risk management. vol. 6 of process systems engineering (elsevier academic press, san diego, ca) 2005 [2] as iec 61882-2003: hazard and operability studies (hazop studies) application guide [3] venkatasubramanian, v., rengaswamy, r., yin, k., kavuri, s. n. a review of process fault detection and diagnosis part i: qualitative modelbased methods, computers and chemical engineering, 2003, 27(3), 293–311 [4] venkatasubramanian, v., zhao, j. s., viswanathan, s. intelligent systems for hazop analysis of complex process plants, computers and chemical engineering, 2000, 24(9-10), 2291–2302 [5] seligmann, b. j., németh, e., hangos, k. m., cameron, i. t. a blended hazard identification methodology to support process diagnosis, journal of loss prevention in the process industries, 2012, 25 , 746–759 [6] németh, e., lakner, r., cameron, i., hangos, k. m. fault diagnosis based on hazard identification results, in preprints of the 7th ifac symposium on fault detection, supervision and safety of technical processes, barcelona, spain, june 30 july 3, pp. 1515–1520 [7] tóth, a., hangos, k. m. , werner-stark, a. hazid information based operational procedure diagnosis method, in 12th international phd workshop on systems and control, veszprém, 2012. aug. 27 (a. magyar, ed.), isbn 978-615-5044-71-7 (university of pannonia, veszprem), pp. 1–6 (on cd) hungarian journal of industry and chemistry veszprém vol. 41(1) pp. 65-75 (2013) role of steady state data reconciliation in process model development barbara farsangb1, sándor németh1, and jános abonyi1 1university of pannonia, department of process engineering, h-8200 veszprém, egyetem street 10., hungary be-mail: farsangb@fmt.uni-pannon.hu in chemical and hydrocarbon industry operational efficiency is improved by model-based solutions. historical process data plays an important role in the identification and verification of models utilized by these tools. since most of the used information are measured values, they are affected by errors influencing the quality of these models. data reconciliaton aims the reduction of random errors to enhance the quality of data used for model development resulting in more reliable process simulators. this concept is applied to the development and validation of the complex process model and simulator of an industrial hydrogenation system. the results show the applicability of the proposed scheme in industrial environment. keywords: data reconciliation; flowsheeting simulator; validation; balance equation; industrial hydrogenation system introduction in recent years, development of industrial technologies has been determined by the proliferation of computing and information technology. today’s technologies are characterized by widespread application of process engineering tools. the success of these tasks depends on the accuracy of data and applied models [1]. thanks to the evolution of information technology, on-line and historical process data — coming from chemical process systems — are available. the collected data provide the opportunity for engineers to better understand the processes, anomalies, and malfunctions [2]. monitoring of process variables allows us to ensure the consistent product quality. collected data can also be used for the development and validation of process simulators. however, measurements are always affected by errors during the measurement, processing and transmission of the measured signal. errors (gross, random, bias) in measured data affect the quality of process models and can lead to significant decrease in plant performance. estimation of true conditions of process states is important to achieve optimal process monitoring, control and optimization. therefore, several methods have been developed to minimize measurement errors thereby enhancing the reliability, accuracy and precision of data. first, analogue and digital filters were used to reduce the effect of high frequency noise [3]. gross errors were detected with various data validation methods, which include checking whether the measured data and the rate at which it is changing is within predefined operational limits. nowadays, smart sensors are used for determine whether there is any hardware problem or the measured data are appropriate. new methods were statistical quality control tests that are applied to each measured variable separately. although these methods improve the reliability and accuracy of the measured data, they do not ensure consistency of the data with respect to the inter-relationships between different process variables. therefore new methods – data reconciliation and gross error detection – are developed in chemical engineering [4]. the main difference between data reconciliation and other filtering methods is that data reconciliation uses process model constraints and that the results satisfy constraints and balance equations. data reconciliation techniques can be applied to reduce random errors of measurements, while the other techniques mentioned above do not. gross error detection can be used for eliminate systematic errors so simultaneous data reconciliation and gross error detection have emerged as a key of online optimization [5] (see fig. 1). data reconciliation techniques take minimal corrections of the measured variables to satisfy a set of model constraints. based on the difference between the measured and reconciled data, the following questions can be answered. can we consider a related set of measurements acceptable based on our previous knowledge of the system? are the measurements consistent? if not, what can be the source of the error? based on the available measurements and a prior knowledge, what is the most likely state of the system? answers to these questions are important in development of technology (e.g., monitoring, optimization, simulation, control, instrument maintenance). using this technique, we can verify the acceptability of measurements, improve the accuracy of measurements, estimate model parameters and unmeasured variables, and it can be used 66 applications s ys te m s ta tu s id en tif ic at io n r e a l ti m e d a ta b a se reconciliation gross error detection variable classification steady state identification data filtration detection of abnormalities figure 1: general methodology for on-line data correction [6] for fault detection. in order to ensure the consistency of measured process variables, models are used in data reconciliation. during data reconciliation, information is obtained from both measurements and process models. depending on the types of the models, data reconciliation techniques can be separated into two different problems: steady state and dynamic (see fig. 2). in the case of steady state data reconciliation, model constraints are algebraic equations. if we are dealing with dynamic processes, differential equations are used as model constraints. in the case of linear data reconciliation, model constraints are defined by linear equations. the simplest data reconciliation technique is the steady state linear method that can describe, e.g., the mass balance of technology. moreover, most chemical processes have nonlinear characteristics and constraints are nonlinear equations; this problem can be called as nonlinear data reconciliation. the goal of the presented research is to propose a methodology to support the development and validation of complex process models and simulators based on increasing the quality of measurement data used for (kinetic) parameter identification and validation. in section literature survey, a historical background of steady data data reconciliation is briefly reviewed. the basic method of linear and nonlinear steady state data reconciliation is described in section theoretical background of steady state data reconciliation. data reconciliation cannot be used in process development only, but it is a useful tool in model improvement too. the principle of this application is introduced in section combined application of data reconciliation and flowsheeting simulator. our approach aims the reduction of random errors to enhance the quality of data using data reconciliation and flowsheeting simulator simultaneously. the method is described in subsection the developed model based data reconciliation technique. the proposed approach is illustrated based on an industrial hydrogenation system. figure 2: types of data reconciliation [7] in section case study, the analyzed technology is introduced and the applicability of the method is illustrated on the basis of the mass balance of the hydrogenation system. then, some consequences are drawn in section conclusion. literature survey kuhan and davidson presented the first study about minimizing measurement errors in chemical process industry using a data reconciliation technique in 1961 [4]. they described the steady state linear data reconciliation technique and demonstrated a general solution for mass balance of technology. this seminal paper has started a new research area in process engineering. nogita [8] and mah [9] improved a new method capable of detection of gross errors. later, mah [10] found that the base method requires a process system in steady state conditions and that the process constraints must be linear. cao and rhinehart confirmed that the methodology will be successful if process data come from steady state conditions [11]. in these cases, data reconciliation problems can be solved with standard numerical methods like sequential quadratic procedures [12] and quasi-newton algorithms [13]. a multiple gauss-jordan elimination algorithm was published by madron and veverka [14]. the classification method is based on matrix decomposition and permutation. the linear method was improved by crowe (1986) who published a new technique to solve nonlinear data reconciliation using matrix projection [15]. furthermore, bagajewicz and jiang [16] presented an improved method that is applicable for dynamics system. the developed method from prata [17] is suitable for examination of dynamic nonlinear process systems. despite of the numerous good reviews of data reconciliation techniques, industrial application of this method started only in the 1980s. there are several complex software packages supporting data 67 table 1: industrial application of data reconciliation (newer industrial scenario and publications are added to prata’s summary [18]) industrial scenario author (year) absorption refrigeration systems maradiaga et al. (2013) [19] beverage alcohol distillation plant meyer et al. (1993), nounou and bakshi (1999), schladt and hu (2007) chemical extraction plant holly et al. (1989) ethylene and ammonia plant sanchez et al. (1992), sanchez and romagnoli (1996), plácido and loureiro (1998) exxon chemical process mcbrayer et al. (1998) , soderstrom et al. (2000) gas pipeline systems bagajewicz and cabrera (2003) gases network in an iron and steel making plant yi and han (2004) hydrogen plant bussani et al. (1995), chiari (1997), sarabia et al. (2012) [20] industrial coke-oven-gas purification process faber et al. (2006) hu and shao (2006) industrial distillation column islam (1994), weiss et al. (1996), sanchez et al. (1996), bourouis et al. (1998), li et al. (2001), bhat and saraf (2004), chatterjee and saraf (2004), chen et al. (2013) [21], keller et al. (2012) [22] industrial etbe reactor domingues et al. (2012) [23] industrial furnace pierucci et al. (1996), eksteen et al. (2002) industrial hydrometallurgical plants for a gold extraction de andradelima (2006) industrial polymerization reactor vieira et al. (2003), prata et al. (2006, 2008, 2009, 2010 [24]) industrial synthesis gas for production of ammonia christiansen et al. (1997) industrial utility plant lee et al. (1998) methyl-terc-butyl-ether plant al-arfaj (2006) mineral and metallurgical plants vasebi et al(2012) [25] nuclear power reactor valdetaro (2011) [26] refinery piccolo and douglas (1996), zhang et al. (2001) sulfuric acid plant chen et al. (1998), ozyurt and pike (2004) turbine cycle of a boiling water reactor sunde and berg (2003) vinyl acetate and ketene plants dempf and list (1998) water processes martins et al. (2010) [27] 68 reconciliation (for instance sigmaïňąne, datacon, vali, inlibra). these tools have interfaces to information systems used to manage process data and have special model building functionalities that allow almost automatic building of plant-wide balance equations. nowadays, data reconciliation is widely applied in various processing industries (e.g. refining, chemical industry, metals, mining, and power industry). despite of this fact, relatively few articles deal with industrial applications (prata et al. prepared a summary in 2009 [18]; newer applications and papers are collected in table 1). stanley et al. classified variables as observable and unobservable [28]. crowe categorized the variables from another point of view: the basis of classification is the given measured variable can be calculated from other measured variables using process models or not. the names of the two classes are redundant and nonredundant measurements [29]. ali and narasimhan applied graph theory to analyse the sensor network, classify the variables, and compute the redundancy degree of each variable. they claim that not only measured variables can be redundant. those unmeasured variables that can be estimated in multiple ways are also termed as redundant [30]. theoretical background of steady state data reconciliation in this section, the basis of linear and nonlinear data reconciliation techniques are described. different values are distinguished. real values (without error) of variables are designated by diacritic caron (̌ ), measured values by tilde (̃ ), while estimated values by circumflex (̂ ). in general, optimal estimates for process variables by data reconciliation are solutions to a constrained least-squares or maximum likelihood objective function, where measurement errors are minimized with process model constraints. the steady state data reconciliation problem can be formulated as an optimization problem by minimizing j(y̌, ž) = (ỹ � y̌)t v�1 d̃ (ỹ � y̌) (1) subject to f(y̌, ž) = 0 (2) and g(y̌, ž) � 0. (3) the solution of the optimization problem is performed with the following simplifying assumptions • the measurement error is independent from the balance variables. • the expected value of measurement error is zero. • the measurement error is in a normal (gauss) distribution. • errors of measurements are independent from each other (diagonal covariance matrix). • the covariance matrix is positive definite, so its inverse matrix exists. in the following two subsections, solution methods are presented in the cases of linear and nonlinear models. linear data reconciliation in the linear case, when all variables are measured, eq. (1) means minimizing j(y̌, ž) = (ỹ � y̌)t v�1 d̃ (ỹ � y̌) subject to ay̌ = 0. (4) gauss distribution (d̃ ⇠ n � 0,vd̃ � ) is assumed, so the density function of measurement error is f ⇣ d̃ ⌘ = c · exp h �0.5 · d̃tv�1 d̃ d̃ i (5) from which it follows that f (ỹ) = c · exp h �0.5 · (ỹ � y̌)t v�1 d̃ (ỹ � y̌) i (6) and that the f̌ = ay̌ � b = 0 (7) criterion is satisfied in accordance with the balance equation. the essence of the most likely estimation: if ỹ is given and its density function is known, which ỹ ! ŷ parameter of density function will be f (function vector of equality model constraints). since the logarithm function is strictly monotonously increasing, the maximum of the logarithm of the f(y) function recording only positive values is at the same place where the maximum of the argument is. exploiting it on the above function and using the lagrange multipliers method, the result is a vector equation system with two unknowns: v�1 d̃ ŷ �at �̂ = v�1 d̃ ỹ (8) aŷ = b (9) the solution of the vector equation system is ŷ = ⇣ i�vd̃a t � avd̃a t ��1 a ⌘ ỹ + vd̃a t � avd̃a t ��1 b (10) thus, the estimation requires a matrix-vector multiplication and a vector addition. because ỹ is only the variable, in the other operations there are only constants [31]. in practice, not all streams and properties are measured in plant due to physical and economical reasons. the data reconciliation technique is suitable for estimating unmeasured variables. in this case, the optimization problem can be solved by the method of 69 projection matrix. in the first step, the incidence matrix is separated into two parts: ayy̌ + az ž = 0. (11) unmeasured flows (ž) should be eliminated by premultiplying both sides by a projection matrix, such as paz ž = 0. eq. (4) then can be rewritten as min j(y̌, ž) = (ỹ � y̌)t v�1 d̃ (ỹ � y̌) (12) subject to payy̌ = 0. (13) the projection matrix is from q-r factorization of matrix az: az = qr = [q1 q2] [r1 0] t (14) the projection matrix is the transformation of q2 matrix (p = qt 2 ). if a matrix is replaced by matrix pay in eq. (10), then ŷ = ⇣ i�vd̃(pa)t � (pa)vd̃(pa)t ��1 (pa) ⌘ ỹ + vd̃(pa)t � (pa)vd̃(pa)t ��1 b. (15) after reconciled values of measured variables are obtained, the next step is to estimate the unmeasured variables using the information from process models (eq. (11)) as ayy̌ = �az ž (16) this linear equation can be solved to get estimated values of the unmeasured variables. usually, the number of equations is greater than the number of unmeasured variables. the least-squares technique can be applied and the solution is ẑ = �(at z az) �1at z (ayŷ). (17) nonlinear data reconciliation the data reconciliation problem can be extended to nonlinear steady state models. it is necessary because processes in chemical industry cannot be described only by linear models; behaviour of chemical processes are often nonlinear. if we wish to simultaneously reconcile mass flow, composition, or temperature measurements, mass, component, or energy balances have to be included as constraints. sometimes, inequality constraints have to be defined (e.g. mass/mole fraction of components have to be in the [0:1] interval). moreover, if we take thermodynamic equilibrium relationships and complex correlations for thermodynamic and physical properties as constraints, nonlinear data reconciliation techniques have to be used. if all variables are measured, the bilinear data reconciliation problem can be reduced to a linear problem by introducing the “measured” compound flows (‘component flows’ or ‘energy flows’). therefore, solution of the nonlinear data reconciliation problem is figure 3: integrated application of statistical and white box models [32] presented on the basis of the situation when measured and unmeasured variables occur. the objective function is the same as in the previous case (eq. (1)). the difference is that constraints are nonlinear equations. this problem can be reduced to the linear case. this method is referred to as successive linearisation: nonlinear constraints can be linearised around working points using first-order taylor series. the solution of the linearisation can be written as h = byy̌ +bz ž� f(y̌i, ži). (18) the initial values are usually the raw values. after linearisation the procedures of data reconciliation is described in subsection linear data reconciliation (qr factorization, reconciliation of measured values, then estimation of unmeasured variables). if the reconciled and initial values are far from each other, new iteration begins. the initial value will be the result of the previous iteration. different criteria can be defined: number of iteration or ||ŷn � ŷn�1|| is smaller than the specified tolerance values. successive linearisation is a relatively simple and fast solution, but variable bounds cannot be handled with this method. another option to solve nonlinear data reconciliation problem is using nonlinear programming (nlp) techniques that can estimate measured and unmeasured variables simultaneously. sequential quadratic programming (sqp) and generalized reduced gradient (grg) are usual techniques in handling nonlinear problems. these methods are more computationally demanding, but they are numerically more robust [33]. 70 figure 4: iterative model development combined application of data reconciliation and flowsheeting simulator mathematical models describe the connection between the relevant properties of the analyzed phenomena, process, or activities. in the case of complex chemical processes, mathematical models usually contain differential equations whose solution is not always possible analytically. the process simulator (it is often applied to improve complex industrial processes) contains models of the equipments so their mathematical description is unnecessary for the users. in addition, it includes different thermodynamic models and component databases. the flowsheeting simulator can be defined as “use of a computer program to quantitatively model characteristic equations of a chemical process” [34]. the simulator is used in batch processing, integrated process engineering (for example, economic analysis and supply chain forecast, supervisory process control, on-line modeling and optimization, safety and reliability analysis), and process synthesis and design (for instance, heat integration, conceptual design). however, lots of information are needed from technology for the simulator to describe the real process exactly. many of the needed data are measured (e.g., flow, composition, temperature, pressure). if the input of the simulator is faulty, the simulator cannot give reliable results. a new direction is the combination of simulators and data based statistical models that can handle random and gross errors [23, 35]. the structure of these hybrid models are shown in fig. 3. • in the first case, the statistical model is the input of the physical model in the form of differential or algebraic equations or a complex flowsheeting simulator. in this case, the statistical model is used to estimate parameters and phenomena that are figure 5: options of data processing in flowsheeting simulator difficult to model. • combination 2 shows the case when outputs of the physical model are transformed by a statistical model. • in the third option, the difference between measured and calculated variables are the inputs of the statistical model used for correction. model-based data reconciliation techniques are similar to the third approach. using data reconciliation technique random errors can be filtered. when accurate data are available, the flowsheeting simulator gives more reliable results that make further development of models possible. this means that data reconciliation allows us to check the reliability of these measurements [36] and reconsolidated data can be used to build accurate models. the developed model based data reconciliation technique our goal is to design an expert system that can be used to check the acceptability of measurements and improve the flowsheeting simulator of technology. the proposed method is based on model-based data reconciliation techniques. using data reconciliation, faulty measurements can be found. random errors can be filtered using discrete fourier transform. the frequency of the noise is much higher than the frequency of basic process so the discrete fourier transform gives a graphical view about the differences between the basic process and the noise. thus, the filtration of the frequency can be determined so the noise can be separated from the basic process. if the amplitude of the noise is known, the standard deviation can be estimated. thereby, input of simulator is error-free, so systematic model mismatch can be recognized and the tuning of the model can be initiated. data reconciliation requires an accurate model whose parameters require reconciled process data. in th case of an efficient iterative procedure, a properly working simulator can be developed (see fig. 4). since the simulator is able to process historical measured data, the difference between the theoretically achievable values and the measured outputs can give useful information (see fig. 5). four different output 71 figure 6: flowsheet diagram of the c3 hydrogenation system values can be compared in the case of the same variable. measured output values are known. if all necessary information is available for data reconciliation, we get the reconciled output value. in addition, if process model is prepared in the flowsheeting simulator, we have two options for analysis: the input of the simulator can be the measured or the reconciled value. the difference between outputs can be used for two purposes. if the difference is insignificant, the measured data is acceptable and measuring instruments operate properly; calibration is not necessary. moreover, it helps in the development of the flowsheeting simulator. if the calculated results with reconciled input are far from the reconciled output, the simulator do not describe the real process properly; maybe a parameter is not accurate or it needs structural change. the proposed method is illustrated on the basis of an industrial hydrogenation system. the case study shows examples for both cases; when the difference indicates the conformity of measurements and when it warns that some model parameters are incorrect. case study the tisza chemical group plc. (tvk) is the largest petrochemical company of hungary where polymer raw materials (ethylene, propylene, butylenes, etc.) are produced by steam cracking of naphtha or gasoline. at high temperature, numerous free radical reactions occur. cracked gas includes light components that are produced in larger amounts, for example, methane, ethane, ethylene, acetylene, propane, propylene, methyl-acetylene, propadiene, n-butane, isobutane, 1,3-butadiene, etc. some of them are undesirable, because they poison the catalysts for polymerization reactions (e.g. acetylene, methyl-acetylene, propadiene). another problem is that separation of these components is difficult from the main products by distillation. due to these problems, undesirable hydrocarbons are hydrogenated. hydrogenation process of methylacetylene and propadiene is presented in this case study (see fig. 6). the c3-selective hydrogenation process transforms methyl-acetylene and propadiene to propylene by catalytic reaction avoiding the transformation of propylene to propane. the methyl-acetylene and propadiene content of hydrogenated c3 fraction should be less than 1000 ppm. the concentration of the main components (methyl-acetylene, propane) is measured by online analysers (a1, a2 and a3) and there are two places where sample is taken twice a day for laboratory analysis (l1 and l3). hydrogen and liquid olefin stream are fed to the reactor where chemical reactions take place. outlet stream of the reactor is cooled by water so the gaseous c3 component condenses and the hydrogen and the liquid olefin phases are separated. the recirculated stream has two important functions: cools the reactor and dilutes the inlet c3 stream. blowdown is required due to the accumulation of inert components. the most frequent type of hydrogenation reactors is the trickle-bed reactor in the olefin plant. liquid olefin feed and gaseous hydrogen pass through the catalyst bed in the same direction: from top to bottom. cooling of reactor is provided by vaporization liquid flow. the reactions occur in the top region of the reactor. the 72 figure 7: measured and filtered values of product c3 fraction reactions release a large amount of heat. the heat generation is influenced by the methyl-acetylene and propadiene (mapd) content of the inlet c3 and by the partial pressure of the hydrogen. the mapd content of the inlet flow of system is high, so the inlet flow of the reactor is diluted. in the range of 10 � 80 �c temperature, the average reaction heat of main reactions are the following: ma+h2 = c3h6 �hr = �164.8 kj/mole (19) pd+h2 = c3h6 �hr = �172.2 kj/mole (20) c3h6 +h2 = c3h8 �hr = �124.6 kj/mole (21) in the following sections, released heat vaporizes a part of the liquid phase. this phenomenon also ensures the cooling of the product flow. the simulator has been developed in aspen plus software as part of an expert system used for the monitoring and qualification of the operation of the technology. calculations provide useful information about unmeasured variables, validity of on-line analyzers, and efficiency of catalysts. the residence time is small (less than one minute). the sample time was five minutes, so the steady state simulation gives the same result as the dynamic simulation. historical process data entered the simulator by aspen simulation workbook. the developed excel and visual basic macro based framework allows the comparison of the measured data and the calculated results. results and discussion the process has two inlet streams (c3 fraction and hydrogen) and two outlet streams (hydrogenated liquid c3 fraction and blowdown). mass flows of every stream are measured. based on the law of conservation of mass (there is no accumulation): inlet c3 + h2 = blowdown + product c3 (22) figure 8: measured and reconciled values of product c3 fraction if we check whether the measured data satisfy the balance equation, we find that eq. (22) is not fulfilled, so data reconciliation is necessary. steps of the procedure are introduced based on mass flow of c3 product fraction. first time random error is separated from basic process using discrete fourier transformation. fig. 7 shows the measured and the filtered values of product c3 fraction. we defined the random noise as the difference between the measured and filtered values so the standard deviation and covariance matrix of random error (vd̃) can be calculated. since there is no accumulation (i.e., b = 0) eq. (10) is simplified to ŷ = ⇣ i�vd̃a t � avd̃a t ��1 a ⌘ ỹ. (23) since two input and two output streams are in the system, the incidence matrix is a = [1 1 � 1 � 1]. every needed information are known so the matrix operation can be performed. real industrial data are analyzed, so dimensionless units are included in the figures. the result of reconciliation is visible in fig. 8. the result shows that the proposed method gives a minor improvement of the process values. thanks to the validated accuracy of the mass measurements, these process values can be directly used for the validation of the simulator. in the next step, we compare the reconciled output with the values calculated by the simulator in two different ways. first, the input of the simulator is the measured data, then, the reconciled input data. the result of the comparison is shown in fig. 9. first, we thought that the three curves coincide. however, as a portion is zoomed, the difference became apparent (see fig. 10). if the input of simulator is the reconciled data, the calculated and the reconciled output are nearly the same. although the difference between the two calculated curves may seem small in dimensionless space, do not forget that the small percentage difference can mean significant mass flow values in a real industrial process. 73 figure 9: calculated and reconciled data of product c3 fraction if the input of the simulator is the measured and reconciled data figure 10: reconciled and calculated outputs of simulator in case of product c3 fraction we calculated the square error in both cases (deviation from the reconciled output) and found that the difference decreased by 87% if the reconciled values are the input of the simulator. this shows that the simulator gives more accurate results if previously data are reconciled. the simulator supported by data reconciliation can be applied in fault diagnosis. fig. 11 shows how the hydrogen flow changes over time. the continuous line represents the simulator results without data reconciliation, while the dashed line shows the reconciled values. fig. 11 shows the similarity of the calculated and the measured values. after 300 hours of operation the calculated values exceed the measured data. there are several possible reasons. less hydrogen goes to this system if • the mapd content of the inlet stream is lower, because the mass flow of hydrogen is controlled in proportion of the mapd mole flow of the input c3 figure 11: calculated and reconciled dimensionless mass flow of h2 if the input of the simulator is the measured data fraction. • after the regeneration when catalyst is active. • other reactor is regenerated or reactivated. in this case, another reactor in the olefin 2 plant was reactivated (after 300 hours). the reactivation process needed a lot of hydrogen so the hydrogen for the studied reactor was reduced. the received data did not include the rate of reduction. the result of the simulation showed that something was changed in the technology. this shows the technique can be used for monitoring and diagnostics of complex processes because it can be discovered if the operating condition has changed. conclusion data reconciliation is an effective method to obtain accurate process data that satisfy balance equations using process constraints. the application of steady-state data reconciliation is widespread in the process industry. simulators are often applied to improve industrial processes, optimize operation, and identify bottlenecks of technology. historical process data can be used for the identification and verification of models utilized by these tools. usually, measured data do not satisfy balance equations, because all measurements are incorrect to some extent. thus, it is necessary to develop a method which can simultaneously and iteratively improve data and model performance. a method based on data reconciliation technique has been developed for this purpose. an industrial c3 selective hydrogenation process has been analysed as a case study. the steady state simulator of the process has been developed in aspen plus flowsheeting software. calculated and historical process data were compared using aspen simulation workbook. 74 the proposed technique can be used for monitoring complex processes. results showed that the proposed technique slightly improves the quality of flow data. thanks to the accuracy of flow measurements, these process values are directly applicable for the validation of simulator and suitable for further studies, e.g., for the determination of kinetic parameters. acknowledgements this research of barbara farsang and janos abonyi was supported by the european union and the state of hungary, co-financed by the european social fund in the framework of támop 4.2.4. a/2-11-1-2012-0001 ‘national excellence program’. the infrastructure of the research has been supported by the european union and the hungarian republic through the támop 4.2.2/a11/1/konv-2012-0071 project. symbols a incidence matrix ay incidence matrix of balances in terms of measured flows az incidence matrix of balances in terms of unmeasured flows by jacobian matrix of measured variables bz jacobian matrix of unmeasured variables b source of extensive quantity d y � y̌ error f function vector of equality model constraints f̃ balance error (aỹ � b vector) f̂ balance error (a˜̂y � b vector) g function vector of inequality model constraints i identity matrix ma methyl-acetylene mapd methyl-acetylene and propadiene pd propadiene p projection matrix vd̃ covariance matrix of measurements y̌ vectors of real values of measured variables ỹ vectors of measured variables ŷ vectors of reconciled measured variables ž vectors of real values of unmeasured variables z̃ vectors of unmeasured variables ẑ vectors of estimated unmeasured variables � lagrange multiplier �hr reaction heat references [1] bauer, m., craig, i. k. economic assessment of advanced process control a survey and framework, journal of process control, 2008, 18(1), 2–18 [2] pach, f. p. , feil, b. , németh, s., árva, p. , abonyi, j. process data warehousing based operator support system for complex production technologies, ieee transactions on systems, man and cybernetics, part a, special issue on ’advances in heterogeneous and complex system integration’, 2006, 136–153 [3] tietze, u., schenk, c. analóg és digitális áramkörök (műszaki könyvkiadó) [4] kuhen, d., davidson, h. computer control ii. mathematics of control, chemical engineering progress, 1961, 57, 44–47 [5] narasimhan, s. introduction to data reconciliation and gross error diagnosis (2013), url: www.che.iitm.ac.in/ naras/ ch544/introdrged.pdf [6] bellec, s., jiang, t., kerr, b., diamond, m., stuart, p. on-line processing and steady state reconciliation of pulp and paper mill process data, 91st annual meeting preprints-book b, 2005, 105– 110 [7] thibault, j. introduction to data reconciliation 2013, url: www.polymtl.ca/namp/docweb/ modules_web/m11_tier1_chap1-3.pdf [8] nogita, s. statistical test and adjustment of process data, ind. eng. chem, process des. dev., 1972, 11, 197–200 [9] mah, r. s. h., stanley, g. m., downing, d. m. reconciliation and rectification of process flow and inventory data, ind. eng. chem, process des. dev., 1976, 15, 175–183 [10] mah, r. s. h. chemical process structures and information flows, aiche journal, 1993, 39(4), 730 [11] cao, s., rhinehart, r. an efficient method for on-line identification of steady state, journal of process control, 1995, 5(6), 363–374 [12] tjoa, i. b., biegler, l. t. simultaneous solution and optimization strategies for parameter estimation of differential � algebraic equation systems, industrial and engineering chemistry research, 1991, 30, 376–385 [13] britt, h. i. , luecke, r. h. the estimation of parameters in nonlinear implicit models, technometrics, 1973, 15, 233–247 [14] madron, f., veverka, v. optimal selection of measuring points in complex plants by linear models, american institute of chemical engineering 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(elsevier) 2012, pp. 1002–1006 [24] prata, d. m. , schwaab, m., lima, e. l., pinto, j. c. simultaneous robust data reconciliation and gross error detection through particle swarm optimization for an industrial polypropylene reactor, chemical engineering science, 2010, 65(17), 4943–4954 [25] vasebi, a., poulin, e., hodouin, d. dynamic data reconciliation in mineral and metallurgical plants, annual reviews in control, 2012, 36(2), 235–243 [26] valdetaro, e. d., schirru, r. simultaneous model selection, robust data reconciliation and outlier detection with swarm intelligence in a thermal reactor power calculation, annals of nuclear energy, 2011, 38(9), 1820–1832 [27] martins, m. a., amaro, c. a., souza, l. s., kalid, r. a. , kiperstok, a. new objective function for data reconciliation in water balance from industrial processes, journal of cleaner production, 2010, 18(12), 1184–1189 [28] stanley, g., mah, r. observability and redundancy in process data estimation, chemical engineering science, 1981, 36(2), 259–272 [29] crowe, c. m. observability and redundancy of process data for steady state reconciliation, chemical engineering science, 1989, 44(12), 2909–2917 [30] ali, y., narasimhan, s. redundant sensor network design for linear processes, american institute of chemical engineering journal, 1995, 41(10), 2237 [31] almasy, g.: mérlegegyenletek mérési hibák (egyetemi kiadó, veszprém) 1996 [32] nakaya, m., li, x. on-line tracking simulator with a hybrid of physical and just-in-time models, journal of process control, 2013, 23(2), 171–178 [33] thibault, j. tate data reconciliation for bilinear systems, 2013, url: www.polymtl.ca/namp/docweb/ modules_web/m11_tier1_chap4-5.pdf [34] flores, a.: introduction to aspen plus (12. 09. 2001) [35] kanoa, m., nakagawa, y. data-based process monitoring, process control and quality improvement: recent developments and applications in steel industry, computers and chemical engineering, 2008, 32, 12–24 [36] kadlec, p., gabrys, b., strandt, s. datadriven soft sensors in the process industry, computers and chemical engineering, 2009, 33, 795–814 advertise upcoming meetings, conferences, and workshops; make public announcements; introduce your research laboratory; a new product or a service in the hungarian journal of industry and chemistry please contact us if interested! editorial office: university of pannonia p.o. box 158, veszprém h-8201 (hungary) tel.: +36 (88) 624-298, e-mail: hjic@almos.uni-pannon.hu; web: hjic.mk.uni-pannon.hu felelős szerkesztő: szilágyi róbert, phd kiadja: pannon egyetem, 8200 veszprém, egyetem u. 10. levélcím: h-8201 veszprém, postafiók 158, tel.: (88) 624-000 hungarian journal of industry and chemistry veszprém vol. 41(1) pp. 77-82 (2013) statistical process control based performance evaluation of on-line analysers tibor kulcsár1 and jános abonyib1 1 department of process engineering, university of pannonia, egyetem street 10., h-8200 veszprém, hungary be-mail: janos@abonyilab.com on-line analyzers can provide accurate and timely information for process control and monitoring. statistical process control (spc) techniques can be effectively utilized to support the development and maintenance of these tools. the d629910 astm standard details how on-line analyzers should be validated. the applicability of this standard is demonstrated through the analysis of industrial data collected from an on-line gas chromatograph. the results confirm that automatized spc can effectively improve the reliability of advanced process control systems. keywords: on-line analyzer, software sensor, statistical process control, spc, process monitoring introduction process variables characterizing and influencing product quality have a significant role in process control and optimization. off-line laboratory tests mostly take more than two hours. this time delay can cause control problems resulting in economic loss. in such situations, an improved on-line monitoring system is required. on-line analyzers eliminate the dependence on laboratory data. analysers are valuable instruments for real time control because of their fast response time (1-4 minutes) (see fig. 1) [1]. quality control techniques can be effectively used to support the development of on-line analyzers [2] and advanced process control systems [3]. the d 6299 astm standard (applying statistical quality assurance techniques to evaluate analytical measurement system performance) provides information for the design and operation statistical quality control (qc) tools to monitor and control of analytical measurement systems using a collection of statistical quality control (sqc) tools [4]. the goal of the performance monitoring is the perifigure 1: soft sensors and on-line analyzers enable feedback control odic comparison of the on-line analyzer’s results to the reference value of the same sample measured by laboratory test methods. precision and bias (see fig. 2) are calculated to provide information for updating test methods as well as for indicating areas of potential improvements. control charts and other statistical techniques can be used for performance monitoring. statistical estimates of the measurement system precision and bias can be calculated on the basis of periodically updated data. plotting and interpreting these test results can ascertain the instatistical-control status of the measurement system [5]. on-line statistical process control (spc) based real-time validation of measurement systems has been already refigure 2: type of faults. the dashed line shows when the fault occurs. �: data free of fault; • corrupted data for the following cases: (a) bias, (b) complete failure, (c) drifting, and (d) precision degradation [4] 78 figure 3: illustrative example: mol aromatic block gas chromatograph ip benzene content (m/m %), lab, analyser and apc soft sensor ported in 1997 [6]. the spc based approach can also be applied for off-line performance evaluation [7]. this approach has a wide range of application areas like steel industry [8], electronic device assembling [9], and buildings’ energy demand monitoring [10]. the goal of this paper is to present the theoretical background and application details of spc based performance evaluation of on-line analyzers. the applicability of the concepts is illustrated by a case study based on data collected from an on-line gas chromatograph of the mol plc (see fig. 3) . typical patters that show out of control status of the system are also presented. to check the normality of the residuals, an easily applicable and interpretable tool is proposed. the developed demonstration tools are available at the website of the authors (www.abonyilab.com). control chart based evaluation of system performance the studied d6299 practice is devoted to a special testing of analyzers [4]. quality control (qc) test specimen samples from a specific lot are introduced and tested in the analytical measurement system on a regular basis to establish system performance history in terms of both stability and precision. the control chart is one of the seven basic tools of qc. control charts also known as shewhart charts are used to determine if process is in a state of statistical control. the analysis of the control chart indicates whether the process is currently under control. this means that these charts are used to check the stability of the production. in stable operation, the variations of the process and quality variables are only random, normally distributed variables. in these cases, no corrections of the control parameters are needed. when the chart indicates that the monitored process is out-of-control, the analysis of the chart can help to determine the sources of the variation. typically, control charts are used for time-series data, though they can be used for data that have logical comparability [11]. in this section, we present these charts and detail how these should be applied for the performance assessment of on-line analyzers. control charts run chart the run chart is a plot of sample values in chronological order (fig. 4). the run chart can be used to screen data for unusual patterns such as continuous trending in either direction, unusual clustering, and cycles. the run chart of the data used in our case study is shown in fig. 3. the plotted time series shows the signal of the on-line analyzer and the related laboratory measurements. i chart the i (individual) chart is a run chart to which control limits and center line have been added (see top panel of fig. 5). the center line is based on the mean of the samples, ī = pn i=1 ii n (1) figure 4: example for a run chart 79 figure 5: i and mr charts show out of control samples of the gas chromatograph ip benzene content (m/m) % while the upper and lower control limits are based on the estimated variance (range of the data) mr [12] mr = pn�1 i=1 |ii+1 � ii| n� 1 , (2) ucli = ī + 2.66mr, (3) lcli = ī � 2.66mr. (4) individual values that are outside the upper or lower control limits are indications of an unstable system, and efforts should be made to determine the cause [5]. optionally, any one of the following occurrences should be considered as potential signs of instability: 1. two out of three consecutive results on the i chart that are more than 1.77mr distant from the center line in the same direction; 2. five consecutive results on the i chart that are more than 0.89mr distant from the center line in the same direction; 3. eight or more consecutive points in the i chart that fall on the same side of the center line. mr chart mr (moving range) charts are also used to detect unusual patterns by plotting the sequential range of two values given by �i = mri = |ii � ii�1| , (5) and connecting each point (see fig. 6 for an example). there is no lower control limit for an mr chart [5]. the upper control limit for the mr chart is given by uclmr = 3.27mr. (6) figure 6: example for a mr chart figure 7: example for an ewma chart ewma chart an ewma (exponentially weighted moving average) chart is used to enhance the sensitivity in detecting mean shifts that are small relative to the measurement system precision (see fig. 7 for an example). each ewma value is a weighted average of the current result and previous results with the weights decreasing exponentially with the age of the reading [5]: ewma1 = i1, (7) ewmai = (1� �)ewmai�1 + �ii, (8) where � is the exponential weighting factor. for application of this practice, a � value of 0.4 is recommended. the control limits for the ewma chart are calculated using a weight (�) as follows: ucl� = ī + 2.66mr r � 2� � , (9) lcl� = ī � 2.66mr r � 2� � . (10) the complexity of multivariate and autocorrelated processes makes it difficult to use standard control charts. to construct simple and interpretable charts, dimensional reduction could also be used as simoglu and martin have done [13], but in case of autocorrelated data, modelbased control charts should be applied as kim and jitpitakler have done in their research [14]. pretreatment of test results assessment, control charting, and evaluation are applied only to appropriately pretreated test results. the purpose 80 of pretreatment is to standardize the control chart scales so as to allow for data from multiple check standards to be compared on the same chart. for qc sample test results, no data pretreatment is typically used since results for different qc samples are generally not plotted on the same chart. in our case, the difference between the measurements and their accepted reference values (arvs) are monitored. arv serves as an agreed-upon reference for comparison and that is derived based on (1) a theoretical value, based on scientific principles, (2) an assigned value, based on experimental work, or (3) a consensus value, based on collaborative experimental work under the auspices of a scientific or engineering group. i = test result�arv. (11) assessment of initial results in the initial phase of the application assessment techniques are applied to test results collected during the startup phase of or after significant modifications to a measurement system. it is required to perform the following assessment after at least 15 pretreated results have become available. the purpose of this assessment is to ensure that these results are suitable for deployment of control charts. pretreated results should first be visually screened for values that are inconsistent with the remainder of the data set, such as those that could have been caused by transcription errors. those flagged as suspicious should be investigated. discarding data at this stage must be supported by evidence gathered from the investigation. if after discarding suspicious pretreated results there are less than 15 values remaining, collect additional data and start over. the next step is to examine the pretreated results for non-random patterns such as continuous trending in either direction, unusual clustering, and cycles. one way to do this is to plot the results on a run chart and examine the plot. if any non-random pattern is detected, investigate for and eliminate the root cause(s). typical control chart patterns in the previous sessions, the main charts used for performance measurement were presented. in spc, the western electric rules are the decision rules for detecting “outof-control” or non-random conditions on control charts. locations of the observations relative to the control chart control limits (typically at ±3 standard deviations) and centerline indicate whether the process in question should be investigated for assignable causes. the western electric rules were codified by a specially-appointed committee of the manufacturing division of the western electric company and appeared in the first edition of its statistical quality control handbook in 1956 [15]. their figure 8: this process is out of control because a point is either above the ucl or below the lcl. for example, in fig. 5-b at sequence number 28 there is a unique point below the lcl figure 9: in this case the system produce 2 out of 3 consecutive points either in or beyond zone a. the process on fig. 5-b shows this behaviour at sequence number 45 where the values are close to the upper control limit. purpose was to ensure that line workers and engineers interpret control charts in a uniform way [5, 12]. the eight standard western electric rules are: 1. the most recent point plots outside one of the 3sigma control limits (see fig. 8). if a point lies outside either of these limits, there is only a 0.3% chance that this was caused by the normal process. 2. two of the three most recent points plot outside and on the same side as one of the 2-sigma control limits (see fig. 9). the probability that any point will fall outside the warning limit is only 5%. the chances that two out of three points in a row fall outside the warning limit is only about 1%. 3. four of the five most recent points plot outside and on the same side as one of the 1-sigma control limits. in normal processing, 68% of points fall within one sigma of the mean, and 32% fall outside it. the probability that 4 of 5 points fall outside of one sigma is only about 3%. 4. eight out of the last eight points plot on the same side of the center line, or target value. sometimes you see this as 9 out of 9, or 7 out of 7. there is an equal chance that any given point will fall above or below the mean. the chances that a point falls on the same side of the mean as the one before it is one in 81 two. the odds that the next point will also fall on the same side of the mean is one in four. the probability of getting eight points on the same side of the mean is only around 1%. 5. six points in a row increasing or decreasing. the same logic is used here as for rule 4 above. sometimes this rule is changed to seven points rising or falling. 6. fifteen points in a row within one sigma. in normal operation, 68% of points will fall within one sigma of the mean. the probability that 15 points in a row will do so, is less than 1%. 7. fourteen points in a row alternating direction. the chances that the second point is always higher than (or always lower than) the preceding point, for all seven pairs is only about 1%. 8. eight points in a row outside one sigma. since 68% of points lie within one sigma of the mean, the probability that eight points in a row fall outside of the one-sigma line is less than 1% (see fig. 10). normality checks since the control chart and limits prescribed in this practice are based on the assumption that the data behavior is adequately modeled by the normal distribution, it is recommended that a test of this normality assumption be conducted. one way to do this is to use a normal probability plot and the anderson-darling statistic [16]. if the results show obvious deviation from normality, the statistical control charting techniques described are not directly applicable to the measurement system [5]. quantile-quantile plot (q-q plot) is a graphical tool for comparing two probability distributions by plotting their quantiles against each other. the normality plot of the process can be obtained by comparing the empirical distribution of the data against a standard normal distribution figure 10: long runs (8 or more consecutive points) either above or below the centerline. (see fig. 5-a in range 28-40) figure 11: normality check of the studied gas chromatograph. (see fig. 11). when the results are normally distributed, the plot should be approximately linear. major deviations from linearity are an indication of non-normal distributions of the differences [17, 16]. conclusions we showed that statistical process control can be effectively used to support the development and maintenance of on-line process analyzers. a case study is presented based on the analysis of data taken from the chemical process industry. the proposed concept has been implemented in matlab. the results illustrate the applicability the developed tools in improving the reliability of advanced process control systems. acknowledgements this research of janos abonyi was supported by the european union and the state of hungary, co-financed by the european social fund in the framework of tamop 4.2.4. a/2-11-1-2012-0001 national excellence program. the infrastructure of the research has been supported by the european union and the hungarian republic through the tamop 4.2.2/a11/1/konv-2012-0071. the work of tibor kulcsar was supported by the hungarian scientific research fund under grant k77955. references [1] gidwani, k. k. , beckman, r. f. evaluation of refinery control systems, isa transactions, 1994, 33(3), 217–225 82 [2] roberto, m. f., dearing, t. i. , martin, s., marquardt, b. j. integration of continuous flow reactors and online raman spectroscopy for process optimization, journal of pharmaceutical innovation, 2012, 7(2), 69–75 [3] smith, c. advanced process control: beyond single loop control (john wiley & sons), 2011 [4] a. international: applying statistical quality assurance techniques to evaluate analytical measurement system performance (astm international), 2010 [5] montgomery, d. introduction to statistical quality control (john wiley & sons, inc.), 2009 [6] converse, j. real time validation of on-line measurements utilizing internal standard introduction, isa transactions, 1997, 36(2), 151–158 [7] colledani, m., tolio, t. performance evaluation of production systems monitored by statistical process control and off-line inspections, international journal of production economics, 2009, 120(2), 348–367 [8] kano, m., nakagawa, y. data-based process monitoring, process control, and quality improvement: recent developments and applications in steel industry, computers & chemical engineering, 2008, 32(1-2), 12–24 [9] reis, m. s., delgado, p. a large-scale statistical process control approach for the monitoring of electronic devices assemblage, computers & chemical engineering, 2012, 39, 163–169 [10] braga, l., braga, a. r., braga, c. on the characterization and monitoring of building energy demand using statistical process control methodologies, energy and buildings, 2013, 65, 205–219 [11] poots, a. j. , woodcock, t. statistical process control for data without inherent order, bmc medical informatics & decision making, 12, 2012 [12] chandra, m. statistical quality control (crc press llc), 2001 [13] simoglou, a., martin, e., morris, a. multivariate statistical process control of an industrial fluidised-bed reactor, control engineering practice, 2000, 8, 893–909 [14] kim, s. b. , jitpitaklert, w., park, s.-k. , hwang, s.-j. data mining model-based control charts for multivariate and autocorrelated processes, expert systems with applications, 2012, 39(2), 2073–2081 [15] thomas, d., et al. statistical quality control handbook (western electric co., inc), 2011 [16] thode, h. c. testing for normality (crc press llc), 2002 [17] harris, t., seppala, c., desborough, l. a review of performance monitoring and assessment techniques for univariate and multivariate control systems, journal of process control, 1999, 9(1), 1– 17 microsoft word 00.00 inner cover.docx hungarian journal of industry and chemistry vol. 43(1) pp. 45–48 (2015) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2015-0008 biological purification of chemically pre-treated dairy wastewater before discharge into a municipal sewage systems gábor gulyás,* bence fazekas, regina varga, and árpád kárpáti department of environmental engineering, university of pannonia, egyetem u. 10, veszprém, 8200, hungary dairy production is one of the most inefficient processes with respect to water usage in the food industry. it was estimated that the production of a litre of milk creates three to four litres of wastewater. dairy wastewater contains a high amount of dissolved and suspended solids. moreover, it contains high concentrations of fat, protein, and carbohydrate. consequently, the dairy wastewater content of organic compounds is high and so is its chemical oxygen demand. the majority of organic compounds are biodegradable with a high biological and chemical oxygen demand ratio. in this work, we examined the biological purification of physico-chemically pretreated wastewater from a hungarian milk-processing factory before it was discharged into the public sewage system. the chemical oxygen demand of the pre-treated wastewater ranged from 500 to 2500 mg dm-3. we found that it was possible to achieve efficient organic material removal from nutrient-poor wastewater without nutrient dosage contrary to the literature. the activated sludge system manifested efficient organic material removal that required a smaller biological volume. experiments with biofilms have shown that a thicker biofilm needs more dissolved oxygen, which dictates oxygen input levels to be sufficient for creating an aerobic environment. keywords: activated sludge, biofilm, dairy wastewater, chemical oxygen demand, nutrient-poor wastewater 1. introduction milk processing requires high specific water consumption and considerable raw material waste effluents [1]. wastewater composition depends mainly on the produced material, production process, actual operations of the production process, and the water usage [2]. clean water is practically used in all the process operations, like cleaning, sterilisation, heating and cooling. wastewaters produced in these plants are usually polluted with chemicals, used for cleaning the containers, pipes, and some other equipment [2–4]. on average processing a cubic metre of milk produces 3–4 m3 of wastewater [5]. milk processing effluents (dairy wastewaters dww) contain high concentrations of dissolved and suspended solids. they contain high concentrations of fat, protein mainly as fine colloids, and carbohydrate (lactose and lactic acid) [6–9]. among the carbohydrates, lactose can be found in a high ratio [5]. however, the lactic acid content can also be very considerable in the case of the discharge of whey. suspended solids of dairy wastewater originate from cheese and cottage cheese as well, but their final concentration highly depends on the processing methods at a given plant. *correspondence: gulyasg@almos.uni-pannon.hu as a result of these ingredients of an approximate total concentration of around 2 g/g of the effluent, dairy wastewaters can exhibit high chemical oxygen demand (cod) . the majority of the organic contaminants are biodegradable. the ratio of biological and chemical oxygen demand (bod/cod) of the dww-s is high [10]. all organic contaminants are in principle nutrients for microorganisms of the active sludge (as) biological treatment. however, preliminary physico-chemical removal of particular components of the dww, such as fats, most of the proteins, and casein considerably decreases the cost of biological purification required for permitting the discharge of this industrial effluent into municipal sewage systems. 2. material and method we studied the biological purification of physicochemically pre-treated wastewater from a hungarian milk processing and dairy factory located in székesfehérvár. polyaluminium chloride, hydrochloric acid, and polyelectrolyte were used before flotation. presently, the mixed wastewater after this treatment is discharged into the public sewage collection system. intermittently, its cod concentration is higher than the prescribed limit, which results in an extra fee being charged for the discharge and municipal purification. gulyás, fazekas, varga, and kárpáti hungarian journal of industry and chemistry 46 cod of the pre-treated wastewater normally changed between 0.5 and 2.5 g dm-3 during the measurements, while the limit value was 1 g dm-3. the total organic material content was commensurable with the suspended solid concentration at the same time the magnitude of dissolved organic compounds was constant. the ammonium concentration in the pretreated wastewater was low (3–10 mg dm-3), while the phosphorous content was negligible. thus, the wastewater we purified biologically was lacking in n and p-nutrients. we intentionally did not add any n or p-nutrients. we carried out parallel studies in an activated sludge sequencing batch reactor (as-sbr) and a biofilm system, moving bed biofilm sequencing batch reactor (mbbr-sbr). the activated sludge reactor was inoculated with municipal activated sludge. the growth of biofilm was initiated by the addition of municipal wastewater during the first and second weeks. there were aerobic and anoxic periods in the sbr cycles (approximately in a 3 to 1 ratio) to cater for the needs of different microorganisms. anoxic periods were used to improve the sludge settling. during the aerobic periods, the maximum dissolved oxygen concentration was set to 2 mg dm-3. mechanical mixing was used during the anoxic phases. the activated sludge concentration in the as-sbr reactor was between 3 and 5 g dm-3, on the contrary in the mbbr reactor it was at most 1 g dm-3 in the first part of the experiment. the volume of biofilm carrier in the reactor was 0.5 dm3 and the total volume of the mbbr-sbr reactor was 2 dm3 giving a filling ratio of 25%. the biofilm reactor was continuously aerated and the dissolved oxygen level had to be increased, when the specific biofilm load considerably increased. 3. results and analysis the sludge-loading rate in both systems was increased continuously throughout the experiment. at the beginning, it was approximately 0.2–0.3 g cod/g mlss and was slowly raised to over 2 g cod/g mlss by the end. on the contrary, the cod of the purified wastewater did not change considerably (fig.1). it was between 20 and 50 mg dm-3. the cod was simultaneously measured from the filtered effluents to observe the influence of the suspended sludge content of these effluents. the treated wastewater was nutrient-poor. according to the demands of microorganisms in biological wastewater treatment, a c : n : p ratio of around 100 : 5 : 1 is optimal. this ratio is typical for communal wastewater. the average relative sludge yield rate is 0.7 g mlss/g cod if the nutrient ratio is optimal. in our study, we could only measure a low specific sludge yield of approximately 0.1 g mlss/g cod, which we rationalise by the lack of nitrogenand phosphorous-nutrients. the cod removal was very effective even at very high sludge loads and with a lack of nutrients. in the mbbr system (fig.2), the variability of organic material removal was observable. cod of the purified wastewater varied between 50 and 200 mg dm-3. the main reason for lower cod removal values was probably due to the inefficient settling of the fine biofilm particles. they could not aggregate as much as the as sludge flocks can. during the course of settling, the biofilm carriers float up to the surface of the water. this can also limit the proper settling of the sludge if the treated wastewater contained so much suspended sludge. figure 1. the chemical oxygen demand of the studied activated sludge sequencing bach reactor system. biological purification of chemically pretreated dairy wastewater 43(1) pp. 45–48 (2015) doi: 10.1515/hjic-2015-0008 47 the biofilm loading rate was between 0.2 and 2.0 mg cod/g biofilm mlss. the biofilm concentration in the mbbr-sbr system was 0.5–1.5 g biofilm dm-3 in contrast to the as-sbr reactor where the activated sludge concentration was 3–5 g mlss dm-3. the mbbr-sbr reactor was operated by a lower hydraulic load. when the dissolved oxygen concentration was set to 2 mg dm-3 over 1 g cod/g biofilm mlss loading rate, the biofilm could not survive due to limited oxygen diffusion from the liquid phase to inside the biofilm. this corresponds to anoxic conditions at the carrier surface. we had to increase the dissolved oxygen concentration to 3 mg dm-3. when the biofilm loading rate increased to 2 g cod/g biofilm mlss, the dissolved oxygen concentration should be increased further to 5 mg dm-3 in order to achieve efficient organic material removal. 4. conclusion we observed that it was possible to achieve efficient organic material removal as expressed by the chemical oxygen demand values from pre-treated dairy wastewater both in as and biofilm treatments without a dose of nand p-nutrients. this is contrary to what has been proposed in the literature. in the similar active sludge treatment of apple juice effluents even with a proper dosage of urea and phosphate, sometimes we could measure serious sludge bulking because of a lack of micronutrients. our results showed that the activated sludge system ensured efficient organic material removal even around 2 g cod/g mlss loading rate in the case of the pre-treated dairy wastewater. at the same time, the specific sludge load of the municipal sewage treatment plants without nitrification and denitrification is at most 1 g cod/g mlss. when we have to nitrify and denitrify the organic carbon load has to be around a third of this value. high loaded systems require a smaller biological volume. iron ions, which remained in pre-treated wastewater, facilitated the settling of activated sludge, therefore in the as-sbr system this gives an opportunity for increasing the sludge concentration. because of an extended sludge concentration the biological volume demand would be reduced. our experiments with the biofilm system show that the thicker biofilm requires a much greater dissolved oxygen concentration. this fact is mentioned also in some other studies. the oxygen input needs to be balanced against the level for creating an aerobic environment for the biofilm. references [1] !bref 2006, integrated pollution prevention and control, reference document on best available techniques in the food, drink and milk industries (european commission) 2006 [2] britz, t.j.; schalkwyk, c.; hung, y.t.: treatment of dairy processing wastewater, in waste treatment in the food processing industry, eds.: wang, l.k.; hung, y.-t.; lo, h.h.; yapijakis, c. (taylor and francis group, new york, usa) 2006, pp. 1–29 [3] demirel, b.; yenigun, o.; onay, t.t.; anaerobic treatment of dairy wastewaters: a review, process biochem., 2005 40(8), 2583–2595 10.1016/j.procbio.2004.12.015 [4] zielinski, m.; janczukowicz, w.; dezbowski, m.: biodegradability evaluation of dairy effluents originated in selected sections of dairy production, bioresources technol., 2008 99(10), 4199–4205 10.1016/j.biortech.2007.08.077 figure 2. the chemical oxygen demand of the moving bed biofilm sequencing batch reactor (mbbr-sbr) system. gulyás, fazekas, varga, and kárpáti hungarian journal of industry and chemistry 48 [5] adulkar, t.v.; rathod, v.k.: ultrasound assisted enzymatic pre-treatment of high fat content dairy wastewater, ultrason. sonochem., 2014 21(3), 1083-1089 10.1016/j.ultsonch.2013.11.017 [6] gadhe, a.; sonawane, s.s.; varma, m. n.: kinetic analysis of biohydrogen production from complex dairy wastewater under optimised condition, int. j. hydrogen energy, 2014 39(3) 1306–1314 10.1016/j.ijhydene.2013.11.022 [7] orhon, d.; gorgun, e.; germirli, f.; artan, n.: biological treatability of dairy wastewaters, water res., 1993 27, 625-633 [8] burak, d.; orhan, y.; turgut, t.o.: anaerobic treatment of dairy wastewater: a review, process biochem., 2005 40(8) 2583–2595 10.1016/j.procbio.2004.12.015 [9] perle, m.; kimichic, s.; shelf, g.: some biochemical aspects of the anaerobic degradation of dairy wastewater, water res., 1995 29(6) 1549– 1554 10.1016/0043-1354(94)00248-6 [10] kaewsuk, j.; thanuttamavong, m.: application of photosynthetic bacteria used for dairy wastewater treatment by a submerged membrane bioreactor, eng. j. kasetsart univ., 2007 61(20) 76–86 hungarian journal of industry and chemistry vol. 47(1) pp. 57–63 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-09 modeling and calculation of the global solar irradiance on slopes roland bálint *1, attila fodor1, istván szalkai2, zsófia szalkai3, and attila magyar1 1department of electrical engineering and information systems, faculty of information technology, university of pannonia, egyetem u. 10, veszprém, 8200, hungary 2department of mathematics, faculty of information technology, university of pannonia, egyetem u. 10, veszprém, 8200, hungary 3eötvös loránd university, egyetem tér 1-3, budapest, 1053, hungary the first step with regard to a simple model of a photovoltaic power plant is developed in this paper based on astronomical and engineering principles. a solar irradiance model is presented in this paper that can be used to forecast the solar energy a surface on earth is exposed to. the obtained model is verified against engineering expectations. the developed model can serve as a basis for forecasting the power of solar energy. keywords: solar irradiance, modeling, solar geometry, inclined surface 1. introduction as sustainable development is becoming highly important all over the world, the power production forecast of photovoltaic power plants (pvpps) is becoming ever more necessary. the sun is the greatest potential energy source available. the thermal energy it emits can be transformed into electrical energy, or its irradiance can be converted into electricity by solar panels. the amount of energy produced by both of the solutions above is directly dependent on the solar irradiance. several works have focused on the determination or forecast of this energy and its dependence on the geometrical parameters of the surface. a general model of the angle of incidence of solar irradiance with regard to the azimuth is derived in ref. [1] that is used for both fixed and tracking surfaces. in ref. [2], a simple spectral model is given that is applicable to inclined surfaces and clear skies. a very good comparative study was proposed in refs. [3] and [4] where different area-specific models were analysed with regard to the optimal tilt angle. unfortunately, the hungarian region is not covered by the models used in this study. a semi-empirical method for short-term (hourly) solar irradiance forecasting was proposed in ref. [5] founded on the widely used ångströmprescott model. the aim of this work is to propose a model that is not only able to handle clear-sky conditions but clouds as *correspondence: balazs.istvan@virt.uni-pannon.hu well. the computational complexity of the model is also a key factor which should be kept to a minimum. the organization of this paper is as follows: section 2 introduces the problem at hand and also presents the motivation of the paper. afterwards, the elementary astronomical relationships are collected and the proposed model is developed in section 3. the mathematical model is verified against basic engineering expectations in section 4. finally, some concluding remarks are presented. 2. problem statement the produced energy forecast of the renewable energy sources is one of the main problems of the distributed energy resource management system. the operators of the electrical grids need precise mathematical models of renewable power plants, e.g. pvpps, wind farms or hydroelectric power plants. the first step to develop a simple model of a pvpp is presented in this paper based on first astronomical then engineering principles. the energy production of a pvpp is a function of the following: • parameters of the pvpp, • weather (cloud, temperature, wind), • quality of the atmosphere (dust, relative humidity), • activity of the sun (11-year solar cycle). the parameters of the pvpps are the following: • position, mailto:balazs.istvan@virt.uni-pannon.hu 58 bálint, fodor, szalkai, szalkai, and magyar • orientation of the pv solar panels, – tilt angle, – azimuth angle, • surface area (or the number of pv solar panels), • nominal power of the pv solar panels, • efficiency of the solar inverter. by using the first four parameters, the solar energy can be calculated by the developed solar irradiance model which is presented in this paper. 3. astronomical relationships sun-earth geometries to estimate the solar irradiance from the sun, some astronomical (geometrical) calculations to define the position of the sun relative to the local horizontal surface need to be conducted. many different equations are found in the literature to calculate the same parameter. the size of these equations, in addition to the frequency of measurements, vary significantly. in this section some equations are compared. 3.1 comparison of the available solar geometry models due to the elliptic orbit of the earth around the sun, some parameters exist with a 1-year cycle. these parameters can be calculated with different equations and the difference between values of these equations varies due to discrepancies in the description of the method. the calculations regard a year as consisting of 365 days. most of the results were obtained from ref. [6] and references therein. relative sun-earth distance the first parameter is the reciprocal of the square of the sun-earth distance during the year. the elliptic orbit of the earth causes this to change in value. this relative distance can be calculated from equations e0 = (r0 r )2 = 1.000110+ + 0.034221 cos ( 2π dn − 1 365 ) + + 0.001280 sin ( 2π dn − 1 365 ) + + 0.000719 cos ( 4π dn − 1 365 ) + + 0.000077 sin ( 4π dn − 1 365 ) (1) and e0 = (r0 r )2 = 1 + 0.033 cos ( 2π dn 365 ) (2) 0 50 100 150 200 250 300 350 0.96 0.98 1 1.02 1.04 3 january 4 april 4 july 5 october the day of the year e 0 eq. 1 eq. 2 figure 1: the calculated value of the reciprocal of the square of the sun-earth distance (e0) using eqs. 1 and 2 eqs. 1 and 2 are from refs. [6] and [7]. e0 denotes the reciprocal of the square of the sun-earth distance, r0 represents the mean sun-earth distance (1 au) and r stands for the sun-earth distance on the dnth day of the year. values of e0 using various equations are shown in fig. 1. this change will change the solar constant too. the solar constant, i0, yields the following solar irradiance value (in w/m2) at the edge of the earth’s atmosphere. this constant value is 1367 w/m2 if the earth is a distance of 1 au (astronomical unit) from the sun. this value is greater at perihelion (minimum sun-earth distance ≈ 0.983 au on 3 january) and less at aphelion (maximum sun-earth distance ≈ 1.017 au on 4 july). since the irradiance is proportional to the surface area, which is inversely proportional to the square of the distance, the corrected solar irradiance can be calculated from in = i0e0. (3) solar declination the declination of the sun, δ, yields the latitude above which the path of the sun follows. therefore, the zenith angle is zero at local noon. this value can be calculated from the following equations [6]: δ = ( 0.006918− − 0.399912 cos ( 2π dn − 1 365 ) + + 0.070257 sin ( 2π dn − 1 365 ) − − 0.006758 cos ( 4π dn − 1 365 ) + + 0.000907 sin ( 4π dn − 1 365 ) − − 0.002697 cos ( 6π dn − 1 365 ) + + 0.00148 sin ( 6π dn − 1 365 )) 180° π (4) hungarian journal of industry and chemistry modeling and calculation of the global solar irradiance on slopes 59 0 50 100 150 200 250 300 350 −23.5° −10° 0° 10° 23.5° 20/21 march 21/22 june 22/23 september 21/22 december the day of the year δ eq. 4 eq. 5 eq. 6 eq. 7 figure 2: the calculated value of the declination of the sun (δ) using eqs. 4–7 δ = arcsin ( 0.4 sin ( 360 365 (dn − 82) )) (5) δ = 23.45° sin ( 2π 365 (dn + 284) ) (6) and δ = arcsin ( 0.39779 sin ( 4.8888 + 0.017214dn+ + 0.033 sin(0.017214dn) )) (7) the results of different equations that calculate the declination of the sun are shown in fig. 2. the sun is above the equator on 20/21 march (vernal equinox) and 22/23 september (autumnal equinox), moreover, the winter solstice is on 21/22 december and the summer solstice on 21/22 june. the difference between the equations in fig. 2 is minimal. the maximum change in the declination when calculated on a daily basis is less than 0.5° (|δ(dn+1)− δ(dn)|). equation of time a solar day varies in length throughout the year. a day on earth is 24 hours long and is based on the rotation of the earth around its polar axis. a solar day is based on the rotation of the earth around its polar axis and on its motion around the sun. the elliptic orbit of the earth causes a difference between the time of day and the solar time of day (astronomical). this means that noon in local and astronomical times (the sun is in the southern hemisphere) differ. this time difference can be calculated from the following equations [6]: et = [ 0.000075 + 0.001868 cos ( 2π dn − 1 365 ) − − 0.032077 sin ( 2π dn − 1 365 ) − − 0.014615 cos ( 4π dn − 1 365 ) − −0.04089 sin ( 4π dn − 1 365 )] 229.18 (8) 0 50 100 150 200 250 300 350 −20 −10 0 10 20 the day of the year e t [m in ] eq. 8 eq. 9 eq. 10 data series † figure 3: the values of the equation of time over a year using eqs. 8–10 and a series for the year 2018 et = [ 0.043 sin ( 2 ( 4.8888 + 0.017214dn+ + 0.033 sin(0.017214dn) )) − − 0.03342 sin(0.017214dn)+ + 0.2618tutc − π ] 229.18 (9) and et =− 7.655 sin ( 2π dn 365 ) + + 9.873 sin ( 4π dn 365 + 3.588 ) . (10) eqs. 8 and 9 yield et in radians and the constant 229.18 converts this into minutes. this constant can be calculated from 229.18 = 360° 2π 360° 24 · 60 min 16 min (11) fig. 3 shows the results according to eqs. 8–10 over a whole year, together with astronomical data for the year 2018. the largest difference was calculated by eq. 10 when compared with the other data. 3.2 solar beam equations using the equations in section 3.1, the position and angles of the sun at a local (geological) position can be calculated with the gps coordinates φlat and φlong. fig. 4 shows the path of the sun and the angles of the actual position of the sun. the nomenclature is as follows: • α: solar altitude angle • θz: solar zenith angle • ψ: solar azimuth angle since the altitude (α) and zenith angles (θz) are complementary angles, α+ θz = 90°, (12) the local solar hour angle can be calculated from [6] †http://www.ppowers.com/eot.htm 47(1) pp. 57–63 (2019) 60 bálint, fodor, szalkai, szalkai, and magyar s n e w zenith sunset sunrise α ψ θz ψ < 0 ψ > 0 geological position path of sun path of sun projection of figure 4: the local position of the sun with important angles h = 180°− 15° ( tutc + et 60 ) − φlong, (13) where tutc is the local time in time zone +0 in hours and φlong is the local longitudinal position in degrees. the cosine of the solar zenith angle can be calculated by using the solar declination, local latitudinal position and solar hour angle. according to eq. 12, cos(θz) = sin(δ) sin(φlat)+ + cos(δ) cos(φlat) cos(h), (14) and cos(θz) = sin(α), (15) (eq. 14 is from ref. [6]) the solar azimuth angle (ψ) can be calculated from cos(ψ) = sin(α) sin(φlat)− sin(δ) cos(α) cos(φlat) (16) and sin(ψ) = cos(δ) sin(h) cos(α) . (17) 3.3 global solar irradiance the solar irradiance can be calculated in a simple form: i = inq tmz sin(α), (18) where q denotes the clear sky transmissivity through a thickness of one atmosphere, tm represents the linke turbidity factor of the air and z stands for the relative path length of the solar beam through the atmosphere. parameter q is a constant with a value of 0.93 (when the sky is dry and clear and the zenith angle is equal to zero). the value of tm determines how many clear atmospheres should be stacked to achieve the actual spectral transmittance. this value depends on the amount of water vapor, dust, smog, etc. in the eu, tm is between 1.8 and 4. the suggested formula for the calculation of parameter z is z = latm rearth − rearth , (19) where latm denotes the path length of the solar beam through the atmosphere, rearth represents the mean radius of the earth’s surface and rearth stands for the radius of the earth when the atmosphere is included (rearth− rearth is the thickness of the atmosphere). the value of latm depends on the solar altitude and can be calculated using the law of cosines which yields l2atm−2 rearth latm cos(α+ 90°)+ + (r2earth −r2 earth) = 0. (20) the correct value of latm is the positive root of eq. 20. eq. 18 yields the solar irradiance under ideal conditions. however, aerosols in the atmosphere cause diffuse scattering and absorb a proportion of the solar irradiance. furthermore, clouds also have an effect on the irradiance. some models divide the global solar irradiance into two parts: • direct solar irradiance • diffuse solar irradiance irradiance on a horizontal surface various models exist to calculate the global solar irradiance on a horizontal surface, e.g., a hungarian model [8] is presented in g = ( in sin(α) + a )( 1 + b1n b2 ) , (21) where in denotes the corrected solar constant, n represents the cloudy parameter between 0 and 1 (0 when clear, 1 when overcast). a is a local correction value (a negative constant in w/m2, and b1 as well as b2 are locally constant in terms of the cloud correction. this hungarian model [8] takes the cloud cover into consideration but not the transparency of the atmosphere (q, tm and latm). a german model [9] accounts for atmospheric conditions. equation g = in sin(α)ad e −bdtmz(1− adn bd) (22) shows the global solar irradiance and equation s = in sin(α)ad q tmz(1−n bd) (23) presents the direct solar irradiance formula. the parameters ad, bd, ad and bd are place-dependent values. a typical parameter set is ad = 0.72, bd = 3.2, ad = 0.7 and bd = 0.027. the diffuse solar irradiance can be calculated by a simple subtraction. d = g− s (24) the calculated global solar irradiance is shown in fig. 5 over a year with weekly resolutions during clear sky conditions in veszprém, hungary. the red curve tracks the maximum values of the astronomical noons on each curve (analemma curve). this curve shows the effect of hungarian journal of industry and chemistry modeling and calculation of the global solar irradiance on slopes 61 5 10 15 20 0 200 400 600 800 hour g [w / m 2 ] global irradinace analemma curve figure 5: calculated global solar irradiance on a horizontal surface over the year in veszprém according to weekly resolutions and the analemma curve (astronomical noon times) the et, the duration of which is approximately 11 hours because the longitudinal position of veszprém is 17.9° and this causes a delay of about 1 hour (the local time zone is +1). fig. 5 clearly illustrates the difference in irradiance between the winter and summer periods. irradiance on the slope for the sake of simplicity the cartesian coordinate system is used, the axes of which are s (south), w (west) and z (zenith). the azimuth angle ψ in the direction sw-n-e-s and the altitude of the sun α have been calculated, so the normed vector that points towards the sun is −→ os = [cos(α) cos(ψ), cos(α) sin(ψ), sin(α)]>. if the surface σ exhibits an angle of inclination of β to the horizon and an orientation of γ, which defines γ as negative, positive or zero if and only if the surface faces se, sw or s, respectively, then the normed vector of the surface (contained within the same half-space as the sun) is −→n and exhibits the altitude ν = 90o − β so −→n = [cos(ν) cos(γ), cos(ν) sin(γ), sin(ν)]>. the angle between −→ os and −→n is θsurf = arccos ( cos(α) cos(ψ) cos(ν) cos(γ)+ + cos(α) sin(ψ) cos(ν) sin(γ)+ + sin(α) sin(ν) ) = arccos ( cos(α) cos(ν) ( cos(ψ) cos(γ)+ + sin(ψ) sin(γ) ) + sin(α) sin(ν) ) , (25) since −→ os and−→n are normed. so −→ os meets σ at the angle αsurf = 90o − θsurf . eq. 23 yields the direct solar irradiance on a horizontal surface with solar altitude angle α. the solar altitude s n e w zenith α ψ γ βo p q surface θsurf figure 6: the angle of the solar beam and the zenith angle between the surface and the slope β and orientation γ angle on the slope is αsurf . to calculate the corrected direct solar irradiance, equation ssurf = s sin(αsurf) sin(α) (26) must be used. calculation of the diffuse solar irradiance is far from trivial. if the diffuse solar irradiance is consistent with the all-sky, equation dsurf = d 1 + cos(β) 2 (27) can be used to estimate the value of the irradiance. the global solar irradiance of the slope is the sum of the direct and diffuse solar irradiances: gsurf = ssurf +dsurf . (28) 4. model verification the aim of this section is to verify the solar irradiance model proposed in the previous section against basic engineering expectations. figs. 7 and 8 show the results of the implemented model on 1 march (dn = 60) and 1 july (dn = 121) and the geographical position of veszprém, hungary. both figures present the value of the solar irradiance for various orientations as well as the tilt and azimuth angles. 6 8 10 12 14 16 0 200 400 600 800 hour g [w /m 2 ] horizontal β = 10°; γ = 0° β = 30°; γ = 0° β = 45°; γ = 0° β = 30°; γ = −45° figure 7: calculated global solar irradiance on sloping terrain of various orientations on 1 march in veszprém, hungary 47(1) pp. 57–63 (2019) 62 bálint, fodor, szalkai, szalkai, and magyar 5 10 15 20 0 200 400 600 800 hour g [w /m 2 ] horizontal β = 10°; γ = 0° β = 30°; γ = 0° β = 45°; γ = 0° β = 30°; γ = −45° figure 8: calculated global solar irradiance on sloping terrain of various orientations on 1 july in veszprém, hungary irradiance on a horizontal surface is denoted by a blue solid line. the other curves show the value of the solar power with a non-zero tilt angle: 10° (magenta dotted line), 30° (orange dashed line with an azimuth angle of zero, purple dashed dotted line with an azimuth angle of −45° (south-east)) and 45° (green dashed dotted line). the peak values of the curves in fig. 7 correlate with the tilt angle (β). as the tilt angle increases, so does the irradiance when the azimuth angle is constant (γ = 0°). as the azimuth angle changes towards the southeast, the peak of the curve shifts towards the sunrise. the effect of the tilt angle is somewhat different in fig. 8. on 1 july, the absolute peak can be observed for cases β = 10° and β = 30° but the irradiance for the whole day is higher if the tilt angle is smaller. this effect is caused by the angle of the solar altitude (smaller zenith angle). if the tilt angle is greater than the minimum horizontal zenith angle, the solar irradiance will decrease on the slope. on 1 march the maximum angle of the solar altitude did not reach 45°. in other words, a greater tilt angle generates more power on sloping terrain. the effect of the azimuth angle can be seen in fig. 7. 5. conclusions a solar irradiance model is presented in this work that can be used for forecasting the solar energy absorbed by an inclined surface, e.g. a pvpp. the developed model is preliminary in nature and serves as a basis for further developments, e.g. forecasting the power of the solar energy under cloudy conditions. the novel element of the model is that the relative path length of the solar beam in the atmosphere can be calculated more accurately. the calculated irradiance an inclined surface is exposed to is another novel element. the proposed model has been verified against engineering expectations and the results show that it works well. the next step will be the validation of the model using real measured parameters and meteorological data. by extending the model with an electrical power module, it will also be possible to forecast the amount of electrical energy produced. acknowledgement we acknowledge the financial support of széchenyi 2020 under the efop-3.6.1-16-2016-00015. we acknowledge the financial support of széchenyi 2020 under the ginop-2.2.1-15-2017-00038. a. magyar was supported by the jános bolyai research scholarship of the hungarian academy of sciences. references [1] braun, j.e.; mitchell, j.c.: solar geometry for fixed and tracking surfaces, sol. energy, 1983 31(5), 439– 444, doi: 10.1016/0038-092x(83)90046-4 [2] bird, r.e.; riordan, c.: simple solar spectral model for direct and diffuse irradiance on horizontal and tilted planes at the earth’s surface for cloudless atmospheres, j. clim. appl. meteorol., 1986 25(1), 87–97, doi: 10.1175/15200450(1986)025%3c0087:sssmfd%3e2.0.co;2 [3] danandeh, m.a.; mousavi g., s.m.: solar irradiance estimation models and optimum tilt angle approaches: a comparative study, renew. sust. energy rev., 2018 92, 319–330, doi: 10.1016/j.rser.2018.05.004 [4] li, d.h.w.; chau, t.c.; wan, k.k.w.: a review of the cie general sky classification approaches, renew. sust. energy rev., 2014 31, 563–574, doi: 10.1016/j.rser.2013.12.018 [5] akarslan, e.; hocaoglu, f.o.; edizkan, r.: novel short term solar irradiance forecasting models, renew. energy, 2018 123, 58–66, doi: 10.1016/j.renene.2018.02.048 [6] iqbal, m.: an introduction to solar radiation (academic press, london, uk), 1st edn., 1983, doi: 10.1016/b978-0-12-373750-2.x5001-0, isbn: 978-0-12373750-2 [7] duffie, j.a.; beckman, w.a.: solar engineering of thermal processes (john wiley & sons, new jersey, usa), 2013, doi: 10.1002/9781118671603 isbn:978-0-47087366-3 [8] práger, t.; ács, f.; baranka, g.; feketéné nárai, k.; mészáros, r.; szepesi, d.; weidinger, t.: a légszennyezõ anyagok transzmissziós szabványainak korszerũsítése iii. fázis részjelentés 2., 1999 [9] kasten, f.: strahlungsaustausch zwischen oberflächen und atmosphäre, vdi-bericht, 1989 (nr. 721. s.), 131–158 hungarian journal of industry and chemistry https://doi.org/10.1016/0038-092x(83)90046-4 https://doi.org/10.1175/1520-0450(1986)025%3c0087:sssmfd%3e2.0.co;2 https://doi.org/10.1175/1520-0450(1986)025%3c0087:sssmfd%3e2.0.co;2 https://doi.org/10.1016/j.rser.2018.05.004 https://doi.org/10.1016/j.rser.2013.12.018 https://doi.org/10.1016/j.rser.2013.12.018 https://doi.org/10.1016/j.renene.2018.02.048 https://doi.org/10.1016/j.renene.2018.02.048 https://doi.org/10.1016/b978-0-12-373750-2.x5001-0 https://doi.org/10.1002/9781118671603 modeling and calculation of the global solar irradiance on slopes 63 appendix: nomenclature symbol description value/dimension e0 reciprocal of the relative sun-earth squared distance (r0/r) 2 r0 mean sun-earth distance (astronomical unit: [au]) 1 au r actual sun-earth distance in au [au] dn the day of the year 1-365 i0 solar constant 1367 w/m2 in corrected solar constant i0e0 δ sun’s declination ±23.5° et equation of time ∼ ±15 min tutc the time in utc 0-24 φlat geographic latitude ±90° φlong geographic longitude ±180° α the angle of the solar altitude 0°-90° θz solar zenith angle 90°− α ψ solar azimuth angle ± 180° h the solar hour angle 0°-360° q clear sky transmissivity 0.93 tm linke turbidity factor 1.8-4 in central eu z relative solar beam length in the atmosphere latm length of the path of the solar beam through the atmosphere [km] rearth median radius of the earth including the atmosphere ∼ 6470 km rearth median radius of the earth from the ground ∼ 6370 km g global solar irradiance [w/m2] n cloudy parameter 0-1 ad place-dependent constant bd place-dependent constant ad place-dependent constant bd place-dependent constant d diffuse solar irradiance [w/m2] s direct solar irradiance [w/m2] β angle above the surface from the horizontal position 0°–90° γ surface azimuth angle ±90° θsurf the solar zenith angle on the surface 90°− αsurf αsurf the angle of the solar altitude on the surface 0°-90° ssurf direct solar irradiance on the surface [w/m2] dsurf diffuse solar irradiance on the surface [w/m2] gsurf global solar irradiance on the surface [w/m2] 47(1) pp. 57–63 (2019) introduction problem statement astronomical relationships sun-earth geometries comparison of the available solar geometry models relative sun-earth distance solar declination equation of time solar beam equations global solar irradiance irradiance on a horizontal surface irradiance on the slope model verification conclusions page 1 page 2 page 3 page 4 page 5 page 6 page 7 page 8 page 9 page 10 page 11 page 12 page 13 page 14 page 15 page 16 page 17 page 18 page 19 page 20 page 21 page 22 page 23 page 24 page 25 page 26 page 27 page 28 page 29 page 30 page 31 page 32 page 33 page 34 page 35 page 36 page 37 page 38 page 39 page 40 page 41 page 42 page 43 page 44 page 45 page 46 page 47 page 48 page 49 page 50 page 51 page 52 page 53 page 54 page 55 page 56 page 57 page 58 page 59 page 60 page 61 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energetics h-8200 veszprém, egyetem u. 10., hungary e-mail: banyait@almos.uni-pannon.hu esterification of oleic acid with short carbon chain alcohols gives biofuels, with long chain alcohols biolubricants can be produced. previously biolubricants was successfully produced from fusel oil and isoamyl-alcohol substrates by enzyme catalised esterification, but solution of polar substrates was problematic, that was solved by using ionic liquids. the optimal reaction parameters such as substrate molar ratios, initial water content, amount of enzyme and type of ionic liquid were determined by experimental design using statistica software. some of the ionic liquids have catalytic effect by itself, therefore control reactions were necessary to determine which ionic liquid has negligible catalytic effect. in five of the six investigated ionic liquid the yield was the same without enzyme, while in case of b[mim]pf6, the yield was negligible. in shorter time higher yield was achieved in presence of ionic liquid against other methods. increasing the temperature results higher yield till a limit, higher temperature does not make more product, but thermal desactivation of the enzyme was not occur. keywords: enzyme biocatalysis, biolubricant, oleate production, ionic liquid two phase system, lipase, esterification introduction crude oil is a limited source for fuels, lubricants. furthermore, it is not renewable and environmentally friendly. petroleum based lubricants usually deposited in the environment, endangering our planet. to solve this problem, lubricants should be manufactured from plant oil derivatives. at the last ten years more and more product appeared on the market which based on plant oils, for example biodiesel components and biolubricants [1]. there are several industrial application possibilities for fatty acid esters, as natural compounds [2]. esterification of plant oils, mainly occurs oleic acid and other long-chain fatty acids (12–20 carbon atoms) reaction. chain length of the alcohol substrate determinates the usage of the product. short-chain (3-5 carbon atoms) and low molecular weight alcohols: biodiesel, biofuel components can be produced [3], beyond fuel production, significant users the food, detergent, cosmetic and pharmaceutical industries [4]. long-chain alcohol (5 to 12 carbon atoms) reactions give lubricants [5]. the demands against biolubricants are that they should provide maximal protection during the usage, do not pollute the environment and do not accumulate. usage of biolubricants can reduce the chemical risk, because of the possibility of biodegradability [6]. important physical effect of ester group is to reduce the volatility and increase the flash point [7], as well as providing a good lubricating ability, because the polar ester group facilitates the bonding to the metal surface. good viscosity-temperature characteristic is their typical property and due to the high molecular weight, low evaporation loss, as well. general expectations over against lubricants that tolerate the mechanical effects and stress, biolubricants can resist these criteria. the disadvantages of biolubricants are low oxidative stability and poor cold flow properties [8]. they have wide area of application, machinery moving parts friction between the surfaces, at not too high temperature locations can be used with considerable lubricant loss, as well as in areas with increased exposition to nature, into the bypass. examples for application: the transmission system of military vehicles, in several other outdoor activities: forestry machines, chain saws, mining, railway vehicles and installations, water transport, fisheries and agricultural machines [9]. fusel oil is a by-product of distilleries, its average composition is 10% ethanol, 13% n-propanol, 15% i-butanol, 51% isoamyl-alcohol, 11% miscellaneous alcohols and water. nowadays fusel oil is usually burned at the distilleries to complete the energy necessities. the ionic liquids are organic salts which are built up by cations and anions (not including neutral molecules), they have low-melting point, and up to 300–400 °c they remain liquid without dissolution. they are non-volatile, non-flammable, possessing excellent thermal and chemical stability. due to low melting point they are usually liquids at room temperature. furthermore, these cations and anions are almost unlimited variable, there is a possibility to prepare the best medium important for the reaction, taking into consideration for example the solubility of substrates [10]. ionic liquids are organic 396 salts, which are empirically built up by cations and anions, do not contain neutral components. they have good thermal stability and low vapour pressure, different combinations of cations and anions can generate wide scale of properties, therefore they are considered as modern, environmentally friendly reaction media. they are non-volatile and flammable, therefore they begun to replace the conventional organic solvents as reaction media. ionic liquids can be suitable media for biocatalytic synthesis because of their enzyme stabilization effect, reusability and negligible vapour pressure [11]. many enzymes, especially lipases showed higher activity and greater selectivity in ionic liquids than in organic solvents [12]. the stability of candida antarctica lipase b (calb) in ionic liquid was found to be higher than in organic solvent [13]. the main advantages of ionic liquid + enzyme system are milder, lower reaction temperature comparing with conventional chemical synthesis, it needs less energy investment, can be better-controlled, attended with less side-reaction, furthermore the product more readily separable [12,13]. in this work the purpose was to find a utilization of fusel oil where biolubricants can be manufactured in ionic liquid. in our earlier work several enzymatic esterification reactions were investigated in solvent free system and in ionic liquids as well. in the earlier course of our experiments mixture of oleates were prepared successfully using fusel oil and oleic acid as substrates and enzyme catalytic esterification as method in different solvents and in solvent free system, as well [14]. at these experiments low conversions were achieved, therefore it became necessary to develop a better method, which is energy efficient, able to achieve higher conversion, furthermore environmental friendly, however waste materials may be as natural substrates. our aim is to optimize the parameters of production, enhance the yield improving the advantages of enzyme + ionic liquid system. materials and methods enzyme: triacylglycerol hydrolase, e.c. 3.1.1.3., novozym 435, novo nordisk (bagsværd, denmark). plu 1u = 7000 mol/g, 15 min, 1 atm (plu: propyl laurate unit), water content 1-2% ionic liquids: 1-butyl-3-methyl-imidazolium hexafluoro phosphate b[mim]pf6, 1-butyl-3-methyl-imidazolium tetrafluoro-borate b[mim]bf4, tributyl tetradecyl phosphonium dodecilbenzol sulfonate (cyphos-201), trihexil tetradecyl phosphonium bis(2,2,4-trimetilpentil)-phosphate (cyphos-104), tetradecyl phosphonium trihexil dekanoate (cyphos-105) trihexyl tetradecyl phosphonium hexafluoride, phosphate (cyphos-110) (iolitec gmbh, germany) chemicals: 96% oleic acid (merck, germany), isoamyl-alcohol 96% modeling fusel oil (scharlau gmbh), n-hexane (reanal), ethyl alcohol, diethyl ether, potassium hydroxide (spectrum 3d). gc analysis: gow-mac series 600 gas chromatograph, hp-ffap column (macherey-nagel), head pressure: 140 kpa, he flow rate: 12 cm3/min, h2 flow rate: 30 cm3/min, air flow rate: 300 cm3/min, 1:6 split-ratio, starting time and temperature: 130 °c, 3 min, end temperature and time: 240 °c, 5 min, heating rate 10 °c/min, injection temperature: 250 °c, fid detector. at every measurement point three parallel measurements were made, in each 4 μl samples were taken directly from the reaction mixture. measuring of acid content: the fatty acid concentration was determined by conventional acidbase titration with 0.1 m ethanolic potassium hydroxide solution. shaking, incubation: all reactions were carried out in flasks in an ika ks 4000 shaking incubator. reaction mixture composition: under the preinvestigations, the reaction mixture was the follow: 6.36 mmol of oleic acid, 36.95 mmol of isoamyl alcohol, 304.35 mmol n-hexane and 50 mg novozym 435 lipase (this mixture was applied only for calibrating the analytical methods). in the course of the main experiment: 1.23 mmol of ionic liquid, 0.16 mmol oleic acid, 1.41 mmol isoamyl-alcohol were used. the reaction mixtures were shaken with an intensity of 150 rpm at 40, 50 and 60 ºc temperatures for 4 hours. experimental design: statistica 8.0 software results and discussion the esterification reaction of oleic acid with the isoamyl-alcohol occurs as follows: ch3(ch2)7ch=ch(ch2)7cooh + (ch3)2chch2ch2oh = ch3(ch2)7ch=ch(ch2)7coo(ch3)2chch2ch2 + h2o. in this reversible reaction the molar ratio of substrates, temperature, amount of enzyme and ionic liquid are the variables affecting the conversion. effect of ionic liquid ionic liquids are not only green solvents, they can have catalytic effect. our aim was to investigate separately the enzyme stabilization effect, therefore preliminary experiments were necessary. through these the most important investigated criterium was to verify if the ionic liquid itself had catalytic effect for the reaction without enzyme. basic criterion was to be work in a two-phase reaction, where separation is easier, since the application of a new solvent can be avoid [15]. two of the investigated ionic liquids (cyphos-105 and cyphos110) were mixed with the substrates, so they were not investigated further. henceforth the reactions were carried out at 50 °c, the ester yield was followed by gc and the decreasing oleic acid concentration using titrimetry. the percentage esterification was calculated from the values obtained for the blank and the test samples. the further phosphonium-type ionic liquids, cyphos-201 and cyphos-104 without the presence of enzyme greatly catalyze the process as it shown on fig. 1. 397 figure 1: oleate ester concentration in case of using different phosphonium-type ionic liquids (reaction time: 180 min) figure 2: oleate ester concentration in case of using different imidazolium-type ionic liquids (reaction time: 180 min) for imidazolium-cation containing ionic liquids literary data show that these types of ionic liquids are the most suitable for esterification, transesterification reactions [16]. both investigated imidazolium-type ionic liquids were successfully applied in earlier experiments, where natural aroma esters production was the aim. as the results show on fig. 2 in case of b[mim]bf4 there were no significant differences in the detected oleate concentration if enzyme was added or not. for b[mim]pf6 without the presence of the enzyme only negligible product formation was observed, in the presence of enzyme, higher concentrations were achived than in the experiments where n-hexane was used as solvent. therefore for further investigations this ionic liquid was chosen. in case of ionic liquids for water solubility cations are responsible. comparing the same cation having b[mim]bf4 and b[mim]pf6 shows that while the first not miscible with water, the later has an unlimited solubility in water. thus, the hydrophilic b[mim]bf4 ionic liquid often distracts the absorbed water layer from the surface of the enzyme which should be necessary for the active conformation. therefore the enzyme is deactivated [17]. further advance that in case of using b[mim]pf6 side-reactions were not observed. acid / alcohol molar ratio acid/alcohol molar ratio is one of the most important parameters in enzymatic esterifications. as the reaction is reversible, an increase in the amount of one of the substrates will result higher ester yields and as expected, this will shift the chemical equilibrium towards the product side. one way of shifting the reaction toward the synthesis is to increase the alcohol concentration. however, high alcohol concentration may slow down the reaction rates due to inhibition. therefore, it is necessary to optimize the actual excess nucleophile concentration in a given reaction. the optimal parameters of the batch production were determinated using experimental design software application. in doing so statistica 8.0 program was applied. based on earlier studies substrate molar ratio, amount of enzyme and ionic liquid were chosen as key factors [14]. each factor was prepared in two levels: -1 for low level and +1 for high level. concrete values were applied in a design matrix. it is evident that increasing reaction temperature enhances the reaction rate, that is way that its affect will be investigated later separately. during the experiments different, software-defined combinations of the previously selected values of experimental parameters were investigated. other parameters were fixed: temperature 50 °c, 150 rpm shaking intensity, 5 hours reaction time. water content of the reaction mixture was also followed as an important parameter of esterification reactions which may shift the equilibrium, but there was not detectable concentration change using carl-fischer titration. the aim was to find the optimal parameter values of the isoamyl-oleate production. the results are shown on fig. 3, fig. 4 and fig. 5. figure 3: influence of the acid/alcohol molar ratio and amount of ionic liquid on the synthesis of isoamyl-oleate 398 figure 4: influence of the acid/alcohol molar ratio and amount of enzyme on the synthesis of isoamyl-oleate figure 5: influence of the amount of enzyme and ionic liquid on the synthesis of isoamyl-oleate as it shown, increasing amount of ionic liquid results in higher oleate yield, which gives evidence for the advantageous enzyme stabilization effect. complex investigation of the three chosen key factors shows that the highest ester conversion was obtained in the case of application the highest acid/alcohol molar ratio, amount of enzyme and ionic liquid. relatively high yield was obtained also around medium values, around the center points. there was no inhibition effect observed neither in 1:16 acid/alcohol molar ratio. as none of the point of parameters could be an optimal value, because the highest yield belonging to the highest values, therefore further investigations will necessary to find the optimal values. effect of temperature in case of using conventional reaction media the increasing reaction temperature results the same yield in shorter time, but till a limit due to thermal desactivation of enzyme. beside of the structure stabilization effect of ionic liquids the enzyme can be resist in the active conformation at higher temperatures [17]. for these investigations that mixture was chosen, in which the highest oleate yield was obtained. the results are shown on fig. 6. figure 6: influence of reaction temperature on the synthesis of isoamyl-oleate the yield-time functions in all cases show the saturation curve. increasing the temperature equilibrium yield was not changed, but shorter time was necessary to achieve it. as it shown neither at 80 °c became the enzyme desactivation significant, but increasing up from 70 °c did not shorten the reaction time till achieving the equilibrium. conclusions our investigations have proven that an ester type biolubricant could be prepared from isoamyl-alcohol and oleic acid by lipase enzyme in ionic liquid two phase system. compared to the product obtained in solvent free system, higher conversion in shorter time was achieved. despite the lack of water removal in the biolubricant there was no trace of oleic acid since complete conversion was achieved. determining the optimal reaction mixture composition high amount of ionic liquid and enzyme, large excess of alcohol was closest to the optimal. there was no inhibition effect neither at application of 1:16 acid/alcohol molar ratio. increasing the temperature to 70 °c had a positive impact on the process, at 80 °c desactivation of the enzyme was not occurred, although the yield was unchanged. acknowledgement the research work was supported by the támop projects 4.2.1/4.8 b identification number “mobility and environment: automotive, energy and environmental research in central and west pannon region” and 4.2.2/b-10/1-2010-0025. these projects are supported by the european union and co-financed by the european social fund. 399 references 1. s. z. erhan, s. asadauskas: lubricant base stocks from plant oils, ind. crops prod., 11 (2000) 277–282 2. y. watanabe, y. shimada, a. sugihara, h. noda, h. fukuda, y. tominaga: continuous production of biodiesel fuel from vegetable oil using immobilized candida antarctica lipase, j. am. oil. chem. soc., 77 (2000) 355–360 3. j. o. metzger: fats and oils as renewable feedstock for chemistry, eur. j. lipid 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1084–1085 16. m. moniruzzaman, n. kazunori, k. noriho, g. masahiro: recent advances of enzymatic reactions in ionic liquids, biochem. eng. journal, 48 (2010) 295–314 17. f. van rantwijk, r. a. sheldon: biocatalysis in ionic liquids, chem. rev., 107 (2007) 2757–2785 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 /colorconversionstrategy /cmyk /dothumbnails false /embedallfonts true /embedopentype false /parseiccprofilesincomments true /embedjoboptions true /dscreportinglevel 0 /emitdscwarnings false /endpage -1 /imagememory 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word a_12_kollar_r.doc hungarian journal of industrial chemistry veszprém vol. 39(1) pp. 21-25 (2011) the examination of the instruments of local economic development, particularly in consideration of vienna k. kollár széchenyi istván university, department of regional studies and public policy h-9026 győr, egyetem square 1. hungary e-mail: kollark@sze.hu the process of local economic development is extremely complex. different authors diversely aggregate its concept, objectives and actors. according to the literature local economic development is an intervention to the functioning of the economy. its purpose is to ensure sustainable local development and to increase the standard of living. the intervention requires the involvement of many actors, who approach the process from various sides. but the instruments, which are used by them, are very similar. in this paper i will make a short overview of the instruments of local economic development, then i will analyse the practice of vienna. keywords: local economic development instrument, local economic development strategy, human resource development, direct service development, economic development scheme of vienna introduction as we examine the international and national literature we can see that the regulatory and organizational system of the countries are quite differentiated and diverse but in the case of economic development tools used by local actors the situation isn't the same, in fact they are very similar. widespread economic development tools are for example tax exemption or tax benefits, the providing of domiciles, the development of infrastructure, the promotion of smes or training programmes. the installation of industrial parks, industrial zones and incubator houses are frequent as well. obviously there are some very special instruments for economic development, but such exceptions are not usually found in central and eastern europe but in countries outside europe. for example the u.s. government has often used such lending practices; has provided such guarantees which in central and eastern europe would not be feasible. of course in the region there can also be such differences as a result of which the application of a certain instrument is not allowed in one country but proves to be the best practice in another one. in our study, on the basis of the literature we examined, we look at the most popular and widely used tools grouped by the author dealing with the research of local economic development. the local economic development instruments the local economic development strategies, which are defined by blakely and bradshaw, contain the following tools: a community-based economic development strategy's tools are for example: ● the creation of local enterprise agencies ● the support of minorities and disadvantaged communities by providing loans ● the creation of community development bodies ● marketing activities tools belonging to a business development strategy are: ● incubators, the establishment of enterprise zones ● the establishment of industrial parks and technology parks ● supporting r&d ● advisory centers supporting business activity ● the promotion of new businesses, entrepreneurs ● business information centers domicile development strategy among others includes the followings: ● infrastructure development ● tourism development ● the development of public services ● housing improvement ● industrial area formation, land expropriation ● the simplification of legislation ● the construction of shopping centres. 22 human resource development strategy uses tools such as ● the providing of vocational training that meets the requirement of the enterprises ● the providing of training for disadvantaged and longterm unemployed ● programs for part-time and intermittent employees to facilitate permanent employment ● programs for school leavers to encourage employment ● vocational training meeting the sectors' needs ● the establishment of centres that register unemployed people and deal with labour market mediation. [1] linder and peters distinguish four groups of local economic development tools, namely the tools of direct service development, exhortation, subvention and regulation. direct service development tools are for example: ● the improvement of drinking water supply ● the improvement of public safety ● the improvement of conditions for pedestrians ● road network development ● the improvement of parking facilities ● the improvement of sewage management system ● the ensuring and improvement of scavengering. the tools of regulation are the followings: ● land expropriation ● the improvement of the formation system of industrial zones and residential zones ● the regulation of the streetscape ● the regulation of waste management ● the improvement of construction management system ● the appointment of an ombudsman to handle the occurring problems the tools of exhortation include: ● the support of existing enterprises ● the visit of potential investors ● attendance at conferences and events ● database operation ● the publication of promotional publications subventions contain among others: ● the providing of tax exemption, tax credits/benefits ● land donation ● in-kind services ● the reduction of the rate of profit ● warranty for private investors ● providing direct loans and loan guarantees ● the funding of tax increase. [2] on the basis of alan norton's research mezei examined local development tools and practices applied by a few european, american and asian countries. in his opinion the most commonly used instruments include: ● the ensuring of domiciles ● tax exemption, tax reduction ● the support for the establishment of industrial parks and industrial zones ● job creation ● the providing of preferential loans ● the encouragement of the establishment of new technologies ● the providing of guarantee ● the support and the facilitation of r&d activities ● the fostering of education, professional training. [3] in his work wrote at the millennium mcguire made the following groups of economic development policy instruments: table 1: the classification of economic development policy instruments [4] endogenous exhortation subsidy direct provision the rehabilitation of buildings visit to existing business tax abatement the improvement of watersupply employee training/ retraining attendance at conferences the financing of tax increase the improvement of sewage disposal the development of export markets business roundtable direct loans the improvement of public safety services source: own compilation based on [4], p. 284. in 2005 capkova [5] studied local economic development practices in central and eastern european countries. in his study he distinguished five different groups of incentives. the categories are the followings: ● financial tools one of the ways to support existing enterprises and to attract new investment projects, as we know, is to take financial incentives. local tax credits, local tax examptions, credits, loans and guarantees can be mentioned as such incentives. property taxes in central and eastern european countries are more infrequent than they are in the english-speaking countries. in our region the most common forms of supports are the benefits in connection with local tax rates. however, this form of stimulation of economic development is restrained. actually, if we consider any tool belonging to this group, we can say that their usage is usually limited due to the scarce budget of municipalities. ● property-related tools the municipal property can also be used to support local businesses, but the use of this instrument also has a limit, which lies in the amount of available property. we can mention industrial parks, the formation of industrial zones and reduced rentals or sales as wealth-related instruments. each tool is widely used to support newly settled enterprises. from the category of property-related tools in most central and eastern european countries local municipalities often establish industrial zones, business parks and business incubators. the latter one provides 23 wide range of business services and aims to support the development and growth of small enterprises. in addition, of course, it serves as a domicile for new businesses as well. in favour of new enterprises, municipalities can also act as guarantors for loans, but for them it has a reasonably high risk. ● marketing municipalities are forced by global competition and rapid changes in all areas of economy to use intense and increasing promotion in their target markets. these target markets include all the residents, visitors, enterprises and export markets. the promotion, also known as “place marketing”, is a widely used tool by municipalities for local economic development in the vast majority of countries. ● infrastructure development economic development certainly includes the provision of and support for the availability of infrastructure. the accepted view is that companies take three cost components into account when they decide about location: the costs of transportation, labour and energy. municipalities play an active role so that the settlement can become more attractive to investors based on these criteria. the investment into physical infrastructure can appear as a reason for economic development and also as a consequence of it. therefore it can be said that the availability and quality of traditional infrastructural services have become an essential criteria in the last few years. their absence is a barrier for the growth of local businesses and hinders success in attracting investors. the importance of human capital investment shouldn't be neglected either, because this is one possible tool, which promotes economic development and generate spillover effects, which will increase the productivity of local labour force. ● the providing of technical and information assistance swinburn [6] divides local economic development practices and their approaches and instruments into three stages. the first period lasted from the mid-1960s to the early 1980s. at that time, the development actions focused on disadvantaged areas and relied primarily on resources from outside the region. the significant strategic directions contained the attraction of manufacturing companies and foreign capital and the deployment of the necessary physical infrastructure. both in the funding and the implementation the public sector had a clear, emphatic role. from the tools of local economic development tax credits, subsidies, the ensuring of cheap domiciles and labour were the most popular ones. the second stage of local economic development began in the early 1980s and lasted to the mid-1990s. in this phase the key strategic direction was to retain and grow existing businesses. external resources were still important, but the focus was no longer on attracting them, but on integrating them. the public sector remained typically dominant, but companies also joined to the financing of development. local economic development instruments included the benefits and subventions mentioned in the first stage, but these targeted the large companies and small and mediumsized enterprises. smes got a special attention, not just in the form of grants and benefits, but they also got specialized business development services. in relation to the infrastructure the soft components became more important than the hard ones, for example the entrepreneurial skills or the improvement of skilled workforce got bigger attention. from the mid-1990s local economic development practices can be described with the followings: table 2: the third stage of local economic development [6] focus instruments key strategies: -integrated local and regional development strategies to create favorable business environment focus on territorial not sectoral development to improve the quality of life and security the improvement of the skills of the workforce organization: the facilitation of clusters partnerships led by the public sector the support of disadvantaged implementation: conflict management partnership of public, private and community sectors programs aiming to increase the quality of life funding: tailored business development services the domination of public sector, but the contribution of the businesses and the civil sector increases strategic planning, swot source: own compilation based on [6], p. 5. as the table shows, in this period the public sector lost from its dominance and the businesses and civil sectors got a more important role. moreover, the availability of european union funds appeared besides domestic resources. the top-down approach was replaced by the bottom-up strategies. the local economic development approach focused on local business environment, the development of innovation potential and the retraining and attraction of skilled labour forces. the organization, implementation and funding of the development is based on the partnership of public, private and civil sectors. a significant public role, however, still remains. [6] local economic development in vienna the last development plan was discussed in 2005. this plan brings into focus the thinking and acting based on a european perspective. the plan is based on the following principles: ● sustainability ● participation ● gender mainstreaming and ● diversity. 24 the aims of the strategies are to reinforce vienna’s competitive position and to overcome the challenges. the city accounts for 28% of total added value generated in austria and 23% of total number of workplaces. the level of economic development is the highest in vienna among the other austrian regions and holds leading position in europe. although in the past years the economic structural change caused decline in the number of the jobs in the secondary sector, the quality of economic activity has improved. the development in the last 20 years was very strong in sectors with low qualification requirement and high share of women and in the know-how intensive sectors. tourism plays a key role for the city.vienna’s share in total overnight stays in austria is of 7%. sales revenues and the overnight stays have developed dynamically. the secondary sector is changing. we can see that in the consumer goods industry a downturn was revealed, but in the exporting industries, for example automobile and vehicle manufacturing, electronics or the chemical industry, there is a dynamic growth. the research and development plays an important role in the city, too. significant amounts are spent on research and development by the universities, research organisations and enterprises alike. the structure of labour market illustrates on the one hand a structural change and the economic and social problems of the economy on the other. that is: ● the level of unemployment is higher than in other parts of austria. ● more than 75% are employed in the tertiary sector. ● the employment has been developing less expeditiously than in average in austria. all the same, in female employment an increase could be experienced, because of the rising number of parttime jobs and the larger number of jobs in the tertiary sector. ● but the qualification levels of employees are higher in the city than the average of the country. there are specific structures of enterprises in vienna’s economy. the majority of workplaces are given by small enterprises, which ensure the 35% of all jobs in the city. the significance of small and medium sized enterprises is very high. the municipality pays remarkable attention to the maintaining of these existing enterprises and to the support of their development. the demand for urban planning is becoming wider and wider. the quality of living plays a significant role and has an impact on location decisions. the structure of vienna’s economy commands widespread variety of building and location types, too. now urban planning has to be harmonized with project development, transport planning or for example with zoning. the economic development scheme includes the following elements: ● the development areas of great importance ● the determination of the city’s agricultural structural development plan and ● measures which assure the existing corporation structure the local centers play decisive economic role in vienna and certainly in the other cities, too. the city has important economic function and the municipality always makes an effort to retain and strengthen it. in reference to the retail trade the government and its measure aims to improve availability, to raise the demand and to revise the quality of the streets. but the shopping centers, the specialized markets and the ascendant competition take attenuative effect on the retail trade. vienna’s development project brings into focus to develop the city, improve and preserve its attractive position. according to the economic development scheme the development areas, which have strategic significance for the economy, are for example siemens allissen, bahnhof wien-europa mitte-aspang-erdberger mais or flugfeld aspern. the municipality creates several master plans, urban settlement schemes, projects and presents services in connection with availability by excellent quality and high-capacity transport infrastructure. the infrastructure plan aims to improve accessibility and attractiveness. the development plan has formulated temporal and spatial priorities based on the infrastructural planning. according to the development scheme the development will also focus in the future primarily on those areas which are available by high-capacity public transport. the gründerzeit city is the other important part of vienna. the city acts as feasible field for economic development. the aims of the development are to preserve existing activities and expand further the possibilities. in addition the industrial and commercial areas are secured, because there are very important foundations of the urban economy. the production technology is intent on becoming less and less polluting to the environment. unfortunately in the industrial zones the demand for large spaces is decreasing. the governance of the city purposes to make an analysis of development tendencies and compose measures which are based on the analysis. the city will continue the policy of sustainable and economically-realizable urban expansion. they want to ensure location at the borders of vienna for recreational aims and nature; furthermore they will apply such building methods that save energy and space in those areas, which are newly built-up. (according to the information heard at the drc summer university.) conclusion is intervention needed in local economy? the answer is very difficult and controversial. according to the researchers, in most cases local actors trusting in success argue in favour of intervention. the confidence, the will to act may arise from the possible inability of the government. however, it can be seen that the local level has limited room for manoeuvre. in this work i made a short summary of the instruments of local economic development on the basis of literature review. the regulatory and organizational systems of the countries are quite differentiated, but in 25 the case of economic development tools used by local actors, the situation isn't the same, they are very similar. i analysed the practice of vienna on the grounds of its last development plan. the plan brings into focus the thinking and acting in a european perspective and the aims are to reinforce vienna’s competitive position and to overcome the challenges. acknowledgement the study is prepared within the confines of the „tamop-4.2.1/b-09/1/konv-2010-0003: mobility and environment: researches in the fields of motor vehicle industry, energetics and environment in the middleand west-transdanubian regions of hungary”. the project is supported by the european union and co-financed by the european regional development fund. references 1. e. j. blakely, t. k. bradshaw: planning local economic development. theory and practice. london. sage publications ltd. (2002) 2. s. h. linder, b. g. peters: instruments of government: perceptions and contexts, journal of public policy, 9, (1989), 35–58 3. c. mezei: a helyi gazdaságfejlesztés szerepe a települések versenyképességének alakulásában. in: fiatal regionalisták iii. országos konferenciája elektronikus kiadványa. győr, magyarország, mta rkk nyuti (2002) 4. m. mcguire: collaborative policy making and administration. the operational demands of local economic development, economic development quarterly, 3, (2000), 278–291 5. s. capková (ed.): local government and economic development, budapest, open society institute (2005) 6. g. swinburn (ed.): talk is cheap. turning local economic development strategies into reality in transition countries. local government and public service reform initiative, budapest, open society institute (2007) << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice hungarian journal of industry and chemistry vol. 46(2) pp. 85–90 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0024 effects of different heat treatments on the chemical and microbiological characteristics of egg-free and quail egg dried pasta ildikó szedljak *1, viktória tóth1, judit tormási1, anikó kovács1, lászló somogyi1, lászló sipos2, and gabriella kiskó3 1department of grain and industrial plant processing, faculty of food science, szent istván university, villányi út 23, budapest, 1113, hungary 2department of logistics and sensory analysis, faculty of food science, szent istván university, villányi út 23, budapest, 1113, hungary 3department of microbiology and biotechnology, faculty of food science, szent istván university, villányi út 23, budapest, 1113, hungary in hungary, dried pasta products are very popular amongst all groups of society. in recent years the demand for not only dried pasta made from hen eggs (gallus gallus domesticus) but from alternative types of ingredients has increased. however, according to the literature the chemical and microbiological characteristics of this type of pasta have yet to be studied in depth. the effects of the use of quail eggs and heat treatments at different temperatures were studied by chemical and microbiological measurements. the activity of oxidative enzymes and nutritional characteristics (watersoluble total polyphenol content, water-soluble antioxidant capacity, peroxidase enzymatic activity, water-soluble protein content and yellow pigment content) was tested during our experiments. the data were evaluated by relevant statistical methods. significant differences were found both between heat treatments and between the egg content of the dried pasta samples. the peroxidase enzymatic activity and yellow pigment content increased with temperature. however, the usage of quail eggs provides a higher water-soluble protein content and water-soluble antioxidant capacity. the presence of microorganisms is decreased by increasing the drying temperature. the number of all the examined microorganisms was within limits. keywords: dried pasta, quail egg, heat treatment, chemical and microbiological characteristics 1. introduction present-day problems of globalization have led to a need for more diverse, long-lasting and convenient food products of high nutritional value. mindful consumers look for products that have positive physiological effects and have been subject to a minimal degree of processing. in hungary, dried pasta products are popular amongst all groups of society. their position in the global market is safe because these products possess all of the aforementioned qualities and fall within an affordable price range too. the amount of dried pasta products consumed in recent years has elevated [1], therefore, the food industry continuously tries to lower production costs as well as improve profits and their nutritional value [2]. one of the important ingredients of pasta are eggs. for the industrial processing of dried pasta only two kinds of eggs are usable; hen and quail eggs. the most commonly used type of eggs are hen eggs (gallus gallus domesticus). pasta products made from *correspondence: ildiko.szedljak@gmail.com this type of eggs have been well studied. however, recently a need has emerged for more unconventional dried pastas made from alternative ingredients [3]. quail egg pasta (coturnix coturnix) is one of these innovations. quail eggs as an ingredient are of a relatively high nutritional value. when compared to hen eggs they possess more protein but less carbohydrate and fat [4]. chemical changes during processing define the quality of the end product. the most determinative factors are the temperature of the drying process and its changes during the process [5]. significant changes in chemical behavior occur even at lower temperatures. enzymeactivated changes like protein denaturation and pigment oxidation take place below 60 ◦c. at temperatures higher than 80 ◦c the oxidative enzymes deactivate and the maillard reaction occurs, simultaneously the lysine concentration of the pasta decreases [6]. therefore, choosing the most suitable drying temperature is an important step when it comes to the quality of the heat-treated products, especially in the case of dried pastas. when designing and processing products with long mailto:ildiko.szedljak@gmail.com 86 szedljak, tóth, tormási, kovács, somogyi, sipos, kiskó storage and shelf lives, another important concern is the microbiological safety of the product. with the diminished water activity of these kinds of foods, the activity of microorganisms also decreases. the main parameter in this case is the number of microorganisms when processing commences. during drying the microbes deactivate and their numbers decrease [7]. chemical and microbiological properties depend on the nutritional characteristics and drying properties of the pasta. since the chemical and microbiological characteristics of quail egg pasta, according to the literature, have yet to be studied in depth, our goal was to expand this knowledge. studying the properties of this product is beneficial to both advancing the technology and food safety. 2. experimental the aim of our study was to examine and compare the chemical and microbiological characteristics of the eggfree and quail egg dried pasta that had been subjected to different heat treatments. changes caused by the presence of quail eggs were sought. differences made by varying the temperature of heat treatments were examined. moreover, a connection between the microbiome and heat treatments was characterized. materials the wheat flour, triticum aestivum l., used and the quail eggs were bought from commercial sources. the reagents for the chemical and microbiological measurements were provided by reanal laborvegyszer kereskedelmi kft. the bacterial substrates were produced by merck kft. samples the tests were conducted on the samples of egg-free and “four hen egg pasta” doughs using sufficient quantities of quail eggs. all the pastas were made from triticum aestivum l. flour, water and quail eggs for the egg pasta. to improve the heat distribution the pastas were shaped into the form of linguine. the pasta doughs were treated at three different temperatures (40 ◦c, 60 ◦c and 80 ◦c) for twenty-five minutes in an armfield-type fluid bed dryer. the samples were subjected to chemical and microbiological measurements. in preparation for the chemical tests the samples were first grated then 100 mg/ml extracts were taken using distilled water. every analytical method was conducted on five parallel samples. chemical analysis the moisture content was determined by an ma50 sartorius moisture analyzer. the water activity was measured by a novasina ms1 water activity meter. for the measurement of color the konica minolta cr-310 chroma meter with a tristimulant objective in a laboratory coordinate system was used. to measure the ph, the sg23 mettler-toledo sevengo duo ph/conductivity meter was used. the acid values of the extracted samples were titrated with 0.1 m naoh solution in the presence of the indicator phenolphthalein. the determination of ph and acid value was conducted based on hungarian standards [8]. the water-soluble total polyphenol content was measured by folin-ciocalteu reagent [9] and expressed in gallic acid equvalent (gae). water-soluble antioxidant capacity was measured using a frap (ferric reducing antioxidant power) assay kit [10]. the peroxidase enzymatic activity was given by using oda (o-dianisidine) as a hydrogen donor [11] and the data converted into ascorbic acid equivalent (aae). for measuring the watersoluble protein content, a method by layne [12] was used. the yellow pigment content of the samples was determined according to hungarian standards extracted by butanol [13]. microbiological analysis microbiological measurements were conducted given the relevant standards [14– 16]. three parallel measurements were made from each sample. all samples were tested for coliform bacteria, staphylococcus aureus and molds. in addition, the presence of salmonella using a european standard [17] was tested for. statistical evaluation all the measurements were replicated five times using xlstat software [18]. given the parallel samples, non-parametric probes were used. the kruskal-wallis test was applied to calculate the pvalue (α = 0.05) and dunn’s post hoc pair-wise test was used with bonferroni correction on significant results. the correlation between parameters was determined by spearman’s rank correlation coefficient (non-parametric equivalent of pearson’s correlation) (α = 0.05). 3. results and analysis 3.1 chemical analysis moisture content the moisture content of the dried pasta samples decreased as the temperature of heat treatment increased. the moisture content of all the dried pasta products was below the maximum set by hungarian standards [19] of 13 %. when treated at the same temperature the quail egg pastas always contained less moisture than the egg-free samples. however, significant differences were not determined. water activity this parameter is important for determining the initial microbial count and activity of samples during storage. the water activity of the samples decreased as the temperature of the heat treatment increased. in the quail egg pastas, the numbers were higher (aw(80◦c) = 0.6254 ± 0.0313) compared to commercially available pastas (aw < 0.6). thus, at this level of water activity the xerotolerant and xerofil microbes could survive and reproduce. a significant difference was not determined. hungarian journal of industry and chemistry quality features of egg-free and quail egg dried pasta 87 figure 1: water-soluble total polyphenol content of the samples in mg/g gallic acid equivalent. ph the ph also plays a key role in the reproduction and survival of microorganisms as well as in the activity of peroxidase. the ph of the quail egg samples was always lower than the egg-free samples. a significant difference was only measured in the quail egg (3.572 ± 0.128) and egg-free (5.898 ± 0.019) samples treated at 40 ◦c. since the molds are capable of reproducing at a lower ph (ph = 2–4) [20], this value of the quail egg pasta poses a threat from a microbiological point of view. acid value (av) this parameter was always lower in the quail egg samples. in the samples dried at 60 ◦c, significant differences were observed. all the acid values of measured samples were between 3.15 and 3.66 ◦sh, which falls within the codex alimentarius hungaricus’ guidelines [19] (in dried pastas av = maximum of 5 ◦sh). water-soluble total polyphenol content for evaluating the water-soluble total polyphenol content (tpc) of the samples, the data was calibrated with the gallic acid equivalent as shown in fig. 1, which gives the polyphenolic components in mg of gallic acid equivalent found in 1 gram of dried pasta. the presence of the quail eggs resulted in higher water-soluble total polyphenol contents in each case. significant differences based on the coupled comparison’s pvalues were only observed between the samples that were not heat treated. based on the results of the kruskal-wallis test a significant difference is observed between the tpc values of quail egg pastas. among the quail egg samples, based on the comparison of pairwise p-values, a difference is found for at least two samples. this can be detected between the samples that were not heat treated and those treated at 80 ◦c as well as between samples treated at 60 ◦c and at 80 ◦c. based on these results, it can be stated that the tpc may be influenced by heat treatment. figure 2: peroxidase enzyme activity of the samples in u/g ds. peroxidase enzymatic activity the peroxidase enzymatic activity was calculated on the basis of data from the literature and its value was given in terms of dry matter content (björkstén, 1968). the graph in fig. 2 clearly shows the effect of heat treatment. the enzymatic activity decreases as the temperature of the heat treatment increases and is always lower in the quail egg samples. the cause of this difference could be the different ph of the two types of pastas. in both cases a significant difference is observed between the samples treated at 60 ◦c and those not subjected to heat treatment. in the results of the egg-free pastas, the decline is less than in the quail egg samples. water-soluble protein content the water-soluble protein content was always higher in the quail egg samples. significant differences were observed between both the separate and cumulative evaluations. a significant difference was measured in the p-values in terms of the comparison of egg content when heat treated at 40 ◦c. in addition differences were observed between the eggfree samples that were not subjected to heat treatment and those heat treated at 80 ◦c, as well as between the quail egg samples that were not heat treated and those treated at 40 ◦c and 80 ◦c. from these results it can be stated that the examined treatments influence the water-soluble protein content of the samples. water-soluble antioxidant capacity the measurements of the water-soluble antioxidant capacity were converted into ascorbic acid equivalent. the antioxidant capacity of the pastas rose as the temperature of the heat treatments increased, in terms of the egg-free samples, the maximum was observed at 60 ◦c. the statistical evaluation revealed significant differences in every case. the increase in the antioxidant capacity as the temperature of heat treatment rises is common in the literature [21, 22]. 46(2) pp. 85–90 (2018) 88 szedljak, tóth, tormási, kovács, somogyi, sipos, kiskó figure 3: yellow pigment content of samples given in mg carotene/kg ds. yellow pigment content and color measurement the yellow pigment content was only measured on samples of dried pasta. both the egg-free and quail egg pastas exhibited significant differences between samples treated at 40 ◦c and 80 ◦c. as seen in fig. 3 in the case of the quail egg samples, a significant decline in the yellow pigment content was observed as the temperature of heat treatment increased. even so, the noticeable drop in the yellow pigment content of quail egg samples was still higher than in the case of the egg-free samples (except for the decline at 80 ◦c). for the assessment of color the “lab” color chart was used. the l∗ value denotes the lightness and positive rate of the b∗ value which represents the intensity of the color yellow. neither of these two values changed significantly in the presence of the quail eggs. however, the heat treatment resulted in significant changes in both color rates. a significant change in the lightness has already been observed in all the samples treated at 40 ◦c. as shown in fig. 4 the b∗ value increased as the temperature of heat treatment rose, therefore, the pastas became yellower as the temperature increased. in both types of pastas, significant differences were observed between figure 4: yellow color intensity of samples from the cielab color space. figure 5: the results of the microbiological analysis of egg-free pastas. the samples that were not subjected to heat treatment and those treated at higher temperatures (60 ◦c and 80 ◦c). the results of the yellow pigment content and color measurements are controversial in terms of the quail egg samples. the b∗ value – which shows the intensity of the color yellow – increases while the yellow pigment content decreases. the seemingly ambiguous data might be caused by chemical and microbiological changes not examined by us. the yellow pigment content continuously decreases during the drying process, therefore, choosing the most suitable drying temperature is critical. from these results, to retain the maximum amount of yellow pigments in the finished products, heat treatment at 60 ◦c is recommended. 3.2 microbiological measurements the microbiological contamination of egg-free samples remained below the limit (figs. 5 and 6). however, in the case of the quail egg pasta, the coliform bacteria appeared in the samples treated at 40 ◦c. the presence of the coliforms is not surprising since they figure 6: the results of the microbiological analysis of quail egg pastas. hungarian journal of industry and chemistry quality features of egg-free and quail egg dried pasta 89 table 1: spearman correlation matrix of the six studied parameters, “r” values (r = 0 no linear correlation, r = −1 perfect negative correlation, r = 1 perfect positive correlation). variables pox tpc l∗ b∗ antioxidant capacity yellow pigment content peroxidase enzymatic activity 0 0.2283 0.0000 0.0159 0.7815 0.8270 total polyphenol content 0.2283 0 0.0502 0.0009 0.0001 0.0024 l∗ <0.0001 0.0502 0 0.5675 0.6137 0.4238 b∗ 0.0159 0.0009 0.5675 0 0.0016 0.1523 antioxidant capacity 0.7815 0.0001 0.6137 0.0016 0 0.1723 yellow pigment content 0.8270 0.0024 0.4238 0.1523 0.1723 0 values in bold are different from 0 with a significance level α = 0.05 table 2: spearman coefficient determination matrix of the six studied parameters, “p” values variables pox tpc l∗ b∗ antioxidant capacity yellow pigment content peroxidase enzymatic activity 1 0.0512 0.4894 0.1930 0.0028 0.0017 total polyphenol content 0.0512 1 0.1307 0.3397 0.4304 0.2910 l* 0.4894 0.1307 1 0.0117 0.0092 0.0228 b* 0.1930 0.3397 0.0117 1 0.3118 0.0717 antioxidant capacity 0.0028 0.4304 0.0092 0.3118 1 0.0653 yellow pigment content 0.0017 0.2910 0.0228 0.0717 0.0653 1 are found in the feces of warm-blooded animals (bíró, 2014). as a result of the heat treatment the number of microbes decreased in both types of pasta. based on these results it can be clearly seen that heat treatment increases the quality of both types of pasta from a microbiological standpoint. the higher the temperature of the heat treatment, the more microbiologically advantageous it is. 3.3 statistical evaluation in addition to the examination of significant differences between our data, correlation studies were conducted on six selected variables of the evaluated factors: peroxidase enzymatic activity (pox), water-soluble total polyphenol content (tpc), l∗ and b∗ values, yellow pigment content and water-soluble antioxidant capacity. since five parallel measurements were taken, spearman correlations were determined [23], which is the nonparametric equivalent of the pearson’s correlation. based on the obtained “r” and “p” values (tables 1 and 2), two positive and three negative correlations were identified. the positive correlations were between the water-soluble total polyphenol content and yellow pigment content as well as between the water-soluble antioxidant capacity and b∗ values. the negative correlations were identified between the peroxidase enzymatic activity and l∗ value as well as b∗ values, the water-soluble total polyphenol content and b∗ values, in addition to the water-soluble total polyphenol content and water-soluble antioxidant capacity. 4. conclusion the aim of this study was to expand the literature on the chemical and microbiological characteristics of quail-egg dried pastas. with regard to the nutritional value of the pastas almost all of the examined characteristics declined as the temperature of the heat treatment increased except for the water-soluble antioxidant capacity. from our study it was found that the heat treatments at 80 ◦c were the most effective. based on these results, heat treatments at high temperatures (80 ◦c) are recommended especially from a microbiological point of view. the samples should also be maintained at this temperature for at least twenty-five minutes. such treatment would ensure the production of higher quality and safer products. while the industrial use of quail eggs causes technological and economic problems, this study could be a starting point for further research in this field. references [1] international pasta organization – survey. the world pasta industry in 2012; 2013. 46(2) pp. 85–90 (2018) 90 szedljak, tóth, tormási, kovács, somogyi, sipos, kiskó http://www.internationalpasta.org [2] kumar s. b., prabhasankar p., low glycemic index ingredients and modified starches in wheat based food processing: a review, trends food science technology 2014 35(1), 32–41 doi: 10.1016/j.tifs.2013.10.007 [3] csapó j., vargáné v. é., élelmiszerkémia (food chemistry), (university of kaposvár, kaposvár) 2011 http://www.tankonyvtar.hu/hu/tartalom/ tamop425/0059_elelmiszerkemia/adatok.html [4] miguel m., manso m. a., lopez-fandino r., ramos m., comparative study of egg white proteins from different species by chromatographic and electrophoretic methods, european food research and technology 2005 221(3), 542–546 doi: 10.1007/s00217-005-1182-8 [5] anese m., nicoli m. c., massini r., lerici c. r., effects of drying processing on the maillard reaction in pasta, food research international 1999 32(3), 193–199 doi: 10.1016/s0963-9969(99)00076-9 [6] dexter j. e., tkachuk r., matsuo r. r., amino acid composition of spaghetti: effect of drying conditions on total and available lysine, journal of food science 1984 49(1), 225–228 doi: 10.1111/j.1365-2621.1984.tb13713.x [7] lang e., zoz f., iaconelli c., recovery estimation of dried foodborne pathogens is directly related to rehydration kinetics, plos one 2016 11(8), e0160844 doi: 10.1371/journal.pone.0160844 [8] msz 6369-1:1985 flour test methods. sensory analysis. scoring and qualification [9] singleton v. l., rossi j. a. jr., colorimetry of total phenolics with phosphomolybdic-phosphotungstic acid reagents, american journal of enology and viticulture 1965 16(3), 144–158 doi: 10.12691/ijebb2-1-5 [10] benzie i. f., strain j. j., the ferric reducing ability of plasma (frap) as a measure of “antioxidant power”: the frap assay, analytical biochemistry 1996 239(1), 70–76 doi: 10.1006/abio.1996.0292 [11] björkstén f., participation of horseradish oxyperoxidase (compound 3) in interenzymic reaction steps, biochimica et biophysica acta 1968 154(1), 309– 311 doi: 10.1016/0005-2744(68)90196-4 [12] layne e., spectrophotometric and turbidimetric methods for measuring proteins (colowick p. s. and kaplan n. o., eds., methods in enzymology, academic press, inc., new york) 1957, 447–454 oclc number: 757246524 [13] msz 20500-2:1985 pastry products. test methods. chemical analysis [14] msz iso 7954:1999 microbiology general guidance for enumeration of yeasts and moulds colony count technique at 25 ◦c [15] iso 4832:2006 microbiology of food and animal feeding stuffs horizontal method for the enumeration of coliforms colony-count technique [16] msz en iso 6888-1:2008 microbiology of food and animal feeding stuffs. horizontal method for the enumeration of coagulase-positive staphylococci (staphylococcus aureus and other species). part 1: technique using baird-parker agar medium (iso 6888-1:1999) [17] msz en iso 6579:2006 microbiology of food and animal feeding stuffs. horizontal method for the detection of salmonella spp. (iso 6579:2002) [18] xlstat software, addinsoft 28 west 27th street, suite 503, new york, ny 10001 usa [19] codex alimentarius hungaricus 2-321 dried pasta products [20] bíró g., élelmiszer-higiénia (food hygiene) (agroinform kiadó, educatio) 2014 https://www. tankonyvtar.hu/hu/tartalom/tamop425/2011_ 0001_533_elelmiszerhigienia/index.html [21] muyonga j. h., andabati b., ssepuuya g., effect of heat processing on selected grain amaranth physicochemical properties, food science and nutrition 2014 2(1), 9–16 doi: 10.1002/fsn3.75 [22] phisut n., jiraporn b., characteristics and antioxidant activity of maillard reaction products derived from chitoan-sugar solution, international food research journal 2013 20(3), 1077–1085 [23] sajtos l., mitev a., spss kutatási és adatelemzési kézikönyv (spss research and data analysis manual) 2007 (budapest, alinea kiadó, 203–245) isbn: 978-963-9659-08-7 hungarian journal of industry and chemistry http://www.internationalpasta.org https://doi.org/10.1016/j.tifs.2013.10.007 https://doi.org/10.1016/j.tifs.2013.10.007 http://www.tankonyvtar.hu/hu/tartalom/tamop425/0059_elelmiszerkemia/adatok.html http://www.tankonyvtar.hu/hu/tartalom/tamop425/0059_elelmiszerkemia/adatok.html https://doi.org/10.1007/s00217-005-1182-8 https://doi.org/10.1007/s00217-005-1182-8 https://doi.org/10.1016/s0963-9969(99)00076-9 https://doi.org/10.1111/j.1365-2621.1984.tb13713.x https://doi.org/10.1111/j.1365-2621.1984.tb13713.x https://doi.org/10.1371/journal.pone.0160844 https://doi.org/10.12691/ijebb-2-1-5 https://doi.org/10.12691/ijebb-2-1-5 https://doi.org/10.1006/abio.1996.0292 https://doi.org/10.1016/0005-2744(68)90196-4 https://www.tankonyvtar.hu/hu/tartalom/tamop425/2011_0001_533_elelmiszerhigienia/index.html https://www.tankonyvtar.hu/hu/tartalom/tamop425/2011_0001_533_elelmiszerhigienia/index.html https://www.tankonyvtar.hu/hu/tartalom/tamop425/2011_0001_533_elelmiszerhigienia/index.html https://doi.org/10.1002/fsn3.75 introduction experimental results and analysis chemical analysis microbiological measurements statistical evaluation conclusion hungarian journal of industry and chemistry vol. 45(2) pp. 23–27 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0016 the effect of advanced oxidation pre-treatment on the membrane filtration parameters of dairy wastewater mihály zakar, 1,2 ildikó kovács, 1 péter muhi, 1 erika hanczné lakatos, 2 gábor keszthelyi-szabó, 1 zsuzsanna lászló 1, * 1 institute of mechanical and process engineering, faculty of engineering, university of szeged, moszkvai krt. 9, szeged, 6724, hungary 2 institute of food sciences, széchenyi istván university, lucsony u. 15-17, mosonmagyaróvár, 9200, hungary the dairy industry generates wastewater characterised by high levels of biological and chemical oxygen demands representative of their high degree of organic content; mainly carbohydrates, proteins and fats that originate from milk. several investigations have been conducted into the reuse of dairy wastewater, e.g. membrane processes are a promising method to treat such wastewater. earlier works have proven that with membrane filtration an appropriate degree of retention can be achieved and the permeate can be reused. however, membrane fouling is a limiting factor in these processes. advanced oxidation processes (aops) are widely used in the fields of water and wastewater treatments and are known for their capability to mineralise a wide range of organic compounds. aops also exhibit some other effects on the filtration process, e.g. the microflocculation effect of ozone may play a significant role in increasing the elimination efficiency and causing a decreased level of irreversible fouling. by comparing ozone and fenton pre-treatment (fpt) processes it can be shown that the fouling propensity of pre-treated pollutants does not depend on the pre-treatment method, while fpt was proven to be more efficient in improving the level of flux. keywords: ultrafiltration, ozone pre-treatment, fenton-reaction, fouling resistances, dairy wastewater 1. introduction the dairy industry is considered to be the largest source of food-processing wastewater in many countries. dairy wastewater exhibits high degrees of biological oxygen demand (bod) and chemical oxygen demand (cod); contains high levels of dissolved or suspended solids including fats, oils and grease; as well as nutrients such as ammonium ions or phosphates. therefore, proper attention must be paid to them before disposal [1]. there are several research projects that aim to identify possibilities of reusing or recycling dairy wastewater [29]. membrane treatment of dairy wastewater with the aim of water reuse could simultaneously lower the total water consumption and effluent production of dairy plants, as the purified water produced could be reused in a dairy plant to heat or cool water. besides additional advantages, e.g. a high degree of separation efficiency in the absence of chemical changes and low levels of energy intensity, membrane filtration also has drawbacks, namely compounds in dairy wastewater that contain protein were found to be significant foulants in terms of existing membrane materials [10-12]. *correspondence: zsizsu@mk.u-szeged.hu the combination of membrane separation and pretreatment with advanced oxidation processes (aops: using ozone, hydrogen peroxide, uv light, or a combination of these) opens up new opportunities, since the ozone and the resulting oxidizing radicals (mainly hydroxyl radicals) efficiently change the characteristics of the colloidal particles or oxidizing compounds, which cause membrane fouling [13]. earlier studies have shown that the microflocculation effect of ozone may play a significant role in increasing the elimination efficiency and may decrease the extent of membrane fouling and increase the degree of gel formation. in addition, aops can be used as a pre-treatment stage before a biological step in order to increase the biodegradability of the recalcitrant compounds and thus lower the toxicity of the wastewaters [13-14]. according to economic evaluation studies, the fenton process is more economical than ozone pretreatment [15]. however, there is little data concerning its effect on membrane filtration parameters. the aim of the present work was to investigate and compare the effect of ozone pre-treatment and the fenton’s reaction on ultrafiltration parameters, fouling mechanisms and the pollutant removal efficiency on a model dairy wastewater. zakar, kovács, muhi, lakatos, keszthelyi-szabó, and lászló hungarian journal of industry and chemistry 24 2. experimental 2.1. samples and measurements model solutions were prepared from milk powder (milk quick, instantpack kft., hungary) composed of 0.3% (g/g) concentrations, 32% (g/g) proteins, 5% (g/g) fat and 50% (g/g) lactose. ozone was produced from oxygen (linde, 3.0) with a flow-type ozone generator (ozomatic modular 4, wedeco ltd., germany). the ozone-containing gas was bubbled continuously through a batch reactor during the treatment. the volume of the treated water was 0.45 dm3. the durations of the treatment were 5, 10 and 20 mins; and the flow rate was 1 dm3 min–1. the ozone concentrations of the bubbling gas before and after it was passed through the batch reactor were measured with a ultraviolet–visible (uvvis) spectrophotometer (nanocolor nuv 0113) at a wavelength of 254 nm (fig.1). the absorbed ozone concentrations were 6.8·10–4 m, 1.43·10–3 m and 2.67·10–3 m, respectively. fenton’s reaction was conducted in a batch stirred ultrafiltration cell with 1.5 mmol dm-3 feso4×7h2o (purity 99%, spektrum-3d, eu) adjusted to ph 3 with h2so4 (purity 96%, farmitalia carlo erba spa, italy), 0.3 wt.% milk powder solution and h2o2 solution (30%, purity 99%, spektrum-3d kft.), the [h2o2]:[fe] ratio was 5:1 (fenton (5:1)) or 50:1 (fenton (50:1)). the ozone or fenton pre-treated samples were used as a feed in ultrafiltration (uf) experiments. the uf experiments were carried out in a batch stirred ultrafiltration cell (millipore, serial n°94, usa) with a capacity of 50 cm3, and the filtrations were performed at transmembrane pressures of 0.1 (only in the case of fenton (50:1)) or 0.3 mpa and the feed solutions were stirred at 350 rpm. for filtration experiments, flat sheet polyethersulfone (pes) membranes (pes-10 series, new logic research inc., usa) and a molecular weight cut-off (mwco) of 10 kda were used with an effective membrane surface area of 1.73 dm2. the initial feed volume was 50 cm3, the ultrafiltration experiments were conducted until 40 cm3 of the total sample had been filtered, when the volume reduction ratio (vrr) was equal to 5. determination of the cod was based on the standard method involving the oxidation of potassium dichromate; for the analysis, standard test tubes (lovibond tintometer ltd.) were used. the digestions were conducted in a cod digester (lovibond et108 thermoreactor); and the cod values were measured with a cod photometer (lovibond pccheckit). for the determination of the residual amount of hydrogen peroxide, cod measurements were performed before and after the addition of the enzyme catalase. 2.2. theoretical methodologies in order to investigate mechanisms of membrane fouling, filtration resistances were calculated according to the resistance-in-series model, eqs.(1-4). the membrane resistance ( mr , m-1) was calculated as 1 m w w [m ] p r j    (1) where p is the difference in pressure either side of the membrane (in mpa), wj is the water flux of the clean membrane, and w is the viscosity of water (in pa·s). the total resistance ( tr , in m–1), can be evaluated from the steady-state flux by using the resistance-inseries model: revt m irrevr r r r   (2) where irrevr is the irreversible resistance (mainly caused by the fouled pores) and revr is the reversible resistance. the irreversible resistance was determined by measuring the water flux through the membrane after filtration, rinsing it with deionized water to remove any particles of the residue layer from the surface, and subtracting the resistance of the clean membrane: mirrev ww a p r r j     (3) where waj is the water flux after concentration tests. the reversible resistance of the layer deposited on the membrane surface was calculated as: r e v mir r e v w wc p r r r j      (4) where cj is the constant flux at the end of the concentration test and ww is the viscosity of the wastewater viscosity [16]. mathematical modelling of the fouling mechanism was studied based on the hermia’s model [17]. the hermia’s model describes the mechanism of membrane fouling based on blocking filtration laws, consisting of complete pore blocking, standard pore blocking and intermediate pore blocking, in addition to cake filtration (table 1) to illustrate the different fouling mechanisms. figure 1. experimental set-up of ozonation. effect of advanced oxidation pre-treatment 45(2) pp. 23–27 (2017) 25 the hermia’s model was then linearized for each model using a fitting equation in terms of the permeate flux versus time as presented in table 1. in terms of the evaluation of the results these models were fitted to experimental data. in table 1, j is the flux, j0 is the initial flux, the various k’s are the fouling coefficients, and a is a constant. to compare the performance of different aops, the oxygen-equivalent chemical-oxidation capacity (occ, kg o2 m-3) was used to quantify the oxidants used in the ozone treatment and fenton’s reaction, and was determined based on stoichiometric calculations [14]: occ =1.000[o3] = 0.471[h2o2] (5) where [o3] is the required ozone concentration (kg o3 m-3), and [h2o2] is the required hydrogen peroxide concentration (kg h2o2 m -3). 3. results and analysis 3.1. experiments the effect of pre-oxidation on filtration parameters was investigated by fitting equations in table 1 to measured data. based on the value of the coefficient of determination, the cake layer filtration yielded the best correlation. in order to compare the different pre-oxidation methods, normalised values of the initial flux (j0, l m-2 h-1 bar-1) and fouling coefficients (k) were calculated and compared (figs.2 and 3). it was found that the effect of ozone treatment and fenton-treatment is different in the case of initial normalised flux. not only the fenton pre-treatment but the addition of reagents in the absence of hydrogen peroxide exhibited coagulationflocculation effects that resulted in an enhanced initial flux. in the case of the fenton’s reaction this effect is independent of the [h2o2]:[fe] ratio. the fouling coefficient also changes by the addition of oxidants, (fig.3) but in this case, the tendency is more likely to depend on the occ than on the applied aop method. at lower oxidation capacities the fouling coefficient decreases resulting in lower degrees of fouling than in non-treated solutions, however, at higher oxidation grades, the fouling coefficient increases. to obtain more information concerning the fouling mechanisms, the filtration resistances of ozone-treated and fenton (5:1) pre-treated solutions were calculated and compared (fig.4). it was found that in accordance with the values of the fouling coefficient filtration resistances decrease as the duration of oxidation pretreatment increases. in particular, mainly pre-treatments of short durations decreased the irreversible fouling resistance and increased the reversible fouling resistance. 4. discussion as an effect of the pre-oxidation of model dairy wastewater two typical pathways were observed that influence membrane filtration parameters: the i) microfigure 2. normalised initial flux values as a function of occ. 0 5 10 15 20 25 0,0000 0,0050 0,0100 0,0150 j 0 (l / m 2 h b a r) occ (kg o2/m3) fenton (50:1) fenton (5:1) ozone untreated figure 3. fouling coefficient as a function of occ. 0 0,001 0,002 0,003 0,004 0,005 0,006 0,00 0,10 0,20 0,30 0,40 0,50 k occ (kg o2/m3) fenton (50:1) fenton (5:1) ozone untreated figure 4. filtration resistances of untreated, fenton (5:1) and ozone pre-treated solutions. 0,00e+00 1,00e+13 2,00e+13 3,00e+13 4,00e+13 5,00e+13 6,00e+13 7,00e+13 f il tr a ti o n r e si st a n ce s (1 / m ) rm r(irrev) r(rev) rt table 1. hermia’s filtration laws. fouling mechanism filtration law constant-pressure filtration j0 a = cont. complete pore blocking j = j0 e -kt ln j = ln j0 kt gradual pore blocking (standard pore blocking) j = j0·(1 + ½ ks (a·j0 ) ½·t)-2 1/j0.5 =1/j0 0.5+ks·t ks = 0.5 ks a 0.5 intermediate filtration j = j0 · (1 + ki·a·j0 ·t) -1 1/j = 1/j0 + ki·t ki = ki a cake filtration j = j0 · (1 + 2kc(a·j0) 2·t)-0.5 1/j2 = 1/j0 2 + kc·t kc = 2kc a 2 zakar, kovács, muhi, lakatos, keszthelyi-szabó, and lászló hungarian journal of industry and chemistry 26 flocculation effect produces associated colloidal particles, and ii) degradation of organic matter (fig.5). the former resulted in decreased fouling of membrane pores as shown by the decreased fouling coefficient and irreversible resistance. this can be observed only during short-term ozone or fenton treatments (occ < 0.05 kg o2 m -3). the latter point may increase the degree of pore fouling [13, 18] due to the formation of small degradation by-products, which can enter membrane pores as the increased values of irreversible resistance also prove. by comparing the ozone and fenton pretreatment processes with similar occs, it can be concluded that the fenton pre-treatment may be more effective in terms of enhancing the flux, probably due to the coagulation-flocculation effect of the ferrous salts themselves. 5. conclusion the comparison of ozone and fenton processes as pretreatments before ultrafiltration of a model sample of dairy wastewater showed that such pre-treatments may improve the filtration parameters in terms of flux or fouling mitigation. by examining the effect of the oxidation capacities of ozone and fenton pre-treatment processes, it was found that the fouling propensity of pollutants does not depend on the pre-treatment method. however, it depends on the occ of the pre-treatment method. although the method of pre-treatment affects the flux, the fenton pre-treatment proved to be more efficient in terms of enhancing the value of the flux. symbols rm membrane resistance (m–1) rrev reversible resistance (m–1) rirrev irreversible resistance (m–1) p pressure difference between the two sides of the membrane (mpa) j flux (1/s) jw water flux (1/s) jc constant flux at the end of the concentration (1/s) j0 initial flux 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density profiles dezső boda,b1 and dirk gillespie2 1department of physical chemistry, university of pannonia, egyetem u. 10., veszprém, 8200, hungary 2department of molecular biophysics and physiology, rush university medical center, 1750 w. harrison st., chicago, usa be-mail: boda@almos.vein.hu computer simulations of the planar double layer geometry provide the charge profile with statistical noise. to compute the mean electrostatic potential profile from the charge profile, one must solve poisson’s equation with appropriate boundary conditions (bc). in this work, we show that it is advantageous to use the neumann or dirichlet bcs at the boundaries of the simulation domain with an integrated version of poisson’s equation. this minimises errors from the simulation’s noisy density profiles, in contrast to traditional convolution integrals that amplify the noise. the neumann bc, where the electric field is prescribed, can be used in both the constant surface charge and constant electrode voltage ensembles. in the constant voltage ensemble, where the potential difference between the confining electrodes is prescribed, one can also use the dirichlet bc, where the potentials at the boundaries are set. we show that the new methods provide converged results for the potential profile faster than the convolution integral does. keywords: electrical double layer, poisson equation, boundary conditions, computer simulation introduction the electrical double layer (dl) is formed by a charged surface and a phase (usually, a liquid) containing mobile charge carriers near the surface. depending on the material carrying the mobile charges, dls appear in electrolytes, molten salts, ionic liquids, plasmas, and even fast ion conductors (solid electrolytes). dls in solutions of dissolved ions are particularly important in electrochemistry, biology, and colloid chemistry. dls near electrodes differ from dls near charged objects carrying a fixed surface charge (such as colloids, macromolecules, and porous bodies), because the surface charge on the electrode can be controlled by an external voltage. theoretical studies of dls began with the poissonboltzmann (pb) theory known as the gouy-chapman (gc) theory [1,2] in electrochemistry, the debye-hückel (dh) theory [3] in solution chemistry, and the derjaguinlandau-verwey-overbeek (dlvo) theory [4, 5] in colloid chemistry. the pb theory is still very popular in applications because of its simplicity in spite of the fact that it neglects ionic correlations and effects due to the finite size of ions (e.g., excluded volume). more powerful statistical mechanical theories that are able to take these correlations into account have been developed [6–16]. computer simulations are a versatile method of studying dls in various geometries for various models of the constituents (ions, water, and electrode) [17–35]. this paper focuses on computing the electrical field and potential from a charge distribution obtained from computer simulations. computer simulations of systems containing charged particles must be performed in accordance with the laws of both electrostatics and statistical mechanics [36, 37]. this means that the electrical potential must be computed accurately for every configuration sampled in a monte carlo (mc) simulation. alternatively, the electrical field must be computed accurately in every time step of a molecular dynamics (md) simulation. every configuration of the system (positions of ions) corresponds to a microscopic state. in this case, we consider the system at the microscopic level. a simulation that samples the possible microscopic states must be performed properly according to the probability distribution of a given statistical mechanical ensemble. one typical simulation method to handle various ensembles is mc. the density distribution of ionic species i, h⇢ i (r)i, is obtained as an ensemble average from the simulation. from these, the average charge distribution can be obtained as q(r) = hq(r)i = x i z i e h⇢ i (r)i , (1) where q(r) is the charge distribution in a microscopic state, e is the electronic unit charge and z i is the valence of ionic species i. the average (mean) electrostatic potential can be obtained “on the fly” by computing the potential in the simulation cell for every configuration (denoted by (r)) and then taking the ensemble average, (r) = h (r)i. in this work, we use upper-case symbols for the microscopic quantities ( (r) and q(r)), while we use lowercase symbols for their macroscopic counterparts, namely, 124 their ensemble averages ( (r) and q(r)). the electrical potential in a configuration of the mc simulation, (r), can be computed analytically from coulomb’s law or numerically using a poisson solver. in both cases, we apply electrostatic bcs at the microscopic level. the reverse order, when we compute the ensemble average of the charge distribution (eq.(1)) and then solve poisson’s equation for the mean potential r2 (r) = � 1 ✏ 0 q(r) (2) is more usual (✏ 0 is the permittivity of vacuum). this equation applies to either explicit or implicit solvent models. in the explicit solvent framework, q(r) also contains the charge distribution of the water molecules (in addition to their ionic charges). in the implicit solvent framework, where water is represented by a dielectric background characterised by a dielectric constant, ✏, q(r) also contains polarisation charges induced in the dielectric (in the simplest case, q(r) is the ionic charges divided by ✏). because we are solving a differential equation, we must use appropriate boundary conditions (bcs) when solving eq.(2). because we want an ensemble averaged result, we apply the bcs at the macroscopic level. this paper describes how to numerically integrate the poisson equation with appropriate bcs to efficiently compute the mean electrostatic potential profile from the mean charge profile obtained from simulations. the statistical ensemble applied in the simulation determines which bc to use. in this paper, we consider the two basic ensembles, one where the electrode charges are fixed (constant charge ensemble) and one where the difference between the electrode potentials is fixed (constant voltage ensemble). in the constant charge ensemble, the traditional method of computing the potential profile is via a convolution integral. here, we show that this method is errorprone and numerically inefficient and instead, it is more advantageous to use a different integration scheme with neumann bcs, where the normal electric fields at the boundaries of the system are fixed [38]. in the constant voltage ensemble developed by kiyohara and asaka [39], the electrode potentials are known in advance. therefore, we can also use dirichlet bcs, where the potentials at the boundaries of the system are prescribed. in the following, we describe our model in detail. then, we consider all three issues discussed above (bcs at the microscopic level, statistical mechanical ensembles, and bcs at the macroscopic level) and present various possibilities for the macroscopic bc depending on the statistical mechanical ensemble used. we present results of model calculations to show the self-consistency of these calculations. model and boundary condition at the microscopic level at the microscopic level, we have a system that contains localised discrete and/or continuous distributions of charges q(r). in practice, there are two traditional schools to compute the electrostatic energy (in mc) or forces (in md) for a configuration sampled by a computer simulation. in one school, the potential is computed on a grid from poisson’s equation (eq.(2)) using a partial differential equation (pde) solver with appropriate boundary conditions. this method is generally used in md simulations of explicit solvent systems. in the other school, coulomb’s law is used to calculate the potential: (r) = 1 4⇡✏ 0 ✏ z q(r0)g(r, r0)dr0, (3) where g(r, r0) is the appropriate green’s function. this method is generally used for simulations with implicit solvents. the planar dl geometry means that we have a rectangular simulation cell of length l 2 �l 1 and with a base h ⇥h confined by two planar electrodes at the two ends (x = l 1 and x = l 2 ) carrying surface charges � 1 and � 2 . periodic boundary conditions (pbc) are used in the y, and z dimensions, which means that the green’s function is g(r, r0) = 1x j=�1 1x k=�1 1 |r� r0 + jhn y + khn z | (4) where the sum over j and k represents the interaction with the periodic image charges in the replicas of the central simulation cell in the y and z dimensions set by the unit vectors n y and n z . the term j = k = 0 corresponds to the interaction with the charge in the central simulation cell computed explicitly. in this paper, the interaction with periodic replicas is taken into account using the charged sheet method by smearing these charges into a sheet carrying q/h2 surface charges with a h2 square hole in the middle. the interaction with the holed sheet can be integrated. for further details, see ref. [18, 29]. the statistical mechanical ensemble determines which thermodynamic variables are fixed in the simulation. the attempts in the mc simulations are designed to ensure sampling according to the probability distribution of the given ensemble. moreover, the simulation must be self-consistent in the sense that a prescribed thermodynamic variable must agree with its value computed as an output of the simulation. for example, in an npt simulation (where the pressure is fixed), the pressure can also be computed from the virial sum as an ensemble average in both nv t and npt simulations. this value must be equal to the one prescribed in the npt ensemble. in practice, however, the accuracy of the pressure computed from the virial sum depends on the size of the system, and one obtains the same relationship between pressure 125 and density from nv t and npt simulations only in the limit of very large simulation cells. from the point of view of the dl problem, the question is whether we perform the simulation in the constant charge or constant voltage ensemble. in the constant charge ensemble the surface charges on the confining walls of the simulation cell are fixed. this is the traditional simulation setup used in dl simulations since torrie and valleau [17, 18]. the output of the simulation is the density profiles of the various ionic species h⇢ i (x)i (the pbc applied in the y and z dimensions ensures that the profiles depend on x only), from which the x-dependent charge profile, q(x), is obtained (see eq.(1)). the corresponding form of poisson’s equation is d2 (x) dx2 = � 1 ✏ 0 ✏ q(x), (5) where ✏ is now included so q(x) constrains only ionic and electrode charges. recently, kiyohara and asaka [39] introduced the constant voltage ensemble, where the potential difference between the two confining walls (the electrodes) is prescribed. a special mc step, where a small amount of charge, ��, is transferred from one electrode to the other, has been introduced. the charge exchange is accepted on the basis of the boltzmann factor min  1, exp ✓ ��u kt + h2 � ⇤ �� kt ◆� (6) where �u is the energy change associated with the charge movement and � ⇤ = (l 2 ) � (l 2 ) is the prescribed voltage. here, the surface charges on the electrodes fluctuate, while the potential difference between the electrodes (� ⇤) is an independent, prescribed variable of the ensemble. the mean potential profile can be computed from eq.(5). the computed voltage, namely, the potential difference between the electrodes, � = (l 2 )� (l 2 ), must be equal to the prescribed voltage, � ⇤. in the following, we describe various ways to apply bcs at the macroscopic level using a case study of a 1:1 electrolyte, where the ions are modeled as charged hard spheres with diameters d + = d� = 3 å and the dielectric constant of water is 78.46. the concentration is 1 m and the temperature is 298.2 k. we show results for the special case of � 1 = �� 2 = � = 0.1 cm�2 and l 1 = �l 2 = l, but the equations are presented for the general case. we used 200/200 ions in the mc simulations performed in the canonical (nv t ) ensemble. the dimensions of the cell are l = 50 å and h = 57.2 å. boundary conditions at the macroscopic level boundary conditions set in the bath: the convolution integral let us distinguish between the charge of the ions obtained from the simulation, q ion (x), and the surface charges, p k � k �(x� x k ), at x 1 = l 1 and x 2 = l 2 (in this work, we assume only two charged surfaces at l 1 and l 2 , but there can be more as in the simulations of kiyohara et al. [40–50] for porous electrodes). the total charge is the sum of these: q(x) = q ion (x) + x k � k �(x� x k ). (7) the ionic charge profile is obtained as an ensemble average. the electrode charges are prescribed in the constant charge ensemble, while they are obtained as ensemble averages in the constant voltage ensemble. at the macroscopic level, the issue of electrostatic self-consistency appears when we ask the question: what kind of bc should be applied when we solve poisson’s equation (eq.(5)). the traditional answer to this question is that the bc is set in the bulk electrolyte, where the average electrical field and electrical potential are zero. the corresponding solution of poisson’s equation can then be obtained in the form of a convolution integral (x) = � 1 ✏ 0 ✏ z 1 x (x0 � x)q ion (x0 )dx0. (8) this solution was probably inspired by theories that usually consider an isolated dl where the bcs are set in infinity. because theories (unlike simulations) provide smooth charge profiles (with the property lim x!1 q(x) = 0) without any noise, this integral works well for theories. to the best of our knowledge, the majority of researchers (among others, the authors of this paper) have used this equation in the past [6–35]. in this work, we show that this equation, from a numerical point of view, is a poor choice to compute the potential in simulation studies. the reason is that the upper integration limit is not well defined and that q(x) is subject to a large statistical noise. in practice, the upper integration limit is set somewhere in the middle of the cell where a bulk electrolyte is. here we will use exactly the middle of the cell (x = 0) as the upper integration limit. because of x�x0 in the integrand, this integral is very sensitive to the noise in q(x), because the noise is amplified as one moves further away from the electrode. the results of a very short (200 mc cycles; 1000 attempts to move ions were made in an mc cycle) simulation are shown in fig.1. the density and charge profiles are very noisy. when we compute the potential from eq.(8), the result is subject to a large error and is far from what we are supposed to get (fig.2, top panel). the slope is not necessarily zero in the bath (which means that the electrical field is not zero). if the simulation was run for longer, we would get a completely different result. in general, long simulations are needed to produce a smooth charge profile and a well established potential profile. the problem is even more serious when we try to reproduce small effects, such as the value of the electrode potential at zero electrode charge (pzc) for asymmetric electrolytes. the value of the pzc potential is very small 126 0 1 2 3 4 5 d en si ty p ro fi le s / m -60 -40 -20 0 20 40 60 x / å -4 -2 0 2 4 c ha rg e pr of ile / m figure 1: density profiles (top panel) and a charge profile (bottom panel) obtained from a short (200 mc cycles) constant charge simulation using � 1 = �� 2 = �0.1 cm�2. the charge profile is obtained from p i z i ⇢ i (x), so its unit is m (mol dm�3) and the effect of the noise is dramatic. extremely long simulations are needed to obtain convergent results for the potential [51]. to illustrate this weak convergence, we have plotted the left electrode potential ( (l 1 )� (0), top panel) and the voltage ( (l 2 )� (l 1 ), bottom panel) as computed from eq.(8) as functions of the performed mc cycles in fig.3 (red dashed curves). these potential values fluctuate strongly. the calculated values depend not only on the simulation time, but on the upper integration limit. if we shift that point a bit, we get a different result (data not shown). neumann boundary conditions and the constant charge ensemble here we propose, instead, to use neumann or dirichlet bcs at the boundaries of the simulation cell (at l 1 and l 2 , or, equivalently, at �1 and 1). in the case of the neumann bc, the normal electrical field is prescribed, while in the case of the dirichlet bc, the electrical potential is prescribed at the confining walls. our simulation setup ensures that the simulation cell is always charge neutral. then, gauss law states that the average electrical field is zero outside the cell for the regions z < l 1 and z > l 2 . this information makes the neumann bc applicable both in the constant charge and constant voltage 0 1 2 3 4 ψ (x ) neumann convolution (left) convolution (right) -60 -40 -20 0 20 40 60 x / å 0 0.1 0.2 0.3 0.4 0.5 0.6 q to t(x ) figure 2: potential profiles (top panel) as computed from the neumann bc (eq.(11)) and the convolution integral (eq.(8)). the upper limit of the convolution integral is x = 0 and it is computed for the leftand right-hand sides separately. the bottom panel shows the integral of the charge profile (q tot (x), see eq.(7)). it is closely related to the electric field through eq.(13). the profiles have been obtained from the curves of fig.1. the electrostatic potential is shown in units of kt/e throughout this paper ensembles. in the constant charge ensemble, the potential difference between the electrodes is an output of the calculation. therefore, we cannot use it as a bc, so we cannot apply the dirichlet bc in this case. in the constant voltage ensemble, on the other hand, the potential difference is known in advance (see the next section). in the constant voltage ensemble, therefore, both neumann and dirichlet bcs can be used and they should give the same answer (apart from errors related to the size of the system, see later). the neumann bc for eq.(8) is that the electrical field is zero outside the system: e(x ! �1) = � d (x) dx ���� x!�1 = 0 (9) and the same for x ! 1. by integrating poisson’s equation once, we obtain d (x) dx = � 1 ✏ 0 ✏ z x �1 q(x0 )dx0 + c 1 (10) where c 1 is an integration constant. taking eq.(10) at 127 -4 -3.5 -3 -2.5 -2 -1.5 -1 ψ (l 1)ψ (0 ) neumann convolution 0 200 400 600 800 1000 mc cycle 2 3 4 5 6 ψ (l 2)ψ (l 1) figure 3: convergence of the left electrode potential (top panel) and the voltage (bottom panel) as computed from the neumann bc (eq.(11)) and the convolution integral (eq.(8)) in the constant charge ensemble. any location x < l 1 (where q(x) = 0) and using the bc (eq.(9)), we get c 1 = 0 for the integration constant. if we use eq.(7) for q(x), we obtain d (x) dx = � 1 ✏ 0 ✏ z x l1 q ion (x0 )dx0 � 1 ✏ 0 ✏ � 1 (11) for l 1 < x < l 2 . the change in the lower integration limit was possible because ions exist only between the two electrodes (q ion 6= 0 only for l 1 < x < l 2 ). introducing q tot (x) = z x l1 q ion (x0 )dx0 (12) for the integral of the ionic charge profile (the total charge density per area in the [l 1 , x] interval), the electrical field can be given as e(x) = 1 ✏ 0 ✏ q tot (x) + 1 ✏ 0 ✏ � 1 (13) for l 1 < x < l 2 . the q tot (x) profile is shown in the bottom panel of fig.2. for the special case of � 1 = �� 2 , the total ionic charge is zero in the system, so q tot (l 2 ) = 0. the nearly constant but noisy profile in the middle of the cell represents the bulk region. integrating once more, we obtain (x) = � 1 ✏ 0 ✏ z x l1 q tot (x0 )dx0 � 1 ✏ 0 ✏ � 1 (x� l 1 ) + c 2 , (14) -3.5 -3 -2.5 -2 ψ (l 1)ψ (0 ) dirichlet neumann convolution 0 200 400 600 800 1000 mc cycle 4 5 6 7 ψ (l 2)ψ (l 1) figure 4: convergence of the left electrode potential (top panel) and the voltage (bottom panel) as computed from the neumann bc (eq.(11)), the dirichlet bc (eq.(17)), and the convolution integral (eq.(8)) in the constant voltage ensemble where c 2 is another integration constant. its value is inconsequential because we can set the zero level of the potential arbitrarily. fig.2 shows the (x) profile where c 2 = 0. it is usual, however, to set the ground in the bulk, so c 2 = � (0), where (0) is the average of the potential profile over the bulk. kiyohara and asaka [39, 52] used an equation of a convolution form that can be shown to be equivalent to eq.(14), but they seemed to leave out the linear term containing � 1 . eq.(14) is different from the convolution integral (eq.(8)) because it does not suffer from the uncertainty in the upper integration limit and from errors originating from the noise of the q ion (x) profile. the integration is performed for a well defined finite domain from the left electrode to x. fig.3 shows that this equation provides a much better convergence as a function of simulation time for the same simulation (same q ion (x)). this procedure was used in our papers for inhomogeneous electrolyte systems to compute the mean electrostatic potential [53–56]. it was especially useful for electrolytes adsorbed in narrow slits [55,56]. in this case, the dls formed at the walls of the slit overlap so a bulk electrolyte does not form in the middle of the slit and the slit is not charge neutral. the neumann bc is then the natural bc so the electric field is zero behind the walls. in another example, the neumann bc is used to compute the potential for a dl model, where the electrode, the 128 inner layer, and the electrolyte have different dielectric constants [54]. in this case, the polarisation charge induced at the dielectric boundaries must also be included in eq.(14). dirichlet boundary conditions and the constant voltage ensemble an alternative method is the constant voltage ensemble of kiyohara and asaka [39]. here, the electrode charges fluctuate and the potential between the electrodes is prescribed. therefore, we can also apply dirichlet bcs, where (l 1 ) = 0 (15) and (l 2 ) = � ⇤. (16) the general solution for the potential profile in the l 1 < x < l 2 range is (x) = � 1 ✏ 0 ✏ z x l1 q tot (x0 )dx0 +c 1 (x�l 1 )+c 2 , (17) where we integrate from the right-hand side of the electrode at x = l 1 , so the surface charge � 1 is now excluded from the integration. the bc at x = l 1 (eq.(15)) provides the integration constant c 2 = 0, while the bc at x = l 2 (eq.(16)) provides the integration constant c 1 = 1 l 2 � l 1 " � ⇤ + 1 ✏ 0 ✏ z l2 l1 q tot (x)dx # . (18) of course, we can calculate the potential profile using the neumann bcs too. in that case, we must use h� 1 i in eq.(14) instead of � 1 because the electrode charge is now fluctuating so its value is not known in advance. therefore, its ensemble average should be used in eqs.(7-14). in the constant voltage ensemble we need the value of the voltage that corresponds to � 1 = �0.1 cm�2 as used in the previous constant charge simulation. this value we estimated with a very long (50,000 mc cycles) constant charge simulation and was obtained as � ⇤ = 4.398 kt/e. this value was used in the constant voltage simulation as an input parameter. fig.4 is the analogous version of fig.3. the black solid curves are the results obtained from the dirichlet bcs (eqs.(17) and (18)). the red short-dashed curves show the results of the neumann bc using h� 1 i in eq.(14). the convolution integral results (blue longdashed curves) are inaccurate and poorly converged for such a short simulation. in the constant voltage ensemble the electrode charge is a fluctuating quantity. fig.5 shows its convergence. its limiting value is not equal to that used in the constant charge simulation that provided the input voltage value � ⇤ = 4.398 kt/e. the deviation is due to finite size of the system. using a larger simulation box (larger h), a smaller deviation is observed (data not shown). this deviation is also observed in fig.4. the limiting value of the 0 200 400 600 800 1000 mc cycle -0.1 -0.095 -0.09 e le ct ro de c ha rg e / c m -2 figure 5: convergence of the electrode charge in the constant voltage ensemble potential difference � = (l 2 )� (l 1 ) obtained from the calculation using the neumann bc (bottom panel) is different from the prescribed value (the value used in the dirichlet bc, see also bottom panel). this behaviour is analogous to that discussed earlier regarding the example of the pressure computed in the nv t and npt ensembles. the constant charge ensemble corresponds to the nv t , while the constant voltage ensemble corresponds to the npt ensemble. in the constant charge ensemble, the voltage is computed using the neumann bc, just as the pressure is computed in the nv t ensemble from the virial sum. in the constant voltage ensemble, the voltage is prescribed, just as the pressure is prescribed in the npt ensemble. the voltage can also be computed from the neumann bc, just as the pressure can also be computed from the virial sum in the npt ensemble. conclusion we propose that the neumann or dirichlet bcs should be used in computing the mean electrostatic potential for the planar dl geometry studied by computer simulations. the commonly used convolution integral of eq.(8) requires a vaguely defined upper integration limit and also suffers from numerical problems because it magnifies the effect of the noise in the charge profile that is always present in computer simulations. the problem of noise in the density profiles is unique to simulations and therefore more care must be taken in computing the electrostatic potential. on the other hand, theories [6–16], which produce smooth, noise-free density profiles, can use the convolution integral. we have shown here that the numerical method we proposed is much more efficient than the convolution integral, because we use unambiguous parameters in the bc, specifically, the electrode charge in the case of the neumann bc and the voltage in the case of the dirichlet bc. also, the simulation cell is necessarily finite, therefore, the boundaries of the system are always well de129 fined. overall, our method leads to converged results with very short simulations. acknowledgement the present publication was realised with the support of the projects támop-4.2.2/a-11/1/konv-2012-0071 and támop-4.1.1/c-12/1/konv-2012-0017. references [1] gouy g.: sur la constitution de la charge electrique a la surface d’un electrolyte (english title please), j. phys. 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department of control engineering and information technology, budapest university of technology and economics, magyar tudósok krt. 2, budapest, 1111, hungary be-mail: patarticsbalint@gmail.com this paper focuses on the development of state estimation methods for mechanical systems with uncertain frictional parameters. the goal of the study is to provide reliable angle estimation for state-feedback-based crane control solutions, designed to reduce load sway. cranes are underactuated systems, usually unequipped with the sensors necessary to measure the swinging angle, therefore the damping of their oscillatory behaviour is a challenging task. two estimators are proposed for the calculation of the unmeasured states. one is based on an ’unknown input kalman filter’ (uikf), the other applies the ’unscented kalman filter’ (ukf) with load prediction. simulation results are provided to demonstrate the accuracy of the algorithms. keywords: overhead crane, state estimation, nonlinear systems, unknown inputs, kalman filter introduction the sway of the load carried by cranes is an unwanted phenomenon. friction may decouple load motion from the remaining crane mechanism. this causes difficulty for inexperienced operators, especially when they try to land the cargo. the friction present in the crane mechanism makes the reduction of the swinging particularly demanding. therefore the goal of the design of crane control systems is often to ensure minimal swinging along a specified trajectory [1–6]. there are numerous algorithms available in the literature for the solution to this problem. the design of such a control system can be addressed using soft computing methods such as fuzzy logic and neural network with genetic algorithm. these solutions require however the measurement of the load position, which is often based on workspace visualization [1]. hard commuting techniques are also widely applied for sway reduction. an h2 optimal solution is described in ref.[2], which also relies on image processing for the measurement of the load coordinates. there are a variety of algorithms taking advantage of the flatness property (or exact linearizability) of overhead cranes [7]. the control systems in refs.[3] and [4] consider all the states measurable, however an estimator is proposed in ref.[3] for the computation of the uncertain parameters. in the case of navy cranes, local asymptotic stability can be achieved without the measurement of the swinging angle, if trajectory planning exploits the flatness property of the system [6]. there is also a tracking control algorithm specifically designed for overhead cranes, that is capable of effectively reducing the sway despite the friction [5]. for the calculation of the unmeasured states, this controller uses a linear observer. in this paper we propose new methods of state observation for systems that take into account friction, and are applicable to overhead cranes. these estimators can replace the linear observer in ref.[5] or the need to measure the load coordinates in any other state-feedback-based method to enhance the precision of the control. our estimation methods are based on the assumption that the effect of the friction on the inputs can be reduced. this is true for most mechanical systems (including overhead cranes), where the actuating signals are usually forces and torques. in the following section, the modelling of lagrangian mechanical systems is overviewed, and it is shown how the friction can be handled as an input disturbance. in the next section the state estimation techniques are presented based on the possible approaches of interpreting the friction. the next section describes the results of the application of these methods to the state estimation problem of overhead cranes and presents the simulation results. lagrangian-based models of mechanical systems the nonlinear dynamics of the controlled system can be obtained using the euler-lagrange equations. if the generalized coordinates are q = ( q1 q2 . . . qn )t and the generalized forces are τ = ( τ1 τ2 . . . τn )t , the eulerlagrange equations read d dt ∂l ∂q̇i − ∂l ∂qi = τi, (1) 72 where l is the so-called lagrangian, the difference between the kinetic and potential energy of the system, q̇i = dqi dt and i = 1, 2, . . . n. using these equations, under some conditions the controlled system’s model can be written in the form h(q)q̈ + h(q, q̇) + hs(s) = τ, (2) where h(q) is the inertia matrix, h(q, q̇) comprises the centrifugal, coriolis and gravitational terms, and hs(s) is the frictional term with s being the vector of the frictional forces. in this form hs(s) can be reorganized to the right-hand-side of the equation. introducing the disturbance torques as τ̃ = τ − hs(s), eq.(2) yields h(q)q̈ + h(q, q̇) = τ̃ . (3) the state-space representation of the model is ẋ = f(x, u) y = g(x), (4) where x is the state, u is the input, y is the output of the system, and f and g are nonlinear functions. this form can be obtained from eq.(5) assuming that xt =( qt q̇t ) , and the output is not directly dependent on the torques. the state-space equations read ẋ = ( q̇ −h−1(q)h(q, q̇) ) + ( 0 h−1(q) ) τ̃ y = g(x). (5) the inputs of mechanical systems are usually forces and torques, consequently they are only dependent on τ̃ . this means, that the effect of the friction can be reduced to the actuated degrees of freedom of the system. if it is necessary for the design of the control system, the nonlinear dynamics can be approximated by a first order taylor series expansion around a setpoint (x0, u0). the linear model then becomes δẋ = aδx+bδu δy = cδx, (6) where the quantities prefixed with δ mean the distance from the setpoint, e.g. δx = x− x0, and the matrices are jacobians [8]. state estimation methods since the friction can be interpreted in our setup as an input disturbance, we consider two ways for its compensation in the state estimation. either all input variables can be disregarded, or the additive disturbance can be estimated using a load predictor. these ideas form the basis of the two estimator design techniques described as follows. the computations of the controllers implemented in embedded systems are based on sampled signals. hence the design of the estimators is done in discrete-time. unknown input approach consider the discrete-time linear stochastic system model x[k + 1] = φx[k] + γdd[k] + ω[k] z[k] = cx[k] + v[k], (7) where x is the state, d is the unknown input (disturbance) of the system and z is the measurement of the output y[k] = cx[k]. φ and γd are obtained from the matrices of eq.(6) in the form of φ = eats , γd = ∫ ts 0 eatb dt, (8) where ts is the sample time. the measurement and process noise v and ω are assumed to be additive, white, and gaussian with mean of zero. notice, that in eq.(7), all of the system inputs are considered to be disturbances. the state and the unknown input of such a system can be estimated using an ’unknown input kalman filter’ (uikf) [9], if the system satisfies the conditions dim{d} ≤ dim{y} (9) rank{c} = dim{y} (10) rank{γd} = dim{d} (11) rank{cγd} = dim{d} . (12) additive disturbance approach in the case of input disturbances, load prediction is often applied. let us introduce the discrete-time nonlinear model of a system in the form x[k + 1] = φ(x[k], ũ[k]) + ω[k] z[k] = g(x[k]) + v[k], (13) where ũ is the disturbed input of the system, and φ and g are nonlinear functions. we will follow the assumption, that the disturbance is additive to the input, thus ũ[k] = u[k] + λd[k], where u is the vector of actuating signals, and λ is a constant matrix. we also assume a constant disturbance model with process noise ωd, d[k + 1] = d[k] + ωd[k], resulting in the model x̃[k + 1] = φ̃(x̃[k], u[k]) + ω̃[k] z[k] = g̃(x̃[k]) + v[k]. (14) in eq.(14) x̃t = ( xt dt ) is the extended state and ω̃t = ( ωt ωtd ) is the extended process noise. the extended nonlinear mappings of the system are given by g̃(x̃[k]) = g(x[k]) and φ̃(x̃[k], u[k]) = ( φ(x[k], u[k] + λd[k]) d[k] ) . (15) in most cases the continuous-time differential equation of the observed system is available, in the form 73 m uf uc r ` θ j ρ cartwinch m load rail figure 1: the two-dimensional ovearhead crane of eq.(4). the discrete-time state-transition equation can then be obtained by φ(x[k], u[k]) = x[k] + (k+1)ts∫ kts f(x, u[k]) dt, (16) where the input is piecewise constant and u[k] = u(kts). if the integral in eq.(16) cannot be given in closed form and ts is sufficiently small, the left rectangle rule approximation (k+1)ts∫ kts f(x, u[k]) dt ≈ tsf(x[k], u[k]). (17) can be used. substituting this into eq.(15), the expression reads φ̃(x̃[k], u[k]) = ( x[k] + tsf(x[k], u[k] + λd[k]) d[k] ) . (18) for the observation of the system described by eq.(14) and eq.(18) the ’unscented kalman filter’ (ukf) [10] is applicable. we chose one of the implementation variants of this filter from ref.[10]. application of the methods to overhead cranes system dynamics we will now consider the state estimation problem of the two-dimensional overhead crane (fig.1). let us denote the horizontal displacement of the cart by `, the length of the rope by r and the angle between the vertical and the rope by θ. the generalized coordinates of the system are chosen to be q = ( ` r θ )t , and the state is x =( ` r θ ˙̀ ṙ θ̇ )t . based on the sensors available, the output is y = ( ` r ˙̀ ṙ )t . overhead cranes is a typical example of underactuated systems. it is actuated by two motors, one applying the force uf on the cart, and another delivering the estimated system s λ + + u u system model s = η(x, ẋ, u) ẋ = f(x, ũ) y = g(x) ũ y∫ẋ x figure 2: dynamics of the estimated system torque uc to the winch. the system input consists of these, u = ( uf uc )t . the parameters of the system are the mass of the cart m , the mass of the load m, the moment of inertia of the winch j and the radius of the winch ρ. the acceleration in the gravitational field is denoted by g. the following assumptions are made of the system. • the rope connecting the load to the winch is massless and behaves as a rigid rod during the motion. • the load is a point mass. • m , m, j and ρ are known. • in the initial state of the system the unmeasured states are zero: θ = 0 rad and θ̇ = 0 rad/s. • the effect of the aerodynamic resistance is negligible. the lagrangian of overhead cranes reads l = 1 2 (m +m) ˙̀2 + 1 2 j ρ2 ṙ2 + + 1 2 m ( ṙ2 + r2θ̇2 ) +ml̇ṙ sin θ +ml̇rθ̇ cos θ +mgr cos θ. (19) using eq.(1), the model can be written in the form of eq.(2), where the expressions become h(q) =  ( m +m sin2 θ ) m sin θ 0 m sin θ ( j ρ2 +m ) 0 cos θ 0 r  , (20) h(q, q̇) = − m(rθ̇2 + g cos θ) sin θ mrθ̇2 +mg cos θ −2ṙθ̇ − g sin θ  , (21) hs(s) = − sfsc 0  , τ =  uf −uc ρ 0  , (22) where sf is the frictional force between the cart and the rail and sc is the frictional force applied to the winch. the continuous-time linear model of the crane is computed around the setpoint x0 = ( 0 r0 0 0 0 0 )t , u0 = ( 0 mgρ )t , and sf = sc = 0 is substituted 74 table 1: numeric values of the parameters value unit m 5 kg m 0.05 kg j 3.802 · 10−4 kg m2 ρ 0.02 m g 9.81 m s−2 ts 1 ms r0 0.47 m `d 0.5 m into eq.(5). the resulting jacobians are a =  0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 m m g 0 0 0 0 0 0 0 0 0 0 0 −m+m mr0 g 0 0 0  , b =  0 0 0 0 0 0 1 m 0 0 − ρ mρ2+j − 1 mr0 0  , c =  1 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0  . (23) substituting eq.(22), the disturbance torque term in eq.(3) reads τ̃ =  uf + sf − 1 ρ (uc − ρsc) 0  . (24) eq.(24) shows, that the disturbed input of the system can be introduced in the form ũ = u+ λs, where λ = ( 1 0 0 −ρ ) . (25) the frictional forces usually depend on the actuating signals, state variables, and the derivative of the state as well. the general characteristics of the friction reads as s = η(x, ẋ, u). the block diagram of the dynamics of the system is illustrated in fig.2. only the system model block is used for estimator design, which is eq.(5) if the effect of the friction is disregarded, hs(s) = 0. proposition 1. the discrete-time linear crane model obtained from the matrices in eq.(23) and using eq.(8) satisfies the design conditions of the uikf in eq.(9-12). proof. it is clear that dim{y} = 4, dim{d} = 2 and rank{c} = 4, thus eq.(9) and (10) are satisfied. using eq.(8) and the numerical values in table 1, γd = 10−2  0.0001 0 0 −0.025 −0.0002 0 0.2 0 0 −49.975 −0.4255 0  , cγd = 10−2  0.0001 0 0 −0.025 0.2 0 0 −49.975  . (26) we obtain rank{γd} = 2 and rank{cγd} = 2, which are both equal to the number of unknown inputs. this satisfies eqs.(11) and (12). the continuity argument holds for the rank of the matrices in eq.(26), therefore there exists a neighbourhood around our parameter set where the design conditions are still satisfied. simulation the estimation results were obtained by simulation of overhead cranes in a closed-loop scenario using a simple discrete-time pole-placement-based linear controller. the simulation also took into account friction. there are various models of the friction phenomenon, ours included coulomb, stribeck, viscous friction, and stiction [11]. the numerical values of the parameters used in the simulation are given in table 1. because of friction, but mainly stiction, the position of the crane can not be accurately controlled without integrators in the controller. consequently we included the integral of the measurable positions in the controller design as proposed on page 309 of ref. [8]. the outputs to be integrated are yi = ( ` r )t . integrals of these quantities are approximated by the left rectangle rule as xi [k+ 1] = xi [k] +tsyi [k] = xi [k] +tscix[k], (27) where ci is defined so that yi [k] = cix[k]. in our case ci is the first two rows of c in eq.(23). using eq.(27) and eq.(7) a new system model is introduced in the form x̃[k + 1] = φ̃x̃[k] + γ̃u[k] y[k] = c̃x̃[k]. (28) where the expanded state is x̃t = ( xt xti ) and the matrices are φ̃ = ( φ 0 tsci i ) , γ̃ = ( γd 0 ) , and c̃ = ( c 0 ) . (29) for the controller design the process and measurement noises are omitted. 75 ∫ dac system in fig. 2 adc ukf k ki u[k] y y[k]u u0 + ++ yid + xd adc x[k] x yi [k] = (`[k] r[k]) t y[k] yi [k] x̂[k] ŝ[k] uikf x̂[k] ˆ̃u[k] u[k] ckf x̂[k] figure 3: closed-loop estimation setup used in the simulation 0 1 2 3 4 5 6 7 time [s] −10 0 10 20 30 40 50 60 u f , ˆ̃ u f , [n ] uf uikf ukf 0 1 2 3 4 5 6 7 time [s] −1.0 −0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 u c , ˆ̃ u c , [n m ] uc uikf ukf figure 4: actuating signals and the estimated inputs of the system we want the state-feedback controller to output u[k] = −k̃x̃[k] = −kx[k] − kixi [k]. the gain k̃ can be computed using the eigenvalue placement method implemented in matlab’s place algorithm: k̃ = place(φ̃, γ̃, λ), where λ contains the chosen eigenvalues of the closed-loop system. in continuous time they are −1 + 0.5j, −1− 0.5j, −5.1, −5.2, −5.3 −5.4, −5.5, and −5.6. the controller gains are k =  100.594 −0.1273 0.6011 −1.6765 −185.407 0.0458 81.4011 −0.0558 0.0562 −0.3166 −4.2257 −0.0195  t , and ki = ( 46.641 1.6026 −0.074 −2.955 ) . (30) the closed-loop setup is illustrated in fig.3. here the integration is done using the left rectangle rule, and the 0 1 2 3 4 5 6 7 time [s] −0.1 0.0 0.1 0.2 0.3 0.4 0.5 m ea su re d st a te s [m , m / s] ` r ˙̀ ṙ 0 1 2 3 4 5 6 7 time [s] −0.4 −0.3 −0.2 −0.1 0.0 0.1 0.2 u n m ea su re d st a te s [r a d , ra d / s] θ θ̇ figure 5: state evolution of the controlled crane using the true states as feedback adc and dac blocks are analogue-digital and digitalanalogue converters respectively. the dac uses the zeroorder hold method for signal reconstruction. the desired state of the system is xd = ( `d r0 0 0 0 0 )t , `d is the desired position of the cart and yid = cixd. since we only want to demonstrate the results of the state estimation, first the real states are fed back to the controller. to compare the accuracy of our methods to a traditional solution, the classical kalman filter (ckf) [12] is also implemented. as a result, the kalman filters compute the estimated state of the system x̂[k], and they also provide information about the input. the uikf estimates the friction loaded actuating signals directly, while the ukf estimates the frictional forces superposed to the actuating signals. the actuating signals along with the estimates of the real inputs provided by the filters can be seen in fig.4. here, the estimated input of the ukf is computed as ˆ̃u = u[k]+λŝ[k]. because of friction, the real inputs are estimated to be 76 0 1 2 3 4 5 6 7 time [s] 0.00000 0.00005 0.00010 0.00015 0.00020 0.00025 0.00030 0.00035 ` − ˆ̀ [m ] uikf ukf 0 1 2 3 4 5 6 7 time [s] −0.001 0.000 0.001 0.002 0.003 0.004 0.005 ˙̀ − ˆ̇ ` [m / s] uikf ukf figure 6: error of the position and velocity estimations much less than the actuating signals. the large offset in fig.4 is a consequence of the stiction, the cart will not move until uf becomes greater than a certain value (in our case about 28 n). when the cart finally stops moving, the fluctuation of uf tries to counter the load sway, during which the measured states do not change. this is the reason why the estimators find the input to be zero. fig.5 shows the transient of the states in a closedloop. results show that the controller can bring the system into the desired state, but friction prevents it from stopping the low amplitude swinging of the load, because it makes quick, short motions impossible. error estimates are illustrated by figs. 6 and 7. in all cases, the error becomes zero when the crane reaches the desired state. this is not true for the angle and its derivative in fig.8. the error decreases at the end of the state transient, but does not become zero. when the cart stops and the load swings, the measurements are all constant thus they carry no information regarding θ and θ̇. in these situations the cart and winch are usually also motionless due to friction. consequently, the estimation error of these quantities never becomes zero. it is possible to decrease the estimation error using two laser slot sensors. with the help of such devices, θ can be measured accurately in two positions and through the application of proper sensor fusion techniques the estimation of the angle can become more precise in between the chosen positions as well. in fig.9 the estimation error of θ and θ̇ is illustrated using ckf. the filter was designed for the dynamics given by eq.(7) except that it does not consider the inputs unknown. the results show that the error is substantially higher than in the case of the uikf or ukf. 0 1 2 3 4 5 6 7 time [s] −0.00005 0.00000 0.00005 0.00010 0.00015 r − r̂ [m ] uikf ukf 0 1 2 3 4 5 6 7 time [s] −0.0010 −0.0005 0.0000 0.0005 0.0010 0.0015 0.0020 0.0025 0.0030 0.0035 ṙ − ˆ̇ r [m / s] uikf ukf figure 7: error of the rope length and hoisting velocity estimations 0 1 2 3 4 5 6 7 time [s] −0.003 −0.002 −0.001 0.000 0.001 0.002 0.003 0.004 0.005 θ − θ̂ [r a d ] uikf ukf 0 1 2 3 4 5 6 7 time [s] −0.020 −0.015 −0.010 −0.005 0.000 0.005 0.010 0.015 0.020 0.025 θ̇ − ˆ̇ θ [r a d / s] uikf ukf figure 8: error of the angle and angular velocity estimations fig.8 shows the estimation error of the ukf to be less. we applied this estimator in a closed-loop scenario identical to the one presented in fig.3, but instead of x[k] the x̂[k] of the ukf was used in the feedback loop. the state evolution of the crane in this simulation is illustrated in fig.10. the system’s behaviour is only slightly different from the case when the actual states were used in the feedback control in fig.5. 77 0 1 2 3 4 5 6 7 time [s] −0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 θ − θ̂ [r a d ] 0 1 2 3 4 5 6 7 time [s] −5 −4 −3 −2 −1 0 1 2 3 θ̇ − ˆ̇ θ [r a d / s] figure 9: error of the angle and angular velocity estimations using ckf conclusion it was shown that in most mechanical systems the disturbing effect of friction can be reduced to the actuating signals. based on this statement, two estimation methods were provided for the computation of the unmeasured states. one of these techniques considers the inputs completely unknown and uses uikf for the estimation. the other algorithm treats the inputs as distorted by an additive disturbance, and applies ukf with a load predictor extension. simulation results in a closed-loop controlled scenario were provided to prove the applicability of the concepts. it was also pointed out, that the precision of the estimators could be improved using laser slot sensors. this will be the subject of a forthcoming paper. references [1] hyla p.: the crane control systems: a survey, proc. 17th int. conf. methods and models in automation and robotics (mmar), 2012, 505–509 [2] schindele d., menn i., aschemann h.: nonlinear optimal control of an overhead travelling crane, proc. 18th ieee int. conf. control applications, 2009, 1045–1050 [3] boustany f., d’andrea novel b.: adaptive control of an overhead crane using dynamic feedback linearization and estimation design, proc. ieee int. con. robotics and automation, 1992, 1963–1968 0 1 2 3 4 5 6 7 time [s] −0.1 0.0 0.1 0.2 0.3 0.4 0.5 m ea su re d st a te s [m , m / s] ` r ˙̀ ṙ 0 1 2 3 4 5 6 7 time [s] −0.4 −0.3 −0.2 −0.1 0.0 0.1 0.2 u n m ea su re d st a te s [r a d , ra d / s] θ θ̇ figure 10: state evolution of the controlled crane using the ukf’s estimated states as feedback [4] neupert j., hildebrandt a., sawodny o., schneider k.: trajectory tracking for boom cranes using a flatness based approach, proc. int. joint conf. sice-icase, 2006, 1812–1816 [5] rózsa t., kiss b.: tracking control for towdimensional overhead crane, proc. 8th int. conf. informatics in control, automation, and robotics, icinco, 2011, 1, 427–432 [6] kiss b., levine j., mullhaupt p.: a simple output feedback pd controller for nonlinear cranes, proc. 39th ieee conference on decision and control, 2000, 5, 5097–5101 [7] kiss b., lévine j., müllhaupt p.: modelling, flatness and simulation of a class of cranes, electrical engineering, 1999, 43, 215–225 [8] lantos b.: theory and design of control systems i., akadémia kiadó, 2001 (in hungarian) [9] darouach m., zasadzinski m., onana a.b., nowakowski s.: kalman filtering with unknown inputs via optimal state estimation of singular systems, int. j. sys. sci., 1995, 26(10), 2015–2028 [10] haykin s.s.: kalman filtering and neural networks, john wiley & sons, inc., 2001 [11] armstrong-hélouvry b., dupont p., de wit c.c.: a survey of models, analysis tools and compensation methods for the control of machines with friction, automatica, 1994, 30, 1083–1138 [12] kalman r.e.: a new approach to linear filtering and prediction problems, journal of basic engineering, 1960, 82, 35–45 editorial hungarian journal of industry and chemistry veszprém vol. 42(1) pp. 43–50 (2014) effects of ultrasonic disintegration, hot-compressed liquid water pre-treatment, and steam explosion on solvolysis and digestibility of grain sorghum stover dániel capári,! and andrás dallos department of physical chemistry, university of pannonia, egyetem str. 10, veszprém, h-8200, hungary !e-mail: capari.daniel@gmail.com one of the most promising renewable energy crops and biomass feedstock for biogas production in europe is the c4 plant grain sorghum due to its high photosynthetic efficiency. the release of lignocellulosic material and therefore the acceleration of degradation processes of sorghum stalks and leaves can be achieved using mechanical and thermal pretreatments, which assist to hydrolyse the cell walls and speed the solvolysis of biopolymers. this study is focused on hotcompressed liquid water, steam explosion and ultrasonic pre-treatments of grain sorghum stover. the effectiveness of pre-treatments was evaluated by means of soluble chemical oxygen demand, biochemical oxygen demand, and by the biogas and methane productivities. the results show that the pre-treatments disintegrated the lignocellulosic structure, increased and accelerated the biogas and methane production, and increased the mesophilic anaerobic digestion potential of grain sorghum stover. our laboratory tests demonstrated that the steam exploded grain sorghum stover possess the highest biogas productivity. keywords: grain sorghum stover; hot-compressed liquid water pre-treatment; steam explosion; ultrasonic disintegration, biogas digestion. introduction the grain sorghum is a possible carbohydrate resource for the simultaneous production of bioethanol and biogas due to its advantages over the traditional agricultural crops. the plants have remarkably good co2 absorption ability. grain sorghum is the fifth most important cereal crop grown in the world. the drought tolerance of sorghum is greater than that of corn. furthermore, it is able to regenerate after a period of drought. its productivity is also higher than that of corn, even in dry periods or in lower quality soils. in hungary, sorghum grows in arid areas as a substitution for fodder corn. therefore sorghum could be used to cultivate alternative feedstock for bioethanol production [1] and could be a sustainable crop for energy production in europe. the sorghum grain contains approximately the same amount of starch compared to corn kernels, which makes it attractive as raw material for the production of bioethanol. the agricultural byproduct of sorghum-based bioethanol production, the sorghum stover is a valuable bioenergy substrate for biogas digesters, despite the complex lignocellulosic structures of sorghum stalks and leaves and its resistance to decomposition. the utility and the economic feasibility in biogas power plants can be highly increased by different pre-treatment methods, to assist the disruption of the cell wall structure and to speed-up the solubilisation of the biopolymers in the biogas feedstock [2–4]. the purpose of pre-treatments is to remove lignin and hemicellulose, reduce cellulose crystallinity, and increase porosity [5,6] (fig.1). liquid hot-compressed water (lhcw) pre-treatment is a commonly used hydrothermal method. high temperature and high pressure are applied to maintain liquid phase and to avoid vaporization. during the pretreatment, water is penetrated into the cell structure of the biomass, hydrating cellulose, solubilizing hemicellulose, and slightly removing lignin. lhcw pre-treatment is highly effective for enlarging the accessible and susceptible surface area of cellulose and improving cellulose degradability for microbes and their enzymes [7,8]. after the hydrothermal treatment, the biogas production was increased for pig manure, for municipal sewage sludge and for fruit/vegetable waste figure 1: the disintegration of lignocellulosic material by pre-treatments 44 [9]. the hot water treatment increases the enzymatic hydrolysis and digestion of corn leaf, stalk and fibre [10,11] and the dissolution of solids and xylan of destarched corn fibre [12]. the liquid hot water pretreatment of sorghum bagasse produced higher solubilisation of hemicellulose and cellulose content enrichment [13]. combining hydrothermal treatment and enzymatic hydrolysis of sorghum bagasse resulted in improvement of cellulose and total polysaccharides hydrolysis [14]. steam explosion (se) is one of the most effective methods for the pre-treatment of lignocellulosic biomass. in this process, the biomass is heated with high-pressure steam for a certain period, than the pressure is reduced to atmospheric pressure as quickly as possible. the biomass is undergone on an explosive decompression by this swift reduction of pressure [6,7]. the high efficiency of the steam explosion treatment is due to the thermo-mechano-chemical destruction applied in the method. steam-explosion has been used to treat various kinds of lignocellulosic biomass (i.e. softwood, sugarcane bagasse, corn stalk) for enhanced bioethanol and biogas production [15–19]. sipos et al. [20] demonstrated the efficient effect of pre-treatment by steam on sorghum bagasse characterized by high degree of cellulose hydrolysis. zhang et al. [21] compared four pre-treatment processes including liquids, steam explosion, lime and dilute acid for enzymatic hydrolysis of sorghum bagasse and pointed out that steam-explosion showed the greatest improvement on enzymatic hydrolysis. the biogas yields of anaerobic digestion can be also increased by ultrasonic treatments (ut) to support the solubilisation of raw materials. during the ultrasonic treatment, a cyclic sound pressure is used to disintegrate the cell walls by cavitation. the parameters of the sonication are the power, frequency and time of sonication [3,22]. zhang et al. [23] showed that ultrasonic pre-treatments caused indistinctive effects on bio-hydrogen production. the ultrasonic treatment accelerated the enzymatic hydrolysis of corn stover and sugar cane bagasse cellulose [24] and improved the liquefaction and saccharification of sorghum flour [25]. imam et al. [26] pointed out the positive effects of ultrasonic plus hot water pre-treatment on the conversion of sweet sorghum to hexose and pentose sugars and on lignin, cellulose and hemicellulose concentrations. however, no systematic studies on pre-treatments of grain sorghum stover are available in literature. a correct comparison of the various pre-treatments and the selection of the suitable processes for the disintegration of grain sorghum stover as feedstock for enhanced biogas production are the goals and the novelty of this paper. however, the main message of this work is that a perfect testing is only possible, if there are no differences in the microbial communities in different biogas fermenters, in the inocula used, in the substrates cultivated and in the methods applied to assess pretreatments: chemical analysis, batch tests or continuous ad. therefore this work is focused on liquid hotcompressed water, steam explosion and ultrasonic pretreatments of grain sorghum stover using both fast analytical, biochemical and biomethane potential ad tests to study and comparison the effects of pretreatments on anaerobic digestion without addition of chemicals. the influence of temperature, contact time of thermal treatments, and the effect of sonication energy on decomposition of lignocellulose on a chemical level were determined using laboratory scale experimental techniques. the effectiveness of thermal and ultrasonic treatments was evaluated by scod and bod5 concentrations and by the biogas and methane productivities during mesophilic fermentations. experimental materials sorghum stover investigated in this work consists of leaves and stalks of commercial grain sorghum (milo) hybrid named mexican sweet (code: hf1) harvested from the b12 field at kétegyháza, hungary, and used for pre-treatments and biogas production experiments. this easily grown hybrid with mid-early maturation was developed by j. feczák (agroszemek ltd., szeged, hungary). post-harvest residue grain sorghum stover samples were chopped, homogenized, and analysed for dry substance (ds, 93.6%), organic dry substance (94.5%), and ash (5.5%). deionized water was used in all experiments after cation and anion exchange. liquid hot-compressed water treatments the lhcw pre-treatments were carried out in a 2 l capacity parr 4843 type high-pressure reactor at the temperatures of 100, 150 and 175 °c (0.1, 0.5 and 0.9 mpa, respectively) and at various treating time from 10 to 120 minutes. 25 g of grain sorghum stover were used in each experiment and were added to 1000 g of water. the suspension was introduced in the thermal reactor at room temperature and heated to the set temperature. the pulp slurry was mixed by a built-in stirrer at 300 rpm during the entire treating process to avoid temperature gradients. after treatment, the reactor was cooled down to 30 °c by the built-in cooling system of the reactor using cold water-flow and the treated slurry was removed from the vessel. steam explosion pre-treatments se treatments were performed in a steam explosion laboratory unit (fig.2) consisted of a steam generator (2), a digester vessel (6) and a separator cyclone (8). a 2 l capacity parr 4843 reactor was used for the production of steam with temperatures of 185, 200, and 215 °c and working pressures of 1.1 mpa, 1.6 mpa, and 2.1 mpa, respectively. the se unit operated in batches and equipped with a digester vessel (6) of 200 cm3 volume. the digester vessel was filled with 10 g 45 feedstock per batch and was heated to the desired temperature, directly with saturated steam led to the vessel, by opening the steam inlet valve (5). no catalysts (additional chemicals) were applied in the process. after the steaming time (1–10 minutes), the expansion valve (7) was opened to rapidly reduce the vessel pressure to the atmospheric one. the steamed sample slurry explosively released into the separator cyclone (8). ultrasonic treatments the ultrasonication was performed in a vibracell vcx 750 (sonics & materials, usa) ultrasonic processor operated at constant sonication frequency of 20 khz with maximum power input of 750 w. the radiation was carried out by a 25.4 mm diameter titan alloy (ti6al-4v) probe with removable tip and maximum amplitude of 35 µm. samples of the mixture of grain sorghum stover (1 g) and water (99 g) placed in a temperature-controlled vessel. they were subjected to ultrasonic pre-treatment without additional agitation at different power inputs by adjustment of the amplitude (50, 70 and 100%) and at various sonication durations of from 1 to 10 minutes for each power level. the temperature of the vessel was held constant at 25 °c during the treatment by a high-precision thermoregulator (huber kältemaschinenbau gmbh, germany). aliquot parts of the resulting sorghum stover pulp slurries of samples obtained from pre-treatments were used as substrate in ad test. the rests were filtered to separate the solid fraction from the liquid fraction for analytical measurements (scod, bod5, ph). a set of untreated, blank samples was also tested for chemical analysis and methane potential by ad as the control points of reference for the treated samples. mesophilic anaerobic digestions the anaerobic degradability of untreated, lhcw, se, and ut pre-treated grain sorghum stover slurries was determined in laboratory scale, using a fermenter system contained 12 pyrex batch reactors of 1 l capacities. inoculum for the ad tests was taken from the effluent line of an anaerobic pilot fermenter [27] treating a mixture of swine manure and corn stillage (spent mash remaining after bioethanol distillation) at biogas test facility of denk ltd (kövegyűrpuszta, hungary). the batch reactors were inoculated by 700 g inocula. afterwards a batch of 100 g of grain sorghum stover pulp slurry samples was added under nitrogen atmosphere. furthermore, the digester materials were bubbled with nitrogen gas for 10 minutes to get rid of the air from the liquid phase before each experiment. the batch reactors were kept in a temperaturecontrolled water bath at 37 °c until they stopped producing biogas. the mesophilic ad tests performed for grain sorghum stover substrates including controls were all done in duplicate. during the 36–40 days mesophilic ad tests the flows of the produced biogas were on-line measured by digital flow meters and the daily and cumulated biogas volumes were stored digitally. the methane content was determined by gas chromatography. analytical and biochemical measurements the scod, ph, and bod5 measurements were carried out on the liquid fractions after 10 min centrifugation at 14,000 rpm and 20 °c with a refrigerated universal high-speed, filtration (0.45 µm) centrifuge (unicen mr, herolab, germany). colorimetric scod concentration was measured by the standard methods procedure [28] using a nanocolor vario compact heating block (macherey-nagel, germany) and a multidirect photometer (tintometer/lovibond, germany) according to din iso 15705. biochemical oxygen demand (bod5) was determined according to en 1899-1 and en 1899-2 by using oxitop control 6 oc 100 (wtw, germany) system. the ph values were measured by a c831 type ph meter (consort, belgium) with an ra-0903p sensor (radelkis, hungary) after two-point ph calibration (ph = 4.01 ± 0.01 and ph = 7.00 ± 0.01) using duracal ph buffers (hamilton, switzerland). the surfaces of the grain sorghum stalk were investigated by a philips xl30esem environmental scanning electron microscope (esem) with 20 kv accelerating voltage and resolution of 3.5 nm, in secondary electron image mode (sei), and backscattered electron image mode (bei). results and discussion liquid hot-compressed water treatments the influence of lhcw pre-treatments at various temperatures and treating times on scod concentration of grain sorghum stover slurry is visualized by 3d mesh segmentation on fig.3. the results of lhcw pre-treatments show that hotcompressed water has a positive effect in grain sorghum stover disintegration, leading to significant increments in scod concentration: +262% at 100 °c, +419% at figure 2: scheme of the steam explosion apparatus (1. input valve, 2. steam generator, parr 4843 reactor, 3. pressure gauge, 4. evacuation valve, 5. steam inlet valve, 6. digester vessel, 7. expansion valve, 8. cyclone, 9. sampling valve, 10. steam outlet valve) 46 150 °c and + 698% at 175 °c with an operating time of 60 min, respectively. the control experiments were performed using untreated grain sorghum stover suspension. both temperature and time have positive, but not linear effects on scod and not to the same degree. the temperature raising has more effect on the solubilisation of grain sorghum stover after 60 minutes than the treating time in agreement with the results of valo et al. [29] who found that treating time had less influence than temperature during thermal treatment of sludge. it is notable that higher solvolysis temperatures resulted in more acidic products as reflected by the low ph level of the grain sorghum stover slurry (fig.4). steam explosion pre-treatments the pressures and temperatures of se pre-treatments had significant effect on digestibility of grain sorghum stover. elevated pressures and temperatures resulted in enhanced solubilisation (fig.5). the positive pressure effect may be explained by the increased disintegration caused by higher-pressure drop at the end of treatment. compounds that are more soluble were released from the grain sorghum stover during the steam explosion and made the resulting slurry available to subsequent bacterial degradation. the pressure effect is quasi-linear and the effect of contact time can be modelled by an exponential-tomaximum function. compared to the untreated grain sorghum stover, the scod concentrations of the slurries increased by a factor of 8.9, 9.6, 10 at 185, 200, and 215 °c, respectively, with an operating time of 3 min, respectively. additional, the ph value decreased with pre-treatment pressure (steam temperature) and with the contact time (fig.6). the formation of acidic degradation products during disintegration of grain sorghum stover slurry by steam explosion agree well with the observation of guo et al. [30] at corn stalk steam explosion. ultrasonic treatments the efficiency of ultrasonic irradiation of grain sorghum stover was quantified by scod concentration of the slurry as a function of contact time and power input in terms of ultrasonic amplitude level (%) and specific sonication energy. results of ultrasonic treatments are shown in fig.7, where the values of the scod figure 4: acidity of grain sorghum stover slurries as the function of lhcw contact time and temperature (!: experimental data point) figure 3: effects of temperatures and contact times of lhcw pre-treatments on scod concentration of grain sorghum stover suspension (!: experimental data points) figure 5: effects of steam pressures on scod concentration levels of grain sorghum stover slurries as the function of the contact time during steam explosion (!: experimental data points) figure 6: the effect of steam explosion on ph values of treated grain sorghum stover slurry at various steam pressures as the function of the treatment time (!: experimental data points) 47 concentrations are presented for each value of the ultrasonic amplitude level (%), and sonication time. the scod of the pulps increased with the ultrasonic power demonstrating the effectiveness of the cavitation energy to disrupt the cell walls of the plant parts. the scod concentration excess reached +105%, +109%, and +133% at 50%, 70%, and 100% amplitude level, respectively, with a contact time of 3 min. the ultrasonic power and the pre-treatment time affect the scod to a different degree. the raising of scod values by treating time is stabilized after 3 minutes. these can be described by an exponential-tomaximum function. the effect of energy-input on scod is quasi-linear (r2 = 0.942) as demonstrated by the data shown in fig.8, where scod values are plotted against the specific sonication energy. the scod concentrations were increased by the sonication energy; however, no power-saturation phenomenon was observed. the sonication energy over the minimal energy of 1kj g-1 ds is the most effective for breaking up cells [31]. the ph values of the sonicated grain sorghum stover slurries decreased monotonously with pre-treatment time and sonication power on a small scale (fig.9) suggesting that local temperature effects caused by cavitation bubbles were not enough to accelerate the hydrolytic processes resulted in acidic degradation product. environmental scanning electron microscopy the esem pictures of the surfaces on untreated and by ultrasonic treated grain sorghum stalks are shown in fig.10 at 100× magnification. the surface of the treated sorghum stalk was altered (fig.10b) from the appearance of defective plant tissues. fig.10b shows a heterogeneous appearance compared to the homogeneous surface of the untreated stalk (fig.10a). the comparison of the pre-treatment results of the chemical analysis, the scod concentration, and ph changes of grain sorghum stover slurries suggested that the most effective disintegration method is the steam explosion to disrupt the lignocellulosic structure of grain sorghum stover and partial hydrolysis of it molecular components. however, results of these fast methods can only indicate how much structures of lignocellulosic materials broke down on a chemical level. nevertheless, greater decomposition of the lignocellulose structures does not necessarily prove enhanced biogas production, because inhibitors for methanogenesis reactions can also be produced through hydrolytic processes during steam explosion. furthermore, one has to take into account the high energy needs of treatments at elevated temperatures. according to the results of fast chemical analyses (scod and ph), the optimal conditions for the lhcw, steam explosion and ultrasonic treatment of grain sorghum stover were established as 150 °c / 30 min, 200 °c / 3 min and 100% ultrasound amplitude / 3 min (at 25 °c), respectively. however, to study the real effect of optimal conditions of the investigated pre figure 8: scod change in grain sorghum stover slurry as a function of specific sonication energy (!: experimental data points) figure 7: the effect of sonication energy on scod concentration level of grain sorghum stover slurry as the function of sonication time and relative ultrasound amplitude (!: experimental data points) figure 9: the effect of sonication power on the ph values of grain sorghum stover slurries as the function of the sonication time (!: experimental data points) figure 10: esem pictures of the surface on untreated (a) and by ultrasonic treated (b) grain sorghum stalks at 100× magnification 48 treatments additional biochemical tests like bod and biomethane potential determinations are necessary. biochemical oxygen demand a comparison of the biochemical oxygen demands of filtrates of grain sorghum stover slurries after pretreatments at the optimal conditions is given in fig11. the results of the bod5 tests support the observations from chemical analysis. actually, all three methods investigated are appropriate for pre-treatment of grain sorghum stover, because the bod5 values systematically increased in filtrates of grain sorghum stover slurries with the treatment time under the conditions investigated. however, the highest bod5 values were obtained in filtrates after steam explosion, therefore the steam explosion seems to be the most effective disintegration method to disrupt the lignocellulosic structure of grain sorghum stover and to partially hydrolyse its molecular species, resulting in the formation of bacterially digestible substrate. biogas production by mesophilic anaerobic digestions biogas and biomethane production tests were carried out using grain sorghum stover slurries pre-treated under stated optimal conditions (lhcw: 150 °c / 30 min, steam explosion: 200 °c / 3 min, and ultrasonic treatment: 100% ultrasound amplitude / 3 min at 25 °c). daily as well as the final biogas and methane production (normalized volumes at 0 °c and 101.15 kpa) were determined. the results are shown as a function of the digestion time in figs.12 and 13. the specific gas productions were calculated by dividing the cumulated gas amount with the total ds of the substrates. as reference, the untreated material was used in the same amount. in agreement with the results of chemical analytical and biochemical tests after pretreatments, the specific total biogas and methane yields obtained for treated grain sorghum stover substrates were significant higher than that of the untreated control. as seen in fig.12, biogas productions began immediately, without a lag period after starting the degradation of grain sorghum stover. the fastest biogas production at the beginning was detected at the ultrasonicated substrate. however, the highest biogas production was observed during the fermentation of steam-exploded substrate. the biogas production proceeded in constant and high daily biogas production for treated substrates until the 30th day of hydraulic retention time. this observation is notable, because the application of pre-treatments can decrease the usual cycle time for biogas fermentation and increase the production of biogas with higher methane content. the comparison of the biomethane yields is given in fig.13. methane production, as the major result of anaerobic digestion of pre-treated grain sorghum stover, was markedly increased by the three pre-treatments. the highest biomethane production rate was observed at the substrates after ultrasonic and steam explosion pretreatments. the biomethane production rate of lhcw figure 11: comparison of the bod5 test of filtrates of grain sorghum stover slurries after various pre-treatment methods figure 12: specific cumulative biogas yield (ncm3/g ds) of grain sorghum stover substrates after pre-treatments figure 13: specific cumulative methane yield (ncm3 g-1 ds) of grain sorghum stover substrates after pre-treatments 49 treated substrate was lower, probably due to the low ph of the pre-treated grain sorghum stover slurry. our laboratory tests have shown that the steam exploded substrate possess has the highest biogas production potential (439 ncm3 g-1 ds) during hydraulic retention times of 36 days with 55% methane content. the steam explosion pre-treatment increased the biomethane yield by +72% to 242 ncm3 g-1 ds. the lhcw pre-treated substrate has the second highest biogas production potential (403 ncm3 g-1 ds) during hydraulic retention times of 36 days with 52% methane content, the lhcw pre-treatment increased the biomethane yield by 49% to 210 ncm3 g-1 ds. this yield increment is higher than that was obtained by qiao et al. [9] for various biomass wastes after hydrothermal treatment. the substrate after ultrasonic pre-treatment has a biogas production potential of 383 ncm3 g-1 ds during hydraulic retention times of 36 days with 44% methane content, the ultrasonic pre-treatment increased the biomethane yield by 18% to 167 ncm3 g-1 ds. the low biogas and methane yields of ultrasonic treated grain sorghum stover can be explained by the superficial effect of ultrasonic cavitation. conclusions the results of chemical, biochemical analyses and biogas/biomethane potential test obtained by mesophilic anaerobic digestion were presented. it was found that lhcw treatment and steam explosion are the most effective biomass pre-treatment for increasing the solubilisation of the organic matters of grain sorghum stover. laboratory testing of anaerobic digestibility of pre-treated slurries have shown that the grain sorghum stover has high biogas potential. it can serve as biogas feedstock and could reduce the energy consumption of sorghum-based bioethanol production in the future. the lhcw and steam explosion biomass pre-treatment techniques can reduce the cycle time and improve the biogas production via disintegration of the complex and compact plant structures of grain sorghum stover. acknowledgements this research was supported by támop 4.2.4. a/2-111-2012-0001 „national excellence program – elaborating and operating an inland student and researcher personal support system”. the project was subsidized by the european union and co-financed by the european social fund. authors also gratefully acknowledge the support of the hungarian state and european union under the támop-4.2.2.a11/1/konv-2012-0071 project. references [1] saldivar s.r.o.s., carrillo e.p., alvarez m.m.: method for obtaining bioethanol from sorghum grain (sorghum bicolor l.moench) comprising steps involving decortication and hydrolysis with proteases. patent application number: us 20110014671 a1, 2011 [2] mcmillan j.d.: pre-treatment of lignocellulosic biomass, in: enzymatic conversion of biomass for fuels production (eds: m.e.himmel, j.o.baker, r.p.overend), acs symposium series, 1994, 566, 292–324 [3] cesaro a., naddeo v., amodio v., belgiorn v.: enhanced biogas production from anaerobic codigestion of solid waste by sonolysis, ultrasonics sonochemistry, 2012, 19(3), 596–600, [4] harun m.y., radiah a.z.d., zainal abidin z., yunus r.: effect of physical pre-treatment on dilute acid hydrolysis of water hyacinth (eichhornia crassipes), biores. technol., 2011, 102(8), 5193–5199 [5] sun y., cheng j.: hydrolysis of lignocellulosic materials for ethanol production: a review, biores. technol., 2002, 83(1), 1–11 [6] haghighi mood s., hossein golfeshan a., tabatabaei m., salehi jouzani g., najafi g.h., gholami m., ardjmand m.: lignocellulosic biomass to bioethanol, a comprehensive review with a focus on pre-treatment. renew. sustain. energy rev., 2013, 27, 77–93 [7] zheng y., zhao j., xu f., li y.b.: 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c., brewer m., hendrickson r., ladisch m.: pre-treatment of corn fiber by pressure cooking in water, appl. biochem. biotech., 1998, 73(1), 1–17 [13] rohowsky b., häuler t., gladis a., remmele e., schieder d., faulstich m.: feasibility of simultaneous saccharification and juice cofermentation on hydrothermal pretreated sweet sorghum bagasse for ethanol production, appl. energy, 2013, 102, 211–219, 50 [14] dogaris i., karapati s., mamma d., kalogeris e., kekos d.: hydrothermal processing and enzymatic hydrolysis of sorghum bagasse for fermentable carbohydrates production, biores. technol., 2009, 100(24), 6543–6549 [15] söderström j., pilcher l., galbe m., zacchi g.: two-step steam pre-treatment of softwood by dilute h2so4 impregnation for ethanol production, biomass bioene., 2003, 24(6), 475–486 [16] kaar w.e., gutierrez c.v., kinoshita c.m.: steam explosion of sugarcane bagasse as a pretreatment for conversion to ethanol, biomass bioene., 1998, 14(3), 277–287 [17] xu g.z., fan s.y., zhang b.l., liu j.b.: anaerobic fermentation characteristics of corn straw pretreated by steam explosion, adv. mat. res., 2012, 512–515, 334–337 [18] wang x.t., cai h.z., liu l.s.: experimental study on anaerobic fermentation of steam explosion pretreated corn stalk, adv. mat. res., 2011, 183–185, 1975–1978 [19] varga e., réczey k., zacchi g.: optimization of steam pre-treatment of corn stover to enhance enzymatic digestibility, appl. biochem. biotechnol., 2004, 113–116, 509–23 [20] sipos b., réczey j., somorai zs., kádár zs., dienes d., réczey k.: sweet sorghum as feedstock for ethanol production: enzymatic hydrolysis of steam-pretreated bagasse, appl. biochem. biotechnol., 2009, 153(1–3), 151–162 [21] zhang j., ma x., yu j., zhang x., tan t.: the effects of four different pre-treatments on enzymatic hydrolysis of sweet sorghum bagasse, biores. technol., 2011, 102(6) 4585–4589 [22] apul o.g., sanin f.d.: ultrasonic pre-treatment and subsequent anaerobic digestion under different operational conditions, biores. technol., 2010, 101(23) 8984–8992 [23] zhang k., ren n., guo c., wang a., cao g.: effects of various pre-treatment methods on mixed microflora to enhance biohydrogen production from corn stover hydrolysate, j. env. sci., 2011, 23(12), 1929–1936 [24] yachmenev v., condon b., klasson t., lambert a.: acceleration of the enzymatic hydrolysis of corn stover and sugar cane bagasse celluloses by low intensity uniform ultrasound, j. biobased mat. bioene., 2009, 3(1), 25–31 [25] shewale s.d., pandit a.b.: enzymatic production of glucose from different qualities of grain sorghum and application of ultrasound to enhance the yield, carbohydr. res., 2009, 344(1), 52–60 [26] imam t., capareda s.: ultrasonic and hightemperature pre-treatment, enzymatic hydrolysis and fermentation of lignocellulosic sweet sorghum to bio-ethanol, int. j. ambient ene., 2012, 33(3), 152–160 [27] förhécz j., regős j., göblös sz., dallos a.: planning, construction and testing of a biogas pilot plant with mesophilic biodigester, prof. 37th international conference of slovak society of chemical engineering, tatranské matliare, slovakia, ed.: markos, j., 2010, pp. 325 [28] apha, standard methods for the examination of water and wastewater, 20th ed.american public health association, washington, dc, usa, 1999, [29] valo a., carrère h., delgenès j.p.: thermal, chemical and thermo-chemical pre-treatment of waste activated sludge for anaerobic digestion, j. chem. technol. biotechnol., 2004, 79, 1197–1203 [30] guo p., mochidzuki k., cheng w., zhou m., gao h., zheng d., wang x., cui z.: effects of different pre-treatment strategies on corn stalk acidogenic fermentation using a microbial consortium, biores. technol., 2011, 102(16), 7526–7531 [31] bourgrier c., carrère h., delgenès j.p.: solubilisation of waste-activated sludge by ultrasonic treatment, chem. eng. j., 2005, 106, 163–169 page 1 page 2 page 3 page 4 page 5 page 6 page 7 page 8 page 9 page 10 page 11 page 12 page 13 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578 page 579 page 580 page 581 page 582 page 583 page 584 hungarian journal of industrial chemistry veszprem vol. 30. pp. 7779 (2002) fine bubble generation in a column reactor by placement of a diaphragm across a low frequency sound field k. m. sw amy1·* and f. j. keil** (department of chemical engineering, technische universitat hamburg-harburg, eissendorfer strasse 38, d-21071 hamburg, germany 1regional research laboratory, bhubaneswar-751 013, india) received: october 25, 2001 low frequency sound (50500 hz) is known for improving mass transfer in a gas-liquid medium. for fast reactions in bubble . columns low frequency sound waves can be used for the enhancement of mass transfer. any reduction in ~ener~t10~ of fine bubbles will result in increasing the yield for mass transfer area controlled reactions. in the present mvestlgation, through placement of a diaphragm across a sound field, bubble sizes were further reduced by about 8.3%. these phenomena are demonstrated in the present paper. keywords: bubble generation, diaphragm, column reactor, sound field introduction fast reactions in bubble columns are mass transfer controlled. therefore, an acceleration of mass transfer is of great importance for an increased bubble column reactor performance. gas dispersion typically supplies the gas needed for a chemical reaction in a liquid, or the oxygen demanded by organisms in bioengineering. in all such processes, a compone11t is required to be transferred from the gas bubbles to the surrounding liquid. for fast chemical reactions, the overall processes are limited by the efficiency of transfer of gas from the bubbles to the liquid phase. the present paper reports the development of a novel diaphragm which reduces the bubble diameter mainly owing to a wetting effect, and as a consequence the mass transfer rate per unit volume is increased. additionally, low-frequency sound applied to a bubble column enhances fast reactions by avoiding coalescence and breakage of large bubbles and an accelerated flow arround the bubble. the energy input into the bubble column by a low frequency vibrator is an order of magnitude less than that for a stirred gas-liquid vessel. the vibration frequency has to be tuned to obtain a maximum area per unit volume. this effect was demonstrated by harboum and hourghton [1], baird [2], jameson and davidson, [3], jameson [4], bartsch [5], andkrishna et al. [6]. experimental the preliminary measurements and characterization of bubbles generated are performed using a configuration. shown schematically in fig. i, by means of video technique. the vibration device is mounted at the bottom of the column as displayed. the column is filled with demineralised/degassed water. the volumetric gas flow of 5% of the total volume of a column nearly 400 cc/min was maintained constant throughout the experiment and the quantity of air is measured. with a view to demonstrate resonance-induced bubble production, experiments have been carried out in a 40 mm diameter glass column having a double walled cell with a height of 1.2 m. sound vibration in the frequency range from 10hz to 5khz, in the power range of 530 w was produced by a vibrator which can deliver 500w. at various positions along the column. the bubble size distribution is recorded using a video camera: sony ssc m 370 ce ( it was a ccd black and white camera) along with camera adapter: lis ·w 130 p. further details of the system used are: cannon tv zoom lens ph 6x8~ii. 8-48 mm. 1:1.0 (no. 112 054), .:guest scientist on senior daad fellowship. e-mail: km_swamy@yahoo.com; author to whom correspondence is to be made: tel: +49-40/42878-3042 fax: +49-40/42878-2 i 45; e-mail: keu@tu-harburg.de 78 video camera frequency generator g g 8 0 g 8 g 0 q 0 8 0 0 8 0 0 +amplifier t------. g () ~ ~ g 0 0 8 0 0 0 0 g 8 0 g q 8 0 8 0 0 g 8 & 0 fig.l experimental test set up small bubbles cloth/grid coagulation air inlet made in japan, in association with a video recorder jvc hr.-86900 eg. the data were evaluated by a computer programm called image grabber 24 by neotech. development of a novel diaphragm a metal plate as a gas sparger has been designed with radial slots, as shown in fig.2, arranged in three concentric rings of slots. each slot is of 1.5 mm width and 2.5 mm length. eddying and high pressure is avoided by the flow distribution through the slots of the plate. the radial slot plate has shown some improvement in generating fine bubbles reducing an average bubble size by 4% compared to conventional needle system~ which is not a remarkable achievement. therefore, a new diaphragm was developed, see fig.3. it consists of two elements, a thin copper plate and a filter cloth fastened on it. a copper plate of 35 rom diameter was taken and six concentric circles having 6.10~15,20,25 .. and 30 mm. diameters were marked. leaving the central circle, a number of holes were pierced in the space available between alternate rings using a 0.45 mm diameter fine needle. about 40 holes per sq. em. are approximately made in the available annular space. then in a composite style the diaphragm was made by fastening together the copper plate with a filter cloth which was attached to the copper plate by glue put on the outer edge as well as in the inner annular space available between concentric rings having holt$. at the centre of this system a hollow metal tube of 6 mm diameter is fumly fixed for holding the system as wen as to facilitate the gas to flow through. a set of four cable binders are used for holding the system firmly and to maintain concentricity and for keeping it coaxially with the glass column. slot detail i1i lmglli e 2.5 mm .j. . width = 1.5 rom orifice plate fig.2 radial slot plate for improved bubble generation filter cloth ( ~35mm0~ .·,<,l~·· .. ~ fig.3 a composite novel diaphragm developed results and discussion initially gas is injected through a conventional needle sparger at a rate of 400 cc/min. bubbles are formed successively emerging out from the needle tips. as soon as the sound is applied (using 50 hz frequency, 25 w power) the bubbles are recorded by a videa camera, and the bubble size distribution is determined at a distance of 50 em above the sound source. then using a thin copper plate along with a filter cloth, as shown in fig.3, it has been observed that the bubble size radii were considerably reduced. in order to get a bubble size reduction, the frequency of the vibrator and the distance of the diaphragm from the column bottom have to be fine-tuned. the diaphragm should be placed at a position where the liquid convection owing to the vibrator is strong. gas of about nearly 5% by volume was injected from bottom through needles at a rate of 400 cc/min. in an these experiments the diaphragm is placed in such a way that always the metal foil was facing the sound source at the bottom, whereas the filter cloth was located upwards. the positive effect of introducing the newly developed diaphragm in improving bubbles to finer sizes can be clearly seen in fig.4. the effect of the newly developed diaphragm is that bubbles are smaller with uniform distribution. a comparative study of bubbles· produced before (without) and after (with) the introduction of new fig.4 bubble distribution with new diaphragm when placed across a sound field composite diaphragm clearly reveals that introduction or replacement of new composite diaphragm across a low frequency sound field produces finer bubbles, and, therefore, leads to a further increased surface area responsible for enhanced mass transfer. by measuring the bubble diameters for at least 100 bubbles on either side of the central vertical axis, the average sauter mean diameter values of bubbles were computed. the average bubble diameters thus obtained without and with the use of the new diaphragm are 1503 and 1378 j..tm respectively. this study demonstrates that about 8 9% smaller "bubbles can be obtained by inserting the new diaphragm into the sound field. in the present study, chances of bubble coalescence is low since the bubbles released through the neighbouring zones maintain definite time lag intervals caused by sound vibrations. the interfacial area per unit volume for the above set of conditions was evaluated. the results revealed that there has been a 1.4 times increase in interfacial area by the introduction of the new diaphragm across the existing sound field. hence the 79 results are encouraging. one should keep in mind that the vibrator increases the surface area already by 50%. an important finding in this investigation is that the bubble size depends mostly on the materhil of which the filter cloth is made rather than the port or mesh sizes of the metal or filter cloth. conclusions 1. the newly developed diaphragm when placed across the sound field can produce at least 8 9% smaller bubbles compared to the bubble size obtained by the vibrator alone. the vibrator together with the diaphragm gives an increase in the transfer surface by a factor of 2.1. this leads for fast reactions to considerably higher yields per unit time and volume owing to an improved mass transfer. 2. if the diaphragm is closely placed to the sound source, further improved effects are expected. acknowledgements one of the authors (dr. kms) grateful to the german academic exchange service (daad) bonn, germany for awarding a senior daad fellowship and to dr.vibhuti n misra, the director of the regional research laboratory (council of scientific and industrial research, new delhi), bhubaneswar, india for deputation. the author is grateful to dr. a. bartsch for helping in conducting experiments in a column at technical university hamburg-harburg. references 1. harboum k. l. and hourghton g.: chern. eng. sci., 1960, 13,90-92 2. baird m. n. 1.: chern. eng. sci., 1963, 18, 685 687 3. jameson g. j. and davidson j. f.: chern. eng. sci., 1966, 21, 2934 4. jameson g. j.: chern. eng. sci., 1966, 21, 3548 5. bartsch a.: z. naturforsch, 1995, 50a. 228 234. 6. krishna r., eu.enberger j., urseanu m. i. and keil f. j.: naturwissenschaften z(}(x), 87, 455 459 7. valentin f. h. h. and preen b. v.: chern. ing.tech. 1962, 34, 194199 page 73 page 74 page 75 microsoft word a_16_miokovics_r.doc hungarian journal of industrial chemistry veszprém vol. 39(1) pp. 127-131 (2011) effects of surfactants on the aggregate stability of soils e. miókovics , g. széplábi, a. makó, h. hernádi, t. hermann university of pannonia, georgikon faculty, department of crop production and soil sciences 16. deák f. st. keszthely, h-8360, hungary e-mail: miokovics.eszti@gmail.com in spite of surfactants being widely used and their toxic effects on living organisms has been well known we have only little information about how they influence the different properties of soils. however, surfactants may cause changes in the physical, chemical and microbiological parameters of soils. they can modify the structure of soils through the aggregate stability, as well as the fertility indirectly. in our study we investigated the effects of cetilpyridinium chloride (a cationic surfactant) on aggregate stability of eight different soil horizons. aggregate stability measurements were performed based on the wet sieving method immediately following various pre-treatment procedures. there were compared the sas values (percentages of the stable aggregates) of soils pre-treated with distilled water or surfactant solutions of various concentrations. it was found that the aggregate stability of soils increases to the highest level in case of the soil samples treated with moderate amounts of surfactant which form nearly monomolecular adsorptive layer on soil surfaces. keywords: soil pollution, surfactant, aggregate stability, wet sieving method introduction surfactants are one of the most common organic pollutants in the subsurface environment. they originate mainly from detergents used by households and industry. the amount of surfactants in the soil system is increasing due to wastewater irrigation and land application of sewage sludge. moreover, they are indispensable components of agrochemicals because they are used during pesticide formulations [1-3]. surfactants are also frequently used in remediation technologies to remove napl (nonaqueous-phase liquids, such as fuels, chlorinated solvents) from the subsurface [4, 5]. it is possible to control water infiltration into the soil during irrigation using surfactant treatments of soils [6]. surfactants are organic molecules composed of strongly hydrophilic and hydrophobic groups or moieties. this is often referred to as amphiphilic because of its dual nature. the hydrophobic portion of the surfactant molecule is typically a long alkyl chain (lengths of c10 to c20). the hydrophilic group often includes anions or cations, has an electrical charge, or is polarized, and can form hydrogen bonds [7]. surfactants may contaminate the soils in relatively high concentrations [8-10]. depending on the extent of accumulation or adsorption of surfactants on gasand solid-liquid interfaces, surfactants may affect the physical properties of soils, including hydraulic conductivity [11, 12], water retention [3] or stability of soil aggregates [13]. although the potential effects of surfactants on soil– water interactions have been discussed in the literature [14-16], little information is available regarding the changes in aggregate stability caused by surfactant adsorption. the soil aggregate stability may change, if the adsorbed surfactants modify the soil hydrophobicity, destroying the cementing agents of aggregates or exchange the cations. the altered soil aggregate stability enables changes in soil porosity and pore size distribution and thereby affects the fluid retention and fluid conductivity of soils [17]. the aim of this study was to improve our understanding the effects of surfactant adsorption on the soil aggregate stability. aggregate stability measurements were performed using the traditional wet sieving method involving different hungarian soils pre-treated with a cationic surfactant (cetilpyridinium chloride). materials and methods in our investigation a cationic surfactant, cetilpyridinium chloride (cpc) was used in three different concentrations. cpc has a positive charged pyridine end and it is a widely used cationic quaternary compound of several household products, for example anti-static additives and emulsifiers. properties of the investigated eight soil samples from six different soil types are shown in table 1. 128 table 1: the origin and properties of the studied soil samples c la y + fe ox ih yd ra te s % (< 0. 00 2 m m ) si lt % (0 .0 02 -0 .0 5 m m ) sa nd % (> 0. 05 m m ) h um us (% ) c ac o 3 (% ) sa m pl e nu m be r wrb soil classification & name of the closest city sy m bo l a nd d ep th o f ge ne tic h or iz on s ( cm ) solid part of the soil (100 %) c e c (m ge q/ 10 0 g) 1 vertic stagnic solonetz (clayic) karcag b 5–30 51.09 45.90 0.88 2.00 0.13 40.85 2 hortic terric cambisol (dystric. siltic) keszthely a 0–30 21.09 33.13 44.28 1.45 0.05 11.84 3 hortic terric cambisol (dystric. siltic) keszthely b 30–50 22.90 33.87 42.29 0.93 0.00 12.38 4 cutanic luvisol (siltic) várvölgy a 0–20 15.27 29.35 54.05 1.33 0.00 10.36 5 cutanic luvisol (siltic) várvölgy b 20–50 22.30 26.56 50.49 0.65 0.00 12.78 7 vertic gleyic luvisol (manganiferric. siltic) magyarszombatfa b 20–50 38.96 25.93 34.61 0.49 0.00 16.78 9 vermic calcic chernozem (anthric. siltic) kápolnásnyék a 0–30 27.60 51.68 7.50 3.70 9.52 30.25 12 gleyic vertisol (clayic) kisújszállás a 0–30 53.88 41.19 1.05 3.89 0.00 35.69 figure 1: wet sieving apparatus for aggregate stability measurement equipment used during the aggregate stability measurements was constructed by the federal agency for water management, institute for land & water management research (from petzenkirchen, austria) (fig. 1). it works according to the principle of wet sieving method [18]. however, in this case not the soil but the water surrounding the soil sample is moved, thus water percolates through the soil during the shaking. the aggregate stability measurements were done according to the wet sieving method, mentioned below. to separate the fractions between 1 and 2 mm, air dried soil samples were sieved for the pre-treatments. it is not allowed to pulp or destroy the samples during drying nor or sieving, only to crumble them gently. after sieving we placed the different sized soil particles into a measuring pot and four grams of them in three repetitions were weighted with an analytical scale. we had to be very careful not to disturb the soil particles. the soil samples were thereafter pre-treated with distilled water or solutions or there remained in dry untreated condition (see below). then the samples were taken in the six small sieves of the equipment. the mesh of the sieves was 0.25 mm in diameter. 80 ml distilled water was poured into the iron cups which were fixed to the upper side of the measuring equipment. after that the cups and the soil samples were taken into the apparatus. as we wetted the soil samples with some distilled water, the floating soil particles sank down to the bottom of the iron cup. after five minutes of wet sieving the soil samples were dried at 105 °c for 48 hours (drying 1). the weights of the dried samples were measured. to determine the amount of the residual aggregates of the investigated soil samples after wet sieving, the aggregates were destroyed using sodium hexametaphosphate. thus the aggregates were separated from the sand particles larger than 0.25 mm and from the organic and inorganic debris. after disaggregating the samples we repeated the wet sieving and the drying stages. finally, the weight of soil samples were measured again (drying 2) and the percentage of the stable aggregates (sas) was calculated according to the eq 1. 100 20 21 ⋅ − − = mm mmsas (1) where: m1 – weight of the soil sample after the first drying (g), m2 – weight of the soil sample after the second drying (g), m0 – weight of the originally used dry soil sample (g). the aggregate stability measurements were performed after applying various pre-treatment methods. first the soil aggregate stability was measured according to the 129 standard method. it means that the soil aggregates were taken in dry condition on the small sieves of wet sieving apparatus, without any previous soaking in distilled water or surfactant solution. secondly the aggregate stability measurements were performed with soil samples which were previously soaked in distilled water or surfactant solution for two days. based on the results of our preliminary experiments, there were used surfactant solutions of three different concentrations (table 2). the applied surfactant concentration values were determined based on the soil sample with the highest adsorption capacity (sample 12, gleyic vertisol) (table 1). at the sample 12 the effect of wetting procedure was also investigated. it was compared the aggregate stability of with distilled water gradually and normally wetted soils. table 2: the different concentration of surfactant solutions concentration of surfactant solutions (g/ 1000 ml) k. 1 k. 2 k. 3 30.9700 3.0970 0.3097 results fig. 2 shows the results of our preliminary experiments with sample 12. the aggregate stability of this highly clayey soil sample was relatively high at all pre-treatments. comparing the standard method with soaking in distilled water is visible that two days soaking destroys some aggregates. the effect of carefully wetting was moderate. if we compare the percentages of stable aggregates between distilled water and surfactant treated samples (after two days soaking) it is ascertainable that the surfactant adsorption increases the aggregate stability. the highest stability was observed in case of applying surfactant solution in medium concentration. this was the concentration at which the solution covers the surface of the soil particles approximately in monomolecular layer. our results showed that the aggregates were less stable both in case of the applied minimum (k3) and the maximum concentration (k1). figure 2: the aggregate stability of soil sample 12 as the results of the standard measurement demonstrate in fig. 3, the sample 1 (vertic stagnic solonetz) (which tends to be strongly dispersed because of its high sodium content) was the less stable and the sample 4 (cutanic luvisol) was found to have the most stable aggregates. that might be caused by the combined effect of clay minerals, humus materials and fe-oxihydrates as cementing agents. the effectiveness of the surfactant treatment at different soils was evaluated according the rate of stable aggregates of surfactant treated and non-treated (two days in distilled water soaked) soils. fig. 4 shows the effects of the different pre-treatment methods on soil aggregate stability at the different soil samples. it is visible how the surfactant solutions in various concentrations change the resistance of soil particles against water. fig. 4 does not contain the results of the sample 1 because the change of this sample’s aggregate stability was extreme and not comparable with the other samples in that case (fig. 5). figure 3: the results of the aggregate stability measurements according to the standard figure 4: increasing in aggregate stability in case of different concentration of surfactant solutions the sample 2 has favorable aggregate stability states, both after using the standard method as well as after 2 days of soaking because of the relative high organic matter and clay content of the soils. different rate of effects of surfactants on the soil sample’s aggregate stability was observed in case of all three surfactant concentrations. according to our results sample 3 has the same stability both after the standard method and also with soaking. a decrease of aggregate stability was observed at high surfactant concentration (k1), which was caused by the multilayer adsorption of surfactants on the surfaces of soil particles. in that case the surfactant might create a partly hydrophilic layer on the surfaces which may lead to the dispersion of the particles. the highest aggregate stability values were measured in case of medium surfactant concentration. at this concentration the soil 130 surfaces are covered with surfactant molecules in approximately monomolecular layer and therefore the soil show hydrophobic characteristics. using the k3 concentration the soils weren’t able to adsorb enough surfactant molecules, the surfaces remained partly hydrophilic. similarly to sample 3, the cpc had the same stability effects on sample 4-9. the big amount of adsorbed surfactant at k1 concentration caused the highest decreasing of stability rate at sample 7. the pre-treatment with k3 surfactant solute enhanced the stability moderately and the surfactant adsorption from k2 solute caused stable aggregates. the aggregate stability value of sample 1 (vertic stagnic solonetz) was nearly 100% (fig. 5). this was the only soil whose aggregate stability was the highest in case of maximum surfactant solution concentration. this might be explained with the large surface area, increasing the efficiency of the surfactant and the high amount of exchangeable sodium ions. however, almost all of the aggregates were disaggregated by the two days soaking in distilled water. figure 5: aggregate stability values of soil sample 1 discussion in each case the highest aggregate stability was observed if cetilpyridinium chloride being applied in medium concentration. this cpc concentration value means those surfactant amounts, which could form approximately a monolayer hydrophobic coating on solid surfaces protecting the soil aggregates against the destructive effect of dipole water molecules. decrease in the aggregate stability of soils was experienced in case of the wet sieving being performed with both the lower and higher concentrations of surfactant solutions, because of the partial hydrophilisation of the soil aggregates. acknowledgement we acknowledge the financial support of this work by the hungarian state and the european union under the tamop-4.2.1/b-09/1/konv-2010-0003 project. thanks for the work and their assistance to the employee of the department of crop production and soil sciences, especially to erzsébet borbély and ágnes nemes, and the members of the “biotalaj” workgroup. references 1. s. b. wild, k. s. waterrath, k. f. jones: organic contaminants in an agricultural soil with a known history of sewage sludge amendments, environ. sci. technol., 24(11), (1990), 1706–1711 2. z. q. ou, a. yediler, y. w. he, l. q. jia, a. kettrup, t. h. sun: adsorption of linear alkylbenzene sulfonate (las) on soils, chemosphere, 32(5), (1996), 827–839 3. a. karagunduz, k. d. pennell, m. h. young: influence of a nonionic surfactant on the water retention properties of unsaturated soils, soil sci. soc. am. j. 65, (2001), 1392–1399 4. j. h. harwell, d. a. sabatini, r. c. knox: surfactants for ground water remediation, colloids surf., a 151, (1999), 255–268 5. d. f. lowe, c. l. oubre, c. h. ward: surfactants and cosolvents for napl remediation, a technology practices manual, lewis publishers, boca raton, (1999), 412 6. r. d. lentz: inhibiting water infiltration with polyacrylamide and surfactants: applications for irrigated agriculture, j. soil water conserv., 58, (2003), 290–300 7. c. c. west, j. h. harwell: surfactants and subsurface remediation, environmental science and technology, 26(12), (1992), 2324–2330 8. m. s. holt, s. l. bernstein: linear alkylbenzenes in sewage sludges and sludge amended soils, water res. 26, (1992), 613–624 9. u. zoller: non-ionic surfactants in reused water: are activated sludge/soil aquifer treatments sufficient? water resour., 281, (1994), 1625–1629 10. l. q. jia, z. q. ou, z. y. ouyang: ecological behavior of linear alkylbenzene sulfonate (las) in soil-plant systems, pedosphere, 15(2), (2005), 216–224 11. b. allred, g. o. brown: surfactant induced reduction in soil hydraulic conductivity, ground water monitoring and remediation, 14(2), (1994), 174–184 12. p. rao, m. he, x. yang, y. zhang, s. sun, j. wang: effect of an anionic surfactant on hydraulic conductivities of sodiumand calciumsaturated soils, pedosphere 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(1998), 771 18. e. j. murer, a. baumgarten, g. eder, m. h. gerzabek, e. kandeler, n. rampazzo: an improved sieving machine for estimation of soil aggregate stability (sas), geoderma, 56, (1993), 539–547 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 /colorconversionstrategy /cmyk /dothumbnails false /embedallfonts true /embedopentype false /parseiccprofilesincomments true /embedjoboptions true /dscreportinglevel 0 /emitdscwarnings false /endpage -1 /imagememory 1048576 /lockdistillerparams false /maxsubsetpct 100 /optimize 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word 2012_dr_bodor_endre_hjic.doc hungarian journal of industrial chemistry veszprém vol. 39(3) pp. 387-390 (2011) the role of methanol in microbial fuel cells b. vajda , k. bélafi-bakó, n. nemestóthy university of pannonia, research institute on bioengineering, membrane technology & energetics veszprém, egyetem u. 10, h-8200, hungary e-mail: vajdab@almos.uni-pannon.hu several new technologies based on renewable energy resources are to be developed nowadays. fuel cells are well-known examples and their enhancement is one of the most important goals of the scientists worldwide. in this work the operation of two fuel cells were compared, which are different in some principles: the microbial fuel cell (mfc) and the direct methanol fuel cell (dmfc). the mfc is a bioreactor converting chemical energy of organic compounds to electrical energy by catalytic reactions of microbes under anaerobic conditions. in the dmfc the liquid methanol (ch3oh) is oxidized in the presence of water at the anode generating co2, h+ ions and the electrons that travel through the external circuit as the electric output of the fuel cell. the aim of this work was to decide and clarify the role of methanol. based on the experiments we found that – although the microbes were able to form methanol – the electron flow was the result of the metabolic breakdown of substrates by the microbes in the mfcs. keywords: microbial fuel cell, direct methanol fuel cell, microorganisms introduction microbial fuel cells are electrochemical systems which convert chemical energy directly into electrical energy by microorganisms. in our laboratory multi-culture (mesophilic anaerobic sludge) and mono-culture (shewanella putrefaciens) mfcs were studied. in both systems it seemed sensible to investigate whether the electron transfer in the mfcs occurs according to the “classical” and expected microbiological way or according to the mechanism described in the direct methanol fuel cells, since methanol may be formed during the metabolism of both mfc cultures studied. in direct methanol fuel cells (dmfc) methanol is supplied as an energy source and a polymer membrane is used to separate the two chambers and as an electrolyte. its scheme is shown in fig. 1. the system eliminates the need for a fuel reformer and allows pure methanol to be used as a fuel. figure 1: schematic diagram of a direct methanol fuel cell the pure methanol is mixed with steam and fed directly into the cell at the anode. here the methanol is converted to carbon dioxide and hydrogen ions by the catalyst located on the anode. the electrons are then transported through an external circuit to produce electricity (before returning to the cathode) while the hydrogen protons pass across the electrolyte to the cathode, as it occurs in a standard pem fuel cell. at the cathode the protons and electrons combine with oxygen to produce water [1-3]. the microbial fuel cells (mfcs) have generated considerable worldwide interest in recent years. classic mfcs have two chambers; an anaerobic anode chamber and an aerobic cathode chamber. microbes in the anodic cell oxidize the substrates generating electrons and protons in the process. electrons are attracted by the anode and are transported to the cathode through an external circuit (wire), while protons are passing through the membrane and enter the cathode cell where they combine with oxygen to form water [4-8]. metabolic pathways of microbial consortia converting biomass to acetate include three main biochemical steps [9]: hydrolysis of polymeric substances into smaller molecules and residues acid formation where not only acidic compounds, but hydrogen, co2 and alcohols (methanol!) are formed acetogenic phase the microbial consortia works in the biogas fermenter according to the scheme (fig. 2), but supplemented with the final steps where acetate and/or co2 + h2 are converted to biogas. however this system might be able to produce 388 electric energy, as well. the hundreds of various strains work together in close symbiotic way. in the intracellular space a central nadh → nad transformations occur during the process providing free electrons [9]. methanol, however, might be formed as well, as a by-product of the metabolism. figure 2: metabolic routes from biomass to acetate shewanella putrefaciens is a gram-negative, facultative anaerobic bacterium. it has the ability to reduce iron and manganese, hence it can use iron and manganese as the terminal electron acceptor in the electron transport chain [10-15]. metabolic pathway of shewanella putrefaciens might also include a route to form methanol during the metabolism [16], as it can be seen in fig. 3. figure 3: metabolic pathway of shewanella putrefaciens in our work it was questioned whether it is truly the metabolic breakdown of the substances by the microorganisms that results in electrons or not. since methanol formation cannot be entirely excluded in both systems, an electrocatalytic oxidation might take place in the anode space where – according to our assumption – electrons and protons are generated from methanol, and the flow of these electrons can be detected by our data collecting system. in this case we cannot talk about mfc rather about a direct methanol fuel cell. materials and methods a two-chamber microbial fuel cell shown in fig. 4 was designed and built in our laboratory. the fuel cell had 240 ml anode and cathode chamber volume. in the anode cell graphite electrode and in the cathode space graphite electrode shot by platinum were applied. the surface of the cathode was 46 cm2 and the surface of the anode was chosen to be first 49 cm2 and then 91 cm2. the two cells were separated by a nafion 0125 type proton selective membrane with the surface of 25 cm2. the fuel cell was placed in a bio-thermostat in order to keep it at the constant desired temperature. effectiveness of the cells were determined as electrical power (p = v·i) calculated from the measured voltage (v) and the current (i = v/r) calculated by the known 10 ω resistance (r) built in the circuit. the voltage transmitted by the cell was measured and stored by a computerized data collecting system using labview 8.5 software. figure 4: picture of the used laboratory equipment in the mfc the liquids in both cells were possible to circulate and stir. in the cathodic cell air was entered continuously into the distilled water by a pump to ensure aerobic environment, while n2 was sparged through the anodic cell to assure the anaerobic conditions. the mfc reactor was initially inoculated with anaerobic sludge (from a local working biogas plant) in case of the multiculture system, and shewanella putrefaciens in the monoculture system. then the microorganisms started to operate in the cell and they were allowed to adapt the actual conditions. shewanella putrefaciens was grown on the nutrients summarized in table 1 [13, 14]. 389 table 1: the applied nutrients nutrients concentration (g/100ml) meat extract 0.3 peptone 0.5 agar 1.5 results the aim of this work was to decide and clarify the role of methanol in mfcs. therefore experiments were carried out in both mfcs by mesophilic anaerobic sludge and shewanella putrefaciens, where the effect of methanol added on the power generation was determined. the operation of the multicultural system was studied and it has turned out that mfc was able to work reliably and generate power for a long period of time (over 60 hours) [17]. the voltage data observed were ~5 mv, while the power density value was around 1 mw/m2, which was increased up to 2.0–5.1 mw/m2 by adding nutrients like glucose and acetate. based on these experiences another serial of experiments was designed and conducted: methanol was added into the anodic cell (fig. 5). figure 5: the effect of methanol on the voltage data at multicultural mfc as it can be seen there was no effect at all on the voltage data, which confirmed that the equipment operates as a mfc. in the first experiments with the microbial fuel cell operated with the bacteria strain shewanella putrefaciens growth curve was studied (fig. 6). we found that at least seven days were necessary to reach the optimal microbe number, this is the minimal adaptation period. figure 6: growth curve of shewanella putrefaciens following the necessary incubational stage, the effect of nutrient addition was investigated. first glucose solution was added in the system. – (0.5% final) glucose concentration in the anode space. according to the expectations, the voltage values transmitted by the system showed a sudden increase as an effect of the extra nutrients. this can be clearly seen in fig. 7. figure 7: the effect of glucose supply on the voltage data at monocultural mfc due to the received data it could not be stated for sure whether the electrons and protons were produced directly by the microorganism from the given nutrients or by the produced methanol. methanol might also be produced from the added nutrients and the electrons and protons could be then formed in the electrocatalytic transformation of the methanol catalysed by undefined micro polluters present in the system. therefore, further measurements should be carried out to decide which one of the two options really happens. as a next step, the effect of the methanol as nutrient solution on the electron production was studied. in this case the amount of the methanol given to the anode chamber was also selected so that the glucose concentration was 0.5% in the liquid phase. the vital parameters of the fuel cell, such as temperature, cell mass, etc. were monitored and kept constant to reach a fully grown up culture similar to the one previously studied. as it is seen in fig. 8, the voltage values achieved by the cell significantly decreased right after the methanol was added to the system. figure 8: the effect of methanol on the voltage data at monocultural mfc methanol 390 the data indicate that methanol as a nutrient had a negative effect on the operation of the system. therefore the methanol cannot be used by the microorganisms for their own metabolic processes. the determined values show that after adding the methanol solution to the system a decline can be observed instead of stagnation in the voltage data. hence it is possible that an inhibition phenomenon occurs. in the case of shewanella putrefaciens bacterium, the electrochemical activity of the microorganisms is restrained by methanol. if methanol could be produced by the microbe the measured voltage would be expected to increase proportionally as an effect of the extra methanol in the system. however in our case, the opposite happens, the process of metabolic increase can be observed in the microbial fuel cells. therefore it can also be stated that micro polluters that could help the electrocatalytic oxidation of the methanol are not present in the system. conclusion the aim of our investigation was to decide if our systems were mfcs or dmfcs. in our work it was questioned whether it is truly the metabolic breakdown of the microorganisms that results in electron flow. the values determined show that after adding the methanol solution to the systems there was no effect (multicultural system) or a decline could be observed instead of the voltage stagnation (monocultural system). thus, the experimental results proved that neither of our systems could be dmfc, but they really work as mfcs. acknowledgements the authors would like to thank dr. zbynek pientka (institute of macromolecular chemistry, cas, prague, czech republic) and dr. petra cserjési (university of pannonia, veszprém, hungary) for their valuable contributions. references 1. s. basri, s. k. kamarudin: process system engineering in direct methanol fuel cell, int. j. hydrogen en., 36 (2011) 6219–6236 2. s. k. kamarudin, f. achmad, w. r. w. dauad: overview on the application of direct methanol fuel cell (dmfc) for portable electronic devices, int. j. hydrogen en., 34 (2009) 6902–6916 3. t. s. zhao, w. w. yang, r. chen, q. x. wu: towards operating direct methanol fuel cells with highly concentrated fuel, journal of power sources, 195 (2009) 3451–3462 4. b. e. logan, j. m. regan: electricity-producing bacterial communities in microbial fuel cells, trends in microbiology, 14 (2006) 512–518 5. b. e. logan: microbial fuel cells – challenges and applications, environmental science and technology, 40 (2006) 5161–5586 6. b. e. logan: microbial fuel cells, wiley & sons, new york, 2008 7. www.microbialfuelcell.org 8. d. pant, g. van bogaert, l. diels, k. vanbroekhoven: a review of the substrates used in microbial fuel cells (mfcs) for sustainable energy production, bioresource technology, 101 (2010) 1533–1543 9. p. v. rao, s. s. baral, r. dey, s. mutnuri: biogas generation potential by anaerobic digestion for sustainable energy development in india, renewable and sustainable energy reviews, 14 (2010) 2086–2094 10. y. mohan, s. n. muthu kumar, d. das: electricity generation using microbial fuel cells, int. j. hydrogen en., 33 (2008) 423–426 11. d. r. bond, d. r. lovley: electricity production by geobacter sulfurreducens attached to electrodes, appl. env. microbiol., 69 (2003) 1548–1555 12. m. a. rosenbaum, h. y. bar, q. k. beg, d. segré, j. booth, m. a. cotta, l. t. angenent: shewanella oneidensis in a lactate-fed pure-culture and a glucose-fed co-culture with lactococcus lactis with an electrode as electron acceptor, bioresource technology, 102 (2011) 2623–2628 13. d. h. park, b. h. kim: growth properties of the iron-reducing bacteria, shewanella putrefaciens ir-1 and mr-1 coupling to reduction of fe(iii) to fe(ii), the journal of microbiology, 39 (2001) 273–278 14. h. j. kim, h. s. park, m. s. hyun, i. s. chang, m. kim, b. h. kim: a mediator-less fuel cell using a metal reducing bacterium, shewanella putrefaciens, enzyme and microbial technology, 30 (2002) 145–152 15. j. h. scott, k. h. nealson: a biochemical study of the intermediary carbon metabolism of shewanella putrefaciens, journal of bacteriology, 176 (1994) 3408–3411 16. http://www.genome.jp/keggbin/show_pathway?org_name=spc&mapno=00680 &mapscale=1.0&show_description=show 17. k. belafi-bako, b. vajda, n. nemestothy: study on operation of a microbial fuel cell using mesophilic anaerobic sludge, desalination and water treatment, 35 (2011) 222–226 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 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page 427 page 428 page 429 page 430 page 431 page 432 page 433 page 434 page 435 page 436 page 437 page 438 page 439 page 440 page 441 page 442 page 443 page 444 page 445 page 446 page 447 page 448 page 449 page 450 page 451 page 452 page 453 page 454 page 455 page 456 page 457 page 458 page 459 page 460 page 461 page 462 page 463 page 464 page 465 page 466 page 467 page 468 page 469 page 470 page 471 page 472 page 473 page 474 page 475 page 476 page 477 page 478 page 479 page 480 page 481 page 482 page 483 page 484 page 485 page 486 page 487 page 488 page 489 page 490 page 491 page 492 page 493 page 494 page 495 page 496 page 497 page 498 page 499 page 500 page 501 page 502 page 503 page 504 page 505 page 506 page 507 page 508 page 509 page 510 page 511 page 512 page 513 page 514 page 515 page 516 page 517 page 518 page 519 page 520 page 521 page 522 page 523 page 524 page 525 page 526 page 527 page 528 page 529 page 530 page 531 page 532 page 533 page 534 page 535 page 536 page 537 page 538 page 539 page 540 page 541 page 542 page 543 page 544 page 545 page 546 page 547 page 548 page 549 page 550 page 551 page 552 page 553 page 554 page 555 page 556 page 557 page 558 page 559 page 560 page 561 page 562 page 563 page 564 page 565 page 566 page 567 page 568 page 569 page 570 page 571 page 572 page 573 page 574 page 575 page 576 page 577 page 578 page 579 page 580 page 581 page 582 page 583 page 584 editorial hungarian journal of industry and chemistry (hjic) formerly (until 2012) hungarian journal of industrial chemistry the hjic is an international periodicals that focuses on results of fundamental and applied research in the field of • biotechnology • chemical engineering science • chemical processes • energetics • environmental chemistry • environmental engineering & technology • industrial management • material science • mechanical engineering • mechatronics • process & system engineering • recycling in the form of original papers, reviews, short communications, and conference proceedings written in english. editorial board editor-in chief: róbert k. szilágyi department of chemistry and biochemistry, montana state university, bozeman, mt, u.s.a. honorary senior editor: géza horváth department of chemical engineering science, university of pannonia, veszprém, hungary associate editors: jános abonyi department of process engineering, university of pannonia, veszprém, hungary dezső boda department of physical chemistry, university of pannonia, veszprém, hungary norbert miskolczi mol department of hydrocarbon and coal processing, university of pannonia, veszprém, hungary dóra rippel pethő department of chemical engineering science university of pannonia, veszprém, hungary editors: lászló bartha mol department of hydrocarbon and coal processing, university of pannonia, veszprém, hungary katalin bélafi-bakó research institute of bioengineering, membrane technology and energetics, university of pannonia, veszprém, hungary peter czermak institute of bioprocess engineering and pharmaceutical technology, mittelhessen university of applied sciences, giessen, germany dénes fodor institute of mechanical engineering, university of pannonia, veszprém, hungary maria gavrilescu department of environmental engineering and management, gheorghe asachi technical university of iasi, romania lászló gubicza research institute of bioengineering, membrane technology and energetics, university of pannonia, veszprém, hungary jenő hancsók mol department of hydrocarbon and coal processing, university of pannonia, veszprém, hungary jiří klemeš centre for process integration and intensification, university of pannonia, veszprém, hungary zoltán kovács department of management, university of pannonia, veszprém, hungary jános kristóf department of analytical chemistry, university of pannonia, veszprém, hungary istván szalai institute of physics and mechatronics, university of pannonia, veszprém, hungary ferenc szeifert department of process engineering, university of pannonia, veszprém, hungary jános szépvölgyi research centre for natural sciences, university of pannonia, veszprém, hungary imre tímár institute of mechanical engineering, university of pannonia, veszprém, hungary gyula vatai department of food engineering, corvinus university of budapest, hungary gábor veress federation of technical and scientific societies – mtesz budapest, hungary ibolya zsoldos department of material science and technology, széchenyi istván university, győr, hungary editorial office: university of pannonia, p.o. box 158, veszprém h-8201 (hungary) tel.: +36 (88) 624-746, e-mail: hjic@almos.uni-pannon.hu; web: hjic.mk.uni-pannon.hu felelős szerkesztő: szilágyi róbert károly phd kiadja: pannon egyetem, 8200 veszprém, egyetem u. 10. levélcím: h-8201 veszprém, postafiók 158, tel.: (88) 624-000 felelős kiadó: a pannon egyetem, mérnöki kar dékánja editorial preface the editorial board of hjic dedicates this issue to the national scientific students’ associations (tudományos diákkör, in hungarian, abbreviated as tdk) that is a real hungaricum with a 62 years old tradition. this association includes all the universities and colleges of hungary, where scientific research of any kind is being conducted. the members of the association are the faculty members, scientific advisors, and their b.sc. or m.sc. students. participation in the work of tdk is completely voluntary. students spend some of their free time with a faculty mentor, choose a research topic, learn the basics of the field, do the measurements or the calculations under the supervision of the chosen teacher/researcher in addition to their regular academic duties. at the end, they write a dissertation based on their results. these dissertations are peer reviewed and then presented at yearly institutional tdkconferences, where the students receive suggestions from a panel of scientists and professors, receive a score for their written documents and oral presentations. based on these scores, they may win legitimacy to present their results at the national tdk-conference. tdk is a remarkable organization in hungary that was kept alive by people who do their work from pure enthusiasm for the love of their profession. it is not an exaggeration to say that the tdk-students form the elite of all the university students. they are the ones who proceed to m.sc. level, become phd students, and, at the end, ideally become colleagues of their former faculty advisors. during their work as part of tdk, students learn systematic problem-solving, formulating good questions, critical thinking, composing their thoughts into concise, wellformulated sentences, preparing meaningful figures, elaborating the literature of the field, and presenting their result in front of a scientific panel and an audience. even those students who do not continue their life in the academia tend to remember their time spend on tdk activities as useful and memorable. often, the skills acquired while being involved in a tdk project are not part of the regular education at a given university. tdk gives them something extra. this issue contains selected articles from students and their supervisors about their results presented at the tdk conferences during 2013-2014. with this issue, the editorial board wishes to honour the effort of all tdk students and their advisors for keeping this unique tradition alive with their devoted work. dezső boda and tibor dulai university of pannonia, veszprém, hungary guest editors hung. j. ind. & chem. 2014, vol. 42(1), pp. 1-56 table of contents comparative assessment of the mussel micronucleus test versus bacterial bioassays for genotoxicity testing of benzo[a]pyrene bettina eck-varanka, eszter horváth, árpád ferincz, gábor paulovits, nóra kováts ............................................................................................................................................ 1-5 improving the interfacial properties of glass fibre reinforced and unreinforced waste sourced low density polyethylene/acrylonitrile butadiene styrene/polystyrene composites jános sója, vladimir sedlarik, pavel kucharczyk, norbert miskolczi ......................... 7-12 application of online and laboratory methods for the investigation of surface water janka bobek, zsófia kovács, zoltán zsilák ........................................................................ 13-18 adsorption and intercalation of small molecules on kaolinite from molecular modelling studies attila táborosi, róbert kurdi, róbert k. szilágyi ........................................................... 19-23 impact of size heterogeneity of core-shell packing materials on chromatographic separation of large biomolecules diána lukács, krisztián horváth ......................................................................................... 25-29 effects of washing of raw material on properties of carbon nanotube containing poly(ethylene-terephthalate) composites tímea molnár, csilla varga, lászló bartha ..................................................................... 31-37 investigation the properties of y-ba-cu-oxide superconductors prepared by hydraulic pressing and moulding anna maloveczky, margit enisz-bódogh, tamás kulcsár .............................................. 39-42 effects of ultrasonic disintegration, hot-compressed liquid water pre-treatment and steam explosion on solvolysis and digestibility of grain sorghum stover dániel capári, andrás dallos ............................................................................................... 43-50 development of a reaction structure identification tool jános kontos, lászló richárd tóth, tamás varga ............................................................ 51-56 hungarian journal of industry and chemistry veszprém vol. 42(1) pp. 1–5 (2014) comparative assessment of the mussel micronucleus test versus bacterial bioassays for genotoxicity testing of benzo[a]pyrene bettina eck-varanka,1! eszter horváth,1 árpád ferincz,1 gábor paulovits,2 and nóra kováts1 1 department of limnology, university of pannonia, egyetem str. 10, veszprém, h-8200, hungary 2centre for ecological research, hungarian academy of sciences, balaton limnological institute, klebelsberg k. str. 3., tihany, h-8237, hungary !e-mail: kovats@almos.vein.hu polycyclic aromatic hydrocarbons are hazardous compounds to the environment and human health, thus their detection is an important task. in this study the genotoxic effect of benzo[a]pyrene (b[a]p) was examined on a freshwater mussel unio pictorum and results were compared to bacterial tests, such as the ames test and sos chromotest. the aim of the study was to calibrate the sensitivity of the mussel micronucleus test to that of the two bacterial tests using b[a]p as a reference chemical. the ames and the micronucleus tests gave similar response both in sensitivity and in concentrationresponse pattern. these two tests are proposed to be applied in a battery for genotoxicity testing. keywords: micronucleus test, ames fluctuation test, sos chromotest, pah introduction polycyclic aromatic hydrocarbons (pahs) are ubiquitous widespread contaminants. the us environmental protection agency (epa) created a list of priority pollutants that have the greatest concern due to potential exposure and adverse health effects on humans. there are 16 pahs on this list, of which the most hazardous are acenaphthene, fluoranthene, naphthalene, benzo[a]anthracene and benzo[a]pyrene [1]. these compounds have proven to have carcinogenic and mutagenic effects on animals and humans, hence their regulation is very important [2]. major sources of pahs are internal combustion engines, residential heating, incineration, and coke production. there are also natural sources, such as forest fires or volcanoes. pahs are present in the atmosphere as gas and/or particulate phases and might be transported to other environmental compartments such as soil, sediment, and water via dry or wet deposition. heavier pahs, such as benzo[a]pyrene (b[a]p), are almost totally adsorbed onto particles. their further environmental fate in solid compartments is mostly influenced by their low water solubility. however, once taken up by the organism, the detoxification mechanism converts these compounds into more soluble molecules. it was shown that the seawater bivalve, mytilus sp. can activate b[a]p to mutagenic compounds and produce reactive oxygen species (ros) [3]. for assessing environmental exposure, benzo[a]pyrene seems to be a good indicator, due to the strong correlation between b[a]p and other pahs [4]. in iarc monograph volume 3 it was concluded that benzo[a]pyrene produced tumours in a wide range of animals tested, following exposure by many different routes (oral, dermal, inhalation, intratracheal, intrabronchial, subcutaneous, intraperitoneal, intravenous). it had both a local and a systemic carcinogenic effect [5]. there are various reasons why the genotoxicity of pahs as well as of other mutagenic compounds is tested on mussels. first of all, bivalves are sedentary creatures, being exposed to both water and sediment contamination. secondly, their ability to bioaccumulate contaminants is well known and widely used in biomonitoring studies. actually, the fact that they can not only bioaccumulate waterborne mutagens, but also metabolise them into active forms, on one hand increase their usefulness in these studies but on the other hand may enhance the potential risk to consumers [6]. of genotoxicity markers, the micronucleus test (mn) is the most widely established, relatively easy-toperform test. micronuclei formation indicates chromosomal dna damage occurring as a result of either chromosome breakage or chromosome missegregation during mitosis [7]. banni et al. used digestive gland cells of the marine mussel mytilus galloprovincialis in an acute test. in this assay, mussels were exposed to 75 nm b[a]p for different exposure time. micronucleus frequency started to show significant response after 24 hours exposure, reaching the maximum after 72 hours [8]. woznicki et al. also tested b[a]p genotoxicity using the mn test, but 2 on another species, the freshwater sinanodonta woodiana (referred to anodonta woodiana in the original article) [9] in which the time-dependency of ecological effect was demonstrated. maximum micronucleus formation was experienced after 4 days of exposure, but after it started to decrease, most possibly due to adaptive mechanisms. the mussel micronucleus (mn) test has also been used in real-world environments, especially for detecting contamination from oil spills. bolognesi et al. demonstrated that even 10 years after the wreck of the tanker haven at the ligurian coast of italy, micronucleus frequency in caged oysters was a reliable way to detect the release of genotoxic compounds [10]. martins et al. assessed genotoxicity of sediment containing pahs and metals after dredging operations. the sediment previously was classified as ’trace contaminated’, but dredging modified the mobility of pollutants, which was clearly visible in the mussel mn test [11]. in addition to the mn test for eukaryotic organisms, which results in chromosomal damage, several bacterial tests are also available for screening purposes due to their rapid response and short exposure time. the sos chromotest is a short-term, enzymatic colorimetric assay for the detection of the presence of genotoxic compounds using escherichia coli pq 37 strain as described by quillardet et al. [12]. the sos system is a complex, dna-damage activated response under the regulation of the sos promoter. in e. coli pq 37 the only functioning β-galactosidase gene (lacz) is fused to the bacterial sfia sos operon. thus, sos response initiates lacz transcription, and β-galactosidase activity is detected spectrophotometrically by the addition of x-gal (5-bromo-4-chloro-3-indolyl-β-dgalactopyranoside) [13, 14]. the ames bacterial reverse mutation assay applies genetically engineered strains of salmonella typhimurium. the method is based on the chemical triggered reversion of histidine producing ability of the strains, enabling them to grow on histidine free medium. several different methods have been developed, including the plate incorporation assay, the preincubation method, and the fluctuation test [15–17]. the ames fluctuation test is a microplate adapted version of the salmonella reverse mutation assay with a ph change indicated colorimetric endpoint. this method is suitable for the screening of large numbers of samples, and because of its sensitivity it is ideal for water sample testing [18]. the ability of both the sos chromotest and the ames test to detect genotoxicity of b[a]p has been long established [19, 20]. b[a]p was also used as a reference chemical for calibrating the newt micronucleus test or jaylet test [21]. the correlation between the genotoxic substances and the number of micronuclei in an organism has been used in water toxicological tests since the 1980’s [22]. the micronuclei are small bodies containing dna parts that appear near the nucleus as a result of chromosome breakage or mitotic spindle dysfunction. this process can occur without external factors as well, but the effect of genotoxic substances made a far greater number of micronuclei than normal. therefore the micronuclei frequency may characterise the extent of genetic damage that accumulate over the life of the individual [23]. the mn test, performed on freshwater mussel species, is widely distributed for assessing genotoxic effects triggered by environmental pollutants [24, 25]. still, the micronucleus test has gained relatively low attention in hungary, therefore a native freshwater mussel, unio pictorum was introduced as test organism. main aim of the study was to calibrate this test also using b[a]p as reference chemical, by comparing its sensitivity to that of the bacterial assays. materials and methods test organisms unio pictorum specimens were collected from lake balaton and were kept in a flow-through aquarium. water source was lake balaton water, therefore not only proper oxygenation was ensured, but a constant food supply as well. animals were acclimatized for 4 weeks prior to testing. test conditions and treatment the assay was performed based on the protocol described by wozniczki et al. with some modifications. a b[a]p stock solution was prepared in acetonitrile in 1 mg cm-3 concentration for the following series: 70 µg dm-3, 175 µg dm-3, 350 µg dm-3 and 700 µg dm-3. for solvent control 0.07% acetonitrile was used, and solvent quantity was adjusted to 0.07% in each treatment. u. pictorum specimens with length of 5–8 cm were used. treatments were performed in triplicates. for each concentration and for the controls, the volumes of the aquaria were 3 l. they were aerated during the experiment and temperature was set at 22 oc. exposure time was 4 days. micronucleus test after 4 days, haemolymph was taken from the posterior adductor using the non-lethal technique described by gustafson et al. [26]. a 1 ml aliquot of haemolymph was mixed with 0.3 ml, 10% acetic acid in methanol as a fixative and centrifuged at 1000 rpm for 5 minutes. the supernatant was discarded and the rest was fixed in 1 ml 80 % ethanol. in this way the sample can be kept refrigerated for several weeks. for processing the samples, refrigerated samples were centrifuged again at 1000 rpm for 5 minutes. the supernatant was discarded and the pellet containing the cells was smeared onto a microscope slide and allowed to dry. after that the slides were fixed in 80 % methanol, dried and stained with 5 % giemsa in distilled water for 20 minutes. photos were taken by a zeiss axioscope a1 microscope with an axiocam icc1 camera and zen 2011 program at 400x magnification. micronuclei were 3 identified according to fenech [27]. for each animal 250 cells were counted. one-way anova with tukey post hoc test was used to compare the mean mn numbers between the treatments. for sos chromotest the sos chromotest tm kit (ebpi – environmental bio-detection products inc.) was used according to the manufacturer’s instructions, and in compliance with the oecd guidelines no 471:1977 [28]. b[a]p concentrations were 1400 µg dm3, 700 µg dm-3, 350 µg dm-3, 175 µg dm-3, 87.5 µg dm-3, 43.75 µg dm-3, 21.88 µg dm-3, 10.9 µg dm-3, 0 µg dm-3. acetonitrile concentration was adjusted to 0.07% in each sample, and an additional dmso solvent control was also used. the absorbance of samples was detected on 615 and 405 nm with diareaderelx800 elisa device. the sos repair system induction was measured by the calculation of induction factor (if) and induction potential (sosip) according to krifaton [29]. samples with 1.5 or higher if were considered genotoxic. ames test the fluctuation ames test was performed according to hubbard with slight modification. in short, salmonella typhimurium ta100 cells were pre-cultured overnight in nutrient broth (oxoid) on 37 ºc. cells were washed twice in davis minimal medium (67.4 mm po4 3-, 8.38 mm so4 2-, 15.1 mm nh4 +, 5.1 mm na+, 98.1 mm k+, 0.83 mm mg2+, 1.7 mm citrate, 139 µm glucose 10 µg cm-3 histidine, 0.1 mg cm-3 d-biotin) and cell number was adjusted to 106 cells cm-3. b[a]p was added to the samples in 700 µg dm-3, 350 µg dm-3, 175 µg dm-3, 70 µg dm-3 and 0 µg dm-3 and acetonitrile concentration was adjusted to 0.07%. samples were distributed in 200 µl volumes to 96 well microplates. cell free control, a solvent free negative control, and a positive control with 0.5 µg cm-3 concentration nan3 were also applied. plates were incubated in humid chamber for 72 hours in 37 ºc. on the day of evaluation 20 µl of 2 mg cm-3 aqueous solution of bromcresolpurple was added to each sample. purple colour signified negative, yellow positive (cell growth) result. intermediate shades were regarded positive. the experiment was also performed with s9 activation, in which case 10 ml suspension contained 2.5 ml s9 mix (ebpi) assembled according to the producer’s guide (s9 activation simulates metabolic processes in the liver of higher organisms). for positive control 2-amino-antracene was used in 100 µg cm-3 concentration. for the evaluation of mutagenic effect the χ2-test was applied with 95% confidence level [30]. results and discussions genotoxic response is expressed as number of micronuclei/250 cells in case of the mussel micronucleus test, percentage of positive wells in case of the ames test and if value in case of the sos chromotest. significant difference between the control and all treatments was observed in case of micronucleus numbers (anova: f = 12.015; df = 5; p < 0.00001, tukey post hoc: p < 0.002); however, only the highest concentration treatment differed from the acn-control (tukey post hoc p = 0.02). the difference between the lowest (70 µg dm-3) and highest (700 µg dm-3) concentrations was also indicated (fig.1). χ2-square tests indicated significant differences between the control and all treatments in case of ratios of ames fluctuations test (p < 0.0017) (fig.2). the results of sos chromotest are shown in fig.3. to date no assessment has been published for comparing the sensitivity of the mussel micronucleus test and bacterial genotoxicity assays. there are a few comparative works; however, those are based on amphibian micronucleus tests. one protocol uses xenopus laevis embryos and the end-point of the test is number of micronucleated erythrocytes per thousand. the test is standardised, international and some national figure 1: result of the mn test with b[a]p showing significant difference compared to control (a), to acn control (b) and to 70 µg dm-3 b[a]p (c) figure 3: result of the s9 supplemented sos chromotest with b[a]p figure 2: result of the s9 supplemented fluctuation ames test with b[a]p (significant difference compared to control (a)) 4 test protocols apply, e.g. the afnor nft 90-325 procedure [31]. mouchet et al. tested genotoxicity of pah-contaminated soil leachates on the amphibian mn test and two bacterial tests (ames and mutatox) [30]. the latter test developed by the microbics company (now azur environmental) uses dark mutants of the luminescent bacterium vibrio fischeri. in the presence of mutagenic compounds, these mutants can revert and recover their luminescence, which is easily measurable by a luminometer. it was found that the mn test was able to detect genotoxicity, while the ames test was not. sensitivity of the mutatox test was intermediate. it should be noted that chemical analysis of both soil and leachate samples revealed much lower individual pah concentration in leachates than in the soil samples. le curieux et al. used the sos chromotest, the ames fluctuation test and another amphibian, the newt pleurodeles waltl for a comparative assessment of 7 chemicals, including b[a]p. in their study, the newt micronucleus test was the most sensitive, the fluctuation test and the sos chromotest gave practically similar but lower response [33]. in our study all three tests gave positive response, but analysis of the concentration-response graphs shows somewhat different patterns. bacterial tests gave positive response only with s9 activation. ideal concentration-response graphs were found for the mn test and the s9 supplemented ames test. ideal concentration-response curve is observed when the response steadily increases for each higher effluent concentration [34]. main difference is the response given in the acn control, which elucidated micronucleus formation but the ames test gave practically the same response for both controls. notably, wozniczki et al. did not find concentration-response relationship when tested b[a]p on sinanodonta woodiana. in the sos chromotest after s9 activation, positive response was given for the lowest concentration, but no clear concentration-response relationship could be established. in general, sensitivity of the sos chromotest is considered lower than that of the ames test. for example, there are mutagenic compounds that do not induce the sos response, such as benzidine, cyclophosphamide, acridines, and ethidiumbromide [13]. conclusions the very similar response of the ames test and the micronucleus test (considering both sensitivity and concentration-response pattern) indicate that b[a]p elucidates both chromosomal aberrations and point mutation, and is genotoxic for prokaryotes and eukaryotes as well; however, this is not necessarily the case for all potentially genotoxic chemicals. as such, for testing genotoxicity of either individual compounds or environmental samples, application of both tests can be advised, defining the minimum necessary battery as the mn and ames tests. acknowledgements this work was supported by the támop-4.2.2.a11/1/konv-2012-0064 research program. this project is supported by the european union and co-financed by the european social fund. references [1] usepa: priority pollutants list (appendix a to 40 cfr part 423). u.s. environmental protection agency, office of water, 2000 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jourdain m.j., ferrier v., triffault g., devauxe a.: biomonitoring of the genotoxic potential of aqueous extracts of soils and bottom ash resulting from municipal solid waste incineration, using the comet and micronucleus tests on amphibian (xenopus laevis) larvae and bacterial assays (mutatox® and ames tests), sci. total environ., 2006, 355, 232–246 [33] le curieux f., marzin d., françoise e.: comparison of three short-term assays: results on seven chemicals. potential contribution to the control of water genotoxicity, mutation res., 1993, 319, 223–236 [34] usepa: method guidance and recommendations for whole effluent toxicity (wet) testing (40 cfr part 136). epa 821-b-00-004, u.s. environmental protection agency, office of water, 2000 advertise upcoming meetings, conferences and workshops; make public announcements; introduce your research laboratory; a new product or a service on the pages of the hungarian journal of industry and chemistry please contact us if interested! editorial office: university of pannonia p.o. box 158, veszprém h-8201 (hungary) tel.: +36 (88) 624-746, e-mail: hjic@almos.uni-pannon.hu; web: hjic.mk.uni-pannon.hu felelős szerkesztő: szilágyi róbert, phd kiadja: pannon egyetem, 8200 veszprém, egyetem u. 10. levélcím: h-8201 veszprém, postafiók 158, tel.: (88) 624-000 hungarian journal of industrial chemistry veszprém vol. 42(1) 7–12 (2014) improving the interfacial properties of glass fibre reinforced and unreinforced waste sourced low density polyethylene/acrylonitrile butadiene styrene/polystyrene composites jános sója,1 vladimir sedlarik,2 pavel kucharczyk,2 and norbert miskolczi1! 1 mol department of hydrocarbon & coal processing, institute of chemical engineering and process engineering, faculty of engineering, university of pannonia, egyetem u. 10, veszprém, h-8200, hungary 2 centre of polymer systems, university institute, tomas bata university in zlin, nad ovcirnou 3685, zlín, 76001, czech republic !e-mail: mnorbert@almos.uni-pannon.hu this work is focused on compatibilization of immiscible waste sourced low density polyethylene (ldpe), acrylonitrile butadiene styrene (abs), and polystyrene (ps) blends by different surface modifying routes. to reach better mechanical properties of the given reused waste blends 20% glass fibre was used. the ratio of waste ldpe/abs/ps was 3.6/2.0/1.0 both in the presence and absence of glass fibre, while the applied concentration of the surface modifying routes was 1% in each case. blends of raw materials had been manufactured by two roll mill, and specimens were obtained by the press moulded plates. the properties of samples were studied by mechanical testing. results show that blending of the three kinds of waste polymers without compatibilizers resulted immiscible blends with poor mechanical properties. this could be significantly improved by the application of the commercial and synthetic surface treatment additives. generally, favourable properties were found in the presence of 20% glass fibre. especially ad-1 and ad-2 experimental and commercial γ-aminopropylsilane additives showed the best results. keywords: immiscible, compatibilizer, waste mechanical recycling, tensile strength introduction owing to the increasing application of polymers, the utilization of wastes plastics causes serious challenges. according to reports the energetic utilization of polymer wastes were mainly investigated, such as incineration, chemical recycling, and/or mechanical recycling [1–7]. it is also well known that the industrially used plastics are not exchangeable with other constructional materials (glass, metals, etc.). excess energy use and/or more greenhouse gas emissions would be incurred upon replacement of plastics with other materials. therefore most of the key industrial segments, such as transportation, aviation, packaging, civil engineering, cannot function without polymers. from the 50s' the plastic industry went through a significant development, which is a reason for their wide-spread and diverse applications often for highly specific purposes. in the case of plastic composites, they provide alternative solutions to problems of increasing strength, maintaining compatibility and malleability [2, 4, 6–14]. the mechanical recycling of polymers is a reshaping process using waste polymeric materials or even the mixtures of unused and waste polymers. basically the waste polymer can be originated from two sources. in “closed-loop” recycling, the same product is manufactured from the same recycled components. for instance, the material of bottles (in some cases) can be recycled. in contrast, there is a recycling route, when the repeated remanufactured products are becoming less valuable [10–12, 15, 16]. a major challenge in mechanical recycling of polymers is immiscibility that leads to phase separation causing significant reductions in mechanical properties of the polymer mixtures. there are specific kinds of polymers that are immiscible with each other, such as polyolefin-pa, polyolefin-abs, polyolefin-pet. therefore, polymer blends may contain two phases, such as disperse and continuous. generally, the difference in chemical and physical properties of phases are the source of the above mentioned immiscibility problem. therefore, coupling agents with special chemical structure can be used to create adequate chemical/physical interaction between the constituents of polymer mixtures. for this purpose grafted-ma or silane based compounds are widely used. these compatibilizers are able to increase the interfacial tension in boundary layer of polymer blends, which results in better chemical/physical interactions [17, 18]. 8 in this work, the feasibility of mechanical recycling of automotive industry waste mixtures of low-density polyethylene (ldpe), acrylonitrile butadiene styrene (abs), and polystyrene (ps) were studied. the effects of various compatibilization techniques on mechanical properties of the prepared ternary abs/lspe/ps systems were studied. materials and methods raw materials waste polymers used as raw materials in our experimental work were selectively collected directly from automotive industry. the main properties of the plastic wastes are summarized in table 1. the ldpe has the lowest tensile strength (15.8 mpa), which is followed by the polystyrene (25.6 mpa), and the abs (34.4 mpa). tensile modulus showed similar order as well. due to the chemical structure of plastics, the ldpe had the highest elongation (351.5%), while abs the lowest (4.7%). the average particle size for each tested plastic wastes were in the range of 4–5 mm, with moisture content of 0.7–0.8 %. moreover, significant differences were noticed in the charpy impact strength of samples; because the maximum value was measured in the case of abs (10.5 kj mm-2), while the smallest regarding ldpe (3.8 kj mm-2). as known, blends of abs and ldpe are immiscible phases in the most cases. therefore, the mechanical properties of abs and ldpe blend are significantly worse than that of the constituents, either abs or ldpe. in order to enhance their properties, the interfacial forces must be improved between the constituents. in our work, different commercial and synthetic compatibilizers were used for improving the interfacial properties and decrease the interfacial tension of composites. two commercially available compounds of γ-aminopropyl silane (c-1) (aldrich chemistry), and polyethylene grafted with maleic anhydride (c-2) (viba spa) were used as compatibilizer agents. the synthetic agents were maleic anhydride intermediates made from different olefins at the department of mol hydrocarbon and coal processing, university of pannonia with significantly different physical and chemical properties. the main properties of the four additives are summarized in table 2. sample preparation blends of waste ldpe/abs/ps were prepared by two roll mill. then sample plates were manufactured by press moulding. fig.1 demonstrates the flow of the experimental work. for composite manufacturing a labtech two roll mill (labtech ltd, thailand) was used. the temperatures of the rolls were 170 °c and 190 °c with friction ratio of 0.5. the compositions of samples are summarized in tables 3 and 4. in selected cases e-type unsized glass fibre with 4–5 cm average length was also added to the composites in its 20%. the e-type gf was produced by ovens table 1: the main properties of waste polymers ldpe abs ps tensile strength, mpa 15.8±1.4 34.4±2.5 25.6±1.9 tensile modulus, mpa 420±33 1750±88 1720±95 elongation, % 351.5±35.5 4.7±0.3 189.6±10.2 flexural strength, mpa 29.0±2.2 21.0±1.7 flexural modulus, mpa 1820±79 1140±73 charpy strength, kj mm-2 3.8±0.4 10.5±1.1 5.9±0.4 table 2: the main of experimental coupling agents ad-1 ad-2 ad-3 ad-4 appearance solid dense liquid solid solid side chain c16-c18 polyisobutylene styrene c20-c22 figure 1: sample preparation and testing table 3: sample compositions without glass fibre in weight % sample no. 1 2 3 4 5 6 7 8 ldpe 55 54 54 54 54 54 54 54 abs 30 30 30 30 30 30 30 30 ps 15 15 15 15 15 15 15 15 c-1 1 c-2 1 ad-1 1 ad-2 1 ad-3 1 ad-4 1 peroxide 1 9 corning and it contained mainly sio2, cao and al2o3. the ratio of waste ldpe/abs/ps was 3.6/2/1 both in the presence and absence of glass fibre, while the applied concentration of the additives was 1% in each case. the additives were directly added to the molten polymer during the sample sheet manufacturing. in two cases organic peroxide (di-tercier-butyl-peroxide) was used to modify the interfacial surface of composites. the sample blending composites were press moulded at 180 °c using 6.8 ton loading and then specimens with dimension of 1 mm x 10 mm x 100 mm were cut from the composite plates. determination of tensile strength the tensile properties of the composites were determined by instron 3345 universal tensile machine using 90 mm/min crosshead displacement rate. during the tests, the ambient temperature was 23 °c, and the relative humidity was 35 % in all cases. preloading was not applied. determination of flexural strength the three point flexural tests were performed by also the before mentioned instron 3345 universal tensile tester. the crosshead displacement rate was 20 mm min-1 in all cases. determination of charpy impact properties a ceast resil impactor was used for determination of charpy impact strength. the machine was equipped with a 4j hammer, while the specimens were cut. results and discussion tensile properties fig.2 compares the tensile strength of samples. it can be seen that the tensile strength has changed in the range of 13.8 and 24.1 mpa. however, the reinforced composites have significantly better resistance against constant tensile loading (13.8–24.1 mpa), than that of unreinforced (14.2–18.5 mpa). according to data the highest values were obtained in the case sample containing a-1 surface modifier agent in the presence of gf (24.1 mpa), while that was the highest in using ad3 additive without gf (18.5 mpa). from table 1, the raw materials had 34.4 mpa (abs), 25.6 mpa (ps) and 15.8 mpa (ldpe) tensile strength. on the contrary, the untreated ldpe/abs/ps composites have tensile strength of 15.3 mpa without fibres, and 16.8 mpa in the presence of 20% glass fibre. it means that presumably owing to the immiscible phases the ldpe/abs/ps composites without surface modifying additive has lower strength than its constituents. in three samples (c-1, ad-2, and ad-4) the tensile strength of glass fibre free, but treated composites was lower than that of untreated. this is probably due to the reason of the additive has been disadvantageously altered in surface characteristics of the plastic mixture. the largest increase in the tensile strength occurred for ad-1 (+12%) and ad-3 (+21%) additives without gf, while the peroxide (+23%), and ad-1 (43%) samples have resulted the best properties using 20% glass fibre, as well. the young’s modulus, as the measure of the elastic property of sample, changed in the range between 1015 and 1685 mpa in the presence of glass fibre, while the values were between 937 and 1579 mpa without gf reinforcing (fig.3). the maximum value of tensile modulus was found by the using ad-1 surface treating agent both presence and absence of gf (1579 mpa and table 4: sample compositions with glass fibre in weight % sample no. 10 11 12 13 14 15 16 ldpe 43 43 43 43 43 43 43 abs 24 24 24 24 24 24 24 ps 12 12 12 12 12 12 12 gf 20 20 20 20 20 20 20 c-1 1 c-2 1 ad-1 1 ad-2 1 ad-3 1 ad-4 1 peroxide 1 figure 2: tensile strength of samples figure 3: tensile modulus of ldpe/abs/ps samples 10 1685 mpa). on the basis of data in table 1, the tensile modulus of ldpe, abs and ps raw materials were 420, 1750 and 1720 mpa, respectively. the untreated ldpe/abs/ps samples had significantly lower tensile moduli with 937 mpa and 1173 mpa in the presence and absence of gf, respectively. presumably it was the consequence of the phase separation occurring the immiscible polymers. the compatibility of immiscible polymer blends could be significantly improved by the above mentioned additives, because not only the tensile strength, but also the tensile modulus was significantly increased e.g. by the application of ad-1 additive (+44 % with gf and +69% without gf). in general, the tensile modulus was higher in the presence of glass fibre than without that. the relative elongation refers to the change in sample length during the tensile tests. rigid materials (polyamide, abs, etc.) have low value of elongation, while that of significantly higher in case of soft or rubber like elastic polymers (polyethylene, pp, ps, rubber, etc.). the relative elongation (fig.4) follows the opposite trends than tensile strength or modulus. it is changed in the range of 2.33 and 4.29% without gf, or 2.09 and 3.16% with gf. it means that the glass fibre presence resulted lower values of relative elongation. the surface treating agents have only slight effect to the elongation apart from ad-1 sample, because the difference between the treated and untreated samples was 63% in case of ad-1. in any other cases this value was less than 20%. flexural properties results from flexural tests are summarized in figs.5 and 6. the flexural strength was in the range of 17.3 and 22.6 mpa in case of gf reinforced ldpe/abs/ps composites and between 13.7 and 19.9 mpa in case of unreinforced specimens. the best result was found when the interfacial surface of ldpe/abs/ps composite and/or the glass fibre surface were modified by ad-3 additive (22.6 mpa). in the presence of ad-3 additive the unreinforced ldpe/abs/ps blend had 19.9 mpa flexural strength value. generally, the tensile properties were favourable in case of reinforced, than that of unreinforced samples. according to table 1, the waste abs and ps raw materials had flexural strength of 29.0 mpa and 21.0 mpa, respectively. on the other hand, the flexural strength of unreinforced ldpe/abs/ps was 15.3 mpa, which can be increased to 17.3 mpa in the presence of gf. it means that the flexural strength was below the lowest value of constituent (ps, 21.0 mpa) even in the presence of gf. co mparing tensile and flexural strength, it can be concluded that the effect of the surface modifying agents were more significant to the tensile than to the flexural properties. the negative effect of surface modifying agents was observed in some cases. for instance, flexural strength was reduced in case of c-1 and peroxide additives. regarding the flexural strength the largest increase occurred in the presence of ad-3 (+30%) and c-2 (+22%) additives without glass fibre reinforcements. the increasing in flexural strength was 30% (without gf) and 31% (with gf) in case of ad-3 additive, while that of was 22% (without gf) and 17% (with gf). regarding flexural modulus, similar results were obtained as discussed above. abs and ps raw materials have 1820 and 1140 mpa flexural modulus, respectively. according to fig.6, the flexural modulus was 1080 mpa and 1285 mpa in case of unreinforced and reinforced ldpe/abs/ps composite without surface treating agents. the flexural modulus indicates the rigidity. higher modulus means greater rigidity. results demonstrate that the flexural modulus changes in the range 1285 and 2015 mpa in the presence of gf, whereas values were between 1040 and 1637 mpa in case of the non-reinforced composites. the maximum value of flexural modulus was given specimens figure 5: flexural strength of ldpe/abs/ps samples figure 6: flexural modulus of abs/ldpe/ps samples figure 4: elongation of samples measured at tensile test 11 containing c-2 surface treating additives both with and without glass fibres. charpy impact strength the charpy impact test determines the amount of energy absorbed by a material during fracture. fig.7 summarizes the charpy impact strength of samples as a function of surface treatment additives. the impact strength of the samples ranged from 4.7 to 9.1 kj mm-2, in which reinforced composite materials was between the higher range of 5.9 and 9.1 kj mm-2. the highest value was in a sample including ad-1 surface modification agent, and glass fibre (9.1 kj mm-2). in case of the same additive without reinforced fibre the impact strength was 7.1 kj mm-2. results show that the impact strength could be increased in each case due to surface treatment. the impact strength of ldpe/abs/ps composite was 4.7 kj mm-2 without reinforced and 6.8 kj mm-2 in reinforced by glass fibres. the largest growth was observed in the case of the sample containing c-2 (+53%) and ad-1 (+51%) additives for samples without glass fibres. contrary, the least growth was observed in the case of the sample containing ad-2 (+4%) additives. regarding the gf reinforced samples, the largest growth was observed when the ad-1 (+34%) and c-2 (+29%) additive were used. only the ad-2 additive resulted in lower impact strength, than abs/ldpe/ps excluding any additive (-13%). conclusion in this paper the efficiency of different compatibilizers in waste sourced ldpe/abs/ps composite were investigated both in absence and presence of 20% etype glass fibre. it was found that both the tensile and flexural properties of samples could be significantly improved by both synthetic and commercial coupling agent. the tensile strength and elastic modulus were the best when ad-1, a c16-c18 olefin containing polyakenyl polymaleic anhydride compatibilizers and 20% gf were applied. thus, compared to the ldpe/abs/ps composite without glass fibre and surface modifying additives, the tensile strength showed 58 %, and the elastic modulus showed an 80 % increase. regarding flexural properties similar result were observed, but not with ad-1, rather than ad-3, a polyakenyl polymaleic anhydride additive that resulted in the best properties, such as increase of 22.6 mpa in flexural strength. charpy impact strength increase was the largest (9.1 kj mm-2) in a sample containing ad-1 agent in the presence of glass fibres, which converts to about 90% increase relative the ldpe/abs/ps blend without gf and compatibilizing additives. synergistic effect of glass fibres and some of the compatibilizers can lead to increase of charpy impact strength by 94% in comparison to unmodified ldpe/abs/ps sample. acknowledgements v.s. and p.k are thankful for support from the project of operational programme research and development for innovations co-funded by the european regional development fund (project cz.1.05/2.1.00/03.0111). references [1] lai s.-m., li h.-c., liao y.-c.: properties and preparation of compatibilized nylon 6 nanocomposites/abs blends: part ii – physical and thermal properties, eu. polymer j., 2007, 43(5), 1660–1671 [2] majumdar b., keskkula h., paul d.r.: morphology of nylon 6/abs blends compatibilized by a styrene/maleic anhydride copolymer, polymer, 1994, 35(15), 3164–3172 [3] hale w., keskkula h., paul 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hungarian journal of industry and chemistry veszprém vol. 42(1) pp. 13–18 (2014) application of online and laboratory methods for the investigation of surface waters janka bobek,1! zsófia kovács,1 and zoltán zsilák2 1 institute of environmental engineering, university of pannonia, egyetem str. 10, veszprém h-8200, hungary 2 department of general and inorganic chemistry, university of pannonia, egyetem str. 10, veszprém h-8200, hungary !e-mail: bobek.janka@gmail.com pollutions in surface waters run down quickly, so the pollution waves cannot be detected by traditional point sampling. remote controlled online monitoring methods can make the tracking of pollutants possible. these solutions ensure that we can immediately access up-to-date information. the goal of our paper was to compare online monitoring and laboratory measurement techniques. during our work, we investigated the chemical and physical properties of the séd creek in veszprém with two different online monitoring systems. furthermore, we made parallel laboratory measurements of samples taken weekly to evaluate the measurement results of online methods. we discuss the difficulties of installation and operation of online systems and problems arising during emergencies caused by weather. keywords: séd creek, on-line monitoring systems, comparing measurement techniques introduction the 2000/60/ec eu water framework directive (wfd) prescribes that by 2015 all surface water bodies have to reach a good ecological and chemical status. to ensure this, we need to have information about the status of water quality. a desirable feature would be the possibility of continuously track the status of our water bodies with a cost effective monitoring system. the goal of our work was to introduce online monitoring systems and laboratory methods used to measure the physical-chemical parameters of the séd creek in veszprém. in order to continuously monitor water quality, two online monitoring systems were installed, which operate on different principles. the majority of our work was to test the mobile monitoring station (no. 1), which was developed at the environmental engineering institute of the university of pannonia. in addition, we had the opportunity to follow up the operation of a more complex mobile monitoring station (no. 2), which was manufactured by combit it ltd. the two monitoring stations were placed strategically that the effect of the town of veszprém on the stream could be measured. with the help of measurements made online and control measurements made in the laboratory, we mapped the loads effecting the séd creek and to detect pollutant waves travelling down the stream. materials and methods the investigated water body is the middle section of séd creek. the water body belongs to the danube catchment and in it to the northern-mezőföld and eastern-bakony subunit. the séd originates in the bakony, then flows through the city of veszprém, and joins nádor canal at ősi. the total length of sédsárvíz-mill canal is 71.82 km. point pollutions are caused on the territory by communal and industrial wastewater inlets. intensive agriculture and husbandry are characteristic. because of the side-point sources, we also have to focus on the investigation of diffuse pollutions [4]. description of installed online monitoring stations two online water quality mobile monitoring stations were installed on the middle section of séd creek. the evaluated period of continuous measurement was between the august 4, 2013 and october 11, 2013. the two stations were different with respect of place of installation, power source, size, security, sampling, measured physical-chemical parameters, as summarized in table 1. mobile monitoring station 1 (fig.1) was located at the section of séd creek, where it enters veszprém, while mobile monitoring station 2 is at the exit point from the city (fig.1). 14 results and discussion online measurements during the period of august 4, 2013 and october 11, 2013, a tendency was observed for every measured parameter. in fig.3, the ph measured at the examined section of séd was between 7.3–8.0. the average value of conductivity is 720 µs cm-1, the value of turbidity is 30 ntu. differences and jumps compared to the baseline indicate pollution, heavy rain or malfunction. owing to the placing of the mobile monitoring stations changes could be detected in the ph values between the two sampling points. at mobile monitoring station 1 ph value was in average 0.4–0.5 points higher (7.85) than at mobile monitoring station 2 (7.45) (fig.4). there are numerous karst water inflows into the séd as it flows through the city, which causes the lowering of ph. possible acidic pollutants from roadways, rainwater inlets and industrial areas can also add to the mild acidification of the water body. in the case of measured ionic concentrations (fig.5) it was observed that all components have a background baseline with a well-defined average concentration. the differences from the baseline appear as peaks that can indicate pollutants or rainy weather. the baseline concentrations are 0.09, 0.03, 0.02, and 4.5 mg dm-3 for po4 3--p, nh4 +-n, no2 --n, and no3 --n, respectively from their average values. when evaluating the timecourse of all chemical parameters, salient values can be identified and associated with some kind of an event. if we compare figs.3 and 5 carefully, we can see that peaks appear at the same time for all components. during the evaluation of data, we identified pollutants, which were washed into the creek due to precipitation. table 1: properties of mobile monitoring stations monitoring station no.1 monitoring station no.2 location of installation entry point into veszprém in inner defense area of the waterworks exit point from veszprém on an industrial area size 85×85×85 cm outer size monitoring station made of hardened plastic 2.4×2.4 m base area, 2.5 m height monitoring station transportation car truck with crane power source 2 pcs of 12 volt lead battery line power (220v) measured parameters ph [11] turbidity [9] conductivity [8] water temperature [11] dissolved oxygen concentration [10] polyaromatic hydrocarbon concentration [17] ph [12] turbidity [3] conductivity [2] nh4 +-n concentration [13] po4 3--p concentration [16] no3 ±-n concentration [14] no2 --n concentration [15] sampling every 15 minutes every hour maintenance weekly battery replacement cleaning of the probes changing reagents and blind reagent calibration (biweekly) supplying distilled water (biweekly) cleaning of sample dispenser vessel sampling tubes figure 1: location of installed mobile monitoring stations figure 2: structure of mobile monitoring station 1 and 2 15 in addition, we detected pollution waves in two occasions. as can be expected, point sampling cannot give detailed information about the status of a water body. the advantage of online methods is clear due to their continuous monitoring, even if they are only operated for a short period of time. thus, we will get a more holistic picture about the status of a water body toward implementing efficient measures for water quality protection. pollutant leaching from precipitation to identify events, we used data from measurement station 2. in addition, water level data were downloaded from the water management web page of the ministry of interior, hungary. the water level of séd is at an average of 20 cm. from the time points in figs.3–5, we select an event occurred on september 30, 2013. around the time of the event, the water level started rising, the concentrations of physical-chemical parameters have also started to change. the pollutant downwash was detected between 04:00 and 06:00 according to the results; the concentration peak appeared at 05:00. viewing physical parameters (fig.6) the value of turbidity has risen, and after reaching the positive peak (14.6 ntu) it started to decrease. other physical parameters were seen as negative troughs. in the falloff phase all parameters moved back to the average value. looking at the chemical components (fig.6) as an effect of the rising water level, nh4 +-n, po4 3--n and no2 --n concentrations have risen, while no3 --n concentration appeared as a negative trough. outstanding physical-chemical parameters (e.g. po4 3--p at 0.15 mg dm-3 level) measured as an effect of pollutants washed in during precipitation. afterwards, the po4 3--p level moved back to its near average range of 50 µg dm-3. detecting pollutants pollutant waves were identified as events, when water level rise did not support the deviations of data points from their expected average values. alternatively, as a result of precipitation, water level of séd doubled relative to its average value without the presence of in pollutant waves. as an example, we analyze here the effect of a pollution wave appeared on september 26, 2013. the pollution was detected between 17:00 and 19:00 with reaching its peak at 18:00. looking at physical parameters (fig.7) turbidity values doubled relative to the average of 60 ntu. conductivity decreased significantly from 700 µs cm-1 to 640 µs cm-1. the ph decreased by 0.1 unit to 7.3. when we look at ion concentrations in fig.7, nh4 +-n concentration rose fourfold compared to the baseline (0.19 mg dm-3). po4 3-p and no2 --n concentrations also showed significant rise (30–180 µg dm-3). no3 --n displayed a negative trough at 40 µg dm-3, but this component was the least sensitive to the change. measurement of polyaromatic hydrocarbons based on the data points taken every 15 minutes by the polyaromatic hydrocarbon (pah) probe (trios) at measuring station 1 (fig.8) a pah pollutant wave was not detected during the investigated period. the baseline of pah compounds was measured to be 6–7 µg dm-3 and 13–15 µg dm-3. values significantly differing from figure 3: results of physical parameters measured (blue: station1, red: station 2) figure 4: variation of ph value as a result of discharge from the city (blue: station1, red: station 2) figure 5: change of concentration of measured ions figure 6: effect of precipitation on the physico-chemical components 16 the baseline (35 µg dm-3) can be counted as measurement errors. evaluation of laboratory measurement results in the duration of the investigation, we have taken point samples at the two measurement sites 13 times. the samples were always taken according to standard msz iso 5667–1:2007 [6] in the same time when the monitoring stations recorded data. the samples were transported in a cooler according to standard msz en iso 5667–3:2004 [7], and were analyzed on the day of sampling. table 2 summarized the type of instruments used for measurements. we compared the data obtained at measurement station 2 with the results of laboratory measurements (fig.9). correlation can be found for the outliers measured at the monitoring station (250 µg dm-3 po4 3-p) and in the laboratory (310 µg dm-3 po4 3--p). however, difference was found in the no3 --n concentrations between the laboratory and measurement station results showing around half values for the laboratory measurements than those from the measurement stations. based on these observations we proposed that the analyzer at the mobile monitoring station measures higher concentration than the real concentration. the effect of the city of veszprém on séd using laboratory measurements, the effect of the city of veszprém on the creek’s water quality was measured. the results obtained for averages of 13 samples are shown in fig.10. it can be seen that there was no significant change in the concentration of nh4 +-n (26.4–27.3 mg dm-3) between the entry and exit points of the creek with respect of the city. jumps in the concentration of nh4 +-n are characteristic during pollutant waves and precipitation. decrease in concentration of po4 3--p is notable (131–100 µg dm-3) at the exit section. at the entry section, séd flows near to agricultural areas, backyard gardens. we correlate the decrease of phosphate concentration within city limits with the presence of pure karst water inflows resulting in significant dilution effect. in the case of no3 --n and no2 --n concentrations (fig.10) an obvious increase can be seen (1.3–2.6 mg dm-3; 4.3–5.6 mg dm-3), which is related to the high nitrate content of the incoming karst water. the discharges from rainwater drains, backyard gardens, the canal of the zoo, and inflow from roads add to the increase of these concentrations. figure 7: effects of a pollutant wave on the physical-chemical parameters components figure 8: change in pah concentration in the investigated timeframe figure 9: comparing mobile monitoring station 2 and laboratory results 17 measurement of polyaromatic hydrocarbon concentrations the two goals of the measurements were the testing the reliability of the results by enviroflu and evaluating whether the probe can detect other pah compounds that are not fluorescent. to check reliability, we used the addition method with epa tcl polynuclear hydrocarbons mix chemical from sigma-aldrich. furthermore, we also used naphtaline-disulphonate compound for inducing disturbing effect. we measured three solutions as shown in table 3 with probe and we have taken emission spectra. laboratory control measurements (msz 1484-6) [5] were done by elgoscar 2000. comparison of the laboratory and probe results showed significant difference (table 3). if we deduct the values obtained for the sample from séd creek as base values, we get similar results. the reliability of results obtained this way was confirmed by spectra taken by a perkin elmer ls50b type fluorimeter (fig.11) [1]. the enviroflu probe detects fluorescent light at 360 nm. when looking at the curves at 360 nm, we can see that the proportions of intensity differences between the spectra of a sample from séd and artificially polluted samples correspond to the concentration differences. the significant difference between the laboratory and probe results comes from the fact that the probe senses all compounds giving fluorescence at a given wavelength. this was further elaborated by the significant concentration difference when the sample contained naphtaline-disulphonate. water quality according to water framework directive the middle section of séd belongs to type 3, or alpine, calcic-rough bed material, medium catchment water flow according to water management plan [18] on the basis of water framework plan [19.] we have prepared table 2: devices used to measure physical and chemical properties of water samples mobile monitoring station 1 mobile monitoring station 2 laboratory ph neotekponsel, pheht sentek pi11 consort c902 conductivity neotekponsel, c4e endress+hauser indumaxp cls 50 consort c902 turbidity neotekponsel, ntu sensor endress+hauser turbimax w cus41/cus41w po4 3--p µmac c lovibond pc spectro nh4 +-n no3 --n no2 --n pah trios, evirofluhc figure 10: the effect of the city of veszprém on the investigated section of séd creek table 3: comparison of laboratory and online measurement results enviroflu (µg dm-3) laboratory (µg dm-3) sample form séd 13.01 0.13 séd + 20 µg dm-3 pah mix 25.27 13.7 séd +100 µg dm-3 naphtaline-disulphonate 21.03 0.15 figure 11: emission spectra taken with fluorimeter table 4: monthly average values for water quality parameters august september october ph 7.64 7.45 7.43 conductivity, µs cm-1 711.22 707.16 720.74 oxygen saturation, % 84.15 93.4 77.32 dissolved oxygen, mg dm-3 9.39 10.28 8.73 nh4 +-n, µg dm-3 33 31 26 no2 --n, µg dm-3 31 17 15 no3 --n, mg dm-3 5.12 4.02 4.14 po4 3--p, µg dm-3 113.79 96.58 92.04 18 water qualification in the observed timeframe in monthly divisions. for dissolved oxygen and oxygen saturation values we used the results of mobile monitoring station 1 and for other components the results of mobile monitoring station 2. we have calculated monthly average values of water quality parameters (table 4). in addition, we classified each component on a five-level scale and then made class averages. the class minimums provided classifications for each month. the minimum of class average for august, september, and october were 2.5, 3, and 3, respectively; which resulted in water quality that did not reach a good status. conclusions the advantage of online measurement methods was demonstrated due to the possibility of continuously monitoring the quality of the examined creek. with online devices events can be detected that can be missed by point sampling, such as daily fluctuations, pollution waves in extreme time points. another advantage of online methods is the remote controllability, which does not require personnel except for maintenance. a drawback of the larger and more complex mobile monitoring station 2 compared to more portable mobile monitoring station 1 is the need for significant chemical, distilled water and maintenance time. the measurement stations can reveal trends, the results provided by them are in the same magnitude, but it cannot compete with the accuracy of an accredited laboratory. the goal of online measurements is to detect pollutant waves and extreme values. in order to enhance the accuracy of online measurements follow up laboratory control measurements is needed. in addition to the entry and the exit sections of the séd creek, the catchment management plan requires monitoring the physical and chemical parameters of the middle section of séd that are missing. the results presented in the given paper may help in the drafting of the measurement plans. acknowledgements this work was supported by the european union and co-financed by the european social fund in the frame of the támop-4.2.2/b-10/1-2010-0025. references [1] kristóf j.: chemical analysis ii. (instrumental analysis), ve 13/2000. veszprém, pannon egyetemi kiadó, 2000 (in hungarian) [2] endress+hauser conductivity sensor indumaxp cls 50: technical information (ti 182c/07,en, no 51517565), endress+hauser in germany, 2007 [3] endress+hauser solids content sensor turbimax w cus 41/cus 41-w: technical information (ti 177c/07,en, no 51517577), endress+hauser in germany, 2007 [4] water management of central transdanubia: significant water management issues 1–13; northern and eastern bakony field land planning sub-unit, székesfehérvár, 2007 (in hungarian) [5] msz 1484-6:2003: testing of waters. determination of policyclic aromatic hydrocarbons (pah) content gas chromatographic-mass spectrometry, hungarian standards institution standards bulletin, 2003 (in hungarian) [6] msz iso 5667-1:2007: water quality. sampling; part 1: guidance on the design of sampling programmes and sampling techniques, hungarian standards institution standards bulletin, 2007 (in hungarian) [7] msz en iso 5667-3:2004: water quality. sampling; part 3: guidance on preservation and handling of water samples, hungarian standards institution standards bulletin, 2004 (in hungarian) [8] neotek-ponsel digital sensorc4e: conductivity/salinity datasheet, neotek-ponsel in france, 2009 [9] neotek-ponsel digital sensor nephelometric turbidity datasheet, neotek-ponsel in france, 2009 [10] neotek-ponsel digital sensor odot: optical dissolved oxygen datasheet, neotek-ponsel in france, 2009 [11] neotek-ponsel digital sensor pheht: ph, redox, temperature datasheet, neotek-ponsel in france, 2009 [12] sentek electrochemical sensor specialists pi 11 ph elektrode manual, sentek in uk, 2008 [13] systea s.p.a: ammonia in water 0–0.4 ppm n-nh3 (lfa-nh3-05 rev.1 common.609) , systea s.p.a., italy, 2000 [14] systea s.p.a: nitrate in water dtpa uv reduction 0–100 mg dm-3 n-no3 -+n-no2 (lfa-no3dtpa-02 rev.1 comm. 896) systea s.p.a., italy, 2000 [15] systea s.p.a: nitrite in water and seawater 0–5 ppm n-no2 (lfa-no2-01 rev2.comm. 896) systea s.p.a., italy, 2000 [16] systea s.p.a: orthophosphate in water and seawater 0–20 ppm (lfa-po4-02 rev.1 comm.896) systea s.p.a., italy, 2000 [17] trios gmbh: trios optical sensors enviroflu-hc manual submersible fluorimeter for the detection of polycyclic aromatic hydrocarbons (pahs) in water, trios gmbh in germany, 2004 [18] directorate for water and environmental protection: water management plan for the danube river basin in hungary, 2009 (in hungarian) [19] eu water framework directive: the european parliament and of the council, water framework directive (2000/60/ec), ojl 327, 22 december 2000, 1–73 hungarian journal of industry and chemistry veszprém vol. 42(1) pp. 19–23 (2014) adsorption and intercalation of small molecules on kaolinite from molecular modelling studies attila táborosi,1! róbert kurdi,1 and róbert k. szilágyi2 1 surfaces and nanostructures laboratory, institute of environmental engineering, university of pannonia, veszprém, h-8201, hungary 2 department of chemistry and biochemistry, montana state university, bozeman, mt 59717, u.s.a. !e-mail: taborosia@almos.uni-pannon.hu kaolinite is an abundant natural material with considerable industrial potential. despite its simple composition (al2si2o5(oh)4 and layered structure being a phyllosilicate), it is notable that only little known about the interaction of kaolinite sheets with small organic reagents at the molecular level. these assumed to govern intercalation, delamination, and then the complete exfoliation processes. a common methodology to model the molecular structure of kaolinite is the employment of periodic boundary conditions. the application of molecular cluster models gained importance nowadays by capitalizing on the availability of wide range of theoretical tools for describing structural features and reaction mechanisms. in this study, we present our results using theoretical methodologies and modelling strategies from literature that are applied for adsorption and intercalation of urea, ethylene glycol, and potassium acetate. keywords: kaolinite, intercalation, adsorption, hydrogen bonding, molecular cluster model introduction a significant hindrance in the design, optimization, and execution of experimental research involving clay minerals is the lack of our understanding of molecular level processes occurring at the outer (adsorption) or at the inner surface (intercalation) of layers of clay. molecular modelling approaches have the potential to aid experimental design, mitigating cost of chemicals used, rationalizing unsuccessful trial-and-error experiments, and thus contributing to tailored utilization of clay minerals as industrial raw materials. given the periodic nature of the crystalline clay minerals, a common approach in modelling is the use of periodic boundary conditions [1–4]. a competitive approach is based on molecular cluster models [5–9]. an advantage of using the latter is the availability of a broad range of quantum chemical tools for studying the local chemical environment of the site(s) of adsorption and/or intercalation. in the given study, we have utilized kaolinite, which is a member of the 1:1 class of clay minerals. this implies that the layers of this simplest phyllosilicate are composed of octahedral (o) and tetrahedral (t) sheets. the o-sheet contains hexacoordinate al3+ ions, while the t-sheet has tetracoordinate si4+ ions. the oand tsheets are connected via tricoordinate oxide anions, while the separate ot or 1:1 layers are connected through hydrogen bonds (h-bonds) (fig.1). computational methods the computational models were created from the unit cell of the experimental x-ray diffraction structure of crystalline kaolinite [10]. we will discuss results here for models for separate oand t-sheets with figure 1: schematic presentation of adjacent ot layers of delaminated kaolinite 20 stoichiometry of al6o24h30 and si6o18h12, respectively (figs.2a and c). these are the smallest possible cluster models for the hexagonal, honeycomb like units of the oand t-sheets. in addition, two larger models of al10o38h46 and si10o29h18 were also considered (figs.2b and d) for the larger intercalating agents (ethylene glycol, potassium acetate). the unit cell of kaolinite was multiplied in all crystal dimensions to create a super-cell. this was then truncated to the cluster models presented above. the charge neutrality was achieved by terminating dangling bonds with protons at the periphery of the models. the initial positions of the adsorbent reagents were set at the centre of the hexagonal honeycomb-like unit of both oand tsheets and it was allowed to fully relax during optimizations. given that the computational models shown in fig.2 are simplifications of the experimental crystal structure environment, structural constrains were applied during geometry optimizations. in all calculations, the atoms of the organic reagents, the surface hydroxide groups (sho-) of the o-sheet, and the bridging oxide groups (bo2-) of the t-sheets were allowed to move, while the positions of the rest of the atoms were kept fixed. after structural optimizations, the positions and relative arrangements of the organic reagents with respect of the outer and inner surfaces, the shortest distances of possible ion/dipole interactions or h-bonds were noted. for computational models of t…reagent…o intercalation, the basal spacing was set at the beginning of calculations to the experimental values of 10.7, 9.5, 11.5 å, and 14.2 å for urea [11], ethylene glycol [12], and potassium acetate in the absence or in the presence of water [13], respectively. the calculations were carried out using the b3lyp hybrid density functional [14,15] with lanl2dz basis set [16] as implemented in gaussian09 [17]. the interaction energies were not considered in this work due to the modest level of theory and lack of consideration of explicit or implicit solvation shell. the main focus of the given work is to establish initial structural models for rationalizing experimental observations and prepare for more advanced computational modeling. the optimized structures presented in this work were made available at computational.chemistry.montana.edu/si. results and discussions kaolinite-urea interactions the lowest energy, optimized structure for the adsorbed urea on o-sheet can be characterized by two short o(urea)…s-hodistances of 1.92 and 1.95 å, while one of the amide groups approaches the opposite s-ho group within 1.73 å as shown in fig.3a. the presence of both donor and acceptor interactions for the same reagent molecule result in a tilted orientation of the urea. an alternative orientation in which only the carbonyl group is interacting with three s-hogroups (see below for intercalation model) was not found to be a stationary structure at this level of theory. figs.3b and c illustrate the two different orientations of the urea at the t-sheet, where the amide groups are h-bonded to the b-o2groups of the same si4+ ion (geminal) with nh…b-o2distances of 2.03 and 2.12 å or two different si4+ ions (vicinal) with 2.02 and 2.08 å figure 2: computational models for the hexagonal honeycomb-like units of [6al] (a) and [10al] (b) octahedral, [6si] (c) and [10si] (d) tetrahedral cluster models for oand t-sheets of kaolinite, respectively 21 distances. the energetic difference between the germinal and vicinal coordination is not significant (less than 10 kj mol-1) at this level of theory. when the adsorption of urea considered simultaneously at both the oand t-sheets, a model can be obtained for a plausible structure of the urea intercalated between two ot-layers (fig.4). in this computational model, the carbonyl group of urea forms three h-bonds at 1.74, 1.78, and 1.83 å distances with three s-hogroups of the hexagonal o-sheet cross from each other. at the same time, the intercalated urea forms two h-bonds with the geminal b-o2groups at 1.94 and 2.62 å distances. the tilted orientation of the urea is the consequence of the experimental basal spacing of 10.7 å, which was kept fixed during the structural optimizations. it is important to recognize that according to our computational model, there is not enough room between the expanded layers of kaolinite to accommodate urea perpendicular to the basal planes or with parallel carbonyl groups to the crystallographic ‘c’ axis. kaolinite-ethylene glycol interactions ethylene glycol is generally used in exchangeintercalation as a step followed by initial dimethyl sulfoxide or potassium acetate intercalation. as shown in fig.5a, the donor interaction between the reagent hydroxyl group and the al3+ bound s-hois much shorter (1.66 å) than those seen for urea adsorption (1.73 å), while the acceptor interaction is slightly longer (1.99 å). given that the b-o2groups of the tsheet can only act as h-bond acceptors with ethylene glycol, the reagent spans the entire hexagonal honeycomb-like unit of the t-sheet by forming longer (2.05 and 1.94 å), thus weaker h-bond interactions than with the o-sheet. the complementarity of the oand t-sheets with respect of being h-bond donor and acceptor, respectively, allows for an ideal orientation of the functional groups of ethylene glycol for maximizing the strength of h-bond interactions. the o-sheet forms a short (1.61 and 1.79 å) interaction between the o(glycol)…s-hogroups. the t-sheet accepts the ho groups of the ethylene glycol at 1.73 and 1.88 å distances. comparison of the urea (fig.5) and ethylene figure 3: computational models for urea absorption at o(a) and t-layers in geminal (b) and vicinal (c) arrangements figure 5: computational models for the adsorption of ethylene glycol at the (a) oand (b) t-sheets figure 4: computational model for intercalation of urea in kaolinite 22 glycol (fig.6) intercalated models, the network of interactions between the layers and reagents parallel well the different experimental basal spacing (10.7 vs. 9.5 å, respectively). while the urea opens the interlayer space more; however, it anchors the two layers with a stronger set of interactions than ethylene glycol. this can be correlated with the limited reactivity of urea/kaolinite complex in exchange intercalation; while ethylene glycol often provides the last step before complete delamination and exfoliation of clays. kaolinite-potassium acetate interactions a limitation of the in vacuo models used in this study greatly hinders the dissociation of the potassium ion from acetate and thus in both adsorption models the cation remained at the centre of the hexagonal honeycomb-like model for the oand the t-sheets in the vicinity of the anion acetate. in addition, the ionized carboxylic group of the reagent form two short and thus strong h-bonding interactions at 1.65 and 1.89 å distances with two germinal s-hogroups of the osheet. the shortest acetate c-h…b-o2distance in fig.7b is 2.95 å, which indicates the presence of weak interactions between the methyl group and the b-o2 groups. in the adsorption model for the t-sheet, the acetate appears to be held in place by the cation at about 2.66 and 2.68 å. some of the plausible structures for the intercalation of potassium acetate were obtained from simulations in the absence (fig.8a) and presence (fig.8b) of solvent water. similarly to the other models the values of basal spacing were set to their corresponding experimental values of 11.5 and 14.2 å, respectively. the 2.7 å difference allows for the accommodation of a water molecule as shown in fig.8b. in agreement with the absorption models in fig.7, we found short h-bond distances between the carboxylate group and the s-ho of the o-sheet at 1.59 and 1.83 å distances. when water figure 7: computational models for the adsorption of potassium acetate on (a) oand (b) t-sheets figure 6: computational model for ethylene glycol intercalation in kaolinite figure 8: computational models for potassium acetate intercalation in the (a) absence and (b) presence of solvent water 23 is present, it is likely to solvate the negatively charged end of the acetate ion with a characteristic -coo-…hoh distance of 1.63 å. the interaction of the water and the o-sheet is asymmetrical with 1.77 and 2.08 å o(water)…s-hodistances. given the energetic preference of the o-h…ohhbonding interaction, the methyl group of the acetate will only interact with anionic groups of the t-sheet with representation c-h…b-o2distances of 3.15 and 3.25 å. the lack of a representative solvent environment is of less importance for the position of the potassium ion in the intercalation models, since the inner environment of this model will likely be only exposed to bulk solvent only to a limited extent. conclusions we have started with a few notable preliminary results the establishment of a structural database for reference models related to the adsorption and intercalation of small molecules and kaolinite. we found that even a modest level of theory with respect of the basis set can provide reasonable structures. these results allow us for visualizing molecular structures in order to rationalize experimental observables and generate new ideas for research directions. furthermore, these models can be considered as initial structures for higher-level calculations that are currently in progress in our laboratory. acknowledgement this research was supported by the european union and the state of hungary, co-financed by the european social fund in the framework of támop 4.2.4.a/2-111-2012-0001 ‘national excellence program’ (rks and at) and támop-4.2.2.a-11/1/konv-2012-0071 (rk). the authors acknowledge the helpful discussions with prof. jános kristóf and prof. erzsébet horváth. we acknowledge the use of the computational facilities at montana state university, bozeman, mt. references [1] smrcok l., tunega d., ramirez-cuesta a.j., ivanov a., valuchova j.: the combined inelastic neutron scattering and solid-state dft study of hydrogen-atoms dynamics in kaolinitedimethylsulfoxide intercalate, clays clay minerals, 2010, 58(1), 52–61 [2] mercier p.h.j., le page y.: rational ab initio modeling for low energy hydrogen-bonded phyllosilicate polytypes, eu. j. mineral., 2011, 23(3), 401–407 [3] geatches d.l., jacquet a., clark s.j., greenwell h.c.: monomer adsorption on kaolinite: modeling the essential ingredients, j. phys. chem. c, 2012, 116(42), 22365–22374 [4] tunega d., bucko t., zaoui a.: assessment of ten dft methods in predicting structure of sheet silicates: importance of dispersion corrections, j. chem. phys., 2012, 137(11), 114105 [5] ható z., makó é., kristóf t.: water-mediated potassium acetate intercalation in kaolinite as revealed by molecular simulation, j. mol. mod. 2014, 20(3), 1–10 [6] michalkova a., robinson t.l., leszczynski j.: adsorption of thymine and uracil on 1:1 clay mineral surfaces: comprehensive ab initio study on influence of sodium cation and water, pccp, 2011, 13(17), 7862–7881 [7] dawley m.m., scott a.m., hill f.c., leszczynski j., orlando t.m.: adsorption of formamide on kaolinite surfaces: a combined infrared experimental and theoretical study, j. phys. chem. c, 2012, 116(45), 23981–23991 [8] scott a.m., dawley m.m., orlando t.m., hill f.c., leszczynski j.: theoretical study of the roles of na+ and water on the adsorption of formamide on kaolinite surfaces, j. phys. chem. c, 2012, 116(45), 23992–24005 [9] song k.h., wang x., qian p., zhang c., zhang q.: theoretical study of interaction of formamide with kaolinite, comp. theor. chem., 2013, 102, 72–80 [10] bish d. l.: rietveld refinement of the kaolinite structure at 1.5-k, clays clay minerals, 1993, 41(6), 738–744 [11] makó é., kristóf j., horváth e., vágvölgyi v.: kaolinite-urea complexes obtained by mechanochemical and aqueous suspension technics-a comparative study. j. colloid inter. sci., 2009, 330(2), 367–373 [12] gardolinski j.e.f.c., lagaly g.: grafted organic derivatives of kaolinite: i. synthesis, chemical and rheological characterization, clay minerals, 2005, 40(4), 537–546 [13] frost r.l., kristóf j., kloprogge j.t., horváth e.: rehydration of potassium acetateintercalated kaolinite at 298 k. langmuir, 2000, 16(12), 5402–5408 [14] lee c.t., yang w.t., parr r.g.: development of the colle-salvetti correlation energy formula into a functional of the electron-density, phys. rev. b, 1988, 37(2), 785–789 [15] becke a.d.: density-functional thermochemistry 3 the role of exact exchange, j. chem. phys. 1993, 98(7), 5648–5652 [16] dunning jr. t.h., hay p.j., (ed.: schaefer iii h.f.): modern theoretical chemistry: methods of electronic structure theory, plenum, new york 1976, vol. 3, pp. 1–28 [17] frisch m.j.t., trucks g.w., schlegel h.b., scuseria g.e., robb m.a., cheeseman j.r.; et alas: revision d.01 ed., gaussian, inc., wallingford ct, 2009 acknowledgement the dedicated issue of the hung. j. ind. & chem. and in part the organization of the 2014 spring scientific students’ meeting at university of pannonia were made possible from support provided by the national talent program of the educational research and development institute and the human resource support program of the ministry of human resources within the framework of “support of tdk workshops recognized by the council of national scientific students’ association” (ntp-tdk-13) köszönetnyilvánítás jelen kiadvány és részben a 2014. évi tavaszi tudományos diáknap a pannon egyetemen az emberi erőforrások minisztériuma megbízásából az oktatáskutató és fejlesztő intézet és az emberi erőforrás támogatáskezelő által gondozott nemzeti tehetség program „az országos tudományos diákköri tanács által elismert tdk-műhelyek támogatása” (ntp-tdk-13) című pályázatának köszönhetően valósult meg. national scientific students’ association hungarian journal of industry and chemistry veszprém vol. 42(1) pp. 25-29 (2014) impact of size heterogeneity of core-shell packing materials on chromatographic separation of large biomolecules diána lukács and krisztián horváthb department of analytical chemistry, university of pannonia, 8200 veszprém, egyetem st. 10., hungary be-mail: raksi@almos.uni-pannon.hu the effect of particle size heterogeneity of core-shell stationary phases on the efficiency of chromatographic separation of large biomolecules was studied. it was shown that the column efficiency was affected significantly by the breadth of particle size distribution. the chromatographic efficiency decreased as the heterogeneity of particle sizes increased. although the absolute decrease of separation efficiency was affected by the linear velocity, u, of the eluent, the relative change of hetp was independent of u in the practical range of eluent velocities. the results showed that the affect of particle size distribution was the highest in case of fully porous phases, and it decreased as the diameter of the inner core decreased. it was shown that, in the usual range of particle size heterogeneity of core-shell phase, the peak capacities did not change significantly even at high eluent velocities. keywords: high performance liquid chromatography, particle size heterogeneity, separation efficiency, core-shell phases introduction modern analytical applications of liquid chromatography require efficient stationary phases. before the introduction of core-shell particles – particles with a porous layer surrounding a solid core (fig. 1) – the use of monolithic silica rods [1, 2], or of sub-2 µm particles offered today the most satisfactory results. due to their excessive radial heterogeneity, however, the efficiency of monolithic columns currently is lower than that of sub-2 µm particles. columns packed with fine particles, however, have a low permeability [5–7]. thus, efficiency of columns packed with core-shell particles similar to the columns packed with sub-2 µm particles, but can be operated with the same instruments as those used for conventional columns. the use of core-shell phases is particularly advantageous in the separation of large biomolecules [8]. recently, coreshell phases were optimized for the separation of large biomolecules [9, 10]. besides their unique structure, the high efficiency of core-shell phases is in part due to the very narrow particle size distribution, with a relative standard deviation around 5–10% vs. 20–40% for most totally porous particles [7]. in literature, fairly contradictory information can be found about the effect of particle size distribution, psd, on the separation efficiency. some results suggest that the large particle size variance has no influence on the column efficiency, while according to other data the wide psd decreases the efficiency of chromatographic separation. halász and naefe [11] were the first ones who examined the effect of particle size distribution porous shell non-porous core r core r p � shell figure 1: structure of core-shell particles on the column efficiency in case of particles that were larger than 50 µm. in their work, no experimental result was found for the change of chromatographic efficiency even in case of wide psds (⇠ 40%). two years after halász’s work, significantly smaller, 1-10 µm, particles were tested by endele et al. [12]. no change in the permeability and in the chromatographic efficiency were observed as long as the average particle size remained the same. dewaele and verzele prepared columns packed with mixtures of different compositions of reversed phase particles of 3 and 8 µm and investigated the effect of the psd on the column efficiency [13] with similar results. billen et al. found that the breadth of the distribution of the stationary phase particles has no effect on the chromatographic efficiency as long as no fines are present. in the presence of fines, the efficiency decreases significantly [14]. they emphasized that 26 different conclusions can be drawn about the goodness of a chromatographic column depending on the definition used for the particle size distribution. the effect of the psd on the chromatographic efficiency of sub-2 µm particles was studied by cabooter et al. by analyzing kinetic plots of these phases [15]. in their work, they showed that not just the psd is important but also the separation efficiency one wants to achieve. it was concluded that the greater the achievable number of theoretical plates, the more the psd affects the separation efficiency. in their experiments, the authors obtained better results by using columns with a narrower psd than by using columns of the same dimensions but packed with particles with broader psd. recently, gritti et al. found that the chromatographic efficiency of the columns can be optimized if a small amount of greater particles is added to the sub-3µm particles which leads to better bead homogeneity [16]. manufacturers practice matches these, because on their confession they add a small amount of larger particles to the bathes to optimize the pressure drop along the column. experimental study of the effect of psd on chromatographic efficiency is rather complex, because the column packing procedure is hardly reproducible. it is particularly true when we work with stationary phases which have different psds. the quality of column packing also affects the column efficiency significantly. theoretical models can provide more reliable data on this field because it does not affected by the variability of column packing. the goal of this work is to study the effect of particle size heterogeneity on the chromatographic efficiency of separation of large biomolecules on core-shell stationary phases on a theoretical basis. theory in hplc, one of the measure of separation efficiency is the height equivalent to a theoretical plate, hetp [17]. the higher the plate height, the less efficient the separation is. the general rate model of chromatography [18] permits the calculation of hetp of columns packed by core-shell phases [8]: h(d p ) = 2d l u + k2 1 1 + k2 1 ⌦ u d2 p 30fd p + u d p 3fk f ! , (1) where d p is the diameter of particles of packing material, u the linear velocity of the eluent in the interstitial volume, k 1 the interstitial retention factor, f the phase ratio, d l and d p the axial and pores diffusion coefficients, respectively, and k f the external mass transfer coefficient. ⌦ is given by the relationship ⌦ = (1� ⇢) 1 + 3⇢+ 6⇢2 + 5⇢3 (1 + ⇢+ ⇢2) 2 , (2) where ⇢ represents the ratio of the radius of the inner solid core, r core , to the radius of the particle, r p (see fig. 1): ⇢ = r core r p . (3) accordingly, ⇢ is zero for fully porous particle and one for non-porous particle. for a core-shell particle, the interstitial retention factor is k 1 = (1� " e ) (1� ⇢3) " e [k a (1� " p ) + " p ] , (4) where " e is the external bed porosity, " p is the porosity of the porous shell, and k a is the adsorption equilibrium constant (henry constant). the particle size distribution is usually described by log-normal distribution [19]. the psd of a packing material with mean µ and variance �2 is fdp = 1 d p p 2⇡✓ exp 0 b@� ⇣ ln dp µ + 1 2 ✓ ⌘ 2 2✓ 1 ca , (5) where ✓ = ln ✓ �2 µ2 + 1 ◆ . (6) on the basis of the equations above, the probability density function of local hetps, fh , can be derived by applying the change-of-variables rule [20]: fh = ���� d dh d p (h) ���� frp (dp(h)) , (7) where d p (h) is the inverse function of h(d p ) (see eq. (1)). the observable hetp of the column is the first moment of eq. (7): h col = 1z 0 h fh dh. (8) methods of calculations for the calculation of h col (eq. (8)) a software written in c++ language, using the adaptive quadrature routine provided by gnu scientific library (gsl, v. 1.15) [21]. the integration region was divided into subintervals, and on each iteration the subinterval with the largest estimated error was bisected. as a result, the overall error reduced rapidly, as the subintervals became concentrated around local difficulties in the integrand. these subintervals were managed by the gsl library, which handled the memory for the subinterval ranges, results and error estimates too. the relative error of integration was set to 10 �10. the source code of the program was compiled by g++ shipped by gnu 27 0 50 100 150 200 h e t p [ m ] 0 10 20 30 40 50 eluent velocity [cm/min] = 0.8 m = 0.6 m = 0.4 m = 0.2 m = 0.0 m figure 2: van deemter plots of large biomolecules in case of different standard deviations of particle size distributions of 2.6 µm core-shell stationary phases compiler collection ver. 4.7.2 using o1 optimization. the calculations were performed on a pentium iv computer (2.80 ghz) running gnu linux operating system (debian wheezy). the function fh (eq. (7)) for the numerical integration was derived symbolically by mathematica 8.0 (wolfram research, inc.). h (eq. (1)) was calculated as it is described in ref. [8]. the internal (" p ) and external column porosities (" e ), were 0.05 and 0.4, respectively. the distribution coefficient of the compounds were set to 3. the ratio of the molecule size and the average pore diameter were assumed to be 0.68. the molecular diffusivity was 2.5⇥10�5 cm2/min. the value of “eddy” diffusion term, the internal and external obstruction factors were 1.3, 0.31 and 0.6, respectively. the linear velocity of the eluent was varied between 0.1 and 50 cm/min. the average pore size was 80 å. it was assumed that the quality of the column packing remained identical in all cases. results and discussion in fig. 2 the calculated van-deemter curves of large biomolecules separated on 2.6 µm core-shell phases can be seen. the ratio of the radius of the inner solid core to the radius of the particle, ⇢, is 0.7 representing the typical core size of commercial core-shell phases. the standard deviation of particle size distribution is varied between 0.0–0.8µm that corresponds to 0–30% relative standard deviation. close examination of fig. 2 highlights that the hetp values of large biomolecules are approximately directly proportional to the eluent velocity. fig. 2 shows that the heterogeneity of particle sizes has a significant effect on the separation efficiency of large biomolecules. the separation efficiency is the highest when the variance of particle size distribution is zero (solid black line). increasing breadth of particle size distribution decreases the efficiency of separation. the decrease in the efficiency is more significant at higher eluent velocities. at 10 cm/min, the difference between 1.00 1.05 1.10 1.15 1.20 r el at iv e h e t p 0 10 20 30 40 50 eluent velocity [cm/min] = 0.8 m = 0.6 m = 0.4 m = 0.2 m figure 3: relative van deemter plots of large biomolecules in case of different standard deviations of particle size distributions of 2.6 µm core-shell stationary phases the two extremes (� = 0 and � = 0.8) is less than 5 µm that is approximately 15% of the total plate height at this eluent velocity in ideal case (� = 0). in case of 30, 40, and 50 cm/min the differences are significantly larger: ⇠15, ⇠20, and ⇠25µm, respectively. note, however, that the relative increase is ⇠15% in each case suggesting that the relative change of hetp is independent from the eluent velocity. in fig. 3 the relative hetp, h rel , values of large biomolecules can be seen as a function of eluent velocity. h rel were calculated as h rel = h� h 0 , (9) where h� and h 0 are hetp values at �2 and 0 variance of psd. in fig. 3, it can be seen that raising eluent velocity increases the relative hetp. above ⇠8 cm/min, however, a plateau is reached and the change of relative hetp becomes negligible. it suggests that, at low eluent velocities, the interstitial dispersion is the governing effect in band dispersion. as the velocity of eluent increases, the pore diffusion becomes more and more significant. accordingly, in practice (u > 10 cm/min), it is the dominant effect in band dispersion. fig. 4 shows the effect of core size on the chromatographic efficiency at different breadth of coreshell particle distribution. the linear velocity of the eluent was 15 cm/min that is a typical value in chromatographic applications. it can be seen that, as expected from eq. (1), the efficiency of stationary phase increases as the thickness of porous layer decreases. the effect of width of particle size distribution is less significant at larger ⇢ values. while in case of fully porous particles, the difference is almost 17µm between the hetp values of the two extremes (� = 0 and � = 0.8), it is slightly more than 4µm at ⇢= 0.8. the relative hetps calculated as in case of fig. 3 do not change significantly with the diameter of nonporous core until ⇢ = 0.8 (fig. 5). above that value, 28 0 20 40 60 80 100 120 140 h e t p [ m ] 0.0 0.2 0.4 0.6 0.8 1.0 = 0.8 m = 0.6 m = 0.4 m = 0.2 m = 0.0 m figure 4: hetp of columns packed with 2.6 µm core-shell particles 1.00 1.05 1.10 1.15 1.20 re la ti v e h e t p 0.0 0.2 0.4 0.6 0.8 1.0 = 0.2 m = 0.4 m = 0.6 m = 0.8 m figure 5: relative hetps of columns packed with 2.6 µm core-shell particles h rel s decrease abruptly, at ⇢ = 1 there is no difference between the cases. it can be explained by considering that the separation efficiency of large biomolecules is affected mainly by the pore diffusion (second term of eq. (1)). as the thickness of porous layer of core-shell particles decrease, the diffusion paths reduce as well. as a result, the impact of pore diffusion on band broadening is less and less significant. the difference between the distinct particles vanishes. finally, at ⇢ = 1, only the interstitial band spreading (first term of eq. (1)) influences the efficiency of separation. since d l is not affected by the particle size distribution, h rel s become unity. besides the plate heights, the change of peak capacities were also studied. peak capacity, n c , is a practical measure of separation potential in hplc. n c is defined as the maximum number of components that can be resolved completely between the peaks of the least and most retained solutes [22]. several expressions exist for the calculation of peak capacity [23] depending on the mode of chromatography. in case of isocratic mode of separation, nc can be calculated as nc = 1 4 p n (t max � t min ) ln t max t min , (10) where t max and t min are the retention times of the first and last eluting peaks, and n the number of theoretical 0.90 0.92 0.94 0.96 0.98 1.00 r el at iv e p ea k ca p ac it y 0 10 20 30 40 50 eluent velocity [cm/min] = 0.2 m = 0.4 m = 0.6 m = 0.8 m figure 6: relative peak capacities of columns packed by 2.6 µm core-shell particles; l = 10 cm, t 0 = 10/9, t max = 100/9 plates (n = l/h). in fig. 6 the peak capacities of 2.6 µm core-shell phases can be seen as a function of eluent velocity in case of separation of large biomolecules. the calculated peak capacities were normalized for value that belongs to zero variance of psd. the figure shows that the achievable peak capacity of a column packed with core-shell particles is affected by the heterogeneity of particle sizes. the decrease of peak capacities, however, is significantly smaller than the decrease of column efficiencies (fig. 2). that is because n c is proportional to the reciprocal square root of h . accordingly, 15% increase in the plate height results in ⇠7% loss of peak capacity that is not significant in practice. conclusions since their introduction, core-shell stationary phases became very popular for the analysis of large biomolecules. the morphology of these phases results in less band broadening compared to fully porous particles and thus delivers extremely high efficiencies. in this work, the effect of particle size heterogeneity of core-shell stationary phases on the efficiency of chromatographic separation of large biomolecules was studied. the results showed that slopes of van deemter curves were affected by the breadth of particle size distribution. as a result of widening psd the column efficiencies decreased significantly. the analysis of peak capacities showed that the maximum number of large biomolecules that can be resolved by core-shell phases was not affected significantly, even if the psd was wide. considering that the relative standard deviations of pdss of core-shell phases are between 0.2–0.4µm for 2.6 µm particles, it can be concluded that the efficiency of these phases is affected significantly by the size heterogeneity of the particles. further efforts from column manufacturers in order to improve the psd do not give any more advantages and are not profitable. 29 acknowledgements this research was supported by the european union and the state of hungary, co-financed by the european social fund in the framework of támop-4.2.4.a/211/1-2012-0001 ‘national excellence program’. the research infrastructure was supported by the hungarian scientific research fund (otka pd104819) and the hungarian state and the european union under the támop-4.2.2.a-11/1/konv-2012-0071 project. references [1] nakanishi k., soga n.: phase separation in gelling silica–organic polymer solution: systems containing poly(sodium styrenesulfonate), j. am. ceram. soc., 1991, 74, 2518–2530 [2] minakuchi h., nakanishi k., soga n., ishizuka n., tanaka n.: octadecylsilylated porous silica rods as separation media for reversedphase liquid chromatography, anal. chem., 1996, 68, 3498–3051 [3] kirkland j., langlois t., destefano j.: fused core particles for hplc columns, american laboratory, 2007, 39, 18–21 [4] destefano j.j., langlois t.j., kirkland j.j.: characteristics of superficially-porous silica particles for fast hplc: some performance comparisons with sub-2-µ m particles, j. chromatogr. sci., 2008, 46, 254–260 [5] gritti f., cavazzini a., marchetti n., guiochon g.: comparison between the efficiencies of columns packed with fully and partially porous c-18-bonded silica materials, j. chromatogr. a., 2007, 1157, 289–303 [6] cavazzini a., gritti f., kaczmarski k., marchetti n., guiochon g.: masstransfer kinetics in a shell packing material for chromatography, anal. chem., 2007, 79, 5972– 5979 [7] gritti f., leonardis i., shock d., stevenson p., shalliker a., guiochon g.: performance of columns packed with the new shell particles, kinetex-c18, j. chromatogr. a., 2010, 1217, 1589–1603 [8] horváth k., gritti f., fairchild j.n., guiochon g.: on the optimization of the shell thickness of superficially porous particles, j. chromatogr. a., 2010, 1217, 6373–6381 [9] wagner b.m., schuster s.a., boyes b.e., kirkland j.j.: superficially porous silica particles with wide pores for biomacromolecular separations, j. 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terryn h., lynen f., sandra p., desmet g.: kinetic plot and particle size distribution analysis to discuss the performance limits od sub-2 µm and supra-2 µm particle columns, j. chromatogr. a., 2008, 1204, 1– 10 [16] gritti f., farkas t., heng j., guiochon g.: on the relationship between band broadening and the particle-size distribution of the packing material in liquid chromatography: theory and practice., j. chromatogr. a., 2011, 1218, 8209–8221 [17] snyder l., kirkland j., dolan j.: introduction to modern liquid chromatography (john wiley, hoboken, nj) 2010 [18] guiochon g., felinger a., shirazi d.g., katti a.m.: fundamentals of preparative and nonlinear chromatography (academic press, amsterdam) 2006 [19] johnson n.l., kotz s., balakrishnan n.: continuous univariate distributions, vol. 1 (wiley, new york), second edn. 1994 [20] weisstein e.w.: change of variables theorem, from mathworld – a wolfram web resource, url http://mathworld.wolfram.com/ changeofvariablestheorem.html [21] galassi m., davies j., theiler j., gough b., jungman g., alken p., booth m., rossi f.: gnu scientific library reference manual third edition, network theory ltd. 2009 [22] horvath c., lipsky s.r. : peak capacity in chromatography, anal. chem., 1967, 39, 1893– 1893 [23] grushka e.: chromatographic peak capacity and the factors influencing it, anal. chem., 1970, 42, 1142–1147 advertise upcoming meetings, conferences and workshops; make public announcements; introduce your research laboratory; a new product or a service on the pages of the hungarian journal of industry and chemistry please contact us if interested! editorial office: university of pannonia p.o. box 158, veszprém h-8201 (hungary) tel.: +36 (88) 624-746, e-mail: hjic@almos.uni-pannon.hu; web: hjic.mk.uni-pannon.hu felelős szerkesztő: szilágyi róbert, phd kiadja: pannon egyetem, 8200 veszprém, egyetem u. 10. levélcím: h-8201 veszprém, postafiók 158, tel.: (88) 624-000 hungarian journal of industry and chemistry veszprém vol. 42(1) pp. 31–37 (2014) effects of washing of raw material on properties of carbon nanotube containing poly(ethylene-terephthalate) composites tímea molnár,1 csilla varga,1! and lászló bartha1 1 department of mol hydrocarbon & coal processing, university of pannonia, egyetem str.10, veszprém, h-8200, hungary !e-mail: vcsilla@almos.uni-pannon.hu our interest has been focused on mechanical recycling of poly(ethylene-terephthalate) (pet) bottle waste, because recycling of plastic waste has crucial importance nowadays. the present article deals with the effects of washing of the secondary raw materials on properties of carbon nanotube (cnt) reinforced composites. in the first step advantageous washing compounds and their concentration were determined. after selecting the proper washing method extrusion moulding characteristics of pet granulates were investigated, and effects of carbon nanotubes as reinforcing additives and also application of coupling agents on the mechanical and rheological properties of composites were studied. keywords: carbon nanotubes, coupling agent, poly(ethylene-terephthalate), bottle waste recycling introduction almost all human activities result in waste generation either directly or indirectly. satisfying the daily needs for growing amounts of products results in higher consumption of raw materials, higher quantities of processing waste, and also higher amounts of wastes after the end of product life [1–4]. selectively collected pet bottles derived from municipal solid waste considered as waste plastics of a specific type, but the liquid stored in them contaminates their surfaces. fig.1 shows the typical treatment cycle and possible recycling methods for plastic wastes, especially for the pet bottles collected selectively. washing the surface of the waste materials is an important issue as biofilm can be formed. therefore, this raw material will be contaminated with some biological content. removing biofilm can be carried out in water, acidic or alkaline solvents. effectiveness of the method is measured by using reactions with folin reagent. pet has excellent mechanical and chemical properties, therefore, its resistance against chemicals and irradiation is outstanding; however, it can also have serious impact on the environment, because the biodegradation requires a long time, and expensive pretreatment methods are needed in order to bring them within reach of decomposing enzymes [3–8]. carbon nanotubes (cnt) are members of the family of fullerenes with cylindrical shapes, where carbon atoms are located at the surface of a cylinder. typical diameter is between the 1–50 nm regime, length can exceed even the 10 µm scale. carbon nanotubes have non-polar character. their surface contains only a few functional groups, which can react with polymers. in order to enhance the interaction between nanotubes and polymer matrices, the nanotube surface needs to be modified by application of coupling agents [7–11]. the given study deals with mechanical recycling of pet bottle wastes by applying secondary raw material for polymer matrix of cnt reinforced composites. after selecting the proper washing method, extrusion moulding characteristics of pet granulates were investigated. furthermore, the effects of carbon nanotubes as reinforcing additives, and application of coupling agents on the mechanical and rheological properties of composites were studied. experimental materials selectively collected pet bottles waste was used as the polymer matrix in the composites in washed and figure 1: pre-treatment and recycling of plastic wastes 32 unwashed form. mfi values of the pet granulates were measured, and changed in the interval of 10–14 g (10 min)-1 (255 °c, 2.16 kg). multi-walled carbon nanotubes (mwcnt) were produced at 700 °c by chemical vapour deposition (cvd) process over fe-co bimetallic catalyst at the department of chemical engineering, institute of chemical and process engineering, university of pannonia. purity of mwcnt was higher than 90 wt%, diameter was between 10 nm and 20 nm, the average length was above 30 µm and the betsurface was 200 m2 g-1. carbon nanotubes were applied in pet matrix in pristine and surface treated form. for treating surface of the carbon nanotubes experimental olefin-maleic-anhydride copolymer based coupling agents (fig.2) were used with the properties summarized in table 1. the ratios of the functional groups in coupling agents were determined by measuring acid value and saponification number by classical analytical methods and on the second hand the ratios were estimated by a previously developed ft-ir method [12]. production of composite samples cnt/pet composites were produced by a laboratory twin/screw extruder (lte 20-44, labtech engineering, fig.3). temperature profiles and screw rotation speed for production were previously determined [13]. washing of the waste material after the washing process, raw materials from selectively collected pet and pet derived directly from waste deposit were compared. the solutions with 0.05 m concentration were used for both acidic and alkaline washing method. citric acid and potassium hydroxide were chosen for the acidic and the alkaline wash. measurements to determine the tensile properties of the extruded strings (namely strength, modulus, and extension) an instron 3345 universal tensile testing machine was used. the temperature in the laboratory was 23 °c, while relative humidity was 37% during the mechanical tests that were carried out at 90 mm min-1 crossheadspeed. rheological measurements were carried out in a ceast smart rheo 2000 capillary rheometer at 265 °c. before measurements, 180 second preheating was applied to all samples. structural information about the developed coupling agent was obtained by ir technique using a tensor 27 ftir spectrometer (resolution: 3 cm-1, illumination: sicglobar light, detector: rt-dlatgs type) in the 400–4000 cm-1 spectral range. scanning electron microscopy (sem) was used to study the morphology of fractured faces of specimens and to follow possible interaction between the reinforcements and matrices on a phillips xl30 esem instrument. results and discussion surface treating effects of surface treatment were studied in two applications. firstly, the coupling agents on the cnt surface was investigated, thereby properties of pristine cnt were compared to properties of two different coupling agent treated cnts. bet-surface was measured and surface energy measurements were conducted. secondly, the effects of concentration of the coupling agent applied on the cnt surface were studied with additive concentration to be 15% and 20%. by the surface treatment the bet surface of pristine cnt reduced at least by 35–40% (table 2). on the basis of mesopore volume distribution results (fig.4), it was determined that coupling agents mainly attached to pores with diameters below 10 nm, because numbers of that pore size decreased the most. structure table 1: main properties of coupling agents property ca-1 ca-2 acid value, mg koh (g sample)-1 12.8 33.1 saponification number, mg koh (g sample)-1 95.3 126.5 molecular weight (mw)*, g mol-1 3520 3660 polydispersity factor 1.10 1.40 ratio of functional group, % anhydride 7.9 12.0 semi-ester 2.7 37.6 ester-amide 44.7 25.2 imide 44.7 25.2 * related to ps standard figure 2: structure of the ester-amide-imide derivative of the experimental olefin-maleic-anhydride copolymer (r1: alkyl group with length of the olefinic monomer (c16-c18); r2: alkyl group with r1-2 carbon number; a: 3-40, b: 3-32; k: 0,2-2; l: 1-7; m: 1-7 and n: 0,3-2) figure 3: production of pet composites in a twin-screw extruder table 2: bet-surface of different carbon nanotubes samples surface area pristine 191.1 m2 g-1 20% ca-1 coupling agent 125.5 m2 g-1 15% ca-2 coupling agent 172.3 m2 g-1 20% ca-2 coupling agent 102.1 m2 g-1 33 of the coupling agent had considerable impact on the distribution since different ratios of decrease were measured in the mesopore volumes, therefore surface interactions with different strength may were evolved between the coupling agent and the cnt. concentration of the coupling agent on the cnt surface also influenced the results (fig.5). decreasing the concentration from 20% to 15% resulted in an increase in the mesopore volumes to such an extent that almost the values for pristine cnts were achieved. properties of heterogeneous polymer systems are influenced by interfacial interactions and structure; however, no direct method is available to determine strength of interactions. therefore, models are used generally for their estimation. inverse gas chromatography measurements can be a useful tool for measuring the surface properties of different fillers and thus, the strength of interactions can be estimated. the dispersive component of surface energy describes london-interactions that can be used for estimation of the non-polar character, while other types of interactions (hydrogen-bond, polar, acid-base, etc.…) are included in the specific component (fig.6). we found that the dispersive surface energy of the coupling agent treated cnt was half of the pristine one at 70 °c (fig.6). this is indicative of the surface treated carbon nanotubes likely having lower tendency for agglomeration than pristine cnts. constant for the acid-base interactions were calculated based on the gutmann equation [14] as summarized in table 3. on the basis of these results it can be stated that acid character of the pristine cnts do not change significantly after surface treatment but the basic character improved. on the surface of the treated cnt-s weak basic active centres were predominant over acidic ones. effects of washing both acidic and alkaline washing were shown to be effective by which biofilm had been removed from surface of pet granulates with 100% efficiency. since biofilm cannot stick to the surface of pet due to its crystalline structure biofilm can be removed by application of weak acid or lye. ft-ir spectra of the granules before and after washing gave the opportunity to study the changes in functional groups of the plastic. it is important to highlight that no significant differences were observed between ft-ir spectra of acidic and alkaline washed samples. therefore, none of the compounds during washing deteriorated structure of pet (fig.7). effect of screw rotational speed pet samples were produced at various screw rotational speeds to study their rheological behaviour and also their mechanical properties. screw rotational speed during processing caused significant differences in viscosities in the low shear rate regime (beyond 500 s-1) (fig.8). figure 4: changes in mesopore volume distribution due to surface treatment (20% coupling agent) figure 5: changes in mesopore volume distribution due to surface treatment with various coupling agent (ca-2) concentrations figure 6: dispersive surface energy based on schultz-method (temperature: 70 °c) table 3: acid-base constants calculated by gutmann equation [14] at 70 ºc sample r2 pristine cnt ka 0.086 0.928 kb 0.000 15% coupling agent treated cnt (ca-1) ka 0.086 0.806 kb 0.253 20% coupling agent treated cnt (ca-1) ka 0.090 0.849 kb 0.213 34 in the medium shear rate region (500-5000 s-1) differences among the viscosities of the samples continuously disappeared. no differences were observed at higher shear rates, above 5000 s-1 dedicated to shear rates characteristic for injection moulding. that indicated that all the samples could probably be injection moulded at the same parameters. all the tensile properties (yield strength, modulus) improved by increasing screw rotational speed during processing (figs.9 and 10). the highest values for the tensile properties were measured for samples produced at the highest screw rotational speed. sample produced at the lowest rotational speed had values nearly identical to literature data [15]. however, samples processed at the highest rotational speed had 35–40% higher yield strength than the original material used for bottle production. it is important to note that washed pet granulates with the lowest rotational speed could not be produced at the same temperature profile as the plastic melted. pet composites containing pristine cnt washing the raw material caused 15% deterioration in yield strength, but the modulus did not change. untreated cnt could be introduced into the polymer melts at 2 wt% level both into washed and unwashed pet raw materials by the same side feeder screw rotational speeds. application of pristine cnt did not influence yield strength of the composites (figs.11 and 12), so yield strength of cnt/pet samples did not depend on the previous washing of the raw material. the pet raw materials had ca. 2000 mpa tensile modulus either for washed and unwashed plastic, so rigidity of the samples was stated to be the same. figure 8: effect of screw rotational speed on rheological behaviour of pet raw material figure 7: ft-ir spectra of pet sample in the 4000-600 cm-1 wavenumber range (purple: potassium-hydroxide; green: citric acid; blue: without washing) figure 10: effect of screw rotational speed on tensile modulus of pet raw material figure 9: effect of screw rotational speed on yield strength of pet raw material figure 11: effects of cnt application on yield strength of pet figure 12: effects of cnt application modulus of pet 35 pristine cnt containing washed pet had 20% lower modulus than unwashed pet based samples had, thereby; the property of the pet raw material was achieved. adding pristine cnt to washed pet plastic no difference was measured in the modulus compared to the washed pet without any reinforcing. effects of type and concentration of coupling agent two different, previously successfully applied coupling agents [13] were used on the surface of cnts. concentration of the coupling agents varied from 15% (conc-1) to 20% (conc-2) related to the weight of the pristine cnt. with respect of processing, surface treated cnts were much easier to introduce into the polymer melt. cnt concentration could be elevated up to 2.7–2.9 wt% in the polymer matrix at the same processing parameters using coupling agent treated cnts instead of pristine type. yield strengths of washed pet based composites increased with increasing concentration in the presence of both coupling agents compared to the pristine cnt containing pet sample (figs.13 and 14). improvement of 78% for ca-1, and 30% for ca-2 was realized in the presence of coupling agents at the higher concentration (20%). using unwashed pet, as raw material also resulted in enhancement of yield strength, but to a different extent, such as ca-1 resulting in 55%, while ca-2 causing 16% increase. based on the above results, the ca-1 additive was worth applying in higher (20%) concentration due to the achieved more than 50% higher yield strength relative to the pristine cnt containing pet composite. raw material is worth washing before processing if cost of washing could be balanced by the advantage of the 10 mpa increase in yield strength applying ca-1 coupling agent in 20% concentration. in case of ca-2 additive washing did not influence the properties at the lower (conc-1) concentration level, but with higher additive concentration (conc-2) a 14% difference was measured between the composites made from the two raw materials. comparing the samples with various additive concentrations an increase was observed in the modulus with increasing concentration for both raw materials and coupling agents. applying unwashed raw material 34% improvement was realized with ca-1 coupling agent and 32% with ca-2 additive if the concentration increased from 15% to 20%. a lower degree of improvements were measured for washed pet based samples making the same comparison. comparison of pristine and surface treated cnt containing samples showed that coupling agent was advantageous to be applied in higher concentration from the point of view of the modulus either. for unwashed pet based composites application of coupling agents resulted in 10–15% decrease in modulus related to the pristine cnt containing sample. for washed pet based samples making the same comparison changes were calculated to be +45% in case of ca-1, and +20% for ca-2 additive. the most advantageous observation based on the results is the lack of an effect on the mechanical properties in the investigated interval of raw material quality with respect of washing pet bottle waste, when used as polymer matrix for cnt reinforced composites. this could be realized in easier handling and pretreating of the raw material before recycling. sem graphs broken surfaces of samples were studied by scanning electron microscopy. cnts concentrated at one side of the extruded string in pristine cnt containing samples (fig.15a). diameter of the probable carbon nanotube nucleation centres varied (figs.15b and c). there were agglomerates with diameter of 30–40 µm and also with 5-10 µm number of the latter seemed to be higher. in addition, there were only a few nucleation centres both for washed and unwashed pet based composites. on the cross section of the extruded strings a crystalline part was rendered likely in larger areas in coupling agent treated cnt containing samples than in pristine cnt/pet samples. in pet containing 15% ca2 coupling agent a likely crystalline part was found at the middle of the extruded sample (fig.16). more nucleation centres and more homogeneous structure were observed (fig.16) than in pristine cnt containing sample from the same pet raw material. it is in accordance with the 15% lower cnt content of the pristine cnt/pet composite than the treated cnt containing one. the diameters of the nucleation parts were in the range of 20–30 µm. area related to the probable crystalline structure was higher in washed pet based sample on the sem graphs of the extruded strings (fig.17a). nucleation parts were figure 13: tensile properties of surface treated cnt containing pet composites figure 14: tensile properties of surface treated cnt containing pet composites 36 located in the middle of the sample and connected to each other diameters were identical to the former sample that was treated (fig.17b). based on the sem graphs it was concluded that carbon nanotubes were easier to handle and distribute more homogeneously due to surface treating both for washed and unwashed pet raw material, and on the other hand numbers of the nucleation parts and sizes could be influenced. conclusions the present article gave a brief insight into mechanical recycling of pet bottle wastes by applying that secondary raw material for polymer matrix of cnt reinforced composites. after selecting the proper washing method extrusion moulding characteristics of pet granulates were investigated and it was concluded that tensile properties improved by increasing screw rotational speed. effects of washing in carbon nanotubes containing pet composites were also investigated where carbon a b c figure 15: sem graphs of pet sample containing pristine cnt a b figure 16: sem graphs of unwashed pet based sample containing 15% ca-2 coupling agent treated carbon nanotube a b figure 17: sem graphs of washed pet based sample containing 20% ca-1 coupling agent treated carbon nanotube 37 nanotubes were applied either in pristine or surface treated form. washing of the waste plastic did not affected yield strength in case of pristine carbon nanotubes containing samples but for coupling agent containing composites mechanical properties significantly changed. if the proper coupling agent was applied in higher concentration, 20% e.g. yield strength improved by higher than 60% while modulus increased at least 20%. acknowledgements this research was supported by the european union and the state of hungary, co-financed by the european social fund in the framework of támop-4.2.4.a/211/1-2012-0001 ‘national excellence program’. the authors are also grateful for the financial support of this work by the hungarian state and the european union under the támop-4.2.2.a-11/1/konv/2012-0071 project. references [1] la mantia f.: handbook of plastic recycling, shrewsbury, rapra technology, 2002 [2] wégner k.: towards more efficient waste management, yearbook of hungarian plastic and rubber industry, 2013, 27–32 (in hungarian) [3] wu g., li j., xu z.: triboelectrostatic separation for granular plastic waste recycling: a review, waste mngnt., 2013, 33, 585–597 [4] fortelny i., michalková d., krulis z.: an efficient method of material recycling of municipal plastic waste, polym. degrad. stabil., 2004, 85, 975–979 [5] aksa w., medles k., rezoug m., boukhoulda m.f., bilici m., dascalescu l.: two stage electrostatics separator for the recycling of plastic from waste electrical and electronic equipment, j electrost., 2013, 71, 681–688 [6] sánchez a.c., collinson s.r.: the selective recycling of mixed plastic waste of polylactic acid and polyethylene terephthalate by control of process conditions, eu. polym. j., 2011, 47, 1970–1976 [7] wang y., gao j., ma y., agarwal u.s.: study on mechanical properties, thermal stability and crystallization behavior of pet/mmt nanocomposites, composites part b, 2006, 37, 399–407 [8] logakis e., pissis p., pospiech d., korwitz a., krause b., reuter u., pötschke p.: low electrical percolation threshold in poly(ethylene terephthalate)/multi-walled carbon nanotube nanocomposites, eu. polym. j., 2010, 46, 928–936 [9] li z., luo g., wei f., huang y.: microstructure of carbon nanotubes/pet conductive composites fibers and their properties, composites sci. techn., 2006, 66, 1022–1029 [10] fiedler b., gojny f.h., wichmann m.h.g., nolte m.c.m., schulte k.: fundamental aspects of nano-reinforced composites, composites sci. techn., 2006, 66, 3115–3125 [11] borrell a., rocha v.g., torrecillas r., fernández a.: surface coating on carbon nanofibers with alumina precursor by different synthesis routes, composites sci. tehn., 2011, 71, 18–22 [12] varga cs.: production and investigation of compatibilizing additives for polymer composites, phd thesis, university of pannonia, veszprém, 2010 (in hungarian) [13] molnár t.: effects of carbon nanotubes and coupling agents in poly(ethylene-terephthalate) polymer, itdk report, university of pannonia, veszprém, 2011 (in hungarian) [14] gutmann v.: the donor-acceptor approach to molecular interactions, plenum press, new york, 1978 [15] pál k.: recycling of plastics wastes as secondary raw material, műanyagipari szemle, 2006/2 acknowledgement the dedicated issue of the hung. j. ind. & chem. and in part the organization of the 2014 spring scientific students’ meeting at university of pannonia were made possible from support provided by the national talent program of the educational research and development institute and the human resource support program of the ministry of human resources within the framework of “support of tdk workshops recognized by the council of national scientific students’ association” (ntp-tdk-13) köszönetnyilvánítás jelen kiadvány és részben a 2014. évi tavaszi tudományos diáknap a pannon egyetemen az emberi erőforrások minisztériuma megbízásából az oktatáskutató és fejlesztő intézet és az emberi erőforrás támogatáskezelő által gondozott nemzeti tehetség program „az országos tudományos diákköri tanács által elismert tdk-műhelyek támogatása” (ntp-tdk-13) című pályázatának köszönhetően valósult meg. national scientific students’ association hungarian journal of industry and chemistry veszprém vol. 42(1) pp. 39–42 (2014) investigation the properties of y-ba-cu-oxide superconductors prepared by hydraulic pressing and molding anna maloveczky,! margit enisz-bódogh, and tamás kulcsár institute of materials engineering, university of pannonia, egyetem str. 10., veszprém, 8200, hungary !e-mail: anna.maloveczky@gmail.com levitation applications of superconductors require the fabrication of bulk ceramic superconductors with special shapes. the conventional hydraulic pressing is not suitable for the production of superconductors with complicated forms, so we have applied slip casting to shape bulk superconductors. superconducting powders with different yba2cu3oy (123) and y2bacuo5 (211) phase content and different (pt, pb, ce) additives were prepared by solid-state reactions. the nonsuperconducting (211) particles can be considered as flux pinning centres; thus the magnetic properties can be influenced by their amount and particle sizes. the addition of a few weight percent of dopant in the nominal composition can modify the particle size and distribution of the (211) grains. we have investigated and compared the phase compositions, morphologies and magnetic levitation forces of bulk superconductors formed by hydraulic pressing and moulding. the shielding abilities of a moulded superconductor were simulated with the comsol multiphysics 4.4 software. keywords: ybco superconductor, moulding, shielding, modelling introduction the use of superconductivity is promoted by the need for stable high magnetic fields. the high-temperature superconductors are attractive for engineering applications, such as contactless superconducting bearings, trapped field magnets, levitation trains, fusion reactors, and nmr spectrometers. an important application of superconducting magnets is the magnetic resonant imaging (mri). superconducting magnetic shielding can be used simultaneously to protect the personnel and other medical equipment from the strong magnetic fields produced by an mri system. the relative magnetic permeability of type i superconductor is theoretically zero, which means when we use it for shielding, it expels the magnetic fluxes from itself. the high-tc superconductors can also be used for shielding sensitive electronic devices from external electromagnetic fields. due to the meissner effect [1,2], it is sufficient to surround the volume to be protected by a thin film. for quasi-monocrystalline films of ybacuo thickness of 1 µm would be sufficient for virtually perfect shielding. a granular ceramic layer would require a larger thickness, but in all cases the thickness and weight of the superconducting shields would be much less than those of magnetic materials providing a comparable effect. for these applications of high-tc superconductors outstanding magnetic properties and special shapes are required. the scientific literature suggests two main ways for improving the magnetic properties of superconductors that are structure damaging or doping [3–9]. both methods work the same way, such as by increasing the amount of pinning centres (such as 211 phase) in the superconducting (123) material and decreasing the size of these centres by addition of different dopants. the damaging method could be done by ion or neutron radiation to destruct the bulk of the material and generate faults. preparation of high-tc superconductors with special, complicated forms is a particular challenge due to their brittle nature. slip casting, namely pouring low viscosity water-containing slurry into moulds is the oldest ceramic forming method for production of special shapes. for superconductors slip casting of shapes is also possible although the use of water as liquid phase is not optimal due to hydrolysis and other reactions. another preparation method for ceramic superconductors is tape casting of viscous slurry containing ceramic particles in organic solvent [10]. materials and methods in this work, y-ba-cu-oxid-based superconductive powders were prepared with different 123/211 phase content and different (pt, pb, ce) additives. shaped bulk superconductors were produced from these powders with hydraulic pressing and moulding. the effects of these parameters were investigated on the phase compositions, morphologies and magnetic levitation forces of the sintered bulk superconductors. for modelling the superconductor as a shield in different geometries, comsol multiphysics 4.4 software was used that provides a simulating and 40 modelling environment using the finite element method. instead of the original ac-dc module of comsol, a module by roberto bambilla was used, which was developed for modelling ybco superconductors. results and discussions samples made by hydraulic pressing the superconducting samples were prepared by using y2o3, ba(oh)2·8h2o and cuo. the latter was obtained by the calcinations of cu(oh)2·cuco3·nh2o with a specific surface area of 18.4 m2 g-1, ptcl4, pbo and ce(no3)3·6h2o starting materials. the 123:211 molecular ratio of the nominal compositions was changed in the range of 1.00:0.15. samples were prepared without additives as well as with 2.0 wt% ce + 0.5 wt% pt, and 2.0 wt% ce + 0.5 wt% pb dopants. for sample preparations, barium-hydroxide was ground in agate mortar, but in some cases the pulverization and grinding was made in the presence of alcohol. the mixture of raw materials was homogenized by thoroughly mixing with alcohol in an agate mortar and compacted into disks of 25 mm × 3mm by hydraulic pressing at 70 mpa. firstly, the samples were prereacted at 960 °c for 4 hours to obtain the desired (123+211) phases by solid-state reaction. the heattreated samples were ground and the powders were pressed into pellets by hydraulic pressing using a pressure of 70 mpa. the relatively dense structure was obtained by liquid state sintering at 1010 °c peak temperature for 6 hours in oxygen atmosphere [11]. the levitation force of the samples after the heat treatments is shown in fig.1. as described in the literature, we also found that the levitation force shows an increasing trend with increasing amount of 211 phases. in the case of ce+pt and ce+pb dopant containing samples higher levitation forces can be obtained after the first heat treatment at 960 °c. it is notable that the samples prepared from barium hydroxide ground in the presence of alcohol showed improved magnetic properties. samples made by moulding part of the pre-reacted at 960°c ground samples were used for shaping superconductors by moulding. previously, superconductive slurries were prepared with different organic liquid additives and those were burnt out during the annealing. from these materials only a few were good enough for further studies. samples providing a proper cohesion and appearing to be homogeneous were selected for future analysis. after heat treatment, x-ray diffraction analysis was used to study the phase composition changes caused by addition of organic materials for deciding if any of the dopants has a negative influence on the superconductor properties. as shown in table 1, the metylan reduces the amount of the superconducting phase (123) and this leads to the tetragonal, non-superconducting structure. polyvinyl formal did not have a negative influence on the formation of 123 phase. thus, the polyvinyl formal binder was chosen with dioxane for further experiments. with respect of ideal concentrations, it was found that 1 wt% of polyvinyl formal/dioxane must be added to the superconducting powders to obtain a slurry with a density of 2.4 g cm-3, which was dense enough, but still can be poured. the second step was to find the appropriate mould form. different types of materials were investigated, such as stainless steel, glass, plastic, gypsum, and silicone rubber. the prepared slurries stuck to most of these materials rendering them useless for moulding with the exception of silicone rubber as sample could be removed perfectly. using this type of moulds we can make superconductors with complex geometry. the moulded samples were heat treated at the same program as used for hydraulic pressed samples. the moulding technique applies no pressing thus provides a porous structure. however, the pores can lead to poor superconductor properties. to decrease the porosity melt-producing dopants were applied. ag and pb with ce proved to be good in the case of hydraulic pressed samples. table 1: the peak intensity of the crystalline phases samples peak intensity, counts binder solvent 123 d=2.72 å 211 d=2.99 å 011 bacuo2 d=3.05 å cuo d=2.52 å baco3 d=3.72 å 1. polyvinyl formal dioxane 4460 1122 562 956 2. metylan dest. water 2952 919 737 725 3. metylan ethanol 1477 765 679 459 figure 1: levitation forces of the heat treated samples 41 it was found that only in the moulded samples prepared from barium hydroxide ground in alcohol provide enough melt for efficiently fill the pores. the use of dopants alone toward this goal was not sufficient. furthermore, with this grinding technique, the peritectic temperature of the superconducting phase (123) decreased, which allowed for a more economical heat treatment. it can be proposed that this grinding resulted in particle size reduction of barium hydroxide and the higher specific surface area leading to higher reactivity. in this case bulk superconductor with higher density can be obtained, which has an oriented, large plate-like 123crystalls containing structure (figs.2 and 3). modelling ybco as magnetic shield ybco can shield from magnetic fluxes due to the meissner effect. it works the opposite way than the commonly used ferromagnetic materials, which means that superconductor expels the magnetic fluxes from itself, while iron collects them. using the comsol multiphysics 4.4 package, the shields of iron and superconductor were compared in figs.4 and 5. the shielding ability of the superconductor is comparable with iron, and even better. it has the advantage that in alternating magnetic field it does not get heated. the ferromagnetic materials shield poorly in too small and too big fields because they have saturation flux density. superconductors are being used as shields in various devices [12–16]. with a geometry shown in fig.6, very sensitive magnetic devices could be fully shielded and vice versa the environment could be protected from a device, which induces strong magnetic field. with the shape in fig.7, for example a skull could be protected in the mri in case of presence of metal implants in the head. theoretically moulding could be used to prepare these shields. it would be cheaper and thin layers could be made, thus more economical wall could be produced by a few thin layers. figure 2: sem micrograph of the moulded sample ground conventionally figure 3: sem micrograph of the molded sample ground in alcohol figure 4: simulation of iron shield figure 5: simulation of superconductor shield figure 6: simulation of shielding for sphell geometry 42 conclusion in the case of the hydraulic pressed pellets, the results confirmed those from the literatures. improved magnetic properties were noticed with the increasing of the 211 phase content. this was further enhanced by the presence dopants. it was found that pb performs as good as pt or even a little bit better, which is preferred due to the price of pt. the grinding of barium-hydroxide in the presence of alcohol provided a denser structure and more melt phase leading to better superconducting properties. furthermore, it seems that this method decreases the peritectic temperature of the superconducting 123 phase. the homogenization needs to take place after grinding in alcohol to be effective. the adequate liquid-to-material ratio to make a slurry with 1 wt% polyvinyl formal in dioxane and the ideal moulding form of silicone rubber were determined. this allowed for making complex shaped superconductors. the melt-producing dopants cannot reduce the porosity enough to sufficiently improve the levitation force. alternative heat treatment programs with slow annealing up to 500 ºc, while all of the organic materials burn out, can avoid the cracks in the structure. application of vacuum during the moulding can also be useful, since it can eliminate trapped air bubbles from the mass. simulations carried out using comsol multiphysics 4.4 software indicated ybco being a good shielding material. utilization of complex geometries, sensitive devices can be protected, such as skull protection during mri measurements. references [1] takash m., tomioka y., miyauchi t., sato s., murai a., ido t., wakita k., terada h., ohkido s., matsubara m.: characterization of a large-scale non-doped yba2cu3o7-x superconductor prepared by plastic forming without high-pressure molding, j. amer. ceram. soc. 2007, 90(7), 2032–2037 [2] evetts j.: concise encyclopaedia of magnetic and superconducting materials, pergamum press, oxford, 1992, pp. 532–533 [3] monot i., leblond c., marinel s.m., desgardin g.: precursor and microstructure control for melt texturing of high-tc superconductive ybco ceramics, development of high-temperature superconducting alternators combining rotating and levitating principles, russian academy of science, saint-petersburg, 2002, pp. 27–45 [4] shlyk l., nenkov k., krabbes g., fuchs g.: melt-processed ybco with pt or ce additions: comparison of pinning behaviour, physica c 2005, 423, 22–28 [5] riches j.d., alarco j.a., barry j.c.: effects of pto2 and ceo2 additives on the microstructures of the quenched melts of y–ba–cu–o materials physica c superconductivity, 2000, 336, 43–56 [6] leblond c., monot i., provost j., desgardin g.: optimization of the texture formation and characterization of large size top-seeded-meltgrown ybco pellets, physica c, 1999, 311, 211–222 [7] hardy v., simon c., provost j., groult d.: pinning forces in bi-2212 single crystals irradiated by 6 gev pb ions, physica c, 1993, 206, 220–226 [8] wesche r.: magnetic relaxation and flux pinning in yba2cu3o7 a high-tc oxide irradiated by 5.3 gev pb ions, physica north-holland c 1992, 190, 289–298 [9] horvat j., wang x.l., dou s.x.: vortex pinning in heavily pb-doped bi2212 crystals physica c 1999, 324, 211–219 [10] grader g.s., johson d.w.: forming methods for high tc superconductors, thermochimica acta, 1991, 174, 239–251 [11] komlai k.: investigation of the the properties of the incongruent melting reaction of yba2cu3o-y superconductor phase, m.sc. thesis, university of pannonia, 2013 (in hungarian) [12] tavernier s.p.k., van den bogaert f., van lancker l.: the design of a magnetic shielding for an array of photomultipliers in a strong external field, nucl. instrum. methods, 1979, 167, 391–398 [13] bitter t., eisert f., el-muzeini p., kessler m., kinkel u., memt e., lippert w., meienburg w., werner r.: a large volume magnetic shielding system for the ill neutron-antineutron oscillation experiment, nucl. instrum. methods phys. res., 1991, a309, 521–529 [14] tripathi a., vedavathy t.s.: electromagnetic shielding using superconductors, pergamon press ltd, oxford,vol. 2, no. i, 1994, pp. l–5 [15] spillantini p.: active shielding for long duration interplanetary manned missions, adv. space res., 2010, 45, 900–916 [16] yusuf s.m., osgood iii r.m., jiang j.s., sowers c.h., bader s.d., fullerton e.e., felcher g.p.: magnetic profile in nb/si superconducting multilayers, j. magnet. magnetic mat., 1999, 198–199, 564–566 figure 7: simulaton of shielding using a semi-sphell geometry hungarian journal of industry and chemistry veszprém vol. 42(1) pp. 43–50 (2014) effects of ultrasonic disintegration, hot-compressed liquid water pre-treatment, and steam explosion on solvolysis and digestibility of grain sorghum stover dániel capári,! and andrás dallos department of physical chemistry, university of pannonia, egyetem str. 10, veszprém, h-8200, hungary !e-mail: capari.daniel@gmail.com one of the most promising renewable energy crops and biomass feedstock for biogas production in europe is the c4 plant grain sorghum due to its high photosynthetic efficiency. the release of lignocellulosic material and therefore the acceleration of degradation processes of sorghum stalks and leaves can be achieved using mechanical and thermal pretreatments, which assist to hydrolyse the cell walls and speed the solvolysis of biopolymers. this study is focused on hotcompressed liquid water, steam explosion and ultrasonic pre-treatments of grain sorghum stover. the effectiveness of pre-treatments was evaluated by means of soluble chemical oxygen demand, biochemical oxygen demand, and by the biogas and methane productivities. the results show that the pre-treatments disintegrated the lignocellulosic structure, increased and accelerated the biogas and methane production, and increased the mesophilic anaerobic digestion potential of grain sorghum stover. our laboratory tests demonstrated that the steam exploded grain sorghum stover possess the highest biogas productivity. keywords: grain sorghum stover; hot-compressed liquid water pre-treatment; steam explosion; ultrasonic disintegration, biogas digestion. introduction the grain sorghum is a possible carbohydrate resource for the simultaneous production of bioethanol and biogas due to its advantages over the traditional agricultural crops. the plants have remarkably good co2 absorption ability. grain sorghum is the fifth most important cereal crop grown in the world. the drought tolerance of sorghum is greater than that of corn. furthermore, it is able to regenerate after a period of drought. its productivity is also higher than that of corn, even in dry periods or in lower quality soils. in hungary, sorghum grows in arid areas as a substitution for fodder corn. therefore sorghum could be used to cultivate alternative feedstock for bioethanol production [1] and could be a sustainable crop for energy production in europe. the sorghum grain contains approximately the same amount of starch compared to corn kernels, which makes it attractive as raw material for the production of bioethanol. the agricultural byproduct of sorghum-based bioethanol production, the sorghum stover is a valuable bioenergy substrate for biogas digesters, despite the complex lignocellulosic structures of sorghum stalks and leaves and its resistance to decomposition. the utility and the economic feasibility in biogas power plants can be highly increased by different pre-treatment methods, to assist the disruption of the cell wall structure and to speed-up the solubilisation of the biopolymers in the biogas feedstock [2–4]. the purpose of pre-treatments is to remove lignin and hemicellulose, reduce cellulose crystallinity, and increase porosity [5,6] (fig.1). liquid hot-compressed water (lhcw) pre-treatment is a commonly used hydrothermal method. high temperature and high pressure are applied to maintain liquid phase and to avoid vaporization. during the pretreatment, water is penetrated into the cell structure of the biomass, hydrating cellulose, solubilizing hemicellulose, and slightly removing lignin. lhcw pre-treatment is highly effective for enlarging the accessible and susceptible surface area of cellulose and improving cellulose degradability for microbes and their enzymes [7,8]. after the hydrothermal treatment, the biogas production was increased for pig manure, for municipal sewage sludge and for fruit/vegetable waste figure 1: the disintegration of lignocellulosic material by pre-treatments 44 [9]. the hot water treatment increases the enzymatic hydrolysis and digestion of corn leaf, stalk and fibre [10,11] and the dissolution of solids and xylan of destarched corn fibre [12]. the liquid hot water pretreatment of sorghum bagasse produced higher solubilisation of hemicellulose and cellulose content enrichment [13]. combining hydrothermal treatment and enzymatic hydrolysis of sorghum bagasse resulted in improvement of cellulose and total polysaccharides hydrolysis [14]. steam explosion (se) is one of the most effective methods for the pre-treatment of lignocellulosic biomass. in this process, the biomass is heated with high-pressure steam for a certain period, than the pressure is reduced to atmospheric pressure as quickly as possible. the biomass is undergone on an explosive decompression by this swift reduction of pressure [6,7]. the high efficiency of the steam explosion treatment is due to the thermo-mechano-chemical destruction applied in the method. steam-explosion has been used to treat various kinds of lignocellulosic biomass (i.e. softwood, sugarcane bagasse, corn stalk) for enhanced bioethanol and biogas production [15–19]. sipos et al. [20] demonstrated the efficient effect of pre-treatment by steam on sorghum bagasse characterized by high degree of cellulose hydrolysis. zhang et al. [21] compared four pre-treatment processes including liquids, steam explosion, lime and dilute acid for enzymatic hydrolysis of sorghum bagasse and pointed out that steam-explosion showed the greatest improvement on enzymatic hydrolysis. the biogas yields of anaerobic digestion can be also increased by ultrasonic treatments (ut) to support the solubilisation of raw materials. during the ultrasonic treatment, a cyclic sound pressure is used to disintegrate the cell walls by cavitation. the parameters of the sonication are the power, frequency and time of sonication [3,22]. zhang et al. [23] showed that ultrasonic pre-treatments caused indistinctive effects on bio-hydrogen production. the ultrasonic treatment accelerated the enzymatic hydrolysis of corn stover and sugar cane bagasse cellulose [24] and improved the liquefaction and saccharification of sorghum flour [25]. imam et al. [26] pointed out the positive effects of ultrasonic plus hot water pre-treatment on the conversion of sweet sorghum to hexose and pentose sugars and on lignin, cellulose and hemicellulose concentrations. however, no systematic studies on pre-treatments of grain sorghum stover are available in literature. a correct comparison of the various pre-treatments and the selection of the suitable processes for the disintegration of grain sorghum stover as feedstock for enhanced biogas production are the goals and the novelty of this paper. however, the main message of this work is that a perfect testing is only possible, if there are no differences in the microbial communities in different biogas fermenters, in the inocula used, in the substrates cultivated and in the methods applied to assess pretreatments: chemical analysis, batch tests or continuous ad. therefore this work is focused on liquid hotcompressed water, steam explosion and ultrasonic pretreatments of grain sorghum stover using both fast analytical, biochemical and biomethane potential ad tests to study and comparison the effects of pretreatments on anaerobic digestion without addition of chemicals. the influence of temperature, contact time of thermal treatments, and the effect of sonication energy on decomposition of lignocellulose on a chemical level were determined using laboratory scale experimental techniques. the effectiveness of thermal and ultrasonic treatments was evaluated by scod and bod5 concentrations and by the biogas and methane productivities during mesophilic fermentations. experimental materials sorghum stover investigated in this work consists of leaves and stalks of commercial grain sorghum (milo) hybrid named mexican sweet (code: hf1) harvested from the b12 field at kétegyháza, hungary, and used for pre-treatments and biogas production experiments. this easily grown hybrid with mid-early maturation was developed by j. feczák (agroszemek ltd., szeged, hungary). post-harvest residue grain sorghum stover samples were chopped, homogenized, and analysed for dry substance (ds, 93.6%), organic dry substance (94.5%), and ash (5.5%). deionized water was used in all experiments after cation and anion exchange. liquid hot-compressed water treatments the lhcw pre-treatments were carried out in a 2 l capacity parr 4843 type high-pressure reactor at the temperatures of 100, 150 and 175 °c (0.1, 0.5 and 0.9 mpa, respectively) and at various treating time from 10 to 120 minutes. 25 g of grain sorghum stover were used in each experiment and were added to 1000 g of water. the suspension was introduced in the thermal reactor at room temperature and heated to the set temperature. the pulp slurry was mixed by a built-in stirrer at 300 rpm during the entire treating process to avoid temperature gradients. after treatment, the reactor was cooled down to 30 °c by the built-in cooling system of the reactor using cold water-flow and the treated slurry was removed from the vessel. steam explosion pre-treatments se treatments were performed in a steam explosion laboratory unit (fig.2) consisted of a steam generator (2), a digester vessel (6) and a separator cyclone (8). a 2 l capacity parr 4843 reactor was used for the production of steam with temperatures of 185, 200, and 215 °c and working pressures of 1.1 mpa, 1.6 mpa, and 2.1 mpa, respectively. the se unit operated in batches and equipped with a digester vessel (6) of 200 cm3 volume. the digester vessel was filled with 10 g 45 feedstock per batch and was heated to the desired temperature, directly with saturated steam led to the vessel, by opening the steam inlet valve (5). no catalysts (additional chemicals) were applied in the process. after the steaming time (1–10 minutes), the expansion valve (7) was opened to rapidly reduce the vessel pressure to the atmospheric one. the steamed sample slurry explosively released into the separator cyclone (8). ultrasonic treatments the ultrasonication was performed in a vibracell vcx 750 (sonics & materials, usa) ultrasonic processor operated at constant sonication frequency of 20 khz with maximum power input of 750 w. the radiation was carried out by a 25.4 mm diameter titan alloy (ti6al-4v) probe with removable tip and maximum amplitude of 35 µm. samples of the mixture of grain sorghum stover (1 g) and water (99 g) placed in a temperature-controlled vessel. they were subjected to ultrasonic pre-treatment without additional agitation at different power inputs by adjustment of the amplitude (50, 70 and 100%) and at various sonication durations of from 1 to 10 minutes for each power level. the temperature of the vessel was held constant at 25 °c during the treatment by a high-precision thermoregulator (huber kältemaschinenbau gmbh, germany). aliquot parts of the resulting sorghum stover pulp slurries of samples obtained from pre-treatments were used as substrate in ad test. the rests were filtered to separate the solid fraction from the liquid fraction for analytical measurements (scod, bod5, ph). a set of untreated, blank samples was also tested for chemical analysis and methane potential by ad as the control points of reference for the treated samples. mesophilic anaerobic digestions the anaerobic degradability of untreated, lhcw, se, and ut pre-treated grain sorghum stover slurries was determined in laboratory scale, using a fermenter system contained 12 pyrex batch reactors of 1 l capacities. inoculum for the ad tests was taken from the effluent line of an anaerobic pilot fermenter [27] treating a mixture of swine manure and corn stillage (spent mash remaining after bioethanol distillation) at biogas test facility of denk ltd (kövegyűrpuszta, hungary). the batch reactors were inoculated by 700 g inocula. afterwards a batch of 100 g of grain sorghum stover pulp slurry samples was added under nitrogen atmosphere. furthermore, the digester materials were bubbled with nitrogen gas for 10 minutes to get rid of the air from the liquid phase before each experiment. the batch reactors were kept in a temperaturecontrolled water bath at 37 °c until they stopped producing biogas. the mesophilic ad tests performed for grain sorghum stover substrates including controls were all done in duplicate. during the 36–40 days mesophilic ad tests the flows of the produced biogas were on-line measured by digital flow meters and the daily and cumulated biogas volumes were stored digitally. the methane content was determined by gas chromatography. analytical and biochemical measurements the scod, ph, and bod5 measurements were carried out on the liquid fractions after 10 min centrifugation at 14,000 rpm and 20 °c with a refrigerated universal high-speed, filtration (0.45 µm) centrifuge (unicen mr, herolab, germany). colorimetric scod concentration was measured by the standard methods procedure [28] using a nanocolor vario compact heating block (macherey-nagel, germany) and a multidirect photometer (tintometer/lovibond, germany) according to din iso 15705. biochemical oxygen demand (bod5) was determined according to en 1899-1 and en 1899-2 by using oxitop control 6 oc 100 (wtw, germany) system. the ph values were measured by a c831 type ph meter (consort, belgium) with an ra-0903p sensor (radelkis, hungary) after two-point ph calibration (ph = 4.01 ± 0.01 and ph = 7.00 ± 0.01) using duracal ph buffers (hamilton, switzerland). the surfaces of the grain sorghum stalk were investigated by a philips xl30esem environmental scanning electron microscope (esem) with 20 kv accelerating voltage and resolution of 3.5 nm, in secondary electron image mode (sei), and backscattered electron image mode (bei). results and discussion liquid hot-compressed water treatments the influence of lhcw pre-treatments at various temperatures and treating times on scod concentration of grain sorghum stover slurry is visualized by 3d mesh segmentation on fig.3. the results of lhcw pre-treatments show that hotcompressed water has a positive effect in grain sorghum stover disintegration, leading to significant increments in scod concentration: +262% at 100 °c, +419% at figure 2: scheme of the steam explosion apparatus (1. input valve, 2. steam generator, parr 4843 reactor, 3. pressure gauge, 4. evacuation valve, 5. steam inlet valve, 6. digester vessel, 7. expansion valve, 8. cyclone, 9. sampling valve, 10. steam outlet valve) 46 150 °c and + 698% at 175 °c with an operating time of 60 min, respectively. the control experiments were performed using untreated grain sorghum stover suspension. both temperature and time have positive, but not linear effects on scod and not to the same degree. the temperature raising has more effect on the solubilisation of grain sorghum stover after 60 minutes than the treating time in agreement with the results of valo et al. [29] who found that treating time had less influence than temperature during thermal treatment of sludge. it is notable that higher solvolysis temperatures resulted in more acidic products as reflected by the low ph level of the grain sorghum stover slurry (fig.4). steam explosion pre-treatments the pressures and temperatures of se pre-treatments had significant effect on digestibility of grain sorghum stover. elevated pressures and temperatures resulted in enhanced solubilisation (fig.5). the positive pressure effect may be explained by the increased disintegration caused by higher-pressure drop at the end of treatment. compounds that are more soluble were released from the grain sorghum stover during the steam explosion and made the resulting slurry available to subsequent bacterial degradation. the pressure effect is quasi-linear and the effect of contact time can be modelled by an exponential-tomaximum function. compared to the untreated grain sorghum stover, the scod concentrations of the slurries increased by a factor of 8.9, 9.6, 10 at 185, 200, and 215 °c, respectively, with an operating time of 3 min, respectively. additional, the ph value decreased with pre-treatment pressure (steam temperature) and with the contact time (fig.6). the formation of acidic degradation products during disintegration of grain sorghum stover slurry by steam explosion agree well with the observation of guo et al. [30] at corn stalk steam explosion. ultrasonic treatments the efficiency of ultrasonic irradiation of grain sorghum stover was quantified by scod concentration of the slurry as a function of contact time and power input in terms of ultrasonic amplitude level (%) and specific sonication energy. results of ultrasonic treatments are shown in fig.7, where the values of the scod figure 4: acidity of grain sorghum stover slurries as the function of lhcw contact time and temperature (!: experimental data point) figure 3: effects of temperatures and contact times of lhcw pre-treatments on scod concentration of grain sorghum stover suspension (!: experimental data points) figure 5: effects of steam pressures on scod concentration levels of grain sorghum stover slurries as the function of the contact time during steam explosion (!: experimental data points) figure 6: the effect of steam explosion on ph values of treated grain sorghum stover slurry at various steam pressures as the function of the treatment time (!: experimental data points) 47 concentrations are presented for each value of the ultrasonic amplitude level (%), and sonication time. the scod of the pulps increased with the ultrasonic power demonstrating the effectiveness of the cavitation energy to disrupt the cell walls of the plant parts. the scod concentration excess reached +105%, +109%, and +133% at 50%, 70%, and 100% amplitude level, respectively, with a contact time of 3 min. the ultrasonic power and the pre-treatment time affect the scod to a different degree. the raising of scod values by treating time is stabilized after 3 minutes. these can be described by an exponential-tomaximum function. the effect of energy-input on scod is quasi-linear (r2 = 0.942) as demonstrated by the data shown in fig.8, where scod values are plotted against the specific sonication energy. the scod concentrations were increased by the sonication energy; however, no power-saturation phenomenon was observed. the sonication energy over the minimal energy of 1kj g-1 ds is the most effective for breaking up cells [31]. the ph values of the sonicated grain sorghum stover slurries decreased monotonously with pre-treatment time and sonication power on a small scale (fig.9) suggesting that local temperature effects caused by cavitation bubbles were not enough to accelerate the hydrolytic processes resulted in acidic degradation product. environmental scanning electron microscopy the esem pictures of the surfaces on untreated and by ultrasonic treated grain sorghum stalks are shown in fig.10 at 100× magnification. the surface of the treated sorghum stalk was altered (fig.10b) from the appearance of defective plant tissues. fig.10b shows a heterogeneous appearance compared to the homogeneous surface of the untreated stalk (fig.10a). the comparison of the pre-treatment results of the chemical analysis, the scod concentration, and ph changes of grain sorghum stover slurries suggested that the most effective disintegration method is the steam explosion to disrupt the lignocellulosic structure of grain sorghum stover and partial hydrolysis of it molecular components. however, results of these fast methods can only indicate how much structures of lignocellulosic materials broke down on a chemical level. nevertheless, greater decomposition of the lignocellulose structures does not necessarily prove enhanced biogas production, because inhibitors for methanogenesis reactions can also be produced through hydrolytic processes during steam explosion. furthermore, one has to take into account the high energy needs of treatments at elevated temperatures. according to the results of fast chemical analyses (scod and ph), the optimal conditions for the lhcw, steam explosion and ultrasonic treatment of grain sorghum stover were established as 150 °c / 30 min, 200 °c / 3 min and 100% ultrasound amplitude / 3 min (at 25 °c), respectively. however, to study the real effect of optimal conditions of the investigated pre figure 8: scod change in grain sorghum stover slurry as a function of specific sonication energy (!: experimental data points) figure 7: the effect of sonication energy on scod concentration level of grain sorghum stover slurry as the function of sonication time and relative ultrasound amplitude (!: experimental data points) figure 9: the effect of sonication power on the ph values of grain sorghum stover slurries as the function of the sonication time (!: experimental data points) figure 10: esem pictures of the surface on untreated (a) and by ultrasonic treated (b) grain sorghum stalks at 100× magnification 48 treatments additional biochemical tests like bod and biomethane potential determinations are necessary. biochemical oxygen demand a comparison of the biochemical oxygen demands of filtrates of grain sorghum stover slurries after pretreatments at the optimal conditions is given in fig11. the results of the bod5 tests support the observations from chemical analysis. actually, all three methods investigated are appropriate for pre-treatment of grain sorghum stover, because the bod5 values systematically increased in filtrates of grain sorghum stover slurries with the treatment time under the conditions investigated. however, the highest bod5 values were obtained in filtrates after steam explosion, therefore the steam explosion seems to be the most effective disintegration method to disrupt the lignocellulosic structure of grain sorghum stover and to partially hydrolyse its molecular species, resulting in the formation of bacterially digestible substrate. biogas production by mesophilic anaerobic digestions biogas and biomethane production tests were carried out using grain sorghum stover slurries pre-treated under stated optimal conditions (lhcw: 150 °c / 30 min, steam explosion: 200 °c / 3 min, and ultrasonic treatment: 100% ultrasound amplitude / 3 min at 25 °c). daily as well as the final biogas and methane production (normalized volumes at 0 °c and 101.15 kpa) were determined. the results are shown as a function of the digestion time in figs.12 and 13. the specific gas productions were calculated by dividing the cumulated gas amount with the total ds of the substrates. as reference, the untreated material was used in the same amount. in agreement with the results of chemical analytical and biochemical tests after pretreatments, the specific total biogas and methane yields obtained for treated grain sorghum stover substrates were significant higher than that of the untreated control. as seen in fig.12, biogas productions began immediately, without a lag period after starting the degradation of grain sorghum stover. the fastest biogas production at the beginning was detected at the ultrasonicated substrate. however, the highest biogas production was observed during the fermentation of steam-exploded substrate. the biogas production proceeded in constant and high daily biogas production for treated substrates until the 30th day of hydraulic retention time. this observation is notable, because the application of pre-treatments can decrease the usual cycle time for biogas fermentation and increase the production of biogas with higher methane content. the comparison of the biomethane yields is given in fig.13. methane production, as the major result of anaerobic digestion of pre-treated grain sorghum stover, was markedly increased by the three pre-treatments. the highest biomethane production rate was observed at the substrates after ultrasonic and steam explosion pretreatments. the biomethane production rate of lhcw figure 11: comparison of the bod5 test of filtrates of grain sorghum stover slurries after various pre-treatment methods figure 12: specific cumulative biogas yield (ncm3/g ds) of grain sorghum stover substrates after pre-treatments figure 13: specific cumulative methane yield (ncm3 g-1 ds) of grain sorghum stover substrates after pre-treatments 49 treated substrate was lower, probably due to the low ph of the pre-treated grain sorghum stover slurry. our laboratory tests have shown that the steam exploded substrate possess has the highest biogas production potential (439 ncm3 g-1 ds) during hydraulic retention times of 36 days with 55% methane content. the steam explosion pre-treatment increased the biomethane yield by +72% to 242 ncm3 g-1 ds. the lhcw pre-treated substrate has the second highest biogas production potential (403 ncm3 g-1 ds) during hydraulic retention times of 36 days with 52% methane content, the lhcw pre-treatment increased the biomethane yield by 49% to 210 ncm3 g-1 ds. this yield increment is higher than that was obtained by qiao et al. [9] for various biomass wastes after hydrothermal treatment. the substrate after ultrasonic pre-treatment has a biogas production potential of 383 ncm3 g-1 ds during hydraulic retention times of 36 days with 44% methane content, the ultrasonic pre-treatment increased the biomethane yield by 18% to 167 ncm3 g-1 ds. the low biogas and methane yields of ultrasonic treated grain sorghum stover can be explained by the superficial effect of ultrasonic cavitation. conclusions the results of chemical, biochemical analyses and biogas/biomethane potential test obtained by mesophilic anaerobic digestion were presented. it was found that lhcw treatment and steam explosion are the most effective biomass pre-treatment for increasing the solubilisation of the organic matters of grain sorghum stover. laboratory testing of anaerobic digestibility of pre-treated slurries have shown that the grain sorghum stover has high biogas potential. it can serve as biogas feedstock and could reduce the energy consumption of sorghum-based bioethanol production in the future. the lhcw and steam explosion biomass pre-treatment techniques can reduce the cycle time and improve the biogas production via disintegration of the complex and compact plant structures of grain sorghum stover. acknowledgements this research was supported by támop 4.2.4. a/2-111-2012-0001 „national excellence program – elaborating and operating an inland student and researcher personal support system”. the project was subsidized by the european union and co-financed by the european social fund. authors also gratefully acknowledge the support of the hungarian state and european union under the támop-4.2.2.a11/1/konv-2012-0071 project. references [1] saldivar s.r.o.s., carrillo e.p., alvarez m.m.: method for obtaining bioethanol from sorghum grain (sorghum bicolor l.moench) comprising steps involving decortication and hydrolysis with proteases. patent application number: us 20110014671 a1, 2011 [2] mcmillan j.d.: 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a reaction structure identification algorithm jános kontos,1! lászló richárd tóth,2 and tamás varga2 1 department of physical chemistry, university of pannonia, egyetem st. 10, veszprém, h-8200, hungary 2 department of process engineering, university of pannonia, egyetem st. 10, veszprém, h-8200, hungary !e-mail: kontosjan@gmail.com the most important step in the design procedure of a chemical reactor is the understanding the chemical reaction network (crn), which will take place in that reactor. the structure of a crn as representation of the reaction mechanism contains all the elementary reaction steps that are required to convert the reagents into products. the aim of the reaction mechanism analysis is the identification of the route how the system goes from its initial to the end state. in order to do this, a lot of knowledge is required about chemistry supplemented with some analytical measurements. in this work, we focus on the development of an algorithm, which requires a few data inputs to reveal all the reaction steps that are important in the reactor design point of view. it is trivial that the structure of a dynamic system cannot be determined without the identification of the model parameters that belong to that structure. hence, the algorithm reported here can be used to obtain the parameters of the reaction rate equations for each identified chemical reaction. first, the structure is identified followed by its parameters. in this study the processed data are obtained by a crn generator, which is applied to generate random crns based on some specified parameters to reach maximal reaction order. concentration profiles, which characterize each crn at a specific reaction rate constants combination, are obtained as a result of simulations based on the randomly generated crns. the developed algorithm for reaction mechanism identification is based on a modified type of linear least-squares method (llsm) in which the searching variables must be higher than zero, since the reaction rate constants cannot have negative values. the developed algorithm is tested in different cases to check the applicability of llsm in reaction structure identification procedure and the obtained results show that with some further improvements the proposed algorithm can be applied solving more complex identification tasks. keywords: chemical reaction network, structure identification, non-negative least-squares method, crn generator introduction one of the most important tasks during the design procedure of any chemical technology is the engineering design of the conversion subsystem and to ensure the optimal and safe operation. hence, before starting the design of a technology phenomena with impact on the dynamic behaviour of the subsystem must be identified. the most crucial part of the conversion subsystem is the chemical reactor in which we try to control the processes that was identified on the basis of laboratory experiments. in this work we proposed a method to support the identification of the individual reaction steps and their rates in a chemical reaction network (crn). numerous literature examples can be found that describe different methodologies to generate the structure of crns, as representations for reaction mechanisms [1, 2]. the reaction mechanism of a reaction system represents all the elementary reaction steps, which are required to convert the reagents into products. hence, the aim of reaction mechanism identification is the determination of the intermediate steps, which take the starting materials to the final products. trivially, it is challenging to follow and model the movements of all the molecules in a system in full detail. however, we can describe a reaction system on the basis of the cumulative effects of great number of molecules in specific states. such specific states are the formation of stable intermediates. the intermediates are chemical species produced in the elementary reaction steps. often, it is possible to detect them by experimental methods. the produced amount of these intermediates is sometimes very low and they react very fast to produce another intermediate or final product. hence, the identification of the latter components and the measurement of their concentrations can be challenging. most of the reactions take place through multiple intermediate steps. these scenarios are called multi-step reactions. in a single reaction step, the sign of stoichiometric coefficients represent that a given molecule is a reagent (-) or product (+), and the absolute value of these coefficients give how many moles are consumed/formed. the transient states of a reaction system and the intermediates can be investigated with two kinds of methods on the basis of whether a priori knowledge of reaction kinetics is available or not [3]. the foundation of the reaction mechanism analysis is the precise identification of all intermediates and their 52 concentration. with the lack of this information the stoichiometry of the reaction cannot be revealed reliably. the nature and the amount of the products can contain as much information as a well-qualified chemist requires identifying the reaction mechanism of an unknown reaction system. the proposed algorithm can support this process in case we have lack of experience in the identification of the structure of a crn and parameters of kinetic expressions, which describe the rate of the reaction steps considered in the crn. the essence of the parameter identification process is the solution of a constrained minimization problem in which the objective function can be the sum of squared error between the measured and the calculated component concentration profiles. the searching variables are the unknown parameters in the kinetic expressions (i.e. pre-exponential factor, activation energy, reaction order). the role of the structure identification is the definition of correlated variables and their mathematical formalization. in our case, the identification means the selection of reaction steps that can take place in the reactor. the identification tasks can be solved by the application of linear least-squares method (llsm) [4]. the main challenges using this method are the definition of the correct initial conditions for the applied searching algorithm and the speed up of the identification procedure. one of the most important simultaneous methods is the incremental approach, which applies a hierarchical modelling methodology to decompose the complex identification problem into simpler sub-problems [5]. the method applies target factor analysis to identify the suitable structure of the unknown crn. this method has been successfully applied in reaction mechanism identification process in a multi-phase system based on concentration and calorimetric measurements [6]. correlation metric method was developed to analyse the strength of the connections between the components in the system, which is based on the qualitative analysis of the measured data [7]. qualitative trend analysis was also applied in reaction mechanism identification algorithms to divide the entire experimental time into shorter periods in which the correlations are analysed between the concentrations of components [8]. in this work, our aim is to develop a simple, but reliable method for structure identification of crns, which need as few data as possible. in our case the input of the algorithm is only the list of components and concentration profiles, which are the result of the simulation based on randomly generated crns. these crns were generated based on user specified parameters, such as maximal reaction order. on the basis of the randomly generated crns, the concentration profiles for each crn at a specific reaction rate constants combination are determined. the algorithm developed for reaction mechanism identification is based on a modified llsm method, in which the searching variables must be higher than zero, since the reaction rate constants cannot have negative values. development of simulation methods since our aim is to develop a generally applicable algorithm to support the identification process of crns with unknown structure, we developed a crn generator, which can be applied to randomly generate crns based on some structural parameters, such as the maximum number of components or reactions in crn. there are many examples in literature for developing a crn generator that analyses the affinity of molecules taking part in reactions [9], applies mixed integer programming to build up reaction networks [10], or using group contribution method to generate the structure of the crn and the kinetic parameters of the reaction steps in that network [11]. in this work we developed a simple crn generator that randomly generates a crn from randomly generated components. in this generator, we define probabilities in situations for building different kinds of crns. for example, if we would like to have more decomposition reactions in the crn then the probability of this type of reaction is increased. the scheme of the developed crn generator can be seen in fig.1. the first step of the algorithm of the crn generator is the definition of the parameters of the desired crn, such as the probabilities of the different types of reactions. in this step the maximal number of building block types in a component and the maximal number of specific building blocks in a component are defined. figure 1: the scheme of the proposed crn generator 53 the next step is the development of the first reaction step in which we define a new component next to the components that are already in the component list. the stoichiometric coefficients of the reaction are randomly generated based on the user-defined parameters. the composition and the chemical formula of the added component are determined based on the material balance of the reaction. with the first reaction step, it is checked whether the numbers of components and reactions in the generated crn are enough. if the user defined value of these parameters are higher than the current values the crn generator starts to build a new reaction with selecting the reaction type, the components. based on the crn parameters it randomly generates stoichiometric factors for that new reaction and checks the material balance. components that are involved in more reactions have a smaller chance to be chosen for the next new reaction building iteration. if there are enough components or reactions in the generated crn, the algorithm steps to the next phase in which it randomly generates the reaction kinetic constants for reactions in the crn. in this phase, the algorithm randomly generate kinetic parameters, while maintaining the same order of magnitude of the reaction rates, to make it harder to find out the structure of the generated crn. particle swarm optimization method has been applied to solve this constrained optimization problem, where the objective function is defined as the difference of the integral of reaction rates over the time [12]. general reactor model the kinetic experiments are usually performed in a tempered flask that can be modelled as an isothermal batch reactor. all the reagents are added to the unit with or without catalyst and samples are taken from the reaction mixture in specific times. as mentioned earlier the simplest case is considered as we have only concentration measurements from a batch reactor. however, the developed algorithm can be improved and the processability of data can be widened with the application of mathematical models of other reactor types. hence, at this point of the development of the proposed algorithm, we consider that the unit in which the kinetic experiments are performed is a well-mixed, isothermal batch reactor. the model of a batch reactor should be developed first to contain component mass balance equations. applying the well-mixed assumption the component mass balances can be simplified and we obtain the equations: { } ,;...c;b;air dt dc i i == (1) where i identifies the components in the system in which we have nc components; ci is the concentration of the ith component [mol m-3]; ri is the component source of the ith component [mol m-3 s-1], which can be calculated as: ri = υ ji ⋅ rj j=1 nr ∑ , (2) where j identifies the reaction in the system; nr gives the number of reactions considered; νji is the stoichiometric coefficient of the ith component in the jth reaction; rj is the reaction rate of the jth reaction [mol m3 s-1], which is calculated with following expression: rj = k j ci n ji i= a;b;c;...{ } ∏ , (3) where nji denotes the order of ith component in jth reaction [1], kj is the reaction rate constant of the jth reaction [the unit is dependent on the order of the reaction, [mol1-n m3n-1 s-1], where n is the summarized reaction order in jth reaction: n = nji i= a;b;c;...{ } ∑ . (4) this summarized reaction order is equal to the absolute value of the stoichiometric coefficient of the ith component in the jth reaction, if the given component is a reagent in a given reaction, otherwise it is 0. the developed general reactor model has been implemented in matlab. proposed algorithm for structure identification of crn our primary aim is to develop an algorithm, which can be efficiently applied in reaction mechanism identification tasks on the basis of concentration profiles. in this phase, we considered that the concentration profiles are known for all the components in the system. it is a simplification with respect of practical problems; however, in this work we aim to evaluate if a simple method of llsm is suitable for a complex task. llsm is based on the minimization of a special model error, which is based on comparing the measured to the calculated time series. in our case, the time series are the numerical derivatives of the concentration profiles. based on the measured concentration profiles the change in concentration during two sampling steps can be calculated as a numerical derivative with respect to length of that time step. if we have nk samples, the difference in kth sample can be defined as follows: δĉ i δt k( ) = ĉ i k( )− ĉ i k −1( ) , (5) where k is the current sample; δĉ i is the difference of the measured concentration of ith component in between k and k-1 sampling steps; tδ is the time difference between k and k-1 sampling steps. if we calculate this difference for all the components and in every sampling steps we get a matrix which has k-1 rows and as many columns as many components we assume in the system. based on the calculated concentration profiles another matrix can be built with the calculated variables. in our case the sum of the 54 squared differences between these two matrices is defined as the model error, which should be minimized during the identification process: e = δĉ i δt k( )− δci δt k( ) # $ % & ' ( 2 k=1 nk ∑ i= a;b;c;...{ } ∑ , (6) where e is the calculated model error, which is basically the difference of the measured and calculated component sources defined with eq.(2); δci is the calculated changes in concentrations of ith component from eq.(1), but the steps is equal with the sample times of measurement. to make it easier to follow the process we define eq.(6) using vectors instead of sums: e = δĉ ___ − δc ___# $ % & ' ( t δĉ ___ − δc ___# $ % & ' ( , (7) where the length of vectors are nc(nk-1) (i.e. the change in concentrations of components should be calculated in every sample time except in the initial phase) and defined with the following structures: δĉ ___ = δĉa 1( ) δĉb 1( ) ! δĉa 2( ) δĉb 2( ) ! δĉa k( ) δĉb k( ) ! " # $ $ $ $ $ $ $ $ $ $ $ $ $ $ % & ' ' ' ' ' ' ' ' ' ' ' ' ' ' , δc ___ = δca 1( ) δcb 1( ) ! δca 2( ) δcb 2( ) ! δca k( ) δcb k( ) ! " # $ $ $ $ $ $ $ $ $ $ $ $ $ $ % & ' ' ' ' ' ' ' ' ' ' ' ' ' ' . (8) the task in llsm is the minimization of the model error defined in eq.(7) by manipulating the model parameters, such as the reaction rate constants of all the possible reaction steps, which are the building blocks of the unknown crns. hence, to use llsm in reaction mechanism identification process first we need to collect all the possible reaction steps, which can take place in the system based on the defined component list. to get the necessary reaction steps, we generate all the possible combination of reactions, which satisfy the material balances. a given reaction step has to be further processed, since some reaction steps can be produced from each other with linear combinations. thus, only the independent reactions should be kept in the reaction set. the resulted reaction set is represented in a matrix (i.e. in stoichiometric matrix): =υrs , ba ba ba ! ! ! " # $ $ $ % & υυ υυ !"" # # " # 22 11 2 1 (9) which has the same number of rows and columns as the number independent reactions and components are considered in the system, respectively. after the possible reaction steps have been automatically collected, all the reaction steps of the set are considered as the part of the unknown crns. based on the reaction set the mathematical model of the system is automatically generated based on eqs.(1)-(3). the unknown parameters in this model are the reaction rate constants for all reactions in the reaction set. the calculated concentration differences in eq.(7) can be obtained using eq.(10) on the basis of the general reactor model (eqs.(1-3)): ,ckc ___ υ=δ (10) where c denotes a special matrix in which a diagonal matrix is repeated from sample time to sample time and in the diagonal matrices we calculate the concentration product term in eq.(3) in every sample time. the following general matrix shows the structure of the resulting diagonal matrix in this step if we have nr reactions in the reaction set: =c ci 0( )( )n1i i= a;b;c;...{ } ∏ 0 ! 0 ci 0( )( )n2i i= a;b;c;...{ } ∏ ! " " # ci 1( )( )n1i i= a;b;c;...{ } ∏ 0 ! 0 ci 1( )( )n2i i= a;b;c;...{ } ∏ ! " " # ci k −1( )( )n1i i= a;b;c;...{ } ∏ 0 ! 0 ci k −1( )( )n2i i= a;b;c;...{ } ∏ ! " " # # $ % % % % % % % % % % % % % % % % % % % % % % % % & ' ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( (11) υ denotes a special matrix in which the stoichiometric matrix representing the reaction set (eq.(9)) is repeated as many times as the sample times minus one: =υ υrs υrs ! ! " # # # # # $ % & & & & & (12) k indicates reaction rate constant vector for all the reactions in the reaction set. by applying llsm, the structure of the unknown crn can be identified since the reaction rate constants that can be the part of the unknown crn will have different values than zero at the end of the identification process and all the other reactions in reaction set get zero value. based on eqs.(7) and (10) we can solve the minimization problem and the following expression is the result for the calculation of reaction rate constants for all reactions in the generated reaction set: 55 ___''''' ĉccck δ×## $ % && ' ( ×# $ %& ' (υ× * * + , . / ## $ % && ' ( ×# $ %& ' (υ×## $ % && ' ( ×# $ %& ' (υ= −1 (13) reactions with zero reaction rate constants indicate that they cannot be part of the unknown crn. this means that at the end of the identification process we get the reaction rate constants as well, next to the structure of the crn. results and discussion since we do not have measurements from a real system in this work the developed crn generator has been applied to randomly generate some crns. table 1 shows two reaction steps in the unknown crn. we have defined five components (a-e) in the system. a and b components are reagents in the first reaction step (r01), in which c and d components are produced. however, in the second reaction (r02) only e is consumed while 2 moles of a and 1 mole of d are produced. the last column of table 1 shows the exact values of reaction rate constants. the unit of reaction rate constants can be determined for the jth reaction based on the sum of the reaction orders of each component in that reaction: mol m3 ! " # $ % & 1− nji i= a;b;c;...{ } ∑ ! " # # $ % & & ⋅ 1 s (14) table 2 shows the five components (a-e) that are built from nine (a-j) building elements. these building elements can be imagined as atoms or groups. the numbers in the matrix represents the stoichiometric coefficients of composition. the last row shows a fictitious molecular mass of the components in the system. based on the molecular mass and the number of building elements in the components all the independent reaction steps were generated as shown in table 3. the 22 possible reaction steps can be found for the five components from table 2. the unknown reaction mechanism should be built from these reaction steps. in table 1 we saw that we need only two of these steps and as it can be seen in the last column of table 3 with the proposed algorithm we can find these two reactions of rs01 and rs16. however, the algorithm identifies a third possible reaction step, rs13, which can be the part of the unknown crn. as can be seen in the last column of table 3, the reaction rate constant corresponding to this reaction step is very low. this means rs13 should not be considered as the part of the unknown crn. after the above simple task, we tested our method in nine other cases. we defined a quantitative measure to check the correctness of the identified kinetic parameters as the mean average difference between the known and the identified reaction rate constants: mae = 1 ndr k̂l − kl l=1 ndr ∑ (15) where ndr is the number of reactions in unknown crn; l identifies the current reaction rate constant; k̂ is the reaction rate constant value what we are looking for, such as the last column in table 1 for crn01. table 4 presents the number of reaction steps in the unknown crn (ndr), the number of components (nc) in the system, the number of the possible reaction steps (nr) as a representation of the size of the reaction set, if the algorithm can find the perfect reaction steps or not, and mae values when available from eq.(15). table 1: a randomly generated crn with crn generator a b c d e k [-] r01 -1 -1 1 1 0 1.5590 r02 2 0 0 1 -1 1.0184 table 2: the generated compound matrix a b c d e a 9 0 1 8 26 b 10 0 8 2 22 c 7 1 1 7 21 d 2 10 7 5 9 e 4 12 13 3 11 f 12 0 1 11 35 g 8 0 6 2 18 h 11 5 7 9 31 j 6 1 3 4 16 m [mass mol-1] 359 195 252 302 1020 table 3: the resulted reaction step matrix with the identified reaction rate constant rs id a b c d e k [-] rs01 -1 -1 1 1 0 1.626 rs02 -3 -1 1 0 1 0 rs03 -2 0 0 -1 1 0 rs04 -2 6 3 -4 0 0 rs05 -3 5 4 -3 0 0 rs06 -4 4 5 -2 0 0 rs07 -5 3 6 -1 0 0 rs08 0 4 5 0 -2 0 rs09 -3 3 6 0 -1 0 rs10 5 -3 -6 1 0 0 rs11 3 -3 -6 0 1 0 rs12 4 -4 -5 2 0 0 rs13 0 -4 -5 0 2 0.004 rs14 3 -5 -4 3 0 0 rs15 2 -6 -3 4 0 0 rs16 0 -6 -3 3 1 0 rs17 2 0 0 1 -1 1.051 rs18 0 -2 2 3 -1 0 rs19 1 1 -1 -1 0 0 rs20 0 2 -2 -3 1 0 rs21 3 1 -1 0 -1 0 rs22 0 6 3 -3 -1 0 56 based on the results in table 4 it can be seen that the proposed algorithm has some limitations in this phase. however, if the size of the reaction set is relatively small it gives very good agreement with the desired parameters. this means that we should improve this method to make possible the analysis of more complex problems with it. if the algorithm cannot find the perfect match for the unknown crn a ratio is given which shows how many of the reaction steps are correctly identified from the unknown mechanism. conclusions the structure of a crn represents all the elementary reaction steps that are required to convert the reagents into products. hence, the aim of reaction mechanism identification is to discover the intermediate steps, which connect starting materials with the final product. the proposed algorithm can support this process even in the case, when we lack knowledge about the reaction mechanism and/or kinetic parameters. the applied structure identification method is based on linear least-square method. the measured and calculated concentration profiles are compared and the difference between these profiles is minimized during the identification process. the proposed algorithm for reaction mechanism identification was implemented in matlab. the results of initial testing showed promising results for this simple method being applicable for a complex task; however, the proposed algorithm should be improved toward processing reaction sets. the given implementation of the algorithm for batch reactor models can be easily extended to other reactor models, which enables to employ our method to realistic problems from chemical industry. acknowledgements this research was supported by the european union and the state of hungary, co-financed by the european social fund in the framework of támop 4.2.4.a/2-111-2012-0001 ‘national excellence program’. references [1] delvin s.: organic reaction mechanism, sarup & sons, new delhi, 2002 [2] grossman r.b.: the art of writing reasonable organic reaction mechanisms, springer, new york, 2003 [3] friess s.l., lewis e.s.: investigation of rates and mechanisms of reactions, john wiley & sons, new york, 1963 [4] walter e.: identification of parametric models from experimental data, springer-verlag, berlin 1997 [5] bendel m.l., bonvin d., marquardt w.: incremental identification of kinetic models for homogeneous reaction systems, chem. eng. sci., 2006, 61, 5404–5420 [6] srinivasan s., billeter j., bonvin d.: extentbased incremental identification of reaction systems using concentration and calorimetric measurements, chem. eng. j., 2012, 207–208, 785–793 [7] samoilov m., arkin a., ross j.: on the deduction of chemical reaction pathways from measurements of time series of concentrations, chaos, 2001, 11, 108–114 [8] varga t.: qualitative analysis based reaction mechanism identification, chem. eng. trans., 2013, 35, 769–774 [9] ratkiewicz a., truong t.n.: application of chemical graph theory for automated mechanism generation, j. chem. inf. comput. sci., 2003, 43, 36–44 [10] first e.l., gounaris c.e., flouda c.a.s: stereochemically consistent reaction mapping and identification of multiple reaction mechanisms through integer linear optimization, j. chem. inf. model, 2012, 52, 84–92 [11] west r.h., allen j.w., green w.h.: automatic reaction mechanism generation with group additive kinetics, cheminform., 2012, 43, 36–258 [12] kennedy j., eberhart r.: particle swarm optimization in neural networks, proc. ieee international conference on neural networks, perth, australia, 1995, 4, 1942–1948 table 4: testing the developed algorithm in case of 10 crns crn id ndr nc nr match mae [-] crn01 2 5 22 y 0.0498 crn02 3 5 40 n (1/3) crn03 3 5 11 y 0.0983 crn04 2 5 17 y 0.0268 crn05 4 5 26 y 0.1197 crn06 2 5 13 y 0.0146 crn07 3 5 10 y 0.0216 crn08 4 5 119 n (0/4) crn09 3 5 85 n (0/3) crn10 4 5 19 y 0.0748 acknowledgement the dedicated issue of the hung. j. ind. & chem. and in part the organization of the 2014 spring scientific students’ meeting at university of pannonia were made possible from support provided by the national talent program of the educational research and development institute and the human resource support program of the ministry of human resources within the framework of “support of tdk workshops recognized by the council of national scientific students’ association” (ntp-tdk-13) köszönetnyilvánítás jelen kiadvány és részben a 2014. évi tavaszi tudományos diáknap a pannon egyetemen az emberi erőforrások minisztériuma megbízásából az oktatáskutató és fejlesztő intézet és az emberi erőforrás támogatáskezelő által gondozott nemzeti tehetség program „az országos tudományos diákköri tanács által elismert tdk-műhelyek támogatása” (ntp-tdk-13) című pályázatának köszönhetően valósult meg. national scientific students’ association hungarian journal of industry and chemistry vol. 48(1) pp. 1–1 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-01 editorial preface to the special issue dedicated to the workshop “self-driving vehicles" istván szalai1 1institute of mechatronics engineering and research, university of pannonia, gasparich márk utca 18/a, zalaegerszeg h-8900, hungary in the 22nd november 2019 a workshop was held in the automotive proving ground, zalaegerszeg, hungary. the title of workshop was "self-driving vehicles. sensors, algorithms, intelligent materials." the workshop collected experts from the university of pannonia, veszprém, and the széchenyi istván university, győr. the workshop was supported by efop-3.6.2-16-2017-00002. the lectures were mostly presented by talented graduate and postgraduate students, who represent future’s professionals. they will be graduated from the two universities and hopefully will seek career in the automotive industry of hungary, especially, in the industry of slefdriving vehicles. this area of technology is developing fast and strongly supported by governments and various players of the economy due to its potential to drive the development of state-of-the-art technologies. the workshop showed that the research groups working in these two universities can contribute to this development with novel results. this issue of the hungarian journal of industry and chemistry contains the contributions of the lectures. istván szalai professional leader ”research of autonomous vehicle systems related to the autonomous test track in zalaegerszeg“ (efop-3.6.2-16-2017-00002) https://doi.org/10.33927/hjic-2020-01 microsoft word inner cover.docx hungarian journal of industry and chemistry veszprém vol. 41(2) pp. 131–136 (2013) degradation of reinforced and unreinforced waste polyamides during mechanical recycling jános sója and norbert miskolczi! mol department of hydrocarbon and coal processing, institute of chemical engineering and process engineering, university of pannonia, egyetem u. 10, 8200, hungary !email: mnorbert@almos.uni-pannon.hu the paper discusses the degradation of waste polyamides during mechanical recycling from the automotive sector. two different polyamides were investigated: glass fibre reinforced and unreinforced. raw materials were reprocessed twenty times and the changes in their properties were investigated as a function of reprocessing number. considerable differences were found in relation to the specimen properties between reinforced and unreinforced waste materials. for example, the tensile strengths of reinforced and unreinforced polyamide 6.6 wastes were 84.2 and 165.2 mpa, respectively, which dropped to 38.0 and 97.0 mpa after the twentieth reprocessing cycle. specimens from the reprocessing procedure have been investigated by fourier transformed infrared spectroscopy in the spectral range of 400–4000 cm-1. due to mechanical stress between the rotating screw and plasticising cylinder, the reinforcements broke. the average length of the glass fibre was decreased as a function of the reusing cycle number from 1890 to 580 µm. keywords: polyamide, mechanical recycling, degradation, ftir introduction as a result of the continuously increasing trend in the demand for polymer worldwide, ever increasing amounts of waste polymers are generated. polyamides (pa) are expensive engineering plastics, especially if they are reinforced. in particular, glass fibre composites are widespread among fibre-reinforced materials, as a results of their favourable mechanical and economical properties. the application of glass fibre results in improved tensile and flexural properties. thermoplastic polyamides contain typically 10-30% glass fibres as reinforcements and are applied in many industries such as the automotive sector, civil engineering, packaging, and biomedical applications [1-9,11,16]. a grand challenge is the utilisation of plastic wastes. polymer materials have a high resistance to different environmental and mechanical effects, which yields their favourable characteristics. such advantageous properties can easily become disadvantage owing to waste polymers inability to decompose within a reasonable time frame. unfortunately, a vast amount of polymer waste ends up to landfills, where nondegradable plastics together with other materials accumulate and pollute the environment [10,12-15]. the most studied recycling technologies are mechanical or chemical. chemical recycling is a thermal process for cracking the long carbon chains of polymers into gases and liquid hydrocarbons in the absence of oxygen within in temperature range of 400-1000 °c. the other technology is mechanical recycling, when waste polymers are mixed with original granulates and newly shaped by injection moulding or extrusion. mechanical recycling is a good option for reusing waste plastic, only when selectively collected polymers of high purity are available. similarly to the chemical process, the polymer chains can degrade due to mechanical and thermal stresses during the pre-treating and shaping steps. therefore, it is important to know the behaviour of polymer chains when exposed to thermal and mechanical stresses [9,11-16]. the goal of our work was to investigate the mechanical recycling of reinforced and unreinforced waste polyamides. waste polymers have been reprocessed twenty times and the changes of mechanical amongst other properties were investigated. the effects of reinforcements on the loss of properties during the reshaping procedures were followed. experimental plastics glass fibre reinforced and unreinforced waste polyamides were used as raw materials. the main properties of the raw materials are shown in table 1. table 1: the main properties of raw materials reinforced unreinforced mfi,* g (10 min)-1 15.1 11.8 ash content, % 30.6 0.03 tensile strength, mpa 165.2 84.2 charpy strength, kj m-2 13.4 12.1 * 275 ºc, 5 kg 132 sample preparation due to pa samples being sensitive to humidity, raw materials before processing and samples before testing were dried. drying was carried out in an air circulated drying box at 90 ºc for 2 h. the injection moulding of the specimens was carried out by a microprocessorcontrolled injection moulding machine. the dimensions of dog-boned injection moulded specimens were 3 mm × 10 mm in cross-section and 50 mm in length. fig.1 illustrates the main experimental steps. methods the tensile and three point flexural properties (mainly stress and extension) (msz en iso 527-1-4:1999, msz en iso 14125:1999) were determined using an instron 3345 universal tensile testing machine. the temperature and relative humidity in the laboratory were 23 ºc and 60% respectively, during the mechanical tests. tensile tests were carried out at a crosshead speed of 80 mm min-1. during the investigation of flexural properties, the crosshead testing speed was 20 mm min-1. samples were also investigated by infrared spectroscopy with a tensor 27 type ftir spectrometer (resolution: 3 cm-1, illumination: sic globar light, detector: rt-dlatgs type) within the 400-4000 cm-1 wave number range. a ceast resil impactor was applied to measure the charpy impact strength of the produced samples according to the msz en iso 179-2:2000 standard. results and analysis tensile properties the tensile properties of reshaped specimens are summarised in figs.2a-2c. the tensile strength of reinforced and unreinforced polyamide 6.6 wastes were 84.2 mpa and 165.2 mpa, respectively, which were reduced to 38.0 mpa and 97.0 mpa after the twentieth reprocessing cycle (fig.2a). it is important to note that the decreasing trends were considerably different in the two cases: a fourth order trend line in the case of reinforced samples and a second order one in the case of unreinforced samples were found as shown in fig.2a. a short section with a barely decreasing slope can be found both at the beginning (before the third cycle) and at the end (after the fifteenth cycle) of the trend line for figure 1: the main experimental steps figure 2: tensile properties of reinforced and unreinforced polyamide 6.6 wastes: a) tensile strength, b) elongation and c) tensile modulus c b a number of cycles number of cycles number of cycles number of cycles 133 the reinforced specimens. in the case of unreinforced specimens a similar phenomenon was found only up to the ninth cycle. the elongations of specimens are shown in fig.2b. owing to the rigid property of polyamides the relative elongations are rather small (below 3.8%). as results demonstrate the change in elongations was rather linear, but the gradient was different when the reinforced (tan α = 0.033) and unreinforced (tan α = 0.054) raw materials were investigated; because a slower ratio in change was found in the presence of glass fibres in polyamide wastes. as demonstrated by the tensile strength, tensile moduli show a decreasing trend as well. furthermore, the trend line is highly similar to the measured data for tensile strength. the e-modulus of reinforced and unreinforced wastes was 8219 mpa and 3226 mpa, respectively. those were decreased to 3606 mpa and 1022 mpa according to the mathematical equations in fig.2c. flexural properties the flexural properties of reshaped specimens are summarised in figs.3a-3c. the change in both flexural strength and e-modulus followed a decreasing trend, while the trend in terms of elongation was rather increasing. the results were similar to the tensile properties discussed above. it is important to note that the shapes of trend lines were also similar to results demonstrated before. when reinforced polyamide 6.6 waste material was reprocessed the flexural strength, elongation and e-modulus changed from 248.5 mpa, 4.42% and 5622 mpa to 166.0 mpa, 4.86% and 3416 mpa, respectively. by taking into consideration the results of both tensile and flexural tests it can be concluded that the glass fibre reinforcement helps to keep the high values of strengths and e-moduli in the case of reinforced polymers at the start of property curves as a function of processing cycle number. approximately after the third-to-fifth reprocessing cycles, the dropping ratio was increased step by step. presumably this was the consequence of the glass fibres degrading into pieces. on the contrarily, a relatively constant dropping ratio was found in the unreinforced case. charpy impact strength the charpy impact strength test is one of the most widely specified mechanical tests of polymeric materials to provide information about impact properties. results of charpy tests were summarised in fig.4. the change in charpy impact strength followed a decreasing trend in both cases. moreover, a similar trend in the changes could be found, because the gradients were 13.38 and 12.18 for reinforced samples and unreinforced specimens, respectively. the charpy impact strengths were 12.1 kj m-2 and 13.4 kj m-2 without any reprocessing, and decreased to 8.4 kj m-2 and 9.4 kj m-2 respectively by the end of the procedure. naturally the reinforced samples gave higher values of impact strength. figure 3: flexural properties of reprocessed reinforced and unreinforced polyamide 6.6 wastes a) flexural strength, b) elongation and c) flexural modulus a b c figure 4: charpy impact strength of reprocessed reinforced and unreinforced polyamide 6.6 wastes number of cycles number of cycles number of cycles number of cycles c 134 linear extension coefficient the coefficient of thermal expansion describes the change in dimensions of samples against changing temperature at a constant pressure. regarding polymers the linear extension coefficient is used to classify the materials. as it is known, thermal expansion decreases with increasing bond energy and the thermal extension of the amorphous phase is higher than that of the crystalline phase, because rearrangements in the structure can be achieved at the glass transition temperature. a change in ratio of amorphous and crystalline phases occurs. the coefficients of linear extension are demonstrated in fig.5. results demonstrate well that the coefficient changes randomly in both cases between 2.05 and 2.27 with approximately the same average value of 2.18 ºc-1 for the reinforced and unreinforced specimens within 0.01 ºc-1. presumably no rearrangements in the structures of the tested materials occurred during the reprocessing and the ratio of the amorphous to crystalline phases remained similar. in other words, the specimens a have relatively permanent stability of shape. fourier transformed infrared spectroscopy samples from the reprocessing procedure were also investigated by fourier transformed infrared spectroscopy (ftir), which provides a measure of changes in molecular structures through molecular vibrational excitations. the ftir spectra of reinforced and unreinforced waste polymers as a function of the reprocessing cycles are shown in figs.6a and 6b. by this method, modifications in the molecular structures of polymers could be observed as a result of changes in their chemical bonds. a typical spectrum of polyamide can be described as follows: " stretching vibration of -ch2and -ch3 groups between 2800–3000 cm-1 " symmetric and asymmetric deformation stretching of -ch3 groups between 1430 and 1470 cm-1 and 1365 and 1395 cm-1 " βasymmetricch2 of -ch2groups at 720 cm-1 " bands at 3350, 1730 cm-1, and 630 cm-1 as well referring to the n–h and c=o bonds from –nh– and –co functional groups. the methyl/methylene group (–ch3/–ch2–) ratio in an average molecule was calculated based on the ftir peak intensities in the range of 2800–3000 cm-1. results are summarised in fig.7. as shown, the ratio of methyl and methylene groups slowly decreased in both cases as a function of reprocessing cycles. this suggests that the numbers of methyl groups increased, while the methylene groups decreased in an average molecule. this is a consequence of polymer degradation, when the c-c bonds of main polymer chains are cleaved, which resulted in shorter chains containing less methylene groups. figure 5: coefficient of linear heat extension of reprocessed reinforced and unreinforced polyamide 6.6 wastes figure 6: ftir spectra of reinforced (a), and unreinforced polyamide (b) b a figure 7: the change in the –ch3/–ch2– ratio of an average molecule and the value of log(i/i0) from ftir spectra at 720 cm-1 as a function of the reprocessing cycles in the cases of reinforced and unreinforced polyamides number of cycles number of reprocessing cycles number of reprocessing cycles 135 scanning electron microscope graphs as the polyamide matrix covered the fibres, it was difficult to determine their average length. therefore to investigate the average length of the reinforcements and thus gain insights into their degree of degradation, the samples were burned and the remaining glass fibres were investigated by sem techniques. the results are shown in fig.8. as shown, the average length of the glass fibre reinforcements decreased as a function of the reusing cycle number. the length of glass fibres suddenly decreased from 1890 µm to 660 µm during the first four cycles of reprocessing. then the average length exhibited a relatively constant value between 550 and 640 µm. the mean and standard deviation were 581 µm and 28 µm between the fifth and twentieth cycles, respectively. the cause for the degradation of the reinforcement fibres was the mechanical stress caused by the rotating screw and plasticising cylinder. conclusions we investigated the reprocessing of waste glass fibre reinforced and unreinforced polyamide 6.6 materials. it was found that the mechanical properties of both wastes deteriorated as a function of reprocessing. for example, the tensile strengths of reinforced and unreinforced polyamide 6.6 wastes were 84.2 mpa and 165.2 mpa, respectively, which decreased to 38.0 mpa and 97.0 mpa after the twentieth reprocessing cycle. on the other hand, the trend lines of the changes were significantly different in the case of reinforced and unreinforced wastes. more gradually decreasing ratios could be measured regarding unreinforced plastics until the tenth cycle. based on infrared spectra, it was concluded that the deterioration in mechanical properties presumably was the consequence of polymer degradation. the c-c bonds of the main polymer chains were broken and resulted in the formation of shorter polymer chains. the lengths of glass fibres suddenly decreased from 660 µm to 1890 µm during the first four cycles of reprocessing. then, the average length exhibited a relatively constant value between 550 and 640 µm. the coefficients of linear heat extension changed randomly in both cases between 2.05 and 2.27 ºc-1. the average value was 2.18 ºc-1 for both reinforced and unreinforced samples within 0.01 ºc-1. references [1] troev k., todorova n., mitova v., vassileva st., gitsov i.: phosphorus-containing oligoamides obtained by a novel one-pot degradation of polyamide-6, polymer degrad. stabil., 2006, 91(4), 778-788 [2] pedroso a.g., mei l.h.i., agnelli j.a.m., rosa d.s.: the influence of the drying process time on the final properties of recycled glass fiber reinforced polyamide 6, polymer testing, 2002, 21(2), 229-232 [3] gröning m., eriksson h., hakkarainen m., albertsson a.c.: phenolic prepreg waste as a functional filler with an antioxidant effect in polypropylene and polyamide-6, polymer degrad. stabil., 2006, 91(8), 1815-1823 [4] goitisolo i., eguiazábal j.i., nazábal j.: effects of reprocessing on the structure and properties of polyamide 6 nanocomposites, polymer degrad. stabil., 2008, 93(10), 1747-1752 [5] bernasconi a., davoli p., armann c.: fatigue strength of a clutch pedal made of reprocessed short glass fibre reinforced polyamide, int. j. fatigue, 2010, 32(1), 100-107 [6] la mantia f.p., scaffaro r.: melt stabilization of wet polyamide 6, polymer degrad. stabil., 2002, 75(3), 473-477 [7] bernasconi a., davoli p., rossin d., armanni c.: effect of reprocessing on the fatigue strength of a fibreglass reinforced polyamide, composites part a: appl. sci. manufact., 2007, 38(3), 710-718 [8] hassan m.m., badway n.a., gamal a.m., elnaggar m.y., hegazy e.s.a.: studies on mechanical, thermal and morphological properties of irradiated recycled polyamide and waste rubber powder blends, nuclear instruments and methods in physics research section b: beam interactions with materials and atoms, 2010, 268(9), 14271434 [9] yu s., liu m., ma m., qi m., lü z., gao c.: impacts of membrane properties on reactive dye removal from dye/salt mixtures by asymmetric cellulose acetate and composite polyamide nanofiltration membranes, j. membrane sci., 2010, 350(1-2), 83-91 [10] ghidossi r., poupot c., thibon c., pons a., darriet p., riquier l., de revel g., peuchot m.m.: the influence of packaging on wine conservation, food control, 2012, 23(2), 302-311 figure 8: the average length of glass fibre reinforcements as a function of reprocessing cycles number of cycles 136 [11] hassan m.m., badway n.a., gamal a.m., elnaggar m.y., hegazy e.s.a.: effect of carbon black on the properties of irradiated recycled polyamide/rubber waste composites, nuclear instruments and methods in physics research section b: beam interactions with materials and atoms, 2010, 268 (16), 25272534 [12] hassan m.m., badway n.a., gamal a.m., elnaggar m.y., hegazy e.s.a.: studies on mechanical, thermal and morphological properties of irradiated recycled polyamide and waste rubber powder blends, nuclear instruments and methods in physics research section b: beam interactions with materials and atoms, 2010, 268(9), 14271434 [13] huang s.h., hung w.s., liaw d.j., lo c.h., chao w.c., hu c.c., li c.l., lee k.r., lai j.y.: interfacially polymerized thin-film composite polyamide membranes: effects of annealing processes on pervaporative dehydration of aqueous alcohol solutions, separ. purific. techn., 2010, 72(1), 40-47 [14] yu s., liu m., ma m., qi m., lü z., gao c.: impacts of membrane properties on reactive dye removal from dye/salt mixtures by asymmetric cellulose acetate and composite polyamide nanofiltration membranes, j. membr. sci., 2010, 350(1-2), 83-91 [15] kiliaris p., papaspyrides c.d., pfaendner r.: influence of accelerated aging on clay-reinforced polyamide 6, original research article polymer degradation and stability, 2009, 94(3), 389-396 [16] shen z., bateman s., wu d.y., mcmahon p., dell’olio m., gotama j.: the effects of carbon nanotubes on mechanical and thermal properties of woven glass fibre reinforced polyamide-6 nanocomposites, composites sci. techn., 2009, 69(2), 239-244 page 1 page 2 page 3 page 4 page 5 page 6 page 7 page 8 page 9 page 10 page 11 page 12 page 13 page 14 page 15 page 16 page 17 page 18 page 19 page 20 page 21 page 22 page 23 page 24 page 25 page 26 page 27 page 28 page 29 page 30 page 31 page 32 page 33 page 34 page 35 page 36 page 37 page 38 page 39 page 40 page 41 page 42 page 43 page 44 page 45 page 46 page 47 page 48 page 49 page 50 page 51 page 52 page 53 page 54 page 55 page 56 page 57 page 58 page 59 page 60 page 61 page 62 page 63 page 64 page 65 page 66 page 67 page 68 page 69 page 70 page 71 page 72 page 73 page 74 page 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page 506 page 507 page 508 page 509 page 510 page 511 page 512 page 513 page 514 page 515 page 516 page 517 page 518 page 519 page 520 page 521 page 522 page 523 page 524 page 525 page 526 page 527 page 528 page 529 page 530 page 531 page 532 page 533 page 534 page 535 page 536 page 537 page 538 page 539 page 540 page 541 page 542 page 543 page 544 page 545 page 546 page 547 page 548 page 549 page 550 page 551 page 552 page 553 page 554 page 555 page 556 page 557 page 558 page 559 page 560 page 561 page 562 page 563 page 564 page 565 page 566 page 567 page 568 page 569 page 570 page 571 page 572 page 573 page 574 page 575 page 576 page 577 page 578 page 579 page 580 page 581 page 582 page 583 page 584 hungarian journal of industry and chemistry vol. 46(2) pp. 63–66 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0020 investigations into flour mixes of triticum monococcum and triticum spelta katalin kóczán-manninger *1 and katalin badak-kerti1 1department of grain and industrial plant processing, szent istván university, villányi út 29-43, budapest, 1118, hungary bread samples were made using flour mixes of triticum monococcum (tr. monococcum) and triticum spelta (tr. spelta). they were tested for their rheological behaviour over the first 3 days of storage at room temperature, and for their characteristics based on a hungarian standard. parameters were set such as the volume of the baked product, baking loss, crumb characteristics and elasticity of crumbs. the behaviour of flour from einkorn wheat is different to that of tr. spelta. the properties of the tested flour mixes measured by a farinograph show that tr. spelta produces an acceptable dough, on the other hand, the dough of tr. monococcum develops quickly but is very unstable so weakens within minutes of being kneaded. this also suggests that doughs composed of einkorn wheat flour require a different type of kneading than those of tr. spelta (or tr. aestivum, also referred to as common wheat) flours. breads composed of tr. spelta were comparable with those made with tr. aestivum, the crumb elasticity was above 90 % on the day of baking, which indicates high quality. the tr. monococcum breads, however, were of low grade: the volume of the breads decreased by increasing the ratio of tr. monococcum to tr. spelta and the elasticity reduced to unacceptable levels (less than 60 %). it should be mentioned that the grading was based on breads made purely from tr. aestivum flours. keywords: spelt, einkorn, bread, texture analysis 1. introduction as a result of the increasing number of cases of celiac disease and allergies, as well as the growing popularity of conscious nutrition, interest in older varieties of wheat is once again on the rise. in general, consumers think that these species of wheat are potentially less immunogenic than their modern equivalents. the manufacturing properties of doughs produced from ancient varieties of wheat are much weaker than those of common wheat. in order to obtain good quality bakery products, it may be necessary to use mixtures of flours from different varieties. in our research, the properties of the flour of einkorn and spelt wheats in addition to breads that consist of different proportions of these flours were prepared and investigated. during measurements, attempts were made to determine whether these wheat species – which are in theory suitable for baking bread – could improve the baking performance or whether a significant difference exists between the characteristics of the finished products of various compositions. crossing more modern varieties results in higher yields, greater resistance, more uniform ripening times and higher gluten contents. although these breeding procedures facilitated processing, the genetic diversity and nutritional value decreased significantly which virtually *correspondence: koczan.gyorgyne@etk.szie.hu resulted in the total displacement of indigenous species [1, 2]. one reason for this is that tr. monococcum was consumed primarily as a mush or simply cooked; these methods did not require proofing, which was originally used in ancient egypt during bread baking [3]. bread made from spelt flour is also of lower quality than that of common wheat, both in terms of specific volume and crumb structure [4]. according to previous research, spelt wheat flour produces less stable and elastic but stickier dough than plain flour. due to its sticky and soft nature after kneading, it is difficult to handle [5, 6]. breads made from einkorn flour exhibit a wide range of possible specific volumes, ranging from very low to high. although only a few subtypes are suitable for making breads, most versions are suitable for preparing pasta or biscuits [7], or utilisation for special purposes like fermentation processes [8]. the first phase of the investigations concerned the quality of the gluten, followed by the preparation and testing of loaves of bread. the main question concerned how the blends of flours of these species of wheat influence the quality of the final products. mailto: koczan.gyorgyne@etk.szie.hu 64 kóczán-manninger and badak-kerti 2. experimental 2.1 samples and measurements triticum monococcum (einkorn) and triticum spelta wheat flours were manufactured by szabó hengermalom kft. using conventional technology and contained no additives or bread improvers. for the measurements fine flours were used, i.e. small grain particles with low bran content, to ensure they contained only a negligible amount of outer shell. the determination of wet gluten content was performed according to a standard using the glutomatic system. after gluten washing, a gluten index was also calculated using a gluten centrifuge. the moisture content was determined by a sartorius moisture analyser. the uniformly dispersed sample of 2.5 g was dried at 105 ◦c to a constant weight (which has not changed for 20 seconds more than 1 mg). the change in mass could be deduced from the moisture content of the whole test substance. the determination of water absorption was conducted by a brabender farinograph in accordance with a hungarian standard (msz 6369-6:2013) in duplicates, followed by further experimentation using a baking test (msz 6369-8:1988). the volume of the bread samples was measured by placing a loaf in a container of known volume and pouring in a known quantity of mustard seeds around the loaf until the container was full. by measuring the amount of seeds remaining once the container was full, the volume of the loaf could be calculated. the quality of the bread texture was evaluated by a ta.xtplus texture analyser (stable micro systems, surrey, uk), following a modified american association of cereal chemists (aacc) international approved method (74-09) and expressed as crumb firmness (force, 1/g) and relative elasticity (%). a 40 % compression of a 25 mmthick sample was achieved, following a resting time of 30 seconds (at the same compression depth) and then the measuring head was slowly lifted and the springiness of the sample calculated. thus, it was a “measure of force in compression” test using an aacc 36mm-diameter cylinder probe with radius (p/36r). the analyser was set at a ‘return to start’ cycle with a pre-test speed of 1 mm s−1, a test speed of 0.5mm s−1, a post-test speed of 10 mm s−1 and a pre-defined percentage (40 %) of the original sample height. the relative elasticity was calculated from the difference between the original height and the height to which the sample recovered (after pressing and releasing the pressure). measurements were conducted in triplicates. statistical evaluations were carried out using anova (analysis of variance) tests in excel. bread samples were stored at room temperature in plastic bags. texture measurements were taken on the day of baking after the bread had been cooled to room temperature (day 0) and on the following 2 days, namely days 1 and 2. table 1: composition of the samples (%) 100a 80a 60a 40a 20a 100t tr. monoc. (a) % 100 80 60 40 20 0 tr. spelta (t) % 0 20 40 60 80 100 water % 57 62 64 65.4 65.8 71 yeast % 4 4 4 4 4 4 salt % 1.2 1.2 1.2 1.2 1.2 1.2 the ingredients consisted of 250 g of flour, 10 g of yeast and 3 g of salt, the only variable parameter was the amount of water used to make the dough. initially, the dough consisted of approximately 60 % (150 ml) water based on the weight of the flour, and the amount of water was increased to form a homogeneous dough. the final compositions are shown in table 1. 3. results and discussion 3.1 experiments in the case of the einkorn flour, gluten washing was ineffective as it could not be washed out. after the mixing phase, a yellowish substance remained on the bottom of the washer. in the case of spelt flour, gluten tests could be conducted without any problems. the wet gluten content of the tr. spelta flour was 46.73 %. according to the hungarian regulations bread wheat flours must have a minimum wet gluten content of 28 % and for wheat flours used to improve the baking quality a minimum of 34 %. bakers consider a gluten content in excess of 30 % to be good. the wet gluten content of the spelt flour examined is well above this value, but other factors are also taken into account to determine the quality of flour. the gluten index, a measure of gluten quality, of spelt flour was 45.73 %. a value of between 60 and 90 % is considered to be ideal, below 60 % weak and in excess of 90 % too strong. thus, the gluten quality of the spelt flour was clearly weak. the gluten quality calculated from the results of the farinograph tests for spelt flour was 98 % which is acceptable but does not fully reflect the quality of the flour. although the kneading and stability times of the doughs fell within the range of expected values, the planimetric area was greater due to the degree of softening. thus, the quality score obtained by hankóczy’s evaluation method was smaller. the farinogram of spelt flour more closely resembles a flour of medium quality (fig. 1). this is especially true for the tr. monococcum flour. it reaches its maximum consistency very quickly; the top of the curve barely exceeds the consistency line (500 bu – brabender units). the degree of softening is enormous, as is reflected well by the large planimetric area. the qualitative value assigned to the curve is very low (fig. 2). hungarian journal of industry and chemistry investigations into flour mixes of triticum monococcum and triticum spelta 65 figure 1: farinogram of triticum spelta flour. a direct correlation was identified between the volume of the bread samples and the amount of spelt flour in the flour blend (fig. 3). this is in accordance with the gluten quality of the flour blends, as is seen from the results of the farinograph measurements. the crumb hardness of the bread samples is shown in fig. 4. as the samples started to age the compression force increased. by examining the initial and final forces (measures of crumb hardness), it can be stated that sample 60a showed the best results. in this case, the force increased by 29 % between day 0 and day 2. for samples containing less einkorn flour the crumbs seemed to be softer and the relative increase in hardness during storage less (when values on day 2 were compared to those on day 0). even though sample 80a was initially even softer than 60a, by the end of day 2 it needed 1.7 times the force to compress it. an explanation of this phenomenon can also be given with regard to the different compositions of the starch molecules in einkorn flour compared to those in spelt flour. the staling of bread is related to the crystallization processes of starch molecules. significant differences between samples consisting of 100 % spelt flour and those of 20 % einkorn flour mixed with 80 % spelt flour were shown by the results. the increase in crumb hardness during storage resulted in significant differences in all samples of identical compositions. figure 2: farinogram of triticum monococcum flour figure 3: volume of bread samples (a – einkorn flour, t – spelt flour; the numbers are the percentages of einkorn flour in the flour blend) the elasticity of the bread crumbs increased as the amount of spelt flour increased in the flour blend (fig. 5). this tendency persisted during storage as well. the slight increase in the elasticity of the bread composed of 100 % triticum monococcum flour was probably due to improper handling of the samples, i.e. improper cooling before being packed, although it is questionable whether any moisture originating from the headspace of the packaging could cause such a change. taking into account that the results obtained could be derived from measurement and/or calculation errors, it may be worthwhile to consider the role of the chemical structure of einkorn flour during the baking process, and its effect on the elasticity during further targeted experiments. by using a rating system for the tr. aestivum flours, the bread samples can be classified. although the same judgment about the “marketability” of the bread samples cannot be made for breads based on these special types of flour, trends can clearly be observed. by adding more einkorn flour to the flour blends, the “quality” of the crumb structure decreased. most of the samples did not achieve an elasticity of 80 % meaning that they did not return to 80 % of their original height after compression. with these values, most of the breads fall into the non-marketable category. elasticfigure 4: crumb hardness (force, 1/g) as a function of different flour compositions over 3 days 46(2) pp. 63–66 (2018) 66 kóczán-manninger and badak-kerti figure 5: change in the elasticity of the bread samples during storage at room temperature ities of between 90 and 95 % are indicative of good quality breads. such values were only achieved when 100 % triticum spelta flour was used. after 2 days of storage at room temperature, the crumbs of 100 % spelt flour bread degraded to an average quality. 4. conclusion the purpose of our investigations was to examine the quality of flours from varieties of ancient wheats. gluten could not be washed out of einkorn samples and the wet gluten content of tr. spelta was also very low. farinograph measurements revealed that when only einkorn flour is used, the dough forms very fast but is very soft and almost completely unstable. by mixing einkorn and spelt flours bread can be made, however, an acceptable ratio would not exceed 20 % of einkorn to 80 % of tr. spelta flour. with this flour blend, the resulting bread volume is comparable to the accepted low values of bread composed of 100 % spelt flour. the hardness and elasticity of the bread crumbs already changed significantly at the lowest mixing ratios. further studies on the sensory characteristics of these breads and consumer tests are needed before deciding on the use of flour blends of triticum monococcum and triticum spelta in the absence of any addition of triticum aestivum flour. references [1] draskovics, m. r.: seed plants (spermatophyta) in: turcsányi, g. (ed.) agricultural botany, mezőgazdasági szaktudási kiadó, budapest, hungary, 2000 pp 363-365 isbn: 9633563593 [2] dinu, m.; whittaker, a.; paglia, g.; benedettelli, s.; sofi, f.: ancient wheat species and human health: biochemical and clinical implications. j. nutr. biochem., 2018 52, 1-9 doi: 10.1016/j.jnutbio.2017.09.001 [3] brandolini, a.; hidalgo, a.: chapter 8: einkorn (triticum monococcum) flour and bread in flour and breads and their fortification in: preedy v. r.; watson r. r.; patel v. b.: health and disease prevention, academic press/elsevier, uk, 2011 pp 7988 isbn: 978-0-12-380886-8 [4] abdel-aal, e-s. m.; hucl, p.; sosulski, w.; bhirud, p. r.: kernel, milling and baking properties of spring-type spelt and einkorn wheats. j. cereal sci., 1997 26, 363-370 doi: 10.1006/jcrs.1997.0139 [5] callejo, m. j.; vargas-kostiuk, m. e., rodríguezquijano, m.: selection, training and validation process of a sensory panel for bread analysis: influence of cultivar on the quality of breads made from common wheat and spelt wheat. j. cereal sci., 2015 61, 55-62 doi: 10.1016/ j.jcs.2014.09.008 [6] frakolaki, g.; giannou, v.; topakas, e.; tzia, c.: chemical characterization and breadmaking potential of spelt versus wheat flour. j. cereal sci., 2017 79, 50-56 doi: 10.1016/j.jcs.2014.09.008 [7] hidalgo, a., brandolini, a.: lipoxygenase activity in wholemeal flours from triticum monococcum, triticum turgidum and triticum aestivum. food chem., 2012 131, 1499-1503 doi: 10.1016/j.foodchem.2011.09.132 [8] hetényi, k.; németh, á.; sevella, a.: examination of medium supplementation for lactic acid fermentation. hung. j. ind. chem., 2008 36(1-2) 49-53 hungarian journal of industry and chemistry https://doi.org/10.1016/j.jnutbio.2017.09.001 https://doi.org/10.1016/j.jnutbio.2017.09.001 https://doi.org/10.1006/jcrs.1997.0139 https://doi.org/10.1016/ j.jcs.2014.09.008 https://doi.org/10.1016/j.jcs.2014.09.008 https://doi.org/10.1016/j.foodchem.2011.09.132 https://doi.org/10.1016/j.foodchem.2011.09.132 introduction experimental samples and measurements results and discussion experiments conclusion microsoft word 1429 bálint 108.docx hungarian journal of industry and chemistry veszprém vol. 42(2) pp. 97–101 (2014) a network model for simulating the dynamic behaviour of an energy distribution network levente bálint,1* tibor dulai,2 ágnes stark-werner,2 gergely apostol,1 and ádám tompos1 1 faculty of information technology, university of pannonia, egyetem u. 10., veszprém, 8200 hungary *e-mail: balintlevente.z@gmail.com 2 department of electrical engineering and information systems, faculty of information technology, university of pannonia, egyetem u. 10., veszprém, 8200 hungary the aim of this paper is to present the planning and implementation of a network model for an energy distribution network for simulating its dynamical behaviour. the model includes different types of energy sources, distribution centres and consumers. the prepared simulation environment makes it possible to add/remove/modify any type of node – to/form/in the model. other actions that may be carried out are the initiation/termination of an energy source or change to its production level. the main goal of the simulation is to investigate the effect of an immediate event (such as a power plant failure, decreased production, etc.) on the network and search for the most appropriate substitute possible. the search may happen either on cost bases or time bases. the system created is based on web technology, any user is able to create/save/load his own model and do simulations on it. this work serves as a basis for further work, which involves more complex electrical knowledge and possibilities regarding the network. keywords: energy distribution network, energy sources, dynamical behaviour, network model, simulation introduction energy efficiency has an increasing importance due to costand environment-related factors. at the same time, the customer demands have to be satisfied. these circumstances result in a largely heterogeneous energy producing and distributing environment. renewable energy is applied to a considerable degree in addition to the electricity produced by traditional power plants [1]. this resulted in a system, where different types of energy sources – with different properties, like cost, response time, etc. – are applied in a mixed way. it is a non-trivial task to decide, which sources to apply even in the case of pre-determined demands. moreover, in practice the amount of the demand appears only when needed. earlier efforts implemented simulation environments for analysing the effect of the hybrid manner of an electric network [2, 3]. however, the problem becomes more complex when an immediate negative event happens, e.g. an energy source becomes unavailable or has to decrease its output suddenly. the optimal answer depends on many factors: e.g. how quickly a new energy source can be applied or how much it will cost. moreover, some types of energy sources are only able to produce discrete levels of output power. this paper describes a web-based system, which makes it possible to create and modify an energy distribution network (including different types of energy sources and customers, too) with the goal of simulating different immediate events. the requirements to be collected and the network model and its elements are introduced, followed by details of the implementation and simulation. requirements: the desired properties of the system functional requirements include mainly the creation and manipulation of network models and simulations. fig.1 presents the possible applications of the system. the interface contains a tree graph-based model whose root is the power source, the inner nodes are the network stations and the leaves are the consumers. the graph’s edges are the connections between the components. there are multiple projects in the system, each project contains a model. the main functions of the system are available through the modeling and simulation interfaces. during the simulation the components can be switched on and off. after two hours of simulation a statistic diagram can be viewed for each component of the model, showing its consumption or production. information about components can be edited while the system is not simulating. next to the functional requirements, the system-related requirements are that: • the system has to be web-based, • no user authentication is needed, • the reaction time is less than 1 s, even if there are 100 users, and • any system or communication failure has to be presented by an unambiguous alert to the user. 98 the interface the interface of the system contains four important elements. on the upper edge is the modelling control bar with the component adding buttons, background theme switcher and save/load buttons. by pressing the load button, the system opens the project selector. the save button must be pressed before loading another project in order to save the current one. under the right side of the control bar, there is the simulation control panel. there are buttons on it for editing corporate and residential priority orders, and sliders for the importance of certain properties while calculating the priority order of the power sources. there are buttons for starting, stopping, and restarting simulation time. the simulation time begins at 6:00 am and the step time can be set from 1 to 60 minutes. in the bottom left-hand corner, the event-log is located, which indicates the basic events like start/stop simulation, add/remove components in black and important events like system failure or insufficient power in red. all events have a time-stamp. while hovering the mouse over a component, the system shows the detailed properties of the element. double clicking selects a component or deletes a connection. while a component is selected, the edit, delete and diagram buttons appear in the modelling control bar. the diagram button works only after a minimum of two hours of simulation. in simulation mode the modelling control bar is hidden and double clicking switches a component on/off. the network model and its elements as the system’s main potential is in handling different types of network nodes and making the investigation of a heterogeneous energy producing and distribution system possible, the elements of the network models and their properties have a huge role. the network nodes can be classified as follows. energy sources the system considers renewable energy sources (water, bio, wind, solar, and geo), non-renewable energy sources (natural gas, petrol, coal, nuclear), and quick start-up energy sources (gas turbines) when the energy provided by power plants is insufficient for consumers. each energy source has a unique name and a maximum output, which defines an upper limit for the source (fig.2). a minimum output is defined as a lower limit, below that the operation is not profitable. start-up cost is the cost needed to switch on the source, and starttime is the time required to start producing energy. the operational cost is a financial value which is needed for one hour of operation. power sources have an environmental multiplier. this multiplier is 1 for renewable sources, 0.2 for non-renewable ones and 0.1 for quick start-up sources by default, but it can be edited any time during the modelling. larger values are better, the maximum is 1 but the value cannot be 0. the system calculates an order between sources from their start-up cost, operational cost and environmental multiplier. this order can be modified by the user before starting the simulation. distributing elements distributing elements for the system are power plant stations that distribute the energy to multiple network stations that further distribute the energy to retail stations directly transmit the energy to consumers. distributing stations have only two properties (fig.3). they have a unique name to identify them and a maximum throughput, which is the maximum power that the station can distribute to lower stations or consumers. if that limit is reached the station will not pick up more power even if the consumers need more. figure 1: example uses of the prepared system figure 3: edit station properties (név: name or location, teljesítmény: power) figure 2: edit power source properties (név: name or location, bekapcsolási költség: cost of starting up, indítási idő: start-up time, üzemköltség: operational cost, környezeti szorzó: environmental factor, optimális sorrend: optimal order) 99 consumers the residential consumers are linked to the model through homes, while corporate consumers include factories, public institutions, etc. consumers have a rate of consumption that describes their maximum required power. current consumption is estimated during the daytime in the simulation. consumers also have an order of priority that can be modified by the user but corporate consumers always have priority over residential consumers (fig.4). connections connections have a length property, which will be used for calculating the loss, dissipated by the cables resistance. networks can be built up by the previously introduced network nodes by connecting them appropriately. the order of connectivity is as follows: • power sources, • power plant distribution station, • network distribution station, • retail distribution station, and • consumer. connections can be established only in this order regardless of the performance of individual components. database and implementation details properties of the network model elements and the network formed are stored in an associative array that can be used directly by the system. at each time it is saved, this array is stored in javascript object notation (json) format in a text file for each project separately. the database array contains an entry for all components of the model. every component has an id, a name, a type and position on the modelled field. energy sources also have a fuel type, start-up time, start-up cost, running cost, environmental factor, and minimum and maximum performance level attributes. stations have a defined maximum tolerance. for consumers, there is a stored average consumption rate, which dynamically changes over time. each object has a sub-array, which stores the id of any other components that are connected to the current one. consumer objects have priority numbers that define the relevance of the consumer. if the power source cannot produce enough energy to satisfy all needs, then the consumer that has the highest priority number will be switched off from the network. the priority order equals the order of creation of components, but the corporate consumers always have preference. the order can be changed by the user any time in modelling mode and during the simulation. implementation details the program is implemented in javascript language with plug-ins like jquery and jsplumb. the plug-in jquery is the most popular extension of the javascript language. it makes it easier to select, move, remove or modify the elements on the interface by selecting the element by its id and modifying its properties. the system uses an in-house jquery plug-in, windows.js. this plug-in creates free movable small windows on the interface and fills them with appropriate content defined by the programmer. the jsplumb plug-in is an opensource plug-in for javascript, created to visually connect elements on the interface with straight lines or bezier curves. the database is stored in json format text files, created and edited by hypertext preprocessor (php) functions and called asynchronously by javascript’s asynchronous javascript and xml (ajax) protocol. php is a server-side scripting language, but in our case its only function is to properly save and load database files to the server computer. the whole software can be started in a browser on the user’s computer and it connects to the server only while loading or saving the project. the interface is fully interactive, in modelling mode the objects can be moved or removed, in simulating mode switched on and off. simulation possibilities the system was created for simulating immediate events during the operation of a modelled energy distribution network. after forming the network, the software makes it possible to cause different immediate events. these severe a connection or switch on/off sources, stations and/or consumers. all of these events can be carried out on the graphical interface of the software (fig.5). the simulation is daytime-based. it starts at 6:00 am. users can set the step time from 1 min or sec to 60 min or sec. at the beginning the system distributes the energy produced by the power plant(s) to all consumers in a user defined order. if a power plant does not produce enough power then the last consumer will be switched off and so on. the electricity-related behaviour will be implemented in the future into the software. a possible solution is to build an ideal flow model as a cooperative game over a graph with the sources and consumers located at the nodes, each described by a maximum supply or desired demand and the power lines figure 4: edit consumer properties (név: name or location, fogyasztás: consumption, prioritás: priority) 100 represented by the edges, each with a given power transmission capacity and admittance value describing their ability to transmit electricity. [4] the user is able to initiate immediate events and the system reacts to them in real-time and recalculates the distribution. calculation of the consumption rate is based on the hungarian average with a small random factor. an example for a simulation let us assume that we have a power plant with a maximum power of 100 kw. the model has one of each type of stations, three households (10-10 kw maximum) and a factory (80 kw maximum) (fig.6). normally, all of the consumers are satisfied, but in the peak times, when the factory and the houses also approach their maximum consumption, the power will not be enough for every consumer, so the system switches off the retail consumer that is last in the priority order. there will not be a consumption reduction, but a complete shutdown. subsequently, the plant will have to produce 95% of the maximum power. in this example all of the stations can transfer the maximum of 100 kw, but if a station cannot transfer this, then the consumer with the largest priority number connected to this station will be switched off, regardless of the current level of the power source. if the consumption is too high, it is possible that complete distribution stations are switched off. further developments the current system can model and simulate a fictional power network with components and connections, but the main goal of the project is to create a simulating software that can model and simulate a real electrical network. it is important to emphasize that the unit of the power of the sources and the consumption are now only kw. we need to include that the voltage of connection cables depends on the length of the connection and the diameter of the cable that are required to calculate the amperage from the resistance of the cable. international connections transmit 750 kv, and the main network in hungary transmits 400 kv starting from the power plants (fig.7). the distribution stations transform and divide it to lower values until the voltage reaches the necessary 250 v for retail and 360 v (or more) for corporate consumers. during the transformations, the system needs to use kirchhoff’s current law that states that at any node in an electrical circuit, the sum of currents flowing into that node is equal to the sum of currents flowing out of that node. that means that the system has to calculate amperages for every incoming and outgoing connection of the distribution stations based on the consumption of the consumers and the target voltage of the cables. the biggest problem of power distribution networks in reality is to satisfy all consumers at all the time, even if the load is very low, without making large changes to the output of the power sources everyday. the current solution in hungary is nighttime power. households using electric water heaters have nighttime electric meters, when the consumption of corporate consumers is drastically reduced. this solution slightly optimizes the operation of power plants. figure 5: the graphical interface of the software (új erőmű: new powerplant, új fogyasztó: new consumer, új állomás: new station, új kapcsolat: new connection, mentés: save, betöltés: load, lakossági sorrend: order of households, céges sorrend: order of companies, maxköltség: maximum cost, környezet: environment, bekaps: start-up, indulás: begin, indítás: start, leállítás: stop, újraindítás: restart figure 6: the model of our example (méter: distance in m) 101 conclusion this paper presented the planning phase and implementation of a web-based system that makes it possible to construct an energy distribution network together with different types of energy sources and consumers. the simulations are carried out to determine the most effective response to different immediate events (e.g. a sudden network problem or failure of an energy source). the simulation takes into account both cost-related and time-related properties, too. the present state of the software provides a basis for further works, which intend to add deeper electricity-related properties and behaviour to the system. acknowledgement the authors are thankful for scientific guidance by prof. katalin m. hangos from the computer and automation research institute. we acknowledge the financial support of the hungarian state and the european union under the tamop-4.2.2.a11/1/konv-2012-0072 project. references [1] breitner m.h.: modeling the transformation of the german energy system until 2050: a multi-criteria, long term optimization problem with many constraints, operations res. proc. 2012, 369-374 [2] geysen d., booiy p., warmer c.: a framework for simulation and control of hybrid energy networks, proc. energycon 2014, dubrovnik, croatia, 2014 [3] padulles j., ault g.w., mcdonald j.r.: an integrated sofc plant dynamic model for power systems simulation, int. j. power sources 2000, 86, 495-500 [4] csercsik d., kóczy l.á.: externalities in the games over electrical power transmission networks, iehas discussion papers, 2011, no 1125 figure 7: the hungarian transmission network microsoft word b_18_monostori_r.doc hungarian journal of industrial chemistry veszprém vol. 39(2) pp. 225-227 (2011) finite element method analysis of hip-joint prosthesis r. monostori , i. dudás university of miskolc, department of production engineering, 3515 miskolc, egyetemváros; miskolc e-mail: hr2003@freemail.hu damage in the joints may entail deterioration of life quality to a great extent. more than seven hundred thousand big joint (hip-, knee, etc.) prostheses are implanted annually in the world to improve the quality of life, and this number in hungary amounts to approximately ten thousand. currently the lifetime of the prosthesis is approximately 10 years. unfortunately, prosthesis loosens beyond this period, thus replacement is needed. in this paper we present the geometric construction, modelling and finite element analysis of the hip-joint prosthesis. keywords: hip joint prosthesis, 3d measurement, finite element method. introduction big joint prosthesis operations provide one of the most outstanding possibilities of locomotor surgery, and development is in progress. the hip joint prosthesis (fig. 1) is one of the most complicated big joint prostheses, since it has to ensure a three-dimensional motion. metal parts (for example, the stem and the sphere head) of hip prostheses are made of either stainless steel or another metal, for example, titanium. the companion piece (for example socket) is made of polythene [1]. the metal sphere head rotates in the polythene companion piece, which is inserted into the hip bone. the polythene has a number of favourable physical and chemical properties, for example, great strength, flexibility and chemical neutrality. however, the prosthesis made of this relatively ductile and resistant material, still wears. figure 1: hip joint prosthesis parts of the hip prosthesis the anatomic hip prosthesis may be cemented and cementless depending on the type of fixation used to hold the implant in place. construction: socket; metal head; metal stem of different types. basic materials the hip-joint stem and head are made of forged, heat treated, cobalt-based, patented special metal alloys, marked bmh-1, protected by a patent, and featuring a chemical composition in compliance with standard iso 5832-6. the strength characteristics of the tissue-friendly material are the best. the high toughness (impact work), the special texture and chemical composition of the practically unbreakable metal result in the maximum resistance of the hip-joint stems manufactured from this material to the most unfavourable voltage corrosion fatiguing stresses. the hip-joint socket is made of ultra-high molecular weight polyethylene in compliance with standard iso 5834-2, and is applied successfully worldwide, on the basis of a procedure in which the material preserves its warranted characteristics. stem the geometry of the stem (fig. 2) is formed in a way that the curved contour line of the stem in the planar section of the plane of bending fully coincides with the cortical contour of the medullary space on the side 226 towards the centre of the body, this way, due to the large contact surface the applied load is transmitted evenly. this is favourable for the use of the bone. the wedging, straight stems are fixed in full length. figure 2: stem [2] head the hip-joint head is attached in a self-locked way to the conical neck part of the hip-joint stem (fig. 3). figure 3: head [2] socket there are cams on the outer surface of the sphere to ensure the equal thickness of bone cement. in a special case a serrated-edge version of asymmetric arrangement is also available to increase the support function. the socket is fitted with marker wires at the right angles to enable x-ray check-ups after implantation (fig. 4). the use of bone cement is necessary for the implantation. figure 4: socket [2] modelling for creating the 3d model of the sphere head and the socket (fig. 5) we used the results of the 3d measurement of the ”etalon” socket and the data appearing in the specifications of the sphere head and the socket. we used the solid edge planning software to do the planning as the 3d model formed in this way can be used in the research with the fem software. figure 5: head and socket models finite elements method analysis the fem analysis is executed with the help of the so called ansys fem software [3]. introduction of the ansys fem analysis software the ansys workbench is the framework upon which the industry’s broadest suite of advanced engineering simulation technology is built. an innovative project schematic view ties together the entire simulation process, guiding the user through even complex multiphysics analyses with drag-and-drop simplicity. with bidirectional cad connectivity, an automated project update mechanism, pervasive parameter management and integrated optimization tools, the ansys workbench platform delivers unprecedented productivity that truly enables simulation driven product development [4]. the tests were made in two different ways: 1. first we put the sphere head and the socket in each other and some force was applied towards the centre (fig. 6). after the test we analysed the findings separately for the sphere head and the socket (figs 7 and 8). figure 6: the analysis of tension and deformation, in a complex state 227 figure 7: the analysis of tension and deformation on the head figure 8: the analysis of tension and deformation on the socket 2. in the second stage we applied the torque to the system and we examined tension and values of deformation (figs 9, 10 and 11). figure 9: position of torque and analysis of tension and deformation figure 10: tension and deformation in the case of the sphere head figure 11: tension and deformation in the case of the socket summary we created the 3d models of the sphere head and the socket with the help of solid edge planning software. using these models we analysed the values of tension and deformation of the sphere head and the socket with the help of the ansys fem software. first, we examined the head and the socket together in each case, and then they were analysed separately. the received results live up to our expectations, that is why later we would like to consider the case when not only one force and one torque is applied but the combination of these (reflecting the reality). references 1. http://www.metrimed.hu (2008) 2. http://www.protetim.hu (2007) 3. f. szabó, z. bihari, f. sarka: products, structures, machinery parts finite element modeling and optimization, professional engineering notes, miskolc 2006 4. http://www.econengineering.com (2010) 5. g. horányi: life prosthetics (talking with prof. imre bertóti, in hungarian). élet és tudomány, 57(11), (2002), 329–331 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 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(adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word b_27_r.doc hungarian journal of industrial chemistry veszprém vol. 38(2). pp. 193-196 (2010) risk methods and chance of practices g. n. tóth1, l. berek2 1university of obuda, 1081 budapest népszínház utca 8, hungary e-mail: toth.georgina@bgk.uni-obuda.hu 2zrínyi miklós university of national defence e-mail: berek.lajos@zmne.hu risk analysis is made in several fields of science, moreover in business, manufacturing, protection of enviroment, disaster recovery, hygiene, labour safety, or in the increasingly important information security. laws and standards control the risk assessement in many cases, however they don’t contain any guide for the execution. the aim of this article is to highlight some well-defined risk analysis methods in my article and shortly present the possible adaptations thereof. in case of different processes the most difficult task is to adjust the processes to the problems in a way, which enables to minimize deviations and faults resulting from men’s subjective judgement. both qualitative and quantitative processes are contained the methods, and advantages, disadvantages, application possibilities thereof in details are presented. keywords: risk methods, risk management software introduction many forces are obliging safety design; legal requirements, quality, costs, market and international influences, competition, the desire to have knowledge and the costs of retraining engineers. the aim of the risk assessment is to reduce risks to a tolerable level. many times the zero risk level is not realizable. risk assesment although many industries use different risk assessment methods, the traditional risk assessment process includes the same basic steps: ● identify risks, ● assess risk, ● minimize risk, ● accept remainder risks ● documenting the results and continuous monitoring in many cases individuals or organizations start with a going risk assessment method, but it’s not always suitable. so they need better methods. the research could take one of two paths. one of them, that looks for other methods and adopts all. the other one that modifies an extant technique to create a method better suited for the given application. [1, 2, 3] figure 1: process of the risk assesment [4] a cleary distinction is usually made among three main types of methods, as two primary ones and hybrid methods of risk which are the mixture of the two above ones: ● qualitative methods ● quantitative methods ● hybrid methods in this arrticle these types and some risk assessment methods are presented [2, 3]. 194 qualitative risk analysis methods in these methods risk is analyzed with the help of adjectives without using mathematical tools. qualitative methods are simple and easy to use but in some cases result in inconsistent outcomes. such techniques don’t use tools like mathematics and statistics to model the situation. the results of method are mostly depended on the team. the problem of the qualitative methods are the subjective results thereof. [1, 2, 3] quantitative risk analysis methods these methods use statistical and mathematical tools to estimate risks. in course of quantitative risk analysis methods intensive mathematical measures are used to model different types of risks, due to the enviromental elements, the model applied, furthermore the subject of the model istelf are complex. today’s complex risk situations cannot be modelled only by using quantitative methods. [1, 2, 3] hybrid method a selected combination of the previous two methods. these methods are generally applied to implement the components utilizing pieces of information and minimizing the metrics to be calculated and collected. fewer numerical calculations and cheapness compared to a fully deep analysis are the advantages. [1, 2] risk analysis methods, techniques hazard and operability studies(hazop) the hazop was developed in the 1970s by imperial chemical industries ltd. this technique is generally known as an application of a formal systematic critical examination of the process and engineering intentions of new or existing facilities. with the hazop tool the hazard potential arising from deviation in design specifications and the consequential effects on the facilities as a whole is assessed. hazard and operability studies can be used to hazard analysis. problems and threats are explored systematically. the methods are widely applied in chemical industries. the advantage of the method is that the modification of the components can be easily followed and any deviations to the limits and pertaining effects can be checked. on the other hand, experts are only in the position to utilize them in an appropriate way, furthermore, the methods are time and cost consuming. [5, 6] cramm (ccta risk analysis and management method) cramm is applied in it security. it is a qualitative risk analysis and management tool. it is developed by uk government’s central computer and telecommunications agency in 1985. it’s a method for information systems security reviews. figure 2: cramm process [8] the method provides the risks of the threats in details, however, it needs waste of time and resources, hence the daily usage thereof is expensive. cramm modell comprises three basic components needed for an occurance of a security occasion (attack): ● threat ● asset ● vulnerability as a result of the above elements the measure of the risk can be determined as a product of threat, vulnerability and asset values: risk = threat * asset * vulnerability cramm modell consists of three levels. on the first level security considerations are determined. the second level means the assessment of the risks. the third one comprises the elaborating of the defensive measures. [1, 7] tree based techniques the tree based technique is considered a multidisciplinary tool, successfully applied in several fields of studies. it is generally utilized in some territories of quality assurance and it is a widely used application in it to visualize database structures (binary tree). it is also capable to easily access to data in course of programming. the tree based technique is a graphical tool, which enables to user to present different types of relationships (hierarchical, horizontal). the quantification of the results is halting, nevertheless the method can be easily used to demonstrate the logical relations. in such a case, the relations among the components can be described with “logical operators”. it is basically applied as a part of cause-consequence technique in quality assurance, and in fmea procedures as well. 195 a tree diagramms have couple of types: fault-tree analysis(fta), event-tree analysis(eta), cause consequence analysis(cca), management oversight risk tree(mort) and safety management organisation review technique (smort). the fauls tree is also capable for quantitative assessment, however, it is difficult that the users need to have great experience in the given field. [1, 5, 9] figure 3: example of the fault-tree analysis(fta) [5] fmea-failure mode effects and analysis a fmea process was successfully introduced in ford automobil company. it is practically to apply this process both in product develompent and technology planning. the omissions, the possibility and consequencies of the construction and the steps of the manufactoring process in case of either products or technology can be explored by using this method. the process itself is construed as an inductive method, in course of which omissions, causes of fauls and consequencies of the occurance likelihood systematically explored are scored in 1 to 10 scale from severity (s), occurrence (o) and detection (d) perspective. in course of setting up the scale the specific nature of the given field, additionally, the human subjectivity may present difficulty. risk priority number (rpn) can be determined from the product generated based on the points, which rpn is capable for ranking each sources of threats. rpn= s*o*d where: rpnrisk priority number sseverity ooccurrence ddetection. in the assessment process by using pareto-diagramm, risk components which need action can be determined. following the decrease of risk value it is practical to re-determine the value of rpn, then being aware of remainder risk continue the evaulated activity. from time to time a review needs to be made for a continuous development. figure 4: steps of the fmea process [10] providing a detailed overview on the vulnerability of a system by using simple mathematical operations is the advantage of the method, but at the same time the preknowledge of the process is needed and practical experiences regarding the system and the awareness of test results are essential. we can receive failure mode, effects and criticality analysis (fmeca) by extending fmea, as a result of which the most critical failaure of the investigated system can be determined. in most recent days the process can be made more effective with computer-supported team work [4, 5, 9]. risk management softwares a couple of softwers providing the aforementioned methods are accessible in the software market. all of them promise easy applicability, however in most cases it is difficult to implement a tailor made method as per the need of the company. most of the computer programs are capable for easing the administration, but are not suitable for solving problems resulting from the usage of the method. i tried some risk softwares. i would like to emphasize skill designer pro /fmea software relating to fmea method. it makes easy to handle the complicated administration of the fmea documents and linkage thereof. virtual teamwork can be executed provided some conditions exist. i examined one of the most general software, risk optimizer 5.5, which enables to prepare risk assessment. by relating to microsoft excel, the platform is not strange for the user. we can calculate the risk costs and easy to choose the most economical results 196 conclusion risk analysis is made in several fields of science, moreover in business, manufacturing, protection of enviroment, disaster recovery, hygiene, labour safety, or in the increasingly important information security. laws and standards control the risk assessement in many cases, however they don’t contain any guide for the execution. some risk methods are executed in the article. after the grouping of the methods, three techniques are presented in general, which techniques are used in different fields. methods can be implemented to a given bulk of problems. finally, i have dealt with a couple of risk assessment supporting programs and summarized my experience thereon. references 1. sans institute infosec reading room; a qualitative risk analysis and management tool –cramm, sans institute 2002. (http://www.sans.org/reading_room/whitepapers/au diting/qualitative-risk-analysis-management-toolcramm_83) (2010.08.17.) 2. j. w. meritt: cissp: a method for quantitative risk analysis 22nd national information systems security conference 1999 october 18-21. (http://csrc.nist.gov/nissc/1999/proceeding/papers/ p28.pdf ) (2010.08.17.) 3. b. karabacak, i. sogukpinar: isram: information security risk analysis method, computers & security, 24 (2), march 2005, 147–159. 4. http://gpengineering.co.uk/risk_method_manage ment.html (2010.08.17.) 5. tan hiap keong: risk analysis methodologies. (http://pachome1.pacific.net.sg/~thk/risk.html) (2010.08.18.) 6. g. cseh: a hazai veszélyes üzemek által súlyos baleseti veszélyek azonosítására és kockázatok értékelésére alkalmazott módszerek összehasonlító vizsgálata internetes publikáció. /in: www.mbf.hu/seveso2.html/ magyar műszaki biztonsági hivatal. 2004.09.11. 30p. 7. cramm modell. (http://hu.wikipedia.org/wiki/cramm-modell) (2010.08.18) 8. risk management as taught at meerkat manor – (cramm lite – the “r” in “roc” analysis) 23 january 2010. (http://thinkingproblemmanagement.blogspot.com/2 007/10/risk-management-as-taught-bymeerkat.html) (2010.08.19.) 9. j. kalapács: minőségirányítás, minőségtechnikák, x-level kft. 2001. budapest p. 506 pp. 555-560. 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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of industry and chemistry vol. pp.45(1) pp. 5–8 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0002 separation of gases by membranes: the effects of pollutants on the stability of membranes nándor nemestóthy* research institute of bioengineering, membrane technology and energetics, university of pannonia, egyetem u. 10, veszprém, h-8200, hungary the long-term stability of membranes is determined mainly by their sensitivity to pollutants. their stability was tested using a novel, multichannel measuring system, which is based on pressure differences. this measuring system is suitable to determine the changes in permeability of polymer membranes. the damaging effects of h2s, btx and n-dodecane were investigated in terms of polyimide gas separation membranes using nitrogen gas. keywords: multichannel test equipment, pressure difference, hydrogen sulphide, btx 1. introduction previously, it was thought that the stability of membranes is determined by the mechanical stress (shear) and the natural aging of polymers. recently, however, it has been confirmed that their stability is limited mainly by the sensitivity of membranes to certain pollutants. these aggressive compounds, pollutants, e.g. chlorine, hydrogen sulphide, hydrocarbons, etc., may damage the structure of the polymer, thus its physical and chemical properties change, and consequently the permselectivity of the membrane changes, as well. it is known that polymeric reverse osmosis membranes are sensitive to strong oxidising agents, especially chlorine compounds [1], therefore, intensive research has been conducted to avoid or at least reduce any damage [2-3]. similar levels of membrane degradation are observed in proton-exchange membrane (pem) fuel cells and batteries containing membranes, where oxidising compounds are in contact with the membranes, as well [4-5]. the stability of polymeric gas separation membranes has hardly been investigated. the long-term effects of h2s on inorganic membranes has been studied by australian researchers at low concentrations (50 ppm) [6]. however, h2s may not only cause long-term, but immediate damage, mainly in the form of swelling, which strongly influences the gas transport properties of membranes. koros and co-workers presented the effects of extremely high h2s concentrations on a polymer membrane (50,000 100,000 ppm) [7]. in the field of membrane technology, sensitivity can be measured by a sort of effectiveness unit. the *correspondence: nemesn@almos.uni-pannon.hu product of the concentration and time period yields a value where the effectiveness of the membrane decreases from 95 to 90 and then to 70% of its original value (e.g. 1000 ppm*hour means that the membrane was exposed to 1000 ppm of pollutant for 1 hour, or 0.1 ppm of pollutant for 10,000 hours during the tests). according to the literature these types of measurements have yet to be published for gas separation membranes, thus the aim of this work was to design, construct and operate a piece of test equipment that conducts reliable laboratory tests. for the determination of stability, direct and indirect methods can be used to measure the gas volumes passing through the membranes. direct methods are usually preferred, and – if the composition of the gas is known – are more exact than indirect ones. however, when the gas composition varies and small amounts of gases need to be measured, indirect methods are often more suitable. in this work an indirect method based on a pressure differential technique was chosen, where the pressure of a closed vessel is measured and the varying pressure yields information about the volume of the gas passing through the membrane. during the investigation the effects of pollutants on the permeability of nitrogen was to be studied. the following pollutants were used:  compounds containing sulphur at associated gas  btx mixture (benzene, toluene, xylene)  heavy hydrocarbons in this research the aim was to determine quantitatively the effects of pollutants on the membranes to define the tolerance range of particular membranes. nemestóthy hungarian journal of industry and chemistry 6 figure 1. the small modules constructed for the tests 2. experimental for this series of measurements, polyimide gas separation membranes (synthesised by ube) were used. they were taken from a hollow fibre module and can accurately model the properties of industrial gas separation membranes. from the hollow fibres small modules containing 6 capillaries were constructed (fig.1) and their ends were closed, thus their tests were carried out in a “sack” configuration. in the design of the test system it was important that several parallel measurements should be conducted and the measuring channels combined with each other. the scheme of a measuring channel can be seen in fig.2 the gas was introduced into the measuring system through valve v1 (which can be adjusted by valve v2 if necessary). before measurements were taken the pressure of the vessel was checked by pressure transducer pt1. to start the test the pressure was adjusted by regulating valve pv1, which was checked by pressure transducer pt2. then the membrane was installed into the thermostatic system in a way that ensured its mobility was not restricted, thus the permeation of gas could not influence the flux. a photograph of the measuring system is shown in fig.3. for the permeability measurements nitrogen gas from a cylinder was used (99.5%; messer hungarogáz kft., hungary). the permeability of the membrane was determined from the pressure of the vessel and the transmembrane pressure measured on-line during the experiments. in the experiments, h2s, methyl mercaptan and ammonia (compounds containing s or n), oleic acid, ethyl figure 2. the scheme of the test system figure 3. the test system alcohol, moreover, a benzene-toluene-xylene mixture (btx) and n-dodecane (as a heavier hydrocarbon) were used as pollutants. for the stability experiments the small membrane modules were put in a closed vessel (fig.4) where the headspace was saturated with the given pollutant. the vessels were placed in a thermostatic incubator at 27 °c usually for between 1 and 7 days. certain materials (e.g. btx) damaged the epoxy resin glue used to adhere the fibres of the membranes, therefore, these experiments were repeated using polyether-sulfone glue instead. 3. results the nitrogen permeability of the membranes was determined before and after the incubations. in the preliminary experiments, the ammonia solution and methyl mercaptan severely damaged the surface of the membranes, thus no flux could be measured. oleic acid and ethyl alcohol hardly influenced the flux, while btx, h2s and n-dodecane changed the permeability of nitrogen considerably. for further investigation of the pollutants an experimental design was constructed, using appropriate figure 4: the membranes in the closed vessel the effects of pollutants on the stability of membranes 45(1) pp. 5–8 (2017) 7 table 1. the parameters of the experimental design pollutant cmin ppm cav ppm cmax ppm tmin d tav d tmax d h2s 100,000 300,000 500,000 1 3.5 7 btx mixt. 1,000 750 500 1 3.5 7 dodecane 1,000 5,500 10,000 1 3.5 7 statistical methods. the parameters selected were the concentrations of the pollutants (minimum, maximum and average) and the incubation time (minimum, maximum and average). the statistica 8 computer program was applied to the design presented in table 1. firstly the effect of h2s on the nitrogen permeability of the membranes was measured. the experimental results are presented in fig.5. it can be seen that the permeability of nitrogen increased even when the concentrations of pollutants were low and rose by using higher concentrations and longer periods of exposure. from the h2s concentration and the incubation time it was possible to calculate a special parameter of exposure with the unit of ppm*h. permeability was presented as a function of this parameter (fig.6), where an almost linear relationship was observed. the results suggest that the process can be described as a first-order reaction, which means that no safe limit can be determined where h2s is regarded as harmless, on the contrary, it should be considered at all times. the effect of the btx mixture was studied using a similar methodology. the results are summarized in fig.7. this figure shows that the permeability of nitrogen increased at low concentrations of the btx mixture. at higher concentrations and over longer periods of time, no further significant changes were observed. the exposure parameter was also calculated in the unit of ppm*h and permeability was presented as its function (fig.8). the diagram can be described as a saturation-type curve. 2**(2-0) design; ms residual=49886.27 > 2000 < 2000 < 1500 < 1000 < 500 < 0 figure 5. the effect of h2s on the nitrogen permeability exposure [m ppm * h] 0 20 40 60 80 100 p e rm e a b ili ty c h a n g e [ % ] 0 500 1000 1500 2000 2500 figure 6. permeability changes against exposure to h2s 2**(2-0) design; ms residual=2675.592 > 400 < 360 < 310 < 260 < 210 < 160 < 110 < 60 figure 7: the effect of the btx mixture in the last series of experiments, the effect of exposure to n-dodecane was investigated experimentally. the results are presented in fig.9. n-dodecane caused – unlike h2s and btx – a reduction in the permeability of nitrogen even at low concentrations. the flux fell to zero at higher concentrations and over longer incubation periods. permeability was investigated as a function of exposure (fig.10). the process can be described as a first-order reaction, thus the effect of heavier hydrocarbons, e.g. n-dodecane, should always be considered. exposure [k ppm * h] 0 20 40 60 80 100 120 140 160 180 p e rm e a b ili ty c h a n g e [ % ] 0 100 200 300 400 figure 8: permeability changes against btx exposure nemestóthy hungarian journal of industry and chemistry 8 2**(2-0) design; ms residual=40.32141 > 100 < 96 < 76 < 56 < 36 figure 9: the effect of n-dodecane 4. conclusion the long-term stability of polyimide gas separation membranes was tested against various pollutants: h2s, a btx mixture and n-dodecane. these compounds significantly affected the nitrogen permeability of the membranes which were described by using a special parameter of exposure. it was found that h2s and the btx mixture increased the permeability, while ndodecane reduced the permeability of the membranes. further investigations are planned to investigate the effect of other pollutants, moreover, to determine the permeability of additional gases, e.g. carbon dioxide, methane, etc. acknowledgement we acknowledge the financial support of széchenyi 2020 under the efop-3.6.1-16-2016-00015 project. this research was supported by the jános bolyai research scholarship of the hungarian academy of sciences. references [1] glater, j.; hong, s.k.; elimelech, m.: the search for a chlorine-resistant reverse osmosis membrane, desalination, 1994 95(3), 325-345 doi: 10.1016/0011-9164(94)00068-9 exposure [ k ppm * h] 0 50 100 150 200 p e rm e a b ili ty c h a n g e [ % ] 0 10 20 30 40 50 60 70 figure 10. change in permeability against exposure to n-dodecane [2] zhang, y.; zhao, c.; yan, h.; pan, g.; guo, m.; na, h.; liu, y.: highly chlorine-resistant multilayer reverse osmosis membranes based on sulfonated poly(arylene ether sulfone) and poly(vinyl alcohol), desalination, 2014 336, 58-63 doi: 10.1016/j.desal.2013.12.034 [3] gohil, j.m.; suresh, a.k.: chlorine attack on reverse osmosis membranes: mechanisms and mitigation strategies, j. membr. sci., 2017 541, 108-126 doi: 10.1016/j.memsci.2017.06.092 [4] huang, x.; pu, y.; zhou, y.; zhang, y.; zhang, h.: in-situ and ex-situ degradation of sulfonated polyimide membrane for vanadium redox flow battery application, j. membr. sci., 2017 526, 281292 doi: 10.1016/j.memsci.2016.09.053 [5] lapicque, f.; belhadj, m.; bonnet, c.; pauchet, j.; thomas, y.: a critical review on gas diffusion micro and macroporous layers degradations for improved membrane fuel cell durability, j. power sources, 2016 336, 40-53 doi: 10.1016/j.jpowsour.2016.10.037 [6] uhlmann, d.; smart, s.; diniz da costa, j.c.: h2s stability and separation performance of cobalt oxide silica membranes, j. membr. sci., 2011 380(1), 48-54 doi: 1016/j.memsci.2011.06.025 [7] kraftschik, b.; koros, w.j.; johnson, j.r.; karvan, o.: dense film polyimide membranes for aggressive sour gas feed separations, j. membr. sci., 2013 428, 608-619 doi: 10.1016/j.memsci.2012.10.025 hungarian journal of industrial chemistry veszprem vol. 30. pp. 149154 (2002) comparison of mathematical programming and pinch~based techniques for mass exchange network synthesis z. szitkai, a k. msiza 1, d. m. fraser 1, e. rev, z. lelkes and z. fony6 (chemical engineering department, budapest university of technology and economics, h-1521 budapest, hungary 1chemical engineering department, university of cape town, private bag, rondebosh, 7701, south africa) received: march 27,2002 in this paper two design techniques, based on mathematical programming, for the synthesis of mass exchange networks (mens) are compared. problems not generally dealt with in literature, and associated with these techniques, are highlighted. a method is presented for generating several feasible initial solutions to avoid accepting poor local solutions as final designs. methods of handling the discontinuity of the kremser equation used for determination of the number of stages are also discussed. in addition, a method of generating minlp (mixed integer non-linear programming) solutions that feature integer stage-numbers is also presented. it is shown that insight-based superstructures assuming vertical mass transfer may fail to include the optimal structure of the men. an minlp based design technique is selected for the solution of several men synthesis example problems. our minlp solutions are compared to the advanced pinch solutions taken from literature. both simple and advanced capital costing functions are used for the estimation of the total annual cost (tac) of the mens. keywords: mass exchange n~orks, mathematical programming, pinch technology introduction mass exchange networks (mens) are systems of interconnected direct-contact mass-transfer units that use process lean streams or external mass separating agents to selectively remove certain components (often pollutants) from rich process streams. the notion of mass exchange network synthesis (mens) and a pinch-based solution methodology for the problem were presented ftrst by el-halwagi and manousiouthakis [1,2,3]. subsequently, papalexandri et al. presented a mixed integer non-linear programming (minlp) design technique for mens [4]. later, hallale and fraser extended the pinch design method by setting up capital cost targets ahead of any design [5,6,7]. recently, comeaux [8] presented an optimisation based design methodology where the notion of vertical mass transfer is used to develop a superstructure optimised by non-linear programming (nlp). using optimisation­ based techniques, capital and variable costs of the network can be optimised simultaneously even in cases of large and multi-component design problems. our objective is to compare the design methods above. mens problems taken from literature wiu be solved. mens got by the different methods will be evaluated against each other, and the design methods will be rated based on the properties of the resulting networks. in the first part of the paper the nlp design method of comeaux is compared to the minlp method of papalexandri. after dealing with practical problems of the mathematical programming methods, the last part of this paper presents minlp solutions for thirteen example problems solved with pinch methodology by hallale [7]. comparison of two optimisatiob-based teclmiques the optimisation (mathematical programming) -b~ approach of design or synthesis consists of three major steps. the first step is the development of a superstructure (a representation of alternatives of ~hich the optimum solution is selected). the second ~tep ts u:e formulation of a mathematical program. the thtrd one 1s the solution of the optimisation model. the values of the model variables in the optimal solution define the structure of the desired mass exchange network. and its optimal operating parameters simultaneously, general reviews of the area are given by {9,10,! 1]. the major achievement of the mathematical programming approach is that it replaces the multi-step iterative pinch 150 table 1 total annual costs of the different solutions of hallale' s example problem 5.1 solution method simple capital advanced capital costing costing advanced pinch *320,000 usd/yr. method of hallale *228,000 usd/yr. and fraser (target) nlp method of comeaux *332,000 usd/yr. 249,150 usd/yr. minlp method of 221,357 usd/yr. papalexandri 306,108 usd/yr. *original solutions of the referred authors are marked by an asterisk design method, and enables the design of multicomponent mens as well. on the other hand, depending on the mathematical formulation, optimisation models cannot always be solved for global optimality [12]. in tl).is section the minlp method of papalexandri [41 and the insight-based nlp solution of comeaux [8] are compared. both methods are mathematical programming based but differ in the way the superstructure is generated, and in the general classification of the mathematical programming model. the superstructure of papalexandri [4] contains all the imaginable matches (stream pairings) and bypasses, without considering whether a certain match is thermodinamically feasible or not. then the su~rstru~ture is formulated as an minlp problem, in whrch bmary variables denote the existence of the matche~. this method is simple in" the sense that during the design process no preliminary knowledge about the network is needed. on the other hand, the resulting minlp model may be superfluously large and hence difficult to solve. commercially available minlp solvers [13,14,15] may fail finding the global optimum of !he problem. • because of the mathematical difficulties, many efforts were made to combine thermodinamical insights and mathematical programming [8,16]. one of these attempts is the method of comeaux [8}. using stream data and the principle of vertical mass transfer an insight based superstructure is generated, which contains thermodinamically feasible matches only. having cutted out many of the matches, the resulting superstructure and the corresponding mathematical program is much smaller, compared to that of papa1exandri. comeaux's further simplification is omitting binary variables. he formulates mens as pt~:e nlp problems. mass exchangers exchaging only a small amount of mass in the solution are regarded as non--existing ones. the pure nlp formulation (called the "cover and eliminate method" in another way) is one ?f the oldest ~ptimisation based design concepts. still, m may ca_ses tt can successfully be used, for example when solvmg wastewater treatment problems [ 17]. for the sake of a parctical comparison the mens example problem s.l ofhallale (11 is solved using both of the methods outlined above. since the selection of the objective function is a crutial point of the mathematical o.dl total annual cost; operating cost: 0.01473 249,150usd 173,400usd fig.l insight-based nlp solution for hallale's example problem 5 .1. comeaux's method is used. the capital cost of the network is calculated by hallale's advanced capital costing method programming method, two different methods were used for calculating the total annual costs (tacs) of the networks. the two costing procedures differ in the way the capital costs are calculated. at first, a simple capital costing procedure is applied, where it is assumed that the capital cost of an exchanger (in usd/yr) can be calculated by multiplying its theoretical number of stages by 4552 (see papalexandri et al., [4]). secondly, the advanced, exchanger volume-based capital costing of hallale and fraser [5,6,7] is used. the latter one gives more realistic estimates for the capital and hence for the total annual costs. total annual costs (t a c) of the designed mens can be found in table 1. as a basis for further comparison, in table 1 tacs of the supertargeted pinch solutions of hallale [7} are shown as well. throughout this paper, optimisation problems are solved using the gams program package [13,14]. conopt -1 was used to solve the nlp models and dicopt++ (running osland conopt-1) was used for the minlp solutions. ' the network obtained by the insight based nlp method using advanced capital costing is presented in fig.j. our minlp designs based on papalexandri's method can be seen in figs.2 and 3 with simple and advanced capital costing structures, respectively. table 1 shows that the tac of the minlp designs and the advanced pinch solutions are approximately the same. this is seen more clearly when the structures of these solutions are compared. the costs also become closer when rounding up the stage numbers of the minlp solutions (to $322 000 and $226 000 respectively). table 1 also shows that comeaux's method gives more expensive solutions. hallale's design (see fig.5.4 ofhauale [7j) cannot be reproduced by using the insight-based nlp method of comeaux. this is because the insight based superstructure for the example {see fig.4.2 of comeaux [8]) does not enclose the structure ofhallale's sohtion. in order to be able to find hallale's solution, additional possible matches should be added to the superstructure generated using the principle of vertical mass transfer. although the 0.006 }--!--~"·":::..3 ---411, i kg/s 5 kg/s 3 kg/s ~~-r---r-~~-------lr-~~~ 0.0248 oms total annual cost: operating cost: 306,108 usd 203,414 usd fig.2 minlp solution ofhallale's example problem 5.1. the solution is obtained by papalexandri' s method, using a simple capital cost correlation nlp-based design method is computationally simpler than the minlp method, it lacks the advantages of the latter. logical conditions for fixed costs, integer stage numbers, etc. cannot be handled in an nlp model. because of the reasons outlined above, authors of this article decided to use papalexandri's minlp method for the synthesis of mens. three practical problems of using optimisation­ based design techniques for mass exchange network synthesis generation of feasible iilitial solutions global optimality for a given minlp solution by gams/dicopt (the outer approximation algorithm) is guaranteed when both the objective function and the feasibility region of the minlp model are convex. the feasibility region of the minlp problem is convex when all the equalities consist of linear functions and the inequalities consist of convex functions [12,11]. in most cases however, these conditions carmot be satisfied, or they can be satisfied only by oversimplifying the physico-chemical model of the design problem. for example, the minlp or nlp models for men synthesis problems contain non-linear equality constraints (mass balances, phase equilibria), non-convex equations (e.g. the kremser equation), as well as non-convex terms in the objective function (e.g. typical cost functions like cost = canst . (size r'' etc.). non-linear equalities, non-convex inequalities and a non-convex objective function can be handled using convexifying techniques [18] or piecewise linearisation [9]. using these techniques, many additional binary and continuous variables have to be included into the minlp model, and this way the problem size increases steeply. in general we can state that non-convexity is an inherent property of rigorous minlp models for process design. though the minlp solver gamsjdicopt ++ can handle nonconvexities to some 151 0.0013 0.00365 o.ois ~~~--~----------------0.533 . kg/s t-otal annual cost: operating cost: 221,357usd j56,5!4usd fig.3 minlp solution of hallale' s example problem 5 .1. the capital cost of the network is calculated by the advanced capital costing method of hallale and fraser. papalexandri's minlp method is used extent, global optimality is not guaranteed for the solution [14]. in consequence of the above, solutions obtained from different initial values have to be compared to prevent the selection of poor local solutions as final designs. once a feasible solution is found starting from a particular initial solution, several other feasible initial values can be generated, by changing the objective function of the original problem, or by adding artificial constraints. a solution featuring minimum msa flowrates can, for example, be used as the initial solution for the original problem. simple pinch solutions can also serve as initial solutions. if the problem is not severely non-convex, the initial feasible solution can be obtained from any nonzero set of irutial values for the variables in the model. having several initial values on hand, the solution of the original nlp or minlp problem is started from all of them, now using the original objective function. the best solution with the lowest total annual cost is selected as the final solution. though this procedure involves the elements of a "trial and error" method, it performs well in the computational practice. since there is no algorithm, which could deliver the globally optimal solution for a non-convex minlp problem, this is a reasonable way of calculation when using commercially available minlp solvers. the discontinuity problem of the kremser equation assuming linear phase equilibrium relations, capital investment calculations of the mass exchangers (absorbers, extractors) are most commonly based on. the kremser equation [19], which gives the requt~ed number of equilibrium stages for a given separation task. depending on the value of the removal factor a. the kremser equation for a given component z has two different forms. if a;t;l then 152 ( 1 r /" -m .x 1 " -b. ) 1 1-' j }. j +a aut mba y1 -mixi i n mi =___.l..--~-l-n....,...(a~) _ ___:_!.__l (1) where (2) if a=l then na=i in out y; -yt (3) in the formulas above y:• ,y;"1 denote the inlet and outlet concentrations of the ith rich stream, x~" ,x~"1 denote the inlet and outlet concentrations of the jth lean stream, and li,g1denote the lean and rich flow rates. the equilibrium relation between the ith rich stream and the jth lean stream is given in the form of ijui in b y; =mixi + r the removal factors of the units are design variables when solving the minlp synthesis problem. because of this, the a values have to be able to vary freely between their possible bounds. the a value can be either greater, less or equal to the value 1. the theoretical number of stages as a function of the removal factor a have a removable discontinuity at a=l. in case of calculating the number of theoretical stages ata=1, eq.(3) has to be used. using only the first form of the kremser equation (eq.(l)) usually leads to a division by zero error or provides a solution that has no physical meaning. to be more precise, the solver sets as many a values to i as possible because at a=l the number of theoretical stages can be zero, independently from the concentrations (see eq.(l)). restricting the values of a , under or over 1 excludes the real optimal solution from the search space. no reasonable mens can be expected from the minlp method without solving this numerical difficulty. how the discontinuity of the kremser equation can be handled when using commercially available minlp solvers, is extensively discussed in onr previous papers {20,21]. when the mens problem is formulated as a pure nlp problem, binary variables cannot be used for handling the discontinuity of the kremser equation. for the pnre nlp case here we present a method [2"1, which is an approximation, still it can be used effectively. eq.(4) for an of the mass exchangers can be introduced: a-1 =(a-l+e)·w (4) where a is the absorption factor of the mass exchange unit, and e is a sman positive number (eg. 0.001). the variable w rakes the value of zero when and is close to one when a:t:l. then eq.(s) is used in the model for choosing between the two stage numbers (see also eqs.( 1) and (.3 }). using this method, the total cost of the network must be recalculated after optimisation. experience has shown that differences between the real and the approximated stage numbers are usually small. it has to be noted that eq.(5) is a bilinear equality constraint, hence it renders the nlp problem nonconvex. an obvious solution for the kremser discontinuity problem could be the introduction of eq.(6), which prevents a from taking the value of unity: (6) using this constraint only eq.(l) should be used, when calculating the theoretical number of stages of the units. according to onr computational experience however, this method leads to severe numerical problems during the solution of the nlp, and therefore cannot be applied. integer stage numbers the designer may often want to get solutions whereby the number of stages (n) are reported as integers. buliding up the integer-values according to eq.(7) requires the introduction of additional binary variables (z;) in the minlp model. n = 2° · z1 + 21 • z2 + 22 • z3 + ... (7) when the expected number of stages for the exchangers in the superstrucnre is large, the additional binary variables may extend the minlp problem size over the solvability limit. the same method however, can be used in a two-level optimisation approach. after obtaining the solution with non-integer stage numbers, a second optimisation can be carried out, where the structure of the network is now fixed to that of the first solution (with non integer stage numbers). in the second level only the operating parameters of the network and the stage numbers around the first solution are optimised. for example, if an exchanger in the first level optimum has 16.3 stages then in the second level eq.(8) is introduced, allowing the number of stages of that particular unit to change between 15 and 18: (8) in this way fewer binary variables are needed. however, the two-level method fails to find the optimum when the rounding affects the optimal structure of the network. solved mens example problems in section two it has been shown that in spite of its difficulties, the minlp method of papalexandri [4] is stin better applicable than the nlp optimisation of comeaux's insight based superstructure {8]. in section three some important practical problems of the optimisation based mens have been identified, and table 2 comparison of our minlp solutions and the advanced pinch solutions ofhallale [7]. cap indicates that the network was optimised only for its capital cost at fixed lean stream flow rates (operating costs). theoretical number of stages, hence capital costs are rounded up where staged vessels are used exam le objec~ve pinch solution of 0 minlp 100* p function nick hallale ::otution (cminiycpinch)/ target i design cminlp 3.1 cap 830 000 i 860 000 i 044 285 +17.6% 3.2 cap 448 000 i 455 000 453 302 -0.4% 3.3 cap 819 0001751 000 637280 -17.8% 3.4 cap 591 760 1637 000 637000 0.0% 4.1 cap 296 000 1298 000 255 068 -16.8% 5.1 'l'ac 226 000 1228 000 226 000 -0.9% 5.2 tac 226 000 i 228 000 226000 -0.9% 5.3 tac 226 000 1228 000 226 000 -0.9% 5.4 tac 49 000 i 49 000 50279 +25% 5.5 tac 524 000 i 526 000 527 000 +0.2% 6.1 tac 692 000 /706 000 720000 +1.9% 6.2 tac 28 000 128 000 32000 +12.5% 6.3 cap 591 0001539 000 536 000 -0.6% tactotal annual cost in usd/yr, capannualised capital cost in usd, c cost solutions for these problems were presented, too. now we are in position to solve mens problems that had already been solved in literature using pinch technology. in this section minlp solutions for most of the mens example problems of the thesis of hallale [7] are presented. our results are summarised in table 2. the first column shows the reference number of the examples in hallale's thesis. the second column of the table indicates the type of the objective function. some of the pinch solutions are optimised only. for the capital cost of the exchangers at fixed mass separating agent (msa) flow rates. the objective functions of these examples are indicated by cap (capital cost), because the fixed msa flow rates define the variable costs of the networks. the costs of the pinch targets and final designs are shown in column three, while the costs of our minlp solutions can be found in the fourth one. theoretical number of stages, hence capital costs are rounded up where staged vessels are used. column five shows how many percents the cost of our minlp solution is cheaper or more expensive than that of the pinch solution. optimising for tac, in most cases equally good solutions are obtained. total annual costs of the minlp and pinch solutions do not really differ from each other. in case of examples 5.1, 5.2, 5.3 the minlp solutions, in case of examples 5.4, 5.5, 6.1 the pinch solutions prove to be a bit cheaper. the only exception is example 6.2 where the advanced pinch solution is 12.5 % cheaper than the minlp solution. the difference in this particular case can be accounted for the fact that the concentration range of this example extends over six orders of magnitude. the concentration variables cannot be scaled. having great differences in the values of the 153 l; (kgls) 3.097e-2 2 _ 208 kg/s 6.154e-4 3.5e-3 0.225 kg/s annual capital cost of tills minlp design: 615 287usd when rounding up the stage numbers: 637280usd fig a minlp solution of hallale' s example problem 3.3. papalexandri's minlp method and simple capital costing are used this minlp design: n. hallale~s solution: 255,068 lisp 298,000 usd fig.5 minlp solution of hallale' s example problem 4.1. papalexandri' s minlp method and advanced capital costing are used. mass exchangers are packed columns here model variables causes numerical difficulties for the minlp solution algorithm. optimising just for the annualised capital cost (cap), usually better or equally good minlp solutions are obtained. out of the six examples, the minlp and pinch solutions are almost the same in the cases of examples 3.2, 3.4, 6.3. minlp solutions of examples 3.3, 4.1 are significantly better (17.8 % and 16.8 % cheaper) than the corresponding pinch solutions, while in the case of example 3.1 the advanced pinch solution proved to be 17.6% cheaper. . why the pinch solutions are not always reached wtth minl.p can be accounted for the inherent nonconvexity of the problem. thoj;~gh in many cases solutions can be improved by starting the calculations from different initial values, it is not guaranteed at all that better (cheaper) solutions can always be found. a good illustration for this is the minlp solution of example 3.1. as our solutions show. the advanced pinch targeting method of hauak~ and fraser delivers a good estimate for the capital and total annual costs. nevertheless, it has to be noted that the pinch targets are not rigorous, 154 since in the case of examples 3.3 and 4.1, using minlp even the targeted costs could be surpassed in design. the minlp solutions of examples 3.3 and 4.1 are shown in figs.4 and 5 respectively. based on the experience, obtained during the solution of the thirteen single component example problems we conclude that the time consuming, heuristic pinch design method can be replaced by the minlp design concept. nevertheless, knowing the drawbacks of the methods, it is advisable to consider both methodologies when solving a problem. conclusions the minlp design method of papalexandri seems to be superior to the nlp optimisation of insight-based superstructures. it is shown that insight based supersructures constructed using the vertical mass tran,sfer principle may not enclose the optimal structure of the mass exchange network. the practical problems which were identified in optimisation-based mens, namely generation of feasible initial solutions, discontinuity of the kremser equation and integer stage numbers can effectively be handled, as described in section 3. based on the experience, obtained during the solution of thirteen single component example problems we conclude that the time consuming, heuristic pinch design method can be replaced by the minlp design technique. this work has been supported by otka (hung. sci. res. fund) grants no. f035085, t030176 and t037191. references 1. el-halwagi m. m. and manouthiousakis v.: ajchej,1989,8,1233-1244 2. el-halwagi m. m.: "pollution prevention through process integration", academic press 525 b street, suite 1900, san diego, california 921014495, usa, (www.apnet.com) 1997 3. el~halwagi m. m. and manousiouthakis v.: chem.bng.sci., 1990, 45(9), 2813-2831 4. papalexandri k. p., pistikopoulos e. n. and flouoas c. a.: trans icheme, 1994, 72, part a, 279-293 5. hallale n. and fraser d. m.: chem. eng. science, 1998, 53(2), 293-313 6. hallale n. and fraser d. m.: trans i chern e 2000,78, part a, p.202-216 ' 7. hallale n.: capital cost targets for the optimum synthesis of mass exchange networks, phd thesis, university of cape town, dept. of chemical engineering, 1998 8. comeaux r. g.: synthesis of mens with minimum total cost, msc thesis, dept.of process integration, umist, manchester, england, 2000 9. biegler l. t., grossmann i. e. and westerberg a w.: "systematic methods of chemical process design", prentice hall international series in the physical and chemical engineering sciences, 1997 10. grossmann i. e.: minlp optimization strategies and algorithms for process synthesis. proc. of focapd'89, snowmass, colorado, 1989 11. duran m. a. and grossmann i. e.: ajche journal, 1986, 32, 592 12. duran m. a. and grossmann i. e.: math. program 1986,36,307 13. brook, kendrick, maereus: gams a user's guide, release 2.25, scientific press, 1992 14. gams development corporation, 1217 potomac street washington, dc 20007, usa, "gams-the solver manuals, gams/dicopt", (www.gams.com) 15. schweiger c. a and floudas c. a.: "minopt: a modeling language and algorithmic framework for linear, mixed-integer, nonlinear, dynamic, and mixed integer nonlinear optimization", princeton university, (http://titan.princeton.edu/mlnopt) 1998 16. hostrup m., gani r., kravanja z., sorsak a. and grossmann i. e.: computers and chemical engineering, 2001, 25,73-83 17. benko n., rev e.,szitkai z. and fony6 z.: computers chem. engng., 1999, 23, supp. pp. s157-s160 18. p6rn r., harjunkoski i. and westerlund t.: computers chern. engng., 1999, 23, pp.439-448 19. kremser a.: natl.petrol.news, 1930, 22(21), pp. 42 20. szitkai z., lelkes z., rev e. and· fony6 z.: solution of men synthesis problems using minlp: formulations of the krernser equation, escape11, elsevier, 2001 21. szitkai z., lelkes z., rev e. and fony6 z.: ,,handling of removable discontinuities in minlp models for process synthesis problems, formulations of the kremser equation", accepted for publication in computers · and chemical engineering., 2002, in press 22. szitkai z., msiza a. k., fraser d. m., rev e., lelkes z. and fony6 z.: "comparison of different mathematical programming techniques for mass exchange network synthesis", escape-12 proceedings, in press page 147 page 148 page 149 page 150 page 151 page 152 microsoft word 2012_dr_bodor_endre_hjic.doc hungarian journal of industrial chemistry veszprém vol. 39(3) pp. 369-373 (2011) investigation of storage stability of biodiesels s. kovács , gy. pölczmann, j. hancsók university of pannonia, institute of chemical and process engineering mol department of hydrocarbon and coal processing, veszprém, h-8201, p.o.box: 158, hungary, e-mail: kovacss@almos.uni-pannon.hu the production and application of fuels from agricultural origin have emerged into focus in the last couple of years. a number of environmental, political and economical factors has confirmed and strengthened this process. the main reason of this tendency is the energy policy of the european union, namely to reduce the green house gas emission of fuels, to decrease the significant dependence of eu on import energy and crude oil and to support rural development. to achieve these objectives, the european union created the 2003/30/ec and 2009/28/ec directives, which regulate the application of biomass derived fuels. the main purpose is to promote the use of biofuels in transportation by recommending and specifying the share of the bio-components. this proposed value (10 energy % share of biofuels in the transport sector by 2020 in the eu) can be reached by the conversion of different triglyceride-containing biofeedstocks (e.g. vegetable oils, used frying oils, animal fats, algae oils, brown grease, etc.) to different biofuels or blending components. nowadays fame (fatty acid methyl esters), called as first generation biofuel, is mostly used as diesel bio blending component. but this biofuels due to its chemical structure the presence of the double bond in the molecule have a high reactivity with the oxygen, especially when it placed contacting air. that is why the long term storage stability of biodiesel is an important issue. the aim of our research work was to investigate the long term storage stability of biodiesel samples originated from different feedstock. the effects of the real storage conditions on the properties (induction period, acid value, iodine value, density, water content and kinematic viscosity) of the different biodiesels were investigated. results showed that the acid number and the water content increased, while the induction period and the iodine number decreased with increasing storage time of biodiesel samples. keywords: biodiesel, storage stability, oxidation stability, rancimat method introduction the production and application of the agricultural origin fuels have emerged into focus in the last couple of years. a number of factors which affect the whole mankind has confirmed and strengthened this process, which are of environmental, political and economic nature [1]. the main reason of this tendency is the energy policy of the european union, namely to reduce the green house gas emission of fuels, to decrease the significant dependence of eu on import energy and crude oil and to support rural development. to achieve these objectives, the european union created the 2003/30/ec and 2009/28/ec directives, which regulate the application of biomass derived fuels. the main purpose is to promote the use of biofuels in transportation by recommending and specifying the share of the biocomponents [2, 3]. this proposed value (10 energy % share of biofuels in the transport sector by 2020 in the eu) can be reached by the conversion of different triglyceride-containing biofeedstocks (e.g. vegetable oils, used frying oils, animal fats, algae oils, brown grease, etc.) to different biofuels or blending components. nowadays fame (fatty acid methyl esters), called as first generation biofuel, is mostly used as diesel bio blending component. the chemical structure of these alternative fuels and the applied feeds determined its quality and performance properties. due to the presence of significant amount of unsaturated fatty acids, the oxidation stability has high importance during long term storage. the amount and structure of the fatty acids and ester bonds are major factors influencing these properties outside the storage conditions [4-9]. the storage stability can be worsen due to storage conditions, such as light and air exposure, high temperature, different pollutants and the presence of water, which are catalyzing the harmful reactions. hydroperoxides are formed during these oxidation reactions and they react with other free radicals. insoluble deposits and gums are formed in these reactions too. these degradation products in engine causing operational problems; like fuel filter plugging, injector fouling and deposit formation in engine combustion chamber. this increase the kinematic viscosity of the degraded fatty acid methyl ester samples. the products of the primary oxidation reaction they can be further oxidised to form aldehydes, ketones and shorter chain fatty acids. these compounds cause corrosions in the injection system (fig. 1). 370 kezdő lépés rh + i r˙ + hi láncnövekedés r˙ + o2 roo˙ roo˙ + rh rooh + r˙ lánczárás r˙ + r˙ r r roo˙ + roo˙ stabil termékek initiation propagation termination stable products figure 1: mechanism of the biodiesel oxidation process however, the natural antioxidants can prevent or delay these reactions [4, 5]. storage stability of biodiesel is its ability to resist degradation in contact with environment and storage conditions. the preservation of this during storage is an important issue for the viability and sustainability of the biodiesels [5, 10, 11]. experimental as previously mentioned the aim of our research work was to investigate the long term storage stability of biodiesel samples originated from different feedstock. the effects of the real storage conditions on the physical and chemical properties of the different biodiesels were investigated. materials the applied biodiesels main properties and fatty acid composition is summarized in table 1. the raw material of “a” and “c” biodiesels were rapeseed oil with different fatty acid composition. in case of sample “b” the raw material was sunflower oil with high oleic acid content. table 1: the main properties and the fatty acid composition of the biodiesel samples property a b c en 14214 density, 15 °c, kg/m3 883.2 884.9 883.7 860–900 sulfur content, mg/kg 3 5 7 max. 10 kinematic viscosity, 40°c, mm2/s 4.523 4.473 4.400 3.5–5.0 acid value, mgkoh/g 0.09 0.08 0.35 max. 0.5 iodine value, gi2/100g 112 83 101 max. 120 water content, mg/kg 101 256 420 max. 500 fatty acid composition, % palmitic acid c16:0 4.9 2.4 4.0 palmitoleic acid c16:1 0.2 0.1 0.2 stearic acid c18:0 1.5 2.5 1.7 oleic acid c18:1 61.5 91.8 75.5 linoleic acid c18:2 21.2 1.2 12.3 linolenic acid c18:3 8.1 0.6 5.2 arachidic acid c20:0 0.6 0.8 0.3 gondoic acid c20:1 1.3 0.5 0.7 behenic acid c22:0 0.3 0.1 0.1 erucic acid c22:1 0.3 0.0 0.0 lignoceric acid c24:0 0.1 0.0 0.0 test methods the oxidation stability of biodiesel samples was evaluated according to the rancimat method en 14112 (fig. 2). during the measurements of the oxidation is induced by constant air flow of 10 l/h through 3 g of biodiesel sample kept at 110 °c. the vapors released during the oxidation process together with the air are passed into a flask containing distilled water and fitted with an electrode for measuring the conductivity. the formation of volatile carboxylic acids (mainly formic and acetic) in the sample and its absorption in the water increase the conductivity in the measuring vessel. the time that elapses until the secondary oxidation products are detected, is known as the induction period. during the storage other analytical and performance properties of the samples were determined by standard test methods specified, complying with the specified precision data (table 2). air inlet reaction vessel sample heating block measuring cell conductivity cell adsorption solution (water) figure 2: schematic of rancimat test 371 table 2: test methods properties test methods density, 15 °c en iso 12185:1996 sulfur content en iso 20846:2004 viscosity, 40 °c en iso 3104:1996 acid value en 14104:2003 iodine value en 14111:2003 water content en iso 12937:2000 oxidation stability, 110 °c en 14112:2003 fatty acid composition en iso 5509:2000; en 14103:2003 results and discussion during our experimental work the effect of real storage conditions on the physical and chemical properties of the different biodiesels were investigated. the ambient temperature fluctuations and the contact with the air in case of sampling had effect to the samples. the analytical measurements were carried out in every second week. oxidation stability – induction period the biodiesel samples originated from different sources showed different induction periods, but always decreased. the difference in the measurement results is due to the different fatty acid compositions (the different raw material). the sample a was found below the minimum induction period (6 h) after 25 weeks. the other two samples (b and c) satisfied the oxidation stability requirements of the valid standard after 30 weeks (fig. 3). 0.0 2.0 4.0 6.0 8.0 10.0 12.0 0 5 10 15 20 25 30 in du ct io n pe ri od , h weeks of storage a b c en 14214 figure 3: changes in the induction period of the biodiesel samples based on the results the induction period of the biodiesel samples decreased in the order “b”, “c”, “a”. the reason of this the decreasing oleic acid content and the increasing linoleic and linolenic acid content of the biodiesels. the lower amount of polyunsaturated c18 fatty acids methyl esters (c18:2, c18:3) in the biodiesel is favourable to the oxidation stability, because its relative oxidation rate is approx. 1200 or 2500 times higher than that of c18:0 stearic acid methyl ester (table 3) [12]. table 3: the induction periods and relative oxidation rates of several fatty acid methyl esters (25 °c) fatty acid methyl ester symbol induction period, h relative oxidation rate c18:0 1 c18:1 82 100 c18:2 19 1200 c18:3 1.34 2500 acid value as expected, the experimental results showed an increasing trend in case of all samples but none of the samples exceeded the requirement of the standard 0.5 mg koh/ g (fig. 4). 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0 5 10 15 20 25 30 a ci d va lu e, m g k o h /g weeks of storage a b cen 14214 figure 4: changes on the acid value of the biodiesel samples the acid value increasing due to the oxidation of the primary oxidation products of the esters. during these reactions aldehydes, ketone and shorter chain fatty acids are formed. the hydrolysis of the fatty acid esters are resulted the increasing acid value. the products of this reaction are the different alcohols and acids. the higher water content of biodiesel “c” is the reason of the high initial acid value (table 1). based on the experimental results it can be concluded the change of this parameter correlates well with the degradation of the biodiesel samples. iodine value the iodine value is in context with the number of the double bonds of the hydrocarbons. in case of biodiesels shows how the material is prone to polymerization and form deposits in the storage vessels and in the engines. the iodine value of the samples decreased gradually (fig. 5). this indicates the decrease of the number of double bonds and the progress of the deterioration (the polymerization reaction). the reason of the iodine value differences was the different fatty acid composition. the observed slight decrease of iodine number in the case of biodiesel “b” due to the lower amount of polyunsaturated fatty acids (1.8%) (table 1). 372 80 85 90 95 100 105 110 115 120 125 0 5 10 15 20 25 30 io di ne v al ue , g i 2 /1 00 g weeks of storage a b cen 14214 figure 5: changes on the iodine value of the biodiesel samples water content water in biodiesel can initiate hydrolysis reactions, could increase the microbial contamination and the risk of emulsification. based on the water content of the biodiesel samples it can be concluded that it showed increasing trend in all cases (fig. 6). 0 100 200 300 400 500 600 700 800 900 1000 0 5 10 15 20 25 30 w at er c on te nt , m g/ kg weeks of storage a b c en 14214 figure 6: changes on the water content of the biodiesel samples based on the experimental results it can be concluded that the water content of biodiesel c on week 10 exceeded the requirements (500 mg/kg) of the valid standard. the biodiesel is hygroscopic and absorbs the water content of the air. the difference in the results caused by the different initial water content. the systematic study of this property is important because of the standard set values and the microbial contamination. density according to the literature the change of the density correlates well the changes during the storage. based on the measurement results we did not find a clear trend. however in case of all sample the measured density satisfied the valid standard (fig. 7). the change of the density does not reflect the results of the rancimat method. this measurement is not suitable for tracking the biodiesel degradation. but this is a standard property and it is important to do the test periodically. 875.0 876.0 877.0 878.0 879.0 880.0 881.0 882.0 883.0 884.0 885.0 886.0 887.0 888.0 889.0 890.0 0 5 10 15 20 25 30 d en si ty , k g/ m 3 weeks of storage a b c en 14214 860-900 kg/m3 figure 7: changes on the density of the biodiesel samples kinematic viscosity based on the results of the viscosity measurement we did not find clear tendency (fig. 8). the values are satisfied the requirements of the valid standard in all cases. the change of the viscosity does not reflect the results of the rancimat method. but this is a standard property and it is important to do the test periodically. 3.500 3.700 3.900 4.100 4.300 4.500 4.700 4.900 0 5 10 15 20 25 30 k in em at ic v is co si ty , m m 2 /s weeks of storage a b c en 14214 3.5-5.0 mm2/s figure 8: changes on the kinematic viscosity of the biodiesel samples summary the main objections of our biodiesel long term storage stability experiments are the followings: ● the biodiesel samples originated from different sources showed different induction periods, but in every case it decreased. based on the experimental results we concluded that the storage stability of the biodiesel samples largely dependent of the initial storage stability of the samples. it is no coincidence that the en 14214 standard is recommended the addition of stabilizers to improve the oxidation stability of fame immediately after production or before blending to fossil gas oils. 373 ● the storage stability of samples the better their polyunsaturated fatty acids content are smaller. ● the acid value is an excellent feature of the biodiesel quality change because the formed acidic components gave information about the rate of hydrolysis and oxidation reaction. the experimental results are correlating with will the results of rancimat test. ● the water content of the biodiesel samples showed increasing trend in all cases. ● in case of density and viscosity the measurement results did not show clear trends. the change of these properties does not reflect the results of the rancimat method. in case of the investigation of long term storage stability of biodiesel the history of the samples can be a important information. acknowledgments “this work was supported by the european union and co-financed by the european social fund in the frame of the tamop-4.2.1/b-09/1/konv-2010-0003 and tamop-4.2.2/b-10/1-2010-0025 projects.” references 1. a. demirbas: biorefineries: current activities and future developments, energy conversion and management, 50 (2009) 2782–2801 2. directive 2003/30/ec of the european parliament and of the council, (2003) 3. directive 2009/28/ec of the european parliament and of the council, (2009) 4. g. knothe: some aspects of biodiesel oxidative stability, fuel processing technology, 88 (2007) 669–677 5. s. jain, m. p. sharma: stability of biodiesel and its blends, renewable and sustainable energy reviews, 14(2) (2010) 667–678 6. d. baker: biodiesel – a role for sae. sae motor vehicle council, march 31, (2006) 7. j. hancsók, m. krár, sz. magyar, l. boda, a. holló, d. kalló: investigation of the production of high cetane number bio gas oil from prehydrogenated vegetable oils over pt/hzsm-22/al2o3, microporous and mesoporous materials, 101 (2007) 148–152 8. g. knothe: dependence of biodiesel fuel properties on the structure of fatty acid alkyl esters, fuel processing technology, 86 (2005) 1059–1070 9. j. hancsók, m. krár, sz. magyar, l. boda, a. holló, d. kalló: investigation of the production of high quality bio gas oil from pre-hydrogenated vegetable oils over pt/sapo-11/al2o3, studies in surface science and catalysis, 170 b (2007) 1605– 1610 10. g. karavalakis, s. stournas, d. karonis: evaluation of the oxidation stability of diesel/biodiesel blends, fuel, 89 (2010) 2483–2489 11. a. bouaid, m. martinez, j. aracil: long storage stability of biodiesel from vegetable and used frying oils, fuel, 86 (2007) 2596–2602 12. h. p. schmiedel: fame im mineralölprodukten insbesondere hel. deutsche wissenschaftliche gesellschaft für erdöl, erdgas und kohle e.v., 2001 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 /colorconversionstrategy /cmyk /dothumbnails false /embedallfonts true /embedopentype false /parseiccprofilesincomments true /embedjoboptions true /dscreportinglevel 0 /emitdscwarnings false /endpage -1 /imagememory 1048576 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page 427 page 428 page 429 page 430 page 431 page 432 page 433 page 434 page 435 page 436 page 437 page 438 page 439 page 440 page 441 page 442 page 443 page 444 page 445 page 446 page 447 page 448 page 449 page 450 page 451 page 452 page 453 page 454 page 455 page 456 page 457 page 458 page 459 page 460 page 461 page 462 page 463 page 464 page 465 page 466 page 467 page 468 page 469 page 470 page 471 page 472 page 473 page 474 page 475 page 476 page 477 page 478 page 479 page 480 page 481 page 482 page 483 page 484 page 485 page 486 page 487 page 488 page 489 page 490 page 491 page 492 page 493 page 494 page 495 page 496 page 497 page 498 page 499 page 500 page 501 page 502 page 503 page 504 page 505 page 506 page 507 page 508 page 509 page 510 page 511 page 512 page 513 page 514 page 515 page 516 page 517 page 518 page 519 page 520 page 521 page 522 page 523 page 524 page 525 page 526 page 527 page 528 page 529 page 530 page 531 page 532 page 533 page 534 page 535 page 536 page 537 page 538 page 539 page 540 page 541 page 542 page 543 page 544 page 545 page 546 page 547 page 548 page 549 page 550 page 551 page 552 page 553 page 554 page 555 page 556 page 557 page 558 page 559 page 560 page 561 page 562 page 563 page 564 page 565 page 566 page 567 page 568 page 569 page 570 page 571 page 572 page 573 page 574 page 575 page 576 page 577 page 578 page 579 page 580 page 581 page 582 page 583 page 584 hungarian journal of industrial chemistry veszprém vol. 33(1-2). pp. 113-117. (2005) evolutionary strategy in iterative experiment design j. madár, b. balaskó, f. szeifert and j. abonyi* department of process engineering, university of veszprém, veszprém, egyetem u. 10, h-8200, hungary, www.fmt.vein.hu/softcomp, abonyij@fmt.vein.hu process models play important role in computer aided process engineering, since most of advanced process monitoring, control, and optimization algorithms relay on a model of the process. in most of the cases, some parameters of the model should be estimated based on some experiments. one of the factors affecting the model prediction quality is the accuracy of these estimated parameters. establishing optimal experiment design can maximise the confidence on the parameters, hereby increasing the confidence on the model prediction. the aim of this paper is to work out a modern experiment design tool to minimize the number of experiments while maximizing of their information content. this paper illustrates the applicability of es for the design of feeding profile for a fed-batch biochemical reactor. the results illustrate that if the model structure is not accurate, the evolutionary strategy can result in more satisfactory parameter values than the classical sequential quadratic programming and nonlinear least squares algorithms. keywords: experiment design, model identification, fed-batch bioreactor introduction process models play important role in computer aided process engineering since most of advanced process monitoring, control, and optimization algorithms relay on a model of the process. unfortunately often some of the parameters of these models are not known a priori, so they must be estimated from experimental data. the accuracy of these parameters largely depends on the information content of the experimental data presented to the parameter identification algorithm [1]. establishing optimal experiment design (oed) can maximise the confidence on the parameters. for the identification of the parameters of dynamic models this approach has been utilized in [2-5]. in these studies experiment design is concerned with the following questions: how does one adjust time-varying controls, initial conditions, and/or other design parameters of the experiments to generate the maximum amount of information for the purpose of estimating the parameters with greatest precision. for nonlinear models, oed is based on an iterative algorithm because the optimal parameters of the experiments depend on the model parameters that are going to be estimated based on the result of the designed experiment. consequently, oed estimates the model parameters and designs the experiment iteratively. both parameter estimation and experiment design are based on nonlinear optimization of certain cost-functions. in practice, the applied nonlinear optimization algorithms have great influence on the whole procedure, because for nonlinear dynamical models the design of the experiment is a hard optimization problem. as an effective optimization algorithm, this paper proposes the application of evolutionary strategy (es) for this purpose. es is a stochastic optimization algorithm that uses the model of natural selection [7]. in this paper, oed are applied for fed-batch biochemical reactor. one of the factors affecting the modelling of biochemical systems is that accurate description of biochemical reaction is generally not available a priori. hence usually a simplified kinetic model, e.g. monod model, is used to describe the microbial dynamics. some results were presented for experiment design of biochemical systems in [4-6], but these works assumes that the model structure is perfectly known. this paper discusses the application of oed based on models that have structural uncertainty. our results illustrate that although the model structure used for the design of the experiments is not accurate, oed with es can result in satisfactory parameter values. the paper organized as follows: the first section reviews the theory of optimal experiment design. the second section proposes the application of evolutionary strategy for oed. the third section presents the application example. finally, conclusions are given in the fourth section. correspondence concerning this article should be addressed to j. abonyi (abonyij@fmt.vein.hu) 114 optimal input design for parameter estimation the case study considered in this paper belongs to the following general class of process models: ( ) ( ) ( )( ) (1) ( ) ( )( )tt t,ut t t xgy pxfx = = , d d where u is the manipulated input, y is the output (vector), x is the state (vector) of the system and p denotes the unknown model parameters. the p parameters are unknown and should be estimated based on data taken from experiments. for the estimation of these parameters classical parameter identification approach is used that is based on the minimization of the square error between the output of the system and the output of the model: ( )( )p p ,min tuj mse (2) where ( )( ) ( ) ( ) ( )( ( ) ( )( ) ( )( )pyye eqep ,~ d1, 0 t tutut tttt t tuj ft tf mse −= ⋅⋅= ∫ = ) (3) in which is the output of the system for a certain u(t) input profile, and y is the output of the model for the same u(t) input profile with p parameters, q is a user supplied square weighting matrix that represents the (variance of the) measurement error. y~ the accuracy of the parameter estimation depends on the applied u(t) input profile. the goal of the experiment design is to determine an optimal input profile in the sense of the parameter estimation leads to optimal parameters with maximal confidence. the basic element of the experiment design methodology is the fisher information matrix f, which combines information on (i) the output measurement error and (ii) the sensitivity of the model output with respect to the model parameters: ( ) ( ) ( ) ( )∫ = == ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ∂ ∂ ⋅⋅⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ∂ ∂ = ft t pppp f tttt t 0 t 0 d,,1 00 p p yqp p ypf (4) in which p0 is the nominal parameter vector. the fisher information matrix f provides an approximate quantification of the attainable parameter estimation quality in the neighbourhood of the nominal parameter vector p0 for a particular experiment as the inverse of matrix f approximates the parameter estimation covariance matrix. the optimal design criterion aims the minimization of a scalar function of the f matrix. among the existing criteria, the d-optimal criterion and the modified eoptimal criterion suggested by bernaerts et al. [1] are studied in this work. i. the d-optimal criterion minimizes the determinant of the covariance matrix, and thus minimizes the volume of the joint confidence region: ( ) ( ) ( )f f det max =d dtu j j (5) ii. e-optimal criterion minimizes the condition number of f, i.e. the ratio of the largest to the smallest eigenvalue of f: ( ) ( ) ( ) ( ) ( )f ff f min max min λ λ =e etu j j (6) these values correspond to the uncertainty of the parameter estimation problem. fig. 1 and 2 illustrate the effect of the input profile on the model output in case of the case study that will be presented later in the application example session. the contour plots show the square error of model output with respect to its parameters around the p0 nominal parameters: ( ) ( ) ( )(∫ = −= ft f i tty t j 0t 20 d,t,y1 ppp ) (7) one can see that when an e-optimal input profile is used, then the parameter uncertainty region is smaller. this means that, if the p0 nominal parameters are close to the optimal p* parameters, the parameter estimation based on this profile (fig. 1) most likely results in accurate parameters than the estimation based on a manually selected profile (fig. 2). these figures suggest that when one has only a draft estimate on the parameters of a complex dynamical model, he/she should use it to design an u(t) input profile for a parameter estimation procedure (eq. 2-3) rather than to use data taken from a non-optimized input profile for the identification. in the following session a new optimization algorithm will be presented for the effective design of the experiments. for nonlinear models, oed results in an iterative procedure due to the fact that the parameters of the designed experiment depends on the model parameters itself, see fig. 3. 0 5 10 15 20 25 30 35 40 0 0.1 0.2 t u µm/µm 0 k s/k s0 0.99 0.995 1 1.005 1.01 0.9 1 1.1 10 20 30 fig. 1 contour plots of the identification cost (ji) with respect to parameters for an e-optimized feeding profile 115 0 5 10 15 20 25 30 35 40 0 0.1 0.2 t u µm/µm 0 k s/k s0 0.99 0.995 1 1.005 1.01 0.9 1 1.1 100 200 300 400 500 fig. 2 contour plots of the identification cost (ji) with respect to parameters for a manually selected feeding profile initial parameters experiment design experiment parameter estimation more experiment? end p0 u(t) )(~ ty p0 yes no fig. 3 scheme of parameter estimation with oed both the parameter estimation and the experiment design steps of this iterative scheme represent a complex nonlinear optimization problem, hence the effectiveness of the applied optimization algorithms have great influence on the performance of the whole procedure. the classical solution is to use nonlinear least squares (nls) algorithm for parameter estimation eq. 2-3, and sequential quadratic programming (sqp) for the experiment design eq. 5 or eq. 6. evolutionary strategy this paper proposes the application of evolutionary strategy (es) instead of the utilization of nls and sqp. es is a stochastic optimization algorithm that uses the model of natural selection. the advantage of es is that it has proved particularly successful in problems that are highly nonlinear, that are stochastic, and that are poorly understood [7]. evolution strategy is the member of evolutionary algorithms. the design variables in es are represented by n-dimensional vector , where x [ ]t,2,1, ,,, njjjj xxx k=x j represents the jth potential solution, i.e. the jth the member of the population. the mutation operator adds zj,i normal distributed random numbers to the design variables: xj,i = xj,i + zj,i, where zj,i = n(0,σj,i) is a random number with σj,i standard deviation. to allow better adaptation to the objective function’s topology, the design variables are accompanied by these standard deviation variables which are so-called strategy parameters. hence the σj strategy variables control the step size of standard deviations in the mutation for jth individual. so en es-individual aj = (xj, σj) consist of two components: the design variables and the strategy variables. before the design variables are changed by mutation operator, the standard deviations σj are mutated using a multiplicative normally distributed process: ( ) ( )( )1,0n1,0nexp i )1( , )( , ⋅+⋅′= − ττσσ t ij t ij (8) the ( )( )1,0nexp ⋅′τ is a global factor which allows an overall change of the mutability, and the ( )( )1,0nexp i⋅τ allows individuals to change of their mean step sizes σj,i. so τ’ and τ parameters can be interpreted as global learning rates. schwefel suggests setting them as [8]: nn 2 1, 2 1 ==′ ττ (9) throughout this work discrete recombination of the object variables and intermediate recombination of the strategy parameters were used: ( ) 2/ or ,,, ,,, imifij imifij xxx σσσ += = (10) where f and m denotes the parents, j is the index of the new offspring. application example the case study of this paper is a fed-batch bioreactor with non-monotonic kinetics [6]. the following equation describes the mass balance of the reactor: u c x x v x s dt d ins ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ + ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡− = ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ 1 0 0 , µ σ (11) where s is the mass of the substrate [g], x is the mass of the micro-organism [g dw], v is the volume [l], u is the inlet flowrate [l/h], cs,in = 500 g/l is the substrate concentration in the inlet feed, σ = µ/yx/s + m is the specific substrate consumption rate, where, yx/s = 0.47 g dw/g, m = 0.29 g/g dw h, while µ [1/h] is the kinetic rate. the initial conditions: s(t=0) = 500 g, x(t=0) = 10.5 g dw, v(t=0) = 7 l. the maximum volume is vmax = 10 l, and the maximum inlet flowrate is umax = 0.3 l/h. two kinetic models of the µ kinetic rate were considered: monotonic kinetic (monode model): ( ) ss s s m ck cc + = maxµµ (12) non-monotonic kinetic (haldane model): ( ) issp s ms h kcck cc /2++ = µµ (13) where cs = s/v. 116 the majority of the oed applications in the literature assume that the structure of the model used for the design of the experiment is perfectly known. however, the model structure is often inaccurate in practice. for example, a simplified kinetic model is often used to describe the microbial dynamics due to the lack of lack of accurate knowledge of the microbial dynamics. the purpose of this study is to illustrate the complications that may arise from this structural uncertainty. therefore, in this simulated example, we use different kinetic models during the simulation of the system (considered as a real, unknown process) and in the model itself. it is assumed that the ‘true’ process can be described by a non-monotonic kinetic equation (eq. 13), while the model contains a monotonic kinetic model (eq. 12). the system was simulated with µm = 0.1 1/h, kp = 1 g/l and ki = 500 g/l. the goal was to find the unknown parameters of the model: µmax and ks (the other parameters were assumed to be accurately known). the µmax and ks parameters were estimated by optimization, see eq. 2 and 3. because the measurement of the micro-organism concentration cx is quite difficult in practice, it was assumed that only the substrate concentration cs is measured. consequently, in this application example, the system output is s~~ =y [g], which was generated by the simulation of equations (11) and (12), and the model output is y = s [g], which it was calculated with the use of equations (11) and (13). we applied the iterative oed methodology to design the feeding profile u(t) with e-optimal criterion equations (4) and (6). the d-optimal criterion was not used, because our experience showed that the eoptimality is better suited for this problem. because the number of experiments and the length of experiments are limited in practice, the number of iterations was limited to 3 and the length of one experiment was 40 h. the sample time was 4 h. in this example, three methods were examined: method 1: manually selected input profiles. to compare and analyze the effectiveness of oed, firstly the parameters were estimated with two feeding profiles. the first profile was: u(t) = 0.077 l/h, 0 h < t < 40 h, while the second profile was: u(t) = 0 l/h, t < 20 h and u(t) = 0.15 l/h, 20 h < t < 40 h. method 2: iterative oed with nls in the parameter estimation step and sqp in the experiment design step. method 3: iterative oed with es in both of the parameter estimation and experiment design steps. because the result depends on the initial parameter estimation, two initial estimations were applied: = 0.05 1/h, = 0.5 g/l and = 0.1 1/h, = 1 g/l. init maxµ init sk init maxµ init sk certainly, there is no ‘perfect’ solution for this problem. to analyze the results, the obtained monotonic µm(cs) functions were compared to the ‘true’ nonmonotonic µh(cs) function: ( ) ( )( )∫ = −= 50 0 2 d 50 1 sc ss h s m mse ccce µµ (14) as table 1 and fig. 4 show, method 3 proved to be the best, it found relatively good solutions. one can see that method 2 was sensitive to the initial parameter estimation. if the initial parameter were = 0.05 1/h, = 0.5 g/l this method got stuck into a local minima and resulted in rather wrong parameter values. if = 0.1 1/h, = 1 g/l initial estimations were used, method 2 resulted in better solution. in contrast, method 3 always resulted in a relatively good solution independently the initial parameter values. because es is a stochastic optimization algorithm six independent runs were performed and we got very similar parameters in each case. init maxµ init sk init maxµ init sk fig. 5 and 6 demonstrate that the obtained models output (by method 2 and method 3) and the system output for two input profiles. one can see that the obtained models have relatively good prediction capability. the results support the conclusion that if the model structure is not accurate, the oed with evolutionary strategy can result in more satisfactory parameter values than the classical oed with sequential quadratic programming and nonlinear least squares algorithms. table 1 estimated parameters and the cost values of the obtained kinetic functions (µmax, ks ) emse·106 (0.0893, 0) 98.0 method 1* (0.0893, 0) 98.0 (0.0881, 0) 96.0 method 2* (0.0894, 1.02) 35.0 method 3** (0.0895, 0.416) 15.6 * these methods were initialized with two parameter vectors, see above. ** the means of the emse values of six independent runs. two initial parameter vectors were used for 3-3 runs. 0 10 20 30 40 50 0 0.05 0.1 µ [1 /h ] 0 10 20 30 40 50 0 0.05 0.1 µ [1 /h ] 0 10 20 30 40 50 0 0.05 0.1 cs [g/l] µ [1 /h ] fig. 4 the obtained kinetic functions vs. the ‘true’ kinetic top: method 1, middle: method 2, bottom: method 3 solid line: ‘true’ kinetic, dashed line: obtained kinetic 117 0 10 20 30 40 0 0.2 0.4 u [l /h ] 0 10 20 30 40 0 50 100 c s [g /l ] 0 10 20 30 40 0 20 40 c x [g /l ] t [h] fig. 5 the obtained model output vs. the ‘true’ solid: system, dashed: method 2 dotted: method 3 0 10 20 30 40 0 0.2 0.4 u [l /h ] 0 10 20 30 40 0 50 100 c s [g /l ] 0 10 20 30 40 0 20 40 c x [g /l ] t [h] fig. 6 the obtained model output vs. the ‘true’ solid: system, dashed: method 2 dotted: method 3 conclusions the estimation of model parameters largely depends on the information content of the experimental data presented to the parameter identification algorithm. establishing optimal experiment design (oed) can maximise the confidence on the model parameter, hereby increasing the confidence on the model prediction. both the parameter estimation and experiment design tasks represent a complex nonlinear optimization problem, hence the effectiveness of the applied optimization algorithms has great influence on the performance of the whole procedure. this paper proposes the application of evolutionary strategy (es) for this purpose. es is a stochastic optimization algorithm that uses the model of natural selection. in this paper, this es based oed technique has been applied for fed-batch biochemical reactor. one of the factors affecting the modelling of biochemical systems is that accurate description of biochemical reaction is generally not available a priori. hence, this paper addressed the application of oed for models that have inaccurate structure. we illustrated that although the model structure used for the design of the experiments is not perfectly known, oed can result in satisfactory parameter values. our results support the conclusion that when the model structure is not accurate, the oed with evolutionary strategy can result in more satisfactory parameter values than the classical oed with sequential quadratic programming and nonlinear least squares algorithms. acknowledgements the authors would like to acknowledge the support of the cooperative research centre (vikkk) (project 2003-i), and founding of the hungarian research found (otka t037600). references 1. bernaerts, k., servaes, r.d., kooyman, s. and versyck, k.j. and van impe, j.f.: optimal temperature design for estimation of the square root model parameters: parameter accuracy and model validity restrictions, int. jour. of food microbiology, 2002, 73, 145-157 2. asprey, s.p. and macchietto, s.: designing robust optimal dynamic experiments, journal of process control, 2002, 12, 545-556 3. espie, d.m. and macchietto, s.: the optimal designs of dynamic experiments, aiche j., 1989, 35, 223-229 4. versyck, k.j., bernaerts, k., geearerd, a.h. and van impe j.f.: introducing optimal experiment design in predictive microbiology: a motivating example. int. journ. of food microbiology, 1999, 51(1), 39-51 5. asprey, s.p. and macchietto, s.: statistical tools for optimal dynamic model building, comp. chem. eng., 2000, 24, 1261-1267 6. smets, i.y.m, versyck, k.j.e and van impe, j.f.: optimal control theory: a generic tool for identification and control of (bio-)chemical reactors, annual reviews in control, 2002, 26, 5773 7. madár, j. and abonyi, j.: evolutionary algorithms, chapter 2.10. in instrument engineers' handbook, 4th edition, volume 2 process control, editor: b. liptak, crc press, 2005 8. schwefel, h.: numerical optimization of computer models. wiley, chichester, 1995 44 troška, mandžáková, hradski, ševčík and masár figure 1: a scheme of the cc microchip with conductivity detection. c-le = the first (itp) separation channel (volume of 4.5 µl) filled with a leading electrolyte; c-be = the second (cze) separation channel (volume of 4.3 µl) filled with a background electrolyte; c-te = the third channel (volume of 0.8 µl) filled with a terminating electrolyte; c-s = sample injection channel (volume of 9.9 µl); d1, d2 = pt conductivity sensors; bf = bifurcation section; be, le, te, s = inlets for the background, leading, terminating and sample solutions to the microchip channels, respectively; w = an outlet channel for the waste container. cc technology employed on the microchip with contact conductivity detection enables online capillary zone electrophoresis (cze) to be coupled with the isotachophoresis (itp) sample pretreatment. samples of urine and saliva were simplified by solid-phase microextraction (spme) prior to the itp-cze separations on the microchip. spme based on silverand barium-form resins provided a high degree of compatibility with mce and a high level of selectivity, whilst simultaneously removing a huge amount of chloride and sulfate in the analyzed samples of body fluids. 2. experimental itp-cze separations were carried out on a poly(methyl methacrylate) microchip (fig.1) with the cc technique and integrated conductivity detection sensors (ionchiptm 3.0, merck, darmstadt, germany). chemicals used for the preparation of electrolyte solutions and model samples were obtained from sigma-aldrich (bratislava, slovakia), fluka chemikabiochemika (buchs, switzerland), serva electrophoresis gmbh (heidelberg, germany) and erba lachema s.r.o. (brno, czech republic). samples of urine and saliva were collected from volunteers. before the analysis, the samples were homogenized and analyzed after being diluted appropriately with deionized water, and pretreated by spme to remove chloride and sulfate. solid-phase extraction (spe) microcolumns of 0.5 ml in volume containing silverand barium-form resins (alltech, grace davison discovery sciences, deerfield, illinois, usa) were used for this purpose. 3. results and discussion itp-cze separations were performed in a hydrodynamically closed separation system with suppressed electroosfigure 2: electropherogram from the itp-cze separation of hcy in the presence of discrete spacers. the sample injected onto the microchip: 100 µmol/l apm, 15 µmol/l hcy, 150 µmol/l thr in a 50 % terminating electrolyte. apm = aminopimelate; hcy = homocysteine; thr = threonine; g = conductivity. motic flow. these working conditions effectively reduce the fluctuations in the total migration velocity of the analytes which is crucial to obtain reproducible results, especially on the microchip with short separation paths [21]. in the itp separations, a leading electrolyte with a ph of 9.1 and glycine as a terminating electrolyte were used. in the cze step of the itp-cze technique, the ph of the background electrolyte was 9.8. the itp realized in the first separation channel on the microchip (fig. 1) preconcentrates the analyte and other constituents of the sample for the cze separation step. on the other hand, the close migration configuration of the constituents in the itp stage of the itp-cze technique can be a limiting factor for achieving the required resolution of the analyte from matrix constituents, especially on the microchip with short separation channels. in such a case, discrete spacers (dss) are effectively used to define the fraction of the sample transferred to the second cze channel when the cc technique is employed. then, the constituents of the sample migrating outside of the mobility interval defined by the dss are removed from the separation system. in this way, itp works as an online sample clean-up technique prior to the cze. in our case aminopimelate and threonine were used as the front and rear dss, and the undesirable constituents of the sample were electrophoretically removed from the separation system by column switching prior to the cze separation realized in the second channel (fig. 2). a 1.4 µmol/l limit of detection (lod) for hcy was obtained by the itp-cze technique on the microchip. a relatively large volume of the sample that was injected onto the microchip (9.9 µl) contributed to achieving the low value of lod when a universal and relatively low-sensitive conductivity detector was used. under the working and separation conditions employed, the reproducible migration velocities (the relative standard devihungarian journal of industry and chemistry determination of homocysteine by microchip electrophoresis 45 figure 3: electropherograms from itp-cze analyses of urine samples after spme pretreatment with various additions of hcy. sample injected on the microchip: urine diluted twice, 400 µmol/l apm, 200 µmol/l thr in 50 % terminating electrolyte with (a) 0; 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gonin, j.; wilcox, c.s.; wainer, i.w.: determination of reduced and oxidized homocysteine and related thiols in plasma by thiolspecific pre-column derivatization and capillary electrophoresis with laser-induced fluorescence detection, j. chromatogr. b biomed. sci. appl., 1999 735(2), 219–227 doi: 10.1016/s0378-4347(99)00425-9 [19] furmaniak, p.; kubalczyk, p.; głowacki, r.: determination of homocysteine thiolactone in urine by field amplified sample injection and sweeping mekc method with uv detection, j. chromatogr. b anal. technol. biomed. life sci., 2014 961, 36–41 doi: 10.1016/j.jchromb.2014.04.051 [20] chand, r.; han, d.; islam, k.; yeon, i.j.; ko, s.s.; kim, y.s.: microchip capillary electrophoresis based separation and detection of cysteine and homocysteine, adv. mat. res., 2013 647, 482–486 doi: 10.4028/www.scientific.net/amr.647.482 [21] kaniansky, d.; masár, m.; bodor, r.; žúborová, m.; ölvecká, m.; jöhnck, m.; stanislawski, b.: electrophoretic separations on chips with hydrodynamically closed separation systems, electrophoresis, 2003 24(12–13), 2208–2227 doi: 10.1002/elps.200305474 hungarian journal of industry and chemistry introduction experimental results and discussion conclusion hungarian journal of indus1rial chemistry veszprem vol. 30. pp. 103105 (2002) on the purification of gases containing impurities of small concentration c. boy adjiev (bulgarian academy of sciences, institute of chemical engineering, "acad. g.bontchev" str.,bl.l03, 1113 sofia, bulgaria) received: november 05, 2001 a theoretical analysis was made of the methods used for the purification of gas, containing impurities of small concentrations. a comparison is proposed between absorption and adsorption methods. it is shown that adsorption processes are more advantageous in these cases. keywords: gas purification, absorption, adsorption, comparative analysis introduction numerous ecology problems are related to the purification of air from its impurities.~ the main problem occurred in the case, when the concentration of the impurity is really small. in these cases absorption in a packed column is frequently used. a high absorption rate should be realized by a suitable chemical reaction between the gas impurity and a liquid absorbent. in reality, the absorption rate is usually very small and as a result, a very high absorption column has to be applied, to reach the expected efficiency. absorption if a gas of q(m3 is) flow rate has to be purified from its impurity with concentration of c (kg i m3 gas) in a packed column (diameter d (m) and a height of the active zone h (m), height of the packing). the concentration of the impurity (an active component of the gas) is equal to zero as result of the chemical reaction between this component and the absorbent. in this case the concentration difference in the equation of the mass transfer rate is equal to c . the concentration difference is changing along the active zone height. thus, it should be used the average value of the concentration difference ilc(kg / m3 gas}: contact information: e-mail: chboyadj @bas.bg .tlc (1) where c1 and c2 (kg i m3 gas) are the inlet and exit concentrations of the active component in two ends of the active zone. the chemisorption rate in the column is j (kg/ s) and the volumetric chemisorption rate is j (kg i s.m3 active zone). if u (m/ s), v {m3 ) are the gas velocity and active zone volume, then: 7td2 v = s.h, q = s.u, s == --. (2) 4 if k (m3 gas/ s.m3 actve zone} is the volumetric mass transfer coefficient and ks (m3 gas/ s.m2 mass transferswface) is the surface mass transfer coefficient, the chemisorption rate equation has the following form: (3) where s(m2 masstransfersuiface/m3 actvezone) is the specific mass transfer surface in the active zone. eq.( 3) shows that if the volume concentration of the active component is small and the diameter of the 104 table 1 comparison between the absorption and the adsorption: q=0.4m%ec, c=0.01kg/m3 , 1j.==99% .n2 parameters 1 the gas velocity, u {jnjs) 2the column section, s (m~) 3the column diameter, d (m) 4the volume mass transfer coefficient, k (s-1) 5the active zone volume, v (m1 ) 6the active zone height, h (m) 7the relative decreasing of the volume, a v vn3 ) 8the relative increasing of the height, m (m) 9the stoichiometric quantity of a liquid phase, l (m3 is) 1 othe real quantity a liquid phase, l (m3 j s) 11 the relative increasing of the liquid phase .al (m3 is) 12the relative increasing of the consummations for the liquid phase, i1e 13the pressure drops, !j.rp mm h 2 0 column is constant, the increasing rate of chemisorption is a result of the active zone height increase or the increase of the volume mass transfer coefficient: (4) under the chemisorption conditions, when the gas velocity and chemical reaction rate are constant, the mass transfer coefficient does not change significantly. thus, from eq.(4) follows that the increase of the input concentration c1 (respectively ac) needs the increase of the specific mass transfer surface, s . the specific active surface in packed columns is limited by the specific surface of the packing. as a result. it is not possible to i'ncrease the volumetric mass transfer coefficient, i.e. for increasing of the column height. this shows that it is better to use adsorption process for gas purification because its specific mass transfer surface is significantly greater compared to packed columns. the chemisorption in the active zone may be realized by means of absorption in a packed column (s=l02 m2/m3 ) or by the adsorption of a synthetic adsorbent (s= 108 m2 /m3 ) .. because the ratio of the volumetric mass transfer coefficients of the adsorption and absorption is 104 • the experimental data for volumetric mass transfer coefficient in the case the sa}. adsorption by synthetic anionite shows that k = 12.1 u m3 gas/ s.m3 active zone. {s) the experimental data for the gas absorption in the packed column [4] show that the volumetric mass transfer coefficient in gas phase for raschig rings (502t50x2)mm is k = l.4kg/m3 .bar.s. {6} adsorption 0.7 0.57 0.85 8.5 0.046 0.081 25 3.3 w-s 3.3 w-s 1 80 0.1 4 2.25 1.2 0.32 0.081 1 25 3.3 to·5 3.3 w·s 1 1 24 absorption 1 0.4 0.71 0.5 0.79 2 25 3.3 w-s 6710"5 20 500 24 if the gas velocity is 1 m/ s and the liquid flow rate is 6m3/m2 h. from (6) it is immediately obtained, that: k = 0.5 m3 gas/ s.m3 active zone. (7) these data allow possibility to make a comparative analysis on the absorption and adsorption, on the basis of the next example (table 1.). let to purify airflow of q = 0.4m3 /s with concentration of 802 c =0.0lkgjm3 with 11 =99%. efficiency. the values of the process parameters of chemisorption under the absorption and adsorption conditions are shown in the table 1. the results in the table show that an increase of the volume av and m in the case of absorption, compared to the adsorption. in the table 1 the stoichiometric quantity of the liquid phase l (m3 is) 200 g /l na2 co3 is obtained immediately. the real quantities of the liquid phase l~n3 / s) are obtained immediately under the adsorption condition l = l from the liquid flow rate under an . absorption condition. the relative increase of the liquid flow rate in the case of absorption compared to the absorption condition m can be obtained immediately. the consummations of the liquid phase movement are linear function of the liquid flow rate l and the active zone height. h. as a result. the consummation of the relative increase ae is /j.l : m = al.ah . raschig rings (50x50x5) mm are used for the pressure drops comparison. the second adsorption data are valid in the case of lower gas velocity (u = 0.1 m/ s). conclusions the obtained results show that the adsorption process is significantly more effective for gas purification compared to the absorption, when the concentration impurities are small. in these conditions the saturation of the adsorbent is very slow and this is another cause for a real use of adsorption processes for solving ecology problems. symbols c concentration, (kg/ m3 gas) c1, c2 input and output concentration of the active component, (kg/ m3 gas) a.c average value of the concentration difference, (kg/m3 gas) d column diameter, (m) de relative increasing of the consummations for liquid phase, h column height, (m) a.h increasing of the column height, (m) 1 chemisorption rate, (kg/ s) j k volume chemisorption rate, (kg/ s.m3 active zone) volume mass transfer coefficient, (m3 gas/ s.m3 active zone) surface mass transfer coefficient, (m3 gas/ s.m2 mass transfer surface) l u q s u v a.v 1] 8.cp 105 stoichiometric quantity of the liquid phase, (m3/s) real quantity of the liquid phase, (m 3 /s) relative increasing of the liquid flow rate, (m3 /s) gas flow rate, (m3 / s) specific mass transfer surface, (m2 mass transfer surface/ m3 active zone) gas velocity, (m/ s) active zone volume, (m3 ) increasing active zone volume, (m3 ) purification degree, (%) pressure drops, mm h 20 references 1. l. pantovchiev a and chr. boy adjiev: bulg. chern. commun., 1995, 28, .n2 %, 780-794 2. chr. boyadjiev, l. pantovchieva and j. christov: theor. found. chern. eng., 2000, 34, 2, 141-144 3. j. christov, chr. boyadjiev and l. pantofchieva; theor. found. chern. eng., 2000, 34, 5, 439-443 4. v. m. ramm: gas absorption, chemistry, moscow, 1976 page 103 page 104 page 105 hungarian journal of industry and chemistry vol. 47(2) pp. 5–10 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-14 production of the enzyme cyclodextrin glycosyltransferase using different fermentation techniques réka czinkóczky1 and áron németh *1 1department of applied biotechnology and food science, budapest university of technology and economics, műegyetem rkp. 3, budapest, 1111, hungary cyclodextrins produced by cyclodextrin glycosyltransferase (cgtase) are widely used in the pharmaceutical industry to improve the solubility of drug substances as well as protect them against oxidation. the use of this enzyme in the cosmetics industry is also significant. cgtase is an enzyme that belongs to the α-amylase family, which is part of the group of non-leloir glycosyltransferases. enzyme-catalysed transglycosylation reactions may involve cyclization, coupling and disproportionation processes. the enzyme cgtase is mostly used to produce cyclodextrins (cds). cgtase can produce α-, βand γ-cds during transglycosylation reactions, depending on the number of glucopyranose units involved (6, 7 or 8). the enzyme cgtase can also be used for enzymatic bioconversion, e.g., in the development of alternative sweeteners, where the bitter aftertaste of the product is reduced during the enzymatic bioconversion of steviol glycosides, thereby obtaining an even sweeter and more advantageous material. in our research, the enzyme cgtase was produced using different fermentation techniques to compare the activity and amount of cgtase produced by each process and optimize the subsequently planned scale-up. in our studies, the strain dsm 13 of bacillus licheniformis was used, which produced cgtase extracellularly. during the experiments the batch, fed-batch and semi-continuous fermentation techniques were compared in terms of enzymatic production. all cultivation processes were carried out in a desktop lab scale fermenter. keywords: cyclodextrin glycosyltransferase, fermentation, cyclodextrins, bacillus licheniformis 1. introduction cyclodextrin glycosyltransferase (cgtase, ec 2.4.1.19) is a starch-degrading enzyme, which is a member of the α-amylase family. the formal name of cgtase is [1,4-αd-glucan 4-α-d-(1,4-α-glucano)-transferase(cyclizing). kuriki et al. [1] reported that cgtase has the same four highly conserved regions as the α-amylases. cgtase catalyses four kinds of transglycosylation reactions (fig. 1): cyclization, coupling, disproportionation and hydrolysis. these reactions are all transglycosylations, in which cyclization is intramolecular, coupling and disproportionation are intermolecular, and hydrolysis is the conversion of sugar to h2o [2]. the formation of cyclodextrin (cd) by the enzyme cgtase is an intermolecular transglycosylation reaction [3]. many microorganisms are capable of producing cgtase, e.g., bacillus macerans [4, 5], bacillus amyloliquefaciens [6], bacillus clarkii [7], bacillus megaterium [8], bacillus subtilis [9], bacillus licheniformis [10, 11], bacillus firmus [12,13], bacillus circulans [14,15], bacillus ohbensis [16, 17], geobacillus stearothermophilus [18], thermoanaerobacter sp. [19], klebsiella pneumoniae, and klebsiella oxytoca [20]. *correspondence: naron@f-labor.mkt.bme.hu figure 1: cgtase-catalysed reactions: a: cyclization, b: coupling, c: disproportionation, d: hydrolysis https://doi.org/10.33927/hjic-2019-14 mailto:naron@f-labor.mkt.bme.hu 6 czinkóczky and németh figure 2: general structure of cyclodextrins (n: number of glucopyranose units, n = 6 α-cd, n = 7 β-cd, n = 8 γ-cd) (figure adapted from: https://commons.wikimedia.org/wiki/file:cyclodextrin.svg cc by-sa 3.0) (08.07.2019) ) the molecular weight of cgtases may vary from 60 to 110 kda, typically its proteins have a mass of 75 kda [21]. the most important demand of metal ions for them is ca2+, which protects the protein against heat denaturation. most cgtases are strongly inhibited by zn2+, cu2+ and fe2+ [22]. cyclodextrins, produced from starch or its derivatives via enzymatic conversion, proceed through an intramolecular transglycosylation reaction using cgtases and to a lesser extent α-amylases [3]. they are cyclic oligosaccharides composed of α-1,4-glycosidic-linked glucosyl residues [23]. three different types of cyclodextrins exist and are characterised according to the number of glucosyl residues in the molecule: α-, βand γcyclodextrins consist of 6, 7 and 8 glucose units, respectively (fig. 2). cyclodextrins are cyclic molecules with a hydrophilic exterior and a hydrophobic cavity that enables them to form specific inclusion complexes with small hydrophobic molecules [24]. cyclodextrins are chiral non-reducing oligosaccharides. glucose is the decomposition product of all cyclodextrins in acidic solutions. the rate of hydrolysis follows the order of γ > β > α. under acidic conditions, cyclodextrins are more slowly hydrolyzed than maltooligosaccharides. the glycosidic bonds in the cyclodextrins can be hydrolyzed by α-amylase, but β-amylase is unable to perform this hydrolysis. the rate of enzymatic hydrolysis is the fastest for γ-cd, followed by βthen α-cd. all cds are very stable and soluble in alkaline solutions at high ph. cds are more resistant to acid or alkaline degradation than starch. cds do not even degradate at temperatures as high as that of caramelization (> 200 ◦c, sterilization) under both dry or aqueous conditions of between ph 2 and 12. they are also stable up to 250 ◦c under an inert atmosphere of, for example, nitrogen [20, 25, 26]. the widespread use of cyclodextrins is due to their specific structure. since each guest molecule is uniquely surrounded by the cd (or one of its derivatives), it is microencapsulated from a molecular microscopic point of view. this can result in beneficial changes to the chemical and physical properties of guest molecules, e.g., lightor oxygen-sensitive materials can be stabilized; very volatile substances fixed; the chemical reactivity of molecules modified; the solubility of materials improved; changes between phases achieved from liquid substances into powders; degradation of microorganisms avoided; bad smells and tastes masked; and pigments or colors of materials coated. as a result of these characteristics, cds (and their derivatives) can be used in analytical chemistry, agriculture, the pharmaceutical as well as food industries and other masking areas. cgtase can be used for the transglycosylation of stevioside to rebaudioside through which the edulcorant quality can also be improved by increasing the substitution of steviol glycoside with the help of cornstarch hydrolyzate and cgtase [27–30]. 2. materials and methods 2.1 cultivation of the bacteria the applied bacterial strain was bacillus licheniformis b.01470 (dsm 13) purchased from the national collection of agricultural and industrial microorganisms in hungary. bacillus licheniformis is a gram-positive, rodshaped, endospore forming, facultatively anaerobic bacteria. nutrient agar was used to maintain the bacterium in petri dishes [31]. in our research, three types of fermentation techniques for the production of cgtase were compared: batch, fed-batch, and semi-continuous fermentation techniques. all cultivation processes were carried out in a benchtop lab scale fermenter (fig. 3) (biostat q, b. braun biotech international, germany). in the fed-batch fermentation, after 24 hours 15 v/v % of the medium was fed into the bioreactor. during the semi-continuous fermentation at the end of each cycle, 80 % of the broth was replaced by fresh media. for the experiments in the bioreactor, horikoshi ii medium was used for the cultivation of bacteria containing 1.0 % soluble starch, 0.5 % peptone, 0.5 % yeast extract, 0.1 % k2hpo4, 0.02 % mgso4 •7 h2o, and 1.0 % na2co3 (all concentrations are given in w/v in distilled water) [32]. hungarian journal of industry and chemistry https://creativecommons.org/licenses/by-sa/3.0/deed.en production of the enzyme cyclodextrin glycosyltransferase 7 figure 3: the bioreactor used in the experiments 2.2 the modelling of microbial growth in order to monitor the growth of bacterial cells, samples were taken during fermentations and the optical density (od) measured at 600 nm. microbial growth is described by µx = 1 x dx dt , (1) where µx is the specific growth rate of the microbe. it was evaluated through fitting the generalized logistic function z = zmax 1 + exp(a+ bt+ ct2 + dt3) (2) to the measured cell dry weight (cdw) values (calculated from at od600). to fit the curve, sigmaplot version 12.0 software was applied. if the coefficient of determination (r2) was not high enough, the last two members of the generalized logistic function were omitted resulting in z = zmax 1 + exp(a+ bt) , (3) figure 4: colorimetric analysis of cgtase activity which also corresponds to the modified monod model. the derivative of the fitted function is dz dt = −z ( 1− z zmax ) dh dt (4) where dh dt = b+ 2ct+ 3dt2 (5) is the derivative of the internal function. the auxiliary variable z in eq. 2, 3, and 4 was x (biomass in g/l), s (substrate in g/l), and pi (product in g/l), respectively, while zmax was xmax, s0 and pi,max, respectively. if the fit was successful, then, by using determined constants of the model, the velocities and specific growth rates could be calculated by derivation from eq. 4. 2.3 measurement of cgtase activity during the fermentations, samples were regularly extracted into eppendorf tubes, which were centrifuged at 12,000 rpm for 6 minutes, then the cell-free supernatants were used to determine the enzyme activity. the measurement of extracellular cgtase activity was adapted from the method of kaneko et al. [33] with slight modifications (with a reduced concentration of phenolphtalein). the colorimetric reaction (fig. 4) was measured by a spectrophotometer at 550 nm. the experiments were conducted in 15 ml centrifuge tubes in a water bath at 40 ◦c. first, 4.5 ml 50 mm trishcl buffer (ph = 9) was added containing a 1 % (w/v) water-soluble starch suspension, then 0.5 ml of cell-free supernatant containing the extracellular cgtase enzyme was introduced and homogenized thoroughly with a vortex mixer. then four 0.5 ml samples were taken from each tube which were boiled for 5 minutes to inactivate the enzyme. the boiled samples were transferred into 2 ml cuvettes that contained a staining solution (1.2 ml 0.06 mm phenolphthalein in 0.5 m na2co3 solution). four absorbances at 550 nm of a given assay were plotted against time and the gradient (mmol/min) converted into enzyme activity with the help of a molar extinction coefficient (32, 263 m−1cm−1) resulting in the cgtase activity in unit/ml supernatant. 47(2) pp. 5–10 (2019) 8 czinkóczky and németh figure 5: microbial growth during the batch fermentation figure 6: microbial growth during the fed-batch fermentation 3. results and discussion 3.1 batch fermentation fig. 5 shows the microbial growth during the batch fermentation and also represents the changes in the specific growth rate. the maximum value of the specific growth rate was 0.53 1/h. at the end of the fermentation, the final activity of cgtase was 0.3 u/ml and the productivity was 11.8 mu/(ml h). 3.2 fed-batch fermentation fig. 6 represents microbial growth during the fed-batch fermentation. unfortunately, due to poorly scheduled sampling, it was not possible to adjust the generalized logistic equation, therefore, it was impossible to calculate the specific growth rate. a fresh medium of 15 % was injected after 24 hours. the final enzyme activity was 0.5 u/ml and the enzyme productivity was 12.3 mu/(ml h). 3.3 semi-continuous fermentation the semi-continuous fermentation is shown in fig. 7, which consisted of 3 cycles. the highest value of the maximum growth rate was during the first cycle (0.5 1/h). as the fermentation progressed, the maximum specific growth rate decreased. figure 7: optical density and specific growth rate changes during the semi-continuous fermentation figure 8: cgtase activities at the end of each cycle fig. 8 shows that the enzyme activity of cgtase increased as the fermentation progressed. 3.4 comparison of the different fermentation techniques table 1 summarizes the enzyme activities and productivities achieved by each fermentation technique. the maximum specific growth rates reached in the batch and semicontinuous fermentations were approximately the same, which is characteristic of when the microorganism can multiply. the enzyme activities at the end of the fermentations table 1: comparison between the results of the different fermentation techniques type µmax [1/h] final enzyme activity [u/ml] productivity [mu/(ml h)] batch 0.53 0.3 11.8 fed-batch n.d. 0.5 12.3 semicontinuous 0.50 2.4 29.95± 0.3 hungarian journal of industry and chemistry production of the enzyme cyclodextrin glycosyltransferase 9 rose as the complexity of the fermentation technique increased. while the fed-batch fermentation elongated the declining phase of the microbial growth cycle, in the semi-continuous fermentation technique an attempt was made to operate in the exponential growth phase. it is assumed that this difference caused the higher activity and productivity in the case of the semi-continuous fermentation. 4. conclusion in our experiments, the effect of the fermentation technique on the activity of the produced enzyme cgtase was investigated. there was no significant difference between the activities of the produced cgtase and productivities of the systems when the batch and fed-batch fermentations were compared. in contrast, bacteria produced a much more active enzyme during the semi-continuous fermentation, moreover, the productivity of this system was also significantly higher than that of the other two fermentation techniques. from the results, it can be assumed that the microbes produce the enzyme during the exponential growth phase, since no significant difference was observed between the batch and fed-batch fermentations. meanwhile, a repeated exponential growth phase resulted in a much higher activity and productivity. this suggests that cgtase production follows growth associated-type product formation. acknowledgement the research was supported by the gedeon richter’s talentum foundation, founded by gedeon richter plc. 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https://doi.org/10.1016/s0734-9750(02)00020-4 https://doi.org/10.1016/j.foodchem.2012.10.124 https://doi.org/10.1134/s0003683806010030 https://doi.org/10.1134/s0003683806010030 https://www.dsmz.de/microorganisms/medium/pdf/dsmz_medium1.pdf https://www.dsmz.de/microorganisms/medium/pdf/dsmz_medium1.pdf https://doi.org/10.1080/00021369.1989.10869443 https://doi.org/10.5458/jag1972.34.45 introduction materials and methods cultivation of the bacteria the modelling of microbial growth measurement of cgtase activity results and discussion batch fermentation fed-batch fermentation semi-continuous fermentation comparison of the different fermentation techniques conclusion hungarian journal of industry and chemistry vol. 45(1) pp. 23–27 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0005 replacement of biased estimators with unbiased ones in the case of student's t-distribution and geary’s kurtosis gergely tóth* and pál szepesváry institute of chemistry, faculty of science, eötvös loránd university, 1/a pázmány péter sétány, budapest, h-1117, hungary the use of biased estimators can be found in some historically and up to now important tools in statistical data analysis. in this paper their replacement with unbiased estimators at least in the case of the estimator of the population standard deviation for normal distributions is proposed. by removing the incoherence from the student’s t-distribution caused by the biased estimator, a corrected t-distribution may be defined. although the quantitative results in most data analysis applications are identical for both the original and corrected tdistributions, the use of this last t-distribution is suggested because of its theoretical consistency. moreover, the frequent qualitative discussion of the t-distribution has come under much criticism, because it concerns artefacts of the biased estimator. in the case of geary’s kurtosis the same correction results (2/π)1/2 unbiased estimation of kurtosis for normally distributed data that is independent of the size of the sample. it is believed that by removing the sample-size-dependent biased feature, the applicability domain can be expanded to include small sample sizes for some normality tests. keywords: unbiased estimator, normal distribution, anscombe-glynn test, jarque-bera test, bonett-seier test 1. introduction the student's t-distribution [1] is one of the most widely used statistical functions in experimental practice. it is well documented that experts active in analytical, physical and clinical chemistry, biology, agriculture, ecology, economy as well as forensic science or even legal representatives apply this tool to formulate solid statements, e.g. population means, to differentiate between two sample means, etc., which are in most cases necessarily based on a limited number of observations. fortunately, scientists are in this respect soundly supported by a lot of textbooks, standards, software, software systems, and last but not least trained in elements of statistics. however, it should be a moral obligation to be aware of the evolution of this routinely used method, its principles and often tacitly supposed assumptions. although not crucial in daily use, it is worthwhile to know that besides student’s t-distribution there are different functions which may be suitable for the determination of percentiles in the same way as the t-distribution. they may differ mainly in terms of alternate estimators for the population mean and population standard deviation. an attractive variant is presented in this work emphasizing its theoretically fully consistent feature on the contrary to the student's t-distribution. *correspondence: toth@chem.elte.hu the student’s t-distribution corresponds to a ratio of normally distributed random variables to chidistributed random variables (see the references in the historical review of zabell [2]). chi-distributed variables postulate normally distributed data as well. gosset [1] used in his definition an estimate of the standard deviation which is biased relating the population standard deviation and even the variance in the case of normally distributed random variables as was shown earlier by helmert [3-4]. amazingly, when fischer proposed a transformation of gosset’s original z variable to 1 nzt [5-6], he chose an estimate for the standard deviation which is also biased relating σ. a corrected tcdistribution is proposed that fulfils all theoretical requirements and yields a more normal distribution-like shape. it is consequently based on normal sample data and uses an unbiased estimator. a similar correction can be applied to geary’s kurtosis that is the ratio of the mean deviation to the standard deviation [7]. in this work the use of the correction is proposed in order to eliminate the sample-size dependency of the mean geary’s kurtosis on normally distributed data. finally, some remarks are made on statistical tests based on sample-size dependent values in order to extend their applicability to small sample sizes. tóth and szepesváry hungarian journal of industry and chemistry 24 2. theoretical background the square root of the mean of the square of the centred observations of the random variable, y,   n yy s n i i n     1 2 (1) may be an estimator of the population standard deviation, σ, of a sample. n is the sample size and y denotes the sample mean. bessel pointed long before to the bias of sn and proposed:   1 1 2      n yy s n i i . (2) although �� is already an unbiased estimator of the variance, ��, irrespective of the distribution of y, the statistics �� and � are both biased in terms of the standard deviation, �. however, there is a correction [5-6, 89]: , 2 1 2 1 2 )(4                  n n n nc (3) which applies to � by transforming it, in the case of normally distributed variables, into an unbiased statistic:  nc s s 4 c  . (4)  nc4 follows from helmert’s papers or cochran's theorem [10]. for normally distributed y, )(1 sn  exhibits a chi distribution with n-1 degrees of freedom.  nc4 is the expected value of s/σ. there is a  nc2 value as well, that is equal to the expected value of �� �⁄ . the correcting effect of  nc4 may be considerable for low values of n (table 1). table 1. selected c4(n) corrections n c4(n) 2 0.7979 3 0.8862 4 0.9213 5 0.9400 10 0.9727 20 0.9869 30 0.9914 figure 1. student’s t-distribution compared with the standard normal distribution the correction term is frequently used in statistical process control (spc) to define ±3σ intervals and process standard deviations that are determined for samples of different sizes. 3. results and discussion 3.1. discussion of the density functions of the student’s t-distribution let y be an independent n(μ,σ2) variable. the ns y t /   (5) statistic exhibits the usual student t-distribution with n1 degrees of freedom. the density function (eq.(6)) can be derived as the quotient of normal and chi-distributed random variables. the independency of the nominator and denominator can be shown and it is also proved by a series of theorems that t defined in eq.(5) follows a student’s t-distribution with n-1 degrees of freedom (see the references in [2]):   22 1 1 2 1 2 1 1 )( n n t n n n tf                              (6) the distribution sketched in fig.1 is widely known and needs no comments except for its flaw: it is based on the biased statistic (eq.(2)) for σ. by replacing the standard deviation of the sample, s, in eq.(5) with the unbiased equivalent one, sc, corrected by c4(n), results in a new value: ns y t /c c   , (7) and in the density function: note on student’s t-distribution 45(1) pp. 23–27 (2017) 25       2 2 4 2 c 2 2 4 2 c 4 c 1 1 2 1 1 1 2 1 1 2 )( 1 )( n n nc t nc t n n n nc tf                                         . )( )( )1,2/(crit 4 )1,2/(crit 4 )1,2/(crit cc     n nn st nct nc s ts   table 2. sample-size dependence of geary’s and pearson’s kurtosis. the c4(n)-corrected geary’s and the size-corrected pearson’s kurtosis [11] provided the ∞ limit values for all sample sizes within the statistical uncertainty of the 105 random samples. n geary’s kurtosis pearson’s kurtosis 3 0.9004 1.5000 4 0.8659 1.8005 5 0.8489 1.9996 6 0.8385 2.1437 7 0.8319 2.2501 8 0.8267 2.3340 9 0.8233 2.4006 10 0.8200 2.4557 20 0.8085 2.7141 50 0.8021 2.8820 100 0.7999 2.9408 ∞ 0.7979 3.0000 (8) which is shown in fig.2. as expected, the corrected student’s t-distribution (student’s tc-distribution) consists of more distinct peaks, it exhibits fatter tails than the standard normal distribution, but rather oddly at its maximum, i.e. when tc = 0, the value f(tc) does not depend on n and is represented by the value 2/1 , the same as for those of normal distribution. the function f(tc) and the student’s t-distribution without a doubt differ in this respect. the obvious differences between the student and modified student distributions do not complicate their daily usage. the confidence intervals calculated using s and t or sc and tc estimators and distributions, respectively, n ts y n )1(,2/ cc    and n st y n )1(,2/    (9) do not differ, because (10) evidently, corresponding estimators and functions should be used. 3.2. the effect of the correction to geary’s kurtosis geary’s kurtosis [7], wn, is the ratio of the mean absolute deviation (mad) to the standard deviation (eq.(11)). it is an alternative to pearson’s kurtosis based on the fourth moment. the expected value of geary’s kurtosis depends on the sample size even for normally distributed data [7]. the mean values of 105 random samples from standard normal distributions are shown in table 2. n n i i n s yy n w     1 1 (11) if the c4(n) corrections (table 1) are applied during the calculation of the nominator of the ratio as wn,corr=wn c4(n), the expected value of the kurtosis is (2/π)1/2 for all sample sizes. this means that the platykurtic and the leptokurtic features of a sample can be found without searching for the size-dependent dividing value in tables. 3.3. sample-size bias in statistical tests geary’s kurtosis and its transformed values are used in normality tests due to their enhanced sensitivity to some leptokurtic deviations from normality [12]. contrary to the case of the student’s t-distribution, where the correction has no effect on the t-test, here the effect of the correction is not cancelled. generally, the size dependence decreases the performance of the tests for small sample sizes. this feature is interpreted by users as a recommendation that the tests are unsuitable for small sample sizes. in the same way, neglect of sample-size dependence is applicable in tests where pearson’s kurtosis is used. the calculated mean value of pearson’s kurtosis is shown in table 2 but its convergence is rather weak to the theoretical value of 3. it should be noted here that the sample-size unbiased estimator of kurtosis can be easily calculated [11]. figure 2. corrected student’s t-distribution compared with the standard normal distribution tóth and szepesváry hungarian journal of industry and chemistry 26 table 3. sample-size dependence of five normality tests based on unbiased or sample-size-dependent biased estimators. the numbers show the ratio of the rejected null hypotheses to all trials at a significance level of 0.05 from 105 random samples. n shapirowilk d’ agostino anscombeglynn bonettseier jarque -bera 4 0.0502 5 0.0521 0.0373 6 0.0477 0.0189 0.0087 7 0.0492 0.0343 0.0282 8 0.0505 0.0365 0.0348 9 0.0507 0.0538 0.0369 0.0390 0.0024 10 0.0498 0.0528 0.0394 0.0417 0.0058 20 0.0497 0.0525 0.0406 0.0421 0.0089 50 0.0498 0.0500 0.0466 0.0470 0.0241 100 0.0499 0.0493 0.0533 0.0490 0.0368 in table 3 the type-i error of some normality tests calculated on 105 standard normal samples is shown. in the calculation the ‘moments’ package in r was used [13]. table 3 contains the ratio of the samples to all samples where the h0 hypothesis of normality was rejected at the significance level of 0.05. the shapirowilk method [14] uses the ratio of two unbiased estimators of the variance, and is suitable for all data sizes. the skewness test of d’agostino [15] slightly overestimates the number of rejected cases. it is based on the normalized third-order central moment definition of skewness, where the expected value is estimated without bias. the anscombe-glynn [16] test applies pearson’s kurtosis without size correction using a biased estimation of normally distributed data. the bonettseier [12] test shown here uses geary’s kurtosis and the jarque-bera test [17] combines skewness and pearson’s kurtosis. the performance of the last three tests was rather weak for small sample sizes, whereof one cause might be the lack of correction for small sample sizes even for normally distributed data. these tests are usually only recommended for medium and large sample sizes. the correction should extend the applicability domain to small sample sizes. of course, the type-i error of normally distributed data is only one narrow aspect of a test, detailed analysis should be performed to investigate the effect of correction on many distributions, like, e.g. in ref. [12]. 4. conclusion nowadays, data are evaluated by computers and biased estimators can be replaced by unbiased ones, even if their calculation schemes are complex. it has been shown that, in terms of student’s tdistributions, to decide upon the confidences of statistics one has two functions which are completely equivalent as far as practical applicability is concerned. they can, however, be distinguished theoretically. the assertion that only the unbiased estimator should be recognized as the correct one implies the use of the corrected student’s t-distribution, f(tc). in that case the known shape of the student’s t-distribution may be labelled as an artefact and the usual application of the student’s tdistribution as a production of “correct numbers by an incoherent theory”. in the case of geary’s kurtosis, the correction removes the sample-size dependence from the expected value. this change of distinguishing platykurtic or leptokurtic features of the sample is simpler than using the original version of geary’s kurtosis. furthermore, subtracting (2/π)1/2 results in a number to be interpreted in a similar way to the excess kurtosis obtained by subtracting 3 from the pearson’s kurtosis. as a further study, the use of unbiased/samplesize-dependent corrections to extend the applicability domain to small sample sizes in the case of normality tests is recommended. it is believed that the use of biased estimators was acceptable before the age of computers and a systematic change to unbiased ones might be necessary in terms of statistics and standards with regard to industrial processes. acknowledgement the authors are sincerely grateful for the valuable comments of prof. s. kemény and other participants during the scientific discussion after the presentation concerning student’s t-distribution at the scac 2010 conference in budapest in september 2010. references [1] student (gosset, w.s.): the probable error of a mean, biometrika 1908 6(1), 1–25 doi: 10.2307/2331554 [2] zabell, s.l.: on student’s 1908 article “the probable error of a mean”, j. am. stat. assoc. 2008 103(481), 1–7 doi: 10.1198/016214508000000049 [3] helmert, f.r.: über die wahrscheinlichkeit der potenzsummen der beobachtungsfehler und über einige damit in zusammenhang stehende fragen, z. math. phys. 1876 21, 192–218 [4] helmert, f.r.: die genauigkeit der formel von peters zur berechnung des wahrscheinlichen beobachtungsfehles directer beobachtungen gleicher genauigkeit, astronomische nachrichten 1876 88(8-9), 113–131 doi: 10.1002/asna.18760880802 [5] fischer, r.a.: applications of “student’s” distribution, metron 1925 5, 90–104 [6] fischer, r.a.: statistical methods for research workers, (oliver & boyd, edinburgh and london) 1925. 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2002 40(3), 435–445 doi: 10.1016/s0167-9473(02)00074-9 [13] komsta, l.; novomestky, f.: moments r package, version 0.14, 2015 at http://cran.r-project.org, accessed in october 2017 [14] shapiro, s.s.; wilk, m.b.: an analysis of variance test for normality (complete samples), biometrika 1965 52(3/4), 591–611 doi: 10.1093/biomet/52.3-4.591 [15] d’agostino, r.b.: transformation to normality of the null distribution of g1, biometrika 1970 57(3), 679–681 doi: 10.1093/biomet/57.3.679 [16] anscombe, f.j.; glynn, w.j.: distribution of the kurtosis statistic b2 for normal samples, biometrika 1983 70(1), 227–234 doi: 10.1093/biomet/70.1.227 [17] jarque, c.m.; bera, a.k.: efficient tests for normality, homoscedasticity and serial independence of regression residuals, economic letters 1980 6(3), 255–259 doi: 10.1016/0165-1765(80)90024-5 page 1 page 2 page 3 page 4 page 5 page 6 page 7 page 8 page 9 page 10 page 11 page 12 page 13 page 14 page 15 page 16 page 17 page 18 page 19 page 20 page 21 page 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word b_22_pezsa_r.doc hungarian journal of industrial chemistry veszprém vol. 39(2) pp. 321-324 (2011) bioethanol production from paper sludge pretreated by subcritical water n. pézsa1 , p. ailer2 1budapest university of technology and economics, department of automobiles, 1111 budapest stoczek str 6 bld j, hungary, e-mail:pezsa.nikolett@auto.bme.hu 2kecskemét college, department of vehicle technology, 6000 kecskemét, izsáki str 10, hungary the depletion of oil reserves, energy dependency and rising greenhouse gas emissions urge for alternatives in all of the affected sectors. the transport sector contributes to 25% of global anthropogenic greenhouse gas emission and its energy dependency is 98%. it has to be emphasised that in the transport sector such a general solution as petrol nowadays is unlikely to be found in the future. the evaluation of alternatives depends on a lot of factors. biofuels might serve as alternatives if they are produced in a sustainable way. paper sludge is a waste stream of the paper industry and has a high cellulose content, which makes it appropriate for bioethanol production. the aim of this paper is to show an alternative for bioethanol production from paper sludge. paper sludge is pre-treated by subcritical water which is followed by an enzymatic hydrolysis and a fermentation step. optimum condition for the pre-treatment and the enzymatic hydrolysis were determined previously. this paper aims at showing the optimum conditions for the fermentation step. experiments were performed in shake flasks. keywords: bioethanol, paper sludge, pretreatment, optimum consitions introduction alternative transport fuels have raised attention all over the world. it has to be emphasised that among the different alternatives there is no “best” option nowadays. the evaluation of the different alternatives depends on a lot of factors. concerning biofuels the food versus fuel debate seems to be solved with the appearance of second generation biofuels and with biofuels produced from waste streams. however it is still a question whether biofuel production of these feedstocks is cost competitive and sustainable. the aim of this paper is to show experimental results of bioethanol production from paper sludge as feedstock. paper sludge is a residue of the paper industry. in japan 5.5 million ton paper sludge is produced yearly. due to its high cellulose content it might be an appropriate feedstock for bioethanol production. cellulose is a polysaccharide hard to access. several methods have been investigated in the literature to make the cellulose content more easy to access. in these experiments subcritical water and enzymatic hydrolysis were used as pretreatment methods. optimum conditions for the pretreatment were determined previously. the pretreatment steps were followed by a fermentation step. [1, 2] materials and methods microorganism and culture media the yeast strain used was saccharomyces cerevisiae atcc 9763. the composition (per dm3) of the liquid nutrient medium used in the experiments was as follows d(+)glucose, 50 g; (nh4)2so4, 7.5 g; kh2po4, 3.5 g; mgso4·7h2o, 0.75 g; cacl2·h2o 1 g; yeast extract 5 g; bacto peptone 5 g; znso4·7h2o 0.04 g; mnso4·7h2o 0.009 g; cuso4·5h2o, 0.008 g in distilled water. the composition of the precultivation medium was as follows 5% ypd, 0.04% adenine in distilled water. yeast cells were stored on ypd agar slants at 4 °c. ypd agar medium was made up of 5% ypd and 1.5% agar dissolved in distilled water. composition of paper sludge paper sludge has a varying composition. the composition always depends on the paper type produced at the factory. average composition of paper sludge is shown in table 1 and 2. 322 table 1: inorganic components in paper sludge as a percentage of the total inorganic material component % caco3 6.07 mg3si4o10(oh)2 23.97 al4si4o10(oh)8 16.15 tio2 14.19 al2o3 24.15 fe2o3 1.28 p2o5 0.41 unknown 13.78 table 2: organic components in paper sludge as a percentage of the total organic material component % ash 38 tree resin 1.45 lignin 5.28 α-cellulose 24.23 β-cellulose 18.83 γ-cellulose 9.73 unknown 2.48 analytical methods ethanol and glucose concentrations were measured by hplc (shimadzu lc-20ab prominence liquid chromatograph) using an rid detector (shimadzu rid 10a), shodex sugar ks-g g804181 and shodex sugar ks-802 h806003 columns at 80 °c, distilled water as mobile phase at a flow rate of 1 ml/min. dry cell weigth was determined photometrically at 600 nm using a jasco v-550 uv-vis specrophotometer. a calibration curve between dry cell weight and absorbance was set previously. fermentation experiments liquid nutrient medium composition was used as described in microorganism and culture media. ph was adjusted with hcl and naoh solutions. inoculum levels or ph values were altered, but only 1 parameter was changed at one time. experiments were carried out in shake flasks. the precultivation medium was incubated for 24 hours at 30 °c and 100 rpm. the main cultivation medium was incubated for 48 hours at 30 °c and 100 rpm. initial glucose concentration was in all cases 50 g/l. samples were taken at 0, 3, 6, 9, 12, 18, 21, 24, 36, 48 hours of the fermentation medium scale fermentation on paper sludge as substrate was performed in a fermentor with a working volume of 7 dm3. mathematical methods for modeling microbial kinetics the following equations were used. these model functions represent inhibition free substrate limitation kinetics. biomass and product formations were based on the monod equation where the specific production rates depend on the concentration of the limiting substrate (glucose) and on some parameters such as saturation constant and specific rate constants [2]. numerical calculations were performed by matlab simulink® software package. the main purpose of the numerical calculation was to estimate the parameters of the equations above in order to describe the fermentation process as close as possible to the measurements. the kinetic parameters were estimated by nelder-mead simplex algorithm, where the target function was to minimize the error between the calculated and the measured biomass, substrate and product function-values. the error were defined as the sum of the squares of the differences between the experimental and the calculated data. results and discussion experimental results two types of experiments were carried out using glucose and pretreated paper sludge as substrates for ethanol production. the aim of the experiments carried out on glucose as substrate was to determine the optimum conditions for the microorganism saccharomyces cerevisiae atcc9763. the effect of different ph values and different inoculum levels was examined. glucose consumption, ethanol production and cell growth was determined at 5 different ph levels (ph=3.5; ph=4; ph=4.5; ph=5; ph=5.5) and at 5 different inoculum levels (2%; 6%; 10%; 20%; 60%). the determination of the ph range at which the microorganism can work is needed, because the optimum ph for enzymatic hydrolysis and fermentation steps is likely to be different. the determination of the effect of the initial inoculum levels is required to determine the maximum ethanol production in the shortest time possible. this might be preferable on indusatrial scale, where maximum product formation should be reached as soon as possible and therefore production costs can be reduced. 323 after detemining the optimal conditions for the fermentation using glucose as substrate paper sludge was used as substrate. since the enzymatic hydrolysis was performed in acetic acidic buffer, first the acetic acid had to be removed from the medium, because it was an inhibitor for the fermentation. this was done by vacuum evaporation. after that the conditions used for paper sludge were the optimal conditions determined on glucose as substrate. optimum conditions for the microorganism were ph=5 with 10% inoculum. ph dependence and inoculum dependence are shown in fig. 1 and 2. as it can be seen on fig. 1 glucose consumption is the fastest at ph=5, in this case all the glucose present in the reaction mix is consumed by 12 hours and the maximum ethanol concentration is reached in 12 hours. experiments at other ph values (ph=3.4; 4; 4.5; 5.5) show slower glucose consumption, all of the glucose is consumed only 3 hours later (at 15 hours) compared to experiments carried out at ph=5. maximum ethanol concentration is less than that measured at ph=5. figure 1: ph dependence of glucose consumption and ethanol production figure 2: the effect of inoculum size on glucose consumption and ethanol formation fig. 2 shows that maximum ethanol yield (19.3 g/l) is reached in the shortest time using 60% inoculum. however this maximum ethanol yield is less than that reached with 10% inoculum (21.38 g/l). the results observed with 20% inoculum differ slightly from those obtained using 10% inoculum. the application of 10% inoculum is however less cost intensive, therefore this has been chosen as optimum condition. after the optimum conditions for the microorganism have been found the experiments were performed using pretreated paper sludge as substrate. initial glucose concentration of the paper sludge hydrolysate was 10.9 g/l on average. maximum ethanol concentration was 4.1 g/l (yield: 82%) on average which is in agreement with the experimental results carried out on glucose as substrate. medium scale experiments were performed in a fermentor with a working volume of 7 l. initial glucose concentration was 16.53 g/l and maximum ethanol production was 6.8 g/l which is in agreement with the shake flask experiments on glucose as substrate and on paper sludge as substrate. simulation results data gained from the shake flask fermentation experiments on glucose as substrate with different initial ph values and different inoculum levels were used to model glucose consumption, ethanol production and biomass production by saccharomyces cerevisiae. three parameter rate equations were used. the fit of the perfomance curves to the experimental data was tested. parameters were optimized to find the maximum ethanol concentration. optimized parameter simulation results for experiments carried out at ph=5 are shown on figs 3, 4, 5. figure 3: modeled and measured parameters of biomass concentration 324 figure 4: modeled and measured parameters of ethanol production figure 5: modeled and measured parameters of glucose consumption conclusion paper sludge is a waste stream with high cellulose content which makes it appropriate for bioethanol production. the combined pretreatment with subcritical water and enzymatic hydrolysis provides glucose for the the further fermentation step. the aim of this paper was to find optimum conditions for the fermentation. therefore experiments were carried out on pure glucose as substrate. optimum conditions were found to be at intitial ph=5 and with an inoculum level of 10%. optimization was also performed by modeling and the parameters for optimal conditions (maximum ethanol concentration ) were determined. experiments on paper sludge were performed with the optimum conditions preciously determined. these experiments were in agreement with those performed on glucose as substrate. ethanol yields obtained were always above 5% which is the minimum conentration needed for ditillation. paper sludge was found to be an alternative for bioethanol production. acknowledgements experiments were carried out in japan at shizuoka university. the authors gratefully acknowledge the support of the suzuki foundation. references 1. a. b. thomsen, a. s. schmidt: further development of chemical and biological processes for production of bioethanol: optimisation of pre-treatment processes and characterisation of products, 1999, isbn 87-550-2533-1 2. m. muto, s. kondo, i. okajima, t. sako: hydrolysis of paper sludge by subcritical water, supergreen 2009, international conference on supercritical fluid 3. g. birol, p. doruker, b. kirdar, z. i̇. önsan, k. ülgen: mathematical description of ethanol fermentation by immobilised saccharomyces cerevisiae, process biochemistry 33(7), (1998), 763–771 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 /colorconversionstrategy /cmyk /dothumbnails false /embedallfonts true /embedopentype false 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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/pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice hungarian journal of industry and chemistry vol. 48(1) pp. 25–31 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-05 lidar-based collision-free space estimation approach miklós unger∗1, ernő horváth1, and csaba hajdu1 1research center of vehicle industry, széchenyi istván university, egyetem tér 1, győr, 9026, hungary as autonomous technologies flourish within the vehicle industry, an increasing number of academic autonomous competitions are appearing. one of them is the shell eco-marathon autonomous urban concept competition (sem auc) which seeks to provide hands-on experience for the academic community to design, build and test their own driverless vehicles within a realistic infrastructure. the team at our university participates in this competition and our concept is to rely on simple and robust algorithms. this paper presents a simple collision-free space estimation algorithm for the lidar sensor. keywords: autonomous vehicle, voronoi, delaunay 1. introduction nowadays autonomous technology is not only important in the automotive industry but increasingly in the fields of academia and reasearch as well. a sign of this tendency is the increasing number of academic competitions, one of which is the shell eco-marathon autonomous urban concept competition (sem auc). 1.1 shell eco-marathon the shell eco-marathon is a competition for engineering students to design and build the most ultra-efficient car. the participating teams come from all over the world. two main classes of vehicles compete, namely urban concepts and prototypes. both classes can participate in the autonomous category where five different challenges await the teams as follows: • complex track section • maneuverability • obstacle avoidance • the unknown challenge • autonomous distance in this paper, a simple solution for the autonomous distance challenge is presented. 1.2 our team the szenergy team is comprised of students from széchenyi istván university, assisted by tutors and researchers from the fields of the development and construction of electric vehicles. since 2008, the team has ∗correspondence: unger.miklos@ga.sze.hu figure 1: our car szemission. been competing each year in the shell eco-marathon, the biggest fuel-efficiency competition in the world. our team participates in the electric vehicle category of the urban concept class by performing autonomous challenges and regular races using the same car. since 2019, a new car called szemission has been used as shown in fig. 1. 2. the challenge challenges of the auc will be undertaken on the same standard track as the other competitions at the sem or on similar but modified track sections. the track is 970 m long and includes inclines since the track partially consists of closed-off roads (fig. 2). for all five challenges, protective barriers are installed on both sides of the track. the barriers are 0.5 m high separated by small gaps, though the size of these gaps is unspecified. contact with these barriers is forbidden, cars are limited to a top speed of 25 km/h and every car is driven separately on the track. the minimum width of the track is 6 meters unless otherwise specified. https://doi.org/10.33927/hjic-2020-05 mailto:unger.miklos@ga.sze.hu 26 unger, horváth, and hajdu figure 2: simple layout of the challenge. our goal is to create an algorithm that despite the noisy surroundings robustly finds the coordinates of free route between the barriers without touching them based on the output of 3d lidar signals. the route must also be unambiguous. 3. lidars lidar stands for light detection and ranging or laser imaging detection and ranging and is a sensor commonly used in autonomous vehicles to map the environment. the sensor contains a transmitter and receiver. the transmitter fires laser beams towards the ground which interact with the objects of the environment then are deflected back to the receiver. the distance can be computed using a simple formula, where do denotes the distance to the object, cl represents the speed of light, and ∆t stands for the time of flight: do = cl∆t 2 , (1) where the time of flight is measured indirectly by determining the phase shift between the transmitted and received signals, fmod denotes the frequency modulation, ϕr represents the measured difference between the transmitted and received wavelengths [1], and ∆t = ϕr 2πfmod . (2) lidar sensors on autonomous vehicles autonomous vehicles use these rotating beam sensors to scan the environment and detect obstacles. two main types of lidars, the 2d and 3d, are used. 2d lidars, also referred to as lidars with one channel, provide information about the environment in one plane only, hence the objects above and below the lidars are not detected. 3d lidars use more channels (16, 32, 64 or even 128), thus yield all x, y and z coordinates of the surroundings. velodyne’s puck (vlp-16) is a lidar with 16 channels that give a 360◦ three-dimensional view. 4. simulation with ros 4.1 ros in general autonomous vehicles can be regarded as four-wheeled robots. in our project, an ros (robot operating system) is used. it is an open-source, flexible framework for writing robot software. the most important components of it are as follows: topics topics are named buses, in which data is exchanged using ros messages. each topic has a specific name, moreover, one node publishes data to a topic and another node reads the data from the topic by subscribing to it. messages every topic consists of a type of message, moreover, topics send and receive data in the form of ros messages. ros messages form a data structure used by ros nodes to exchange data. different topics send different types of messages, namely 2d lidars use laserscan’s, while 3d lidars use point cloud’s. rosbags bags are a useful utility for the recording and playback of ros topics. while working on autonomous vehicles, some situations may arise where it is necessary to work without actual hardware. using rosbags, sensor data can be recorded and bag files copied to other computers to inspect data by playing it back. gazebo gazebo stands for open source robotic simulators tightly integrated with ros. in this environment, various types of robots, indoor sensors and outdoor elements could be implemented. the values of sensors can be accessed by the ros through topics. rviz rviz is a 3d visualizer in ros to visualize 2d and 3d values from ros topics and parameters which helps to visualize data such as robot models, robot 3d transform data (tf), point clouds, laser and image data, as well as a variety of sensor data [2]. 4.2 simulation simulations are based on models with which we try to copy the physics and geometry of the real world. the more factors that are built into them, the more likely what is expected to happen will actually occur in a real-world test. our car acts as a robot, modelled on a cad program. in this phase of the algorithm, the layout of the car is not important so a nissan leaf was used as our race car. in gazebo, numerous types of sensors are available, the parameters of which can be defined as real-world lidar signals as mentioned in section 3. unfortunately, the exact layout of the racetrack is unknown, so one was created. our track consists of straight sections, curves with hungarian journal of industry and chemistry lidar-based collision-free space estimation approach 27 figure 3: simulation in rviz. different topics can be visualized at the same time. it can be seen that the 3d lidar point cloud originates from two 2d beams, one above the other. different radii as well as white and red protective barriers on both sides. as 3d sensors are used, not only the track but its surroundings are also important. therefore, buildings, trees in addition to cones between and beyond the two barriers were implemented. when the simulation was completed, it was possible to drive a lap of the track in the simulation and collect the ros topics data via rosbags. moreover, with rviz, the following points could be visualized as presented in fig. 3. 5. steps of the algorithm 5.1 filtering our lidar sensor gives information over 360 degrees which is very useful in many cases, however, in this challenge, only information about points in front of the car is needed. if information about displacement of the sensors on the car is available, it can be assumed that the front of the car and all points smaller than the linear equation x = −b+ y m (3) will be deleted, where b denotes the y-intercept and m represents the gradient. 5.2 clustering as from our simulation only raw data (only x, y and z coordinates) are obtained, which points belong to each object has to be defined. clustering is the task of dividing the population or data points into a number of groups such that the data points in a group are more similar to other data points in the same group than to data points in other groups. it is basically a collection of objects arranged according to how similar or dissimilar they are to each other. for us the most effective method is dbscan (density-based spatial clustering of applications with noise), a well-known data clustering algorithm that is commonly used in data mining and machine learning. based on a set of points, dbscan groups together points that are in close proximity to each other based on a distance measurement (usually the euclidean distance) and a minimum number of points. it also marks as outliers the points that are in low-density regions [3]. the dbscan algorithm basically requires two parameters: eps specifies how close points should be to each other to be considered as parts of a cluster. this means that if the distance between two points is smaller or equal to this value (eps), these points are considered to be neighbors. minpoints the minimum number of points to form a dense region. for example, if the minpoints parameter is set as 5, then at least 5 points are needed to form a dense region. after clustering, all of the points belong to a group as shown in fig. 4. 5.3 convex hull even though the point cloud of a 3d lidar stands for more than one thousand points, only a proportion of them is needed, thus points should be filtered. the clustered points have to be packed by each group into a convex hull. the convex hull of a set of points is defined as the 48(1) pp. 25–31 (2020) 28 unger, horváth, and hajdu figure 4: the different clusters denoted by different colors. smallest convex polygon that encloses all of the points in the set [4]. for the purposes of clarification, only the vertices of a convex polygon are used as shown in fig. 5. vertices are side points which form the simplified shape of a polygon. 5.4 delaunay triangulation and voronoi diagram the delaunay triangulation for a given set p of discrete points in a plane is a triangulation dt(p ) such that no point in p is inside the circumcircle of any triangle in dt(p ) [5]. delaunay triangulations maximize the minimum angle of all the angles of the triangles in the triangulation as presented in fig. 6. the circumcenters of delaunay triangles are the vertices of the voronoi diagram. in the 2d case, the voronoi vertices are connected via edges that can be derived from adjacency relations of the delaunay triangles. if two triangles share an edge in the delaunay triangulation, their circumcenters are to be connected with an edge in the voronoi tessellation as shown in fig. 7. for a set of points in 2d space, the voronoi diagram creates cells whose edges are the same distance from two neighboring points. this property grants that all reference points are exactly between two detected items and the edges of voronoi cells are ideal for the representation of a reference line. unfortunately, real environments are never ideal and this method would provide more route options in the presence of noise as presented in fig. 8. figure 5: to clarify the large number of points, only the vertices of the convex hull were used. figure 6: the delaunay triangulation with all the circumcircles and their centers (marked in red). 5.5 ransac at this stage of the algorithm, no information is available about which side of the car the detected points are on. as the reference lines should only be between the two middle barriers, this information is important. for this process, an estimator must be implemented. ransac (random sample consensus) is an iterative method to estimate parameters of a mathematical model from a set of observed data that contains outliers which do not influence the values of the estimated parameters. the input to the ransac algorithm is a set of observed data values, a method of fitting some kind of model to the observations and several confidence parameters. ransac achieves its goal by repeating the following steps [6]: 1. selecting a random subset of the original data, refigure 7: a voronoi diagram is constructed by connecting the centers of the circumstances. hungarian journal of industry and chemistry lidar-based collision-free space estimation approach 29 figure 8: a real scenario from the algorithm. the detected points are denoted in orange, the green points represent the centers of the circumstances, and the black lines stand for the voronoi edges which also represent the reference lines. ferred to as the hypothetical inliers; 2. fitting a model to the set of hypothetical inliers; 3. then testing all other data against the fitted model. those points that fit the estimated model well, according to a model-specific loss function, are considered to be part of the consensus set. 4. the estimated model is reasonably good if a sufficient number of points are classified as part of the consensus set. 5. finally, the model may be improved by reestimating it using all members of the consensus set. if ransac is used for the set of voronoi midpoints, a line is obtained between the protective barriers on either side of the track (fig. 9). now the linear equation for y with its gradient can be written: y = mx+ b, (4) where b denotes the y-intercept and m represents the gradient. points with higher and lower values of y belong to the leftand right-hand sides, respectively. as ransac is an estimator, sometimes it yields wrong results as shown in fig. 10. figure 9: the ransac line (denoted in blue) splits the space into two parts. figure 10: the estimator sometimes yields wrong results. to avoid producing wrong results, some criteria must be declared: • the starting point of the line should be between the protective barriers. • the line must be sufficiently long over the full range of the x-axis. • if the ransac line intersects any of the lines of the convex hull, it must be rotated until it no longer intersects them. 5.6 delete unnecessary reference lines one of our main criteria is that the reference line should exclusively be between the two barriers. to ensure that our car moves in such a way, all unnecessary voronoi midpoints must be eliminated. now all the points that belong to each side can be collected, however, since they are unsorted, an andrew’s monotone chain convex hull algorithm was used [7]. this algorithm sorted the points into a lexicographical order (first by x-coordinates, and should any be equal, by y-coordinates) and then constructed upper and lower hulls of the points as seen in fig. 11. some naive approaches concerning how to use the upper and lower sides of the convex hulls exist. firstly, an attempt was made to copy the shape of the upper hull with a single line using equation (eq. 4), but was not possible when used at corners. figure 11: the leftand right-hand sides were packed into another convex hull. 48(1) pp. 25–31 (2020) 30 unger, horváth, and hajdu figure 12: the reference line along straight sections affected by noise. another idea was that since the borderline was not a single straight line, it could be divided into as many sections as the number of vertices found in the upper hull, however, this resulted in a wavy line which in some cases also deleted inlier voronoi points. then it was realized that the easiest solution would be to delete all the voronoi midpoints which lie inside the left and right convex hulls. 6. results and future works by following the aforementioned steps, the algorithm drew an unambiguous reference line by connecting voronoi midpoints which lie in the middle of the road of the required territory. furthermore, this method also works along straight sections and at corners as shown in figs. 12 and 13. for safety reasons, vehicle speed is limited to 25 km/h. our algorithm is designed to operate at this speed range. the algorithm is based on voronoi cells so its complexity is o(n) [8]. in our test environment the algorithm could estimate the free space with 90 % confidence. with the aid of voronoi diagrams, every detected object has an effect on our reference line. fortunately, the majority of these points are filtered by the steps outlined in section 5.6, however, outliers between the barriers cannot be dealt with. these points have a detrimental effect on the unambiguity of the reference line and lead to the creation of several nodes resulting in some multiplechoice decisions that need to be made by our car. to make our algorithm robust, these points should be eliminated. now a single ransac line divides the sides of the road and works well for the layouts of simple corners, however, one simple line cannot satisfy the criteria for more difficult layouts, e.g. chicanes, because the ransac line is unable to intersect any lines of the convex hull. to avoid this, the line should be divided into smaller sections that need to follow on from each other and determine if any parts of the linked line intersect the line of the convex hull. our path-following algorithm requires that the reference points which follow on from each other are the same distance apart. for this purpose, our reference points must be joined into one line and as many points as the algorithm requires must be generated. figure 13: the reference line at corners. this algorithm has only been examined using test data and has yet to be tested in real environments. 7. conclusion in 2020, our team will participate in the autonomous distance challenge of the shell eco-marathon. the results of this algorithm are promising but a significant amount of research and development has yet to be done until this algorithm can operate and lead our car around a single lap. one of the benefits of the proposed method is that it involves widely used and, over time, highly improved geometric algorithms like delaunay triangulation and voronoi diagrams. acknowledgements the research was carried out as part of the “autonomous vehicle systems research related to the autonomous vehicle proving ground of zalaegerszeg (efop-3.6.216-2017-00002)” project in the framework of the new széchenyi plan. the completion of this project is funded by the european union and co-financed by the european social fund. references [1] verőné wojtaszek, m.: fotointerpretáció és távérzékelés 3., a lézer alapú távérzékelés. 2010 nyugat-magyarországi egyetem [2] lentin, j.: ros robotic projects. (packt publishing ltd., birmingham, uk) 2017, isbn: 978-1-783-55471-3 [3] kriegel, h.-p.; kröger, p.; sander, j.; zimek, a.: density-based clustering, wires data mining knowl. discov., 2011, 1 231–240 doi: 10.1002/widm.30 [4] chazelle, b.: an optimal convex hull algorithm in any fixed dimension, discrete comput. geom., 1993, 10 377–409 doi: 10.1007/bf02573985 [5] de berg, m.; cheong, o.; van kreveld, m.; overmars, m.: computational geometry: algorithms and applications (springer-verlag, berlin, germany) 2008, doi: 10.1007/978-3-540-77974-2 hungarian journal of industry and chemistry https://doi.org/10.1002/widm.30 https://doi.org/10.1002/widm.30 https://doi.org/10.1007/bf02573985 https://doi.org/10.1007/978-3-540-77974-2 lidar-based collision-free space estimation approach 31 [6] fischler, m. a.; bolles, r. c.: random sample consensus: a paradigm for model fitting with applications to image analysis and automated cartography, commun. acm, 1981, 24(6) 381–395 doi: 10.1145/358669.358692 [7] andrew, a. m.: another efficient algorithm for convex hulls in two dimensions, inf. process. lett., 1979, 9(5) 216–219 doi: 10.1016/0020-0190(79)90072-3 [8] seidel, r.; adamy, u.; on the exaxt worst case query complexity of planar point location, j. algorithms, 2000, 37 189–217 doi: 10.1006/jagm.2000.1101 48(1) pp. 25–31 (2020) https://doi.org/10.1145/358669.358692 https://doi.org/10.1145/358669.358692 https://doi.org/10.1016/0020-0190(79)90072-3 https://doi.org/10.1006/jagm.2000.1101 introduction shell eco-marathon our team the challenge lidars simulation with ros ros in general simulation steps of the algorithm filtering clustering convex hull delaunay triangulation and voronoi diagram ransac delete unnecessary reference lines results and future works conclusion hungarian journal of industry and chemistry vol. 48(1) pp. 11–17 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-03 theoretical background and application of multiple goal pursuit trajectory follower ernő horváth*1,2, claudiu pozna3, péter kőrös2, csaba hajdu2, and áron ballagi2 1department of computer engineering, széchenyi istván university, egyetem tér 1, h-9026 győr, hungary 2research center of vehicle industry, széchenyi istván university, egyetem tér 1, h-9026 győr, hungary 3faculty of electrical engineering and computer science, transilvania university of brasov, b-dul eroilor nr. 29, 500036 brasov, romania autonomous and self-driving technology is a rapidly emerging field among automotive-related companies and academic research institutes. the main challenges include sensory perception, prediction, trajectory planning and trajectory execution. the current paper introduces a design strategy and the mathematical background of the optimization problem with regard to the multiple goal pure pursuit algorithm. the aim of the algorithm is to provide a low degree of computational complexity and, therefore, a fast trajectory-tracking approach. finally, in terms of our approach, not only the theoretical questions but the application challenges will be described as well. keywords: autonomous, self-driving, algorithm, trajectory-tracking 1. introduction the current paper deals with the design strategies, theoretical background and application of trajectory tracking. the trajectory-follower approach that is discussed is called the multiple goal pure pursuit algorithm, in particular the windowed version. in mobile robots or vehicles, the trajectory design strategy seeks to identify the best possible trajectory which approximates a desired trajectory based on waypoints. this also assumes that the trajectory design phase has already created the desired trajectory. this paper is organized as follows. the first section introduces the general problem and summarizes the stateof-the art and most relevant results. the second section deals with the design strategy of trajectory tracking and defines the problem precisely. the third section defines the optimization problem and possible solutions, while the fourth section summarizes the results. finally, the last section includes a summary and conclusions. the current state-of-the-art results the essence of pure pursuit is to choose a look-ahead point from the desired trajectory in front of the vehicle and steer according to it. this simple idea can be realized in many different ways, e.g., the classical pure pursuit algorithm uses a fixed look-ahead distance. this means that on the given track, a look-ahead point can be determined as a subset *correspondence: herno@ga.sze.hu of waypoints, which are a fixed distance from the vehicle. choosing a look-ahead distance is a tradeoff between control overshoots and precision. if the look-ahead distance is small, the overshoot will appear because the chosen point is so close that the vehicle cannot react instantaneously, thus continuously exceeds its target. in this case, the absolute distance (error) is smaller but the vehicle will oscillate. in contrast, if the chosen point is too far away, the vehicle will follow the point after the following corner so cuts off the bend. this behavior can be eliminated if the look-ahead distance is adjustable or changeable. one of the most obvious ways to modify the look-ahead distance is to scale the speed of the vehicle accordingly [1]. the other method of modifying the look-ahead distance involves a fuzzy controller that automatically adjusts the look-ahead distance based on path characteristics, velocity and tracking errors [2, 3]. similarly to the fuzzy approach [4], it was shown that an autonomous vehicle can drive at a velocity of approximately 80 km/h along explicit paths using differential gps data. to improve the classical pure pursuit algorithm and eliminate steering latency, cf-pursuit [3] replaced the circles employed in pure pursuit with a clothoid curve to reduce fitting errors. although many papers have examined this domain, the available source code is rather rare. a few of the most notable versions are autoware [5], python [6] and raptor unmanned ground vehicle (ugv) [7]. our research group also introduced a pure pursuit method based on multiple look-ahead points [8], in this paper its updated https://doi.org/10.33927/hjic-2020-03 mailto:herno@ga.sze.hu 12 horváth, pozna, kőrös, hajdu, and ballagi version will be presented. 2. the design strategy the motivation of our research was to construct a simple but flexible kinematic trajectory tracking approach. in addition, the implementation of a more human-like thinking was sought, in other words, to track and follow more goal points on a road simultaneously. drivers also take multiple considerations into account, e.g., not only is lanekeeping an important task but a cyclist in the same lane also influences planning. in our previous work the multiple goal pursuit algorithm can be viewed as a supplement to the pure pursuit algorithm. the most significant change was the calculation of curvature. assuming the reference trajectory is given with a set of geometric points t , position p , steering angle γ and orientation θ of the vehicle, g ⊆ t is defined as the set of selected goal points with a preset length n = |g|: g = {g1, g2, . . . , gn |gk, (l+o) ≤ k < (l+o+n)} (1) an angle αf from a domain of possible angles [αmin, αmax] is assumed (presumably the wheel angle limits). a sequence of curvatures can be calculated each with a radius pf = −2/α and a centre point cf . a goal pointgk from setg to anycf determines a line segment: the normalized difference between the length of this segment and radius pf is the distance d ∈ r+ from the curvature. the metric for selecting a good angle is the sum of this difference for each goal point. dsum = n∑ k=0 ∣∣∣ ∥∥∥−−−→cfgk ∥∥∥−ρf ∣∣∣. (2) here dsum denotes the total distance for goal point set g. the aim is to minimize this distance. this paper introduces a new approach to the multiple goal pure pursuit algorithm, which is based on windowing. this algorithm is not regarded as a classical trajectory tracker since it slightly redesigns the original trajectory. with this method, a trajectory similar to the original one is created, but slight modifications render it more suitable for our vehicle to track. the design strategy consists of identifying the optimum trajectory which approximates a desired trajectory defined by a set of chosen points. this means that the aforementioned set is initial data and a minimum problem must be defined. from the multitude of possibilities, the minimum problem will be defined starting with the following hypothesis: 1. during the approximation, the steering angle γ is constant; 2. changing the steering angle γ is an instantaneous process. if the previous hypotheses are correlated, it can be concluded that the initial set of points is approximated by a figure 1: the windowed goal pursuit strategy trajectory composed from arcs of a circle. the transition from one arc to another is instantaneous. for a particular arc of the circle, a subset (referred to here as the working set) is selected from the initial set. the following decisions are subjects of debate: • the number of points included in the working set; • the number of commune points which belong to different working sets; • the position of the car when the next working set is defined. the aforementioned observations are shown in fig. 1, where a possible strategy is illustrated. the figure contains two referential systems. the first, 0, is the global (stationary) referential system; the second, 1, 2, 3, is the mobile referential system attached to the vehicle. the blue triangles denote the abstraction of the vehicle. two windows are labelled as w1,2. each of them contains a working set of three points. the trajectory is a composition of two arcs of a circle, c1 and c2. the first (c1) is defined in referential frame 1 using the window w1, i.e., the points 0x1 , 0x2 and 0x3 . the second (c2) is defined in referential frame 2 using the window w2, i.e. the points 0x4 , 0x5 and 0x6 . each of the mentioned points is defined in referential frame 0. 3. the optimization problem using m windows and n points for each window, the mathematical definition of the problem is rj = arg ( min m∑ i=1 ei ) , (3) where rj denotes the radius of arc cj , ei stands for the distance from point i to arc cj , j represents the current window number j = 1, . . . ,m, and i is the current point number which belongs to window j. the distance from point xi to cj is also debatable. fig. 2 illustrates two possibilities: the first (fig. 2a) only considers one coordinate of the current point. in contrast, in fig. 2b the shortest distance is considered. hungarian journal of industry and chemistry multiple goal pursuit trajectory follower 13 figure 2: possible ways of computing the distances for the first choice: ei = yi − cj (xi) , (4) where jxi jyi 1  = j 0t 0xi =  cθ −sθ 0 sθ cθ 0 0 0 1  xi yi 1  0xi; (5) θ denotes the orientation of the referential system j; and xj , yj represent the coordinates of the origin of referential system j. if this definition is assumed, it is evident that this is a quadratic regression problem with the analytical solution 1 r = κ = ( xtx )−1 ( xty ) , (6) where x =  x2 1 + y2 1 . . . x2 n + y2 n  (7) y =  2y1 . . . 2yn  (8) for the second choice: ei = ∣∣∣∣ r− ∣∣∣∣[ xi yi −r ]∣∣∣∣ ∣∣∣∣ = ∣∣∣∣r−√x2 i + (yi −r) 2 ∣∣∣∣ (9) which has a numerical solution. 3.1 algorithm flowchart in fig. 3, a flowchart is presented in order to understand the approach more comprehensively. the algorithm uses the vehicle parameters, pose, trajectory points and input parameters as inputs. the vehicle parameters are wheelbase b, steering angle γ and its position. also, the points: 0xk are part of the initial data. the algorithm parameters are: working set n, skyline d and curvature limit. this limit decides whether the locomotion is based on a linear or circular trajectory window. for every iteration, a new window is calculated. 4. discussion 4.1 simulation the simulation uses the previous algorithm for a kinematic model which is in accordance with the starting hyfigure 3: algorithm flowchart 48(1) pp. 11–17 (2020) 14 horváth, pozna, kőrös, hajdu, and ballagi xu x(k) x(k + 1) xu+1 x(k + 2) xu+2 xu+3 e(k) figure 4: the definition of lateral deviation pothesis, i.e., the steering is instantaneous. in the first simulation, the following kinematic bicycle model ẋ = v cos (θ) ẏ = v sin (θ) θ̇ = v l tan (γ) γ = ct (10) was used. to analyze the results, the lateral approximation error was defined: • the lateral deviation error of the current position e(k) is the distance between this position and the current segment of the desired trajectory (fig. 4); • the total deviation error et is the sum of the error throughout the simulation from 1 to n ; • the relative deviation error er is the ratio of the total error to the total number of simulated points. e(k) = distance ( x(k), 0xu0xu+1 ) = = ∣∣∣x(k)xu+1 − x̂uxu+1 ( x(k)xu+1 · xuxu+1 )∣∣∣ (11) et = n∑ k=1 e(k) (12) er = et n (13) these errors are dependent on the number of points included in the working set (n) referred to as the skyline and the position of the decision point (d). for the desired trajectory, a study relative to this dependency was conducted and the relative errors for each case were obtained (n, d). the non-instantaneous steering was also simulated (fig. 5). in this case, the kinematic bicycle model can be modified as follows: ẋ = v cos(θ) ẏ = v sin(θ) θ̇ = v l tan(γ) γ = γ0 + γ̇t γ̇ = ct (14) the steering angle is a linear function where the steering velocity is constant during the steering process. the figure 5: simulation result: the blue dots denote the waypoints, the red line represents the trajectory generated by our model trajectory of the robot is no longer an arc of a circle but a combination of two curves. the first of which is a clothoid (also referred to as an euler spiral) when γ = γ0 + γ̇t and an arc of a circle when γ = ct. in this case, the simulation result shows a lower quality of approximation. given this phenomenon, the robot orientation angle error is defined as the difference between the orientation angle in the hypothesis where the steering is instantaneously modified to the final value and the orientation angle in the hypothesis where the steering angle is continuously modified from the initial to the final value. eθ = v l ( tan (γf) ∆t− ∫ ∆t 0 tan(γ0 + γ̇τ)dτ ) = = v γ̇l ( tan (γf) ∆γ − log ( cos(γ0) cos(γf) )) (15) where γ0 denotes the initial steering angle, γf = arctan(lκ represents the final steering angle, γ̇ stands for the steering angle velocity, and ∆t is the steering time. it is observed that eq. 12 is in accordance with our intuitions: if the steering angle velocity increases the orientation error angle will decrease; in contrast, the velocity is proportional to the error. a strategy where a maximum orientation error eθmax is allowed can now be contemplated and since the maximum steering velocity γ̇ is an actuator parameter (which is constant), the following function for the vehicle velocity is proposed: vnew = eθmax eθ vold. (16) in conclusion, the algorithm must be improved in order to yield better results. the following possibilities are suggested (fig. 6): • refine the input set of points: interpolate new points; • change the vehicle velocity during locomotion (eq. 16); hungarian journal of industry and chemistry multiple goal pursuit trajectory follower 15 figure 6: the proposed new strategy • define the new windows by including the points which succeed the decision point in the new working set. with regard to an examined sample trajectory, a 3d graph (fig. 7) is provided which shows the relative dependency obtained in terms of the relative error value in each case (n, d). in fig. 7, the x axis denotes the skyline (n), the figure 7: the relative error depends on the skyline (n) and decision point (d) figure 8: typical behaviors of the examined approaches y axis represents the decision point (d), and the z axis stands for the relative error. 4.2 experiments firstly, the behavior of the algorithm in its own simulation environments was tested; the two presented approaches (the plain multiple goal pursuit and the windowed multiple goal version) were developed in parallel in python and matlab. these simulations also used real-world trajectories and the vehicle model was first a kinematic, and later a dynamic one. subsequently, it became necessary to even test the algorithms in open source robotics foundation’s (osrf) gazebo for two reasons. firstly, implementation of the algorithm as a robot operating system (ros) node was sought and secondly, a more precise dynamic model of the vehicle already existed in gazebo. gazebo also facilitated the integration of the useful software as well as agile migration between development and target. for these purposes, the algorithm had to be recreated in c++ not only because of the ros compatibility but computational resources as well. simulation-based execution yielded no significant deviation from the simulated tests. in fig. 8, some of our results are shown regarding the examined trajectories. the x and y axes are in meters. this simulation is based on real-world measurements taken at the zalazone automotive test track in zalaegerszeg and the gps coordinates are assigned using universal transverse mercator (utm) because of the minimal degree of distortion involved. the follow the carrot and speed ratio-based pure pursuit algorithms had to be implemented in order to experiment with them in the same environment. in another experiment, autonomous functionalities were installed in an electric vehicle (nissan leaf). fig. 9 represents the vehicle in operation. the operational domain of this vehicle was limited to the zalazone auto48(1) pp. 11–17 (2020) 16 horváth, pozna, kőrös, hajdu, and ballagi figure 9: the vehicle used in our experiments motive test track and the university campus, moreover, it was required to reach a relatively slow speed of 25 km/h. the vehicle has front-wheel drive, with a wheelbase of 2.70 meters and a track width of 1.77 meters. to ensure instantaneous localization of the vehicle, two highly accurate real time kinematic (rtk)-capable gpss were used. one was kvh’s fiber optic gyro 3d inertial navigation system (geo-fog 3d ins), the other was swift navigation’s duro inertial rtk. these sensors were also used to capture reference trajectories. our software was based on osrf’s ros [9]. our computing platform first features the nvidia jetson tx2, later the nvidia jetson agx xavier. low-level control is realized by using a national instruments’ compactrio controller, namely crio-9039, as the real-time and fpga modules the ni-9853 can, ni-9403 di, ni9205 voltage input and ni-9264 voltage output modules to be exact. after the algorithm exhibited satisfactory behavior in the simulation environment, it was tested in a realworld scenario. during the experiment, the nvidia jetson tx2 was used in the nissan leaf. the nvidia jetson tx2 is a 7.5-watt embedded controller in which the ubuntu 18.04 lts bionic beaver along with the ros melodic morenia were used. the embedded controller had a memory capacity of 8 gb and memory bandwidth of 59.7 gb/s as well as nvidia’s denver2, quad-core arm cortex-a57 cpu and integrated 256-core pascal gpu installed. during our experiments, only the kvh’s geo-fog 3d ins sensor was used as the source of localization, the wheel angle reference signal in addition to the speed reference via can were provided, and the wheel angle and speed were measured back in the same protocol. nevertheless, during acquisition of the data, all the sensory information was logged by two of velodyne’s 16-channel lidars, sick’s 1-channel laser measurement sensor lms111 and the camera stream into ros bag files. the following chart (fig. 10) shows an example of how the algorithm generated reference trajectories for two bends on the routine track, moreover, the measured wheel angle is shown. the waypoints for the algorithm were provided by driving through a predetermined path then saving as well as filtering the position and speed data via the waypoint_saver node. in this experiment, only the multiple goal pursuit al-4 -2 0 2 4 6 8 10 12 14 0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 an gl e (d eg ) time (s) wheel angle measurements wheel angle reference wheel angle figure 10: changes in the wheel angle around two bends gorithm with one parameter set was used. this set is better compared to autoware’s pure pursuit algorithm in terms of lateral deviation, but the speed ratio-based version worked even better. as a result, the multiple goal pursuit algorithm was able to control the vehicle with the aforementioned embedded controller at slow speeds of approximately 25 km/h. the algorithm is able to perform smooth and continuous movements along a predefined trajectory, even maneuvering around bends and along edges. 5. conclusion the current paper described the development of a trajectory-tracking approach, namely the multiple goal pursuit, and summarized the mathematical and theoretical background needed to understand its working principles. enhancements to and variations in the basic approach are also described with regard to their benefits and weaknesses. furthermore, a brief insight into the development process is given. firstly, an initial version was developed in our own simulation environment, later the code became an ros node and the simulation environment was replaced by gazebo. finally, real-world tests showed the viability of the new algorithm, which was tested by an autonomously guided vehicle in a closed but real-world traffic environment. one of the benefits of this algorithm is that it can be tuned more precisely around bends, moreover, it involves more human-like thinking, that is, tracks and follows more waypoints on the road simultaneously. furthermore, this approach provides quick and reliable reference signals for car-like robot kinematics, thus can follow the trajectory with relatively small errors. the discussed algorithm was implemented in matlab and c++ as a robot operating system node and our measurements were based on debug data generated by this node. this implementation is currently publicly available on github in addition to other measurements, videos, results and source codes: https://github.com/szenergy/ szenergy-public-resources. hungarian journal of industry and chemistry https://github.com/szenergy/szenergy-public-resources https://github.com/szenergy/szenergy-public-resources multiple goal pursuit trajectory follower 17 acknowledgements the research was carried out as part of the “autonomous vehicle systems research related to the autonomous vehicle proving ground of zalaegerszeg (efop-3.6.216-2017-00002)" project in the framework of the new széchenyi plan. the completion of this project is funded by the european union and co-financed by the european social fund. references [1] paden, b.; čáp, m.; yong, s. z.; yershov, d.; frazzoli, e.: a survey of motion planning and control techniques for self-driving urban vehicles, ieee trans. intell. veh., 2016, 1(1), 33–35 doi: 10.1109/tiv.2016.2578706 [2] ollero, a.; garcía-cerezo, a.; martinez, j.: fuzzy supervisory path tracking of mobile reports, control eng. practice, 1994, 2(2), 313–319 doi: 10.1016/09670661(94)90213-5 [3] samuel, m.; hussein, m.; mohamad, m. b.: a review of some pure-pursuit based path tracking techniques for control of autonomous vehicle, int. j. computer applications 2016, 135(1) 35–38 doi: 10.5120/ijca2016908314 [4] rodríguez-castaño, a.; heredia, g.; ollero, a.: analysis of a gps-based fuzzy supervised path tracking system for large unmanned vehicles, ifac proceedings volumes, 2000, 33(25) 125–130 doi: 10.1016/s1474-6670(17)39327-8 [5] kato, s.; tokunaga, s.; maruyama, y.; maeda, s.; hirabayashi, m.; kitsukawa, y.; monrroy, a.; ando, t.; fujii, y.; azumi, t.: autoware on board: enabling autonomous vehicles with embedded systems, in proceedings of the 9th acm/ieee international conference on cyber-physical systems, 2018, 287–296 doi: 10.1109/iccps.2018.00035 [6] sakai, a.; ingram, d.; dinius, j.; chawla, k.; raffin, a.; paques, a.: pythonrobotics: a python code collection of robotics algorithms, 2018, arxiv: 1808.10703 [7] giesbrecht, j.; mackay, d.; collier, j.; verret, s.: path tracking for unmanned ground vehicle navigation: implementation and adaptation of the pure pursuit algorithm, defence research and development canada (drdc), suffield, alberta, canada, 2005. https://apps.dtic.mil/sti/pdfs/ada599492.pdf [8] horváth, e.; hajdu, cs.; kőrös, p.: novel purepursuit trajectory following approaches and their practical, in 10th ieee international conference on infocommunications (coginfocom), naples, italy, 2019. [9] quigley, m.; conley, k.; gerkey, b.; faust, j.; foote, t.; leibs, j.; wheeler, r.; ng, a. y.: ros: an open-source robot operating system, icra workshop on open source software, 2009 3(2) 48(1) pp. 11–17 (2020) https://doi.org/10.1109/tiv.2016.2578706 https://doi.org/10.1109/tiv.2016.2578706 https://doi.org/10.1016/0967-0661(94)90213-5 https://doi.org/10.1016/0967-0661(94)90213-5 https://doi.org/10.5120/ijca2016908314 https://doi.org/10.5120/ijca2016908314 https://doi.org/10.1016/s1474-6670(17)39327-8 https://doi.org/10.1016/s1474-6670(17)39327-8 https://doi.org/10.1109/iccps.2018.00035 https://arxiv.org/abs/1808.10703 https://arxiv.org/abs/1808.10703 https://apps.dtic.mil/sti/pdfs/ada599492.pdf introduction the design strategy the optimization problem algorithm flowchart discussion simulation experiments conclusion hungarian journal of industrial chemistry veszprem vol. 30. pp. 171176 (2002) direct calculation of sulfur dioxide absorption by water drops * t a a t a. saboni, s. alexandrova, • ssenov (groupe ecoulements transferts de matiere et de chaleur, ltp, universite de caen, dept gte, 120 rue de l'exode, 50 000 saint lo, france 1department of chemical engineering, university of chemical technology and metallurgy, 8 k. ohridski blvd, 1756 sofia, bulgaria) received: july 21, 2000; revised: march 11,2002 absorption of pollutant gases into water drops is one of the major removal mechanism i~ clouds: ra~n a~d scrubbers. the aim of this article is to present a new model for prediction of the mass transfer m gas-hqmd di.spersed. sy~ten:s encountered in scrubber or atmospheric systems. in the liquid phase, a model based on local scales, mterfactal hqmd friction velocity and drop size diameter is used. in the continuous gas phase the well known beard and_pruppache~ model is applied. data obtained by the modelling of the s02 absorption in a single_ drop are c?mpared to pu~hs~ed expenmental results and a fairly good agreement was found. finally, we present a particular ~d 1idportant application of the abo~e model as an illustration of its use. as an example, sulfur dioxide washout by ram, falling through a polluted plume, is considered. key words: absorption, sulfur dioxide, modelling, drops introduction removal of sulfur oxides plays an important role in the air pollution control. in the atmosphere, chemical reactions occur between sulfur oxides, aerosol particles, and trace gases, such as nitrogen oxides. some products of the reactions, absorbed by the cloud and rain drops, render the acidic precipitation. a knowledge of the mass transfer mechanism in the case of gas absorption (from i into) drops is necessary to understand the scavenging of trace gases in clouds, rain and wet scrubbers. mass transfer between gas phase and water drops depends on the physical and chemical properties of the diffusing gas, the drop size and the hydrodynamics around and inside the moving drops. the transport of trace gases from the air into the falling drop is controlled by molecular diffusion, as well as by the convective mass transfer outside and inside the falling drops. the internal circulation, generated by the aerodynamic drag on the drop surface, facilitates the redistribution of the absorbed gas [3, 19, 7}. for instance, the short residence time of some gases in the atmosphere is due to the fact that these gases are preferentially absorbed by cloud and rain droplets and removed in this way from the air. as a consequence the acidic precipitations are strongly affecting the aquatic ·corresponding author deterioration and material degradation, resulting in agricultural productivity, forest growth and known or anticipated effect on human health . a number of mathematical models have been proposed and many experimental investigations have been carried out in the area of air-pollution control in order to provide better understanding of the scavenging of trace gases in clouds, rain drops, and industrial wet scrubbers. for drops, falling in a well soluble gas medium (in this case the transfer resistance is located in the gas phase), the survey of the published works [4, l, 11, 19] show that a number of good numerical n:o~els exist, as well as experimental correlations for predtctlon of the mass transfer coefficients in the gas film. for liquid phase controlled resistance, [16] proposed a model based on local scales, interfacial liquid friction velocity and drop diameter. the model were validated experimentally by amokrane et al. (2] compared literature models with the experimental data of gamer and lane [9}, kaji et al. [11] walcek et al. [19] and lindhjem [lj. they found considerable discrepancies between the experimental data and the published models. on the contrary, they observed that the saboni model {16] fits the experimental data very well. the experimental study and model validation in _the case of sulfur dioxide absorption by water drops faumg through 172 high gas concentration (few%) has been described in details by amok:rane et al. [2]. the purpose of this article is to test a new model to predict the s02 absorption and desorption by falling drops in air containing traces of sulfur dioxide. if absorption is to be modeled as local process, based on the overall simulation of the two phase flows , two approaches are possible ; a) to compute the hydrodynamics and the mass transfer at each point in the system as a function of the local conditions. b) using the experimental results together, with a complete numerical simulation, to develop and refine approximate· models for the mass transfer between the two phases. at the present time option (a) is completely excluded by limitations in computational power. the calculations will be prohibitively expensive and impractical for routine application to the description of scrubber and atmospheric systems. an example of option (b), similar to that used by walcek et al. [17, 18, 19}, is presented in this article. the authors proposed a simplified theoretical approach which was validated by experimental data. they applied it to describe the scavenging of trace gases by drops. their simplified theory has an important advantage over the rigorous ·model (navier-stokes and diffusion-convection equations), as it is computationally much faster, since the two dimensional problem is transformed into a !­ dimensional one. however calculations remain too slow for routine application (in cloud models and mesoscale pollution transport models, as mentioned by mitra et al., [14]). in this study, an application, which simplify considerably the computati0ns, is presented. model formulation starting from the expression for mass flux across the interface, we can write : (1) where s1 and vi are the surface area and the droplets volume respectively, where k1 is the local liquid mass transfer coefficient, cu is the equilibrium concentration at the interface and c1is the average concentration in the jrop. according to saboni {16] and amokrane et al. [2], the liquid mass transfer coefficient is given as : with k1 =o.sjd~u· u* :::u~pg cd pt 2 (2) {3) where dt is the liquid phase molecular diffusivity, u * is the interfacial liquid friction velocity, p is the gas g density and p is the liquid density. l the total drag coefficient, cv can be deduced from the equation proposed by berry and pranger [6]: ln(re)= -3.126 + 1.013 *ln(c0 re 2 )­ + 0.01912 * [ln(c v re 2 )] 2 (4) in this relation the reynolds number range between 1 and 3550 and the term cvre2 between 2.4 and 107 mass transfer across the interface reduces the concentration of the diffusing specie in one of the phases and increases it in the other. the change in each of the two phases is given by: (5) where vg and v1 are the volume of the gas and the liquid phase, respectively and tis the time. cg and cl are the concentration of the diffusing specie in the continuous and the dispersed phase, respectively. local equilibrium is supposed at the interface between liquid and gas phase concentration. for this reason and supposing that the ph value does not exceed 5.5 we can wtite : (6) where kh and k1 are the equilibrium constants and c . is gl the gas concentration at the interface. in addition to equilibrium, mass flux continuity across the interface give the gas concentration at the interface: with 8 = 2a g sh (8) where c8= is the bulk gas concentration, where k 8 is the local gas mass transfer coefficient. the gas concentration boundary layer, 8g, is calculated from the expression for the sherwood number in the gas phase (beard and pruppacher [5]; pruppacher and rasmussen [15]): sh =l61+0.718re05 sc()33 (9) where sc is the schmidt number. only results for the total sulfur concentration will be presented. c = [h2s03] + [hs03-l + [s03=j, the concentrations of the individual species being obtained from the total concentrations by simple relations (appendix). 2.5 2 ~ 0 1.5 .s ~ 0 ~ . u <> experlm ents of mitra et al (1992} 0.5 50 100 150 200 250 300 time (s) fig. i concentration within a drop as a function of time of exposure to s02 (for a 2.88 mm drop radius, drop temperature =10 °c, [s02] = 1035 ppbv) .. = 0 1.5 .s • ;! . -u 0.5 20 40 --present model <> experiments of mitra et al (1992) ~a time (o) 80 • 100 120 fig.2 concentration within a drop as a function of time of exposure to s02 (for a 2.88 mm drop radius, drop temperature =12.5 oc, [s02] = 97 ppm) results and discussion comparison with laboratory studies for a constant gas concentration , which is the typical case for laboratory studies, the eqs.(l), (2), (6) and (7) are sufficient to describe sulfur dioxide absorption by individual freely falling large water drops. in order to evaluate the model adequacy, we test the model for the case of low and intermediate gas concentration (the mass transfer resistance is located both in the gas and the aqueous phase). the comparison is made between the model and the experimental results for sulfur dioxide absorption from individual large water drops. the model is compared to the mitra et al. [13] and mitra et al. [14] experimental results concerning two broad categories of sulfur dioxide absorption. the experiments were carried out in a vertical wind tunnel which allows to freely suspend a single drop in the vertical air stream of the tunnel. in the first category a 2.88 mm radius drop were exposed to sulfur dioxideair mixture. fig.l shows the evolution 173 0.8 --present model <> experiments of mftra & hannemann (1993) ~ 0.6 e= u 0.4 0.2 20 40 60 80 100 120 time (s) fig.3 the variation of the rate cvcinitial of s(iv) desorption with time exposure s02 (for a 2.88 tnm drop radius, drop temperature= 15 °c, c;nitial = 3.39 10'3 mole liter'1) of the average total sulfur dioxide concentration vs. the time exposure in the case of 1035 ppbv s02 concentration in the gas phase. in fig.2 results are reported for the absorption in the case of 97 ppm so2 concentration in the gas phase. from fig.l and fig.2, we observe that the values predicted by the present model are in good agreement with the experimental results. in the second category of experiments (mitra et al., [14]), a drop initially containing s(iv) was exposed to sulfur-free air to determine the rate of sulfur dioxide desorption. fig.3 shows the evolution of the average total sulfur dioxide concentration vs. the time exposure for a 3.39 10·3 mol liter·1 drop initial concentration. the results obtained from the model agree well with those from experiments. example of model application a brief illustration of the proposed model, applied to the sulfur dioxide washout by rain falling through a polluted plume, is shown below. this case is of growing interest, because the precipitation scavenging constitutes an important sink for gases in the atmosphere and can influence their local, regional and global distributions. a similar attempt was first made by barrie [4j extended by walcek et al. [17, 18, 191 and hannemann et al. [10]. the walcek et al. [17, 18, 19] procedure, adapted to the present model, may be summarized by the following: let us consider a vertical column containing of air and sulfur dioxide. we suppose ·gaussian concentration distribution in the plume with a peak centered 200 m above the ground. assuming the absence of s02 initially, the drops are supposed to fall sequentially in the air column that is devised into 300 layers, each of one meter in height. the drops enters a given layer of air with concentration ctop and exit at its bottom with concentration cbot· cbo! is calculated from eqs.(l), (2), (6) and (7), and represents the c1op value for the next layer. 174 300 250 200 .§. .. 150 .s:; "' ;; :1: 100 "' --lnitl~i plume ~ .... /: '• i --plume after 1 em rain '• i i 50 i\ i i i -----plume after2 em rain ......... plume after 3 em rain i ., i ~ 0 0 0.2 0.4 0.6 0.8 concentration, c /c g gmax figavariation of s02 concentration with height in pollution layer after specified amounts of raindrops have fallen through. initial concentration is 500 ppb (v). rainfall rate, r = 1 mmlh the gas phase concentration is calculated from eq.(5) which is rewritten in discrete form as: vd (cbot -ctop) vg ru (10) where c 8 n and c8n+l are the concentration in the layer before and after the drops have passed trough . vg is the air volume and vd is the volume of raindrops falling through the layer. the same equatien was applied to each layer as the drop progress through the entire column. from eq.(jo) the gas concentration in each layer is determined according to, c;+l = c; (cbo, c,op )aq (11) az where aq is the rainfall increment and az is the layer height (respectively 0.1 rum and 1m, in this study). the gas profile will be modified after each aq, (corresponding to a given set of drops falling through the column). another set of drops is allowed to fall through this new profile and the procedure is repeated until the trace gas reaches a certain gas concentration. for further simplification, we consider the mean raindrop radius, r m representative for this distribution: (12) where r m is given in rum and the rainfall rate, r, in mmlh. plume washout results plume washout was calculated for 'precipitation intensity, r, of 1 mmlh and 15 mmlb. fig.4 shows the time evolution of the specified gaussian distribution of sulfur dioxide concentration as a population of drops faits the plume pollution with an initial peak profile concentration of 500 ppb (v). in the case of 300 250 200 ~: .§. e 150 ~ " :1: 100 50 0 0 . t' '( 'i 'i : i i \ {: ! ,, :j tl il ,: 0.2 0.4 --lnil!al plume -plume after 1 em rain -----plume after 2 em rain · · · ·-plume after 3 em rain ......... plume after 4 em rain 0.6 0.8 concentration, c /c g gmax fig.5 variation of s02 concentration with height in pollution layer after specified amounts of raindrops have fallen throngh. initial concentration is 500 ppb (v). rainfall rate, r = 15 mm/h 1 mmlh rainfall rate , corresponding to small drop size ( <dm> = 1.1 rum), the drops absorb and desorb the sulfur dioxide rapidly. we see that the gas concentration have a maximum and that the corresponding heightmax depends on rainfall quantity passed through the plume. the maximum gas concentration is displaced to shorter height with increasing rainfall quantity. for rainfall rate of 15 mmlh (fig.5), corresponding to larger raindrop ( <dm> = 2.06 rom), the average concentration is reduced, while the height of the plume remains roughly constant to. explain the difference between these two cases, combination of the following two effects has to be considered : residence time (drop terminal velocity) and the absorption ability (drop diameter and gas concentration). from figa and 5, we can note also that the scavenging is mainly controlled both by the total amount and intensity of the rainfall, which is in agreement with some in situ observations (see for example durana et al. [8]). conclusion in the first part of this paper, a simple analytical model was used to determine the sulfur dioxide absorption/desorption by freely falling drops. data obtained by the model of the so2 absorption/desorption by single drop are compared with published experimental data and a fairly good harmony was found. in the second part, a particular important application of the above model is presented as an illustration of its predictive ability. as an example, sulfur dioxide washout by rain, falling through a pollution plume, is considered. the model predicts the redistribution of the plume through which the raindrops had fallen as function of the rainfall rate. although the observed agreement between model and experimental results, from which some useful predictions on the atmospheric scavenging can be drawn, further investigations are needed for the initial rate under realistic conditions. effects as multicomponent gas phase, oxidation, break-up and/or coalescence, evaporation, air motions, have to be considered. symbols a radius of drop c dimensionless concentration cg bulk gas concentration c interface gas concentration gi cd drag coefficient (z concentration of drop eli equilibrium concentration of drop d drop diameter d molecular diffusivity gas/liquid phase g,l kt liquid mass transfer coefficient kg gas mass transfer coefficient r rainfall rate re reynolds number r radial coordinate tm mean drop radius s surface area sc schmidt number sh sherwood number t dimensional time u terminal velocity * interfacial liquid friction velocity u v drop volume p g,l fluid density ( gas/liquid) references 1. altwicker e. r. and llndidem c. e.: aiche j., 1988, 34(2), 329-332 2. amokrane h., saboni a. and caussade b.: aiche j., 1994, 40, 1950-1960 3. baboolal l. a., pruppacher h. r. and topalian j. h.: j. atmos. sci, 1981, 38, 856-870 4. barrie l. a.: atmospheric environment, 1978, 12, 407-412 5. beard k. v. and pruppacher h. r.: j. atm. sci., 1971,28,1455-1464 6. berry e. x. and pranger m. r.: j. appl meteor., 1974, 13, 108-113 7. caussade b. and saboni a.: in s. e. schwartz and w. g. n. slinn {eds.), precipitation scavenging and atmosphere-surface exchange, vol. 1 hemisphere publishing corp., washington, 29-40, 1992 8. durana n., casado h., ezccura a., garcia c., lacaux j.p., and dinh p. v.: experimental study of the scavenging process by mean of sequential precipitation collector: preliminary results. atmospheric environment part a: general topics 26a(13), 2437-2443, 1992 9. garner f. h. and lane j. j.: tran. inst. cbem. eng., 1959, 37, 162 10. hannemann a. u., mitra s. k. and pruppacher h. r.: j. atm. chern., 1996,24,271-284 175 11. kaji r., hishinumay. and kuroda h.: j. chern. eng. japan, 1985, 18(2),169 12. maahs h. g.: sulfur dioxide water equilibria between 0 an 50 °c. in d. r. schryer (ed.). heterogenous atmospheric chemistry. am. geophy. union., 187-195,1982 13. mitra s. k., w altrop a. hannemann a. u., flossmann and pruppacher h. r.: in s. e. schwartz and w. g. n. slinn (eds.), precipitation scavenging and atmosphere-surface exchange, vol. 1 hemisphere publishing corp., washington, 123-141, 1992 14. mitra s. k. and hannemann a. u.: j. atm. chern., 1993, 16, 201-218 15. pruppacher and rasmussen: j. atmos. sci, 1979, 36, 1255-1260 16. saboni a.: these de doctorat de l'inp de toulouse, 1991 17. walcek c. j. and pruppacher h. r.: j. atm. chern., 1984, 1, 269-289 18. w alcek c. j., pruppacher h. r., topalian j. h. and mitra s. k.: j. atm. chern., 1984, l, 290-306 19. w alcek c. j. and pruppacher h. r.: j. atm. chern., 1984, 1, 291-306 appendix equilibrium relations for sulfur dioxide in water when sulfur dioxide is absorbed into water, the resulting equilibrium relations (walcek et al. [17, 18, 19}, amokrane et al.,[2]) are written us: (al) hso~ + h 20 ¢::? h 30+ +so; (a3) the values of the equilibrium constants k8 , k1 and k2 , of the reactions ai, a2 and a3 are respectively (maahs [121, mitra et al [131): [h so j {~-6.sz1) k h ::: 2 3 = 10 r rt (moles/moles) (a4) [s02 ] [hso;j[h30+] =10( 8:-·m) (moles/liter) (a5) [h2s03 ] rso=jrh o+j (621.91_9.278) k1 = 3 3 == 10 t (moles/liter) (a6} [hso;] where t is the absolute temperature expressed in kelvin. the total sulfur concentration [s} is written as {sj={h2s03 ]+[hs0i]+[so~] (a7) after several manipulations from eqs.(a4}-(a6), together with the following conditions. 176 • condition of electroneutrality: (a8) • condition of water ionization: • the equilibrium constant of the ionization of water is defined by: kw =[h30+][0h-] (thatiskw =10-14 at25 ·c) (alo) • the total sulfur concentration as function of ph of the solution is given by: _( + -~j[h30+] 2 +k1[h30+]+k!kz (all) [s]-l[h30 ] [h30+] kl[h30+]+2k!kz for ph< 5.5, reaction a3 may be neglected. thus the total s concentration is then given by: [h o+f +k [h o+] [sj = [h2s03 1 + [hso; j = 3 k 1 3 (al2) l which may be written in this form: [s]=[h2s03]+[hso;j=kh[s02 ] 8 +~k1 kh[s02 ] 8 (al3) page 174 page 175 page 176 page 177 page 178 page 179 microsoft word b_54_totha_r.doc hungarian journal of industrial chemistry veszprém vol. 39(2) pp. 313-315 (2011) seasonal changes in weed vegetation on arable pannonian sand and loess lands in hungary a. tóth 1, á. balogh1, b. wichmann1, i. dancza2, cs. szalkay1, k. penksza1 1szent istván university, faculty of agricultural and environmental sciences department of nature conservation and landscape ecology, h-2103 gödöllő, 1 páter street, hungary toth.andrea@kti.szie.hu 2h-1039 budapest, hímző u. 1. vii/38. coenological records were made in hungary's main sand and loess agricultural habitat types. the coverage of each species in monthly changes and their expansion can be tracked from the edge to the inner area of arable areas. tests were made in autumn and spring aspect monthly. during recording percent estimation method was applied. sample areas have been identified randomly and theses were modified 1×1 m quadrates according to németh (2002). from each plots, six boxes were tested. both edges and infield areas were assessed in 3-3 replicates. recordings were made in 2010 and 2011, but former data were also used in order to review the rating of the last 50 years. results clearly separated the weed species of sand and loess areas. besides common species, incremental plants also appeared. monthly recordings drew the phenological phases of species. weed vegetation changes can be tracked and the results help to improve defense efficiency against weeds. keywords: national weed survey, arable plants, invasive weed introduction five national weed surveys on arable lands have been carried out in hungary since world war ii. these surveys covered the whole country and were conducted primarily for plant protection purposes. their principal goal was to assess expansion and coverage of the most dangerous weed species. in the last one and a half decade restructuring of land ownership passed off. as a result, both the number of farmers possessing small lands and the extent of these cultivated lands increased. owing to these processes, significant changes appeared in the dominance relations of arable weed species, thus invasion of some of them intensified, while others were forced back. national weed surveys on arable lands provide opportunity to create a database that includes the results of not only the present, but also of former surveys. from this database changes of the past 50 years are traceable, consequently weed conditions of certain regions, state of expanding and declining species can all be followed accurately, while integrated weed control techniques are also applicable more effectively. the aim of the present work was to investigate weed conditions on two agricultural fields situated on loess and sandy bedrock typical for the pannonian region. materials and methods studies were carried out on those agricultural fields on loess and sandy areas of pest county which had been involved in the fifth national weed survey in 20072008 [1]. exact designation of sampling sites was based on the description of study areas of the second national weed survey [2]. surveys were conducted in the outskirts of two settlements, dömsöd and kartal. researches have been performed in the autumn and spring aspects monthly since 2010 with the application of percentage cover assessment method [3, 4]. regarding sandy sites at dömsöd samplings were carried out on the following agricultural parcels: 1. corn field, 2. corn stubble, 3. alfalfa parcel, 4. old alfalfa (small parcel), 5. old alfalfa (large parcel), 6. corn field, 7. fallow, 8. wheat field, 9. old alfalfa (ecological farming, small parcel), 10. wheat parcel (ecological farming). sampling units of 1×1 m modified quadrates (after németh, 2002) were chosen randomly. on each agricultural parcel 6 quadrates were studied. both edges and inner parts of the parcels were recorded in 3 replicates [5]. 314 on the loess-covered sites at kartal 2 transects were studied. on each site, 3 quadrates were sampled in the edges and 3 within the agricultural parcels. for identification of the species nomenclature of simon (2000) was used [6]. in the case of the species names eppo codes were applied as well. for statistical evaluation of the results heatmap analysis was used which is a two way clustering is a graphical way of displaying measured values by using colours that represent numerical values. lower values tend towards green, while higher values tend towards red tones. rearranged rows and columns of the table grouped together represent similarity of dendrograms on the two axes. results and conclusions data about determinant species according to the results of sampling on the loess experimental site at kartal in september and october 2010 are published on fig. 1. the figure represents mean percentage weed species cover as the result of all 3 surveys conducted on the agricultural field. significant coverage differences are observable. tripleurospermum inodorum, being an important species as regards for weed control [7] occurred with considerable percentage of cover. based on these data it is still a question whether tripleurospermum inodorum belongs to t4 or t2 life form species. although according to ujvárosi [2, 8] it is a weed of t4 life form, as a consequence of the changing environmental factors and because of its good adaptability it can overwinter easily and shows patterns of t2 life form. 0 5 10 15 20 25 recording 1 recording 2 recording 3 recording 1 recording 2 recording 3 quadrates c ov er ag e in p er ce nt ag e chenopodium hybridum l. amaranthus chlorostachys willd. brassica napus l. tripleurospermum inodorum (l.) schultz-bip. datura stramonium l. chenopodium album l. figure 1: survey results of autumn sampling at kartal, 1. transect, within agricultural parcel dendrogam of the autumn sampling on sandy fields near dömsöd shows that records of the different agricultural parcels form separated groups (fig. 2). this fact is supported by the two-way classification analysis (heat map) as well (fig. 3). as for surveys performed on the edges of arable parcels, even if records of the same parcels are linked together on very low difference levels, the following sampling sites edges are observed to be grouped together: parcels 4., 5., 9., parcels 2., 6. and parcels 1., 3., 8. and 10. (fig. 4). considering values of percentage cover and highlighting the four most frequently occurred species – medicago sativa /medsa/, stellaria media /steme/, triticum aestivum /trzax/, capsella bursa-pastoris /capbp/ – significant differences can be observed (fig. 5). wheat parcels stand out clearly. figure 2: classification of survey results from agricultural parcel at dömsöd based on 2 autumn surveys (a-alfalfa, w-wheat stubble, c-corn stubble, first numbers refer for the different areas examined while second numbers refers to the different quadrates) figure 3: results of the two-way classification of survey results from agricultural parcel at dömsöd based on 2 autumn surveys figure 4: classification of survey results from the edges of agricultural parcels at dömsöd based on 2 autumn surveys 315 0 20 40 60 80 100 120 stab ble a 1 corn st ab ble a 2 fall ow a 7 wheat a 8 whea t 1 0 a empty b 1 corn st ab ble b 2 aban do ned alfa lfa b 3 whea t b 6 fall ow b 7 whea t b 8 whea t b 10 corn c 1 sunflo wer c 3 aban do ned al fal fa c 3 whea t c 6 corn c 7 wheat c 8 whea t c 10 alfa lfa a 3 alfa lfa a 4 alfa lfa a 5 alfa lfa a 6 alfa lfa 9 a alfa lfa b 4 alfa lfa b 5 alfa lfa b 10 alfa lfa c 4 alfa lfa c 5 alfa lfa c 9 quadrates c ov er ag e in p er ce nt ag e medsa steme trzax capbp figure 5: percentage cover values of the four most frequent species based on the surveys at dömsöd conclusions the two last national weed surveys produced comparable results as the order of the first 10 most important weed species differ barely in the two cases [9, 10]. the most drastic changes appeared after the 50s owing to the introduced large-scale farming methods. during the process of establishing collective farms agricultural lands were united and brought under intensive cultivation. large-scale application of herbicides, being the most responsible factor for the transformation of weed species composition in hungary was initiated in those years as well. the following significant change came along with the political transition, when huge part of the agricultural fields came under private ownership again. at this point once more the number of farmers running small fields and the extent of these cultivated lands increased, as did the territory of fallow lands, while area under chemical weed-control decreased. as a consequence, new and dangerous weed species appeared on arable lands. comparing our research results with data from earlier weed surveys it can be concluded that the order of the most important weed species did still not change [9, 10]. however, coverage value and frequency of tripleurospermum inodorum did increase, which is important regarding plant protection aspects. defensive measures against this weed species should be reorganized on loess arable lands. weeds appeared adjusted to agricultural parcels which demands another way of defence strategy as well. as transformed agricultural structure does not enable large-scale weed control any more, local conditions and variability of cultivated fields should become driving factors behind defence. although variability of edges makes weed control even more difficult, they are important because of species diversity on arable land [11, 12, 13]. references 1. dancza: beszámoló az ötödik országos szántóföldi gyomfelvételezés (2007-2008) előzetes eredményeiről. iii. magyar növényorvos nap, budapest, a szakmai rendezvény kiadványa pp.: 8–9 2. m. ujvárosi: a második országos gyomfelvételezés a szántóföldeken i-vi (1975). mezőgazdasági és élelmezésügyi minisztérium, budapest 3. f. balázs: elméleti előismeretek a gyakorlati mezőgazdasági növényszociológiához, (1944) növénytermesztési kutatószolgálat, kolozsvár 4. j. braun-blanquet: pflanzensoziologie (1964). wien new-york 5. dancza, l. szentey: útmutató az ötödik országos szántóföldi gyomfelvételezéshez (2007). mezőgazdasági szakigazgatási hivatal központ, növény talajés agrárkörnyezet-védelmi igazgatóság, budapest 6. t. simon: a magyar edényes flóra határozója (2000). tankönyvkiadó, budapest 7. hunyadi, g. kazinczi: a gyom és az ember, növényvédelem, 27(9), (1991), 403–404 8. m. ujvárosi: gyomnövények (1973a). mezőgazdasági kiadó, budapest 9. t. henn: a szántóföldi gyomnövényzet változása az utóbbi öt évtized során az v. országos gyomfelvételezés tükrében (2009), pécs 10. dancza, l. szentey: tájékoztató az ötödik országos szántóföldi gyomfelvételezésről (2008). in: 18. keszthelyi növényvédelmi fórum kiadványa, előadás összefoglaló, p.: 82 11. h. bunting: some reflections on the ecology of weeds. in: j. l. harper (ed): the biology of weeds, (1960) blackwell, oxford, pp.: 11–16 12. kiss, k. penksza, f. tóth: evaluation of fields and field margins in nature production capacity with special regard to plant protection (1995). – proceedings of international conference, the landscape and nature production capacity of organic/ sustainable types of agriculture. wageningen, pp. 55–63 13. j. kiss, k. penksza, f. tóth, f. kádár: evaluation of fields and field margins in nature production capacity with special regard to plant protection, agriculture, ecosystems & environment, 63(2-3), (1997), 227–232 14. gy. pinke: veszélyeztetett szegetális gyomnövények és fenntartásuk lehetőségei európai tapasztalatok alapján, kitaibelia, 4(1), (1999), 95–110 15. j. braun-blanquet: pflanzensoziologie (1951), grundzüge der vegetationskunde. aufl springer, wien 16. ujvárosi: szántóföldjeink gyomnövényfajai és életforma-analízisük (1952). növénytermelés 1: 315–354 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjdffile false /createjobticket false 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(adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice hungarian journal of industrial chemistry veszprem vol. 30. pp. 187190 (2002) the influence of water concentration on the corrosion of low alloy steels in the system methanolethylene glycol­ malonic acid d.sutiman (faculty of industrial chemistry, technical university "gh.asachi", d.mangeron, 71a, iasy-6600, romania) received: july 3, 2002 the behaviour of three type of steel, with a variable carbon concentration (from 0.20 to 0.40 %) is studied in medium of methanol 10 % ethylene glycol 5 % malonic acid with water concentration varying between 1 % to 5 %. the weight losses are measured; also the polarisation curves are plotted and the corrosion parameters are established. sem visualized the metallic surface. the corrosion compounds are analysed by ir spectroscopy, x-ray diffraction and chemical analysis. keywords: steel corrosion introduction in organic medium, in which water is present as impurity, the corrosion mechanisms of metals, in general, are different than those that occurs in aqueous solutions. in non-aqueous media the formation of oxyhydroxylic layer does not use the hogroups derived from water as it happens in aqueous solutions [1-4]. this is possible only if the number of water moles is higher than the corrosive acid, meaning the ratio water/acid being higher than 4/1 [5-6]. it is known that the h+ ion co-ordinates 4 water molecules. also, some other impurities contained in organic media presented a much higher influence over the corrosion process than their presence in aqueous solutions. their influence is shown in changings that appear in the conductivity values and also in the dissociation constant [7 -8]. this paper continues the study about the influence of water concentration over steels with different carbon concentration. the steels have the composition situated at the limit between cementite and fe-c solution_ the corrosion reagents are organic acids and the medium in methanol with 10% ethylene glycol [9-13]. in this paper, malonic acid is the corrosive reagent. experimental the steel samples that are used for the corrosion, ol 37, ol 50 and ol 60 have the chemical composition presented in table 1. contact information: e-mail: sutiman@ch.tuiasi.ro the steel samples of 5 cm2 active metallic surface were cut up from a cylindrical bar. they were polished and dyeing protected the surface that should not be corroded. the corrosion system contained methanol, 10% ethylene glycol, 5% malonic acid, hooc-ch2cooh and the water concentration varied between 1 % and 5 %. karl-fisher method was used to determine tlie water content. we used merck reagents and the water was hi-distilled, having electrical conductivity of 12 t-ts cm-1 • also the ph-variation of the corrosion medium was measured with a hach ph-meter. before introducing the samples in the corrosive system, they were submitted to a degreasing process in boiling benzene for 30 minutes and then degreased in a solution of hydrochloric acid 3 % for 3 minutes. the corrosive system was open, allowing the permanent access of oxygen from the atmosphere. for every value of the water concentration, six metallic samples were used and were placed in the same time in the corrosive system, being subsequently taken off from 10 to 10 days, degreased with hydrochloric acid (3 %) for 15 seconds and then were weighed by an analytical balance. from the values of weight losses, the gravimetric figure k (g m·2 h-1 ) and the penetration figure p (mm m2 year-1) were calculated. the metallic surfaces were visualized by electron microscopy of a tesla b300 microscope. for the value of 5 % of water concentration, the polarization curves were plotted on a digital electrochemical analyser dba 332, made by radiometer, copenhagen, denmark. from the shape of the polarization curves the kinetics parameters 188 table 1 the composition of the tested steels steel %c %mn %s %si %p ol37 0.20 0.80 0.06 0.40 0.06 ol50 0.30 0.80 0.05 0.40 0.05 ol60 0.40 0.80 0.05 0.40 0.05 table 2 the values of k and p figures %h20 0137 0150 0160 kip kip kip 1 0,383/0,34 0,372/0,33 0,365/0,33 2 0,397/0,36 0,387/0,35 0,375/0,34 3 0;418/0,38 0,403/0,36 0,396/0,36 4 0,445/0,40 0,422/0,38 0,411/0,37 5 0,466/0,48 0,448/0,40 0,429/0,39 a b fig.l the metallic surface of the ol 60 sample in the system with 5 % water concentration (ax 60; b x 1200) ( ssb scor and icor) of the corrosion process were calculated. the final corrosion compounds, for every value of water concentration~ were insoluble in the system. they were analysed by x-ray diffraction on a hzg 4c karl zeiss yena diffractometer using co(ko_) radiation, by ir spectroscopy on a specord m82. the chemical composition (c, h, 0 and fe) of the final compounds were also determined. results and discussion the value of the ph in the anhydrous system is 1.67. when water is added. the ph-value decreases until 1.60 1.61, fact proving that the dissociation process of the malonic acid occurs in organic solvents. if water is present* probably the h+ ion is transferred from the solvent molecules to water molecules that have a higher polarity: ch30h + hooc ch 2 cooh ..._..! ..2 ch30h;+-ooc -ch1 -cooh table 3 the values of the kinetic parameters of the corrosion type of steel bcormv c51 mv icor pa./cm 2 0137 -535 -550 28,08 ol50 -525 -540 27,86 ol60 -506 -535 26,28 in i [a/cm2] tc{1 (j~ 10-4 '\ ff -s 10 \ tivi \.ill 106 tva 1wl hull lit! i un: -800 -700 -600 -!loti -4110 e (mv) fig 2 the polarisation curves in the system with 5 % water. ( • ol 37 ; x ol 50 ; o ol 60) c2h40 2 + hoocch2 cooh~ .2. c20 2h;+-00c-ch2 -cooh c20 2h; + h 20 .2. c2h 40 2 + h 30+ the values for the weight losses converted in gravimetric figure, k and penetration figure, p are presented in table 2. from the presented data is observed that the corrosion rate increases with water concentration, because the oxyhydroxilic layer is not formed to assure the anticorrosive protection. the metallic surface visualized by sem presents for all steels, the pitting corrosion, unexpected for this type of organic acid. in the fig. i, the metallic surface of ol 60 sample is presented. the polarisation curves were plotted for 5 % water concentration and are shown in fig.2. from the aspect of these curves, an easy passivation tendency is observed for the values of potentials shown below: ol 37:-535 + -485 mv ol 50: -505 + -465 m v ol 60: -525 + -475 mv the values of the corrosion parameters are presented in table 3. from the values of density current is observed that the most stable steel is ol 60 with the higher carbon concentration, this behaviour is also explained by the smallest value for the weight loss. the corrosion products are insoluble in the system at an water concentration and do not present x-ray diffraction spectra. table 4 the chemical composition of the corrosion compounds % ol37 ol50 ol60 c 22,35 22,86 23,12 h 2,89 3,06 2,77 0 41,23 41,75 42,06 fe 33,53 32,33 32,05 1705 256 fig 3 the ir spectrum of the corrosion compounds resulted from ol 60 in the system with 5 % water concentration the ir-spectra of the corrosion compounds derived from the system with all different water concentration are identical, meaning that they present peaks at the same wave number. the ir absorption spectra of the corrosion compounds resulted from ol 60 in the system with 5 % water concentration is presented in fig.3. in this spectrum, two peaks are observed at 256 cm-1 and 430 cm-i, both corresponding to fe-0 bonds, but the first is due to a strong bond and the second to a much weaker one. the value of the absorption peak for coogroup from malonic acid is displaced from value 1730 to 1705 cm-1 _ that explains a stronger oxygen bonding. the displacement of the absorption peak of the hogroup contained in alcohol, from 1080 to 1060 cm-1 also shows the oxygen participation in stronger bonding. the peak situated at 1860 cm-1 is specific for the hofrom the water molecules bounded in bridge bonding [14-15]. the other peaks from their spectrum are characteristic for the c-c and c-h rotation and vibration bonds [14-15]. chemical elemental analysis of the corrosion compounds presents the same value for the constituents with an error smaller than 2 % for all resulted products in all the systems with different concentration. in table 4, the media chemical composition of these compounds is presented. this composition corresponds to a molecular rate fe/malonate radical of 1/1 with a smaller iron content (<3 %). from the data presented the following corrosion mechanism is assigned: fe~ fe2+ + 2e189 a fig.4 the structure of the corrosion compounds fe(ill) polymalonate. (a-linear; b-cyclic) nfe(oh)3 +nhooc-ch2 -cooh-t -t [fe(ooc-ch2 -coophl +2nh20 the structure of the polymer compound of iron with malonic acid is shown in fig.4. the hexacoordination of the fe is determined by water molecules and/or by hogroups in bridge bonding. also~ the polymer chain is accomplished by glycolate groups. notable is also the fact that in literature indications is not specified the existence of a polymer malonate of iron or a basic malonate. conclusions • all steels types are corroded in the studied medium. • the best behaviour is presented by the steel with the highest carbon concentration (0.4 % ). that is due to the existence in the steel structure of the solid fe-c solution that determines a superior -stability of the material [16]. • water is not used in the passive layer formation even if it is present in molar rates higher than 4/l (when the system contain 4 % water the molar rate water/acid has the value 4.58/1 ). the fact that water does not participate in anticorrosive protection can by justified by the existence of two groups cooin the structure of the acid that require a higher quantity of water in order to accomplish the oxyhydroxilic passive layer formation, using the 0 1 dissolved. • the corrosion mechanism is a complexing one with formation of insoluble compounds non~adherent on the surface of the corroded metal. these compounds presented an amorphous polymer structure. 190 • remarkable is the fact that the malonic acid determines a pitting corrosion process. references 1. lorentz w. j. and geona d.: electrochim. acta, 1975, 20, 273-278 2. lorentz w. j. and helman h.: corrosion, 1979 27, 101-108 ' 3. larbeer p. and lorentz w. j.: corrosion science, 1980,20,405-410 4. larbeer p. and loren1z w. j.: electrochim. acta 1980, 25, 375-401 ' 5. banas j. and stypula b: metalurgy and foundry engineering, 1995, 6, 2, 112-119 6. stypula b.: coor. resit. alloy, 1965, 1, 252-257 7. kamato 0., saito h. and shffiata t.: corrosion science, 1984,24, 807-814 8. lorentz w. j. and heusler k.: anodic dissolution of iron group metals in corrosion mechanism, ed. f.mansfeld, dekker, new york, 1987 9. sutiman d., cioroianu t. and georgescu g. 0: hung. j. ind. chern, 1999, 27, 107-110 10. sutiman d. and cailean a.: hung. j. ind. chern, 2001, 29, 17-20 11. sutiman d. and cailean a.: hung. j. ind. chern, 2002,30, 37-39 12. sutiman d. and vizitiu m.: hung. j. ind. chern, 2002, 30, 33-36 13. sutiman d., cretescu i. and nemtoi g.: rev. chim., 1999, 50,766-770 14. avram m.: infrared spectroscopy, ed. tehnica, bucuresti, 1960 (in romanian) 15. the sadler of handbook of infrared spectra, sadler hayden, london, 1978 16. cartis g.: thermal treatments, ed. facia, timisoara, 1882 (in romanian) page 189 page 190 page 191 page 192 page 1 page 2 page 3 page 4 page 5 page 6 page 7 page 8 page 9 page 10 page 11 page 12 page 13 page 14 page 15 page 16 page 17 page 18 page 19 page 20 page 21 page 22 page 23 page 24 page 25 page 26 page 27 page 28 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page 370 page 371 page 372 page 373 page 374 page 375 page 376 page 377 page 378 page 379 page 380 page 381 page 382 page 383 page 384 page 385 page 386 page 387 page 388 page 389 page 390 page 391 page 392 page 393 page 394 page 395 page 396 page 397 page 398 page 399 page 400 page 401 page 402 page 403 page 404 page 405 page 406 page 407 page 408 page 409 page 410 page 411 page 412 page 413 page 414 hungarian journal of industry and chemistry vol. 45(2) pp. 29–33 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0017 microencapsulation of vegetable oil: alternative approaches using membrane technology and spray drying krisztina albert,* gyula vatai, and andrás koris department of food engineering, szent istván university, ménesi út 44, budapest, 1118, hungary microencapsulation technology is a method that is widely used in the food industry. by comparing the latest encapsulation techniques, a significant number of publications concern membrane technology. the term “membrane-based encapsulation” entails that the first step of the technique is the preparation of emulsion with the help of microporous membranes. generally, in microencapsulation technologies, the wall material is dissolved in a continuous phase and oil is dispersed within it. in the present investigation, a new method of preparing microcapsules composed of vegetable oil and maltodextrin was developed. in the first step, the wall material (maltodextrin) was dissolved in oil and considered as a dispersed phase, subsequently, it was introduced into a continuous phase (water) through a microporous membrane. a comparative study was conducted between conventional microencapsulation techniques and one developed in our laboratory. the average particle size of microcapsules prepared by our method is smaller than the size allowed by other methods. after encapsulation preparation, fine-tuned microcapsules were produced by spray drying. however, the main disadvantage of our proposed technology is rapid membrane fouling, because of high concentrations of solute in the dispersed phase. this problem can be eliminated by judicious and systematic investigations. keywords: vegetable oil, microencapsulation, membrane technology, spray drying 1. introduction the controlled release of food ingredients at the right place and the right time is a key functionality that can be provided by microencapsulation. in food products, fats and oils, aroma compounds, vitamins, minerals, colourants and enzymes are encapsulated. the process of the encapsulation of sensitive compounds consists of two steps: the first is often emulsion production: emulsification of core materials with dense solutions of wall material; the second is drying or cooling of emulsion by some chemical or mechanical process; and at the end of these processes microparticles can be obtained [1]. the two major industrial encapsulation processes are spray drying and extrusion [2]. table 1 summarizes literature reviews that focus on these technologies, where the two steps of microencapsulation are performed by the combination of so-called membrane emulsification and spray drying. membrane emulsification (me) is a relatively new, simple emulsion-production method which can be conducted with the use of a microporous membrane. other emulsification processes within this category, besides me and spray drying, include simple blending as well as homogenization; and secondary reactions that recover the capsules from the emulsion are interfacial *correspondence: albert.krisztina@etk.szie.hu polymerization, vacuum heat treatment, solvent diffusion and freeze drying. different materials are used as the dispersed phase and wall materials of the microcapsules. the continuous phase is typically water. 2. experimental the main objective of this study was to initially prepare emulsions and form microcapsules using three different methods. the first approach was conventional membrane emulsification. the second one was conducted by a modified me process. the third involved the use of a laboratory blender. in all three cases, the second step was the spray-drying technique to recover the microcapsules from the emulsions. 2.1. samples and measurements all chemicals (maltodextrin, tween-80 emulsifier) were procured from shop.builder, hungary and sigmaaldrich, germany. commercial-grade sunflower-seed oil was purchased from a local market in the vicinity of budapest. 2.2. membrane emulsification apparatus a cross-flow membrane emulsification system was used as the emulsification process (fig.1). the apparatus included two manometers positioned at the opposite albert, vatai, and koris hungarian journal of industry and chemistry 30 ends of the membrane to measure the drop in pressure along the membrane. the pressure of the dispersed phase was guaranteed by compressed air from an air pump which was injected from the outer surface of the membrane. the continuous phase was recirculated on the lumen side of the membrane by a pump. a rotameter, placed at the exit of the membrane, allowed the flow rate of the continuous phase to be measured. 2.3. microencapsulation process microcapsules were prepared by a tubular ceramic membrane with a pore size of l.4 μm (pall austria filter gmbh). the membrane was composed of αalumina and the surface area of the active membrane was 50 cm2. cross-flow operation was adopted for emulsion production. the first emulsion was prepared using a conventional membrane emulsification technique. the wall material (maltodextrin) was dissolved in the continuous phase (water) and sunflower-seed oil was dispersed into it. the direction of flow of the dispersed phase was tangential with the surface of the membrane. otherwise, in the second case the wall material was mixed with sunflower-seed oil. this mixture was considered as the dispersed phase and it was pressed through the membrane pores under pressure. in both cases the pressure of the dispersed phase was 2.5 bars and the recirculation flow rate of the continuous phase was 150 dm3 h-1. in the third case the emulsion was prepared at room temperature using a laboratory blender at 2,000 rpm for 40 minutes. 2.4. spray drying the emulsions prepared were spray dried with a laboratory-scale spray dryer (labplant sd-05) equipped with a nozzle of 0.5 mm in diameter. the pressure of the compressed air in terms of the flow of the spray was adjusted to 3.6 bars. the air temperature at the inlet was maintained at 180±5 °c, and the feed rate was adjusted to 475 cm3 h-1, respectively. emulsions were prepared during the spray drying process and were continuously stirred by a magnetic stirrer throughout. the microcapsules were collected from the collecting chamber and stored in darkness until analysed. 2.5. analysis of microcapsules following the emulsion preparation, the average droplet size and span value were measured by a fritsch laser particle sizer analysette 22 nanotec. each sample was analyzed three times and the average data reported. the span value was considered as an indication of the dispersity of the droplet size. the lower the span value, the more monodisperse the emulsion. a vhx-6000 digital microscope manufactured by keyence was used to check the formation of microcapsules and evaluate their morphology. 2.6. surface-oil content and microencapsulation efficiency the procedure modified by calvo et al. [9] to determine the surface-oil content and microencapsulation efficiency was employed to measure the amount of unencapsulated oil present on the surface of the powders. briefly, 5 g of microcapsules were precisely table 1. summary of examples from the literature of microencapsulation technologies. emulsification secondary reaction dispersed phase / wall material membrane emulsification spray-drying oil / polyvinylpyrrolidone (pvp) [3] fish oil / whey protein isolate (wpi), whey protein hydrolysate (wph), sodium caseinate, maltodextrin [4] interfacial polymerization benzene, xylene, liquid paraffin / terephthaloyl dichloride (tdc) [5] vacuum heat treatment oil / polyethersulphone (pes) [6] solvent diffusion oil / polycaprolactone (pcl), dichloromethane (dcm) [7] freeze-drying chloroform + curcumin / poly(lactic-co-glycolic acid) (plga) [8] blending and homogenization spray-drying extra virgin olive oil / gelatin, gum arabic, starch, lactose, maltodextrin [9] olive oil + α-tocopherol / maltodextrin, agave inulin, acacia gum [10] walnut and chia oil / maltodextrin, (hydroxypropyl)methyl cellulose [11] ginger oil / cashew gum, inulin [12] walnut oil / skimmed milk powder (smp), smp+tween 80, smp+maltodextrin [13] nigella sativa oil / sodium caseinate, maltodextrin [14] chili seed oil / sodium octenylsuccinate starch, maltodextrin [15] freeze-drying ziziphora clinopodiodes essential oil / whey protein isolate (wpi), pectin [16] figure 1. experimental set-up for the cross-flow membrane emulsification process: (1) continuous phase tank, (2) graduated disperse phase tank, (3) membrane module, (4) pump, (5) compressor, (6) pressure meter, (7) rotameter, (8) pressure controller, (9) valve on drain, (10) valve, (11) heating / cooling (thermostat). microencapsulation of vegetable oil 45(2) pp. 29–33 (2017) 31 weighed in a beaker and 50 cm3 of hexane was added and shaken by hand for 15 s at ambient temperature to extract the superficial oil. the solvent mixture was then filtered through filter paper, and subsequently the unencapsulated oil was collected after evaporation of the hexane under a vacuum. to measure the total amount of encapsulated oil, the same procedure was conducted, but the powder of microcapsules in hexane as an extraction solvent was stirred for 4 h using a magnetic stirrer. for the production of microcapsules in oil, the encapsulation efficiency (ee) is an important parameter which is strongly related to the amount of oil on the surface, and was calculated using the following equation: �� = ����� ��� – ������� ��� ����� ��� × 100 (1) 3. results and analysis the first part of this section presents the results in terms of the production of sunflower-seed oil/water emulsions by conventional and modified-membrane emulsification techniques using a laboratory blender, then the encapsulation efficiency and the physical characterization of the obtained microcapsules are presented. 3.1. results of emulsification the results of particle-size measurements are summarized in table 2. the average droplet sizes were 9.18 µm, 7.58 µm and 7.12 µm in the three different emulsification cases. the average droplet size of microcapsules prepared in the modified way, when the wall material was mixed with the dispersed phase, was lower than those prepared using the conventional technique. in 2000, joscelyne, along with his co-worker, reported that for membrane emulsification, the size of synthesized emulsion particles might be 2-10 times greater than the pore size of the membrane. the present investigators used a microporous membrane with a pore size of 1.4 μm and it was found that in all three cases the average size of the synthesized microcapsules is in line with the conclusion reached by a previously mentioned research group [17]. as an example, the shape and morphology of synthesized microcapsules prepared by the modified me methods are shown in fig.2. 3.2. spray-drying results sunflower-seed oil microcapsules were obtained by spray drying the oil-in-water (o/w) emulsions. the novelty of the approach adopted in the present study is that it utilizes membrane emulsification, which is a lowenergy technology, to produce sunflower-seed oil/water emulsions stabilized by maltodextrin which has been dried by spray drying. the results, represented in table 3, show that the encapsulation efficiency is enhanced by this modern method, the highest values correspond to microcapsules produced by this membrane technology. by comparing the encapsulation efficiency of microcapsules produced by conventional microencapsulation techniques with our laboratorydeveloped method, it should be mentioned that there is figure 2. microscopic image of emulsion sample at 1000 magnification. table 3. oil encapsulation efficiency of microcapsules. conventional method with me (1) 36.4 % new method with me (2) 34.5 % laboratory blender (3) 28.2 % table 2. results of emulsification. conventional method using me (1) droplet size = 9.18 µm span = 1.5 average flux = 368.36 dm3 m-2 h-1 new method using me (2) droplet size = 7.58 µm span = 1.72 average flux = 159.29 dm3 m-2 h-1 laboratory blender (3) droplet size = 7.12 µm span = 1.88 figure 3. image of microencapsulated sunflower-seed oil powder produced by conventional me at 500 magnification. albert, vatai, and koris hungarian journal of industry and chemistry 32 no significant difference in terms of encapsulation efficiency. the surface and external morphologies of the microcapsules of sunflower-seed oil were studied using optical microscopy (figs.3-5). in terms of particle morphology, the microstructures of the powders containing maltodextrin as a wall material were generally spherical in shape, homogeneous and exhibited a smooth surface as seen in the microscopic images. in 2015, koç et al. [18] reported that the smooth surface of microencapsulated extra virgin olive oil using maltodextrin is related to the low-molecularweight sugar content of maltodextrin. these low molecular weight sugars may act as plasticizers on the surface of the particles during spray drying. in their study, when wpi (whey protein isolate) was selected as the wall material, the particles exhibited a rough surface compared to those containing maltodextrin. 4. conclusion our work focused on basic research in terms of microcapsule production under a laboratory set-up. the main aim of the present investigation was to gain experience with regard to the preparation of microcapsules by membrane emulsification in combination with spray drying using a novel technique and to compare it with the conventional one. the operation of the process and its basic correlations were the primary foci of this paper. based on the results obtained it is possible to draw up experimental plans that refine and optimize the process. the results of this work demonstrate that a modified membrane emulsification technique, in which the wall material is mixed with the dispersed phase and not with the continuous phase, combined with spray drying can be used to produce microcapsules of sunflower-seed oil that possess an appropriate oil-encapsulation efficiency. acknowledgement the authors acknowledge the financial support of the únkp-16-3-iii new national excellence program of the ministry of human capacities. they would like to thank keyence magyarország for providing the microscopic images. references [1] madene, a.; jacquet, m.; scher, j.; desobry, s.: flavour encapsulation and controlled release – a review, ijfst, 2006 41(1), 1–21 doi 10.1111/j.13652621.2005.00980.x [2] gouin, s.: microencapsulation: industrial appraisal of existing technologies and trends, tifs, 2004 15(7-8), 330–347 doi 10.1016/j.tifs.2003.10.005 [3] choi, h.g.; yong, c.s.; yang, k.y.: oral solid preparation composition containing 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method, food bioprocess technol., 2015 8, 301–318 doi 10.1007/s11947-014-1404-9 hungarian journal of industry and chemistry vol. 48(1) pp. 117–121 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-17 geospatial data manipulation supporting the implementation of driving simulation environments ferenc speiser∗1, krisztián enisz1, and dénes fodor1 1research institute of automotive mechatronics and automation, university of pannonia, egyetem u. 10, veszprém, 8200, hungary a lot of highly detailed geospatial information (obtained by mobile mapping and spatial data processing) is available that can be used to describe the exact road parameters for simulation and modeling. a gap between the freely available geospatial information and the descriptive standards of the road is present that is used in driving/traffic simulation as well as the systems of test vehicles. the toolset of gis (geographic information systems) provides wide-ranging functionality for spatial data processing, but is yet to offer support for standard formats of road description (opendrive data). this paper describes a method for gathering and converting road-network information from openstreetmap to opendrive data format. using a similar conversion tool, the scenario generation and synthesis of realistic road networks for driving simulator applications can be more convenient and faster. keywords: opendrive, openstreetmap, road-network conversion 1. introduction location information plays an important role in our everyday lives. to go somewhere, e.g. shopping, our exact position and destination is required. this location information can be obtained by gps or a cellular network even with a high degree of accuracy, depending on the application area. however, other data (map, road network, terrain model) may be required to reach the destination. detailed route planning can be achieved by these collected data (spatial databases) and has a great degree of significance in driver assistance. the reliability of positioning and location awareness plays a crucial role in the field of autonomous vehicles and communication between them. it is important to validate the entire functionality of vehicles in all possible circumstances that could occur in real life during the development of all systems, subsystems and sensors of the advanced driver-assistance systems (adas) [1]. this kind of testing is expensive and requires a lot of resources to provide real-life conditions, e.g. the establisment of a proving ground like zalazone in hungary. during the first development stages of a function, it is appropriate to test basic functionality in a simulation environment. this environment can simulate all the information that is needed by the sensors of the control unit that runs the test build of the development. of course, the more detailed the simulation environment, the more accurate the validated test result can be. this means that ∗correspondence: kohlrusz.gabor@mk.uni-pannon.hu if a simulation environment were to be established, which can provide data in exactly the same mode as would occur in real life, the number of real-life tests necessary during the development of a functionality could decrease. therefore, the rate of product development would accelerate and development costs decrease [2]. how can a simulation environment emulate real-life signals? software-in-the-loop (sil), hardware-in-theloop (hil) and model-in-the-loop (mil) solutions are able to emulate the signal level of real environments. all the necessary signals are obtained by the software, hardware or model components in the simulation as would be obtained in real life. the location information is a parameter that can also be loaded for the software, hardware or model component that is being tested. what kind of location data can be used for testing, and how can the route, road as well as terrain on which the vehicle drives be described? a huge amount of location data is available, but the accuracy of data is the key question with regard to usability. nowadays, many leading data-mapping and location-data service companies have access to a huge amount of data and services in the traffic-navigation industry partnered with large automotive manufacturers facilitating the development of adas, e.g. here hd live map [3]. the goal of these companies is to provide a high-quality, self-healing map that is a clear representation of the physical world for the navigation services. however, in terms of testing, not only navigation matters. it is important to have the tools necessary to create the data-mapping environment for the https://doi.org/10.33927/hjic-2020-17 mailto:kohlrusz.gabor@mk.uni-pannon.hu 118 speiser, enisz, and fodor simulations. this paper elaborates on the options available to provide the proper format of location data for the tesis dyna4 hil/sil environment toolset of gis (geographic information system). an overview will be given of the available road data formats as well as the available crowdsourced openstreetmap data. a lot of highly detailed geospatial information (obtained from mobile mapping and spatial data processing) is available that can be used to describe the exact road parameters for simulation and modeling. a gap exists between the freely available geospatial information and descriptive standards of roads that is used in driving/traffic simulation and systems of test vehicles. the goal is to provide an accessible, opensource and easy-to-use solution that is able to generate logical data concerning the description and visualization of roads for driving simulation environments based on available map data. 1.1 nds building blocks the navigation data standard (nds) is a standardized format for automotive-grade navigation databases established by automotive original equipment manufacturers (oems), map-data providers and navigationdevice/application providers. this is a standardized binary database format that allows the exchange of navigation data between different systems. the goal is to separate layers of data from the layers of software, mainly for navigation purposes. the following layers of data could be used from the nds in a simulation environment: • digital terrain model • traffic information • basic map display • routing • lane information 1.2 opendrive road format opendrive is an open format specification to describe the road networks developed by vires. it is a standard road description format that should help data exchange between different driving simulation environments. it has direct support without the necessity to convert into dyna4, ipg’s carmaker or carsim formats. opendrive has special features like complex road networks with junctions, crossfall, superelevation, road markings and barriers, traffic signs and lights, gantries, as well as the ability to integrate high-resolution road surface profiles in opencrg format [4]. the toolset of gis (geographic information system) provides a wide range of functions for spatial data processing, but is yet to offer support for the opendrive standard road-description format [5]. this paper describes a way of gathering and converting road network information from openstreetmap into opendrive format. using a conversion tool like this, the generation and synthesis of a scenario with regard to real-life road networks for driving simulator applications can be more convenient and faster. figure 1: the filtered osm dataset of veszprém 1.3 roadxml like opendrive, this is also an open file format for the logical description of road networks. the goal is to simplify the production of road databases as well as improve the consistency and ensure the interoperability of simulation models. this is an xml-based file format that can be easily edited to enhance road descriptions with custom data using a simple text editor. roadxml is used by many driving simulator software programs as an alternative file format for describing road networks [3]. 1.4 freely available map data other commonly used formats for road networks, e.g. openstreetmap and landxml, are available for geographical needs, but are not suitable for adas simulation purposes, however, they can be used as an input source since these have worldwide coverage. openstreetmap is a free, editable map of the whole world that is being built, by and large, from scratch using crowdsourcing methods and has been released under a creative commons share-alike license. the data records are mostly based on gps navigation data that can be used to create configurations of road networks based on the line segments of the database [6]. further descriptive data is necessary to fulfill the needs of simulation environments. a question that might be raised is whether and how vector data can be used in geographic information systems? geofabrik is a free, community-maintained data extraction service from openstreetmap [7]. this can provide the necessary road-segments data in addition to other information to describe the segments, e.g. the number of lanes, traffic signs, etc. (fig. 1). another option to obtain road-vector data is overpassturbo.eu. using this service, interesting map data can be hungarian journal of industry and chemistry geospatial data manipulation for driving simulation environments 119 figure 2: main components of the ni-based system selected by a special query language, downloaded, displayed and used in gis applications. other data sources can be used to obtain other descriptive information. information concerning elevation can be derived from the digital terrain model produced with the aid of satellites (esa’s copernicus sentinel-1 and sentinel-2) and/or aerial images. 1.5 open source gis software if the necessary map data is downloaded, a data management and process system is needed to make further data preparations for this gis software to be used. gis software (geographical information system) is an application that enables geographical data to be managed on different platforms. quantum gis (qgis) is one of the most popular open-source software solutions. qgis is an official project of the open source geospatial foundation (osgeo) that runs on all operating systems and supports numerous vectors, rasters and database formats as well as functionalities, moreover, allows conversion between different reference systems. this has been selected to implement the data management tasks on the downloaded road data. 1.6 simulation software environment the road models are mainly necessary for testing and validating position estimation algorithms as well as advanced driving support systems for autonomous vehicles. a hard real-time environment based on national instruments devices has already been built for testing, and a soft real-time simulation system based on vector’s vt system is currently under construction. ni’s labview as well as veristand are the base software programs, and matlab/simulink-based tesis dyna4 software is used for automotive simulation purposes. veristand provides the connection between the models and hardware components, while labview and dyna4 provide opportunities to develop new models as well as other software components. in addition, ni’s teststand can be used to create tests and automated test sequences as needed (fig. 2). tesis dyna4 is also the development environment for vehicle simulations in the vector-based simulation environment. other software components and add-on models can be developed primarily in visual studio and cafigure 3: main components of the vector-based system noe in this environment, moreover, vteststudio provides a framework for creating tests and test sequences (fig. 3). tesis dyna4 serves as the vehicle simulation development environment in both cases, which is why the initial goal was to be able to use the data exported from the map databases in this environment. 2. results and analysis an important aspect of simulation tests is how to model the different sections of road. this location information can be obtained from real measurements or map databases. the selected sampling area is a short track in veszprém. using the service of geofabrik.de, it is possible to download the latest dataset of the city from the osm database (fig. 4). this dataset provides the network level which consists of more data layers, roads and traffic signs, moreover, the buildings can probably be used as an information base for the description of roads. the necessary information was selected and processed by qgis desktop gis software, moreover, the coordinate information of the points from the selected segment of road was exported in a suitable input format for data conversion. after the data collection task, the next step is to convert the data into the appropriate road-description format figure 4: selected track designated for testing in veszprém (osm) 48(1) pp. 117–121 (2020) 120 speiser, enisz, and fodor figure 5: transformation process that can be imported by the selected simulation environment. dyna4 has a conversion option that can create a track model in its own format from plain gps coordinates, but has limitations. it does not allow the width of the road segments to be changed significantly, as well as data concerning the width of roads, number of lanes to specific coordinates or data concerning imported traffic signs and lights to be assigned, therefore, no descriptive information with regard to traffic levels can be found. furthermore, the dyna4-converted road description cannot be exported into other formats of road data exchange, e.g. opendrive or roadxml. 2.1 data conversion to solve these problems, a self-developed conversion program was created that can create dyna4-compliant path models from csv and xls file formats. the necessary conversion steps are the following: import coordinates (osm); convert input data and normalize (proj); define track segments and calculate; generate descriptive text; and define descriptive parameters, e.g. width, length and number of lanes as well as heights (fig. 5). the program reads the descriptive csv/xls file formats and then converts the coordinate data from the wgs84 geographic coordinate system to the cartesian coordinate system to simplify the calculations. the hd72 – hungarian national datum (epsg:23700 srid) was selected, which is a meter-based coordinate system. a proper coordinate transformation is necessary for transformation between the two coordinate reference systems that is provided by the proj library a special projection string was applied during the transformation, so the standard transformation error remained below 1m. the program creates an approximate path according to the input points based on spatial geometry calculations figure 6: testing track in veszprém compiled from lines, circles and splines corresponding to the dyna4 format. based on the path created in this way, dyna4 files are created that can already be used directly in tesis projects (fig. 6). 3. discussion even though the conversion program worked properly, it has one disadvantage. the dyna4 format does not support the creation of complex intersections and multi-lane roads. further development is needed to solve this problem. the conversion tool has to be able to save data in opendrive format so much more complex track models can be created as well as in other simulation software formats such as ipg’s carmaker. the coordinate transformation also causes a bottleneck because a meter-based coordinate system is needed for the geometric calculations. not all projected and geographic coordinate systems are appropriate for simple meter-based calculations. it is important to apply an accurate transformation method that places the coordinate points accurately. the projection string that was used is only suitable in hungary. 4. conclusion this paper introduced a map-tool that can be applied for the conversion of open-source map data to open road data formats. the converted road-description file can be used in different vehicle test systems as a basis for the functional testing of vehicle dynamics and driver assistance systems. the main advantage of the proposed framework is that if some kind of road network data is available from an area, it is possible to convert it into a road-description format. the created description file can be imported into most vehicle test systems. however, some limitations should be taken into consideration. although a lot of road data can be found from open-source map databases, currently not all of it is available, e.g. traffic signs and lights, and the quality of the data content needs to be enhanced. our goal is to perform data collection tasks on the tracks that have been used in this case study. hungarian journal of industry and chemistry geospatial data manipulation for driving simulation environments 121 acknowledgements the research was supported by efop-3.6.2-16-201700002 “research of autonomous vehicle systems related to zalazone autonome proving ground”. references [1] dupius, m.; strobl, m.; grezlikowski, h.: opendrive 2010 and beyond – status and future of the de facto standard for the description of road networks, proceedings of the driving simulation conference europe 2010, 2010, pp. 231-242 isbn: 978-2-85782-6859 [2] richter, a.; fischer, m.; frankiewicz, t.; schnieder, l.; köster, f.: reducing the gap between simulated and real life environments by introducing highprecision data, driving simulator conference 2015 europe, 16–18 sep. 2015, tübingen, germany isbn 978-3-9813099-3-5 [3] chaplier, j.; nguyen, t.; hewatt, m.; galee, g.: toward a standard: roadxml, the road network database format, proceedings of the driving simulation conference europe 2010, 2010, pp. 211-221 isbn: 978-2-85782-685-9 [4] richter, a.; scholz m.: deploying guidelines and a simplified data model to provide real world geodata in driving simulators and driving automation, transp. res. part f traffic psychol. behav. 2019, 61, 305– 313 doi: 10.1016/j.trf.2017.04.004 [5] despine, g.; baillard, c.: realistic road modelling for driving simulators using gis data, advances in cartography and giscience, 2011, 2, 431–448 doi: 10.1007/978-3-642-19214-2_29 [6] over, m.; schilling, a.; neubauer, s.; zipf, a.: generating web-based 3d city models from openstreetmap: the current situation in germany. comput. environ. urban syst., 2010, 34(6), 496–507 doi: 10.1016/j.compenvurbsys.2010.05.001 [7] kulawiak, m.; dawidowicz, a.; pacholczyk, m. e.: analysis of server-side and client-side webgis data processing methods on the example of jts and jsts using open data from osm and geoportal, comput. geosci., 2019, 129, 26–37 doi: 10.1016/j.cageo.2019.04.011 48(1) pp. 117–121 (2020) https://doi.org/10.1016/j.trf.2017.04.004 https://doi.org/10.1007/978-3-642-19214-2_29 https://doi.org/10.1007/978-3-642-19214-2_29 https://doi.org/10.1016/j.compenvurbsys.2010.05.001 https://doi.org/10.1016/j.compenvurbsys.2010.05.001 https://doi.org/10.1016/j.cageo.2019.04.011 https://doi.org/10.1016/j.cageo.2019.04.011 introduction nds building blocks opendrive road format roadxml freely available map data open source gis software simulation software environment results and analysis data conversion discussion conclusion hungarian journal of industry and chemistry vol. 45(1) pp. 67–71 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0010 initial electrical parameter validation in lead-acid battery model used for state estimation bence csomós, dénes fodor, * and gábor kohlrusz department of automotive mechatronics, institute of mechanical engineering, university of pannonia, egyetem u. 10., veszprém, h-8200, hungary the paper presents a current impulse-based excitation method for lead-acid batteries in order to define the initial electrical parameters for model-based online estimators. the presented technique has the capability to track the soc (state of charge) of a battery, however, it is not intended to be used for online soc estimations. the method is based on the battery’s electrical equivalent randles’ model [1]. load current impulse excitation was applied to the battery clamps during discharge while the voltage and current was logged. based on the randles’ model, a model function and a fit function were implemented and used by exponential regression based on the measured data. the diffusion-related non-linear characteristic of the battery was approximated by a capacitorlike linear voltage function for speed and simplicity. the initial capacitance of this bulk capacitor was estimated by linear regression on measurements recorded in the laboratory. then, the rc parameters of the equivalent battery model were derived from exponential regression on transients during each current impulse cycle. the battery model with initial rc parameters is suitable for model-based online observers. keywords: battery, soc, exponential regression, randles’ model, load current impulse 1. introduction in our daily lives, the number of mobile devices and utilities that can operate without grid connections is increasing. even though lithium batteries possess better performance properties and energy indicators, lead-acid batteries are still cheaper, significantly present in commercial applications and almost fully recyclable. therefore, any developments in lead-acid battery systems are still of interest. according to ref. [1], several methods exist to estimate a battery’s state of charge (soc) and state of health (soh) but model-based prediction is the most widespread because of its reliablity and robustness. model-based methods, as the name suggests, need a valid, properly detailed electric battery model. the randles’ model as a standard battery model is very popular in the contexts of lead-acid and lithium-ion batteries because of its cost-effectiveness and the similarities of both types. by similarity it is meant that the same model can be reasonably used for the parameter estimation of both battery types [2-3]. some additions to the standard randles’ model can be made if more details in electrochemistry are required such as diffusion in the bulk and porosity amongst others. the model requires values of initial resistance (r) and capacitance (c). the more accurate the initial *correspondence: fodor@almos.vein.hu parameters of the model, the faster and more reliable the convergence of a model-based predictor to the actual state, that is, the actual soc. the scope of the present work is to identify the initial values of rc components (parameters) by evaluating the voltage impulse responses excited by load currents in the time domain. 2. battery model for impulse excitation in this paper, a standard randles’ model [7-12] was analyzed that consists of charge-transfer resistance, rct, battery serial resistance, rs, double-layer capacitance, cdl, and bulk capacitance, cb (fig.1). the voltage references of the capacitors and currents in fig.1 were set for discharge. figure 1. randles’ battery model applied to a discharging battery pack rct cdl cb udl ub ibi(t) uocv(t) rs ict idl csomós, fodor, and kohlrusz hungarian journal of industry and chemistry 68 2.1. state-space model and model function by neglecting the intermediate mathematical steps and rearranging the state-space model, the system can be written in the following form: i c c u u rc u u dt d                                   b dl b dl ctdl b dl 1 1 00 0 1 (1) ir u u u s10 01 ocv b dl              . (2) by solving the output in eq.(2) in terms of the time domain using a current impulse as the system input, the output function in eq.(2) can be expressed by eq.(3) that can be considered as the model function of the system. this form of the output equation serves as a basis for creating a fit function on measured voltage data and then, derive r and c values from the fit parameters. for clarity, each of the terms of the output equation are grouped by alphabetical letters: dbtaetu t   )(ocv (3) where tags a, b and c can be written according to )(ctdl0 tirua  (4) t u c ti b 0b b )(  (5) )()( cts tirrd  (6) where uocv is the battery’s open-circuit voltage,  is the system’s time constant, t is the measurement time, and i(t) is the impulse load current. since the proposed method is based on load and relaxation cycles that follow each other during the analysis, ub0 represents the initial voltage of the bulk capacitor while udl0 is the initial voltage of the double-layer capacitor at the beginning of each impulse cycle. it should be noted that changes in current during each impulse cycle can be neglected as a result of working in the short time-constant region of the discharge curve, thus the current can be considered as a constant. the battery model shown in fig.1 is prepared for short-time transient analysis. even though the model can be used and remains valid for modelling discharge processes that last for several hours, that is, for longtime transients, the accuracy of the model becomes poor under such circumstances. the reason for this is that the battery model presented excludes the diffusion effect that can even be observed by the initial valley-like voltage drop and later as a circle-like voltage response on the long-time discharge voltage curve (fig.2). such an exclusion was made because the scope of the current work is to focus on short-time voltage responses to avoid excessive measurement time intervals and computational resources. consequently, the battery model was optimized for fast soc detection by shorttime battery checks. 2.2. determining the initial capacity of cb in eq.(1), the ub voltage represents the equilibrium voltage of the battery, therefore, it is related to the battery’s main charge and as a result its soc. if the battery is excited by small c/10 c/30 currents, ub and uocv can be considered equal. instead of ub, uocv can be measured at the battery terminals. therefore, the relationship between uocv and soc is important and can be determined from laboratory ocv measurements. a small discharge current was applied to the battery terminals under controlled conditions until the battery’s ocv reached the factory’s minimum voltage threshold from a fully charged state. the voltage, current and temperature were logged while the soc could be calculated by the simple coulomb-counting method during the process and saved in a lookup table. then, the lookup table could be used to determine a discrete relationship betwen uocv and soc in itself. the uocv soc characterisation method can be extended by the regression on lookup data in order to create a continous uocv soc relationship. a linear function, such as a capacitor-like regression of uocv soc characteristics can be legitimate if the battery’s excitation current is small, i.e. between c/10 and c/15 and is not discharged under 20-25% of soc. this could be the case when low-power devices are considered as loads. in the case of plain discharge, the soc changes can be basically tracked by the basis of the b term like in eq.(5) as conducted in the coulomb-counting method [1]. in the presented battery model, the b term provides information on the long-term state of the battery and requires initial parameters such as cb and ub0. the former represents the battery’s initial capacity, the latter is related to the battery’s initial voltage at the beginning of each impulse cycle. right before the first current impulse, ub0 is equal to the battery’s equilibrium voltage since a relaxation time of between 30 minutes and one hour is sufficient for chemical processes to decay. figure 2. discharge characteristics of a 15ah agm battery excited by different load currents initial electrical parameter validation in lead-acid battery model 45(1) pp. 67–71 (2017) 69 the initial value of cb is crucial because it has a strong influence on both the initial voltage drop and the gradient of the long-time discharge voltage curve. in the proposed model, a simplified, that is, capacitor-like formula was used for initial battery capacity estimation so it approximates the battery non-linear discharge characteristic linearly. the introduction of a regression error of a few percent, however, can lead to an easier and faster determination of the initial capacity cb. the calculation of the battery’s initial capacity was realized according to [4]. the fully charged battery at room temperature needed to be slowly discharged by a c/15 current until its ocv voltage reached the factory recommended minimum voltage threshold. once the discharge had finished, 2 hours of relaxation had to be observed in order to return the battery back to its almost equilibrium state. then, a c/15 slow charge had to proceed until the battery’s ocv voltage reached the factory recommended maximum voltage threshold. in both cases, the battery’s ocv voltage, current and temperature were recorded (fig.3/a). after averaging the discharge and charge-voltage measurements, linear regression was conducted on it according to 0bb b 15/c| )( 1 )( utq c tuocv  (7) where qb(t) can be estimated by qb(t) = i0 t. eq.(7) can be identified by the standard form of the linear curve y=mx+b. in eq.(7), cb is the battery’s initial capacity, qb(t) is the actual charge of the battery and ub0 is the actual voltage of cb at the beginning of the impulses. by rearranging eq.(7), cb can be determined. even though charge/discharge currents and soc levels are constrained, the ambient temperature should be controlled as well to provide a constant temperature during the test periods. the value of cb was calculated as 37766 f at 22°c using c/15 load currents. 3. exponential regression to derive rc model parameters the evaluation of measurement data and the comparision of measurements and simulations were realized using matlab. the rc parameters in the model shown in fig.1 and later in an orcad circuit were derived by an exponential regression using an appropriate fit function on the measured voltage data. the regression error between the measured and modelled characteristics can be minimized if the fit function follows the form of the model function, that is, both of them implement similar dynamics and the physical background of the inspected system. therefore, the fit function can be written as beatu t ˆˆ)( ˆ ocv     (8) in a form that is similar to eq.(3). the hat sign means that the form of eq.(8) is similar to eq.(3), but uses a different reference system. when using eq.(8) attention must be paid to the determination of rc parameters. eq.(8) gives voltage references with respect to the ground, that is the x-axis, while eq.(3) yields the references udl and us which correspond to ub. references used by eqs.(3) and (8) must be matched to derive correct rc parameters (fig.3/b). it can be seen that eq.(8) neglects the linear term from eq.(3). since the effect of continuous slow discharge of the battery, which is linked to the cb bulk capacitance in the battery model, possesses a timeconstant several orders of magnitude higher than the cdl-rct subsystem, it cannot be observed during the short impulse cycles. however, it should be considered during the whole discharge process so eqs.(3) and (8) need to be used together to estimate the soc during long-term discharge processes. according to refs. [5-6], it is practical to evaluate only the discharge component of the voltage responses during every load cycle. this method is also supported by the fact that the dynamic behaviour of the battery for both load and relaxation states can be described by the same battery model since both responses originate from the same battery structure. because load curves are only needed, the measured voltage should be separated from global data and then, concatenated right after each other. since voltage data has been prepared in this way, a b figure 3. (a) linear regression on the average of c/15 discharge and charge voltage data to derive initial value of cb. initial cut-off has been filtered. (b) references of model function and fit function csomós, fodor, and kohlrusz hungarian journal of industry and chemistry 70 regression can be made during every discharge impulse cycle simultaneously. the relaxation time during each impulse was set to provide enough time for the battery’s double-layer capacitance to almost fully discharge. it is practical because it simplifies eq.(8) by reducing the effect of the udl0 term in eq.(4). the load time was set taking into consideration the time constant of the cdl rct subsystem. according to experiments, it is within the range of 1 4s. the calculation method of the term b̂ in (8) is based on the calculation of the limit of the exponential term in eq.(8). practical experiments have proven that maintaining a load cycle of 4 in length can speed up and correct the regression. the rc values change during discharge. due to offline voltage response evaluation, it is not possible to optimise these parameters according to load conditions. therefore, the average rc values can be used for the whole period of discharge though this introduces a slight misalignment between the measured and modelled voltage characteristics. by applying eq.(8) on the prepared measurement data, the average rc parameters shown in table 1 were derived. 4. model implementation and validation of the impulse excitation method in orcad the aim of the orcad implementation was to validate the proposed battery model and the applicability of the impulse excitation method for rc parameter determination. the equivalent circuit model shown in fig.1 was transformed into an electric circuit. the duration of the simulation was set to 1 hour and the time step was equal to the sample time of the real measurement, namely 100 ms. 4.1. initialization of the orcad simulator and rc elements the initial voltages of the capacitors and the proper directions of orcad elements should be set carefully. orcad uses a reference system of its own that influences the current references of each component. this should be considered while placing an element in the circuit editor and when comparing the electric circuit references to the randles’ model. the initial voltages of the capacitors, udl and ub, were set to describe the battery’s discharge process and thus also follow the voltage references of the randles’ model, shown in fig.1. the values of initial capacitor voltages were derived from the chemical background and assumptions. cdl can be considered fully discharged through rct after the battery had relaxed (no load) for 2 hours so its initial voltage, udl, was set to 0. the bulk capacitance of the battery, cb, reflects the lengthy time constant as well as diffusion-related processes and is related to the main charge storage capability of the battery. if the relaxation time is sufficiently long, the battery reaches an equilibrium state and its ocv becomes equal to ub. an optimal relaxation time that is sufficiently long was derived from preceding measurements of discharge/charge cycles by applying different load currents and relaxation times. based on experiments, a relaxation time of 2 hours was applied and as a result the ocv could be considered equal to ub. using these assumptions, the initial voltage, ub, was set to 12.7 v and udl to 0 v. the introduction of the load current as an impulse excitation can be achieved through a switched power resistor element which is setup in a similar way to the real arrangement (fig.3/b). the switching routine of the orcad element was tuned in accordance with real load-relaxation cycles that were applied to the real testbench. the resistor sets the load current that discharges the battery. during this work, a load current of 3a was used with a load of 5s and relaxation cycles that lasted 10s. all of the initial values are summarized in table 2. 4.2. comparing the simulation with the battery model in fig.4/a, the results of measured and simulated voltage responses are shown. the validity of the model was analyzed by the comparison of measured and simulated voltages. according to the setup, the comparison is performed within a time frame of 5,600 s. the blue curve that represents the simulated data has a longer tail than the red one because filtering needed to be performed on the measured data to cut the initialization process at the beginning of the testbench. the zoomed-in segment shows the fitness of the simulated voltage response. the difference between the curves is relatively small, around 0.05 v to be precise. this error occurred because average rc values were used in the model instead of online tuned ones. table 2. initial values of simulation parameters that need to be set before a run simulation parameter initial value simulation step time 100 ms simulation duration 1 hour udl0 0 v ub0 12.7 v relaxation time / cycles 10 s load time / cycles 5 s load current 3 a (with a 4 ohm load) table 1. derived rc values of the battery model from regression derived parameter name average value rct 0.032 ohm cdl 92 f rs 0.056 ohm soc after discharge 87.9 % initial electrical parameter validation in lead-acid battery model 45(1) pp. 67–71 (2017) 71 5. conclusions this work shows a current impulse-based excitation method that can be used to either track soc changes during moderate discharge or find proper rc model values for model-based algorithms. the method is founded on an equivalent model-based approach that can implement the dynamic behaviour of a battery without using excessive chemical equations. the technique uses offline analysis of a battery, therefore, it is not able to reasonably track soc changes in real-time. this technique is not intended to estimate the soc of batteries by itself, indeed, it estimates good set points for online estimators such as kalman filters or other model-based observers. the advantages of the presented approach are its rapid nature and simplicity while minimising the error of soc estimation. the disadvantages of this method are its offline nature and related consequences. this technique could potentially be applied to embedded systems and commercially. 6. acknowledgement this research was supported by the efop-3.6.1-162016-00015 project. the project was supported by the hungarian government and co-financed by the european social fund. the project was supported by the european union and co-financed by the european social fund (efop3.6.2-16-2017-00002). references [1] piller, s.; perrin, m.; jossen, a.: methods for stateof-charge determination and their application, journal of power sources, 2001 96(1), 113–120 doi: 10.1016/s0378-7753(01)00560-2 [2] spagnol, p.; rossi, s.; savaresi, s.m.: kalman filter soc estimation for li-ion batteries, ieee international conference on control applications, 2830 sept. 2011, denver, usa, issn 1085-1992 [3] devarakonda, l.; wang, h.; hu, t.: parameter identification of circuit models for lead-acid batteries under non-zero initial conditions, american control conference, 4-6 june 2014, portland, usa [4] platt, g.l.: battery modeling, vol. i., 2015 isbn-13: 978-1-63081-023-8 [5] banaei a.; fahimi b.: real time condition monitoring in li-ion batteries via battery impulse response, ieee vehicle power and propulsion conference (vppc), 1-3 sept. 2010, lille, france issn 1938-8756 [6] banaei a.; khoobroo a.; fahimi b.: online detection of terminal voltage in li-ion batteries via impulse response, ieee vehicle power and propulsion conference, 2009. vppc '09, 7-10 sept. 2009, dearborn, usa issn 1938-8756 [7] kularatna, n.: dynamics and modeling of rechargeable batteries, ieee power electronics magazine, 2014 1(4), 23–33 doi: 10.1109/mpel.2014.2361264 [8] lee, y.-d.; park, s.-y.; han, s.-b.: online embedded impedance measurement using high-power battery charger, ieee transactions on industry applications, 2015 51(1), 498-508 doi: 10.1109/tia.2014.2336979 [9] kiani, m.: high resolution state of charge estimation in electrochemical batteries, applied power electronics conference and exposition (apec), twenty-eighth annual ieee, 17-21 march 2013, long beach, usa [10] kujundzic, g.; ileš, š.; matuško, j.; vašak, m.: optimal charging of valve-regulated lead-acid batteries based on model predictive control, applied energy, 2017 187 189–202 doi: 10.1016/j.apenergy.2016.10.139 [11] bhangu b.s.; bentley, p.; stone, d.a.; bingham c.m.: observer techniques for estimating the stateof-charge and state-of-health of vrlabs for hybrid electric vehicles, vehicle power and propulsion 2005 ieee conference, 2005 doi: 10.1109/vppc.2005.1554646 [12] wang, y.; fang, h.; zhou, l.; wada, t.: revisiting the state-of-charge estimation for lithium-ion batteries, ieee control systems magazine, 2017 37(4), 73–96 doi: 10.1109/mcs.2017.2696761 a b figure 4. (a) validation of modelled (orcad) and measured voltage data in matlab environment (b) battery testbench used during the analyzis hungarian journal of industry and chemistry vol. 48(1) pp. 51–59 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-08 modeling of autonomous ev vector-controlled power conversion system for battery management system design gábor kohlrusz∗1 and dénes fodor1 1research institute of automotive mechatronics and automation, university of pannonia, egyetem u. 10, veszprém, 8200, hungary abstract since the energy consumption of electric drivetrains can be optimized in an automatically controlled system, the driving ranges and efficiency of driverless electric cars can be enhanced. the analysis of a model of the electric power conversion system provides the opportunity to consider different driving circumstances, moreover, it is possible to evaluate the performance of a power conversion system when the vehicle is driven along different routes. the results provide detailed information on the transient operation of all the power modules as well as their components, and on the overall performance of the power conversion system. in this study, a permanent-magnet synchronous machine (pmsm) acts as the traction motor in the autonomously driven electric car. besides the pmsm, the power electronics and battery are also modeled in an orcad pspice circuit-simulation environment that serves as a model of an electric power conversion system for the simulation and testing of a battery management system algorithm. the battery management system and control algorithm are modeled in simulink and can be tested together with the pspice-modeled circuits utilizing an interconnected simulation environment. the input of the power conversion system model was a driving scenario that included uphill and downhill sections. the performance of the implemented battery management system algorithm was analyzed and evaluated. keywords: electric power conversion system, autonomous vehicle, battery management, interconnected simulation 1. introduction a driverless car is an automated system where the driving task is a self-acting function. as a result, it is possible to optimize the energy efficiency of the car in order to increase its driving range and reduce its energy consumption. the optimal operation can be achieved by applying well-designed control algorithms and battery management functions. the electric power conversion system of an autonomous vehicle is a very complex system, especially when the electronic control unit is also considered to be part of the system. during the test procedure of such a complexly controlled electric power conversion system, several unforeseen or unexpected behaviors can occur which may lead to damage. in order to avoid damage, it is essential to identify unexpected system behaviors as early as possible. in the early phase of development, the testing and design of these systems should be performed simultaneously to take advantage of the interconnected simulation environment. a mixed-signal simulation environment supports the analysis of controlled electric power conversion systems where digital and analogue domains ∗correspondence: kohlrusz.gabor@mk.uni-pannon.hu can be connected and run simultaneously [1]. simulations can be performed by taking into account practical aspects that introduce cycle times and delays into the model. in such a realistic simulation environment, the reliable design of a battery management system can be achieved. 2. electric power conversion system model a system model, including a model of the electronic control unit, is a prerequisite to the simulation. the electric part of the system can be accurately modelled in a circuit design environment, while the digital environment and control algorithm should be implemented in an environment that is capable of running numerical computations. the electronic components were modeled in orcad pspice environment while the control algorithm was realized in matlab-based simulink. the electric parts of the modeled power conversion system can be seen in fig. 1. the system consists of a nickel manganese cobalt oxide (nmc)-type li-ion battery, a three-phase inverter and a permanent-magnet synchronous machine as the traction motor. the modeled system is a low-power counterpart of a vehicle power conversion system assumhttps://doi.org/10.33927/hjic-2020-08 mailto:kohlrusz.gabor@mk.uni-pannon.hu 52 kohlrusz and fodor figure 1: structure of the modeled power conversion system ing that the system behavior is independent of the power rating. 2.1 modeling of energy storage the energy storage element of the modeled power conversion system is a li-ion battery. the modeled battery cell consists of 4 individual nmc-type sony vtc4a 2100 mah battery cells connected in series. as fig.2 shows, the model of the battery contains a state-ofcharge (soc)-dependent voltage source and three passive components. the model of the battery cell was developed and validated by using measurement data. a fully charged sony vtc4a 2100 mah battery cell was discharged slowly by setting the discharge current to a c/10 value until its voltage reached the recommended minimum voltage level. the time, battery voltage and discharge current were recorded and the soc values were determined by timeintegration of the current. using the voltage and soc time series, the u(soc) function of the battery cell could be obtained by curve fitting. the best fit was achieved by u = 0.227 log10 ( 0.1 ( soc + 3.35 · 10−5 )) + 0.535 soc3 + 3.8926 (1) the fitted curve and the measured voltages are shown together in fig. 3 as a function of the soc. in order to complete the battery model, it is also necessary to obtain the electrical parameters of the battery cell. the values of the passive components were provided by measurements which put the transient behavior of the battery cell into focus. in table 1, the values of all three parameters can be seen. figure 2: equivalent circuit model of the battery figure 3: approximation of the voltage response of the battery 2.2 modeling of the three-phase inverter the energy conversion between the electric motor and the battery was provided by a three-phase full-bridge inverter with 2 metal–oxide–semiconductor field-effect transistor (mosfet) semiconductors in each leg. the drive circuit was connected through a gate resistor to avoid an inrush current at the gate of the mosfets. the pulse-width modulated (pwm) gate-source voltages were provided by the digital controller which was implemented in the matlab-based simulink environment. a schematic diagram of the inverter can be seen in fig. 4. as the figure shows, a shunt resistor was added to each phase wire for current sensing. 2.3 modeling of the three-phase pmsm in the modeled system, the traction motor was a permanent-magnet synchronous motor. the implemented model is valid for constructions with surface-mounted magnets on the rotor and distributed winding in the wyewound stator. the electrical model was created by determining the voltages across the stator windings which consisted of table 1: equivalent circuit model parameters of the battery circuit parameter notation value series resistance rs 0.1ω charge transfer resistance rct 0.0052ω double-layer capacitance cdl 0.9 f hungarian journal of industry and chemistry modeling of autonomous ev power system for bms design 53 figure 4: three-phase full-bridge inverter the resistive drop, the voltage across the inductor and the back electromotive force (back emf). in the orcad environment, it was quite easy to create the electric part of the motor model due to the fact that the voltage across the inductor in each phase could be represented by defining time-dependent selfand mutual inductances as passive components of the circuit, while their analytical modeling would have been complicated. the simulation of the motor requires the implementation of the mechanical submodel as well. papers dealing with the model of the three-phase pmsm also included the electromagnetic torque [2, 3], however, it was challenging to determine the expanded form of an expression which could be easily implemented in an orcad environment. in ref. [4], a suitable form is presented for implementation in an orcad environment, hence this model was used in this work to obtain the mechanical model. in the simulation, a maxon ec-4pole 252463 type motor was considered. the parameters of the motor can be seen in table 2. 3. modeling of electronic control unit the electronic control unit was modeled in a matlabbased simulink environment which is suitable for quick algorithm and was equipped with an interface to orcad pspice circuit simulation software. a realistic electronic control unit could be modeled using a trigger-activated simulink function which run the control algorithm when a trigger signal is received. the trigger signals were generated to fit the operating frequency of the digitally controlled discrete-time system. this solution ensured that the control algorithm only ran once during each sampling period, consequently, the pulse width modulation (pwm) signals of each mosfet were generated only once during each sampling period. this solution is able to accurately simulate the operation of a microcontroller or even an electronic control unit. the discrete-time control algorithm was implemented in the trigger-activated block. the structure of the algorithm can vary depending on how the difference equation is determined. table 2: pmsm model parameters motor parameter notation value phase resistance r 0.49 ω leakage inductance lsl 33 µh mean value of the mutual inductances lso 92 µh amplitude of inductance fluctuation lx 10 µh amplitude of permanent magnet-created flux linkage ψpm 22.4 mwb friction coefficient b 5.25×10−5 nms rotor inertia j 220 gcm2 number of pole pairs zp 2 3.1 discrete-time control algorithm the frequently used proportional integral (pi) algorithm was implemented to control the power conversion system. the structure of the control system is shown in fig. 5. as the figure shows, a speed-cascaded torque control loop and a magnetic field control loop were created. this strategy is the widespread field-oriented control scheme of three-phase alternating current (ac) motors. in the case of a pi controller, the only dynamic component of the controller is the integrator since the proportional component simply multiplies the error signal. consequently, the proportional component can be implemented in the same form as in a continuous-time algorithm, however, the discrete-time form of the integrator has to be determined by using a z-transform. the transformation can be conducted using different formulae to approximate the continuous-time system. an easy way to determine the discrete-time form of the integrator is to use the backward euler method. using this method, the value of the integral at time j is yj = yj−1 + ejtti (2) where yj denotes the result of the integral at time j, yj−1 represents the result of the integral at time j−1, ej stands for the error signal at time j, t is the sampling time and ti denotes the integral gain. a drawback of this method is that a continuous-time system could be unstable in its discrete-time form using the backward euler method [5]. the bilinear transform (also known as tustin’s method) could be a more reasonable technique to obtain the discrete-time representation of a system since it preserves stability. the value of an integral at time j is determined by this method as follows: yj = yj−1 + ( ej + ej−1 ) tti 2 (3) where yj denotes the result of the integral at time j, yj−1 stands for the result of the integral at time j − 1, ej represents the error signal at time j, ej−1 is the error signal 48(1) pp. 51–59 (2020) 54 kohlrusz and fodor figure 5: vector-controlled power conversion system of an electric vehicle at time j − 1, t denotes the sampling time and ti stands for the integral gain. the realization of a controller that applies the backward euler method is easier and this form generally provides a stable operation, thus in the implemented model of a controller, the integrator was approximated by eq. 2. 3.2 design of the controller parameters the implemented controllers were pi controllers in parallel form, that is the integral and proportional terms were independent of each other. one of the simplest controller design procedures is the pole-zero cancellation but this method provides a frequency bandwidth for the controller that is identical with that of the controlled system resulting in poor performance occasionally. this problem is particularly severe when a system with a large time constant is controlled by a slow integrator with the same time constant as the system [6]. a better controller performance can be achieved by another analytical tuning method where the closed-loop poles are chosen to obtain an arbitrarily determined closed-loop transfer function. the closed-loop is shaped by utilizing some predefined parameters such as the desired damping factor and bandwidth of frequencies. the parameters of the pi controller can be computed as kc = 2ξω0τ − 1 k (4) where kc denotes the proportional gain of the controller, ω0 stands for the natural frequency of the desired closedloop system, ξ represents the desired damping factor of the second-order closed-loop system, τ is the time constant of the controlled first-order subsystem, and k denotes the gain of the controlled first-order subsystem. the value of the integral gain is determined as ti = ω2 0τ k (5) where ω0 denotes the natural frequency of the desired closed-loop system, τ stands for the time constant of the controlled first-order subsystem, and k represents the gain of the controlled first-order subsystem. the damping ratio was chosen to ensure an overshoot of approximately 1%, therefore, for the computations, ξ = 0.85 was applied. the desired natural frequency of the closed-loop system (ω0) was obtained by determining the desired settling time of the controlled variable by considering a desired error band: ω0 = − ln p ξtb (6) where p denotes the difference between the reference signal and the value of the controlled variable as a percentage of the reference value, ξ stands for the desired damping factor of the second-order closed-loop system, and tb represents the period of time until the controlled variable is expected to reach the desired error band [7–9]. 3.3 implementation of the smith predictor when a discrete-time unit controls a system, a time delay is always present. during each time period, some measurements serve as the basis of control signal generation. hungarian journal of industry and chemistry modeling of autonomous ev power system for bms design 55 however, the calculated control signals are only realized as controller outputs during the following time period, which leads to a delay of one period in duration. compensation for this one-period delay can be solved by implementing a smith predictor. the predictor is an algorithm which modifies the actual measurement signal by extrapolation based on former measurements. the implementation of a smith predictor requires the difference equation of the controlled variable as a function of the controller output to be obtained. based on the difference equation, the measurement signal was compensated by predicting the measurement value of the following time period: 1. at time t1, measurement signal û1 is considered for the computation of controller output y2 which will only take effect at time t2. 2. from y2, it is possible to compute the predicted measurement value û2 that can be used to obtain û1− û0 3. û1 = u1 + (û1 − û0) is the corrected measurement signal, which is used to compute y2 as has already been stated in step 1: where u1 denotes the measured value of the controlled variable at time t1 modified by the correction term, y2 stands for the controller output at time t2, û2 represents the predicted value of the measurement at time t2, and û1 and û1 are the computed values of the controlled variable at times t1 and t0, respectively. in step 2, the difference equation of the controlled subsystem is used for the computation of the predicted û2 at time t2. in the case of the current controllers, the prediction algorithm is ı̂2 = (t2 − t1) r l ( u2 r − ı̂1 ) + ı̂1 (7) where the current ı̂2 is the predicted value of the measurement signal at time t2, which was the basis of the calculation of the correction term ı̂1 − ı̂0. the measured current i1 could be corrected as ı̂1 = i1 + (̂ı1 − ı̂0) . (8) the predictor was the same in both the id and iq current controllers, only the parameters were different as ld was substituted for eq. 7 in case of the id control loop and lq was substituted for eq. 7 in case of the iq control loop. the smith predictor in the cascade control loop requires the difference equation of the angular velocity as a function of the current iq: ω̂2 = (t2 − t1) 1.5zpψpmiq,1 −bω̂1 −mt j +ω̂1 (9) the measured speed ω1 could also be corrected by calculating the values ω̂1 and ω̂0 from ω̂2: ω̂1 = ω1 + (ω̂1 − ω̂0) (10) figure 6: testing of the id and iq current controllers 4. testing of the controlled power conversion system model the testing was performed with an operating frequency of 25 khz in the control loop. the current controllers were designed to provide a settling time of tb = 2 ms with p = 0.02 that equated to an error of 2% which resulted in the desired frequency bandwidth of ω0 = 2301 rad/s. by taking into consideration the frequency bandwidth, the calculated controller parameters were kc,id = 0.12 (11) ti,id = 824 (12) for the d-axis current controller and kc,iq = 0.238 (13) ti,iq = 985 (14) for the q-axis current controller. the testing of the controllers was performed without the implementation of the cascaded speed control loop. a reference current was set up for both current loops, d and q. the results can be seen in figs. 6 and 7. it is shown in fig. 6 that the current id overshot the reference value of 0.5 a and started to oscillate around the setpoint with an amplitude of 50 ma, which is 10% of the reference value. the current iq tracked its setpoint of 0 a with an inappreciable error. the results show that the integral gain of the current id should be decreased, therefore, the controllers were tested with redesigned id figure 7: results of the redesigned current controllers 48(1) pp. 51–59 (2020) 56 kohlrusz and fodor (a) speed of the electric motor (b) performance of the d-axis current controller with and without the smith predictor figure 8: simulation results of the controlled system using the smith predictor in the current controllers controller while the iq controller parameters remain unchanged. kc,id = 0.12 (15) ti,id = 275 (16) for the current controller d. in fig. 7, the results for the d-axis controller testing are presented. the performance of the redesigned daxis current controller id was enhanced. the controlled variable reached the setpoint and stabilized after approximately 2 ms. the angular velocity ω was controlled by a cascaded pi controller in the q-axis current loop. the controller parameters were obtained by determining the desired frequency bandwidth which provided a settling time of tb = 0.05 s and p = 0.05, which equated to an error of 5%: kc,ω = 0.038 (17) ti,ω = 1.627 (18) fig. 8a shows the controlled motor-speed signal which has a reference value of 20 rad/s. it can be seen that the speed signal overshot slightly and stabilized after 0.065 s which was acceptable since the designed settling time was defined as tb = 0.05 s. 4.1 testing of the smith predictor the predictor was only implemented for the current controllers since the speed tracking performance of the system was satisfactory without the application of a predictor. the implemented predictor was tested under the same conditions as the current controllers, that is the current references id and iq were set at 0.5 a and 0 a, respectively. fig. 8b shows the controller performance with and without the smith predictor. in fig. 8b, it can be seen that the controller performed better when the smith predictor modified the error in the input signal of the controller by correcting the measured current signal. the controlled current id stabilized faster and in a steady state it could be observed that the pwmrelated high-frequency oscillation of the current occurred with a reduced amplitude compared to when the smith predictor was not applied. the behavior of the current signal iq did not change significantly since its reference value was set at 0 a and no dynamic changes in the reference signal needed to be handled. 5. battery management system design the controlled power conversion system was validated by tests. the created model of the complex system is suitable for simulations that are intended to analyze the operation of the system. by analyzing the operation of the power conversion system, the design aspects of a battery management system can be summarized. simulation of the power conversion system can be a suitable procedure to validate the operation of the designed battery management system under realistic conditions. 5.1 implementation of a battery management system when a battery management strategy is implemented, it influences both the hardware and software components of the supervised system. battery management solutions actuate in order to ensure efficient system operation as well as keep the system safe. if the management algorithm is used to ensure the system operates safely, all the avoided situations should be summarized during the design phase. moreover, for each undesirable situation, a hardware solution has to be designed, which can be activated when necessary. in this study, a battery overcharge protection system was analyzed as a battery management system. for this purpose, the power electronics had to be extended by additional power switches that were capable of changing operation mode when overcharging occurred (see fig. 9). the implementation of the battery management system also included augmentation of the software. in fig. 9, a power semiconductor (m1) can be seen that ensures an alternative path for the current when the battery cannot be charged. in this case, the recuperated energy is dissipated into a resistor. when switch m1 is hungarian journal of industry and chemistry modeling of autonomous ev power system for bms design 57 figure 9: the analyzed battery management system turned on, another switch (m2) becomes responsible for decoupling the battery, otherwise the battery would be discharged through the resistor. in certain situations, generation of the pwm signal is also affected by the battery management algorithm. in this case, the pwm signals are generated in the same way whether the battery protection circuit operates or not. 5.2 simulation of a driving cycle of a vehicle the simulation of a driving cycle of a vehicle provides the opportunity to observe the efficiency of the battery management strategy of the power conversion system and its interactions with the components of the system. the results serve as a basis for implementing different battery management strategies or modifying the implemented one. a driving cycle can be simulated by defining different load torques of the traction motor. when an uphill or downhill stretch of road should be represented, the motor is loaded with a positive or negative load torque, respectively. if the gradients of the uphill and downhill sections of road are unchanged, the load torque remains constant. a simulation of 5.5 s in duration was performed. the simulated driving cycle consisted of uphill, downhill and flat sections (see fig. 10). in the picture, the load torques of the pmsm can also be seen below the corresponding sections of road. during the driving cycle, the speed of the vehicle was expected to be constant, hence the angular velocity was assumed to also be constant at 20 rad/s. at the beginning of the simulation, it was assumed that the battery was fully charged. the results of the simulation can be seen in figs. 11 and 12. in fig.11, the speed of the traction motor can be seen throughout the driving cycle. it can be observed that the changes in load torque influenced the speed of the motor, however, the controller promptly compensated for the transient overshoots. figure 10: simulated vehicle path and related load torques the currents of the power conversion system are presented in fig. 12. the braking current and the current of the battery are also shown in fig. 9. in fig. 12, it can be noted that the q-axis current controller achieved precise and fast reference tracking when the system was perturbed by changes in load torque. if the reference current iq was negative, the energy was recuperated, that is the traction motor was in generator operation mode. since the battery was fully charged, energy must have been dissipated into the braking resistor. in the simulation, two cases when the battery management system activated the braking circuit can be seen in the figure after t1 = 1.7 s and t2 = 4.4 s. when the current flowed through the resistor the battery current was zero due to decoupling performed by switchm2. in the figure, a current spike can be easily observed when the battery was connected to the circuit after reference current iq became positive. 6. conclusions this paper presents models of the power conversion system of an autonomous electric vehicle as well as the electronic control unit. an interconnected simulation environment enables an integrated model to be simulated. this kind of simulation is useful for the comparative performance analysis of different control algorithms as well 48(1) pp. 51–59 (2020) 58 kohlrusz and fodor figure 11: simulated motor speed during the driving cycle of a vehicle figure 12: the simulated currents of the power conversion system with bms as system level analysis of interactions between different system modules and components. a power conversion system model is very complex and it is hard to predict interactions between components of the system following dynamic changes at system inputs. furthermore, the validation of the controllers is only plausible if the simulation model includes all relevant components of the system and all significant factors such as sampling of the measured data or time delays in the control loop. the simulation is very useful if the operation of the hardware level system is the focus of observations and analyses. however, the simulation of the top-level management system of an autonomous electric vehicle is not feasible due to lengthy simulation times. in order to analyze the performance of different controllers, the simulation must be run with a sampling time of 2 µs or less, while the effectiveness of a higher-level management system can be measured after a few hours of driving. in cases when the analysis of the efficiency of the management system takes into consideration the performance of the digital controller, it is essential to identify a modeling procedure which provides a model of the system that is suitable for long-time simulation. acknowledgements the project has been supported by the european union, co-financed by the european social fund. (efop3.6.216-2017-00002). references [1] kohlrusz, g.; csomós, b.; enisz, k.; fodor, d.: electric energy converter development and diagnostics in mixed-signal simulation environment, acta imeko, 2018, 7(1), 20–26 doi: 10.21014/acta_imeko.v7i1.512 [2] hang, j.; zhang, j.; cheng, m.; huang, j.: online interturn fault diagnosis of permanent magnet hungarian journal of industry and chemistry https://doi.org/10.21014/acta_imeko.v7i1.512 modeling of autonomous ev power system for bms design 59 synchronous machine using zero-sequence components, ieee transactions on power electronics, 2015, 30(12), 6731–6741 doi: 10.1109/tpel.2015.2388493 [3] qi, y.; bostanci, e.; gurusamy, v.; akin, b.: a comprehensive analysis of short-circuit current behavior in pmsm interturn short-circuit faults, ieee transactions on power electronics, 2018, 33(12), 10784–10793 doi: 10.1109/tpel.2018.2809668 [4] kohlrusz, g.; szalay, i.; fodor, d.: orcad pspice implementation of a realistic three-phase pmsm model for diagnostic purposes, san diego, ca, usa, 2019, 372–376 doi: 10.1109/iemdc.2019.8785371 [5] leveque, r. j.: finite difference methods for ordinary and partial differential equations: steadystate and time-dependent problems (society for industrial and applied mathematics, philadelphia, pa, usa), 2007 isbn: 978-0-898716-29-0 [6] åström, k. j.; hägglund, t.: pid controllers : theory, design, and tuning (2nd edition) (international society for measurement and control, research triangle park, n.c., usa), 1995 isbn: 1556175167 9781556175169 [7] kuo, b. c.; golnaraghi, f.: automatic control systems (john wiley and sons inc., new york, ny, usa), 2002 isbn: 0470048964 [8] katsuhiko, o.: modern control engineering, (5th edition) (pearson), 2009 isbn: 0136156738 [9] guzmán, j. l.; moreno, j. c.; berenguel, m.; moscoso, j.: inverse pole placement method for pi control in the tracking problem, in ifac-papersonline, 51(4), 406–411 doi: 10.1016/j.ifacol.2018.06.128 48(1) pp. 51–59 (2020) https://doi.org/10.1109/tpel.2015.2388493 https://doi.org/10.1109/tpel.2018.2809668 https://doi.org/10.1109/iemdc.2019.8785371 https://doi.org/10.1016/j.ifacol.2018.06.128 https://doi.org/10.1016/j.ifacol.2018.06.128 introduction electric power conversion system model modeling of energy storage modeling of the three-phase inverter modeling of the three-phase pmsm modeling of electronic control unit discrete-time control algorithm design of the controller parameters implementation of the smith predictor testing of the controlled power conversion system model testing of the smith predictor battery management system design implementation of a battery management system simulation of a driving cycle of a vehicle conclusions hungarian journal of industry and chemistry vol. 46(2) pp. 33–36 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0015 comparison between static and dynamic analyses of the solid fat content of coconut oil vinod dhaygude *1, anita soós1, ildikó zeke2, and lászló somogyi1 1department of grain and industrial plant technology, szent istván university, villányi út 29–43, budapest, 1118, hungary 2department of refrigeration and livestock products technology, szent istván university, ménesi út 43-45, budapest, 1118, hungary the objective of this work was to compare the physical and thermal characteristics of two coconut oils and their blends which were observed by the results of differential scanning calorimetry (dsc) and pulsed nuclear magnetic resonance (pnmr). fat blends composed of different ratios (fully hydrogenated coconut oil / non-hydrogenated coconut oil: 25/75, 50/50 and 75/25) were prepared and examined for solid fat content. the solid fat content of samples was determined as a function of temperature by pnmr. the dsc technique determines the solid fat index by measuring the heat of fusion successively at different temperatures. dsc calculates the actual content of solids in fat samples and how it changes throughout the duration of heating or cooling. a characteristic curve is constructed by the correlation of enthalpies. based on our results, it is clear that both dsc and pnmr techniques provide very practical and useful information on the solid fat content of fats. dsc is dynamic and pnmr is static. a difference in the values of the solid fat indexes of samples was observed which may be due to a fundamental difference between the two techniques. these data can be used by food manufacturers to optimize processing conditions for modified coconut oil and food products fortified with coconut oil. keywords: solid fat content, solid fat index, pnmr, dsc, and coconut oil 1. introduction nowadays, a proper understanding of the crystallization and melting properties of coconut oil systems is essential to increase the number of applications in the food industry. coconut oil is considered as a multi-component mixture of various triglycerides which determines the physical properties that affect the structure, stability, flavor as well as sensory and visual characteristics of foods [1]. modification of the properties of solid fat has received much attention in research recently because of its importance during the processing and production of new food products. the crystallization and melting properties of modified fat used as a shortening in bakery products are critical [2]. the crystal networks present in modified fat strongly enhance its texture, stability and acceptance of fatty-food products. an essential aspect of the industrial manufacture of edible oils and fats is the ability to measure the physical and thermal properties of the materials such as melting and crystallisation profiles, solid fat content (sfc), solid fat index (sfi) and enthalpy. nuclear magnetic resonance (nmr) spectroscopy and differential scanning calorimetry (dsc) are easier to implement and faster techniques than dilatometry which is time-consuming and inaccurate *correspondence: vinod.dhaygude05@gmail.com [3]. nmr has been widely used for the analysis of food materials such as dairy products, fats and oils, in addition to wine and beverages. over the past two decades, dsc has been increasingly utilised for the thermodynamic characterisation of edible oils and fats as well as the sfi determination of food fats. considering the significant scientific and practical importance of the physical properties of coconut oil from a few studies, the solid fat content determined by nmr and dsc methods was investigated and the obtained results compared. ultimately, this research study is beneficial to the food industry which continues to reformulate many products. 2. experimental 2.1 materials in this research study, barco coconut oil was used as a source of non-hydrogenated coconut oil (nhco) which was kindly provided by mayer’s kft. in budapest. the fully hydrogenated coconut oil (fhco) was obtained from local industry in hungary. blends of nhco and fhco were mixed in 25:75, 50:50 and 75:25 (w/w) proportions. the blends were melted and maintained at 80 ◦c for 30 mins to erase crystal memory. subsequently, mailto:vinod.dhaygude05@gmail.com 34 dhaygude, soós, zeke, and somogyi table 1: fatty acid composition (%) of nhco, fhco and their blends. fatty acid fhco fhco:nhco nhco (%) 75:25 50:5 25:75 c6:0 0.1 0.225 0.35 0.475 0.6 c8:0 1.9 3.175 4.45 5.725 7 c10:0 2.7 3.4 4.1 4.8 5.5 c12:0 53.3 51.425 49.55 47.675 45.8 c12:1 0.1 0.075 0.05 0.025 − c14:0 21.3 20.675 20.05 19.425 18.8 c16:0 10 10.025 10.05 10.075 10.1 c18:0 10 8.25 6.5 4.75 3 c18:1 trans 0.03 0.0575 0.085 0.1125 0.14 c18:1 cis 0.3 2.0 3.7 5.4 7.1 c18:2 trans − 0.02 0.05 0.08 0.11 c18:2 cis 0.1 0.5 0.9 1.3 1.7 c20 0.1 0.1 0.1 0.1 0.1 other 0.02 0.03 0.05 0.065 0.08 all blends and pure samples of fat were stored in a refrigerator at 10 ◦c until use. 2.2 methodologies static analysis the static analysis of the solid fat content was conducted by pulsed nuclear magnetic resonance (pnmr) apparatus (bruker minispec 300, bruker gmbh, germany) according to the official method cd 16b-93 of the american oil chemists’ society (aocs) [4]. the solid fat content was measured at 5 ◦c, 10 ◦c, 15 ◦c, 20 ◦c, 25 ◦c and 30 ◦c. three parallel measurements were conducted and average values reported (fig. 1). additionally, these sfc values were converted into percentages where the initial value was considered to be 100 %. these percentage sfcs were compared with the sfis. dynamic analysis dynamic analyses of the samples were studied by dfc according to aocs official method cj 1–94 [4]. samples of nearly 20 mg were loaded onto the middle of the aluminum pans using a small spatula and hermetically sealed by an empty pan that served as a reference. samples were cooled to 0 ◦c at a rate of 1 ◦c min−1 and maintained at this temperature for 10 mins. the heating of blends and pure samples of oil was performed until a temperature of 80 ◦c was achieved at the same rate as for the cooling. the samples were maintained at 80 ◦c for 30 mins. the cooling process started after this period and the rate of cooling was 1 ◦c min−1 until the temperature reached −20 ◦c. before being heated again to ambient temperature, the samples were maintained at this temperature for 10 mins. after that, heating commenced once more at a rate of 5 ◦c min−1 up to 20 ◦c at which point calorimetric measurements ended. three parallel measurements were taken and the average thermogram was reported. the sfi of fat is expressed as a function of temperature. the numbers of solids in the samples of oil in relation to the temperature were estimated on the basis of the calorimetric results. areas of the thermograms were figure 1: solid fat content profiles of two coconut oils and their blends. calculated and correlated with the percentage of solids in the samples. 3. results and discussion 3.1 fatty acid composition samples were characterized by their fatty acid composition (see table 1). the dominant fatty acids in the sample of coconut oil were lauric acid (c12:0) 45.8-53.3 % and myristic acid (c18:0) 18.8-21.3 %. the nhco exhibited a higher percentage of medium-chain fatty acids and a lower percentage of unsaturated fatty acids. the fhco was rich in polyunsaturated fatty acids (pufa) and monounsaturated fatty acids (mufa). 3.2 solid fat content according to nmr the composition of fatty acids and triacylglycerols (tag) would contribute to the percentage of solid fat particles in liquid oil at various temperatures. the sfc profiles of the original fats and their blends at temperatures ranging from 5 ◦c to 30 ◦c are presented in fig. 1. the sfc profile of nhco exhibited low values of 81.06 %, 69.70 %, 54.61 %, 34.54 %, 25.86 % and 0.17 % over the temperature range of 5 ◦c – 30 ◦c because of the concentration of fatty acids. in the case of fhco, the solid fat content was high at 90.49 %, 81.28 %, 69.29 %, 54.15 %, 48.30 % and 4.46 % over the same temperature range. the sfc profiles of blends changed following the addition of fhco to nhco. an increase in the maximum values of sfc was also observed by ribeiro et al. following the addition of fully hydrogenated soybean oil to soybean oil [5]. this can be explained by the changes in the composition of triacylglycerols of the blends. at 5 ◦c, the blends exhibited sfcs ranging from 84.94 % to 90.02 %, which decreased non-linearly until melting completely at 30 ◦c. during the blending, the concentration of tags with high melting points increased and subsequently the sfc values of blends were modified. in all blends, the sfc values at 30 ◦c were almost identical to the sfc of the fhco. hungarian journal of industry and chemistry static and dynamic analyses of the solid fat content of coconut oil 35 figure 2: melting profiles of two coconut oils and their blends. table 2: thermal properties of nhco, fhco and their blends. sample max. peak temperature enthalpy (◦c) (j/g) fhco 24.61 80.24 75:25(w/w)fhco:nhco 24.30 76.21 50:50(w/w)fhco:nhco 23.96 63.44 25:75(w/w)fhco:nhco 23.52 55.84 nhco 23.27 46.38 3.3 melting characteristics the melting profiles of nhco in the presence of fully hydrogenated coconut are depicted in fig. 2. the melting behavior of the original oils and blends was characterized by only one endothermic peak. a similar thermal behavior of coconut oil and hydrogenated coconut oil was observed by one major peak in various studies [6, 7]. components with the lowest melting points tend to melt first and represent the most unsaturated triglycerides, while components with higher melting points that represent the most saturated triglycerides melt later. similarly, results showed that nhco started melting first compared to other samples because of its higher content of unsaturated triglycerides. the addition of fhco to nhco did not alter the melting behavior but as the content of fhco was increased, the peaks according to the melting profiles of blends shifted towards the highmelting temperatures (fig. 2). this melting profiles provided an indication of the amount of crystallized fat and the occurrence of polymorphic transitions. the thermal characteristics of the original oils and their blends are shown in table 2. no significant differences were observed between the values of onset temperature (ton) and peak temperature (tp) in addition to the enthalpies of nhco and fhco. ton ranged from 15.60 ◦c to 20.50 ◦c while tp ranged from 23.27 ◦c to 24.61 figure 3: solid fat index profiles of two coconut oils and their blends. ◦c. melting enthalpies of nhco following the addition of fhco increased from 46.38 j/g to 80.24 j/g (see table 2). 3.4 solid fat index (sfi) the solid-liquid ratio in fats expressed as solid fat content is determined from the melting curves that result from dsc by partial integration. the heat flow into or out of samples of fat was measured as they were heated and cooled isothermally. the estimation of the sfis of samples is dependent upon the onset and final temperatures of melting. the sfi profiles of all samples calculated by melting thermographs are shown in fig. 3. nonhydrogenated coconut oil exhibited a characteristic steep slope and a rapid decrease in the percentage of solids at 20 ◦c. this ratio of solids to liquids decreases differently in these blends of fat as the temperature rises and is at its minimum for all blends at around 30 ◦c (see fig. 3). 4. discussion the results obtained from two methods exhibited a wide range of solid fat content values of the same samples. the values of sfc calculated from pnmr results were lower than values of sfi according to dsc where dsc is a dynamic method and nmr is a static method. the values of the percentages of sfc for each blend at 15 ◦c calculated by dsc were 87.55 %, 88.38 % and 95.95 % (see fig. 3) but 68.05 %, 68.83 % and 72.35 % when calculated by pnmr, respectively (see fig. 4). dsc samples exhibited a sharp decline in their sfi or ratio of solids to liquids when heated from 15◦c to 25◦c, however, the sfc of samples according to nmr exhibited a gradual slope. dsc measurements of physical behavior were observed under controlled heating conditions. the results of dsc describe the whole melting process whilst being heated. the nmr results indicate the statistical values of solid fat content. the difference between the two measurements was possibly due to the time-dependent process concerning the development of crystal structure where sfi describes the status of the fat system and sfc 46(2) pp. 33–36 (2018) 36 dhaygude, soós, zeke, and somogyi figure 4: solid fat content (%) of two coconut oils and their blends. the solid status after stabilization. in addition nmr identified state vise crystals at respective temperatures. the difference in values may be due to the method of tempering, the rate of heating or cooling, and the degree of accuracy. 5. conclusion the results revealed that by combining fhco with nhco the melting behavior of blends of coconut oils was modified, leading to significant increments in the melting point and in the maximum solid fat content. these two methods yielded more descriptive and clear information about melting behaviour by determining amounts of solids in the samples of coconut oil in relation to the temperature. static and dynamic analytical methods showed a difference in the solid-to-liquid ratio of samples which may be due to fundamental differences. the blending of fhcos with vegetable oils can produce valuable blends of fat of good consistency and with reduced or even in the absence of trans-isomers of unsaturated fatty acids suitable for margarine. acknowledgement this research was supported by the doctoral school of food sciences at szent istván university. references [1] dayrit, f. m.: the properties of lauric acid and their significance in coconut oil. j. am. oil chem. soc., 2015 92, 1–15 doi: 10.1007/s11746-014-2562-7 [2] o’brien, r. d.: fat and oils formulating and processing for applications boca raton, fl crc/taylor & francis, 2009, usa isbn: 9781420061666 [3] walker, r. c.; bosin, w. a.: comparison of sfi, dsc and nmr methods for determining solidliquid ratios in fats. j. am. oil chem. soc., 1971 48, 50–53. doi: 10.1007/bf02635684 [4] aocs: official method cd 16b-93 solid fat content (sfc) by low-resolution nuclear magnetic resonance; in: firestone, d. (ed.) official methods and recommended practices of the aocs. the american oil chemists society, 2005 , champaign, usa. isbn: 9780935315974 [5] ribeiro, a.; grimaldi, r.; gioielli, l. a.; gonçalves, l.: zero trans fats from soybean oil and fully hydrogenated soybean oil: physicochemical properties and food applications. food research international, 2009 42, 401–410 doi: 10.1016/j.foodres.2009.01.012 [6] tan, c. p.; che man, y. b.: differential scanning calorimetric analysis of palm oil, palm oil based products and coconut oil: effects of scanning rate variation. food chemistry, 2002 76, 89–102 doi: 10.1016/s0308-8146(01)00241-2 [7] shen, z.; birkett, a.; augustin, m. a.; dungey, s.; versteeg, c.: melting behavior of blends of milk fat with hydrogenated coconut and cottonseed oils. j. am. oil chem. soc., 2001 78, 387–394 doi: 10.1007/s11746-001-0273-4 hungarian journal of industry and chemistry https://doi.org/10.1007/s11746-014-2562-7 https://doi.org/10.1007/bf02635684 https://doi.org/10.1016/j.foodres.2009.01.012 https://doi.org/10.1016/j.foodres.2009.01.012 https://doi.org/10.1016/s0308-8146(01)00241-2 https://doi.org/10.1016/s0308-8146(01)00241-2 https://doi.org/10.1007/s11746-001-0273-4 https://doi.org/10.1007/s11746-001-0273-4 introduction experimental materials methodologies results and discussion fatty acid composition solid fat content according to nmr melting characteristics solid fat index (sfi) discussion conclusion microsoft word b_49_szabol_r.doc hungarian journal of industrial chemistry veszprém vol. 39(2) pp. 295-300 (2011) separation of multicomponent mixtures l. szabó , s. németh, f. szeifert university of pannonia, department of process engineering, pob 158 , h-8200 veszprém, hungary e-mail: szabol@fmt.uni-pannon.hu rectification is the main separation technology used for purifying the products in the chemical and petroleum industry. development of distillation equipments and processes is important because of their vast energy needs and their incidence. recently, systematic synthesis of separation sequences is developed significantly. this paper presents a case study of the separation of a multicomponent cracked gas. a separation system created by heuristic rules and an “optimal” structure characterized by minimal costs were compared. rules that can be generalized based on the actual example of the separation sequence synthesis are emphasized. the separation structure developed by applying these generalized rules unambiguously depend on the thermodynamics properties of the multicomponent mixture and the specification of the products. keywords: separation of multicomponent, separation system synthesis, boiling point order (bpo), difference of boiling points (dbp), cracked gas. introduction in the chemical industry separation systems are used to cover the purity of the products. distillation is the most often used fluid separation technology which based on differences the volatility of components. it is common that the separation systems have more than two product. the separation tasks can be carried out with number of columns depending on the components and products number. conventional distillation columns separate the feed stream into two products (head product, bottom product). the complex column configurations (side product, side stripper, etc.) can be decomposed into a sequence of conventional columns. therefore the separation of a multicomponent mixture can be realized as a sequence or sequences of separation steps with two products. the separation system synthesis is a complex problem because the number of possible system structure rises exponentially by increasing the number of products. several methods are known for the determination of the best separation sequence [1, 2], for example: ● algorithmic approaches involving established optimization principles (algorithmic methods), ● heuristic methods based on rules of thumb, ● evolutionary strategies wherein improvements are systematically made to an initially created separation sequence, and ● thermodynamic methods involving applications of heat cascade principles. in some cases two or more methods are often combined in the process synthesis of distillation systems. disadvantages of the evolutionary and algorithmic methods are that their applications requires special mathematical background and computational skills from the user. although heuristic rules can be applied easily to narrow down the number of possible separation sequences, several heuristic rules unfortunately contradict each other, [3]. table 1 shows the most often used heuristic rules [4, 5, 6]. table 1: historical overview of the development of main heuristic rules heuristic rules author, year perform the easiest separation first harbert, 1957; douglas, 1988 perform equimolar splits (50/50) harbert, 1957; heaven, 1969; king, 1971; douglas, 1988 the heaviest separation last rudd, 1973; douglas, 1988 first remove the most plentiful component nishimura in hiraizumi, 1971; king, 1971; rudd, 1971; douglas, 1988 the cheapest separation first harbert, 1957; rudd, 1973; douglas, 1988 perform separation with the lowest cds [2, 7] nath in mothard, 1981 perform separation with the highest ces [2, 7] nadgir in liu, 1983 perform separation with the lowest energy index lien, 1983 perform direct sequence king, 1971 perform sequence without non-key components king, 1971;gomez in seader, 1976 296 although the individual heuristic rules often contradict each other still the heuristic rules decrease the number of solutions of a multi-solution problem. accordingly the final decision can only be made based on the detailed technical and economical analysis of the individual structures. such planning can identify the optimal structure only from a narrower set of solutions. if the heuristic rules are appropriate, the number of possible solutions is reduced while the optimal solution still being in the set of possible solutions. the essence of algorithmic methods is that the best separation system is selected from all the possible separation systems with the help of an objective function. applying this method, the optimal system according to the given objective function can always be determined. in this paper, separation structures determined by “heuristic method” and “algorithmic method” are compared. the separation system developed by heuristic method was published in our earlier work [8]. determination of separation task a cracked gas from an olefin plant was separated in this case study. the cleaned and cooled cracked gas consists of 36 components; the main compounds of which are methane (no. 3) ethylene (no. 4) propylene (no. 6) and n-octane (no. 12) [9]. table 2: products mark of products components of products name of products a 1-3 light gas fraction b 4 ethylene c 5 ethane d 6 propylene e 6-8 light c3 fraction f 7-9 heavy c3 fraction g 10-16 c4 fraction h 17-29 c5 fraction i 30-36 aromatic fraction nine products of the separation system were defined primarily based on market considerations, also taking thermodynamic possibilities into consideration. the products of the separation task are presented in table 2. a product might consist of a single component, or it can be a group of components with close boiling point. separation system synthesis by heuristic method so far in our research we have determined systems capable to solve the separation task [8]. heuristic rules were applied during the determination of the separation system, emphasizing those rules that can be generalized over the given example. in order to determine the structure of the separation system, the components of the multicomponent mixture was ordered according to their boiling points at the operational pressure in the first step. this sequence is called the boiling point order (bpo). in this case, the bpo is defined at 1 bar pressure in all steps. in the following, the components are signed with their number in the bpo, the most volatile component being the first one. the “concentration and difference of boiling point (dbp)” curve of the cracked gas was also plotted (fig. 1). the dbp is the difference in the boiling points of two “neighbouring” components in the bpo. the “concentration and dbp” curve is used to determinate the thermodynamic limitations of the separation. in the next steps, the structure of the separation system was determined by recreating the “concentration and dbp” diagram for the feed of the given separation step. the place of the separation and the key components were defined with the help of these figures. the separations were carried out with the short cut method, prescribing a 99% yield for the key components. the separation system developed with this method is presented in fig. 2. a b c d e-f g h i 0 0,1 0,2 0,3 0,4 0 10 20 30 40 50 60 70 80 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 m as s fr ac tio n ( -) d b p (k ) components difference of boiling point concentration of feed figure 1: concentration and dbp diagram 297 experience gained during the case study is summarized by the following general rules [8]: ● beside the application of different indicators measuring the difficulty of the separation, it is expedient to order the components of the mixture to be separated according to their boiling point and plotting concentration and dbp of the components (before all separation steps). ● the “concentration and dbp” diagram helps to define the exact definition of n pieces of product class. ● the “concentration and dbp” diagram helps to define the place of separation and the key components. ● the cut of separation should be placed at the boundary of two neighbouring products. ● the key components should be close to each other in bpo and their concentrations should be relatively high. 6 f, g, h, i f, g h, i 8 h i f 7 g 3 b, c d, e 5 d e b 4 c b, c, d, e 2 aa, b, c, d, e 1 a, b, c, d, e f, g, h, i figure 2: structure of the separation system by heuristic rules (a3,b3) synthesis of the separation system by algorithmic method in this paper, the separation system generated by the application of above heuristic rules and the optimal separation system were compared. in order to determine the structure of the optimal separation system, all possible structures were implemented and evaluated from an economical point of view. in the case study, the separation system was created by sequencing two-product single-feed columns. the number of possible connections rises radically by increasing the number of products. for a separation with c products, the number of possible connections is given by eq. 1, while table 3 illustrates the radical growth. the separation can be realized with c-1 columns. 9 products were determined in the case study, which makes the number of possible separation systems 1430. the implementation of such an extensive simulation is time-consuming, that forced us to narrow down the number of possible connections. therefore the first separation was taken out and considered as the first step of all the created separation systems. these are high purity separations since the key components are neighbours except in the first column. this way the separation of the products of the first column is considered as a unique separation task. in processing the head products, one has to examine the possible variations of a 5-product separation system (products: a, b, c, d, e), while the number of bottom products is 4 (f, g, h and i). fig. 3 and 4 summarize these structures. the different column configurations are marked with numbers, the configurations for the head product separation are tagged with the letter “a”, and the configurations for the bottom product separation are tagged with the letter “b”. the necessary calculations were performed with the aspenplustm simulation software. the short cut method was used for the examinations, defining 99% recovery for the key components. a microsoft excel application was developed. it implements all the possible separation systems with the help of the aspen simulation workbook, after defining the mixture to be separated, and the products. the investigations were conducted by using this application. ( )[ ] ( )!1c!c !1c2nc −⋅ −⋅ = (1) table 3: number of possible connections number of products 2 3 4 5 6 7 8 9 number of connections 1 2 5 14 42 132 429 1430 b1 6 f, g, h, i h, i g, h, i 7 h i f 8 g b2 6 f, g, h, i g, h g, h, i 7 h i f 8 g b3 6 f, g, h, i f, g h, i 8 h i f 7 g b4 6 f, g, h, i g, h i 7 h f, g, h f 8 g b5 6 f, g, h, i f, g i 7 h f, g, h f 8 g figure 4: possible variations of a 4-product separation system 298 a1 3 b, c, d, e d, e c, d, e 4 d e b 5 c 2 aa, b, c, d, e a2 3 c, d c, d, e 4 d e b 5 c b, c, d, e 2 aa, b, c, d, e a3 3 b, c d, e 5 d e b 4 c b, c, d, e 2 aa, b, c, d, e a4 3 c, d e 4 d b, c, d b 5 c b, c, d, e 2 a a, b, c, d, e a5 3 b, c e 4 d b, c, d b 5 c b, c, d, e 2 a a, b, c, d, e a6 d, e 4 c, d, e c 5 d e 2 a, b, c, d, e a, b a 3 b a7 c, d 4 c, d, e c 5 d e 2 a, b, c, d, e a, b a 3 b a8 2 a, b, c, d, e d, e 3 d e b, c 4 a, b, c a 5 b c a9 2 a, b, c, d, e d, e 3 d e a, b 4 a, b, c a 5 b c a10 3 a, b, c, d c, d b, c, d 4 c d a 5 b e 2 a, b, c, d, e a11 3 a, b, c, d b, c b, c, d 4 c d a 5 b e 2 a, b, c, d, e a12 3 a, b, c, d a, b c, d 5 c d a 4 b e 2 a, b, c, d, e a13 3 a, b, c, d b, c d 4 c a, b, c a 5 b e 2 a, b, c, d, e a14 3 a, b, c, d a, b d 4 c a, b, c a 5 b e 2 a, b, c, d, e figure 3: possible variations of a 5-product separation system in the case study, the different separation systems were compared with an economical objective function. the cost of the separation system was estimated by eq. 2. the amortization time was defined over 10 years. eq. 3 describes the investment cost [5], while eq. 4 describes the operational cost. figs. 5 and 6 contain the auxiliary energy costs. two different cases are defined in this case study: in the first case the pressure of the separations are constant 1 bar, in second case the pressure of the separations is varies. in the second case pressure of the separation is the optimal pressure (pressure with minimal cost). ∑ ∑ − = − = += 1 1 1 1 c i c i copi cinvi csum τ (2) 65,0 65,0 65,0 65,0 14321 5000 328 280 & 11250 328 280 & 323 & i cond i i reb i i p iiiii b ii vhsm vhsm cfffncfsmcinv ⋅⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ δ ⋅⋅+ +⋅⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ δ ⋅⋅+ ++⋅⋅⋅++⋅= (3) condcond i rebreb ii tphtphcop )()( ⋅δ+⋅δ= (4) where c is number of products; csum is cost of separation system; cinvi is investment cost of column number i; copi is operation cost of column number i; τ is amortization time; m&s is marshall and swift index; δhi reb is reboiler duty of column number i; δhi cond is condenser duty of column number i; vi is vapor rate in the column number i; p(t)reb is cost of the hot utility (depend on temperature); p(t)cond is cost of the cold 299 utility (depends on temperature); fi 1-4 factor of column number i [10]; cb, t, p1 i variable of column number i [10]; ni number of stages of column number i. 0,0001 0,001 0,01 0,1 1 -200 -100 0 100 200 temperature (°c) p( t) co nd ($ /m j) figure 5: cost of cold utility 0 0,002 0,004 0,006 0,008 0,01 0,012 -200 -100 0 100 200 300 temperature (°c) p( t) re b ( $/ m j) figure 6: cost of hot utility results the given cost functions can be rendered to each structure, that makes the configurations comparable and allows determining the structure of the optimal separation system. the results show that, the costs of the separation systems in the first case are significantly higher than in the second case. tables 4-7 show the results. the cost order of the structures changed significantly in both cases, however the optimal structure in the process of the head product remained the same. in the first case the results show that, in processing the bottom product, the separation system created by heuristic rules and the optimal structure are the same (b3). however, in processing the head product, the cost of the separation system created by heuristic rules (a3) is more than the cost of the optimal separation system and takes only the 12th place in the cost sequence. in the second case the results show that, in processing the head product, the cost of the separation system created by heuristic rules takes last place in the cost sequence. in processing the bottom product, the separation system created by heuristic rules takes 2nd place in the cost sequence. table 4: 1st case processing the head product number of structure cost ($/h) a14 33959 a7 33976 a12 34001 a9 34666 a6 34748 a13 35584 a8 36298 a10 50481 a11 50723 a2 65675 a1 66447 a3 66647 a4 67097 a5 67340 table 5: 1st case processing the bottom product number of structure cost ($/h) b3 1370 b1 1373 b2 1554 b4 1557 b5 1570 table 6: 1st case processing the head product pressure of splits (bar) number of structure cost ($/h) 2nd 3rd 4th 5th a14 1534 1 1 5 13 a13 1770 1 1 17 5 a12 1862 1 1 13 3 a10 1898 1 28 5 3 a11 1960 1 28 5 5 a9 2097 1 1 5 13 a2 2214 24 5 1 3 a7 2249 1 13 1 3 a4 2325 24 3 5 3 a8 2333 1 1 17 5 a5 2387 24 3 5 5 a1 2401 24 5 5 1 a6 2432 1 13 3 1 a3 2453 24 5 5 1 table 7: 1st case processing the bottom product pressure of splits (bar) number of structure cost ($/h) 6th 7th 8th b1 282 13 5 3 b3 290 7 1 3 b2 299 1 1 5 b4 303 1 1 5 b5 320 1 7 1 300 conclusion the results of the investigations can be summarized as follows: ● the results of the heuristic methods and the algorithmic methods might be the same (“bottom product”) or substantially different (“head product”). the significant difference between the results is caused by the cost of the coldest utility. the effect of the cost of the coldest utility is not taken into account any heuristic rule. ● if the cost of the hottest or the coldest utility is significantly higher, the product with maximum or minimum boiling should be recovered in the last separation step. ● the cost orders of the structures basically change if the pressure of the separations varies. ● the algorithmic methods based on economic information require many calculations but the results are reliable. ● the cost of pressure change is not considered in the case study: taking into account this cost the cost order is supposed to change. acknowledgement lászló szabó is grateful for the support of the phd fellowship of the mol plc. this work has been supported in part by the tamop-4.2.2/b-10/1-2010-0025 project. references 1. m. k. kattan, p. l. douglas: a new approach to thermal integration of distillation sequences, can j. of chem. eng, 64(1), (1986), 162–170 2. v. m. nagdir, y. a. liu: studies in process design and synthesis: part v: a simpleheuristic method for systematic synthesis of initial sequences for multicomponent separations, aiche j, 29(6), (1983), 926–934 3. zs. fonyó, gy. fábry: vegyipari művelettani alapismeretek (2004) (unit operations), isbn: 96319-5315-7 4. a. k. modi, a. w. westerberg: distillation column sequencing using marginal price, ind. eng. chem. res., 31, (1992), 839–848 5. j. m. douglas: conceptual design of chemical processes, isbn: 0-07-017762-7 (1988) 6. n. nishida, g. stephanopoulos, a. w. westerberg: a review of process synthesis, aiche j, 27(3), (1981), 321–351 7. r. nath, r. l. motard: evolutionary synthesis of separation processes, aiche journal, 27(4), (1981), 578–587 8. l. szabo, s. nemeth, f. szeifert: analysis of separation possibilities of multicomponent mixtures; computer aided chemical enginering, (2011); p 341–345, isbn: 978-0-444-53711-9 9. t. gál, b. g. lakatos: pirolizáló kemence matematikai modellezése és számítógépes szimulációja (modelling and simulation of cracking furnace), phd thesis, univesity of pannonia, veszprém, hungary (2006) 10. s. walas chemical process equipment, (1990) isbn 0-7506-9385-l << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjdffile false 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/leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice 14 bodor, nečasová, pechová and masár table 1: electrolyte systems. electrolyte parameter es1 es2 le1 leading ion chloride concentration [mmol/l] 10 10 counter ion 6-aminocaproate concentration [mmol/l] 12 12 eof supressor methylhydroxyethylcellulose concentration [% w/v] 0.1 0.1 ph 3.4 3.4 le2 leading ion chloride concentration [mmol/l] 5 2 counter ion 6-aminocaproate concentration [mmol/l] 6 2.4 eof supressor methylhydroxyethylcellulose concentration [% w/v] 0.1 0.1 ph 3.8 3.9 te terminating ion caproate concentration [mmol/l] 20 20 counter ion 6-aminocaproate concentration [mmol/l] 15 15 eof supressor methylhydroxyethylcellulose concentration [% w/v] 0.1 0.1 ph 4.7 4.7 using built-in peristaltic pumps. between analyses a relatively short rinsing procedure (ca. 1 min) with electrolyte solutions was used. 2.1 samples the bovine blood samples were collected using pvc taking set with an integrated needle hemos (gama group, české budějovice, czech republic), and immediately transferred to the test tube containing k3-edta. the samples after dilution, required for hemolysis, were filtered prior to the analysis using a syringe filter with a glass fiber membrane and a pore size of 1 µm. during the dilution step a thiol-masking agent and naoh were added to each sample. 3. results and discussion 3.1 separation conditions the combination of two columns with different ids and the employment of a column-switching technique is beneficial for the citp determination of analytes present in the multicomponent sample at low concentrations and/or at different concentration levels. the first (wider) capillary allowed the separation of sample constituents injected at a relatively high volume (37 µl). typical macroconstituents, e.g. chloride and ethylenediaminetetraacetic acid (edta), migrated out of the separation path through figure 1: a scheme of the electrophoresis system. autosampler: s – sample loop, sp – syringe pump, 6wv – 6-way valve. interface: during the injection the septums are pierced by the needles (n). interface*: during the separation the autosampler is disconnected from the analyzer. separation and electrolyte unit: v1-v4 – pinch valves, e1e3 – driving electrodes, p1-p3 – peristaltic pumps, im – injection module, w – waste, d1-cd, d2-cd, d2-uv – contactless conductivity and absorbance detection cells, m – membrane, bf – bifurcation, te, le1, le2 – terminating and leading electrolytes. a bifurcation block, and as a result they were removed from the separation compartment. during this stage of the separation the driving current flowed between electrodes e1 and e3 (fig. 1). the very small isotachophoresis (itp) zones of analytes created in the first column were insufficient for their concentrations to be determined. as a result of switching the direction of the driving current through both columns (by connecting electrodes e2 and e3, fig. 1), the separated constituents were transferred to the second column. the signal from d1-cd was used to determine an appropriate time to switch the current (fig. 1). in the second (narrower) capillary the itp zones of analytes were prolonged. in addition, due to the low gssg concentration in the samples of blood (not in excess of tens of µmol/l), their itp zone length was further extended by a reduction in the concentration of leading ions (es2, table 1) in the second column (fig. 2). a higher degree of sensitivity in es2 is also evident from the parameters of regression equations for the analytes (table 2). hungarian journal of industry and chemistry capillary isotachophoresis of glutathione 15 figure 2: isotachopherograms from the separations of gssg and gsh performed in the electrolyte systems es1 (a) and es2 (b). the isotachopherograms were recorded by d2-cd (fig. 1). the concentrations of gssg and gsh in the injected sample were both 25 µmol/l. 3.2 stabilization of glutathione the stability of gsh and its oxidation to gssg during the period between the collection of the sample and its analysis is the main source of systematic errors. in the sample of bovine blood a much higher concentration of gssg and a lower concentration of gsh than expected was measured. to avoid this problem, a thiol-masking agent was used, namely iodoacetic acid (ia) [18]. the substitution reaction between ia and gsh formed s(carboxymethyl)glutathione (gs-mc). under the itp separation conditions used, gs-mc migrated in front of gssg (fig. 3). the optimum conditions for the reaction between ia and gsh were determined by the itp separations of reaction mixtures at different periods after the reagents were mixed. these experiments were conducted with both model and real samples. under neutral and slightly alkaline conditions the reaction was very slow. an excess of ia (2 mmol/l) and the presence of naoh (4 mmol/l) in the reaction mixture led to the fast (less than 20 mins.) and quantitative conversion of gsh to gs-mc (figs. 3 and 4) without an table 2: parameters of regression equations. analyte range a b r2 [µmol/l] [s l/µmol] [s] gssg1 5-50 0.67 1.45 0.999 7 gssg2 2-25 1.66 2.01 0.9992 gsh1 10-50 0.48 0.25 0.9999 gsh2 10-50 1.24 0.60 0.9994 gsh (gs-mc)2 40-120 1.98 -6.60 0.9969 1 electrolyte system es1 and 2 es2 used for data evaluation. regression equation: y = ax + b. figure 3: isotachopherograms from the separation of the reaction mixture present in the electrolyte system es2. the isotachopherograms were recorded by d2–cd. the mixture contained 15 µmol/l of gssg, 80 µmol/l of gsh, 2 mmol/l of ia, 4 mmol/l of naoh, and 10 % of te. the sample was injected 5 mins (dot), 15 mins (dash) and 20 mins (solid) after the reagents were mixed. increase in the concentration of gssg. for the purpose of a quantitative analysis, ia and naoh was added to the sample of bovine blood immediately after its collection (during the sample dilution step required for hemolysis). blood samples that had been diluted by a factor of ten were directly analyzed after their filtration through a syringe filter with a pore size of 1 µm. the concentrations of gssg and gsh that were measured in the diluted blood samples were 4.4 µmol/l and 63.4 µmol/l, respectively. the average concentrations figure 4: dependence of the itp zone length on the reaction time of the mixture containing 15 µmol/l gssg, 80 µmol/l gsh, 2 mmol/l ia, 4 mmol/l naoh and 10 % te. 46(1) pp. 13-17 (2018) 16 bodor, nečasová, pechová and masár calculated from eight repetitive measurements of identical samples were in good agreement with those determined by enzymatic methods. the degrees of precision of the method, expressed by the relative standard deviation (rsd) values of the measured concentrations of gssg and gsh, were 10.3% and 4.4%, respectively. 4. conclusion the sensitive and simultaneous determination of gsh and gssg concentrations in entire samples of bovine blood is facilitated by the capillary isotachophoretic method developed. the simple and rapid preparation of blood samples, that only involves the masking of thiol group of gsh and the dilution and filtration of the sample, increases the accuracy of the gssg concentration measured. no adverse effects caused by the proteins present in the real blood samples on the separation efficiency or detector response was observed. it can be assumed that this method is also suitable for the analysis of blood samples from other mammals. acknowledgement this research was supported by the slovak research and development agency under the project apvv-0259-12, and the scientific grant agency of the ministry of education, science, research and sport of the slovak republic and the slovak academy of sciences under the project vega 1/0342/15. andrea nečasová is very much grateful for the financial support of mobility grant 2017fvhe-11. references [1] meister, a.; anderson, m.e.: glutathione, annu. rev. biochem., 1983 52(1), 711–760 doi: 10.1146/annurev.bi.52.070183.003431 [2] schulz, j.b.; lindenau, j.; seyfried, j.; dichgans, j.: glutathione, oxidative stress and neurodegeneration, eur. j. biochem., 2000 267(16), 4904–4911 doi: 10.1046/j.1432-1327.2000.01595.x [3] monostori, p.; wittmann, g.; karg, e.; túri, s.: determination of glutathione and glutathione disulfide in biological samples: an in-depth review, j. chromatogr. b anal. technol. biomed. life sci., 2009 877(28), 3331–3346 doi: 10.1016/j.jchromb.2009.06.016 [4] pastore, a.; federici, g.; bertini, e.; piemonte, f.: analysis of glutathione: implication in redox and detoxification, clin. chim. acta, 2003 333(1–2), 19– 39 doi: 10.1016/s0009-8981(03)00200-6 [5] camera, e.; picardo, m.: analytical methods to investigate glutathione and related compounds in biological and pathological processes, j. chromatogr. b anal. technol. biomed. life sci., 2002 781(1–2), 181–206 doi: 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z.; chen, x.: quantification of glutathione and glutathione disulfide in human plasma and tobacco leaves by capillary electrophoresis with laser-induced fluorescence detection, talanta, 2005 65(4), 986-990 doi: 10.1016/j.talanta.2004.08.030 [14] jin, w.; wang, y.: capillary zone electrophoresis with end-column amperometric detection for the determination of glutathione at a gold/mercury amalgam microelectrode without deoxygenation, anal. chim. acta, 1997 343(3), 231-239 doi: 10.1016/s00032670(96)00464-3 [15] jin, w.; li, w.; xu, q.: quantitative determination of glutathione in single human erythrocytes by capillary zone electrophoresis with electrochemical detection, electrophoresis, 2000 21(4), 774779 doi: 10.1002/(sici)1522-2683(20000301)21:4<774::aidelps774>3.0.co;2-m hungarian journal of industry and chemistry capillary isotachophoresis of glutathione 17 [16] lee, r.; britz-mckibbin, p.: differential rates of glutathione oxidation for assessment of cellular redox status and antioxidant capacity by capillary electrophoresis-mass spectrometry: an elusive biomarker of oxidative stress, anal. chem., 2009 81(16), 7047-7056 doi: 10.1021/ac901174g [17] bayle, c.; caussé, e.; couderc, f.: determination of aminothiols in body fluids, cells, and tissues by capillary electrophoresis, electrophoresis, 2004 25(1011), 1457-1472 doi: 10.1002/elps.200305874 [18] winther, j.r.; thorpe, c.: quantification of thiols and disulfides, biochim. biophys. acta, 2014 1840(2), 838-846 doi: 10.1016/j.bbagen.2013.03.031 46(1) pp. 13-17 (2018) introduction experimental samples results and discussion separation conditions stabilization of glutathione conclusion hungarian journal of industry and chemistry vol. 47(2) pp. 11–15 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-15 analysis of crude oil in terms of fouling and corrosion richárd katona1, roland lócskai1,2, gergő bátor1,2, antal krójer1, and tibor kovács*1 1institute of radiochemistry and radioecology, university of pannonia, egyetem u. 10, veszprém, 8200, hungary 2social organisation for radioecological cleanliness, józsef attila u. 7/a, veszprém, 8200, hungary the present-day oil refining market has the potential to process opportunity crudes. the degree of corrosion and fouling issues has increased in terms of processing opportunity crudes. in the case of changing crude slates, predicting the impacts of crude oil on production is necessary to ensure safe and profitable processing. crude oil can be characterized by the quantitative and qualitative analyses of saturates, aromatics, resins, asphaltenes and contaminants as well as the determination of its physical and chemical properties. the complementary nature of these analyses is necessary to identify the root causes of fouling and corrosion problems and quantify the impact of them. in this study, analytical methods were developed to investigate the effect of crude oils on production in terms of fouling and corrosion, which can be used to characterize crude oil from different sources. the compatibility, emulsification tendency and fouling potential of crude oil were analyzed by the developed analytical methods. the measurement method to assess the compatibility of crude oils is based on the determination of the flocculation tendency of asphaltenes in oils. a porla glx step analyzer was used for the compatibility tests. emulsification and fouling tendencies were measured by our in-house designed laboratory equipment. these measurements were conducted under typical operating conditions. the developed analytical methods were validated by crude oils from five different sources. keywords: crude oil, fouling, corrosion, emulsion, desalter, compatibility, asphaltenes 1. introduction refineries have had to handle problems associated with fouling and corrosion for a prolonged period of time. the degree of corrosion and fouling issues has increased since the processing of opportunity crudes and co-processing of renewable feeds were introduced [1, 2]. it is well known that crude oils contain water, chloride salts and organochlorine compounds [3]. when crude oils are preheated in the heat exchangers of crude units, the hydrolysis of chloride salts and organochlorine compounds occurs. in these chemical reactions, gaseous hydrochloric acid is released. the gaseous hydrochloric acid present in the steam phase can easily dissolve in condensed water, resulting in very low ph values. the concentrated caustic solution can cause general corrosion of equipment in crude units composed of carbon steel [4, 5]. desalting is the first line of defense against corrosion induced by the hydrochloric acid [6]. earlier studies showed that the efficiency of desalter apparatus is influenced by the stability of the emulsion generated. the stability of the emulsion increases and the efficiency of the desalter decreases when the asphaltene content of the crude oil is high [7]. besides the desalting process, *correspondence: kt@almos.uni-pannon.hu neutralizers and corrosion inhibitors are also used against corrosion in crude units [8]. fouling deposits can be categorized into inorganic and organic types. organic fouling results from asphaltenes and high molecular weight hydrocarbons which become insoluble in the system [9]. the asphaltene molecules can become unstable due to the effect of blending and heating incompatible crude oils. the precipitated molecules can be deposited on the surface of heat exchangers [10]. corrosion products of iron (fes, fe2o3) and inorganic contaminants in crude oils can cause inorganic fouling. in the crude oil preheat train, the viscosity of the oil is lowered because of heating and the deposition of inorganic contaminants increases. regardless of the cause, high fouling rates can lead to excessive equipment cleaning requirements and costs. chemicals–such as dispersants and inhibitors–are used to effectively reduce fouling in several critical areas throughout a refinery [11]. in the case of changing crude slates, predicting the impacts of crude oil on production is necessary for safe and profitable processing [12]. in this study, analytical methods were developed to investigate the effect of crude oils on production with regard to fouling and corrosion, which can be used for characterizing crude oil from difhttps://doi.org/10.33927/hjic-2019-15 mailto: kt@almos.uni-pannon.hu 12 katona, lócskai, bátor, krójer, and kovács figure 1: schematic drawing of laboratory desalter model equipment. ferent sources. the key causes of crude oil processing issues are incompatibility, the emulsification tendency and the fouling potential [3]. 2. experimental five crude oils from different sources were used in this study to validate the developed procedure. api gravity, total acid number (tan), water content, asphaltene content, inorganic contaminants and the distillation curve of crude oils were measured in accordance with astm d4052, astm d664, astm d4807, msz en 459, msz en iso 9029 and astm d7096. in addition, the total chlorine content of one desalted crude oil was measured by neutron activation analysis. 2.1 emulsification tendency in the first section of the determination of the emulsification tendency, 950 ml of crude oil and 50 ml of water were agitated using an ultra-turrax stirrer at 75 °c and 13, 500 rpm for 5 minutes. then 80 ml of emulsion was poured out into a tube that was made according to the standard test method astm d96. after that the emulsification tendencies of crude oils were analyzed by our in-house-designed laboratory desalter simulator. the schematic drawing of the equipment used is shown in fig. 1. the desalter simulator apparatus consists of a thermoblock, 8 transformers and toroidal transformers. the emulsion separation tubes are located in the aluminium thermoblock. the electric field in the tubes is controlled by the installed transformers. the connection between tubes and toroidal transformers is provided by special caps with two isolated electrodes. the temperature of the thermoblock can be adjusted by the control unit of the apparatus. during the measurement, the temperature was 110 °c and the electrical voltage was 2, 500 v. the emulsion was resolved in the separation tubes in accordance with the known method of providing an electric field to polarize water droplets. the volume of water that dropped into each tube was recorded after 10, 20, 30, and 60 minutes. the more water that dropped and the clearer the water phase, the more effective the desalting process [13]. 2.2 fouling tendency the fouling tendency was measured in the highperformance thermoblock. the equipment is an aluminium thermoblock in which 8 places for special tubes and an electric heater coil are located. the heating can be regulated by a control unit. the special tubes are pressure vessels 100 ml in volume. into the tubes, 25 g of crude oil samples were measured. the samples were heated at 250 °c for 48 hours then cooled to 80 °c and filtered under a vacuum through a 0.7 µm membrane filter. the filter along with the residue was washed with petrol, dried and weighed to yield the final result. in order to measure the amount of generated deposits on the wall of the tubes, they were washed with petrol and then the petrol wash was filtered under a vacuum through a 0.7 µm membrane filter too. the deposit was calculated from s = 10000 (m2 −m1)100 25 , (1) where the mass of the filter is denoted by m1, the mass of the filter with the deposit by m2 and the amount of deposits in ppm by s [14]. 2.3 neutron activation analysis neutron activation analysis determines the total chlorine content in the sample regardless of its oxidation, inorganic or organic states. the measurement is capable of handling inhomogeneous samples of greater masses, thus mitigating the uncertainties of sampling. the measuring range spans several times the magnitude of the range of alternative techniques, and has a small measurement error [15]. samples were prepared in 1 ml vials and sealed in polyethylene bags. the samples were then placed in larger 5 cm plastic vials that were irradiated. to provide redundancy in the case of a leakage, the outer vial was heat sealed using a hot iron. the masses of the samples were approximately 1 g and were irradiated by a 1.1 mw mark ii triga reactor at the university of texas in austin. in order to examine the total chlorine content, samples were irradiated using a reactor power of 500 kw for 5 minutes. thermal neutrons were used due to favorable cross-sections for radiative capture within this range. the following reaction was used to determine the total chlorine content: 37cl(n, γ)38cl with its half-life of 37 minutes. samples were allowed to decay for 15 minutes prior to being counted by a gamma-ray spectrometer. the samples themselves were counted for between 600 and 2, 700 seconds, depending on the net count rate under the 1, 642 kev photopeak for chlorine. hungarian journal of industry and chemistry analysis of crude oil in terms of fouling and corrosion 13 table 1: summary of the properties of the crude oils crude oil a b c api 29 46 42 tan (mg koh/g) 0.19 0.0448 0.0459 water content (%) 0.1 0 0 asphaltene content (%) 2.42 0.017 0.25 inorganic contamination (ppm) 260 110 82 total chlorine content after desalting (ppm) 8.08± 0.18 yield of fractions (%) c1-c10 18 40 32 c11-c14 9 12 12 c15-c25 23 27 26 c26-c50 25 16 19 c51+ 25 5 11 emulsification tendency fig. 2 s (ppm) 1286 472 248 sbn (-) 77.6 43.3 64 in (-) 44.6 lower lower crude oil d e api 29 31 tan (mg koh/g) 0.17 0.0726 water content (%) 0 0 asphaltene content (%) 2.05 1.6 inorganic contamination (ppm) 149 198 yield of fractions (%) c1-c10 18 20 c11-c14 8 5 c15-c25 22 25 c26-c50 25 27 c51+ 27 23 emulsification tendency fig. 2 s (ppm) 1187 772 sbn (-) 79.5 68.4 in (-) 30.8 25.1 2.4 compatibility the compatibility test of crude oils is based on the oil compatibility model. this model enables the insolubility number (in) and solubility blending number (sbn) of crude oils to be calculated. two tests were carried out to measure the solubility parameter. the first test involved determining the maximum volume of n-heptane that can be added to a given volume of oil without the precipitation of asphaltenes. then the minimum percent of toluene in the mixture with n-heptane to dissolve asphaltenes was determined. the volume percentage of toluene in the toluene–n-heptane mixture was plotted against the volume ratio of oil to the toluene–n-heptane mixture. the insolubility number is where a line drawn through the two points intercepts the y-axis. the solubility blending number can be calculated by sbn = in [ 1 + ml heptane ml oil ] . (2) the criterion for the compatibility of the oil mixture is that the volume average sbn is greater than the in of all types of oil in the mixture. it follows that the higher the sbn, the more compatible the crude oil is [16, 17]. a porla glx step analyzer was used to analyze the compatibility of crude oils. the laboratory analyzer performs the dilution in an aromatic solvent and the titration with paraffin hydrocarbon automatically. the analyzer was used in accordance with the factory-preset program. insoluble asphaltenes were detected by an optical detector according to the intensity of scattered visible light. the wavelength of the light was selected to be sensitive enough to detect even minute concentrations of asphaltene particles in the measuring solution. 3. results and discussion the results of analytical measurements are summarized in table 1. samples b and c are light crude oils, while a, d and 47(2) pp. 11–15 (2019) 14 katona, lócskai, bátor, krójer, and kovács figure 2: the emulsification tendencies and the pictures of emulsions after the measurements. the order of the crude oils in the pictures from left to right is the following: crude oil a, b, c, d and e. e are medium crude oils according to api gravity. the crude oils in order of asphaltene content from lowest to highest are: b, c, e, d and a. it is recognized that the highest emulsification of water occurs when the asphaltene content is high [6]. in bluefig. 2, it can be seen that the crude oil with the highest content of asphaltenes (a) formed the most stable emulsions. on the other hand, the emulsification tendencies of crude oils b and c showed that the emulsion of light crude oil can be easily resolved. the quantities of water phases following the measurements are presented in fig. 2. the water phases of stable emulsions are oily, while those of emulsions with lower asphaltene contents are clear. the total chlorine content of desalted crude oil was measured by neutron activation analysis. the total chlorine content in the desalted crude oil may be the result of the remaining dissolved salts and organic chlorides. organic chlorides present a more significant problem in crude oil refineries when compared to inorganic chlorides, since they are not removed by the desalting process [18]. the fouling tendency can also be correlated with the asphaltene content. the lowest amount of deposit was measured for the crude oil of the lowest content of asphaltenes (crude oil b). from table 1, it can be seen that the higher the asphaltene content of crude oil, the greater the amount of the deposit. however, the asphaltene content of crude oil c is higher than that of b, but the amount of the deposit of crude oil c is lower than figure 3: compatibility test results of a mixture of crudes b-d. figure 4: compatibility test results of a mixture of crudes a-c. figure 5: compatibility test results of a mixture of crudes c-e. that of b. this is explained by the amount of inorganic contaminants which is higher for crude oil b than c. furthermore, as the results of the compatibility test show, lower sbns belong to the light crude oils with low asphaltene contents. in figs. 3-5, the evaluation of three crude oil blends is shown. inmax denotes the greater in of the two respective crude oils that were blended. in all three cases, the volume average sbn is always greater than the inmax, so the mixtures of crude oils b-d, c-a and c-e are compatible with any blending ratios. the ins of crude oils b and c were not determined because the software of the analyzer just shows the highest in among the blended crude oils. 4. conclusion fouling and corrosion exact significant economic and operational penalties. the risk of prosecution has increased with the processing of opportunity crudes and coprocessing of renewable feeds [19]. in this paper, some laboratory methods were developed to investigate the effect of crude oils on production in terms of fouling and hungarian journal of industry and chemistry analysis of crude oil in terms of fouling and corrosion 15 corrosion. the emulsification tendency as well as the effect of blending and heating on crude oils were measured by the developed laboratory methods. these methods can be used for characterizing crude oil from different sources. the results of developed laboratory methods were compared with the composition of crude oils. as is confirmed by the results, asphaltenes and high molecular weight hydrocarbons have a significant impact on the production of crude oils in terms of fouling and corrosion. the cost and complexity of the determination of total chlorine content by neutron activation analysis make it unfit for routine analytical purposes, but the precision of the results makes it a perfect choice as a reference method [20]. our plan is to propose methods to quantify lower amounts of total chlorine content in crude oils using neutron activation analysis as a reference method. references [1] ropital, 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http://www.solublesolutions.com/wp-content/themes/twentyeleven_child/images/foulchem2001.doc http://www.solublesolutions.com/wp-content/themes/twentyeleven_child/images/foulchem2001.doc https://www.osti.gov/biblio/6358216 http://www.eptq.com/view_article.aspx?intaid=1197 http://www.eptq.com/view_article.aspx?intaid=1197 https://doi.org/10.1590/0104-6632.20150321s00002755 https://doi.org/10.1520/d4807-05r15 https://doi.org/10.1021/ef9901342 https://www.digitalrefining.com/article/1000381 https://www.digitalrefining.com/article/1000381 https://nvlpubs.nist.gov/nistpubs/legacy/sp/nbsspecialpublication674.pdf https://nvlpubs.nist.gov/nistpubs/legacy/sp/nbsspecialpublication674.pdf https://doi.org/10.31031/pps.2018.02.000539 https://doi.org/10.31031/pps.2018.02.000539 https://www.digitalrefining.com/article/1001216 https://www.digitalrefining.com/article/1001216 https://doi.org/10.1016/j.aca.2006.04.011 introduction experimental emulsification tendency fouling tendency neutron activation analysis compatibility results and discussion conclusion hungarian journal of industry and chemistry vol. 47(1) pp. 3–9 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-02 non-technical loss diagnosis in electrical networks with a radial layout anna i. pózna *1, attila fodor1, and katalin m. hangos2 1department of electrical engineering and information systems, university of pannonia, p. o. box 158, veszprém, 8201, hungary 2institute for computer science and control, hungarian academy of sciences, p. o. box 63, budapest, 1518, hungary a network-oriented non-technical loss detection and localization methodology is presented in this paper. the basic idea behind the proposed methodology is the deviation of the measured voltages from their nominal values. the operation of the algorithm was investigated by simulation experiments using an (ieee) european low voltage test feeder benchmark network. the simulation results show that the proposed method is able to detect and localize multiple occurrences of nontechnical losses caused by fraudulent meters. keywords: power network, diagnosis, non-technical loss, load-flow 1. introduction the demand for electrical energy is continuously increasing on a global scale. electrical energy is generated by power plants or renewable energy sources and is transmitted from the source of generation to consumers through distribution stations and power lines. during transmission, technical losses, that originate from dissipation in conductors, transmission lines and substation transformers as well as magnetic losses in transformers, reduce the efficiency of power delivery. the proportion of technical losses is about 20 % of the total energy transmitted. besides the technical losses, non-technical losses (ntls) may be present as well. these are unnecessary losses which are not expected and cannot be anticipated. the ntls are usually related to energy theft and fraudulent consumption behavior. energy theft has been a widespread and major issue for many years and various techniques of energy theft are present from unregistered users to hacking meters [1]. following this unwanted phenomena, several methods of non-technical loss detection have appeared in the literature. it can be stated that no golden rule exists for detecting energy theft, rather, several different approaches are available [2]. papers [3] and [4] provide very good reviews on the most frequently used methods in this field. the majority of solutions available in the literature are based on the analysis of consumption data using some statistical or machine-learning methods, for example, the authors of [5] used a linear regression-based pro*correspondence: pozna.anna@virt.uni-pannon.hu cedure that not only detects energy theft but defects of smart meters as well. a probabilistic neural networkbased classification approach is presented in [6] where the levenberg-marquardt method is used for training the network. a support-vector machine-based solution is given in [7], where a parallel computer architecture was proposed in order to enhance computation. another approach to non-technical loss detection is based on network topology, such network-oriented methods use readings from grid sensors and smart meters. in [8], the authors proposed state estimation with a kalman filter to identify currents and biases in a microgrid network. the currents and biases are estimated separately using two different filters. if the estimated bias of a customer exceeds the predefined threshold, then this user has committed fraud. the authors of [9] suggest a probabilistic power flow approach to ntl detection. the output of the algorithm is a probability distribution of ntls in the subnetwork. besides the above classes, other methods of localizing illegal electricity usage exist, e.g. in [10] a power lines inspection robot was applied to find ntls. the approach followed in the present work belongs to the network-oriented class and it is based on analyzing the differences between the measured and nominal voltages. the uncertainty in the model parameters together with the measurement uncertainties are taken into account to ensure the approach is applicable to real-world cases. the structure of the paper is as follows. the basic notions and problems are introduced in section 2. section 3 mailto:pozna.anna@virt.uni-pannon.hu 4 pózna, fodor, and hangos contains the main contribution of the paper and presents the proposed novel diagnostic method in detail. afterwards, the proposed method is subject to simulationbased analysis in section 4. 2. problem statement 2.1 non-technical losses according to a source non-technical losses (ntls) can be classified as follows [11]: before meter: illegal tapping of distribution lines or feeders meter: inaccurate power readings due to a meter being faulty (e.g. changes to the calibration), reversed, disconnected or bypassed billing: non-payment of electricity bills, inaccurate billing, faulty operation of the billing system, a cyber attack against the billing system, etc. ntls caused by companies in the us were estimated to cost between 0.5 % and 3.5 % of annual gross revenues. the ntls may account for more than 15 % of the generated power in some countries [2] and [12]. in the remaining part of the paper only the following type of non-technical loss is examined that belongs to the first class above: • fraud committed by tampering with the meter (reversing or hacking the hardware or software, or calibration of the meter), • bypassing the meter. 2.2 detection and localization in general, two main parts of the diagnostic procedure exist: fault detection and fault identification. the aim of detection is to decide if any fault has occurred in the system. the exact type and localization of the occurred fault is determined in the identification phase. in the case of non-technical loss diagnosis, detection and localization are defined as follows: detection of non-technical loss means that the loss is acknowledged. localization means that the fraudulent user is identified if the illegal consumption of power occurs at the meter. in the case of multiple ntls, every fraudulent meter is to be identified by the method. illegal load is a load that originates from a fraudulent meter, i.e. the consumer uses illegal power. 2.3 basic assumptions during development of the non-technical loss detection and localization method, the following assumptions were made: • the electrical network is represented by its static linear model. the known parameters of the model are the resistances of the transmission lines, the current and voltage of the feeding point (transformer), and the currents of the loads. • the structure of the electrical network is radial (for more details see section 3.2). • every load has a smart meter that measures the current, voltage and power consumption of the load. • at least one illegal load may be present in the network. if more than one illegal load exists then each is located in a different part of the network (see section 3.2 for more details). 2.4 uncertainties and measurement errors the main uncertainties that affect the voltages and currents in a public electrical grid can be classified as follows: • uncertainties about the parameters of the transmission lines the resistance of the transmission lines is the main source of uncertainty. this resistance can be computed from its diameter, curvature and length, which are functions of temperature. the function is approximately linear in the domain −50 ◦c to 100 ◦c: ρ = ρ0(1 + α(t − t0)), (1) where ρ and t stand for the values of resistance and temperature, respectively, while ρ0 and t0 denote the nominal resistance and temperature, respectively, and finally α represents the temperature modulus. the main uncertainty over the line is the small difference between the planned and installed transmission line. the losses, which are justifiable given these technical reasons, contribute to approximately 2–3 %. • measurement errors the presence of smart meters in our electrical network is assumed. the precision of smart meters varies from ±0.2 % to ±2 % depending on their precision and the percentage of nominal power, see international standards iec 62051, iec 62052-11, iec 62052-21 and iec 62052-31. in this paper the effects of the harmonic currents [13] are not investigated, rather, it is assumed that the voltages and currents are sinusoidal. the effects of asymmetrical loads [14] are also not investigated because a single-phase grid is assumed. a three-phase grid can be assembled from three single-phase grids with one n line. hungarian journal of industry and chemistry non-technical loss diagnosis in electrical networks with a radial layout 5 ut i1 i2 i3 in it iw1 r1 iw2 r2 iw3 r3 iwn rn figure 1: single-feeder layout 3. diagnostic method the proposed diagnostic method uses the topology and electrical parameters of the network together with the nominal and measured voltages as well as current values to detect and localize the illegal loads. the nominal voltage and current values are generated from the topology and the parameters of the network determined by solving its linear time-invariant model using the known feeder voltage and current values [15]. input data it is assumed that the model of the network is present together with the nominal values of its elements. current and voltage readings with measurement errors are available from smart meters of all loads. detection the proposed diagnostic method is based on analyzing the difference between the measured and nominal voltages. it is assumed that the currents measured are the nominal currents of the network. the presence of an illegal load is detected if a difference between the sum of the measured currents ( ĩi, i = 1, . . . , n ) and the measured current of the transformer (it) exists. n∑ i=1 ĩi − it > ε (2) localization the localization method starts with the simulation of the network assuming the nominal current values. during the simulation, the voltages of the loads are computed. the simulated voltages are considered to be the nominal voltages. subsequently the nominal voltages are compared to the measured voltages. localization is based on the evaluation of deviations in voltage from the nominal values. the measurement error is taken into account in such a way that only deviations that fall outside the maximum measurement error are considered during the diagnosis. 3.1 single-feeder layout the single-feeder layout is the simplest topology of electrical networks. it contains a single feeding point with several loads connected to it along a transmission line (fig. 1). the difference between the nominal and measured voltage levels is computed as: ∆ui = ũi − ui, i = 1, ..., n, (3) where ũi and ui are the measured and nominal voltages of the ith load, respectively. larger drops in voltage than the nominal ones are caused by illegal loads. therefore, ut it i1 in im1 imnm i11 i1n1 iw1 r1 iwn rn iw11 r11 iwm1 rm1 ug r1n1 iw1n1 rmnm iwmnm figure 2: radial feeder layout the value of ∆ui is negative. if the illegal load is in the kth load, differences in voltage of subsequent loads are equal to the kth load. this difference is proportional to the magnitude of the illegal current and the resistance of the transmission line: ∆ui = iill ∑i j=1rj , if i < k iill ∑k j=1rj , if i ≥ k (4) if, by starting from a certain load, the voltage differences of the loads are equal, then the load in question consumes power illegally. in practice two differences in voltage are considered to be equal if the difference between them is less than the measurement error. therefore, localization of the illegal load is quite straightforward in a singlefeeder layout: the load in question needs to be identified and from this the differences in voltage start to become equal. this method can be generalised if more than one illegal load in a single-feeder network is present. in this case, sections in the sequence of voltage differences where consecutive voltage differences are equal exist. the illegal loads are located at the start of these sections. 3.2 radial layout the radial-feeder layout is commonly used in lowvoltage networks. the general structure of a radial-feeder network can be seen in fig. 2. this type of network can be decomposed into single-feeder subnetworks by identifying and cutting off the branches (for further details see [16]). the loads are considered to be part of the same subnetwork if they are connected to the same bus. after decomposition, a set of disjoint single-feeder networks is formed which can be processed in parallel. from a diagnostic point of view, two types of subnetworks should be distinguished. the first type is when the subnetwork contains more than one load (referred to as multiple load subnetwork hereinafter). the structure of this subnetwork is similar to the single-feeder layout (fig. 1). the second type of subnetworks is the special case when the subnetwork contains only one load (referred to as single load subnetwork hereinafter). one illegal load in a multiple load subnetwork if only one illegal load is present in the whole network and it is 47(1) pp. 3–9 (2019) 6 pózna, fodor, and hangos located in a subnetwork with several loads, then it can be clearly localized using the diagnostic method described in section 3.1. one illegal load in a single load subnetwork in the case when the subnetwork contains only one load, the voltage difference cannot be compared to any other voltage difference within this subnetwork. therefore, the diagnostic procedure in section 3.1 cannot be used. in this case, the voltage deviations need to be analyzed globally. the increased consumption causes the biggest deviation in the voltage at the location of the illegal load. in this case, the diagnostic procedure to determine the minimum voltage difference is identical. more illegal loads in multiple load subnetworks if more than one illegal load is present and are located in different multiple load subnetworks, then their locations can be determined independently of each other. more illegal loads in single load subnetworks in this case, local minima in the voltage differences indicate the locations of the illegal loads. the local minima are determined in such a way that the voltage differences of the single loads can be compared to the voltage differences of their two nearest neighbors. if the voltage difference of the single load is smaller than that of its neighbors, then an illegal load is present at the single load. 3.3 diagnostic algorithm the four aforementioned cases in the radial layout can be merged into one algorithm, the flowchart of which can be seen in fig. 3. during the diagnosis the illegal loads identified are collected in a set calledntl. at the beginning of the diagnostic algorithm, the set ntl is empty. the diagnostic algorithm searches for illegal loads in different parts of the network. the algorithm consists of three main parts: searching in multiple load subnetworks, searching for one illegal load in single load subnetworks, and searching for more illegal loads in single load subnetworks. detection the inputs of the combined algorithm are the measured currents and voltages as well as the network structure. first, to detect the illegal consumption, the inequality in eq. 2 is checked. if the difference between the sum of the measured currents and the transformer current exceeds a predefined threshold, then illegal consumption occurs in the network, otherwise the network operates normally. if illegal loads are detected, then the algorithm tries to determine their locations. to do this, the network is simulated using the measured current to obtain the nominal voltage values. isolation ntls in multiple load subnetworks this algorithm starts to search for illegal loads in the multiple load subnetworks using the method described in section 3.1. the illegal loads identified are added to the set ntl. in this step, all of the illegal loads in the multiple load subnetworks are localized. measurement data: ĩ , ũ , it ∑ ĩ−it > ε initialize: ntl = ∅ simulate network with ĩ normal operation search in multiple load subnetworks ntl = ∅ find minimum of ∆u in single load subnetworks is new load found? ntl = ∅ illegal load is not found calculate illegal currents (iill) ∑ (ĩ+iill)− it > ε find local minimum of ∆u in single load networks calculate illegal currents (iill) ∑ (ĩ+iill)− it > ε calculate illegal currents (iill) ∑ (ĩ+iill)− it > ε not all illegal loads are found set of illegal loads: ntl yes no yes no no yes yes no yes no no yes yes no figure 3: flowchart of the diagnostic procedure hungarian journal of industry and chemistry non-technical loss diagnosis in electrical networks with a radial layout 7 figure 4: structure of the ieee 2015 european low voltage test feeder network before proceeding, the algorithm checks if any illegal loads have been identified in the multiple load subnetworks. if the setntl is empty, then no illegal loads were found, therefore, they should be located in the single load subnetworks. if at least one illegal load is identified in the multiple load subnetworks, then their illegal currents are calculated using eq. 4. the currents of the illegal loads are substituted by the calculated currents and the inequality of eq. 2 is checked. if the inequality is false, then all of the illegal loads are localized and the algorithm stops. if the inequality is true, then at least one illegal load is still present in the single load subnetworks. ntl in a single load subnetwork to identify the illegal load in single load subnetworks, the algorithm searches for the minima of the voltage differences. the illegal load possesses the minimum voltage difference. if during this step no new illegal loads are identified, then two scenarios are possible: (i) if set ntl is still empty, then the illegal load has not been found and the algorithm proceeds to the second search in the single load networks. (ii) if the set ntl is not empty, then the illegal currents are calculated and the inequality of currents checked. if no significant difference is present, then all illegal loads have been identified and the algorithm stops. if the inequality is true, then a second search of the single load networks is performed. more ntls in single load subnetworks during this step, the voltage difference of the single loads is compared to the voltage difference of their two nearest (left and right) neighbors. if the voltage difference of the single load is minimal between the three differences, then the single load is an illegal load. after this search the inequality of the currents is verified again. if a difference is still present, then not all the illegal loads have been identified, otherwise all of the illegal loads have been found and the algorithm stops. figure 5: loads in phase a 4. case study the diagnostic algorithm was tested on the ieee 2015 european low voltage test feeder [17] which is a benchmark provided by the power system analysis, computing & economics (psace) committee. it is a threephase radial distribution feeder with one feeding point. the network contains 1 transformer, 55 loads and 905 lines. the structure of the network can be seen in fig. 4. the algorithm was tested by only taking into consideration one phase (namely phase a) of the system. 21 loads are present in this phase which are displayed in fig. 5 along with their identifiers. at the time of the test, the minimum and maximum power consumed by these loads was 35 w and 64.9 w, respectively. during the diagnosis, the measurement error was set at 0.2 % of the measured currents. the network belonging to phase a can be decomposed into 13 subnetworks, 5 of which are single load networks and 8 are multiple load networks consisting of 2 loads each. the decomposition and diagnostic algorithm was implemented in matlab. the simulation of the network was also performed in matlab [18] using the method of nodal potentials. 4.1 case 1: one illegal load at first, it is assumed that only one illegal load is present in the network, more specifically in a single or multiple load subnetwork. let us consider the subnetwork that contains the loads no. 25 and 30. load no. 25 increases its consumption by 80 % of its nominal value but deceives the current meter, therefore, the registered current value is not suspicious. the network is simulated using the nominal current values. the difference between the nominal and measured voltages is presented in fig. 6. it can be seen that the voltage differences are equal in the multiple load subnetworks, e.g. loads 1 and 3 as well as 20 and 22, except for the subnetwork of loads 25 and 30. since the absolute voltage deviation at load no. 25 exceeds that at load no. 30, the illegal consumption is located at load no. 25. 47(1) pp. 3–9 (2019) 8 pózna, fodor, and hangos figure 6: voltage differences of the loads in case 1 4.2 case 2: more illegal loads in different subnetworks in the second case, it is assumed that two illegal loads are present in different subnetworks. the first illegal load is no. 46 which is located in a single load subnetwork. the power consumption of load no. 46 is 50 % more than its nominal value. the second illegal load is load no. 54 which is located in a multiple load subnetwork along with load no. 51. the consumption of load no. 54 is increased by 80 % of its nominal value. the difference between the simulated and measured voltages can be seen in fig. 7. at first the diagnostic algorithm searches for illegal loads in the multiple load subnetworks. in the subnetwork of loads no. 51 and 54, the voltage deviation of load no. 54 exceeds the voltage deviation of load no. 51, therefore, load no. 54 is identified as an illegal load. the illegal current is calculated using eq. 4. in the other multiple load subnetworks, the voltage differences of the loads within a subnetwork are equal, therefore, it can be stated that no illegal loads are present in these subnetworks. the algorithm checks if some remaining illegal currents are present thereafter. a difference between the current of the transformer and the sum of the measured currents is still present which is indicative of at least one illegal load that is yet to be identified. these illegal loads should be located in single load networks. the minimum of the voltage differences is located at load no. 46, therefore, it is an illegal load. after calculating the illegal current of load no. 46 and checking the inequality in eq. 2, it can be stated that no additional illegal loads are present in the network. 5. conclusions and future work a novel diagnostic method for detecting and locating illegal loads in electrical radial networks is proposed in this figure 7: voltage differences between the loads in case 2 paper that utilizes the topology of the network and is capable of taking the uncertainties and measurement errors into account. a preprocessing step decomposes the radial layout of single-feeder subnetworks with single or multiple loads, and the method is capable of locating the illegal load(s) in the subnetworks in parallel. the proposed method can detect and locate multiple independent illegal loads under certain conditions. future work will include the extension of the diagnostic methods to general, not necessarily radial, topology and to develop the computational model of a network to handle the uncertainties related to network parameters (resistances). furthermore, the effect of the uncertainties and measurement errors on the diagnostic accuracy should also be investigated. acknowledgement we acknowledge the financial support of széchenyi 2020 under the efop-3.6.1-16-2016-00015. we acknowledge the financial support of széchenyi 2020 under the ginop-2.2.1-15-2017-00038. this research is partially supported by the national research, development and innovation office nkfih through grant no. 115694. references [1] ahmad, t.; chen, 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https://doi.org/10.1016/s0301-4215(03)00182-4 https://doi.org/10.1016/s0301-4215(03)00182-4 https://doi.org/10.1016/j.epsr.2018.01.005 https://doi.org/10.1016/j.epsr.2018.01.005 https://doi.org/10.1016/j.rser.2017.05.193 https://doi.org/10.1016/j.rser.2017.05.193 https://doi.org/10.1016/j.ijepes.2017.04.005 https://doi.org/10.1016/j.ijepes.2018.01.036 https://doi.org/10.1016/j.ijepes.2012.10.031 https://doi.org/10.1109/tpwrs.2015.2406311 https://doi.org/10.1016/j.epsr.2012.12.008 https://doi.org/10.1007/s11042-014-2022-2 https://doi.org/10.1007/s11042-014-2022-2 https://doi.org/10.1016/j.rser.2017.01.100 https://doi.org/10.1109/pecon.2008.4762604 https://doi.org/10.1109/speedam.2010.5545079 https://doi.org/10.1109/speedam.2010.5545079 https://doi.org/10.1016/j.jclepro.2016.11.119 https://doi.org/10.1016/j.ifacol.2018.03.045 https://doi.org/10.1109/tpwrs.2017.2760011 introduction problem statement non-technical losses detection and localization basic assumptions uncertainties and measurement errors diagnostic method single-feeder layout radial layout diagnostic algorithm case study case 1: one illegal load case 2: more illegal loads in different subnetworks conclusions and future work hungarian journal of industrial chemistry veszprem vol. 30. pp. 113118 (2002) instrumentation and control of industrial wastewater treatl\1ent processes m. pisko, j. nahlik and v. hanta (department of computing and control engineering, institute of chemical technology, prague, technicka 5, 166 28 prague 6, czech republic) received: november 15,2001 requirements for treated wastewater are becoming increasingly more stringent. this, in combination with increasing loads, and limited availability of resources, calls for efficient methods of wastewater treatment processes. at present, the most widely used biological treatment process for industrial wastewater is activated sludge. this paper describes devices used for on-line measurement and monitoring of wastewater together with analyses used to characterize wastewater, as well as options available for control of the wastewater treatment process. expert systems, fuzzy logic, and neural networks are discussed and introduced to be concerned with dynamic features, nonlinearities, not clearly stated control goals and the use of qualitative information about these processes. potential benefits of thermophilic aerobic digestion, a promising technology of wastewater treatment, are also discussed. keywords: activated sludge, thermophilic, aerobic, biological treatment, control, wastewater, artificial intelligence introduction development of industry plays an important role in consumption of water. it leads to a great increase in water usage. new water supplies all over the world are being searched for, and methods for recycling and re­ using the already existing ones are developed. when practically applicable, biological processes are preferred because of economical considerations [1]. biological processes are generally classified as either aerobic or anaerobic. aerobic systems tend to be more resilient in being able to handle a larger variety of waste streams and more difficult-to-degrade waste streams, whereas anaerobic systems produce much less sludge and have lower energy requirements because they do not require aeration. at present, the most widely used biological process for industrial wastewater treatment is activated sludge. it refers to a continuous or semi-continuous aerobic method for industrial wastewater treatment. in the presence of adequate nutrients and oxygen~ a high rate of microbial growth and respiration is achieved, causing high rate removal of biodegradable organics and other contaminants. in addition, the treatment system is required to produce a good clarifying and settling sludge by well flocculation and control of proliferation of filamentous organisms. wastewater treatment plant at present time, unit operations and processes are grouped together to provide primary. secondary, and · advanced (tertiary) treatment [2]. in primary treatment, physical operations such as screening and sedimentation remove the floating and settleable solids found in wastewater. in secondary treatment, biological and chemical processes remove most of the organic matter. microorganisms themselves are removed afterwards by sedimentation under aerobic conditions. part of the settled sludge is recycled to the aeration basin to maintain a high concentration of microorganisms; the rest is drawn off as waste. in advanced treatment, additional combinations of unit operations and processes remove other constituents (nitrogen. phosphorus) not reduced significantly by secondary treatment (fig.l). the important contaminants of concern in wastewater treatment are listed in table i. the analyses used to characterize wastewater vary from precise quantitative chemical determinations to the rather qualitative biological and physical determinations. 114 table i important contaminants in wastewater [2] contaminants reason for importance biodegradable organics composed principally of proteins, carbohydrates, and fats, biodegradable organics are measured traditionally in tenns of bod and cod. if discharged untreated to the environment, their biological stabilization can lead to the depletion of natural oxygen resources and the development of septic conditions. suspended solids suspended solids can lead to the development of sludge deposits and anaerobic conditions when untreated wastewater is discharged in the aquatic environment. pathogens communicable diseases can be transmitted by the pathogenic organisms in wastewater. nutrients both nitrogen and phosphorus, along with carbon, are essential nutrients for growth. discharged to the aquatic environment they can lead to the growth of undesirable aquatic life. discharged in excessive amounts on land they can also lead to the pollution of groundwater. priority pollutants organic and inorganic compounds selected based on their known or suspected carcinogenicity, mutagenicity, or high acute toxicity. refractory organics these organics tend to resist conventional methods of wastewater treatment. typical examples include surfactants, phenols, and agricultural pesticides. heavy metals heavy metals are usually added to wastewater from commercial and industrial activities. dissolved inorganics inorganic constituents such as calcium, sodium, and sulphate are added to the original domestic water supply as a result of water use. • &if grit ptin.uy kmion soooodacy ch!!mical se-n eha.rnbtr hdlml.nt$ttion tank utlirmntation t~nt --.fli wll•!llt 1/1 fig.j a common layout of a wastewater treatment plant [2] instrumentation and control when properly designed and operated. the activated sludge process is capable of high-quality performance, including the removal of nitrogen and phosphorus. however, it has the reputation of being difficult to , operate and can exhibit gross process failure such as sludge bulking, foaming or the loss of nitrifying ability. therefore. the first objective of the control system must be the prevention of process failure. this is especially important for the activated sludge process since a substantial amount of time (weeks) may be required to fully recover from process failure. excessive pollution of the receiving water thus takes place not only during the failure period but also during the recovery period. once satisfied th.1t the control system is protected against failure. the major concern then becomes 1-. · gh quality effluent in order to satisfy the permit requirements. only after these two objectives are attained. becomes a third objective. minimization of costs. a matter of concern [3]. although a plant has many measurements and manipulated variables. most of control loops can be decoupled. it is usually not necessary to apply complex muiti·inputlmulti .. output controllers, instead a large number of local control loops keep the plant running. in its basic configuration the secondary treatment. process consists \lf an aerated tank and the settler (fig. 2). chemicals i antifoam ss bod, cod ~i respirometry influent \.?) j> microscope 1-----'-~ observation ·····(.:do ~~{';ph ~:t ssbod n,p effluent fig.2 basic control mechanisms in the activated sludge process for the control of an activated sludge system, it is necessary to understand which measurements to make and how they relate to the process behaviour. important types of measurements are biochemical oxygen demand (bod), chemical oxygen demand (cod), total organic carbon, phosphorus fractions, nitrogen in ammonia, nitrite and nitrate, ph, suspended solids (ss) in different units, alkalinity, temperature, dissolved oxygen (do) in different locations, flow rates between different plant units, air flow rates and air pressure, sludge levels and sludge flow rates. further, we shall discuss the most important and novel types of process measurements and also typical mechanisms used in control of the activated sludge process. biochemical oxygen demand the most widely used parameter of organic pouution applied to wastewater is the five-day bod (bod5). unfortunately, the bods is unsuitable for control purposes. as it requires a five days lasting analysis. therefore, methods enabling the continuous measurement of the bod for monitoring purposes have been developed. these methods yield a short-term bod (bodst), which is a more valuable variable for control purposes. the bodst monitoring methods are classified into three categories [4]: state estimation from a model of the activated sludge, bod probe method, and respirometric method. a bod probe consists of immobilized living cells, a membrane and a dissolved oxygen electrode. a signal of the probe is a measure of the substrate concentration in the water. the linear range of bod probes is below the bodst of most wastewaters, so that samples have to be diluted, which is unsuitable for continuous measurement. bod measurement is often used in control of the sludge distribution over the process. there are basically three control variables for the sludge inventory in an activated sludge system. the waste activated sludge flow rate controls the total sludge mass in the system and the sludge retention time can be kept at a desired level. the sludge distribution within the system is controlled by the step feed flow distribution (where step feeding is possible) or the return sludge flow rate. the former can dynamically redistribute the sludge within aerator while the latter can shuffle sludge between the settler and the aerator [3]. respirometry respirometry is the measurement and interpretation of the biological oxygen consumption rate under well­ defined experimental conditions. because oxygen consumption is directly associated with both biomass growth and substrate removal, respirometry is one of the most important means of modelling, monitoring and operation of the activated sludge process. all respirometers are based on measuring the rate at which biomass takes up do from the liquid [5]. this can be done directly by measuring do or indirectly by measuring gaseous oxygen. most techniques based on the measurement of oxygen in the liquid phase use an electrochemical do sensor. do mass balance over the liquid phase is used to determine the respiration rate of the biomass. the main advantage of measuring oxygen in the gas phase is elimination of possible difficulties, like formation of sludge film on the sensor. oxygen is one of the few gases that show paramagnetic characteristics, so it can be measured quantitatively in a gaseous mixture. however, in addition to the mass balance on the liquid phase, a balance on the gas phase must be also considered. respirometric data obtained with effluent sample are often used to adjust both return sludge flow rate and waste sludge flow rate to maintain the sludge concentration at a level desired for quality of wastewater remediation. although the incoming wastewater flow cannot be manipulated at will, some possibilities may exist where detention basins are available. a feed-forward strategy based on 115 respirometric measurements of the incoming wastewater may be used to alert and handle the situations concerning the toxic or high strength wastewater inflow. it is also possible to combine the respiration rate of the incoming wastewater with the respiration rate of the return sludge to calculate the return sludge flow rate necessary to handle the organic matter. chemical oxygen demand and suspended solids on-line measurement of uv absorption and turbidity can be ttsed to estimate the actual level of cod and ss in the wastewater. the relationship between cod and uv absorption, and between ss and turbidity are linear [ 6]. ss data may be used to estimate actual biomass concentration or to evaluate effectiveness of capturing suspended particles in settling tanks. dissolved oxygen control common do sensors are normally used to obtain data on dissolved oxygen concentration in different plant units. the choice of the optimal do setpoint is a crucial question for the control of the process. in order to obtain high effluent quality, the sludge needs to have a combination of good clarification and thickening properties.. this can be reached by use of a mixed population model having two competing organism types, floc-forming and filamentous organisms. a time­ varying do concentration controlled according to a time-varying setpoint can lead to the co-existence of both population types thus resulting in sludge with ideal settling properties. however, even the static do setpoint control involves several difficulties. the do dynamics is both nonlinear and time-varying. moreover, considering the long time constants and random influent disturbances, any tuning of a conventional controller becomes tedious. using cascade control with secondary measurement of gas flow and secondary feedback controller of gas flow the dynamic response to load changes may be greatly improved [3]. a disadvantage of conventional feedback control or cascade control is that the correction for disturbances does not begin until the process output deviates from the setpoint. feedforward control using measurement of disturbances offers large improvements in this case. the use of the adaptive controllers (ko et al. [7]) should also be considered. foaming control filamentous microorganisms are responsible for the foam formation in most cases. the application of toxicants is effective for au foam-formers. the control of foam· forming microorganisms by toxicants has to be accompanied by a regular microscopic examination of the consortium of both foam and mixed liquor to avoid overdosing. 116 on.nn• deta 61ackboard ·····/ fuzzy expert judgement module analytical and ob$ervation data input fig.3 blackboard concept an expert system may be used to simplify this rather complex problem so that someone with minimal microbiological training can identify the general health of the biological reactor and process data from microscopic observations [8, 9]. methods for the on-line image ·processing are also used [10] to monitor conditions of the activated sludge process. the application of antifoam agents is a rather costly and uncertain method. that is why foaming is also addressed by the use of mechanical foam breakers [11]. dosage of chemicals and ph control dosage control of chemicals is often based on feedback, such as flow rate. in some cases the dosage rate may be adjusted to the water quality obtained in lab tests or on­ line measurements. possible approach may be the dosage adjusted from historical data and regularly corrected by off-line quality tests (3]. the ph control is important for cell growth rate in biological systems. however, ph control has difficulties due to its nonlinearities and time-varying properties. ' lee et al. [ 12] propose the use of the titration curve to transform the measured ph value to the total ion concentration. then the pi controller is used to control the total ion concentration value rather than the ph value. application of artificial intelligence it is obvious that overall modelling of wastewat.!r treatment system by a single knowledge representation is almost impossible~ since biological wastewater treatment processes have very characteristic features that must be considered [13]: nonlinearity~ unsteadiness. complexity of the process, poor process understanding and dependence on empirical knowledge. lack of kinetic information on bacteria and the change of control objectives under irregular conditions. mathematical dynamic model can describe the unsteady .. complex~ and nonlinear nature of the target system. on the other hand, linguistic representation. t i oc 80 70 60 50 40 30 20 10 0 -10 -20 fig.4 classification of biological processes according to the temperature such as an expert system, is necessary to describe the bulking phenomenon and to judge circumstances that may require a change in control objectives. a fuzzy controller is very useful to incorporate the rules of thumb of operators. the applications of communities of such modules, which interact by cooperation, coexistence or competition, are discussed in several publications [14, 15] and are used in creating so called knowledge-based control systems. in this context the blackboard architecture [8, 13] is adopted to organize various knowledge representations, data manipulation methods, and modelling methods. the blackboard concept is a widely used control metaphor in the field of artificial intelligence, where multiple software agents must contribute collaboratively to achieve system objectives. based on this concept all reusable data are stored in abstract database and used in the knowledge-based control system (fig.3). expert systems are intended to solve those aspects of problems that are traditionally solved using expert human judgement and experience. both on-line and off­ line expert systems are used to operate wastewater treatment process. the on-line system recognises process failures from on-line signals and immediately starts the diagnosis and gives proper advice. the off­ line systems are used for the diagnosis of process upsets and solving of simulated plant problems as well as the choice of control parameters [16]. as mentioned above, the activated sludge process is characterised by a lack of relevant instrumentation, the use of qualitative information in decision making, poorly understood complex biological behaviour mechanisms. and control goals that are not always dearly stated. as such it appears to be an ideal candidate for fuzzy control [17~ 18]. recent approaches seem to focus on gaining learning capability using neural nets in hybrid architecture with fuzzy control and fuzzy expert methodologies [8. 19], where the artificial neural network is used as a fuzzy rule extraction method. proposed system of fuzzy rule acquisition method demonstrated better performance than the conventional fuzzy system. thermophilic aerobic treatment systems according to the growth temperature biological processes are classified as psychophilic, mesophilic, semi-thermophilic, thermophilic and hyper-thermophilic (fig.4). thermophilic aerobic degradation systems combine the best features of both anaerobic and aerobic processes, because they have the kinetic resilience of conventional aerobic systems while having the low sludge production characteristics of anaerobic systems. the higher temperatures employed in thermophilic systems tend to facilitate the biodegradation of waste streams that contain components more soluble at higher temperatures (e.g. fats, oils, and grease wastes). moreover aerobic thermophilic processes are able to deal with waste streams with high salt concentrations that are problematic for anaerobic systems [1]. thermophilic aerobic systems are very similar to the activated sludge systems. however, thermophilic aerobic digestion also presents it's own difficulties. first of all, it is difficult to transfer oxygen in high temperature fluids because of the reduced saturation value for oxygen at higher temperatures. a foaming tendency also exists because of two combined factors. the first factor is that thermophilic aerobic biological treatment systems are usually operated at high biomass concentrations (10 to 30 g/1 of suspended solids). the maintenance of high solids concentrations results in the accumulation of relatively high levels of microbial surfactants, which are foaming agents. this situation along with the fact that relatively high levels of air are introduced into a thermophilic aerobic biological reactor creates the potential for foaming and associated operational problems. also high reactor temperatures in thermophilic aerobic systems alter the physical, chemical and biological characteristics of the treatment process. all this means that the knowledge base for conventional activated sludge operations no longer directly applies and has to be adapted along with control methods themselves. conclusions the paper describes an essential part of a preliminary background research concerning measurement, modelling and control of the activated sludge wastewater treatment process with the aim to apply these methods for control of relatively new and promising thermophilic aerobic digestion process for industrial (mainly food) wastewater remediation. theoretical problems of measurement, modelling and control of these processes and practical aspects of the creation of an appropriate knowledge-based control system using artificial intelligence methods are discussed as well. 117 thermophilic processes as a kind of biological processes have all their typical characteristics as complexity, nonlinearity and time-dependence. that is why it is supposed that different knowledge representations and artificial intelligence control methods will be of a great importance for solving control task and will be mainly applied. on the other hand, despite automation, the role of a human supervisor is still very important. his abi1ity of sensual perception of many phenomena and his reasoning is superior to any sensor. a combination of automatic control and computer assistance for the operator seems to be a powerful tool for better operation. acknowledgement this study has been supported by the european community fifth framework programme under contrad no. qlk3-ct-1999-00004 henhanced, intelligent processing of food and related wastes using thermophilic populations". symbols bod biochemical oxygen demand cod chemical oxygen demand do dissolved oxygen n nitrogen p phosphorus ss suspended solids t temperature references 1. rozich a. and colvin r.: design and operational considerations for thermophilic aerobic reactors treating high strength wastes and sludges. purdue industrial waste conference, west lafayette, usa. 1997 2. tchobanoglous g. and burton f.: wastewater engineering: treatment, disposal and reuse. mcgraw-hill~ new york, ny, usa, 1991 3. andrews j.: dynamics and control of the activated sludge process, technomic publishing, lancaster, p a, usa, 1992 4. spanjers h., olsson g. and klapwijk a.: wat. sci. tech., 1993, 28(11-12)~ 401-414 5. spanjers h. and van rolleghem p.: respirometry in control of the activated sludge process: principles. sciemific and technical report no.7, iawq 1998 6. ruban g., marchandise p. and scrivener 0.: wat. sci. tech., 1993. 28(11-12), 67~78 7. ko k. y .• mcinnis b. c. and goodwin g. c.: automatica, 1982, 18(6), 727-730 8. patry g. and chapman d.: dynamic modelling and expert systems in wastewater engineering. lewis publishers. boca raton. fl. usa. 1989 118 9. ichikawa m. and simizu k.= wat. sci. tech., 1993, 28 (11-12), 231-238 10. watanabe s., baba k. and yoda m.: wat. sci. tech., 1993, 28(11-12), 325-332 11. wanner j.: activated sludge bulking and foaming control. technomic publishing, lancaster, pa, usa, 1994 12. lee b. k., sung s. w., chun h. d. and koo j. k.: wat. sci. tech., 1998, 37(12), 141-148 13. ohtsuki t., kawazoe t. and masui t.: wat. sci. tech., 1998, 37(12), 77-85 14. baeza j., gabriel d. and lafuente j.: environmental modelling & software, 1999, 14(5), 383-390 15. paraskevas p. a., pantelakis i. s. and lekkas t. d.: knowledge-based systems, 1999, 12(7), 355-361 16. ladiges g. and kayserr.: wat. sci. tech., 1993, 28(11-12), 157-164 17. tong r. m., beck m. b. and latten a.: automatica, 1980, 16(6), 695-701 18. tsai y. p. and ouyang c. f.: wat. scl tech., 1993, 28(11-12), 355-367 19. enbutsu i. and baba k.: wat. sci. tech., 1993, 28(11-12), 333-340 page 112 page 113 page 114 page 115 page 116 page 117 hungarian journal of industrial chemistry veszprem vol. 30. pp. 247-251 (2002) preparation of feed grade dicalcium phosphate from commercial phosphoric acid t. yassine*, r. baidoun, j. stas and r. al-merey (department of chemistry, atomic energy commission of syria, p.o.box 6091. damascus, syria) received: may 3, 2002 feed grade dicalcium phosphate was prepared by treatment of uranium barren c?mmercial ~hosphoric acid with2~alcium hydroxide, and precipitation of dicalcium phosphate in two stages. the undesrred contannnants, such. as s04 an~ f were isolated in first precipitation stage using calcium hydroxide at ph 2.7~.9, where th~ co~centrat10ns of c.ad~um and other trace elements were reduced by adding a small amount of ammomum sulfide m this stage, then dicalcmm phosphate was precipitated by addition of calcium hydroxide in second stage at ph 67. x-ray diffraction study showed that the resulting product was mainly a brushite (cahp04·2h20). keywords: commercial phosphoric acid, dicalcium phosphate, feed introduction in addition to their value as fertilizer, phosphate compounds are essential as phosphorus supplement for living. these compounds have found large applications in several fields such as medicine, industry and as additive for livestock and poultry feed. phosphate rocks contain different levels of harmful contaminants such as fluoride, hazardous trace elements, and radioactive elements, which could be transferred to phosphoric acid produced by wet­ process. such contaminants lead to disuse this acid in food and feed industry [1]. the high cost furnace­ process produced phosphoric acid is mostly used for preparation of pure phosphatic compounds for such above mentioned applications. several manufacturers have started to prepare some phosphatic compounds such as dicalcium phosphate and ammonium phosphate for nourishment purposes starting with wet-process phosphoric acid, after purification or isolation of undesired impurities during the processing procedures. dicalcium phosphate cahp04 is produced by treatment of either phosphate ores or phosphoric acid with sulfuric acid or calcium minerals respectively [2]. care should be considered for undesired impurities in the final products. yang applied a procedure by mixing the phosphate rock with sulfuric acid and sodium chloride. ca.hp04 was precipitated from filtrate after reacting with calcium alkaline [3]. zao and duan mentioned that, dicalcium phosphate for nourishment purposes was produced by mixing calcium carbonate with pure phosphoric acid [4]. kondo et al prepared high purity material of calcium phosphate by treatment of commercial phosphoric acid with ammonia at ph range of 2-4, followed by addition of edt a2na in the presence of calcium solution cach, cac03 and ca(oh)z. the obtained solutions were mixed together and added to a solution consisting of nj40h and (nij4)2:hp04 at ph7 [5]. luo et al mixed a ratio of (0.5~0.8):1 phosphate rock: sulfuric acid, then the solution was adjusted to a ph value of about 3.2 by adding lime or calcium alkaline, cahp04 was then precipitated from filtrate after reacting with lime or calcium at a ph value of 6.5 [6]. giulietti and cekinski precipitated calcium phosphate in two stages. the first one is in the range of ph 2.7-3.4, and the second one is in the range of ph 4-7 either from phosphoric acid medium or from the product of digesting phosphate rock with sulfuric acid using calcium source [7]. fluoride is the worst impurity found in phosphate roc:k, which must be eliminated. its percentage must not exceed one part per hundred parts of phosphorous in the product [8]. rychnova succeeded in reducing fluoride co~tent to 40-50 %, of its value in phosphate rock solutions ~y reacting it with silicate and potassium salts or sulfurtc acid at the temperature range of 6()..80 °c [9}. abdel­ aal reduced fluorine content to less than 0.17 % from • author forcorrespondence: e-mail: atomic@net.sy; fax 00963~11~6112289 248 commercialgrade phosphoric acid (48% pzos, 0.8% f) by reacting the acid with silica dust, then dicalcium phosphate for animal feed supplement was prepared by addition of sodium hydroxide [10]. baidoun et al reported methods of fluorine reduction in syrian commercial phosphoric acid, raffinate, by mixing the raffinate with silica gel in three stages and under three different conditions: reduced pressure (0.5-15 torr), high temperature (80-90 °c) and room temperature, the fluorine reduction was about 94-97 %, 98% and 97 %, respectively [11]. tian et al purified phosphoric acid first by extracting it with tri-octyl amine and di-chloromethane in kerosene leading to reduction in the fluoride level in diclacium phosphate to less than 0.15% [12]. this work will focus on the preparation of dicalcium phosphate by reacting uranium barren commercial phosphoric acid with calcium hydroxide at a bench scale level and investigation of parameters, affecting this process and determination of the optimal conditions. experimental materials the following materials have been used: 1. orthophosphoric acid from bdh (88 w/w% ). 2. calcium hydroxide ca(oh)z (97 %) from riedel-de haen. 3. ammonium sulfide (nh4hs (20 %) from merck. 4. syrian purified commercial phosphoric acid from uranium, gypsum and other organic materials, raffi.nate which was obtained from the micro-pilot in horns (24.1 % pzos). 5. double distilled water. instrumentatiorz and equipment the following apparatus have been used: 1. fluorometer (om) from gmbh. 2. atomic absorption spectrometer 2380 from perkin­ elmer. 3. compact x.ray diffraction system p.w 1840/01/11 from philips. 4. anodic stripping voltammetry 694 va stand and 693 va processor. 5. gamma-ray spectrometry with high pure germanium (hpge) solid state detector. of 25% relative efficiency and 1.85 ke v resolution at 1332 kev gamma peak of 60co. 6. ph/ion meter ( 692) from metrohm combined with fluoride selective electrode and silver/silver chloride reference electrode or combined with ph glass electrode. 7. micro-balance (no. a-a-160) from denever instrument. 8. gallenkamp oven 300 plus series. 9. electrical mixer: nuova ii from sybron. 10. whatman 41 filter paper. methods and measurements preparation dicalcium phosphate compounds have been prepared by mixing fixed amounts of uranium barren commercial phosphoric acid (p20 5 24%) with appropriate amounts of calcium hydroxide in slurry form with a continuous stirring at fixed temperature (15-30 °c), where a water cooling jacket was used for this purpose. the precipitation was carried out either by one or two stages at various ph values, after that, the precipitates were filtered, dried and analyzed. measurements chemical analyses of phosphoric acid and products were carried out according to well known methods adopted by association of florida phosphate chemist [13]. concentration of p20 5 was determined using spectrophotometric method, where the absorbance of molybdovanadophosphate complex was measured at a. = 460nm. sulfate ion (so/") concentration was determined by the well known gravimetric method by precipitating it in the form of barium sulfate. fluoride concentration was measured in the commercial phosphoric acid and solid samples using ion selective electrode method where internal standard addition method was applied to delete. the effect of interferences. density was determined using density flask. most of elements (ca, zn, fe, ai, mg) existed in the phosphoric acid w~re analyzed by atomic absorption technique. while, lead was identified by x-ray fluorescence technique. cadmium was determined by polarography, and arsenic was determined by neutron activation analysis. uranium was determined in phosphoric acid and solid samples using fluorometry. the percentage of acid insoluble ash of dicalcium phosphate has been determined by taking a known weight of the dried sample and placed in a muffle furnace at high temperature in order to eliminate all organic material. then, sufficient amount of hci (5n) was added and the mixture was heated using water bath, filtered and dried at 135 °c for three hours. this process was repeated until a constant weight, then the percentage of acid insoluble ash was calculated. the mineralogical composition of all prepared compounds was determined using powder x-ray diffraction technique. table 1 specifications of uranium barren commercial phosphoric acid major components trace elements % j..tg.mr1 pzos so;f al fe mg zn 24.1±1.11 4.2±0.4 0.11±0.01 810±13 1350±91 4300±383 251±15 density u as pb cd 1.344±0.05 3.3±0.5 -0.5-1 <1 2.74±0.11 table 2a characterization of dicalcium phosphate obtained by two stages of precipitation ca(oh)2 precipitate sample added ph of weight code* (g) precipitation (g) zn (j..tg.g-1) c1 11.47 1.0 14.82 184±4 l1 25.53 7.20 66.13 268±6 cz 13.69 1.50 16.71 189±4 lz 23.31 7.40 68.58 282±6 c3 15.91 2.0 17.35 216±5 l3 21.09 7.45 64.96 314±7 c4 17.5 2.50 19.67 233±17 l4 17.5 7.0 61.54 380±27 cs 17.39 2.65 25.26 259±18 ls 19.61 7.25 55.86 408±29 c6 19.04 2.85 27.73 341±24 l6 16.22 7.0 51.69 431±30 c1 16.65 3.10 31.72 401±28 ~ 20.35 7.1 50.0 348±25 *c, l: refer to the first and second precipitation stage respectively results and discussion in this work, the optimal conditions for the precipitation of dicalcium phosphate from uranium barren commercial phosphoric acid with calcium hydroxide were determined. calcium phosphate compounds have been precipitated either by one or two stages at various ph values. ~ ca > s ~ product precipitate composition f (%) 0.06±0.01 0.19±0.02 0.07±0.01 0.19±0.02 0.13±0.01 0.16±0.02 0.09±0.01 0.16±0.02 0.10±0.01 0.16±0.02" 0.22±0.02 0.10±0.01 0.24±0.02 0.10±0.01 110 100 90 80 70 60 50 40 30 20 io so;(%) 36.6±0.5 <3 30.6±0.4 <3 27.3±0.4 <3 30.3±0.4 <3 25.8±0.3 <3 17;8±0.2 <3 16.6±0.2 <3 2 3 4 ph p (%) 10.1±0.2 17.3±0.4 10.9±0.2 17.3±0.4 11.7±0.2 17.5±0.4 11.9±0.2 17.5±0.4 13.6±0.3 18.4±0.4 12.1±0.2 18.0±0.4 13.4±0.3 16.7±0.3 + 0 a. 5 249 ca 140±5 ca (%) 16.5±0.3 24.1±0.5 16.5±0.3 22.5±0.5 17.3±0.4 23.8±0.5 17.8±0.7 18.9±0.8 24.8±1.0 19.8±0.8 14.0±0.6 22.0±0.9 28.7±0.6 29.5±0.6 sol f p 6 7 8 table 1 shows the characteristics of uranium barren syrian phosphoric acid, which was used in this work. the major impurities in this acid were the fluoride (0.11 %) and sulfate (-4 % ), which should be reduced in the final product because they are considered as harmful impurities. one stage precipitation of dicalcium phosphate at ph value of about 6, will lead to complete transfer of these ions to the products producing levels of about 0.19% of fluoride and 7% of sulfate. the two levels are high and should be reduced. fig. i removal of major impurities at different ph value in order to determine the ph value at which the precipitation process can remove most of the impurities without a major loss in the p20 5 content, several precipitation processes were carried out at fixed ph values ranged between 0.2 7 .2. fig. i shows that about 90% of so/ions are precipitated at ph value of about 1, where this percentage increased with increasing ph value to reach complete precipitation at ph -2.5. fluoride also showed high precipitation rate at ph values between 2.5-3, where about third of its amount is precipitated at ph value of 2.6. at this value of ph. 250 table 2b recovery of fluoride, sulfate and phosphorus in precipitate sample recovery of recovery of recovery of fluoride sulfate phosphorus code (%) (%) (%) c1 6±2 96±6 11±1 ll 95±10 85±5 c2 9±2 90±5 13±1 l2 98±11 88±5 c3 17±3 94±5 15±1 l3 81±9 84±5 c4 13±3 105±6 17±1 l4 74±8 80±5 c5 18±3 100±6 25±2 l5 67±7 76±5 c6 48±8 100±5 25±1 l6 39±6 69±4 c7 58±7 94±6 32±2 l7 40±5 62±4 about 20 % of phosphorus content is precipitated where it almost showed similar behaviour to that of fluoride. these results reveal the possibility of elimination of all sulfate impurities and about 35 % of fluoride impurities with calcium phosphate precipitated at ph value of about 2.6-2.7. this precipitation also removes about 20 % of phosphorus. re-precipitation of phosphorus remained in the solution ( -80 %) at hig~ ph value -7, could produce more pure dicalcium phosphate. tables 2a and 2b show the results obtained when 100 ml of syrian phosphoric acid was treated with calcium hydroxide in two stages. the ph value of precipitation was controlled by the amount of ca{oh)2 added. the precipitation rate at first stage was slow with increasing ph value up to a ph value of 2.5. all precipitatioh processes carried out in this ph range had removed all sulfate impurities with less than 13% of the fluoride impurities and less than 17 % of phosphorus content. re-precipitation of the remained solution at ph of about 7 led to produce dicalcium phosphate with high content of fluoride ( -q.l6 % ), which is higher than the allowed limit (table 3). therefore the ph of first precipitation medium was slightly increased up to about 2.85. at this stage the removal of fluoride had increased up to about 50 % with some increase in the amount of precipitate where the percentage of removed phosphorus increased to about 25 %. re-precipitation of the remained solution had led to about 52 g of dicalcium phosphate with composition of 22% calcium, 18%, phosphorus, and 0.1 % fluoride. this composition is in accordance with syrian standard limits for feed grade dicalcium phosphate (ca>21 %, p>l6 %, f:so.l %). therefore the resulting precipitate in the second stage can be used as feed additive dicalcium phosphate. furthermore~ trace elemental analysis of the resulting dicalcium phosphate prepared in accordance table 3 specifications of feed grade dicalcium phosphate contents concentration limit* obtained value ca% >21.0 22.0 p% >16.0 18.0 f% ::.;; 0.1 0.10 pb f.tg.g-1 <30 <1 as flg.g-1 < 10 <1 cdj.tg.g-1 <1 zn j.tg.g-1 <200 uj.tg.g-1 <2 acid insoluble ash % < 1.0 0.40 moisture% <7.0 2.70 *these limits are according to syrian standard certificate n° 580, 1988 with above mentioned method showed very low levels of harmful elements such as pb, as and cd (table 3). the highest level of trace elements was found for zn (~400 j.lg.g-1 ). although this element is not classified as harmful one, but its level could be reduced to less than a half of this value by addition of 5 ml of 1 % ammonium sulfide, (nh4) 2s solution to the mixture before first stage of precipitation. in this case most of the trace elements like pb, as and cd were precipitated in first stage at ph -2.85 and the final product obtained from the second stage was almost free from trace elements. uranium level in the final product was found to be about 4 j.lg·g-1 without treatment with ammonium sulfide in frrst stage of precipitation. addition of ammonium sulfide in first stage of precipitation reduced the level of uranium in the final precipitate to less than 2 j.lg·g-1.this figure is also reduced in the feed at least by factor of 10 since dicalcium phosphate is added to the feed mixture with percentage of about 10%. this amount of uranium in the feed is equivalent to about 5 bq·kg-1 radioactivity where the total radioactivity limit allowed in the feed is about 500 bq·kg-1 . x-ray diffraction analysis of the resulting dicalcium phosphate showed that more than 95% of it was in the form of brushite (cahp04·2h20), while about 5 % of it was as monetite (cahp04). water and acid insoluble ash of the resulting dicalcium phosphate was about 2.7% and 0.4% respectively and these two values are much less than syrian standard limits 7 % and 1 % respectively. conclusion feed grade dicalcium phosphate could be prepared from uranium barren syrian phosphoric acid without pre­ purification from impurities. most of undesired impurities could be isolated by precipitation of calcium phosphate at low ph medium (ph 2.85). this process led to precipitation of sulfate, -50 % of fluoride and some other trace elements impurities. addition of sulfide ions at this stage led also to isolation of several trace elements like pb, as, cd and u. re-precipitation of the resulting solution at ph 7 led to pure feed grade dicalcium phosphate with recovery of about 70 % of phosphorus. the precipitate obtained in the first stage, which contains about 25 % of total phosphorus, could be used as fertilizer since the percentage ofp20 5 is about 25· %. acknowledgment the authors wish to express their thanks to dr. i. othman director general of syrian atomic energy commission for help and financial support, and also many thanks to dr. g. zayzafoon head of department of chemistry for fruitful discussions. 251 references 1. u.s. pat. 4,877,594 (1989) 2. czech. cs 245,120 (1987) 3. cn1,038,251 (1989) 4. zao x. and duan j.: xiangtan daxue ziran kexue xuebao, 1990, 12(1), 60-2 5. jp 0234,507 [9034,507] (1990) 6. cn1,048,015 (1990) 7. braz, pedido pi br 8904,99 (1991) 8. eyal a., haidu k. and baniel a.: solvent extr. ion exch., 1984, 2(4-5), 659-75 9. czech. cs 220,107 (1985) 10. abdel-aal e. a.: hung. j. ind. chern., 1999, 27, 165 11. baidoun r., abu-hilal j. and allaf a. w.: afinidad., 2001, 493, 197-209 12. tian h., tangs. and su y.: huadong huagong xueyuan xuebao, 1988, 14 (5), 551-8 13. afpc: methods used and adopted by the association of florida phosphate chemist ,bartow, florida 33830, 6th edition, 1980 page 253 page 254 page 255 page 256 page 257 hungarian journal of industrial chemistry veszprem vol. 30. pp. 73 -76 (2002) measurement of the swelling force of some sodium starch glycolate products with new software a. kelemen1 , a. szollosi, a. zsoter, k. pintye-h6di, c. tdr6k2 and i. eros (~epartment ofph~ceutical 'j'ec?nolog~, u~vertity of szeged, eotvos str. 6, h-6720 szeged, hungary department of me~cal informatics, umvers1ty of szeged, koranyi fasor 9, h-6720 szeged, hungary agrokemia sellye ltd, malom str. 1 h-7960 sellye, hungary) received: october 12, 2001 the swelling properties of several experimental sodium starch glycolates (ssg) were investigated with new equipment and s.oft~are. the charact~ristic ~~elling time (tt;3.2%? was calculated. the effects of the molecular structure (degree of subs~tutwn~ _on the swelling abthty were also studied. it was found that the degree of cross-linking influenced the swell~ng abthty of ssg products. the described equipment and the developed software are suitable for study of the swelhng process and characterization of the different disintegrants. keywords: disintegrant, swelling force, force-time curve, characteristic swelling time introduction disintegrants are always added to conventional tablets in order to promote the break-up of the tablets when they are placed in an aqueous environment. the flrst step in the process of dissolution of the drug is disintegration. the disintegrant causes rapid disintegration of the tablet~ the increase in the surface area of the tablet promoting rapid release of the drug. the mechanism of disintegration is influenced by different factors, among which the water uptake and swelling play very important roles [1-3]. the uptake of water by disintegrants is thought to initiate the process of disintegration [4, 5]. the swelling force is responsible for the breaking-up of the tablet. list and muazzam [5] drew attention to the importance of the swelling force, and caramella et al. (6, 9] also dealt with measurement of the swelling force. the most common disintegrant employed in tablet formulation is starch. there are many types of modified starches (sodium starch glycolate = ssg) on the market. this material can be regarded as a super -disintegrant. it is official in the usp, bp and ph.eur. while the quantity of starch required is about 20%, 4-5% of ssg is sufficient. many reports have been published on primojel and explotab [8-16], the most widely used types. the effectiveness of ssg is influenced by various factors. the degree of substitution, the degree of crosslinking and the sodium chloride content play important roles in the disintegration of the tablets [12. 16]. the present article reports an examination of the influence of the above-mentioned parameters on the swelling process. the most informative factor, the characteristic swelling time (4;3_2<j>), was calculated from the modified weibull equation (rosin-rammler­ sperling-benett-weibull = rrsbw) by nonlinear regression, 4;3.2% being the time needed to attain 63.2% of the maximum swelling force. this factor could be utilized to compare the different disintegrants. experimental materials the present experimental ssg samples (from agrochemia co., sellye, hungary) are based on a sodium salt of a partially substituted carboxymethyl ether of potato starch. they have a moisture content that is lower than that of starches (<10%). the sodium chloride content is less than 1%. different types are produced as regards the degree of crosslinking. the degree of substitution is the same {table 1). indifferent tablets were prepared from the ssg products with the aim of a study of the swelling (table 2). dicalcium phosphate dihydrate (panncompress 11 • parmentier ag, germany) was used as binder. it was 74 table 1 parameters of ssg products nacl nadegree of. product content glycolate sedimentation substitution (ml/100 ml) (mol-cooh/ (%) (%) mol starch) ssgl 0.65 0.80 82 0.24 ssg2 0.62 0.80 57 0.24 ssg3 0.72 1.00 48 0.25 ssg4 0.74 1.00 36 0.25 ssgs 0.81 1.05 28 0.24 . ssg6 0.94 1.10 17 0.24 c:!j; i 2 i. punch, 2. holder. 3. water container, 4. water fig. i measuring part of swelling force equipment necessary to apply a lubricant as well (magnesium stearate<t ph.eur. 3ro.). these materials do not swell in aqueous medium. methods sedimentation: a 2.00 g sample was suspended in 200 ml boiled distilled water. 100 ml of this suspension was poured into a cylinder. the volume of the sediment was ~read off after 24 hours. mixture: after sieving (0.8 mm wire distance), the components were blended at 50 rpm for 10 min in a turbula mixer (willy a. bachofen maschinenfabrik~ switzerland). the moisture content of powder mixtures was determined gravimetrically, through water removal with an 'ir lamp mounted on a quick dryer (organic chemistry co.. budapest. hungary). the moisture content was in every case 0.3~0.4%. compression: pressing was carried out with a korsch eko eccentric tablet machine (e. korsch mascbinenfabrik, germany) mounted with strain gauges and a displacement transducer was applied: punches: simple. 10 mm in diameter pressure force: 5~ 10 and 15 ± l kn mass of tablet: 40% air temperature: rate of pressing: 23°c 36 tablets/min table 2 compositions of tablets materials ssg (1-6) parmcompress ma esium stearate total mass ( ) 4.8 114.6 0.6 120.0 mass fig.2 scheme of measurement swelling force measurement (%) 4 95.5 0.5 100.0 the equipment used to measure the swelling force (sf) was prepared on the basis of the principle of the list apparatus [5]. the measurement is performed with a balance (sartorius microbalance) with electronic compensation, which is built in the equipment. the tablet-holder is a copper cylinder 10 mm in diameter with slits in the side. in this cylinder, a copper punch with the same diameter is fitted. the tablet-holder is in a copper cup. the tablet is placed in the holder and 5 m1 distilled water is injected at the start of the measurement. the water penetrates into the tablet through the slits. the force that builds up inside the comprimate as it absorbs the water is transmitted vertically and is detected by the balance (fig.l). the equipment is linked with a pc by a rs232 cable (fig.2). software has been developed for data acquisition, evaluation and demonstration· of the sweuing process. the monitor displays the sf vs. time curve with the important parameters (sf, time characteristic swelling time (4l3.2%)}. mirroring the close logical or functional relationship between them, the sf functions are arrayed in separate groups (acquisition, settings, analysis). under the acquisition menu poin~ it is possible to receive data from the serial port. during acquisition, the monitor shows the current sf and baseline values. at the end of the acquisition, the software saves the data on disk. with the settings menu point, it is possible to configure the system (e.g. serial communication, acquisition file name, etc.). with the analysis menu point, it is possible to evaluate the saved data. the screen depicts the sf vs. time curves (a maximum of 5) with the important parameters (time, sf. baseline, f<i3.l%) and df/dt). the user can evaluate curves manually with the cursor, create reports. or print screen shots to the bitmap or to the printer. the characteristic swelling time and shape parameter were calculated from the following form: table 3 results of the swelling test pressure swelling force force f3 ~3.2% (kn) (n) (s) 5 8.56 0.830 119.13 rsd=5.57 ssg1 10 10.09 0.836 108.82 rsd=9.95 15 12.49 0.858 125.87 rsd=5.46 5 5.45 0.858 66.35 rsd=ll.56 ssg2 10 7.16 0.832 61.67 rsd=8.74 15 14.23 0.830 78.99 rsd=11.09 5 6.96 0.816 48.55 rsd=6.44 ssg3 10 8.18 0.814 47.48 rsd=7.62 15 18.33 0.830 95.03 rsd=3.80 5 6.92 0.864 53.36 rsd=6.21 ssg4 10 8.14 0.808 30.10 rsd=9.74 15 9.59 0.832 33.10 rsd=ll.09 5 9.94 0.832 89.24 rsd=7.36 ssg5 10 13.81 0.819 82.33 rsd=8.58 15 13.49 0.831 40.71 rsd=3.11 5 8.59 0.825 40.38 rsd=0.37 ssg6 10 11.25 $ 0.813 48.88 rsd=4.22 15 11.87 0.816 38.74 rsd=2.85 fj m(t)=m~{l-exp{-[~] ) } "c where "cis the time parameter, f3 is the shape parameter, mmax is the maximum value of the swelling, m is the swelling at time t, and t0 is the start time. it is possible to calculate the characteristic swelling time. f3=1 implies ftrst-order kinetics in the swelling process; f3<1 impliest fast swelling at the beginning of the process, followed by a slower swelling; 13> 1 implies a sigmoid curve: slow swelling is followed by a faster swelling process. in the literature, these parameters are generally calculated by means of the weibull distribution equation rearranged in linearized form [8]. another way to solve this equation is nonlinear fitting. in the present paper, this method was used with global software (http://www.jate.u-szeged.hu#csendes.htm) (fig.3). 75 titte ; 34.6 .ll..l jill& b) sf 4.6n 91.. : .1.0'19 d#f/dt : o,ijoll sf max: ?.407 tc63,ji): 34.6lla sh-(j): o . .-u sf= swelling force (where the vertical measuring line is); bl = basic line; sfmax = maximum value in swelling force; t(63.2) =characteristic swelling time; dsf/dt =the speed of changing of force (where the vertical measuring line is) fig.3 swelliilg force profile (1) and nonlinear fitting according to rrsbw equation (pressure force: 5 kn) 12.36 .. , i 6.18 fil• n-: $$02-15.002 (1} ssoo -11; ooa 121 es~-11.00~ (3) 0 (1) sf o.ooo ill 1.040 dsf,.dt : o.ooo sf .tyx : a.aa& t(6ll.2>1 811.,6? 0 (2) o.ooo .1.030 o.ooo -.i .. :t,s. 46.620 (3) o.:at>3 t.0"/9 u.tltlo 11.aaa 45.62.1. au i•l sf= swelling force (where the vertical measuring line is); bl = basic line; sfmax = maximum value in swelling force; t(63.2) =characteristic swelling time; dsf/dt =the speed of changing of force (where the vertical measuring line is) fig.4a swelling process of ssg2. ssg3 and ssg5 comprimates (pressure force: 5 k:n) results and discussion results are shown in table 3. it can be seen that at 5 kn the ssg5 comprimates exhibited the highest, and the ssg2 comprimates the smallest sf (table 3. figs.4/a and 4/b). the ssgl and ssg6 comprimates (5 k.n) had almost the same sf maximum~ but there was. a considerable difference in the l63.~ values. the sf increased at higher pressure force, but to different degrees. the reason lies in the texture of the comprimates and in the properties of the mate~als. increase of the pressure force generally resulted m a decrease in the porosity. the texture of the comprimates is more compact. this has an imjx>rtant role in the disintegration. if the character of the composition is 76 :.1?!18.04.30 <h> r-r---------:;:-------, !1.!13 fu• ..-.: $$1jf-5.~ (11 ug4~5.~ !2) tlim-;s.oq.;i (3) 0 yo-----~--~.~35~--~----~.16~70 m (2) (3) (s) *"' : o.on o.ooo o.qoo 1lll: 1.040 .1.00.1 o.,9j. dsi"i'dt ; o.ooo o.ooo l),oi)q $1" ,_ ; ••••• "·"1& 8.6 .... 1 t<,:t.a>: ua.a!l4 u.,;sa 3.1.soa sf= swelling force (where the vertical measuring line is); bl = basic line; sfmax = maximum value in swelling force; t(63.2) =characteristic swelling time; dsf/dt =the speed of changing of force (where the vertical measuring line is) fig.4b swelling process of ssgl, ssg4 and ssg6 comprimates (pressure force: 5 kn) hydrophilic, the sf (disintegration force) can be better mediated by the water and the disintegration process will be rapid. the degree of the increase in the sf depends on the properties and the swelling ability of the disintegrants. by changing the disintegrant at the same composition, it is possible to study the influence of the pressure force on the sf. the data allow the samples to be arranged in sequence. for the sf: skn: ssg5 >ssg6= ssgl > ssg4=ssg3> ssg2 10 kn: ssg 5 > ssg 6 >ssg 1 >ssg 4 =ssg 3 >ssg 2 15kn: ssg3 > ssg2> ssg5 >ssg 1 > ssg6>ssg4 for taz": skn: ssg6<ssg3<ssg4<ssg2<ssg5 <ssg 1 lokn: ssg4>ssg6=ssg3 <ssg2 <ssg5 <ssg 1 15 kn: ssg4<ssg6=ssg5 <ssg2 <ssg3 <ssg 1 it can be stated that increase of the degree of crosslinking and of the sodium chloride content led to a higher sf. however, this effect was observed only at pressure forces of 5 and 10 kn. the degree of crosslinking influenced the swelling ability of the ssg products. it was seen that, for the samples with a smaller degree of cross-linking (ssgi~ssg3)., the sf increased in a stepwise manner with increase of the pressure force., the samples with a higher degree of crosslinking (ssg4-ssg6) demonstrated an increase in swelling only between 5 and 10 kn. but not when the pressure force was increased from i 0 to 15 kn. the reason is the inflexible skeleton with a compact texture. it can further be seen that the characteristic water­ uptake time (tu2~) is influenced primarily by the deformability of the particles and by the texture of the comprimates. conclusion the results of these experiments suggest that the maximum sf and the factor lci3.2% may be used to compare the intrinsic capability of a disintegrant. study of the swelling process is also important with respect to the pressure force. the porosity of the tablets depends on the deformability of the particles and the porosity has an important role in water transport into the interior of the tablets and hence in the swelling process, too. on the basis of such results, it is possible to choose the pressure force suitable for tableting. if increase of the pressure force causes no change or only a very small change in the sf, it is unnecessary to use a high pressure force during tableting. the described equipment and the developed software are suitable for study of the swelling process and for comparison and characterization of the different disintegrants. references 1. lowenthal w.: j. pharm. sci. 1972, 61, 16951711 2. kanig j. l. and rudnic e. m.: pharm. technol. 1984,8,50-58,61-63 3. bolhuis g. k., van kamp h. v., lerk c. f. and sessink f. g. m.: acta pharm. technol. 1982, 28, 111-114 4. van kamp h. v., bolhuis g. k., de boer a. h., lerk c. f. and lie-a-huen l.: pharm. acta helv. 1986,61,22-29 5. list p. h., muazzam u. a.: pharm. ind. 1979, 41, 459-464 6. caramella c., colombo p., conte u. and la manna a.: drug dev. ind. pharm.1986,12, 17491766 7. colombo p., conte u., caramella c. and geddo m.: j. pharm. sci.1984, 73,791-705 8. ferrari f., geddo m., gazzaniga a., caramella c. and conte u.: s.t.p. pharma, 1988,4,481-484 9. caramella c.: pharm technol. int. 1990, sept. 30-40, oct. 30-37 10. bouiuis g. k., kamp h. v., lerk c. f., gielen j. w., arends a. w. and stunt g. k.: acta pharm. technol.j984,30,24-32 11. rudnic e. m., kanig j. l. and rhodes c. t.: j. phann. sci. 1985, 14, 647-650 12. graf e., ghanem a. h. and mahmoud h.: phann.ind.1985,47, 773-776 13. sakr a., rivera d. and jimenez w.: pharm. ind. 1986,48,522-525 14. wan l. s. c. and prasad p. p.: acta pharm technot1988,34,2~203 15. johnson j. r., wang l-h., gordon m.s. and chowlan z. t.: j. pharm. sci.l991, 80,469-471 16. miseta m., pintye-hodi k.~ szab6-revesz p., szalay l. and sa.ghl p.: pharm. ind. 1993, 55, 515-518 page 69 page 70 page 71 page 72 microsoft word b_01_arpad_r.doc hungarian journal of industrial chemistry veszprém vol. 39(2) pp. 163-167 (2011) investigation of sensible heat storage and heat insulation in the exploitation of concentrated solar energy i. árpád university of pannonia, doctoral school of chemical engineering and material sciences 10, egyetem street, h-8201 veszprém, hungary e-mail: arpad.istvan@hotmail.com mvm erbe power engineering & consulting ltd. 95, budafoki road, h-1117 budapest, hungary this paper analyses the exploitation of solar energy by wholly relying on it to heat homes by 100% solar heating in hungary. it determines the necessary amount of heat and the heat storage capacity and considers the time sequence between charge and discharge. further, it provides a feasible technology for sensible heat storage and it determines the sizes of heat storebuilding, the thickness of heat insulation and it calculates the heat losses of heat storage. on the basis of the results, the paper provides proposals for the method of heat storage and for the technical parameters to be considered for the heat insulation. it describes the application of the heat storage method for district heating and electricity generation. keywords: solar energy, sensible heat storage, heat insulation, 100% solar heating of home, electrical energy generation introduction we have been striving for a long time to be capable of collecting the energy of solar radiation and of storing it. certainly, we would like to store and use solar energy for a long time without suffering any great losses. the question is, whether the collected and stored energy could provide 100% of the homes’ heatingthe whole year round or whether it could generate electricity over several months? to achieve that several problems need to be solved: the flux of solar energy is low. there is no harmony between energy generation and consumption and it is incalculable as a function of time. because of that big energy storage is needed. efficient and economic energy storage for a long time is an unsolved problem. this paper analyses this issue and presents a feasible technological solution of how the buildings could continuously be supplied with heat energy from the direct solar radiation and how the energy must be stored as sensible heat storage and how the heat insulation of the heat storage facilities must be planned [1]. calculations for the size of solar radiation field and for the heat storage capacity the solar radiation, that passes directly through the atmosphere to the earth’s surface, is called direct solar radiation. the period, when the direct radiation is more than 210 w/m2, is called sunny hours. in hungary, the number of sunny hours varies between 1900–2200 hours per year, which is quite long compared to that in the world. the indicated data are based on statistics of several years [2, 3, 4]. the direct radiation is approx. 1000 w/m2 on the surface of the earth in fine weather. this value is lower under cloudy weather conditions and during air pollution. we use in the following calculations the average sunny hours of 400 w/m2 (fig. 1). in a year’s time period, perpendicularly to the direction of solar radiation, we can estimate the amount of the collectable direct solar energy as below: 2 2 2000 3600 400 2880 ( ) h s w year h m mj m year ⋅ ⋅ = = ⋅ ⋅ (1) figure 1: intensities of direct solar radiation 164 heat energy consumption of a family house in a dwelling-house. heat energy is used for heating and hot water production. without detailed explanation of the calculations, we have estimated alltogether 80000 mj heat energy consumption per year for five persons and an average house of cc. 100 m2. that number is equivalent to approx. 2350 m3 natural gas (34 mj/m3). table 1 shows the energy consumption (heating and hot water generation) in each month of a year. as a matter of fact, new houses and block houses have lower energy requirements. the task is to collect the above indicated 80000 mj heat energy and the heat losses of the heat storage “tank”. sizes of the solar field we can collect energy of approx. 400 w on a surface area of 1 m2. this energy can be collected by a surface right-angle to solar radiation in sunny hours and if there are approx. 2000 sunny hours/year in hungary. we can calculate this surface area of solar radiation by using the following formula (the calculation relates to the demand of 80000 mj energy): 2 2 2 80000 400 2000 3600 ( ) 27.75 28 mj yeara j sh s m h m m = = ⋅ ⋅ ⋅ = ≈ (2) this 28 m2 does not include the heat losses. table 1: energy consumption of a dwelling-house per year period (days) sunny hours collectable direct solar energy per m2 [mj/m2] charge [mj] collected solar energy on 27.75 m2 heating [mj] hot water production [mj] discharge [mj] total heat energy requirement amount of energy to be stored [mj] apr (30) 187 269 7470 1840 1200 3040 4430 may (31) 253 364 10110 900 1240 2140 12400 june (30) 267 384 10670 0 1200 1200 21870 july (31) 297 428 11870 0 1240 1240 32500 aug (31) 278 400 11110 0 1240 1240 42370 sept (30) 202 291 8070 260 1200 1460 48980 oct (31) 139 200 5550 1900 1240 3140 51390 ≈52000 mj nov (30) 63 91 2520 9470 1200 10670 43240 dec (31) 40 58 1600 14730 1240 15970 28870 jan (31) 57 82 2280 16830 1240 18070 13080 feb (28) 83 120 3320 12100 1120 13220 3180 mar (31) 136 196 5430 7360 1240 8600 10 year (365) 2002 2883 80000 65390 14600 79990 capacity of heat storage a heat storage “tank” shall be used due to the sequence of time between charge and discharge. table 1 shows the calculating of the capacity of heat storage “tank”. the heat capacity depends on the charge and the discharge. the total capacity of the heat storage “tank” amounts to 52000 mj. this size of heat storage “tank” can ensure heat energy supply for a house all the year round. method of heat storage and sizes of the heat storage “tank” the method of sensible heat storage is the simplest one. we have surveyed many heat storage materials and have chosen magnesite brick. calculations with magnesite brick showed the best results. table 2 shows the properties of the magnesite brick. corundum (95% al2o3) brick is also a very good heat storage material: its density of energy amounts to 3.3 mj/(m3k) and its melting point is 2020 °c. table 2: properties of magnesite brick [5, 6] content application range of temperature δt specific heat j/(kgk) density kg/m3 density of energy mj/(m3k) heat conductivity w/(mk) price $/ton 37–98 % mgo 1–60 % cao and/or cr2o3 65–500 °c (melting point: 2852 °c) 1172 3020 3.54 8.4 (on 500 °c) 100–500 165 we can calculate the mass and volume of magnesite brick from the energy capacity of heat storage “tank” (≈52000 mj), from the planned range of temperature (∆t = 500 – 65 °c = 435 °c) and from its specific heat and density. the following calculation is applicable: qq c m t m c t = ⋅ ⋅δ → = ⋅δ (3.a) 952 10 101997 1172 435 102 jm kgj k kg k m tons ⋅ = = ⋅ ⋅ ≈ (3.b) 3 3 3 102 33,7 3,02 34 m tonsv mtons m v m ρ = = = ≈ (4) this size seems to be a normal value and normal scale. if the end point of maximum temperature were just 430 °c, the size of heat receiver would be 40 m3. however, the 500 °c of maximum temperature is real too, scilicet the thermooils (heat transfer fluids) work on 580 °c (1060 °f) in the existing concentrated solar power plants. the temperature difference, needed to the heat exchange, is ensured. heat insulation and heat losses heat store-building made of bricks hereinafter, the heat storage “tank” will be named as heat store-building because there is no tank in the construction. we analyise here only a cubic shaped heat store-building. the construction is shown in fig. 2. we make a difference between the bottom and the upper parts of the store-building as follows [7]: figure 2 1 − external wall, 2 − coat of heat insulation from rock wool, 3 − magnesite bricks, 4 − concrete pad, 5 − gravel bed, 6 − pipe of heat transfer fluid the bottom part is in contact with the soil and the upper parts of the store-building are in contactwith the the ambient air. the upper parts are built up from lateralwalls and from the roof. we calculated these parts (wall and roof) in the same way. the thermal resistance of the upper part and of the bottom part (rcond = δ/λ, respectively rconv = 1/α) are indicated below: joint 1 1 conv rad r α α α = = + (5) ruppers = rcond + rjoint (6) ruppers = rins + rbrick + rjoint (7) rbottom = rconcret + rgravel + rsoil (8) the value of the heat transfer coefficient between the external side of the wall and the ambient air is α = 24 w/(m2k). this value has been derived from a hungarian architectural standard (msz 04-140-02). the foundation of the store-building would be constructed from cellular concrete: its density is 700 kg/m3 and its bearing strength is more than 150 n/m2. table 3 shows the material properties of the storebuilding, which we have used in the calculation process [6, 7, 8,]. table 3: applied value of λ thermal conductivities and δ coating thickness rock woll brick/barge stone cellular concrete gravel soil °c w/(mk) 500−400 0.180 400−300 0.100 300−200 0.070 200−100 0.049 <100 0.038 0.64 w/(mk) < 0.17 w/(mk) 0.35 w/(mk) 1.3 w/(mk) δins= to be determined δbrick = 0.12 m δconcrete = 0.6 m δgravel = 0.3 m δsoil = 0.4 m 166 the thermal conductivity of the heat insulation (rock wool) increases significantly with the rise of temperature λ(t). the curve can be seen in fig. 3. the above mentioned function λ(t) has been considered in the calculation process. actually, in every month we experienced various heat resistances. table 4 shows the values of the ambient temperature and the soil temperature at a dept of 1 m. figure 3: thermal conductivity of rock wool versus temperature heat losses of the heat store-building we calculated the heat current as heat conduction through the flat wall. the heat transfer between the external surface of the wall and the ambient air (at the joint) equals to the conductive heat current in the wall. if we know the temperature of the external surface of the wall, the internal temperature δtconductiv = tmagnesite brick – toutside wall (9) δtconductiv = tint – text (10) and the thickness of heat insulating material δins, we are able to calculate the heat current q& [w/m2]: transfer cond transfer cond t tq és q r r δ δ = =& & (11,12) ;cond transfer cond ins transfer t r r q t δ δ ⋅ = → δ & (13) q q a= ⋅& (14) we designed the maximum internal temperature (tint) and the maximum external temperature of the wall’s surface area (text) to be 16 °c under conditions in october. further, we calculated 40 cm thick insulating material (rock wool), which represents a realistic value. table 4 shows the heat losses suffered in each month and all the year round. the calculations were performed on one house (with a store building volume of 34 m3), on 50 houses (with a store building volume of 1700 m3) and on 100 houses (with a store building volume of 3400 m3). it is a remarkable result that the specific heat losses fall with increasing store-building size (m³). the amount of decrease is remarkable. the cause of that is that the specific surface “a/v – surface/volume” decreased. further, we calculated the following values: the specific heat loss is as high as 14% in the case of store-building of 500 dwelling-houses ( with size of 17000 m3) and it is as high as 11% in the case of 1000 dwelling-houses (34000 m3)! we analysed the dependence of specific surface area “a/v” on the volume “v”. we performed the analysis by using a cube. table 5 shows the results of the volume (v [m3]) and the specific surface (a/v [m2/m3]) with different lengths of the edge of the cube. then we graphed them in fig. 4. table 4: the heat losses of different sized heat store-buildings with 40 cm thickness of the rock wool 34 m3 1700 m3 3400 m3 tint [°c] text [°c] tamb [°c] qupper [w/m²] tsoil [°c] qbottom [w/m²] qtotal [gj] qtotal [gj] qtotal [gj] apr (30) 102 12 12 8 10 20 1.6 22 35 may (31) 168 18 17 16 14 33 3.2 43 68 june (30) 247 21 20 28 18 49 5.1 70 111 july (31) 335 24 22 45 20 67 8.2 111 177 aug (31) 417 24 21 69 21 84 12.1 164 260 sept (30) 472 21 17 94 19 97 15.4 209 332 oct (31) 492 15 11 104 14 102 17.5 237 377 nov (30) 424 9 6 74 10 88 12.5 169 268 dec (31) 305 4 2 40 7 63 7.4 100 159 jan (31) 174 1 0 18 5 36 3.5 48 76 feb (28) 91 2 2 8 4 19 1.5 20 32 marc (31) 65 6 6 5 5 13 1.1 14 23 total heat losses of a year [gj] 89.1 1209 1919 total heat consumption of a year [gj] 80.0 4000 8000 heat losses versus heat consumption per cent [%] 111% 30% 24% 167 table 5: the specific surface area of a cube versus its size a [m] 1 2 3 4 5 6 7 8 9 10 20 30 40 50 a [m²] 6 24 54 96 150 216 294 384 486 600 2400 5400 9600 15000 v [m³] 1 8 27 64 125 216 343 512 729 1000 8000 27000 64000 125000 a/v [m²/m³] 6.00 3.00 2.00 1.50 1.20 1.00 0.86 0.75 0.67 0.60 0.30 0.20 0.15 0.12 the next algebraic formula describes the function of fig. 4: 3 6y x = (15) figure 4: specific surface versus volume of cube conclusions the paper sets out that it is possible to store solar energy all the year round or for a long period. the stored heat energy stored can meet the total heating demand of the houses or can also generate electricity in hungary. we can keep the heat losses at low level (<20%). certainly we must consider some technical facts. heat energy shall be stored as below: at high temperature: the higher the better, using materials with high energy density [mj/(m3k)] (using one of solid materials, for example magnesite brick) and in store-building whose size is big enough, because the heat losses shall be low. we would emphasize here that the increase of size, up to a certain size, is one of the best heat insulation technique. the heat storage in solid material is easy and safe. no steel tank is used and the brick isn’t flammable and explosive. in my opinion this method should be used for district heating and for electricity generation. our next goals are: to determine the optimum size of the heat storebuilding and the thickness of heat insulation coat [9, 10] and to investigate different heat transfer materials. we would like to achieve higher temperature in the store-building. perhaps gaseous materials would be good heat transfer materials from the solar trough to the store building. references 1. i. árpád: investigation of the sensible heat storage and the heat insulation in the exploitation of solar energy (in hungarian). 19th international conference on mechanical engineering april 28 – may 1 2011. oget 2011. p. 31–34, sumuleu ciuc, romania 2. gy. major, a. v. morvay, f. weingartner, o. farkasné takács, zs. zemplényiné tárkányi (eds.): solar radiation in hungary (in hungarian). official publication of hungarian meteorological service, no. 10, budapest, hungary, 1976, isbn 9637701052 3. homepage of hungarian meteorological service, data of climate, www.met.hu 4. i. barótfi: exploitation of solar energy (in hungarian). handbook for users of energy. környezettechnikai szolgáltató kft., budapest, hungary, 1994 5. i. szűcs, á. b. palotás, n. hegman: effect of inhomogeneous radiation coefficient on the surface temperature field of refractory lining using thermovision (in hungarian). sciences of material and metallurgy, research report, miskolc, hungary, 2000 6. f. tamás (ed.): handbook of silicate industry (in hungarian). műszaki könyvkiadó, budapest, hungary, 1982 7. k. c. kwon: engineering model of liquid storage utility tank for heat transfer analysis. international joint power generation conference, minneapolis, 1995 8. brochures of rockwool. insulation of high temperature applications. rockwool hungary kft., budapest 9. i. timár, i. árpád: optimization of pipes’ insulation. (in hungarian). energiagazdálkodás 27(10), (1986), 449–459, budapest, hungary 10. i. timár: optimierung ebener fachwerke mit mehreren zielfunktionen. forschung im ingenieurwesen, 68, (2004), 121–125 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 /colorconversionstrategy /cmyk /dothumbnails false /embedallfonts true /embedopentype false /parseiccprofilesincomments true /embedjoboptions true /dscreportinglevel 0 /emitdscwarnings false /endpage -1 /imagememory 1048576 /lockdistillerparams false /maxsubsetpct 100 /optimize true 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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/pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word 00.00 inner cover.docx the hungarian journal of industry and chemistry (hjic) formerly (until 2012) the hungarian journal of industrial chemistry the hjic is an international periodical that focuses on results of fundamental and applied research in the field of • biotechnology • chemical engineering science • chemical processes • energetics • environmental chemistry • environmental engineering & technology • industrial management • material science • mechanical engineering • mechatronics • process & system engineering • recycling in the form of original papers, technical reports, reviews, communications, and conference proceedings written in english. editorial board editor-in-chief: róbert k. szilágyi department of chemistry and biochemistry, montana state university, bozeman, mt, u.s.a. associate editors: jános abonyi department of process engineering, university of pannonia, veszprém, hungary dezső boda department of physical chemistry, university of pannonia, veszprém, hungary norbert miskolczi mol department of hydrocarbon and coal processing, university of pannonia, veszprém, hungary dóra rippel pethő department of chemical engineering science, university of pannonia, veszprém, hungary editors: katalin bélafi-bakó research institute of bioengineering, membrane technology and energetics, university of pannonia, veszprém, hungary peter czermak institute of bioprocess engineering and pharmaceutical technology, mittelhessen university of applied sciences, giessen, germany dénes fodor institute of mechanical engineering, university of pannonia, veszprém, hungary maria gavrilescu department of environmental engineering and management, gheorghe asachi technical university of iasi, romania dirk gillespie department of molecular biophysics and physiology, rush university medical center, chicago, u.s.a lászló gubicza research institute of bioengineering, membrane technology and energetics, university of pannonia, veszprém, hungary jenő hancsók mol department of hydrocarbon and coal processing, university of pannonia, veszprém, hungary jiří klemeš centre for process integration and intensification, university of pannonia, veszprém, hungary zoltán kovács department of management, university of pannonia, veszprém, hungary jános kristóf department of analytical chemistry, university of pannonia, veszprém, hungary istván szalai institute of physics and mechatronics, university of pannonia, veszprém, hungary jános szépvölgyi research centre for natural sciences, university of pannonia, veszprém, hungary gyula vatai department of food engineering, corvinus university of budapest, hungary gábor veress federation of technical and scientific societies – mtesz budapest, hungary ibolya zsoldos department of material science and technology, széchenyi istván university, győr, hungary editorial office: university of pannonia, p.o. box 158, veszprém, 8201 (hungary) tel.: +36 (88) 624-746, e-mail: hjic@almos.uni-pannon.hu; web: hjic.mk.uni-pannon.hu felelős szerkesztő: szilágyi róbert károly nyelvi lektor: matthew chen kiadja: pannon egyetem, 8200 veszprém, egyetem u. 10. elektronikus terjesztés: de gruyter open (formerly versita), warsaw, poland levélcím: h-8201 veszprém, postafiók 158, tel.: (88) 624-000 felelős kiadó: a pannon egyetem, mérnöki kar dékánja (prof. dr. szalai istván, ph.d.) editorial preface in addition to food and energy, access to water is a strategic issue influencing everyday life of over 7 billion people worldwide. although water is available in vast quantities on earth, the amount of fresh water is only approximately 3% of the total. about 68% of fresh water is captured in polar ice caps and glaciers, and 30% is present in the soil as ground water. the amount of surface water in lakes, rivers, and swamps is only 0.3%. currently humans consume 54% of the renewable fresh water. this figure is predicted to increase to 70% by 2025. it is anticipated that by 2050 the fresh water demand will increase by an additional 70%. thus, the shortage of water will be very soon a critical issue leading to local and even global geopolitical conflicts unless effective measures are taken. the inefficient use of or simply wasting water in the developed countries makes this delicate issue even more complicated. in a modern household, 60% of good quality water is used to flush toilettes and for washing, while only 20% is utilised in the kitchen, and another 20% in the bathroom. the desired “green growth with blue sustainability” requires immediate actions for handling the consequences of climate change (floods, droughts) and environmental pollution. wastewater should be considered as “water wasted”. thus, a good water management must find balance between economy, society, and environment via a series of actions, such as analysis, monitoring, and implementation. since approximately 80% of water discharged worldwide is polluted, there is a need for resource-oriented science and technology that encourages green innovation. this must be done by simultaneously keeping in mind development in engineering, financial resources, and social acceptance. the growing demand of industry for water can only be handled with the introduction of closed loop technologies, where water is reused and recycled. the water issue is more and more in the mainstream of politics as exemplified by the budapest water summit in 2013 and international conferences since then. there is a chance now for making radical and innovative actions with the proper combination of governance, technology, and finance for eliminating imbalance in water use. the university of pannonia in veszprém, hungary was the first to introduce environmental engineering education in hungary. it took the leading role in environmental monitoring and in the development of expert systems for wastewater treatment. in june 2014 the „first national conference on water chemistry and technology” was held in veszprém in the frame of the támop-4.1.1.c-12/1/konv-2012-0015 project supported by the european union and co-financed by the european social fund. in this thematic issue of the hungarian journal of industry and chemistry, selected papers are presented from the conference program that represent some of the important topics of the water sector: e.g. heavy metal removal from waste water and monitoring the bioavailability of heavy metals in river catchment areas; nitrogen removal from municipal waste water; mineralisation of herbicides in water; equilibrium calculations to solve complex aqueous speciation problems; photocatalytic remediation of pesticide-contaminated ground water; purification of dairy-food waste water via biofilms, and novel plasma spectroscopic methods in the analysis of aqueous solution. we do hope that these topics will be of interest to the broad scientific community. veszprém, june 2015 prof. dr. jános kristóf, d.sc. guest editor of the thematic issue project leader dr. viola somogyi, ph.d. guest editor of the thematic issue conference organiser de gruyter open hung. j. ind. chem., 2015 43(1), 1–53 table of contents heavy metal balance in a communal wastewater treatment plant gábor gulyás, viktória pitás, bence fazekas, and árpád kárpáti .............................. 1–5 doi: 10.1515/hjic-2015-0001 multi-elemental inductively coupled plasma-optical emission spectroscopic calibration problems of the sequential extraction procedure for the fractionation of the heavy metal content from aquatic sediments györgy heltai, ilona fekete, gábor halász, katalin kovács, márk horváth, anita takács, norbert boros, and zoltán győri ........................................................ 7–13 doi: 10.1515/hjic-2015-0002 nitrogen removal controlled by an ammonium-analyser at the north pest wastewater treatment plant zsófia kassai ................................................................................................................ 15–18 doi: 10.1515/hjic-2015-0003 evaluation of the heavy metal content of the upper tisza river floodplain soils over the last decade zoltán győri, norbert boros, péter sipos, emese bertáné szabó, katalin kovács, márk horváth, anita takács, and györgy heltai ...................................... 19–23 doi: 10.1515/hjic-2015-0004 toxicology aspects of the decomposition of diuron by advanced oxidation processes tünde alapi, gergő simon, gábor veréb, krisztina kovács, eszter arany, krisztina schrantz, andrás dombi, and klára hernádi ............................................ 25–32 doi: 10.1515/hjic-2015-0005 organisation of the analytical, stoichiometric and thermodynamic information for water chemistry calculations rita földényi and aurél marton ................................................................................ 33–38 doi: 10.1515/hjic-2015-0006 groundwater remediation using biological and photocatalytic methods sándor guba, viola somogyi, and erzsébet szabóné bárdos .................................. 39–43 doi: 10.1515/hjic-2015-0007 biological purification of chemically pre-treated dairy wastewater before discharge into a municipal sewage systems gábor gulyás, bence fazekas, regina varga, and árpád kárpáti ........................... 45–48 doi: 10.1515/hjic-2015-0008 study of the interference effects of aluminium on the atomand ion-lines of alkaline earth metals in aqueous solutions using an icp spectrometer with axially viewed plasma olivér bánhidi .............................................................................................................. 49-53 doi: 10.1515/hjic-2015-0009 hungarian journal of industry and chemistry vol. 43(1) pp. 1–5 (2015) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2015-0001 heavy metal balance in a communal wastewater treatment plant gábor gulyás,* viktória pitás, bence fazekas, and árpád kárpáti department of environmental engineering, university of pannonia, egyetem u. 10, 8200 veszprém, hungary heavy metal removal from a municipal wastewater treatment plant was evaluated in the given study. the aim of the work was to find water or sludge streams in the technology that could be treated separately for heavy metal removal to maximise the efficiency of the entire treatment. the results proved that in the plant studied 70–80% of the metal content was discharged. only 5–20% was retained in the digested sludge. a small percentage of the metal content of the influent could only be measured in the primary and secondary sludges. otherwise, there were very similar metal concentrations in these sludge streams. the reject water exhibited an inconsiderable level of metal recycling in the technology, no more than 2–3% of the influent load. some 2–10% of the heavy metal content of the inlet was removed from the sand trap. we did not find the separate heavy metal removal from the sludge streams efficient as most of the heavy metal load finally was discharged from the treatment plant with the treated effluent into the recipient. keywords: activated sludge, heavy metals, mass balance, municipal wastewater 1. introduction industrial discharges into municipal wastewaters from metal refining and other industrial sources are hazardous with regard to purification process due to their heavy metal contents. that is why nowadays heavy metal removal from these discharges at the site of the waste production is strictly regulated. the next possibility for removing heavy metals from wastewater is the activated sludge process of the publicly owned treatment works (potws) [1]. the mechanism of heavy metal removal in the activated sludge process is not completely understood yet [2]. even the inhibition effects of some metals for specific microorganisms are not properly known. that is why our study tried to summarise the heavy metal removal of an activated sludge plant on the basis of its detailed mass balance. we excluded from this study the influence of any technological parameters like oxygen supply, ph, sludge age, complexing agents, etc. or the microbial composition of the working biomass [2–3]. an overview of the possibility of the removal of metals from sludges of sewage treatment plants has already been presented [2, 4]. rather different removal efficiencies were published from many measurements all over the world. these studies concluded that around 70% of the mn and cu load can be accumulated in the activated sludge, while 50–60% of the cr, cd, pb, fe, ni, and zn will leave the plant as it is discharged into the recipient with the treated *correspondence: gulyasg@almos.uni-pannon.hu effluent. it is well known, that some special forms of these heavy metals in the sludge or activated sludge process are more critical than their total concentrations [5]. in our study, we measured the heavy metal concentrations in the different liquid and sludge streams of a hungarian wastewater treatment unit in veszprém treating municipal effluent relatively free of industrial metal discharges. we calculated a total mass balance for the plant and evaluated the feasibility of the separate removal of some metal contaminants from the sludge residue to produce more valuable agricultural soil amendment. 2. materials and method the studied activated sludge process treats daily 13,000 m3 of sewage, while its nominal daily capacity of 21,000 m3 shows considerable underutilisation. it has a proper digestion capacity for the primary and secondary sludge of the main stream. we considered that it is important to measure the heavy metal concentrations at the inflow and in purified effluent in some mixed liquid streams and the final dried sludge as well. from the material balance established from these data, it seemed possible to decide about the reality of the use of some separate heavy metal removal steps in the treatment line. to establish a heavy metal mass balance, we took samples several times from the liquid, mixed sludge and dried sludge as well. the sampling points in the technology can be seen in fig.1. gulyás, pitás, fazekas, and kárpáti hungarian journal of industry and chemistry 2 samples 1 to 4 were collected during the day every other hour. samples 5–8 were collected when sludge pumping or drying was in operation. these were homogenised, cooled, and stored as prescribed by hungarian standard msz 318-2:1985 protocol. the dissolution of the metal content was followed by the atomic absorption spectrophotometric measurement for eight (cd, co, mn, ni, cr, cu, fe, and pb) metal contaminants. from these data, the metal content of the sludge phases was determined for the suspended (ss) and total solid (ts) contents for samples 5–8. it was assumed that the dissolved heavy metal content of the liquid phase equals to that of the treated effluent in samples 6 and 7 and with that of the reject water in sample 8. for measuring ss and ts contents of the sludge containing samples (no. 6–8), we used the hungarian standard msz 260/3-73 standardised method. the average daily amount of the reject water had to be calculated for the calculation of the material balance from these measured values, as the flow was not measured in the plant. dissolution of the metals from the different samples was carried out by a mars 6 microwave digester. the temperature program of the digester was optimised in a preliminary study [6]. for the addition of chemicals for digestion, we followed the recommendation of hungarian standard msz 1484-3 protocol (chapter 4.2.2.3). before digestion, 3 ml of 68% hno3 and 9 cm3 of concentrated hcl was given to every 0.5 cm3 sample. the microwave digestion of the sludge samples was carried out according to the same heating program for all samples. after 20 min of heating, digestion was completed in 10 min at 180 ºc. after digestion and dilution, the heavy metal concentrations were measured by a thermo scientific ice 3000 atomic adsorption spectrophotometer. 3. results and discussion during the control study, the samples were taken over three one week-long periods. we measured the weekly homogenised samples stored in a refrigerator a week later than sampling in triplicates. the average metal contents for the entire measurement period are shown in table 1. as shown in table 1, there was no pb detected in the influents of the wastewater treatment plant. the cd concentration was low (0.03 mg dm-3). mn and ni levels were a bit higher within the range of 0.08–0.15 mg dm-3. co exhibited a slightly higher concentration (0.1–0.3 mg dm-3) than mn and ni. the cu content was constant at around 0.2 mg dm-3. these values are as expected from our earlier measurements at this plant. the fe had the highest concentration in the inflow (up to 356 mg dm-3) and it remained similarly high relative to the other metal contaminants in the outflow from the plant. to calculate the heavy metal mass balance in the process, the flow rates and sludge production had to be taken into account. as the hydraulic retention time (hrt) in the plant was more than one day and the sludge age was nearly 20 days, we used average figure 1. the technology and sampling points for checking heavy metal concentrations. heavy metal balance in a communal wastewater treatment plant 43(1) pp. 1–5 (2015) doi: 10.1515/hjic-2015-0001 3 numbers for the calculation of the balance. the same was used for the primary and secondary sludge streams, as their removal was not continuous, but the material we examined had been properly homogenised. the average daily values for the streams are summarised in table 2. some parameters required for the calculation were not measured at the plant. the average daily quantity of the reject water was calculated from the ss concentration of the digested sludge stream entering the drying centrifuge and that of the dried digested sludge. the quantity of the dried digested sludge was calculated from the volume of the sludge transported from the centrifuges to the solar drying part of the plant and its average dry solid content determined. this resulted in negligible errors (less than 0.1 g/g) since the dissolved material content of the sludge water or reject water was low enough. flows were calculated (table 3) using the concentrations and daily flows of heavy metals in these sewage and mixed liquids (tables 1 and 2). in the sewage entering the plant, the concentration of the different heavy metals did not change considerably. as a result, their mass stream had to change according to the volumetric load of the plant. this was not true for the sludge streams, as the plant had a great equalisation for the total sludge mass. from tables 1 and 3, it can be seen that the concentrations of the measured heavy metals did not change or decrease significantly in the sewage streams or even in the treated effluent. at the same time, the sludge containing streams containing around 1 and 3–4% dry material showed much higher heavy metal levels. heavy metals removed from the influent (dissolved and solid) were expected to concentrate in the sludge phase of these streams and in the dried sludge as well. this means that the removal of heavy metals in this treatment facility was very poor. we hypothesise that the low specific organic material load (estimated daily value of 0.2 g koi per g mlss) and the high sludge age (more than 20 days) may result in the dissolution of the heavy metals into the liquid phase. from data in table 1, the leftover heavy metal content of the different streams can be calculated. the results are shown in table 4. according to the results, cd was not removed from the sewage by the activated table 1. the total heavy metal concentrations (mg dm-3) of the liquid and sludge-containing streams of the activated sludge process (variation in concentrations is in the order of ±31%). samples cd co mn ni cr cu fe pb raw wastewater 0.023 0.169 0.123 0.123 0.185 0.231 7.938 <0.001 after grit removal 0.023 0.166 0.105 0.120 0.174 0.223 7.819 <0.001 primary clarified wastewater 0.022 0.161 0.094 0.109 0.168 0.214 7.168 <0.001 treated effluent 0.021 0.152 0.062 0.107 0.161 0.202 0.079 <0.001 reject water 0.005 0.128 0.093 0.048 0.160 0.095 10.147 <0.001 thickened primary sludge 0.021 0.462 1.973 0.414 0.565 0.750 58.509 <0.001 thickened secondary sludge 0.019 0.673 2.709 0.633 0.696 1.030 355.813 <0.001 table 2. the main technological parameters (volumes are in m3, solid content in mass percent) used to calculate heavy metal mass-balances (variation in flow rates is in the order of ±22%). volume of wastewater thickened sludge streams sludge drying influent effluent volume dry solid content i. stream ii. stream total common primary secondary before after 7250 6500 13750 13190 112 134 243 2.4 23 table 3. daily heavy metal mass (in grams per day) in the streams shown in figure 1. samples cd co mn ni cr cu fe raw wastewater 150.0 1,100.0 800 800.0 1,200.0 1,500.0 51,600 after grip removal 149.0 1,080.0 682 778.0 1,132.0 1,448.0 50,826 primary clarified wastewater 144.0 1,048.0 614 706.0 1,093.0 1,388.0 46,595 treated effluent 139.0 991.0 400 697.0 1,049.0 1,310.0 516 reject water 1.6 38.5 28 14.4 48.0 28.5 3,044 thickened primary sludge 2.4 51.7 221 46.4 63.3 84.0 6,553 thickened secondary sludge 1.5 42.9 170 52.8 78.0 82.5 44,170 digested dried sludge 2.5 90.2 363 84.8 93.3 138.0 47,679 table 4. relative quantity of the heavy metals in streams measured as mass percentage of the influent concentrations in raw wastewater (100%). samples cd co mn ni cr cu fe after grit removal 99.0 98.1 85.2 97.2 94.3 96.5 98.5 primary clarified wastewater 96.2 95.2 76.7 88.3 91.1 92.5 90.3 treated effluent 92.5 90.1 50.0 87.1 87.4 87.3 1.0 reject water 1.3 3.5 3.5 1.8 4.0 1.9 5.9 thickened primary sludge 1.6 4.7 37.6 5.8 5.3 5.6 12.7 thickened secondary sludge 1.0 3.9 31.3 6.6 6.5 5.5 85.6 gulyás, pitás, fazekas, and kárpáti hungarian journal of industry and chemistry 4 sludge process. it was absent in the reject water of the plant and only 1.0+1.6% of the cd load was adsorbed in the final sludge produced. the load of co, mn, ni and cu was one order of magnitude bigger within a narrow daily load range (800–1,600 g per day). a significant portion of all these metals left the plant with the treated effluent. no more than 4–5% of the co remained in the dried sludge according to our measurements and only 1–3% of the total load was recycled to the inlet point with the reject water. approximately less than half of the mn remained in the purified water and the rest was concentrated in the dried sludge. around 1.5% of the mn content of this sludge was recycled at the inlet with the centrifuge water. the metal adsorption of the primary and secondary sludge seemed to be similar, which also suggested that about three quarters of the inlet mn load remained in the sewage stream after primary purification. in the case of ni, only 15–20% remained in the solid residue and one tenth of that was recycled at the inlet with the reject water. the ni seemed to be adsorbed and present in the two types of sludge in a similar ratio. cr seemed to be bound to the primary sludge while only a small portion was removed by the biological step. these two stages of the sludge processes could not remove more than 5% of the initial level. however, this removal efficiency seems to be enough, since the inlet concentration is low enough (< 0.5 mg dm-3) the removal efficiency of the treatment for cu seemed better than for other metals, but it was no more than 15–20%. most of the removed cu was captured in the secondary sludge. it has been observed before that some municipal sewage sludge contains high concentrations of cu due to the high cu content of the raw sewage. according to the given study, fe exhibits the highest concentration in the sewage, around 500 times greater than the other metals studied here. the fe is oxidised in the activated sludge process and is present in the biomass as hydroxide. the removal efficiency was 99% according to the measurements. table 3 indicates that sand removal has practically no influence on the metal content of the sewage. in the primary purifier, metal removal is poor except for the cases of mn and fe. removal of metals within the secondary sludge was a bit more efficient than within the primary one. only mn was better adsorbed onto the biomass (around 50%). however, fe was almost totally removed within the sludge phase (99% removal). concentrations of the other metals studied decreased by only a modest 5–15%. depending on the sludge removal from the digesters to centrifuges the average daily reject water quantity is around 200 m3. with this flow only 2–3% of the heavy metal load is recycled into the sewage stream entering the plant. this is such a small percentage that separate metal removal from that stream is not needed. however, the biggest problem of this sewage treatment facility is the poor removal of the heavy metals within the sludge. a similar average removal of heavy metal pollutants from the sewage can be seen from the inflow and treated effluent concentrations in table 1 and the removal percentages of the metals in different processing steps in table 4. from other investigations, we learnt that around half or a slightly greater proportion of these metals can be removed within the sludge residue. in our studies, we could not measure such high levels of removal neither in the primary nor secondary sludges. moreover, only a small ratio of the metal content of the raw sludge can be dissolved during anaerobic digestion. according to our measurements, most of the heavy metals left the plant within the effluent. changes to the total heavy metal content of the different streams in the plant tested are graphically illustrated in fig.2 for most of the metals studied here. fe is an exception, as it is efficiently removed within the different sludge fractions. it cannot be dissolved even in the digester, its hydroxides and sulphides of limited solubility are strongly adsorbed by the bioproduct of the treatment. fig.2 clearly indicates that heavy metals are recycled within the reject water in a small ratio. the dried digested sludge also removed a very small ratio of the sewage load. 4. conclusions according to our measurements in an activated sludge at a publicly owned municipal sewage treatment plant, figure 2. removal of the heavy metals in the activated sludge of a publicly owned treatment works (percentages indicate the average daily quantities relative to the inflow values for the studied metal except fe). heavy metal balance in a communal wastewater treatment plant 43(1) pp. 1–5 (2015) doi: 10.1515/hjic-2015-0001 5 the removal of heavy metals can be moderate, which is far from the removal efficiencies published by previously. a large proportion of the heavy metal content of the inflow sewage remains in the aqueous phase and leaves within the treated effluent. only a minor ratio of approximately 5-15% is adsorbed in the sludge or taken up by the biomass produced in the treatment. the primary and secondary sludges exhibited similar heavy metal removal efficiencies except for iron, which is mainly removed by the secondary sludge. the heavy metal content of the mixed primary and secondary sludges decreased by a small extent (5-15%) during digestion. the reject water containing the dissolved metals exhibited such low metal concentrations that treatment of it separately does not seem to be economical. it contains only 2–3% of the total heavy metal load of the plant. at the same time 80–90% of that leaves the plant within the treated effluent. consequently, we could not find high heavy metal concentrations in the dried digested sludge of this plant. the sludge reprocessing and reuse pose no problems in the plant with respect to heavy metal content. the low influent concentrations of the heavy metals at the same time can be correlated with the merely pure municipal effluent from the small town and its surrounding villages. acknowledgement this research was financed by the baross gábor project of 2009-2010 “infrastructure of research development kd_infra_09-szviszap (qualification of the sewage sludge of the hungarian publicly owned treatment works for possible decrease of their heavy metal content)”, hungarian national research and technology office (national innovation office). references [1] lester, j.n.: significance and behaviour of heavy metals in wastewater treatment processes. i. sewage treatment and effluent discharge, sci. total environ., 1983 30, 1–4 10.1016/0048-9697(84)90340-1 [2] karvelas, a.; katsoyiannis, a.; samara, c.: occurrence and fate of heavy metals in the wastewater treatment process, chemosphere, 2003 53, 1201–1210 10.1016/s0045-6535(03)00591-5 [3] özbelge, t.a.; özbelge, h.ö.; tursun, m.: effects of hydraulic residence time on metal uptake by activated sludge, chem. engng. proc., 2005 44, 23–32 10.1016/j.cep.2004.04.004 [4] stephenson, t.; jester, j.n.: heavy metal behaviour during the activated sludge process i. extent of soluble and insoluble metal removal, sci. total environ., 1987 63, 199–214 10.1016/00489697(87)90046-5 [5] álvarez, e.a.; mochón, m.c.; sánchez, j.c.j.; rodríguez, m.t.: heavy metal extractable forms in sludge from wastewater treatment plants, chemosphere, 2002 47, 765–775 10.1016/s00456535(02)00021-8 [6] gulyás, g.; pitás, v.; kárpáti, á.: measuring the heavy metal concentrations of digested dewatered sewage sludge with the help of microwave digestion, maszesz newsletter, 2013 (3–4), 3–11 (in hungarian) hungarian journal of industry and chemistry vol. 43(1) pp. 7–13 (2015) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2015-0002 multi-elemental inductively coupled plasma-optical emission spectroscopic calibration problems of the sequential extraction procedure for the fractionation of the heavy metal content from aquatic sediments györgy heltai,1* ilona fekete,1 gábor halász,1,2 katalin kovács,1 márk horváth,1,2 anita takács,1 norbert boros,3 and zoltán győri2 1 department of chemistry and biochemistry, szent istván university, pater k. u. 1., gödöllő, 2100, hungary 2 regional knowledge centre, szent istván university, pater k. u. 1., gödöllő, 2100, hungary 3 department of environmental and chemical engineering, university of debrecen, ótemető u. 2-4., debrecen, 4028, hungary for the characterisation of the environmental mobility of heavy metal contamination in aquatic sediments, the eu bureau of reference has proposed a fractionation by sequential extraction procedure. for its validation, the crm-701 sample is available containing cd, cr, cu, ni, pb, and zn. in this paper, the matrix-matched calibration problems are presented. a multi-elemental inductively coupled plasma-optical emission technique is employed for the detection of heavy metals in the extracts. it was established that the sensitivities are strongly influenced by the extractants, which causes significant matrix effects: the sensitivities are strongly influenced by the solvents applied in extraction steps; the summarised recoveries show an acceptable agreement with the certified values; however, in the individual extraction steps for certain elements significant differences may occur due to the neglected interferences. therefore, further optimisation is required utilising the flexible line selection possibility offered by the horiba jobin yvon activa-m instrument. keywords: fractionation, sequential extraction, multi-elemental icp-oes, matrix-matched calibration, heavy metal contamination, sediments 1. introduction environmentally toxic elements, such as heavy metals, are the most significant inorganic pollutants. the role of different chemical elements in food production has been an important question of agrochemical research since the middle of the nineteenth century. numerous extraction methods have been developed for determining biologically available fractions of nutritionally relevant elements in soils. environmental researchers have confronted similar problems over the last few decades of the twentieth century in characterising the humanand eco-toxicological impacts of increasing heavy metal pollution. this challenge has created new requirements for analytical methodology and contributed to the development of speciation analytical chemistry. this scientific discipline provides the foundation for the evaluation of toxicological impacts of chemical elemental species detectable in environmental systems [1,2]. in such procedures, the original physico-chemical structural forms of chemical elements present in the system must be preserved during sampling and sample preparation. then, appropriate separation methods must be applied before element specific analytical detection (fig.1). *correspondence: heltai.gyorgy@mkk.szie.hu the european union established the european virtual institute for speciation analysis in 2002 for promoting cooperation, collection, reviewing, and discussion of information and knowledge related to chemical speciation analysis (www.speciation.net). attention was drawn to the mobility and biological impact of heavy metals in environmental systems influenced by their chemical speciation. biological risk assessment of contaminated areas therefore requires the total speciation of all chemical elements present in the system. however, due to the complex structure of solid environmental samples (e.g. soils, sediments, gravitation dust, mining waste, etc.), these analytical tasks in practice cannot be fully completed. as a compromise, the fractionation of the heavy metal content according to environmental mobility and estimation of biological availability by sequential extraction procedures have become the main research approaches. papers published in this area and their citations exponentially increased in the period of 1995 figure 1. scheme of the speciation analysis procedure. sampling preservation of the intact species preparation extraction separation analysis detection of the elemental species heltai, fekete, halász, kovács, horváth, takács, boros, and győri hungarian journal of industry and chemistry 8 and 2013: from 200/year to 700/year; according to related citations from 1000/year to 19,000/year based on thomson reuters, web of science database. a primary risk assessment of heavy metal contamination in the soil/water/atmosphere system was based on the fractionation of metallic element content of environmental samples according to their environmental mobility. the term “fractionation” was recommended by the iupac in 2000 [2]. the mobility of an element according to the different solubilities of different binding classes can be estimated by solvents sequentially applied containing physico-chemically increasingly aggressive reagents [3,4]. in agricultural chemistry, the serial single step strategy (fig.2), in environmental chemistry the strategy of sequential extraction has become dominant (fig.3). the first sequential extraction procedure for the characterisation of the mobility of heavy metals in aquatic sediments was developed by tessier et al. [5], who classified the metal content of sediments according to the solubility and binding forms of metallic species as presented in scheme 1. based on this essential work [5], numerous 5-8step sequential extraction schemes have been developed by which the original chemical structures (binding forms) are gradually dissolved and/or decomposed [9]. the complete duration of these procedures is 5–6 days, while the duration of the batch leaching steps is determined by a long setup time of solubility and heterogeneous chemical equilibria. the proposal for a 3(+1)-step sequential extraction procedure issued by bcr in 1993 is a simplified version of the above-mentioned schemes [6], but it is still time-consuming and labourintensive. as shown in scheme 1, the water soluble, weakly adsorbed, and carbonate-associated metal fractions are extracted simultaneously by acetic acid in the first leaching step. in the second step, the metal fractions associated with reducible fe and mn oxides are produced after reduction by hydroxylamine. a fraction of metals coordinated to organic molecules and associated with sulphides is extracted after oxidation by h2o2 in the third step. in the extra step, the residual fraction can be obtained by means of digestion with aqua regia or hno3/h2o2. re-adsorption of extracted metals during phase separation can lead to analyte losses. in the extracts, the high concentration of the reagent may cause strong matrix effects during spectrochemical element detection. the crm 601 sediment reference material issued in 1997 has been certified for this procedure only for cd, cr, ni, pb, and zn [7,8]. during the analysis of the bcr 701 sediment materials, the original bcr procedure was modified to avoid analyte loss during the second leaching step due to ph instability [10–13]. however, this modification in bcr procedure may cause significant differences relative to previously obtained data. the bcr procedures in their original and modified versions were successfully applied to aquatic sediments and soils; however, soil crm has not been issued for this procedure up to now [14–21]. it can be concluded that the tessier-based fractionation procedures [5] are widely used for heavy metal contamination assessments in soils and aquatic sediments, but the realistic interpretation of these data requires standardisation. however, this has been hindered due to methodological problems of measurements and analysis [22–23]. these problems limiting the application of the bcr sequential figure 2. strategy of serial single-step extractions. figure 3. strategy of sequential extractions (s(r) stands for solvent(reagent)). scheme 1. element fractions in aquatic sediment as classified by kersten and förstner [4], caroli [3], and tessier [5] (left-hand side) and the original bcr sequential extraction steps [6-8] (right-hand side) icp-oes multi-elemental calibration problems 43(1) pp. 7–13 (2015) doi: 10.1515/hjic-2015-0002 9 extraction procedure have initiated a cooperative research project between szent istván university gödöllő and the technical university košice as summarised in table 1. the aim of the given study was the evaluation of changes in the environmental mobility of heavy metals at two polluted areas (upper tisza/2000–2001 and gödöllőisaszeg lake system/1995–1998) by means of the repeated bcr fractionation of heavy metals in the sediments and soils [31–34]. a flexible, multi-elemental inductively coupled plasma-optical emission (icpoes) technique with a charge-coupled device (ccd)detection system was employed instead of the formerly applied flame atomic absorption spectroscopy (faas). the latter had to be optimised for each analyte element individually. hereby, the problems of the matrix-matched multi-elemental calibration of the icp-oes method are described using different solvent applied from the bcr procedure. the validation of the calibration was controlled by the fractionation of the crm 701 sample. 2. experimental 2.1. elemental analysis and instrumentation for element detection in different extractant matrices, the horiba jobin yvon activa-m icp-oe spectrometer was employed, which is able to record the entire uv-vis spectrum range by rapid scanning ccddetection. it also makes possible the flexible analytical line selection for 75 elements. the wavelength scale calibration of recorded spectra is based on a reference line position set by the user. the c 193.026 nm line is proposed by the manufacturer in routine analytical applications. the instrument’s scheme and technical parameters are presented in fig.4. introduction of the sample can be performed by a concentric glass nebuliser and glass cyclone spray chamber fed by a 3-channel peristaltic pump. 2.2. icp-oes operation parameters the operation parameters of icp-oes were selected on the basis of the manufacturer’s manual proposed for multi-elemental analysis as follows: • incident power: 1000 w, • plasma gas flow: 13.14 dm3 min-1, • sheath gas flow: 0.32 dm3 min-1, • nebuliser gas flow: 0.28 dm3 min-1, • nebuliser gas pressure: 2.86 bar, and • nebuliser sample flow uptake: 0.85 cm3 min-1. 2.3. matrix matched calibration solutions amounts of 1 mg dm-3 (in cc hno3) mono-elemental cd, co, cr, cu, fe, mn, ni, pb, v, and zn (précis certified standards for icp spectroscopy, horiba scientific, france) standard solutions corresponding to 0, 5, and 20 mg dm-3 concentrations were pipetted into a 50 cm3 volumetric flask and then diluted by solvents applied in the bcr sequential extraction procedure: • 1st step: 0.11 m acetic acid. • 2nd step: 0.1 m hydroxylamine-hydrochloride. • 3rd step: 1 m ammonium acetate. • extra step: 13 g/g nitric acid. 2.4. analytical lines the following analytical lines were selected according to the manufacturer’s proposal for multi-elemental analysis: • cd 214.441 nm • co 230.785 nm • cr 205.571 nm • cu 324.754 nm • fe 259.940 nm and 240.489 nm • mn 257.610 nm • ni 222.296 nm (instead of 221.650 nm!) • pb 220.353 nm • v 309.311 nm • zn 213.857 nm in the first, second, and extra step, the wavelength readout started from the c 193.026 nm reference line. in the third step, the correct wavelength readout was only figure 4. scheme of the horiba jobin yvon activa-m icp-oe spectrometer and relevant technical parameters table 1. overview of the cooperative research projects between szent istván university gödöllő and the technical university košice limitations of the bcr scheme achievements by szie and tu košice research groups does not match the natural mobilisation pathways → better modelling of environmental mobility by the application of h2o and h2o/co2 solvents [24]. does not preserve the intact species of the sample → application of aqueous extractions for the elaboration of biological tests [25]. time consuming (4-5 days) → acceleration of batch leaching by means of sonification [26]. → development of continuous flow operation in the supercritical fluid extractor for co2, h2o and h2o/co2 solvents [24] cross-contamination during operation and applied reagent ↗ → reduction of operations and reagents limited applicability and validation: validation and available crm only for sediments → extension of the application to other matrices: soils, gravitation dusts, biofilms, red mud, and composts [26-30]. validation of the procedure for cd, cr, cu, ni, pb, zn → multi-elemental calibration and validation for different matrices and extracts [27]. high reagent and organic content of the extracts ↗ focal length = 0.64 m dual back-to-back gratings: optical resolution < 10 pm for 120–430 nm and < 18 pm for 430–800 nm nebuliser 2048×512 pixels (13.5×13.5 µm) peltier cooling (-20 ºc) heltai, fekete, halász, kovács, horváth, takács, boros, and győri hungarian journal of industry and chemistry 10 possible when the readout started from the ar 404.442 nm reference line due to the use of 1 m ammonium acetate solution. 2.5. validation for validation of the crm 701 sediment, the reference sample was applied. the fractionation of its element content was performed according to the modified bcr proposal [10–13] in triplicates. for the extraction of the residual fraction in the extra step and for the determination of the pseudo total element content microwave supported cc hno3/h2o2 digestion was applied. table 2. the calibration lines (y = mx+b, at wave length λ in nm), correlation r2 values, residual standard deviations (rsd), background equivalent concentrations (bec in µg dm-3), and detection limits (cl(3σ) in µg dm-3) obtained by a 0.11 m acetic acid matrix. λ cl(3σ) bec m b r2 rsd cd 214.441 0.5 65 43778 2867 0.9999 1.1% co 230.785 0.8 145 41860 6064.7 0.9997 2.5% cr 205.571 1.5 174 18298 3184.2 0.9996 2.9% cu 324.754 0.2 121 159951 19374 0.9998 2.0% fe 259.940 0.5 72 205720 14716 0.9999 1.2% mn 257.610 0.2 105 902188 94673 0.9999 1.8% ni 222.296 2.0 115 7154 823.38 0.9998 2.0% pb 220.353 3.5 17 4087.4 68.946 1.0000 0.3% v 309.311 0.6 34 259817 8897 1.0000 0.5% zn 213.857 0.6 148 60540 8951 0.9998 2.2% table 3. the calibration lines (y = mx+b, at wave length λ in nm), correlation r2 values, residual standard deviations (rsd), background equivalent concentrations (bec in µg dm-3), and detection limits (cl(3σ) in µg dm-3) obtained by a 0.10 m hydroxylamine-hydrochloride matrix. λ cl(3σ) bec m b r2 rsd cd 214.441 0.9 87 47809 -4145.2 0.9999 1.5% co 230.785 1.4 19 44538 -856.49 1.0000 0.3% cr 205.571 1.4 14 18911 -258.4 1.0000 0.2% cu 324.754 0.9 72 163871 11765 1.0000 1.0% fe 259.940 0.3 1 204879 236.82 1.0000 0.2% mn 257.610 0.2 63 911472 57160 0.9999 1.1% ni 222.296 3.7 63 7505.8 471.04 1.0000 1.0% pb 220.353 3.9 4 4375.2 -17.636 1.0000 0.2% v 309.311 0.2 58 260057 -15164 1.0000 1.0% zn 213.857 1.5 45 63846 2845.5 1.0000 0.5% table 4. the calibration lines (y = mx+b, at wave length λ in nm), correlation r2 values, residual standard deviations (rsd), background equivalent concentrations (bec in µg dm-3), and detection limits (cl(3σ) in µg dm-3) obtained by a 1.00 m ammoniumacetate matrix. λ cl(3σ) bec m b r2 rsd cd 214.441 0.6 57 70051 -4008.3 1.0000 1.0% co 230.785 1.4 2 54840 -119.26 1.0000 0.03% cr 205.571 1.2 21 25579 546.52 1.0000 0.3% cu 324.754 2.5 213 151053 32156 0.9994 3.5% fe 259.940 15.8 160 258243 41379 1.0000 0.6% mn 257.610 0.4 2 1291505 2013 1.0000 0.02% ni 222.296 2.3 17 9902 -170.25 1.0000 0.3% pb 220.353 3.5 148 5905.2 -874.08 0.9997 2.6% v 309.311 1.4 85 312207 26636 0.9999 1.4% zn 213.857 14.5 33 79775 2643.2 0.9968 1.9% table 5. the calibration lines (y = mx+b, at wave length λ in nm), correlation r2 values, residual standard deviations (rsd), background equivalent concentrations (bec in µg dm-3), and detection limits (cl(3σ) in µg dm-3) obtained by a 13 g/g nitric acid and hydrogen peroxide matrix. λ cl(3σ) bec m b r2 rsd cd 214.441 0.4 392 74770 29293 0.9980 6.6% co 230.785 3.5 319 50151 16009 0.9986 5.4% cr 205.571 1.7 328 23088 7580.7 0.9986 5.5% cu 324.754 0.9 343 104399 35859 0.9985 5.6% fe 259.940 0.7 219 216961 47594 0.9995 3.2% mn 257.610 0.5 211 1056725 222941 1.0000 3.6% ni 222.296 0.5 320 9282.3 2974.7 0.9987 5.4% pb 220.353 8.7 265 6483.7 1717.4 0.9991 4.4% v 309.311 0.7 54 256488 13775 1.0000 0.9% zn 213.857 17.3 517 87624 45308 0.9968 8.3% table 6. results for the bcr-fractionation of element content (in µg dm-3) of the crm 701 sample. steps measured certified recovery 1st cd 6.45 ± 0.07 7.34 ± 0.35 88% co 1.68 ± 0.06 cr 1.88 ± 0.08 2.26 ± 0.16 83% cu 44.93 ± 0.25 49.3 ± 1.7 91% fe 57.74 ± 2.53 mn 133.17 ± 6.52 ni 12.52 ± 0.34 15.4 ± 0.9 81% pb 1.92 ± 0.19 3.18 ± 0.21 60% v 0.06 ± 0.23 zn 160.07 ± 4.22 205 ± 6 78% 2nd cd 3.96 ± 0.08 3.77 ± 0.28 105% co 2.71 ± 0.03 cr 26.53 ± 0.78 45.7 ± 2 58% cu 87.61 ± 0.81 124 ± 3 71% fe 5648 ± 50 mn 106.99 ± 2.90 ni 19.55 ± 0.35 26.6 ± 1.3 73% pb 92.17 ± 2.24 126 ± 3 73% v 8.50 ± 0.09 zn 98.77 ± 2.27 114 ± 5 87% 3rd cd 1.17 ± 0.01 0.27 ± 0.06 435% co 1.80 ± 0.08 cr 196.4 ± 8.24 143 ± 7 137% cu 63.59 ± 2.92 55.2 ± 4 115% fe 4652 ± 133 mn 43.65 ± 1.25 ni 24.49 ± 0.35 15.3 ± 0.9 160% pb 60.14 ± 0.82 9.3 ± 2 647% v 5.86 ± 0.21 zn 66.44 ± 0.62 45.7 ± 4 145% extra cd 1.38 ± 0.01 co 7.63 ± 0.18 cr 101.12 ± 4.79 cu 49.48 ± 1.92 fe 24988 ± 805 mn 302.9 ± 3.7 ni 44.50 ± 1.36 pb 12.77 ± 0.30 v 40.30 ± 0.67 zn 127.12 ± 1.36 icp-oes multi-elemental calibration problems 43(1) pp. 7–13 (2015) doi: 10.1515/hjic-2015-0002 11 3. results and analysis the parameters of analytical calibration lines, background equivalent concentrations (bec) and detection limits (cl(3σ)) obtained by different extraction matrices are summarised in tables 2–5. it can be established that the extraction matrix solvents significantly influence the sensitivity (b) values for all elements in the order of b(3rd) > b(extra) > b(2nd) > b(1st) as a function of steps taken. with the exception of some outliers, the residual standard deviation values are in the range of 1–2% and the detection limits are in the range of 0.5–2 µg dm-3. the outliers for pb, zn and fe in certain matrices refer to neglected spectral interferences. the results of the fractionation of the element content of the crm 701 sample by applying the matrix matched calibration for determining the element contents in the extracts are summarised and compared with the certified and pseudo-total values in tables 6–8. it can be seen that the metal content in bcr steps 1–3 shows an acceptable agreement (< mg dm-3) with certified values. in the individual steps, there are larger differences for elements than are acceptable: 1st step: pb; 2nd step: cr, cu, and pb; 3rd step: cd, ni, pb, and zn. 4. conclusion based on the results presented here, it can be concluded that the extractants applied in the bcr sequential extraction procedure cause significant matrix effects even in the case of matrix-matched multi-elemental calibration of the icp-oes determination of element content. the sensitivities were strongly influenced by the extractant media, therefore, a much higher incident power was required to eliminate these differences to ensure conditions that are more robust. the recoveries of certified values of the crm 701 sample were within the acceptable range when the summary of extracted amounts in the bcr steps 1–3 was compared. significant differences occurring in individual extraction steps between the measured and certified values refer to neglected spectral interferences. this requires a detailed study utilising the flexible line selection possibility offered by the horiba jobin yvon activa-m instrument. acknowledgement this work was supported by the hungarian scientific research fund (otka 108558), ktia aik-12-1-20120012 and the research centre of excellence 85265/2014/tudpol. references [1] gunn, a.m.; winnard, d.a.; hunt, d.t.e. : trace metal speciation in sediment and soils, in metal speciation: theory, analysis and application, eds.: kramer, j.r.; allen, h.e. (lewis publications, boca raton, fl, usa) 1988 isbn 0873711408 9780873711401 [2] templeton, d.m.; ariese, f.; cornelis, r.; danielsson, l.g.; muntau, h.; van leeuwen, h.p.; lobinski, r.: guidelines for terms related to chemical speciation and fractionation of elements. definitions, structural aspects, and methodological approaches, pure appl. chem., 2000 72, 1453–1470 10.1351/pac200072081453 [3] caroli, s.: element speciation in bioorganic chemistry (wiley, new york, usa) 1996 isbn 0471-57641-7 [4] kersten, m.; förstner, m.: speciation of trace metals in sediments and combustion waste. in chemical speciation in the environment, eds.: ure, a.m.; davidson, c.m. (blackie academic and professional, london, u.k.) 1995, pp. 237275 [5] tessier, a.; campbell, p.g.c.; bisson, m.: sequential extraction procedure for the speciation of particulate trace metals, anal. chem., 1979, 51, 844–851 10.1021/ac50043a017 [6] ure, a.m.; quevauviller, ph.; muntau, h.; griepink, b.: speciation of heavy-metals in soils and sediments an account of the improvement and harmonization of extraction techniques undertaken under the auspices of the bcr of the commission of the european communities, int. j. envir. anal. chem., 1993 51, 135–151 10.1080/0306731908027619 table 7. comparison of the summarised element content (in mg kg-1) extracted in bcr steps 1-3 using certified values for the crm 701 sample. steps 1-3 certified recovery cd 11.58 11.38 102% co 6.19 cr 224.8 191.0 118% cu 196.1 228.5 86% fe 10358 mn 283.8 ni 56.6 57.3 99% pb 154.2 138.5 111% v 14.42 zn 325.3 364.7 89% table 8. comparison of the summarised element content (in mg kg-1) extracted in bcr steps 1-3 using pseudo-total values. steps 1-3+extra pseudo-total recovery cd 12.96 9.63 135% co 13.81 10.68 129% cr 325.9 290.5 112% cu 245.6 257.7 95% fe 35323 31285 113% mn 586.4 567.7 103% ni 101.0 77.2 131% pb 167.0 158.2 106% v 54.68 39.20 140% zn 452.3 417.7 108% heltai, fekete, halász, kovács, horváth, takács, boros, and győri hungarian journal of industry and chemistry 12 [7] quevauviller, p.; rauret, g.; lópez-sánchez, j.f.; rubio, r.; ure, a.; muntau, h.: certification of trace metal extractable contents in a sediment reference material (crm 601) following a threestep sequential extraction procedure, sci. total environ., 1997 205, 223–234 10.1016/s00489697(97)00205-2 [8] lópez-sánchez, j.f.; sahuquillo, a.; fiedler, h.d.; rubio, r.; rauret, g.; muntau, h.; quevauviller, ph.: crm 601, a stable material for its extractable content of heavy metals, analyst, 1998 123, 1675– 1677 10.1039/a8022720j [9] gleyzes, c.; tellier, s.; astruc, m.: fractionation studies of trace elements in contaminated soils and sediments: a review of sequential extraction procedures, trends anal. chem., 2002 21, 451-467 10.1016/s0165-9936(02)00603-9 [10] rauret, g.; lópez-sánchez, j.f.; sahuquillo, a.; rubio, r.; davidson, c.; ure, a.; quevauviller, ph.: improvement of the bcr three step sequential extraction procedure prior to the certification of new sediment and soil reference materials, j. envir. monit., 1999 1, 57–61 10.1039/a807854h [11] sahuquillo, a.; lópez-sánchez, j.f.; rubio, r.; rauret, g.; thomas, r.p.; davidson, c.m.; ure, a.m.: use of a certified reference material for extractable trace metals to assess sources of uncertainty in the bcr three-stage sequential extraction procedure, anal. chim. acta, 1999 382, 317–327 10.1016/s0003-2670(98)00754-5 [12] pueyo, m.; rauret, g.; lück, d.; yli-halla, m.; muntau, h.; quevauviller, ph.; lópez-sánchez, j.f.: certification of the extractable contents of cd, cr, cu, ni, pb and zn in a freshwater sediment following a collaboratively tested and optimised three-step sequential extraction procedure, j. envir. monit., 2001 3, 243–250 10.1039/b01025k [13] rauret, g.; lópez-sánchez, j.f.; lück, d.; ylihalla, m.; muntau, h.; quevauviller, ph.: certification of the extractable contents of cd, cr, cu, ni, pb and zn in a freshwater sediment following a collaboratively tested and optimised three-step sequential extraction procedure, european commission bcr information reference materials bcr 701, 2001 isbn 92-894-0755-7 [14] sahuquillo, a.; 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ponta, m.; cordos, e.: use of sequential extraction to assess metal fractionation in soils from bozanta mare, romania, acta univers. cibiniensis ser. f chemia, 2005 8(2), 5–12 http://saiapm.ulbsibiu.ro/rom/cercetare/art/art2.pdf [19] okoro, h.k.; fatoki, o.s.; adekola, f.a.; ximba, b.j.; snyman, r.g.: a review of sequential extraction procedures for heavy metals speciation in soil and sediments, open access sci. rep., 2012 1(3): 181 10.4172/scientificreports.181 [20] jena, v.; gupta, s.; dhundhel, r.s.; matic, n.; frančišković bilinski, s.; devic, n.: determination of total heavy metal by sequential extraction from soil. int. j. res. environ. sci. technol., 2013 3(1), 35–38 issn 2249-9695 [21] zimmerman, a.j.; weindorf, d.c.: heavy metal and trace metal analysis in soil by sequential extraction: a review of procedures. int. j. anal. chem., 2010 7, article id 387803 10.1155/2010/387803 [22] zimmerman, a.j.; weindorf, d.c.: heavy metal and trace metal analysis in soil by sequential extraction: a review of procedures, int. j. anal. chem., 2010 7, 387803 10.1155/2010/387803 [23] dabek-zlotorzynska, e.; kelly, m.; chen, h.; chakrabarti, c.l.: application of capillary electrophoresis combined with a modified bcr sequential extraction for estimating of distribution of selected trace metals in pm2.5 fractions of urban airborne particulate matter, chemosphere, 2005 58, 1365–1376 10.1016/j.chemosphere.2004.09.082 [24] heltai, gy.; fehér, b.; percsich, k.; barabás, b.; fekete, i.: application of sequential extraction with supercritical co2, subcritical h2o, and an h2o/co2 mixture for estimation of environmentally mobile heavy metal fractions in sediments, anal. bioanal. chem., 2002 373(8), 863–866 10.1007/s00216-0021388-6 [25] heltai, gy.: chemical interpretation of a new sequential extraction scheme based on supercritical co2 and subcritical h2o solvents, bull. szent istván university, 2005, 107–122 [26] rusnák, r.; halász, g.; horváth, m.; remeteiová, d.: preliminary results on the intensification of the bcr sequential extraction with sonication for sediments, soils, and gravitation dust sediment samples, toxicol. environment. chem., 2010 92(3), 443–452 10.1080/02772240903300139 [27] horváth, m.; halász, g.; kucanová, e.; kuciková, b.; fekete, i.; remeteiová, d.; heltai, gy.; flórián, k.: sequential extraction studies on aquatic sediment and biofilm samples for the assessment of heavy metal mobility, microchem. j., 2013 107(3), 121–125 10.1016/j.microc.2012.05.024 icp-oes multi-elemental calibration problems 43(1) pp. 7–13 (2015) doi: 10.1515/hjic-2015-0002 13 [28] flórián, k.; matherny, m.; nickel, h.; pliešovská, n.; uhrinová, k.: environmental characteristics of the atmosphere of residential agglomerations i. dustiness of the agglomerations, chem. pap., 2003 57(5), 369–373 [29] flórián, k.; matherny, m.; nickel, h.; pliešovská, n.; uhrinová, k.: environmental characteristics of the atmosphere of residential agglomerations ii. main, minor, and trace elements in the gravitation dust sediments, chem. pap., 2003 57(5), 374–381 [30] remeteiová, d.; sminčáková, e.; flórián, k.: study of the chemical properties of gravitation dust sediments, microchim. acta, 2007 156(1-2), 109– 113 10.1007/s00604-006-0603-0 [31] shiowatana, j.; tantidanai, n.; noobkaew, s.; nacapricha, d.: a novel continuous–flow sequential extraction procedure for metal speciation in solids, j. environ. qual., 2001 30, 1195–1205 10.2134/jeq2001.3041195x [32] heltai, gy.; fekete, i.; gémesi, z.; percsich, k.; flórián, k.; tarr, zs. : environmental evaluation of a local lake chain affected by wastewater by means of spectrochemical analytical methods, microchem. j., 1998 59, 125–135 10.1006/mchj.1998.1574 [33] győri, z.; alapi, k.; szilágyi, sz.: effects of heavy metal on floodplain soils and pastures of the river tisza, hungary i. in natural attenuation of metals along the tisza river–floodplain–wetlands continuum (university of debrecen, debrecen, hungary) 2003, pp. 146–160 isbn: 963 472 726 3 [34] győri, z.; alapi, k.; sipos, p.; zubor, á.: effects of heavy metal on floodplain soils and pastures of the river tisza, hungary ii. in natural attenuation of metals along the tisza river–floodplain– wetlands continuum (university of debrecen, debrecen, hungary) 2003, pp. 161–163 isbn: 963 472 726 3 ! ! about water for water − water and wastewater treatment system operating engineer postgraduate specialist training course with the co-operation of one of hungary’s oldest historical universities and a company of international reputation “water is essential for life on earth as much as good quality education is for professional experts.” the university of pannonia faculty of engineering and the nagykanizsa campus along with hidrofilt water and wastewater treatment ltd. are offering a postgraduate course programme in water and wastewater treatment. hungary has long been recognised as a great water power with a historical background in the field of water treatment and purification. the university of pannonia has a long tradition of academic excellence based on the training of engineering specialists for industry and the economy. the faculty of engineering and the nagykanizsa campus of the university of pannonia are committed to forging partnerships with industry. our aim is to create a generation of engineers that will take a lead in the development of innovative and sustainable technologies. the water and wastewater treatment system operation programme is designed for those engineering and non-engineering graduates who wish to pursue a career in water and wastewater treatment. the nagykanizsa campus offers a wide spectrum of quality programmes that not only enhance students’ professional development, but also familiarise them with the natural and historic values of hungary. mentors will assist students in organising their educational programmes and review their theses. each student benefits from the opportunity of acquiring a broad range of transferable skills towards their future career within an outstanding academic environment. duration of the course programme: 2 semesters/4 months. theoretical training in water and wastewater treatment technologies is provided by the university of pannonia, and hidrofilt ltd. practical work and laboratory sessions will be carried out with the help of professional mentors from hidrofilt ltd. the faculty of engineering provides course materials and notes that are included in the package. competencies to be acquired: " classification and adequate employment of the theoretical knowledge and practical methods acquired in the field; independent decision-making and development skills. " ability to analyse the qualitative and quantitative characteristics of water and wastewater; creating, implementing and assessing measurement plans. " optimal employment and management of state-of-the-art water and wastewater treatment technologies. " operating, planning and managing water supply and water and wastewater treatment technologies. " knowledge and employment of quality assurance and technical control. " analytical skills in technical, economical, and social relations in water and wastewater treatment. " evaluation of conceptions and programmes regarding water on national and international levels. the qualification provides skills and abilities that can be employed profitably not only on a national but also on an international level. graduates are able to design and implement investments related to water and wastewater treatment and maintain systems in operation. we offer a practice-oriented training programme in addition to high-quality academic education. those participating in the study programme gain state-of-the-art knowledge that fits the needs of the market and acquire the most advanced water purification technologies applied in the industry. information available from: info@sooswrc.hu hungarian journal of industry and chemistry vol. 43(1) pp. 15–18 (2015) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2015-0003 nitrogen removal controlled by an ammonium-analyser at the north pest wastewater treatment plant zsófia kassai budapest sewage works pte ltd., asztalos sándor u. 4., budapest, 1087, hungary at the north pest wastewater treatment plant, a nutrient removal process has been in operation since 2011. new tanks have been built, which can receive approximately half of the pre-settled wastewater. a predenitrification system has been planned and built both to the old and new lines. due to the relatively small anoxic zones, periodic aeration was initiated first in the new line to achieve the lowest possible effluent total nitrogen concentration. because of its positive impact, the operation of periodic aeration was initiated in the old line as well. ammonium-analysers are used to control the aeration periods. due to this process, the plant can provide a very low total nitrogen effluent value (below 10 mg dm-3 on average) as well as save energy and operational costs. keywords: wastewater treatment, nitrogen removal, nitrification, denitrification, ammoniumanalyser, operation control, periodic aeration 1. introduction in the north pest wastewater treatment plant, the nutrient removal phase has been in operation since 2011. the pre-settled wastewater is divided into two parts: one part is led to the “a” biological line and the other to the “b” line. both biological lines were constructed for pre-denitrification with anoxic selectors. since the volume of these selectors is relatively small, the operation of periodic aeration is carried out in order to provide more time for the denitrifying bacteria to use the slowly biodegradable particulate chemical oxygen demand (cod) as well. the aim of its operation is to keep the effluent total nitrogen (tn) concentration under an annual average value of 10 mg dm-3. therefore, the precise control of periodic aeration is important to fulfil this aim and save energy and costs as well. 1.1. nitrification and denitrification in the case of municipal wastewaters, the hydrolysis of nitrogen containing compounds takes place mainly in the sewage system. therefore, ammonium is the main form of nitrogen present in the influent wastewater. the nitrogen content of the filtration originates from the sludge treatment technology, which could also be significant for wastewater treatment plants. the first step of the biological nitrogen removal process is nitrification, which is the biological oxidation of ammonia or ammonium to nitrite followed by the oxidation of the nitrite to nitrate. the process is performed by autotrophic bacteria as follows: correspondence: kassaizs@fcsm.hu [nh4]+ + o2 + co2 → (moa) → (moa)’ + nox + 2 h+ where (moa) and (moa)’ stand for autotrophic bacteria. the growth rate and specific sludge production of the nitrifying bacteria are lower than for heterotrophic bacteria, thus the growth of the autotrophic bacteria has to be in the appropriate ratio of wastewater quality to amount of sludge production [1, 2]. therefore, appropriate sludge loading can balance out the conditions for the growth of the two groups of bacteria. increasing the sludge retention time and decreasing the organic loading rate of the activated sludge could balance out the disadvantage posed by the nitrifying bacteria [3, 4]. the second step of nitrogen removal is denitrification, when special heterotrophic facultative anaerobic bacteria produce molecular nitrogen (n2) from nitrate as follows: nox + bod5 + h+ → (moh) → (moh)’ + n2 + co2 where bod5, (moh), and (moh)’ stand for biological oxygen demand, and heterotrophic bacteria, respectively. 2. experimental setup during the construction of the nutrient removal phase a pre-denitrification system was built both in the “a” and “b” lines with 2–2 ganged, rectangular, mixed anoxic reactors for each section. both “a” and “b” lines have four parallel sections. in the case of the “a” line, the anoxic selectors were separated from the beginning of kassai hungarian journal of industry and chemistry 16 the existing rectangular aeration tanks (fig.1). as for the “b” line, the new anoxic reactors were built before the new caroussel type aeration tanks (fig.2). the volume of the anoxic tanks is relatively small, since only 18 vol.% of the total activated sludge can be held in both lines. the best available effluent total nitrogen value was chosen for the design of the control system of the nitrogen removal program instead of the smallest ammonium nitrogen value. the standard value for total nitrogen is 35 mg dm-3, but the aim of the plant was to keep the effluent total nitrogen under 10 mg dm-3 as an annual average. the problem was that for the small anoxic volumes there was not enough time for the denitrification to take place completely. the other challenge was that the quality of the incoming wastewater had changed, since the original design of the nutrient removal phase was made. the incoming wastewater was diluted, but the rate of dilution was not the same for each parameter (table 1). 3. results and analysis the organic matter content (cod, bod5) and the total suspended solids (tss) decreased the most, while the decrease in nutrients, especially in the nitrogen forms was only modest. the difference was caused by the filtration water of the sludge dewatering system (table 2). at the wastewater treatment plant, there are two operating mesophilic digesters with a volume of 12,000 m3 each. these digesters receive not only the thickened sludge from the plant, but other wastes containing high quantities of organic matter, such as dried sludge, industrial wastewater, and animal protein. in table 2, it can be seen that the nitrogen content of the filtration is very high so the ratio of the nitrogen in the influent wastewater is higher, too. considering the planned values from table 1, the cod:tn ratio is 11.5:1 while the actual ratio is only 7– 8:1. previous experiments showed that the readily biodegradable soluble cod (ss) content of the wastewater is only about 20% [5], thus the total amount of organic matter isn’t available for the denitrifying bacteria in the anoxic zones. the average hydraulic retention time in the anoxic zones is about 3.5 hours. with periodic aeration (fig.3), the denitrifying bacteria can consume not only the ss, but the slowly biodegradable particulate cod, which becomes available as a result of hydrolysis. table 1: planned and real daily loads in kg. load planned actual deviation in % annual 2013 annual 2014 1st quarter 2013 annual 2014 1st quarter cod 133 406 73 103 74 692 55 56 bod5 72 800 41 390 42 043 57 58 tss 63 336 41 408 37 316 65 59 nh4-n 7 553 6 298 6 357 83 84 tn 11 575 9 137 9 487 79 82 tp 1 984 1164 1279 59 65 loads: cod = chemical oxygen demand, bod5 = biological oxygen demand, tss = total suspended solids, nh4-n = ammonium nitrogen, tn = total nitrogen , tp = total phosphorous figure 2. schematic layout of the “b” line. figure 1. schematic overview of anoxic selectors in the “a” line. table 2. average cod and nitrogen content of the filtration water in mg dm-3. cod n (nh3-nh4) tn cod:tn ratio 2013 847 1,163 1,326 ~1:1.6 2014 1st quarter 815 1,091 1,262 ~1:1.5 figure 3. effluent total nitrogen values between july and december 2010. nitrogen removal controlled by ammonium-analyser 43(1) pp. 15–18 (2015) doi: 10.1515/hjic-2015-0003 17 first, the periodic aeration system was evaluated in the “b” line as shown in fig.3. the blue diagram shows the effluent total nitrogen values from the “b” line, the red from the “a” line. it can be seen that with periodic aeration the effluent values from the “b” line are much lower compared to the “a” line. due to this positive effect, the periodic aeration process has been used in the “a” line since 2011 as well. 3.1. controlling periodic aeration in the case of the “b” line, controlling the system is quite simple, because the treated wastewater coming from four parallel, activated sludge tanks is mixed before the final settling tanks. there is a short channel before the wastewater is divided and led to the eight rectangular secondary sedimentation tanks, where a ‘hach lange amtax sc.’-type ammonium-analyser is set up. aeration is controlled by the measured ammonium-nitrogen value (table 3). due to the carousel race-track type activated sludge tanks, aeration can be switched off even for 3 hours, because the four agitators in each section do not let the sludge settle. controlling the “a” line was much more difficult partly because there are no agitators in the rectangular activated sludge tanks. on the other hand, the wastewater coming from four sections is only mixed after the final settling. thus, the ammonium-nitrogen level has to be measured separately for each section. there are two ‘amtax sc.’-type ammoniumanalysers in dual channel mode for the “a” line for sections 1–2 and separately for sections 3–4. because of the lack of agitators, there is a time limit in order to prevent the sludge from settling. after 60 minutes, the aeration has to be switched on even if the measured ammonium is not over the set value. in the “a” line, all the sections are controlled separately. the hours when aeration is switched on and off can be chosen. there are “manual”, “time control”, and “automatic” modes as shown in fig.4. in “time control” mode the operator can fill in a timetable with aeration periods (green). yellow areas show the hours when the aeration is turned off. in “automatic” mode, the program calculates an average nh4-n for each section from the past hour and compares it to the set values. if the average value is under the minimum in a section then there will be two hours with aeration on and one hour off (fig.4). if the value is between the limits, there will be three aeration hours and one without. if the average value is over the maximum limit, aeration remains on until the value decreases below the limit. the operation of the blowers is also an important parameter. aeration must not be switched off in every section at once. fig.5 shows the effluent total nitrogen levels for the controlled periodic aeration of both lines. in may, the “a” line operated under “time control”, thus the effluent results were much better in the “b” line. automatic control of the “a” line was turned on in the summer of 2014 as shown in fig.5. sometimes the effluent values in the “a” line are better according to the tn than in the “b” line as can be seen from data point 06.2014. due to periodic aeration, the effluent total nitrogen level was under the annual average of 10 mg dm-3 (table 4). 4. conclusion our study indicates that with periodic aeration external carbon sources are not needed at the north pest wastewater treatment plant in order to ensure the requested total nitrogen value. for optimal operation, control by ammonium analysers is essential, while the time-controlled system did not prove to be sufficient. figure 4: aeration control in the “a” line figure 5: effluent total nitrogen levels between april and august 2014. table 4. average effluent values in mg dm-3 between january and august 2014 load effluent standard cod 30 125 bod5 < 10 25 tss 5 35 nh4-n 2.54 10 tn 9.63 35 tp 1.39 5 loads: cod = chemical oxygen demand, bod5 = biological oxygen demand, tss = total suspended solids, nh4-n = ammonium nitrogen, tn = total nitrogen , tp = total phosphorous table 3. control parameters for aeration in the “b” line. nh4-n level (mg dm-3) sections with aeration on [pcs] sections with aeration off [pcs] < 5.0 1 3 5.0 7.0 2 2 7.0 10.0 3 1 > 10.0 4 0 kassai hungarian journal of industry and chemistry 18 acknowledgement this work was supported by the staff of the north pest wastewater treatment plant and the laboratory of budapest sewage works ltd. references [1] kárpáti, á.: ways of development in activated sludge systems – i. bod and nitrogen removal. – 1-14. ii. biological phosphorous removal and optimal utilization of organic carbon sources. 1424. in activated sludge systems and control. no. 2. ed.: kárpáti, á. (university of veszprém, department of environmental engineering and chemical technology, veszprém, hungary) 2002, pp. 97 (in hungarian) [2] kárpáti, á.; pásztor, i.; pulai, j.: current and future perspectives of nitrogen removal in wastewater treatment, vízmű panoráma, 2004 7(2) 17–22 (in hungarian) [3] grady, l.c.p.; lim, h.c.: biological wastewater treatment. theory and applications (marcel dekker, new york, usa) 1980 [4] henze, m.; gujer, w.; mino, t.; matsuo, t.; wentzel, m.c.; marais, g.v.r.: activated sludge model no. 2. (iawq scientific and technical report, london, uk) 1995 [5] kassai, zs.: modeling processes undergoing under anoxic conditions with nur test, proc. mht meeting, sopron, hungary, pp. 1-7 2010 (in hungarian) hungarian journal of industry and chemistry vol. 43(1) pp. 19–23 (2015) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2015-0004 evaluation of the heavy metal content of the upper tisza river floodplain soils over the last decade zoltán győri,1* norbert boros,2 péter sipos,2 emese bertáné szabó,2 katalin kovács,3 márk horváth,3 anita takács,3 and györgy heltai3 1 institute of regional economics and rural development, szent istván university, páter k. u. 1, gödöllő, 2100, hungary 2 institute of food science, university of debrecen, böszörményi u. 138, debrecen, 4032, hungary 3 department of biochemistry and chemistry, szent istván university, páter k. u. 1, gödöllő, 2100, hungary in early 2000, two contamination events at baia mare first and baia borsa second involving large amounts of toxic elements impacted the hungarian section of the river tisza with disastrous ecological and economical impacts. we evaluated the sortand long-term effects of this pollution by determining the total and bioavailable concentrations of potentially toxic metals from soil samples collected along the tisza (tivadar, vásárosnamény, rakamaz, and tiszacsege) in 2000 and between 2011 and 2013. the current and previous results were compared in respect of copper and lead contents. keywords: river tisza, floodplain soils, heavy metal pollution, lakanen-erviö extraction, nitric acid/peroxide extraction 1. introduction there were intensive cu, zn, pb, au, and ag mining activities during early 2000 in the catchment area of the river tisza [1]. in the last two decades of the previous century, the processing of tailings pond using cyanide was popular as a recovery technology. the resulting wastewaters contain fine-grained sediments with heavy metal contents [2]. in early 2000, two contamination events (at baia mare first and baia borsa second) involved the release of large amounts of toxic elements that impacted the hungarian section of the river tisza with disastrous ecological and economical consequences. the first one released 100,000 m3 wastewater that contaminated with cyanide and heavy metals the river tisza via its tributary lápos-szamos. the second disaster sent about 20,000 tons of mud containing heavy metals into the river lápos-tisza along with a simultaneous flood settling, forming a layer of approximately 5-10 cm in depth on the pre-existing soil [3-8]. metals were primarily bound to floating material and deposited in floodplain areas. the metal pollution of the floodplains was also observable [9, 10]. the environmental risk of this type of soil contamination is that the buffer capacity of new layer is smaller than the previously and the potential *correspondence: gyori.zoltan@gtk.szie.hu decreases in ph enhance metal bioavailability and toxicity. the mobility and phytoavailability of metals depend on their chemical forms [11]. the speciation justifies the use of sequential extraction method (sep) for analyzing these soil samples. considering the above information, it is likely that the residual heavy metal load may entail economic effects that cannot be envisaged at the moment as the valley of river tisza is under agricultural use (pastures, meadows, orchards, and arable land). this is the reason why intensive research has aimed at testing and monitoring the ecological systems of both water and floodplains. this paper presents only the vertical distribution and forms of heavy metals in polluted areas, although plant relations were also examined [6]. the aim of this study was to evaluate the effects of these sources of pollution on the total and bioavailable metal contents of soil samples collected in 2000 and between 2011 and 2013 from floodplains and pastures along the tisza (tivadar, vásárosnamény, rakamaz, and tiszacsege) and compare these results to earlier ones. 2. materials and methods soil samples were collected in 2000 after the flood and in april 2011 and september 2013 by deep drilling using a nordmeyer drill (nordmeyer holland, overveen, the netherlands). we sampled the 3 m-deep soil layer in triplicates. sampling sites are represented in table 1. győri, boros, sipos, bertáné-szabó, kovács, horváth, takács, heltai hungarian journal of industry and chemistry 20 soil samples were air dried and sieved (< 2 mm) for further analysis. the chemical analysis was carried out in accordance with a hungarian standard [12], using hno3h2o2 digestion, which yields total elemental contents. the extraction of the easily available metal contents was conducted according to lakanen and erviö [13]. sequential extractions were performed to determine the concentration of metals associated with different operationally defined soil fractions, in the course of which, stronger and stronger extractants are used to remove metals from the sample. in this case the mcgrath method [14] was used, which uses 0.1 m cacl2 to determine water soluble and exchangeable metal fractions, 0.5 m naoh to determine the fraction of metals bound to organic matter; 0.05 m na2edta to determine metals bound to carbon and finally, destruction using aqua regia determines the residual fraction. in order to obtain the standard data we used a merck-made (e. merck, darmstadt, germany) analytical grade hno3 (65%) solution. merck and bdh standard solutions were used to prepare the stock solutions, and reanal (budapest, hungary) solid chemicals were used. ultrapure water was used to prepare the solutions (millipore, paris, france). samples were analysed using an inductively coupled plasma optical emission spectrometer (icpoes) to determine cu content (perkin-elmer optima 3300 dv; perkin-elmer ltd., shelton, usa). the pb content was measured by a qz 939 gf-aas (unicam) in 2000 and by an x7 icp-ms (thermo fischer scientific) between 2011 and 2013. target analytics were al, ba, ca, cd, co, cr, cu, fe, k, la, li, mg, mn, mo, na, ni, p, pb, s, and zn. in this study, we focused on cu and pb, because these elements were connected to the contamination on the floodplain. certified standard materials used in qa/qc were bcr crm 141r: calcareous loam soil [15]; bcr crm 142r: light sandy soil [16], and bcr crm 143r: sewage sludge amended soil [17]. we assumed that the investigation of the upper 30 cm soil layer every five years using sequential extraction could give accurate information about the changes in the bioavailability of heavy metals and the rearrangement among fractions. all statistical analyses were performed using spss (version 22.0). 3. results and discussion figs.1 and 2 show the total elemental composition for the four sampling sites. although replicate cores and sampling locations differ, they show an overall trend. the cu content of the topsoil was higher than that of the lower layers formed earlier. data indicates that the cu and pb contents of the topsoil are greater in vásárosnamény compared to in tivadar, possibly due to the combined effects of the two contamination incidents convening at the confluence of the rivers tisza and szamos. the 70 to 170 cm soil layers at vásárosnamény show high lead content. the lakanen-erviö soluble element content is shown in figs.3 and 4. data indicate that the heavy metal content of the floodplain soils is greater in vásárosnamény compared to in tivadar. from this point downstream, the level of contamination appears to decrease with distance, with the lowest value (data not shown) in the topsoil of the arboretum at tiszakürt (275 river km) where atmospheric deposition may be the table 1. summary of sampling sites. sampling sites geographical coordinates river km types of samples additional information tivadar n 48o 04' 00.6'' e 22o 31' 04.8'' 709 active floodplain affected by the second pollution event vásárosnamény n 48o 07' 46.5'' e 22o 19' 39.5'' 683 pasture affected by the first and second pollution events rakamaz n 48o 07' 43.8'' e 21o 26' 28.7'' 543 pasture affected by the first and second pollution events tiszacsege n 47o 42' 59.9'' e 20o 57' 08.7'' 455 active floodplain affected by the first and second pollution events 8 years ago the area was refilled with soil ! figure 1. hno3-h2o2-extractable copper concentration of different layers of soils (blue: tivadar; burgundy: vásárosnamény; yellow: rakamaz; and light green: tiszacsege). figure 2. hno3-h2o2-extractable lead concentration of different layers of soils (blue: tivadar; burgundy: vásárosnamény; and yellow: rakamaz; light green: tiszacsege). evaluation of heavy metal content 43(1) pp. 19–23 (2015) doi: 10.1515/hjic-2015-0004 21 source of pollution. the cu content of the upper 10 cm soil layer is nearly twice as high as levels measured in the other layers. the bioavailable cu and pb contents at vásárosnamény exceeded the temporary limit values of lakanen-erviö extractable metal contents for soil contamination [18], while the upper soil layer of the tivadar floodplain appeared to be uncontaminated. the mcgrath method of sequential extraction can be used for assessing the contents of toxic and potentially toxic elements in soil, and their biological effects, i.e. for the determination of the amounts bound to various forms of compounds in soils. the proportion of the water soluble and exchangeable fractions (cacl2 extraction fraction) is negligible as regards cu and pb. the ratio of metals bound to organic matter (naoh extraction) is low, according to the expectations, as metals bound to carbonates (na2edta extraction) is higher in the vásárosnamény and tiszacsege soils, but lower at the other sites. the residual fraction of metals (aqua regia extraction) is the largest amongst the samples (figs.5 and 6). we determined the cu and pd content of the floodplain soils after ten years of the previous waves of contamination. figs.7 and 8 illustrate the vertical distribution of hno3/h2o2 extractable cu and pb contents. there is no statistically proven difference between the results of the samples taken at two different times. figs.9–12 show the lakanen-erviö soluble element contents of the same core. there is no statistically significant difference between the results of the samples taken at the two different times. the effect of the second source of pollution (baia borsa, march 2000) on the available metal contents of the tivadar floodplain was not detectable, which is in accordance with the results of szabó et al. [19]. figure 5. proportions of the different cu fractions in the topsoil (solid: cacl2 soluble, hollow: naoh soluble, small dotted: na2edta soluble, checked:aqua regia soluble). figure 6. proportions of the different pb fractions in the topsoil (solid: cacl2 soluble, hollow: naoh soluble, small dotted: na2edta soluble, checked:aqua regia soluble). figure 7. total cu concentration (hno3/h2o2 soluble) at vásárosnamény (dark: 2002, light: 2013). figure 8. total pb concentration (hno3/h2o2 soluble) at vásárosnamény (dark: 2002, light: 2013). figure 3. ammonium-acetate-edta (lakanenerviö)-extractable cu concentration of different layers of soils (blue: tivadar; burgundy: vásárosnamény; yellow: rakamaz; and light green: tiszacsege). figure 4. ammonium-acetate-edta (lakanenerviö)-extractable pb concentration of different layers of soils (blue: tivadar; burgundy: vásárosnamény; yellow: rakamaz; and light green: tiszacsege). győri, boros, sipos, bertáné-szabó, kovács, horváth, takács, heltai hungarian journal of industry and chemistry 22 4. conclusion the cu and pb contents of the topsoil were found to be the highest in the upper 10 cm layer as a result of the latest sources of contamination. the degree of this effect varies according to the sampling sites. the lowest element content was measured at tivadar, while samples from vásárosnamény showed a maximum for many elements because of the first coincidence of the two pollution waves. according to the core samples, higher element contents could be found in some of the deeper layers as marks of former sources of pollution. the investigation of the upper 30 cm soil layer in the coming years using sequential extraction could give accurate information about the changes in the bioavailability of heavy metals and the rearrangement among fractions in addition to laboratory experiments of the effects on soil acidity. acknowledgement this work was supported by köm 811, nsf-mtaotka, ktia_aik_12-1-2012-0012, and otka 108558 projects. references [1] nguyen, h.l.; braun, m.; szaloki, i.; baeyens, w.; grieken, r.; van leermakers, m.: tracing the metal pollution history of the tisza river through the analysis of a sediment depth profile, water air soil pollut., 2009 200, 119—132 10.1007/a11270-0131525-1 [2] macklin, m.g.; brewer, p.a.; balteanu, d.; coulthard, t.j.; driga, b.; howard, a.j.; zaharia, s.: the long term fate and environmental significance of contaminant metals released by the january and march 2000 mining tailings dam failures in maramures county, upper tisza basin, romania, appl. geochem., 2003 18, 241–257 10.1016j/apgeochem.2013.04.013 [3] unep/ocha: spill of liquid and suspended waste at the aurul s. a. retreatment plant in baia mare assessment mission report, geneva, 2000 [4] bird, g.; brewer, p.a.; macklin, m.g.; balteanu, d.; driga, b.; serban, m.; zaharia, s.: the solid state partitioning of contaminant metals and as in river channel sediments of the mining affected tisza drainage basin, northwestern romania and eastern hungary, appl. geochem., 2003 18, 1583– 1595 10.1016/j.apgeochem.2013.04.013 figure 10. soluble cu contents of the 110 cm deep soil profile at tivadar (dark: 2002, light: 2013). figure 9. soluble pb contents of the 110 cm deep soil profile at tivadar (dark: 2002, light: 2013). figure 11. soluble pb contents of the 110 cm deep soil profile at vásárosnamény (dark: 2002, light: 2013). figure 12. soluble cu contents of the 110 cm deep soil profile at vásárosnamény (dark: 2002, light: 2013). evaluation of heavy metal content 43(1) pp. 19–23 (2015) doi: 10.1515/hjic-2015-0004 23 [5] brewer, p.a.; macklin, m.g.; balteanu, d.; coulthard, t.j.; driga, b.; howard, a.j.; bird, g.; zaharia, s.; serban, m.: the tailings dam failures in maramures county, romania and their transboundary impacts on the river system, nato sci. ser.: iv: earth environ. sci., 2003 20, 73–83 issn: 1568-1238 [6] győri, z.; alapi, k.; sipos, p.; zubor, á.: effects of heavy metals on floodplain soils and pastures of the river tisza, hungary ii. examination of soil and herbaceous plants in the upper tisza. in natural attenuation of metals along the tisza river–floodplain wetlands continuum, eds.: adriano, d.; németh, t.; győri, z., (university of debrecen, debrecen, hungary) 2003, pp. 161–173 isbn: 963-472-726-3 [7] osán, j.; kurunczi, s.; török, s.; van grieken, r.: x–ray analysis of riverbank sediment of the tisza (hungary): identification of particles from a mine pollution event, spectrochim. acta part b atomic spec., 2002 57, 413–422 issn: 0584-8547 [8] wehland, f.; panaiotu, c.; appel, e.; hoffmann, v.; jordanova, d.; jordanova, n.; denut, i.: the dam breakage of baia mare – a pilot study of magnetic screening, phys. chem. earth, 2002 27, 1371–1376 issn: 1474-7065 [9] kraft, c.; tümpling, w.; zachmann, d.w.: the effect of mining in northern romania on the heavy metal distribution in sediments of the rivers szamos and tisza (hungary), acta hydrochim. hyrdobiol., 2005 34(3), 257–264 10.1002/aheh.200400622 [10] győri, z.; alapi, k.; prokisch, j.; németh, t.; adriano, d.; sipos, p.: cd, cu, pb and zn content of the riparian zone of the tisza river (hungary) after heavy metal pollution, agrochem. soil sci., 2010 59, 117–124 10.1556/agrokem.59.2010.1.14 [11] kabata-pendias, a.; pendias, h.: trace elements in soils and plants, 3rd ed. (crc press, ltd. boca raton, fl usa) 2001 isbn: 978-1-4200-9368-1 [12] msz 21470-50: environment protection. testing of soils. determination of total and soluble toxic element, heavy metal and chromium(vi) content. hungarian standard, 1998 (in hungarian with english summary) [13] lakanen, e.; erviö, r.: a comparison of eight extractants for the determination of plant available micronutrients in soil, acta agr. fenn., 1971 123, 223-232 [14] mcgrath, s.p.; cegarra, j.: chemical extractability of heavy metals during and after long-term applications of sewage sludge to soil, j. soil sci., 1992 43, 313–321 10.1111/j1365-2389.1992.tb00139.x [15] quevauviller, ph.; muntau, h.; fortunati, u.; vercoutere, k.: the certification of the total contents (mass fractions) of cd, co, cr, cu, hg, mn, ni, pb and zn and aqua regia soluble contents (mass fractions) of cd, co, cr, cu, hg, mn, ni, pb and zn in a calcareous loam soil. (crm 141r). bcr information. commission of the european communities, 1996 isbn 92-827-7412-0 [16] maier, e.a.; griepink, b.; muntau, h.; vercoutere, k.: certification of the total contents (mass fractions) of cd, co, cu, pb, mn, hg and ni and the aqua regia soluble contents (mass fractions) of cd, pb, ni and zn in a light sandy soil. (crm 142r). bcr information. commission of the european communities, 1994 cd-na-15284-en-c [17] maier, e.a.; griepink, b.; muntau, h.; vercoutere, k.: certification of the total contents (mass fractions) of cd, co, cu, pb, mn, hg and zn and the aqua regia soluble contents (mass fractions) of cd, cr, pb, mn, ni and zn in a sewage sludge amended soil. (crm 143r). bcr information. commission of the european communities, 1994 cd-na-15284-en-c [18] kádár, i.: about the examination of contaminated soils. handbook for rehabilitation 2. (ministry of environmental protection, budapest, hungary) 1998 [19] szabó, sz.; posta, j.; gosztonyi, gy.; mészáros, i.; prokisch, j.: heavy metal content of flood sediments and plants near the river tisza, agd landscape environ., 2008 2, 120–131 issn 17897556 ! ! soós ernő water technology research and development centre was established in 2014 by the faculty of engineering at the university of pannonia, nagykanizsa municipality of county rank and hidrofilt water treatment ltd. the activities at the research centre are built on decades of experience and expertise gained in nagykanizsa in the field of water treatment and water purification. the goal of the centre is to perform international-level research activities in different areas of water purification and treatment. nagykanizsa aims to become a centre of knowledge in national and international relations as well. besides the fundamental research, the research centre plays an active role in industrial development activities, putting a great emphasis on drinking water treatment, power plants, the water management of cooling towers, horticulture and irrigation water treatment, seawater desalination, pharmaceutical and infusion solutions, water supply technologies and related control procedures, and areas of measurement technology. the areas utilising the development results include: • treatment methods for drinking and process water, • purified water, ultra pure water, and the pre-treatment of water for the injection of pharmaceuticals, • water treatment for horticulture and irrigation, • wastewater treatment in the oil and gas industries, • grey-water recycling, • seawater and brackish desalination, • water treatment for swimming pools, • monitoring and the control of water treatment, and development of instrumentation. the soós ernő research centre is named after a pioneer in the water treatment field who was a chemical and environmental engineer. he made great contributions to the field with his innovative thinking. several patents in water treatment are tied to his name. the desire of the research team is to advance his work by drawing on his leadership and scientific work as new frontiers in water treatment are pursued. as an initiative of this decision, the research centre organised its first scientific conference in december 2014, entitled water and wastewater treatment in industry. nearly 50 presenters attended the conference from both industry and academia with about 170 participants. based on unanimous support, this conference has become international. in addition to industry and academia, companies from the service sector are also invited. the conference will be held on 28th october 2015, and will be preceded by a project partner meeting. at the conference, the winners of the soós ernő young researchers award will also be announced. this award is a scientific grant for msc and phd candidates. the candidates are invited to submit their theses for nomination from the field of water and wastewater treatment and related disciplines. the university of pannonia has a long tradition of academic excellence based on the training of engineering specialists for industry and the economy. the faculty of engineering and the nagykanizsa campus of the university of pannonia are committed to forging close and productive partnerships with industry. the water and wastewater treatment system operation programme is designed for engineering and non-engineering graduates who are interested in pursuing a career within companies and organisations involved in water and wastewater treatment. high-quality academic education is offered together with hands-on training. by participating in the study programme, state-of-the-art knowledge compatible with the current needs of industries and the most advanced water purification technologies applied are acquired. hungarian journal of industry and chemistry vol. 43(1) pp. 25–32 (2015) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2015-0005 toxicology aspects of the decomposition of diuron by advanced oxidation processes tünde alapi,1,2* gergő simon,1,2 gábor veréb,1 krisztina kovács,3 eszter arany,1 krisztina schrantz,1,4 andrás dombi,1 and klára hernádi1,5 1 research group of environmental chemistry, university of szeged, rerrich béla tér 1, szeged, 6720, hungary 2 department of inorganic and analytical chemistry, university of szeged, dóm tér 7, szeged, 6720, hungary 3 institute of isotopes for energy security and environmental safety, centre for energy research, hungarian academy of sciences, p.o. box 49, budapest, 1525, hungary 4 laboratory for high performance ceramics, empa – swiss federal laboratories for materials science & technology, überlandstrasse 129, dübendorf, 8600, switzerland 5 department of applied and environmental chemistry, university of szeged, rerrich béla tér 1, szeged, 6720, hungary diuron is a phenylurea-based residual herbicide with toxic and endocrine disrupting effects. the aims of the present work were the comparison of the efficiency of various advanced oxidation processes, such as direct ultraviolet photolysis, ozonation, their combination, and heterogeneous photocatalysis from the point of view of the transformation rate of diuron, rate of mineralisation and dehalogenation, formation of aromatic intermediates, and ecotoxicological effects of the formed multicomponent solutions during the treatments. the initial rates of transformation of diuron are in the order of ozonation < heterogeneous photocatalysis < uv photolysis < combination of uv photolysis and ozonation. each method provided similar tendencies in the decrease of the concentration of organically bound chlorines (aox) since, until the diuron was completely degraded, the concentration of aox decreased almost to zero in each case. however, only heterogeneous photocatalysis was found to be effective in terms of mineralisation. ecotoxicological results showed that in each case, except for ozonation, the toxicity of the treated solutions changed through a maximum during the transformation of diuron. the maximum value was found to be lower in the case of heterogeneous photocatalysis. thus, the formation and decomposition of by-products of relatively higher toxicity than diuron can be supposed. our results confirmed that the amount of the formed (aromatic) intermediates, their quality and specific toxicity strongly depend on the applied processes. keywords: phenylurea, ozonation, ultraviolet photolysis, heterogeneous photocatalysis, daphnia magna, vibrio fischeri 1. introduction diuron (3-(3,4-dichlorophenyl)-1,1-dimethylurea, fig.1) is a phenylurea-type residual herbicide that is widely used throughout the world. it is registered in the european union’s pesticide database, in the u.s. epa, and the australian apvma. its use is strictly controlled due to its known toxic and presumed endocrine disrupting effects. it has a broad spectrum of uses, mainly as a total herbicide in non-agricultural areas (roads and railways) for the preand post-emergence control of weed-type plants, but it also has plant protection purposes in the case of certain species (e.g. sugar cane and corn) [1]. another application is as an antifouling agent, either in aquariums or in paint, to prevent algal growth on hulls of boats for example [2]. diuron has a relatively low water solubility of 42 mg dm-3 at 25 °c. it is quite *correspondence: alapi@chem.u-szeged.hu persistent in soil with a typical half-life of 75.5 days and in water-sediment of 48 days [3]. based on these data and other investigations [4], it can be concluded that this compound and its metabolites pollute the environment over an extended period of time, by leaching and run-off into ground and surface waters. this causes concerns regarding the ecosystem, mainly for aquatic plants (as the main method of action of the compound is to block photosynthesis), but also lower aquatic animals, and later presumably even more advanced organisms in the wild as well as the human body. therefore, contaminated soils and waters have to be treated in an efficient and environmentally friendly figure 1. schematic chemical structure of diuron (n(3,4-dichlorophenyl)-n,n-dimethylurea). alapi, simon, veréb, kovács, arany, schrantz, dombi, hernádi hungarian journal of industry and chemistry 26 manner. for water treatment purposes advanced oxidation processes (aops) seem to be sensible choices as secondary treatments, as they are effective, environmentally friendly and economical methods for the elimination of pollutants such as pesticides. these treatments are based mainly on the generation of highly reactive hydroxyl radicals that can induce the degradation of organic matter. the transformation of the target substance can be induced by direct photolysis given that the target molecule is able to absorb irradiating light. it can also be induced by ozonation, which is used as an industrial scale supplementary water treatment method. alternatively, heterogeneous photocatalysis, the fenton-reaction or a combination of all the above can also be used [5–9]. benítez et al. [10] investigated the transformation of phenylurea herbicides during the ozonation of natural waters and determined the reaction rate constants of diuron with both ozone (16.5±0.6 mol dm-3 s-1) and the hydroxyl radical (6.6±0.1×105 mol dm-3 s-1). during the oxidative transformation of diuron several aromatic by-products form. the main attack sites for hydroxyl radicals are the aromatic ring and the methyl group, leading to de-chlorinated or demethylated derivatives. in some cases, the reaction with the hydroxyl radical can lead to ring opening byproducts. the most important intermediates are 1-(3,4dichlorophenyl)-3-methylurea, n'-(3-chlorophenyl) n,n-dimethylurea, 1-(3,4-dichlorophenyl)urea and 3,4dichloroaniline [4]. toxicological studies regarding diuron and its metabolites showed that the parent compound is usually less toxic than a multicomponent solution containing its metabolites; however, total toxicity decays with treatment time [4]. the mode of action of diuron is to block the hill reaction during photosynthesis. two of its metabolites, 1-(3,4-dichlorophenyl)-3-methyl-urea) and n'-(3-chlorophenyl)-n,n-dimethylurea, retain this specific effect; however, the demethylation of diuron decreases its ability to bind to photosystem ii [11]. the aim of the present work was the comparison of the efficiencies of various advanced oxidative processes, such as direct ultraviolet (uv) photolysis, ozonation, the combination of these and heterogeneous photocatalysis. this comparison was made regarding the rate of transformation of diuron, the rate of mineralisation and dehalogenation, the formation of aromatic intermediates and the ecotoxicological effects of the multicomponent solutions formed as a result of the treatments. 2. experimental 2.1. the light sources and experimental apparatus for ozonation and its combination treatment, the light source was a low-pressure mercury vapour lamp, which emits 254 nm ultraviolet (uv) and 185 nm vacuum ultraviolet (vuv) light (uv/vuv lamp). this lamp (gcl307t5vh/cell, lighttech, hungary) was covered with a high purity quartz sleeve, which transmits both 185 nm vuv and 254 nm uv light. ozone was generated by the vuv photolysis of pure molecular oxygen in the gas phase. for direct uv photolysis, the sleeve of the same low-pressure mercury vapour lamp made of commercial quartz (gcl307t5/cell, lighttech, hungary), which transmits 254 nm uv light and absorbs 185 nm vuv light (uv lamp). another light source, a specific fluorescent uv lamp (lightech, hungary) emitting between 300 and 400 nm (maximum intensity at 365 nm) was applied during heterogeneous photocatalysis. the electric (15 w electric input) and geometric parameters (227 mm arc length, 307 mm length and 20.5 mm external diameter of the sleeves) of the different light sources corresponded to each other. the emitted photon fluxes were determined by ferrioxalate actinometry [12] and were found to be 8.10±0.65 × 10-6 mol photon(254nm) s-1 for low-pressure mercury vapour lamps (uv/vuv and uv) and 1.20(±0.06) × 10-5 mol photon(300–400nm) s-1 for the specific fluorescent lamp. all experiments were performed in the same photoreactor (fig.2). the light source, surrounded by an envelope was centred in a water-cooled, tubular glass reactor (340 mm length, 46 mm inner diameter). in the course of the measurements, envelopes (320 mm length and 28 mm internal diameter) made of various materials were used. the thermostat controlled (25±0.5 °c) solution of pesticide (500 cm3, c0 = 1.7×10-4 mol dm-3) was circulated (375 cm3 min-1) continuously and stirred with a magnetic stirrer bar in the reservoir. before each experiment, air was bubbled through the solution at least for 10 min. the injection of the air was continued throughout the experiment. the kinetic measurements were initiated by switching on the light source. ozonation, uv photolysis or the combination of these methods could be applied by the careful selection of the light source and apparatus envelope. ozonation figure 2. the experimental apparatus. 1: power supply; 2: teflon packing ring; 3: light source with sleeve; 4: envelope; 5: reactor; 6: reservoir; 7: magnetic stirrer; 8: pump; 9: thermostat; 10: air bottle; 11: flow meter from ref. [13]. toxicology aspects of the decomposition of diuron 43(1) pp. 25–32 (2015) doi: 10.1515/hjic-2015-0005 27 was performed using a uv/vuv lamp and perforated glass envelope. oxygen flowed through the teflon packing ring between the wall of the lamp and envelope, which separates the gas phase and aqueous solution, as shown in fig.2. the ozone was generated by the direct vuv photolysis of molecular oxygen and bubbled through the perforated envelope into the solution. using a uv lamp and non-perforated quartz envelope, uv photolysis at 254 nm could be investigated. in the case of the combination of uv photolysis with ozonation, a perforated quartz envelope was used. when heterogeneous photocatalysis was applied, the specific fluorescent lamp and nonperforated glass envelope were used. thus, the efficiency of these processes could be compared using the same energy consumption. 2.2. analytical methods and materials the concentration of diuron was determined using an hplc system (merck hitachi l-7100 with l-4250 uvvis detector). the separation of aromatic compounds was achieved with an rp-18 column (licrospher 100), using 60 % methanol and 40 % water as eluents, with a flow rate of 0.8 cm3 min-1. the quantification wavelength for uv detection was 210 nm. spectra (200 to 400 nm) of the samples during each degradation measurement were acquired on an agilent 8453 spectrophotometer using 2 mm cuvettes. the concentration of ozone in the gas phase was measured using the same spectrophotometer in a flow cell at 254 nm (ε(254 nm) = 2,952 mol-1 dm3 s-1 [14]), and was found to be 1.37×10-5 m, using oxygen gas. the adsorbable organic halogen (aox) content was recorded using an aox analyser, which consisted of an analytik jena multix 2500 aox sample unit and an apu2 sample preparation unit. samples were adsorbed on active carbon, transferred into the aox furnace and burned at 950 °c under an oxygen flow. chlorine was quantified using a micro-coulometric method. the total organic carbon (toc) content was determined using a multi n/c 3100 analyser (analytik jena). the toxicity towards daphnia magna was determined using daphtoxkit f™ magna (microbiotests inc.) tests according to the iso standard 6341. the ephippia were used after 72–90 h of hatching time at 21 °c, applying 6000 lx bottom illumination and after 2 h of pre-nourishment. the zooplankton containing samples were incubated under the same conditions for 48 h, and 8–10 neonates were added to each sample. the number of the neonates was counted using a 3×/8× table-gooseneck magnifier (vwr). mortality values were given as the percentage of the dead and/or immobilised neonates compared to their initial number. the toxicity towards vibrio fischeri luminescent bacteria was determined by measuring the natural light emission of these microorganisms using a hachlange lumistox 3000 luminometer. the inhibition of the light emission in the presence of the sample was determined against a non-toxic control. nacl was added to each sample to obtain a 2 % solution. the samples were diluted by half with 1.0 mol dm-3 naoh and 1.0 mol dm-3 hcl solutions to achieve a ph value of 7±0.2. samples containing bacteria were incubated at 15 °c for 15 min before the toxicity measurements. samples for the toxicity tests were taken at the same degradation degrees (0, 12, 25, 50, 75, 100, and above 100 %) of diuron for the treatments. the decomposition of diuron, as characterised by the initial rate of transformation, which was obtained from linear regression fits to the actual concentration of pesticide versus the time of irradiation, up to 30 % of the concentration of the transformed target compound. diuron (3-(3,4-dichlorophenyl)-1,1-dimethylurea, purity 98 %) was purchased from sigma-aldrich and used without further purification. ultrapure water obtained from a millipore milli-q system was utilised for the preparation of all stock solutions and hplc eluents. hplc-grade methanol was purchased from hipersolv chromanorm. the degussa p25 photocatalyst (49 m2 g-1 surface area, 90:10 anatase/rutile ratio with 25.4 and 40 nm primary particle sise, respectively) with 0.5 g dm-3 loading was used during the heterogeneous photocatalytic experiments. 3. results and discussion 3.1. the rate of transformation of diuron in the present work, the initial rate (r0) of transformation of diuron was determined using various advanced oxidation processes. these can be ranked as ozonation (r0 = 1.0±0.05 × 10-8 mol dm-3 s-1) < heterogeneous photo catalysis (r0 = 7.9±0.3 × 10-8 mol dm-3 s-1) < uv photolysis (r0 = 13.6 ± 1.2 × 10-8 mol dm-3 s-1) < combination of uv photolysis and ozonation (r0 = 27.3±1.2 × 10-8 mol dm-3 s-1) (fig.3). the rate of direct photolytic transformation is determined by the molar absorbence of the target compound and quantum yield of the photolytic process. the absorption coefficient of diuron at the irradiation wavelength of the lamp (254 nm) was determined by using the beer-lambert law, and was found to be ε = 15,000 mol-1 dm3 cm-1. djebbar et al. [15] determined figure 3. kinetic curves of the transformation of diuron using ozonation (!), heterogeneous photocatalysis (�), direct uv photolysis (") and the combination of uv photolysis with ozonation (#). alapi, simon, veréb, kovács, arany, schrantz, dombi, hernádi hungarian journal of industry and chemistry 28 the quantum yield of the photolysis of diuron at 254 nm to be 0.0125, insensitive to ph within the range 2–8.5. the apparent quantum yield of the photoinitiated transformation of diuron was calculated on the basis of the absorbed photon flow and initial transformation rate of the target molecule. in the present work, this value was found to be 0.008. at the applied initial concentration (c0 = 1.70×10-4 m), the solution of diuron fully absorbed the emitted photons. ozonation was found to be the least effective method (fig.3). in aqueous solutions, the decomposition of ozone yields reactive oxygen containing species such as hydroxyl radicals, which are generally a stronger oxidising agent than molecular ozone. the decomposition of ozone in an aqueous solution is initiated by hydroxide ions. at a neutral ph and/or under acidic conditions, molecular ozone should be the dominant oxidant species. during the ozonation of diuron the ph strongly decreased from 8.3 to 4.1, consequently, ozone reacts with diuron mainly as molecular ozone and the formation of hydroxyl radicals is irrelevant. referring to the reaction mechanisms, molecular ozone can react with organic substrates either through cycloaddition to unsaturated bonds or in electrophilic and nucleophilic reactions [16]. nucleophilic reactions occur at molecular sites exhibiting an electron deficit and, more frequently, on carbons carrying electron-withdrawing groups, such as chlorine. based on the values of the initial rate of decomposition, it can be concluded that, by applying the combination of uv photolysis and ozonation, the synergistic effect occurred. the addition of ozone, although in a relatively low concentration, caused the rate of decomposition to double (r0 (254 nm / o3) / r0 (254 nm) = 2.0) (fig.3). both uv photolysis and ozonation are quite selective methods in the oxidative transformation of organic substances. their combination via uv photolysis of ozone itself can produce reactive species, mainly hydroxyl radicals. consequently, the combination of uv photolysis with ozonation generally results in a less selective and more effective method for the oxidative transformation of organic substances. it has to be mentioned, that the relative contribution of direct photolysis to the transformation probably remains high, because of the high molar absorbence of diuron and the relatively low concentration of ozone. under the employed experimental conditions, light absorption of ozone was negligible compared to that of diuron. in the present work, the light emitted by the fluorescent lamp was suitable for the excitation of tio2. the direct photolysis of the compound was excluded by the chosen experimental conditions. this was controlled during the measurements. upon irradiation in the near uv range, electron hole pairs are formed in the tio2 nanoparticles. these charges may reach the surface of the catalyst particle, and undergo redox reactions with substrates or dissolved molecular oxygen, producing highly reactive species such as hydroxyl radicals and hydroperoxyl or superoxide radicals, which can efficiently oxidise the organic pollutants. besides, contaminants adsorbed on the surface of the catalyst particles can directly react with the photochemically formed holes and electrons, promoting the processes of mineralisation. comparing the efficiency of heterogeneous photocatalysis to direct photolysis, this method is less efficient, but much more efficient than ozonation in the case of the transformation of diuron (fig.3). 3.2. spectrophotometric measurements spectrophotometric measurements were carried out on each treatment experiment. the spectra of solutions show that the absorbence at 277 nm increased during the decomposition of diuron while the absorbence at 248 nm changed according to the maximum curves in uv irradiated solutions (fig.4a). it has to be mentioned, that the absorbence at 277 nm decreased slowly after the decomposition of diuron. this suggests that aromatic figure 4. spectra of the samples treated with uv photolysis (a), ozonation (b), combination of uv photolysis with ozonation (c) and heterogeneous photocatalysis (d) at 0, 25, 50, 75 and 100 % decomposition of diuron (inserted figures show the absorbences at 248 nm (!) and 277 nm ($) versus the decomposed diuron). toxicology aspects of the decomposition of diuron 43(1) pp. 25–32 (2015) doi: 10.1515/hjic-2015-0005 29 intermediates accumulated and probably decomposed during the uv initiated transformation. the maximum value of the absorbence at 277 nm was found to be much higher in uv irradiated solutions (0.145) (fig.4a) than in the case of the combination of ozonation with uv photolysis (0.09) (fig.4c). this suggests that the addition of ozone strongly enhanced the rate of formation and decomposition of these intermediates and consequently, hindered their accumulation, most likely due to radical based reactions. the time dependence of the relative absorption at 277 nm suggests that not only the formation, but also the decomposition of these aromatic intermediates took place. this latter process was partly completed in parallel with the transformation of the parent compound, and partly after its transformation. the colour of the aqueous solution of diuron changed from colourless to intensive yellow-pink when uv photolysis was applied. at the same time, when the combination of uv photolysis with ozonation was applied, the change in colour was less intensive. each solution became colourless after the decomposition of diuron. using ozonation (fig.4b) or heterogeneous photocatalysis (fig.4d) neither the change in colour of the solution, nor increase in absorbence at 277 nm was observed. this suggests that the coloured aromatic intermediates were most probably formed mainly during the direct uv photolysis of diuron. these results and observations also suggest that the amount and quality of the aromatic intermediates strongly depend on the applied process. 3.3. dehalogenation and mineralisation uv photolysis, ozonation, the combination of these and heterogeneous photocatalysis provided similar tendencies with respect to the decrease in concentration of adsorbable organically bound chlorines (aox), since in each case, until the 100 % transformation of diuron was achieved, the concentration of aox decreased by almost 100 % (fig.5a). this means that not only the pesticide itself, but the formed halogenated by-products were also de-chlorinated simultaneously within the timeframe of transformation of the parent substance. it has to be mentioned, that the rate of dechlorination was higher in the case of uv photolysis than heterogeneous photocatalysis, mainly at the beginning of the treatment. direct uv photolysis is a quite selective method for the transformation of organic substances and can be effective for the transformation of compounds, which highly absorb at 254 nm (such as diuron and probably its aromatic intermediates), mainly by the dissociation of the carbon-halogen bond. on the other hand, in the case of heterogeneous photocatalyis, adsorption has an important role. competitive adsorption can occur between the aromatic compounds containing chlorine atom(s) and the formed intermediates, which do not contain chlorine atom, and exhibit better adsorptivity (mainly carboxylic acids). consequently, the formation of these intermediates and their adsorption on the surface of the photocatalyst can cause a relatively slow decrease in the rate of dechlorination (fig.5a). ozonation is a quite selective method for the transformation of organic substances, similar to direct uv photolysis. these methods are generally not effective in terms of mineralisation, as also observed in this work (fig.5b). in the case of the combination of these methods the toc content slightly decreased, most likely because of the hydroxyl radical based reactions. in the case of heterogeneous photocatalysis, the rate of mineralisation was very low at the beginning, but the toc decreased rapidly in the final stage of decomposition of diuron (fig.5b). compared to uv photolysis and ozonation, heterogeneous photocatalysis is a less selective method and generally results in the transformation and, in most cases, the mineralisation of a large variety of organic substances. however, the transformation of compounds takes place on the surface of tio2 particles, thus adsorption has a crucial role in this case, as mentioned previously. it is probable that the superior adsorptivity of aliphatic intermediates (mainly carboxylic acids) is the reason why mineralisation takes place in parallel with the transformation of parent compounds. this explanation is in agreement with the observation that the rate of the change in concentration of aox increased when mineralisation became dominant (fig.5). 3.4. ecotoxicological measurements the results obtained from both daphtoxkit ftm and vibrio fischeri luminescence inhibitory tests showed that the toxicity of the treated solutions changed through a maximum value within the time frame of transformation of diuron in solutions irradiated with 254 nm uv light (figs.6a and 7a). consequently, the figure 5. kinetic curves of the transformation of diuron using ozonation (!), heterogeneous photocatalysis (�), direct uv photolysis (") and the combination of uv photolysis with ozonation (#). alapi, simon, veréb, kovács, arany, schrantz, dombi, hernádi hungarian journal of industry and chemistry 30 formation and decomposition of by-products exhibiting relatively higher toxicities than expected from diuron. during ozonation, both the mortality and inhibitory effect increased, which can be explained by the formation and accumulation of intermediates more toxic than the parent compound (figs.6b and 7b). the tendencies of mortality and the inhibitory effect were similar, although mortality increased slightly, and the inhibitory effect increased strongly during the transformation of diuron. it can be supposed, that vibrio fischeri is more sensitive to the presence of the intermediates formed due to the reaction of molecular ozone with diuron, which can be the reason for this observation. in the case of the combination of uv photolysis with ozonation, the mortality and inhibitory effect changed through maxima (figs.6c and 7c), in a similar way to direct uv photolysis. however, in this case the maxima were reached at 25 % and 50 % decomposition of diuron (figs.6c and 7c), while during uv photolysis the maxima were reached at 50 % and 75 % decomposition of diuron (figs.6a and 7a). using heterogeneous photocatalysis, the mortality and inhibitory effect changed also through maxima (figs.6d and 7d). at the same time, it has to be mentioned, that in this case, the values of the maxima were found to be lower than those determined in the case of uv photolysis and its combination with ozonation, mainly in the case of results obtained using the daphtoxkit ftm test. the mortality using heterogeneous photocatalysis did not reach 40 %, while in the case of uv photolysis and its combination with uv photolysis it exceeded 60 %. this confirms that the amount of the aromatic intermediates was less, and/or their specific toxicity was lower than in the case of uv photolysis and its combination with ozonation. at this point, a correlation can be established between the results of spectrophotometric measurements and ecotoxicological tests. in the case of uv photolysis, the formation and accumulation of aromatic intermediates were supposed, while in the case of the combined method, their amount was likely to be lower. at the same time, in the case of heterogeneous photocatalysis, their formation was less favourable than in the presence of 254 nm uv light. these observations, together with the results of the ecotoxicological tests, suggest that the toxic intermediates are most likely aromatic by-products. 4. conclusion in this work, various advanced oxidation processes, such as uv photolysis at 254 nm, ozonation, their combination and heterogeneous photocatalysis were investigated and compared regarding the oxidative transformation of diuron. the initial rates of transformation were determined at the same electric energy input and exhibited the following order: ozonation < heterogeneous photocatalysis < uv photolysis < combination of uv photolysis and ozonation. the results obtained from spectrophotometric measurements suggested that aromatic intermediates accumulated during the uv initiated transformation of diuron. the addition of ozone of relatively low concentration strongly enhanced the rate of formation and/or decomposition of these intermediates. using ozonation or heterogeneous photocatalysis, the amount figure 6. mortality of daphnia magna after uv photolysis (a), ozonation (b), the combination of uv photolysis with ozonation (c) and heterogeneous photocatalysis (d) at 0, 12, 25, 50, 75, 100 % and above 100 % (samples taken 10 minutes after total decomposition) decomposition of diuron. figure 7. inhibition values for vibrio fischeri after uv photolysis (a), ozonation (b), the combination of uv photolysis with ozonation (c) and heterogeneous photocatalysis (d) at 0, 12, 25, 50, 75, 100 % and above 100 % (samples taken 10 minutes after total decomposition) decomposition of diuron. toxicology aspects of the decomposition of diuron 43(1) pp. 25–32 (2015) doi: 10.1515/hjic-2015-0005 31 of the formed aromatic intermediates was likely to be lower. uv photolysis, ozonation, their combination and heterogeneous photocatalysis provided similar tendencies in the decrease of the concentration of adsorbable organically bound chlorines (aox) since, in each case, until the 100% degradation of diuron was achieved, the concentration of aox decreased by almost 100%. on the other hand, only heterogeneous photocatalysis was found to be effective in terms of mineralisation during the decomposition of diuron. in this case, the rate of mineralisation was low at the beginning, but the total organic carbon content decreased rapidly in the final stage of the decomposition of diuron. ecotoxicological measurements were carried out with both daphtoxkit ftm and vibrio fischeri luminescence inhibitory tests. the results showed that the toxicity of the treated solutions changed through a maximum curve within the time of transformation of diuron in each case, except for with ozonation. thus, the formation and decomposition of by-products, having relatively higher toxicity than diuron, can be supposed. using heterogeneous photocatalysis, the mortality and inhibitory effect also changed through maxima, but the values of the maxima were found to be lower than that determined in the case of uv photolysis and its combination with ozonation. our observations and results confirmed that the aromatic intermediates formed, their quantity, and specific toxicity strongly depend on the applied process. acknowledgement this research was supported by the european union and the state of hungary, co-financed by the european social fund in the framework of támop-4.2.4.a/ 211/1-2012-0001 ‘national excellence program’. the financial help of the “társadalmi megújulás operatív program” (támop-4.2.2.a-11/1/konv-2012-0047) is also highly appreciated. the environmental chemistry research group would like to thank the swiss contribution (sh7/2/20) for its financial support. references [1] holmes, g.: australia’s pesticide environmental risk assessment failure: the case of diuron and sugar cane, marine pollut. bull., 2014, 88(1–2), 7–13 10.1016/j.marpolbul.2014.08.007 [2] yebra, d.m.; kiil, s.; dam-johansen, k.: antifouling 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arany, schrantz, dombi, hernádi hungarian journal of industry and chemistry 32 [14] atkinson, r.; baulch, d.l.; cox, r.a.; crowley, j.n.; hampson, r.f.; hynes, r.g.; jenkin, m.e.; rossi, m.j.; troe, j.: evaluated kinetic and photochemical data for atmospheric chemistry: volume i gas phase reactions of ox, hox, nox and sox species, atmos. chem. phys., 2004 4, 1461-1738 10.5194/acp-4-1461-2004 [15] djebbar, k.; sehili, t.; mazellier, p.; de laat, j.: phototransformation of diuron in aqueous solution by uv irradiation in the absence and in the presence of h2o2, environ. technol., 2003 24, 479–489 10.1080/09593330309385583 [16] hoigné, j.; bader, h.: rate constants of reactions of ozone with organic and inorganic compounds in water i: non-dissociating organic compounds, water res., 1983 17, 173-183 10.1016/00431354(83)90098-2 hungarian journal of industry and chemistry vol. 43(1) pp. 33–38 (2015) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2015-0006 organisation of the analytical, stoichiometric, and thermodynamic information for water chemistry calculations rita földényi* and aurél marton department of environmental science, university of pannonia, egyetem u. 10., veszprém, 8200, hungary a common feature of the chemical processes of the hydrosphere and water treatment plants is that essentially the same types of chemical equilibrium reactions occur in both fields. these equilibria could be acid/base, complexation, redox, precipitation, and interfacial processes. since these reactions may also occur in combination, the aqueous environments are unavoidably multispecies systems. due to multiple equilibria, the state of aggregation, the state of oxidation, as well as the electric charge of the species may change dramatically. calculation of the equilibrium concentration of the species is facilitated by the availability of analytical, stoichiometric, and thermodynamic information that are consistently organised into an asti matrix. the matrix makes it possible to apply a uniform algebraic treatment for all occurring equilibria even, if later on, further reactions have to be included in the chemical model. the use of the asti matrix enables us to set up the necessary mass balance equations and equilibrium relationships, which together form a non-linear system of equations (nlse). the goal of our paper is to show that the use of the asti matrix approach in cooperation with the powerful engineering calculation software, mathcad14, results in fast and easy handling of the nlse-s and, consequently, the calculations of speciation in aqueous systems. the paper demonstrates the method of application in three examples: the calculation of the ph dependence of the solubility of calcite in closed and open systems, the calculation of the ph and pε in a system where acid/base reactions, complexation equilibria, and redox equilibria occur, and a study of adsorption of lead ions on aluminium oxide. keywords: multiple solution equilibria, asti matrix method, solubility of calcite, redox calculation, adsorption of lead 1. introduction information on the speciation profile of aqueous systems is of primary importance in many fields of chemistry. the usual acid/base, complexation, redox, precipitation, and interfacial reactions may occur simultaneously leading to the formation of a large number of species in both natural and artificial aquatic systems. contemporary numerical and graphical treatments of aqueous equilibria were presented in seminal publications in the fields of environmental engineering [1], natural aquatic systems [2–7] and geochemistry [8, 9]. an important aspect of the recent approaches is the systematic organisation of the analytical, stoichiometric, and thermodynamic information relevant to the studied system. the input of structured information became particularly indispensable in the use of the modern computer programs dedicated to chemical equilibrium modelling: mineql [10], mineql+ [11], minteqa [12], phreeqc [13], and wham [14], to name a few. *correspondence: foldenyi@almos.uni-pannon.hu 2. methods 2.1. organisation of information into the asti matrix in order to collect and organise data for the equilibrium calculations a strict distinction has to be made between the terms: reagent, reactions, species and components. under laboratory conditions, reagents (denoted hereafter by a) are simply those chemicals that are present at the beginning of reactions. each reagent is characterised by its analytical molar concentration (c in mol dm-3 or m). under environmental conditions, we have to assume the presence of a ‘contaminating’ compound of reagents: e.g. acid rain forms as a result of due to the presence of nitric acid in rainwater. when reagents are mixed, several reactions may take place (the total number of reactions is denoted by r). for each reaction, the relevant equilibrium constant (k) refers to the correct stoichiometry of the reaction, such as h2co3 ⇄ hco3 + h+, k1 = 10-6.35 (1) hco3 ⇄ co3 2+ h+, k2 = 10-10.33 (2) földényi and marton hungarian journal of industry and chemistry 34 where the k values are given for a specified temperature (25 ºc), pressure (101.3 kpa), and ionic strength (0.1 m). the considered reactions or chemical models generate a large number of chemical particles with appreciable stabilities. this set of entities is called species (the number of species is denoted by s). the smallest subset of selected species that enable us to describe the formation of all the other species of the system are called components (their number is denoted by c). in order to meet the requirements of the gibbs phase rule [15], the needed number of components has to be calculated from the relationship c = s r. if there are 6 reactions and 10 species then from the list of species four species have to be selected as component c = 4. the concept of this component is the “key and door” to the organisation of the database and, consequently, to equilibrium calculations. in principle, any subset of the species can be selected (promoted) as a component, but chemical considerations dictate some rules that have to be kept in mind: 1. h2o and h+ have to always be selected as components, 2. species with fixed activities whose concentrations do not change during the reactions have to be selected as components too; such species are the solvent (h2o), solid phases (e.g. caco3), and gases of known pressure (e.g. atmospheric co2, p = 10-3.5 atm), and 3. species that are presumably present in dominant concentrations will also be selected as components. after selecting the components, the formation reactions for the rest of the species have to be written up in terms of these components. the equilibrium (formation) constant of the species is calculated by hess’s law using algebraic manipulation of the reactions, in such a way, to obtain the target reaction. the left-hand side of the target reaction only contains components and the right-hand side only displays the species e.g.: if in the studied system co3 2is selected as a component (besides h2o and h+) then by using eqs.(1) and (2), the formation of the hco3 and h2co3 species should be given as: co3 2+ h+ ⇄ hco3 , (k2)-1 (3) co3 2+ 2h+ ⇄ h2co3 . (k1·k2)-1 (4) when the formation of all the (s c) species is expressed in this way then the stoichiometric relationship between the components and species is revealed. in addition to this, the stoichiometric connection between the components and reagents has to be established too. this can be done by synthesising the reagents through the reaction of the components, just like in the case of species, but now only the stoichiometric coefficients are relevant. the above procedure highlights the central role of the component and allows us to arrange the available analytical, stoichiometric and thermodynamic information into a coherent matrix abbreviated hereafter as the asti matrix. the columns and rows of the matrix list the c number of components and all the s number of species, respectively. the elements of the matrix are filled with the respective stoichiometric coefficients (including zeros too). analytical concentrations (c) and the equilibrium constants (k) are introduced into this matrix as shown in the examples discussed below. for the calculation of the unknown concentration of s species, we need the s stoichiometrically independent equation. the main purpose of our effort to develop the asti matrix is to draw up the required s equations. based on the columns and rows matrix two types of equations can be drawn up. the mass balance equations (mb) are based on the columns of the asti matrix and are drawn up usually for all the c components (in exceptional cases, not all the mb equations are needed, see example 1. below). the mb equation is, in fact, an additive relationship showing the weighed concentration sum of all species containing the particular component. the weighing factors are the respective stoichiometric coefficients. the other type of equations, based on the asti matrix, are the equilibrium relationships (er). this multiplicative type of equations are drawn up on the basis of the rows of the species. the er gives the equilibrium concentration of the (s c) species expressed as a product of the concentration of all the c components raised to the power of the stoichiometric coefficients (which could be zeros too). consequently, the er-s expresses the concentration of the species in terms of the concentration of the components. it is worth noting, that a different choice of components yields different mb equations and er (a further indication of the importance of the choice of component in the equilibrium calculation). the application of these principles will be shown in the examples below. the mass balance equations together with the equilibrium relationships form a (usually) non-linear system of equations (nlse) for calculating the concentration of all the s species. 2.2. solving the non-linear system of equations (nlse) using mathcad mathcad 14 (ptc. inc.) is a versatile and powerful engineering calculation software. it works seamlessly with numbers, units, equations, texts, and graphs. after giving the required k, analytical concentration data, and assigning initial values for the unknown variables, the s number of nlse is introduced on the screen between the given and find commands. mathcad then rapidly solves the nlse by using the iterative levenberg marquardt algorithm [16]. for example, the solution of the nlse with ten unknowns takes only a couple of seconds. to assign a good guess for ten variables is rather cumbersome; therefore, the algebraic reduction of the number of unknowns is desirable. this can be done by substituting the equilibrium relationships into the mass balance equations, which reduces the number of variables against the number of components (c < s). in organisation of the analytical, stoichimetric, and thermodynamic information 43(1) pp. 33–38 (2015) doi: 10.1515/hjic-2015-0006 35 this case, the solution of the c number of nlse (instead of the s) returns the equilibrium concentration of the components, which are then substituted into the applicable er to obtain the concentration of the (s c) species. in addition to this algebraic method of the reduction of variables, chemical considerations may also be applied to reduce the number of species. chemical background information often suggests that certain species of the system are present in minor concentrations only. these terms may then be safely omitted from the additive type of mb equations and neglected from the set of er-s. this principle works for the opposite case too. sometimes it is desirable to improve the original chemical model by including further equilibria. this can be done seamlessly if the new equilibria are expressed also in terms of the components and the asti matrix is augmented by the required new data. the above considerations clearly highlight the appreciable advantage of using the asti matrices in association with mathcad. the asti matrix can be decomposed and treated by the well known methods of matrix algebra. here; however, we like to keep chemistry in focus, so the matrix algebraic solution is not treated here explicitly, because its elegant and concise formalism conceals chemical insights. 3. simulation results 3.1. calculation of the ph dependence of the solubility of calcite in open and closed systems (example 1) the solubility of caco3(s) in water is calculated as a function of ph for an open and a closed system. the open system is exposed to the atmosphere where pco2 is 10-3.5 atm, where the exchange of co2 molecules between the solution and gas phases is allowed. considering the similarities between the two systems, and for brevity, the process leading to the asti matrix and the nlse is shown only for the open system, while the results are presented for both systems. in the open system, we have three species whose equilibrium concentrations (activity, a) are known (h2o(l) with a = 1, caco3(s) with a = 1, pco2 = 10-3.5 atm) so, according to rules of selection from above, they have to be selected as components. the details of the procedure are shown below: reagents, a=3: h2o(l) a = 1, caco3(s) a = 1, pco2= 10-3.5 reactions, r = 5: h2o ⇄ h+ + oh kv = 10-14 ca2+ + co3 2⇄ caco3(s) ks = 108.35 co2(g) + h2o ⇄ h2co3 * kh = 10-1.5 co3 2+ h+ ⇄ hco3 k1 = 1010.3 hco3 + h+ ⇄ h2co3 * k2 = 106.3 species, s = 9: h2o, h+, oh-, co3 2-, hco3 -, h2co3 *, co2(g), caco3(s), ca2+ components, c = s – r = 4 h2o, h+, caco3(s), co2(g) asti matrix s/c h2o h+ co2(g) caco3(s) k (logk) h2o 1 h+ 1 co2(g) 1 caco3(s) 1 oh1 -1 kw (-14) ca2+ 2 -1 1 ks -1·kh -1·k1·k2 (9.8) h2co3 * 1 1 kh (-1.5) hco3 1 -1 1 kh·k2 -1 (-7.8) co3 21 -2 1 kh·(k1·k2)-1 (-18.1) a/tot m a(h2o) 1 1 a(caco3(s)) 1 1 pco2(g) 1 10-3.5 mass balance equations, mb toth = [h+] [oh-] + 2[ca2+] [hco3 -] 2[co3 2-] = 0 equilibrium relationships, er [oh-] = kv·[h+]-1 [ca2+] = ks -1·kh -1·k1·k2 ·(pco2)-1·[h+]2 [h2co3*] = kh· pco2 [hco3 -] = kh·k2 -1·pco2·[h+]-1 [co3 2-] = kh·(k1·k2)-1·pco2·[h+]-2 the required six equations (mb + er) are therefore available for the calculation of the six unknown concentrations (h+, oh-, co3 2-, hco3 -, h2co3 *, and ca2+). the nlse was solved by mathcad and the results are shown in table 1. for the closed system, the asti matrix can be obtained by omitting the co2 from the list of reagents, species and components as well as the kh equilibria from the list of reactions. as shown in table 1, the dissimilarity between the ph values is the most remarkable difference between the equilibrium systems. the solubility of the caco3(s) was also calculated for both systems as a function of ph. fig.1 shows that in a closed system the solubility tends to be a limiting value as ph increases. the solubility vs. ph function changes dramatically, if the system is open to the atmosphere, pco2 = 10-3.5 atm, as shown in fig.2. as opposed to the closed system, when the calcium-carbonate-water system is open to the atmosphere (pco2 = 10-3.5 atm), the solubility continuously decreases as ph increases (compare figs.1 and 2). table 1. comparison of speciation in the caco3(s)h2o(l) (closed) and caco3(s)-h2o(l)-co2(g) (open with pco2 = 10-3.5 atm) systems both at 25 ºc. -log c closed system open system ph 9.9 8.3 -logca 3.9 3.3 -logco3 24.4 5.0 -loghco3 4.1 3.0 -logh2co3 7.8 5.0 földényi and marton hungarian journal of industry and chemistry 36 3.2. calculation of speciation in the iron(ii)/iron(iii) system involving complexation (example 2) the ph and pε values are calculated for the ferrous/ferric ion redox system involving the complexation of the metal ion with the oh-, cland f ions starting from a hypothetical solution of fecl2, fecl3, nacl, and naf. two additional questions were also addressed, such as what is the measurable redox potential of the system, and if a trace quantity of arsenic gets into this system, what will be the dominant redox form of the arsenic. the organisation of information follows the same flow as outlined above. reagents, a c(fe2+) = 10-4 m, c(fe3+) = 10-4 m, c(cl-) = 105·10-4 m, c(na+) = 105·10-4 m, c(f-) = 5·10-4 m reactions, r = 6 h2o ⇄ h+ + oh kw = 10-14 fe3+ + e ⇄ fe2+ kr = 1013 pε° = 13 fe3+ + h2o ⇄ fe(oh)2+ + h+ k1 = 10-2.19 fe3+ + 2h2o ⇄!fe(oh)2 + + 2h+ k2 = 10-5.67 fe3+ + f⇄ fef2+ k3 = 106.2 fe3+ + cl⇄ fecl2+ k4 = 101.48 species, s = 13: h2o, h+, oh-, fe3+, fe2+, fe(oh)2+, fe(oh)2 +, f-, fef2+, cl-, fecl2+, na+, e components, c = s – r = 7: h2, h+, fe3+, f-, cl-, na+, e asti matrix s /c h+ fe3+ fclna+ ek h+ 1 fe2+ 1 f 1 cl 1 na+ 1 e 1 oh-1 kw fe(oh)2+ -1 1 k1 fe(oh)2 + -2 1 k2 fef2+ 1 1 k3 fecl2+ 1 1 k4 fe2+ 1 1 kr tot m cfecl2 1 2 1 10-4 cfecl3 3 10-4 cnacl 1 1 10-2 cnaf 1 5·10-4 mass balance equations, mb toth = [h+] [oh-] [fe(oh)2+] – [2fe(oh)2 + ] = 0 totfe = [fe3+] + [fe(oh)2+] + [fe(oh)2 +] + [fef2+] + + [fecl2+] + [fe2+] = 2·10-4 totf = [f-] + [fef2+] = 5·10-4 totcl = [cl-] + [fecl2+] = 3·10-4 + 2·10-4 + 10-2 totna = [na+] = 10-2 + 5·10-4 tote = [e-] + [fe2+] = 10-4 equilibrium relationships, er [oh-] = kw ⋅ [h+]-1 [fe(oh)2 +] = k1 ⋅ [h+]-1⋅[fe3+] [fe(oh)2 +] = k2 ⋅ [h+]-2⋅[fe3+] [fe(f)2+] = k3·[fe3+]·[f-] [fe(cl)2+] = k4·[fe3+]·[cl-] [fe2+] = kr·[fe3+]·[e-] the system of nlse generated by seven mb and six er equations was solved by mathcad and the results are summarised in table 2. since the charge and oxidation state of the introduced arsenic species are controlled by the ph and pε values of the environment, the calculated ph and pε data make it possible to visualise, which oxidation state would dominate the studied redox-complex system. the relevant predominance area (pε vs. ph) diagram is shown in fig.3. according to fig.3, the calculated ph = 4 and pε = 10 values corroborate the existence of the h2aso4 anionic arsenic species in this hypothetical system. figure 2. change in the -log(solubility) = -log[ca2+] of the caco3(s) in an open system as a function of ph (graphs for -log[co3 2-] and -log[hco3 -] are also presented). figure 1. change in the -log(solubility) = -log[ca2+] of the caco3(s) in a closed system as a function of ph (graphs for -log[co3 2-] and -log[hco3 -] are also presented). organisation of the analytical, stoichimetric, and thermodynamic information 43(1) pp. 33–38 (2015) doi: 10.1515/hjic-2015-0006 37 3.3. adsorption of lead(ii) ions on the surface of γ-al2o3 adsorbent (example 3) the asti matrix based approach of the equilibrium calculation makes it possible to include heterogeneous reactions in the calculation like e.g. adsorption and ion exchange. here the adsorption of the pb(ii) ions from pbcl2 on γ-al2o3 is studied as a function of ph and the concentration of chloride ions from excess nacl. the active surface group, -oh of the adsorbent is denoted here by ≡xoh. the mechanism of lead adsorption is interpreted using the surface complexation model [5] leading to the formation of the surface complex defined by the symbol ≡xopb+. reagents: m(γ-al2o3) = 0.3846 g volume of the solution, v = 500 cm3 adsorption capacity, q = 1.3·10-4 mol g-1 concentration of surface sites, c≡x = m·q/v = 10-4 m c(pb2+) = 10-5 m; c(cl-) = 0.1002 m; c(na+) = 0.1 m; ph = 6 reactions, r = 6: h2o ⇄ h+ + oh kw = 10-14 pb2+ + h2o ⇄ pboh+ + h+ k1 = 10-7.7 pb2+ + cl⇄ pbcl+ k2 = 101.6 ≡xo+ h+ ⇄ ≡xoh k3 = 107.7 ≡xoh + h+ ⇄ ≡xoh2 + k4 = 106 ≡xopb+ ⇄ ≡xo+ pb2+ k5 = 10-6.1 species, s = 11: h2o, h+, oh-, pb2+, pboh+, cl-, pbcl+, ≡xo-, ≡xoh, ≡xoh2 +, ≡xopb+ components, c = s – r = 5: h2o, h+, pb2+, cl-, ≡xoh2 + asti matrix: s /c h+ pb2+ ≡xoh2 + clk h+ 1 oh-1 kw pb2+ 1 pboh+ -1 1 1 k1 cl pbcl+ 1 1 k2 ≡xoh2 + 1 ≡xoh -1 1 (k4)-1 ≡xo-2 1 (k3·k4)-1 ≡xopb+ 1 1 (k3·k4·k5)-1 tot m cpb 1 10-5 c≡x 1 1.3·10-4 cnacl 1 0; 0.1; 0.5 mass balance equations, mb: (mb for water is usually omitted, if the ph is fixed then toth is not needed and clis known): totpb =[pb2+] + [pboh+] + [≡xopb+] + [pbcl+] = cpb totxoh2=[≡xoh2 +] + [≡xoh] + [≡xo-] + [≡xopb+]= c≡x equilibrium relationships, er: [pboh+] = k1⋅[pb2+]⋅[h+]-1 [pbcl+] = k2⋅[pb2+]⋅[cl-] [≡xoh] = (k4)-1 ⋅[≡xoh2 +]⋅[h+]-1 [≡xo-] = (k3⋅k4)-1⋅[≡xoh2 +]⋅[h+]-2 [≡xopb+] = (k3⋅k4⋅k5)-1⋅[≡xoh2 +]⋅[pb2+]⋅[h+]-2 the two mb-s and five er-s define the unique value of the concentration of the seven dissolved and surface species. the mathcad solution of the nlse yields the data summarised in table 3. considering that the er equations are valid at all ph values and chloride concentrations, arbitrary useful functions can be defined by using these concentration functions. let this function now be the distribution coefficient widely used in liquid chromatography and defined as the ratio of the total concentrations of the lead (totpb) in the two phases: figure 3. predominance area (pourbaix) diagram of the arsenic showing the existence of the species of various oxidation states (from p.193 of ref [8]). table 2. calculated ph and pε values and the concentration of the species occurring in the fe2+/fe3+ redox system containing the oh-, cland f coordinating ligands. the measurable electromotive force (emf) with respect to a calomel reference is also shown (εref = 0.244 v). ph = 4.13 pε = 9.93 [fe2+] = 1.0·10-4 [fe3+] = 8.5·10-8 [fe(oh)2+]= 7.4·10-6 [fe(oh)2 +] = 3.3·10-5 [fecl2+] = 2.7·10-8 [fef2+] = 5.9·10-5 [f-] = 4.4·10-4 [cl-] = 1.0·10-2 εind = 0.059·pε = 0.59 v; emf = εind εref = 0.35 v table 3. speciation of pb(ii) in the presence of adsorbent (γ-al2o3), in 0.1 m nacl solution at ph = 6. species molarity ≡xoh 6.3·10-5 ≡xoh2 + 6.3·10-5 ≡xopb+ 2.4·10-6 ≡xo1.3·10-6 pb2+ 1.5·10-6 pbcl+ 6.0·10-6 pboh+ 3.0·10-8 földényi and marton hungarian journal of industry and chemistry 38 d = totpb on the ads. totpb in the solutn. = [xopb+ ] [pb2+ ]+[pboh+ ]+[pbcl+ ] (5) after substituting the appropriate er relationship into the above equation the distribution coefficient can be calculated as a function of ph and the chloride ion concentration. the result is shown in fig.4. as shown in fig.4, the adsorption of lead increases sharply with the increase of ph, since the formation of surface complexes is preferred at higher ph values. it is interesting to observe that at ph 6 the adsorption of the positive pb(ii) species is significant despite the fact that the surface species, ≡xoh2 +, is also positively charged at this ph. 4. conclusion in order to solve complex aqueous speciation problems a logical scheme for arranging the available data is needed. this convenience scheme is provided by the tabulated form of the arrangement of analytical, stoichiometric, and thermodynamic information. this matrix of data allows us to set up the necessary mass balance and equilibrium equations of the calculation. this paper presented typical examples of the use of these principles in the field of water chemistry. symbols a number of reagents asti analytical stoichiometric and thermodynamic information c number of components er equilibrium relationship h2co3* h2co3 + co2(aq) k equilibrium constant mb mass balance nlse non-linear system of equations r number of reactions s number of species totx total concentration of species ‘x’ acknowledgement the research was supported by támop-4.1.1.c12/1/konv-2012-0015. references [1] brezonik, p.l.; arnold, w.a.: water chemistry (oxford university press, oxford, uk) 2011 [2] stumm, w.; morgan, j.j.: aquatic chemistry, 3rd ed. (wiley interscience, new york, usa) 1996 [3] snoeyink, v.l.; jenkins, d.: water chemistry (j. wiley and sons, new york, usa) 1980 [4] pankow, j.f.: aquatic chemistry concepts (lewis publ., chelsea, mi, usa) 1991 [5] morel, f.m.m.; hering, j.g.: principles and applications of aquatic chemistry (j. wiley and sons, new york, usa) 1993 [6] benjamin, m.m.: water chemistry (mcgraw-hill, new york, usa) 2002 [7] jensen, j.n.: a problem-solving approach to aquatic chemistry (j. wiley and sons, new york, usa) 2003 [8] drever, j.: geochemistry of natural waters (prentice-hall, englewood cliffs, nj, usa) 1982 [9] zhu, c.; anderson, g.: environmental applications of geochemical modelling (cambridge university press, cambridge, uk) 2002 [10] westall, j.c.; zachary, j.l.; morel, f.m.m.: mineql, a computer program for the calculation of chemical equilibrium of aqueous systems (dept. of civil engineering, mass. inst. technol., cambridge, ma, usa) technical note 18, 1976 [11] mineql+ver.4.6, a chemical equilibrium modeling system (environmental research software, hallowell, mn, usa) 2008 http://mineql.com [12] u.s. epa. 2006. minteqa2 (ver. 4.03) http://www.epa.gov/ceampubl/mmedia/minteq [13] parkhurst, d.; charlton, s.; riggs, a.: reactiontransport modeling in ground-water systems. phreeqc ver.2. a computer program for speciation, batch-reaction, one-dimensional transport, and inverse geochemical calculation (us geol. survey, reston, va, usa) 2008 [14] tipping, e.: humic ion binding model vi: an improved description of the interaction of protons and metal ions with humic substances. aquat. geochem., 1998 4, 3-48 [15] atkins, p.w.: physical chemistry (oxford university press, oxford, uk) 1978 [16] mathcad user’s guide (1995) mathsoft inc. cambridge, mass., usa p. 637 figure 4. change in the distribution of the pb(ii) ions as a function of ph at different chloride ion concentrations. the second index of d refers to the chloride ion concentration (eq.(5)): 0 = no chloride, 1 = 0.1 m, 2 = 0.5 m. hungarian journal of industry and chemistry vol. 43(1) pp. 39–43 (2015) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2015-0007 groundwater remediation using biological and photocatalytic methods sándor guba,1* viola somogyi,2 and erzsébet szabóné bárdos3 1 institute of physics and mechatronics, university of pannonia, egyetem u. 10, veszprém, 8200, hungary 2 institute of environmental engineering, university of pannonia, egyetem u. 10, veszprém, 8200, hungary 3 department of general and inorganic chemistry, university of pannonia, egyetem u. 10, veszprém, 8200, hungary the degradability of two commercially available pesticides was studied using heterogeneous photocatalytic and activated sludge treatment methods. the first pesticide contained 5% quizalofop-p-ethyl as an active ingredient and petroleum naphtha as a solvent, the latter causing difficulties both in photocatalytic and biological treatment methods. the active ingredient of the second compound was acetamiprid. the photocatalysis proved to be effective both under laboratory conditions (using uv light) and when exposed to sunlight, but the pesticides remained stable during the employed biological treatment. preliminary information on its behaviour in soil was obtained from transport modelling. keywords: heterogeneous photocatalysis, groundwater remediation, quizalofop-p-ethyl, acetamiprid, biological treatment 1. introduction the drinking water supply of hungary largely relies on underground water resources. the water quality has been endangered by both industry over the last century and the still significant pesticide-intensive agriculture. excessive amounts of pesticides contaminating soil may be fully or partially degraded by natural chemical and biochemical reactions. the latter may lead to bioaccumulation. the transport into groundwater and/or surface water bodies is affected by several factors, such as precipitation, evapotranspiration, infiltration, and runoff besides the physicochemical characteristics of soil and the attributes of the substance. the application of pesticides is an inefficient procedure, since only a small amount is utilised for the desired purpose. most of the compound is released unused into the soil and if it degrades partially or at a slower pace, the pesticide might accumulate and enter the food chain. in order to avoid the release of pesticides that are persistent and harmful to the environment and humans, it is necessary to have licencing procedures and strict controls on the use of such materials [1]. in hungary, authorisation is regulated by the decree 89/2004 of the ministry of agriculture and rural development in agreement with the council directive 91/414/eec [2]. *correspondence: gubas@almos.uni-pannon.hu a common method to treat contaminated aquifers is groundwater pump-and-treat technology [3], where extraction wells are used to remove the contaminated water that is treated with adequate techniques after which it is re-injected into the aquifer or released into a surface water body. the treatment method is dependent on the degradability and toxicity of the pollutant. bioremediation cannot be used in cases when the compound is not biodegradable or even toxic to microorganisms. oxidative methods, such as heterogeneous photocatalysis may be adequate in such cases [4]. in this process, the radicals formed due to the photogenerated charge-carriers on the surface of the semiconductor. they react with the pollutant molecule initiating its degradation. the catalyst is often reusable and recycled. the semiconductor catalyst has to be chemically and biologically inert, but photocatalytically active. it should be easily produced and economical. since tio2 fits these requirements, it is the best among the semiconductors for extensive use [5]. research over the past years has proved that on a laboratory scale different organic compounds (aliphatic and aromatic hydrocarbons [6], alcohols and organic acids [7], phenols [8] and chlorinated compounds [9]) could be effectively degraded to inorganic end products using heterogeneous photocatalysis [10]. the aim of this paper is to report on the degradability of organic contaminants in the soil and groundwater with biological and photocatalytic methods using model compounds. their behaviour in the soil guba, somogyi, szabóné bárdos hungarian journal of industry and chemistry 40 was determined by hydraulic and transport models. the model compounds were a herbicide (leopard 5 ec) and an insecticide (mospilan 20 sg). both fall into category iii meaning that they are available without a special licence. their metabolites remain stable in soil for a long period. 2. methods and materials the substance with the brand name leopard 5 ec contains 5% quizalofop-p-ethyl (scheme 1a) as an active ingredient, 77-83% petroleum naphtha as a solvent and other emulsifying excipients. the active substance is especially dangerous to mammals, aquatic organisms, and birds and moderately toxic to bees. it is insoluble in water; it emulsifies due to the additives. its metabolites are more soluble in water, but do not hydrolyse. their half-lives are between 35 and 39 days. the active ingredient of the insecticide called mospilan 20 sg is 20% acetamiprid (scheme 1b), which is highly toxic to mammals and birds and moderately toxic to aquatic organisms. the substance is very soluble in water, hence its high mobility upon infiltration. its metabolite is not easily degraded under natural conditions in soil and water (its half-life is 133 days), and it is moderately toxic to aquatic life. heterogeneous photocatalytic irradiation experiments were performed in a photoreactor with an effective volume of 2.5 dm3. internal recirculation was provided in the tube reactor. tio2 was used as a catalyst with a concentration of 1 g dm-3, while the air flow was 40 dm3 h-1. the radiation source placed in the axis of the reactor was a 40 w fluorescent lamp specially manufactured for such purposes. the vast majority of light emitted is of a longer wavelength than 300 nm. biological treatment was carried out in an activated sludge, aerated sequenced batch reactor. an operating cycle lasted for a day. the effective volume of the reactor was 5 dm3 and the sludge concentration was kept at 4 g dm-3. the rate of aeration was kept constant throughout the process. a non-adapted municipal sludge was used for the experiments. modelling was carried out using processing modflow for windows (pmwin) 5.3. this version is freely available, while later versions can be obtained commercially. the test area was chosen to be the size of 1 acre divided vertically into three homogenous layers with average hungarian properties. simulations were run for 1–3–13–113 day intervals. the environmental factors taken into consideration were the following: groundwater flow and porosity, infiltration due to precipitation (1.9 mm day-1), and evapotranspiration (1.2 m day-1) [11]. the hydraulic conductivity was 129.6 mm day-1 for all three layers [12]. 3. results and analysis 3.1. leopard 5 ec the degradability of the substance with heterogeneous photocatalysis was examined under laboratory (uvlight) and natural (sunlight) conditions. the initial concentration of the active ingredient was 3.26 g dm-3. the solution was heavily foaming whilst the reactor was being filled. during irradiation, the majority of the catalyst deposited onto the bottom or adhered to the walls of the reactor and buffer tank after an hour despite being stirred. the organic carbon content of the mixture did not change, which indicates that no degradation took place. in the biological treatment, the components of the solution entering the cycle were: 100 cm3 of herbicide with a concentration of 3.26 g dm-3, 100 cm3 of acetic acid (0.93 g dm-3), 10 cm3 of ammonium chloride solution (30 mg n dm-3), and 10 cm3 of sodium phosphate (30 mg p dm-3). after turning the stirrer and aeration on the liquid started to foam heavily and smelled strongly of oil. at the end of the cycle in the settling phase the effluent was turbid. colloids and a part of the activated sludge deposited on the wall of the figure 1. the concentration of quizalofop-p-ethyl in the second layer in the case of normal use (a unit equals 2 m). scheme 1. schematic structures of pesticides studied in this work (a: quizalofop-p-ethyl, ref: dpx 79376, http://sitem.herts.ac.uk/aeru/ppdb/en/reports/583.htm (11.05.2015); b: acetamiprid, ref: ni 35, http://sitem.herts.ac.uk/aeru/ppdb/en/reports/11.htm (11.05.2015)). groundwater remediation with biological and photocatalytic methods 43(1) pp. 39–43 (2015) doi: 10.1515/hjic-2015-0007 41 sequenced batch reactor and surface of the sensors and dried there. the following cycle ended with the same results. the treatment using activated sludge turned out to be ineffective due to the experienced foaming and cumulated active ingredient. inspections revealed that the degradation of the solvent did not start either. the transport models created with the software (fig.1) showed that pesticide under normal conditions of use did not threaten drinking water resources and due to hydrolysis the concentration decreased by half in the second stratum over 113 days. in the case of accidental spillages (the same amount of compound was hypothetically released over a 2 m2 area) the effect was significant, the concentration was a thousand times grater compared to normal use scenarios. 3.2. mospilan 20 sg in the experiments the concentration of mospilan used was 170 mg dm-3 in agreement with the suggested concentration of application. a 20% active ingredient content was achieved by an acetamiprid solution with a concentration of 34 mg dm-3. photodegradation was monitored by recording the uv-vis spectra of the mixture and measuring the organic carbon content (toc). the solution was first irradiated with uv-light without a catalyst under atmospheric pressure for three hours. during this time neither the toc concentration nor the ph of the mixture changed; the variation of the results stayed within the measurement error, which suggested that the insecticide was not degradable by uv-light in itself. the second experiment was carried out with tio2 as a catalyst and the process was not stopped for seven hours. during this time the rate of light absorption between 200 and 300 nm gradually decreased and the maximum of the band shifted from 245 nm to 230 nm (fig.2). these spectral changes indicate clearly that the compound degraded in the heterogeneous photocatalytic experiments. the suspension was circulated in the reactor for 20 minutes before irradiation. from changes in toc concentration, it can be concluded that during this period a proportion of the organic material had adsorbed onto the catalyst particles. the rate of adsorption in terms of toc was 10%. by the end of the process, the toc concentration of the suspension reduced by 76% while the cod amount became 78% less. according to the data, the initial rate of decay was calculated to be 13.59 mg dm-3 h-1 based on the curve fitted to the toc. a major advantage of the heterogeneous photocatalyst is that the reaction may be carried out with solar radiation; thus, costs and also environmentally harmful emissions can be reduced. photons are on the one hand ‘pure’ reagents and on the other hand ‘pure’ energy. the changes in the spectrum, such as the decrease in absorbence and the shift in location of band peaks were the same under laboratory conditions, while the reaction rate was lower. the initial rate of decay due to solar radiation was 6.07 mg dm-3 h-1. during measurements the uv-b radiation was “strong” (uv index 6.5, hungarian meteorological service). the results show that the heterogeneous photocatalytic degradation of the insecticide may be efficiently achieved by using sunlight. this can be utilised when disposing of different chemical residues. the organic contaminants may be mineralised using solar radiation on site in a carefully designed “reactor”. the biodegradability of the pesticide was studied with a prepared solution based on an average concentration of application. in the first case, an additional substrate (acetic acid) was added to the sequenced batch reactor while in the second case only the insecticide was supposed to serve as a substrate. based on the results (fig.3), it can be stated that the biodegradation of mospilan cannot be achieved with municipal activated sludge under the employed conditions. the results of the transport model (fig.4) show that acetamiprid acts in a similar way to quizalofop-p-ethyl. since it does not hydrolyse the active ingredient, it would remain for longer in soil and accumulation might appear therefore the compound may more easily enter the food chain. in the case of accidental spillages of the substance over a small area, the effect would be more significant just as was the case with quizalofop-p-ethyl. figure 2. spectra of mospilan suspension treated with catalyst (optical path length: 0.5 cm) (a); chemical oxygen demand and total organic carbon concentrations as function of time (b). a ds or be nc e guba, somogyi, szabóné bárdos hungarian journal of industry and chemistry 42 the concentration in soil would be a thousand fold greater. besides it would not decrease significantly over time, since the compound is stable in aqueous media. 4. conclusion the studied leopard 5 ec and mospilan 20 sg pesticides are available to purchase without any permit, although they are toxic to different extents to mammals, birds and aquatic organisms. their improper application might cause serious environmental damage. the degradability of the two substances was studied by means of heterogeneous photocatalysis and biological treatment. in the case of leopard 5 ec neither of the methods was successful. the petroleum naphta solvent and/or the emulsifiers poisoned the tio2 catalyst. the dollops formed settled and the surface of the catalyst particles was reduced greatly due to the adhesion effect of the organic material. the photocatalytic degradation reaction could not take place. a similar process was observed in the biological reactor. the mixture together with the biomass adhered to the surface of the sequenced batch reactor and sensors. in both cases the conditions made the treatment processes impossible. in order to be able to study the degradation of the compound, pre-treatment, possibly the destabilisation of the emulsion is needed. mospilan 20 sg could be treated using heterogeneous photocatalysis both under laboratory conditions (with a uv lamp) and utilising solar radiation. however, it can be stated that the insecticide cannot be treated with municipal activated sludge under the applied conditions based on the results of sequenced batch reactor experiments. according to the simulation results, neither of the pesticides poses a threat to drinking water resources in the case of normal use in compliance with the specifications provided by the manufacturer. nonetheless, mospilan 20 sg is likely to accumulate if used multiple times or for extended periods. should there be an emergency the impact on the environment might multiply. the results of the present study show that unlicensed use does not necessarily mean easily degradable substances. the biological method was unsuccessful in both cases, photocatalysis is not applicable for water-immiscible chemicals but in the case of hydrophilic organic materials, the treatment may be efficient. acknowledgement the research was carried out with financial support from the project támop-4.1.1.c-12/1/konv-20120015. references [1] the stockholm convention on persistent organic pollutants (stockholm convention) 2014 cchm.pops.int figure 4. the concentration of acetamiprid in the second layer in the case of normal use (a unit equals 2 m). figure 3. changes in absorbence spectra during biological treatment with (a) and without additional substrate (b) (optical length: 0.5 cm). a ds or be nc e groundwater remediation with biological and photocatalytic methods 43(1) pp. 39–43 (2015) doi: 10.1515/hjic-2015-0007 43 [2] solymosné majzik, e.: determination of concentration of pesticide active ingredients in groundwater and surface water samples applying various spe methods, phd thesis (university of pannonia, veszprém, hungary) 2006 (in hungarian) [3] khan, f.i.; husain, t., hejazi, r.: an overview and analysis of site remediation technologies, j. environ. mgmt., 2004 71, 95–122 10.1016/j.jenvman.2004.02.003 [4] fujishima, a.; honda, k.: electrochemical photolysis of water at a semiconductor electrode, nature, 1972 238, 37–38 10.1038/238037a0 [5] fujishima, a.; rao, t.n.; tryk, d.a.: titanium dioxide photocatalysis, j. photochem. photobiol. c: rev., 2000 1, 1–21 10.1016/s1389-5567(00)00002-2 [6] cazoir, d.; fine, l.; ferronato, c.; chovelon, j.m.: hydrocarbon removal from bilgewater by a combination of air-stripping and photocatalysis, j. hazard. mat., 2012 235–236, 159–168 10.1016/j.jhazmat.2012.07.037 [7] irawaty, w.; edi soetaredjo, f.; ayucitra, a.: understanding the relationship between organic structure and mineralization rate of tio2-mediated photocatalysis, procedia chem., 2014 9, 131–138 10.1016/j.proche.2014.05.016 [8] esplugas, s.; giménez, j.; contreras, s.; pascual, e.; rodrı́guez, m.: comparison of different advanced oxidation processes for phenol degradation, water res., 2002 36, 1034–1042 10.1016/s0043-1354(01)00301-3 [9] malato rodríguez, s.; blanco gálvez, j.; maldonado rubio, m.i.; fernández ibáñez, p.; gernjak, w.; oller alberola, i.: treatment of chlorinated solvents by tio2 photocatalysis and photo-fenton: influence of operating conditions in a solar pilot plant, chemosphere, 2005 58, 391– 398 10.1016/j.chemosphere.2004.09.043 [10] dombi, a., ilisz, i.: advanced oxidation processes in environmental chemistry, in novel results of chemistry (akadémiai kiadó, budapest, hungary) 2000, vol. 86 (in hungarian) [11] jolánkai, m., birkás, m.: global climate change impacts on crop production in hungary, agriculturae conspectus scientificus, 2007 72, 17– 20 [12] gribovszki, z.: fundamentals of agricultural infrastructure 7, drainage as a part of complex water management: basics of hydrology and hydraulics (university of west hungary, sopron, hungary) 2010 (in hungarian) ! ! about water for water − water and wastewater treatment system operating engineer postgraduate specialist training course with the co-operation of one of hungary’s oldest historical universities and a company of international reputation “water is essential for life on earth as much as good quality education is for professional experts.” the university of pannonia faculty of engineering and the nagykanizsa campus along with hidrofilt water and wastewater treatment ltd. are offering a postgraduate course programme in water and wastewater treatment. hungary has long been recognised as a great water power with a historical background in the field of water treatment and purification. the university of pannonia has a long tradition of academic excellence based on the training of engineering specialists for industry and the economy. the faculty of engineering and the nagykanizsa campus of the university of pannonia are committed to forging partnerships with industry. our aim is to create a generation of engineers that will take a lead in the development of innovative and sustainable technologies. the water and wastewater treatment system operation programme is designed for those engineering and non-engineering graduates who wish to pursue a career in water and wastewater treatment. the nagykanizsa campus offers a wide spectrum of quality programmes that not only enhance students’ professional development, but also familiarise them with the natural and historic values of hungary. mentors will assist students in organising their educational programmes and review their theses. each student benefits from the opportunity of acquiring a broad range of transferable skills towards their future career within an outstanding academic environment. duration of the course programme: 2 semesters/4 months. theoretical training in water and wastewater treatment technologies is provided by the university of pannonia, and hidrofilt ltd. practical work and laboratory sessions will be carried out with the help of professional mentors from hidrofilt ltd. the faculty of engineering provides course materials and notes that are included in the package. competencies to be acquired: " classification and adequate employment of the theoretical knowledge and practical methods acquired in the field; independent decision-making and development skills. " ability to analyse the qualitative and quantitative characteristics of water and wastewater; creating, implementing and assessing measurement plans. " optimal employment and management of state-of-the-art water and wastewater treatment technologies. " operating, planning and managing water supply and water and wastewater treatment technologies. " knowledge and employment of quality assurance and technical control. " analytical skills in technical, economical, and social relations in water and wastewater treatment. " evaluation of conceptions and programmes regarding water on national and international levels. the qualification provides skills and abilities that can be employed profitably not only on a national but also on an international level. graduates are able to design and implement investments related to water and wastewater treatment and maintain systems in operation. we offer a practice-oriented training programme in addition to high-quality academic education. those participating in the study programme gain state-of-the-art knowledge that fits the needs of the market and acquire the most advanced water purification technologies applied in the industry. information available from: info@sooswrc.hu hungarian journal of industry and chemistry vol. 43(1) pp. 45–48 (2015) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2015-0008 biological purification of chemically pre-treated dairy wastewater before discharge into a municipal sewage systems gábor gulyás,* bence fazekas, regina varga, and árpád kárpáti department of environmental engineering, university of pannonia, egyetem u. 10, veszprém, 8200, hungary dairy production is one of the most inefficient processes with respect to water usage in the food industry. it was estimated that the production of a litre of milk creates three to four litres of wastewater. dairy wastewater contains a high amount of dissolved and suspended solids. moreover, it contains high concentrations of fat, protein, and carbohydrate. consequently, the dairy wastewater content of organic compounds is high and so is its chemical oxygen demand. the majority of organic compounds are biodegradable with a high biological and chemical oxygen demand ratio. in this work, we examined the biological purification of physico-chemically pretreated wastewater from a hungarian milk-processing factory before it was discharged into the public sewage system. the chemical oxygen demand of the pre-treated wastewater ranged from 500 to 2500 mg dm-3. we found that it was possible to achieve efficient organic material removal from nutrient-poor wastewater without nutrient dosage contrary to the literature. the activated sludge system manifested efficient organic material removal that required a smaller biological volume. experiments with biofilms have shown that a thicker biofilm needs more dissolved oxygen, which dictates oxygen input levels to be sufficient for creating an aerobic environment. keywords: activated sludge, biofilm, dairy wastewater, chemical oxygen demand, nutrient-poor wastewater 1. introduction milk processing requires high specific water consumption and considerable raw material waste effluents [1]. wastewater composition depends mainly on the produced material, production process, actual operations of the production process, and the water usage [2]. clean water is practically used in all the process operations, like cleaning, sterilisation, heating and cooling. wastewaters produced in these plants are usually polluted with chemicals, used for cleaning the containers, pipes, and some other equipment [2–4]. on average processing a cubic metre of milk produces 3–4 m3 of wastewater [5]. milk processing effluents (dairy wastewaters dww) contain high concentrations of dissolved and suspended solids. they contain high concentrations of fat, protein mainly as fine colloids, and carbohydrate (lactose and lactic acid) [6–9]. among the carbohydrates, lactose can be found in a high ratio [5]. however, the lactic acid content can also be very considerable in the case of the discharge of whey. suspended solids of dairy wastewater originate from cheese and cottage cheese as well, but their final concentration highly depends on the processing methods at a given plant. *correspondence: gulyasg@almos.uni-pannon.hu as a result of these ingredients of an approximate total concentration of around 2 g/g of the effluent, dairy wastewaters can exhibit high chemical oxygen demand (cod) . the majority of the organic contaminants are biodegradable. the ratio of biological and chemical oxygen demand (bod/cod) of the dww-s is high [10]. all organic contaminants are in principle nutrients for microorganisms of the active sludge (as) biological treatment. however, preliminary physico-chemical removal of particular components of the dww, such as fats, most of the proteins, and casein considerably decreases the cost of biological purification required for permitting the discharge of this industrial effluent into municipal sewage systems. 2. material and method we studied the biological purification of physicochemically pre-treated wastewater from a hungarian milk processing and dairy factory located in székesfehérvár. polyaluminium chloride, hydrochloric acid, and polyelectrolyte were used before flotation. presently, the mixed wastewater after this treatment is discharged into the public sewage collection system. intermittently, its cod concentration is higher than the prescribed limit, which results in an extra fee being charged for the discharge and municipal purification. gulyás, fazekas, varga, and kárpáti hungarian journal of industry and chemistry 46 cod of the pre-treated wastewater normally changed between 0.5 and 2.5 g dm-3 during the measurements, while the limit value was 1 g dm-3. the total organic material content was commensurable with the suspended solid concentration at the same time the magnitude of dissolved organic compounds was constant. the ammonium concentration in the pretreated wastewater was low (3–10 mg dm-3), while the phosphorous content was negligible. thus, the wastewater we purified biologically was lacking in n and p-nutrients. we intentionally did not add any n or p-nutrients. we carried out parallel studies in an activated sludge sequencing batch reactor (as-sbr) and a biofilm system, moving bed biofilm sequencing batch reactor (mbbr-sbr). the activated sludge reactor was inoculated with municipal activated sludge. the growth of biofilm was initiated by the addition of municipal wastewater during the first and second weeks. there were aerobic and anoxic periods in the sbr cycles (approximately in a 3 to 1 ratio) to cater for the needs of different microorganisms. anoxic periods were used to improve the sludge settling. during the aerobic periods, the maximum dissolved oxygen concentration was set to 2 mg dm-3. mechanical mixing was used during the anoxic phases. the activated sludge concentration in the as-sbr reactor was between 3 and 5 g dm-3, on the contrary in the mbbr reactor it was at most 1 g dm-3 in the first part of the experiment. the volume of biofilm carrier in the reactor was 0.5 dm3 and the total volume of the mbbr-sbr reactor was 2 dm3 giving a filling ratio of 25%. the biofilm reactor was continuously aerated and the dissolved oxygen level had to be increased, when the specific biofilm load considerably increased. 3. results and analysis the sludge-loading rate in both systems was increased continuously throughout the experiment. at the beginning, it was approximately 0.2–0.3 g cod/g mlss and was slowly raised to over 2 g cod/g mlss by the end. on the contrary, the cod of the purified wastewater did not change considerably (fig.1). it was between 20 and 50 mg dm-3. the cod was simultaneously measured from the filtered effluents to observe the influence of the suspended sludge content of these effluents. the treated wastewater was nutrient-poor. according to the demands of microorganisms in biological wastewater treatment, a c : n : p ratio of around 100 : 5 : 1 is optimal. this ratio is typical for communal wastewater. the average relative sludge yield rate is 0.7 g mlss/g cod if the nutrient ratio is optimal. in our study, we could only measure a low specific sludge yield of approximately 0.1 g mlss/g cod, which we rationalise by the lack of nitrogenand phosphorous-nutrients. the cod removal was very effective even at very high sludge loads and with a lack of nutrients. in the mbbr system (fig.2), the variability of organic material removal was observable. cod of the purified wastewater varied between 50 and 200 mg dm-3. the main reason for lower cod removal values was probably due to the inefficient settling of the fine biofilm particles. they could not aggregate as much as the as sludge flocks can. during the course of settling, the biofilm carriers float up to the surface of the water. this can also limit the proper settling of the sludge if the treated wastewater contained so much suspended sludge. figure 1. the chemical oxygen demand of the studied activated sludge sequencing bach reactor system. biological purification of chemically pretreated dairy wastewater 43(1) pp. 45–48 (2015) doi: 10.1515/hjic-2015-0008 47 the biofilm loading rate was between 0.2 and 2.0 mg cod/g biofilm mlss. the biofilm concentration in the mbbr-sbr system was 0.5–1.5 g biofilm dm-3 in contrast to the as-sbr reactor where the activated sludge concentration was 3–5 g mlss dm-3. the mbbr-sbr reactor was operated by a lower hydraulic load. when the dissolved oxygen concentration was set to 2 mg dm-3 over 1 g cod/g biofilm mlss loading rate, the biofilm could not survive due to limited oxygen diffusion from the liquid phase to inside the biofilm. this corresponds to anoxic conditions at the carrier surface. we had to increase the dissolved oxygen concentration to 3 mg dm-3. when the biofilm loading rate increased to 2 g cod/g biofilm mlss, the dissolved oxygen concentration should be increased further to 5 mg dm-3 in order to achieve efficient organic material removal. 4. conclusion we observed that it was possible to achieve efficient organic material removal as expressed by the chemical oxygen demand values from pre-treated dairy wastewater both in as and biofilm treatments without a dose of nand p-nutrients. this is contrary to what has been proposed in the literature. in the similar active sludge treatment of apple juice effluents even with a proper dosage of urea and phosphate, sometimes we could measure serious sludge bulking because of a lack of micronutrients. our results showed that the activated sludge system ensured efficient organic material removal even around 2 g cod/g mlss loading rate in the case of the pre-treated dairy wastewater. at the same time, the specific sludge load of the municipal sewage treatment plants without nitrification and denitrification is at most 1 g cod/g mlss. when we have to nitrify and denitrify the organic carbon load has to be around a third of this value. high loaded systems require a smaller biological volume. iron ions, which remained in pre-treated wastewater, facilitated the settling of activated sludge, therefore in the as-sbr system this gives an opportunity for increasing the sludge concentration. because of an extended sludge concentration the biological volume demand would be reduced. our experiments with the biofilm system show that the thicker biofilm requires a much greater dissolved oxygen concentration. this fact is mentioned also in some other studies. the oxygen input needs to be balanced against the level for creating an aerobic environment for the biofilm. references [1] !bref 2006, integrated pollution prevention and control, reference document on best available techniques in the food, drink and milk industries (european commission) 2006 [2] britz, t.j.; schalkwyk, c.; hung, y.t.: treatment of dairy processing wastewater, in waste treatment in the food processing industry, eds.: wang, l.k.; hung, y.-t.; lo, h.h.; yapijakis, c. (taylor and francis group, new york, usa) 2006, pp. 1–29 [3] demirel, b.; yenigun, o.; onay, t.t.; anaerobic treatment of dairy wastewaters: a review, process biochem., 2005 40(8), 2583–2595 10.1016/j.procbio.2004.12.015 [4] zielinski, m.; janczukowicz, w.; dezbowski, m.: biodegradability evaluation of dairy effluents originated in selected sections of dairy production, bioresources technol., 2008 99(10), 4199–4205 10.1016/j.biortech.2007.08.077 figure 2. the chemical oxygen demand of the moving bed biofilm sequencing batch reactor (mbbr-sbr) system. gulyás, fazekas, varga, and kárpáti hungarian journal of industry and chemistry 48 [5] adulkar, t.v.; rathod, v.k.: ultrasound assisted enzymatic pre-treatment of high fat content dairy wastewater, ultrason. sonochem., 2014 21(3), 1083-1089 10.1016/j.ultsonch.2013.11.017 [6] gadhe, a.; sonawane, s.s.; varma, m. n.: kinetic analysis of biohydrogen production from complex dairy wastewater under optimised condition, int. j. hydrogen energy, 2014 39(3) 1306–1314 10.1016/j.ijhydene.2013.11.022 [7] orhon, d.; gorgun, e.; germirli, f.; artan, n.: biological treatability of dairy wastewaters, water res., 1993 27, 625-633 [8] burak, d.; orhan, y.; turgut, t.o.: anaerobic treatment of dairy wastewater: a review, process biochem., 2005 40(8) 2583–2595 10.1016/j.procbio.2004.12.015 [9] perle, m.; kimichic, s.; shelf, g.: some biochemical aspects of the anaerobic degradation of dairy wastewater, water res., 1995 29(6) 1549– 1554 10.1016/0043-1354(94)00248-6 [10] kaewsuk, j.; thanuttamavong, m.: application of photosynthetic bacteria used for dairy wastewater treatment by a submerged membrane bioreactor, eng. j. kasetsart univ., 2007 61(20) 76–86 hungarian journal of industry and chemistry vol. 43(1) pp. 49–53 (2015) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2015-0009 study of the interference effects of aluminium on the atomand ion-lines of alkaline earth metals in aqueous solutions using an icp spectrometer with axially viewed plasma olivér bánhidi institute of chemistry, university of miskolc, miskolc-egyetemváros, miskolc, 3515, hungary the main advantage of inductively coupled plasma spectrometers with axially viewed plasma relative to the radially viewed plasma is the better detection power. the detection limits of the former are about 5–10 times lower than the latter. on the other hand, the axially viewed plasma has disadvantages. the most notable is the increased number of interference effects. in this paper, the study of the interference effects of aluminium on the atomand ion-lines of alkaline earth metals are presented by examining different types of sample-introduction devices, such as a simple meinhart-type concentric nebuliser, a v-groove nebuliser using a sturman-masters spray chamber, and an ultrasonic nebuliser. keywords: aluminium interference effects, icp atomand ion-lines, alkaline earth metals, sampleintroduction device, axially viewed plasma 1. introduction inductively coupled plasma-atomic emission spectrometry (icp-aes) is a widely used method for the elementary analysis of different types of material due to its advantageous features. the axial plasma view offers an increased detection power, which is important when the element of interest is present in trace levels. on the other hand, the emitted light is subjected to strong interferences as it reaches the entrance slit of the optical system of the spectrometer. therefore, it is an important task to understand the origin and nature of the interference effects [1–3]. the interference may affect both the sampleintroduction and excitation processes taking place in the plasma. in the first case, they may have different effects on the different types of sample-introduction devices, while they might affect the atomand ionlines of a given element in different ways [4]. icp is commonly used for the analysis of liquid samples, where different types of nebulisers are the most frequently applied devices for sampleintroduction. during nebulisation, the liquids to be analysed are dispersed into small droplets. the difference regarding the different nebulisers lies partially in different processes resulting in small liquid droplets and the nebulisation efficiency. these kinds of effects may be different when different nebulisers are applied, while they appear in the case of both radially and axially viewed plasma. correspondence: akmbo@uni-miskolc.hu the spectral interferences are stronger and more frequent when an axially viewed icp source is used. this is due to the light being emitted from the hot internal part of the plasma that has to travel a long way to reach the entrance slit of the optical system. on its way, the emitted light goes through layers of plasma at a lower temperature. this process may be subjected to strong self-absorption effects. consequently, the intensity of the ionand atom-lines of a given element may change. this change affects the relationship between the emitted line intensity and analyte concentration in the sample, and thus the calibration procedure. the alkaline earth metals may be present from trace up to high concentration levels in different materials, such as surface and groundwater, different types of rocks and minerals, metal alloys, etc. in many cases, these materials may contain aluminium in high concentrations that contributes to the observation of interferences [2,3]. in the present work, we studied the effect of aluminium on the spectral lines of alkaline earth metals present in lowconcentrations in aqueous solutions, as well as the influence of different sample-introduction devices. 2. experimental 2.1. icp spectrometer for the presented experiments, a varian 720 es spectrometer was used, which is an axially viewed, instrument with key parameters summarised in table 1. bánhidi hungarian journal of industry and chemistry 50 due to the layout of the optical system, many (even several hundred) spectral lines can be measured simultaneously, which makes the study of the interferences on several atomand ion-lines of a given element possible. in the course of line selection, care was taken in choosing both more and less sensitive lines, where enough lines were available. the spectral lines examined in this study are summarised in table 2. 2.2. the sample-introduction devices three types of sample-introduction device were used in the given set of experiments: a concentric nebuliser, a v-groove nebuliser, and an ultrasonic nebuliser. the concentric nebuliser is the one that is used most commonly for the icp-aes analysis of liquid samples. its nebulisation efficiency is rather low, but it can be operated easily, and its maintenance demand is low. generally, it is used in combination with a cyclone-type glass spray chamber. the v-groove nebuliser eventually becomes a modified babington-type nebuliser. it is used with a sturman-masters type spray chamber, which has a special plastic surface and is resistant to almost all chemicals including hydrogen fluoride. its detection power is slightly less than that of the concentric nebuliser, but it has an excellent salt-enduring ability. the cetac 5000 type ultrasonic nebuliser boasts a detection power 10 times better than the former two devices. on the other hand, its operation is more difficult and it may be sensitive to higher matrix concentration levels. 2.3. samples used the solution samples contained some acid, the alkaline earth analyte elements and aluminium as a matrix component. the matrix element was diluted from a spectrascan (teknolab) stock solution containing aluminium at a concentration of 10 g dm-3. the aluminium concentration in the sample solutions was 0, 200, 500, 1000, and 5000 mg dm-3. the analyte elements were diluted from a multi-element spectrascan solution of 0.1 g dm-3. the concentrations of the elements studied were in the range of 0.1 and 10 mg dm3. the solutions contained hydrochloric acid in a concentration of 0.5 mol dm-3. 2.4. measurements each of the solutions was measured at a 1050 w output of high frequency power. the recorded signal intensity was averaged from 3–10 s long replicates. the raw intensities were corrected applying the so-called twoside off-peak background correction method. in order to easily evaluate the effects, the net intensities measured using sample solutions containing no aluminium were used as reference values, and the net intensity values measured in the presence of aluminium were divided by these reference values. in other words, the evaluation presented here is based upon the relative intensities. 3. results in the experiments, we studied the intensity changes of several atomand ion-lines of the alkaline earth metals as a function of aluminium concentration, analyte concentration and that of the device used for sampleintroduction. the results measured using a concentric nebuliser are presented in figs.1–10. the net intensities obtained using a v-groove nebuliser (figs.11 and 12) and an ultrasonic nebuliser (figs.13 and 14) are also presented for the case of calcium ions. 4. discussion figs.1–10 show that by using the concentric nebuliser both atomicand ionic-lines of all alkaline earth metals are affected by aluminium. nevertheless, substantial differences can be seen depending on the element, type table 2. the spectral lines (wavelength λ in nm and excitation energy e in ev) studied. element type of the line λ e be be i 234.861 5.30 be be i 249.473 5.01 be be ii 313.042 3.99 be be ii 313.107 3.99 mg mg i 285.213 4.38 mg mg i 383.829 3.23 mg mg ii 279.553 4.47 mg mg ii 280.270 4.59 ca ca i 422.673 2.96 ca ca ii 317.933 3.93 ca ca ii 393.366 3.18 ca ca ii 396.847 3.15 sr sr i 460.780 2.71 sr sr ii 216.596 5.76 sr sr ii 407.771 3.07 sr sr ii 421.552 2.96 ba ba i 705.994 1.77 ba ba ii 233.527 5.36 ba ba ii 455.403 2.75 ba ba ii 493.408 2.53 table 1. characteristics of the icp spectrometer used in the given study. plasma-view: axial the frequency and power of the rf generator: 40 mhz, 900–1500 w adjustable via software the optical system employed: echelle build-up with a double monochromator detector used: two-dimension ccd wavelength range: 160 – 780 nm available sampleintroduction systems: concentric (k-type) nebuliser, v-groove nebuliser, ultrasonic nebuliser controlling software: icp expert ii (microsoft win xp os) study of the interference effects of aluminium 43(1) pp. 49–53 (2015) doi: 10.1515/hjic-2015-0009 51 of spectral line studied, concentration of aluminium, and that of the analyte. at low beryllium concentrations (0.1 mg dm-3) the intensities on all lines are heavily affected even at relatively low aluminium concentration (1 g dm-3) levels. higher aluminium concentrations cause only a moderate reduction in the signal. similar behaviour can be observed in the case of magnesium, strontium, and barium. as for calcium, the greatest decrease was observed also at an aluminium concentration of 1 g dm-3, but higher aluminium concentrations cause a smaller decrease, even some increase can be observed in the ion-lines. it can also be observed that atom-lines are usually more strongly affected than ion-lines. at higher analyte concentrations, the effect of aluminium is greater on all the lines examined and increases with increasing aluminium concentration. the only exception is the intensities measured at an aluminium concentration of 1 g dm-3, where in the case of each analyte the relative intensities are significantly lower than both the values gained at aluminium concentrations of 0.5 and 2 g dm-3 concentration, though the extent of the effect is different. this effect is larger or even larger in the case of beryllium, magnesium, and barium, and it is less profound for calcium and strontium. with respect to the different types of lines, in the case of beryllium, where all the lines studied are sensitive, one of the atom-lines (234.861 nm) is less, while the other (249.473 nm) is more affected than the ion-lines. one of the atom-lines (383.829 nm) of magnesium is a weak line, while the other one (285.213 figure 1. the relative intesities of 0.1 mg dm-3 be as a function of al concentration, using a concentric nebuliser. figure 2. the relative intesities of 10 mg dm-3 be as a function of al concentration, using a concentric nebuliser. figure 3. the relative intesities of 0.1 mg dm-3 mg as a function of al concentration, using a concentric nebuliser. figure 4. the relative intesities of 10 mg dm-3 mg as a function of al concentration, using a concentric nebuliser. figure 5. the relative intesities of 0.1 mg dm-3 ca as a function of al concentration, using a concentric nebuliser. figure 6. the relative intesities of 10 mg dm-3 ca as a function of al concentration, using a concentric nebuliser. bánhidi hungarian journal of industry and chemistry 52 nm) is sensitive. the first is heavily affected by aluminium, while the other lines manifest smaller effects. in the case of calcium and strontium, the atomline is much more affected than the ion-lines, while the reverse can be observed for barium. its atom-line is much less affected than its sensitive ion-lines. the effect of the sample-introduction devices in figs.11–14 in the case of calcium manifests that at low analyte concentrations (0.1 mg dm-3) almost the same type of curve is observed with the help of an ultrasonic nebuliser. using a v-groove type device, only slight effects were detected. at higher analyte concentrations, all the lines are affected using the v-groove nebuliser; while in the case of the ultrasonic device the sensitive ion-lines (393.366 nm and 396.847 nm) are only slightly affected. 5. conclusion using the axially viewed plasma, the light emitted from the high-temperature inner part of the plasma has to pass through the flame to reach the entrance slit of the optical system. as the photons travel, they pass through plasma layers of lower and lower temperatures. in the cooler environment, self-absorption, secondary excitation, and scattering processes can take place. these processes depend on the local temperature, which is also influenced by the high/higher concentration of elements in the sample than the analyte. all these processes make the relationship between line-intensities emitted and analyte concentration rather complicated. figure 7. the relative intesities of 0.1 mg dm-3 sr as a function of al concentration, using a concentric nebuliser. figure 8. the relative intesities of 10 mg dm-3 sr as a function of al concentration, using a concentric nebuliser. figure 9. the relative intesities of 0.1 mg dm-3 ba as a function of al concentration, using a concentric nebuliser. figure 11. the relative intesities of 0.1 mg dm-3 ca as a function of al concentration, using a v-groove nebuliser. figure 12. the relative intesities of 10 mg dm-3 ca as a function of al concentration, using a v-groove nebuliser. figure 10. the relative intesities of 10 mg dm-3 ba as a function of al concentration, using a concentric nebuliser. study of the interference effects of aluminium 43(1) pp. 49–53 (2015) doi: 10.1515/hjic-2015-0009 53 it can be concluded that aluminium exhibits a strong interference effect on the emitted spectral line intensities of all alkaline earth elements studied. it can also be seen that atom-lines are usually more affected than ion-lines. although the relationship between the interferences and line intensities is complicated, in practice it can be eliminated by careful matrixmatching, i.e. the calibration solutions must contain the interfering element (al) possibly at the same concentration level as the analyte in the samples. in addition, calibration curves can be extended, only with care in the presence of al, as it could be observed that the extent of the interference is different at low and high analyte concentrations. acknowledgement this research was supported by the támop-4.2.1.b10/2/konv-2010-0001 project and carried out as part of the támop-4.2.2.a-11/1/konv-2012-0019 project in the framework of the new széchenyi plan. this project was supported by the european union, and cofinanced by the european social fund. references [1] záray, gy.: modern methods of elementary analysis, gas discharge plasmas and their application (university press, budapest, hungary) 2006 (in hungarian) [2] bánhidi, o.: examination of the interference effects in the course of icp-aes determination of strontium content of aluminium alloys, proc. 24th microcad conf. (university of miskolc, miskolc, hungary) 2012, section c [3] dubuissan, c.; pousserl, m.; mermet, j-m.: comparison of axially and radially viewed inductively coupled plasma atomic emission spectrometry in terms of signal to background ratio and matrix effects, j. anal. at. spect., 1997 12(3), 281–286 10.1039/a606445k [4] brenner, i.b.; zander, a.t.: axially and radially viewed inductively coupled plasmas a critical review, spectrochim. acta, part b, 2000 55(8), 1195–1240 10.1016/s0584-8547(00)00243-3 figure 13. the relative intesities of 0.1 mg dm-3 ca as a function of al concentration, using an ultrasonic nebuliser. figure 14. the relative intesities of 10 mg dm-3 calcium as a function of al concentration, using an ultrasonic nebuliser. ! ! soós ernő water technology research and development centre was established in 2014 by the faculty of engineering at the university of pannonia, nagykanizsa municipality of county rank and hidrofilt water treatment ltd. the activities at the 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inserted into the text at the time of proofreading. 7. authors who are less practiced with written english are urged to have their manuscripts checked by scientists who are working in the author’s respective field and proficient in english. editorial board of the hungarian journal of industry and chemistry microsoft word 16.08 mátrai.docx hungarian journal of industry and chemistry vol. 44(2) pp. 71–79 (2016) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2016-0008 route planning based on urban mobility management tamás mátrai,1* jános tóth,1 and márton tamás horváth2 1 department of transport technology and economics, budapest university of technology and economics, műegyetem rkp. 3, budapest, 1111, hungary 2 department of control for transportation and vehicle systems, budapest university of technology and economics, műegyetem rkp. 3, budapest, 1111, hungary mobility management centres play a significant role in urban transport, taking into account several factors that have an effect on the flow of vehicles. in the present paper a mobility management centre equipped with necessary information and information technologies for travellers is presented that can provide route plans. a route guidance methodology is described that combines current transportation demands with the results of the traditional four-step model. keywords: mobility management, route planning, urban mobility, demand management 1. introduction the mobility management centre (mmc) as an organization helps to realize and manage mobility demand. the centre controls both private and public transport modes, as well as the provision of information for individual users with the aim of optimizing the entire transport network. the main goal is to provide safe and quick transportation for everyone. during the optimization process the system satisfies the mobility demands with the best available transport modes and routes, the 4r-s principles can be used (reduce, retime, reroute, revise mode) [1]. fig.1 shows the main tasks of the mobility management centre. usually in an urban environment, private transport users are supported by the traffic lights from the mobility management centres. the centres can control all traffic lights in the city based on network level principles. additionally, dynamic parking management can be developed, where the free spaces are displayed on variable message signs and in a further developed version individuals can be guided towards free spaces. private users can be informed about the actual transport situation and weather conditions via various channels. nowadays the most used channels are internet-based mobile applications, but there are also radio-based solutions like rds-tmc services or roadside infrastructure like variable message signs. if the individual users expect a response and guidance from the mmc for their route choices and do not decide their routes individually, then these centres can optimize the demand on the level of transport network system. in this case they can manage the *correspondence: tamas.matrai@mail.bme.hu demand to avoid congestion – the overuse of certain routes – during peak hours, in other words, they can distribute the demand in terms of a network evenly. currently these solutions have not yet been developed enough, due to the lack of communication among centres and users. currently only a very small proportion of vehicles receive dynamic information from the centre. it should be mentioned here that the slow but steady shift towards shared vehicles and ondemand modes has become an emerging trend, especially in conjunction with public transport. ideally, these services would be integrated together to provide a sustainable and equally convenient alternative to private cars for door-to-door mobility. the realisation of such figure 1. tasks of the mobility management centre. mátrai,tóth, and horváth hungarian journal of industry and chemistry 72 an alternative has set in motion the development of a new mobility concept known as the mobility-as-aservice (maas), which is a user-centric, digital and intelligent mobility distribution model in which the major transport needs of users are met via a single platform and are offered by a single service provider [2]. there is a strong connection between short-term traffic forecasts and route planning. users would like to receive route suggestions not only based on the current situation but also the forecasted one. either they are preparing the route on their own device or they are obtaining a plan from the centre. therefore, an efficient and acceptable level of prediction is essential. automatic vehicle location (avl) is one of the key elements in the accurate running of public transport systems in urban areas. as soon as the dispatchers identify any deviation from the predefined schedule, they initiate certain actions based on a pre-defined rulebook. one action from this rulebook can be to provide priority for those vehicles that are late, this priority provision can be achieved via certain junctions which are equipped with the necessary functions. the traffic lights at these junctions can change their signal plan dynamically in order to provide a green signal to the late public transport vehicles. other main task of the mmc is the provision of information concerning both static timetables and current traffic situations of public transport, which can be achieved through different channels. different information is necessary on different channels before a journey commences (e.g. internet-based route planning services, mobile applications) and during the trip (e.g. at the public transport stop, on the vehicle). the users are expecting to get not only information, but also suggestions especially from the integrated services (e.g. connections, local public transport, railway services, coach services) based on their individual preferences [3]. the most advanced version of this approach is a dynamic multimodal journey planner which provides the ability to adjust to a variety of anomalies (i.e. network disruptions, high capacity usage, etc.) concerning the transport network and evaluates the most efficient routes to get from a to b allowing for efficient traffic management [2]. it has to be mentioned here, that a feedback loop is essential; in order to continuously fine-tune the algorithm in the background, it needs to be determined if the users are really heeding the advice of the route planner. in functional urban areas, such as agglomerations with high levels of connectivity between urban centres and hinterland, one of the main goals is to promote the shift in mode of the commuters from private cars to more sustainable modes of transport. therefore, the provision of information with regards to other services such as p+r facilities and their saturation is vital. in this regard, the transfers should be seamless and the information beforehand should be sufficient to help make the right decision. there are different options to ease the level of inconvenience of the transfers, e.g. visual aids of the location of the p+r, information regarding available free spaces, guidance concerning public transport services at the parking facilities, and on-the-spot information about public transport schedule. 2. database of mobility management centres all the aforementioned tasks are feasible if the mmc is based on complex data collection. from these data, the mmc can create the information necessary to manage mobility demands and give information to travellers. fig.2 shows such a possible database. there are several public transport providers with their own data, which must be integrated into a joint database. thus, the timetable, network, real-time data, travel conditions and services at stops or interchange points are available. connecting timetables is particularly important when trips are satisfied by several transport modes. the intermodal hub cannot function without it. the public transport network itself is an integrated network because more public transport companies use the same routes, stops, or stations. dynamism of data is essential for real-time services (e.g. disturbances on a network). the accurate information is sent according to the current position and status of vehicles. vehicles equipped with a tracking system are necessary for fleet management. tariff is an integral part of travel conditions; the passengers must be informed about prices (e.g. is there a transport association selling common tickets) and fares for different passenger groups, etc. the data concerning fares and travel conditions remain unchanged for long periods of time; they are static or semi-dynamic data. information systems often figure 2. schematic overview of an integrated transport database [4] (sp = service provider). route planning based on urban mobility management 44(2) pp. 71–79 (2016) doi: 10.1515/hjic-2016-0008 73 lack such services at stops or stations. it could be helpful for passengers to spend time whilst waiting constructively. the database of private transport consists of network data, traffic data (presenting the actual situation on the network and also including historical data), weather conditions, parking data, and data regarding environmental effects, and other services. the network data are static, but sometimes include semi-dynamic or dynamic data (e.g. shortor long-term road construction). traffic data shows accidents, traffic jams, traffic volumes, etc. on the network in real-time and historically. the historical data are very important for traffic forecasting. numerous methods are based on the comparative examination of present and past situations. parking data can be static (location and capacity of parking area) or dynamic (parking occupation). advanced parking systems help to find a free parking place. p+r plays an outstanding role in encouraging drivers to change their modes transport. more and more travellers are sensitive to the environment. they are easily encouraged to use environmentally friendly modes of transport. therefore, the importance of the data of environmental effects is more accentuated. data regarding other services includes all the data concerning available services during trips. 2.1. mobility management centre solutions according to the needs of modern society, online planning software plays an increasingly important role in optimizing the flow of traffic, and utilizing the capacity of dynamic network traffic models that are strongly connected with real-time traffic management systems. several models developed for a city may not easily be applied to other cities. the rapid development of it equipment and the efforts to standardise protocol have facilitated the development of design software for traffic management purposes. the main aim of such software is to support decision made by dispatchers based on actual traffic situations. 2.1.1. sydney coordinated adaptive traffic system (scats) scats is a fully adaptive urban traffic control system that optimises traffic flow. the basic goal is to coordinate traffic lights at junctions in order to improve traffic flow and to reduce travel and waiting times. the main advantage of the system is its ability to adapt to changes in traffic conditions with the modification of the programming of traffic lights. fig.3 shows the daily changes of the cycle length of traffic light. the red borderline represents the previous period (before scats), the light blue area is the cycle length optimized by scats, and the dark blue area is the time saved. different travel demands have different goals: • low traffic demand: minimising the number of stops; • normal traffic demand: minimising the waiting time; • heavy traffic: maximising the throughput capacity. the system can prioritise public transport. in cooperation with trips (traffic modelling) software, traffic forecasting is also feasible (fig.4). 2.1.2. helsinki – helutc, finland this mobility management system in helsinki controls traffic lights, parking and public transport management systems. the concept of controlling traffic lights involves choosing a suitable cycle length according to traffic conditions. there are 10-12 different programmes for each junction. the coordinated intersections have identical cycle lengths. the system can prioritise public transport. variable message signs are applied to show parking information. it is very simple: are there any free spaces (fig.5). the public transport management figure 3. changing cycle length in the scats system (source: www.scats.com.au). figure 4. estimating the expected travel time using scats. figure 5. variable message signs for parking as part of the helutc system. mátrai,tóth, and horváth hungarian journal of industry and chemistry 74 system provides passengers with dynamic information at stops, in vehicles and pre-trips via an internet home page or mobile application. fig.6 shows a diagram for the system. 2.1.3. 5t system in turin, italy the name of the system is “telematic technologies for transport and traffic in torino”. fig.7 shows an overview of the system. the main goals of the system are to change the travel behaviour of passengers, increase the utilisation of public transport, and optimise travel time, energy consumption, and emissions. subsystems of 5t consist of traffic control, public transport management including vehicle priority, environmental control, information for travellers (via variable message signs, the internet, mobile applications), and parking management. every subsystem has its own management centre, but on the city management level all the information required for coordinating the subsystems is concentrated. the general strategy aims to avoid the overloading of network. the centre consists of seven modules as follows: • status monitoring module (treating subsystem information); • origin-destination estimation module; • modal split module (demand estimation for private and public transport); • traffic assignment module; • management module (cooperation with subsystems); • operator interface module (creating a connection between the operator and system); • database module (handling and storing the data of the operating system). in order to decrease travel time public transport has priority at junctions, and individual drivers are informed about the status of the network and the shortest route for their trip. all the public transport vehicles equipped with avl (automatic vehicle location) to give real-time information at stops and on vehicles, via the internet and mobile applications. the parking management subsystem uses vms to show the number of free spaces. the subsystem considers historical data to account for the filling up process of the parking area. the goal is to provide information about the supposed status of the parking lot in the near future, i.e. when the vehicle arrives at the entrance. 2.1.4. split cycle offset optimisation technique (scoot) the scoot system was developed by the transport research laboratory (trl) in the uk in order to manage and control traffic lights in cities by taking into account real traffic flows. this system is used in several cities around the globe such as london, santiago and beijing. since scoot is designed to update automatically to compensate for the effect of incidents. scoot achieved an average reduction of delays of about 25%, when compared with up-to-date fixed-time plans in nijmegen, the netherlands [5]. the system also offers additional opportunities: • providing priority to buses as part of the pt system; • providing gate effects; • incident detection; • online density measurements; • traffic flow estimation. all static data, e.g. the physical parameters of the transport network and traffic lights are stored in the scoot database. as an adaptive system, scoot requires good quality traffic data, so that it can respond to changes in flow. the system should calculate traffic volumes in every section of the controlled network. detectors are normally required at every link. their location is important and they are usually positioned at the upstream end of the approach link. inductive loops are normally used, but other methods are also available. for the schematics of data collection and processing see fig.8. when vehicles pass the detector, scoot receives the information and converts the data into its internal units in order to construct "cyclic flow profiles" for figure 6. diagram of the public transport management system in helsinki. figure 7. overview of the 5t system. route planning based on urban mobility management 44(2) pp. 71–79 (2016) doi: 10.1515/hjic-2016-0008 75 each link. the sample profile shown in the diagram is colour coded green and red according to the state of the traffic lights when vehicles arrive at the stop line at normal cruise speed. vehicles are modelled down the link at cruise speed and join the back of the queue (if present). whilst green, vehicles depart from the stop line at the validated saturation flow rate. the data from the model is then used by scoot in three optimisers, which are continuously adapting to three key traffic control parameters the number of green lights for each approach (split), the time between adjacent signals (offset) and the time allowed for all approaches to a signalised intersection (cycle time). these three optimisers are used to continuously adapt these parameters to all intersections in the scoot controlled area, minimising wasted green time at intersections and reducing stops and delays by synchronising adjacent sets of signals. this means that signal timings evolve as the traffic situation changes without the inconvenience of changing fixed time plans of more traditional urban traffic control systems (see fig.9). the combination of these optimisers provides the necessary solution to deal with the fluctuation in different traffic scenarios, and maintain the stability of different interventions. the split module is optimizing every status change, offset module optimizes the duration of every phase of the signalling system, while the cycle time module optimizes the length of the signal cycle in a certain region of the network. providing bus priority happens on three levels, namely (i) equal priority for all buses, (ii) different level of priority for punctual and delayed buses, and (iii) extra priority. priority provision and intervention are independent from the detection of the buses. in order to detect pt vehicles, the cities usually develop automatic vehicle location systems (avl), in some cities selective vehicle detection is applied. vehicle location monitoring is conducted at the avl centre. these location data are then incorporated into the selective priority algorithm. as it can be programmed to calculate the length of delays, the vehicle with the longest delay should receive the highest priority. it is possible to provide local priorities under the supervision of scoot. a schematic of an example system in london can be seen in fig.10 [6]. 2.1.5. mobility management in budapest in budapest the following mobility management tasks are in service: • public transport management and control (futár) o fleet management o vehicle priority o provision of information o route planning • private transport management and control o traffic management o provision of information o route planning o police monitoring centre • other services o bike sharing figure 9. illustration of the operation of the scoot model [6]. figure 8. data collection and analysis in scoot [6]. figure 10. schematic of the london bus scoot system [6]. mátrai,tóth, and horváth hungarian journal of industry and chemistry 76 these tasks are centralized in the same building, but there are three different management systems for the main tasks. they are connected, but there is no common supervisory system. the information flows, although not seamlessly, among them but traffic incidents are managed independently. the aim of project futár was to completely renew the provision of information and traffic management system at bkv zrt. this renewal only concentrated on the surface transport network: trams, buses, and trolley buses. the project consisted of four main steps. the first one was the development of the dispatcher centre and the main central server system. this consists of 32 dispatcher workplaces and all the connecting software and hardware developments. every dispatcher can view the location of all vehicles in the network in real time and are able to intervene in order to maintain schedules especially when some incidents occur. the second step was the developments of invehicle unit. budapest has one of the largest surface transport vehicle fleets in europe. therefore, equipping these vehicles with the necessary on-board units, communication devices, and vehicle location systems was a long and demanding task. this system has been installed in 2295 vehicles and some of them have also received new displays (2024). the third step was the deployment of roadside equipment. all over the capital 257 new displays have been deployed. these displays contain information concerning the route number of the next vehicle, while it terminate and the waiting time for this vehicle. additionally, these displays can provide information remotely through their loudspeakers for visually impaired persons. the last step was the introduction of the radio system. this is an integrated part of the network, which connects the dispatchers to the drivers. moreover, the system is capable of providing priority for public transport vehicles at 30 different intersections. fig.11 shows a schematic of the futár system. budapest also has a private transport management centre, which in 2012 started to use a new itraffic version 1.6 developed by siemens. the new system replaced the old and outdated migra central system, which was installed in 2002. one of the main reasons for the changes was that support for the operation system required by migra was no longer provided. this meant that the replacement of hardware element was hardly possible. of course, not only operating systems, hardware, or communication possibilities but also traffic management systems have evolved over the past 10 years. the new version of the centre possesses several new features. the communication systems have been replaced with a modern ip-based system: open communication interface for road traffic control systems (ocit) and canto. this wireless technology has also been integrated into the system (gprs at intersections), which is able to use any network topology or data transfer media. all the control devices which use the old befa 12, 15 or 16 communication systems can be supported by the new system, either as a sub-centre or as an outstation access point. the software has also been upgraded. it has received a new clear gui, some statistical analysis tools and further developed motion logistics. some new variable message signs have also been integrated into this system. 3. a pilot system in budapest the aim of the pilot system presented in this paper is to demonstrate how a mobility management centre equipped with the necessary information and information systems can provide tailor-made multimodal route advice to individual users by not only taking into account the average state of the transport network, but incorporating the current demand, too. this solution can be more elaborate than already existing private services such as waze application, for the following reasons: • this pilot system uses o-d matrices; • the continuous monitoring of the network is not required; therefore, the number of loop detectors, floating cars or other devices can be reduced; • it provides real multimodal alternatives before trips in order to choose the best transport mode for the current trip; • it uses already existing services; therefore, it does not require any major investment; • it is a module-based system; therefore, easily configurable to match local needs. the distribution of the demand on the network cannot be estimated without a transport model, which assigns the demand to the available transport network. fig.12 shows the proposed concept of this pilot system. the main concept behind this approach is to use the conventional, static demand matrices for the first iteration of the network load, but later on these matrices will be fine-tuned based on current demands. during the route planning phase, actual road traffic disturbances, e.g. road construction, accident; dynamic information from the avl system; and the current availability of other services like bikes at the nearest bike sharing station, are taken into account. based on the combination of this information and predefined user preferences, the system provides a tailor-made route for the user that is compared with at least two alternatives. figure 11. illustration of the operation of the futár model. route planning based on urban mobility management 44(2) pp. 71–79 (2016) doi: 10.1515/hjic-2016-0008 77 the system will use time intervals of 15 minutes to calculate the average situation, based on pre-defined static demand matrices (sdm) for each 15 minute-long time interval of the day, starting from midnight. the current demand, which is the sum of the number of queries concerning a specific route between distinct points of the network, is recorded in an actual demand matrix (adm). in order to obtain the current state of the network the sum of the sdm and adm is necessary. however, sdm already indirectly contains the demands of the adm. however, only as a static estimation from which the real state, represented by the adm, can differ. therefore, the adm cannot be added directly to the sdm, so the system will use a complex method to create a dynamic demand matrix (ddm), which correctly incorporates the actual demand. the static demand matrix is reduced proportionally by the corner sum of the actual demand matrix. then the adm and sdm are added together resulting in the new matrix (ddm) for the next 15 minute period. route suggestions will be provided based on the current state of the transport network. 4. discussion as described in the methodology chapter, the concept of the pilot project has already been elaborated. the existing matrix of the budapest macroscopic transport model [5] will be used as a daily static matrix and create matrices for each 15 minute interval of the day. demand matrices will be created for every mode individually (4 freight categories, car, bike, public transport). however, only car and bike matrices will be updated with the current demand. the averaging method described in the previous chapter is valid until the sum of the actual demand matrix corner sum reaches 30% of the static demand. over this scale, the averaging might yield false results and a different method will need to be applied. an important assumption is that the sum of the corner of the average daily matrix is fixed, in other words, each day the same number of trips is conducted on the network. a public transport model will not be developed in this pilot case, since an online journey planner exists which is based on real-time data and can make queries. alternatively, the existing interface of the futár system will be used to provide public transport route suggestions. for car and bike users, a search for the shortest route will be based on the results of traffic assignments obtained by visum software. disturbance to the road network will be added as changes in link or node capacity occur. in this case, a simple approach can be formulated, but in the end it represents the real disruption to the network. a description of the entire procedure is shown in fig.13. the entire procedure consists of two main phases: the preparation and elaboration periods. the preparation period can be done any time before the system starts. the elaboration period can be divided into 15 minute intervals that are represented in the figure by time periods of between 1 and t. time period 0 is an initialising period that differs slightly from the others, since there are no measurements beforehand. the indexing of time periods and time are the following: τ represents the time when a routing request arrives in the system, (t-1) and (t) are the start and end times of t, t is the time period when τ occurs. during the preparation period the 15 minute-long matrices are created for each mode and the basic static equilibrium assignment sta[prep] has to be run. these assignments run for roughly 45 minutes for each time period on an average pc using visum. the results of these assignments are the basic loads of the network. time period 0 is the initial period, there is no routing request that is filled before that period. therefore, disruptions only exist for the average state. the routing can be drawn from this state and the requests are collected in an actual demand matrix. in this period a traffic assignment sta[0] runs which incorporates the traffic disturbance reported at the beginning (period -1) of the period and the static demand matrix for the next period (period 1). this assignment usually runs for 8-10 minutes on an average pc running visum. figure 12. concept overview of the pilot system introduced in budapest. mátrai,tóth, and horváth hungarian journal of industry and chemistry 78 time period t is the current period, when current routing requests arrive and are collected in an actual demand matrix. an all-or-nothing assignment dta[t] is run using the dynamic matrix t-1 and the corrected capacity based on road traffic disturbances in (t-1). this assignment usually runs for less than 5 seconds. sta[t] is the same type of assignment as sta[0], but with the relevant data. the routing algorithm uses an average level of disturbance from sta[t-1] and dta[t] to determine the shortest route for car and bike users. time period t can represent any subsequent period as well, where the procedure is identical. 5. conclusion this paper introduces the concept of mobility management centres. it provides an overview of the tasks, responsibilities and opportunities of mobility management centres together with some international best practices. later an innovative pilot system is described in detail that will be elaborated in budapest. certainly, as this is a pilot system, it has several limitations and points for further research have been identified. some of the limitations arise from the required run times of the transport model, e.g. a shorter time interval than 15 minutes cannot be used. from the description of the process, it is evident that it includes averaging in several instances. this system assumes that all the planned journeys will be made; however, under real circumstances there are more planned than actual journeys. this can be one area of further research, since a good approach can be used to determine the proportion of planned journeys that are actually made. as suggested, a model like this should provide feedback, but this will not be developed during the pilot study. the validation of the proposed system is important. it can be validated by data from inductive loops and floating cars, but the above mentioned feedback loop would be an asset. there is another validation step, which should be done regarding the capacity reduction of the road traffic disturbance. the current system operates with some educated guesses, but appropriate values can be calculated with actual data. the planned approach for this is to collect incident data from the road network and at the same time collect data from loop detectors in close proximity to the incidents. the current pilot system is based on a series of static equilibrium assignments, but such a system should use dynamic user equilibria or dynamic stochastic assignments. the authors are currently analysing the possibilities of this approach, but it might require greater computing demands as well as more input data, which are currently not available in budapest. nevertheless, this is one of the most important research steps. figure 13. list of processes of the pilot system introduced in budapest. route planning based on urban mobility management 44(2) pp. 71–79 (2016) doi: 10.1515/hjic-2016-0008 79 acknowledgement we acknowledge the financial support of this work by the hungarian state under the vksz_12-1-2013-0088 project. the authors are grateful for the comments from colleagues at the bme department of transport technology and economics. references [1] juhász, m.; mátrai, t.; gál, g.; kerényi, l.s.: mobility management survey for the 2012 olympic games on the basis of published data for "transport for london", közlekedéstudományi szemle 2013 2, 11–19 (in hungarian) [2] kamargianni, m.; matyas, m.; li, w.; schäfer, a.: feasibility study for ‘mobility as a service’ concept in london, ucl energy institute, dept. transp. 2015, 1–82 doi: 10.13140/rg.2.1.3808.1124 [3] esztergár-kiss, d.; csiszár, c.: evaluation of multimodal journey planners and definition of service levels, int. j. intel. transp. syst. res. 2015 13(3), 154–165 doi: 10.1007/s13177-014-0093-0 [4] tóth, j.: its international trends, proc. xi. current issues of urban transport: organisations, innovation, quality service (közlekedéstudományi egyesület, balatonfenyves, hungary) 2011 (in hungarian) [5] mátrai, t.; ábel, m.; kerényi, l.s.: how can a transport model be integrated to the strategic transport planning approach: a case study from budapest, proc. 2015 int. conf. model. technol. intel. transp. syst. pp. 192–199, 2015 doi: 10.1109/mtits.2015.7223256 [6] scoot advice leaflet 1: the "scoot" urban traffic control system, available at scootutc.com/documents/1_scoot-utc.pdf. microsoft word 16.11 pál.docx hungarian journal of industry and chemistry vol. 44(2) pp. 93–98 (2016) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2016-0011 mobile data synchronization methods miklós pál and gábor láner capture it solutions and consulting, záhony u. 7 building b, budapest, 1031, hungary the study introduces and compares the performance of a classical and two innovative mobile data synchronization methods. a customized test environment will be created for every selected method researched. performance, stability, and other measurement results will be produced from these environments, which will be the major outcome of the study. keywords: mobile synchronization, comparison, performance measurement, data optimization, slow network connections 1. introduction the main goal of mobile workforce management software is to make fieldwork easier and more efficient. this requires all necessary data to be available and in sync with the server databases. this is why the synchronization module is one of the most important parts of mobile workforce management software. during the fieldwork, there are various data connection conditions that the application needs to be conformed with. there are several data objects, e.g. task, user, client, etc., and multipart objects, e.g. document files, images to be synchronized. the usability of an application highly depends on the efficiency of this synchronization. the main problem that synchronization needs to solve is to transfer data between the devices and the data source. the solution begins with the data source and through the communication channel ends with the saved data on the device. three potential implementation methods will be introduced and compared in this article. 2. experimental all three considered solutions have different technical backgrounds. the first one is a soap (simple object access protocol) web service implementation based on xml communication. this is the classical way to transfer data between two different platforms. the protocol originally was designed for microsoft in 1998. the xml-based web service is a widespread solution because it is platform independent and built on industrywide standards. it was one of the first ways to build service-oriented, modular architectures using smaller *correspondence: www.capture.hu applications is by the communication of web services instead of robust, monolithic systems. as the technology was mainly used in enterprise environments, and has been in use for more than 15 years, naturally it consists of an antiquated approach compared to modern, lightweight services. while the technology is based on standard http protocols, the requests and responses travel in objects called envelopes. all of the envelopes have a header and a body part, where the body contains the actual payload, the data that is the main reason of communication. the format of the envelopes is strict, and furthermore, there are several encoding, formatting, and parsing standards that have been created since the birth of the protocol. unfortunately, not all implementations are compatible, it is easy to create a server that cannot digest the client’s request, while both endpoints use valid but different soap formats, even though the raw format of the envelope is an easily readable xml file. the strict format has both benefits and inconveniences. when the service at the server is ready, it is easy to generate a unique description xml, called wsdl (web services description language). this file not only helps the development of the client side, but there are several tools available that can generate almost all of the client-side code, that can be used to connect to the service. overall, it is a strict, old fashioned, but really reliable way to approach services in the modern mobile world. the second tested solution is the restful (representational state transfer) service in the architecture of microservices. rest is also known as restful architectural design, and was represented in 2000 by roy thomas fielding in his dissertation at the university of california, irvine [1]. rest has become the main architectural design for web and mobile development over the last few years. according to ‘programmableweb’, 69% of the newly created apis were using rest while only 22% were using soap in 2014. pál and láner hungarian journal of industry and chemistry 94 there are many advantages of this architectural design. the first is its solid performance, due to the high level approach of the solution. it typically communicates over http (hypertext transfer protocol) using http verbs like get, post and put. rest supports more message formats, e.g. xml, csv (comma-separated values), json (javascript object notation), etc. the primary communication format is json, which is structured text data type. this message format requires significantly less metadata than the xml format, thus greatly increasing the network efficiency as the valuable data can fit in smaller network packages. the spread of the json message format is shown in fig.1. the diagram shows the percentage of json versus xml message formats used by apis in the ‘programmable web directory’ between 2005 and 2013 [2]. another great advantage of restful is its simplicity. it is easy to implement and maintain due to its structure. it clearly separates the client and server implementations. today’s trends point in a direction where developers need to create highly availabile applications exhibiting high level of scalability that are ready to run in cloud environments. microservice architecture is a method of developing software applications as a suite of independently deployable, small, modular services in which each service runs a unique process and communicates through a well-defined, lightweight mechanism to serve a business goal. the most wellknown microservice architecture users are netflix and amazon. applications based on this architecture are easy to understand and modify because of the independent parts. instead of a robust application which contains all functions, logics and millions lines of code, there are many separated services with a focused function. these applications or application modules are able to run on multiple copies of multiple machines which makes them highly scalable, available and capable of running in cloud environments. patterns in programming are reusable solutions to a problem occurring in a particular context. in the world of microservice architecture there are many patterns available to choose from. from the aspect of deployment there are two main patterns: • multiple services per host there is one physical server with all services installed on it. • single service per host in this case, there is a standalone host for each service. the host could be a virtual machine or a container. the communication methods between the clients and servers are described with the api gateway communication pattern. in this pattern the gateway is a service discovery between the client and server. this service is the single entry point. from the aspect of the database there are two main patterns. the shared database pattern uses only one database for all services. the database per service pattern uses a standalone database for every single service. finally, the third solution is a distributed nosql implementation of mobile data synchronization. early versions of nosql databases have existed since the 1960s but the technology started to spread only in the twenty-first century. nosql in other words means nonrelational database. one of the main benefits of these databases is the simplicity in design, because they store data in a key-value structure. the other main benefit is the horizontal scalability with the support of clustered environments and cloud infrastructure. these types of databases are mainly used in big data environments. all three applications have the same functionalities. during the experimental three demonstration applications were created. one separated environment for each featured solution. all the applications have three main modules with the same functionalities: (i) database at the backend side to store test data and (ii) synchronization module to transfer data between the backend and mobile application. mobile applications exist with the capability to connect to the synchronization module and synchronize data to the mobile device. additionally, there are some status checking and logging functionalities on this side. every mobile application was created with its own mobile database to store synchronized records. the data source of solutions was tested, which contains up to 50 thousand historical roadwork items of data from 2011 until 2016. the structure and an example record of the database are shown in table 1. test data is stored in a single table with a sequence number as a primary key. the architecture of soap web service implementation is shown in fig.2. on the database side figure 1. percentage of apis added to the programmableweb directory based on communication types over the years [2]. p er ce ta ge s of a p i t yp es years table 1. data structure used in tests with the field data types and typical contents. column type example id numeric la reference numeric 476483 promoter character vultron street character stonegate road locality character meanwood works type character standard easting numeric 428804 northing numeric 437215 location character opp stainbeck avenue description character vultron ducting for mains cable to display in bus shelter works start date date 19/03/2008 works end date date 08/06/2013 mobile data synchronization methods 44(2) pp. 93–98 (2016) doi: 10.1515/hjic-2016-0011 95 there is a postgresql server (version: "postgresql 9.0.3, compiled by visual c++ build 1500, 64-bit") installed. for the experimental, a separated database was created with pg_default tablespace and utf-8 encoding. inside the database test, tables were created in a public scheme. the application server is a j2ee web application implemented with the springboot framework, which builds a standalone runnable jar application that includes a war web application and also grants an embedded apache tomcat application server. this solution provides a monolithic architecture, which is widely used in the enterprise environment. the core framework of the application server is springboot (version 1.3.6.-release), where the embedded tomcat server version is 8.0.36. the web service itself is provided by spring-ws (version 2.3.0.-release). the getroadworklistrequest web service provides the main query about synchronization logic. this service performs a select * from roadworks query through the persistence layer and returns the whole list of the currently stored roadworks. the response is the xml representation of the data table presented in table 1. as a persistence layer the application uses the eclipsellink jpa provider version 2.5.0. the mobile application of soap implementation was built for the android sdk version 24.0.0. android does not offer any built-in library to handle soap calls. there are several third-party libraries to fill the gap, but one could not be found that could be a fully satisfactory solution to our problem. in the tests, the ksoap2 (version 3.6.1) implementation was used that also has some very uncomfortable limitation, but during the test it was working reliably. the synchronized data is saved into the sqlite database in the mobile device. sqlite is the built-in android database that offers a relational database with functionalities to access and store data. the architecture of the restful service implementation is shown in fig.3. this architecture is a typical microservice architecture where the service itself implements the synchronization functions. the mobile application implements the mobile-device functions like synchronization calls and status reports. a shared database pattern was used by sync service, which means the database used by synchronization service is a database used by other services, too. the same postgresql database was used at the database level in the rest implementation as used before for the soap test application. thus, the database version and database configuration were the same. the service is implemented as a standalone java application supported by jetty (version 9.2.1.v20140609). jetty provides a lightweight embeddable web server and it has support for rest apis of web socket. these features make jetty ideal to use in microservice architecture. sync service provides a rest api for mobile clients to conduct synchronization. the main api is the get /rest/sync/roadworks http/1.1; content-type: application/json service that responds with the whole list of roadworks as a json content type. the roadworks data is accessed with a full table selected from a database over an eclipselink persistence layer. the same jpa provider (eclipselink version 2.5.0) is used for this service as it is for the soap application. the mobile application of the rest implementation was also built for the android sdk version 24.0.0. however, android has its own http client provider, in this article android-async-http (version: 1.4.9) was used for asynchronous http client functionalities at the mobile application level. this is a well-featured and widely used library by top developers like instagram and pinterest [3]. the sqlite database was used to store synchronized data in the mobile device as well as in soap implementation. it was experienced during development that implementing rest api calls in the mobile environments is relatively easy to perform since it is a widely supported method of communication. couchbase was used to build the nosql database because it offers a complete solution with a server-side database (couchbase server), synchronization gateway and mobile-side database (couchbase lite). the architecture of this solution is shown in fig.4. the data layer is a couchbase server (version 4.0.0-4051 community edition (build-4051)). the database has a single server node configured. the server node in couchbase represents an instance of the database. in our test only one instance was run. in production environments, more instances are necessary to improve server availability. the node contains the physical data representation objects, called buckets. a new bucket was configured for the article as a couchbase bucket type with 200 mb of memory allocated per node. the optimization of disk i/o figure 2. the soap based test application’s logical architecture. the communication between the client and server component is based on xml / soap messages. figure 3. the rest based test application’s logical architecture. the communication between the client and server component is based on json / rest messages. pál and láner hungarian journal of industry and chemistry 96 operations was set to default, which means the disk i/o priority is low for this bucket. in this article this is an issue, because there are no other buckets in use. the auto-compaction settings are also set to default which means auto-compaction should run if the fragmentation is above 30%. the sync gateway (version 1.2.1 was installed) is located at the server side as a standalone application. this module implements database read / write functions and solution specific apis to transfer data to and from mobile devices. it has a built-in versioning logic, which adds revision information to the documents stored in the server of the database and handles synchronization metadata like synchronization cycles and user data. the sync gateway is configured. it was created to setup the gateway to sync every document type without any user authorization. in this case every connected device synchronizes every document without restrictions between the client and server. the mobile application of nosql implementation is similar to the previous solutions built for android sdk version 24.0.0. the most significant difference here is the mobile database, which is couchbase lite (version 1.3.0). this is a mobile database created for couchbase and sync gateway. it contains the mobile database engine, the mobile database handler and the synchronization interface implementation. the synchronization supports both push and pull requests with version checking so only modified documents are transferred during a call. 2.1. samples and measurements four types of measurements were performed during the experiment: speed test between server and devices for different numbers of datasets (small 1-10, medium 1,000-10,000 and a large number of records up to 50,000). speed tests were performed during data transfer to and from the devices and with mixed directions. speed and stability tests were performed using text and binary data types with a high amount of data to transfer. during the tests, all data packages and sizes of the packages were monitored, as well as the performance of mobile applications, synchronization gateways and databases. 3. results and analysis 3.1. experiments during the analysis an attempt was made to provide constant conditions with the following hardware infrastructure. an asus k53s notebook with intel® core™ i7-2630qm cpu, 8 gb ram and hdd wdc wd7500bpvt-80hxz was used as the server to run the database, application server, synchronization service and synchronization gateway. a samsung galaxy smg935f (s7 edge) smart phone with android 6.0.1 (build number mmb29k.g935fxxs1apg2) was used as the mobile environment. every test was run on the same local network. the network used a 100 mb/s wifi router. the server was connected to the router with a local area network (lan) cable, the mobile device was connected via a wifi network. this way the network speed during the experiment was constant. during the experiment, six test rounds were run on the three different solutions. the amount of data was raised in every step from 1 row to 50,000 rows. one test round with 100,000 records was also planned, but the tests revealed the limitation of the mobile hardware, for around 30 mb of data, the response could not be parsed in one batch, mainly due to the lack of memory. to achieve realistic conclusions from the measurements, every step was repeated three times. overall, a total of 54 tests were run. measurement results were collected using several methods. in soap and rest implementations, most of the information was collected from the mobile platform. both applications were provided with a logger module that provided log entries in every main step of the synchronization. these steps were the following: • synchronization initialized • synchronization started (request was sent from the mobile device to the server) • synchronization finished (the response came back from the server) • parse start (when the mobile application started to process the response) • parse done (when processing finished and all records from the response were saved in the database of the mobile client) in the case of the nosql solution, the monitoring was a bit different because there was no way to write a custom logger module for the built-in processes. fortunately, the couchbase sync gateway provides a fine-grained log where nearly all equivalent steps can be found that we redefined for the previous tests. the performance and mobile database monitoring was the other main part of the analysis. this part was the same for all solutions including nosql. the performance was monitored continuously with an android debug tool while the database was monitored from the application with a status screen. it was expected that the soap web service implementation would be significantly slower than the restful and nosql solutions mainly because of the larger data packets transferred in xml format. figure 4. the couchbase based test application’s logical architecture. the communication between the client and server component is based on the database standard synchronization gateway. mobile data synchronization methods 44(2) pp. 93–98 (2016) doi: 10.1515/hjic-2016-0011 97 the measured results refuted these expectations. as fig.5 and table 2 show, the average sync times are not just nearly the same but with smaller data amount the soap is even faster than the rest. in this result, the nosql lags behind the other two solutions, but the sync time gets closer as the amount of data increases. the reason for this difference could be the additional versioning features of couchbase. furthermore, nosql is built for working with high amounts of data. the synchronized data amount on the horizontal axis is increasing nearly logarithmically because of this, a logarithmic view of this result set (fig.6) could yield a better understanding. fig.6 shows the key point is at 1,000 rows. here is the point where all solutions start to converge into each other. from this point, increase in the sync time becomes more directly proportional to the increased in the data amount. by taking into consideration the result, numbers and sync time per row values in table 3, is can be seen that the minimum value using soap is at 1,000 records, using rest the minimum value is at 10,000 and using nosql the minimum is above 50,000. the results above were calculated using synchronization and data processing. if data processing is skipped, the results change as shown in table 4. again, the key point here is the limit where the number of records is 1,000. after that point the synchronization using rest increases much faster. as shown in fig.7, the soap sync time rises sharply while the rest sync time rises less rapidly. the size of the messages can only be monitored for the soap and rest implementations. the results of these measurements were the same as expected. due to the strict data format, the xml structure requires larger amount of data transfer packages than json, as shown in table 5. the logarithmic diagram in fig.8 shows that the increase in size is directly proportional to the number of transferred rows. figure 6. the synchronization time required for each test application with different record counts, in seconds, on logarithmic scale. table 3. the time needed to synchronize one record for each test applications in different package sizes. number of rows soap sync time (s/record) rest sync time (s/record) nosql sync time (s/record) 1 0.06533 0.33833 6.67100 10 0.01280 0.03390 0.67633 100 0.00393 0.00621 0.06169 1,000 0.00309 0.00376 0.00817 10,000 0.00341 0.00343 0.00539 50,000 0.00451 0.00433 0.00526 table 4. the synchronization time required for the soap and rest based test applications with different record counts, in seconds, without data parsing and persisting. number of rows soap sync time – without parsing (s) rest sync time – without parsing (s) 1 0.044 0.278 10 0.090 0.239 100 0.134 0.243 1,000 0.815 0.764 10,000 6.842 3.589 50,000 26.540 7.020 figure 7. the synchronization time required for the soap and rest based test applications with different record counts, in seconds, without data parsing and persisting. figure 5. the synchronization time required for each test application with different record counts, in seconds. table 2. the synchronization time required for each test application with different record counts, in seconds. number of rows soap sync time (sec) rest sync time (sec) nosql sync time (sec) 1 0.065 0.338 6.671 10 0.128 0.339 6.763 100 0.393 0.621 6.169 1,000 3.094 3.757 8.169 10,000 34.084 34.324 53.922 50,000 225.444 216.492 262.898 table 5. the size of the data packages using xml and json format, in kilobytes for different record counts. number of rows soap xml size (kb) rest json size (kb) 1 0.727 0.272 10 6.200 3.700 100 55.400 32.900 1,000 554.400 331.600 10,000 5,734.000 3,481.600 50,000 29,286.000 17,920.000 pál and láner hungarian journal of industry and chemistry 98 the last measured value is the size of mobile database after data synchronization. the soap and rest implementations have the same database size because both of them used an sqlite database with the same data. this is the reason why only sqlite and couchbase lite databases were compared in table 6. as shown in table 6 and fig.9, the size of the couchbase lite database is much bigger than that of sqlite. the difference increases as the amount of data rises. 4. conclusion finally, we need to state that soap performed surprisingly well during the experiment performance tests. the biggest limitation with regards to it is the minimal support in mobile development. because in enterprise companies soap is still the most common technique this architecture is still popular. more measurement data confirmed that there is a common key point where there is only a minimal difference between the selected solutions. this point is around 1,000 records per transaction, which is the point where it does not matter which solution is used. this is not the optimal point of performance for all solutions but it could be a good compromise. the best choice is the rest synchronization, if the goal is to quickly implement a customizable, reliable, scalable, and extendable, cloud-ready modern solution. any amount of data is supported from small datasets to big data solutions. the bottleneck of this solution occurs during data processing. the best choice is the soap synchronization if the goal is to create an enterprise-ready highly secure and auditable solution. this solution is not recommended for big data environments, but up to medium amounts of data, it could offer a real alternative to restful service. working with soap has many limitations in mobile development. nosql is the best choice for big data environments where a very large amount of data needs to be processed and there is a limited time for development. acknowledgement we acknowledge the financial support of this work by the hungarian state under the vksz_12-1-2013-0088 project. references [1] fielding, r.t.: architectural styles and the design of network-based software architectures, ph.d. dissertation, university of california, irvine, 2000 [2] duvander, a.: json's eight year convergence with xml, 2013 www.programmableweb.com/ news/jsons-eight-year-convergence-xml/2013/12/26 [3] smith, j.: android asynchronous http client, 2016 loopj.com/android-async-http table 6. the size of the database on the client device using sqlite and couchbase lite databases for different record counts. number of rows sqlite database size (kb) couchbase lite database size (kb) 1 3,993.600 7,168.000 10 4,003.840 7,372.800 100 4,044.800 7,536.640 1,000 4,167.680 8,325.120 10,000 5,457.920 15,656.960 50,000 14,704.640 47,462.400 figure 8. comparison of the size of the data packages between the xml and json format on a logarithmic scale. figure 9. comparison of the size of the databases between the sqlite and couchbase databases. hungarian journal of industry and chemistry vol. 47(1) pp. 79–83 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-12 rule-base formulation for clips-based work ergonomic assessment benedek szakonyi *1, tamás lőrincz1, ágnes lipovits2, and istván vassányi1 1department of electrical engineering and information systems, university of pannonia, egyetem u. 10, veszprém, 8200, hungary 1department of mathematics, university of pannonia, egyetem u. 10, veszprém, 8200, hungary modern societies are dominated by computer-based work. as a result, people tend to be seated for most of their working life. prolonged sedentariness is known to significantly increase the risk of developing unwanted conditions. this paper presents the development of a rule-based expert system module using clips that provides ergonomic assessment. the system was validated by evaluating pre-recorded user logs from real-life office environments. the tests showed that the system is able to perform the required basic assessment functionality, thus, the implementation of more complex features to advance its development is viable. keywords: expert system, clips, work ergonomics 1. introduction civilization-related diseases have become more widespread over time, although small improvements to our lifestyle could effectively reduce both their severity and number of sufferers. as adults spend a significant proportion of time working, which for the vast majority involves sitting in front of a computer [1], under what conditions this time is spent is very much relevant. thanks to tools of information technology and ergonomics experts, it is possible to provide automated solutions, in terms of monitoring and assessing user behaviour, to help more employees avoid the adoption of undesirable and harmful postures whilst at work. research has already shown that providing such real-time feedback to users can promote this, thus, reducing the impact of related negative effects [2, 3]. but in these cases, wearable sensors were used to track user motion, which can be considered problematic to be applied in real life applications. a possible solution to this might be microsoft’s kinect sensor [4] that, being a good value-formoney motion capture device, has already been used in similar cases [5, 6]. in spite of this, just as in numerous other papers that concern work-related assessment [7–10], considerably more focus is placed on manual labour where “blue-collar workers” are subject to physically demanding conditions (e.g. production lines, agricultural or construction work, etc.). even though these fields are of equal importance, such conditions cannot be applied to office environments, where “white-” and *correspondence: benedek.szakonyi@virt.uni-pannon.hu “pink-collar workers” spend most of their time, as here the majority of problems does not originate from incorrect movement (e.g. bad techniques when lifting heavy items) but rather from the (utter) lack of movement itself and prolonged sedentariness. the aim of this research was to develop an expert system module for ergonomic assessment (based on a previously created lifestyle coach framework [11] as shown in fig. 1 with an emphasis placed on the formulated work ergonomics-based rule set, and to investigate if such a system is capable of properly evaluating user behaviour in office environments. 2. experimental 2.1 the framework used the lifestyle coach framework used in the development process is a rule-based expert system framework using clips (c language integrated production system) [12]. the main reason for using a rule-based solution (instead of neural networks, fuzzy logic, etc.) is the fact that most healthcare experts can express their knowledge using simple if-then-like statements, which is exactly how rule-based systems work. the clips runtime is responsible for providing the basic functionality of evaluating the current state of the system and deducing the most suitable response and reactions. the statements that describe the current state and different events are called facts, while rules convey the relevant information concerning what actions to take in mailto:benedek.szakonyi@virt.uni-pannon.hu 80 szakonyi, lőrincz, lipovits, and vassányi figure 1: the components of the framework used. the event (or absence) of such facts, in the form of “simple” if-then expressions. the majority of these components are neither predefined nor hardcoded in the framework itself (except for those that are automatically generated) but are to be defined in light of the specific topic and task at hand in the form of a rule set. hence the framework can be applied in different fields as long as the problem is interpretable as the evaluation of a log of successive events. these events are transmitted to the system via the protobuf interface (that uses google protobuf [13]), which also serves as a tool to receive the corresponding responses. the messages of which can be categorized into two types, namely control and event. the former is used to manage the expert system itself, e.g. to signal that a unit of time has passed and re-evaluation of the state of the system should be commenced. the latter serves as a way of inserting new facts (incoming data) and handling consequences (outgoing reactions). how such messages are interpreted and forwarded is the responsibility of the event dispatcher. apart from bridging the gap between the interface and clips runtime, it is also connected to a database that is used to initialize (i.e. it stores the rulebase used), record system behaviour and act as a backup should anything fail. 2.2 work ergonomics to create the rule base required for ergonomic evaluation, methods used to estimate the risks of developing musculoskeletal disorders (msds) were analysed, with the help of ergonomics experts. the most popular and widely accepted tools used for such tasks are rula (rapid upper limb assessment) [14], reba (rapid entire body assessment) [15], owas (ovako working posture analysis system) [16] and harm (hand arm risk-assessment method) [17]. rula applies a scoring method for measuring the physical load that workers are subjected to when adopting specific postures by taking into consideration six main body regions: neck, trunk, legs, upper arms, forearms and wrists. reba works in a similar fashion by using scores but takes into consideration the whole body when such postures are adopted. owas uses a 4-digit score for each posture where the digits describe the back, arms, legs and load. harm accounts for the head, neck, arms and wrists as well as the forces that are applied and the duration over which each posture is adopted. however, these methods cannot be used directly for the matter at hand as originally none of them were intended to be used in regular office environments: rula was developed to assess work in the textile industry, reba in healthcare, owas in the steel industry, and harm in hand-intensive professions (e.g. barbers, product assembly/disassembly, woodwork, etc.). based on these tools, a basic method of postural assessment was derived as presented in table 1. it is important to note that when subject to these constraints, the values used were chosen as initial limits as a proof of concept in light of the fact that they may need to be updated. for each body part, the relevant axes of movement were selected and for each axis, ranges were defined. a range can be characterised into three types: appropriate, incorrect and harmful. appropriate ranges define the desired position the user should take, while harmful ones represent postures that should be avoided or even prohibited. incorrect ones fall somewhere between the other two categories, when, as far as is feasible, a posture should be prevented since it is considered unhealthy, however, when adopted for short intervals of time it is still acceptable. for the ranges of the inappropriate postures, a frequency is given, that describes that in one work hour, how much time spent in them (in total) is still considered as tolerable. apart from evaluating specific body parts based on their position, the time the user spends sitting was also selected to be taken into account, as a general aspect. 2.3 rule-base formulation the formulation of the constraints introduced in table 1 that are applied to a clips-based rule set could have been determined using numerous different approaches. the one that was selected, builds on the fact that the implementation of these aspects has the same general structure: 1. there are numerical measurement values to be evaluated over each time interval 2. there is a constraint that the measured values are compared to when evaluated 3. there is a frequency that, if exceeded, should trigger a warning to be sent. therefore, instead of creating multiple rules for each aspect, one main rule can be defined and applied during the evaluation which can make use of an “aspect template” to check if the related conditions have been adhered to or not. to achieve this, as rules in clips are governed by facts, the aspects are to be in the form of facts. in fig. 2 the template used for defining aspects is shown. the aspect_type serves as a name/identifier for the aspect, while measurement_type defines which measurements hungarian journal of industry and chemistry rule-base formulation for clips-based work ergonomic assessment 81 table 1: the advised constraints to be used in the formulated rule base. for each body part, separate ranges were used for the different planes of movement. the acceptable duration within each range was defined (as % of 1 working hour). body part axis range frequency head/neck sagittal < 0 < 20% 0 < < 10 10 < < 30 < 40% 30 < < 20% horizontal < ±10 ±10 < < ±30 < 40% ±30 < < 20% frontal < ±5 ±5 < < ±10 < 40% ±10 < < 20% trunk sagittal < 0 < 40% 0 < < 15 15 < < 25 < 40% 25 < < 20% horizontal < ±5 ±5 < < ±10 < 40% ±10 < < 20% frontal < ±5 ±5 < < ±10 < 40% ±10 < < 20% upper arm sagittal < −10 < 20% −10 < < 0 < 40% 0 < < 10 10 < < 45 < 40% 45 < < 20% frontal < 10 10 < < 20 < 40% 20 < < 20% forearm sagittal < 60 < 20% 60 < < 80 < 40% 80 < < 100 100 < < 110 < 40% 110 < < 20% should be inspected. in spite of some axes, where ranges of constraints are “evenly distributed” or “symmetrical” (e.g. head frontal, trunk sagittal), the relation between the measured data and the constraint must be provided in the constraint_type template, as for other cases, the ranges are “uneven”. this type can be either smaller than or equal to, or greater than or equal to, followed by the value to use in the value_constraint. the horizon_minute slot is used to determine the duration of measurement that is to be examined (e.g. the last 60 minutes). as cases may occur when, despite being warned, users continue to follow their unhealthy lifestyle, a feature that permits repeated warnings of increasing severity (or even more extensive interventions such as turning off the computer screen) could be useful. in the logic developed, checking whether the user has taken the advice given or not is considered to takes less time than the original evaluation interval (this will have an impact on the main evaluating rule, that is detailed later on). with regard to this feature, apart from the first_occurrence_constraint that corresponds to the frequency in table 1 and the first_reaction_event_code that defines what actions to take if the limit has been reached, (deftemplateaspect_to_monitor (slot aspect_type (type symbol)(default ?none)) (slot measurement_type (type symbol)(default ?none)) (slot constraint_type (type symbol)(default ?none)) (slot value_constraint (type number)(default ?none)) (slot horizon_minute (type number)(default ?none)) (slot first_occurrence_constraint (type number)(default ?none)) (slot first_reaction_event_code (type number)(default ?none)) (slot repeated_occurrence_constraint (type number)) (slot repeated_reaction_event_code (type number)) (slot repeated_feedback_horizon (type number)) ) figure 2: the clips fact template used for describing the structure of ergonomic aspects. optional repeated_ slots can be used for this purpose in the template. as the evaluating clips rule is lengthy, only a short explanation of the logic behind it is provided here. over each evaluation interval, the number of measurements that exceed the given constraints during the corresponding time horizon is counted, and if this value is above the acceptable limit, a request to send feedback is made and the related measurements are labelled as evaluated (according to the current aspect). if only a few “bad” measurements are identified, the evaluation is considered to be finished, unless repeated feedback is received with regard to the current aspect. in that case, it must be determined if a “first feedback” was given recently, and if it was, the number of measurements that exceed the limit must be compared to the occurrence constraint of the second feedback. if this is exceeded, a second feedback is sent. 2.4 experiments for rule-base validation as the aim of the research was to provide feedback for users concerning their postures by using a rule base consisting of ergonomic rules, a method for recording and identifying their postures was needed. to accomplish this, a microsoft kinect v2 sensor was used. as it is an easy-to-use and relatively small device, it was possible to insert it into the real working setups of the willing participants, with only slight modifications in their environments. the general setup that was created for all users was the following: each user was seated at a desk with a personal computer that consisted of 1 or 3 displays, a keyboard, a mouse and a landline telephone. the sensor was placed on a tripod behind and slightly above the “main” screen (i.e. the one in front of the user). the kinect was tilted forward in order to ensure as much of the participant as possible was in view (from the top of the head down to the waist/hips). users were monitored according to two different “behaviour modes”, one being general “everyday” attitude where they completed their daily computer-based tasks as usual. as this inherently meant that users might have had to leave their desks, long measurement sessions were recorded (up to 8 hours in duration) where logging was 47(1) pp. 79–83 (2019) 82 szakonyi, lőrincz, lipovits, and vassányi suspended once the absence of the participant was detected until their return, when it was resumed (such “gaps”, of course, were then taken into account as part of the evaluation). in the other “mode”, where considerably shorter measurement intervals were used in order to ensure sessions that definitely consisted of unsuitable behaviour, the users were asked to adopt some evidently inappropriate postures. as the framework used offers a customisable time unit for defining when an interval stops (i.e. it can last for an hour, a minute, a second, etc.), it was possible to load and evaluate the logs gathered using this method quickly. 3. results and discussion based on the evaluation method suggested by the ergonomist experts, a total of 11 aspects have been formulated (by using 34 facts), 9 for the positions of the body parts (one for each axis using the constraints shown in table 1) and 2 regarding sedentariness, where the acceptable duration of continuous sitting was chosen to not exceed 60 minutes (the first aspect was related to sending a warning once this limit had been reached, the second was used to alert when a participant had been sitting continuously for 3 hours). subsequently the recorded user logs were evaluated, for the majority of aspects used (10 out of 11) the expected functionality was achieved. however, in the case of the facts responsible for assessing head positions, considerably more warnings were sent by the system than was acceptable. as for manually created input (simulated user postures), this behaviour had not emerged again, examination of the monitoring software developed have begun. upon inspection of the logs created, it was found that this error was a result of improper calibration: the inaccuracy of the sensor itself was higher than anticipated and the distortions that resulted meant that even when the user evidently adopted a suitable posture, the logged value exceeded the threshold defined as acceptable. based on this information, the related constraints were adjusted accordingly and this undesirable behaviour of the system was successfully removed. this source of inconvenience, however, highlights the possible sensitivity and dependency of the system, i.e. the reliability of the measurement data received. still, its significance might be diminished by utilizing methods developed for improving the accuracy and error tolerance of kinect, such as the ones proposed in [18–20]. in general, it can be said that the system developed and the initial rule set created are capable of providing the required functionality. however, there is still room for improvement as the constraints involved could be fine-tuned and additional or more precise aspects implemented. moreover, a more complex system capable of adapting to user behaviour could also be created, the main goal of which would be to assist users, without being too rigorous or repetitive, by changing how frequently and in what manner its responses are displayed. this could help to maintain the motivation of workers to break bad habits concerning improper postures whilst seated. even though the number of participants in the experiments conducted was sufficient to validate the initial version of the expert system, further investigations with considerably larger user groups are desirable as they would provide a more thorough validation and may yield additional insight into what other aspects the system could provide assistance to users. additionally, while the recording sessions, on average of 5-6 hours in duration, implemented so far have been useful, by extending these to a few days or even a couple of weeks, more complex behavioural patterns could be identified and analysed. furthermore, by providing real-time assessment over much longer periods, the effects caused by this intervention could be investigated and subsequently the methods used to assist users improved. nevertheless, from the results that have already been logged, it can be clearly seen that the global tendency of users to be seated for longer periods of time than is advisable was also exhibited by the cases investigated. most participants reported that over such prolonged sessions whilst seated, a need to change position is common, however, usually a better alternative cannot be found. a solution to this problem could be to provide workers with electric height adjustable desks, which may facilitate the ability to switch easily between sitting and standing working postures and customise the height of desks to match the anthropometric features of the individual. moreover, such furniture could enable the expert system itself to “take action”, when needed, to raise the desk when users fail to heed previous warnings. it should be noted that, when asked, most of the participants considered such a monitoring and assessment system to be useful, however, some, while welcoming the idea of an adjustable desk, expressed concerns about personal security and were reluctant to be “continuously monitored”. this reveals that if such a system enters the market, apart from providing the necessary security measures, assuring users that their personal data is safe would also be necessary. 4. conclusion in this research a proof-of-concept clips-based rulebase for an expert system was created to facilitate ergonomic evaluation of users in office environments. it has been shown that such a system is capable of thoroughly evaluating user behaviour, thus, implementing interventions in order to decrease the negative effects of prolonged sedentariness. acknowledgement the research was supported by the únkp-18-3 new national excellence program. the authors thank the assistance of the department of ergonomics and psychology of the budapest university of 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http:\developers.google.com/protocol-buffers https://doi.org/10.1016/s0003-6870(99)00039-3 https://doi.org/10.1016/0003-6870(77)90164-8 https://doi.org/10.1016/j.ergon.2013.09.003 https://doi.org/10.1016/j.ergon.2013.09.003 https://doi.org/10.1007/s11042-016-3546-4 https://doi.org/10.1007/s11042-016-3546-4 https://doi.org/10.1109/tcyb.2013.2275945 https://doi.org/10.1145/2671015.2671021 introduction experimental the framework used work ergonomics rule-base formulation experiments for rule-base validation results and discussion conclusion hungarian journal of industrial chemistry veszprem vol. 30. pp. 177 -180 (2002) investigation of the production of gas oil of low aromatic content j. hancsok and z. varga (department of hydrocarbon and coal processing, university ofveszprem, h-8201 veszprem, p.o. box 158, hungary) received: may 21,2002 the demand on gas oil of low aromatic content was increasing significantly in the last years. the reasons of this the more and more stricter quality requirements of diesel fuels, partly the extending use of these products as good quality feedstocks of steam cracking for producing light olefms. in hungary, the growing demand on gas oil of low aromatic content is expected in the near future. its reason is that the restriction of the polyaromatic content of diesel fuels came into force in the european union in the year 2000 and the assumed growing in the quantity requirements of ethylene and propylene may cause extended inquiry for this base stock. the experimental results of producing gas oil of low aromatic content are presented. in the first step of the dual stage process the sulphur content of the gas oil was reduced (slo ppm), in the second one the hydrodearomatization of the product on pt/al20 3 catalyst was studied. the effects of the process parameters (temperature, lhsv, pressure, etc.) on the yield and product quality are discussed. on the base of experimental results the advantageous key process parameters were determined. the possible applications of the obtained gas oils as diesel fuel blending components and the feedstock of the steam cracking were examined. keywords: hydrodearomatization, gas oil, emission reduction, steam cracking feed, noble metal catalyst introduction the restriction of the exhaust gas emission (co, s02, nox, particulate matter) have been kept stricter in europe (for example the emission limits of light duty diesel engines are given in table 1) and other parts of the world [1, 2, 3, 4, 5, 6]. to satisfy all requirements is only possible by developing of engine construction, improving the quality of fuels and using exhaust gas treating system (oxidizing catalysts, particle filters, nox-trap) [7, 8, 9, 10, 11]. the present and the future quality requirements of diesel fuels are summarized in table 2. from the aspect of exhaust gas emissions of the diesel engine very important compounds are the aromatics, mainly the polyaromatics, which have carcinogenic effect in themselves, further the soot originating from the partial burning of these compounds in the engine are carcinogen as well [12, 13, 14, 15). besides the human health and environmental effects the aromatic compounds may cause problems in the engine because they have low cetane number. in addition to diesel fuel the petrochemical industry uses gas oil in growing quantity as base stock of steam cracking, where the aromatic compounds have also harmful effect, as they increase the quantity of the less valuable fuel oil, tar and coke il6, 17]. the aim of the present study was to identify and quantify the key process parameters for the hydrodearomatization (hda) of a previously hydrodesulphurized gas oil fraction on pt/a120 3 catalyst. we studied the effects of key process parameters on the saturation of aromatic compounds. on the basis of the experimental results the advantageous process parameters were determined. the obtained products were qualified from the point of view using them as blending components of diesel fuel and feedstock of steam cracking. experimental the experiments were carried out in a high pressure twin reactor system at the university of veszprem department of hydrocarbon and coal processing. this system consists of a tubular reactor of 100 cm3 efficient volume, as well as equipment and devices applied in tbe reactor system of hydrotreating plants (pumps, 178 table 1 the emission limits of light duty diesel engines in the european union standard emission limits, g/km pm no, hc co hc+no, euro20.080 1.06 0.71 1996 euro 30.050 0.50 0.64 0.56 2000 euro 40.025 0.25 0.50 0.30 2005 table 2 the present and the future quality requirements of diesel fuels en590 eu requirements (2000) (2005) cetane number, min. 51 51 density kg/~' 820-845 820-845 15°c,max. polyaromatics, %,inax. total aromatic content, %, max. distillation of 95lv% ac, max. 11 360 sulphur content 350 ppm, max. 11 360 50* eu (2008/ 2009) ? ? ? ? ? 10 world wide fuel charter, category 3 4 55 55 820-840 820-840 2 2 15 15 340 340 30 5-10 *from the year 2003 tax allowance in germany for motor fuels having 10 ppm separators, heat exchangers, temperature and pressure regulators, gas flow regulators), see fig.l. the feedstock was a light gas oil fraction previously hydrodesulphurized to avoid the poisoning of the pt/al20 3 catalyst; its main properties before and after the treatment are given in table 3. the temperature range of the experiments was 1803000c, the total pressure 40 bar; the liquid hourly space velocity {lhsv) varied between 0,5 h-1 and 2,0 h-1 and the volume ratio of hydrogen-to-hydrocarbon was 600 dm3b:im3 • the experiments were carried out on a pt/y-ah03 type catalyst having 0.58 % pt-content. the properties of the feedstock and products were determined by standard test methods: sulphur content by x-ray fluorescence spectrometry, aromatic content by hplc. the experiments were carried out on catalyst of permanent activity and by continuous operation. the repeatability of the experimental results was higher than 95% considering the ensemble errors of the technological experiments and test methods. table 3 the main properties of the feedstock before and after the hydrotreating' properties method feed untreated treated density, 15°c, kg/m3 astm d4052-96 826 816 cetane number msz en iso 5165 49 54.5 cold filter plugging point, mszen 116 -30 cfpp, oc sulphur content, astm d2622-98 650 <2 ppm aromatics, % ip 391:1995 mono 8.8 9.9 di 7.5 7.0 poly 1.7 1.0 total 18.0 17.9 distillation data astmd86-97 initial bp., oc 198 190 10 vol. %, oc 219 216 50 vol. %, ac 245 243 90vol. %, oc 283 286 final bp., °c 297 294 bmci* 27.6 23.0 *bureau of mine correlation index fig.l the flow diagram of the reactor system; notations: 1, 6, 11, 13, 14, 18, 20, 22, 30, 34, 36, 37, 38: closing valves; 2, 8, 31, 39: control valves; 3, 7, 9, 15: manometers, 4: oxygen converter; 5: dryer; 10, 32: gas filter; 12: gas flow meter/controller; 16, 23: back valve; 17, 19: liquid feeds burettes; 21: liquid pump; 24: pre-heater; 25: reactor, 26: sampling valve, 27, 29: cooler, 28: separator; 33: pressure recorder; 35: pressure controller; 40: wet gas flow meter results and discussion after the experiments we determined the yields of the liquid product which were above 99% in every case. these results showed that hydrocracking reactions take place only a little extent or not at all. fig.2 displays the change of total aromatic content of the products as function of temperature and lhsv. it shows that both process parameters have significant effect on the saturation of aromatics. studying the effect of temperature on the reduction of aromatic content in case of lhsv o~s and 0.8 b"1 , table 4 summary of the results of the advantageous experiments properties experiment am/i am/2 am/3 am/4 process conditions temperature, oc 280 280 300 300 pressure, bar 40 40 40 40 lhsv,h'1 0.5 0.8 1.2 2.0 h2/hc, dm3 /dm3 600 600 600 600 yield,% 99.6 99.7 99.5 99.6 product quality density, kg/m3 810 811 811 813 sulphur content, <2 ppm <2 <2 <2 aromatics, % mono 0.5 1.6 2.9 3.6 di 0.08 0.09 0.1 0.4 poly 0.05 o.d7 0.08 0.09 total 0.63 1.76 3.08 4.09 distillation data, d86, oc initial bp. 185 186 187 187 10 vol.% 214 215 215 215 50vol.% 241 242 242 243 90vol.% 285 285 285 284 final bp. 294 294 295 296 flash point, oc 78 78 78 79 cetane number 57.5 57.0 57.0 56.5 cfpp, °c -30 -30 -31 -31 bmci 20.5 20.8 20.8 21.8 respectively, it . can be assessed that the increase in temperature to about 280°c reduces the aromatic content to a minimum point and then it rises gradually. it can be explained that from the point of view of kinetics the increase of temperature is advantageous for the saturation of aromatic rings until a point where thermodynamic hindrance, which arises from the exothermity of the reaction, begins to exert a significant effect on the rate of reaction. in case of higher lhsv 1.2 and 2.0 h-1 , respectively, we found that the aromatic content did not reach a minimum point, but it is expected that further increase in temperature would have the same effect. studying the effect of the lhsv it can be stated that lower lhsv, that is longer mean residence time, is favourable for reducing the aromatic content. . on the basis of experimental results we assessed that the maximum of the saturation of aromatics was in the temperature range of 280-300°c, within the applied process conditions (e.g. catalyst, feedstock, etc.). so the other properties of products obtained in this range were determined; the results are given in the table 4. these data display that the aromatic content of the products is significantly lower compared to the feedstock, that caused improve in other properties as well (e.g. cetane number), further the properties of the products meet all the demands of en 590 standard. 179 table 5 emission potential of the products and feedstock emission, g/km co hc nox pm 18 ;;:. 16 114 = b 12 ~ 10 ~ 8 " :a 6 feed untreated treated 1.230 0.092 0.920 0.044 1 '-+-0,si .--~~--o,sj ~-r-1,21 1.201 0.065 0.918 0.037 experiment am/1 am/2 am/3 am/4 1.185 1.188 1.188 1.194 0.055 0.057 0.057 0.060 0.917 0.917 0.918 0.918 0.035 0.035 o.d35 0.036 ~ 4 2 o+-~~~~~2~'~--~~~+-~~~~~~~ 160 170 }80 190 200 210 220 230 240 250 260 270 280 290 300 310 temperatul'l), "c fig.2 effect of temperature and lhsv on the reduction of the total aromatic content in addition the polyaromatic content and the cetane number of the products satisfy the ec limits which came into force in the year 2000 and the quality requirements of the world wide fuel charter categories 3 and 4. we estimated the emissions of the products of the experiments. the equations approved by the epefe (european programme on emissions, fuels and engine technologies) for the light duty diesel vehicles were used to determine the potential of emitting co, hydrocarbon (hc), nox and particulate matter (pm) [18]. co(g i km) = -1.3250726+0.003037 ·d0.025643. cpa -0.015856. cn + (1) +0.0001706·795 hc(gl km) =-d.293192+0.0006759·d0.0007306. cpa 0.0032733. cn(2) -0.000038 · tg5 nox(g j km) = 1.0039726-0.0003ll3·d + + 0.027263. cpa -0.0000883. cn(3) -0.0005805 • t95 pm(g i km) = [-{).3879873+0.0004677 ·d + where + 0.0004488. cpa + 0.0004098. cn + (4) + 0.0000788 · t95 1· ·[1-0.00016· (450-c.)j d ·density,. kg/m3 c,. polyaromatic content, % 180 cn cetane number t9s -back-end volatility, oc c., sulphur content, ppm. the data concerning the products and the feedstock are summarized in table 5. on the basis of these data we established that reduction of the aromatic and sulphur content significantly contributes to the decrease of emission, except nox. on the basis of these data it can be assessed that production of good quality diesel fuel blending components is only possible by using hds and hda processes together. to determine the applicability of the products as base stocks of the steam cracking we applied the bureau of mine correlation index (bmci), see eq.(5), which refers to the hydrocarbon types in the petroleum products. polyaromatic hydrocarbons have the highest bmci values (above 100) and paraffin hydrocarbons the smallest ones (below 20). bmci = 48640 +473.7 ·d15 . 6 -456.8 vabp 15 . 6 where v abp -volume average boiling point, k di;:~ -density, g/cm3 (5) the decrease in bmci value of the products showed the saturation of the aromatic, mainly the polyaromatic compounds, that improves the quality of the products from the aspect of applying them as base stocks of steam cracking. conclusions we were able to produce diesel fuel blending components on the applied catalyst which satisfy the present (year 2000) and the future (year 2005) requirements. the aromatic content of the feedstock can be reduced in one step to a great extent, and this decreases significantly the tailpipe emission of the diesel engine, except nox content. the obtained product is applicable as diesel fuel blending component in itself or together with others in order to suit the standard specifications of commercial products that contributes to the reduction of emission of diesel engines. the obtained products are applicable as good and less expensive base stocks of steam cracking. lhsv hda hplc symbols liquid hourly space velocity hydrodearomatization high performance liquid chromatography cfpp bmci hc pm d cold filter plugging point bureau of mine correlation index hydrocarbon particulate matter density polyaromatic content sulphur content, ppm cetane number back-end volatility references 1. mcarragher j. s.: fuel quality, vehicle technology and their interaction, conca we, brussels, 1999 2. purmor, p. d.: minerali.iltechnik, 1996, 2, 1-23 3. aama, acea, jama: world-wide fuel charter, 2000 4. hancsok j.: fuels for engines and jet engines, 2nd part: diesel fuels, veszprem university press, veszprem, 1999 5. pundir b. p.: diesel fuel quality for low emissions,. 3rd international colloquium on fuels, esslingen, pp. 239-245, 2001 6. lee c. k. and mcgovern s.: petroleum technology quarterly, 2001, 6(4), 35-40 7. shelef m. and mccabe r. w.: catalysis today, 2000, 62, 35-50 8. signer m.: fuel quality influence on engine performance and emissions, 3rd annual world fuels conference, brussels, 1998 9. farrauto r. j. and heck r. m.: catalysis today, 2000,55,179-187 10. varga z., hancsok j. and tolvaj g.: investigation of the deep hydrodesulfurization of gas oil fractions, 40th international petroleum conference, bratislava, 2001 11. tock r. w.: world refining, 1999, 9(2), 53-62 12. abd-alla g. h.: energy· conversion and management, 2002,43, 1027-1042 13. hancs6k j., valasek i. and lakatos i.: fuels and their use, tribotechnik kft., budapest, 1998 14. pal r.: mol professional and science papers, 1998, (1), 168-181 15. jungbluth h. and riciiter b.: regeneration von partikelfiltem mit additiven, 2nd international colloquium on fuels, esslingen, 9.4, 1999 16. hancs6k j.: production of middle distillates of low aromatic content, transactions of the university of veszprem department of hydrocarbon and coal processing, 1997 17. hillier w. j.: petroleum technology quarterly, 1998, 3(4), 39-44 18. macklnven r. and mcarragher j. s.: review of the european auto/oil programme and epefe, 1st international colloquium on fuels, esslingen, 1.3, 1997 page 180 page 181 page 182 page 183 microsoft word 15.13 eisenberg.docx 44(1) pp. 1–28 (2016) doi: 10.1515/hjic-2016-0001 hungarian journal of industry and chemistry vol. 44(1) pp. 1–28 (2016) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2016-0001 mass action and conservation of current robert s. eisenberg* department of molecular biophysics and physiology, rush university medical center, chicago il 60612, usa the law of mass action does not force a series of chemical reactions to have the same current flow everywhere. interruption of far-away current does not stop current everywhere in a series of chemical reactions (analyzed according to the law of mass action), and so does not obey maxwell’s equations. an additional constraint and equation is needed to enforce global continuity of current. the additional constraint is introduced in this paper in the special case that the chemical reaction describes spatial movement through narrow channels. in that case, a fully consistent treatment is possible using different models of charge movement. the general case must be dealt with by variational methods that enforce consistency of all the physical laws involved. violations of current continuity arise away from equilibrium, when current flows, and the law of mass action is applied to a nonequilibrium situation, different from the systems considered when the law was originally derived. device design in the chemical world is difficult because simple laws are not obeyed in that way. rate constants of the law of mass action are found experimentally to change from one set of conditions to another. the law of mass action is not robust in most cases and cannot serve the same role that circuit models do in our electrical technology. robust models and device designs in the chemical world will not be possible until continuity of current is embedded in a generalization of the law of mass action using a consistent variational model of energy and dissipation. keywords: law of mass action, current continuity, chemical device design, variational methods, ion channels 1. introduction* the law of mass action is used widely, nearly universally, in chemistry to describe chemical reactions. the law of mass action does not automatically conserve current, as is clear from the mathematics of a simple case, chosen to illustrate the issues involved (fig.1). if current is not conserved in a theory, charges accumulate that cannot accumulate in the real world. in the real world, tiny charge accumulation much less than one percent produces forces that change predictions of the theory a great deal. indeed, in the real world tiny charge accumulation produces forces that destroy biological membranes and thus living systems, forces large enough to ionize atoms, creating the ionized plasma of electrons, we call a spark, or lightning, that can destroy laboratory apparatus, if not the laboratory itself. turning to mathematics for proof. readers should distrust a claim of conflict between long established laws and so i turn to mathematics for proof to show the conflict unambiguously, hopefully without argument. consider the chemical reaction x! y! z: the currents in the two reactions x! y and y! z are not the same, ixy ≠ iyz. rather, the difference in current is shown to be ixy iyz = zxkxyf[x] *correspondence: beisenbe@rush.edu zykyxf[y] zykyzf[y] + zzkzyf[z]. the difference is not zero in general circumstances, nor robust. the difference can be zero only under special circumstances (details are in eqs.(6–11) below). the appendix shows that the current imbalance ixy iyz between the reactions quickly produces enormous forces. enormous forces are not observed and we conclude that the law of mass action cannot be generally true, although it can be useful (and true) under special circumstances, as also shown in the appendix, and of course in the special circumstance of equilibrium, when current does not flow. law of mass action is an incomplete truth. the ‘law’ of mass action seems to be an example of an “ … incomplete truth [that] may become ingrained and taken as the whole truth … [thereby confusing] … what is only sometimes true with what is always true…” (slight rewording of richard feynman, p. 15–61 of ref. [1]). the ‘laws’ of science are usually learned early in figure 1. current flow is not the same in a series of classical reactions. eisenberg hungarian journal of industry and chemistry 2 our careers before we have refereed grants and papers, before our critical skills are honed. these scientific laws are honored because of their historical role, as much as their logical importance. the laws are often residues of revolutions that once gave us new knowledge. old ideas can have a life of their own, a momentum that is hard to change when knowledge expands. it is easy to continue to use old ideas uncritically even after they have been overtaken by new knowledge. law of conservation of current is different: it is universal. conservation of current is as universal as any law in science. it is a law that has not aged as the law of mass action has. maxwell’s equations and conservation of current have a present role and validity at least as important as their historical one. they are said to be exact at any single time and over any distance scale that can be observed, from sub-atomic, and much smaller, to interstellar, from times much shorter than those of atomic motion to the years it takes light to travel from stars and nearby galaxies. their daily use in high energy accelerators involving inconceivably small distances and brief times, their use in the microwave and faster devices of modern technology, and their use in interstellar astronomy are convincing practical proofs of the nearly universal validity of these equations of electrodynamics. the role of maxwell’s equations depends on the subtle idea of displacement current in a vacuum, current not carried by the movement of mass, and this idea is easy to lose sight of in chemical applications where other forms of displacement current involving the properties of matter (usually called ‘polarization’ in the chemistry literature, along with quite different phenomena, e.g. charge distribution in a carbonyl bond or peptide linkage) receive more attention. the displacement current needs to be incorporated into chemical models, in my view, if it is to satisfy both conservation of mass and conservation of current. both material displacement current accompanying polarization phenomena, and vacuum displacement current need to be incorporated. on the time-scale of atomic motions, 10-16 s, both displacement currents are substantial, and must be incorporated if conservation of current is to be enforced. an important question is how the law of mass action has produced such useful chemistry, over so many years, if it does not conserve current flow? the answer is that chemistry has not been interested in nonequilibrium systems of molecules with current flow, as much as it has been interested in the molecules themselves. chemists make molecules, not currents, with the notable exception of electrochemists, and there the difficulties in dealing with long-range electric fields have long been recognized [2–4]. in classical biochemistry, the law of mass action has been used in another context, more biological, with less attention to the virtues of consistency and invariant physical parameters [5]. a senior biochemist recently said, “the art of biochemistry is to study enzymes under conditions that give insights into biological function, even if the rate constants do not fit results over a range of conditions. the art is to choose experimental conditions in which biochemical reactions are well behaved and rate constants resemble those in real biological systems, so results are useful in understanding how living systems work.” the law of mass action was developed to deal with isolated systems, originally with perfect gases [6–10], and allowed chemists to deal with molecular and atomic reactions before physicists became convinced that atoms existed. but isolated chemical reactions must contact the outside world to pass signals and interact with it, just as electronic systems contact the outside world and pass signals through inputs and outputs. biological systems contact surrounding solutions and cells through ion channels and transporters. the law of mass action was not designed to contact the outside world. it was designed to help chemists build and understand individual molecules. signals and connections with the outside world almost always involve electricity because charge flows through the contacts that connect chemical reactions with the outside world. the contacts are usually the boundary conditions of mathematical models. engineering deals with systems that are not isolated. its devices contact the world through power supplies and inputs and outputs. devices have outputs that follow inputs according to simple rules, for example, the output of an amplifier follows the input according to the gain. the input-output rules are derived from kirchhoff’s current law, i.e. continuity of current in one dimension, and kirchhoff’s voltage law. biology deals with systems that are not isolated. living systems usually have inputs and outputs and are driven by concentration gradients that are power supplies. biological systems interact with surrounding solutions, cells, and tissues. the law of mass action must be extended to deal with inputs and outputs and flow of electrical current if theories and simulations of nanodevices (technological or biological) are to be useful under more than one set of conditions. ionic solutions satisfy three conservation laws, conservation of mass, conservation of charge, and conservation of current. chemistry uses mass conservation almost everywhere, in the form of the law of mass action [11–13] (see eqs.(6–11) below). physics uses conservation of charge and current whenever it deals with electricity [1, 14–21]. the flow of charge is continuous in maxwell’s equations, without loss in series circuits, ∇⋅ i = 0 (1) the current i is simple in a vacuum and in a vacuum that also contains particles, e.g. electrons in a vacuum tube. in the latter case, the total current is what i call the maxwell current imxw because this is the invariant introduced by maxwell to allow the light waves of his equations to propagate forever through a vacuum. mass action and conservation of current 44(1) pp. 1–28 (2016) doi: 10.1515/hjic-2016-0001 3 imxw = iparticles +ε0 ∂e ∂t (2) current in matter is more complex than in a vacuum tube because it includes complex movements of charged particles (and charge inside particles) as well. the complex movement of particles must be described by coupled field equations because the movements are driven by many forces, e.g. mechanical, convectional, thermal, diffusional, as well as electrical. the issues involved are illustrated in fig.2 [5] and the following extensive discussion. i then advocate using variational treatments of forces and movements because variational methods automatically enforce consistency with the field equations of all the forces. the material displacement current accompanying polarization ipol is customarily treated differently from the rest of the movement of particles in a tradition started by faraday and reinforced by maxwell who did not recognize the existence of permanent, i.e. fixed charge [26]. the polarization of matter is the distortion of the distribution of charge produced by the electric field (roughly analogous with the distortion of the oceans produced by the gravitational field of the moon, that produces tides on our beaches twice a day). material displacement current ipol can be separated from the complex movements of particles in matter by two properties: (1) material displacement current is transient. if an electric field is applied to matter, ipol flows as the spatial distribution of charge changes, i.e. as it polarizes, but eventually, flow ceases and ipol → 0, as t → ∞ even if the local electric field remains constant. (2) if an electric field is applied, and then turned off, the charge qpol = ipol0 ∞ ∫ dt that flows when the field is turned on is equal to the charge that flows when the field is turned off, when measured for long enough time periods. the total displacement current idis is often isolated and identified by these features in experiments involving transients. in experiments involving sinusoidal applied fields, idis is usually recognized by its ninety degree phase shift. i dis = εrε0 ∂e ∂t disi totaldisplacement current ! = ε0 ∂e ∂t vacuum displacement current! + ipol material displacement current! ; ipol material displacement current! = εr −1( ) susceptibility !"# $# ε0 ∂e ∂t (3) the vacuum displacement current is a large fraction (say half) of the displacement current on the time-scale of atomic motions, less than 10-15 s. all current produces a magnetic field, according to maxwell’s extension of ampere’s law ∇×b = µ0i = µ0 imxw + ipol( ) = µ0 iparticles + idis( ) = µ0 iparticles + ε0 ∂e ∂t vacuum displacement current! + εr −1( ) susceptibility !"# $# ε0 ∂e ∂t ⎛ ⎝ ⎜ ⎜ ⎜ ⎜ ⎜ ⎞ ⎠ ⎟ ⎟ ⎟ ⎟ ⎟ (4) the divergence operator ∇⋅ f evaluates the conservation of flow in the vector field f it acts on (as its derivation from integral relations shows nicely [27]) ∇⋅ ∇×b( ) =∇⋅ µ0iparticles +µ0ε0 ∂e ∂t + εr −1( )µ0ε0 ∂e ∂t ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ | = µ0 ∇⋅ imxw +∇⋅ ipol( ) = 0 so ∇⋅ i = 0 (5) where we use the vector identity that the divergence of a curl is always zero. b is the magnetic vector field; µ0 is the magnetic constant, the magnetic ‘permeability’ of a vacuum; and ε0 is the corresponding ‘electrostatic constant’, the permittivity of free space. note that µ0 ε0 = c-2, where c is the velocity of light. magnetism only arises from current flow. it is mysterious that magnetic charges (monopoles) do not exist, i.e. ∇⋅b = 0 . maxwell’s equations eqs.(1) and (5) guarantee that current is exactly the same everywhere in a series of two terminal devices. if parameters or geometry are changed, electrical forces and potentials change automatically to ensure the same current flows everywhere (in a series system involving maxwell’s equations). interruption of current anywhere in a series circuit interrupts current flow everywhere, even signals carried by currents far away from the interruption. the law of mass action needs to be extended to deal with displacement current so it can enforce global continuity of current flow. if a particular chemical reaction is at equilibrium, and no current flows, conservation of charge can be enforced easily on the law of mass action. but current flow presents a different situation because the law of mass action must then be modified to deal with the global properties of the electric field. if we are dealing with technological or biological nanodevices, chemical reactions are connected to the outside world and the law of mass action must be extended to enforce continuity of current flow everywhere under all conditions. biological systems involve both chemical reactions and charge. biological systems are always embedded in ionic solutions, and nearly always involve chemical reactants and enzymes with electrical charge, even if (like water), their net charge is zero. substrates of reactions catalyzed by enzymes are usually charged and are nearly always dissolved in complex solutions containing the ions na+, k+, and cl− and often ca2+. eisenberg hungarian journal of industry and chemistry 4 trace concentrations of calcium are often used by biological systems as controls that turn biological function on or off. reactants are almost always charged in biological systems. reactants almost always flow and carry current in biological systems. equilibrium and death are nearly synonymous in life. biological systems must satisfy conservation of current along with conservation of matter. we face a problem when we try to apply both conservation laws together: the law of mass action does not conserve current. ‘the law of mass action does not conserve current’ seems an unlikely statement and so mathematical proof is needed more than verbal argument. a simple sequence of chemical reactions was examined and the questions “does the law of mass action conserve current? is current the same everywhere in the series of reactions? do the potentials change automatically so current is always the same everywhere in a series circuit?” were asked. the same questions can then be asked of whatever series of reactions are of interest. sometimes the answer will be that current does not flow or does not matter and the law of mass action can be easily modified to conserve current. in some symmetrical reactions, the answer will be that current and mass are both conserved, as shown in the appendix. more often, the answer will be that current and mass are not both conserved, as shown in more detail in the appendix. in that case, the law of mass action must be extended to maintain continuity of current. eq.(6) shows the reactions we use to illustrate the problem: x kxy kyx ! ⇀!!!↽ !!!! y kyz kzy ! ⇀!!!↽ !!!! z (6) the reactions of eq.(6) were chosen to show the problem in the simplest case. we define ‘law of mass action’ for this paper as just eqs.(6) and (9) with the symbols defined below. the rate constants in eqs.(6) and (9) are taken as constants and thus of course are uncorrelated and independent of each other. if the law was robust, the rate constants found experimentally under one set of conditions would be found under another set of conditions. such is sometimes the case, but not very often [5, 28]. generalizations of rate constants are sometimes made but, as discussed below in the section ‘how to extend the law of mass action?’, generalizations in the literature [11, 13] deal with ‘chemical correlations’4 and the non-ideality of some types as opposed to current flow, to the best of my knowledge. they do not allow the law of mass action defined here by eqs.(6) and (9) to globally satisfy the conservation of current eq.(1). the generalizations are well designed to deal with systems close to equilibrium with some types of nonideality, but the generalizations do not discuss current flow, and include little3 or no4 discussion about the nonidealities produced by the ionic atmosphere (in the equilibrium case [29]), and changes of shape of the ionic atmosphere (in the non-equilibrium case [30–37]). current flow is important in most applications of the law of mass action. it is almost always present if the reaction is part of a device that communicates with the outside world. the global nature of the electric field (illustrated in fig.1) allows remote devices and boundary conditions to change local atomic flows, an effect not necessarily present at equilibrium. in a nonequilibrium system, electrical forces and potentials change everywhere automatically as a result of the equations of the electric field to ensure the same current flows in all places (in a series system). indeed, interruption of current in a series of reactions stops current anywhere, even far away. of course, there are special cases in which mass action can by itself conserve current flow exactly and those in fact may be the cases where it has proven most quantitatively useful, particularly when extended to deal with non-ideality [11, 13]. in addition, reactions may conserve current approximately. in other cases, like in eq.(6), the reaction will not conserve current, even approximately. each case needs to be studied separately. the appendix provides more detail. the central fact that applies to any chemical reaction, not just to eqs.(6) and (9) is that the global realities of the electric field need to be embedded in the atomic-scale treatment of the reaction, particularly when current flows. proof the current flow in the reactions of eq.(6) is easily shown to be: ixy = fzx ⋅ kxy x!"# $ %&− fzy ⋅ kyx y ! "# $ %& iyz = fzy ⋅ kyz y!"# $ %&− fzz ⋅ kzy z ! "# $ %& (7) units for net current [38] ixy are (c/dm3)/s = c dm-3 s-1 and (moles/dm3)/s = moles dm-3 s-1 for unidirectional flux jxy. double brackets like [[x]] indicate activities, i.e. the generalization of concentration (number density) needed in biological solutions, as discussed below. units for rate constants are (moles/(dm3 s))/(moles/dm3) = 1/s. the valences, i.e. charges on one molecule of each reactant are zx or zy. f is faraday’s constant. in general, the conservation of current law illustrated in eq.(5) is violated ixy ≠ iyz, (8) for a range of concentrations, rate constants, or charges. the main result of eqs.(7) and (8) and the appendix is simple: the law of mass action itself conserves current only under special symmetric circumstances. the law of mass action does not automatically change the electrical potentials to ensure mass action and conservation of current 44(1) pp. 1–28 (2016) doi: 10.1515/hjic-2016-0001 5 that the current flow in a series circuit is the same everywhere. details of proof. rate equations equivalent to chemical reactions involve net flux like j xy . the chemical reactions in eq.(6) define the net fluxes in units of moles/(dm3 s), j xy = kxy x ! "# $ %&− kyx y ! "# $ %& jyz = kyz y ! "# $ %& − kzy z ! "# $ %& (9) with the definitions of rate constant kxy, for example kxy = j xy x!"# $ %& = j xy − d dt x!"# $ %& j yx= 0 (10) remark. unidirectional fluxes like jxy are conventionally measured by tracers originally radioactive isotopes, now usually fluorescent probes flowing into an acceptor solution in which the concentration of tracer is zero. the concentration in the acceptor solution of the substance is not zero in most cases, although the concentration of the tracer is (nearly) zero. note that the activity [[x]] depends on the concentration of all of the other ions in a significant way in non-ideal solutions [5, 34, 39–65]. in non-ideal solutions, changes in the concentration of one substance [y] change the activity of another substance [[x]] and also change its flow. the proof of eq.(7) is completed by writing net fluxes like j xy = jxy jyz as the difference of unidirectional fluxes. net flux is converted into net current like ixy using the proportionality constant fz (where z is the species in question) between flux and current: ixy = fzx ⋅ kxy x!"# $ %&− fzy ⋅ kyx y ! "# $ %& iyz = fzy ⋅ kyz y!"# $ %&− fzz ⋅ kzy z ! "# $ %& (11) obviously, ixy ≠ iyz. this ends the proof. it seems unlikely that conservation of current and conservation of mass are in conflict in the law of mass action, so mathematics is needed to show that current is not conserved. i treat a simple but widely used case, hoping that this will be more convincing than words and easier to extend to other reaction schemes. the methods used can be applied to any series of reactions to see if they satisfy both conservation of current and conservation of mass. in general, an additional constraint and equation is needed to enforce the global continuity of current flow. the additional constraint is introduced in the special case where the chemical reaction describes spatial movement through narrow channels. in that case, a fully consistent treatment is possible using a variety of models for charge movement. the general case where chemical reactions describe covalent bond changes is not worked out in detail here. in my view, the general case must be dealt with by variational methods that enforce consistency of all the physical laws. energetic variational methods appropriate for this purpose (in dissipative systems like ionic solutions) are described. the appendix shows that charge imbalance predicted by the law of mass action would likely have noticeable effects. a small charge imbalance quickly produces potentials and forces that destroy membranes (~0.3 v), molecules in a liquid (~2 v, h2o, with ag|agcl electrode), molecules in a gas (~480 v for h2o gas), and atoms in a gas (~14 ev for n2). these figure 2. a demonstration that current in one physical system being quite different from current in another. charge flow is not simply the physical movement of particles of definite charge (and mass). current in a vacuum capacitor, in an ionic solution, and in a wire are all quite different. current is not just the movement of ions, electrons or protons. note that the electric charge in different devices varies on very different scales from subatomic (in dielectrics) to atomic (in diodes, ionic conductors, etc.) to macroscopic. thus, treatments of charge and current must be multi-scale (redrawn from ref. [5]). eisenberg hungarian journal of industry and chemistry 6 effects would destroy experiments and are not found in the laboratory, which would also soon be destroyed. we conclude that theories that predict charge imbalance because they do not conserve current flow are not acceptable approximations in the world of experiments or life. 2. current flow in complex systems we now discuss current flow in some detail. as we discuss current flow through salt water, vacuum capacitors, dielectric capacitors, vacuum tube diodes, semiconductor diodes, resistors, wires and batteries we will see the bewildering number of ways in which the electric field changes to ensure that current flow is always continuous. current is an abstraction that is conserved. physicists teach that conservation of charge and current are universally true, exact from very small to very large scales and very small times to very large times [68]. what physicists often do not teach clearly is that charge and current are abstract ideas. many students believe that current is always carried by particles and so conservation of mass (of charged particles) implies conservation of charge and current. this is not true. current is carried between the plates of a vacuum capacitor as a displacement current that does not involve the movement of particles [1, 14–16]. current flow in semiconductors is carried by mathematical fictions called quasi-particles that move according to classical physics [17–21], not involving solutions of schrödinger’s equation. this is an important property of semiconductors [69–70], crucial to their use. an essential idea of electricity and magnetism as explained in textbooks [14–16] is that current is continuous (without loss in a series circuit) no matter what the physical nature of the current. electrical potentials and forces change automatically to guarantee continuity of current flow under all conditions, in experiments and in the equations of electromagnetism. i found saslow’s [14] treatment of continuity of current particularly clear and useful. fig.2 tries to show this idea in a concrete way that is easy to build in a lab. ‘completing the circuit’ implies that current in every device is the same. continuity of current the same as kirchhoff’s current law in a one dimensional sequence of reactions states that timevarying currents are the same in any series of devices even if they exhibit very different physics and different constitutive laws, even if they involve chemical reactions (fig.1 and eq.(6)). ionic conductor. the ionic conductor in fig.2 is a cylinder containing nacl. here, current flow (at a frequency say of 1 hz in a 0.02 m solution) is almost entirely the physical movement of charged particles, of ions, say sodium and chloride ions, and follows simple constitutive laws (when concentrations are < 0.02 m and flows are not large enough and do not last long enough to change concentrations). these ions are hard spheres. the finite size of these spheres is significant in the ionic mixtures found everywhere in biology and in general at concentrations greater than say 0.02 m. the finite size makes constitutive equations (valid at all concentrations of mixtures of different types of ions) much more difficult than the classical constitutive equations for quasi-particles that are points. finite size implies saturation effects space cannot be filled more than once and these imply that ‘everything interacts with everything else’. numerical difficulties in dealing with spheres are substantial. spheres must be computed in three dimensions because spheres do not exist in one and two dimensions. that is to say, objects with a single radius have very different surface to volume ratios in one, two and three dimensions and so fill space very differently. phenomena in which spheres fill a significant fraction of three-dimensional space are not easily approximated in one or two dimensions. computation of the forces that prevent overlap of spheres is difficult because those forces are strong and vary significantly in three dimensions. bottom line: non-ideal solutions remain a challenge, as documented below. vacuum capacitor. let’s move on to a vacuum capacitor, in which the space between the two plates is completely empty of matter (as it would be in outer space, for example). the current flow through this capacitor is just as real as the movement of ions of nacl in the cylinder even though no particles or spheres are present, and no mass moves at all. the displacement current between the plates of the vacuum capacitor is a property of the electric field itself, as explained in textbooks of electricity and magnetism [1, 14–16] and is described by the exact and simple constitutive equation for the vacuum idisplacement = c(∂v/∂t), where the displacement current idisplacement (amps) is strictly proportional to the capacitance c (farads) and the time rate of change ∂v/∂t of the voltage across the vacuum capacitor. unlike other constitutive equations, the constitutive equation for vacuum current is exact, valid to some eighteen significant figures [15]. this displacement current induces a magnetic field just as current carried by ions produces a magnetic field. indeed, without displacement current in a vacuum, maxwell’s equations do not allow sunlight to propagate through the vacuum of space. with this exact expression for displacement current, light propagation is a solution of the maxwell equations, and in fact the speed c of propagation of light can be computed from measurements of electrical and magnetic constants, entirely independent of measurements of light itself, by maxwell’s remarkable formula c =1 µ0ε0 . light propagates according to maxwell’s equations over astronomical distances, so we know that the constitutive equation that calculates that speed must be accurate to many significant figures. dielectric capacitor. in the dielectric capacitor in fig.2 (filled with for example the plastic polytetrafluoroethylene = ptfe = teflon), current flow is more complex, and involves the effect of an applied electric field on the spatial distribution of the electric mass action and conservation of current 44(1) pp. 1–28 (2016) doi: 10.1515/hjic-2016-0001 7 charge intrinsic to the atoms, molecules, and substances of the dielectric. (‘intrinsic’ here means the distribution of charge present when there is no applied electric field). note that the electric charge in a dielectric, an ionic solution, a protein or nucleic acid, for that matter, varies significantly on all scales from subatomic to macroscopic. the properties of dielectrics cannot be described in detail here because they vary so much with material, voltage, and time. but some properties need to be emphasized. intrinsic charges do not move from plate to plate in a real capacitor. the current that flows from plate to plate and within the dielectric is a dielectric displacement current not carried by the movement of mass (any substantial distance). the current in a real capacitor is an abstraction. it is the sum of the vacuum displacement current and the material displacement current ipol (in the dielectric) produced by the distortion of intrinsic charges. the material displacement current describes the movement of a charge on a non-linear time-dependent spring (with damping) that eventually stops moving after being perturbed by an external electric field for a finite time. calculating this material displacement current involves solving a non-equilibrium time-dependent version of the schrödinger equation, a difficult task, involving a macroscopic number of atoms and millisecond timescales in cases of biological interest. ideal dielectrics do not approximate ionic solutions. scientists have avoided the difficulties of solving the schrödinger equation in a macroscopic system like a dielectric, or ionic solution, by using approximations. they discuss an ideal dielectric with properties independent of field strength and independent of time. the approximation over a wide range of electric field strengths is satisfactory in most materials. the approximation of a time-independent ideal dielectric is poor over a wide range of times. for example, most solutions of ions in water need effective dielectric coefficients to describe the polarization charge induced by permanent charges. this dielectric charge changes after a step electric field is applied from about 2 to about 80 as time progresses, from zero to 10-15 sec to say 10-5 sec and the change in dielectric charge depends on the substance [71]. there is not a universal constitutive law or approximation for the time dependence of dielectric properties. a factor of 40 change with time is not small. multi-scale analysis must deal with this multi-scale problem because atomic motion has macroscopic consequences on all timescales. the time dependence of real dielectrics needs to be dealt with in biological applications: ideal dielectrics do not approximate the properties of ionic solutions in which biology occurs. the time dependence of polarization charge in proteins has been extensively studied [72–74] and varies over the whole time-scale from atomic to macroscopic. it often has slow components, 10-3 sec or slower. biology is controlled by atomic structures that move significantly in 10-15 sec but have dramatic effects on biological functions between 10-5 sec and 10 sec later. the time dependence of these induced polarization charges appears in simulations (with atomic resolution) as changes in the orientation and induced polarization of water molecules, and in the distribution of ions, as well as in the distribution in proteins of permanent charges, permanent dipoles, and induced dipoles. atomic-scale simulations must last a long time. atomic-scale simulations seeking agreement with experimental data available for a wide range of solutions [71], and proteins [72–74] must last long enough to account for the discrete charge movements that produce an effective dielectric coefficient of 80, as measured experimentally. otherwise, substantial changes in the electric field will not be seen in the simulation, even if those changes in the electric field have great biological significance. electric fields in biology are strong. a nerve signal is a change in an electric field of the greatest biological significance. information transfer in the nervous system, coordination of contraction in muscle, including the coordination of cardiac contraction that allows the heart to pump blood, are all directly controlled by the action potential, the biological name for the nerve signal. electric fields during a biological action potential are slow (say 10-3 sec), and macroscopic in scale, transmitting 10-3 meters, propagating one meter (in humans), and they are remarkably multi-scale. handfuls of atoms in a channel protein control the macroscopic propagation and the nerve signal itself is current carried by ions (that are single atoms) moving through those proteins. the electric field of the action potential is strong, typically some 0.1 v across a 2×10-9 meter-thick membrane or a 3×10-10 meter-long selectivity filter (eeee group in a calcium channel), 5×107 to 3×108 v/m. these electric fields distort the intrinsic distribution of charge within the dielectric on many scales of time and distance, including electrons inside molecules and atoms. they reorient polar molecules that have an intrinsic asymmetric distribution of charge. charges only move a small amount in dielectrics in response to the applied electric field reminiscent of the sloshing of tides in an ocean and on beaches on earth created by the moon’s gravitational field and they eventually return to their resting position when the field is turned off but those small movements of charge produce large effects because the electric field is so strong. dielectric currents ipol share some of the properties of vacuum displacement currents but they do not follow a universal exact constitutive law, not even approximately. it is important not to confuse dielectric ipol and vacuum displacement currents ε0 ∂e/∂t. it is important to realize dielectric displacement currents can be large and produce large effects in biology, as they do in semiconductors. non-linear components of dielectric current are important in biology. non-linear components of dielectric displacement current have large effects important in biology (e.g. in muscle [75], where they were first discovered, and nerves [76]) where they eisenberg hungarian journal of industry and chemistry 8 control the opening and closing of the channels that produce the action potential [77] and some enzyme functions [78], as well. these non-linear dielectric (i.e. displacement) currents can be recorded as ‘gating’ currents because of the shockley-ramo theorem [79], which is a restatement of continuity of current. the dielectric currents involve a tiny fraction of all the charges in and near to an ionic channel, far less than one percent (see appendix “size of effects” near eq.(28)), but continuity of current and the strength of the electric field make gating currents easily measurable in the hands of skilled experimentalists. any electric field is extraordinarily strong compared to diffusion. tiny displacement currents can be recorded routinely in many laboratories because the electric field is so strong. if it were not so strong, these tiny concerted movements of atoms would be lost amongst the brownian thermal motion. extraordinarily small changes in net charge are enough to guarantee that currents are the same in all elements of a series circuit because the capacitances (ratio of charge to potential) involved are often some 10-17 farads, see appendix. continuity of current flow is guaranteed by changes in electrical forces and potential resulting from very small amounts of charge. concentration effects are very small. on the other hand, a one percent deviation in density of mass has a tiny effect on diffusion and chemical reactions, which is hardly noticeable. diffusion forces are tiny perturbations in the electric force field and energies involved in diffusion are tiny perturbations in the total energy of charged systems. electric forces and energies are not small parts of the total energy and it is not wise to say the least to treat them as perturbations of uncharged systems. small changes in charge distribution produce large changes in flow because flow tends to be an exponential function of the spatial profile (even when the profile does not have a large, single, symmetrical peak [80] of potential energy) and the profile of energy is a sensitive function of permanent and dielectric charge, ionic conditions, etc. [81]. it is not wise [82] to neglect the effect of permanent charges of the channel protein on the shape and size of the electric field as is done in many continua [83–105] and rate models of gating and permeation of ion channels, and most treatments of enzyme function and catalysis. current is indeed an abstraction. in each of the devices in fig.2, charge follows different laws, because it has different physical properties, sometimes carried by charged particles, sometimes produced by the rate of change in electric field (displacement current), sometimes as a result of the ‘movement’ of quasiparticles, and sometimes as a consequence of the ‘movement’ of electrons in a macroscopically delocalized quantum state of a wire. current always flows without loss in each device. this abstract property of current is always true, because the potentials change automatically to ensure continuity of current. however, the ‘laws’ describing current as a function(al) of time and potential (for example) depend on the physical nature of the charge and its movement. different devices have different relationships between current, voltage, and time. these different ‘constitutive’ equations are described in engineering literature in great detail. the different constitutive equations combine with kirchhoff’s current law to describe current flow from one place and one device to another. together, the equations describe the universal fact that interrupting current flow in one chemical reaction (of a series of reactions) will interrupt current flow in every other reaction (in that series) even if the interruption is meters away from a chemical reaction being studied on the atomic scale (scale = 1 å). together the equations describe the experimental fact that electric fields, forces, and potentials automatically rearrange so that kirchhoff’s current law and continuity of current flow are always present exactly on all scales no matter what is ‘carrying’ the current. indeed, the physics of current flow changes to accommodate the continuity of current. one is reminded of the power of the electric field when one unplugs a computer. interruption of a circuit meters away from the diodes of the computer’s power supply stops the flow of quasi-particles holes and semi-electrons across atomic-scale junctions of semiconductor diodes, often of the pn variety. the electric potential changes so strongly in response to the interruption (because the power input of the computer power supply stores a great deal of charge) that the electric field exceeds the dielectric strength of air. the automatic change in the electric field needed to maintain continuity of current flow is enough to ‘change the physics’ of the system. electrons are stripped off the atoms of air resulting in a plasma, a spark. we should be frightened of sparks and their electric fields. sparks start fires, sometimes in upholstery or drapes. vacuum tubes. we consider charge movement in a vacuum tube diode as the next device in fig.2. vacuum tubes control the flow of electron current by changes in their internal electric fields and were called ‘valves’ in the uk for that reason. vacuum tubes, semiconductors and even some open ion channels follow simple constitutive laws of rectifiers, as described in textbooks of electronic devices or ion channels. in vacuum tubes, current is indeed carried by a stream of isolated charged particles, electrons with a definite mass and charge, moving through a vacuum, interacting only through their electric fields. at 1 hz, essentially all the current in a vacuum diode is carried this way. current through a diode is not proportional to the voltage across the diode because the electric fields within the diode change shape, despite the simple physics of conduction. the fields change shape as the voltage across the diode is changed because of screening and shielding. the electric fields within the tube are different at small and large potentials. the different internal electric fields change current flow, creating rectification. the electric field creates a large barrier in one direction so current in that direction is small; the electric field creates a small barrier in the mass action and conservation of current 44(1) pp. 1–28 (2016) doi: 10.1515/hjic-2016-0001 9 other direction, and current in that other direction is large. rectification is of historical interest because vacuum tubes allowed the early detection of radio waves in american homes in the 1920’s, as valves did in the uk. the demand for portable radios led to solidstate diodes, then solid-state ‘triodes’, field effect transistors, integrated circuits, and our modern digital world [106]. vacuum tube diodes had certain difficulties they were big (10-2 m at their smallest), hot, greedy consumers of power, cost about $3 in the 1950’s, and electrically unstable: they drifted continuously. they were quickly replaced with semiconductor diodes that cost less than $10-10 each, do not drift significantly, and can be as small as 10-8 meters nowadays. we turn now to the semiconductor diode that operates on a very different scale from the vacuum diode. the rectification of both diodes that is their function depends on essentially the same physics, namely the shape of the electric field and its change in shape with the direction of current flow. the electric field of charge must be respected on both the scale of vacuum diodes and that of semiconductor 10-2 meters of vacuum tubes, 10-9 meters of semiconductor diodes indeed on all scales because the electric field has such large effects on all scales. the immediate implication is that theory and simulation must calculate the electric field on all scales, using an explicitly multi-scale analysis, since it seems unlikely that any one type of simulation or theory can span atomic to biological to laboratory distances and times, let alone the interstellar scales on which the laws of electricity are known to be valid. semiconductor diodes. current in semiconductor diodes is carried by quasi-particles [70], called holes and ‘electrons’ (better named quasi-electrons, or semielectrons in my view). these quasi-electrons and holes are defined because they interact much more simply than the totality of real electrons and lattice of atoms in semiconductors [21, 70, 107–109]. they simplify the quantum mechanical many-body problem into the much simpler motion of imagined quasi-particles. current is carried in semiconductors by rearrangements of charge in the entire lattice of atoms that make up the semiconductor. fortunately in terms of our technology and daily life, current in germanium and silicon can be approximated by classical theories that deal with one quasi-electron or one quasi-hole at a time as they move in mean fields, without requiring a solution to the schrödinger equation at all [17–21]. as a textbook puts it eloquently (p. 68 of ref. [69]): “electron is a quasi-particle consisting of a real electron and an exchange correlation hole … a cloud of effective charge of opposite sign due to exchange and correlation effects arising from interactions with all other electrons of the system. hole is a quasi-particle, like the electron, but of opposite charge; it corresponds to the absence of an electron from a single particle state that lies just below the fermi level”. the motion of these quasi-particles is described by mean field models, evaluated both by simulations [17, 21] and theories [17– 21], e.g. the poisson drift-diffusion equations [110], often called pnp (for poisson nernst planck) in biophysics and nanotechnology [56, 61, 111–117]. pnp is of particular importance because it is used widely, nearly universally, to design and understand the devices of our semiconductor technology, from transistors to computer chips. pnp is used rather widely in nanotechnology these days and increasingly in membrane biophysics, mathematical biology, and electrochemistry, including battery technology, as well as the technology of cement. rectification in biological membranes. early treatments of rectification in biological membranes, then called ionic conductances, ([83]; appendix of [118]) in fact drew heavily on mott’s (nearly) contemporaneous treatments of rectification in diodes [119], but none of these were consistent: they assumed the electric field, instead of computing it. the charge in the system did not produce the assumed electric field if substituted into poisson’s equation. goldman [83], then a graduate student of k.s. cole, recognized the problem, but did not know how to remedy it, nor did these workers [83, 118] understand that electric fields in diodes or open channels were not constant in any sense, including space (numerous personal communications to me from k.s. cole, 1960–1962, and a.l. hodgkin, 1960–1995). mott soon realized [120] that the change in shape of electric fields was a crucial phenomenon in semiconductor diodes, updating the constant field assumption of his original paper [119]. biophysicists were evidently not aware of the evolution of mott’s understanding [121]. semiconductor physicists understood that consistent treatments produced electric fields that varied greatly with conditions, as the fields change to force continuity of current [122]. indeed, transistor design would not be possible [21, 106, 123–124] if computational electronics had assumed constant fields the way some physicists did early on [119], but not for long [120]. in biophysics, the importance of computing the fields from the charges (so the fields and charges were consistent) was not realized (as far as i know) until much later [81, 111–112]. until then, and even after, nernst-planck equations were used in biophysics without including the ionized acid and base groups of the channel protein, i.e. without including the permanent charge of the protein [85–105, 121]. these ionized groups render polymers into ion exchangers [125]. the equivalent doping profiles convert semiconductors into devices. leaving out ionized groups “is like studying a galaxy without stars”, as a prominent physical chemist once told me. the distribution of permanent charge creates a baseline electric field. changes in shape of the electric field with concentration, amino acid composition of the channel protein, etc. are responsible for many of the important properties of these systems. unfortunately, the importance of changes of shape in the electric field, and of the fixed charges involved, were and still are often ignored. eisenberg hungarian journal of industry and chemistry 10 charge carriers in semiconductors can be really quite strange from a physical point of view. charge carriers in silicon and germanium do not exist outside the lattice of the semiconductor as distinct entities. they do not exist in the same sense that na+ and cl− ions exist, but are mathematical representations, with lifetimes sometimes as short as milliseconds. quasiparticles are the second derivative of a fermi surface of silicon and germanium semiconductors, under particular conditions. they are defined, as mentioned above, to allow easy classical analysis compared to the intractable quantum mechanical many-body problem of a macroscopic semiconductor. much of the success of our semiconductor, digital, and video technology is due to the accuracy of the constitutive pnp equations describing holes and semielectrons. they robustly describe the characteristics of semiconductor devices of many different types, with very different input-output relations, as different as an exponentiator and a logarithmic convertor. pnp is so useful because almost all the devices of our digital technology work under a restricted set of conditions in which flows are crucial but are of the special type, well described by quasi-particles moving in a mean field. treatment of distortions of the electric field of all the atoms in macroscopic devices is not needed. almost all of the devices of electronics use power supplies to maintain different voltages at different locations far from the pn junctions of the device itself (and thus require a global treatment of the electric field). these voltages perturb the distribution of velocities of charged particles so the distribution exhibits net flow [80, 126]. the slight perturbation is enough to imply the pnp equations and those provide enough non-linearity to make amplifiers, switches, and the full set of logical circuits necessary to make a computer [21, 107–109]. in fact, in this case the pnp equations can be solved analytically and exactly to give intuitive, pleasingly simple formulae for current flow, once the shape of the electric field is known [80]. pnp equations describe a wide variety of current voltage relations and devices. the pnp equations are the constitutive laws used to describe semiconductor devices as their current voltage relations change drastically (with voltage, for example) from that of a linear amplifier, to a switch, exponentiator, multiplier or even logarithmic converter [21, 107–109]. non-linear input-output relations, as varied as these, enable a rich variety of devices. non-linear input-output relations as diverse as these are not described easily or described at all for that matter in most areas of physics and chemistry. all the non-linear devices in a computer are actually mathematical solutions of the pnp equations in a complex silicon structure built to have the particular spatial distribution of permanent charge (‘doping’) that produces the desired properties of the device, i.e. the input-output relations. the predictive power of pnp is very important in the design of robust semiconductor devices that do not fail even when used many millions of times a second in computers that contain a trillion transistors. in fact, the intrinsic physical properties of semiconductors are adjusted by their designers so pnp remains a good description [127–130], even though the size of the device has been dramatically decreased. the concentrations of fixed charge dopants, geometries, and recently even dielectric coefficients are adjusted by semiconductor engineers in their successive iterations of moore’s law [131–133], so pnp remained a good description as performance increased by factors of a billion or so, over 50 years. evidently, reliable design is more important than raw performance. it seems more important for the designers (and marketplace) that an equation describes behavior robustly and accurately over a range of conditions than that the device be as fast or small as possible [127–130]. evolutionary selection in biology also seems to choose robustness over efficiency in many cases. devices of nanotechnology need to be similarly robust, i believe, before they will be used extensively. pnp is not enough, however, when ionic solutions are involved. a great deal of effort has been spent applying pnp equations to electrochemical systems [56, 61, 111–117] hoping they might serve as adequate robust constitutive equations, but that is not the case. the non-ideality of ionic solutions, arising in large measure from saturation effects produced by the finite size of ions, demands more powerful mathematics than the partial differential equations of pnp used in computational electronics. resistor. the next device we discuss in fig.2 is a resistor, which in some ways is the easiest to describe because current is proportional to voltage with a single proportionality constant over a wide range of voltages, times, and conditions. a resistor follows ohm’s constitutive law with a resistance independent of potential over a wide range from 10-5 v to say 100 v, and for values of resistance from 10-1 ω to 108 or 109 ω. the range of validity of ohm’s law is an enormous help in circuit design. circuit models involving resistors, capacitors, inductors, and operational amplifiers are transferrable. they behave as real devices behave without changes in parameters. largely for that reason, designs are inexpensive and robust. despite the simplicity of resistors, the actual current carrier in a carbon resistor is unclear, at least to me. no one cares very much i suspect because the device works nearly perfectly. the carrier of charge does not matter very much. what matters is the constitutive law that describes the relation between current, voltage, and time. the constitutive law should satisfy conservation of mass, charge, and current. it is instructive to write the constitutive law for a resistor ohm’s law for only particle current, using a conservation of particle (mass) formulation, and then write it again for particle plus displacement current from one terminal to another. if you apply a step function of current (or potential for that matter) to the purely particle formulation, a paradox arises. the potential changes but the particle current flowing into the resistor mass action and conservation of current 44(1) pp. 1–28 (2016) doi: 10.1515/hjic-2016-0001 11 from the left is exactly equal to the particle current flowing out on the right at all times. why does the potential change if there is no accumulation of charge? the paradox can be resolved in two (nearly) equivalent ways: (1) the constitutive equation of ohm’s law can be used with the extended definition of current that includes the displacement current. in this case, there is continuity of generalized current, but there is not continuity of particle current at all times. the transient accumulation of particle current provides the charge that changes the potential. (2) alternatively, the circuit model of the resistor in fig.2 can be changed to have an explicit capacitor in parallel with it. in this case, the charge accumulates on the capacitor, and the resistor itself can have continuity of flux of particles at all times and follow ohm’s law using the current/flux of particles (and not the displacement current). the charge accumulating on the capacitor creates and changes the electric field. maxwell himself repeatedly used capacitors in this spirit to understand the role and significance of displacement current. sections 102, 125, 199 and chapter 8 are some examples in ref. [134]. we (following the insight and advice of wolfgang nonner) have used capacitors as a low resolution, consistent way to connect permanent charges (specifically, ionized side chains in a channel protein away from the pore) and electrical potentials in the pore of a channel protein, e.g. the potassium channel [135]. current flow in wires can also be strange. the current carriers in a wire are delocalized electrons in the simple case of a single solid conductor of metal, and follow the simplest constitutive law of all over long(ish) time-scales, say times longer than 10-5 sec. nevertheless, most of the electronics in our digital technology operate over time-scales much shorter than that. now we confront the importance of the time variable. the physical nature of current flow depends on time-scales, even in wires [14, 16]. the range of timescales in our technology is enormous, from more than one second to less than 10−9 sec. over shorter timescales (< 10-4 s) the wires that must be used are often twisted pairs [136], each made itself of many very fine wires. without twisting, these pairs of wires do not allow successful connections to the internet because rapidly changing signals are not carried reliably by single wires [137]. over those short time-scales, currents flow outside wires, guided by the conductor, to be sure, but outside the conductor nonetheless [16, 137]. the twisting of wires is a necessity if they are to carry signals robustly and reliably so we can use them in our video devices and smartphones, even in old-fashioned hard-wired telephones [136] that only need to amplify audio signals heard by adult humans (< 10,000 hz). the physical nature of current depends on time-scale. the physical nature of current in almost any system depends on the time-scale, and differs at different times as much as it differs in different devices. constitutive equations depend on time. different devices have different constitutive equations with different time dependences. again, current is an abstraction, a different abstraction at different times in one device, as well as different in different devices. charge movement in batteries. batteries are present in fig.2 both as an isolated device and as the ag||agcl interface between wires and nacl solution in the conducting cylinder previously discussed. i hesitate to describe a constitutive equation for the flow of charge in batteries in general because the flow is so very complex, different in different devices, and important for the practical daily use of batteries [138–139], and its interaction with surface charges is also subtle and important [140]. it is enough to say here that current flow through electrochemical systems is carried by different electrochemical systems differ dramatically and change in dramatically with time, frequency, composition and concentration of ionic solutions, as well as electrical potential, and current flow. over short time-scales, e.g. 10-6 sec that are still long compared to the time-scales important in computers current flow from the ag wire and agcl electrode material into the nacl solution is entirely displacement current lagging behind voltage. however, over the longer time-scales characteristic of biological systems (greater than say 0.1 sec), the current is carried by a complex combination of ag+ and cl− ions with negligible displacement current. we conclude that current is indeed an abstraction with different physical meanings in different systems and over different time-scales. no one can visualize and no one knows at least i do not know anyone who knows why or even how this abstraction can be so perfectly conserved under all conditions and over all scales, from angstroms to meters, from femtoseconds to seconds. it is truly amazing to think of the changes in electric forces needed to accommodate and enforce continuity of current in salt water, vacuum capacitors, dielectric capacitors, vacuum tube diodes, semiconductor diodes, resistors, wires and batteries from atomic time-scale 10-16 sec and distances of 10-11 meters to the biological scales of seconds and meters from inside atoms (pp. 8–9 of ref. [1]) to intercontinental distances (in submarine cables) and interstellar space. 3. general remarks about current flow the discussion of fig.2 leads to some general remarks about current flow. the interplay of conservation of matter and conservation of charge and current is different in each system, according to the constitutive law of the system. the idea of a current flow is an abstraction built to accommodate the physics of each system, while maintaining the main feature of eisenberg hungarian journal of industry and chemistry 12 electrodynamics, the exact conservation of current, at any one time, on any scale. conservation of mass is certainly also followed in these systems, but in a more relaxed way. significant deviations are allowed for a time. mass can accumulate for a time without catastrophic results. accumulation of mass does not have dramatic effects. in the systems considered here, the accumulation of mass does not usually have dramatic effects. a one percent accumulation of mass has a small effect on chemical potentials, although of course exceptions can occur. there is no general law for the accumulation of matter. the effect depends on the constitutive law, and its interplay with conservation of matter, charge, and current. accumulation of charge has dramatic effects. the accumulation of charge is different. a one percent accumulation of charge has a huge effect. as feynman memorably mentions at the very beginning of his textbook [1], one percent excess of charge in a person at arm’s length produces a large enough force to lift the earth! the accumulation of charge follows an exact law: the displacement current is the sum of all the other charge flows and it changes the rate of change of the electric field in a precise way so total current is conserved precisely. continuity of current is obeyed and so such enormous forces do not occur. if continuity of current were not obeyed exactly, enormous forces would soon develop (see appendix). such forces are of course incompatible with life or laboratory experiments. fortunately, accumulated charge is easier to deal with in theory than accumulation of mass: the vacuum displacement current does not depend on constitutive laws, it simply depends on the time derivative of potential and so can be calculated. accumulated charge is much simpler than accumulated mass. accumulated charge has universal properties, independent of the physical nature of the charge. particle and quasi-particle currents that accumulate at a junction change the time derivative of electric potential so the electrical potential carries away a displacement current. this displacement current is exactly equal to the sum of the other currents flowing into the junction without known error, to about one part in 1018. continuity of current is exact independent of constitutive laws if current is re-defined to include displacement current. the displacement current (and equivalently ∂v/∂t ‘take up the slack’ so that kirchhoff’s current law (using the extended definition of current) is exact in one dimensional systems like a sequence of chemical reactions. no charge accumulates at all beyond that defined by the integral of the displacement current. the electrical forces and ∂v/∂t change so the displacement current is exactly equal to the sum of the other currents, and continuity of generalized current is exact. accumulation of charge is special because it is universal. the precise linkage between potential change, charge accumulation, and displacement current is a special feature of electromagnetism because it is universal. it is a property of a vacuum, the constitutive equation of a vacuum, if poetic license is allowed. in this sense charge is more fundamental and universal than mass, a fact which certainly came to me as a surprise [141]. then i learned that charge is constant at all velocities according to the ‘lorentz (relativistically) invariant’, whereas mass is not. mass depends on velocity and charge does not. special relativity seems to make charge a more fundamental physical property than mass. the reader may have difficulty visualizing the interactions that enforce conservation of the abstraction ‘charge/current’ in all these devices with all these properties over the entire time-scale. i certainly do. however, current flow and charge are conserved on and between all scales under all conditions, even if we cannot visualize how that manages to be so. experiments demonstrate that fact. current does flow continuously without loss in a circuit. consider a battery feeding a circuit. if a wire is cut far from the battery, current flow stops everywhere. the chemical reaction in the battery is disrupted on an atomic scale, by the (lack of) current flow meters away. those of us living in colder climates have seen the effects of starting a car with another car’s battery. we have learned to be careful because even a twelve volt battery can produce dangerous sparks in air, even though air has nearly infinite resistance ( > 1011 ω for dry air), and is in that way, nearly a vacuum. abstract current is conserved ‘exactly’ even if we cannot visualize how that happens. science often contains mysteries that cannot be visualized consider maxwell’s attempts to visualize his equations as properties of an ether. science often poses questions that cannot be answered. why is there no magnetic charge? why is the charge on an electron 1.6 ×10−19 c? why is charge independent of velocity in special relativity when mass, distance, and even time are not? why are physical laws invariant when locations s move at constant velocity ∂s/∂t mass, distance, or at constant acceleration ∂2s/∂t2 general relativity but not when other time derivatives of location are constant, like a constant third derivative ∂3s/∂t3 or linear combinations of ∂ns/∂tn, perhaps even fractional derivatives? as practical people, scientists cannot afford to just wait while we wonder about such things. scientists wonder a bit and then move on, hoping our successors can do better than we have. biologists and engineers in particular cannot afford to linger on mysteries they do not understand. so many of those mysteries in biology have turned out to be caused by low resolution of our instruments, unable to resolve crucial structures. think of thomas henry huxley looking at the shortening of the striations of muscle [142] that were not understood until one of his grandsons (andrew huxley) studied them many years later working in cambridge, uk [143]. think of lee de forest using vacuum tubes without understanding how they work. biologists and engineers cannot afford to wait to understand everything. they must isolate the mysteries and move on to study other things. here, we mass action and conservation of current 44(1) pp. 1–28 (2016) doi: 10.1515/hjic-2016-0001 13 move on to discuss devices and the theories and simulations used to understand them. biological implications of continuity of current. it is important to note that the continuity of current law has important biological implications in systems more general than a series of chemical reactions. the continuity of current law implies the cable equations (called the telegrapher’s equations in mathematics literature), see derivation from the three dimensional theory in [144–147] and pp. 218–238 of [148]. the cable equation [149] is the foundation of the hodgkinhuxley model [150–154] of the action potential of nerve and muscle fibers. kirchhoff’s current law links the atomic properties of ions, the molecular properties of ion channels, and the centimeter-scale spread of current and potential that create the propagating action potential in nerve fibers meters in length. in short or round(ish) cells, or in organelles like mitochondria, continuity of current forces coupling between multiple pathways of current crossing membranes, even if the currents are carried by different ions, or by electrons, through different structures nanometers apart in the membrane of the finite cells or organelles. the flux-coupling characteristic of active transport systems including the coupled flows in chemiosmotic systems that perform oxidative phosphorylation or photosynthesis might arise in this manner. coupling of flows of charges, whether electrons or ions, is an unavoidable consequence of the global conservation of charge and current, of kirchhoff’s current law globally enforced in three dimensions, and not a consequence of local chemical interactions, just as coupling of membrane currents with axial currents in a nerve fiber is an unavoidable consequence of kirchhoff’s current law, not of local chemical reactions. it is interesting to compare the incorrect chemical theory of nerve propagation by nobel laureate a.v. hill [155] with the correct electrical theory of the then undergraduate [156–157], later nobel laureate [150– 154], alan hodgkin. kirchhoff’s current law in the form of the cable equation [149] was the key to hodgkin’s understanding. the classical voltage clamp experiments were designed to remove difficult terms and isolate membrane terms in the cable equation personal communication, a.l. hodgkin, 1961 that today we know describe ion channels, opening, closing and conducting [121, 158–159]. the cable equation links movement of atoms inside channel proteins to macroscopic current flow that produces nerve propagation of the macroscopic electrical potential, the nerve signal that spreads meters. macroscopic potentials modify atomic movements involved in gating and conduction. atomic movements create macroscopic electrical potentials. equations of the electric field are true on all scales and so allow a unique linkage between models of atomic motion, protein behavior, and macroscopic propagation of electrical signals. i suspect linkage equations of this type valid on all scales will be needed to make any multi-scale analysis robust and transferrable, if it reaches from atoms to meters, from femtoseconds to minutes as models of nanodevices must. models, devices, effective parameters, and transferrable theories. parameters of models or devices can often be chosen so an incomplete theory or simulation describes a system under one set of conditions but not another. experiments often show that rate constants must be adjusted dramatically as conditions change, and the adjustments can rarely be predicted ahead of time by theory. chemistry and biology are filled with examples of non-transferable models. chemical reactions follow rate equations, but the rates are not constant and not independent of one another as conditions change, even though traditional theory assumes they should be [5]. biology describes enzymes with one set of parameters but finds those change when conditions change and attributes that, somewhat mysteriously, to ‘allosteric effects’ and conformation changes. non-transferable theories have limited use. biology and much of chemistry works under a wide range of conditions and so incomplete theories with effective parameters have limited use. even if sensible or valid, theories (and simulations) with effective parameters like these are not accurate enough to design robust devices. by leaving out something important, those theories or simulations omit an energy term that almost certainly varies with conditions. the resulting effective parameters change in large and unpredictable ways. incomplete theories and simulations are not very useful over a range of experiments and conditions. incomplete theories are not likely to be transferable (from one set of conditions to another) in the language of the chemistry literature. devices designed from incomplete theories or simulations are unlikely to be robust or work well under a range of conditions. biological systems analyzed with non-transferable theories (or simulations) are unlikely to be realistic in general because biological systems usually work in a range of ionic concentrations different from those used in the laboratory. simulations must deal with trace ca2+. biological systems usually work in mixtures with a range of ca2+ concentrations, in which the ca2+ concentration has important practical effects, often turning systems on or off or controlling their rate monotonically. simulations and theories in biology have limited use until they are calibrated so we can be sure they actually are correct under the range of conditions and ca2+ concentrations the biological systems use. simulating ca2+ activity in pure solutions is a challenging problem [160]. simulating ca2+ activity in biological mixtures within the 10-8 to 20 m concentration range that are physiological has not been attempted to date. 10-8 m concentrations of ca2+ are found inside most cells, while 20 m concentrations of ca2+ are found in and near ion channels, nucleic acids, and enzyme active sites, where the chemistry of life is catalyzed and controlled. eisenberg hungarian journal of industry and chemistry 14 biological and chemical sciences will benefit enormously if theories and simulations can be made transferable, using one set of parameters to describe systems under a range of conditions, as many physical and most engineering theories and simulations do. i believe the law of mass action must be extended to conserve current before theories and simulations can be made transferable from condition to condition and from physics to chemistry to biology using only mathematics. how to extend the law of mass action so it conserves current? an obvious way to extend the law of mass action is to include activities and electrical potential in the rate constant to ‘right the rates’ by making them (typically exponential) functions of potential [2–4, 11, 13]. this in fact has been done for a very long time in the study of reactions at the electrodes of electrochemical cells and recently in other ways in the treatment of the formation of concrete [161–163]. the butler-volmer and tafel equations [2] include electrical potential in rate constants in an empirical way with limited [3–4] but real success. success is limited i suspect because difficulties of embedding an electrical potential in rate constants are formidable if current flows. we must ‘fix the fields’ so they are global and depend on current flow everywhere. otherwise, they cannot conserve charge flow and support continuity of current as required by maxwell’s equations: the way to ‘right the rates’ is to fix the fields, everywhere. 4. additional perspectives some additional general remarks may be helpful: (1) a thermodynamic treatment is clearly impossible since the goal is to calculate large fluxes and currents that do not occur in a thermodynamic system at equilibrium by definition without flows. (2) a rate treatment of the frictional treatment of flux over a large potential barrier is needed. the classical brownian motion problem of kramers [164–165] is a necessary step forward, even if it is inconsistent because it does not compute the potential barrier from the charges in the system. kramers’ treatment need not be restricted to large barriers. a simple expression for rates over any shape barrier is available [80] and needed [166] because so few barriers are both symmetrical and large as required in classical high barrier approximations. (3) the rate constants over one barrier must depend on the electrical potential in distant locations. otherwise, interrupting current flow in a distant location cannot interrupt current locally. this requirement implies that the electrical potential must be determined by a global equation like poisson’s equation, including boundary conditions far from the individual chemical reactions and barriers. the barriers of kramers’ model are variable and not constant as conditions change, including conditions far from the barrier itself. the fields and energy landscapes change and it is indeed their change that allows continuity of current, as illustrated in eq.(1), to be satisfied. (4) the rate constants over one barrier are likely to depend on concentrations in other places because the solutions containing the reactants are not ideal. a general characteristic of non-ideal solutions is that ‘everything depends on everything else’. more specifically, the activity of one reactant (the free energy per mole) depends on the concentrations of other species in practice, as well as in principle. (5) a general theory of all non-equilibrium processes is not likely to be useful: a general theory has to describe too much. a general theory must include hydrodynamic behavior of considerable complexity, since aqueous solutions are fluids satisfying the navier-stokes equations of fluid mechanics. a general theory would also include explosions since they occur with regrettable frequency at electrodes of electrochemical cells, when h2 gas is generated (inadvertently) by an overvoltage. fortunately, non-equilibrium processes in biology and much of technology occur in ionic solutions in which atomic motion is heavily damped. that damping ensures that the distribution of velocities is a displaced maxwellian [126], as it is in semiconductor devices [21, 167–168]. the displaced maxwellian exhibits non-zero mean velocity and so allows flux and current through the system from power supplies to outputs. that flux and current is enough to produce the very nonlinear devices of our digital (semiconductor) technology [17–21], and non-linear phenomena like the propagating signal of the nervous system, the action potential [152–154]. boundary conditions are needed to extend the law of mass action to deal with the outside world. equilibrium statistical mechanics and thermodynamics were designed to avoid the complexities of boundary conditions using the ‘thermodynamic limit’ to allow analysis. but when current flows, interactions with the outside world, are unavoidable the thermodynamic limit is not appropriate, and boundary conditions describing those interactions are needed. it is difficult if not impossible to deal in general with boundary conditions for the laws of mass action, and chemical reactions, because of the wide variety of chemical interactions and physical geometries captured in a phase space of very high dimension. boundary conditions are easier to deal with in three dimensional physical space, where the law of mass action is widely, nearly universally, used to describe ion motion through narrow channels [80, 121, 169–170]. current in channels. current flow through a ‘hole in a (insulating) wall’ is a subject of great significance because the hole in the wall allows for control of the current. holes in proteins, membranes, and channels in field effect transistors are all nanovalves providing essential functions to a large fraction of biology and semiconductor technology, and of great mass action and conservation of current 44(1) pp. 1–28 (2016) doi: 10.1515/hjic-2016-0001 15 interest in electrochemistry. indeed, biological channels are nearly picovalves allowing a handful of atoms to control macroscopic flow. it is hard to imagine a smaller valve that could control macroscopic flow. we consider models of current flow through such holes and show how boundary conditions can be applied to nanovalves and systems of this type. we do not consider simulations here because they do not deal with the essential features of these systems. simulations have considerable difficulties in computing the actual currents through systems controlled by a handful of atoms. the currents are macroscopic phenomena, occurring in the world of milliseconds to minutes, and spatial dimensions from say 10-9 to 1 meter. the currents are controlled by atomic-scale structures in biology and near atomic-scale (10-8 meter) structures in semiconductors and electrochemistry. changing a few atoms changes macroscopic currents as is shown in biophysical experiments (usually involving site directed mutagenesis) every day. the macroscopic currents are driven by chemical and electrochemical potentials involving large numbers (>1015) atoms in most cases. simulations must then compute macroscopic-scale inputs and outputs while preserving atomic-scale spatial resolution of the controlling atoms. these issues must be all dealt with at once, because they all exist at once in the systems of interest, and they must be dealt with accurately, because valves typically depend on the balance of nearly equal forces, e.g. electrostatic and diffusion. each force must be quite accurately calculated because it is the difference that controls function. it will be some time before simulations can surmount these problems and be used to make practical devices [171–173]. meanwhile, we use the mesoscopic approach, which has been so fruitful in computational electronics [18, 21, 122] where atomicscale simulations are rarely if ever used. the key to the mesoscopic approach is the choice and treatment of correlations. not all correlations can be handled (see the infinite series in [174] which of course has not been shown to converge). we consider the poisson equation and use the treatment in barton [175] (p. 168) to illustrate the issues in connecting a nanovalve to the outside three dimensional world. ∇2φ(r) = −ρ(r) (12) an integral (‘kirchhoff’) representation of an equation inside the nanovalve is kvol(r) + ksurf(r), where kvol(r) involves the usual free-space green’s function gfree (r̂ | r) =1 4π (r̂ − r). kvol (r) = dv̂vol vol ∫ ρ(r̂)gfree (r̂ | r) where gfree (r̂ | r) = 1 4π 1 r̂ − r (13) ksurf (r) = dŝsurf surf ∫ ∂nφ(r̂)ĝ free (r̂ | r) − dŝsurf surf ∫ φ(r̂)∂nĝ free (r̂ | r) (14) here we use barton’s notation for the normal derivative ∂nφ(r̂) of the potential (for example) as a function of the location of the source r̂ . inside the nanovalve the volume kvol(r) and surface terms ksurf(r) are combined to give the solution φ(r) of poisson’s equation as shown in eq.(12) kvol (r)+ ksurf (r) = φ(r) r is inside the nanovalve kvol (r)+ ksurf (r) = 0 r is outside the nanovalve (15) the free-space green’s function gfree (r̂ | r) is of course the average of the free-space potential in atomicscale simulations. the special properties of nanovalves depend a great deal on the properties of their surfaces because nanovalves are so small. structural biology determines the surface of the protein nanovalve and the amino acids forming that surface. physics determines the surface green’s function ∂nĝ free (r̂ | r) and thus the surface normal derivative ∂nφ(r̂ | r) and the surface charge. determining these properties is the goal of analysis of specific nanovalves and does not concern us here. it is enough to mention that these properties can be determined from experiments analyzed by the mathematical solution [176] of the appropriate inverse problem. the spatial distribution of structure and permanent structure can be determined from measurements of current-voltage relations under a wide range of ionic conditions, concentrations, and voltages ± 6 kbt/e (150 mv). the large amount of accurate data allows for an accurate solution of the inverse problem. connection of the nanovalve to the external world is what concerns us here. in mathematical language, the problem reduces to the kirchhoff representation of the end of the channel, written from eq.(14) by isolating the surface of the ends from the rest of the structure. kend (r) = dŝend end ∫ ∂nφ(r̂)ĝ free (r̂ | r) − dŝend end ∫ φ(r̂)∂nĝ free (r̂ | r) (16) in general, this problem can be complex involving interactions of all sorts between the interior of the nanovalve or channel and the external world. indeed, in some biological channels (calcium channels) this may be important (although so far little studied). in general, however, nanovalves are devices designed to work reasonably robustly and independently of the world eisenberg hungarian journal of industry and chemistry 16 around them. robust devices need to be transferable from one place to another and so the complex interactions are minimized by the design and evolution of the systems. if we oversimplify to make the point clearly: nanovalves are exceedingly narrow where they allow control but widen dramatically outside that region so ‘resistance’ to flow is concentrated in the narrow region. control is robust, available under a wide range of surrounding conditions. in the nanovalves of semiconductor technology, buffer regions isolate the nanovalve and allow it to have robust properties. the connection to the outside world is through a buffer region of a semiconductor separating the metallic contact from the nanovalve itself. in the nanovalves of biology, the buffer regions are the antechambers of the channel and the surrounding ionic baths between the ag|agcl wire (or salt bridge) and the ion channel. these regions are designed (or evolved) so the current in the buffer region is ‘ohmic’ independent of time during the function of the nanovalve. these regions are designed to minimize the layers of charge of eq.(16) that create undesirable complex behavior not easily controlled by the valve itself. the connection of the nanosystem to the outside world is the current flowing in and out of the channel, and of the potential at the ends of the channel. the charges flowing in and out of the channel is not equal because of transient-charge storage (‘capacitive’ properties, famously voltage-dependent and non-linear), which is large and significant in semiconductor valves [21, 107, 177–179]. in biological channels, voltagedependent charge storage phenomena are present as well, where they are called ‘gating currents’ [75–76, 180]. these non-linear displacement currents flowing in channels and associated structures are small but they are controllers of biological function of great importance, and link the motions of handfuls of atoms to macroscopic function. these currents are small because they are produced by motions of a small number of charges compared to the total number of charges in the system. they can be measured because continuity of current guarantees that charge movements arising in conformation changes must also flow in the electrodes and circuits connected to them [181]. the currents flowing in and out of the nanovalves are the connections to the outside world and need to be included in the analysis of the nanovalve itself. these are the currents that are continuous. the currents are the same everywhere in a series-connected system like those described in eq.(6). the rate constants of mass action models of particle movement can be connected to the external world using a theory that accounts for current flow everywhere, along with diffusion, and perhaps migration as well. rate constants for nanovalves. analytical expressions for the rate constants for movement of charged particles in channel structures can be derived in quite a general way, starting with langevin equations for the thermal motion of ions [80, 126, 182–184]. it is necessary to use the full langevin equation (including second derivatives with respect to location) if the treatment is to allow for two boundary conditions (i.e. electrochemical potential on the inside and also the outside of the channel) and macroscopic flux. (if one uses only the smoluchowski, high-friction version of the langevin equation, with only first order spatial derivatives, the distribution of velocities of particles has mean zero and no net flux). trajectories can be doubly conditioned, allowing separate boundary conditions for the two sides of the channel, and the resulting multiple integrals can be performed analytically, somewhat surprisingly, to give the expressions simulated in ref. [166], derived in ref. [126], as shown in ref. [80]. left kf k b ⎯ →⎯⎯← ⎯⎯⎯ right (17) where jk = l ⋅ k f ⋅ck left( ) unidirectional efflux jout! "## $## − l ⋅ kb ⋅ck right( ) unidirectional influx jin! "## $## (18) the rate constants are conditional probabilities derived using the theory of stochastic processes from the properties of doubly conditioned brownian trajectories [126, 182–184]. jk = ck l( ) source concentration !"# dk l ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟ diffusion velocity ! prob {r | l} conditional probability ! "$$ #$$ unidirectional efflux % &$$$$$$$ '$$$$$$$ −ck r( ) dk l ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟ ↑ channel length prob l r{ } unidirectional influx % &$$$$ '$$$$ (19) or jk = l ⋅ k f ck left( ) unidirectional efflux jout! "## $## − l ⋅ kbck right( ) unidirectional influx jin! "## $## (20) where k f ≡ jout ck left( ) = k right left{ }= dkl2 prob right left{ } = dk l2 exp(zkfvtrans / rt ) 1 l exp(zkfφ(ζ ) / rt )dζ 0 l⌠ ⌡ ; kb ≡ jin ck right( ) = k left right{ }= dkl2 prob left right{ } = dk l2 1 1 l exp(zkfφ(ζ ) / rt )dζ 0 l⌠ ⌡ . (21) mass action and conservation of current 44(1) pp. 1–28 (2016) doi: 10.1515/hjic-2016-0001 17 r is the gas constant, f is faraday’s constant, t is the absolute temperature, and vtrans is the electrical potential across the channel not including potential drops outside the channel. the coupling to the long-range fields and flows is through the expressions for the electrical potential φ(x) because the regions outside the channel are decently ohmic [185–189]. first order dependence on concentration in the bath can be described by changes in the concentrations on the left ck(l) and the right ck(r). the changes in concentration can often be described adequately this way because they are slow and small. the potential is computed in all space (channel and surrounding baths) by a consistent theory, of one flavor or another. pnp [20, 56, 81, 113–114] deals with the motion of point charged particles; envara [190] deals with spherical particles that can diffuse, migrate or flow by convection, steric-pnp [191] is an approximate version much easier to compute, and pnp-fermi [192– 194] deals with finite size by enforcing a fermi distribution that prevents over filling and accounts for saturation of space (by spheres), and no doubt there are many other appropriate models in the vast literature (which includes semiconductor applications, ionic solutions, ion channels, and formation of concrete). these models produce potential profiles that automatically change with conditions so rate constants change and produce currents that are continuous and satisfy maxwell equations. nanovalves are obviously a small subset of the applications of the law of mass action, but it is some comfort to see how consistent analysis can be done in this case so the laws of mass action and continuity of current can both be satisfied. the general case is much harder. it is difficult to grasp all the dimensions of chemical reactions at this stage. one can reach in that direction by studying specific chemical reactions, where simple representations (involving one-dimensional reaction paths) are enough to describe important phenomena. variational methods can extend the law of mass action. if the goal is to build transferable systems, so we can build robust devices, as in electronic technology, we must use mathematics that allows interactions between charges and fields, currents and fluxes and flows of solvent, extending from atomic to macroscopic scales. variational methods are designed to deal with systems with multiple forces and flows in which interactions are unavoidable and complex. in these systems, interactions must be included in all analyses. otherwise, theories have more adjustable parameters than can be determined experimentally and still cannot deal with a range of conditions because interactions change with conditions in ways too complex for ordinary theories. theories of ionic solutions have difficulties. sadly, theories of ionic solutions seem to have these difficulties theories of ionic solutions need a large number of adjustable parameters and still cannot describe biological solutions, for example. the first step of analysis seems to be the identification of properties of single ions from measurements of solutions that always contain at least two types of ions, cation, and anion, because of electrical neutrality. the identification of properties of single ions remains ‘elusive’ even in hünenberger and reif’s [195] six hundred-page paper containing more than two thousand references. hünenberger and reif’s title itself characterizes single ion solvation as elusive even in the infinitely dilute solutions they consider. the ionic solutions needed to sustain life (and used in much of electrochemical technology) are much more concentrated and have many more and stronger interactions among solutes; interactions between solutes and water; and interactions with far-field boundary conditions. they do not resemble infinitely dilute solutions [39–45]. references [34, 39, 41–42, 50–51, 55, 62, 196–198] draw particular attention to the difficulties and remind readers that almost all biology and electrochemistry occurs in solutions more concentrated than 0.1 m, often in solutions much more concentrated. solutions tend to be most concentrated where they are most important, near electrodes (in electrochemistry) and in and near nucleic acids, binding sites of proteins, enzyme active sites [199], ion transporters and ion channels [200–204]. almost all of biology occurs in ionic mixtures and involves flow and so is described particularly poorly by existing theories and simulations [56, 65, 196–197, 205–206]. the sad limitations of our understanding of ionic mixtures, like those in which all of biology occurs, are not widely known, and so embarrassing that many do not want to know of them, as i did not for many years. it is necessary then to document the frustration by quotations from leading workers in that field. the classical text of robinson and stokes [40] is still in print and widely used. it is a book not noted for emotion that still gives a glimpse of its authors’ feelings of frustration (p. 302). “in regard to concentrated solutions, many workers adopt a counsel of despair, confining their interest to concentrations below about 0.02 m,... ” [207]. in a recent comprehensive treatment [51] of nonideal properties of solutions, the editor werner kunz says (p. 11 of [52]): “it is still a fact that over the last decades, it was easier to fly to the moon than to describe the free energy of even the simplest salt solutions beyond a concentration of 0.1 m or so.” new mathematical tools are needed to resolve a stalemate that has existing since the 1920’s. the powerful tools of variational calculus automatically deal with interactions that vary dramatically with conditions. if the mathematics does not deal with interactions, those interactions will not be computed correctly and will wreak havoc with theories that are based on algebraic descriptions of interactions or theories based on the law of mass action with constant rate constants. eisenberg hungarian journal of industry and chemistry 18 energy variational approach. the energy variational approach envara is defined by the eulerlagrange process [208] as generalized by liu, and colleagues, into an energy/dissipation functional. the generalized functional combines two variations yielding a single set of euler-lagrange equations (in eulerian coordinates of the laboratory) using push-back and pullforward changes of variables [190, 209–212]. in this way, envara can deal with dissipation (friction) and ionic solutions. envara describes conserved energy using the classical hamiltonian variational principle of least action described in textbooks of mechanics. it deals with friction using the rayleigh dissipation principle described in textbooks of irreversible thermodynamics. when combined, these principles allow energy to be degraded into entropy as matter and charge flow in frictional materials [213], like electrolyte solutions. ionic solutions experience friction because an ionic solution is a condensed phase essentially without empty space. ice floats on water, so liquid h2o has greater density than solid h2o and presumably less space between its atoms than the solid. atoms and molecules in a condensed phase cannot move without colliding. collisions randomize originally correlated motions and make them into the kind of randomized motion that we call heat [214]. the variance of the displacement is what we call temperature. the macroscopic names for the conversion of translational to randomized zero-mean (nearly) brownian motion, are dissipation and friction. energetic variational methods are particularly useful because they allow multi-scale derivation of partial differential equations (and far-field boundary conditions) from physical principles when multiple fields are involved, like convection, diffusion, steric exclusion, and migration in an electric field. energetic variational principles have recently become available for systems involving friction [209, 211, 215], that is to say, for systems involving ionic solutions [117, 190, 210, 216]. energetic variational principles combine the full power of the navier-stokes equations (a) with either a lennard-jones representation of finite-size ions or (b) with a density functional theory of ionic solutions built from rosenfeld’s density functional theory of liquids [190, 217]. computations must be done in three dimensions because spheres do not exist in one and two dimensions. these theories and their simplifications [191, 218–219] are difficult to compute in three dimensions because of the steeply singular forces used to ensure that atoms do not overlap. overlap must not be permitted because spheres cannot overfill space: space can be saturated with spheres. saturation effects are a main cause of nonideality, particularly in the extremely crowded conditions in and near enzyme active sites, ionic channels, nucleic acids, and the working electrodes of electrochemical cells where twenty molar solutions are not uncommon [199]. (as a rule of thumb, ions are crowded and electric fields are largest [220–222] where they are most important in technology and biology). if saturation is described by a fermi-like distribution as recently derived for spheres of unequal sizes [211, 223] some of these difficulties can be attacked [192–194]. a fourth order partial differential equation can be written [192] which is easily integrated in three dimensions, after it is reduced to a pair of second order partial differential equations (with carefully defined boundary conditions) and computed with appropriate numerical methods. but it is still not clear how best to apply any of these methods to chemical reactions (fig.1) described by the law of mass action with rate constants extended to be functions or functionals and not constants. we now have the tools, and we now see the goal a global treatment combining conservation of mass in chemical reactions described by the law of mass action with conservation of charge flow and current described by kirchhoff’s current law everywhere. coda: our grasp must be sure, but our reach should exceed our grasp, as we do our science. we must grasp both charge/current conservation and mass action before we can produce robust theories (or simulations) of chemical reactions in ionic solutions that successfully use one set of parameters over a range of conditions, and include the global properties of electric fields. correct calculations are needed because there is no engineering without numbers and accurate computations [171–173]. calculations from theories and simulations of electronic-, ionic-, or biologically inspired devices must be checked and calibrated against known results. otherwise devices built from those calculations will not work [56, 65, 196–197, 205–206]. if theories and simulations of electrical devices were not robust, if parameters had to be changed as conditions changed, our electronic technology would be severely limited, to say the least. chemical reactions involving current flow must be within our theoretical grasp before we can develop transferable theories. then we can build devices that perform as expected, as electronic devices usually do. only then can we expect exponential growth in molecular engineering whether biological or technological. it seems no coincidence that exponential growth in electronic technology came after scientists had a secure grasp of global electrostatics and the pnp equations of electrodiffusion in semiconductors. let us hope that energetic variational methods can grasp ions and chemical reactions in water as well and as successfully as pnp has grasped the useful properties of holes and (semi-)electrons in silicon and germanium. 5. conclusion the law of mass action is used widely, nearly universally, in chemistry to describe chemical reactions. mass action and conservation of current 44(1) pp. 1–28 (2016) doi: 10.1515/hjic-2016-0001 19 the law of mass action does not automatically conserve current, as is clear from the mathematics of a simple case, chosen to illustrate the issues involved. if current is not conserved in a theory, charges accumulate that cannot accumulate in the real world. in the real world, tiny charge accumulation much less than one percent produces forces that change predictions of the theory a great deal. indeed, in the real world tiny charge accumulation produces forces large enough to destroy biological membranes and thus living systems, forces large enough to ionize atoms, create a plasma of electrons (like sparks or lightning) and thus make experiments impossible in normal laboratory settings. the mathematics in this paper shows that the law of mass action violates conservation of current when current flows if the rate constants depend only on the potential (chemical and electrical) in one location and its immediate vicinity. the same difficulty arises when rate models of the markov type deal with the movement of charge. the implication is that such models cannot deal with current through an open channel, with the gating properties of channels if the gating mechanism is charged, or with the gating current produced by that mechanism, for example. the essential issue is that rate constants are local functions of potential (at one place or in a small region) so they cannot know about current flow far away or at boundary conditions. if current is interrupted far away, local chemical reactions obviously change, but rate constant models show no change. consider, for example, what happens in a battery when current flow is interrupted far from the battery. these problems can be fixed by computing the potential (chemical and electrical φ(x)) globally and using the neighborhood values of potential that are the result of the global calculation. rate constants in this case have simple physical interpretations and simple expressions involving only one integration, explained in eq.(19). jk = ck l( ) source concentration !"# dk l ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟ diffusion velocity ! prob r l{ } conditional probability ! "$ #$ unidirectional efflux% &$$$$$ '$$$$$ −ck r( ) dk l ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟ ↑ channel length prob l r{ } unidirectional influx% &$$$$ '$$$$ prob right left{ }= exp(z k fv trans /rt ) 1 l exp(z k fφ(x)/rt )dx 0 l⌠ ⌡ ⎮ ; prob left right{ }= 1 1 l exp(z k fφ(x)/rt )dx 0 l⌠ ⌡ ⎮ . of course, the rate model and the global potentials interact and must be solved together so they are consistent. variational methods guarantee such consistency. energetic variational methods are needed if the systems are dissipative. ions in water and channels are dissipative systems because they are condensed phases with little empty space. when ions move, they collide with atoms and dissipate energy in the form of heat. acknowledgement fred cohen, eduardo rios, and brian salzberg provided most useful criticisms and suggestions of an earlier version of this paper. many thanks! ardyth eisenberg edited the manuscript with vigor and love, for which i am most grateful, as it motivates me every day. references [1] feynman, r.p.; leighton, r.b.; sands, m.: the feynman lectures on physics, mainly electromagnetism and matter (addison-wesley publishing co., new york) 1963 vol. 2, p. 592 www.feynmanlectures.caltech.edu/ii_toc.html [2] bard, a.j.; faulkner, l.r.: electrochemical methods: fundamentals and applications (2nd ed.; john wiley & sons, new york) 2000 [3] gutman, e.m.: can the tafel equation be derived from first principles? 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mass action conserve current? what are the effects of discontinuity in current flow? size of discontinuity of current flow. the difference in current in two sequential chemical reactions is shown in eq.(22). the difference is the discontinuity of current, the violation of kirchhoff’s law of continuity of current flow. the difference can be zero only in special circumstances. the difference is not zero in general circumstances, nor robustly. ixy − iyz f = zx ⋅ kxy x⎡⎣ ⎤⎦− zy ⋅ kyx y⎡⎣ ⎤⎦− zy ⋅ kyz y⎡⎣ ⎤⎦+ zz ⋅ kzy z⎡⎣ ⎤⎦ (22) when are both conservation laws satisfied? when ixy iyz = 0 in eqs.(22–25), the law of mass action is consistent with kirchhoff’s current law and conservation of mass and conservation of charge/current are all satisfied. special cases. units of current ixy iyz here are c s-1 dm-3. special case a: if all concentrations are set equal to one, the currents (in the special case with a tilde) equal !ixy − !iyz f ⋅1 mole liter = zx ⋅ kxy − zy ⋅ kyx − zy ⋅ kyz + zz ⋅ kzy ; concentrations = 1 mole liter (23) special case a*: if we also set all charges equal to one, along with concentrations equal to one, î xy − îyz f ⋅1 mole liter = kxy − kyx − kyz + kzy ; concentrations = 1 mole liter ; zx = zy = zz =1 (24) in this special case of eq.(24), labelled a*, asymmetry (net difference) in rate constants determines the discontinuity of current, the violation of kirchhoff’s current law. special case b: alternatively, we can set all rate constants and all concentrations equal to one, ⌢ ixy − ⌢ iyz f ⋅1 mole liter 1 sec = zx − zy − zy + zz ; concentrations = 1 mole liter ; rate constants = 1 1 sec (25) in this special case of eq.(25), labelled b, asymmetry (net difference) of charges (valences) determines the discontinuity of current, the violation of kirchhoff’s current law. asymmetry of parameters violates conservation of charge/current and produces discontinuity in current from device to device, i.e. it produces accumulation of charge, with sizable effects, as shown next and are to be expected, given the strength of the electric field as discussed in the text. size of effects. to estimate the effect on electrical potential v, we need to know the size of the system. imagine a spherical capacitor of radius r. its capacitance to ground or coefficient of the self-energy, if one prefers the phrase in the chemical literature, is c = q/v = 4πεrε0r or numerically 4π×8.85×10-12 [farad/meter] εrr = 1.11×10-10 εrr [farad], where εr is the relative dielectric coefficient, about 80 in water solutions over longish times (say greater than 10-5 s). then, a 1 nm radius capacitor with dielectric coefficient 80 has a capacitance of 8.9 × 10-18 farads. small charges produce large voltages in such a tiny capacitor. even the charge on just one ion (1.6×10-19 c) would produce 18 mv, large enough (compared to the thermal potential of 25 mv) to have a noticeable (~50%) effect in theories and simulations, because exp (−18/25) = 0.49 (components of rates often vary exponentially according to exp(-v/kbt)). a unit discontinuity in current ixy iyz in eqs.(23-25) lasting for a second would produce a voltage of v = q/c = (1/f)/(8.9×10-18) = 1.14×1012 v. eisenberg hungarian journal of industry and chemistry 28 of course, 1 second is a long time for current to flow. if current flowed on a biological time-scale, for 1 ms in a structure 1 nm in radius, with dielectric coefficient 80, the electrical potential would be much less, ‘only’ 109/εr v, somewhat less than 107 v at low frequencies in water. current flow of even a microsecond, would produce nearly ten thousand volts. rate of change of potential. we can also look at the effect on the rate of change of potential. the discontinuity of current is connected to the rate of change of potential by a version of coulomb’s law: ∂v ∂t = 1 c i (26) if we apply this formula to the discontinuity of current in the special case of eq.(24) labelled a*, we can estimate how quickly that discontinuity of current would change the potential: ∂v ∂t = î xy − îyz f ⋅1(mole/liter) ⋅ f c = î xy − îyz f ⋅1(mole/liter) ⋅ f 4πεrε0r = f kxy − kyx − kyz + kzy 4πεrε0r (27) for a capacitor r = 1 nm with εr = 80 and capacitance of 8.9 ×10-18 farads (see above): ∂v ∂t =1.1×1017 ×f kxy − kyx − kyz + kzy( ) in v/s (28) in other words, the breakdown voltage (~ 0.2 v) of membranes and proteins would be reached in 1.1×10-22/(kxy kyx kyz + kzy) seconds. the breakdown voltage for matter in general (say 106 v) would be reached very quickly. we conclude that failure of the law of mass action to conserve current is likely to have noticeable effects. hungarian journal of industry and chemistry vol. 47(1) pp. 17–23 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-04 simulation of color afterimages: an approach to computing virtual color perception lőrinc garai *1 and andrás horváth2 1doctoral school of multidisciplinary engineering sciences (mmtdi), széchenyi istván university, egyetem tér 1, győr, 9026, hungary 2department of physics and chemistry, széchenyi istván university, egyetem tér 1., győr, 9026, hungary afterimages are a common and frequent perceptual phenomenon of everyday life. when looking into a high-intensity light source and suddenly turning away from it, a temporary “ghost” of the light source remains visible, for a while. the computer-graphics simulation of afterimages is based on biophysical and mathematical models as published in the literature. a subordinate of afterimages defined in our research is virtual color perception, that is in our interpretation an unusual and intense temporary color perception provoked by a rapid change in the color of the incident light. in research, the modelling of virtual color perception is a field that is by and large untouched. our publication presents a kinetic model established to characterize the intensity and duration of virtual color perception as a function of rapid changes in the color of the incident light. keywords: afterimage, rod and cone photoreceptors, photopigment, kinetics 1. introduction in our vision, an afterimage is an illusionary image that appears after having been exposed to a prior one. color afterimages are experienced in everyday life, for example, when driving at night the headlights of oncoming cars are so bright that when the driver looks away from them, the illusion of bright headlights still remains in perception [1]. when photorealistic images are rendered [1–4], some papers reported simulations of color afterimages by combining mathematical models [5–9]. a subordinate of afterimages defined in our research is virtual color perception, a phenomenon that originates from chromatic adaptation in photoreceptors influenced by environmental color interactions, and based on the sensitivity to light and adaptibility of each cone receptor. the physiological background of virtual color perception in brief is as follows: human photopic (daylight) color vision is a combined response of type l (long wavelengths), m (medium wavelengths) and s (short wavelengths) cone receptors to adequate stimuli of light. the photopigment rhodopsin plays a key role in the process; the equilibrium of its relative concentration is achieved by the opposing processes of rapid cleavage when exposed to light and slow resynthesis in darkness [10, 11]. adaptations of cone receptors to changes in the color of the incident light is time-consuming [12, 13], hence, a *correspondence: garailorinc@garailorinc.hu rapid change in the color of the incident light facilitates unusual and intense temporary color perception, the socalled virtual color perception. for example, when exposed to red light the sensitivity of l cone receptors is low and in this case is accompanied by the high sensitivity of m and s cone receptors. following a rapid change in color from red to blue in the incident light, the sensitivity of s cone receptors remains temporarily high, resulting in perception of the color bright blue that transforms into common blue after a short period of time during which the relative concentration of photopigment is equilibrated (restored), i.e. this is the duration of virtual color perception. the purpose of our work is to develop a computational kinetic model capable of simulating and quantifying virtual color perception. in our research chromaticity diagrams are used. note that changes in the xy coordinates [14] are not proportional to human color perception. to overcome this distortion, several chromaticity coordinates were defined, for example, cie u′v′ [15]. the gamut of a device is the complete subset of colors it can produce. usually, in an rgb (red, green, blue) device, it consists of a color triangle with two-dimensional chromaticity coordinates. a gamut is characteristic of the given display (screen) currently in use, for example, modern rgb led displays are characterized by wider gamuts compared to old-fashioned cold cathode fluoresmailto:garailorinc@garailorinc.hu 18 garai and horváth table 1: gamut points ccfl rgb led gamut point x y x y b 0.2091 0.2218 0.1563 0.0307 b3r1 0.2753 0.2518 0.2837 0.1056 b2r2 0.3415 0.2817 0.4111 0.2181 b1r3 0.4077 0.3115 0.5385 0.3024 r 0.4739 0.3415 0.6658 0.3305 r3g1 0.4420 0.3837 0.5687 0.4236 r2g2 0.4101 0.4239 0.4717 0.5632 r1g3 0.3783 0.4652 0.3746 0.6679 g 0.3464 0.5064 0.2775 0.7028 g3b1 0.3121 0.4353 0.2472 0.5348 g2b2 0.2778 0.3641 0.2169 0.2827 g1b3 0.2434 0.2930 0.1866 0.0937 cent lamp (ccfl) displays that were frequently used about 10 years ago. in our work, gamuts characteristic of ccfl and rgb led desktop monitors were measured first. following this, the simulation of virtual color perception obtained by gamut data as a result of a rapid change in the color of the incident light was conducted. finally, preliminary validation tests were run on the aforementioned rgb led desktop monitor in use [16]. 2. experimental 2.1 measurement of the gamuts of the displays used in our experiments and key parameters of our model the spectral power distribution of the red, green and blue primaries of two displays was measured by a spectroradiometer (a flame miniature spectrometer by ocean optics, inc. calibrated 12 strong lines of he, ne, ar and h2 flashtubes). one of the displays used was that of an old notebook using a ccfl as a backlight and the other was a more modern one (hp zr2440w) with a display using rgb leds as a backlight. based on the spectral power distributions measured, the cie 1931 (x, y) chromaticity coordinates were calculated for all three primaries of both displays, using a color matching function (cmf) of 10° at a resolution of 1 nm between the wavelengths of 360 nm and 830 nm. intermediate gamut point coordinates were calculated by interpolation. gamut point numbers in table 1 and fig. 1 were further referred to as colors of incident light. in our kinetic model, actual color perception is compiled from the generally known mathematical relations [8, 9, 17] shown below. the actual color perception j of a single (l, m or s) cone receptor can be calculated by the formula j = dep, (1) where d denotes a conversion constant between the cleavage of rhodopsin and neural impulses and here is figure 1: chromaticity diagram of gamut points: an old ccfl display of a notebook (inner gamut) and an hp zr2440w display (outer gamut) equal to 1. the variable e represents the intensity of incident light expressed in trolands (td). during the calculations a maximum luminance of the monitor of 300 cd/m2 was used and a diameter of the pupil of 5 mm assumed. therefore, the maximum retinal illuminance was equal to 5890 td. the variable p denotes the relative concentration of photopigment (between 0 and 1). the time differential of p determined from the rate of photopigment synthesis (qs), spontaneous photopigment cleavage (qc) and photoinduced cleavage (qi) is calculated by dp dt = qs −qc −qi. (2) the variables of eq. 2 are calculated by qs = 1 τ , (3) qc = p τ , (4) and qi = e e0 p τ , (5) where the time constant τ = 99 1/s and e0 = 20, 000 are used [13]. the following differential equation is composed from eqs. 2–5: dp dt = 1 τ − p τ − e e0 p τ . (6) the solution of eq. 6 yields the actual relative concentration of photopigment: p(t) = 1 b [1 − (1 − p0b)] e −tb/τ, (7) where p0 denotes the initial relative concentration of photopigment. hungarian journal of industry and chemistry biophysical model of color afterimages 19 finally, the equilibrium with regard to the relative concentration of photopigment pe and percentage of photopigment cleaved b are related as follows: pe = 1 b = e0 e + e0 . (8) 2.2 simulation formula in accordance with cie 1931 [18, 19], the actual coordinates of color perception x(t), y(t) and z(t) are calculated from the color coordinates of incident light xi, yi and zi by equations eqs. 9–24. in the equations below, variables indexed with l, m and s apply to cone receptors l, m and s, respectively. el = emultip ·m1,1-3 × [xi, yi, zi] (9) em = emultip ·m2,1-3 × [xi, yi, zi] (10) es = emultip ·m3,1-3 × [xi, yi, zi] (11) bl = bm = bs = 1 + emultip e0 (12) emultip, which is equal to 6, 000, denotes the light intensity of the display. the actual relative concentration of photopigment is calculated from the initial relative concentrations of photopigment p0l, p0m and p0s: pl(t) = 1 bl (1 − (1 − p0lb))e −tb/τ (13) pm(t) = 1 bm (1 − (1 − p0mb))e−tb/τ (14) ps(t) = 1 bs (1 − (1 − p0sb))e −tb/τ (15) for the purposes of iteration in simulations, the initial relative concentration of photopigment p0 was equal to 0.1. from the actual relative concentrations of photopigment eqs. 13–15, the color perception coordinates are as follows jl(t) = d · pl · el, (16) jm(t) = d · pm · em, (17) js(t) = d · ps · es, (18) where jl, jm and js denote the cone receptors of long, medium and short wavelengths, respectively. to obtain more accurate color perception coordinates, tristimulus values were calculated: x(t) = m−11,1-3 × [jl, jm, js], (19) y (t) = m−12,1-3 × [jl, jm, js], (20) z(t) = m−13,1-3 × [jl, jm, js], (21) figure 2: an example of fast color change leading to virtual color perception. color point yellow shows primary color perception. color points bright blue show virtual color perception as reflected by the tendency to reach equilibrium in photopigment relative concentration. where m denotes a transformation matrix between tristimulus values x , y and z, and the actual color perception j . the actual color perception coordinates x(t), y(t), z(t) are calculated by the following equations: x(t) = x(t) x(t) + y (t) + z(t) , (22) y(t) = y (t) x(t) + y (t) + z(t) , (23) z(t) = 1 − x(t) − y(t). (24) in accordance with the cieluv (1976) chromaticity diagram, the actual color perception coordinates x(t), y(t) and z(t) are transformed into coordinates u′(t) and v′(t) by an easy-to-compute method [19] : u′(t) = 4x(t) 12y(t) − 2x(t) + 3 , (25) v′(t) = 6y(t) 12y(t) − 2x(t) + 3 . (26) the intensity of the actual virtual color perception is determined by ∆c = √ (u′(t) − u′e) 2 + (v′(t) − v′e) 2 , (27) where u′e and v′e denote color coordinates at equilibrium following restoration from virtual color perception (see restoration to the equilibrium in fig. 2). a summary of variables and parameters is shown in notations at the end of this paper. 2.3 simulation to understand the calculations, a graphical approach is shown in fig. 2. gamut color point 1 stands for the primary perception of the actual incident light, which is yellow here. with a rapid change in color from yellow to 47(1) pp. 17–23 (2019) 20 garai and horváth table 2: example of iteration t(s) xi yi u′(t) v′(t) ∆c 0.0 0.4250 0.56875 – – – 10.0 0.4250 0.56875 0.1893 0.3802 – 20.0 0.4250 0.56875 0.1892 0.3802 – 30.0 0.4250 0.56875 0.1891 0.3802 – 30.1 0.1400 0.05000 0.1748 0.0836 0.02075 30.2 0.1400 0.05000 0.1748 0.0837 0.02066 30.3 0.1400 0.05000 0.1747 0.0838 0.02057 30.4 0.1400 0.05000 0.1747 0.0838 0.02048 30.5 0.1400 0.05000 0.1746 0.0839 0.02039 30.6 0.1400 0.05000 0.1745 0.0840 0.02031 30.7 0.1400 0.05000 0.1745 0.0840 0.02022 30.8 0.1400 0.05000 0.1744 0.0841 0.02013 30.9 0.1400 0.05000 0.1744 0.0842 0.02004 31.0 0.1400 0.05000 0.1743 0.0842 0.01995 31.1 0.1400 0.05000 0.1743 0.0843 0.01987 31.2 0.1400 0.05000 0.1742 0.0844 0.01978 . . . . . . . . . . . . . . . . . . 63.9 0.1400 0.05000 0.1611 0.0991 0.000126 64.0 0.1400 0.05000 0.1611 0.0991 0.000101 64.1 0.1400 0.05000 0.1611 0.0992 0.000092 64.2 0.1400 0.05000 0.1611 0.0992 0.000102 blue, a bright blue color appears in perception that transforms into common blue after a short period of time necessary for the restoration of the equilibrium in terms of the relative concentration of photopigment, which is the time period required for virtual color perception, namely for the perception of bright blue (fig. 2). our kinetic simulation model (section 2.2) is illustrated in table 2. the first five lines in the first four columns show the same values of the color coordinates of incident light xi, yi, zi, against time (0 − 30 seconds). figure 3: photopigment relative concentration values in the iteration in table 2 over this 30 second-long period, the u′(t) and v′(t) values of color perception are quasi identical. however, after 30 seconds, a rapid change in color of the incident light from red to blue results in virtual color perception, as demonstrated by line 6 and column 5. the values of ∆c in column 7 concern the intensity of virtual color perception. (∆c)max denotes the peak intensity in virtual color perception and the minimum ∆c stands for the duration of virtual color perception (tvirtcol). actual relative concentrations of photopigment of cone receptors l, m and s are shown in the diagram in fig. 3. in terms of simulating virtual color perception, rapid changes in the color of incident light were indicated on ccfl and rgb led monitors by the assignment of defined gamut points to each other (fig. 1). altogether, 24 changes in color were simulated. 2.4 validation of the simulation our kinetic model was validated by a test that consisted of 20 subjects involving an in-house piece of software run in a python environment. accordingly, a homogeneous solid colored circle is displayed on a homogeneous background of a different color for 30 seconds (fig. 4), then the circle disappears (fig. 5) and the intensity and duration of virtual color perception is determined by the key inputs of the user. further details concerning the test are found below: • first, the test subject looked at a white screen for 30 seconds. figure 4: second screen of validation test. figure 5: third screen of validation test: circle removed. hungarian journal of industry and chemistry biophysical model of color afterimages 21 table 3: comparison of virtual color perception intensity in model situations and in validation test results ranking in model ranking category ranking in validation test results id rank id median of ranking correlation r → g 1 high b → g 1.00 no g2b2 → r 2 b2r2 → g 2.00 yes g1b3 → r 3 r → g 3.00 yes b2r2 → g 4 b → r2g2 4.00 no r → g2b2 5 medium r → g2b2 4.00 yes r2g2 → b 6 low g1b3 → r 4.50 no g → b2r2 7 g2b2 → r 5.00 no b → g 8 g → b2r2 5.00 yes b → r2g2 9 r2g2 → b 7.00 yes matching percentage between model and validation test results: 56% table 4: comparison of virtual color perception time period in model situations and in validation test results ranking in model ranking category ranking in validation test results id rank id median of ranking correlation r → g2b2 1 high b → g 1.00 no r → g 2 g1b3 → r 2.00 no g → b2r2 3 b → r2g2 3.00 no b2r2 → g 4 r → g2b2 4.00 yes r2g2 → b 5 medium g2b2 → r 4.00 no g2b2 → r 6 low g → b2r2 4.50 no b → r2g2 7 b2r2 → g 5.00 no g1b3 → r 8 r → g 5.00 no b → g 9 r2g2 → b 7.00 no matching percentage between model and validation test results: 11% • second, the eyes of the subject were fixed on a circle at the center of the subsequent colored image (fig. 4) for 30 seconds. according to our definition, the color of the central circle represents the first gamut point, while the color of the background represents the second gamut point. altogether, 9 assignments of gamut points have been validated so far. • third, the central circle suddenly disappeared (fig. 5) and the subject responded according to the intensity and duration of virtual color perception experienced. • the intensity of virtual color perception was rated on a four-grade scale, where zero stands for the absence of virtual color perception and 4 denotes its highest intensity. the duration of virtual color perception was indicated by the subject pressing a key as the perception faded away. first, the assignments of gamut points for each test subject were ranked according to the intensity (table 3) and duration (table 4) of virtual color perception induced. then, the median of the rank order with regard to the intensity and duration of virtual color perception was calculated. table 5: intensity and time period of virtual color perception related to gamut points assignments (∆c)max tvirtcol(s) color point 1 color point 2 ccfl rgb led ccfl rgb led b r3g1 0.00792 0.01212 30.9 24.5 b r2g2 0.00553 0.00513 36.3 27.5 b r1g3 0.00339 0.00197 41.9 16.0 r3g1 b 0.00794 0.01210 33.5 29.5 r2g2 b 0.00852 0.01367 34.9 32.2 r1g3 b 0.00953 0.01523 37.2 34.6 g3b1 r 0.00931 0.02381 27.1 29.3 g2b2 r 0.00958 0.02187 27.5 27.6 g1b3 r 0.00994 0.01989 28.1 25.8 r g3b1 0.00920 0.02298 46.9 44.2 r g2b2 0.00821 0.01686 51.2 52.8 r g1b3 0.00735 0.01260 50.2 38.2 g b3r1 0.00807 0.01789 48.2 41.1 g b2r2 0.00648 0.01362 45.8 42.2 g b1r3 0.00693 0.01722 30.5 31.0 b3r1 g 0.00324 0.01337 25.0 27.8 b2r2 g 0.00524 0.01799 33.7 33.7 b1r3 g 0.00749 0.02256 41.4 38.7 b r 0.01036 0.01786 28.8 23.8 r b 0.00788 0.01053 33.3 26.6 r g 0.00980 0.02707 48.2 43.1 g r 0.00915 0.02571 26.7 30.8 g b 0.01084 0.01677 40.1 37.0 b g 0.00234 0.00868 17.8 20.5 since the number of test subjects was limited, the results could not be divided according to their age and gender. further tests are needed to ensue virtual color perception with regard to gender and age. 3. results and discussion in table 5, the maximum (∆c)max for the ccfl and rgb led displays were identified during the rapid change in the color of incident light from gamut point g to b (from green to blue) and r to g (from red to green), respectively. when compared to the ccfl display, the rgb led display appears to yield higher (∆c)max values with the exception of rapid changes in the color of the incident light from gamut point b to r2g2 (from blue to orange). with regard to our results, the duration of virtual color perception seems to be platform-free, i.e. tvirtcol displayed on both the ccfl and rgb led monitors was identical. however, rapid changes in the color of the incident light from gamut point b to r1g3 (from blue to yellowish green) was an exception with regard to the values of tvirtcol. as is shown in table 5, tvirtcol computed on the ccfl display has doubled in value compared to that computed on the rgb led display. the kinetic simulation results so far point to the likelihood of the appearance of virtual color perception on all 47(1) pp. 17–23 (2019) 22 garai and horváth display platforms. as for our preliminary tests performed on 20 test subjects so far as well as the parameters (∆c)max and tvirtcol, a correlation between model situations (simulations) and the results of a validation test cannot be confirmed at present. further tests, statistical evaluations and the introduction of additional parameters are also necessary to achieve more accurate conclusions. 4. conclusion photopic human color vision is a combined response to the stimulation from light of red, green and blue cone receptors. cone receptors adapt individually to the actual color of the incident light. since the adaptation of cone receptors is time-consuming, virtual color perception can be achieved in the meantime by rapid changes in the color of the incident light. our kinetic model developed for individual cone receptors is based on mathematical correlations that simulate the intensity and duration of virtual color perception which result from rapid changes in color. according to our model, virtual color perception can result from both ccfl and rgb displays. our preliminary validations are yet to confirm a correlation between model situations (simulations) and the results of a validation test. some refinements to the simulation by the introduction of additional parameters as well as further validation tests with regard to the gender and age of participants are indispensable to reach more accurate conclusions. acknowledgement this research would not have been possible without the participation of volunteers from széchenyi istván university as test subjects. notations symbol meaning unit j in actual color perception: jl = red cone receptors specific for long wavelength jm = green cone receptors specific for medium wavelength js = blue cone receptors specific for short wavelength dimensionless p relative photopigment concentration dimensionless (range:0 . . . 1) d conversion constant between rhodopsin cleavage and neural impulses dimensionless (value: 1) e incident light intensity troland qs synthesis of photopigment dimensionless qc spontaneous cleavage of photopigment dimensionless qi light induced cleavage of photopigment dimensionless τ time constant in rhodopsin synthesis seconds symbol meaning unit p0 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doi: 10.1002/9780470175637 47(1) pp. 17–23 (2019) https://doi.org/10.18136/pe.2016.642 http://konyvtar.uni-pannon.hu/doktori/2016/csuti_peter_dissertation.pdf http://konyvtar.uni-pannon.hu/doktori/2016/csuti_peter_dissertation.pdf https://doi.org/10.1088/1475-4878/33/3/301 https://doi.org/10.1088/1475-4878/33/3/301 https://doi.org/10.1002/9780470175637 https://doi.org/10.1002/9780470175637 introduction experimental measurement of the gamuts of the displays used in our experiments and key parameters of our model simulation formula simulation validation of the simulation results and discussion conclusion microsoft word 00.00 inner cover.docx hungarian journal of industry and chemistry vol. 43(1) pp. 1–5 (2015) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2015-0001 heavy metal balance in a communal wastewater treatment plant gábor gulyás,* viktória pitás, bence fazekas, and árpád kárpáti department of environmental engineering, university of pannonia, egyetem u. 10, 8200 veszprém, hungary heavy metal removal from a municipal wastewater treatment plant was evaluated in the given study. the aim of the work was to find water or sludge streams in the technology that could be treated separately for heavy metal removal to maximise the efficiency of the entire treatment. the results proved that in the plant studied 70–80% of the metal content was discharged. only 5–20% was retained in the digested sludge. a small percentage of the metal content of the influent could only be measured in the primary and secondary sludges. otherwise, there were very similar metal concentrations in these sludge streams. the reject water exhibited an inconsiderable level of metal recycling in the technology, no more than 2–3% of the influent load. some 2–10% of the heavy metal content of the inlet was removed from the sand trap. we did not find the separate heavy metal removal from the sludge streams efficient as most of the heavy metal load finally was discharged from the treatment plant with the treated effluent into the recipient. keywords: activated sludge, heavy metals, mass balance, municipal wastewater 1. introduction industrial discharges into municipal wastewaters from metal refining and other industrial sources are hazardous with regard to purification process due to their heavy metal contents. that is why nowadays heavy metal removal from these discharges at the site of the waste production is strictly regulated. the next possibility for removing heavy metals from wastewater is the activated sludge process of the publicly owned treatment works (potws) [1]. the mechanism of heavy metal removal in the activated sludge process is not completely understood yet [2]. even the inhibition effects of some metals for specific microorganisms are not properly known. that is why our study tried to summarise the heavy metal removal of an activated sludge plant on the basis of its detailed mass balance. we excluded from this study the influence of any technological parameters like oxygen supply, ph, sludge age, complexing agents, etc. or the microbial composition of the working biomass [2–3]. an overview of the possibility of the removal of metals from sludges of sewage treatment plants has already been presented [2, 4]. rather different removal efficiencies were published from many measurements all over the world. these studies concluded that around 70% of the mn and cu load can be accumulated in the activated sludge, while 50–60% of the cr, cd, pb, fe, ni, and zn will leave the plant as it is discharged into the recipient with the treated *correspondence: gulyasg@almos.uni-pannon.hu effluent. it is well known, that some special forms of these heavy metals in the sludge or activated sludge process are more critical than their total concentrations [5]. in our study, we measured the heavy metal concentrations in the different liquid and sludge streams of a hungarian wastewater treatment unit in veszprém treating municipal effluent relatively free of industrial metal discharges. we calculated a total mass balance for the plant and evaluated the feasibility of the separate removal of some metal contaminants from the sludge residue to produce more valuable agricultural soil amendment. 2. materials and method the studied activated sludge process treats daily 13,000 m3 of sewage, while its nominal daily capacity of 21,000 m3 shows considerable underutilisation. it has a proper digestion capacity for the primary and secondary sludge of the main stream. we considered that it is important to measure the heavy metal concentrations at the inflow and in purified effluent in some mixed liquid streams and the final dried sludge as well. from the material balance established from these data, it seemed possible to decide about the reality of the use of some separate heavy metal removal steps in the treatment line. to establish a heavy metal mass balance, we took samples several times from the liquid, mixed sludge and dried sludge as well. the sampling points in the technology can be seen in fig.1. gulyás, pitás, fazekas, and kárpáti hungarian journal of industry and chemistry 2 samples 1 to 4 were collected during the day every other hour. samples 5–8 were collected when sludge pumping or drying was in operation. these were homogenised, cooled, and stored as prescribed by hungarian standard msz 318-2:1985 protocol. the dissolution of the metal content was followed by the atomic absorption spectrophotometric measurement for eight (cd, co, mn, ni, cr, cu, fe, and pb) metal contaminants. from these data, the metal content of the sludge phases was determined for the suspended (ss) and total solid (ts) contents for samples 5–8. it was assumed that the dissolved heavy metal content of the liquid phase equals to that of the treated effluent in samples 6 and 7 and with that of the reject water in sample 8. for measuring ss and ts contents of the sludge containing samples (no. 6–8), we used the hungarian standard msz 260/3-73 standardised method. the average daily amount of the reject water had to be calculated for the calculation of the material balance from these measured values, as the flow was not measured in the plant. dissolution of the metals from the different samples was carried out by a mars 6 microwave digester. the temperature program of the digester was optimised in a preliminary study [6]. for the addition of chemicals for digestion, we followed the recommendation of hungarian standard msz 1484-3 protocol (chapter 4.2.2.3). before digestion, 3 ml of 68% hno3 and 9 cm3 of concentrated hcl was given to every 0.5 cm3 sample. the microwave digestion of the sludge samples was carried out according to the same heating program for all samples. after 20 min of heating, digestion was completed in 10 min at 180 ºc. after digestion and dilution, the heavy metal concentrations were measured by a thermo scientific ice 3000 atomic adsorption spectrophotometer. 3. results and discussion during the control study, the samples were taken over three one week-long periods. we measured the weekly homogenised samples stored in a refrigerator a week later than sampling in triplicates. the average metal contents for the entire measurement period are shown in table 1. as shown in table 1, there was no pb detected in the influents of the wastewater treatment plant. the cd concentration was low (0.03 mg dm-3). mn and ni levels were a bit higher within the range of 0.08–0.15 mg dm-3. co exhibited a slightly higher concentration (0.1–0.3 mg dm-3) than mn and ni. the cu content was constant at around 0.2 mg dm-3. these values are as expected from our earlier measurements at this plant. the fe had the highest concentration in the inflow (up to 356 mg dm-3) and it remained similarly high relative to the other metal contaminants in the outflow from the plant. to calculate the heavy metal mass balance in the process, the flow rates and sludge production had to be taken into account. as the hydraulic retention time (hrt) in the plant was more than one day and the sludge age was nearly 20 days, we used average figure 1. the technology and sampling points for checking heavy metal concentrations. heavy metal balance in a communal wastewater treatment plant 43(1) pp. 1–5 (2015) doi: 10.1515/hjic-2015-0001 3 numbers for the calculation of the balance. the same was used for the primary and secondary sludge streams, as their removal was not continuous, but the material we examined had been properly homogenised. the average daily values for the streams are summarised in table 2. some parameters required for the calculation were not measured at the plant. the average daily quantity of the reject water was calculated from the ss concentration of the digested sludge stream entering the drying centrifuge and that of the dried digested sludge. the quantity of the dried digested sludge was calculated from the volume of the sludge transported from the centrifuges to the solar drying part of the plant and its average dry solid content determined. this resulted in negligible errors (less than 0.1 g/g) since the dissolved material content of the sludge water or reject water was low enough. flows were calculated (table 3) using the concentrations and daily flows of heavy metals in these sewage and mixed liquids (tables 1 and 2). in the sewage entering the plant, the concentration of the different heavy metals did not change considerably. as a result, their mass stream had to change according to the volumetric load of the plant. this was not true for the sludge streams, as the plant had a great equalisation for the total sludge mass. from tables 1 and 3, it can be seen that the concentrations of the measured heavy metals did not change or decrease significantly in the sewage streams or even in the treated effluent. at the same time, the sludge containing streams containing around 1 and 3–4% dry material showed much higher heavy metal levels. heavy metals removed from the influent (dissolved and solid) were expected to concentrate in the sludge phase of these streams and in the dried sludge as well. this means that the removal of heavy metals in this treatment facility was very poor. we hypothesise that the low specific organic material load (estimated daily value of 0.2 g koi per g mlss) and the high sludge age (more than 20 days) may result in the dissolution of the heavy metals into the liquid phase. from data in table 1, the leftover heavy metal content of the different streams can be calculated. the results are shown in table 4. according to the results, cd was not removed from the sewage by the activated table 1. the total heavy metal concentrations (mg dm-3) of the liquid and sludge-containing streams of the activated sludge process (variation in concentrations is in the order of ±31%). samples cd co mn ni cr cu fe pb raw wastewater 0.023 0.169 0.123 0.123 0.185 0.231 7.938 <0.001 after grit removal 0.023 0.166 0.105 0.120 0.174 0.223 7.819 <0.001 primary clarified wastewater 0.022 0.161 0.094 0.109 0.168 0.214 7.168 <0.001 treated effluent 0.021 0.152 0.062 0.107 0.161 0.202 0.079 <0.001 reject water 0.005 0.128 0.093 0.048 0.160 0.095 10.147 <0.001 thickened primary sludge 0.021 0.462 1.973 0.414 0.565 0.750 58.509 <0.001 thickened secondary sludge 0.019 0.673 2.709 0.633 0.696 1.030 355.813 <0.001 table 2. the main technological parameters (volumes are in m3, solid content in mass percent) used to calculate heavy metal mass-balances (variation in flow rates is in the order of ±22%). volume of wastewater thickened sludge streams sludge drying influent effluent volume dry solid content i. stream ii. stream total common primary secondary before after 7250 6500 13750 13190 112 134 243 2.4 23 table 3. daily heavy metal mass (in grams per day) in the streams shown in figure 1. samples cd co mn ni cr cu fe raw wastewater 150.0 1,100.0 800 800.0 1,200.0 1,500.0 51,600 after grip removal 149.0 1,080.0 682 778.0 1,132.0 1,448.0 50,826 primary clarified wastewater 144.0 1,048.0 614 706.0 1,093.0 1,388.0 46,595 treated effluent 139.0 991.0 400 697.0 1,049.0 1,310.0 516 reject water 1.6 38.5 28 14.4 48.0 28.5 3,044 thickened primary sludge 2.4 51.7 221 46.4 63.3 84.0 6,553 thickened secondary sludge 1.5 42.9 170 52.8 78.0 82.5 44,170 digested dried sludge 2.5 90.2 363 84.8 93.3 138.0 47,679 table 4. relative quantity of the heavy metals in streams measured as mass percentage of the influent concentrations in raw wastewater (100%). samples cd co mn ni cr cu fe after grit removal 99.0 98.1 85.2 97.2 94.3 96.5 98.5 primary clarified wastewater 96.2 95.2 76.7 88.3 91.1 92.5 90.3 treated effluent 92.5 90.1 50.0 87.1 87.4 87.3 1.0 reject water 1.3 3.5 3.5 1.8 4.0 1.9 5.9 thickened primary sludge 1.6 4.7 37.6 5.8 5.3 5.6 12.7 thickened secondary sludge 1.0 3.9 31.3 6.6 6.5 5.5 85.6 gulyás, pitás, fazekas, and kárpáti hungarian journal of industry and chemistry 4 sludge process. it was absent in the reject water of the plant and only 1.0+1.6% of the cd load was adsorbed in the final sludge produced. the load of co, mn, ni and cu was one order of magnitude bigger within a narrow daily load range (800–1,600 g per day). a significant portion of all these metals left the plant with the treated effluent. no more than 4–5% of the co remained in the dried sludge according to our measurements and only 1–3% of the total load was recycled to the inlet point with the reject water. approximately less than half of the mn remained in the purified water and the rest was concentrated in the dried sludge. around 1.5% of the mn content of this sludge was recycled at the inlet with the centrifuge water. the metal adsorption of the primary and secondary sludge seemed to be similar, which also suggested that about three quarters of the inlet mn load remained in the sewage stream after primary purification. in the case of ni, only 15–20% remained in the solid residue and one tenth of that was recycled at the inlet with the reject water. the ni seemed to be adsorbed and present in the two types of sludge in a similar ratio. cr seemed to be bound to the primary sludge while only a small portion was removed by the biological step. these two stages of the sludge processes could not remove more than 5% of the initial level. however, this removal efficiency seems to be enough, since the inlet concentration is low enough (< 0.5 mg dm-3) the removal efficiency of the treatment for cu seemed better than for other metals, but it was no more than 15–20%. most of the removed cu was captured in the secondary sludge. it has been observed before that some municipal sewage sludge contains high concentrations of cu due to the high cu content of the raw sewage. according to the given study, fe exhibits the highest concentration in the sewage, around 500 times greater than the other metals studied here. the fe is oxidised in the activated sludge process and is present in the biomass as hydroxide. the removal efficiency was 99% according to the measurements. table 3 indicates that sand removal has practically no influence on the metal content of the sewage. in the primary purifier, metal removal is poor except for the cases of mn and fe. removal of metals within the secondary sludge was a bit more efficient than within the primary one. only mn was better adsorbed onto the biomass (around 50%). however, fe was almost totally removed within the sludge phase (99% removal). concentrations of the other metals studied decreased by only a modest 5–15%. depending on the sludge removal from the digesters to centrifuges the average daily reject water quantity is around 200 m3. with this flow only 2–3% of the heavy metal load is recycled into the sewage stream entering the plant. this is such a small percentage that separate metal removal from that stream is not needed. however, the biggest problem of this sewage treatment facility is the poor removal of the heavy metals within the sludge. a similar average removal of heavy metal pollutants from the sewage can be seen from the inflow and treated effluent concentrations in table 1 and the removal percentages of the metals in different processing steps in table 4. from other investigations, we learnt that around half or a slightly greater proportion of these metals can be removed within the sludge residue. in our studies, we could not measure such high levels of removal neither in the primary nor secondary sludges. moreover, only a small ratio of the metal content of the raw sludge can be dissolved during anaerobic digestion. according to our measurements, most of the heavy metals left the plant within the effluent. changes to the total heavy metal content of the different streams in the plant tested are graphically illustrated in fig.2 for most of the metals studied here. fe is an exception, as it is efficiently removed within the different sludge fractions. it cannot be dissolved even in the digester, its hydroxides and sulphides of limited solubility are strongly adsorbed by the bioproduct of the treatment. fig.2 clearly indicates that heavy metals are recycled within the reject water in a small ratio. the dried digested sludge also removed a very small ratio of the sewage load. 4. conclusions according to our measurements in an activated sludge at a publicly owned municipal sewage treatment plant, figure 2. removal of the heavy metals in the activated sludge of a publicly owned treatment works (percentages indicate the average daily quantities relative to the inflow values for the studied metal except fe). heavy metal balance in a communal wastewater treatment plant 43(1) pp. 1–5 (2015) doi: 10.1515/hjic-2015-0001 5 the removal of heavy metals can be moderate, which is far from the removal efficiencies published by previously. a large proportion of the heavy metal content of the inflow sewage remains in the aqueous phase and leaves within the treated effluent. only a minor ratio of approximately 5-15% is adsorbed in the sludge or taken up by the biomass produced in the treatment. the primary and secondary sludges exhibited similar heavy metal removal efficiencies except for iron, which is mainly removed by the secondary sludge. the heavy metal content of the mixed primary and secondary sludges decreased by a small extent (5-15%) during digestion. the reject water containing the dissolved metals exhibited such low metal concentrations that treatment of it separately does not seem to be economical. it contains only 2–3% of the total heavy metal load of the plant. at the same time 80–90% of that leaves the plant within the treated effluent. consequently, we could not find high heavy metal concentrations in the dried digested sludge of this plant. the sludge reprocessing and reuse pose no problems in the plant with respect to heavy metal content. the low influent concentrations of the heavy metals at the same time can be correlated with the merely pure municipal effluent from the small town and its surrounding villages. acknowledgement this research was financed by the baross gábor project of 2009-2010 “infrastructure of research development kd_infra_09-szviszap (qualification of the sewage sludge of the hungarian publicly owned treatment works for possible decrease of their heavy metal content)”, hungarian national research and technology office (national innovation office). references [1] lester, j.n.: significance and behaviour of heavy metals in wastewater treatment processes. i. sewage treatment and effluent discharge, sci. total environ., 1983 30, 1–4 10.1016/0048-9697(84)90340-1 [2] karvelas, a.; katsoyiannis, a.; samara, c.: occurrence and fate of heavy metals in the wastewater treatment process, chemosphere, 2003 53, 1201–1210 10.1016/s0045-6535(03)00591-5 [3] özbelge, t.a.; özbelge, h.ö.; tursun, m.: effects of hydraulic residence time on metal uptake by activated sludge, chem. engng. proc., 2005 44, 23–32 10.1016/j.cep.2004.04.004 [4] stephenson, t.; jester, j.n.: heavy metal behaviour during the activated sludge process i. extent of soluble and insoluble metal removal, sci. total environ., 1987 63, 199–214 10.1016/00489697(87)90046-5 [5] álvarez, e.a.; mochón, m.c.; sánchez, j.c.j.; rodríguez, m.t.: heavy metal extractable forms in sludge from wastewater treatment plants, chemosphere, 2002 47, 765–775 10.1016/s00456535(02)00021-8 [6] gulyás, g.; pitás, v.; kárpáti, á.: measuring the heavy metal concentrations of digested dewatered sewage sludge with the help of microwave digestion, maszesz newsletter, 2013 (3–4), 3–11 (in hungarian) untitled hungarian journal of industry and chemistry vol. 45(1) pp. 73-84 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0011 simulating ion transport with the np+lemc method. applications to ion channels and nanopores. dávid fertig ∗1, eszter mádai1, mónika valiskó1, and dezső boda1,2 1department of physical chemistry, university of pannonia, egyetem u. 10., veszprém, h-8200, hungary 2institute of advanced studies kőszeg (iask), chernel u. 14., kőszeg, h-9730, hungary we describe a hybrid simulation technique that uses the nernst-planck (np) transport equation to compute steady-state ionic flux in a non-equilibrium system and uses the local equilibrium monte carlo (lemc) simulation technique to establish the statistical mechanical relation between the two crucial functions present in the np equation: the concentration and the electrochemical potential profiles (boda, d., gillespie, d., j. chem. theor. comput., 2012 8(3), 824–829). the lemc method is an adaptation of the grand canonical monte carlo method to a non-equilibrium situation. we apply the resulting np+lemc method to ionic systems, where two reservoirs of electrolytes are separated by a membrane that allows the diffusion of ions through a nanopore. the nanopore can be natural (as the calcium selective ryanodine receptor ion channel) or synthetic (as a rectifying bipolar nanopore). we show results for these two systems and demonstrate the effectiveness of the np+lemc technique. keywords: ion transport, nernst-planck, monte carlo simulation, nanopore, ion channel 1. introduction we dedicate this paper to honoring professor jános liszi, who was the supervisor of one of the authors (db) and respected senior to another (mv), supporting to the careers of both. we (db and vm) publish this paper together with our students (df and em) to demonstrate that the lesson of professor liszi — one of the most important goals of senior scientists is to pave the way to the junior ones — has not been left unconsidered. the goal of this work is to present a computer simulation technique for computing steady-state ion transport that was developed and applied in our research group with the essential help of dirk gillespie [1]. the method is based on the nernst-planck (np) transport equation coupled to the local equilibrium monte carlo (lemc) simulation technique and is described in sec.(2) in detail. the method, called np+lemc, was applied for various problems in the last couple of years. these problems include particle transport through model membranes [1, 2], ion channels [3–5], and nanopores [6–8]. the basic goal is to have a computationally efficient simulation technique using reduced models of steady-state systems, where particles (ions being the focus) diffuse as a result of a maintained driving force that is a concentration gradient and/or an electrical potential gradient (that is, an electrochemical potential gradient). we tend to regard these kind of systems as nanode∗correspondence: fertig.david92@gmail.com vices that yield a macroscopic output signal (electrical current, for example) as a response to an input signal (voltage, for example). reduced models have the advantage of including those degrees of freedom of the manyparticle system that are essential in reproducing device behavior, namely, the relationship of the output and input signals [6]. we present two case studies here to demonstrate both the effectiveness (and also possible source of errors) of the method and the power of reduced models. in the ryanodine receptor (ryr) calcium release ion channel, we needed to model only those amino acids of the channel protein that are inside or near the selectivity filter and hang into the ionic pathway. in the bipolar nanopore, we needed to reproduce the variation of the electric field along the pore axis properly. the most important reduction in the degrees of freedom, however, is that we model water as a dielectric continuum. the effect of using implicit solvent instead of an explicit solvent model was discussed in our previous work [6] through comparisons to molecular dynamics (md) simulations. our computational method is not the only one that is able to determine ionic current through biological and synthetic nanopores using reduced models. while the brownian dynamics (bd) simulation method [9–14] is the obvious candidate to simulate this problem, it has disadvantages from the point of view of sampling the flux of ions. the poisson-nernst-planck (pnp) theory [11, 15–18] also uses the np equation to compute flux, but uses a mean-field approach, the poisson-boltzmann 74 fertig, mádai, valiskó, and boda (pb) theory, to describe the statistical mechanical relationship between the concentration and electrochemical potential profiles. to use something more state-of-the-art to provide this relationship beyond the pb level is the essence of our approach. we suggest the lemc technique, which is a particle simulation method based on a three-dimensional model producing all the ionic correlations missing from pb. gillespie et al. proposed a different technique, in which a density functional theory (dft) was coupled to the np equation [19, 20] and used to method (np+dft) to describe the behavior of the same ion channel that we study here, the ryr ion channel [21–23]. dft is a continuum theory, but a very sophisticated one, where ionic correlations are included through a series expansion of the free energy functional and the finite size of ions is taken into account through the fundamental measure theory [24]. its accuracy was demonstrated by computing electrical double layers in extreme conditions and comparing to monte carlo (mc) simulations [25, 26]. the disadvantage of this method is that it can be used efficiently only in one dimension. this reduction in dimensionality, however, is often feasible provided that we reduce the model in an intelligent way. 2. modeling and methodology a good model should be able to explain complex phenomena in a simplified way while it stays in agreement with experimental data. the nanopore systems (both natural and synthetic) studied in this work have some common features. the primitive model of electrolytes, that represents ions as charged hard spheres, is used. the interaction potential between two ions is defined by coulomb’s law in a dielectric material: uij(r) =    ∞ if r < ri +rj 1 4πε0ε qiqj r if r ≥ ri +rj (1) where ri and rj are the radii, qi and qj are the charges of the different ionic species, ε0 is the permittivity of vacuum, ε = 78.5 is the relative permittivity of the solvent, and r is the distance between two ions. solvent (water, in this work) is not modeled explicitly; it is rather represented by two response functions. energetically, solvent acts as a dielectric background that screens the electric field of ions by just dividing by ε in the coulombpotential (eq.(1)). dynamically, solvent molecules collide with ions and impede their diffusion; we take that effect into account by a diffusion coefficient function, di(r). the ions of the electrolyte diffuse through a pore between two bulk containers (see fig.1). the pore penetrates a membrane that separates the two containers. the pore and the membrane are also modeled in a reduced way; they are confined by hard walls with which the hard sphere ion cannot overlap. other details of the figure 1: simulation cell used in the application of the np+lemc method. the model is rotationally symmetric: the three-dimensional model is obtained by rotating the figure about the z-axis. the domain confined by the blue line is the non-equilibrium transport region (the solution domain of the np+lemc system) that includes the pore and the two access regions. the electrochemical potential in this region is not constant, but changes from one constant value to another (the values in the two bulk regions) in a monotonic manner to provide the driving force of ionic transport. parameters r and h characterize system size. pores (amino acid side chains and surface charges) will be presented in sec.(3) for the respective ion channel and nanopore systems. ion transport is steady-state; concentrations and electrical potentials, therefore, are kept fixed at the boundaries of the two baths on the two sides of the membrane (blue line in fig.1). we assume that ion transport is described by driftdiffusion. our procedure is a hybrid method that separates the configuration degrees of freedom of ions (ion positions) from the kinetic degrees of freedom (ion velocities). in bd simulations they are treated together and ionic current is measured by counting ions that pass through the pore. the bd method has the disadvantage of weak sampling of flux especially at low concentrations (as in our ion channel example) and in cases, when current is limited by ionic depletion zones (as in our bipolar nanopore example). separation of the two parts of the phase space is a usual practice in equilibrium statistical mechanics, where the kinetic part is described by the ideal gas equations, while the excess quantities that produce all the peculiarities beyond ideal-gas behavior are from the potential energy, that, in turn, depends only on the configuration coordinates [27–30]. out of equilibrium, however, this separation is not so obvious. classical mechanics is still valid, so particles’ motion can be described by newton’s equations of motion (md simulations can be used). in the conhungarian journal of industry and chemistry simulating ion transport with np+lemc 75 tinuum solvent framework, langevin’s equation is used in bd simulations. the meaning of various thermodynamic quantities, however, loses the solid ground that it has in equilibrium. there is no well-established non-equilibrium statistical mechanics finding its way into textbooks despite the fact that many authors made considerable advances in this field [31–36]. the most problematic quantities are those containing entropic effects, such as the chemical potential, µi. in the case of charged particles, we use the term electrochemical potential, but we talk about the same thing. this is a crucial quantity, because its homogeneity defines thermodynamic equilibrium (let us assume that the other two intensive parameters, temperature and pressure, are constant). if µi is not constant, species i will diffuse until it becomes constant according to the second law of thermodynamics. the gradient of µi(r), therefore, is the driving force of particle diffusion. the empirical transport equation that is most widely used to describe transport of charged particles (electrodiffusion) is the np equation, ji(r) = − 1 kt di(r)ci(r)∇µi(r), (2) where di(r) is the diffusion coefficient profile of ionic species i, ci(r) is the concentration profile, µi(r) is the electrochemical potential profile, ji(r) is the particle flux density, k is boltzmann’s constant and t = 298.15k is the temperature. the resulting ji(r) must satisfy the continuity equation: ∇ · ji(r) = 0. (3) the np equation separates the configuration and kinetic parts of the phase space in a way that it provides flux as a function of three profiles that, in turn, depend only on configuration coordinates. thus, we reduced our statistical mechanical task to averaging over states in the configuration space just as we did in the case of equilibrium statistical mechanics. if we treat di(r) as a parameter, the task is reduced to finding the proper relation between ci(r) and µi(r). defining local concentration in a nonequilibrium situation is the same as in equilibrium: we compute the average number of particles in a small volume element and divide it with the volume of that element (though we will also compute concentration in a different way on the basis of the potential distribution theorem [37], see later). eletrochemical potential, on the other hand, is more problematic. the trick in this case is that we assume local equilibrium (le). if we divide the simulation cell into subvolumes bα, we can characterize this subvolume with the electrochemical potential, µα i , and assume that this value is constant in bα. we designate the µα i and cαi values to the mass centers of the bα volume elements. the assumption of le is also present in other methods (though not necessarily stated explicitly), where the ci(r) vs. µi(r) relationship is considered, such as in the pnp theory or in the np+dft method of gillespie et al. [19, 20]. the main proposal of our technique was to use an mc method for this purpose. we assumed that the subvolumes are open systems and they are in le with a constant volume (v α), temperature (t ), and electrochemical potential (µα i ). thus, we suggested to use grand canonical monte carlo (gcmc) simulations, where particle insertion/deletions are attempted in the simulation cell. the acceptance probability depends on which subvolume we try to insert to (or where is the particle that we try to delete): min(1; pαi,χ(r)), where pαi,χ(r) = nα i !(v α)χ (nα i + χ)! exp ( − ∆u(r)− χµα i kt ) . (4) here, nα i is the number of ions of type i in subvolume bα before insertion/deletion, ∆u(r) is the change of the system’s potential energy during particle insertion to position r (or deletion from there), χ = 1 for insertion, and χ = −1 for deletion. the difference between this method and equilibrium gcmc is that µi is space-dependent and the acceptance criterion is referred to a given subvolume instead of the whole simulation cell. the effect of the surrounding of subvolume bα, however, is taken into account in the simulation through the energy change that includes all the interactions from other subvolumes, not only interactions between ions in bα. although it is tempting to view the subvolume bα as a distinct thermodynamic system with its own ensemble of states and to include the effect of other subvolumes as an external constraint, this is not the case. the ensemble of states belongs to the whole system, because ion configurations in subvolume bα should be collected for every possible ion configurations of all the other subvolumes. therefore, the independent variables of this ensemble are t and {v α, µα i }, where α and i run over the volume elements and particle species, respectively. for comparison, the variables in global equilibrium are t , v , and µi, where v is the total volume and µi does not depend on space. we solve the np+lemc system in an iterative way. the electrochemical potential is adjusted until conservation of mass (∇ · ji(r) = 0) is satisfied. the procedure can be summarized as µα i [n] lemc −−−−→ cαi [n] np −−→ jαi [n] ∇·j=0 −−−−→ µα i [n+ 1]. (5) the electrochemical potentials for the next iteration, µα i [n+ 1], are computed from the results of the previous iteration, cαi [n], on the basis of the divergence-theorem (also known as gauss-ostrogradsky’s theorem). the continuity equation is converted to a surface integral: 0 = ∫ bα ∇ · ji(r) dv = ∮ sα ji(r) · n(r) da, (6) where volume bα is bounded by surface sα and n(r) denotes the normal vector pointing outward at position 45(1) pp. 73-84 (2017) 76 fertig, mádai, valiskó, and boda r of the surface. every sα surface is divided into sαβ elements. along these elements, bα and bβ are adjacent cells. it is assumed that the concentration, the gradient of the electrochemical potential, the flux density and the diffusion coefficient are constant on a surface sαβ . they are denoted by hat: ĉαβi , ∇µ̂αβ i , ĵαβi , and d̂αβ i . the ĉαβi values are obtained from the values cαi and cβi via linear interpolation. the ∇µ̂αβ i values are also obtained from µα i and µβ i assuming linearity. thus the integral in eq.(6) for a given surface sα is replaced by a sum over the surface elements that constitute sα: 0 = ∑ β,sαβ∈sα ĵ αβ i · nαβaαβ , (7) where aαβ is the area of surface element sαβ and nαβ is the outward normal vector in the center of sαβ . the iteration procedure is described by the following steps: 1. an appropriately chosen initial set of electrochemical potentials is chosen (µα i [1]; in general: µα i [n], where [n] denotes the nth iteration). 2. using these µα i [n] parameters as inputs, lemc simulations are performed. the resulting concentrations are denoted by cαi [n]. 3. the flux computed from the {µα i [n], c α i [n]} pair usually does not satisfy eq.(7). the next set of electrochemical potential is calculated by assuming that the {µα i [n + 1], cαi [n]} pair does satisfy eq.(7). if we write the value of ĵαβi as given by the np equation into eq.(7), we obtain 0 = ∑ β d̂αβ i ĉαβi [n]∇µ̂αβ i [n+ 1] · nαβ aαβ , (8) where β runs over all the surface elements sαβ that constitute sα. eq.(8) is a system of linear equations; the unknown variables are denoted by µα,cal i [n + 1], where cal refers to the fact that these values come from calculations by solving eq.(8). 4. to achive faster and more robust convergence in the case of large driving forces, the electrochemical potential used in the (n+ 1)th iteration is mixed from the values calculated in the (n+ 1)th iteration from eq.(8) and the values mixed in the nth iteration: µα,mix i [n+ 1] = biµ α,cal i [n+ 1] + (1− bi)µ α,mix i [n], (9) where bi is a mixing parameter that determines the ratio of mixing. if the parameter is close to 1, faster iteration can be achieved, however, it may result in the system fluctuating between local minima. smaller bi values prevent this fluctuation at the price of making the convergence slower. 5. the input of the (n + 1)th lemc simulation is µα,mix i [n+ 1]. the system of linear equations contains the boundary conditions for the electrochemical potential and concentration via the boundary elements that are at the system’s boundaries (blue line in fig.1). if the sαβ face is on the system’s boundary, the values of ĉαβi and µ̂αβ i are those prescribed on that face. the electrochemical potentials on the left (l) and right (r) boundaries are computed from µl i = kt ln cli + µex,l i + qiφ l (10) and µr i = kt ln cri + µex,r i + qiφ r, (11) where µex,l i and µex,r i are the excess chemical potentials in the absence of an external field (determined by the adaptive gcmc method of malasics et al. [38]), while qiφ l and qiφ r are the interactions with the applied electrical potentials. prescribing φl and φr on the system’s boundary means that we use an electrostatic dirichlet boundary condition. voltage is defined as u = φl−φr. ultimately, we have boundary conditions for ion concentrations on the two sides of the membrane and for the voltage (ground is on the right in this study). the energy change ∆u contains not only the interactions between particles (and interactions of particles with the pore), but also the interaction with an external electrical potential, φappl(r). this applied potential is calculated by solving laplace’s equation ∇2φappl(r) = 0 (12) for the system (inside the blue line) with the prescribed dirichlet boundary condition on the system’s boundaries (φl and φr on the left and right blue line, respectively). in the portion of the blue line inside the membrane, we interpolate between φl and φr. we solve this equation with the induced charge computation method [39, 40]. in the present geometry, the elementary cells are ∆z× ∆r rectangles in the (z, r) plane. in three-dimensional space, these correspond to concentric rings with the zaxis in their centers. the concentration in an elementary cell bα can be computed from dividing the average number of ions in the cell with the volume of the cell. this route is disadvantageous if ion concentrations are small. an alternative method is based on the potential distribution theorem [37] that practically corresponds to the widom particle insertion method [41, 42]. the total excess chemical potential (containing also the interaction with the applied field) is µα i − kt ln cαi and can be computed as exp [− (µα i /kt − ln cαi )] = 〈exp [−∆uα i /kt ]〉 , (13) where ∆uα i is the energy change associated with the insertion of a test particle of species i into a randomly chosen position in the elementary cell α. this is the same energy computed in the particle insertion step of the lemc technique, therefore, it does not require additional computational cost. the concentration can be calculated from hungarian journal of industry and chemistry simulating ion transport with np+lemc 77 eq.(13) because µα i is known (that is the input of the simulation) and the ensemble average on the right hand side can be obtained from the lemc insertions. this route provides a more accurate value for cαi , because this sampling is not discrete as just counting particles, but rather continuous, because we always gain information from the simulation at every ion insertion via the energy ∆uα i . the route of counting particles, however, might be better, when concentrations are very large in the volume element. in the case of long enough simulations, the two methods give identical results (within a statistical error). because of this statistical error, the iteration does not converge to an exact value of the ionic flux density, but it fluctuates around a limiting value. the final solution is obtained from a running average over iterations. longer lemc simulations and more iterations result in a more reliable outcome. the net flux of the diffusing ions through the cross section of the pore is calculated via averaging: ji(z) = 2π ∫ r(z) 0 rji(z, r) · nz dr (14) where r(z) denotes the radius of the pore at coordinate z (|z| < hmemb/2, where hmemb is the thickness of the membrane) and nz is the unit vector along the z-axis. the electrical current of an ion is then ii = qiji, (15) and the total current is i = ∑ i qiji. (16) 3. results and discussion 3.1 calcium release channel there are two important classes of calcium channels that have been our focus. the l-type calcium channel is found in excitable cell membranes [43] such as those of nerve cells and muscle cells (both cardiac and skeletal). these are strongly ca2+ selective channels, meaning that the presence of only a µm ca2+ in the bulk decreases the na+ current to half of its value compared to its value in the absence of ca2+. this is called micromolar ca2+ affinity (or ca2+ block) because a very small amount of ca2+ is enough to block the channel [44]. the price of high ca2+ selectivity is low ca2+ current through this channel. the ca2+ ions flow into the muscle cell when the l-type calcium channels open in response to an electrical signal (action potential) in a small quantity that is not sufficient to initiate muscle contraction. the solution of nature for this problem is an amplification mechanism. a large amount of ca2+ ions are stored in organelles, the sarcoplasmic reticulum (sr), that are situated inside the muscle cells. there are calcium release channels (also known as ryr calcium channels) embedded in the membrane of the sr that are opened by the ca2+ ions provided by the l-type channel (in cardiac muscle) or via a direct link between the two types of calcium channels (in skeletal muscle). the ryr channels provide the large ca2+ flux that is necessary for muscle contraction by binding to tropomyosins on the actin filaments and allowing myosin to climb up the filament. these channels are wider (also, less ca2+ selective) than the l-type channels. a large amount of experimental data is available for this channel [45–47]. on the basis of this database, gillespie et al. developed a model for the ryr channel [21,22]. although the model was a onedimensional reduction, studied with a one-dimensional np+dft, they were able to reproduce hundreds of experimental current-voltage curves. later, when the np+lemc method became available, we developed [4] a three-dimensional version of the model of gillespie et al. the model is similar to that used by boda et al. [3, 4, 40, 48–54] for the l-type calcium channel inspired by the “space-charge competition mechanism” proposed by nonner et al. [55]. from the point of view of ion selectivity and permeation, the important part of the channel is the selectivity filter, the bottleneck of the pore. this region is lined by four p-loops that are parts of the four membrane-spanning subunits. these loops contribute four glutamic acids (in the l-type calcium channel) to the filter-lining region (the eeee locus). the coo− groups of the carboxyl side chains are thought to reach into the pore lumen and interact with the passing ions [44]. in the case of the ryr channel, they are four aspartates (d4899, see fig.2). gillespie et al. [21–23, 46, 47] identified additional e and d amino acids in the two vestibules on the cytosolic and luminal sides (fig.2). it has been shown [3, 4, 40, 48–55] that the strong ca2+ selectivity can be reproduced by a reduced model where eight half-charged oxygen atoms (o1/2−) of the four coo− groups force a strict competition between ca2+ and na+ ions for space in the crowded filter. the exact positions of the o1/2− ions are not known and even irrelevant from the point of view of the selectivity of the model. what matters is that they attract the cations into the filter with their charge, and, at the same time, they exert a hard sphere exclusion and make it difficult for the cations to find space in the filter. therefore, it proved to be sufficient to model the structural groups of the filter as mobile o1/2− ions that are confined to the filter region. the profiles shown in fig.2 are results of the simulations and show how the eight o1/2− ions distribute in a given segment of the channel. there are 32 such o1/2− ions, plus point charges placed on a ring on the luminal side. the geometrical features (filter radius is 5.5 å, filter length is 15 å, and radii of left and right vestibules are 22 and 9 å, respectively) are also designed on the basis of gillespie’s model that, in turn, are based on fitting to experimental data. this model was designed and used unchanged in ev45(1) pp. 73-84 (2017) 78 fertig, mádai, valiskó, and boda figure 2: the three-dimensional model [4] of the ryr calcium channel based on the model of gillespie et al. [21,22]. each curve shows the distribution of eight o1/2− ions that are confined to the given region but otherwise free to move there. the charges of the e4902 amino acids are represented as point charges (−1/2e) at fixed positions on a ring. the thickness of the membrane is hmemb = 46 å. the dielectric constant is ε = 78.5. ery calculation. what remains to be specified are the diffusion coefficient profiles of the various ionic species. these profiles depend only on z, di(z); we assume no variation in the radial dimension. the values outside the channel and in the selectivity filter, db i and df i , respectively, are constant. in the vestibules at the two entrances of the channel, the diffusion constant profiles are interpolated between the db i and df i values in a way that their value changes in proportion with the cross section of the channel. the bulk vales, db i , are taken from experiments; they are 1.334 ·10−9, 7.92 ·10−10, and 2.032 ·10−9 m2s−1 for na+, ca2+, and cl−, respectively. the values inside the cylindrical selectivity filter are fitted to two experimental data points: 250 mm symmetric nacl at 100 mv for na+, while added 10 mm luminal cacl2 at -100 mv for ca2+. the resulting values (1.27·10−10 and 1.27·10−11 for na+ and ca2+, respectively) are fixed and never changed. the cl− value is irrelevant, because cl− ions do not carry significant current. these values have been obtained for a moderate system size (h = 54 å, r = 48 å). currents, and, therefore, diffusion coefficients fitted to currents can depend on system size (see later). here, we show results for a nacl-cacl2 mixture, where there is 250 mm na+ on both sides of the membrane, while there is 4 µm ca2+ on the cytosolic (left) and 50 mm ca2+ on the luminal (right) side. the voltage is changed from -150 mv to 150 mv with the ground on the right. the current vs. voltage curves are shown figure 3: currents vs. voltage curves as obtained from experiment [21], the model of gillespie et al. [21, 22] obtained from dft coupled to the np equation, and from the np+lemc method. in the case of the np+lemc method, the currents carried by na+ and ca2+ are also shown. in fig.3. total currents are shown in black as obtained from experiments (× symbols), gillespie’s np+dft calculations (dashed line), and our np+lemc calculations (solid line with filled triangles). agreement with experiment is very good using both models. the slope of the i − u curve is larger for positive voltages than for negative voltages. more details and understanding can be gained from the current curves for the separate ions, na+ and ca2+ (blue and red curves, respectively). at positive voltages, the ca2+ current is practically zero, so the total current is carried by na+ ions. at negative voltages, on the other hand, both na+ and ca2+ ions contribute to the current. the explanation of this behavior can be drawn from concentration and electrochemical potential profiles shown in fig.4. let us discuss the na+-profiles first (blue curves). the driving force for the na+ ions is the voltage because na+ concentration is the same on the two sides. the difference between na+ currents at -100 and 100 mv voltages, therefore, is the result of the different competition between na+ and ca2+ ions at the two voltages. to understand the difference in this competition, we need to understand the behavior of ca2+ ions. at 100 mv, the driving force for ca2+ ions is small because the concentration difference balances the electrical potential difference (see the ca2+ electrochemical potential profile in the right panel of fig.4b). this results in a small ca2+ current. ca2+ concentration is small in the left bulk, therefore, a ca2+ depletion zone is formed in the left vestibule and in the selectivity filter of the channel (beware the logarithmic scale of the concentration axis). that depletion zone results in a decreased concentration of ca2+ ions compared to na+ ions inside the channel. in the case of -100 mv, on the other hand, the ca2+ depletion zone in the left vestibule is absent because ca2+ ions arrive from the right and “fill up” the left hungarian journal of industry and chemistry simulating ion transport with np+lemc 79 (a) (b) figure 4: (a) concentration and (b) electrochemical potential profiles of na+ and ca2+ for two opposing voltages: -100 mv (left panels) and 100 mv (right panels). the striped parts indicate the cytosolic and luminal vestibules, while the gray area is the selectivity filter. vestibule. there is a more balanced competition between ca2+ and na+ ions in the channel and ca2+ ions can use the free-energetic advantage that they have over na+ [22, 53]. this means that ca+ ions are favored by the crowded selectivity filter, because they provide twice the charge (compared to na+ ions) to balance the charge of o1/2− ions while occupying about the same space (their diameters are similar: 1.98 and 1.9 å for ca2+ and na+, respectively). the finite size of the ions plays a crucial role in the selectivity mechanism. this kind of selectivity could not be produced with the pnp theory. because ca2+ concentration is large in the left vestibule of the channel, it drops quickly to the 4 µm value at the left boundary of the solution domain. this introduces a severe system-size dependence into the calculations in this case that is analyzed in fig.5. small ca2+ concentration on the left hand side corresponds to a large debye-length in the double layer at left hand side of the membrane (in the left access region). that double layer should fit into the simulation cell (as it does in the case of a larger cell, see black curves in fig.5). if the cell is too small (see red curves in fig.5), there is not enough space for the ca2+ concentration to reach the 4 µm limiting value at the left boundary of the cell. the electrochemical potential cannot reach its limiting value either (see the bottom panel). the np+lemc calculation, however, provides a solution in this case too, because the layer near the left outer boundary of the cell takes care of the missing access region in an averaged manner. the concentration has a small value in the layer, figure 5: concentration (top panel) and electrochemical potential (bottom panel) profiles of ca2+ for -100 mv. the results of simulations for two system sizes are shown: h = 54 å (red) and h = 180 å (black). while the electrochemical potential profile drops abruptly (large driving force). an appropriate value of the ci∇µi product, therefore, is provided by the self-consistent solution so that the continuity equation is satisfied. this solution, however, is approximate. a large portion of the access region with considerable resistance is taken into account in an averaged way by the layer near the system edge. this introduces an error into the value of the ca2+ current that is indicated in fig.5 for both cases. the good behavior of the current-voltage curves compared to experiments and dft calculations is due to the fit of the ca2+ diffusion coefficient, df ca2+ , inside the filter. that value was fitted for negative voltage at the given system size balancing the system-size error. this result points out the importance of system size in the case of small ionic concentrations, but it also shows the role of the diffusion coefficient profile in np+lemc calculations. in confined geometries, the di(r) profile, although it has a strong relation to the mobility of ions, is primarily an adjustable parameter that is fitted to experiments (as in the present case) or to md results [6]. the value of df i takes into account interactions that are absent in the reduced model or accounts for resistances of regions that are absent in the model. in the case of the ryr channel, for example, the diffusion coefficient profile includes effects of the parts of the ion channel not included in the model: the real ryr channel is much larger than the 46 å portion modeled here. that region also tunes the total current, but it is not selective. the selectivity filter and its close neigh45(1) pp. 73-84 (2017) 80 fertig, mádai, valiskó, and boda figure 6: bipolar nanopore geometries: cyl: cylindrical; sc: single conical; dc: double conical. the pore is positively charged on the left hand side (−30 < z < 0 å), while negatively charged on the right hand side (0 < z < 30 å) keeping the surface charge fixed (σ = ±0.1 c/m2). minimal and maximal pore radii are 10 and 20 å, respectively. borhood modeled here determines ion selectivity and is able to reproduce complex behavior such as anomalous mole fraction experiments discussed previously by gillespie [21–23] and boda [4]. 3.2 rectifying bipolar nanopores ion channels are natural nanopores with stable welldefined structures that are very narrow at their selectivity filters (often below 1 nm in radius) to make them suitably selective. the disadvantages, however, are considerable. the structures are often unknown. they are difficult to handle experimentally. their manipulation is cumbersome with point mutations. synthetic nanopores, therefore, quickly gained attention due to the fact that they have special properties compared to those of micropores. these special properties arise because the screening length of the electrolyte is comparable to the radius of the nanopore. this fact gives nanopores properties that resemble those of ion channels. one advantage of synthetic nanopores is that are relatively easy to fabricate [56–63]. they are either solid state nanopores using ion-beam or electron-beam sculpting in, for example, silicon compound membranes, or they are track etched into polymer membranes. two basic properties of such nanopores are their geometry (shape) and the pattern of surface charge on the pore wall. figure 7: current-voltage relations for the three nanopore geometries (cyl, sc, and dc from bottom to top). currents carried by na+ (solid blue), cl− (dashed red), and their sum (dot-dashed black) are shown as a function of voltage. the insets magnify the results for negative voltages. in our previous works, we studied the bipolar nanopore, where the surface charge is positive on the left hand side of the pore, while it is negative on the right hand side [6, 7]. these nanopores rectify ionic current, meaning that they let a much larger amount of ions through at a given sign of voltage than at the opposite sign. in those papers, we used a cylindrical geometry for the nanopore and focused on the effect of the charge pattern, pore radius, and concentration. here, we discuss the effect of pore geometry on the rectification properties of a bipolar nanopore. we performed np+lemc calculations for three different geometries, the cylindrical (cyl), single conical (sc), and double conical (dc) shown in fig.6. simulations for different voltages have been performed from -150 mv to 150 mv. the concentration of the electrolyte was 0.1 m on both sides. the electrolyte is a 1:1 system (let us call it nacl), but the diameters of the cations and anions are the same in order to avoid effects from ion size asymmetry. for the same reason, the same diffusion coefficients were used for the two ions. this makes it possible to focus on the balance of charge and geometrical asymmetries. if the nanopore’s shape is symmetric, for example, the cations and anions carry the same amount of current (cyl and dc). figure 7 shows the current-voltage relations. rectification is observed in all three geometries: current is much larger at positive than at negative voltages. the rectifihungarian journal of industry and chemistry simulating ion transport with np+lemc 81 figure 8: rectification (defined as the absolute value of the current ratio in the on and off states) as a function of the absolute value of the voltage for the three nanopore geometries. cation is defined as the ratio of currents at positive (on state) and negative voltages (off state). the results are shown in fig.8. the basic explanation of rectification can be depicted from the concentration profiles (fig.9). there are depletion zones for cations in the positively charged half region (left), while there are depletion zones for anions in the negatively charged half region (right). in the off state (negative voltage) these depletion zones are deeper than in the on state (positive voltage). more detailed explanation have been given in our previous works [6,7]. here we focus our discussion to the effect of pore shape. total currents are larger in the sc and dc geometries due to their wider entrances. interestingly, total currents are the same in the sc and dc geometries despite the quite different pore shapes. whether this is a coincidence or it has a deeper explanation requires further investigation. what is different in the sc and dc geometries is the partitioning of the total current between na+ and cl−. while na+ and cl− currents are the same in the dc geometry due to the symmetric shape, they are different in the sc geometry. the current carried by na+ ions is smaller than the current carried by cl− ions (middle panel of fig.7). this is reflected in concentration profiles (see middle panel of fig.9). the explanation is that the tip of the sc nanopore (left entrance) is positively charged so the depletion zones of na+ ions there is deeper than the depletion zone of cl− ions on the other side where the pore is wider. deeper depletion zones result in smaller currents. therefore, na+ current is smaller in the whole voltage range, but more so in the off state at negative voltages. rectification is largest in the cyl geometry because the depletion zones are the deepest in that geometry for both ions. the deepest points of the depletion zones are formed around |z| = 10 å. there are different effects that form the concentration profiles inside the pore. in the left region, for example, (1) the positive surface charge on the pore wall repels na+ ions, (2) the negative surface charge figure 9: concentration profiles of na+ (blue) and cl− (red) in the on (solid lines) and off (dashed lines) states for the three nanopore geometries (cyl, sc, and dc from bottom to top). on the right hand side attracts them, (3) the 0.1 m bulk region acts as a source for the ions, (4) applied potential in the off state drives na+ ion to the right, where they have a peak, and (5) cl− ions (that have a peak on the left) attract them. the balance of all these effects forms the deep depletion zone of na+ at z ≈ −10 å in the off state. because the cyl geometry has the smallest radius at the |z| ≈ 10 å positions, this geometry provides the deepest depletion zone as a result of the dominant effect from the above list, the effect of repelling surface charge. 4. summary we presented the np+lemc method that is a hybrid technique, harvesting the advantageous properties of both the np transport equation (fast calculation of flux) and lemc particle simulation method (correct calculation of ionic correlations). we applied the method to compute ionic currents through reduced models of an ionic channel and a bipolar nanopore. reduced models have the advantage of fast calculation (lemc would not be feasible for an explicit-water model) and intellectual focus. with these models, we can concentrate on those properties of the system that are important to reproduce its behavior as a device. for the ryr calcium channel, for example, the reduced model is able to reproduce complex selectivity behavior in agreement with experiments by modeling only the “important” amino acids in a reduced way 45(1) pp. 73-84 (2017) 82 fertig, mádai, valiskó, and boda [21,22]. for the bipolar nanopore, the reduced model using implicit water is able to reproduce md results for an explicit-water model [6]. with further methodological and model development, we intend to simulate nanodevices as close to their real size as possible. acknowledgement the financial support of the national research, development and innovation office (nkfih k124353) is gratefully acknowledged. the present article was published in the frame of the project no. ginop-2.3.2-15-201600053 and supported by the unkp-17-4 (to m.v.) and unkp-17-1 (to e.m.), the new national excellence program of the ministry of human capacities. we thank dirk gillespie for helpful discussions. references [1] boda, d., gillespie, d.: steady state electrodiffusion from the nernst-planck equation coupled to local equilibrium monte carlo simulations, j. chem. theor. comput., 2012 8(3), 824–829, doi: 10.1021/ct2007988 [2] ható, z., boda, d., kristóf, t.: simulation of steady-state diffusion: driving force ensured by dual control volumes or local equilibrium monte carlo, j. chem. phys., 2012 137(5), 054109, doi: 10.1063/1.4739255 [3] boda, d., kovács, r., gillespie, d., kristóf, t.: selective transport through a model calcium channel studied by local equilibrium monte carlo simulations coupled to the nernst-planck equation, j. mol. liq., 2014 189, 100, doi: 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fundamental studies and practical applications of bioinspired smart solid-state nanopores and nanochannels, nano today, 2016 8(3), 1470–1478, doi: 10.1016/j.nantod.2015.11.001 hungarian journal of industry and chemistry hungarian journal of lndustrial chemistry veszprem vol 30. pp. 289-293 (2002) modification of flax fibre through graft copolymerization with methyl methacrylate and evaluation of swelling, moisture absorbance and thermal behaviour a. s. singha, b. s. kaith and b. d. sarwade1 (department of applied sciences, national institute of fechnology [nit], hamirpur 177 005 [h. p] india 1division of polymer chemistry, national chemical laboratory [nclj, pune [maharashtra] india) received: october 30, 2002 flax fibre has been modified through grafting of methyl methacrylate in presence of potassium persulphate and ferrous ammonium sulphate as reaction initiators. maximum graft yield of 40.23% was obtained at optimum reaction conditions and the graft copolymer was subjected to evaluation of swelling behaviour in different solvents, moisture absorbance under different humidity levels and thermal stability behaviour. the graft copolymers synthesized were characterized by usual spectroscopic techniques. keywords: flax, methyl methacrylate, graft copolymer, swelling, thermal stability introduction incorporation of different desired properties onto polymeric materials through grafting is an active area of current interest. grafting offers scope for developing new cellulosics for various end uses. modification of fibrous proteins and cellulosics by this method has been reported by various workers [1-5]. thermal degradation behaviour of cellulosics is very important [6, 7]. hurduc and schneider [8], varma and narashima [9] and mukherjee and sanyal [10] have reported the thermal behaviour of mma grafted viscose cellulose and cotton with decrease in thermal stability of the grafted fibres as compared to that of ungrafted one. kokot et al. [11] studied the effect of reaction medium, lattice structure and degree of polymerization on thermal stability of different cotton samples. uv and eerie ammonium nitrate initiated cotton graft copolymers were reported to exhibit lesser thermal stability with increase in add­ on [12]. flax one of the most important cellulosic material containing about 85% cehulose content, offers tremendous potential for cost effective technologies. however, no much work has been reported on this fibre. in this paper studies on the graft copolymerization of methyl methacrylate (mma) onto flax and evaluation of different parameters such as optimum reaction conditions, swelling, moisture absorbance and thermal behaviour have been reported. experimental purification of materials flax fibre was purified by refluxing with acetone for 72 hrs. in soxhlet. methyl methacrylate was purified by giving washings with 5 % naoh and subsequent drying over anhydrous sodium sulphate which was followed by distillation. middle fraction was used for grafting. potassium persulphate(kps) (bdh) was used as received and ferrous ammonium sulphate (fas) (bdh) was recrystallized from hot water before use. graft co-polymerisation 0.5 g of flax fibre was kept immersed in 100 m1 of distilled water for 24 hrs. prior to graft copolymerization. known amount of fas~kps was added to the reaction medium which was followed by the addition of mma in small quantities. the reaction mixture was stirred constantly for a particular time interval at a definite temperature. optimum reaction conditions were evaluated. homo-polymer was separated by soxhlet extraction with acetone for 48 h. graft co-polymer thus obtained was dried at 50 °c to a constant weight. the results have been shown in contact information: e-mail: amar_singha@yahoo.com; bskaith@yahoo.co.in 290 table 1 optimization of reaction conditions for maximum graft copolymerization of mma onto flax sr. temp time [mma] molar ratio pg pe no. (oc) (min) x 10·3 fas:kps mol/l 1. 45 120 1.96 0.5:1 25.00 5.10 2. 55 120 1.96 0.5:1 33.53 6.84 3. 65 120 1.96 0.5:1 32.53 6.64 4. 75 120 1.96 0.5:1 25.00 5.10 5. 85 120 1.96 0.5:1 25.00 5.10 6. 55 60 1.96 0.5:1 32.45 6.62 7. 55 90 1.96 0.5:1 35.00 7.14 8. 55 120 1.96 0.5:1 33.53 6.84 9. 55 150 1.96 0.5:1 27.98 5.71 10. 55 180 1.96 0.5:1 26.95 5.50 11. 55 210 1.96 0.5:1 25.00 5.10 12. 55 90 1.96 0.25:1 38.13 7.78 13. 55 90 1.96 0.75:1 38.75 7.91 14. 55 90 1.96 1:1 35.05 7.15 15. 55 90 1.96 1.25:1 31.73 6.47 16. 55 90 1.96 0.75:1 26.25 5.36 17. 55 90 1.96 0.75:1 26.50 5.41 18. 55 90 1.96 0.75:1 25.00 5.10 19. 55 90 1.96 0.75:1 26.25 5.36 20. 55 90 0.98 0.75:1 25.03 5.11 21. 55 90 1.47 0.75:1 26.45 5.40 22. 55 90 2.45 0.75:1 27.60 5.63 23. 55 90 2.94: 0.75:1 40.23 8.21 24. 55 90 3.43 0.75:1 28.75 5.87 25. 55 90 3.92 0.75:1 25.00 5.10 table i. the percentage grafting (p g) and percentage efficiency (p e) were calculated as follow : w -w p == & jlll& xloo .r wjui.r w -w p = ' jlll& xloo ~ wilt where w .~~~~&• w, and w m are the weights of un-grafted fibre, grafted fibre and monomer. swelling. moisture absorbance and thermal studies swelling behaviour studies were carried out in dmso, dmf~ h20 and n~propanol as per the method reported in earlier work [13]. moisture absorbance studies were done using humidity chamber at different humidity jevels ranging from 20 % to 90 % and the percent moisture absorbance (%mabs) was calculated as: w -w. %mabs1 1 xloo w, fig.1 13c solid-state nmr of raw flax / •/••··· .......................... : ..... , ... : . oe:··¥·: .... ···> . : .. : ....... . fig.2 13c solid-state nmr offlax-g-poly (mma) (sample 14 of table 1) where wi and wf are initial and final weights of the samples. both the grafted and ungrafted samples were subjected to thermo-gravimetric analysis (tga) studies as per the method reported in the literature [14, 15]. characterization of ungrafted and grafted fibres ir spectra of flax fibre and its graft co-polymer were taken in kbr pellets on bomem, hartmann & braun (mb-series) spectrometer. flax fibre showed a broad peak at 3420 cm·1 due to bonded -oh and at 2925.5, 1458.6 and 1055.87 cm·1 arising from -ch2, c-c and c­ o stretching. respectively. an additional band at 1730 cm·1 was observed due to the presence of carbonyl grour, in offlax-g-poly(mma). 1 c solid-state nmr (125.76 mhz) of graft copolymer (fig.2) showed additional signals at 177.87 for carbon corresponding to added carbonyl group and 51.73 and 44.37 for methyl and methylene groups of methyl methacrylate in addition to normal peaks at 104.46(c-6), 74.1l(c-2) and 71.34(c-3) shown by the 13c nmr spectrum of the raw flax (fig. i). comparison of scanning electron micrographs of flax (fig.3) and its copolymer (fig.4) indicates that upon grafting, a considerable amount of polymer is deposited onto flax surface. a physical mixture of flax-g-poly{mma) (1.0 g) was mixed with equal amount of poly(mma) and was stirred in acetone for about 24 h. homopolymer recovered after filteration was to the extent of 99 %. fig.3 scanning electron micrograph of raw flax the solid sample left after filteration was dried to constant weight. and it was observed that there was no weight loss. this clearly shows that homopolymer was quantitatively recovered from the reaction mixture. results and discussion in cellulosic materials like flax c2, c3 and c6 hydroxy is and c-h groups are active sites for the incorporation of polymeric chains through grafting . potassium persulphate is known to take part in a redox reaction with fe2+ through the following chemical equation: fe2++-03s-o-o-so~ --7fe3+ +so;+so;* in the aqueous medium oh* are generated by interaction of 804-* with h20 which is responsible for graft copolymerization and homopolymerization [16]. the following mechanistic steps are suggested for explaining the grafting of poly(mma) onto flax in the presence of fas-kps system: so;* +h20--7hso~ +oh* (1) so;* +fxcell-oh--7hso~ +fxcell-0* (2) fxcell-oh+oh* --7fxcell-o* +h20 (3) m+oh* --70h-m* ~oh-(m):+1 (4) oh(m):+l + fxcelloh ----7 --7fxcell-0* +oh-{m)n+l -h fxcell-0* +m--7fxcell-o-m* ~ ~ fxceli-0(m):+l fxcell-0(m):+l + * (m)n+i oh ~ ----7 fxcell-0{m)2n+z oh fxcell-0(m):+l + fe3+ ----7 ----7 fxcell-0(m)n+l + fe2 + where fxcell-oh = flax cellulose and m= monomer (5) (6) (7) (8) it is evident from the above mechanism that both so.*· and oh"' may be involved in grafting process. however, initiation of grafting by so./" (2) is unlikely 291 fig.4 scanning electron micrograph offlax-g-poly(mma) (sample 14 of table 1) as the concentration of persulphate used is very small, if the grafting is carried-out in absence of swelling agent. on the other hand, s04 *in aqueous medium reacts with h20 to generate oh* which can initiate the graft co­ polymerization and the resulting polymeric chain can abstract hydrogen atom from the back-bone polymer flax to generate the macro-radical (fxcell-0*) where grafting can take place. alternately, oh* can directly generate macro-radical (fxcell-0*) by hydrogen abstraction. since initiation of graft co-polymerization is a faster reaction than hydrogen abstraction by oh* so the generation of macro-radical by the former process is more likely to occur. termination of growing chains may occur by either process (7) or (8) or both. since fe3+ is involved in the termination of growing grafted chains, its presence can have great impact on graft yield. fe3+ arises from the interaction of fas with kps and consequently, the relative amounts of kps and fas should influence the percent grafting. effect of molar ratio of fas-kps maximum graft yield has been found at the molar ratio of fas-kps = 0.75: 1 and further increase in molar ration decreases the percent grafting. this is due to the formation of more fe3+ ion at higher molar ratio which results in the termination of growing grafted chains leading to the decrease in p g as is evident from the eq.(8). when the molar ratio of the fas-kps is less than the critical value, the concentration of oh* is low and the percent grafting is decreased (eq.(3)). from the above it is evident that molar ratio off as-kps plays an important role for getting maximum grafting. effect of monomer concentration it is evident from the above mechanism that initially percent grafting increases with increase in the monomer concentration and after reaching maximum value of 40.20 %, further increase in monomer concentration decreases the graft yield. this happens due to the predomination of homo·polymerization over graft co~ polymerization. homo-polymerization also cau~s increase in viscosity of the me£hum thereby decreasmg 292 60 _._ouso 50 --dmf ~ --water -; 40 -n-propanol ~ (/) ... 30 1: ~ q) f 20 q) 0. 10 0 0 10 20 30 40 50 percent grafting figs effect of percent grafting ofmma with flax on swelling behaviour in different solvents the mobility of the radicals to the active sites on the polymeric back-bone. effect of reaction temperature and time as the reaction temperature is increased from 45 °c to 55 °c, the graft yield is increased. further increase in temperature beyond 55 °c results in decreased p g· this is probably due to formation of considerable amount of homopolymer and setting-up of various hydrogen abstraction reactions at high temperature resulting in wastage of monomer by its participation in side reactions. as it is evident from table 1 maximum graft yield is obtained at 90 min. with further increase in reaction time, the graft yield is decreased. this phenomenon can be explained in terms ·of predominance of homo­ polymerization over graft co-polymerization and also due to other side reactions. swelling and moisture absorbance behaviour of flax and its graft co-polymer swelling studies in different solvents(fig.5) show that behaviour of the graft co-polymer varies as a function of pg and the trend follows the order: dmso > dmf > h20 > n-propanol. in case of original flax the order is: h20 > dmso > dmf > n~propanol. it can be due to the fact that water having great affinity for hydroxyl groups and hydrogen bonding present in cellulose, penetrates deeper into the matrix and causes swelling in original fibre which is not possible in case of dmso~ dmf and n-propanol. however, the grafted fibre containing methyl methacrylate chains are solvolysed by dmso and dmf to the greater extent. hence more swelling in dmso followed by dmf with increasing p g has been observed. h20 and n-propanol cannot interact with methyl methacrylate to the same degree as dmso and dmf. therefore. a different pattern for percent swelling in different solvents for the grafted samples is observed. further. it can be added that during grafting the hydroxyl groups and other active sites of the fibre are substituted with poly(mma) chains and thus a shift 20 18 -pg=25 -pgzo33.53 16 -pg=35 :e 14 -pg=3b.75 ... 12 -pg:40.23 s:: -raw flax cl) 10 u 8 "" cl) a. 6 4 2 0 0 20 40 60 80 100 percent humidity fig.6 effect of percent grafting ofmma with flax on moisture absorbance at different humidity levels· in sorption behaviour of grafted fibre from h20 to dmso is observed. graft co-polymerization has a great impact on the moisture absorbance behaviour of flax-g-poly(mma) vis-a-vis raw fibre. as it is evident from fig.6, moisture absorbance varies at different humidity levels as a function of pa. percent moisture absorbance (% mabs) decreases with increase in p g· the explaination for this behaviour lies in the fact that with increase in p g• the sites for maximum moisture absorbance are blocked after incorporation of methyl methacrylate chains through graft co-polymerization which has less affinity for moisture content as compared to hydrogen bondings and -oh groups present in the original matrix. further, higher % mabs. in case of original flax can be attributed to the fact that moisture has high interaction with active sites including c2, c3, c6 and free hydroxyl groups present in cellulose thereby softening the matrix and hence more penetration into the lattice of the fibre. thermal behaviour of flax and its graft co-polymer thermogravimetric analysis (tga) o~ flax fibre and flax-g-poly(mma) was carried-out on perkin elmer thermal analyser under nitrogen atmosphere at a heating rate of 10 °c/min. the decomposition of both the fibres was studied as a function of %weight loss v/s temperature (fig.7). primary reactions like thermo­ oxidation, dehydration, depolymerization and glucosan formation decomposes the ungrafted fibre. these processes take place in the region between 157 °c to 253 °c and is followed by the breaking down of c-c and c-0 bonds. initial decomposition begins at 270 °c (idt) and continues upto 340 °c with a constant 8.0 % weight loss. in the temperature range of 358 °c to 380 °c, 23 % weight loss has been observed. further decomposition at 425.3 °c shows that the amorphous region of the cellulose content of the fibre is disturbed with loss of h-bonded structure and a higher temperature of 446.2 °c (fdt) is required to break­ down the crystalline region. on the other hand, in case of flax-g-poly(mma) fibre, the initial decomposition begins at 260 °c (idt) and continues upto 285 °c at a constant loss of %. a sharp weight loss of % is observed in the temperature range of 295 °c to 310 °c. inflexions between 330 °c 293 raw flax flax-g-poly (mma) ~ q :d 70 bjl ~ ~ ooj 50 temperature ec) fig. 7 tg curves of flax and flax-g-poly (mma) (sample 14 of table 1) and 365 °c show that the amorphous region of the cellulose content of the grafted fibre is disturbed with loss of h-bonded structure and a higher temperature (370 °c to 375 °c, fdt) is required to break-down the crystalline region. higher idt of 270 °c and fdt of 446.2 °c of pure fibre as compared to 260 °c (idt) and 375 °c (fdt) of flax-g-ploy(mma) fibre show a decrease in thermal stability after grafting which may be due to disturbance in the original crystal lattice of the . fibre because of impregnation of monomer chains in the matrix. similar results have also been reported by other workers [8-12]. conclusion graft co-polymerization of methylacrylate onto flax fibre shows that the properties like moisture resistance and swelling behaviour are entirely the functions of pg. tga studies show that grafted fibre has lesser thermal stability as compared to that of original fibre. keeping in view the modified behaviour of the fibre after grafting, new eco-friendly materials can be synthesized to replace the existing non-bio-degradables. these materials could also be used as the precursors for the synthesis of future membranes and gels. a comprehensive research work is already in progress in our material laboratory. references 1. trivedi i. m. and mehta p. c.: cell. chern. techno!., 1975, 9, 583 2. haque m. m., habmuddowla m. and mahmood a. j.: j. polym. sci. chern., 1980, 18, 1447 3. misra m., mohanty a. k. and singh b. c.: j. appl. polym. sci., 1987, 33,2809 4. chauhan g. s., lal h., singha a. s. and kaith b.s.: ind. j. fibr. text. res., 2001,26,302 5. chauhan g. s., kaith b. s. and guleria l. k.: res. j. chern. environ., 2000, 4, 35 6. ghosh p. and ganguly p. k.: j. appl. polym. sci., 1994, 52, 77 7. ghosh p., samanta a. k. and dev d.p.: j. appl polyrn. sci., 1997,64,2473 8. hurduc n. and schneider i. a.: cell. chern. techno!., 1970,4, 195 9. varma d. s. and narashima v.: j. appl. polym. sci., 1972, 16, 3325 10. mukherjee a. k. and sanyal s.: cell. chern. tech., 1979, 13, 13 11. yang p. y. and kokot s.: j. appl. polym. sd., 1996,62,49 12. shukla s. r. and athalye a. r.: j. appl. polym. sci., 1995,57,983 13. chauhan g. s., bhati s. s., kaur 1., singha a. s. and kaithb. s.: j. polym. mater., 2000, 17,363 14. dalvi t. s.: m. phil. thesis, university of poona. chapter 2, 12, 1985 15. boti'ei r. s. and gerase p. l.: j. inorg. nucl. chern. 1961,23,245 16. misra b. n., dogra r., mehta i. k. and singha a. s.: die angewandte makromolekulare chemie 1980,90~83 17. sharma v. n. and daruwalla e. h.: cellul. chern. technol. 1979, 13, 433 18. el-alfy e., khalil m. i. and hebeisha j.: polym. sci. polym. chern. ed.,j98j,l9, 3137 19. sood d. s., kishore j., misra b. n.: j. macromol. sci. cb~m. a .• 1985, a22(3}. 263 page 291 page 292 page 293 page 294 page 295 hungarian journal of indus1rial chemistry veszprem vol. 30. pp. 299 ~ 303 (2002) hydrotreating of full range fcc gasoline j. hancsok, s. magyar and a. lengyel1 (department of hydrocarbon and coal processing, university of veszprem, h-8201 veszprem, p.o. box 158, hungary 1molhungarian oil and gas co., h-2443 szazhalombatta, p.o. box 1, hungary) received: november 20, 2002 sulphur content of engine gasoline must be reduced below 50 ppm in the european union from 2005, and gasoline containing 10 ppm sulphur will have tax allowance [1 ,2]. fcc gasoline is one of the blend stocks being applied in largest amount (about 20-50%). the sulphur content of this is significant (about 50-2000 ppm), therefore 50-95% of the sul~hur species of gasoline originates from this stream. selective hydrotreating of fcc gasoline may be a fav~urable techmque among the numerous new desulphurising methods. achievements of a research work, made for hydrotreating a £?11 r~ge of fcc gasoline, are presented in this paper. the authors were able to find combinations of process parameters bemg smtable to produce gasoline blend stock of 11 ppm sulphur content with only 2 units loss of octane number. keywords: fcc gasoline, desulphurization, olefin saturation, octane loss introduction further reduction of the automotive emission can be achieved effectively with complex development of fuels, engine construction, lubricants and other parts of vehicles (catalytic converter, tyre etc.). currently the sulphur specifications have dominant importance from the point of view of engine gasoline, because combustion products of sulphur species beside air pollutionare poison the vehicle catalysts. thus further significant reduction of sulphur content can be expected (table i) [3]. three main long-run methods are offered for reducing sulphur content of gasoline, each of which results in lower sulphur content of fcc gasoline: reduction by hydrofining of fcc feed, application of new catalysts and catalyst additives in the fcc unit and desulphurisation of fcc gasoline [4, 5]. these strategies can be used either in themselves or in combination. nevertheless, desulphurisation of fcc gasoline cannot generally be avoided to meet ultra low sulphur specifications of engine gasoline. the loss of octane number can be very significant (up to 10-15 units) applying conventional hydrotreating of fcc gasoline. accordingly, this process is not economical from two aspects: partly due to considerable loss of octane number, partly because significant hydrogen consumption. a number of desulphurising processes for fcc gasoline have ~n develope4 which can economically be used to produce low sulphur fcc gasoline with acceptable loss of octane number [6-1_7]. the new desulphurising processes are wldel y diversified in respect of their principle and technical configuration (selective hydrotreating, adsorption. extractive distillation, caustic extraction etc.). options for desulphurisation of fcc gasoline are summarized in table 2 [18]. some of these processes treat full range fcc gasoline, but others accomplish desulphurisation with only a portion of fcc gasoline. it is extremely important in the latter processes tha~ the colun:n for the distillation of gasoline has to be optunally destgned and the cut point well selected [19]. . fig.} illustrates the major optional pathways tor post-treating of fcc gasoline: the main features of the processes indicated on th1s figure . were . a~eady presented in table 2. in some cas~s th~ hght fracuon_ of fcc gasoline is sent to an ethenficatto~ or alkylatl?n unit for boosting the octane number, while the ~ea~1er fraction is hydrotreated. this kind of combmatmn reduces the overall octane loss of tx>shreating. these processes were not indicated on fig.l. during the research, the possibility of desulphurisation of a full. range fc~ gasoline on pt,pdlzeolite has been investigated. the rum of the study was to examine the effect of process parame~ers (primarily temperature and liquid hourly space veloc1ty} on the yield and quality of liquid product and to determine the advantageous process parameters. 300 region, country, state usa california eu japan process naphtha hydrotreating (nht) nht+octane increase selective nht selective nht + octane increase adsorption extractive distillation oxidation alkylation bio processing table 1 actual and planned motor gasoline specifications maximum sulphur content ppm maximum olefin content v n % (actual) (planned) (actual) (planned) 500 30 (2006) 25 no change 30 15 (end of2002) 4 no change 150 50 (2005) 18 still not decided 100 10 (2008?) not specified still not decided table 2 options for the desulphurisation of fcc gasoline key feature industrial application conventional yes zeolite+ isomerisation yes rt-225 yes dual catalyst yes catalytic distillation yes combination yes zn adsorbent yes alumina adsorbent pilot selective solvent sys. yes peroxyacid pilot ultrasou,nd pilot solid acid pilot bio catalysis no h2-consumption octane loss high high high low medium low medium low medium low medium low low low none none none low none low low low low low low low isal i octgaln i prlme-g+i scan fining conventional hydrotratlng i !sal i octgaln i prlm&-g+i name of process various octgain, isal scan fining prime-g+ cd hydro/ cdhds scanfining ii szorb irvad gt-desulf . . ced sulphco oats fig, j major optional pathways for the desu1phurisation of fcc gasoline licensors a number of firms exxonmobil, uop exxonmobil ifp cd tech exxonmobil philips alcoa gtc petro star bechtel bp enchira ~ydrogen, ·-t>~~ m1rogen 1 2 3 31 ~liquid product 301 fig.2 simplified drawing of the test apparatus. notations: 1, 6, 11, 13, 14, 18, 20, 22, 30, 34, 36, 37, 38: closing valves; 2, 8, 31, 39: control valves; 3, 7, 9, 15: manometers, 4: oxygen converter; 5: dryer; 10, 32: gas filter; 12: gas flow meter/controller; 16.23: back valve; 17, 19: liquid feeds burettes; 21: liquid pump; 24: pre-heater; 25: reactor, 26: sampling valve, 27,29: cooler, 28: separator; 33: pressure recorder; 35: pressure controller; 40: wet gas flow meter experimental apparatus desulphurisation of fcc gasoline has been carried out in a high-pressure reactor system (fig.2) at the department of hydrocarbon and coal processing, university of veszprem. this consists of a tubular reactor of 100 cm3 efficient volume and is free of back mixing. it contains the same equipments and devices applied in the reactor system of desulphurising plants (pumps, separators, heat exchangers, as well as regulators of temperature, pressure and gas flow). catalysts the hydrodesulphurising experiments were carried out on pt,pd/zeolite catalyst, applying 80 cm3 of it. feedstock as feedstock of the desulphurising experiments a full boiling range (data of simulated distillation: 6-228 °c) fcc gasoline were used. the major quality features are summarised in table 3. methods compositions of feedstock and liquid products were analysed by gas chromatography (chromocf ane} and the quality characteristics were calculated by a software from these compositions. composition of gas products was determined, by gas chromatography (astm d 5134-90). sulphur content was measured by pyro­ fluorescence method (astm d 5453). the experiments were carried out on catalyst of steady-state activity. by continuous operation. results and discussion process parameters of the experiments (table 4) were selected and based on literature data and on earlier results of the department. from the results of the experiments it can be stated that crack reactions resulting in lighter hydrocarbons have not proceeded in the investigated temperature range, because the yield of liquid products was high (>99.5 %) at every combination of process parameters. the degree of desulphurisation of fcc gasoline depended on the process conditions. sulphur content of the products (fig.3) became lower with increasing temperature and decreasing lhsv. the highest level of desulphurisation (80 %) was reached at 280 oc and irsv = 1.0 (fig.4). under these conditions the product contained 11 ppm sulphur. 302 table 3 main properties of the feedstock density (15,6°c), g/cm3 0.7423 sulphur, ppm 63 nitrogen, ppm 13 research octane number 93.4 motor octane number 81.7 (ron+ mon)/2 87.6 composition. % n-paraffins 4.0 i-paraffins 31.8 ole fins 24.9 aromatics 31.7 naphthenes 7.6 i 35 ~30+---~~~~~~~----------------~ .:r !~+---------~~~~~~~----------~ ~ 20 r-------------=~~...2~~::------~ ~ 15 5+---~--------~--~----~----~--~--~ 220 230 240 250 270 280 tih!lperatuno, •c fig.3 sulphur content of products as function of temperature 100 ~ 90 .: ao ~ ~ 70 i 00 l 50 40 :t: 30 20 220 230 fig.4 hydrodesulphurisation as function oftemperature taking into account the composition of the feedstock and products it can be stated that the olefin content of each product decreased in proportion to the feedstock. the degree of saturation of olefins as function of temperature is shown on fig.5. higher temperature and tower lhsv resulted in higher olefin saturation. the highest olefin saturation (approx. 50%) occwted when desulphurisation was the lowest. ~iainly paraffins have formed from the olefins. but in a less degree also aromatics and naphthenes. evaluating the change of the concentration of paraffins it was stated that more n~paraffins than i~paraffins were formed from the olefins. every product had lower iso/normal paraffin ratio than the feedstock (8.0). this ratio is presented on fig.6 as function of temperature. the ratio was lower at higher temperatures and lower lhsv. this can be attributed to thermodynamic reasons. because higher temperature binders isomerisation. table 4 applied process parameters parameter reaction temperature, oc reaction pressure, bar liquid hourly space velocity, h"1 hzfhydrocarbon ratio, m3/m3 60 50 ;.!: g 40 ~ 30 = c i 20 '6 10 0 220 230 240 250 260 270 property 230-280 30 1,0-3,0 300 280 290 temperature, •c fig.5 olefin saturation as function of temperature 7,0 .2 6,0 'e ~ 5,0 ; ~ .!! 4,0 3,0 220 230 240 250 260 270 280 290 temperatura, •c fig.6 iso/n-paraffin ratio as function of temperature 2,5 ~ z 0 2,0 ~ 0 1,5 !!:. ~ 1,0 . ~ 0,5 8 0,0 220 230 240 250 260 270 280 200 temperatuta, ·c fig.7 loss of octane number as function of temperature the outcome of the mentioned chemical changes was the lower octane number of the products. fig. 7 illustrates the loss of octane number as function of temperature. the largest loss of octane number (2 units in [ron+mon]/2: the average of ron and mon) was observed at 280 °c, lhsv = 1.0 h-1 • sensibility of every product became lower due to saturation of olefins. by desulphurisation to the same degree, the lowest loss of octane number could be reached with the largest lhsv (3.0 n·1 ). removal of the light fraction of fcc gasoline could result in significant reduction of the loss of octane number. or lower sulphur content could be reached with the same loss of octane number. conclusions from the results of the investigation carried out on pt,pd/zeolit catalyst with the use of full range fcc gasoline, having 63 ppm sulphur content it can be stated that at advantageous process conditions (280°c; jo bar; lhsv=l,o; h2/hc = 300) fcc gasoline of 11 ppm sulphur content can be produced with high yield and only 2 units decrease of octane number ([ron+mon]/2: average of ron and mon). about 75 %of the olefins are in the light fraction of the feedstock (below 70 °c). this light fraction may contain very little sulphur, because it was passed through a merox unit in the refinery, which extracts the mercaptans from the light fraction. below 70 oc thiophenes are not present. this means that if we would cut the feedstock at 70 oc and we would only hydrotreat the heavier fraction, significant octane loss reduction could be reached, but only about 2 or 3 ppm of sulphur wou~d bypass the desulphurisation with the light fractron. furthermore, we can raise the temperature of the reactor, and we can reach higher level of desulphurisation without facing further significant octane loss. however, we have to confirm this with further experiments, and this is the aim of our next research work. nevertheless, our results confirm the opinion that hydrodesulphurisation of fcc gasoline can mainly be accmr~plished effectively and economically by expedient refinement of light and heavy fractions gained by fractionation. acronyms fcc fluid catalytic cracking hcn heavy cracked naphtha lcn light cracked naphtha lhsv liquid hourly space velocity mcn medium cracked naphtha mon motor octane number ron research octane number references 1. dixon-decleve s.: world refining, 2001, 12(9), 8 303 2. anon.: oil gas european magazine 2001 27(1) 42-43 ' , ' 3. sweed n. h.: petroleum technology quarterly, autumn, 2001, 6(3), 45-51 4. reidt. a., brevord e. and laan m. n. t.: the challenge of meeting future gasoline specifications: pre-treating vs. post-treating options around the fccu, european catalyst technology conference, antwerp, 2001 5. bavaro v.: world refining, 2000, 10(2), 30-37 6. maple r. e.: hydrocarbon engineering, 2000. 5~,%~2 . 7. burneit p. a., huff g. a., pradhan v. r., glaseit j. a. and hurst p.: bp low gasoline technology oats™, ertc 5th annual meeting, rome,2000 8. gentry j., khanmamedov t., and wytcherley w.: hydrocarbon engineering, 2002, 7(2), 43-44 9. d~buissc~rt q., nocca j.l. and cariou j.p.: pnme-g+ : the key to fcc gasoline desulfurization, proceedings of the interfaces '2002 conference, budapest, 2002 10. upson l. l. and schnaith m. w.: petroleum and coal, 2001, 40(3), 139-146 11. shih s. s., owens p. j., palit s. and tryjanowski d. a.: mobil's octgain™ process: fcc gasoline desulfurization reaches a new performance level, npra 1999 annual meeting, san antonio, texas, 1999 12. stun1z g. f. and plantenga f. l.: new technologies to meet the low sulfur fuel challange. 17th world petroleum congress. block 2:excelling in refining and delivering qualily petrochemicals, rio de janerio, 2002 13. anon.: world refining, 2001, 12(8), 23 14. rock k. l.: cdhydro/cdhds for ultra low gasoline sulfur, ectc 2002, amsterdam. 2002 15. irvine r. l. and varraveto d. m.: petroleum technology quarterly, summer 1999, 37-44 16. gislason j.: hydrocarbon engineering, 2002, 7(2 l 39-42 17. turk b., gupta r. and arena b.. a new continuous catalytic process for desulfurization of syngas and hydrocarbons, 2002 npra annual meeting, san antonio, texas, 2002 18. o'connor p. and mayo s.: division of fuel chemistry preprints, 2001, 46(2), 381-386 19. goldens. w., hanson d., w. and fulton, s. a.: hydrocarbon processing, 2002, 81(2). 67-72 page 300 page 301 page 302 page 303 page 304 hungarian journal of industrial chemistry veszprem vol. 30. pp. 281-284 (2002) stochastic model of first order chemical reactions taking place in particles t. buckle, a. bezegh1 and c. mihalyk62 (research institute of chemical and process engineering, university of kaposvar, egyetem u. 2., veszprem, h-8200, hungary 1department of environmental economics and technology, budapest university of economic sciences and public administration, fovam ter 8., budapest:, h-1093, hungary 2department of mathematics and computing, university ofveszprem, veszprem, p.o. box 158, h-8201, hungary) received: october 17, 2002 experimental observation had been made in the 1950s, that the application of the fluidisation method increases the formation rate and homogeneity of the iron oxide red product. results of the interpretation of this observation by the recently developed mathematical models had been presented. the interpretation is based on the stochastic treatment of the virtual rate constant due to the random temperature differences of the particles at heating processes. the stochastic model is derived from the first order kinetic equations assuming uniform distribution for the rate constant and includes the momentum equations. discussion of the model is described for different sets of parameters. keywords: stochastic model, particle dispersion processes, iron oxide red production, conversion rate, product homogeneity, momentum equation, particulate system introduction during the years of the '50s, an intensive research was lead by prof. k. polinszky, to study the properties of inorganic pigments and their production methods. this had been summarised elsewhere [1]. it is a crucial question what result can be obtained, if we treat the virtual rate constant as a stochastic parameter, due to the random temperature differences of the particles in thermal processes? the models of the first order processes are presented in the following: a group of inorganic pigments are produced by heat treatment of solid particles. for example: minium, from lead oxide, chromium oxide green, from potassium dichromate, iron oxide red from iron oxide black and yellow and from ferrous sulphate heptahydrate. at that time one of the authors, t. blickle, dealt with mathematical modelling and the application of fluidisation, respectively. as it was experienced, in a fluidised bed the conversion rate was higher than that in a rotating kiln, or in a steady layer. it was impossible to explain these phenomena by the available mathematical models. the mathematical models of particle dispersion processes, including stochastic processes as well, had been studied in the recent and past decades [2-7]. here we present the results of the interpretation of observations, gained by the recently developed mathematical model. stochastic model the kinetic equations: de~ * 1-=-k.c. dt j j (l) where c ~ is the concentration of the initial component, j ci is the concentration of the final component in the j4.11 particle, a. is the stochiometric factor. the virtual rate constant, k. is a stochastic variable with the probability density function, 8( ld and its ki values are assigned randomly to the j-dt particle by drawing according to this density function, i.e. ~ is a realisation of k. in the moment of the start, the 282 concentration frequency density function of the particles in the system is given by: n[c(o), c * (0),0] (3) from eqs.(l) and (2), the transition functions can be obtained: (4) (5) density function n[c(o),c*(o),o] and eqs.(4) and (5) yield the following model of the integral transformation equation: k [c(t)ac * (t)(ekt -1),] n~(t),c * (t),t ]= jn c * (t)ekt ,0 . (6) k., • ekt b(k)dk the momentum equation is: 1 1 m 1 (t) = j j c1 (t)n[c(t),c * (t),t]dc(t)dc * (t) (7) 00 using the eq.(6), one can get: 1 1 k 1 ) [c(t)ac * (t)(ekt -1),] 11c (t n · m 1 (t) = j j j c* (t)ekt ,0 (8) ook .. kt * · e b(k )dkdc(t)dc (t) by applying eqs.(4) and (5), and after transformation: 1 1 ku[c(o) + c * (o)il(le-kt)]1 • m (t) = if i (9) 1 0 0 t .. · n[c(o).c * (o),ojb(k)dkdc(o)dc * (0) assuming that the distribution of k values are uniform in the range of km ku: kk'" +ku ai. k l1k ,. ak 2 _,oj{.= .y-k,n, ak = .jli, a;;= k values k.t and ku ar~ the lower and upper limits of a uniform distribution, k is the average value of the uniformly distributed virtual rate constant, l:jc is the width and ty~; is the standard deviation of its range. while a 1 is the coefficient of variation (relative standard deviation} of the uniformly distributed virtual rate constant. until now it was assumed, that the values of ki,, which had been drawn at t = 0 stay unchanged during the entire process. however, in many cases there are such effects in the system which make it necessary to draw again periodically, after each e. here, when the elapsed time, r between two drawings is 0 < r 50 and t time is: t=l·e>+-r (12) where lis the number of drawing. if c(o) = 0 and -r * 0, then: 1e-k't 2 . fe .juak [ sinh fe .jl2a k ] 1 c(t) = ilc * (0) 2 (13) ·[sinhf.r~l k jiiak 7:-2 if c(o) = 0 and -c = 0, then: [ [ sinh fe ..jyia k ] 1 ] c(t) = ilc * (0) 1-e -kt ..fij? (13a) ke 12o-" 2 if ti(o) = u*2(0) = 0 and -c * 0, then: if rl(o) = u*2(0) = 0 and 7: = 0, then: o.s j.() 1.5 2.0 25 3.0 3.5 4.0 45 5.0 kt fig. i plot of conversion against time, at different relative ranges of the virtual rate constant ( sinh 'kejua-k 'jt kejlia-k -2 'j/ cjz (t) = k c * (o)e-zkt [ . .j12 " ]~ smhkg--a 2 k (14a) because limx-to sinh x = 1 if r and 0 converges to 0, x while t is constant: (15) (16) discussion of the stochastic model eqs.(13a) and (14a) are used. r = 0; l = 1; c(o) = 0 (in this case t = 8 ). while discussing the function c(t) +kt let ak be 0; 0.25; ..1-c* (0) 0.5. (see fig.l.) t = 0; l = 1, c(o) = 0, tt\0) = 0'* 2(0) = 0. here we discuss cr(t) = ~(t) +kt relationship, if 8k = 0.25; 0.5. c(t) (fig.2.) i rr(ij f(ll ojj 1.0 2.0 3jj 4.0 283 i i i i i ! kt s.u i fig.2 plot of relative concentration variance against time, at different relative ranges of the virtual rate constant i 8,0 ' i i i 7,0 i 6/.j i ~) l i.e • (0.) ~ 4.'j i i 2/! fig.3 plot of conversion against the relative range of the virtual rate constant, at different times here the c(t) is studied at different (0.8, 0.9, 0.95) ac * (0) values of the necessary timet (if r= 0, l = 1, ~(0) = 0 j as a function of 8k. (see fig.3.) we studied c and a 2(t) at different l values. let r = 0 ; and for example kt = 1, &a = 2 . eq.( 13aj is then: -; . -1 • 1 [ (l c(t) = ac (0) 1-e (smh/) j (17) and eq.( 14a): 284 i 0.7 .-·--·-·--'"··~><······-· 0.65 1------1"----+----t-----;j 1 0.6v i ~ o.ss 1------1"----+----t-----; os '----....-l--~--'----...,.1---_...; 1 fig.4 plot of conversion against the number of drawings fig.4 shows the c(t) +l relationship according llc* (0) to eq.( 17), while the [ <r~t) ] 2 + l function according llc (t) to eq.(l8) is plotted in fig.5. conclusions on the basis of the above discussions it could be concluded: i. the conversion time and the relative standard deviation of the product concentration are increasing as the relative standard deviation of the virtual rate constant increases. (fig. i, fig.2 andfig.3.) ii. at a given e a~ l increases the conversion increases and the variance decreases. (fig.4 and fig.5.) iii. in steady layer system 7: -t 0 and l = 1; in rotating kiln when e is a given value: l = !._ (that e is the time of one revolution) and cr is less then in a steady layer; while in fluidised layer e -t 0 , l -t oo and a~ 0. iv. these all, in our opmwn, support the experimental observation: at the ferric oxide red production the fluidisation increased the rate of conversion and the homogeneity of the product. summary it is an experimental observation made in the years of the '50s. that the application of the ftuidisation method i [ 11(1) ]' ).7(t) fig.5 plot of concentration variance against the number of drawings has increased the formation rate and homogeneity of the iron oxide red product. it could be explained by the models developed later that, the virtual rate constant is a stochastic variable due to the variation of the temperature in the fluidised bed. this stochastic model showed the most important tendencies as well. references 1. polinszky k.: further examinations on the chemistry and technology of iron oxide pigments. (in hungarian) veszprem, 1960 2. blickle t., mffialyk6 c. and lakatos b.: mathematical models of particle dispersion systems and their processes.(in hungarian). proceedings of the conference of technical chemistry days, veszprem, 7-13, 2000 3. blickle t., mffialyk6 c. and lakatos b.: stochastic and deterministic models of processes taking place in operation units (in hungarian) proceedings of the conference of technical chemistry days, veszprem, 25-30, 20ch 4. chen x. -q. and pereira j. c. f.: international journal of heat and mass transfer, 1997,40, 17271741 5. marchisio d. l., barresi a. a. and garbero m.: aiche journal, 2002, 48, 2039-2050 6. hill p. j. and ng k. m.: chern. eng. sci., 2002, 57' 2125-2138 7. jones a. g., hostomsky. j. and wachi. s.: chern. eng. comm., 1996, 146, 105-130 page 283 page 284 page 285 page 286 microsoft word 00.00 inner cover.docx hungarian journal of industry and chemistry vol. 43(1) pp. 39–43 (2015) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2015-0007 groundwater remediation using biological and photocatalytic methods sándor guba,1* viola somogyi,2 and erzsébet szabóné bárdos3 1 institute of physics and mechatronics, university of pannonia, egyetem u. 10, veszprém, 8200, hungary 2 institute of environmental engineering, university of pannonia, egyetem u. 10, veszprém, 8200, hungary 3 department of general and inorganic chemistry, university of pannonia, egyetem u. 10, veszprém, 8200, hungary the degradability of two commercially available pesticides was studied using heterogeneous photocatalytic and activated sludge treatment methods. the first pesticide contained 5% quizalofop-p-ethyl as an active ingredient and petroleum naphtha as a solvent, the latter causing difficulties both in photocatalytic and biological treatment methods. the active ingredient of the second compound was acetamiprid. the photocatalysis proved to be effective both under laboratory conditions (using uv light) and when exposed to sunlight, but the pesticides remained stable during the employed biological treatment. preliminary information on its behaviour in soil was obtained from transport modelling. keywords: heterogeneous photocatalysis, groundwater remediation, quizalofop-p-ethyl, acetamiprid, biological treatment 1. introduction the drinking water supply of hungary largely relies on underground water resources. the water quality has been endangered by both industry over the last century and the still significant pesticide-intensive agriculture. excessive amounts of pesticides contaminating soil may be fully or partially degraded by natural chemical and biochemical reactions. the latter may lead to bioaccumulation. the transport into groundwater and/or surface water bodies is affected by several factors, such as precipitation, evapotranspiration, infiltration, and runoff besides the physicochemical characteristics of soil and the attributes of the substance. the application of pesticides is an inefficient procedure, since only a small amount is utilised for the desired purpose. most of the compound is released unused into the soil and if it degrades partially or at a slower pace, the pesticide might accumulate and enter the food chain. in order to avoid the release of pesticides that are persistent and harmful to the environment and humans, it is necessary to have licencing procedures and strict controls on the use of such materials [1]. in hungary, authorisation is regulated by the decree 89/2004 of the ministry of agriculture and rural development in agreement with the council directive 91/414/eec [2]. *correspondence: gubas@almos.uni-pannon.hu a common method to treat contaminated aquifers is groundwater pump-and-treat technology [3], where extraction wells are used to remove the contaminated water that is treated with adequate techniques after which it is re-injected into the aquifer or released into a surface water body. the treatment method is dependent on the degradability and toxicity of the pollutant. bioremediation cannot be used in cases when the compound is not biodegradable or even toxic to microorganisms. oxidative methods, such as heterogeneous photocatalysis may be adequate in such cases [4]. in this process, the radicals formed due to the photogenerated charge-carriers on the surface of the semiconductor. they react with the pollutant molecule initiating its degradation. the catalyst is often reusable and recycled. the semiconductor catalyst has to be chemically and biologically inert, but photocatalytically active. it should be easily produced and economical. since tio2 fits these requirements, it is the best among the semiconductors for extensive use [5]. research over the past years has proved that on a laboratory scale different organic compounds (aliphatic and aromatic hydrocarbons [6], alcohols and organic acids [7], phenols [8] and chlorinated compounds [9]) could be effectively degraded to inorganic end products using heterogeneous photocatalysis [10]. the aim of this paper is to report on the degradability of organic contaminants in the soil and groundwater with biological and photocatalytic methods using model compounds. their behaviour in the soil guba, somogyi, szabóné bárdos hungarian journal of industry and chemistry 40 was determined by hydraulic and transport models. the model compounds were a herbicide (leopard 5 ec) and an insecticide (mospilan 20 sg). both fall into category iii meaning that they are available without a special licence. their metabolites remain stable in soil for a long period. 2. methods and materials the substance with the brand name leopard 5 ec contains 5% quizalofop-p-ethyl (scheme 1a) as an active ingredient, 77-83% petroleum naphtha as a solvent and other emulsifying excipients. the active substance is especially dangerous to mammals, aquatic organisms, and birds and moderately toxic to bees. it is insoluble in water; it emulsifies due to the additives. its metabolites are more soluble in water, but do not hydrolyse. their half-lives are between 35 and 39 days. the active ingredient of the insecticide called mospilan 20 sg is 20% acetamiprid (scheme 1b), which is highly toxic to mammals and birds and moderately toxic to aquatic organisms. the substance is very soluble in water, hence its high mobility upon infiltration. its metabolite is not easily degraded under natural conditions in soil and water (its half-life is 133 days), and it is moderately toxic to aquatic life. heterogeneous photocatalytic irradiation experiments were performed in a photoreactor with an effective volume of 2.5 dm3. internal recirculation was provided in the tube reactor. tio2 was used as a catalyst with a concentration of 1 g dm-3, while the air flow was 40 dm3 h-1. the radiation source placed in the axis of the reactor was a 40 w fluorescent lamp specially manufactured for such purposes. the vast majority of light emitted is of a longer wavelength than 300 nm. biological treatment was carried out in an activated sludge, aerated sequenced batch reactor. an operating cycle lasted for a day. the effective volume of the reactor was 5 dm3 and the sludge concentration was kept at 4 g dm-3. the rate of aeration was kept constant throughout the process. a non-adapted municipal sludge was used for the experiments. modelling was carried out using processing modflow for windows (pmwin) 5.3. this version is freely available, while later versions can be obtained commercially. the test area was chosen to be the size of 1 acre divided vertically into three homogenous layers with average hungarian properties. simulations were run for 1–3–13–113 day intervals. the environmental factors taken into consideration were the following: groundwater flow and porosity, infiltration due to precipitation (1.9 mm day-1), and evapotranspiration (1.2 m day-1) [11]. the hydraulic conductivity was 129.6 mm day-1 for all three layers [12]. 3. results and analysis 3.1. leopard 5 ec the degradability of the substance with heterogeneous photocatalysis was examined under laboratory (uvlight) and natural (sunlight) conditions. the initial concentration of the active ingredient was 3.26 g dm-3. the solution was heavily foaming whilst the reactor was being filled. during irradiation, the majority of the catalyst deposited onto the bottom or adhered to the walls of the reactor and buffer tank after an hour despite being stirred. the organic carbon content of the mixture did not change, which indicates that no degradation took place. in the biological treatment, the components of the solution entering the cycle were: 100 cm3 of herbicide with a concentration of 3.26 g dm-3, 100 cm3 of acetic acid (0.93 g dm-3), 10 cm3 of ammonium chloride solution (30 mg n dm-3), and 10 cm3 of sodium phosphate (30 mg p dm-3). after turning the stirrer and aeration on the liquid started to foam heavily and smelled strongly of oil. at the end of the cycle in the settling phase the effluent was turbid. colloids and a part of the activated sludge deposited on the wall of the figure 1. the concentration of quizalofop-p-ethyl in the second layer in the case of normal use (a unit equals 2 m). scheme 1. schematic structures of pesticides studied in this work (a: quizalofop-p-ethyl, ref: dpx 79376, http://sitem.herts.ac.uk/aeru/ppdb/en/reports/583.htm (11.05.2015); b: acetamiprid, ref: ni 35, http://sitem.herts.ac.uk/aeru/ppdb/en/reports/11.htm (11.05.2015)). groundwater remediation with biological and photocatalytic methods 43(1) pp. 39–43 (2015) doi: 10.1515/hjic-2015-0007 41 sequenced batch reactor and surface of the sensors and dried there. the following cycle ended with the same results. the treatment using activated sludge turned out to be ineffective due to the experienced foaming and cumulated active ingredient. inspections revealed that the degradation of the solvent did not start either. the transport models created with the software (fig.1) showed that pesticide under normal conditions of use did not threaten drinking water resources and due to hydrolysis the concentration decreased by half in the second stratum over 113 days. in the case of accidental spillages (the same amount of compound was hypothetically released over a 2 m2 area) the effect was significant, the concentration was a thousand times grater compared to normal use scenarios. 3.2. mospilan 20 sg in the experiments the concentration of mospilan used was 170 mg dm-3 in agreement with the suggested concentration of application. a 20% active ingredient content was achieved by an acetamiprid solution with a concentration of 34 mg dm-3. photodegradation was monitored by recording the uv-vis spectra of the mixture and measuring the organic carbon content (toc). the solution was first irradiated with uv-light without a catalyst under atmospheric pressure for three hours. during this time neither the toc concentration nor the ph of the mixture changed; the variation of the results stayed within the measurement error, which suggested that the insecticide was not degradable by uv-light in itself. the second experiment was carried out with tio2 as a catalyst and the process was not stopped for seven hours. during this time the rate of light absorption between 200 and 300 nm gradually decreased and the maximum of the band shifted from 245 nm to 230 nm (fig.2). these spectral changes indicate clearly that the compound degraded in the heterogeneous photocatalytic experiments. the suspension was circulated in the reactor for 20 minutes before irradiation. from changes in toc concentration, it can be concluded that during this period a proportion of the organic material had adsorbed onto the catalyst particles. the rate of adsorption in terms of toc was 10%. by the end of the process, the toc concentration of the suspension reduced by 76% while the cod amount became 78% less. according to the data, the initial rate of decay was calculated to be 13.59 mg dm-3 h-1 based on the curve fitted to the toc. a major advantage of the heterogeneous photocatalyst is that the reaction may be carried out with solar radiation; thus, costs and also environmentally harmful emissions can be reduced. photons are on the one hand ‘pure’ reagents and on the other hand ‘pure’ energy. the changes in the spectrum, such as the decrease in absorbence and the shift in location of band peaks were the same under laboratory conditions, while the reaction rate was lower. the initial rate of decay due to solar radiation was 6.07 mg dm-3 h-1. during measurements the uv-b radiation was “strong” (uv index 6.5, hungarian meteorological service). the results show that the heterogeneous photocatalytic degradation of the insecticide may be efficiently achieved by using sunlight. this can be utilised when disposing of different chemical residues. the organic contaminants may be mineralised using solar radiation on site in a carefully designed “reactor”. the biodegradability of the pesticide was studied with a prepared solution based on an average concentration of application. in the first case, an additional substrate (acetic acid) was added to the sequenced batch reactor while in the second case only the insecticide was supposed to serve as a substrate. based on the results (fig.3), it can be stated that the biodegradation of mospilan cannot be achieved with municipal activated sludge under the employed conditions. the results of the transport model (fig.4) show that acetamiprid acts in a similar way to quizalofop-p-ethyl. since it does not hydrolyse the active ingredient, it would remain for longer in soil and accumulation might appear therefore the compound may more easily enter the food chain. in the case of accidental spillages of the substance over a small area, the effect would be more significant just as was the case with quizalofop-p-ethyl. figure 2. spectra of mospilan suspension treated with catalyst (optical path length: 0.5 cm) (a); chemical oxygen demand and total organic carbon concentrations as function of time (b). a ds or be nc e guba, somogyi, szabóné bárdos hungarian journal of industry and chemistry 42 the concentration in soil would be a thousand fold greater. besides it would not decrease significantly over time, since the compound is stable in aqueous media. 4. conclusion the studied leopard 5 ec and mospilan 20 sg pesticides are available to purchase without any permit, although they are toxic to different extents to mammals, birds and aquatic organisms. their improper application might cause serious environmental damage. the degradability of the two substances was studied by means of heterogeneous photocatalysis and biological treatment. in the case of leopard 5 ec neither of the methods was successful. the petroleum naphta solvent and/or the emulsifiers poisoned the tio2 catalyst. the dollops formed settled and the surface of the catalyst particles was reduced greatly due to the adhesion effect of the organic material. the photocatalytic degradation reaction could not take place. a similar process was observed in the biological reactor. the mixture together with the biomass adhered to the surface of the sequenced batch reactor and sensors. in both cases the conditions made the treatment processes impossible. in order to be able to study the degradation of the compound, pre-treatment, possibly the destabilisation of the emulsion is needed. mospilan 20 sg could be treated using heterogeneous photocatalysis both under laboratory conditions (with a uv lamp) and utilising solar radiation. however, it can be stated that the insecticide cannot be treated with municipal activated sludge under the applied conditions based on the results of sequenced batch reactor experiments. according to the simulation results, neither of the pesticides poses a threat to drinking water resources in the case of normal use in compliance with the specifications provided by the manufacturer. nonetheless, mospilan 20 sg is likely to accumulate if used multiple times or for extended periods. should there be an emergency the impact on the environment might multiply. the results of the present study show that unlicensed use does not necessarily mean easily degradable substances. the biological method was unsuccessful in both cases, photocatalysis is not applicable for water-immiscible chemicals but in the case of hydrophilic organic materials, the treatment may be efficient. acknowledgement the research was carried out with financial support from the project támop-4.1.1.c-12/1/konv-20120015. references [1] the stockholm convention on persistent organic pollutants (stockholm convention) 2014 cchm.pops.int figure 4. the concentration of acetamiprid in the second layer in the case of normal use (a unit equals 2 m). figure 3. changes in absorbence spectra during biological treatment with (a) and without additional substrate (b) (optical length: 0.5 cm). a ds or be nc e groundwater remediation with biological and photocatalytic methods 43(1) pp. 39–43 (2015) doi: 10.1515/hjic-2015-0007 43 [2] solymosné majzik, e.: determination of concentration of pesticide active ingredients in groundwater and surface water samples applying various spe methods, phd thesis (university of pannonia, veszprém, hungary) 2006 (in hungarian) [3] khan, f.i.; husain, t., hejazi, r.: an overview and analysis of site remediation technologies, j. environ. mgmt., 2004 71, 95–122 10.1016/j.jenvman.2004.02.003 [4] fujishima, a.; honda, k.: electrochemical photolysis of water at a semiconductor electrode, nature, 1972 238, 37–38 10.1038/238037a0 [5] fujishima, a.; rao, t.n.; tryk, d.a.: titanium dioxide photocatalysis, j. photochem. photobiol. c: rev., 2000 1, 1–21 10.1016/s1389-5567(00)00002-2 [6] cazoir, d.; fine, l.; ferronato, c.; chovelon, j.m.: hydrocarbon removal from bilgewater by a combination of air-stripping and photocatalysis, j. hazard. mat., 2012 235–236, 159–168 10.1016/j.jhazmat.2012.07.037 [7] irawaty, w.; edi soetaredjo, f.; ayucitra, a.: understanding the relationship between organic structure and mineralization rate of tio2-mediated photocatalysis, procedia chem., 2014 9, 131–138 10.1016/j.proche.2014.05.016 [8] esplugas, s.; giménez, j.; contreras, s.; pascual, e.; rodrı́guez, m.: comparison of different advanced oxidation processes for phenol degradation, water res., 2002 36, 1034–1042 10.1016/s0043-1354(01)00301-3 [9] malato rodríguez, s.; blanco gálvez, j.; maldonado rubio, m.i.; fernández ibáñez, p.; gernjak, w.; oller alberola, i.: treatment of chlorinated solvents by tio2 photocatalysis and photo-fenton: influence of operating conditions in a solar pilot plant, chemosphere, 2005 58, 391– 398 10.1016/j.chemosphere.2004.09.043 [10] dombi, a., ilisz, i.: advanced oxidation processes in environmental chemistry, in novel results of chemistry (akadémiai kiadó, budapest, hungary) 2000, vol. 86 (in hungarian) [11] jolánkai, m., birkás, m.: global climate change impacts on crop production in hungary, agriculturae conspectus scientificus, 2007 72, 17– 20 [12] gribovszki, z.: fundamentals of agricultural infrastructure 7, drainage as a part of complex water management: basics of hydrology and hydraulics (university of west hungary, sopron, hungary) 2010 (in hungarian) hungaru\njournal of industrial chemistry veszprem vol. 30. pp. 87-93 (2002) kinetic study and mathematical modelling of growth of arthrobacter oxydans cells covalently immobilized on cellulose granules l.yotov a1 , i. tsibranska, i. lalov1 , m. karsheva and m. krysteva 1 (dept. of chemical engineering, university of chemical technolugy and metallurgy sofia; "kl.ochridsky" bul. 8, 1756 sofia, bulgaria 1dept. of biotechnology; university of chemical technology and metallurgysofia; "kl.ochridsky" bul. 8, 1756 sofia, bulgaria) received: february 12,2001 the kinetics of covalently immobilized cells' growth in comparison with that of free cells was studied experimentally and numerically. cells of arthrobacter oxydans were covalently immobilized to regenerated and partially deacetylated acetylcellulose granules consecutively activated with sodium periodate, urea and formaldehyde. the comparison of the data obtained showed that free and immobilized cells have the typical three phases of growth. the initial phase of free cells lasted about 10 hours and for immobilized ones ~ not more then 5 hours. the second exponential phase showed much more significant difference for both types of cells. the curve for immobilized cells is steeper than that of free oyes and attains twice faster the third phase. the glucose utilization by immobilized cells was completed about the 15th hour, for the free cells about 25th hour. the reproducibility of the data was quite satisfactory {mean error 7.42 %). a mathematical model was used to describe and analyse the effect of the different mass transfer and reaction kinetic parameters. it shows that replication of immobilized cells is a complex process including mother cells and the new born ones. the application of the results of this study could be concerned with the use of the immobilized cells as a permanent source of free ones. they are viable and possess a long lasting capacity for urea transformation. keywords: arthrobacter oxydans, covalent immobilized cells of arthrobacter oxydans, mathematical modelling of immobilized cells' growth introduction immobilization of microbial cells for the production of useful products has been widely studied in recent years [1]. the use of immobilized cells instead of immobilized enzymes has many advantages like avoiding the stage of isolation and purification of the enzyme, addition of co­ factors and increasing the stability of enzyme system. that is the reason of the intensive development of immobilization of intact cehs to insoluble carriers over the last years. microbial cells can be immobilized to insoluble matrices by adsorption [2], microcapsulation [3] or covalent binding [4]. the later technique has not been widely used because of toxic nature of the reagents used for binding, causing the cells' death even during the immobilization. on the other hand the covalent binding offers advantages concerning the absence of diffusion limitations and allows the direct contact between the bound cells and the substrate solution which results in an intense (fast) controlled reaction. a new method for immobilization of proteins to cellulose derivatives was reported recently. it involves subsequent treatment of the matrix with sodium periodate, urea and formaldehyde [5] and was also applied to covalent binding of a.simplex cells [6]. the aim of the present investigation was to study the growth kinetics of covalently immobilized cells to insoluble matrices via hydroxymethyl groups and to compare it with free ones and to propose a mathematical model properly describing the process. for these studies we choose the covalently immobilized cells of arthrobacter oxydans. 88 materials and methods chemicals urea, formaldehyde, potassium hydroxide and sodium periodate were supplied by merck (germany); potassium dihydrogen phosphate, sodium hydrogen phosphate and glucose were obtained from reanal (hungary). all other chemicals were of reagent grade or better. granules of triacetylcellulose were obtained by treatment of waste film tapes as described elsewhere [8]. microorganisms and culture conditions arthrobacter oxydans strain 1388 from the national collection for industrial and cell cultures (bulgaria) was cultured on solid agar medium for 48 hours at 28°c. after this incubation colonies were picked off and suspended in meat peptone broth containing 1 g/1 sorbitol and incubated for 48 hours at 28°c. after centrifugation (20 min, 3500 g), the cell mass was suspended in nutrient medium according to schneider and kaltwasser [7]. the composition of the nutrient media in respect to 11 quantity was 9 g na2hp04.12 h20, 2g kh2p04.7h20, 0.7 g mgs04.1h20, 0.02 g cach.2h20, sg of glucose, 0.3 g of urea and 0.002 g nicl2. the mineral trace elements solution for 100 ml was as follows: 0.3g feci3.6h20, o.lg nazmo04.2h20, 0.4g hb03, 1.34g cac12.2h20. one ml of this solution was added to a litre of nutrient medium. the ph of the sterilized nutrient medium was 7 .0. the cultivation of free cells was done in a water bath shaker at 28°c for 48 hours. the cell mass was separated by centrifugation, washed with o.im phosphate buffer (ph 7) and stored at 4°c. immobilization procedure treatment of the cellulose carrier acetylcellulose granules with diameters in the range 1 3 mm were subjected to partial hydrolysis of acetyl groups according to chen and tsao [8]. the quantity of 0.28 g dry beads was treated with o.im koh and 5% (v/v) ethanol at hydromodule 1:15 for 24 hours. 1 ;te urea derivative was then prepared by oxydation of the cellulose granules with 0.25m sodium periodate at 22± 2°c at ph 5 for 2 hours in darkness. after complete removal of sodium periodate by filtration and washing the granules were treated with 15% urea solution for 14 hours in presence of 0.9% (v/v) sulphuric acid at 60°c according to krysteva et al. [sj. the beads were washed with water in a buchner funnel until a neutral reaction of the rinsing water. the resulting urea derivative of the regenerated cellulose acetate beads contained 3.3 % nitrogen. this urea derivative cellulose granules were activated in 100 ml of 0.1 n phosphate buffer ph 7.5, containing 12.5% (v/v) formaldehyde and stirred for four hours at 45°c in a closed vessel. then the granules were thoroughly washed until the complete absence of formaldehyde in the rinsing water. immobilization of arthrobacter oxydans the activation procedure of the carrier was followed by an immediate addition of arthrobacter oxydans cell suspension with a concentration of 50 mg/ml. the binding was carried out at ph 8 and careful stirring at a temperature 20°c for 20 hours. the cell loaded granules were washed with water and 0.1m phosphate buffer (ph 7) until complete absence of free cells in the rinsing water, followed spectrophotometrically at 660 nm wave length. after the immobilization procedure the obtained biocatalysts granules were resuspended in the culture medium as already described and incubated for 45 hours to initiate their replication. analytical procedures measurement of cell growth biomass of free cells and those, produced by immobilized cells was measured spectrophotometrically at 600 nm wave length (perkinelmer spectrophotometer, lambda 2, germany). cell growth was also determined by the dry cell weight according to mallette [10]. the samples were dried until a constant weight at 105°c. the analysis were checked up by determination of protein content, using modified lowry's method [13]. enzyme assays urease activity of free and immobilized cells was determined according to melnyk and olean [12]. the enzymatic reaction was carried out in batch vessel with magnetic stirrer. after 15 min the reaction was interrupted by cooling the mixture in 2°c bath. an aliquot (i ml) was tested for ammonia presence using nessler reagent. glucose determination the amount of the glucose consumed was determined colorimetricauy at 540 nm 1ly the dinitrosalicylic acid method according to miller [13]. ~5 r:: 0 '.;::> i!! 1: 4 0) 0 r:: 0 0 3 0) g 'iii .0 2 ::l (/) 10 15 20 25 30 time,(h) fig .i a kinetic of substrate utilization at initial concentrations for the free cells: 40.0 mg/1 (1); 118 mg/g (1 ')and for the immobilized cells: 38.4 mg/1 (2); 126mg/l (2') s ~1o 15 20 25 30 time,(h) fig.j b kinetic of cells' growth at initial concentrations for the free cells: 40.0 mg!l (1); 118 mg/g (1 ')and for the immobilized cells: 38.4 mg!l (2); 126mg!l (2') kinetic experiments the experiments on the kinetics of growth of free and immobilized cells of arthrobacter oxydans were performed by batch process in shake flask cultures at ph=7, temperature of 28°c under continuous aeration. during the experiments the biomass and substrate concentrations were measured every 2 hours. the decrease of glucose concentration was also followed. th~ cells of arthrobacter oxydans were seeded in 50 em cultural medium 3 this inoculate was us~ for kin~tic studies (15 em of the inoculate seeded m 150 em of nutrient medium). the initial concentration of dry cells was varied from 40 mgll up to 118 mg/1. the initial concentration of the immobilized cells was varied in the same range as for the free ones (from 38.4 mgll to 126 mgll). 89 1.150 ~1.25 >{ .r:: ~1.00 e 0) ~0.75 .q .00.50 10 15 20 25 30 time,(h) fig.2a reproducibility of substrate utilization for free cells: first experiment (1); second experiment (1') and for im­ mobilized cells: first experiment (2); second experiment (2') 10 15 20 25 30 time,(h) fig.2b reproducibility of cells' growth for free cells: first experiment (1); second experiment (1 ')and for immobilized cells: first experiment (2); second experiment (2') results and discussion batch experiments a set of experiments for monitoring of growth of free and immobilized cells of arthrobacter oxydans was done by analysing the biomass growth (fig.ja) and the substrate consumption (fig.jb). for both cases the three typical growth phases were observed but their duration for the free and the immobilized cells was different. as it could be seen in fig.}, the initial phase for the free cells was about two times longer that that of the immobilized ones. this difference becomes more significant for the phase of exponential growth. the curve of immobilized cells is much steeper than that of the free ones which results in twice faster reaching of the third phase. these observations are confirmed by monitoring of substrate consumption for the two types of ceus: the glucose utilization of the immobilized cells was completed at 90 fig.3 electronmicroscopic photographs of immobilized cells x 25000 about 15th hour and for the free ones about the 25th hour. to check the reproducibility of the results obtained, parallel experiments were done. the results of two of them are given in fig.2a and b. the obtained reproducibility of the data is quite satisfactory (mean error 7.42% ). the microscopic picture of immobilized cells of arthrobacter oxydans is presented in fig.3. it was found that the cells of a. oxydans are superficially well situated on the matrix which made us suggest the absence of diffusion limitations. in the same time their covalent binding is probably limited to permit them a free reproduction. the results for the growth of young cells produced by the immobilized ones confirm this suggestion. the urease activities of free, immobilized and new born cells, produced by immobilized cells were respectively: 0.325 mol!(min.g), 0.156 moll(min.g) and 0.327 moll(min.g), based on dry cells weight. these values remained almost constant after tenfold transformations after preinoculation of the immobilized cells in a nutrient medium. these results are better than those for escherihia coli oa5 cells with urease activity entrapped in alginate-poly-l-lysine-alginate .. microcapsules. in this case bacteria leakage has been found to occur when encapsulated bacteria were used for a four-cycle transformation [13]. in other investigations with immobilized fungi in nylon webs for enzymes production the successively repeated batch cultivations were 6 [9] or only 2 [14}. mathematical modelling first the free cells runs were analysed using the simple monod kinetic model: s jl = f.l. k s + s ' in order to obtain the parameters jam and k5• as a first approximation the experimental curves were fitted with a linear kinetics <i-;=ol and the obtained value of j.1m was confirmed by the one obtained from the linear part of the plot ln(x/x 0 ) vs. {t-t~a,) of the e:xf!frimental data. best results were found for j..tm= 0.2.h and t..,= 3h. obtained from the analysis of the experimental data of fig.2a and b. further fit of the experimental data with different values of ks confirmed the linear kinetics for the free cells growth (ks=o.ol). the plateau of the curve is mainly affected by the yield coefficient y, so from this part of the curve a value of y =0.24-0.27 was obtained. the results of the simulation are given on fig.5a, where a satisfactory correspondence between experimental and calculated data is observed. a mathematical model, proposed to describe the kinetic experiments with immobilized cells, should account for the reaction kinetics and mass transfer limitations in the reactor. first, the statement of the model is based on the following approximations: 1. the reactor is considered as a reactor with perfect mixing; 2. different kinetic parameters for the immobilized and the free cells is supposed, assuming a simple monod-type rate equation. 3. the enlargement of the beads size during the fermentation is negligible (i.e. particles of constant radius r are supposed) the following set of 4 balance equations per unit volume of the reactor will result: for the immobilized cells: where index r corresponds to immobilization on the particles surface. for the substrate on the surface of the granules: dsr =-_.!_ sr x +k '(s-s) dt y f-lm k + s r f r r sr r (2) the mass transfer coefficient across the liquid film around the particles is denoted by kr' for the substrate and km' for the cells, resp. for the free cells in the reactor: for the substrate in the reactor: the following initial conditions can be added: for t = 0: s = s0 ; sr = 0; x = 0: x = x · , r ro• (4) i.e. the influence of the free ceus initially in the broth is negligible. this set of equations can be further simplified, as the experimental data give some evidence about the absence of mass transfer limitation for the new-born cells. as mentioned in the previous paragraph, ~ 1,6 x 1,2 ~· §1 0,8 "' ~ 0,4 0 • • -1-kf.oos ~---2-kf.oi -3-kf.02 -4-kf.oj -5-kf.04 -6.kf.05 • exp :e 0~~~+-+-+-~~~~ 0 3 6 9 12 15 18 21 24 27 30 time,(h) fig.4al kinetic curves x(t) for different values of the mass transfer coefficient xr=0.126gll ,...... 1,6 :§ • • -0,9 x· 1,2 -0,8 ~ §1 0,8 ~ e 0,4 .9 -0,7 -0,6 -0,4 -0,2 • expl .d 0 0 3 6 9 12 15 18 21 24 27 30 time, (h) fig.4bl kinetic curves x(t) for different values of the specific growth rate xr=0.126gll 1,6 .-------------~ § x· 1,2 ~ §1 0,8 "' ~ 0,4 0 :e • • 0 3 6 9 12 15 1? 21 24 27 30 time,{h) · -kso.ol -ksoj -ks0.2 -ks0.3 -ks0.4 •exp fig.4cl kinetic curves x(t) for different values of the monod constant xr=0.126g!i microscopic pictures of the immobilized cells {as the one shown in fig.3) prove the constancy of the immobilized cells concentration, i.e.: dxr --=0 and xr =const = xro· (a) dt in such a situation a small or negligible mass transfer coefficient for the substrate is to be expected. this was verified by numerical experiments. taking into account eq.(a), eqs.(l) and (3) are reduced to one simple equation for the cells' growth of the immobilized and the new born free cells: dx s x sr ii + x (1') --;j/ = rm. k s + s f.l.mr. k :rr + s r ro ~ 1,2 ,------:;;;;~--iifl x .r::" ~ 0,8 §1 .i 0,4 .d 0+*~~--+--r~-~~-+--~ 0 3 6 9 12 15 18 21 24 27 30 time,(h) 91 -1-kf.oos -2-kf.ol -3-kf.02 -4-k£03 -5-kf.04 -6.kf.05 • expl • exp2 fig.4a2 kinetic curves x(t) for different values of the mass transfer coefficient xr=0.038g/l § 1,2 ,------:;~;;;::::~~'l x· .d' ~ 0,8 §1 ~ 0,4 :e -0.8 -0,7 -0,6 -0,4 -0,2 • expl • exp2 0 3 6 9 12 15 18 21 24 27 30 time,(h) fig.4b2 kinetic curves x(t) for different values of the specific growth rate xr=0.038g/i 0 3 6 9 12 15 18 21 24 27 30 time,(h) -i-kf00.5 -2-kf.ol -3-kf02 -4-kf03 -5-kf.04 -6,kf.05 • cxpl • cxp2 fig.4c2 kinetic curves x(t) for different values of the monod constant 1-xr=0.126g!l; 2 xr=0.038g/l eq.( 1') accounts for two parallel uniformly distributed volume sources of mass the reaction terms for the free and immobilized cells. for the free (the new born) cells we used the values of jim, k8 and y obtained before from the batch experiments with free cells .. the set of eqs.(l'), (3) and (4) was used in the simulations to illustrate the sensibility of the kinetic curves to variations of the model parameters, as shown in figs. 4al-4c2. in this case a slightly greater value of y r=0.3 was used a fact well coinciding with the experimental data, where a 5-10 % greater yield was found for the immobilized cells in comparison with the free ones. figs. from 4al to 4c2 are calculated for two different initial concentrations xr=0.038 and o.l26gfl, the initial 92 ~ 8.9 x c 0 'f 1.2 6~ e b 01 c:: ! 0.8 4 8 .s :§0.4 2! .0 :::1 (() 10 15 20 25 30 time, (h) fig.5a comparison between experimental and numerical results for free cells: biomass growth (1)experimental ~-j:) and numerical ( +) curves; substrate utilization 2 experimental (i0) and numerical (e) curves ~ ~ 1.6 8..91 c 0 x "" f 1.2 6~ cll g ~ 0.8 4 8 ~ n :§ 0.4 2'lii .g (() fig.sb comparison between experimental and numerical results for free cells: biomass growth (1) experimental (0) and numerical (ii) curves; substrate utilization 2 experimental (8) and numerical (a.) curves substrate concentration being s0=5-5.4 gil. on the same figures the experimental points are shown. the basic set of values for the parameters, used in the simulations was llmr.=0.6h-1 ·, ksr:::;q.2-0.3 gil. they were chosen as physically reasonable and allowing for a satisfactory description of the data with two different initial concentrations. as can be seen from fig.4al to fig.4c2, the increase of xr leads to stronger effect of the mass transfer coefficient kf ~ while the importance of 1j.m:r and ksr decreases. with fixed kr and greater immobilized cells source xro the effect of the mass " transfer between free and immobilized cells is greater. high mass transfer flux value makes the kinetic curve less sensible to variations of j.1mr and ksr. from the numerical data a value of kj=0.02-0.03 h-1 can be supposed. calculated on the base of the specific area of the grain it gives a value of kpl-1.5.10"3 crrjs. corresponding to small mass transfer resistance across the fluid film around the particles. the numerical results were also examined tvwards the separate importance of each one of the two reaction terms in eq.( 1'). fi~ 6 shows the calculated specific growth rate for the mother and the new born cens. according to eq.(l') and the specified values of the kinetic parameters f.tm, jlmr~ k5• ksr• y and y r· it can be seen that until the 5th hour the two terms are comparable and equal. because of the small amount of reproduced new cells. after the 5th hour the curve increases sharply and the rate of the process is mainly controlled by the new born cells. after the 12th hour it drops sharply because of the substrate exhausting. in the case of substrate addition it 0.18 bfc 0.16 (l) ~ ~ 0.12 e 0) ,g o.oa '6 8. 00 0.04 0.0 5 10 15 20 25 time, {h) fig.6 specific growth rates for newborn (1) and immobilized (mother) cells (2) should be increasing with the time. these results are in agreement with the experimental evidence. they allow for the description of the status of immobilized (mother cell), as well as the replication status of the new born cell in the nutrient medium and do explain the steeper kinetic curves for immobilized cells (fig.2a and b) in comparison with those obtained from experiments with only free ones (fig.] a and b). a satisfactory description of the experimental results in both cases was observed, as shown in fig.5a and b. the correspondence is poorer in the initial part of the curves (as expected for the lag­ phase) and better for the part of the exponential cell growth. conclusions from the results obtained with covalently immobilized arthrobacter oxydans cells the following mechanism of cell growth could be proposed: the kinetics of growth for immobilized cells is different and their replication is faster than those of the free ones. the complex process of parallel reproduction of mother cells and new born ones can be satisfactorily described by a monod kinetics. mass transfer resistance in the liquid film around the particles is small and can be practically neglected. the immobilized cells are viable and active, possess a long lasting capacity for urea transformation and can be used as a permanent source of free ones. it seems that the special feature of the cell wall of the gram-positive microorganisms like arthrobacter oxydans allows their covalent binding by this method. symbols kr' mass transfer coefficient, m.s-1 ks monod constantt g.l-1 s substrate concentration. g.r1 t time~ h x dry cells concentration per l fermentation medium. g.r1 y yield coefficient, dry cell mass pef dry mass of total medium, greek letters j1, specific growth rate, h-1 indices m maximum r at granules surface references 1. shashi b. m. and lpsita m.: phytochemistry, 1993, 34,883-898 2. haapala r., parkninen e., suominen p. and linko s.: enzyme and microbial techno!., 1996, 18,495-501 3. uwnska a., deckwer w. and hecht v.: biotechnol. bioeng., 1995,46, 80-87 93 4. krischke w., shroder m. and trosch w.: appl. microbiology biotechnology, 1991, 34, 573-578 5. krysteva m., blagov s. and sokowv t.: j. of appl. biochemistry, 1984, 6, 367-373 6. krysteva m. and grigorova p.: enzyme microb. technol., 1987, 9, 538-541 7. schneider j. and kaltwasser h.: arch. microbiol., 1984, 139, 355-360 8. chen l. f. and tsao g. s.: biotechnol. bioeng., 1976, 18, 1507-1516 9. kumakura m. and kaetsu i.: biotechnol. appl. biochem., 1986, 8, 195-200 10. malletie m.: methods of microbiology,(eds. t. r.norris and d. w.ribbons) v.1, academic press, new york, pp. 521-566, 1969 11. schacterlee g. r. and pollak l. r.: anal. biochemistry, 1973,51,654-656 12. melnyk j. and olean y.: bioreactors with immobilized enzymes and cells ( ed.moo-young m.) elsevier appl. sci., london and new york, pp101l10, 1988 13. miller g. l.: anal. chem., 1969, 31, 426-428 14. santoyo a. b., rodriquez b. j., carrasco j. l., gomez g. e., rojo a. i. and teruel l. m.: enzymeandmicrob. technol., 1996,19,176-180 page 89 page 90 page 91 page 92 page 93 page 94 page 95 page 1 page 2 page 3 page 4 page 5 page 6 page 7 page 8 page 9 page 10 page 11 page 12 page 13 page 14 page 15 page 16 page 17 page 18 page 19 page 20 page 21 page 22 page 23 page 24 page 25 page 26 page 27 page 28 page 29 page 30 page 31 page 32 page 33 page 34 page 35 page 36 page 37 page 38 page 39 page 40 page 41 page 42 page 43 page 44 page 45 page 46 page 47 page 48 page 49 page 50 page 51 page 52 page 53 page 54 page 55 page 56 page 57 page 58 page 59 page 60 page 61 page 62 page 63 page 64 page 65 page 66 page 67 page 68 page 69 page 70 page 71 page 72 page 73 page 74 page 75 page 76 page 77 page 78 page 79 page 80 page 81 page 82 page 83 page 84 page 85 page 86 page 87 page 88 page 89 page 90 page 91 page 92 page 93 page 94 page 95 page 96 page 97 page 98 page 99 page 100 page 101 page 102 page 103 page 104 page 105 page 106 page 107 page 108 page 109 page 110 page 111 page 112 page 113 page 114 page 115 page 116 page 117 page 118 page 119 page 120 page 121 page 122 page 123 page 124 page 125 page 126 page 127 page 128 page 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plug flow reactor t. renganathan and k. krishnaiah (department of chemical engineering, indian institute of technology madras, chennai 600 036, india) received: december 30, 2001; revised: july 8, 2002 ~is paper. pro~es the ~athem~tical equivalenc~ of infinite mixed flow reactors in series and a plug flow reactor. in the ?me d~mam usmg an impulse mput. the proof is mathematically less complicated, compared to the previous statements m the literature. keywords: chemical reactors, mixed flow reactor, plug flow reactor, residence time distribution, convergence introduction the basic concept, that infinite mixed flow reactors (mfr) in series give the same performance as a plug flow reactor (pfr) is well known in chemical engineering for many years. but, only a few mathematical proofs of this concept are available in literature. villermaux [1] proved the convergence in the laplace domain. molin and gervais [2] showed the convergence in time domain with step input using limiting values of incomplete gamma function. chen [3] used asymptotic equation for treatment of incomplete gamma function and proved the convergence in time domain with step input. in this work, the mathematical equivalence of a plug flow reactor and infinite mixed flow reactors in series is shown in time domain using an impulse input (dirac delta function). the mathematical complexity is less, compared to the previous works. proof of equivalence a series of mixed flow reactors (mfrs) with delta input are shown in fig.l. the dimensionless exit age distribution function, e( 8), for n tanks in series can be derived easily [4] as n(n8)n -le -no e(b) = (n -1)! (l) where 8 = th: is the dimensionless time, t is the time variable and -r the average residence time of the entire system. the response curves, eq.( 1 ), for different number of mfrs in series (n = 1, 2, 5, 20, 50, 100, 200, 500 and oo) are shown in fig.2. as the number of tanks approaches infinity, the response approaches an impulse output with a time lag of average residence time r ( 8 = 1) of the entire system. this response is characteristic of a piug flow reactor with delta input. by definition of plug flow, each cross-section should correspond to an ideal mixer. therefore intuitively a plug flow reactor can be considered as infinite mixed flow reactors in series. this is validated here mathematically, by proving that the function e((}) tend~ towards a dirac delta function with point of impulse at e = 1, as n tends towards oo, which is the response of a plug flow reactor to an impulse input. using stirling's approximation, n! =nn e-n .j21rn and rearranging, eq.( 1) can be written as e{-n(-in9-l-t6)-ln9+(112)1nn) e(fj)= .fbi (2) (3) to show that eq.(3) approaches a dirac delta function when n tends towards infinity, the following have to be proved [5]: such that e(fl) = oo =0 ... 8=1 o:t=l j e(8)dfj = l (4a) (4b) 192 2 fig.l schematic ofmfrs in series at 8= 1, fromeq.(3), e(8)= jn en n therefore as n approaches=, e((j) tends towards oo. (5) 109 8 7 6 & 200 ~ 5 4 for values of e in the intervals [0,1) and (1, oo], -ln8 -1 +8 is always positive. therefore, the leading term in the exponent of eq.(3) i.e. -n(-ln8 -1+8) tends towards·oo as n approaches oo. so in these intervals, e((j) tends 0 -~:=.::~~~!zll_:c~ss~~=~ towards 0 as n tends to =. now, since negative values ofe are inadmissible, j e(o)d8 = j e(8)d8 = ~ j 8n-te-ne d8 (6) _.,.. o (n -1)! o using the definition of gamma function [5], j= 8 n-1e-ne db = r(n) = (n -1)! nn nn 0 (7) therefore, from eq.(6), je(o)do = 1 n?.1 (8) 0 thus for infinite mfrs in series, the function e( 8) converges to a dirac delta function characteristic of a plug flow reactor. conclusion using an impulse input, the equivalence of a series of infinite mixed flow reactors to a plug flow reactor is proved mathematically in the time domain. the proof is less complicated compared to the previous works in the literature. symbols e( 8) dimensionless exit age distribution function n number of mfrs in series t time variable, s 0 0.5 1 8 1.5 fig.2 rtd curves for mfrs in series greek letters e dimensionless time 1: average residence time, s r(n) gamma function references 2 1. villermaux j.: genie de la reaction chimique, tee et doc, lavoisier, paris, 1993 2. molin p. and gervais p.: aiche j., 1995, 41, 1346-1348 3. chenw. y.: hung. j. ind. chern., 1995,23,21-24 4. levenspiel 0.: chemical reaction engineering, 3rd edn., john wiley & sons, new york, pp. 321-323, 1999 5. wylie c. r.: advanced engineering mathematics, 3rd edn., mcgraw-hill, new york, 1966 page 193 page 194 microsoft word inner cover.docx the hungarian journal of industry and chemistry (hjic) formerly (until 2012) the hungarian journal of industrial chemistry the hjic is an international periodical that focuses on results of fundamental and applied research in the fields of • biotechnology • chemical engineering science • chemical processes • energetics • environmental chemistry • environmental engineering & technology • industrial management • material science • mechanical engineering • mechatronics • process & system engineering • recycling in the form of original papers, reviews, short communications, and conference proceedings written in english. editorial board editor-in-chief: róbert k. szilágyi department of chemistry and biochemistry, montana state university, bozeman, mt, u.s.a. honorary senior editor: géza horváth department of chemical engineering science, university of pannonia, veszprém, hungary associate editors: jános abonyi department of process engineering, university of pannonia, veszprém, hungary dezső boda department of physical chemistry, university of pannonia, veszprém, hungary norbert miskolczi mol department of hydrocarbon and coal processing, university of pannonia, veszprém, hungary dóra rippel pethő department of chemical engineering science, university of pannonia, veszprém, hungary editors: lászló bartha mol department of hydrocarbon and coal processing, university of pannonia, veszprém, hungary katalin bélafi-bakó research institute of bioengineering, membrane technology and energetics, university of pannonia, veszprém, hungary peter czermak institute of bioprocess engineering and pharmaceutical technology, mittelhessen university of applied sciences, giessen, germany dénes fodor institute of mechanical engineering, university of pannonia, veszprém, hungary maria gavrilescu department of environmental engineering and management, gheorghe asachi technical university of iasi, romania lászló gubicza research institute of bioengineering, membrane technology and energetics, university of pannonia, veszprém, hungary jenő hancsók mol department of hydrocarbon and coal processing, university of pannonia, veszprém, hungary jiří klemeš centre for process integration and intensification, university of pannonia, veszprém, hungary zoltán kovács department of management, university of pannonia, veszprém, hungary jános kristóf department of analytical chemistry, university of pannonia, veszprém, hungary istván szalai institute of physics and mechatronics, university of pannonia, veszprém, hungary ferenc szeifert department of process engineering, university of pannonia, veszprém, hungary jános szépvölgyi research centre for natural sciences, university of pannonia, veszprém, hungary imre tímár institute of mechanical engineering, university of pannonia, veszprém, hungary gyula vatai department of food engineering, corvinus university of budapest, hungary gábor veress federation of technical and scientific societies – mtesz budapest, hungary ibolya zsoldos department of material science and technology, széchenyi istván university, győr, hungary editorial office: university of pannonia, p.o. box 158, veszprém, 8201 (hungary) tel.: +36 (88) 624-746, e-mail: hjic@almos.uni-pannon.hu; web: hjic.mk.uni-pannon.hu felelős szerkesztő: szilágyi róbert károly nyelvi lektor: matthew chen kiadja: pannon egyetem, 8200 veszprém, egyetem u. 10. levélcím: h-8201 veszprém, postafiók 158, tel.: (88) 624-000 felelős kiadó: a pannon egyetem, mérnöki kar dékánja hung. j. ind. & chem. 2013, vol. 41(2), pp. 83–136 table of contents review corrosion protection with ultrathin graphene coatings andrás gergely, tamás kristóf ......................................................................................... 83–108 articles investigations of bio-gasoil production péter solymosi, zoltán varga, jenő hancsók ................................................................ 109–114 the energy balance of separation opportunities in microalgae technologies zoltán hodai, dóra rippel-pethő, géza horváth, lászló hanák, róbert bocsi ..... 115–118 solid-liquid extraction of chlorophyll from microalgae from photoautotroph open-air cultivation éva molnár, dóra rippel-pethő, róbert bocsi ............................................................... 119–122 calculating the electrostatic potential profiles of double layers from simulation ion density profiles dezső boda, dirk gillespie .................................................................................................. 123–130 degradation of reinforced and unreinforced waste polyamides during mechanical recycling jános sója, nórbert miskolczi ........................................................................................... 131–136 hungarian journal of industry and chemistry veszprém vol. 41(2) pp. 83–108 (2013) corrosion protection with ultrathin graphene coatings: a review andrás gergely ! and tamás kristóf department of physical chemistry, institute of chemistry, university of pannonia, egyetem u. 10., veszprém 8200, hungary !email: gergelyandras@almos.uni-pannon.hu developments in surface treatment or finishing, and modification of structural metals have probably never been so dynamic than in recent years due to the need for new approaches to efficient corrosion protection. the application of coatings is a strategy to be followed to physically separate corrosive environments from metal surfaces. the overall protection efficiency depends on the coating’s barrier properties. traditional alternatives to coating suffer from inefficient physical protection in cases of low film thicknesses and at elevated temperatures. one of the most advanced options is to apply ultrathin atomic films to ensure complete separation of the metallic surface from the fluid media. among the numerous materials and methods, exceptional chemical resistance and high domain size make graphene a promising candidate for constituting ultrathin coatings with interfacial atomic layers adherent and homogeneous coverage to feature firm barrier behaviour. this review focuses on the major efforts with notable results and points out some short comings that must be resolved to serve as a basis for further progress in this field. keywords: ultrathin coatings, graphene, metals, corrosion protection introduction nowadays graphene (gr) is undoubtedly of great interest in many fields of science and engineering. the attention is due to its unique structure, electrical properties [1, 2], efficient heat spreading [3], wetting transparency [4], surface wetting tenability [5], and high reflectivity (mirrors for the beams of he and h2) [6]. the gr’s practical impermeability to gases [7-9] is a result of the combination of its strong structure (carbon bond energy and intrinsic strength are 4.9 ev and 43 n m-1, respectively) and its morphology that makes gr to be the thinnest and most impermeable membrane [10]. in addition, because of its chemical inertness [11], especially against oxidation [12, 13], it is highly resistant to corrosion [14] under conditions where other substances would undergo chemical reactions [15, 16]. as a lightweight mono-atomic coating, gr can function as one of the most advanced electronand ion-transfer barriers at the metal-electrolyte interface, without notably altering optical properties and thermal conductivity of the substrates. gr on metal surfaces is expected to afford oxidation resistance [11] based on its airtight balloon behaviour associated with its excellent barrier nature against oxygen diffusion [7]. nevertheless, coherence, and uniformity of gr coatings are apparently vital to achieve good corrosion protection. in accordance with general expectations, electrochemical properties of gr [17, 18] and its coated derivatives were extensively investigated. the main results achieved recently are described in the following sections that are organised from the viewpoint of synthesis techniques and application purposes. pure graphene coatings direct chemical vapour deposition (cvd) on metal surfaces early studies were inspired to synthesise full surface covering gr films of the highest domain (single sheet) size and integrity to exert impermeability over macroscopically large surfaces. later findings proved the viability of this concept as interfacial construction of thin layers is a promising way to provide durable corrosion protection for metallic substrates [19]. generally, coatings play a vital role in improving surface quality and protection of substrates, since much effort has been made to produce films featuring excellent properties. graphene is certainly one of the most prominent representatives of this kind and subsequently has been studied in almost all scientific and engineering fields. this new generation material has been a novel subject to incorporate into the latest corrosion protecting coatings. achievements in utilising gr as a pure and composite coating were first reviewed by tong et al. [20]. the synthesis and functionalisation of gr were briefly discussed and future perspectives suggested. 84 the simplest way is to grow gr directly on metal surfaces, even though this strategy does not provide the most protective coatings due to low adherence of the inorganic layers as consequence of weak interaction. by direct cvd, metals like nickel [21], cobalt [22], iridium [23], ruthenium [24] and copper [21, 25-27] were coated with gr (on large areas in certain cases) [25] using methane or acetylene as a carbon source [28, 29]. deposition kinetics of carbon and the formation of gr layers on copper were thoroughly explored; surface mediation theory was proved when poly-crystalline films were characterised with the domain size of 10 µm2 [30]. except for assessing the influence of grain orientation, the effect of other growth parameters was estimated. the most relevant findings are as follows: 1. the density of gr nuclei decreased, conversely flake domain size increased as temperature increased and partial pressure of the carbon source decreased. 2. when the pressure dropped below a critical threshold then no gr nucleation was observed and film formations terminated before reaching full surface coverage. 3. to achieve complete surface coverage, the partial pressure of methane must have been increased above 500 mtorr then full coverage was reached within 2 to 3 min. only a supersaturated surface relaying on a critical threshold of partial pressure ~285 mtorr was suggested to drive the formation of fully coated copper substrates with a continuous layer of gr flakes. thus, carbon nuclei formed in the first step under a lower pressure followed by a second step of nuclei growth at a higher pressure, promoting full surface coverage. the effects of these parameters coupled with the investigation of the orientation of metal crystals on gr domain size were quantitatively evaluated at low temperatures [31]. the activation energy for gr nucleation under atmospheric pressure was noticeably higher (9 ev) than under low-pressure cvd procedures (4 ev). such a difference was attributed to copper sublimation at low pressure, because copper evaporation probably has a decisive impact on the desorption rate of carbon from the surface. copper evaporation is restricted under atmospheric pressure, so the activation energy is assigned to the desorption of carbon clusters. close to the melting point of copper, large single-crystal gr synthesis was proposed at the highest possible temperature (probably to maintain the highest rate of interfacial mass-transfer, diffusion coefficient of the decomposed and fragmented precursor agents). by following these principles, single gr crystals with a domain size of ~1 mm could be synthesised. the nucleation density was higher on (111) than on (100) and (101) surfaces without any identifiable preference at higher temperatures [32]. under carefully optimised conditions, continuous films of some layers were obtained on polycrystalline nickel without void areas at the flake boundaries [21]. in that case, ambient pressure cvd was to grow gr films of 1-12 layers, with flake sizes of up to 20 µm for singleand bilayers (bls). an ultra high vacuum (uhv) chamber was not needed [33, 34] to finely balance nucleation and growth processes, instead, thermal annealing was employed leading to the emergence of single-crystalline nickel with grain sizes of 1-20 µm. grain surfaces became atomically flat with some terraces and steps similar to single-crystals usually used for epitaxial uhv experiments and gr growth took place probably via the precipitation of carbon in the metal. because metallic grains may independently affect film thickness as a result of the high density of atomic steps at grain boundaries, multi-layer (ml) nucleation occurred mainly at those areas. by using atmospheric pressure cvd, high quality gr was grown on copper, eliminating all the major difficulties associated with the low-pressure method. parameter optimisation involved evaluating the influence of the thickness, purity, morphology and crystallographic orientation of the metal foils on growth rates and the number of gr layers. scanning electron microscopy (sem) images illustrating gr flakes on polished foils besides xrd patterns of annealed foils are presented in fig.1 showing large copper domains on nr foils. the effects of copper impurities on the density of bilayers are signified; complete surface coverage on aa2 (the purest foil (99.999%) without double layers), aa1 and nr. in fig.2, gr quality is presented at various distances along the tube reactor. the methane concentration was higher at the inlet leading to a greater abundance of mls (darker islands in the images). gradual increase of concentration resulted in the formation of single-layer (sl) gr growth over the entire length. a constant methane concentration yielded a high percentage of mls at the inlet, incomplete coverage in the middle and separated single domains (seen as darker islands) at the outlet. as a method of surface pre-treatment, electropolishing [36, 37] in phosphoric acid seemed to be a good choice to achieve an appropriate degree of surface cleaning and minimised roughness. acetic acid was highly efficient at cleaning the copper surface, but only capable of removing oxidised species without any further etching. etching with ferric chloride solution generally gave similar results to electropolishing despite the greater roughness of the fecl3 treated copper foils. this was probably due to the considerable scale of copper recrystallisation during annealing at temperatures close to the melting point of copper before the cvd process, leading to the evolution of a smoother surface with a low density of defects serving as nucleation sites. additionally, the growth rate was estimated depending on the purity and crystallographic orientation of copper but by far not as much as the partial pressure of hydrogen, because the amount of dissolved hydrogen depends less on the thickness of the copper substrate. crystallographic orientation was found to be an important factor, since the growth rate on the surface of substrates characterised by miller indexes (100) was faster than on (111) surface under ambient pressure. in contrast, at low pressure and temperature the (111) surface facilitates the fastest growth rate [38]. furthermore, optimal conditions to achieve full surface covering films with the minimum proportion of mls might greatly vary with purity of the metal specimens. high purity substrates contribute to the formation of sl 85 films, and low purity metals support the evolution of multi-layer (ml) gr coatings. due to the multiple aspects of the reaction mechanism, optimal conditions for long foils are related to low and varied concentrations of carbon sources along the tube reactors, similarly to the application of temperature gradients (furnace dimensions and its relation to foil size) as well. figure 1: sem images illustrate (a) gr growth rate on polished aa1 and polished nr foils. xrd of annealed aa1 shows (100) orientation, the nr foil with the majority of (111) with smaller contributions from (110) and (311); (b) the effect of copper impurities on the density of bilayers [35] (republished by courtesy of the publisher, elsevier) figure 2: gr films at various distances along the cvd reactor used at atmospheric pressure. (a) gradual methane concentration, single-layer gr growth over the tube reactor; (b) multilayers at the inlet, incomplete surface coverage in the middle and separated single domains at the outlet [35] (republished by courtesy of the publisher, elsevier) 86 the gradual increase of methane concentration from 30 to 100 ppm in the mobile phase helps resolve the changing rate of activated carbon production [39]. because methane concentration near the outlet increases slowly as a result of thermal decomposition and deposition, the main purpose of the gradually increasing methane concentration was to minimise bilayer growth at the inlet over the synthesis duration and to ensure full surface coverage near the outlet with the highest concentration of the carbon source. in fact, optimisation in the case of the atmospheric pressure cvd is more complicated than vacuum ones, which process in long tube chambers with small foils. a steady methane concentration at the inlet surely results in an increasing proportion of mls at the inlet and incomplete coverage at the outlet, with visibly separated flake boundaries. the initial methane concentration of less than 30 ppm exclusively led to sl gr at the inlet. high quality gr grows with >99% monolayer coverage and in some cases films consisted of flake sizes of around 100 µm. high temperature etching with oxygen led to the visualisation of inter-domain boundaries as etching started at these boundaries and expanded into domains in a dendritic pattern, leaving diagonal stripes etch-free. efficient corrosion resistive film properties were reported when experiments were made with samples exposed to air at 300 ºc, showing no sign of oxidation (oxygen enrichment in the metallic phase) over gr coated areas in comparison to bare substrates. according to a similar preference, growing gr layers on copper is favourable, because copper does not dissolve carbon as much as nickel at high temperatures. however, it is also possible to grow mls with highly ordered crystalline structures suing atmospheric cvd with controlled film thickness [40]. both pure nickel and copper were covered with cvd grown gr films detected as covering the majority of the metals in a sl form besides some areas of double and fragmented mls (less than 5% of the coating) [41]. an optical micrograph and raman map with the respective raman spectra obtained from the ni–gr and cu–gr surfaces are presented in figs.3 and 4, respectively. electrochemical tests indicated that such coatings substantially reduced the corrosion rate of the substrates. by raman spectroscopy investigation, sl gr showed sharp g (1580 cm-1) and 2d (2650–2700 cm-1) bands with a small g/2d ratio, whereas ml gr with a high g/2d ratio and an altered, less sharp 2d band were detected. hence, 80 and 60% of the copper/nickel surface was covered with gr as a singleor few-layers coating without uniformity on nickel. scanning electron micrographs of the samples showed different thicknesses of the films with various scales of folding, full of wrinkles and edges. thus, the overall conclusion was reached that coherent sl gr is hard to obtain by direct deposition processes. immersion type corrosion tests indicated open circuit potentials (ocps) or free corrosion potentials of copper and nickel shifted towards the positive potential region. the electrochemical test conditions are summarised in table 1. a potential ennoblement of about 0.3 v was measured for the corroding system of nickel/gr and a cathodic shift of ~0.2 v observed with coated copper samples. the cathodic reduction processes were affected, inhibited by the gr layer on copper and the rate of anodic half-reactions was apparently reduced near the steady free corrosion potential. however, during extended linear potential scanning gr/nickel showed higher anodic currents than uncoated substrates opposed to the modified copper that exhibited no changes in the anodic branch after gr deposition. as an oxidation barrier for liquid and liquid–vapour phase-change cooling systems almost the same heat transfer efficiency was reported using bare and gr/copper surfaces in liquid-phase and two-phase thermal performance tests [42]. after thermal treatment, figure 3: optical micrograph, raman map of ~2700 cm–1 peaks and respective raman spectra of the areas on the ni–gr surface [41] (republished by courtesy of the publisher, elsevier) 87 analysis revealed oxide formation on the entire surface of bare copper and limited oxidation at grain boundaries on the coated substrate. in conclusion, few gr layers acted as a protective layer even under vigorous flow conditions near the boiling point of the fluid phase. graphene prepared by microwave (mw) assisted cvd protected substrates from chemical oxidation when samples were heated under atmospheric conditions in a sequential multi-step procedure with dwelling times from 15, or 30 min to 1 h [43]. a very low degree of chemical oxidation of gr over copper was indicated by xps and the presence of cuprous oxide was found on the entire surface of bare specimens. there are special applications such as steering and focusing elements for neutral atomic and molecular beams in de broglie microscopes [44]. these mirrors utilise the quantum reflection of an atomic beam on metal surfaces since interaction volume is strictly limited to an extremely thin atomic layer of the metals. oxidation and any other form of corrosion or adsorption of atmospheric gases might well lead to far lower reflectivity of the metallic surfaces, and the coatings of more than a few atomic layers are unacceptable. thus, there are exceptional requirements of protective coatings and gr films were expected to provide the solution in this matter too. complete and uniform monolayers could be grown on polycrystalline ruthenium of a columnar structure on fused silica, exposing flat surface facets [45]. single-layer gr protects underlying metals with special structures like concave focusing mirrors and non-planar microelectrode arrays from oxidation under ambient gases. ruthenium was recovered by heating the samples under ambient conditions at 250 ºc for half an hour in an ultra-high vacuum, which was indicated by missing peaks in the oxygen (1s) region of the xps spectra. gr on copper provided mediocre protection against electrochemical degradation in chloride environments [46]. impedance measurements showed increased resistance at the metal/solution interface as anodic and cathodic current densities decreased with about hundred times higher charge-transfer resistance besides about thousand times lower double-layer capacitance in comparison to uncoated copper. ennoblement of the free corrosion potential was also observed and related to the good barrier nature of the film. the protection of copper against corrosion by the growing number of gr layers was in part demonstrated [47]. to enable reliable and complete mechanical blockage by the coating exploiting its impermeability and chemical inertness, preparation parameters were balanced to obtain an appropriate film structure. in fig.5, cyclic voltammograms (cvs) of the bare and passivated copper (the latter with 1-3 gr layers) are shown along with the intensity of oxidative currents besides the atomic force microscope image of the cu/gr after etching. fig.6 depicts cvs of gr-coated copper and grcopper post-treated with aluminium oxide (alox) of different thicknesses, along with the comparison of their peak currents. nonetheless, nanometre size structural defects at flake boundaries were the main source of deficiency, decisive in the often-observed limited protection efficacy. to circumvent this problem, a general strategy is to grow ml island-free gr films. selective coverage of defect areas was achieved by atomic layer deposition, resulting in enhanced protection of ~99%. bare copper in an aerated sulphate solution indicated a pitting corrosion rate of ~9 nm s-1 with a density of ~1 µm-2. the estimated diffusion rate of the reactants was above 1 m s-1 limiting the rate of corrosion processes. figure 4: an optical micrograph, raman map of ~2700 cm–1 peaks and respective raman spectra of the areas on the cu–gr surface [41] (republished by courtesy of the publisher, elsevier) 88 interestingly, in the case of the ml gr films, mass transport remained fast across the sheets and parallel along their planes, which was anticipated by the outcome of a water permeation experiment [8]. this may explain the unchanged chemical inertness of the gr coating, owing to the fast mass transport along and across the layers as etchant species permeate through unburied areas in outer layers and diffuse laterally while finding open areas in layers underneath. inertness to electrochemical reactions could only be attained by thin layer deposition of aluminium oxide (within ~5 nm) by the means of an atomic layer deposition technique on gr/copper. only by this way could unburied regions on the copper surface be made void-free. after 160 atomic layer deposition cycles with a ~16 nm thick passivating film inhibition efficiency was ~99%. this was partly confirmed by tafel analysis giving instantaneous general corrosion rates of ~99% to the copper-single layer gr with 16 nm aluminium oxide and 87% to sl gr/cu, in comparison with bare copper. the approach of the direct loading of a precursor, i.e., acetone on copper then annealing it to convert its vapours into gr was investigated [47]. monolayers formed with nearly 100% coverage after rapid thermal annealing. under optimal conditions, acetone derived films with good crystallinity compared to common cvd grown counterparts. the passivity of the metal coated/masked with sl gr was attributed to remarkably inhibited cathodic reduction reactions and barrier action against the diffusion of anions accessing the underlying substrate. so, sl gr/copper exhibited ca. forty times lower corrosion rates compared to the mechanically polished copper, which means an inhibition efficacy of up to 97%. nevertheless, optimal protection performance was proposed to be achieved by the application of four gr layers with their short-term inhibitions of up to 99%. the corrosion current of the gr/copper reduced by ca. sixty times compared to mechanically polished substrates and the ocp shifted towards the negative potential region. electrochemical impedance spectroscopy (eis) indicated ten thousand times lower electrolyte-metal interfacial capacitance (cdl) of the gr/copper samples than those of the mechanically polished specimens. such a notable drop suggests a significant shrinkage of the exposed surface to the electrolyte. cdl of the gr/copper was ca. three times higher in nacl solution (0.6 m) than in its diluted media (0.1 m), but 6.4 times lower than that obtained in 0.1 m na2so4. cdl and constant phase element (cpe) of the gr/copper samples suggest an electrochemically smaller active surface to interfacial charging (discharging) and adsorption (like a non-faradaic helmholtz capacitor) as the density of conductive pathways decreases besides the lower effective surface roughness than that of the mechanically polished substrate. the cpe was 2.7 times higher than that table 1: metallic substrate, type and growth parameters to obtain gr films by direct cvd deposition substrate preparation type & parameters corrosion test parameters surface of the working electrode (cm2) types of electrochemical test ref. cu & ni cvd grown on metal surfaces flat-cell, 0.1 m nacl 0.07 potentiodyn. pol., scan rate: 1 mv s-1, after min at ocp [41] cu cvd grown flow-cell, mass velocity: 38 kg m-2 s-1 for 9 h, t = 59.5±0.5oc 3.06 none [42] cu mw assisted cvd heating at 150oc, in air at 1 atm for 1 h unknown none [43] ru cvd ambient exposure unknown none [45] cu cvd 0.1 m nacl 0.785 potentiodyn. pol., scan rate: 0.5 mv s-1 from ocp, eis after 1 h [46] cu cvd aerated 0.1 m na2so4 0.24 cyclic voltammetry, scan rate: 10 mv s-1 [47] ni cvd treated at 600 ºc in air, then 31 wt.% h2o2 for up to 2 h unknown none [49] cu & ni cvd & mech. transferred by spin-coating with pmma at 4000 rpm for 45 s 0.1 m naso4 0.4 potentiodyn. pol. & cv, scan rate: 0.005 mv s-1, eis [50] cu & si cvd then transfer of layers with pmma cured at 165 ºc ox. at 225 ºc for 60 min and red. of cu at 450 ºc for 90 min under o2 and h2 flow unknown none [60] cu cvd, thiol func.: slg-cu treated with hcl & h2o then 7.5 mm thiol-ethanol treatment for 2 h lymphocyte transformation test & in vivo experiment 1.4 tests: cu conc. by icpoes, cell viability & stimulation index for lymphocyte [80] ni template directed cvd anode in glucose based electrolyte, ni in ferricyanide catholyte 8 cv and eis [116] 89 measured in nacl solution (0.1 m) and over ten times lower than in na2so4 solution (0.1 m). the resistance of coated copper to corrosion (rcorr) was ca. thirty five times higher than those of mechanically polished ones 6×104 and 1.6×103 ω cm2, respectively. rcorr was appreciably lower than that of nacl and higher than with na2so4 solutions. thus, inhibition efficacy was found as follows; >97% in 0.6 m and >71% in 0.1 m nacl. thus, performance was sensitive to the integrity of the gr film as mechanically polished samples indicated rapid protection efficiency losses with increasing chloride concentrations in the test solutions. rigorous corrosion testing of nickel/cvd grown gr films revealed low intensity oxidation of the substrate by heat treatment. oxidation resistance was effective up to 500 ºc for 3 h, and with durable exposure (2 h) to essential hydrogen peroxide (31 wt.%) solution [49]. both nickel and copper were coated with ml gr films [14] by mechanical transfer. cv measurements indicated a remarkable restriction of the evolution of anodic and cathodic current transients, resulting in the effectively decreased electrochemical activity of the metal substrates. fig.7 depicts cvs of bare and grcoated copper samples, and xps spectra of copper under ambient conditions, at 100 mv and sputter cleaning. region (i) and (ii) contains a shoulder and a peak due to cuo and cu2o/cu, respectively. the third part of the figure shows sem images of cu and gr/cu before and after voltammetry scans. based on tafel analysis, corrosion rate assessment (quantification prediction) for bare substrates gave the following results: ca. 6×10-13 and ca. 3×10-14 m s-1 for copper and nickel respectively. graphene/copper indicated lower corrosion rate of ca. 8×10-14 m s-1 up to ca. seven times less than the bare substrate. the gr/nickel showed a reduced rate of ca. twenty times to 2×10-15 m s-1. with two or four folds of gr layers, the corrosion rate of nickel decreased to 2×10-14 and 8×10-15 m s-1 respectively, which is considered as a notable performance improvement. eis measurements suggested an undamaged state of gr, but the metal surface might corrode at high rates around void areas in the film. the most probable electrical network included resistive elements of the solution; rs ≈ 40 (6.5 ω cm2) and charge-transfer at the interface; initial rct ≈ 3±0.5 kω cm2 due to faradaic processes. the mass transport process was modelled with a warburg element (w ≈ 1.0±10-3 ω-1 s0.5 cm-2) as a semi-infinite diffusion component. the inhomogeneity of the surface was handled by incorporating a cpe as a non-ideal capacitance in the circuit due to the impedance dispersity of the electrical double layer component at the metal-liquid interface. double layer capacitance was best achieved with 2.2 µf cm-2 and the cpe was yo ≈ 7.6±10-5 ω-1 s cm-2. increased resistance coupled in series was caused by the electrical surface resistance of gr (≈1 kω) with a double layer capacitance of ~3.8 cm-2. average fitting parameters were changed figure 6: cvs of (a) cu/gr/al samples, (b) peak currents of cu(0) for cu/gr/al with different aluminium thicknesses and in comparison to cu/gr with 1-3 gr layers (adapted with permission from ref. [47] copyright (2014) american chemical society) figure 5: cvs of (a) bare cu and cu passivated by 1-3 layers of gr, (b) intensity of oxidation currents under various passivation conditions, (c) atomic force microscope image of cu/gr after etching (adapted with permission from ref. [47] copyright (2014) american chemical society) 90 accordingly as follows: cdl ≈ 9±5.0 µf cm-2, cpe: yo ≈ 2±10-5 ω-1 s cm-2, w ≈ 3±0.5 ω-1 s0.5 cm-2, and rct ≈ 10±1.2 kω cm-2. the cdl was ca. ten times lower than measured with bare copper, which seemed to be unrealistic. such a difference is thought to originate from the quantum capacitance of the gr film as a contribution in series with the cdl. this is partly due to the small density of states in the gr, which is in good agreement with the reported quantum capacitance of 7– 10 µf cm-2 [50]. the increased rct of the copper samples in comparison with the one measured at the beginning of corrosion test suggested that the minor proportion of the metal substrate was uncoated with gr, participated in corrosion processes. the proportion of this unburied area was estimated to be unexpectedly high (a ≈ 0.3), exceeding the scale impressed by microscopy images (a < 0.05). such a difference was attributed to the access to larger substrate areas by the diffusing depolarisator species and a subsequent greater proportion of helmholtz capacitance then pseudocapacitance based on electrochemical activation of metallic substrates for anodic reactions. nevertheless, the ability of gr to catalyse, and depolarise cathodic reactions such as oxygen reduction [51] by well-coupling micro-galvanic cells in contact with the poly-aromatic sheets [52] either in planar or concentric forms (according to the function of the surface quinone group on carbon electrodes, i.e. garten and weiss’s mechanism) is almost always a concern. thus, protection efficiency depends largely on the deposition technique, quality, and epitaxial pile structure of the gr sheets, affecting ionic and electrical transport through the films. due to low adherence as a result of the lack of direct grafting or anchoring type chemisorption, direct cvd-grown films are classified as fragile coatings liable for potential polarisation and charging of the surface due to their structural alterations [53]. to increase the small domain size of the flakes, high temperature annealing at ~1035 ºc on the metal surface offers a resolution promoting further development of coherency of the films composed of large domains [54]. however, there are many problems with direct cvd deposition on metals like nickel because of the film formation mechanism of polyaromatic carbon materials. the mechanisms of surface catalysis and adsorption during gr growth on copper were determined [13, 55] to be different from film growth on nickel, which is governed by the combination of catalysis and adsorption as well as solubility and rejection. as the cvd technique enables the synthesis of gr on larger metal surfaces [22, 56], carbon sources are thermally decomposed and fragmented into smaller segments, then atoms arrange into 2d honeycomb lattices. the preparation of cvd grown gr films takes place readily on surfaces with face-centred cubic and hexagonal close-packed crystal structures. methane and ethylene, which decompose at a temperature of ~1000 ºc are used as main precursors [24, 25] even though such a high temperature might significantly affect the metallographic state of the substrate, nucleation and deposition kinetics. metals with close to zero solubility of carbon at the reaction temperature, e.g., copper, deposit via a catalytic mechanism and they are more likely to assist the formation of sl gr instead of ml ones owing to the lack of catalytic effect after the first layer is deposited. thus, the metal surface acts as a catalyst facilitating gr growth in the form of a finishing coating, as deposition is restricted to sl [57]. film growth on metals with mediocre carbon solubility at reaction temperatures undergoes via a complicated mechanism in which carbon diffuses into the bulk metal, e.g., nickel, and is rejected during the cooling process because of the decreasing solubility at lower temperatures. the rate of carbon rejection is critical to the development of ml gr coatings. hence, these films form preferentially instead of sls on copper. further complications may arise by the use of thicker metal specimens because thicker substrates dissolve larger amounts of carbon during the cooling phase since they release more carbon to produce larger amounts of carbon soot. although any process that needs to be scaled-up must be optimised for engineering alloys, there are many results of theoretical interests as well. figure 7: cvs of (a) bare cu and gr/cu samples with the blue line corresponds to the measurement with n2 bubbled through the solution; (b) xps spectra of copper under ambient conditions at 100 mv and sputter cleaning with regions (i) and (ii) are due to cuo and cu2o/cu(0), respectively; (c) sem images of cu and gr/cu before and after cv scan (adapted with permission from ref. [14] copyright (2014) american chemical society) 91 a thesis [58] thoroughly investigated the protection efficacy of direct cvd grown gr on copper, depending on flake size and uniformity, duration and temperature of the heat treatment. key factors leading to firm protection performance both in terms of instantaneous and long-term functions are identified as to eliminate defects in the gr sheets, flakes must build up a flawlessly continuous, coherent, and uniform film. low nucleation and high growth rates must be maintained under low pressure to gain a low density of carbon spots (as probability of deposition decreases) and coherent films with the absence of unburied areas at flake boundaries. the films with large flake sizes were tested in a number of experiments to optimise growth parameters in order to reduce the amount of disorders, defects and void areas. a series of chemical oxidation experiments were performed by heating bare and coated copper foils at various temperatures and for various time frames. ellipsometry helped characterise the thickness of oxide layers on the highly reflective copper. heat treatment was carried out at 120 ºc under air for up to 76.5 hours. the growth rate of copper oxide layers, as an inherent indicator of the oxidation rate, almost linearly increased with time and the difference was only ca. a factor of six between the bare and coated copper foils. corrosion deterioration was located at two spots where air leaked through defects in the gr film and around its flake boundaries. following growth time in low pressure cvd experiments, films were grown in a way that their flakes were not connected. therefore, flake growth stopped before expanding sufficiently to connect with one another. then oxidation was performed at 190 ºc for up to 37 h and 26 min. optical microscopy images revealed a remarkable difference between the bare and coated copper samples. then oxidation was repeated with closely spaced gr flakes investigated by optical and sem. the samples with closely spaced flakes gave very good results after a 30 min treatment at 190 ºc. a 13.5 h treatment led to minor deterioration in the substrate exhibiting black oxide patches on the surface but a 23 h and 35 min annealing resulted in corrosion of nearly the entire surface. in a series of experiments, copper substrates coated with continuous gr flakes were treated at 190 ºc for various periods of time. after a 30 min heating, samples exhibited a fine condition with some proportion of the surface composed of dark copper oxide. after a 10 h and 45 min treatment, migration of the corrosion front on the copper surface (cuo formation) proved to be far advancing and the heavily corroded areas showed a homogeneous distribution in the form of tree roots. optical microscope images after 35 hours of heating indicated heavy corrosion, but the surface was not fully covered with oxides. raman spectroscopy quantitatively characterised copper oxidation, which could proceed at flake boundaries as they feature the least hindrance to mass transport of depolarisators and the large sheets did not damage or etch oxidatively inside. apart from growth related issues, electrochemical aspects of the shortfalls may also be relevant. gr films, acting as physical separators, might take part in electron transport, helping interfacial charge-transfer perpendicular to the surface based on good coupling and ballistic electron transport parallel to the basal plane of the sheets. oxygen adsorption and reduction reactions with low activation energies may further complicate the application of this material, which has been recently underlined in a shortand long-term performance test of gr/cu and si substrates [59]. results clarified that the samples heated at 250 ºc for 6 min showed heavy oxidised spots on bare copper, but little oxidation on the gr coated one. therefore, gr served as a sufficient oxidation barrier helping to preserve the metallic state from chemical oxidation over a short time period at high temperatures. nonetheless, long-term annealing of coated copper led to severe oxidation probably because oxygen diffusion proceeded through discontinuities and defects around gr sheets. after 17 h at 250 ºc, coated copper became heavily oxidised in a way indistinguishable from the bare specimens subjected to the same conditions. similarly, a 15 min treatment at 185 ºc resulted in partial oxidisation of bare copper but coated samples remained almost entirely in a pristine state. nevertheless, after 17 h annealing in air at 185 ºc, both bare and monolayer coated substrates became severely corroded and the products were identified as cupric oxide (cuo) in a stoichiometric ratio. the timescale of protection against thermal oxidation by gr on copper was estimated to be ~1 h at 185 oc and ca. ten times faster at 250 ºc. to explore the long-term protection ability under less severe conditions, bare and coated copper specimens were stored under ambient conditions (at 25 ºc) at low but variable humidity levels for up to two years. bare copper showed relatively slow oxidation at room temperature. gr/cu tested after up to eighteen months exhibited oxide-free condition over the first two weeks but within a month the surface started to tarnish non-uniformly (in several hundreds of micrometres in size). within a few months, most of the regions became heavily oxidised with an estimated oxide layer thickness of tens or hundreds of nanometres. alignment between the substrate grains and gr flakes was concluded to have an influence on oxygen and water diffusion along the surface. after eighteen months, the entire surface had become oxidised as edax analysis revealed a predominant percentage of cuprous oxide (cu2o) in the oxide phase. gr/silicon gave similar results as bare and coated samples were compared to each other after one week under atmospheric conditions, indicating an increased oxygen content of silicon as time of exposure increased. according to the outcome of the series of experiments, short-term oxidation testing reflected some degree of protection but long-term propagation unveiled extensive wet corrosion, similar to that seen in the case of bare copper specimens. the high rate of the wet corrosion of copper is due to promoted galvanic cell formation on a micrometre scale at ambient temperature, especially over long-term exposure. as a special field, the majority of medical applications require metals even today, in bone and joint replacements [60, 61], stents [62, 63] dental materials [64, 65], pacemakers and generators [66, 67]. stainless 92 steel, titanium and cobalt alloys are the most common orthopaedic materials for joint prostheses articulated with a plastic bearing surface for many body parts [68, 69]. there are areas that require the use of alloys of mercury, silver, tin, copper along with limited amounts of zinc, palladium, indium, selenium and titanium in dental surgery [70, 71]. despite the numerous successes, the main disadvantage of most of the alloys in medicine is their corrosion and the resulting physical deterioration (disintegration), quantity loss and contingent toxic side effects. the increased concentration of the aforementioned elements as soluble metals surely leads to chemical reactions of altered enzyme functions. it has been proven that soluble metals released because of corrosion processes can induce an innate monocytesmacrophage response and trigger immune responses, causing toxic, inflammatory, allergic or mutagenic reactions to patients [72]. in addition, corrosion leads to the adverse formation of metallic debris; solid particles and inorganic or organometallic compounds, in the periprosthetic soft tissues causing metallosis [73]. furthermore, the corrosion degraded structural integrity leads to the premature failure and loosening of the metal devices [74]. therefore, corrosion protection of metals used in physiological environments is of paramount importance and needs to be properly addressed for the sake of durable successful biomedical applications. currently ceramic coatings are the most widely used to isolate metals from body fluids, e.g., zirconia transited from a zirconium alloy minimises corrosion in knee implants but the implants roughen with time. nano-size diamond coatings and apatite-nano-diamond composites are promising candidates for the protection of metallic implants [75, 76], but they are highly permeable and greater surface roughness notably decreases their performance. nowadays, atomic thin gr films enhance the bioand hemo-compatibility of implants to some extent [77, 78]. interestingly, the outcome of almost all cell viability tests showed the biocompatibility of gr on the nickel-titanium surface with some protection. after considering these facts, studies focused on clarifying the possibility of application of gr as a corrosion protective film on structural metals used for biomedical devices. the most important future application would be the efficient corrosion protection of metallic prosthetics to avoid serious health problems to patients. in an effort to offer an alternative to protect metallic implants, gr was proposed as a biocompatible and protective film as well [79]. copper was the substrate for cell viability tests to reveal any change in immune response (lymphocyte transformation test) and the metal sensitivity test because of its high toxicity [80] making the experiment sensitive to reflect any significant protection. in vivo experiments served to study the protection of copper in live animals to evaluate gr as a biocompatible film in physiological conditions. corrosion inhibition of copper with gr films was studied by the way of release and accumulation of copper ions in biological aqueous environments of phosphate buffered saline, fatal bovine serum and hank’s balanced salt solution. cell culture figure 8: concentration of cu(ii) ions from different biological solutions: in (a) pbs, (b) fbs, (c) hbss solutions, and (d) cell culture media in the presence of sl (black) and bl gr/cu (red), cu (blue) and blank solutions as controls (pink) measured by inductively coupled plasma-mass spectrometry (icp-ms). all results are presented in a mass ratio (ppm) [79] (republished by courtesy of the publisher, nature publishing group) 93 media were monitored with inductively coupled plasma optical emission spectroscopy (icp-oes) for five days. single-layer gr/copper indicated slightly varied but very good conditions on average. the copper ion release rate was found to be at least an order of magnitude lower compared to bare copper that correlates almost linearly with time. the copper concentration in the solutions was higher when bilayer gr/specimens propagated as compared to those of the tests with sl gr obtained in all solutions. this was attributed to the stronger adhesion of sl films to metallic surfaces than bilayer ones, probably because of the better adaption to surface topography with high flexibility [81]. fig.8 shows the concentration of copper ions detected in different biological solutions such as phosphate buffered saline (pbs), fetal bovine serum (fbs), hank's balanced salt solution (hbss) and cell culture media with sl and bl gr films and blank solutions as controls. cell viability tests indicated almost the same results with singleand bilayer gr/copper samples showing ±2.2 and 2.6% differences respectively compared to the control samples after the first day. nonetheless, the results produced by low concentrations of dissolved copper in test solutions do not mean good results overall because the ion concentration could be much higher in a micro-milieu between the cells and coated substrate. the point of such a difference can explain why the cell viability dropped remarkably by more than 90% over the second, third, and fourth days of the test compared to the gr contained samples although the copper concentration in the solutions remained very low (less than 70 ppm). probably interfacial accumulation of metal ions must play a pivotal role in exceeding the toxicity limit, inevitably triggering lower cell viability. to resolve this problem, a further modification of the metal surface was necessary [82, 83]. by self-assembly monolayer treatment with decanethiol, bare and gr/copper was modified with decanethiol, which was obviously assembled on the bare surface around the boundaries of gr flakes. this is because the seemingly proper protection of copper was accompanied by much improved cell viability over three days (fig.9). the thiol modified sl gr/cu indicated that cell viability was ca. 55.8% after an incubation period of three days compared to sl gr/cu (fig.10). thiol modified copper showed an improvement of up to 2% in comparison to the less than 1% viability observed for bare copper. these results suggest that gr on copper is the major factor for protection, which can be appropriately enhanced by thiol modification. the film was also found to reduce immune response to copper in a clinical setting by a lymphocyte transformation test. animal experiments indicated a positive outcome to coated copper samples tested under in vivo conditions. the copper concentration was less than 3 and ~4.5 ppm in blood samples extracted from living rats implanted with sl coated and bare foils, reflecting the potential of thin gr films in biomedical applications. cvd-grown graphene loading on metal surfaces by mechanical and electrical techniques spin-coating there are a number of techniques to obtain high quality thin films. static and dynamic dispense techniques such as dip [84-86], angle-dependent dip [87, 88], and hot dip spin, spin [89-92], spray [93], flow [94, 95], capillary [96, 97], roll [98], and reverse roll coating [99, 100] have developed thin layers on solid surfaces. by careful design, it is also possible to complement one another, offering a way to be tailored to application demands. optimisation of these techniques is mostly dependent on actual parameters of the fluid phases and molecular or colloid solutions such as concentration, temperature, pressure, partial pressure or volatility of substances and solvents, dynamic or kinetic viscosity, and surface tension of fluid phases. the texture (roughness) of the substrate surface has much less influence (except for the surface energy) on the quality and quantity of casting. drying and curing might later take place. from them, the ones featuring well controllable gr growth are detailed in the following. both spin-coating (sc) and kinetic spray (ks) are relatively novel techniques enabling us to form coatings of good quality on any sort of surface texture regardless of the substrates. sc is figure 9: relative cell viability and concentration of cu(ii) ions as a function of time. (a) relative cell viability vs. time for slg/cu, blg/cu and cu; (b) concentration of cu(ii) ions in the cell culture medium after incubation with slg/cu. blg/cu and cu (calculated from icp-ms). a medium taken from a regular cell culture without cu foils was used as the control [79] (republished by courtesy of the publisher, nature publishing group) 94 suitable to work out and implement practical deposition methods for atom-thick films on various metals, although a different approach must be applied for newtonian [101] and non-newtonian fluids [102]. uniform coatings can be obtained over large areas with reproducible thicknesses in a good controllable manner, but only on planar substrates, which is a major limitation of this technique. sc starts by applying a small puddle onto the centre of the substrate, then spinning commences at initially a lower then, within a matter of seconds, at a higher rotational speed (two stages of centrifugation up to ~3000 rpm). the centrifugal force and centripetal acceleration result in excessive spreading of the fluids on the surface (wetting and covering depend on multiple physical-chemical parameters) and an inevitable loss (can be recycled) around the edges of the substrate until the spin-off time is completed. then, a thin film forms releasing solvents and curing takes place, because of chemical reactions. kinetic spray kinetic spray (ks) utilises a laval nozzle to spray gr colloid solutions at a very high speed and the supersonic acceleration leads to the production of very small droplets that evenly disperse then evaporate reducing the tendency of flake aggregation. besides the uniform and smooth layers, defects in the gr flakes were not observed. hence, high quality film production by ks depends on the energy of the impact stretches gr sheets then carbon atoms arrange into flawless hexagons based on plasticity probing of the gr flakes [103]. transmittance of graphene oxide (gro) film spray deposited on soda-lime glass (from a 10 wt.% colloid solution of gro in ethanol) was 73% and sheet resistance was 19 kω sq-1 using incident light at the wavelength of 550 nm. the electrical conductivity of the coatings increased by up to a thousand times after hydrazine reduction and annealing at 400 ºc. additional thermal annealing at 1100 ºc further enhanced conductivity by ca. 10 times. soda-lime glass with a transparency of 80% and electrical conductivity of 209 s cm-1 (or sheet resistance; rs = 2 kx sq-1) as applied to a 14 nm thick gr film [104]. ks is a reliable technique of wide commercial availability and offers a flexible solution to large-scale using according to recently reported corrosion tests [105-107]. electrospinning electrospinning (es) creates polymer fibres with a diameter range of between 40 and 2000 nm. the fibres can be made from solutions or from fused materials, controlling diameter size through the adjustment of figure 10: relative cell viability of (a) bone cells incubated with sl gr and sl gr/cu-sh, cu-sh and bare cu foil for 3 days. control is a regular cell culture without cu foils; (b) relative cell viability of bone cells incubated with tr-sl gr/cu, bare cu, tr-sl gr/cu-sh, and cu-sh for 1 day; (c) concentrations of cu(ii) ions in blood samples extracted from live rats with concentrations of cu(ii) from normal rats before implantation as control (black square), rats with implanted slg/cu foils (blue triangles) and rats with implanted cu foils (red dots) as a function of time [79] (republished by courtesy of the publisher, nature publishing group) 95 surface tension, solution concentration, conductivity and so forth [108-110]. es occurs when the electric force of the surface overcomes the surface tension of the fluid phase triggering an electric spark, results in the solution being expelled from a syringe forming jet flow impacts and deposits. when the expelled material dries out or solidifies, it forms an electrically charged fibre that can be directed or speeded up by electric forces. so, a polymer solution stored in a syringe is charged to a high electrical potential. as the jet stretches and dries, radial electrical forces cause it to splash repeatedly. dried, solidified fibres are collected on an electrically conductive (metal) screen. by es, the composition of nylon 6-6 and gr was prepared and deposited on porous silica then tested under various conditions [111]. oxidation and reduction potentials in acidic, alkaline, and peroxide solutions were assessed by dynamic polarisation. sem observations determined that treatment with acidic and basic solutions led to the formation of solid aggregates and slightly folded gro flakes. thermal treatment at 700 ºc gave samples with a porous structure. after annealing, a subsequent chemical derivatisation with acidic, basic and peroxide solutions assisted with ultrasonication facilitated the separation of gro sheets, leading to a solid composed of lower dimensional flakes, especially in the case of oxidation. oxidation was carried out in koh and the reduction in h2so4 solution. eis data obtained in the immersion test with a na2so4 solution indicated decreasing interfacial capacitance of the es produced samples with the ny-gro coatings. the eis data calculated at 0.8 hz changed between 1.4–4.5×10-5 and 7.5–8.9×10-7 f cm-2 (depending on the concentration of the electrolyte) with the gro content increasing from 0.4 wt.% to 2 wt.%. electrophoresis electrophoretic deposition (epd) is a promising technique to fabricate functionally graded [112-114] and hybrid composites [115, 116], laminated nano-ceramics [117, 118], and functional, nanostructured films and coatings [119-121]. in the last couple of years, numerous epd applications have emerged as industries count on commercial advantages over other fabrication routes. it is a versatile and cost effective technique with acceptable levels of control over microstructure, stoichiometry, and macroscopic-microscopic dimensions and properties [122, 123]. epd is a two-step colloid process in which electrostatically charged particles, suspended in a liquid medium, migrate according to the electric field towards the oppositely charged electrode. then particles deposit, and flocculate on the electrode surface forming a relatively dense, homogeneously packed, bonded layer. increasing the volume fraction of the nanoparticles and their deposition on the surface of any electrically conductive material is relatively easy. usually, a post-treatment is required to increase the density of deposits and eliminate porosity [122]. sometimes special modifications are required to render surfaces with notable properties such as increasing hydrophobicity by silylation. epd is performed in stable colloid solutions in which there are plenty of electrostatically charged particles migrating in response to an impressed dc electric field and deposit either as a loose homogeneous or compact film onto the oppositely charged electrodes. to make deposits denser and eliminate porosity, additional epd or heat treatment is required. oxide particles, conductive polymers [124] and highly dispersed activated carbon [125] of nearly any size in colloidal suspensions [122] were deposited by this method, reflecting its high versatility. furthermore, by electrophoresis uniform thin layers can be made on highly ragged, complex surfaces. moderate electrical conductivity of the resulting substrates is the only requirement. the sample surface is treated as a whole in a uniform manner, whereas dimensions, deposition rate, uniformity and scale up features are also favourable. epd is a preferable alternative to many other methods like slurry dipping, thermal and plasma spraying, sputtering, and physical/chemical vapour deposition. in the course of thick gr layer deposition on copper by epd [126], deoxygenation of carbon was hinted at by bathochromic shifts in the uv spectra because of the electrochemical configuration and reaction mechanism. potentiodynamic scanning showed positively shifted corrosion potentials and lower corrosion currents (icorr), which suggested only mediocre protection by the thick gr films in the initial phase of immersion propagation. the composite coating of reduced gro was prepared by cathodic epd in an aqueous solution in a symmetrical cell-electrode arrangement [127]. optimum conditions for cathodic deposition were found to produce a thickness of ~40 nm by applying 10 v for 30 s. sem observations revealed the size of the gro sheets being 1–2 µm, covering the surface uniformly. the composite coating was shown to protect copper firmly from electrochemical corrosion. potentiodynamic measurements indicated an ennobled free corrosion potential with slightly reduced anodic and cathodic current branches, suggesting a lower corrosion rate of the composite coated copper compared to its bare form during the early phase of propagation. experimental conditions are summarised in table 2. by electrophoresis, gro was uniformly deposited on a permanent magnet, e.g., ndfeb and the coating was subsequently reduced to partially remove functional groups containing oxygen [128]. the epd gro coating showed substantially better adhesion to the substrate compared to the spin-coated ones. the surface of the bare ndfeb was rough and porous but site-dependent topography of the epd-gro modified samples depended on the amount loaded. the relationship between the increasing thickness and decreasing adhesion of the coating with an extension of deposition time was determined. raman, infrared, and x-ray photoelectron spectroscopy (xps) results reflected the strong adhesion of epd films and that was connected to the koble-type decarboxylation mechanism [129, 130] of the surface yielding gro flakes. an unexpected outcome was that several deterioration reactions were observed in gro. the signal of epoxy groups decreased 96 after deposition, which might be explained by the high anodic electrode potential applied to the working electrode and the large potential drop at the interface. the decrease in current density during potentiodynamic scanning and the positive shift in the free corrosion potential of the system reflected efficient initial protection but lower cohesion and adhesion of the thicker coatings, leading to a poorer protection potential. the gro-acrylic polymer composite fully covered the copper substrates, but the sheets were separated far from one another in an island like manner consequently a large percentage of the surface remained unburied [131]. as for the reagents, solution and cell arrangement, epd conditions e.g. voltage (10 v) and deposition time (30 s) proved to be optimal to obtain crack-free films of an average thickness of 45 nm. an electrochemical investigation indicated insignificant protection performance of the composite coating under immersion propagation. a steady corrosion current extrapolated to the ocp region showed slight changes over the anodic and cathodic regions. a current density drop of 38.3–3.5 µa cm-2 was observed in comparison to the bare copper. a polarisation resistance of the composite covered specimen was assessed by eis, assigning an increased charge-transfer resistance of ~25 ω cm-2 (bare copper: ~8 ω cm-2). stainless steel specimens with an exposed geometrical surface of 100 cm2 were almost uniformly deposited with gro in h2so4 solution by coupling the substrate cathodically [132]. for transferring purposes, chemical and electrochemical etching was developed to delaminate the reduced gro film, giving coherent freestanding membranes or deposit them onto other substrates. by optimising electrophoretic parameters, a low voltage of 3 v was found to consolidate reduced gro layers preferentially aligned in an in-plane direction through a cohesive electrophoretic squeezing force in near volume range of the electrode (cathode). the free-standing gr membrane was reduced, annealed at 1000 ºc then a graphite-like architecture evolved with a d-spacing of 3.42 å and c/o ratio of 16.7. electrical conductivity was of high as 5.5×105 s m-1. graphene coated metals in electrochemical cells and batteries because corrosion is a serious problem in energy storage devices like batteries and fuel-cells [133], the application of gro as a barrier coating to inhibit the corrosion of aluminium electrodes in lithium ion batteries is considered to be an innovative solution. spin-coating was employed to coat aluminium with gro and decrease the corrosion rate when the electrode was subjected to the electrolyte of lipf6 (1.0 m) dissolved in ethylene carbonate and dimethylcarbonate (50:50 vol.%) [134]. sem observations with energy dispersive x-ray spectroscopy analysis and atomic force microscopy (afm) scanning suggested increasing surface roughness of aluminium with lower gro quantity, but its greater amount helped reduce the roughness remarkably. the average roughness of the bare substrate was around 350 nm, which changed to 199-154 nm for the gro loaded one. the thickness of the film showed great epitaxial variety even though the coating was relatively thick. cyclic voltammetry showed a decreasing electrochemical current response of the gro coated electrodes with increasing surface loading. this indicated hindered and impeded chargetransfer through the electrode interface without any direct implication of capacitive and adsorption charge loss in the current transients. accordingly, chronoamperometry curves exhibited moderately changing characteristics (as a consequence of altered electrode kinetics) in the early phase of the transients and table 2: metallic substrate, type and growth parameters to obtain gr film by epd and chronoamperometry substrate preparation types and their parameters corrosion test parameters work-electrode surface (cm2) types of potentiodynamic tests ref. cu gro, epd in sol. c = 1.0 mg cm-3, e=1 v / 10 mm-1, 10 min air ox. at 200 ºc for 4 h, in 30 wt.% h2o2 for 2 min, then 0.1 m nacl solution unknown after 1 h at ocp, scan rate: 1 mv s-1 [131] cu red. gro with polyiso-cyanate cured with haa (hydroxyl acrylic acid), epd for 30 s, at e = 10 v 10 mm-1, 0.1 m nabh4 red. for 5 min 3.5 wt.% nacl, at 25 ºc 1 after 2 h at ocp, scan rate: 1 mv s-1 [132] ndfeb gro red., epd in sol. of 1 mg cm−3 gro, ndfeb anode & pt cathodic dep., e=10 v / 10 mm-1, 3.5 wt.% nacl solution at room temperature unknown eis [133] cu gro isocyanate cured with hydroxy acrylic, then silylation, epd on cu at 10-30 v 10 mm-1 3.5 wt.% nacl, at 25 ºc 1 eis [136] cu chronoamperometry of gro at −1.5 v for 10 min in sol. c = 2 g dm-3, in 0.1 m kcl, at −1.5 v for 10 min, then gro red. nabh4 (0.1m) for 5 min ocp 3.5 wt.% nacl sol. after 1 h 1 eis [138] mild steel epd in ni sol. at ph = 3, iρ = 1 a dm-2, at t = 40oc, gr c=100 mg dm-3 3.5 wt.% nacl, at 27 ºc 1 scan rate: 0.01 v s-1, eis [169] 97 decreasing base currents over the complete timescale because of the smaller electroactive surface. eis spectra suggested a somewhat higher resistance against pitting, the lower susceptibility to localised corrosion. thus, gro restricted aluminium oxidation, behaving as a charge-transfer barrier. otherwise, the lower capacity and potential of the cells should have been measured by the set-ups with the gro loaded electrodes during charge–discharge testing. instead, surprisingly the opposite was reported. nevertheless, enhanced cyclelife stability (lower rate of capacity loss) of the modified electrode compared to the cell configuration with bare aluminium is of course self-explanatory. self-discharge was lower as a decreasing rate of open circuit voltage decline was observed to the modified aluminium samples. gro films did not show any corrosion and the underlying native oxide layer remained intact under test conditions. microbiologically induced corrosion (mic) severely limits the structural integrity and lifetime of metallic structures in technological processes and applications because of frequently evolving mechanisms, i.e., crevice and pitting local corrosion phenomena. a microbial fuel cell (mfc) is a galvanic cell producing an electric current that causes bioelectro-chemical oxidation of organic substances on anodes and abiotic reduction on cathodes [135]. mfcs have been used as a galvanic tool to simulate extracellular electron transfer mechanisms of microbes and the bio-electrochemical oxidation of organic substances. in addition, metals are not used as anodes in mfcs due to their fast galvanic corrosion. owing to this, gr films are employed as barrier coatings and the corrosion rate of the working nickel electrode was evaluated by galvanic coupling in the mfc set-up [136]. regarding the experiment, it was determined that the geometrical ratio of the working and counter electrodes was the guarantee to maximise, and concentrate current densities on the working electrode. nevertheless, the cell design did not allow the assessment of adequate kinetic parameters (general corrosion rate) because of the large uncompensated ohmic drop and unfavourable cell geometry. these are all relevant in dc techniques, although inadequate voltammetric data could provide a rough estimation, even though 5 mv s-1 was higher than recommended and might have resulted in the considerable rate of adsorption and pseudo-capacitive current during the measurement. in relation to the impedance measurement and its evaluation, these data are even more sensitive to inappropriate cell design. the protection efficacy of the gr film was assessed under realistic operating conditions, the bare and coated nickel electrodes represented a 3d microporous structure. the overall outcome confirmed a retardation of corrosion processes by the gr film for extended periods. cv scanning showed decreased current transients of coated nickel, which was ca. ten thousand times lower than measured for the bare nickel electrode based mfc after a propagation for 2800 h. nickel dissolution rates of the gr coated anodes were at least ten times lower than the baseline (uncoated) electrode. eis characterisation confirmed impeded mic on the gr/nickel for ca. 40 folds in comparison with uncoated electrodes. the effective masking of nickel from the mixture of microorganisms and their metabolic products was concluded. composite graphene coatings physically mixed and in situ polymerised mixtures chronoamperometry was successfully employed to prepare gr coated copper, starting from an aqueous colloid solution of gro [137]. as a result of the epd process, a seemingly compact and void of area without coating; and polymer film with gr inclusion was obtained. nevertheless, the distribution of gr flakes was highly uneven and inhomogeneous (random), whereas the sheets showed various degrees of folding and overlapping in the polymer matrix. in addition, the fast reduction of gro in the polymer proves the high permeability of the matrix, although it reached a thickness of several micrometres. on the other hand, the coatings with reduced gro provided moderate protection for copper with an initial inhibition rate of 94% drawn from the potentiodynamic polarisation measurement data (at nil impressed potential). the corrosion rate reduced to 0.2 mm yr-1 from the rate for pure copper of ca. 3.65 mm yr-1. this assessment was only made at the beginning of the immersion test (after an hour), whilst waiting for stabilisation of the freshly installed cell set-up. in comparison with the eis investigation, the composite coating provided electrical insulation and ionic diffusion hindrance to the copper surface. so, the protection was related to the increased polarisation resistance of gr loaded coatings of ca. 26 ω cm2 compared to bare copper of 9 ω cm2. intrinsically conducting polymers (icps) like electroactive polyaniline (pani) have been widely used materials for some time providing corrosion protection regardless of the long-standing disagreement over the anodic protection mechanism and the generally less effective barrier nature. pani is a preferable electronconducting polymer with favourable properties over other alternatives. under optimal conditions, the protection mechanism leads to the formation of a passive (dense) metal oxide layer [138-140]. to increase protection performance, many substances such as well dispersed clay [141] with an aspect ratio of ca. 200 was aimed at lengthening mass transport pathways through the composite films for all redox active species. these polymer-clay mixtures exhibited notable protection improvements over neat polymers. besides the several attempts to combine of carbon nanotubes (cnts) with organic [142-156], inorganic, and metal [157-160] matrixes for corrosion protection and resistance, respectively, there are examples from the literature about testing gr-polymer composites for various purposes [160-162]. the main focus of these works was the exploitation of high relative aspect ratio of gr (ca. 500) [163] in comparison to exfoliated clay minerals. hence, gr is a key filler in advanced gas barrier materials, motivating studies to 98 achieve very low oxygen permeability using low filler contents (compared to neat polystyrene and the best polymer-clay mixture known at that time) [164] and underscore the possible obliteration of traditional claypolymer composites [165-169]. thus, a carefully designed and well-prepared pani-gr mixture exhibited outstanding impermeability characteristics against the diffusion of molecular oxygen and water vapour versus neat pani and pani-montmorillonite using a filler content of 0.5 wt.% and the excellent protection performance of steel substrates. potential ennoblement of steel electrodes with coatings of increasing gr content was considerable and an approximately fifteen times lower steady corrosion current was reported. the main reason for the success is mostly related to the high dispersity of gr in the composite of microscopically isolated and macroscopically non-percolating distribution [170]. experimental conditions are summarised in table 3. lower electrical and ionic conductivities always provide better corrosion protection. therefore, metals coated with gr filled composites of electrically less or non-conducting (practically insulating) matrices like epoxy (in the case of high dispersity) can behave as a super-hydrophobic interface [171-176]. these composites are characterised by a water contact angle of at least 150º making them repellent, resistant to water absorption [177] and their exceptionally good antiwetting properties results in good corrosion prevention potentials. the nano-casting prepared epoxy-gr composite featured high hydrophobicity and provided excellent protection for cold-rolled steel (crs) panels [178]. fig.11 shows tafel plots of bare, epoxy, hydrophobic epoxy (he) and hydrophobic epoxy-gr composite (hegc) coated crs panels. the open circuit potential of the immersion tested steel panels coated with epoxygr showed appreciable ennoblement of ca. 0.3 v and ca. ten times lower corrosion currents compared to neat epoxy coated steel. the much higher polarisation resistance was partly attributed to the more hindered mass transport through the gr loaded coating (with less than half the oxygen permeability) and access to its interface on the fluid side as a result of the finely patterned structure of the outer surface. the reproducibility of the data is questionable because parameters were not representative to properly describe the kinetic processes of the system, proceeding at the metal-solution interface. as in other cases, electrochemical techniques gave instantaneous rate assessments (in the first 30 min of the tests). thus, the reported data are not suitable for forecasting long-term corrosion rates. table 3: metallic substrate, type and growth parameters to obtain gr films by spin coating and solution casting. types and settings of corrosion tests and electrodes with the reference number of the article substrate preparation type and parameters corrosion test parameters work-electrode surface (cm2) types of electrochemical tests ref. porous silica electrospin gr-nylon 6-6 in formic acid agitated for 12 h then add. of gro, es at 12 kv, flow rate: 0.2 ml h-1 for hours, electrode: polymer solution 90 wt.% of formic acid with 0.36-2 wt.% gro and ny potentiostatic oxidation in koh (0.5 m) for 3.5 h, reduction in h2so4 at ph = 2 for 8 h, eis in na2so4 in (110-1-10-2-10-3 m) for hours unknown potentiostatic treatment, potentiodynamic polarisation, scan rate: 100 mv min-1, eis [112] alox gro sonication in ethanol then spincoating lipf6 in ethylene carbonate and dimethyl-carbonate (50:50 vol.%); at 1.0 m 100 cyclic voltammetry, chronoamperometry, potentiodynamic polarisation and eis [114] cu spin-coating of gr with acetone (20 cm3 cm-2) then rapid annealing 8001000 ºc for 3 min seawater 3.0–3.5% nacl 0.25 potentiodynamic polarisation, scan rate: 2 mv s-1, eis [136] steel pani-gr comp. (nmp complex and casting) 3.5 wt.% nacl solution unknown potentiodynamic polarisation [153] coldrolled steel gro red. with n2h2, pressing powders then curing (thickness: ~120 µm) 3.5 wt.% nacl, at 25oc 1 potentiodynamic scanning at 10 mv min-1, after 30 min eis [161] low alloy steel 2 wt.% gr/mwcnt/pei & 20 wt.% gr/pei comp.-s, dispersion in paa cured at 150 ºc for 5 min, then 250 ºc for 5 min for imidisation 3.5 wt.% nacl solution 9.62 potentiodynamic polarisation (scan rate: 1.67 mv s-1) [7] figure 11: tafel plots of the (a) bare, (b) epoxy-coated, (c) he coated, and (d) hegc-coated crs electrodes [178] (by courtesy of the publisher, elsevier) 99 a more exotic approach is to develop metal-gr composites for corrosion protection, although this strategy may have more disadvantages than advantages like with the metal-cnts [179-182] because of the cnt activity towards catalytic oxygen reduction reactions [183-185]. electrodeposited thin films of nickel matrix with gr inclusion indicated a slight improvement in general protection performance; ennobled ocps by ~0.1 v and steady corrosion currents reduced by over 50% were observed in comparison with pure nickel coated mild steel [186]. as a result of greatly affected nucleation and growth rate, measurement results are much more related to the highly altered crystalline structure of the nickel host matrix (lower electrical conductivity was unfortunately not characterised) as a consequence of the inclusion of gr sheets, but differences in the texture and hardness of pure nickel and the gr-nickel coatings were reported. similarly to many other works, protection efficacy was not evaluated and reported over long-term immersion testing. on the one hand, the tafel analysis of ni and ni–gr performed in 3.5 wt.% nacl solution (in fig.12) was carried out using high voltage rate scanning without ohmic drop compensation, leading to distorted current legs over both potential regions (from the open-circuit or free corrosion potential of the electrode). a less representative transient is due to the low proportion of faradaic charge-transfer current primarily assigned to the credible corrosion rate assessment. probably due to these reasons, there is not much difference between the given corrosion currents of ni and ni-gr samples. the gr incorporation, cathodic and anodic tafel regions exhibited almost ideal symmetry. this should mean the same scale of activation (expressed as a transfer function) in the cathodic (reduction and deposition) and anodic (oxidation and dissolution and/or deposition) processes. this feature is a kind of ineffectively blocked electrode behaviour, a quite reversible characteristic with less viable hindrance either in the anodic or cathodic processes. this suggestion seems to be confirmed by the reported similar corrosion currents. on the other hand, the adequacy of eis data may also be doubtful as basic requirements of system stability (in the time domain), linearity (immediate response), and causality (the unquestionable relationship between perturbation and type-degree of response) might not be met. the time frame of 5 min to wait for a stationary or a steady-state condition then making measurements is in itself questionable. the large variation in the solution resistance (between the pure and composite ni coating) is surely inadequate. in addition, the highly varied interfacial and coating resistance (swop between them) along with a hundred times difference in the coating capacitance are also unbelievable and can lead only to false interpretation. the depressed semicircle is a result of the complexity of the ni/gr electrode interface. the electrode was a porous electron and ion conductor and such systems need to be carefully handled (modelled with at least two transmission lines) when evaluation of impedance spectra in relation to structure and mechanistic behaviour of a complicated interface comes into the picture. therefore, presented data and the corresponding evaluation are not appropriate and even misleading. an innovative approach is the composite of multiwalled cnts (mwcnts) and exfoliated gr embedded in polyether-imide (pei) serving as a coherent and porefree matrix [187]. this endeavour was made in an attempt to achieve a uniform dispersion of the nano-size additives in the host matrix (without functionalisation of the filler phase) and good adhesion of tailored pei to the substrate, facilitating the maximum attainable corrosion protection performance. the protection mechanism was delineated according to the following: the composite protects steel alloys by a complex, active–passive way, serving as a physical barrier to water permeation against the evolution of ion channels to the metal surface and passivating metal surface by electron depletion at the interface based on the schottky barrier effect [188-190]. figure 12: tafel curves of ni and ni–gr materials [186] (by courtesy of the publisher, elsevier) figure 13: cryo-fractured sem images of (a) and (b), pei, (c) and (d) 2 wt.% nfg/mwcnt/pei, (e) and (f) 20 wt.% unfg/pei [187] (published with permission from the! american ceramic society bulletin) 100 exfoliated but non-functionalised gr was derived from ultrasonication in a solution of n-methyl-pyrrolidone (nmp). pei as a host matrix was selected for its flexibility under a high glass transition temperature (155 ºc), thermal stability, firm resistance against radiation and appropriate interaction with carbon fillers via π–π stacking [191-193]. in situ synthesis and the imidisation protocol yielded coatings with appropriate adhesion properties to the steel surface of a thickness of 15– 20 µm, whereas agglomeration and phase segregation of the fillers were low with the mwcnts. the sem investigation revealed a fairly smooth surface finish without cracks or visible pinholes in the coatings. no phase segregation of the gr and mwcnt fillers was observed in the mixtures around the interface as its clearly seen in fig.13 of the cryo-fractured samples of non-functionalised gr (nfg), carbon nanotubes and pei in 2 wt.% (c and d) and nfg/pei of 20 wt.% (e, f) in comparison with pure pei (a and b). ocps were positively shifted by ~0.6 v, meaning a remarkable ennoblement. this was inferred, although substrates with high resistance coatings showing notable positive potentials must be at least partially attributed to the potential drop through the coatings [194] as a result of masking the real corrosion potential of the metalcoating interface to various extents. a potentiodynamic test indicated current densities of several orders of magnitudes lower (~10-9 a cm-2) for composite coated specimens compared to bare low-alloy and galvanised steel samples with current densities of ~10-5 a cm-2. immersion tested samples were characterised quantitatively with regards to the perspective of corrosion rate or protection of steel substrates by weight-loss measurement (according to the astm-g1 protocol) after 3,144 hours. the substrate coated with 20 wt% gr-pei performed best with ca. thousand times lower corrosion rates (ca. 8.5×10-4 mm year-1) than bare low-alloy steel samples (ca. 1.2×10-1 mm year-1). however, the pei film containing gr and mwcnt (ca. 9.2×10-3 mm year-1) manifested a moderate average corrosion rate of ca. 5.5×10-4 mm year-1 compared to the neat pei film. concluding remarks overall, it is evident that atomic pure graphene films lack uniformity and partly this leads to insufficient instantaneous protection performance. therefore, some sort of physical and/or chemical post-treatment is needed to facilitate long-term protection performance from direct deposition techniques, the broadly and thoroughly investigated cvd technique is undoubtedly a viable alternative when large-scale continuous surface finishing is highly demanded. however, it is far from the best choice when corrosion protection efficiency and durability are the priorities, due to the complexity of growing cohesive films on the surface of metal substrates with preferable orientation of the grains, and weak adherence of gr films sensitive to mechanical and surface charging effects. when performance is an essential preference then spin-coating, kinetic spray, electro-spinning, and electrophoretic deposition should be employed depending on the complexity of the surface, conductivity of the substrate and additional technological aspects in relation to further processes. among them, spin-coating and kinetic spray techniques develop good quality and homogeneous coatings of greatly varied thicknesses. thin and ultra-thin films feature high a dispersity, and an even distribution and sometimes even improved quality of the nanoparticles. when thicker coatings are obtained on electrically conducting substrates with strong adhesion to complex surface geometries without the matter of a certain degree of alteration of the nanoparticles, then electrophoretic deposition must be used. with respect to the 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(eds.): handbook of corrosion protection, theory and practice of electrochemical protection processes, third edition, golf publishing company, houston tx, usa, 1997 hungarian journal of industry and chemistry veszprém vol. 41(2) pp. 109–114 (2013) investigations of bio-gasoil production péter solymosi, ! zoltán varga, and jenő hancsók mol department of hydrocarbonand coal processing, university of pannonia, egyetem u. 10., veszprém, 8200, hungary !email: solymosip@almos.uni-pannon.hu liquid engine fuels are the main source of power for transportation in the passenger sector. it is the projection of the european union (eu) to reach 10% utilisation of renewable fuels by 2020. to achieve this goal the eu created the 2003/30/ec and furthermore the 2009/28/ec directives. for example, the feedstocks of these renewable engine fuels can be non-edible oil plant hybrids, such as rapeseed oils with high euric acid content obtained from special hybrids of rape (e.g. brassica napus) waste lards (used cooking oil and slaughterhouse lards). if the preconditions of utilisation are given with respect to the sustainability and technical compatibility of motor engines and vehicle construction, these bio components can be blended with motor fuels in large quantities. considering the properties of currently used first generation biofuels, the maximum amount of bio-component in engine fuels is approximately 7 (v/v)% fatty acidmethylester in diesel fuels. a reliable production technology of second generation biofuels, which can be blended into diesel fuels is the heterogenic catalytic hydrogenation of triglycerides and waste lards. furthermore, isomerisation can improve the quality of a bio-paraffin mixture. in this context, we studied the isomerisation of bio-paraffin mixtures, which were obtained from the hydrodeoxygenation of vegetable oil. the characteristics of these products were favourable, such as their cetane number being higher than 75, for example. the actual en590:2013 standard does not limit the blending ratio of the paraffinic bio-component in diesel fuels. consequently, these products obtained by the catalytic hydrogenation of vegetable oils can be blended into gasoil by up to 10 % or even more to meet the above eu requirements with respect to the utilisation of renewable fuels. keywords: bio gasoil, hydrodeoxygenation, catalytic conversion, biofuels, blending diesel fuels introduction interest in alternative fuels is on the rise due to the unequal presence of the fossil energy carriers, the periodic rise in the price of fossil fuels, the need for decreasing dependence on crude oil, and the regulations of the european union. they can play a significant role in achieving the eu plan to reach a 10% energy ratio of total fuel consumption using alternative fuels by 2020. thus, the application of the biofuels can be increased to a large degree in the longand medium-terms. for example, in some countries the domestic demand on biofuels could increase to 20% by 2030, along with the decrease in the demand for engine fuels that could be up to 70%. the world’s energy production from biomass could reach 5% by 2050 [4, 5]. accordingly, to ensure the availability of this feedstock the production costs could decrease. to achieve these goals, the eu created several directives (1998/70/ec, 2001/77/ec, 2003/17/ec, 2003/30/ec, 2003/87/ec, 2009/28/ce, and 2009/30/ce). natural triglycerides like vegetable oils (edible or non-edible/waste) can be feedstock for biofuels as alternative energy sources [6, 7], such as special breeding non-edible oil plants [8, 9], animal fats or waste cooking oil [10, 11]. during the conversion of natural triglyceride molecules to bio-gasoil the following reactions take place [1, 2, 3]: • full saturation of double bonds (hydrogenation), • heteroatom removal o oxygen removal " hydrodeoxygenation (hdo reaction, and reduction) " decarboxylation, " decarbonylation o removing of other heteroatoms (sulphur, nitrogen, phosphorous, and metals), • isomerisation of n-paraffins that are formed during the removal of oxygen • different side reactions o hydrocracking of the fatty acid chain of triglyceride molecules, o water-gas shift reaction o methanisation, o cyclisation, aromatisation, etc. during the hdo reduction reaction normal paraffins are formed with carbon numbers that are equal to the fatty acids in triglycerides. in the case of decarboxylation and decarbonylation reactions (hdc) normal alkanes are produced, where the carbon number is one less than that of fatty acids of the original vegetable (fig.1). bio-gasoil is a mixture of gasoil with the boiling range of isoand normal-paraffins. it can be obtained by the hydrogenation of vegetable oils and natural triglycerides 110 from other sources. these constitute the second generation biofuel components of diesel engines. they have good quality characteristics, such as high cetane number, good flow properties, unlimited mixability with engine fuels, and the a production line compatible with existing refinery structures [18, 19]. the actual en 590:2013 standard does not limit the blending ratio of second generation bio-components, while the blending of biodiesel is limited to 7 v/v%. all the above mentioned aspects of alternative fuels can rationalise the investigation of the hydrogenation of non-traditional feedstock sources. these are the vegetable oils that can be obtained from non-edible hybrid oil-plants, rapeseed oil from brassica napus with high euric acid content to produce diesel fuel blending components with good flow properties in colder conditions (below +5 °c). the freezing point of iso-paraffins from bio-sources is lower than for equal chain length normal-paraffins (fig.1) [12-15, 17]. thus, products with high iso-paraffin contents have more favourable cold flow properties (cfpp) with cloud points at lower temperatures (fig.2). the aim of our work was the production of diesel gasoil blending components via the isomerisation of paraffin mixtures obtained from the hydrodeoxygenation of rapeseed oil with high euric acid content. experimental in this work, a diesel gasoil bio-blending component production technique was investigated that meets the requirements of the en:590 standard with the possibility of blending it with engine fuels in unlimited quantities. thus, the hydrodeoxygenation of natural triglycerides and further the isomerisation of the obtained bio-paraffin mixture were investigated over the pt-sapo-11 catalyst [16] developed in-house. the effect of the operation parameters, such as temperature, pressure, and liquid hourly space velocity (lhsv) was studied on the yield, composition, and utilisation properties of the products. experimental apparatus and product separation the experimental tests were carried out in one of the measured sections of a high-pressure reactor system containing two tubular reactors with a isothermal catalyst volume of 100 cm3. the reactor system contained all the equipment and devices applied in the reactor system of a hydrotreating plant. the apparatus is suitable for maintaining if not succeeding the industrial precision of main process parameters. analytical methods the main properties of the feedstock materials and products were determined by standard methods. the hydrocarbon composition of the bio-paraffin mixture was determined by high temperature gas chromatography (shimadzu 2010 gc [column: phonomenex zebron mxt]). process parameters the ranges of the applied process parameters in the isomerisation test on the basis of our earlier experimental results [13, 14, 17, 20-23] were as follows: temperature 300–360 °c, total pressure 20–80 bar, liquid hourly space velocity (lhsv) 1.0 h-1, and h2/feed volume ratio of 400 nm3 m-3. feedstock materials the feedstock of the catalytic tests was a bio-paraffin mixture, which was obtained from the hydrodeoxygenation of rapeseed with euric acid produced in hungary. it was properly filtered as a pre-treatment. the main properties of the feedstock material are shown in table 1. the catalyst was pt-sapo-11 (0.5 % pt), the main properties of this can be found in table 2. figure 1: pathways for the removal of oxygen from vegetable oils figure 2: the freezing point of iso-paraffins as a function of the branch position 111 results and analysis the first step was to produce a bio-paraffin mixture with a boiling range of gasoil from rapeseed with a high euric acid content. the properties of the bio-paraffin are summarised in table 1. the commercially available nimo/al2o3 catalyst was utilised for the production of the bio-paraffin mixture. during the catalytic test the employed operation parameters were as follows: 320– 380 °c, 20–80 bar, lhsv = 1.0 h-1, and h2/ch ratio of 600 nm3 m-3 [8]. it was found that the favourable operation parameters are 340 °c, 40 bar, lhsv=1.0 h-1, and h2/ch ratio of 600 nm3 m-3. the tested catalyst is suitable for the production of bio-paraffin mixtures with high yields from natural triglycerides. due to the moderate acidity of this catalyst, the formation of isoparaffins was lower (5 wt%, fig.3). accordingly, the cfpp of the products was found to be high (27 °c). the product fraction produced in this way, in practice, cannot be blended into diesel fuels in low temperate zone countries. it is necessary then for the improvement of cfpp via the catalytic isomerisation of this mixture with high normal-paraffin content [10, 11]. a large amount of bio-paraffin mixture was produced in a thousand hour, long-term catalytic test. the target fraction of the isomerisation tests was the 180–360 °c boiling range, which is the boiling range of gasoil. the yield of the target products was higher than 94 % in all operation parameter combinations (fig.4). the lighter fraction with a boiling range of up to 180 ºc contains mainly iso-paraffins, which can be outstanding gasoline blending components due to their high octane numbers (>85). we found that by adjusting the operation parameters, such as increasing the temperature, and decreasing the lhsv, the yield of the target fraction was decreased due to the higher yield of the cracking reaction. the target fraction obtained between 70% and 80% table 1: selected properties of the feedstock materials properties rapeseed oil bio-paraffin mixture kinematic viscosity at 40 °c, mm2 s-1 46.56 3.493 density at 15 °c, g cm-3 0.9804 0.7923 cloud point, °c 16 32 cetane number 42 104 compositions, % fatty acid paraffin c16:0 2.3 c140.2 c16:1 0.1 c14 0.1 c18:0 1.2 c15 0 c18:1 28.8 c16 2.3 c18:2 12.4 c17 29.5 c18:3 8.3 c18 28.8 c20:0 0 c19 6.1 c20:1 4.8 c20 5.6 c22:0 0.1 c21 14.8 c22:1 41.8 c22 12.5 other 0.2 c22+ 0.1 figure 3: hydrogenation of rapeseed oil with high euric acid content (diamond: residual triglyceride, square: iso-paraffin content, cross c21/c22 ratio) table 2: selected properties of the isomerisation catalyst used properties pt/sapo-11 pt content, w% 0.5 pt dispersity, % 69 bet surface area, m2 g-1 105 average pore size, nm 0.61 micropore volume, cm3 g-1 0.06 macropore volume, cm3 g-1 0.20 total pore volume, cm3 g-1 0.26 acidity, mmol nh3 g-1 0.13 acidity (rel.), mmol nh3 m-2 cat. 0.0012 112 contained c17–c22 hydrocarbons, as well as other (c13– c16) hydrocarbons from the boiling range of gasoil. the iso-paraffin content of the target fraction increased significantly with the operating temperature (fig.5). the increase of the iso-paraffin concentration occurred at 360 °c then at higher temperatures it started to decrease, due to the thermodynamic hindrance of the exothermic reactions, and the higher rate of cracking reactions. up to ca. 320 °c, mainly mono-branched isoparaffins were formed and were by in large mono-ethylparaffins (fig.6). the freezing points of these products are much lower than normal-paraffins and the cetane number is high enough for a fuel additive. the greater formation of mono-methyl-paraffins over the sapo-11 catalyst can be explained by the reduced formation of iso-paraffins due to steric hindrance. at 340 °c or higher, the formation of multi-branched isomers was significant (fig.6). these compounds have better cold flow properties (below -20 °c), but their cetane numbers are high enough (30–45) as shown in fig.2. the favourable operation parameters in terms of biogasoil yield and iso-paraffin concentration were as follows: t = 360 °c; p = 40 bar; and h2/feedstock ratio = 400 nm3 m-3. the cfpp values of the products as a function of temperature and operation pressures are shown in fig.7. these components have low enough cfpp values to blend into diesel gasoil in moderate amounts. on the basis of the experimental results, it was concluded that the production of bio-gasoil meets the standard’s requirements with a cfpp value of max. +5 °c and 70% iso-paraffin content (fig.8) in the case when the raw material contains 8% c17–c22 isoparaffins. conclusions based on our experimental results, it was concluded that the nimo/al2o3 catalyst is suitable for the long-term production of bio-paraffin mixtures from natural triglycerides via catalytic hydrodeoxygenation. furthermore, the investigated pt-sapo-11 catalyst is suitable for improving the quality of a bio-paraffin mixture that was obtained from the hydrodeoxygenation of rapeseed oil with high euric acid content. during the isomerisation with optimised operation parameters, the yield of the target fraction was higher than 94%. at 340 °c or higher the iso-paraffin content is close to 70%. consequently, the cold flow property of the cloud point is lower than +5 °c. therefore, this approach can produce gasoil bio-blending components with good utilisation properties, such as high cetane number, and low temperature values for cold flow properties. overall, the products described here are suitable for blending components of diesel fuels with concentrations of 10% or higher. figure 6: the composition of the products as a function of operation parameters (pressure: 40 bar, liquid hourly space velocity: 1.0 h-1) figure 7: cffp of the products as a function of operation parameters (liquid hourly space velocity: 1.0 h-1, h2/feed ratio: 400 nm3 m-3) figure 4: the yield of the target fraction as a function of operation parameters (pressure: 40 bar, liquid hourly space velocity square: 1.0 h-1, diamond 2.0 h-1, triangle 3.0 h-1) figure 5: the iso-paraffin concentration of the target fraction as a function of operation parameters (pressure: 40 bar, liquid hourly space velocity: square 1.0 h-1, diamond 2.0 h-1, triangle 3.0 h-1) 113 acknowledgements we acknowledge the financial support of the hungarian state and european union under támop-4.2.2.a-11/1/ konv-2012-0071 and támop-4.1.1.c-12/1/konv2012-0017. references [1] huber g.w., o’connor p., corma a.: processing biomass in conventional oil refineries: production of high quality diesel by hydrotreating vegetable oils in heavy vacuum oil mixtures, appl. catal. a:general, 2007, 329,120-129 [2] da rocha filho g.n., brodzki d., djegamariadassou g.: formation of alkanes, alkylcycloalkanes and alkylbenzenes during the catalytic hydrocracking of vegetable oils, fuel, 1993, 72(4), 543-549 [3] simacek p., kubicka d., sebor g., pospisil m.: fuel properties of hydroprocessed rapeseed oil, fuel, 2010, 89(3), 611-615 [4] schollnberger w.e.: between 2020 and 2030 to be re-joined the course for the global energy mix, erdöl erdgas kohle, 2013, 129(12), 2-7 (in german) [5] shell deutschland oil gmbh: shell study sees great potential for biofuels, erdöl erdgas kohle, 2012, 128(11), 407-411 (in german) [6] krár m., kovács s., kalló d., hancsók j: fuel purpose hydrotreating of sunflower oil on como/al2o3 catalyst, bioresources technology, 2010, 101(23), 9287-9293 [7] krár m., kasza t., kovács s., kalló d., hancsók j.: bio-gasoils with improved low temperature properties, fuel proc. techn., 2011, 92(5), 886-892 [8] solymosi p., baladincz p., hancsók j.: production of motor fuels by the hydrogenation of rapeseed oil with high euric acid content, proc. 19th eu biomass conference and exhibition, berlin, germany, 2011, 2077-2081 [9] solymosi p., kasza t., hancsók j.: investigation of conventional and high oleic acid content rapeseed or sunflower oils, hung. j. ind. chem., 2011, 39(1), 85-90 [10] baladincz p., tóth cs. hancsók, j.: expanding feedstock supplies of the second generation biofuels of diesel engines, hung. j. ind. chem., 2010, 38(1), 1-7 [11] solymosi p., eller z., hancsók j.: motor fuel purpose hydrogenation of used cooking oils, chem. engng. trans., 2013, 35(2), 1351-1356 [12] hancsók j., kasza t., kovács s., solymosi p., holló a.: production of bioparaffins from natural triglycerides, chem. engng. trans., 2011, 25, 821826 [13] kasza t., hancsók j.: isomerisation of bioparaffins over pt-based sapo-11 and almcm-41 catalysts, műszaki kémiai napok, 2011, 29, 220225 (in hungarian). [14] kasza t., holló a., thernesz a., hancsók j.: production of bio-gasoil from bioparaffins over pt/sapo-11, chem. engng. trans., 2010, 21, 1225-1230 [15] hancsók j., kasza t., kovács s., solymosi p., holló a.: production of bio-gasoil from bioparaffins over pt/sapo-11, j. cleaner prod., 2012, 34, 76-81 figure 8: cold flow properties as a function of iso-paraffin concentration (solid squares: cold filtering clugging point, hollow diamonds: cloud point) 114 [16] gergely j., forstner j., balai m., szirmai l., petro j., kovács i., resofszki g., smid l., auer j., baladincz j., szalmásné pécsvári g., tóth l., kubovicsné stotz k., kun j., kántor l., czágler i., lővei j., tóth e., lefkánics gy., tátrai e., pálné borbély g., rosenbergné mihályi m., beyer h., hancsók j.: a selective hydroisomerisation catalyst preparation and application for hydrocarbons hu 225 912, 2001 (in hungarian) [17] kasza t., kalló d., hancsók j.: quality improvement of bio-paraffin mixtures, fuel, 2014, 120, 1-7 [18] hancsók j., krár m., magyar sz., boda l., holló a., kalló d.: investigation of the production of high cetane number biogasoil from pre-hydrogenated vegetable oils over pt/hzsm22/al2o3, micropor. mesopor. mat., 2007, 101(12), 148-152 [19] srivastava s.p., hancsok j.: fuels and fuel additives, wiley and sons, hoboken, nj, usa, 2014, pp. 121-177 [20] kasza t., baladincz p., hancsók j.: production of bio-isoparaffins by the hydroisomerisation of bioparaffins. hung. j. ind. chem., 2009, 37(2), 95–99 [21] kasza t., hancsók j.: production of depressed freezing point bio-gasoil from slaughterhouse waste lard. hung. j. ind. chem., 2010, 38(1), 41– 45. [22] kasza t., hancsók j.: isomerisation of paraffin mixtures produced from sunflower oil. hung. j. ind. chem., 2011, 39(3), 363–368 [23] kasza t.; tóth cs.; hancsók j.: application of improved bio-paraffins in diesel fuels, hung. j. ind. chem., 2012, 40(1), 25–31 hungarian journal of industry and chemistry veszprém vol. 41(2) pp. 115–118 (2013) the energy balance of separation opportunities in microalgae technologies zoltán hodai, ! dóra rippel-pethő, géza horváth, lászló hanák, and róbert bocsi department of chemical engineering science, university of pannonia, veszprém, egyetem u. 10., 8200, hungary !email: hodaiz@almos.uni-pannon.hu algae technology is at the focus of international research and development, since it is a green technology that reduces emissions of harmful chemicals and can be considered as a renewable energy source. carbon dioxide from stack gases and the nitrogen content of wastewater can be considered as food sources for plants and algae. the utilisation of carbon dioxide by algae technologies depends on the technical environment and logistics of teamwork. this technology is a new opportunity in hungary for decreasing emissions. we grew algae populations to utilise the carbon dioxide from a refinery’s stack gas in the continental climate of hungary. critical parameters of the technology are the concentration of the algae suspension and extract, because of high investment and operating costs as well as the long operation time, which determines the feasibility of the algae technology. our specific aim was to separate the algae mass faster and more efficiently from the starting solution. the optimisation of separation operations and technologies took into consideration environmental and economic aspects. keywords: microalgae technology, separation, filtration, renewable energy source introduction the utilisation of microalgae carbon dioxide fixation is an important area of international research and development. the absorption of certain technological exhaust gases is possible on the basis of the photosynthesis of microalgae. the absorption of carbon dioxide can reach a magnitude of hundred ton per hectare. c16-c22 esters are formed in certain algae cells that can be used for the production of biodiesels. this method is thus capable of producing fuels from renewable sources [1-4]. algae production is a promising solution amongst the alternative fuel production processes, because it requires of low specific area for growth and high reproduction rate [5-8]. algae are considered to be one of the most efficient organisms on earth due to their outstanding reproduction rate, and generally high lipid content. for example, they can double their biomass in 24 hours [9-12]. their lipid content on average is 20%, but it can be up to 60-80% for certain species [7, 9, 13, 14]. research into oil production from algae is primarily based on microalgae. these are photosynthesising organisms with a cell size of no greater than 0.5 mm. they can be utilised for carbon dioxide and nitrogen oxide fixation, because they convert these compounds in a photosynthetic energy conversion [15]. the end product of these processes contains a significant amount of solar energy stored as chemical energy. furthermore, considerable amounts of biodiesel can be obtained [16-19]. the composition of a microalgae cell depends on cultivation parameters. we tested the available and applicable species under local climatic conditions. afterwards microalgae that passed the local environmental tests can be considered useable for production. research is being carried out into carbon dioxide fixation from technological flows at our institute [15]. the absorption of carbon dioxide and reduction of the release of other pollutants in wastewater using microalgae are being studied. algae technology utilises waste gases and some environmentally harmful components from wastewaters as nutrients, and thus purifies the growth media. these specific pollutants provide excessive amount of nutrients for the algae, which results in the algae’s exponential growth. in addition to the above-mentioned method of energy extraction, a number of research efforts [4, 5, 8, 10-12, 18, 19 25] are currently dealing with the alternative use of biomass produced in this way, and biomass residue that remains after processing. in addition to the abovementioned advantages, the operating costs can be a limiting factor. the most critical steps in the production of algaebased biofuels are the harvesting of algae (harvesting, dewatering, and drying), and lipid extraction, because of the high level of investment and operating costs. the main challenge of the technology is to reduce costs, which by in large originate from the separation steps that need to be minimised. 116 results and discussions our research focuses on carbon dioxide fixation from technological flows. we designed and built various grower systems at the department of chemical engineering of the university of pannonia (fig.1), as well as at a refinery (figs.2 and 3). by utilising these technological solutions we conducted research into the production of biomass and algae-based products as possible renewable fuels. the propagation and environmental tolerance parameters were examined along with the possibilities of developing the technology. during the experiments, the whole technological chain was examined providing the possibility to optimise the entire chain of operational steps. the utilisation of algae cultures in experimental photobioreactors is examined, together with the optimisation of the operational conditions both for both artificial and natural light with different substrate solutions. the various parameters for algae processing are also determined. the foci of our work were the processing and separation operations. critical points of the technology are the processing steps, such as concentrating the algae suspension and extracting valuable components (lipids). the extraction technologies are of importance because of the high costs of investment and long operation periods. from the literature [5, 10, 12, 15, 17, 22, 23], biodiesel is not yet comparable to fuel produced from petroleum, however the cost of algae technology is dropping. furthermore, algae technology could become viable if we consider the cost of wastewater purification and flue gas adsorption, and the price of products obtained from microalgae. we need to consider separating possibilities and beyond by analysing gains and losses simultaneously. our specific aim was to devise densification and separation processes, which have low energy requirements and advantageous operation times. furthermore, we defined useful components from algae and their optimised extraction, based on the optimisation of extraction techniques and other economical and environmental aspects. separation opportunities harvesting can be carried out by microfiltration, ultra filtration, centrifugation, flocculation, sonochemical techniques, or some new techniques that are under development [21, 22]. in addition to chemical flocculation, clarification, and membrane separation procedures, special attention was paid to auto flocculation phenomena. forms of technology pay more and more attention to convert disposed waste into useful materials. the photosynthesising microorganisms, such as microalgae, utilise solar energy, rapidly reproduce, and do not require any soil to grow in. the biomass product contains solar energy stored in chemical bonds. to process the final product, the suspension, concentration, and extraction of the biomass are the most problematic parts of the methods of algae-based energy production. the main techniques for separation are mechanical operations (filtration, centrifugation, and settling), mechanical operations with admixture (flocculation and defecation), membrane operations (microfiltration and ultrafiltration), and other notable operations (sonochemical techniques, electroflocculation, and flotation). according to examples from the literature [9, 11, 15, 18], there are still only limited generally applicable and proven methods that can be used for biomass production with specific energetic goals. energetic considerations increasingly diluted suspensions were examined during separation operations (fig.4). data from the literature [23-37] need to be brought to a common denominator for carrying out comparisons. for example, our results show that if we want to gradually treat more dilute suspensions using flotation, the energetic considerations can change by orders of magnitude. figure 1: closed grower systems at the university of pannonia figure 2: closed grower systems at a refinery figure 3: open grower systems at a refinery 117 according to fig.4, cross-flow membrane separation, electroflocculation, centrifugation known as “spiral plate”, immersion membrane separation, the flocculation, foam flotation and operation of the flotation by dispersed air are positioned favourably with respect to energetic rating (smaller demand of energy as the energy amount from the separated biomass). the energy balances of chemical flocculation and electroflocculation do not include the costs of the procurement of chemicals and post-treatment, which would complicate the determination of its energy status. the amounts of chemicals used according to the quality of the suspension were between such wide intervals that they could not be considered using simple factors. by energetic rating, we should note the concentration of the kind of algae suspension in the chosen operation. the increase in volume and decrease in concentration of the suspension may require a review of the cost, materials and energy needs of the separation, and thus change its energetic status. for example, we can conduct a thought-experiment for flotation to see whether the treatment of a dilute suspension needs a device with a different energetic rating. because of the fixed size of the flotation’s device, we cannot decrease the amount of gas flow and the dilute suspension could start to foam, which may make it more difficult to handle than the stability and volume of the foam from a more concentrated suspension. due to foaming, it will be more difficult for the algae layer to become thicker in the foam unless we use more chemicals and surfaceactive agents, which result in more parameters to consider. apart from the above, an important question is how we consider the time domain of the technology (periodic, half-continuous, or continuous). the kind of growing system determines how to connect the separation operation. half-continuous or continuous (or almost that) operation is beneficial for industrial biomass production to maximise the capacity of biomass. by running the reactor at the maximum rate of reproduction, we can maximise its capacity. according to the latter, the immersion membrane separation operation would be preferable. conclusions according to our investigations, the usable operations for extraction and concentration in algae cultivation with regards to energetic causes vary greatly with respect to energy demands. for dilute suspensions, flotation and foam flotation are the most useful separation processes. we can use flocculation as well, but we have to consider the costs of and environmental damage caused by waste chemicals. acknowledgements this research was supported by the european union and the state of hungary, and co-financed by the european social fund in the framework of támop 4.2.4. a/211-1-2012-0001 ‘national excellence programme’. references [1] straka f., doucha j., lívansky k.: utilisation of flue gas for cultivation of microalgae (chlorella sp.) in an outdoor open thin-layer photobioreactor, j. appl. phycology, 2005, 17(5), 403-412 [2] olaizola m.: microalgal removal of co2 from flue gases: changes in medium ph and flue gas composition do not appear to affect the photochemical yield of microalgal cultures, biotechn. bioproc. engng., 2003, 8(6), 360-367 [3] lamenti g., prosperi g., ritorto l., scolla g., capuano f., pedroni p.m., valdiserri m.: enitecnologie r&d project on microalgae biofixation of co2: outdoor comparative tests of biomass productivity using flue gas co2 from a ngcc power plant, proc. 7th int. conf. greenhouse gas control technologies, 2005, 2(1), 1037-1042 [4] carlsson a.s., bilen j.b., möller r., clayton d.: mircroand macroalgae: utility for industrial applications, ed.: bowles d., outputs from the epobio project. cpl press, berks, uk, 2008 [5] briggs m., vasudevan p.t.: biodiesel production-current state of the art and challenges, j. ind. microbiol. biotechnol., 2008, 35, 421-430 [6] hwang e.j., shin h.s., chae s.r.: single cell protein production of euglena gracilis and carbon dioxide fixation in an innovative photobioreactor, bioresource technol., 2006, 97(2), 322-329 [7] becker e.w., baddiley j.: microalgae: biotechnology and microbiology, cambridge univ. press, new york, usa, 1994, p. 178 [8] posewitz m.c., jinkerson r.e., subramanian v.: improving biofuel production in phototrophic microorganisms with systems biology tools, biofuels, 2011, 2(2), 125-144 figure 4: the energetic consideration of selected separation processes (the dashed line shows the energy content of algae suspensions on average of 25 mj m-3) 118 [9] kojima e., zhang k.: growth and hydrocarbon production of microalgae botryococcus braunii in bubble column photobioreactors, j. biosci. bioengng., 1999, 87(6), 811-815 [10] briggs m.: wide-scale biodiesel production from algae, ph.d. dissertation, university of new hampshire, 2004 [11] hwang e.j., shin h.s., chae s.r.: single cell protein production of euglena gracilis and carbon dioxide fixation in an innovative photobioreactor bioresource technol., 2006, 97(2), 322-331 [12] chisti y.: biodiesel from microalgae, biotechnol. adv., 2007, 25(3) 294–306 [13] dismukes g.c.: algal photosynthesis, princeton university press, 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33(7), 229–241 [36] collet p., hélias a., lardon l., ras m., goy r.a., steyer j.p.: life-cycle assessment of a microalgae culture coupled to biogas production, bioresoure technol., 2011, 102(1), 207–214 [37] cowarda t., leea j.g., caldwellb g.s.: development of a foam flotation system for harvesting microalgae biomass, algal research 2013, 2(2), 135-144 hungarian journal of industry and chemistry veszprém vol. 41(2) pp. 119–122 (2013) solid-liquid extraction of chlorophyll from microalgae from photoautotroph open-air cultivation éva molnár, ! dóra rippel-pethő, and róbert bocsi department of chemical engineering, institute of chemical and process engineering, university of pannonia, egyetem u. 10., veszprém, 8200, hungary !email: molnare@almos.uni-pannon.hu among industrial pollutants, strict quotas limit the emission of carbon dioxide in the european union. the capturing and deposition of carbon dioxide requires significant expenditures. one of the newer solutions for the reduction of the carbon dioxide emissions is provided by algae technology. in this technology, the absorption of carbon dioxide is achieved by photosynthesis. besides the reduction of pollutants, algae technology has another advantage by supplying valuable products, such as natural pigments, proteins, vitamins and oils from algae biomass. since it has a high reproduction rate, algae cultivation can be a feasible substitute for plants traditionally used in the production of chlorophyll. the viability of the technology is dependent on whether or not the processing can be done economically. an investigation was carried out in order to compare and contrast two extraction methods (soxhlet extraction and leaching) and four solvents (acetone, diethyl ether, ethanol and methanol) to determine the most effective method for the extraction of chlorophylls from dried microalgae (chlorella vulgaris sp.). it was concluded that methanol is the most effective solvent for the extraction of both chlorophylls a and b using both soxhlet extraction and leaching. keywords: microalgae, extraction solvent, extraction, chlorophyll, spectrophotometry introduction energy demand has been rapidly increasing throughout the world, which is mainly met by the combustion of fossil fuels that results in an increase in the concentration of greenhouse gases in the atmosphere. however as a possible remediation strategy, carbon dioxide levels can be reduced with the use of algae technology [1]. algae technology is of significant interest in research and development since it is a ‘green’ technology that is capable of both decreasing the emission of pollutants and serving as a renewable energy source. the algae absorb carbon dioxide for photosynthesis while producing a number of valuable components [2]. microalgae are a collection of various microscopic species capable of photosynthesis and are typically found in water with an exceptionally high reproduction rate. for propagation, they mainly need light, water and co2. some species can even survive in waste water. algae are good alternatives for plants that are traditionally used for the production of chlorophyll. appropriate conditions are required for the successful cultivation of algae (solar energy, temperature, ph, and mixing) [3, 4]. however, the critical point of algae technology is neither cultivation nor processing. the biggest complication concerns the concentration of the microalgae suspension and the subsequent extraction of the valuable components due to the high investment costs and long operational times [5]. there is, however, an increasing demand for microalgae. the reason for this is that their oil content can be as much as 50% of their body mass, making them important in the production of biodiesel. the natural pigments, proteins and vitamins extracted from microalgae are primarily used by the pharmaceutical, cosmetic and food industries [3, 6]. chlorophyll has been used for centuries as a traditional remedy for unpleasant body odours, for the neutralisation of the odours of stool and urine, and detoxification or sterilisation of wounds. nowadays, its use is even more widespread. it is used as a food additive, food colouring, and nutritional supplement, especially because of its detoxifying and excellent basifying effects. it is also a strong antioxidant, which inhibits the harmful oxidative processes in the body and enhances the protection of cells and tissues [7, 8]. however, the processing of algae still needs to be improved with respect to determining the optimal methods, pieces of equipment, solvents, and parameters for the efficient and economic extraction of chlorophyll. extraction is a process that can be carried out in a number of ways. there are also a number of solvents and preparation methods available. also, variables such as pressure, temperature, the efficiency of contact and time all play an important role [9, 10]. chlorophyll is sensitive to extreme light exposure, ph values and temperatures [7-9]. when choosing the solvent, one has to consider the sensitivity of the extracted component. a number of considerations are important, too: density, viscosity, heat of evaporation, price, effect on the environment and health. it is also essential that the 120 solvent does not react with or cause damage to the extracted component and is not corrosive. different methods can be used for different microalgae species [9-10]. experimental in advance of the extraction experiments the algae suspension (chlorella vulgaris sp.) was concentrated, dried at 60 ºc until it reached a constant mass, then ground in a ball mill. chlorophylls a and b products were obtained by the methods detailed in the following sections from this ground algae powder, which contains approximately 4 wt% water. the soxhlet extraction method one of the most well known pieces of equipment for laboratory scale solid-liquid extraction is the soxhlet extractor. in a soxhlet extractor multiple fractional distillations are carried out, the extraction is always done with the pure condensate [10]. the first step of the extraction was to fill a cellulose casing with 1-3 g of algae powder. the filled casing was placed in the middle part of the piece of equipment (fig.1). the lower round-bottom flask was filled with 400 cm3 of solvent. the soxhlet extraction was carried out with methanol, ethanol, and acetone. pumice and a magnetic stirring rod were placed into the lower flask to ensure proper boiling. the cooling water was set to a continuous flow and then the heating was turned on. after the extracting solvents had reached their boiling points and started to evaporate, they condensed in the reflux condenser and dripped back down onto the algae powder at which point the extraction of the chlorophylls started. the liquid level continuously rose in the middle section until it reached the overflow pipe letting the chlorophyll extract pour back into the lower flask. a sample of 4–6 cm3 was taken at the end of every cycle. the extraction continued as long as the absorption spectra measured by the spectrophotometer did not show a significant change. the method of leaching leaching was carried out with so-called ‘cold solvents’ at room temperature. samples of 0.1 g; 0.5 g; and 0.75 g of algae powder were measured into a test tube, then 5– 5 cm3 of solvent was added. the list of solvents was the same as for the soxhlet extraction method with the inclusion of diethyl ether. the weight of the solvent was also measured and recorded in order to have reference data in the later phases of the experiment. the samples were mixed with vortex and centrifuged for 2 minutes at 4000 rpm. a sample was taken from the top layer after centrifuge and its absorbance measured with a spectrophotometer [11, 12]. calculations the chlorophyll contents of the given samples were calculated with empirical formulae according to eqs.(1)-(8). cchlorophyll-a(90% methanol) = 15.65·a666 7.34·a653 (1) cchlorophyll-b(90% methanol) = 27.05·a653 11.21·a665 (2) cchlorophyll-a(96% ethanol) = 13.95·a665 6.88·a649 (3) cchlorophyll-b(96% ethanol) = 24.96·a649 7.32·a665 (4) cchlorophyll-a(100% acetone) = 11.75·a662 2.35·a645 (5) cchlorophyll-b(100% acetone) = 18.61·a645 3.96·a662 (6) cchlorophyll-a(95% diethyl ether) = 10.05·a662 0.76·a644 (7) cchlorophyll-b(95% diethyl ether) = 16.37·a644 3.14·a662 (8) where aλ is the absorbance at λ (in nm) wavelength, and cchlorophyll-a and cchlorophyll-b denote concentrations of chlorophyll a and chlorophyll b in µg cm-3 [12] as a function of solvents. in soxhlet extraction, the mass of the chlorophyll in the extract was calculated by the multiplication of the measured chlorophyll concentration values by the volume of the liquid in the round bottom flask. this also enabled the calculation of efficiency in mg of chlorophyll per g of dry algae units (relative to 100% dry algae powder). in the leaching experiments, the chlorophyll concentration results calculated with the empirical formulae were multiplied by the volume of the solvent that resulted in the relative chlorophyll mass values in the given samples. knowing the mass and water content of the algae, the efficiency of chlorophyll extraction relative to the mass of the dry algae can be calculated. these results were normalised to match the measurements and average values were calculated. figure 1: soxhlet extractor [12] 121 results and discussion soxhlet extraction the chlorophyll concentration measured changed according to a saturation curve as shown in fig.2. it can be concluded that under the given circumstances the solvents reached their maximum efficiency and there was no need for longer extraction times. the ability of the solvents to extract chlorophyll relative to dried algae mass during the soxhlet extraction is given in fig.3. the experiments were carried out using acetone, ethanol and methanol. it can be concluded that under the conditions of soxhlet extraction, methanol is the most potent extracting solvent of chlorophyll a and b from the algae powder, followed by ethanol and acetone respectively. it can also be pointed out that acetone and methanol are more effective for the extraction of chlorophyll b while ethanol is more effective for the extraction of chlorophyll a. the latter experiment was not carried out with diethyl ether due to health and safety considerations. extraction by leaching figs.4 and 5 illustrate the results of leaching. fig.4 depicts the concentration of chlorophyll for different masses of algae powder introduced into the system. the curves approach a saturation point in concentration, but do not reach the maximum. when we added progressively more and more algae powder to the same volume of solvent we observed increasing saturation behaviour. fig.5 presents the chlorophyll extracting ability of the various solvents when mixing 0.1 g of algae powder and 5 cm3 of solvent. as expected, the best result was obtained by utilising at least 0.1 g of algae powder of. the efficiency ranking was similar to that of the soxhlet extraction. methanol proved to be the most efficient solvent, followed by ethanol, acetone and diethyl ether respectively. the results are summarised in table 1, which contains mg of chlorophyll per g of dry algae yields. this comparison enables the different solvents to be ranked and extraction methods, which is as follows according to their efficiency: methanol, ethanol, acetone, and diethyl ether. additionally, significantly more chlorophyll can be extracted from ground algae with soxhlet extraction than with leaching. in the figure 2: changes in chlorophyll concentration during the soxhlet measurements figure 3: the efficiency of chlorophyll extraction of the various solvents during soxhlet extraction figure 4: change in chlorophyll concentration as a function of mass during leaching figure 5: efficiency of leaching using the various solvents 122 experiments conducted with acetone, it was observed that the extraction efficiency of chlorophyll a or chlorophyll b is greatly dependent on the conditions. methanol, the solvent that proved to be the most efficient, could be removed later from the chlorophyll by low temperature evaporation. conclusions from a systematic investigation of solid-phase extraction of chlorophyll a and chlorophyll b using soxhlet extraction and leaching as a function of the employed solvent, it was found that the most efficient solvent is methanol. in both extraction techniques, the extracted amount of chlorophyll using methanol as a solvent is approximately an order of magnitude higher than in acetone and close to three to four times greater than the results of ethanol. references [1] borowitzka m.a.: energy from microalgae: a short history, develop. appl. phycology (springer, the netherlands), 2013, 5, 1-15 [2] najafi g., ghobadian b., yusaf t.f.: algae as a sustainable energy source for biofuel production in iran: a case study, renewable and sustainable energy reviews, 2011, 15 (8), 3870–3876 [3] mata t.m., martins a.a., caetano n.s.: microalgae for biodiesel production and other applications: a review, renewable and sustainable energy reviews, 2010, 14(1), 217– 232 [4] bocsi r., horvath g., hanak l., hodai z.: extraction examinations of microalgae propagated for biodiesel additives, hung. j. ind. chem., 2011, 39(1), 45-49 [5] faizal b.: biotechnological applications of microalgae: biodiesel and value-added products, crc press, bosa roca, fl, united states, 2013, pp. 80 [6] demirbas a., demirbas m.f.: the importance of algae oil as a source of biodiesel, energy conversion and management, 2011, 52(1), 163170 [7] lanfer-marquez u.m., barros r.m.c., sinnecker p.: antioxidant activity of chlorophylls and their derivatives, food res. int., 2005, 38(89), 885–891 [8] hosikian a., lim s., halim r., danquah m.k.: chlorophyll extraction from microalgae: a review of the process engineering aspects, int. j. chem. engng., 2010, article id 391632 [9] simpson n.j.k., wells m.j.m.: introduction to solid-phase extraction, marcel dekker inc, new york, ny, usa, 2000, pp. 1-18 [10] meireles m.a.a.: extracting bioactive compounds for food products, theory and applications contemporary food engineering series, crc press, dublin, ireland 2009, pp. 140159 [11] lan s., wu l., zhang d., hu c., liu y.: ethanol outperforms multiple solvents in the extraction of chlorophyll-a from biological soil crusts, soil biology and biochemistry, 2011, 43(4), 857–861 [12] wellburn a.r., lichtenthaler h.: formulae and program to determine total carotenoids and chlorophylls-a and b of leaf extracts in different solvents, adv. agricul. biotechn., 1984, 2(1), 9-12 table 1: comparison of the chlorophyll (chl.) extraction results soxhlet extraction leaching chl. a chl. b chl. a & b chl. a chl. b chl. a & b acetone 0.164 0.270 0.435 0.183 0.059 0.242 ethanol 1.329 1.290 2.619 0.395 0.259 0.654 methanol 3.206 3.657 6.862 1.109 1.199 2.307 diethyl ether n/a n/a n/a 0.044 0.017 0.062 hungarian journal of industry and chemistry veszprém vol. 41(2) pp. 123–130 (2013) calculating the electrostatic potential profiles of double layers from simulation ion density profiles dezső boda,b1 and dirk gillespie2 1department of physical chemistry, university of pannonia, egyetem u. 10., veszprém, 8200, hungary 2department of molecular biophysics and physiology, rush university medical center, 1750 w. harrison st., chicago, usa be-mail: boda@almos.vein.hu computer simulations of the planar double layer geometry provide the charge profile with statistical noise. to compute the mean electrostatic potential profile from the charge profile, one must solve poisson’s equation with appropriate boundary conditions (bc). in this work, we show that it is advantageous to use the neumann or dirichlet bcs at the boundaries of the simulation domain with an integrated version of poisson’s equation. this minimises errors from the simulation’s noisy density profiles, in contrast to traditional convolution integrals that amplify the noise. the neumann bc, where the electric field is prescribed, can be used in both the constant surface charge and constant electrode voltage ensembles. in the constant voltage ensemble, where the potential difference between the confining electrodes is prescribed, one can also use the dirichlet bc, where the potentials at the boundaries are set. we show that the new methods provide converged results for the potential profile faster than the convolution integral does. keywords: electrical double layer, poisson equation, boundary conditions, computer simulation introduction the electrical double layer (dl) is formed by a charged surface and a phase (usually, a liquid) containing mobile charge carriers near the surface. depending on the material carrying the mobile charges, dls appear in electrolytes, molten salts, ionic liquids, plasmas, and even fast ion conductors (solid electrolytes). dls in solutions of dissolved ions are particularly important in electrochemistry, biology, and colloid chemistry. dls near electrodes differ from dls near charged objects carrying a fixed surface charge (such as colloids, macromolecules, and porous bodies), because the surface charge on the electrode can be controlled by an external voltage. theoretical studies of dls began with the poissonboltzmann (pb) theory known as the gouy-chapman (gc) theory [1,2] in electrochemistry, the debye-hückel (dh) theory [3] in solution chemistry, and the derjaguinlandau-verwey-overbeek (dlvo) theory [4, 5] in colloid chemistry. the pb theory is still very popular in applications because of its simplicity in spite of the fact that it neglects ionic correlations and effects due to the finite size of ions (e.g., excluded volume). more powerful statistical mechanical theories that are able to take these correlations into account have been developed [6–16]. computer simulations are a versatile method of studying dls in various geometries for various models of the constituents (ions, water, and electrode) [17–35]. this paper focuses on computing the electrical field and potential from a charge distribution obtained from computer simulations. computer simulations of systems containing charged particles must be performed in accordance with the laws of both electrostatics and statistical mechanics [36, 37]. this means that the electrical potential must be computed accurately for every configuration sampled in a monte carlo (mc) simulation. alternatively, the electrical field must be computed accurately in every time step of a molecular dynamics (md) simulation. every configuration of the system (positions of ions) corresponds to a microscopic state. in this case, we consider the system at the microscopic level. a simulation that samples the possible microscopic states must be performed properly according to the probability distribution of a given statistical mechanical ensemble. one typical simulation method to handle various ensembles is mc. the density distribution of ionic species i, h⇢ i (r)i, is obtained as an ensemble average from the simulation. from these, the average charge distribution can be obtained as q(r) = hq(r)i = x i z i e h⇢ i (r)i , (1) where q(r) is the charge distribution in a microscopic state, e is the electronic unit charge and z i is the valence of ionic species i. the average (mean) electrostatic potential can be obtained “on the fly” by computing the potential in the simulation cell for every configuration (denoted by (r)) and then taking the ensemble average, (r) = h (r)i. in this work, we use upper-case symbols for the microscopic quantities ( (r) and q(r)), while we use lowercase symbols for their macroscopic counterparts, namely, 124 their ensemble averages ( (r) and q(r)). the electrical potential in a configuration of the mc simulation, (r), can be computed analytically from coulomb’s law or numerically using a poisson solver. in both cases, we apply electrostatic bcs at the microscopic level. the reverse order, when we compute the ensemble average of the charge distribution (eq.(1)) and then solve poisson’s equation for the mean potential r2 (r) = � 1 ✏ 0 q(r) (2) is more usual (✏ 0 is the permittivity of vacuum). this equation applies to either explicit or implicit solvent models. in the explicit solvent framework, q(r) also contains the charge distribution of the water molecules (in addition to their ionic charges). in the implicit solvent framework, where water is represented by a dielectric background characterised by a dielectric constant, ✏, q(r) also contains polarisation charges induced in the dielectric (in the simplest case, q(r) is the ionic charges divided by ✏). because we are solving a differential equation, we must use appropriate boundary conditions (bcs) when solving eq.(2). because we want an ensemble averaged result, we apply the bcs at the macroscopic level. this paper describes how to numerically integrate the poisson equation with appropriate bcs to efficiently compute the mean electrostatic potential profile from the mean charge profile obtained from simulations. the statistical ensemble applied in the simulation determines which bc to use. in this paper, we consider the two basic ensembles, one where the electrode charges are fixed (constant charge ensemble) and one where the difference between the electrode potentials is fixed (constant voltage ensemble). in the constant charge ensemble, the traditional method of computing the potential profile is via a convolution integral. here, we show that this method is errorprone and numerically inefficient and instead, it is more advantageous to use a different integration scheme with neumann bcs, where the normal electric fields at the boundaries of the system are fixed [38]. in the constant voltage ensemble developed by kiyohara and asaka [39], the electrode potentials are known in advance. therefore, we can also use dirichlet bcs, where the potentials at the boundaries of the system are prescribed. in the following, we describe our model in detail. then, we consider all three issues discussed above (bcs at the microscopic level, statistical mechanical ensembles, and bcs at the macroscopic level) and present various possibilities for the macroscopic bc depending on the statistical mechanical ensemble used. we present results of model calculations to show the self-consistency of these calculations. model and boundary condition at the microscopic level at the microscopic level, we have a system that contains localised discrete and/or continuous distributions of charges q(r). in practice, there are two traditional schools to compute the electrostatic energy (in mc) or forces (in md) for a configuration sampled by a computer simulation. in one school, the potential is computed on a grid from poisson’s equation (eq.(2)) using a partial differential equation (pde) solver with appropriate boundary conditions. this method is generally used in md simulations of explicit solvent systems. in the other school, coulomb’s law is used to calculate the potential: (r) = 1 4⇡✏ 0 ✏ z q(r0)g(r, r0)dr0, (3) where g(r, r0) is the appropriate green’s function. this method is generally used for simulations with implicit solvents. the planar dl geometry means that we have a rectangular simulation cell of length l 2 �l 1 and with a base h ⇥h confined by two planar electrodes at the two ends (x = l 1 and x = l 2 ) carrying surface charges � 1 and � 2 . periodic boundary conditions (pbc) are used in the y, and z dimensions, which means that the green’s function is g(r, r0) = 1x j=�1 1x k=�1 1 |r� r0 + jhn y + khn z | (4) where the sum over j and k represents the interaction with the periodic image charges in the replicas of the central simulation cell in the y and z dimensions set by the unit vectors n y and n z . the term j = k = 0 corresponds to the interaction with the charge in the central simulation cell computed explicitly. in this paper, the interaction with periodic replicas is taken into account using the charged sheet method by smearing these charges into a sheet carrying q/h2 surface charges with a h2 square hole in the middle. the interaction with the holed sheet can be integrated. for further details, see ref. [18, 29]. the statistical mechanical ensemble determines which thermodynamic variables are fixed in the simulation. the attempts in the mc simulations are designed to ensure sampling according to the probability distribution of the given ensemble. moreover, the simulation must be self-consistent in the sense that a prescribed thermodynamic variable must agree with its value computed as an output of the simulation. for example, in an npt simulation (where the pressure is fixed), the pressure can also be computed from the virial sum as an ensemble average in both nv t and npt simulations. this value must be equal to the one prescribed in the npt ensemble. in practice, however, the accuracy of the pressure computed from the virial sum depends on the size of the system, and one obtains the same relationship between pressure 125 and density from nv t and npt simulations only in the limit of very large simulation cells. from the point of view of the dl problem, the question is whether we perform the simulation in the constant charge or constant voltage ensemble. in the constant charge ensemble the surface charges on the confining walls of the simulation cell are fixed. this is the traditional simulation setup used in dl simulations since torrie and valleau [17, 18]. the output of the simulation is the density profiles of the various ionic species h⇢ i (x)i (the pbc applied in the y and z dimensions ensures that the profiles depend on x only), from which the x-dependent charge profile, q(x), is obtained (see eq.(1)). the corresponding form of poisson’s equation is d2 (x) dx2 = � 1 ✏ 0 ✏ q(x), (5) where ✏ is now included so q(x) constrains only ionic and electrode charges. recently, kiyohara and asaka [39] introduced the constant voltage ensemble, where the potential difference between the two confining walls (the electrodes) is prescribed. a special mc step, where a small amount of charge, ��, is transferred from one electrode to the other, has been introduced. the charge exchange is accepted on the basis of the boltzmann factor min  1, exp ✓ ��u kt + h2 � ⇤ �� kt ◆� (6) where �u is the energy change associated with the charge movement and � ⇤ = (l 2 ) � (l 2 ) is the prescribed voltage. here, the surface charges on the electrodes fluctuate, while the potential difference between the electrodes (� ⇤) is an independent, prescribed variable of the ensemble. the mean potential profile can be computed from eq.(5). the computed voltage, namely, the potential difference between the electrodes, � = (l 2 )� (l 2 ), must be equal to the prescribed voltage, � ⇤. in the following, we describe various ways to apply bcs at the macroscopic level using a case study of a 1:1 electrolyte, where the ions are modeled as charged hard spheres with diameters d + = d� = 3 å and the dielectric constant of water is 78.46. the concentration is 1 m and the temperature is 298.2 k. we show results for the special case of � 1 = �� 2 = � = 0.1 cm�2 and l 1 = �l 2 = l, but the equations are presented for the general case. we used 200/200 ions in the mc simulations performed in the canonical (nv t ) ensemble. the dimensions of the cell are l = 50 å and h = 57.2 å. boundary conditions at the macroscopic level boundary conditions set in the bath: the convolution integral let us distinguish between the charge of the ions obtained from the simulation, q ion (x), and the surface charges, p k � k �(x� x k ), at x 1 = l 1 and x 2 = l 2 (in this work, we assume only two charged surfaces at l 1 and l 2 , but there can be more as in the simulations of kiyohara et al. [40–50] for porous electrodes). the total charge is the sum of these: q(x) = q ion (x) + x k � k �(x� x k ). (7) the ionic charge profile is obtained as an ensemble average. the electrode charges are prescribed in the constant charge ensemble, while they are obtained as ensemble averages in the constant voltage ensemble. at the macroscopic level, the issue of electrostatic self-consistency appears when we ask the question: what kind of bc should be applied when we solve poisson’s equation (eq.(5)). the traditional answer to this question is that the bc is set in the bulk electrolyte, where the average electrical field and electrical potential are zero. the corresponding solution of poisson’s equation can then be obtained in the form of a convolution integral (x) = � 1 ✏ 0 ✏ z 1 x (x0 � x)q ion (x0 )dx0. (8) this solution was probably inspired by theories that usually consider an isolated dl where the bcs are set in infinity. because theories (unlike simulations) provide smooth charge profiles (with the property lim x!1 q(x) = 0) without any noise, this integral works well for theories. to the best of our knowledge, the majority of researchers (among others, the authors of this paper) have used this equation in the past [6–35]. in this work, we show that this equation, from a numerical point of view, is a poor choice to compute the potential in simulation studies. the reason is that the upper integration limit is not well defined and that q(x) is subject to a large statistical noise. in practice, the upper integration limit is set somewhere in the middle of the cell where a bulk electrolyte is. here we will use exactly the middle of the cell (x = 0) as the upper integration limit. because of x�x0 in the integrand, this integral is very sensitive to the noise in q(x), because the noise is amplified as one moves further away from the electrode. the results of a very short (200 mc cycles; 1000 attempts to move ions were made in an mc cycle) simulation are shown in fig.1. the density and charge profiles are very noisy. when we compute the potential from eq.(8), the result is subject to a large error and is far from what we are supposed to get (fig.2, top panel). the slope is not necessarily zero in the bath (which means that the electrical field is not zero). if the simulation was run for longer, we would get a completely different result. in general, long simulations are needed to produce a smooth charge profile and a well established potential profile. the problem is even more serious when we try to reproduce small effects, such as the value of the electrode potential at zero electrode charge (pzc) for asymmetric electrolytes. the value of the pzc potential is very small 126 0 1 2 3 4 5 d en si ty p ro fi le s / m -60 -40 -20 0 20 40 60 x / å -4 -2 0 2 4 c ha rg e pr of ile / m figure 1: density profiles (top panel) and a charge profile (bottom panel) obtained from a short (200 mc cycles) constant charge simulation using � 1 = �� 2 = �0.1 cm�2. the charge profile is obtained from p i z i ⇢ i (x), so its unit is m (mol dm�3) and the effect of the noise is dramatic. extremely long simulations are needed to obtain convergent results for the potential [51]. to illustrate this weak convergence, we have plotted the left electrode potential ( (l 1 )� (0), top panel) and the voltage ( (l 2 )� (l 1 ), bottom panel) as computed from eq.(8) as functions of the performed mc cycles in fig.3 (red dashed curves). these potential values fluctuate strongly. the calculated values depend not only on the simulation time, but on the upper integration limit. if we shift that point a bit, we get a different result (data not shown). neumann boundary conditions and the constant charge ensemble here we propose, instead, to use neumann or dirichlet bcs at the boundaries of the simulation cell (at l 1 and l 2 , or, equivalently, at �1 and 1). in the case of the neumann bc, the normal electrical field is prescribed, while in the case of the dirichlet bc, the electrical potential is prescribed at the confining walls. our simulation setup ensures that the simulation cell is always charge neutral. then, gauss law states that the average electrical field is zero outside the cell for the regions z < l 1 and z > l 2 . this information makes the neumann bc applicable both in the constant charge and constant voltage 0 1 2 3 4 ψ (x ) neumann convolution (left) convolution (right) -60 -40 -20 0 20 40 60 x / å 0 0.1 0.2 0.3 0.4 0.5 0.6 q to t(x ) figure 2: potential profiles (top panel) as computed from the neumann bc (eq.(11)) and the convolution integral (eq.(8)). the upper limit of the convolution integral is x = 0 and it is computed for the leftand right-hand sides separately. the bottom panel shows the integral of the charge profile (q tot (x), see eq.(7)). it is closely related to the electric field through eq.(13). the profiles have been obtained from the curves of fig.1. the electrostatic potential is shown in units of kt/e throughout this paper ensembles. in the constant charge ensemble, the potential difference between the electrodes is an output of the calculation. therefore, we cannot use it as a bc, so we cannot apply the dirichlet bc in this case. in the constant voltage ensemble, on the other hand, the potential difference is known in advance (see the next section). in the constant voltage ensemble, therefore, both neumann and dirichlet bcs can be used and they should give the same answer (apart from errors related to the size of the system, see later). the neumann bc for eq.(8) is that the electrical field is zero outside the system: e(x ! �1) = � d (x) dx ���� x!�1 = 0 (9) and the same for x ! 1. by integrating poisson’s equation once, we obtain d (x) dx = � 1 ✏ 0 ✏ z x �1 q(x0 )dx0 + c 1 (10) where c 1 is an integration constant. taking eq.(10) at 127 -4 -3.5 -3 -2.5 -2 -1.5 -1 ψ (l 1 )ψ (0 ) neumann convolution 0 200 400 600 800 1000 mc cycle 2 3 4 5 6 ψ (l 2 )ψ (l 1 ) figure 3: convergence of the left electrode potential (top panel) and the voltage (bottom panel) as computed from the neumann bc (eq.(11)) and the convolution integral (eq.(8)) in the constant charge ensemble. any location x < l 1 (where q(x) = 0) and using the bc (eq.(9)), we get c 1 = 0 for the integration constant. if we use eq.(7) for q(x), we obtain d (x) dx = � 1 ✏ 0 ✏ z x l1 q ion (x0 )dx0 � 1 ✏ 0 ✏ � 1 (11) for l 1 < x < l 2 . the change in the lower integration limit was possible because ions exist only between the two electrodes (q ion 6= 0 only for l 1 < x < l 2 ). introducing q tot (x) = z x l1 q ion (x0 )dx0 (12) for the integral of the ionic charge profile (the total charge density per area in the [l 1 , x] interval), the electrical field can be given as e(x) = 1 ✏ 0 ✏ q tot (x) + 1 ✏ 0 ✏ � 1 (13) for l 1 < x < l 2 . the q tot (x) profile is shown in the bottom panel of fig.2. for the special case of � 1 = �� 2 , the total ionic charge is zero in the system, so q tot (l 2 ) = 0. the nearly constant but noisy profile in the middle of the cell represents the bulk region. integrating once more, we obtain (x) = � 1 ✏ 0 ✏ z x l1 q tot (x0 )dx0 � 1 ✏ 0 ✏ � 1 (x� l 1 ) + c 2 , (14) -3.5 -3 -2.5 -2 ψ (l 1 )ψ (0 ) dirichlet neumann convolution 0 200 400 600 800 1000 mc cycle 4 5 6 7 ψ (l 2 )ψ (l 1 ) figure 4: convergence of the left electrode potential (top panel) and the voltage (bottom panel) as computed from the neumann bc (eq.(11)), the dirichlet bc (eq.(17)), and the convolution integral (eq.(8)) in the constant voltage ensemble where c 2 is another integration constant. its value is inconsequential because we can set the zero level of the potential arbitrarily. fig.2 shows the (x) profile where c 2 = 0. it is usual, however, to set the ground in the bulk, so c 2 = � (0), where (0) is the average of the potential profile over the bulk. kiyohara and asaka [39, 52] used an equation of a convolution form that can be shown to be equivalent to eq.(14), but they seemed to leave out the linear term containing � 1 . eq.(14) is different from the convolution integral (eq.(8)) because it does not suffer from the uncertainty in the upper integration limit and from errors originating from the noise of the q ion (x) profile. the integration is performed for a well defined finite domain from the left electrode to x. fig.3 shows that this equation provides a much better convergence as a function of simulation time for the same simulation (same q ion (x)). this procedure was used in our papers for inhomogeneous electrolyte systems to compute the mean electrostatic potential [53–56]. it was especially useful for electrolytes adsorbed in narrow slits [55,56]. in this case, the dls formed at the walls of the slit overlap so a bulk electrolyte does not form in the middle of the slit and the slit is not charge neutral. the neumann bc is then the natural bc so the electric field is zero behind the walls. in another example, the neumann bc is used to compute the potential for a dl model, where the electrode, the 128 inner layer, and the electrolyte have different dielectric constants [54]. in this case, the polarisation charge induced at the dielectric boundaries must also be included in eq.(14). dirichlet boundary conditions and the constant voltage ensemble an alternative method is the constant voltage ensemble of kiyohara and asaka [39]. here, the electrode charges fluctuate and the potential between the electrodes is prescribed. therefore, we can also apply dirichlet bcs, where (l 1 ) = 0 (15) and (l 2 ) = � ⇤. (16) the general solution for the potential profile in the l 1 < x < l 2 range is (x) = � 1 ✏ 0 ✏ z x l1 q tot (x0 )dx0 +c 1 (x�l 1 )+c 2 , (17) where we integrate from the right-hand side of the electrode at x = l 1 , so the surface charge � 1 is now excluded from the integration. the bc at x = l 1 (eq.(15)) provides the integration constant c 2 = 0, while the bc at x = l 2 (eq.(16)) provides the integration constant c 1 = 1 l 2 � l 1 " � ⇤ + 1 ✏ 0 ✏ z l2 l1 q tot (x)dx # . (18) of course, we can calculate the potential profile using the neumann bcs too. in that case, we must use h� 1 i in eq.(14) instead of � 1 because the electrode charge is now fluctuating so its value is not known in advance. therefore, its ensemble average should be used in eqs.(7-14). in the constant voltage ensemble we need the value of the voltage that corresponds to � 1 = �0.1 cm�2 as used in the previous constant charge simulation. this value we estimated with a very long (50,000 mc cycles) constant charge simulation and was obtained as � ⇤ = 4.398 kt/e. this value was used in the constant voltage simulation as an input parameter. fig.4 is the analogous version of fig.3. the black solid curves are the results obtained from the dirichlet bcs (eqs.(17) and (18)). the red short-dashed curves show the results of the neumann bc using h� 1 i in eq.(14). the convolution integral results (blue longdashed curves) are inaccurate and poorly converged for such a short simulation. in the constant voltage ensemble the electrode charge is a fluctuating quantity. fig.5 shows its convergence. its limiting value is not equal to that used in the constant charge simulation that provided the input voltage value � ⇤ = 4.398 kt/e. the deviation is due to finite size of the system. using a larger simulation box (larger h), a smaller deviation is observed (data not shown). this deviation is also observed in fig.4. the limiting value of the 0 200 400 600 800 1000 mc cycle -0.1 -0.095 -0.09 e le ct ro d e ch ar g e / c m -2 figure 5: convergence of the electrode charge in the constant voltage ensemble potential difference � = (l 2 )� (l 1 ) obtained from the calculation using the neumann bc (bottom panel) is different from the prescribed value (the value used in the dirichlet bc, see also bottom panel). this behaviour is analogous to that discussed earlier regarding the example of the pressure computed in the nv t and npt ensembles. the constant charge ensemble corresponds to the nv t , while the constant voltage ensemble corresponds to the npt ensemble. in the constant charge ensemble, the voltage is computed using the neumann bc, just as the pressure is computed in the nv t ensemble from the virial sum. in the constant voltage ensemble, the voltage is prescribed, just as the pressure is prescribed in the npt ensemble. the voltage can also be computed from the neumann bc, just as the pressure can also be computed from the virial sum in the npt ensemble. conclusion we propose that the neumann or dirichlet bcs should be used in computing the mean electrostatic potential for the planar dl geometry studied by computer simulations. the commonly used convolution integral of eq.(8) requires a vaguely defined upper integration limit and also suffers from numerical problems because it magnifies the effect of the noise in the charge profile that is always present in computer simulations. the problem of noise in the density profiles is unique to simulations and therefore more care must be taken in computing the electrostatic potential. on the other hand, theories [6–16], which produce smooth, noise-free density profiles, can use the convolution integral. we have shown here that the numerical method we proposed is much more efficient than the convolution integral, because we use unambiguous parameters in the bc, specifically, the electrode charge in the case of the neumann bc and the voltage in the case of the dirichlet bc. also, the simulation cell is necessarily finite, therefore, the boundaries of the system are always well de129 fined. overall, our method leads to converged results with very short simulations. acknowledgement the present publication was realised with the support of the projects támop-4.2.2/a-11/1/konv-2012-0071 and támop-4.1.1/c-12/1/konv-2012-0017. references [1] gouy g.: sur la constitution de la charge electrique a la surface d’un electrolyte (english title please), j. phys. 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mol department of hydrocarbon and coal processing, institute of chemical engineering and process engineering, university of pannonia, egyetem u. 10, 8200, hungary !email: mnorbert@almos.uni-pannon.hu the paper discusses the degradation of waste polyamides during mechanical recycling from the automotive sector. two different polyamides were investigated: glass fibre reinforced and unreinforced. raw materials were reprocessed twenty times and the changes in their properties were investigated as a function of reprocessing number. considerable differences were found in relation to the specimen properties between reinforced and unreinforced waste materials. for example, the tensile strengths of reinforced and unreinforced polyamide 6.6 wastes were 84.2 and 165.2 mpa, respectively, which dropped to 38.0 and 97.0 mpa after the twentieth reprocessing cycle. specimens from the reprocessing procedure have been investigated by fourier transformed infrared spectroscopy in the spectral range of 400–4000 cm-1. due to mechanical stress between the rotating screw and plasticising cylinder, the reinforcements broke. the average length of the glass fibre was decreased as a function of the reusing cycle number from 1890 to 580 µm. keywords: polyamide, mechanical recycling, degradation, ftir introduction as a result of the continuously increasing trend in the demand for polymer worldwide, ever increasing amounts of waste polymers are generated. polyamides (pa) are expensive engineering plastics, especially if they are reinforced. in particular, glass fibre composites are widespread among fibre-reinforced materials, as a results of their favourable mechanical and economical properties. the application of glass fibre results in improved tensile and flexural properties. thermoplastic polyamides contain typically 10-30% glass fibres as reinforcements and are applied in many industries such as the automotive sector, civil engineering, packaging, and biomedical applications [1-9,11,16]. a grand challenge is the utilisation of plastic wastes. polymer materials have a high resistance to different environmental and mechanical effects, which yields their favourable characteristics. such advantageous properties can easily become disadvantage owing to waste polymers inability to decompose within a reasonable time frame. unfortunately, a vast amount of polymer waste ends up to landfills, where nondegradable plastics together with other materials accumulate and pollute the environment [10,12-15]. the most studied recycling technologies are mechanical or chemical. chemical recycling is a thermal process for cracking the long carbon chains of polymers into gases and liquid hydrocarbons in the absence of oxygen within in temperature range of 400-1000 °c. the other technology is mechanical recycling, when waste polymers are mixed with original granulates and newly shaped by injection moulding or extrusion. mechanical recycling is a good option for reusing waste plastic, only when selectively collected polymers of high purity are available. similarly to the chemical process, the polymer chains can degrade due to mechanical and thermal stresses during the pre-treating and shaping steps. therefore, it is important to know the behaviour of polymer chains when exposed to thermal and mechanical stresses [9,11-16]. the goal of our work was to investigate the mechanical recycling of reinforced and unreinforced waste polyamides. waste polymers have been reprocessed twenty times and the changes of mechanical amongst other properties were investigated. the effects of reinforcements on the loss of properties during the reshaping procedures were followed. experimental plastics glass fibre reinforced and unreinforced waste polyamides were used as raw materials. the main properties of the raw materials are shown in table 1. table 1: the main properties of raw materials reinforced unreinforced mfi,* g (10 min)-1 15.1 11.8 ash content, % 30.6 0.03 tensile strength, mpa 165.2 84.2 charpy strength, kj m-2 13.4 12.1 * 275 ºc, 5 kg 132 sample preparation due to pa samples being sensitive to humidity, raw materials before processing and samples before testing were dried. drying was carried out in an air circulated drying box at 90 ºc for 2 h. the injection moulding of the specimens was carried out by a microprocessorcontrolled injection moulding machine. the dimensions of dog-boned injection moulded specimens were 3 mm × 10 mm in cross-section and 50 mm in length. fig.1 illustrates the main experimental steps. methods the tensile and three point flexural properties (mainly stress and extension) (msz en iso 527-1-4:1999, msz en iso 14125:1999) were determined using an instron 3345 universal tensile testing machine. the temperature and relative humidity in the laboratory were 23 ºc and 60% respectively, during the mechanical tests. tensile tests were carried out at a crosshead speed of 80 mm min-1. during the investigation of flexural properties, the crosshead testing speed was 20 mm min-1. samples were also investigated by infrared spectroscopy with a tensor 27 type ftir spectrometer (resolution: 3 cm-1, illumination: sic globar light, detector: rt-dlatgs type) within the 400-4000 cm-1 wave number range. a ceast resil impactor was applied to measure the charpy impact strength of the produced samples according to the msz en iso 179-2:2000 standard. results and analysis tensile properties the tensile properties of reshaped specimens are summarised in figs.2a-2c. the tensile strength of reinforced and unreinforced polyamide 6.6 wastes were 84.2 mpa and 165.2 mpa, respectively, which were reduced to 38.0 mpa and 97.0 mpa after the twentieth reprocessing cycle (fig.2a). it is important to note that the decreasing trends were considerably different in the two cases: a fourth order trend line in the case of reinforced samples and a second order one in the case of unreinforced samples were found as shown in fig.2a. a short section with a barely decreasing slope can be found both at the beginning (before the third cycle) and at the end (after the fifteenth cycle) of the trend line for figure 1: the main experimental steps figure 2: tensile properties of reinforced and unreinforced polyamide 6.6 wastes: a) tensile strength, b) elongation and c) tensile modulus c b a number of cycles number of cycles number of cycles number of cycles 133 the reinforced specimens. in the case of unreinforced specimens a similar phenomenon was found only up to the ninth cycle. the elongations of specimens are shown in fig.2b. owing to the rigid property of polyamides the relative elongations are rather small (below 3.8%). as results demonstrate the change in elongations was rather linear, but the gradient was different when the reinforced (tan α = 0.033) and unreinforced (tan α = 0.054) raw materials were investigated; because a slower ratio in change was found in the presence of glass fibres in polyamide wastes. as demonstrated by the tensile strength, tensile moduli show a decreasing trend as well. furthermore, the trend line is highly similar to the measured data for tensile strength. the e-modulus of reinforced and unreinforced wastes was 8219 mpa and 3226 mpa, respectively. those were decreased to 3606 mpa and 1022 mpa according to the mathematical equations in fig.2c. flexural properties the flexural properties of reshaped specimens are summarised in figs.3a-3c. the change in both flexural strength and e-modulus followed a decreasing trend, while the trend in terms of elongation was rather increasing. the results were similar to the tensile properties discussed above. it is important to note that the shapes of trend lines were also similar to results demonstrated before. when reinforced polyamide 6.6 waste material was reprocessed the flexural strength, elongation and e-modulus changed from 248.5 mpa, 4.42% and 5622 mpa to 166.0 mpa, 4.86% and 3416 mpa, respectively. by taking into consideration the results of both tensile and flexural tests it can be concluded that the glass fibre reinforcement helps to keep the high values of strengths and e-moduli in the case of reinforced polymers at the start of property curves as a function of processing cycle number. approximately after the third-to-fifth reprocessing cycles, the dropping ratio was increased step by step. presumably this was the consequence of the glass fibres degrading into pieces. on the contrarily, a relatively constant dropping ratio was found in the unreinforced case. charpy impact strength the charpy impact strength test is one of the most widely specified mechanical tests of polymeric materials to provide information about impact properties. results of charpy tests were summarised in fig.4. the change in charpy impact strength followed a decreasing trend in both cases. moreover, a similar trend in the changes could be found, because the gradients were 13.38 and 12.18 for reinforced samples and unreinforced specimens, respectively. the charpy impact strengths were 12.1 kj m-2 and 13.4 kj m-2 without any reprocessing, and decreased to 8.4 kj m-2 and 9.4 kj m-2 respectively by the end of the procedure. naturally the reinforced samples gave higher values of impact strength. figure 3: flexural properties of reprocessed reinforced and unreinforced polyamide 6.6 wastes a) flexural strength, b) elongation and c) flexural modulus a b c figure 4: charpy impact strength of reprocessed reinforced and unreinforced polyamide 6.6 wastes number of cycles number of cycles number of cycles number of cycles c 134 linear extension coefficient the coefficient of thermal expansion describes the change in dimensions of samples against changing temperature at a constant pressure. regarding polymers the linear extension coefficient is used to classify the materials. as it is known, thermal expansion decreases with increasing bond energy and the thermal extension of the amorphous phase is higher than that of the crystalline phase, because rearrangements in the structure can be achieved at the glass transition temperature. a change in ratio of amorphous and crystalline phases occurs. the coefficients of linear extension are demonstrated in fig.5. results demonstrate well that the coefficient changes randomly in both cases between 2.05 and 2.27 with approximately the same average value of 2.18 ºc-1 for the reinforced and unreinforced specimens within 0.01 ºc-1. presumably no rearrangements in the structures of the tested materials occurred during the reprocessing and the ratio of the amorphous to crystalline phases remained similar. in other words, the specimens a have relatively permanent stability of shape. fourier transformed infrared spectroscopy samples from the reprocessing procedure were also investigated by fourier transformed infrared spectroscopy (ftir), which provides a measure of changes in molecular structures through molecular vibrational excitations. the ftir spectra of reinforced and unreinforced waste polymers as a function of the reprocessing cycles are shown in figs.6a and 6b. by this method, modifications in the molecular structures of polymers could be observed as a result of changes in their chemical bonds. a typical spectrum of polyamide can be described as follows: " stretching vibration of -ch2and -ch3 groups between 2800–3000 cm-1 " symmetric and asymmetric deformation stretching of -ch3 groups between 1430 and 1470 cm-1 and 1365 and 1395 cm-1 " βasymmetricch2 of -ch2groups at 720 cm-1 " bands at 3350, 1730 cm-1, and 630 cm-1 as well referring to the n–h and c=o bonds from –nh– and –co functional groups. the methyl/methylene group (–ch3/–ch2–) ratio in an average molecule was calculated based on the ftir peak intensities in the range of 2800–3000 cm-1. results are summarised in fig.7. as shown, the ratio of methyl and methylene groups slowly decreased in both cases as a function of reprocessing cycles. this suggests that the numbers of methyl groups increased, while the methylene groups decreased in an average molecule. this is a consequence of polymer degradation, when the c-c bonds of main polymer chains are cleaved, which resulted in shorter chains containing less methylene groups. figure 5: coefficient of linear heat extension of reprocessed reinforced and unreinforced polyamide 6.6 wastes figure 6: ftir spectra of reinforced (a), and unreinforced polyamide (b) b a figure 7: the change in the –ch3/–ch2– ratio of an average molecule and the value of log(i/i0) from ftir spectra at 720 cm-1 as a function of the reprocessing cycles in the cases of reinforced and unreinforced polyamides number of cycles number of reprocessing cycles number of reprocessing cycles 135 scanning electron microscope graphs as the polyamide matrix covered the fibres, it was difficult to determine their average length. therefore to investigate the average length of the reinforcements and thus gain insights into their degree of degradation, the samples were burned and the remaining glass fibres were investigated by sem techniques. the results are shown in fig.8. as shown, the average length of the glass fibre reinforcements decreased as a function of the reusing cycle number. the length of glass fibres suddenly decreased from 1890 µm to 660 µm during the first four cycles of reprocessing. then the average length exhibited a relatively constant value between 550 and 640 µm. the mean and standard deviation were 581 µm and 28 µm between the fifth and twentieth cycles, respectively. the cause for the degradation of the reinforcement fibres was the mechanical stress caused by the rotating screw and plasticising cylinder. conclusions we investigated the reprocessing of waste glass fibre reinforced and unreinforced polyamide 6.6 materials. it was found that the mechanical properties of both wastes deteriorated as a function of reprocessing. for example, the tensile strengths of reinforced and unreinforced polyamide 6.6 wastes were 84.2 mpa and 165.2 mpa, respectively, which decreased to 38.0 mpa and 97.0 mpa after the twentieth reprocessing cycle. on the other hand, the trend lines of the changes were significantly different in the case of reinforced and unreinforced wastes. more gradually decreasing ratios could be measured regarding unreinforced plastics until the tenth cycle. based on infrared spectra, it was concluded that the deterioration in mechanical properties presumably was the consequence of polymer degradation. the c-c bonds of the main polymer chains were broken and resulted in the formation of shorter polymer chains. the lengths of glass fibres suddenly decreased from 660 µm to 1890 µm during the first four cycles of reprocessing. then, the average length exhibited a relatively constant value between 550 and 640 µm. the coefficients of linear heat extension changed randomly in both cases between 2.05 and 2.27 ºc-1. the average value was 2.18 ºc-1 for both reinforced and unreinforced samples within 0.01 ºc-1. references [1] troev k., todorova n., mitova v., vassileva st., gitsov i.: phosphorus-containing oligoamides obtained by a novel one-pot degradation of polyamide-6, polymer degrad. stabil., 2006, 91(4), 778-788 [2] pedroso a.g., mei l.h.i., agnelli j.a.m., rosa d.s.: the influence of the drying process time on the final properties of recycled glass fiber reinforced polyamide 6, polymer testing, 2002, 21(2), 229-232 [3] gröning m., eriksson h., hakkarainen m., albertsson a.c.: phenolic prepreg waste as a functional filler with an antioxidant effect in polypropylene and polyamide-6, polymer degrad. stabil., 2006, 91(8), 1815-1823 [4] goitisolo i., eguiazábal j.i., nazábal j.: effects of reprocessing on the structure and properties of polyamide 6 nanocomposites, polymer degrad. stabil., 2008, 93(10), 1747-1752 [5] bernasconi a., davoli p., armann c.: fatigue strength of a clutch pedal made of reprocessed short glass fibre reinforced polyamide, int. j. fatigue, 2010, 32(1), 100-107 [6] la mantia f.p., scaffaro r.: melt stabilization of wet polyamide 6, polymer degrad. stabil., 2002, 75(3), 473-477 [7] bernasconi a., davoli p., rossin d., armanni c.: effect of reprocessing on the fatigue strength of a fibreglass reinforced polyamide, composites part a: appl. sci. manufact., 2007, 38(3), 710-718 [8] hassan m.m., badway n.a., gamal a.m., elnaggar m.y., hegazy e.s.a.: studies on mechanical, thermal and morphological properties of irradiated recycled polyamide and waste rubber powder blends, nuclear instruments and methods in physics research section b: beam interactions with materials and atoms, 2010, 268(9), 14271434 [9] yu s., liu m., ma m., qi m., lü z., gao c.: impacts of membrane properties on reactive dye removal from dye/salt mixtures by asymmetric cellulose acetate and composite polyamide nanofiltration membranes, j. membrane sci., 2010, 350(1-2), 83-91 [10] ghidossi r., poupot c., thibon c., pons a., darriet p., riquier l., de revel g., peuchot m.m.: the influence of packaging on wine conservation, food control, 2012, 23(2), 302-311 figure 8: the average length of glass fibre reinforcements as a function of reprocessing cycles number of cycles 136 [11] hassan m.m., badway n.a., gamal a.m., elnaggar m.y., hegazy e.s.a.: effect of carbon black on the properties of irradiated recycled polyamide/rubber waste composites, nuclear instruments and methods in physics research section b: beam interactions with materials and atoms, 2010, 268 (16), 25272534 [12] hassan m.m., badway n.a., gamal a.m., elnaggar m.y., hegazy e.s.a.: studies on mechanical, thermal and morphological properties of irradiated recycled polyamide and waste rubber powder blends, nuclear instruments and methods in physics research section b: beam interactions with materials and atoms, 2010, 268(9), 14271434 [13] huang s.h., hung w.s., liaw d.j., lo c.h., chao w.c., hu c.c., li c.l., lee k.r., lai j.y.: interfacially polymerized thin-film composite polyamide membranes: effects of annealing processes on pervaporative dehydration of aqueous alcohol solutions, separ. purific. techn., 2010, 72(1), 40-47 [14] yu s., liu m., ma m., qi m., lü z., gao c.: impacts of membrane properties on reactive dye removal from dye/salt mixtures by asymmetric cellulose acetate and composite polyamide nanofiltration membranes, j. membr. sci., 2010, 350(1-2), 83-91 [15] kiliaris p., papaspyrides c.d., pfaendner r.: influence of accelerated aging on clay-reinforced polyamide 6, original research article polymer degradation and stability, 2009, 94(3), 389-396 [16] shen z., bateman s., wu d.y., mcmahon p., dell’olio m., gotama j.: the effects of carbon nanotubes on mechanical and thermal properties of woven glass fibre reinforced polyamide-6 nanocomposites, composites sci. techn., 2009, 69(2), 239-244 4 hanáková, potěšil, bernatík, červenka, rádsetoulal, bryja, and zdráhal figure 1: comparison of phosphorylation sites of hdvl3 induced by ck1ε and nek2. experimentally determined phosphorylation sites by ck1ε and nek2 are indicated by green background color. phosphorylation sites identified only by nek2 are indicated by red background color. analyzed by liquid chromatography coupled with mass spectrometry (lc-ms/ms) for protein identification (id run). the rest of the peptide mixture was used for phosphopeptide analysis. ms phosphomix 1, 2, 3 light (sigma aldrich) was added to the samples before the phosphopeptide enrichment step in a concentration of 0.1 pmol. phosphopeptides were enriched using a pierce magnetic titanium dioxide phosphopeptide enrichment kit (thermo fisher scientific, waltham, massachusetts, usa) according to the protocol of the manufacturer and eluted into an autosampler vial. the solution was concentrated under a vacuum to a volume of less than 5 µl, dissolved in water and 0.6 µl of 5% fa was used to obtain 15 µl of the peptide solution before lc-ms/ms analysis. 2.3 mass spectrometry lc-ms/ms analyses of the peptide mixture were conducted using a rslcnano system connected to a orbitrap elite hybrid mass spectrometer (thermo fisher scientific) with a abird (active background ion reduction device; esi source solutions) and a digital picoview dpv550 (new objective) ion source (tip rinsing by 50% acn with 0.1% fa) installed. prior to lc separation, tryptic digests were concentrated online and desalted using a trapping column (100 µm × 30 mm) filled with 3.5-µm of xbridge beh 130å c18 sorbent (waters). after the trapping column was washed with 0.1% fa, the peptides were eluted (flow rate of 300 nl/min) from the trapping column onto a acclaim pepmap100 c18 column (3 µm particles, 75 µm × 500 mm; thermo fisher scientific) along a 65 min-long gradient. mobile phase a (0.1% fa in water) and mobile phase b (0.1% fa in 80% acn) were used in both cases. the gradient elution started at 1% of mobile phase b and increased from 1% to 56% during the first 50 mins (30% in the 35th and 56% in the 50th min), then increased linearly to 80% of mobile phase b over the following 5 mins and remained at this state for the next 10 mins. equilibration of the trapping column and the anlytical column was conducted prior to injection of the sample into the sample loop. the outlet of the analytical column was directly connected to the digital picoview dpv550 ion source. ms data were acquired in a data-dependent strategy by selecting the top 6 precursors based on precursor abundance in the survey scan (350-2000 m/z). the resolution of the survey scan was 60,000 (at 400 m/z) with a target value of 1×106 ions, one microscan and a maximum injection time of 200 ms. high resolution (resolution of 15,000 at 400 m/z) higher energy collisional dissociation (hcd) ms/ms spectra were acquired with a target value of 50,000. the normalized collision energy was 32 % for hcd spectra. the maximum injection time for ms/ms was 500 ms. dynamic exclusion was enabled for 45 s after the acquisition of one ms/ms spectra and early expiration was disabled. the isolation window for ms/ms fragmentation was set to 2 m/z. the analysis of the mass spectrometric raw data files was carried out using the proteome discoverer software (thermo fisher scientific; version 1.4) with utilization of the in-house mascot (matrixscience; version 2.4.1) search engine. ms/ms ion searches were conducted against an in-house database containing the expected protein of interest with additional sequences from the crap (common repository of adventitious proteins) database (downloaded from http://www.thegpm.org/crap/). mass tolerance for peptides and ms/ms fragments were 7 ppm and 0.03 da, respectively. oxidation of methionine, deamidation (n, q) hungarian journal of industry and chemistry semiquantitative analysis of dvl3 phosphorylations 5 figure 2: semiquantitative analysis of phosphorylation site serine 204 (s204) on peptide fsspsteqssasr induced by ck1ε and nek2. precursor and selected fragment traces of corresponding hdvl3 phosphopeptides are shown for ck1ε and nek2 (in skyline). the highest signal intensity was detected in the case of nek2. and phosphorylation (s, t, y) as optional modifications, carbamidomethylation of c as a fixed modification and three miss cleavages of enzymes were set for all searches. the phosphors feature was used for phosphorylation site localization. quantitative information was assessed and manually validated in skyline software (skyline-daily 3.1.1.8884). 3. results and analysis 3.1 identification of phosphorylation sites phosphorylation is important for protein function and regulation. the phosphorylation status of human dvl3 induced by eight individual ser/thr kinases that were previously reported or identified by an unbiased ms screen for dvl-associated kinases was analysed. dvl3 contains 131 serines/threonines, which can be potentially phosphorylated. in total, 88 ser/thr phosphorylation sites and one tyrosine phosphorylation site in dvl3 were identified. 3.2 phosphorylations induced by ck1ε and nek2 based on our experiment, a phosphorylation “map” of the dvl protein was created that described the complex phosphorylation “fingerprint” for each kinase tested. eight of the kinases used to induce phosphorylation include ck1ε and nek2. fig. 1 shows a qualitative comparison of the identified phosphorylation sites using these two kinases. in the case of ck1ε induction, 77 phosphorylation sites were identified, and in the case of nek2, 87 phosphorylation sites were determined from a total of 131 possible ser/thr phosphorylation sites in the dvl3 protein. next in terms of qualitative characterization, a semiquantitative comparison with regard to the occupancy of phosphorylation sites induced by individual kinases was conducted. the skyline software was used for this evaluation. the individual phosphorylated peptides were compared based on their peak areas. a comparison of a selected peptide phosphorylated in the position of s204 by ck1ε and nek2 is shown in fig. 2. the peak area was determined for ck1ε as 7.60e6 and for nek2 as 1.07e9. subsequently, double normalization of the data was performed using a set of phosphopeptide standards (added to the sample prior to the phospho-enrichment step) and by unphosphorylated peptides identified in the identification run. the resulting areas (ck1ε: 1.23e7 and nek2: 1.10e9) were compared with each other. 4. discussion our study focused on the determination of the phosphorylation sites of dvl3 by ms induced by eight kinases. 88 ser/thr phosphorylations from a total of 131 sites and 1 tyrosine phosphorylation were identified which can be potentially phosphorylated. ck1ε-induced phosphorylation was identified at 77 unique sites and 10 more phosphorylation sites were induced by nek2. previous studies in various experimental systems identified several phosphorylation sites spread throughout the structure of the protein dvl3 [3, 4]. our data clearly demonstrate that the phosphorylation of the protein dvl3 is extensive and the number of phosphorylated sites exceeds 60. 5. conclusion an approach based on the sds-page separation of dvl3 immunoprecipitates, tio2 phospho-enrichment followed by lc-ms/ms analysis and data processing using skyline software was utilized for the evaluation of semiquantitative differences in the phosphorylation level of hdvl3 at particular sites within the set of eight selected kinases. 46(1) pp. 3-6 (2018) 6 hanáková, potěšil, bernatík, červenka, rádsetoulal, bryja, and zdráhal differences were observed in terms of the phosphorylation profiles induced by individual kinases, as indicated in fig. 1. based on our results, a “comprehensive map” of the phosphorylations of human dvl3 will be created. acknowledgement this work was carried out with the support of the project ceitec 2020 (lq1601) funded by the ministry of education, youth and sports (meys) of the czech republic under the national sustainability programme ii. the czech infrastructurefor integrative structural biology (ciisb) research infrastructure project lm2015043 funded by meys is gratefully acknowledged for financially supporting our lc-ms/ms measurements at the proteomics core facility. the support from the czech science foundation project no. 15-21789s is also gratefully acknowledged. references [1] kersten, b., agrawal, g. k., iwahashi, h., rakwal, r.: plant phosphoproteomics: a long road ahead, proteomics, 2006 6(20), 5517–5528 doi: 10.1002/pmic.200600232 [2] bernatík, o., šedová, k., schille, c., ganji, s. r., červenka, i., trantírek, l., schambony, a., zdráhal, z., bryja, v.: functional analysis of dishevelled3 phosphorylation identifies distinct mechanisms driven by casein kinase 1 epsilon and frizzled5, j. biol. chem., 2014 34(289), 23520-23533 doi: 10.1074/jbc.m114.590638 [3] yanfeng, w. a., berhane, h., mola, m., singh, j., jenny, a., mlodzik, m.: functional dissection of phosphorylation of disheveled in drosophila, dev. biol., 2011 360, 132–142 doi: 10.1016/j.ydbio.2011.09.017 [4] klimowski, l. k., garcia, b. a., shabanowitz, j., hunt, d. f., virshup, d. m.: site-specific casein kinase 1ε-dependent phosphorylation of dishevelled modulates β-catenin signaling, febs j., 2006 273, 4594–4602 doi: 10.1111/j.1742-4658.2006.05462.x hungarian journal of industry and chemistry introduction experimental cell culture and transfection gel electrophoresis, protein digestion and phosphopeptide enrichment mass spectrometry results and analysis identification of phosphorylation sites phosphorylations induced by ck1 and nek2 discussion conclusion hungar~journal of industrial chemistry veszprem vol. 30. pp. 155 -160 (2002) kinetics and characteristic curve for convective and infra­ red conditions during drying of clay f. zagrouba, d. mihoubi, a bellagi1 and a szalay2 (inrst, b.p. 95, 2050 hammam-lif, tunisia 1enim, av. ibn eljazzar, 5000 monastir, tunisia 2ricv, b.p. 459, 8200 veszprem, ifungary) received: april 30, 2002 in this work, we present the experimental drying curves obtained by two heating modes, namely: convection and infra red. we examined the influence on the drying kinetics of the infrared flux density and of the aerothermic air condition: temperature, velocity and humidity. a comparison of the results obtained by the two heating modes are compared finally, a polynomial equation was fitted to the experimental characteristic drying curve. from the experimental drying kinetics the moisture diffusivity and the heat transfer coefficient values were identified. keywords: internal diffusion, heat transfer introduction in many industrial processes, drying treatment generally, uses some conventional techniques of energy supply as convection and conduction. nevertheless, these heat transfer modes have .limit heat transfer capacities which can be inadequate for same separations. some "new" sources are found in radiative like infra red (ir.), microwave, as the high frequencies technologies. the energy transfer to the product is direct and permits therefore to attain rapidly suitable levels temperature, which activates the fundamental drying mechanisms of the operation. because of their performances, these techniques present currently a strong development. the drying by infra-red radiation has been applied to several products like the agro-food products: [1-21. paint: [3] and pure and homogeneous materials: [4]. however, it is difficult to study the ir drying of foodstuff materials. they possess a complicated structure and, the knowledge of their optic properties is limited. the effect of the emissivity of a deformable ~anu1ated bed during ir drying was investigated only in the constant rate period: [5-8]. though for the drying of paper, the optic characteristics are better known. the problems bound to the effect of the geometry were not discussed in detail: [9]. however, it has been shown that geometric dimensions have a large influence on the. functioning of tlre process: [ 10-llj. the ir drying rate depends essentially on the radiation absorption, on the density of ir flux and on some optic characteristics which vary with geometry, structure and water content. so, the main objective of our work was, to study the experimental ir drying curves and to compare these data the corresponding obtained with the convective drying. infra-red radiation before approaching the drying by ir, it is important to remind some useful essential properties as well as the principal advantages of ir radiation. in fact, the ir radiation differs only from other electromagnetic vibrations: x rays, ultra~ violet rays, visible light and hertzian waves, by its wave length which is included between 0.8j1m and l5j.im (table 1). this physical characteristic distinguish lr from other radiations. however, the essential laws remain identical such as the phenomena of propagation, absorption and transmission. in practice, one could not separate the ir and the visible radiation which are too near: one often detects some visible light in an ir drier. their radiation in the range from 0.76j.lm to 15!j.m can be subdivided normally into three types: the short lr from 0.76~j.m to 2j.tm, the middle lr from 2pm to 4j1m, • the long ir from 4;.un to lsf.lm. contact information: e-mail: zagrouba.fathi@inrst.rnrt.tn; fax: +216 71 430 934 156 table 1 limits of wave of the radiations type of y rays x rays uv rays radiation wave 3.io"'a 0.1a at 200a at length at o.la 200 a 0.4 "m limits ,.. visible lr rays hertzian light waves 0.4f.1m at o.sf.im at 15f.lm at 0.8f.lm 15f.1m some km if the processes of convective drying have already been the object of many studies, it is not the same for the mixed processes associating the convection and the ir heating, for which exists only very little literature in particular for the case of strong radiation densities, ir heating presents the following advantages: very high flux densities (up to lookw/rnz) and compact equipments, no direct contact with the product (dusts), possibility offocalising the energy, very response time which leads to easy control procedure. basis concepts of drying basic principles of convective drying are well known. starting from a very wet capillary product, the moisture is moved to the surface under the form of a continuous liqujd flux (capillary flow). the surface temperat~e of the product is constant (wet bulb temperature), so 1s the air temperature, hence the flux of evaporation remains constant. after a certain time, the capillary forces become inoperant to move liquid water from inside to the surface. new mechanisms of water displacement are found in surface diffusion, and evaporation­ condensation cycles. the front between very wet material and almost dry material receeds towards the core of the product. ir radiation provokes an instantaneous drying of a thin superficial layer its temperature raising well above any wet bulb temperature. the results is then ambiguous: quick drying of a thin layer which in turn will slow down any water movement from inside. thence the ir is reserved for thin materials or superficial drying. material and method infra-red drying experimental apparatus our drying experiences ir radiation is conducted by means of a device composed principally of: some emitters ofir energy, a sample placed at the bottom of the air tunnel, an electronic scale, excess air and steam exhaust. overall kinetics the material was placed inside an aluminium cylindrical support. the mass and thermal exchanges tests n 1 2 3 4 5 table 2 some tests of drying by ir air temperature (oc) initial moisture content (kg/kg) ll "" 0.5 ,.. 0.3 0.2 0.1 0 0 0 160 120 70 120 160 . . * 0.969 1.018 1.087 0.5843 0.72 0 . 0 . 0 * . * \ o 10 2.0 ao 4d so 60 70 eo 90 too time(mn) ... .. a n u ~ ~ m ® u 1 fig.l influence of irradiation on the kinetics of drying (tests 1,2 and3) were supposed unidirectional. the cont~nuous weighting of the sample allowed to determine the drying kinetics. several tests were achieved for different values of moisture and temperature (table 2). globally, experimental data presented on the following figures show distinctly: at constant drying rate: period is sufficiently long and covers a large part of drying time. during this period, quite au the energy provided to the material was used for water evaporation, a decreasing rate period: it is very short and begins with the complete drying up of the surface of the material ; the temperature of the material increases noticeably. one supposes that the drying front receeds into the material. influence of infra-red radiation under ir heating, the drying rate and therefore the water loss, depend directly on the incidental infrared flux. in order to study the quantitative effect of the ir energy on the drying process, we applied different ir table 3 some tests of drying by convection. tests air temperature air humidity air velocity fuitial moisture n (°c) (%) (rnls) content (kg/kg) i 37.5 22.1 2.3 0.49 2 50.8 50.8 1.5 0.538 3 55.7 16.9 2.3 0.69 4 48 20.8 2.2 0.433 5 54.9 13.9 1.6 0.76 flux densities to the clay and we recorded the sample mass versus time. as already noticed [10,13-16], we observed that the drying rate is proportional to the ir emitted flux (fig.l) e.g.: the flux of matter is doubled when the power is doubled. convective drying experimental apparatus the experimental apparatus in which we conducted our tests of convective drying allowed to control the velocity, the temperature and the humidity of the drying air. it was made principally of: a simple aspiration ventilator with adjustable speed of rotation, some electric resistances for the heating of the air, of a humidifier/dehumidifier, allowing to maintain a constant humidity of air, of a sample holder into the vein of measurement on a balance, precision 0.1 mg. data acquisition and treatment is insured:several tests were achieved for different values of moisture, temperature and air velocity (table 3). · influence of air temperature the fig.2 shows that the drying kinetics increase with air temperature because of the increase of heat flux brought by the air to the product, and because the acceleration of the internal water migration bound to the coefficient of diffusion. one notes that the moisture content corresponding to the change of regime is so much more elevated when the temperature increases, whereas the equilibrium moisture content evolves in the opposite sense. influence of air moisture an increase of the relative moisture entrains a reduction of the isenthalpic flux. the moisture content corresponding to the change of regime evolves in the same way as the isenthalpic flux. the equilibrium moisture content increases naturally with an increase of the relative moisture content (fig.3). 157 . m .. ~ .. . 0.7 +. .. ln5 ++ ... .. .. . · .. '• ... .... .,1 0~;;:;;--#~;;_~+tt~-~~li~iji~lll~ll!~l!i~jih~ ;l!ili1coxj&lll}kol\ulxj11ml _, ~.~,~~~~u~m~m~.~.-,7,~ .. ~ .. ~, ..... , fig.2 effect of the temperature of the air on the drying kinetics (tests 1 and 4) characteristic curves of drying the method adopted for the determination of a master­ curve, called characteristic curve of drying (ccd), it. near in its principle to the one reconnnended by [11, 1218], only used in the case of the products presenting a period of constant rate drying. the purpose of ccd consists in establishing a law of drying based on some experimentation ; it derives from some basic knowledge acquired in the domain of drying but remains without complete theoretical justification. consequently, only its aptitude to foresee some drying curves attests of its validity (heuristic approach). a ccd results from the transform of the abscissa and of the ordinate in order to reassemble all the experimental curves (fig.4) on a unique curve: m [~:)-7 f= -[d;) dt i (1) (2) the determination of a reduced variable curve after the transformation appears here very delicate because of the impossibility of reaching the values of ;;u and of [-d;) . we propose a new transformation, derived dt 1 from the previous one: 158 t . t . '• •' . t •• t • . .. t •• t •• t + •••• .. ; i +++t ••• ••• t t .. : + t . . . . .. . .... t .. a m m u ~ ~ m m m ~ 1 fig.3 effect of the moisture of the air on the kinetics of drying (tests 2 and 5) w -hp == w-w,q 0:::; lf>:::; 1 (3) wo -w,q ·m (~)->/" ~( ~l 0~/~1 (4) the application of this new transformation to the whole set of experimental curves of drying by ir radiation led the global fig.5. a polynomial interpolation of the experimental points led us to the following relation: f = f(if> )= 2.79211>3 -4.5175if>z + 2.7556<p + 4.096910-2 {5) coefticient of diffusion the resolution of the model necessitates the knowledge of various physical properties of the day among which the coefficient of diffusion is important in a general way, the coefficient of diffusion d intervenes in the expression of the temporal evolution of fields of the moisture (eq.(6} and (7}): if the product is not deformable, the equation reads: aw =~(d aw) (6) dt ijx ijx if the product is submitted to a unidirectional shrinkage it becol!les: fig.4 comparison between convective and infra-red drying 0,20 0.40 0.110 fig.5 characteristic curve of drying of the clay (7) extracting diffusion coefficients as a function of moisture content from drying curves is very difficultand does not produce satisfactory results. ketelaars attributes this difficulty to the fact that drying curves are sensitive to the moisture concentration dependency of the diffusion coefficient in a limited range. outside this region, the diffusion coefficient has little to no value. only diffusion coefficient derived from internal moisture profiles are valuable. our clay sample g is very similar to clay a used by [24], as their shrinkage curves are similar. with both wr shrinkage limits are in the vicinity of 0.25. nevertheless, we have tried to identify a coefficient of diffusion from drying curves for values of w<o.l. our two results fit in rather well with ketelaars, values near 10·9 m2s·1 (fig.6). a possible expression for the coefficient of diffusion is: . d(w,t)== n{ exp( b:vw) }x{-; j (8) with d0 , a, b and c parameters for adjustment (table 4). heat and mass transfer coefficients the chr..ton-colburn analogy is largely used in drying studies. indeed, if one admits that the temperature and vapour cc·~centration boundary layer are very similar, the convective coefficients heat he and mass km are related by the lewis relation of: table 4 values of parameters of diffusion a b c 4.61 1.8019 0.031 16 __ c -= f(le) = __!!_ h (s )213 kmpcp pr (9) so, the mass transfer coefficient value km can by derived from he, values which are generally calculated from some classical empirical heat transfer correlation. the validity of this pure convection analogy in presence of ir radiation and an important flux of matter was discussed and checked by [17]. transfer of heat by convection the film theory allows to express the flux of heat through a boundary layer of steam by the relation: q =!i_h l (1 cpjta-tsurf)) conv c en+ l pv v (10) in the case of a drying with a weak rate of evaporation, the flux of sensible heat is very much lower compared to the fluxes of latent heat in such a way that one gets: ln(l+ cpjta-tsurf) )=c ta-tsurf (l 1) lv pv lv this equation is then equivalent to eq.(12) of common use: 159 ''"'l t!.ooe-9 * * t.soe-9 ij "' c looe-9 5.00!:·10 o.!loe+o ~."~"! w(kg~odoj~ ().()() fig.6 evolution of diffusion coefficient with the moisture content with: n hcdh . r vadh . g pgfrp-too)dh3 u----, e, r, a. v vz v: kinematic viscosity (mis-1 ), {3: air compressibility. c. equivalent radiative heat transfer coefficient = ry(ts:rt + r; )(tsurt + ta xt.urt t. ) = = h/tsurf ta ) mass transfer coefficient (17) qconv =hit a-tsurf) (12) according to navarri, the coefficient of transfer is independent of the presence variation of the ir flux. in convective heat transfer coefficient if the hydrodynamic and aero thermic regime is well established, the heat transfer coefficient can be estimated from well known relationships: a. forced conv~ction drrros boeltler proposed the following relation taking into account some secondary side effects: nu = 0.023re0·8 pr113(1+6~ j (14) where dh and l are respectively the diameter and the length of the duct. b. natural convection from the grashof's work, one may use: *3.103 <gr<108~ nu=0.27(grprr 5 (15) the case of the humid air, ( ~: j13 :::::i , so it is possible to estimate the mass transfer coefficient: k = ..5:_ m pcp (18) as checked by [17], this analogy also could be applied in the case ofir drying. however, the previous analogy applies only in the case of pure convective heat transfer. in this study and as a measure of simplification, we supposed that the analogy applies to the global coefficient of transfer (h=hc+hr) which is a convenient coefficient for the experimental reality. conclusion in this work, we studied the clay drying kinetics by two different heating modes: convection and ir radiation. in the case of convective or ir heating, the drying kinetics show two drying periods departed by the critical moisture content. the increase of the drying air relative humidity decreases the drying rate in the ease of convection, 160 contrary to the case of ir heating for which this humidity does not have a significant influence. the increase of the air temperature enhances appreciably, in as much as it is tolerated by the product, the drying rate during the constant rate period. the increase of the ir generally flux density implies a very height increase of the drying rate, which reduce the drying time and preserving the quality of the product (fig.4). the concept of characteristic drying curve was checked in order to an overall expression of the drying kinetics. by using an appropriate change of variable, one could determine an empiric expression of the drying kinetics suitable to control and predict the drying process independently of the chosen parameters. in spite of a satisfactory, essentially for small moisture content, identification of the material diffusion coefficient from the kinetics, we will adopt the ketelaars results in the numeric part. as for the coefficients of thermal transfer, we will apply the analogies generally admitted. symbols c specific heat, jkg1 k 1 d diffusion coefficient, m2s·1 h heat transfer coefficient, wm-2k 1 k mass transfer coefficient, ms·1 le lewis number, nu nusselt number,pr prandtl number,·q heat flux, wm'2 t temperature, k t time, s w moisture content, kgkg-1 indexes c convective cr critical eq equivalent o initial references l. saki, n. and hanzawa t.: trends food s~i. toohnot,j994, 5, 357-362 2. afzal t. m. and abet.: j. drying technology, 1999. 17,137-153 3. schrantz j.: ind. paints powder, 1993, 69{11), 2526 4. navarri p., gevaudan a and andrieu j.: preliminary study of drying of coated film heated by infra-red radiation, drying'92, amesterdam, 722-728, 1992 5. hashimoto a, hirota k., honda t., shimizu m. and watanabe a: j. chern. eng. japan, 1991, 24,748-755 6. hashimoto a, yamazaki y., shimizu m. and oshita s.: j. drying technology, 1994, 12, 10291052 7. ojala k., koski e. and lampinen m.: appl. optics, 1992, 31,4582-4589 8. hashimoto a., kameoka k. and vitia m.: food sci. tech., tokyo, 1997, 3, 294-299 9. jacques c.: rev. gen. therm., 1975, 167,863-877 10. biau d.: les applications industrielles du chauffage par rayonnement infrarouge, editions eyrolles, paris, 1986 11. van meel d. a.: chemistrical engineering science, 1958, 9, 36-44 12. schluender e.u.: le sechage, cpcia lectures, paris, 1979 13. kechaou n.: sechage de gels fortement deformables: etude de la diffusion interne de 1' eau et modelisation. these de l'institut national polytechnique de loraine, 1989 14. zagrouba f.: sechage par convection et un apport rayonnant micro-ondes des milieux deformab1es. modelisation des phenomenes de tiansferts de chaleur et de matiere. these de l'institut national polytechnique de loraine, 1993 15. biau d.: les applications industrielles du chauffage par rayonnement infrarouge. editions eyrolles, paris, 1986 16. baguenne m. and bellagi a.: entropie, 1993, 177,51-70 17. navarri p.: these de doctorat, universite claude bernard de lyon, 1992 18. crank i.: the mathematics. of diffusion, 2nd edition, clarendon press, oxford, 1975 19. jaros m., cenkowski s., iayas d. s. and pabis d.: drying technology, 1992, 10(1), 213-222 20. andrieu j., jallut c., stamatopoulos a and zafiropoulos m.: sixth international drying symposium, ids'88 versailles, 1988, 5-8 21. aregba w.: sechage d'un gel et d'une pate. processus internes et procooes adaptes. these de doctorat, universite bordeaux i, 1989 22. jomaa w.: sechage de materiaux fortement deformables. these de doctorat, universite bordeaux i, 1991 23. tanaka t. and fili.mon d. j.: j. chern. phys., 1979, 70, 214-1218 24. ketelaars a. a. j.: drying deformable media. kinetics, shrinkage and stress. thesis, university of technology, eindhoven. netherlands, 1992 page 153 page 154 page 155 page 156 page 157 page 158 hungar~njournal of industrial chemistry veszprem vol. 30. pp. 81-86 (2002) pressure drop in electrochemical cell with fixed bed s.m. serbula, v. d. stankovicandm. m. antonijevic (technical faculty bor, university of belgrade, p.o.b. 50, 19210 bor, yugoslavia) received: january 28, 2000; revised: january 23, 2001 experiments were performed to study hydrodynamic characteristics of three-phase system (solid-liquid-gas) in a cylindrical cell, where a gas phase (hydrogen) was electrochemically generated. two-phase fluid (gas-liquid), in which an electrolyte was a continuous one, flowed through the fixed bed, packed of glass particles (d::::;3 mm, d=2 mm, d::::;l.5 mm). what was examined was the influence that electrolyte velocity, current density and particles diameter had on the relative pressure drop (lip/ lip 0 ) through fixed bed. it was found that with velocity increase of electrolyte flow (w=0.00587-0.03 m/s), the relative pressure drop decreased through the fixed bed. at higher electrolyte velocity (0.03 m/s), fluidisation appeared, whereas at a little lower electrolyte velocity of 0.03 rnfs, gas channels, which form through the bed, enable quicker gas flow and also a lesser pressure drop. with the current density increase, pressure drop increased, since greater gas quantities stayed behind in the fixed bed. besides, it was also found, that relative pressure drop decreased with diameter decrease of glass particles, which formed the bed. keywords: pressure drop, electrolyte velocity, gas, electrochemical cell, gas-liquid-solid, fixed bed, fluidisation introduction electrochemical reactors with a fixed bed (gas-liquid­ solid particles) are used very often in industry, in chemical and biochemical processes, in electrometallurgy as well as in processes of environment protection [1,2,3]. besides, characteristics . of the three-phase system were examined in reactor ·engineering, especially in the part which refers to hydrogenation [ 4-8]. because of that it is good to know the hydrodynamic characteristics of two-phase gas­ electrolyte fluid through a fixed bed. hydrodynamic characteristics of two-phase flow were examined through the fixed bed, in which electrolyte is a continuous phase [9-12]. the following can influence hydrodynamic characteristics: electrolyte velocity, particle size constituting the bed, gas hold-up, geometrical characteristics of the column and so on. what was examined in this work were hydrodynamic characteristics of two-phase gas-electrolyte flow through a fixed bed of spherical particles, where gas phase had been generated electrochemically. during electrolysis of water, oxygen evolved on the anode, whereas hydrogen evolved on the cathode. at the same time, when the cathode surface developed, formation of the nucleus for hydrogen bubbles rising occurred all over the surface. in such a way, the obtained bubbles are smaller than in the case when gas was introduced into electrolyte through a distributor. experimental the experiments were carried out on the experimental set-up, which is schematically presented in fig.]. vertical cylindrical column with the inner diameter of 45 nun and 320 mm in height, was made of plexiglas. platinum net was built in the column, being at the same time a current feeder, the bed bearer and the electrolyte distributor as well. the wire, which made the net, was 0.16 mm thick, and the number of meshes per square centimeter is 378. the total surface of the cathode was 3.154'10-2 m2 • the height of the packed bed of particles through which pressure drop was measured was 50 mm. the anode was placed above the bed, as it is marked in fig.j. it is made of lead sheet having cylindrical form with an outer diameter of 45 mm, height of 30 mm and thickness of 1 nun. the distance between the cathode and the anode was 63 mm. because of the considerable distance between the cathode and the anode, a solution of sulphuric acid was used with the concentration of 3'103 movm3 h2s04 and it had the greatest electric conductivity. electric conductivity of this solution is 82 fig.l experimental set-up: 1 reservoir~ 2 centrifugal pump; 3 flowmeter; 4 differential manometer; 5 column; 6 fixed bed 73.88 s/m [13]. the power supply of direct current is a rectifier of alternating current equipped with voltmeter and ampermeter. three fractions of glass particles 1.5 mm, 2 mm and 3 mm in diameter, were used as a dispersed phase. ml experiments were carried out at ambient temperature. the total volume of liquid phase for all the experiments was the same, 5·10-3 m3 . the electrolyte was transported by a centrifugal pump, from the reservoir through a flowmeter into the column from the bottom upwards, so that the electrolyte passed through the platinum net cathode and carried gas bubbles evolving on the cathode. from the top of the column, the electrolyte returned to the reservoir overflow. both the column and the reservoir were open to the atmosphere so that the gas phase, which was hold-up in the electrolyte, went freely to the atmosphere. a differential "u-tube" manometer filled with carbon tetrachloride measured pressure drop through the bed whose density was 1586.7 kg/m3 • the procedure of performing the experiment went this way: firstly, in the column above the platinum grid electrodebed support, an amount of 0.158'10-3 m3 of glass particles was introduced. an electrolyte of the concentration 3'103 mol/m3 h2s04 was put into the reservoir. after that, centrifugal pump was switched on, so when a constant flow was achieved., then pressure drop (ap0 ) through the bed was measured. then both the power supplier and a chronometer were switched on. on the platinum cathode~ the evolution of hydrogen bubbles started up influencing pressure drop (ap) increase through the bed. this change was monitored every two minutes until it reached constant value. the centrifugal pump was still on. pumping the electrolyte, in order to remove the remained bubbles out of the bed. the system was then ready for the next experiment. results and diseussion the influence of electrolyte velocity when current is on at the platinum cathode, then there is electrolysis of water and also evolution of gas bubbles (hydrogen), which are carried by liquid flow upwards through fixed bed, in which case hold-up of each phase is: (1) solid hold-up in fixed bed is constant, so the voidage of bed e, is equal to the sum of liquid and gas hold-up. (2) that is the liquid hold-up is: £1 =£-£ 8 (3) ifergun's equation [14] is modified: 2 * (1 ) 2 * mo =150· (1-£) wtj-lt +1,75· -£ wl pl (4) l c3d 2 £ 3d with physical characteristics of two phase flow of gas­ liquid. larachi et al. interpret two phase flow by the emulsion theory [3]. thus, dynamic viscosity of gas­ liquid emulsion is given by einsten's equation: j-l; = j-lt [1 + 2,5(1qj g)] (5) according to the same principle two phase flow density is defined: (6) where qj g is a volume part of gas in two phase flow: ~g im qj = 8 w1ap fzpgw1ap (7) thus, modification of ergun's equation is given for two phase flow of gas-liquid: f),p c;w1,u,[l+2,5(1-tp.r)] c;wifp..:lj': +(1-tp,)pj (8) l=l50· (e-e/yd2 +1,75 (e-e.r)3d this equation shows that voidage is decreased for a pari of the space filled with gas bubbles. if bed voidage is decreased for gas hold-up in bed (c£ 8 ), then pressure drop increases for two phase flow, which is experimentally proved. if eqs.(8) and (4) are devided, we get the influence of gas phase on relative pressure drop: 150· c;w,,u,[i + 2,5(1 ~tp~)j + 1,75c;wifp8qj, + (1-tp,)pj !:j> (e-e1)ld~ (e-e 1 ) 3 d (9) the influence of electrolyte velocity was examined in such a way that the velocity varied in the interval of 0.003 mls 0.03 m/s, at the constant current density. two series of experiments were performed, current density of 100 a/m2 being used in the first series, whereas current density of 50 a/m2 was used in the second series. glass particles of 2 mm in diameter were used. the results are shown in fig.2-4. fig.2 shows as the electrolyte velocity decreases, a relative pressure drop increases (for w = 4.or----------------, 3.5 3.0 2.5 .wl== 0.03m.ls xw= o.ol.ull!l/s 0 1\'= o.olal/.s •w= o.oltnmf.i zyf"" u.ol76tra/t& •w= 0.0138111/11 .t.w~ 0.00922m/s +w= o.ooss7m/s .~ w::o:: o.oh~hu/s -l¥""' o.oojm/s + + + + + + + + 0.5 +---+--+----t---+----+--+--1--~ 10 12 14 16 't (min.) fig.2 dependence of relative pressure drop on time for different electrolyte velocities (current density i:::: 100 ajm2 and diameter of glass particles d=2 mm) 0.0058 0.03 m/s). the curves which show the change ap/apo against time, have two parts: the first part matching unsteady state in which ap/apo increases with time, and the second part matching steady state in which pressure drop changes slightly with time and can practically be considered as constant. unsteady state only takes several minutes and lasts shorter when velocities of electrolyte are higher. fig.2 was obtained by measuring pressure drop for electrolyte velocity of 0.00587 m/s, has a characteristic form. a peak is observed on this curve, which can indicate that at a low electrolyte velocity the buoyancy force is low, so as a result, large quantities of gas phase are hold-up in the bed. coalescence of bubbles also was observed. the bubbles, which become big in such a way, going through a bed of particles, disturb the structure of the bed, since they make channels in order to pass through. at the moment of taking those bubbles away, pressure drop de~reases in the bed of particles, all of which lasts four mmutes. the other fluctuations of the pressure are inconsiderable in the stationary part of two-phase fluid flow and take less time. the changes of pressure during two-phase fluid flow upward, where electrolyte was a continual phase through a fixed bed of glass particles, were noticed [11]. in their work, the fluctuations of the pressure are considerably higher and range within ± 20 % of some constant values for the liquid velocity of 0.0068 rn/s and gas velocity which is 0.0132 m/s. the time change of pressure drop at parallel ga~-1iquid flow through a fixed bed was examined by kn.eg et al [ 16]. for the same size of the glass particles, whtch made the bed, they noticed the similar changes of the pressure that was also observed in this work. the obtained results can be explained in the following way: by switching the current circuit on, a constant current density of 100 a/m2 is released through the electrolyte which leads to the electrolysis of water and evolution of hydrogen, forming a two-phase fluid which consists of a continual liquid phase and gas bubbles. the evolved hydrogen~ carried by the electrolyte, go through a bed with a certain quantity, and the rest of the hydrogen is captured in the 83 4.0 apia po 3.5 3.0 2.5 2.0 1.5 . . l.o o.s 0.0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 w(mls) fig:3 relative pressure drop values vs. electrolyte velocity ( d1ameter of glass particles d=2 mm and cultent density i=loo a/m2 ) channels formed by glass particles. the hydrogen, which remains in the bed causes the decrease of the cross-sectional area through which electrolyte may flow, increasing the electrolyte flow resistance that is manifested by increased pressure drop. the more enlarged the quantity of the hydrogen, which was trapped in the bed, the bigger is the fluid flow resistance. at the same time this results in the increase of pressure drop through the bed, with the increase of the volume of hydrogen in the bed. in fig.2 it is shown that only in the first few minutes the content of hydrogen in the bed increases (unsteady state). for each rate of electrolyte flow, there is a maximum quantity of hydrogen in the bed and that quantity defines the plateau value of the pressure drop. it was noticed that with the increase of electrolyte velocity, the change of relative pressure drop through the bed decreases. this means that atinwer velocities of electrolyte in the bed, there is a higher hold-up of hydrogen bubbles, which brings a pressure drop increase. at higher electrolyte velocities buoyancy forces increase which gets hydrogen bubbles carried away from the bed. higher velocities of electrolyte have a higher kinetic energy, and carrying away hydrogen bubbles from the bed more easily, the resistance to electrolyte flow decreases, i.e. at ~hese conditions the change of the relative pressure drop ts smaller. it can also be seen that at higher electrolyte velocities, relative pressure drop does not change significantly with time. at these velocities, the appearance of fluidisation has been remarked, which leads to a decrease of total resistance of electrolyte velocity through the bed, and thus the fluidisation state brings a decrease of pressure drop. this phenomenon was described by stankovic et al. [15] and he has proved that at fluidisation state relative pressure drop is less than one. in fig.3 the dependence of a relative pressure drop against electrolyte velocity is shown. the presented values for ap/apo are those ones corresponding to the steady state relative pressure drop obtained at different electrolyte velocities. as one can see, the relative pressure drop increases with the increase of the velocity of two~phase fluid flow in the fixed bed (1st region). this indicates that, for low electrolyte velocity (0.003 and 0.0042 m/s). coalescence is reduced. at electrolyte velocity of 0.00587 m/s, 84 10 12 14 16 18 20 't(min.) fig.4 dependence of relative pressure drop on time for various electrolyte velocities (diameter of glass particles d=2 mm and current density i=50 alm2 ) pressure drop in the bed is the highest one. after this value, pressure drop in the bed decreases (2nd region). namely, forming of channels through the bed occurs at the velocities higher than 0.00587 rn!s. through these channels two-phase fluid mainly flows, and so under these circumstances, pressure drop through the bed decreases. at electrolyte velocity of about 0.02 rnls there is not any change of pressure drop with the gas phase, indicating that electrolyte velocity is approached to minimum velocity fluidisation. in the third region, fluidisation in the bed exists, so the higher electrolyte velocity, the more intensive fluidisation of the particles is, and the relative pressure drop value is less than one. similar behaviour of the pressure drop with the increase of liquid velocity was observed by chern et al. [9]. namely, in their work, pressure drop decreases to the liquid velocity of 0.02 mls, when the bed transforms to a fluidisation state. a slightly lower minimum fluidisation velocity, in their work, is a consequence of less particle density than liquid density (heads made of polypropylene and polyethylene). the above discussion has been related to the experimental data, which were obtained at current density of 100 a/m2 • in fig.4, the dependence of lip/a.po against time is shown for a cylindrical cell, in which a bed of 2 mm in size is packed of glass particles, and current density used for gas phase generating was 50a/m2 • from fig.4. it can be concluded that with the increase of electrolyte velocity a relative pressure drop through the bed decreases which points to a less hold-up of gas bubbles in the bed. at constant current density. gas evolution intensity will be constant, too. increasing in liquid velocity win lead to the increase in kinetics energy of the liquid phase and its buoyancy force, causing a more efficient detachment of bubbles from t'je particles. transtbrming the bed to the fluidised state~ relative pressure drop reaches the value equal to one. tlze influence of current density based on faraday's laws. the connection between mass of evolved gas in water electrolysis and applied current. is given: 3.0,----------------apia po 25 10 12 14 ,. (min.} fig.5 dependence of relative pressure drop on time for different current densities (diameter of glass particles d=2 mm and electrolyte velocity w=0.0138 rnls) m m=--·1·1: z·f (10) if the mass of the evolved gas, obtained during electrolysis is calculated per unit of time, i.e. a second, then a mass flow rate of the gas is obtained, which, if it is expressed through continuity equation, is the following: equating the eqs.(l) and (2), the velocity of gas evolution may be expressed as follows: l·m i·m ---z · f · p g • ak f · z · p g (12) the influence of current density on pressure drop was examined by performing the experiments in which a change of pressure drop with time was measured at different current densities (50 a/m2 300 a/m2 ), and at constant electrolyte velocity. one series of experiments was carried out. in the series glass particles of 2 mm in diameter were used, and the velocity of eltictrolyte was kept at 0.0138 rn!s. the obtained results are shown in fig.5 in fig.5 it can be seen that the curves representing a dependence of ij.p!iipo on time have similar form to those obtained during investigation of the influence of electrolyte velocity on.t the pressure drop. on these curves there are also recognizable steady and unsteady parts, where it can be observed that the parts of the curves which correspond to the steady state are almost horizontal and parallel to each other, and the plateau is a translator moved towards the vertical axis. the unsteady state parts of these curves have a higher slope for higher current densities. with the increase of current density. the change of relative pressure drop also increases. that assumption can be explained in the following way: after switching on the power supplier a reduction of ir ions on the cathode occurs, and in the continual liquid phase there is a formation of two-phase gas-liquid fluid. as a result of ?as evolution. which in the form of a bubble is captured m the bed. the resistance to electrolyte flow increases, 3.0,-------------:---------, 2.5 2.0 1.5 1.0 0.5 +---+-----l---t----1---+----+__] 50 100 150 200 250 300 i(,vm1 ) fig.6 relative pressure drop vs. current density (diameter of glass particles d=2 mm and electrolyte velocity w=0.0138 rnls) and at the same time there is an increase of the relative pressure drop. in other words, the content of gas in the bed increases with time, heading to the increase of pressure drop. when the maximum content of the gas in the bed is reached, i.e. when the steady state period passes, the change of relative pressure drop reaches maximum value which does not change with time any more. from the electrochemical principles it is well known that there will be more intensive hydrogen evolution on the cathode at higher current density. higher quantities of evolved hydrogen lead to a faster saturation of the bed with gas bubbles in the initial period, leading to an increase in slopes of the curves m>jm>otime. increase of the relative pressure drop in the steady state can be attributed to an increased gas hold-up, due to a higher gas evolution rate occurring at higher current densities. this increase is observed in the whole range of applied current densities. since bubble presence in the fixed bed obstructs electrolyte flow, the enlarged gas hold-up will directly influence the increase in the relative pressure drop. in fig.6 the dependence of m>jm>o against current density for the steady state is shown more clearly. lower current densities correspond to a higher pressure drop change tending to reach a certain value, after which the relative pressure drop remains almost constant. similar behaviour was observed by chern et al. [9] for a semifluidised bed, for the same range of both gas and liquid. the influence of particle size the interspace and channels which are among the particles will depend on the size of the particles. the form of the space can greatly influence hydrodynamic characteristics of two-phase fluid so, because of that, the analysis was made of the influence of particle size on relative pressure drop through a bed. it can also be assumed that the gas phase will be distributed in a different way when passing through a fixed bed than when passing through the bed made up of larger particles. three series of experiments were carried out. 85 2.0 rr=======================::;-! .,.0.0187 .. /• •wao.u24j.m:/s 15 .l\p ..\pn ~ !utlttld-< 0.7:!.52 1.0 ~ 0.5 +-----+---+----1-~-+-------i i.s 2.5 3.5 d(mm) fig. 7 dependence of relative pressure drop on particle size (current density i=loo a/m2 ) in which current density kept constant (100 a/m2 ), whereas electrolyte velocity in the first series was 0.0187 m/s, in the second series the velocity .was 0.0243 m/s, and in the third it was 0.03 m/s. glass particles of 1.5 mm, 2 mm and 3 mm in diameter were used. it was found that the change of relative pressure drop increased with the increase of the diameter of particles. this indicated that, at electrolyte velocity of 0.01870.0243 rn/s in a bed, which was formed from larger particles, the channels, were wider. the coalescence of smaller bubbles of hydrogen in such channels was more evident than in narrower channels, which were formed in the fixed bed of smaller particles. besides, two-phase fluid was distributed in a better way when it passed through a bed of smaller particles, which decreased the total resistance to electrolyte flow. these are the reasons why the change of pressure drop was higher in the bed consisting from larger particles. the fluidisation of particles appeared, at velocities higher than 0.03 m/s, changing the image of the investigated phenomenon. the bed consisting from smaller particle transformed into a fluidised state at smaller velocities of electrolyte, so by the transformation of the bed, the total resistance of electrolyte flow through bed decreased. the influence of particle size on relative pressure drop is presented fig. 7 in which a dependence of m>im>o (values at a steady state) on diameter of particles is shown. in fig.7 one can see the relationship between the relative pressure drop and particle size for different velocities of electrolyte flow to be linear. it can be seen that the lines corresponding to velocities of 0.0187 m/s and 0.0243 m/s have positive slopes, indicating that at those velocities of electrolyte, the relative pressure drop increases with the increase of particle diameter. with a further increase of electrolyte velocity (0.03 rnls) the slope becomes negative, indicating that particle size at those velocities does not play a great part on the change of pressure drop. the negative slope value, which was found for the velocity of w = 0.03 mls, is a consequence of fluidisation, where the gas phase does not increase the relative pressure drop through the bed. stankovic [ 15j has also remarked similar effect. 86 conclusions based on experimental results the following conclusions could be pointed out: the presence of gas phase is evaluated on the electrode in the electrolyte flowing through the fixed bed. this contributes to the pressure drop increase. gas bubbles decrease the existing electrolyte hold­ up, attaching to the particles and bridging the channels in the bed, obstructing electrolyte flow in such a way. relative pressure drop increases with time reaching a constant value after certain time due to an increase of gas hold-up with time. gas evolution intensity, i.e. operating current density, strongly influence the relative pressure drop in such a way that, with increasing of current density, the relative pressure drop increases too. electrolyte velocity through the bed has an opposite effect the relative pressure drop decreases with increasing of electrolyte velocity (for w = 0.00587 o:o3 rnls). such effect results in an increased buoyancy force, enabling bubbles to detach from the particles and to take them out of the bed. achieving the fluidised state, relative pressure drop becomes equal to one or slightly less indicating that in fluidised bed, gas phase has no remarkable influence on the pressure drop. what has also been remarked is a linear dependence of the relative pressure drop increase with the particle size increasing. symbols ak total surface of the cathode, m2 ap cross surface of cell, m2 d diameter of a particle, m f faraday's constant, 96 500 as·mor1 .. g mass flow, kg·s-1 i current. a i current density, a·m·2 l height of a bed, m m molecular mass of the evolved gas, kg·mor1 m mass of gas obtained during water electrolysis kg • vig volume flow of gas evolution, m3·s·1 w electrolyte velocity, m·s·1 w1 liquid velocity, m·s·1 wig velocity of gas evolution, m3·s-t.m·2 z number of exchanged electrons greek letters e bed voidage eg gas hold-up €1 liquid hold-up es solid hold-up l\p pressure drop through the bed, k:pa l\po initial pressure drop through the bed without gas phase, k:pa·m-1 l\pi l\po relative pressure drop q>g volume part of gas 1-li liquid viscosity, pa·s . ~-tt dynamic viscosity of gas-liquid, pa·s pg gas density, kg·m-3 pi liquid density, kg·m·3 pt density of gas-liquid, kg·m·3 't time realisation of the electrochemical process, s references l akman u. and sunol a. k.: chern. eng. sci., 1994,49,3555 2. iliuta i., thyrion f. c. and muntean 0.: chern. eng. sci., 1996, 51, 4987 3. larachi f., cassanello m., laurent a., midoux n. and wild g.: chemical eng. and proc., 1997,36,497 4. hofmann h. p.: in multiphase chemical reactors­ theory, design, scale-up, ed. by a. gianetto and p. l. silveston, hemisphere, 1986 5. van landeghem h.: chern. eng. sci., 1980, 35, 1912 6. ramachandran p. a. and chaudhari r. v.: three phase catalytic 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page 83 page 84 page 85 page 86 page 87 page 88 hungarian journal of industry and chemistry vol. 47(1) pp. 71–77 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-11 comparison of the approximation methods for time-delay systems: application to multi-agent systems áron fehér *1,2 and lőrinc márton1 1department of electrical engineering, sapientia hungarian university of transylvania, c.1., târgu mureş, 547367, romania 2department of mathematics, university of pannonia, egyetem u. 10, veszprém, 8200, hungary this paper presents a review of dominant pole and model-approximation algorithms for delayed systems that can be applied to multi-agent systems. a novel algorithm is proposed to determine an approximation method for multi-agent systems in the platoon configuration with a communication delay. simulations are presented to show the applicability of the proposed algorithm. keywords: time delay, differential equations, asymptotic properties, multi-agent systems 1. introduction a multi-agent system (mas) consists of multiple active agents (e.g. vehicles), passive agents (e.g. obstacles), in addition to cognitive agents and their environment [1]. every active agent is at least partially autonomous and uses a distributed control algorithm [2]. the agents can communicate with each other. this communication structure is defined by a graph, where each vertex corresponds to one agent and each edge to a communication direction. a platoon is a special mas configuration, with a linear communication graph. the leading (first) agent implements a reference tracking algorithm. every other agent implements a consensus with the adjacent agents [3]. with the increase in the number of agents and the physical distance between the agents, the communication delay cannot be neglected. while the stability of such systems is ensured by the consensus protocol [4], the delay will influence the transient behavior of the mas [5]. the goal of this paper is to compare the existing approximation methods for the transient behavior analysis of mas with communication delays and present a novel analysis method which can be applied to any mas system which satisfies a smallness delay condition. 2. modelling of mas a mas is considered with agents that exhibit singleintegrator dynamics [6]. the state-space model of an agent becomes ẋi(t) = ui(t), where xi ∈ r denotes *correspondence: fehera@ms.sapientia.ro the state of the ith agent and ui ∈ r represents the input, i = 1, 2, . . . , n. a mas has an underlying communication graph, in which the vertex is an agent and the edge a communication path [7], so the agent ith in the system is the vertex vi. let ni be the set of neighbors of vi, so that ni contains all vertices that are connected to vi. consensus algorithm the consensus problem of a mas is the procedure of gathering every state from the initial condition to a common steady-state. if the communication graph is connected, the consensus with regard to an agent can be reached with the input (consensus protocol) ui(t) = ∑ j∈ni (xj(t)− xi(t)) . (1) the adjacency matrix a = (aij) ∈ rn×n of a graph with n nodes is defined as aij := { 1, if i 6= j and vi are adjacent to vj 0, otherwise . (2) the degree matrix d = (dij) ∈ rn×n of a graph with n nodes shows the number of neighbors for each vertex and can be defined as dij := { deg(vi), if i = j 0, otherwise , (3) where deg(vi) denotes the degree or the number of edges incident to vertex i. mailto:fehera@ms.sapientia.ro 72 fehér and márton figure 1: the communication topology of a vehicle platoon system consisting of n vehicles with time delay τ in the communication graph. the dashed line symbolizes more nodes in between, while the dotted line represents the reference input of the nodes. with this notation the dynamics of the mas with the consensus protocol is given by ẋ(t) = −lx(t), x(0) = x0, (4) where l denotes the laplacian matrix [8] which is constructed as l = d − a, d stands for the degree matrix, a represents the adjacency matrix of the graph, x = ( x1 x2 . . . xn )> ∈ rn denotes the state vector consisting of the n states of the mas, and x0 ∈ rn is a constant vector of the initial states. according to [9] the eigenvalues of a mas consisting of n agents with a connected communication graph can be ordered as 0 = λ1 > λ2 ≥ · · · ≥ λn. (5) the steady states (equilibria) of the mas xss are the elements of the null space of l. given, according to the definition of the laplacian matrix, ∑ j∈ni lij = 0 [6] for every solution x of (eq. 4): lim t→∞ x(t) = xss = 1 n ∑n i=1 xi(0)1, where 1 = ( 1 1 . . . 1 )> ∈ rn. mas with delayed communication in the case of delayed communication, the consensus protocol is of the form ui(t) = ∑ j∈ni (xj(t− τ)− xi(t)) , (6) where τ ≥ 0 denotes the constant communication delay which is present among adjacent agents. according to refs. [4] and [10], the mas with communication delay (also referred to as multi-agent system with delays (dmas)) is ẋ(t) = −dx(t) +ax(t− τ) +r, (7) x(θ) = x0 ∈ rn, θ ∈ [−τ, 0], 3. platoon of vehicles a platoon of vehicles is a special class of mas with a communication topology shown in fig. 1. the kinematic model of a vehicle can be written as ẋi(t) = ui(t), (8) where xi(t) denotes the position of the vehicle and ui(t) represents the control signal in the form{ u1(t)=kp1(r−x1(t)) ui(t)=ξi(xi−1(t−τ)−d−xi(t)),∀i = 2, ..., n (9) where i ∈ (1, n), n ∈ n, n > 1, d denotes the prescribed inter-vehicle distance, ξi > 0, and kpi > 0 are constant control gains. r is the position reference of the first vehicle. eqs. 8 and 9 can be written as a system of differential equations with delay: ẋ(t) = −φx(t) + γx(t− τ) + f 1 r − f 2 d, (10) where φ = diag{ ( kp1 ξ2 . . . ξn−1 ξn ) } (11) denotes the degree matrix with the state feedback, γ =  0 0 0 . . . 0 0 0 ξ2 0 0 . . . 0 0 0 ... ... ... . . . ... ... ... 0 0 0 . . . ξn−1 0 0 0 0 0 . . . 0 ξn 0  (12) represents the adjacency matrix, and f 1 = ( kp1 0 . . . 0 )> , (13) f 2 = ( 0 ξ2 . . . (n− 1)ξn )> . (14) the homogeneous part of the relation in eq. 10 is of the same form as the relation in eq. 7, and the term f 1 r−f 2 d represents the reference as well as inter-vehicle distance induced inflows. 4. existing methods for the approximation of time-delay systems in this section, the various current approximation methods for time-delay systems are reviewed. the form of the studied systems is shown by the following relation: ẋ(t) = −φx(t) + γx(t− τ), x(h) = x0, (15) which is the homogeneous part of eq. 10, where θ(h) denotes the initial condition with h ∈ [−τ, 0], and has a quasi-polynomial characteristic equation: λin + φ− γe−τλ = 0, (16) where the delay component induces an exponential term. the roots of eq. 16 determine the transient behaviour of the system in eq. 15. as eq. 15 possesses an infinite number of solutions, it is important to develop such an equivalent system which has a finite number of eigenvalues and is a good approximation of the original system in eq. 15. if a good delay-free approximation is available, it hungarian journal of industry and chemistry approximation of multi-agent systems with delays 73 could be applied to the transient behaviour analysis and control design for delayed systems. let a special solution be denoted by x̃, which is uniquely determined by the value x̃(0), and independent of θ(h), h ∈ [−τ, 0), thus forming an n parameter family. in a linear autonomous system, this corresponds to the eigensolution generated by exactly n characteristic roots (multiplicities included) which lies in the half-plane reλ > −1/τ , see ref. [11]. theorem 1. [11] consider a delay differential equation (dde) system of the form shown in relation eq. 15 with a lipschitz criterion of: (‖φ‖+ ‖γ‖)τe < 1, (17) further noted as smallness condition, for every solution x of eq. 15 a globally defined solution x̃ : r→ rn exists that satisfies the growth condition supt≤0 ‖x̃(t)‖et/τ < ∞ such that ‖x(t)− x̃(t)‖ → 0 exponentially as t→∞. for further related discussions, see refs. [12] and [13]. the aforementioned theorem yields n dominant eigenvalues which can accurately represent a dde system. the system shown in the relation in eq. 15 uses the consensus protocol, which ensures that the eigenvalues are located in the left half-plane in the complex region. the final location of the dominant eigenvalues is created as a semicircle with origin 0, radius 1/τ , and a negative real part. 4.1 the modified chain approximation the modified chain approximation method creates an approximating system directly from the state-space representation of the delayed system [14]. for a dde in the form of eq. 15, the modified chain approximation method yields an approximating linear system in the form of ẏ 0 (t) = −φy 0 (t) + m τ inym(t) ẏ 1 (t) = γy 0 (t)− m τ iny1 (t) (18) ... ẏ k (t) = m τ inyk−1 (t)− m τ inyk(t), 2 ≤ k ≤ m the output vector z = y 0 represents the approximation of the solution x of the relation in eq. 15. the approximating system in the form of a matrix is shown in ẏ(t) = gy(t) (19) with g =  −φ 0n 0n · · · 0n m τ in γ −mτ in 0n · · · 0n 0n 0n m τ in −mτ in · · · 0n 0n ... ... ... . . . ... ... 0n 0n 0n · · · m τ in −mτ in  (20) where y ∈ rmn denotes the state vector, g ∈ r(m+1)n×(m+1)n represents the matrices of the system, 0n ∈ rn×n stands for the zero matrix, n is the number of agents and m denotes the number of approximating equations. according to ref. [14] the output of the system (eq. 19) defined as z(t) = y 0 (t) linearly converges into the solution of the original dde system such that c > 0 and supt≥0‖x(t)− z(t)‖ ≤ c m . 4.2 the lambert w function the lambert w function can be used to find the dominant eigenvalues of a quasi-polynomial equation (eq. 16). every w (s) function that satisfies w (s)ew (s) = s (21) by definition is referred to as a lambert w function [15], where s is either a scalar or matrix complex number function. the lambert w function has multiple branches denoted as wk(s) with k = 0,±1,±2, . . . ,±∞ . example 4.1. if a scalar dde is present in the form of ẋ(t) = ax(t) + bx(t− τ) + cu(t), (22) with a, b, c, θ ∈ r, x(h) = θ(h) for h ∈ [−τ, 0], the quasi-polynomial of the homogeneous part can be written as (λ− a)eτλ = b. (23) if both sides are multiplied by τe−aτ , then (λ− a)τeτ(λ−a) = bτe−aτ , (24) which satisfies eq. 21 with w (bτe−aτ ) = (λ− a)τ , and the eigenvalues can be calculated using the branches of the lambert w function as λk = 1 τ wk(bτe−aτ ) + a. (25) in our case, in terms of the relation in eq. 15, the aforementioned solution is generalized as λk = 1 τ wk(γτqk)− φ, (26) 47(1) pp. 71–77 (2019) 74 fehér and márton where qk can be calculated by solving the equation numerically wk(γτqk)ewk(γτqk)−φτ = γτ (27) for qk [16]. although many numerical solvers provide native support for the solution of the scalar lambert w function, the general case requires additional solver tools. therefore, the lambertwdde toolbox [17] was created. the function find_sk assumes τ , γ and−φ. the returned values are the eigenvalues λk and the qk parameters for a given k branch. the toolbox can create the approximating solution for the given system as x̃(t) = m2∑ k=m1 eλktcik , (28) where x̃ is the approximating solution of the original delay system and the parameter cik can be computed with the help of find_ci for a given m1 < k < m2 branch. in the scalar case, cik takes the form of cik = x0 + be−λkτ ∫ τ 0 θ(t− τ)dt 1 + bτe−λkτ . (29) 4.3 the quasi-polynomial root-finder algorithm the quasi-polynomial root-finder algorithm calculates the dominant eigenvalues of a system based directly on the quasi-polynomial equation in eq. 16. the quasi-polynomial equation of the system in eq. 16 can be written as: p (λ) = n∑ k=0 qk(λ)e−αkτλ, (30) whereqk is a polynomial with real coefficients and αk ∈ r. the objective is to compute the spectrum in the region of the complex plane d ⊂ c with boundaries βmin < re(d) < βmax and ωmin < im(d) < ωmax. let the surfaces defined by the real and imaginary parts of p (λ) be: re(p (β, ω)) = 0 (31) im(p (β, ω)) = 0 (32) the eigenvalues can be located at the points of intersection of the zero-level curves of the surfaces re(p (β, ω)) = 0 and im(p (β, ω)) = 0 as shown in ref. [18]. the accuracy of the algorithm is increased by newton’s method and by adapting the grid density of d as shown in ref. [16]. the quasi-polynomial root-finder algorithm (qpmr) [19] is implemented in matlab. the function expects the region of interest [βmin, βmax, ωmin, ωmax] to be in the complex plane of the polynomial coefficient matrix of the quasi-polynomial where one row corresponds to one polynomial multiplied by the same exponential term. the delay vector, computational accuracy and grid step are also required. in our case this translates into a region of interest [− 1 τ , 0,− 1 τ , 1 τ ] if the smallness condition (eq. 17) is satisfied. the first row of the matrix of polynomial coefficients contains the coefficients of the delay-free part so that the delay vector is of the form [0, τ, 2τ, ...]. the algorithm covers the given region with a mesh grid, then evaluates the quasi-polynomial at each point of the grid by splitting it into a real and an imaginary part. the zero-level curves are then mapped with the help of the contour plotting algorithm. the computational error is checked and if it is too large, the algorithm is restarted using a modified grid density as described in ref. [16]. if the computational error is smaller than the given level of tolerance, the computed dominant eigenvalues are returned. 5. explicit matrix approximation method an approximation method was devised where the convergence rate is exponential, the degree of the resulting system in the form of eq. 4 matches exactly the degree of the delayed mas given in eq. 15, and the same properties are exhibited in specific cases. the banach fixed-point theorem was used as discussed in ref. [20] to explicitly find a linear system of the form of eq. 4 which approximates the homogeneous part of the system in eq. 10. if an (x, f) metric space is present and t : b → b is a contraction with a bounded set b ⊂ x , and q < 1 such that f(t (x), t (y)) ≤ qf(x, y) (33) by definition t admits a unique fixed point x̃ such as t (x̃) = x̃, and this fixed point can be found by starting from an arbitrary element x0 ∈ b with the sequence xn = t (xn−1), (34) where xn → x̃. a dde system is defined in eq. 15 by the corresponding smallness condition of eq. 16. since all normed spaces are metric spaces, the metric space x = rn×n is set with f as the induced matrix norm. the contraction t : b → b is present such that t (λ) = −φ + γe−λτ , (35) and b = {λ ∈ rn×n|‖λ‖ ≤ (‖φ‖ + ‖γ‖)e}. the relation in eq. 33 holds true for (‖φ‖+ ‖γ‖)τe < 1. let λ1,λ2 ∈ b such that ‖λ1‖ > ‖λ2‖. the left side of the inequality in eq. 33 can be written as ‖t (λ1)− t (λ2)‖ = ‖γ‖‖e−λ1τ − e−λ1τ‖. it is evident that ‖γ‖ ≤ ‖γ‖ + ‖φ‖ and the maximum norm can be used as ‖e−λ1τ − e−λ1τ‖ ≤ τ‖λ1 − λ2‖eτ max{‖λ1‖,‖λ2|}. hungarian journal of industry and chemistry approximation of multi-agent systems with delays 75 it can be seen that ‖t (λ1)−t (λ2)‖ ≤ τ‖λ1−λ2‖(‖γ‖+‖φ‖)eτ(‖γ‖+‖φ‖)e and by applying the smallness condition ‖γ‖ + ‖φ‖ ≤ 1/(τe) (eq. 17), ‖t (λ1)− t (λ2)‖ ≤ ‖λ1 − λ2‖ is obtained, which proves that t : b → b is a contraction. this shows that by solving λ = −φ + γe−λτ (36) for the λ matrix, a system is created dx̃ dt = λx̃, (37) which approximates the dde system of eq. 15. as a result of the proposed iterative method, the eigenvalues and eigenvectors of eq. 37 approximate, with a given degree of precision, the dominant eigenvalues of eq. 14. 5.1 comparison with the existing methods • chain approximation: + the result is an approximating system with known system matrices (both eigenvalues and eigenvectors are known). the resulting system is of a higher degree than the delay system. the convergence rate of the algorithm is linear. • lambert w function: + the result is a trajectory approximation. + the convergence rate of the algorithm is exponential. the algorithm requires numerical solvers for an exponential matrix equation. multiple branches of the lambert w function must be used to create an accurate approximation, and the number of eigenvalues in a branch cannot be predetermined generally. • qpmr algorithm: + the algorithm determines the exact number of eigenvalues in the given complex domain, with the given computational error. + the convergence rate of the algorithm is exponential. the algorithm uses the quasi-polynomial equation, thus, will not contain any information on the eigenvectors. the algorithm uses numerical solvers to compute the zeros of the zero-level curves created from the quasi-polynomial equation. • approximation of an explicit matrix: + the result is an approximating system. + the resulting system is of the same degree as the approximating system. the algorithm calculates a matrix exponential numerically, which is a compute-intensive task. 6. simulations and results let us consider two cases: a mas consisting of five and twenty-five agents, respectively, with first-order dynamics in a platoon configuration as shown in the relation of eq. 10, with the constant initial condition θ(h) = x0. for the comparisons, a 6th order chain approximation was used. in the case of the lambert w function, the initial matrix q0 = ( 1 1 1 1 ) and the branches k = −2,−1, 0, 1 were used. for the quasi-polynomial rootfinder algorithm (qpmr), a symbolic calculation to find the characteristic quasi-polynomial equation of the system was used, and the plane of the search was set to [−τ, 0]× [−τj, τj]. the algorithm for explicit matrix approximation was used with the initial matrix λ0 = 0n×n. the error threshold 1e−7 was used in every iterative algorithm. the dominant eigenvalues of the system consisting of five agents, with minor differences, was identified by every approximation method. in the case of the larger system, the chain and explicit matrix approximations could generate a result, while the quasi-polynomial root-finder algorithm and the lambert w function were determined by numerical calculations. as such, the smaller system was chosen as a point of comparison for the algorithms. tables 1 and 2 contain a comparative summary of the four aforementioned algorithms: the number of iterations, the overall computation time and the dominant eigenvalues identified for a platoon consisting of five agents as shown in fig. 2. fig. 3 shows that the linear system is generated by the explicit matrix approximation in just twelve steps for the dmas that consists of twenty-five agents. fig. 4 shows that the resultant approximating system exhibits the same steady-state and transient behavior as the original delayed system using the same initial conditions. since the initial position falls within the range of table 1: the number of iterations and the overall computation time for the algorithms. name of algorithm no. of cycles computation time chain approximation 1 0.02 s lambert w function 35 7.5 min qpmr algorithm 12 17.18 s explicit algorithm 4 0.03 s 47(1) pp. 71–77 (2019) 76 fehér and márton table 2: the eigenvalues returned by the studied algorithms. name of algorithm eigenvalues chain approximation -0.1080, -0.9471, -1, -2.4736, -4.2511 lambert w function -0.1081, -0.9482, -1, -2.4658, -4.1603 qpmr algorithm -0.1081, -0.9481, -1, -2.4661, -4.1603 explicit algorithm -0.1080, -0.9481, -1, -2.4661, -4.1603 -4.5 -4 -3.5 -3 -2.5 -2 -1.5 -1 -0.5 0 re( ) -1 -0.5 0 0.5 1 im ( ) figure 2: dominant poles of the dmas consisting of five agents. 0 20 40 60 80 100 120 number of iterations (1) -60 -50 -40 -30 -20 -10 0 10 20 30 tr ( n ) tr( n ) |tr(| n )-tr( n-1 )|=1e-6 figure 3: the explicit matrix approximation returns a valid system after 12 iterations for 25 agents. 0 to 100 m, the error of the approximating system is 8 cm in the transient domain and 5 mm under steady-state conditions, as shown in fig. 5. 7. conclusions an iterative algorithm was proposed and tested based on which a degree-preserving approximation model can be created for a class of mas in a platoon formation consisting of agents that exhibit first-order dynamics in the presence of a small communication delay. the algorithm uses methods of numerical computation. the obtained mas is of the same degree and steady state as the delayed mas, moreover, it correctly approximates the transient behavior. the algorithm was compared with existing methods for approximating eigenvalues and systems. simulations show that the presented algorithm is suitable for the analysis of complex mas. 0 50 100 150 200 250 300 350 400 450 500 time (s) 0 10 20 30 40 50 60 70 80 90 d is ta n c e ( m ) figure 4: the trajectories of the platoon of the delayed mas compared to the platoon of the approximated mas created by the explicit matrix approximation. 0 10 20 30 40 50 60 70 80 90 100 time (s) -0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08 d is ta n c e ( m ) figure 5: the trajectory of the approximation error. acknowledgement the authors would like to express their gratitude to dr. mihály pituk (university of pannonia, hungary) for his useful comments. references [1] kubera, y.; mathieu, p.; picault, s.: everything can be agent!, in proceedings of the ninth international joint conference on autonomous agents and multi-agent systems (aamas’2010) (w. van der hoek, g.a. kaminka, y. lespérance, m. luck, s. sen, eds.) 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47(1) pp. 71–77 (2019) https://doi.org/10.1137/1.9780898718645 https://doi.org/10.1007/978-1-4471-5574-4 https://doi.org/10.1016/0097-3165(78)90067-5 https://doi.org/10.1016/0097-3165(78)90067-5 https://doi.org/10.1515/9781400835355 https://doi.org/10.1109/tac.2011.2152510 https://doi.org/10.1006/jdeq.2000.3824 https://doi.org/10.1006/jdeq.2000.3824 https://doi.org/10.14232/ejqtde.2016.1.72 https://doi.org/10.14232/ejqtde.2016.1.72 https://doi.org/10.1016/j.mcm.2009.12.001 https://doi.org/10.1016/j.mcm.2009.12.001 https://doi.org/10.1007/bf02124750 https://doi.org/10.1007/bf02124750 https://doi.org/10.1007/978-3-319-01695-5 https://doi.org/10.1007/978-3-319-01695-5 https://doi.org/10.3182/20120622-3-us-4021.00008 https://doi.org/10.3182/20120622-3-us-4021.00008 https://doi.org/10.1016/s1474-6670(17)33330-x https://doi.org/10.1007/978-3-319-01695-5_22 http://www.cak.fs.cvut.cz/algorithms/qpmr http://www.cak.fs.cvut.cz/algorithms/qpmr https://doi.org/10.1007/978-3-319-01586-6_2 https://doi.org/10.1007/978-3-319-01586-6_2 introduction modelling of mas platoon of vehicles existing methods for the approximation of time-delay systems the modified chain approximation the lambert w function the quasi-polynomial root-finder algorithm explicit matrix approximation method comparison with the existing methods simulations and results conclusions hungarian journal of industry and chemistry vol. 47(2) pp. 31–42 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-18 gpu-accelerated simulation of a rotary valve by the discrete element method balázs füvesi1 and zsolt ulbert*1 1department of process engineering, university of pannonia, egyetem u. 10, veszprém, 8200, hungary the rotary valve is the most frequently used piece of equipment that is suitable for the controlled feeding or discharging of products in powdered or granular form. it is usually connected to silos, hoppers, pneumatic conveying systems, bag filters or cyclones. in this paper, a simulation study is presented on the discharge of solid particles from a silo through a rotary valve. the discrete element method (dem), which accounts for collisions between particles and particle-wall collisions, was used to model and simulate the motion of individual particles. the diameter of the simulated silo was 0.2 m and a total of 245, 000 particles were calculated. in the simulations, the effect of the geometric and operational parameters of the rotary valve on the mass outflow rate was investigated. the diameter of the rotary valve varied between 0.06 and 0.12 m and the rotational speed of the rotor was changed between 0.5 and 5 s−1. the simulations showed that the mass outflow rate of the particles from the rotary valve changes periodically due to its rotary cell structure. within the lower range of rotational speeds of the rotor, the mass outflow rate of particles changes linearly in correlation with the rotational speed. the identification of this linear section is important in terms of control as this would facilitate the implementation of control devices by applying well-established linear control algorithms. adjacent to the linear section, the dependence of the average mass outflow rate on the rotational speed was found to be nonlinear. within the upper range of examined rotational speeds for each diameter of the rotary valve, the mass outflow rate reaches a maximum then decreases. the simulations were performed using gpu hardware. the application of parallel programming was an essential aspect of the simulations and significantly decreased the calculation time of simulations. in the treatment of particle-wall contacts, a novel flat triangular-based geometric representation technique was used which allows the particle-wall contacts to be calculated more effectively and their treatment implemented more easily into the parallel programming code. using the calculated particle positions, the particles were visualized to view the effect of the interactions between the particles and rotor blades on particle motion. the simulation results showed that the discrete element method is capable of determining the detailed flow patterns of particles through the rotary valve at various rotational speeds. keywords: silo, rotary valve, simulation, discrete element method, gpu 1. introduction the handling of solids is part of many industrial technologies in the chemical, pharmaceutical and food industries amongst others. from simple storage (e.g. storage silo) and transport operations (e.g. pneumatic transport) to gas-solid or liquid-solid two-phase flows (e.g. gassolid fluidization, gas-solid catalytic reactions), a number of technological operations involve solid and particulate materials. a common feature of gas-solid two-phase flow is that the interaction between the solid and gas phases can facilitate effective phase mixing in addition to intensive mass and heat transfer for a variety of operational purposes (e.g. gas-solid chemical reactions). the movement of the solid phase may result in different flow mechanisms and flow patterns, depending on the frequency of collisions between the particles and effects as a result of the gas stream. the experimental investigation of the unit *correspondence: ulbert@fmt.uni-pannon.hu operations of particulate solids is time-consuming and costly. measurements in this type of systems are often inaccurate due to the limitations of the measuring devices and difficulty of taking measurements in a solid flow without changing its flow properties. although a number of advanced measurement techniques for measuring the flow properties of solids, e.g. phase doppler particle analyzer, high-speed video processing, magnetic resonance tomography, positron emission particle tracking, etc., exist which provide useful information on the movement of particles, many factors that significantly influence the flow structure such as the forces between the colliding particles are not yet available. however, experiments can be performed more easily using computer simulation if a sufficiently detailed model is available to investigate the system. the modeling and simulation of the flow of particulate solids are becoming increasingly popular and intensive research has been undertaken in this field. the flow of particulate solids is https://doi.org/10.33927/hjic-2019-18 mailto:ulbert@fmt.uni-pannon.hu 32 füvesi and ulbert always coupled with the flow of the interacting gas phase and in this sense the entire particulate flow can be considered to be a gas-solid two-phase flow. however, the construction of the model depends on the degree of interaction between the solid and gas phases. the effect of the gas phase on the solid particles may vary from one unit operation to another. for example, in terms of the gravity discharge of solids from a silo, the effect of the gas phase is negligible on the motion of the particles and the calculation of any interaction between the solid particles and gas phase and the calculation of the gas phase flow are unnecessary. on the other hand, when pneumatic transportation is used to transport solids, the interaction between the two phases is significant, therefore, the modelling and calculation of flow characteristics of both the solid particles and gas phase as well as their interactions is necessary. two main methods for the treatment of solid particles with regard to gas-solid two-phase flows are proposed by the authors. the euler method considers both the solid and fluid phases as a continuous phase and these methods are referred to as two-fluid models (tfm) in the literature. in these models, both phases are calculated by volume-averaged flow equations that are supplemented by terms which describe the interaction between the two phases. the disadvantage of these methods is that the solid particles are treated as a continuous phase and no information is provided about the motion of individual particles. in another method, the gas phase is treated as a continuous phase and described by volume-averaged flow equations, however, the solid particles are treated as discrete systems with their own mass, independent motion and velocity. the flow equations for the gas phase also include terms that describe the interaction between the solid particles and the gas phase. to model and calculate the forces that result from particle-particle and particle-wall collisions, the discrete element method (dem) based on the softor hard-collision model is used. these calculation methods are referred to as the euler-lagrange, eulerdiscrete element method (euler-dem) or the computational fluid dynamics discrete element method (cfddem). if the effect of the gas phase on the particles is negligible, the motion of the particles can be calculated by applying the discrete element method alone without taking into account any interactions with the gas phase. the discrete element methods have the advantage of providing detailed information about the flow characteristics of solid particles. however, since all the particles are handled independently, they require significant computing capabilities in the case of a large number of particles. in the application of “two-fluid” theory, anderson and jackson [1] first introduced interaction terms in the volume-averaged navier-stokes equation that is used to describe the particle-fluid and particle-particle interactions. in the 1990s, a significant amount of research using tfms in the modeling and simulation of two-phase flow in fluidized beds was conducted by bouillard et al. [2], ding and gidaspow [3], kuipers et al. [4–6] and nieuwland et al. [7]. mckeen et al. [8] simulated the movement of catalyst particles in a fluidized-bed catalytic cracking reactor. wang et al. [9] developed a tfm including chemical reaction source terms that are capable of describing homogeneous and heterogeneous reactions. pougatch et al. [10] simulated particle attrition in a fluidized bed introducing an attrition term into the model. however, given the complexity of two-fluid models, they are unable to describe the discrete particle dynamics and flow properties of individual particles. the rapid development of computers and parallel computing over recent decades has led to the popularization of discrete element methods in terms of the simulations of solid particulate flows and gas-solid two-phase flows. in the application of discrete element methods, the movement of each individual particle in the particulate flow is calculated. the motion of particles is calculated in accordance with newton’s three laws of motion by taking into account the forces acting on the particles as a result of collisions with other particles or from their interactions with the gas phase. over the last two decades, numerous papers have been published regarding the application of the discrete element method. tsuji et al. [11] and kawaguchi et al. [12,13] presented simulations of gas-solid fluidization by applying a soft collision model developed by cundall and strack [14]. in these simulations, the mixing of particles inside the fluidized bed was examined. hoomans et al. [15, 16] used a hard-sphere collision model in their simulations and studied the effect of gas velocity on the flow of particles in a fluidized bed. kaneko et al. [17] also used the cfd-dem simulation method in the simulation of a polymer reactor. using the temperature and velocity field of the gas phase, they calculated the kinetics of the polymerization reaction and the reaction heat for each individual particle. ulbert et al. [18] presented a cfd-dem simulation study on the simulation of a reactive gas-solid two-phase flow in a circulating mediator recirculation integrating technology (merit) fluidized bed combustor. the model proposed by the authors contains the balance equations for the components of the reaction and the shrinking core model was used to describe the gassolid chemical reaction for each particle. tsuji et al. [19] presented a simulation study that calculated the motion of 4.5 million particles in a fluidized bed using parallel computation. yang et al. [20] examined the effect of the surface energy of particles on the transitions between different flow types in a fluidized bed. fan et al. [21] presented a simulation study on the simulation of cohesive particles. accordingly, the cohesive surface interaction between the particles was taken into account when the interacting forces were calculated. hou et al. [22] simulated a fluid bed equipped with heat transfer tubes using the cfd-dem simulation method. the authors examined the heat transfer between the tubes and the fluidized bed. hou et al. [23] studied the effect of the particle-gas interaction, particle-particle collisions, gravity and friction on the transfer of energy between particles in particulate hungarian journal of industry and chemistry gpu-accelerated simulation of a rotary valve 33 figure 1: cross-sectional view of a silo equipped with a rotary valve. solid flows and gas-solid two-phase flows. as can be seen from the aforementioned examples, in addition to the calculation of the motion of discrete particles, the discrete element method is suitable to treat the discrete nature of the solid particle phase by taking into account further characteristics of discrete particles, e.g. temperature, concentration, etc. the subject of this paper is the simulation of the operational characteristics of a rotary valve that is often connected to a silo that stores solids (fig. 1). during the discharge of solids from silos, the effect of the gas phase on the movement of particles is negligible, i.e. it is unnecessary to consider the interaction between solid particles and the gas phase. many examples are documented in the relevant literature related to the simulation of discharging solids from silos using the discrete element method. masson and martinez [24] simulated silo feeding and discharge using the discrete element method. in their simulation studies, the effect of the mechanical parameters of the particles on particle flow was studied. it has been shown that the friction and elasticity of the particles have a significant effect on the properties of particle flows. yang and hsiau [25] simulated silo feeding and discharge. in their research, different types of inserted elements were used and tested to improve the quality of the outflow of solid material from a silo. goda and ebert [26] presented a simulation study that investigated the effect of particles on a wall using the discrete element method. gonzalez-montellano et al. [27] examined a laboratorysized silo experimentally and by simulation to identify the coefficient of friction of the particles. zeng et al. [28] examined the fluctuation in the velocity of the particles being discharged from a silo. they showed that the velocity of particles fluctuates above a critical value of the coefficient of friction. few reports in the literature are related to experimental and simulation studies on rotary valves used to discharge or feed solids. a rotary valve connected to a silo was experimentally studied by al-din and gunn [29]. the authors investigated the dependence of particulate mass flows delivered by the rotary valve on the rotational speed of the rotor and a linear relationship was found between the rotational speed and mass flow only within a certain range of rotational speed. kirkwood et al. [30] used a rotary valve to discharge solids from a silo and examined the mixing and segregation of solids inside the silo by analyzing the residence times. it was found that at low rotational speeds the particles segregated inside the silo and dead spaces developed in which the particles moved down significantly more slowly. however, at higher rotational speeds the entire particle bed of the silo moved evenly downwards, thereby ensuring that the solid layers that were fed into the silo did not mix. the application of rotary valves occurs in all industrial areas where solids are stored in silos. the controlled discharge of the content of silos is important from both technological and control aspects. a deeper understanding of operational characteristics can significantly contribute to their geometric and operational design parameters. the simulation method used in our simulation study is the discrete element method, which provides a detailed insight into the flow of the solid phase inside a rotary valve. the purpose of the simulations is to determine how the geometric and operational design parameters of the rotary valve influence the mass outflow rate of solid material through the rotary valve. the following chapters of this paper describe the discrete element method used in the modeling and simulation of particle flow, the triangular geometric representation technique used in the analysis of particle-wall collisions, the main features of the gpu hardware and parallel programming used in calculations, and the simulation results of the investigation of the effect of geometric and operational parameters of rotary valves on the mass outflow rate of solid particles. 2. discrete element method the discrete element method has become a popular method in the modeling and simulation of particulate flows. it is capable of calculating the motion of individual particles. the interactions between the particles and the boundary of the system are the collisions between particles and the particle-wall collisions which result in contact forces. the total contact force that acts on a single particle is the sum of the contact forces with regard to the forces that proceed from all the neighboring contacts. the individual particles exhibit two types of motion: translational and rotational. translational motion is 47(2) pp. 31–42 (2019) 34 füvesi and ulbert caused by the contact forces and gravity. rotational motion is generated only by the contact forces. in the case of when the effect of the gas phase is negligible, the threedimensional translational and rotational motion of particles is expressed by newton’s three laws of motion as follows: miai = j=qi∑ j=1 (fcn,ij + fct,ij) +mig, (1) iω̇i = j=qi∑ j=1 (tij +mij) , (2) where qi denotes the number of particles simultaneously in contact with particle i. mi, ai, and ω̇i are the mass, translational acceleration, and angular acceleration of particle i, respectively. fcn,ij and fct,ij stand for the normal and tangential components of the contact force between particles i and j, tij is the torque at the point of contact between particles i and j due to the tangential contact force, mij denotes the rolling resistance acting on particle i with regard to particle j, i represents the moment of inertia of particle i, g stands for the gravitational force vector, and ri is a vector from the center of particle i to the point of contact. the torque tij is calculated using the tangential contact force by the vector cross product tij = ri × fct,ij . (3) the rolling resistance mij is expressed by the following equation (wensrich and katterfeld [31]): mij = −µr rirj ri + rj |fcn,ij | (ωiri − ωjrj) , (4) where µris the rolling resistance coefficient and ri and rj denote the radii of particles i and j, respectively. when the particle collides with a wall, eq. 4 is simplified as mij = −µrri |fcn,ij | (ωiri) . (5) after the contact forces and torque have been calculated, the translational and angular accelerations can be expressed from eqs. 1 and 2 and the translational and angular velocities as well as position of particles can be calculated by numerical integration. the calculation of contact forces can be divided into two groups, namely the calculation of normal and tangential contact forces. in our simulation, the contact forces were calculated in accordance with the soft-sphere contact model developed by cundall and strack [14]. in this model, the contact forces are calculated on the bases of simple mechanical models such as spring, dashpot and friction elements (fig. 2 ). these mechanical elements influence particle motion through the parameters of the spring constant k, damping coefficient η and coefficient of friction µ. the sum of the normal forces is yielded by the normal forces generated by the spring and dashpot element: fcn,ij = (−knδn,ij − ηnvr,ij · nij)nij . (6) figure 2: soft-sphere contact model: (a) normal direction, (b) tangential direction. similarly, in the tangential direction, the sum of tangential forces acting on particle i is fct,ij = −ktδt,ij − ηtvrs,ij , (7) where vector nij denotes a unit vector from the center of particle i to the center of particle j, vr,ij represents the relative translational velocity of the colliding particles, δn,ijstands for the normal particle displacement, δt,ij is the tangential particle displacement vector and vrs,ij denotes the relative slip velocity of the particles. 2.1 calculation of the normal and tangential displacement of particles during elastic collisions between particles, at first particles are deformed and compressed, then expand and start to move in the opposite direction. this mechanism is modeled in the soft-sphere contact model by assuming the shape of particles is unchangeable. when two particles collide, they overlap with each other and the distance between their centers becomes smaller than the sum of their radii. based on this overlapping, a normal displacement δn,ij , as shown in fig. 3, can be defined as δn,ij = (di + dj)/2− |pi − pj | , (8) where di and pi in addition to dj and pj are the diameters and position vectors of particles i and j, respectively. the calculation of contact forces in the tangential direction is also based on a displacement defined in the tangential direction. as the particles first make contact, the points of impact a and b are the same points of the space (fig. 3). the location of two points is continuously changing due to the translational and rotational motion of particles and a distance (c) between the two points evolves which is equal to the absolute value of the tangential displacement vector δt,ij . the direction of δt,ij is perpendicular to the unit vector nij and extends from the actual point of contact. as the collision proceeds, the absolute value and direction of the displacement vector hungarian journal of industry and chemistry gpu-accelerated simulation of a rotary valve 35 figure 3: illustration of normal and tangential particle displacement. change according to the instantaneous relative slip velocity at the point of contact. moreover, the directions of the unit vector nij and tangential displacement vector δt,ij also change in accordance with the translational movement of particles during the collision (fig. 4). for this reason, the value of the tangential displacement vector is corrected by two steps. at first, the original value of the tangential displacement vector is transformed into the new position of particles defined by the unit vector nij . in the second step, the transformed tangential displacement vector is corrected by the time integration of the relative slip velocity. 2.2 calculation of the slip velocity the tangential component of the relative translational velocity vrt,ij can be determined as vrt,ij = vr,ij − (vr,ij · nij)nij , (9) where vr,ij = vp,i − vp,j is the relative translational velocity. the circumferential velocity vc at the point of contact is calculated by the angular velocity ω of the particles. for particle i, it is given as vc,i = (|ri|ωi)× nij . (10) by using the circumferential velocities, the relative slip velocity can be determined from vrs,ij = (vc,i − vc,j) + vrt,ij . (11) 2.3 calculation of the slide of particles when two particles come into contact, the normal force fcn,ij presses them together. the sliding motion of surfaces introduces a tangential force of friction that acts on the surface in the direction which opposes the motion. in our simulations, the coulomb’s law of friction is applied to calculate the slide of particles. the magnitude of the tangential contact force vector is verified against the value of µ |fcn,ji|, where µ represents the coefficient of friction between particles i and j. if the absolute value of figure 4: change in particle orientation during the collision. fct,ij exceeds that of µ |fcn,ji|, the particles slide and the value of the tangential contact force is changed in accordance with fct,ij = µ |fcn,ij | tij , (12) where tij = fct,ij/|fct,ij | defines a unit vector. when the particles slide, the tangential contact force fct,ij is considered to be exerted only by the spring. therefore, a new value of tangential displacement vector δt,ij , which is identical to the new value of the tangential contact force, must be calculated: δt,ij = µ |fcn,ij | k δij |δij | . (13) 2.4 calculation of the damping coefficient the damping coefficient η of a dashpot can be related to the coefficient of restitution e according to η = −2 √ mk ln e√ π2 + (ln e) 2 (14) developed by analytically solving the equation that describes a damped oscillatory system containing a mass, spring and dashpot (tsuji et al. [11]). 2.5 treatment of particle-wall collisions particle-wall contacts can be deduced from particleparticle contacts. on the external side of the wall the particle comes into contact with, a mirror particle is placed with an angular velocity of zero (fig. 5). the unit vector nij , from the center of particle i to the center of mirror particle j, is always perpendicular to the wall plane. in the case of a motionless wall, the translational velocity of a mirror particle is zero. consequently, the relative velocity between the contacting and mirror particles is the same as the velocity of the contacting particle. when the particle comes into contact with a moving wall, the translational velocity of the mirror particle is identical to the velocity of the point of impact. under these conditions, the contact forces for particle i can be calculated in a similar way to in the case of particle-particle contacts. 47(2) pp. 31–42 (2019) 36 füvesi and ulbert figure 5: the placement of a mirror particle during a particle-wall collision. 3. conditions of simulation simulation of the three-dimensional motion of particles was conducted in a silo equipped with a rotary valve as shown in fig. 1. the dimensions of the silo and rotary valve are given in table 1. the number of spherical particles of uniform size used in the simulation study was 245, 000. the particle properties used in the simulation are summarized in table 2. the initial particle bed completely filled the silo above the rotary valve as shown in fig. 1. in the simulation study, the effect of the geometric design and operational parameters of the rotary valve on the mass outflow rate was examined. in total 48 simulation runs were accomplished. the diameter of the rotary valve varied between 0.06 and 0.12 m. the rotational speed of the rotor was adjusted between 0.5 and 5 s−1. the parameters of the simulation runs are summarized in table 3. the specifications of the computer and gpu used in the simulation study are shown in table 4. 4. geometric representation of the silo and rotary valve during the discharge of the silo through the rotary valve, particles come into contact with each other and the walls. the walls of the silo are stationary, on the other hand, in the case of the rotary valve, the walls of the body are stationary and the walls of the rotating rotor move. the detection and treatment of particle-wall collisions require the calculation of the distance between the particle and wall which is based on the normal vector of the table 1: geometric and operational parameters. height of silo, m 0.49 diameter of silo, m 0.2 half-angle of cone 45◦ height of rotary valve, m 0.14 diameter of rotary valve, m 0.06, 0.072, 0.084, 0.096, 0.108, 0.12 rotational speed, s−1 0.5, 1, 1.5, 2, 2.5, 3, 4, 5 table 2: particle properties used in the simulations. diameter, m 0.004 density, kg/m3 1190 spring constant, normal direction, n/m 800 spring constant, tangential direction, n/m 800 coefficient of restitution, e 0.6 friction coefficient, µ 0.43 rolling resistance coefficient, µr 10−4 table 3: parameters of simulation runs. number of particles 245, 000 simulation time, s 4 timestep, s 5× 10−5 interval for data saving, s 0.002 number of standing wall elements 500− 600 number of moving wall elements 24 wall surface. in the case of flat walls, the normal vector can be determined easily. however, in the case of curved surfaces, the calculation of the normal vector of the surface and contact point is much more computationally complex. the number of calculations can also be increased significantly when collisions with moving walls are taken into consideration. therefore, in our simulation technique, the equipment walls are approached in accordance with a set of flat triangles which allows wall collisions to be detected and contact forces to be easily calculated. this has two advantages over the conventional treatment of particle-wall collisions using the mathematical definition of curved surfaces. on the one hand, any curvature wall can be easily defined by a set of flat triangles using methods developed in the field of computer graphics. the surfaces and geometries created using computer graphics software can be saved and imported into the simulation program along with the other simulation parameters. as a result, the geometry of the equipment can be altered in the program without changing the programming code. in the case of the application of moving walls, the description of the movement of the triangles is also produced by computer graphics software and imported into the simulation program. another advantage is that the gpu can work more table 4: details of the computer hardware. cpu intel core i5-3570 3.4ghz memory size 16gb motherboard gigabyte ga-z77-d3h gpu nvidia geforce gtx 1080 ti number of cuda cores 3, 584 gpu memory size 11gb gpu gigaflops (single precision) 10, 609 hungarian journal of industry and chemistry gpu-accelerated simulation of a rotary valve 37 figure 6: the flat triangular approximation of the silo geometry. efficiently if the threads need to conduct similar calculations simultaneously. thus, it is advantageous for the gpu to process the treatment of many triangles of the same structure as opposed to just a few but different structures of equations for the surface. a further advantage of the flat triangular approximation is that its accuracy can be increased where required by using more triangles, e.g. the approximation of the silo geometry by a set of flat triangles is shown in fig. 6. in the treatment of particle-wall collisions, it is necessary to determine the position of mirror particles. when using the flat triangular approximation, firstly it is necessary to check whether the given particle can collide with the given triangle. if the particle collides, the point of the triangle closest to the particle is determined using the method developed by mark w. jones [32]. then the position of the particle is mirrored on the opposite side of the triangle in the direction given by the normal vector. 5. application of the gpu to apply the discrete element method effectively, the computer hardware used for the calculations has to be capable of parallel computing the motion of individual particles. in our simulation study, gpu cores and parallel programming were used to calculate the particles in parallel. a gpu core was assigned to each particle. a core can only write data in the memory associated with the particle but can read all the data from the memory associated with the other particles to analyze collisions between particles. as a consequence, all the data that results from the calculation of a collision between two particles is stored in two memory places. this solution had to be applied to avoid problems related to the writing of duplicates. additionally, because of the way data is read, associated problems may arise when new data is calculated from the data in both the previous and current iterations. to overcome these problems, two data units were used, one always contained the data of the previous iteration and the other stored that of the current iteration. the number of particles simulated may exceed the number of cores in the gpu, therefore, particles are calculated in consecutive batches. after calculating a batch of particles assigned to the gpu cores, a new group of particles is added to the gpu cores and they are calculated. this process is repeated until each particle has been calculated, then the next iteration is executed. it is also important to note that during the parallel execution all the calculation data is stored in the memory of the gpu and that the cpu only gives instructions to the gpu about which calculations to perform. therefore, at the beginning of the simulation, all the initial data concerning particles and walls are copied into the memory of the gpu and the cpu is used to instruct the gpu to perform the calculations. since the copying of data between the memories of the gpu and computer (host) is slow, this would increase the run time of the program, so it is important that the copying of data between the two memories is limited. for this reason, two computational cycles were defined. during the internal cycle, only the gpu is working, it executes a defined number of iterations. at the end of the internal cycle, control is passed on to the external cycle and the data is copied to the host memory and saved as a file. it is also important to note that executing the code on the gpu is effective if all the gpu cores conduct the same calculation. attention should be paid to the use of branch instructions as they can significantly impair performance. 6. simulation results and discussion in the aforementioned simulations, the startup process of silo discharge and the effects of the diameter of the rotary valve and rotational speed of the rotor on the mass outflow rate of particles leaving the rotary valve were investigated. 6.1 the startup process of silo discharge the startup process of silo discharge through the rotary valve is shown in a cross-sectional view in figs. 7 and 8 at different rotational speeds. fig. 7 shows the startup process at a rotational speed of 0.5 s−1. the positions of the particles were visualized six times per revolution. at this rotational speed, the particles have sufficient time to fill the entire volume of the cell. particles entering the cell are forced to pass by the blades of the rotor. when a cell reaches the outlet, all the particles fall out of the cell. fig. 8 shows the startup process of discharge at a rotational speed of 5 s−1. in this case, the blades of the rotor rotate so fast that the particles do not have sufficient time to fill the entire volume of the cell. approximately only one third of the volume of the cell is filled with particles. the 47(2) pp. 31–42 (2019) 38 füvesi and ulbert figure 7: the startup process of silo discharge at a rotational speed of 0.5 s−1. blades push the particles so strongly that they collide with the wall of the outlet channel and accumulate. as a result, not all the particles are capable of falling out of the cell and some remain in the rotary valve. 6.2 analysis of the mass outflow rate through the rotary valve during silo discharge through a rotary valve, the mass outflow rate exhibits a pulsating, periodic change over time as a consequence of the rotating cellular structure of the rotary valve. following a finite period of time after the rotary valve starts to operate, a periodic change in the outflow of particles develops of constant amplitude and frequency. depending on the geometric and operational parameters, the amplitude and frequency of this periodic change may vary. to compare the effect of the various geometric and operational parameters on the mass outflow rate, it is necessary to calculate the time-averaged pulsating mass outflow rate. therefore, the simulation time was sufficient to obtain at least ten cycles of change of constant amplitude and frequency. the time-averaged mass outflow rate was calculated from the simulation data saved after certain intervals of time. first, the number of particles discharged from the silo during the time interval between data saves was determined. next, the resulting data was multiplied by the volume and density of the particles and divided by the time interval between data saves to obtain the periodic time variation of the mass outflow rate. finally, the timeaveraged mass outflow rate was obtained by averaging the values throughout the simulation. for example, figs. 9 and 10 show the dynamic change in the mass outflow rate of particles at rotational speeds of 0.5 and 5 s−1 when the diameter of the rotary valve was 0.12 m. when the rotational speed was 5 s−1, only the initial part of the entire simulation observed a highfrequency periodic change in the mass outflow rate more clearly. by comparing the two figures, it can be seen that figure 8: the startup process of silo discharge at a rotational speed of 5 s−1. hungarian journal of industry and chemistry gpu-accelerated simulation of a rotary valve 39 figure 9: the dynamic change in the mass outflow rate at a rotational speed of 0.5 s−1. as the rotational speed increases, a periodic change of higher frequency and smaller amplitude was observed. fig. 11 shows the dependence of the time-averaged mass outflow rate on the rotational speed of the rotor when the diameter of the rotary valve was varied. the curves represent different diameters of the rotary valve. it can be observed that as the diameter increases, the average mass outflow rate rises. in the first section of the curves, the mass outflow rate increases linearly as the rotational speed of the rotor rises. this section is significant in terms of its control. linear industrial controllers are well established and suitable for the application of control theory for linear systems. the linear control theory applies to systems whose output is proportional to their input. these types of systems are governed by simple linear differential equations, while nonlinear systems are often governed by nonlinear differential equations and mathematical techniques developed to handle them are much more complex and far less general. due to the linear dependence of these sections, the mass outflow rate can be easily controlled by common industrial control systems figure 10: the dynamic change in the mass outflow rate at a rotational speed of 5 s−1. figure 11: the dependence of the rotational speed on the time-averaged mass outflow rate using different rotary valve diameters. based on linear control algorithms. in fig. 11, it can also be observed that the length of linear sections depends on the diameter of the rotary valve. the linear section in the case of the smallest diameter of 0.06 m occurs between rotational speeds of 0.5 − 3 s−1, while in the case of the largest diameter of 0.12 m it occurs between rotational speeds of 0.5− 1.5 s−1. since a desired mass outflow rate can be more easily controlled in a linear section with a smaller gradient, it is advisable to keep the diameter as small as possible. following the initial linear section, the mass outflow rate reaches a maximum value, the larger the diameter, the greater the maximum value of the mass outflow rate. if a mass outflow rate in excess of the maximum value is required, this can only be achieved by increasing the diameter and not by raising the rotational speed. as the diameter of the rotary valve decreases, the rotational speed at which the maximum is observed increases, as shown in fig. 11. after the maximum is achieved, a decreasing section follows where the time-averaged mass outflow rate begins to decrease. since the location of the maximum shifts towards higher rotational speeds as the diameter of the rotary valve increases, the decreasing section also shifts. between the rotational speeds of 4 and 5 s−1, the mass outflow rates for each diameter converge. the optimal value of the diameter of the rotary valve can be determined based on the length of the linear section. a given mass outflow rate can only be achieved with a sufficiently large diameter. however, the use of a larger diameter is not recommended as the gradient of the linear range increases as the diameter increases and control of the system becomes less precise. by considering the range beyond the maximum, it is clearly unnecessary to operate a rotary valve of a given diameter at higher rota47(2) pp. 31–42 (2019) 40 füvesi and ulbert figure 12: the flow patterns of particulate flows at different rotational speeds of the rotor. tional speeds to increase the level of performance, since the maximum mass outflow rate cannot be exceeded, in fact it may even decrease. 6.3 flow patterns of the particles at different rotational speeds of the rotor as was shown in figs. 9 and 10, the mass outflow rate exhibits a constant periodic change after the startup process of discharge. in order to understand the phenomena that occur inside the rotary valve with a greater degree of accuracy, the positions of the particles were visualized to obtain the instantaneous particle flow patterns visible at various rotational speeds of the rotor (fig. 12). in all cases, a cross-sectional view of the rotary valve is presented when the rotor blades were in the same position and the operation was already within the range of the constant periodic change. fig. 12 shows the gradual decrease in the charge of cells as the rotational speed increases. at a rotational speed of 0.5 s−1, the cells still have sufficient time to fully recharge. between rotational speeds of 1.0 to 1.5 s−1, an empty volume fraction remains in the cells after being charged. at these rotational speeds, this empty volume fraction is still small and the accelerated feed and discharge periods can compensate for the decreasing mass outflow rate. at a rotational speed of 2 s−1, the time-averaged mass outflow rate reaches its maximum. when the rotational speed was 2.5 s−1, the resulting empty volume fraction of the cells becomes even bigger but the particles rest on the lower blade. at a rotational speed of 3 s−1 a significant change can be observed in the operation. at this rotational speed, the particles seem to float between the blades of the cell, i.e. the speed of the blades is equal to the rate at which the particles drop. at a rotational speed of 4 s−1, the particles are already pushed forward by the top blades. by further increasing the rotational speed (5 s−1), the time the cells have to be recharged is so small that the mass outflow rate begins to decrease even more. 7. conclusions generally speaking, it can be said that by using the discrete element method in particulate flow simulations, it is possible to observe particle flows in detail and to better understand related phenomena. the simulation study presented in this paper focused on the simulation of the discharge of solid particles from a silo controlled by a rotary valve using the discrete element method. in the simulations, the mass outflow rate of particles was analyzed along with different geometric and operational parameters of the rotary valve. by applying the discrete element method, it was possible to dynamically simulate the movement of individual solid particles through the rotary valve and examine the mass outflow rate of particles. by visualizing the individual particles at their positions, the effect of the interaction between the particles and the blades of the rotary valve on the flow patterns of particles at different rotational speeds was observed. the simulations showed that the mass outflow rate of the particles leaving the silo changes periodically due to the rotating cell structure of the rotary valve. the dependence of the time-averaged mass outflow rate on the rotational speed of the rotary valve was found to be nonlinear within the upper range of examined rotational speeds. however, for each diameter of the rotary valve, a range of rotational speeds in which the mass outflow rate changes hungarian journal of industry and chemistry gpu-accelerated simulation of a rotary valve 41 linearly with the rotational speed was observed. within these ranges of linear speed, the rotary valve can be used more advantageously to perform different control tasks. following the linear range, for each diameter of the rotary valve, the mass outflow rate reaches a maximum then decreases. the simulations were performed using gpu hardware. the application of parallel programming is an essential part of the simulations and can significantly decrease the calculation time of simulations from a few days to just a few hours. by considering the treatment of particle-wall contacts, a novel flat triangular-based geometric representation technique was proposed which also made it possible to calculate the particle-wall contacts in parallel by gpu. symbols p position vector of a particle, m v velocity vector of a particle, m/s a acceleration vector of a particle, m/s2 g gravitational acceleration vector, m/s2 f force vector, n t torque vector, nm i moment of inertia of a particle, kgm2 d diameter of a particle, m r radius of a particle, m e coefficient of restitution, dimensionless k spring constant, n/m m mass of a particle, kg n unit vector, dimensionless t unit vector, dimensionless greek letters δ normal displacement, m δ tangential displacement vector, m η damping coefficient, kg/s µ coefficient of friction, dimensionless µr coefficient of rolling resistance, dimensionless ρ density of a particle, kg/m3 ω angular velocity vector, s−1 subscripts c circumferential cn normal contact ct tangential contact n normal direction, normal component r relative rt relative tangential rs relative slip t tangential direction, tangential component acknowledgement this research was supported by the state of hungary within the framework of the project 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https://doi.org/10.1016/0032-5910(83)80005-9 https://doi.org/10.1016/j.powtec.2011.10.057 https://doi.org/10.1016/j.powtec.2011.10.057 http://cs.swan.ac.uk/~csmark/publications/1995_3d_distance.html http://cs.swan.ac.uk/~csmark/publications/1995_3d_distance.html introduction discrete element method calculation of the normal and tangential displacement of particles calculation of the slip velocity calculation of the slide of particles calculation of the damping coefficient treatment of particle-wall collisions conditions of simulation geometric representation of the silo and rotary valve application of the gpu simulation results and discussion the startup process of silo discharge analysis of the mass outflow rate through the rotary valve flow patterns of the particles at different rotational speeds of the rotor conclusions hungarian journal of industrial chemistry veszprem vol. 30. pp. 261-269 (2002) a study of drying process a.k.haghi (guilan university, p.o.box 3756, rasht, iran) received: august 21, 2002 math~matic~ relations are review~d and ~eveloped which may be used to describe the drying behaviour of carpet in a c?mbmed iillcro':a~e and convective envuonment. the effect of important parameters during the drying process are dtscussed and their mfluence are examined in detail using the model. keywords: convective drying, drying behaviour, heat and mass transfer, mathematical model, microwave drying introduction the cost of drying carpets, which is done toward the end of manufacturing process, is quite high. a very common method of removing water from carpet is convective drying. hot air is used as the heat transfer medium and is exhausted to remove vaporized water. considerable thermal energy, about 30 % of the total e~e:gy used, is required to heat make-up air as the hot atr 1s exhausted. thus, reducing the amount of exhaust is clearly a way to conserve energy, but there is little in the literature that can be used as guidelines for optimizing dryer exhaust _flow. in this case the effect of humidity on the drying rates of carpet tile should studied. when the water is deep within the carpet, combined microwave and convective drying, which have faster heat and mass transfer, may be a better choice. to fully understand the heat and mass transfer phenomenon occurring within the carpet during combined microwave and convective drying, it is required to analyse the moisture, temperature, and pressure distributions ?enerated throughout the process. the water remaining m the carpet is 50-60 % of the weight of carpet after mechanical removal is in its thermodynamically favourable position, largely because the low viscosity of the water and connectivity of the pores insure rapid eq~ilib:ation. it is approximated the pores as essentially cylmdncal, with their axis vertical to the carpet backing. the amount of porosity, i.e., the volume fraction of voids within the carpet, determines the capacity of a carpet to hold water; the greater the porosity, the more water can hold the carpet. the carpet is able to absorb 6 times its weight in water. when the water content is reduced to roughly 50-60 % by mechanical extractiont contact information: e-mail: haghi@ kadous.gu.ac.ir free water is probably situated in pores with an effective capill.ary_ diameter of up to 200 j.un. the occupied pores are dtstrtbuted throughout the carpet pile thickness and largely within the yarns. the flow of air through carpet dryers is very complex, and neither simple concurrent or countercurrent flow of air and material takes place. usually there are a set of well mixed zones, throughout which the drying conditions are effectively uniform. the ~om~onest strategy for regulating a dryer's behaviour is feedback control, in which the controlled variables (such as the moisture content of the material) is compared with the desired set point. the difference signal, suitably processed by the controller, is then used to modulate the input parameter being used as the control variable. an ideal three-term controller incorporates proportional, integral and derivative action. the proportional term gives a rapid response to an error signal, ?ut the ~ontrolled variable is permanently offset from its destred value. the integral function compensates for the steady-state error. derivative action is rarely used, except with well defined signals, because noise in the signal can confuse the controller. resulting in a hunting action about some mean value. the difficulties in obtaining online measures of a material's moisture content has led to the use of environmental control of the humidity or temperature within the drying chamber. this strategy, however, can lead to inadequate control, as the wet-bulb depression is the driving force for drying. use of the dry-bulb temperature or relative humidity of the bulk air as the control variable will only be satisfactory as long as the surface conditions of the material remain constant. the difference in temperature between the surface and the bulk air will give a measure of the surface moisture content. 262 provided the material is hygroscopic and all unbound moisture has been driven off. background in general, drying means to make free or relatively free from a liquid. we define it more narrowly in this paper as the vaporization and removal of water from a material. the typical drying curve begins with a warm­ up period, where the material is heated and the drying rate is usually low. the drying rate can be negative in the warm~up period if the gas stream is humid enough. as the material heats up, the rate of drying increases to peak rate that is maintained for a period of time known as the constant rate period. eventually, the moisture content of the material drops to a level, known as the critical moisture content, where the high rate of evaporation cannot be maintained. this is the beginning of the falling rate period. during the falling rate period, the moisture flow to the surface is insufficient to · maintain saturation at the surface. this period can be divided into the first and second falling rate periods. the first falling rate period is a transition between the constant rate period and the second falling rate period. in the constant rate period, external variables such as gas stream humidity, temperature, and flow rate dominate. in the second falling rate period, internal factors such as moisture and energy transport in the carpet dominate. although much of the water is removed in the constant rate period of drying, the time required to reduce the moisture in the product to desired value can depend on the falling rate period. if the target moisture content is significantly lower than critical moisture content, the drying rates in the falling rate period become important. it has been recognized that microwave could perform a useful function in carpet drying in the leveling out of moisture profiles across a wet sample. this is not surprising because water is more reactive than any other material to dielectric heating so that water removal is accelerated. many investigators have attempted to explain the effect of humidity drying rates and the existence of inversion temperatures [1-4]. the explanations are usually based on changes that occur in convective heat transfer. radiative heat transfer, and mass transfer as the humidity and temperature of the gas stream change. we will briefly discuss these explanations. at a given gas stream temperature, convective heat transfer rate can change as the humidity in the gas stream is varied. because product temperature and fluid properties vary v.ith humidity. these effects can be explained using the following relationship for the convective heat transfer rate: where !1_ = convective heat transfer per unit surface a area a, h =heat transfer coefficient, t= =free stream temperature of the drying medium, i; = surface temperature of material being dried. . . · since product temperature is dependent on hum1d1ty, clearly llt is also dependent. further, the heat transfer coefficient h is a function of both product temperature and fluid properties. thus, the convective heat transfer rate changes with humidity, as does the drying rate of a material however, drying in air will always have an advantage over drying in steam because llt is larger for drying in air; this is a consequence of t5 being very nearly the wet bulb temperature. the wet bulb temperature is lowest for dry air, increases ~ith increasing humidity, and reaches the saturation temperature of water for a pure steam environment. thus, lltair will be larger than lltsream , but lltarr!iltsream decreases with increasing too. further, the heat transfer coefficient increases with humidity. apparently, the net effect of the changes in h and llt is that the convective heat transfer rate increases faster for steam than for air with increasing temperature. king and cassie conducted an experimental study on the rate of absorption of water vapor by wool fibers [5]. they observed that, if a textile is immersed in a humid atmosphere, the time required for the fibers to come to equilibrium with this atmosphere is negligible compared with the time required for the dissipation of heat generated or absorbed when the regain changes. mcmahon and watt investigated the effects of heat of sorption in the wool-water sorption system [6]. they observed that the equilibrium value of the water content was directly determined by the humidity but that the rate of absorption and desorption decreased as the heat­ transfer efficiency decreased. heat transfer was influenced by the mass of the sample, the packing density of the fiber assembly, and the geometry of the constituent fibers. crank pointed out that the water­ vapor-uptake rate of wool is reduced by a rise in temperature that is due to the heat of sorption (7]. the dynamic-water-vapor-sorption behaviour of fabrics in the transient state will therefore not be the same as that of single fibers owing to the heat of sorption and the process to dissipate the heat released or absorbed. henry was who started the first theoretical investigation of this phenomenon (8-9]. he proposed a system of differential equations to describe the coupled heat and moisture diffusion into bales of cotton. two of the equations involve the conservation of mass and energy, and the third relates fiber moisture content with the moisture in the adjacent air. since these equations are non-linear. henry made a number of simplifying assumptions to derive an analytical solution. in order to model the two-stage sorption process of wool fibers, david and nordon [ 1 0] proposed three empirical expressions for a description of the dynamic relationship between fiber moisture content and the surrounding relative humidity. by incorporating several features omitted by henry into the three equations, david and nordan were able to solve the model numerically. since their sorption mechanisms (i.e. sorption kinetics) of fibers were neglected, the constants in their sorption-rate equations had to be determined by comparing theoretical predictions with experimental results. farnworth reported a numerical model describing the combined heat and water-vapour transport through fibers [11]. the assumptions in the model did not allow for the complexity of the moisture-sorption isotherm and the sorption kinetics of fibers. wehner et al [12] presented two mechanical models to simulate the interaction between moisture sorption by fibers and moisture flux through the void spaces of a fabric. in the first model, diffusion within the fiber was considered to be so rapid that the fiber moisture content was always in equilibrium with the adjacent air. in the second model, the sorption kinetics of the fiber were assumed to follow fickian diffusion. in these models, the effect of heat of sorption and the complicated sorption behaviour of the fibers were neglected. li and holcombe developed a two -stage model [13], which takes into account water-vapour-sorption kinetics of wool fibers and can be used to describe the coupled heat and moisture transfer in wool fabrics. the predictions from the model showed good agreement with experimental observations obtained from a sorption-cell experiment. more recently, li and luo ( 14] further improved the method of mathematical simulation of the coupled diffusion of the moisture and heat in wool fabric by using a direct numerical solution of the moisture-diffusion equation in the fibers with two sets of variable diffusion coefficients. these research publications were focused on fabrics made from one type of fiber. the features and differences in the physical mechanisms of coupled moisture and heat diffusion into fabrics made from different fibers have not been systematically investigated. the mathematical model describing the coupled heat and moisture diffusion in textiles was first proposed by henry [8-9] and then further developed by david and nordan [10] and li and holcombe [13]. the conservation of heat and moisture can be expressed by the following equations: c aca +(1-c)act = dae d 2 ca (1) at at 7:© ()x2 c jt -a act = k©azt v at at ()x 2 (2) in the equations, both cv and 'a are functions of the concentration of moisture absorbed by the fibers. most textile fibers are of very small diameter and have a very large surface/volume ratio. the assumption in the second equation of instantaneous thermal equilibrium between the fibers and the inter-fiber space does not therefore lead to appreciable error. the two equations in the model are not linear and contain the three unknowns, c p , t and ca . a third equation is needed to solve the equations. 263 henry [8-9] derived a third equation to obtain an analytical solution by assuming that c.r is linearly dependent on t and cs and that fibers reach moisture equilibrium instantaneously with the adjacent air. downes and mackay [15] found experimentally that the sorption of water vapour by wool is a two-stage process, the first stage obeys fick' s law of diffusion with a concentration-dependent diffusion coefficient. the second stage, which involves structural changes within fibers, is much slower than the first. to simulate the two stage-sorption process, david and nordan [10] proposed an exponential function to describe the rate of change of fiber water content, which needed to be adjusted according to the measured fabric moisture content. li and holcombe [ 13] developed a two stq,ge sorption-rate equation to describe the moisture sorption of wool. the first stage is represented by a fickian diffusion with a constant coefficient. the diffusion equation was solved by using crank's truncated solution [7]. the second stage is described by an exponential relationship, which also needs to be adjusted according to the experimental measurements. the relative contributions of the two stages to the total moisture sorption are function of the sorption time and the initial regain of the fibers. li and luo [14] improved the sorption rate equation by assuming that the moisture sorption of wool fiber can generally be described by a uniform-diffusion equation for both stages of sorption: act _ 1 a { ( ) act 1 --;:----;rdt x,t r ul r (jt ar j (3) where d 1 (x,t) are the diffusion coefficients that have different values at different stages of mwsture sorption. in a wool fiber, d 1 (x,t) is a function of water content of the fibers, which is dependent on the time of sorption and the location of the fiber. in the first stage, the diffusion coefficient is concentration-dependent and is assumed to be quadrau~ function of water content when the sorption is less than 540 seconds , as given in eq.(4a). in the second stage, in which the moisture sorption is much slower than 1n the first, the diffusion coefficient of moisture in a wool fiber is attenuated along with the time of sorption when t ~ 540 s. as shown in eq.( 4b ). d )_w' 1/ = 1014 ji 1 )} {1.04 + 68.204wc (t )-} t c -l342.5924wc (t y • (4a) t ~540s dt {w, v )}= 1.616405. · [ 1-ex{e~{ ~;~:,~ ·)} ]w-", (4b) t 2:540 s the second formula for d1 in eq.(4b) shows that the rate of moisture diffusion into a wool fiber (when 264 t ~ 540 s) attenuates in the form of double-exponential function, which may indicate that the attenuating feature of the moisture sorption of wool is due to its microstructural changes and the decreasing number of available polar groups. now, we assume that the sorption process for all the fibers can be described by a uniform diffusion equation from eq.(3), with diffusion-coefficient functions to describe the moisture-sorption kinetics. through a large number of computational experiments in comparison with the measured water-content changes and temperature changes of various fibers, we try to identify whether the moisture-sorption process needs to be described by a two-stage process or a single fickian­ diffusion process. the diffusion-coefficient functions identified for carpets made from wool, cotton, porous acrylic fiber, and polypropylene fiber which is reported by li and planete [16] are listed in the appendix. to generate a solution to the above-mentioned equations, we need to specify an initial condition and boundary conditions at the fiber surfaces of the humidity, moisture content, and temperature. initially, a · fiber is equilibrated to a given atmosphere of temperature (tao) and humidity ( cao and h(uj ), the temperature and moisture content being uniform throughout the fabric at known values: ta (x,o) =tao ca (x,o )= cao c1 {x,r,o)= j(ha0 ,1'rj (5) (6) (7) the fiber then undergoes a step change to a different atmosphere. its boundaries are exposed to an air stream of a new moisture concentration cab and temperature tab. considering the convective nature of the boundary air layers, the boundary conditions can be described by the following equations: (8) d -~tl~ i ) ae~.t=l --lzc\ca -cab (9) k©e~_... ~h,(t-t,.) (10) k©e~ =-hjt-tab) ~x=l (11) these conditions show that the thermal and moisture fluxes across the boundaries are proportional to the differences in the temperature and moisture concentration between the surrounding medium and the fabric surface respectively. eqs.(/) and (2} are solved by a finite-difference method by using the crank-nicolson scheme, and eq.( 3} is solved by using an implicit-difference scheme. together with specification of the initial condition of eqs.(5j~(7}, the boundary conditions of eqs.(8)-(1 1 ). and the fiber properties. details of the solution method have been reported previously by li and luo [14]. before carpet is conveyed into drying oven, most of the water is typically vacuum extracted. after vacuum extraction, the moisture regain is about 50-60 % , indicating that there is still a significant amount of water inside the carpet. this water is usually removed with heat in industrial manufacturing processes. as a general rule, the water is distributed in larger pores. it seems reasonable to anticipate that many of these pores are formed within the pile yarns throughout the thickness of the carpet. the location of this water is of interest to people in the carpet industry.the carpet surface characteristics can be studied using topographical parameter measurement. formulation of the problem it was shown by ilic and turner [17] that a theory based on a continuum approach led to the following equations of motion governing the drying of a slab of material: total mass: ~ (¢sgpg +t/jswpw )+ +v.(xgpgvg +xwpwvw)=o total liquid: ~ {¢s8 pgv +t/jswpw )+ + v.(xgpgvvgv + xwpwvw )= 0 total enthalpy: (12) (13) where 41 is the internal microwave power dissipated per unit volume. in eq.( 14) the effects of viscous dissipation and compressional work have been omitted. the eqs.(12-14) are augmented with the usual thermodynamic relations and the following relations: flux expressions are given as follows: gas flux: _k_k.;:;_8 (_sw_)_p..::;._8 rv p _ p g) j..lg (t) l g g (14a) liquid flux: x v; = kkw(sw)pw. wpw w f..lw(t) (14b) · [v(p8 pc(sw,t) )pwg] vapour flux: x 8p gv v8v = x 8 p gv v8 x 8 p 8 d(r,p8 )mamv v(pqv j m2 pg (14c) air flux: x 8 p ga vga = x g p 8 vg -x 8 p 8 v8v (14d) relative humidity (kelvin effect): lfl w -----ex (s t)pgv _ { 2a(t)mv j ' p8vsct) r(sw )pwrt where pgvs (t) is the saturated vapour pressure given by the clausius-clapeyron equation. differential heat of sorption: mt =rt2 b(lnlfl) w v ar enthalpy-temperature relations: the expressions for k 8 , kw are those given by turner and ilic [18], and j..l 8 , f..lw have had functional fits according to the data by holman [19]. the diffusivity d(t,p 8 ) given by quintard and puiggali [20] and the latent heat of evaporation given by, hvap(t)= h811 -hw after some mathematical manipulations, the one­ dimensional system of three non-linear coupled partial differential equations which model the drying process in a thermal equilibrium environment are given by: 265 asw ar k sl az + kn az + asw ar a ar apg asl -at+ as2 ---;;;= dz + kn dz + k pi az + (15) + kgrl (16) (17) the capacity coefficients asl' atp ap1 and the kinetic coefficients k st , kn , k pi , k sri all depend on the independent variables: saturation sw , temperature t and total pressure p 8 • the boundary conditions are written in one dimension as: at z::::: 0 (drying surface): bsw at bp8 ksr az + ktl az + kpi oz + kgrl = _ kmmv (pgv _ p8vo l rf/jpw t t0 j (18a) [ k bsw + k at +; ke az f/jpwhvap bpx = ar saz raz j +kp ijz +k8r (18b) = q(t-t0 ) (18c} at z = l (impermeable surface): bsw at bp8 _ kst az + kn az + kpi az + kgrl0 {19a) 266 average saturation o.a .convective drying x o.s convective & microwave drying + + 0 x 200 400 600 time (minutes) boo fig. i average saturation profiles in time for drying drying rate 0.01 0.004 0.002 o.o @onvective drying ~ )( + + o.s average saturation o.a fig.2 drying rate curves corresponding to profiles plotted in fig. i (kslks )dsw + (knkr )dr + (jz dz (kpi -kp3)~ +(k8rt -k8r 3 )=0 initially: t(z,o)=~ pf((z.o)= p0 results and discussion (19c) (20a) (20b) (20c) the primary parameter monitored during the drying tests was moisture content. which is calculated as a ration of wet weight minus the final dry weight over the final dry weight the weights include the weight of the entire sample. tufts. and backing. weight loss during drying is predominately due to water evaporation. although other materials such as finish may be driven off during drying. the associated weight loss is insignificant compared to that of water. thus. the determination of moisture content is simple yet accurate. smer kg/kwh 2.5 2.0 1.5 1.0 0.5 convective drying x convective & microwave 0 )( x x 200 400 800 time (minutes) 800 fig.3 specific moisture extraction rate in time for drying liquid flux/10000 o.o (convective drying x) -1.0 x -2.0 x + ~ + -3.0 x + x + -4.0 )( + -5.0 + o.o 0.6 1.2 1-8 2.4 distance (em) fig.4 liquid flux as a function of distance for most industrial carpet tile operations, the target moisture content is set so that the weight of moisture on the tiles is approximately 5 % of the weight of the face yarns. considering the weight of the entire sample, as we did for this investigation, the target moisture content in industry is typically about 0.9 %. drying rates below this level are of little concern. fig. 1 show a comparison of convective drying with and without microwaves. whilst for convective drying there are definite constant rate and falling rate periods, when microwaves are added the form of the curves change and the use of the words constant and falling rate may no longer apply. in hot air drying the constant rate period is the period of drying before the drying front recedes below the outer boundary. during this period the convective heat transfer is used for evaporation only, resulting in a constant surface temperature and drying rate(see horizontal plateau in fig.2). fig.3 present the specific moisture extraction rate ( smer). as a function of time for both cases of drying. smer is defined as the energy required to extract a unit of water from the product. fig.3 shows the smer for the microwave case is much lower than the convective case. the liquid flows to the surface initially in a linear fashion (figa). as the material begins to dry out, there is a liquid flux up to what can confidently be explained gas rate of evaporation 0.6 ~-~~~-----, 0.4 0.2 0.0 convective drying )( convective 8: micro¥tave drying ... 0.6 h )( + + + 1-2 1.8 distance (em) 2.4 fig.5 rate of evaporation as a function of distance as the position of evaporation front and then there is no movement of liquid from that point to the surface.the rate of evaporation for both case of drying is plotted in fig.5. the uneven during of carpet in convection ovens is often a problem that lengthens drying times and causes variable moisture distribution. conclusion more than 80 % of the water in a completely wetted cut­ pile carpet is trapped between the yarns and only a small portion of the water (about 10-15 %) is stored inside yarns. in summary, we can conclude that combined microwave and convective drying can provide faster drying time. the results show that the use of combined microwave and convective drying can improve drying time and give higher drying rate. d symbols water-vapour concentration in the air filling the inter-fiber void space (kg m -3 ) water-vapour concentration in the fibers of the fabric (kg m -3 ) specific heat (jkg-1k-1 ) volumetric heat capacity of the fabric (kj m-3 oc-1) diffusivity (m2s-1 ) d a diffusion coefficient of water vapour in the air (m2s-t) d 1 diffusion coefficient of water vapor in the fibers of the fabric (m2s-1 ) g gravitational constant(ms-2 ) h intrinsic averaged enthalpy (jkg -l) hvap latent heat of evaporation (jkg -t) he convective-mass-transfer coefficient (ms-1 ) ht convective-heat-transfer coefficient m-z k-1) l:lhw differential heat of sorption (jkg -j) k intrinsic permeability (m -2) thermal conductivity (kw m-1 k-1 ) relative permeability of gas km mass transfer coefficient (ms-1 ) kw relative permeability of water l thickness of the fabric (m) m molarmass (kg mor1 ) 267 (kw pabs power absorbed in the material per unit area (wm-2) q r r s t tab t x,z a e p (j a c g v w 0 l heat transfer coefficient (wm-2k-1 ) universal gas constant (1 mol-1 k-1 ) radial co-ordinate of fiber (m) volume saturation real time from change in conditions (s) temperature of the ambient air ( °c ) temperature of the fabric ( oc) averaged velocity (ms -t) water content of the fibers in the fabric, wc=c1 1p distance (m) heat of sorption or desorption of water vapour by the fibers (kj/kg) non-dimensional temperature density of the fibers (kg m -3 ) surface tension (nm -l) effective porosity of the fabric non-dimensional time porosity (m3m-3 ) surface porosity (m 2m-2 ) internal microwave power source (wm-3 ) relative humidity dynamic viscosity of gas (kg m-1s-1 ) dynamic viscosity of water (kg m -ts-1 ) permeability of free space (hm -t) subscripts air capacity gas vapour liquid atmospheric initial 268 references 1. haghi a. k.: acta polytechnica, 2001, 41, 55-57 2. haghi a. k.: acta polytechnica, 2001, 41, 20-24 3. haghi a. k.: j. of computational and applied mechanics, 2001, 2, 195-204 4. haghi a. k.: j. of theoretical and applied mechanics, 2002, 32(2), 47-62 5. king g. and cassie a.: trans faraday soc., 1940, 36,445-453 6. mcmahon g. b. and watt i. g.: text. res. j., 1965, 35, 37-44 7. crank j .: the mathematics of diffusion, clarendon press, oxford, uk, 1975 8. henryp.: proc. roy. soc., 1939, 171a, 215-241 9. henry p.: disc. faraday soc., 1948, 3, 243-257 10. david h. g. and nordon p.: text. res. j., 1969, 39, 166-172 11. farnwortii b.: text. res. j., 1986, 56, 653-665 12. wehner j. miller b. and rebenfeld l.: text. res. j., 1988, 58, 581-592 13. li y. and holcombe b.: text. res. j., 1992, 62, 211-217 14. li y. and luo z.: text. res. 1.,1999, 69,760-768 15. downes j. g. and mackay b.: j. polym. sci., 1958, 28~ 45-67 16. li y., planete, a.m., and holcombe b. v.: text. res. j., 1995, 65, 316-324 17. ilic m. and turner i. w.: int. j. heat mass transfer, 1989, 32 (12), 2351-2362 18. turner i. w. and llic m.: int. comm. heat mass transfer, 1990, 17(1),"39-48 19. holman j. p.: heat transfer, me graw-hill book company. 1989 20. quintard m. and puiggali j. r.: j. heat and technology, 1986, 4(2), 34-45 appendix physical characteristics ( li and planete [16]) diffusion coefficient of water vapour in fiber; ( m 2s-1 ) • lst stage: d1 =(l04+68.20wc -1342.59w"~)i0-14 , (al) t <540s diffusion coefficient of water vapour in fiber ; ( m 2s-1 ) -2nd stage: d1 = l.6164{l-exp{-l8.163exp(-28.0wc )}jlo-•" ~ (a2) t?! 540 s diffusion coefficient in the air: (a3) volumetric heat capacity of fiber: ( kj m -3 k) cv =373.3+4661.0wc +4.221t (a4) thermal conductivity of fiber: k == ~8.49-0.720wc +0.113wc2 -0.002wc3 j0-3 (as) heat of sorption: ( kj kg -l ) a= 1602.5exp(-11.72wc )+ 2522.0 (a6) diffusion coefficient of water vapour in fiber; ( m2 s-t) -1st stage: d 1 = (o.8481 + 50.6wc -noow; }o-1 \ (a7) t < 540 s diffusion coefficient of water vapour in fiber; ( m 2s-1 ) -2nd stage: d 1 = 2.5{1exp[3.5385 exp{45wc )]10-14 , t ;?:540 s diffusion coefficient in the air: da =2.5e-5 volumetric heat capacity of fiber: ( kj m -3 k) (1663.0+4184.0wc) (l+wcft6l0.9 thermal conductivity of fiber: k =(44.1+63.0w)0-3 . heat of sorption: ( kj kg -l) a= 1030.9exp(-22.39wc )+ 2522.0 porous acrylic fiber: (a8) (a9) (a10) (all) (a12) diffusion coefficient of water vapour in fiber; ( m 2s-1 ) -1st stage: d1 = (l12-410wc -8200wr2 )o-13 ~ (a13) t <540s diffusion coefficient of water vapour in fiber ; (m2s-i) -2nd stage: d 1 = (6.23)10-13 , t?! 540 s (al4) diffusion coefficient in the air: (a15) volumetric heat capacity of fiber: (kj m-3 k) cv = 1610.9 (a16) thermal conductivity of fiber: k = 28.8 ·10-3 (kw m-1 k-1 ) (al7) heat of sorption: ( kj kg -i ) a.= 2522 kj kg-1 (a18) polypropylene fiber: diffusion coefficient of water vapour in fiber; ( m 2s-1 ) 1st stage: (a19) diffusion coefficient of water vapour in fiber; ( m 2s-1 ) -2nd stage: diffusion coefficient in the air: da = 2.5e-5 (a21) volumetric heat capacity of fiber: ( kj m -3 k) cv =1715.0 (a22) thermal conductivity of fiber: k=51.80·10-3 (kw m-1 k-1 ) (a23) heat of sorption: ( kj kg -i) a= 2522 kj kg-1 kinetic coefficients (cpv -cpaxlsw )dmamv jpcv k s2 = k s + ....:...__!;...:__-~.:.....__.;_..:.._____.: __ cpwpwmrt jsw k __ kkw dpc t</jj-lw (}t k _ k + (1-sw )dmamv jpgv tl t pwmrt ar (cpv -cpaxl-sw)dmamv jpgv k = k + ,..!_!;:..:.._____::_.:::..:...:.._...;..:_:__-=-rz t c p mrt jt pw w k =kkw p <pi-lw 269 (a24) kkgmvpgv jpgv (1-sw )dmamvpt;\' k = k + _...;:.___..:::,._ p 1 p <fjj-lgpwmrt at pwrtmpt: page 264 page 265 page 266 page 267 page 268 page 269 page 270 page 271 page 272 hungarian journal of industry and chemistry vol. 48(1) pp. 3–10 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-02 improving the efficiency of neural networks with virtual training data jános hollósi*1,2, rudolf krecht2, norbert markó2, and áron ballagi2,3 1department of information technology, széchenyi istván university, egyetem tér 1, győr, 9026, hungary 2research center of vehicle industry, széchenyi istván university, egyetem tér 1, győr, 9026, hungary 3department of automation, széchenyi istván university, egyetem tér 1, győr, 9026, hungary at széchenyi istván university, an autonomous racing car for the shell eco-marathon is being developed. one of the main tasks is to create a neural network which segments the road surface, protective barriers and other components of the racing track. the difficulty with this task is that no suitable dataset for special objects, e.g. protective barriers, exists. only a dataset limited in terms of its size is available, therefore, computer-generated virtual images from a virtual city environment are used to expand this dataset. in this work, the effect of computer-generated virtual images on the efficiency of different neural network architectures is examined. in the training process, real images and computer-generated virtual images are mixed in several ways. subsequently, three different neural network architectures for road surfaces and the detection of protective barriers are trained. past experiences determine how to mix datasets and how they can improve efficiency. keywords: neural network, virtual training data, autonomous vehicle 1. introduction shell eco-marathon is a unique international competition held by royal dutch shell plc. this event challenges university students to design, develop, build and drive the most energy-efficient racing cars. our university’s racing team, the szenergy team, has been a successful participant in the shell eco-marathon for over 10 years. two years ago, shell introduced the autonomous urbanconcept (auc) challenge, which is a separate competition for self-driving vehicles that participate in the shell eco-marathon. participants in the auc challenge have to complete five different tasks, e.g. parking in a dedicated parking rectangle, obstacle avoidance on a straight track, drive one lap of the track autonomously, etc. our long-term goal is to prepare for the auc challenge. one of the main tasks is to create an intelligent system, which perceives the environment of our racing car, e.g. other vehicles, the road surface, other components of the racing track, etc. in this paper, only the segmentation of the road surface and of the protective barriers is taken into consideration. an approach based on neural networks will determine the segmentation, because such networks are one of the best tools to solve problems concerning visual information-based detection and segmentation, e.g. image segmentation. many high-performance neural network architectures are available such as alexnet by krizhevsky et al. [1], vggnet by simonyan and zisser*correspondence: hollosi.janos@sze.hu man [2], googlenet by szegedy et al. [3], fully convolutional networks by shelhamer et al. [4], u-net by ronneberger et al. [5], resnet by he et al. [6] and pyramid scene parsing network by zhao et al. [7]. training neural networks requires a large amount of training data. however, in this case, the number of training samples is insufficient, e.g. no training images of protective barriers are available and the generation and annotation of real world data is labour-intensive and time-consuming. computer simulation environments will be used to generate training data for this task. some attempts that apply virtually generated data to train neural networks have been made. peng et al. [8] demonstrated cad model-based convolutional neural network training for joint object detection. tian et al. [9] presented a pipeline to construct virtual scenes and virtual datasets for neural networks. they proved that mixing virtual and real data to train neural networks for joint object detection helps to improve performance. židek et al. [10] presented a new approach to joint object detection using neural networks trained by virtual model-based datasets. in this paper, an attempt is made to show the effects of computer-generated training data on the learning process of different network architectures. the paper is structured as follows: in section 2, the virtual simulation environment that is used for generating training data is described; in section 3, our neural network architectures are presented; in section 4, the training process of the networks is outlined; in section 5, our https://doi.org/10.33927/hjic-2020-02 mailto:hollosi.janos@sze.hu 4 hollósi, krecht, markó, and ballagi results and experiences are shared; finally, in section 6, our conclusions are stated. 2. our virtual environment our aim is to create highly realistic image sets that depict racing tracks which follow the rulebook of the shell ecomarathon autonomous urbanconcept. in order to ensure repeatability and simple parameter setup, the creation of complete, textured 3d-models of the racing tracks is advised. these simulated environments can be used to create images with desired weather and lighting conditions by scanning the track environment using a camera moving at a predefined constant speed. the images created using this method can be processed further, e.g. segmentation and clustering of different types of objects such as the road surface, protective barriers and vegetation. based on the characteristics of the predefined task, the requirements of the simulation environment can be enumerated: • highly realistic appearance, • easy use of textures, • fast workflow, • characteristics definable by parameters (parametric lights, weather conditions), • modular environment construction, • importability of external cad models. unreal engine 4 [11] is a games engine designed for the fast creation of modular simulated environments by the use of modular relief, vegetation and building elements. in these environments, actors based on external cad models could be used. fields of engineering that apply different visual sensors and cameras require very similar computer simulation technologies to the video game industry. video games need to be highly realistic as well as efficient due to limited computational capacity. the requirements are the same for the simulation of vehicles mounted with cameras. highly realistic computer simulations reduce the cost and duration of real-life tests and camera calibrations. it is also important to mention that by using technology implemented and/or developed by the video game industry, the support of a vast developer community is available. since our goal is to develop image-perceiving solutions for the shell eco-marathon autonomous urbanconcept challenge, it is important to carefully follow the rules of this competition with regard to the racing tracks. the simulated environments and racing tracks created by unreal engine strictly follow the rules defined by the aforementioned rulebook. these rules define that the self-driving vehicles have to compete on racing tracks equipped with protective barriers of a known height painted in alternating red and white segments. it is also defined that every racing track consists of three figure 1: example images from the training set. painted line markings, one that is green to denote the starting position, a yellow one to trigger the self-driving mode, and another that is red to mark the finish line. because the racing tracks and tasks are well defined, it is crucial to create accurate models of the expected environments. differences between real and simulated environments might lead to further developments in the wrong direction. two simulated test environments were created. the first one was based on a readily available city model with streets corresponding to a typical racing track. barrier elements were added to the roads to ensure that the racing track complies with the requirements outlined in the rulebook. this model includes defects in and textures of the road surface to ensure detection of the road surface is robust. in order to create image sets based on this environment model, a vehicle model equipped with a camera travelled around the racetrack on a pre-defined path. the camera was set to take pictures at pre-defined time intervals. the image set was annotated by using a module called airsim. airsim is an open-source, cross-platform simulator simulation platform built on unreal engine, but it also has a unity release. this simulator module consists of a built-in python-based api (application programming interface) which was developed for image segmentation. by using this api, the necessary realistic and segmented image datasets were created. some example pairs of images from our virtual dataset are presented in fig. 1. in order to prepare for all the tasks defined in the rulebook, multiple models of racing tracks were created. all such models are based on the same environment model, which includes vegetation and the sky as shown in fig. 2. the models of sections of racing track were realized according to the challenges defined in the rulebook. the cad models representing elements of the racing track were custom-made to comply with the shapes, sizes and colors outlined in the rulebook. the sections of racing track generated can be used to simulate handling hungarian journal of industry and chemistry improving the efficiency of neural networks with virtual training data 5 figure 2: basic environment of racing tracks. figure 3: parking place and slalom course. (slaloming) and parking tasks. this virtual racing track is shown in fig. 3. the image sets were created by a moving camera in the environment and segmentation was carried out by changing the textures. 3. neural network architectures three different neural network architectures are implemented in this work: fcn, u-net and pspnet. all neural networks are designed for image segmentation, where the size of input images is 256×512×3, and the size of output ones is 256×512×1. every network is trained for the segmentation of the road surface and protective barriers. 3.1 fcn the fully convolutional network (fcn) [4] architecture is based on fully convolutional layers, where the basic idea is to extend effective classification neural networks to conduct segmentation tasks. our fcn architectures are shown in fig. 4. let: γ = (conv, bn, relu) (1) b1 = (γ, γ,mp) (2) b2 = (γ, γ, γ,mp) (3) figure 4: fcn architecture. 48(1) pp. 3–10 (2020) 6 hollósi, krecht, markó, and ballagi figure 5: u-net architecture. where conv denotes a convolutional layer, bn represents a batch normalization layer, relu stands for a rectified linear activation unit and mp is a max pooling layer. let: b1 = (b1, b1, b2) (4) b2 = (b2) (5) b3 = (b2, γ, γ, γ) (6) x = (conv, bn) (7) y = (relu, softmax) (8) z = (relu, softmax) (9) where softmax denotes a softmax layer. in this implementation, the dimensions of all convolutional layers are 3× 3, except for the three fully connected layers in block b3. the dimensions of these convolutional layers are 7×7. in block b1, the first two convolutional layers both contain 64 filters, the third and fourth both contain 128 filters, and the last three convolution blocks each contain 256 filters. the convolutional layers in block b2 contain 512 filters in total. the first three convolutional layers in block b3 contain 512 filters in total, and the fully connected layers are based on 4096 filters in total. 3.2 u-net the u-net [5] neural network architecture was originally created for biomedical image segmentation. it is based on fcn, where the neural network can be divided into two main blocks, namely the downsampling and upsampling figure 6: psp net architecture. blocks. our implementations are shown in fig. 5. let: d1 = d2 = (γ, γ, maxpooling) (10) d3 = d4 = b = (γ, γ, γ,maxpooling) (11) u1 = u2 = u3 = ( convt, bn, relu, γ, γ ) (12) u4 = ( convt, bn, relu, γ, γ, conv, softmax ) (13) where convt is a transposed convolution layer. in the unet neural network, the dimensions of all convolutions and transposed convolutions are 3× 3, and 2× 2, respectively. the number of convolutional filters are as follows: each convolutional layer in d1 consists of 64, in d2 of 128, in d3 of 256 and in d4 as well as b of 512 filters. the upsampling block is very similar. u1 consists of 512, u2 of 256, u3 of 128 and u4 of 64 filters. 3.3 pspnet the pyramid scene parsing network (pspnet) [7] was judged to be the best architecture in the imagenet scene parsing challenge in 2016 [12]. the main building block of the pspnet is a pyramid pooling module, where the network fuses features under four different pyramid scales. our pspnet-based architecture is shown in fig. 6. hungarian journal of industry and chemistry improving the efficiency of neural networks with virtual training data 7 let: b1 = (γ, γ, γ,maxpooling) (14) c = (γ, γ, conv, bn)+ (conv, bn) (15) i = (γ, γ, conv, bn) (16) p = (avg, conv) (17) p1 = (p) (18) p2 = (p, p) (19) p3 = (p, p, p) (20) p4 = (p, p, p, p) (21) b2 = ( γ, dropout, conv, convt, softmax ) (22) where avg denotes an average pooling layer and dropout represents a dropping out unit. in block b1, the dimensions of all convolutions are 3× 3. in blocks c and i , the dimensions of every first & third and every second convolution are 3×3 and 1×1, respectively. in blockb2, the dimensions of the first convolution are 3× 3 and the second 1× 1. the dimensions of the transposed convolution are 16 × 16. each of the first two convolutions in block b1 consist of 64 filters, and the last one of 128. the first block c and first two i blocks contain 64, 64, 256 filters, respectively, while the second block c and the following three i blocks consist of 128, 128 and 512 filters, respectively. the third block c and the following five i blocks contain 256, 256 and 1024, respectively, and the fourth block c along with the last two i blocks consist of 512, 512 and 2048 filters, respectively. 4. training with virtual data an attempt was made to improve the accuracy of neural networks using computer-generated virtual training data that originates from the virtual city environment. some mixed datasets were compiled which contain real-world images and computer-generated virtual images. the realworld images originate from the cityscapes dataset, a large-scale dataset for semantic segmentation [13]. the dataset contains 5000 annotated images with fine annotations created in 50 different cities under various weather conditions. 30 object classes are included, e.g. roads, sidewalks, people, vehicles, traffic lights, terrain, sky, etc. but in this research, only road surface segmentation is examined. the computer-generated images originate from the simulation environment described in section 2. for road surface segmentation, five different datasets are created from the cityscapes dataset and our collection of virtual images. table 1 shows how these two collections were mixed. our goals are to use a minimum amount of data from a real-world dataset, and when the number of virtual images is changed, to observe how the efficiency of the neural networks is affected. dataset a only contains real-world images, therefore, this is regarded as the basic dataset, while the others were compared to it. dataset b already contains the same number of virtual images as real-world images. here, observations of how the introduction of virtual images changes table 1: number of images in our mixed datasets dataset name training set validation set virtual real-world virtual real-world a 0 500 0 125 b 500 500 0 250 c 1500 500 0 500 d 1500 1000 0 625 e 1500 1500 0 750 the initial degree of efficiency are sought. dataset c contains three times more virtual images than dataset b. if the number of virtual images is much higher than the number of real-world images, the efficiency may be reduced. a future paper of ours will investigate this. in datasets d and e the number of real-world images was increased. for the segmentation of protective barriers, only virtual training data were used. how efficiently the neural network recognizes real objects, if only trained by virtual data, will now be shown. the effect of increasing the number of real-world images on efficiency was investigated. adam optimization was used for training with a learning rate of 10−4 and a learning rate decay of 5×10−4. as the objective function, categorical crossentropy is used: l (y, ŷ)= −y×log (ŷ) (23) and the dice coefficient measured: dc (y, ŷ)= 1−2×y×ŷ+1 y+ŷ+1 (24) where y ∈ {0, 1} is the ground truth and 0 ≤ ŷ ≤ 1 is the result of the neural network. 5. results an attempt was made to examine the efficiency of road surface detection, while the composition of the dataset was modified. for examining changes in efficiency, the most useful datasets were a, c and e. dataset a is the basic dataset, which only contains a small set of real-world images. dataset c is based on dataset a, but contains three times as many virtual images as real-world images. dataset c shows how performance changes, when virtual world images are integrated into a small dataset. in dataset e, the size of the collection was expanded. this dataset shows how much greater the efficiency of a larger mixed dataset is. fig. 7 shows the validation accuracy over the training process of road surface detection, while fig. 8 shows the best dice coefficient values for road surface segmentation. fcn is much simpler than both u-net and pspnet neural network architectures. hence the efficiency of the fcn on dataset a is a little less than for the other networks. u-net and pspnet are very robust and complex, therefore, mixed datasets do not significantly increase the efficiency of these architectures. however, for simpler networks like fcn, this method improves the efficiency. fig. 9 shows the perfor48(1) pp. 3–10 (2020) 8 hollósi, krecht, markó, and ballagi figure 7: road surface segmentation performance mances with regard to the segmentation of protective barriers. only virtual images were used to train the neural networks that determine the segmentation of protective barriers. this would not have been possible in the case of road surface segmentation, because the road surface is too complex. the texture of the protective barriers is very simple, therefore, it is possible to recognize it from virtual images alone. it is our intention to use an environment detection system in a low-budget racing car, where the hardware resources available are limited and detection must occur in real time with a high degree of detection accuracy. therefore, the neural network should be designed to be as simple as possible. if the neural network architecture is too simple, it is more difficult to train for complex recognition tasks. moreover, the dataset concerning the racing track, protective barriers, etc. is not large. in this case, it is helpful to be able to train simpler neural networks, e.g. fcn, with virtual datasets to achieve higher degrees of efficiency. experience has shown that the efficiency of road surface detection is improved by using three times as many virtual images, while for protective barrier detection it is sufficient to only use virtual images. 6. conclusion this paper presents how to use computer-generated virtual images to train artificial neural networks when the amount of available real-world images is limited. three different neural network architectures, namely fcn, unet and pspnet, were investigated and these networks trained with mixed datasets. it was shown that virtual imhungarian journal of industry and chemistry improving the efficiency of neural networks with virtual training data 9 figure 8: best accuracy of road segmentation figure 9: barrier segmentation performance ages improve the efficiency of neural networks. our research demonstrates that when the texture of the objects is simple, e.g. that of protective barriers, it is sufficient to only use virtual image-based training datasets. this work may help us to create an efficient environment detector for the shell eco-marathon, where special objects have to be detected in the absence of real-world datasets. acknowledgements the research was carried out as part of the “autonomous vehicle systems research related to the autonomous vehicle proving ground of zalaegerszeg (efop-3.6.216-2017-00002)” project in the framework of the new széchenyi plan. the completion of this project is funded by the european union and co-financed by the european social fund. references [1] krizhevsky, g. a.; sutskever, i.; hinton, g. e.: imagenet classification with deep convolutional neural networks, commun. acm, 2017 60(6), 84–90 doi: 10.1145/3065386 [2] simonyan, k.; zisserman, a.: very deep convolutional networks for large-scale image recognition, 3rd international conference on learning representations, san diego, usa, 2015 [3] szegedy, c.; liu, w.; jia, y.; sermanet, p.; reed, s.: going deeper with convolutions, ieee conference on computer vision and pattern recognition (cvpr), boston, ma, usa, 2015 doi: 10.1109/cvpr.2015.7298594 [4] shelhamer, e.; long, j.; darrell, t.: fully convolutional networks for semantic segmentation, ieee transactions on pattern analysis and machine intelligence, 2017 39(4) 640–651 doi: 10.1109/cvpr.2015.7298965 [5] ronneberger, o.; fischer, p.; brox, t.: u-net: convolutional networks for biomedical image segmentation, in: navab, n.; hornegger, j.; wells, w.; frangi, a. 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https://www.unrealengine.com/en-us/ [accessed 14 september 2019] [12] russakovsky, o.; deng, j.; su, h.; krause, j.; satheesh, s.;ma, s.; huang, z.; karpathy, a.; khosla, a.; bernstein, m.; berg, a. c.; fei-fei, l.: imagenet large scale visual recognition challenge, int. j. computer vision, 2015 115 211–252 doi: 10.1007/s11263-015-0816-y [13] cordts, m.; omran, m.; ramos, s.; rehfeld, t.; enzweiler, m.; benenson, r.; franke, u.; roth, s.; schiele, b.: the cityscapes dataset for semantic urban scene understanding, ieee conference on computer vision and pattern recognition (cvpr), las vegas, nv, usa, 3213–3223 2016 doi: 10.1109/cvpr.2016.350 hungarian journal of industry and chemistry https://www.unrealengine.com/en-us/ https://doi.org/10.1007/s11263-015-0816-y https://doi.org/10.1109/cvpr.2016.350 introduction our virtual environment neural network architectures fcn u-net pspnet training with virtual data results conclusion microsoft word hjic 2015 43(2) 55-101.docx hungarian journal of industry and chemistry vol. 43(2) pp. 91–95 (2015) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2015-0015 mineral matter in nigerian coals and tar sand and their implications in binary blend formulation and co-carbonisation solomon a. ryemshak,1,2 aliyu jauro,1* istifanus y. chindo,1 and eno o. ekanem1 1 department of chemistry, abubakar tafawa balewa university, p.m.b. 0248, bauchi, bauchi state, 740003, nigeria 2 fuels and energy division, national metallurgical development centre (nmdc), p.m.b. 2116, jos, plateau state, 930001, nigeria in blend simulation for metallurgical applications, the knowledge of the type and amount of mineral matter in coal and other additives, as well as their derivatives as a result of combustion is important in assessing the coke quality and blast furnace efficiency. x-ray diffraction (xrd) and x-ray fluorescence (xrf) techniques were used in assessing the mineral matter contents and oxides produced up on combustion of the following nigerian coals: afuze (afz), garin-maiganga (gmg), lamza (lmz), shankodi-jangwa (skj), and chikila (chk) in addition to a tar sand from ondo (ots). coal samples from afuze (afz) and chikila (chk) were found to contain quartz, hematite, and anhydride as the dominant minerals. the garin-maiganga coal sample (gmg) was found to contain quartz, magnetite, anhydride, and magnesite. quartz and hematite were dominant in lamza coal (lmz), while shankodi-jangwa coal (skj) is associated with dolomite and quartz. the bitumen was found to contain quartz, kaolinite, and rutile. the xrf analysis revealed the presence of sixteen elemental oxides: the most abundant being silicon dioxide, ferric oxide, aluminium oxide, sulphur trioxide, calcium oxide, and titanium oxide. amongst the coal samples, chk, afz and gmg coals have low acidic/basic and basic/acidic ratios, which indicate that cokes originating from them may form the least slag with the best blast furnace efficiency. keywords: coke, mineral content, slag formation, fouling, flux, iron extraction 1. introduction mineral matter and ash resulting from decomposition processes are some of the main determining factors that produce straight carbonisation and develop blend coking technology for metallurgical coke production in the iron and steel industries. the mineral matter of coal is commonly, but incorrectly termed as ash content. coals contain mineral matter, but not ash. the latter is the solid residue, different from the mineral matter in both amount and composition that is obtained during the combustion of coal. mineral matter has negative and positive effects on coal resource utilisation and disposal. therefore, the characterisation of minerals in coal is essential in order to assess the beneficial and detrimental effects, which a given mineral matter may have both on the combustion process and on ultimate application. for example, even though phosphorousbearing minerals are often minor constituents of coal, they can be transferred from coal to coke and interact with iron ore, providing difficulties in steel production [1]. consequently, coke containing a maximum value of 0.2% phosphorus is required for iron and steel production [2]. *correspondence: ajauro@atbu.edu.ng compositional analysis of coal and coke ash is useful in the total coal quality description. knowledge of the ash composition is useful in predicting the slagging and fouling characteristics of combustible materials in combustion chambers, as well as the potential utilisation of ash by-products, and environmental pollution [3]. it is well known that ash deposition on heat transfer surfaces during coal combustion is a common concern for all coal-firing boilers [4]. it is difficult to quantify the mineral matter content of a coal used in high-temperature operations (combustion and coking processes), because the minerals in coal react with organic particles. on combustion, some of the original minerals decompose and the residual substance may recombine or interact with other derivatives of the coal ash. this may lead to abrasion, corrosion, and clogging as well as fouling of the catalyst and slag formation. the ash, being inevitably a heterogeneous mixture leftover after combustion, is therefore not a true measure of the nature or amount of mineral matter originally present in the sample [5]. this paper assesses the mineral matter contents of nigerian coals and ondo tar sand and their implications in binary-blend formulation for coke production. ryemshak, jauro, chindo, ekanem hungarian journal of industry and chemistry 92 2. experimental 2.1. samples and sample preparation coal samples were collected from the following coal fields: garin-maiganga (gmg), chikila (chk), lamza (lmz), shankodi-jangwa (skj) and afuze (afz). tar sand was obtained from ondo (ondo tar sand, ots). the coal samples were shade dried for three days to remove the free moisture (external or primary moisture fraction). the samples were then ground, and sieved through a 250 micron (0.25 mm) mesh. 2.2. methodologies 2.2.1. xrd analysis the powdered samples were placed into a sample holder and pressed with a piston. they were then loaded into the xrd spectrometer to determine the ore mineral contents of the samples. copper kα radiation was used as the source. the spectrometer was operated at 40 kv and 30 ma using continuous scan mode from 2 to 80 degrees. 2.2.2. xrf analysis coal samples were ashed at a temperature of 825 oc for 1 hour in a muffle furnace. 5.00 g of the ash was mixed with a binder (cellulose flakes) in a ratio of 5:1 g/g and pelletised at a pressure of about 15 ton inch-2 in a pelletising machine. the prepared samples were run on an energy-dispersed x-ray fluorescence (ed-xrf) machine by appropriating programmes for various elements, and the various oxides present detected as percentages. 3. results and discussion 3.1. sample description previously published data show that with the exception of shankodi-jangwa coal that is bituminous in rank, all other samples (afz, lmz, and chk) are of subbituminous rank [6–9]. 3.2. mineral matter results from the xrd analysis of the major mineral matter in the coal samples and the ondo tar sand (ots) are shown in figs.1 and 2. the xrd results of the coal samples and the tar sand (ots) revealed that quartz is dominant in all the samples, with the exception of afz, where hematite content is slightly higher than quartz (fig.1). apart from quartz, halide, and anhydride were also detected in chk (fig.1); anhydride, magnetite and magnesite in gmg (fig.1); hematite in lmz (fig.2); dolomite in skj (fig.2); kaolinite and rutile in ots (fig.2). the observed minerals are commonly reported in coal samples worldwide [10]. a mineral is an inorganic substance that affects both the processing and utilisation of an organic material. xrd analysis is a useful tool in the study of the effects of mineral matter on coal industrial applications like gasification, and liquefaction. knowledge of the mineral matter can also be used to evaluate the behaviour of a particular coal in different utilisation processes, including to control the characteristics of fly ash, slag and other combustion byproducts [11]. coal and tar sand occur in association with mineral matters, and have different mineral compositions depending on their origins. based on the association, there are excluded minerals (minerals that are separate from the macerals) and included minerals (minerals closely associated with the organic matter) [12]. the common major minerals identified in coals are quartz, kaolinite, illite, calcite, pyrite, plagioclase, feldspar and gypsum, and occasionally dolomite, ankerite, siderite, iron-oxyhydroxides and sulphates [10]. the amount, mode of occurrence, and composition of the mineral matter in coal are factors of great practical importance in determining its marketability and economic value. the yield and quality of the product obtained by the use of coal also depends upon the characteristics of its mineral matter. consequently, the quality of the coke figure 1. x-ray diffractogram of ash from a) afz coal (quartz 38%, hematite 41%, anhydrite 21%); b) chk coal (quartz 63%, halite 13%, anhydrite 25%); c) gmg coal (quartz 56%, magnetite 12%, anhydrite 18%, magnesite 14%). c co un ts b co un ts a co un ts mineral matter in nigerian coals and tar sand 43(2) pp. 91–95 (2015) doi: 10.1515/hjic-2015-0015 93 also depends heavily on the type and quantity of mineral matter present in the coke after carbonisation. minerals in coals have different technological problems in metallurgy. for example, clay minerals reduce the calorific value of coal [13]. excluded quartz and pyrite could result in the abrasion and wearing of grinding equipment [14] and pyrite could lead to slagging and fouling. however, these challenges can be mitigated by understanding coal composition, its mineralogical association and abundance. the xrd analysis results of these samples (coals and tar sand) showed that both the coal and tar sand samples contain mineral matter impurities such as quartz and anhydride, commonly found associated with coal deposits (fig.3). the minerals in these samples such as kaolinite, hematite, anhydrite, etc., are potential sources of raw materials of chemical industries. some of the minerals in these coal samples, such as silica, dolomite (calcium magnesium carbonate) or calcium and aluminium are acidic, basic and neutral fluxes respectively, and are useful when combined with other impurities in the formation of slag in iron production [15]. 3.3. mineral matter and ash content during combustion some mineral matter is naturally harmful, and some can decompose to form compounds or combine with other organic components to form other derivatives during combustion. alkali and alkali earth metals such as li, na, k, and ca, mg, respectively, at high temperatures disturb the regularity of blast furnace operation by inducing major furnace incidents like frozen hearth and burnt tuyers that cause inconsistency in iron quality. these metals also interact with other elements resulting in problems, such as clinkering, fouling, slagging and corrosion [16–17]. alkali metals also cause lines of fracture by insertion in the carbon mass of the coke. generally, alkaline elements were found to have a serious impact on coke production by causing decreased burden permeability and low yields [18]. the alkaline vapour sometimes acts as a glue in binding impacting ash particles together and enhancing fouling at high temperatures [19]. ash is the inorganic residue that remains after ignition of the combustible substance, and a reduction in ash content improves the coking quality. the ash in coke is of great significance in metallurgy. according to tivo et al. original coal ash contains various kinds of minerals, coexisting as crystal and non-crystal minerals at different temperatures [20]. coke ash affects the operation of blast furnaces and cupolas due to both its amount and chemical composition. industrial experience indicates that a weight percent increase of ash in the coke reduces metal production by 2 or 3 weight percent [21]. the disposal of ash is also a big problem that increases operational costs and poses some environmental challenges [22]. ash content of less than 10% is recommended for a good coking coal [23]. 3.4. slag formation and blast furnace efficiency coal particles can behave differently particularly in terms of carbon conversion, mineral transformation, char fragmentation, and ash formation depending on the association of the organic (maceral) and inorganic (mineral) matter when fed into a gasifier or boiler [12]. this behaviour, which affects the efficiency of the boiler, can be predicted using the data from the xrf analysis of the samples. table 1 shows the xrf analysis results of ash from the coals and tar samples. figure 2. x-ray diffractograms of ash from a) lmz coal (quartz 72%, hematite 28%); b) skj coal (quartz 80%, dolomite 20%); c) ots sample (quartz 86%, kaolinite 6%, and rutile 8%). figure 3. mineral distribution in coal samples and the tar sand. a b c co un ts co un ts co un ts ryemshak, jauro, chindo, ekanem hungarian journal of industry and chemistry 94 a total of 16 elemental oxides were detected in the ashes resulting from combustion, but the most prominent ones are sio2, fe2o3, al2o3, and cao. even though the results of the oxides (ash composition) fall within the acceptable limit for iron production with the exception of silicon dioxide in ots, which is above the maximum limit of 64% [2]. the ratio of acidic-to-basic (a/b) oxides (al2o3+sio2 versus fe2o3+cao+mgo) characterises the ash with respect to refractoriness. the a/b ratio indicates the ash fusion temperature and blast furnace efficiency, a high ratio leads to a high fusion temperature resulting in a high slag volume and low blast furnace efficiency [24]. the basic constituents are iron, alkali earth metals (ca, mg) and the alkali metals (na, k). the acidic constituents are si, al, and ti. for instance, the coke from skj coal (fig.4), which has the highest a/b ratio is expected to exhibit the highest fusion temperature and the lowest efficiency during blast furnace operation, while the one from chk coal would guarantee the highest efficiency of the furnace. considering the high a/b ratio value of 12 for the ots sample (fig.4), a small quantity of its bitumen may be good for blend formulation with the coal samples. the ratio of basic-to-acidic oxides (b’/a’ calculated from fe2o3+cao+mgo+k2o+na2o content versus sio2+al2o3+tio2 content [25]), corresponds to the slagging tendency of the coal; the higher the ratio the lower the slag formation [25]. ash with a high b’/a’ ratio, generally exhibits high ash fusion and melting temperatures. however, ash with a medium b’/a’ ratio, tends to exhibit low fusion and melting temperatures, hence high slag volume. ash with a low fusion temperature can cause problems during combustion. the melting and viscosity behaviour has been described as a function of the composition of the coal ash in terms of acids and bases. therefore it is expected that chk and afz coals with high b’/a’ ratios (fig.5), would generate coke that may exhibit the least slag formation, closely followed by gmg coal. the highest slag volume is expected in ots and skj coal. overall, the parallel values of a/b and b’/a’ ratios for chk, afz, and gmg coals in fig.6 indicate that cokes produced from them may form the least slag and therefore the best blast furnace efficiency. excessive ash in metallurgical coke gives rise to high slag volume and low blast furnace efficiency. 4. conclusion the relatively low ash contents of these coal samples suggest that they can safely form part of blend formulation for the production of both domestic and industrial cokes without any or significant adverse effects on fouling and slagging, and minimal corrosion and clogging tendencies. the high a/b and low b’/a’ ratios of the tar sand (ots), suggest that a small amount of bitumen may be beneficial for binary blend formulation with the coals, for coke production. based on the oxide ratios, chk, afz and gmg coals may produce cokes by coking technology that may create the least slag with the best blast furnace efficiency. acknowledgement we acknowledge the department of chemistry atbu in bauchi and the national metallurgical research and development centre in jos for the use of their laboratories. the publication of this article was table 1. chemical composition (% oxide content) of the coals and tar sand ashes from xrf measurements. oxide afz chk gmg lmz skj ots sio2 24.61 29.41 38.60 46.40 57.36 70.39 tio2 1.87 1.90 2.40 4.46 2.32 1.62 al2o3 7.31 8.93 7.19 15.81 16.20 14.33 fe2o3 23.97 18.28 16.26 22.53 19.30 5.31 so3 13.70 14.70 11.00 6.20 1.10 0.09 cao 11.20 25.00 21.10 1.64 1.36 1.26 mgo 0.35 0.31 1.96 0.11 0.20 0.49 na2o 0.07 0.15 0.10 0.05 0.33 0.30 k2o 0.04 0.87 0.07 0.30 1.46 0.96 mno 0.40 0.04 0.41 0.04 0.06 v2o5 0.07 0.10 0.08 0.23 0.14 0.07 cr2o3 0.03 0.03 0.02 0.04 0.04 0.03 cuo 0.08 0.07 0.03 0.20 0.08 0.03 bao 0.30 0.17 0.77 0.13 zno 0.04 0.07 nio 0.04 0.02 0.04 0.03 0.02 figure 4. blast furnace efficiencies of the coal samples. figure 5. slag formation tendencies of the coal and tar sand samples. figure 6. slag formation tendencies and blast furnace efficiencies. mineral matter in nigerian coals and tar sand 43(2) pp. 91–95 (2015) doi: 10.1515/hjic-2015-0015 95 supported by professor jános szépvölgyi (hungarian academy of science, research centre for natural sciences), professor jude onwudili (university of leeds) and dr. biswajit ruj (csir-central mechanical engineering research institute). references [1] ward, c.r.; corcoran, j.f.; saxby, j.d.; read, h.w.: occurrence of phosphorous mineral in australian coal seams, int. j. coal geol., 1996, 30(3), 185–210 doi: 10.1016/0166-5162(95)00055-0 [2] astm: petroleum products, lubricants and 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r. desollar.: springer, new york, usa), 1996, pp. 237–244 doi: 10.1007/978-1-4757-9223-2 hungarian journal of industry and chemistry vol. 45(1) pp. 49–59 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0008 adapting the sdewes index to two hungarian cities viktor sebestyén, viola somogyi,* szandra szőke, and anett utasi institute of environmental engineering, university of pannonia, 10 egyetem str., veszprém, h-8200, hungary numerous cities aim to mitigate their contribution to climate change and provide a liveable environment in the context of sustainable development. in order to measure these efforts, benchmarking performance would be a good solution. methods for environmental analysis have their limitations when it comes to evaluating a city and other aggregated indicators focus on certain aspects of a sustainable or liveable settlement. the sdewes index was used for benchmarking several cities of different sizes in terms of metrics related to energy, water and environmental systems successfully thus it was chosen to compare the performance of veszprém and zalaegerszeg, two environmentally conscious hungarian county seats of roughly the same size and population. the sdewes index consists of 7 dimensions, namely energy consumption, industrial profile with co2 emissions, co2-saving measures, r&d, renewable energy potential and utilization, water and environmental quality, and social environment and sustainability policy. each dimension is composed of 5 indicators that provide information on sustainable development of energy, water and environmental systems in cities. using the sdewes index the strengths and weaknesses of the two cities are highlighted, locating those key parameters where improvement can be achieved. both for veszprém and zalaegerszeg progress could be realized concerning energy-saving measures and the proportion of green areas could be increased. to improve the method and facilitate a more comprehensive comparison of cities of differing sizes, data should be provided concerning the territory or population. also, the definition and inclusion of a worst and best case scenario that takes into account the parameters would be advantageous in terms of a comparison. these were named ‘horror’ and sdewes cities by the authors, respectively. keywords: sdewes index, sustainability, city development, sustainable energy action plan, city sample 1. introduction sustainability is a key issue when it comes to the development of cities. in 2014, 54% of the world’s population lived in urban areas and according to the prognosis, the proportion will be as high as 66% by 2050 [1]. while the number and population of megacities is on the rise, 43% of urban dwellers lived in settlements consisting of less than 300,000 inhabitants in 2014 (in europe the corresponding data was 58%) and only a modest decrease is estimated by 2030 [2]. looking at these numbers, it is easy to notice that urbanised areas have a huge impact on achieving sustainable development. various cities have started to address this issue and several indicators and comparisons were created to measure specific aspects of sustainable development. a few of these numerous examples are listed in this paper. the city development index [3] studies the municipalities from social and governance aspects. the global power city index (gpci) has ranked 40 metropolises since 2008 [4] considering 70 individual indicators regarding the environment, liveability and *correspondence: somogyiv@uni-pannon.hu r&d among others. the green city index is focused on the environmental sustainability of large cities [5]. carbon footprints of twelve metropolitan areas [6] and the san francisco bay area [7] were determined. several others are listed by lópez-ruiz et al. [8] but usually smaller towns do not fall within the scope of these benchmarks. environmental analysis, on the other hand, facilitates the evaluation of the impacts of human activities (different actions, projects or investments) with regard to the local environment, economy and society. in this way it provides information on the status quo and helps the practical implementation of sustainable development by focusing attention on the points to be improved [9]. several methods have been developed to carry out the procedure: checklists [10], the matrix technique [11], the network approach [12], gis-based methods [13] and quantitative methods [14] may be used to evaluate environmental impacts. aggregating methods such as the global pollution index (ipg) [15] may be suitable up to a point in providing a comprehensive sustainability analysis as they are only based on immission values. several multiple-criteria decision-making (mcdm) techniques designed to assist with decision-making, e.g. the analytic hierarchy process (ahp) [16] or the technique for order preference by similarity to ideal solution systems (topsis) [17] combined with simple sebestyén, somogyi, szőke, and utasi hungarian journal of industry and chemistry 50 additive weighting (saw) [18], can be used as well [19]. these hierarchical methods (topsis, saw and ahp) rank the examined parameters which may be useful when deciding between options of individual investments but are problematic in terms of adapting them to the decision-making process with regard to development strategies of the settlements. the sustainable development of energy, water and environment systems (sdewes) city sustainability index was developed to overcome the disadvantages and limitations of other measures with regard to benchmarking the performance of cities in terms of energy, water and environment systems. so far a list of 58 cities assessed by the sdewes index can be accessed online on the sdewes centre homepage [20]. also, articles concerning the benchmarking of 12 south east european cities (such as athens and belgrade) [21], 22 mediterranean port cities (e.g. barcelona and venice) [22], and a further 18 south east european cities (including budapest and pécs) [23] were published, and the inventory will no doubt be expanded upon in the near future. in this paper two cities were evaluated by using the composite sdewes index and to test the method itself. veszprém and zalaegerszeg are two hungarian county seats of roughly the same size and population, both are environmentally conscious, and are aiming to become environmentally friendly, liveable and sustainable cities. veszprém is near lake balaton with a population of around sixty-two thousand people and and a surface area of 126.9 km2. the city has won the climate star award † [24] and aims to become an eco-city. in its energy strategy [25] the following objectives were set by 2026:  20% of the energy demand should be satisfied by renewable energy resources while the energy renovation of public and residential buildings should be 70% complete resulting in a reduction in greenhouse gas (ghg) emissions of 25%;  35% of transportation has to be conducted by means of public transport with environmentally friendly vehicles that are less than 10 years old and 10% of the vehicle-kilometres should be undertaken by bicycles;  increasing the proportion of green areas to 25 m2/capita and 60% of rainwater should be reused in some way. zalaegerszeg is situated in the west of the country and consists of sixty-two thousand inhabitants and a surface area of 100 km2. since the millennium its urban development strategies have focused on becoming a “sustainable city”. in the strategy formulated in 2014 † the climate star award was founded by the climate alliance with the aim of demonstrating how climate protection initiatives can be implemented from the grass roots up [24]. cities with initiatives in the fields of sustainable energy, mobility, consumption, urban and regional development, and citizen involvement may apply for the call in four categories. [26] a major goal was to improve energy efficiency by 20% while producing more than 20% of its energy using local renewable resources by 2030. this would result in a reduction of 36% in terms of energy-related costs. taking 2005 as a base the ghg emissions should be reduced by 20% by 2030 while the particle pollution pm10 is planned to be mitigated by 10% by 2023. besides achieving these indicators, the city council aims to create and strengthen its image of being an environmentally conscious, modern and sustainable green city. 2. experimental the sdewes index consists of 7 dimensions and 35 main indicators (table 1). the indicators of each dimension are explained in detail in ref. [21]; only those that need further clarification or some sort of adjustment due to problems concerning the access of data are highlighted in this paper. the data for each indicator were normalised according to the min-max method [27]. depending on whether the lower or higher values are more desirable, either eq. (1) or (2) is used [21-22]. an example of the first case, i.e. when lower values are favourable, would be co2 emissions, while the normalised data for the number of local universities would be calculated by eq. (2). since the leader (��,����� = max���,��) equals 1 and the laggard (��,����� = min���,��) 0, if only two cities are compared and the values are identical, the denominator would become 0. to avoid this ��,����� should be set to 0 for such cases. another solution would be to include further cities in the benchmark. ��,����� = ���,������max���,��� �min���,���max���,��� (1) ��,����� = ���,������min���,��� �max���,���min���,��� (2) where: i – normalised value of the indicator, x – dimension number, y – indicator number within a dimension, cj – jth city, i – data input before normalization. value aggregation is done according to sdewes���� = ∑ ∑ �� � ��� ��,����� � ��� , (3) where ∑ �� = 1� ��� and αx is the weight of the xth dimension. the sdewes index of the jth city is calculated by a double summation, where α1 and α5 are 0.22 since these dimensions include energy and co2 emissions data. other dimensions are weighed less (αx=0.11) as they are not directly related to the sustainable energy action plan [21-22]. adapting the sdewes index 45(1) pp. 49–59 (2017) 51 table 1. the dimensions and indicators [21-23]. dimensions d1: energy consumption and climate d2: penetration of energy and co2-saving measures d3: renewable energy potential and utilization d4: water and environmental quality d5: co2 emissions and industrial profile d6: city planning and social welfare d7: r&d, innovation and sustainability policy in di ca to rs energy consumption of buildings [mwh] sustainable energy action plan (seap) solar energy potential [wh/m2/day] domestic water consumption [m3/capita] co2 emission of buildings [t co2] price of a public transport ticket [eur] r&d and innovation policy orientation energy consumption of transport [mwh] combined heat and power-based district (h/c) wind energy potential [m/s] water quality index [/100] co2 emissions of transport [t co2] urban form and protected sites national patents in clean technologies total energy consumption per capita [mwh/capita] energy savings in end-usage (buildings) geothermal energy potential [mw/m2] annual mean pm10 concentration [µg/m3] average co2 intensity [t co2/mwh] gdp per capita [ppp$ national] local public/private universities heating degree days (hdd) [day °c] density of the public transport network renewable energy usage for electricity [%] ecological footprint [gha/capita] number of co2-intense industries inequality adjusted wellbeing (hpi) national hindex of scientific publications cooling degree days (cdd) [day °c] efficient publiclighting armatures biofuel share in transport [%] biocapacity [gha/capita] airport carbon accreditation (levels) tertiary education rate (national) reduction target for co2 emission reduction (2020) 2.1. data of veszprém and zalaegerszeg as of october 2017, neither of the cities are signatories of the covenant of mayors movement, therefore, alternative sources of data had to be found. besides the sources suggested by the developer of the index, the energy and integrated city development strategies were used to retrieve data. necessary changes and the simplification of the original method is explained in detail below. 2.1.1. energy consumption and climate (d1): the energy consumption of buildings (municipal, residential and commercial) and transportation (public, private and the municipal vehicle fleet) are indicators on their own (table 2) but also included in terms of the total energy use per capita [21]: � �(��) = �∑ �b � ��� �∑ �� � ��� ��g��d� ����� (4) where  e – total energy consumption (mwh),  p(cj) – population of the jth city (capita),  eb – energy consumption of buildings (1: municipal, 2: residential and 3: commercial) (mwh),  et – energy consumption of transport (1: public, 2: private and 3: municipal vehicle fleet) (mwh),  eg – energy consumption of public lighting (mwh),  ed – energy consumption of industry (mwh). the energy consumption of transport was calculated based on the number of vehicles registered according to the energy strategies of the cities [25-26] by presuming an average mileage of 15,000 km/year and average consumption of 7.5 l/100 km [25]. the energy content of diesel and gasoline was assumed to be 10.83 kwh/l and 8.89 kwh/l, respectively. data for commercial buildings are only included in the total energy consumption indicator as the consumption of the service sector and industries was not collected separately by the cities. as for the municipal vehicle fleet, due to a lack of data for veszprém, this had to be neglected for both towns. it has to be noted that the data for veszprém were from between 2007 and 2009 as stated in the strategy while for zalaegerszeg information sebestyén, somogyi, szőke, and utasi hungarian journal of industry and chemistry 52 could only be obtained from between 2012 and 2013. in later documents, only improvements are mentioned, newly obtained data on overall consumption is not stated. monitoring the energy consumption of public buildings and lighting is an issue for both cities that needs to be solved. 2.1.2. penetration of energy and co2-saving measures (d2): neither of the cities have a sustainable energy action plan (seap) as of 2017 [31], therefore, both received zero for the first indicator (table 3) though veszprém is currently in the process of creating its sustainable energy and climate action plan (secap). in the case of veszprém, a cogeneration plant was recently installed [29] while there are only plans for such a system in zalaegerszeg (though one district heating system operates using geothermal energy) [30]. energy savings have been accomplished and are continuously implemented in both cities by renovating public buildings and installing photovoltaic systems, e.g. on the flat roofs of a grammar and primary school in veszprém and on the mayor’s office in zalaegerszeg (the performance of which can be accessed online from the webpage of the city). nonetheless, there is no building with net zero co2 emissions, that is why both cities received 1 point for the ‘energy savings in endusage’ indicator. the difference in size of the cities does not necessitate different types of public transport; both zalaegerszeg and veszprém have local bus routes that are operated by the same regional bus company. further points could have been allocated for tram and subway lines (2 for existing, 1 for planned) and an extra point would have been given to the city with the longest tram/subway network [20]. led technology is considered an efficient public lighting solution (1 point) and an additional point can be gained if solar energy is used to power armatures. recent investments were made in both cities to improve the energy efficiency of public lighting after the introduction of the cited strategies. 2.1.3. renewable energy potential and utilization (d3): the renewable energy potential is highly dependent on the location, topology and geology of the area but the local government can have a strong influence on the utilisation of these resources. while regional data could be gathered for the potentials, national data [32] had to be used for the share of renewable sources in terms of electricity production and biofuel use in transport indicators because there was no reliable local information for veszprém (table 4). for zalaegerszeg biogas from the regional municipal wastewater treatment plant is converted to provide the local buses with liquid fuel. based on a presentation [33] the tanked volume is known for 2015, therefore, the biofuel utilization in terms of transportation was modified accordingly. to attain an accurate comparison the national value for 2015 was considered in the case of veszprém. table 4. the data of the renewable energy potential and utilization (d3) indicator veszprém zalaegerszeg solar energy potential [wh/m2/day] 3,425 [25] 3,014 [26] wind energy potential [m/s] 4.921 [34] 3.505 [34] geothermal energy potential [mw/m2] 60 [35] 90 [35] renewable energy usage for electricity [%] 8.76 [32] 8.76 [32] biofuel utilization in terms of transport [%] 4.15 [32] 5.46 [32-33] table 2. the data of energy consumption and climate (d1) indicator veszprém zalaegerszeg energy consumption of buildings [mwh] 309,393 [25] 313,434 [26] energy consumption of transport (mwh] 225,479 [25] 217,228 [26] total energy consumption [mwh/capita] (in brackets: population) 19.50 (61,721) [25] 11.65 (59,499) [26] number of heating degree days (hdd) 2,890 [28] 2,850 [28] number of cooling degree days (cdd) 1,619 [28] 1,607 [28] table 3. the data of penetration of energy and co2saving measures (d2) indicator veszprém zalaegerszeg sustainable energy action plan (seap) 0 [31] 0 [31] combined heat and power-based district heating/cooling system 2 [25] 1 [26] energy savings in endusage (buildings) 1 [25] 1 [26] density of public transport network 1 [29] 1 [30] efficient public lighting armatures 2 1 adapting the sdewes index 45(1) pp. 49–59 (2017) doi: 10.1515/hjic-2017-0049 53 2.1.4. water and environmental quality (d4): there were no available local data for the domestic blue water footprint, ecological footprint and biocapacity, therefore, national values were applied in the calculation. air quality is only described in terms of the pm10 concentration [20]. the water quality index was ambiguous as the articles [21-22] referred to the indicator as drinking water quality but the water quality index (watqi) refers to natural water quality [36]. the index relies on the global database of the united nations gems/water programme and includes five indicative parameters: dissolved oxygen, ph, conductivity, total nitrogen and total phosphorous. unfortunately the watqi of countries are only available for 2008 [37], from 2012 the water quality index was replaced with access to sanitation and drinking water in terms of the aggregated environmental performance. it has to be noted that in the case of hungary the drinking water is supplied from underground reservoirs that are only linked indirectly to surface waterbodies while in other countries these serve as direct sources of drinking water. thus using water quality indices for inland water bodies may be good indicators of safe access to water. 2.1.5. emissions and industrial profile (d5): as in the case of the first dimension the emission values of the commercial buildings and municipal vehicle fleet were unavailable, therefore, these could not be included in the calculation. information on co2-intense industries was gathered by going through an online company database [41]. the indicator carbon accreditation of airports became zero for both cities for different reasons: veszprém has no airport and the one near zalaegerszeg has no accreditation. since the first case means no emissions while in the second case the existing emissions are not measured, the purpose of the indicator is not fully achieved. the original aim was to include the emissions of the airports in some way in the sdewes index as the seaps do not take them into consideration [21]. table 6. the data of co2 emissions and industrial profile (d5) indicator veszprém zalaegerszeg co2 emissions of buildings [t co2] 87,882 [25] 82,579 [26] co2 emissions of transport [t co2] 71,711 [25] 70,282 [26] average co2 emissions [t co2/mwh] 0.393 0.292 number of co2 intense industries 4 [41] 4 [41] carbon accreditation of airport [levels] 0 0 [42] 2.1.6. city planning and social welfare (d6): two indicators need further explanation (table 7). the prices of public transport were introduced in ref. [21] instead of the share of public transport in terms of total passenger kilometres [22], the latter not being accessible in all cases. the more a single ticket costs, the less likely people will choose public transport. on the other hand, easy access to public transport should result in positive externalities such as cleaner air and less traffic jams, by and large a more liveable city. the urban form and protected sites indicator is an aggregation of several factors (table 8): compact city form (whether it is mono or polycentric), urban green areas and surrounding green corridors are evaluated. to determine the compactness of the cities, the energy consumption of transport compared against population density was chosen, as a compact city can be described as of high population density [47] and because of the short distances cars are less likely to be used. thus the smallest value received 3 points while the highest received 1. urban green spaces were examined in table 5. the data of water and environmental quality (d4). indicator veszprém zalaegerszeg domestic water consumption [m3/capita] 7 [38] 7 [38] water quality index [/100] 92 [37] 92 [37] average air quality pm10 [µg/m3] 23.59 [39] 29.60 [39] ecological footprint [gha] 2.9 [40] 2.9 [40] biocapacity [gha] 2 [40] 2 [40] table 7. the data of city planning and social welfare (d6) indicator veszprém zalaegerszeg price of public transport ticket [eur] (1 eur = 310 huf) 1.07 [43] 1.10 [43] urban form and protected sites 1 2 gdp per capita [ppp$ national] 25,068.9 [44] 25,068.9 [44] inequality adjusted well-being (hpi) 4.3 [45] 4.3 [45] tertiary education rate (national) [%] 21 [46] 21 [46] sebestyén, somogyi, szőke, and utasi hungarian journal of industry and chemistry 54 comparison with the hungarian county seats [48]: 0-30 m2/capita: 1 point, 30-50 m2/capita: 2 points and over 50 m2/capita: 3 points. green corridors were also assessed on a county basis [49] instead of using the suggested gisbased method [20]. the categories were determined from 1-3 by only taking the green corridor areas of hungarian counties into consideration. 2.1.7. r&d, innovation and sustainability policy (d7): results for the seventh dimension are listed in table 9. the number of public and private universities yielded an unexpected result for the two cities in question. universities seated in the town and those where only a faculty is based there were equally counted. if only those universities that are seated in the said city were taken into consideration, veszprém would have 2 versus 0 in zalaegerszeg. additional points were given if the university was listed in the scimago institutions rankings [53]. the energy strategy of veszprém envisions a 25% co2 emissions reduction by 2026, the basis being 2007 [25], while zalaegerszeg aims to achieve a 36% reduction by 2030, compared to 2012 [26]. to facilitate a comparison, goals for 2020 were calculated by linear interpolation. 3. results after processing the necessary calculations, the sdewes indices of both veszprém and zalaegerszeg were 1.54. as is clear in fig.1, the values are integers and, except for one case (d5), veszprém achieved better or equal results. it also has to be noted that on several occasions the difference between the data was very small. still, the better city was awarded with 1 and the worse value with zero in the normalisation process. in order to eliminate this problem, a third city was included in the benchmark. ohrid was chosen as the size of this historical macedonian town is similar to the other two and all data were available from kilkis [21]. also, this was the only city in this comparison that had no seap. as an alternative solution the ‘average south east european (see) city’ from the same article was included to put the two hungarian cities to the test to see where they would be in the ranking of the see cities of that sample. the inclusion of these two examples changed the order of the cities (table 10). while the results of both veszprém and zalaegerszeg improved, zalaegerszeg gained more from the inclusion of another city from a different country in the benchmark. the reason for the improvement of the indices is that in several cases the national data had to be included in the calculation and hence, the indicator became 0. while both veszprém and zalaegerszeg gained points from increasing the sample size, the accumulated increase was larger for zalaegerszeg (10.03 compared to 8.12). the arrows show in which direction the indicators changed. in the case of veszprém, data for d3 and d6 decreased but not significantly, for zalaegerszeg there was no change in d3 and only a slight decline in d5. the sdewes index results are similar, the difference between the highest and lowest values is 0.37. nonetheless, heterogeneity exists with regard to the individual indicators. results for each dimension are visualised in fig.2. both hungarian towns performed well concerning d1 (energy consumption and climate), d4 (water and environmental quality) and d7 (r&d, innovation and sustainability policy), while there is room for improvement in the fields of co2-saving measures and city planning. the average see city, on the other hand, possesses lower values regarding energy consumption and environmental and water quality. table 8. data for grading urban form and municipal management veszprém zalaegerszeg urban form and protected sites 1 2 compact city form 1 3 monocentric x x polycentric population density [capita/km2] 486.38 580.99 urban green spaces 1 2 urban park intensity [m2/capita] 21 [29] 34.6 [30] green corridors 1 1 protected sites x x national park/ramsar x x table 9. the data of the r&d, innovation and sustainability policy (d7) indicator veszprém zalaegerszeg r&d and innovation policy orientation 3 [50] 2 [50] national patents in clean technologies 2.5 [51] 2.5 [51] number of public/private universities (city) 3 [52-53] 5 [52-53] h-index of scientific publications 301 [54] 301 [54] reduction target for co2 emissions (2020) [%] 18 [25] 16 [26] adapting the sdewes index 45(1) pp. 49–59 (2017) 55 figure 1. results of the first comparison on radar charts. 4. conclusion the process of gathering data revealed that both veszprém and zalaegerszeg need to collect and measure data related to energy efficiency and other indicators of sustainable development more precisely. creating a database of detailed information on energy use, co2 emissions and use of renewable sources which is regularly updated would help to achieve the ambitious goal of becoming a sustainable city within a relatively short timespan. also, the development of a seap or secap and becoming a member of the covenant of mayors would be advantageous and for which veszprém has started taking steps. based on the dimensions of the sdewes index, veszprém needs to improve in terms of d3 and d6. the individual indicators highlight that the energy consumption of public transport could be reduced, based on the example of zalaegerszeg, and also utilization of renewable energy should be improved. in terms of city planning and social welfare the number and area of urban parks can be increased more easily than that of protected sites. establishing green areas is included within the urban development strategy of the city [29], so improvements may be expected in terms of this indicator. also, progress in developing a compact city form is anticipated based on the plans to reform the public transport system and relocate the central bus station to next to the railway station [29]. in the case of zalaegerszeg, dimensions d2, d3 and d6 are lower. energy-saving measures could be improved by constructing a cogeneration plant to improve the penetration of district heating, using solar panels in public lighting, and also using the wastewater heat to facilitate the full utilization of biogas as a liquid biofuel [55]. in the case of d3, the potential of solar and wind energy cannot be increased and no information concerning the local use of renewable energy resources in terms of electricity was found. as for d6 the same suggestions as in the case of veszprém can be made to increase the values of the individual indicators. it has to table 10. results of calculating the sdewes index veszprém zalaegerszeg ohrid average see city d1 3.53 ↑ 3.93 ↑ 3.78 1.43 d2 2.45 ↑ 0.95 ↑ 2.00 3.50 d3 1.99 ↓ 2.00 1.60 3.12 d4 4.17 ↑ 3.43 ↑ 2.45 1.16 d5 2.28 ↑ 2.79↓ 3.00 2.45 d6 0.98 ↓ 1.95 ↑ 4.00 3.65 d7 3.72 ↑ 3.97 ↑ 1.08 1.75 sdewes 2.74 ↑ 2.83 ↑ 2.71 2.47 sebestyén, somogyi, szőke, and utasi hungarian journal of industry and chemistry 56 figure 2. results of the second comparison on radar charts. be pointed out though that the use of the ticket price for public transport resulted in an unjust outcome: since in ohrid there is no means of local public transport, this indicator became zero, which could also mean that transportation is free. therefore, ohrid will always receive the highest value in terms of the process of normalisation as long as there are no local buses in the city. in terms of the process of evaluating the two hungarian county seats, the benchmarking method was assessed as well. without a doubt, the sdewes index has its benefits. it uses environmental, economic and social indicators, gives credit to co2 reduction goals and also considers the possible use of renewable resources. also, human resources are included presuming that higher education and research and development seek to achieve sustainability. on the other hand, the authors identified some drawbacks, too. the first and the fifth dimensions both focus on energy consumption and co2 emissions. since these data strongly correlate with each other, the inclusion of both measures leads to redundancy. also, these two dimensions are weighed more than the others, therefore, energy-related information outweighs other aspects of sustainability. furthermore, some of the parameters favour smaller cities over larger ones and vice versa. for example if the absolute values of energy consumption of a small city and a capital are compared, the small city will undoubtedly achieve a better result. figure 3. the evaluation intervals of sdewes index indicators adapting the sdewes index 45(1) pp. 49–59 (2017) 57 an example of the opposite would be a city with an accredited airport (aca 3) as opposed to a town with no airport (small towns do not always have airports). similarly in a capital, where subway and tram lines are at one’s disposal, the density of the public transport network would be high while it would be uneconomical to have trams in a smaller town where the bus lines are sufficient. to overcome the problem of favouring results of cities of different sizes, using data which is proportional to area or population is suggested wherever possible. another problem was that the scoring of the qualitative indicators such as the urban form and protected sites was not always clear. if the sdewes index is to be used widely then these calculations have to be made transparently and be well documented. due to the nature of the min-max method, small differences may be magnified and large differences may diminish. also, as the index requires certain data that can only be obtained on a national level, the comparison between cities in the same country is somewhat limited. a solution to this problem may be to include towns from different countries and to choose a range (by including more than two cities) in such a way that provides balanced scales in terms of the indicators. while normalisation facilitates the inclusion of values on different scales, the min-max method makes it difficult to compare the results of two sets of cities. at present, the extremes are defined by the individual parameters of the cities chosen to be included in the benchmark (fig.3). in terms of another comparison with a different batch of cities (that can have a common set as with the previous version) the two evaluation intervals may not be equal (��1 ≠ ��2 since �� ∈ ��2 and �� ∉ ��1). as the two extremities are different in the two benchmarks, the results cannot be compared to each other. in the case of extremities a change in the order might appear as was the case in this paper. including the average of a different batch of cities (given that the average of any parameter is not equal to that of either city) may resolve the limitations of the min-max method but only momentarily. since the ranking is dynamic and changes as the cities develop, the average sdewes index of a previous time period will not provide relevant information with regard to the current situation concerning the sample from which the average city was created and neither on the sample of two cities one wanted to expand. besides the obvious solution of having a sample size of at least three cities, the authors suggest the following: two artificial sets of parameters should be created to serve as absolute extremes of the sdewes index. the worst case scenario is referred to as the ‘horror city’ and the best case scenario is named ‘sdewes city’ after the index itself. the legend for fig.3 is as follows:  ai, bi, ci – the measured/real indicator values of the analysed cities in the first calculation.  si – the measured/real indicator value of the city to be included in the second calculation.  ii1 – the evaluation interval, when the new city’s value is between the other indicator values.  ii2 – the evaluation interval, when the new city’s value falls outside of the other indicator values.  zi – the theoretical minimum value of indicator i, the ‘horror city’.  wi – the theoretical maximum value of indicator i, the ‘sdewes city’. to resolve this problem with regard to the evaluation intervals changing from time to time, the minimum and maximum values of each indicator must be determined in a way that the examined cities could be included in the evaluation intervals: ��1 = ��2 = ��� (5) �� ∈ ��2 , �� ∈ ��1 ... �� ∈ 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http://www.scimagojr.com/countryrank.php, accessed: 4th april 2016 [55] baranyák, z.; kontra, j.; kovács, a.; havas, m.; jani, i.; mayer, z.; pálfi, sz.; garbai, l.; kovács, k.: zalaegerszeg smart city 2050, goodwill consulting, 2016 hungarian journal of industry and chemistry vol. 48(1) pp. 61–65 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-09 nonlinear magnetic properties of magnetic fluids for automotive applications barnabás horváth*1 and istván szalai2 1institute of physics and mechatronics, university of pannonia, egyetem utca 10, veszprém h-8200, hungary 2institute of mechatronics engineering and research, university of pannonia, gasparich márk utca 18/a, zalaegerszeg h-8900, hungary the external magnetic field required to activate a magnetic fluid in an industrial application is sufficiently large that magnetization is no longer a linear function of the external field strength, i.e. magnetic fluids exhibit nonlinear characteristics. the aim of our research was to develop a measuring system which is capable of determining the nonlinear ac susceptibility of magnetic fluids at discrete frequencies and in the presence of a high-intensity driving magnetic field. the measurement of susceptibility is based on the determination of the change in frequency of a low-intensity field, which is generated by an lc oscillator. the application of sinusoidal excitation to the material results in a variation in the susceptibility that modulates the frequency of the measured low-intensity field and in the appearance of higher-order harmonics of the driving field. the higher-order components of the nonlinear ac susceptibility are extracted from the measured response by fourier analysis. by applying the measuring system, the nonlinear susceptibility of water-based ferrofluids (ferrotec’s emg 700) and its dependence on the magnetic field strength were investigated. keywords: ac susceptometry, nonlinear susceptibility, ferrofluid 1. introduction regarding automotive applications, one of the most important characteristics of magnetic fluids is their behavior in magnetic fields. the majority of these applications are for seals [1], vibration damping [2] and torque transmission [3]. in most cases, the magnitude of an external magnetic field required to activate a fluid is on the scale where the m magnetization is no longer a linear function of the h field strength. this means that magnetic fluids show nonlinear characteristics, and the χ = ∂m/∂h susceptibility depends on the magnetic field strength. in the case of magnetic fluids, the nonlinearity is the result of two effects: normal saturation (alignment of the magnetic dipole moments) and formation of structures (particle chains). the latter influences the susceptibility as the magnetic field shifts the equilibrium between the structures with different dipole moments (single particles and particle chains of different sizes). in a weak time-varying he(t) = he0 sin(ωt) magnetic field (where t denotes the time and ω = 2πf represents the angular frequency), the magnetization also changes periodically but lags behind the magnetic field because reorientation of the magnetic dipole moments is not instantaneous. in this case, the dynamic magnetic susceptibility can be defined as a complex quantity χ∗(ω) = *correspondence: bhorvath@almos.uni-pannon.hu χ′(ω) − iχ′′(ω). the real part, χ′, is related to the reversible magnetization process and it is in-phase with the alternating field. within the low-frequency limit, (f → 0) χ′ approaches the initial gradient of the steady-state magnetization (initial dc susceptibility). if f → ∞, the reorientation of the magnetic dipole moments cannot follow the alternating field and χ′ approaches zero. the imaginary, out-of-phase component, χ′′, is proportional to power losses due to energy absorption from the field and peaks at a characteristic frequency, fc. however, if the amplitude of the alternating field is sufficiently large, higher-order harmonics appear in the magnetization due to the nonlinear characteristics. in this case, the real part of the alternating current (ac) magnetic susceptibility is: χ′ = χ0 + χ2ω cos(2ωt) + χ4ω cos(4ωt) + . . . , (1) where χ0 denotes the base component, and χ2ω and χ4ω represent the amplitude of the secondand fourth-order harmonics, respectively [4]. a similar equation holds for the imaginary component, χ′′. in this work, only the harmonics of the real part are considered, because the nonlinear susceptibility at frequencies much higher than the characteristic frequency of the magnetic fluid is investigated, where the imaginary part is very close to zero. by taking magnetic fluids into consideration, the amplitudes of sixthand higher-order harmonics are so small https://doi.org/10.33927/hjic-2020-09 mailto:bhorvath@almos.uni-pannon.hu 62 horváth and szalai pc labview md analyzer oscillator c daq gpib power f(t) l amplifier fm = 957 khz hm0 = 0.022 ka/m measuring field helmholtz coil fe = 1 200 hz he0 = 0.2 3.0 ka/m driving field he(t) hm(t) fft χ2 χ4 figure 1: a block diagram of the nonlinear magnetic measuring system. that they can be neglected. in alternating magnetic fields, only the even-order harmonics appear, because the magnetization of magnetic fluids exhibits inversion symmetry with respect to a change in the direction of h. should a symmetry-breaking dc bias field be superimposed on the ac magnetic field, both the oddand even-order harmonics appear. as the nonlinearity is caused partly by structure formation, the components of the nonlinear susceptibility and their ratios are sensitive to changes in the structure of magnetic fluids. numerous studies have discussed the theoretical description of the nonlinear susceptibility of magnetic fluids [4–7], but experimental results are rather scarce. nevertheless, nonlinear magnetic susceptibility measurements are quite useful for the study of magnetic fluids and provide additional information besides linear ac susceptometry. if the linear response to small-amplitude fields is measured, the relaxation processes of the magnetic dipoles can be studied. however, by applying the nonlinear method, it is possible to obtain information about the structural evolution of an activated magnetic fluid. the aim of our work was to develop a measuring system which is capable of determining the nonlinear ac susceptibility of magnetic fluids at discrete frequencies in the presence of external magnetic fields. the dependence of the 2ndand 4th-order nonlinear ac susceptibility of ferrofluids on the magnetic field strength was investigated by the developed susceptometer. 2. experimental 2.1 nonlinear measurement method and setup the measurement method of susceptibility is based on our nonlinear dielectric system [8], which is adapted to magnetic measurements. with this method, the real part of complex ac susceptibility is determined from the change in frequency of a low-intensity measuring field (hm). an air core solenoid (l) was filled with the sample of fluid, and the inductance determined the frequency of the sinusoidal measuring field generated by an lc oscillator (fig. 1). therefore, any change in the susceptibility of the sample caused the resonance frequency fm to shift. the susceptibility of the sample was measured at this base frequency. inside the solenoid, the amplitude of the measuring field is so small (hm0 = 0.022 ka/m) that within this region, the magnetization curve of the fluid can be regarded as linear, thus no significant structural change can be expected. the oscillator which generated the measuring field was a colpitts-type parallel lc circuit. the active feedback element was a double triode vacuum tube (ecc88). the capacitor bank c was composed of high-quality silver mica capacitors with a low temperature coefficient. the measuring coil l was connected in parallel with the capacitor block, and by changing the coil, the base frequency of the oscillator could be varied. with different inductors, the measuring frequency was set to discrete values, namely 153 khz, 590 khz and 957 khz. the dimensions of the measuring coils were identical: 25 mm in length with an inner diameter of 7.1 mm. they were composed of enameled copper wires of different sizes and wound on coil formers made of plexiglass. the resonance frequency of the lc oscillator was measured by a hewlett packard 53310a modulation domain (md) analyzer. the relationship between the resonance frequency and susceptibility of the sample was determined by calibration using different materials of known susceptibility. a high-intensity driving field (he) was generated by a pair of helmholtz coils which were placed around the measuring coil. the axis of the helmholtz coil and, therefore, the direction of the field, were parallel to the axis of the solenoid. the upper limit on the amplitude of the driving magnetic field with the current setup was he0 = 6.4 ka/m, which was two orders of magnitude greater than the amplitude of the measuring magnetic field. the maximum of he0 depended on the frequency of the field: as the frequency increased, the maximum of he0 decreased. the uniformity of the magnetic field strength in the volume of the sample was better than 1 %. the helmholtz coil was driven by a high-current function generator, which consisted of a labworks pa-138 linear hungarian journal of industry and chemistry nonlinear magnetic properties of magnetic fluids 63 power amplifier and a signal source. the input signal of the amplifier was provided by a multifunction data acquisition (daq) card (national instruments pci-6052e). any arbitrary waveform could be generated by the signal generator, and the waveform offset by a dc value. under the influence of the high-intensity driving field, the susceptibility of the sample changes, therefore, the frequency of the measuring field was modulated. if the driving field is sinusoidal, then the time-domain susceptibility response will contain the higher-order harmonics of the field. the 2ndand 4th-order components of the nonlinear ac susceptibility were extracted from the measured response by fourier analysis. the fast fourier transform (fft) algorithm was implemented using custom-developed labview software, which provided control and data acquisition functions of the measuring system. 2.2 supplemental measurements during the nonlinear measurements, the change in susceptibility relative to the zero-field susceptibility was measured, so the real part of the ac susceptibility of the fluid at the base frequency had to be determined by another method. for this purpose, a spectrum was obtained within the frequency range of 200 hz 1 mhz. the initial dc susceptibility of the ferrofluid was determined from the dc magnetization curve. the ac susceptibility in zero field was measured by an inductive method where the inductance of a solenoid filled with the sample was measured by an impedance analyzer (agilent 4284a). by determining the impedances of the empty air core solenoid and when it is filled with the sample, χ′ was calculated. the solenoid used for these measurements was the same as the measuring coil of the nonlinear setup. 2.3 material by applying the nonlinear magnetic measuring system, the nonlinear properties of ferrotec’s emg 700 ferrofluid were investigated. this material is water-based and contains magnetite particles with a nominal diameter of∼ 10 nm. the volume concentration of the particles is 5.8 %(v/v). the fluid is stabilized by an anionic surfactant. for the measurements, glass-tube sample holders with an inner diameter of 3.1 mm were filled with the ferrofluid. the length of the tube extended beyond the length of the measuring coil at both ends. the volume of the sample was 0.49 cm3. 3. results and discussion according to the dc magnetization curve, the initial dc susceptibility of the emg 700 ferrofluid was χdc = 12.57. this is the limiting value of the real part of the complex susceptibility if f approaches zero. the ac susceptibility spectrum of the ferrofluid is shown in fig. 2. relaxation of χ′ was observed within the lower frequency 10-1 1 10 102 103 104 105 106 0 3 6 9 12 15 c = 0.54 cs = 12.55 f (hz) c' he = 0 fc = 39 hz figure 2: relaxation of the real part of ac susceptibility in the absence of a driving magnetic field (hollow symbols) by applying the cole-cole equation (solid line) together with the estimated parameters of the relaxation. region. the experimental frequency-dependent susceptibility data was fitted by the cole-cole equation (solid line in fig. 2). this relaxation model is suitable for describing the response of dipoles to an alternating field should the relaxation not be ideal (e.g. if instead of a single relaxation time, a distribution of relaxation times exists). the fitting process yielded the static (f → 0) χs = 12.55 ± 0.07 and infinite frequency (f → ∞) χ∞ = 0.54±0.02, susceptibilities and the so-called central characteristic time of the relaxation (τ0). the reciprocal of the characteristic time yielded the characteristic frequency fc = 1/(2πτ0), which is 39 ± 5 hz for the ferrofluid emg 700. the spectrum shows that relaxation occurs at much lower frequencies than the base frequency of the nonlinear susceptibility measurements (fc = 39 hz vs. fm = 957 khz). at the high-frequency end (∼1 mhz) of the spectrum, χ′ decreased to ∼ 0.8 and changed slightly as the frequency increased in this region. at such a large distance from fc, the imaginary part of the complex susceptibility was close to zero, thus it is justified to consider only the real part (see eq. 1). to investigate the nonlinear ac susceptibility, sinusoidal excitation was applied. the frequency of the driving magnetic field was changed from 1 hz to 200 hz with an amplitude as high as he0 = 3 ka/m (depending on fe). the nonlinear ac susceptibility was measured at 957 khz in all cases. at he0 = 0, the real part of the ac susceptibility of the ferrofluid at the measurement frequency of fm = 957 khz was χ′ = 0.78. fig. 3 shows a typical susceptibility response of the ferrofluid emg 700 at an excitation frequency of fe = 1 hz and using different magnetic field strengths. it can be seen that the response contained higher-order harmonics. the magnetic field always caused a decrease in the susceptibility (because of the saturation) regardless of its direction. this inversion symmetry was expressed by the fact that the susceptibility response during the first half period 48(1) pp. 61–65 (2020) 64 horváth and szalai 0.0 0.5 1.0 1.5 2.0 0.63 0.66 0.69 0.72 0.75 0.78 0.81 c'(t) he0 = 0.7 ka/m he0 = 1.1 ka/m he0 = 1.4 ka/m t (s) c' he(t) -1 0 1 2 3 4 5 6 7 h e ( ka /m ) figure 3: the susceptibility response of the ferrofluid emg 700 at various driving field amplitudes (fe = 1 hz). of he(t) was the same as during the second half even if the direction of the field was reversed. therefore, the maxima of the susceptibility responses were always 0.78, which corresponded to the point when he(t) intersected the value zero. the dependence of the 2ndand 4th-order harmonics (χ2ω and χ4ω in eq. 1) on the magnetic field strength extracted from the measured response is shown in figs. 4a and 4b. at a given driving field strength, χ2ω was one order of magnitude larger than χ4ω . the amplitude of both components increased as the magnetic field strength rose (at a given driving field frequency). this occurred be0.00 0.02 0.04 0.06 0.08 0.10 0.0 0.5 1.0 1.5 2.0 2.5 3.0 0.000 0.005 0.010 0.015 c 2 w fe = 1 hz fe = 40 hz fe = 100 hz fe = 200 hz a b c 4 w he0 (ka/m) figure 4: the dependence of the components χ2ω (a) and χ4ω (b) of the nonlinear susceptibility of the ferrofluid emg 700 on the amplitude of the driving field at different driving field frequencies. cause at higher magnetic field strengths, the nonlinearity of the magnetization curve increased as the magnetization approached the saturation level. 4. conclusions a nonlinear magnetic measuring system was developed to determine the nonlinear ac susceptibility of magnetic fluids. the system was applied to measure the components of the nonlinear susceptibility of the water-based ferrofluid emg 700 up to the 4th order. it has been shown that by using the aforementioned system, it is possible to determine the dependence of the nonlinear susceptibility on the magnetic field strength. if the excitation frequency is varied, the relaxation of the nonlinear susceptibility can be also studied. our future aim is to investigate this relaxation and other types of ferrofluids (based on organic carrier and polydisperse fluids), moreover, to study the influence of the magnetite concentration on the nonlinear magnetic properties. acknowledgments this project was supported by the european union and co-financed by the european social fund. efop-3.6.216-2017-00002. references [1] ravaud, r.; lemarquand, g.: mechanical properties of a ferrofluid seal: three-dimensional analytical study based on the coulombian model, prog. electromagn. res. b, 2009, 13, 385–407, doi: 10.2528/pierb09020601 [2] sassi, s.; cherif, k.; mezghani, l.; thomas, m.; kotrane, a.: an innovative magnetorheological damper for automotive suspension: from design to experimental characterization, smart mater. struct., 2005, 14(4), 811–822, doi: 10.1088/09641726/14/4/041 [3] rizzo, r.: an innovative multi-gap clutch based on magneto-rheological fluids and electrodynamic effects: magnetic design and experimental characterization, smart mater. struct., 2017, 26(1), 015007, doi: 10.1088/0964-1726/26/1/015007 [4] wang, g.; huang, j.p.: nonlinear magnetic susceptibility of ferrofluids, chem. phys. lett., 2006, 421(4), 544–548, doi: 10.1016/j.cplett.2006.02.010 [5] huke, b.; lücke, m.: magnetic properties of colloidal suspensions of interacting magnetic particles, rep. prog. phys., 2004, 67(10), 1731–1768, doi: 10.1088/0034-4885/67/10/r01 [6] szalai, i.; nagy, s.; dietrich, s.: linear and nonlinear magnetic properties of ferrofluids, phys. rev. e, 2015, 92(4), 042314, doi: 10.1103/physreve.92.042314 hungarian journal of industry and chemistry https://doi.org/10.2528/pierb09020601 https://doi.org/10.1088/0964-1726/14/4/041 https://doi.org/10.1088/0964-1726/14/4/041 https://doi.org/10.1088/0964-1726/26/1/015007 https://doi.org/10.1016/j.cplett.2006.02.010 https://doi.org/10.1088/0034-4885/67/10/r01 https://doi.org/10.1103/physreve.92.042314 https://doi.org/10.1103/physreve.92.042314 nonlinear magnetic properties of magnetic fluids 65 [7] ivanov, a.o.; kuznetsova, o.b.: magnetic properties of dense ferrofluids, j. magn. magn. mater., 2002, 252, 135–137, doi: 10.1016/s03048853(02)00639-x [8] horváth, b.; szalai, i.: structure of electrorheological fluids: a dielectric study of chain formation, phys. rev. e, 2012, 86(6), 061403, doi: 10.1103/physreve.86.061403 48(1) pp. 61–65 (2020) https://doi.org/10.1016/s0304-8853(02)00639-x https://doi.org/10.1016/s0304-8853(02)00639-x https://doi.org/10.1103/physreve.86.061403 https://doi.org/10.1103/physreve.86.061403 introduction experimental nonlinear measurement method and setup supplemental measurements material results and discussion conclusions hungarian journal of industrial chemistry veszprem vol. 30. pp. 127 ~ 130 (2002) development for selective cesium removal from the evaporation concentrates of the pwr paks s. szoke, g. patzayandl. weiser (department of chemical technology, budapest university of technology and economics, h-1521 budapest, hungary) received: january 14, 2002 at the pressurized water reactor paks the diluted radioactive wastewater is converted to concentrate by evaporation and · d k h · d. i"d · th 1 · 134c 137c d 60c the evaporator bottom 1s store in tan s. t e most important ra tonne 1 es m ese so ut10ns are s, s an o. the volume reduction technologies like selective ion exchange for cesium and the ultrafiltration for cobalt may reduce the volume of the liquid waste and the burial costs. in our research we studied our granular potassium nickel hexacyanoferrate(li) as a cs-selective ion-exchanger. its capacity was depending on the preparation method, tem~erature of pretreatment and age of the ion exchanger. we investigated also the effect of metal ions ( fe2 +, fe3+, mj?+, mg +, ca2+, co2 +, np+, cu2+) on the cs-capacity in the presence of complex forming compounds citrate, oxalate and edt a. the cesium ion exchange capacity was increased in case of addition of inactive cobalt or nickel salts. additionally, we studied filtration, adsorption and ultrafiltration separation processes for cobalt removal. the results showed that only adsorption by active carbon could successfully be used for the cobalt removal from the evaporation concentrates. experiments w_ere also performed in our laboratory and at the pwr paks. keywords: cesium and cobalt removal, ultrafiltration, potassium nickel hexacyanoferrate(ii), selective ion exchange, adsorption, complex compounds introduction approximately 40000 m3 diluted liquid radioactive wastewater is generated yearly in the hungarian pressurized water reactor (pwr) at paks. at this time there is no selective waste collection. the collected liquid waste is the mixture of low or medium activity and/or salt content wastewater and often decontamination solution. the collected solutions are regularly concentrated by evaporation using naoh for stabilization of the sodium borates in the evaporation bottom and are stored in common stainless steel tanks. the major component of the concentrate is sodium borate, and the solution is alkaline (ph=l4). the final disposal of this waste is not solved. sodium borates are incompatible with the embedding matrix material (concrete). in addition the direct cementation of the radioactive waste results a final volume two-three times larger then the volume of the evaporator bottom. consequently it causes increasing burial cost. the major ingredients of the evaporation concentrates are sodium borate. sodium nitrate and sodium hydroxide. they contain long-lived radioactive isotopes ct34cs, 137cs and 60co) in ultra-low concentrations. because 75-90% of the radioactivity is due to cesium isotopes its selective separation before solidification is the most important step. the selective removal and accumulation of these long-lived radionuclides in a small volume ion exchanger reduces the volume of the buried radioactive waste and the cost of the final disposal. [11 it is well known that the heavy metal hexacyanoferrates {nickel-knifc. copper and cobalt­ kcofc) are selective cesium ion exchangers. the review of their properties and preparations can be found in [2]. some methods are known to stabilize and improve their capacity e.g. knifc loaded zeolite [3]. si02-· kcofc composite [4] etc. the aim of the present work is the investigation of the possible improvement of the selective cesium removal using granulated potassium nickel hexacyanoferrate(ii} ion exchangers and development of a suitable granular ion exchanger. in this process we investigated various preparation methods, the effect of other factors, such as temperature, age of the exchanger, and other chemical components present in the solution. the other important long·lived radionudide in the evaporation concentrate is 00co. it is present as contact information: e-mail: szoke-sz.ktt@chem.bme.hu; tel.:463~1945; fax.:463-19l.3 128 table 1 average chemical composition and radioisotope content of the evaporation concentrates of pwr paks ph na+ k" n03 h3bo, evaporated residue 134cs 137cs 60co concentration or specific activit g/dm' g/dm3 gldm' gldm3 gldm3 mbq/dm3 mbq/dm3 mbq/dm3 14 80 24 45 250 534 7.2 38.4 0.7 suspended matter, colloidal particles and in complex form. the dissolved cobalt can be removed by adsorption using for example charcoal [5] or montmorillonit [6]. in our research we investigated the removal of the suspended particulates of cobalt from the evaporation concentrate via filtration and ultrafiltration and the other forms via adsorption. laboratory experiments 1j rb i!!!di!llij18.6 g. ] rf !iimlll!!l!lili!ibl 40.5 i;l g nd •••bwml. i·"i·iiiib·· 59.2 ., i nb jl!la 12.8 0:: nf 23.0 0 20 40 60 removed(%) 80 fig.] effect of preparation techniques for cs-137 removal (r: reverse order of portioning of reagents, n: normal order of portioning of reagents; d: dehydration method, b: boiling-gel method, f: freeze-thaw method) 60% 50% 40% ., " " ~ 30% >4 20% 10% 0% 70 80 90 100 110 120 treatment temperature ( °c ) a mixture of the original evaporation concentrates of fig .l cs-137 removal capacity for treatment temperature the pwr paks was used in the laboratory experiments (table 1). three types of processes were examined, filtration (5 and 1 jlm pore size filter), adsorption with the effects of other factors active carbon and ultrafiltration (molecular weigh cut off 15000 dalton) for its removal development and testing of a cs-selective ion­ exchanger preparation of the ion-exchanger six different techniques were investigated for the preparation of a granular sorbent: freeze-thawing, boiling-gel and dehydration method using normal and reverse order of portioning of reagents (potassium hexacyanoferrate(u) and nickel sulfate solution). the capacity of the produced sorbents was tested by static method. .ion exchange measurement technique in static method 100 mg of the granular ion-exchanger was added to 200 cm3 of thermostated evaporation concentrate and stirred for an hour. then filtered with micropore filter paper. a nai (ti) detector and an 8000 channel emg-8ll0 gamma-spectrum analyzer before and after the handling measured the cs-content of a 100 cm3 sample. the measurement time was 2000 seconds. the results are summarized in fig.j. we found that the best cs sorbent is the "nd" granular product. temperature because the best cs-sorbent was prepared by drying (dehydration) we tried to optimize the treatment temperature of nd granular product. fig.2 shows the cs removal capacity as a function of the dehydration temperature. the optimum is found between 80 and 100 oc. storage time (age of the exchanger) the long-term stability of the product was depending on the temperature of dehydration. the sorbent that was handled at 90 oc was more stable than that at 80 oc. (see fig.3) complexing agents the evaporation concentrates contain complex forming compounds (oxalic acid, citric acid and edta) which decrease the sorbent ion exchange capacity. to minimize this effect by fixing these free complexing agents, in our next ion exchange experiments we applied as inactive reagents eight different metal salt {0.01 m salt concentration in every experiment). two of them caused a significant increase in the cesium ion exchange capacity; namely the nickel sulfate and the cobalt nitrate (fig.4). a 52.4 ~ 8 53. i ~ c 43.7 d 32.5 0 20 40 60 removed(%) fig.3 effect of storage time on cs-137 removal (a: handling at 90 oc two weeks later; b: handling at 90 °c; c: handling at 80 oc two weeks later; d: handling at 80 oc ) 70'/o 60% 50% 140'/o 0 b30'/o ~ 20% 10% 0% <i> z g c 0 (;;" z u.. 0 :::1 "' "' c: q q q ::0 ::0 (;;" u.. tw.atrrenfl! fig .4 effect of metal ions on the cs-137 capacity based on the static experiment results we concluded that the cs-removal capacity depended on the preparation method of the sorbent, the temperature of pretreatment, the storage time and the amonnt of complexing agents (edta, citric acid etc.) and the free complexing agents could be :'deactivated" by reacting with added nickel and cobalt compounds. column tests (dynamic tests) in the column experiments we used a glass ion­ exchange column (id = 5 nnn) filled with 2 cm3 granulated (0.125-0.2 nnn) potassium nickel hexacyanoferrate(il) prepared by dehydration method (nd). the initial flow rate was 50 cm3 (25 bv) per hour. the effluent concentrate was collected in 100 cm3 plastic flasks. the measurement technique was similar to the static test. 100 cm3 of solution was measured during 2000 seconds by nai(ti) detector and an 8000 channel emg-8110 gannna-spectrum analyzer. in our dynamic experiments we compared the efficiency of the cesium removal from the concentrate and from the pretreated (with cobalt-nitrate) concentrate. we found that the pretreatment increased the cs-capacity of the exchanger. the breakthrough curves are shown in fig.s. fig.5 shows that the cs + breakthrough is smaller in case of the pretreated concentrate. this result means that the dosed cobalt compound reacted with the aggressive complex compounds and the decomposition of the exchanger was smaller. 129 table 2 summary of filtration processes microfiltration microfiltration isotope (5 j.ull c1 j.ull pore size) pore size) removed removed 0.18% 0.21% 0% 6.3% 7.2% 6.2% activated carbon filter (with co(no,)z) removed 30.2% 30.4% 78.4% ultrafiltration (i j.ull prefi1tered solution) removed 1.9% 2.4% 5.0% % removed = 100"[1-(solution activity after the treatment/ solution activity before the treatment) j e 45 ~ "' ~~ : ~ 25 ] 20 l 15 fig.s cesium ion exchange breakthrough curves of unand pretreated concentrates fig.6 filtration and ultrafiltration setup filtration, adsorption and ultrafiltration experiments the effective removal of the various forms of the long­ lived radionuclides from evaporation concentrate was also investigated using filtration, ultrafiltration and adsorption processes. in the filtration and ultrafitration experiments we used a wattentechnik microfiltration module and a micro carbosep 40 m5 ultrafiltration membrane (the operating pressure was 2 bar). the experimental setup is shown in fig.6. according to our previous experiments the cesium and cobalt radionuclides may be present in the concentrate as ions, suspended and colloidal particles and in complex forms. the results of our filtration and ultrafiltration experiments showed that a small pru1 of the cobalt content could be removed by filtration (6%) and the ultrafiltration had also low efficiency (5%). although the adsorption of cobalt by an active carbon filter ~med effective means of separation, unfortunately the capacity of the carbon filter is very low. our filtration experiments showed that the long-lived radionuclides definitely occur in non­ filterable (ionic or complex) form (table 2). 130 table 3 summary of filtration processes from the mother lye isotope microfiltration (1 f.iid) removed 0.3% 0% 0% ultrafiltration (1 f.iid prefiltered solution) removed 1.6% 3.5% 0% on-site experiments at the pwr paks the results of the dynamic experiments obtained in our laboratories were controlled and tested at pak:s npp on site. in the experiment we used a freshly ''produced" and an "older" evaporation concentrate solutions. one was the mother lye (partially neutralized evaporator concentrate) of an old stored concentrate (ph=9.5, h3b03 16.1 g/cm3 ) the other a freshly evaporated co11centrate (ph=14, h3b03 109 g/cm3 ). the fresh concentrate contained medium-lived radionuclides such as 54mn, 58co, 57co and the long-lived isotopes ct34cs, 137cs and 60co): all the measurements were performed at the isotope laboratory of the pwr using a calibrated hpge semiconductor detector (1000 seconds measurement time; 100 cm3 sample in plastic flasks). selective ion exchange in this method we used wider.column (id=8 rom) filled with 2 cm3 granulated (0.2-0.3 rom) potassium nickel hexacyanoferrate(ii) prepared by our preparation technique. the flow rate was 100 cm3 (50 bv) per hour. the ion-exchange separation efficiency from the "fresh" concentrate was very low, because manganese dioxide precipitated continuously from the concentrate onto the surface of the exchanger. in the case of the mother lye the efficiency was excellent, the average decontamination factor was 250 and the volume reduction factor more than 1700. we could not determine the breakthrough point because of lack of the limited experimental time. the breakthrough curve is shown in the fig.7. filtration and ultrafiltration the same laboratory filtration and uf equipment were used in these experiments. only 20% of the cobalt could be removed from the fresh concentrate by a i p.m. pol'e size filter and consecutive ultrafiltration. in the case of the mother lye the filtration processes were unsuccessful (table 3 and 4). conclusion according to the laboratory and on-site experiments we conclude that the cobalt content of the evaporation concentrates at the pwr paks is mostly not in suspended and colloidal forms but is rather present in table 4 summary of filtration processes from the fresh concentrate isotope mn 57 co ssco t3•cs 137cs 60co 0,5 0,1 microfiltration(1 f.iid ultrafiltration pore size filter) (1 f.1id prefiltered solution) removed removed 1.1% 9.0% 8.7% 3.7% 4.4% 15.4% 6.5% 11.7% 1.3% 10.6% 0.2% 15.8% . .i ...... / ,/~\ \i ~ 1500 2000 2500 effluent volume {em~ 3000 3500 fig. 7 cesium ion exchange breakthrough curve of the mother lye complexes. the only applied technique that could reduce the quantity of complex form radiocobalt is adsorption on activated carbon. we prepared a granular cs-selective ion exchanger,· determined its optimum parameter of preparation, drying and storage. we successfully tested its selective cesium separation efficiency in laboratory and on-site at the pwr paks. acknowledgment the authors thank peter tilky and ferenc feil for his kind help in the nuclear power plant at pak:s. references i. patzay g., weiser l., t61h b., palma! g. and feil f.: per. polytech. ser. chern. eng., 1995, 39(2), 147-154 2. haas p. a. : sep. sci. tech., 1993, 28, 2479 3. mlmura h., kimura m. and .akma k.: sep. sci. techol., 1999, 34(1), 17-28 4. mardan a., alaz r., mehmood a., raza s. m. and ghaffar a.: sep. pur. tech., 1999, 16, 147158 5. flores r. m., olguin m. t., solache-rios m., longoria s.c. and bulbulian s.: j. radioanal. nucl. chern., 1998, 238(1-2) ,199-201 6. pachero g., nava-galve g., bosch p. and bulbulian s.: j. radioanal. nucl. chern. letters, 1995, 200(3), 259-264 page 126 page 127 page 128 page 129 study the content of exhaled breath condensate 33 hour following the flushing of the mouth with di water was suggested prior to the ebc collection to obtain a relevant ebc sample. 4. conclusion in this work, capillary electrophoresis with contactless conductometric detection was used to study the day-today repeatability of the ionic content of ebc. the ph of ebc before and after degasification with a stream of n2 was studied by a ph microelectrode over five consecutive days. the influence of various foods and drinks on the ionic content of ebc was investigated and exhibited significant differences between ebc samples. it has been shown that ebc is influenced by various parameters. therefore, healthy individuals or patients should provide their ebc samples in the morning before breakfast/brushing teeth or at least one hour after consuming any food or drink last followed by flushing of the mouth with di water. symbols ce capillary electrophoresis c4d contactless conductivity detection ctab cetyltrimethylammonium bromide di deionized ebc exhaled breath condensate his l-histidine id inner diameter mes 2-(n-morpholino)ethanesulfonic acid od outer diameter acknowledgement the authors acknowledge the financial support from the ministry of health of the czech republic (grant no. 17-31945a). part of this research was conducted under the ceitec 2020 project lq1601 with financial support from the ministry of education, youth and sports of the czech republic under the national sustainability programme ii and with institutional support rvo: 68081715. references [1] shaheen, n. j.; hansen, r. a.; morgan, d. r.; gangarosa, l. m.; ringel, y.; thiny, m. t.; russo, m. w.; sandler, r. s.: the burden of gastrointestinal and liver diseases, am. j. gastroenterol., 2006 101(9), 2128–2138 doi: 10.1111/j.1572-0241.2006.00723.x [2] vakil, n.; van zanten, s. v.; kahrilas, p.; dent, j.; jones, r.: the montreal definition and classification of gastroesophageal reflux disease: a global evidence-based consensus, am. j. gastroenterol., 2006 101(8), 1900–1920 doi: 10.1111/j.15720241.2006.00630.x [3] johnston, n.; ondrey, f.; rosen, r.; hurley, b. p.; gould, j.; allen, j.; delgaudio, j.; altman, k. w.: airway reflux, ann. ny. acad. 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a.; mirgorodskaya, e.; olin, a.-c.: effect of airway opening on production of exhaled particles, j. appl. physiol., 2010 108(3), 584–588 doi: 10.1152/japplphysiol.00873.2009 [9] greguš, m.; foret, f.; kindlová, d.; pokojová, e.; plutinskı, m.; doubková, m.; merta, z.; binková, i.; skřičková, j.; kubáň, p.: monitoring the ionic content of exhaled breath condensate in various respiratory diseases by capillary electrophoresis with contactless conductivity detection, j. breath. res., 2015 9, 027107 doi: 10.1088/1752-7155/9/2/027107 [10] kubáň, p.; foret, f.: exhaled breath condensate: determination of non-volatile compounds and their potential for clinical diagnosis and monitoring. a review, anal. chim. acta, 2013 805, 1–18 doi: 10.1016/j.aca.2013.07.049 [11] vitali, l.; fávere, v. t.; micke, g. a.: a new method to determine biological sample volume by short end multiple injection capillary electrophoresis: application in determination of nitrate and thiocyanate in human saliva, j. chromatogr. a, 2011 1218(16), 2327–2333 doi: 10.1016/j.chroma.2011.02.035 [12] vaughan, j.; ngamtrakulpanit, l.; pajewski, t. n.; turner, r.; nguyen, t.-a.; smith, a.; urban, p.; hom, s.; gaston, b.; hunt, j.: exhaled breath condensate ph assays are not influenced by oral ammonia, thorax, 2005 60(1), 27–31 doi: 10.1136/thx.2003.020602 [13] kostikas, k.; papatheodorou, g.; ganas, k.; psathakis, k.; panagou, p.; loukides, s.: ph in expired breath condensate of patients with inflammatory airway diseases, am. j. respir. crit. care med., 2002 165(10), 1364–1370 doi: 10.1164/rccm.200111-068oc 46(1) pp. 29-33 (2018) 34 greguš, ďurč, lačná, foret and kubáň [14] ahmadzai, h.; huang, s.; hettiarachchi, r.; lin, j. l.; thomas, p. s.; zhang, q.: exhaled breath condensate: a comprehensive update, clin. chem. lab. med., 2013 51(7), 1343–1361 doi: 10.1515/cclm-20120593 hungarian journal of industry and chemistry introduction experimental instrumentation chemicals capillary conditioning results and analysis ebc sampling procedure day-to-day repeatability of the ionic content of ebc day-to-day repeatability of the ph of ebc other parameters that influence the ionic content of ebc and the ph conclusion hungarian journal of industrial chemistry veszprem vol. 30. pp. 253-255 (2002) a novel method for detection and estimation of copper (ii) in water m. k. bhutra*, a. vyas and g. l. bhutra (department of chemistry, jai narain vyas university, jodhpur (raj)342005, india) received: july 26, 2002 an improved, simple and sensitive method for quick detection and estimation of copper (ii) in drinking water has been described. the method involves use of ferric thiocyanate along with optimized amount of sodium thiosulphate as field test reagent. the concentration of copper is determined from the time required for disappearance of red brown colour of reagent. the ratio of ferric thiocyanate and sodium thiosulphate solutions should be 1:3 for best results. a time chart is also provided for finding out concentration of copper. the sensitivity limit of reagent for visual observation is 1.0 mg/1. the test is simple, sensitive, rapid, economic and quantitative, hence it can be incorporated in existing water testing field kits. keywords: copper (ii), water sample, ferric thiocyanate reagent, field test introduction copper is widely distributed in nature. copper salts are used in water supply systems to control biological growths in reservoirs and in distribution pipes and to catalyse the oxidation of manganese [1]. corrosion of copper containing alloys in pipe fittings may introduce measurable amount of copper into the water in a pipe system. copper is essential metal required by almost all living organisms in some of their enzyme systems [2]. the adult daily requirement has been estimated as 2.0 mg. deficiency of copper may lead to certain physiological disorders in both plants and animals, but in higher concentrations it works essentially as a pollutant. copper poisoning occurs mostly due to homicidal ingestion of copper containing solutions or consumption of acidic beverages stored in containers of copper [3]. excess of copper in human body is toxic and causes hypertension, sporadic fever, uremia, coma and even death. copper also produces pathological changes in brain tissue [4]. it is also toxic to most aquatic life and particularly algae are very~sensitive to copper. it is toxic to many plants at 0.1 to 1.0 mgll nutrient solutions. thus the presence of copper is to be tested in drinking water for suggesting its potability along with other physicochemical parameters. in the present investigation an attempt is made to detect and estimate copper in drinking water. the permissible limit of copper in drinking water is 1.0 mg/1 as laid down by wh0[5]. experimental reagents a. ferric thiocyanate solution (2.0 g ferric chloride (ar) and 2.5 g potassium thiocyanate (ar) in 100 ml double distilled water). b. sodium thiosulphate (ar) solution 0.1 n (freshly prepared). method to 10 mi water sample add a drop of ferric thiocyanate reagent. a red brown colour appears. now add 3 drops of sodium thiosulphate solution. shake, if red brown colour disappears within 5 minutes it indicates that copper (ii) is present above permissible limit i.e. 1.0 mg/1. the quantitative estimation can be done with the help of time chart provided for ready reference. if the colour of reagent does not disappear within 5 minutes it indicates that copper concentration is well within permissible limit. higher concentration of copper in the tests sample is determined by standard dilution technique. *address for correspondence: 47-nc-1, p.w.d. colony, jodhpur (raj)342 001, india 254 table 2 copper (permissible limit = 1.0 mg/1) reagents characteristics alizarin blue benzidine+ ammonium dithizone ferric thiocyanate + ferric thiocyanate + potassium bromide sodium thiosulphate sodium thiosulphate* bromide (in optimized ratio) medium pyridine acetic acid cone. h3p04 ccl4 water water number of 2 3 2 2 3 3 ingredients sensitivity (ppm) 5.0 5.0 3.0 1.0 0.01 0.01 oxidation state cu (ii) cu (ii) cu (ii) cu (ii) cu (ii) cu (ii) colour and nature of blueppt blue colour violet colour yellow brown brown colour brown colour complex (stable) (stable) (stable) colour disappears disappears (stable) (stable) (stable) interferences co (ill), ni au (iii), many metal ions zn (ii), cd (ii), no interference no interference (ii) interfere fe (iii) interfere pb (ii) interfere interfere remark liquid phase liquid phase liquid phase liquid phase liquid phase liquid phase *modified field test reagent concentration of copper (mg/1) 10.0 5.0 3.0 2.0 1.0 <1.0 table 1 time chart time required for disappearap.ce of reagent colours instantaneous 1 minute 2 minute 4minute 5 minute >5 minutes time chart standard copper sulphate (ar) solutions were prepared in different concentrations ranging from 1.0 to 10.0 mg/1. the time required by different concentrations of copper for disappearance of reagent colour were taken as reference time in the time chart, as shown in table 1. estimation of copper standard copper solutions were made from copper sulphate and estimation of copper (ii) was done using atomic absorption spectrophotomerric method (aas) (6]. results and discussion the methods for estimation of copper [7-20] involve the use of different reagents like alizarin blue, benzidine~ dithizone. ammonium bromide and ferric thiocyanate etc. laboratory studies on these reagents were conducted in view of their adaptability for field determinations. stability, ease and sensitivity of test at different dilutions specially near permissible limit. the results are given in table 2. it is clear from the table 2 that ferric thiocyanate reagent is most suitable under field conditions while others are not suitable due to their complexity, unstability and other limitations. chemistry involved in fer~ic thiocyanate test in the ferric thiocyanate test when a solution of ferric salt reacts with a solution of an alkali thiosulphate a transient red brown colour appears which is unstable, slowly disappears after considerable time. the reaction takes place in two steps: fe3+ + 2s2o;~[fe(s203hr (rapid) (1) red brown complex {fe(s20 3 ) 2r +fe3+ ~2fe2+ +s40~(slow) (2) almost colourless 2fe3+ +2s2o;--72fe2+ +s40~(slow) (3) copper (ii) accelerate the second partial reaction and therefore speed up total reaction. consequently the red brown colour due to [fe(s20 3 ) 2 rion disappears far more rapidly when copper ions are present. the velocity of reaction (disappearance of colour) increases with increase in concentration of copper (ii). the chemistry involved is as follows: [fe(s20 3)zr +cu2+ --7 --7cu+ +fe2+ +s40t (rapid) cu + + fe3+ --7cu 2+ + fe2+ (rapid) cu2+ [fe{s20 3) 2 r + fe3+ --~ --72fe2+ +s4o;(rapid) (4) (5) (6) table 3 comparative studies of rapid field test and standard method (aas) using standard-copper solutions parameters sample no. time required for disappearance of reagent colour after adding field test reagent (in minutes) standard samples having different concentration of cu (ii) a b c d e 5 4 2 inst. concentration of 1.0 2.0 3.0 5.0 10.0 copper using time chart in field test method (mg/1) concentration of 0.988 2.001 3.005 5.001 10.001 copper estimated by standard aas method (mg/1) to make the test quan.titative and specific: the ratio of number of drops of reagent 1 (ferric thiocyanate solution) and reagent 2 (sodium thiosulphate) solution) was optimized. it was found that 1:3 ratio is optimum. with this optimized concentration ratio the test becomes sensitive upto permissible limit. comparative studies of standard methods like atomic absorption spectrophotometric method and rapid field test undertaken on standard copper (ii) solutions have shown (table 3) that the visual colour test exhibited by this method is quite reliable under field conditions. laboratory and field trials on surface water, ground water and irrigation water using this reagent have also been extensively conducted during last two years successfully as shown in table 4. thus this rapid test can be used in field areas for assessing copper (ii) in drinking water. the test is simple, reliable, sensitive and quantitative too and can easily be performed by a person of normal scientific temper. so the test will be a good addition in existing water testing field kits [21]. references 1. clecerri l., greenberg a., andrew d. e.: standard methods for the examination of water and waste water, apha, awwa & wpcf, 3-71, 1998 2. das a. k.: medicinal aspects of rio-inorganic chemistry, 1st ed., 18, 1990 3. kudesia v. p.: water pollution, 1st ed., 205, 1980 4. schubert j.: heavy metal toxicity and environmental pollution of metal ions in biological system, plenum, new york, 239, 1974 5. who, guiidelines for drinking water quality, 182, 1984 6. paus p. e.: atomic absorption spectroscopy, newsletters,j971, 10,69 7. feigl f.: sport test in inorganic analysis, 6th ed .• 203-221, 1972 255 table 4 comparative studies of rapid field test and standard methods using some natural water samples source of water sample concentration of cu (ii) (rng/1) aas field test tapi baori 0.0 0.0 lal sagar 0.01 < 1.0 fateh sagar 0.04 < 1.0 devkund 0.00 0.00 umedbhawan 0.03 < 1.0 kailana 0.00 0.00 gulab sagar 0.21 < 1.0 gorinda baori 2.02 2.00 jalap baori 3.34 3.00 chandpole jhalra 0.04 < 1.0 nagadari mandore 0.00 0.00 jhalara mahila bagh 0.11 < 1.0 kurbija baori 4.45 5.00 ranisar padarnsar 0.01 < 1.0 balsamand 0.00 0.00 shivmandir 0.02 < 1.0 kabutaron ka chowk 0.00 0.00 police line ratanada 0.01 < 1.0 jain bhawan ratanada 1.35 2.00 subhash chowk ratanadda 0.01 < 1.0 baiji ka talab 2.20 2.00 8. bilikova a.: determination of copper and zinc in water, special publication, nr. 44, water research institute, bratislava, 1968 9. gahler a. r.: anal chern., 1954,26,577 10. koch 0. g. and koch g. a.: dedic, handbuch der spurnanalyse, springerverlag, b~rlin, 646, 1974 11. rodier j.: analysis of water, halsted press, wiley, new york, 305, 1975 12. korkisch j., godl l. and gross h.: talanta, 1975,22,289 13. grys s.: microchim acta, 1976, 1, 147 14. welcher f. j. and boschmann e.: organic reagents for copper, krieger, huntington, new york, 1979 15. burns d. t., townshend a., carter a. h.: inorganic reaction chemistry, 1981, 2 16. budavari s.: the merck index, llth ed., rahway. nj, merck, 1989 · 17. theroux f. r., eldridge e. f. and mallmann w. l.: laboratory manual for chemical and bacterial analysis of water and sewage, agro botanical publishers, india, 186, 1992 18. de a. k.: environmental chemistry, 3rd ed., new age international publication, 260-261, 1994 19. flanagan r. j., braithwaite r. a., browns. s., widoop b. and de wolff f. a.: basic analytical toxicology, who publications, geneva, 113-ll5, 1995 20. kumar u. and kakrani b.: water environment and pouution. agrobios.india. 145.2000 21. gopal r., bhargava t. n., bhutra m. k.: j. iww a. 1983, xv. 59-64 page 258 page 259 page 260 microsoft word b_30_czegledi_r.doc hungarian journal of industrial chemistry veszprém vol. 39(2) pp. 251-255 (2011) optimalisation the position of solar cells for vehicles i. lőrincz, d. czeglédi széchenyi istván university, department of automotive and railway engineering, egyetem tér 1. győr e-mail: lorinczi@sze.hu e-mail: czegledid@sze.hu an energy efficient solar power system and electric drive train has been developed with leadership of department of automotive and railway engineering at széchenyi istván university in gyor. this drive train with only solar power also has been successfully driven vehicle model for urban transport even in race conditions. under favorable sunny conditions the energy consumption of the electric motors is less than charge of the photovoltaic system. the system is operating at a positive energy balance. the positive energy balance can be achieved with high-efficiency electric drive, which consists of two bldc motors from emoteq (mf 0210050) and an analog motor drive from advanced motion controls (b40a8). two key elements of the solar driven system are maximizing solar electricity from the sun and minimizing the drag coefficient of vehicle. the main aim of the current research is finding an optimum between these two factors. the optimum placement of solar panels is the horizontal plane. the solar panels on top of the vehicle are parallel with the road plane. this is neither aesthetically correct nor is optimal from the aerodynamic point of view. the compromise of drag coefficient and irradiation conditions can be achieved by an optimization task. we can determine the two-way optimum curvature of the plane radiation and air resistance. the solution is a transparent streamline profile on the horizontal solar plane modules, which meets the requirements. keywords: energy of solar cells, energy management, electric vehicle, battery, mppt, solar car, shell eco-marathon introduction regarding to the tendency of car industry nowadays, electrical powertrains will get more attention. due to the low capacity of battery of this vehicles compared to the internal combustion engines, the efficiency is a main subject, what efficiency can the system transforms the electrical power to kinetic energy. in my essay i would like to optimize the providing and the usage of the electrical energy. we achieve the increase in the energy gathered from the sunlight with the optimization of the organization of the cells, the way of the connections and the charge controlling unit. we modified so the body to decrease drag. we built a vehicle at the department of automotive and railway engineering at széchenyi istván university in gyor, what can lead us with its further development closer to our main aims. the “szevolution car” built in 2010 under race circumstances have already showed its positive skills. at a nearly 30 km/h average speed we were able to charge more than we consumed. with this we were able to win the 2010 shell eco-marathon solar power award in urban concept category. the optimization of the vehicle’s efficiency with the reduction of the drag and increase of charging capacities the shape according to aerodynamic calculations the body’s shape [1] that carries the solar cells is the best if is the shape of a drop. but with this shape the direction of sun lights is different on each cell. with cells connected in series the energy supplied by the circuit will be proportional with the smallest perpendicular component of the sun rays’ angle of incidence with the surface of the solar cells. it is likely that if the aim is to provide the most energy the solar cells’ direction is more important than the surface it is covering. in this case we can get the necessary charging circuit’s energy with a dc/dc converter. with the optimal shape, we can not count with the power of all the cells, but the vehicle can be moved with less energy due to the decreased drag. with solar cells facing in the same direction we can achieve drag reduction by a transparent spoiler. 252 figure 1: details of the subject vehicle, in side view during the combination of the two above discussed solutions we need to consider the connection of the solar circuits, because cells connected in line provide the current of the cell with the lowest value. during the shape's, the charging capability's examination we must optimize the shape and the solar cell placement. at the designing of our car the average speed was an important point of view, due to that the shape specific drag force is proportional to the square of the speed. examining the effect of the drag i was examining the side way view’s shape. on fig. 1 the details of the car and the parameters of the modified rear end can be seen. on fig. 2, you can see the 3d model of the car, in this case a 20° draft was used at the rear end. at the edges a 50 mm fillet were applied. the following four variations were examined. the 2010 vehicle is the base model (model no.0), here the roof is one plane surface. at the first modification (model no.1) the tail part has a 10° angle with the horizontal, at the second modification (model no.2) this angle is 20° and at the third modification (model no.3) it is 28°. figure 2: the 3d model of the car table 1: drag forces, coefficient and the calculated performances at 8 m/s model types model no.0 model no.1 model no.2 model no.3 drag forces fl0 fl1 fl2 fl3 (n) 28.17 22.24 19.37 20.78 drag forces depending on the shape (c) 0.44 0.35 0.30 0.32 performance loss due to the drag force pl0 pl1 pl2 pl3 (w) 225.36 177.92 154.96 166.24 in these four cases the following air drag force and power values, as you can see in table 1, were calculated with solidworks flow simulation. the drag performances were calculated from the drag force multiplied by the speed (8m/s). the drag coefficient is in the fourth column [2]. with this we are able to calculate the drag performances of each speeds, they are shown extracted from the charging performances in fig. 7. on fig. 3 the performance loss due to the drag is shown at each examined models. it is clear to see that in the first three cases the drag force is decreasing with the increase of the angle. but at the last model the drag force is increasing as the shape is diverging from the optimal drop shape. figure 3: the change in the drag power of each model at 8 m/s the changes in the charge power according to incidence of the sun rays angle we are providing the maximum charging performance with a maximum power point tracking (mppt) method [3]. at each solar circuit, the maximum power point is scanned with a micro processor system in the charging control unit that operates the solar circuit at these ideal circumstances. with the in series connection of the solar circuit voltage of the solar cells are added. connecting the circuits in line is useful only if they are facing in the same direction, so they are placed on one plane. in this case they can provide equal amount of energy, all of them can operate the same way. if there is a difference between orientations of the cells, the gathered current will be the current of the weakest cell. if more solar circuits are formed, than these are practical to design them to the same voltages. because at parallel connected circuits they could worse each others power. operating multiple solar circuits in different positions each circuit should be operated by separate charging control unit. there are two factors that need to be kept in mind when placing and linking the cells. these are the solar ray angle of incidence [4] and the shape of the body. at the following body shape i have calculated with an ideal solar cell linking. i have calculated the applicable 253 solar cell performance proportional to the sun’s angle of incidence. i ignored the losses of the connections, wirings and control units. under ideal circumstances the angle of the sun is perpendicular to the cells connected in line. in the case of the top of the vehicle it is the best at noon, but also depends of the geological place of the vehicle. the amount of the direct current supplied by the solar cells is proportional to the smallest perpendicular component of the sun rays’ angle of incidence. figure 4: the measured and calculated performance of a cell in the following measurement i have examined the effect of the light’s angle to the charging performance. i have measured the maximum performances in case of fix light source, with the rotation of the solar cell module that consists of 4x2 cells connected in line. the values (fig. 4) are almost the same as the values provided by the producer of the cells. the blue line shows the values that i measured; the red line is the maximal performance at 0°, multiplied by the perpendicular component of the angle of incidence due to rotation. the two lines are almost the same, except at 90°, where the diffused light also effects the measurement. from solar energy the solar cells placed on the vehicle providing electrical energy. the amount of the energy and performance that we can provide depends of the angle of incidence and the shape of the body. in the following part i will parameterize the vehicle’s charging performance calculating with an optimal charging arrangement. i took the 2010 vehicle’s size and shape for base (fig. 1, model no.0). at the examination of the cell’s arrangement i have calculated only with the solar cells on the top. the cells are on one plane, so we have to calculate with the perpendicular component of the sun rays. i marked the angle of incidence with γ and its values are the following from sunrise to sunset: –90° ≤ γ ≤ +90° the changing parameter of the vehicle during the optimizing is the angle of the top (α). the more we lower the back of the car, the less the drag will be, but the gathered energy will be less. we have to search the maximal performance of the charger with the changing of α. on fig. 1, the 2010 car and the modifications are shown. at the first modification the tail part has a α1=10° angle with the horizontal, at the second modification this angle is α2=20° and at the third modification it is α3=28°. with these modifications two plane surfaces can be covered with solar cells. each solar cell used by our team has a 4.34 w ideal performance. with this value we can calculate that the top of the szevolution car (3.45 m2) can provide maximum 616.5 w. from morning till dawn calculating with angles from -90° to +90° an average 370.6 w is estimated. on the following (fig. 5) diagram the charging performances in connection with the angles of the light are shown. with modifications on the body, i got the values shown in table 2. it is depending on the slope angle of the roof module to the models’ average charging performance. it is shown in on fig. 6. table 2: average charge power of the measured models model types average charging performance (w) modell no.0 pchα=0 370.64 modell no.1 pchα=10 346.44 modell no.2 pchα=20 354.44 modell no.3 pchα=28 365.27 figure 5: charging power in function with the angles of the light figure 6: average charging performance of the models 254 the charge of the first model is significantly worse than others. it is caused by the less applicable cells. in the last case it is almost as good as at model zero. it can be caused by the higher length of the top module, due to the increase of the angle, α. meanwhile the drag also decrease, excepts the 3rd model. summary of the side view shape optimalization at the tested models the tendency of the angle of the light’s effect and the effect of the drag are seem to be the same. figure 7: difference between the charging performances of the models and the drag performances at different speeds the energy used against the drag seems to decrease with lowering the tail, but the gathered energy seems to decrease with this modification, especially at low sun ray angles. the difference between the charging power of the models and the drag power is shown on fig. 7. if the speed is lower, the difference is the bigger. but at 10 m/s at some models we get negative values. so the charging performance is lower than the drag performance. at the race, the average speed is about 8 m/s so the models stay in the positive area. comparing the charging and drag powers the following statements can be set: the charging performance is almost the twice of the drag performance (at 8 m/s). the difference is shown on fig. 8, with a red highlighted line. when this value is higher, than is better the shape according to energetically view. so it is shown that the model no.2 is the best according to my test measurements. here the rear part of the vehicle has an angle of 20° with the horizontal. the difference between the charging and drag performance is shown also on fig. 9. i got the following values approaching with cubic equation. according to aerodynamic and charging views the ideal angle of the rear part is 23°. figure 8: the effect of the shape to the charging and drag performance at 8m/s testing the way of connecting the solar cells the ideal shape is the drop shape. if we would like to cover this surface we would have to use many small cells. each would be facing in a different direction. to be able to connect all this cells into an optimal circuit, we would need a matrix network, with separate units measuring and controlling each cell. the costs and the weight of this system are not likely to be compensated by its benefits. in addition we would need lots of dc/dc converter to increase the charging circuits’ voltage to the needed level. it would cause an additional 5–10% energy loss. that is, why i divided the roof into two plane surfaces. the drag is reduced by 35% and the loose in the charge is only 5%. using the second model, moving with the average speed the total gained efficiency is +37%. this number is calculated from the aerodynamic components and the charging performances with ideal weather and solar cell linking. figure 9: the changing of the difference between the charging and drag performance we have developed our vehicle further by utilizing our experience and measuring results (6, 7) of the vehicles built in the previous years (fig. 10). both electric charging system and the solar cells have been optimized. charging performance of the vehicle has improved significantly, even under non-optimal weather conditions. as a result of the tests executed meanwhile, 255 i expect further efficiency increase from the improvement of the mppt system. improvement of the air-drag coefficient does not reduce the charging power but results in lower energy consumption. by improving the cooling of the solar cells, we want to reduce the negative effects of the higher temperature, we expect at the date of the competition. contrary to early may dates of the previous years, in 2011, the race will be held at the end of may. vehicle construction figure 10: “szevolution car” built in 2010 conclusion efficiency of electric-powered vehicles is extremely important. its improvement results in increase of the driving distance that can be achieved with one charge. it is also our goal with the vehicles we develop for the shell eco-marathon. through increase of the charged power and reduction of the consumption, an efficiency increase up to 10 percent can be achieved in comparison to the vehicle built in previous year. for this result, it is necessary to optimize the shape of the vehicle from the air-drag and charging power points of view. based on the evaluated models, it is to be concluded that energy conditions can be improved the most by using model no.2. with this shape, loss of power due to air-drag can be reduced with 35%. meanwhile, charging power reduces with some 5%. counting with an average racing speed, with the new shape a performance increase up to 37% could be achieved. references 1. www.static.shell.com/static/ecomarathon/downloads/2011/global/sem_rules_2011_final.pdf 2. á. zomotor: gépjármű menetdinamika, már-más bt, budapest, pp. 20–32, 2004 3. c. a. giraldo-castañeda, l. r. orama: selective hopping maximum power point tracking method for pv systems, icset, 522–526, 2008 4. c. sungur: multi-axes sun-tracking system with plc control for photovoltaic panels in turkey, renewable energy 34, (2009), 1119–1125 5. www.boschsolarenergy.com/fileadmin/downloads/datenblaetter/_bosch_solar_cell_m_3bb_en glisch.pdf 6. i. schmidt, i. rajki, gy. vincze: járművillamosság, műegyetemi kiadó, budapest, pp. 170–205, 2002 7. i. emőd, z. tölgyesi, m. zöldy: alternatív járműhajtások, maróti könyvkereskedés és könyvkiadó kft, budapest, pp. 101–127, 2006 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) 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page 215 page 216 page 217 page 218 page 219 page 220 page 221 page 222 page 223 page 224 page 225 page 226 page 227 page 228 page 229 page 230 page 231 page 232 page 233 page 234 page 235 page 236 page 237 page 238 page 239 page 240 page 241 page 242 page 243 page 244 page 245 page 246 page 247 page 248 page 249 page 250 page 251 page 252 page 253 page 254 page 255 page 256 page 257 page 258 page 259 page 260 page 261 page 262 page 263 page 264 page 265 page 266 page 267 page 268 page 269 page 270 page 271 page 272 page 273 page 274 page 275 page 276 page 277 page 278 page 279 page 280 page 281 page 282 page 283 page 284 page 285 page 286 page 287 page 288 page 289 page 290 page 291 page 292 page 293 page 294 page 295 page 296 page 297 page 298 page 299 page 300 page 301 page 302 page 303 page 304 page 305 page 306 page 307 page 308 page 309 page 310 page 311 page 312 page 313 page 314 page 315 page 316 page 317 page 318 page 319 page 320 page 321 page 322 page 323 page 324 page 325 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framework was proposed that models and simulates communication networks. the design and operation of the simulation environment are investigated and a model of electrical components is proposed. after simulation, the simulation results were compared to manual computed results. keywords: energy transmission, electrical networks simulation, distributed energy systems 1. introduction the simulation of electrical networks is important before network planning, development, servicing, etc. is conducted. there are many planning and simulation software solutions on the market, which can simulate electrical networks and grids, e.g. matlab, eplan, wscad. the problem with commercial simulation software is that such software packages cannot be ported to a new system. for example, if the development of a cloudbased electrical network and grid simulation system is required, standard simulation software products and methods cannot be used. to solve this problem, a simulation engine was used, which possesses a gnu licence. the omnet++ discrete event simulator (des) [1] was chosen. mets et alia [2] have previously used the omnet++ simulator environment. omnet++ is an extensible, modular, componentbased c++ simulation library and framework, primarily for building network simulators. omnet++ is not supported directly by the simulation of an electrical grid. to solve this incompetency, a model of the most important electrical components was constructed and as a result, the general simulation engine can be used for cloud-based electrical grid simulation. two methods were implemented in our omnet++ software, which investigated their mathematical foundations, as well. *correspondence: fodor.attila@virt.uni-pannon.hu 2. simulated network according to load distribution the electrical distribution system can be classified as: • fed at one end with one load at the other end; • fed at one end with more loads; • fed at both ends; • radial; • ring; • the distribution system. to test the omnet++ and model of the developed components, a network architecture was chosen, which is convenient and compatible with normal methods for planning of electrical networks. a system has been simulated, which is fed at both ends and consists of three loads (fig.1). of course, this omnet++ simulation project can simulate any distribution systems, though exact values will only be calculated in this case. to simplify our calculations, the wire parameters shown in table 1 were figure 1. distribution system fed at both ends with three loads. table 1. wire parameters ρ 1.85⋅10-8 ωm q 1 mm2 l1 27.027 m l2 54.027 m l3 27.027 m l4 27.027 m sőrés and fodor hungarian journal of industry and chemistry 86 considered. the resistances of all sections of wire are computable using eq.(1). the calculated resistances of the sections of wire are r1 = r3 = r4 = 1 ω and r2 = 2 ω, which were used in the omnet++ simulation. r = 2 ρ l / q (1) the selected resistance values are far from the resistance of wire used in real distribution systems, but the calculations are simplified and the illustration of the results more obvious. the values of current loads for each load were i1 = 10 a, i2 = 16 a, and i3 = 5 a. 2.1. classical method of calculating the voltage drop first, the voltage drop of a distribution system was simulated, in order to calculate the voltage drops using the classical method. our system consists of three loads and it is fed from both ends. the current of the first and second feeding points should be ii and iii, respectively. by applying kirchhoff’s law, eq.(2) is defined as: ii + iii = i1 + i2 + i3 . (2) the total length of the wire is calculated as: σ l = l1 + l2 + l3 + l4 . (3) if ii and iii are known and the load currents are subtracted from one of them, a load that is fed by both ends is identified [4, 5]. afterwards, the electrical network can be separated to obtain two networks fed at one end. the method of calculating, for example, ii is as follows: ii σ l = i3 l1 + i2 (l2 + l3) + i1 (l4 + l3 + l2) . (4) using eqs.(2) and (3), the results of the calculations of the total current, currents of feeding points, and the length of the wire are i1 + i2 + i3 = 31 a, ii = 15.4 a and iii = 15.6 a, and σ l = 135 m, respectively. from ii and iii, it can be determined that the voltage drops accotding to ohm’s law. the voltages of the loads are u1 = 214.6 v, u2 = 203.8 v, and u3 = 214.4 v. 2.2. a method of calculating the voltage drop based on the node-potentials the previously presented method can be easily used to calculate networks consisting of topology fed at one end as well as at both ends. however, our electrical grids are obviously not that simple, see fig.2 or they can even be more complex. furthermore, in this kind of method implemented using omnet++ the presence of a small solar plant on a rooftop is hard to handle. another method of calculating the voltage drops and currents was identified. using the node-potential method, any parameter of an electrical network can be calculated. to apply such a method, the feeding points with voltage sources, the loads with current sources, and the wires with resistances were modelled (fig.3). with this method the feeding points are modelled with voltage sources exhibiting constant voltages, which results in a crucial consequence for more complex networks. if another feeding point is added to the system, some part of it or even the whole network will be parallel to the new feeding point, as it is directly connected to the ground. that would make the investigation of the system and the handling of complex grids easier. of course this is only a theoretical method with many limitations and conditions, but it can be a good basis on which to start our investigation, plus the method can be developed. later new elements, both linear and non-linear, can be added to the network. although the focus of this paper was linear timeinvariant systems. the electrical circuit can be transformed into a directed graph, where the direction of the edges is the same as the direction of the current in calculations. in this case our network possesses six potentials. two potentials of the feeding points, three potentials of the current sources and the ground potential (fig. 4). the index of the nodes is identical to the index of potentials. if we apply kirchhoff’s first law to all nodes, six equations and in ordinary cases five unknown variable potentials from 1 to 5 (the ground potential is 0 figure 2. a more complex electrical network than shown in fig.1. figure 3. the network fed at both ends modelled with electrical elements. figure 4. directed graph of the modelled circuit. simulation of electrical grid with omnet++ 44(2) pp. 85–91 (2016) doi: 10.1515/hjic-2016-0010 87 v) will results so the linear equation system can be solved. they can be arranged them into a vector φ. φ = 𝛷! 𝛷! ⋮ 𝛷! (5) from the potential, voltages can be calculated from eq.(6). u = φi – φi+1 (6) obviously the voltages can be arranged into a vector u, similarly to vector φ. from the resistances, a resistance matrix r or conductance matrix g can be can created. for the node-potential method, a special matrix was used. once again, the central concept is kirchhoff’s first law. the first row of the matrix contains the conductances associated with the first node. the direction of the voltage (likewise the direction of the current) will determine their sign. 𝐆 = −𝐺! 𝐺! 0 … 0 𝐺! −(𝐺! + 𝐺!) 𝐺! … 0 ⋮ ⋮ ⋮ ⋱ ⋮ 0 0 0 … −𝐺! (7) the potential vector can be reduced by omitting φ0 thus yielding a reduced potential vector φr. of course the current matrix labeled i can be used. 𝐈 = 𝐼! 𝐼! ⋮ 𝐼!! (8) ohm’s law helps to calculate the unknown values of the network based on eq.(9). i = g × φ r (9) in the method of node-potentials, the potentials are considered to be unknown, while the other parameters are given. as a result, matrix φr contains all parameters that should be calculated. in the present situation the two potentials of the feeding points are considered to be known, 230 v and the ground potential is 0 v. each current value of the loads is known, but the currents of the feeding points are unknown. therefore, the matrices should be modified so that all unknown variables will be present in one matrix, x, and all known parameters in another one, c, a constant matrix. the g matrix must be used as well and denoted by gm. 𝑿 = 𝛷! 𝛷! 𝛷! 𝐼! 𝐼!! (10) 𝑪 = 𝐺!𝛷! −𝐺!𝛷! + 𝐼! 𝐼! −𝐺!𝛷! + 𝐼! 𝐺!𝛷! (11) 𝑮𝒎 = 𝐺! 0 0 1 0 −(𝐺! + 𝐺!) 𝐺! 0 0 0 𝐺! −(𝐺! + 𝐺!) 𝐺! 0 0 0 𝐺! −(𝐺! + 𝐺!) 0 0 0 0 𝐺! 0 1 (12) by arranging the three matrices into one equation, we get c = gm × x (13) eq.(13) was solved using gauss-jordan elimination method and the same results presented earlier for i1 + i2 + i3, ii and iii, σ l, u1, u2, and u3 were obtained. to make use of the gauss-jordan elimination method, the modified conductance matrix with the constant matrix had to be extended. with the help of a newly created matrix ge, the elimination process yielded the values for vector x directly. the extended conductance matrix (ge) is as follows: 𝐺! 0 0 1 0 𝐺!𝛷! − 𝐺! + 𝐺! 𝐺! 0 0 0 −𝐺!𝛷! + 𝐼! 𝐺! − 𝐺! + 𝐺! 𝐺! 0 0 𝐼! 0 𝐺! − 𝐺! + 𝐺! 0 0 −𝐺!𝛷! + 𝐼! 0 0 𝐺! 0 1 𝐺!𝛷! (14) 2.3. comparison of the two methods although both calculations yield exactly the same results, in our opinion the second one is preferred. the structure of the matrices indicates that it can be applied to even more complex grids, e.g. in radial topology. another advantage of the node-potential-based method is that the direction of the load currents is irrelevant. for example, even a small solar plant on a rooftop can be simulated. 3. simulation with omnet++ the omnet++ 4.x integrated development environment is based on the eclipse platform, which has been extended with new editors, views, wizards, and additional functionality. although omnet++ is not a network simulator in itself, it has gained widespread recognition as a network simulation platform in the scientific community as well as in industrial settings, and has built up a large community of users. the most common area of application of omnet++ is the simulation of telecommunication networks. the simulator itself is message-based, so our electrical distribution system had to “communicate” via sőrés and fodor hungarian journal of industry and chemistry 88 messages, which is rather unusual in terms of physics or electrical engineering. omnet++ provides component architecture for models. components (modules) are programmed in c++, then assembled into larger components and models using a high-level language (ned). omnet++ simulation comprises three different files, which are (i) source code (cpp), (ii) network file (ned), and (iii) configuration file (ini). in omnet++ modules are defined, which can communicate via messages. both modules and messages are special c++ objects. in the source code, we can specialize our modules, and define their tasks precisely. the network file contains the actual topology of the network system, and the position and names of the used modules as well as their connections. with the aid of the configuration file, other network settings can be specified, though none were used in our simulations. all modules have four functions, which can be defined by users. in our simulation, only two of them were used; the initialize() and handlemessage() functions. in the initialize function the initial parameters of the modules can be set, in the handlemessage() function the action in case of an incoming message can be declared. with these functions, completely different modules can be developed. the main idea was to show the current or energy flow via messages in our system. it worked quite well in the case of a system fed at one end. although because of the message and handling of messages inclinations of omnet++ in systems fed at both ends, the energy flow was not so easy to show. 3.1. implementing the distribution system in omnet++ the distribution system shown in fig.1 had to be implemented. it is obvious that we have at least three different types of modules exist in this network as follows: (i) feeding point, (ii) load, and (iii) connection between them. the implemented electrical distribution network is shown in fig.5. by analysing the topology more closely, we could identify another module could be identified, connecting two wires and a load, the node. nodes are important parts not only of grids with their topology, but also of radial grids. the previously used module is not shown in fig.1 but there should be a ground point to make our simulation easier and clearer. this ground point module is the most important as it carries out the main calculations and connects the loads to the producers. table 2 shows the modules and the names used in our source code and files. 3.2. modules and messages the class of messages possesses several variables, including a void-type pointer called contextptr, which is a user-defined pointer. in our simulation, this pointer was used to send data to modules. it points to a class, which contains the used variables such as voltage, current, effective power, reactive power, resistance, etc. of course, some of the variables are used in only one module (e.g. the resistance in wire module), and some in all of the modules (e.g. voltage, current). in the constructor, all variables were set to zero. the simulation consists of cycles. each cycle begins with the producers sending messages, and ends when they receive their messages from ground modules. in simulations, the event logging (ev) function can be used to log the parameters or result(s) of the calculations. there are two feeding points in all simulations, though loads are user-defined (n) in preprocessor instruction where both twoand three-pointloaded networks can also be considered. the first module is called producer. it exhibits a constant voltage value set in pre-processor instruction #define ut 230. in advanced simulations, it should be a user-defined value, and it is not necessarily constant. it could be a function as well, but in this simple simulation, it will remain constant throughout the whole process. at the start of the simulation, only the voltage of the producer is known, but the current and power are unknown parameters until the end of the turn. thus, these values are set to -1 at the beginning. all three parameters are set in the initialize() function. the next stage of the module is handling an incoming message. the incoming message is actually a pointer to the message. at first, in all modules, the values of the pointer were stored as local variables were identified. this is very useful as during simulation some memory allocation problems. the message contains information only about the currents (the voltage remains constant). the current of the producers is set to the value from the message. the power is calculated from the current and voltage values. the module is connected to the ground and one-wire modules. the producer module logs the voltage, current, and power. figure 5. the schematic of the network using omnet++. table 2. summary of modules used in omnet++ simulations. parts of the system module names feeding point producer load consumer connections wire node node ground point ground simulation of electrical grid with omnet++ 44(2) pp. 85–91 (2016) doi: 10.1515/hjic-2016-0010 89 the second module simulates the load and referred to as consumer. it exhibits a constant current and power factor. both users are defined. current values are the same as discussed above in section 2. from these and the voltage from the incoming message, the module calculates the power and reactive power. this block sends the current value to the ground block for further calculations. consumer modules are connected to one node and the ground module, which logs voltage, current, power, reactive power, and the power factor. in real networks, the connecting wires exhibit resistances as well, causing a voltage drop in the system. in our example, this is desirable, almost 1 ohm, but our calculations are simple. in the initialize() function, the lengths from table 1 and r1 to r4 resistances from section 2 are set. the wire module calculates the voltage drop simply with ohm’s law. obviously, it shows a useful value from the second cycle, as the current is negative until that turn. wires are connected to one producer and one node or between two nodes. wires log the voltage drop, current, resistance and length. the node module is especially useful in radial topology, but also implemented here as well. the aim of this module is to distribute current by applying kirchhoff’s first law to our network. it works only after the first ‘initial stage’. the module is connected to two wires and one consumer module. it shows the value of currents. the ground module conducts the main calculations of the simulation. it determines the exact current values for each producer module. the calculations are based upon eqs.(2) and (3). the module takes into consideration the length of each wire and the currents from the consumer modules and distributes them. the ground module is connected to all consumer and producer modules in addition to logging the sum of currents and the currents for each producer. 3.3. simulation as stated before, this omnet++ simulation can be divided into three different stages. at first, the omnet++ simulation engines build the network with the user-defined values for each module. this is referred to as stage 0, and there is no logging occurs here. in other simulations, logging is possible here as well, but in this case this opportunity is omitted. the next stage, or the first cycle, starts when the producers send their first message, and ends when they get their message from the ground module. this part is not necessary in other kinds of simulations. in this part all modules have their own user-defined values, but they do not have any effect on the other modules, e.g. producers exhibit their own voltages, but their current and power are both -1 or the voltage and current of wires are both unknown (-1), as shown in figs.6 and 7. at this stage, the voltage of the consumers is 230 v, and its powers are calculated with this voltage, shown in fig.8. the first cycle of the simulation is examined in fig.9. currents are “delivered” between the modules throughout the whole network system. however, at the end of the initializing stage, the ground module calculates the sum of currents of the consumers and the currents of each feeding point (fig.10). thus, the producers receive their currents, and the correct calculated values, e.g. voltages, powers, etc. will be obtained without any unknown parameters (fig.11). figure 8. consumer logging during the first cycle. figure 9. the first cycle of the omnet++ simulation. figure 10. current distribution. figure 6. wire logging during the first cycle. figure 7. node logging during the first cycle. figure 11. voltage, current and power of the first feeding point. figure 12. logging of wire, node, and consumer modules in the second cycle. sőrés and fodor hungarian journal of industry and chemistry 90 the previously shown modules can be examined and it can be concluded that our voltage and current values are known (fig.12). it could be interesting to see how our nodes work after the first stage, when applying kirchhoff’s first law (fig.13). we have to mention that in the case of node modules iout means the current of the consumer subtracted from iin. 3.4. validation of the simulation results it has been seen that the results of the omnet++ simulation and the results of the classical method of calculating are the same. as an example, the results of the voltage drops are shown in fig.14. 3.5. topology all electric systems have unique topologies the position of the components or element(s) and the wires that connect them. by considering a network fed at both ends with only one node, it conatins one node module and two connecting modules between the feeding points and the node. in the case of a similar network with two loads there are two nodes and three connecting channels, as in the previous case. from this point of view the simulated network can be checked, this one contaists of three loads and four channels. if a gred fed at both ends with n loads (where n is a positive integer) exists then the number of wire modules, w (also a positive integer) can be calculated as follows: w = n + 1 (15) eq.(15) is only true for this type of topology. for example for a topology in which there is only one feeding point, the number of loads obviously is equal to the number of wires (and nodes). a proven formula can be applied to more complex topology variations. the advantage of these formulae are that they automate the creation of ned files either from another piece of software or implemented from omnet++. 4. summary of simulation experiences it can be concluded that our des program works properly as shown in section 3.4. obviously there are some advantages and disadvantages of this method. 4.1. advantages first of all it is an open-source platform, thus it can be modified and developed easily. the use of other auxiliary pieces of software can be added, too. as the program includes a graphical viewer, individual simulation results can be followed. the message direction is the same as the current direction, thus a negative current means failure in the program, or negative values can be defined as unknown parameters. our system can be observed for values of interest. with this definition the model later may be used in transient analysis to consider the reinitialization cycles each time. 4.2. disadvantages on the other hand, as an open-source platform it is still in the development phase. sometimes the program gave us crash reports during the development phase. the message direction is the same as the current direction; however, according to the message sending system of omnet++ extra message(s) can be obtained. another issue is the network description file (ned). each time our network system is modified, the whole code needs to be modified, including the connection definition part, as well as the gate declaration. topology statements are omitted. although the time of the simulation is user-defined, all the steps are to be followed the simulation may be rather lengthy. in this case, the simulation of another type of electrical distribution system was attempted, e.g. for a system fed at only one end, a totally new program has to be written. this program can be solved only if a formula is created for each different type of topology. real electrical grids may be more complex than the situations our des can handle at the present. 5. conclusion the models of the electrical components have been developed in this paper based on engineering principles that are able to describe the behaviour of an electrical grid. it seems that the omnet++ discrete event simulator is suitable for the simulation of electrical grids. at first we need to fix some problems mentioned in section 4.2. a future task would be to implement new electrical network components, e.g. photovoltaic power plants, wind turbines, and different loads, etc. to the simulation environment and subsequently the omnet++ would be suitable to simulate smart grid networks. figure 14. voltage drop of the loads. figure 13. applying kirchhoff’s first law to the node modules. simulation of electrical grid with omnet++ 44(2) pp. 85–91 (2016) doi: 10.1515/hjic-2016-0010 91 symbols des discrete event simulatoion ev event logger i1, i2, i3 currents of the loads ii, iii currents of the feeding points l1, l2, l3, l4 length of the wires connecting loads and feeding points n number of loads w number of wires q diameter of the wire u1, u2, u3 voltages of the loads ut voltage of the feeding point ρ resistivity ned network description file ini initialization file φ potential φ potential vector φr reduced potential vector r resistance matrix g conductance matrix gm modified conductance matrix ge extended conductance matrix i current vector x vector of variables c vector of constants acknowledgement we acknowledge the financial support of this work by the hungarian state under the vksz_12-1-2013-0088 project. references [1] omnet++ discrete event simulator omnetpp.org [2] mets, k.; verschueren, t.; develder, c.; vandoorn, t.l.; vandevelde, l.: integrated simulation of power and communication networks for smart grid applications, proc. ieee 16th int. workshop, computer aided modeling and design of communication links and networks (camad), pp. 61-65, 2011 [3] niemi, r.; lund, p.d.: decentralized electricity system sizing and placement in distribution networks, applied energy 2010 87(6), 1865-1869 doi: 10.1016/j.apenergy.2009.11.002 [4] gonen, t.: electrical power transmission system engineering: analysis and design (crc press, boca raton, fl usa) 2011 [5] jamniczky, á.: electric engines, (university of veszprém press, veszprém, hungary) pp. 31–49, 1994 (in hungarian) microsoft word 16.15 pózna.docx hungarian journal of industry and chemistry vol. 44(2) pp. 121–128 (2016) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2016-0015 diagnosis of technological systems based on the structural decomposition of their coloured petri net model anna i. pózna,1* miklós gerzson,1 adrien leitold,2 and katalin m. hangos1,3 1 department of electrical engineering and information systems, university of pannonia, po box 158, veszprém, 8201, hungary 2 department of mathematics, university of pannonia, po box 158, veszprém, 8201, hungary 3 institute for computer science and control, hungarian academy of sciences, po box 63, budapest, 1518, hungary diagnosing faults during the operation of a system is an essential task when investigating technological systems. in this paper, a new online fault identification method is proposed which is based on the occurrence graph of the coloured petri net model of the system. the model is able to simulate the normal and faulty operations of the system given in the form of event lists, so called traces. the diagnosis is based on the search for deviations between the traces of the normal and the actual operations. in the case of complex technological systems, the occurrence graph can contain hundreds of nodes; therefore, the computational effort and searching-time increase significantly. our proposed structural decomposition method can manage these demands so it has a crucial impact on the practical application of diagnostic processes. the main idea of our method is that the complex systems can be decomposed into technological units. therefore, the diagnosis can be done by components separately and the diagnostic result of a unit can be used for the diagnosis of the other units connected to it. because of the structural decomposition, the diagnosis has to be performed on much smaller occurrence graphs but the effect of faults in previous units is taken into account. the proposed method is illustrated by a simple case study. keywords: technological system, diagnosis, coloured petri net model, structural decomposition, qualitative model 1. introduction identifying faults and analysing their consequences are important tasks during the investigation of technological systems. a number of diagnostic methods are known in the literature and the model-based methods are very popular among them [1]. petri nets and their different extensions (such as coloured, timed or hierarchical nets) are powerful tools for modelling discrete event systems [2]. for example, coloured petri nets are often used for modelling production lines [3]. it is important that the resultant models describe not only the normal (faultless) operation of the system, but they also take into account different, randomly occurring errors in the system. in many cases, the normal or faulty operations of technological processes can be characterised by a series of events possessing discrete or qualitative valued variables. in this case, the occurring deviations can be generated by the comparison of the normal and actual events. the occurring faults can be detected and identified based on the observed deviations. *correspondence: pozna.anna@virt.uni-pannon.hu discrete event systems are usually modelled by automata. in this case, the diagnosis is usually based on the idea of unobservable events [4]. faults can be modelled as unobservable events, which means only the effects of faults can be noticed. the problem with fault detection is specifying whether any fault has occurred or not in the system. fault isolation is the problem of identifying which fault has occurred exactly. since faulty events are unobservable by assumption, the detection and isolation problem must be solved based on the available information of the observed non-faulty events. the diagnosability of discrete event systems was first investigated [5] using the methods of automata theory. besides automata, petri nets are also frequently used for modelling discrete event systems (des). the structural and mathematical representations of petri nets both can be used for diagnostic purposes. methods include various techniques such as analysis of the occurrence graph, marking estimation, linear algebra, integer linear programming, diagnoser nets, or reverse nets. a simple fault detection method based on the measurement of token quantity is given [6]. it is assumed that the given petri net is conservative, and any change in the token quantity is caused by faults. if the difference between measured and initial token number pózna, gerzson, leitold, and hangos hungarian journal of industry and chemistry 122 exceeds a predefined threshold then a fault has occurred. sensor signals are used for token determination instead of modelling the faulty behaviour of the system. the proposed method is very simple and can be used for early fault detection; however, it is not able to isolate faults. faults can also be modelled as unobservable transitions in petri nets. the set of places can be also observable; therefore, the marking of the petri net has to be estimated. the notion of basis marking [7] (set of markings consistent with the observation) and j-vectors (minimal sequences of unobservable transitions to reach basis markings) are introduced. an online algorithm is developed to detect the occurrence of faults, which uses the basis occurrence graph. the main advantage of the proposed algorithm is that in the case of bounded petri nets the basis occurrence graph can be computed offline. it reduces the computational effort of the online diagnosis. the basis occurrence graph can be used as an online diagnoser. sufficient conditions of diagnosability of faulty transitions are given in the form of a system of inequalities [8]. in this method, the marking of places is observable. authors introduce the notion of g-markings (markings with negative elements) and unobservable explanations (sequences of unobservable transitions, whose firings can explain the negative elements of a gmarking). after an observed event, the g-marking is updated according to the petri net equation. when an observed transition fires it removes tokens from its input places and adds tokens to its output places. if this transition is not enabled under the previous g-marking then the removal of tokens causes negative marking. an online fault detection algorithm has also been developed [9], which is based on solving integer linear programming problems and checking the diagnosability conditions. the integer linear programming approach has also been used [10] to determine if the system behaviour is normal, faulty, or ambiguous. the algorithm has further been improved [11], for a more general situation where different observable transitions can share the same label. firing times of transitions are also considered, which add more constraints to the ilp problem making the fault detection algorithm more accurate. timing characteristics have also been used [12], but with a different meaning: the faults affect the firing speed of the transitions. the fault detection is based on the generation of residuals, which are computed by comparing the markings of observable places with the reference model. a bottom-up modelling methodology has been proposed using interpreted petri nets [13]. in the generated model, the faulty and normal states are represented by places. the authors introduce the definition of input-output diagnosability and also give conditions to test this property. the diagnoser model contains the normal behaviour of the system. an online algorithm based on the difference between the system output and the diagnoser model output is developed for detecting faulty markings. in the case of large systems, the models and associated diagnosers can be extremely large. furthermore, the diagnostic methods are computationally expensive. therefore, it is essential to investigate the possibility of distributed diagnosis. the idea of distributed diagnosis is to divide the system into modules or components then make a local diagnoser for each component. the challenging problem is to ascertain the diagnosis state of the whole system from the results of local diagnosers. it usually requires a distributed algorithm and a communication protocol [14]. coloured petri nets (cpn) have the advantage of making compact information representations. a cpn diagnoser equivalent to the classical diagnoser has been built [15]. in this approach, places represent different hypotheses and colours represent diagnosis results. the advantage of the cpn diagnoser is the simplified graphical representation. on the other hand, the coloured diagnoser is not necessarily smaller than the classical diagnoser. decomposition and methods of modular diagnosis of des are also studied by the authors. backward reachability can also be used for diagnosis purposes. if a marking m is reachable from m0, then m0 is backward reachable from m in a petri net. possible sources of failures for this method can be determined. backward reachability is extended to coloured petri nets [16]. transformation techniques for the inversion of cpn are also presented here. 2. basic concepts a brief description of the basic concepts and notions of our method are given in this section. at first qualitative ranges are introduced to characterise the measured values. after that events, traces, and deviations in a technological system are defined, then the most important parts of the coloured petri net model and its analysis are introduced. finally, the structural decomposition-based diagnosis is described in detail. 2.1. qualitative range spaces in many applications, it is not always necessary to know the exact values of the measured signals. qualitative models can be used in this case and it is enough to know whether the value of a signal belongs to a specified range space or not. for example, the measurement range of a sensor can be divided into the following range spaces: qs = { e0, 0, l, n, h, e1 } (1) where 0, l, n, h denote the zero, low, normal and high measured value, respectively, while e0 and e1 may refer to the extremely low and high values caused by sensor errors. the states of actuators, e.g. valves, switches, etc. can be described similarly. for example, a two-state valve can be represented by diagnosis of technological systems 44(2) pp. 121–128 (2016) doi: 10.1515/hjic-2016-0015 123 qv = { op , cl } (2) qualitative range spaces, where op and cl refer to the open or closed state of the valve. 2.2. events, traces, and deviations considering a technological system as a discrete event system, the state of the system can be characterised with the measured values at a given time. the actions in the system, e.g. interactions by operators, modify the values of input and output variables thus the system state changes. an event is defined as the arranged (qualitative) input and output values of the system at a given time instance τ: eventτ = (τ, in1, …, inm, out1, …, outn) . the course of the system can be described as a sequence of consecutive events, so called trace: trace = (event1, …, eventn). in a technological system the most important types of traces with respect to the diagnosis are the nominal, faulty, and characteristic traces. the nominal trace describes the normal operation of a system. the faulty trace contains the occurring events if a known fault is present while the characteristic trace refers to the actual course of the process. in this paper, it is assumed that only one fault may occur in a process unit of the technological system and this fault evolves before the start of the operation and remains unchanged during the course of the process. if a fault occurs then the trace of the system differs from its nominal trace. as a result, deviations between the nominal trace and the current characteristic trace can be defined. in our diagnosis method the following types of deviations are used: • never happened(eventτ) (abbreviated as h(eventτ): this type of deviation refers to the events of the nominal trace which (eventτ) never occur in the characteristic trace of the process. • chronological deviations: if an event of the nominal trace (eventτ) happens later or earlier in the characteristic trace than time point τ, the deviations lat(eventτ) and ear(eventτ) denote them. • quantitative deviations: this type of deviations is used to denote that the ith output value is greater (denoted by grei(eventτ)) or smaller (smli(eventτ)) in the characteristic event at time τ than in the nominal event while the input values are identical. our diagnosis method is based on the search and comparison of the deviation list on the reachability graph of the cpn model of the technological system. 2.3. coloured petri nets coloured petri nets (cpns) are extensions of the ordinary or low-level petri nets. the main differences with respect to ordinary petri nets are that so-called colours can be assigned to tokens and functions can be assigned to arcs and transitions, too. the detailed formal definition is given in ref.[17], only the special concepts used in our models are presented here. • places of the cpn model of the technological system may have three functions. at first input and output variables are represented by places and the colour of the tokens on them denotes the qualitative value of the variable at the current time. on the other hand, places may refer to the occurred fault and the generated deviations. the colours of tokens in these places denote the type of the fault and the occurring deviations, respectively. • there are three transitions in our model, which have different tasks. transition t1 is responsible for the generation of faulty or normal operations at the beginning of the process and the initialisation of the variables according to the investigated operational mode. the function of transition t2 is the timing of the process. it is assumed that the technological process is time-driven and the values of the variables change at the end of the time steps. therefore, t2 fires until the end of the process. transition t3 is used for the generation of the ‘never happened’-type deviations at the end of the process. • arc functions are assigned to the arcs between places and transitions defining the change in the colours and computing deviations. the structure of the coloured petri net for modelling and diagnosing technological systems can be seen in fig.1. places are represented with ellipses and transitions are represented with rectangles. in a technological system, the consequences of a processing step can be stochastic. for example, the step may be completed in a normal way, or a fault occurs. the probabilistic nature of a transition t associated with a processing step can be modelled in a cpn by a fault function, which is built into its guard function. this figure 1. structure of the coloured petri net model. pózna, gerzson, leitold, and hangos hungarian journal of industry and chemistry 124 fault function returns the logical value true or false with predefined probability, and the token values of the adjacent consequence places of transition t can be controlled by this logical value. this type of transition firing is called a stochastically fired transition. the occurrence graph of the cpn is a graph, which contains all of the system states reachable from a given initial state [17]. assuming that the cpn model of the examined system is given, the occurrence graph can be used for its behavioural analysis. the nodes of the graph refer to system states and the arcs connecting them refer to state transitions, e.g. events. different paths on the occurrence graph refer to different operational modes of the system and they can be used for analysing the causes and consequences of a system state. 2.4. diagnosis with structural decomposition the disadvantage of the occurrence graph-based method is the increasing size of the graph as the size, i.e. number of places, of the cpn model increases. in the case of even a simpler technological system containing three or four units, the occurrence graph of its cpn model can contain hundreds of nodes depending on the number of sensors and actuators. the refinement of the qualitative measuring range of sensors or the application of control valves instead of two-state actuators may also cause the growth of occurrence graphs because their branches will be longer. with the growth in the size of the graph, the computational effort and searching-time also increase. this is the reason why the structural decomposition has a crucial impact on the practical application of the diagnostic process. generally speaking, complex systems can be decomposed into technological units. by taking advantage of this, the diagnosis can be done by components separately, and the diagnostic result of a unit can be used for the diagnosis of the other units connected to it. to perform diagnosis with structural decomposition the full trace of the system should be decomposed, too. to do this, first the time instances belonging to the operation of the investigated units have to be selected. then the variables referring to this unit are picked out from the events belonging to the selected time instances. if the trace is represented in tabular form then specific rows and columns should be selected. afterwards, time is shifted back in the case of every unit such that the initial time step of the first event should be 1 in every sub-trace. this means that every unit has its own relative time-scale. by applying this decomposing process, the trace describing the operation of the entire system is disintegrated into the event lists referring to the operation of simpler technological units. as a next step the deviation list of the given subsystem is generated by comparing the nominal trace of the subsystem with its characteristic trace. then the diagnosis is performed using the cpn model and occurrence graph of the subsystem. the task is to compare the generated deviation list with the token distribution of the terminal nodes on the occurrence graph. if the deviation list corresponds with the token distribution of exactly one terminal node then the fault can be determined based on the token of the fault place. if the deviation list matches the token distribution of more than one terminal node then only the set of possibly occurred faults could be determined. if the deviation list cannot be found in the token distribution of any terminal nodes then an unknown failure occurs in the system. in the case of complex systems, it is necessary to take into account the effect of faults that have occurred in subsystems connected to the diagnosed unit. therefore, the cpn model of the units has to be modified such that the place of the fault has to contain not only the actual operating mode, but the operating modes of previous subsystems, too. to store this information the colour set of this place is extended with an attribute referring to the type of fault and to the place where the fault occurred. let us assume that one fault is diagnosed in the first technological unit. this information is added to the fault place of the next unit as a previous fault. then the occurrence graph of this subsystem is generated based on its cpn model where the fault of the previous unit appears as an initial condition. the resultant occurrence graph now contains those states and deviation lists which can occur in this subsystem if the fault of the previous unit is taken into account. the diagnosis is performed on this graph, the possible fault of this unit is determined based on this investigation, and the result is taken into account during the diagnosis of the following unit. in certain cases, the exact type of fault cannot be determined exactly. if the result of the diagnosis of the unit is a set of possible faults then each element of the set is treated separately. this means that the diagnosis of the next unit has to be performed taking into account every one of the possible previous faults. occurrence graphs of the subsystem are generated according to each fault of the previous subsystem. the result of the diagnosis is the union of the obtained faults. the main advantage of the described method is the smaller size of the occurrence graphs of subsystems. therefore, the search requires less time than in the case of the investigation of the entire technological system. 3. simple case studies a simple case study is presented in this section as a practical illustration of the diagnosis of complex technological systems based on their structural decompositions. 3.1. description of the technological process our simple technological example contains three uniform tanks, ta, tb, and tc, which are serially connected as can be seen in fig.2. each tank has an input valve, an output valve (denoted by vx, where x = a, b, c, and d), and a continuous level sensor (lev_x, x diagnosis of technological systems 44(2) pp. 121–128 (2016) doi: 10.1515/hjic-2016-0015 125 = a, b, and c). the short description of the technological process is as follows: as an initialisation, it is assumed that all the valves are closed. the process starts with the opening of the first valve (va) and then the filling of the first tank (ta) starts. the flow of liquid is considered constant so the control of the filling process is based on time. the role of the level sensors is to measure the actual liquid level only. at time step 3, the filling process of tank ta completes and its output valve (vb) is opened. the second tank tb is filled the same way as described for tank ta. at time step 5, the tb tank is full and its output valve (vc) is opened. the filling process of the third tank (tc) happens the same way. during the filling of the second and third tanks, the first (ta) then the second tank (tb) operates as a continuous unit. after the filling of the third tank (tc) has completed, the technological systems work in continuous mode. it is assumed that five possible faults can occur in each tank: • 2 faults of the level sensor: negative or positive bias error. in this case, the sensor signal is lower or higher with qualitative unit than the actual value of the level. • leaking of the tank: it is assumed that all of the incoming liquid runs out through the hole, i.e. it is a “big” hole. • 2 different faults of the output valves vb, vc, and vd: besides their normal operations, they can stay closed or open only halfway. for the sake of simplicity, only one of these faults can occur with each tank and all of the faults evolve before the filling process of the first tank ta starts. 3.2. cpn model of the system for the diagnostic investigation, a coloured petri netbased (cpn) model of the technological system is developed as follows: the system can be decomposed into three subsystems. each subsystem represents a tank together with its input and output valves. as can be seen from the technological description of the system, all the subsystems (tanks with their input and output valves and sensors) work in a very similar way, so the structure of their cpn models is identical. the cpn models were built using cpn tools 3.4.0. the cpn model of a subsystem can be seen in fig.3. the description of the cpn model is as follows: the locations of the petri nets represent input and output variables, i.e. the state of the input and output valves (denoted by in and out), and measured level value (level), respectively. the qualitative values of these variables are represented by different colour sets. • colour set of valves: qvalve = {cl, op}, which represents the closed or open-state of the twostate valve. • colour set of level sensors: qlevel = { e0, 0, l, n, h, e1 }, where 0, l, n, h denotes that the level is zero, low, normal or high, respectively, and e0, and e1 indicate that the level is below or above the measurement range, respectively. three additional places are needed: one to store the operating mode (place fault), one to collect the deviations (place dev) and one for the list of events that have not occurred until a given simulation time step (place never). the cpn model contains three transitions (t1, t2, t3). t1 is the initialisation transition, it fires only once at the start of the simulation. it generates an operating mode (normal or faulty) and updates the variables according to the generated operating mode. afterwards, transition t2 fires until the end of the process. it updates the values of variables in every simulation step and generates quantitative and chronological deviations except for the ‘never happened’-type. the ‘never happened’-type deviations can be generated after the process has ended. this is done by the firing of transition t3, which removes the events that remain at place never at the end of the simulation and attaches the nh guideword to them. the values of variables at a given time step can be read from the trace files. each trace file contains the list of events that describe the process according to the operating mode. all traces were generated by a matlab script. figure 2. the investigated technological example. figure 3. the coloured petri net model of a tank (for the sake of clarity parts of some inscriptions were omitted). pózna, gerzson, leitold, and hangos hungarian journal of industry and chemistry 126 3.3. diagnosis of the system with structural decomposition according to the general description, the technological system consists of three uniform tanks. because of the same structure and operational mode, all three tanks have the same cpn model. this model can be seen in fig.3. the occurrence graph of the cpn model of a tank can be seen in fig.4. at the time of the generation of this occurrence graph, any fault occurring in a previous technological unit was not taken into account. as can be seen in fig.4, node no. 17 refers to normal operation of the system, while the other terminal nodes (no. 20, 21, 23–25) belong to the five different faulty modes. the nominal trace of the complex technological system can be seen in table 1. the input variables of the first tank (tank ta in fig.2) are the states of valves va and vb, while the output variable is the value of level sensor lev_a. the variables of the second tank are vb, vc, and lev_b, while vc, vd, and lev_c belong to the third tank, respectively. the rows belong to time steps 1, 2, and 3, while columns va, vb, and lev_a compose the trace of the first tank. these cells are framed with a dotted line in table 1. similarly, rows 3, 4, and 5 as well as columns vb, vc, and lev_b define the trace of the second tank (framed with a continuous line) while rows 5, 6, and 7, along with columns vc, vd, and lev_c give the trace of the third tank (framed with a dashed line). consider the characteristic trace of the technological system given in table 2. as a next step, the trace pieces belonging to each individual tank are removed from the characteristic trace of the entire system. the initial time step is shifted to 1 for every unit. the resultant event lists belonging to the three tanks can be seen in table 3. the diagnostic process is started with the first tank. by comparing the nominal trace of the first tank with the characteristic trace (first column of table 3) the deviation list is generated. this deviation list is then searched for among the terminal nodes of the occurrence graph of the first tank. (this occurrence graph can be seen in fig.5). it can be stated that terminal node no. 21 contains the same deviation list and based on the token of the fault place the type of fault can be determined: the level sensor exhibits a positive failure bias in the first tank. the diagnosed fault in the first tank is used during the investigation of the second tank. this fault is added to the place fault as a token (pos_bias, prev1) in the model of the second tank. then the occurrence graph of the second tank is generated which contains those states that can occur in the second tank if the sensor of the first tank exhibits a positive bias error. the resultant graph can be seen in fig.6. the deviation list of the second tank is generated by comparing the second column of table 3 with the characteristic trace of the second tank. by checking the terminal nodes of the occurrence graph in fig.6, it can be stated that terminal node no. 24 exhibits the same deviation list. this means that the fault of the second tank is leakage and it can be identified unambiguously. the diagnosed faults of the first and second tanks are added to the model of the third tank in the form of tokens (pos_bias, prev1) and (leak, prev2) belonging to the fault place. based on this information the occurrence graph of the third tank is generated in accordance with fig.7. the nodes on this occurrence graph refer to the states if a positive failure bias occurs in the first tank and leak in the second tank. figure 4. the occurrence graph of a cpn tank model. table 1. decomposition of the nominal trace. dotted line: first tank, continuous line: second tank, dashed line: third tank. time input variables output variables va vb vc vd lev_a lev_b lev_c 1 op cl cl cl 0 0 0 2 op cl cl cl l 0 0 3 op op cl cl n 0 0 4 op op cl cl n l 0 5 op op op cl n n 0 6 op op op cl n n l 7 op op op op n n n table 3. characteristic traces of the three tanks after decomposition. ta tb tc (1, op, cl, l) (1, op, cl, 0) (1, op, cl, 0) (2, op, cl, n) (2, op, cl, 0) (2, op, cl, 0) (3, op, op, n) (3, op, op, 0) (3, op, op, 0) table 2. decomposition of the characteristic trace. dotted line: first tank, continuous line: second tank, dashed line: third tank. time input variables output variables va vb vc vd lev_a lev_b lev_c 1 op cl cl cl l 0 0 2 op cl cl cl n 0 0 3 op op cl cl n 0 0 4 op op cl cl n 0 0 5 op op op cl n 0 0 6 op op op cl n 0 0 7 op op op op n 0 0 figure 5. the occurrence graph of the first tank. diagnosis of technological systems 44(2) pp. 121–128 (2016) doi: 10.1515/hjic-2016-0015 127 the deviation list based on the trace pieces stemming from the filling process of the third tank (see the third column of table 3) is generated and compared to the terminal node of the occurrence graph. it can be stated that terminal nodes no. 21–24 possesses the same deviation list as the deviation list obtained from the characteristic trace of the third tank. this means that the operating mode of the third tank cannot be unambiguously determined, the set of possible operating modes, i.e. normal, leak, or fault, of valves can be defined. 4. conclusion a novel method for online fault diagnosis in a technological system is described in this paper. the method is based on the structural decomposition of a complex technological system. the process starts with the modelling of the technological system in the form of coloured petri nets. for the characterisation of sensor values and actuator states, qualitative value sets are used in the form of coloured tokens. this modelling method allows for the simulation of both normal and known faulty operations of the system. the diagnosis is performed using the occurrence graph of the basic units of the complex system. by generating the deviation list based on the normal and characteristic traces the fault or the set of possible faults can be determined. as a result of the structural decomposition, the diagnosis has to be performed on much smaller occurrence graphs but the effect of faults in previous units are taken into account. our method reduces the demand of computational efforts and search time. the proposed method was illustrated by a simple case study. acknowledgement the authors acknowledge the financial support of the hungarian research fund through grant no. k-115694. references [1] blanke, m.; kinnaert, m.; lunze, j.; staroswiecki, m.: diagnosis and fault-tolerant control (springerverlag, berlin, germany) 2006 doi: 10.1007/9781-84628-877-7 [2] hrúz, b.; zhou, m.: modeling and control of discrete-event dynamic systems with petri nets and other tool (springer-verlag, london, u.k.) 2007 [3] campos, e.j.; seatzu, c.; xie, x.: formal methods in manufacturing (crc press taylor and francis group, boca raton, usa) 2014 doi: 10.1201/b16529 [4] zaytoon, j.; lafortune, s.: overview of fault diagnosis methods for discrete event systems, ann. rev. control 2013 37(2), 308–320 � doi: 10.1016/j.arcontrol.2013.09.009 [5] sampath, m.; sengupta, r.; lafortune, s.; sin namohideen, k.; teneketzis, d.: diagnosability of discrete-event systems, ieee trans. automat. control 1995 40(9), 1555–1575 �� doi: 10.1109/9.412626 [6] prock, j.: a new technique for fault detection using petri nets, automatica 1991 27(2), 239–245 � doi: 10.1016/0005-1098(91)90074-c [7] cabasino, m.p.; giua, a.; seatzu, c.: fault detection for discrete event systems using petri nets with unobservable transitions, automatica 2010 46(9), 1531–1539 � doi: 10.1016/j.automatica.2010.06.013 [8] basile, f.; chiacchio, p.; tommasi, g.d.: sufficient conditions for diagnosability of petri nets, in proc. 9th int. workshop on discrete event systems, wodes (göteborg, sweden) pp. 370– 375, 2008 � doi: 10.1109/wodes.2008.4605974 [9] basile, f.; chiacchio, p.; tommasi, g.d.: an efficient approach for online diagnosis of discrete event systems, ieee trans. automat. control 2009 54(4), 748–759 � doi: 10.1109/tac.2009.2014932 [10] dotoli, m.; fanti, m.p.; mangini, a.m.; ukovich, w.: online fault detection in discrete event systems by petri nets and integer linear programming, automatica 2009 45(11), 2665–2672 � doi: 10.1016/j.automatica.2009.07.021 [11] fanti, m.p.; mangini, a.m.; ukovich, w.: fault detection by labeled petri nets and time constraints, proc. 3rd int. workshop on dependable control of discrete systems (dcds, saarbrucken, germany) pp. 168–173, 2011 � doi: 10.1109/dcds.2011.5970336 [12] lefebvre, d.; aguayo-lara, e.: initial study for observers application to fault detection � and isolation with continuous timed petri nets, ifacpapersonline 2015 48(7), 97–103 doi: 10.1016/j.ifacol.2015.06.479 figure 6. the occurrence graph of the second tank in the case of a positive failure bias in the first tank. figure 7. the occurrence graph of the third tank in the case of a positive failure bias in the first tank and leak in the second tank. pózna, gerzson, leitold, and hangos hungarian journal of industry and chemistry 128 [13] ramirez-trevino, a.; 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577 page 578 page 579 page 580 page 581 page 582 page 583 page 584 microsoft word 16.01 talibov.docx hungarian journal of industry and chemistry vol. 44(1) pp. 33–38 (2016) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2016-0004 vapour pressure of ethanol and 1-propanol binary mixtures misirkhan talibov1 and javid safarov1,2 1 department of heat and refrigeration techniques, azerbaijan technical university, h. javid ave. 25, az1073 baku, azerbaijan 2 institute of technical thermodynamics, university of rostock, albert-einstein str. 2, d-18059 rostock, germany the vapour pressure of binary mixtures containing ethanol and 1-propanol were investigated at temperatures ranging from 274.15 to 443.15 k using two different setups with static methods. the measured values were fitted to a clausius-clapeyron type relationship. the heat of evaporation of mixtures was determined from the vapour-liquid equilibria data. keywords: vapour pressure, ethanol, 1-propanol, static method, pressure transmitters, clausiusclapeyron equation 1. introduction investigation of thermodynamic properties of pure liquids and their mixtures is important in various fields of science, chemical engineering, economy and industry. aliphatic alcohols are commonly applied in chemical, biological, and medical uses as solvents for fats, oils, resins, paints, and nitrocellulose with regard to the manufacture of goods from perfumes to brake fluids [1]. in addition, the studied solutions of ethanol (c2h5oh) and 1-propanol (c3h7oh) are also used as heat transfer fluids in heat reservoirs, solar heating systems, oxygenates in fuels, and cryogenic power generation systems [2]. for the design and modelling of such applications, the determination of flow in pipes, heat transfer, and mass transfer operations requires the knowledge of thermophysical properties. density, vapour pressure, speed of sound, viscosity, and heat capacity often need to be defined for these purposes. this work is a continuation of our previous publications in the field of thermophysical properties of alcohol and their solutions [3–6]. hereby, the vapour pressure of binary solutions of (1-x) c2h5oh + x c3h7oh were investigated. the vapour pressure data of binary solutions of ethanol and 1-propanol at different temperatures and concentrations were determined. after the analysis of the literature using “thermolit” from nist, we concluded that only a few vapour pressure values for these systems have been reported to date [7–11]. *correspondence: javid.safarov@uni-rostock.de early studies by parks and schwenk [7] reported the vapour pressure of a (1-x) c2h5oh + x c3h7oh mixture at 298.15 k using glass apparatus and the differential method. a good commercial grade ethanol (w = 99.9%) and "refined" commercial 1-propanol (w = 99.34%) were used during the preparation of solutions. later, udovenko and frid [8] investigated the vapour pressure of the same mixture, but within a higher temperature range (323.15 to 353.15 k) using the dynamic method. the vapour liquid equilibria (vle) of these systems were analysed using a refractometer. the activity coefficients γ of both pure components were calculated. a series of studies in the early 90s included the work of zielkiewicz [9], who studied the vapour pressure at 313.15 k using the static method. dried ethanol and 1-propanol were used during the preparation of solutions. the temperature and pressure were controlled within ±0.001 k and ±0.004 kpa, respectively. binary samples were prepared by weighing within an uncertainty of ±0.0005 mole fractions. solution preparations were carried out using the dry nitrogen process. furthermore, pradhan et al. [10] investigated the vapour pressures of ethanol and 1propanol solutions at 303.15 k using the static method. for the fitting of obtained values a modified nrtl equation was used. quite recently, cristino et al. [11] carried out high temperature vle measurements for the system of ethanol and 1-propanol solutions within a temperature range of 403.2 to 423.2 k using a flow apparatus. alcohols used during the preparation of solutions had a confirmed purity greater than 99.9 weight percent. the pressure was controlled using two pressure transducers within ranges of 0 – 0.4 (uncertainty of ±0.0002 mpa) and 0–1.7 mpa (uncertainty of ±0.0009 mpa). the talibov and safarov hungarian journal of industry and chemistry 34 temperature was measured using a platinum resistance thermometer with an uncertainty of ±0.1 k. the statistical associating fluid theory for potentials of variable range (saft-vr) was used to model the systems and found to accurately reproduce the experimental data. using this analytical method the uncertainty of solution preparation was ±0.0001 mole fractions. the outcome of a literature survey summarised in table 1 is that only small temperature, pressure, and concentration intervals were investigated to date in addition to older literature examples decades ago that may have used out-dated measurement techniques. in this work, the vapour pressures of binary (1-x) c2h5oh + x c3h7oh solutions were investigated using two highly accurate, fully automatic static experimental setups and ultrapure merck quality chemicals. 2. experimental 2.1. samples and measurements ultra-pure ethanol emplura® (w = 99.995%, cas no. 71-36-3, art. nr. 8.22262.2500) and 1-propanol analyse emsure® acs, reag. ph eur (w = 99.995%, cas no. 71-23-8, art. nr. 1009971000) were purchased from merck schuchardt ohg, germany. the samples were used without further purification. they were carefully degassed in glass flasks with special vacuum leak-proof valves before measurements were taken. the water content is determined by karl fischer titration and was determined to be less than a mass fraction of 20 ppm. 2.2. experimental procedure the vapour pressure measurements of binary solutions of (1-x) c2h5oh + x c3h7oh were measured using two high-accuracy static experimental seweups [12–14]. the glass cells were used for vapour pressure measurements lower than ambient pressure at temperatures from 274.15 to 323.15 k. the metal cell was used for the higher temperature range of 323.15–433.15 k using the static method [12–14]. the glass cell method consists of absolute and differential parts (if the vapour pressure is smaller than the uncertainty of the absolute cell, 30 pa). the vapour pressure of the solution was always higher than the uncertainty of measurements between 274.15 and 323.15 k. the measurements within this temperature range were carried out only using the absolute cell of installation. the internal volume of the glass cell in absolute measurements is approximately 78.56 cm3, and the volume of steel tube cells is 1 cm3. the glass cell static method consists of a bolted-top cell in a water-bath kept at constant temperature (± 0.01 k) using a thermostat. the vapour pressure was measured using a calibrated high accuracy sensor head [type 615a connected to the signal conditioner type 670a, mks baratron, usa] attached to the top of the cell of various keller pressure transmitters: maximum pressure of 300,000 pa with an uncertainty of δp = ±(400 to 1,500) pa, maximum pressure of 1,000,000 pa with an uncertainty of δp = ±(1,000 to 5,000) pa and maximum pressure of 1,600,000 pa with an uncertainty of δp = ±(2,000 to 8,000) pa. the experimental uncertainty of the pressure in the absolute vapour pressure measurement using the glass cell is ±10–30 pa. the internal volume of the measurement cell is approximately 140 cm3. temperatures were measured using two different platinum resistance thermometers, pt-100. the second platinum resistance thermometer, pt-100, transfers the measured temperature in the computer via an omega pt-104a channel rtd input data acquisition module (omega engineering, inc., usa) for the measuring of temperature, with an accuracy of ±0.001 k. experiments were carried out starting from a low temperature (333.15 k) to a high temperature (433.15 k) at 10 k intervals. before the experiments, the measurement cells were washed with water, methanol and acetone and then all residual fluids were removed. this procedure requires approximately 2 to 3 h or more to reach the table 1. summary of the vapour pressure p literature investigations of a (1-x) c2h5oh + x c3h7oh mixture. reference method properties temperature (t in k) concentration (x mole fraction) uncertainty δp fitted density equation purity source parks [7] 1924 ga p, t, ∆h 298.15 0.0000 to 1.0000 99.9% (et) 99.34% (pr) cs udovenko [8] 1948 dm p, t, γ 323.15 – 353.15 0.0000 to 1.0000 cc arg (et) arg (pr) r zielkiewicz [9] 1993 sm p, t 313.15 0.0436 to 0.9291 ±0.004 kpa poch pradhan [10] 1993 sm p, t 303.15 0.0306 to 0.9700 ±0.001 kpa 99.9% (et) 99.6% (pr) ac cristino [11] 2015 fa p, t, vle 403.20 – 423.20 0.0017 to 0.9993 ±0.0002 – ±0.0009 mpa saft-vr 99.9% (et) 99.9% (pr) p (et) fs (pr) ga, glass apparatus; ∆h, heat of mixing; p, vapour pressure; t, temperature; x, mole fraction; et, ethanol; pr, 1-propanol; cs, commercial sample; dm, dynamic method; γ, activity coefficient; cc, clapeyron-clausius equation; arg, analytical reagent grade; r, reachim, ussr; sm, static method; poch, avantor performance materials poland s.a.; ac, aldrich chemical; fa, flow apparatus; saft-vr, statistical associating fluid theory; vle, vapour-liquid equilibrium; p, panreac; fs, fisher scientific. vapour pressure of ethanol and 1-propanol binary mixtures 44(1) pp. 33–38 (2016) doi: 10.1515/hjic-2016-0004 35 desired minimal pressure (20–30 pa). equilibration of the cells is a rapid process and a constant pressure in the stationary regime is reached within 15 minutes. equilibrium pressure readings are performed in triplicate approximately 10 to 20 min intervals. specific quantities of ethanol and 1-propanol were evacuated, degassed in two separate flasks and connected using an adapter [12]. ethanol flowed into a flask containing 1-propanol and the concentration of the solution was determined using the weight of the flask containing the solution on an electronic scale (sartorius ed224s, germany) with an uncertainty of 0.0001 g. a quantity of the solution was injected into the equilibrium cells up to approximately 50% of their volume. the vapour pressures of the water, methanol, acetone, toluene, 1-butanol, etc. were measured as reference substances for testing both setups [12–14]. the experimental vapour pressure results were assessed to be reliable to within an average uncertainty of ±0.05% according to test measurements. 3. results and discussion the measured experimental vapour pressures for an ethanol/1-propanol mixture within the temperature range of 274.15 to 433.15 k are listed in table 2, and are also shown in fig.1. the vapour pressures of pure alcohols were taken from refs. [15–16]. the experimental vapour pressure results, p in pa of investigated solutions were fit to the antoine equation: ln (p) = aa – ba / ( t/k + ca ) (1) table 2. experimental mole fraction x of 1-propanol, and vapour pressure p (in pa) of a solution of (1-x)c2h5oh + x c3h7oh a temperature mole fraction of 1-propanol (x) (k) 0.0000b 0.0989 0.1918 0.4034 0.5935 0.7971 0.9038 1.0000c 274.15 1684 1490 1374 1116 897 672 530 515 278.15 2248 1980 1843 1498 1219 902 739 697 283.15 3155 2810 2620 2149 1761 1330 1102 1008 293.15 5842 5390 5023 4186 3442 2670 2260 2034 303.15 10458 9762 9180 7780 6521 5150 4402 3854 313.15 18054 16872 15880 13558 11502 9260 8030 7048 323.15 29356 27918 26430 22909 19560 15890 13873 12273 333.15 46796 44590 42200 36700 31777 26000 22992 20472 343.15 71902 68812 65321 57200 49784 41400 36903 32867 353.15 108174 103196 98000 86256 75504 63400 56954 50997 363.15 157911 150535 143157 126500 111128 94202 85257 76746 373.15 224798 214272 203797 180800 159521 136296 123958 113402 383.15 313786 298327 284000 252345 223518 192294 176009 161109 393.15 429264 407124 387678 345105 306612 265259 244002 223982 403.15 576481 545340 519543 462803 412430 358865 331402 305477 413.15 759512 718454 684376 610504 545107 476594 441754 408702 423.15 982342 932045 887923 792004 708954 622271 578714 539077 433.15 1254038 1191945 1135123 1012845 907984 800473 746309 702376 443.15 1582042 1505202 1432927 1278187 1147706 1015139 949123 893968 a standard uncertainties u are u(t) = 0.01 k and u(x) = 0.0001 mole fractions and the combined expanded uncertainties uc are uc(p) = 30 pa for p < 0.1 mpa, uc(p) = 1500 pa for p < 3 mpa, and uc(p) = 8000 pa for p < 16 mpa (level of confidence = 0.95); b the vapour pressure values of ethanol were taken from ref. [15]; c the vapour pressure values of 1propanol were taken from ref. [16]. figure 1. plot of vapour pressure p (in kpa) of a (1-x) c2h5oh + x c3h7oh solution mixture as a function of 1-propanol mole fraction x. ¿, 274.15 k; ¢, 278.15 k; ▲, 283.15 k; �, 293.15 k; ▼, 303.15 k; ò, 313.15 k; ì, 323.15 k; ¯, 333.15 k; £, 343.15 k; r, 353.15 k; �, 363.15 k; s, 373.15 k; °, 383.15 k; ⊕, 393.15 k; «, 403.15 k; ¶, 413.15 k, ◐, 423.15 k; x, 433.15 k; ◑, 443.15 k; lines fit to eqs.(3) and (4). talibov and safarov hungarian journal of industry and chemistry 36 the fitted constants aa, ba, and ca for the investigated solutions are summarised in table 3 with the standard mean deviation defined as follows: δp/p =100/n ⋅ (pexp. − pcal. )/pexp.⎡⎣ ⎤⎦ i=1 n ∑ (2) from table 3, it can be seen that coefficients aa, ba, and ca exhibit non-trivial dependence from the mole fraction of 1-propanol. fitting of these coefficients was a challenging task. thus, we also used a clausius– clapeyron-type equation to obtain the vapour pressure results of the investigated solutions from mole fractions of 1-propanol: ln p = acc + bcc t +ccc lnt +dcct , (3) where p is vapour pressure in pa; t is the temperature in k; and acc, bcc, ccc, and dcc are the coefficients of the equation, depending on the mole fraction of the solvent as follows: acc = aix j bcc = bix j i=0 3 ∑ ccc = cix j dcc = dix j i=0 3 ∑ i=0 3 ∑ i=0 3 ∑ (4) the coefficients ai, bi, ci, and di for the investigated ethanol/1-propanol mixtures are tabulated in table 4. the uncertainty of fitting was approximately ur(δp/p) = 0.7678. the plots of deviation of experimental pexp and calculated pcal vapour pressure values as a function of figure 2. deviation of experimental pexp and calculated pcal vapour pressure values versus pressure p using eqs.(3) and (4) at various temperatures and mole fractions. figure 3. deviation of experimental pexp and calculated pcal vapour pressure values versus temperature t using eqs.(3) and (4) at various pressures p and mole fractions. figure 4. deviation of experimental pexp and calculated pcal vapour pressure values versus mole fraction x using eqs.(3) and (4) at various pressures p and temperatures t. table 4. clausius clapeyron equation fitting parameters ai, bi, ci, and di from eqs.(3) and (4). ai bi ci di a0 = 103.156 b0 = -7994.80 c0 = -12.3406 d0 = 0.0098481 a1 = 251.788 b1 = -8366.78 c1 = -42.1398 d1 = 0.0527419 a2 = 222.344 b2 = -7727.52 c2 = -36.8168 d2 = 0.0438405 a3 = -446.740 b3 = 14403.70 c3 = 74.8888 d3 = -0.0951465 table 3. antoine parameters aa, ba, ca and percent deviations (δp/p in %) as a function of 1-propanol mole fraction. mole fraction aa ba ca δp/p 0.0000a 23.1773 3461.23 -54.3818 0.6234 0.0989 22.8524 3275.81 -63.4603 0.0742 0.1918 22.7353 3228.33 -65.9886 0.0689 0.4034 22.4745 3118.11 -72.4808 0.1652 0.5935 22.3425 3077.68 -76.1926 0.2204 0.7971 22.2692 3064.56 -79.8646 0.3263 0.9038 22.1582 3009.02 -84.6711 0.1983 1.0000b 22.7515 3373.18 -70.0769 0.8270 a from ref. [15]; b from ref. [16]. vapour pressure of ethanol and 1-propanol binary mixtures 44(1) pp. 33–38 (2016) doi: 10.1515/hjic-2016-0004 37 pressure, temperature, and mole fraction using eqs.(3) and (4) are shown in figs.2-4, respectively. the enthalpies of vaporisation, δhvap in j mol-1, for the (1-x) c2h5oh + x c3h7oh mixture at the four middle temperatures (293.15, 333.15, 373.15, and 423.15 within temperature ranges of 274.15–313.15 k, 313.15–353.15 k, 353.15–393.15 k, and 373.15–443.15 k, respectively) were defined using eq.(5) from ref. [12]: d ln p d 1 t ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ = − δhv r (5) if we plot ln(p) as a function of 1/t, we can define δhv from the gradient of the line: δhv = −r ⋅ d ln p d 1 t ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ . (6) after the integration of eq.(6) we can find ln p = − δhv r ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ 1 t ⎛ ⎝ ⎜ ⎞ ⎠ ⎟+ intercept (7) δhv = rt (intercept − ln p) (8) the calculated enthalpy of vaporisations δhv in j mol-1 for the (1-x)c2h5oh + x c3h7oh mixture within the temperature range of 274.15–443.15 k are listed in table 5 and compared to the available literature results [7–11] shown in fig.5. when the measured values by parks [7] at t = 298.15 k are compared to our values, we obtain ∆p = ±242 pa or ∆p/p = ±5.24% deviations. the maximum deviation is ∆p = 394 pa at x = 0.759 mole fractions of 1-propanol. the parks’ values [7] are higher than our results and the vapour pressures of ethanol exhibit small deviations compared to ours and all other literature values presented in ref. [15]. the vapour pressure of 1propanol published in ref. [7] exhibits a large deviation from ours and all other literature values presented in ref. [16]. we hypothesise that the vapour pressure values of 1-propanol with high deviation from the literature were used during the analysis of concentration dependence in ref. [7]. the 44 data points of udovenko and frid [8] measured within the range of 323.15 – 353.15 k are mostly higher than our values. the average deviations of both sources are ∆p = ±242 pa and ∆p/p = ±5.24% with maximum deviations of ∆p = 2952 pa at t = 343.15 k and x = 0.5 mole fractions of 1-propanol. the 11 data points of zielkiewicz [9] at t = 313.15 k exhibit small deviations from our results with ∆p = ±33 pa and ∆p/p = ±0.2631% mean deviation. the maximum obtained deviation in ∆p = -59 pa at x = 0.2793 mole fractions of 1-propanol. the next 22 data points of pradhan et al. [10] are mostly higher than our values. the average mean deviation of this comparison is ∆p = ±143 pa and ∆p/p = ±2.2378%. the maximum obtained deviation in ∆p = 209 pa and ∆p/p = ±3.5182% at t = 303.15 k and x = 0.7002 mole fractions of 1-propanol. the last 18 experimental values from the recent work of cristino et al. [11] measured at high vapour pressure intervals of 304.2–967.4 kpa also exhibit small differences from our values as the mean deviation between two experimental sources is ∆p = ±5698 pa and ∆p/p = ±0.9227%. the maximum deviation of this comparison is ∆p = -21134 pa at t = 413.2 k and x = 0.0002 mole fractions of 1-propanol. 4. conclusion vapour pressure measurements for the binary mixture of ethanol and 1-propanol over a wide range of temperatures from 274.15 k to 468.15 k were studied. the antoine and clausius–clapeyron equations were used to fit the experimental results. the enthalpies of vaporisation at four various temperatures were calculated. the available literature values were compared with measured values and small deviations were observed. figure 5. deviation of experimental pexp and literature plit vapour pressure values for the ethanol/1-propanol mixture versus 1-propanol mole fraction using eqs.(3) and (4) at various pressures p and temperatures t. table 5. enthalpy of vaporisation, δhv in kj mol-1 for a (1-x) c2h5oh + x c3h7oh mixture at various temperatures. x 293.15 k 333.15 k 373.15 k 423.15 k 0.0000 43.245 41.210 39.579 37.457 0.1574 43.905 41.300 39.542 37.576 0.2876 44.499 41.416 39.425 37.553 0.5351 45.768 41.989 39.707 37.718 0.7130 46.768 42.811 40.157 38.002 0.8699 47.809 43.815 40.965 38.613 0.9411 47.887 44.441 41.546 39.125 1.0000 47.908 45.052 42.330 39.963 talibov and safarov hungarian journal of industry and chemistry 38 acknowledgement the research was supported by university of rostock and azerbaijan technical university references [1] cano-gómez, j.j.; iglesias-silva, c.a.; ramosestrada, m.; hall, k.r.: densities and viscosities for binary liquid mixtures of ethanol + 1-propanol, 1-butanol, and 1-pentanol from 293.15 to 328.15 k at 0.1 mpa, j. chem. engng. data, 2012 57, 2560−2567 doi 10.1021/je300632p [2] kumagai, a.; yokoyama, c.: liquid viscosity of binary mixtures of methanol with ethanol and 1propanol from 273.15 k to 333.15, int. j. thermophys., 1998 19, 3−13 [3] aliyev, f.sh.; safarov, j.t.; talibov, m.a.; shahverdiyev, a.n.: temperature and pressure dependence of density of the methanol and 1propanol solutions, j. fundam. sci. azerbaijan technical uni., 2008 7(3), 55–61 [4] abdulagatov, i.m.; aliyev, f.sh.; safarov, j.t.; talibov, m.a.; shahverdiyev, a.n.; hassel, e.: high-pressure densities and derived volumetric properties (excess and partial molar volumes, vapour-pressures) of binary methanol + ethanol mixtures, thermochimica acta, 2008 476(1-2), 51– 62 doi 10.1016/j.tca.2008.07.011 [5] aliyev, f.sh.; safarov, j.t.; talibov, m.a.; shahverdiyev, a.n.: (p,ρ,t) properties of ethanol and 1-propanol solutions, j. fundam. sci. azerbaijan technical uni., 2008 7(1), 35–39 [6] safarov, j.t.; aliyev, f.sh.; talibov, m.a.; shahverdiyev, a.n.: experimental densities of methanol + 1-propanol at temperatures from 298.15 to 423.15 k and at pressures up to 40 mpa, proc. 18th eu. conf. thermophysical prop. (pau, france) 2008 p. 45 [7] parks, g.s.; schwenk, j.r.: some physicalchemical prop. of mixtures of ethyl and n-propyl alcohols, j. phys. chem., 1924 28(7), 720–729 doi 10.1021/j150241a004 [8] udovenko, v.v.; frid, ts.b.: evaporation heat in binary mixtures: ii. zh. fiz. khim., 1948 22(9), 1135–1145 [9] zielkiewicz, j.: vapour + liquid equilibria in heptane + ethanol + propan-1-ol at the temperature 313.15 k, j. chem. thermodyn., 1993 25(9), 1077–1082 doi 10.1006/jcht.1993.1105 [10] pradhan, a.g.; bhethanabotla, v.r.; campbell, s.w.: vapour-liquid equilibrium data for ethanoln-heptane-1-propanol and ethanoln-heptane-2propanol and their interpretation by a simple association model, fluid phase equil., 1993 84, 183–206 doi 10.1016/0378-3812(93)85123-4 [11] cristino, a.f.; morgado, p.; galindo, a.; filipe, e.j.m.; palavra, a.m.f.; nieto de castro, c.a.: high-temperature vapour–liquid equilibria for ethanol-1-propanol mixtures and modeling with saft-vr, fluid phase equil., 2015 398, 5–9 doi 10.1016/j.fluid.2015.04.009 [12] safarov, j.t.; kul, i.; talibov, m.a.; shahverdiyev, a.n.; hassel, e.: vapour pressures and activity coefficients of methanol in binary mixtures with 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, j. chem. engng. data, 2015 60(6), 1648–1663 doi 10.1021/je501033z [13] talibov, m.a.; safarov, j.t.; shahverdiyev, a.n.; hassel, e.: vapour pressure of geothermal and mineral waters of yardimli district of azerbaijan, herald kazan state technol. uni., 2014 17(2), 114–118 [14] safarov, j.t.; ahmadov, b.; mirzayev, s.; shahverdiyev, a.n.; hassel, e.: vapour pressures of 1-butanol over wide range of temperatures, chemistry, bulgarian j. sci. ed., 2015 24(2), 226– 246 [15] talibov, m.a.; safarov, j.t.; shahverdiyev, a.n.; hassel, e.: vapour pressure of ethanol in a wide range of temperature, azerbaijan nat. acad. sci., ser. phys. math. techn. sci., 2015 2, 61–71 [16] talibov, m.a.; safarov, j.t.: vapour pressure of 1propanol in a wide range of temperature, azerbaijan nat. acad. sci., ser. phys. math. techn. sci., 2016 2, in press hungarian journal of lndustrial chemistry veszprem vol. 30. pp. 711 (2002) kinetic study of blue m -eb dye sorption on ion exchange resins d. ~uteu, d. bilba and c. zaharia 1 (department of analytical chemistry 1department of environmental engineering, faculty of industrial chemistry, technical university of iasi, blvd. d. mangeron nr. 71a, p.o. box.lo2002, 6600 iassy, romania) received: february 9, 2001 a kinetic study concerning the blue m-eb reactive dye sorption from aqueous solutions on purolite ion exchange resins of macroporous (a 500) and gel (a 400) type has been made. to establish the rate controlling step, the time required for 50% sorption equilibrium( tv2 ), rate constant of the process ( k ), diffusion coefficient and activation energy (ea) for both resins have been calculated. on the basis of the calculated values it is obvious that sorption process is in the diffusion domain, rate-controlling step is the particle diffusion. this result is confirmed by the fact that reactive dye blue m-eb sorption is in good agreement with shell-progressive model. keywords: exchange resins, dye removal, sorption, kinetic study, wastewaters, decontamination introduction the decontamination of natural or wastewaters impurified with organic pollutants has become one of the needs of the day. the great diversity in chemical structure of the dyes as well as the variable concentrations of dyes and co-solutes, such as inorganic salts, sizing agents and surfactants in the effluents of dyehouse operations make impossible a general available method for removing textile dyes from waste water [1-3]. the several traditional wastewater treatment methods (biological processes, ozonation, coagulation, membrane filtration, etc.) are acceptable in decolorizing textile wastewaters with a satisfactorily cost-effectiveness [ 4]. due to the polar nature of the their functional groups, most commonly-used dyes are relatively easy to remove by sorption on various materials: activated carbon [5], non ionic or ionic synthetic polymers [6,7], biomass-based exchangers [8], anionic clay minerals [9] and also adsorbents [loj. the dye binding potential of these materials is affected by physic-chemical characteristics of both sorbent and dye~ there compatibility, as well as the operating conditions (particle size of granulated sorbent, ph, ionic strength, temperature, solution flow rate, etc.) [11]. the economic use of various sorbents in removing color from textile effluents, but also a better understanding of these processes in natural systems require informations on the kinetics of dye uptake. the thermodynamic, kinetic characterization, the mechanism and determinant factors study of the sorption process of reactive dyes on purolite ion exchangers are of major important stages in evaluation of these resins application . in the recovery of wastewaters of textile industry. this paper describes a study of blue m-eb reactive dye sorption kinetics onto purolite anion exchange resins. for this purpose, resin loading as a function of the contact time was monitored. experimental the experiments were carried out using ion exchange resins purchased from purolite international ltd (uk), their typical properties are listed in table 1. the reactive bifunctional monochlortriazinic dye blue m-eb (fig.l) was used as a stock aqueous solution containing 0.4 g l"1 • the working solutions were prepared by appropriate dilution of the stock solution with doubly distilled water. contact information: e-mail: dsuteu@ch.tuiasi.ro.; d. suteu, stejar str., 37 a, bl.ah sc.b. et.l. ap.2, 6600, iasi, romania 8 table 1 properties of purolite resins used in kinetic measurements parameter type of purolite resins a-400 a-500 matrix polystyrene­ divinylbenzene gel r-(ch3)3n+ cr polystyrene­ divinylbenzene macroporous r-(ch3)3w cr structure functional group ionic form mean particle diameter/ 0.64 (± 0.03) 0.64 (± 0.03) mm capacity*/ meqg1 3.72 3.93 * determined by ph-metric titration of resins dried at room temperature for 72 hours table 2 sorption half times, tu2 at different concentrations and temperatures of blue m eb dye solution for the purolite resins tu2f min col gl-1 t/k a-400 a-500 0.10 284.15 20 16 0.10 296.15 17 10 0.14 284.15 14 13 0.20 284.15 11 9 --(hh2 hl~r-nh oll' oh nf!--<n n n.._j~ ~ sj~ n-{ j ~-n-n~-nh n-=n.~ cl n~js sojna na03 naojs so]na fig.] structure of reactive dye blue m-eb the continuous kinetic experiments were performed by the ''limited bath" technique. weighed amounts of anionic resin (1g) were contacted with 250 ml solution containing known amounts of reactive dye, under constant vigorous stirring. the temperature of solutions was held constant (284.15 and 296.15 k) during the experiment with a thermostatic bath. after the predetermined time intervals, varying from 5 to 60 minutes, samples of 2ml supernatant were taken for measurements of dye content. analysis of blue m-eb dye was carried out by spectrophotometric method (amax = 650 nm) with a hach dr 200 uv-vis spectrophotometer. the extent of sorption was expressed by the fractional attainment of equilibrium~ f = !!!._ where, qt is qfj the amount of sorbed dye per gram of resin at time t and qo is the amount of dye sorbed per gram of resin after 24 hours results and discussion in our previous work [ 12], the equilibrium sorption of reactive dye blue m~eb onto purolite anion exchange resins was studied. the low capacity of resins to remove biue m-eb dye from industrial aqueous effluents has 0.9 0.8 0.7 0.6 -tr-o.log/l ij:.. 0.5 --e-0.14g/l 0.4 -e-0.20g/l 0.3 0.2 0.1 0 0 20 40 60 80 tin:e (min) fig.2a rate of sorption of blue m-eb dye on purolite a400 resin at different initial concentration. temperature= 296.15k 1.2 0.8 -e-o.lo!ifl ij:.. 0.6 -e-0.14!ifl 0.4 -e-0.20!ifl 0.2 0 0 20 40 60 80 tirre (nin) fig.2b rate of sorption of blue m-eb dye on purolite a500 resin at different initial concentration. temperature= 296.15k been explained by the inability of large dye molecules to saturate exchange sites of the sorbent (the steric hindrance effect). by potentiometric titration of released chloride it was found that immobilization of the dye on the studied resins takes place by an ion-exchange mechanism, but also 1t-1t interactions between the organic matrix of sorbent and condensed rings of the dye have a considerable importance. the stoichiometry of dye association with the anion exchange sites is a i: 1, such relationship is in good agreement with other workers [ 13]. in this paper the kinetics of blue m-eb reactive dye sorption on purolite anion exchange resins (a-400 and a-500) were studied with respect to the following variables: initial dye concentration, dye solution temperature and structure type of resin. sorption rates were measured for same particle size fractions and for a constant high degree of agitation to minimize the film diffusional resistance. the data, plotted as fractional attainment of equilibrium sorption (f) versus time (t), are reported in figs.2 and 3~ 0.9 0.8 0.7 0.6 0.5 -e-t(l) jl.t 0.4 -e-t (2) 0.3 0.2 0.1 0 0 20 40 60 80 time (min) fig.3a rate of sorption of blue m-eb dye on purolite a 400 resin at different temperatures, t/k, at initial concentration co=o.l gl-1 0.9 0.8 0.7 0.6 jl.t 0.5 -e-t(l) 0.4 -e-t (2) 0.3 0.2 0.1 0 0 20 40 60 80 time (min) fig.3b rate of sorption of blue m-eb dye on purolite a500 resin at different temperatures, t/k, at initial concentration co=o.l gl-1 the influence of equilibrium parameters on the rate of sorption was quantitatively evaluated by means of sorption half-time (t112) (table 2). it is seen that the initial dye concentration has a significant effect on sorption kinetics: increasing the dye concentration gradient between the solution and resins enhances sorption. also~ the increasing of dye solution temperature with -283k has a beneficent effect on the rate of sorption (and increase of 1.2 1.8 times), the results indicate that the process under investigation occurs in diffusion region. in addition, due to the much greater accessibility of the sorption sites (the more open structure), the macroporous resin a-500 provides a better kinetic 9 2 1.2 1.8 1 1.6 10.8 1.4 :! 1.2 n --*-" t(l) 1 6 '-" 0.6 -a-t(2) ;a 0.8 .s i 0.4 i 0.6 0.4 0.2 0.2 0 0 0 20 40 60 80 time (min) fig.4 test of equations land 2 for sorption of the blue m­ eb dye on purolite a500 at c0 = o.lg l-1 and t1 = 284.15k; t2 =296.15k properties toward dye ions than to the gel type resin a400. the ion sorption onto solid ion exchange resins must be considered as a liquid solid phase reaction including the diffusion of ions from the solution to the resin surface, the diffusion of ions within the resin particle itself and chemical reaction between ions and functional groups [14]. the sorption kinetic is governed by the slowest of these processes. in most cases, the rate-determining step in the kinetics has been established to be diffusion through either the externally adherent liquid film or resin particle. rate laws have been derived based on the nernst planck equation for film and particlediffusion controlled process [15]. if the liquid film diffusion controls the rate of process, the following expression can be used: in ( 1 -f) = k t (1) where k = 30~ is the kinetic coefficient or rate r08c constant /sec-1 , dis the diffusion coefficient in the film /cm2s·1• c and c are concentration of the incoming ions in solution and in resin, respectively /mmol l·1 ; r0 is the radius of sorbent particle/em and 3 is the diffusion film thickness /em. the rate equation for intraparticle diffusion control is given as: -ln(j-1!)= kt (2) where k = ~ 2 is the kinetic coefficient /s·1 ~ dis the ro diffusion coefficient in the resin phaselcm2s"1 • the sorption data of blue m-eb dye onto both studied resins were analyzed by the rate equations for the liquid film and the particle diffusion models (figs.4 and 5). although the extremely low concentration of the dye in the initial solution suggests a liquid. film diffusion 10 table 3 kinetic parameters and the energy of activation for sorption of blue m-eb dye ( c0 = 0.1 gl"1 ) onto purolite resins resin t/k k ls-1 d i cm2s-1 ea/ jmor1 a-400 284.15 5.33 x 10-s 1.53 x 10-s 36.25x103 a-400 296.15 9.87 x w-s 2.83 x w-8 a500 284.15 2.99 x w-4 8.36 x w-8 35.94x103 a-500 296.15 5.37 x w-4 3.07 x to·7 2 1 1.8 0.9 1.6 0.8 1.4 0.7 ~ 1.2 0.6 ,..,--1 0.5 ~ .a 0.8 0.4 ..e! 1 -*-t (1) -e-t(2) 0.6 0.3 0.4 0.2 0.2 0.1 0 20 40 60 time (mfu.) fig.s test of equations land 2 for sorption of the blue m­ eb dye on purolite a500 at c0 = o.lg l-1 and t 1 = 284.15k; t2 =296.15k controlled model, a linear correlation between -in (1-f) and time is observed orily during the initial minutes. the linear regression analysis shows that the kinetics of dye sorption onto both studied resins fit the rate equation for the particle diffusion model (the correlation coefficients, r = 0.9994 0.9997). the values of the sorption rate constants and of the diffusion coefficients in the resin phase calculated from the slope of the straight lines (fig.4 and 5), summarized in table 3, show that the macroporous type resin a-500 is faster in reaching equilibrium. also, an increase in temperature is favourable to increase the values of diffusion coefficients of blue m-eb dye sorption with respect to ionites of both structures. taking into account the rate constants, k , at two different temperatures, the activation energy~ ea. required for sorption process was calculated using arrhenius equation: k = koexp( -eairt) (3) where ea is the activation energy/ j mor1 and rgas constant= 8.3144 jmor1 k-1 • the values of activation energy (table 3) have confirmed the diffusion nature of dye sorption. to explain the dye concentration effect on the rate of sorption the .. moving boundary'y model of sorption kinetics bas been considered [16]. this model assumes a 0.8 0.7 0.6 el:;' 0.5 ('.1 ~ 0.4 ~~ 0.3 c';l 0.2 ~ 0.1 0 -0.1 t:itre (min) fig.6a test of equation 5 for sorption of blue meb dye on purolite a400 (d) and a500 (.6.) resins at t1 = 284.15k ~ ~ ~ c';l ~ 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 -0.1 y 1 = 0.0076x0.0032 r2 =0.9991 20 40 t:itre /rrim. fig.6b test of equation 5 for sorption of. blue meb dye on purolitea-400 (d) anda-500 (0) resins at t2 =296.15k sharp boundary that separates a completely reacted shell from an unreacted core and that advances from the surface toward the center of the solid with the progression of sorption. the rate equation for the moving boundary model is given as: (4) k = 6;_,~ is the kinetic coefficient /s-1 , a the qro molar distribution coefficient, q the sorption capacity of the unreacted resin bead at equilibrium i mmol l"1 • in order to test the moving boundary model for dye so~tion onto both purolite resins, the plots of [ 33(1f) 2f 1 versus time have been presented in fig.6. linearity of the plots obtained show the validity of the moving boundary model, yielding correlation coefficients in the 0.9997. conclusions research on the kinetics of blue m-eb reactive dye sorption by using purolite anion exchangers of both gel and macroporous structures has resulted in the conclusion that dye sorption is limited by intraparticle diffusion and follows moving boundary behavior. the dependencies found : ln( 1-f2 ) vs, t and [ 33(1-f)213 2f ] vs, t proves this model. dye sorption using macroporous resin proceeds faster than with gel type resin. the values of diffusion coefficients and activation energy of dye sorption on purolite resins of both structures confrrms that the process in investigation occurs in diffusion region. references 1. namasivayam c. and kanchana n.: chemosphere, 1992, 25(11), 16911705 2. bertea a.: environmental protection (rom. language), ed. by technical university "gh. asachi", iassy, 1997 . 3. suteu d., bilba d. and nacu a.: celuloza §i hartie (bucharest), 1996,45,35-40 4. maconeanu m., teodosiu c. and duca gh.: the avancented clean-up waste waters containing organic unbiodegradable compounds (rom. language) ed. gh. asachijassy, 1997 11 5. yeh r. y. -l. and thomas a.: j. chern. tech. biotechnol., 1995,63,48-54 6. hwang m. c. and chen k. m.: j. appl. polym. sci.,l993,50, 735-744 7. suteu d., bilba d. and gorduza v. m.: bull. polyt.inst(jassy), 1997, 47, 61-66 8. lazlo j. a.: ion exchange developments and application '(proceedings of iex'96), j. a. greig (ed.), royal soc. of chern., cambridge, pp. 128134, 1996 9. welb m.: ion exchange developments and application (proceedings of iex'96), j. a. greig (ed.), royal soc. of chern., cambridge, pp.135142,1996 10. yeh r. y. -l. and thomas a.: j. chern. tech. biotechnol., 1995, 63, 55-59 11. suteu d.: "concentration by sorption in organic analysis", phd. thesis, technical university, iassy, pp.52-55,1997 12. suteu d., bilba d. and nacu a.: revista de chimie (bucharest), 1998, 49(4), 245248 13. symons j. m., fu-p. l. k and kim p. h. -s.: international water conference proceedings book, pittsburgh, p.a. october, pp.92-98,1992 14. helfferich f.: ion exchange, marinsky (ed.), j. a. marcel dekker, ny,vol.l, ch.2, 1966 15. petruzzelli d., kalinitchev a., soldatov v. s. and tiravanti g.: ind. eng. chern. res., 1995, 34,2618-2624 16. chanda m. and rempel g. l.: ind. eng. chern. res. 1994,33,623-630 page 10 page 11 page 12 page 13 page 14 hungarian journal of industry and chemistry vol. 46(2) pp. 47–54 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0018 the initial magnetic susceptibility of dense aggregated dipolar fluids sándor nagy *1 1institute of mechatronics engineering and research, university of pannonia, gasparich m. u. 18/a, zalaegerszeg, h-8900, hungary to correlate the dipole moment and density dependence of the initial magnetic susceptibility on the basis of the former related theories and the probability analysis of chain formation, physically based analytical correlation equation was derived. after the local magnetic field strength and the chaining probability between two particle have been determined the chain and particle distributions came from the geometric distribution. the initial magnetic susceptibility was resulted from the summation of langevin initial susceptibility of k-length chains. two particles were considered in a chain if the interaction energy between them was below a certain limit. by varying slightly this energy limit around 70–75 % good agreement has been obtained between the simulation and theoretical data. monte carlo simulations were used to calculate the initial magnetic susceptibility of dipolar hard sphere system at different dipole moments and densities. keywords: dipolar fluids, initial susceptibility, monte carlo simulation 1. introduction the investigation of dipolar fluids has been induced by the evolution of magnetorheology and electrorheology over the last two decades. the viscosity of electrorheological (er) fluids increases dramatically due to an external electric field. er fluids can be obtained by dispersing solid particles with dielectric permittivity εp in a fluid with dielectric permittivity εf , where εp > εf . the dispersed particles are of between 0.1 mm and 100 mm in diameter. the polarized particles are organized into pairs and chains. the magnetic analogy of the phenomenon described above is the magnetorheological (mr) effect. if the magnetic permeabilities of the liquid and dispersed particles differ, then in an external magnetic field the particles are also arranged in chains. the dispersing medium can be water, oil, an organic solvent, etc. while the dispersed particles can be some kind of iron oxide or ferrit. in this paper, the magnetic terminology and centimetregram-second (cgs) system of units are used. in the figures, the reduced quantities are applied. electroand magnetorheological fluids typically exhibit a reduced density of up to ρ∗ = 0.4 (where ρ∗ = ρσ3; ρ and σ are the concentration and diameter of the suspended particles, respectively). the magnetic properties, e.g. magnetization curve and initial magnetic susceptibility, are well described by the various theories within this range of reduced density. the magnetization m can be obtained by summation of the dipole moments in the *correspondence: sata123.sandor@gmail.com unit volume: m = 1 v ∑ i mi. (1) in the absence of any external magnetic field the fluid is isotropic and according to eq. 1 the magnetization is zero. when any external magnetic field is present, the field-oriented components of dipole moments should be summarized as m = ρm 〈cos θ〉 h0 h0 , (2) where h0 = |h0| and 〈cos θ〉 is the ensemble average of the cosine of the angle between mi and h0, and m = |mi|. since the directions of h0 and m are identical, vector notation can be omitted. the initial magnetic susceptibility is equal to the initial gradient of the magnetization curve χ0 = ∂m ∂h0 ∣∣∣∣ h0=0 . (3) in practice, er and mr fluids can be used for the transmission of torque or force, in vibration dampers and braking systems, etc. the magnetic properties generally are calculated from monte carlo simulations because it is not necessary to know the velocity and acceleration of the particles nor the forces between them. the expressions of the related models are listed in table 1. (one line belongs to one theory and the first line is the head of the table, e.g. table 1: 2.4 refers to the 4th cell in the 2nd line within the 1st table.) three different mailto:sata123.sandor@gmail.com 48 nagy table 1: the expressions of the effective magnetic field, the magnetization and the initial magnetic susceptibility of the related theories. model he – effective magnetic field m – magnetization χ0 – initial magnetic susceptibility 1 “langevin” [1] h0 ρml ( mh0 kbt ) ρm2 3kbt = χl 2 “weiss” [2] h0 + 4π 3 m(he) ρml ( mhe kbt ) χl 1− 4π 3 χl 3 “pshenichnikov” [3] h0 + 4π 3 m(h0) ρml ( mhe kbt ) χl ( 1 + 4π 3 χl ) 4 “ivanov” [4] h0 + 4π 3 m(h0) ( 1 + 4π 48 ∂m ∂h0 ) ρml ( mhe kbt ) χl ( 1 + 4π 3 χl + (4π) 2 144 χ2 l ) 5 “tani” and “szalai” [5, 6] m(h0) = ρml+ 4π 3 ρ 2βm3ll ′ + 1 10ρ 2β2m5ζ ′ idd∆ − 16π2 27 ρ3β2m5ll ′ + 1 3ρ 3β2m5ll ′ idd∆ χl ( 1 + 4π 3 χl + (4π)2 144 χ2 lf(ρ) ) magnetic fields will be used. the applied external magnetic field is denoted by h0 and the sum of the external and generated magnetic fields by he. he is always parallel to h0. the third one is the local magnetic field hl which is of chain-parallel orientation and its formation is due to dipole-dipole interactions between the particles. the well-known langevin function is applied from the initial theory [1] in the magnetization formula (table 1: 1.3), where l(α) = cothα − 1/α. the magnetic dipole moment of the particles is denoted by m and the applied external magnetic field by h0, while the boltzmann constant is represented by kb. the expression of magnetic susceptibility can be written as in table 1: 1.4. this is known as langevin susceptibility which is indicated by χl as well. in this approach the effective magnetic field he exerted on the given particle is equal to the external magnetic field (table 1: 1.2). according to the more accurate model by weiss [2] the effective magnetic field is equal to the sum of the external magnetic field and the magnetic field induced by the magnetization (table 1: 2.2). the formula of the magnetization (table 1: 2.3) is similar to the previous one but h0 is substituted by he. due to the iterative nature of the magnetization expression the initial magnetic susceptibility (table 1: 2.4) exhibits divergence at χl = 3/4π, therefore, overestimates the real values. above this initial magnetic susceptibility limit, when χl ≥ 3/4π, the zerofield magnetization is not equal to zero: m(h0) 6→ +0, ifh0 → +0. moreover, in weak external magnetic fields, one h0 value belongs to three equilibrium magnetization values. the effective magnetic field has been substituted for the external magnetic field in the expression of the effective magnetic field (table 1: 3.2) in the theory by pshenichnikov et al. [3]. the magnetization formula (table 1: 3.3) is the same as in weiss’ theory. the initial magnetic susceptibility (table 1: 3.4) is in good agreement with the simulations but underestimates them at higher densities or higher dipole moments. that is why it seems to be a good method to extend the expression of the effective magnetic field (table 1: 4.2) by ivanov et al. [4]. the magnetization formula is once again identical (table 1: 4.3) but a new term is introduced in the initial magnetic susceptibility (table 1: 4.4). although at higher densities it yields higher values than in pshenichnikov’s model, it underestimates the simulation data as well. the factor of the third term is (4π)2/144 = 1.0966 and perhaps it could be higher, but in this case at low densities the initial magnetic susceptibility overestimates the simulations. the perturbation theory by tani et al. [5] is worth mentioning because a density-dependent correction was used to complete the third term of the susceptibility (table 1: 5.4), where f (ρ) = 9idd∆/π 2 − 16, and idd∆ = 17π2 9 [ 1− 0.93952ρ∗ + 0.36714(ρ∗) 2 1− 0.92398ρ∗ + 0.23323(ρ∗) 2 ] . the formula of the magnetization curve for this perturbation theory was calculated by szalai et al. the expressions that are not mentioned in table 1: 5.2 can be found in ref. [6]. the values of the susceptibility more closely resemble the simulation data but still underestimate those. it is worth mentioning the study by huke and lücke [7] who introduced the so-called “dipolar coupling constant” into the second term of the initial magnetic susceptibility, but the third term was ignored in expressions in table 1: 4.4 and 5.4. thereby their theory at higher densities underestimates and at lower densities overestimates the simulation data. furthermore, the theory of mean-spherical approximation (msa) [8–10] should also hungarian journal of industry and chemistry the initial magnetic susceptibility of dense aggregated dipolar fluids 49 be mentioned which provides a formula for initial magnetic susceptibility and magnetization as well, but the validity of these are within the range of up to m∗ < √ 1.5. with regard to the distribution of chain aggregates in ferrofluids [11, 12], it has been found that in the absence of any external magnetic field, the chain size distribution is proportional to pk exp(−ε), where the chain length is denoted by k and the dimensionless energy parameter ε is a function of the maximum dipole interaction energy but independent from the density, therefore, it is a constant here and the probability of bond formation between two adjacent particles in a chain is p. subsequently, the chain size distribution decreases according to an exponential function because pk = exp(−k/k0), where k0 = −1/ ln p. based on some publications [13, 14], in the case of high dipole moments this exponential expression turns into a power law: g(k) ∝ k−ι, with exponent ι ≈ 2.0− 2.5. our investigation was performed in a dipolar hardsphere (dhs) monodisperse system with a permanent magnetic dipole moment and of fixed density. it is supposed that the chains are perfectly straight and parallel to the local magnetic field. furthermore, the average distance between two neighbouring particles in a chain is the same as the distance between two neighbouring parallel chains. the particles interact with each other only by the evolved mean magnetic field and the applied external magnetic field is superimposed on this, thus, the chains influence each other only by this mean magnetic field. 2. theory 2.1 the appearance of probability analysis in the initial magnetic susceptibility the distribution of chains was calculated with the aid of probability analysis in a zero applied magnetic field. as was mentioned in the “introduction”, weiss’ theory states that the effective (now “local”) magnetic field converges to zero when χl < 3/4π and non-zero values when χl ≥ 3/4π. the central and surrounding particles are under the influence of this local magnetic field. the chain is oriented in the same direction as the local magnetic field. let us denote the probability of chain formation between two particles whose direction relative to each other is parallel to the local magnetic field by p. now using this approach the exact distribution of chain length can be calculated because the probability that the chain length ought to be equal to k follows the geometric distribution with parameter q: gk = qpk−1, (4) where q = 1−p and the “chain distribution” is denoted by gk. according to its definition the geometric distribution shows the probability that a kth particle is connected to a chain of length k − 1 thus forming a chain of length k. a geometric sequence is described in eq. 4, where the common ratio is denoted by p and the first term by q. the sum of the terms of a geometric sequence is s∞ = ft 1−cr , thus, ∑∞ k=1 gk = q 1−p = q q = 1. it is also important to calculate the so-called “particle distribution” that implies the number of those particles which are members of the chains of length k: hk = q2kpk−1. (5) the detailed deduction of hk and the sum of hk terms are described in appendix a. the expected value of the geometric distribution with parameter q is 1/q, thus, here the average chain length is 1/q. the number of chains is equal to the number of particles divided by the average chain length: n 1/q = nq, where the number of particles is denoted by n. until now only the local magnetic field which arises from the strength of interaction energies between neighbouring particles and induces spontaneous magnetization in a random direction has been discussed, thus, the total magnetization of the system of volume v is equal to zero. when an infinitesimal external magnetic field h0 is switched on, non-zero total magnetization is formed. since h0 is parallel to m, scalar notations are used in the following. as was observed from pshenichnikov’s model the effective magnetic field is the sum of the external h0 and secondary (4π/3)m(h0) magnetic fields. the question arises why it is legitimate to use the expression of effective magnetic field from “pshenichnikov” (table 1: 3.2) instead of from “weiss” (table 1: 2.2). the answer is because h0 modifies infinitesimally the orientation of the chains but does not align them with its own direction, thus, the average angle between the local and external or even the effective magnetic fields is not equal to zero. when calculating the initial magnetic susceptibility, a chain of length k is considered as a particle with a dipole moment km, thus, in terms of magnetization the argument of the langevin function is kmhe kbt . the langevin function is weighted by the distribution hk, and finally the gradient of magnetization in an infinitesimal external magnetic field is calculated as χ0 = ∂ ∂h0 ∣∣∣∣ h0=0 ρm ∞∑ k=1 hkl ( kmhe kbt ) . (6) an infinitesimally weak external magnetic field can be written as χ0 = 1 + p 1− p χl ( 1 + 4π 3 χl ) , (7) where the following infinite expression is used (|p| < 1): ∞∑ k=1 pk−1k2 = 1 + p (1− p)3 . (8) the detailed derivation of the initial magnetic susceptibility (eq. 7) is given in appendix b. 46(2) pp. 47–54 (2018) 50 nagy figure 1: the rates of the local magnetic field as a function of the density from eq. 9 at three different dipole moments in the absence of any external magnetic field. 2.2 the numerical calculation of the probability of chain formation “p” the main challenge of our approach is the determination of p. the particles form chains because of the local magnetic field even in the absence of any applied external magnetic field. according to weiss’ model when χl ≥ 3/4π this local magnetic field predicts an infinite initial magnetic susceptibility. the problem with this model is that it assumes that the orientation of the local magnetic field is parallel with the external magnetic field. nevertheless, weiss’ model is applicable to predict the extent of the local magnetic field by the expression (when h0 = 0): hl = 4π 3 ρml ( mhl kbt ) . (9) h∗l as a function of the reduced density ρ∗ at three different dipole moments is presented in fig. 1. the definitions of the reduced quantities are h∗ = h √ σ3/kbt ; m∗ = m √ σ3/kbt ; m∗ = m/ √ σ3kbt . all particles are considered to be influenced by this local magnetic field hl, in the absence of any external magnetic field h0 when calculating the initial magnetic susceptibility. as was mentioned before, the most accepted criterion for chaining is to determine an energy level and if the dipolar energy between two given particles is under this level, the particles are in a bound relationship. generally [15–17], this energy level is 70-75 % of the minimum of the dipolar energy, i.e. u∗lim = −0.7 ∗ 2(m∗)2. here the well-known dipolar energy is defined as the interaction between point dipoles: udd ij = −m 2 r3 ij [3 (m̂i · r̂ij) (m̂j · r̂ij)− (m̂i · m̂j)] , (10) where the particles have dipole moments of strength m as well as an orientation given by unit vectors m̂i and figure 2: the feasible location of a particle between two fixed particles. m̂j . furthermore, the distance between the centers of the particles is denoted by rij and r̂ij = rij/rij . as is shown in fig. 2, according to our model particle j can move along the direction of the chain between the two fixed adjacent particles, namely i and the grey one, in the tube with a light blue background. logically, the minimum distance between two particles in a hard sphere system is σ, on a reduced scale d∗min = 1, while for the maximum distance d∗max = 2 〈r∗〉 − 1, where the reduced average distance between two adjacent particles is denoted by 〈r∗〉. obviously the maximum distance between two neighbouring particles could be greater than d∗max but at higher densities in particular the surrounding particles obstruct the movement of the central particle. assuming that the distance distribution is isotropic, it is given by 〈r∗〉 = 3 √ 1/ρ∗. taken all round to calculate p the probability of those states of particle pairs should be totalled when the dipolar interaction energy is less than or equal to the aforementioned energy limit ulim and the interval of integration in distance is [d∗min, d ∗ max], that is p = ∫ udd≤ulim p (θi)dθip (θj)dθjp (φi)dφip (φj)dφj , (11) where 0 ≤ θ < π and 0 ≤ φ < 2π are the usual spherical angles of the dipoles and the probabilities when magnetic field h (here h = hl) is applied in general are p (θ)dθ = exp ( mh kbt cos θ ) sin θdθ ∫ π 0 exp ( mh kbt cos θ ) sin θdθ (12) and p (φ) dφ = dφ/2π. the calculation of p was performed by numerical integration. particles i and j (fig. 2) are under the influence of the local magnetic field independently from each other. for both particles, all possible values of θ, φ, and r are swept and taken into account if the dipolar interaction energy between particles i and j is less than or equal to ulim. this is expressed by eq. 11. for instance, when ρ∗ = 0.8 and m∗ 2 = 3.0 then h∗l = 5.154 and d∗max = 1.154435. the probability of chaining between particles i and j as a function of distance is shown in fig. 3. the requested probability p is hungarian journal of industry and chemistry the initial magnetic susceptibility of dense aggregated dipolar fluids 51 figure 3: an example calculation of p. the parameters are rho∗ = 0.8, (m∗)2 = 3.0, h∗ l = 5.154, d∗max = 1.154435, and u∗ lim = 0.7u∗ min. the requested probability p is the average of this curve in the interval [d∗min, d ∗ max]. the average of this curve from 1 to d∗max, i.e. p = 0.3454, if u∗lim = 0.7u∗min. 3. simulation results and discussion to determine the initial magnetic susceptibility, monte carlo simulations of dhs fluids were performed using a canonical nvt ensemble. boltzmann sampling [18], periodic boundary conditions and the minimum-image convention were applied. in order to take into account the long-range character of the dipolar interaction, the reaction field method under boundary conditions of conduction was used. after 100,000 equilibration cycles, between 1 and 10 million production cycles were conducted involving n = 512 particles. in the absence of an external magnetic field, the initial magnetic susceptibility was obtained from the following fluctuation formula: χ0 = 1 3kbtv (〈 m2 〉 0 − 〈m〉20 ) , (13) where m = ∑n i=1 mi. the exact results of the probability of chain formation from eq. 11 applied to the local magnetic field, given by eq. 9, are shown in table 2. the data associated with the aforementioned dipole moments were rounded to three non-zero decimals. according to fig. 1 at low densities the values of the local magnetic field are zero, nevertheless, the rates of the probability of chaining are not equal to zero. the value of the energy limit was fitted to the best agreement between the simulation data and our theory lines. our theoretical findings (green lines, eq. 7 ) in terms of the initial magnetic susceptibility according to our monte carlo simulation data (blue dots) and the values of ivanov’s theory (grey lines, table 1: 4.4) are compared in figs. 4-6. the variability is not indicated where its magnitude is comparable to the size of the dot. the values of dipole moments in the order m∗ = 1, m∗ = √ 2 and m∗ = √ 3 are shown in figs. 4-6. table 2: the probability of chaining at three different dipole moments. the applied energy limit at m∗ = 1 and m∗ = √ 2 is ulim = 0.77umin and ulim = 0.71umin at m∗ = √ 3. p ρ∗ m∗ = 1 m∗ = √ 2 m∗ = √ 3 0.1 0.000260 0.000263 0.000580 0.2 0.000426 0.000429 0.000943 0.3 0.000615 0.000617 0.00794 0.4 0.000852 0.00292 0.0250 0.5 0.00117 0.0110 0.0521 0.6 0.00164 0.0253 0.0953 0.7 0.00241 0.0515 0.170 0.8 0.0135 0.107 0.320 0.85 0.0269 0.164 0.471 0.9 0.0539 0.273 0.649 0.95 0.101 0.416 0.775 in the case of m∗ = 1 (fig. 4), the energy limit is ulim = 0.77umin. a significant difference was only observed between ivanov’s theory and the simulation data beyond a reduced density of 0.8 and the simulation dots were tracked by our present theory. the maximum relative deviation from the simulation data is |χ0 sim − χ0 th| /χ0 sim = 4.175%. when m∗ = √ 2, the appropriate energy criterion is ulim = 0.77umin as well. up to a reduced density of 0.6 the former theory and simulation are in good agreement (fig. 5), but in the present theory more than double the surplus is shown in the region of high density compared to table 1: 4.4. the maximum relative deviation from the simulation data is 8.024 %. here it is quite conceivable that the simple series expansion of initial magnetic susceptibility as the summation of positive integer powers of langevin susceptibility is unsatisfactory. by increasing the third coefficient in figure 4: initial magnetic susceptibility of dhs fluid as a function of reduced density with dipole moment m∗ = 1. monte carlo simulation results are denoted by symbols and the solid lines correspond to the present (eq. 7) and ivanov’s (table 1: 4.4) theories. 46(2) pp. 47–54 (2018) 52 nagy figure 5: initial magnetic susceptibility of dhs fluid as a function of reduced density with dipole moment m∗ =√ 2. monte carlo simulation results are denoted by symbols and the solid lines correspond to the present (eq. 7) and ivanov’s (table 1: 4.4) theories. figure 6: initial magnetic susceptibility of dhs fluid as a function of reduced density with dipole moment m∗ =√ 3. monte carlo simulation results are denoted by symbols and the solid lines correspond to the present (eq. 7) and ivanov’s (table 1: 4.4) theories. table 1: 4.4, the initial magnetic susceptibility at lower densities is also increased. when m∗ = √ 3 the difference is even more spectacular between the theories (fig. 6). at high densities the uncertainty of initial magnetic susceptibility is quite large with regard to the simulation data. the best fit curve belongs to an energy limit of 71 %, which is very close to the value from references [15–17] of 70 %. the maximum relative deviation from the simulation data is 15.850 %. when m∗ = 1 and ρ∗ = 0.95, with an energy limit of 70 %, the theoretical value of initial magnetic susceptibility is χ0 = 1.042, and if the energy limit is 75 %, χ0 = 0.937. both values are higher than the corresponding simulation data, thus, the energy limit has to be raised to 77 %. the situation is similar when m∗ = √ 2 and ρ∗ = 0.95, namely χ0 = 8.701 when the energy limit is 70 % and χ0 = 6.363 when it is 75 %. probably at lower dipole moments and higher densities the two adjacent particles cannot be considered as a chain even though the interaction energy exceeds an energy limit of 70 % or 75 % for example because the average kinetic energy is closer to this interaction energy than is the case when m∗ = √ 3. therefore, the duration of chain formation is short to draw the particles together. 4. conclusion the initial magnetic susceptibility of dipolar hard sphere fluids was described by the help of the probability variable p supplemented by pshenichnikov’s well-known theory. the validity of the present theory is up to ρ∗ = 0.95 and at leastm∗ = √ 3. in addition to the theoretical work, monte carlo simulations were run to confirm our investigation. at higher densities, especially with higher dipole moments, the former related theories significantly underestimate the simulation data but good results are also provided by the presented theory within this range. by considering the green curves and blue dots in figs. 4-6, it is obvious that the simple quadratic or tertiary polynomial approach is outdated, therefore, the taylor series expansion of (1 + p)/(1− p) contains powers even as high as infinity. 5. appendix 5.1 appendix a the particle distribution can be obtained by dividing the number of particles in chains of length k by the total number of particles: hk = kgk∑ kgk = kqpk−1∑ kqpk−1 = kpk−1∑ kpk−1 = kpk−1 1 + 2p+ 3p2 + · · · = = kpk−1 (1+p+ p2 + · · · ) + (p+ p2 + p3 + · · · ) + (p2 + p3 + p4 + . . .) + · · · = = kpk−1 (1 + p+ p2 + · · · ) + (p+ p2 + p3 + · · · ) + (p2 + p3 + p4 + · · · ) + · · · = = kpk−1 1 1− p + p 1− p + p2 1− p + · · · = qkpk−1 1 + p+ p2 + · · · = qkpk−1 1 1− p = q2kpk−1. (14) hungarian journal of industry and chemistry the initial magnetic susceptibility of dense aggregated dipolar fluids 53 the sum of hk terms must be equal to one: ∞∑ k=1 hk = ∞∑ k=1 q2kpk−1 = q2 ( 1 + 2p+ 3p2 + . . . ) = q2 [( 1 + p+ p2 + · · · ) + ( p+ p2 + p3 · · · ) + · · · ] = = q2 [ 1 1− p + p 1− p + p2 1− p + · · · ] = q [ 1 + p+ p2 + . . . ] = q 1 1− p = 1. (15) 5.2 appendix b χ0 = ∂ ∂h0 ∣∣∣∣ h0=0 ρm ∞∑ k=1 hkl ( kmhe kbt ) = ∂ ∂h0 ∣∣∣∣ h0=0 ρm ∞∑ k=1 q2kpk−1l km ( h0 + 4π 3 ρml ( mh0 kbt )) kbt  = = q2ρm ∂ ∂h0 ∣∣∣∣ h0=0 ∞∑ k=1 kpk−1l kmh0 kbt + 4π 3 kρm2l ( mh0 kbt ) kbt  = = q2ρm ∞∑ k=1 kpk−1 1 3  km kbt + 4π 3 kρm2 1 3 m kbt kbt  = q2 ∞∑ k=1 k2pk−1 ( 1 3 ρm2 kbt + 1 9 4π 3 ρ2m4 k2 bt 2 ) = q2 ( χl + 4π 3 χ2 l ) ∞∑ k=1 k2pk−1 = 1 + p 1− p χl ( 1 + 4π 3 χl ) . (16) references [1] langevin, p.: sur la théorie du magnétisme, journal de physique théorique et appliquée, 1905 4(1), 678–693 doi: 10.1051/jphystap:019050040067800 [2] weiss, p.: l’hypothése du champ moléculaire et la propriété ferromagnétique, journal de physique théorique et appliquée, 1907 6(1), 661–690 doi: 10.1051/jphystap:019070060066100 [3] pshenichnikov, a. f.; mekhonoshin, v. v.: equilibrium magnetization and microstructure of the system of superparamagnetic interacting particles: numerical simulation, journal of magnetism and magnetic materials, 2000 213(3), 357–369 doi: 10.1016/s0304-8853(99)00829-x [4] ivanov, a. o.; kuznetsova, o. b.: magnetic properties of dense ferrofluids: an influence of interparticle correlations, phys. rev. e, 2001 64(4), 041405 doi: 10.1103/physreve.64.041405 [5] tani, a.; henderson, d.; barker, j. a.; hecht, c. e.: application of perturbation theory to the calculation of the dielectric constant of a dipolar hard sphere fluid, mol. phys., 1983 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zubarev, a. y.; iskakova, l. y.: effect of chainlike aggregates on dynamical properties of magnetic liquids, phys. rev. e, 2000 61(5), 5415–5421 doi: 10.1103/physreve.61.5415 [13] stauffer, d.; aharony, a.: introduction to percolation theory (crc press, london) 1994 isbn: 9780748402533 [14] del gado, e.; kob, w.: a microscopic model for colloidal gels with directional effective interactions: network induced glassy dynamics, soft matter, 2010 6(7), 1547–1558 doi: 10.1039/b916813c 46(2) pp. 47–54 (2018) https://doi.org/10.1051/jphystap:019050040067800 https://doi.org/10.1051/jphystap:019070060066100 https://doi.org/10.1051/jphystap:019070060066100 https://doi.org/10.1016/s0304-8853(99)00829-x https://doi.org/10.1016/s0304-8853(99)00829-x https://doi.org/10.1103/physreve.64.041405 https://doi.org/10.1080/00268978300100621 https://doi.org/10.1080/00268978300100621 https://doi.org/10.1103/physreve.92.042314 https://doi.org/10.1103/physreve.62.6875 https://doi.org/10.1103/physreve.62.6875 https://doi.org/10.1063/1.1676751 https://doi.org/10.1088/0953-8984/20/20/204122 https://doi.org/10.1103/physreve.61.5415 https://doi.org/10.1103/physreve.61.5415 https://doi.org/10.1039/b916813c 54 nagy [15] weiss, j. j.; levesque, d.: chain formation in low density dipolar hard spheres: a monte carlo study, phys. rev. lett., 1993 71(17), 2729–2732 doi: 10.1103/physrevlett.71.2729 [16] levesque, d.; weis, j. j.: orientational and structural order in strongly interacting dipolar hard spheres, phys. rev. e, 1994 49(6), 5131–5140 doi: 10.1103/physreve.49.5131 [17] stevens, m. j.; grest, g. s.: structure of soft-sphere dipolar fluids, phys. rev. e, 1995 51(6), 5962–5975 doi: 10.1103/physreve.51.5962 [18] allen, m. p.; tildesley d. j.: computer simulation of liquids (clarendon press, oxford) 1987 isbn: 978-0198556459 hungarian journal of industry and chemistry https://doi.org/10.1103/physrevlett.71.2729 https://doi.org/10.1103/physreve.49.5131 https://doi.org/10.1103/physreve.49.5131 https://doi.org/10.1103/physreve.51.5962 introduction theory the appearance of probability analysis in the initial magnetic susceptibility the numerical calculation of the probability of chain formation ``p'' simulation results and discussion conclusion appendix appendix a appendix b page 1 page 2 page 3 page 4 page 5 page 6 page 7 page 8 page 9 page 10 page 11 page 12 page 13 page 14 page 15 page 16 page 17 page 18 page 19 page 20 page 21 page 22 page 23 page 24 page 25 page 26 page 27 page 28 page 29 page 30 page 31 page 32 page 33 page 34 page 35 page 36 page 37 page 38 page 39 page 40 page 41 page 42 page 43 page 44 page 45 page 46 page 47 page 48 page 49 page 50 page 51 page 52 page 53 page 54 page 55 page 56 page 57 page 58 page 59 page 60 page 61 page 62 page 63 page 64 page 65 page 66 page 67 page 68 page 69 page 70 page 71 page 72 page 73 page 74 page 75 page 76 page 77 page 78 page 79 page 80 page 81 page 82 page 83 page 84 page 85 page 86 page 87 page 88 page 89 page 90 page 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314 page 315 page 316 page 317 page 318 page 319 page 320 page 321 page 322 page 323 page 324 hungarian journal of industrial chemistry veszprem vol. 30. pp. 235 239 (2002) a new vba software as a tool of food sensory tests z. k6kai, j. heszberger 2 , k. kollar-hunek2 , g. kollar1 (sensory laboratory, postharvest dept., szent istvan university, hll18. budapest, menesi ut 45, hungary 1postharvest dept., szent istvan university h1118. budapest, menesi ut 45, hungary 2 dept of chemical information technology, budapest university of technology and economics, h1521 budapest, pbox.91. hungary) received: october 17, 2002 this paper was presented at the gth international workshop on chemical engineering mathematics, bad honnef, germany, september 18-212002 sensory testing is an essential tool for introducing new products to the market. to achieve reliable sensory data several factors should be controlled from the experimental design, through the coding of the samples to the proper conduct of the analysis. to improve the efficiency of sensory testing computer support of the process is necessary. the target of our project was to develop software, which supports the profile analysis testing method. the selection of the platform (microsoft excel) was motivated by its widespread use and easy accessibility. the preparation of the score sheets is performed on the panel leader's computer; afterwards the copies are moved to the panellists' pes. the software can handle unstructured scales, structured scales, category scales and text fields. data collection is followed by complex data analysis and graphic presentation. keywords: food sensory testing, apple profile analysis, visual basic for excel software introduction sensory analysis is an essential tool to achieve successful marketing strategy in the food sector. though sensory quality is not the only key to meet consumer demands (price strategy, promotion, point of sale and other product characteristics are also essential), sensory data can be utilized in several marketing aspects. sensory testing is generally considered to be subjective) as it relies on human individuals, instead of 'more accurate' equipments of other research fields (e.g.: analytical chemistry, rheology, etc.). since no reliable model exists for transforming analytical and other instrumental data to perceive sensory quality [9], it is necessary to reduce the objective character of sensory testing. due to accelerated research on this field there are several solutions for providing reliable sensory data for decision making [1]. one of the basic principles is, that sensory testing should be considered similarly to instrumental testing. from the practical point of view it means: • proper experimental design; contact information; e-mail: zkokai@omega.kee.hu • understanding the limitation of our 'equipments' (in our case: the assessors) • and suitable statistical analysis of the data. these requirements mentioned above are really just the most basic ones. the importance of these principles is indicated by the fact that already 24 iso standards deal with different aspects of sensory testing. quality oriented sensory research in this way might mean more tasks to deal with, so information technology has a huge impact in saving time and energy. sensory testing before proceeding with the exact details of our research. one more question should be discussed. sensory testing [5, 6] can be performed with: • naive assessors (consumers)~ • trained and selected assessors and • experts 236 these different groups should be considered as different tools (like we have different instruments in an analytical laboratory). consumer tests usually focus on preference, and ask the question 'which product do you prefer?'. in this case it is very important that the people involved should be representative to the target population [10]. testing with selected assessors or experts helps to answer the question 'why is one product preferred, and why is the other one rejected?'. if we use the wrong tool for answering the question (e.g. experts or selected assessors for 'which product do you prefer?') the results will be invalid. in our research we worked mainly with the second group mentioned above (selected assessors). tools of information technology in sensory laboratory of sziu the sensory laboratory of szent istvan university, budapest, hungary has a specially designed sensory booth system, which was established in accordance with the relevant iso standards [3]. during the recent period a local area network (lan) was built in the lab, providing the possibility of pc based testing. this solution greatly improves the efficiency of sensory evaluation. the criti~al point of such a system is the software applied. several software systems are known for supporting sensory analysis. since these software are sold in a moderate number of copies, even the academic prices are considerably high. this motivated us to find a solution more suitable to the possibilities of the hungarian academic sector. finally it has been decided to develop an own software system in visual basic for applications (vb a [7 ,8]) for our specific neeris [ 4]. while thestaff of the sensory laboratory (sziu) provided l~e know-how of sensory testing, the department of chemical information technology, (bute) provided all support on the field of information technology. since one of the current researches was dealing with the method of profile analysis of apples, in the first step this software module was developed. sensory testing methods can be divided into three main groups: • difference testing methods; • ranking methods • and descriptive methods. profile analysis [2] belongs to the group of descriptive methods. these kinds of procedures require trained assessors or experts. the testing session has several steps, which indicates the time demand of the analysis. the nature of the method requires some couective work of the assessors in one phase of the analy.~is. ybaproject {profil_anal.xls) ei ·•~:y microsoft excel objects . ; ·~ thisworkbook ~ -~ worksheetl (basic_data) :. ···~ worksheet2 (scoresheet) . ~ worksheet3 (stat_eval) · ... ~ worksheet4 (diagrams) forms r ·em category _scale ..§ descriptive_scale ,··em identification_of _eval_method ' § name _of _samples \' ·· § scoresheet_editor : i.. em unstructured_line_scale b._{;;:,~ modules l·· ·-4 al_init ~ ... 4 a2_main · · 4 a3 _cell _protection r .. -4, bl_stat_evaluation l.4 b2_diagram_creator fig. i main parts of the profile analysis supporting vba software the vba software created our vba software consists of 5 modules, 6 user forms, and works on 4 excel worksheets, as it is shown on the fig.l. among the modules the al, a2, a3 marked ones create the score sheets for the assessors, including the protection of the cells which should remain unchanged during the sensory testing procedure. the subroutines of these modules call the forms, and they fill out the first two worksheets (basic_data and scoresheet). the bl and b2 marked modules supervise the data collection from the filled out score sheet-files, make statistical evaluation in the third worksheet (stat_eval) and create the diagrams in the fourth worksheet. the usage of the software we show in the next section on a real apple profile analysis. a real apple proide analysis using the software in the first step of profile analysis the assessors get the samples, and they are asked to create a list of sensory attributes, which they consider important. in this step the assessors work individually. the second step is the group discussion, when the assessors decide which attributes should remain in the final evaluation system. the discussion is supervised and helped by the panel leader. for each sensory attribute the group has to choose an evaluating method {e.g. unstructured scale, category scale, descriptive evaluation, etc.}. our software makes it easy to choose the evaluating method and specify the further details {figs.2-5). in this step the screen can be projected to help the work of the group. title of scwesheet: number of attributes? (max 30) j 10 ~ number of samples? (max 6) l 4 ~ number of a5sesments? (max 20) fig.2 the score sheet editor ldenhlacahon of the evaluahon method attribute's number . • • i there are altogether 0 attributes ' deflneci . i currently edited attribute 's 1 number: i.-3-fig.3 setting the evaluation method using the score sheet editor form the assessors specify the title of score sheet, and the number of attributes, samples and assessments. each attribute has a sequence number and a code corresponding to their type (evaluation method). on the figs.4-5 we show the way of setting up two different scales unstructured line and category scales. in both c~ses we specify attribute s name, for the first type we gtve the legends at the start and at the end of the scrollbar belonging to the unstructured line, for the s~cond one the names of the categories are going to be gtven. when all the attributes are defined and the evaluation methods are specified, the software asks to type in the name of the samples (varieties) into a form and thereafter creates a block design for the presentation sequence of the samples. a randomly generated, three­ di~it number code is also assigned to each sample (fzg.6). these techniques are essential to avoid psychological faults during testing. 237 unstructured line scale (, 'ej attribute's name: i red color fig.4 unstructured )jne scale category scale £1 attribute's name lenticell spots components of category scale -components' names few acceptable fig.5 setting up a category scale h k -,_..;. · sample's name ida red jonathan topred sample 10 a 8 c 1 8 a 0 2 c 0 a 3 0 c 8 4 a 8 0 5 8 a c l golden 0 c 8 a c 0 0 3-dl~it s.:~m lecodes 82 356 289 7 675 967 34 167 342 7 861 7~ 829 718 492 584 1 351 21 396 9 609 :j) 219 fig.6 creating the test design automatically with choosing create coresheet from datasheet' (see fig.j) the software creates the core sheets for each assessor. then the score sheets are copied to the pc in the sensory booths and the as e or i ready to te t. thi step of the testing means individual work again (fig.7). 238 table i sensory test of scab resistant apple varieties using jonathan as control variety green flesh white flesh yell ow flesh hardness juicness peel sweet taste sour taste odour aroma taste+ aroma releika remo resi rewena reglindis jonathan 44 53 76 88 65 71 70 57 60 62 62 50 53 59 41 74 53 86 78 78 65 65 74 52 56 66 58 59 50 61 54 65 54 44 59 74 86 73 76 52 64 58 65 64 41 47 59 75 69 71 58 53 50 51 52 47 65 56 78 71 76 46 67 56 59 62 s c . d e_ _f. g h ··'·····. j · szent lstvin university. posth:~rvest oepanmer£ !}t:)!"~-···-, assessor's [)code­ ,sampes' codes attrbies 1235 5$.4 sensory l01bor:rtory ~ ·. }4 apple profile an01lysis ~~-"...~ 182 356 fig.7 filling out the score sheets when the testing session is finished, the data are collected from each pc. the online filling of the questionnaires means, that the time-consuming data input from paper based questionnaires can be skipped. by the vba macros of the module bl_stat_evauationl (see fig.l) the individual data are collected in one worksheet (stat_eval), and statistical analysis takes placa every attribute is analysed for significant differences~ and for the better understanding~ the results are represented in diagrams (figs.8 and 9). after the t1rst experiences in the usage of our new software in laboratory (testing) circumstances we tried to use it on the hortus hungaricus exhibition for the evaluation of the sensory testing of scab resistent apple varieties. organized by the postharvest club. this was a different field where we could use the soft\vare. in the circumstances of the hortus exhibition it was not possible to use computer network and online sensory test data input. we created the score sheets by the software. but in this case we made paper based (nar<:lcopy) questionnaires from the printed out score sheet. on the exhibition the experts filled out these questionnaires, and we could make a real-time evaluation by a laptop. after evaluating the first group of assessors. for the latter visitors we could show a presentation about the results. \ve investigated six varieties: five resistant apples: replica~ reno. resin. rowena and regrinds. as control variety we used the b c d e f 1gt ffi red colour 1?-: 100 19' 80 20 ~ 60 21 40 22 ~ 20 23' 0 :ill !dared jomrtan golden parmen 25 i "'26"1 yellow colour 27 i 1~! i " ~~s·~ 29. }0; i i i i 31 . 32-~ 33 i 34·: ida red jonatan golden parmen fig.8 graphical presentation of the results, according to the properties white flesh fig.9 graphical presentation of the results, according to the apple samples fig.jo comparison of apples· sensory profiles. jomithan (left) and rewena (right) well known and in hungary preferred jonathan. from our result we have got in a short way the fact there seems to be no significant difference between some re­ appjes and on the market preferred jonathan. (table 1, fig.jo) the ,profile analysis" on the hortus exhibition was of course only a first attempt to use our software in non­ laboratory circumstances. we made ranking tests with more than 200 assessors as well. releika jonathan rewena resi remo reglindis table 2 comparison of apples, ranking releika jonathan rewena resi remo no no 1% 1% 40 no 5% 1% 67 27 no 1% 128 88 61 no 167 127 100 39 211 171 144 83 44 reglindis 1% 1% 1% 5% no as one can see on table 2, the evaluation of simple ranking by friedman test doesn't show significant differences between releika, jonathan and rewena. discussion the first experiences with the vba based sensory analysis supporting software showed, that the time demand of both the preparation and testing step can be considerably reduced. online questionnaires mean no data input is necessary from paper-based questionnaires. data analysis and report making is almost real time. some details of the software will be developed (sample code printing, etc.). in our future work we plan to develop similar software modules for other testing methods (difference testing, ranking and other descriptive methods). a database system managing the different data is also planned to be built. acknowledgements the authors wish to express their gratitude to the postharvest club, to the wink ltd (vasarosnameny) to beata kapolna and rita szabo (sziu) the work has been supported by the hungarian national research foundation (otka, grant # t030241!99). 239 symbols bute budapest university of technology and economics lan re-apple sziu vba local area network disease (scab) resistant apple variety szent istvan university visual basic for application references 1. cramwinckel a. b., mazijk-bokslag and d. m­ y an: voedingsmiddelen-technologie, 1990, 23, 14 2. iso 11035: 1994 sensory analysis identification and selection of descriptors for establishing a sensory profile by a multidimensional approach 3. iso 8589: 1988 sensory analysis general guidance for the design of test rooms 4. k6kai z., heszbergerj, kollar-hunek k., szabo r. and kollar g.: proceedings of mkn '02, veszprem, hungary 2002, 1, 177 (in hungarian) 5. msz: iso 8586-1: 2000 sensory analysisgeneral guidance for the selection, training and monitoring of assessors part 1: selected assessors 6. msz: iso 8586-2: 2000 sensory analysis general guidance for the selection, training and monitoring of assessors part 2: experts 7. visual basic bookmark, www.vbbookmark.com/vba.html 8. visual basic home, rnsdn.microsoft.corn/vbasic 9. work t. m., bushway r. j, perkins l. b. et ai.: fruit varieties journal, 1994, 48(1),14 10. zech j.: obstbau, 1989, 14(5), 209 page 236 page 237 page 238 page 239 page 240 hungarian journal of industry and chemistry vol. 48(1) pp. 43–49 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-07 challenges of localization algorithms for autonomous driving hunor medve*1 and dénes fodor1 1research institute of automotive mechatronics and automation, university of pannonia, egyetem u. 10, veszprém, 8200, hungary one could easily believe that the technology surrounding us is already easily capable of determining the current location of a vehicle. whilst many devices, technologies, mathematical models and methods are available in the automotive world, the complexity of the localization problem still cannot be underestimated. the expectation is to determine in real time with a high degree of accuracy the location of a vehicle in order to make correct autonomous decisions and avoid dangerous and potentially damaging situations. various research directions have been undertaken since the birth of autonomous driving from the well-known satellite navigation-based systems that rely on offline maps to the more sophisticated approaches that use odometry and existing sensor data using sensor fusion. the aim of the current work is to review what has been achieved so far in this field and the challenges ahead, e.g. the need for a change in paradigm as today’s global positioning systems are not intended for machines but humans and are based on the abstraction of human thinking and human decision-making processes. keywords: autonomous driving, localization, information fusion, filtering 1. introduction vehicle localization is one of the four functions of autonomous vehicle navigation, namely mapping, localization, motion and interaction, which are the answers to the four basic questions concerning navigation: where am i? where can i move to? how can i do it? how do i interact? if a vehicle is to navigate as expected, these functions need to operate correctly [1]. historically, the purpose of in-car localization was driver assistance in the form of helping the driver to navigate. such systems that are currently in use provide information, with some degree of accuracy, to the driver and then the driver makes decisions based on the information, which can either be accepted and acted upon or rejected in the form of proceeding in another direction. in the case of autonomous driving, it is quite clear that simply rejecting position information since the main control algorithm is not an option as this is the only item of data to be used, therefore, it must be used and a decision made based on it. this raises the question of certainty. the requirement to operate safely anywhere and at anytime makes the performance measures far stricter than ever before. the performance measures are [2]: accuracy the degree of conformity of position information provided by the localization system relative to actual values. *correspondence: medve.hunor@mk.uni-pannon.hu integrity a measure of trust that can be implemented in the information from the localization, which is the likelihood of undetected failures given the specified accuracy of the system. continuity of service the probability of the system continuously providing information without nonscheduled interruptions during the intended working period. availability the percentage of time during which the service is available for use taking into account all the outages irrespective of their origins. the service is available if the requirements concerning accuracy, integrity and continuity are satisfied. over the last 10-15 years, the number of sensors and related advanced driver-assistance systems in passenger vehicles has increased. the primary task of each of these sensors and services is to observe a segment of the surroundings and its status, then assist the driver in that regard. since the data from a single sensor does not contain all the information about the vehicle’s surroundings, further information concerning its absolute location cannot be extracted based on a single sensor. in fact, the sensors provide complementary information and through information fusion the vehicle’s absolute location and status can be obtained. this is shown in fig. 1. the main groups of information sources are the following: https://doi.org/10.33927/hjic-2020-07 mailto:medve.hunor@mk.uni-pannon.hu 44 medve és fodor figure 1: the concept of information fusion • global navigation satellite systems (gnss) • traditional vehicle sensors: – odometer – wheel speed sensor – steering angle sensor • inertial measurement unit (imu): – accelerometer – gyroscope • optical, soundand radio-based sensors: – radar – ultrasonic sensors – vision sensors – lidar (light detection and ranging) • vehicle models with various levels of complexity • databases; offline or cloud-based: – maps – traffic situation • dedicated short-range communication: – vehicle-to-vehicle (v2v) – vehicle-to-infrastructure (v2i). it is important to note that none of these information sources are ideal and error-free. the errors will propagate through the sensor fusion algorithm, moreover, affect the end result and the previously described figures of merit. the following sections address each device family then the fusion methods are analysed. 2. information sources 2.1 global navigation satellite systems the global navigation satellite system (gnss) is a radio positioning-based technology using satellite infrastructure that aims to achieve global coverage. historically, satellite-based sytems have been considered as the core element of localization. currently, a number of systems are in operation, the major ones are gps (usa), beidou (china), glonass (russia) and galileo (eu). every satellite broadcasts a specific signal and its position. the spectral range of the signals is 1.2− 1.6 ghz, utilising frequency bands of between 2 and 40 mhz. any user equipped with a gnss receiver receives the signal and measures the signal propagation delay, then estimates the range of distance from it. by using signals from at least four satellites, the receivers can reduce the estimate to intercept the ranges from each satellite, which basically provides a potential location within the range in terms of geospatial coordinates. it is important to note that the position information is useful only if used together with maps which put the information in context. even though the accuracy of receivers is increased by various augmentation systems, issues resulting from poor satellite constellations, signal blockage and multipath propagation in urban environments cannot be excluded. for this reason, safety-critical applications cannot solely rely on gnss technology. although satellite-based systems are far from perfect, they are and will continue to be the single most important information source of any localization algorithm. 2.2 vehicle model models representing the dynamic model of a vehicle’s range from the simple spring-mass model to a complex multibody multi-level model. a well-known and used model is the single track model [3] with a number simplifications, however, it provides a reasonable solution for modeling lateral dynamics, therefore, it forms the core of the electronic stability program (esp) of many vehicle manufacturers. the inputs of the single track model are lateral acceleration, longitudinal speed and yaw rate, which are provided by the relevant sensors as discussed in section 2.3. another element in a complex model is the tire model which is assumed to be the only part in contact with the road. these models, e.g. pacejka’s magic formula [4], are often semi-empirical. it is important to note that a more detailed model requires more parameters which, in the case of inaccurate identification, may impact the overall accuracy of the model’s output. 2.3 traditional vehicle sensors and inertial measurement unit (imu) a wide range of traditional vehicle sensors have already been installed in most vehicles, moreover, analogue measurements are already being processed digitally. most of them provide basic information to human drivers directly, e.g. the odometer, whilst others are parts of safety features. for autonomous driving, exactly the same information is also required. wheel speed sensors mounted in the wheel drum provide vital inputs to the anti-lock braking system by sensing the movement of the circumference of each tire in a passive or active setting. steering angle sensors are mounted on the steering shaft and measure the steering wheel angle, their outputs are interpreted as the intended direction of the vehicle, which is a key input to the electronic stability program (esp). hungarian journal of industry and chemistry challenges of localization algorithms for autonomous driving 45 accelerometers measure the acceleration of the vehicle on the specified axis, multi-axis accelerometers are also in use. they are primarily used for inertial navigation in combination with yaw-rate sensors. yaw-rate sensors, often referred to as gyroscopes, measure the rotation of the vehicle along the vertical axis. such a sensor provides an input to the single track vehicle model in conjunction with the esp. accelerometers and yaw-rate sensors integrated in one cluster comprise the inertial measurement unit (imu). 2.4 optical as well as soundand radiobased sensors in automotive radar systems, a distinction is made between short range radar (srr) and long range radar (lrr). the detection range of short range radar is from 0.2 to 50 meters with a detection angle of ±35◦, whilst that of the long range radar is from 2 to 150 meters with a detection angle of ±6◦. srr is predominantly used in anti-collision and parking aid systems. radars are able to detect multiple objects as well as measure distance, relative speed and the angle to an object simultaneously. lrr is typically applied in adaptive cruise control and collision avoidance. radar technology is affected by the weather and functionality cannot be guaranteed in extreme conditions. overall information from radars can complement other location-related information sources. vision sensors are primarily used in vehicles to detect and possibly recognise its surroundings, e.g. other vehicles, obstacles, pedestrians and landmarks, which are potentially useful pieces of information for a localization algorithm. charge-coupled (ccd) and complementary metal oxide semiconductor (cmos) devices are the main sensor technologies applied in digital cameras to generate an image of the surroundings, in fact both are semiconductor devices. in cmos devices, every pixel has its own charge-tovoltage conversion and digitalization, so their outputs are digital signals. pixels that perform their own charge-tovoltage conversion decrease their uniformity and image quality as well as remove a useful area from light capture. in ccd sensors, a pixel’s charge signal is sent through a limited number of outputs to be converted into voltage and then transmitted out of the chip as an analogue signal to be processed and digitalized. this requires more time and energy when compared to cmos sensors, however, results in a higher quality but less noisy image. as the cmos manufacturing process is cheaper, recent developments have focused on overcoming the drawbacks of cmos sensors. ultrasonic sensors transmit higher frequency sound waves and evaluate the echo received by the sensors. the sensors also measure the elapsed time between sending and receiving back the signal, then calculate the distance from the object. the types currently used in the automotive industry are able to measure within the range of 0.2 to 1.5 meters, with a horizontal angle of ±60◦ and a vertical angle of ±30◦, and are primarily used in parking aids. nevertheless, the use of such sensors might provide useful inputs for a localization algorithm under given circumstances. lidar (light detection and ranging) measures the distance of an object by emitting laser light and detecting the returning light. the differences in return times and wavelengths then provide the basis for a 3d representation of the surroundings. 2.5 databases and maps maps stored in digital format differ from the classical map representations intended to be read by humans. digital road maps are comprised of nodes and arcs connecting the nodes. arcs are represented in a discrete form and every node and shape point on the arc has geospatial coordinates linked to them. they are often represented as planar models in applications currently on the market. 2.6 dedicated short-range communications for any vehicle to communicate with either the infrastructure (vehicle-to-infrastructure: v2i) or with another vehicle (vehicle-to-vehicle: v2v), it is assumed that a suitable wireless protocol is in place, which allows bidirectional information flow in real time when a vehicle is travelling at high speed and is able to simultaneously handle multiple vehicles. based on these assumptions, only applications related to localization are considered here. the main purpose of v2i communication is to support applications that target safety and mobility. safety applications mainly consist of alerts and warnings, while mobility applications collect data from vehicles in order to capture the actual state of the traffic and provide such information to vehicles. v2v applications determine the state of other nearby vehicles through the transmission of one or several messages. overall, the location-related content of these messages alone might be insufficient for a vehicle to determine its own location, but can still provide useful complementary information to fusion algorithms. 3. fusion algorithms the purpose of information fusion is to obtain more information from the sources than what is accessible from each individual source. this is achieved by combining sources which are complementary, moreover, the use of partially redundant sources reduces the ambiguity of the measured data which, overall, improves the performance of the system. fusion algorithms can be realized in either centralized or decentralized structures, as is shown in fig. 2. 48(1) pp. 43–49 (2020) 46 medve és fodor figure 2: filtering structures: a) centralized, b) decentralized as the name suggests, in centralized structures, one filter performs the filtering of all signals which yields the benefit of minimal information loss as everything is directly available to the filter, while the amount of data to be processed in real time might imply an impractical degree of computational complexity. this is addressed by decentralized filters as every signal is filtered separately before being processed by a master filter. the computational load in general would be significantly less for one filtering unit, however, at the expense of partial information loss and reduced estimation accuracy. in this chapter, selected filtering methods are presented: a conventional and widely used localization method, as well as a linear and a non-linear filtering method. advanced filtering methods require prior knowledge of the system model and dynamics, the type of noise and their probability density functions as these are core elements to design a high-performance filter. the filtering algorithms presented in the following sections are used by the scientific community in various forms but often altered when compared to their originally published format (kalman filter in [5], particle filter in [6]), in order to better suit the actual problem. in this paper, the thought process of [7] is followed. 3.1 simple algorithms: dead reckoning, inertial navigation and map matching the conventional localization algorithm consists of two steps; the first is the gnss which defines the coordinates, the second is to match the given coordinates to a map. this is shown in fig. 3. the process of calculating the position based on its previously known position, elapsed time and speed is referred to as dead reckoning [8]. inertial navigation is a very similar concept where the position is calculated based on data from accelerometers and gyroscopes, also referred to as dead reckoning based on inertial sensors. in the following sections, no specific distinction is made between dead reckoning and inertial navigation. figure 3: conventional localization algorithm traditional vehicle sensors and the inertial measurement unit (imu) provide information about either the first or second order derivatives of the position of the vehicle together with the odometer which measures the distance travelled. all the data provided is relative to the starting position, therefore, none of the sensors provide information about its absolute position. in addition, all data will be incorporated into the coordinate system of the vehicle since all the sensors are mounted on the vehicle, therefore, coordinate transformations to the main coordinate system, which are used for the localization, are required. the measured values are integrated by taking into consideration an initial position and, over time, the errors will be accumulated as part of the integration. it is important to note that the extent to which the error can increase is infinite. despite such a disadvantage, the popularity of the method lies in the fact that it does not rely on external sources of information and the update rate is determined by the system itself, which overall defines the complementary nature of inertial navigation to gnss. map matching is the process of identifying on the map the coordinates given by the gnss on the map. on digital road maps, the road network is represented in a discrete form as nodes and arcs which connect nodes, each of which has geospatial coordinate information linked to it. the purpose of the map matching algorithm is to match the gnss coordinates to the road map. it is highly likely that the map will not contain the exact coordinates defined by the gnss and inertial navigation, therefore, it has to be matched to one of the few possible ones. map matching algorithms assign probabilities to each possible location based on a set of information including previous locations, speed and heading of the vehicle, subsequently the evaluation is concluded based on these probabilities. such algorithms can provide useful inputs to assist a human driver, however, it is easy to realize that rarely rarely can they provide sufficiently reliable inputs for autonomous driving. this creates the need for more reliable algorithms, which are normally more complex and require more computational power. 3.2 linear filtering: the kalman filter the kalman filter is a useful engineering tool in many industries and control applications ranging from robotics, automotive, plant control, aircraft tracking and navigation. in general, they are relatively easy to design and code with an optimal degree of estimation accuracy for linear systems with gaussian noise. let us describe a linear system with the following dishungarian journal of industry and chemistry challenges of localization algorithms for autonomous driving 47 crete state-space model equations: xk = ak−1xk−1 +bk−1uk−1 + wk−1 yk = ckxk + vk (1) where k in subscript refers to states and measurements at each discrete time instant and k − 1 in subscript to those at the previous time instant, xk denotes the vector of the state variable, uk stands for the input or control vector, yk represents the output vector, ak refers to the system matrix, bk and ck denote the input and output matrices, wk and vk stand for the process and measurement noise, respectively, which are white with gaussian distribution and zero mean, and rk and qk are known covariance matrices. wk ∼ (0, rk) vk ∼ (0, qk) e [ wkw t j ] = qkδk−j e [ vkv t j ] = rkδk−j e [ wvtj ] = 0 (2) where δk−j is the kronecker delta function (δk−j = 1, if k = j and δk−j = 0, if k 6= j). the aim is to estimate the system state xk by knowing the system dynamics and the noisy measurements yk. the available information for the state estimation always depends on the actual problem at hand. if all measurements are up to date and accessible, including kth, then a posteriori estimation can be computed, which is denoted by x̂+k . the meaning of the “+” sign in superscript means the estimation is an a posteriori estimation. the best way to estimate the a posteriori estimation is by computing the expected value of xk conditioned to all measurements up to now, including k as well. x̂+k = e [xk|y1, y2, . . . , yk] (3) if all measurements, apart from k, are accessible, then the a priori estimate can be computed, denoted by x̂−k , where the “−” sign in superscript denotes the a priori estimate. the best way to estimate the a priori state estimate is if the expected value of xk conditioned to all measurements up to now, excluding k, is computed: x̂−k = e [xk|y1, y2, . . . , yk−1] (4) it is important to note that x̂−k and x̂+k are estimates of the same quantity, before and after the actual measurement is obtained, respectively. naturally, it is expected that x̂+k is a more accurate estimate as more information is available. at the beginning of the estimation process, the first measurement is obtained at k = 1, therefore, the estimate of x̂+0 (k = 0) is given by computing the expected value of x0: x̂+0 = e [x0] (5) estimation of the error covariance is denoted by pk, therefore, p− k represents the estimation of the error covariance of the a priori estimate x̂−k and p+ k stands for the estimation of the error covariance of the a posteriori estimation x̂+k : p− k = e [( xk − x̂−k ) ( xk − x̂−k )t ] p+ k = e [( xk − x̂+k ) ( xk − x̂+k )t ] (6) the estimation process starts by computing x̂+0 , which is the best available estimate at this time instant for the value of x̂+0 . if x̂+0 is known, x̂−1 can be computed as follows: x̂−1 = a0x̂ + 0 +b0u0 (7) then the general form to compute x̂−k can be established: x̂−k = ak−1x̂ + k−1 +bk−1uk−1 (8) this is referred to as time update from time instants (k − 1) + to k−. no new measurement information is available between the two, therefore, the state estimation propagates from one time instant to the other, and all state estimations are based on knowledge of the system dynamics. the time update is often referred to as the prediction step. the next stage is to compute p , the estimation of the error covariance. the process starts by computing p+ 0 which is the error covariance of x̂+0 . if the initial state is perfectly known, then p+ 0 = 0; if no information is available, then p+ 0 = ∞i . in general, the meaning of p+ 0 is the uncertainty regarding the initial estimation of x0: p+ 0 = e [( x0 − x̂+0 ) ( x0 − x̂+0 )t ] (9) if p+ 0 is known, then p− 1 can be computed as follows: p− 1 = a0p + 0 a t 0 +q0 (10) based on the above, the generic form of the time update of p− k can be stated: p− k = ak−1p + k−1a t k−1 +qk−1 (11) so far, the time update step has been presented, which is based on the system dynamics. the next step is the measurement update, where new information is obtained from the measurements. using the logic from the method of recursive least squares, the availability of the measurement yk changes the value of the constant x in the following way: kk = pk−1c t k ( ckpk−1c t k +rk )−1 = pkc t k r −1 k−1 x̂k = x̂k−1 +kk(yk − ckx̂k−1) pk = (i−kkck)pk−1(i−kkck) t +kkrkk t k = = ( p−1 k−1+c t k r −1 k ck )−1 = = (i−kkck)pk−1 (12) 48(1) pp. 43–49 (2020) 48 medve és fodor where x̂k−1 denotes the estimation and pk−1 stands for the the estimation of the error covariance before processing measurement yk, therefore, x̂k and pk refer to the same informaton but after yk has been processed. if the logic of x̂k−1 → x̂−k and x̂k → x̂+k (a priori and a posteriori, respectively) is applied and the aforementioned equation reformulated, the a posteriori estimation is produced: kk = p− k c t k ( ckp − k c t k +rk )−1 = p+ k c t k r −1 k x̂+k = x̂−k +kk(yk−ckx̂ − k ) p+ k = (i−kkck)p − k (i−kkck) t +kkrkk t k = = [( p− k )−1 +ct k r −1 k ck ]−1 = = (i−kkck)p − k (13) these are the equations for the kalman filter measurement update or a posteriori estimation. the matrix kk is often referred to as the kalman gain. by summarising the kalman filtering algorithm, after initiation, the a priori estimate for every time instant k is given by: x̂−k = ak−1x̂ + k−1 +bk−1uk−1 p− k = ak−1p + k−1a t k−1 +qk−1 (14) and the a posteriori estimation is given by: kk = pkc t k r −1 k−1 x̂+k = x̂−k +kk(yk − ckx̂ − k ) p+ k = (i −kkck)p − k (15) the aforementioned kalman filtering algorithm is the optimal state estimator for linear systems with gaussian unimodal noise processes, however, most real-world systems are nonlinear and, in many cases, with multimodal non-gaussian noise, include a probability density function. a number of variations of kalman filters developed by the scientific community are trying to address the problem of nonlinearity. most of them rely on the basic concept of kalman filters using nonlinear adaptations, e.g. the extended kalman filter which, at its core, is still a linear filter. in general, versions of the nonlinear kalman filter are considered to estimate accuracy well but are often poor compared with the theoretically optimal accuracy, with a real-time computational complexity in the order of d3 where d denotes a dimension of the state vector [9]. 3.3 nonlinear filtering: the particle filter given the concerns about the estimation accuracy of versions of kalman filters, true nonlinear filters or estimators are needed. the particle filter is a statistics-based estimator where at every discrete time instant, a number of state vectors, referred to as particles, are assessed with regard to how likely they are to be the closest to the actual state. the mathematical formulation of the aforementioned idea is summarized in this section. let us describe a nonlinear system using the following equations: xk+1 = fk (xk, wk) yk = hk (xk, vk) (16) where k denotes discrete time instants, xk and yk represent the state and measurement, respectively, and wk and vk stand for the noises of the system and measurement, respectively. the functions fk (·) and hk (·) are a time variant nonlinear system and a measurement function, respectively. the noises of the system and measurement are assumed to be white and independent from each other with known probability density functions. the aim of the generic bayes estimator is to approximate the conditional probability density function xk based on measurements y1, y2, . . . , yk. this conditional probability density function is denoted as follows: p (xk|yk) = xk (17) conditioned on measurements y1, y2, . . . , yk. the particle filter is the numeric implementation of the bayes estimator, in the following section this will be described. at the beginning of the estimation, it is assumed that the probability density function of p(x0) is known, then n number of state vectors based on the probability density function of p(x0) are randomly generated. these state vectors are the particles and are denoted by x+0,i (i = 1, . . . , n). the value of n can be chosen arbitrarily, depending on the expected estimation accuracy and available computational capacity. at every k = 1, 2, 3 . . . discrete time instant, every particle is propagated to the next time instant using process equations fk (·): x−k,i = fk−1 ( x+k−1,i, w i k−1 ) (18) where (i = 1, . . . , n) and every noise vector wi k−1 is randomly generated based on the known probability density function of wk−1. this is the a priori estimate of the particle filter. subsequently, at every time instant k, once the measurement result can be accessed, the relative conditional probability of each x−k,i can be computed and qi = pk ( yk ∣∣∣ x−k,i) evaluated if the nonlinear measurement equation and the probability density function of the measurement noise are known. after the relative conditional probability of each particle has been evaluated, the relative probability of the actual state being equal to each of the particles is correct. the relative probabilities qi are then scaled to the interval [0, 1] as follows: qi = qi∑n j=1 qj (19) hungarian journal of industry and chemistry challenges of localization algorithms for autonomous driving 49 this ensures that the total probability is equal to one. the next stage is the resampling based on the computed and scaled probabilities. this means that a set of new x+k,i particles is generated based on the relative probabilities qi. this is the a posteriori estimation of the particle filter. the resampling is an important step with regard to the implementation due to the required computational capacity which needs to be considered carefully. the distribution of the computed a posteriori x+k,i particles is in accordance with the probability density function pk (xk|yk). based on this, any kind of statistical evaluation can be carried out, for example, of the expected value, which can be considered as the statistical estimation of the actual state vector: e (xk|yk) ≈ 1 n n∑ i=1 x+k,i (20) a number of ways, the resampling algorithm in particular, are available to design and implement the steps of the filter. the number of particles required to achieve a given estimation accuracy increases in direct correlation with the dimension d of the state vector, this is linear for d of a particle filter using a complex resampling algorithm, but exponential for a plain resampling algorithm [10], while the real-time computational complexity is directly proportional to the number of particles. 4. conclusion despite the fact that satellite-based systems are far from perfect, they are and most likely will continue to be the single most important information source of any localization algorithm combined with digital maps. the role of other information sources, on the one hand, is complementary in areas where gnss has its weaknesses, but on the other hand they contribute to an increase in accuracy at the expense of computational complexity. in a practical real-time application, the extra computational capacity and related costs are not necessarily proportional to each other. this seems to be the main drawback of using nonlinear filtering methods, while on the other hand autonomous vehicles are expected, in the long term, to fall into the category of high-volume low-cost products. hybrid approaches can be considered due to the fact that the equations for localization systems are only partially nonlinear or some of the subsystems can provide sufficiently accurate results using a linear approach. the filtering problem can then be divided into a linear and a nonlinear part, where the former, assuming gaussian distributed noise, may be solved by using a simple kalman filter and reducing the computational complexity and, therefore, the cost of the system. the proportion of linear filtering to nonlinear filtering within the full system is determined by the complexity of the system model chosen as the type of filtering is defined by the model, therefore, modeling and filtering cannot be separate elements in the design process. acknowledgements the research was supported by efop-3.6.2-16-201700002 programme of the hungarian national government. references 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https://doi.org/10.1109/msp.2016.2637418 https://doi.org/10.1109/maes.2005.1499276 https://doi.org/10.1109/maes.2005.1499276 https://doi.org/10.1109/aero.2003.1235126 introduction information sources global navigation satellite systems vehicle model traditional vehicle sensors and inertial measurement unit (imu) optical as well as soundand radio-based sensors databases and maps dedicated short-range communications fusion algorithms simple algorithms: dead reckoning, inertial navigation and map matching linear filtering: the kalman filter nonlinear filtering: the particle filter conclusion hungarian journal of industry and chemistry vol. 46(2) pp. 1-11 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0011 tribological behaviour of polymers in terms of plasma treatment: a brief review hayder al-maliki ∗1 and gábor kalácska1 1faculty of mechanical engineering, mechanical engineering phd school, szent istván university, páter károly utca 1, h-2100 gödöllő, hungary a review to enrich the literature concerning the effect of various plasmas on the tribological behaviour of polymers and monitor the developments of plasma for the modification of polymer surfaces over recent decades using up-to-date data. a comparative study of plasmas was conducted to identify the most useful and efficient ones which facilitate optimal improvements with regard to the characterizations of polymer surfaces and tribological properties. the studies included in this review strongly suggest that (besides plasma-immersion ion implantation, piii) atmospheric plasmas (dielectric barrier discharges, dbd) are an effective technique in terms of modifying the characterizations of polymer surfaces thereby enhancing the tribological behaviour of polymers under different operating conditions that extends the operating life of elements within the machine. keywords: polymer, plasma treatment, surface characterization, tribology 1. introduction the term tribology originates from two greek words, namely τριβω (tribo), a verb which means “i rub”; and the suffix -logy which is derived from λωγια (logia) which can be translated as “study of” or “knowledge of”. this word was introduced by the british scientists bowden, tabor [1] and jost in 1964 [2]. luke mitchell, a professor of lubrication, observed the problems caused by increasing the level of friction exerted on machines [3]. tribology is the science which studies the principles and applications of friction, wear and lubrication [4]. friction and wear are widespread phenomena in our daily lives. processes that result in friction occur when moving surfaces are in contact with each other [5]. friction is a consequence of two main non-interacting components (adhesion and deformation) and can be considered as an approach for all materials including polymers. polymers are nonpolar materials that exhibit unique tribological behaviour, and some of them possess good selflubrication characteristics, examples of which are stated in [6, 7]. the rapid development of industry was accompanied by the urgent need to decrease the size of equipment which in turn leads to a higher degree of friction and enhanced rates of wear to be exerted on the elements of machines. this prompted the evolution of several surfacemodification techniques, in particular for polymers, to diminish the disadvantages of friction and wear. the alteration of surface properties such as hydrophilicity, chemical composition and roughness lead to inevitable changes ∗correspondence: haidrlatif@gmail.com in tribological behaviour which provided an opportunity for researchers to govern such behaviour with regard to polymers. therefore, specific techniques have been developed over the last few years to modify the surfaces of polymers to improve frictional behaviour and adhesive bonding performance. a lot of chemical and physical techniques have been developed to treat the surfaces of polymers. chemical techniques are the processes which deal with wet or chemical reactions on surfaces, for instance, wet etching, grafting, acid-induced oxidation and plasma polymerization. physical techniques deal with the modification of physical surfaces such as corona discharge, ion or electron beams, photon beams, plasma discharge and oxidizing flames [8]. experimentally, the chemical treatments of polymer surfaces exhibit some disadvantages such as localized corrosion and environmental pollution. in contrast, physical treatments have been adapted recently to modify the surface of polymers [9]. one of the most effective techniques to modify the surfaces of polymers are plasmas which facilitate changes in the properties of polymer surfaces by several processes, for instance, cleaning, ablation, crosslinking and surface chemical functionalization [10]. recently, plasma surface treatment was referred to as the most accepted method of modifying the surface of polymeric materials due to its remarkable stability concerning the enhancement of surface properties compared to conventional techniques, in particular, atmospheric plasma treatment which has the ability to operate under ambient atmospheric conditions (in terms of temperature haidrlatif@gmail.com 2 al-maliki and kalácska and humidity) and does not require a vacuum [9,11]. the literature often suggests that plasma treatment may improve the hydrophilicity of polymers [12–16], which has also been demonstrated in our previous works [17–19]. even though plasmas often increase the surface roughness of polymers [15, 20, 21], some studies have proven that a decrease in surface roughness might occur after shorter treatment times [16, 22]. the present study attempts to review the tribological aspects of polymeric materials treated by various plasmas and compared to their pristine surface behaviour by taking into consideration the influence of plasmas on the characteristics of polymer surfaces which vastly governs the tribological behaviour of polymers. finally, plasma types that may currently be recommended to utilize and reinforce the tribological properties of polymers are highlighted. 2. plasma modification of plastic surfaces plasma can be defined as a chemically active media. the composition of plasmas varies depending on the way they are generated and their working power. plasmas produce either low or very high temperatures and according to the heat they generate they can be termed as cold or thermal plasmas. thermal plasmas, especially arc plasmas, were widely industrialized by the aeronautic sector in particular. cold plasma technologies have evolved in the microelectronics industry, but they have a limited use due to their vacuum equipment. there have been many attempts to transpose plasmas to work under atmospheric pressure without the need for a vacuum. the research has led to various sources that are described in [23]. it is known that plasma is the fourth state of matter and it is more or less an ionized gas that constitutes about 99 % of the universe. plasma consists of electrons, ions and neutrons; these constituents may exist in fundamental or excited states. from a laboratory point of view, plasma is electrically neutral. however, it contains some free charge carriers thus is electrically conductive [24, 25]. the degree of plasma ionization can range from small values, e.g. 10−4 − 10−6 for partially ionized gases to 100 % for fully ionized gases. in a laboratory, two types of plasma can be generated; the first are hightemperature plasmas which are also referred to as fusion plasmas, the second are low-temperature plasmas or gas discharges [26]. 2.1 classification of plasmas plasmas can be differentiated into several groups depending on the energy supply and amount of energy transferred to them since the properties of a plasma change depending on electronic density or temperature as presented in fig. 1 [23]. there are two major plasma groups the first are thermal equilibrium plasmas and the second are those not in thermal equilibrium. plasmas that consist of figure 1: 2d classification of plasmas (electron temperature versus electron density) [28]. particles (electrons, ions and neutral species) of uniform temperature are known as thermal equilibrium plasmas, for instance, stars and fusion plasmas. usually they are termed as “local thermodynamic equilibrium plasmas” which is abbreviated to lte. high temperatures typically ranging from 4,000 k to 20,000 k are required to obtain thermal equilibrium plasmas. otherwise, plasmas that are not in thermal equilibrium, abbreviated as non-ltes, will be formed, for example, interstellar plasma matter [25]. lte and non-lte plasmas can be distinguished according to the gas pressure the plasma is subjected to. a high gas pressure is indicative of many collisions in the plasma and it could be argued that just a few collisions occur in the plasma when the gas pressure is low, for example, dielectric-barrier discharge and atmospheric pressure glow discharge plasmas. more details about types, sources and applications of plasmas can be found in [27]. 2.2 influence of plasmas on the surface characteristics of polymers different types of plasma treatments have exhibited potential changes in the physical and chemical surface characteristics of polymers. the variation in wettability is a fundamental parameter that controls adhesion, lubrication and/or interactions with molecules. the formation of polar groups at the surface following plasma treatments, such as carbonyl, carboxyl and hydroxyl groups, enhances the surface energy. the enhancement of wettability following plasma treatment can be a combined effect of surface functionalization and an increase in surface roughness. when surface grafting occurs relatively quickly, an increase in surface roughness has mainly been observed following longer treatment times [21]. depending on the selection of adequate parameters, different types of plasma treatment are used for either enhancing as well as diminishing adhesion or surface hardness. experimentally, tóth et al. [29] observed a significant improvement in the surface hardness of ultra-high molecular weight polyethylene (uhmwpe) following nitrogen plasma ion implantation (npii). the hydrogen plasma hungarian journal of industry and chemistry tribological behaviour of polymers 3 figure 2: f/c atomic ratio vs. voltage. immersion ion implantation (hpiii) treatment of the surface of uhmwpe induces amelioration in terms of the scratch resistance, temperature, mean surface roughness, oxygen content, and surface hardness, while the surface slope and elastic modulus often decreased, but it is possible to enhance these characteristics upon treatment. low values of temperature and mean roughness favour the reduction of the surface slope [30]. in parallel, the nanomechanical, chemical and wear properties of the uhmwpe surface have been significantly enhanced following treatment with helium plasma immersion ion implantation (hepiii). over the ranges of the parameters, the surface hardness increased by up to six times, whereas the loss in volume following multipass decreased by up to about 2.5 times [31]. in a related study, the influence of nitrogen plasma immersion ion implantation (npiii) on the surface of uhmwpe was investigated as well. the results suggested a relative increase in surface hardness, macroscopic temperature and mean surface roughness, while the loss in volume decreased. however, the elastic modulus decreased or maybe even increased depending on the actual parameter set applied in the process. according to the parameter range studied, a reduction in wear rate is strongly dependent on thermal effects [32]. a statistical study by tóth et al. [33] that revised the literature of engineering plastics treated by plasma-based ion implantation (pbii) and plasma-based ion implantation and deposition (pbiid) concluded that there is a rapidly trending in the number of related publications. as a consequence, the effect of nitrogen plasma-based ion implantation (npbii) on poly(tetrafluoroethylene) (ptfe) was discovered by kereszturi et al. [34]. the study observed that the f/c atomic ratio significantly decreased in an inverse relationship with the voltage as shown in fig. 2. meanwhile the surface roughness increased inversely with the voltage and correlated directly with fluence as shown in fig. 3. figure 3: mean surface roughness of ptfe vs. fluence and voltage. although a clear relationship between wear volume and the main process parameters was not observed, in general this was improved following treatment along with an increase in surface roughness and o/c atomic ratio. furthermore, the water contact angle recorded increased under low voltages and high fluences. atmospheric dielectric barrier discharge (dbd) plasmas enhance the wettability and surface roughness of polypropylene (pp) proportionally to an increase in the duration of plasma exposure [35]. also, the surface roughness of pp increases linearly with the exposure time of atmospheric dbd plasma due to degradation of the polymer surface and the formation of nodulelike features. these nodules are shaped by highly oxidized short fragments of polymer which are referred to as low-molecular-weight oxidized materials (lmwoms) in the literature [15]. in a subsequent study, kostov et al. [36] reported that modifications in terms of the surface of different engineering plastics, such as polyethylene terephthalate (pet), polyethylene (pe) and pp could be achieved by atmospheric pressure plasma jets (appj). the primary aim of this research was to identify the optimal treatment conditions as well as compare the effect of appjs on another source of atmospheric pressure plasmas, e.g., dbd on the characteristics of polymer surfaces. as a consequence of appj treatment the surface roughness is increased as shown in fig. 4. however, nodule-like structures were produced as well, but were much smaller compared to those constituted in the previous study when the polymer was treated by dbd. this was attributed to the higher degree of polymer degradation during dbd treatment. the adhesion strength of pp and perfluoroalkoxy alkanes (pfas) has been significantly enhanced due to atmospheric plasma treatment under several gas flows. the characteristics of the surface introduced hydrophilic functional groups where the level 46(2) pp. 1-11 (2018) 4 al-maliki and kalácska figure 4: afm images of pp (a) untreated; (b) 30 s treated; (c) 30 s treated and washed; (d) 60 s treated; (e) 60 s treated and washed. all treatments were conducted with sample reciprocations using a signal amplitude of 10 kv, frequency of 37 khz and ar flow of 1.3 l/min. of improvement changed in proportion to the duration of the treatment as illustrated in fig. 5 [37]. although atmospheric pressure glow (apg) discharge plasma treatment is moderate in terms of energy characteristics, apgderived fluoropolymers exhibit similar surface properties under conventional low-pressure plasmas [38]. treating metals and polymers by a cold arc-plasma jet under atmospheric pressure leads to a superficial improvement in hydrophilicity and a decrease in the water contact angle of these materials as shown in fig. 6 [39]. on the other hand, the literature shows that modifications to the surface of aromatic polymers by dielectric barrier discharge (dbd) can achieve a substantial degree of chemical functionalization on the polymer surface by applying relatively low or intermediate levels of power without suffering severe topographical damage [40]. the surface modification of a pet film by an atmosphericpressure plasma in combination with different gas flows promptly improved its hydrophilicity and was followed by hydrophobic recovery after longer durations [41]. in parallel, significant changes in the morphology and reactivity of pet surfaces have been observed [42,43]. when figure 5: effect of gas blowing on wettability of pfa film. figure 6: water contact angles of various materials after treatment. exposed to air the processing parameters, such as discharge power, processing speed, processing duration, and electrode configurations, affect the nature and scale of changes to the surface. in general, longer durations (low processing speed and a high number of cycles) and high levels of power induced greater changes in the surface wettability of the polymer [44]. among the various environmental gases studied, air and oxygen yielded the highest levels of hydrophilicity, while argon and nitrogen resulted in lower degrees of hydrophilicity of the pet surface [45]. cold atmosphericpressure plasmas (surface dielectric barrier discharge sdbd) improve the oxygen and nitrogen contents of pet [46]. in comparison to pet, the effects of plasma treatment on polyether ether ketone (peek) have been studied less frequently, but also lead to enhanced degrees of hydrophilicity and adhesion [47] due to the incorporation of functional groups and greater surface roughness following dbd [48]. the hydrophilicity, which is governed by the oxygenation of peek following dbd in the air, also recovered after several months through loss of the structurally related functional groups, but it remained more stable than other non-aromatic polymers [49]. nylon 6 (pa6) exhibited a reduction in surface roughness, and an increase in the o/c and n/c ratios due to diffuse coplanar surface barrier discharge (dcsbd) plasma treatment in two different gas flows (nitrogen and oxygen). however, the oxygen dcsbd plasma was more efficient in terms of modifying the surface compared to the nitrogen equivalent [16]. also, plasma treatment enhances the contact angle and alters the surface topography of nylon 66 (pa66) [50]. plasma pre-treatment of the surface of the biopolymer poly l lactic acid (plla) leads to the formation of pits in the crystalline phase accompanied by a mild increase in surface roughness [51]. hungarian journal of industry and chemistry tribological behaviour of polymers 5 3. tribology of plasma-treated polymer surfaces 3.1 friction of polymers many studies have dealt with the tribology of polymers [52, 53]. hardness and the elastic modulus are governed by the penetration depth, maximum load and strain rate [54]. microcuttings are a consequence of ploughing, and they may exacerbate the friction force under specific conditions. friction that results from elastic hysteresis is known as the deformation component [55, 56]. “the mechanical component results from the resistance of the softer material to "ploughing" by asperities of the harder one” [57]. the adhesive bonds generated between the surfaces in the frictional contact are referred to as the adhesion component. the adhesion component is higher than the deformation (mechanical) equivalent [58]. the friction force is equal to the sum of the adhesion and deformation components as shown in eq. 1 [59]. from this, the reason for polymer transferred layers forming on the metal counterface during frictional contact can be determined. the transferred films are an essential factor which must be taken into consideration whilst estimating the tribological behaviour of polymers [53]. the effect of load, sliding velocity and temperature on friction are also important parameters that could influence the tribological behaviour of the polymer: ff=fa+fd [n] (1) where ff represents the friction force, fa the adhesion component, and fd the deformation component of friction. under low loads, ff ≈ fa since fd is far smaller than fa. 3.2 wear of polymers wear is the undesirable removal of layers from the surface of a material. wear occurs when two materials come into contact as a result of movement. mechanical stress, temperature and chemical reactions directly influence the characteristics of the surface layer. polymers are sensitive to these factors due to their particular structure and mechanical behaviour. the interface temperature can be significantly higher than the temperature of the environment. the wear of some polymers, that were examined by lancaster [60] whilst being slid against steel, was found to be influenced by temperature with regard to polymers that the pass is minimum at the characteristic temperature. the accurate classification with regard to the wear of a polymer is not a trivial matter due to the highly diverse nature of such mechanisms [53, 61, 62]. however, abrasion, adhesion and fatigue are the three most common types of polymer wear that occur during the sliding process. figure 7: pin-on-disc tribological test system : 1) base frame, 2) pin holder, 3) loading head, 4) positioning rail, 5) rotating steel disc. 3.3 tribological tests of polymers the tribological behaviour of a specific material is not inherent of its properties as far as strength, elastic modulus, etc., are concerned. the influence of friction and wear on the overall performance of a polymer is strongly dependent on the entire configuration of the test. to evaluate the polymer under operating conditions that occur in actual structures, test configurations have to simulate the main sliding mode as accurately as possible in terms of system pair materials, contact geometry, contact pressure, sliding motion, sliding velocity, environmental conditions, mechanical stiffness, etc. as a consequence, regular basis tribo-test systems are assembled from test apparatus that has yet to be standardized. several parameters should be taken into consideration to select the most favourable test system, i.e. the structure of the material (macroor microstructure), contact conditions (whether the contacting bodies possess the same radii of curvature as in a pin-on-disc test or different radii of curvature as in the ball-on-disc test), and energy dissipation (sliding temperature) [63]. the real tribosystem of the elements of a polymer is considered to be the most dependable test, however, due to its expense and impractical nature the test cannot be conducted regularly. the scale of tribological tests varies from ‘field tests’ that consist of ‘large-scale simulation tests’ on real components to ‘laboratory tests’ on artificial samples which are widespread in the field of the tribological research of polymers due to the small apparatus used and their relatively low cost and versatility with regard to the testing of various materials under different test conditions, e.g. pin-on-disc fig. 7). 3.4 tribological behaviour of the surface of polymers treated by plasmas it is hard to accurately predict the effects of plasma surface treatment on the tribological behaviour of polymers, due to the multitude of mechanisms that govern such processes. it can be expected that functionalization, 46(2) pp. 1-11 (2018) 6 al-maliki and kalácska (a) (b) (c) figure 8: tribological behaviour of pristine and npiii-treated pa6; (a) dry conditions; (b) water lubrication conditions; and (c) run-out lubrication conditions. crosslinking and chain scission will affect their chemical and mechanical surface properties after plasma treatment, which in turn will alter friction and wear characteristics. however, it cannot be confirmed whether such alterations lead to improved tribological properties or not, this can only be ascertained after the treated surface is tested. the tribological behaviour of rubber treated by plasma has been thoroughly investigated, indicating improvements in terms of friction and wear resistance [13]. the pin-on-disc test yields the lower friction coefficient of pc and pp, whereas pe and ps exhibit larger coefficients of friction after atmospheric plasma treatment compared to their pristine surfaces. bismarck et al. [64] attributed the significant decrease with regard to the friction coefficient of pc either to the most substantial reduction in contact angle or the changes in the chemical and simultaneously the physical properties of pc after treatment. on the other hand, the increase in the extent of crosslinking after atmospheric plasma treatment resulted in lower levels of friction and wear of peek composites [65], while argon plasma treatment led to a higher friction coefficient of pet [12]. the effects of nitrogen plasma immersion ion implantation (npiii) on pet indicated improvements with regard to scratch resistance [66]. kalácska et al. [67] demonstrated that the benefits of sliding tribological properties are strongly dependent on the sliding conditions: a lower degree of friction and enhanced wear performance of pet treated by piii only occurred in the presence of low pv factors under dry or water-lubricated sliding conditions. five minutes of atmospheric plasma treatment is sufficient to reduce the coefficient of friction and enhance the wear properties of a uhmw-pe film under a constant pv factor [68]. in contrast, uhmw-pe treated by atmospheric pressure gas plasma does not exhibit a significant change in terms of wear properties after a treatment time of two minutes. since the level of wear reduced by half after longer treatment times, the duration a polymer is exposed to a plasma plays a major role with regard to the tribological properties of the treated surface, in particular for uhmwpe [69]. uhmw-pe treated by a cold argon plasma using dielectric barrier discharge (dbd) supports such a finding since (under dry conditions) an increase in the friction coefficient with treatment time was observed whereas the wear volume reduced over the treatment time due to modifications of its surface. under normal saline (n-saline) lubrication conditions, wear volume and friction were reduced over the treatment time which is indicative of an increase in surface wettability and, therefore, enhanced surface lubrication capability [70]. sagbas [71] reported an increase in friction and improvement in the wear properties of conventional uhmw-pe after plasma treatment, whereas the friction coefficient was unaffected in terms of hungarian journal of industry and chemistry tribological behaviour of polymers 7 figure 9: tribological testing under dry sliding conditions at 0.5; 1; and 2 mpa; including online measurements of coefficients of friction, (specific wear and displacement ∆h), and temperature. vitamin-e-blended uhmw-pe under the same test conditions. however, the wear factor slightly decreased compared to the significant improvement with regard to the wear properties of conventional uhmw-pe as a consequence of the highly cross-linked nature of conventional uhmw-pe. according to the brief review above with regard to the effect of some plasmas on different polymers, the ability of plasmas to alter the surface characterization and thereby the tribological behaviour of polymers is unquestionable. however, the tribological behaviour of the treated surface depends on several factors such as the type of plasma, treatment method, exposure time, operating mechanism and lubrication conditions amongst many other factors. kalácska et al. [72] studied the tribological behaviour of pa6 treated by nitrogen plasma immersion ion implantation (npiii) under different conditions (dry, water and oil lubrication) and various pressure velocity factors (pv). the results show that the friction coefficient and specific wear of treated pa6 are lower than that of the untreated one under dry sliding conditions and low pv factors, while the friction coefficient, specific wear and contact temperature of treated pa6 are higher than the pristine equivalent under high pv factors (fig. 8a). on the other hand, the water lubricant reduces the adhesive component of friction after treatment, which was reflected in the fluctuation of the friction behaviour of the treated surface (fig. 8b). however, under continuous oil lubrication, no difference could be detected between the treated and untreated parameters, therefore, the run-out type was preferred in terms of detecting such a difference. test conditions in terms of run-out oil lubrication exhibit a lower friction coefficient for treated pa6 than the pristine equivalent in the presence of low pv factors as a consequence of an increase in the dispersive component (fig. 8c). in contrast, our last work [73] elaborated on the effect of atmospheric dbd plasma on the tribological behaviour of pet under various test conditions (3 “dry” normal load and “run-out lubrication” constant normal load conditions). the effect of dbd plasma treatment on the characterization of the surface was interpreted as an enhancement of the surface energy and reduction in the surface roughness due to the melting of surface asperities. however, increasing the surface wettability induces higher coefficients of friction according to archard’s theory of friction [74]. the dry tribological test yielded unexpected behaviour where the coefficient of friction of the treated surface was lower than the pristine equivalent under different pv factors. also, the specific wear and the vertical deformation were enhanced. however, the interface temperature of the treated surface was higher than the untreated one (fig. 9). the reduction in the coefficient of friction can be theoretically attributed to the smaller contributions of a deformation component. in a related context, a “run-out” oil lubrication test yielded a lower coefficient of friction for the treated surface due to a rise in the surface energy after treatment, leading to a favourable enhancement with regard to the adsorption of the lubricant as shown in fig. 10. by using the analysis and comparison of the previously reviewed studies, it can be said that atmospheric dbd plasma can be an effective technique nowadays for the treatment of polymer surfaces that aims to reduce friction and improve wear under dry and run-out lubrication conditions under various pv factors, especially under lower ones compared to other techniques, e.g. npiii. 4. conclusion in conclusion, the reviewed research and results have apparently shown the capability of plasmas to modify the 46(2) pp. 1-11 (2018) 8 al-maliki and kalácska figure 10: tribological testing under lubricated sliding and “run-out” conditions at 0.5 mpa. surfaces of polymers which results in a change in the tribological properties of surfaces. however, the effect of plasmas depends on several factors such as the sources of plasmas, vacuum, temperature, pressure, etc. the essential points concerning the tribological behaviour of polymers that are subjected to plasma treatment are summarized below: • plasmas can efficiently alter the characterization of polymer surfaces by utilizing different sources such as appj, piii, apg, pbii and dbd and various vacuums which results in the enhancement of surface wettability and an increase in surface roughness with few exceptions. atmospheric dbd plasma can achieve the optimum surface configuration in a shorter time. • there is a paucity of studies which deal with the tribological behaviour of polymers in terms of plasma treatment. most studies focused on the effect of plasmas on the tribology of engineering polymers especially pet, pa6, and in some cases peek. however, no studies appear to deal with polyolefins, except some studies which investigate the tribology of uhmw-pe for medical applications in particular. • uhmw-pe exhibits a higher coefficient of friction and improvements in specific wear after plasma treatment under dry conditions where cross-linking plays a prominent role in terms of controlling the wear rate upon plasma treatment. however, the lubricated tribological test of uhmw-pe resulted in a lower coefficient of friction due to an increase in wettability. • the comparative investigation of engineering polymers treated by different plasmas under the same conditions (pa6 treated by npiii and pet treated by atmospheric dbd) can explain the remarkable effect of atmospheric dbd plasma on the tribological behaviour of pet under dry conditions where the friction coefficient of pet remained 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high-power modular inverter system. the goal was to develop a universal inverter system (motor controller + power electronics) in which the performance of the power stage is scalable. the design concepts, hardware architecture, system components, built-in features and protections are described regarding the power stage. keywords: modular, universal, desaturation, active clamping, protection 1. introduction power electronics and their control algorithms are very important parts of electric vehicles. the whole system can operate reliably, efficiently and with good dynamics only if all elements of the vehicle are well coordinated. before the different electric drivetrains can finally be applied, they should be tested under different circumstances on electric motor or drivetrain test benches. otherwise it would be difficult to test them in-vehicle as they are already built-in. for such testing processes, a flexible test system is a good solution that can be easily modified at both hardware and software levels, especially for institutions like our research center where various types of electric motors from different manufacturers are dealt with. their inverter systems are usually inaccessible without the help of experts. 2. design concept the purpose of the development was to design a universal and scalable (at the power stage) inverter system. thus, the same system can be used for three-phase electrical machines with different power requirements and applications. the first version is capable of 600 a at a nominal system voltage of 400 v. as the motor controller is equipped with standard interfaces, it is able to adapt power stages to different power levels. for the design of the hardware for the motor controller and power stage, state-of-the-art solutions were used. furthermore, different motor control algorithms are dealt with at the research center, so it was decided to use them with the motor controller to ensure the software en*correspondence: szgabor@ga.sze.hu vironment is capable of further developments and different types of motors can be easily adapted to it. motor control software can be implemented using model-based simulation (matlab/simulink) with automatic code generation. as a result, the behaviour of the motor can be determined in advance by simulation and easily adapted to our specific environment. the system supports different communication protocols, e.g. can, rs232, ethernet and flexray, which can be used for control, data acquisition and status information polling. the system is usually used to test threephase electric machines or can be installed in electric vehicles. 3. results and analysis the inverter system (fig. 1) consists of four separate printed circuit boards (pcbs), namely control board, figure 1: hardware structure https://doi.org/10.33927/hjic-2020-04 mailto:szgabor@ga.sze.hu 20 szeli and szakállas power stage, f-s-800 insulated gate bipolar transistor (igbt) interface board, and a current measurement board for current transducers. only commercially available and automotive qualified components were used for the hardware. with regard to the different circuits on the boards, the spice simulator was used to support the design. the main features: • undervoltage protection • overcurrent protection • isolated sensor supply • isolated voltage measurement • isolated dc/dc power supply for the igbt drivers • temperature measurements • built-in protections: – surge protector – short circuit – desaturation – advanced active clamping 3.1 power stage the power stage was designed to be able to drive a maximum of two igbt modules simultaneously (one igbt module can also be used by us). thus, the output power of the inverter is scalable and can easily be doubled should a different igbt module be used. 3.2 isolated power supply for the gate drivers the power stage includes 6 separate flyback dc/dc converters that produce an isolated +15 v / −8 v asymmetrical power supply for igbt gate drivers as seen in fig. 2. figure 2: power stage design parameters according to the system requirements and the flyback converter datasheet [1]: • 8-18 v dc input voltage • −8 v / +15 v output voltage • 10 w output power (due to igbts in parallel, fsw = 20 khz) • 3, 956 w power consumption per igbt module was calculated from [2] pgdr = qg ( vge(on) − vge(off) ) fsw (1) the output power selected was chosen for 2 igbt modules in parallel. the isolated power supply for the gate drivers works as expected in the real circuit, as can be seen in figs. 3 and 4. 3.3 gate drive circuit the igbt modeules were powered by infineon’s 1ed020i12fa2 galvanically isolated single channel igbt gate driver circuits, which were placed on a separate pcb. the maximum output current of the 1ed020i12fa2 driver was ±2 a. because of this low peak current, significantly increased gate resistors were required, which greatly degraded the switching properties of the igbt driver. therefore, it was necessary to figure 3: simulated flyback dc/dc switching waveform (pout = 5 w) figure 4: flyback dc/dc switching oscilloscope waveform (pout = 5 w) hungarian journal of industry and chemistry high-power modular inverter development 21 figure 5: operation of the surge stopper protection use a so-called bipolar totem-pole amplifier between the output of the driver and the igbt gate terminal. the designed bipolar totem-pole circuit was capable of driving the igbt with the use of a resistor of rgoff = 0.82 ω. 3.4 built-in features surge stopper the voltage supply (+8 v – +16 v) was connected to the load through an overvoltage protection circuit. this circuit protects the other parts of the power stage from high voltage spikes and controls the output voltage in case of input overvoltages (load dumps) as shown in fig. 5. it is also equipped with overcurrent and reverse polarity protection as well as an adjustable low-voltage fault detection limit. desaturation protection the igbt driver is a power semiconductor that is normally used to switch operation in the closed and saturation regions. the closed region can be considered to be a broken wire, and in the saturation region it functions as a short circuit. between the igbt collector and emitter terminals, the saturation voltage, vce, can be measured [3]. this voltage depends on the temperature of the semiconductor, its collector current and the voltage applied to the gate. fig. 6 shows the dependence of the saturation voltage of the fs800r07a2e3 figure 6: output characteristics of the fs800r07a2e3 igbt module figure 7: operation of the desaturation protection igbt module with regard to its collector current on the temperature of the semiconductor. the desaturation voltage can be adjusted using zener or fast diodes, so in our case, the threshold voltage, vce, selected of 1.3 v used in the switching will be subject to a 600 a collector current limitation per module at 25 ◦c. the igbt driver circuit is continuously monitoring the vce, using a comparator, and if that exceeds the reference voltage, that is 9 v, of the integrated circuit, the driver forces its output to vee2 (−8 v) within a maximum tdesatout time of 430 ns as shown in fig. 7. with this kind of protection, short-circuit failures can be avoided and a temperature-dependent current limitation realized. the vce can be monitored only after a period of time equal to tblanking +tdesatout(1.8 µs+430 ns= 2.23 µs) has elapsed following the arrival of the control signal [4]. the fault signal is only active when the igbt driver is switched on. advanced active clamping when working with igbts, parasitic inductances inside them and the converter circuits must be taken into consideration. their effects cannot be completely eliminated for physical reasons and their influence on the system behaviour cannot be neglected. fig. 8 shows the parasitic inductances contained in a commutation circuit. figure 8: parasitic inductances in igbts 48(1) pp. 19–23 (2020) 22 szeli and szakállas figure 9: characteristics of the igbt turn-off process voltage transients are produced at the collector of the igbts during their turn-off process, which are caused by the change in current passing through them as shown in fig. 9. the commutation speed and thus, the turn-off overvoltage at an igbt can, in principle, be affected by the turn-off gate resistance rgoff . this technique is used most often in low-power devices where rgoff must be selected for overload conditions such as turn-off of the double rated current, short circuits and a temporarily increased link circuit voltage. during normal operations, this causes increased turn-off switching losses and turnoff delays, which reduce the efficiency of the modules [5]. the fs800r07a2e3 igbt module has a parasitic inductance of 14 nh. to reduce the voltage spikes, a clamping circuit was used that allows charging of the gate-emitter capacitance and flow charges to the base of the proposed bipolar totem-pole over the specified voltage range through a transient-voltage-suppression diode connected between the collector and the gate, driving the igbt into the normal active mode and reducing the current-change rate, dic/dt as seen in figs. 10 and 11. figure 10: the proposed bipolar totem-pole layout with feedback figure 11: operation of the advanced active clamping circuit @ 340 v/ 800 a (single igbt module) this type of control of the bipolar totem-pole circuit reduces the power dissipation as a result of the resistance rgoff whilst operating. 3.5 cooling system to design the cooling system of the inverter, thermal simulations were carried out. the maximum power dissipation of the igbt module was 1500 w, and its operating temperature range was between −40 and 150 ◦c. the thermal resistance between the liquid coolant (50% water, 50% glycol) and the surface of the heatsink was 0.097 k/w. the igbt manufacturing drawings were used to design the 3d model as seen in fig. 12. 4. conclusion the functional testing of an inverter was carried out at the electric motor test bench laboratory of széchenyi istván university. the developed system and the test environment can be seen in figs. 13 and 14. a permanentmagnet synchronous motor (pmsm) was connected to it and different peripherals and built-in functions tested. on the other side of the test bench, the same type of pmsm connected to a 400 v / 500 a, downscaled (single igbt module) version of the inverter was used. at first, the tests were performed at a speed of 1600 rpm and at low load figure 12: the designed coolant space inside the heatsink hungarian journal of industry and chemistry high-power modular inverter development 23 figure 13: the assembled inverter system figure 14: eletric motor test bench with the mounted inverters torques. the inverters were operated alternately, one in torque-control mode, the other in speed-control mode. in a future paper, these inverters will be tested under heavyload conditions, when the motor control algorithms work reliably. acknowledgements the research was carried out as part of the "autonomous vehicle systems research related to the autonomous vehicle proving ground of zalaegerszeg (efop-3.6.216-2017-00002)" project in the framework of the new széchenyi plan. the completion of this project is funded by the european union and co-financed by the european social fund. references [1] linear technology, ”flyback, forward and isolated controllers“, lt8302 datasheet, sept. 2016 rev. c [2] infineon technologies ag, “automotive igbt module explanation of technical information”, application note an2010-09, 2010 [3] avago technologies, “desaturation fault detection”, application note an5324, 2012 [4] infineon technologies ag, ”galvanic isolated gate driver“, 1ed020i12fa2 datasheet, may 2013 rev. 2.0 [5] rüedi,h.; thalheim, j.; garcia, o.: advantages of advanced active clamping, power electronics europe, 2009 8, 27–29 48(1) pp. 19–23 (2020) introduction design concept results and analysis power stage isolated power supply for the gate drivers gate drive circuit built-in features cooling system conclusion hungarian journal of industrial chemistry veszprem vol. 30. pp. 257259 (2002) the influence of water soluble varnishes on the catalyst during enamelling process j. balgaranova (department of fundamentals of chemical technology, university of chemical technology and metallurgy, kl.ohridski 8, sofia, 1756, bulgaria) received: august 21,2002 during the drying process of enamel wires production, enamel varnishes lib~rate large amounts of. vapour from solven~s and diluents, as well as other products from the destruction of the varn1sh base. an appropnate method for their destruction is catalytic combustion. this requires certain characteristics of the catalysts. the use of the new so-called water soluble enamel varnishes, increases the possibilities for catalyst poisoning. the catalytic activity of pd-laid catalyst in destructive oxidat~on of organic substances in .the presence of water vapour was studied on a large-scale production trials. it was established that the greater quantity of. water vapour do~s not decrease the conversion degree. on the contrary, it is slightly increased (by 9-10 %). these c~ntnbute to not only diluent economy and environmental protection, but as well retain the existing technology of enamel wrres. keywords: catalytic combustion, catalyst poisoning, water vapour, water-soluble varnish introduction during drying and polycondensation processes of enamel wires production, enamel varnishes liberate fairly large amounts of vapour from solvents and diluents, as well as other products from the destruction of the varnish base, mainly cresols and di-, and tetramethylbenzenes. these are strong toxins and environmental pollutants. [ 1 j an appropriate method for their destruction is catalytic combustion. the obtained heat, through recirculation of the exhaust gasses, is used in the drying process. [2] this requires certain characteristics from the catalysts, i.e. action at comparatively high temperatures as well as in the presence of multicomponent mixtures of substances, some of which may act as contact poisons. these problems become more important with the use of the new so-called water soluble enamel varnishes~ where .the quantity of water vapour in the exhaust gases inevitably increases. the literature shows at length that during exploitation, the activity of the catalyst is changed under the influence of various factors. generally. this means decrease of the active surface because of sintering or blocking due to precipitation as well as poisoning. t~e most important factor for deactivation is poisoning. it is a process, which lead to catalytic activity decrease and in diffusion limited reactions to activation energy and selectivity changes. it is known that the action of the poison is specific for a particular catalyst and a particular reaction. it is interesting to point out that at times, when the concentration of the poison is not high, instead of deactivating a certain catalyst or reaction, it may have an opposite activating effect [3]. in the sicme (italy) and pgz (hungary) horizontal enamel machines, the catalytic elements of ka tec company {germany) are widely used for air purification process. they have a square shape and look like a metal air filter. the active phase, palladium is laid on a chromium steel crimped band. according to the database of the producer, soot or high molecular compounds could deactivate the catalyst. it is sensitive to halogens, sulphur dioxide, and phosphorous compounds. the catalyst loses about 25 % of its activity after around 8000 hours use [4]. the literature review shows that a number of oxide catalytic systems are sensitive to the comparativel_y weak contact poisons of h20 and c02 [5]. what ts more, a reversible poisoning is detected after the initial action of the poison has ceased. comparatively few data exist on the influence of these poisons on platinum and other catalysts containing noble metals. it is pointed out that usuahy, water in a reduetion conditions acts as a poison on the metal type catalyst [5}. contact information: e-mail: petkov@uctm.edu; tel: ( +359) 2 6254 585 258 table 1 dependence of combustion degree from the concentration and temperature machine varnish cm, coul tin tout ilt combustion type type (mg/m3 ) (mglm3 ) ("c) ("c) ("c) degree,(%) pgz p~940 8.29 4.81 450 525 75 41.98 pgz p-940 7.38 4.46 450 520 70 39.50 pgz hb-91 5.07 2.42 450 515 60 52.26 pgz hb-91 4.95 3.36 450 510 60 52.32 sicme p-940 7.60 4.79 450 520 70 36.97 sicme p-940 8.10 5.18 450 520 70 36.00 sicme hb-91 5.18 2.85 450 500 60 44.98 sicme hb-91 5.34 2.95 450 500 60 44.75 because of this, as well as the development of a new class of water soluble enamel varnishes which meet ecological aims, it is of interest to investigate the catalytic activity of palladium laid catalysts in the destructive oxidation of organic substances in the presence of water vapour. experimental the investigation was carried out with varnishes p-940, esterimide, and the water soluble hb-91, produced in test series, containing dry substance, respectively 27.5% and 41.0 %, with pgz and sicme horizontal machines working with catalyst used for over a year. their activity in the combustion reaction was assessed by determining the total amount of burning organic substances in recycled air, expressed as a content of total organic carbon, 'before and after the catalyst at equal constant volume velocity, by the absorption method [6]. results and discussion results are shown on table 1. clearly the concentration of burning toxic substances in the air using the hb-91 decreases compared to the estherimide varnish. as well as showing smaller temperature differences (tin t ouu in the catalyst layer at the adiabatic temperature increase. the comparatively small temperature difference points to a certain degree of deactivation of the catalysts over the one-year period of work. the main conclusion is that the greater quantity of water vapour does not decrease the catalytic combustion degree, i.e. the degree of activity. on the contrary~ it is slightly increased (by 9-10 % ). this can onty be explained by the regeneration of the catalyst surface owing to the coke deposits from carbohydrates of unknown composition laid on it. as wen as some high-molecular compounds released by the decomposition of the varnishes. in support of this conclusion. the results of other authors regarding the regeneration of pt catalyst may be referred to. usually~ a catalyst containing laid on coke is table 2 characteristics of the water varnish enamelling process varnish dry wire wire productivity energy varnish mass diameter velocity (kg/hlp ass) expense expense (%) (mm) (mls) (kwh/day/ (g/kg) pass) bh-91 41 0.016 1.83/1.80 1.173 57.09 170 ±0.02 p-940 27.5 0.016 1.8311.83 1.173 51.36 157 ±0.02 regenerated by its combustion in airflow at high temperatures. to obtain the necessary oxygen concentration, it is suggested that the air be diluted with inert gases. or steam where the reaction of the latter with carbon plays an essential role [6]. productivity, energy and varnish expenses for both varnish experiments are given on table 2. in comparison, it can be seen only a slight increase of the energy expenses when working with the water-soluble varnish. this could be explained by the lower heat amount released in the catalyst layer, which can be completely compensated by the electrical heaters if necessary. according to these and to the good quality characteristics of the produced wires we consider that the enameling process with the studied water-soluble varnish does not infringe the catalytic combustion of the exhaust gases and fully correspond to the existing technology. conclusions the investigation is of interest in view of the possibility of using water soluble enamel varnishes for production of enamel wires. it was established that the greater quantity of water vapour does not decrease the destruction oxidation degree. on the contrary, it is slightly increased (by 9-10 %). these contribute to not only diluent economy and environmental protection, but correspond with the existing technology of enamel wires. acnowledgement the author expresses her thanks to professor dr.d. klisurskii from the bulgarian acad. of science for the valuable discussions and support. symbols c in• c out the inlet and outlet concentration of combustible organic substances. expressed as total organic carbon tin· t ()ul the inlet and outlet temperature of the catalyst layer references 1. smith s.r.: prog. in environ., 2000,2, 129-146 2. broecherhoff p. and emonts b.: catalytic combustion, a possibility for low emission heat production., proc, intersoc. energy con. vers. england, conf., 29th (pt.3), 1146 1150, 1994 . 3. piperov b. b.: ph.d.thesis, ionh, bulganan academy of science, 175, 1992 259 4. katec-booklet, hasselroth neuenhassland metall. katalysatoren fur wirtschaftliche drahtlackierung, brd, 1989 5. seiterfild ch.: practical course on heterogeneous catalysis. edit. mir., moskow, p. 520,1984 6. balgaranova j.: ph.d. thesis, university of chemical technology and metallurgy, sofia, 145, 1984 7. patent gdr, 234799, (1986) page 261 page 262 page 263 hungarian journal of industry and chemistry vol. 46(2) pp. 37–42 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0016 monitoring of chemical changes in red lentil seeds during the germination process ildikó szedljak *1, anikó kovács1, gabriella kun-farkas2, botond bernhardt3, szabina králik1, and katalin szántai-kőhegyi1 1department of grain and industrial plant processing, szent istván university, villányi út 29-43, budapest, 1118, hungary 2department of brewing and distilling, faculty of food science, szent istván university, villányi út 29-43, budapest, 1118, hungary 3department of soil chemistry and turnover, institute for soil sciences and agricultural chemistry, centre for agricultural research, hungarian academy of sciences, herman ottó út 15, budapest, 1022, hungary red lentils are a very important raw material in the food industry due to their high protein content and high level of healthpromoting components. the nutritive value of red lentils is the most important attribute from a research point of view; it can be increased by germination, soaking as well as physical and biochemical processes. the antinutritive materials are reduced or denatured by the germination process and indigestible components become available to the human body. heat treatment was applied to achieve different temperatures and increase the microbiological stability of germinating samples. the effect of heat treatment on the amounts of certain components and the activity of oxidative enzymes was tested during our experiments; the nutritional characteristics (water-soluble total polyphenol content (wstpc), watersoluble protein content (wspc), water-soluble antioxidant capacity, in addition to peroxidase and polyphenol oxidase enzyme activities) of different treatments in red lentil samples were monitored. the wstpc in our samples ranged from 0.726 mg gallic acid equivalent gae/g dw (dw being dry weight) to 1.089 mg gae/g dw, and the wspc varied from 19.078 g / 100g dw to 29.692 g / 100 g dw. results showed that germination led to an increase in the wstpc and wspc. the peroxidase enzyme activity also exhibited an increase during germination which could result in deepening of the colour of the finished products. germination resulted in the water-soluble antioxidant capacity of red lentil samples decreasing. keywords: red lentil, germination, antioxidant activity, protein, enzyme 1. introduction lentils (lens culinaris m.) are bushy annual plants of the legume family. lentils are grown for the high protein content and high nutritive value of their lens-shaped seeds. lentils are primarily a cool-season crop; they are moderately resistant to high temperatures and droughts. lentils are characterized by their high levels of plant protein, complex carbohydrates (resistant starch, slowly digestible starch and oligosaccharides), fibres (soluble and insoluble) as well as very low sodium and fat content. additionally, lentils are rich in b-vitamins, e.g. folate, thiamin and niacin, and key minerals, namely iron, potassium, magnesium and zinc, make them a highly nutritious food. the most common types of lentils are red, green and black of which red and green are the most commonly traded. the cultivation and consumption of red lentils are considerable in asian countries. on the other hand, con*correspondence: ildiko.szedljak@gmail.com sumer demand for red lentils in the western hemisphere is not high [1]. red lentils are a valuable source of macronutrients (proteins, fats, carbohydrates) and other important components (phytochemicals: phytic acid, phenolic acids, flavonols, flavanols and condensed tannins). lentils have demonstrated many health benefits, e.g. lowering the glycemic index and their gluten-free status for people with metabolic disorders. the consumption of lentils can also lead to weight loss, which is recommended for all overweight and obese individuals [2, 3]. the germinated seeds and their compounds are possible components of functional foods. functional foods play an important role in health promotion and disease prevention. different scientific papers suggest that lentils provide protection against chronic diseases through a multitude of biological activities including anticancer, antioxidant and angiotensin-converting enzyme inhibition. lentils also reduce blood lipid levels and the risk of developing cardiovascular diseases [4, 5]. mailto:ildiko.szedljak@gmail.com 38 szedljak, kovács, kun-farkas, bernhardt, králik, szántai-kőhegyi the nutritive value of lentil seeds can be improved by the germination process. germination is a complex metabolic process during which the lipids, carbohydrates and storage proteins within seeds are broken down in order to obtain the necessary energy and amino acids. these changes influence the bioavailability of essential nutrients [6]. the presence of antinutritional factors might be reduced by germination. red lentils have been gaining increasing attention due to their health benefits as part of the human diet and they are considered to be an excellent source of dietary antioxidants largely because of their high level of bioactive phytochemicals [1, 7] in hungary, small-scale (20 seeds) red lentil germination experiments have already been conducted during which the effect of germination on the lectin content was studied [8]. the main purpose of our research was to examine the suitability of the germinated red-lentil grist as a raw material of dry pasta. red lentils were selected for our experiments due to their aforementioned favourable nutritional characteristics. in addition, its flour can be suitable in the development of gluten-free pasta products in the form of enrichment and gluten-free raw materials. the formation of more digestible water-soluble components was conduced by seed germination, but at the same time a loss may be observed due to the heat treatments (drying pasta) used in the manufacture of the products. the same loss may occur during the boiling process. therefore, it is important to check for all kinds of changes that occur during heat treatment. the control of the activity of enzymes which generate oxidation processes is also essential during germination as is technological / kitchen-technological processing from the point of view of the expected quality of the finished products. developing food diversity by incorporating red lentil seeds and its flour into western diets is highly recommended. 2. experimental the aim of our study was to examine the chemical changes in red lentil seeds during the germination process. the effect of different heat treatments on the amount of certain components and the activity of oxidative enzymes were monitored. moreover, a connection between the parameters and the extent to which these variables interact was sought. 2.1 samples and measurements samples 10 kg of raw organic whole red lentil was purchased from biorganik online kft. 3 kg of which was added to the germination device. 500 g of both soaked and sprouting seeds were sampled and heat-treated at three different temperatures. the heat-treated seeds were milled using a hammer grinder and then homogenized. the aqueous extracts were made from the control samples and the heat-treated grists. steeping, germination and heat treatment steeping and germination were performed in a schmidtseeger, kma-a1-2008 micromalting plant. the micromalting plant was controlled by a personal computer with a special controlled by a personal computer with special software. during germination the temperature of the air was regulated and wetted with special jets. during the steeping process compressed air was dispersed in the steeping water. alternate wet and dry periods were implemented during steeping, because during the latter the oxygen uptake of grains is more effective. wet steeping lasted for 3 hours at 20 ◦c with aerations of 6.67 minutes in duration every 8 minutes. this was followed by a 2 hour-long dry period at 22 ◦c with humidification. the second 2-hour-long wet period was performed at 20 ◦c. steeping was stopped when an adequate moisture content was achieved. germination lasted for 96 hours at 22 ◦c with humidification. during the first 48 hours, the germinating seeds were rotated 30 times every two hours, then every three hours. germinating seeds were not sprayed during the process. germinating red lentil samples were taken daily at the same time. heat treatment was applied at different temperatures (60 ◦c, 80 ◦c, 100 ◦c) in order to increase the microbiological stability of germinating samples. the effect of heat treatment on the amount of certain components and the activity of oxidative enzymes was tested during our experiments. chemical analysis the samples were homogenized and 0.10 ml of distilled water was added to each sample. the centrifugation process was conducted after extraction for 10 minutes at 4 ◦c and 10,000 rpm. the watersoluble polyphenolic content was measured by colorimetric analysis using folin & ciocalteu’s phenol reagent [9] and the results were expressed in gallic acid equivalent (gae) (mg gae/g dw – dw being dry weight). the wspc was measured by a method discovered by layne [10]. the water-soluble antioxidant activity was determined using a ferric reducing antioxidant power (frap) assay kit [11]. the polyphenol oxidase (ppo) enzyme activity was measured by using a synthetic substrate, pyrocatechol. the oxidized form of the substrate can be synthesized photometrically at 420 nm by a spectrophotometer [12]. the peroxidase (pod) enzyme activity of the extracts was determined using o-dianisidine as a hydrogen donor in sodium acetate (ph 5.1) [13]. the reagents for the chemical measurements were provided by sigma-aldrich kft. statistical methods all of the measurements were replicated five times. the kruskal-wallis test was applied to calculate the exact p-value (α = 0.05) and dunn’s post hoc pair-wise test was chosen with an adjustment by bonferroni. the relationship between the parameters was determined by spearman’s rank correlation coeffihungarian journal of industry and chemistry chemical changes in red lentil seeds during the germination process 39 figure 1: water-soluble total polyphenol content in red lentil samples. different letters indicate significant differences between treatments (p ≤ 0.05). cient (non-parametric equivalent of pearson’s correlation coefficient) (α = 0.05) using the xlstat-sensory solution software, version 2013.1.01 (addinsoft, 28 west 27th street, suite 503, new york, ny 10001, usa). during the correlation test the correlation between the variables regardless of their units was examined. 3. results and evaluation 3.1 water-soluble total polyphenol content (wstpc) zhang et al. [14] measured the total polyphenol content (soluble and insoluble in water) using folin ciocalteu’s reagent in raw red-lentil extracts (5.04 ± 0.36 mg gae/g dw – 7.02 ± 0.48 mg gae/g dw). according to their data all extracts of lentils cultivated in canada were significantly different from each other. in contrast to this tpc values changed over a very narrow range (from 5.9 ± 0.1 mg gae/g dw to 5.93 mg gae/g dw) in the samples of red-lentil flour tested [15–17]. the results of tpc are shown in fig. 1. the wstpc in our samples ranged from 0.726 mg gae/g dw to 1.089 mg gae/g dw. our wstpc values were 5 to 10 times smaller than in the aforementioned experiments. by comparing the control and soaked samples, it can be observed that the wstpc increased during the soaking process. these values were higher than the measured data from germinated samples (fig. 1). according to our experiments heat treatment at high temperatures (80 ◦c and 100 ◦c) equalized the wstpc values in red lentil samples. furthermore, germination and heat treatments did not effect the wstpc of the seeds. 3.2 water-soluble antioxidant capacity the results of water-soluble antioxidant capacity were measured using a frap assay kit. the values ranged between 0.177 mg ascorbic acid equivalent (aae)/g dw figure 2: water-soluble antioxidant capacity of red lentil samples. different letters indicate significant differences between treatments (p ≤ 0.05). and 0.815 mg aae/g dw. as a result of the germinating process, the antioxidant capacity of the samples was significantly reduced compared to that of the control sample. however, treatment at a high temperature (100 ◦c) led to a further increase in the amount of new water-soluble components with antioxidant capacity. samples that were not dried during the first 3 days were significantly different from the control samples in all of the categories. moreover, they differed from the sample dried at 100 ◦c on the 4th day (fig. 2). the highest water-soluble antioxidant capacities were measured in the control samples, except for the control sample treated at 100 ◦c. by comparing control samples to germinated samples, it is evident that the germinating process did not result in an increase in the water-soluble antioxidant capacity. our results showed that whilst being soaked the water-soluble antioxidant capacity started to decrease. the water-soluble antioxidant capacity in the heattreated sample on the 3rd day of germination at 80 ◦c decreased drastically compared to the control sample. the same change occurred with the samples that were not dried. nevertheless, the significant decrease had already occurred on the 1st day of germination. no correlation was found between the wstpc and water-soluble antioxidant capacity. 3.3 water-soluble protein content (wspc) wspcs, given in fig. 3, ranged from 19.078 g / 100 g dw (dry weight) to 29.692 g / 100 g dw. by comparing the control and soaked samples, it is evident that the wspc increased during the soaking process. in the case of samples that were not dried in addition to those treated at 80 ◦c and 100 ◦c, no significant differences were observed between treatments except for samples treated at 60 ◦c where those soaked and on their 2nd day of germination had significantly higher values compared to the control sample. the highest wspc was 46(2) pp. 37–42 (2018) 40 szedljak, kovács, kun-farkas, bernhardt, králik, szántai-kőhegyi figure 3: water-soluble protein content in red lentil samples. different letters indicate significant differences between treatments (p ≤ 0.05). measured on the 2nd day of germination at 60 ◦c, which was significantly higher than all the heat-treated control samples as well as samples treated at 100 ◦c except for the value on the 1st day of germination. as the germination process advanced – especially on the 3rd and 4th days – the wspc of samples heat-treated at 80 ◦c and 100 ◦c started to decrease compared to the same phenophases of those that were not dried or heattreated at 60 ◦c. this may be explained by the fact that plant proteins are more easily degraded at higher temperatures over prolonged periods of time. a negative correlation was observed between the wspc and water-soluble antioxidant capacity. the total protein content was determined using the dumas method as described by hefnawy [18]. in this study the total protein content was 26.6 ± 0.50 g / 100 g dw and the effect of the heat treatment was insignificant. 3.4 peroxidase (pod) enzyme activity the changes in pod enzyme activity of red-lentil samples are shown in fig. 4. the pod adversely affects the nutritive value, taste, texture and colour of food products. these enzymes are referred to as heat-tolerant enzymes and can regain their activity following heat treatment and storage (fig. 4). pod enzyme activity ranged from 10.815 u/g dw to 215.785 u/g dw with statistically significant differences. the highest value (215.785 u/g dw) was found in the sample dried at 100 ◦c on the 4th day. the samples that were not dried or heat-treated were identical to each other on the same level (control, soaked, 1st-4th day). pod activity progressively increased during the germination process in almost all cases. the pod activity of the sample dried at 100 ◦c was 20-fold higher than that of the control sample. the pod activity of different tempered lentil samples was also measured by pathiratne et al. [19] and their maximum value was 186.4 figure 4: peroxidase enzyme activity of red lentil samples. different letters indicate significant differences between treatments (p ≤ 0.05). u/g protein. however, in another study by świeca et al. [20], the pod activity of germinated lentil samples was much higher than the aforementioned ones, 10.3 ± 0.24 ku/mg protein. elevated temperatures of heat treatment resulted in an increase in the pod activity during the germination process. 3.5 polyphenol oxidase (ppo) enzyme activity ppos and pods are the most studied enzymes in fruit and vegetables. świeca et al. [20] studied the ppo enzyme activity in sprouts of lentils according to the method described by galeazzi et al. [21] and measured 2.24 ± 0.05 ku/mg protein. they reported that enzymatic markers of the stress metabolism of plants, e.g. ppo activities, did not differ significantly between sprouts. in our study a catechol substrate was also used but no ppo enzyme activity was detected in the samples. 4. conclusion of all the parameters studied, the wspc of red lentils strongly correlated with the values of water-soluble antioxidant capacity measured using the frap assay kit (data not shown). the correlation is inversely proportional, hence, the greater the wspc, the lower the watersoluble antioxidant capacity. seed germination is one of the most important stages in the life cycle of plants and germinated seeds may be a useful source of healthy food. germinated seeds are very complex living matrices and it is very difficult to understand the biochemical changes that occur during sprouting. further studies on the germination process of red lentils are needed to help understand and identify the important parameters that are able to describe such changes. functional foods play an important role in terms of consumer acceptance [22], thus, a more suitable approach hungarian journal of industry and chemistry chemical changes in red lentil seeds during the germination process 41 may well be sensory evaluation in the case of our redlentil samples. the latest development methodologies should be used, namely preference mapping methods, just-about-right (jar) scaling and eye-tracking methods [23–25]. references [1] zhang, b.; deng, z.; tang, y.; chen, p.; liu, r.; ramdath, d. d.; liu, q.; hernandez, m.; tsao, r.: fatty acid, carotenoid and tocopherol compositions of 20 canadian lentil cultivars and synergistic contribution to antioxidant activities. food chem., 2014 161, 296–304. doi: 10.1016/j.foodchem.2014.04.014 [2] papanikolaou, y.; fulgoni, v. l.: bean consumption is associated with greater nutrient intake, reduced systolic blood pressure, lower body weight, and a smaller waist circumference in adults: results from the national health and nutrition examination survey 1999–2002. j. am. coll. nutr., 2008 27(5), 569– 576. doi: 10.1080/07315724.2008.10719740 [3] sravanthi, b.; jayas, d. s.; alagusundaram, k.; chelladurai, v.; white, n. d. g.: effect of storage conditions on red lentils. j. stored prod. res. 2013 53, 48–53. doi: 10.1016/j.jspr.2013.01.004 [4] duane, w. c.: effects of legume consumption on serum cholesterol, biliary lipids, and sterol metabolism in humans. j. lipid res., 1997 38(6), 1120–1128. 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https://doi.org/10.1111/j.1365-2621.1981.tb14551.x 42 szedljak, kovács, kun-farkas, bernhardt, králik, szántai-kőhegyi [22] bagdi, a.; tóth, b.; lőrincz, r.; szendi, sz.; gere, a.; kókai, z.; sipos, l.; tömösközi, s: effect of aleurone-rich flour on composition, baking, textural, and sensory properties of bread. lwt food sci. tech., 2016 65, 762–769. doi: 10.1016/j.lwt.2015.08.073 [23] gere, a.; kovács, s.; pásztor-huszár, k.; kókai, z.; sipos, l.: comparison of preference mapping methods: a case study on flavoured kefirs. j. chemom., 2014 28(4), 293–300. doi: 10.1002/cem.2594 [24] gere, a.; sipos, l.; héberger, k.: generalized pairwise correlation and method comparison: impact assessment for jar attributes on overall liking. food qual. prefer., 2015 43, 88–96. doi: 10.1016/j.foodqual.2015.02.017 [25] gere, a.; danner, l.; de antoni, n.; kovács, s.; dürrschmid, k.; sipos, l.: visual attention accompanying food decision process: an alternative approach to choose the best models. food qual. prefer., 2016 51, 1–7. doi: 10.1016/j.foodqual.2016.01.009 hungarian journal of industry and chemistry https://doi.org/10.1016/j.lwt.2015.08.073 https://doi.org/10.1016/j.lwt.2015.08.073 https://doi.org/10.1002/cem.2594 https://doi.org/10.1016/j.foodqual.2015.02.017 https://doi.org/10.1016/j.foodqual.2015.02.017 https://doi.org/10.1016/j.foodqual.2016.01.009 introduction experimental samples and measurements results and evaluation water-soluble total polyphenol content (wstpc) water-soluble antioxidant capacity water-soluble protein content (wspc) peroxidase (pod) enzyme activity polyphenol oxidase (ppo) enzyme activity conclusion page 1 page 2 page 3 page 4 page 5 page 6 page 7 page 8 page 9 page 10 page 11 page 12 page 13 page 14 page 15 page 16 page 17 page 18 page 19 page 20 page 21 page 22 page 23 page 24 page 25 page 26 page 27 page 28 page 29 page 30 page 31 page 32 page 33 page 34 page 35 page 36 page 37 page 38 page 39 page 40 page 41 page 42 page 43 page 44 page 45 page 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jan kindracki3, and gábor szederkényi1 1faculty of information technology and bionics, pázmány péter catholic university, práter u. 50/a, budapest, 1083, hungary 2electromechanical engineering department, university of technology, al senaha st., baghdad, 10066, iraq 3faculty of power and aeronautical engineering, warsaw university of technology, nowowiejska 24, warszawa, 00-665, poland cubesats provide a cost-effective means of several functions of satellites due to their small size, mass, relative simplicity and short development time. therefore, cubesat technologies have been widely studied and developed by space organizations, companies and educational institutions all over the world. these satellites have certain drawbacks. small surface areas are a consequence of their small size which often imply thermal and power constraints. a novel development of cubesats known as pw-sat has been developed by warsaw university of technology. a control-oriented lumped thermal model of this satellite containing a fuel tank in the form of nonlinear ordinary differential equations is proposed in this paper. the model is able to simulate the thermal behavior of the surface and fuel tank of the satellite in its orbit. for the pw-sat to operate reliably, the temperature of the fuel tank has to be maintained within given safety limits. because of the limited power, passive thermal control is assumed in this case. several simulation results are presented for different surface compositions to determine whether they are able to guarantee the prescribed temperature range throughout the entire orbit or not. keywords: pw-sat, tmm, thermal behavior, propellant tank, dynamical modeling 1. introduction in recent years, interest in cube-satellites (cubesats) has grown tremendously within the space community from space agencies as well as in industry and academia. two factors have influenced this spurt of interest, namely the low-cost nature of access to space and the utilization of commercial off-the-shelf (cots) technologies in the design architecture. these two factors have led to a significantly low overall cost of a cubesat mission [1]. a cubesat is cubic in form with edges 10 cm in length and a mass of up to 1.33 kg. the pw-sat is a cubesat that has been in development for more than a year by different teams at warsaw university of technology [2, 3]. at present, pw-sat has never been flown with an onboard propulsion system. due to the significant and growing interest in cubesat mission capabilities, several propulsion systems have been rapidly developed for use in cubesats such as cold gas propulsion systems, solar sails, electric propulsion systems and chemical propulsion systems [4, 5]. cold gas propulsion systems are relatively simple solutions in cubesats. gas from a high-pressure gas cylinder is simply vented through a valve and nozzle to produce thrust [6, 7]. *correspondence: al.hemeary@itk.ppke.hu the goal of this paper is to propose a lumped dynamical model of temperatures during orbital motion in the main parts of a cubesat that contains a fuel tank. the model is built in the form of nonlinear ordinary differential equations (odes). although advanced thermal simulation tools exist that utilize detailed distributed mathematical models, this simple form of a model has been chosen since it is intended to be used in the model of temperature control design. the overwhelming majority of control design techniques require models in the form of ordinary differential equations [8]. moreover, in the case of nonlinear models such as the cubesat system studied, a low dimensional model is preferred due to the computational complexity of control design. this approach is also supported by control theory and practice, namely that in general such simple models are sufficient for controller design [9]. as a first step in terms of the regulation of temperature, passive control in the form of the appropriate composition of materials covering the surfaces of the satellite is used. during the construction of the model, the standard principles of thermal modeling [10, 11] and their application in aerospace engineering are followed [12, 13]. relevant results can be found in the literature concerning the thermal modeling and analysis of small satelmailto:al.hemeary@itk.ppke.hu 26 al-hemeary, jaworski, kindracki, and szederkényi lites in the form of odes. in [14] a simple thermal dynamical model of a cubesat containing two differential equations is presented. the two lumped balance volumes are the surface and internal parts of the satellite, respectively. it is shown that the problem is mathematically analogous to the forced vibration of a damped mechanical system. in [9], new theoretical results on the qualitative behavior of spacecraft thermal models are provided that contain several nodes (compartments). it is proven that such models exhibit a unique asymptotically stable equilibrium in the positive orthant with constant external disturbance inputs which leads to a stable limit cycle during orbital motion. the analysis concerning the frequency domain of a multi-compartmental model of a satellite is conducted in [15]. the odes are linearized around the equilibrium points which permit the use of fourier analysis. the structure of the paper is as follows: the description starts with the derivation of a simple mathematical model to simulate the transient thermal behavior of the fuel tank as well as the satellite faces in orbit. then, by changing either the optical properties of the surface of the pw-sat or the solar cell ratio of the satellite surface, several simulations are presented to illustrate how different configurations satisfy the given temperature limits. 2. system description and assumptions the intended use of the model developed in this paper is twofold: 1) to study the effect of different surface compositions (including solar cells) on temperature, 2) to evaluate the possibility of installing a propellant tank in the cubesat. with regard to the modeling, the following assumptions are made: 2.1 structural assumption pw-sat is a cubic structural bus with a total mass of 1 kg composed of six faces as walls. the basic structure of these faces is composed of the aluminum alloy 6061-t6 with various optical surface properties. these properties are based on uncoated surfaces for one experiment and coated with a magnesium oxide-aluminum oxide paint for the others. the nitrogen fuel tank, made of stainless steel with a diameter of 5 cm, is planned to be installed in the center of this satellite as shown in fig. 1a and is assumed to contain an internal gas subject to 100 bars of pressure at an initial temperature of 298 k. the solar cells will be attached to sides 1, 2 and 4 of the pw-sat, as shown schematically in fig. 1b, because these faces will be exposed to solar radiation due to the assumed orbit of this satellite. 2.2 orbital assumption the pw-sat is designed for a circular low earth orbit (leo). the total orbital period (p ) is 1.5 h. however, (a) (b) figure 1: pw-sat structure ((a) pw-sat spherical fuel tank set, (b) pw-sat solar cell arrangements). the motion of pw-sat is assumed to be identical when exposed to solar radiation and during shadow passage at an altitude of 300 km and an inclination of zero. face 3 is directed towards the earth throughout its orbit. faces 1, 2 and 4 are exposed to the sun with regard to the orbital motion of the satellite. finally, faces 5 and 6 are directed towards the space along the satellite orbit as shown in fig. 2. 2.3 thermal assumption the six faces of the pw-sat are considered to have a uniform temperature distribution. the conductive heat transfer between the fuel tank and satellite is ignored to simplify the thermal modeling calculations. only face 3 is exposed to infrared radiation from the earth in this orbit and the albedo during the luminous orbit intervals figure 2: pw-sat orbital motion. hungarian journal of industry and chemistry thermal mathematical model 27 [14, 16]. the thermal rate of power dissipation generated from the operation of elements from the satellite is assumed to be 2 w. the thermal limits of the fuel tank are 228 k and 338 k, and for the surface area of the satellite are 173 k and 373 k. 3. thermal mathematical model (tmm) the problem concerns the formulation of the model, which is on the one hand simple enough to limit the expenditure, on the other hand, detailed enough to present an adequate description of the physical surroundings [17]. the main purpose of these calculations is to divide the periodic motion of the satellite (with period p ) into three intervals (parts) as shown in fig. 2. the first interval (p1) starts with an initial time of t = 0 s when face 1 faces the sun and ends at a time of t = 1350 s when face 4 faces the sun. the second interval (p2) is an eclipse interval between t = 1351 s and t = 4050 s. the third interval (p3) starts at t = 4051 s when face 2 faces the sun and ends at the end of the satellite period at t = 5399 s. 3.1 first interval equations interval p1 : t = 0→ t = p 4 (1) the satellite spends a quarter of its orbital period in this luminous part. during this time interval, the surface of the satellite receives direct solar and albedo radiation depending on the position of the satellite due to its motion and the satellite emits thermal ir radiation into space; however, only face 3 receives additional infrared radiation from earth because it faces the earth [18]. the rate of heat transfer between face 1, the external environment and the spherical fuel tank during the first interval can be described by (mal cp +msc c sc p ) dt1 dt = gsa al-sc s a cos ( 2πt p ) + q̇+ q̇f1 − εal-sc ir σat 4 1 (2) where mal denotes the mass of aluminum, cp stands for the specific heat of aluminum (980 j/(kg·k)), msc represents the mass of the solar cell , csc p is the specific heat of the solar cell (1600 j/(kg·k)), t1 denotes the temperature of face 1, gs stands for the solar constant (1367 w/m2), and aal-sc s represents the average solar absorptance of aluminum and the solar cell which is calculated as (al %·aal s +sc %·ascs ), where al % and sc % denote the percentages of aluminum and solar cells in the cover, respectively. a stands for the surface area of the face (0.01 m2), q̇ represents the thermal rate of power dissipation, q̇f1 denotes the radiative heat transfer between face 1 and the tank, εal-sc ir is the average infrared emissivity of al and sc which is calculated as (al %·εal+sc %·εsc) and σ stands for the stefan-boltzmann constant (5.669 · 10−8w/m2 k4) [6]. the rate of heat transfer between face 2, the external environment and the spherical fuel tank during the first interval can be described by (mal cp +msc c sc p ) dt2 dt = q̇+ q̇f2 − εal-sc ir σat 4 2 (3) where t2 denotes the temperature of face 2 and q̇f2 stands for the radiative heat transfer between face 2 and the tank. the rate of heat transfer between face 3, the external environment and spherical fuel tank during the first interval can be described by mcp dt3 dt = af ·gsa al s fsea cos ( 2πt p ) + q̇+ q̇f3 + aal irσat 4 e − εal irσat 4 3 (4) where m denotes the mass of the face (0.04 kg), fse stands for the view factor between the face of the satellite and the earth which is almost one [18], t3 represents the temperature of face 3, q̇f3 is the radiative heat transfer between face 3 and the tank, af denotes the factor on the albedo (0.28), aal s stands for the solar absorptivity of aluminum, aal ir represents the infrared absorptivity of aluminum, te is the reference temperature of the earth (255 k) and εal ir denotes the infrared emissivity of aluminum. the rate of heat transfer between face 4, the external environment and the spherical fuel tank during the first interval can be modeled as( mal cp +msc c sc p ) dt4 dt = gsa al-sc s a sin ( 2πt p ) + q̇+ q̇f4 − εal irσat 4 4 (5) where t4 denotes the temperature of face 4 and q̇f4 stands for the radiative heat transfer between face 4 and the tank. the rate of heat transfer between face 5, the external environment and the spherical fuel tank during the first interval can be described as mcp dt5 dt = q̇+ q̇f5 − εal irσat 4 5 (6) where t5 denotes the temperature of face 4 and q̇f5 stands for the radiative heat transfer between face 5 and the tank. the rate of heat transfer between face 6, the external environment and the spherical fuel tank during the first interval can be described as mcp dt6 dt = q̇+ q̇f6 − εal irσat 4 6 (7) where t6 denotes the temperature of face 6 and q̇f6 stands for the radiative heat transfer between face 6 and the tank. 47(1) pp. 25–32 (2019) 28 al-hemeary, jaworski, kindracki, and szederkényi 3.2 second interval equations interval p2 : t = p 4 → t = 3 4 p (8) these concern the duration of an eclipse. the satellite spends half of its orbital period in an eclipse. during this interval, the surface of the satellite receives neither direct solar nor albedo radiation, whilst face 3 still receives ir radiation from the earth because it faces it. the satellite emits thermal ir radiation into space. therefore, the rates of heat transfer of the faces of the satellite (1, 3 and 4) have slightly changed in their equations compared to the first interval. the rate of heat transfer between faces 1, 3 and 4 as well as the external environment during the second interval can be described by the following equations (mal cp+msc c sc p ) dt1 dt = q̇+q̇f1 −εal-sc ir σat 4 1 (9) mcp dt3 dt = q̇+ q̇f3 + aal irσat 4 e − εal irσat 4 3 (10) (mal cp +msc c sc p ) dt4 dt = q̇+ q̇f4 − εal-sc ir σat 4 4 (11) 3.3 third interval equations interval p3 : t = 3 4 p → t = p (12) the satellite spends a quarter of its orbital period in this second luminous part. during this time interval, the surface of the satellite receives and emits thermal radiation in a similar manner to during interval 1 with only a slight change in the equation of face 2. the rate of heat transfer between this face, the external environment and the spherical fuel tank during the third interval can be modeled as (mal cp +msc c sc p ) dt2 dt = gsa al-sc s a ∣∣∣∣sin(2πt p )∣∣∣∣+ q̇+ q̇f2 − εal−sc ir σat 4 2 (13) 3.4 the transient heat transfer of the spherical propellant tank the rate of heat transfer between the faces of the satellite and the fuel tank can be described by the following equation (ms c s p +mgcv ) dtt dt = − 6∑ 1 q̇fn (14) table 1: material properties of pw-sat. al 6061-t6 uncoated al 6061-t6 coated solar cells specific heat [j/(kg·k)] 980 980 1600 emissivity (thermal) 0.08 0.92 0.85 absorptivity (solar) 0.379 0.09 0.92 table 2: material properties of fuel tank. stainless steel nitrogen specific heat [j/(kg·k)] 504 743 mass [kg] 0.0926 0.0074 table 3: average of optical surface properties of partially covered surfaces. cube face ε a coverage 1,2 and 4 0.89 0.33 70 % al, 30 % sc 0.87 0.67 30 % al, 70 % sc 3,5 and 6 0.92 0.09 al painted where ms denotes the mass of stainless steel, cs p stands for the specific heat of stainless steel (504 j/(kg·k)), mg represents the mass and cv the specific heat of nitrogen (743 j/(kg·k)), and tt is the temperature of the tank. the radiative heat transfer between each face and the tank q̇fn , depending on which face it applies to, can be described as q̇fn = fftεσa(t 4 t − t 4 n) (15) the view factor between the face in question and the fuel tank is given by fft = 1 (1+h)2 (see, e.g. [10, 11]), where h denotes the ratio of the distance between the spherical surface of the tank to the surface of the internal face (h = 0.025 m) in terms of the radius (r = 0.025 m), which is expressed as h = h r . the mass of the solar cell msc per unit area is on average 850 g/m2, thus, the mass of the solar cell as a proportion of the total mass of the face is determined by the equation (msc = 850 g/m2 · a · sc %). the total mass of the tank mt is assumed to be 0.1 kg, so the mass of nitrogen gas was calculated by assuming the initial temperature and total pressure of the tank. the optical surface properties are shown in table 1, and the masses of both nitrogen gas and the tank are shown in table 2. hence, it is necessary to calculate the properties of the average materials to conduct a thermal analysis. the emissivity of infrared radiation from these faces can be calculated as the average of the emissivity of infrared radiation from aluminum and the emissivity of infrared radiation from the solar cell in addition to the absorptivity of these faces as shown in table 3. hungarian journal of industry and chemistry thermal mathematical model 29 (a) (b) figure 3: the thermal behavior using 100 % al during one orbital period ((a) temperatures of the faces and fuel tank, (b) temperature of the fuel tank) (t1, . . . , t6) refers to the temperatures of faces 1, . . ., 6, respectively, and (tt) denotes the temperature of the tank. 4. computational results in this section, the faces and investigations into the thermal behavior of the tank are presented for several cases based on: uncoated surfaces, surfaces coated with magnesium oxide-aluminum oxide paint and different feasible options of the ratios of solar cells from the pw-sat to simulate the temperature of the fuel tank with different optical properties of the surface materials and solar cell ratios. 4.1 the pw-sat faces composed of 100 % uncoated aluminum in this case, the thermal simulations of the faces and fuel tank were conducted according to the assumption that the faces of the satellite are composed of the aluminum alloy 6061-t6. starting with the equations of the intervals and by using the ode45 solver in matlab (the simulation time step was 1 s), the thermal behavior during the orbital motion of the satellite was computed. 1 the thermal simulation of the faces and spherical fuel tank during one orbital period (time span from 0 s to 5399 s) is shown in fig. 3a and the simulation of the temperature of the tank during this orbital period is shown in fig. 3b. it can be seen that the predefined temperature limits are not adhered to in this case, since the minimum (a) (b) figure 4: thermal behaviors using 100 % al during 8 orbital periods ((a) temperatures of the faces and fuel tank, (b) temperature of the fuel tank). temperatures of the faces of the satellite and fuel tank exceed 460 k during its orbital period. 2 the thermal simulation of the faces and spherical fuel tank during several orbits (8 orbital periods with a time span of 12 h to illustrate long-term operations) is shown in fig. 4a, and the simulation of the temperature of the tank during these orbital periods is shown in fig. 4b. 4.2 the faces of the pw-sat are composed of 100 %-coated aluminum the thermal simulations of the faces and fuel tank were conducted according to the assumption that the surface of the satellite was composed of aluminum coated with magnesium oxide-aluminum oxide paint. by using the assumed time span of each interval, the results are shown below: 1 the thermal simulations of the faces and spherical fuel tank during one orbital period (time span from 0 s to 5399 s) are shown in fig. 5a, and the simulation of the temperature of the tank during this orbital period is shown in fig. 5b. it can be seen that all the defined temperature limits are adhered to in this case. 2 the thermal simulation of the faces and spherical fuel tank over 8 orbital periods (time span of 12 h) is shown in fig. 6a, and the simulation of the temperature of the tank during these orbital periods is shown in fig. 6b. 47(1) pp. 25–32 (2019) 30 al-hemeary, jaworski, kindracki, and szederkényi (a) (b) figure 5: thermal behaviors using coated al during one orbital period ((a) temperatures of the faces and fuel tank, (b) temperature of the fuel tank). 4.3 the faces of the satellite exposed to the sun during its orbit are covered with 70 % aluminum and 30 % solar cells in this case, these three sides of the pw-sat are assumed to be composed of 70 % aluminum and 30 % solar cells and the other faces are coated with magnesium oxidealuminum oxide paint. the simulation results are as follows: 1 the thermal simulation of the faces and spherical fuel tank during one orbital period (time span of 0 s to 5399 s) is shown in fig. 7a and the simulation of the temperature of the tank during this orbital period is also shown separately in fig. 7b. the results show that the temperature of the tank varied between a maximum of 281.9 k and a minimum of 265.4 k, while the temperatures of the faces also remained within the given temperature limits. 2 the thermal simulation of the faces and spherical fuel tank over 8 orbital periods (time span of 12 h) is shown in fig. 8a, and the simulation of the temperature of the tank during these orbital periods is shown in fig. 8b. (a) (b) figure 6: thermal behaviors using coated al over 8 orbital periods ((a) temperatures of the faces and fuel tank, (b) temperature of the fuel tank). 4.4 the faces of the satellite exposed to the sun during its orbit are covered with 30 % aluminum and 70 % solar cells the results, according to the assumption that three sides of the pw-sat are composed of 30 % aluminum and 70 % solar cells while the rest of them are coated with magnesium oxide-aluminum oxide paint, are shown below: 1 the thermal simulation of the faces and spherical fuel tank during one orbital period (time span from 0 s to 5399 s) is shown in fig. 9a, while simulation of the temperature of the tank during this orbital period is shown in fig. 9b. the results show that the temperature of the tank varied between a maximum of 302.4 k and a minimum of 270.6 k, while the temperatures of the faces were within thermal limits. 2 the thermal simulation of the faces and spherical fuel tank over 8 orbital periods (time span of 12 h) is shown in fig. 10a, while the simulation of the temperature of the tank during these orbital periods is shown in fig. 10b. 5. conclusion a thermal mathematical model was constructed and studied to compute the temperatures of the surfaces and fuel tank of the pw-sat. several cases were presented using various surface compositions and the results show that the proposed tmm is able to calculate the radiative heat hungarian journal of industry and chemistry thermal mathematical model 31 (a) (b) figure 7: thermal behaviors with 30 % sc during one orbital period ((a) temperatures of the faces and fuel tank, (b) temperature of the fuel tank). (a) (b) figure 8: thermal behaviors with 30 % sc over 8 orbital periods ((a) temperatures of the faces and fuel tank, (b) temperature of the fuel tank). (a) (b) figure 9: thermal behaviors with 70 % sc during one orbital period ((a) temperatures of the faces and fuel tank,(b) temperature of the fuel tank). (a) (b) figure 10: thermal behaviors with 70 % sc over 8 orbital periods ((a) temperatures of the faces and fuel tank, (b) temperature of the fuel tank). 47(1) pp. 25–32 (2019) 32 al-hemeary, jaworski, kindracki, and szederkényi that the pw-sat would encounter during its assumed orbit. initially, the surfaces of the pw-sat were assumed to be composed of 100 % of the aluminum alloy 6061-t6. the corresponding results suggest that the temperatures of the surfaces and fuel tank would be too high. therefore, additional finishes applied to the surfaces were taken into consideration. the first choice of finish was to coat the entire surface of the satellite with magnesium oxidealuminum oxide paint. the obtained results show that the temperatures of the surfaces and fuel tank dropped because of the increasing emissivity and decreasing absorptivity of the surfaces. further simulations were performed of cases in which the faces were exposed to the sun when partially covered with solar cells. the results indicate that the case described in subsection 4.4, which delivers the most electrical power due to the highest percentage of solar cells, still satisfies the temperature limits of the fuel tank and surfaces of the satellite. the results also suggest that it is possible to install a fuel tank inside the pw-sat which could be the first step required to add a propulsion system that can generate thrust for this cubesat. future works will include validation of the model using advanced thermal simulation tools as well as active control design to precisely regulate the temperature of the fuel tank. acknowledgement this work has been partially supported by the european union, co-financed by the european social fund through the grant efop-3.6.3-vekop-16-2017-00002. the support of the university of technology of baghdad and warsaw university of technology is also acknowledged. references [1] tummala, a. r.; dutta, a.: an overview of cube-satellite propulsion technology and trends, aerospace, 2017 4(4), 58. doi: 10.3390/aerospace4040058 [2] mehrparvar, a.: cubesat design specification rev. 13, the cubesat program, cal poly slo, 2015. http://www.cubesat.org/resources [3] pw-sat description (cubesat warsaw university of technology). https://directory.eoportal.org/web/ eoportal/satellite-missions/p/pw-sat [4] lemmer, k.: propulsion for cubesats, acta astronaut., 2017 134, 231–243. doi: 10.1016/j.actaastro.2017.01.048 [5] gaite, j.: nonlinear analysis of spacecraft thermal models, nonlinear dyn. 2011 65, 283–300. doi: 10.1007/s11071-010-9890-4 [6] sutton, g. p.; biblarz, o.: rocket propulsion elements, seventh edition (wiley, new york, usa) 2001. isbn 0-471-32642-9 [7] mueller, j.; hofer, r.; parker, m.; ziemer, j.: survey of propulsion options for cubesats, 57th jannaf propulsion meeting (colorado) 2010 jannaf1425 1–56. https://trs.jpl.nasa.gov/bitstream/ handle/2014/41627/10-1646.pdf [8] isidori, a.: nonlinear control systems (springer, london, uk) 1999. isbn 978-1-84628-615-5 [9] hangos, k. m.; bokor, j.; szederkényi, g.: analysis and control of nonlinear process systems (springer, london, uk) 2004. isbn 978-1-85233-861-9 [10] modest, m. f.: radiative heat transfer, third edition (academic press, oxford, uk) 2013. isbn 9780123869906 [11] sala, a.: radiation heat transfer (in polish) (wnt, scientific and technical publications, warsaw, poland) 1982. isbn 8320403677 [12] gilmore, d. g.: spacecraft thermal control handbook, second edition, vol. 1. (the aerospace press, el segundo, usa) 2002. isbn 1-884989-11-x [13] diaz-aguado, m. f.; greenbaum, j.; fowler, w. t.; lightsey, e. g.: small satellite thermal design, test, and analysis, modeling, simulation, and verification of space-based systems iii, proc. spie, 2006 6221, 622109. doi: 10.1117/12.666177 [14] grande, i. p.; andres, a. s.; guerra, c.; alonso, g.: analytical study of the thermal behaviour and stability of a small satellite, appl. therm. eng., 2009 29(11-12), 2567–2573. doi: 10.1016/j.applthermaleng.2008.12.038 [15] farrahi, a.; pérez-grande, i.: simplified analysis of the thermal behavior of a spinning satellite flying over sun-synchronous orbits, appl. therm. eng. 2017 125, 1146–1156. doi: 10.1016/j.applthermaleng.2017.07.033 [16] jaxa: design standard, spacecraft thermal control system, jerg-2-310 (japan aerospace exploration agency, tsukuba, japan) 2009. http://sma.jaxa.jp/ en/techdoc/docs/e_jaxa-jerg-2-310_08_re.pdf [17] fortoscue, p.; stark, j.; swinerd, g. (eds): spacecraft systems engineering, fourth edition (wiley, chichester, uk) 2011. isbn 978-0-470-75012-4 [18] vanoutryve, c. b.: a thermal analysis and design tool for small spacecraft, master’s thesis, 2008. https://scholarworks.sjsu.edu/etd_theses/3619 hungarian journal of industry and chemistry https://doi.org/10.3390/aerospace4040058 https://doi.org/10.3390/aerospace4040058 http://www.cubesat.org/resources https://directory.eoportal.org/web/eoportal/satellite-missions/p/pw-sat https://directory.eoportal.org/web/eoportal/satellite-missions/p/pw-sat https://doi.org/10.1016/j.actaastro.2017.01.048 https://doi.org/10.1016/j.actaastro.2017.01.048 https://doi.org/10.1007/s11071-010-9890-4 https://doi.org/10.1007/s11071-010-9890-4 https://trs.jpl.nasa.gov/bitstream/handle/2014/41627/10-1646.pdf https://trs.jpl.nasa.gov/bitstream/handle/2014/41627/10-1646.pdf https://doi.org/10.1117/12.666177 https://doi.org/10.1016/j.applthermaleng.2008.12.038 https://doi.org/10.1016/j.applthermaleng.2008.12.038 https://doi.org/10.1016/j.applthermaleng.2017.07.033 https://doi.org/10.1016/j.applthermaleng.2017.07.033 http://sma.jaxa.jp/en/techdoc/docs/e_jaxa-jerg-2-310_08_re.pdf http://sma.jaxa.jp/en/techdoc/docs/e_jaxa-jerg-2-310_08_re.pdf https://scholarworks.sjsu.edu/etd_theses/3619 introduction system description and assumptions structural assumption orbital assumption thermal assumption thermal mathematical model (tmm) first interval equations second interval equations third interval equations the transient heat transfer of the spherical propellant tank computational results the pw-sat faces composed of 100 % uncoated aluminum the faces of the pw-sat are composed of 100 %-coated aluminum the faces of the satellite exposed to the sun during its orbit are covered with 70 % aluminum and 30 % solar cells the faces of the satellite exposed to the sun during its orbit are covered with 30 % aluminum and 70 % solar cells conclusion hungarian journal of industrial chemistry veszprem vol. 30. pp. 295 298 (2002) analysis of parameters influencing the properties and yield of lube-oil extraction products p. kalaichelvi (department of chemical engineering, regional engineering college, trichy620 015, india) received: november 19, 2002 an analysis of the influence of various parameters (mainly the compositional effect of the lube feed stock and the e~traction temperature) on the percentage yield and properties of the lube oil is presented. the experiment is conducted at different temperatures in a single-stage extractor using furfural as the solvent. based on the analysis, a correlation has been developed and verified with the experimental results. keywords: extraction, lube oil introduction crude oil is distilled in atmospheric distillation column to get various useful distillates and the bottom product (residue) is taken to vacuum distillation column from which the lube oil feed stocks -are obtained as distillates. the feed stocks contain saturates, olefins, napthenes, aromatics and asphaltic components [1]. the asphaltic compenents are removed by deasphalting. aromatic components are prone to oxidative and thermal degradation and also have poorest viscometric properties. removal of these aromatics is needed and is done by solvent extraction. various solvents suitable for lube oil extraction are sulphur dioxide, phenol, furfural, n-methyl pyrrolidone(nm.p), duo -sol and propane. comparison of physical properties of the above mentioned solvents shows that nmp is an attractive solvent due to its high solvent power, low toxicity, good selectivity and adaptability [2}. however, due to the availability, low cost and high selectivity furfural is widely used for this purpose [3}. mixer-settler, rotating disc contactors, pulsed columns and centrifugal extractors are used for solvent extraction. rotating disc contactors(rdc) shows better performance when compared with other extraction columns. however, modifying, specifying or designing as extractors from basic principles alone is unsound. effect of various parameters including system behavior c~n only be studied through small scale equipment like smgle stage extractor [4}. lube oil is obtained only from imported crudes. it is also well known that crude composition will change not contact information: e-mail: kalai @rect.ernet.in only with respect to source but also with respect to time. based on this, the compositions of lube feed stocks will also vary. analysis of the above mentioned constrains revealed that there is a need to study the effect of various parameters mainly the effect of composition of lube base stocks on extraction yield and properties of the finished product in single stage extractor using furfural as a solvent [5} experiments a single stage equilibrium set-up as shown in fig.j is used for the present study. this is a cylindrical vessel with outer jacket both made of glass. this is closed at the top with a cork having provisions for thermometer, stirrer inserting and feed solvent charging. hot oil is circulated through the outer jacket from a hot oil bath to heat the content of the vessel at constant temperature. a stirrer driven by an electric variable motor is provided for constant mixing. the bottom tapering end is provided with a stop cork for separating the two phases (bottom phase extract and top phase raffinate ) after extraction. the circulating bath is switched on and the temperature is set at a desired value. the lube oil feed stock and the solvent are charged in a ratio of 1: 1.4 with the help of a funnel. then the content of the inner cylinder is heated to a required temperature and the stirrer is switched on and kept at a desired speed. mixing is done for one hour. after mixing it is ajjowed to settle at the same temperature for one and half hour. mixing and settling times are fixed based on the earlier 296 table i properties of various lube oil feed mixtures feed feed mixtures properties #4 #1 #2 #3 density, 15 oc 0.9254 0.8979 0.8822 0.9536 0.9314 (gmlml) pour point ccc) +42 +42 +45 +39 +39 kinematic viscosity (cst) (i) 100 oc 10.37 9.1 8.3 12.58 10.49 (ii) 75 oc na 18.44 16.42 29.90 23.25 refractive 1.49669 1.47948 1.46888 1.51370 1.50140 index) 75 oc wt % saturates 41 54.2 61.2 28.5 38.2 wt% 59 45.8 38.8 71.5 61.8 aromatics motor opening for charging /and nitrogen purging thermometer hotoilio """ fig. i single stage equilibrium setup studies in the same set-up. then the two phases namely raffinate and extract are separately collected with the help of stop cork. solvents present in two phases viz., raffinate and extract are recovered by simple distillation with nitrogen purging. final traces are removed by evaporation with nitrogen purging. properties of the feed stocks and solvent free raffinates (before and after dewaxing) and extracts are estimated based on the procedures given in astm standard books [6.7]. in this present work solvent/feed (s/f) ratio (by volume) is kept at 1.4 for an the cases for comparison purpose. extraction studies are carried out for lube oil feed stock whose properties are given in table i. to have various feed compositions. different combinations tabl~t 1 extraction resujts for extraction temperatures of 65 oc and sj f ratio of 1.4 feed mixtures properties feed #1 #2 #3 #4 raffinate yield (wt %) 80 90 94 70 77 density, 15 oc 0.9079 0.8856 0.8777 na na (gmlml) pour point +45 +42 +45 +39 +39 (°c) kinematic viscosity (cst) (i) 100 oc 9.35 8.32 8.13 10.22 9.38 (ii) 75 oc 19.31 17.40 15.82 22.33 19.50 refractive index, 75 oc 1.48307 1.47081 1.46475 1.49342 1.48471 wt% na na na 38.2 146.2 saturates wt% na na na 61.8 53.8 aromatics extract yield(wt %) 20 10 6 30 23 kinematic viscosity (cst) (i) 100 oc 26.40 na na 27.63 27.39 (ii) 75 oc 85.73 na na 98.94 94.28 refractive na 1.54395 1.54334 na 1.56569 index, 75 oc of feed + (raffinate/extract) on volume basis are mixed and properties of these mixed feed stocks are also reported along with the original feed stock [5] in table 1. extraction temperatures are fixed based on miscibility temperatures of various combinations of feed mixtures [2,5]. results results of single stage extraction of all the feed mixtures at three different temperatures are obtained in the present study. yields and properties of raffinates and extracts at an extraction temperature viz., 65 °c, 90 °c and 110 °c are estimated and sample data are presented in table 2 for 65 °c. extraction results at other temperatures {90 & 110 °c) are available elsewhere [5]. effect of extraction temperature and feed composition on raffinate yield and quality are discussed based on the results obtained. discussion increase in saturates content in the feed has increased the raffinate yield and quality at all extraction temperatures and decreased the extract yield (shown in fig.2). extractions were not carried out for the feed mixture-3 at 110 °c, since the miscibility temperatures 100 95 -e-65°c 90 -e-90°c ..-,. 85 eft. _._110 oc 1 80 u (i) 75 ·;:;. <ll (tj 70 c ~ 65 0:: 60 55 50 25 30 35 40 45 50 55 60 65 w t % saturates fig.2 plot ofwt% saturates in feed versus raffinate yield (sif= 1.4) 95 90 *85 18o "'0 ~ 75 (]) (ij 70 c ~65 0:: 60 55 __.._#4 60+---~~--~----~----~--~--~ 60 70 80 90 100 110 terrperature oc fig.3 plot of temperature versus raffinate yield for various feed mixtures: #1, #2, #4 of this feed mixture is below (110 °c). effect of feed composition viz., weight % of saturates in feed on raffinate yield can be observed in fig.2. effect of other parameter viz.~ extraction temperature is shown in fig.3. this shows that increase in extraction temperature will decrease the raffinate yield, whereas the quality of raffinate will increase due to the removal of aromatics since at higher temperatures the miscibility of aromatics will be higher. also, since amount of aromatics present in the feed mixtures (1 and 2) is less than that of the original feedstock, it has increased the extraction efficiency , whereas it is reverse in the other two feed mixtures (3 and 4) due to high aromatic content present in them, which can be observed in fig.3. 297 1.9 1.8 1.7 1.6 1.5 1.4 w 0) 1.3 ..q 1.2 1.1 1.0 0.9 0.8 0.7 1.4 1.5 1.6 1.7 1.8 1.9 log a fig.4 logarithmic plot of aromatic content versus extract yield (s/f= 1.4) correlation development kalichevsky [8] has developed series of equations for expressing solubility characteristics of petroleum oils in various solvents and checked over relatively wide ranges of solvent feed ratios and temperatures. he has developed the following equation for calculating extract yield from solvent quantity and temperature based on the assumptions that extract yield linearly varies with solvent quantity and solubility is an exponential function of temperature. log(e) = (m + nt) log(s) + p + qt (l) in this present work, linear relationship is observed between extract yield and aromatic content in feed (fig.4). in liquid-liquid extraction, the above said assumption on solubility is also applicable and hence the equation suggested by kalichevsky is modified as log( e)= (m + nt)iog(a) + p + qt (2) since the sif ratio is maintained constant in the present work, where m, n, p & q are constants. these constants are estimated using the experimental results and the values are m=4.079 n = -9.703 x 10-3 p = -6.588 and q = 2.137 xl0-3 a = aromatic content in the feed t = extraction temperature s = solvent quantity e = extract yield using the above estimated values of co~stants, extract yields are estimated and co~par~ wtth t~e experimental results and this companson 1s sho':"n. m fig.5. from this1 it is inferred that percentage devtatton of extract yield is only(+/-) 2 %. 298 50.0 40.0 #. ~ i 30.0 :5;! (lj ~20.0 ~ x w 10.0 0.0 0 10 20 30 40 50 extract yeak:l (exp.) wt% fig.5 plot of calculated extract yield versus experimental yield conclusion effect of temperature and feed composition on raffinate, extract yield and their qualities have been analysed for a single stage equilibrium set-up and based on this a correlation has been developed and verified with the experimental results. however, this correlation should be modified in such a way that it should include other operating parameters like sif ratio, stirrer speed, geometry of the extraction column and physical properties of the feed stocks and solvents [8,9] for which data can be generated by taking all the above said parameters into account. acknowledgement the authors wish to express their appreciation to madras refineries limited~ chennai for the facilities provided to p.kalaichelvi to carry out this investigation. symbols e extract yield s solvent quantity t extraction temperature a aromatic content in the feed cst critical solution temperature na not available nmp n-methyl pyrrholidone rdc rotating disc ... contactor m constant n constant p constant q constant references 1. treybal r. e.; liquid extraction, mcgraw-hill book company, 1951 2. lobaird and hanson: handbook of solvent extraction, john wiley and sons, 1983 3. sarkar dipak. k., garg madhukar. 0. and chopra. s. j.: hydrocarbon technology, 1991, 15, 55-67 4. adrewkarr: a fresh book at liquid-liquid extraction, chemical eng., 112-120, 1919 5. kalaichelvi. p.: studies on lube oil extraction, m.tech. thesis, anna university, 1992 6. annual book of astm standards, vol5.01,1990. 7. annual book of astm standards, vol5.02,1990. 8. kalichevsky: industrial and engineering chemistry, 1949, 38(10), 1009-1012 9. kalaichelvi. p. and murugesan. t.: bioprocess engineering,l998, 18, 105-111 page 296 page 297 page 298 page 299 page 1 page 2 page 3 page 4 page 5 page 6 page 7 page 8 page 9 page 10 page 11 page 12 page 13 page 14 page 15 page 16 page 17 page 18 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page 583 page 584 hungarian journal of industry and chemistry vol. 48(1) pp. 33–41 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-06 identification of the material properties of an 18650 li-ion battery for improving the electrochemical model used in cell testing bence csomós∗1 and dénes fodor1 1research institute of automotive mechatronics and automation, university of pannonia, egyetem u. 10, veszprém, 8200, hungary the aim of this paper is to present an application of the generalized warburg element and constant phase element (cpe) for non-fickian diffusion modeling. these distributed elements are intended to provide a better fit of low-frequency impedance data than the standard finite-length warburg element in the case of most batteries. in addition, the current study demonstrates the ambiguity of the finite-length warburg element if impedance data is insufficient within the verylow-frequency impedance spectrum. in order to select the appropriate randles circuit for non-fickian diffusion modeling, several configurations have been investigated. based on the best fit of impedance data, the state-of-charge (soc) dependency of the randles circuit parameters has also been analyzed. this study concerns a samsung icr18650-26f 2600 mah battery cell which was subjected to electrochemical impedance spectroscopy (eis) measurements between 10 mhz and 100 khz as a function of soc. the results were plotted and compared in the form of nyquist plots. the randles circuit parameters such as the resistances rs and rct, double-layer cdl, leaky capacitance cpe and warburg coefficients were estimated using zview software. the present paper shows that cpe – and its qpe form – is a recommended choice to yield the best fit in terms of non-fickian diffusion impedance. in addition, using cpe is a better alternative to avoid problems with initial values and multiple local solutions, which may exist in the case of the warburg element. the resultant randles circuit parameters and their soc characteristics can be effectively used in further electrochemical modeling. keywords: li-ion battery, electrochemistry, material, battery model, parameter estimation 1. introduction the state of health (soh) of a battery plays an important role in electric applications since it has a great influence on the available capacity and power of a battery [1]. soh deteriorates with battery usage and the rate of aging is related to the operating history of the battery. therefore, it is recommended to track the state variables of a cell throughout its life cycle and adapt the soh prediction according to the current condition of the battery cell. a common and reliable electrochemical model used in finite element analysis (fea) is based on the work of newman et al. [2]. it consists of charge and mass balance equations in both solid (electrode) and liquid (electrolyte) materials, which describe the main operating characteristics of the cell. even though these formulae could describe the behavior of the cell in 3d, due to their high degree of nonlinearity and complexity, pseudo-2d (p2d) modeling is favorable in terms of fea [3]. it is also sufficiently representative to model wearout for automotive applications [4]. in fig. 1, a typical pseudo-2d structure of a li-ion cell can be seen. ∗correspondence: csomos.bence@gmail.com since battery manufacturing is still a developing sector, the electrochemical composition of a cell constantly changes. therefore, few battery-chemistry standards and complete databases can describe a given cell structure. insufficiently reliable and valid battery data inhibits battery modeling since a cell must always be inspected to determine its electrochemical parameters before modeling. the standard way to obtain these electrochemical data is usually through an equivalent circuit modeling process with which the electrochemical properties of the cell can be extracted from eis measurements. 2. diffusion modeling techniques it is possible to calculate battery-specific data using several techniques, which can basically be grouped into two types in terms of the measurement approach applied: • direct measurements, which typically require disassembly of the cell, special preparations or an experimental open-cell. these measurements can be, for example, different types of electron microscopy (em), computed tomography (ct), titration, postmortem analysis, etc. https://doi.org/10.33927/hjic-2020-06 mailto:csomos.bence@gmail.com 34 csomós and fodor rp electrodeseparator asep a particle + sei layer vsas εs dl ds εl εsep εb vl vtot figure 1: the relationship between the core material parameters and components of the cell. asep is addressed to the area of the separator. εsep, εb, εs, and εl denote the porosities of the separator, binder, solid matrix and void fraction, respectively.dl represents the salt diffusion coefficient in the electrolyte. ds stands for the diffusion coefficient in the solid electrode. vl, vs and vtot are the volumes of the liquid, solid material and whole electrode, respectively. rp and a denote the average radius of each electrode particle and the specific surface area of the electrode. • indirect measurements that do not require disassembly of the cell, e.g. current impulse excitation, electrochemical impedance spectroscopy (eis), galvanometry, potentiometry, chronoamperometry, etc. [5] eis is a well-established and suitable method in the analysis with regard to battery kinetics and has a solid background in the literature [6]. another advantage of eis is that it does not require special preparation of the cell that would be extortionate and time-consuming. electrochemical parameters are formulated from eis data in the form of resistive, capacitive, inductive or distributed elements such as the constant phase element (cpe) or warburg element. 2.1 standard equivalent circuits in order to obtain battery-specific data, a transmissionline model (tlm) was applied that is introduced and expounded on in [7]. it provides a generalized modeling solution for transport processes in porous electrodes by utilizing a finite number of serially connected resistorcapacitor (rc) pairs in parallel, which resolve the ion and electron transport appropriately. the network obtained in this way is considered to be ambiguous since various arrangements can be reduced to the same circuit resulting in identical resistance and capacitance of the circuit [8]. although the number of rc pairs used can increase the resolution of the transport process and thus improve its accuracy, the increase in the number of elements results in stability as well as local and global optima problems due to equivocality. since this is a major disadvantage of extended tlm networks, they are usually avoided. wr ct r s c dl figure 2: randles equivalent circuit consisting of serial resistance rs, charge-transfer resistance rct, double-layer capacity cdl and distributed impedance element w . a simplified form of tlm is the randles equivalent circuit model (fig. 2) which can be obtained if the theoretical rc line of infinite length is reduced to a single z-distributed element. in other words, the z-distributed element models the limiting case of tlm. its fundamental principles and mathematical background are comprehensively described in barsoukov’s book [9]. the standard randles circuit model couples together the individual characteristics of electrodes and electrolytes into one corresponding circuit element. the randles circuit model consists of relaxation components such as the serial resistance of the electrolyters, charge transfer resistancerct, a double-layer capacitor cdl and distributed impedance for modeling the low-frequency diffusive behavior of the cell. usually, the double-layer effect exhibits non-ideal capacitive behavior so a cpe – the equivalent to a “leaky” capacitor – should be used instead of a cdl. all of these detailed parameters of both electrodes are grouped together, thus they represent the combined behavior of the two electrodes. ion transport that occurs in the low-frequency bandwidth of the impedance spectrum can involve diffusion, migration and convection, however, only diffusion is of interest because distributed elements are responsible for diffusion modeling. diffusion modeling is the bottleneck of model development since it is related to a complex and interleaved electrochemical process that mainly characterizes the long-term operation of the battery. ion transport can be, by and large, divided into two parts, namely lithium diffusion in the solid active electrode material and electrolyte. the “tail” at the beginning of the lowfrequency bandwidth in the nyquist plot shows diffusion in the electrolyte while the transition from the tail through an arc to a straightened end of the impedance curve depicts the solid-phase diffusion inside the electrode matrix (fig. 3). in fact, the cathode is composed of a poor ionconducting material. a general rule of thumb is that its diffusion coefficient is 2− 4 orders of magnitude smaller than the diffusion coefficient of lithium ions in the electrolyte, that is, the salt diffusion coefficient of the electrolyte dl falls within the range of 10−10 − 10−11 m2/s while the diffusion coefficient of lithium ions ds in the solid matrix falls between 10−13 and 10−14 m2/s. in other words, the time constant for diffusion of li-ion transport is smaller in the electrolyte (∼ 10 − 100 s) than in the solid matrix (> 100 s). consequently, the two types of diffusion need to be separated and should be modeled based on their different characteristic impedances. hungarian journal of industry and chemistry identification of the material properties of an 18650 li-ion battery 35 -0.07 -0.06 -0.05 -0.04 -0.03 -0.02 -0.01 0.00 0.07 0.09 0.11 0.13 0.15 0.17 0.19 -i m z [ ω ] re z [ω] i. ii. figure 3: a typical nyquist plot of a li-ion cell; i. denotes a “tail” that mainly represents diffusion in the electrolyte; ii. shows a transition from liquid-phase to solid-phase diffusion. generally, diffusion is modeled by the classical warburg impedance in accordance with the following assumptions: diffusion is fickian (planar diffusion); the electrolyte is supporting, symmetric and binary; the cell remains in a quasi-equilibrium state during excitation; and no reaction occurs in the bulk of the electrolyte. under these premises, the standard warburg impedance has an exponent of 0.5 that implies its 45◦ phase angle. if diffusion occurs in an infinite reservoir where the concentration can decrease to zero, infinite-length warburg impedance can be assumed, otherwise diffusion is restricted and finite-length reflective or transmissive warburg impedance can be assumed depending on whether the equivalent circuit is terminated by an open circuit or a resistor, respectively. the former and latter cases can be mathematically expressed by extending the standard infinite-length warburg impedance with the hyperbolic functions tanh and coth, respectively. all three types of warburg elements exhibit the same 45◦ gradient at the beginning of the low-frequency bandwidth in the nyquist plot. in terms of impedance, using finite-length warburg elements is unsuitable if an insufficient number of data points in the low-frequency bandwidth of the impedance spectrum are available to fit the hyperbolic functions well. this occurs when the eis measurements typically run up until 10 mhz but some cells do not show a clear and distinct effect of diffusion in the solid phase. in this case, only the tail part of the impedance spectra can be reasonably modeled. due to a lack of low-frequency data points, the finite-length warburg elements cannot be effectively applied. on the other hand, the tail part of the diffusion impedance can be modeled by cpe according to [11, 12] which is a similar but more robust alternative to the warburg elements. all the transfer functions of the standard types of distributed elements are summarized in table 1. the transfer function of cpe can be expressed in two different forms according to the position of its time constant for diffusion table 1: transfer functions of standard distributed elements used in fickian diffusion modeling [10]. σ denotes the warburg coefficient, ω represents the excitation frequency, τd stands for the diffusion time constant, q is the qpe time constant, j denotes the imaginary unit and rw represents the warburg resistance. name impedance infinite-length warburg zilw(jω)= rw√ jωτd =σ 1√ ω (1−j) finite-length reflective warburg zflrw(ω)=rw coth ( √ jωτd)√ jωτd finite-length transmissive warburg zfltw(ω)=rw tanh ( √ jωτd)√ jωτd cpe zcpe(ω)= 1√ jωτd qpe zqpe(ω)= 1 q √ jω τd . if τd is emphasized from its square root, it is referred to as qpe, which sometimes provides a more stable regression than cpe. up to this point, only fickian diffusion has been considered that can be clearly identified by its square-rootlike frequency dependency in terms of the transfer function of the distributed elements. however, the impedance fit becomes more interesting when the cell impedance exhibits non-fickian behavior, that is, the phase angle is not 45◦ due to diffusion non-idealities. these phenomena were investigated and are mostly related to multi-phase and multi-scale diffusion in porous electrodes [13, 14], diffusion coupled with migration [15, 16] and/or diffusion in non-conventional space [17–19]. non-fickian diffusion can be treated by fractional order circuits which consist of various types of typical configurations. in the literature [20], warburg impedance is referred to as “generalized” if it reflects the fractional intent. in this case, the warburg exponent is generalized and denoted by γ, the dispersion parameter. 2.2 equivalent circuit development for modeling non-fickian diffusion in order to obtain the most accurate fit of the impedance curves, several configurations of the randles circuit were developed. these setups are presented in fig. 4. the key differences between them can be explored in terms of both the position and type of the distributed elements in the circuit. in some papers from the literature, the distributed element is in series withrct [21], while in others, it is placed in series with the parallelrct-cdl orrct-cpe branch. the distributed element can be either the warburg element or cpe/qpe. birkl et al. [22] shows that it is possible to model diffusion with an rc pair instead of a distributed element in the randles circuit model. all of these configurations have been exhaustively expounded 48(1) pp. 33–41 (2020) 36 csomós and fodor r s qpe wr s cpe qpe qpe wr ct c dl r s i. ii. iii. r ct c dl r s wr ct r s cpe iv. v. vi. r ct r s figure 4: different configurations of randles circuits to study regression performance and fitness. w stands for warburg element. the model of circuits i-iv, relaxation and diffusion are presented together while v-vi only focus on the tail part. on in [23]. based on these results, numerous randles circuits have been evaluated to study the regression performance and fitness. in fig. 4, the arrangements of circuits i-iv model relaxation and diffusion simultaneously while v and vi only account for the tail part. the main reason for separation is that the stability and robustness of the impedance regression could be increased using this technique. the standard warburg element and cpe/qpe had to be adjusted to match with the non-fickian diffusion. at first, since only the tail part of the diffusion impedance was modeled, the hyperbolic part of the finite-length warburg elements was neglected. hence, the warburg impedance was simplified to the infinite-length form. therefore, the warburg impedance zw had to be transformed into a generalized form by replacing the square root in the denominator with γ. as a result, the generalized warburg impedance could be written in the following form: zw(ω) = rw (jωτd) γ (1) where rw denotes the warburg resistance, ω stands for the excitation frequency, τd represents the diffusion time constant, j is the imaginary unit and 0 ≤ γ ≤ 1. now, the jγ term should be practically separated into real and imaginary components to reveal the contribution of γ to each part. using euler’s formula, zw was unbundled and grouped into real and imaginary parts: zw (ω) = rw τγdω γ cos ( π 2 γ ) − rw τγdω γ j sin ( π 2 γ ) (2) τd used in eq. 2 was then expressed as τd = l 1/γ eff deff = ε β/γ l,sepl 1/γ 0 εβl,sepdl,0 (3) where leff denotes the effective diffusion length, deff represents the effective diffusion coefficient, εl,sep stands for the liquid fraction in the separator, and β is the bruggeman coefficient. since τd is emphasized from the denominator of eq. 1, the warburg coefficient σ could be expressed as a fraction of rw and τd according to σ = rw τγd . (4) on the other hand, the transfer functions of cpe and qpe had to be transformed into zcpe (ω) = 1 (jωτd) γ (5) zqpe (ω) = 1 τγd(jω)γ (6) the updated transfer functions of the distributed elements enabled the non-fickian diffusion to be properly fitted. 3. experimental setup this study is devoted to a commercial samsung icr 18650-26f cell with a nominal capacity of 2600 mah. it consists of a double-sided nickel-manganese-cobalt (nmc) cathode and graphite anode according to the manufacturer’s datasheet. the samsung icr 18650-26f cell was evaluated by eis within the 10 mhz – 100 khz bandwidth at different states-of-charge (soc). the test was run at ambient temperature, namely 25 ◦c, which was considered to be constant throughout. a solartron si1287 (electrochemical interface) and a schlumberger si 1255 (hf frequency response analyzer) were used for data acquisition. the nyquist plot of the spectrum and the parametric fitting were produced by zplot and zview software, respectively. an auxiliary measurement had to be performed along with eis to determine the cell’s open circuit potential (ocp) characteristic at a 0.1 c-rated load current. the load current was generated by a tenma 72-13210 programmable dc load in constant current (cc) mode. the data was recorded in ni pxi hardware that ran labview-based data acquisition software. 4. analysis of the measurement results the purpose of the eis analysis of the cell was to evaluate the fitness of the different randles circuit models according to non-fickian cell impedance data. on the other hand, the cell underwent another eis measurement to detect how the parameters of the randles circuit model changed during discharge. the eis measurements presented in fig. 5 and 6 were made between 10 mhz and hungarian journal of industry and chemistry identification of the material properties of an 18650 li-ion battery 37 -0.022 -0.017 -0.012 -0.007 0.08 0.09 0.10 0.11 0.12 0.13 0.14 im z [ ω ] re z [ω] measured cdl-w v1 (i.) cdl-w v2 (i.) cpe-w (ii.) cdl-qpe (iii.) cpe-qpe (iv.) std warburg figure 5: nyquist plot of the measured impedance and different fit functions (seen in fig. 4 i-iv). v1 and v2 indicate that warburg-based models were run on the basis of two different sets of initial parameters. the fit was performed between 13 hz and 10 mhz at ambient temperature with a fully charged cell. the “std warburg” was based on model i in fig. 4 but with a warburg exponent of 0.5. -0.018 -0.016 -0.014 -0.012 -0.010 -0.008 -0.006 0.118 0.120 0.122 0.124 0.126 0.128 0.130 0.132 0.134 im z [ ω ] re z [ω] measured r-w r-qpe figure 6: nyquist plot of the measured impedance and different fit functions (seen in models v-vi of fig. 4. the fit was performed between 80 mhz and 10 mhz (only the tail part) at ambient temperature with a fully charged cell. the left part of the solid line is associated with the end of the relaxation semicircle and helps to locate the position of the tail. 13 hz where relaxation and diffusion occur. in the case of r-w and r-qpe pairs, only the tail part was modeled. in fig. 5, only a slight difference between the fits of the model is observed and the cpe-qpe pair shows the best match. despite the insignificant difference between the non-fickian models, a substantial improvement in accuracy can be observed especially with regard to fitting the tail when the standard warburg element was replaced by any of the generalized warburgor cpe/qpe-based models. the changes in the randles circuit parameters during discharge of the cell was also investigated further where only the best matching cpe-qpe pair was used for fitting. the resultant impedance plot is presented in fig. 7. the eis measurements were performed at 20 % soc level increments. every step of the discharge was followed by a 12-hour-long period of relaxation before the eis measurement was made in order to provide sufficient time for the cell to reach its stationary state. the impedance curves show that the degree of relaxation was high when the rate of the electrode reaction decreased or if the transport of li ions became limited. this occurred, for example, as the rate of li diffusion decreased away from the interface. the evolution of changes in the distinctive impedance curves could be tracked by changes in the parameters of the randles circuits. fig. 7 shows that rs and rct significantly increased as soc decreased due to the decreasing amount of li-ion particles engaged in the charge transfer process. furthermore, the electrolyte resistance rs increased due to the decreasing ionic conductivity of the solution. all of these results agree with a well-known phenomenon, namely that the overall resistance of the cell increases during discharge. the shape and position of the plateau at the beginning of the semicircle was apparently due to a solid electrolyte interphase (sei) layer which formed on the anode particles that was unaffected during discharge. the presence of an sei layer ascertains that the calendar and cycle lives of the cell both reduced. since the gradient of the tails show significant similarities between 100 % and 20 % soc, the diffusion time constant and diffusion coefficient of the electrolyte should change slightly during discharge. at 5 % soc, the 48(1) pp. 33–41 (2020) 38 csomós and fodor -0.045 -0.040 -0.035 -0.030 -0.025 -0.020 -0.015 -0.010 -0.005 0.000 0.0600 0.0800 0.1000 0.1200 0.1400 0.1600 0.1800 0.2000 0.2200 im z [ ω ] re z [ω] 100% 80% 60% 40% 20% 5% fit 100% fit 80% fit 60% fit 40% fit 20% fit 5% figure 7: nyquist plots of the samsung icr 18650-26f 2600 mah li-ion cell at different levels of soc. the temperature was assumed to be constant at 25 ◦c. the regression bandwidth was limited to between 13 hz and 10 mhz. the small plateau at approximately 250 hz is a consequence of a solid electrolyte interphase (sei) layer that formed on the anode particles. this shows that the calendar and cycle lives of the cell were reduced. the fit was made by the model of the cpe-qpe pair. utilizable li-ions in the electrode became exhausted leading to a significant decrease in both the rate of diffusion and reaction. on the other hand, the reaction rates did not vary extensively in the normal operating region since the “valley” between the semicircle and tail possesses a similar imaginary component of the impedance. in order to carry out cell characterization in the time domain, a quasi-equilibrium discharge was run using a 0.1 c-rated load current at a constant temperature of 25 ◦c. the ocv against soc curve is presented in fig. 8 that exhibits typical discharge characteristics with a small plateau around 30 % soc and rapidly decreases below 10 % soc. 4.1 determining randles circuit parameters evaluation of eis data in fig. 5 and the impedance regression were carried out by zview software that applies 2.75 2.95 3.15 3.35 3.55 3.75 3.95 4.15 0 20 40 60 80 100 o c v [ v ] soc [%] figure 8: the open circuit voltage (ocv) against stateof-charge (soc) characteristic of the cell. the non-linear least squares method to fit and calculate the randles circuit parameters. the results summarized in table 2 show that slight changes in rs, rct and cdl were observed with this setup. this was due to fitting on an almost ideal semicircle that exhibits a simple rc characteristic in the impedance spectrum. with regard to the estimation of diffusion time constants, diffusion in a real electrochemical battery cell is usually limited due to the relatively thin electrodes. consequently, from a practical point of view, zview only has finite-length warburg elements at its disposal. since finite-length warburg elements should require data from the very low bandwidth that is unavailable in the present case, it is favorable to check the applicability of this type of element in the current case. for this purpose, the warburg parameters were estimated on the basis of two different sets of initial values as is denoted by v1 and v2 in fig. 5. both cases yielded a similar fit but extremely different warburg parameters. therefore, the estimation of warburg parameters ran into multiple local solutions that erroneously characterize the same system with different diffusion time constants. this problem could be efficiently handled by using either the cpe+qpe pair or just qpe instead. the results are presented in table 3. given the γw values, the warburg exponent is clearly far from 0.5, hence the preliminary assumption of exhibiting non-fickian diffusion was substantiated. the maximum phase error between the standard warburg-elementand cpe+qpe pair-based randles circuit models was 2.3 % at 10 mhz. since randles circuit parameters are very sensitive due to the origin of their exponential functions, even a small improvement in hungarian journal of industry and chemistry identification of the material properties of an 18650 li-ion battery 39 table 2: the estimated randles parameters where diffusion was only modeled by a warburg element and a qpe in two different configurations. the qpe+cpe modeling technique was an effective way to avoid the uncertainties of finite-length warburg elements due to a lack of data points in the very low bandwidth. the cell was fully charged and kept at 25 ◦c. randles parameter qpe+cpe w qpe rs [ω] 0.154 0.1968 0.1967 rct [ω] 0.047 cdl [f] tcpe [s] 2.038 γcpe [-] 0.893 γqpe [-] 0.6868 0.595 rw [ωm2] 0.241 τw [s] 893 235.7 γw [-] 0.595 τd [s0.5/ωm2] 339.5 893 235.7 σ [ωm2/s0.5] 0.0015 0.00424 0.0021 fitting can significantly increase the accuracy in further electrochemical calculations based on these data. the randles circuit parameters were measured when the cell was fully charged but changed as the soc level of the cell was altered as was seen in fig. 7. the estimated parameters at different soc levels are summarized in table 4 and their trends presented in fig. 9. the changes in rs and rct exhibited an exponential-like decreasing tendency against soc while rct slightly increased at approximately 100 % soc. the increase in rs was due to the effect of a reduction in the ionic conductivity, while an increase in rct was due to the decreasing rate of liion transfer through the electrode-electrolyte interface. in fig. 10, the characteristics of changes in the cpe capacity and diffusion time constant can be seen. cpe slightly increased with discharge and its overall variance was about 0.4 f. this behavior along with the increase in rct can be attributed to the relaxation effect. furthermore, less charge was available on the anode surface as the cell became fully discharged. the remarkable increase in diffu0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0% 20% 40% 60% 80% 100% r es is ta n c e [ω ] soc level rs rct figure 9: the trend of rs and rct changes with soc level. the cell shows a well-known increasing overall resistance during discharge. table 3: the estimated randles parameters based on the configurations seen in fig. 4 where diffusion and doublelayer effect have been modeled by warburg-element, qpe and cpe in different coupled configurations. in the table heading, w and c stand for warburg and double-layer capacitor, respectively. the cell has been at fully charged state and kept at 25 ◦c. randles c+w c+w c+qpe cpe+w parameter i ii rs [ω] 0.156 0.156 0.156 0.153 rct [ω] 0.041 0.041 0.041 0.047 cdl [f] 1.731 1.731 1.73 tcpe [s] 2.038 γ [-] 0.579 0.893 rw [ωm2] 0.0855 0.168 0.263 τw [s] 179 569.1 693.2 γw [-] 0.578 0.5792 0.687 τd [s0.5/ωm2] 179 569.1 233.9 693.2 σ [ωm2/s0.5] 0.0043 0.0043 0.0023 0.0029 sion time constants at approximately 100 % soc implies that it was intended that diffusion coefficients should decrease at the end of the discharge. this phenomenon plays a significant role in increasing the overall cell resistance especially when one of the electrodes is exhausted in li. 5. conclusions the current work demonstrated an improved method of diffusion modeling. several configurations of randles circuits were studied in order to obtain the best fit of the impedance characteristics of a battery. the inappropriate fit of standard warburg elements with regard to nonfickian diffusion was corrected by applying generalized warburg elements and cpes. the proposed generalized model compensates well for the phase error between the measured and modeled impedances. 0 50 100 150 200 250 300 350 400 1.9 2.0 2.1 2.2 2.3 2.4 2.5 2.6 0% 20% 40% 60% 80% 100% d if fu si o n t im ec o n st an t [s ] c p e c ap ac it y [ f ] soc level c_cpe tau_d figure 10: charactersitics of changes in cpe capacity constants and diffusion time-constant. diffusion timeconstant remarkably increases during discharge that implies diffusion coefficients to decrease. the cpe does not change significantly. 48(1) pp. 33–41 (2020) 40 csomós and fodor table 4: the estimated randles circuit parameters at given soc levels based on the cpe-qpe randles circuit model. soc levels 100 % 80 % 60 % 40 % 20% 5 % rs 0.0764 0.0763 0.0823 0.0909 0.105 0.1305 rct 0.047 0.0406 0.0413 0.0487 0.056 0.0734 ccpe 2.07 2.255 2.394 2.365 2.383 2.503 τd 358 310 306 336 353 172 the finite-length warburg element is a classical and generally applied tool in diffusion modeling, but it should be used carefully in some cases. the proposed work also shows that the finite-length warburg element yields multiple local solutions depending on its initial values if measured impedance data is insufficient within the very low bandwidth of impedance. this leads to ambiguous results in terms of diffusion-related parameters which should be avoided, however, this problem can definitely be solved by applying cpe or qpe instead in diffusion models. the randles circuit parameters were estimated and can be used in further calculations to determine the electrochemical parameters of batteries [24]. symbols binary diffusion coefficient of electrolyte dl,0 m2/s warburg coefficient σ ω/ √ s diffusion time constant τd s ac excitation frequency ω hz warburg exponent γ – electrolyte resistance rs 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https://doi.org/10.1088/0022-3727/49/2/025503 https://doi.org/10.1103/physreva.38.5867 https://doi.org/10.1103/physreva.38.5867 https://doi.org/10.1016/0013-4686(94)e0192-3 https://doi.org/10.1016/0013-4686(94)e0192-3 https://doi.org/10.1016/s0022-0728(98)00115-6 https://doi.org/10.1063/1.472806 https://doi.org/10.1016/j.electacta.2003.08.030 https://doi.org/10.1016/j.electacta.2003.08.030 https://doi.org/10.1049/cp.2013.1889 https://doi.org/10.1016/j.jpowsour.2018.04.033 https://doi.org/10.1149/2.1151814jes introduction diffusion modeling techniques standard equivalent circuits equivalent circuit development for modeling non-fickian diffusion experimental setup analysis of the measurement results determining randles circuit parameters conclusions hungar~journal of indus1rial chemis1ry veszprem vol. 30. pp. 53 59 (2002) parametric sensitivity of free radical polymerization associated with gel and glass effects c. pe1rila and s. curtbanu (department of chemical engineering, technical university "gh. aso.chi", iasi b-dul d. mangeron 71a, 6600 iasi, romania) received: august 17,2001 the parametric sensitivity is studied of an isothermal homopolymerization system exhibiting the gel and glass effects. as example, the initiated radical polymerization of methyl methacrylate to be achieved in a batch bulk process is considered. for the diffusion controlled reactions, a simple model was proposed containing the dependencies of termination and propagation rate constants with monomer conversion, initiator concentration and temperature. the easiness of handling it and the good agreement between simulation and experimental results are the main features of these models, recommending them for complex engineering studies. the sensitivities of the state variables (initiator concentration, monomer conversion and distribution moments of the chain length) and the model outputs (numerical and gravimetrical average polymerization degrees) with respect to various parameters are computed. it is found that the temperature has the strongest influence in the polymerization process, so it is necessary the stabilization of this parameter with a control loop. the analysis shows that the propagation and initiation activation energies are two of the most important parameters governing the system performance. almost all the system parameters have the greatest influence at the gel effect moment. using a calculus based on sensitivity functions, the quantitative estimation of the parameter influence on the system state and output variables are made. keywords: free radical polymerization, sensitivity analysis, metyl methacrylate introduction several constraints are faced in the design of chain polymerization reactors, particularly those exhibiting the gel effect: the large heat of reaction, the low thermal diffusivity and the high viscosity of the reaction mixture. hence, in the design or operation of systems of this type it becomes important to know, a priori, the limits on values of the various parameters associated with the reaction system, arising because of these constraints. these are referred to as parametric sensitivities boundaries and represent conditions at which different state variables, like conversion or molecular weight become extremely sensitive to small changes in the input parameters. these sensitivity studies also help in identifying parameters which are most critical~ and which must, therefore, be controlled or estimated precisely. considerable work has been reported on the parametric sensitivity of chemical systems, but less concerning polymerization processes because of the complexity of these systems and the difficulties involved by their models. studies on parametric sensitivity of polymerization systems started with those of biesenberger et al. [1]. these prior works on thermal runaway in chain polymerizations and copolymerizations were limited to systems which do not exhibit the gel effect. baillagou and soong [2, 3 j realize a parametric sensitivity study for a system exhibiting the gel effect, but the study is somewhat restrictive because it follows an intuitive criteria. tjahjadi et al. [4] have studied temperature and molecular weight sensitivities ·in plug-flow (or well-mixed batch) homopolymerization reactors in the absence of the gel effect. their work is mathematically more precise and less intuitive in nature and uses as example the low density jx>lyethylene system. kapoor, gupta and varma (5] developed .a mathematical technique for studying the parametnc sensitivity of reactors including chain polymerization systems exhibiting the gel and glass effects. they used the model of chiu et al. [6] for the gel and glass effects. this model considers diffusional effects as an integral part of termination and propagation reactions just from the beginning of the polymerization process. the sensitivities of the two temperature maxima with respect contactinformation: e-mail: scurtean@ch.tuiasi.ro; silvia"curteanu, etemitate str., nr.69a. 6600 iasi. romania 54 to various parameters are computed. it is found that all the sensitivities of the gel effect induced temperature peak attain their maximum at the same conditions. this sensitivity boundary is associated with high conversions and high molecular weights. the present work is a frrst part of a complex study starting with parametric sensitivity of the isothermal bulk free radical polymerization of methyl methacrylate in well-mixed batch reactors. it must be emphasized that new correlations for diffusion controlled reactions (gel and glass effects) were used. also, a simple algorithm for sensitivity calculus was used, different of that of the above attempts. to provide practical constraints on reactor design and operation, the qualitative and quantitative estimations of the various parameters influences on the system state and output are made. the quantitative predictions related to polymerization process are very important. kinetic model the initiated radical polymerization of methyl methacrylate (mma) is considered to be achieved in a batch bulk process. for this reaction, the following kinetic diagram is used: initiation propagation {l~2r* r'"+m~if * k * pn +m~~+l chain transfer to monomer * . k * ~ +m~da+f; termination by disproportionation • .. k p,. + pm ~dlt + dm where i, m and r* represent the initiator. monomer~ and primary radical~ respectively; /!* and dn are the macroradical and the dead polymer with n monomer units; kcs, ~. kp, kt.. k. are rate constants for initiator decomposition .. initiation. propagation, chain transfer to monomer. and termination by disproportionationy respectively. based on the kinetic diagram~ one can write the material balance equations for monomer conversion (x), concentration of the initiator (i). and moments of radicals (at) and dead polymer (ijj (k = 0~1.2). which give the distribution of the chain length: dl . 1-x dt = -ktll-le i+ £x ao(kp + k,..) (l) dx = (a: + k )(1x) 1 dt , ,. '"0 (2) dp, i.-x 1-x (8) 2 =k1ao~-j-i.2aoe--(kp +k,,.)+ktmm0--~ dt l+ex l+ex it is assumed that no monomer is consumed in the initiation process and that the quasi-steady-state approximation for the initiator fragment balance is also valid. the e is a parameter accounting for the volume variation during polymerization and t represents time. · to quantify the gel and glass effects, the following dependencies are proposed: k1 = k10 exp(ao + ~ · x + ~ · x2 + a3 • x3 ) (9) kp = kpo exp(b0 + b1 • x + b2 • x 2 + b3 • x3 ) (10) where k{o and kpo are the rate constants for termination and propagation reaction~ in ·the absence of gel and glass effects and ao. ah a2, a3, b0, bh b2 and b3 are empirical constants. for the rate constant of the chain transfer to monomer, a similar decrease to that of propagation rate constant was proposed [7] because both reactions involve the same diffusion mechanism the monomer molecules migrating toward the growing macroradicals. k k =k _l tm tmo k po (11) the empirical parameters depend on initial concentration of the initiator. in. and temperature (t) and can be determined by minimizing the least square errors between experimental conversion data and model predictions [8]. by automatic processing of numerous experimental data {9~ 12]. the best correlations between empirical coefficients of the models (9) and (10} and parameters t and ~ are obtained. a b b. d 2 10 g , =a+-+c·l0 +-+e·l0 + !·-+-+ t t 2 t t 3 h 13 • 1; . 10 + . o+l·-+j·t t2 (12) 55 table 1 numerical values of constants in gel and glass. effect models ao a1 az a3 bo b1 b2 b~ a 6671.494 -62659.663 143947.312 -83550.066 5216.517 -5143.078 115683.384 -65355.732 b -109.433 -0.674 2549.132 -3015.263 c -59.575 574.171 -1355.835 809.742 d 0.983 12.599 -87.026 86.865 e 0.177 -1.749 4.226 -2.583 f 0.658 -0.535 -12.439 15.375 g -0.0688 0.588 -1.276 0.754 h -0.000175 0.00177 -0.00436 0.00271 -0.001009 0.0018 0.0140 -0.0188 j -0.000937 -0.0551 0.295 -0.278 corr 0.976 0.981 0.974 0.974 table 1 contains numerical values for the constants appearing in relations (12). the parameter carr shows the agreement with experimental data. the kinetic model associated with gel and glass effects models were rigorously verified by comparing simulation results with experimental data [ 13]. for the model of mma polymerization one considers: • the state variable vector z = [i x a.o a.l a.2 j..lo j.!.l j.a2]t = -85.750 -47.281 2399.339 -2798.386 -46.544 471.286 -1092.004 637.698 0.954 13.722 -91.356 91.571 0.138 -1.434 3.409 -2.045 0.514 -0.307 -11.475 14.038 -0.0257 -0.151 1.264 -1.268 -0.000137 0.00145 -0.00353 0.00216 -0.000774 0.00126 0.0134 -0.0174 -0.0022 -0.0338 0.225 -0.226 0.961 0.969 0.974 0.977 i = 1,8 j = 1,11 (17) the matrix s; can be calculated using the parametric sensitivity equation [14]: asz (t) = = = _p_= f .. (z(t),p,t)·spz(t)+ jp dt .. (18) =[zl,z2,z3,z4,z5,z6,z7,z8]t (13) with the initial condition s;(o) = 0. • the model output vector containing numerical and gravimetrical average polymerization degrees y = [dpn, dpw]t = [yl, y2]t (14) • the vector of parameters p = fr,f,£,k~,kt00 ,k;:,k!0 ,ed,ei'ep,etmf = [ph pz, p3• p4• ps• p6• p1• pg, pg, pto. pn]t (15) it should be noted that the reaction temperature, t, is an important operating parameter. even the model describes satisfactory the evolution of mma polymerization, establishing' of numerical values of kinetic parameters by experimental techniques may be influenced by uncertainties. therefore, it is necessary to determine the influence of these uncertainties on the model results. the parametric sensitivity calculus the parametric sensitivity matrix of the state, s; , has the following components: szl j!ll szl pz szl pu sz = ~z1 j = !! jlj szz pi sz: pz szz pn (16) sz.. pt sz. 112 sz. pu whose elements are depicted by: in the eq.(18), f z and f p are jacobean matrices of -the vector function f(z(t),p,t) with respect to z(t) and p. the components f1o f2, ... ,f8 of the vectorial function /(z(t),p,t) are the right members of eqs.( 1)(8). = the parametric sensitivity matrix of the output, s; ~ has the form: with elements defined by: s yl (t) a oj.t (t) pj = opj {19) k = 1,2 j = l,ll (20) the parametric sensitivity of the ~output is simply obtained by: s;(t) = gz(~(t),p,t))·s;(t) (21) with ;z jacobian matrix of .the output vector. y. with respect to z(t). to compare and order the influence of parameters on system state and output, the dimensionless parametric sensitivity matrices are defined: s:: = l·:. ]a(s:. <t>..!l] <22) p {;)pi = p1 z,(t) 56 table 2 parameters used in mma polymerization k~ = 1.053 xl015 s"1 (for initiation with aibn) k!o = 4.917 x1<f m3/(mol s) k~ =9.8 x104 m3/(mol s) k!o = 4.66 x106 m3/(mol s) &i= 1.2845 x105 j/mol ep = 1.822 xl04 j/mol & = 2.937 xl03 j/mol bun= 7.428 x 104 j/mol f = 0.58 (aibn) e = ~(0.1946+0.16 x 10-3 x t [°c]) kd = k~ exp(-ed i(rt)) kto = k~ exp(~e/(rt)) kpo = k!o exp(-epi(rt)) ktrri) = k!o exp(-em/(rt)) ls;xlmax 140 120 114.3 107.6 100 80 60 40 20 0 p= ~ f eti & ep bun fig.l the histogram of maximum absolute values, ls;x lllllij( , showing the. influence of parameters on monomer conversion table 3 maximum absolute values !s;zlllllij( parameter ( ) i x state variables (z) a.1 az 32.6 31.7 6.2 114.3 107.6 32.0 951.0 903.9 269.0 1017.5 1237.5 945.3 1109.5 277.4 326.5 results and discussions many simulations were made [13] with the model (1)­ ( 12) using a matlab program based on special functions for solving stiff differential equations. numerical values of the parameters in kinetic model are given in table 2. the calculus of the parametric sensitivity functions requires the integration of the mathematical model (eqs. (/} (12)) and the sensitivity equations (18) for the parametric sensitivity of the system state. the calculus of parametric sensitivity of the system output is performed with eq.(21 ). the integration was carried out directly with odel5s in madab 5.3~ using 10"10 as relative and 10"15 as absolute tolerances. the parametric sensititdty of the state the histograms of maximal absolute values of the dimensionless (normalized) parametric sensitivity functions of the states indicate the measure in which the parameter variations influence the state variables. all the eight diagrams corresponding to the eight state variables have the same shape~ but different values. one of them ~ the influence of parameters on monomer conversion is given in fig./. the parameters with greatest influence on the state variables are: t. e., and ls;zllmx 1400 1200 1000 800 600 400 200 0 z= x ao a.t az jlo jl.l jlz fig.2 the histogram of maximum absolute values, js;ziiij!lx , showing the influence of temperature on state variables ep. the maximum absolute values of the dimensionless parametric sensitivities being given in table 3. generally, among the parameters, the temperature has the strongest influence and the most sensitive of the state variables are the macroradical concentrations, a.o, at. l.2. a suggestive diagram (fig.2) contains the variation domains of the state dimensionless sensitivities as function on temperature. in conclusion, one should take great care choosing the values of ~ and ep in different engineering studies of polymerization processes. also., the thermal regime have to be carefully handled, that means it is necessary the stabilization of the temperature with a good control system. s;~. s;x 140,---------------------------------~ 120 -20 time [min] -40 ..__ _____________________ _ fig.3 the variation in time of sensitivity functions s;i (1), s;x (2) from the sensitivities presented in fig.2 we extracted some of them that have significant non­ dimensional values. thus, fig.3 allows to compare the influence of temperature on the initiator concentration and monomer conversion on the whole time interval of the reaction. the greatest influence of temperature corresponds to the gel effect for the both curves and it is more important for monomer conversion (curve 2 in fig.3). concerning to the shape of curves representing the dimensional sensitivity functions, s;, we can separate the following categories: • diagrams with a positive maximum at the gel effect (about 55 min at t ::::: 70°c and io = 25.8 mol/m3 ) representing an increase of the state z when the parameter p increases. generally, the positive values of the sensitivity functions s; show that increasing the parameter p results in increasing the state z. such · s1 sx s-~o s-1t s~ sllt sp.z s1 curves are. r , r , r , r , r , r , r , 1 , ~·~·~·~·~·~·~·~·~·~· sj.lz s1 sx s~ s~ sp.o sf.l1 sp.z s1 ~· ~· ~· ~· ~· ~· ~· ~· ~· ~·~·~·~·~·~·~·~·~· s~ , s;z . ... ... • diagrams with a negative minimum at the gel effect, showing the decrease of the state value, z, when parameter p increases: s:.' s;,., sz' s~' s:;' s~. s!, s;, s~. s}, s~. s~. s~. s:. , , , , , , , ~.~.sk~.~.sk~'~'~'~·~· m ~o ro ~o ~. m ro s~ s~ s 1 sx sp.i t!o ' t!,0 ' e,.. ' e,.,. • e"" • for two above categories of curves, the domains before and after gel effect are characterized by a zero or weak parameter influence, positive or negative. a distinct category of curve shows a positive maximum or a negative minimum at the gel effect and this influence remains approximately constant after this 57 l s*dpwi p max 200 150 100 50 v p= t f e k~ k,~ k~0 k,~0 ~ bt ep bun fig.4 the histogram of maximum absolute values js;dp,.jmax showing the influence of parameters on gravimetrical average polymerization degree phenomenon. such curves are: s;~ , s;~ , s~2 and "o i jlt p.2 '~'2 ao ,o . ,.,o "" se , se, se , se , sko , se , respectively. p tmo lift a limited group of curves illustrates a continuous . . . . . fl ( silo s~ silo s~~o sjl.o positive mcreasmg m uence r , 1 , 1 , k~ • k~ ' s~~ ' s~) or continuous negative decreasing influence ( s~ , s~ , s:o , s~ , sk~ , s~o ). yet, an increased d ~ lo '"' influence at the gel effect is observed. the majority of curves shows zero influence of the parameters before the gel effect, the critical domain is represented by the gel effect and after this phenomenon the influence may be strong (as to the gel effect) or weak. the parametric sensitivity of the output the maximal absolute values of the dimensionless parametric sensitivities of the output show the influence of the parameter variations on the model output, dp n and dp w· the fig.4 emphasizes that the most important parameters for dpw are t, ed and ep, the same as in the case of parametric sensitivity of the state. qualitatively, the results obtained for dp w are also valid for dp n, numerical values of the sensitivities being different. the parameters t, ed and ep have a major influence on dpn and dpw in the gel effect region. this influence is positive for t and negative for ~ and ep. before and after the gel effect, the negative values of the sr·· and s;r,. mean that an increase of temperature results in a decrease of polymerization degrees. while in the gel effect domain the action of temperature is opposite (fig.5). a positive variation of ~ produces a decrease of dp n and dp w at the gel effect moment and an increase of these outputs in other time intervals of the reaction. the negative values of .:'.>£ .• and :l£;· prove that the increase of f, produces the decrease of the polymerization degrees on the entire time domain. with the greatest decrease at the gel effect moment. 58 sdp. t ' sfpw 5000 4000 3000 1 2000 1000 0 20 ~1000 -2000 time [min] fig.s the variation in time of sensitivity functions s~p,. (1). s~p .. (2) arx 0.16 ...-----------------..., 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0~~~~~~--~~~~~ 0 20 40 60 80 100 time [min] fig.6 the conversion variation caused by temperature . increase; solid line calculus based on sensitivity functions; dotted line calculus based on model simulations the quantitative estimation of the parameter influence on the system states and outputs with the addition of sensitivity functions there were calculated the deviation of the states z when each "p" parameter changes: (24) similar for the system outputs ( a.py = s; · ap ). the first example of using sensitivity functions involves a small variation of temperature, 0.2% (about 0.7°c. respectively). fig.6 shows the conversion variation caused by temperature change ( arx) calculated with sensitivity . functions (solid line): a1x = s; ·at and by model simulation (dotted line). the good agreement between the two curves in fig.6 illustrates the correctness of the sensitivity function conversion 1~------------------~---------. 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 -l------.-------r-----t-----1 40 45 59 55 60 time [min] fig.7th.e influence of temperature increase on monomer conversion; 1 initial conversion; 2 disturbed conversion caused by temperature change values. consequently, these functions can be used to provide quantitative information about the polymerization system. the maximum value of the curves in fig.6 (0.15) means that a temperature increase of 0.2% at t = 55 min (gel effect) determines a conversion increase of 0.15. this is clearly emphasized in fig. 7 where curve noted 1 represents the initial conversion, and curve 2 is the conversion resulted with temperature change. for the simultaneous variation of the three parameters with greatest influence on the states t, ed, epwith variations of 0.2%, -0.1 %, 0.6%, a conversion increase of 0.4 at the gel effect and a decrease of this state of 0.6 at the end of the reaction take place. for the most sensitive parameterst, ed, epvery small changes have been considered. because of strong nonlinear model of the polymerization process in connection with t, ep ed, we cannot appreciate quantitatively the influence of thyse parameters if their changes are greater. but, the sensitivity functions offer important qualitative information. the temperature is one of the parameters with significant influence on polymerization degrees the outputs of the polymerization system under study. an increase of temperatpre with 0.2% determines an initial decrease of polymerization degrees, followed by an important increase at the gel effect moment (approximately with 450 units for dp n and 2700 units for dp w). greater values of polymerization degrees mean. in fact, earlier appearance of the gel effect due to the temperature increase. after the gel effect, the increase of temperature results the decrease of polymerization degrees with 300 units for dp n and approximately 700 units for dp w· the fo~lowing example involves a variation of 2% for the parameter c. this change of e parameter determines an increase of ixjlymerization degrees of lloo units'" approximately7 for dpn (figs.8 and 9) and 5800fordp,.. !l.£dpn 1200 ! 1000 800 600 400 200 0 0 20 40 60 80 100 time [min] fig~8 the variation of numerical average polymerization degree caused by £ parameter change; solid line calculus based on sensitivity functions; dotted line calculus based on model simulations conclusions this paper is dealing with parametric sensitivity of isothermal batch bulk polymerization of methyl methacrylate. the kinetic model including the mathematical relations for diffusion controlled phenomena describes quite well the polymerization process, continuously on the whole conversion domain and for different reaction conditions. the termination and propagation rate constants dependencies of monomer conversion, initial initiator concentration and temperature are the suitaple form for the sensitivity analysis. the sensitivities of the state variables (initiator concentration, monomer conversion and distribution moments of the chain length) and the model outputs (numerical and gravimetrical polymerization degrees) with respect to various parameters (temperature, initiator efficiency, volume variation parameter, frequency factors, activation energies) are computed. it is found that the temperature has the strongest influence on the state and output of the polymerization system. therefore, the thermal regime of the reactor have to be carefully controlled. other two parameters influencing significantly the polymerization process are the propagation and initiation activation energies. consequently, it is important to have precise estimation of these two parameters for good design and operation of the reactor. generally, diagrams of parametric sensitivities show a positive maximum or a negative minimum representing an increase or a decrease of the system variables when the considered parameter increases. these values represent the generalized sensitivity boundaries for reactor design or operation and correspond to the gel effect. a calculus based on sensitivity functions are used to made quantitative estimations of the parameter 59 dpn ,5200 2 4700 ------------------------4200 3700 3200 2700 2200 40 45 50 55 60 time [min] fig.9 the influence of£ parameter change on numerical average polymerization degree; 1 initial dp n; 2 disturbed dpn influence on the system state and output variables. for the most sensitive parameters temperature, initiation and propagation activation energies very small changes have been considered. the sensitivity analysis method cannot be used to appreciate the changes of the system variables at greater variations of the most sensitive parameters because the kinetic model is strongly nonlinear. references 1. biesenberger j. a.: am. chern. soc. symp. ser. 1979, 104, 15. 2. baillagou p. e. and soong d. s.: chern. eng. sci., 1985,40,75. 3. baillagou p. e. and soong d. s.: chern. eng. sci., 1985, 40, 87. 4. tjahjadi m., gupfa s. k., morbidelly m. and varma a.: chern. eng. sci., 1987,42, 2385. 5. kapoor b., gupfa s. k. and varma a.: polym. eng. sci., 1989, 18, 1246. 6. chid w. y., carratt g. m. and soong d. s.: macromolecules, 1983, 16,348. 7. vaid n. r. and gupfa s. k.: polym. eng. sci., 1991, 31(2), 1708. 8. curteanu s., bulacovschi v. and lisa c.: polym. plast. technol. eng., 1999,38 {5), ll~l 9. balke t. s. and hamjelec a. e.: j. appl. polym. sci., 1973, 17,905. 10. ito k. j.: j. polym. sci.. part a-1.1989, 13.401. 11. dua v., saraf d .. n. and gupta s. k.: polym. eng. sci., 1996, 59, 749. 12. curteanu s. and cazacu m .• rev. chim .• in press. 13. curteanu s., petrjla c. and bulacovschi v.: rev. roum. chim .• in press. 14. ungureanu s.: sensibilitatea sistemelor dinamice. ed. tehnic!, bucure§ti, pp. 45, 1988. page 51 page 52 page 53 page 54 page 55 page 56 page 57 hungarian journal · of industrial chemistry veszprem vol. 30. pp. 1318 (2002) on the non-linear mass transfer theory c. boyadjiev (institute of chemical engineering, bulgarian academy of sciences, "acad. g.bontchev" str.,bl.103, 1113 sofia, bulgaria) received: february 19,2001 a theoretical analysis ofnon~linear mass transfer kinetics has been done. the comparison between stephan flow, a flow induced by large concentration gradients and marangoni effect is shown. the conditions of existing of these non-linear effects in mass transfer kinetics are determined. keywords: non-linear effects, stephan flow, marangoni effect introduction a theoretical analysis of non-linear mass transfer has been developed in [1]. the main idea follows from the non-linearity of the convection-diffusion equation: p(c)w(c)gradc = divfp(c)d(c)gradc]+ ken. (1) the velocity w is governed by the hydrodynamic equations. however, the principal non-linear phenomenon is due to the concentration effects on the velocity w(c), density p(c), viscosity jl(c), diffusivity d( c) and on the chemical reaction rate ken (for n ¢ 1 ). it was shown [ 1] that there are a number of cases with non-linear mass transfer behavior. the well-known linear mass transfer theory could be successfully applied in these cases. however, in case of two-phase interphase mass transfer with a flat interface the above equation permits a non-linear mass transfer model to be derived by means of the boundary layer approximation: ( ou . ou . ) {) 2 u · du j dv j (2) p; u1 a: +v1 a:: = p,1 i)y2 1 +a1 • a_;--+ay-=0' (k. oc. i1 2c. u.-1 +v.-1 =d2 1 +b., j=1,2; 1 i1x 'ijy <ry 1 contact information: e~mail: chboyadj@bas.bg where the index 1 is used to denote gas or liquid phase, while the index 2 designates liquid or solid phase. the terms ai and bi (f=l,2) are the contributions of some additional physical effects. the solution of the above set of equations permits the interphase mass transfer rate to oe determined as follows: . (3) there are a number of processes where ui, vi, ji;, pj·, di1 ai1 and bi are independent on the concentration cj (j=l.2). these situations are the basis of the linear mass transfer theory. the mathematical model allows the following principle characteristics of the linear mass transfer to be drawn: the interphase mass transfer rate j does not depend on the mass transfer direction; 14' the interphase mass transfer coefficient kj does not depend on the concentrations cjo (j=l,2). the striving to decrease the size of the industrial devices necessitates process intensification. the systems with intensive mass transfer are characterized by a behavior that deviates considerably from the characteristics mentioned above. the main feature is the higher mass transfer rate, which differs significantly from the value predicted by the linear mass transfer theory. the non-linear effects leading to above have been described [ 1]. in systems with high concentrations and such exhibiting large concentration gradients, the deviations from the linear pick's diffusion law are significant, too. under such conditions, the higher concentrations could affect both the viscosity and the density of the fluid: di=di(ci), vi=j.li(ci), pi=pi(c), j=l,2.(4) the concentration effect introduces a non-linearity in the convection-diffusion equation discussed in details in f,3j. the other non-linear effect due to the non-uniform concentration distributions ai = g(pipo)• pj = pici) (5) leads to a natural convection [ 4,5]. the next cause that may intensify the mass transfer process is the existence of a chemical reaction with a rate b j in the bulk of the phase: (6) the studies developed in [1, 6], show that in the gas­ liquid systems with a chemical reaction: b 1=0, while b2=kcn. moreover, the chemical reaction rate could affect significantly the interphase mass transfer mechanism. the thermal effect of the chemical reactions could lead to the temperature non-uniformity on the interface and to consequent surface tension gradients. this calls for new boundary conditions taking into account the equality of the tangential components of the stress tensor on the interface: y = 0, pi a ul = f.lz a uz -a (j • a y a y ax {7) the investigation of this effect (marangoni effect) [1 ,8] has shown that it is negligible when there are no surfactants in the system. one of the most interesting non-linear effects arises from the conditions imposed by the high concentration gradients. the latter induce secondary flows at the interface. this effect has been discussed in details in { 11 for a large number of systems taken as examples and it has been termed "non~linear mass transfer effect~~. under the conditions imposed by high concentration gradients induced secondary flows occur. they provoke convective components of the mass transfer flux additional to the main mass flux. in this case the mass transfer rate is: 1 = m:p* j(~c) dx, po o y y=o (8) where the secondary flow affects both the diffusion mass transfer j ~c ) and the convective mass transfer l/l y y=o m* _1!_ . in gas-liquid and liquid-liquid systems [9, 10] po the non-linearity has been proven to be the effect of the induced secondary flow on the diffusion transfer. in liquid-solid systems the induced flow affects mainly the convective transfer. these effects are ·clearly demonstrated the electrochemical systems [1, 6] due to the high molecular mass (m) of the metals. all the non-linear effects influence the velocity fields, which lead to changes in the hydrodynamic stability of the system. the loss of stability could cause an increase of the amplitudes of the random disturbances until a new stable state or a stable periodic process is reached [ 1]. the latter is a self-organizing dissipative structure with a mass transfer rate growing sharply which is not the case in the conventional systems. the problem has been discussed in details in [ 4, 5] in the case of non-stationary absorption of pure gases in immobile liquid layer with flat interface. non-linear effects in mass transfer kinetics induced by the secondary flows, lead to quality changes in the mass transfer rate, because they are related to physical mechanisms. in this sense the most interesting are the stephan flow [11], (occurred by volume change at the interface), the flow induced by large concentration gradients [1,12] and the flow resulted from surface tension gradients [7,8]. these secondary flows require introduction of new boundary conditions at the interface between gas solid, gas liquid, liquid liquid and liquid solid phases. a comparative analysis of the occurrence of these secondary flows will be presented. stephan flow the stephan flow occurs in case of heterogenic reactions at the interface between two phases. as a result the substances are disappeared (reagents) or generated (reaction products) at this interface. this ·~disappearance or generation" of substances at the boundary between two phases might be a consequence of chemical reactions, adsorption or desorption processes (the substances connect physically or ~heroically with substances from phase boundary), mterphase mass transfer (the substances "disappearn at phase boundary as a result of the transfer into the other phase), l~quid vapour phase transition (boiling, condensation}. some of the above heterogenic reactions lead to changes in the volume of the phase at the interface, which leads to occurrence of hydrodynamic flow called stephan flow. let's consider the heterogenic reaction [11), presented by the stoichiometric equation: n lv;ai=o, (9) i=l where ~ and v; (i = 1, ... , n) correspond to the symbols of participating substances in the reaction and their stoichiometric coefficients. for the initial substances (reagents) v; > 0, while for the reaction products v; < 0 . the rate of the heterogenic reaction j i (moll m 2 s) is defined for the separate substances (i = 1, ... ,n), where n is their total number. for the reagents ji > 0 , and for the reaction products it < 0 . the reagents (reaction products) are supplied to (took off from) the reaction surface by diffusion and convection: j = -dgradc+ vc, (10) where j is the vector of the mass transfer rate , d(m2 / s) is the diffusivity, gradis the vector of the gradient, c(mol/ m3 ) molar concentration, v velocity vector. for the separate substances the molar flux has the following form: 15 heterogenic reaction (per unit area, per unit time). they can be presented as: (15) where v; (m3 i m2 s) is the volume reaction rate of the substances in the gas (vapour) phase, and w; (m3 i mol) their molar volume. the systems gas (vapour) liquid (solid) will be considered below, where the stephan flow occurs in gaseous (vapour) phase, because it is practically not physically applicable in liquid and solid phases. the summation of the stoichiometric coefficients leads to: (16) where v > o(v < o) means the increase (decrease) of the mols number (the volume) of the reaction mixture as a result of the heterogenic reaction. from (14) directly follows: . vi . . 1 n 1i = h' l = , ... , . (17) vi the summing up of (17) leads to: (18) (11) where the substance a1 we consider as limiting, i.e. the the projection of the vectors in the vector equation over the normal vector of the interface n (in points of the surface) might be noted as: ji = {i;.n~ ~ ~ = (gradci.n1 v = (v.n), (12) where ji (moll m2 s) are molar fluxes, which have to be equal to the rates of the reactions of the separate substances, and oci normal derivate at the interface, v on the rate, induced as a result of heterogenic reaction at certain conditions and is called the velocity of the stephan flow. it is positive when v is oriented to the phase boundary and negative in the opposite case. the introduction of (12) into (11) leads to: . oci . ]; = -di--+ vci, z = 1, ... , n , (13) on where j;{j = l, ... ,n) should be satisfy the condition for the stoichiometry of the flows: jliv1=j2fv2= ... =jn/vn. (14) from {14) can be seen, that the stoichiometry coefficients v; (moll m2 s) present mols of the substances (i = 1, ... , n), which participate in the rate of its reaction limits rate of the heterogenic reaction. in case of gases and vapours we can express the concentration through the partial pressure: p c. =-1 i=l, ... ,n, 1 rt' (19) where r is the universal gas constant, t temperature. in this way from (13) directly follows: . d; o ~ vi} j;== rt on+ rt' i=1, ... ,n. (20) the summation of (20) leads to: ~. 1 ~do~ vp l.,;h =--l.j i--+-, t=t rt i=i on rt (21) n where p = l ~ is the total pressure of the mixture. i=l the velocity of the stephan flow is obtained directly from (18) and (21): rt . 1 ~ d a~ (z2) v=-r h +.£.j ;-;-· p p i=1 un in case of two component mixtures d1 = d2 = d, i.e.: 16 rt . dap v=p-r h +-p;;;;· (23) it can be seen from (23) that the velocity of the stefan flow is determined by the relative change in the volume of the reaction mixture y as a result from changes in the volume velocity vi or in case of phase transition (the change of the molar volume wi ). this velocity decreases as a result of hydraulic resistance ( :: < 0) . at absence of the hydraulic resistance p = eonst and the velocity of stephan flow takes the form: rt . v=-rh· p (24) in case of reduction of the reaction mixture volume as a result of heterogenic reaction the stephan flow is oriented to the reaction interface ( y > o,v > 0 ). in opposite case ( y < o,v < 0) it is oriented from the reaction interface. in case of heterogenic chemical reaction without phase transition: i.e. v > 0 , when the total volume rate of the chemical reaction of the substances iri the mixture is positive and the volume increases. in opposite case v < 0 . in cases when the heterogenic reaction presents the liquid-vapour phase transition at the interface (boiling, condensation) the molar rates and (as a results) their volume rates are equal: 1 1 (26) i.e. in case of condensation (boiling) wl > w;p r < 0, (w.~ > w., r > o) and the stephan flow is oriented to (from) the interface. in cases. when the heterogenic reaction presents adsorption (desorption) vi = v2 ~ f :::: 0. i.e. the conditions for the stephan flow do not exist. the analogous is the case of absorption (desorption)~ where the product transfers into the second phase. i.e. v1 =v2 • v=o. the obtained result (24) shows that stephan flow at interface arises when the heterogenic reaction leads to changes in the summary (total) volume of reaction mixture. obviously this can happen only at phase boondary in gas or vapour phase and it is practically impossible at the boundary in liquid or solid phase. non -linear mass transfer one of the significant effects of nonlinear mass transfer arises in systems with intensive interphase mass transfer, when large concentration gradients induce secondary flows which velocity is normally oriented to the interface. for a simplicity we will consider two-component fluid [ 1, 6], where the component a is a substance dissolved into component b (solvent). the density of the solution p (kg i m3 ) can be presented through the mass concentrations of the component a (m c) and solvent b (m0 c0 ): p =m0 e0 +me= po +me, (27) where m and m 0 are the molar mass (kg i mol) of a and b , c and c0 their molar concentrations (mol 1m3 ). every elementary volume of the solution has a velocity v , which can be expressed through velocities of the substances a ( v) and. b( v 0 ), i.e velocity of the mass flow, transferred by every elementary volume presents a sum of the mass flows of a and b : (28) the equation (28) can be projected over the normal vector n of the phase surface: p* (v.n)= p~(v0.n)+m c*(v.n), (29) where the upper index ( *) notes the values at the interface. from (29) the velocity of the secondary flow v(ml s) induced by the diffusion (large concentration gradient) can be determined: v =(v.n). (30) at the boundary between two non-mixing phases the mass flux is zero, i.e. (31) the molar flux of the dissolved substance (at interface) n (moll m2 s) can be expressed through the rate (moll m2 s) of the diffusion and convective transfer: *( )* joe)* * n=c v.n =-~lon. +vc. (32) the introduction of (30), (31) and (32) into (29) leads to: · md(oc)'" * • v=p~ dn ' po =moco~ (33) * where c0 is the molar concentration of b at the interface. for a flat phase boundary y = 0 is obtained directly [1, 6]: v=-md(~) * a . po y y=o (34) in some approximations [12] n is expressed only by the diffusion flux: n=-j~c) ...,l y y=o (35) and for the velocity of the secondary flow is obtained md(ac) v=----* a , po y y=o p* = p~ +me*. (36) obviously the obtained results (34) and (36) coincide at c * = 0 (for example at desorption of gases). from (34) it is seen that in the systems with an intensive interphase mass transfer the normal component of the velocity differs from zero (as in the systems with linear mass transfer), and depends on the concentration of the transferred substance, i.e. the convection­ diffusion equation is non linear. this requires the boundary condition at y = 0 ( v = 0) to be replaced with (34). the obtained result (34) shows that the local mass flux at phase boundary has diffusion and convective components: z=-m +mvc =-md-* .(37) . ~ ac) * p * ( ac j ay y=o po ay y=o from (37) the mass transfer rate can be directly determined by averaging of the mass flux i (kg i m2 s) over the interface. the comparison between stephan flow's velocity (24) and the velocity of the secondary flow induced by large concentration gradients shows that stephan flow arises in gaseous or vapour phase as a result of the changes in the phase volume at the interphase. such changes occur in some heterogenic chemical reactions accompanied by changes of the reaction mixture volume or phase transition (boiling, condensation). the secondary flow at large concentration gradients is a result of the intensive interphase mass transfer and can be observed in gaseous and liquid phase (the stephan flow in liquid phase is physically impossible). marangoni effect the marangoni effect is a result of secondary flow which velocity is tangentially oriented to the interface and is caused by the surface tension gradient, induced by concentration or temperature gradient at the 17 interface. this effect will be considered in gas liquid systems. the influence of the secondary flows over the mass transfer rate is a result of the velocity component oriented normally to the interface. this creates an intensive convective transfer, which is summarized with the diffusion transfer. at the marangoni effect the induced flow is tangential and the normal component appears from the flow continuity equation: au+~=o. ax ay (38) the flows in the boundary layer are characterized by two characteristic scales of velocity (u0 , v0 ) and two linear scales (8, l), which are related to the dimensionless variables of the flow: x=lx, y=oy, 8 =jj.ll . (39) uop the introduction of (39) into (38) leads to dimensionless equation au+ v0l av =o ax u08 ()y ' (40) where the continuity of the flow is retained at the following ratio between the characteristic scales of the flow: let us suppose that the marangoni effect is a result of temperature gradient at the interface. in this case the characteristic velocity of the marangoni effect can be determined from the equation [ 1]: tt(~~ l =~: =~~ ~:. (42) if introducing (39) in ( 42) (and temperature scale at ) we reach the condition for the existence of marangoni effect and its characteristic velocity: 8 llt aa u =--0 l j1. at· (43) the introduction of (43) in (41) allows the determination of the characteristic velocity of the secondary flow liable for the increase of the mass transfer rate as a result of the marangoni effect: & do' vo=---. pu0l dt (44) in the case of absorption of c02 in h 20 and temperature change because of chemical reaction, the order of the velocity v0 can be determined: (45) 18 in cases of non-linear mass transfer, characteristic scales have to be introduced into (34): j¥. v=v0 v, c=11cc, y=ocy, oc = . (46) 0 from (34) and (46) directly can be obtained the condition for an existence of the non-linear mass transfer effect and its characteristic velocity: vo = m ~c j"•d. (47) po l the v0 order of the velocity in (47) at analogous conditions with ( 45) is determined directly: (48) the obtained results (45) and (48) show, that in systems with an intensive interphase mass transfer the non-linear effects are related to the concentration gradients normally oriented to the interface, and are not related to the temperature gradients at the phase boundary. this proportion between the effect of non­ linear mass transfer and the marangoni effect is based mainly on the following three reasons: the normal component of the velocity v0 is always smaller than the induced tangential component (see (41)); to the large concentration gradient he correspond small temperature gradients at because of the small heat effect of the absorption; · the absence of surface-active substances. the non-linear mass transfer effect and the marangoni effect can determine the mass transfer rate not only by additional convective flows, but also by loss of stability. in these cases accidental disturbances lead to self-organized dissipative structures with very intensive mass transfer £1]. the stability of these systems depends mainly from v0 , which is the reason the process to be limited again from the non-linear mass transfer. conclusion the presented theoretical analysis shows that the effects of the stephan flow and the non-linear mass transfer at large concentration gradients have different physical nature, and as a result different mathematical models. the stephan flow [12] appears at heterogenic chemical reactions (with changing volume of the reaction mixture) or liquid-vapour phase transition at interface (boiling, condensation). the non-linear mass transfer [ 1] appears at interphase mass transfer in gas (liquid) solid, gas­ liquid and liquid-liquid systems as a result of large concentration gradients. the marangoni effect does not appear in gas-liquid and liquid-liquid systems [7 ,8] at absence of surface active agents, because of the small heat effect of the dissolution process. references 1. boyadjiev c. b., babak v. n.: non-linear mass transfer and hydrodynamic stability, elsevier, amsterdam, pp. 500, 2000 2. boyadjiev c. b.: hung. j. ind. chem.,1996, 24, 35-39 3. boyadjiev c. b., halatchev i.: int. j. heat mass transfer, 1998,41,939-944 4. boyadjiev c. b.: int. j. heat mass transfer, 2000, 43, 2749-2757 5. boyadjiev c. b.: int. j. heat mass transfer, 2000, 43, 2759-2766 6. kr.ylov v. s., boyadjiev c. b.: non-linear mass transfer, institute of thermophysics, novosibirsk, pp.231, 1996, (in russian). 7. boyadjiev c. b., halatchev i.: int. j. heat mass transfer, 1998,41, 197-202 8. boyadjiev c. b., doichinova m., hung. j. ind. chern., 1999, 27, 215-219 9. boyadjiev c. b.: hung. j. ind. chern., 1998, 26, 181-187 10. sapundzhiev t., boyadjiev c. b.: russian j. eng. thermophysics, 1993, 3, 185-198 11. frank-kamenetskll d. a.: diffusion and heat transfer in chemical kinetics, science, moscow, pp.491, 1967 12. bird r. b., stewart w. e., lightfoot e. n.: transport phenomena, j. wiley, new york, pp.687, 1965 page 15 page 16 page 17 page 18 page 19 page 20 hungarian journal of industrial chemistry veszprem vol. 30. pp. 271 274 (2002) assessment of degradability in whole effluent toxicity testing using bioluminescent bacteria n. kovats, t. szalay 1 , i. kiss\ a. karpati and g. ?aulovrrs2 (school of environmental engineering and technology, university ofveszprem, 8200 veszprem p.o.box 158 1department of zoology, university of veszprem, 8200 veszprem p.o.box 158 2balaton limnological research institute of the hungarian academy of sciences, 8237 tihany p.o.box 35) received: october 10, 2002 in whole effluent toxicity (wet) testing the aggregate toxicity of an effluent is measured, using different test organisms. although these predicted deleterious effects will occur in natural (real-world) ecosystems, the tests are performed in the laboratory, under strictly controlled conditions. however, there are many reasons why these test results cannot be directly applied for real-world ecosystems. one basic problem is that exposure changes with space and time. several physical, chemical and biological processes can result in significant decreases in exposure concentrations of a test substance over time. for many industrial effluents biodegradation is perhaps the most important process which affects the environmental concentration of the test substance. biodegradation is a specific process as not only appropriate abiotic conditions are necessary but also a competent bacterial population, both anaerob and aerob should be established. our main goal was to assess how toxicity of a selected industrial effluent changes over time, caused by degradation. in order to measure the aggregate toxicity of the effluent the toxalert ®100 luminometer was used, developed by merck. this test is in compliance with iso/en/din 11348. the use of the bioluminescent bacterium vibrio fischeri (or other bacteria) has several advantages comparing to conventional toxicity testing. the test is rapid and causes no ethical problems. our results has shown that toxicity changes caused by degradation can be appropriately followed by bioluminescent bacteria. keywords: whole effluent toxicity, biodegradation, bioluminescence, microtox introduction there is an increasing awareness of the need to protect aquatic habitats, as many chemicals may ultimately find their way into recipients. the role of scientists is to provide environmental decision makers with applicable information on how to assess the impact of man's activities. in order to create the framework for assessing the toxic effects of such chemicals on aquatic organisms, national and international authorities have developed several test guidelines and protocols and are continuing to do so. these aim to produce quantitative data using standardised procedures. by definition, whole effluent toxicity (wet) test methods measure "the aggregate acute and chronic toxicity of an effluent using standardised freshwater, marine, and estuarine plants, invertebrates and vertebrates" [1]. in wet testing our null hypothesis was that there is no difference between the control and the test treatment -in other words, the effluent is not toxic. on the contrary, if there is a statistically significant difference between the control treatment and any other test treatment the effluent is determined to be toxic and our null hypothesis is rejected. basically the main goal of such testing is to determine what risk the effluent might pose to the environment. although these predicted deleterious effects will occur in natural (real-world) ecosystems. the tests are performed in the laboratory. under strictly controlled conditions. however, there are many reasons why these test results cannot be directly applied for real­ world ecosystems. first of all. quite many test organisms have been selected because they can be maintained in the 272 laboratory sufficiently, so they are seldom good representatives of natural ecosystems. in order to use test results for other species not tested in laboratory, specific taxonomic extrapolations are needed, for which some models have been elaborated [2]. different responses can occur within the same species as well kiss et al. [3] investigated how different natural populations of lemna minor behave when tested for potassium-dichromate. significant differences were observed in growth rate expressed as doubling time and growth inhibition as well. another important criteria are life stage and size. under standard test conditions these parameters cannot vary, but do so in natural populations. young organisms for example have incompletely developed organs and metabolic capacities and therefore they are more sensitive to toxic pollutants [4]. for our study, the main factor is exposure. in standard ecotoxicological tests the exposure duration is fixed, in acute tests it mostly takes 24, 48 or 72 hours. as real-world ecosystems have to suffer from exposure duration other than these, interpolation or extrapolation is needed. however, temporal extrapolation models are intended to deal with constant exposure, but exposure concentrations are irregular and significantly change with time. several physical, chemical and biological processes can result in significant declines in exposure concentrations of a test substance over time [5]. the substance in question can be volatile, in this case the main difficulty during the test is to maintain exposure concentration. photo-degradable, hydrolytically unstable, oxidizable and biodegradable substances in addition may form such breakdown products which can be even more toxic than the parent substance was. in many cases where data are absent or insufficient to identify the process responsible for the decline in exposure concentration preliminary tests are suggested to assess the stability of the test substance. the result of the preliminary stability study (which is carried out in the absence of test organisms) will then be used for selecting the exposure regime. the exposure regime can be static (the test medium is not replaced for the duration of the experiment), semi-static (the test medium is periodically replaced on a batch basis), intermittent flow-through (the test medium is replaced over set periods during the exposure) and continuous flow-through (the test medium is continually replaced). for many industrial effluents biodegradation is perhaps the most important process which affects the environmental concentration of the test substance. biodegradation is a specific process as not only appropriate abiotic conditions are necessary but also a competent bacterial population should be established. the ability of cultures of common bacteria such as pseudomonas spp~ flavobacterium spp. or aerobacter spp. to degrade a variety of test chemicals has been extensively examined (6]. however, it was soon demonstrated that mixed cultures of natural origin (lakes. rivers. sewage. etc.) were even more capable to degrade the test compounds. however, present oecd tests [7] for ready biodegradability are not designed to predict in detail the fate and behaviour of a toxicant in a specific compartment of the aquatic environment. this is partly due to the fact that oecd tests are carried out at much higher concentrations than one can expect to occur in real-world ecosystems. moreover, several factors appear to influence the biodegradation of xenobiotic pollutants. therefore although some methods have been described to evaluate the biodegradability of chemicals in natural freshwaters [8], no relevant oecd test guidelines have been proposed so far. instead, simulation tests exist such as the stream model of shimp et al. [9] or the die-away test of anderson et al. [10] in wet testing basically two types of question can be answered: 1. what is the absolute toxicity of the effluent? 2. what is the actual toxicity of the effluent in the receiving system? in the former case, standard synthetic or acceptable natural dilution water is used that matches the organism culture water. in the second case, the local receiving water is suggested for dilution water. the use of receiving water increases the environmental relevance of the test simulating actual effluent/receiving water system. however, it might occur that receiving water is also toxic, which provides inadequate conditions for wet testing. our basic aim was to test how degradation processes, especially biodegradation affect the toxicity of an industrial effluent, and to predict what changes in toxicity can be expected in natural freshwaters. test series was designed in a way that it is in concordance with usep a wet methods but simultaneously direct toxicity is measured. materials and methods bioluminescence inhibition of vibrio fischeri bioluminescence is a rapid indicator of the metabolic status and of the viability of the cell. the enzyme involved in the process is bacterial luciferase. a toxic substance will cause changes in some cellular structures or functions such as the electron transport system, cytoplasmic constituents or the cell membrane, which are directly reflected in a decrease in bioluminescence. the use of the bioluminescent bacterium vibrio fischeri (or other bacteria) has several advantages comparing to conventional toxicity testing. the test is rapid and causes no ethical problems. for our tests the toxaiert ®100 luminometer was used, developed by merck. this test is in compliance with isojen/din 11348. the test is highly recommended for industrial waste waters and effluents [ 11]. test design a textile industrial waste water was used as test substance. the wet method manuals [12, 13] suggest a dilution series of 6.25 %, 12.5 %, 25 %, 50% and 100 % effluent but preliminary toxicity tests showed that the . substance was highly toxic in high concentration therefore a 25 % initial sample concentration was used throughout the tests. selection of the proper dilution water was of crucial importance. in order to simulate the behaviour of the test substance in natural ecosystems the water used for diluting the test substance was collected in the kis-balaton water protection system. in fact this water served as inoculum. this inoculum contained a mixed (aerob­ anaerob) culture, due to the natural characteristics of the water protection system. the diluted sample (50% waste water+ 50% pure water) was kept in an incubator in darkness (thus no photodegradation could take place), at 24 °c. microtox tests were carried out at the following intervals: dayo sample collection day41 assay 9 day 1 assay 1 day73 assay 10 day4 assay 2 day76 assay 11 day6 assay 3 day78 assay 12 day8 assay 4 day80 assay 13 day 15 assay 5 day87 assay 14 day28 assay 6 day 100 assay 15 day32 assay 7 day 104 assay 16 day36 assay 8 analysis sample preparation in order to provide optimal conditions for the test ph of the samples was adjusted to ph 7.0. preparation of liquid dried bacteria reagent and test suspension the reconstitution solution and the liquid dried bacteria are kept at -18 °c. first the reconstitution solution was thawed and shaken well to ensure sufficient dissolved oxygen. the toxalert ®100 luminometer has a separate bloc~ for the liquid dried reagent vials ensuring the reqmred temperature of 15 °c. 12.5 ml of reconstitution solution was added into the microquant vial and kept in the liquid dried reagent block for at least 15 minutes. one vial of liquid dried bacteria was removed from t~e ~reez~r (it is also kept at -18 °c) and placed in the hqmd dried bacteria well for 2 minutes. than 0.5 ml r~onstitution solution was pipetted into the liquid dned bacteria vial and mixed. after 15 minutes the bacteria suspension was transferred back to the microquant vial was used as test suspension. 273 conducting measurements firstly, a pre-incubation time of 15 minutes was set. ?uring this time 500 j.!l of test suspension was pipetted mto all cuvettes, including control cuvettes as well. shortly before contact time begins (before timer reaches zero) cuvette ai was placed into the turret. at contact time t = 0 rlu (relative luminescence unit) of the solu~ion was ~easured. after measurement 500 }ll of sodmm chlonde solution was added to cuvette al and gently mixed by hand. as the intercuvette time was set at 30 seconds, the same procedure followed for cuvette b 1 (the other control cuvette) at t = 30 sec. at t = 60 and 90 sec. a slightly different procedure was followed for sample cuvettes. in their case after measuring rlu 500 }ll of the diluted sample was added and gently mixed by hand. exposure time ended at t = 30 mins. than rlu of all cuvettes was measured again, in the same sequence, also keeping an intercuvette time of 30 sees. calculation of results the toxalert ®100 luminometer calculates all values automatically. firstly the fkt correction factor is calculated from the measured luminescence (eq.( 1 )). fkt= lkt/lo (t = 30 min in our test) (1) where fkt the correction factor for the contact time lkt luminescence intensity in the control sample measured in rlu (relative luminescence unitsy. after the contact time 1o luminescence intensity of the control test suspension. using the correction factor, than the corrected value of for every test sample cuvettes are calculated (eq.(2)). where fkt mean of fkt of the two control samples lo luminescence intensity of the control test suspension let corrected value of for test sample cuvettes immediately before the addition of the test sample then the inhibitory effect lit of the test sample was calculated (eq.(3)). lit= [oct-in/ lct)j x 100 (3) where ht the inhibitory effect of the test sample after the contact time. in% let corrected value for test sample cuvettes immediately before the addition of the test sample in luminescence intensity of the test sample after the contact time. in rlu. 274 table i results of toxicity tests made using toxalert. day 0 represents the day of sample collection days 4 6 8 15 28 32 36 41 73 76 78 80 87 100 104 inhib aver. 34,7 44,05 45,5 55,6 42,6 46,6 46,3 80,9 74,7 63,4 81,95 73,2 71,45 68,75 68,5 66,95 days fig. i degradation expressed as changes in ecotoxicity results and conclusions table 1 and fig. i summarize the results of the toxicity tests. as the trend shows, there was a significant decrease in the toxicity of the samples between day 1 and day 104, as the average bioluminescence inhibition shows. the results have proved our expectations, as far as the whole effluent toxicity changes can be precisely followed by microtox test. it was possible to assess how toxicity of the selected industrial effluent chancres over • 0 ttme caused by biodegradation. in our case the classical wet testing was combined with a chronic test for degradability. degradation can be resulted by various physical, chemical and biological processes. in the present examination the causes are unknown, the decline in exposure concentration can be of any origin including both inorganic and biological processes. however, they are not specifically important in this case. as the basic goal of the test was to determine what risk the effluent might pose to the receiving water. the question arises, what components of the effluents may be responsible for the toxicity. all these constituents are known as environmental toxicants. in this respect there is an interesting result: in spite of the complex composition of the effluent tested the decrease in toxicity ~ evidently being in strong correlation with the degradation can be approximated by a simple regression line. the existence of such a simple mathematical function suggests that the main and limiting component of the degradation mieht be determined by not more than one xenobiotic substance. this material must have a high initial toxicity and a probably slow inherent biodegradation indicated by the relatively high inhibition measured on the lolst day. . in the .futur~ the test system wm be characterised by usmg var1ous effluents and receiving waters. it should also be examined what microorganisms are responsible for the biodegradation. references 1. usep a: method guidance and recommendations for whole effluent toxicity (wet) testing ( 40 cfr part 136). us environmental protection agency, office of water, epa 821-b-00-004, 2000 2. peakall d. b. and tucker r. k.: extrapolation from single species studies to populations, communities and ecosystems. pp. 611-636. in v. b. vouk, g. c. butler, d. g. hoel and d. b. peakall (eds.), methods for estimating risk of chemical injury: human and non-human biota and ecosystems, scope 26. john wiley & sons, new york, 1985 3. kiss i., kovats n. and szalay t.: acta biologica hungarica, 2001, 52(1), 179-185 4. tucker r. k. and lietzke j. s.: pharmac. ther., 1979, 6, 167-220 5. samiullah y.: prediction of the environmental fate of chemicals. elsevier applied science, london,l990 6. payne w. j., wiebe w. j. and christian r. r.: bioscience, 1970, 20(15), 862-865 7. oecd (organisation for economic co-operation and development): detailed review paper on biodegradability testing. environment monograph no. 98,1995 8. means j. l. and anderson s. j.: water air soil poll., 1981, 16, 301-315 9. shimp r. j., schwab b. s. and larson r. j.: environ. toxicol. chern., 1989, 8, 723-730 10. anderson d. j., day m. j., russell n. j. and white g. f.: appl. environ. microbiol., 1990, 56(3), 758-763 . 11. pedersen f., damborg a. and kristensen p.: guidance document for risk assessment of industrial waste water. miljoprojekt nr. 298. ministry of environment and energy, denmark, 1995 12. usepa: methods for measuring the acute toxicity of effluents and receiving waters to freshwater and marine organisms, 4th ed., epa/600/490/~27f. u.s. environmental protection agency, environmental monitoring systems laboratory (currently, national exposure research laboratory}, cincinnati, oh., 1993 13. usepa: short-term methods for estimating the chronic toxicity of effluents and receivina waters to freshwater organisms. 3m ed., ep n60014911~2. u.s. environmental protection agency, environmental monitoring systems laboratory (currently. national exposure research laboratory)t cincinnati, oh .• 1994 page 273 page 274 page 275 page 276 hungarian journal of industry and chemistry vol. 48(1) pp. 95–107 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-15 brownian dynamics simulation of chain formation in electrorheological fluids dávid fertig*1, dezső boda1, and istván szalai2,3 1department of physical chemistry, university of pannonia, egyetem u. 10, veszprém, 8200, hungary 2institute of physics and mechatronics, university of pannonia, egyetem u. 10, veszprém, 8200, hungary 3institute of mechatronics engineering and research, university of pannonia, gasparich márk u. 18/a, zalaegerszeg, 8900, hungary brownian dynamics (bd) simulations based on a novel langevin integrator algorithm are used to simulate the dynamics of chain formation in electrorheological (er) fluids that are non-conducting solid particles suspended in a liquid that has a dielectric constant different from that of the er particles. an external electric field induces polarization charge distributions on the spheres’ surfaces that can be modeled as point dipoles in the centers of the spheres. the interaction of these aligned dipoles leads to formation of chains and other aggregates in the er fluid. in this work, we introduce our methodology and report results for various quantities characterizing the structure of the er system as obtained with bd simulations. these quantities include the potential energy, diffusion constant, average chain length, chain length distributions, and pair correlation functions. their behavior as a function of time is presented as the electric field is switched on. the properties of the er fluid change considerably making this system a potential basic material of many applications. keywords: electrorheological fluids, chain formation, brownian dynamics 1. introduction electrorheological (er) fluids are [1] suspensions of fine non-conducting solid particles in an electrically insulating liquid. if the particles, imagined as closely spherical, have a dielectric constant that is different from that of the solvent, the arising dielectric boundaries respond to an applied electric field. this dielectric response is the polarization of the spheres resulting in a polarization charge distribution whose dominant component in the multipole expansion is the dipole moment. the interactions of these dipoles then lead to a structural change in the er fluid known as the er response. this structural change is basically a formation of chains and other forms of clusters as the polarized spheres are linked together into head-to-tail positions. this structural phase transition is reversible and relatively fast. this structural change results in a dramatic change in the physical properties of the er fluid of which the most important is viscosity. this externally controllable, fast and reversible change in viscosity makes er fluids a kind of a smart material, a central component of devices, such as brakes, clutches, dampers, and valves [2,3]. such devices have crucial importance in the industry of various fields. *correspondence: fertig.david92@gmail.com the continuously shrinking size of devices resulted in the development of nanotechnology. understanding the molecular mechanisms behind the workings of nanodevices is especially important because better understanding of microscopic mechanisms can lead to novel designs. er devices are also based on microscopic mechanisms leading to an emergent macroscopic pattern. no wonder that many modeling studies [4–22] aimed at investigating the microscopic processes behind chain formation and corresponding changes in measurable physical properties. the properties of the er fluid in the absence of an applied electric field have been investigated by heyes and melrose [23]. this means the investigation of the core potential that is either the lennard-jones (lj) fluid or its cut-and-shifted version that is a purely repulsive potential. it has been demonstrated that the repulsive version reproduces experimental behavior better [4]. cluster formation has been investigated via cluster size distribution [4, 9, 11, 12, 20, 22], order parameters [12–15,19], mean square displacement and diffusion constant [4, 6, 12], pair distribution functions [6, 12], and relaxation times [5, 11, 12, 21]. in particular, cao et al. [21] identified relaxation times corresponding to various subprocesses such as initial aggregation, chain formation, and column formation. identifying these subprocesses is https://doi.org/10.33927/hjic-2020-15 mailto:fertig.david92@gmail.com 96 fertig, boda, and szalai e 0 p ε in ε out + + + + + σ figure 1: sketch of an er particle in an external electric field, e0. the dielectric constant inside the sphere is εin, while outside the sphere is εout. the surface charge distribution, σ(r), induced on the dielectric boundary (eq. 1) can be approximated by a point dipole, p, in the center of the sphere (eq. 2). also our long-term goal. it is also our intention to simulate the er system in the presence of shear as several authors did [5, 6, 10, 15, 21]. these authors investigated shear stress, various terms of viscosity, oscillatory strain, and dependence on strain rate. in this paper, we do not apply stress, because our main interest is to study the dynamics of the formation of chains with a newly developed simulation package based on a novel langevin integrator [24–26] as opposed to most studies from the 1990s that used the overdamped limit. we intend to test the program on the er fluid in the absence and presence of an applied electric field and to follow the dynamics of chain formation when the field is switched on. we characterize this dynamics by plotting energy, mean square displacement, diffusion constant, average chain length, chain length distributions, and radial distribution functions as functions of time. we use reduced units in this study (see section 4) that are closely related to various parameters used in the literature. these parameters characterize the relations of various effects in the er fluid. these effects are the polarization (dipole-dipole), thermal, and viscous forces. the relation of the polarization and thermal forces is often denoted by λ and it practically corresponds to the square of the reduced dipole moment used in this study. it expresses the relation of the ordering effect of electrostatic forces and the disordering effect of thermal motion. the relation of the viscous force to the electrostatic force is called the mason number (ma). many authors plot the characteristic physical quantities as functions of the mason number [5,10,15]. the relation of the viscous and the electrostatic forces is called the péclet number. . 2. model: the polarizable dielectric sphere we model the er fluid as dielectric spheres of dielectric constant εin inside the sphere immersed in a fluid of dielectric constant εout (fig. 1). the radius of the spheres is r, while their diameter is d = 2r. when a constant electric field, e0 is applied to this system (in the z direction), the dielectric boundary on the sphere’s surface becomes 0 π/8 π/4 3π/8 π/2 θ -0.004 -0.002 0 0.002 in te rm o le c u la r p o te n ti a l permanent dipoles polarizable dipoles surface charge e 0 e 0 e 0 θ figure 2: interaction potential (arbitrary unit) between two dipoles at r = 1.25d distance from each other at different mutual positions characterized by angle θ that is the angle between e0 and rij . the potential is computed from the interaction of the charge distributions in eq. 1 using the icc method (symbols), from the interactions of the permanent point dipoles induced only by e0 (eq. 2) (dashed line), and from the interaction of the polarizable dipoles when the sphere can be polarized by the electric field of other dipoles too (solid line). polarized. the polarization charge density is σ(θ) = 3ε0 ( εin − εout εin + 2εout ) e0 cos θ, (1) where e0 = |e0|, θ is the angle between the point of on the surface and the z-axis, and ε0 is the permittivity of vacuum. as it was discussed in our previous publication [30], the effect of this surface charge distribution can be approximated with an ideal point dipole placed in the center of the sphere computed as [31] p = 4πε0 ( εin − εout εin + 2εout ) r3e0. (2) in that paper, we showed that the point dipole model is a good approximation to the exact solution obtained from the polarization charge using the induced charge computation method [32]. the agreement is better if the spheres are assumed to be polarizable by the electric fields of all the other particles, but even if it is assumed that an er particle is polarized only by e0, the agreement is reasonable (fig 2). the latter assumption means that the er particles carry only the permanent dipoles of eq. 2 that always point into the z-direction. we further assume that the characteristic time of the rearrangement of the surface charge as the particles move is much smaller than the characteristic time of the rotation of the particles. this means that the p dipole always points into the z direction even if the sphere rotates, because the induced charges (that chiefly correspond to polarization of solvent molecules around the sphere) always have enough time to rearrange themselves according to the applied field, e0. the potential produced by a dipole pj (that is at rj) hungarian journal of industry and chemistry brownian dynamics simulation of chain formation 97 at the position ri of another dipole pi is φj(ri) = 1 4πε0 pj · rij r3 ij , (3) where rij = ri − rj and rij = |rij |. the electric field is ej(ri) = 1 4πε0 3nij(nij · pj)− pj r3 ij , (4) where nij = rij/rij . the interaction potential between the two dipoles is udd ij (rij ,pi,pj) = −pi ·ej(ri) = = − 1 4πε0 3(nij · pi)(nij · pj)− pi · pj r3 ij , (5) while the force exerted on dipole pi by dipole pj is fdd ij (rij ,pi,pj) = −(pi · ∇i)ej(ri) = = 1 4πε0 1 r4 ij {3 [pi(nij · pj) + pj(nij · pi)+ + nij(pi · pj)]− 15nij(nij · pi)(nij · pj)} . (6) note that the forms of these equations are simplified when all the dipoles of magnitude p are aligned in the z direction: udd ij (rij , θ) = − p2 4πε0 3 cos2 θ − 1 r3 ij , (7) and fdd(rij , θ) = 3p2 4πε0 (2 cos θ)k + (1− 5 cos2 θ)nij r4 ij , (8) where k is the unit vector in the direction of the z-axis and θ is the angle between k and nij . there is also a torque acting on the dipole, but because the characteristic time of polarization charge formation is much smaller than the characteristic time of the rotation of the sphere, the rearrangement of surface charges is considered instantaneous without inertia. the torque, therefore, has been neglected. the full interaction potential between two er particles consists of this dipole-dipole (dd) term and a shortrange core potential that defines the finite size of the particles: uij = udd ij + uwca ij . (9) for the core potential, we use the cut & shifted lj potential also known as the weeks-chandler-anderson (wca) potential that is uwca ij (rij) = { ulj ij (rij) + ulj ij (rc) if rij < rc 0 if rij > rc , (10) where ulj ij (rij) = 4εlj [( d rij )12 − ( d rij )6 ] (11) is the lj potential. the wca force is fwca ij (rij) = { flj ij (rij) if rij < rc 0 if rij > rc , (12) where flj ij (rij) = 24εlj [ 2 ( d rij )12 − ( d rij )6 ] rij r2 ij (13) is the lj force. in these equations the cutoff distance is rc = 21/6d that is at the minimum of the lj potential, so this potential is a smooth repulsive core potential used widely in dynamical simulations of large spherical particles. 3. method: brownian dynamics simulation when it comes to simulating the trajectories of particles in the phase space interacting with each other via a systematic force, fij (like those given in eqs. 6 and 12), we use newton’s equation of motion in an md simulation. in this case, the particles move in vacuum and the only forces that we take into account are those exerted by the particles themselves (plus, possibly, external forces). when it comes to simulating the trajectories of particles immersed in a solvent, we use langevin’s equations of motion [33] m dvi(t) dt = fi (ri(t))−mγvi(t) + ri(t), (14) where ri, vi, m, and γ are the position, the velocity, the mass, and the friction coefficient of particle i, respectively. the mass and the friction coefficient are assumed to be the same for every particle, but, in general, they can depend on i. the force has three components. in addition to the systematic force, fi (ri(t)) = ∑ j 6=i fij , there are the frictional force,−mγvi(t), and the random force, ri(t). the former describes friction, while the latter describes random collisions with surrounding solvent molecules. the two additional forces represent the interactions with the heat bath and are coupled through the friction coefficient: 〈r(t)〉 = 0 (15) 〈r(t) ·r(t′)〉 = 2ktmγδ(t− t′) (16) this is also known as the fluctuation–dissipation theorem. the langevin equation is a stochastic differential equation that is solved numerically and, therefore, approximately. several algorithms exist in the literature for its integration [34–37]. here, we employ the simple and effective algorithm of grønbech-jensen and farago (gjf). the original version [24] had a verlet-type formalism. recent modifications by farago (gjf-f) [25] and grønbech jensen and 48(1) pp. 95–107 (2020) 98 fertig, boda, and szalai table 1: reduced quantities quantity symbol unit quantity reduced quantity time t t0 = d √ m kt t∗ = t d √ kt m distance r r0 = d r∗ = r d density ρ ρ0 = 1 d3 ρ∗ = ρd3 velocity v v0 = d t0 = √ kt m v∗ = v √ m kt energy u u0 = kt u∗ = u kt force f f0 = kt d f ∗ = fd kt dipole moment p p0 = √ 4πε0ktd3 p∗ = p√ 4πε0ktd3 friction coefficient γ γ0 = 1 t0 = 1 d √ kt m γ∗ = γt0 = γd √ m kt . grønbech-jensen (gjf-2gj) [26] have a leap-frog formalism using velocities in the half time steps. these modifications have the advantage that they accurately sample both kinetic and configurational properties even for large time steps within the stability limit. the authors demonstrated the efficiency of their algorithms for systems under linear and harmonic potentials. we use the gjf-2gj version in this work that reads as vn+ 1 2 = avn− 1 2 + √ b∆t m fn + √ b 2m ( rn −rn+1 ) (17) rn+1 = rn + √ bvn+ 1 2 ∆t, (18) where rn = r(tn) is any position coordinate of any particle, vn = v(tn) is any velocity coordinate of any particle, a = 1− γ∆t/2 1 + γ∆t/2 , (19) b = 1 1 + γ∆t/2 , (20) ∆t is the time step, tn+ 1 2 = tn+ ∆t 2 , and tn− 1 2 = tn−∆t 2 . the discrete time noise rn+1 = ∫ tn+1 tn r(t′)dt′ (21) is a random gaussian number with properties 〈rn〉 = 0 (22) and 〈rmrn〉 = 2ktγm∆tδmn (23) with δmn being the kronecker-delta. 4. scaling and reduced units competing effects exist in an er system. the dd interactions have an ordering effect. the head-to-tail position, in which the dipoles are aligned along nij (θ = 0) at contact (rij = d), has a minimum energy with the value u0 = − 1 4πε0 2p2 d3 . (24) the magnitude of the force in this position is f0 = 3p2 4πε0d4 . (25) the brownian motion has a disordering effect that expresses the coupling to a thermostat of temperature t and friction with the surrounding solvent with viscosity η. it is usual to characterize the disordering effect of the thermal motion energetically by kt . it is also usual to use reduced units in calculations. in reduced units our quantities are expressed as dimensionless numbers obtained by dividing a quantity in a physical unit by a unit quantity in the same unit, t∗ = t/t0, for example. reduced quantities are useful not only because their values are close to 1, so it is easier to work with them, but also because they express relations between quantities in the numerator and the denominator, a kind of scaling [5]. there are different ways of defining reduced units. we use the convention of building the unit quantities from the mass, m, the particle diameter, d, and kt . thus, the reduced units collected in table 1 can be defined. when we perform simulations in reduced units, these quantities can be chosen freely to see how the system behaves at the different combinations of the reduced parameters. how the reduced parameters are related to real-life physical parameters can be computed independently (see section 5). hungarian journal of industry and chemistry brownian dynamics simulation of chain formation 99 table 2: experimental parameters [38, 39]. εin 4 εout 2.7 η (pa s) 0.5 e0 (v/m) 106 t (k) 300 ρout (kg/m3) 2650 the reduced quantities collected in table 1 are determined by the real physical parameters of the system: the temperature, t , the mass density of the material of the er particle, ρin, the diameter of the er particle, d, the dielectric constant of the er particle, εin, the dielectric constant of the solvent, εout, the viscosity of the solvent, η, and the strength of the applied electric field, e0. for a specific er fluid, these variables are tabulated in table 2. this specific example is used because one of the coauthors (i.sz.) published experimental results for this system [38, 39]. a wide variety of er fluids exists, however. the mass of a particle is computed asm = ρinπd 3/6, so it scales with d3. the dipole moment of a particle is given by eq. 2 that shows that p scales with d3. an important parameter is the ratio of the dipolar energy and the thermal energy that is expressed by the square of the reduced dipole moment: (p∗)2 = πε0e 2 0 4kt ( εin − εout εin + 2εout )2 d3 = kd3 (26) that scales with d3. if p∗ is large, the dipolar interactions are strong enough to induce chain formation. if p∗ is too large, the chains freeze, and the er particles solidify (note that the fluid itself does not solidify). if p∗ is small, thermal motion prevents chain formation and/or breaks the chains. the friction coefficient can be computed from stokes’ law as γ = 3πηd m = 18η ρin d−2. (27) so it scales with d−2. the value of γ∗ describes the strength of the coupling with the solvent and it scales with d1/2. if γ∗ is large, friction and the disordering effect of the random force are strong. the diffusivity of the particles in the fluid, therefore, will be smaller. the diffusion constant in the high coupling limit can be expressed by einstein’s relation: d = kt mγ , (28) or, in reduced units,d∗ = 1/γ∗. if γ∗ → 0, the frictional and the random forces vanish, and the langevin equation goes into the newton equation. the particles move in vacuum without a thermostat; this practically corresponds to an md simulation in the microcanonical ensemble. if γ∗ is small, we talk about an md simulation with a langevin thermostat. in the case of the er fluids, we are in the regime of large γ∗. as we will see, γ∗ is in the order of 104 − 106. in this case, our concern is how to make the simulation efficient in order to collect enough information about the dynamics of the system in a reasonable amount of computer time. the parameter with which we can tune the speed of sampling is the time step, ∆t∗. this parameter is also subject of optimization. if ∆t∗ is too small, the simulation will evolve slowly at the price of expensive computation time. if ∆t∗ is too large, the spheres might overlap and the repulsive core force (eq. 12) becomes so large that the particles shoot apart resulting in unphysical movements. this leads to instabilities in solving the langevin equation. various solutions have been proposed in the literature to cope with this problem. if the langevin integration algorithm allows changing the time step during the simulation, it is a reasonable suggestion to reduce the time step if we observe problems (generally, big jumps) in the movements of particles [6,13]. displacements, velocities, or forces can be monitored for unusual events. berti et al. [40] used a uniform time step, while their solution for the jump-problem was that they went back the necessary number of time steps and started again with a different random number seed for the random force. if such a problem is rare, this can be a good solution, because the computational cost of going back a couple of times is balanced by the large time step used in the simulation. they used their simulations for ion channels whose selectivity filter is a high-density region, so overlaps can occur. chain formation in the er fluid also brings particles close to each other, so we need to be careful with large time steps. we can estimate in advance the danger of overlap and judge the optimization between slow simulations (small ∆t) and jumping particles (large ∆t). we can introduce the average distance that a particle moves in a time step with the average thermal velocity, v̄ = √ 3kt/m. let us introduce ∆s∗ = v̄∆t d = √ 3∆t∗, (29) that characterizes the average distance with respect to the particle size. this is proportional to ∆t∗. this reduced distance, and, consequently, the reduced time step should be smaller than 1. this imposes a strict limit to the time step. the product γ∆t = γ∗∆t∗ characterizes how close we are to the overdamped limit. basically, at a fixed γ∗, we can increase ∆t∗ up to the threshold limit to save computer time at the price of losing information about dynamics due to coarser time resolution. the last parameter that we can choose relatively freely is the energy parameter of the lj potential, εlj, see eqs. 10–12. changing this parameter practically changes the effective diameter of the particles. fig. 3 shows the curves of the core potential (eq. 10) for varying values of εlj. smaller values of εlj allows for the particles to 48(1) pp. 95–107 (2020) 100 fertig, boda, and szalai 0.4 0.6 0.8 1 1.2 r/d 0 2 4 6 8 10 u c o re (r )/ k t ε lj =1kt ε lj =10 -1 kt ε lj =10 -2 kt ε lj =10 -3 kt ε lj =10 -4 kt ε lj =10 -5 kt figure 3: the core potential, uwca(r), for varying energy parameters, εlj. approach each other closer: the r/d values at which the core potential reaches large values in kt are smaller for smaller εlj values. the effective diameter, deff , therefore decreases with decreasing εlj. this results in larger dipole-dipole interactions at contact positions that, in turn, increases the weight of the dipolar interactions with respect to the thermal noise. using smaller εlj, and, consequently, smaller deff , however, makes our parameter dwith which we reduced every variable meaningless. we would like the diameter used in the reduced quantities to be the real diameter of the spheres. for this reason, we do not change εlj and fix it at the value of kt . 5. relating reduced units to real er fluids to connect to a real system, we consider the er fluid studied by horváth and szalai [38, 39] experimentally. the experimental parameters are collected in table 2. note that the diameters used in these studies were quite small in order to prevent sedimentation. diameters used in other er fluids are larger reaching 1 µm. we change two parameters in this analysis, the particle diameter, d, and the reduced time step, ∆t∗. according to eq. 2, the dipole moment can be written as p = kd3, where k = 1.922 × 10−6 cm−2 for the parameters in table 2. table 3 contains various quantities computed for different values of d. it is seen that p∗ falls into the regime simulated in this study around d = 1 µm. for diameters below 100 nm, at least, at the present value of k, the reduced dipole moment is too weak to counterbalance the thermal motion and to produce considerable chain formation. the reduced friction coefficient also depends on d; it increases with d1/2. it is in the regime of γ∗ ≈ 105−106. this looks simulatable, though it will require considerable computer time, because ∆t∗ is limited. the parameter ∆s∗ is the same for every diameter; it practically equivalent to ∆t∗. to look at the effect of ∆t∗, we show the same data for varying ∆t∗ at a fixed d (100 nm) in table 4. table 3: change of various variables as the diameter of spheres is changed from 10 to 10,000 nm for time step ∆t∗ = 0.001. d (nm) 10 100 1,000 10,000 ∆t∗ 0.001 m (kg) 1.387e-21 1.387e-18 1.387e-15 1.387e-12 t0 (s) 5.788e-09 1.830e-06 5.788e-04 1.830e-01 v̄ (m/s) 2.993e+00 9.463e-02 2.993e-03 9.463e-05 p (cm) 1.922e-30 1.922e-27 1.922e-24 1.922e-21 p∗ 0.00283 0.0896 2.833 89.60 ∆t (s) 5.788e-12 1.830e-09 5.788e-07 1.830e-04 ∆s∗ 0.00173 0.00173 0.00173 0.00173 γ (1/s) 3.396e+13 3.396e+11 3.396e+09 3.396e+07 γ∗ 1.966e+05 6.216e+05 1.966e+06 6.216e+06 γ∆t 1.966e+02 6.216e+02 1.966e+03 6.216e+04 table 4: change of various variables as the reduced time step ∆t∗ is changed from 0.0001 to 0.1 for diameter d = 100 nm. d (nm) 100 ∆t∗ 0.0001 0.001 0.01 0.1 m (kg) 1.387e-18 1.387e-18 1.387e-18 1.387e-18 t0 (s) 1.830e-06 1.830e-06 1.830e-06 1.830e-06 v̄ (m/s) 9.463e-02 9.463e-02 9.463e-02 9.463e-02 p (cm) 1.922e-27 1.922e-27 1.922e-27 1.922e-27 p∗ 0.0896 0.0896 0.0896 0.0896 ∆t 1.830e-10 1.830e-09 1.830e-08 1.830e-07 ∆s∗ 0.000173 0.00173 0.0173 0.173 γ (1/s) 3.396e+11 3.396e+11 3.396e+11 3.396e+11 γ∗ 6.216e+05 6.216e+05 6.216e+05 6.216e+05 γ∆t 6.216e+01 6.216e+02 6.216e+03 6.216e+04 6. results and discussion in this study, we use a relatively small number of particles (n = 128) in order to save on computer time and be able to explore a wide range of parameters in reduced units. we also fix the packing fraction expressed in term of the reduced density at ρ∗ = 0.05. at these values the width of the simulation cell is l = 13.68 d. the computer code has been written (in fortran) in a way that we perform m0 time steps in the absence of applied electric field (e0 = 0), and me time steps in the presence of it. that way, we can study the dynamics of chain formation after the electric field is switched on. to improve statistics, we can perform several of this mc = m0 +me cycles and average over the cycles. when we start a cycle over, we can choose between two options. we can either continue the simulation from the previous phase state point (configurations and velocities) only without dipoles, or we can restart from a freshly generated initial configuration. in this work, we choose the second option. this choice ensures that we start the simulation with nonzero e0 in a completely disordered state without chains. the first option makes it possible to study the dynamics of the deconstruction of the chains. hungarian journal of industry and chemistry brownian dynamics simulation of chain formation 101 figure 4: typical snapshot of a simulation from the front (perpendicular to the z axis, left panel) and top (parallel to the z axis, right panel) for a state when chains are formed. 6.1 quantities studied as the chains are being formed, certain physical quantities change, so they directly or indirectly characterize chain formation quantitatively. in chains, particles are aligned into head-to-tail position along the z-axis as shown in fig. 4. there are longer and shorter chains and the distribution of chains of various lengths changes continuously as the simulation evolves. since the head-to-tail position is the lowest energy configuration of the er spheres (see fig. 2 and eqs. 24 and 25), the average one-particle dipole-dipole energy, 〈udd〉b/kt , is a good indicator of chain formation. as it turns out, it is the best converging indicator. by average, we mean average over a block in the simulation, denoted by 〈. . . 〉b. the length of a block (mb is the number of time steps in a block), again, is a subject of optimization. if a block is too short, the physical quantities averaged over a block will have bad statistics. if a block is too long, we loose information about the dynamics of the system. diffusion constant when the particles are “frozen” into chains, their mobility decreases. chains are frozen only at very large dipole moments, when even columnar structures are formed. in a moderate range of (p∗)2, chains move around, break apart, and rejoin, see the video clip at https://youtu.be/owxsuz6p0w4. a snapshot of this video clip is shown in fig. 5. the isotropic diffusion constant is computed as the slope of the mean square displacement (msd) as a function of time: db = 〈r2(t)〉b 2tb , (30) where 〈. . . 〉b denotes an average over time steps in a block and particles and tb is the length of the block in time. the exact equilibrium diffusion constant is obtained in the limit of tb →∞. here, we must be satisfied with an approximate value of db obtained over a block of limited length. fig. 6 shows the msd as a function of t∗ for six equidistantly chosen blocks. in this particular case, γ∗ = 5000, so the slope is d∗ = msd/t∗b ≈ 0.0002 for the wca fluid as figure 5: a snapshot of the video clip at https://youtu.be/owxsuz6p0w4. 48(1) pp. 95–107 (2020) https://youtu.be/owxsuz6p0w4 https://youtu.be/owxsuz6p0w4 102 fertig, boda, and szalai 0 200 400 600 800 1000 t* 0 0.05 0.1 0.15 0.2 m s d 1 2 3 4 5 6 figure 6: the mean square displacement for six selected blocks. the blocks are selected in equidistant time periods in way that the first three belong to the e = 0 phase, while the second three belongs to the er phase. parameters: (p∗)2 = 6, γ∗ = 5,000, ∆t∗ = 0.02,mb = 50,000. also expressed by the einstein relation (d∗ = 1/γ∗, eq. 28). here, the time-length of the block is t∗b = ∆t∗mb = 1,000, because ∆t∗ = 0.02 and mb = 50,000. the first three lines are in the e = 0 regime, while the second three lines are in the er regime. the slope apparently is smaller in the er case than in the wca case, but the scattering is large. the sampling can be improved by averaging over cycles, but this does not help on the problem of the diffusion constant being approximate obtained for a too short block. chain length distributions the chain formation can be directly followed by identifying chains in every configuration. if that is done, we can obtain the number of chains, ns, having length s. the average chain length can be computed as l = ∑ s sns∑ s ns . (31) 10000 20000 30000 40000 50000 t* 2 4 6 8 10 a v e ra g e c h a in l e n g th λ e =0.5 λ e =0.7 λ g =1.1 λ g =1.2 figure 7: the trend of the change in the average chain length with various definitions of a chain: energetic with λe = 0.5 and 0.7, geometrical with λg = 1.1 and 1.2. parameters: (p∗)2 = 6, γ∗ = 10,000, ∆t∗ = 0.01, mb = 10,000. 5 10 15 20 chain length 0 1 2 3 4 5 c h a in l e n g th d is tr ib u ti o n 10000 < t* < 250000 25000 < t* < 65000 65000 < t* < 100000 figure 8: chain length distribution averaged over three time intervals at the beginning (10,000 < t∗ < 25,000), in the middle (25,000 < t∗ < 65,000), and at the end (65,000 < t∗ < 100,000) of chain formation. parameters are the same as at fig. 7. this quantity than can be averaged over time steps in a block, so chain formation can be followed by plotting the average chain length, 〈l〉b, as a function of time in steps of t∗b. a chain, however, can be defined in various ways. one simple definition is geometrical. if two particles are closer to each other than a predefined distance: rij < λgd, (32) they are said to be part of the same chain. another definition is energetic. if the dipole-dipole interaction energy is smaller than a predefined threshold: udd ij (rij , θ) < λeu0, (33) then they are said to be part of the same chain, where u0 is the dd interaction energy in the head-to-tail position (eq. 24). fig. 7 shows the increase of the average chain length as a function of time as obtained from different chain definitions and thresholds λe and λg. in general, the trends as shown by the various definitions are the same. the dynamic process of chains breaking up and reforming have the same effect in the cases of the various definitions. this process can be characterized by time constants obtained from fitting exponential functions. these time constants are insensitive to the choice of the chain definition. here, we will use the geometrical definition with the parameter λg = 1.2. the geometrical definition is advantageous, because it can also be used in the absence of an electric field. the average chain length is an informative, but averaged quantity. from the simulations, we have the more detailed ns vs. s chain length distributions that give the average number of chains of different lengths as a function of s. this function varies with time, see the video clip at https://youtu.be/owxsuz6p0w4. to show the dynamics of this function, we average it for three distinct time intervals. the first one refers to the hungarian journal of industry and chemistry https://youtu.be/owxsuz6p0w4 brownian dynamics simulation of chain formation 103 0 200 400 600 800 1000 t* 0 2 4 6 8 10 a v e ra g e c h a in l e n g th 6-12 13-20 210 5 10 15 20 a v e ra g e c h a in l e n g th 2 3 4 5 figure 9: the variation of the number of chains of various lengths in time. top: chains of lengths 2, 3, 4, and 5. bottom: number of chains belonging to the ranges 6−12, 13 − 20, and above 21. parameters are the same as at fig. 7. beginning of the time period in the presence of the field when the chains start forming. in the second, intermediate time interval (25,000 < t∗ < 65,000) longer chains are formed, while in the third time interval (65,000 < t∗ < 100,000), full chains crossing the simulation box are formed. fig. 8 shows these three time-averaged functions. at the beginning, there are many pairs and short chains (black curve). in the intermediate time interval, the number of short chains decreases and longer chains are formed. in the third time interval, a well-defined peak at s = 14 appears that corresponds to the full chains crossing the simulation box of length l = 13.68d. we can get a much better impression of the dynamics of chain formation, if we plot ns as a function of time. because there are too many possible ns numbers to plot, again, we average over certain regions of chain lengths as seen in fig. 9. in the top panel, the behavior of short chains from pairs to s = 5 is shown. the behavior of these chains is qualitatively similar. first, as the electric field is switched on, their numbers increase abruptly, then, as longer chains absorb them, or they fuse into longer chains, their numbers gradually decreases. practically, they behave like reactive intermediates in chemical reactions: their formation is a first necessary step towards the formation of the end products. the number of chains whose lengths are between 6 and 12 (bottom panel) behaves similarly. the curve for the chains whose lengths are between 13 and 20, however, saturates around ns = 4. this means that there are 1 2 3 4 5 6 r* 1 10 r a d ia l d is tr ib u ti o n f u n c ti o n 0 < t* < 10000 10000 < t* < 25000 25000 < t* < 65000 65000 < t* < 100000 figure 10: radial distribution functions averaged over four time intervals in the absence of the electric field (0 < t∗ < 10,000), at the beginning (10,000 < t∗ < 25,000), in the middle (25,000 < t∗ < 65,000), and at the end (65,000 < t∗ < 100,000) of chain formation. parameters are the same as at fig. 7. generally about 4 full chains in the simulation box (this value, of course, depends on system size and packing fraction). they are often accompanied by shorter chains as seen in fig. 4 and the video clip. chains longer than 20 also exist. it can also occur that two chains are stuck together. whether it is a stable, long time-span configuration, depends on the strength of the dipole moment (the electric field, in reality). a particle is attracted to another particle in a chain, if they are aligned in a way that θ = π/4, see fig. 2. this is a relatively weak attraction compared to the head-to-tail position. the chains displace due to thermal motion, so the chains move out of these mutual positions that favors aggregation of chains. if two chains move in a way that the particles get next to each other (θ = π/2), a repulsive force replaces the weak attractive one. so, a strong dipole moment is needed to overcome the thermal motion if we want to see stable columnar aggregations of chains as seen many times in the literature. pair distribution functions as particles aggregate into chains, the structure of the fluid, generally expressed with pair distribution functions, changes. in an anisotropic dipolar fluid, we generally use the series expansion of the pair correlation function of axially symmetric molecules as g(ij) = ∑ nml hmnl(rij)u mnl(ij). (34) this expansion separates distance and angular dependence in such a way that the projections hmnl(rij) depend only on the distance of particles and the projections umnl(ij) are rotational invariants. the projection g(rij) = h000(rij) is the usual radial distribution function (rdf): g(rij) = ∫ g(ij)dωidωj , with u000 = 1, (35) 48(1) pp. 95–107 (2020) 104 fertig, boda, and szalai 0 1 2 3 4 5 6 r* 1 10 100 r d f i n t h e x y p la n e 0 < t* < 10000 10000 < t* < 25000 25000 < t* < 65000 65000 < t* < 100000 figure 11: the xy-plane radial distribution functions averaged over four time intervals as in fig. 10. parameters are the same as at fig. 7. where ωi denotes molecular orientation. in a fluid phase, h000(rij) → 1 when rij → ∞ both in isotropic and anisotropic phases. other projections, called angular correlation functions, can also characterize chain formation, but we will discuss only the rdf in this study. similar to fig. 8, we plot the rdf averaged over the time intervals discussed at the chain length distributions. in addition to those three time intervals, we also consider the time interval 0 < t∗ < 10,000 here, which is the time of the electric field being switched off. fig. 10 shows that the g(r) function behaves like a typical rdf for a dense real gas (ρ∗ = 0.05) in the absence of e0. as the electric field is switched on, however, larger and larger peaks appear as time goes by and longer and longer chains are formed. the peaks appear at every integer multiples of d values that correspond to particles in the chain. a more detailed behavior of g(r) can be followed in the video clip: https://youtu.be/ owxsuz6p0w4. when the chains are formed, they are relatively stable, but they diffuse around in the xy plane. therefore, we also define the rdf in the xy plane to follow how the chains are distributed over the xy plane. we will denote it with gxy(r) and is calculated the same way as the threedimensional rdf. fig. 11 shows these functions averaged over the time periods as in fig. 10. a similar conclusion can be drawn as from that figure except that the first peak now appears at r∗ = 0, where now r = √ ∆x2 + ∆y2. this peak represents particles belonging to the same chain. peaks represent probable distances between chains. the shape of the curve indicates that this er system ((p∗)2 = 6) behaves like a two-dimensional fluid of chains. at a given time (or, in a given block), these series of peaks are absent. snapshots of gxy(r) show where the chains are in a given moment. this can be followed in the video clip: https://youtu.be/owxsuz6p0w4. the gxy(r) function averaged over a longer time period characterizes the behavior of the chains as a twodimensional fluid. -10 -5 0 d ip o le -d ip o le e n e rg y / k t 0.6 0.8 1 1.2 d / d (e = 0 ) 0 5×10 4 1×10 5 2×10 5 2×10 5 5 10 15 a v e ra g e c h a in l e n g th ∆t*=0.005 ∆t*=0.01 ∆t*=0.02 (µ*) 2 =6 γ*=10000 figure 12: the one-particle dipole-dipole energy (top panel), the diffusion constant relative to its value in the absence of e0 (middle panel), and the average chain length (geometrical definition with λg = 1.2, bottom panel) as functions of time using different time steps. parameters: (p∗)2 = 6 and γ∗ = 10,000. themb is changed in a way that ∆t∗ ×mb is constant. 6.2 the effect of time step first, let us consider the effect of the choice of the time step, ∆t∗. fig. 12 shows the variation of the one-particle dipole-dipole energy, the diffusion constant, and the average chain length (geometrical definition with λg = 1.2) for different values of ∆t∗. the length of a block measured in t∗ is kept fixed. it is seen that the measured quantities behave the same way as a function of time, which indicates that the bd simulation algorithm is robust and provides results that are independent of the time step. also, we monitored the temperature computed from the kinetic energy, 〈t 〉 = m〈v2〉/3k, and found that the algorithm reproduces the prescribed temperature very precisely even for this highly anisotropic fluid. this supports the claim of the developers that this algorithm provides a very good langevin thermostat [24–26]. if we change ∆t∗, but we keep mb at the same value, meaning that we change the time length of the block, the dipole-dipole energy and the average chain length are still insensitive to the choice of ∆t∗ (data not shown). the diffusion coefficient, however, changes with the length of the blocks as already discussed above (at fig. 6). this hungarian journal of industry and chemistry https://youtu.be/owxsuz6p0w4 https://youtu.be/owxsuz6p0w4 https://youtu.be/owxsuz6p0w4 brownian dynamics simulation of chain formation 105 -10 -5 0 d ip o le -d ip o le e n e rg y / k t γ*=1000 γ*=2000 γ*=5000 γ*=10000 0.2 0.4 0.6 0.8 1 1.2 d / d (e = 0 ) 0 5×10 4 1×10 5 2×10 5 2×10 5 5 10 15 20 a v e ra g e c h a in l e n g th (µ*) 2 =6 ∆t*=0.01 figure 13: the one-particle dipole-dipole energy (top panel), the diffusion constant relative to its value in the absence of e0 (middle panel), and the average chain length (geometrical definition with λg = 1.2, bottom panel) as functions of time using different friction coefficients. parameters: (p∗)2 = 6 and ∆t∗ = 0.01. means that we have a trade-off between satisfactory sampling over a block and good resolution in time. we do not consider viscosity in this paper; we refer it to future studies. this trade-off will be present in the case of the viscosity (and the stress tensor) as well. it will be even more serious, because the viscosity is even a more poorly converging quantity than the diffusion constant. 6.3 the effect of friction coefficient we fix the dipole moment at (p∗)2 = 6 and the time step at ∆t∗ = 0.01, and change the friction coefficient from γ∗ = 1,000 to 10,000. as discussed in the next section, realistic er fluids have friction coefficients even larger than 10,000, but we refer studying that regime to future publications. as γ∗ is increased, the curves tend to their equilibrium values as e0 is switched on at a lower rate. fitting exponential functions to these curves and identifying processes of different time lengths as parts of the complex process of chain formation will also be the subject of future studies. the change in γ∗ does not influence the value where the energy and the average chain length converge to. -12 -10 -8 -6 -4 -2 0 d ip o le -d ip o le e n e rg y / k t (p*) 2 =2 (p*) 2 =4 (p*) 2 =6 0.5 0.6 0.7 0.8 0.9 1 1.1 d / d (e = 0 ) 0 5×10 4 1×10 5 2×10 5 2×10 5 5 10 15 a v e ra g e c h a in l e n g th ∆t*=0.01γ*=10000 6 6 6 4 4 2 2 2 figure 14: the one-particle dipole-dipole energy (top panel), the diffusion constant relative to its value in the absence of e0 (middle panel), and the average chain length (geometrical definition with λg = 1.2, bottom panel) as functions of time using different dipole moments. parameters: γ∗ = 10,000 and ∆t∗ = 0.01. this figure shows two m0 +me cycles. they converge to the same value but with a different rate. changing friction, however, changes the diffusion constant. fig. 13 shows the diffusion constant relative to its value in the absence of the field computed asd∗ = 1/γ∗. the diffusion constant decreases to a smaller value relative to d∗(e = 0) at smaller values of γ∗. the average chain length shows that smaller γ∗ results in a more wildly fluctuating system than a larger γ∗. the particles diffuse faster and produce larger variations in configurations during a given time period. 6.4 the effect of dipole moment our simulations show (fig. 14) that the quantity that determines the structure of the er fluid is the reduced dipole moment, namely, the relation of the dipole-dipole energy to the thermal energy unit, kt . fig. 14 shows that these quantities converge to their equilibrium values exhibiting a similar trend. the dipole moments studied in this work belong to the regime where the er fluid considered as a collection of chains is still a fluid, namely, it does not solidify. several papers in the literature study solidification of the er 48(1) pp. 95–107 (2020) 106 fertig, boda, and szalai chains [5, 6, 15, 16, 22]. 7. summary in this work, we use a newly developed integrator algorithm to solve the langevin equations and to perform bd simulations for er fluids. our focus was on the methodological development and identifying appropriate system parameters through which we can follow the dynamics of chain formation in the system. the usefulness of computer simulations lies not only in the fact that we can follow the particles’ trajectories, but also in the fact that we can gain a profound amount of information from these trajectories. in the bd simulations, for example, we can follow how the average number of chains of varying lengths changes in time. from that detailed information we can deduce time constants for characteristic processes during chain formation. we intend to dig into those details in subsequent studies. also, we want to examine the behavior of the chains under a 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https://doi.org/10.1119%2f1.18725 https://doi.org/10.1103%2fphysrevb.17.1302 https://doi.org/10.1080%2f00268978200100491 https://doi.org/10.1016%2f0009-2614%2884%2980098-6 https://doi.org/10.1016%2f0009-2614%2884%2980098-6 https://doi.org/10.1093%2famrx%2fabs010 https://doi.org/10.1103%2fphysreve.86.061403 https://doi.org/10.1103%2fphysreve.86.061403 https://doi.org/10.1103%2fphysreve.92.042308 https://doi.org/10.1103%2fphysreve.92.042308 https://doi.org/10.1021/ct4011008 introduction model: the polarizable dielectric sphere method: brownian dynamics simulation scaling and reduced units relating reduced units to real er fluids results and discussion quantities studied the effect of time step the effect of friction coefficient the effect of dipole moment summary hungarian journal of industry and chemistry vol. 47(1) pp. 33–39 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-06 automated labeling process for unknown images in an open-world scenario dávid papp *1 and gábor szűcs1 1department of telecommunications and media informatics, budapest university of technology and economics, magyar tudósok krt. 2., h-1117 budapest, hungary most of the recognition systems presume a controlled, well-defined research setting, where all possible classes that can appear during a test are known a priori. this environment is referred to as the “closed-world” model, while the “open-world” model implies that unknown classes can be incorporated into a recognition algorithm whilst being predicted. therefore, recognition systems that operate in the real world have to deal with these unknown categories. our objective was not only to detect data that originate from categories unseen during training, but to identify similarities between pieces of unknown data and then form new classes by automatically labeling them. our double probability model was extended by an image clustering algorithm, in which kernel k-means was used. a new procedure, namely the cluster classification algorithm for the detection of unknowns and automated labeling, is proposed. these approaches facilitate the transition from openset recognition to an open-world problem. the fisher vector (fv) was used for the mathematical representation of the images and then a support vector machine introduced as a classifier. the measurement of similarity was based on the fv representations. experiments were conducted on the caltech101 and caltech256 datasets of images and the rand index was evaluated over the unknown data. the results showed that our proposed cluster classification algorithm was able to yield almost the same rand index, even though the number of unknown categories increased. keywords: open-world problem, cluster classification, image classification, open-set recognition, image clustering 1. introduction in scenarios in the real world, the size of the available dataset continues to increase, therefore, any machine learning algorithm that operates in such an environment has to be capable of preventing growth. this is especially true in the case of image classification, because the growing dataset of tests can pose many difficulties, e.g. it is possible that some of the test images originate from categories that are unseen during training. recognition systems should detect these unknown images and handle them in an appropriate way. in the rest of the paper the terms "unknown class or category" represent classes or categories that are unseen during training, and “unknown image” denotes images that originate from unknown classes or categories. one way of handling detected unknown images is to measure their similarities and identify new categories. subsequently, these new categories can be added to the set of known classes. based on this, three modules are required to solve such problems in the real world, namely a recognition system equipped with an unknown detector, a labeling process and an incremental learning process. *correspondence: pappd@tmit.bme.hu let us assume that there are k known classes (c1, c2, . . . ck) and u unknown classes in the test set at any given moment, where sk and su denote the sets of known and unknown classes, respectively. few distinguishable cases depend on the value of u : 1. u = 0, 2. u = 1, 3. u > 1. furthermore, a few more cases depend on the amount and type of available information concerning su : (a) training images, (b) set of attributes, (c) number of unknown categories (u ), (d) nothing. the cases that include 1 or a (e.g. 1a, 2a, 1b, 1c) produce the general multiclass classification because all categories are known a priori and positive-negative samples are available for each category during training. when mailto:pappd@tmit.bme.hu 34 papp and szűcs u = 1, the task is only to identify the unknown images because they originate from the same category, therefore, the similarity measurement is unnecessary. in this paper, the situation when u > 1 is considered. as has been mentioned, 3a represents the traditional multiclass classification. 3b+3c is referred to as transfer learning or zero-shot learning [1], whereas according to the literature the case of 3c+3d is known as open set recognition [2,3] or the open-world problem [4]. the former refers to the detection of images that originate from unknown classes, and the latter includes the detection of unknown images and a labeling process to identify new classes, followed by the incremental learning of these new categories. our goal was to tackle the open-world problem as well as develop an algorithm that is able to detect the unknown images and then introduce new classes by automatically labeling the unknown data using unsupervised learning. previously an algorithm referred to as the double probability model (dpm) [5] was proposed, which is suitable as an unknown detector in an open-set environment. there are several works that use a variant of support vector machine (svm) to solve the unknown detection problem, such as the support vector data description [6], one-class svm [7, 8], reject option svm (ro-svm) [9] and the novel weibull-calibrated svm (w-svm) [3]. the latter one was developed to operate under the compact abating probability model, where the probability of class membership decreases (abates) as points move from known data towards unknown space. scheirer et al. claim that w-svm outperforms their previous solutions, namely the 1-vs-set machine training algorithm [2] and the pi-svm [10]. on the other hand, it was shown that dpm outperforms w-svm [5], therefore, in this paper the dpm was used for unknown detection. bendale and boult defined open world recognition and presented the nearest non-outlier algorithm in [4], which adds object categories incrementally while detecting outliers and managing open space risk. they defined open world recognition in the form of three sequential steps: a multiclass open set recognition function with a novelty detector, a labeling process and an incremental learning algorithm. although all of these steps should be automated, they presumed labels were obtained by human labeling. the main objective of our work and this paper is to propose an automated labeling process, the so-called cluster classification (cc). in the next section, the dpm and image clustering methods are reviewed, subsequently, a baseline method is suggested for an open-world problem and finally our proposed algorithm, the cc, is presented. the third section contains experimental results and in the last section our conclusion is discussed. 2. proposed open-world recognition system 2.1 double probability model the dpm [5] is based on the likelihood of a classifier and can be used with any kind of classifier that provides class membership probabilities for the images. as a result, after training the classifier, it is capable of making predictions with reliability values (scores) for each class, i.e. decision vectors. the range of the scores depends on the type of classifier (sometimes it is from 0 to 1 but it can be over any range. only one condition is required, namely the larger score for class ci should represent the higher likelihood of being a member of class ci. in the training set or a validation set, the instances with corresponding scores are investigated in each class. the ground truth is known for this set, so the positive elements can be selected from each class. in order to calculate the conditional probability that a new instance belongs to class ci according to its score, the cumulative distribution function (cdf) of positive scores should be determined, therefore, a reverse cdf of negative scores was created: fpi (x) = p (ci|score < x) , (1) fni (x) = p (¬ci|score > x) , (2) where pi and ni denote the positive and negative elements, respectively. note that the sum of these probabilities is not always equal to 1 (this is not a requirement). a dpm was constructed based on the cdf and reverse cdf functions. during testing, the focus is on the likelihood of the occurrence of an unknown class compared with any of the known classes. before the comparison, the probabilities of the known classes should be calculated. scores (scorei for class ci) for a new instance are obtained as outputs from the original classifier, and based on them the probability of class ci occurring can be expressed as described in pci = fpi (scorei) k∏ j=1,j 6=i fnj (scorej). (3) an expression for the probability of class ck+1 is pck+1 = k∏ j=1 fnj (scorej). (4) if the probability of being a member of class ck+1 is higher than for any other (known) class, then the new instance will be a member of the unknown class. otherwise the prediction is based on the original classifier, i.e. the class with the largest score will be selected. the decision with regard to the prediction of test instance j is formalized as dj = { ck+1 | pck+1 > maxi {pci } argmaxj {scorej} | otherwise (5) hungarian journal of industry and chemistry automated labeling process for unknown images 35 at this point the algorithm is able to make a decision about test data if it originates from an unknown category. also, should it originate from a known category, then based on the output of the classifier its known category can be determined. 2.2 unknown image clustering the image representations were created according to the bag-of-words [11, 12] model. based on their visual content, each image was represented by a single high dimensional vector. in order to create these high-level descriptors, the local attributes of the images were investigated by calculating the low-level scale invariant feature transform (sift) [13] descriptor. next, the gaussian mixture model (gmm) [14–16] was used to define the visual code words and the fisher vectors [17, 18] to encode the low-level descriptors into high-level descriptors based on the visual code words. the fisher vectors were the final representations (image descriptors) of the images and were used as the input data for the clustering algorithm. after the final clusters of fisher vectors were formed, the image clusters could be produced by substituting the fisher vectors for the corresponding images. the basis of our clustering approach is the wellknown k-means clustering algorithm [19] which consists of two important inputs, namely the initial cluster centers and the number of clusters. the k-means clustering algorithm aims to minimize the sum of squared distances from all points to their cluster centers: e = min ( k∑ l=1 ∑ xi∈cl ‖xi − zl‖2 ) , (6) where k denotes the number of clusters, xi represents a member of cluster cl and zl stands for the center of it. however, the fisher vector consists of 65,791 dimensions, and the basic k-means clustering algorithm performs less efficiently when the clusters are non-linearly separable or the data contains arbitrarily shaped clusters of different densities. therefore, an upgraded version of the k-means clustering algorithm was applied in the recognition system referred to as kernel k-means [20–22]. the objective function of kernel k-means is still to minimize the sum of squared distances, but it uses the kernel trick to transform the data points into infinite feature space xi → ϑ (xi), as can be seen in e = min  k∑ l=1 ∑ xi∈cl ∥∥∥∥∥∥∥ϑ (xi)− ∑ xj∈cl ϑ (xj) nl ∥∥∥∥∥∥∥ 2 , (7) where nl denotes the number of images in cluster cl. the trick here is that explicit calculations in the feature space are never required, since transformed data points are only present as part of an inner product. therefore, they can be substituted for their kernel representatives (the gaussian kernel was implemented here). in order to reduce the randomness of final clusters, the plusplus cluster center initialization algorithm was used before the iterative steps, which was proposed by d. arthur and s. vassilvitskii [23]. this approach aims to spread out the initial cluster centers and accelerate their convergence. the first cluster center is randomly selected from the data points, after that each subsequent cluster center is chosen from the data points with a probability proportional to its squared distance from the closest existing cluster center. in the following sub-sections, the usage of the presented methods is discussed. 2.3 baseline method in this section, a baseline method of open world recognition is presented. first, at training time the classifier of the training data is trained with k known classes, then, at testing time classification of the test data (k+u classes) is performed. the dpm is applied to the output of the classifier to detect unknown images udpm: udpm = nu⋃ j=1 {ij |dj = ck+1} (8) where ij represents test instance j, nu denotes the number of test instances in the test data, dj stands for the decision of the dpm, and ⋃ {. . . } is the operation of union. now, let us assume that information concerning u was provided (as in the case 3c), and u was used as the number of clusters. the kernel k-means plusplus cluster center initialization algorithm (kk++) was performed on udpm with k = u clusters (which is the input parameter for the kk++), and then the appropriate labels were assigned to the unknown images: lj = ck+i|i = out ( kk++ ) j = 1 . . .m, i = 1 . . . u (9) where m represents the number of unknown images; lj and ci denote the label of unknown image udpm j and cluster identity, respectively. this concludes the baseline method for automated labeling. at this point the classifier can be retrained based on the previously known and new labels, and then the new test data classified. 2.4 cluster classification in this section our proposed cc approach is presented, which is suitable for unknown detection and automated labeling. this algorithm contains extended training and testing phases. in training time, a classifier of the training data is trained with k known classes, then a pseudocluster is also created based on the k known categories. this means that the ground truth class labels are implemented rather than a clustering algorithm (to determine the final clusters), i.e. each category is a cluster. subsequently, the images are substituted for their fisher vector 47(1) pp. 33–39 (2019) 36 papp and szűcs representations and the cluster centers calculated which will be used in the testing phase. let us assume t categories are found in the testing phase, and that t > k. the test data is classified into the k known categories and a dpm applied based on the decision vectors to detect the unknown images udpm. the next step is to form clusters using the kernel k-means clustering algorithm starting from the k cluster centers that were calculated at training time from the pseudocluster. afterwards, the remaining t -k cluster centers are determined following the plusplus initiation protocol. furthermore, the training and test datasets were used together as the input data. basically, with these modifications it was possible to guide the clustering algorithm, therefore, create more accurate clusters. the following step of the testing phase is to classify the clusters {ci} by weighted majority voting of the members of the cluster. the vote is based on the class membership probabilities (pci ; i = 1 . . .k + 1) calculated in eqs. 3–4. as was seen in section 1, the definition of problem 3c assumes that the number of unknown categories exceeds 1. nonetheless, the output of the dpm only yields k + 1 alternatives instead of t . in spite of this, the classification of clusters that depend on {pci} can increase the number of alternatives to t as will be seen later. in section 1, a differentiation was made between known and unknown images, and now this differentiation is broken down even more. the training data contains only known images, because each of them belongs to one of the set of known categories (sk). from now on, the union of known images of the training data will be denoted by kgt as can be seen in: kgt = nk⋃ j=1 {ij} (10) where nk stands for the number of images in the training data. on the other hand, the test data contains both known and unknown images. furthermore, based on the output of dpm, the test data can be divided into two different subsets, namely predicted known images (kdpm) and predicted unknown images (udpm), as can be seen in eqs. 11 and 8, respectively. kdpm = nu⋃ j=1 {ij |dj 6= ck+1} (11) the weight of the images can be calculated based on the cluster coherence. the coherence of a cluster can be determined by comparing the number of known images to the number of predicted unknown images inside that given cluster. it should be noted that known images inside the clusters either originate from kgt or kdpm, while the predicted unknown images are all part of udpm. if the number of known images exceeds the number of unknown images it is implied that a cluster exhibits “known coherence” (kc), and “unknown coherence” (uc) vice versa, as described in: ccoh = { kc | ∥∥{kgt ∪kdpm }∥∥ ≥ ∥∥udpm ∥∥ uc | ∥∥{kgt ∪kdpm }∥∥ < ∥∥udpm ∥∥ (12) where ‖x‖ represents the number of elements in x , and the superscript coh indicates the coherence of cluster c. the weights can be calculated as described in eqs. 13 and 14. intuitively, if an image is known and located inside cluster uc, then it is “punished” by assigning a lower weight to it; and vice versa, an unknown image is given a lower weight inside cluster kc. moreover, the larger the difference between the numbers of known and unknown images implies a more severe punishment with regard to the value of weights. wkc j =  1 + (#known−#unknown) (#known+#unknown) | ij /∈ udpm 1− (#known−#unknown) (#known+#unknown) | ij ∈ udpm (13) wuc j =  1 + (#known−#unknown) (#known+#unknown) | ij ∈ udpm 1− (#known−#unknown) (#known+#unknown) | ij /∈ udpm (14) thereafter the final decision vector of cluster ci can be calculated as: vi = 1 ni ni∑ j=1 wj × dj (15) where ni denotes the number of images in cluster ci, wj represents the weight and dj stands for the decision vector ({pci }) of image j. note that dj possesses k + 1 elements (+1 from dpm), therefore, vector vi also possesses k + 1 elements. consequently, the element with the maximum value of vi determines the category of cluster ci. the classification of cluster ci is formalized in: di = { new class | vk+1 = maxj{vj} argmaxi{vi} | otherwise (16) the results of the classification of the clusters can be considered as a labeling proposal, i.e. label each image inside cluster ci according to di. when decision di for cluster ci is that it is part of a known category, then each image inside ci gets labeled with the same category. on the other hand, when di = a new class, a new category is created and each image in ci gets labeled with the new category. basically, the cc algorithm follows this labeling proposal. 3. experimental results in order to measure the efficiency of the labeling process, experiments were conducted on the caltech101 [24] and hungarian journal of industry and chemistry automated labeling process for unknown images 37 figure 1: example images from the caltech101 and caltech256 datasets. the airplane, butterfly and windmill categories are represented by the left, middle and right columns, respectively. caltech256 [25] datasets. example images from these datasets are shown in fig. 1. the former consists of 101 categories and 8, 677 images, while the latter is composed of 30, 607 images from 256 different classes. to create an open-world environment, 50 known and 50 unknown categories were randomly selected from the caltech101 dataset, and 100 of both categories from the caltech256 dataset. these ranfigure 2: averaged results of the 5-5 different test datasets that were randomly selected from the caltech101 and caltech256 datasets. the ri is plotted against the number of unknown categories. the diagrams compare the labeling performance of the dpm with kernel k-means (dpm+kk) against the cc. table 1: summary of the results obtained from the test data with the baseline (dpm+kk) and cc methods using the caltech101 and caltech256 datasets. the baseline column contains the ri values evaluated which depend on the number of unknown categories (un. cat.), and the cc column presents the improvements that result from cc as a percentage. caltech101 caltech256 un. cat. base-line cc (%) un. cat. base-line cc (%) 5 0.629 6 10 0.514 1 10 0.594 13 20 0.489 9 15 0.567 15 30 0.484 6 20 0.561 16 40 0.478 9 25 0.550 17 50 0.452 13 30 0.514 28 60 0.448 13 35 0.536 18 70 0.433 19 40 0.522 23 80 0.426 17 45 0.505 24 90 0.412 22 50 0.497 25 100 0.397 21 dom selections were repeated 5 times in order to calculate the average of the results of each experiment to obtain a more comprehensive overview of the efficiency of the cc algorithm with regard to these datasets. all of the known categories were available from the beginning of the tests, but the unknown categories were added incrementally over 10 steps, and in each step the rand index (ri), ri = tp + tn tp+ fp + tn+ fn , (17) was evaluated over the unknown images, where tp, tn, fp, and fn denote the number of true positive, true negative, false positive and false negative decisions, respectively. the ri measures the similarity between the ground truth and predicted labels of the unknown images, in other words, the percentage of correct decisions. two methods were assessed and compared, namely the baseline method (dpm+kk) and the cc, which were discussed in section 2.3 and 2.4, respectively. both procedures used fisher vectors to mathematically represent the images encoded from 128 dimensional sift descriptors using a gmm consisting of 256 code words; a svm equipped with a radial basis function (rbf) kernel was applied as a classifier. the results can be seen in fig. 2 and table 1. the first diagram shows the results obtained from the caltech101 dataset and the second from the caltech256 dataset. the dpm with kernel k-means and the cc are represented by dashed and solid lines, respectively. in both experiments, the cc algorithm yielded a higher ri, although during the first step the difference between the two methods was minimal. it can be seen that the ri of dpm+kk starts to decrease as the number of unknown categories increases, while the cc remains by and large unchanged. 47(1) pp. 33–39 (2019) 38 papp and szűcs 4. conclusion in this paper, the problem of open world recognition was reviewed and the possible cases were differentiated based on our prior knowledge and actual information about the test data and, thus, the unknown space. the dpm and kernel k-means algorithm were also reviewed in brief, followed by the presentation of two approaches, which perform multi-class classification, automatically detect unknown images and propose a labeling for them. the first method is a baseline technique where dpm was sequentially applied followed by kernel k-means with a plusplus cluster center initialization algorithm. however, our proposed cc is a complex method of combining the unknown detector and clustering algorithm that seeks to determine the identity of formed clusters, while refining the decisions made by the classifier and unknown detector. the cc algorithm constructs a specific weight system to reward or punish images which were placed into a category that is presumably unsuitable for their estimated identity. multiple experiments were conducted on two large datasets (caltech101 and caltech256), and the ri evaluated with regard to the unknown images. the results showed that the cc outperformed the baseline method, and was able to maintain almost the same ri, while the number of unknown categories increased. acknowledgement the research was supported by the únkp-18-3 new national excellence program of the ministry of human capacities. references [1] lampert, c. h.; 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szűcs, g.: mmkk++ algorithm for clustering heterogeneous images into an unknown number of clusters, elcvia: electronic letters on computer vision and image analysis, 2017 16(3), 30–45 doi: 10.5565/rev/elcvia.1054 [23] arthur, d.; vassilvitskii, s.: k-means++: the advantages of careful seeding, in: proceedings of the eighteenth annual acm-siam symposium on discrete algorithms, (society for industrial and applied mathematics, philadelphia, usa) 2007, pp. 1027–1035 isbn: 978-0-898716-24-5 [24] fei-fei, l.; fergus, r.; perona, p.: learning generative visual models from few training examples: an incremental bayesian approach tested on 101 object categories, comput. vis. image und., 2007 106(1), 59–70. doi: 10.1016/j.cviu.2005.09.012 [25] griffin, g.; holub, a.; perona, p.: the caltech 256, caltech, tech. rep., 2012 47(1) pp. 33–39 (2019) https://doi.org/10.1109/cvpr.2007.383266 https://doi.org/10.1109/cvpr.2007.383266 https://doi.org/10.1007/978-3-642-15561-1_11 https://doi.org/10.1007/978-3-642-15561-1_11 https://doi.org/10.1145/2020408.2020558 https://doi.org/10.1145/2020408.2020558 https://doi.org/10.1145/1014052.1014118 https://doi.org/10.5565/rev/elcvia.1054 https://doi.org/10.1016/j.cviu.2005.09.012 introduction proposed open-world recognition system double probability model unknown image clustering baseline method cluster classification experimental results conclusion hungarian journal of industry and chemistry vol. 46(2) pp. 13-17 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0012 application of 2n design of experiment method for the evaluation of the efficiency and cross-effects of oilfield chemicals zoltán lukács ∗1 and tamás kristóf1 1department of physical chemistry, institute of chemistry, university of pannonia, egyetem u. 10, veszprém, h-8201, hungary it has been known for a long time that oilfield chemicals used for different purposes (corrosion and scale inhibitors, scavengers, biocides, etc.) can modify the efficiency of each other. these cross-effects can exhibit adverse or beneficial impacts and may modify the overall corrosiveness of the medium to a great extent. however, there is no standard procedure in order to evaluate the cross-effects, i.e. the extent to which the effect of one of the chemicals is modified by the addition of another. the 2n design of experiment (doe) method provides a robust and simple statistical way to evaluate the change in efficiency of oilfield chemicals owing to the addition of other additives. the 2n doe method can also be applied to other systems. in the present work the effects and cross-effects in systems consisting of a corrosion inhibitor, as well as an oxygen and a hydrogen sulphide scavenger are investigated and successfully demonstrated in a typical oilfield corrosion system with electrochemical corrosion monitoring methods. keywords: oilfield chemicals, corrosion inhibitor, design of experiment 1. introduction the chemical treatment of wet oils that are produced is a widely used method for mitigating unfavorable phenomena in the production, transportation and processing of crude oils: corrosion, scaling, emulsion forming, etc. on the way from the oil well to the refinery a variety of oilfield treatment chemicals are added to the oil: corrosion and scale inhibitors, biocides, hydrogen sulfide and oxygen scavengers (typically with wash waters), demulsifiers, anti-foam agents, etc. [1–4]. the effects of these chemicals are typically well defined in themselves, but the cross-effects, i.e. the influence on each other, are rarely discussed and even more rarely investigated, especially in situ. the reason for this is rather complex. from a practical perspective, there is no standard or wellestablished procedure for such testing. from a theoretical standpoint, the evaluation of such tests, if any, is rather problematic because if the effects of factors are strongly correlated (i.e. one or more “cross-effects” are significant in the system) then the evaluation of the effects by usual means (i.e. least square model fitting [5–7]) is subject to a significant error, if not impossible. in order to formulate the problem, let us consider a dependent variable, y, e.g. the corrosion rate, and assume that it is a quantitative function of some other quantitative ∗correspondence: lukacs600131@gmail.com independent variables: y = p1x1 + p2x2 + · · · + pnxn. (1) this is an uncorrelated multilinear model, that is, the (p1, · · · , pn) parameter set, the set of the factor coefficients, is invariant throughout the whole (x1, ·, xn) model variable space. if the (p1, ..., pn) parameter set is dependent on the location in the model variable space then the following correlated multilinear model can be applied: y = p1x1 + p2x2 + · · · + pnxn + (2) +q1,2x1x2 + · · · + qn−1,nxn−1xn, where the q1,2, · · · qn−1,n coefficients represent the cross-effects coefficients (the effect of quadratic and higher order contributions is not discussed here). if the cross-effects are significant in a model, i.e. the coefficients of the cross-effects are comparable to the coefficients of the factors, then severe computational difficulties may occur, especially if a remarkable error (random or systematic) is superimposed on the measurement data. in such cases conventional parameter-fitting procedures generally fail to provide realistic and accurate model coefficients. for the investigation of cross-effects, a viable technique is the so-called 2n design of experiment (doe) method. as this method is not widely used in the field of corrosion science and technology, its basic concepts are outlined in brief here. mailto:lukacs600131@gmail.com 14 lukács and kristóf in the methodology of the design of experiment technique the independent variables are known as factors and the values of the factors are referred to as factor levels. the factor levels are fixed, discrete values (in contrast to the continuous range of the independent variables). the variance in the factor levels, if any, will be transformed into a variance of the dependent variable. the design of experiment methods are typically used in industrial quality assurance testing, where the fixed factor levels correspond to certain standardized levels of the factors that are assumed to influence a quality parameter (i.e. the dependent variable). in oilfield chemical performance tests a fixed value with regard to the factor of the “corrosion inhibitor” can be the concentration recommended by the supplier. apart from the fixing of the factor levels, the general design of experiment schemes and the supporting mathematical apparatus basically do not differ from conventional multilinear parameter fitting. however, a special type of doe, the 2n design of experiment method, possesses some noteworthy mathematical properties that make it especially applicable for studying cross-effects. in the 2n doe method every factor possesses exactly two factor levels and they are normalized to −1 and +1. in some cases, if all the factors are quantitative, a factor level of 0 exists in order to test the linearity of the model. with the normalization of the factor levels to −1 and +1, all the factors and cross-effects are orthogonal, i.e. independently calculable from each other. this is a great advantage, making the method applicable to study cross-effects. on the other hand, the normalization of the factor levels to the arbitrary −1 and +1 levels is costly. the coefficients of the factors and cross-effects, determined after the calculations, do not have any direct physical meaning, they can only be interpreted in terms of a comparison with one another and to the variance of the measurement data. a comparison of the factors and cross-effects with one another can yield a series of more and less significant effects and a comparison to the variance can provide information on the statistical significance of the respective factor/cross-effect. obviously, the value of the obtained factor and cross-effect coefficients is dependent on the chosen spread between the two factor levels, therefore, this choice must be made with careful consideration. for example, if effects and interactions of oilfield chemicals are investigated, then one of the factor levels would be proposed to be “no chemical added” (concentration = 0) and the other factor level would be termed as the chemical added to the fluid within the recommended range. the purpose of this work was to demonstrate the applicability of the 2n doe method for studying the factors and cross-effects of oilfield chemicals in a suitably chosen model system. 2. experimental the model system was chosen as a typical corrosion system, containing a carbon steel electrode in a wellbuffered, slightly acidic electrolyte (0.1 m nahso4 + 0.1 m na2so4), which maintains a nearly constant corrosiveness and reduces the accumulation of solid corrosion products on the surface of the electrode which also improves the reproducibility of the tests. as the aim was to simulate the effects and cross-effects of oilfield chemical treatment additives (corrosion inhibitor, as well as hydrogen sulfide and oxygen scavengers), 1 mm of na2s was added to the solution. the carbon steel plates (three specimens) were applied for three parallel runs in each measurement set. the specimens were abraded with emery paper and then degreased in acetone for one hour. before each run the species were etched in 5 % hcl, degreased in an alkaline degreasing solution and etched in 5 % hcl again (all dippings lasted for a duration of 5 minutes). 600 cm3 of the solution was poured into a cylindrical test cell of 1000 cm3 in volume and a carbon steel plate electrode with a surface area of 17 cm2 was introduced into the cell, equipped with a silver/silver chloride (3.5 m) reference electrode and two mixed metal oxide-coated titanium tube counter electrodes both 3 mm in diameter and 50 mm in length. the solution was not de-aerated and the measurements were conducted at room temperature (25 ◦c). the corrosion rate was determined by impedance measurements carried out at 1 khz and 0.1 hz with a 20 mv p-p amplitude ac signal superimposed on the corrosion potential, which was established to a satisfactorily stationary level (max. 1 mv/min drift) of no more than 10 minutes. the polarization resistance of the electrode was determined by subtracting the high-frequency resistance (solution resistance) from the low-frequency resistance. the measurements were conducted by an electroflex ef430 potentiostat and a picoscope 3403d oscilloscope. the results were cross-checked by a metrohm potentiostat. in order to simulate the components of a typical oilfield chemical treatment procedure, a commercial corrosion inhibitor (bpr 81100, baker hughes, 100 ppm), zinc acetate as a model compound for a hydrogen sulfide scavenger at a concentration of 2 mm, and sodium metabisulfite (na2s2o5) also at a concentration of 2 mm were added. all chemicals were of p.a. quality. the 2n doe scheme is shown in table 1 below. all experimental sets were repeated 3 times with different electrodes. 3. results and discussion the effect of three factors (a corrosion inhibitor, as well as hydrogen sulfide and oxygen scavengers) was studied on the polarization resistance (compensated for by the ohmic drop in the solution, see the previous section) and the corrosion current. the relationship between the pohungarian journal of industry and chemistry application of 2n design of experiment method for oilfield chemicals 15 table 1: levels of factors and cross-effects of factors in the doe sets. factors factor cross effects set # corrosion inhibitor hydrogen sulfide scavenger oxygen scavenger corrosion inhibitor × hydrogen sulfide scavenger corrosion inhibitor × oxygen scavenger hydrogen sulfide scavenger × oxygen scavenger 1 -1 -1 -1 1 1 1 2 -1 -1 1 1 -1 -1 3 -1 1 -1 -1 1 -1 4 -1 1 1 -1 -1 1 5 1 -1 -1 -1 -1 1 6 1 -1 1 -1 1 -1 7 1 1 -1 1 -1 -1 8 1 1 1 1 1 1 larization resistance and the corrosion current was calculated as: j0[a] = 1 2.303 ( b−1 a [v ] + b−1 c [v ] )−1 rp[ω] = 1 2.303 0.04[v ] rp[ω] , (3) with a typical value of ba = 0.06 v/decade and bc = 0.12 v/decade, furthermore,rp is measured in ohms and j0 in amperes. the units of measurement are shown in square brackets. the design of experiment scheme is shown in table 1 the scheme consists of 23 = 8 sets. the levels of interactions (cross-effects) are simply the product of the levels of the respective factors. the original assumption of the work was that the polarization resistance and/or the corrosion current of the test specimen depend on the factors according to the following model: ys = y + ∑ f afef + ∑ i biei, (4) where ys stands for the value of the target function in the respective set (the polarization resistance or corrosion current), y denotes the total average of the same,ef table 2: factors (in diagonal cells), cross-effect coefficients and the variance of the measurement data for the evaluation of polarization resistance values. values larger than the standard deviation are set in bold. factors corrosion inhibitor hydrogen sulfide scavenger oxygen scavenger corrosion inhibitor 3.359 −1.086 −3.319 hydrogen sulfide scavenger 0.022 −0.082 oxygen scavenger −3.087 standard deviation of measurement data 2.125 and ei represent the level of the respective factor/crosseffect in the respective set (−1 or +1), andaf andbi are the values of the respective effect/interaction coefficients. the overall standard deviation of the measurement data was determined via σ(y ) = √√√√ 1 s(j − 1) s∑ s=1 j∑ j=1 ( ys,j − y s )2 , (5) where s = 8 is the number of sets, j = 3 stands for the number of runs per set, ys,j denotes the measurement result (polarization resistance or the corrosion current) and y s represents the average of the latter for a certain set. the results based on the model of eq. 4 are included in tables 2 and 3 for the polarization resistance and corrosion current, respectively. by comparing the coefficients in the tables above it is striking at first sight that – apart from the coefficient of the corrosion inhibitor factor, which possesses the greatest absolute value in both tables – there is great variation in the relative significance of the corresponding values. it could be expected that if a factor/cross-effect is more significant in the model describing the variations of the table 3: factors (in diagonal cells), cross-effect coefficients and the variance of the measurement data for the evaluation of corrosion current values. values larger than the standard deviation are set in bold. factors corrosion inhibitor hydrogen sulfide scavenger oxygen scavenger corrosion inhibitor −9.06 · 10−4 7.39 · 10−4 8.71 · 10−4 hydrogen sulfide scavenger −7.31 · 10−4 7.45 · 10−4 oxygen scavenger −3.98× 10−4 standard deviation of measurement data 4.55 · 10−4 46(2) pp. 13-17 (2018) 16 lukács and kristóf table 4: factors (in diagonal cells), cross-effect coefficients and the variance of the measurement data for the evaluation of the logarithm of the polarization resistance values. values larger than the standard deviation are set in bold. factors corrosion inhibitor hydrogen sulfide scavenger oxygen scavenger corrosion inhibitor 0.275 −0.143 −0.266 hydrogen sulfide scavenger 0.110 −0.117 oxygen scavenger −0.110 standard deviation of measurement data 0.172 polarization resistance, then the same factor/cross-effect will exhibit approximately the same relative significance in the model of the corrosion current. however, in this case great differences exist in terms of the relative significance. the coefficient of the factor concerning the hydrogen sulfide scavenger and its cross-effect with the oxygen scavenger are both negligible in the model of the polarization resistance ( table 2) and much more significant (compared to the standard deviation of the measurement data in table 3). this magnitude of the differences cannot simply be attributed to some changes with regard to the weighing of measurement data due to the reciprocal transformation from the polarization resistance to the corrosion current (cf. eq. 3 and raises doubts suggesting that the model in eq. 4 is invalid. eq. 4 suggests that the contribution of the additives (corrosion inhibitor and the scavengers) to the dependent variable is a linear function of the concentration. however, if it is taken into consideration that the effects of the additives are basically kinetic, then it can be implied that instead of the linear eq. 4 a logarithmic approximation might exist: lnys = lny + ∑ f af lnef + ∑ i bi lnei, (6) which is in agreement with the general experience that the effects (activities) of components are proportional to the logarithm of concentration. by applying eq. 6, the factors and cross-effect coefficients of the models for the polarization resistance and corrosion current will be identical apart from a multiplicator of (−1). the model-fitting results of eq. 6 are shown in table 4 for the polarization resistance data. from the results it can be concluded that the corrosion inhibitor has the greatest effect on the system and it increases the polarization resistance significantly. the hydrogen sulfide scavenger also decreases the corrosion rate in itself, but its application along with the corrosion inhibitor is less favorable. the use of an oxygen scavenger is not at all advisable under these conditions. 4. summary the general aspects of the 2n design of experiment method and also a specific application for a chemical treatment model system were discussed. the effects and interactions of a corrosion inhibitor, as well as hydrogen sulfide and oxygen scavenger model compounds were studied. the linear model for these additives yielded controversial results, namely the fitting of the model on the polarization resistance data provided totally different results to those on the corrosion current data. by applying the logarithmic model, the results are consistent and their interpretation straightforward. it has been proven that – by carefully selecting the appropriate mathematical model – the proposed method is applicable for the investigation of the effects and crosseffects of different oilfield treatment chemicals. acknowledgement present article was published in the frame of the project ginop-2.3.2-15-2016-00053 (“development of engine fuels with high hydrogen content in their molecular structures (contribution to sustainable mobility)”). references [1] rahmani, kh.; jadidian, r.; haghtalabb, s.: evaluation of inhibitors and biocides on the corrosion, scaling and biofouling control of carbon steel and copper–nickel alloys in a power plant cooling water system, desalination, 2016 393(1), 174–185 doi: 10.1016/j.desal.2015.07.026 [2] barmatov, e.; hughes, t.; nagl, m.: efficiency of film-forming corrosion inhibitors in strong hydrochloric acid under laminar and turbulent flow conditions, corr. sci., 2015 92, 85–94 doi: 10.1016/j.corsci.2014.11.038 [3] papavinasam, s.: corrosion control in the oil and gas industry, chapter 7 – mitigation – internal corrosion (elsevier, amsterdam) 2014 p. 361 isbn: 978-0-12-397022-0 [4] song, g.-l.: the grand challenges in electrochemical corrosion research, front. mater., 2014 1(2), 1–3 doi: 10.3389/fmats.2014.00002 [5] giunta, a.a.; wojtkiewicz jr., s.f.; eldred, m.s.: overview of modern design of experiments methods for computational simulations, proceedings of 41st aerospace sciences meeting and exhibit 2003; reno, nv; usa. aiaa 2003-0649 hungarian journal of industry and chemistry https://doi.org/10.1016/j.desal.2015.07.026 https://doi.org/10.1016/j.desal.2015.07.026 https://doi.org/10.1016/j.corsci.2014.11.038 https://doi.org/10.1016/j.corsci.2014.11.038 https://doi.org/10.3389/fmats.2014.00002 https://doi.org/10.3389/fmats.2014.00002 application of 2n design of experiment method for oilfield chemicals 17 [6] garud, s.s.; karimi, i.a.; kraft, m.: design of computer experiments: a review, comput. chem. eng., 2017 106, 71–95 doi: 10.1016/j.compchemeng. 2017.05.010 [7] kemény, s.; deák, a.: kísérletek tervezése és kiértékelése [design and evaluation of experiments, in hungarian] (műszaki könyvkiadó, budapest) 2002 isbn: 978-963-2799-12 46(2) pp. 13-17 (2018) https://doi.org/10.1016/j.compchemeng. 2017.05.010 https://doi.org/10.1016/j.compchemeng. 2017.05.010 introduction experimental results and discussion summary microsoft word 16.05 bobek.docx hungarian journal of industry and chemistry vol. 44(1) pp. 51–54 (2016) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2016-0006 selective hydrogen sulphide removal from acid gas by alkali chemisorption in a jet reactor janka bobek,* dóra rippel-pethő, éva molnár, and róbert bocsi department of chemical engineering science, university of pannonia, egyetem str. 10, veszprém, 8200, hungary natural gas is a primary energy source that contains a number of light paraffins. it also contains several undesirable components, such as water, ammonia, hydrogen sulphide, etc. in our study, a selective hydrogen sulphide removal process was achieved by alkali chemisorption in a custom-designed jet reactor. several model gas compositions (co2-h2s-n2) were evaluated to find parameters that enable h2s absorption instead of co2. the negative effect of the presence of co2 in the raw gas on the efficiency of h2s removal was observed. the beneficial effect of the low residence time (less than 1 s) on the efficiency of h2s removal was recognized. optimal operational parameters were defined to reach at least a 50% efficiency of h2s removal and minimal alkali consumption. keywords: acid gas, h2s selective removal, co2, competition with h2s, chemisorption 1. introduction natural gas is one of our primary energy sources, which contains mainly methane. however, it us comprised of several undesirable components like carbon dioxide (co2), hydrogen sulphide (h2s), ammonia (nh3), water (h2o), etc. [1]. table 1 shows a typical composition of natural gas [2]; however, the content significantly depends on locality. in most cases, natural gas contains h2s in various quantities between 10 to 20,000 ppm [1]. the gases with a measurable amount of h2s are called sour gases. the acid gases are defined as gases containing some acidic component such as co2 or h2s [3]. the h2s containing hydrocarbon gases causes problems during the delivery, processing, and storage. h2s is converted into so2 during combustion, which poses a health hazard and causes acid rain, smog. in the presence of water, acid components cause corrosion in pipelines and containers. consequently, h2s removal from natural gas is absolutely necessary [3]. there are several methods for reducing the h2s content of natural gas. membrane techniques also exist, but the adsorption and absorption processes are the most widespread. in the adsorption process, the fixed bed construction is the most common. the adsorber is usually filled with metal ions (iron, copper, zinc, cobalt, etc.) and an impregnated solid host (zeolite, activatedcarbon, etc.). the disadvantage of this technique is the huge energy demand of adsorber regeneration. in the absorption process, one of the main points is the high ph value of the medium due to h2s dissociation. there *correspondence: bobekj@almos.uni-pannon.hu are numerous solvents for absorbing h2s, namely alcanol-amines (mea, dea, dipa, tea, mdea, etc.), alkali-hydroxides (koh, naoh), water, and ammonia. the alcanol-amines and the alkali-hydroxides are the most efficient. the alcanol-amines are widely used in h2s removal, but their selectivity can be problematic and foaming appears during the process [4]. the use of alkali-hydroxides seems to be the most efficient process. by choosing the correct parameters, such as residence time, ph, solvent concentration, and intake, the procedure can be h2s selective. in an alkalihydroxide medium competitive chemisorption takes place between co2 and h2s. although co2 is a stronger acid than h2s, it is a slower adsorber, thus h2s absorption can be achieved over a short residence time. intensive phase connection and fast phase separation afterwards are essential steps to facilitate a h2s selective process [2]. the spray technique is a widespread method for the intensification of the reaction between the reactants. the pneumatic nozzles act as two-phase sprayers, because the gas at high speed breaks up the liquid into little droplets [5]. table 1. a typical composition of natural gas [2]. component concentration (%, m3/m3) methane (ch4) 97 nitrogen (n2) 0.936 ethane (c2h6) 0.919 carbon dioxide (co2) 0.527 propane (c3h8) 0.363 butane (c4h10) 0.162 oxygen (o2) 0-0.800 noble gases (ar, he, ne) trace other (e.g. h2s) 0-0.001 bobek, rippel-pethő, molnár, and bocsi hungarian journal of industry and chemistry 52 2. experimental the aim of our research is selective hydrogen sulphide removal from model gases that also contain co2. our goal is to achieve the highest h2s removal efficiency with the lowest alkali specificity as defined by the ratio of naoh and h2s expressed in moles. to find the parameters that support h2s removal several experiments were carried out in a custom-designed jet reactor (fig.1). owing to the construction of the reactor, the gas pressure, gas flow, alkali inlet flow, and alkali concentration were variable. all experiments were carried out at 30 bar total pressure. the absorbent was an aqueous naoh solution of different concentrations, such as 0.5, 1.5, and 2.5% (g/g). the model gas mixtures (table 2) were produced in an acid-proof gas mixing bridge. for the first set of samples the h2s content of the model gas mixtures was kept approximately constant; thus, the effect of co2 could be studied. for the last three samples, the co2 content was kept approximately constant; thus, the sensitivity of the process with regards to the variation of h2s concentration could be investigated. 3. results and analysis first, the effect of naoh concentration, naoh inlet flow, gas flow (residence time), and co2 concentration were investigated on the efficiency of h2s removal. 3.1. effect of residence time to observe the effect of residence time on the efficiency of h2s removal, the gas flow rate as a single parameter was varied. by increasing the gas flow rate, the residence time decreased. the gas flow rates were 3.9, 3.2, 2.4, and 1.6 n m3 h-1, which correspond to residence time rates of 0.05, 0.06, 0.09, and 0.13 s, respectively. fig.2 shows the effect of decreasing residence time. at a constant specific alkali value, the efficiency of h2s removal increased as a result of a decrease in residence time. furthermore, fig.2 also shows that the alkali specificity values decreased by raising the gas flow rate under a constant efficiency of h2s removal. 3.2. effect of naoh concentration the value of alkali specificity depends on the h2s content of the raw gas, the concentration and the flow rate of the absorbent. by increasing the concentration and the flow rate of the absorbent, the efficiency of h2s removal is increased. however, the efficiency could not be improved after a point by the absorbent concentration or flow rate, because the efficiency reached a nearly constant value while the alkali specificity continued to increase (fig.3). 3.3. effect of co2 concentration model gases of different co2 concentrations were used to study the effect of co2 concentration on the efficiency of h2s removal. the difference in h2s concentrations of model gases is a result of non-exact gas mixing, but this does not affect the comparability of the results. fig.4 shows that the efficiency of h2s removal is decreased by increasing co2 content. the competition between h2s and co2 in alkali absorbents is documented. figure 1. experimental device equipped with a 1. gas cylinder, 2. gas inlet, 3. alkali vessel, 4. chemical feeder pump, 5. alkali inlet, 6. reactor space, 7. nozzle, 8. separation space, 9. wastewater removal, 10. drop catcher, 11. outlet of purified gas, 12. gas sampling, and 13. gas analyzer. figure 2. effect of different residence times on the efficiency of h2s removal (gas mixture 4, 30 bar, 2.5% (g/g) naoh). table 2. composition of the tested model gas mixture samples. samples co2 % (m3/m3) h2s ppmv n2 % (m3/m3) 1 0 100 99.999 2 23 90 76.999 3 41 80 58.999 4 60 80 39.999 5 76 85 23.999 6 72 520 27.999 selective hydrogen sulphide removal 44(1) pp. 51–54 (2016) doi: 10.1515/hjic-2016-0006 53 3.4. effect of h2s concentration the influence of h2s concentration on the efficiency of h2s removal was investigated under a nearly constant co2 level (76 and 72% (m3/m3)) and greatly differing h2s (85 and 520 ppmv) containing model gases. when the 85 ppmv h2s containing gas was compared to the 520 ppmv h2s sample, the alkali specificity value measured was five times less (fig.5). on the other hand, fig.5 shows that the efficiency of h2s removal does not depend on the h2s concentration in this process. the alkali hydroxide absorbent technique shows little sensitivity to the changes in the h2s content of the inlet gas. 3.5. optimization of operational parameters based on the above-mentioned results, our aim was to find the optimal operational parameters for model gases of any composition in order to achieve an h2s removal efficiency of at least 50%, while applying the minimal amount of alkali specificity. this efficiency of h2s removal can be achieved by increasing the naoh concentration. a low alkali specificity value can be achieved by adopting a low residence time. as shown in table 3, when the co2 content is below 50% (m3/m3), 1.5% (g/g) naoh absorbent is enough to achieve an h2s removal efficiency of 50% in the given type of reactor at a pressure of 30 bar. a gas flow rate of 2.5 nm3 h-1 with a 0.08 s residence time is needed. when the co2 content is above 50% (m3/m3), 2.5% (g/g) naoh is necessary to achieve a removal efficiency of 50%. the applied gas flow rate needs to be 3.8 nm3 h-1 corresponding to 0.05 s residence time in the given type of reactor at a pressure of 30 bar. 4. discussion in this study, model gases with different h2s-co2-n2 contents were investigated in a custom-designed jet reactor. our aim was to achieve a h2s removal efficiency of at least 50% with minimal alkali consumption. the effect of the naoh, co2, and h2s concentrations, and the residence time on the efficiency of h2s removal was studied. during our experiments co2 absorption was not investigated because the dräger x-am 7000 analyser we used is only able to measure the co2 concentration in percent magnitude. a positive effect of low residence time on h2s removal was observed. by increasing the gas flow rate, the efficiency of h2s removal was increased under constant alkali specificity. if the efficiency of h2s removal is constant, the alkali specificity can be reduced by decreasing the residence time. by increasing the naoh concentration and flow rate, the efficiency of h2s removal was improved until a point after which it nearly remained constant while the alkali specificity was still rising. to study the effect of different co2 concentrations on the efficiency of h2s removal, several co2 concentrations were investigated under nearly the same h2s levels. the removal efficiency was reduced radically by increasing the co2 concentration. when comparing the model gases that contain different h2s concentrations, a reduction in the alkali specificity was observed. the alkali specificity value decreased as the h2s content increased. the removal efficiency remained constant irrespective of the h2s concentration of the model gases, which improves the efficiency of the alkali absorption process in terms of selective removal of h2s. figure 4. effect of different co2 concentrations on the efficiency of h2s removal (gas mixtures 0-5, 30 bar, 0.08 s residence time, 0.5% g/g naoh). figure 3. effect of different naoh concentrations on the efficiency of h2s removal (gas mixture 2, 30 bar, 0.2 s residence time). figure 5. effect of different h2s concentrations on the efficiency of h2s removal (gas mixtures 5-6, 30 bar, 0.09 s residence time, 1.5% (g/g) naoh). bobek, rippel-pethő, molnár, and bocsi hungarian journal of industry and chemistry 54 we observed that when the co2 concentration was less than 50% (m3/m3), a 1.5% (g/g) naoh concentration and 0.08 s residence time is necessary to achieve an h2s removal efficiency of 50% at a pressure of 30 bar under the given experimental conditions. when the co2 concentration was above 50% (m3/m3), we found that this is sufficient to provide a naoh concentration of 2.5% (g/g) over a residence time of 0.05 s at a pressure of 30 bar. based on our experiments a high efficiency of h2s selective removal can be achieved by naoh absorption. references [1] balogh, k.: sedimentology iii (akadémia kiadó, budapest, hungary), 1992 (in hungarian) [2] vágó, á.; rippel-pethő, d.; horváth, g.; tóth, i.; oláh, k.: removal of hydrogen sulphide from natural gas, a motor vehicle fuel, hung. j. ind. chem., 2011, 39(2) 283–287 [3] wu, y.; caroll, j.j.; zhu, w.: sour gas and related technologies (scrivener publishing llc, beverly, ma, usa) 2012 pp. xiv–xvii [4] kohl, a.l.; nielsen, r.b.: gas purification (gulf publishing company, houston, tx, usa) 1997 pp. 40–466 [5] tuba, j.: carburators (műszaki könyvkiadó, budapest, hungary), 1976 pp. 23–24 (in hungarian) table 3. the best operational parameters of the tested model gases at a pressure of 30 bar. co2 content, % (m3/m3) naoh concentration, % (g/g) alkali specificity, mol naoh (mol h2s)-1 h2s removal efficiency, % residence time, s gas flow rate, nm3 h-1 23 0.5 15 44 0.20 1.0 1.5 14 51 0.08 2.5 2.5 19 51 0.10 2.0 41 0.5 12 44 0.20 1.0 1.5 15 50 0.08 2.5 2.5 20 50 0.10 2.0 60 0.5 6 27 0.06 3.0 1.5 24 41 0.09 2.3 2.5 24 55 0.05 3.8 76 0.5 6 20 0.07 3.0 1.5 16 47 0.05 3.8 2.5 22 56 0.05 3.8 hungarian journal of industry and chemistry vol. 48(1) pp. 77–80 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-12 torque transmission time-constant examination of a disktype magnetorheological clutch sándor mester*1 and istván szalai1 1institute of mechatronics engineering and research, university of pannonia, gasparich márk utca 18/a, zalaegerszeg, 8900, hungary in this paper, the torque transmission time-constant of a simple disk-type magnetorheological (mr) clutch is investigated. by using mr fluid, controlled torque transmission can be easily implemented, facilitating the widespread use of similar systems. in order to describe the dynamical properties of the system, time constants were measured at different speeds and magnetic inductions. the time constants were derived by fitting an exponential function to the data. keywords: magnetorheological fluid, clutch, torque transmission 1. introduction the implementation of intelligent materials has significantly increased not only in everyday life, but in the industrial environment as well. magnetorheological fluids are suspensions that consist of at least two phases, whose apparent viscosity changes quickly (within 20 − 30 ms) in the presence of an external magnetic field. the suspension usually consists of small ferromagnetic particles of approximately 10 µm in diameter dispersed in oil. usually surface active agents are also present in the fluid to prevent the particles from being attracted to each other. in the presence of an external magnetic field, the particles gain an induced dipole moment and form pairs, followed by chain-like structures. if the fluid is exposed to shearing, these chain-like structures oppose each other leading to an increase in apparent viscosity which can be used in shock absorbers, torque transmission, superfinishing of optical lenses and civil engineering [1–4]. in addition to the rapid change in apparent viscosity, its low power requirement makes mr fluid ideal for use in semiactive shock absorbers and variable torque-transmission clutches. the most basic forms of magnetorheological clutches are the disk and cylindrical types. the differences between the two types are the transmittable torque and the volume of the idling waste. a stream of particles is present in disk-type clutches due to the centrifugal force. in the cylindrical type, the effect is less significant [5, 6]. this study focuses on a disk-type clutch with a welldefined mathematical model [7]. *correspondence: hollosi.janos@sze.hu 2. experimental the model of our magnetorheological clutch is shown in fig. 1. the clutch consisted of the following main components: 1. dc servomotor with a gearbox; 2. toothed belt drive with 1 : 1 gear ratio; 3. input or drive shaft; 4. input shaft bearings; 5. lower disk; 6. upper disk; 7. upper or driven shaft; 8. upper shaft bearings; 9. torque sensor; and 10. toothed belt drive with 4 : 1 gear ratio. the electromagnetic coil, which consisted of approximately 1000 turns, was located around the disks with the coils encircling them, providing magnetic field lines parallel to the shafts. the mr fluid was loaded into the lower disk. the diameter of the disks was 116 mm and the gap between them was 1 mm. the input and output signals were read and recorded by an national instruments (ni) usb-6281 data acquisition device with a sampling rate of 1 khz. the complete magnetorheological clutch is shown in fig. 2. for future measurements, a 3-phase ac induction motor with a frequency inverter was installed to serve as an artificial load. 2.1 samples and measurements a hall effect sensor, located at the top of the upper disk, measured the magnetic field. an encoder was located at the bottom of the drive shaft of the clutch to measure the input speed. the control and measurement tasks were carried out by a ni usb-6281 data acquisition device controlled by labview software. the input speed and output torque were recorded. the mr fluid used was lord mrf-122eg fluid diluted by 50 m/m% with silicone oil. https://doi.org/10.33927/hjic-2020-12 mailto:hollosi.janos@sze.hu 78 mester and szalai figure 1: model of a disk-type magnetorheological clutch the output side of the clutch was fixed at the torque sensor with the intention of measuring the torque transmission time-constants, so the output speeds at both the sensor and driven shaft were zero. the measurement cycles, using a preset magnetic field, consisted of a 3second-long mixing phase in the absence of a magnetic field, followed by a 6-second-long measurement period with the magnetic field turned on, and finally another 3second-long mixing phase, all at a constant speed. after the cycle, a new speed was set and a new cycle started. the speeds measured were 11.5, 17.5, 23.5, 29.5, 35.5, 40.5, and 46.5 rpm. the magnetic induction was controlled by currents of 1.8, 2.5, 3.3, and 4.4 a applied to the coil, thereafter the corresponding magnetic inductions were 114, 144, 173, and 202 mt. figure 2: complete magnetorheological clutch figure 3: transmission torque from when the magnetic field was turned on at a speed of n = 11.38 rpm and using different magnetic inductions figure 4: transmission torque from when the magnetic field was turned on at a speed of n = 46.5 rpm and using different magnetic inductions 3. results and discussion 3.1 experiments using the aforementioned method, a series of 12 measurements were carried out at each speed and in each magnetic field by taking into consideration the uncertainty of the mechanical parts (toothed belts, bearings, etc.). examples of the measurements can be seen in fig. 3 (n = 11.38 rpm) and fig. 4 (n = 46.50 rpm), as well as a periodicity due to the inaccuracies of the mechanical parts. the maximum output torque was m = 0.85 nm. 3.2 calculation of time constants time constants were determined by fitting an exponential function to the measured data: m(t) = a ( 1− e− t τ ) (1) where m denotes the transmission torque, t represents the time, and τ stands for the time constant. the hungarian journal of industry and chemistry torque transmission time-constant of a disk-type magnetorheological clutch 79 figure 5: cfitted curve of measurements at a speed of n = 46.5 rpm and a magnetic induction of b = 202 mt figure 6: time constants as a function of magnetic induction at different speeds fitting was carried out according to the measurements. an example of the fitting is shown in fig. 5. the fitted curve correlates well with the measurement data. the results of the fitting were averaged to obtain the time constants for the applied magnetic inductions and rotational speeds. the time constants are shown in fig. 6 as a function of magnetic induction. the measured time constants took into account the whole system, including the effects of the mr fluid as well as mechanical parts. by increasing the magnetic field strength, the time constants decreased. in the weakest magnetic field and at the lowest speed, the time constant was extremely high, greater than 1 second to be exact, due to the characteristics of the fluid. the time constants as a function of the speeds are shown in fig. 7. increasing the speed also resulted in a reduction in the time constant that was less significant than in stronger magnetic fields. in strong magnetic fields, the influence of the speed on the time constants was insignificant, therefore, its effect was almost negligible. figure 7: time constants as a function of speed using different magnetic inductions 4. conclusion based on the measurement results, the torque transmission time-constants for our magnetorheological clutch using the mr fluid were obtained. the time constants differed greatly from the response times of a magnetorheological fluid due to the inertia of the mechanical components. in the future, the influence of the mechanical parts on the time constants will be measured. acknowledgements this research was supported by the european union and co-financed by the european social fund under the project efop-3.6.2-16-2017-00002. references [1] rankin, p. j.; ginder, j. m.; klingenberg, d. j.: electroand magneto-rheology. current opinion in colloid & interface science, 1998, 3(4), 373–381 doi: 10.1016/s1359-0294(98)80052-6 [2] olabi, a. g. ; grunwald, a.: design and application of magneto-rheological fluid, mater. des., 2007, 28(10), 2658–2664 doi: 10.1016/j.matdes.2006.10.009 [3] mazlan, s. a. ; ekreem, n. b.; olabi, a. g.: an investigation of the behaviour of magnetorheological fluids in compression mode, j. mater. process. technol., 2008, 201(1–3), 780–785 doi: 10.1016/j.jmatprotec.2007.11.257 [4] lampert, s. g. e. ; van ostayen, r. a. j.: experimental results on a hydrostatic bearing lubricated with a magnetorheological fluid, curr. appl. phys., 2019, 19(12), 1441–1448 doi: 10.1016/j.cap.2019.09.004 [5] törőcsik, d.: some design issues of multi-plate magnetorheological clutches, hungarian j. ind. chem., 2011, 39(1), 41–44 https://mk.uni-pannon. hu/hjic/index.php/hjic/article/view/380 [6] rabinow, j.: the magnetic fluid clutch, trans. am. inst. electr. eng., 1948, 67(2), 1308–1315 doi: 10.1109/t-aiee.1948.5059821 48(1) pp. 77–80 (2020) https://doi.org/10.1016/s1359-0294(98)80052-6 https://doi.org/10.1016/j.matdes.2006.10.009 https://doi.org/10.1016/j.jmatprotec.2007.11.257 https://doi.org/10.1016/j.jmatprotec.2007.11.257 https://doi.org/10.1016/j.cap.2019.09.004 https://mk.uni-pannon.hu/hjic/index.php/hjic/article/view/380 https://mk.uni-pannon.hu/hjic/index.php/hjic/article/view/380 https://doi.org/10.1109/t-aiee.1948.5059821 https://doi.org/10.1109/t-aiee.1948.5059821 80 mester and szalai [7] decsi, p.; mester, s.; szalai, i.: tárcsás magnetoreológiai tengelykapcsoló modellezése, a rendszer időbeli viselkedésének vizsgálata, ogét xxvi. nemzetközi gépészei konferencia 2018, 91–94 hungarian journal of industry and chemistry introduction experimental samples and measurements results and discussion experiments calculation of time constants conclusion hungarian journal of industry and chemistry vol. 45(1) pp. 17–22 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0004 dynamic simulator-based apc design for a naphtha redistillation column lászló szabó, 1 * klára kubovicsné stocz, 1 laura szabó, 1 sándor németh, 2 and ferenc szeifert 2 1 department of technology and development, mol plc., olajmunkás u 2., százhalombatta, h-2443, hungary 2 department of process engineering, university of pannonia, egyetem u 10., veszprém, h-8200, hungary in this simulation study the operation of a naphtha redistillation column (a column with two feeds and three products) was analyzed with the application of aspen hysys ® software. the simulator, structure of local controllers and the product-quality estimators were based on the data of an industrial column in the danube refinery. the aim of the analysis was to identify the dynamic and steady-state effects of heating and cooling as well as the sidestream of product qualities. the relationship between the tray temperatures and the quality of the products was also identified and inferential calculations were made. based on the identified relationships, a twolevel hierarchical control structure was developed. on the lowest level of the hierarchy are the local controllers of flowrates, liquid levels, pressure and duty. the inferential calculations are important components of the controller which serve as the controlled variables at the coordination level. the inputs of the estimators are the process data of the column, e.g. temperature, pressure and flowrate. on the top level of the control hierarchical structure the quality of the products are controlled by manipulating the setpoint of the local controllers. based on the analysis of the controlled variable – manipulated variable relationship, closed-loop quality control was achieved with pid controllers. the result of the analysis may form the basis of advanced process controller implementation. keywords: distillation, multilevel control, mimo, inferential, naphtha distillation, plant data 1. introduction distillation is the most widely used separation technique in the chemical and petrochemical industries. around 95 % of the separation tasks of components are performed using distillation in the chemical industry, and the distillation units use approximately 3% of the total energy consumption of the world [1]. therefore, the improvement of distillation controllers and processes is important because of their widespread use and huge levels of energy consumption. distillation is a complex task because all of the equipment are multiple input, multiple output (mimo) objects from a control point of view with strong interactions [2]. the performance of distillation controllers directly affects the productivity rates, utility usage and product quality. during the operation, attaining a sufficient level of product quality is the final goal. hence, the precise calculation of the qualities is very important from an economic point of view. in this work, the multilevel control structure of the naphtha redistillation column has been analyzed (fig.1). furthermore, a simulator with the same local control *correspondence: lszaboszhb@mol.hu structure as the existing distillation column in the danube refinery was created. the model was adapted according to the data of the sensors and laboratory measurements. the controlled quality values were provided by inferential calculations based on archived data of the unit. during the analyses a control structure was created which could be suitable for the quality control of the column, and also the resulting models can be used in the implementation of advanced process controllers (apc). figure 1. structure of the control system szabó, kubovicsné stocz, szabó, németh, and szeifert hungarian journal of industry and chemistry 18 2. experimental for the analyses of dynamic responses a piece of commerical simulation software was used. data evaluation and parameter identification of the inferential calculations were performed with r programming language. 2.1. separation task the column has two feeds, the light naphtha feedstock possesses an initial boiling point of 12 °c and a final boiling point of 150 °c, while the boiling range of the heavy naphtha feedstock stretches from 57 to 197 °c. the task of the column is to separate the two feeds into three different naphtha products. the specification of the product streams are the following: distillate final boiling point should be between 58 and 65 °c, the final boiling point of the side product should be between 87 and 147 °c, and the initial boiling point of the bottom product should be between 99 and 103 °c. the simulator was implemented using aspen hysys ® software. the structure of the simulator is shown in fig.2. 2.2. simulator the implementation of the column was achieved over two main steps. in the first step, a steady-state simulator of the column was developed. the structure of the simulator follows the process flow diagram in fig.2. the column is divided into two parts, the light feedstock is loaded into the upper section (column 107), and the heavy feedstock is fed into the lower section (column 102). the towers, air coolers and heat exchangers were simulated with rigorous blocks and the model was adapted to data of the sensors and laboratory measurements. in the second step, the dynamic simulator was created based on the steady-state model. during the implementation of the dynamic simulator the calculation blocks were defined from the sizes of the actual equipment, e.g. the parameters of the trays in the tower. in some cases, pseudo pieces of equipment had to be defined to achieve a more realistic simulator, e.g. the bottom of the columns were modelled with a vertical drum to create a more detailed model. 2.3. measurement disturbances before determining the parameters of the controller, noise and time delays were applied to the calculated values. the disturbaces were determined based on our previous experience. transfer function blocks were used to simualte measuring instruments. their parameters can be seen in table 1. these signals were used later as controlled values. 2.4. control structure of column fig.1 represents the overall structure of controllers. on the lower level of the hierarchy the local controllers can be found. on this level, the controllers maintain the operating conditions (pressure and liquid level controllers) of the column and eliminate the disturbances (mass flowrate controllers) of the environment. the controller output variables are the valve positions and the process variables are the mass flowrates, liquid levels and pressure. the structure of the local controllers can be seen in fig.2, which is the same as the structure of the controller in the real column. the fc1 and fc2 controllers eliminate the fluctuation of the feed mass flowrate. the pc and the tc controllers compensate for weather changes and the fluctuation of fuel gas. the liquid level controllers (lc1, lc2 and lc3) were necessary to ensure normal operation because the refluxes and the boil-up flowrate would be zero if there is no liquid phase in the reflux drum and at the bottom of the columns [3]. pi controllers were applied at the local level. the degree of separation is based on the sustenance of the temperature difference between table 1. disturbances value type noise delay lag mass flowrate 1.0 % 15 s 0 s pressure 0.2 % 0 s 0 s temperature 0.3 % 30 s 60 s level 1.0 % 60 s 0 s figure 2. structure of the simulator dynamic simulator-based apc design 45(1) pp. 17–22 (2017) 19 products. the main target of the operation is to achieve specified product qualities. the provision of online quality values for the control is an important task in the industry. one of the feasible solutions is to apply inferential calculations. generally the inputs of these calculations are temperatures, because the quality of products is strongly correlated with the tray temperatures of the columns. consequently, the temperature and quality controls serve the same purpose. therefore, in this paper the quality of the products was controlled at the top level of the control hierarchy. the controller outputs on this level were the setpoints of the local controllers (fc3, fc5 and tc) and the controlled values were the outputs of the inferential calculations. 3. results and analysis 3.1. validation of the simulator in the first analysis, the dynamic behavior of the simulator was validated. (the steady-state accuracy was validated during the construction of the model.) the model was compared to the historical data of the real column. as fig.3 shows, the coil outlet temperature (cot) of the furnace was changed over two steps. during this process the top temperature of column 107 was controlled. the head and bottom temperatures of column 102 were analyzed, because the effect of the cot was significant on these parameters. the operating point of the real column was different from the simulated one, however, in this analysis only its dynamic behavior was evaluated. therefore, in the simulator the setpoint of the cot was changed in the same direction and by the same amount as the measured data. the signals were normalized in order to compare the trends easily. it can be seen that the curves possess the same correlation in both the simulated and real columns. the dynamics of the responses were also identical in both cases, thus the simulator was found reliable for further analyses. 3.2. analysis of local controllers for the tuning of the local controllers previous experiences were drawn on [4]. it was assumed that the controllers exhibit no significant interactions so they can be tuned independently. before determining the parameters of the controllers, filters were applied, hence, the dynamics of the loops were approximated to the real control loops. the control loops were tuned in the following order: flowrate (fc1-7), the liquid level (lc1-3) and pressure (pc) controllers. in the last step the parameters of the coil outlet temperature controller (tc) were determined. for the loops, honeywell equation b [5-6] was used, and the proportional and integrating parameters were determined using the built-in autotuner tool. after automatic tuning, the loops were tested and fine tuning was carried out to avoid fluctuation of the loops. the behavior of the fc1 is presented in fig.4. as the figure shows, the controllers follow the setpoint without exceeding it, which ensures a robust local controller system. the raw calculated signal, the signal loaded with noise and the filtered (controlled) signals are also presented in fig.4. as the results show, the control of the raw values is stable and is the first signal to reach a setpoint. 3.3. inferential calculations the quality estimators were created for the final boiling points of the distillate and the side product and for the initial boiling point of the bottom product. for the inferential fitting the laboratory and process data was used; the data was collected over a period of one year. in the case of the process data, all relevant measurement points of the column were considered (flowmeters, figure 4. fc1 controller figure 3. validation of the simulator szabó, kubovicsné stocz, szabó, németh, and szeifert hungarian journal of industry and chemistry 20 temperature and pressure measurements). one hourlong periods were aggregated from the online data before each laboratory sample time. from these values pressure compensated temperatures (pct) and ratios of the mass flowrates were also calculated. the inputs of the equations (see table 2) were determined using correlation analysis, thus the qualities were calculated from the most relevant values. the parameters of the equations were calculated using linear regression. the results of the fittings are presented in fig.5. 3.4. structure of quality controllers according to the separation task the controlled variables (cv) are: distillate final boiling point (cv1), sideproduct final boiling point (cv2) and bottom product initial boiling point (cv3). the manipulated variables are the following: setpoints of fc3 (mv1), fc5 (mv2) and tc (mv3). the structure of the quality controllers was determined with the help of the relative gain array (rga) [7]. to create the array, a step test was performed for each manipulated variable (mv) in the simulator. the rga is presented in table 3. the elements of the matrix evaluate a possible loop with the given mv – cv pair. if the element of the array is negative, closing other loops will reverse pairing gain. this configuration will become unstable if the other loops operate. if the element of the rga exceeds one, interaction with other loops has an inhibiting effect. closing other loops decreases pairing gain. if the value is between 0 and 1 then pairing gain will increase by closing the other loops; the interaction is the greatest at 0.5. in the case of this pairing the loop should be tuned when the other loops are automated. if the rga value is 1 then the other loops have no effect on the pairing gain. in the case of the cv1 the evident manipulated variable is mv1. the other two can be paired in two ways. according to the rga, the obvious pairing should be cv2 – mv2 / cv3 – mv3. however, there is a primary effect between mv2 and cv2, and it possesses a negative gain. this behavior could make the control loop instable, or the settling time of the controlled object would be large. the dynamic responses are presented in fig.6. in this analysis the mvs were stepped during the first minute. only the local controllers were in closed loops during the analyzed period. table 2. input parameters of inferential calculations inferential input 1 input 2 final boiling point of distillate pct of 107 head temperature final boiling point of side product pct of 107 bottom temperature ���ℎ� ���ℎ�ℎ� ���ℎ� ���� initial boiling point of bottom product pct of 102 bottom temperature figure 6. open loop test cv2 – mv2 table 3. relative gain array mv1 mv2 mv3 cv1 7.7 -1.2 -5.5 cv2 -6.9 1.9 6.0 cv3 0.2 0.3 0.5 figure 5. performance of inferential calculations dynamic simulator-based apc design 45(1) pp. 17–22 (2017) 21 the following final control pairings were applied: cv1 – mv1, cv2 – mv3 and cv3 – mv2. according to this analysis quality control can be achieved using simple pid control loops. therefore, the analysis of the closed-loop quality control in the following chapter was performed using only pid loops. this analysis was also the basis of an apc implementation. the initial apc models can be seen in fig.7. 3.5. operation of quality controllers in this analysis the operation of the quality controllers was analyzed in the case of a disturbance. the mass flowrate of the light naphtha feed was changed at 5 o’clock. during the analyzed period all of the local and quality controllers were in closed loops. according to the results in fig.8, the controller system can compensate for this change. in the figure the values of the mvs were normalized between their minimum and maximum limits. in the case of cv1 this quality did not violate the specification limit, and the controlled variable was close to the setpoint after 2.5 hours. this parameter possessed the smallest peak of the three cvs at approximately 1.3 °c. cv2 exhibited a peak at approximately 2 °c, nevertheless, this was well within the specification limit so it did not violate it. the settling time was about 7.5 hours. cv3 exhibited a peak at approximately 3 °c which violated the specification limit. after 2.5 hours the cv once again exceeded the limit. the settling time was ~15 hours. as can be seen the outputs (op) were moved after the settling of the cvs, but because of the long settling time the whole time period was not presented. figure 8. operation of quality controllers figure 7. apc models szabó, kubovicsné stocz, szabó, németh, and szeifert hungarian journal of industry and chemistry 22 4. conclusion for the analysis of the naphtha redistillation column at mol plc. the dynamic simulator of the unit was adapted to the data of the real equipment. the steadystate accuracy and the dynamic behavior of the model were evaluated. the simulator is reliable for the analysis of the column. for the operation of the distillation column a twolevel control structure was implemented in the simulator. on the lower level of the control hierarchy controllers were created which facilitated normal operating conditions of the column (pressure and liquidlevel controllers) and eliminated the disturbances of the environment (mass flowrate controllers). to ensure quality signals, inferential calculations were created based on the historical data of the real column. the inputs of the calculations were mainly the temperature measurements of the columns. hence, the controlled temperatures were chosen during the correlation analysis of the inferential calculations; on the top level of the control hierarchy the controlled variables were the outputs of the quality estimators. the manipulated variables were the setpoints of the local controllers. the pairing of the manipulated and controlled variables should be defined carefully. the first aspect of the pairing was the gain between the variables, however, the dynamic responses were also considered. to eliminate the interaction and to improve the performance of the quality controller, decoupling [8] or a model predictive controller [9] was recommended. the simulator-based column analysis can be a good foundation for an advanced process controller. the cv-mv pairing and resulting single input-single output models can be used as initial models in advanced process controllers. furthermore, the simulator can be used for the analysis of column operation issues in the plant. the resulting inferential calculations have already been implemented and are available for the operators to facilitate quality control. acknowledgements we acknowledge the financial support of széchenyi 2020 under the project efop-3.6.1-16-2016-00015. references [1] mansour, k.; mansour, e.: rigorous optimization of heat-integrated and petlyuk column distillation configurations based on feed conditions, clean techn. environ. policy, 2009 11(1), 107–113 doi: 10.1007/s10098-008-0171-6 [2] skogestad, s.; morari, m.: the dominate time constant for distillation columns, computers and chemical engineering, 1987 11(6), 607–617 doi: 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kezmanová , mišlanová, and vojs staňová 4. conclusion in our experimental work, the use of advanced mass spectrometry techniques in combination with highperformance liquid chromatography-mass spectrometry (hplc-msn) for the analysis and identification of polyphenolic compounds in extracts prepared from different types of green foods was our focus. from the hplc-msn data obtained by analyzing extracts from different types of green food, it was possible to obtain information about the composition of the analyzed extracts as well as information about the nature and structure of the polyphenolic compounds represented therein. using the developed hplc-esi-it-tof-ms method, the presence of 13 antioxidants in the sample of nettle extracts and 16 antioxidants in the sample of garlic extracts was confirmed. based on the results obtained, it can be stated that the developed hplc-msn method is a suitable tool for the characterization and identification of polyphenolic compounds in extracts prepared from green foods. acknowledgement this research was supported by the grants vvce-007007 and apvv-0583-11 of the slovak research and development agency (srda) and grant of comenius university guk/321/2017. references [1] gil, e. s.; couto, r. o.: flavonoid electrochemistry: a review on the electroanalytical applications, revista brasileira de farmacognosia, 2013 23(3), 542–558 doi: 10.1590/s0102-695x2013005000031 [2] boros, b.; jakabová, s.; dörnyei, á.; horváth, g.; pluhár, z.; kilár, f.; felinger, a.: determination of polyphenolic compounds by liquid chromatography–mass spectrometry in thymus species, j. chromatography a, 2010 1217(51), 7972–7980 doi: 10.1016/j.chroma.2010.07.042 [3] ginjom, i.; d’arcy, b.; caffin, n.; gidley, m.: phenolic compound profiles in selected queensland red wines at all stages of the wine-making process, food chemistry, 2011 125(3), 823–834 doi: 10.1016/j.foodchem.2010.08.062 [4] atoui, a.; mansouri, a.; boskou, g.; kefalas, p.: tea and herbal 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instrumentation chemicals sampling and sample preparation results and discussion conclusion hungarian journal of industrial chemistry veszprem vol. 30. pp. 119126 (2002) present status and perspectives of co-combustion in german power plants w. scheurer*, u. richersl**, h. seifert1** andk. r. g. heln* (universitat stuttgart, ivd, pfaffenwaldring 23, 70569 stuttgart, germany 1forschungszentrum karlsruhe gmbh, institut fiir technische chemic, d-76021 karlsruhe, germany received: december 03, 2001 various approaches to the future waste management policy in germany are currently under discussion. one problem arising in this connection, this is the suitability of existing furnaces for the co-combustion of waste. the use of sewage treatment sludge in power plants is already being practiced on a technical scale. co-combustion in power plants is of interest also because of the c02 problem, as renewable resources can also be used for this purpose. this ruiicle documents the technical status of co-combustion in germany and the available quantities of selected supplementary fuels. moreover, experience accumulated in german coal fired power plants in using supplementary fuels is compiled. future possibilities are assessed. introduciion as a consequence of political criteria, waste management in germany will be characterised in the future by a high degree of separation of waste streams for which optimum ways of utilisation will be sought after. where recycling makes no sense, thermal treatment of waste is a possibility. until the late eighties, emissions constituted the main point in debates about thermal waste treatment. nowadays, it is the costs of waste management, which are becoming more and more important. moreover, greater attention is being devoted to the efficiency of waste management plants against the background of the c02 problem and the greenhouse effect. one possibility of thermal waste treatment or regenerative fuel combustion with high efficiency and at relatively low cost is co-combustion in existing power plants. in germany, various waste materials are used in coal frred power plants among other facilities. in this study, the current state of knowledge about co-combustion in power plants is described. further potentials of co-combustion are presented on the basis of existing power plants. electricity generation the studies were performed on the basis of an analysis of the german electricity market. in 1998, 982 german power plants generated a total of 520,000 million kwh of electricity for use in industry and private households. a 27% share was generated by the combustion of hard coal, a 25% share by the combustion of brown coal [1]. these quantities did not change greatly throughout the nineties. analysis of the installed electric capacity of german power plants shows by far the largest fraction (89.5%) to be owned by public electricity utilities. table i shows more detailed information about electricity generation. in considering the possibilities of more extensive co­ combustion of waste materials, the furnace technology and plant sizes must be taken into account. according to [2], public utilities in germany generate 99% of their power output on sites with more than 50 mw electric power. the furnace technologies used by public utilities are listed in table 2. according to table 2, the dominating firing systems used are pulverised-fuel furnaces, for which two modes of operation are possible. wet-bottom furnaces. in which the ash is removed as molten stag and dry-bottom firings in which the ash is present as solid particles. ln contact information:"' phone: ++49 711685 3762, fax: ++49 711 685 3491 ** phone: ++49 7247 82 4656, fax: ++49 7247 82 6715 120 table 1 installed electrical capacity and power production in german coal-fired power plants industry german railways total public power utilities installed capacity 1998 brown coal 17861 mw 780mw 110mw 18751 mw (36.2 %) (1.6 %) (0.2 %) (38.0 %) hard coal 26248mw 3700mw 595mw 30543mw (53.2 %) (7.5 %) (1.2 %) (62.0 %) total 44109mw 4480mw 705mw 49294mw (89.5 %) (9.1 %) (1.4%) (100 %) power production 1998 brown coal 122450 million kwh 4790 million kwh (45.7 %) (1.8 %) hard coal 122000 million kwh 15530 million kwh (45.6 %) (5.8 %) total 244450 million kwh 20320 million kwh (91.3 %) (7.6 %) table 2 firing systems in germany firing system stoker furnace fluidised-bed furnace multi-fuel furnace pulverised-coal furnace share 2,2% 2,3% 6,9% 89,1% germany, dry-bottom furnaces dominate, holding a share of 59.2%. wet-bottom furnaces are installed on 40.8% of the sites. because of this dominating role, this study will concentrate on pulverised-coal furnaces. a look at the geographic distribution of power plants over the territory of germany shows the expected relationship with the population density. highly populated areas mainly have hard-coal-fired power plants, while brown-coal-fired power plants are to be found in brown-coal mining areas so as to avoid long transport routes. new coal-fired plants are being built mainly to replace old brown coal fired units [1] [3]. the liberalisation has caused an upheaval in the electricity market in germany. it is safe to assume that existing overcapacities will result in power plants being shut down. particular some power plants installed as standby facilities to guarantee the continuity of electrical power supply are no longer required as a consequence of mergers of large electricity companies. however~ no reliable data are available for this ongoing process. legal framework in germany~ power plants and waste incmeration plants must meet different emission limits. emissions from power plants with thermal powers in excess of 50 m\vth are regulated by the ordinance on large power plants [4]. while waste incineration plants must meet the lower limits of the ordinance on incinerators for waste and similar combustible materials (5}. where waste materials are used as fue1s in power plants. the emission limits must be calculated on the basis of the emission limits and criteria contained in the two ordinances. this calculation. the so called mixing rule~ takes into account the calorific values. specific flue gas volumes+ and other data. one problem arising in this 550 million kwh 127790 million kwh (0.2 %) (47.7 %) 2470 million kwh 140000 million kwh (0.9 %) (52.3 %) 3020 million kwh 267790 million kwh (1.1 %) (100 %) connection is that the ordinance on incinerators for waste and similar combustible materials contains requirements on pollutants not listed in the ordinance on large power plants. for this reason, extensive measurements of emissions of a power plant may be necessary to obtain a permit for co-combustion of waste. a summary of chosen limits is included in table 3. the eu has decided a new directive on waste incineration with criteria about the co-combustion of waste in power plants. as far as waste incineration is concerned, the limits contained in the eu [6] directive are based on the requirements of ordinance on incinerators for waste and similar combustible materials. in co-combustion the emission limits for heat shares of recovered fuels up to 40% are calculated by a mixing rule always starting at a minimum share of 10 %. the eu directive states emission limit values for the power plants cprocess to be used in the mixing rule together with the emission limit values for waste incineration cwaste to calculate the allowed emission limit value. for the pollutants not listed in the ordinance on large power plants, the directive contains total emission limit values. supplementary fuels and their properties in germany, various management pathways exist for sludge arising in the treatment of municipal and industrial sewage. in germany, sewage sludge is covered by waste management legislation. next to agricultural uses, composting, and landfilling, thermal treatment has become an established disposal pathway. especially municipal sewage treatment sludge is important when it comes to co-combustion in power plants. because most of the residues from industrial sewage treatment plants are being incinerated already. relatively exact data exist about the treatment of municipal sewage in germany. accordingly, the 10 522 municipal sewage treatment plants in operation [7] annually produce 2 642 200 t of dry sludge. treatment pta~t sizes and sewage sludge arising yield/output differ regtonally and; as expected, depend on the population density. taking into account the sludge fraction from municipal sewage treatment plants already incinerated, 121 table 3 emission limits'for waste incineration plants and power plants 13th bimscbv 17th bimschv eu-directive co-combustion power plants waste incineration wa~te incineration (c waste) power plants >300mwth cement kilns daily average daily average half hour daijy average half hour daily average daily average (6% 0 2) (11 % oz) average (11% oz) average (6% 02) (10% oz) com_eound unit (11% oz) (11 % oz) co mglm3<t 250 50 100 50 x<t3 x(9 150 (:! 100 org. compounds as mglm3<t 10 20 10 x<j3 w<n total carbon 20 particulate matter mg/m3 <1 50 10 30 10 30 30(1:! 30(11 s02/ s03 as soz mg/m30 400 50 200 50 200 200(12 5o<u sulfur emission % 15 factor 5(12 no u. noz as nox mgfm3<i soo<3 200 400 200 400 200 (300°0) (lz soo<ll hcl mg/m30 100 10 60 10 60 x<j3 10(11 hf mgfm3<t 15 1 4 1 4 x<t3 1 (11 itlandcd mglm3<t o.o5<4 o.os<6 0.05(6,ll 0.05(6,!1 hg flg/m30 0.03 0.05 0.05 (6 0.05(6,ll 0.05(6' 11 l sb, as, pb, cr, co, cu, mn, ni, v, mg!m3<t 0.5 (4 u.s (6 0.5 (s,ll 0.5 {8,11 sn pcdd/pcdf nglm3<t 0.1 (5 0.1 (7,{s 0.1 (7,11 0.1 (7,ll (1 reference standard cubic meter, dry (7 (2 concentration based on the mass which can't be violated by more than (s 10 % of all measurements within a time period of 24 hours (9 0 average over sampling time (at least 6 h; maximum 8 h) withoutsn to be set by the competent authority biomass (3 for the emission control the state of the art should be applied g 1 (4 average over sampling time (at least 0.5 h; maximum 2 h) total emission limit value for this process (c emission) emission limit value to be used for mixing rule (c process) mixing rule with the limits as stipulated and c waste (5 average over sampling time (at least 6 h; maximum 16 h) (12 (6 average over sampling time (at least 0.5 h; maximum 8 h) (l3 a maximum of 2.3 million t of sewage treatment sludge (dry) can be available for co-combustion in power plants. the consideration of wood for co-combustion in coal-fired power plants demands a distinction among very different wood fractions. forest wood residues, arising in the tending of woods normally contain no pollutants. the quantities available are influenced by forest areas in a region, weather conditions, such as heavy storms, and by other factors. the quantities of forest wood residues available in germany are based on statistical calculations in which, among other factors, the forest areas of the regions considered, the tree species, and ecological aspects are taken into account. it may be assumed that approximately 7.5 million t of raw wood can be used in power plants in germany. [8] (9] moreover, the optimum solution to the disposal of waste wood is being discussed in germany. waste wood arises in a variety of industrial sectors or private households and may carry a variety of pollutants, such as wood preservatives or paints containing heavy metals. determining the quantities of waste wood in germany is difficult for a variety of reasons. different interpretations of the term "waste wood" are used and sawdust and similar materials from the wood industry are not always taken into account. additional new legal regulations, in particular on regional level have to be taken into account. moreover, the amount of waste wood is influenced by local waste management the quantities of waste wood which can be used for cocombustion, consequently, can be determined only with major uncertainties. an estimate conducted on this basis results in a total quantity of 4.1 to 11.7 mil1ion t per annum. a breakdown into the different fractions of waste wood is shown in fig.]. straw is another supplementary fuel of interest arising as a by-product in the cultivation of wheat, barley etc .. straw so far has mostly been left on the fields or used in stock farming. in the industrialised countries, straw has never been used for energy production, but that use is already being pushed in denmark by law. the quantities of straw that could be used for co­ combustion are determined by the present agricultural uses of existing areas, by weather conditions, and by soil properties. the quantities of straw are determined in a similar way as the amounts of forest wood residues. in germany, a total of approx. 41.4 million t of straw arise annually [8] which, however. cannot be fully used for co-combustion. if the quantities required in stock farming and other areas are taken into account, then, according to [8], only 15% of the total amount, namely 5.9 million t of straw per annum, would be available for thermal utilization. other authors assume that between 10.1 and 17.2 million t of straw can be used annually [9]. estimates of the potential of recovered fuels from post user waste materials in germany are shown in table 4. the potential is quoted with 5.2r.4 million tons/a. in this table production residues (pre~user wastes) are not quoted due to the limited data available. estimates received from waste management companies 122 packaging (max) packaging {min) furniture, etc .. (min) construction and demolition (max) ~~~~-~~~~·~~~~~~·0 2 3 4 5 6 7 amount [million metric tons/yr.] fig.l range of waste wood arising from packing, used furniture and the construction sector table 4 potentials for recovered fuels from high calorific fractions of selected waste materials [10] total high calorific potential for fraction recovered fuels [million t/a] [%] [million t/a]* household waste 11.1 40-50 2.7-4.4 industrial waste similar to 4.8 50-60 1.4-1.2 household waste bulky waste 1.8 75-85 0.81.2 sorting residues 0.8 65-75 0.3-0.5 (dsd) total 18.5 5.2-8.4 * calculated from 60% of the lower and 80 % of the higher estimate of the hiah calorific fraction, without considering the possible additionat' streams that might go into municipal solid waste (msw) incinerators table 5 fuel analysis of coals and selected supplementary fuels hard coal brown coal lhv* (raw) [mj/kg] 28 9 moisture (raw) [%] 5.1 50.4 volatile matter (dry) [%] 34.7 52.11 ash (dry) [%] 8.25 5.1 fixedc (dry) [%] 57.1 42.83 c (dry) [%] 72.48 65.9 h (dry) [%] 5.64 4.9 n (dry) [%] 1.28 0.69 s (dry) [%] 0.94 0.39 cl (dry) [%] 0.128 <0.1 0 (dry) [%1 11.1 23 ash fusion temperature [ocj 1250 1050 *lower heating value **refuse derived fuel average at 2 million tons total, which would yield about i miliion tons/a recovered fuel. the co-combustion of sewage sludge, wood and straw in a power plant effects the power plant operation. these influences are determined by the fuel characteristics and the chemical compositions. table 5 lists the most important fuel data for a number of selected examples. most of the supplementary fuels considered mostly have lower calorific values than hard coal. as a rule~ waste wood has a humidity of approx. 10% and a calorific value on the order of 17 mj/k.g. in the case of sewage treatment sludge. the calorific value is between 2 and 12 mj/k.g. depending on the water content. the water content and the ash fraction have a major influence on the calorific value of bio fuels, for which is to 18 mj/kg is to be expected. the large ash share in sewage sludge increases the amounts of fly ash by co-combustion. although the a h content of straw can be compared to that of regular fuels. the low melting points may cause problems in operation as a result of caking. moreover the chlorine content must be considered which has a major impact on corrosive processes. especially straw normally has a relatively high chlorine content. waste wood may contain up to 3'rnitrogen and heavy metals. wood straw rdf* dried sewage sludge 12.4 15 23.5 10.58 33 10.6 4.1 3 83.2 74.4 82.6 49.52 0.34 6.1 12.2 45.1 16.5 19.9 5.2 2.39 48.7 47.4 56.8 25.01 5.7 4.5 7.9 4.88 0.13 0.4-0.78 0.74 3.2 0.05 0.05-0.11 0.25 1.1 <0.1 0.4-0.73 0.82 <0.1 45 40.4 21.3 17.69 1200 850 ll20 1200 fig.2 schematic diagram of a typical pulverized-coal-fired power plant with flue gas treatment system basic principles of co-combustion in power plants the co-combustion of supplementary fuels in power plants is based on the principle of using existing plants without major modifications. possible ways of feeding supplementary fuels are shown in fig.2. the coal crushed in coal mills is fed into the combustion chamber by air as transport medium. thermal energy of the hot flue gases is transferred in the boiler to the water·steam system for electricity generation or other uses. tht=" pollutants are separated in the flue gas treatment system, which is mostly made up of a selective catalytic reactor (scr) de nox reactor, an electrostatic precipitator and a flue gas desulphurisation plant. supplementary fuels can be fed in two very different ways. one possibility, which will be the main focus in this study, is direct feeding to the combustion chamber together with the standard fuel. in this case, there may be need for an additional preparation step, i.e., drying or crushing. another possibility is thermal pre-treatment by pyrolysis or gasification in a separate reactor. the products of this pre-treatment are then fed to the combustion chamber after passing varying steps of cleaning or heat recovery. existing power plants were designed for a specific fuel throughput. the influence of co-combustion on the different plant components may be very different. one example to be mentioned is the fuel volume flow increase resulting from the co-combustion of biomass. if approximately 10 % of the thermal output of the furnace system ise supplied as biomass, the fuel volume flow almost doubles. common grinding and feeding of biomass and standard fuel may then result in problems. the melting point of ashes produced in the combustion chamber can be reduced as a result of co­ combustion. compared to operation with the standard fuel, this may cause increased slagging and fouling in the combustion chamber and the heat exchangers. problems of this kind may arise in particular when bio fuels are used whose ash melting point is very low. in power plants which, due to their mode of operation, generate molten slag, low melting temperatures of the ashes are desirable. in the region of convective heating surfaces, there may be increased contamination or erosion when secondary fuels with high ash share are used. especially for sewage sludge, this is an aspect of importance. bio fuels, because of their lower ash fractions, are not problematic in this respect. it should also be examined whether co-combustion of supplementary fuels results in changes in the flue gas volume and the flow rate, respectively. any change in the flow rate influences the heat transfer in the boiler and also has an impact on the flue gas purification system. higher flow rates may increase erosion. another critical point is the high chlorine content of straw or other supplementary fuels, which may give rise to high-temperature corrosion and wastage of the heating surfaces. the possible effects of co-combustion on the flue gas purification plant are determined by the placement of the denox-system. in the case of the high-dust placement shown in fig.2, deactivation of the denox catalyst by components of the fly ash, such as alkali metals, arsenic, phosphorus, or fluorine, is quite possible. for co-combustion of waste materials, a low-dust arrangement of the denox-system downstream of the flue gas desulphurization plant is advantageous with a view to potential poisoning of the denox catalyst. the price to be paid is reheating of the flue gases to the operating temperature of the catalyst. dust removal may cause problems especially when sewage sludge with its high ash content is used. in 123 addition to the increased amount of ash, the removal behaviour of mixed ashes can be different from that of the ashes produced by the use of standard fuel. the effects of co-combustion on the flue gas desulphurisation plant are determined by the chemical composition of the supplementary fuel as a consequence of sulphur concentrations, bio fuels reduce the sulphur input, while sewage sludge tends to increase it. in addition to sulphur, arsenic, lead, mercury, and other heavy metals can be removed in the flue gas desulphurisation plant. as a consequence, the utilisation of gypsum produced in flue gas desulphurisation can be influenced. in the case of chlorine containing supplementary fuels it must be taken into account that chlorine increases the solubility of gypsum. status of co-combustion in the course of this study, those power plant locations in germany were listed which have experience in the co-combustion of supplementary fuels. the list is based on literature and other sources. because of the large number of sources, no references will be indicated. table 6, table 7 and table 8 show the locations plus information about the respective power plants. at the present time, experience in the co-combustion of sewage sludge has been accumulated at 17 locations. the operating permit for co-combustion of sewage sludge was granted to twelve plants, but is being used by only nine plants. this results in an capacity for co­ combustion of sewage sludge of approx. 350,000 t of sewage treatment sludge per annum. according to table 7, biomass or waste wood are being used as supplementary fuels at two locations. experiments about co-combustion have been documented for six other sites, and conceptual design studies exist for two locations. as far as the other waste materials are concerned, these are specific solutions for industrial locations where specific wastes arise in large quantities. there have been tests in several additional power plants, of which results have not been published. after the occurrence of bse cases on the european mainland, interest shifted and co-firing of meat and bone meal has been established in several german power plants. there is not sufficient data published to draw an accurate picture about range of co-firing and the effects of co-firing on the power plants. depending on the legal and political developments co-ftring of meat and bone meal might be a temporary solution. potentials the use of supplementary fuels in electricity generation can be estimated on the basis of the primary energy of coal used, which amounted to 2708 pj in 1998. under the assumption that 10% of the energy could be substituted by a supplementary fuel with a calorific value of 10 mj/kg, german power plants could use an annual 27 million t of supplementary fuels. due to 124 table 6 german power plants experienced with co-combustion of sewage sludge sewage sludge proportion site i company firing system boiler size supl. fuel status capacity % by wt % -th. berrenrath brown coal 235 mw., dewatered since 1995 4 3.5 max. rhein braun fluidized bed cont. operation 65 000 t ts/yr. * box berg 111 veag brown coal dry2x500mwo~ dewatered since 1999 3-5 approx. 1 approx. bottom cont. operation (6% *) 30 000 t ts/yr. braunsbedra ewag brown coal stoker 4x7 mw., dewatered 1996 tests up to 50 approx. 25 100% wood performed buschhaus brown coal dry930mw., dried since 1998 5 * <5 approx. bkb bottom dewatered cont. operation 80 000 t ts/yr. duisburg h. hard coal 200mwih dewatered cont. operation 9 <os approx. stadtwerke wet-bottom 365 mw., 16 000 t ts/yr. farge bremen hard coal 356mwc~ dewatered permission but 9 <05 approx. preussco elektra !lry-bottom noo ration 10 000 t ts/yr. franken ii hard coal 1047 mw., dewatered since 1998 cont. 5 % ts* < 1.5 approx. bayernwerke dried operation 35 000 t ts/yr. l:leilbronn 1933 mw., dewatered since 1998 4 < 1.1 approx. enbw dried cont. operation (4 %*) 40 000 t ts/yr. lausward 170 dried permission but 21 ii 1994-1996 stadlw. dilsseld. no !:l~jeration (15%* 20 000 i ts/yr. liinen lnnovatherm hard coal fluidized 9mwc~ de watered since 1997 cont. coal addition until approx. bed operation lhv>4200 mj/kg 100 000 t/yr. mumsdorf mibrag brown coal n.a. dewatered tests performed n.a. n.a. dry-bottom dried karlsruherdk hard coal 1280 mw., dewatered 1998 tests 1.25 0 .07 enbw dry-bottom performed voerde hard coal 350 mw .. dried 1989 tests approx. 20 steag wet-bottom performed wahlheim hard coal 382 mwih dried 1996 tests 12.5 5 eckarwerke wet-bottom performed weiher u saarenergie bard coal 195mwih dewatered since 1996 cont. 5 (15%*) approx. dried operation 10 000 t ts/yr. weisweiler 913 mwih de watered cont. operation 7.5 max. 140 000 t /yr. • rwe starting 5/2000 zolling bayemwerke 1080mw., de watered since 1999 9 .6 2.76 approx. cont. operation 5 %ts* 10 000 t ts/yr. tests cont. operation .a.: not available table 7 german power plants with co-combustion of biomass and waste wood biomass & waste wood proportion site and company firing system boiler size supl. fuel status capacity %-wt %-tb. afferd el.werke hard coal fluidized 124mw., waste wood since 1997 up to up to wesertal bed cont. operation 100% 100% n.a. berrenrath rheinbraun brown coal 235 mw., waste wood 1999 tests test with flu.idi zed bed cont. operation approx. 8 t/h .a. heilbronn bard coal 1933mw111 wood feasibility study 1996 20 tlh enbw dry-bottom straw 8 80000 t/yr. janschwalde eag brown coal .a. waste wood tests running possible: dry-bottom .a. .a. i 00 000 t/yr. lubbenau brown coal 100mwd wood chip 1993 tests veag dry-bottom 7 .a. moabit bard /brown c. 240mw., wood 1995 tests performed bewag fluidized bed .a. i to 13 pformeim stadtwerke hard coal wood, waste wood, ~ . . . flujdized bed bay eas•b•lity study 1997 substitution of about 20 mw111 possible scbwandorf browncoa1 straw 1996 tests up to 20 % bayem~erke dry-bottom ince 6/1999 cont. 8 12 operation 100 000 t/a tests • value stipulated in the license issued 125 table 8 german power plants experienced with co-combustion of waste materials waste materials bremen entsorg.betrieb several wastes conceptional study materials janschwalde veag brown coal n.a. rdf tests running n.a. n.a. possible dry-bottom 100 000 t/yr. leverkusen hkw bayer hard coal fluidized 105mwih polystyrene resin concepts 0.375 0.5 330 t/a ag bed schwarze pumpe veag brown coal n.a. tar residues 12194-6/98 cont. <i until6/98 dry-bottom operation 250 000 t wolfs burg hard coal n.a. lacquer sludge cont. operation up to vw wet-bottom used oil 30000 t/yr. gasification i pyrolysis firing system boiler size supl. fuel status technique & capacity proportion site and company berrenrath rhein braun brown coal plastics, rdf, tests since ' 86 fluidized bed up to 30 t!h sewage sludge gasification hamrn vewenergie hard coal 770mwih plastics, car shred, start up phase rotary kiln pyrolysis 2x50 000 t/yr. wet-bottom industrial waste 60mw(jo %) tests cont. operation * value stipulated in the license issued table 9 fuel and energy potentials of the chosen supplementary fuels heating value share on primary energy consumption '> fuel potential energy content hard coal brown coal total [million t/a] [mj/kg] [pj] [%] [%] [%] sewage sludge 2.3 (ts) 12 28 2.0 2.1 1.0 waste wood 8.5 i) 16.5 140 10.2 10.4 5.2 straw 5.9 14.5 86 6.3 6.4 3.2 forest residue 7.5 10 2) 75 5.5 5.6 28 rdf-fuets 4,5 n•> 76 5.6 5.7 2 total 404 29.6 30.2 15.0 i) average of 4.1 12.7 mio. t/a 2) depending on storage time 1 0 60 % moisture, or 6-15 mj/kg; here: 40 % moisture or i 0 mj/kg 3) primary energy consumption 1998: hard coal= 1363 pj; brown coal= 1345 pj; total= 2708 pj 4) assumed average heating value logistical and operational limitations these heat shares might not be achieved in operation. the results of the calculation of energy potentials on the basis of the calorific values of the supplementary fuel quantities listed in this work are shown in table 9. the supplementary fuel potential incorporates an energy volume of approx. 404 pj, which corresponds to approx. 15 %of the energy input into german coal-fired power plants. if this supplementary fuel were used exclusively in lignite or hard-coal fired power plants, a nearly 30 % contribution would be possible. of all the fuels considered, waste wood constitutes the largest single item. the potential c02 reduction as a percentage of the total releases by coal-fired power plants is between 12.2% for the substitution of hard coal only, and 17.7% for brown coal. the reason is the higher specific c02 emission of brown coal. comparison of the capacities of co-combustion in german power plants on the basis of table 6, table 7 and table 8 with the fuel potential in table 9 indicates a major discrepancy. co-combustion capacities exist for approx. 15 % of the arising sewage sludge. in the case of waste wood, a co-combustion capacity of approx. 200,000 t per annum must be compared with an annual amount of approx. 8 million t per annum. obstacles co-combustion of waste in power plants in germany on a larger scale is hampered by a variety of obstacles. first and foremost, the fuel supply of power plants must be guaranteed to maintain continuous operation. in the case of coal and other standard fuels, supply on international markets is easy. in some regions of germany, the supply of sewage sludge is organised by industrial associations or municipal authorities. on the other hand, however, there are no institutions in germany which could reliably supply power plants with biological fuels, such as forest wood waste or straw. availability is influenced also by the fuels themselves. while sewage sludge arises continuously the year over as a residue from sewage treatment, seasonal differences and risks re ulting from climatic influences affect the availability of traw and other bio fuel s. 126 in addition to these problems, also the requirements to be met in recycling combustion residues must be borne in mind, because the use of these materials in the cement and building industries must meet specific criteria. the high ash content of sewage sludge affects the properties of fly ash even at low contributions to the thermal power plant capacity. moreover, the co-combustion of sewage sludge, waste wood or other supplementary fuels requires amendments to the operating permits which may entail considerable expenses. in this connection, the lack of a precise definition of the terms "utilization" and "disposal" in german legal requirements represents an additional problem, with ''disposal" implying considerably more stringent regulations. in germany, the co-combustion of sewage sludge is considered both, utilization and disposal, depending on the permit stipulated in the specific case. where waste materials are used, the legal requirements from waste incineration must additionally be taken into account in germany. applications for permits require measurement programs, which may be quite extensive, on the basis of which emission limits are determined by the mixing rule. another problem is the capital costs. in addition to the costs for the storage and transport of supplementary fuels, the use of waste materials gives rise to costs also for modifying emission measurement systems and instrumentation and control systems. as a consequence of deregulation in the electricity market, capital investments are made only with great reluctance at the present time. because of the mergers of power companies, which give rise to increasingly tougher competition, long-term planning is not possible at the present time. another important item is fuel costs. while a cost benefit is likely to arise from the combustion of waste material, biomasses, such as forest wood residues or ::.traw, give rise to costs between dm 75 and 225/t (dry) ' [!oj. summary at first sight, the work performed confirmed that the co­ combustion of sewage sludge is a technology established on an industrial scale. although there are precise regulations about permits for co-combustion, the use of sewage sludge should be examined critically with respect to highly volatile pollutant residues, such as mercury and mercury compounds. in addition, the existing power plant spectrum in germany offers possibilities for the co-combustion of forest wood residues, straw, recovered fuels or waste wood. the co-combustion of these materials is technically feasible even though altered compositions of residues and other details have not yet been clarified. in addition to the technical aspects, activities seeking to further co-combustion are influenced by economic concerns against the background of the deregulation of the electricity market in germany. the expected financial benefits make co-combustion attractive for the use not only of sewage sludge, but also of other waste materials. there are two main reasons why co-combustion of biomasses has not yet been carried out on a technical scale in germany. for economic reasons, co­ combustion is possible only with financial support by the government. moreover, there are no fuel markets to supply power plants with these fuels. acknowledgement the authors are grateful to the german federal ministry for education, science, research, and technology for the financial support made available under grant no. 0326864 and to the european community for the funding under the contract number erk5-ct -199900021. literature 1. vereinigung deutscher elektrizitatswerke (vdew e.v.): strommarkt deutschland 1998; frankfurt am main; 1999 2. vereinigung deutscher elektrizitatswerke (vdew e.v.): vdew-statistik 1996 betriebsmittel, frankfurt am main; 1997 3. technische vereinigung der grosskraftwerksbetreiber e.v. (vgb): tatigkeitsbericht 1996/1997, vgb-verlag, essen 4. dreizehnte verordnung zur durchfiihrung des bundes-immissionsschutzgesetzes (ordinance on large power plants), juni 1983 5. siebzehente verordnung zur durchfiibnmg des bundes-immissionsschutzgesetzes (ordinance on incinerators for waste and similar combustible materials), februar 1999 6. richtlinie 2000176/eg des europaischen parlaments und des rates vom 4. dezember 2000 tiber die verbrennung von abfallen 7. esch b. and kroger g.: korrespondenz abwasser,l999, 46(6), 943-952 8. kaltschmitf m. and wiese a.: erneuerbare energietrager in deutschland. potentiale und kosten, springer-verlag, berlin, 1993 9. lemle l., rosch c. and wintzer d.: nachrichten forschungszentrum karlsruhe, 1997, 29(2), 113122 10. braungart m., ketelhut r. and gallenkemper b.: entsorgungspraxis 2000, 18(2), 31-33 11. siegle v.: biogene brennstoffe in aufbereitung und verbrennung; dissertation universitlit stuttgart, 1999 page 118 page 119 page 120 page 121 page 122 page 123 page 124 page 125 hungarian journal of industrial chemistry veszprem vol. 30. pp. 241-245 (2002) classification neural networks improve:ment using genetic algorithms a. woinaroschy, v. plesuand k. woinaroschy (department of chemical engineering, university politehnica of bucharest, 1-5, polizu street, bucharest 78126, romania) received: april 8, 2002 the aim of the present work consists the development of a procedure capable to realize a high accurate classification neural network with a reduced number of neurons. in order to avoid local minima. the weights of a proposed three-layer network were computed using a common genetic algorithm. the performances of the genetic algorithm were strongly improved by several means that make an increased balance between exploration and exploitation of the search space. thus, in order to decrease the number of genes, respectively weights, the dimension of the output vector was minimized by identification of classes with binary numbers. a very favorable effect was obtained by seeding the initial population with a good chromosome obtained by the use of the classical "delta-rule" learning procedure. it was also investigated the effect of the initial population size, the bounds imposed to the weights of the inter-neuronal connections, the number of neurons in the hidden layer, fitness expression, etc. keywords: neural networks, genetic algorithms, classification introduction an important field of neural network applications in bioprocessing and chemical engineering consists in classification problems, like process fault detection and diagnosis, detection and location of gross errors in experimental data sets, spectral analysis, models discrimination and identification of model parameters, etc. there are several types of neural networks used for classification problems: back-propagation, radial-basis­ function, learning-vector-quantization, probabilistic networks, networks based on adaptive-resonance-theory, and so on. each type has some advantages and consequently disadvantages, depending on the nature of the problem. representatives for chemical and biochemical processes are the problems with non­ uniform decision regions where the data points of each class are scattered. for these problems radial-basis­ function and back-propagation networks perform better [1,2]. the use of gradient of the error function during the learning stage affects the performances of these networks due to ending into a local minimum. in fact, the gradient technique is an example of a hill-climbing ~trategy, which exploits the best solution for possible improvement; on the other hand, it neglects exploration of the search space. random search is a typical example of a strategy, which explores the search space ignoring the exploitations of the promising regions of the space. for small spaces, classical exhaustive methods usually suffice; for larger spaces special artificial intelligence techniques must be employed. genetic algorithms are among such techniques, being a class of general purpose (domain independent) search methods which strike a remarkable balance between exploration and exploitation of the search space [3]. for several years, genetic algorith.ms have been used to evolve the neural networks structure. as well as the weights of the inter­ neuronal connections (e.g. see (4-71). the aim of the present work consists in an extended investigation of the features of genetic algorithms in order to realize a high accurate classification neural network with a reduced number of neurons. methodology the investigations were done on the three layers networks with linear transfer function for the input layer, and sigmoid transfer function for the hidden and output layers. because the number of neurons in the input layer is imposed by the number of elements of the vectors that are classified, the structural variables of these networks 242 table 1 the effects of several factors on the performances of chemical reactor fault-diagnosis network b nh n0 rms error percentage of wrong s;p classifications (%) 100 [-100; 100] 3 4 0.3478 27.20 200 [-100; 100] 3 4 0.3418 26.25 500 [-100; 100] 3 4 0.2974 25.00 500 [-50; 50] 3 4 0.3827 26.25 500 [-100; 100] 3 4 0.2974 25.00 500 [-250; 250] 3 4 0.4840 37.50 500 [-100; 100] 3 4 0.2974 25.00 500 [-100; 100] 5 4 0.2701 21.25 500 [-100; 100] 7 4 0.1845 16.25 500 [-100; 100] 9 4 0.2395 18.75 500 [-100; 100] 3 4 0.2974 25.00 500 [-100; 100] 3 3 0.1411 20.00 500 [-100; 100] 3 2 0.2398 21.25 equal the number of neurons in the hidden and output layers. the number of neurons in the output layer depends on the rule of classes codification. there are no theoretical guidelines to establish the number of hidden neurons. different from the mentioned works, here each chromosome corresponds with a complete set of the weights of the inter-neuronal connections for a given structure of the network (respectively , each gene represent a weight). the structural variables, respectively, the number of neurons in the hidden and output layers, were step-by-step modified in an external loop: the procedure starts with the minimum numbers of the corresponding neurons and these are progressively increased up to imposed limits. the genetic algorithm used is a matlab implementation [8] that can be downloaded at ftp://ftp.eos.ncsu.edu/pub/simul/gaot. float . representation of chromosomes has been used. the selection of candidate chromosomes for crossover and mutation is made according with a ranking selection function based on the normalized geometric distribution. three types, of crossover are applied: simple, interpolated, and ext:rapolated crossover. in_ the simple eroesover, the crossover point is randomly selected. the ~lated c.roowve:r performs an interpolation along the line formed by the two parents. the extrapolated ~ves performs an extrapolation along the line fonned by the two parents in the direction of better parent. four types of mutation are applied: boundary, multi-nonuniform. nonuniform, and uniform mutation. boundary mutation changes one gene of the selected chromosome randomly either to its upper or lower bound. multi-nonuniform mutation changes au genes. whereas nonuniform mutation changes one of the genes in a chromosome on the base of a non-uniform probability distribution. this gaussian distribution starts wide~ and narrows to a point distribution as the current generation approaches to the maximum generation. uniform mutation changes one of the genes based on a uniform probability distribution. the numbers of applications of the different crossover and mutati~n operators are imposed as parameters of the genetic algorithm. the investigation of the effects of these parameters was out of the aims of the present work, and their default· values have been used, respectively for each generation: 2 simple, 2 interpolated, and 2 extrapolated crossover, 4 boundary, 6 multi-nonuniform, 4 nonuniform, and 4 uniform mutation. due to the use of a maximization algorithm, the chromosome fitness corresponds to the negative value of rms error. the attempts to use o~her expressions for chromosome fitness (e.g. the average relative error) did not give meaningful improved results. applications chemical reactor fault-diagnosis this application and the corresponding data are presented in [9]. the input vector contains reactor inlet temperature, reactor inlet pressure, and feed flowrate. the elements of the output vector are three fault classes: low conversion, low catalyst selectivity, and catalyst sintering. the following factors were studied: a) the size of initial population (sip); b) the bounds imposed to the weights of the inter­ neuronal connections (b); c) the number of neurons in the hidden layer (nh); d) the.number of neurons in the output layer (no); the last factor corresponds to different rules of classes codification. there are four types of outputs, corresponding to four classes: the correct operating regime, and the three fault regimes. ~he classical codification corresponds to the use of four output neurons, as follows: [1 0 0 0]; [0 1 0 0]; [0 0 1 0]; [0 0 01]. also, there are possible other two codification methods: a codification using three output neurons, respectively: [0 0 0]; [1 0 0]; [0 1 0]; [0 0 1], and a codification with two output neurons: [0 0]; [0 1]; [1 0]; [1 1]. the last codification is in fact the binary representation of each class number. our investigations in the field of classification neural networks indicated that the activity and corresponding response of the output neurones must close to 0 or 1. a neural network with one output neuron (having the smallest number of the inter-neuronal connections weights) for which the above mentioned 4 classes are codified with the activity domains: 0-0.25; 0.25-0.5; 0.50.75; 0.75-1 cannot be trained to give a correct classification. due to the random generation of the initial population of the genetic algorithm, each test was repeated five times. the results presented in the table 1 represents the corresponding average values. in all tests, for a correct comparison of the results, the total number of generations (the stopping criterion) was the same, respectively 1000. fig.] the evolution of mean( .... ) and best (-)fitness for the optimum neural network the analysis of these results indicates that: expansion of the initial population size has a favorable effect due to increasing the probability to generate individuals with a good fitness. unfortunately, this effect is present only in simple cases, for well-defined problems with smooth response surface. for highly complex. problems, the search space in which genetic algorithm usually operates is so large, that taking few additional chromosomes into initial population cause a very small, or no detectable effect, unless the problem surface is very smooth. a too small, or a too large range of the weights values has a non-favorable effect: in the first situation the optimization solution is arbitrarily restricted, and in the second case the search space is unreasonably enlarged. as in the case of gradient-based learning algorithms, there is an optimum number of neurons in the hidden layer for each neural network application, and the corresponding value must be establish through an iterative procedure. similarly, the best rule of classes codification and the corresponding number of neurons in the output layer must be found by iterations. with the best values of the investigated factors from table 1, respectively sip= 500; b= [-100; 100]; nh= 1; no= 3, and by the aid of the genetic algorithm the weights of the corresponding neural network were established. this exhibit excellent results: rms error = 0.007 and no wrong classification (related to the training set, due to the absence in the original mentioned reference [9] of a test set). the corresponding evolution of the genetic algorithm is represented in fig.l. it is remarkable that the best values of rms error obtained for this example by baughman and liu [9] (using the classical "delta rule" as learning procedure) at the end of 50,000 training iterations were: 0.088 for a network with 3 neurons in the· hidden layer and sigmoid transfer function, and 0.037 for a network with 5 243 neurons in the hidden layer and hyperbolic tangent transfer function. consistency analysis of fuzzy sets this case study was already presented in literature [10] as an application of a modified back-propagation neural network. the reason of the actual selection consists in the fact that the· application represents a difficult classification problem· involving non-linearly separable patterns. in many chemical processes due to several reasons there are some variables that cannot be measured directly on-line (e.g. biological or catalyst activity). in these cases the values of measured variables are fuzzy sets. related to system constraints and feasible domains of the variables these fuzzy sets must be consistent. in order to use a graphic representation, a hypothetical example with two measured variables, x1 and x2, and one unmeasured variable, x3, all restricted to a system of three strongly non-linear constrains, was considered: o.sx3+0.275x1x3+0.261x; x3+0.18xt x3+x2=0 (3) the feasible domains of the variables are: the number of variables is incidentally ~e same as the number of constraints. usually, the number of variables is greater than the number of constraints. the measured values of the variables correlated with the feasible domains of all variables, and with constraints' violations will generate several classes of errors, depending on combination of violated restrictions. for this application the following four classes were considered: a -all restrictions are satisfied; b -constraint (1) is violated regardless of constraint (2) and constraint (3); cconstraint (2) is violated and constraint (1) and constraint (3) are respected; d -constraint (3) is violated regardless of constraint (1) and constraint (2). these four domains, the data from the training set (points numbered from 1 to 124), and test data (prefix t) are indicated in fig.2. it can be observed that all learning data correspond to points placed on. or near the bounds. the best results obtained by the aid of the genetic algorithm at the end of 500 generations are exposed in table 2. the best result obtained in [10j using the classical "delta rule" as learning procedure corresponds to a 244 table 2 the best results obtained by the aid of the genetic algorithm with no-seeding and with seeding the initial population with a chromosome having rms error= 0.1012 (s;p = 500; b = [-130; 130]; nh= 5; no= 2) procedure trial number rms error percentage of wrong classifications(%) no-seeding 1 0.2816 25.00 no-seeding 2 0.2506 22.58 no-seeding 3 0.2466 20.77 o-seeding 4 0.1445 12.10 no-seeding 5 0.2446 20.97 o-seeding mean 0.2336 20.32 seeding 1 0.0907 3.22 seeding 2 0.0895 6.45 seeding 3 0.0902 5.65 seeding 4 0.0894 6.45 seeding ·5 0.0902 4.84 seeding mean 0.0900 5.32 fig._ the four patterns das ification e ample percentage of wrong cla sifi ations of 9.70 ~ and ' as gi en by a modified ba k-propagation neural netv ork with neuron in the hidden layer neuron in the out ut layer and hyperb lie tangent transfer fun tion. it i bvious that in thi ca e the results gi en by genetic algorithm are wor e than that obtained using the las ical "delta rule" learning pro edure. due to thi fact, a hybrid pro edure was propo ed: in a fir t stage the arch is made with the aid of "delta rule" learning procedure; next in the second tage the initial population of chromo omes is eeding \! rith the be t olution fr m the end of the fir t stage. th resul obtained with thl " e ding" procedure are encouraging. thu for th con idered network. "delta rule" learning pr edure give thew ights orresponding "th a error of 0.1012. thi olution a improved \i ith 10% by the genetic algorithm. th re ults obtain d ith eeding the initial population are gi en al in table -1 n n n "' "' "' " =f i i ~ i i ~ ~ i ~ ~ rd ~ rd rd connection fig.3 changes of the weights of the inter-neuronal . connections between the input and hidden layers ( i input; h -hidden; b -bias) 9 0 0 0 ~ 0 c\1 c\1 c\1 9 0 0 i c\j cj, .;. rb i c\j cj, i i i i i i connection fig.4 changes of the weights of the inter-neuronal connections between the hidden and output layers ( h­ hidden; 0output; bbias) the improved solution was obtained mainly due to changes of the weights of the inter-neuronal connections between the hidden and output layers (figs.3 and 4). for this difficult classification problem, the mean percentage of wrong classifications given by this hybrid procedure is with 82% better than the best solution corresponding to a larger neural network obtained in [10]. the corresponding evolutions of the genetic algorithm for "no-seeding" and "seeding" procedure are repre ented in fig.5, and respectively fig.6. conclusions the genetic algorithms are an exciting way to realize high a urate classification multilayer neural networks. different from other works, we search for the network tru ture in an external iterative loop. we consider that this twotage procedure gives a better control of the re ults. also, this procedure allows the selection of a ne tructural variable, respectively the number of neurons in the output layer. thi means different rules of las es codification, and the equivalent modifications in the training data sets. to realize these in a single optimization loop seems to be a little bit complicated. aybe the twotage procedure i many computer time fig.5 the evolution of mean( .... ) and best (-)fitness for "no-seeding" procedure consumers, but our interest was focused on the accuracy of the results. it is obvious that, in order to realize high accurate classification multilayer neural networks for practical applications (e.g. process control or expert systems), the network performances are much more important than the computer time spent for this. another direction of investigation in this work was the performance of a hybrid algorithm composed from "delta rule" and genetic algorithms. in fact this hybridization was realized by seeding the initial population from the genetic algorithm with the best solution obtained with classical "delta rule" learning procedure. despite the warning of some authors [111 that by seeding the genetic algorithm chases after a local minimum, and takes time to find its way out, very good results were obtained with this procedure in a difficult classification problem. our research, realized in the frame of two applications, finished with good results, so we can conclude that the use of the genetic algorithms represents a promising way to realize high accurate classification multilayer neural networks. symbols b bounds imposed to the weights of the interneuronal connections nh number of neurons in the hidden layer no the number of neurons in the output layer sip size of initial population xi variables in eqs. (1)-(3) 245 fig.6the evolution ofmean ( .... )and best (-)fitness for "seeding" procedure references 1. aldrich c. and van devenier j. s. j.: chern. eng. sci., 1994, 49(9), 1357-1368 2. aldrich c. and vandeventer j. s. j.: ind. eng. chern. res., 1995, 34(1), 216-224 3. michalewicz z.: genetic algorithms + data structures = evolution programs, 3rd ed., springer verlag, berlin, 1996 4. harps. a., samad t. and guha a.: towards the genetic synthesis of neural networks in: davies, l. (ed.): handbook of genetic algorithms, van nostrand reinhold, new york, 1991 5. maniezzo v.: lee trans. neural net., 1994, 5 (i), e~3 . 6. gao f., lim., wang f., wang b. and yue p. l.: ind. eng. chern. res., 1999, 38(11), 4330-4336 7. boozarjombhry r. b. and svrcek w. y.: comput. chern. engng., 2001, 25(10), 1075-1088 8. houck c. r., joines j. a. and kay m. g.: ncsu­ ie, technical report, north carolina state university, 95-09, 1995 9. baughman d. r. and liu y. a.: neural networks in bioprocessing and chemical engineering, academic press, san diego, 1995 10. woinaroschy a., isopescu r., nita i. and dinu s.: data filtering via artificial neural nets. 5lh world congress of chemical engineering, san diego, vol. i, 1011-1016, 1996 11. haupt r. l. and haupt s. e.: practical genetic algorithms, wiley, new york,1998 page 248 page 249 page 250 page 251 page 252 editorial the hungarian journal of industry and chemistry (hjic) formerly (until 2012) the hungarian journal of industrial chemistry the hjic is an international periodicals that focuses on results of fundamental and applied research in the field of • biotechnology • chemical engineering science • chemical processes • energetics • environmental chemistry • environmental engineering & technology • industrial management • material science • mechanical engineering • mechatronics • process & system engineering • recycling in the form of original papers, reviews, short communications, and conference proceedings written in english. editorial board editor-in-chief: róbert k. szilágyi department of chemistry and biochemistry, montana state university, bozeman, mt, u.s.a. honorary senior editor: géza horváth department of chemical engineering science, university of pannonia, veszprém, hungary associate editors: jános abonyi department of process engineering, university of pannonia, veszprém, hungary dezső boda department of physical chemistry, university of pannonia, veszprém, hungary norbert miskolczi mol department of hydrocarbon and coal processing, university of pannonia, veszprém, hungary dóra rippel pethő department of chemical engineering science, university of pannonia, veszprém, hungary editors: lászló bartha mol department of hydrocarbon and coal processing, university of pannonia, veszprém, hungary katalin bélafi-bakó research institute of bioengineering, membrane technology and energetics, university of pannonia, veszprém, hungary peter czermak institute of bioprocess engineering and pharmaceutical technology, mittelhessen university of applied sciences, giessen, germany dénes fodor institute of mechanical engineering, university of pannonia, veszprém, hungary maria gavrilescu department of environmental engineering and management, gheorghe asachi technical university of iasi, romania lászló gubicza research institute of bioengineering, membrane technology and energetics, university of pannonia, veszprém, hungary jenő hancsók mol department of hydrocarbon and coal processing, university of pannonia, veszprém, hungary jiří klemeš centre for process integration and intensification, university of pannonia, veszprém, hungary zoltán kovács department of management, university of pannonia, veszprém, hungary jános kristóf department of analytical chemistry, university of pannonia, veszprém, hungary istván szalai institute of physics and mechatronics, university of pannonia, veszprém, hungary ferenc szeifert department of process engineering, university of pannonia, veszprém, hungary jános szépvölgyi research centre for natural sciences, university of pannonia, veszprém, hungary imre tímár institute of mechanical engineering, university of pannonia, veszprém, hungary gyula vatai department of food engineering, corvinus university of budapest, hungary gábor veress federation of technical and scientific societies – mtesz budapest, hungary ibolya zsoldos department of material science and technology, széchenyi istván university, győr, hungary editorial office: university of pannonia, p.o. box 158, veszprém, 8201 (hungary) tel.: +36 (88) 624-746, e-mail: hjic@almos.uni-pannon.hu; web: hjic.mk.uni-pannon.hu felelős szerkesztő: szilágyi róbert károly nyelvi lektor: matthew chen kiadja: pannon egyetem, 8200 veszprém, egyetem u. 10. levélcím: h-8201 veszprém, postafiók 158, tel.: (88) 624-000 felelős kiadó: a pannon egyetem, mérnöki kar dékánja editorial preface the editorial board of hjic dedicates this issue to the national scientific students’ associations (tudományos diákkör, in hungarian, abbreviated as tdk) that is a real hungaricum with a 62 years old tradition. this association includes all the universities and colleges of hungary, where scientific research of any kind is being conducted. the members of the association are the faculty members, scientific advisors, and their b.sc. or m.sc. students. participation in the work of tdk is completely voluntary. students spend some of their free time with a faculty mentor, choose a research topic, learn the basics of the field, do the measurements or the calculations under the supervision of the chosen teacher/researcher in addition to their regular academic duties. at the end, they write a dissertation based on their results. these dissertations are peer reviewed and then presented at yearly institutional tdkconferences, where the students receive suggestions from a panel of scientists and professors, receive a score for their written documents and oral presentations. based on these scores, they may win legitimacy to present their results at the national tdk-conference. tdk is a remarkable organization in hungary that was kept alive by people who do their work from pure enthusiasm for the love of their profession. it is not an exaggeration to say that the tdk-students form the elite of all the university students. they are the ones who proceed to m.sc. level, become phd students, and, at the end, ideally become colleagues of their former faculty advisors. during their work as part of tdk, students learn systematic problem-solving, formulating good questions, critical thinking, composing their thoughts into concise, wellformulated sentences, preparing meaningful figures, elaborating the literature of the field, and presenting their result in front of a scientific panel and an audience. even those students who do not continue their life in the academia tend to remember their time spend on tdk activities as useful and memorable. often, the skills acquired while being involved in a tdk project are not part of the regular education at a given university. tdk gives them something extra. this issue contains selected articles from students and their supervisors about their results presented at the tdk conferences during 2013-2014. with this issue, the editorial board wishes to honour the effort of all tdk students and their advisors for keeping this unique tradition alive with their devoted work. dezső boda and tibor dulai university of pannonia, veszprém, hungary guest editors hung. j. ind. & chem. 2014, vol. 42(1), pp. 1-56 table of contents comparative assessment of the mussel micronucleus test versus bacterial bioassays for genotoxicity testing of benzo[a]pyrene bettina eck-varanka, eszter horváth, árpád ferincz, gábor paulovits, nóra kováts ............................................................................................................................................ 1-5 improving the interfacial properties of glass fibre reinforced and unreinforced waste sourced low density polyethylene/acrylonitrile butadiene styrene/polystyrene composites jános sója, vladimir sedlarik, pavel kucharczyk, norbert miskolczi ......................... 7-12 application of online and laboratory methods for the investigation of surface water janka bobek, zsófia kovács, zoltán zsilák ........................................................................ 13-18 adsorption and intercalation of small molecules on kaolinite from molecular modelling studies attila táborosi, róbert kurdi, róbert k. szilágyi ........................................................... 19-23 impact of size heterogeneity of core-shell packing materials on chromatographic separation of large biomolecules diána lukács, krisztián horváth ......................................................................................... 25-29 effects of washing of raw material on properties of carbon nanotube containing poly(ethylene-terephthalate) composites tímea molnár, csilla varga, lászló bartha ..................................................................... 31-37 investigation the properties of y-ba-cu-oxide superconductors prepared by hydraulic pressing and moulding anna maloveczky, margit enisz-bódogh, tamás kulcsár .............................................. 39-42 effects of ultrasonic disintegration, hot-compressed liquid water pre-treatment and steam explosion on solvolysis and digestibility of grain sorghum stover dániel capári, andrás dallos ............................................................................................... 43-50 development of a reaction structure identification tool jános kontos, lászló richárd tóth, tamás varga ............................................................ 51-56 editorial preface systems and control theory is a constantly evolving scientific area and the dominant driving force in key industries and engineering fields e.g. process engineering, automotive engineering, bioengineering, and the energy industry. the aim of the current issue (volume 42, number 2) is to provide an overview of research topics pursued by selected phd students. the papers presented here were selected from contributions at the 13th international phd workshop on systems and control conference held on august 25, 2014 (virt.uni-pannon.hu/phdws2014). the objective of the conference was to establish an international forum for young researchers. the meeting provided opportunities for the participants to present and discuss the latest results and up-to-date applications in systems and control. this issue represents the entire spectrum of systems and control engineering as follows: • process modelling and analysis • control (traditional, intelligent, adaptive, etc.) • process monitoring and supervision • system identification and signal processing • bioengineering • traffic control • reaction kinetic networks • modelling of complex systems (classical, hierarchical, bayesian, fuzzy, networks) • image processing and pattern recognition • artificial intelligence • soft computing (neural, genetic, fuzzy algorithms, etc.) • software (parallel computing, distributed and network computing, data visualization) • decision making (decision support, data mining) • applications of systems and control theory the organizers are grateful for the contributions of the authors. the tradition of the international phd workshop continues. you are invited to participate at the 14th international phd workshop in veszprém in 2015! attila magyar university of pannonia, veszprém, hungary guest editor hung. j. ind. & chem. 2014, vol. 42(2), pp. 57-113 table of contents a comparison of advanced non-linear state estimation techniques for ground vehicles györgy max, béla lantos ...................................................................................................... 57-64 telemedical heart rate measurement for lifestyle counselling mario salai, gergely tuboly, istván vassányi, istván kósa .......................................... 65-70 the application of unknown input estimators to damp load oscillations of overhead cranes bálint patartics, bálint kiss ................................................................................................. 71-77 challenges of enterprise policy compliance with smartphone enablement or an alternative solution based on behaviour-based user identification sándor dobos, attila kovács ................................................................................................ 79-84 measurement-based modelling and simulation of a hydrogen-generating dry cell for complex domestic renewable energy systems attila göllei, péter görbe, attila magyar, lászló neukirchner ................................. 85-89 quasi-polynomial representation-based control of mechanical systems lászló neukirchner, attila magyar .................................................................................... 91-95 a network model for simulating the dynamic behaviour of an energy distribution network levente bálint, tibor dulai, ágnes stark-werner, gergely apostol, ádám tompos ........................................................................................................................... 97-101 on the parametric uncertainty of weakly reversible realizations of kinetic systems györgy lipták, gábor szederkényi, katalin m. hangos .............................................. 103-107 stability and parameter sensitivity analyses of an induction motor attila fodor, roland bálint, attila magyar, gábor szederkényi ........................... 109-113 hungarian journal of industry and chemistry veszprém vol. 42(1) pp. 1–5 (2014) comparative assessment of the mussel micronucleus test versus bacterial bioassays for genotoxicity testing of benzo[a]pyrene bettina eck-varanka,1! eszter horváth,1 árpád ferincz,1 gábor paulovits,2 and nóra kováts1 1 department of limnology, university of pannonia, egyetem str. 10, veszprém, h-8200, hungary 2centre for ecological research, hungarian academy of sciences, balaton limnological institute, klebelsberg k. str. 3., tihany, h-8237, hungary !e-mail: kovats@almos.vein.hu polycyclic aromatic hydrocarbons are hazardous compounds to the environment and human health, thus their detection is an important task. in this study the genotoxic effect of benzo[a]pyrene (b[a]p) was examined on a freshwater mussel unio pictorum and results were compared to bacterial tests, such as the ames test and sos chromotest. the aim of the study was to calibrate the sensitivity of the mussel micronucleus test to that of the two bacterial tests using b[a]p as a reference chemical. the ames and the micronucleus tests gave similar response both in sensitivity and in concentrationresponse pattern. these two tests are proposed to be applied in a battery for genotoxicity testing. keywords: micronucleus test, ames fluctuation test, sos chromotest, pah introduction polycyclic aromatic hydrocarbons (pahs) are ubiquitous widespread contaminants. the us environmental protection agency (epa) created a list of priority pollutants that have the greatest concern due to potential exposure and adverse health effects on humans. there are 16 pahs on this list, of which the most hazardous are acenaphthene, fluoranthene, naphthalene, benzo[a]anthracene and benzo[a]pyrene [1]. these compounds have proven to have carcinogenic and mutagenic effects on animals and humans, hence their regulation is very important [2]. major sources of pahs are internal combustion engines, residential heating, incineration, and coke production. there are also natural sources, such as forest fires or volcanoes. pahs are present in the atmosphere as gas and/or particulate phases and might be transported to other environmental compartments such as soil, sediment, and water via dry or wet deposition. heavier pahs, such as benzo[a]pyrene (b[a]p), are almost totally adsorbed onto particles. their further environmental fate in solid compartments is mostly influenced by their low water solubility. however, once taken up by the organism, the detoxification mechanism converts these compounds into more soluble molecules. it was shown that the seawater bivalve, mytilus sp. can activate b[a]p to mutagenic compounds and produce reactive oxygen species (ros) [3]. for assessing environmental exposure, benzo[a]pyrene seems to be a good indicator, due to the strong correlation between b[a]p and other pahs [4]. in iarc monograph volume 3 it was concluded that benzo[a]pyrene produced tumours in a wide range of animals tested, following exposure by many different routes (oral, dermal, inhalation, intratracheal, intrabronchial, subcutaneous, intraperitoneal, intravenous). it had both a local and a systemic carcinogenic effect [5]. there are various reasons why the genotoxicity of pahs as well as of other mutagenic compounds is tested on mussels. first of all, bivalves are sedentary creatures, being exposed to both water and sediment contamination. secondly, their ability to bioaccumulate contaminants is well known and widely used in biomonitoring studies. actually, the fact that they can not only bioaccumulate waterborne mutagens, but also metabolise them into active forms, on one hand increase their usefulness in these studies but on the other hand may enhance the potential risk to consumers [6]. of genotoxicity markers, the micronucleus test (mn) is the most widely established, relatively easy-toperform test. micronuclei formation indicates chromosomal dna damage occurring as a result of either chromosome breakage or chromosome missegregation during mitosis [7]. banni et al. used digestive gland cells of the marine mussel mytilus galloprovincialis in an acute test. in this assay, mussels were exposed to 75 nm b[a]p for different exposure time. micronucleus frequency started to show significant response after 24 hours exposure, reaching the maximum after 72 hours [8]. woznicki et al. also tested b[a]p genotoxicity using the mn test, but 2 on another species, the freshwater sinanodonta woodiana (referred to anodonta woodiana in the original article) [9] in which the time-dependency of ecological effect was demonstrated. maximum micronucleus formation was experienced after 4 days of exposure, but after it started to decrease, most possibly due to adaptive mechanisms. the mussel micronucleus (mn) test has also been used in real-world environments, especially for detecting contamination from oil spills. bolognesi et al. demonstrated that even 10 years after the wreck of the tanker haven at the ligurian coast of italy, micronucleus frequency in caged oysters was a reliable way to detect the release of genotoxic compounds [10]. martins et al. assessed genotoxicity of sediment containing pahs and metals after dredging operations. the sediment previously was classified as ’trace contaminated’, but dredging modified the mobility of pollutants, which was clearly visible in the mussel mn test [11]. in addition to the mn test for eukaryotic organisms, which results in chromosomal damage, several bacterial tests are also available for screening purposes due to their rapid response and short exposure time. the sos chromotest is a short-term, enzymatic colorimetric assay for the detection of the presence of genotoxic compounds using escherichia coli pq 37 strain as described by quillardet et al. [12]. the sos system is a complex, dna-damage activated response under the regulation of the sos promoter. in e. coli pq 37 the only functioning β-galactosidase gene (lacz) is fused to the bacterial sfia sos operon. thus, sos response initiates lacz transcription, and β-galactosidase activity is detected spectrophotometrically by the addition of x-gal (5-bromo-4-chloro-3-indolyl-β-dgalactopyranoside) [13, 14]. the ames bacterial reverse mutation assay applies genetically engineered strains of salmonella typhimurium. the method is based on the chemical triggered reversion of histidine producing ability of the strains, enabling them to grow on histidine free medium. several different methods have been developed, including the plate incorporation assay, the preincubation method, and the fluctuation test [15–17]. the ames fluctuation test is a microplate adapted version of the salmonella reverse mutation assay with a ph change indicated colorimetric endpoint. this method is suitable for the screening of large numbers of samples, and because of its sensitivity it is ideal for water sample testing [18]. the ability of both the sos chromotest and the ames test to detect genotoxicity of b[a]p has been long established [19, 20]. b[a]p was also used as a reference chemical for calibrating the newt micronucleus test or jaylet test [21]. the correlation between the genotoxic substances and the number of micronuclei in an organism has been used in water toxicological tests since the 1980’s [22]. the micronuclei are small bodies containing dna parts that appear near the nucleus as a result of chromosome breakage or mitotic spindle dysfunction. this process can occur without external factors as well, but the effect of genotoxic substances made a far greater number of micronuclei than normal. therefore the micronuclei frequency may characterise the extent of genetic damage that accumulate over the life of the individual [23]. the mn test, performed on freshwater mussel species, is widely distributed for assessing genotoxic effects triggered by environmental pollutants [24, 25]. still, the micronucleus test has gained relatively low attention in hungary, therefore a native freshwater mussel, unio pictorum was introduced as test organism. main aim of the study was to calibrate this test also using b[a]p as reference chemical, by comparing its sensitivity to that of the bacterial assays. materials and methods test organisms unio pictorum specimens were collected from lake balaton and were kept in a flow-through aquarium. water source was lake balaton water, therefore not only proper oxygenation was ensured, but a constant food supply as well. animals were acclimatized for 4 weeks prior to testing. test conditions and treatment the assay was performed based on the protocol described by wozniczki et al. with some modifications. a b[a]p stock solution was prepared in acetonitrile in 1 mg cm-3 concentration for the following series: 70 µg dm-3, 175 µg dm-3, 350 µg dm-3 and 700 µg dm-3. for solvent control 0.07% acetonitrile was used, and solvent quantity was adjusted to 0.07% in each treatment. u. pictorum specimens with length of 5–8 cm were used. treatments were performed in triplicates. for each concentration and for the controls, the volumes of the aquaria were 3 l. they were aerated during the experiment and temperature was set at 22 oc. exposure time was 4 days. micronucleus test after 4 days, haemolymph was taken from the posterior adductor using the non-lethal technique described by gustafson et al. [26]. a 1 ml aliquot of haemolymph was mixed with 0.3 ml, 10% acetic acid in methanol as a fixative and centrifuged at 1000 rpm for 5 minutes. the supernatant was discarded and the rest was fixed in 1 ml 80 % ethanol. in this way the sample can be kept refrigerated for several weeks. for processing the samples, refrigerated samples were centrifuged again at 1000 rpm for 5 minutes. the supernatant was discarded and the pellet containing the cells was smeared onto a microscope slide and allowed to dry. after that the slides were fixed in 80 % methanol, dried and stained with 5 % giemsa in distilled water for 20 minutes. photos were taken by a zeiss axioscope a1 microscope with an axiocam icc1 camera and zen 2011 program at 400x magnification. micronuclei were 3 identified according to fenech [27]. for each animal 250 cells were counted. one-way anova with tukey post hoc test was used to compare the mean mn numbers between the treatments. for sos chromotest the sos chromotest tm kit (ebpi – environmental bio-detection products inc.) was used according to the manufacturer’s instructions, and in compliance with the oecd guidelines no 471:1977 [28]. b[a]p concentrations were 1400 µg dm3, 700 µg dm-3, 350 µg dm-3, 175 µg dm-3, 87.5 µg dm-3, 43.75 µg dm-3, 21.88 µg dm-3, 10.9 µg dm-3, 0 µg dm-3. acetonitrile concentration was adjusted to 0.07% in each sample, and an additional dmso solvent control was also used. the absorbance of samples was detected on 615 and 405 nm with diareaderelx800 elisa device. the sos repair system induction was measured by the calculation of induction factor (if) and induction potential (sosip) according to krifaton [29]. samples with 1.5 or higher if were considered genotoxic. ames test the fluctuation ames test was performed according to hubbard with slight modification. in short, salmonella typhimurium ta100 cells were pre-cultured overnight in nutrient broth (oxoid) on 37 ºc. cells were washed twice in davis minimal medium (67.4 mm po4 3-, 8.38 mm so4 2-, 15.1 mm nh4 +, 5.1 mm na+, 98.1 mm k+, 0.83 mm mg2+, 1.7 mm citrate, 139 µm glucose 10 µg cm-3 histidine, 0.1 mg cm-3 d-biotin) and cell number was adjusted to 106 cells cm-3. b[a]p was added to the samples in 700 µg dm-3, 350 µg dm-3, 175 µg dm-3, 70 µg dm-3 and 0 µg dm-3 and acetonitrile concentration was adjusted to 0.07%. samples were distributed in 200 µl volumes to 96 well microplates. cell free control, a solvent free negative control, and a positive control with 0.5 µg cm-3 concentration nan3 were also applied. plates were incubated in humid chamber for 72 hours in 37 ºc. on the day of evaluation 20 µl of 2 mg cm-3 aqueous solution of bromcresolpurple was added to each sample. purple colour signified negative, yellow positive (cell growth) result. intermediate shades were regarded positive. the experiment was also performed with s9 activation, in which case 10 ml suspension contained 2.5 ml s9 mix (ebpi) assembled according to the producer’s guide (s9 activation simulates metabolic processes in the liver of higher organisms). for positive control 2-amino-antracene was used in 100 µg cm-3 concentration. for the evaluation of mutagenic effect the χ2-test was applied with 95% confidence level [30]. results and discussions genotoxic response is expressed as number of micronuclei/250 cells in case of the mussel micronucleus test, percentage of positive wells in case of the ames test and if value in case of the sos chromotest. significant difference between the control and all treatments was observed in case of micronucleus numbers (anova: f = 12.015; df = 5; p < 0.00001, tukey post hoc: p < 0.002); however, only the highest concentration treatment differed from the acn-control (tukey post hoc p = 0.02). the difference between the lowest (70 µg dm-3) and highest (700 µg dm-3) concentrations was also indicated (fig.1). χ2-square tests indicated significant differences between the control and all treatments in case of ratios of ames fluctuations test (p < 0.0017) (fig.2). the results of sos chromotest are shown in fig.3. to date no assessment has been published for comparing the sensitivity of the mussel micronucleus test and bacterial genotoxicity assays. there are a few comparative works; however, those are based on amphibian micronucleus tests. one protocol uses xenopus laevis embryos and the end-point of the test is number of micronucleated erythrocytes per thousand. the test is standardised, international and some national figure 1: result of the mn test with b[a]p showing significant difference compared to control (a), to acn control (b) and to 70 µg dm-3 b[a]p (c) figure 3: result of the s9 supplemented sos chromotest with b[a]p figure 2: result of the s9 supplemented fluctuation ames test with b[a]p (significant difference compared to control (a)) 4 test protocols apply, e.g. the afnor nft 90-325 procedure [31]. mouchet et al. tested genotoxicity of pah-contaminated soil leachates on the amphibian mn test and two bacterial tests (ames and mutatox) [30]. the latter test developed by the microbics company (now azur environmental) uses dark mutants of the luminescent bacterium vibrio fischeri. in the presence of mutagenic compounds, these mutants can revert and recover their luminescence, which is easily measurable by a luminometer. it was found that the mn test was able to detect genotoxicity, while the ames test was not. sensitivity of the mutatox test was intermediate. it should be noted that chemical analysis of both soil and leachate samples revealed much lower individual pah concentration in leachates than in the soil samples. le curieux et al. used the sos chromotest, the ames fluctuation test and another amphibian, the newt pleurodeles waltl for a comparative assessment of 7 chemicals, including b[a]p. in their study, the newt micronucleus test was the most sensitive, the fluctuation test and the sos chromotest gave practically similar but lower response [33]. in our study all three tests gave positive response, but analysis of the concentration-response graphs shows somewhat different patterns. bacterial tests gave positive response only with s9 activation. ideal concentration-response graphs were found for the mn test and the s9 supplemented ames test. ideal concentration-response curve is observed when the response steadily increases for each higher effluent concentration [34]. main difference is the response given in the acn control, which elucidated micronucleus formation but the ames test gave practically the same response for both controls. notably, wozniczki et al. did not find concentration-response relationship when tested b[a]p on sinanodonta woodiana. in the sos chromotest after s9 activation, positive response was given for the lowest concentration, but no clear concentration-response relationship could be established. in general, sensitivity of the sos chromotest is considered lower than that of the ames test. for example, there are mutagenic compounds that do not induce the sos response, such as benzidine, cyclophosphamide, acridines, and ethidiumbromide [13]. conclusions the very similar response of the ames test and the micronucleus test (considering both sensitivity and concentration-response pattern) indicate that b[a]p elucidates both chromosomal aberrations and point mutation, and is genotoxic for prokaryotes and eukaryotes as well; however, this is not necessarily the case for all potentially genotoxic chemicals. as such, for testing genotoxicity of either individual compounds or environmental samples, application of both tests can be advised, defining the minimum necessary battery as the mn and ames tests. acknowledgements this work was supported by the támop-4.2.2.a11/1/konv-2012-0064 research program. this project is supported by the european union and co-financed by the european social fund. references [1] usepa: priority pollutants list (appendix a to 40 cfr part 423). u.s. environmental protection agency, office of water, 2000 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jourdain m.j., ferrier v., triffault g., devauxe a.: biomonitoring of the genotoxic potential of aqueous extracts of soils and bottom ash resulting from municipal solid waste incineration, using the comet and micronucleus tests on amphibian (xenopus laevis) larvae and bacterial assays (mutatox® and ames tests), sci. total environ., 2006, 355, 232–246 [33] le curieux f., marzin d., françoise e.: comparison of three short-term assays: results on seven chemicals. potential contribution to the control of water genotoxicity, mutation res., 1993, 319, 223–236 [34] usepa: method guidance and recommendations for whole effluent toxicity (wet) testing (40 cfr part 136). epa 821-b-00-004, u.s. environmental protection agency, office of water, 2000 advertise upcoming meetings, conferences and workshops; make public announcements; introduce your research laboratory; a new product or a service on the pages of the hungarian journal of industry and chemistry please contact us if interested! editorial office: university of pannonia p.o. box 158, veszprém h-8201 (hungary) tel.: +36 (88) 624-746, e-mail: hjic@almos.uni-pannon.hu; web: hjic.mk.uni-pannon.hu felelős szerkesztő: szilágyi róbert, phd kiadja: pannon egyetem, 8200 veszprém, egyetem u. 10. levélcím: h-8201 veszprém, postafiók 158, tel.: (88) 624-000 hungarian journal of industrial chemistry veszprém vol. 42(1) 7–12 (2014) improving the interfacial properties of glass fibre reinforced and unreinforced waste sourced low density polyethylene/acrylonitrile butadiene styrene/polystyrene composites jános sója,1 vladimir sedlarik,2 pavel kucharczyk,2 and norbert miskolczi1! 1 mol department of hydrocarbon & coal processing, institute of chemical engineering and process engineering, faculty of engineering, university of pannonia, egyetem u. 10, veszprém, h-8200, hungary 2 centre of polymer systems, university institute, tomas bata university in zlin, nad ovcirnou 3685, zlín, 76001, czech republic !e-mail: mnorbert@almos.uni-pannon.hu this work is focused on compatibilization of immiscible waste sourced low density polyethylene (ldpe), acrylonitrile butadiene styrene (abs), and polystyrene (ps) blends by different surface modifying routes. to reach better mechanical properties of the given reused waste blends 20% glass fibre was used. the ratio of waste ldpe/abs/ps was 3.6/2.0/1.0 both in the presence and absence of glass fibre, while the applied concentration of the surface modifying routes was 1% in each case. blends of raw materials had been manufactured by two roll mill, and specimens were obtained by the press moulded plates. the properties of samples were studied by mechanical testing. results show that blending of the three kinds of waste polymers without compatibilizers resulted immiscible blends with poor mechanical properties. this could be significantly improved by the application of the commercial and synthetic surface treatment additives. generally, favourable properties were found in the presence of 20% glass fibre. especially ad-1 and ad-2 experimental and commercial γ-aminopropylsilane additives showed the best results. keywords: immiscible, compatibilizer, waste mechanical recycling, tensile strength introduction owing to the increasing application of polymers, the utilization of wastes plastics causes serious challenges. according to reports the energetic utilization of polymer wastes were mainly investigated, such as incineration, chemical recycling, and/or mechanical recycling [1–7]. it is also well known that the industrially used plastics are not exchangeable with other constructional materials (glass, metals, etc.). excess energy use and/or more greenhouse gas emissions would be incurred upon replacement of plastics with other materials. therefore most of the key industrial segments, such as transportation, aviation, packaging, civil engineering, cannot function without polymers. from the 50s' the plastic industry went through a significant development, which is a reason for their wide-spread and diverse applications often for highly specific purposes. in the case of plastic composites, they provide alternative solutions to problems of increasing strength, maintaining compatibility and malleability [2, 4, 6–14]. the mechanical recycling of polymers is a reshaping process using waste polymeric materials or even the mixtures of unused and waste polymers. basically the waste polymer can be originated from two sources. in “closed-loop” recycling, the same product is manufactured from the same recycled components. for instance, the material of bottles (in some cases) can be recycled. in contrast, there is a recycling route, when the repeated remanufactured products are becoming less valuable [10–12, 15, 16]. a major challenge in mechanical recycling of polymers is immiscibility that leads to phase separation causing significant reductions in mechanical properties of the polymer mixtures. there are specific kinds of polymers that are immiscible with each other, such as polyolefin-pa, polyolefin-abs, polyolefin-pet. therefore, polymer blends may contain two phases, such as disperse and continuous. generally, the difference in chemical and physical properties of phases are the source of the above mentioned immiscibility problem. therefore, coupling agents with special chemical structure can be used to create adequate chemical/physical interaction between the constituents of polymer mixtures. for this purpose grafted-ma or silane based compounds are widely used. these compatibilizers are able to increase the interfacial tension in boundary layer of polymer blends, which results in better chemical/physical interactions [17, 18]. 8 in this work, the feasibility of mechanical recycling of automotive industry waste mixtures of low-density polyethylene (ldpe), acrylonitrile butadiene styrene (abs), and polystyrene (ps) were studied. the effects of various compatibilization techniques on mechanical properties of the prepared ternary abs/lspe/ps systems were studied. materials and methods raw materials waste polymers used as raw materials in our experimental work were selectively collected directly from automotive industry. the main properties of the plastic wastes are summarized in table 1. the ldpe has the lowest tensile strength (15.8 mpa), which is followed by the polystyrene (25.6 mpa), and the abs (34.4 mpa). tensile modulus showed similar order as well. due to the chemical structure of plastics, the ldpe had the highest elongation (351.5%), while abs the lowest (4.7%). the average particle size for each tested plastic wastes were in the range of 4–5 mm, with moisture content of 0.7–0.8 %. moreover, significant differences were noticed in the charpy impact strength of samples; because the maximum value was measured in the case of abs (10.5 kj mm-2), while the smallest regarding ldpe (3.8 kj mm-2). as known, blends of abs and ldpe are immiscible phases in the most cases. therefore, the mechanical properties of abs and ldpe blend are significantly worse than that of the constituents, either abs or ldpe. in order to enhance their properties, the interfacial forces must be improved between the constituents. in our work, different commercial and synthetic compatibilizers were used for improving the interfacial properties and decrease the interfacial tension of composites. two commercially available compounds of γ-aminopropyl silane (c-1) (aldrich chemistry), and polyethylene grafted with maleic anhydride (c-2) (viba spa) were used as compatibilizer agents. the synthetic agents were maleic anhydride intermediates made from different olefins at the department of mol hydrocarbon and coal processing, university of pannonia with significantly different physical and chemical properties. the main properties of the four additives are summarized in table 2. sample preparation blends of waste ldpe/abs/ps were prepared by two roll mill. then sample plates were manufactured by press moulding. fig.1 demonstrates the flow of the experimental work. for composite manufacturing a labtech two roll mill (labtech ltd, thailand) was used. the temperatures of the rolls were 170 °c and 190 °c with friction ratio of 0.5. the compositions of samples are summarized in tables 3 and 4. in selected cases e-type unsized glass fibre with 4–5 cm average length was also added to the composites in its 20%. the e-type gf was produced by ovens table 1: the main properties of waste polymers ldpe abs ps tensile strength, mpa 15.8±1.4 34.4±2.5 25.6±1.9 tensile modulus, mpa 420±33 1750±88 1720±95 elongation, % 351.5±35.5 4.7±0.3 189.6±10.2 flexural strength, mpa 29.0±2.2 21.0±1.7 flexural modulus, mpa 1820±79 1140±73 charpy strength, kj mm-2 3.8±0.4 10.5±1.1 5.9±0.4 table 2: the main of experimental coupling agents ad-1 ad-2 ad-3 ad-4 appearance solid dense liquid solid solid side chain c16-c18 polyisobutylene styrene c20-c22 figure 1: sample preparation and testing table 3: sample compositions without glass fibre in weight % sample no. 1 2 3 4 5 6 7 8 ldpe 55 54 54 54 54 54 54 54 abs 30 30 30 30 30 30 30 30 ps 15 15 15 15 15 15 15 15 c-1 1 c-2 1 ad-1 1 ad-2 1 ad-3 1 ad-4 1 peroxide 1 9 corning and it contained mainly sio2, cao and al2o3. the ratio of waste ldpe/abs/ps was 3.6/2/1 both in the presence and absence of glass fibre, while the applied concentration of the additives was 1% in each case. the additives were directly added to the molten polymer during the sample sheet manufacturing. in two cases organic peroxide (di-tercier-butyl-peroxide) was used to modify the interfacial surface of composites. the sample blending composites were press moulded at 180 °c using 6.8 ton loading and then specimens with dimension of 1 mm x 10 mm x 100 mm were cut from the composite plates. determination of tensile strength the tensile properties of the composites were determined by instron 3345 universal tensile machine using 90 mm/min crosshead displacement rate. during the tests, the ambient temperature was 23 °c, and the relative humidity was 35 % in all cases. preloading was not applied. determination of flexural strength the three point flexural tests were performed by also the before mentioned instron 3345 universal tensile tester. the crosshead displacement rate was 20 mm min-1 in all cases. determination of charpy impact properties a ceast resil impactor was used for determination of charpy impact strength. the machine was equipped with a 4j hammer, while the specimens were cut. results and discussion tensile properties fig.2 compares the tensile strength of samples. it can be seen that the tensile strength has changed in the range of 13.8 and 24.1 mpa. however, the reinforced composites have significantly better resistance against constant tensile loading (13.8–24.1 mpa), than that of unreinforced (14.2–18.5 mpa). according to data the highest values were obtained in the case sample containing a-1 surface modifier agent in the presence of gf (24.1 mpa), while that was the highest in using ad3 additive without gf (18.5 mpa). from table 1, the raw materials had 34.4 mpa (abs), 25.6 mpa (ps) and 15.8 mpa (ldpe) tensile strength. on the contrary, the untreated ldpe/abs/ps composites have tensile strength of 15.3 mpa without fibres, and 16.8 mpa in the presence of 20% glass fibre. it means that presumably owing to the immiscible phases the ldpe/abs/ps composites without surface modifying additive has lower strength than its constituents. in three samples (c-1, ad-2, and ad-4) the tensile strength of glass fibre free, but treated composites was lower than that of untreated. this is probably due to the reason of the additive has been disadvantageously altered in surface characteristics of the plastic mixture. the largest increase in the tensile strength occurred for ad-1 (+12%) and ad-3 (+21%) additives without gf, while the peroxide (+23%), and ad-1 (43%) samples have resulted the best properties using 20% glass fibre, as well. the young’s modulus, as the measure of the elastic property of sample, changed in the range between 1015 and 1685 mpa in the presence of glass fibre, while the values were between 937 and 1579 mpa without gf reinforcing (fig.3). the maximum value of tensile modulus was found by the using ad-1 surface treating agent both presence and absence of gf (1579 mpa and table 4: sample compositions with glass fibre in weight % sample no. 10 11 12 13 14 15 16 ldpe 43 43 43 43 43 43 43 abs 24 24 24 24 24 24 24 ps 12 12 12 12 12 12 12 gf 20 20 20 20 20 20 20 c-1 1 c-2 1 ad-1 1 ad-2 1 ad-3 1 ad-4 1 peroxide 1 figure 2: tensile strength of samples figure 3: tensile modulus of ldpe/abs/ps samples 10 1685 mpa). on the basis of data in table 1, the tensile modulus of ldpe, abs and ps raw materials were 420, 1750 and 1720 mpa, respectively. the untreated ldpe/abs/ps samples had significantly lower tensile moduli with 937 mpa and 1173 mpa in the presence and absence of gf, respectively. presumably it was the consequence of the phase separation occurring the immiscible polymers. the compatibility of immiscible polymer blends could be significantly improved by the above mentioned additives, because not only the tensile strength, but also the tensile modulus was significantly increased e.g. by the application of ad-1 additive (+44 % with gf and +69% without gf). in general, the tensile modulus was higher in the presence of glass fibre than without that. the relative elongation refers to the change in sample length during the tensile tests. rigid materials (polyamide, abs, etc.) have low value of elongation, while that of significantly higher in case of soft or rubber like elastic polymers (polyethylene, pp, ps, rubber, etc.). the relative elongation (fig.4) follows the opposite trends than tensile strength or modulus. it is changed in the range of 2.33 and 4.29% without gf, or 2.09 and 3.16% with gf. it means that the glass fibre presence resulted lower values of relative elongation. the surface treating agents have only slight effect to the elongation apart from ad-1 sample, because the difference between the treated and untreated samples was 63% in case of ad-1. in any other cases this value was less than 20%. flexural properties results from flexural tests are summarized in figs.5 and 6. the flexural strength was in the range of 17.3 and 22.6 mpa in case of gf reinforced ldpe/abs/ps composites and between 13.7 and 19.9 mpa in case of unreinforced specimens. the best result was found when the interfacial surface of ldpe/abs/ps composite and/or the glass fibre surface were modified by ad-3 additive (22.6 mpa). in the presence of ad-3 additive the unreinforced ldpe/abs/ps blend had 19.9 mpa flexural strength value. generally, the tensile properties were favourable in case of reinforced, than that of unreinforced samples. according to table 1, the waste abs and ps raw materials had flexural strength of 29.0 mpa and 21.0 mpa, respectively. on the other hand, the flexural strength of unreinforced ldpe/abs/ps was 15.3 mpa, which can be increased to 17.3 mpa in the presence of gf. it means that the flexural strength was below the lowest value of constituent (ps, 21.0 mpa) even in the presence of gf. co mparing tensile and flexural strength, it can be concluded that the effect of the surface modifying agents were more significant to the tensile than to the flexural properties. the negative effect of surface modifying agents was observed in some cases. for instance, flexural strength was reduced in case of c-1 and peroxide additives. regarding the flexural strength the largest increase occurred in the presence of ad-3 (+30%) and c-2 (+22%) additives without glass fibre reinforcements. the increasing in flexural strength was 30% (without gf) and 31% (with gf) in case of ad-3 additive, while that of was 22% (without gf) and 17% (with gf). regarding flexural modulus, similar results were obtained as discussed above. abs and ps raw materials have 1820 and 1140 mpa flexural modulus, respectively. according to fig.6, the flexural modulus was 1080 mpa and 1285 mpa in case of unreinforced and reinforced ldpe/abs/ps composite without surface treating agents. the flexural modulus indicates the rigidity. higher modulus means greater rigidity. results demonstrate that the flexural modulus changes in the range 1285 and 2015 mpa in the presence of gf, whereas values were between 1040 and 1637 mpa in case of the non-reinforced composites. the maximum value of flexural modulus was given specimens figure 5: flexural strength of ldpe/abs/ps samples figure 6: flexural modulus of abs/ldpe/ps samples figure 4: elongation of samples measured at tensile test 11 containing c-2 surface treating additives both with and without glass fibres. charpy impact strength the charpy impact test determines the amount of energy absorbed by a material during fracture. fig.7 summarizes the charpy impact strength of samples as a function of surface treatment additives. the impact strength of the samples ranged from 4.7 to 9.1 kj mm-2, in which reinforced composite materials was between the higher range of 5.9 and 9.1 kj mm-2. the highest value was in a sample including ad-1 surface modification agent, and glass fibre (9.1 kj mm-2). in case of the same additive without reinforced fibre the impact strength was 7.1 kj mm-2. results show that the impact strength could be increased in each case due to surface treatment. the impact strength of ldpe/abs/ps composite was 4.7 kj mm-2 without reinforced and 6.8 kj mm-2 in reinforced by glass fibres. the largest growth was observed in the case of the sample containing c-2 (+53%) and ad-1 (+51%) additives for samples without glass fibres. contrary, the least growth was observed in the case of the sample containing ad-2 (+4%) additives. regarding the gf reinforced samples, the largest growth was observed when the ad-1 (+34%) and c-2 (+29%) additive were used. only the ad-2 additive resulted in lower impact strength, than abs/ldpe/ps excluding any additive (-13%). conclusion in this paper the efficiency of different compatibilizers in waste sourced ldpe/abs/ps composite were investigated both in absence and presence of 20% etype glass fibre. it was found that both the tensile and flexural properties of samples could be significantly improved by both synthetic and commercial coupling agent. the tensile strength and elastic modulus were the best when ad-1, a c16-c18 olefin containing polyakenyl polymaleic anhydride compatibilizers and 20% gf were applied. thus, compared to the ldpe/abs/ps composite without glass fibre and surface modifying additives, the tensile strength showed 58 %, and the elastic modulus showed an 80 % increase. regarding flexural properties similar result were observed, but not with ad-1, rather than ad-3, a polyakenyl polymaleic anhydride additive that resulted in the best properties, such as increase of 22.6 mpa in flexural strength. charpy impact strength increase was the largest (9.1 kj mm-2) in a sample containing ad-1 agent in the presence of glass fibres, which converts to about 90% increase relative the ldpe/abs/ps blend without gf and compatibilizing additives. synergistic effect of glass fibres and some of the compatibilizers can lead to increase of charpy impact strength by 94% in comparison to unmodified ldpe/abs/ps sample. acknowledgements v.s. and p.k are thankful for support from the project of operational programme research and development for innovations co-funded by the european regional development fund (project cz.1.05/2.1.00/03.0111). references [1] lai s.-m., li h.-c., liao y.-c.: properties and preparation of compatibilized nylon 6 nanocomposites/abs blends: part ii – physical and thermal properties, eu. polymer j., 2007, 43(5), 1660–1671 [2] majumdar b., keskkula h., paul d.r.: morphology of nylon 6/abs blends compatibilized by a styrene/maleic anhydride copolymer, polymer, 1994, 35(15), 3164–3172 [3] hale w., keskkula h., paul 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hungarian journal of industry and chemistry veszprém vol. 42(1) pp. 13–18 (2014) application of online and laboratory methods for the investigation of surface waters janka bobek,1! zsófia kovács,1 and zoltán zsilák2 1 institute of environmental engineering, university of pannonia, egyetem str. 10, veszprém h-8200, hungary 2 department of general and inorganic chemistry, university of pannonia, egyetem str. 10, veszprém h-8200, hungary !e-mail: bobek.janka@gmail.com pollutions in surface waters run down quickly, so the pollution waves cannot be detected by traditional point sampling. remote controlled online monitoring methods can make the tracking of pollutants possible. these solutions ensure that we can immediately access up-to-date information. the goal of our paper was to compare online monitoring and laboratory measurement techniques. during our work, we investigated the chemical and physical properties of the séd creek in veszprém with two different online monitoring systems. furthermore, we made parallel laboratory measurements of samples taken weekly to evaluate the measurement results of online methods. we discuss the difficulties of installation and operation of online systems and problems arising during emergencies caused by weather. keywords: séd creek, on-line monitoring systems, comparing measurement techniques introduction the 2000/60/ec eu water framework directive (wfd) prescribes that by 2015 all surface water bodies have to reach a good ecological and chemical status. to ensure this, we need to have information about the status of water quality. a desirable feature would be the possibility of continuously track the status of our water bodies with a cost effective monitoring system. the goal of our work was to introduce online monitoring systems and laboratory methods used to measure the physical-chemical parameters of the séd creek in veszprém. in order to continuously monitor water quality, two online monitoring systems were installed, which operate on different principles. the majority of our work was to test the mobile monitoring station (no. 1), which was developed at the environmental engineering institute of the university of pannonia. in addition, we had the opportunity to follow up the operation of a more complex mobile monitoring station (no. 2), which was manufactured by combit it ltd. the two monitoring stations were placed strategically that the effect of the town of veszprém on the stream could be measured. with the help of measurements made online and control measurements made in the laboratory, we mapped the loads effecting the séd creek and to detect pollutant waves travelling down the stream. materials and methods the investigated water body is the middle section of séd creek. the water body belongs to the danube catchment and in it to the northern-mezőföld and eastern-bakony subunit. the séd originates in the bakony, then flows through the city of veszprém, and joins nádor canal at ősi. the total length of sédsárvíz-mill canal is 71.82 km. point pollutions are caused on the territory by communal and industrial wastewater inlets. intensive agriculture and husbandry are characteristic. because of the side-point sources, we also have to focus on the investigation of diffuse pollutions [4]. description of installed online monitoring stations two online water quality mobile monitoring stations were installed on the middle section of séd creek. the evaluated period of continuous measurement was between the august 4, 2013 and october 11, 2013. the two stations were different with respect of place of installation, power source, size, security, sampling, measured physical-chemical parameters, as summarized in table 1. mobile monitoring station 1 (fig.1) was located at the section of séd creek, where it enters veszprém, while mobile monitoring station 2 is at the exit point from the city (fig.1). 14 results and discussion online measurements during the period of august 4, 2013 and october 11, 2013, a tendency was observed for every measured parameter. in fig.3, the ph measured at the examined section of séd was between 7.3–8.0. the average value of conductivity is 720 µs cm-1, the value of turbidity is 30 ntu. differences and jumps compared to the baseline indicate pollution, heavy rain or malfunction. owing to the placing of the mobile monitoring stations changes could be detected in the ph values between the two sampling points. at mobile monitoring station 1 ph value was in average 0.4–0.5 points higher (7.85) than at mobile monitoring station 2 (7.45) (fig.4). there are numerous karst water inflows into the séd as it flows through the city, which causes the lowering of ph. possible acidic pollutants from roadways, rainwater inlets and industrial areas can also add to the mild acidification of the water body. in the case of measured ionic concentrations (fig.5) it was observed that all components have a background baseline with a well-defined average concentration. the differences from the baseline appear as peaks that can indicate pollutants or rainy weather. the baseline concentrations are 0.09, 0.03, 0.02, and 4.5 mg dm-3 for po4 3--p, nh4 +-n, no2 --n, and no3 --n, respectively from their average values. when evaluating the timecourse of all chemical parameters, salient values can be identified and associated with some kind of an event. if we compare figs.3 and 5 carefully, we can see that peaks appear at the same time for all components. during the evaluation of data, we identified pollutants, which were washed into the creek due to precipitation. table 1: properties of mobile monitoring stations monitoring station no.1 monitoring station no.2 location of installation entry point into veszprém in inner defense area of the waterworks exit point from veszprém on an industrial area size 85×85×85 cm outer size monitoring station made of hardened plastic 2.4×2.4 m base area, 2.5 m height monitoring station transportation car truck with crane power source 2 pcs of 12 volt lead battery line power (220v) measured parameters ph [11] turbidity [9] conductivity [8] water temperature [11] dissolved oxygen concentration [10] polyaromatic hydrocarbon concentration [17] ph [12] turbidity [3] conductivity [2] nh4 +-n concentration [13] po4 3--p concentration [16] no3 ±-n concentration [14] no2 --n concentration [15] sampling every 15 minutes every hour maintenance weekly battery replacement cleaning of the probes changing reagents and blind reagent calibration (biweekly) supplying distilled water (biweekly) cleaning of sample dispenser vessel sampling tubes figure 1: location of installed mobile monitoring stations figure 2: structure of mobile monitoring station 1 and 2 15 in addition, we detected pollution waves in two occasions. as can be expected, point sampling cannot give detailed information about the status of a water body. the advantage of online methods is clear due to their continuous monitoring, even if they are only operated for a short period of time. thus, we will get a more holistic picture about the status of a water body toward implementing efficient measures for water quality protection. pollutant leaching from precipitation to identify events, we used data from measurement station 2. in addition, water level data were downloaded from the water management web page of the ministry of interior, hungary. the water level of séd is at an average of 20 cm. from the time points in figs.3–5, we select an event occurred on september 30, 2013. around the time of the event, the water level started rising, the concentrations of physical-chemical parameters have also started to change. the pollutant downwash was detected between 04:00 and 06:00 according to the results; the concentration peak appeared at 05:00. viewing physical parameters (fig.6) the value of turbidity has risen, and after reaching the positive peak (14.6 ntu) it started to decrease. other physical parameters were seen as negative troughs. in the falloff phase all parameters moved back to the average value. looking at the chemical components (fig.6) as an effect of the rising water level, nh4 +-n, po4 3--n and no2 --n concentrations have risen, while no3 --n concentration appeared as a negative trough. outstanding physical-chemical parameters (e.g. po4 3--p at 0.15 mg dm-3 level) measured as an effect of pollutants washed in during precipitation. afterwards, the po4 3--p level moved back to its near average range of 50 µg dm-3. detecting pollutants pollutant waves were identified as events, when water level rise did not support the deviations of data points from their expected average values. alternatively, as a result of precipitation, water level of séd doubled relative to its average value without the presence of in pollutant waves. as an example, we analyze here the effect of a pollution wave appeared on september 26, 2013. the pollution was detected between 17:00 and 19:00 with reaching its peak at 18:00. looking at physical parameters (fig.7) turbidity values doubled relative to the average of 60 ntu. conductivity decreased significantly from 700 µs cm-1 to 640 µs cm-1. the ph decreased by 0.1 unit to 7.3. when we look at ion concentrations in fig.7, nh4 +-n concentration rose fourfold compared to the baseline (0.19 mg dm-3). po4 3-p and no2 --n concentrations also showed significant rise (30–180 µg dm-3). no3 --n displayed a negative trough at 40 µg dm-3, but this component was the least sensitive to the change. measurement of polyaromatic hydrocarbons based on the data points taken every 15 minutes by the polyaromatic hydrocarbon (pah) probe (trios) at measuring station 1 (fig.8) a pah pollutant wave was not detected during the investigated period. the baseline of pah compounds was measured to be 6–7 µg dm-3 and 13–15 µg dm-3. values significantly differing from figure 3: results of physical parameters measured (blue: station1, red: station 2) figure 4: variation of ph value as a result of discharge from the city (blue: station1, red: station 2) figure 5: change of concentration of measured ions figure 6: effect of precipitation on the physico-chemical components 16 the baseline (35 µg dm-3) can be counted as measurement errors. evaluation of laboratory measurement results in the duration of the investigation, we have taken point samples at the two measurement sites 13 times. the samples were always taken according to standard msz iso 5667–1:2007 [6] in the same time when the monitoring stations recorded data. the samples were transported in a cooler according to standard msz en iso 5667–3:2004 [7], and were analyzed on the day of sampling. table 2 summarized the type of instruments used for measurements. we compared the data obtained at measurement station 2 with the results of laboratory measurements (fig.9). correlation can be found for the outliers measured at the monitoring station (250 µg dm-3 po4 3-p) and in the laboratory (310 µg dm-3 po4 3--p). however, difference was found in the no3 --n concentrations between the laboratory and measurement station results showing around half values for the laboratory measurements than those from the measurement stations. based on these observations we proposed that the analyzer at the mobile monitoring station measures higher concentration than the real concentration. the effect of the city of veszprém on séd using laboratory measurements, the effect of the city of veszprém on the creek’s water quality was measured. the results obtained for averages of 13 samples are shown in fig.10. it can be seen that there was no significant change in the concentration of nh4 +-n (26.4–27.3 mg dm-3) between the entry and exit points of the creek with respect of the city. jumps in the concentration of nh4 +-n are characteristic during pollutant waves and precipitation. decrease in concentration of po4 3--p is notable (131–100 µg dm-3) at the exit section. at the entry section, séd flows near to agricultural areas, backyard gardens. we correlate the decrease of phosphate concentration within city limits with the presence of pure karst water inflows resulting in significant dilution effect. in the case of no3 --n and no2 --n concentrations (fig.10) an obvious increase can be seen (1.3–2.6 mg dm-3; 4.3–5.6 mg dm-3), which is related to the high nitrate content of the incoming karst water. the discharges from rainwater drains, backyard gardens, the canal of the zoo, and inflow from roads add to the increase of these concentrations. figure 7: effects of a pollutant wave on the physical-chemical parameters components figure 8: change in pah concentration in the investigated timeframe figure 9: comparing mobile monitoring station 2 and laboratory results 17 measurement of polyaromatic hydrocarbon concentrations the two goals of the measurements were the testing the reliability of the results by enviroflu and evaluating whether the probe can detect other pah compounds that are not fluorescent. to check reliability, we used the addition method with epa tcl polynuclear hydrocarbons mix chemical from sigma-aldrich. furthermore, we also used naphtaline-disulphonate compound for inducing disturbing effect. we measured three solutions as shown in table 3 with probe and we have taken emission spectra. laboratory control measurements (msz 1484-6) [5] were done by elgoscar 2000. comparison of the laboratory and probe results showed significant difference (table 3). if we deduct the values obtained for the sample from séd creek as base values, we get similar results. the reliability of results obtained this way was confirmed by spectra taken by a perkin elmer ls50b type fluorimeter (fig.11) [1]. the enviroflu probe detects fluorescent light at 360 nm. when looking at the curves at 360 nm, we can see that the proportions of intensity differences between the spectra of a sample from séd and artificially polluted samples correspond to the concentration differences. the significant difference between the laboratory and probe results comes from the fact that the probe senses all compounds giving fluorescence at a given wavelength. this was further elaborated by the significant concentration difference when the sample contained naphtaline-disulphonate. water quality according to water framework directive the middle section of séd belongs to type 3, or alpine, calcic-rough bed material, medium catchment water flow according to water management plan [18] on the basis of water framework plan [19.] we have prepared table 2: devices used to measure physical and chemical properties of water samples mobile monitoring station 1 mobile monitoring station 2 laboratory ph neotekponsel, pheht sentek pi11 consort c902 conductivity neotekponsel, c4e endress+hauser indumaxp cls 50 consort c902 turbidity neotekponsel, ntu sensor endress+hauser turbimax w cus41/cus41w po4 3--p µmac c lovibond pc spectro nh4 +-n no3 --n no2 --n pah trios, evirofluhc figure 10: the effect of the city of veszprém on the investigated section of séd creek table 3: comparison of laboratory and online measurement results enviroflu (µg dm-3) laboratory (µg dm-3) sample form séd 13.01 0.13 séd + 20 µg dm-3 pah mix 25.27 13.7 séd +100 µg dm-3 naphtaline-disulphonate 21.03 0.15 figure 11: emission spectra taken with fluorimeter table 4: monthly average values for water quality parameters august september october ph 7.64 7.45 7.43 conductivity, µs cm-1 711.22 707.16 720.74 oxygen saturation, % 84.15 93.4 77.32 dissolved oxygen, mg dm-3 9.39 10.28 8.73 nh4 +-n, µg dm-3 33 31 26 no2 --n, µg dm-3 31 17 15 no3 --n, mg dm-3 5.12 4.02 4.14 po4 3--p, µg dm-3 113.79 96.58 92.04 18 water qualification in the observed timeframe in monthly divisions. for dissolved oxygen and oxygen saturation values we used the results of mobile monitoring station 1 and for other components the results of mobile monitoring station 2. we have calculated monthly average values of water quality parameters (table 4). in addition, we classified each component on a five-level scale and then made class averages. the class minimums provided classifications for each month. the minimum of class average for august, september, and october were 2.5, 3, and 3, respectively; which resulted in water quality that did not reach a good status. conclusions the advantage of online measurement methods was demonstrated due to the possibility of continuously monitoring the quality of the examined creek. with online devices events can be detected that can be missed by point sampling, such as daily fluctuations, pollution waves in extreme time points. another advantage of online methods is the remote controllability, which does not require personnel except for maintenance. a drawback of the larger and more complex mobile monitoring station 2 compared to more portable mobile monitoring station 1 is the need for significant chemical, distilled water and maintenance time. the measurement stations can reveal trends, the results provided by them are in the same magnitude, but it cannot compete with the accuracy of an accredited laboratory. the goal of online measurements is to detect pollutant waves and extreme values. in order to enhance the accuracy of online measurements follow up laboratory control measurements is needed. in addition to the entry and the exit sections of the séd creek, the catchment management plan requires monitoring the physical and chemical parameters of the middle section of séd that are missing. the results presented in the given paper may help in the drafting of the measurement plans. acknowledgements this work was supported by the european union and co-financed by the european social fund in the frame of the támop-4.2.2/b-10/1-2010-0025. references [1] kristóf j.: chemical analysis ii. 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(lfa-no2-01 rev2.comm. 896) systea s.p.a., italy, 2000 [16] systea s.p.a: orthophosphate in water and seawater 0–20 ppm (lfa-po4-02 rev.1 comm.896) systea s.p.a., italy, 2000 [17] trios gmbh: trios optical sensors enviroflu-hc manual submersible fluorimeter for the detection of polycyclic aromatic hydrocarbons (pahs) in water, trios gmbh in germany, 2004 [18] directorate for water and environmental protection: water management plan for the danube river basin in hungary, 2009 (in hungarian) [19] eu water framework directive: the european parliament and of the council, water framework directive (2000/60/ec), ojl 327, 22 december 2000, 1–73 hungarian journal of industry and chemistry veszprém vol. 42(1) pp. 19–23 (2014) adsorption and intercalation of small molecules on kaolinite from molecular modelling studies attila táborosi,1! róbert kurdi,1 and róbert k. szilágyi2 1 surfaces and nanostructures laboratory, institute of environmental engineering, university of pannonia, veszprém, h-8201, hungary 2 department of chemistry and biochemistry, montana state university, bozeman, mt 59717, u.s.a. !e-mail: taborosia@almos.uni-pannon.hu kaolinite is an abundant natural material with considerable industrial potential. despite its simple composition (al2si2o5(oh)4 and layered structure being a phyllosilicate), it is notable that only little known about the interaction of kaolinite sheets with small organic reagents at the molecular level. these assumed to govern intercalation, delamination, and then the complete exfoliation processes. a common methodology to model the molecular structure of kaolinite is the employment of periodic boundary conditions. the application of molecular cluster models gained importance nowadays by capitalizing on the availability of wide range of theoretical tools for describing structural features and reaction mechanisms. in this study, we present our results using theoretical methodologies and modelling strategies from literature that are applied for adsorption and intercalation of urea, ethylene glycol, and potassium acetate. keywords: kaolinite, intercalation, adsorption, hydrogen bonding, molecular cluster model introduction a significant hindrance in the design, optimization, and execution of experimental research involving clay minerals is the lack of our understanding of molecular level processes occurring at the outer (adsorption) or at the inner surface (intercalation) of layers of clay. molecular modelling approaches have the potential to aid experimental design, mitigating cost of chemicals used, rationalizing unsuccessful trial-and-error experiments, and thus contributing to tailored utilization of clay minerals as industrial raw materials. given the periodic nature of the crystalline clay minerals, a common approach in modelling is the use of periodic boundary conditions [1–4]. a competitive approach is based on molecular cluster models [5–9]. an advantage of using the latter is the availability of a broad range of quantum chemical tools for studying the local chemical environment of the site(s) of adsorption and/or intercalation. in the given study, we have utilized kaolinite, which is a member of the 1:1 class of clay minerals. this implies that the layers of this simplest phyllosilicate are composed of octahedral (o) and tetrahedral (t) sheets. the o-sheet contains hexacoordinate al3+ ions, while the t-sheet has tetracoordinate si4+ ions. the oand tsheets are connected via tricoordinate oxide anions, while the separate ot or 1:1 layers are connected through hydrogen bonds (h-bonds) (fig.1). computational methods the computational models were created from the unit cell of the experimental x-ray diffraction structure of crystalline kaolinite [10]. we will discuss results here for models for separate oand t-sheets with figure 1: schematic presentation of adjacent ot layers of delaminated kaolinite 20 stoichiometry of al6o24h30 and si6o18h12, respectively (figs.2a and c). these are the smallest possible cluster models for the hexagonal, honeycomb like units of the oand t-sheets. in addition, two larger models of al10o38h46 and si10o29h18 were also considered (figs.2b and d) for the larger intercalating agents (ethylene glycol, potassium acetate). the unit cell of kaolinite was multiplied in all crystal dimensions to create a super-cell. this was then truncated to the cluster models presented above. the charge neutrality was achieved by terminating dangling bonds with protons at the periphery of the models. the initial positions of the adsorbent reagents were set at the centre of the hexagonal honeycomb-like unit of both oand tsheets and it was allowed to fully relax during optimizations. given that the computational models shown in fig.2 are simplifications of the experimental crystal structure environment, structural constrains were applied during geometry optimizations. in all calculations, the atoms of the organic reagents, the surface hydroxide groups (sho-) of the o-sheet, and the bridging oxide groups (bo2-) of the t-sheets were allowed to move, while the positions of the rest of the atoms were kept fixed. after structural optimizations, the positions and relative arrangements of the organic reagents with respect of the outer and inner surfaces, the shortest distances of possible ion/dipole interactions or h-bonds were noted. for computational models of t…reagent…o intercalation, the basal spacing was set at the beginning of calculations to the experimental values of 10.7, 9.5, 11.5 å, and 14.2 å for urea [11], ethylene glycol [12], and potassium acetate in the absence or in the presence of water [13], respectively. the calculations were carried out using the b3lyp hybrid density functional [14,15] with lanl2dz basis set [16] as implemented in gaussian09 [17]. the interaction energies were not considered in this work due to the modest level of theory and lack of consideration of explicit or implicit solvation shell. the main focus of the given work is to establish initial structural models for rationalizing experimental observations and prepare for more advanced computational modeling. the optimized structures presented in this work were made available at computational.chemistry.montana.edu/si. results and discussions kaolinite-urea interactions the lowest energy, optimized structure for the adsorbed urea on o-sheet can be characterized by two short o(urea)…s-hodistances of 1.92 and 1.95 å, while one of the amide groups approaches the opposite s-ho group within 1.73 å as shown in fig.3a. the presence of both donor and acceptor interactions for the same reagent molecule result in a tilted orientation of the urea. an alternative orientation in which only the carbonyl group is interacting with three s-hogroups (see below for intercalation model) was not found to be a stationary structure at this level of theory. figs.3b and c illustrate the two different orientations of the urea at the t-sheet, where the amide groups are h-bonded to the b-o2groups of the same si4+ ion (geminal) with nh…b-o2distances of 2.03 and 2.12 å or two different si4+ ions (vicinal) with 2.02 and 2.08 å figure 2: computational models for the hexagonal honeycomb-like units of [6al] (a) and [10al] (b) octahedral, [6si] (c) and [10si] (d) tetrahedral cluster models for oand t-sheets of kaolinite, respectively 21 distances. the energetic difference between the germinal and vicinal coordination is not significant (less than 10 kj mol-1) at this level of theory. when the adsorption of urea considered simultaneously at both the oand t-sheets, a model can be obtained for a plausible structure of the urea intercalated between two ot-layers (fig.4). in this computational model, the carbonyl group of urea forms three h-bonds at 1.74, 1.78, and 1.83 å distances with three s-hogroups of the hexagonal o-sheet cross from each other. at the same time, the intercalated urea forms two h-bonds with the geminal b-o2groups at 1.94 and 2.62 å distances. the tilted orientation of the urea is the consequence of the experimental basal spacing of 10.7 å, which was kept fixed during the structural optimizations. it is important to recognize that according to our computational model, there is not enough room between the expanded layers of kaolinite to accommodate urea perpendicular to the basal planes or with parallel carbonyl groups to the crystallographic ‘c’ axis. kaolinite-ethylene glycol interactions ethylene glycol is generally used in exchangeintercalation as a step followed by initial dimethyl sulfoxide or potassium acetate intercalation. as shown in fig.5a, the donor interaction between the reagent hydroxyl group and the al3+ bound s-hois much shorter (1.66 å) than those seen for urea adsorption (1.73 å), while the acceptor interaction is slightly longer (1.99 å). given that the b-o2groups of the tsheet can only act as h-bond acceptors with ethylene glycol, the reagent spans the entire hexagonal honeycomb-like unit of the t-sheet by forming longer (2.05 and 1.94 å), thus weaker h-bond interactions than with the o-sheet. the complementarity of the oand t-sheets with respect of being h-bond donor and acceptor, respectively, allows for an ideal orientation of the functional groups of ethylene glycol for maximizing the strength of h-bond interactions. the o-sheet forms a short (1.61 and 1.79 å) interaction between the o(glycol)…s-hogroups. the t-sheet accepts the ho groups of the ethylene glycol at 1.73 and 1.88 å distances. comparison of the urea (fig.5) and ethylene figure 3: computational models for urea absorption at o(a) and t-layers in geminal (b) and vicinal (c) arrangements figure 5: computational models for the adsorption of ethylene glycol at the (a) oand (b) t-sheets figure 4: computational model for intercalation of urea in kaolinite 22 glycol (fig.6) intercalated models, the network of interactions between the layers and reagents parallel well the different experimental basal spacing (10.7 vs. 9.5 å, respectively). while the urea opens the interlayer space more; however, it anchors the two layers with a stronger set of interactions than ethylene glycol. this can be correlated with the limited reactivity of urea/kaolinite complex in exchange intercalation; while ethylene glycol often provides the last step before complete delamination and exfoliation of clays. kaolinite-potassium acetate interactions a limitation of the in vacuo models used in this study greatly hinders the dissociation of the potassium ion from acetate and thus in both adsorption models the cation remained at the centre of the hexagonal honeycomb-like model for the oand the t-sheets in the vicinity of the anion acetate. in addition, the ionized carboxylic group of the reagent form two short and thus strong h-bonding interactions at 1.65 and 1.89 å distances with two germinal s-hogroups of the osheet. the shortest acetate c-h…b-o2distance in fig.7b is 2.95 å, which indicates the presence of weak interactions between the methyl group and the b-o2 groups. in the adsorption model for the t-sheet, the acetate appears to be held in place by the cation at about 2.66 and 2.68 å. some of the plausible structures for the intercalation of potassium acetate were obtained from simulations in the absence (fig.8a) and presence (fig.8b) of solvent water. similarly to the other models the values of basal spacing were set to their corresponding experimental values of 11.5 and 14.2 å, respectively. the 2.7 å difference allows for the accommodation of a water molecule as shown in fig.8b. in agreement with the absorption models in fig.7, we found short h-bond distances between the carboxylate group and the s-ho of the o-sheet at 1.59 and 1.83 å distances. when water figure 7: computational models for the adsorption of potassium acetate on (a) oand (b) t-sheets figure 6: computational model for ethylene glycol intercalation in kaolinite figure 8: computational models for potassium acetate intercalation in the (a) absence and (b) presence of solvent water 23 is present, it is likely to solvate the negatively charged end of the acetate ion with a characteristic -coo-…hoh distance of 1.63 å. the interaction of the water and the o-sheet is asymmetrical with 1.77 and 2.08 å o(water)…s-hodistances. given the energetic preference of the o-h…ohhbonding interaction, the methyl group of the acetate will only interact with anionic groups of the t-sheet with representation c-h…b-o2distances of 3.15 and 3.25 å. the lack of a representative solvent environment is of less importance for the position of the potassium ion in the intercalation models, since the inner environment of this model will likely be only exposed to bulk solvent only to a limited extent. conclusions we have started with a few notable preliminary results the establishment of a structural database for reference models related to the adsorption and intercalation of small molecules and kaolinite. we found that even a modest level of theory with respect of the basis set can provide reasonable structures. these results allow us for visualizing molecular structures in order to rationalize experimental observables and generate new ideas for research directions. furthermore, these models can be considered as initial structures for higher-level calculations that are currently in progress in our laboratory. acknowledgement this research was supported by the european union and the state of hungary, co-financed by the european social fund in the framework of támop 4.2.4.a/2-111-2012-0001 ‘national excellence program’ (rks and at) and támop-4.2.2.a-11/1/konv-2012-0071 (rk). the authors acknowledge the helpful discussions with prof. jános kristóf and prof. erzsébet horváth. we acknowledge the use of the computational facilities at montana state university, bozeman, mt. references [1] smrcok l., tunega d., ramirez-cuesta a.j., ivanov a., valuchova j.: the combined inelastic neutron scattering and solid-state dft study of hydrogen-atoms dynamics in kaolinitedimethylsulfoxide intercalate, clays clay minerals, 2010, 58(1), 52–61 [2] mercier p.h.j., le page y.: rational ab initio modeling for low energy hydrogen-bonded phyllosilicate polytypes, eu. j. mineral., 2011, 23(3), 401–407 [3] geatches d.l., jacquet a., clark s.j., greenwell h.c.: monomer adsorption on kaolinite: modeling the essential ingredients, j. phys. chem. c, 2012, 116(42), 22365–22374 [4] tunega d., bucko t., zaoui a.: assessment of ten dft methods in predicting structure of sheet silicates: importance of dispersion corrections, j. chem. phys., 2012, 137(11), 114105 [5] ható z., makó é., kristóf t.: water-mediated potassium acetate intercalation in kaolinite as revealed by molecular simulation, j. mol. mod. 2014, 20(3), 1–10 [6] michalkova a., robinson t.l., leszczynski j.: adsorption of thymine and uracil on 1:1 clay mineral surfaces: comprehensive ab initio study on influence of sodium cation and water, pccp, 2011, 13(17), 7862–7881 [7] dawley m.m., scott a.m., hill f.c., leszczynski j., orlando t.m.: adsorption of formamide on kaolinite surfaces: a combined infrared experimental and theoretical study, j. phys. chem. c, 2012, 116(45), 23981–23991 [8] scott a.m., dawley m.m., orlando t.m., hill f.c., leszczynski j.: theoretical study of the roles of na+ and water on the adsorption of formamide on kaolinite surfaces, j. phys. chem. c, 2012, 116(45), 23992–24005 [9] song k.h., wang x., qian p., zhang c., zhang q.: theoretical study of interaction of formamide with kaolinite, comp. theor. chem., 2013, 102, 72–80 [10] bish d. l.: rietveld refinement of the kaolinite structure at 1.5-k, clays clay minerals, 1993, 41(6), 738–744 [11] makó é., kristóf j., horváth e., vágvölgyi v.: kaolinite-urea complexes obtained by mechanochemical and aqueous suspension technics-a comparative study. j. colloid inter. sci., 2009, 330(2), 367–373 [12] gardolinski j.e.f.c., lagaly g.: grafted organic derivatives of kaolinite: i. synthesis, chemical and rheological characterization, clay minerals, 2005, 40(4), 537–546 [13] frost r.l., kristóf j., kloprogge j.t., horváth e.: rehydration of potassium acetateintercalated kaolinite at 298 k. langmuir, 2000, 16(12), 5402–5408 [14] lee c.t., yang w.t., parr r.g.: development of the colle-salvetti correlation energy formula into a functional of the electron-density, phys. rev. b, 1988, 37(2), 785–789 [15] becke a.d.: density-functional thermochemistry 3 the role of exact exchange, j. chem. phys. 1993, 98(7), 5648–5652 [16] dunning jr. t.h., hay p.j., (ed.: schaefer iii h.f.): modern theoretical chemistry: methods of electronic structure theory, plenum, new york 1976, vol. 3, pp. 1–28 [17] frisch m.j.t., trucks g.w., schlegel h.b., scuseria g.e., robb m.a., cheeseman j.r.; et alas: revision d.01 ed., gaussian, inc., wallingford ct, 2009 acknowledgement the dedicated issue of the hung. j. ind. & chem. and in part the organization of the 2014 spring scientific students’ meeting at university of pannonia were made possible from support provided by the national talent program of the educational research and development institute and the human resource support program of the ministry of human resources within the framework of “support of tdk workshops recognized by the council of national scientific students’ association” (ntp-tdk-13) köszönetnyilvánítás jelen kiadvány és részben a 2014. évi tavaszi tudományos diáknap a pannon egyetemen az emberi erőforrások minisztériuma megbízásából az oktatáskutató és fejlesztő intézet és az emberi erőforrás támogatáskezelő által gondozott nemzeti tehetség program „az országos tudományos diákköri tanács által elismert tdk-műhelyek támogatása” (ntp-tdk-13) című pályázatának köszönhetően valósult meg. national scientific students’ association hungarian journal of industry and chemistry veszprém vol. 42(1) pp. 25-29 (2014) impact of size heterogeneity of core-shell packing materials on chromatographic separation of large biomolecules diána lukács and krisztián horváthb department of analytical chemistry, university of pannonia, 8200 veszprém, egyetem st. 10., hungary be-mail: raksi@almos.uni-pannon.hu the effect of particle size heterogeneity of core-shell stationary phases on the efficiency of chromatographic separation of large biomolecules was studied. it was shown that the column efficiency was affected significantly by the breadth of particle size distribution. the chromatographic efficiency decreased as the heterogeneity of particle sizes increased. although the absolute decrease of separation efficiency was affected by the linear velocity, u, of the eluent, the relative change of hetp was independent of u in the practical range of eluent velocities. the results showed that the affect of particle size distribution was the highest in case of fully porous phases, and it decreased as the diameter of the inner core decreased. it was shown that, in the usual range of particle size heterogeneity of core-shell phase, the peak capacities did not change significantly even at high eluent velocities. keywords: high performance liquid chromatography, particle size heterogeneity, separation efficiency, core-shell phases introduction modern analytical applications of liquid chromatography require efficient stationary phases. before the introduction of core-shell particles – particles with a porous layer surrounding a solid core (fig. 1) – the use of monolithic silica rods [1, 2], or of sub-2 µm particles offered today the most satisfactory results. due to their excessive radial heterogeneity, however, the efficiency of monolithic columns currently is lower than that of sub-2 µm particles. columns packed with fine particles, however, have a low permeability [5–7]. thus, efficiency of columns packed with core-shell particles similar to the columns packed with sub-2 µm particles, but can be operated with the same instruments as those used for conventional columns. the use of core-shell phases is particularly advantageous in the separation of large biomolecules [8]. recently, coreshell phases were optimized for the separation of large biomolecules [9, 10]. besides their unique structure, the high efficiency of core-shell phases is in part due to the very narrow particle size distribution, with a relative standard deviation around 5–10% vs. 20–40% for most totally porous particles [7]. in literature, fairly contradictory information can be found about the effect of particle size distribution, psd, on the separation efficiency. some results suggest that the large particle size variance has no influence on the column efficiency, while according to other data the wide psd decreases the efficiency of chromatographic separation. halász and naefe [11] were the first ones who examined the effect of particle size distribution porous shell non-porous core r core r p � shell figure 1: structure of core-shell particles on the column efficiency in case of particles that were larger than 50 µm. in their work, no experimental result was found for the change of chromatographic efficiency even in case of wide psds (⇠ 40%). two years after halász’s work, significantly smaller, 1-10 µm, particles were tested by endele et al. [12]. no change in the permeability and in the chromatographic efficiency were observed as long as the average particle size remained the same. dewaele and verzele prepared columns packed with mixtures of different compositions of reversed phase particles of 3 and 8 µm and investigated the effect of the psd on the column efficiency [13] with similar results. billen et al. found that the breadth of the distribution of the stationary phase particles has no effect on the chromatographic efficiency as long as no fines are present. in the presence of fines, the efficiency decreases significantly [14]. they emphasized that 26 different conclusions can be drawn about the goodness of a chromatographic column depending on the definition used for the particle size distribution. the effect of the psd on the chromatographic efficiency of sub-2 µm particles was studied by cabooter et al. by analyzing kinetic plots of these phases [15]. in their work, they showed that not just the psd is important but also the separation efficiency one wants to achieve. it was concluded that the greater the achievable number of theoretical plates, the more the psd affects the separation efficiency. in their experiments, the authors obtained better results by using columns with a narrower psd than by using columns of the same dimensions but packed with particles with broader psd. recently, gritti et al. found that the chromatographic efficiency of the columns can be optimized if a small amount of greater particles is added to the sub-3µm particles which leads to better bead homogeneity [16]. manufacturers practice matches these, because on their confession they add a small amount of larger particles to the bathes to optimize the pressure drop along the column. experimental study of the effect of psd on chromatographic efficiency is rather complex, because the column packing procedure is hardly reproducible. it is particularly true when we work with stationary phases which have different psds. the quality of column packing also affects the column efficiency significantly. theoretical models can provide more reliable data on this field because it does not affected by the variability of column packing. the goal of this work is to study the effect of particle size heterogeneity on the chromatographic efficiency of separation of large biomolecules on core-shell stationary phases on a theoretical basis. theory in hplc, one of the measure of separation efficiency is the height equivalent to a theoretical plate, hetp [17]. the higher the plate height, the less efficient the separation is. the general rate model of chromatography [18] permits the calculation of hetp of columns packed by core-shell phases [8]: h(d p ) = 2d l u + k2 1 1 + k2 1 ⌦ u d2 p 30fd p + u d p 3fk f ! , (1) where d p is the diameter of particles of packing material, u the linear velocity of the eluent in the interstitial volume, k 1 the interstitial retention factor, f the phase ratio, d l and d p the axial and pores diffusion coefficients, respectively, and k f the external mass transfer coefficient. ⌦ is given by the relationship ⌦ = (1� ⇢) 1 + 3⇢+ 6⇢2 + 5⇢3 (1 + ⇢+ ⇢2) 2 , (2) where ⇢ represents the ratio of the radius of the inner solid core, r core , to the radius of the particle, r p (see fig. 1): ⇢ = r core r p . (3) accordingly, ⇢ is zero for fully porous particle and one for non-porous particle. for a core-shell particle, the interstitial retention factor is k 1 = (1� " e ) (1� ⇢3) " e [k a (1� " p ) + " p ] , (4) where " e is the external bed porosity, " p is the porosity of the porous shell, and k a is the adsorption equilibrium constant (henry constant). the particle size distribution is usually described by log-normal distribution [19]. the psd of a packing material with mean µ and variance �2 is fdp = 1 d p p 2⇡✓ exp 0 b@� ⇣ ln dp µ + 1 2 ✓ ⌘ 2 2✓ 1 ca , (5) where ✓ = ln ✓ �2 µ2 + 1 ◆ . (6) on the basis of the equations above, the probability density function of local hetps, fh , can be derived by applying the change-of-variables rule [20]: fh = ���� d dh d p (h) ���� frp (dp(h)) , (7) where d p (h) is the inverse function of h(d p ) (see eq. (1)). the observable hetp of the column is the first moment of eq. (7): h col = 1z 0 h fh dh. (8) methods of calculations for the calculation of h col (eq. (8)) a software written in c++ language, using the adaptive quadrature routine provided by gnu scientific library (gsl, v. 1.15) [21]. the integration region was divided into subintervals, and on each iteration the subinterval with the largest estimated error was bisected. as a result, the overall error reduced rapidly, as the subintervals became concentrated around local difficulties in the integrand. these subintervals were managed by the gsl library, which handled the memory for the subinterval ranges, results and error estimates too. the relative error of integration was set to 10 �10. the source code of the program was compiled by g++ shipped by gnu 27 0 50 100 150 200 h e t p [ m ] 0 10 20 30 40 50 eluent velocity [cm/min] = 0.8 m = 0.6 m = 0.4 m = 0.2 m = 0.0 m figure 2: van deemter plots of large biomolecules in case of different standard deviations of particle size distributions of 2.6 µm core-shell stationary phases compiler collection ver. 4.7.2 using o1 optimization. the calculations were performed on a pentium iv computer (2.80 ghz) running gnu linux operating system (debian wheezy). the function fh (eq. (7)) for the numerical integration was derived symbolically by mathematica 8.0 (wolfram research, inc.). h (eq. (1)) was calculated as it is described in ref. [8]. the internal (" p ) and external column porosities (" e ), were 0.05 and 0.4, respectively. the distribution coefficient of the compounds were set to 3. the ratio of the molecule size and the average pore diameter were assumed to be 0.68. the molecular diffusivity was 2.5⇥10�5 cm2/min. the value of “eddy” diffusion term, the internal and external obstruction factors were 1.3, 0.31 and 0.6, respectively. the linear velocity of the eluent was varied between 0.1 and 50 cm/min. the average pore size was 80 å. it was assumed that the quality of the column packing remained identical in all cases. results and discussion in fig. 2 the calculated van-deemter curves of large biomolecules separated on 2.6 µm core-shell phases can be seen. the ratio of the radius of the inner solid core to the radius of the particle, ⇢, is 0.7 representing the typical core size of commercial core-shell phases. the standard deviation of particle size distribution is varied between 0.0–0.8µm that corresponds to 0–30% relative standard deviation. close examination of fig. 2 highlights that the hetp values of large biomolecules are approximately directly proportional to the eluent velocity. fig. 2 shows that the heterogeneity of particle sizes has a significant effect on the separation efficiency of large biomolecules. the separation efficiency is the highest when the variance of particle size distribution is zero (solid black line). increasing breadth of particle size distribution decreases the efficiency of separation. the decrease in the efficiency is more significant at higher eluent velocities. at 10 cm/min, the difference between 1.00 1.05 1.10 1.15 1.20 r el at iv e h e t p 0 10 20 30 40 50 eluent velocity [cm/min] = 0.8 m = 0.6 m = 0.4 m = 0.2 m figure 3: relative van deemter plots of large biomolecules in case of different standard deviations of particle size distributions of 2.6 µm core-shell stationary phases the two extremes (� = 0 and � = 0.8) is less than 5 µm that is approximately 15% of the total plate height at this eluent velocity in ideal case (� = 0). in case of 30, 40, and 50 cm/min the differences are significantly larger: ⇠15, ⇠20, and ⇠25µm, respectively. note, however, that the relative increase is ⇠15% in each case suggesting that the relative change of hetp is independent from the eluent velocity. in fig. 3 the relative hetp, h rel , values of large biomolecules can be seen as a function of eluent velocity. h rel were calculated as h rel = h� h 0 , (9) where h� and h 0 are hetp values at �2 and 0 variance of psd. in fig. 3, it can be seen that raising eluent velocity increases the relative hetp. above ⇠8 cm/min, however, a plateau is reached and the change of relative hetp becomes negligible. it suggests that, at low eluent velocities, the interstitial dispersion is the governing effect in band dispersion. as the velocity of eluent increases, the pore diffusion becomes more and more significant. accordingly, in practice (u > 10 cm/min), it is the dominant effect in band dispersion. fig. 4 shows the effect of core size on the chromatographic efficiency at different breadth of coreshell particle distribution. the linear velocity of the eluent was 15 cm/min that is a typical value in chromatographic applications. it can be seen that, as expected from eq. (1), the efficiency of stationary phase increases as the thickness of porous layer decreases. the effect of width of particle size distribution is less significant at larger ⇢ values. while in case of fully porous particles, the difference is almost 17µm between the hetp values of the two extremes (� = 0 and � = 0.8), it is slightly more than 4µm at ⇢= 0.8. the relative hetps calculated as in case of fig. 3 do not change significantly with the diameter of nonporous core until ⇢ = 0.8 (fig. 5). above that value, 28 0 20 40 60 80 100 120 140 h e t p [ m ] 0.0 0.2 0.4 0.6 0.8 1.0 = 0.8 m = 0.6 m = 0.4 m = 0.2 m = 0.0 m figure 4: hetp of columns packed with 2.6 µm core-shell particles 1.00 1.05 1.10 1.15 1.20 re la ti v e h e t p 0.0 0.2 0.4 0.6 0.8 1.0 = 0.2 m = 0.4 m = 0.6 m = 0.8 m figure 5: relative hetps of columns packed with 2.6 µm core-shell particles h rel s decrease abruptly, at ⇢ = 1 there is no difference between the cases. it can be explained by considering that the separation efficiency of large biomolecules is affected mainly by the pore diffusion (second term of eq. (1)). as the thickness of porous layer of core-shell particles decrease, the diffusion paths reduce as well. as a result, the impact of pore diffusion on band broadening is less and less significant. the difference between the distinct particles vanishes. finally, at ⇢ = 1, only the interstitial band spreading (first term of eq. (1)) influences the efficiency of separation. since d l is not affected by the particle size distribution, h rel s become unity. besides the plate heights, the change of peak capacities were also studied. peak capacity, n c , is a practical measure of separation potential in hplc. n c is defined as the maximum number of components that can be resolved completely between the peaks of the least and most retained solutes [22]. several expressions exist for the calculation of peak capacity [23] depending on the mode of chromatography. in case of isocratic mode of separation, nc can be calculated as nc = 1 4 p n (t max � t min ) ln t max t min , (10) where t max and t min are the retention times of the first and last eluting peaks, and n the number of theoretical 0.90 0.92 0.94 0.96 0.98 1.00 r el at iv e p ea k ca p ac it y 0 10 20 30 40 50 eluent velocity [cm/min] = 0.2 m = 0.4 m = 0.6 m = 0.8 m figure 6: relative peak capacities of columns packed by 2.6 µm core-shell particles; l = 10 cm, t 0 = 10/9, t max = 100/9 plates (n = l/h). in fig. 6 the peak capacities of 2.6 µm core-shell phases can be seen as a function of eluent velocity in case of separation of large biomolecules. the calculated peak capacities were normalized for value that belongs to zero variance of psd. the figure shows that the achievable peak capacity of a column packed with core-shell particles is affected by the heterogeneity of particle sizes. the decrease of peak capacities, however, is significantly smaller than the decrease of column efficiencies (fig. 2). that is because n c is proportional to the reciprocal square root of h . accordingly, 15% increase in the plate height results in ⇠7% loss of peak capacity that is not significant in practice. conclusions since their introduction, core-shell stationary phases became very popular for the analysis of large biomolecules. the morphology of these phases results in less band broadening compared to fully porous particles and thus delivers extremely high efficiencies. in this work, the effect of particle size heterogeneity of core-shell stationary phases on the efficiency of chromatographic separation of large biomolecules was studied. the results showed that slopes of van deemter curves were affected by the breadth of particle size distribution. as a result of widening psd the column efficiencies decreased significantly. the analysis of peak capacities showed that the maximum number of large biomolecules that can be resolved by core-shell phases was not affected significantly, even if the psd was wide. considering that the relative standard deviations of pdss of core-shell phases are between 0.2–0.4µm for 2.6 µm particles, it can be concluded that the efficiency of these phases is affected significantly by the size heterogeneity of the particles. further efforts from column manufacturers in order to improve the psd do not give any more advantages and are not profitable. 29 acknowledgements this research was supported by the european union and the state of hungary, co-financed by the european social fund in the framework of támop-4.2.4.a/211/1-2012-0001 ‘national excellence program’. the research infrastructure was supported by the hungarian scientific research fund (otka pd104819) and the hungarian state and the european union under the támop-4.2.2.a-11/1/konv-2012-0071 project. references [1] nakanishi k., soga n.: phase separation in gelling silica–organic polymer solution: systems containing poly(sodium styrenesulfonate), j. am. ceram. soc., 1991, 74, 2518–2530 [2] minakuchi h., nakanishi k., soga n., ishizuka n., tanaka n.: octadecylsilylated porous silica rods as separation media for reversedphase liquid chromatography, anal. chem., 1996, 68, 3498–3051 [3] kirkland j., langlois t., destefano j.: fused core particles for hplc columns, american laboratory, 2007, 39, 18–21 [4] destefano j.j., langlois t.j., kirkland j.j.: characteristics of superficially-porous silica particles for fast hplc: some performance comparisons with sub-2-µ m particles, j. chromatogr. sci., 2008, 46, 254–260 [5] gritti f., cavazzini a., marchetti n., guiochon g.: comparison between the efficiencies of columns packed with fully and partially porous c-18-bonded silica materials, j. chromatogr. a., 2007, 1157, 289–303 [6] cavazzini a., gritti f., kaczmarski k., marchetti n., guiochon g.: masstransfer kinetics in a shell packing material for chromatography, anal. chem., 2007, 79, 5972– 5979 [7] gritti f., leonardis i., shock d., stevenson p., shalliker a., guiochon g.: performance of columns packed with the new shell particles, kinetex-c18, j. chromatogr. a., 2010, 1217, 1589–1603 [8] horváth k., gritti f., fairchild j.n., guiochon g.: on the optimization of the shell thickness of superficially porous particles, j. chromatogr. a., 2010, 1217, 6373–6381 [9] wagner b.m., schuster s.a., boyes b.e., kirkland j.j.: superficially porous silica particles with wide pores for biomacromolecular separations, j. chromatogr. a., 2012, 1264, 22–30 [10] schuster s.a., wagner b.m., boyes b.e., kirkland j.j.: optimized superficially porous particles for protein separations, j. chromatogr. a., 2013, 1315, 118–126 [11] halász i., naefe m.: influence of column parameters on peak broadening in high-pressure liquid chromatography, anal. chem., 1972, 44, 76– 84 [12] endele r., halász i., unger k.: influence of the particle size (5-35 µm) of spherical silica on column efficiency in hplc, j. chromatogr., 1974, 99, 377–393 [13] dewaele c., verzele m.: influence of the particle size distribution of the packing material in reversed-phase high-performance liquid chromatography, j. chromatogr., 1983, 260, 13–21 [14] billen j., guillarme d., rudaz s., veuthey j.l., ritchie h., grady b., desmet g.: relation between the particle size distribution and the kinetic performance of packed columns. application to a commercial sub-2 µm particle material, j. chromatogr. a., 2007, 1161, 224–233 [15] cabooter d., billen j., terryn h., lynen f., sandra p., desmet g.: kinetic plot and particle size distribution analysis to discuss the performance limits od sub-2 µm and supra-2 µm particle columns, j. chromatogr. a., 2008, 1204, 1– 10 [16] gritti f., farkas t., heng j., guiochon g.: on the relationship between band broadening and the particle-size distribution of the packing material in liquid chromatography: theory and practice., j. chromatogr. a., 2011, 1218, 8209–8221 [17] snyder l., kirkland j., dolan j.: introduction to modern liquid chromatography (john wiley, hoboken, nj) 2010 [18] guiochon g., felinger a., shirazi d.g., katti a.m.: fundamentals of preparative and nonlinear chromatography (academic press, amsterdam) 2006 [19] johnson n.l., kotz s., balakrishnan n.: continuous univariate distributions, vol. 1 (wiley, new york), second edn. 1994 [20] weisstein e.w.: change of variables theorem, from mathworld – a wolfram web resource, url http://mathworld.wolfram.com/ changeofvariablestheorem.html [21] galassi m., davies j., theiler j., gough b., jungman g., alken p., booth m., rossi f.: gnu scientific library reference manual third edition, network theory ltd. 2009 [22] horvath c., lipsky s.r. : peak capacity in chromatography, anal. chem., 1967, 39, 1893– 1893 [23] grushka e.: chromatographic peak capacity and the factors influencing it, anal. chem., 1970, 42, 1142–1147 advertise upcoming meetings, conferences and workshops; make public announcements; introduce your research laboratory; a new product or a service on the pages of the hungarian journal of industry and chemistry please contact us if interested! editorial office: university of pannonia p.o. box 158, veszprém h-8201 (hungary) tel.: +36 (88) 624-746, e-mail: hjic@almos.uni-pannon.hu; web: hjic.mk.uni-pannon.hu felelős szerkesztő: szilágyi róbert, phd kiadja: pannon egyetem, 8200 veszprém, egyetem u. 10. levélcím: h-8201 veszprém, postafiók 158, tel.: (88) 624-000 hungarian journal of industry and chemistry veszprém vol. 42(1) pp. 31–37 (2014) effects of washing of raw material on properties of carbon nanotube containing poly(ethylene-terephthalate) composites tímea molnár,1 csilla varga,1! and lászló bartha1 1 department of mol hydrocarbon & coal processing, university of pannonia, egyetem str.10, veszprém, h-8200, hungary !e-mail: vcsilla@almos.uni-pannon.hu our interest has been focused on mechanical recycling of poly(ethylene-terephthalate) (pet) bottle waste, because recycling of plastic waste has crucial importance nowadays. the present article deals with the effects of washing of the secondary raw materials on properties of carbon nanotube (cnt) reinforced composites. in the first step advantageous washing compounds and their concentration were determined. after selecting the proper washing method extrusion moulding characteristics of pet granulates were investigated, and effects of carbon nanotubes as reinforcing additives and also application of coupling agents on the mechanical and rheological properties of composites were studied. keywords: carbon nanotubes, coupling agent, poly(ethylene-terephthalate), bottle waste recycling introduction almost all human activities result in waste generation either directly or indirectly. satisfying the daily needs for growing amounts of products results in higher consumption of raw materials, higher quantities of processing waste, and also higher amounts of wastes after the end of product life [1–4]. selectively collected pet bottles derived from municipal solid waste considered as waste plastics of a specific type, but the liquid stored in them contaminates their surfaces. fig.1 shows the typical treatment cycle and possible recycling methods for plastic wastes, especially for the pet bottles collected selectively. washing the surface of the waste materials is an important issue as biofilm can be formed. therefore, this raw material will be contaminated with some biological content. removing biofilm can be carried out in water, acidic or alkaline solvents. effectiveness of the method is measured by using reactions with folin reagent. pet has excellent mechanical and chemical properties, therefore, its resistance against chemicals and irradiation is outstanding; however, it can also have serious impact on the environment, because the biodegradation requires a long time, and expensive pretreatment methods are needed in order to bring them within reach of decomposing enzymes [3–8]. carbon nanotubes (cnt) are members of the family of fullerenes with cylindrical shapes, where carbon atoms are located at the surface of a cylinder. typical diameter is between the 1–50 nm regime, length can exceed even the 10 µm scale. carbon nanotubes have non-polar character. their surface contains only a few functional groups, which can react with polymers. in order to enhance the interaction between nanotubes and polymer matrices, the nanotube surface needs to be modified by application of coupling agents [7–11]. the given study deals with mechanical recycling of pet bottle wastes by applying secondary raw material for polymer matrix of cnt reinforced composites. after selecting the proper washing method, extrusion moulding characteristics of pet granulates were investigated. furthermore, the effects of carbon nanotubes as reinforcing additives, and application of coupling agents on the mechanical and rheological properties of composites were studied. experimental materials selectively collected pet bottles waste was used as the polymer matrix in the composites in washed and figure 1: pre-treatment and recycling of plastic wastes 32 unwashed form. mfi values of the pet granulates were measured, and changed in the interval of 10–14 g (10 min)-1 (255 °c, 2.16 kg). multi-walled carbon nanotubes (mwcnt) were produced at 700 °c by chemical vapour deposition (cvd) process over fe-co bimetallic catalyst at the department of chemical engineering, institute of chemical and process engineering, university of pannonia. purity of mwcnt was higher than 90 wt%, diameter was between 10 nm and 20 nm, the average length was above 30 µm and the betsurface was 200 m2 g-1. carbon nanotubes were applied in pet matrix in pristine and surface treated form. for treating surface of the carbon nanotubes experimental olefin-maleic-anhydride copolymer based coupling agents (fig.2) were used with the properties summarized in table 1. the ratios of the functional groups in coupling agents were determined by measuring acid value and saponification number by classical analytical methods and on the second hand the ratios were estimated by a previously developed ft-ir method [12]. production of composite samples cnt/pet composites were produced by a laboratory twin/screw extruder (lte 20-44, labtech engineering, fig.3). temperature profiles and screw rotation speed for production were previously determined [13]. washing of the waste material after the washing process, raw materials from selectively collected pet and pet derived directly from waste deposit were compared. the solutions with 0.05 m concentration were used for both acidic and alkaline washing method. citric acid and potassium hydroxide were chosen for the acidic and the alkaline wash. measurements to determine the tensile properties of the extruded strings (namely strength, modulus, and extension) an instron 3345 universal tensile testing machine was used. the temperature in the laboratory was 23 °c, while relative humidity was 37% during the mechanical tests that were carried out at 90 mm min-1 crossheadspeed. rheological measurements were carried out in a ceast smart rheo 2000 capillary rheometer at 265 °c. before measurements, 180 second preheating was applied to all samples. structural information about the developed coupling agent was obtained by ir technique using a tensor 27 ftir spectrometer (resolution: 3 cm-1, illumination: sicglobar light, detector: rt-dlatgs type) in the 400–4000 cm-1 spectral range. scanning electron microscopy (sem) was used to study the morphology of fractured faces of specimens and to follow possible interaction between the reinforcements and matrices on a phillips xl30 esem instrument. results and discussion surface treating effects of surface treatment were studied in two applications. firstly, the coupling agents on the cnt surface was investigated, thereby properties of pristine cnt were compared to properties of two different coupling agent treated cnts. bet-surface was measured and surface energy measurements were conducted. secondly, the effects of concentration of the coupling agent applied on the cnt surface were studied with additive concentration to be 15% and 20%. by the surface treatment the bet surface of pristine cnt reduced at least by 35–40% (table 2). on the basis of mesopore volume distribution results (fig.4), it was determined that coupling agents mainly attached to pores with diameters below 10 nm, because numbers of that pore size decreased the most. structure table 1: main properties of coupling agents property ca-1 ca-2 acid value, mg koh (g sample)-1 12.8 33.1 saponification number, mg koh (g sample)-1 95.3 126.5 molecular weight (mw)*, g mol-1 3520 3660 polydispersity factor 1.10 1.40 ratio of functional group, % anhydride 7.9 12.0 semi-ester 2.7 37.6 ester-amide 44.7 25.2 imide 44.7 25.2 * related to ps standard figure 2: structure of the ester-amide-imide derivative of the experimental olefin-maleic-anhydride copolymer (r1: alkyl group with length of the olefinic monomer (c16-c18); r2: alkyl group with r1-2 carbon number; a: 3-40, b: 3-32; k: 0,2-2; l: 1-7; m: 1-7 and n: 0,3-2) figure 3: production of pet composites in a twin-screw extruder table 2: bet-surface of different carbon nanotubes samples surface area pristine 191.1 m2 g-1 20% ca-1 coupling agent 125.5 m2 g-1 15% ca-2 coupling agent 172.3 m2 g-1 20% ca-2 coupling agent 102.1 m2 g-1 33 of the coupling agent had considerable impact on the distribution since different ratios of decrease were measured in the mesopore volumes, therefore surface interactions with different strength may were evolved between the coupling agent and the cnt. concentration of the coupling agent on the cnt surface also influenced the results (fig.5). decreasing the concentration from 20% to 15% resulted in an increase in the mesopore volumes to such an extent that almost the values for pristine cnts were achieved. properties of heterogeneous polymer systems are influenced by interfacial interactions and structure; however, no direct method is available to determine strength of interactions. therefore, models are used generally for their estimation. inverse gas chromatography measurements can be a useful tool for measuring the surface properties of different fillers and thus, the strength of interactions can be estimated. the dispersive component of surface energy describes london-interactions that can be used for estimation of the non-polar character, while other types of interactions (hydrogen-bond, polar, acid-base, etc.…) are included in the specific component (fig.6). we found that the dispersive surface energy of the coupling agent treated cnt was half of the pristine one at 70 °c (fig.6). this is indicative of the surface treated carbon nanotubes likely having lower tendency for agglomeration than pristine cnts. constant for the acid-base interactions were calculated based on the gutmann equation [14] as summarized in table 3. on the basis of these results it can be stated that acid character of the pristine cnts do not change significantly after surface treatment but the basic character improved. on the surface of the treated cnt-s weak basic active centres were predominant over acidic ones. effects of washing both acidic and alkaline washing were shown to be effective by which biofilm had been removed from surface of pet granulates with 100% efficiency. since biofilm cannot stick to the surface of pet due to its crystalline structure biofilm can be removed by application of weak acid or lye. ft-ir spectra of the granules before and after washing gave the opportunity to study the changes in functional groups of the plastic. it is important to highlight that no significant differences were observed between ft-ir spectra of acidic and alkaline washed samples. therefore, none of the compounds during washing deteriorated structure of pet (fig.7). effect of screw rotational speed pet samples were produced at various screw rotational speeds to study their rheological behaviour and also their mechanical properties. screw rotational speed during processing caused significant differences in viscosities in the low shear rate regime (beyond 500 s-1) (fig.8). figure 4: changes in mesopore volume distribution due to surface treatment (20% coupling agent) figure 5: changes in mesopore volume distribution due to surface treatment with various coupling agent (ca-2) concentrations figure 6: dispersive surface energy based on schultz-method (temperature: 70 °c) table 3: acid-base constants calculated by gutmann equation [14] at 70 ºc sample r2 pristine cnt ka 0.086 0.928 kb 0.000 15% coupling agent treated cnt (ca-1) ka 0.086 0.806 kb 0.253 20% coupling agent treated cnt (ca-1) ka 0.090 0.849 kb 0.213 34 in the medium shear rate region (500-5000 s-1) differences among the viscosities of the samples continuously disappeared. no differences were observed at higher shear rates, above 5000 s-1 dedicated to shear rates characteristic for injection moulding. that indicated that all the samples could probably be injection moulded at the same parameters. all the tensile properties (yield strength, modulus) improved by increasing screw rotational speed during processing (figs.9 and 10). the highest values for the tensile properties were measured for samples produced at the highest screw rotational speed. sample produced at the lowest rotational speed had values nearly identical to literature data [15]. however, samples processed at the highest rotational speed had 35–40% higher yield strength than the original material used for bottle production. it is important to note that washed pet granulates with the lowest rotational speed could not be produced at the same temperature profile as the plastic melted. pet composites containing pristine cnt washing the raw material caused 15% deterioration in yield strength, but the modulus did not change. untreated cnt could be introduced into the polymer melts at 2 wt% level both into washed and unwashed pet raw materials by the same side feeder screw rotational speeds. application of pristine cnt did not influence yield strength of the composites (figs.11 and 12), so yield strength of cnt/pet samples did not depend on the previous washing of the raw material. the pet raw materials had ca. 2000 mpa tensile modulus either for washed and unwashed plastic, so rigidity of the samples was stated to be the same. figure 8: effect of screw rotational speed on rheological behaviour of pet raw material figure 7: ft-ir spectra of pet sample in the 4000-600 cm-1 wavenumber range (purple: potassium-hydroxide; green: citric acid; blue: without washing) figure 10: effect of screw rotational speed on tensile modulus of pet raw material figure 9: effect of screw rotational speed on yield strength of pet raw material figure 11: effects of cnt application on yield strength of pet figure 12: effects of cnt application modulus of pet 35 pristine cnt containing washed pet had 20% lower modulus than unwashed pet based samples had, thereby; the property of the pet raw material was achieved. adding pristine cnt to washed pet plastic no difference was measured in the modulus compared to the washed pet without any reinforcing. effects of type and concentration of coupling agent two different, previously successfully applied coupling agents [13] were used on the surface of cnts. concentration of the coupling agents varied from 15% (conc-1) to 20% (conc-2) related to the weight of the pristine cnt. with respect of processing, surface treated cnts were much easier to introduce into the polymer melt. cnt concentration could be elevated up to 2.7–2.9 wt% in the polymer matrix at the same processing parameters using coupling agent treated cnts instead of pristine type. yield strengths of washed pet based composites increased with increasing concentration in the presence of both coupling agents compared to the pristine cnt containing pet sample (figs.13 and 14). improvement of 78% for ca-1, and 30% for ca-2 was realized in the presence of coupling agents at the higher concentration (20%). using unwashed pet, as raw material also resulted in enhancement of yield strength, but to a different extent, such as ca-1 resulting in 55%, while ca-2 causing 16% increase. based on the above results, the ca-1 additive was worth applying in higher (20%) concentration due to the achieved more than 50% higher yield strength relative to the pristine cnt containing pet composite. raw material is worth washing before processing if cost of washing could be balanced by the advantage of the 10 mpa increase in yield strength applying ca-1 coupling agent in 20% concentration. in case of ca-2 additive washing did not influence the properties at the lower (conc-1) concentration level, but with higher additive concentration (conc-2) a 14% difference was measured between the composites made from the two raw materials. comparing the samples with various additive concentrations an increase was observed in the modulus with increasing concentration for both raw materials and coupling agents. applying unwashed raw material 34% improvement was realized with ca-1 coupling agent and 32% with ca-2 additive if the concentration increased from 15% to 20%. a lower degree of improvements were measured for washed pet based samples making the same comparison. comparison of pristine and surface treated cnt containing samples showed that coupling agent was advantageous to be applied in higher concentration from the point of view of the modulus either. for unwashed pet based composites application of coupling agents resulted in 10–15% decrease in modulus related to the pristine cnt containing sample. for washed pet based samples making the same comparison changes were calculated to be +45% in case of ca-1, and +20% for ca-2 additive. the most advantageous observation based on the results is the lack of an effect on the mechanical properties in the investigated interval of raw material quality with respect of washing pet bottle waste, when used as polymer matrix for cnt reinforced composites. this could be realized in easier handling and pretreating of the raw material before recycling. sem graphs broken surfaces of samples were studied by scanning electron microscopy. cnts concentrated at one side of the extruded string in pristine cnt containing samples (fig.15a). diameter of the probable carbon nanotube nucleation centres varied (figs.15b and c). there were agglomerates with diameter of 30–40 µm and also with 5-10 µm number of the latter seemed to be higher. in addition, there were only a few nucleation centres both for washed and unwashed pet based composites. on the cross section of the extruded strings a crystalline part was rendered likely in larger areas in coupling agent treated cnt containing samples than in pristine cnt/pet samples. in pet containing 15% ca2 coupling agent a likely crystalline part was found at the middle of the extruded sample (fig.16). more nucleation centres and more homogeneous structure were observed (fig.16) than in pristine cnt containing sample from the same pet raw material. it is in accordance with the 15% lower cnt content of the pristine cnt/pet composite than the treated cnt containing one. the diameters of the nucleation parts were in the range of 20–30 µm. area related to the probable crystalline structure was higher in washed pet based sample on the sem graphs of the extruded strings (fig.17a). nucleation parts were figure 13: tensile properties of surface treated cnt containing pet composites figure 14: tensile properties of surface treated cnt containing pet composites 36 located in the middle of the sample and connected to each other diameters were identical to the former sample that was treated (fig.17b). based on the sem graphs it was concluded that carbon nanotubes were easier to handle and distribute more homogeneously due to surface treating both for washed and unwashed pet raw material, and on the other hand numbers of the nucleation parts and sizes could be influenced. conclusions the present article gave a brief insight into mechanical recycling of pet bottle wastes by applying that secondary raw material for polymer matrix of cnt reinforced composites. after selecting the proper washing method extrusion moulding characteristics of pet granulates were investigated and it was concluded that tensile properties improved by increasing screw rotational speed. effects of washing in carbon nanotubes containing pet composites were also investigated where carbon a b c figure 15: sem graphs of pet sample containing pristine cnt a b figure 16: sem graphs of unwashed pet based sample containing 15% ca-2 coupling agent treated carbon nanotube a b figure 17: sem graphs of washed pet based sample containing 20% ca-1 coupling agent treated carbon nanotube 37 nanotubes were applied either in pristine or surface treated form. washing of the waste plastic did not affected yield strength in case of pristine carbon nanotubes containing samples but for coupling agent containing composites mechanical properties significantly changed. if the proper coupling agent was applied in higher concentration, 20% e.g. yield strength improved by higher than 60% while modulus increased at least 20%. acknowledgements this research was supported by the european union and the state of hungary, co-financed by the european social fund in the framework of támop-4.2.4.a/211/1-2012-0001 ‘national excellence program’. the authors are also grateful for the financial support of this work by the hungarian state and the european union under the támop-4.2.2.a-11/1/konv/2012-0071 project. references [1] la mantia f.: handbook of plastic recycling, shrewsbury, rapra technology, 2002 [2] wégner k.: towards more efficient waste management, yearbook of hungarian plastic and rubber industry, 2013, 27–32 (in hungarian) [3] wu g., li j., xu z.: triboelectrostatic separation for granular plastic waste recycling: a review, waste mngnt., 2013, 33, 585–597 [4] fortelny i., michalková d., krulis z.: an efficient method of material recycling of municipal plastic waste, polym. degrad. stabil., 2004, 85, 975–979 [5] aksa w., medles k., rezoug m., boukhoulda m.f., bilici m., dascalescu l.: two stage electrostatics separator for the recycling of plastic from waste electrical and electronic equipment, j electrost., 2013, 71, 681–688 [6] sánchez a.c., collinson s.r.: the selective recycling of 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alumina precursor by different synthesis routes, composites sci. tehn., 2011, 71, 18–22 [12] varga cs.: production and investigation of compatibilizing additives for polymer composites, phd thesis, university of pannonia, veszprém, 2010 (in hungarian) [13] molnár t.: effects of carbon nanotubes and coupling agents in poly(ethylene-terephthalate) polymer, itdk report, university of pannonia, veszprém, 2011 (in hungarian) [14] gutmann v.: the donor-acceptor approach to molecular interactions, plenum press, new york, 1978 [15] pál k.: recycling of plastics wastes as secondary raw material, műanyagipari szemle, 2006/2 acknowledgement the dedicated issue of the hung. j. ind. & chem. and in part the organization of the 2014 spring scientific students’ meeting at university of pannonia were made possible from support provided by the national talent program of the educational research and development institute and the human resource support program of the ministry of human resources within the framework of “support of tdk workshops recognized by the council of national scientific students’ association” (ntp-tdk-13) köszönetnyilvánítás jelen kiadvány és részben a 2014. évi tavaszi tudományos diáknap a pannon egyetemen az emberi erőforrások minisztériuma megbízásából az oktatáskutató és fejlesztő intézet és az emberi erőforrás támogatáskezelő által gondozott nemzeti tehetség program „az országos tudományos diákköri tanács által elismert tdk-műhelyek támogatása” (ntp-tdk-13) című pályázatának köszönhetően valósult meg. national scientific students’ association hungarian journal of industry and chemistry veszprém vol. 42(1) pp. 39–42 (2014) investigation the properties of y-ba-cu-oxide superconductors prepared by hydraulic pressing and molding anna maloveczky,! margit enisz-bódogh, and tamás kulcsár institute of materials engineering, university of pannonia, egyetem str. 10., veszprém, 8200, hungary !e-mail: anna.maloveczky@gmail.com levitation applications of superconductors require the fabrication of bulk ceramic superconductors with special shapes. the conventional hydraulic pressing is not suitable for the production of superconductors with complicated forms, so we have applied slip casting to shape bulk superconductors. superconducting powders with different yba2cu3oy (123) and y2bacuo5 (211) phase content and different (pt, pb, ce) additives were prepared by solid-state reactions. the nonsuperconducting (211) particles can be considered as flux pinning centres; thus the magnetic properties can be influenced by their amount and particle sizes. the addition of a few weight percent of dopant in the nominal composition can modify the particle size and distribution of the (211) grains. we have investigated and compared the phase compositions, morphologies and magnetic levitation forces of bulk superconductors formed by hydraulic pressing and moulding. the shielding abilities of a moulded superconductor were simulated with the comsol multiphysics 4.4 software. keywords: ybco superconductor, moulding, shielding, modelling introduction the use of superconductivity is promoted by the need for stable high magnetic fields. the high-temperature superconductors are attractive for engineering applications, such as contactless superconducting bearings, trapped field magnets, levitation trains, fusion reactors, and nmr spectrometers. an important application of superconducting magnets is the magnetic resonant imaging (mri). superconducting magnetic shielding can be used simultaneously to protect the personnel and other medical equipment from the strong magnetic fields produced by an mri system. the relative magnetic permeability of type i superconductor is theoretically zero, which means when we use it for shielding, it expels the magnetic fluxes from itself. the high-tc superconductors can also be used for shielding sensitive electronic devices from external electromagnetic fields. due to the meissner effect [1,2], it is sufficient to surround the volume to be protected by a thin film. for quasi-monocrystalline films of ybacuo thickness of 1 µm would be sufficient for virtually perfect shielding. a granular ceramic layer would require a larger thickness, but in all cases the thickness and weight of the superconducting shields would be much less than those of magnetic materials providing a comparable effect. for these applications of high-tc superconductors outstanding magnetic properties and special shapes are required. the scientific literature suggests two main ways for improving the magnetic properties of superconductors that are structure damaging or doping [3–9]. both methods work the same way, such as by increasing the amount of pinning centres (such as 211 phase) in the superconducting (123) material and decreasing the size of these centres by addition of different dopants. the damaging method could be done by ion or neutron radiation to destruct the bulk of the material and generate faults. preparation of high-tc superconductors with special, complicated forms is a particular challenge due to their brittle nature. slip casting, namely pouring low viscosity water-containing slurry into moulds is the oldest ceramic forming method for production of special shapes. for superconductors slip casting of shapes is also possible although the use of water as liquid phase is not optimal due to hydrolysis and other reactions. another preparation method for ceramic superconductors is tape casting of viscous slurry containing ceramic particles in organic solvent [10]. materials and methods in this work, y-ba-cu-oxid-based superconductive powders were prepared with different 123/211 phase content and different (pt, pb, ce) additives. shaped bulk superconductors were produced from these powders with hydraulic pressing and moulding. the effects of these parameters were investigated on the phase compositions, morphologies and magnetic levitation forces of the sintered bulk superconductors. for modelling the superconductor as a shield in different geometries, comsol multiphysics 4.4 software was used that provides a simulating and 40 modelling environment using the finite element method. instead of the original ac-dc module of comsol, a module by roberto bambilla was used, which was developed for modelling ybco superconductors. results and discussions samples made by hydraulic pressing the superconducting samples were prepared by using y2o3, ba(oh)2·8h2o and cuo. the latter was obtained by the calcinations of cu(oh)2·cuco3·nh2o with a specific surface area of 18.4 m2 g-1, ptcl4, pbo and ce(no3)3·6h2o starting materials. the 123:211 molecular ratio of the nominal compositions was changed in the range of 1.00:0.15. samples were prepared without additives as well as with 2.0 wt% ce + 0.5 wt% pt, and 2.0 wt% ce + 0.5 wt% pb dopants. for sample preparations, barium-hydroxide was ground in agate mortar, but in some cases the pulverization and grinding was made in the presence of alcohol. the mixture of raw materials was homogenized by thoroughly mixing with alcohol in an agate mortar and compacted into disks of 25 mm × 3mm by hydraulic pressing at 70 mpa. firstly, the samples were prereacted at 960 °c for 4 hours to obtain the desired (123+211) phases by solid-state reaction. the heattreated samples were ground and the powders were pressed into pellets by hydraulic pressing using a pressure of 70 mpa. the relatively dense structure was obtained by liquid state sintering at 1010 °c peak temperature for 6 hours in oxygen atmosphere [11]. the levitation force of the samples after the heat treatments is shown in fig.1. as described in the literature, we also found that the levitation force shows an increasing trend with increasing amount of 211 phases. in the case of ce+pt and ce+pb dopant containing samples higher levitation forces can be obtained after the first heat treatment at 960 °c. it is notable that the samples prepared from barium hydroxide ground in the presence of alcohol showed improved magnetic properties. samples made by moulding part of the pre-reacted at 960°c ground samples were used for shaping superconductors by moulding. previously, superconductive slurries were prepared with different organic liquid additives and those were burnt out during the annealing. from these materials only a few were good enough for further studies. samples providing a proper cohesion and appearing to be homogeneous were selected for future analysis. after heat treatment, x-ray diffraction analysis was used to study the phase composition changes caused by addition of organic materials for deciding if any of the dopants has a negative influence on the superconductor properties. as shown in table 1, the metylan reduces the amount of the superconducting phase (123) and this leads to the tetragonal, non-superconducting structure. polyvinyl formal did not have a negative influence on the formation of 123 phase. thus, the polyvinyl formal binder was chosen with dioxane for further experiments. with respect of ideal concentrations, it was found that 1 wt% of polyvinyl formal/dioxane must be added to the superconducting powders to obtain a slurry with a density of 2.4 g cm-3, which was dense enough, but still can be poured. the second step was to find the appropriate mould form. different types of materials were investigated, such as stainless steel, glass, plastic, gypsum, and silicone rubber. the prepared slurries stuck to most of these materials rendering them useless for moulding with the exception of silicone rubber as sample could be removed perfectly. using this type of moulds we can make superconductors with complex geometry. the moulded samples were heat treated at the same program as used for hydraulic pressed samples. the moulding technique applies no pressing thus provides a porous structure. however, the pores can lead to poor superconductor properties. to decrease the porosity melt-producing dopants were applied. ag and pb with ce proved to be good in the case of hydraulic pressed samples. table 1: the peak intensity of the crystalline phases samples peak intensity, counts binder solvent 123 d=2.72 å 211 d=2.99 å 011 bacuo2 d=3.05 å cuo d=2.52 å baco3 d=3.72 å 1. polyvinyl formal dioxane 4460 1122 562 956 2. metylan dest. water 2952 919 737 725 3. metylan ethanol 1477 765 679 459 figure 1: levitation forces of the heat treated samples 41 it was found that only in the moulded samples prepared from barium hydroxide ground in alcohol provide enough melt for efficiently fill the pores. the use of dopants alone toward this goal was not sufficient. furthermore, with this grinding technique, the peritectic temperature of the superconducting phase (123) decreased, which allowed for a more economical heat treatment. it can be proposed that this grinding resulted in particle size reduction of barium hydroxide and the higher specific surface area leading to higher reactivity. in this case bulk superconductor with higher density can be obtained, which has an oriented, large plate-like 123crystalls containing structure (figs.2 and 3). modelling ybco as magnetic shield ybco can shield from magnetic fluxes due to the meissner effect. it works the opposite way than the commonly used ferromagnetic materials, which means that superconductor expels the magnetic fluxes from itself, while iron collects them. using the comsol multiphysics 4.4 package, the shields of iron and superconductor were compared in figs.4 and 5. the shielding ability of the superconductor is comparable with iron, and even better. it has the advantage that in alternating magnetic field it does not get heated. the ferromagnetic materials shield poorly in too small and too big fields because they have saturation flux density. superconductors are being used as shields in various devices [12–16]. with a geometry shown in fig.6, very sensitive magnetic devices could be fully shielded and vice versa the environment could be protected from a device, which induces strong magnetic field. with the shape in fig.7, for example a skull could be protected in the mri in case of presence of metal implants in the head. theoretically moulding could be used to prepare these shields. it would be cheaper and thin layers could be made, thus more economical wall could be produced by a few thin layers. figure 2: sem micrograph of the moulded sample ground conventionally figure 3: sem micrograph of the molded sample ground in alcohol figure 4: simulation of iron shield figure 5: simulation of superconductor shield figure 6: simulation of shielding for sphell geometry 42 conclusion in the case of the hydraulic pressed pellets, the results confirmed those from the literatures. improved magnetic properties were noticed with the increasing of the 211 phase content. this was further enhanced by the presence dopants. it was found that pb performs as good as pt or even a little bit better, which is preferred due to the price of pt. the grinding of barium-hydroxide in the presence of alcohol provided a denser structure and more melt phase leading to better superconducting properties. furthermore, it seems that this method decreases the peritectic temperature of the superconducting 123 phase. the homogenization needs to take place after grinding in alcohol to be effective. the adequate liquid-to-material ratio to make a slurry with 1 wt% polyvinyl formal in dioxane and the ideal moulding form of silicone rubber were determined. this allowed for making complex shaped superconductors. the melt-producing dopants cannot reduce the porosity enough to sufficiently improve the levitation force. alternative heat treatment programs with slow annealing up to 500 ºc, while all of the organic materials burn out, can avoid the cracks in the structure. application of vacuum during the moulding can also be useful, since it can eliminate trapped air bubbles from the mass. simulations carried out using comsol multiphysics 4.4 software indicated ybco being a good shielding material. utilization of complex geometries, sensitive devices can be protected, such as skull protection during mri measurements. references [1] takash m., tomioka y., miyauchi t., sato s., murai a., ido t., wakita k., terada h., ohkido s., matsubara m.: characterization of a large-scale non-doped yba2cu3o7-x superconductor prepared by plastic forming without high-pressure molding, j. amer. ceram. soc. 2007, 90(7), 2032–2037 [2] evetts j.: concise encyclopaedia of magnetic and superconducting materials, pergamum press, oxford, 1992, pp. 532–533 [3] monot i., leblond c., marinel s.m., desgardin g.: precursor and microstructure control for melt texturing of high-tc superconductive ybco ceramics, development of high-temperature superconducting alternators combining rotating and levitating principles, russian academy of science, saint-petersburg, 2002, pp. 27–45 [4] shlyk l., nenkov k., krabbes g., fuchs g.: melt-processed ybco with pt or ce additions: comparison of pinning behaviour, physica c 2005, 423, 22–28 [5] riches j.d., alarco j.a., barry j.c.: effects of pto2 and ceo2 additives on the microstructures of the quenched melts of y–ba–cu–o materials physica c superconductivity, 2000, 336, 43–56 [6] leblond c., monot i., provost j., desgardin g.: optimization of the texture formation and characterization of large size top-seeded-meltgrown ybco pellets, physica c, 1999, 311, 211–222 [7] hardy v., simon c., provost j., groult d.: pinning forces in bi-2212 single crystals irradiated by 6 gev pb ions, physica c, 1993, 206, 220–226 [8] wesche r.: magnetic relaxation and flux pinning in yba2cu3o7 a high-tc oxide irradiated by 5.3 gev pb ions, physica north-holland c 1992, 190, 289–298 [9] horvat j., wang x.l., dou s.x.: vortex pinning in heavily pb-doped bi2212 crystals physica c 1999, 324, 211–219 [10] grader g.s., johson d.w.: forming methods for high tc superconductors, thermochimica acta, 1991, 174, 239–251 [11] komlai k.: investigation of the the properties of the incongruent melting reaction of yba2cu3o-y superconductor phase, m.sc. thesis, university of pannonia, 2013 (in hungarian) [12] tavernier s.p.k., van den bogaert f., van lancker l.: the design of a magnetic shielding for an array of photomultipliers in a strong external field, nucl. instrum. methods, 1979, 167, 391–398 [13] bitter t., eisert f., el-muzeini p., kessler m., kinkel u., memt e., lippert w., meienburg w., werner r.: a large volume magnetic shielding system for the ill neutron-antineutron oscillation experiment, nucl. instrum. methods phys. res., 1991, a309, 521–529 [14] tripathi a., vedavathy t.s.: electromagnetic shielding using superconductors, pergamon press ltd, oxford,vol. 2, no. i, 1994, pp. l–5 [15] spillantini p.: active shielding for long duration interplanetary manned missions, adv. space res., 2010, 45, 900–916 [16] yusuf s.m., osgood iii r.m., jiang j.s., sowers c.h., bader s.d., fullerton e.e., felcher g.p.: magnetic profile in nb/si superconducting multilayers, j. magnet. magnetic mat., 1999, 198–199, 564–566 figure 7: simulaton of shielding using a semi-sphell geometry hungarian journal of industry and chemistry veszprém vol. 42(1) pp. 43–50 (2014) effects of ultrasonic disintegration, hot-compressed liquid water pre-treatment, and steam explosion on solvolysis and digestibility of grain sorghum stover dániel capári,! and andrás dallos department of physical chemistry, university of pannonia, egyetem str. 10, veszprém, h-8200, hungary !e-mail: capari.daniel@gmail.com one of the most promising renewable energy crops and biomass feedstock for biogas production in europe is the c4 plant grain sorghum due to its high photosynthetic efficiency. the release of lignocellulosic material and therefore the acceleration of degradation processes of sorghum stalks and leaves can be achieved using mechanical and thermal pretreatments, which assist to hydrolyse the cell walls and speed the solvolysis of biopolymers. this study is focused on hotcompressed liquid water, steam explosion and ultrasonic pre-treatments of grain sorghum stover. the effectiveness of pre-treatments was evaluated by means of soluble chemical oxygen demand, biochemical oxygen demand, and by the biogas and methane productivities. the results show that the pre-treatments disintegrated the lignocellulosic structure, increased and accelerated the biogas and methane production, and increased the mesophilic anaerobic digestion potential of grain sorghum stover. our laboratory tests demonstrated that the steam exploded grain sorghum stover possess the highest biogas productivity. keywords: grain sorghum stover; hot-compressed liquid water pre-treatment; steam explosion; ultrasonic disintegration, biogas digestion. introduction the grain sorghum is a possible carbohydrate resource for the simultaneous production of bioethanol and biogas due to its advantages over the traditional agricultural crops. the plants have remarkably good co2 absorption ability. grain sorghum is the fifth most important cereal crop grown in the world. the drought tolerance of sorghum is greater than that of corn. furthermore, it is able to regenerate after a period of drought. its productivity is also higher than that of corn, even in dry periods or in lower quality soils. in hungary, sorghum grows in arid areas as a substitution for fodder corn. therefore sorghum could be used to cultivate alternative feedstock for bioethanol production [1] and could be a sustainable crop for energy production in europe. the sorghum grain contains approximately the same amount of starch compared to corn kernels, which makes it attractive as raw material for the production of bioethanol. the agricultural byproduct of sorghum-based bioethanol production, the sorghum stover is a valuable bioenergy substrate for biogas digesters, despite the complex lignocellulosic structures of sorghum stalks and leaves and its resistance to decomposition. the utility and the economic feasibility in biogas power plants can be highly increased by different pre-treatment methods, to assist the disruption of the cell wall structure and to speed-up the solubilisation of the biopolymers in the biogas feedstock [2–4]. the purpose of pre-treatments is to remove lignin and hemicellulose, reduce cellulose crystallinity, and increase porosity [5,6] (fig.1). liquid hot-compressed water (lhcw) pre-treatment is a commonly used hydrothermal method. high temperature and high pressure are applied to maintain liquid phase and to avoid vaporization. during the pretreatment, water is penetrated into the cell structure of the biomass, hydrating cellulose, solubilizing hemicellulose, and slightly removing lignin. lhcw pre-treatment is highly effective for enlarging the accessible and susceptible surface area of cellulose and improving cellulose degradability for microbes and their enzymes [7,8]. after the hydrothermal treatment, the biogas production was increased for pig manure, for municipal sewage sludge and for fruit/vegetable waste figure 1: the disintegration of lignocellulosic material by pre-treatments 44 [9]. the hot water treatment increases the enzymatic hydrolysis and digestion of corn leaf, stalk and fibre [10,11] and the dissolution of solids and xylan of destarched corn fibre [12]. the liquid hot water pretreatment of sorghum bagasse produced higher solubilisation of hemicellulose and cellulose content enrichment [13]. combining hydrothermal treatment and enzymatic hydrolysis of sorghum bagasse resulted in improvement of cellulose and total polysaccharides hydrolysis [14]. steam explosion (se) is one of the most effective methods for the pre-treatment of lignocellulosic biomass. in this process, the biomass is heated with high-pressure steam for a certain period, than the pressure is reduced to atmospheric pressure as quickly as possible. the biomass is undergone on an explosive decompression by this swift reduction of pressure [6,7]. the high efficiency of the steam explosion treatment is due to the thermo-mechano-chemical destruction applied in the method. steam-explosion has been used to treat various kinds of lignocellulosic biomass (i.e. softwood, sugarcane bagasse, corn stalk) for enhanced bioethanol and biogas production [15–19]. sipos et al. [20] demonstrated the efficient effect of pre-treatment by steam on sorghum bagasse characterized by high degree of cellulose hydrolysis. zhang et al. [21] compared four pre-treatment processes including liquids, steam explosion, lime and dilute acid for enzymatic hydrolysis of sorghum bagasse and pointed out that steam-explosion showed the greatest improvement on enzymatic hydrolysis. the biogas yields of anaerobic digestion can be also increased by ultrasonic treatments (ut) to support the solubilisation of raw materials. during the ultrasonic treatment, a cyclic sound pressure is used to disintegrate the cell walls by cavitation. the parameters of the sonication are the power, frequency and time of sonication [3,22]. zhang et al. [23] showed that ultrasonic pre-treatments caused indistinctive effects on bio-hydrogen production. the ultrasonic treatment accelerated the enzymatic hydrolysis of corn stover and sugar cane bagasse cellulose [24] and improved the liquefaction and saccharification of sorghum flour [25]. imam et al. [26] pointed out the positive effects of ultrasonic plus hot water pre-treatment on the conversion of sweet sorghum to hexose and pentose sugars and on lignin, cellulose and hemicellulose concentrations. however, no systematic studies on pre-treatments of grain sorghum stover are available in literature. a correct comparison of the various pre-treatments and the selection of the suitable processes for the disintegration of grain sorghum stover as feedstock for enhanced biogas production are the goals and the novelty of this paper. however, the main message of this work is that a perfect testing is only possible, if there are no differences in the microbial communities in different biogas fermenters, in the inocula used, in the substrates cultivated and in the methods applied to assess pretreatments: chemical analysis, batch tests or continuous ad. therefore this work is focused on liquid hotcompressed water, steam explosion and ultrasonic pretreatments of grain sorghum stover using both fast analytical, biochemical and biomethane potential ad tests to study and comparison the effects of pretreatments on anaerobic digestion without addition of chemicals. the influence of temperature, contact time of thermal treatments, and the effect of sonication energy on decomposition of lignocellulose on a chemical level were determined using laboratory scale experimental techniques. the effectiveness of thermal and ultrasonic treatments was evaluated by scod and bod5 concentrations and by the biogas and methane productivities during mesophilic fermentations. experimental materials sorghum stover investigated in this work consists of leaves and stalks of commercial grain sorghum (milo) hybrid named mexican sweet (code: hf1) harvested from the b12 field at kétegyháza, hungary, and used for pre-treatments and biogas production experiments. this easily grown hybrid with mid-early maturation was developed by j. feczák (agroszemek ltd., szeged, hungary). post-harvest residue grain sorghum stover samples were chopped, homogenized, and analysed for dry substance (ds, 93.6%), organic dry substance (94.5%), and ash (5.5%). deionized water was used in all experiments after cation and anion exchange. liquid hot-compressed water treatments the lhcw pre-treatments were carried out in a 2 l capacity parr 4843 type high-pressure reactor at the temperatures of 100, 150 and 175 °c (0.1, 0.5 and 0.9 mpa, respectively) and at various treating time from 10 to 120 minutes. 25 g of grain sorghum stover were used in each experiment and were added to 1000 g of water. the suspension was introduced in the thermal reactor at room temperature and heated to the set temperature. the pulp slurry was mixed by a built-in stirrer at 300 rpm during the entire treating process to avoid temperature gradients. after treatment, the reactor was cooled down to 30 °c by the built-in cooling system of the reactor using cold water-flow and the treated slurry was removed from the vessel. steam explosion pre-treatments se treatments were performed in a steam explosion laboratory unit (fig.2) consisted of a steam generator (2), a digester vessel (6) and a separator cyclone (8). a 2 l capacity parr 4843 reactor was used for the production of steam with temperatures of 185, 200, and 215 °c and working pressures of 1.1 mpa, 1.6 mpa, and 2.1 mpa, respectively. the se unit operated in batches and equipped with a digester vessel (6) of 200 cm3 volume. the digester vessel was filled with 10 g 45 feedstock per batch and was heated to the desired temperature, directly with saturated steam led to the vessel, by opening the steam inlet valve (5). no catalysts (additional chemicals) were applied in the process. after the steaming time (1–10 minutes), the expansion valve (7) was opened to rapidly reduce the vessel pressure to the atmospheric one. the steamed sample slurry explosively released into the separator cyclone (8). ultrasonic treatments the ultrasonication was performed in a vibracell vcx 750 (sonics & materials, usa) ultrasonic processor operated at constant sonication frequency of 20 khz with maximum power input of 750 w. the radiation was carried out by a 25.4 mm diameter titan alloy (ti6al-4v) probe with removable tip and maximum amplitude of 35 µm. samples of the mixture of grain sorghum stover (1 g) and water (99 g) placed in a temperature-controlled vessel. they were subjected to ultrasonic pre-treatment without additional agitation at different power inputs by adjustment of the amplitude (50, 70 and 100%) and at various sonication durations of from 1 to 10 minutes for each power level. the temperature of the vessel was held constant at 25 °c during the treatment by a high-precision thermoregulator (huber kältemaschinenbau gmbh, germany). aliquot parts of the resulting sorghum stover pulp slurries of samples obtained from pre-treatments were used as substrate in ad test. the rests were filtered to separate the solid fraction from the liquid fraction for analytical measurements (scod, bod5, ph). a set of untreated, blank samples was also tested for chemical analysis and methane potential by ad as the control points of reference for the treated samples. mesophilic anaerobic digestions the anaerobic degradability of untreated, lhcw, se, and ut pre-treated grain sorghum stover slurries was determined in laboratory scale, using a fermenter system contained 12 pyrex batch reactors of 1 l capacities. inoculum for the ad tests was taken from the effluent line of an anaerobic pilot fermenter [27] treating a mixture of swine manure and corn stillage (spent mash remaining after bioethanol distillation) at biogas test facility of denk ltd (kövegyűrpuszta, hungary). the batch reactors were inoculated by 700 g inocula. afterwards a batch of 100 g of grain sorghum stover pulp slurry samples was added under nitrogen atmosphere. furthermore, the digester materials were bubbled with nitrogen gas for 10 minutes to get rid of the air from the liquid phase before each experiment. the batch reactors were kept in a temperaturecontrolled water bath at 37 °c until they stopped producing biogas. the mesophilic ad tests performed for grain sorghum stover substrates including controls were all done in duplicate. during the 36–40 days mesophilic ad tests the flows of the produced biogas were on-line measured by digital flow meters and the daily and cumulated biogas volumes were stored digitally. the methane content was determined by gas chromatography. analytical and biochemical measurements the scod, ph, and bod5 measurements were carried out on the liquid fractions after 10 min centrifugation at 14,000 rpm and 20 °c with a refrigerated universal high-speed, filtration (0.45 µm) centrifuge (unicen mr, herolab, germany). colorimetric scod concentration was measured by the standard methods procedure [28] using a nanocolor vario compact heating block (macherey-nagel, germany) and a multidirect photometer (tintometer/lovibond, germany) according to din iso 15705. biochemical oxygen demand (bod5) was determined according to en 1899-1 and en 1899-2 by using oxitop control 6 oc 100 (wtw, germany) system. the ph values were measured by a c831 type ph meter (consort, belgium) with an ra-0903p sensor (radelkis, hungary) after two-point ph calibration (ph = 4.01 ± 0.01 and ph = 7.00 ± 0.01) using duracal ph buffers (hamilton, switzerland). the surfaces of the grain sorghum stalk were investigated by a philips xl30esem environmental scanning electron microscope (esem) with 20 kv accelerating voltage and resolution of 3.5 nm, in secondary electron image mode (sei), and backscattered electron image mode (bei). results and discussion liquid hot-compressed water treatments the influence of lhcw pre-treatments at various temperatures and treating times on scod concentration of grain sorghum stover slurry is visualized by 3d mesh segmentation on fig.3. the results of lhcw pre-treatments show that hotcompressed water has a positive effect in grain sorghum stover disintegration, leading to significant increments in scod concentration: +262% at 100 °c, +419% at figure 2: scheme of the steam explosion apparatus (1. input valve, 2. steam generator, parr 4843 reactor, 3. pressure gauge, 4. evacuation valve, 5. steam inlet valve, 6. digester vessel, 7. expansion valve, 8. cyclone, 9. sampling valve, 10. steam outlet valve) 46 150 °c and + 698% at 175 °c with an operating time of 60 min, respectively. the control experiments were performed using untreated grain sorghum stover suspension. both temperature and time have positive, but not linear effects on scod and not to the same degree. the temperature raising has more effect on the solubilisation of grain sorghum stover after 60 minutes than the treating time in agreement with the results of valo et al. [29] who found that treating time had less influence than temperature during thermal treatment of sludge. it is notable that higher solvolysis temperatures resulted in more acidic products as reflected by the low ph level of the grain sorghum stover slurry (fig.4). steam explosion pre-treatments the pressures and temperatures of se pre-treatments had significant effect on digestibility of grain sorghum stover. elevated pressures and temperatures resulted in enhanced solubilisation (fig.5). the positive pressure effect may be explained by the increased disintegration caused by higher-pressure drop at the end of treatment. compounds that are more soluble were released from the grain sorghum stover during the steam explosion and made the resulting slurry available to subsequent bacterial degradation. the pressure effect is quasi-linear and the effect of contact time can be modelled by an exponential-tomaximum function. compared to the untreated grain sorghum stover, the scod concentrations of the slurries increased by a factor of 8.9, 9.6, 10 at 185, 200, and 215 °c, respectively, with an operating time of 3 min, respectively. additional, the ph value decreased with pre-treatment pressure (steam temperature) and with the contact time (fig.6). the formation of acidic degradation products during disintegration of grain sorghum stover slurry by steam explosion agree well with the observation of guo et al. [30] at corn stalk steam explosion. ultrasonic treatments the efficiency of ultrasonic irradiation of grain sorghum stover was quantified by scod concentration of the slurry as a function of contact time and power input in terms of ultrasonic amplitude level (%) and specific sonication energy. results of ultrasonic treatments are shown in fig.7, where the values of the scod figure 4: acidity of grain sorghum stover slurries as the function of lhcw contact time and temperature (!: experimental data point) figure 3: effects of temperatures and contact times of lhcw pre-treatments on scod concentration of grain sorghum stover suspension (!: experimental data points) figure 5: effects of steam pressures on scod concentration levels of grain sorghum stover slurries as the function of the contact time during steam explosion (!: experimental data points) figure 6: the effect of steam explosion on ph values of treated grain sorghum stover slurry at various steam pressures as the function of the treatment time (!: experimental data points) 47 concentrations are presented for each value of the ultrasonic amplitude level (%), and sonication time. the scod of the pulps increased with the ultrasonic power demonstrating the effectiveness of the cavitation energy to disrupt the cell walls of the plant parts. the scod concentration excess reached +105%, +109%, and +133% at 50%, 70%, and 100% amplitude level, respectively, with a contact time of 3 min. the ultrasonic power and the pre-treatment time affect the scod to a different degree. the raising of scod values by treating time is stabilized after 3 minutes. these can be described by an exponential-tomaximum function. the effect of energy-input on scod is quasi-linear (r2 = 0.942) as demonstrated by the data shown in fig.8, where scod values are plotted against the specific sonication energy. the scod concentrations were increased by the sonication energy; however, no power-saturation phenomenon was observed. the sonication energy over the minimal energy of 1kj g-1 ds is the most effective for breaking up cells [31]. the ph values of the sonicated grain sorghum stover slurries decreased monotonously with pre-treatment time and sonication power on a small scale (fig.9) suggesting that local temperature effects caused by cavitation bubbles were not enough to accelerate the hydrolytic processes resulted in acidic degradation product. environmental scanning electron microscopy the esem pictures of the surfaces on untreated and by ultrasonic treated grain sorghum stalks are shown in fig.10 at 100× magnification. the surface of the treated sorghum stalk was altered (fig.10b) from the appearance of defective plant tissues. fig.10b shows a heterogeneous appearance compared to the homogeneous surface of the untreated stalk (fig.10a). the comparison of the pre-treatment results of the chemical analysis, the scod concentration, and ph changes of grain sorghum stover slurries suggested that the most effective disintegration method is the steam explosion to disrupt the lignocellulosic structure of grain sorghum stover and partial hydrolysis of it molecular components. however, results of these fast methods can only indicate how much structures of lignocellulosic materials broke down on a chemical level. nevertheless, greater decomposition of the lignocellulose structures does not necessarily prove enhanced biogas production, because inhibitors for methanogenesis reactions can also be produced through hydrolytic processes during steam explosion. furthermore, one has to take into account the high energy needs of treatments at elevated temperatures. according to the results of fast chemical analyses (scod and ph), the optimal conditions for the lhcw, steam explosion and ultrasonic treatment of grain sorghum stover were established as 150 °c / 30 min, 200 °c / 3 min and 100% ultrasound amplitude / 3 min (at 25 °c), respectively. however, to study the real effect of optimal conditions of the investigated pre figure 8: scod change in grain sorghum stover slurry as a function of specific sonication energy (!: experimental data points) figure 7: the effect of sonication energy on scod concentration level of grain sorghum stover slurry as the function of sonication time and relative ultrasound amplitude (!: experimental data points) figure 9: the effect of sonication power on the ph values of grain sorghum stover slurries as the function of the sonication time (!: experimental data points) figure 10: esem pictures of the surface on untreated (a) and by ultrasonic treated (b) grain sorghum stalks at 100× magnification 48 treatments additional biochemical tests like bod and biomethane potential determinations are necessary. biochemical oxygen demand a comparison of the biochemical oxygen demands of filtrates of grain sorghum stover slurries after pretreatments at the optimal conditions is given in fig11. the results of the bod5 tests support the observations from chemical analysis. actually, all three methods investigated are appropriate for pre-treatment of grain sorghum stover, because the bod5 values systematically increased in filtrates of grain sorghum stover slurries with the treatment time under the conditions investigated. however, the highest bod5 values were obtained in filtrates after steam explosion, therefore the steam explosion seems to be the most effective disintegration method to disrupt the lignocellulosic structure of grain sorghum stover and to partially hydrolyse its molecular species, resulting in the formation of bacterially digestible substrate. biogas production by mesophilic anaerobic digestions biogas and biomethane production tests were carried out using grain sorghum stover slurries pre-treated under stated optimal conditions (lhcw: 150 °c / 30 min, steam explosion: 200 °c / 3 min, and ultrasonic treatment: 100% ultrasound amplitude / 3 min at 25 °c). daily as well as the final biogas and methane production (normalized volumes at 0 °c and 101.15 kpa) were determined. the results are shown as a function of the digestion time in figs.12 and 13. the specific gas productions were calculated by dividing the cumulated gas amount with the total ds of the substrates. as reference, the untreated material was used in the same amount. in agreement with the results of chemical analytical and biochemical tests after pretreatments, the specific total biogas and methane yields obtained for treated grain sorghum stover substrates were significant higher than that of the untreated control. as seen in fig.12, biogas productions began immediately, without a lag period after starting the degradation of grain sorghum stover. the fastest biogas production at the beginning was detected at the ultrasonicated substrate. however, the highest biogas production was observed during the fermentation of steam-exploded substrate. the biogas production proceeded in constant and high daily biogas production for treated substrates until the 30th day of hydraulic retention time. this observation is notable, because the application of pre-treatments can decrease the usual cycle time for biogas fermentation and increase the production of biogas with higher methane content. the comparison of the biomethane yields is given in fig.13. methane production, as the major result of anaerobic digestion of pre-treated grain sorghum stover, was markedly increased by the three pre-treatments. the highest biomethane production rate was observed at the substrates after ultrasonic and steam explosion pretreatments. the biomethane production rate of lhcw figure 11: comparison of the bod5 test of filtrates of grain sorghum stover slurries after various pre-treatment methods figure 12: specific cumulative biogas yield (ncm3/g ds) of grain sorghum stover substrates after pre-treatments figure 13: specific cumulative methane yield (ncm3 g-1 ds) of grain sorghum stover substrates after pre-treatments 49 treated substrate was lower, probably due to the low ph of the pre-treated grain sorghum stover slurry. our laboratory tests have shown that the steam exploded substrate possess has the highest biogas production potential (439 ncm3 g-1 ds) during hydraulic retention times of 36 days with 55% methane content. the steam explosion pre-treatment increased the biomethane yield by +72% to 242 ncm3 g-1 ds. the lhcw pre-treated substrate has the second highest biogas production potential (403 ncm3 g-1 ds) during hydraulic retention times of 36 days with 52% methane content, the lhcw pre-treatment increased the biomethane yield by 49% to 210 ncm3 g-1 ds. this yield increment is higher than that was obtained by qiao et al. [9] for various biomass wastes after hydrothermal treatment. the substrate after ultrasonic pre-treatment has a biogas production potential of 383 ncm3 g-1 ds during hydraulic retention times of 36 days with 44% methane content, the ultrasonic pre-treatment increased the biomethane yield by 18% to 167 ncm3 g-1 ds. the low biogas and methane yields of ultrasonic treated grain sorghum stover can be explained by the superficial effect of ultrasonic cavitation. conclusions the results of chemical, biochemical analyses and biogas/biomethane potential test obtained by mesophilic anaerobic digestion were presented. it was found that lhcw treatment and steam explosion are the most effective biomass pre-treatment for increasing the solubilisation of the organic matters of grain sorghum stover. laboratory testing of anaerobic digestibility of pre-treated slurries have shown that the grain sorghum stover has high biogas potential. it can serve as biogas feedstock and could reduce the energy consumption of sorghum-based bioethanol production in the future. the lhcw and steam explosion biomass pre-treatment techniques can reduce the cycle time and improve the biogas production via disintegration of the complex and compact plant structures of grain sorghum stover. acknowledgements this research was supported by támop 4.2.4. a/2-111-2012-0001 „national excellence program – elaborating and operating an inland student and researcher personal support system”. the project was subsidized by the european union and co-financed by the european social fund. authors also gratefully acknowledge the support of the hungarian state and european union under the támop-4.2.2.a11/1/konv-2012-0071 project. references [1] saldivar s.r.o.s., carrillo e.p., alvarez m.m.: method for obtaining bioethanol from sorghum grain (sorghum bicolor l.moench) comprising steps involving decortication and hydrolysis with proteases. patent application number: us 20110014671 a1, 2011 [2] mcmillan j.d.: 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a reaction structure identification algorithm jános kontos,1! lászló richárd tóth,2 and tamás varga2 1 department of physical chemistry, university of pannonia, egyetem st. 10, veszprém, h-8200, hungary 2 department of process engineering, university of pannonia, egyetem st. 10, veszprém, h-8200, hungary !e-mail: kontosjan@gmail.com the most important step in the design procedure of a chemical reactor is the understanding the chemical reaction network (crn), which will take place in that reactor. the structure of a crn as representation of the reaction mechanism contains all the elementary reaction steps that are required to convert the reagents into products. the aim of the reaction mechanism analysis is the identification of the route how the system goes from its initial to the end state. in order to do this, a lot of knowledge is required about chemistry supplemented with some analytical measurements. in this work, we focus on the development of an algorithm, which requires a few data inputs to reveal all the reaction steps that are important in the reactor design point of view. it is trivial that the structure of a dynamic system cannot be determined without the identification of the model parameters that belong to that structure. hence, the algorithm reported here can be used to obtain the parameters of the reaction rate equations for each identified chemical reaction. first, the structure is identified followed by its parameters. in this study the processed data are obtained by a crn generator, which is applied to generate random crns based on some specified parameters to reach maximal reaction order. concentration profiles, which characterize each crn at a specific reaction rate constants combination, are obtained as a result of simulations based on the randomly generated crns. the developed algorithm for reaction mechanism identification is based on a modified type of linear least-squares method (llsm) in which the searching variables must be higher than zero, since the reaction rate constants cannot have negative values. the developed algorithm is tested in different cases to check the applicability of llsm in reaction structure identification procedure and the obtained results show that with some further improvements the proposed algorithm can be applied solving more complex identification tasks. keywords: chemical reaction network, structure identification, non-negative least-squares method, crn generator introduction one of the most important tasks during the design procedure of any chemical technology is the engineering design of the conversion subsystem and to ensure the optimal and safe operation. hence, before starting the design of a technology phenomena with impact on the dynamic behaviour of the subsystem must be identified. the most crucial part of the conversion subsystem is the chemical reactor in which we try to control the processes that was identified on the basis of laboratory experiments. in this work we proposed a method to support the identification of the individual reaction steps and their rates in a chemical reaction network (crn). numerous literature examples can be found that describe different methodologies to generate the structure of crns, as representations for reaction mechanisms [1, 2]. the reaction mechanism of a reaction system represents all the elementary reaction steps, which are required to convert the reagents into products. hence, the aim of reaction mechanism identification is the determination of the intermediate steps, which take the starting materials to the final products. trivially, it is challenging to follow and model the movements of all the molecules in a system in full detail. however, we can describe a reaction system on the basis of the cumulative effects of great number of molecules in specific states. such specific states are the formation of stable intermediates. the intermediates are chemical species produced in the elementary reaction steps. often, it is possible to detect them by experimental methods. the produced amount of these intermediates is sometimes very low and they react very fast to produce another intermediate or final product. hence, the identification of the latter components and the measurement of their concentrations can be challenging. most of the reactions take place through multiple intermediate steps. these scenarios are called multi-step reactions. in a single reaction step, the sign of stoichiometric coefficients represent that a given molecule is a reagent (-) or product (+), and the absolute value of these coefficients give how many moles are consumed/formed. the transient states of a reaction system and the intermediates can be investigated with two kinds of methods on the basis of whether a priori knowledge of reaction kinetics is available or not [3]. the foundation of the reaction mechanism analysis is the precise identification of all intermediates and their 52 concentration. with the lack of this information the stoichiometry of the reaction cannot be revealed reliably. the nature and the amount of the products can contain as much information as a well-qualified chemist requires identifying the reaction mechanism of an unknown reaction system. the proposed algorithm can support this process in case we have lack of experience in the identification of the structure of a crn and parameters of kinetic expressions, which describe the rate of the reaction steps considered in the crn. the essence of the parameter identification process is the solution of a constrained minimization problem in which the objective function can be the sum of squared error between the measured and the calculated component concentration profiles. the searching variables are the unknown parameters in the kinetic expressions (i.e. pre-exponential factor, activation energy, reaction order). the role of the structure identification is the definition of correlated variables and their mathematical formalization. in our case, the identification means the selection of reaction steps that can take place in the reactor. the identification tasks can be solved by the application of linear least-squares method (llsm) [4]. the main challenges using this method are the definition of the correct initial conditions for the applied searching algorithm and the speed up of the identification procedure. one of the most important simultaneous methods is the incremental approach, which applies a hierarchical modelling methodology to decompose the complex identification problem into simpler sub-problems [5]. the method applies target factor analysis to identify the suitable structure of the unknown crn. this method has been successfully applied in reaction mechanism identification process in a multi-phase system based on concentration and calorimetric measurements [6]. correlation metric method was developed to analyse the strength of the connections between the components in the system, which is based on the qualitative analysis of the measured data [7]. qualitative trend analysis was also applied in reaction mechanism identification algorithms to divide the entire experimental time into shorter periods in which the correlations are analysed between the concentrations of components [8]. in this work, our aim is to develop a simple, but reliable method for structure identification of crns, which need as few data as possible. in our case the input of the algorithm is only the list of components and concentration profiles, which are the result of the simulation based on randomly generated crns. these crns were generated based on user specified parameters, such as maximal reaction order. on the basis of the randomly generated crns, the concentration profiles for each crn at a specific reaction rate constants combination are determined. the algorithm developed for reaction mechanism identification is based on a modified llsm method, in which the searching variables must be higher than zero, since the reaction rate constants cannot have negative values. development of simulation methods since our aim is to develop a generally applicable algorithm to support the identification process of crns with unknown structure, we developed a crn generator, which can be applied to randomly generate crns based on some structural parameters, such as the maximum number of components or reactions in crn. there are many examples in literature for developing a crn generator that analyses the affinity of molecules taking part in reactions [9], applies mixed integer programming to build up reaction networks [10], or using group contribution method to generate the structure of the crn and the kinetic parameters of the reaction steps in that network [11]. in this work we developed a simple crn generator that randomly generates a crn from randomly generated components. in this generator, we define probabilities in situations for building different kinds of crns. for example, if we would like to have more decomposition reactions in the crn then the probability of this type of reaction is increased. the scheme of the developed crn generator can be seen in fig.1. the first step of the algorithm of the crn generator is the definition of the parameters of the desired crn, such as the probabilities of the different types of reactions. in this step the maximal number of building block types in a component and the maximal number of specific building blocks in a component are defined. figure 1: the scheme of the proposed crn generator 53 the next step is the development of the first reaction step in which we define a new component next to the components that are already in the component list. the stoichiometric coefficients of the reaction are randomly generated based on the user-defined parameters. the composition and the chemical formula of the added component are determined based on the material balance of the reaction. with the first reaction step, it is checked whether the numbers of components and reactions in the generated crn are enough. if the user defined value of these parameters are higher than the current values the crn generator starts to build a new reaction with selecting the reaction type, the components. based on the crn parameters it randomly generates stoichiometric factors for that new reaction and checks the material balance. components that are involved in more reactions have a smaller chance to be chosen for the next new reaction building iteration. if there are enough components or reactions in the generated crn, the algorithm steps to the next phase in which it randomly generates the reaction kinetic constants for reactions in the crn. in this phase, the algorithm randomly generate kinetic parameters, while maintaining the same order of magnitude of the reaction rates, to make it harder to find out the structure of the generated crn. particle swarm optimization method has been applied to solve this constrained optimization problem, where the objective function is defined as the difference of the integral of reaction rates over the time [12]. general reactor model the kinetic experiments are usually performed in a tempered flask that can be modelled as an isothermal batch reactor. all the reagents are added to the unit with or without catalyst and samples are taken from the reaction mixture in specific times. as mentioned earlier the simplest case is considered as we have only concentration measurements from a batch reactor. however, the developed algorithm can be improved and the processability of data can be widened with the application of mathematical models of other reactor types. hence, at this point of the development of the proposed algorithm, we consider that the unit in which the kinetic experiments are performed is a well-mixed, isothermal batch reactor. the model of a batch reactor should be developed first to contain component mass balance equations. applying the well-mixed assumption the component mass balances can be simplified and we obtain the equations: { } ,;...c;b;air dt dc i i == (1) where i identifies the components in the system in which we have nc components; ci is the concentration of the ith component [mol m-3]; ri is the component source of the ith component [mol m-3 s-1], which can be calculated as: ri = υ ji ⋅ rj j=1 nr ∑ , (2) where j identifies the reaction in the system; nr gives the number of reactions considered; νji is the stoichiometric coefficient of the ith component in the jth reaction; rj is the reaction rate of the jth reaction [mol m3 s-1], which is calculated with following expression: rj = k j ci n ji i= a;b;c;...{ } ∏ , (3) where nji denotes the order of ith component in jth reaction [1], kj is the reaction rate constant of the jth reaction [the unit is dependent on the order of the reaction, [mol1-n m3n-1 s-1], where n is the summarized reaction order in jth reaction: n = nji i= a;b;c;...{ } ∑ . (4) this summarized reaction order is equal to the absolute value of the stoichiometric coefficient of the ith component in the jth reaction, if the given component is a reagent in a given reaction, otherwise it is 0. the developed general reactor model has been implemented in matlab. proposed algorithm for structure identification of crn our primary aim is to develop an algorithm, which can be efficiently applied in reaction mechanism identification tasks on the basis of concentration profiles. in this phase, we considered that the concentration profiles are known for all the components in the system. it is a simplification with respect of practical problems; however, in this work we aim to evaluate if a simple method of llsm is suitable for a complex task. llsm is based on the minimization of a special model error, which is based on comparing the measured to the calculated time series. in our case, the time series are the numerical derivatives of the concentration profiles. based on the measured concentration profiles the change in concentration during two sampling steps can be calculated as a numerical derivative with respect to length of that time step. if we have nk samples, the difference in kth sample can be defined as follows: δĉ i δt k( ) = ĉ i k( )− ĉ i k −1( ) , (5) where k is the current sample; δĉ i is the difference of the measured concentration of ith component in between k and k-1 sampling steps; tδ is the time difference between k and k-1 sampling steps. if we calculate this difference for all the components and in every sampling steps we get a matrix which has k-1 rows and as many columns as many components we assume in the system. based on the calculated concentration profiles another matrix can be built with the calculated variables. in our case the sum of the 54 squared differences between these two matrices is defined as the model error, which should be minimized during the identification process: e = δĉ i δt k( )− δci δt k( ) # $ % & ' ( 2 k=1 nk ∑ i= a;b;c;...{ } ∑ , (6) where e is the calculated model error, which is basically the difference of the measured and calculated component sources defined with eq.(2); δci is the calculated changes in concentrations of ith component from eq.(1), but the steps is equal with the sample times of measurement. to make it easier to follow the process we define eq.(6) using vectors instead of sums: e = δĉ ___ − δc ___# $ % & ' ( t δĉ ___ − δc ___# $ % & ' ( , (7) where the length of vectors are nc(nk-1) (i.e. the change in concentrations of components should be calculated in every sample time except in the initial phase) and defined with the following structures: δĉ ___ = δĉa 1( ) δĉb 1( ) ! δĉa 2( ) δĉb 2( ) ! δĉa k( ) δĉb k( ) ! " # $ $ $ $ $ $ $ $ $ $ $ $ $ $ % & ' ' ' ' ' ' ' ' ' ' ' ' ' ' , δc ___ = δca 1( ) δcb 1( ) ! δca 2( ) δcb 2( ) ! δca k( ) δcb k( ) ! " # $ $ $ $ $ $ $ $ $ $ $ $ $ $ % & ' ' ' ' ' ' ' ' ' ' ' ' ' ' . (8) the task in llsm is the minimization of the model error defined in eq.(7) by manipulating the model parameters, such as the reaction rate constants of all the possible reaction steps, which are the building blocks of the unknown crns. hence, to use llsm in reaction mechanism identification process first we need to collect all the possible reaction steps, which can take place in the system based on the defined component list. to get the necessary reaction steps, we generate all the possible combination of reactions, which satisfy the material balances. a given reaction step has to be further processed, since some reaction steps can be produced from each other with linear combinations. thus, only the independent reactions should be kept in the reaction set. the resulted reaction set is represented in a matrix (i.e. in stoichiometric matrix): =υrs , ba ba ba ! ! ! " # $ $ $ % & υυ υυ !"" # # " # 22 11 2 1 (9) which has the same number of rows and columns as the number independent reactions and components are considered in the system, respectively. after the possible reaction steps have been automatically collected, all the reaction steps of the set are considered as the part of the unknown crns. based on the reaction set the mathematical model of the system is automatically generated based on eqs.(1)-(3). the unknown parameters in this model are the reaction rate constants for all reactions in the reaction set. the calculated concentration differences in eq.(7) can be obtained using eq.(10) on the basis of the general reactor model (eqs.(1-3)): ,ckc ___ υ=δ (10) where c denotes a special matrix in which a diagonal matrix is repeated from sample time to sample time and in the diagonal matrices we calculate the concentration product term in eq.(3) in every sample time. the following general matrix shows the structure of the resulting diagonal matrix in this step if we have nr reactions in the reaction set: =c ci 0( )( )n1i i= a;b;c;...{ } ∏ 0 ! 0 ci 0( )( )n2i i= a;b;c;...{ } ∏ ! " " # ci 1( )( )n1i i= a;b;c;...{ } ∏ 0 ! 0 ci 1( )( )n2i i= a;b;c;...{ } ∏ ! " " # ci k −1( )( )n1i i= a;b;c;...{ } ∏ 0 ! 0 ci k −1( )( )n2i i= a;b;c;...{ } ∏ ! " " # # $ % % % % % % % % % % % % % % % % % % % % % % % % & ' ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( (11) υ denotes a special matrix in which the stoichiometric matrix representing the reaction set (eq.(9)) is repeated as many times as the sample times minus one: =υ υrs υrs ! ! " # # # # # $ % & & & & & (12) k indicates reaction rate constant vector for all the reactions in the reaction set. by applying llsm, the structure of the unknown crn can be identified since the reaction rate constants that can be the part of the unknown crn will have different values than zero at the end of the identification process and all the other reactions in reaction set get zero value. based on eqs.(7) and (10) we can solve the minimization problem and the following expression is the result for the calculation of reaction rate constants for all reactions in the generated reaction set: 55 ___''''' ĉccck δ×## $ % && ' ( ×# $ %& ' (υ× * * + , . / ## $ % && ' ( ×# $ %& ' (υ×## $ % && ' ( ×# $ %& ' (υ= −1 (13) reactions with zero reaction rate constants indicate that they cannot be part of the unknown crn. this means that at the end of the identification process we get the reaction rate constants as well, next to the structure of the crn. results and discussion since we do not have measurements from a real system in this work the developed crn generator has been applied to randomly generate some crns. table 1 shows two reaction steps in the unknown crn. we have defined five components (a-e) in the system. a and b components are reagents in the first reaction step (r01), in which c and d components are produced. however, in the second reaction (r02) only e is consumed while 2 moles of a and 1 mole of d are produced. the last column of table 1 shows the exact values of reaction rate constants. the unit of reaction rate constants can be determined for the jth reaction based on the sum of the reaction orders of each component in that reaction: mol m3 ! " # $ % & 1− nji i= a;b;c;...{ } ∑ ! " # # $ % & & ⋅ 1 s (14) table 2 shows the five components (a-e) that are built from nine (a-j) building elements. these building elements can be imagined as atoms or groups. the numbers in the matrix represents the stoichiometric coefficients of composition. the last row shows a fictitious molecular mass of the components in the system. based on the molecular mass and the number of building elements in the components all the independent reaction steps were generated as shown in table 3. the 22 possible reaction steps can be found for the five components from table 2. the unknown reaction mechanism should be built from these reaction steps. in table 1 we saw that we need only two of these steps and as it can be seen in the last column of table 3 with the proposed algorithm we can find these two reactions of rs01 and rs16. however, the algorithm identifies a third possible reaction step, rs13, which can be the part of the unknown crn. as can be seen in the last column of table 3, the reaction rate constant corresponding to this reaction step is very low. this means rs13 should not be considered as the part of the unknown crn. after the above simple task, we tested our method in nine other cases. we defined a quantitative measure to check the correctness of the identified kinetic parameters as the mean average difference between the known and the identified reaction rate constants: mae = 1 ndr k̂l − kl l=1 ndr ∑ (15) where ndr is the number of reactions in unknown crn; l identifies the current reaction rate constant; k̂ is the reaction rate constant value what we are looking for, such as the last column in table 1 for crn01. table 4 presents the number of reaction steps in the unknown crn (ndr), the number of components (nc) in the system, the number of the possible reaction steps (nr) as a representation of the size of the reaction set, if the algorithm can find the perfect reaction steps or not, and mae values when available from eq.(15). table 1: a randomly generated crn with crn generator a b c d e k [-] r01 -1 -1 1 1 0 1.5590 r02 2 0 0 1 -1 1.0184 table 2: the generated compound matrix a b c d e a 9 0 1 8 26 b 10 0 8 2 22 c 7 1 1 7 21 d 2 10 7 5 9 e 4 12 13 3 11 f 12 0 1 11 35 g 8 0 6 2 18 h 11 5 7 9 31 j 6 1 3 4 16 m [mass mol-1] 359 195 252 302 1020 table 3: the resulted reaction step matrix with the identified reaction rate constant rs id a b c d e k [-] rs01 -1 -1 1 1 0 1.626 rs02 -3 -1 1 0 1 0 rs03 -2 0 0 -1 1 0 rs04 -2 6 3 -4 0 0 rs05 -3 5 4 -3 0 0 rs06 -4 4 5 -2 0 0 rs07 -5 3 6 -1 0 0 rs08 0 4 5 0 -2 0 rs09 -3 3 6 0 -1 0 rs10 5 -3 -6 1 0 0 rs11 3 -3 -6 0 1 0 rs12 4 -4 -5 2 0 0 rs13 0 -4 -5 0 2 0.004 rs14 3 -5 -4 3 0 0 rs15 2 -6 -3 4 0 0 rs16 0 -6 -3 3 1 0 rs17 2 0 0 1 -1 1.051 rs18 0 -2 2 3 -1 0 rs19 1 1 -1 -1 0 0 rs20 0 2 -2 -3 1 0 rs21 3 1 -1 0 -1 0 rs22 0 6 3 -3 -1 0 56 based on the results in table 4 it can be seen that the proposed algorithm has some limitations in this phase. however, if the size of the reaction set is relatively small it gives very good agreement with the desired parameters. this means that we should improve this method to make possible the analysis of more complex problems with it. if the algorithm cannot find the perfect match for the unknown crn a ratio is given which shows how many of the reaction steps are correctly identified from the unknown mechanism. conclusions the structure of a crn represents all the elementary reaction steps that are required to convert the reagents into products. hence, the aim of reaction mechanism identification is to discover the intermediate steps, which connect starting materials with the final product. the proposed algorithm can support this process even in the case, when we lack knowledge about the reaction mechanism and/or kinetic parameters. the applied structure identification method is based on linear least-square method. the measured and calculated concentration profiles are compared and the difference between these profiles is minimized during the identification process. the proposed algorithm for reaction mechanism identification was implemented in matlab. the results of initial testing showed promising results for this simple method being applicable for a complex task; however, the proposed algorithm should be improved toward processing reaction sets. the given implementation of the algorithm for batch reactor models can be easily extended to other reactor models, which enables to employ our method to realistic problems from chemical industry. acknowledgements this research was supported by the european union and the state of hungary, co-financed by the european social fund in the framework of támop 4.2.4.a/2-111-2012-0001 ‘national excellence program’. references [1] delvin s.: organic reaction mechanism, sarup & sons, new delhi, 2002 [2] grossman r.b.: the art of writing reasonable organic reaction mechanisms, springer, new york, 2003 [3] friess s.l., lewis e.s.: investigation of rates and mechanisms of reactions, john wiley & sons, new york, 1963 [4] walter e.: identification of parametric models from experimental data, springer-verlag, berlin 1997 [5] bendel m.l., bonvin d., marquardt w.: incremental identification of kinetic models for homogeneous reaction systems, chem. eng. sci., 2006, 61, 5404–5420 [6] srinivasan s., billeter j., bonvin d.: extentbased incremental identification of reaction systems using concentration and calorimetric measurements, chem. eng. j., 2012, 207–208, 785–793 [7] samoilov m., arkin a., ross j.: on the deduction of chemical reaction pathways from measurements of time series of concentrations, chaos, 2001, 11, 108–114 [8] varga t.: qualitative analysis based reaction mechanism identification, chem. eng. trans., 2013, 35, 769–774 [9] ratkiewicz a., truong t.n.: application of chemical graph theory for automated mechanism generation, j. chem. inf. comput. sci., 2003, 43, 36–44 [10] first e.l., gounaris c.e., flouda c.a.s: stereochemically consistent reaction mapping and identification of multiple reaction mechanisms through integer linear optimization, j. chem. inf. model, 2012, 52, 84–92 [11] west r.h., allen j.w., green w.h.: automatic reaction mechanism generation with group additive kinetics, cheminform., 2012, 43, 36–258 [12] kennedy j., eberhart r.: particle swarm optimization in neural networks, proc. ieee international conference on neural networks, perth, australia, 1995, 4, 1942–1948 table 4: testing the developed algorithm in case of 10 crns crn id ndr nc nr match mae [-] crn01 2 5 22 y 0.0498 crn02 3 5 40 n (1/3) crn03 3 5 11 y 0.0983 crn04 2 5 17 y 0.0268 crn05 4 5 26 y 0.1197 crn06 2 5 13 y 0.0146 crn07 3 5 10 y 0.0216 crn08 4 5 119 n (0/4) crn09 3 5 85 n (0/3) crn10 4 5 19 y 0.0748 hungarian journal of industry and chemistry veszprém vol. 42(2) pp. 57–64 (2014) a comparison of advanced non-linear state estimation techniques for ground vehicles györgy max! and béla lantos 1 department of control engineering and informatics, budapest university of technology and economics, magyar tudósok körútja 2, budapest, 1117, hungary !email: max@iit.bme.hu this paper presents a comparative examination of state-of-the-art non-linear state estimation techniques. first, the sigmapoint (spkf) stochastic estimators are investigated on the basis of the unscented transformation. this is followed by the technique of non-linear symmetry-preserving observers for non-linear dynamics on the basis of symmetrical lie groups. the variety of the deterministic and stochastic state estimation algorithms is studied the kinematics of ground vehicles. two cases are described that deal with the reliability of path tracking, the convergence and speed of off-line calibration. keywords: state estimation, invariant observers, unscented kalman filter, vehicle kinematics introduction vehicles are indispensable in modern society, and vehicle safety is consequently of importance in everyday life. a lack of information about the state of vehicle and parameters presents a major obstacle for the development of vehicle control systems. the effectiveness of vehicle stability control largely depends on the accuracy of the vehicle state parameters that are measured by appropriate sensors. unfortunately, measurements from these sensors contain bias, as well as electrical noise, and can drift with temperature changes. however, the state estimation method is also able to dramatically reduce errors introduced by measurement and process noise contained in the signal. the focus of this work is the non-linear state estimation techniques. firstly, the ‘sigma-point kalman filter family’ (spkf) is discussed on the basis of the ‘unscented transformation’ (ut) and sterling’s interpolation [3, 5, 6]. secondly, the symmetry-preserving observer is presented [15, 16, 18], which is based on lie-transformation of invariant frames. the various state estimation procedures are then examined and compared through an illustrative nonlinear example of vehicle kinematics. sigma-point kalman filters sigma-point kalman filter [2, 4, 7] is a collective name for derivativeless kalman filters that employs the deterministic sampling based sigma-point approach to calculate the optimal terms of the state estimation. common methods use the scaled unscented transformation [4] and sterling’s polynomial interpolation. the former replaces the original set of sigma-points with a transformed set in order to minimize the errors of higher order terms, the latter approximates the derivation of the divided difference filter [10, 11] and central difference filter in [12]. the scaled unscented transformation the scaled unscented transformation (sut) has two steps. first, a fixed number of sigma points is chosen to capture the desired moments (at least mean and covariance) of the original distribution. then the sigma points are propagated through the non-linear function and the moments of the transformed variables are estimated. the advantage of sut over the taylor series based approximation is that sut is better at capturing the higher order moments caused by the non-linear transformation, as discussed in [1, 8-10]. consider a non-linear function y = g(x) and assume x has mean x and covariance xp . the first two moments of y are calculated by the following two steps: 1) weighted sigma-point selection: x0 = x xi = x + (l +λ)px( )i=1…l xi = x − (l +λ)px( )i=l+1…2l (1) with weights w0 m = λ l+λ w0 c = λ l+λ + (1−α2 +β ) wi m = wi c = λ 2(l+λ ) (2) 58 where wi m, and wi c are associated with the ith sigmapoint such that 1 2 0 =∑ = l i iw . symbols λ, α, and β denote scaling parameters and ( ) ixpl )( λ+ is the ith column of the matrix square root of the weighted xpl )( λ+ covariance matrix. 2) propagation: )( ii xgy = y ≈ wi myi i=0 2l ∑ py ≈ wi c(yi − y )(yi − y )t i=0 2l ∑ pxy ≈ wi c(xi − x )(yi − y )t i=0 2l ∑ (3) where y , yp , and xyp are the approximated mean, covariance and cross-covariance respectively. the unscented kalman filter (ukf) the algorithm of the ukf according to refs. [3, 7, 8] consists of the following steps: 1) initialization: x̂0 = e x0[ ] , px0 = e (x0 − x0 )(x0 − x0 ) t" # $ % (4) x̂0 a = e x̂0 a! " # $= x̂0 t v0 t n0 t! "% # $& t (5) p0 a = px0 0 0 0 rv 0 0 0 rn ! " # # # # $ % & & & & (6) 2) state estimation for ∞= …1k : a) calculate sigma-points: xk−1 a = x̂k−1 a x̂k−1 a +γ pk−1 a x̂k−1 a −γ pk−1 a" # $ % & ' (7) b) time-update: xi,k|k−1 x = f (xi,k−1 x ,xk−1 v ,uk−1), i = 0,…, 2l x̂k − = wi mxi,k|k−1 x i=0 2l ∑ pxk − = wi c(xi,k|k−1 x − x̂k −)(xi,k|k−1 x − x̂k −)t i=0 2l ∑ (8) c) measurement-update: yi,k|k−1 = h(xi,k|k−1 x ,xk−1 n ), i = 0,…, 2l ŷk − = wi myi,k|k−1 i=0 2l ∑ pŷk = wi c(yi,k|k−1 − ŷk −)(yi,k|k−1 − ŷk −)t i=0 2l ∑ pxkyk = wi c(xi,k|k−1 x − x̂k −)(yi,k|k−1 − ŷk −) i=0 2l ∑ (9) kk = pxkyk pŷk −1 x̂k = x̂k − +kk (yk − ŷk −) pxk = pxk − −kkpŷkkk t (10) where xk a = xk t vk t nk t! "# $ %& t and xk a = (xk x )t (xk v )t (xk n )t! "# $ %& t are the l dimension vectors of the augmented states and sigma-points respectively, vr and nr are the covariances of the process and measurement noise respectively, λγ += l , λ = α2(l+κ)+l, α = 10-3, κ = 0, β = 2, and wi is the weighting parameter defined in eq.(2). the central-difference kalman filter this approach is based on sterling’s polynomial interpolation, which was used in the derivations of divided difference filter [10, 11] and central difference filter in ref. [12]. the result of this approximation can be used for sigma-point approach as in the case of sut. the algorithm consists of the following steps: 1) weighted sigma-point selection: x0 = x xi = x + h px( )i=1…l xi = x − h px( )i=l+1…2l (11) with weights w0 m = h2−l h2 , wi m = 1 2h2 , wi c1 = 1 4h2 , wi c2 = h2−1 4h2 , (12) where wi m, and wi c are associated with i = 1, …, 2l sigma-point. 2) initialization: the same as defined in eqs.(4-6) 3) state estimation for k = 1, …, ∞: a) sigma-points for time-update: x̂k−1 av = x̂k−1 v" # $ % , pk−1 av = pxk−1 0 0 rv " # $ $ % & ' ' (13) xk−1 av = x̂k−1 av x̂k−1 av + h pk−1 av x̂k−1 av − h pk−1 av " # $ % & ' (14) b) time-update: xi,k|k−1 x = f (xi,k−1 x ,xk−1 v ,uk−1), i = 0,…, 2l x̂k − = wi mxi,k|k−1 x i=0 2l ∑ pxk − = wi c1 (xi,k|k−1 x − xl+i,k|k−1 x )2 + i=1 l ∑ wi c2 (xi,k|k−1 x + xl+i,k|k−1 x − 2x0,k|k−1 x )2 i=1 l ∑ (15) 59 c) sigma-points for measurement-update: x̂k−1 an = x̂k − n" #$ % &' , pk|k−1 an = pxk − 0 0 rn " # $ $ % & ' ' (16) xk|k−1 an = x̂k|k−1 an x̂k|k−1 an + h pk|k−1 an x̂k|k−1 an − h pk|k−1 an " # $ % & ' (17) d) measurement-update: yi,k|k−1 = h(xi,k|k−1 x ,xk|k−1 n ), i = 0,…, 2l ŷk − = wi myi,k|k−1 i=0 2l ∑ pŷk = wi c1 (yi,k|k−1 −yl+i,k|k−1)2 i=0 2l ∑ + wi c2 (yi,k|k−1 +yl+i,k|k−1 − 2y0,k|k−1)2 i=0 2l ∑ pxkyk = w1 c1pxk − (y1:l,k|k−1 −yl+1:2l,k|k−1)t kk = pxkyk pŷk −1 x̂k = x̂k − +kk (yk − ŷk −) pxk = pxk − −kkpŷkkk t (18) symmetry-preserving observers among many problems in control theory, the symmetric nature of the system can be utilized, such as in the case of optimal control for feedback or regulations. the symmetry properties can also be used in the design of observers. symmetry-preserving observers are also known as invariant observers that are based on the differential geometric background of abstract liegroups [15, 16, 18]. the constructive algorithm can be defined for designing invariant observers, which is based on the group transformation of symmetry. the aim is to produce invariant frames and invariant output errors to transform a locally asymptotically convergent observer around an equilibrium point into an invariant one, retaining its first-order approximation. the method in refs. [16, 18] benefits from the fact that the error equations and the first-order approximation can be calculated explicitly and the relationships can be defined globally. in addition, the invariant error equations make stability issues easier to deal with [1921]. assumptions suppose g is a lie-group with identity e on manifold σ. the group transformation (ϕg )g∈g on σ is a smooth mapping (g,ξ )∈g ×σ→ϕg(ξ )∈ σ (19) such that ϕe(ξ ) = ξ and ϕg2 (ϕg1 (ξ )) =ϕg2g1 (ξ ) for ζ, g1, and g2. the transformation group is local if ϕg(ξ ) is defined only when g lies sufficiently near to e. we consider only local transformations. invariant observers are designed for the smooth nonlinear system d dt x = f (x,u) , y = h(x,u) (20) where x, u, and y belong to the open subsets x ⊂ ℝn, ⊂u ℝm, and ⊂y ℝp respectively and p ≤ n . let r ≤ n be the dimension of the lie-group. we assume that for each x the mapping x→φg(x) is full rank. time functions u(t) and y(t) are known. invariant pre-observer for the differential geometric description of the symmetric observers [14], the following definitions and theorems should be introduced: definition 1. the group of local transformation on manifold ux× is expressed by (x,u) = (φg(x),ψg(u)) (21) where φg(x),ψg(u) is local diffeomorphism and g ∈g definition 2. system d dt x = f (x,u) is g-invariant, if f (φg(x),ψg(u)) = dφg(x) ⋅ f (x,u) for g, x, u. thus, the system remains unchanged for the local transformation, !x = f (x,u) . definition 3. the output y = h(x,u) is g-equivariant, if there exists ρg transformation on y, such that g ∈g and h(φg(x),ψg(u)) = ρg(h(x,u)) for g, x, u. thus, the output remains unchanged for the local transformation, y = h(x,u) . definition 4. the vector field w is g-invariant on manifold x, if d dt x = w(x) is invariant to the transformation, i.e. w(φg(x)) = dφg(x) ⋅w(x) for g, x. definition 5. an invariant frame (w1, w2, …, w3) consists of n linearly point-wise independent ginvariant vector fields on x thus (w1(x),w2(x),…,wn (x)) is a basis of the tangent space tx(x) . lemma 1. the invariant frame can be constructed from the canonical basis of x. the vector field defined by wi(x) = (dφγ (x) ) −1 ⋅ ∂∂xi (22) for i = 1, …, n forms an invariant frame. definition 6. the system d dt x̂ = f(x̂,u, y) is a preobserver, if f(x,u,h(x,u)) = f (x,u) is satisfied for x and u. furthermore, if lim x̂(t) = x(t) as t→∞ , then the pre-observer is asymptotic. 60 definition 7. the pre-observer is g-invariant, if ),,ˆ()ˆ())(),(),ˆ(( yuxfxdyuxf gggg ⋅= ϕρψϕ (23) is satisfied for g, x̂ , u, and y i.e. the observer remains unchanged for the group transformation on yu,,x . thus, x = φg(x) , u =ψg(u) , y = ρg(y) , and d dt x̂ = f(x̂,u,y ) . an invariant observer is an asymptotic g-invariant pre-observer. moreover, if the pre-observer is ginvariant and rank (f) = dim y , then the output map y is g-equivariant. definition 8. smooth map (x̂,u, y)→ e(x̂,u, y)∈ ℝp is an invariant output error if a) y→ e(x̂,u, y) is invertible for x̂ , u, and y b) e(x̂,u,h(x̂,u)) = 0 for x̂ and u c) e(φg(x̂),ψg(u),ρg(y)) = e(x̂,u, y) for x̂ , u, and y. the first two properties mean e is an output error, the third expresses the invariance. the introduction of the invariant error is necessary, because the output error ŷ− y does not usually preserve the geometry of the system [21]. the following three theorems [15, 16] support the construction of the symmetry-preserving observers. theorem 1. the observer d dt x̂ = f(x̂,u, y) is a ginvariant pre-observer for the g-invariant non-linear eq.(20) with a g-equivariant output if and only if f(x̂,u, y) = f (x̂,u)+ li(i(x̂,u),e(x,u, y)) i=1 n ∑ wi(x̂) (24) where e is an invariant output error, (x̂,u)→ i(x̂,u)∈ ℝn+m&r is a full rank function, li is a smooth function, such that li(i(x̂,u), 0) = 0 and (w1,w2,…,wn ) is an invariant frame. since li(i,e) = li(i,e)e li(i,e)wi i=1 n ∑ = wi(li(i,e) i=1 n ∑ e) = w1 … wn( ) l1(i,e) ! ln (i,e) " # $ $ $ $ % & ' ' ' ' e (25) the observer can be written as follows f(x̂,u, y) = f (x̂,u)+w (x̂)l(i(x̂,u),e(x̂,u, y))e(x̂,u, y). (26) theorem 2. the following statements are valid: • (x̂,u, y)→ e(x̂,u, y) invariant output error exists, • there is a (x̂,u)→ i(x̂,u)∈ℝn+m&r invariant function, • every other invariant output error has the form of !e(x̂,u, y) = l(i(x̂,u),e(x̂,u, y)) (27) where l is a smooth function such that l(i, 0) = 0 and e →l(i,e) is invertible. theorem 3. consider the equilibrium of a non-linear system f (x,u ) = 0 and y = h(x,u ) assume that the linearized system a,b,c,d around this equilibrium is observable, where a = ∂f ∂x (x,u ) , b = ∂f ∂u (x,u ) ,c = ∂h ∂x (x,u ) , a = ∂h ∂u (x,u ) and let l be such that a+ lc is a stable matrix. from the locally asymptotically convergent observer d dt x̂ = f (x̂,u)+ l(ŷ− y) , ŷ = h(x̂,u) (28) an invariant observer can be constructed by the same linear approximation d dt x̂ = f (x̂,u)+w (x̂)l(i(x̂,u),e(x̂,u, y))e(x̂,u, y) (29) where l = −w (x)−1lv−1 and v = ∂e ∂y(x,u,y ) is an invertible matrix of pp× dimensions. there is no general algorithm for designing the li gain functions of theorem 1. however, if we consider the following invariant state error η(x, x̂) = φγ (x)(x̂)−φγ (x)(x) (30) instead of the xx −ˆ state error, where )(xγ is the solution of φg a (x) = c (31) with respect to g, then the invariant error will only depend on the i(x,u) trajectories. constructive algorithm consider an invariant system, i.e. unchanged by transformation eq.(21) with an equivariant output (definition 3). the non-linear observer design for nonlinear dynamic systems [10, 11] can be divided into the following steps: a) choose a g lie-group and a group transformation taking into account the symmetrical properties of the system. b) solve the normalization eq.(31). build an invariant error e and the complete set of scalar invariants i. c) construct the invariant frame eq.(22). d) determine the pre-observer eq.(25). e) linearize the system f (x,u ) = 0 around the equilibrium and obtain a,b,c,d matrices. check the observability and design an invariant observer from the chosen linear observer by using theorem 3. choose an appropriate l . f) choose the parameters of the linearized error equations, based on the invariant state-errors η, such that the invariant system will be asymptotically stable. 61 then the non-linear symmetry-preserving observer is asymptotically stable, and converges locally and exponentially along all system trajectories. case study: a non-holonomic vehicle in this section, the previously introduced state estimation procedures are employed for an example of a non-holonomic vehicle tracking control. the wellknown model in the robotics of the simplified vehicle kinematics is considered. the tracking is maintained by satisfying the kinematic constraints with the appropriate choice of reference signals. kinematic model the simplified kinematic model of the vehicle can be written in the following form !x !y !θ ! " # # # $ % & & & = ucosθ usinθ uv ! " # # # $ % & & & , h(x, y,θ ) = (x, y) (32) where u is the velocity, v is the curvature, i.e. a function of the steering angle and h is the measured output. all signals contain additive gaussian noise. the model assumes that the contact point of the wheel and the ground does not slip. notice, that the linearized system is not observable. tracking for path tracking the control signals are set to satisfy the kinematic constraints, thus u and v are calculated as follows: u(t) = !xr 2(t)+ !yr 2(t) and v(t) = !!yr (t) !xr (t)− !xr (t)!!yr (t) u3(t) (33) where xr(t) and yr(t) are time functions of the reference signal. the initial conditions for tracking control is θr (0) = tan −1 !yr (0) !xr (0) " # $ % & ' . (34) hence, the reference signals for the vehicle velocity and steering function can be calculated. in the simulations, sinusoidal path tracking is implemented using the reference signals xr (t) = t, and yr (t) = asin(ωt). invariant observer design group transformation eq.(32) is independent of the origin and of the orientation of the frame chosen, i.e. it is invariant with regards to the group of rotations and translations. we chose the lie-group g = se(2) and defined the group transformation as follows: φ(xg,yg,θg )(x, y,θ ) = xg yg θg ! " # # # # $ % & & & & ⋅ x y θ ! " # # # $ % & & & = = x cosθg − ysinθg + xg xsinθg + ycosθg + yg θ +θg ! " # # # # $ % & & & & (35) ψ(xg,yg,θg )(u,v) = u v ! " # $ % & ρ(xg,yg,θg )(x, y) = x cosθg − ysinθg + xg xsinθg + ycosθg + yg ! " # # $ % & & one can check that eq.(32) is invariant to the transformations ϕ, and ψ in terms of definition 1 and the output is equivariant to transformation ρ in terms of definition 3. invariant output errors the normalization eq.(31) for :0=c 0 = x cosθγ − ysinθγ + xγ 0 = xsinθγ + ycosθγ + yγ 0 =θ +θγ (36) the solution of eq.(36), the scalar invariants and output errors can be written as follows respectively xγ yγ θγ ! " # # # # $ % & & & & = x y θ ! " # # # $ % & & & −1 = −x cosθ − ysinθ xsinθ − ycosθ −θ ! " # # ## $ % & & && = γ x y θ ! " # # # $ % & & & (37) i(x, y,θ,u,v) =ψγ (x,y,θ )(u,v) = u v ! " # $ % & (38) e = ρ(xγ ,yγ ,θγ )(x̂, ŷ)− ρ(xγ ,yγ ,θγ )(x, y) = cosθ̂ sinθ̂ −sinθ̂ cosθ̂ " # $ $ % & ' ' x̂ − x ŷ− y " # $$ % & '' (39) invariant frame w = (dφγ (x,y,θ )(x, y,θ )) −1 ∂ ∂(x,y,θ ) = = dφγ (x,y,θ )(x, y,θ ) = cosθ −sinθ 0 sinθ cosθ 0 0 0 1 # $ % % % & ' ( ( ( . (40) 62 invariant pre-observer d dt x̂ ŷ θ̂ ! " # # # $ % & & & = ucosθ̂ usinθ̂ uv ! " # # # # $ % & & & & + cosθ̂ −sinθ̂ 0 sinθ̂ cosθ̂ 0 0 0 1 ! " # # # # $ % & & & & l × cosθ̂ sinθ̂ −sinθ̂ cosθ̂ ! " # # $ % & & x̂ − x ŷ− y ! " ## $ % && (41) where l is a smooth 23× gain matrix, whose elements depend on the invariant error e and the invariants i. error equations and error dynamics η = ηx ηy ηθ ! " # # # # $ % & & & & = γ (x̂, ŷ,θ̂ ) x̂ ŷ θ̂ ! " # # # $ % & & & −γ (x̂, ŷ,θ̂ ) x y θ ! " # # # $ % & & & = = (x̂ − x)cosθ̂ + (ŷ− y)sinθ̂ −(x̂ − x)sinθ̂ + (ŷ− y)cosθ̂ (θ̂ −θ ) ! " # # # # $ % & & & & (42) !ηx !ηy !ηθ ! " # # # # $ % & & & & = u(1− cosηθ )+ (uv+ l31ηx + l32ηy )ηy usinηθ − (uv+ l31ηx + l32ηy )ηx 0 ! " # # # # $ % & & & & + +l ηx ηy ! " # # $ % & & (43) it can be seen that the invariant error equations are independent of the trajectory and only depend on the relative quantities ηx, ηy, and ηθ and the i invariants. stability and convergence the weighting matrix is defined as follows l = − |u | a ubey −uv uv−ubey − |u | c 0 −ub " # $ $ $ $ % & ' ' ' ' , (44) where a and b are care positive scalars and ey = ηy. the invariant error dynamics can be made locally asymptotically stable. furthermore, the resulting symmetry-preserving observer is almost globally asymptotically convergent, i.e. it converges any initial condition except for one as described in refs. [15-16]. simulation results the state estimation techniques are illustrated in two tracking examples. for comparative purposes, the following algorithms have been implemented: extended kalman filter (ekf), central difference and unscented kalman filter (ckf, ukf) and the symmetry preserving observer (sym) discretized by the sample time of the sigma-point estimators. the reference paths are xr (t) = t, and yr (t) = asin(ωt) , where a = 3 m and ω = π/5 rad s-1. zero mean additive gaussian noise is assumed with standard deviations of 0.01 and 0.005 for the process noise and 0.02 for the measurement noise. the sampling time is ts = 0.1 s. the initial values are x0 est = y0 est =θ0 est =1 , and x0 = y0 = 0 . example 1 the vehicle starts from the origin of the xy-plane with large initial estimation error and tracks a sinusoidal path. fig.1 shows the estimated output positions of the vehicle using sigma-point kalman filters and symmetry-preserving observers. the estimation errors of different algorithms can be seen in figs.2 and 3. the errors are smaller and show smoother signals in the case of the spkf estimators, which was expected, since the sym observer is deterministic. large errors appear at the peak values of the reference signals; however, both estimation techniques achieved the same satisfactory results in spite of the relatively small sampling frequency. figure 2: estimation errors of the sigma-point and extended kalman filters from example 1 63 root-mean-square errors can be seen in table 1. we can conclude that among the processes of state estimation techniques the sym observer is competitive with spkf estimators. example 2 in this example the vehicle performs an off-line estimation before movement starts, followed by an online estimation along a sinusoidal path. it is notable that in the stationary state the velocity is zero and at the beginning of movement the velocity changes to a nonzero value abruptly, see eq.(33). figs.4-7 illustrate the estimated output positions and the measurement errors for the sigma-point estimators and the invariant observers respectively the error signals show a quick convergence in the case of the symmetry-preserving observer. the speed of convergence depends on the parameters set in the l matrix; however, high gains can cause the observer to be divergent and make larger errors. since there are no u and δ signals in the stationary position and the orientation is not directly measured, the orientation can only be estimated after the vehicle starts moving. the error signal oscillates around zero in a similar way to example 1. due to calibration, smaller errors appear. the invariant observer and sigma-point estimators have the same magnitude of error components. the root-mean-square errors of the simulation can be seen in table 2. figure 3: estimation errors of the symmetry-preserving observer (sym) from example 1 figure 6: estimation errors of the sigma-point and the extended kalman filters from example 2 figure 4: estimated output position of the vehicle using sigma-point state estimation (ukf, ckf) and extended kalman filter (ekf) from example 2 figure 5: estimated output position of the vehicle using symmetry-preserving observer (sym) from example 2 figure 7: estimation errors of the symmetrypreserving observer (sym) from example 2 table 1: root-mean-squared errors of the estimated signals from example 1 rmse x, m y, m θ, rad ukf 0.1368 0.1587 0.0338 ckf 0.1366 0.1577 0.0336 ekf 0.1371 0.1551 0.0352 sym 0.1371 0.1628 0.0455 table 2: root-mean-square errors of the estimated signals from example 2 rmse x, m y, m θ, rad ukf 0.0998 0.1180 0.0627 ckf 0.0993 0.1175 0.0628 ekf 0.1013 0.1165 0.0648 sym 0.1264 0.1453 0.0760 64 conclusion in this paper we presented a comparison of two different recently developed state estimation techniques. the sigma-point (spkf) stochastic estimator is based on the unscented transformation and the non-linear symmetry-preserving observers are based on the group transformation of symmetrical lie groups and invariant frames. two examples are considered for the estimation of vehicle kinematics: the first example deals with the path tracking reliability of the vehicle; the second example examines the convergence and the speed of the off-line calibration followed by path tracking. the examples illustrate that for non-linear systems in noisy environments the use of stochastic stateestimators is needed. moreover the sigma-point approach provides more accurate estimation results than the commonly used non-linear ekf state estimators. the symmetry preserving observers for non-linear systems benefit from their constructive design method, which provides local asymptotic convergence. this method can be utilized by non-linear applications in which the physical and mechanical symmetry properties of the system can be exploited. references [1] bar-shalom y., li x.-r., kirubarajan t.: estimation with applications to tracking and navigationm, wiley interscience, new york, ny, u.s.a., 2001 [2] särkkä s.: recursive bayesian inference on stochastic differential equations, phd thesis, helsinki university of technology, helsinki, finland, 2006 [3] julier s.j., uhlmann j.k.: unscented filtering and nonlinear estimation, proc. ieee, 2004, 92(3), 401–422 [4] van der merwe r., wan e.a., julier s.: sigma-point kalman filters for nonlinear estimation and sensorfusion: applications to integrated navigation, proc. aiaa guidance, navigation & control conference (gnc), providence, ri, u.s.a. 2004 [5] van der merwe r.: sigma-point kalman filters for probabilistic inference in dynamic state-space models, phd thesis, oregon health & science university, eugene, or, u.s.a., 2004 [6] julier s.j., uhlmann j.k.: corrections to unscented filtering and non-linear estimation, proc. ieee, 2004, 92(12), 1958–1958 [7] julier s.j., uhlmann j.k.: unscented filtering and nonlinear estimation, proc. ieee, 2004, 92(3), 401–422 [8] wan e.a., van der merwe r.: the 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3461–3464 [14] salam eran: filtering algorithms and avionics systems for unmanned aerial vehicles, phd thesis, mines paristech, paris, france, 2010 [15] bonnabel s., martin p., rouchon p.: non-linear symmetry preserving observers on lie-groups, ieee transactions on automatic control, 2009, 54(7), 17091713 [16] bonnabel s., martin p., rouchon p.: symmetrypreserving observers, ieee transactions on automatic control, 2008, 53(11), 2514–2526 [17] bonnabel s., martin p., rouchon p.: a non-linear symmetry-preserving observer for velocity aided inertial navigation, proc. 2006 american control conference, minneapolis, mn, u.s.a., 2006 [18] ayhanman n., rouchon p.: on invariant asymptotic observers, cdc, 2002 [19] rouchon p., guillaume d.: observation and control of simplified car, ifac, 1998 [20] bonnabel s.: symmetries in observer design: review of some recent results and application to ekf-based slam, robot motion and control 2011, lecture notes in control and information sciences 2012, 422, 3–15 [21] collon c., rudolph j., woittennek f.: invariant feedback design for control systems with liesymmetries – a kinematic car example, discrete cont. dyn. sys. 2011, 2(11), 312–321 hungarian journal of industry and chemistry veszprém vol. 42(2) pp. 65–70 (2014) telemedical heart rate measurements for lifestyle counselling mario salai,! gergely tuboly, istván vassányi, and istván kósa faculty of information technology, university of pannonia, egyetem u. 10.,veszprém, 8200, hungary !email: mario.salai@gmail.com in this paper we analyse a low-cost commercial chest belt to be integrated into a lifestyle counselling system as a source of heart rate data. we compared data from a schiller ecg holter device, which serves as a reference to a cardiosport device. due to missing data in the cardiosport device caused by loss of contact with the body, the creation of special algorithms was necessary for synchronization and data validation. the results show that when using our synchronization algorithms the average absolute percentage error between the two signals was 2% with correlation of more than 99%. using a data validation algorithm, we were able to get on average more than 70% of the signal with an absolute percentage error of 3% and a high average correlation of 99%. the mean rr interval values and standard deviation of rr intervals are very close to those of the reference device using both the synchronization and data validation algorithms. when using the data validation algorithm, the reference measurements produced only slightly better results with regard to false detections of atrial defibrillation than the cardiosport device. in conclusion, we found that with a simple preprocessing algorithm, cardiosport as a low-cost device can be safely integrated into a lifestyle support system as a telemedical solution. keywords: telemedicine, lifestyle counselling, heart rate monitor introduction low-cost telemedical sensors are often used in modern ambient assisted living (aal) telemonitoring and selfmanagement systems for providing inputs to medical intelligence algorithms [1]. such systems extend the scope of traditional health care that is based purely on data measurement. however, the proper interpretation and reliability of the results depends on the reliability of the measured data and the sensor itself. nevertheless, there are still surprisingly few reviews reported in the literature to date on the validation of the information content of such low-cost sensors compared to the clinically accepted reference device. an example of a device that was tested for validity is the sensewear hr armband [2]. in this study, they used the reference device simultaneously with the tested device as a way of validating data. however, most of the compared devices are expensive high-end devices, which present an obstacle for their wide use in telemedicine. in this proof-of-concept paper, we analyse a simple commercial chest belt chosen to be integrated into the lavinia lifestyle mirror system [3] as a source of heart rate (hr) data. in the lavinia system, the hr signal of the patient will be used to (i) estimate the calories burnt by physical activity, (ii) calculate the heart rate variability (hrv) in order to detect periods of mental or emotional stress, and (iii) analyse arrhythmia patterns (poincare plots) for atrial fibrillation detection. our approach involves the comparison of the hrv and poincare plots computed from the filtered chest belt signal, with those parameters computed from a reference holter device. methods measurements two devices were used simultaneously by a healthy volunteer over a 24 hour period. a schiller mt101/mt-200 holter device was our reference device designed for clinical use. the chest belt was a cardiosport tp3 heart rate transmitter device. since this device does not have its own memory for storing data, we used a nexus 7 tablet with android version 4.4.2 to connect the device via the bluetooth 4.0 protocol and store the measured data on the tablet. although both devices were worn by volunteers for 24 hours, only 12 hours of the overall signal were used for analysis due to frequent detachments of the device from the body during nighttime. the measurements of 12 hours were repeated on 4 additional healthy male subjects. signal analysis the direct comparison of measured data was not possible due to the different designs of the reference and the telemedical devices. however, we wanted to 66 compare signals directly in terms of time and also to develop a data validation algorithm for removing the noisy parts of the cardiosport device measurements reliably without using the reference data. the problem was that the chest belt was not firmly attached to the body and sudden movements of the device caused signal loss. therefore, we needed to create a software module for synchronization and data validation before any analysis. data validation means removing obviously bad data (artefacts) and keeping only ‘good’ data segments of sufficient length, because, as a rule of thumb, both hrv and poincare plot computations require data chunks of at least 5 minutes. even though the data validation algorithm removed a considerable amount of data from the original signal, we still had enough useful data for analysis from the daytime. the synchronization algorithm our simple algorithm for signal synchronization uses a sliding window that passes from the beginning of the chest belt signal to the end and calculates the absolute error between the two signals. when sliding finishes, the location of the sliding window with the minimum absolute error is considered as the point where the two signals should be synchronized. this applies only if the correlation of the data in the sliding window and the same amount of data from the reference device are higher than a minimum set by the user. if these conditions are met, the algorithm copies data from the sliding window into a newly generated third signal, which represents the chest belt signal fully synchronized with the reference signal. if conditions are not met, the third signal is filled with zeros. finally, the algorithm extracts all the highly correlated segments from the third signal ignoring zero values. also, a file with all the merged segments is generated for general analysis. the algorithm uses the following 5 main parameters that can be set up by the user: 1. window size: amount of data copied from the signal into the sliding window (default: 200), 2. window shift step: the number of samples by which we shift the sliding window in each iteration (default: 50), 3. absolute error window: amount of data used for calculating the minimum absolute error (default: 200), 4. maximum error distance: the number of samples by which we shift the absolute error window in order to find the minimum absolute error (default: 1000), 5. minimum correlation: minimum correlation, expressed as a percentage, required for the two signals to consider data in the chest belt signal as accurate (default: 97%). each parameter’s default value was determined empirically. after running the synchronization process, we obtained segments of highly correlated data. fig.1 shows the distribution of the lengths of signal segments. we can see that most segments are 3 to 18 minutes long. the longest highly correlated segment with the reference data is 110 minutes long. the default parameter settings minimize the number of overly short (< 5 min) segments. most of the bad segments (fig.2) are shorter than one minute, and only one bad segment was 60 minutes long. data validation algorithm another type of algorithm was used in the real telemedical scenario for finding good parts of the signal without relying on reference data. this implies finding gaps and abnormal values and omitting them. first, we compared the timestamp of each data point with the timestamp of the previous one. if the difference between the timestamps was longer than 3 seconds, we marked this as a ‘gap’. the 3-second gap detection was enabled by the chest belt’s buffering system that can tolerate short detachments of the device from the body. in the second step we identified abnormal values in the signal that were treated as gaps. the abnormal values are identified by observing the mean value of 20 neighbouring data points (10 before and 10 after a given point). if the mean value differs from the value of the figure 1: the distribution of strongly correlated segment lengths for all subjects figure 2: the distribution of weakly correlated segment lengths for all subjects 67 current sample by more than 300 units, we consider it invalid and mark it as a gap/error in the signal. finally, we extract the good segments from the signal with a length of more than 5 minutes. we implemented the above algorithm in a simple software tool (fig.3). on the left-hand side we can load the two signals and set the parameter values as well as the amount of data to be analysed. the graph shows two signals after the synchronization process was completed. the user can examine signals by clicking the previous and next buttons. general statistics are shown in the middle part of the screen, while in the lower part, we can see the histogram, and save the histogram and results as a file. two tabs in the top left-hand corner allow the user to switch between synchronization and data validation algorithms. statistical analysis time and frequency domain analyses, correlation comparisons, mean absolute percentage errors, and the slopes of scatter plot diagrams were compared between two measurements for hrv analysis. the specificities of a self-developed atrial fibrillation detector algorithm were compared for atrial fibrillation analysis. the latter algorithm is based on the k-means clustering of poincaré plots (consisting of rr intervals) the time and frequency domain analyses for hrv were performed using kubios hrv analysis software, while the rest of the analysis for hrv and atrial fibrillation was performed in microsoft excel. atrial fibrillation detection was done using the matlab environment and the results were saved as microsoft excel workbooks. results and analysis heart rate variability after the synchronization process, we got strongly correlated (greater than 97%) synchronized data segments of various durations. table 1 summarizes the duration of signals analysed. table 2 shows results in the time domain for schiller and cardiosport devices after using the algorithm for the synchronization of signals. time domain analysis shows similar values for mean rr values and standard deviation (std rr in eq.(1)). the average mean rr values for the schiller and cardiosport devices are 851 and 871 respectively. the average std rr for the schiller device is 108 and 110 for the cardiosport device. figure 3: synchronization and data validation software table 1: signal duration after the synchronization process subject duration (h:m:s) #1 10:53:28 #2 8:45:40 #3 10:30:17 #4 7:46:56 68 !"#!!! = ! !!! (!!! − !!)!! !!! (1) the frequency domain analysis for the synchronization process is presented in table 3. the absolute power was compared for very low frequencies (vlf: 0-0.04 hz), low frequencies (lf: 0.04-0.15 hz), high frequencies (hf: 0.15-0.4 hz) and ratios between low frequencies and high frequencies (lf/hf). results show no significant difference between schiller and cardiosport device values. the average mean absolute percentage error (mape) between two signals is 2% with a high average correlation of close to 100%. using the data validation algorithm, we extracted data points from the collected signals. the duration of the resulting signal is shown in table 4. it is important to note that due to the noise on schiller device recordings, we had to remove noisy parts from the original signal. therefore, even though the signal was recorded continuously for 12 hours, overall duration is much less. calculations show that in the worst scenario only 45% of the signal can be used for analysis using this data validation method, while in the best scenario this number reaches 95%. this leads to a conclusion that results are rather subject dependent. the results of data analysis in the time domain after the removal of bad parts using the validation algorithm can be seen in table 5. the mean rr intervals for schiller and cardiosport devices are 851 and 871 and standard deviations are 104 and 106, respectively. the cardiosport device has slightly greater values, but these are practically identical. the frequency domain analysis for the data validation process is presented in table 6. the absolute power was compared for very low frequencies (vlf: 00.04 hz), low frequencies (lf: 0.04-0.15 hz), high frequencies (hf: 0.15-0.4 hz), and ratios between low frequencies and high frequencies (lf/hf). as in the synchronization process, the results show no significant difference between the schiller and cardiosport device values. the minimum, maximum and average percentage errors on whole signals were calculated using 5 minute long sliding windows with one minute long shift steps (table 7). only one subject had a high maximum error value of 34%. by visual examination, it was determined that the cause of such a high error was the artefact of the schiller device. in spite of that, the average error remained low (2%). table 2: time domain analysis after synchronization mean rr (ms) a std rr (ms) b subject schiller cardiosport schiller cardiosport #1 738 755 123 125 #2 704 720 91 93 #3 908 929 90 93 #4 855 875 145 148 #5 937 959 107 109 average 851 871 108 111 a with 2% error, b with 1-3% error table 3: frequency domain analysis after synchronization schiller cardiosport error subject absolute power (ms2) absolute power (ms2) % % % % vlf lf hf lf/hf vlf lf hf lf/hf vlf lf hf lf/hf #1 7937.6 3086 1578 1.956 8444 3224 1330 2.4235 6 4 19 19 #2 5431.5 626.6 245 2.557 5723 659.3 250.9 2.6281 5 5 2 3 #3 4251.2 1927 494.4 3.898 4543 2055 538.8 3.8146 6 6 8 2 #4 12682 1790 636.5 2.813 13514 1869 621.5 3.0077 6 4 2 6 #5 6139.8 1212 476.7 2.542 6465 1274 481.4 2.6459 5 5 1 4 table 4: signal duration after data validation subject duration (h:m:s) #1 1:28:10 #2 11:20:03 #3 6:15:38 #4 9:27:07 #5 4:29:44 table 5: time-domain analysis after data validation mean rr (ms) a std rr (ms) b subject schiller cardiosport schiller cardiosport #1 701 724 136 139 #2 700 717 91 93 #3 899 921 100 100 #4 846 866 139 142 #5 958 981 88 90 average 851 871 105 106 a with 2% error, b with 0-2% error table 6: frequency domain analysis after data validation schiller cardiosport error subject absolute power (ms2) absolute power (ms2) % % % % vlf lf hf lf/hf vlf lf hf lf/hf vlf lf hf lf/hf #1 10414 2297 1171 1.96 10847 2442 1004 2.43 4 6 17 19 #2 5446 631 245 2.57 5718 654 245 2.67 5 3 1 4 #3 5163 1990 523 3.80 5424 2054 540 3.80 5 3 3 0 #4 11683 1769 616 2.87 12149 1831 594 3.08 4 3 4 7 #5 4356 1235 317 3.89 4522 1303 330 3.95 4 5 4 1 69 fig.4 represents a typical relationship between cardiosport and schiller devices. all gradient values are close to 1. the lowest slope value is 0.98 while the highest value is 1.02. the average mean absolute percentage error (mape) between two signals was 3% with a strong average correlation of 99%. atrial fibrillation we carried out the detection of atrial fibrillation (afib) by analysing poincaré plots consisting of 30 rr intervals. we considered 30 rr intervals per iteration and in each iteration after constructing the poincaré plot we calculated the dispersion around the diagonal line and used k-means based cluster analysis to determine the number of the clusters. if the dispersion was too high (greater than 0.06) and the number of clusters was 1, or the number of clusters was more than 9; we assigned “afib” to that series of rr intervals, otherwise to “non-afib”. the details of the algorithm can be seen in our previous study [16]. since our data set did not contain real afib cases, only specificity could be calculated with regard to the efficiency of detection. the evaluation of atrial fibrillation detection results for synchronized data validation can be seen in tables 8 and 9. conclusion even though the cardiosport device may suffer from signal loss due to its design, we managed to determine that it can be safely used for telemedical purposes of measuring hrv and atrial fibrillation. we found only a few usable data segments that were less than 5 minutes long. with our algorithm that detects gaps and errors in table 7: the minimum, maximum and average percentage errors subject minimum error maximum error average error #1 0.1% 3.5% 1.5% #2 0.0% 7.7% 2.1% #3 0.0% 33.9% 3.2% #4 0.1% 6.7% 1.9% #5 0.1% 5.1% 2.2% average 0.1% 13.4% 2.4% figure 4: comparison of the cardiosport and schiller devices after data validation table 8: results from the synchronized data related to atrial fibrillation detection subject number of iterations schiller mt-101/mt-200 system cardiosport tp3 heart rate transmitter afib cases non-afib cases afib cases non-afib cases #1 331 26 8% 305 92% 31 9% 300 91% #2 1796 9 1% 1787 99% 3 >1% 1793 ~100% #3 1120 7 1% 1113 99% 5 1% 1115 99% #4 1427 11 1% 1416 99% 16 1% 1411 99% #5 964 46 5% 918 95% 45 5 919 95% min 1% 92% >1% 91% max 8% 99% 9% ~100% mean 3% 97% 3% 97% std 3% 3% 4% 4% table 9: results from the data validation process related to atrial fibrillation detection patient number of iterations schiller mt-101/mt-200 system cardiosport tp3 heart rate transmitter afib cases non-afib cases afib cases non-afib cases #1 241 3 1% 238 99% 8 3% 233 97% #2 1879 29 2% 1850 98% 2 >1% 1877 ~100% #3 808 15 2% 793 98% 3 >1% 805 ~100% #4 1296 10 1% 1286 99% 20 2% 1276 98% #5 544 6 1% 538 99% 7 1% 537 99% min 1% 99% >1% 97% max 2% 99% 3% ~100% mean 1% 99% 1% 99% std >1% >1% 1% 11% 70 the signal and removes them with an average effectiveness of more than 70%, which translates into having enough data to calculate hrv and atrial fibrillation from daytime measurements. regarding atrial fibrillation detection, we can conclude that by using the developed data validation algorithm the reference schiller mt-101/mt-200 measurements produced only slightly better results with regard to false detections than the cardiosport tp3 heart rate transmitter. in two cases the cardiosport measurements proved to be even better than schiller records, which implies that some relatively simple heart rate recorders are equivalent to some holter devices after signal processing using the data validation algorithm. we have to emphasize; however, that we have not performed any measurements on actual atrial fibrillating patients yet. therefore, the investigation of the sensitivity of our atrial fibrillation detection algorithm under the presented circumstances could be the subject of further studies. in summary, the cardiosport as a low-cost device can easily be integrated into a lifestyle support system as a telemedical solution. acknowledgments this research was supported by the european union and co-funded by the european social fund “telemedicinefocused research activities in the field of mathematics, informatics and medical sciences” támop-4.2.2.a11/1/konv-2012-0073. references [1] patel s., park h., bonato p., chan l., rodgers m.: a review of wearable sensors and systems with application in rehabilitation, j. neuroengng. rehab., 2012, 9(21), 1–17 [2] kristiansen j., korshøj m., skotte j.h., jespersen t., søgaard k., mortensen o.s., holtermann a.: comparison of two systems for long-term heart rate variability monitoring in freeliving conditions a pilot study, biomed eng. online, 2011, 10(27), 1–14 [3] kósa i., vassányi i., nemes m., kálmánné k.h., pintér b., kohut l.: a fast, android based dietary logging application to support the lifestyle change of cardio-metabolic patients, global telemedicine and ehealth updates: knowledge resources, eds.: m. jordanova, f. lievens, 2014, 7, 553–556 [4] salai m., tuboly g., vassanyi i., kosa i.: reliability of telemedical heart rate meters, ime j., 2014, 8(5), 49–55 hungarian journal of industry and chemistry veszprém vol. 42(2) pp. 71–77 (2014) the application of unknown input estimators to damp load oscillations of overhead cranes bálint patarticsb and bálint kiss department of control engineering and information technology, budapest university of technology and economics, magyar tudósok krt. 2, budapest, 1111, hungary be-mail: patarticsbalint@gmail.com this paper focuses on the development of state estimation methods for mechanical systems with uncertain frictional parameters. the goal of the study is to provide reliable angle estimation for state-feedback-based crane control solutions, designed to reduce load sway. cranes are underactuated systems, usually unequipped with the sensors necessary to measure the swinging angle, therefore the damping of their oscillatory behaviour is a challenging task. two estimators are proposed for the calculation of the unmeasured states. one is based on an ’unknown input kalman filter’ (uikf), the other applies the ’unscented kalman filter’ (ukf) with load prediction. simulation results are provided to demonstrate the accuracy of the algorithms. keywords: overhead crane, state estimation, nonlinear systems, unknown inputs, kalman filter introduction the sway of the load carried by cranes is an unwanted phenomenon. friction may decouple load motion from the remaining crane mechanism. this causes difficulty for inexperienced operators, especially when they try to land the cargo. the friction present in the crane mechanism makes the reduction of the swinging particularly demanding. therefore the goal of the design of crane control systems is often to ensure minimal swinging along a specified trajectory [1–6]. there are numerous algorithms available in the literature for the solution to this problem. the design of such a control system can be addressed using soft computing methods such as fuzzy logic and neural network with genetic algorithm. these solutions require however the measurement of the load position, which is often based on workspace visualization [1]. hard commuting techniques are also widely applied for sway reduction. an h2 optimal solution is described in ref.[2], which also relies on image processing for the measurement of the load coordinates. there are a variety of algorithms taking advantage of the flatness property (or exact linearizability) of overhead cranes [7]. the control systems in refs.[3] and [4] consider all the states measurable, however an estimator is proposed in ref.[3] for the computation of the uncertain parameters. in the case of navy cranes, local asymptotic stability can be achieved without the measurement of the swinging angle, if trajectory planning exploits the flatness property of the system [6]. there is also a tracking control algorithm specifically designed for overhead cranes, that is capable of effectively reducing the sway despite the friction [5]. for the calculation of the unmeasured states, this controller uses a linear observer. in this paper we propose new methods of state observation for systems that take into account friction, and are applicable to overhead cranes. these estimators can replace the linear observer in ref.[5] or the need to measure the load coordinates in any other state-feedback-based method to enhance the precision of the control. our estimation methods are based on the assumption that the effect of the friction on the inputs can be reduced. this is true for most mechanical systems (including overhead cranes), where the actuating signals are usually forces and torques. in the following section, the modelling of lagrangian mechanical systems is overviewed, and it is shown how the friction can be handled as an input disturbance. in the next section the state estimation techniques are presented based on the possible approaches of interpreting the friction. the next section describes the results of the application of these methods to the state estimation problem of overhead cranes and presents the simulation results. lagrangian-based models of mechanical systems the nonlinear dynamics of the controlled system can be obtained using the euler-lagrange equations. if the generalized coordinates are q = � q1 q2 . . . qn �t and the generalized forces are ⌧ = � ⌧1 ⌧2 . . . ⌧n �t , the eulerlagrange equations read d dt @l @q̇i � @l @qi = ⌧i, (1) 72 where l is the so-called lagrangian, the difference between the kinetic and potential energy of the system, q̇i = dqi dt and i = 1, 2, . . . n. using these equations, under some conditions the controlled system’s model can be written in the form h(q)q̈ + h(q, q̇) + hs(s) = ⌧, (2) where h(q) is the inertia matrix, h(q, q̇) comprises the centrifugal, coriolis and gravitational terms, and hs(s) is the frictional term with s being the vector of the frictional forces. in this form hs(s) can be reorganized to the right-hand-side of the equation. introducing the disturbance torques as ⌧̃ = ⌧ � hs(s), eq.(2) yields h(q)q̈ + h(q, q̇) = ⌧̃ . (3) the state-space representation of the model is ẋ = f(x, u) y = g(x), (4) where x is the state, u is the input, y is the output of the system, and f and g are nonlinear functions. this form can be obtained from eq.(5) assuming that xt =� qt q̇t � , and the output is not directly dependent on the torques. the state-space equations read ẋ = ✓ q̇ �h�1 (q)h(q, q̇) ◆ + ✓ 0 h�1 (q) ◆ ⌧̃ y = g(x). (5) the inputs of mechanical systems are usually forces and torques, consequently they are only dependent on ⌧̃ . this means, that the effect of the friction can be reduced to the actuated degrees of freedom of the system. if it is necessary for the design of the control system, the nonlinear dynamics can be approximated by a first order taylor series expansion around a setpoint (x0, u0). the linear model then becomes �ẋ = a�x+b�u �y = c�x, (6) where the quantities prefixed with � mean the distance from the setpoint, e.g. �x = x� x0, and the matrices are jacobians [8]. state estimation methods since the friction can be interpreted in our setup as an input disturbance, we consider two ways for its compensation in the state estimation. either all input variables can be disregarded, or the additive disturbance can be estimated using a load predictor. these ideas form the basis of the two estimator design techniques described as follows. the computations of the controllers implemented in embedded systems are based on sampled signals. hence the design of the estimators is done in discrete-time. unknown input approach consider the discrete-time linear stochastic system model x[k + 1] = �x[k] + �dd[k] + ![k] z[k] = cx[k] + v[k], (7) where x is the state, d is the unknown input (disturbance) of the system and z is the measurement of the output y[k] = cx[k]. � and �d are obtained from the matrices of eq.(6) in the form of � = eats , �d = z ts 0 eatb dt, (8) where ts is the sample time. the measurement and process noise v and ! are assumed to be additive, white, and gaussian with mean of zero. notice, that in eq.(7), all of the system inputs are considered to be disturbances. the state and the unknown input of such a system can be estimated using an ’unknown input kalman filter’ (uikf) [9], if the system satisfies the conditions dim{d}  dim{y} (9) rank{c} = dim{y} (10) rank{�d} = dim{d} (11) rank{c�d} = dim{d} . (12) additive disturbance approach in the case of input disturbances, load prediction is often applied. let us introduce the discrete-time nonlinear model of a system in the form x[k + 1] = �(x[k], ũ[k]) + ![k] z[k] = g(x[k]) + v[k], (13) where ũ is the disturbed input of the system, and � and g are nonlinear functions. we will follow the assumption, that the disturbance is additive to the input, thus ũ[k] = u[k] + ⇤d[k], where u is the vector of actuating signals, and ⇤ is a constant matrix. we also assume a constant disturbance model with process noise !d, d[k + 1] = d[k] + !d[k], resulting in the model x̃[k + 1] = ˜�(x̃[k], u[k]) + !̃[k] z[k] = g̃(x̃[k]) + v[k]. (14) in eq.(14) x̃t = � xt dt � is the extended state and !̃t = � !t !t d � is the extended process noise. the extended nonlinear mappings of the system are given by g̃(x̃[k]) = g(x[k]) and ˜�(x̃[k], u[k]) = ✓ �(x[k], u[k] + ⇤d[k]) d[k] ◆ . (15) in most cases the continuous-time differential equation of the observed system is available, in the form 73 m uf uc r ` ✓ j ⇢ cartwinch m load rail figure 1: the two-dimensional ovearhead crane of eq.(4). the discrete-time state-transition equation can then be obtained by �(x[k], u[k]) = x[k] + (k+1)tsz kts f(x, u[k]) dt, (16) where the input is piecewise constant and u[k] = u(kts). if the integral in eq.(16) cannot be given in closed form and ts is sufficiently small, the left rectangle rule approximation (k+1)tsz kts f(x, u[k]) dt ⇡ tsf(x[k], u[k]). (17) can be used. substituting this into eq.(15), the expression reads ˜�(x̃[k], u[k]) = ✓ x[k] + tsf(x[k], u[k] + ⇤d[k]) d[k] ◆ . (18) for the observation of the system described by eq.(14) and eq.(18) the ’unscented kalman filter’ (ukf) [10] is applicable. we chose one of the implementation variants of this filter from ref.[10]. application of the methods to overhead cranes system dynamics we will now consider the state estimation problem of the two-dimensional overhead crane (fig.1). let us denote the horizontal displacement of the cart by `, the length of the rope by r and the angle between the vertical and the rope by ✓. the generalized coordinates of the system are chosen to be q = � ` r ✓ �t , and the state is x = � ` r ✓ ˙` ṙ ˙✓ �t . based on the sensors available, the output is y = � ` r ˙` ṙ �t . overhead cranes is a typical example of underactuated systems. it is actuated by two motors, one applying the force uf on the cart, and another delivering the estimated system s ⇤ + + u u system model s = ⌘(x, ẋ, u) ẋ = f(x, ũ) y = g(x) ũ y r ẋ x figure 2: dynamics of the estimated system torque uc to the winch. the system input consists of these, u = � uf uc �t . the parameters of the system are the mass of the cart m , the mass of the load m, the moment of inertia of the winch j and the radius of the winch ⇢. the acceleration in the gravitational field is denoted by g. the following assumptions are made of the system. • the rope connecting the load to the winch is massless and behaves as a rigid rod during the motion. • the load is a point mass. • m , m, j and ⇢ are known. • in the initial state of the system the unmeasured states are zero: ✓ = 0 rad and ˙✓ = 0 rad/s. • the effect of the aerodynamic resistance is negligible. the lagrangian of overhead cranes reads l = 1 2 (m +m) ˙`2 + 1 2 j ⇢2 ṙ2 ++ 1 2 m ⇣ ṙ2 + r2 ˙✓2 ⌘ +m ˙lṙ sin ✓ +m ˙lr ˙✓ cos ✓ +mgr cos ✓. (19) using eq.(1), the model can be written in the form of eq.(2), where the expressions become h(q) = 0 b@ � m +m sin 2 ✓ � m sin ✓ 0 m sin ✓ ⇣ j ⇢2 +m ⌘ 0 cos ✓ 0 r 1 ca , (20) h(q, q̇) = � 0 @ m(r ˙✓2 + g cos ✓) sin ✓ mr ˙✓2 +mg cos ✓ �2ṙ ˙✓ � g sin ✓ 1 a , (21) hs(s) = � 0 @ sf sc 0 1 a , ⌧ = 0 @ uf �uc ⇢ 0 1 a , (22) where sf is the frictional force between the cart and the rail and sc is the frictional force applied to the winch. the continuous-time linear model of the crane is computed around the setpoint x0 = � 0 r0 0 0 0 0 �t , u0 = � 0 mg⇢ �t , and sf = sc = 0 is substituted 74 table 1: numeric values of the parameters value unit m 5 kg m 0.05 kg j 3.802 · 10�4 kg m 2 ⇢ 0.02 m g 9.81 m s �2 ts 1 ms r0 0.47 m `d 0.5 m into eq.(5). the resulting jacobians are a = 0 bbbbbb@ 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 m m g 0 0 0 0 0 0 0 0 0 0 0 �m+m mr0 g 0 0 0 1 cccccca , b = 0 bbbbbb@ 0 0 0 0 0 0 1 m 0 0 � ⇢ m⇢2+j � 1 mr0 0 1 cccccca , c = 0 bb@ 1 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0 1 cca . (23) substituting eq.(22), the disturbance torque term in eq.(3) reads ⌧̃ = 0 @ uf + sf � 1 ⇢ (uc � ⇢sc) 0 1 a . (24) eq.(24) shows, that the disturbed input of the system can be introduced in the form ũ = u+ ⇤s, where ⇤ = ✓ 1 0 0 �⇢ ◆ . (25) the frictional forces usually depend on the actuating signals, state variables, and the derivative of the state as well. the general characteristics of the friction reads as s = ⌘(x, ẋ, u). the block diagram of the dynamics of the system is illustrated in fig.2. only the system model block is used for estimator design, which is eq.(5) if the effect of the friction is disregarded, hs(s) = 0. proposition 1. the discrete-time linear crane model obtained from the matrices in eq.(23) and using eq.(8) satisfies the design conditions of the uikf in eq.(9-12). proof. it is clear that dim{y} = 4, dim{d} = 2 and rank{c} = 4, thus eq.(9) and (10) are satisfied. using eq.(8) and the numerical values in table 1, �d = 10 �2 0 bbbbbb@ 0.0001 0 0 �0.025 �0.0002 0 0.2 0 0 �49.975 �0.4255 0 1 cccccca , c�d = 10 �2 0 bb@ 0.0001 0 0 �0.025 0.2 0 0 �49.975 1 cca . (26) we obtain rank{�d} = 2 and rank{c�d} = 2, which are both equal to the number of unknown inputs. this satisfies eqs.(11) and (12). the continuity argument holds for the rank of the matrices in eq.(26), therefore there exists a neighbourhood around our parameter set where the design conditions are still satisfied. simulation the estimation results were obtained by simulation of overhead cranes in a closed-loop scenario using a simple discrete-time pole-placement-based linear controller. the simulation also took into account friction. there are various models of the friction phenomenon, ours included coulomb, stribeck, viscous friction, and stiction [11]. the numerical values of the parameters used in the simulation are given in table 1. because of friction, but mainly stiction, the position of the crane can not be accurately controlled without integrators in the controller. consequently we included the integral of the measurable positions in the controller design as proposed on page 309 of ref. [8]. the outputs to be integrated are yi = � ` r �t . integrals of these quantities are approximated by the left rectangle rule as xi [k+1] = xi [k] +tsyi [k] = xi [k] +tscix[k], (27) where ci is defined so that yi [k] = cix[k]. in our case ci is the first two rows of c in eq.(23). using eq.(27) and eq.(7) a new system model is introduced in the form x̃[k + 1] = ˜ �x̃[k] + ˜ �u[k] y[k] = ˜cx̃[k]. (28) where the expanded state is x̃t = � xt xt i � and the matrices are ˜ � = ✓ � 0 tsci i ◆ , ˜ � = ✓ �d 0 ◆ , and ˜c = � c 0 � . (29) for the controller design the process and measurement noises are omitted. 75 r dac system in fig. 2 adc ukf k ki u[k] y y[k]u u0 + ++ yid + xd adc x[k] x yi [k] = (`[k] r[k])t y[k] yi [k] x̂[k] ŝ[k] uikf x̂[k] ˆ̃ u[k] u[k] ckf x̂[k] figure 3: closed-loop estimation setup used in the simulation 0 1 2 3 4 5 6 7 time [s] �10 0 10 20 30 40 50 60 u f , ˆ̃ u f , [n ] uf uikf ukf 0 1 2 3 4 5 6 7 time [s] �1.0 �0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 u c , ˆ̃ u c , [n m ] uc uikf ukf figure 4: actuating signals and the estimated inputs of the system we want the state-feedback controller to output u[k] = � ˜kx̃[k] = �kx[k] � kixi [k]. the gain ˜k can be computed using the eigenvalue placement method implemented in matlab’s place algorithm: ˜k = place(˜�, ˜�, �), where � contains the chosen eigenvalues of the closed-loop system. in continuous time they are �1 + 0.5j, �1� 0.5j, �5.1, �5.2, �5.3 �5.4, �5.5, and �5.6. the controller gains are k = 0 bbbbbb@ 100.594 �0.1273 0.6011 �1.6765 �185.407 0.0458 81.4011 �0.0558 0.0562 �0.3166 �4.2257 �0.0195 1 cccccca t , and ki = ✓ 46.641 1.6026 �0.074 �2.955 ◆ . (30) the closed-loop setup is illustrated in fig.3. here the integration is done using the left rectangle rule, and the 0 1 2 3 4 5 6 7 time [s] �0.1 0.0 0.1 0.2 0.3 0.4 0.5 m ea su re d st at es [m , m /s ] � r �̇ ṙ 0 1 2 3 4 5 6 7 time [s] �0.4 �0.3 �0.2 �0.1 0.0 0.1 0.2 u n m ea su re d st at es [r ad , ra d /s ] � �̇ figure 5: state evolution of the controlled crane using the true states as feedback adc and dac blocks are analogue-digital and digitalanalogue converters respectively. the dac uses the zeroorder hold method for signal reconstruction. the desired state of the system is xd = � `d r0 0 0 0 0 �t , `d is the desired position of the cart and yid = cixd. since we only want to demonstrate the results of the state estimation, first the real states are fed back to the controller. to compare the accuracy of our methods to a traditional solution, the classical kalman filter (ckf) [12] is also implemented. as a result, the kalman filters compute the estimated state of the system x̂[k], and they also provide information about the input. the uikf estimates the friction loaded actuating signals directly, while the ukf estimates the frictional forces superposed to the actuating signals. the actuating signals along with the estimates of the real inputs provided by the filters can be seen in fig.4. here, the estimated input of the ukf is computed as ˆũ = u[k]+⇤ŝ[k]. because of friction, the real inputs are estimated to be 76 0 1 2 3 4 5 6 7 time [s] 0.00000 0.00005 0.00010 0.00015 0.00020 0.00025 0.00030 0.00035 ` � ˆ̀ [m ] uikf ukf 0 1 2 3 4 5 6 7 time [s] �0.001 0.000 0.001 0.002 0.003 0.004 0.005 ˙̀ � ˆ̇̀ [m /s ] uikf ukf figure 6: error of the position and velocity estimations much less than the actuating signals. the large offset in fig.4 is a consequence of the stiction, the cart will not move until uf becomes greater than a certain value (in our case about 28 n). when the cart finally stops moving, the fluctuation of uf tries to counter the load sway, during which the measured states do not change. this is the reason why the estimators find the input to be zero. fig.5 shows the transient of the states in a closedloop. results show that the controller can bring the system into the desired state, but friction prevents it from stopping the low amplitude swinging of the load, because it makes quick, short motions impossible. error estimates are illustrated by figs. 6 and 7. in all cases, the error becomes zero when the crane reaches the desired state. this is not true for the angle and its derivative in fig.8. the error decreases at the end of the state transient, but does not become zero. when the cart stops and the load swings, the measurements are all constant thus they carry no information regarding ✓ and ˙✓. in these situations the cart and winch are usually also motionless due to friction. consequently, the estimation error of these quantities never becomes zero. it is possible to decrease the estimation error using two laser slot sensors. with the help of such devices, ✓ can be measured accurately in two positions and through the application of proper sensor fusion techniques the estimation of the angle can become more precise in between the chosen positions as well. in fig.9 the estimation error of ✓ and ˙✓ is illustrated using ckf. the filter was designed for the dynamics given by eq.(7) except that it does not consider the inputs unknown. the results show that the error is substantially higher than in the case of the uikf or ukf. 0 1 2 3 4 5 6 7 time [s] �0.00005 0.00000 0.00005 0.00010 0.00015 r � r̂ [m ] uikf ukf 0 1 2 3 4 5 6 7 time [s] �0.0010 �0.0005 0.0000 0.0005 0.0010 0.0015 0.0020 0.0025 0.0030 0.0035 ṙ � ˆ̇ r [m /s ] uikf ukf figure 7: error of the rope length and hoisting velocity estimations 0 1 2 3 4 5 6 7 time [s] �0.003 �0.002 �0.001 0.000 0.001 0.002 0.003 0.004 0.005 � � �̂ [r ad ] uikf ukf 0 1 2 3 4 5 6 7 time [s] �0.020 �0.015 �0.010 �0.005 0.000 0.005 0.010 0.015 0.020 0.025 �̇ � ˆ̇ � [r ad /s ] uikf ukf figure 8: error of the angle and angular velocity estimations fig.8 shows the estimation error of the ukf to be less. we applied this estimator in a closed-loop scenario identical to the one presented in fig.3, but instead of x[k] the x̂[k] of the ukf was used in the feedback loop. the state evolution of the crane in this simulation is illustrated in fig.10. the system’s behaviour is only slightly different from the case when the actual states were used in the feedback control in fig.5. 77 0 1 2 3 4 5 6 7 time [s] �0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 � � �̂ [r ad ] 0 1 2 3 4 5 6 7 time [s] �5 �4 �3 �2 �1 0 1 2 3 �̇ � ˆ̇ � [r ad /s ] figure 9: error of the angle and angular velocity estimations using ckf conclusion it was shown that in most mechanical systems the disturbing effect of friction can be reduced to the actuating signals. based on this statement, two estimation methods were provided for the computation of the unmeasured states. one of these techniques considers the inputs completely unknown and uses uikf for the estimation. the other algorithm treats the inputs as distorted by an additive disturbance, and applies ukf with a load predictor extension. simulation results in a closed-loop controlled scenario were provided to prove the applicability of the concepts. it was also pointed out, that the precision of the estimators could be improved using laser slot sensors. this will be the subject of a forthcoming paper. references [1] hyla p.: the crane control systems: a survey, proc. 17th int. conf. methods and models in automation and robotics (mmar), 2012, 505–509 [2] schindele d., menn i., aschemann h.: nonlinear optimal control of an overhead travelling crane, proc. 18th ieee int. conf. control applications, 2009, 1045–1050 [3] boustany f., d’andrea novel b.: adaptive control of an overhead crane using dynamic feedback linearization and estimation design, proc. ieee int. con. robotics and automation, 1992, 1963–1968 0 1 2 3 4 5 6 7 time [s] �0.1 0.0 0.1 0.2 0.3 0.4 0.5 m ea su re d st at es [m , m /s ] � r �̇ ṙ 0 1 2 3 4 5 6 7 time [s] �0.4 �0.3 �0.2 �0.1 0.0 0.1 0.2 u n m ea su re d st at es [r ad , ra d /s ] � �̇ figure 10: state evolution of the controlled crane using the ukf’s estimated states as feedback [4] neupert j., hildebrandt a., sawodny o., schneider k.: trajectory tracking for boom cranes using a flatness based approach, proc. int. joint conf. sice-icase, 2006, 1812–1816 [5] rózsa t., kiss b.: tracking control for towdimensional overhead crane, proc. 8th int. conf. informatics in control, automation, and robotics, icinco, 2011, 1, 427–432 [6] kiss b., levine j., mullhaupt p.: a simple output feedback pd controller for nonlinear cranes, proc. 39th ieee conference on decision and control, 2000, 5, 5097–5101 [7] kiss b., lévine j., müllhaupt p.: modelling, flatness and simulation of a class of cranes, electrical engineering, 1999, 43, 215–225 [8] lantos b.: theory and design of control systems i., akadémia kiadó, 2001 (in hungarian) [9] darouach m., zasadzinski m., onana a.b., nowakowski s.: kalman filtering with unknown inputs via optimal state estimation of singular systems, int. j. sys. sci., 1995, 26(10), 2015–2028 [10] haykin s.s.: kalman filtering and neural networks, john wiley & sons, inc., 2001 [11] armstrong-hélouvry b., dupont p., de wit c.c.: a survey of models, analysis tools and compensation methods for the control of machines with friction, automatica, 1994, 30, 1083–1138 [12] kalman r.e.: a new approach to linear filtering and prediction problems, journal of basic engineering, 1960, 82, 35–45 advertise upcoming meetings, conferences, workshops, new products or services; make public announcements, introduce your research laboratory on the pages of the hungarian journal of industry and chemistry please contact us if interested! editorial office: university of pannonia p.o. box 158, veszprém h-8201 (hungary) tel.: +36 (88) 624-746, e-mail: hjic@almos.uni-pannon.hu; web: hjic.mk.uni-pannon.hu felelős szerkesztő: szilágyi róbert károly, phd kiadja: pannon egyetem, 8200 veszprém, egyetem u. 10. levélcím: h-8201 veszprém, postafiók 158, tel.: (88) 624-000 felelős kiadó: a pannon egyetem, mérnöki kar dékánja hungarian journal of industry and chemistry veszprém vol. 42(2) pp. 79–84 (2014) challenges of enterprise policy compliance with smartphone enablement or an alternative solution based on behaviour-based user identification sándor dobos! and attila kovács department of information technology, elte university budapest, budapest, 1117, hungary !email: sandor.dobos@hu.ibm.com current trends show the intense growth in the role and importance of mobile technology (smartphones, tablets, etc.) in business due to economic, social and technological reasons. the social element drives a powerful convenience expectation called “bring your own device” (byod) for taking notes and accessing internal and external network resources. apparently, the future is leading toward a more extensive enablement of smartphones and tablets with their enterprise applications. internal security standards along with applicable regulatory ones to achieve ‘policy enforcement’ as types of solutions and controls; however, this allows for merely one aspect of compliance. an alternative solution could be behaviour-based analysis to identify the user, attacker or even a malicious program accessing resources on phone or internal networks. complex networks can be defined by graphs, such as connections to resources on smartphones and serve as a blueprint. in case the motif is different from the user’s actual behaviour, the company can initiate specific actions to avoid potential security violations. this document reviews the it security challenges related to smartphones as well as the concept of graph-based user identification. the challenges of the latter are the identification of motif, selection of search algorithm and defining rules for what is considered a good or bad behaviour. keywords: mobile device security, “bring your own device” (byod) management, secure data communication, behaviour-based identification of threat, graph-based user identification introduction enterprise policy enforcement with current mobile technology management tools (mobile device management (mdm), virus detection, and other necessary modules) ensure only the compliance of piece of equipment. within enterprise, mdm servers initiate the compliant actions, if the smartphone client fails the access privilege is taken away; however, this has an immediate impact on revenue through operational efficiency affecting the business. the enterprise compliance of the smartphone device is only a validated response, which can be altered by understanding the mobile technology, such as the application structures or the way mdm technology works. hackers are heavily attacking smart devices with malicious software (malware). these can be viruses, spyware, adware, and other types of attacks. a specific example is the “obad.a trojan”, which is now being distributed via mobile botnets. the trojans are occupying a larger space and becoming more complex, which shows the need for it security to find new ways to detect them. the secure enterprise environment is crucial for organizations to ensure the business strategy and continuity of operation, irrespective of its environment being production, service delivery, or customer support related. companies are following the trend to ensure efficiency and simplify service accessibility for their customers, business partners or employees. it is an essential element of the it security strategy to be aligned with the business strategy due to (i) the intense growth of mobile technology and (ii) pressure from enterprise that has transformed business operations. forrester research from the q2 foresights security survey shows (fig.1) that mobile security is of primary concern amongst enterprise leaders. ceos are concerned about the risk of data loss, particularly due to device loss or theft. another worry regards data protection or data leak prevention usually in connection with data related to finance and innovation. figure 1: degree of concern of ceos from forrester research, foresights security survey 80 current challenges within today’s economic environment, profit-driven organizations are challenged from revenue, growth or profit target perspectives. in order to meet such expectations, organizations are under high pressure to offer innovative products (services) within newly identified channels and more accessible yet-to-bepenetrated markets to a demanding customer base, especially in the area of providing smartphone solutions. on the other hand, regulatory bodies are alarmed at mobile enablement and organizations in general striving to protect critical financial systems better, in particular via identity and access management. at the same time, organizations need to maintain operational resiliency and perform risk management assessments as an integrated part of day-to-day operations. the cost perspective is an important factor for customers facing the task of achieving a lower total cost of ownership (tco) although, by this shift in paradigm, they move from reactive protection to proactive value creation mode. the alignment of the current it strategy to business strategy is a challenge for corporations as it is a service provider within an enterprise also offering business enablement leads. companies need to manage security policy at the corporate level, assess the security health of the heterogeneous it environment, monitor the security weakness(es) in processes and systems and, of course, meet the plethora of banking laws, regulations and standards including sox, basel iii, glba, and pci compliance. with the adaptation of the byod concept in business practices, mobile technology itself contributes to additional and more complex challenges. enterprises are not the owners of those smart devices with access to enterprise networks and their data. fig.2 illustrates how smartphones with applications developed by unknown sources could be a threat to enterprise’s sensitive data. business drivers for change as introduced above an active need is emerging for more effective mobile solutions. it is not only a reflection of the compliance requirements but a real protective solution against mobile threats without any restrictions on financial growth or cutbacks on efficiency initiatives. there are compelling reasons to act and change now including data potentially at risk, pressure from regulatory bodies and audit firms to be compliant with the applicable data handling regulations, and the implementation of mobile security into an existing security structure. highlights of a political-economic-social-technology (pest) analysis politicians are setting high standards for data management regardless of platforms, even if they are related to mobile devices or mobile applications. these regulations mostly focus on the handling of financial data such as the sarbanes–oxley act of 2002 (sox). there are new developments regarding data (pictures, text, etc.) ownership such as the stop online privacy act (sopa). the preventing real online threats to economic creativity and theft of intellectual property act or in short protect ip act (pipa) will have an even more rigorous norm for enterprises who need to meet these regulations in order to obtain permission to operate in a certain field or market (market player). the economic situation puts more pressure on businesses as the trend still shows stagnancy on a macro level while in some segments it is still in decline. firms have high demands for business achievements measured by revenue and profit perspectives to meet shareholder expectations. one way to do so is to improve cost structures with mobile enablement (particularly byod). society wants to live more comfortably by searching for easily accessible services, such as online mobileenabled bank transfers or online mobile retail orders. companies aim to reach their customers via mobile applications that are more easily accessible through user-friendly interfaces, such as social network platforms. as usual, this trend is typical for major market areas, such as north america or, western europe; however, other regions are expected to follow. the trend in technology continues to be more vivid from a computing power and portability perspective. internet service providers are granting access to higher bandwidth networks for new applications and online content. policy enforcement and its weaknesses to manage the various types of mobile devices in an enterprise, a solution was introduced in 2008 by stricklen, mchale, caminetsky and reddy based on pattern definition for mobile device management (mdm). mdm is the most common approach how mobile devices (including smartphones, tablets) are managed within the enterprise as a management tool for monitoring and policy enforcement. even though this technology is available and wide-spread, according to abi research, mobile threats grew by 261% just in the figure 2: graphical illustration of mobile phone technology security threats 81 last quarter of 2012; however, mdm technology is not growing at a comparable rate to the number of vulnerabilities and attacks. one of the components of mdm is the registration module, which is responsible for identifying mobile devices within the enterprise network, where the identifier indicates the platform of each mobile device, e.g. smartphone and tablet. the other significant element is the management module. its job is to receive a management function definition performed on mobile devices using identifiers from mobile devices. the management module is responsible for instructions for the first platform to perform the management tasks and provides instructions for the other modules specific to the second platform to perform the management task on at least the second device. however, mdm is not the ultimate solution for mobile device security within the enterprise environment due to some concerns regarding the verifiable device integrity. there are attempts at identifying mdm solutions to detect modifications of the underlying platform, but since the mdm agent has limited privileges and was susceptible to compromise by malicious privileged software, these stand little chance of detecting a targeted attack. the us national security agency (nsa) describes an immutable cryptography, as the ‘root of trust’ on a specific platform, to be available for leveraging by mdm or other software, providing a means of countering this type of threats. encryption enables devices to attest their integrity on an enterprise and carry out any local policy decisions. the availability of this ‘root of trust’ to other software can vigorously complement a chain of trust that begins when booting and extends into the system runtime. an additional benefit of an immutable root of trust is that it allows a company to bind the unique identifier of that device together with other credentials to restrict company access to only those devices. in effect, the device itself can become one of the factors of a multi-factor access. in summary, mdm’s current capabilities support the byod and enterprise-owned use of mobile devices with certain gaps for high-security issues. management capabilities are limited to those provided for mdm products by the underlying mobile os (ios, android, and other platforms), and therefore, these capability gaps cannot be closed by mdm providers alone. ongoing cooperation between enterprise customers, os vendors, and mdm vendors is critical to the continued advancement of enterprise-level security for mobile devices. closing stated holes will enable the deployment of commercially available mobile devices to tackle high-security use issues common in sensitive industrial and governmental environments. secure data networks need to guarantee integrity, confidentiality and availability; this is when security is fulfilled. policy enforcement with the mdm can be too liberal, but then there is no real need for mdm or strictly constraining users thus limiting the value-add. the proposed solution is to identify the user based on behaviour and compare behaviour changes. behaviour analysis and challenges growing recognition drove the importance of network science related to the behaviour of sophisticated systems that is shaped by relations among their constituent elements. the rising availability and tractability of large and high quality data sets on a wide range of complex systems [1-3] have led to a primary insight: substantially diverse complex systems often share core key organizational principles. these can be quantitatively characterized by the same parameters, which means that they show remarkably similar macroscopic behaviour despite reflective differences in the low-level details of the components of each system or their mechanisms of interaction. the behaviour as described above can be modelled by mathematical graphs, where the graphs are defined simply as a set of nodes called vertices linked together in direct or indirect ways by connections (edges). from a mathematical point of view, g(v, e) are canonical graphs as the vertices and edges are labelled. in network science, methodological advances permit research to quantify other topological properties of complex systems, such as modularity [4], hierarchy [5], centrality [6] and the distribution of network hubs [7,8]. there have also been significant efforts to form the development or evolution of complex networks [9], to link network topology to network dynamics, and to explore network robustness and vulnerability. these topics are likely to become more relevant in relation to behavioural studies. structural and functional behaviour maps can be created using graph theory through the following four steps: 1. define the network nodes. 2. estimate a continuous measure of association between nodes. 3. generate an association model by compiling all pairs of associations between nodes and usually apply a threshold to each element of this model to produce a binary adjacency matrix or undirected graph. 4. calculate the network parameters of interest in this graphical model of the behaviour network and evaluate them against the equivalent parameters of a population of random networks. the elements such as defined network nodes, relationship of nodes, generated association matrix and network parameters give the basis of the behaviour type of “blueprint” of a user. a mobile user can be defined as an identity based on certain features of this behavioural “blueprint” as the key points of a fingerprint within the enterprise company. in fig.3 the darker highlighted edges could be the essential elements for the identifier. access to resource driven networks is defined in the graph theory as a set of nodes or vertices and the edges or lines, plus the connections between them. the graph topology can be quantitatively captured by a wide variety of measures used to generate the key points of the blueprint. the most important measurement is the node degree. the degree of a node is the number of 82 connections it links to the rest of the network. based on this definition, it is the most elementary network measure, and most other measures are ultimately linked to the node degree. the degrees of all the network’s nodes identified form a degree distribution [10]. in randomly selected networks all of the connections are equally probable, i.e. the result is a gaussian distribution. however, complex networks in general have non-gaussian distributions, often with a long tail towards higher degrees. the degree distributions of the scale-free networks follow a power law [11]. this landmark study [11] was the first to describe the scalefree organization of many complex networks and proposed a simple growth rule for their formation. the number of connections could give a large graph network that could be used for usability needs to define clustering, coefficients, and motifs. if the nearest neighbours of a node are also directly linked to each other, they form a cluster, and the clustering coefficient quantifies the number of connections that subsist between the nearest neighbours of a node as a quantity of the maximum number of possible connections [12]. the randomly selected networks exhibit low average clustering, whereas compound networks displays high clustering. interactions between neighbouring nodes can also be counted by counting the occurrence of small motifs of interconnected nodes [13]. the distribution of different motif classes (nodes efl and kmj in fig.3) in a network provides information about the types of local interactions that the network can support [14]. the numbers of reachable nodes and hops needed for connectivity are defined by the path length and efficiency. the path length is the minimum number of edges that must be passed through to start moving from one node to another. random, complex networks have short mean path lengths; they exhibit high global efficiency of parallel information transfer, whereas regular patterns exhibit long mean path lengths. efficiency is inversely related to path length. nevertheless it is numerically easier to estimate topological distances between elements of disconnected graphs. moreover, the link density or cost of the route provides further description. the connection density is the actual number of the network edges in the graph as a proportion of the total number of possible edges and is the simplest estimator of the physical cost of the network. hubs are nodes of high degree, where the centrality of a node measures how many of the shortest paths exist between all other node pairs in the network passing through it. it can be asserted that nodes with high centrality are thus crucial to efficient communication [15]. the importance of an individual node to network effectiveness can be assessed by deleting it and estimating the efficiency of the severed network. the robustness property refers either to the structural integrity of the network following the deletion of nodes, edges or effects of perturbations on local or global network states. finally, modularity is the property that has significant influence on the “blueprint” of the behaviour. there are algorithms that estimate the modularity of the network on the basis of hierarchical clustering [16]. each module contains several densely interconnected nodes, and there are relatively few connections between these nodes in different modules. airline hubs described this as a function of their roles in community structure [17]. provincial hubs are connected mainly to nodes in their modules where the connector hubs are connected to nodes in other modules. graph based analysis of smartphone usage previously, the challenges of using mobile devices in the enterprise environment were discussed. it is important to identify the activities on the device in order to take either preventive or corrective actions. g(v, e) used for the behaviour identification and description graphs. vertices are defined as applications, more precisely, vertices within the device or network addresses and sites. edges are the connections between the vertices applications called websites, network addresses, useror process-initiated connections. • network nodes can be defined as the resource access, i.e. applications, programs, and device elements access initiated by the user or application calls. • association between network nodes could be defined as the connections of the applications (calls, connections, as web access), usually resources are connecting together. • based on the above elements, network nodes and associations provide the details to calculate the association matrix. • the following steps include network parameter analysis calculated from the above. the question is not whether mobile activity can be defined as a complex network and describable by graph, but whether the process identies a user by a motif. however, before this question can be answered certain challenges need to be faced: • identify motifs as maximum independent set, • search motif in the complex network, • define „approved behaviours” according to the identification of user behaviour. figure 3: an example of a mobile user’s identity on the basis of a “blueprint” network 83 identification of the motif in the graph the task is to find the maximum independent set (mis) of a particular graph as was defined by garey and johnson [18] as np-complete and remains so even for bounded degree graphs. according to feige et al. [19] mis cannot be approximated even within a factor of |v|1 − o(1) in polynomial time. the greedy algorithm (gmis) can provide a solution for the identification of the maximum independence set. the algorithm selects a vertex of minimum degree, deletes that vertex and all of its neighbours from the graph, and repeats this process until the graph becomes empty. a recent detailed analysis of the gmis algorithm has shown that it produces reasonably good approximations of the mis for boundedand lowdegree graphs defined by halldorsson and radhakrishnan [20]. in particular, for a graph g with a maximum degree δ and an average degree !, the size |i| of the mis satisfies eq.(1). |!| ≤ min! ∆!! ! |gmis ! |, !!!! |gmis ! | (1) where |gmis(g)| is the size of the approximate mis found by the gmis algorithm. eq.(1) provides an upper-bound of the number of edge-disjoint embeddings of a particular sub-graph, and will use this bound to obtain a computationally tractable problem formulation that is guaranteed not to miss any sub-graphs that can potentially be frequent. searching for a discover motif in the graph the grochow-kellis method [21] can be used to find all examples of sub-graphs of a given size, similar to exhaustive methods. in the background, all nonisomorphic graphs are generated of a particular size using mckay’s tools [22]. then for each graph, the method evaluates its significance. due to symmetries, a set sub-graph of g may be mapped to a set query graph h multiple times. therefore, a simple mapping-based search for a query graph will locate every case of the query graph as many times as the graph has symmetries. to avoid this, the method computes and enforces several symmetry-breaking conditions, which ensure that there is an exclusive map from the query graph h for each case of h in g, so that the search only spends time finding each instance once isomorphicextensions (f,h,g[,c(h)]: finds all isomorphic extensions of partial map f : h → g [satisfying c(h)] start with an empty list of isomorphism. let d be the domain of f. if d=h, return a list consisting solely of f. (or write to disk.) let m be the most constrained neighbour of any d � d (constrained by degree, neighbours mapped) for each neighbour n of f (d) if there is a neighbour d � d of m such that n is not neighbours with f(d), or if there is a non-neighbour d � d of m such that n is neighbours with f(d) [or if assigning f (m)=n would violate a symmetrybreaking condition in c (h)], then continue with the next n. otherwise, let f=f on d, and f (m)=n. find all isomorphic extensions of f. append these maps to the list of isomorphism. return the list of isomorphism the symmetries of a graph h equals automorphism (self-isomorphism). the collection of automorphism of h is indicated by aut(h). for a set a of automorphism, two nodes are stated to be “a-equivalent” if there is some automorphism in a which maps one to the other, or just “equivalent” if a =aut(h). given a set of conditions c, α preserves the conditions c if, given a labelling l1 of h which satisfies c, the corresponding labelling l2: h → z given by l2(n) = l1(α(n)) also satisfies c. we are thus searching for setting c, such that the only automorphism preserving c is the identity. this ensures exactly one map from h onto each of its instances in g to satisfy the conditions. to find these conditions, an aut(h)-equivalence class {n0, ..., nk} of nodes of h, and the condition l(n0) < min (l(n1), ..., l(nk)) imposed. any automorphism must send n0 to one of the ni, since these are all of the nodes equivalent to n0. however to preserve this state, an automorphism must send n0 to itself. then the process continues recursively, replacing aut(h) with set a of automorphisms that send n0 to itself. because findsubgraphinstances starts with a particular node that node can be considered already fixed. the main reasons for the selection of the grochow and kellis method are summarized as follows: • capable of finding more significant motifs by enabling exhaustive discovery of motifs up to seven nodes. to find even larger motifs, the method samples a connected subgraph, and then finds all its occurrences and assesses their significance using this method. this practice has enabled the algorithm to find motifs of up to fifteen nodes and examine subgraphs of up to thirty-one nodes; • capable of quering a particular subgraph by querying whether a particular subgraph is significant; • capable exploring motif clustering; because the algorithm finds all occurrences of a given subgraph, it can be used to examine how these cases cluster together to form larger structures; • time and space applied to all subgraphs of a set size, takes exponentially a smaller amount of time than previous methods, even when implementing the previous method with the hashing scheme. conclusions apparently the current policy enforcement solutions are not sufficient because they mainly focus on policy compliance based on the response of the device. the installation of malicious applications could alter the mobile devices response (jailbreak on ios or android 84 and software imitating a response to the mdm server) taking to more serious security issues. similarly to the recently identified malware oldboot.b, which can install malicious applications in the background, it can inject malicious modules into the system process that prevents malware applications from uninstalling. oldboot.b can change the browser setup (set a new and unwanted home page), and it also can uninstall or disable installed mobile antivirus software, and even steal data such as credit card information or any other critical data. this malware is especially dangerous as it implements evasion techniques to stay undetected. in order to optimize current threat detection, which is also in line with business requirements, additional and different methodologies are required such as user identification based on the blueprint of the behaviour of the user. to create a working model of the graph-based user identification, several tasks await completion. the running tasks are the edges started by the system or user defined as the connections between them. once the complex network and graph are set up the motif can be identified with a greedy algorithm and search of the global graph with the grochow-kellis algorithm. in order to have a behaviour-based decision making system, all of the above algorithms will be tested to further develop the behaviour-based system. references [1] amaral l.a.n., scala a., barthelemy m., stanley h.e.: classes of small-world networks, proc. natl acad. sci. usa 2000, 97, 11149–11152 [2] amaral l.a.n., ottino j.m.: complex networks. augmenting the framework for the study of complex systems, eur. phys. j. b 2004, 38, 147– 162 [3] barabási a.l., oltvai z.n.: network biology: understanding the cell’s functional organization, nature rev. genet. 2004, 5, 101–113 [4] girvan m., newman m.e.j.: community structure in social and biological networks. proc. natl acad. sci. usa 2002, 99, 7821–7826 [5] ravasz e., barabási a.l.: hierarchical organization in complex networks, phys. rev. e stat. nonlin. soft matter phys. 2003, 67, 026112 [6] barthélemy m.: betweenness centrality in large complex networks, eur. phys. j. b 2004, 38, 163– 168 [7] guimera r., amaral l.a.n.: functional cartography of complex metabolic networks, nature 2005, 433, 895–900 [8] guimera r., mossa s., turtschi a., amaral l.a.: the worldwide air transportation network: anomalous centrality, community structure and cities’ global roles, proc. natl acad. sci. usa 2005, 102, 7794–7799 [9] kashtan n., alon u.: spontaneous evolution of modularity and network motifs, proc. natl acad. sci. usa 2005, 102, 13773–13778 [10] amaral l.a.n., scala a., barthelemy m., stanley h.e.: classes of small-world networks, proc. natl acad. sci. usa 2000, 97, 11149–11152 [11] barabási a.l., albert r.: emergence of scaling in random networks, science 1999, 286, 509–512 [12] watts d.j., strogatz s.h.: collective dynamics of “small-world” networks, nature 1998, 393, 440–442 [13] amaral l.a.n., ottino j.m.: complex networks. augmenting the framework for the study of complex systems, eur. phys. j. b 2004, 38, 147– 162 [14] barabási a.l., oltvai z.n.: network biology: understanding the cell’s functional organization. nature rev. genet. 2004, 5, 101–113 [15] freeman l.c.: a set of measures of centrality based on betweenness, sociometry 1977, 40, 35– 41 [16] girvan m., newman m.e.j.: community structure in social and biological networks. proc. natl acad. sci. usa 2002, 99, 7821–7826 [17] guimerà r., mossa s., turtschi a., amaral l.a.: the worldwide air transportation network: anomalous centrality, community structure and cities’ global roles. proc. natl acad. sci. usa 2005, 102, 7794–7799 [18] garey m.r., johnson d.s.: computers and intractability: a guide to the theory of npcompleteness. new york: w. h. freeman and company, 1979 [19] feige u., goldwasser s., lovasz l., safra s., szegedy m.: approximating clique is almost np complete, proc. 32nd ieee symposium on foundations of computer science (focs), 1991, 2–12 [20] halldorsson m.m., radhakrishnan j.: greed is good: approximating independent sets in sparse and bounded-degree graphs, algorithmica, 1997, 18(1), 145–163 [21] grochow j.a., kellis m.: network motif discovery using subgraph enumeration and symmetry-breaking, computer science and ai laboratory, m.i.t. broad institute of m.i.t. and harvard, 2007 [22] mckay b.d.: isomorph-free exhaustive generation, j. algorithms, 1998, 26, 306–324 hungarian journal of industry and chemistry veszprém vol. 42(2) pp. 85–89 (2014) measurement-based modelling and simulation of a hydrogen generating dry cell for complex domestic renewable energy systems attila göllei,! péter görbe, attila magyar, and lászló neukirchner department of electrical engineering and information systems, university of pannonia, egyetem u. 10., veszprém, 8200, hungary !e-mail: golleia@almos.uni-pannon.hu nowadays, the growing need for energy from renewable sources and growing revulsion towards fossil and nuclear fuels puts sustainable and green energy in the limelight. producing (electrical) energy in domestic power plants from renewable sources (mainly solar and wind) hardly results in difficulties, but the storage of energy not consumed immediately is a great engineering challenge. in the present paper a complex model has been developed by investigating renewable energy sources, the surplus energy not actually consumed and stored in electrical vehicle (ev) batteries, the conversion to hydrogen for storage purposes and how the main grid is fed. a measurement-based model of a hydrogen generating cell developed for the simulation of complex energetic systems. the parameter estimation of the static model was based on the collected measurement data coming from the detailed examination of a built demonstration cell. the novel element of this work is the matlab simulink model for the hydrogen generation cell. using this model, a dynamic simulator of a complex domestic power plant is made available using renewable energy sources and hydrogen generation cells. hydrogen generation enables the lossless long-term storage of surplus electric energy collected, but not consumed or injected into the low voltage grid. the generated hydrogen can be consumed for transportation purposes in suitable vehicles or it can be applied in fuel cells generating direct electrical energy for energy-deficient low voltage network situations. energetic situations potentially occurring in practice were simulated in our complex model. simulations showed that the presented model is suitable for domestic scale low voltage complex energetic systems. keywords: hydrogen generation, renewable energy sources, domestic power plants, modelling and simulation, measurement-based modelling introduction producing hydrogen gas (h2) from excess energy is not a new idea. this is an alternative way to store and convert renewable energy for further utilization. the produced hydrogen can be stored or used in power cells to be converted back to electric energy or in vehicles for hydrogen propulsion [1]. although the described procedure is efficient and able to produce a high quantity of h2 it is not suitable for application in combination with domestic power plants. the most relevant from of h2 production is when the energy consumption and quantity of produced h2 are controlled. when power consumption and generation are continuous (and not necessarily deterministic) functions of time, the h2 production depends solely on the excess energy of the grid. the best solution is the usage of supervisory control and data acquisition systems (scada) of management [2]. the domestic applicability of this technology in the future depends on the cost of scada system installation. producing hydrogen and oxygen gases from water using electricity in a laboratory is a simple electrochemical process that can be performed easily and in a very demonstrative way. producing hydrogen on a large scale or in industrial quantities calls for an optimized or near-optimized cell model. in an energy demanding process only a few percent of variance in efficiency could mean a significant energy surplus or shortage [3]. the electrochemical parameters of a dry cell (fig.1) that are used here are discussed to simulate hydrogen and oxygen gas production. compared to wet oxyhydrogen (hho) cells where the entire unit is underwater, the plates of dry cells are separated with rubber seals. these seals stop the water from leaking from the cell. the electrical connections and edges of figure 1: the theoretical setup of a dry hho block 86 the plates do not touch the electrolyte. these parts of the unit stay dry, thus the name dry cell. to make sure the gas made from the electrolyte gets out of the cell and the solution flows between the plates, there are holes on the top (for the gas) and bottom (for the electrolyte) on the metal slats (fig.1). the application of dry hho units has two main advantages. the surface of the dry cell plates enables one to use smaller amounts of electrolyte compared to with wet cells; therefore, the volume and weight of the cell is smaller. furthermore, the connectors of dry cells remain dry, i.e. they do not corrode unlike to wet cells, where the connectors are underwater therefore their surface slowly corrodes [4]. electrochemical foundations electrochemical cells can be considered as galvanic batteries where the electrochemical reactions are supported by an external current supply. they are composed of two electrodes and a conductive electrolyte fluid. if the electrode material does not participate directly in the electrode reaction, it is called an indifferent electrode (e.g. graphite). during electrolysis, if there is more than one possible type of electrochemical reaction, then a simple anion will detach from the positive anode (e.g. chloride), without this anion, howill be created by water splitting. the dissolution voltage of water is 1.23 v at 25 °c, the temperature coefficient is -0.85 mv/k, which means that at 100 °c this voltage decreases to 1.17 v. therefore, in the light of these data, the specific energy demand to make hydrogen via electrolysis at 25°c can be calculated from eqs.(1–4). the amount of charge needed to evolve 1 kg of h2 gas is q = zfm = 2⋅96487⋅0.5 = 96487 a s mol-1 = = 26801 ah kg-1 (1) wh2 = qemf = 26801⋅1.23 = 32966 wh kg-1 (2) since the volume of 1 kg of standard state h2 is 12474 dm3, the amount of energy required to produce 1 dm3 of h2 gas is: wh2 = 32966 12474 = 2.64 wh dm−3 (3) to generate 1 dm3 of hydrogen gas, 1.5 dm3 of hho gas is needed and thus the energy demand of producing 1 ldm3 of hho gas (0.667 dm3 h2) is: wh2(hho) = 0.667⋅2.64 = 1.76 wh dm-3 (4) the unit has been measured at 10 different electrolyte concentrations, using different currents. at the same time, the voltage on the plates and amount of gas produced by electrolysis has also been measured. the hho cell unit the setup of one block of the unit is shown in fig.2. usually five cells make up one block giving one gasproducing block. the block’s electrical connections are on the ends of two plates (fig.1). four of the six electrode plates are neutral electrodes, as there is no voltage connected to them. the potential is divided between the neutral plates according to voltage division in series connections. it means that the voltage between two electrodes is one fifth of the voltage on one whole block. in the experiment, a unit with three blocks connected in parallel has been used. besides the hho cell, a water reserve tank to infuse the electrolyte into the cell was necessary. a tube between the gas outlet and the tank has also been installed since due to bubbling, electrolyte comes out of the tube that needs to be recycled back into the system. then, as the electrolyte drips back into the tank, the gas can escape into the bottle through another hose. the produced h2 volume and the production speed are measured with this bottle. a power supply (manson sps9600) has been connected to the electrical connections of the hho unit, in this way the input current was controlled (table 1). matlab model of the dry cell the model of the dry cell considered was implemented in matlab simulink using the simpowersystems toolbox. two unknown functional relationships between the generated h2 volume, the cell current and the koh concentration and between cell voltage, cell current and koh concentration were approximated using fourth and third order polynomials, respectively figure 2: the setup of a hho gas generator cell block table 1: experimental results electrolyte concentration, g dm-3 mmwa, cm3 min-1 w-1 gas production, dm3 min-1 power of unit, w 1 2.13 0.20 10.8 2 2.66 0.75 34.4 3 2.66 1.37 55.8 4 2.59 1.51 82.2 5 2.72 1.90 90.6 6 2.63 2.52 119.5 7 2.67 2.96 140.0 8 2.65 2.76 125.0 9 2.46 2.28 105.6 10 1.82 2.15 103.2 a millilitres per minute per watt 87 using the matlab surface fitting tool. as the fitted polynomials do not have a physical connection to the given device, the model is applicable to any similar electrochemical h2 generation device with an electric two-pole system. in the different linear and non-linear physical and chemical models different coefficients become dominant. the voltage relationship is given by eq.(5), where icell denotes the cell current and ckoh stands for the koh concentration. parameters can be found in table 2. ucell(icell,ckoh) = p00 + p10 icell + p01 ckoh + p20 icell 2 + p11 icellckoh + p02ckoh 2 + p30icell 3 + p21icell 2 ckoh (5) the volume of the generated h2 is given by eq.(6). h2 (icell,ckoh ) = p00 + p10 icell + p01 ckoh + p20 icell 2 + p11 icellckoh + p02 ckoh 2 + p30 icell 3 + p21 icell 2 ckoh + p12 icellckoh 2 + p03 ckoh 3 + p40 icell 4 + p31 icell 3 ckoh +p22 icell 2 ckoh 2 + p13 icellckoh 3 (6) table 3 and figs.3-4 show representative results for the model. as expected, the h2 generation speed decreases and the cell finally stops working as the amount of water decreases and the koh concentration increases. a simulink block scheme of the cell model is depicted in fig.5. this simulink model was validated by considering a system with the same parameters as the layout of the experimental cell. in this layout, we ran a simulation for 24 h using this model, decreasing water and increasing koh concentrations. the results of this simulation can be seen in fig.6. it can be seen that the hydrogen gas generated is reduced because of the rising koh concentration. the exact values are in good agreement with our measurements. dry cell model in complex energetic systems the model for h2 generating cells described in the previous section was investigated in the matlab simulink simulation environment that studies the energy flow conditions of a complex energetic system consisting of a renewable source with a gridtable 2: coefficients of the polynomial relationship describing the cell voltage value value value p00 1.429 p10 0.2548 p01 -0.1226 p20 -0.008571 p11 -0.01191 p02 0.008257 p30 0.0001141 p21 -8.76e-05 p12 0.0009697 table 3: coefficients of the polynomial relationship for the generated h2 gas value value value p00 -0.1695 p10 0.1687 p01 -0.01765 p20 -0.007486 p11 -0.03234 p02 0.03446 p30 -0.0001077 p21 0.00412 p12 -0.004094 p03 -0.004061 p40 -4.269e-06 p13 6.169e-05 p22 -0.0005518 p13 0.0009544 figure 3: simulation of the cell model with a constant current of 5 a for 1 day figure 4: generated h2 as a function of koh concentration and dry cell current figure 5: matlab simulink model of the hho cell. the functional blocks implementing eqs.(5) and (6) are denoted by different background colours figure 6: simulation of a cell model with a constant current of 5 a for 1 day 88 synchronized inverter, a low voltage grid, an intermediate voltage controller [3,5] and a lithium ion battery. we replaced the lithium ion battery in this cell model, which reduces the potential energy flow modes, because this cell can only adsorb current for storing energy in hydrogen production. it cannot reverse the electrochemical process for electrical energy generation from hydrogen gas. the structure of the system can be seen in fig.7, where it is apparent that the cell model is connected directly only to the grid-synchronized inverter module of the system. the system depicted in fig.7 operates in different discrete states according to the energy flow direction. four cases can be defined: • normal inverter mode: the energy flows from the renewable source to the grid only (fig.8a). • normal inverter and hydrogen generation mode: the energy flows from the renewable source to both the dry cell and the grid (fig.8b). • hydrogen generation only mode: the energy flows from the grid to the dry cell only (fig.8c). • distortion reduction only mode: the energy flows from the grid into the intermediate capacitance and from the intermediate capacitance into the grid. the energy balance is zero for a period, and the active power is zero (fig.8d). model verification was performed by changing the energy flow modes in subsequent time intervals, and this was implemented by changing the energy balance of the system with outer current loads (iouter load). the different values for the simulations as parameters can be figure 7: simulink model of a complex energetic system with an hho cell model inside figure 8: complex energetic system energy flow modes: a: normal inverter mode, b: inverter and hydrogen generator mode, c: hydrogen generation only mode, d: distortion reduction only mode 89 seen in table 4. the simulation results are shown in fig.9, where uconn is the effective value of the voltage at the connection point, ihho is the current value of the dry cell, vh2 is the volume of generated hydrogen gas, ckoh is the koh concentration of the electrolyte and vwater is the volume of water inside the cell system. these values are plotted as a function of time. the results of the simulation show that the behaviour of the simulated electronic two-pole system is identical to that of the measured database. conclusion we developed a complex model to investigate renewable energy sources, for the conversion of surplus energy to hydrogen gas for storage and to represent how a main grid is fed. we built a measurement-based model of a hydrogen-generating cell for the simulation of complex energy systems in matlab simulink environment. we estimated the parameters of the model based on measurements collected during the detailed examination of a demonstration cell. we carried out a series of experiments on a hho gas producing dry cell to find the optimal electrolyte concentration, current value, etc. or change the setup by altering the distance between the plates with koh electrolyte solution. we monitored the experimental setup in several regards, for example cell voltage, and gas production. the novel element is the temperature and concentration dependent matlab simulink model of the hydrogen generation cell, which was found to be suitable for simulation purposes. we tested it in a simulation of a complex domestic power plant using a renewable energy source and hydrogen generation cell. hydrogen generation enables the long-term storage of surplus electrical energy collected, but not consumed or injected into the low voltage grid. the generated hydrogen can be consumed by vehicles for transportation purposes or it can be applied in fuel cells generating direct electrical energy for energy-deficient low voltage network situations. we simulated all the potential energetic situations in this complex model of an energetic system. the simulations showed that the presented model of a hydrogengenerating cell performed well. acknowledgement we acknowledge the financial support of this work by the hungarian state and the european union under the tamop-4.2.2.a-11/1/ konv-2012-0072 project. references [1] koutsonikolasa d.e., kaldisa, s.p., pantoleontosb, g.t., zaspalisac, v.t., sakellaropoulosc, g.p.: techno-economic assessment of polymeric, ceramic and metallic membranes integration in an advanced igcc process for h2 production and co2 capture, chem. engng. trans. 2013, 35, 715-720 [2] ziogoua c., elmasidesb c., papadopoulouca s., voutetakisa s.: supervisory control and unattended operation of an off-grid hybrid power generation station with hydrogen storage chem. engng. trans. 2013, 35, 529-534 [3] görbe p., magyar a., hangos k.m.: line conditioning with grid synchronized inverter's power injection of renewable sources in nonlinear distorted mains, proc. 10th international phd workshop on systems and control, 2009, 978-980 [4] al-rousan a.a.: reduction of fuel consumption in gasoline engines by introducing hho gas into intake manifold, int. j. hydrogen energy, 2010, 35, 12930-12935 [5] görbe p., magyar a., hangos k.m.: thd reduction with grid synchronized inverter’s power injection of renewable sources, proc. 20th int. symp. power electronics, electrical drives, automation and motion (speedam) 2010, 13811386 figure 9: simulation results of a complex energetic system using a cell model short time range (5 sec) advertise upcoming meetings, conferences, workshops, new products or services; make public announcements, introduce your research laboratory on the pages of the hungarian journal of industry and chemistry please contact us if interested! editorial office: university of pannonia p.o. box 158, veszprém h-8201 (hungary) tel.: +36 (88) 624-746, e-mail: hjic@almos.uni-pannon.hu; web: hjic.mk.uni-pannon.hu felelős szerkesztő: szilágyi róbert károly, phd kiadja: pannon egyetem, 8200 veszprém, egyetem u. 10. levélcím: h-8201 veszprém, postafiók 158, tel.: (88) 624-000 felelős kiadó: a pannon egyetem, mérnöki kar dékánja hungarian journal of industry and chemistry veszprém vol. 42(2) pp. 91–95 (2014) quasi-polynomial representation-based control of mechanical systems lászló neukirchnerb and attila magyar department of electrical engineering and information systems, university of pannonia, egyetem u. 10., veszprém, 8200, hungary be-mail: neu.groszber@gmail.com a simple kinematic model of a differential steering mobile robot is investigated using a nonlinear technique based on the quasi-polynomial representation of the dynamical model. dynamical systems can be embedded in the generalized lotka-volterrs (or quasi-polynomial) form under mild conditions. quasi-polynomial systems are good candidates for a general nonlinear system representation, since their global stability analysis is equivalent to the feasibility of a linear matrix inequality. the stabilizing quasi-polynomial state feedback controller design problem is equivalent to the feasibility of a bilinear matrix inequality. the classical stabilizing state feedback problem for quasi-polynomial systems was extended with the ability of tracking time-dependent reference signals. it is shown that the stabilizing quasi-polynomial controller design is equivalent to a bilinear matrix inequality. the results are applied to the model of the differential steering mobile robot. the goal reaching quasi-polynomial controller is shown to be a special kind of proportional state feedback. keywords: quasi-polynomial, robotics, differential drive robot, control systems, kinematics, lotka-volterra system introduction trajectory and goal tracking of mobile robots is an intensively studied field of modern robotics as well as modern control theory. several papers deal with an adaptive output feedback approach [1]. on the other hand some groups try to apply neural network-based methods for the task [2]. another direction is to describe the problem as an optimal control problem and apply optimal control results for it [3]. the class of quasi-polynomial (qp) systems plays an important role in the theory of nonlinear dynamical systems because nonlinear systems with smooth nonlinearities can be transformed into quasipolynomial form ref.[4]. this means, that any applicable method for quasi-polynomial systems can be regarded as a general technique for nonlinear systems [5]. the aim of this work is to widen the applicability of the quasipolynomial representation-based methods to the class of mechanical systems, more precisely to mobile robots. the goal reaching problem of a differential steering mobile robot is reformulated as a globally stabilizing feedback design problem in the quasi-polynomial framework. basic notions differential drive mobile robot kinematics the chosen mechanical system is the kinematic model of a two wheeled differential drive mobile robot eq.(1). the model deals with the geometric relationships that govern the system. it calculates the motion without considering the affecting forces. the system’s states are the cartesian coordinates x, and y and the orientation ✓ of the mobile robot. the basic kinematic model of the differential drive robot is given by ˙✓ = r 2a (!left � !right) ẋ = r 2 cos(✓)(!left + !right) ẏ = r 2 sin(✓)(!left + !right), (1) where a is half the shaft’s diameter, r is the radius of the wheels and ! is the angular velocity of the right or left wheel. to order the robot to reach a specific goal, it is acceptable to design a proportional controller to govern the expected trajectory eq.(2) [6] . in this case, the model is modified to calculate the state errors between the ordered and the present value. the new error model with proportional gain is ẋ = kv(edis cos(✓)� x(t)) ẏ = kv(edis sin(✓)� y(t)) ˙✓ = kh(eang � ✓(t)) edis = q (xg � x(t))2 + (yg � y(t))2 eang = arctan ✓ 2 yg � y(t) xg � x(t) ◆ , (2) where kv is the velocity control gain, kh is the rotational velocity control gain, edis is the distance error, eang is the 92 angular error, and xg, yg are the cartesian coordinates to reach. quasi-polynomial representation of nonlinear systems some basic notions of quasi-polynomial and lotkavolterra systems are summarised in this section. generalised lotka-volterra form representing an ode in generalised lotka-volterra (glv) form can increase the structural simplicity in exchange for increasing its dimension. the glv or quasipolynomial (qp) form: ẋ i = x i ✓ � i + mp i=1 a ij · nq k=1 x bij k ◆ , i = 1, . . . , n, m � n (3) where a and b are n ⇥ m, m ⇥ n real matrices, and � 2 rn is a vector. the set of non-linear odes can be embedded into qp form if it meets two requirements: (i) the non-linear odes should follow this form: ẋ s = p is1...isn,js a is1...isn,jsx is1 1 . . . xisn n f(x̄)js , x s (t0) = x0 s , s = 1 . . . n (4) where a is1...isn,js✏r, s = 1 . . . n, and f(x̄) is some scalar function which cannot be reduced to quasy-monomial form. (ii) the partial derivatives of the system eq.(4) should fulfil: @f @x s = p es1...esn,es b es1...esn,esx es1 1 . . . xesn n f(x̄)es , (5) where b es1...esn,es✏r, s = 1 . . . n. by embedding, we introduce the new auxiliary variable: y = fq nq s=1 xps s . q 6= 0 (6) differentiating the new, substituted equations we get the qp representation of the original equation eq.(4): ẋ s = x s 2 4 x is1...isn,js ⇣ a is1...isnjsy js/q ny k=1 xisk��sk�jspk/q !# , s = 1 . . . n (7) where � sk = 1 if s = k and 0 otherwise. a new additional dimension appears as the ode of the new variable y: ẏ = y " x is1...isn,js ✓ p s x�1 s ẋ s + + x is↵,js es↵,es a is↵,jsbis↵,jsqy (es+js�1)/q ⇥ ⇥ ny k=1 x isk+esk+(1�es�js)pk k ◆# . ↵ = 1 . . . n (8) it is important to mention that the new ode is not unique because we can choose the parameters p s and q. the quasi-monomial transformation is defined as: x i = nq k=1 xcik k , i = 1 . . . n (9) where c is an arbitrary invertible matrix. the matrices of glv can be modified as ˆb = b · c, ˆa = c�1 · a, and ˆ� = c�1 ·�, and the transformed set is also in glv form. lotka-volterra models the above family of models is split into classes of equivalence according to the values of the products m = ba and n = bl. the lotka-volterra form gives the representative elements of these classes of equivalence. if rank(b) = n, then the set of odes in eq.(3) can be embedded into the following m-dimensional set of equations, the so-called lotka-volterra model: ż j = z j n j + mx i=1 m ji z i ! , j = 1, . . . ,m (10) where m = ba, n = bl, and each z j represents a so-called quasi-monomial: z j = ny k=1 y bjk k , j = 1, . . . ,m. (11) input-affine qp model the well known input-affine model of nonlinear systems is given in the following state space model: ẋ = f(x)+ pp j=1 gj(x)uj where f 2 rn ! rn, and gj 2 rn ! rn are qp functions and the input variable u is p-dimensional. in 93 figure 1: membership functions for angular error this case we need a qp form with the matrices from the glv form ode set: ẋ i = x i 0 @� i + mx j=1 a0 ij ny k=1 x bjk k 1 a + + px l=1 x i 0 @µ li + mx j=1 c lij ny k=1 x bjk k 1 au l . i = 1 . . . n (12) it can be proven that if u = h(x) state feedback is in qp form, the closed-loop system remains in qp form as well, but the quasi-monomials of the system will be greater, than the system’s without the feedback. global stability analysis global equilibrium points can be obtained by finding a lyapunov function v (·). for lv systems there is a well known lyapunov function family: v (z) = mx i=1 c i ✓ z i � z⇤ i � ln z i z⇤ i ◆ , c i � 0, i = 1 . . .m (13) and the time derivative: ˙v z = @v (z) @z · @z @t = = 1 2 (z � z ⇤ )(c m +m t c)(z � z ⇤ ), (14) where z ⇤ = (z⇤1 . . . z ⇤ m ) t is the unique positive equilibrium point, c = diag(c1, . . . , cm) and m is the invariant coefficient matrix of the lv form. if cm t +m c is negative semi-definite then z ⇤ is stable and if negative definite then z ⇤ is asymptotically stable. the global stability analysis is thus equivalent to the linear matrix inequality cm t +m c  0 c > 0. (15) the presented lyapunov function eq.(13) can be extended to glv systems by embedding the system using the lv coefficient matrix m = ba. it is necessary to solve the lmi system eq.(15) for the stability analysis of the qp and lv system: ✓ c 0 0 �cm t �m c ◆ > 0 (16) controller design in quasi-polynomial representation the globally stabilizing qp state feedback design problem for qp systems can be formulated as follows [7]. consider arbitrary quasi-polynomial inputs in the form: u l = rx i=1 k il q̂ i , l = 1 . . . , p (17) where q̂ i = q̂ i (y1, . . . , yn), i = 1, . . . , r are arbitrary quasi-monomial functions of the state variables of the system and k il is the constant gain of the quasi-monomial function q̂ i in the l-th input u l . the closed-loop system will also be a qp system furthermore, the closed-loop lv coefficient matrix m̂ can also be expressed in the form m̂ = b̂ â = m0 + px l=1 rx i=1 k il mil. (18) then the global stability analysis of the closed-loop system with unknown feedback gains k il leads to the following bilinear matrix inequality m̂ t c +cm̂ = m0 t c +cm0+ px l=1 rx i=1 k il ⇣ mil t c +cmil ⌘  0. (19) the variables of the bmi are the p ⇥ r k il feedback gain parameters and the c j , j = 1, ..,m parameters of the lyapunov function. if the bmi above is feasible then there exists a globally stabilizing feedback with the selected structure. quasi-polynomial control of a differential drive mobile robot quasi-polynomial representation of the kinematic model with the given differential drive robot model eq.(1) and the explained error model eq.(2) the qp representation can be built. the fist step as mentioned, is to find the new auxiliary variables, that help to eliminate the non-qp expressions. the newly chosen auxiliary variables are: ↵ = cos(✓), � = sin(✓), � = arctan ✓ 2 yg � y xg � x ◆ , � = (xg � x)2 + (yg � y)2, and ✏ = p � + (xg � x). (20) 94 �2 0 2 4 6 0 2 4 6 start finish x [m] y [ m ] pid qp fuzzy figure 2: comparison of different controllers by substituting them into the original system eq.(2) and performing the differentiation of the new equations eq.(20): ẋ = x kv p �↵ x �kv ! ẏ = y kv p �� y �kv ! ˙✓ = ✓ ✓ kh� ✓ �kh ◆ ↵̇ = ↵ ✓ �� ↵ ◆ ˙� = � ✓ ↵ � ◆ (21) �̇ = �· ⇣ � 2kv� p � �✏ + kvy �✏ �kvxg� �✏ + kvx� �✏ + kvxgy �✏ p � �kvxy �✏ p � + kvyg↵ �✏ �kvy↵ �✏ �kvygx �✏ p � + kvxy �✏ p � ⌘ (22) ˙� = � ⇣ � 2kvxg↵p � + 2kvxgx � + 2kvx↵p � � 2kvx 2 � � 2kvyg�p � + 2kvygy � + 2kvy�p � � 2kvy 2 � ⌘ (23) ✏̇ = ✏ ⇣ �kvxg↵ ✏ + kvx↵ ✏ + kvxgx ✏ p � �kvx 2 ✏ p � �kvyg� ✏ + kvy� ✏ + kvygy ✏ p � �kvy 2 ✏ p � + kv↵ ✏ �kvx ✏ p � ⌘ (24) figure 3: membership functions for distance error the closed-loop qp system eq.(21-24) has 29 quasimonomials. x : ↵ p �x�1 y : � p �y�1 ✓ : �✓�1 ↵ : �↵�1 � : ↵��1 � : � p ���1✏�1, y��1✏�1, ���1✏�1, x���1✏�1, y��1��1/2✏�1, ↵��1✏�1, y↵��1✏�1, x��1��1/2✏�1 � : ↵��1/2, x��1, x↵��1/2, x2��1, ���1/2, y��1, y���1/2, y2��1 ✏ : ↵✏�1, x↵✏�1, x✏�1��1/2, x2✏�1��1/2, �✏�1, y�✏�1, y✏�1��1/2, y2✏�1��1/2, (25) the qp system eq.(21-24) can obtain the glv form invariants with the help of monomials. these matrices are: a the coefficient matrix, b the exponential matrix and � the constant’s matrix. the invariant matrix product ba results in the lv coefficient matrix m , which is necessary for the global stability analysis. controller design as the original model eq.(2) already contains the proportional controller parameters kh and kv, they naturally appear in the qp and lotka-volterra forms, respectively. the closed-loop lotka-volterra coefficient matrix m contains the proportional gains in a linear manner eq.(26) [7] m = m0 +kh mh +kv mv, (26) where m 2 r29⇥29. this means, that the globally stabilizing feedback design bmi can be formulated, and checked for feasibility. the controller design is practically solved as a control-lyapunov function-based state feedback. the prescribed lyapunov function parameters are c1,2,3 = 0.1, c4,5 = 1 and c6�29 = 0. the control gains are obtained by solving an lmi version of the feedback design bmi by substituting c into eq.(19). the obtained values are kh = 2.78 and kv = 0.8. 95 table 1: rules for the fuzzy controller ^ ^ eang edis !left !right zero zero ) zero zero pos zero pos neg zero neg pos zero pos pos pos pos pos pos zero pos zero pos comparison of results for different controller types the first and most basic method was the proportional controller approach. this was explained in the second chapter. this is a more systematic approach, but with the increasing non-linearities it is becoming a more difficult method to solve. fig.3 shows that the robot moves on a significantly wider curve compared to the other two designs. secondly a fuzzy controller was designed to compare the original design to. this is a much more intuitive approach, the physical nonlinearities were easily implementable with the cost of inaccuracy. this can be seen in fig.3, where the robot travels on a much smaller curve. table 1 shows the definition of the rules. the membership functions follow simple triangular shapes according to the acceptable rate of angular and velocity changes. the qp controller performance can be seen in fig.3. where a classical pid controller and a fuzzy logic controller are also shown. it is apparent, that the qp controller performs well by means of the length of the trajectory. conclusions a quasi-polynomial representation-based nonlinear control design method has been applied to the kinematics of a differential steering mobile robot in this work. it has been shown, that the quasi-polynomial model of the mobile robot’s kinematics extended with the tracking error dynamics has 29 quasi-monomials, i.e. the sizes of matrices appearing in the bilinear matrix inequality that should be solved for a globally stabilizing feedback controller acknowledgement this research was supported by the european union and the state of hungary, co-financed by the european social are reasonably great. the resulting controller and the trajectory were compared to the trajectories of a reference pid controller and a fuzzy logic controller. it can be seen that the controller performs satisfactorily. possible future directions include the application of the lmi and /or bmi cost function to introduce some optimality measure to the problem to be minimised. a next step would be the application of a time dependent goal position (i.e. a trajectory). fund in the framework of the támop 4.2.4. a/2-11-12012-0001 ’national excellence programme’. references [1] huang j., wen c., wang w., jiang z.-p.: adaptive output feedback tracking control of a nonholonomic mobile robot, automatica, 2004, 50(3), 821– 831 [2] mohareri o., dhaouadi r., rad a.b.: indirect adaptive tracking control of a nonholonomic mobile robot via neural networks, neurocomputing, 2012, 88, 54–66 [3] li j., guo x., li z., chen w.: stochastic adaptive optimal control of under-actuated robots using neural networks, neurocomputing, 2014, 142, 190-200 [4] hernández-bermejo b., fairén v.: nonpolynomial vector fields under the lotka-volterra normal form, phys. lett. a, 1995, 206, 31–37 [5] magyar a., fodor a.: quasi-polynomial control of a synchronous generator, hung. j. ind. chem., 2013, 41(1), 55–61 [6] tzafestas s.g.: mobile robot control i: the lyapunov-based method, in introduction to mobile robot control (tzafestas s.g., ed.) elsevier, oxford, 2014, 137–183 [7] magyar a., szederkényi g., hangos k. m.: globally stabilizing feedback control of process systems in generalized lotka-volterra form, j. proc. contr., 2008, 18(1), 80–91 advertise upcoming meetings, conferences, workshops, new products or services; make public announcements, introduce your research laboratory on the pages of the hungarian journal of industry and chemistry please contact us if interested! editorial office: university of pannonia p.o. box 158, veszprém h-8201 (hungary) tel.: +36 (88) 624-746, e-mail: hjic@almos.uni-pannon.hu; web: hjic.mk.uni-pannon.hu felelős szerkesztő: szilágyi róbert károly, phd kiadja: pannon egyetem, 8200 veszprém, egyetem u. 10. levélcím: h-8201 veszprém, postafiók 158, tel.: (88) 624-000 felelős kiadó: a pannon egyetem, mérnöki kar dékánja hungarian journal of industry and chemistry veszprém vol. 42(2) pp. 97–101 (2014) a network model for simulating the dynamic behaviour of an energy distribution network levente bálint,1! tibor dulai,2 ágnes stark-werner,2 gergely apostol,1 and ádám tompos1 1 faculty of information technology, university of pannonia, egyetem u. 10., veszprém, 8200 hungary !e-mail: balintlevente.z@gmail.com 2 department of electrical engineering and information systems, faculty of information technology, university of pannonia, egyetem u. 10., veszprém, 8200 hungary the aim of this paper is to present the planning and implementation of a network model for an energy distribution network for simulating its dynamical behaviour. the model includes different types of energy sources, distribution centres and consumers. the prepared simulation environment makes it possible to add/remove/modify any type of node – to/form/in the model. other actions that may be carried out are the initiation/termination of an energy source or change to its production level. the main goal of the simulation is to investigate the effect of an immediate event (such as a power plant failure, decreased production, etc.) on the network and search for the most appropriate substitute possible. the search may happen either on cost bases or time bases. the system created is based on web technology, any user is able to create/save/load his own model and do simulations on it. this work serves as a basis for further work, which involves more complex electrical knowledge and possibilities regarding the network. keywords: energy distribution network, energy sources, dynamical behaviour, network model, simulation introduction energy efficiency has an increasing importance due to costand environment-related factors. at the same time, the customer demands have to be satisfied. these circumstances result in a largely heterogeneous energy producing and distributing environment. renewable energy is applied to a considerable degree in addition to the electricity produced by traditional power plants [1]. this resulted in a system, where different types of energy sources – with different properties, like cost, response time, etc. – are applied in a mixed way. it is a non-trivial task to decide, which sources to apply even in the case of pre-determined demands. moreover, in practice the amount of the demand appears only when needed. earlier efforts implemented simulation environments for analysing the effect of the hybrid manner of an electric network [2, 3]. however, the problem becomes more complex when an immediate negative event happens, e.g. an energy source becomes unavailable or has to decrease its output suddenly. the optimal answer depends on many factors: e.g. how quickly a new energy source can be applied or how much it will cost. moreover, some types of energy sources are only able to produce discrete levels of output power. this paper describes a web-based system, which makes it possible to create and modify an energy distribution network (including different types of energy sources and customers, too) with the goal of simulating different immediate events. the requirements to be collected and the network model and its elements are introduced, followed by details of the implementation and simulation. requirements: the desired properties of the system functional requirements include mainly the creation and manipulation of network models and simulations. fig.1 presents the possible applications of the system. the interface contains a tree graph-based model whose root is the power source, the inner nodes are the network stations and the leaves are the consumers. the graph’s edges are the connections between the components. there are multiple projects in the system, each project contains a model. the main functions of the system are available through the modeling and simulation interfaces. during the simulation the components can be switched on and off. after two hours of simulation a statistic diagram can be viewed for each component of the model, showing its consumption or production. information about components can be edited while the system is not simulating. next to the functional requirements, the system-related requirements are that: • the system has to be web-based, • no user authentication is needed, • the reaction time is less than 1 s, even if there are 100 users, and • any system or communication failure has to be presented by an unambiguous alert to the user. 98 the interface the interface of the system contains four important elements. on the upper edge is the modelling control bar with the component adding buttons, background theme switcher and save/load buttons. by pressing the load button, the system opens the project selector. the save button must be pressed before loading another project in order to save the current one. under the right side of the control bar, there is the simulation control panel. there are buttons on it for editing corporate and residential priority orders, and sliders for the importance of certain properties while calculating the priority order of the power sources. there are buttons for starting, stopping, and restarting simulation time. the simulation time begins at 6:00 am and the step time can be set from 1 to 60 minutes. in the bottom left-hand corner, the event-log is located, which indicates the basic events like start/stop simulation, add/remove components in black and important events like system failure or insufficient power in red. all events have a time-stamp. while hovering the mouse over a component, the system shows the detailed properties of the element. double clicking selects a component or deletes a connection. while a component is selected, the edit, delete and diagram buttons appear in the modelling control bar. the diagram button works only after a minimum of two hours of simulation. in simulation mode the modelling control bar is hidden and double clicking switches a component on/off. the network model and its elements as the system’s main potential is in handling different types of network nodes and making the investigation of a heterogeneous energy producing and distribution system possible, the elements of the network models and their properties have a huge role. the network nodes can be classified as follows. energy sources the system considers renewable energy sources (water, bio, wind, solar, and geo), non-renewable energy sources (natural gas, petrol, coal, nuclear), and quick start-up energy sources (gas turbines) when the energy provided by power plants is insufficient for consumers. each energy source has a unique name and a maximum output, which defines an upper limit for the source (fig.2). a minimum output is defined as a lower limit, below that the operation is not profitable. start-up cost is the cost needed to switch on the source, and starttime is the time required to start producing energy. the operational cost is a financial value which is needed for one hour of operation. power sources have an environmental multiplier. this multiplier is 1 for renewable sources, 0.2 for non-renewable ones and 0.1 for quick start-up sources by default, but it can be edited any time during the modelling. larger values are better, the maximum is 1 but the value cannot be 0. the system calculates an order between sources from their start-up cost, operational cost and environmental multiplier. this order can be modified by the user before starting the simulation. distributing elements distributing elements for the system are power plant stations that distribute the energy to multiple network stations that further distribute the energy to retail stations directly transmit the energy to consumers. distributing stations have only two properties (fig.3). they have a unique name to identify them and a maximum throughput, which is the maximum power that the station can distribute to lower stations or consumers. if that limit is reached the station will not pick up more power even if the consumers need more. figure 1: example uses of the prepared system figure 3: edit station properties (név: name or location, teljesítmény: power) figure 2: edit power source properties (név: name or location, bekapcsolási költség: cost of starting up, indítási idő: start-up time, üzemköltség: operational cost, környezeti szorzó: environmental factor, optimális sorrend: optimal order) 99 consumers the residential consumers are linked to the model through homes, while corporate consumers include factories, public institutions, etc. consumers have a rate of consumption that describes their maximum required power. current consumption is estimated during the daytime in the simulation. consumers also have an order of priority that can be modified by the user but corporate consumers always have priority over residential consumers (fig.4). connections connections have a length property, which will be used for calculating the loss, dissipated by the cables resistance. networks can be built up by the previously introduced network nodes by connecting them appropriately. the order of connectivity is as follows: • power sources, • power plant distribution station, • network distribution station, • retail distribution station, and • consumer. connections can be established only in this order regardless of the performance of individual components. database and implementation details properties of the network model elements and the network formed are stored in an associative array that can be used directly by the system. at each time it is saved, this array is stored in javascript object notation (json) format in a text file for each project separately. the database array contains an entry for all components of the model. every component has an id, a name, a type and position on the modelled field. energy sources also have a fuel type, start-up time, start-up cost, running cost, environmental factor, and minimum and maximum performance level attributes. stations have a defined maximum tolerance. for consumers, there is a stored average consumption rate, which dynamically changes over time. each object has a sub-array, which stores the id of any other components that are connected to the current one. consumer objects have priority numbers that define the relevance of the consumer. if the power source cannot produce enough energy to satisfy all needs, then the consumer that has the highest priority number will be switched off from the network. the priority order equals the order of creation of components, but the corporate consumers always have preference. the order can be changed by the user any time in modelling mode and during the simulation. implementation details the program is implemented in javascript language with plug-ins like jquery and jsplumb. the plug-in jquery is the most popular extension of the javascript language. it makes it easier to select, move, remove or modify the elements on the interface by selecting the element by its id and modifying its properties. the system uses an in-house jquery plug-in, windows.js. this plug-in creates free movable small windows on the interface and fills them with appropriate content defined by the programmer. the jsplumb plug-in is an opensource plug-in for javascript, created to visually connect elements on the interface with straight lines or bezier curves. the database is stored in json format text files, created and edited by hypertext preprocessor (php) functions and called asynchronously by javascript’s asynchronous javascript and xml (ajax) protocol. php is a server-side scripting language, but in our case its only function is to properly save and load database files to the server computer. the whole software can be started in a browser on the user’s computer and it connects to the server only while loading or saving the project. the interface is fully interactive, in modelling mode the objects can be moved or removed, in simulating mode switched on and off. simulation possibilities the system was created for simulating immediate events during the operation of a modelled energy distribution network. after forming the network, the software makes it possible to cause different immediate events. these severe a connection or switch on/off sources, stations and/or consumers. all of these events can be carried out on the graphical interface of the software (fig.5). the simulation is daytime-based. it starts at 6:00 am. users can set the step time from 1 min or sec to 60 min or sec. at the beginning the system distributes the energy produced by the power plant(s) to all consumers in a user defined order. if a power plant does not produce enough power then the last consumer will be switched off and so on. the electricity-related behaviour will be implemented in the future into the software. a possible solution is to build an ideal flow model as a cooperative game over a graph with the sources and consumers located at the nodes, each described by a maximum supply or desired demand and the power lines figure 4: edit consumer properties (név: name or location, fogyasztás: consumption, prioritás: priority) 100 represented by the edges, each with a given power transmission capacity and admittance value describing their ability to transmit electricity. [4] the user is able to initiate immediate events and the system reacts to them in real-time and recalculates the distribution. calculation of the consumption rate is based on the hungarian average with a small random factor. an example for a simulation let us assume that we have a power plant with a maximum power of 100 kw. the model has one of each type of stations, three households (10-10 kw maximum) and a factory (80 kw maximum) (fig.6). normally, all of the consumers are satisfied, but in the peak times, when the factory and the houses also approach their maximum consumption, the power will not be enough for every consumer, so the system switches off the retail consumer that is last in the priority order. there will not be a consumption reduction, but a complete shutdown. subsequently, the plant will have to produce 95% of the maximum power. in this example all of the stations can transfer the maximum of 100 kw, but if a station cannot transfer this, then the consumer with the largest priority number connected to this station will be switched off, regardless of the current level of the power source. if the consumption is too high, it is possible that complete distribution stations are switched off. further developments the current system can model and simulate a fictional power network with components and connections, but the main goal of the project is to create a simulating software that can model and simulate a real electrical network. it is important to emphasize that the unit of the power of the sources and the consumption are now only kw. we need to include that the voltage of connection cables depends on the length of the connection and the diameter of the cable that are required to calculate the amperage from the resistance of the cable. international connections transmit 750 kv, and the main network in hungary transmits 400 kv starting from the power plants (fig.7). the distribution stations transform and divide it to lower values until the voltage reaches the necessary 250 v for retail and 360 v (or more) for corporate consumers. during the transformations, the system needs to use kirchhoff’s current law that states that at any node in an electrical circuit, the sum of currents flowing into that node is equal to the sum of currents flowing out of that node. that means that the system has to calculate amperages for every incoming and outgoing connection of the distribution stations based on the consumption of the consumers and the target voltage of the cables. the biggest problem of power distribution networks in reality is to satisfy all consumers at all the time, even if the load is very low, without making large changes to the output of the power sources everyday. the current solution in hungary is nighttime power. households using electric water heaters have nighttime electric meters, when the consumption of corporate consumers is drastically reduced. this solution slightly optimizes the operation of power plants. figure 5: the graphical interface of the software (új erőmű: new powerplant, új fogyasztó: new consumer, új állomás: new station, új kapcsolat: new connection, mentés: save, betöltés: load, lakossági sorrend: order of households, céges sorrend: order of companies, maxköltség: maximum cost, környezet: environment, bekaps: start-up, indulás: begin, indítás: start, leállítás: stop, újraindítás: restart figure 6: the model of our example (méter: distance in m) 101 conclusion this paper presented the planning phase and implementation of a web-based system that makes it possible to construct an energy distribution network together with different types of energy sources and consumers. the simulations are carried out to determine the most effective response to different immediate events (e.g. a sudden network problem or failure of an energy source). the simulation takes into account both cost-related and time-related properties, too. the present state of the software provides a basis for further works, which intend to add deeper electricity-related properties and behaviour to the system. acknowledgement the authors are thankful for scientific guidance by prof. katalin m. hangos from the computer and automation research institute. we acknowledge the financial support of the hungarian state and the european union under the tamop-4.2.2.a11/1/konv-2012-0072 project. references [1] breitner m.h.: modeling the transformation of the german energy system until 2050: a multi-criteria, long term optimization problem with many constraints, operations res. proc. 2012, 369-374 [2] geysen d., booiy p., warmer c.: a framework for simulation and control of hybrid energy networks, proc. energycon 2014, dubrovnik, croatia, 2014 [3] padulles j., ault g.w., mcdonald j.r.: an integrated sofc plant dynamic model for power systems simulation, int. j. power sources 2000, 86, 495-500 [4] csercsik d., kóczy l.á.: externalities in the games over electrical power transmission networks, iehas discussion papers, 2011, no 1125 figure 7: the hungarian transmission network advertise upcoming meetings, conferences, workshops, new products or services; make public announcements, introduce your research laboratory on the pages of the hungarian journal of industry and chemistry please contact us if interested! editorial office: university of pannonia p.o. box 158, veszprém h-8201 (hungary) tel.: +36 (88) 624-746, e-mail: hjic@almos.uni-pannon.hu; web: hjic.mk.uni-pannon.hu felelős szerkesztő: szilágyi róbert károly, phd kiadja: pannon egyetem, 8200 veszprém, egyetem u. 10. levélcím: h-8201 veszprém, postafiók 158, tel.: (88) 624-000 felelős kiadó: a pannon egyetem, mérnöki kar dékánja hungarian journal of industry and chemistry veszprém vol. 42(2) pp. 103–107 (2014) on the parametric uncertainty of weakly reversible realizations of kinetic systems györgy lipták b1, gábor szederkényi1,2 and katalin m. hangos1,3 1process control research group, mta sztaki, kende u. 13-17, budapest, 1111, hungary 2faculty of information technology, péter pázmány catholic university, práter u. 50/a, budapest, 1083, hungary 3department of electrical engineering and information systems, university of pannonia, egyetem u. 10, veszprém, 8200, hungary be-mail: lipgyorgy@gmail.com the existence of weakly reversible realizations within a given convex domain is investigated. it is shown that the domain of weakly reversible realizations is convex in the parameter space. a lp-based method of testing if every element of a convex domain admits weakly reversible realizations is proposed. a linear programming method is also presented to compute a stabilizing kinetic feedback controller for polynomial systems with parametric uncertainty. the proposed methods are illustrated using simple examples. keywords: parametric uncertainty; computational methods; optimization; kinetic systems introduction the notion of parametric robustness is well-known and central in linear and nonlinear systems and control theory [1]. it is used for ensuring a desirable property, such as stability, in a given domain in the parameter space around a nominal realization having the desired property. the aim of the paper is to extend the notions and tools of parametric robustness for a class of positive polynomial systems, namely a class of kinetic systems. only the very first steps are reported here that offer a computationally efficient method for checking one of the many important properties of kinetic systems, their weak reversibility. basic notions and methods the basic notions and tools related to reaction kinetic systems and their realizations are briefly summarized in this section. kinetic systems, their dynamics and structure deterministic kinetic systems with mass action kinetics or simply chemical reaction networks (crns) form a wide class of non-negative polynomial systems, that are able to produce all the important qualitative phenomena (e.g. stable/unstable equilibria, oscillations, limit cycles, multiplicity of equilibrium points and even chaotic behaviour) present in the dynamics of nonlinear processes [2]. the general form of dynamic models studied in this paper is the following ẋ = m · (x), (1) where x 2 rn is the state variable and m 2 rn⇥m. the monomial vector function : rn ! rm is defined as j(x) = ny i=1 x yij i , j = 1, . . . ,m (2) where y 2 nn⇥m 0 . the system eq.(1) is kinetic if and only if the matrix m has a factorization m = y ·ak. (3) the kirchhoff-matrix ak has non-positive diagonal and non-negative off-diagonal elements and zero column sums. the matrix pair (y,ak) is called the realization of the system eq.(1). the chemically originated notions: the chemically originated notions of kinetic systems are as follows: the species of the system are denoted by x1, . . . , xn, and the concentrations of the species are the state variables of eq.(1), i.e. xi = [xi] � 0 for i = 1, . . . , n. the structure of kinetic systems is given in terms of its complexes ci, i = 1, . . . ,m that are non-negative linear combinations of the species i.e. ci = pn j=1[y ]jixj for i = 1, . . . ,m, and therefore y is also called the complex composition matrix. the reaction graph: the weighted directed graph (or reaction graph) of kinetic systems is g = (v,e), where 104 v = {c1, c2, . . . , cm} and e denote the set of vertices and directed edges, respectively. the directed edge (ci, cj) (also denoted by ci ! cj) belongs to the reaction graph if and only if [ak]j,i > 0. in this case, the weight assigned to the directed edge is ci ! cj is [ak]j,i. stoichiometric subspace: stoichiometric subspace s is given by the span of the reaction vectors s = {[y ]·i � [y ]·j | [ak]ij > 0}. (4) the stoichiometric compatibility classes of a kinetic system are the affine translations of the stoichiometric subspace: (x0 + s) \ rn �0. structural properties and dynamical behaviour it is possible to utilize certain structural properties of kinetic systems that enable us to effectively analyze the stability of the system. deficiency: there are several equivalent ways to define deficiency. we will use the following definition � = dim(ker(y ) \ im(bg)), (5) where bg is the incidence matrix of the reaction graph. it is easy to see that deficiency is zero if ker(y ) = {0} or equivalently rank(y ) = m. weak reversibility: a crn is called weakly reversible if whenever there exists a directed path from ci to cj in its reaction graph, then there exists a directed path from cj to ci. in graph theoretic terms, this means that all components of the reaction graph are strongly connected components. deficiency zero theorem: a weakly reversible kinetic system with zero deficiency has precisely one equilibrium point in each positive stoichiometric compatibility class that is locally asymptotically stable (conjecture: globally asymptotically stable). computing weakly reversible realizations formulated as an optimization problem in this section, first a method for computing weakly reversible realization based on ref.[3] is briefly presented. we assume that we have a kinetic polynomial system of the form eq.(1). we use the fact known from the literature that a realization of a crn is weakly reversible if and only if there exists a vector with strictly positive elements in the kernel of ak, i.e. there exists b 2 rn + such that ak · b = 0 [4]. since b is unknown, too, this condition in this form is not linear. therefore, we introduce a scaled matrix ãk ãk = ak · diag(b) (6) where diag(b) is a diagonal matrix with elements of b. it is clear from eq.(6) that ãk is also a kirchhoff matrix and that 1 2 rm (the m-dimensional vector containing only ones) lies in kernel of ãk. moreover, it is easy to see that ãk defines a weakly reversible network if and only if ak corresponds to a weakly reversible network. then, the weak reversibility and the kirchhoff property of ãk can be expressed using the following linear constraints mx i=1 h ãk i ij = 0, j = 1, . . . ,m mx i=1 h ãk i ji = 0, j = 1, . . . ,m h ãk i ij � 0, i, j = 1, . . . ,m, i 6= j h ãk i ii  0, i = 1, . . . ,m. (7) moreover, the equation eq.(3) is transformed by diag(b) (we can do this, because diag(b) is invertible): m · diag(b) = y ·ak · diag(b)| {z } ãk (8) finally, by choosing an arbitrary linear objective function of the decision variables ãk and b, weakly reversible realizations of the studied kinetic system can be computed (if any exist) in a lp framework using the linear constraints eq.(7) and (8). weakly reversible crn realizations in this section, first the convexity of the weakly reversible kirchhoff matrix will be shown. after that the practical benefits of this property will be demonstrated in the field of system analysis and robust feedback design. convexity of the weak reversibility in the parameter space theorem 1. let a (1) k and a (2) k be m ⇥ m weakly reversible kirchhoff matrices. then the convex combination of the two matrices remains weakly reversible. proof. the idea behind the proof is based on ref.[5]. a kirchhoff matrix is weakly reversible if and only if there is a strictly positive vector in its kernel. therefore strictly positive vectors p1, p2 exist such as a(1) k · p1 = 0 and a (2) k · p2 = 0. let us define the following scaled kirchhoff matrix: â(1) k = a (1) k · diag(p1) and â (2) k = a (2) k · diag(p2). these scaled matrices have identical structures to the original ones. moreover, â(1) k ·1(m) = 0 and â (2) k ·1(m) = 0 where the vector 1(m) denotes the m dimensional column vector composed of ones. for that (�â(1) k + (1� �)â(2) k ) · 1(m) = 0. (9) for any � 2 [0, 1]. therefore the convex combination of the original two realizations has to be weakly reversible. 105 (a) (b) (c) figure 1: a weakly reversible reaction graphs of the three realizations (y,a(1) k ), (y,a(2) k ) and (y,a(3) k ) weak reversibility of crn realizations with parametric uncertainty we assume that a crn with parametric uncertainty is given as ẋ = m · (x), (10) where x 2 rn is the state variable, 2 rn ! rm contains the monomials and the matrix m 2 rn⇥m is an element of the following set m = � lx i=1 ↵imi | (8i : ↵i � 0) ^ lx i=1 ↵i = 1 . (11) the goal is to find a method for checking the weak reversibility of the system eq.(10) for all matrices m 2 m. when all vertices mi have a weakly reversible realization (y,a(i) k ) then any element of the set m has a realization (y,ak) such that ak is the convex combination of the kirchhoff matrices a (i) k . the obtained realization ak will be weakly reversible due to theorem 1. therefore, it is enough to compute a weakly reversible realization for each matrix mi by using the previously presented lp-based method. a simple example let us consider the following polynomial system  ẋ1 ẋ2 � = m · 2 4 x1 x2 x1x2 3 5 , (12) where m is an arbitrary convex combination of the following three matrices m1 =  0 1 �1 1 �1 0 � , m2 =  �1 1 0 1 �1 0 � , and m3 =  0 1 �1 0 0 0 � . figure 2: a weakly reversible realization of the convex combination m = 0.2m1 + 0.4m2 + 0.4m3 in order to show weak reversibility for all possible convex combinations, we have to find a weakly reversible realization for each matrix m1, m2 and m3. the resulting weakly reversible reaction graphs are depicted in fig.1, while fig.2 illustrates an inner point realization which is weakly reversible too. computing kinetic feedback for a polynomial system with parametric uncertainty besides the possible application of the above described lp-based method for robust stability analysis, it can also be used for stabilizing feedback controller design. for this purpose, a generalized version of our preliminary work on kinetic feedback computation for polynomial systems to achieve weak reversibility and minimal deficiency [6] is used here. the feedback design problem we assume that the equation of the open-loop polynomial system with linear constant parameter input structure is given as ẋ = m · (x) +bu, (13) where x 2 rn is the state vector, u 2 rp is the input and 2 rn ! rm contains the monomials of the open-loop system. the input matrix is b 2 rn⇥p, the corresponding complex composition matrix is y with rank m, and m 2 rn⇥m is an element of the following set m = ( lx i=1 ↵imi | (8i : ↵i � 0) ^ lx i=1 ↵i = 1 ) . (14) moreover, a positive vector x 2 rn >0 being the desired equilibrium point is given as a design parameter. note that the above polynomial system is not necessarily kinetic, i.e. not necessarily positive, and may not have a positive equilibrium point at all. 106 the aim of the feedback is to set a region in the state space r ✓ rn �0 where x is (at least) a locally asymptotically stable equilibrium point of the closed-loop system for all m 2 m. for this purpose we are looking for a feedback in the form u = k (x) (15) which transforms the open-loop system into a weakly reversible kinetic system with zero deficiency for all m 2 m with the given equilibrium point x. feedback computation similarly to the realization computation, the matrix k will be determined by solving an lp problem. the convexity result shows that it is enough to compute one weakly reversible realization (y,a(r) k ) in each vertex mr to ensure weak reversibility for all possible closed-loop systems. all realizations will have zero deficiency, because of the rank condition rank(y ) = m [7]. first we note, that the realization (y,a(r) k ) that corresponds to the closed-loop system is mr +b ·k = y ·a(r) k . (16) where the matrix a (r) k should be kirchhoff mx i=1 [ãk]ij = 0, j = 1, . . . ,m [ãk]ij � 0, i, j = 1, . . . ,m, i 6= j [ãk]ii  0, i = 1, . . . ,m. (17) in order to obtain a weakly reversible closed-loop system with an equilibrium point x, the matrix a (r) k should be weakly reversible and has to have the vector (x) in its right kernel, i.e. a (r) k · (x) = 0. (18) finally, by choosing an arbitrary linear objective function of the decision variables a (1) k , . . . , a (l) k and k, the feedback gain k can be computed (if it exists) in a lp framework using the linear constraints eqs.(16-18). with the resulting feedback gain k, the point x will be an equilibrium point of all possible closed-loop systems, and x will be locally asymptotically stable in the region s = (x+s)\rn �0, where s is the stoichiometric subspace of the closed-loop system. example let the open-loop system be given as ẋ = m 2 4 x1x2 x2x3 x1 3 5+ 2 4 0 1 0 3 5 u (19) figure 3: weakly reversible realization of the closed-loop system, where m = 0.6m1 + 0.2m2 + 0.2m3 where m is an arbitrary convex combination of the following three matrices: m1 = 2 4 �1 1 0 2 1 2 1 �1 0 3 5 , m2 = 2 4 0 0 0 1 1 3 0 0 0 3 5 , and m3 = 2 4 0 1 �1 2 0 3 0 �1 1 3 5 . the desired equilibrium point x = [1 1 1]t . we are looking for a feedback law with gain k which transforms the matrices mi into weakly reversible kinetic systems with the given equilibrium point. by solving the feedback design lp optimization problem using the linear constraints eqs.(16-18), the computed feedback is in the following form: u = ⇥ 2 1 2 ⇤ (x). (20) fig.3 depicts a weakly reversible realization of the closed-loop system. the obtained closed-loop system in an inner point of the convex set m has the following stoichiometric subspace: s = span 0 @ 2 4 1 1 0 3 5� 2 4 0 1 1 3 5 , 2 4 1 1 0 3 5� 2 4 1 0 0 3 5 1 a . (21) therefore, the equilibrium point x will be asymptotically stable with the region s = (x+s)\rn �0. note, that one should choose the initial value of the state variables from s . fig.4 shows the time dependent behaviour of the closed-loop solutions started from different initial points in s . 107 figure 4: time-domain simulation of the closed-loop system conclusion it is shown in this paper that the domain of weakly reversible realizations is convex in the parameter space. this property is utilized for developing methods in system analysis and robust control design. an lp-based optimization method is proposed for testing if every element of a convex domain given by its extremal matrices admits a weakly reversible realization. an lp-based feedback design method is also proposed that guarantees stability with a desired equilibrium point. the proposed methods are illustrated with simple examples. references [1] siljak d.: parameter space methods for robust control design: a guided tour, aut. contr., ieee transactions on, 1989, 34(7), 674–688 [2] angeli d.: a tutorial on chemical network dynamics, eur. j. contr., 2009, 15, 398–406 [3] szederkényi g., hangos k. m., tuza z.: finding weakly reversible realizations of chemical reaction networks using optimization, match commun. math. comp. chem., 2012, 67, 193–212 [4] feinberg m., horn f.: chemical mechanism structure and the coincidence of the stoichiometric and kinetic subspaces, arch. rational mechanics and analysis, 1977, 66(1), 83–97 [5] rudan j., szederkényi g., hangos k.m., péni t.: polynomial time algorithms to determine weakly reversible realizations of chemical reaction networks, j. math. chem., 2014, 52(5), 1386–1404 [6] lipták g., szederkényi g., hangos k.m.: kinetic feedback computation for polynomial systems to achieve weak reversibility and minimal deficiency, 13th eur. control conf. ecc, strasbourg, france, 2014, 2691–2696 [7] angeli d., lenhee, p.d., sontag e.d.: on the structural monotonicity of chemical reaction networks, proc. 45th ieee conf. decision and control, 2006, 7–12 advertise upcoming meetings, conferences, workshops, new products or services; make public announcements, introduce your research laboratory on the pages of the hungarian journal of industry and chemistry please contact us if interested! editorial office: university of pannonia p.o. box 158, veszprém h-8201 (hungary) tel.: +36 (88) 624-746, e-mail: hjic@almos.uni-pannon.hu; web: hjic.mk.uni-pannon.hu felelős szerkesztő: szilágyi róbert károly, phd kiadja: pannon egyetem, 8200 veszprém, egyetem u. 10. levélcím: h-8201 veszprém, postafiók 158, tel.: (88) 624-000 felelős kiadó: a pannon egyetem, mérnöki kar dékánja hungarian journal of industry and chemistry veszprém vol. 42(2) pp. 109–113 (2014) stability and parameter sensitivity analyses of an induction motor attila fodor1, roland bálintb1, attila magyar1, and gábor szederkényi2 1department of electrical engineering and information systems, university of pannonia, egyetem u. 10., veszprém, 8200, hungary 2pazmány péter catholic university, práter u. 50/a, budapest, 1083, hungary be-mail: balint.roland27@gmail.com a simple dynamical model of an induction motor is derived and analyzed in this paper based on engineering principles that describe the mechanical phenomena together with the electrical model. the used state space model consists of nonlinear state equations. the model has been verified under the usual controlled operating conditions when the speed is controlled. the effect of load on the controlled induction motor has been analyzed by simulation. the sensitivity analysis of the induction motor has been applied to determine the model parameters to be estimated. keywords: induction motor, stability analysis, sensitivity analysis introduction induction motors (im) are the most commonly used electrical rotating machines in several industrial applications. irrespective of size and the application area, these motors share the most important dynamical properties, and their dynamical models have a similar structure. because of the specialties and great practical importance of ims in industrial applications, their modelling for control purposes is well investigated in the literature. besides basic textbooks [1-3], there are several papers that describe the modelling and use the developed models for the design of different types of controllers: vector control [1, 4], sensorless vector control [5] and direct torque control (dtc) [6]. the aim of this paper is to build a simple dynamical model of the im and to perform its parameter sensitivity analysis. the results of this analysis will be the basis of the next step since the final aim of our study is to estimate the parameters of the im and design a controller that can control the speed and torque of the im. the state space model has been implemented in the matlab/simulink environment which enables us to analyze the parametric sensitivity based on simulation experiments. nonlinear model of an induction motor in this section a state space model of an induction motor (im) is presented. the model development is largely based on refs.[1, 8-10]. for constructing the im model, the following modelling assumptions are made: 1. a symmetrical triphase stator winding system is assumed, 2. the flux density is radial in the air gap, 3. the copper loss and the slots in the machine can be neglected, 4. the spatial distribution of the stator fluxes and apertures wave are considered to be sinusoidal, 5. stator and rotor permeability are assumed to be infinite with linear magnetic properties. according to the above modelling conditions the mathematical description of the im is developed through the space-vector theory. if the voltage of the stator is presumed to be the input excitation of the machine, then the spatial distribution along the stator of the x phase voltage can be described by the complex vector v sx (t). we can determine the orientation of the voltage vector v s , the direction of the respective phase axis and the voltage polarity. i s (t) = 2 3 � a0 · i sa (t) + a1 · i sb (t) + a2 · i sc (t) � = p 2 · i e↵ (t) · ej!0t+⇡ 2 +' i , (1) where a is the ej120 o vector and i sa , i sb and i sc are the following: i sa (t) = re(a0 · i s (t)) = re(i s (t)), i sb (t) = re(a2 · i s (t)), and i sc (t) = re(a1 · i s (t)). in eq.(1), 2/3 is the normalizing factor. the flux density distribution can be obtained by integrating the current density wave along the cylinder of the stator. the flux linkage wave is a system variable, because it contains detailed information about the winding geometry. 110 figure 1: the equivalent circuit of the im the rotating flux density wave induces voltages in the individual stator windings. thus stator voltage v s (t) can be represented as the overall distributed voltages in all phase windings: v s (t) = 2 3 � a0 · v sa (t) + a1 · v sb (t) + a2 · v sc (t) � = p 2 · v e↵ (t) · ej!0t+⇡ 2 +' u , (2) where a is the ej120 o vector and i sa , i sb and i sc are the following: v sa (t) = re(a0 · u s (t)) = re(u s (t)), v sb (t) = re(a2 · u s (t)), and v sc (t) = re(a1 · u s (t)). considering the stator of the im as the primer side of the transformer, then using kirchoff’s voltage law the following equation can be written (fig.1): v s (t) = i s (t) ·r s + d� s (t) dt . (3) as for the secondary side of the transformer, it can be deduced that the same relationship is true for the rotor side space vectors: v r (t) = ir(t) ·rr + d� r (t) dt = 0. (4) eqs.(3) and (4) describe the electromagnetic interaction as the connection of first order dynamical subsystems: � s (t) = i s (t) · l s + i r (t) · l m , and (5) � r (t) = i s (t) · l m + i r (t) · l r . (6) since four complex variables (i s (t) , i r (t) , � s (t) , and � r (t)) are presented in eqs.(5) and (6), flux equations are needed to complete the relationship between them. the mechanical power (p mech (t)) of the im can be defined as: p mech (t) = w mech (t) dt , (7) where the mechanical energy (p mech (t)) in the rotating system can be given by the following expression: p mech (t) = w mech (t) dt = t mech (t) · ! r , (8) where t e (t) is the torque and ! r is the angular velocity of the im. afterwards the energy balance of the im is as follows: w e = w mech +w r +w field , (9) figure 2: the equivalent circuit of the d-axis of the im figure 3: the equivalent circuit of the q-axis of the im where p e = w e (t) dt = 3 2 re (u s · i s + u r · i r ) (10) is the input electrical power, p r = w r (t) dt = 3 2 re � r s · |i s |2 +r r · |i r |2 � (11) represents the resistive power losses and p field = w field (t) dt = 3 2 re ✓ d� s dt i s + d� r dt i r ◆ (12) is the air gap power. using eqs.(8-12), p mech (t) = t mech (t) · ! r = 3 2 · lm l r · � s (t)⇥ i s (t), and (13) t e = 1.5p · (� ds i qs � � qs i ds ). (14) the equivalent circuit of the im can be decomposed to direct axis and quadratic axis components by park’s transformation as shown in figs.2 and 3. the actual terminal voltage v of the windings can be written in the form v = ± jx j=1 (rj ij)± jx j=1 ✓ d�j dt ◆ , (15) where ij are the currents, rj are the winding resistances, and �j are the flux linkages. the positive directions of the stator currents point out of the im terminals. by composing the d and q axes of the im the following equations can be written: v qs = r s · i qs + � qs dt + ! · � ds , (16) v ds = r s · i ds + � ds dt � ! · � qs , (17) v qr = r0 r · i0 ds + �0 dr dt + (! � ! r ) · �0 dr , and (18) v dr = r0 r · i0 dr + �0 dr dt � (! � ! r ) · �0 qr . (19) 111 figure 4: response to the step change of the speed-controlled im d! m dt = 1 2h (t e � f · ! m � t mech ) (20) where ! is the reference frame angular velocity, ! r is the electrical angular velocity, � qs = l s · i qs + l m i0 qr , (21) � ds = l s · i ds + l m i0 dr , (22) � qr = l r · i0 qr + l m i0 qs , and (23) � dr = l r · i0 dr + l m i0 ds . (24) the above model can be written in state space form by expressing the time derivative of the fluxes and ! from the voltage and swing equations eqs.(21-24). the nonlinear state space model of the im is given by eqs.(25-29): d� qs dt = �r s l s � l2 m l0 r · � qs r s · l m l0 r (l s � l2 m l0 r ) · �0 qr � ! · � ds + v qs , (25) d� ds dt = �r s l s � l2 m l0 r · � ds + r s · l m l0 r (l s � l2 m l0 r ) · �0 dr � ! · � qs + v ds , (26) d�0 qr dt = �r0 r l m � l0 r·ls lm · � qs + �r0 r · l s l m · (l m � l0 r·ls lm ) · �0 qr � ! · �0 dr + ! r · �0 dr + v qr , (27) d�0 dr dt = �r0 r l m � l0 r·ls lm · � ds + �r0 r · l s l m · (l m � l0 r·ls lm ) · �0 dr + ! · �0 qr � ! r · �0 qr + v dr , and (28) d! r dt = 1 2h · 1.5 · p · l m l m · (l s � l2 m l0 r ) · �0 dr · � qs � 1 2h · 1.5 · p · l m l m · (l s � l2 m l0 r ) · �0 qr · � ds � f 2h · ! r � t m 2h . (29) the state vector of the above model is x=[� qs , � ds , �0 qr , �0 dr , ! r ]t 2 r5, and the input variables are organized in terms of the the input vector u=[v q , v d , �t mech ]t 2 r3. it is assumed that all the state variables can be measured i.e. y = x. model validation the dynamical properties of the im have been investigated. the response of the speed-controlled motor has been tested under step-like changes. the simulation results are shown in fig.4, where the fluxes (� qs , � ds , �0 qr , and �0 dr ) and the angular velocity (!) are shown. model analysis the above model eqs.(21-24) has been verified by simulation against engineering intuition. local stability analysis as the final aim of our research is to estimate the parameters of a particular grundfos im, first of all the resistances (r s and r r ) of the im were measured. afterwards the values of the inductances (l ls , l lr and l m ) and the mechanical parameters (h and f ) of a similar im with similar r s and r r found in the literature have been used. the parameters used during the model and the sensitivity analyses are the following: r s = 0.196 ohm r r = 0.0191 ohm l ls = 0.0397 h l lr = 0.0397 h l m = 1.354 h h = 0.095 f = 0.0548 p = 1 (30) 112 figure 5: the model state variables for a ±50% change of l m it can easily be seen that the im model is nonlinear since there are products of two state variables in the following equations: • eq.(27): �0 dr is multiplied by ! r • eq.(28): �0 qr is multiplied by ! r • eq.(29): �0 dr is multiplied by � qs • eq.(29): �0 qr is multiplied by �0 ds for the local stability analysis we have to calculate the eigenvalues of the system. the examined equilibrium point is � qs = �0.744 vs � ds = 1.0287 vs �0 qr = �0.174 vs (31) �0 dr = �0.087 vs ! r = 48.477 s�1 the numerical value of the jacobian of the nonlinear model (i.e. the state matrix of the locally linearized model) is as follows: 2 66664 �2.504 �50 2.4328 0 0 50 �2.504 0 2.4328 0 0.2370 0 �0.244 �1.522 0 0 0.2370 1.5222 �0.244 0 �8.617 17.077 0 0 �0.288 3 77775 . (32) the eigenvalues of the state matrix of the linearized systems are: � 1,2 = �2.504 ± j49.98, � 3,4 = �0.243 ± j1.534, and � 5 = �0.288 (33) figure 6: the model state variables for a ±50% change in r s it is apparent that the real parts of the eigenvalues are negative with small magnitudes. parameter sensitivity analysis the sensitivity of the nonlinear model to the mutual inductance has been investigated. the steady state value of the system variables does not change (as is apparent in fig.5) even for a considerably large change in l m . sensitivity analysis of the inductances l lr , l ls of the stator and rotor, resistances of the stator r s and the damping constant f has also been investigated. in this investigation it can be seen that the values of the state variables were changed a bit, as shown in fig.6. the analysis of the resistances of the rotor r0 r and the inertia h of the rotor showed that every value of the state variables changed significantly, as shown in fig.7. as a final result of the sensitivity analysis, we can define the following groups of parameters: • not sensitive: mutual inductance l m . since the state space model of interest is insensitive in this respect, the values of this parameter cannot be reliably determined from measurement data using any parameter estimation method. • sensitive: these sensitive parameters are candidates for parameter estimation. – less: inductances l lr and l ls , resistance of the stator r s and the damping constant f . – more: resistances of the rotor r0 r and the inertia h of the rotor. • critically sensitive: none. 113 figure 7: the model state variables for a ±50% change in h conclusion the simple nonlinear dynamical model of an im has been investigated in this paper. it has been shown that the model is locally asymptotically stable with regards to a physically meaningful equilibrium state. the effect of the controlled generator has been analyzed by simulation using a traditional pi controller. it has been found that the controlled system is stable and can follow the set-point changes. seven parameters of the model were selected for sensitivity analysis, and the sensitivity of the state variables has been investigated. as a result, the parameters were partitioned into three groups. based on the results presented here, a future aim is to estimate the parameters of the model for a real system from measurements. the sensitivity analysis enables us to select the candidates for estimation that are inductances l lr and l ls , resistances r s and r r , the damping constant f and the inertia h . an additional future aim is to develop a model for control purposes and investigate different controllers before applying them on real systems. acknowledgement we acknowledge the financial support of this work by the hungarian state and the european union under the tamop-4.2.2.a-11/1/konv-2012-0072 project. we acknowledge also the investigated im of grundfos hungary producer ltd. symbols c 1 , c 2 , c 3 constant f damping constant � qs and � ds q and d components of the stator flux �0 qr and �0 dr q and d components of the reduced rotor flux h inertia constant i qs and i ds q and d components of the stator current i0 qr and i0 dr q and d components of the reduced rotor current l m mutual inductance p number of pole pairs r r and l r rotor resistance and inductance r0 r and l0 r reduced value of rotor resistance and inductance r s and l s stator resistance and inductance v d and v q q and d components of the stator voltage ! angular velocity of the magnetic field ! r angular velocity of the rotor t mech mechanical torque references [1] vas p.: artifical-intelligence-based electrical machines and drives, oxford university press, 1999 [2] vas p.: sensorless vector and direct torque control. oxford university press, 1998. [3] zheng l., fletcher j.e., williams b.w. he x.: dual-plane vector control of a five-phase induction machine for an improved flux pattern, ieee transac. ind. elec., 2008, 55(5), 1996–2005 [4] levi e.: impact of iron loss on behavior of vector controlled induction machines, ieee transac. ind. appl., 1995, 31(6), 1287–1296 [5] hasegawa m., matsui k.: robust adaptive full-order observer design with novel adaptive scheme for speed sensorless vector controlled induction motors, proc. 28th annual conf. industrial electronics society, ieee 2002, 2002, 1, 83–88 [6] geyer t., papafotiou g., morari m.: model predictive direct torque control-part i: concept, algorithm, and analysis, ieee transac. ind. elec., 2009, 56(6), 1894–1905 [7] krause p.c., wasynczuk o., sudhoff s.d.: analysis of electric machinery, ieee press, new york, 1995 [8] mohan n., undeland t.m., robbins w.p.: power electronics: converters, applications, and design, john wiley & sons inc., new york, 1995 [9] hatos p., fodor, a., magyar a.: parameter sensitivity analysis of an induction motor, hung. j. ind. chem., 2011, 39(1), 157–161 advertise upcoming meetings, conferences, workshops, new products or services; make public announcements, introduce your research laboratory on the pages of the hungarian journal of industry and chemistry please contact us if interested! editorial office: university of pannonia p.o. box 158, veszprém h-8201 (hungary) tel.: +36 (88) 624-746, e-mail: hjic@almos.uni-pannon.hu; web: hjic.mk.uni-pannon.hu felelős szerkesztő: szilágyi róbert károly, phd kiadja: pannon egyetem, 8200 veszprém, egyetem u. 10. levélcím: h-8201 veszprém, postafiók 158, tel.: (88) 624-000 felelős kiadó: a pannon egyetem, mérnöki kar dékánja hungarian journal of industrial chemistry veszprem vol. 30. pp. 107112 (2002) the computer assisted synthesis for optimal heat exchanger network at styrene pol ymerisation r. diaconescu and r. z. tudose (technical university "gh. asachi" i~i, department of chemical engineering, b-dul d. mangeron no. 71a, 6600 ia~i, romania) received: november 07,2001 in this paper a synthesis of an optimal heat exchang~r network has b~e~ studi~d to re~lize the required thermal regime at styrene bulk polymerisation in a continuous operatwn. the synthesis is realized usmg a method based o~ the balance calculations, and supposes: the thermal balance over each chemical reactor, the heat exc~anger calculatwn~ and the determination of the optimal heat exchanger network. the calculation of the heat exchangers mvolves the selectwn of the exchanger type, the choice of the thermal agents and the cost calculation. the optimal heat e_xchan?er_network can be obtained by selecting the heat exchanger for each reactor, which corresponds to the technological cntenons and has the minimum total cost. key words: heat exchanger, network synthesis, styrene polymerisation, and thermal regime introduction the heat exchanger network synthesis has two main objectives: the determination of the maximum heat amount which can be recovered from process, respectively, the obtaining of the heat exchanger network realizing the minimum cost. the synthesis of the heat exchanger networks is the well-tested problem from those of the synthesis of different subsystems, like separation sequence synthesis or reactor systems. gundersen and n aess [ 1], in an ample detailed review, note more than 200 papers in this field. further, gundersen [2] is referring at 30 papers on the same topic. jezowski [3, 4] presents and analyses 142 works for the synthesis of heat exchanger networks. recently, some papers present synthesis methods for retrofitting flexible or multi-period heat exchanger networks [5] and, respectively, heat exchanger networks under uncertainty [6]. in order to systematize such a literature, the available synthesis methods of heat exchanger networks are classified in two groups: methods based on the balance calculation and methods using the optimising techniques. the methods using the optimising techniques solve the heat exchanger network synthesis problem like a formal optimising problem, by mathematical instruments, while the methods based on the balance calculation avoid the mathematical techniques and involve the knowledge of the problem. the thermodynamics laws and the logical judgments. in this work, a method based on balance calculation for synthesizing optimal heat exchanger networks is presented. the method is applied to the optimal heat exchanger network synthesis which realizes the required thermal regime at the styrene bulk polymerisation in a continuous operation. the optimal heat exchanger network, by its capacity and thermal regime, belongs to a system containing an optimal industrial reactor network. the realization of the pre-established thermal regime, during the styrene bulk polymerisation, is a very difficult problem, which is unsolved yet. the difficulty is due to a very complicated reaction system having a large number of reaction components and reactors. to those, the special behaviour of the polymer during polymerisation must be added, when the conversion and temperature is changing. the temperature increase complicates the problem because of strong exothermal reaction and its influence upon the polymer properties. from the above considerations, it results the necessity of an optimal system synthesis of heat exchangers to realize the required thermal regime for the polystyrene production. the synthesis algorithm supposes the thermal balance over each reactor, the calculation of the heat exchangers and the determination of the optimal h~t exchanger network. this algorithm was impl:mented ~n mathcad 2000 professional in the modelhng and m the optimisation of the heat exchangers, all required parameters have been established. the optimal heat 108 mv" pfr / fig.] reactor network for polystyrene production by bulk polymerisation exchanger network for the styrene polymerisation has been obtained taking into consideration the technical and economical criterions, the technical criterions are the most important. for given initial conditions and specified thermal regime, the optimal network contains five coil heat exchangers. the results of the system synthesis of heat exchangers attest the viability of the optimal reactor network obtained preliminarily for polystyrene production, in which the thermal regime problem was solved. problem formulation the optimal heat exchanger network has been synthesized on an optimal reactor network, obtained also by computer assisted synthesis [7]. this network is presented in fig.l. the considered reactor network represents an industrial system, it produces· 2000 polystyrene tones /year. the thermal regime is in the 80 oc 200 °c range, according to the production scale technologies [8, 9]. the reactor network for the styrene bulk polymerisation, in a continuous system, contains eight reactors, working in isothermal conditions, as follows: two continuous stirred tank reactors, cstrl and cstr2, with parallel connection, operate at 80°c. these provide the required capacity of the polymerisation system. other six plug flow reactors (pfr) provide the required conversion, of 97%, and 641 numerical average polymerisation degrees. these operate in isothermal conditions for temperatures of l 00°c for pfri and pfr2. 150°c for pfr3, 180°c for pfr4 and pfrs. and 200°c for pfr6. in the specified conditions.. the problem solved in this paper is formulated as follows: one gives the reaction mixture containing styrene, polystyrene and initiating agent~ each one having a specified initial temperature, the required exit temperature. the specific heat and the flow rate and. also, a set of thermal agents for beating and cooling and their properties ( entbalpies, working temperature). the heat exchanger network bringing the reaction mixture at desired temperature is synthesizing and the annual cost for operating and investment charge is minimizing. since the reaction mass follows a pre-established way by the reactor network, the heating or cooling is realized only with thermal agents who can be associated between them. synthesis algorithm the synthesis problem is decomposed in sub-problems treating each reactor with a distinct thermal regime. as long as, both of the continuous stirred tank reactors for pre-polymerisation (fig.j) work in the same condition regarding feed and temperature, it is enough a single calculation. also, the plug flow reactors working in the same conditions, in a series arrangement, it can be considered as a single reactor. thus, one treats together the plug flow reactors, pfrl and pfr2, working at 1 00°c, and pfr4 and pfrs working at 180°c. for each considered reactor, the design calculation of the heat exchangers realizes the required heat transfer using the available thermal agents. the agent can be at its first use or can be a thermal agent which was heated /cooled in other heat exchanger, by taking-up or transfer of the excess heat of the reaction mass from other reactor. from the above considerations, it results that the algorithm of the optimal heat exchanger network synthesis has the following steps; the effectuation of the thermal balance over each reactor in order to determine the needed heat to be transferred and the sense of the heat transfer leading to heating or cooling of the reaction mass. the calculation of the heat exchangers involving1:he selection of the heat exchanger and of the thermal agents, taking into account the technological characteristics of the polymerisation and the heat amount to be transferred. for the selected heat exchangers, one calculates the flow rate, the overall heat transfer coefficient, the heat transfer surface area and the coil length. ·finally, for one year operation (8000 hours), the cost of the heat exchangers and of the thermal agents is calculated. the determination of the optimal heat exchanger network consisting in the selection, for each reactor, of the heat exchanger which respects the technological criterions and has the minimum total cost (operating cost and investment charge). the obtained network by the interconnection of the selected heat exchangers is the network realizing the required thermal regime for a total minimum cost and, consequently, this is the optimal network. thermal balance over reactors the thermal balance has been realized over each reactor having a distinct thermal regime in the polymerisation system. one considers the steady state. the energy conservation law is: the amount of inlet heat plus the generated heat are equal to the outlet heat. 109 table 1 reactor network characteristics for polystyrene production by bulk polymerisation reactor inlet outlet conversion final position flow flow average concentration on rec.:ctor degree in conversion in the for for network reactor reactor m~i mvi cj,t cj,2 cp,o cp,l (vs) (vs) (movl) (movl) (movl) (movl) 3.9xl0·2 0.110 7.187 5.285xl0·3 9.69x1o-9 1.96xl0·5 2 3.9xl0·2 0.110 7.187 5.285xl0·3 9.69xl0·9 1.96xto·5 3 0.110 0.126 5.19 8.638xl04 6.875xl0·9 1.79xl0"5 4 0.126 0.141 4.25 3.99xto·5 5.515xto·9 1.655xl0·5 5 0.141 0.152 3.31 1.05x10-6 7.035x10·9 1.65xto·5 6 0.152 0.167 2.205 3.735xi0-10 7.12x1o·9 1.38x10·5 7 0.167 0.255 1.112 1.195xl0-9 7.07x10·9 1.375xl0·5 8 0.255 0.465 0.458 2.39x10·9 7.00xl0·9 1.365xl0·5 for a j reactor, the inlet heat is the sum of the reaction mixture heat and polymerisation reaction heat (strong exothermal, ~h=671,238 j/kg [10]). inlet heat inj reactor: qi . =mw ·c . -l st,1 st p st,1 1 (1) (2) qi -m i . w ·cp . ·t. pob,1 pob pob,1 1 (3) qr. =mw -(x. -x. )·ah 1 st 1 1-1 (4) outlet heat from j reactor: qe . =mw -(i-x ·)·t~ st,1 st 1 1 (5) qe =mw ·c . ·te pob,j pob p pob,j j (6) qe t . = mw t ·x . · cp . · t~ ps ,1 s 1 pst,] 1 (7) the transferred heat is: (8) obviously, for q~ > q; it is necessary the cooling, and for q~ < q; the heating of the reaction mass. the thermal balance over the reactors of the optimal synthesis network for the polystyrene production by bulk polymerisation has been realized by the eqs.( 1 )­ (8). for the first reactor, the heat losses have not been considered because these favour the cooling. for the other reactors, the heat losses have been 1% of the inlet heat. the flow of the reaction mass components and the conversion of each reactor are presented in table i. the specific heats for the inlet and outlet streams were taken from the available literature [10~ 11]. the results of the thermal balance over the optimal reactor network for the styrene bulk polymerisation are presented in table 2. the j reactor degree cp,2 cj,4,0 cj,4,1 cj,4,2 xj xr (mol/1) (movl) (mol/1) (movl) 7.91xto·2 4.72xl0·3 0.522 3.01xl03 0.350 0.350 7.91xto·2 4.72xl0·3 0.522 3.01x103 0.350 0.350 0.104 5.lxl0·3 0.588 3.88xl03 0.166 0.458 0.106 5.265xto·3 0.558 6.05xl03 0.199 0.566 0.078 4.765x1o·3 1.335 8.825x103 0.248 0.674 0.055 4.84xl0·3 2.065 1.18xl04 0.449 0.820 0.055 4.08xl0·3 2.265 1.185x104 0.583 0.925 0.055 2.595x1o-3 1.61 8.225xl03 0.600 0.970 table 2 thermal balance results over each reactor of the network for polystyrene manufacturing by bulk polymerisation reactor inlet heat (w) outlet transferred sens of heat heat the heat (w) (w) transfer cs1r working at 80°c 9.45·103 4.97-103 4.48-103 cooling cs1r working at 80°c 9.45-103 4.97·103 4.48-103 cooling pfr working at 1 00°c 2.03·104 1.25·104 7.76·103 cooling pfr working at 150°c 1.78-104 2.05-104 2.77·103 heating pfr working at 180°c 3.27-104 2.95·104 3.18·103 cooling pfr working at 200°c 3.19-104 3.39·104 1.98-103 heating heat exchangers calculation the selection of the heat exchangers and of the thermal agents is based on the thermal balance results. due to the difficulty of the heat transfer between the reaction mass and the thermal agent, the coil heat exchangers have been considered. because the heat amount transferred into the reactor network is small, a jacket heat exchanger is not necessary. since the reaction mass has a very high viscosity in the last reactor (pfr6), the reynolds number is small and the heat transfer rate is reduced, therefore electrical heating has been chosen. in the continuous stirred tank reactors, being connected in parallel, the temperature is 80 °c, one can use water of different temperatures as cooling agent. for the variants with high outlet water temperatures from reactors, for instance, 50°c for inlet temperature and 60°c for outlet temperature, even if the water consumption is larger and the coil length is also larger, there is the advantage of a small temperature variation into the reaction mass and its properties are unchanged. in the plug flow reactors pfrl and pfr2. the inlet temperature of the reaction mass is 80°c and outlet temperature is l00°c. consequently, the cooling agent for reaction mass is the water with different temperatures. the plug flow reactor working at 150°c (pfr3 ), according to the thermal balance, needs the beating. as 110 table 3 the calculation results for the heat exchanger design realizing the needed thermal regime in a cstr e e '(;$ § ~~ +"' i ~ ~ c1) ~·"""' .s~ .. ~s g ~ ,d ~ ~ q ~u c1:l '"" "0 ,d"'"' g§ "' c1:l ..9 §~ q),....,_ f3"g ~ ~ ~ g"~ a q,) 1 i3".£-j !:i; bl} <1)0 .g! d a.e .s.... '-' ~'-'~m~ ..... <1) ~ c1:l u 0 d >~ ~ § <1)~ ·s ~ ~ ~ a c1:l 0"''...s 0 f:: g ::=a,s ::z:: fi1 c.; 15 30 638.1 0.0713 0.359 7.15 4.11·108 gp .. 15 40 8 536.1 0.0428 0.497 9.86 2.47·108 ~j 25 40 oo 676.0 0.0713 0.395 7.85 4.11·108 ~ ..,f 25 50 565.7 0.0428 0.568 11.3 2.47·108 heating agent steam of different pressures or dowtherm a is used. the plug flow reactors (pfr4 and pfr5) working at 180 °c, needs cooling. due to the high temperatures, one proposed boiling water under pressure of 1 bar or 2 bar, as cooling agent. · conclusively, for each reactor from the synthesis network, the amount of heat to be transferred, the heat exchanger type and the available thermal agents have been established. hereinafter, for each reactor, the needed thermal agent flow rate, the overall heat transfer coefficient, the heat transfer surface area, the coil length and the total cost have been calculated. investment charge can be calculated with the relation: (9) where a is the heat transfer surface area, a and f3 are specific constants for the heat exchanger type: a =145 and f3=0,65-0,95 [12, 13]. the operating cost is co i = mw · cu · nh , where cu represents the unit cost for the thermal agent and nh=sooo the hours number of operating a year. therefore. the total cost for thermal transfer to realize the needed isothermal regime into reactor is: crj; ci + coj (10) table 3 presents the calculation results for the heat exchanger design using water of different temperatures~ in order to realize and maintain the constant temperature of 80 °c, of the stirred tank reactor. the plug flow reactors working at 100 °c (pfr1 and pfr2)~ based on the thermal balance result~ both need the cooling of the reactton mass (table 2). to this gt 11. the water with different inlet/outlet temperatures has been chosen. being that. from stirred tank reactors results water of 40 °c and 50 °c (table }). this can be used for the reaction mass cooling from the plug flow reactors working at i 00 °c. the overall heat transfer coefficient kpfr12 has been calculated as function of individual heat transfer coefficient and thermal resistance of the wall. the calculation of the individual heat transfer coefficient was made using the relations obtained from literature [h-j•h. table 4 the needed characteristics for the heat exchanger design realizing the needed thermal regime in the pfr 1 and pfr2 15 30 15 40 20 20 25 25 30 40 40 50 40 60 50 70 139.1 0.125 0.835 8.86 7.20-108 131.0 0.075 0.994 10.54 4.32·108 143.5 0.189 0.851 9.03 1.09·109 8 136.1 0.094 0.961 10.19 5.41-108 ~ 140.9 0.126 0.975 10.34 7.26·108 r..: 134.8 0.075 1.108 11.76 4.32·108 140.4 0.095 1.382 14.97 5.47·108 140.3 0.095 1.892 20.08 241.49 the needed characteristics for the heat exchangers design are presented in table 4, for different cooling water types. the thermal balance over pfr3 working at 150 °c, showed that, for a good polymerisation, it is needed to supply a heat amount of 2,77·103 w. to this aim, the proposed thermal agent is either steam with different temperatures or liquid dowtherm a. the steam flow for the heating of the reaction mass has been obtained as function of needed heat amount for the heating and steam characteristics. in the following, the individual heat transfer coefficient for the reaction mass was calculated. the reaction mass properties were taken from literature [10], at average temperature in the reactor working at 90 °c, for a conversion degree of 67, 4%. in these conditions, the laminar regime was obtained with very low repfr3 = 5.55. this allows considering the free convection. because the heat transfer coefficient for steam, used as heating agent. is much higher than that for the reaction mass, the thermal resistance for steam can be neglected. when dowtherm a is used as thermal agent, the thermal resistance can be also neglected. for the required heat transfer realization, the overall transfer coefficient, the thermal transfer surface area~ the coil length and the total length have been calculated. the obtained results are presented in table 5. the plug flow reactors pfr4 and pfrs work at 180°c. the thermal balance shows that the elimination of the heat from the inside reactors is necessary. for tr 3 • both. q pfr45 = 3.18·10 w. the thermal agent was the water under pressure, so that by its evaporation, the water takes up a large amount of heat. the properties of the water under pressure were taken from [11]. for the overall heat transfer coefficient determinationt the individual heat transfe1 ~oefficient of the reaction mass was calculated, flmrwr•s= 147.14 w m"2k"1• the reaction mass properties are taken from [ 1 0] for 92.5 % conversion degree. table 5 the calculation results for the heat exchanger design realizing the needed thermal regime in the pfr3 6 158.1 1.32 7 164.2 1.33 steam 8 170 1.35 9 175 1.36 10 179 1.37 dowtherm 1.2 190 8.78 a 1.5 225 9.19 138.818 0.57 6.04 3.04-107 138.818 0.51 5.39 3.06·107 138.818 0.44 4.70 3.11·107 138.818 0.40 4.27 3.13·107 138.818 0.37 3.92 3.16·107 133.268 0.32 3.39 1.01-109 133.268 0.21 2.20 1.06·109 also, here the heat transfer coefficient for the water, boiling under pressure in the coil is much larger than that of the reaction mass and its value was admitted. the calculation results for pfr4 and pfrs, including the total costs of the required heat transfer, are presented in table 6. one can assert that, for all considered reactors, the thermal resistance has the largest value for the reaction mass. because the last reactor (pfr6) uses electrical heating, the heat calculation cannot be any more the objective for the heat transfer optimisation. determination of the" optimal heat exchanger network the heat exchangers realizing the required thermal transfer for each considered reactor have been chosen from the lists presented in tables 3, 4, 5 and 6. for selection, the technological criterions had the maximum importance. hereby, the temperature variations, larger than 10°c for the reaction mass, have not been accepted. consequently, for instance, the cooling water had a higher input temperature. also, for heating, when the thermal agent can be the steam or dowtherm a, the dowtherm a was chosen because this can provide a higher temperature, and, finally the required quality of the reaction mass. in the same sense, a thermal agent has been recycled even if the heat transfer surface area has been larger and, thereafter, the investment charge (heat exchanger) has been higher, due to the driving force decrease. from technological point of view, the recycling was preferred because the operating expenses have to be reduced. the economical criterions, given by the total cost for the thermal transfer, have been used for the thermal agents' selection. the heat exchangers and the corresponding thermal agents have been selected on the above criterions and composed the optimal heat exchanger network, because this realizes the required thermal regime under adequate technological conditions with minimum cost. ill table 6 the calculation results for the heat exchanger design realizing the needed thermal regime in the pfr 4 and pfr 5 water 99.1 0.00141 120.95 0.399 4.23 1.62·107 p~:s~:e 2 119.6 0.00144 3 ' 179 . 103 111.96 0.625 6.64 1.66·107 cnm:.ofoptiwizatednetwork: 1.26 .10'u.c, fig.2 optimal heat exchanger network for polystyrene manufacturing by bulk polymerisation the described synthesis algorithm has been implemented in mathcad 2000 professional. the synthesized optimal heat exchangers network is presented in fig.2. for the initial conditions and the specified thermal regime, the network contains five coil heat exchangers. as following: two heat exchangers realize the required isothermal regime (80°c) in the continuous stirred tank reactor (cstri and cstr2). these are using the cooling water as thermal agent having 25°c inlet temperature and 50°c outlet temperature. for the pfrl and pfr2 requiring an isothermal regime at 1 00°°c, a heat exchanger recycling the resulted water from cstri and cstr2, having 50°c temperature has been used. the outlet water temperature is 60°c. pfr3 works at 150°c. the corresponding heat exchanger uses dowtherm a at 190°c. the last heat exchanger, using cooling water at 2 bar pressure, realizes the isothermal regime, at 180°c, in pfr4 and pfrs. one asserts that the optimal heat exchanger network cannot use the heat of the reaction mass because this has a pre-established way which cannot be modified. also, the single thermal agent enabling the recycling was the cooling water which results from cstri and cstr2. conclusions the optimal heat exchanger network realizing the required thermal regime for the reactor system at 112 styrene production, by bulk polymerisation in a continuous system has been determined by the computer assisted synthesis. the considered system has industrial capacity and operates at the thermal regime for commercial scale. firstly, the synthesis method supposes the thermal balance effectuation over each reactor having a distinct thermal regime. then, the heat exchangers have been calculated and the optimal heat exchanger network has been determined. the accurate analysis of the technological process and of the offered possibilities by system calculation allows solving the problem under optimal technological and economical conditions. the proposed heat exchanger network realizes the pre-established thermal regime under given conditions and for a minimum cost. this shows that the reactor network can be used in a practical application. we notice that the proposed synthesis method is efficient but depends on the designer experience in the field. the designer establishes the type exchangers, the thermal agents and the accepted temperature difference, based on the knowledge of the technological process. in the issue, the utilized synthesis method is recommended for the approached problem type of synthesis the realizing of thermal regime for the manufacturing of the reaction mass in a known reactor network. the problem appears frequently in the industrial chemical processes and, especially, in the polymerisation process, which are strongly exothermic. j q!t,j q~st,j q~.j mw.st mwpob cp.st,j cppob.j t' j x f'x j-t ah qrj q~.j q~t.j q~.j tj symbols index for reactors inlet styrene heat in the j reactor, w outlet polystyrene heat in the j reactor, w inlet initiating agent in the j reactor, w styrene mass flow rate, kg/s initiating agent mass flow rate, kg/s styrene specific heat capacity at the inlet/outlet styrene temperature~ for j reactor, j/(kg·k) specific heat capacity of the initiating agent at the inlet/outlet temperature for j reactor. j/(kg·k) inlet reaction mass temperature for j reactor. oc monomer conversion degree in j/j-i reactor polymerisation heat. j/kg reaction heat in the j reactor. w outlet styrene heat for reactor j .. w outlet polystyrene heat for j reactor. w outlet initiating agent heat for j reactor. w outlet temperature for j reactor. °c ~ qj qjr a cj coj mw uc nh ctj a,~ cstr pfr inlet heat for j reactor, w outlet heat for j reactor, w transferred heat for j reactor, w thermal transfer surface area, m2 investment charge for j reactor, u. c. operating cost for j reactor, u.c. mass flow of thermal agent, kg/s unit cost of the thermal agent, u.c. hours number of operating a year total cost of the thermal transfer for j reactor, u.c. specific constants for the heat exchanger type continuous stirred tank reactor plug flow reactor references 1. gundersen t. and naess l.: computers chern. eng., 1988, 12,505-530 2. gundersen t .: retrofit process design research and applications of systematic methods, proceed. ofthe 3rd conf on foundations of computer aided process design, 213-240, snowmass village, colorado, july 1990, elsevier public 3. jezowski j.: hung. j. ind. chern., 1994, 22, 279294 4. jezowski j.: hung. j. ind. chern., 1994, 22, 295308 5. bochenek r. and jezowski j.: hung. j. ind. chern., 1999,27,896. jezowski j. and jezowska a.: hung. j. ind. chern., 1999,27, 177. diaconescu r., tudose r. z. and curteanu s., polymerplastics technology & eng., in press 8. grigorevich s. n.: studies of control during runaway of polymerisation reaction to improve both safety of industrial reactors and product quality, istc project: 1529, 1998 9. continuous bulk polymerisation process for manufacturing high impact polystyrene, iceet, 1998. 132 10. bernhardt e. c.: pererabotka tennoplasticimh materiajov, ed. himiia, moscova, p. 650-687, 1965 11. pavwv c. f., romankov p. g. and noskov a. a.: process and apparate in chemical industry, ed. teh., bucure§ti, p. 155-211, 1981 12. woinaroschy a. and smigelschi 0.: engineering systems and chemical process optimisation , ed. did. ~i ped., bucure~ti, 1983 l3. biegler l. t., grossman i. e. and westerberg a. w.: systematic methods of chemical process design, new jersey: prentice hall ptr, p. 527-567, 1997 14. $tefanescu d., marr'~escu m. and danescu a.: heat transfer in technics, vol. i, ll, ed. teh., bucure$ti, p. i 982 page 106 page 107 page 108 page 109 page 110 page 111 hungarian journal of industry and chemistry vol. 45(1) pp. 61–66 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0009 surface energy heterogeneity profiles of carbon nanotubes with a copolymer-modified surface using surface energy mapping by inverse gas chromatography fruzsina gerencsér, 1 norbert rieder, 1 csilla varga, 2 jenő hancsók, 2 and andrás dallos 1* 1 department of physical chemistry, university of pannonia, 10 egyetem str., veszprém, h-8200, hungary 2 mol department of hydrocarbon and coal processing, university of pannonia, 10 egyetem str., veszprém, h-8200, hungary the effectiveness and quantitative control of the surface transition of multi-walled carbon nanotubes (mwcnts) was characterized by inverse gas chromatography (igc). the surface energy profile of carbon nanotubes compatibilized with an olefin-maleic-anhydride-ester-amide (omaea)-type coupling agent was determined by a surface energy analyzer (sea). the surface energetic heterogeneity with energy distributions of dispersive and specific (acid-base) components of the surface energy of the mwcnts were determined at various surface coverages. the results of the surface energy mapping showed that surface treatment significantly reduced the dispersive surface energy of mwcnts and increased the specific surface energy. furthermore, the surface modification enhanced its lewis basic character and simultaneously decreased the acidic character of mwcnts. it has been demonstrated that the surface treatment modified the heterogeneity profiles of the energetic surface of the carbonaceous nanomaterials. keywords: carbon nanotubes, surface treatment, inverse gas chromatography, surface energy analysis 1. introduction carbon nanotubes (cnts) can serve as excellent candidate materials for uses in numerous industrial applications because of their considerable advantages. cnts are one of the best reinforcing constituents for nanocomposites [1] and hopefully catalytic metal–support in heterogeneous catalysis [2]. cnts could replace the common catalyst supports of ni/mo-catalysts used in the production of fuel components of engine fuels with high hydrogen contents in their molecular structures [3]. carbon nanotube-supported co/mo-catalysts with different co/mo atomic ratios were successfully used in the hydrocracking reaction of the vacuum residue of crude oil from gudao oil field [4]. in the fischer–tropsch process (ftp), cnts that supported transition metal catalysts are used to increase catalytic activities. an excellent study of ftp on co catalysts supported by cnts was reported by tavasoli et al. [5]. chen et al. [6] demonstrated that fe nanoparticles encapsulated in cnts are promising catalyst in ftp to synthesize light olefins. the catalytic consequence of hydrothermal liquefaction of microalgae to produce bio-oil over cnt *correspondence: dallos@almos.vein.hu supported transition metal (co, ni, pt) catalysts was reported by chen et al. [7]. to change the wettability and chemical character of the cnts or to avoid agglomeration in nanocomposites, the cnt surfaces are often exposed to surface functionalization [2] and modification processes using polyfunctional anchoring, capping, and coupling agents [8]. research has shown that metal–support bindings can be strengthened by functional groups that are covalently bonded (grafted) to the support. functionalized carbon nanotube-supported pt nanoparticles were applied with favourable results in terms of selective olefin hydrogenation [9]. because cnts adsorb molecules well, functionalized cnts are attractive chromatographic stationary phases for separation of normal and isoalkanes and aromatic compounds in the development of alternative fuels with high hydrogen/carbon ratios [10]. however, non-covalent functionalization using coupling agents or compatibilizers does not perturb the structure of the carbon nanotubes, establishes proper interactions between carbon nanotubes and the polymer matrix, and prevents the formation of nanotube agglomerates [11]. in terms of the properties of the reinforced composites of cnts, the couplings between the nanotubes and the matrix are important beside the mechanical properties of the building parts [12]. these interactions depend on the surface properties and energies of the two materials. the surfaces of chemically derivatizated cnts were investigated by means of various ana gerencsér, rieder, varga, hancsók and dallos hungarian journal of industry and chemistry 62 lytical methods, e.g. thermal analysis [9-10,13-14], infrared spectroscopy (ir) [10,13], transmission electron microscopy (tem) [13,16], raman [16] and atomic force microscopy [10], and inverse gas chromatography (igc). igc is a precise analytical method which is suitable for determining the surface energetic characteristics of the cnts [13,15-17]. igc was used for the characterization of the chemical character of the surface and was utilized to measure dispersive and specific surface energies, of numerous cnt substances [18]. the quantitative characterization of surface functionalization by surface energy mapping is of great importance. however, previous papers have presented surface energy values for functionalized cnts over unclear surface coverages without energetic profiles and surface energy distribution functions, which, therefore, could not give correct information on the surface of the cnts. in this study, the dispersive, specific (acid-base) components of the surface energy with their heterogeneity charts and energy probability density functions of untreated and compatibilized mwcnts are presented. a comparative quantitative characterization of the effectiveness and quantitative control of surface treatment is given. the exclusive energy scaling of the surfaces of the mwcnts by energy heterogeneity charts with surface energy probability density functions over wide surface coverages is the new approach and main novelty of this paper. 2. experimental and methods 2.1. samples and measurements multi-walled carbon nanotubes (mwcnts) were manufactured at 973 k by the chemical vapour deposition (cvd) process over a fe/co bimetallic catalyst at the department of chemical engineering science (university of pannonia, veszprém, hungary) [19]. their diameter was between 10 and 20 nm and their average length was above 30 μm. an olefin-maleic-anhydride-ester-amide (fig.1) copolymer (omaea) was used as a compatibilizer. the coupling agent was synthesized at the department of mol hydrocarbon and coal processing (university of pannonia, veszprém, hungary). the surface of mwcnts was covered by the compatibilizer from a hydrocarbon solution of the coupling agent while the mixture was stirred for 1 hour at 333 k. the solvent was subsequently evaporated and the treated mwcnts were dried at 383 k for 2 hours in air [11]. the surface energies of as-received and compatibilized samples of mwcnts were measured by a surface energy analyzer (igc-sea, surface measurement systems ltd., alperton, uk) over a series of surface coverages from (n/nm) = 0.005 to (n/nm) = 0.030. igc samples were produced by filling 20-25 mg of cnts into silanized pyrex glass tubes of i.d. = 3 mm under a vacuum and moderate vibration. the samples of mwcnts were stabilized in the column with plugs of silanized glass wool. the samples were preconditioned in the column at the actually measured temperature for 60 minutes before each measurement. the igc experiments were carried out at a column temperature of 353 k, with a helium carrier gas flow of 10 cm3/min. methane gas was used as a dead-time marker using a flame ionization detector; and n-hexane, n-heptane, n-octane, n-nonane, chloroform and toluene as test compounds. the surface energy values were estimated using the specific retention volumes of the test compounds [20]. the specific retention volumes were obtained from the adjusted retention times: spw mvtv /c ' r  (1) the mean flow rate of the carrier gas in the column, cv , was evaluated as given in ref. [20]. 2.2. theoretical methodologies the dispersive component of the surface energy ( d s ) and its heterogeneity profile of samples of mwcnts were calculated using the dorris-gray method [21] over different surface coverages:   2 ch c,1c, ch d s 22 /ln 4 1             an vvrt nwnw   (2) when plotting rtln(vw,nc) against carbon number, nc, for the n-alkane probes, a straight line is generated from the gradient from which the dispersive free energy of the sample surfaces of the mwcnts, d s , can be calculated. the specific (lewis acid-base) surface energy ab s of samples of mwcnts was calculated from the basic component (  s ) and the acidic component (  s ) of the surface energy:  ss ab s 2  (3) the basic and acidic components of the surface energy were obtained from the specific parts of free enthalpy changes of adsorption ab ,ads ig of polar probes i: figure 1. structure of the olefin-maleic-anhydrideester-amide copolymer (omaea) coupling agent, where r1: alkyl chain with length of the olefinic monomer; r2: alkyl chain with r1–2 carbon number; a, b: 2–21; k: 0.2–2; l: 1–7; m: 1–7 and n: 0.3–2 [11] surface energy heterogeneity profiles of carbon nanotubes 45(1) pp. 61–66 (2017) 63        ss ab ,ads 2  iiii ang (4) applying the van oss-chaudhury-good theory [22] with the della volpe scale [23]. the specific free energy changes of adsorption of the polar probes were obtained as suggested by donnet et al. [24]. 3. results and analysis 3.1. experiments the dispersive surface energy profiles of the untreated samples of mwcnts and those treated with the olefinmaleic-anhydride-ester-amide copolymer (omaea) coupling agent compatibilized at 353 k and over low surface coverages (n/nm) are presented in fig.2. the energy profiles show reasonable devaluation of dispersive surface energy for mwcnts after surface modification detected by n-alkane molecular probes: the dispersive surface energy ( d s ) of the mwcnts decreased to half of its initial value. the untreated samples of mwcnts exhibited dispersive surface energies of ~110 mj/m2 at 353 k, which is comparable to the values reported by other researchers studying carbon nanotubes [13-15] and graphitic carbon materials [25]. the relatively high values of the dispersive surface energy of untreated mwcnts can be attributed to a strong nonpolar interaction potential to build physical long-range keesom, debye, and london attractions, which explains their high tendency to agglomerate [14]. however, the anchoring of olefinmaleic-anhydride-ester-amide (omaea) up on the mwcnts surface caused a marked decrement in dispersive part of surface energy from ~110 mj/m2 to ~48 mj/m2 at 353 k. the large drop in the value of d s of surface-treated mwcnts shows that the dispersive surface energy of mwcnts has been obviously altered by the coupling agent. the surface treatment also affected the dispersive surface energy heterogeneity profile of the mwcnts. the surface energy mapping of the samples of mwcnts indicated that the dispersive components of surface energies of untreated samples of mwcnts are almost constant within the region of low surface coverage. consequently, the surface of the untreated mwcnts can be considered quasi-homogeneous. however, the dispersive surface energy heterogeneity profiles of the treated mwcnts prove that the copolymer-modified mwcnt surface is energetically slightly heterogeneous, because the dependence of d s on surface coverage is relatively strong within the region of low surface coverage. in addition, the distributions of the dispersive surface energies (fig.3) obtained by point-by-point integration of dispersive surface energy profiles over the investigated range of the surface coverage support in a more illustrative manner also results in an increase in the dispersive surface energy heterogeneity. the dispersive surface energy probability function of the mwcnts became more spread out after modification of the surface indicated a greater degree of energetic surface inhomogeneity. the specific surface energy ( ab s ) profiles of the untreated samples of mwcnts and those treated with omaea compatibilized at 353 k and over various surface coverages (n/nm) are presented in fig. 4. the untreated samples of mwcnts possess specific surface energy of ~10 mj/m2 at 353 k, which value is near to that given by lou et al. (8.84 mj/m2) for pristine carbon nanotubes at 373 k and over undefined degrees of surface coverage [14]. the quantitative surface energy analysis obtained by igc-sea methodology demonstrated that surface treatment of mwcnts resulted in figure 3. dispersive surface energy probability functions of untreated samples of mwcnts and those treated with an olefin-maleic-anhydride-ester-amide copolymer (omaea) coupling agent compatibilized at 353 k (the solid correlation lines are only to improve visualization). figure 2. dispersive surface energy profiles of untreated samples of mwcnts and those treated with an olefin-maleic-anhydride-ester-amide copolymer (omaea) coupling agent compatibilized at 353 k and over various surface coverages (the dotted correlation lines are only to improve visualization). gerencsér, rieder, varga, hancsók and dallos hungarian journal of industry and chemistry 64 significant changes in surface energies: the specific surface energy of cnt surfaces increased more than fourfold, from ~10 mj/m2 to ~41 mj/m2. furthermore, the dependence of ab s on surface coverage is pronounced for the compatibilized samples of mwcnts which indicates that energetic heterogeneity attributed to chemical heterogeneity and the existence of electron donor-acceptor atomic groups on the surface. however, the quasi-constant specific component of surface energy for untreated mwcnts suggests an energetically homogeneous surface and the absence of high specific energy surface sites. the specific surface energy values of compatibilized mwcnts are much higher than those of the untreated surfaces, declared the enhanced connection between compatibilized mwcnts and polar analytes. the observed diversity in specific surface energies is accomplished from the adsorbed polar atomic clusters: namely the moderately electron-withdrawing maleic anhydride groups; and the electron-donating ester and amide groups with different nucleophilic or electrophilic characteristics. the specific surface energy distributions in fig. 5 represent the heterogeneity of the samples of mwcnts and reveal that the untreated mwcnts exhibited ab s values which varied from 9.9 to 10.3 mj/m2. this small variation in the specific surface energy demonstrated a fairly energetically homogeneous surface for untreated mwcnts. however, as surface treatment increased the concentrations of polar clusters on the surface of mwcnts, the modified surface exhibited great variations in ab s (from 37.3 to 42.9 mj/m2), implying that the compatibilized mwcnts are surface energetic heterogeneous. the surface treatment also modified the chemical characteristics of the mwcnts. the acid-base surface energy mapping of the samples of mwcnts (figs.6 and 7) indicate that both the electron-accepting and donating abilities of the mwcnts were raised appreciably after compatibilization of untreated mwcnts consistent with the adsorption of electron-withdrawing and electron-donating atomic groups on the surface. the untreated samples of mwcnts possess base surface energy of ~16 mj/m2 at 353 k, which value is near to that given by lou et al. (12.97 mj/m2) for pristine carbon nanotubes at 373 k and over undefined surface coverage [14]. the surface energy mapping using the igc-sea methodology confirms that the surface treatment of mwcnts raised the basic component (  s ) of surface energy of mwcnts: it resulted in a sevenfold increase from ~16 mj/m2 to ~112 mj/m2. the acidic component of surface energy  s of untreated samples of mwcnts was measured as ~1.7 mj/m2 at 353 k, which is in good agreement with that reported by lou et al. (1.51 mj/m2) for pristine carbon nanotubes at 373 k and over undefined surface coverages [14]. the surface modification of mwcnts resulted in a more than twofold increase in the value of the acidic component (  s ) of the surface energy of mwcnts from ~1.7 mj/m2 to ~3.7 mj/m2. however, the profiles of acid-base surface energy heterogeneity of the treated mwcnts also prove that the copolymer-modified mwcnt surface became energetically more heterogeneous, because the dependencies of  s and  s on surface coverage are relatively stronger than those of the untreated mwcnts. the presence of non equi-energetic active surface centers exposes that the surfaces of the compatibilized mwcnts are not energetically uniform for specific acid-base interactions and the surface treatment considerably altered the ability of mwcnts to connect with molecular species by specific interactions. figure 5. specific surface energy probability functions of untreated samples of mwcnts and those treated with an olefin-maleic-anhydride-ester-amide copolymer (omaea) coupling agent compatibilized at 353 k (the solid correlation lines only improve visualization). figure 4. specific surface energy profiles of untreated samples of mwcnts and those treated with an olefinmaleic-anhydride-ester-amide copolymer (omaea) coupling agent compatibilized at 353 k and over various surface coverages (the dotted correlation lines only improve visualization). surface energy heterogeneity profiles of carbon nanotubes 45(1) pp. 61–66 (2017) 65 the larger change in the base component of the surface energy (  s ) after compatibilization with a polyalkenyl-poly-maleic-anhydride-ester-amide additive indicates a higher concentration of electron-donating ester and amide groups on the surface. the large value of  s (relative to  s ) implies a more basic characteristic and donor properties of the surface of the treated mwcnts. 4. conclusion the experimental data demonstrated that igc is a useful methodology of characterizing the variation in the surface characteristics of mwcnts after non-covalent functionalization. the exclusive energy scaling of the sea methodology using energy heterogeneity charts with surface energy probability density functions over wide surface coverages presents profitable additional information on the differences in terms of the nature, homogeneity and heterogeneity of surface energies resulting from surface transformations. the multilateral surface energy analysis of sea presents a quantitative control of the effectiveness of surface treatment and demonstrates the importance of the dependence of surface energy analysis on coverage. acknowledgement the present work was published within the framework of the project ginop-2.3.2-15-2016-00053. symbols 2cha , ai cross sectional area of an adsorbed methylene group and of probe i ab ,ads ig specific free enthalpy of adsorption msp mass of the adsorbent in the column n avogadro’s number r gas constant t temperature ' rt adjusted retention time cv mean flow rate of the carrier gas vw specific retention volume ab s , d s specific and dispersive parts of the surface energy of solid sample material 2ch surface energy of a methylene group  s ,  s acid-base components of the surface energy of solid sample material  i ,  i acid-base components of the surface tension of polar liquid probe i θ=n/nm surface coverage references [1] dresselhaus, m.s.; dresselhaus, g.; avouris, p.: carbon nanotubes: synthesis, structure, properties, and applications (springer-verlag gmbh, berlin, germany) 2001 doi: 10.1007/3-540-39947-x figure 6. basic component profiles of surface energy of untreated samples of mwcnts and those treated with an olefin-maleic-anhydride-ester-amide copolymer (omaea) coupling agent compatibilized at 353 k and over various surface coverages (the dotted correlation lines only improve visualization). figure 7. acidic component profiles of surface energy of untreated samples of mwcnts and 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sibioni, s.: some reflection on acid-base solid surface free energy theories, j. colloid interf. sci., 1997 195(1), 121-136 doi: 10.1006/jcis.1997.5124 [24] donnet, j.b.; park, s.j.; balard, h.: evaluation of specific interactions of solid surfaces by inverse gas chromatography. a new approach based on polarizability of the probes, chromatographia, 1991 31, 435-440 doi: 10.1007/bf02262385 [25] donnet, j.b.; park, s.j.: surface characteristics of pitch-based carbon fibers by inverse gas chromatography method, carbon, 1991 29(7), 955-961 doi: 10.1016/0008-6223(91)90174-h hungarian journal of industry and chemistry veszprém vol. 42(2) pp. 109–113 (2014) stability and parameter sensitivity analyses of an induction motor attila fodor1, roland bálintb1, attila magyar1, and gábor szederkényi2 1department of electrical engineering and information systems, university of pannonia, egyetem u. 10., veszprém, 8200, hungary 2pazmány péter catholic university, práter u. 50/a, budapest, 1083, hungary be-mail: balint.roland27@gmail.com a simple dynamical model of an induction motor is derived and analyzed in this paper based on engineering principles that describe the mechanical phenomena together with the electrical model. the used state space model consists of nonlinear state equations. the model has been verified under the usual controlled operating conditions when the speed is controlled. the effect of load on the controlled induction motor has been analyzed by simulation. the sensitivity analysis of the induction motor has been applied to determine the model parameters to be estimated. keywords: induction motor, stability analysis, sensitivity analysis introduction induction motors (im) are the most commonly used electrical rotating machines in several industrial applications. irrespective of size and the application area, these motors share the most important dynamical properties, and their dynamical models have a similar structure. because of the specialties and great practical importance of ims in industrial applications, their modelling for control purposes is well investigated in the literature. besides basic textbooks [1-3], there are several papers that describe the modelling and use the developed models for the design of different types of controllers: vector control [1, 4], sensorless vector control [5] and direct torque control (dtc) [6]. the aim of this paper is to build a simple dynamical model of the im and to perform its parameter sensitivity analysis. the results of this analysis will be the basis of the next step since the final aim of our study is to estimate the parameters of the im and design a controller that can control the speed and torque of the im. the state space model has been implemented in the matlab/simulink environment which enables us to analyze the parametric sensitivity based on simulation experiments. nonlinear model of an induction motor in this section a state space model of an induction motor (im) is presented. the model development is largely based on refs.[1, 8-10]. for constructing the im model, the following modelling assumptions are made: 1. a symmetrical triphase stator winding system is assumed, 2. the flux density is radial in the air gap, 3. the copper loss and the slots in the machine can be neglected, 4. the spatial distribution of the stator fluxes and apertures wave are considered to be sinusoidal, 5. stator and rotor permeability are assumed to be infinite with linear magnetic properties. according to the above modelling conditions the mathematical description of the im is developed through the space-vector theory. if the voltage of the stator is presumed to be the input excitation of the machine, then the spatial distribution along the stator of the x phase voltage can be described by the complex vector vsx(t). we can determine the orientation of the voltage vector vs, the direction of the respective phase axis and the voltage polarity. is(t) = 2 3 ( a0 · isa(t) + a1 · isb(t) + a2 · isc(t) ) = √ 2 · ieff(t) · ejω0t+ π 2 +ϕi , (1) where a is the ej120o vector and isa, isb and isc are the following: isa(t) = re(a0 · is(t)) = re(is(t)), isb(t) = re(a2 · is(t)), and isc(t) = re(a1 · is(t)). in eq.(1), 2/3 is the normalizing factor. the flux density distribution can be obtained by integrating the current density wave along the cylinder of the stator. the flux linkage wave is a system variable, because it contains detailed information about the winding geometry. 110 figure 1: the equivalent circuit of the im the rotating flux density wave induces voltages in the individual stator windings. thus stator voltage vs(t) can be represented as the overall distributed voltages in all phase windings: vs(t) = 2 3 ( a0 · vsa(t) + a1 · vsb(t) + a2 · vsc(t) ) = √ 2 · veff(t) · ejω0t+ π 2 +ϕu , (2) where a is the ej120o vector and isa, isb and isc are the following: vsa(t) = re(a0 · us(t)) = re(us(t)), vsb(t) = re(a2 · us(t)), and vsc(t) = re(a1 · us(t)). considering the stator of the im as the primer side of the transformer, then using kirchoff’s voltage law the following equation can be written (fig.1): vs(t) = is(t) ·rs + dφs(t) dt . (3) as for the secondary side of the transformer, it can be deduced that the same relationship is true for the rotor side space vectors: vr(t) = ir(t) ·rr + dφr(t) dt = 0. (4) eqs.(3) and (4) describe the electromagnetic interaction as the connection of first order dynamical subsystems: φs(t) = is(t) · ls + ir(t) · lm, and (5) φr(t) = is(t) · lm + ir(t) · lr. (6) since four complex variables (is(t) , ir(t) , φs(t) , and φr(t)) are presented in eqs.(5) and (6), flux equations are needed to complete the relationship between them. the mechanical power (pmech(t)) of the im can be defined as: pmech(t) = wmech(t) dt , (7) where the mechanical energy (pmech(t)) in the rotating system can be given by the following expression: pmech(t) = wmech(t) dt = tmech(t) · ωr, (8) where te(t) is the torque and ωr is the angular velocity of the im. afterwards the energy balance of the im is as follows: we =wmech +wr +wfield, (9) figure 2: the equivalent circuit of the d-axis of the im figure 3: the equivalent circuit of the q-axis of the im where pe = we(t) dt = 3 2 re (us · is + ur · ir) (10) is the input electrical power, pr = wr(t) dt = 3 2 re ( rs · |is|2 +rr · |ir|2 ) (11) represents the resistive power losses and pfield = wfield(t) dt = 3 2 re ( dφs dt is + dφr dt ir ) (12) is the air gap power. using eqs.(8-12), pmech(t) = tmech(t) · ωr = 3 2 · lm lr · φs(t)× is(t), and (13) te = 1.5p · (φdsiqs − φqsids). (14) the equivalent circuit of the im can be decomposed to direct axis and quadratic axis components by park’s transformation as shown in figs.2 and 3. the actual terminal voltage v of the windings can be written in the form v = ± j∑ j=1 (rj ij)± j∑ j=1 ( dφj dt ) , (15) where ij are the currents, rj are the winding resistances, and φj are the flux linkages. the positive directions of the stator currents point out of the im terminals. by composing the d and q axes of the im the following equations can be written: vqs = rs · iqs + φqs dt + ω · φds, (16) vds = rs · ids + φds dt − ω · φqs, (17) vqr = r′r · i′ds + φ′dr dt + (ω − ωr) · φ′dr, and (18) vdr = r′r · i′dr + φ′dr dt − (ω − ωr) · φ′qr. (19) 111 figure 4: response to the step change of the speed-controlled im dωm dt = 1 2h (te − f · ωm − tmech) (20) where ω is the reference frame angular velocity, ωr is the electrical angular velocity, φqs = ls · iqs + lmi ′ qr, (21) φds = ls · ids + lmi ′ dr, (22) φqr = lr · i′qr + lmi ′ qs, and (23) φdr = lr · i′dr + lmi ′ ds. (24) the above model can be written in state space form by expressing the time derivative of the fluxes and ω from the voltage and swing equations eqs.(21-24). the nonlinear state space model of the im is given by eqs.(25-29): dφqs dt = −rs ls − l2 m l′ r · φqs rs · lm l′r(ls − l2 m l′ r ) · φ′qr − ω · φds + vqs, (25) dφds dt = −rs ls − l2 m l′ r · φds + rs · lm l′r(ls − l2 m l′ r ) · φ′dr − ω · φqs + vds, (26) dφ′qr dt = −r′r lm − l′ r·ls lm · φqs + −r′r · ls lm · (lm − l′ r·ls lm ) · φ′qr − ω · φ′dr + ωr · φ′dr + vqr, (27) dφ′dr dt = −r′r lm − l′ r·ls lm · φds + −r′r · ls lm · (lm − l′ r·ls lm ) · φ′dr + ω · φ′qr − ωr · φ′qr + vdr, and (28) dωr dt = 1 2h · 1.5 · p · lm lm · (ls − l2 m l′ r ) · φ′dr · φqs − 1 2h · 1.5 · p · lm lm · (ls − l2 m l′ r ) · φ′qr · φds − f 2h · ωr − tm 2h . (29) the state vector of the above model is x=[φqs, φds, φ ′ qr, φ ′ dr, ωr] t ∈ r5, and the input variables are organized in terms of the the input vector u=[vq, vd, −tmech] t ∈ r3. it is assumed that all the state variables can be measured i.e. y = x. model validation the dynamical properties of the im have been investigated. the response of the speed-controlled motor has been tested under step-like changes. the simulation results are shown in fig.4, where the fluxes (φqs , φds, φ′qr, and φ′dr) and the angular velocity (ω) are shown. model analysis the above model eqs.(21-24) has been verified by simulation against engineering intuition. local stability analysis as the final aim of our research is to estimate the parameters of a particular grundfos im, first of all the resistances (rs and rr) of the im were measured. afterwards the values of the inductances (lls, llr and lm) and the mechanical parameters (h and f ) of a similar im with similar rs and rr found in the literature have been used. the parameters used during the model and the sensitivity analyses are the following: rs = 0.196 ohm rr = 0.0191 ohm lls = 0.0397 h llr = 0.0397 h lm = 1.354 h h = 0.095 f = 0.0548 p = 1 (30) 112 figure 5: the model state variables for a ±50% change of lm it can easily be seen that the im model is nonlinear since there are products of two state variables in the following equations: • eq.(27): φ′dr is multiplied by ωr • eq.(28): φ′qr is multiplied by ωr • eq.(29): φ′dr is multiplied by φqs • eq.(29): φ′qr is multiplied by φ′ds for the local stability analysis we have to calculate the eigenvalues of the system. the examined equilibrium point is φqs = −0.744 vs φds = 1.0287 vs φ′qr = −0.174 vs (31) φ′dr = −0.087 vs ωr = 48.477 s−1 the numerical value of the jacobian of the nonlinear model (i.e. the state matrix of the locally linearized model) is as follows: −2.504 −50 2.4328 0 0 50 −2.504 0 2.4328 0 0.2370 0 −0.244 −1.522 0 0 0.2370 1.5222 −0.244 0 −8.617 17.077 0 0 −0.288  . (32) the eigenvalues of the state matrix of the linearized systems are: λ1,2 = −2.504 ± j49.98, λ3,4 = −0.243 ± j1.534, and λ5 = −0.288 (33) figure 6: the model state variables for a ±50% change in rs it is apparent that the real parts of the eigenvalues are negative with small magnitudes. parameter sensitivity analysis the sensitivity of the nonlinear model to the mutual inductance has been investigated. the steady state value of the system variables does not change (as is apparent in fig.5) even for a considerably large change in lm. sensitivity analysis of the inductances llr, lls of the stator and rotor, resistances of the stator rs and the damping constant f has also been investigated. in this investigation it can be seen that the values of the state variables were changed a bit, as shown in fig.6. the analysis of the resistances of the rotor r′r and the inertia h of the rotor showed that every value of the state variables changed significantly, as shown in fig.7. as a final result of the sensitivity analysis, we can define the following groups of parameters: • not sensitive: mutual inductance lm. since the state space model of interest is insensitive in this respect, the values of this parameter cannot be reliably determined from measurement data using any parameter estimation method. • sensitive: these sensitive parameters are candidates for parameter estimation. – less: inductances llr and lls, resistance of the stator rs and the damping constant f . – more: resistances of the rotor r′r and the inertia h of the rotor. • critically sensitive: none. 113 figure 7: the model state variables for a ±50% change in h conclusion the simple nonlinear dynamical model of an im has been investigated in this paper. it has been shown that the model is locally asymptotically stable with regards to a physically meaningful equilibrium state. the effect of the controlled generator has been analyzed by simulation using a traditional pi controller. it has been found that the controlled system is stable and can follow the set-point changes. seven parameters of the model were selected for sensitivity analysis, and the sensitivity of the state variables has been investigated. as a result, the parameters were partitioned into three groups. based on the results presented here, a future aim is to estimate the parameters of the model for a real system from measurements. the sensitivity analysis enables us to select the candidates for estimation that are inductances llr and lls, resistances rs and rr, the damping constant f and the inertia h . an additional future aim is to develop a model for control purposes and investigate different controllers before applying them on real systems. acknowledgement we acknowledge the financial support of this work by the hungarian state and the european union under the tamop-4.2.2.a-11/1/konv-2012-0072 project. we acknowledge also the investigated im of grundfos hungary producer ltd. symbols c1, c2, c3 constant f damping constant φqs and φds q and d components of the stator flux φ′qr and φ′dr q and d components of the reduced rotor flux h inertia constant iqs and ids q and d components of the stator current i′qr and i′dr q and d components of the reduced rotor current lm mutual inductance p number of pole pairs rr and lr rotor resistance and inductance r′r and l′r reduced value of rotor resistance and inductance rs and ls stator resistance and inductance vd and vq q and d components of the stator voltage ω angular velocity of the magnetic field ωr angular velocity of the rotor tmech mechanical torque references [1] vas p.: artifical-intelligence-based electrical machines and drives, oxford university press, 1999 [2] vas p.: sensorless vector and direct torque control. oxford university press, 1998. [3] zheng l., fletcher j.e., williams b.w. he x.: dual-plane vector control of a five-phase induction machine for an improved flux pattern, ieee transac. ind. elec., 2008, 55(5), 1996–2005 [4] levi e.: impact of iron loss on behavior of vector controlled induction machines, ieee transac. ind. appl., 1995, 31(6), 1287–1296 [5] hasegawa m., matsui k.: robust adaptive full-order observer design with novel adaptive scheme for speed sensorless vector controlled induction motors, proc. 28th annual conf. industrial electronics society, ieee 2002, 2002, 1, 83–88 [6] geyer t., papafotiou g., morari m.: model predictive direct torque control-part i: concept, algorithm, and analysis, ieee transac. ind. elec., 2009, 56(6), 1894–1905 [7] krause p.c., wasynczuk o., sudhoff s.d.: analysis of electric machinery, ieee press, new york, 1995 [8] mohan n., undeland t.m., robbins w.p.: power electronics: converters, applications, and design, john wiley & sons inc., new york, 1995 [9] hatos p., fodor, a., magyar a.: parameter sensitivity analysis of an induction motor, hung. j. ind. chem., 2011, 39(1), 157–161 hungarian journal of industrial chemistry veszprem vol. 30. pp. 1 5 (2002) water temperature distribution in a vertical cross-section of a wet counterflow cooling tower d. skobalj, z. zavarg6 1 and l. juhasz1 (" vujic-valjevo", alekse dundica 61/1, 14000 valjevo, yu 1faculty of technology, university of novi sad, bul. cara lazara i, 21000 novi sad, yu) received: november 29, 2000 the conventio_nal method of ~ooling tower calculation does not take into account heat exchange under the fill the basic reas~ns for this are: substantially less amount of heat is exchanged under the fill than in the fill and the definition of phys1cal model of heat transfer is rather complicated. nevertheless, in the case of cooling tower of greater dimension this method of ~alcu~atio~ may give uncorrect results. there are very few authors who treat this problem by experiments: the results obtained m this work show that the heat exchange under the fill is significiant. keywords: cooling tower, heat exchange, temperature distribution, counterflow introduction in industrial and energetic plants, water is commonly used as cooling medium. due to lack of industrial water, in most countries, there are in use only recirculated cooling systems. the main part of these systems are cooling towers in which water is cooled by atmospheric air. in the commonly used wet cooling tower the water and the air are in direct contact. there are several types of cooling towers depending on the air and water stream direction. one of the types is the counterflow cooling tower (fig. i). the first theorethical formulation of water cooling in the counter cooling towers was given by walker et al. [ 1]. according to this theory there are two independent coefficients: heat and mass transfer coeffi­ cients. merkel [2] was the ftrst who realized the conec­ tion between these two phenomena. the amount of heat transferred from water to air, according to merkel, is proportional to the difference in the enthalpy of the satu­ rated air and the enthalpy of the humid air. merkel [2] was the first who recognised the relation between these two processes. he gave the first appliciable formulation of differential equation of water cooling proces. ac­ cording to this formulation, the amount of heat transfer is proportional to the difference in enthalpy of the satu­ rated air and the humid air in the main stream. in deter­ mining the value of heat transfer it is sufficiant to use only one empirical coefficient; which includes both heat and mass transfer processes. the results of experimental investigation gave a certain deviation from the merkel theory. according to some references this deviation is due to approximation in the merkel equation [3] while in some others the merkel theory is fully rejected [4]. there are also a great deal of engineering ·calculation procedures which are differing in a level of approxima­ tion of the theory. the main reason for such great num­ ber of procedures lies in the fact that simultaneous mo­ mentum, heat and mass transfer in the cooling towers is one of the most complicated processes in the enginerring practice. most of these procedures are based on the merkel theory. because of its simplicity and relatively satisfactory results, the merkel theory is widely used and accepted in most well known international standards as a procedure for cooling tower performance calculation [5,6]. however, heat and mass transfer, according to this procedure, are taken into account only in the fill, while the space above and under the fill are neglected. the relatively high.price of the cooling tower fill demand the need to include the effect of water cooling in the zone under the fill. the experimental investigation shows that effect of cooling in the zone under the fill cannot be neglected. it enables to use less fill, keeping the same cooling intensity. 2 fig. i wet counterflow cooling tower merkel theory the wellknown international standards (din, cti) used in the merkel formulation for counterflow cooling tower performance calculations, often called as standard pro­ cedure [5,7]. the equation which describes heat and mass transfer according to merkel is: madha =:= {j(has -ha)·dv (i) setting air heat gain equal to water heat loss ma·dha =mw·dhw =mw· cpw" dt {2) combining with eq.( 1) we have (3) the integral term in the above equation is known as merkel number (4) the analytic solution of the integral (4) is not known. one way to solve it is to have an approximate analytic function between has and tw (linear or parabolic for ex­ ample}. another way is to solve the integral (4) numeri­ cally. the left side of eq.( 3} can be written in the fol­ lowing form. connecting it with the fib characteristics: (5) distributor cs1 cs2 cs3 cs4 ~1 ~1 ta1 t41 . . . . ~2 ~ ~ t42 t,3 tn tu t.a . . . . ~4 ~ ta. t .. . . . . (s (s (. .t<ig i·,.,' i·"" ·i·"" ·i'"' 'i i basin lew fig.2 thermoelements arrangement in the investigated cooling tower experimental water temperature measurement the schematic arrangement of ni-crni thermoelements is shown on fig.2. the following temperatures were measured: the inlet hot water temperature thw, the outlet cold water temperature tcw; 16 temperatures in the fill {four in each vertical cross-section) and four tempera­ tures under the fill. the thermoelements are mounted in a way to ensure the water film temperature measurement and not the two-phase or fill temperature. the used ar­ rangement of thermoelements enables us to have a tem­ perature field in the whole cooling tower and not only in the inlet and outlet of the system. the measurement results are given in tables 1-4. the vertical water temperature distribution in each ver­ tical cross-section are shown on figsa-5. the fill to increase contact surfaces, as well as time exposure, a fill is installed below the water distribution system, in the path of the air. the two types of fill in use are splash-type and film type. in the splash-type fill the wa­ ter is cascaded through successive elevations of splash bars arranged in staggered rows. film-type fill maxi­ mises contact area and time by causing the water to flow in a thin layer over closely spaced sheets, principally polyvinil chloride (pvc), that are arranged vertically. the aim is to have a fill of minimum size and maximum -contact surface. in this work pvc film-type was used. the me num­ ber vs. a is given on fig.3 [8]. 2,0 1,0 0,8 0,6 0,4 0,2 3 table 1 water temperature distribution in the investigated wet counterflow cooling tower mw = 13.27 kgls; rna = 19.30 kg/s; n = 975rpm; "twb = 9.0°c t in the distributor t in the fill t under the fill t in the basin csl tl1=22.sooc t12 = disconnected tjj= 16.00°c tu= 15.00°c vertical cross-sections cs2 cs3 tu =23.00°c t22 = 19.00°c t23 = 18.50°c tu= 16.00°c t11 = 18.25°c t32 = 17 .sooc t11= 17.25°c tj. = 16.oooc tcw = 11.50°c cs4 t.~1 = 22.25°c tn = 20.00°c t.j = 16.00°c t#= 14.50°c table 2 water temperature distribution in the investigated wet counterflow cooling tower t in the distributor ' t in the fill t under the fill t in the basin "'. ~ ......... ............. 0,4 ' csl tu =27.50°c t12 = disconnected t13 = 19.00°c tl4 = i7 .sooc me = 1.32 · j..o,ss " ~ .......... •' ~· • "" ....... ~~ 0,6 0,8 1,0 1 2,0 a. fig.3 the investigated pvc fill me number results and discussion vertical cross-sections cs2 cs3 tu = 27.75°c tjz = 21.25°c tn = 23.50°c tn = 19.75°c t21 = 22.25°c t11 = 19.00°c fu= 19.00°c t34= 17.50°c tzs = 16.oooc tjs = 13.50°c cs4 t,l = 27.50°c t.12 = 26.00°c t,j = 19.25°c t#= 17.75°c t.s = 15.00°c in the vertical cross-section 3(cs3) there is a great heat transfer in the zone between the distributor and the fill. the great temperature drop in this zone is due to disproportional water distribution in the distributor and disproportional fill packing. the effect of this is that less amount of water is in contact with greater amount of air, this is that consequence we have a more intensive cool­ ing in the zone between the distributor and the fill. the analysis of other vertical cross-sections shows that the water distribution is similar, and the temperaturedrops in the cooling tower zones are logical. from table 3 (csl) it is evident that the temperature drop above the fill is close to 4% and under the fill 26% of the whole tem­ perature drop in the cooling tower in the other experi­ ment, table 4, these temperature drops are about 3% and20%. conclusion the measured temperature values are given in tables 1 and 2. the water vertical temperature distributions are presented on figs.4 and 5. from these figures the tem­ perature drops above the fill, in the fill and under the fill are determined. the obtained temperature drops are presented in tables 3 and 4. the conventional method of cooling tower calculation does not take into account heat exchange under the fill. the heat transfer under the fill can be neglected in the case of cooling towers of smaller dimension. in the case of cooling towers of greater dimension the zone under the fill can be significiant and the temperature drop in this zone cannot be neglected. the results of this ex­ periment lead to this conclusion. 4 table 3 water temperature drops in the investigated wet counterflow cooling tower mw =13.27 kgls ;ma =19.30 kgls;n =975rpm; fwb =9.0°c cs1 cs2 cs3 absolute t drop [°c ] mcf 0.45 0.1 3.45 lltf 8.60 8.15 4.80 mnr 3.20 3.50 4.00 mror 12.25 11.75 12.25 relative t drop [°c ] cs4 0.85 8.60 2.55 12.00 mw'mror 0.0367 0.0085 0.282 0.072 m/atror l1tn/ mror i . tf'c] hw (23,2~) . . : . . . . i ' fabow: l fill ~ ~ 0,4m , :• ''if 0.700 0.260 0.723 0.298 0.392 0.326 i . cs4 : cs3 . . i i 0.72 0.21 _____ 33:::.;:_,(17,25) ~ 34(16.00) . . i . cs2 (19,00} : 23 (18,50x 24(16,00) cs1 : 15 11,00) flu.. : under flu. f : 0,6m : )o'l( 'i 1,0m 2,0m l(m] fig.4 vertical water temperature distribution according to tabl~ i table 4 water temperature drops in the investigated wet counterflow cooling tower rhw =13.27 kg/s ;rna =13.27 kgls ;n =750rpm; fwb =9.5°c l1tcf l1tf mn mror l1tv/mror m/l1tror l1tn/ l1tror i trcj hw(28,25} trcj hw (28,25~ cs1 0.45 10.80 2.75 14.00 0.0322 0.7714 0.1964 cs2 cs3 absolute t drop [°c ] 0.45 5.05 9.40 6.60 2.40 3.10 12.25 14.75 relative t drop [°c ] 0.0368 0.7673 0.1959 0.3423 0.4474 0.2103 i i cs4 cs3 cs4 0.65 10.20 2.40 13.25 0.0491 0.7698 0.1811 (15,00) 31 (21,25) : 32 (19,75) : 33 (19,00} ' 34(17,50} cs2 22(23,50) i 23 (22,25): i 24(19,00) i i . t . cs1 fill 1,0m :underfill. : 0,6m 20m l(m] fig.5 vertical water temperature distribution according to table2 symbols a fill coefficient, m1 cpw water heat capacity, jmol -1 k -1 ha enthalpy of air, jmor1 has enthalpy of saturated air, jmor1 hw enthalpy of water, jmor1 l fill height, m l height, m • 111a • t11w v air mass flow rate, kgs-1 water mass flow rate, kgs-1 merkel dimensionless number revolution per minute, rpm. dimensionless fill coefficient in eq. ( 5) temperature, °c water temperature, °c inlet water temperature, °c outlet water temperature, °c hot (inlet) water temperature, °c cold water temperature (in the basin), °c ~et-bulb temperature, °c temperature in the i-th vertical cross-section and j-th horizontal cross-section, °c fill volume, m3 greek symbols volumetric heat and mass transfer coefficient, kgm-3s air number temperature drop distributor-fill, °c temperature drop in the fill, °c 5 lltfb temperature drop fill-basin, °c mror temperature drop distributor-basin, °c abbreviations cs1,cs2, ... cw vertical cross section 1, 2, ... cold water hw hot water ij i-th column, j-th row references 1. walker w. h., lewis w. k. and me adams w. h.: principles of chemical engineering, mcgraw­ hill, new york 1923 2. merkel f.: verdunstungskiihlung, vdi for­ schunsarbeiten, 1925, no. 275 3. vadigarogjn g. and pastor e. j.: an investi­ gation of the accuracy of the merkel equation for evaporative cooling tower calculations, asme paper no. 54-h7-59, proc. of the aiaa/asme thermographys and heat transfer conference, boston, 1974 4. klenke w.: heat and mass transfer at evapora­ tive cooling and testing of cooling towers (in german), diss.techn.univ., braunschweing, 1964 5. cooling tower institute: cooling tower perform­ ance curves, houston,1967 6. din 1947: leistungs versuche an kiihltiirmen (vdi-kiihltiirmegelen), 1951 7. cooling tower institute: acceptance test code for water cooling towers: atc-105, houston, 1982 8. ninic, n. and vehauc a.: investigation and characterization of cooling tower plastic fills, insti­ tution boris kidric vinca, beograd, 1986 page 5 page 6 page 7 page 8 page 9 hungarian journal of industrial chemistry "veszprem vol. 30. pp. 37 39 (2002) the influence of water concentration on the corrosion of low alloy steels in the system methanolethylene glycol n-butiric acid d. sutiman and a. cailean (faculty of industrial chemistry, technical university "gh. asachl", d.mangeron 71a, iasi 6600, romania) received: aprillo, 2001 the behaviour of three types of steel with a variable carbon content (from 0,2 to 0,4 % ) is studied in medium of methanol10% ethylene glycol5% n-butiric acid with water concentration between 1% to 5 % . the weight loss are measured and the gravimetric figure k (g·m·2·h-1) and the penetration figure p (mm • m·2·year-1) are calculated. also, the kinetic corrosion parameters are established. the methods used for identification and analysis of the corrosion compounds are: elemental analysis, i.r. spectra and x-ray diffraction. also, by electron microscopy, a corrosion mechanism is assigned. introduction this paper is a continuation of studies of the corrosion behaviour of low alloy steel types in methanol medium and/or ethylene glycol, having as corrosion reagent, saturated monoand di-carboxyl organic acids [1-5]. this corrosion system and also the studied acids are the main responsible agents for the corrosion process that appears in the synthetic fiber industry. experimental the three steel types studied for the corrosion are: ol 37, ol 50, and ol 60 having the chemical composition presented in table]. the metallic samples used for corrosion were cut up from a cylindrical bar with 5 cm2 active surface. a single basis of the cylinder was corroded after preliminary grinding and polishing. dyeing protected the other basis and the lateral surface. the corrosion system contained methanol, 10 % ethylene glycol and 5 % n-butiric acid, the water concentration varied between 1 % and 5 %. we used merck reagents and the water was bidistilled, having electrical conductivity of 12 jis·cm-1 • karl-fischer method was used to determine the water content. the variation of ph values in the corrosion anhydrous system and at different water concentration was measured with a hach ph-meter. before introducing the samples in the corrosive system, they were submitted to a degreasing process in boiling benzene for 30 minutes and then degreased in a solution of hydrochloric acid (3 %) for 3 minutes. the corrosion system was open, allowing the permanenr access of oxygen from the atmosphere, reproducing the industrial process conditions. the final weight loss was converted to gravimetric figures k (g·m ·2·h ·1 ) and penetration figures p (mm·m ·2·year'1). for establishing the corrosion type. the metallic surface was visualised by electron microscopy on a tesla b 300 microscope. for the values of 1 % , 3 % and 5 % water concentration, the polarisation curves were plotted on a tacussel s8r potentiometer with input impedance of 1012 n. from the shape of these curves, the kinetic corrosion parameters (sst, scor and icor) were calculated. the corrosion final compounds, for every value of water concentration, were soluble in the system. they were obtained in solid state by evaporating the corrosive solutions at 40 °c, in inert atmosphere for avoiding the oxidation process that could take place because of the increasing temperature. after separation and drying. these compounds were analysed by x~ray diffraction on a hzg 4c karl zeiss jena diffractometer using co(l{j radiation, by ir spectroscopy on a specord m82. the chemical composition (c. h. 0 and fe) of the final compounds was afso determined. 38 table i the composition of steels used for corrosion test steel ol37 ol50 ol60 %c 0.20 0.30 0.40 %mn 0.80 0.80 0.80 %s 0.06 0.05 0.05 %si 0.40 0.40 0.40 %p 0.06 0.05 0.05 table 2 the values of indices k and p for the studies steels 1 2 3 4 5 ol37 kip 0.303/0.27 0.312/0.28 0.325/0.29 0.306/0.27 0.301/0.27 ol50 kj!p 0.293/0.26 0.307/0.28 0.315/0.28 0.301/0.27 0.295/0.26 ol60 kip 0.286/0.26 0.293//0.26 0.305/0.27 0.287/0.26 0.273/0.25 fig.] the metallic surface ofol 60 in the system methanol­ ethylene glicoln-butiric acid3% water (x 1200) results and discussion studying the ph values, we observed that in anhydrous system. the ph value is 2.7 and adding water, it is very slowly decreased to 2.6, at 5% water concentration. this practically constant ph-variation showed that n-butiric acid ionisation occurred with the help of the two solvents. water had not a significant importance in modifying the dissociation of the acid. in table 2. the values of weight losses converted into k and p figures are presented. from these values, we can observe a significant decrease the corrosion rate between 3 % and 4 % water concentration. this observation leads us to the conclusion that for values higher than 3 %~ water molecules participate in the formation of passive oxyhydroxyde layer establishing. the metallic surface~ visualised by electron microscope had the same aspect for an three types of steel, indicating a generalised corrosive process with a corrosive compound .layer on the entire surface. this layer is not uniform~ presenting holes~ and cannot accomplish an efficient anticorrosive protection. in fig./. the aspect of the metallic surface of ol 60 in the system with 3 % water concentration. magnified by 1200 times is presented. the polarisation curves were plotted for the values of 3% and 5<.iwater concentration. they had the same table 3 the values of the corrosion parameters in the system methanol 10% ethylene glycol n-butiric acid water types of esbmv ecor, mv icov ~cm2 3% 5% 3% 5% 3% 5% steels h~o h20 h20 h20 hzo h20 ol37 -483 -427 -510 -440 2.03 1.32 ol50 -467 -403 -480 -415 1.86 1.28 ol60 -449 -395 -465 -410 1.73 1.05 fig.2 the polarization curves in the system methanol ethylene glicoln-butiric acid3% water (• ol 37; x ol 50; o ol 60) 15 xt12an·' 7 fig.3 the ir spectra of the corrosion compounds obtained in the system methanol ethylene glicol n-butiric acid 3% water shape, as presented in fi'g.2. from the shape of these curves. the kinetic corrosion parameters were calculated and presented in table 3. the value of the corrosion current density, that practically shows the corrosion rate, decreases after the 3 % water concentration in the system. this observation is in concordance with the determined value for the corrosion rate, observed by the weight loss. studying the values of weight losses and also of the corrosion current density, we observed that the steel with the best behaviour is ol 60. in order to establish a corrosion mechanism. the final corrosion compounds were analysed. the x ray diffraction spectra of the corrosion compounds, of all types of steel, are the same and are being characteristic to the amorphous compounds. table 4 the chemical composition of the corrosion compounds in the system methanol 10% ethylene glycol n­ butiric 3% water % ol37 ol50 ol60 c 42.17 42.86 42.56 h 7.04 7.35 6.87 0 28.56 28.47 23.03 fe 22.23 21.32 21.54 the ir spectra are also identical, meaning that they present the same absorption bands at the same wave number; the ir-spectrum of the corrosion compound in the system containing 3 % water is presented in fig.3. in this spectrum, as it is mainly observed, the displacement of the characteristic peak of n-butiric acid, for the group coo-, from the value 1729 cm-1 to 1690 cm-1 • this fact is explained by a stronger bonding of carboxylic oxygen. also, the splitting in two peaks at this value explains the existence of two types of bonds, one covalent and the other coordinative [6]. the peak from 1550 cm-1 shows that this group is asymmetrically bonded. the absorption bands of hoare placed at 3400 cm-1 and 2900 cm·i, case in which water is coordinative bonded through oxygen and also, they indicate that these groups participate to a bridge linkage fe+--0-fe [7]. in the ir-spectrum, a peak at 1080 cm-1 is also observed, characteristic for the oh groups~ from alcohol [6-8]. the remaining maxima from the spectrum correspond to the vibration and rotation movements of c-c and c-h bonds. the elemental chemical composition of the corrosion compounds is similar for all water concentrations (variation of 2 %). in table 4, the chemical composition of the corrosion compound derived from the system with 3 % water is presented. from the presented data the following mechanism is assigned: fe0 -> fe3+ + 2e· hz0+1120z+2e-> 2ho­ fe2+ + ho-7 fe(oh)2 fe(oh)z + 2 c3h7cooh -7 fe(c3h~oo)z + h20 2fe(c3h~oo)z + h20+1/2 0z ~ 2 [fe(c3h~oo)zoh] n[fe(c3h~oo)zoh} poumerization ) [fe(c3h7c00)20h]n the structure of iron(iii) polybutirate is presented in fig.4. also, it is very important to mention that in the studied references, were not found the data related to the compounds of iron with n-butiric acid. the hexacoordination of iron and the bond of the final chain molecules are realised through ch30and hoch2 ch2ogroups. conclusions • ail three types of steel there is a given water concentration where the corrosion rate has a maximum value. 39 fig.4 the structure of the polymer compound of the iron with the n-butiric acid • the molar ratio water/acid, from which the corrosion rate decreases is 2.39, is smaller than the one presented in literature [9 11] for achieving an oxyhydroxylic passive layer. in literature, the value for this molar ratio is 4. the smaller value can be justified by the fact that the acid is dissociated in ions and, through the two organic solvents, water molecules are able to participate at smaller concentrations in the formation of the passive layer. this is in concordance with the minimum variation of ph, if into the system, more water is added. • the steel with the highest stability in all the cases is ol 60, which has the highest carbon content; the stability may be connected to the existence in the steel structure of a solid iron­ carbon solution, that is formed when the carbon concentration is grater than 0.3 % [12]. the corrosion mechanism is a complex one involving oxygen from the atmosphere. references 1. sutiman d., cretescu i. and cailean a.: rev. chim., 1998,49, 11,813-818 2. sutiman d., cioroianu t. and georgescu 0.: hung. j. ind. chem.j999, 27, 107-110 3. sutiman d., cretescu i. and nemtoi g.: rev. chim., 1999,50, 10,766-770 4. sutiman d., cretescu i. and cailban a.: rev. chim., 2000,51, 11, 889-892 5. sutiman d., cretescu i. and vizitiu m.: rev. chim. 2000,51, 12,986-989 6. avram m.: infrared spectroscoy, ed. tehnica, bucuresti, p. 15-86, 1960 (in romanian) 7. balaban a. t., baciu m. and pooany 1.: the physical methods applied in organic chemistry, ed. stiintifica si enciclopedica, p. 98-146, 1983 (in romanian) 8. the sandler handbook of infrared spectra, sandler hayden, london, 1978 9. banas j.: electrochim acta, 1987,32,871-875 10. banas j.: mat. i odlew, 1990, 16, 73-80 11. hoor t. p.: j. ele.ctrochim. soc., 1990, 16,73-77 12. cartis g.: thermal treatments, ed. facia. timisoara, p. 112-134, 1982 (in romanian) page 37 page 38 page 39 hungarian journal of industry and chemistry vol. 45(2) pp. 41–44 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0019 state-of-the-art recovery of fermentative organic acids by ionic liquids: an overview konstantza tonova* institute of chemical engineering, bulgarian academy of sciences, acad. g. bonchev str., bl. 103, 1113 sofia, bulgaria the main achievements of liquid–liquid extraction (lle) of fermentative organic acids from their aqueous sources using a diverse range of ionic liquids are summarized since the first study appeared in 2004. the literature survey is organized in consideration of the distinct chemical structures of the organic acids. the acids discussed include mono– or dicarboxylic ones (butyric, l-malic and succinic acids), acids bearing both carboxyl and hydroxyl groups (l-lactic, citric and mevalonic acids), and volatile organic acids (mainly acetic acid). information is given about ionic liquids applied in recovery, and the resultant extraction efficiencies and partition coefficients. as the topic is novel and experimental studies scarce, the selection of the ionic liquids that were tested still seems random. this may well change in the future, especially after improving the ecological and toxicological characteristics of the ionic liquids in order to bring about an “in situ” method of extraction without harming the microbial producers of the organic acids. keywords: extraction, ionic liquid, organic acid, recovery, re–extraction 1. introduction room temperature ionic liquids (ils) exist as molten salts at ambient temperature and consist entirely of ions, usually a charge–stabilized organic cation and an inorganic or organic anion. ils can be tailored to a wide variety of applications by combining different ions [1] and for this reason they are often called “designer solvents”. ils exhibit a broad range of unique properties, including negligible vapor pressure, high thermal stability and low chemical reactivity [2]. the union of these particular properties, together with finely tunable density, viscosity, polarity and miscibility with other common solvents favor the application of ils in different kinds of separation and reaction processes [3– 8]. considering the benefits that arise from the properties of ils, matsumoto et al. [9] first proposed an environmentally friendly system for the extraction of fermentative l-lactic acid. they used hydrophobic [cnc1im][pf6] instead of volatile organic solvents as diluents of reactive organic bases. these ils proved to be nontoxic towards the lactic acid producing bacterium lactobacillus rhamnosus, but provided low degrees of solubility of the reactive amines which resulted in insufficient levels of extraction efficiency. nevertheless, these results suggest possible applications of ils in extractive fermentations. *correspondence: konstantzatonova@yahoo.com 2. discussion on the organic acids extracted and the ionic liquids applied 2.1. butyric acid and phosphinate–based ils the most remarkable results regarding the partition coefficient of an organic acid in an il have been documented with regards to the extraction of butyric acid, the four–carbon fatty acid, with phosphinate-based ([phos]) ils. [p6,6,6,14][phos] and a novel ammonium phosphinate, [cncncnc1n][phos], were studied [10-11]. distribution coefficients of about 80 were obtained using the low concentrations of butyric acid, and the extraction efficiency was just as high in the pure (water saturated) il as in the il/water/dodecane reversed micellar solution. the ammonium phosphinate absorbed a relatively high amount of water until saturation was achieved, ca 21 wt%. (about 12 water molecules per ion pair of the il), which implies that an aqueous biphasic system was formed. 2.2. dicarboxylic acids and phosphoniumor imidazolium-based ils among phosphonium-based ils, [p6,6,6,14]cl seems the most suitable extractant for the recovery of low and moderate concentrations of dicarboxylic l-malic acid in aqueous solutions [12]. the other phosphonium-based ils and higher acid concentrations entrain third-phase formation, especially in the case of [p6,6,6,14][phos] when a large amount of the acid content (ca 40%) remains tonova hungarian journal of industry and chemistry 42 uncovered in both phases. the [p6,6,6,14]cl–rich phase is also the best extractant for another dicarboxylic acid, succinic acid [12]. extractions with [dec]and [phos]– based ils resulted in a substantial amount of undetectable acid in both phases, which was attributed to the formation of complexes between the organic acid and the extractants that were not quantified. more recently succinic acid attracted special attention in a comprehensive study where the extraction was carried out by aqueous biphasic systems (abs) of alcohols/salts or imidazolium-based ils/salts [13]. successful recovery was achieved by both systems. succinic acid preferentially migrates to the il–rich phase in all systems formed of [c6c1im]br and a kosmotropic salt (phosphate, sulfate, carbonate or citrate). the il salted out by (nh4)2so4 or k2co3 exhibited the highest levels of extractability. the ph values of these systems were quite different. the ph of the system with (nh4)2so4 was 3.43 which is below the pka values of succinic acid (pka1 = 4.21, pka2 = 5.72), while ph = 10.50 for k2co3 greatly exceeded the pkas. this suggests that unlike the aqueous biphasic systems with alcohols, the extraction capacity of the il/salts systems towards succinic acid is not ph–dependent and is most likely related to the proper nature of the solvent (il/salt) and the solute (acid). for the same il, [c6c1im]br, an excellent solvating capacity to the lactic acid was reported [14] so that the acid could be extracted from a concentrate of white wine. this way the extraction efficiencies of the abs of [c6c1im]br/(nh4)2so4 or k2co3 are comparable to those obtained with the hydrophobic il [p6,6,6,14]cl [12]. moreover, the re–extraction efficiency achieved was superior at ~71%. succinic acid was obtained in a crystalline form by direct precipitation with sodium hydroxide. 2.3. acids with both hydroxyl and carboxyl groups and phosphoniumor imidazolium-based ils different types of phosphonium-based il biphasic systems were applied for l–lactic acid recovery. an extraction efficiency of above 80% was achieved by using either pure [p6,6,6,14][phos] [12] or a mixed biphasic system of [p6,6,6,14]cl and an inorganic kosmotrope, mgso4 [15]. the kosmotropic salt engages more water molecules when hydrated thus rendering the microenvironment of the acid more hydrophobic which favors the undissociated form of acid suitable for extraction. all extraction systems of phosphoniumbased ils with long side chains suffer from the common disadvantage of forming stable emulsions or a third phase between the il–rich phase and aqueous solution. this drawback is avoided by applying ils of an imidazolium cationic moiety, however, in the majority of the cases these ils exhibit low levels of extraction efficiency towards lactic acid [9,16] and other acids bearing both hydroxyl and carboxyl groups (citric and mevalonic acids) [16]. an advantageous abs of imidazolium saccharinate, that possesses a long side chain, [c8/10c1im][sac], has been exploited lately and it was shown that when it is combined with an inorganic kosmotropic salt (that retains water from solubilization into the il–rich phase) an extraction efficiency of 81% and partition coefficient of 5.5 could be achieved [17]. the extraction yield of lactic acid was as high as 90% in a two–step recovery by [c8c1im][sac] with or without the addition of a kosmotropic salt (mgso4). moreover, successful acid re–extraction of 95% from the il–rich phase was attained by means of a solution containing an alkaline kosmotrope, k2hpo4. 2.4. volatile fatty acids and phosphoniumbased ils apart from culture broths, fermented wastewater streams still represent an unexploited source of platform chemicals, including volatile organic acids. volatile fatty acids are versatile carboxylic acids involved in the synthesis of bioplastics and other value–added chemicals [18]. the composition of fermented wastewater typically contains ~1 wt% of volatile fatty acids, but also a significant amount of various dissolved salts. the low concentrations of the volatile fatty acids and the large quantity of inorganic salt–originating ions result in ph–values of between 4 and 6, which are in favor of the deprotonated acid form and thus do not support complexation with the il. the distribution of acetic acid between model solutions with or without salts and different solvents, including phosphoniumbased ils, was recently studied [19]. similarly to the butyric and lactic acids [10,20], the low concentration of acetic acid and the use of [p6,6,6,14][phos] were the best conditions to obtain the highest partition coefficient in the il–rich phase starting from an idealized aqueous solution containing only the acetic acid. in the presence of salts (kcl, na2so4 or na2hpo4), however, the partition coefficients reported for [p6,6,6,14]cl were the highest in the series of ils tested and exceeded even those obtained in the classical extraction by trioctylamine (toa)/n-octanol. [p6,6,6,14]cl as a solvent has an inevitable drawback related to its measurable level of leaching into the aqueous phase due to the hydrophilicity of the [cl]–. contrary to [p6,6,6,14]cl, [p6,6,6,14][phos] and [p6,6,6,14][n(cn)2] were found to be highly stable as significant leaching was not detected in the aqueous phases [19]. extraction by [p6,6,6,14][phos], however, was strongly affected by the ions of the salts present in the feed, while [p6,6,6,14]cl and [p6,6,6,14][n(cn)2] kept extraction capacities constant for acetic acid. when the source contained different acids, mimicking actual fermented wastewater, it was found that the growing hydrophobic domain in the acid leads to higher degrees of extraction. butyric acid was the most extracted acid from the fermented wastewater, while lactic acid was the most challenging acid to extract. by modifying the solvent properties of [p6,6,6,14][phos] by sparging pressurized co2, a further increase in the extractability of acetic acid was observed recovery of fermentative organic acids by ionic liquids: overview 45(2) pp. 41–44 (2017) 43 [21]. the effect was attributed to the altered structure of the fluid which becomes more accessible for the acetic acid. this finding constitutes a general concept for the improvement of extraction processes other than those involving volatile fatty acids. ils can act as solvents and simultaneously mediate reactive extraction to valorize low–titer volatile fatty acids. this has been recently shown through an il– mediated esterification of acetic acid recovered from dilute aqueous streams [22]. the acids produced in anaerobic digestion or fermentation were transferred to a nonvolatile hydrophobic phase where they reacted with an alcohol (ethanol) in order to generate volatile, value–added esters of low solubility. [p6,6,6,14]–ils were selected for their potentially high extracting capacity and hydrophobicity. their hydrophobic character provides a water-excluding site for esterification and a nonvolatile carrier for the evaporation of the ester produced. significant accumulation of acetic acid in the il was achieved by using [p6,6,6,14][n(cn)2], but this was mainly due to the exchange of [n(cn)2] – for the acetate anion as the dicyanamide anion was found to hydrolyze under the extraction conditions used, including at an elevated temperature (75 °c). contrary to the extraction, [p6,6,6,14][n(cn)2] and [p6,6,6,14]cl appeared to be the worst media for performing esterification, while the best was [p6,6,6,14][tf2n], which, however, is poor and costly extractant. thus an il of combined anions, cl– + [tf2n]–, was tested which could be used in a multistage way. starting from an aqueous stream of 0.33 mol dm-3 acetic acid, 0.44 mol dm-3 accumulated in the mixed [p6,6,6,14]cl+[tf2n] which allowed an esterification conversion of 56% to be achieved over 30 min. 3. conclusion ils are commonly considered more sustainable than classical organic solvents. it is well known that the toxicity level of conventional solvents to microbes limits their compatibility with fermentation broths. however, the label of “green solvent”, assigned to the ils, has led to the delusion that they are nontoxic and biodegradable, which is not true about some of the most employed ils. for example, the commonly used [p6,6,6,14]cl may be regarded as toxic in aquatic environments exhibiting much higher levels of ecotoxicity compared to ordinary organic solvents [23]. the biocompetitiveness and biodegradability of ils are not still convincingly argued for [24-25]. the need for novel extractants with improved characteristics from ecological and toxicological standpoints can be put forward. by taking into account that aqueous streams and bioorganics are treated, the environmental impact of ils should be resolved as a result of future studies. symbols il’s cationic moiety: [cnc1im] 1-alkyl-3-methylimidazolium [cncncnc1n] trialkylmethylammonium [p6,6,6,14] tetradecyl(trihexyl)phosphonium il’s anionic moiety: [dec] decanoate [n(cn)2] dicyanamide [phos] bis(2,4,4-trimethylpentyl)phosphinate [sac] saccharinate (which is a benzoic sulfimide) [tf2n] bis(trifluoromethylsulfonyl)imide other: toa trioctylamine acknowledgement this research was supported by the bulgarian science fund (contract grant dfni–b01/23). references [1] blundell, r.k.; licence, p.: quaternary ammonium and phosphonium based ionic liquids: a comparison of common anions, phys. chem. chem. phys., 2014 16(29), 15278–15288 doi: 10.1039/c4cp01901f [2] freemantle, m.: an introduction to ionic liquids (rsc publishing, cambridge, uk) 2009 [3] mutelet, f.; jaubert, j.-n.: interactions between organic compounds and ionic liquids. selectivity and capacity characteristics of ionic liquids, chapter 10 in ionic liquids: theory, properties, new approaches, ed.: kokorin, a. 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(intech) 2011 doi: 10.5772/15463 [25] egorova, k.s.; ananikov, v.p.: toxicity of ionic liquids: eco(cyto)activity as complicated, but unavoidable parameter for task–specific optimization, chem. sus. chem., 2014 7(2), 336– 360 doi: 10.1002/cssc.201300459 hungarian journal of industrial chemistry veszprem vol. 30. pp. 131135 (2002) the simulation of cluster formation process in fine particles dispersion under the influence of external magnetic field a. pristovnik, l. c. lipus, a. krope and j. krope1 (faculty of mechanical engineering, university of maribor, smetanova 17, 2000 maribor, slovenia 1 faculty of chemistry ar1d chemical engineering, university of maribor, smetanova 17, 2000 maribor, slovenia) received: january 18,2002 the magnetic water treatment (mwt) devices for scale control can be used with great economical and ecological benefits. according to experimental results in well-controlled laboratory conditions it can be established that effects of mwt devices are highly dependent on composition of treated dispersion system and their working conditions. to investigate the effects of magnetic field on cluster formation process in fine particle dispersion under the influence of external magnetic field of the mwt device, a theoretical model on the dl vo theory and statistical monte carlo metropolis method have been used. the "open source" computer programs for the simulation and graphical presentation of clustering under the influence of external magnetic field have been developed. obtained results have been an.uyzed by cluster analysis based on the partitioning and hierarchical methods (fuzzy, agglomerative and divisive analysis). keywords: magnetic water treatment, scale prevention, monte carlo metropolis method, cluster analysis introduction the magnetic water treatment (mwt) is frequently used non-chemical method for scale control. it is economically favorable and is one of the most controversial scale prevention methods. scale prevention is achieved by passing the water through the magnetic field. despite several decades of intensive research work done in this area, no scientifically confirmed theoretical explanation exists yet, which adequately describes how mwt devices work and what are the conditions under which is their operation most effective. supplied natural waters are rich dispersion systems, which contain many colloids, ions, etc. due to natural supersaturating of supplied water or supersaturating by changed operation conditions (such as pressure drop, temperature and ph) a hard scale precipitates on pipeline and equipment walls. the magnetic water treatment is particularly promising technique for manipulation and controlling the interactions between micrometer-sized colloidal particles dispersed in fluid suspensions [1}. although many processes affect colloidal behaviour, the balance between the thermal, attractive and repulsive terms determines a criterion of the stability of colloid dispersions in natural waters. d.etailed consideration of this interplay is the basis of the dlvo [2] theory. the tendency of particles to aggregate via the short range van der waals-london force is counter act by a charged layer on the particles. thus the total interaction energy ( et ) between two colloidal particles is the sum of the double layers energy of interaction (repulsive energy e,) and the energy of the interaction particles themselves due to van der waals-london forces (attraction energy e. )[2]: (1) the repulsive energy ( e,) between two relatively large spherical particles depends on radii.is of interacting spheres (a ), length between centers of particles ( r ) and dielectric constant ( e ) of dispersion medium: (2) where ( s ) represents the ratio between distance and radius { s ""r/a) between centers of these two spheres. the extension of the double layer { 8 ) is in the order of 1/k, where k is the debye-huckel parameter and bas the dimension of reciprocal length: 132 --. 30 f----"-+-....._+-..,-+--+-~+.-=--i-=·~--~ -::..._ .. -.. _ :!0 20 30 40 50 60 70 fig.l random distributed spherical particles in a two dimensional square cell (a=70 units, d=l unit, n=300) 1 {j =-, k 2 8nne~z k =--ckt (3) for oxides in water, the surface potential ( q;o) of particles is determined by the ph of suspension [2,3]. the energy of attraction ( ea) between two spherical particles with identical radius is defined by eq.(4): e =-kh ·(-2-+3._+lnsz-4l a 6 s2 4 s 2 s2 j (4) where k11 is the hamaker constant. magnetostatic particle interactions modify the behavior of the fluid and can have a detrimental effect on the colloidal stability. when a dispersion of colloidal particles is placed in an external magnetic field additional magnetic force arises, which decreases the stability of the colloid particles when attractive. the energy of the magnetic attraction ( em ) between two spherical particles separated by a distance ( rr) depends ' g >n magnetic field density ( b ) and angle of the external magnetic field, radius of the particles (a ) and magnetic properties of the particles: 32m6xaba e =(5) m 9f,t.,r~ thus the total energy of interaction ( e, ). of colloid particles in the external magnetic field is: (6) statistical numerical methods known as monte carlo methods ate methods that utilize sequences of random numbers to perform the simulation. the presented model is based on the monte carlo metropolis [4,13] method and bas been used to investigate the properties of colloid particle dispersion in water under the influence of magnetic field [:2,3,5,6,7]. the model is based on a two-dimensional iquare ceu with side length (a) containing (n) random distributed spherical particles (fig. i). au the particles are identical. " a , ~ ~'*"" y a jl~ \if\ ~ ... (xj.yj) !>' ~~ l v la_ ~ x fig.2 a pair of spherical particles (i, j) in a two dimensional square cell under the magnetic field applied at angle \jl [8] the position of any particle is known and can be specified with coordinates (x, y ,8), where (8) is the angle between the magnetic moment of the particle and the applied magnetic field [6] (fig.2). the base energy of the system ( e8 ) is determined as the sum of the total energy of interaction of all colloid particles in that square cell: n es = let(i) i=l (7) the technique consists of calculating the energy change ( ae) when the coordinates of one particle of the representative ensemble are changed at random by a small amount. if the new total energy of the system is less than previous, the particle stays in new position, otherwise the factor ( p ) is calculated and compared with random number(x; xe [0,1]): -lie p=ekt (8) if factor p is greater than random number the particle retains its new position, otherwise it is returned on its original position. this procedure is applied for of n particles in a square cell experimental a computer program for the simulation of cluster formation well-known theories from the field of colloid, statistic and mathematics science have been taken into the consideration and been applied in the magnetic water treatment research. an "open source" computer program (mcm) [14] for-two-dimensional simulation of the cluster formation process in fine particles dispersion under the influence of external magnetic field which according to some authorst9.lll1, take place in y 25.00 18.75 12.5g 0.00 0.00 6.25 fig.ja position of the particles after 10 moves [8] mwt device, was developed. for the graphical presentation (mcm view) [8] and cluster analysis (fanny&twins) [11j the set of computer programs were used. the data are entered with two input files. in the first input file the size of the cell, number and physical properties of the particles are determined and structure for the intermediate output files is defined. in the second input file the origin position of the particles is determined. the results of simulation are written in various formats and can presented with the programs such as microsoft excel [14] or microcal origin [14] as a front end. for the graphical presentation the "mcm view" program has been developed on the basis of compaq array visualiser [14]. the results have been further analysed with the partitional and hierarchical methods for cluster analysis of authors kaufman and rousseauw [11] (fuzzy, agglomerative and divisive analysis). for that purposes programs ''fanny" any "twins" have been used. results and discussion as the reference data for the primary numerical calculations, the physical properties of the hematite particles ( fez03 ) in aqueous dispersion have been used. on this basis, the numerical calculations for some of the scale forming minerals in the water such as: diamagnetic calcium carbonate { cac03 ), calcium sulfate ( cas04 ), silicon dioxide ( si02 ), paramagnetic hematite ( fe20 3 ), goethite ( feooh) and ferrimagnetic magnetite ( fe,04 ) have been carried out. for all of the enumerated minerals, the simulation of cluster formation has been carried following out physical and chemical conditions: • different number of particles and their radius in the square cell; 133 y 25.dj 1&.75 12.50 ~-25 0.00 13.75 25.00 figs& position of the particles after 600 moves [8] different angle(1jf) of the applied magnetic field (0, 30, 60 and 90 degree); different retardation potential (<p), which determine the strength of the repulsion force (10, 20 and 30 mv); different density (b) of the applied magnetic field (from 0 to it); different ph values of the aqueous dispersions and others181• the total interaction energy for the paramagnetic hematite particles ( n = 40 + 300 ) with the diameter ( d = 1 + 10 pm ), volume magnetic susceptibility (x= 0.02) and hamaker constant ( kh = 5-10-20 j ) in square unit cell with side length (a == 25 + 70jlm) has been computed. the absolute temperature and ph of the dispersion, have been set to 300 k and 7.0, respectively. according to the previous research [ 6] the recommended rate of convergence is up to 600 moves per particle. the origin position of the particles has been set up as 5x8 matrix. fig.3 presents position of the particles after 10 and 600 moves under magnetic field of density 0.5 t, applied at 30° angle. fig.3b it is quite easy to perceive the formation of one major and two minor clusters, which are well arranged in the direction of applied magnetic field. from the same figure, the intensity or even the size of the cluster cannot be obtained. thus the results have to be analyzed with the adequate mathematical method suitable for cluster analysis. the fuzzy clustering method, as a generalization of partitioning, was used in computer program fanny. the intensity of the cluster formation process had been measured with the !alue of normalized version of the partition coefficient ( sk~s ). fig.4 shows the intensity of the cluster formation process of the hematite particles at the different retardation potentials and under the magnetic field applied at different angles. according to experimental results (12], the effects of the magnetic water treatment devices are high dependent on composition of treated dispersion system. 134 0,80 0,70 ~ ./"" --0,40 ~ 0,50 0,75 '¥ =30",<p = 20mv 1,00 b(l) 0,80 ,.......----------·----, 0,70 .j------------------1 s 0,6u ~=::::::==::;=--======t ~ 0,50 -1-------------l 0,40 +----------------; (),30 +------------------1 0,20 +----~----.-------1 o.zs 0,50 0,75 b(l} 1,00 '¥ = 60" ,<p= 20mv 0,80-.--------------. / 0,70 -1----------~----:r'--l s 0,60 +"'" ... ..............,=--------------::?""c__---l ~ 0,50 +-----=""---""""'--------l 0,40-!---------------j 0,30-t---------------j 0,20 +---------------~ 0,2s 0,50 0,75 b(l) 1,00 '¥ = 90" ,<p = 20mv 0,80 0,70 s 0,60 ~ 0,50 0,40 0,30 0,20 ~ 0,25 0,30 0,70 s o.ro ~ 0,50 0~40 0~30 0.20 0,25 0,50 0,75 '¥ =30" ,<p=30mv 0,50 0,15 '¥ = 60",q>=30mv ~ l 1,00 b(i') ~ i 1,00 b(f) 0,80,------------, 0,70f-------------:j s o.ro-l-,_-=....--"'=~:::::::::~~----1 ' ~ i ~ o,s<>.j-----------""'~~------jj 0,40.j--------------"'ooo;;:-j ·"! 0,30f-------------:! 0,20-t--------~-----i 0,25 0,15 1.00 0,5<> b(f) '¥ = 90" ,<p = 30mv fig a the intensity of the cluster formation process (normalized version of the dunn's partition coefficient, s k~s ) under the magnetic field of density 0.5 t applied at different angles and different retardation potentials [8] ! ' 0,411 •• • • y. •• o,:lli " i o.30c " i.i i 0~-~---~~--~4-~~---~-~~~~+-~--l 1 2 3 4 5 , .... ,.._..,.(~! g 7 a ~ w u a a m pll(~ figs the intensity of the cluster formation process with ph change and graph approximation with the polynomial of second order [8] and working conditions. the ph value of the system is on~ of the most influential conditions for the duster formation process. for the successful clustering of hematite particles the optimal ph range of treated dispersion (figs) is from5.6 and up to !0.3. condusions despite the large volume of research work in past decades. the theoretical understanding of mwt mechanism is still incomplete. this is the main problem in design of efficient mwt devices. the mwt mechanism is very complex and directly depends on chemical composition of water as solution/dispersion system and working conditions. · the theoretical model. for simulation of duster formation with hematite particles as the reference data has been supplement and widens to the region of magnetic water treatment. the model is based on the dl vo theory, monte carlo metropolis method and cluster analysis theory. with the computer programs based on presented model, the numerical calculations for most of the scale forming minerals, have been done. the obtained results have show that the model well predict the essential operational conditions for the effective use of mwt devices, if the chemical composition of supplied water is known. symbols a radius of interacting spheres b magnetic field density e0 electron chargel.6·io·''l as ea attraction energy repulsive energy (m) (vslm2 ) (as) (j) (j) e, total interaction energy kh hamaker constant n, n number of particles r length between centers of particles s ratio between distance and radius t absolute temperature z1 ion valence 8 extension of the double layer £ dielectric constant 8 angle between the magnetic moment of the (j) (/) (i) (m) (i) (k) (i) (m) (f) particle and the applied magnetic field (rad) cflo surface potential (j/as=v) \jf angle of the external magnetic field (rad) references 1. grier d. g. and behrens s. h.: interactions in the colloidal suspensions, the james franck institute, the university of chicago, 2001 2. svoboda j.: international journal of mineral processing, 1981,8,377-390 3. svoboda j.: ieee transactions on magnetics, 1982, 18(2), 796-800 4. metropolis n., rosenbluth a. w., rosenbluth m. n., teller a. h. and teller e.: j.chem. phys., 1953,21, 1087-1092 5. chantrell r. w., bradbury a., popplewell j. and charles s. w.: j. phys. d: appl. phys., 1980, 13(3), 119-122 6. chantrell r. w., bradbury a., popplewell j. and charles s. w.: joqrnal appl. phys., 1982, 53(3), 2742-2744 135 7. miles j. j., chantrell r. w. and parker m. r.: journal appl. phys., 1985, 57(1), 4271-4273 8. prjstovnik a. j.: configuration and formation of clusters from dispersion particles during the magnetic water treatment, draft of doctoral dissertation, university of maribor, faculty of chemistry and chemical engineering, unpublished work, 2001 9. iovchev m.: the effect of magnetic field on an iron-oxygen water system, khim. tekhnol. inst. 19:73-84, 1966 10. herzog r. e., shi 0., patil j. and katz j. l.: american chemical society, langmuir, 1989, 5(3), 861 11. kaufman l. and rousseeuw p. j.: finding groups in data-an introduction to cluster analysis, a wiley-interscience publication, new york, toronto, 1990 12. kulskii l. a., kochmarsky v. z. and krivtsov v. v.: khimiya i tekhnologiya vody, 1983, 5(4), 296-301 13. csep: introduction to monte carlo methods, electronic book, http://csepl.phy.ornl.gov/csep/ mc/mc.html, copyright (c) 1991, 1992, 1993, 1994, 1995 by the computational science education project 14. computer programs: mcm, mcmr_z_a in mcm view, copyright© 1997-2001 andrej pristovnik compaq array visualizer 1.1 copyright© 1998-1999 digital equipment corporation microsoft®excel, version 97, copyright© 1985-1996 microsoft corporation microcal tm origin, version 6.0, copyright© 1991-1990 microcal software, inc. page 130 page 131 page 132 page 133 page 134 hungarian journal of industrial chemistry veszprem vol. 30. pp. 199 206 (2002) application of fourier transformation for waste minimization in batch plants. 1. analysis of production recipes n. g. vaklieva-bancheva, e. g. shopova and b. b. ivanov (institute of chemical engineering bulgarian academy of sciences, "acad. g. bontchev" street, bu03, 1113 sofia, bulgaria) received: july 2j, 2002 in the present study an alternative system oriented approach for determining the environmental impact assessments is proposed. it is based on the application of fourier transformation for presenting the discontinuous functions of waste-w mass rates as continuous ones. using the fourier transformation the respective environmental impact indices are presented as functions of time and the environmental impact assessments for the given pollutant and for the entire plant are obtained. the approach is used for environmental impact analysis of production recipes based on the example of curd processing. the optimal milkfat content is obtained so that the global bod generated in the process is minimal. the distribution of the environmental impact level into the production cycle is presented. keywords: environmental impact assessment, fourier transformation introduction aiming to meet increased environmental regulations, the problems of pollution reduction have taken a significant place in the scientific research in the last few years. the waste decreasing concept has shifted from the "end of pipe" treatment to waste minimization at the sources [1, 2]. following this trend, a number of systematic methodologies for waste minimization have been proposed and developed during the last decade. hilaly and sikdar [3, 4] have introduced the concept of generic pollution balance of a process in order to develop a systematic methodology and the resulting war algorithm for waste minimization. by defining a pollution index of a product for a process war assesses the waste generation in a given process, provides options for waste reduction and carries out a systematic handling sensitivity analysis of waste minimization tasks on the target process modifications. at the same time, linninger at al., [5] proposed another systematic approach for batch process conceptual design. according to it a synthesis of utopian process with zero a voidable pollution (zap) is carried out first. which is then followed by a guided evaluation to the process with minimum avoidable pollution (map). the approach is implemented through a computer~aided tool batchdesign-kit [6]. the new development in this direction is a methodology for minimum environmental impact contact information: e-mail: vaklieva@bas.bg (mel), developed by pistikopoulos and others and introduced firstly for continuous processes p, 8], and further extended for batch plants [9]. the mel methodology embeds the principles of life cycle analysis within an optimization framework and involves the following steps: i) definition of a process system boundary; ii) environmental impact assessment~ and iii) incorporation of environmental impact criteria explicitly as objectives together with economics in different optimization problems. in step (ii), the environmental impact assessment is carried out using appropriately defined environmental impact indices. these indices are measures for air pollution critical air mass, ctam (defined for continuous processes [7, 8] as [(pollutant mass rate in kg wastelh)/(standard limit value in kg waste/kg air)}), for water pollution critical water mass., ctwm , for solid wastes solid mass disposal, smd , etc. similar indices could be defined by using other ecological "indicators" such as bod, cod. tss, etc. the integral values of the defined indices over a time period h produce the environmental impact assessments: environmental impact for a given pollutant-w • elw. and global environment<tl impact for the entire process gel. however, in batch plants {9]. the mass rate of pollutants is not constant with time due to process 200 discreetness. this requires the environmental indices to be defined with regard to the mass of pollutant processed at discreet time intervals t. for example, the index for air pollution ctam is: ct am = mass of pollutant at interval t (kg pollutant w) ( 1) rw standard limit value (kg pollutant wlkg air) thus, to obtain the environmental impact assessments, the process/unit assignments over the time horizon (which is divided in a number of finite time intervals) must be firstly carried out, followed by calculation of the processed mass of the waste-w and the environmental impact indices at each time interval. the environmental impact assessmenteihw for a pollutant­ w, is obtained by summarizing the respective environmental indices in the time horizon h: h e!hw = l,[ctamrw ctwmzw sdmzw ... ] (2) t=i and, the global assessment for the entire processge!y is: (3) the procedure for environmental impact assessment calculation results in the use of binary variables in optimization problems to describe process/unit/waste states at the time intervals. taking into account the fact that a great part of batch productions are manufactured cyclically, the aim of this study is to propose an alternative system oriented approach for determining the environmental impact assessments. the approach is based on the application of fourier transformation for presenting the discontinuous functions of waste-w mass rates as continuous ones. this allows the environmental impact indices to be defined similarly to those for continuous processes, through waste mass rate. moreover, this presentation demonstrates the distribution of the waste­ w mass rate, and/or respective impact indices into the horizon h~ and provides opportunities for pollution control in the case of posed environmental limits. the paper is structured as follows: application of the fourier transformation for polluting description from periodic waste sources and determination of the environmental impact indices and assessments by using the transformed functions are presented in the first part. the second part presents a practical application of the proposed approach for environmental impact analysis of production recipes based on the example of curd processing. comments and discussion of the obtained results are given in the third part. fourier transformation for podution description from routine waste sources generally~ the manufacture of products in batch plants follows discreet sequences of individual production tasks, which appearance onto the time horizon h depends on the corresponding cycle time tc. while their duration is specified by the production time t. the absence of a strong process/unit assignment leads to the existence of a number of production routes with different batch sizesb. the waste sources also appear discreetly into time and their place in the plant depends on the chosen process/unit assignment. commonly, the waste sources in batch plants are considered routine and non-routine. the routine sources are expected to appear in product manufacture. they depend on the chosen production recipes, the type and quality of the raw materials solvents and other used compounds, production tasks and determined process/unit assignment, scheduling, cleaning technology etc. the amount of processed wastes from routine sources and their impact on the environment can be assessed in advance. the non-routine waste sources come as a result of units breakdown, human mistake or other accidental events. the amount of the processed waste cannot be predicted in advance but the appearance of such waste sources can be avoided by increasing system reliability and decreasing its sensitivity with regard to the affect of human factors. consequently, the appearance of routine waste source related to a given production task l of product i, follows the corresponding cycle time tci into the time horizon. supposing that the mass rate of the pollutant-w is a constant during processing time tu then the discreet function <i> wil (t) of w-polluting for one production cycle is: 1 0 for o~t~tsil <l> wu (t) = b;~wil for ts 11 ~ t ~ tsil + ~~ ' 0 for tsu+~1 ~t~tc; when: tsil is the starting time of task -l with regard to the cycle beginning; bi [kg] is the batch size; and mwu [kg/kg] is the mass of the waste w processed from the production task l per a unit target product. bimwil the expression [kglh] presents the waste w r;l, mass rate. the function <i> wu (t) depicts a cyclic discontinuous function with a period tc; into the time horizon h, as is shown on fig.l. it is well known that each discontinuous function with a period t > 0 can be approximated with the fourier series: a .. 'p(t) =--.!!.. + l [a1 sin(k~pt )+ b1 cos{ktpt }1 t ~ t ~ t, (5) 2 k=l when k is a series order. the function confessions are determined as follows: 2r a0 =-jlf(t)dt, to (6) lit lit lit t [h] fig. i cyclic discontinuous function of the polluting from the routine waste source 2t ak =-j 'i'(t)sin(kqjt }lt, to 2t bk =-j 'i'(t)cos(kqjt )dt. to (7) (8) the discreet periodic function <i> wil (t) can also be approximated with a fourier series into the horizon h _ where the determined confessions according to (6)-(8) are: (9) [ co{ k 2 n ts;z il-co{ k 2 n ~~ j] + b;mwil tc; tc; a(wil)k = k~z . ( k2n j . ( k2n j +sm --tsil sm --~1 tc; tc; (10) the function. <i> wit (t) transformed in the fourier series into the timy horizon his 21! where = (/j· tci ' (12) for05:t$h the new function fw;t (t) "wraps up" the emissions from a given routine source into a "shell" which is 201 continuous in the time horizon. it describes adequately the w-waste mass rate from a given routine source because it is presented through w-waste mass balance per a unit target product, and contains such parameters as batch size, cycle time and processing time that characterize the product i manufacture in the plant. the function fwu (t) allows determination of the w­ waste mass rate at any moment t from h. by using functions fwu (t) the routine sources of the waste· w which belong not only to a given product but also to a system of compatible products can be ~·wrapped up" into a common "shell" in the time horizon: where: fw(t) = llfwil(f), i l 'r;f/ eli, "die i, for 0'5t'5. h (13) li is a number of production tasks of product i ; and i is a number of products compatible in the horizon h. the function fw(t) presents the w-waste mass rate in the time horizon and can be used for the determination of the respective environmental impact indices. if the pollutantw is emitted into the air, when using eq.(13) the respective environmental indices are expressed as a function of t. for example for air pollution they are: where: 1 ctam w(t) =-l.lfwil(t), )-tt41 i l "'il e lp vie /, for0'5.t'5.h (14~1 j-lw is the standard limit value for the pollutant· w into the air. the environmental impact indices can also be presented in accordance with the eq.( 1) for a whole horizon h. in this case the processed w-waste mass from one routine source or from a set of routine sources belonging to one or a system of compatible products is obtained through integrating over the time horizon h: h (m wil )h == f f14.if (t)dt (15) 0 11 (m .... )h = llf f ... 11 (t}dt. i l 0 (16} 'v l e l, 'vie i using (16) the environmental impact indices ctam hw, ctwm 11..,, sdm 11,.,., etc. at the whole horizon h are: 202 table 1 content of the standardized whole milk. bod = 10 composition 1. water 2. total solids milkfat lactose proteins total casein 87% 13% content 3.6% 5% 3.25% 2.85% 1 h ctamhw = l,l,-ffwu(t)dt (17) i l f..lw 0 it is obvious that eq.(l7) is integrated over h eq.(14). it is important to note that ·the eq.( 17) has an analytical solution at h and the fourier series at k = 1 could be used for the purposes of waste minimization problems. using (17) the respective environmental assessments elhw for a pollutant -w, and for the entire process geih are: ei hw = [ctam hw ctwm hw sdm nwl (18) the application of the fourier transformation, for adequate description of pollution from discreet routine sources of batch plants has been presented. by using it, the periodic discontinuous fiction of the w-pollutant mass rate from a given source is approximated with a continuous one in the time horizon. this approximation is extended to the sources that belong not only to one product but also to a system of compatible products in a given horizon. using the fourier transformation the respective environmental impact indices are presented as functions of time. their integrals over the time horizon h are used for determination of the environmental impact assessments for the given pollutant and for the entire plant. environmental impact analysis of production recipes on the example of curd production the biochemical oxygen demand bod, is a measure of effluent strength in terms of the amount of dissolved oxygen utilized by microorganisms during the oxidation of organic components. the wastewater discharged from dairy plants contains a significant amount of proteinst milkfat, lactose and other organic matters. some of these pollutants come as a result of dairy processing such as pasteurization, vat-processing draining etc. while the rest are due to losses of raw materialy by-product and product, for example spined and leaked milk or whey~ coagulated milk, butter, curds or cheese particles glued to unit wans. generauy1 the bod loading from dairy processing depends on the composition and the amount of processed raw materials whole and/or skimmed milk. the biochemical oxygen demand of the milk is: table 2 description of the production tasks in curds processing. cyl(x)* is yield of curds by-product and xis milkfat content in skimmed milk production task tasks duration input/output task 1 30 min. in. skim-milk out. pasteurized skim-milk task 2 240 min. in. skim-milk in. culture out. curds by-product out. whey fractions 1 0.88 0.12 cyl(x)* 1-cyl(x) task3 30 min. in. curds by-product 1 out. curds target product 0.9 out. drained whey 0.1 bodm =0.89.mf%+1.03l.mp%+0.69.ml% (20) where (mf% ), (mp%) and (ml%) are the content of the main milk components milkfat, proteins and lactose. it is accepted in the world practice [10, 11] to standardize the whole milk (table 1) which is the base for determining the milk composition required for products manufacturing and to account bod "processed" in different production tasks. the contribution of product losses could reach up to 80% of the common bod load. that is why the bod is used as a loss measure during handling and processing [10]. taking into account that losses cannot be avoided, it is a common practice to assess their impact by using the established levels of the inherent losses. purpose of the analysis generally, the purpose of the environmental impact analysis of production recipes is to find the optimal conditions for product manufacturing at minimum environmental impact. it is very impqrtant to note that this analysis is carried out with regard to 1-kilogram target product processed and the particular process/unit assignment is not taken into account. using the proposed approach, the aim of the environmental impact analysis of curd production recipe is: i. to determine the optimal milkfat content of the used skimmed milk in such a way that the global environmental impact assessmentglobal bod is minimal. in the analysis both bod "processed" in production tasks and bod due to accounted inherent losses are considered; 2. to show the distribution of the environmental impact level into the production cycle at different operational modes. production recipe and products content the curd is a 1owfat milk product it contains about 80% water and 20% solidsproteins (mainly casein) fat, minerals, microelements and other milk compounds. table 3 the product compositions and calculated values of the recovery factors composition of the curd target values of the recovery products factors moisture % fc % cc % sc % rs rc fdm rf a 80 0.3 11.3 20 1.724 0.96 0.015 0.075 b 81.58 1.009 12.28 18.42 1.386 0.96 0.055 0.231 the curd is processed from milk skimmed in the boundaries of 0.05% ~ x ~ 1.4% (x is % of milkfat) by direct acidification with lactic acid-producing bacteria or acidifiers. the curd production is a cyclic batch process. its flow chart and the description of the respective production tasks are presented on fig.2 and in table 2 [9-11]. the yield of the target product depends on the milkfat and casein content in the skim-milk. the lactose is fully passed into the whey. the van slyke equation for yield calculation is used [12]: where: x cy(x)= [rf.x+rc.mc%(x)]rs sc% (21) is milkfat content in the skim-milk mc%(x) casein content in the skim-milk presented as a function of milkfat content. rc, rf, rs are factors of casein, milkfat and other solids recovery from the milk; sc% is the solids content in the target product. one is accepted rc ::::: 0.96 , while rs is determined sc% as rs ~ where cc%, fc% are the cc%+fc% casein and fat content in the curd. the fat recovery factor rf is calculated by using fat in dry matter factorfdm at milkfat x = 1 % [12]: fdm and rf.(x=1%) [rf.(x=l%)+rcmc%(x=1%)}rs' fdm total fat retained in curds total solids in curds (22) for the purpose of the environmental impact analysis two types of curds target products data are used. the first one, called product a contains 0.3 % fat, while the second product b contains 1.0 % fat. the product compositions and calculated values of the above factors are presented in table 3. each of the above production tasks is source of pollution in curds processing due not only to the process hut also to the inherent losses associated with the by­ product and target product. each of the pollutants is characterized with the own bod load. 203 whey bydrained fig.2 flow chart of the curd processing. task 1 skim-milk pasteurization. task 2 acidification. task 3 draining waste sources and pollutant task 1 -pasteurization. the pollutant processed in pasteurization is due to coagulated milk glued to the pasteurizer's walls. the bod "generated" from this task depends on the mass of the pasteurized milk. the associated bod at each kilogram processed milk is bodp = 1.5.10-3 kg 02 kg pasteurized milk task 2acidification. the pollution from this task results from spilled whey. it is accounted for as inherent loss. the leak is wl % = 1.6 % from the processed whey mass. the bod load of !-kilogram acid whey is bodw =32.10-3 kgo-:. . kg acid whey task 3draining. the polluting from this task is due to: 1. discharging of drained whey which remained in the curd. the amount of the waste depends on its fraction in the curd by-product (see table 2). the bod load of 1-kilogram acid whey is bodw =32.10-3 kg 02 . kg acid whey 2. inherent loss of target product as a result of gluing to the drainer's walls. the leak depends on the curd fat content and is determined as cl% =0.0017.fc%, where fc % is curd fat content which for producrs a and b is 0.3% and 1,009% respectively. the bod load of !-kilogram curd depends on the curd yield and the bod of used skimmed milk for it manufacturing bodc(x) = cy(x).bodm (x) kg 0~ • kg curds consequently, the effluent from curd production will contain the three types of waste processed from its three tasks routine sources. environmental impact indices. global bod. the total amount of bod generated in the horizon h measures the curd processing global environmental impact. it is called global bod. in order for it to be determined (see section l) a description of polluting from respective routine sources and their environmental impact indices could be carried out. generally, the bod "processed" in the sources, depends on the mhkfat content. which affects the processed materials and product and by-products yield. 204 ~ .. ; botxx) gi g 1 ~ ..0.01414<. 0.0113$35 00113525 o.oit352 0.05 0.2 0.4 0.6 0.8 x mii:jattontentin~ product a ~ ollodtxl 0.01412 @~ 0 0.2 0.4 0.6 0.8 nos x mikt'tltcattmtin~ productb 1.2 1.4 1.5 1.2 1.4 1.5 fig.3 the functions gbodrc (x) for products a and b to express the milkfat dependence of the environmental impact indices the production tasks mass balance is used to determine the mass of the wastes referred to 1kilogram target product processed at each routine source m(x)wl [kg/kg]: 0 1-cy(x) 1+-[ 0.1] -----==---0-.9-=.wl% cy(x) 0 w = 1,2,3; l = 1.2,3 0 0.1 0.9 l.cl% (23) the batch size is considered equal to 1-kilogram curd. the bod of one kilogram pasteurized milk~ whey and curd are: [ bodp l bod(x)w:::: bodw . , w= lt2,3 (24) bodc(x) to define the respective indices in accordance with eq.( 17) time data are required. the duration of the time horizon is very important. curd production is a cyclic process~ consequently the time horizon equals the duration of production cycle detennined by the cycle time. the cycle time depends on the chosen·operational mode. for the purpose of analysis, the two most used operational modes are discussed: j. operation with cycles overlapping case a. where tc=max7; =240[min}: 2. operation without cycles overlapping case b. j where tc= }:,1; =300[min]. 1•1 other time data in [min] for tasks duration and for tasks starting time referred to the cycle beginning for both cases are: ~=[:j [210] ts1 = 0 , l =1,2,3 (25-case a) 240 ~=[~:]. ts1 =[~o j l = 1,2,3 (25case b) 270 using (23-25) the environmental impact indices are presented as functions of the milkfat content: 3 tc bodrc(x)w = 'l,bod(x)w j f:,1(x,t)dt (26) where l=i 0 2bm(x),..1 1 + l 1 tc 2 k k({jt; · (1cos(k({jt; )) + . [ cos(k({jts1 )· l + sin(k({jts1 )· ·sin(k({jt;) ·sin(k({jt)+ + · (cos(k({jt; )-1)+ . [ sin(k({jts1 )· l +cos(k({jts1 )· ·sin(k({jt;) ·cos(k({jt) 27r for 0 ~ t ~ tc and-= ({j tc (27) the global bod (gbod) assessing the environmental impact of the !-kilogram curd processing over one production cycle presented as a function of the milkfat content-xis: 3 gbod(x) = lbodrc(x)w · (28) w=l minimum of function (28) min gbod(x), 0.05~1.4 (29) corresponds to the milkfatx in skimmed milk at which the global bod at interval 0 ~ t ~ tc is minimal. results: based on the fourier transformation the global bod for one production cycle is presented as continuous function of the milkfat content. the functions (28) for both products a and b are shown on fig.3. the minimal values of gbod for both products and corresponding optimal milkfat content x are presented in table 4. the yield of curd from one kilogram milk at the determined milkfat content according to eq.(21 )is 0.248 kg for product a and 0.23 kg for product b. the values of the impact indices calculated according (26) for the processing routine sources at the table 4 the minimal values of gbod for products a and b and corresponding optimal milkfat content x products product a productb ~ gbod [kgoz] 1.1352xlo-2 1.4084x10-2 ~ gboo(t) 1°10-4 ~ .,2.707849·10-6• 0 0 so case a ~-10-4 li,766046·10-4 .1 r----. 1.5·10-4 ·~ l gbqi)(t) t•i0-4 i~ s·w-5 l6.28216•to-6 .. 0 0 100 caseb 100 ' x milkfat content in % ' [min] [nnn] iso 0.858 1.052 200 240 i j 250 joo joo fig.4 distribution of the level of the biological oxygen demand for product a processing at x = 0.858 into the production cycle for both operational modes (case a and case b) determined optimal milkfat content for both products are summarized in table 5~ from the table it is seen that the bod due to accounted inherent losses has a significant contribution to the gbod and constitutes 21,8 % and 33,9 % for products a and b respectively. the increased contribution of product b results from its higher fat content. distribution of the environmental impact level into the production cycle. the distribution of the environmental impact indices in the time interval h can be presented based on eq.(l4). using functions (27) the distribution of the level of the biological oxygen demand for curds processing into the production cycle 0 ~ t ~ tc can be expressed at the calculated optimal values of milkfat content as: 3 3 gbodrc(x,t)w:::: llbod(x)w.fw1(x,t) (30) x=0.858 w=l 1=1 or x=l.052 results: for both operational modes case a and case b functions (30) are presented on fig.4 for product a and on fig.5 for product b. it is obvious from both figures 205 table 5 the values of the impact indices according (26) for the processing routine sources at the determined optimal milkfat content values of the environmental impact product source indices [kg 0 2] pollutant pollutant pollutant curds pasteurization whey target product a task 1 5.32xlo-3 x=0.858 task2 1.495xlo-3 task3 3.556x10-3 9.87><104 b taskl 5.749xl0-3 x= 1.052 task2 1.661xl0·3 task3 3.556x10·3 3.118xlo-3 i r i i i ,;;!.!i0089h06. 0 l____b=l:::==±===::l:==:::±::li_...j 0 100 case a i '"""j 1!10 240 "l"i0-4 .-----.----.---.----.----.-....._., .,l.215397·i0-4, ·ii 2"10-4 1=----, ~ ~ gbojl{r) ~ 1'10-4 1r1 i olo~=±!io==~,oo====~~~====~===d~~~~ caseb 1 !""'' 110 fig.5 distribution of the level of the biological oxygen demand for product b processing at x=1.052 into the production cycle for both operational modes (case a and case b) that the level of the environmental impact during curdsprocessing is greatest in the first and last 30 minutes of the cycle duration. for case a the overlapping of tasks 2 and 3 at the beginning of the time interval and this of 2 and i at its end fonns the impact level, while for case b it is formed from task 1 in its beginning and task 3 in its end. moreover it can be seen from both figures that the higher fat content of product b makes the impact level of task 3 dominating compared to product a where the impact level of task 1 is dominating. the above results could be used to look for opportunities for environmentally efficient control of batch processes. conclusions and comments the example above illustrates the opportunities of the proposed alternative system oriented approach for determination of environmental impact assessments. 206 based on the application of the fourier transformation, it adequately describes polluting from discreet routine sources. the approach is used for environmental impact analysis of the curd production recipe. the optimal milkfat content is obtained so that the global bod generated in the process is minimal. the distribution of the environmental impact level into the production cycle is presented. the obtained results show that: 1. the minimum value of the global bod is reached at different milkfat content depending on the target product fat content (x = 0.858 for product a and x= 1.052). 2. the inherent losses have a significant contribution to the gbod. they constitute 21,8 % and 33,9 % for products a and b. consequently, they must be taken into account in the environmental impact assessment of dairy processing. 3. the operational mode affects the level and distribution of environmental impact into the production cycle, which is very important for -environmentally efficient control of batch processes. the environmental impact analysis of production recipes provides the optimal conditions for product manufacturing at minimum environmental impact which could be used at the scheduling and controlling levels of batch plants. the proposed system oriented approach based on the fourier transformation application can find a number of practical applications in different engineering problems. acknowledgement this study is conducted with the financial support of the bulgarian national science fund under the contract x1108/01. b cc% cl% fc% fdm h i l mc% rc rf rs sc% t tc ts symbols batch sizes [kg]; casein content in the curd; inherent loss of curd; fat content in the curd; fat in dry matter factor; time horizon [hj ; number of products; number of production tasks; casein content in the skim-n;lilk; factors of casein recovery from the milk; factors of milkfat recovery from the milk; factors of other solids recovery from the milk; solids content in curd; production time (h1 ~ cycle time [h]; starting time of task with regard to the cycle beginning; · .wl% m inherent loss of whey; mass of waste processed from the production task per a unit target product [kg/kg] ; time [h]; x milkfat content in skim-milk. subscripts: product; k a series order; production task; w waste. greek the standard limit value for the pollutant. references 1. rlitmeyer r. w.: chern. eng. prog., 1991, may, 56-62 2. smith r. and petela e.: tce, 1991, 31 october, 24-25 3. hilaly a. k. and sikdar s. k.: j. air waste manage. assoc., 1994,44, 1303-1308 4. hilaly a. k. and sikdar s. k.: ind. eng. chern. res., 1995,34,2051-2059 5. linninger a. a .• shalim a. a., s1ephanopolous e., han c. and s1ephanopolous g.: aiche symposium series, pollution prevention via process and product modification, 1994, 90(303), 46-58 6. linninger a. a., s1ephanopolous e., shalim a. a., han c. and s1ephanopolous g.: computers&chem. eng., 1995, 19, s7-s13 7. pistikopoulos e. n., s1efanis s. k., livingston a. g.: aiche symposium series, pollution prevention via process and product modification, 1994,90(303), 139-150 8. s1efanis s. k., livingston a. g. and pistikopoulos e. n.: computers&chem. eng., 1995, 19, s39-s44 9. stefanis s. k., livingston a. g. and pistikopoulos e. n.: computers&chem. eng., 1997, 21, 1073-1094 10. carawan r. e., chambers j. v. and zall r. r.: spinoff on dairy processing water management, extension special report no am-18.b, the north carolina agricultural extension service, january 1979 ii. overview of dairy processing, cleaner production assessment in dairy processing, cowl consulting engineers and planners as, denmark, for unep and danish epa, 7-11, 2000 12. johnson m.: dairy pipeline, 2()(}(), 12(2), 9-11 page 201 page 202 page 203 page 204 page 205 page 206 page 207 page 208 hungarian journal of industry and chemistry vol. 47(2) pp. 53–61 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-20 programmable process structure based analysis of hydrogen supply chains mónika varga *1, catherine azzaro-pantel2, josé manuel flores-perez2, and béla csukás1 1institute of methodology, university of kaposvár, guba sándor u. 40, kaposvár, 7400, hungary 2laboratoire de génie chimique, université de toulouse, 4 allée emile monso, toulouse, 31030, france the planning and operation of hydrogen supply chains (hsc) often require easily extensible, generic dynamic simulation tools. in this paper, the non-conventional modeling and simulation methodology of programmable process structures is applied for the description of these process systems. programmable process structures of hsc models are generated from the two general functional meta-prototypes of the method and from the description of the studied hsc network. the actual program prototypes of production, transformation, transportation, utilization and intermediate storage are copied from the meta-prototypes and filled with the locally executable declarative program code for the various classes of elements. the actual state and transition elements are parameterized and initialized according to their case-specific prototypes. the execution of the programmed hsc structures is solved by the general purpose kernel program. the application of methodology, developed in other fields, is illustrated by a fictitious, simplified hsc example. analysis of this example model illustrates that the coordination of the hectically changing energy production of renewable resources with its seasonally and tendentiously changing demands is in need of dynamic simulation-based planning. keywords: hydrogen supply chains, dynamic simulation, model generation, simulation-based planning, programmable process structures 1. introduction according to the recently published special section of the aiche journal about “hydrogen deployment” [1], the importance of hydrogen energy is expected to grow in the future because stakeholders have just started to discover the potential advantages of it worldwide [2]. hydrogen supply chains (hscs) contain geographically distributed, heterogeneous elements, while many of them are time-specifically constrained by meteorological or seasonal characteristics. having analyzed some comprehensive case studies [3–5], it is obvious that the zero emissions of hydrogen burning and the relatively easy storage of hydrogen is perspectivic. at present, a deadlock exists because a lack of infrastructure inhibits production, while a lack of production impedes the development of infrastructure. dynamic modeling and simulation-based design tools may play an important role in accelerating developments. primary renewable resources of hydrogen production are solar radiation, wind power and hydroelectric power produced by environmental systems. the utilization of solar energy requires natural or cultivated land, which is a special finite resource that is also generated for use in other industries, e.g. food-producing agriculture. *correspondence: varga.monika@ke.hu the direct utilization of solar energy is achieved by various photovoltaic processes with a limited degree of efficiency and capacity. intensive research and developments are in progress that make use of many new resources involving special organisms (e.g. microalgae [6]) or artificial biomimetic systems (e.g. artificial leaves [7]). the indirect utilization of solar energy is realized by the construction of power plants, which also compete for land suitable for food production. wind farms and some smaller hydroelectric power stations produce electrical energy periodically (often randomly), so on-site conversion to electrical energy is necessary for their effective utilization. however, electrical grids do not tolerate such erratic changes and no good solutions for temporary electricity buffering and storage exist. primary non-renewable resources are nuclear raw materials, natural gas and coal. nuclear raw materials need to be transported to specifically located nuclear power stations. natural gas is available from widespread pipelines. on the contrary, coal-based processing requires stations to be constructed in the vicinity of mining sites. large hydroelectric and nuclear power plants produce easily transportable electrical energy that can contribute to buffered hydrogen production by on-site electrolysis. https://doi.org/10.33927/hjic-2019-20 mailto:varga.monika@ke.hu 54 varga, azzaro-pantel, flores-perez, and csukás the most frequently applied process, steam methane reforming (smr), competes with other applications of natural gas but can produce hydrogen-containing gas anywhere in the vicinity of pipelines. on the contrary, coal gasification has to be conducted near to the resource, even though it produces more expensive hydrogen-containing gas from a resource, which is less convenient for traditional applications and petrochemical production, than natural gas. in addition, everything depends on short-term prices, however, thorough preparation for the future requires longer-term decisions. intermediate energy-containing products and byproducts exist in hsc networks, which originate from many distributed districts. biomass energy plants as well as some agricultural byproducts and waste appear seasonally, however, municipal biological wastes are constantly emitted. biomass is processed by gasification, while biological wastes produce biogas by anaerobic fermentation. the enrichment of the hydrogen content in the fermentation process is supported by some experimental results [8, 9]. energy-consuming, direct hydrogen-producing resources are electrical energy resulting from various chains, and hydrogen-containing gases that originate from smr and gasification processes. the two corresponding kinds of hydrogen production processes are electrolysis and the different methods of gas separation for hydrogen enrichment, e.g. membrane separation, pressure swing adsorption, etc. the produced raw hydrogen has to be conditioned in production sites by liquefaction or compression. the resultant liquidized or compressed hydrogen product needs a production or storage site for liquid or gaseous hydrogen, respectively. hydrogen can be transported from production to consumption sites by tanker trucks, tube trailers, railway tankers, railway tube cars or pipelines. pure liquid or gaseous hydrogen needs to be stored at the site of consumption. the utilization of hydrogen is connected to these storage sites. in addition to fueling cars and other vehicles, especially aircraft, hydrogen can be used to generate thermal energy as well as in various industrial processes, e.g. ammonia production, synthesis of organic products, metal processing, etc. in the long-term development of energy supply, hydrogen can serve as a clean and safe energy carrier that contributes to the adoption of a low-carbon economy. considering the slow but definite development towards a hydrogen economy, the optimal design, planning and operation of a hydrogen supply chain have come to the fore of research over the last decade. supply chain network design is a dynamic field of research, not only in the context of hsc but in general. a comprehensive set of various fields of applications was reviewed by govindan [10]. regarding the generally applied modeling methods for the planning and design of hsc, a review from 2012 lists the main approaches [11] such as mathematical optimization as well as geographic information system (gis) based models and frameworks. in conclusion, mainly mathematical programming-based optimization methods are used to design and plan hscs worldwide. in 2017, another paper [12] provided an overview once more about the actual situation on the basis of almost 100 references. various mathematical optimization methods such as mixed-integer linear programming (milp), mixed-integer nonlinear programming (minlp), mathematical programming problem (mpp), mathematical optimization (mop) as well as gis-based approaches and transition models illustrate progress over the last five years. regardless of some alternatively applied system dynamics (sd) and agent-based modeling (abm) solutions, mathematical programming-based optimization methods are still the most widely used tools in planning and design. this preferred approach is based on mixed-integer linear programming (milp) in which binary variables denote the selection of technologies and establishment of transportation links, while continuous ones denote mass and energy flows, capacities of the supply chain nodes, as well as the cost and environmental performance metrics. these decision variables are optimized subject to mass balance constraints, capacity limitations and calculations of objective functions [13, 14]. life cycle analysis (lca) is an appropriate methodology to evaluate the environmental performance and potential impacts associated with a product system across its entire life cycle. among various lca studies that evaluated the environmental benefits of using hydrogen over conventional energy sources, the so-called well-towheels (wtw) studies an lca approach to evaluate the environmental advantages of alternative fuel vehicles (afvs) over conventional engine vehicles across the entire automotive fuel pathway are studied including hydrogen supply chains [15]. multiple spatial and temporal scales imply a big challenge. samsatli et al. [16] highlights the need for the combined consideration of various temporal scales. a simple example of this is that the representation of energy storage requires a short (e.g. hourly) timescale, so taking into consideration years-long planning may result in computationally intensive models. dynamic simulation-based approaches (including the actually studied programmable process structures) may contribute towards solutions to these problems. another big challenge is the question of managing uncertainty throughout the design optimization procedure. accounting for multiple criteria, e.g. costs, environmental impacts, safety, etc., is an obvious expectation of green supply chain design, while the incorporation of these issues generates another interesting task to be solved [17]. many aspects of these challenges in design, deployment and operation in the field of hsc have been summarized in a recently published book [18]. hungarian journal of industry and chemistry analysis of hydrogen supply chains 55 dynamic simulation automatic generation meteo data, changing demands evaluated results of hsc two general meta-prototypes local program of specific classes description of hsc structure initial values and parameters actual hsc to be studied figure 1: scheme of hsc model generation by the method of programmable process structures. 2. applied modeling method: programmable process structures by considering the aforementioned overview of challenges that computational model-supported hsc planning and operation face, a simple trial with our nonconventional approach was conducted. accordingly, the methodology of programmable process structures (pps) [19, 20] was applied for the simulation-based analysis of a fictitious but typical hydrogen supply chain. in pps (see fig. 1), the locally programmable structure of process models can be generated from the graphml-based graphical implementation of one state and one transition defining meta-prototypes, as well as from the unified textual description of the studied hsc network automatically resulting in a dynamic structure of the standardized state and transition elements. the programmable prototype elements that describe production, transformation, transportation, utilization and intermediate storage in the model can also be derived from the two general meta-prototypes. the freely editable, actual program of the prototypes contain symbolic input, parameter and output variables, as well as a locally executable gnu prolog [21] code. in the various cases, the actual state and transition elements can be modeled with the same or a similar reusable local program, while the number of program prototypes is considerably less than the number of actual elements. the state and transition elements of the programmable hsc structures can be parameterized and initialized concerning their case-specific prototypes. during the simulation, the actual elements are executed by the prototypes associated with them. this execution results in cyclically stepwise, connection-based communication of the state and transition elements of the programmed structure with the general-purpose kernel that works like an operational system. when the simulation is run, the actual elements start with the initial conditions and parameters, while the output values are recalculated stepwise by taking into consideration the knowledge of input and parameter data in accordance with the associated local program prototypes. distinguished input and output connectors as well as connections exist for the conservation measures (extensive/intensive properties) and signals, respectively. this solution supports the combined execution of the balancebased and signal-based functionalities, i.e. the hybrid models of hybrid processes. 3. modelling and analysis of hydrogen supply chains by programmable process structures 3.1 description of the example hsc process network in the following sections, the following notations of prolog syntax shall be used: anything* = list of anything; [h|t] = list of any elements or functors with a head h and a list of tail t; [] = empty list; full stop = end of logical sentence; if (or :-) implication in the sense of horn clauses; comma in the program body of clauses = and. the general declarations of multi-compartment (multilevel, multi-scale) state and transition elements are as follows: states(coordlist,statelist). transitions(coordlist,transitionlist). coordlist = coord* statelist = state* transitionlist = transition* the transition-based declaration of the structures is described by the individual transitions as follows: trans(transition,inpconcs,outcomps,inpsigns, outsigns). inpconcs; inpsigns; outcomps; outsigns= specified_state* specified_state = n(coordlist,state) where the n() functors of inpconcs, inpsigns, outcomps and outsigns contain the coordinate and name of the state connected with the given input measure, input signal, output measure or output signal, respectively. this solution allows the same state names in the various compartments, levels or scales to be used because they are identified by the spatial coordinate and name together. our simplified example process network contains 38 state and 39 transition elements altogether in four regions, i.e. coordinates. the interpretation and abbreviation of the elements is explained in table 1. the declaration of the process network is illustrated by a characteristic part of the definitions as follows: states([0], [raw_renew,raw_gas,raw_nucl,h2heating,co2,o2]). states([1], [h2cons,demand,h2carfuel,eleng,hydrogen,h2prod ]), etc ... transitions([0],[]). transitions([1], [t_h2refuel1,t_photovolt1,t_nucl1, t_electrolysis1,t_compression1, t_tankertruck11,t_h2heat1]), 47(2) pp. 53–61 (2019) 56 varga, azzaro-pantel, flores-perez, and csukás table 1: list of involved state and transition elements. type of element name of element short symbol renewable resources raw_renew cultivated land raw_land natural gas raw_gas raw materials for nuclear energy raw_nucl energy-producing biomass biomass biological waste biowaste electrical energy eleng state hydrogen-containing gas h2contgas element raw hydrogen produced hydrogen compressed h2 produced h2prod compressed h2 available for consumers as a fuel h2cons fuel demand of cars demand h2 utilized as a motor fuel h2carfuel heat energy h2heating carbon dioxide co2 oxygen o2 cultivation of land t_cultivation photovoltaic process t_photovolt wind power station t_wind hydroelectric power station t_hydro nuclear power station t_nucl steam methane reforming t_smr transition biomass gasification t_gasify element anaerobic fermentation t_ferment electrolysis t_electrolysis gas separation t_gassep compression t_compression transportation (tanker truck) t\tankertruck refueling cars (vehicles) t_h2refuel heat production t_h2heat etc ... trans(t_h2refuel1,[n([1],h2cons)],[n([1],h2cons ), n([1],h2carfuel)],[n([1],demand)],[]). trans(t_h2refuel2,[n([2],h2cons)],[n([2],h2cons ),n([2],h2carfuel)],[n([2],demand)],[]). trans(t_h2refuel3,[n([3],h2cons)],[n([3],h2cons ),n([3],h2carfuel)],[n([3],demand)],[]). trans(t_h2refuel4,[n([4],h2cons)],[n([4],h2cons ),n([4],h2carfuel)],[n([4],demand)],[]). trans(t_tankertruck11,[n([1],h2prod)],[n([1], h2prod),n([1],h2cons)],[n([1],h2cons)],[]). trans(t_tankertruck22,[n([2],h2prod)],[n([2], h2prod),n([2],h2cons)],[n([2],h2cons)],[]). trans(t_tankertruck33,[n([3],h2prod)],[n([3], h2prod),n([3],h2cons)],[n([3],h2cons)],[]). trans(t_tankertruck31,[n([3],h2prod)],[n([3], h2prod),n([1],h2cons)],[n([1],h2cons)],[]). trans(t_tankertruck32,[n([3],h2prod)],[n([3], h2prod),n([2],h2cons)],[n([2],h2cons)],[]). trans(t_tankertruck44,[n([4],h2prod)],[n([4], h2prod),n([4],h2cons)],[n([4],h2cons)],[]). trans(t_tankertruck41,[n([4],h2prod)],[n([4], h2prod),n([1],h2cons)],[n([1],h2cons)],[]). trans(t_tankertruck42,[n([4],h2prod)],[n([4], h2prod),n([2],h2cons)],[n([2],h2cons)],[]). trans(t_compression1,[n([1],hydrogen)],[n([1], hydrogen),n([1],h2prod)],[],[]). trans(t_compression2,[n([2],hydrogen)],[n([2], hydrogen),n([2],h2prod)],[],[]). trans(t_compression3,[n([3],hydrogen)],[n([3], hydrogen),n([3],h2prod)],[],[]). trans(t_compression4,[n([4],hydrogen)],[n([4], hydrogen),n([4],h2prod)],[],[]). etc ... 3.2 meta-prototypes-based generation and analysis of the example model generation of the programmable process structure originates from the graphml description of general metaprototypes that belong to the methodology (see their illustration in the upper part of fig. 2) and from the aforementioned description of the actual process network. the initial values and parameters of state elements as well as the parameters of transition elements can be added automatically from an excel based text file. the generated general-purpose algorithm results in a graphml file that contains the two meta-prototypes and structure of the whole hsc model in addition to the initial values and parameters. the example structure is illustrated in fig. 2. the graphml model can be further edited by various graph editors (yed graph editor to be precise). the structure also contains the two empty meta-prototypes. the generated programmable process structure describes all of the state (storage of resources, intermediates and products) and transition elements that represent the transformation and transportation in the various compartments (spatial scales) individually, because they may have different parameters and connections. by default, the transportations belong to the sending compartment. this representation does not result in the multiplication of the program code because many elements are executed by the same meta-prototypes that contain the local programs (see the next section). the connections from the state to transition elements represent the causally right transfer of quantitative and qualitative amounts and signals necessary for the calculation of the transitions. the connections from the transition to state elements represent the increases and decreases in the corresponding additive measures as well as the calculated signals. accordingly, the model is prepared for the common but distinguished representation of the extensive/intensive properties as well as of the signals and rules. consequently, the programmable process structures make both the elements and structure visible during the simulation process. this supports the easy (optionally multiscale) temporal consideration of external data, e.g. related to meteorology, the climate and supply & demand. moreover, the flux routes and influence routes can be seen and evaluated explicitly. furthermore, this (apparently too abundant) knowledge representation makes the unified execution of quite hungarian journal of industry and chemistry analysis of hydrogen supply chains 57 figure 2: programmable process structure of the investigated hsc. different hybrid dynamical models possible by applying the same kernel program. figure 3: some meta-prototypes-based case-specific prototypes of hsc networks. 3.3 meta-prototypes-based functional prototypes of the example model first, the programmable prototypes have to be prepared by making copies from the application-independent meta-prototypes. afterwards, the declaration of the actual local program follows. the implementation of state and transition prototype elements of the hsc model needs creative collaboration between the modeller and field experts. the preparation of the case-specific local programs is supported by the meta-knowledge embedded in the meta-prototypes, in accordance with the generated programmable process structure. the basic meta-prototypes and some actual programmed prototypes are illustrated in fig. 3. the example prototypes in fig. 3 are as follows: transition prototypes: prot_compr: compression of hydrogen; prot_electrol: electrolysis; prot_nucl: nuclear reactor-based electrical energy supply; prot_photovolt: photovoltaic system-based electrical energy supply; prot_refueling: hydrogen utilization by the refueling of cars (planes); prot_truck: transportation of hydrogen by truck ; prot_wind: wind power system-based electrical energy supply; state prototypes: prot_demand: scheduled hydrogen demand; 47(2) pp. 53–61 (2019) 58 varga, azzaro-pantel, flores-perez, and csukás prot_storage: hydrogen storage; prot_condstorage: hydrogen storage, associated with condition signaling capabilities. as an example, see the simplified local program of prot_photovolt that calculates the produced electrical energy as a function of the actual meteorological conditions. this textual code is to be embedded into the respective prototype element as follows: program\prot\photovolt = ’permutation(parameters, [d(area,[area],m2),d(coeff,[coeff],nd)\textbar \], time(\,t,\), abs\time(t,y,m,d), meteo(y,m,d,radiation,\,\,\,\,\), g(dt,dt), energy is coeff*area*radiation*dt, report = [d(energy,[energy],kwh)], outcomps = [d(eleng,[energy],kwh)], outsigns = [],!.’ 3.4 generation and simulation of the example hsc system programming of the process structure is followed by its automatic interpretation into the executable dynamic databases of the given model. now the general model generator of the kernel reads the graphml file and generates: • the facts that describe the actual state & transition elements and those that determine state → transition and transition → state connections in the “user” file; • the clauses that declare the program prototypes in the “expert” file. the resultant user and expert files contain a detailed description of the process model, including the locally executable program prototypes as well as the actual elements and connections that contain the initial data and parameters. having generated the model, the executable code has to be supplemented by the (optionally scale-specific) global data, e.g. g(dt,dt ), that also declares the main time step in the previous example code. dynamic simulation is executed by the general kernel program that comprises the cyclically repeated processing of state elements, state → transition connections, transition elements and transition → state connections. for example, the execution of all transitions associated with the prototype of prot_photovolt are executed by the the unification of them, e.g. a(y,t_photovolt2,[2],prot_photovolt,[c( antecedent,dl,[]),c(consequence,dl,[]),c( cond,dl,[]),c(param,dl,[d(area,[1000],m2),d (coeff,[0.20000000000000001],nd)])],[i(inp, dl,[]),i(conc,dl,[])],[o(comp,dl,[]),o(out, dl,[]),o(report,dl,[])],[],[],[]). is unified with the prototype v(y,spatial,prot_photovolt,[c(antecedent,dl, antecedent),c(consequence,dl,consequence),c (cond,dl,conditions),c(param,dl,parameters) ],[i(inp,dl,inpsigns),i(conc,dl,inpconcs) ],[o(comp,dl,outcomps),o(out,dl,outsigns),o (report,dl,report)],temporal,possibilities, evaluations) :program_prot_photovolt. where program_prot_photovolt refers to the example code above. the variables in prototypes are described by alphanumeric symbols that start with a capital letter. the variables and constants in the functors i(), c() and o() are described by lists of the triplets d(identifier, variable_list, instructions). 3.5 analysis of the simulated results some characteristic parameters in these illustrative examples were the following: coefficient of photovoltaic model: 0.2 photovoltaic areas: 1000, 2000, 3000, 800 m2 coefficient of wind-power units: 20 kw h3/km3/ unit number of units: 100, 200 power consumption of electrolysis: 52.5 kwh/kg power consumption of compression: 3.0 kwh/kg some of the simulated results are illustrated with a specific part of a simplified hsc model. in this case, a seasonally and randomly changing continuous increase in the demand of cars for hydrogen fueling over the next decade was assumed, as can be seen in fig. 4. in terms of production, the available capacity of photovoltaic power stations and wind farms in the studied region was investigated. these renewable resources produce electrical energy depending on the actual meteorological conditions (solar radiation and wind speed). however, the available climate scenarios did not contain data concerning radiation and wind speed, so meteorological data from the past ten years was used to imitate realistic changes in radiation and wind speed. the calculated electrical energy production of the investigated system is illustrated in fig. 5. 0 2000 4000 6000 8000 10000 12000 14000 16000 k g/ d a y time, day daily hydrogen fuel consumption figure 4: hypothetical data for the seasonally changing and increasing demand for hydrogen. hungarian journal of industry and chemistry analysis of hydrogen supply chains 59 0 500000 1000000 1500000 2000000 2500000 3000000 3500000 0 5000 10000 15000 20000 25000 30000 35000 40000 p h o to vo lt a ic , k w h /d time, day photovoltaic and wind based electric energy pv production, kwh/d wind w in d , k w h /d figure 5: electrical energy production of the involved wind power and photovoltaic systems (to be converted into hydrogen by electrolysis). in the studied area, wind power can produce more electrical energy than photovoltaic systems, however, it fluctuates very erratically. the contribution of photovoltaic systems is smoother with characteristic seasonal changes. increasing demands for hydrogen production can be met by more renewable energy production or additional hydrogen production from the available electrical energy (e.g. originating from nuclear power stations) and additional hydrogen production (e.g. from steam-methane reforming, biomass gasification, etc.). in the case of lower fuel demands for cars (over a short initial period), the solar energy-based renewable resources can produce the necessary energy for hydrogen production. furthermore, some extraordinary surplus amounts can be produced over randomly appearing short periods by wind farms, as can be seen in figs. 5 and 6. the results underline that dynamic simulation models need to be applied to solve planning problems in the case of rapidly changing supply and demand. 4. discussion as has been summarized in the introduction, mainstream hsc planning and operation applies mathematical programming, where a simplified model is usually embedded in a superstructure-based optionally multi-objective optimization program. the suggested non-conventional approach might have some potential advantages. having analyzed the characteristics of hydrogen supply chains and their typical elements, programmable process structures may offer some useful options: • the methodology tolerates case-specific multiscale extensions (e.g. when a proportion of the elements is in need of a more detailed model and/or refined spatial or temporal resolution). • by taking into consideration the intensive development of new hydrogen-producing methods, pro-20000 -10000 0 10000 20000 30000 40000 50000 60000 k g h 2/ d a y time, day uncovered daily h2 demand figure 6: the change in hydrogen demand produced by the available direct renewable resources. grammable process structures are capable of embedding any detailed prototypes of nonlinear dynamic models into existing structures. • the extensibility of programmable process structures favours stepwise structural and functional changes in supply and demand without reformulation of the model. • optional multiscale compartmentalization helps to represent multiple districts and sites via the optional connection between spatial coordinates of the elements with an external gis tool. • individual elements and connections can be associated with a time-driven execution at given points in time and/or over prescribed time intervals. • material and energy balances can be combined with signal and rule-based, event-driven processes. • a programmable process structure has built-in capabilities for robust communication with external (e.g. meteorological) databases and collaborating (e.g. metaheuristic optimization) programs. • the method supports the handling of the extraordinary uncertainty of coefficients of cost and some other parameters over a longer time horizon. the embedded elementary evaluations and elements of evaluation may be prepared for a multi-objective case involving a set of time-invariant natural objective functions. 5. conclusion regardless of the well-established mathematical programming-based methods of the planning and operation of hydrogen supply chains, problem-solving in terms of these systems might also require an easily modifiable, generic dynamic simulation-based approach. as was also shown by the studied illustrative example, the representation of energy storage corresponding to renewable resources requires a short (e.g. hourly, daily) 47(2) pp. 53–61 (2019) 60 varga, azzaro-pantel, flores-perez, and csukás timescale as opposed to a years-long planning time horizon. the reason for this is that these large-scale, long-term supply chains are not only affected by uncertainly changing demands, but by erratically changing supply, partly originating from natural resources, determined by erratically changing extreme weather conditions and a slowly changing climate. by considering these challenges with regard to the planning and operation of a hydrogen supply chain, the non-conventional modeling and simulation methodology of programmable process structures was implemented as developed in other multidisciplinary fields. the suggested programmable process structures may contribute to the solution to these problems. programmable process structures of hsc models can be generated from the description of a (optionally geographically determined and multiscale) process network and two general functional meta-prototypes, automatically. the case-specific, functional program prototypes can be derived from the two meta-prototypes. simultaneously, the actual elements of the process network can be parameterized and initialized according to the case-specific prototypes. the simulation of the model can be solved by a general-purpose kernel program. the method also allows different time steps for the various classes of elements to be used. the application of programmable process structures was illustrated by a fictitious example of a simple hydrogen supply chain. planned future work, in collaboration with hsc experts, will focus on the application of a repeated forward/backward simulation-based iterative methodology to reach a reasonable compromise between changing demands and supplies. furthermore, programmable process structures will be combined with metaheuristic optimizers for the multi-objective optimization of hsc planning. notations gis geographic information system graphml a comprehensive and easy-to-use file format for graphs hsc hydrogen supply chain milp mixed integer linear programming minlp mixed-integer nonlinear programming mpp multi-period problems mop multi-objective problems pps programmable process structure acknowledgement this research was supported by the tét_16-1-20160116 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(petroleum processing research centre, east china university of science and technology, mei long road 130, shanghai, 200237, china) received: july 20, 2001; revised: march 7, 2002 the present invention relates to a method of a design suggested for a desulfurization of light oils through organic two phase liquid-liquid extraction, photochemical oxidation and photodecomposition of the sulfur compounds, using a high pressure mercury lamp. photochemical desulfurization process is comprised of two stages. the first consist of the transfer of sulfur-containing compounds from the light oil to an aqueous-soluble polar solvent. this is then followed by the photooxidation and photodecomposition of the sulfur-containing compounds in the solvent by ultraviolet irradiation from a high pressure mercury lamp. the process is carried out under conditions of room temperature and atmospheric pressure. solvent extraction with acetonitrile was investigated at differents oil/solvent ratios. after extraction with acetonitrile the sulfur content in gasoline decreased from 316 ppm to 47.7 ppm, and that in light gas oil from 988 ppm to 101.2 ppm or with 84.9 and 89.75 %, respectively. mercury lamp photochemical process and effect of solvent have been discussed. keywords: photochemical, desulfurization, liquid-liquid extraction, light oil introduction in the last ten years aroused considerable interest on the desulfurization of light oil · and automotive fuels. automotive fuels (gasoline, gas oil ) create corrosive combustion by-products, releases sulfur oxides into the atmosphere, and increase deposits on fuel injection and combustion systems [1]. in automobile engines sulfur-containing compounds are converted to sulfur oxides (sox) after combustion and hence they are one of the main sources of acid rain and air pollution, which causes serious environmental problems in the world [4]. sulfur-containing compounds are also undesirable in the refining processes because they tend to deactivate various catalysts used in downstream processing and in the upgrading of hydrocarbons. a catalytic hydrodesulfurization (hds) method using co-mo, ni­ mo or others catalysts were widely used in industiiial scale, but required both high hydrogen pressure (up to 1, 000 psig) and high temperature (400550°c), and to produce desulfurized fuels, the demand of hydrogen inevitably increased. in addition, the hydro­ desulfurization method is complicated in the desulfurization of dibenzothiophenes (dbt) and its derivatives among sulfur-containing compounds in light oil [2, 3]. mercury lamps as ultraviolet irradiation sources there are three types of mercury arc discharge lamps, low pressure arc lamps (called also resonance lamps), medium pressure arc lamps, and high pressure arc lamps. a low pressure mercury lamp primarily emits two bands of irradiation, centered at 184.9 and 253.6 nm. these lamps operate at room temperature. · low pressure mercury lamps have a low total radiant flux (total radiant power) and for that reason they are often mounted parallel to or coiled about the reaction cell the low pressure mercury lamps are applicable for the study of mercury-sensitized reactions and are often used where direct photolysis at 253.7 nm is desired in mercury-free systems. the absorption coefficients of mercury at 184.9 and 253.6 nm are so large that, the major fraction of the radiation of the lamp is absorbed by the mercury atoms, even if they are in a very low concentration. in order to avoid mercury­ photosensitized reactions, all experimental devices should be free of mercury traces. contact infonnation: e-mail: ala_ibrahim@hotmail.com; telephone 86-21-64245299; fax:86-2l-64020577; po.box 6666, chen yuan hotel sol 162 medium-pressure arc lamps operate at 1 atm or higher pressures, emit radiation of different wave lengths. at higher operating temperatures or pressures the lines tend to broaden, the longer-wavelength visible lines are increased in intensity, compared with those of shorter wavelengths and the continuum is increased to the line strength. the relatively high total radiant flux and the near-line character of the emission spectra make these lamps particularly well suited for photochemical use with monochromator and filter systems, and so they are extensively used in photochemical works [5]. high-pressure mercury lamps (commonly known as mercury arc capillary lamps) operate at very high pressure and are the most intensive source of ultraviolet, visible and infrared radiation. as these lamps operate at very high temperatures, forced-air, or circulating water cooling is required to avoid melting the quartz envelope. the minimum quantity of cooling water needed for a 300-500 w lamp is 1 to 3.5 iitres/min. high-pressure mercury lamps consist of a small-bore quartz tube with two electrodes immersed in mercury at either end. they operate on either alternating or direct current with suitable auxiliary ballast equipment. they have to be started in a horizontal position but operate in any position. operation on direct current or vertically on alternating current leads to an unequal distribution of mercury. each time before the lamp is switched on, it has to be taken out of the holder and checked for impurities and mercury distribution. at the same time, care must be taken to insure that the cooling water circulation is functioning properly and is deprived of air. the lamp must not switch on until the water is running [5]. photochemical processes all photochemical processes obey four photochemical jaws which can be applied generally in photochemistry: a photochemical reaction may occur only if light of sufficient energy is absorbed by the system. each photon or quantum absorbed, activates only one molecule in the primary excitation step of a photochemical sequence. each photon or quantum absorbed by a molecule has a certain probability of populating either the lowest exited singlet state (sj) or the lowest triplet state (t 1) the lowest excited singlet (s1) and triplet (t1) states are the starting levels (in solution) of most organic photochemical processes. photochemical processes usually occur in two stages, the primary photochemical reaction is the reaction, which is directly due to the absorbed photon or quantum involving electronically excited states. this process was found to be independent on temperature. the secondary photochemical reactions (aiso called dark reactions) are reactions of radicals. radical ions and electrons which were produced by the primary photochemical reaction. most of the organic compounds, which emit luminescence (aromatic molecules) have an even number of n electrons, g1vmg a ground singlet electronic state (s0). the ground singlet electronic state (s0) is a state, in which the electron spins are paired. when a molecule absorbs electromagnetic radiation, its energy increases by an amount, equal to the energy of the absorbed photon. excited singlet states (s1, s2, s3, ••• , s;) are formed after absorption of the photon. the spins of the n electrons are paired in singlet excited states. the photochemical reactions may occur mainly from the lowest excited singlet state (s1) [6]. effect of solvent on photochemical reactions the selection of a solvent is very important if photochemical reactions are studied in solution. there are probably very few photochemical reactions which are totally unaffected by the solvent. too often the effect of the solvent is ignored when a photochemical reaction is under investigation. any solvent used for the study of a photochemical reaction should satisfy the following requirements: the solvent should not absorb the incident light. solvents should be spectrally or high-grade pure. some impurities present in solvents may act as photosensitizers or quenchers. solvents should be photochemically stable and should not participate in primary and secondary reactions. in many solvents, photooxidation reactions may occur much faster than the same reaction in pure reagents. solvent radicals formed from photolysis of the solvent may react with reagents, completely changing the mechanism and kinetics of the observed reactions. knowledge of the photochemistry of solvents is necessary in order to correct the additional effects, which disturb the photoprocess. paraffinic hydrocarbons and 1fcohols are unreactive when irradiated in the 200-700 urn range but they may react if free formed in primary photochemical processes. benzene, when irradiated with ultraviolet light in an oxygen-free atmosphere, can isomerize to fulvene and benzalvene, whereas in the presence of oxygen the ring-opening reaction produces long-chain conjugated dialdehydes. chloroform or carbon tetrachloride during ultraviolet irradiation, produces very reactive c1· and. cci3• free radicals. tetrahydrofaran(thf) in the presence of oxygen, produces free thf radicals and fmal products of its reactions with oxygen, such as· butyrolactone, a.­ hydroxytetrahydrofurane (ho-thf) and a.­ hydroperoxy-tetrahydrofurane (hoo-thf) [6]. extractants were selected from among acetonitrile, propionitrile, butyronitrile, nitromethane, nitroethane, nitropropane, nitrobenzene, dimethylsulfoxide, n, n dimethylacetamide, n-methylpyrrolidinone, trimethyl phosphate, triethylphosphate, hexamethylphosphoric amide, phosphorane [7}. table i properties of light oils used in extraction process property atmospheric fcc gas oil gasoline density kg/m3 0.7310 0.8702 boiling point oc 78 220 sulfur content wt % 0.0316 0.0988 physical and chemical properties of acetonitrile colourless liquid with structural formula (ch3cn) and sweet ethereal odour. transparent liquid with extraordinary fragrance like ether. density (d4 15 ) 0.7830 melting point -41 °c, boiling point 82 oc, flash point 5.56 oc: soluble in water and alcohol, high dielectric constant, high polarity and strongly reactive. refractive index (n l 0 ) 1.34423, viscosity 0.35 mpa!s at 20 °c. critical temperature 274.7 °c, critical pressure 4.8332 mpa. poisonous; flammable and when it burns the flame is bright. acetonitrile is poisonous and flammable. its explosion range in the air is 3-16 %(vol %) [8, 9, 10}. experimental section materials atmosheric light gasoline and fcc light gas oil were supplied by shanghai refinery (table 1). acetonitrile of 99% purity was supplied by shanghai ling feng chemical agents comp'!:ny. analysis after extraction, the gasoline and gas oil were tested for sulfur content. the sulfur content in both gasoline and gas oil was analyzed by standard test method for sulfur in petroleum products. (x-ray spectrometry, astm d 2622). results and discussion apparatus and procedure the light gasoline and fcc gas oil were put in a flask and mixed vigorously with acetonitrile, using a magnetic stirrer. the oil, after 40 minutes of contacting with acetonitrile, was transferred with a polar solvent to a separatory funnel, shaked for 5 minutes and then the funnel was put on a carrier vertically for about 10-15 minutes until the two phases appeared clearly and the oil separated from the solvent. the extraction was investigated at 1, 2 and three stages and different volume ratios (111, 111.5, 112, 112.5, and 113 ) l--------aromatics.andsull'ur compounds 163 fig. i flow diagram of photochemical reaction and desulfurization of light oil. 1. extraction column; 2. photochemical reactor; 3. acetonitrile elution column; 4. acetonitrile distillation column; 5. product washing column flow scheme a flow scheme for photochemical desulfurization was constructed. the suggested scheme of this desulfurization process which includes the liquid-liquid extraction, photochemical oxidation and photodecomposition of sulfur-containing compounds, is shown on fig.l. light oil (gasoline or gas oil) and acetonitrile in the extraction column undergo liquid­ liquid extraction. the product from the bottom of the column contains sulfur-compounds and acetonitrile. the extractor. the product, coming from the top of the column is desulfurized gasoline or gas oil acetonitrile is transferred to column no 2 (photochemical reactor ) where the sulfur compounds are photodecomposed. in the presence of some external photoirradiation and oxidation. the reacted liquid is transferred to the acetonitrile elution column no.3, and water is added to remove the aromatics and sulfur compounds from the solvent. in the column acetonitrile and water mix, sulfur containing materials form product. at the same time acetonitrile-water mixture is transferred to no.4 washing /distillation column, while aromatics and sulfur compounds are leaving from the top of the column. after distillation, acetonitrile is recycled to the extraction column. the water phase from the bottom of the distillation column can be transferred to no.3 and 5 columns for recycling purposes. since the desulfurization is finished in the column no.1 the desulfurized oil leaving the column no.1 contains minor quantities of acetonitrile, therefore in column no.5 water is used to remove the acetonitrile and purified product leaves the top of the column. this novel technology of extraction/ photooxidation and photodecomposition process is used for the first time in this country for removing sulfur compounds from light oils (gasoline, gas oil, etc.). the desulfurization method should be a distinct line in technological methods, the efficiency can be improved by adding oxidation agent. besides, this method has high desulfurization efficiency (89% and above), low investment cost, operation conditions (temperature, pressure) are moderate and extractant can be recycled. there are various applications for generated sulfur-containing compounds. these materials can be utilized in atomic industry, as a special feature. this has a bright scope from the high quality research and valuable point of view. 164 table 2 sulfur contents of gasoline after extraction with table 3 sulfur contents of gas oil after extraction with acetonitrile acetonitrile sample extraction oil/solvent sulfur content ppm sample extraction oil/solvent volume sulfur content no. stage volume ratio no. stage ratio ppm 1 1 stage 1/1 158.5 1 1 stage 1/1 594 2 1 stage 1/1.5 133.8 2 1 stage 1/1.5 465 3 1 stage 1/2 109 3 1 stage 1/2 453 4 1 stage 112.5 96.2 4 1 stage 1/2.5 389.5 5 1 stage 113 85.4 5 1 stage 1/3 227.6 6 2 stages 1/1 117.3 6 2 stages 1/1 431 7 2stages 1/1.5 80.7 7 2 stages 1/1.5 259.7 8 2 stages 1/2 55.9 8 2 stages 1/2 214.7 9 2stages 1/2.5 55.2 9 2 stages 1/2.5 158.4 10 2stages 1/3 49.7 10 2 stages 1/3 113.3 11 3 stages 1/1 110.2 11 3 stages 1/1 398.4 12 3 stages 1/1.5 72.9 12 3 stages 1/1.5 267.5 13 3 stages 1/2 54.9 13 3 stages 1/2 200.6 14 3 stages 1/2.5 51.3 14 3 stages 1/2.5 114.1 15 3 stages 1/3 47.7 15 3 stages 1/3 101.2 ~ -----: 180 140 -....-----·----------. 160 g_ 140 ·c. 'e 120 -e 100 8 80 .... :e 60 ji 40 20 0 2 3 4 5 gasoline/solvent volume ratio fig.2 sulfur content in gasoline after 1 stage extraction with acetonitrile at different oil/solvent volume ratios liquid-liquid extraction the extraction of the sulfur-containing compounds from two light oils (atmospheric gasoline and fcc gas oil) were investigated by contacting both of the two oils with acetonitrile at room temperature and atmospheric pressure. acetonitrile was contacted with the oil for 40 · :minutes and transferred to a seperation funnel and after ten minutes, the oil phase was separated from the acetonitrile phase. after extraction, the light oil appeared more clean and pure. the extraction of atmospheric gasoline and fcc gas oil were investigated at different volume ratios of oh/solvent (lll, 111.5, l/2, l/2.5, 113). the rate of the desulfurization was found to increase effectively with increasing the extraction stage. in the same time the desulfurization rate was increased with increasing the ratio of the solvent in the total ( oivsolvent) solution volume. this is shown on the tables 2 and 3 and on the figs.2 to 7. the yield of e 120 c. 2" 100 c .l!l 80 c 8 60 .... .2 40 :; (/) 20 0 2 3 4 5 gasoline/solvent volume ratio fig.3 sulfur content in gasoline after 2 stage extraction with acetonitrile at different oil/solvent v:olume ratios desulfurized oil is varying according to the oil/solvent volume ratio and the extraction stages (1, 2, and 3 stage). the yield of raffinate varies from 78 to 52 vol% for light gasoline, and from 68 to 43 vol% for light gas oil. the sulfur content for gasoline was decreased from 318 ppm to 47.7 ppm, and that for gas oil from 988 ppm to 101.2 ppm after extraction or with 84.9% for gasoline and 89.75% for gas oil. conclusions a liquid~iiquid solvent extraction of sulfur compounds in light oil (atmospheric gasoline and and fcc gas oil was investigated with the following results: after the extraction with acetonitrile, the sulfur compounds being in gasoline were decreased from 318 ppm to 47.7 ppm and that in gas oil from 989 ppm to wl2ppm. i 120 i e 100 i q. q. ..... 80 i i 1: i ! i 1: 60 0 i i () i .. 40 :::s 3 i (/) 20 i i ! 0 i 2 3 4 5 i gasoline/solvent volume ratio i fig.4 sulfur content in gasoline after 3 stages extrac~ion with acetonitrile at differents oil/solvent volume ratws 700 e 600 8: 500 1: ! 400 1: 0 300 () .. :::s 200 3 (/) 100 0 2 3 4 5 gas oil/solvent volume ratio fig.5 sulfur content in gas oil after 1 stage extraction with acetonitrile at differents oil/solvent volume ratios the transfer of sulfur-containing compounds from the light oil to the solvent was found to proce~d more effectively in gas oil (89.6%) than that m gasoline (85%) a flow diagram for desulfurization was investigated. the generated sulfur will be used in atomic industry production. references i. boisvert p., argonne technology transfer, 1999, oct. 2. shira!sffi y., hirai t. and komasawa l, ind.eng.chem.res., 1988,37,203 3. hnwu t., smra!sffi y., ogawa k. and komassawa i., ind.eng.chem.res., 1997, 36, 530 165 2 3 4 5 gas oil/solvent volume ratio i l_-----------~------------------~ fig.6 sulfur content in gas oil after 2 stages extraction with acetonitrile at differents oil/solvent volume ratios 450~~~--~------~------~ 400 ~ 350 2300 1: ! 250 1: 8 200 s 150 :t: jl 100 50 0 2 3 4 5 gas oil/solvent volume ratio fig.7 sulfur content in gas oil after 3 stages extraction with acetonitrile at differents oil/solvent volume ratios 4. hirai t., ogawa k. and komasa i., ind.eng.chem.res., 1996,35,586 5. rabek j. f., experimental method in photochemical and photophysics. part 1., sweden, 1982 6. rabek j. f., experimental method in photochemical and photophysics.part 2., sweden, 1982 7. european pat. 0565324 ai (1993) 8. u.s.environmental protection agency.health and environmental effects profile for acetonitrile. office of health and environmental assessment.office of research and development. cincinnati, oh.l985 9. u.s environmental protection agency, environmental criteria and assessment office cincinnati, oh 1999 10. the merck index. an encyclopedia of chemicals, drugs and biologicals.llthed ed s. budavari. merck and co. inc., rahway, nj. 1989 page 165 page 166 page 167 page 168 page 169 hungarian journal of industry and chemistry vol. 48(2) pp. 9–12 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-22 the role of water activity in terms of enzyme activity and enantioselectivity during enzymatic esterification in nonconventional media piroska lajtai-szabó1, nándor nemestóthy1, and lászló gubicza *1 1research institute on bioengineering, membrane technology and energetics, university of pannonia, egyetem u. 10, veszprém, 8200, hungary during enzymatic esterification in non-conventional media, the activity and enantioselectivity of the enzyme is significantly influenced by the water content of the reaction medium, which continuously changes as water is produced during the esterification. to provide constant reaction parameters, water activity should be kept constant. the commonly used salt hydrate pairs may be difficult to apply and often hinder enzyme activity. during the enantioselective esterification of racemic 2-bromopropanoic acid in various solvents (organic solvents, ionic liquids), it was proven that the conditions related to the optimal water content required for kinetic examinations can be provided without using any salt or salt hydrate pairs. this conclusion is based on the realization that the optimal water activity can be set by first determining the initial water content that is necessary to achieve the maximum reaction rate in the given solvent. keywords: enzymatic enantioselective esterification, non-conventional media, ionic liquid, racemic acid, effect of water content 1. introduction the history of the intentional use of enzymes as biocatalysts stretches back several decades. in recent years, intensified interest has been shown in applying enzymes in chemical reactions. enzyme technology as an important discipline of biotechnology has begun to develop rapidly. nowadays, it is of great importance in the pharmaceutical and pesticide industries where, in many cases, it has produced intermediates and active substances with enzymes or microorganisms more easily than by chemical synthesis and usually with a high degree of (enantio)selectivity [1–3]. the known advantages of these reactions are the mild reaction conditions, pure products, high yield and, in many cases, environmentally friendly by-products. at first, enzymes were only applied in aqueous media as they exert their catalytic activity under such conditions in various organisms. later, the recognition that enzymes can exert their catalytic activity in organic solvents promoted intensive investigation among organic chemists who tested more and more enzymes from various classes as catalysts of organic chemical reactions [1, 4–7]. contradictory results concerning how the activity and enantioselectivity of a lipase depend on the physical and chemical properties of the solvents can be found in the literature. in some cases, the different enzyme activities and *correspondence: gubiczal@almos.uni-pannon.hu enantioselectivities observed in various organic solvents are not only affected by the solvents, e.g., when solvents with very different polarities are compared without fixing the water activity. in these experiments, the variation in the water activity probably contributes to the change in enzyme activity [6, 8–10]. in terms of the reaction, the water content of the reaction medium is twice as significant. to keep the enzyme activity and enantioselectivity of the lipase constant, a constant amount of water should be provided. as the content of the reaction medium changes as the conversion proceeds, the water adsorption capacity of the reaction medium does not remain constant during the reaction either. water activity is an index which indicates how much water is accessible to the enzyme. polar solvents can adsorb more water, while in non-polar solvents less water is required to achieve saturation and form a new aqueous phase where the water activity of the organic solvent is equal to one (aw = 1). therefore, two solvents of different polarities but equal water activities may contain significantly different amounts of water [11–13]. based on the aforementioned considerations, in the literature a constant water activity is sought instead of a constant concentration of water during enzymatic reactions, e.g. by pervaporation of salt hydrates [14–16]. in reactions where water is not produced, the initial water activity of the reaction medium is fixed and the change in water activity, which is caused by changes in the polarity https://doi.org/10.33927/hjic-2020-22 mailto:gubiczal@almos.uni-pannon.hu 10 lajtai-szabó, nemestóthy and gubicza of the reaction medium, is neglected. in the case of esterifications, where the water activity of the reaction medium significantly increases as the reaction proceeds, the water activity must be constantly controlled [16–19]. in this study, the resolution of (r,s)-2bromopropanoic acid was analyzed. changes in the activity and enantioselectivity of the enzyme candida rugosa lipase, which is suitable when the water content of the reaction medium is changed during the aforementioned reaction, were investigated. identification of the simplest method to sustain a constant water activity required for kinetic examinations was also sought. 2. experimental 2.1 samples and measurements all chemicals were commercially available and used without further purification. candida rugosa lipase (ec 3.1.1.3) (nominal activity: 920 umg−1 enzyme) was obtained from sigma-aldrich (st. louis, usa). racemic 2-bromopropanoic acid and the ionic liquids used, namely [bmim]pf6 (1-butyl-3methylimidazolium hexafluorophosphate), [nmim]pf6 (1-methyl-3-nonylimidazolium hexafluorophosphate) and [bmim]bf4 (1-butyl-3-methylimidazolium tetrafluoroborate), were obtained from merck kgaa (darmstadt, germany). butan-1-ol as well as all the other organic solvents and salts used were manufactured by reanal laboratory chemicals ltd. (budapest, hungary). in a typical experiment, 2 mmol of racemic 2bromopropanoic acid and 12 mmol of butan-1-ol were added to 5 ml of solvent. the water concentration of the reaction mixture was measured using a mettler dl35 karl fischer titrator. the water activity was adjusted using salts of different aw values (licl (aw = 0.11), mgcl2 (aw = 0.33), nabr (aw = 0.57), ki (aw = 0.69), kcl (aw = 0.84) and k2so4 (aw = 0.97)). the reaction was started by adding 0.1 g of enzyme and the closed flasks were shaken in a new brunswick g-24 horizontal shaker incubator. 2.2 analysis the (r)and (s)-esters produced were analyzed by an hp 5890a gc (gas chromatograph) using a 25 m fs-lipodex e chiral capillary gc column from macherey-nagel (aachen, germany). the samples from organic solvents were directly injected into the gc after being extracted from ionic liquids using nhexane. the activity of the lipase was characterised by the amounts of (r)and (s)-esters produced. 3. results and analysis 3.1 experiments to investigate the actual effect of solvents on the enzyme’s activity, the same water activity should be provided in the reaction media to avoid differences in enzyme activity originating from variations in water activity. by choosing the most suitable method, the application of [bmim]bf4 must be considered, which is a polar solvent and miscible with water. the setting of the water activity with salt hydrate pairs and saturated salt solutions can be hindered as salts dissolve in ionic liquids [19]. as an alternative, the fact that the maximum enzyme activity of candida rugosa lipase is achieved at the same water activity in any solvent was exploited [16]. according to the polarity of the solvents, the same water activity results in different water contents in various solvents, namely the reaction rate or conversion that indicate enzyme activity will be at their maxima with different water contents. an opportunity arises from the inversion of these considerations: the optimal initial water activity, required for kinetic examinations, can be set by determining the initial water content that provides the maximum reaction rate for each solvent. naturally, to precisely set a given water activity, the reaction rate should be measured by monitoring the water content infinite times. instead of this, at least five different initial concentrations of water were set for each solvent. to calculate the reaction rates, the amounts of (r)and (s)-2-bromopropanoic acid butyl esters produced until 10% conversion was achieved or over two hours were considered. to determine the equilibrium constant necessary for calculating the enantiomeric ratio, quick reactions with (r)-2-bromopropanoic acid butyl ester were studied in organic solvents until the equilibrium concentration was reached. in contrast, with ionic liquids numerous reaction media had to be prepared as many samples were taken because for gas chromatography (r)and (s)2-bromopropanoic acid butyl esters had to be extracted from the ionic liquids using n-hexane and the subsequent extracts analysed. as a result, 15 reaction media were prepared simultaneously and the products extracted from them when samples were taken. 3.2 effect of water content the reaction rate altered as a function of water content according to optimum curves (fig. 1). the highest reaction rate was obtained in n-hexane and the ionic liquid [bmim]pf6 when the concentrations of water were 0.15 mol dm−3 (8.9× 10−3 mol h−1 g−1) and 0.38 mol dm−3, respectively. the esterification reaction rate was very similar in toluene and [bmim]pf6 (3.2× 10−3 mol h−1 g −1 and 3.0 × 10−3 mol h−1 g−1, respectively), while in the more polar tetrahydrofuran, [bmim]bf4 esters were produced at a very low reaction rate (10−3 mol h−1 g−1) which was observed to be only slightly dependent on the concentration of water. the enantioselectivity of candida rugosa lipase also varied as a function of water content according to optimum curves, however, was shown to be less dependent on the concentration of water than the reaction rate (fig. 2). hungarian journal of industry and chemistry enzyme activity in non-conventional media 11 figure 1: dependence of the reaction rate on the initial concentration of water the enantioselectivities in [nmim]pf6 and [bmim]pf6 were modest (25 and 19, respectively), while were significantly lower in the other solvents. the highest enantioselectivity (e = 10) was obtained in n-hexane among other classic organic solvents. 3.3 discussion in table 1, the concentrations of water are summarized. it is shown that the maximum reaction rate (cw(conv)) or enantioselectivity (e) (cw(e)) can be achieved at 30 ◦c after 2 hours. the enzyme activity and enantioselectivity of candida rugosa lipase varied according to optimum curves that plots water activity, moreover, the maximum reaction rate and enantioselectivity can be obtained at the same water activity regardless of the solvent used. based on these observations, it is probable that the water activity will be the same in reaction media if a suitable cw(conv) concentration of water is set in every solvent. similarly, the water activity of reaction media will be approximately the same by setting the suitable cw(e) concentration of water. it is possible to set approximately the same water activity in reaction media indirectly, even in the absence of salt pairs or salt hydrates. however, it should be mentioned that the cw values required to reach the maximum conversion or enantioselectivity are not necessarily the same. as can be observed in the case of the ionic liquid [bmim]pf6, a maximum conversion of 29.0% was achieved when cw(conv)= 0.38 mol dm−3, while only a conversion of 26.2% was obfigure 2: dependence of the enantioselectivity on the initial concentration of water tained when cw(e)= 0.31 mol dm−3 required for the maximum enantioselectivity of just 20.0. similar observations may be seen in the case of organic solvents, e.g. n-hexane in which a maximum conversion (36.1%) was achieved when e = 8, while maximum enantioselectivity (e = 10) resulted when the conversion was only 31.7%. therefore, it must be decided whether reaching the maximum conversion or maximum enantioselectivity is the aim. the determination of the maximum conversion as a function of the required enantioselectivity will be the subject of future research. 4. conclusion in this study, it has been proven by the esterification of 2-bromopropanoic acid in the presence of candida rugosa lipase that during reactions conducted in such nonconventional media, the determination of the optimal water content can be significantly simplified by setting the optimal concentration of water instead of the water activity, which is difficult to accomplish. for this purpose, the initial water content required to achieve the maximum reaction rate must be determined. as the water contents needed to achieve the maximum conversion or maximum enantioselectivity are usually different, further optimization tasks are necessary. acknowledgement the financial support of széchenyi 2020 under the project efop-3.6.1-16-2016-00015 is acknowledged. table 1: conversion and enantioselectivity during the enantioselective esterification reaction at the optimum cw(conv) and cw(e) values in different solvents (t =30 ◦c, t = 2 h). solvent logp cw (conv) conversion e cw(e) conversion e mol dm−3 % mol dm−3 % [bmim]bf4 -2.44 0.54 4.6 5 0.46 4.0 6 [bmim]pf6 -2.38 0.38 29.0 18 0.31 26.2 20 [nmim]pf6 -2.19 0.31 13.4 24 0.23 8.9 25 tetrahydrofuran 0.50 0.38 4.3 4 0.31 3.2 5 toluene 2.50 0.23 13.9 3 0.15 10.1 5 n-hexane 3.50 0.15 36.1 8 0.08 31.7 10 48(2) pp. 9–12 (2020) 12 lajtai-szabó, nemestóthy and gubicza references [1] carrea, g.; riva, s.: organic synthesis with enzymes in non-aqueous media (wiley-vch verlag gmbh & co. kgaa, weinheim, germany) 2008, pp. 169-190 isbn: 978-3-527-31846-9 [2] bommarius, a. s.; riebel, b. r.: biocatalysis (wiley-vch verlag gmbh & co. kgaa, 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1-butyl-3methylimidazolium bis[(trifluoromethyl)sulfonyl]amide, biotechnol. lett., 2002, 24(10), 763–767 doi: 10.1023/a:1015563801977 hungarian journal of industry and chemistry https://doi.org/10.1002/3527602364.ch12 https://doi.org/10.1002/3527602364.ch12 https://doi.org/10.1186/s13065-017-0276-2 https://doi.org/10.14440/jbm.2015.60 https://doi.org/10.1021/cr0683820 https://doi.org/10.1016/j.ijbiomac.2012.06.020 https://doi.org/10.1016/j.ijbiomac.2012.06.020 https://doi.org/10.1016/j.molcatb.2004.07.003 https://doi.org/10.1016/j.molcatb.2014.01.001 https://doi.org/10.1016/j.molcatb.2014.01.001 https://doi.org/10.3923/jas.2010.337.342 https://doi.org/10.3923/jas.2010.337.342 https://doi.org/10.1021/jf026071u https://doi.org/10.1002/bit.260440502 https://doi.org/10.1016/s0141-0229(03)00219-9 https://doi.org/10.1016/s0141-0229(03)00219-9 https://doi.org/10.4014/jmb.0905.05051 https://doi.org/10.4014/jmb.0905.05051 https://doi.org/10.1039/b810009h https://doi.org/10.1016/j.memsci.2006.04.012 https://doi.org/10.1016/j.memsci.2006.04.012 https://doi.org/10.1002/bit.10627 https://doi.org/10.1002/bit.10627 https://doi.org/10.1515/hjic-2017-0018 https://doi.org/10.1515/hjic-2017-0018 https://doi.org/10.3109/10242429408992127 https://doi.org/10.1023/a:1015563801977 introduction experimental samples and measurements analysis results and analysis experiments effect of water content discussion conclusion hungarian journal of industry and chemistry vol. 46(1) pp. 1-46 (2018) hjic.mk.uni-pannon.hu contents editorial preface to special issue dedicated to the 14th international interdisciplinary meeting on bioanalysis andrás guttman and herbert lindner 1-1 semiquantitative assessment of dishevelled-3 phosphorylation status by mass spectrometry kateřina hanáková, david potěšil, ondřej bernatík, igor červenka, matěj rádsetoulal, vítězslav bryja, and zbyněk zdráhal 3–6 phosphoglycolipid profiling of bacterial endotoxins anikó kilár, ágnes dörnyei, viktor sándor, ferenc kilár, and béla kocsis 7–11 capillary isotachophoresis determination of trace oxidized glutathione in blood róbert bodor, andrea nečasová, alena pechová, and marián masár 13–17 cold plasma: the way to improve the repeatability of sald icp-ms analysis marek stiborek, jan preisler, masoud shekargoftar, viktor kanický, and jakub kelar 19–22 capillary electrophoretic analysis of exhaled breath condensate in the diagnosis of gastroesophageal reflux disease petr kubáň, pavol ďurč, júlia lačná, michal greguš, františek foret, jiří dolina, štefan konečný, martina doubková, dagmar kindlová, eva pokojová, and jana skřičková 23–27 study of various parameters that influence the content of exhaled breath condensate used in the diagnosis of gastroesophageal reflux disease michal greguš, pavol ďurč, júlia lačná, františek foret, and petr kubáň 29–33 analysis and identification of polyphenolic compounds in green foods using a combination of hplc-esi-it-tof-ms/ms pavel škvára, júlia kezmanová, csilla mišl’anová, andrea vojs staňová 35–38 silica monolithic capillary columns for hilic separations dana moravcová and josef planeta 39–42 determination of homocysteine in urine and saliva by microchip electrophoresis peter troška, anna mandžáková, jasna hradski, juraj ševčík, and marián masár 43–46 hungarian journal of industry and chemistry vol. 46(1) pp. 1-46 (2018) hjic.mk.uni-pannon.hu contents editorial preface to special issue dedicated to the 14th international interdisciplinary meeting on bioanalysis andrás guttman and herbert lindner 1-1 semiquantitative assessment of dishevelled-3 phosphorylation status by mass spectrometry kateřina hanáková, david potěšil, ondřej bernatík, igor červenka, matěj rádsetoulal, vítězslav bryja, and zbyněk zdráhal 3–6 phosphoglycolipid profiling of bacterial endotoxins anikó kilár, ágnes dörnyei, viktor sándor, ferenc kilár, and béla kocsis 7–11 capillary isotachophoresis determination of trace oxidized glutathione in blood róbert bodor, andrea nečasová, alena pechová, and marián masár 13–17 cold plasma: the way to improve the repeatability of sald icp-ms analysis marek stiborek, jan preisler, masoud shekargoftar, viktor kanický, and jakub kelar 19–22 capillary electrophoretic analysis of exhaled breath condensate in the diagnosis of gastroesophageal reflux disease petr kubáň, pavol ďurč, júlia lačná, michal greguš, františek foret, jiří dolina, štefan konečný, martina doubková, dagmar kindlová, eva pokojová, and jana skřičková 23–27 study of various parameters that influence the content of exhaled breath condensate used in the diagnosis of gastroesophageal reflux disease michal greguš, pavol ďurč, júlia lačná, františek foret, and petr kubáň 29–33 analysis and identification of polyphenolic compounds in green foods using a combination of hplc-esi-it-tof-ms/ms pavel škvára, júlia kezmanová, csilla mišl’anová, andrea vojs staňová 35–38 silica monolithic capillary columns for hilic separations dana moravcová and josef planeta 39–42 determination of homocysteine in urine and saliva by microchip electrophoresis peter troška, anna mandžáková, jasna hradski, juraj ševčík, and marián masár 43–46 hungarian journal of industry and chemistry vol. 0(0) editorial preface hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0001 editorial preface to special issue dedicated to the 14th international interdisciplinary meeting on bioanalysis andrás guttman ∗1,2 and herbert lindner3 1horvath csaba laboratory of bioseparation sciences, research center for molecular medicine, faculty of medicine, university of debrecen, debrecen, nagyerdei krt. 98., 4032, hungary 2research institute for biomolecular and chemical engineering, university of pannonia, veszprém, egyetem u. 10., 8200, hungary 3division of clinical biochemistry, biocenter, innsbruck medical university, innsbruck, tirol, austria the cece-2017, 14th international interdisciplinary meeting on bioanalysis was held in veszprém, hungary on 8-11 october, 2017. the symposium was organized by the mta-pe translational glycomics research group, mukki, university of pannonia. the funding idea of this conference series was “bring together scientists from different disciplines who may not meet at other meetings”. following this initiative, 17 world-class invited speakers delivered stimulating lectures not only about cuttingedge bioanalysis but also about other hot topics, such as aerosol chemistry, etc. the informal atmosphere of the meeting supported direct networking between wellestablished senior researchers and young scientists at the beginning of their carrier. the first two days of invited lectures was extended with cece junior, a dedicated day for phd students and postdocs, providing them an opportunity to present their results and catch the attention of colleagues both from academia and industry. more than 120 registered participants attended the event during the three days. the scientific program was preceded by a unique hungarian social event, a sausage making exercise on sunday. this national tradition was an exceptional gettogether party, where invited speakers, participants, students, sponsors and organizers made spicy and tasty sausage under strict quality control by the father of cece series, frantisek foret. as an accompanying section, the horváth csaba memorial exhibition was reopened on the occasion of opening an exhibition for another great hungarian chromatographer professor ervin sz. kováts. the joint display was dubbed as hungarian “chromatography” mafia exhibition and these two good friends are together as examples for the next generations. overall, the program was of very high scientific level. in this symposium issue, selected contributions are published after normal peer-review process covering very diverse topics of the bioanalytical field. at this point, the chair andrás guttman and co-chair herbert lindner would like to thank the hard work of colleagues and students namely brigitta mészáros, beáta borza, lászló hajba, márton szigeti, balázs reider and gábor járvás from the hungarian side and bettina sarg and klaus faserl from the austrian side. last but not least, this event would not have happened without the financial support of our sponsors – sciex, unicam hungary, thermo-fischer scientific, bio-science, agilent, kromat, watrex, waters, university of pannonia, city of veszprém and the hungarian society of separation sciences. in 2018 the series will return to its home town brno on 15-17 october, 2018, see you there! andrás guttman and herbert lindner hungarian journal of industry and chemistry vol. 46(1) pp. 3-6 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0002 semiquantitative assessment of dishevelled-3 phosphorylation status by mass spectrometry kateřina hanáková1,2, david potěšil2, ondřej bernatík3, igor červenka3, matěj rádsetoulal3, vítězslav bryja3, and zbyněk zdráhal ∗1,2 1national centre for biomolecular research, faculty of science, masaryk university, brno, 62500, czech republic 2central european institute of technology, masaryk university, brno, 62500, czech republic 3department of experimental biology, faculty of science, masaryk university, brno, 62500, czech republic the focus of this paper is the human dishevelled 3 protein (hdvl3), an essential component of the wnt signalling pathway that contributes to their regulation. mass spectrometry-based analysis of hdvl3 phosphorylations induced by eight associated kinases was performed revealing several dozens of phosphorylation sites. the main outcome of this study was the description of dvl phosphorylation “patterns” induced by individual kinases. keywords: phosphorylation, dishevelled 3, mass spectrometry, ck1ε, nek2 1. introduction reversible protein phosphorylation belongs to posttranslational modification which is of high biological significance mainly due to its role in regulating cellular processes such as gene expression, cell division, signal transduction, metabolism, differentiation, apoptosis, etc. [1] dishevelled-3 (dvl3) is a protein involved in the wnt signalling pathways and gets heavily phosphorylated in response to pathway activation by wnt ligands [2]. in our study, sodium dodecyl sulfate polyacrylamide gel electrophoresis (sds-page) separation of hdvl3 immunoprecipitates was combined with titanium dioxide phosphopeptide enrichment followed by liquid chromatography-tandem mass spectrometry (lcms/ms). data were processed using skyline software to obtain a semiquantitative assessment with regard to the occupancy of phosphorylation sites induced by individual kinases. 2. experimental 2.1 cell culture and transfection the cell line hek293 was used for this study. cells were seeded in dishes 15 cm in diameter and transfected at a confluence of 60%. two days after transfection, after reaching confluence, they were harvested for immunoprecipitation. a chilled np-40 lysis buffer with protease inhibitors, dithiothreitol (dtt), phosphatase inhibitors and ∗correspondence: zdrahal@sci.muni.cz n-ethylmaleimide (nem) was used for cell lysis. the lysate was incubated with the antibody anti flag m2. 2.2 gel electrophoresis, protein digestion and phosphopeptide enrichment immunoprecipitates were separated by sds–page, fixed with acetic acid in methanol, and stained with coomassie brilliant blue for 1 hour then partially destained. corresponding 1-d bands were excised. after destaining, the proteins in gel pieces were incubated with 10 mm of dtt at 56 ◦c for 45 mins. after the removal of dtt excess samples were incubated with 55 mm of iodoacetamide (iaa) at room temperature in darkness for 30 mins, then an alkylation solution was removed and gel pieces were hydrated for 45 mins at 4 ◦c in a digestion solution (5 ng/µl trypsin, sequencing grade, promega, fitchburg, wisconsin, usa, in 25mm ammonium bicarbonate (ambic)). the trypsin digestion proceeded for 2 hours at 37 ◦c on a thermomixer (at 750 rpm; eppendorf ag, hamburg, germany). subsequently, the tryptic digests were cleaved by chymotrypsin (5 ng/µl, sequencing grade, roche, basel, switzerland, in 25mm ambic) for 2 hours at 37 ◦c. digested peptides were extracted from gels using 50% acetonitrile (acn) solution with 2.5% formic acid (fa) and concentrated in a speedvac concentrator (eppendorf ag, hamburg, germany). the aliquot (1/10) of the sample was transferred to an autosampler vial and concentrated under a vacuum. water was used to produce 15 µl of the peptide solution which was directly mailto:zdrahal@sci.muni.cz 4 hanáková, potěšil, bernatík, červenka, rádsetoulal, bryja, and zdráhal figure 1: comparison of phosphorylation sites of hdvl3 induced by ck1ε and nek2. experimentally determined phosphorylation sites by ck1ε and nek2 are indicated by green background color. phosphorylation sites identified only by nek2 are indicated by red background color. analyzed by liquid chromatography coupled with mass spectrometry (lc-ms/ms) for protein identification (id run). the rest of the peptide mixture was used for phosphopeptide analysis. ms phosphomix 1, 2, 3 light (sigma aldrich) was added to the samples before the phosphopeptide enrichment step in a concentration of 0.1 pmol. phosphopeptides were enriched using a pierce magnetic titanium dioxide phosphopeptide enrichment kit (thermo fisher scientific, waltham, massachusetts, usa) according to the protocol of the manufacturer and eluted into an autosampler vial. the solution was concentrated under a vacuum to a volume of less than 5 µl, dissolved in water and 0.6 µl of 5% fa was used to obtain 15 µl of the peptide solution before lc-ms/ms analysis. 2.3 mass spectrometry lc-ms/ms analyses of the peptide mixture were conducted using a rslcnano system connected to a orbitrap elite hybrid mass spectrometer (thermo fisher scientific) with a abird (active background ion reduction device; esi source solutions) and a digital picoview dpv550 (new objective) ion source (tip rinsing by 50% acn with 0.1% fa) installed. prior to lc separation, tryptic digests were concentrated online and desalted using a trapping column (100 µm × 30 mm) filled with 3.5-µm of xbridge beh 130ĺ c18 sorbent (waters). after the trapping column was washed with 0.1% fa, the peptides were eluted (flow rate of 300 nl/min) from the trapping column onto a acclaim pepmap100 c18 column (3 µm particles, 75 µm × 500 mm; thermo fisher scientific) along a 65 min-long gradient. mobile phase a (0.1% fa in water) and mobile phase b (0.1% fa in 80% acn) were used in both cases. the gradient elution started at 1% of mobile phase b and increased from 1% to 56% during the first 50 mins (30% in the 35th and 56% in the 50th min), then increased linearly to 80% of mobile phase b over the following 5 mins and remained at this state for the next 10 mins. equilibration of the trapping column and the anlytical column was conducted prior to injection of the sample into the sample loop. the outlet of the analytical column was directly connected to the digital picoview dpv550 ion source. ms data were acquired in a data-dependent strategy by selecting the top 6 precursors based on precursor abundance in the survey scan (350-2000 m/z). the resolution of the survey scan was 60,000 (at 400 m/z) with a target value of 1×106 ions, one microscan and a maximum injection time of 200 ms. high resolution (resolution of 15,000 at 400 m/z) higher energy collisional dissociation (hcd) ms/ms spectra were acquired with a target value of 50,000. the normalized collision energy was 32 % for hcd spectra. the maximum injection time for ms/ms was 500 ms. dynamic exclusion was enabled for 45 s after the acquisition of one ms/ms spectra and early expiration was disabled. the isolation window for ms/ms fragmentation was set to 2 m/z. the analysis of the mass spectrometric raw data files was carried out using the proteome discoverer software (thermo fisher scientific; version 1.4) with utilization of the in-house mascot (matrixscience; version 2.4.1) search engine. ms/ms ion searches were conducted against an in-house database containing the expected protein of interest with additional sequences from the crap (common repository of adventitious proteins) database (downloaded from http://www.thegpm.org/crap/). mass tolerance for peptides and ms/ms fragments were 7 ppm and 0.03 da, respectively. oxidation of methionine, deamidation (n, q) hungarian journal of industry and chemistry semiquantitative analysis of dvl3 phosphorylations 5 figure 2: semiquantitative analysis of phosphorylation site serine 204 (s204) on peptide fsspsteqssasr induced by ck1ε and nek2. precursor and selected fragment traces of corresponding hdvl3 phosphopeptides are shown for ck1ε and nek2 (in skyline). the highest signal intensity was detected in the case of nek2. and phosphorylation (s, t, y) as optional modifications, carbamidomethylation of c as a fixed modification and three miss cleavages of enzymes were set for all searches. the phosphors feature was used for phosphorylation site localization. quantitative information was assessed and manually validated in skyline software (skyline-daily 3.1.1.8884). 3. results and analysis 3.1 identification of phosphorylation sites phosphorylation is important for protein function and regulation. the phosphorylation status of human dvl3 induced by eight individual ser/thr kinases that were previously reported or identified by an unbiased ms screen for dvl-associated kinases was analysed. dvl3 contains 131 serines/threonines, which can be potentially phosphorylated. in total, 88 ser/thr phosphorylation sites and one tyrosine phosphorylation site in dvl3 were identified. 3.2 phosphorylations induced by ck1ε and nek2 based on our experiment, a phosphorylation “map” of the dvl protein was created that described the complex phosphorylation “fingerprint” for each kinase tested. eight of the kinases used to induce phosphorylation include ck1ε and nek2. fig. 1 shows a qualitative comparison of the identified phosphorylation sites using these two kinases. in the case of ck1ε induction, 77 phosphorylation sites were identified, and in the case of nek2, 87 phosphorylation sites were determined from a total of 131 possible ser/thr phosphorylation sites in the dvl3 protein. next in terms of qualitative characterization, a semiquantitative comparison with regard to the occupancy of phosphorylation sites induced by individual kinases was conducted. the skyline software was used for this evaluation. the individual phosphorylated peptides were compared based on their peak areas. a comparison of a selected peptide phosphorylated in the position of s204 by ck1ε and nek2 is shown in fig. 2. the peak area was determined for ck1ε as 7.60e6 and for nek2 as 1.07e9. subsequently, double normalization of the data was performed using a set of phosphopeptide standards (added to the sample prior to the phospho-enrichment step) and by unphosphorylated peptides identified in the identification run. the resulting areas (ck1ε: 1.23e7 and nek2: 1.10e9) were compared with each other. 4. discussion our study focused on the determination of the phosphorylation sites of dvl3 by ms induced by eight kinases. 88 ser/thr phosphorylations from a total of 131 sites and 1 tyrosine phosphorylation were identified which can be potentially phosphorylated. ck1ε-induced phosphorylation was identified at 77 unique sites and 10 more phosphorylation sites were induced by nek2. previous studies in various experimental systems identified several phosphorylation sites spread throughout the structure of the protein dvl3 [3, 4]. our data clearly demonstrate that the phosphorylation of the protein dvl3 is extensive and the number of phosphorylated sites exceeds 60. 5. conclusion an approach based on the sds-page separation of dvl3 immunoprecipitates, tio2 phospho-enrichment followed by lc-ms/ms analysis and data processing using skyline software was utilized for the evaluation of semiquantitative differences in the phosphorylation level of hdvl3 at particular sites within the set of eight selected kinases. 46(1) pp. 3-6 (2018) 6 hanáková, potěšil, bernatík, červenka, rádsetoulal, bryja, and zdráhal differences were observed in terms of the phosphorylation profiles induced by individual kinases, as indicated in fig. 1. based on our results, a “comprehensive map” of the phosphorylations of human dvl3 will be created. acknowledgement this work was carried out with the support of the project ceitec 2020 (lq1601) funded by the ministry of education, youth and sports (meys) of the czech republic under the national sustainability programme ii. the czech infrastructurefor integrative structural biology (ciisb) research infrastructure project lm2015043 funded by meys is gratefully acknowledged for financially supporting our lc-ms/ms measurements at the proteomics core facility. the support from the czech science foundation project no. 15-21789s is also gratefully acknowledged. references [1] kersten, b., agrawal, g. k., iwahashi, h., rakwal, r.: plant phosphoproteomics: a long road ahead, proteomics, 2006 6(20), 5517–5528 doi: 10.1002/pmic.200600232 [2] bernatík, o., šedová, k., schille, c., ganji, s. r., červenka, i., trantírek, l., schambony, a., zdráhal, z., bryja, v.: functional analysis of dishevelled3 phosphorylation identifies distinct mechanisms driven by casein kinase 1 epsilon and frizzled5, j. biol. chem., 2014 34(289), 23520-23533 doi: 10.1074/jbc.m114.590638 [3] yanfeng, w. a., berhane, h., mola, m., singh, j., jenny, a., mlodzik, m.: functional dissection of phosphorylation of disheveled in drosophila, dev. biol., 2011 360, 132–142 doi: 10.1016/j.ydbio.2011.09.017 [4] klimowski, l. k., garcia, b. a., shabanowitz, j., hunt, d. f., virshup, d. m.: site-specific casein kinase 1ε-dependent phosphorylation of dishevelled modulates β-catenin signaling, febs j., 2006 273, 4594–4602 doi: 10.1111/j.1742-4658.2006.05462.x hungarian journal of industry and chemistry https://doi.org/10.1002/pmic.200600232 https://doi.org/10.1002/pmic.200600232 https://doi.org/10.1074/jbc.m114.590638 https://doi.org/10.1074/jbc.m114.590638 https://doi.org/10.1016/j.ydbio.2011.09.017 https://doi.org/10.1016/j.ydbio.2011.09.017 https://doi.org/10.1111/j.1742-4658.2006.05462.x hungarian journal of industry and chemistry vol. 46(1) pp. 7-11 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0003 phosphoglycolipid profiling of bacterial endotoxins anikó kilár ∗1,2, ágnes dörnyei2, viktor sándor1, ferenc kilár1, and béla kocsis3 1institute of bioanalysis, university of pécs, szigeti út 12, pécs, 7624, hungary 2department of analytical and environmental chemistry and szentágothai research centre, university of pécs, ifjúság útja 6, pécs, 7624, hungary 3department of medical microbiology and immunology, university of pécs, szigeti út 12, pécs, 7624, hungary much interest is at present focused on bacterial endotoxins, also known as lipopolysaccharides (lps), as they are responsible for the development of clinical symptoms of gram-negative sepsis which is the leading cause of death in intensive care units. endotoxicity is associated with the special phosphoglycolipid part of lps, termed lipid a. main challenges in the structural elucidation of lipid a arise from its amphiphilic character and inherent heterogeneity. a mass spectrometrybased de novo method combined with reversed-phase liquid chromatography for the detailed structural characterization of complex lipid a mixtures (obtained by mild acid hydrolysis of lps) from different bacterial sources has been developed. tandem mass spectrometric measurements were performed with an electrospray-ionisation quadrupole time-of-flight (esi-q-tof) mass spectrometer in both negativeand positive-ionization modes in order to explore fragmentation pathways. it was found that characteristic product ions in the positive-ion mode could be used for the unambiguous assignment of the phosphorylation site, whereas the use of both ionization modes provided consistent and/or complementary information about the fatty acyl distribution between the two glucosamine moieties of lipid a. since the immunostimulatory (advantageous) vs. proinflammatory (endotoxic) effect of the lipid a is closely related to the fine chemical structure, our relatively simple structural elucidation strategy could offer great potential in the bioanalysis of native lipid a samples and lipid a-based vaccines. keywords: lipid a, hplc, tandem mass spectrometry, positive-ion mode, negative-ion mode 1. introduction bacterial endotoxins are important initiators of clinical symptoms of gram-negative sepsis, a serious medical condition with a high mortality rate among patients in intensive care units worldwide. endotoxins, chemically lipopolysaccharides (lps) or lipooligosaccharides (los), are found on the surface of gram-negative bacteria. they are essentially composed of two regions: a heteropolysaccharide chain (divided into the oligosaccharide core and the o-side chain – this component is missing from los) that extends outwards from the bacterial cell surface, and a phosphoglycolipid, termed lipid a, which is anchored in the outer membrane (fig. 1). specifically, the endotoxic activity is related only to the lipidic domain of endotoxins. with regard to the toxicity of lipid a the crucial factors are the acylation and phosphorylation status. this most biologically potent molecule, capable of inducing septic shock, consists of an asymmetrically hexaacylated, bisphosphorylated glucosamine disaccharide [1]. other lipid a species that deviate from this structure have lower endotoxicity or may even have beneficial ∗correspondence: aniko.kilar@aok.pte.hu effects. consequently, the structural analysis of the lipid a moiety is of fundamental interest in terms of clinical aspects and vaccine development. the structural characterization of lipid a poses a unique analytical challenge, as lipid a isolated from a single bacterial strain generally consists of a mixture of differently acylated and phosphorylated species. furthermore, the relative abundances of the different structures can vary with growth conditions, e.g. temperature, culture figure 1: schematic representation of the chemical structure of an enterobacterial outer membrane lipopolysaccharide (endotoxin). mailto:aniko.kilar@aok.pte.hu 8 kilár, dörnyei, sándor, kilár, and kocsis media and ph. within this field, tandem mass spectrometry (ms/ms or msn) has emerged as a core technology for the in-depth structural elucidation of lipid a species [2]. however, separation and simultaneous quantification of singular components by powerful separation methods prior to ms would be highly desirable to adequately characterize the heterogenic structures. here, a brief presentation of an alternative method to multiple-stage ms for the differentiation of various lipid a species – including isobars – within a bacterial sample is provided. our method is based on a reversedphase high-performance liquid chromatography (rphplc) separation and online esi-q-tof mass spectrometric detection of molecular species in native lipid a isolates. the exact structures of the lipid a molecules in the complex mixtures were deduced from specific fragmentation patterns obtained in both the negative[3, 4] and positive-ion modes [5]. 2. experimental 2.1 chemicals and reagents methanol, isopropyl alcohol, water (lc-ms grade), dichloromethane (hplc, ≥99.9%), triethylamine (et3n) and acetic acid (acoh) were purchased from sigmaaldrich (steinheim, germany). 2.2 bacterial strains and lipid a isolation the strains escherichia coli o111 and proteus morganii o34 were cultured in a laboratory fermenter, and then collected by centrifugation. the bacterial lps was extracted from acetone-dried organisms by the traditional hot phenol-water procedure and lyophilized. lipid a was released from lps by mild-acid hydrolysis with 1% (v/v) acoh at 100◦c for 1 h, then the solution was centrifuged (8000×g, 4◦c, 20 mins). the sediment (containing lipid a) was washed four times with distilled water and lyophilized. lipid a samples were dissolved in methanol/dichloromethane (95:5, v/v) at a final concentration of 0.5 mg/ml. 2.3 liquid chromatography – mass spectrometry measurements separation and mass spectrometric detection of lipid a samples were performed with an 1290 infinity ultra-high performance liquid chromatography (uhplc) system (agilent technologies, waldbronn, germany) coupled to a 6530 accurate-mass q-tof lc/ms system (agilent technologies, singapore), using a kinetextm coreshell c18 column (100 mm×4.6 mm, 2.6 µm particle size, phenomenex). mobile phase a was methanol/water (95:5, v/v) and mobile phase b was isopropyl alcohol, both containing 0.1% et3n and 0.1% acoh (v/v). the injection volume was 3 µl. separation was performed at figure 2: hplc–ms base peak chromatograms of the native, heterogeneous e. coli o111 lipid a preparation acquired in the a) positiveand b) negative-ion modes. a constant flow rate of 0.5 ml/min at 50◦c. a linear gradient of 50 min started at 0% of mobile phase b and ramped up to 50% of mobile phase b, and was then maintained at 50% of mobile phase b for 2 mins. negativeand positive-ion mass spectra of the column eluate were recorded between m/z 100 and 3,200. the esi ion source was operated using the following conditions: pressure of nebulizing gas (n2), 30 psi; temperature and flow rate of drying gas (n2), 325◦c and 8 l/min, respectively; temperature and flow rate of sheath gas, 300◦c and 11 l/min, respectively; capillary voltage, 4 kv; nozzle voltage, 2 kv; fragmentor potential, 100 v; and skimmer potential, 70 v. for the targeted ms/ms analysis, the following parameters were used: mass range, m/z 70– 2000; acquisition rate, 333.3 ms/scan; quadrupole isolation width, 1.3 m/z; collision energy, 70–100 v; maximum number of precursor ions/cycle, 4; and active charge state of the precursor ion, 1. 3. results and analysis 3.1 hplc-ms of bacterial lipid a crude lipid a preparations from e. coli o111 and p. morganii o34 bacteria were used as training sets for the development of the method. the hplc separation conditions were optimized in order to find a balance between solubility, adequate separation and ionization of the intact lipid a’s. fig. 2 shows the hplc–ms analysis in the positiveand negative-ion modes for the e. coli o111 lipid a isolate, only. it was found that the lipid a samples expressed extreme structural heterogeneity, showing the presence of numerous bis-, monoand nonphosphorylated structures and diverse acylation states ranging from dito hepta-acylation. the most abundant chromatographic peak from both bacteria was a hexaacylated, monophosphorylated species. the elution order of the separated compounds was consistent with their relative hydrophobicity, defined mainly by the total numhungarian journal of industry and chemistry phosphoglycolipid profiling of bacterial endotoxins 9 ber and length of hydrophobic acyl chains, followed by the number of polar phosphate groups. several isomers of identical mass could be identified in which the length and/or position of the acyl chains varied. since the phosphoglycolipids are acidic in nature, they could readily be ionized as deprotonated ions, i.e. [m – h]− in the negative-ion mode, whereas their ionization in the positive-ion mode was enhanced by adduct formation with triethylamine used as an eluent additive, i.e. [m + h + et3n]+ adducts were formed. 3.2 tandem mass spectrometric analysis of lipid a species in order to investigate the fragmentation behavior under low-energy collision-induced dissociation (cid) conditions of each separated lipid a precursor ion, esims/ms experiments were performed in both ionization modes. based on previously published data on the acyl distribution of the c4’-monophosphorylated, hexaacylated lipid a molecule from e. coli o111 [6], ions observed in the tandem mass spectra (not shown) of this lipid a species (appearing at tr = 29.2 mins in fig. 2) could be structurally assigned in both ionization modes [3,5]. using this as a standard, the cid mass spectral profiles of other monophosphorylated lipid a species separated by chromatography were compared, and the fragmentation preferences for each of them, in both ionization modes, were explored. fig. 3 presents an example of the correlation between the phosphoglycolipid structure and the fragmentation profiles in the case of the main hepta-acylated lipid a compound (tr = 42.5 mins in fig. 2) from e. coli o111. the site-specific cleavages are assigned with a number denoting the carbon of the glucosamine to which the substitution is attached, and a greek letter designating the position of the bond which was cleaved. in the tandem mass spectrum of the [m + h + et3n]+ triethylammonium adduct of this lipid a species (fig. 3a), only a few ions resulting from the neutral loss of acyl chains are present, however, in that of the deprotonated form (fig. 3b), the abundances of product ions in the higher m/z region straightforwardly indicated the consecutive dissociation order of the ester-linked fatty acids. thus, their position could be assigned. each tandem mass spectrum also exhibited diagnostic intra-ring (a-type ions in the negative-ion mode) or inter-ring (band y-type ions in the positive-ion mode) cleavage products, which confirmed the substitution position of the fatty acids on the two glucosamine residues. fig. 4 shows the tandem mass spectra of the c1 phosphorylation isomer of this hepta-acylated lipid a species. the location of the single phosphoryl group (i.e. at c1 or c4’) could be directly assessed from the positive-ion mode tandem mass spectra by calculating the mass difference between the m/z of the precursor ion and that of the product ion resulting from the cleavage of the 1α bond figure 3: tandem mass spectra in a) positiveand b) negative-ion modes and a depiction of the identified structure of the c4’-monophosphorylated hepta-acylated lipid a from the e. coli o111 bacterium. site-specific cleavages are indicated next to the ion signals. (compare figs. 3a and 4a). namely, the mass difference of 199 u corresponded to the combined loss of triethylamine and an orthophosphoric acid molecule, indicating that a phosphoric acid molecule had esterified the c1 hydroxyl group of the reducing end. on the other hand, a mass difference of 119 u resulted from the combined loss of triethylamine and a water molecule, indicating the presence of a free hydroxyl group at c1 (consequently, the phosphoryl group must be located at c4’). the change in the phosphorylation site also resulted in a distinctive tandem mass spectrum in the negativeion mode (fig. 4b). the main differences were the complete lack of a-type cross-ring fragments, and instead the appearance of z-type inter-ring cleavage products. furthermore, the intensities of the product ions resulting from the neutral loss of acyl chains were of about the same magnitude, indicating strong competition between the fatty acyl eliminations during the cid process, instead of their stepwise dissociation (compare with fig. 3b). the fragmentation behavior of nonand bisphosphorylated lipid a species under both negative and positive cid conditions was investigated, as well. for these, a different sequencing of the acyl-chain cleavages could be observed in the negative-ion mode [3, 4], whereas similar fragmentation pathways to that of the monophosphorylated species in the positive-ion mode were identified [5]. besides the a-type ions (nonreducing end), complementary x-type fragment ions (reducing end) appeared in the negative-ion mode tandem mass 46(1) pp. 7-11 (2018) 10 kilár, dörnyei, sándor, kilár, and kocsis figure 4: tandem mass spectra in the a) positiveand b) negative-ion modes and depiction of the identified structure of the c1-monophosphorylated hepta-acylated lipid a from e. coli o111. spectra of the nonphosphorylated lipid a species [4]. 4. discussion the online hplc–ms/ms methodology enabled the simultaneous structural characterization of both phosphorylated and nonphosphorylated lipid a variants within a single run. the main advantage of using the collision cell of a q-tof mass spectrometer was that several generations of precursor/product ions – that would otherwise be generated only at higher ms stages with ion-trap experiments – were observed simultaneously in the tandem mass spectra of the separated lipid a species. this facilitated new fragmentation rules to be set for the variety of phosphorylated and acylated lipid a compounds by a simple ms/ms experiment [3–5]. specifically, the acylation profile of the non-, c4’-mono and bisphosphorylated lipid a species could be inferred partly from the positiveand fully from the negative-ion mode ms/ms analyses [3–5], whereas the complementary use of both ionization modes [3, 5] was needed for the full structural characterization of c1-monophosphorylated lipid a. as an example, the complete structural elucidation strategy by ms/ms of a hepta-acylated c1’monophosphorylated lipid a is as follows. first, observation of the 1α cleavage product in the positive-ion mode is essential to clarify the site of phosphorylation (vide supra). next, the linkages at the 2′ε (only from the btype ion) and 2ε positions can be determined from the positive-ion mode analysis. by knowing the fragmentation preference of the secondary ester bonds (which is 2′ε > 3′ε > 2ε [5]), substitutions at these sites can be deconvoluted from the negative-ion mode analysis by observing the 2′ε, 3′ε, 2ε, and 3α cleavage products in the upper m/z region and those resulting from the 3′α, 2′ε + 3′ε, 2′ε + 2ε, 2′ε + 3α, and 3′ε + 3α cleavages displayed in the middle m/z region. here, the dephosphorylated z-type ion in the lower m/z region indirectly specifies the linkage at the 2α position. finally, the remaining 2’α substitution can be deduced from the intact b-type ion (positive-ion mode). 5. conclusion an efficient hplc separation before the ms detection of natural lipid a mixtures has proven particularly useful in terms of revealing the diversity and relative amount of the various lipid a structures present in bacteria. such investigations could help to explore the relative contributions of different lipid a structures to the overall activation of the innate immune system. moreover, knowledge of the chemical and biological aspects of lipid a heterogeneity is crucial in order to design antimicrobial drugs which overcome the evasion strategy of the pathogen. our technique could be well suited for phosphoglycolipid profiling from different bacterial strains or vaccine preparations. acknowledgement this research was supported by the grants otka k125275 and únkp-17-4-iii provided by the new national excellence program of the ministry of human capacities. references [1] munford, r.s.: sensing gram-negative bacterial lipopolysaccharides: a human disease determinant? infect. immun. 2008, 76(2), 454–465. doi: 10.1128/iai.00939-07 [2] kilár, a.; dörnyei, á.; kocsis, b.: structural characterization of bacterial lipopolysaccharides with mass spectrometry and onand off-line separation techniques. mass spectrom. rev. 2013, 32(2), 90–117. doi: 10.1002/mas.21352 [3] sándor, v.; dörnyei, á.; makszin, l.; kilár, f.; péterfi, z.; kocsis, b.; kilár, a.: characterization of complex, heterogeneous lipid a samples using hplc-ms/ms technique i. overall analysis with respect to acylation, phosphorylation and isobaric distribution. j. mass spectrom. 2016, 51(11), 1043– 1063. doi: 10.1002/jms.3839 [4] sándor, v.; kilár, a.; kilár, f.; kocsis, b.; dörnyei, á.: characterization of complex, heterogeneous lipid a using hplc–ms/ms technique ii. structural elucidation of non-phosphorylated lipid a by negativeion mode tandem mass spectrometry. j. mass spectrom. 2016, 51(8), 615–628. doi: 10.1002/jms.3786 hungarian journal of industry and chemistry https://doi.org/10.1128/iai.00939-07 https://doi.org/10.1128/iai.00939-07 https://doi.org/10.1002/mas.21352 https://doi.org/10.1002/jms.3839 https://doi.org/10.1002/jms.3786 phosphoglycolipid profiling of bacterial endotoxins 11 [5] sándor, v.; kilár, a.; kilár, f.; kocsis, b.; dörnyei, á.: characterization of complex, heterogeneous lipid a samples using hplc–ms/ms technique iii. positive-ion mode tandem mass spectrometry to reveal phosphorylation and acylation patterns of lipid a. j. mass spectrom. 2018, 53(2), 146–161. doi: 10.1002/jms.4046 [6] madalinski, g.; fournier, f.; wind, f.l.; afonso, c.; tabet, j.c.: gram-negative bacterial lipid a analysis by negative electrospray ion trap mass spectrometry: stepwise dissociations of deprotonated species under low energy cid conditions. int. j. mass spectrom. 2006, 249–250, 77–92. doi: 10.1016/j.ijms.2005.12.049 46(1) pp. 7-11 (2018) https://doi.org/10.1002/jms.4046 https://doi.org/10.1002/jms.4046 https://doi.org/10.1016/j.ijms.2005.12.049 hungarian journal of industry and chemistry vol. 46(1) pp. 13-17 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0004 capillary isotachophoresis determination of trace oxidized glutathione in blood róbert bodor ∗1, andrea nečasová2, alena pechová2, and marián masár1 1department of analytical chemistry, faculty of natural sciences, comenius university in bratislava, ilkovičova 6, bratislava, sk-84215, slovak republic 2department of animal protection, welfare and behaviour, faculty of veterinary hygiene and ecology, university of veterinary and pharmaceutical sciences brno, palackého tř. 1/3, brno, cz61242, czech republic a capillary isotachophoresis (citp) method performed in a column-coupling apparatus has been developed for the simultaneous determination of glutathione (gsh) and glutathione disulfide (gssg) concentrations in blood samples. the determination of gssg and gsh concentrations in biological samples is important because of their roles in oxidative stress. different concentrations of a leading ion in the coupled columns (concentration cascade) and a large volume (37 µl) of the injected sample facilitated a gssg concentration of between 2 and 25 µmol/l. a reaction between iodoacetate and gsh under alkaline conditions was used to prepare the sample in order to avoid oxidation of gsh to gssg. this step eliminated the main source of systematic errors with regard to the determination of the gssg concentration. a linear relationship (r2=0.9969) between the zone length of s-(carboxymethyl)glutathione (the product of the reaction between gsh and iodoacetate) and the concentration of gsh (40-120 µmol/l) was obtained. the method was applied to the analysis of bovine blood samples that had been diluted by a factor of ten with satisfactory results. keywords: glutathione, glutathione disulfide, isotachophoresis, bovine blood 1. introduction glutathione (gsh), a thiol containing tripeptide, plays an important role in the antioxidant system of eukaryotic cells [1]. upon oxidation, gsh is transformed into glutathione disulfide (gssg) [1]. the concentrations of gsh and gssg and their molar ratio are indicators of cell functionality as well as oxidative stress [2]. different aspects of the determination of gsh and gssg concentrations in biological samples, including sample pretreatments, were recently reviewed [3–5]. the main problems are related to the non-enzymatic oxidation of gsh when the ph exceeds 7, enzymatic conversion of gsh, a need for the removal of proteins prior to the analysis, blocking of free thiol groups, reduction of disulfides, and derivatization of thiol groups [3,6]. among a wide variety of analytical methods, capillary electromigration (ce) methods, mainly ce coupled with different detectors (uv absorbance [7–10], fluorescence [11] and laser-induced fluorescence (lif) [12, 13], electrochemical [14, 15] and mass spectrometry [16], have been used to determine the concentration of glutathione [5, 17]. the aim of this work was to develop a capillary isotachophoresis (citp) method that involves minimal sample pretreatment for the simultaneous determination of ∗correspondence: robert.bodor@uniba.sk gssg and gsh concentrations in bovine blood samples. determination of trace analytes in regular citp, when the quantitation is based on the measurement of the zone length, is not very common. in this work, two key problems were solved: (1) lowering the quantitation limit of the citp method, and (2) stabilization of gsh without protein precipitation to ensure the accurate determination of the gssg concentration. 2. experimental an ea 202a electrophoretic analyzer (villa labeco, spišská nová ves, slovakia) was used for citp separations. this fully automated ce system was equipped with two columns. in the first column, a fluoroplastic capillary tube with an inside diameter (id) of 800 µm and contactless conductivity detection were used. in the second column, a fused silica capillary with an id of 300 µm, contactless conductivity and uv photometric detectors were used. the citp separations were performed using the electrolyte systems shown in table 1 at a constant driving current, and in the anionic mode (electrode e3 in fig. 1 used as a cathode). at the beginning and end of the day, the separation and electrolyte units as well as the sample loop of the autosampler were rinsed with deionized water mailto:robert.bodor@uniba.sk 14 bodor, nečasová, pechová and masár table 1: electrolyte systems. electrolyte parameter es1 es2 le1 leading ion chloride concentration [mmol/l] 10 10 counter ion 6-aminocaproate concentration [mmol/l] 12 12 eof supressor methylhydroxyethylcellulose concentration [% w/v] 0.1 0.1 ph 3.4 3.4 le2 leading ion chloride concentration [mmol/l] 5 2 counter ion 6-aminocaproate concentration [mmol/l] 6 2.4 eof supressor methylhydroxyethylcellulose concentration [% w/v] 0.1 0.1 ph 3.8 3.9 te terminating ion caproate concentration [mmol/l] 20 20 counter ion 6-aminocaproate concentration [mmol/l] 15 15 eof supressor methylhydroxyethylcellulose concentration [% w/v] 0.1 0.1 ph 4.7 4.7 using built-in peristaltic pumps. between analyses a relatively short rinsing procedure (ca. 1 min) with electrolyte solutions was used. 2.1 samples the bovine blood samples were collected using pvc taking set with an integrated needle hemos (gama group, české budějovice, czech republic), and immediately transferred to the test tube containing k3-edta. the samples after dilution, required for hemolysis, were filtered prior to the analysis using a syringe filter with a glass fiber membrane and a pore size of 1 µm. during the dilution step a thiol-masking agent and naoh were added to each sample. 3. results and discussion 3.1 separation conditions the combination of two columns with different ids and the employment of a column-switching technique is beneficial for the citp determination of analytes present in the multicomponent sample at low concentrations and/or at different concentration levels. the first (wider) capillary allowed the separation of sample constituents injected at a relatively high volume (37 µl). typical macroconstituents, e.g. chloride and ethylenediaminetetraacetic acid (edta), migrated out of the separation path through figure 1: a scheme of the electrophoresis system. autosampler: s – sample loop, sp – syringe pump, 6wv – 6-way valve. interface: during the injection the septums are pierced by the needles (n). interface*: during the separation the autosampler is disconnected from the analyzer. separation and electrolyte unit: v1-v4 – pinch valves, e1e3 – driving electrodes, p1-p3 – peristaltic pumps, im – injection module, w – waste, d1-cd, d2-cd, d2-uv – contactless conductivity and absorbance detection cells, m – membrane, bf – bifurcation, te, le1, le2 – terminating and leading electrolytes. a bifurcation block, and as a result they were removed from the separation compartment. during this stage of the separation the driving current flowed between electrodes e1 and e3 (fig. 1). the very small isotachophoresis (itp) zones of analytes created in the first column were insufficient for their concentrations to be determined. as a result of switching the direction of the driving current through both columns (by connecting electrodes e2 and e3, fig. 1), the separated constituents were transferred to the second column. the signal from d1-cd was used to determine an appropriate time to switch the current (fig. 1). in the second (narrower) capillary the itp zones of analytes were prolonged. in addition, due to the low gssg concentration in the samples of blood (not in excess of tens of µmol/l), their itp zone length was further extended by a reduction in the concentration of leading ions (es2, table 1) in the second column (fig. 2). a higher degree of sensitivity in es2 is also evident from the parameters of regression equations for the analytes (table 2). hungarian journal of industry and chemistry capillary isotachophoresis of glutathione 15 figure 2: isotachopherograms from the separations of gssg and gsh performed in the electrolyte systems es1 (a) and es2 (b). the isotachopherograms were recorded by d2-cd (fig. 1). the concentrations of gssg and gsh in the injected sample were both 25 µmol/l. 3.2 stabilization of glutathione the stability of gsh and its oxidation to gssg during the period between the collection of the sample and its analysis is the main source of systematic errors. in the sample of bovine blood a much higher concentration of gssg and a lower concentration of gsh than expected was measured. to avoid this problem, a thiol-masking agent was used, namely iodoacetic acid (ia) [18]. the substitution reaction between ia and gsh formed s(carboxymethyl)glutathione (gs-mc). under the itp separation conditions used, gs-mc migrated in front of gssg (fig. 3). the optimum conditions for the reaction between ia and gsh were determined by the itp separations of reaction mixtures at different periods after the reagents were mixed. these experiments were conducted with both model and real samples. under neutral and slightly alkaline conditions the reaction was very slow. an excess of ia (2 mmol/l) and the presence of naoh (4 mmol/l) in the reaction mixture led to the fast (less than 20 mins.) and quantitative conversion of gsh to gs-mc (figs. 3 and 4) without an table 2: parameters of regression equations. analyte range a b r2 [µmol/l] [s l/µmol] [s] gssg1 5-50 0.67 1.45 0.999 7 gssg2 2-25 1.66 2.01 0.9992 gsh1 10-50 0.48 0.25 0.9999 gsh2 10-50 1.24 0.60 0.9994 gsh (gs-mc)2 40-120 1.98 -6.60 0.9969 1 electrolyte system es1 and 2 es2 used for data evaluation. regression equation: y = ax + b. figure 3: isotachopherograms from the separation of the reaction mixture present in the electrolyte system es2. the isotachopherograms were recorded by d2–cd. the mixture contained 15 µmol/l of gssg, 80 µmol/l of gsh, 2 mmol/l of ia, 4 mmol/l of naoh, and 10 % of te. the sample was injected 5 mins (dot), 15 mins (dash) and 20 mins (solid) after the reagents were mixed. increase in the concentration of gssg. for the purpose of a quantitative analysis, ia and naoh was added to the sample of bovine blood immediately after its collection (during the sample dilution step required for hemolysis). blood samples that had been diluted by a factor of ten were directly analyzed after their filtration through a syringe filter with a pore size of 1 µm. the concentrations of gssg and gsh that were measured in the diluted blood samples were 4.4 µmol/l and 63.4 µmol/l, respectively. the average concentrations figure 4: dependence of the itp zone length on the reaction time of the mixture containing 15 µmol/l gssg, 80 µmol/l gsh, 2 mmol/l ia, 4 mmol/l naoh and 10 % te. 46(1) pp. 13-17 (2018) 16 bodor, nečasová, pechová and masár calculated from eight repetitive measurements of identical samples were in good agreement with those determined by enzymatic methods. the degrees of precision of the method, expressed by the relative standard deviation (rsd) values of the measured concentrations of gssg and gsh, were 10.3% and 4.4%, respectively. 4. conclusion the sensitive and simultaneous determination of gsh and gssg concentrations in entire samples of bovine blood is facilitated by the capillary isotachophoretic method developed. the simple and rapid preparation of blood samples, that only involves the masking of thiol group of gsh and the dilution and filtration of the sample, increases the accuracy of the gssg concentration measured. no adverse effects caused by the proteins present in the real blood samples on the separation efficiency or detector response was observed. it can be assumed that this method is also suitable for the analysis of blood samples from other mammals. acknowledgement this research was supported by the slovak research and development agency under the project apvv-0259-12, and the scientific grant agency of the ministry of education, science, research and sport of the slovak republic and the slovak academy of sciences under the project vega 1/0342/15. andrea 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britz-mckibbin, p.: differential rates of glutathione oxidation for assessment of cellular redox status and antioxidant capacity by capillary electrophoresis-mass spectrometry: an elusive biomarker of oxidative stress, anal. chem., 2009 81(16), 7047-7056 doi: 10.1021/ac901174g [17] bayle, c.; caussé, e.; couderc, f.: determination of aminothiols in body fluids, cells, and tissues by capillary electrophoresis, electrophoresis, 2004 25(1011), 1457-1472 doi: 10.1002/elps.200305874 [18] winther, j.r.; thorpe, c.: quantification of thiols and disulfides, biochim. biophys. acta, 2014 1840(2), 838-846 doi: 10.1016/j.bbagen.2013.03.031 46(1) pp. 13-17 (2018) https://doi.org/10.1021/ac901174g https://doi.org/10.1002/elps.200305874 https://doi.org/10.1016/j.bbagen.2013.03.031 hungarian journal of industry and chemistry vol. 46(1) pp. 19-22 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0005 cold plasma: the way to improve the repeatability of sald icp-ms analysis marek stiborek1,2, jan preisler ∗1,2, masoud shekargoftar3, viktor kanický1,2, and jakub kelar3 1department of chemistry, masaryk university, kamenice 753/5, brno, 625 00, czech republic 2ceitec central european institute of technology, masaryk university, kamenice 753/5, brno, 625 00, czech republic 3r&d centre for low-cost plasma and nanotechnology surface modifications, department of physical electronics, masaryk university, kotlářská 2, brno, 611 37, czech republic this work deals with the preparation of model biological microsamples for substrate-assisted laser desorption inductively coupled plasma mass spectrometry (sald icp-ms). this technique provides the direct and fast analysis of liquid samples deposited onto polyethylene terephthalate (pet) plates (substrates) in the form of dried droplets with minimal sample preparation and submicrolitre sample volume requirements. furthermore, sald icp-ms allows for the direct analysis of samples in organic solvents, which cannot be directly nebulised to icp-ms. these benefits are, however, balanced out by the low degree of repeatability of the assay, which is typically about 30%. one of the approaches to increase the repeatability is a modification of the substrate surface by diffuse coplanar surface barrier discharge (dcsbd) with the addition of an internal standard to the sample. using this approach, a relative standard deviation (rsd) of less than 10% for model biological samples can be achieved. the only limitation of this technique is the occurrence of the so-called “aging effect”, i.e. the gradual return of the modified physicochemical surface properties to their original state. keywords: sald icp-ms, plasma treatment, dcsbd, microsample, internal standard 1. introduction the determination of elements in biological samples is often complicated by complex matrices, the presence of organic solvents, and trace amounts of the elements of interest. for this reason, it is necessary to select a technique that bridges the obstacles mentioned above. such a technique is substrate-assisted laser desorption inductively coupled plasma mass spectrometry (sald icp-ms), which is capable of analysing liquid samples of submicrolitre volumes in the form of dried droplets (stains) on a polyethylene terephthalate (pet) substrate [1–3]. the greatest difficulty of this technique is the low repeatability of the assay. this is caused mainly by the poorly reproducible deposition of droplets that consist of submicrolitre volumes and the inhomogeneity of the stains produced in terms of the area and thickness of the layer of solid residue in the stain. the assay repeatability can be increased by increasing the surface energy of the substrate and using internal standards that can correct the mentioned effects. one way to increase the surface energy, i.e. wettability of the substrate, is to expose it briefly to cold plasma, ∗correspondence: preisler@chemi.muni.cz specifically diffuse coplanar surface barrier discharge (dcsbd) [4, 5]. the plasma system of the so-called dcsbd is composed of regularly alternating silver electrodes to which high alternate voltages are applied. the electrodes are located in a dielectric structure consisting of dielectric oil and thin ceramic plates. the most common arrangement of electrodes in this device is in the form of two intermeshing combs. surface discharges are then generated on the surface of the ceramic plate, serving as a dielectric barrier. this electrode arrangement (plasma in contact with only inert and highly resistant ceramics) can consist of a theoretically infinite amount of 20×8 cm dcsbd units and thus, it is theoretically possible to achieve an infinite plasma area. the principle of substrate surface treatment is based on the excitement and ionization of the species by a high voltage discharge and subsequent introduction of the resulting species onto the substrate surface in the form of radicals, ions and excited molecules. a disadvantage of this technique over other physicochemical modifications is the gradual decrease in surface tension compared to its original value prior to the modification, or the so-called “aging effect” [6]; this period is in the order of several months. factors influencing the qualmailto:bpreisler@chemi.muni.cz 20 stiborek, preisler, shekargoftar, kanický, and kelar table 1: ablation parameter settings monitored in addition to the other isotopes of interest. isotope integration time 0.1 s flow rate of the he carrier gas 1.0 l·min−1 flow rate of the ar auxiliary gas 0.6 l·min−1 flow rate of the ar plasma gas 15 l·min−1 laser pulse repetition rate 10 hz laser-beam waist 250 µm laser fluence ∼ 0.75 j·cm−2 ity of the modification are the voltage and frequency of the electromagnetic field, the composition of the gaseous atmosphere, the exposure time and the geometries of the sample and electrodes. 2. experimental in the first experiment, a dcsbd device (rps400roplass plasma system 400 w, roplass, czech republic) was used to increase the surface energy of the pet substrate (bayer materialscience, germany). the substrate surface was modified at 300 w for one, five and ten seconds. subsequently, 1µl of 0.5 mm trisodium citrate (sigma-aldrich, usa) solution was deposited onto ten replicates of the pet substrate as a model biological sample. the contact angles were measured by the instrument (see system e, advex instruments, czech republic) using a technique called “sitting droplet on a solid foundation”. the device consists of a charge-coupled device (ccd) camera placed on a sliding table in front of which a substrate plate is positioned. using a micropipette, a 1µl droplet of the sample is deposited onto the substrate and the see system software calculates the contact angle based on the interpolation of the height and width of the arc that describes the shape of the drop. the size of the contact angle was evaluated immediately after modification of the substrate surface as well as after one, seven and 31 days. based on the previous experiment, where the aging of the modified surface was monitored by varying the contact angle and size of the stain, depending on the dropping time that elapsed from the surface modification, a complementary experiment was performed. 1ml of trisodium citrate sample was mixed with cadmium and indium standards (aqueous calibration solutions, certified reference materials (crm), analytika, czech republic) so that the resulting solution contained 400 ng·l−1 of these standards. five replicates of the 200 nl droplet sample solutions prepared were immediately applied using a micropipette to the surface of the modified pet substrate as well as one, three and six days after the modification. the cd and in standards, chosen because of their similar atomic masses and first ionization energies, were used figure 1: dependence of the contact angle of droplets of 0.5 mm trisodium citrate solution on the pet surface modified by dcsbd after one, five and ten seconds; droplets were deposited immediately as well as one, seven and 31 days after the modification. to correct the intensity of the monitored signals. the purpose of this experiment was to demonstrate whether aging of the substrate affects the intensities of the signals. at the same time, the size of the stains was measured. ideally, the application conditions should be identical to the experiment where aging was observed by measuring contact angles. however, this was not possible due to different sample-volume requirements for the given measuring technique. 1 µl was required to measure contact angles and 0.2 µl for sald icp-ms. the plate with samples was then inserted into the ablation cell (up213 model, new wave research, inc., usa) equipped with a 213-nm pulsed nd:yag laser, 3d positioning system and built-in ccd camera for visual control of the ablated samples. the dry aerosol created during ablation was analysed by the icp mass spectrometer (agilent 7500ce icp-ms, agilent, usa). in order to determine the beginning and end of the ablation process, the 13c isotope was isotope was monitored in addition to the other isotopes of interest. for the ablation of the stains, a “zig-zag” ablation trajectory was selected with a 170 µm ablation line and a 160 µm·s−1 scanning speed. the remaining basic ablation parameters are shown in table 1. 3. results and discussion first, the contact angle formed by 1 µl droplets of 0.5 mm trisodium citrate onto a pet substrate surface was evaluated immediately after modification of the substrate surface as well as after one, seven and 31 days. ten replicates of the substrate surface were modified for one, five and ten seconds. fig. 1 shows that the droplets of 0.5 mm trisodium citrate solution that were applied to the substrate surface of pet modified by dcsbd for one second exhibited the greatest contact angle, hence the least wettability; i.e., a longer duration of dcsbd modification causes a higher degree of wettability. it is also evident from fig. 1, howhungarian journal of industry and chemistry cold plasma: the way to improve the repeatability of sald icp-ms analysis 21 table 2: integrated sald icp-ms signals of 111cd and 115in from stains of 0.5 mm trisodium citrate deposited at different times after pet surface modification. deposition time [days] 111cd 115in 115in / 111cd stain size [mm] 0 x [cps]* 0.44 11 25 1.2±0.1 rsd [%] 14 10 7.5 1 x [cps]* 1.4 31 22 1.6±0.2 rsd [%] 34 38 7.2 3 x [cps]* 2.2 48 23 1.4±0.2 rsd [%] 32 29 12 6 x [cps]* 2.8 58 22 1.2±0.3 rsd [%] 34 24 19 ∗cps·106 ever, that the surfaces with the longest dcsbd modification times exhibited the fastest tendency to return to their original states in the long term. in the following experiments, the aging effect of the substrate surface modified by dcsbd on the intensity of sald icp-ms signals was monitored. five replicates of 200 nl droplets containing 0.5 mm trisodium citrate solution and 400 ng·l−1 of cadmium and indium standards were immediately deposited onto the modified pet surface as well as one, three and six days after modification. from table 2, it is apparent that the stain sizes, which should be theoretically dependent on the wettability rate and the aging effect of the modified substrate surface, do not affect the repeatability of the assay for the given samples. furthermore, it is evident that the immediate average integrated intensity of the 111cd and 115in signals from the stain ablation of the 0.5 mm trisodium citrate sample as well as one, three and six days after modification of the pet surface differed. this finding is contrary to the assumption that these values should be identical, because in all cases the same amount of sample solution was deposited and the spots were practically 100% ablated by visual inspection. the repeatability of the ablation was low and relative standard deviation (rsd) values exceeded 30%. such high values of rsds could be attributed, in particular, to the character of the sample itself, which was crystalline after drying, and the analytes as they were inhomogeneously distributed therein. however, when quantifying the signal intensity ratio of 115in to 111cd, this inhomogeneity could be corrected, as a result the rsd values varied by around 7.5% for samples deposited immediately and one day after surface modification of the pet. the samples on the treated surfaces exhibited the highest wettability and, therefore, it was possible to assume that the analytes were homogeneously dispersed in the stain. the ablation records in figs. 2a and 2b also show a higher degree of homogeneity of the stains. samples applied three and six days after modification exhibited higher corrected values of rsds: 12 % and 19 %, refigure 2: ablation record of stains of 0.5 mm trisodium citrate deposited a) immediately, as well as b) 1, c) 3 and d) 6 days after pet substrate surface modification. spectively, mainly due to a higher level of inhomogeneity (figs. 2c and 2d). average 115in/111cd integrated signal intensity values for the spots applied one, three and six days after surface modification could be used for quantification of the monitored analytes as the values almost coincided. however, the average value of the integrated signal from droplets applied to the substrate immediately after the modification differed. this could be caused by extreme changes in the physical properties of the substrate surface immediately after modification. 4. conclusion dcsbd technology was chosen for surface modification, i.e. to increase the energy and wettability of the sub46(1) pp. 19-22 (2018) 22 stiborek, preisler, shekargoftar, kanický, and kelar strate surface. however, the disadvantage of this technique is the aging of the treated surface, i.e. the return of the modified physicochemical properties of the substrate surface to their original state prior to the modification. the experiments showed that the integrated signal intensities of the selected analytes, 111cd and 115in, present in the desorbed spots of 0.5 mm trisodium citrate solution, that were deposited onto the substrate surface at various time intervals following its modification differed. also, the repeatability of the analysis of individual samples expressed as rsds changes with deposition time. rsd values were approximately 30% for 0.5 mm trisodium citrate samples. when quantifying the ratio of integrated 115in/111cd signals, it was found that the values did not differ significantly from each other and could be used in quantitative analysis. using internal standards, rsd values were reduced to less than 10% for trisodium citrate samples. acknowledgement we gratefully acknowledge the financial support of the czech science foundation (15-05387s and 18-16583s) and the ministry of education, youth and sports of the czech republic under the project ceitec 2020 (lq1601). references [1] peš, o.; jungová, p.; vyhnánek, r.; vaculovič, t.; kanickı, v.; preisler, j.: off-line coupling of capillary electrophoresis to substrate-assisted laser desorption inductively coupled plasma mass spectrometry. anal. chem. 2008 80(22), 8725–8732 doi: 10.1021/ac801036x [2] navrátilová, j.; jungová, p.; vanhara, p.; preisler, j.; kanickı, v.; šmarda, j.: copper ions regulate cytotoxicity of disulfiram to myeloid leukemia cells. int. j. mol. med. 2009 24(5), 661–670 doi: 10.3892/ijmm_00000277 [3] nehybová, t.; šmarda, j.; daniel, l.; stiborek, m.; kanickı, v.; spasojevič, i.; preisler, j.; damborskı, j.; beneš, p.: wedelolactone acts as proteasome inhibitor in breast cancer cells. int. j. mol. sci. 2017 18(4), 729–742 doi: 10.3390/ijms18040729 [4] černák, m.; černáková, l’.; hudec, i.; kováčik, d.; zahoranová, a.: diffuse coplanar surface barrier discharge and its applications for in-line processing of low-added-value materials. eur. phys. j. appl. phys. 2009 47(2), 1–6 doi: 10.1051/epjap/2009131 [5] štěpánová, v.; kelar, j.; galmiz, o.; zemánek, m.; slavíček, p.; buček, a.; černák, m.: areal homogeneity verification of plasma generated by diffuse coplanar surface barrier discharge in ambient air at atmospheric pressure. contrib. plasm. physic. 2017 57(4), 182–189 doi: 10.1002/ctpp.201600093 [6] prysiazhnyi, v.: atmospheric pressure plasma treatment and following aging effect of chromium surfaces. jsemat 2013 3(2), 138–145 doi: 10.4236/jsemat.2013.32018 hungarian journal of industry and chemistry https://doi.org/10.1021/ac801036x https://doi.org/10.1021/ac801036x https://doi.org/10.3892/ijmm_00000277 https://doi.org/10.3892/ijmm_00000277 https://doi.org/10.3390/ijms18040729 https://doi.org/10.1051/epjap/2009131 https://doi.org/10.1002/ctpp.201600093 https://doi.org/10.4236/jsemat.2013.32018 https://doi.org/10.4236/jsemat.2013.32018 hungarian journal of industry and chemistry vol. 46(1) pp. 23-27 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0006 capillary electrophoretic analysis of exhaled breath condensate in the diagnosis of gastroesophageal reflux disease petr kubáň *1, pavol ďurč1, júlia lačná1, michal greguš1, františek foret1, jiří dolina2, štefan konečný2, martina doubková3, dagmar kindlová3, eva pokojová3, and jana skřičková3 1department of bioanalytical instrumentation, ceitec masaryk university, veveří 97, 602 00 brno, czech republic 2department of internal gastroenterology, faculty hospital brno, faculty of medicine, masaryk university, jihlavská 340/20, 625 00 brno, czech republic 3department of pulmonary diseases and tuberculosis, faculty hospital brno, faculty of medicine, masaryk university, jihlavská 340/20, 625 00 brno, czech republic in this work, capillary electrophoresis with contactless conductometric detection (ccd) was used for the analysis of the ionic content of exhaled breath condensate (ebc) to differentiate between healthy individuals and patients with gastroesophageal reflux disease (gerd). the exhaled breath condensate was collected using a miniature sample collection device and the content analyzed using a separation electrolyte composed of 20 mm 2-(n-morpholino)ethanesulfonic acid, 20 mm l-histidine, 2 mm 18-crown-6 and 30 µm cetyltrimethylammonium bromide. the separation of anions took less than 2.5 minutes, while the cations were separated in less than 1.5 minutes. the most significantly elevated ions in the group of patients suffering from gastroesophageal reflux disease were chloride, nitrate, propionate and butyrate. although the number of subjects was too small to draw definite conclusions with regard to the discriminatory power of these ions, the pilot data are promising for ebc as a useful non-invasive alternative for other methods used in the diagnosis of gastroesophageal reflux disease. keywords: capillary electrophoresis, exhaled breath condensate, ionic analysis, diagnosis, gastroesophageal reflux disease 1. introduction capillary electrophoresis is an attractive separation technique that is particularly suitable for the analysis of biological samples. non-invasive sampling and the analysis of alternative biofluids are gaining scientific attention as these samples are acquired easily, can be obtained repeatedly without any particular stress to the patient, and often are formed of a simple matrix. one such sample is exhaled breath condensate (ebc). ebc is obtained by cooling exhaled breath using suitable pieces of cooling equipment and apparatus. ebc is the aqueous part of the exhaled breath that mainly contains condensed water from breath and volatile compounds that are soluble in water, in addition to small respiratory droplets that provide information concerning the condition, inflammation and oxidative/nitrosative stress of the lungs. ebc was first used as a diagnostic sample by sidorenko in the 1980s [1] and since then numerous articles on ebc have been published, including some re*correspondence: petr.kuban@gmail.com cent reviews [2, 3]. ebc is attractive not only in terms of studying the condition of the lungs [4, 5], but possibly in the identification of other applications, for instance, in the assessment of inflammatory conditions of the trachea and esophagus. the latter is of particular importance because gastroesophageal reflux disease (gerd) is one of the most common diseases in the western world. between 20 and 30% of the general population in europe and usa will suffer from gerd [6] and about 60% of the adult population will experience some type of gerd during their lifespan. gerd is often diagnosed using invasive instruments such as 24-hour multichannel intraluminal impedance and ph monitoring (mii-ph) [7], during which the patient is required to continuously wear a narrow catheter in the esophagus. this device measures the spread and volume of gases, liquids as well as solids through the esophagus and evaluates the composition of refluxate. the data are eventually used to evaluate whether the person is suffering from the disease based on the number of recorded reflux episodes and the demeester score [8] which describes the severity of reflux. mailto:petr.kuban@gmail.com 24 kubáň, ďurč, lačná, greguš, foret, et al. the use of mii-ph is, however, rather unpleasant and up to one third of subjects report discomfort. in this paper, the replacement of the above-mentioned mii-ph method with a significantly less invasive technique for analyzing ebc was attempted. ebc was collected using a specially designed miniature sampler [4, 9, 10] that was previously developed in our laboratory. ebc samples were collected from several healthy volunteers and a group of patients suffering from symptoms attributed to gastroesophageal reflux disease. capillary electrophoresis was used to analyze the ionic content of ebc samples and differences in selected ion concentrations were identified between the groups. 2. experimental 2.1 instrumentation an in-house-built ce instrument was used for all electrophoretic separations at ± 15 kv using a high voltage power supply unit (spellman cze2000r start spellman, pulborough, uk). two pt wires (with an outer diameter (od) of 0.5 mm, 3 cm in length, advent research materials ltd., eynsham, uk) were inserted into the electrolyte vials to serve as electrodes. fused-silica (fs) capillaries (with an inner diameter (id) of 50 µm, od of 375 µm, 39 cm in total length, polymicro technologies, phoenix, az, usa) were used for the separation. all ce experiments were performed at ambient temperature. a custom-made contactless conductometric detector (ccd) (version 5.06, admet s.r.o., prague, czech republic) operating at a frequency of 1.8432 mhz and a voltage of 50 vp−p was used for the detection of the separated analytes. data were collected using an orca 2800 24-bit a/d converter and ecomac software ver. 0.254 (ecom spol s.r.o., prague, czech republic). in all experiments, hydrodynamic injection was applied to the samples, consisting of the elevation of the sample vial to a height of 10 cm for 20 s. the sampler for the collection of ebc has been developed in our group previously [9]. briefly, it was constructed from a 2 ml syringe (b. braun melsungen ag, melsungen, germany) cooled by a 5 cm-long hollow aluminum cylinder with an od of 2.5 cm and an id identical to the od of the syringe (see fig. 1). the cylinder was kept in dry ice at -80 °c prior to the collection of ebc and an insulation sleeve was used during its collection. a straw with an od of 6 mm, and a wall thickness of 0.2 mm (purchased in a local store) was used to exhale the air through the sampler. the end of the syringe was enclosed with a parafilm septum to avoid loss of ebc. 2.2 chemicals all chemicals were of reagent grade (sigma-aldrich, steinheim, germany) and deionized (di) water (purite, figure 1: the photograph and scheme of the ebc sampler used in this work. neptune, watrex, prague, czech republic) was used for the preparation of stock solutions and dilutions. background electrolytes (bges) for ce measurements were prepared daily by diluting 100 mm of stock solutions of 2-(n-morpholino)ethanesulfonic acid (mes), l-histidine (l-his) and 18-crown-6 to the required concentrations. cetyltrimethylammonium bromide (ctab) was prepared as a 10 mm stock solution in 5 % acetonitrile. the separation electrolyte that was used for separation and quantitation of inorganic anions, cations and organic acids consisted of 20 mm mes, 20 mm l-his, 2 mm 18-crown-6 and 30 µm ctab. 2.3 capillary-conditioning procedure prior to its first use, the separation capillary was preconditioned by flushing it with 0.1 m naoh for 30 mins., then with di water for 30 mins. and finally with a solution of bges for 10 mins. between two successive injections, the capillary was flushed with the bge solution for 1 min. at the end of a working day, the capillaries were washed with di water for 15 mins., followed by the application of a vacuum for 5 mins. before being stored dry overnight. 2.4 sample-collection procedure the ebc was collected in the morning, the subjects did not eat or drink beforehand. the ebc was collected using the previously described ebc-sampler. the subject was asked to exhale deeply 3-5 times into the sampler, but depending on the lung capacity of each, the number of exhalations was modified to collect approximately 100 µl of their ebc. after the sampling of ebc was completed, the condensate from the walls of the syringe was forced to the tip of the syringe by the plunger and transferred to the sample vial for ce analysis. part of the ebc sample was also used in another experiment published elsewhere, in which the ph was measured using a microelectrode. hungarian journal of industry and chemistry ce analysis of ebc in gerd diagnosis 25 figure 2: separation of a model mixture consisting of 4 inorganic anions and 4 organic acids. bge: 20 mm mes/lhis, 2 mm 18-crown-6, 30 µm ctab. hv: positive +15 kv, c4d detection. ion concentrations in the parentheses in µm: acetate (200); chloride, nitrate, lactate, propionate, butyrate (25); nitrite, sulfate (10). 2.5 selection of patients and healthy individuals in this initial screening, a group of healthy individuals and a group of patients diagnosed with asthma and pulmonary fibrosis were selected. the healthy individuals had no history of gerd or heartburn and were free from other related symptoms. the healthy individuals selected were from approximately the same age group as the patients, i.e., the average age of healthy subjects was 48 and that of patients was 56. the patients suffered from asthma and pulmonary fibrosis and were from the department of pulmonary diseases and tuberculosis at the faculty hospital brno. 3. results and analysis 3.1 electrolyte selection to separate the ionic content of the ebc, the bges composed of mes and l-his was chosen as this electrolyte allows for the analysis of anions, organic acids, and cations with good degrees of sensitivity. mes and lhis fulfill the criteria for suitable coions and counterions in ce separation using contactless conductivity detection (c4d). the conductance of the respective bge components is low, thus analytes including small organic acids (acetate, lactate, butyrate) will be detected as positive peaks. the addition of 18-crown-6 to the separation electrolyte improves the resolution of k+ and nh+ 4 cations figure 3: separation of a model mixture of 5 inorganic cations. bge: 20 mm mes/l-his, 2 mm 18-crown-6, 30 µm ctab. hv: negative -15 kv, c4d detection. ion concentrations in the parentheses in µm: ammonium (1000); calcium (25); potassium, sodium and magnesium (10). and does not influence the selectivity of other measured cations to a great extent, nor does it influence the separation of anions and organic acids. ctab is added to the separation electrolyte to decrease the electroosmotic flow (eof). it should be noted here that although this separation electrolyte allows for the simultaneous separation of anions and cations using dual-opposite end injection [11], in this work anions and cations were determined separately by switching the high-voltage polarity. the separation of a model mixture consisting of 8 anions in less than 2.5 mins. is shown in fig. 2. the ion concentrations were selected to be similar to those found in ebc samples. the separation of cations using the same conditions but using reverse-polarity voltage is shown in fig. 3. the ammonium cation is usually present at a concentration 100 times greater than other cations in the ebc, its concentration was thus also increased to 1000 µm to reflect the expected concentration. note that even with this significant excess the separation of nh+ 4 from k+ is sufficient and the bge composition can be used for real sample analysis. 3.2 analysis of anions in ebc samples from each subject, the ebc sample was collected as described previously. about 50 µl of the sample was transferred into an eppendorf tube and hydrodynamically injected into the ce system. the ebc samples were analyzed first for anions and organic acids using positive hv polarity and then for cations using negative hv polarity, 46(1) pp. 23-27 (2018) 26 kubáň, ďurč, lačná, greguš, foret, et al. figure 4: separation of anions in ebc samples of healthy persons as well as patients with acid reflux or weakly acid reflux. bge: 20 mm mes/l-his, 2 mm 18-crown-6, 30 µm ctab. hv: positive +15 kv, c4d detection. with the hv electrode placed in the detection vial. the concentrations of all 13 ions in the samples were evaluated using calibration curves measured with standard solutions. the parameters such as the calibration curve, regression coefficient (r2) and concentration range are shown in table 1. in this initial screening the analysis of several samples from the healthy group and patients that were diagnosed as having the acid reflux or weakly acid reflux was attempted and the ions that would be significantly different in these groups identified. a series of electropherograms of anions and organic acids in a healthy individual, patient with acid reflux and patient with weakly acid reflux is shown in fig. 4. one can clearly see that the concentrations of several anions, most notably chloride, nitrate and organic acids, are significantly higher in the group of patients than in that of the healthy volunteers. some small inorganic anions such as nitrite and nitrate are often found in the ebc of patients with respiratory diseases as markers of nitrosative stress. on the other hand, the presence of an increased concentration of chloride and organic acids may be a significant step towards the diagnosis of gerd. 3.3 analysis of cations in ebc samples the analysis of cations in the same samples can be seen in fig. 5. although higher concentrations of the ammonium cation were found in patients compared to healthy individuals, the content was not significantly different from that of healthy individuals, and this applied for other cations (k+, na+, ca2+, mg2+) as well. figure 5: separation of cations in ebc samples of healthy persons as well as those with acid reflux and weakly acid reflux. bge: 20 mm mes/l-his, 2 mm 18-crown-6, 30 µm ctab. hv: negative -15 kv, c4d detection. 4. discussion a limited number of subjects were tested and the determination of whether a simple ebc sample could be used as a surrogate for more invasive, expensive and tedious diagnostic methods attempted. the analysis of anions showed some promising results with regard to the small inorganic anions (chloride and nitrate) collected and the concentration of organic acids that were elevated in the patients table 1: calibration equations of all separated anions, cations and organic acids. bge: 20 mm mes/l-his, 2 mm 18-crown-6, 30 µm ctab. hv: positive +15 kv or negative -15 kv, c4d detection. ion calibration equation r2 range (µm) cl− y = 0.0278x+ 0.0258 0.9957 0.6-25 no− 2 y = 0.0270x+ 0.0023 0.9994 0.6-25 no− 3 y = 0.0315x+ 0.0166 0.9987 0.6-25 so2− 4 y = 0.0656x+ 0.0143 0.9980 0.25-10 acetate y = 0.0156x+ 0.0200 0.9995 1-200 lactate y = 0.0207x+ 0.0097 0.9996 0.6-25 propionate y = 0.0189x+ 0.0024 0.9983 0.6-25 butyrate y = 0.0188x− 0.0001 0.9990 0.6-25 nh+ 4 y = 0.0211x− 0.1437 0.9993 25-1000 k+ y = 0.0347x+ 0.0013 0.9994 0.25-10 ca2+ y = 0.0528x+ 0.0059 0.9995 0.6-25 na+ y = 0.0356x+ 0.0079 0.9996 0.25-10 mg2+ y = 0.0618x− 0.0054 0.9995 0.25-10 hungarian journal of industry and chemistry ce analysis of ebc in gerd diagnosis 27 suffering from gerd symptoms, compared to healthy volunteers. unfortunately, with regard to the analysis of cations, the differences were not significant and cations were deemed unsuitable. 5. conclusion capillary electrophoretic analysis of ebc was used for the first time in an attempt to distinguish the groups of patients with gerd from healthy individuals. ce with c4d was used for the analysis of small inorganic anions, cations and organic acids present in the ebc samples. although it has been shown that selected samples had elevated concentrations of chloride, nitrate, butyrate and propionate, the number of subjects was too small to draw definite conclusions concerning the discriminatory power of these ions. it also seems that although there is a difference between groups of healthy individuals and sufferers of acid reflux/weakly acid reflux, the results with regard to acid reflux and weakly acid reflux are very similar and these two groups cannot be distinguished based on the current data. a larger scale clinical study, in which the ebc of patients and healthy individuals is scrutinized with regard to the ion content, ph and concentration of other biomarkers (for instance pepsin in saliva) to obtain statistically significant results for evaluation is currently being undertaken. nevertheless, the initial data is somewhat promising for ebc as a useful non-invasive alternative for other methods used in gerd diagnostics. symbols bge background electrolyte ce capillary electrophoresis c4d contactless conductivity detection ctab cetyltrimethylammonium bromide di deionized ebc exhaled breath condensate gerd gastroesophageal reflux disease l-his l-histidine id inner diameter mes 2-(n-morpholino)ethanesulfonic acid od outer diameter acknowledgement this research was supported by grant no. 17-31945a from the ministry of health of the czech republic. references [1] sidorenko, g.i.; zborovskii, e.i.; levina, d.i.: surface-active properties of the exhaled air condensates (a new method of studying lung function), ter. arkh., 1980 52, 65–68 [2] kubáň, p.; foret, f.: exhaled breath condensate: determination of non-volatile compounds and their potential for clinical diagnosis and monitoring. a review, anal. chim. acta, 2013 805, 1–18 doi: 10.1016/j.aca.2013.07.049 [3] hayes, s.a.; haefliger, s.; harris, b.; pavlakis, n.; clarke, s.j.; molloy, m.p.; howell, w.m.: exhaled breath condensate for lung cancer protein analysis: a review of methods and biomarkers, j. breath res., 2016 10(3), 034001 doi: 10.1088/1752-7155/10/3/034001 [4] greguš, m.; foret, f.; kindlová, d.; pokojová, e.; plutinskı, m.; doubková, m.; merta, z.; binková, i.; skřičková, j.; kubáň, p.: monitoring the ionic content of exhaled breath condensate in various respiratory diseases by capillary electrophoresis with contactless conductivity detection, j. breath res., 2015 9, 027107 doi: 10.1088/1752-7155/9/2/027107 [5] aldakheel, f.m.; thomas, p.s.; bourke, j.e.; matheson, m.c.; dharmage, s.c.; lowe, a.j.: relationships between adult asthma and oxidative stress markers and ph in exhaled breath condensate: a systematic review, allergy, 2016 71(6), 741–757 doi: 10.1111/all.12865 [6] el-serag, h.b.; sweet, s.; winchester, c.c.; dent, j.: update on the epidemiology of gastro-oesophageal reflux disease: a systematic review, gut., 2014 63(6), 871–880 doi: 10.1136/gutjnl-2012-304269 [7] tutuian, r.; castell, d.o.: review article: complete gastro-oesophageal reflux monitoringcombined ph and impedance, aliment. pharmacol. ther., 2006 2, 27–37 doi: 10.1111/j.1365-2036.2006.03039.x [8] johnson, l.f.; demeester, t.r.: twenty-four-hour ph monitoring of the distal esophagus. a quantitative measure of gastroesophageal reflux, am. j. gastroenterol., 1974 62, 325–332 [9] greguš, m.; foret, f.; kubáň, p.: single-breath analysis using a novel simple sampler and capillary electrophoresis with contactless conductometric detection, electrophoresis, 2015 36(4), 526–533 doi: 10.1002/elps.201400456 [10] greguš, m.; foret, f.; kubáň, p.: portable capillary electrophoresis instrument with contactless conductivity detection for on-site analysis of small volumes of biological fluids, j. chromatogr. a, 2016 14(27), 177–185 doi: 10.1016/j.chroma.2015.11.088 [11] kuban, p.; karlberg, b.; kuban, p.; kuban, v.: application of a contactless conductometric detector for the simultaneous determination of small anions and cations by capillary electrophoresis with dualopposite end injection, j. chromatogr. a, 2002 964, 227–241 doi: 10.1016/s0021-9673(02)00656-8 46(1) pp. 23-27 (2018) https://doi.org/10.1016/j.aca.2013.07.049 https://doi.org/10.1016/j.aca.2013.07.049 https://doi.org/10.1088/1752-7155/10/3/034001 https://doi.org/10.1088/1752-7155/9/2/027107 https://doi.org/10.1111/all.12865 https://doi.org/10.1111/all.12865 https://doi.org/10.1136/gutjnl-2012-304269 https://doi.org/10.1111/j.1365-2036.2006.03039.x https://doi.org/10.1002/elps.201400456 https://doi.org/10.1002/elps.201400456 https://doi.org/10.1016/j.chroma.2015.11.088 https://doi.org/10.1016/s0021-9673(02)00656-8 hungarian journal of industry and chemistry vol. 46(1) pp. 29-33 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0007 study of various parameters that influence the content of exhaled breath condensate used in the diagnosis of gastroesophageal reflux disease michal greguš ∗1,2, pavol ďurč1,2, júlia lačná1,2, františek foret1,3, and petr kubáň1,2,3 1department of bioanalytical instrumentation, ceitec masaryk university, veveří 97, 602 00 brno, czech republic 2department of chemistry, masaryk university, kotlářská 267/2, 611 37 brno, czech republic 3department of bioanalytical instrumentation, institute of analytical chemistry of the czech academy of sciences, v.v.i., veveří 97, 602 00 brno, czech republic in this work, various parameters that influence the ionic content and ph of exhaled breath condensate in terms of the noninvasive diagnosis of gastroesophageal reflux disease were studied. exhaled breath condensate samples were collected using a miniature and inexpensive sampling device. capillary electrophoresis with contactless conductometric detection was used to monitor the ionic content of exhaled breath condensate. background electrolyte composed of 20 mm of 2-(n-morpholino)ethanesulfonic acid, 20 mm of l-histidine, 2 mm of 18-crown-6 and 30 µm of cetyltrimethylammonium bromide facilitated the rapid separation of anions and cations, both in less than 2 minutes. the possibility of contamination of the exhaled breath condensate by saliva is discussed in detail. the day-to-day repeatability (n=5) of the ionic content and ph of the exhaled breath condensate was studied and was satisfactory, reflecting mainly the physiological variability. keywords: capillary electrophoresis, exhaled breath condensate, ionic analysis, ph, gastroesophageal reflux disease 1. introduction gastroesophageal reflux disease (gerd) is a disease caused by the backflow of gastric contents into the esophagus due to the failure of physiological antireflux mechanisms and can lead to symptoms such as a chronic cough, globus sensation, laryngitis, pharyngitis, rhinosinusitis, otitis media, bronchial asthma, chronic obstructive pulmonary disease, sleep apnea and noncardiac chest pain [1, 2]. currently, no suitable, non-invasive diagnostic method for gerd is applicable in clinical practice. nowadays, the gold standard with regard to the diagnosis of gerd is a 24-hour multichannel intraluminal impedance-ph technique (mii-ph) that is rather invasive [3]. non-invasive sampling is becoming more important. exhaled breath condensate (ebc) as one of several noninvasive samples can be easily obtained by the cooling and subsequent condensation of exhaled breath. the ebc is composed mainly of water, however, it also contains volatile and non-volatile compounds (inorganic ions, organic acids) that can be useful as biomarkers of various diseases [4]. the identification of ions in ebc samples is easily achieved by capillary electrophoresis (ce). the main ad∗correspondence: gregus@mail.muni.cz vantage of this method is that it is able to cope with a minute volume of samples and analyses are often very rapid. another parameter that is often used to diagnose gerd is ph, measured by a conventional mii-ph probe, which is both invasive and costly. the ph can also be measured in collected samples of ebc [5] which is noninvasive and cheaper. monitoring various parameters of ebc in patients suffering from symptoms of extraesophageal/gastroesophageal reflux disease is an attractive, simple and non-invasive approach that could be used as a surrogate for other, more invasive diagnostic methods. however, to obtain relevant results, various parameters that can affect the results such as sampling procedures, effects of food and drinks and the intraday variability of individuals have to be studied prior to the use of ebc sampling in diagnostics. 2. experimental 2.1 instrumentation a purpose-built ce instrument was used for all ce analyses. the separation voltage was provided by a highvoltage power-supply unit (dx250, emco high voltage, sutter creek, ca, usa). a custom-made contactless conductivity detector (c4d, version 5.06, admet mailto:gregus@mail.muni.cz 30 greguš, ďurč, lačná, foret and kubáň 10 cm 2 ml syringe straw hollow aluminum cylinderseptum figure 1: the photo of the components used to build a miniature ebc sampling device. s.r.o., prague, czech republic) operating at a frequency of 1.8432 mhz and a voltage of 50 vp−p using a 24-bit a/d converter (orca 2800, ecom s.r.o., prague, czech republic) was used to detect separated analytes and collect data. ce analyses were performed in fused-silica capillaries (inner diameter (id) of 50 µm, outer diameter (od) of 375 µm, total length of 40 cm, effective length of 17 cm, microquartz gmbh, munich, germany). injection of a standard solution and samples was performed hydrodynamically. two pt wires (od of 0.5 mm, length of 3 cm, advent research materials ltd., eynsham, england) were inserted into the electrolyte vials to serve as electrodes. all ce experiments were performed at ambient temperature. to measure the ph of the ebc samples, co2 present in these samples was removed by a stream of n2 gas (nitrogen generator, rp-ze-n2l3000). the ph was measured using a ph microelectrode (mi-410 microcombination ph probe, microelectrodes, inc., bedford, new hampshire, usa) and ph-meter (orion startm a111 ph benchtop meter, thermo fisher scientific, waltham, massachusetts, usa). ebc samples were collected from the volunteers using an ebc sampler previously developed by our group [6,7]. briefly, the sampler for collection of ebc was constructed from a 2-ml syringe (b. braun melsungen ag, melsungen, germany) and a 5 cm-long hollow aluminum cylinder (see fig. 1) with an outer diameter (od) of 2.5 cm and an inner diameter (id) precisely matching the outer diameter of the syringe to facilitate efficient cooling of the walls. the cylinder was kept in a deep freezer at -17◦c and an insulation sleeve was used during collection to maintain the temperature for the whole duration of the sampling procedure. another aim of this insulation sleeve was to prevent frostbite during collection of the sample. straw (purchased from a local store) with an od of 6 mm and wall thickness of 0.2 mm was used to exhale the air through the sampler. the end of the syringe was enclosed with a parafilm septum to avoid ebc loss. 2.2 chemicals all chemicals were of reagent grade, and deionized (di) water was used for preparation and dilution of the stock solution. stock solutions (10 mm) consisting of inorganic anions and cations were prepared from their sodium and chloride salts (nacl, nano3, nano2, na2so4, kcl, cacl2, mgcl2) with the exception of ammonium, the stock solution of which was prepared from ammonium fluoride (all from pliva-lachema, brno, czech republic). the stock solutions of anions from organic acids were prepared from lithium acetate dihydrate, lithium lactate, propionic acid and butyric acid (all from sigmaaldrich, steinheim, germany). the background electrolyte (bge) for ce measurements was prepared daily by diluting 100 mm stock solutions of 2-(n-morpholino)ethanesulfonic acid (mes), l-histidine (his) and 100 mm 18-crown6 (all sigma–aldrich) to the required concentration. hexadecyltrimethylammonium bromide (ctab, sigma–aldrich) was prepared as 10 mm stock solution in 5 % acetonitrile and was added to the bge to yield the final concentration of 30 µm. 2.3 capillary conditioning prior to its first use, the separation capillary was preconditioned by flushing it with 0.1 m naoh for 30 mins, di water for 30 mins and bge solution for 20 mins. between two successive injections, the capillary was flushed with bge solution for 1 min. at the end of a working day, the capillaries were washed with di water for 15 mins and stored in di water overnight. 3. results and analysis 3.1 ebc sampling procedure the collection of ebc consists of several steps: deep exhalation until the lungs were as empty as possible, followed by rapid inhalation (1-2 s) and finally gradual complete exhalation into the sampling device (8-10 s). this procedure was suggested by almstrand et al. [8] and yielded the highest concentration of respiratory droplets and, therefore, the highest concentrations of non-volatile substances present in ebc. the volunteer was asked to exhale three times into the sampling device according to the proposed procedure. after the ebc sampling had been completed, the condensate from the syringe walls was wiped with the plunger of the syringe as far as the tip of the syringe and transferred to the sample vial for ce analysis. often, only one exhalation (30 µl of the sample) was sufficient to obtain a sizable amount of ebc for ce analysis. during the wiping procedure, the condensate collected from the walls is naturally mixed and hungarian journal of industry and chemistry study the content of exhaled breath condensate 31 0.5 1 1.5 2 time (min) c 4 d s ig n a l (m v ) ebc clla cta te aceta te 1 mv pro pio nate no2buty ra te so42no3scnebc + saliva figure 2: anionic separation of an ebc sample and an ebc sample spiked with human saliva. bge: 20 mm mes/his, 2 mm 18-crown-6, 30 µm ctab. hv: positive +15 kv, c4d detection. injection: hydrodynamic for 30 s at a height of 10 cm. a representative ebc sample is thus obtained. to maintain the simplicity, low costs and wide availability of the components necessary for the ebc sampler, a saliva trap was not included. therefore, one can occasionally expect interference from saliva droplets. this can happen especially when sampling of long durations is applied or ebc is collected from patients with serious lung diseases and/or children. nevertheless, saliva contamination is very rare and happened in ca. 1 in every 100 samples. contaminated samples were easily identified and excluded from further investigations. fig. 2 shows the ce separation of anions from two ebc samples; an ebc sample obtained from 3 deep exhalations (≈ 100µl of ebc) and the same ebc sample spiked with 1 µl of human saliva (to simulate saliva contamination). the ebc sample spiked with saliva displayed a huge increase in the concentration of all anions which significantly exceeded the upper limits of concentrations found in healthy individuals or patients suffering from various lung diseases [9,10]. another even more suitable indicator is the thiocyanate, normally present in human saliva [11] but not in ebc. cationic analysis of the same two samples (fig. 3) exhibited the highest increase in sodium and potassium, again way above the normal levels as far as the concentrations of healthy people and sufferers are concerned. other cations also exhibited increases. 0.5 1 1.5 time (min) c 4 d s ig n a l (m v ) ebc nh4+ k+ na+ ca2+ 1 mv mg2+ebc + saliva figure 3: cationic separation of an ebc sample and an ebc sample spiked with human saliva. bge: 20 mm mes/his, 2 mm 18-crown-6, 30 µm ctab. hv: negative -15 kv, c4d detection. injection: hydrodynamic for 30 s at a height of 10 cm. 3.2 day-to-day repeatability of the ionic content of ebc in the next part of the study, the day-to-day repeatability of the ionic content of ebc (over the following 5 days) obtained from three healthy persons (#1, #2 and #3) was studied. samples were collected in the morning, before breakfast, and all volunteers were asked not to drink or eat before the sampling, the only exception was the consumption of tap water. ebc samples were obtained from single exhalations by using the ebc sampler. all samples were analyzed by ce-c4d and peak areas of all ions in the electropherograms were integrated. the resultant peak areas (pa) for selected ions (ammonium, sodium, acetate and nitrite) were plotted against each of the five 0 5 10 15 20 25 1 2 3 4 5 a re a ( m v /s ) day ammonium #1 #2 #3 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 1 2 3 4 5 a re a ( m v / s) day sodium #1 #2 #3 0 1 2 3 4 5 6 1 2 3 4 5 a re a ( m v / s) day acetate #1 #2 #3 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 1 2 3 4 5 a re a ( m v /s ) day nitrite #1 #2 #3 figure 4: pa of selected ions found in ebc from a day-today study consisting of 5 days. separation and detection conditions as in figs. 2 and 3. 46(1) pp. 29-33 (2018) 32 greguš, ďurč, lačná, foret and kubáň 5.0 5.5 6.0 6.5 7.0 7.5 8.0 1 2 3 4 5 p h day ph before and after degasification #1, before #1, after #2, before #2, after #3, before #3, after figure 5: the trend over 5 days in the ph of ebc samples obtained from three healthy volunteers. the ph of ebc before (solid line) and after degasification with n2 (dashed line). days (fig. 4). from this figure, a sufficient repeatability of all ions present in ebc samples over the five days can be seen. although the spread might seem large, this is caused mainly by the physiological variability of the ion concentration in ebc. 3.3 day-to-day repeatability of the ph of ebc except for cations and anions, which were measured by ce-c4d, other parameters, e.g. exhaled breath volume (measured by spirometry) or the ph of ebc, can be necessary for standardization and diagnostic purposes [12, 13]. the ph of ebc samples was measured and the current experimental setup allowed for ph measurements to be made from as little as 10 µl of ebc. the ph of ebc obtained from a single exhalation can thus be easily measured. the ph of ebc samples obtained in the previous section (day-to-day repeatability) was measured before and after degasification with n2 (1.8 atm for 5 mins.), and the resultant data can be seen in fig. 5. it is known that the degasification of liquids by an inert gas, such as n2, can remove dissolved gases, e.g. co2 [14]. our experiments support this premise since an increase in the ph of all samples was observed after degasification with n2. moreover, degasification of the ebc samples significantly increased the repeatability of ph values over the 5 days of the day-to-day study. 3.4 other parameters that influence the ionic content of ebc and the ph the influence of various foods, drinks and meals on the ionic content and ph of ebc was also examined. two ebc control samples (taken in the morning, before breakfast during which only water could be drunk) were obtained from one healthy person. these samples were compared with the two ebc samples from the same day and after one of the following foods/drinks/meals – breakfast, lunch, chocolate, coffee, orange juice, milk, chewing gum or after cleaning teeth with toothpaste or 0 0.5 1 1.5 2 2.5 3 time (min) c 4 d s ig n a l (m v ) a clla cta te aceta te 0.5 mv pro pio nate no2buty ra te so42no3b c figure 6: separation of anions in different ebc samples. ebc samples collected in the morning (a), after the ingestion of orange juice (b), and after chewing a piece of chewing gum (c). bge: 20 mm mes/his, 2 mm 18crown-6, 30 µm ctab. hv: positive +12.4 kv, c4d detection. injection: hydrodynamic for 20 s at a height of 12.5 cm. dentifrice. the time lag between each of the influences and sample collections was 10 minutes. examples of the separation of anions and cations in ebc samples collected in the morning, after the ingestion of orange juice and chewing a piece of chewing gum are shown in figs. 6 and 7. overall, significant differences were found between samples and, therefore, a time lag of at least one 0.5 1 1.5 time (min) c 4 d s ig n a l (m v ) nh4+ k+ na+ ca2+ 2 mv mg2+ a b c figure 7: separation of cations in different ebc samples. ebc samples collected in the morning (a), after the ingestion of orange juice (b), and after chewing a piece of chewing gum (c). bge: 20 mm mes/his, 2 mm 18crown-6, 30 µm ctab. hv: negative -14.5 kv, c4d detection. injection: hydrodynamic for 20 s at a height of 12.5 cm. hungarian journal of industry and chemistry study the content of exhaled breath condensate 33 hour following the flushing of the mouth with di water was suggested prior to the ebc collection to obtain a relevant ebc sample. 4. conclusion in this work, capillary electrophoresis with contactless conductometric detection was used to study the day-today repeatability of the ionic content of ebc. the ph of ebc before and after degasification with a stream of n2 was studied by a ph microelectrode over five consecutive days. the influence of various foods and drinks on the ionic content of ebc was investigated and exhibited significant differences between ebc samples. it has been shown that ebc is influenced by various parameters. therefore, healthy individuals or patients should provide their ebc samples in the morning before breakfast/brushing teeth or at least one hour after consuming any food or drink last followed by flushing of the mouth with di water. symbols ce capillary electrophoresis c4d contactless conductivity detection ctab cetyltrimethylammonium bromide di deionized ebc exhaled breath condensate his l-histidine id inner diameter mes 2-(n-morpholino)ethanesulfonic acid od outer diameter acknowledgement the authors acknowledge the financial support from the ministry of health of the czech republic (grant no. 17-31945a). part of this research was conducted under the ceitec 2020 project lq1601 with financial support from the ministry of education, youth and sports of the czech republic under the national sustainability programme ii and with institutional support rvo: 68081715. references [1] shaheen, n. j.; hansen, r. a.; morgan, d. r.; gangarosa, l. m.; ringel, y.; thiny, m. t.; russo, m. w.; sandler, r. s.: the burden of gastrointestinal and liver diseases, am. j. gastroenterol., 2006 101(9), 2128–2138 doi: 10.1111/j.1572-0241.2006.00723.x [2] vakil, n.; van zanten, s. v.; kahrilas, p.; dent, j.; jones, r.: the montreal definition and classification of gastroesophageal reflux disease: a global evidence-based consensus, am. j. gastroenterol., 2006 101(8), 1900–1920 doi: 10.1111/j.15720241.2006.00630.x [3] johnston, n.; ondrey, f.; rosen, r.; hurley, b. p.; gould, j.; allen, j.; delgaudio, j.; altman, k. w.: airway reflux, ann. ny. acad. sci., 2016 1381, 5–13 doi: 10.1111/nyas.13080 [4] emilsson, o. i.; gislason, p.; olin, a. c.; janson, c.; olafsson, i.: biomarkers for 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analytical chemistry, faculty of natural sciences, comenius university, ilkovičova 6, bratislava, sk-842 15, slovakia the beneficial effects of green foods on human health are well known. these benefits are mainly due to polyphenol content. the aim of this work was the development and utilization of an advanced mass spectrometry (ms) technique combined with high-performance liquid chromatography (hplc) for the analysis and identification of polyphenolic compounds in green foods. hplc-esi-ms/ms analyses of selected extracts prepared from various types of green food (urtica dioica l. and allium ursinum l.) and their polyphenolic profiles were performed by an lcms-it-tof analyzer equipped with electrospray ionization. hplc separation was conducted by a kinetex xb-c18 column (100×2.1 mm; 2.6 µm) using gradient elution (water + 0.1% formic acid: acetonitrile + 0.1% formic acid) with a flow rate of 0.2 ml/min. the ms1-ms3 analyses were performed within a 50-1000 m/z range in both positive and negative ionization modes. the total analysis time was 20 minutes and injected volumes were 2 µl and 5 µl, respectively. keywords: polyphenolic compounds, green food, hplc-ms analysis, identification 1. introduction from a chemical point of view, antioxidants are phenolic compounds derived from simple phenols up to complex polyphenols. an antioxidant is a substance whose molecules limit the activity of oxygenated compounds, namely reduce their likelihood or convert them into a less reactive state. antioxidants limit the oxidation process in the body or in the mixtures in which they are found. in food, they extend their expiration date. in the body, they reduce the likelihood of certain types of diseases [1]. the main reason for monitoring the presence and activity of antioxidants is their beneficial effect on the human organism. their health benefits include antioxidant, antibacterial, anticarcinogenic, anti-allergenic and anti-inflammatory properties [2–4]. antioxidants in green foods belong to a group of low-molecular-weight natural antioxidants whose scientific name is phenolic compounds [5]. green foods are characterized into four basic groups: herbs and spices, fruits, vegetables and nuts. despite the fact that numerous polyphenolic compounds have been detected in green food, there is still a need for new reliable analytical methods. the most common procedures for the identification and determination of polyphenolic compounds in green food are based on sample pretreatment by liquid-liquid extraction followed by separation and identification using high-performance liquid chromatography coupled with tandem mass spec∗correspondence: skvara1@uniba.sk trometry (hplc–ms/ms) [6]. several authors are concerned with the identification and characterization of phenolic compounds in green foods using a combination of high-performance liquid chromatography and mass spectrometry with electrospray ionization (hplc-esi-ms) and atmospheric pressure chemical ionization (hplcapci-ms). for example, hplc-esi-ms was used to separate and identify phenolic acids in custard apples [7], tannins in chestnut samples [8], phenolic compounds in groundnuts [9], tomatoes [10], spinach [11], and gingerol-related species (gingerols and shogaols) in ginger [12]. the hplc-apci-ms/ms method was used to identify carotenoids in samples of mango and citruses [13]. the hplc-esi-ms method was also used to analyze samples of nettles [14] and bear’s garlic [15]. the aim of this work was to analyze and identify polyphenolic compounds in selected samples of green food using a combination of high-performance liquid chromatography and high-resolution mass spectrometry techniques. 2. experimental 2.1 instrumentation all hplc-esi-ms/ms analyses were performed by using a shimadzu lcms-it-toftm mass spectrometer (shimadzu, kyoto, japan). this mass spectrometer combines an electrospray ionization (esi), a 3d quadrupole ion trap (it) and an orthogonal acceleration time-of-flight mailto:skvara1@uniba.sk 36 škvára, kezmanová , mišlanová, and vojs staňová analyzer (tof) to provide both a high degree of sensitivity and resolution of ions. the hplc part consisted of an autosampler (sil-20a), high pressure pumps (lc20ad), a thermostat (cto-20a), a diode array detector (spd-m20a), a degasser together with a mixing system (dgu-20a5) and system controller (cbm-20a). lcms solutions v. 3.5.1 (shimadzu) software was used for data acquisition and evaluation. chromatographic separation of the polyphenolic compounds was performed on a kinetex xb-c18 column (100 × 2.1 mm; 2.6 µm) (phenomenex, torrance, ca, usa). acidified water and acetonitrile (both with an addition of 0.1 % or 10 mmol/l of formic acid) were used as mobile phases. gradient elution of the mobile phase was used. the flow rate of the mobile phase was 0.2 ml/min. the gradient program was 0 min.: 5% b; 3 min.: 10% b; 8 min.: 40% b; 10 min.: 60% b; 11 min.: 90% b; 12 min.: 90% b; 12.1 min.: 5% b; and 20 min.: 5% b. the chromatographic column was thermostated at 40 ◦c. all ms analyses were performed in both positive and negative ionization modes. the voltages at the esi capillaries were +4.5 kv and −3.5 kv. the range of recorded values was set at 50 − 1000 m/z. the temperatures of the curved desolvation line (cdl) capillary and heat block were set at 200 ◦c. the injected volume of the sample was 2 µl and 5 µl, respectively. 2.2 chemicals the following chemicals were used to prepare the solutions and mobile phases: water for lc-ms, acetonitrile for lc-ms (both from lichrosolv, merck, darmstadt, germany), and formic acid for lc-ms (sigma-aldrich, steinheim, germany). standard selected polyphenolic compounds were obtained from sigma-aldrich. 2.3 sampling and sample preparation the samples of nettle (urtica dioica l.) were collected in march 2017 in the geographical area of hruštín, after which they were dried and stored in a dry and dark place. samples of bear’s garlic (allium ursinum l.) were collected in march 2017 in the geographical area of bratislava, after which they were dried and stored in a dry and dark place. prior to the analysis, the extracts of each sample were prepared as follows: approximately 0.5 g of each was weighed and 50 ml of water was poured onto them at 97 ◦c. the extraction times were 5, 10 and 15 mins. the extracts were then filtered through filter paper and cooled to room temperature. after cooling, the samples were filtered through a syringe microfilter (pvdf with pore size 0.22 µm) and then analyzed using hplcesi-ms/ms or stored in a refrigerator at 4 ◦c for a maximum of 24 hours. 3. results and discussion the first part of the experimental work focused on the optimization of conditions for the chromatographic separation of phenolic compounds in selected extracts prepared figure 1: hplc-esi-ms analysis of the nettle extract (5 min extraction) with the addition of 10 mmol/l formic acid to the mobile phases. tic (total ion current) in the positive mode – top: tic in the negative mode – bottom and middle: eic (extracted ion chromatogram) records of identified phenolic compounds included. figure 2: hplc-esi-ms analysis of the nettle extract (5 min extraction) with the addition of 0.1% formic acid to the mobile phases. tic in the positive mode – top: tic in the negative mode – bottom and middle: eic records of identified phenolic compounds included. from different plant species. after hplc separation, optimization with regard to the composition of the mobile phase in terms of the ionization of the analytes was performed. to confirm the effect with regard to the composition of the mobile phase on the resulting ms signal, a simple experiment was proposed. hplc-esi-ms/ms analysis of the bear’s garlic and nettle extracts used mobile phases, which varied according to only the concentration of the added formic acid. gradient elution utilized the following mobile phases with the addition of different concentrations of formic acid: 0.1% formic acid in water (a) / 0.1% formic acid in acetonitrile (b), and 10 mmol/l formic acid in water (a) / 10 mmol/l formic acid in acetonitrile (b). for illustrative purposes, figs. 1 and 2 show the results from the hplc-esi-ms analysis of the 5-minutelong extraction of nettles. after comparing these results with the results of measuring a 5-minutelong extraction of nettles with the addition of 0.1% (26.5 mmol/l) formic acid to the mobile phases, it is clear that the use of a higher concentration of formic acid is more appropriate for the analysis of nettle extracts (promoting the protonation of molecules). a similar procedure was used to select the appropriate composition of the mobile phases for hplc-esims analysis of the garlic extract. the results of the 15minute-long extraction of bear’s garlic with the addition of 0.1% formic acid to the mobile phases can be seen in fig. 3. the results of the 15-minute-long extraction of garlic with the addition of 10 mmol/l formic acid are recorded in fig. 4 and suggest this is preferable for the hungarian journal of industry and chemistry analysis and identification of polyphenolic compounds in green foods 37 figure 3: hplc-esi-ms analysis of the garlic extract (15 min extraction) with the addition of 0.1% formic acid to the mobile phases. tic in the positive mode – top: tic in the negative mode – bottom and middle: eic records of identified phenolic compounds included. figure 4: hplc-esi-ms analysis of the bear’s garlic extract (15 min extraction) with the addition of 10 mmol/l formic acid to the mobile phases. tic in the positive mode – top: tic in the negative mode – bottom and middle: eic records of identified phenolic compounds included. analysis of the garlic samples. the final conditions for chromatographic separation and mass spectrometric detection are described in detail in the experimental section. on the basis of the data gathered from hplc-esims analyses, it is possible to obtain a better overview of the composition of individual extracts prepared from different plant species as well as information on the nature and structure of the phenolic compounds contained therein. the characterization and identification of individual polyphenolic compounds in plant extracts was performed by the analysis of the ms1-ms2 spectra that were recorded. the ms1 and ms2 spectra of the coumaric acid in the sample of the nettle extract can be seen in fig. 5. in the ms1 spectrum an ion with m/z 163.0471 related to the coumarone [m-h]− ion is observed. in the ms2 spectrum obtained by the fragmentation of coumaric acid, the ion with m/z 119.0612, which was formed by cleaving the carboxyl group from the coumaric acid molecule, is visible. another analyte found in the nettle sample was figure 5: ms1 and ms2 spectra corresponding to coumaric acid obtained by hplc-esi-ms/ms analysis of the nettle extract (15 min extraction) in the negative ionization mode. figure 6: ms1 and ms2 spectra of the corresponding chlorogenic acid obtained by hplc-esi-ms/ms analysis of the nettle extract (15 min extraction) in the negative ionization mode. chlorogenic acid, the presence of which was confirmed by the ms1 and ms2 spectra shown in fig. 6. the ms1 spectrum is dominated by the ion with m/z 353.0780 corresponding to the [m-h]− ion of chlorogenic acid. in the ms2 spectrum obtained by the fragmentation of the ion with m/z 353.0780, the ion with m/z 191.0557, which was obtained by cleaving -c9o3h7 from the chlorogenic acid molecule, is identified. in this spectrum another ion with m/z 179.0378, which was formed by cleaving -c7o5h6 from the chlorogenic acid molecule, is observed. in the ms2 spectrum an ion with m/z 173.0451 is also seen, which corresponds to this cleavage. an ion with m/z 135.0459 in ms2 seen in the chlorogenic acid spectrum was probably generated by cleaving the carboxyl group from the ion m/z 179.0378. as in the case of the hplc-esi-hrms analysis of nettle extracts, tandem mass spectrometry was used to identify polyphenolic substances in garlic extracts. as an illustration, the ms1 and ms2 chlorogenic acid spectra are presented in fig. 7. in the ms1 spectrum the molecular ion [m-h]− with m/z 353.0844, which is associated with chlorogenic acid, in a sample of the garlic extract is seen. in the ms2 spectrum the ions with m/z 191.0496 and 179.0298, which were formed from the precursor ion (m/z 353.0844) and belong to the illustrated chlorogenic acid fragments, are observed. the identification of each polyphenolic compound was possible by recording the retention time as well as mass spectra of samples and authentic standards. figure 7: ms and ms/ms spectra corresponding to chloroformic acid obtained by hplc-esi-ms/ms analysis of the bear’s garlic extract (10 min extraction) in the negative ionization mode. 46(1) pp. 35-38 (2018) 38 škvára, kezmanová , mišlanová, and vojs staňová 4. conclusion in our experimental work, the use of advanced mass spectrometry techniques in combination with highperformance liquid chromatography-mass spectrometry (hplc-msn) for the analysis and identification of polyphenolic compounds in extracts prepared from different types of green foods was our focus. from the hplc-msn data obtained by analyzing extracts from different types of green food, it was possible to obtain information about the composition of the analyzed extracts as well as information about the nature and structure of the polyphenolic compounds represented therein. using the developed hplc-esi-it-tof-ms method, the presence of 13 antioxidants in the sample of nettle extracts and 16 antioxidants in the sample of garlic extracts was confirmed. based on the results obtained, it can be stated that the developed hplc-msn method is a suitable tool for the characterization and identification of polyphenolic compounds in extracts prepared from green foods. acknowledgement this research was supported by the grants vvce-007007 and apvv-0583-11 of the 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sciences, veveri 97, 602 00 brno, czech republic the monolithic capillary columns (0.1 mm × 150 mm) prepared by the acidic hydrolysis of tetramethoxysilane (tmos) in the presence of polyethylene glycol (peg) and urea were modified by zwitterionic stationary phases and evaluated under hilic separation conditions by employing a mixture containing nucleosides and nucleotides. the polymeric layer of zwitterions did not affect the high separation efficiency of the original silica monolith. the prepared zwitterionic columns exhibited high separation efficiencies in a range 61,000–289,000 theoretical plates/m for a 2methacryloyloxyethyl phosphorylcholine-based stationary phase and in a range 59,000–135,000 theoretical plates/m for a [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide-based stationary phase under optimal separation conditions. the grafted layer of zwitterions on the silica monolithic surface also significantly improved the separation selectivity to compounds of interest. keywords: hilic, silica monolith, nucleoside, nucleotide, capillary chromatography 1. introduction silica-based monolithic columns were developed by nakanishi and co-workers in the early 1990s [1, 2]. the preparation procedure of the columns has been improved over the years [3]. the unique structure of silica-based monoliths facilitates a high degree of permeability of separation beds and good mass transfer kinetics leading to a high separation efficiency. thus, liquid chromatography has been identified as an alternative to particle packed columns. while silica-based monolithic columns dedicated to reversed-phase separations are well established, the new stationary phases of hydrophilic interaction chromatography (hilic) separation are still a focus of research. concerning the published papers, the preparation of silicabased monoliths via the so-called “one-pot” process prevails. on the other hand, the chemical modification of preformed silica monoliths offers a well-defined silica skeleton of almost the same permeability and separation efficiency for all designed stationary phases. this contribution presents a characterization of silica-based monolithic capillary columns prepared by employing the second approach. the zwitterionic monomers [2-(methacryloyloxy)ethyl]dimethyl-(3sulfopropyl)ammonium hydroxide (medsa) and 2methacryloyloxyethyl phosphorylcholine (mepc) were used to prepare the desired stationary phases. the prepared columns were evaluated under hilic separation ∗correspondence: moravcova@iach.cz conditions by employing a mixture containing nucleosides and nucleotides. 2. experimental 2.1 material and instrumentation medsa and mepc monolithic capillary columns were prepared following a protocol outlined in our previous study [4]. in order to obtain a stable polymeric layer of mepc on the silica-based monolith, the polymerization time was prolonged to 6 hours. toluene, adenosine, uridine, cytidine and nucleotides – adenosine monophosphate (amp), adenosine diphosphate (adp), adenosine triphosphate (atp), cytidine monophosphate (cmp), cytidine diphosphate (cdp), uridine monophosphate (ump), and uridine diphosphate (udp) – were purchased from sigma–aldrich (prague, czech republic). acetic acid, ammonium hydroxide and acetonitrile (acn) (chromasolv, hplc gradient grade) were obtained from riedel-de haën (seelze, germany). high-performance liquid chromatography (hplc) equipment consisted of two identical syringe pumps (100dm model with a d-series controller, teledyne isco, lincoln, nebraska, usa) directly connected to a static nano mixer (60 nl volume) (upchurch scientific, oak harbor, washington, usa). the injection was performed by an electrically actuated e90-220 injection valve with a 60 nl internal loop (valco instruments, houston, texas, usa) and a t-splitter with a restrictor (fused mailto:moravcova@iach.cz 40 moravcová and planeta figure 1: hilic separation of four purine bases in a bare silica monolithic capillary column. mobile phase: 95% (v/v) acn, 5% (v/v) 100 mm ammonium acetate ph=4.5; flow rate 500 nl/min; uv detection at 210 nm. peak identification: 1 – toluene (unretained compound), 2 – xanthine, 3 – caffeine, 4 – theobromine, and 5 – hypoxanthine. silica capillary 0.025 mm × 150 mm in length). the inlet section of the monolithic column was inserted through the body of the splitter into the injection valve to minimize extra-column dispersion. the outlet of the monolithic column was connected to a spectra 100 uv/vis detector (thermo separation products, waltham, massachusetts, usa) via a 0.035 mm × 120 mm-long fused silica capillary (with an optical bubble cell window inner diameter (id) 0.110 mm) using a polytetrafluoroethylene (ptfe) sleeve. uv detection was performed at 210 nm. the detector signal was processed by the chromatography station software clarity (dataapex, prague, czech republic). 3. results and discussion 3.1 chromatographic properties of the bare silica monolith the prepared bare silica monolithic capillary columns were evaluated under hilic conditions by employing a mixture containing toluene as an unretained compound and four purine bases, namely xanthine, caffeine, theobromine and hypoxanthine. the obtained chromatogram table 1: the retention factor (k), the height equivalent to the theoretical plate (h), the number of theoretical plates per meter (n ), and peak asymmetry (as) obtained on the silica monolithic column. see fig. 1 for separation conditions. compound k h/µm n as toluene – 7.4 135,185 0.67 xanthine 0.03 4.5 222,547 0.88 caffeine 0.13 5.8 172,795 1.00 theobromine 0.19 5.2 192,528 1.13 hypoxanthine 0.87 4.8 209,601 1.33 table 2: the retention factor (k), number of theoretical plates per meter (n ), and peak asymmetry (as) obtained on the mepc column. see fig. 2 for the separation conditions. compound k n as toluene – 138,955 1.0 adenosine 0.16 201,048 1.0 uridine 0.25 289,537 1.1 cytidine 0.41 244,314 0.9 amp 1.24 206,697 1.3 ump 1.66 183,465 1.5 cmp 2.50 157,760 1.4 adp 3.98 122,169 2.0 udp 5.34 112,389 2.4 cdp 7.58 81,476 2.8 atp 9.73 61,462 2.1 where all purine bases are baseline separated and have narrow symmetrical peaks is presented in fig. 1. the prepared column exhibits a high degree of separation efficiency reaching values of between 135,000 and 220,000 theoretical plates/m which corresponds to the minimum plate height within the range of 4.5–7.4 µm, as outlined in table 1. 3.2 hilic separation of nucleosides and nucleotides the commercially available methacrylate-based monomers medsa and mepc were selected for the preparation of zwitterionic stationary phases. the bare silica monolith prepared in a 0.1 mm id fused silica capillary was modified by 3-(trimethoxysilyl)propyl methacrylate and a polymer layer, with the appropriate zwitterion grafted onto it. the suitability of these columns for the isocratic hilic separation of nucleosides and nucleotides was studied. chromatograms for selected compounds obtained on medsa (fig. 2a) and mepc (fig. 2b) capillary columns are presented in fig. 2. an enhanced degree of separation was obtained on the mepc column (fig. 2b) where all 11 compounds present in a sample mixture were well separated within 25 mins. the value of peak asymmetry (as) reflects the change in the molecular shape of the analyte and increases slightly as the number of phosphate groups increases in the relevant nucleotide, as presented in table 2. on the other hand, the separation efficiency decreases along with the number of phosphate groups in the molecule of nucleotide exhibit lower values of n compared to nucleosides. a similar trend was also observed on the medsa-modified monolithic capillary column. the medsa-modified monolithic column exhibits a poorer separation efficiency than the mepc column for all nucleosides and nucleotides, even the number of theoretical plates per meter for toluene is comparable, as illustrated in table 3. the medsa column also exhibits hungarian journal of industry and chemistry silica monolithic capillary columns for hilic separations 41 figure 2: separation of nucleosides and nucleotides on prepared medsa (a), mepc (b) and bare silica (c) monolithic columns. mobile phase: 70% (v/v) acn/30% (v/v) 50 mm ammonium acetate ph = 4.5; flow rate 500 nl/min; uv detection at 210 nm. a lower retention factor for selected compounds, especially for diand triphosphates of the relevant nucleosides. this can be explained by the fact that monomers used for column modification differ in terms of their terminal groups, which affects the selectivity of the prepared stationary phases. the medsa monolithic capillary column contains negatively charged terminal sulfo groups which decrease the retention factor of negatively charged nucleotides. on the other hand, the mepc monomer provides the stationary phase with a slightly positive charge originating from the phosphorylcholine functional group which improves the retention factor of negatively charged table 3: the retention factor (k), number of theoretical plates per meter (n ), and peak asymmetry (as) obtained on the medsa column. see fig. 2 for the separation conditions. compound k n as toluene – 131,000 1.2 adenosine 0.12 135,641 1.1 uridine 0.19 129,895 1.2 cytidine 0.28 130,754 1.2 amp 0.46 101,991 1.5 ump 0.66 89,032 1.0 cmp 0.91 90,838 1.1 adp 0.97 71,440 1.7 udp 1.40 48,371 5.1 cdp 1.78 49,250 3.1 atp 1.78 59,378 3.5 nucleotides under the hilic separation conditions, e.g. the retention factor k for atp is approximately 5 times higher on the mepc column compared to the medsa column. the separation of nucleosides and nucleotides on a bare silica monolithic capillary column is shown in fig. 2c. the bare silica monolith does not exhibit a sufficient degree of selectivity to compounds of the target. all compounds are eluted from the column within 1 min and accompanied with the coelution of most compounds. 4. conclusion a silica-based monolith in a capillary format coated with zwitterionic polymer layers is a good alternative for the analysis of complex mixtures containing highly polar compounds such as nucleosides and nucleotides. in particular, the mepc stationary phase containing positively charged terminal groups enables the highly selective hilic separation of nucleosides and nucleotides to be achieved. the utilization of such a stationary phase with regard to the analysis of real samples, where usually other highly polar-interfering species originating from complex matrices are present and complicate the analysis, should be evaluated in the future. acknowledgement this research was supported by the czech science foundation (project no. 16-03749s), the ministry of the interior of the czech republic (project no. vi20172020069), and by the czech academy of sciences (institutional support rvo:68081715). references [1] nakanishi, k., soga, n.: phase separation in silica sol-gel system containing polyacrylic acid i. gel formation behavior and effect of solvent composition, j. non-cryst. solids, 1992 139 1–13 doi: 10.1016/s0022-3093(05)80800-2 46(1) pp. 39-42 (2018) https://doi.org/10.1016/s0022-3093(05)80800-2 https://doi.org/10.1016/s0022-3093(05)80800-2 42 moravcová and planeta [2] minakuchi, h., nakanishi, k., soga, n., ishizuka, n., tanaka, n.: octadecylsilylated porous silica rods as separation media for reversed-phase liquid chromatography, anal. chem., 1996 68(19) 3498–3501 doi: 10.1021/ac960281m [3] ikegami, t., tanaka, n.: recent progress in monolithic silica columns for high-speed and highselectivity separations, annu. rev. anal. chem., 2016 9, 317–342 doi: 10.1146/annurev-anchem-071114040102 [4] moravcová, d., planeta, j., kahle, v., roth, m.: zwitterionic silica-based monolithic capillary columns for isocratic and gradient hydrophilic interaction liquid chromatography, j. chromatogr. a, 2012 1270, 178–185 doi: 10.1016/j.chroma.2012.11.005 hungarian journal of industry and chemistry https://doi.org/10.1021/ac960281m https://doi.org/10.1146/annurev-anchem-071114-040102 https://doi.org/10.1146/annurev-anchem-071114-040102 https://doi.org/10.1016/j.chroma.2012.11.005 hungarian journal of industry and chemistry vol. 46(1) pp. 43-46 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0010 determination of homocysteine in urine and saliva by microchip electrophoresis peter troška ∗1, anna mandžáková1, jasna hradski1, juraj ševčík2, and marián masár1 1department of analytical chemistry, faculty of natural sciences, comenius university in bratislava, mlynská dolina ch-2, ilkovičova 6, sk-84215 bratislava, slovak republic 2department of analytical chemistry, faculty of science, palacký university olomouc, 17. listopadu 12, cz-77146 olomouc, czech republic an online combination of isotachophoresis (itp) and capillary zone electrophoresis (cze) was employed on a microchip with a column-coupling technology for the determination of homocysteine in various body fluids. itp with its high concentration ability was used as a sample pretreatment and injection technique for cze, which facilitated the rapid and sensitive determination of homocysteine. the resolution of the analyte from other constituents present in real complex samples was enhanced by discrete spacers, which were added to the injected sample. a solid-phase microextraction (spme) pretreatment technique based on silverand barium-form resins was used prior to the itp-cze analysis to remove high concentrations of chloride and sulfate naturally present in the analyzed samples. the combination of the micropretreatment and microelectrophoresis techniques facilitated the determination of trace concentrations of homocysteine in samples of urine and saliva. keywords: homocysteine, body fluids, microchip electrophoresis, solid-phase microextraction 1. introduction homocysteine (hcy) is a non-proteinogenic sulfurcontaining amino acid whose metabolism is at the intersection of two metabolic pathways: remethylation and transsulfuration. in remethylation, hcy acquires a methyl group from n5-methyltetrahydrofolate or from betaine to form methionine. the reaction with n5methyltetrahydrofolate occurs in all tissues and is vitamin b12-dependent, whereas the reaction with betaine is confined mainly to the liver and is vitamin b12-independent. a considerable proportion of methionine is then activated by atp to form s-adenosylmethionine [1]. increased concentration levels of hcy in body fluids are considered to be an important risk factor or marker of various diseases, particularly cardiovascular ones [2]. in review papers [3–5], individual methods of determining hcy in biological samples are summarized. analytical methods using high-performance liquid chromatography (hplc) to separate hcy are some of the most commonly used. hplc methods for the quantification of hcy utilize derivatization procedures as well as procedures with non-derivatized hcy by electrochemical detection (ecd). the growing interest in clinical analyses has generated increased attention due to the rapid determination of hcy using automated methods. for this reason, the immunoas∗correspondence: peter.troska@uniba.sk say of hcy in plasma has become a preferred analytical approach [5]. recently several procedures have been published for the determination of hcy by capillary electrophoresis (ce). ce compared to hplc is more advantageous in terms of the need for a very small sample volume, good resolution, short analysis time, simplicity of automation and elimination of various (toxic) solvents. this is evidenced by many of the works that have dealt with the determination of hcy in body fluids, e.g. in plasma [6–18], serum [13] or urine [16, 19]. most of them dealt with the use of laser-induced fluorescence (lif) as a detection technique, however, uv detection was also used. a miniaturized form of ce, microchip electrophoresis (mce), was used for the separation and detection of hcy and glutathione. the analysis time on the glass microchip using amperometric detection was less than 80 s [6]. a polydimethylsiloxane (pdms) microchip produced by a simple photolithographic technique facilitated the rapid separation of hcy and cysteine [20]. mce analyses are more favorable than ce because they are considerably shorter, achieve higher degrees of separation efficiency and, in particular, reduce overall costs associated with chemical consumption and waste production. this paper deals with the development of a new method for the determination of hcy in various body fluids on a microchip with coupled-channels (cc). the mailto:peter.troska@uniba.sk 44 troška, mandžáková, hradski, ševčík and masár figure 1: a scheme of the cc microchip with conductivity detection. c-le = the first (itp) separation channel (volume of 4.5 µl) filled with a leading electrolyte; c-be = the second (cze) separation channel (volume of 4.3 µl) filled with a background electrolyte; c-te = the third channel (volume of 0.8 µl) filled with a terminating electrolyte; c-s = sample injection channel (volume of 9.9 µl); d1, d2 = pt conductivity sensors; bf = bifurcation section; be, le, te, s = inlets for the background, leading, terminating and sample solutions to the microchip channels, respectively; w = an outlet channel for the waste container. cc technology employed on the microchip with contact conductivity detection enables online capillary zone electrophoresis (cze) to be coupled with the isotachophoresis (itp) sample pretreatment. samples of urine and saliva were simplified by solid-phase microextraction (spme) prior to the itp-cze separations on the microchip. spme based on silverand barium-form resins provided a high degree of compatibility with mce and a high level of selectivity, whilst simultaneously removing a huge amount of chloride and sulfate in the analyzed samples of body fluids. 2. experimental itp-cze separations were carried out on a poly(methyl methacrylate) microchip (fig.1) with the cc technique and integrated conductivity detection sensors (ionchiptm 3.0, merck, darmstadt, germany). chemicals used for the preparation of electrolyte solutions and model samples were obtained from sigma-aldrich (bratislava, slovakia), fluka chemikabiochemika (buchs, switzerland), serva electrophoresis gmbh (heidelberg, germany) and erba lachema s.r.o. (brno, czech republic). samples of urine and saliva were collected from volunteers. before the analysis, the samples were homogenized and analyzed after being diluted appropriately with deionized water, and pretreated by spme to remove chloride and sulfate. solid-phase extraction (spe) microcolumns of 0.5 ml in volume containing silverand barium-form resins (alltech, grace davison discovery sciences, deerfield, illinois, usa) were used for this purpose. 3. results and discussion itp-cze separations were performed in a hydrodynamically closed separation system with suppressed electroosfigure 2: electropherogram from the itp-cze separation of hcy in the presence of discrete spacers. the sample injected onto the microchip: 100 µmol/l apm, 15 µmol/l hcy, 150 µmol/l thr in a 50 % terminating electrolyte. apm = aminopimelate; hcy = homocysteine; thr = threonine; g = conductivity. motic flow. these working conditions effectively reduce the fluctuations in the total migration velocity of the analytes which is crucial to obtain reproducible results, especially on the microchip with short separation paths [21]. in the itp separations, a leading electrolyte with a ph of 9.1 and glycine as a terminating electrolyte were used. in the cze step of the itp-cze technique, the ph of the background electrolyte was 9.8. the itp realized in the first separation channel on the microchip (fig. 1) preconcentrates the analyte and other constituents of the sample for the cze separation step. on the other hand, the close migration configuration of the constituents in the itp stage of the itp-cze technique can be a limiting factor for achieving the required resolution of the analyte from matrix constituents, especially on the microchip with short separation channels. in such a case, discrete spacers (dss) are effectively used to define the fraction of the sample transferred to the second cze channel when the cc technique is employed. then, the constituents of the sample migrating outside of the mobility interval defined by the dss are removed from the separation system. in this way, itp works as an online sample clean-up technique prior to the cze. in our case aminopimelate and threonine were used as the front and rear dss, and the undesirable constituents of the sample were electrophoretically removed from the separation system by column switching prior to the cze separation realized in the second channel (fig. 2). a 1.4 µmol/l limit of detection (lod) for hcy was obtained by the itp-cze technique on the microchip. a relatively large volume of the sample that was injected onto the microchip (9.9 µl) contributed to achieving the low value of lod when a universal and relatively low-sensitive conductivity detector was used. under the working and separation conditions employed, the reproducible migration velocities (the relative standard devihungarian journal of industry and chemistry determination of homocysteine by microchip electrophoresis 45 figure 3: electropherograms from itp-cze analyses of urine samples after spme pretreatment with various additions of hcy. sample injected on the microchip: urine diluted twice, 400 µmol/l apm, 200 µmol/l thr in 50 % terminating electrolyte with (a) 0; (b) 10; (c) 20; (d) 40 µmol/l hcy. apm = aminopimelate; hcy = homocysteine; thr = threonine; imp. = impurity; g = conductivity. ations (rsds) of migration times were between 0.5 and 1.2 %) and determinations of trace concentrations of hcy (rsds of peak areas were 1.2 %) were achieved. considering the high concentration levels of chloride and sulfate in urine and saliva samples, these interfering anions were removed before itp-cze analysis from real samples. for this purpose, spme using silverand barium-form resins was conducted. the content of hcy in samples of body fluid was evaluated by the method of standard addition using itp-cze analysis after spme pretreatment. the hcy concentrations in the tested samples of urine and saliva were approximately 22 µmol/l and 6 µmol/l (fig. 3), respectively. 4. conclusion the spme-itp-cze method performed on the microchip with conductivity detection and the cc technique enabled the fast (total analysis time of approximately 20 mins.) and reliable determination of the trace concentrations of hcy in biological samples such as urine and saliva. acknowledgement this research was supported by the grants apvv-025912, vega 1/0787/18 and uk/312/2017. references [1] selhub, j.: homocysteine metabolism, annu. rev. nutr., 1999 19, 217–246 doi: 10.1146/annurev.nutr.19.1.217 [2] kubalczyk, p.; bald, e.; furmaniak, p.; głowacki, r.: simultaneous determination of total homocysteine and cysteine in human plasma by capillary zone electrophoresis with ph-mediated sample stacking, anal. methods, 2014 6(12), 4138–4143 doi: 10.1039/c4ay00287c [3] amores-sánchez, m.i.; medina, m.a.: methods for the determination of plasma total homocysteine: a review, clin. chem. lab. med., 2000 38(3), 199– 204 doi: 10.1515/cclm.2000.028 [4] 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of medicine, university of debrecen, debrecen, nagyerdei krt. 98., 4032, hungary 2research institute for biomolecular and chemical engineering, university of pannonia, veszprém, egyetem u. 10., 8200, hungary 3division of clinical biochemistry, biocenter, innsbruck medical university, innsbruck, tirol, austria the cece-2017, 14th international interdisciplinary meeting on bioanalysis was held in veszprém, hungary on 8-11 october, 2017. the symposium was organized by the mta-pe translational glycomics research group, mukki, university of pannonia. the funding idea of this conference series was “bring together scientists from different disciplines who may not meet at other meetings”. following this initiative, 17 world-class invited speakers delivered stimulating lectures not only about cuttingedge bioanalysis but also about other hot topics, such as aerosol chemistry, etc. the informal atmosphere of the meeting supported direct networking between wellestablished senior researchers and young scientists at the beginning of their carrier. the first two days of invited lectures was extended with cece junior, a dedicated day for phd students and postdocs, providing them an opportunity to present their results and catch the attention of colleagues both from academia and industry. more than 120 registered participants attended the event during the three days. the scientific program was preceded by a unique hungarian social event, a sausage making exercise on sunday. this national tradition was an exceptional gettogether party, where invited speakers, participants, students, sponsors and organizers made spicy and tasty sausage under strict quality control by the father of cece series, frantisek foret. as an accompanying section, the horváth csaba memorial exhibition was reopened on the occasion of opening an exhibition for another great hungarian chromatographer professor ervin sz. kováts. the joint display was dubbed as hungarian “chromatography” mafia exhibition and these two good friends are together as examples for the next generations. overall, the program was of very high scientific level. in this symposium issue, selected contributions are published after normal peer-review process covering very diverse topics of the bioanalytical field. at this point, the chair andrás guttman and co-chair herbert lindner would like to thank the hard work of colleagues and students namely brigitta mészáros, beáta borza, lászló hajba, márton szigeti, balázs reider and gábor járvás from the hungarian side and bettina sarg and klaus faserl from the austrian side. last but not least, this event would not have happened without the financial support of our sponsors – sciex, unicam hungary, thermo-fischer scientific, bio-science, agilent, kromat, watrex, waters, university of pannonia, city of veszprém and the hungarian society of separation sciences. in 2018 the series will return to its home town brno on 15-17 october, 2018, see you there! andrás guttman and herbert lindner hungarian journal of industry and chemistry vol. 46(1) pp. 3-6 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0002 semiquantitative assessment of dishevelled-3 phosphorylation status by mass spectrometry kateřina hanáková1,2, david potěšil2, ondřej bernatík3, igor červenka3, matěj rádsetoulal3, vítězslav bryja3, and zbyněk zdráhal ∗1,2 1national centre for biomolecular research, faculty of science, masaryk university, brno, 62500, czech republic 2central european institute of technology, masaryk university, brno, 62500, czech republic 3department of experimental biology, faculty of science, masaryk university, brno, 62500, czech republic the focus of this paper is the human dishevelled 3 protein (hdvl3), an essential component of the wnt signalling pathway that contributes to their regulation. mass spectrometry-based analysis of hdvl3 phosphorylations induced by eight associated kinases was performed revealing several dozens of phosphorylation sites. the main outcome of this study was the description of dvl phosphorylation “patterns” induced by individual kinases. keywords: phosphorylation, dishevelled 3, mass spectrometry, ck1ε, nek2 1. introduction reversible protein phosphorylation belongs to posttranslational modification which is of high biological significance mainly due to its role in regulating cellular processes such as gene expression, cell division, signal transduction, metabolism, differentiation, apoptosis, etc. [1] dishevelled-3 (dvl3) is a protein involved in the wnt signalling pathways and gets heavily phosphorylated in response to pathway activation by wnt ligands [2]. in our study, sodium dodecyl sulfate polyacrylamide gel electrophoresis (sds-page) separation of hdvl3 immunoprecipitates was combined with titanium dioxide phosphopeptide enrichment followed by liquid chromatography-tandem mass spectrometry (lcms/ms). data were processed using skyline software to obtain a semiquantitative assessment with regard to the occupancy of phosphorylation sites induced by individual kinases. 2. experimental 2.1 cell culture and transfection the cell line hek293 was used for this study. cells were seeded in dishes 15 cm in diameter and transfected at a confluence of 60%. two days after transfection, after reaching confluence, they were harvested for immunoprecipitation. a chilled np-40 lysis buffer with protease inhibitors, dithiothreitol (dtt), phosphatase inhibitors and ∗correspondence: zdrahal@sci.muni.cz n-ethylmaleimide (nem) was used for cell lysis. the lysate was incubated with the antibody anti flag m2. 2.2 gel electrophoresis, protein digestion and phosphopeptide enrichment immunoprecipitates were separated by sds–page, fixed with acetic acid in methanol, and stained with coomassie brilliant blue for 1 hour then partially destained. corresponding 1-d bands were excised. after destaining, the proteins in gel pieces were incubated with 10 mm of dtt at 56 ◦c for 45 mins. after the removal of dtt excess samples were incubated with 55 mm of iodoacetamide (iaa) at room temperature in darkness for 30 mins, then an alkylation solution was removed and gel pieces were hydrated for 45 mins at 4 ◦c in a digestion solution (5 ng/µl trypsin, sequencing grade, promega, fitchburg, wisconsin, usa, in 25mm ammonium bicarbonate (ambic)). the trypsin digestion proceeded for 2 hours at 37 ◦c on a thermomixer (at 750 rpm; eppendorf ag, hamburg, germany). subsequently, the tryptic digests were cleaved by chymotrypsin (5 ng/µl, sequencing grade, roche, basel, switzerland, in 25mm ambic) for 2 hours at 37 ◦c. digested peptides were extracted from gels using 50% acetonitrile (acn) solution with 2.5% formic acid (fa) and concentrated in a speedvac concentrator (eppendorf ag, hamburg, germany). the aliquot (1/10) of the sample was transferred to an autosampler vial and concentrated under a vacuum. water was used to produce 15 µl of the peptide solution which was directly hungarian journal of industry and chemistry vol. 46(1) pp. 7-11 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0003 phosphoglycolipid profiling of bacterial endotoxins anikó kilár ∗1,2, ágnes dörnyei2, viktor sándor1, ferenc kilár1, and béla kocsis3 1institute of bioanalysis, university of pécs, szigeti út 12, pécs, 7624, hungary 2department of analytical and environmental chemistry and szentágothai research centre, university of pécs, ifjúság útja 6, pécs, 7624, hungary 3department of medical microbiology and immunology, university of pécs, szigeti út 12, pécs, 7624, hungary much interest is at present focused on bacterial endotoxins, also known as lipopolysaccharides (lps), as they are responsible for the development of clinical symptoms of gram-negative sepsis which is the leading cause of death in intensive care units. endotoxicity is associated with the special phosphoglycolipid part of lps, termed lipid a. main challenges in the structural elucidation of lipid a arise from its amphiphilic character and inherent heterogeneity. a mass spectrometrybased de novo method combined with reversed-phase liquid chromatography for the detailed structural characterization of complex lipid a mixtures (obtained by mild acid hydrolysis of lps) from different bacterial sources has been developed. tandem mass spectrometric measurements were performed with an electrospray-ionisation quadrupole time-of-flight (esi-q-tof) mass spectrometer in both negativeand positive-ionization modes in order to explore fragmentation pathways. it was found that characteristic product ions in the positive-ion mode could be used for the unambiguous assignment of the phosphorylation site, whereas the use of both ionization modes provided consistent and/or complementary information about the fatty acyl distribution between the two glucosamine moieties of lipid a. since the immunostimulatory (advantageous) vs. proinflammatory (endotoxic) effect of the lipid a is closely related to the fine chemical structure, our relatively simple structural elucidation strategy could offer great potential in the bioanalysis of native lipid a samples and lipid a-based vaccines. keywords: lipid a, hplc, tandem mass spectrometry, positive-ion mode, negative-ion mode 1. introduction bacterial endotoxins are important initiators of clinical symptoms of gram-negative sepsis, a serious medical condition with a high mortality rate among patients in intensive care units worldwide. endotoxins, chemically lipopolysaccharides (lps) or lipooligosaccharides (los), are found on the surface of gram-negative bacteria. they are essentially composed of two regions: a heteropolysaccharide chain (divided into the oligosaccharide core and the o-side chain – this component is missing from los) that extends outwards from the bacterial cell surface, and a phosphoglycolipid, termed lipid a, which is anchored in the outer membrane (fig. 1). specifically, the endotoxic activity is related only to the lipidic domain of endotoxins. with regard to the toxicity of lipid a the crucial factors are the acylation and phosphorylation status. this most biologically potent molecule, capable of inducing septic shock, consists of an asymmetrically hexaacylated, bisphosphorylated glucosamine disaccharide [1]. other lipid a species that deviate from this structure have lower endotoxicity or may even have beneficial ∗correspondence: aniko.kilar@aok.pte.hu effects. consequently, the structural analysis of the lipid a moiety is of fundamental interest in terms of clinical aspects and vaccine development. the structural characterization of lipid a poses a unique analytical challenge, as lipid a isolated from a single bacterial strain generally consists of a mixture of differently acylated and phosphorylated species. furthermore, the relative abundances of the different structures can vary with growth conditions, e.g. temperature, culture figure 1: schematic representation of the chemical structure of an enterobacterial outer membrane lipopolysaccharide (endotoxin). 8 kilár, dörnyei, sándor, kilár, and kocsis media and ph. within this field, tandem mass spectrometry (ms/ms or msn) has emerged as a core technology for the in-depth structural elucidation of lipid a species [2]. however, separation and simultaneous quantification of singular components by powerful separation methods prior to ms would be highly desirable to adequately characterize the heterogenic structures. here, a brief presentation of an alternative method to multiple-stage ms for the differentiation of various lipid a species – including isobars – within a bacterial sample is provided. our method is based on a reversedphase high-performance liquid chromatography (rphplc) separation and online esi-q-tof mass spectrometric detection of molecular species in native lipid a isolates. the exact structures of the lipid a molecules in the complex mixtures were deduced from specific fragmentation patterns obtained in both the negative[3, 4] and positive-ion modes [5]. 2. experimental 2.1 chemicals and reagents methanol, isopropyl alcohol, water (lc-ms grade), dichloromethane (hplc, ≥99.9%), triethylamine (et3n) and acetic acid (acoh) were purchased from sigmaaldrich (steinheim, germany). 2.2 bacterial strains and lipid a isolation the strains escherichia coli o111 and proteus morganii o34 were cultured in a laboratory fermenter, and then collected by centrifugation. the bacterial lps was extracted from acetone-dried organisms by the traditional hot phenol-water procedure and lyophilized. lipid a was released from lps by mild-acid hydrolysis with 1% (v/v) acoh at 100◦c for 1 h, then the solution was centrifuged (8000×g, 4◦c, 20 mins). the sediment (containing lipid a) was washed four times with distilled water and lyophilized. lipid a samples were dissolved in methanol/dichloromethane (95:5, v/v) at a final concentration of 0.5 mg/ml. 2.3 liquid chromatography – mass spectrometry measurements separation and mass spectrometric detection of lipid a samples were performed with an 1290 infinity ultra-high performance liquid chromatography (uhplc) system (agilent technologies, waldbronn, germany) coupled to a 6530 accurate-mass q-tof lc/ms system (agilent technologies, singapore), using a kinetextm coreshell c18 column (100 mm×4.6 mm, 2.6 µm particle size, phenomenex). mobile phase a was methanol/water (95:5, v/v) and mobile phase b was isopropyl alcohol, both containing 0.1% et3n and 0.1% acoh (v/v). the injection volume was 3 µl. separation was performed at figure 2: hplc–ms base peak chromatograms of the native, heterogeneous e. coli o111 lipid a preparation acquired in the a) positiveand b) negative-ion modes. a constant flow rate of 0.5 ml/min at 50◦c. a linear gradient of 50 min started at 0% of mobile phase b and ramped up to 50% of mobile phase b, and was then maintained at 50% of mobile phase b for 2 mins. negativeand positive-ion mass spectra of the column eluate were recorded between m/z 100 and 3,200. the esi ion source was operated using the following conditions: pressure of nebulizing gas (n2), 30 psi; temperature and flow rate of drying gas (n2), 325◦c and 8 l/min, respectively; temperature and flow rate of sheath gas, 300◦c and 11 l/min, respectively; capillary voltage, 4 kv; nozzle voltage, 2 kv; fragmentor potential, 100 v; and skimmer potential, 70 v. for the targeted ms/ms analysis, the following parameters were used: mass range, m/z 70– 2000; acquisition rate, 333.3 ms/scan; quadrupole isolation width, 1.3 m/z; collision energy, 70–100 v; maximum number of precursor ions/cycle, 4; and active charge state of the precursor ion, 1. 3. results and analysis 3.1 hplc-ms of bacterial lipid a crude lipid a preparations from e. coli o111 and p. morganii o34 bacteria were used as training sets for the development of the method. the hplc separation conditions were optimized in order to find a balance between solubility, adequate separation and ionization of the intact lipid a’s. fig. 2 shows the hplc–ms analysis in the positiveand negative-ion modes for the e. coli o111 lipid a isolate, only. it was found that the lipid a samples expressed extreme structural heterogeneity, showing the presence of numerous bis-, monoand nonphosphorylated structures and diverse acylation states ranging from dito hepta-acylation. the most abundant chromatographic peak from both bacteria was a hexaacylated, monophosphorylated species. the elution order of the separated compounds was consistent with their relative hydrophobicity, defined mainly by the total numhungarian journal of industry and chemistry phosphoglycolipid profiling of bacterial endotoxins 9 ber and length of hydrophobic acyl chains, followed by the number of polar phosphate groups. several isomers of identical mass could be identified in which the length and/or position of the acyl chains varied. since the phosphoglycolipids are acidic in nature, they could readily be ionized as deprotonated ions, i.e. [m – h]− in the negative-ion mode, whereas their ionization in the positive-ion mode was enhanced by adduct formation with triethylamine used as an eluent additive, i.e. [m + h + et3n]+ adducts were formed. 3.2 tandem mass spectrometric analysis of lipid a species in order to investigate the fragmentation behavior under low-energy collision-induced dissociation (cid) conditions of each separated lipid a precursor ion, esims/ms experiments were performed in both ionization modes. based on previously published data on the acyl distribution of the c4’-monophosphorylated, hexaacylated lipid a molecule from e. coli o111 [6], ions observed in the tandem mass spectra (not shown) of this lipid a species (appearing at tr = 29.2 mins in fig. 2) could be structurally assigned in both ionization modes [3,5]. using this as a standard, the cid mass spectral profiles of other monophosphorylated lipid a species separated by chromatography were compared, and the fragmentation preferences for each of them, in both ionization modes, were explored. fig. 3 presents an example of the correlation between the phosphoglycolipid structure and the fragmentation profiles in the case of the main hepta-acylated lipid a compound (tr = 42.5 mins in fig. 2) from e. coli o111. the site-specific cleavages are assigned with a number denoting the carbon of the glucosamine to which the substitution is attached, and a greek letter designating the position of the bond which was cleaved. in the tandem mass spectrum of the [m + h + et3n]+ triethylammonium adduct of this lipid a species (fig. 3a), only a few ions resulting from the neutral loss of acyl chains are present, however, in that of the deprotonated form (fig. 3b), the abundances of product ions in the higher m/z region straightforwardly indicated the consecutive dissociation order of the ester-linked fatty acids. thus, their position could be assigned. each tandem mass spectrum also exhibited diagnostic intra-ring (a-type ions in the negative-ion mode) or inter-ring (band y-type ions in the positive-ion mode) cleavage products, which confirmed the substitution position of the fatty acids on the two glucosamine residues. fig. 4 shows the tandem mass spectra of the c1 phosphorylation isomer of this hepta-acylated lipid a species. the location of the single phosphoryl group (i.e. at c1 or c4’) could be directly assessed from the positive-ion mode tandem mass spectra by calculating the mass difference between the m/z of the precursor ion and that of the product ion resulting from the cleavage of the 1α bond figure 3: tandem mass spectra in a) positiveand b) negative-ion modes and a depiction of the identified structure of the c4’-monophosphorylated hepta-acylated lipid a from the e. coli o111 bacterium. site-specific cleavages are indicated next to the ion signals. (compare figs. 3a and 4a). namely, the mass difference of 199 u corresponded to the combined loss of triethylamine and an orthophosphoric acid molecule, indicating that a phosphoric acid molecule had esterified the c1 hydroxyl group of the reducing end. on the other hand, a mass difference of 119 u resulted from the combined loss of triethylamine and a water molecule, indicating the presence of a free hydroxyl group at c1 (consequently, the phosphoryl group must be located at c4’). the change in the phosphorylation site also resulted in a distinctive tandem mass spectrum in the negativeion mode (fig. 4b). the main differences were the complete lack of a-type cross-ring fragments, and instead the appearance of z-type inter-ring cleavage products. furthermore, the intensities of the product ions resulting from the neutral loss of acyl chains were of about the same magnitude, indicating strong competition between the fatty acyl eliminations during the cid process, instead of their stepwise dissociation (compare with fig. 3b). the fragmentation behavior of nonand bisphosphorylated lipid a species under both negative and positive cid conditions was investigated, as well. for these, a different sequencing of the acyl-chain cleavages could be observed in the negative-ion mode [3, 4], whereas similar fragmentation pathways to that of the monophosphorylated species in the positive-ion mode were identified [5]. besides the a-type ions (nonreducing end), complementary x-type fragment ions (reducing end) appeared in the negative-ion mode tandem mass 46(1) pp. 7-11 (2018) 10 kilár, dörnyei, sándor, kilár, and kocsis figure 4: tandem mass spectra in the a) positiveand b) negative-ion modes and depiction of the identified structure of the c1-monophosphorylated hepta-acylated lipid a from e. coli o111. spectra of the nonphosphorylated lipid a species [4]. 4. discussion the online hplc–ms/ms methodology enabled the simultaneous structural characterization of both phosphorylated and nonphosphorylated lipid a variants within a single run. the main advantage of using the collision cell of a q-tof mass spectrometer was that several generations of precursor/product ions – that would otherwise be generated only at higher ms stages with ion-trap experiments – were observed simultaneously in the tandem mass spectra of the separated lipid a species. this facilitated new fragmentation rules to be set for the variety of phosphorylated and acylated lipid a compounds by a simple ms/ms experiment [3–5]. specifically, the acylation profile of the non-, c4’-mono and bisphosphorylated lipid a species could be inferred partly from the positiveand fully from the negative-ion mode ms/ms analyses [3–5], whereas the complementary use of both ionization modes [3, 5] was needed for the full structural characterization of c1-monophosphorylated lipid a. as an example, the complete structural elucidation strategy by ms/ms of a hepta-acylated c1’monophosphorylated lipid a is as follows. first, observation of the 1α cleavage product in the positive-ion mode is essential to clarify the site of phosphorylation (vide supra). next, the linkages at the 2′ε (only from the btype ion) and 2ε positions can be determined from the positive-ion mode analysis. by knowing the fragmentation preference of the secondary ester bonds (which is 2′ε > 3′ε > 2ε [5]), substitutions at these sites can be deconvoluted from the negative-ion mode analysis by observing the 2′ε, 3′ε, 2ε, and 3α cleavage products in the upper m/z region and those resulting from the 3′α, 2′ε + 3′ε, 2′ε + 2ε, 2′ε + 3α, and 3′ε + 3α cleavages displayed in the middle m/z region. here, the dephosphorylated z-type ion in the lower m/z region indirectly specifies the linkage at the 2α position. finally, the remaining 2’α substitution can be deduced from the intact b-type ion (positive-ion mode). 5. conclusion an efficient hplc separation before the ms detection of natural lipid a mixtures has proven particularly useful in terms of revealing the diversity and relative amount of the various lipid a structures present in bacteria. such investigations could help to explore the relative contributions of different lipid a structures to the overall activation of the innate immune system. moreover, knowledge of the chemical and biological aspects of lipid a heterogeneity is crucial in order to design antimicrobial drugs which overcome the evasion strategy of the pathogen. our technique could be well suited for phosphoglycolipid profiling from different bacterial strains or vaccine preparations. acknowledgement this research was supported by the grants otka k125275 and únkp-17-4-iii provided by the new national excellence program of the ministry of human capacities. references [1] munford, r.s.: sensing gram-negative bacterial lipopolysaccharides: a human disease determinant? infect. immun. 2008, 76(2), 454–465. doi: 10.1128/iai.00939-07 [2] kilár, a.; dörnyei, á.; kocsis, b.: structural characterization of bacterial lipopolysaccharides with mass spectrometry and onand off-line separation techniques. mass spectrom. rev. 2013, 32(2), 90–117. doi: 10.1002/mas.21352 [3] sándor, v.; dörnyei, á.; makszin, l.; kilár, f.; péterfi, z.; kocsis, b.; kilár, a.: characterization of complex, heterogeneous lipid a samples using hplc-ms/ms technique i. overall analysis with respect to acylation, phosphorylation and isobaric distribution. j. mass spectrom. 2016, 51(11), 1043– 1063. doi: 10.1002/jms.3839 [4] sándor, v.; kilár, a.; kilár, f.; kocsis, b.; dörnyei, á.: characterization of complex, heterogeneous lipid a using hplc–ms/ms technique ii. structural elucidation of non-phosphorylated lipid a by negativeion mode tandem mass spectrometry. j. mass spectrom. 2016, 51(8), 615–628. doi: 10.1002/jms.3786 hungarian journal of industry and chemistry hungarian journal of industry and chemistry vol. 46(1) pp. 13-17 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0004 capillary isotachophoresis determination of trace oxidized glutathione in blood róbert bodor ∗1, andrea nečasová2, alena pechová2, and marián masár1 1department of analytical chemistry, faculty of natural sciences, comenius university in bratislava, ilkovičova 6, bratislava, sk-84215, slovak republic 2department of animal protection, welfare and behaviour, faculty of veterinary hygiene and ecology, university of veterinary and pharmaceutical sciences brno, palackého tř. 1/3, brno, cz61242, czech republic a capillary isotachophoresis (citp) method performed in a column-coupling apparatus has been developed for the simultaneous determination of glutathione (gsh) and glutathione disulfide (gssg) concentrations in blood samples. the determination of gssg and gsh concentrations in biological samples is important because of their roles in oxidative stress. different concentrations of a leading ion in the coupled columns (concentration cascade) and a large volume (37 µl) of the injected sample facilitated a gssg concentration of between 2 and 25 µmol/l. a reaction between iodoacetate and gsh under alkaline conditions was used to prepare the sample in order to avoid oxidation of gsh to gssg. this step eliminated the main source of systematic errors with regard to the determination of the gssg concentration. a linear relationship (r2=0.9969) between the zone length of s-(carboxymethyl)glutathione (the product of the reaction between gsh and iodoacetate) and the concentration of gsh (40-120 µmol/l) was obtained. the method was applied to the analysis of bovine blood samples that had been diluted by a factor of ten with satisfactory results. keywords: glutathione, glutathione disulfide, isotachophoresis, bovine blood 1. introduction glutathione (gsh), a thiol containing tripeptide, plays an important role in the antioxidant system of eukaryotic cells [1]. upon oxidation, gsh is transformed into glutathione disulfide (gssg) [1]. the concentrations of gsh and gssg and their molar ratio are indicators of cell functionality as well as oxidative stress [2]. different aspects of the determination of gsh and gssg concentrations in biological samples, including sample pretreatments, were recently reviewed [3–5]. the main problems are related to the non-enzymatic oxidation of gsh when the ph exceeds 7, enzymatic conversion of gsh, a need for the removal of proteins prior to the analysis, blocking of free thiol groups, reduction of disulfides, and derivatization of thiol groups [3,6]. among a wide variety of analytical methods, capillary electromigration (ce) methods, mainly ce coupled with different detectors (uv absorbance [7–10], fluorescence [11] and laser-induced fluorescence (lif) [12, 13], electrochemical [14, 15] and mass spectrometry [16], have been used to determine the concentration of glutathione [5, 17]. the aim of this work was to develop a capillary isotachophoresis (citp) method that involves minimal sample pretreatment for the simultaneous determination of ∗correspondence: robert.bodor@uniba.sk gssg and gsh concentrations in bovine blood samples. determination of trace analytes in regular citp, when the quantitation is based on the measurement of the zone length, is not very common. in this work, two key problems were solved: (1) lowering the quantitation limit of the citp method, and (2) stabilization of gsh without protein precipitation to ensure the accurate determination of the gssg concentration. 2. experimental an ea 202a electrophoretic analyzer (villa labeco, spišská nová ves, slovakia) was used for citp separations. this fully automated ce system was equipped with two columns. in the first column, a fluoroplastic capillary tube with an inside diameter (id) of 800 µm and contactless conductivity detection were used. in the second column, a fused silica capillary with an id of 300 µm, contactless conductivity and uv photometric detectors were used. the citp separations were performed using the electrolyte systems shown in table 1 at a constant driving current, and in the anionic mode (electrode e3 in fig. 1 used as a cathode). at the beginning and end of the day, the separation and electrolyte units as well as the sample loop of the autosampler were rinsed with deionized water hungarian journal of industry and chemistry vol. 46(1) pp. 19-22 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0005 cold plasma: the way to improve the repeatability of sald icp-ms analysis marek stiborek1,2, jan preisler ∗1,2, masoud shekargoftar3, viktor kanický1,2, and jakub kelar3 1department of chemistry, masaryk university, kamenice 753/5, brno, 625 00, czech republic 2ceitec central european institute of technology, masaryk university, kamenice 753/5, brno, 625 00, czech republic 3r&d centre for low-cost plasma and nanotechnology surface modifications, department of physical electronics, masaryk university, kotlářská 2, brno, 611 37, czech republic this work deals with the preparation of model biological microsamples for substrate-assisted laser desorption inductively coupled plasma mass spectrometry (sald icp-ms). this technique provides the direct and fast analysis of liquid samples deposited onto polyethylene terephthalate (pet) plates (substrates) in the form of dried droplets with minimal sample preparation and submicrolitre sample volume requirements. furthermore, sald icp-ms allows for the direct analysis of samples in organic solvents, which cannot be directly nebulised to icp-ms. these benefits are, however, balanced out by the low degree of repeatability of the assay, which is typically about 30%. one of the approaches to increase the repeatability is a modification of the substrate surface by diffuse coplanar surface barrier discharge (dcsbd) with the addition of an internal standard to the sample. using this approach, a relative standard deviation (rsd) of less than 10% for model biological samples can be achieved. the only limitation of this technique is the occurrence of the so-called “aging effect”, i.e. the gradual return of the modified physicochemical surface properties to their original state. keywords: sald icp-ms, plasma treatment, dcsbd, microsample, internal standard 1. introduction the determination of elements in biological samples is often complicated by complex matrices, the presence of organic solvents, and trace amounts of the elements of interest. for this reason, it is necessary to select a technique that bridges the obstacles mentioned above. such a technique is substrate-assisted laser desorption inductively coupled plasma mass spectrometry (sald icp-ms), which is capable of analysing liquid samples of submicrolitre volumes in the form of dried droplets (stains) on a polyethylene terephthalate (pet) substrate [1–3]. the greatest difficulty of this technique is the low repeatability of the assay. this is caused mainly by the poorly reproducible deposition of droplets that consist of submicrolitre volumes and the inhomogeneity of the stains produced in terms of the area and thickness of the layer of solid residue in the stain. the assay repeatability can be increased by increasing the surface energy of the substrate and using internal standards that can correct the mentioned effects. one way to increase the surface energy, i.e. wettability of the substrate, is to expose it briefly to cold plasma, ∗correspondence: preisler@chemi.muni.cz specifically diffuse coplanar surface barrier discharge (dcsbd) [4, 5]. the plasma system of the so-called dcsbd is composed of regularly alternating silver electrodes to which high alternate voltages are applied. the electrodes are located in a dielectric structure consisting of dielectric oil and thin ceramic plates. the most common arrangement of electrodes in this device is in the form of two intermeshing combs. surface discharges are then generated on the surface of the ceramic plate, serving as a dielectric barrier. this electrode arrangement (plasma in contact with only inert and highly resistant ceramics) can consist of a theoretically infinite amount of 20×8 cm dcsbd units and thus, it is theoretically possible to achieve an infinite plasma area. the principle of substrate surface treatment is based on the excitement and ionization of the species by a high voltage discharge and subsequent introduction of the resulting species onto the substrate surface in the form of radicals, ions and excited molecules. a disadvantage of this technique over other physicochemical modifications is the gradual decrease in surface tension compared to its original value prior to the modification, or the so-called “aging effect” [6]; this period is in the order of several months. factors influencing the qualcold plasma: the way to improve the repeatability of sald icp-ms analysis 21 table 2: integrated sald icp-ms signals of 111cd and 115in from stains of 0.5 mm trisodium citrate deposited at different times after pet surface modification. deposition time [days] 111cd 115in 115in / 111cd stain size [mm] 0 x [cps]* 0.44 11 25 1.2±0.1 rsd [%] 14 10 7.5 1 x [cps]* 1.4 31 22 1.6±0.2 rsd [%] 34 38 7.2 3 x [cps]* 2.2 48 23 1.4±0.2 rsd [%] 32 29 12 6 x [cps]* 2.8 58 22 1.2±0.3 rsd [%] 34 24 19 ∗cps·106 ever, that the surfaces with the longest dcsbd modification times exhibited the fastest tendency to return to their original states in the long term. in the following experiments, the aging effect of the substrate surface modified by dcsbd on the intensity of sald icp-ms signals was monitored. five replicates of 200 nl droplets containing 0.5 mm trisodium citrate solution and 400 ng·l−1 of cadmium and indium standards were immediately deposited onto the modified pet surface as well as one, three and six days after modification. from table 2, it is apparent that the stain sizes, which should be theoretically dependent on the wettability rate and the aging effect of the modified substrate surface, do not affect the repeatability of the assay for the given samples. furthermore, it is evident that the immediate average integrated intensity of the 111cd and 115in signals from the stain ablation of the 0.5 mm trisodium citrate sample as well as one, three and six days after modification of the pet surface differed. this finding is contrary to the assumption that these values should be identical, because in all cases the same amount of sample solution was deposited and the spots were practically 100% ablated by visual inspection. the repeatability of the ablation was low and relative standard deviation (rsd) values exceeded 30%. such high values of rsds could be attributed, in particular, to the character of the sample itself, which was crystalline after drying, and the analytes as they were inhomogeneously distributed therein. however, when quantifying the signal intensity ratio of 115in to 111cd, this inhomogeneity could be corrected, as a result the rsd values varied by around 7.5% for samples deposited immediately and one day after surface modification of the pet. the samples on the treated surfaces exhibited the highest wettability and, therefore, it was possible to assume that the analytes were homogeneously dispersed in the stain. the ablation records in figs. 2a and 2b also show a higher degree of homogeneity of the stains. samples applied three and six days after modification exhibited higher corrected values of rsds: 12 % and 19 %, refigure 2: ablation record of stains of 0.5 mm trisodium citrate deposited a) immediately, as well as b) 1, c) 3 and d) 6 days after pet substrate surface modification. spectively, mainly due to a higher level of inhomogeneity (figs. 2c and 2d). average 115in/111cd integrated signal intensity values for the spots applied one, three and six days after surface modification could be used for quantification of the monitored analytes as the values almost coincided. however, the average value of the integrated signal from droplets applied to the substrate immediately after the modification differed. this could be caused by extreme changes in the physical properties of the substrate surface immediately after modification. 4. conclusion dcsbd technology was chosen for surface modification, i.e. to increase the energy and wettability of the sub46(1) pp. 19-22 (2018) hungarian journal of industry and chemistry vol. 46(1) pp. 23-27 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0006 capillary electrophoretic analysis of exhaled breath condensate in the diagnosis of gastroesophageal reflux disease petr kubáň *1, pavol ďurč1, júlia lačná1, michal greguš1, františek foret1, jiří dolina2, štefan konečný2, martina doubková3, dagmar kindlová3, eva pokojová3, and jana skřičková3 1department of bioanalytical instrumentation, ceitec masaryk university, veveří 97, 602 00 brno, czech republic 2department of internal gastroenterology, faculty hospital brno, faculty of medicine, masaryk university, jihlavská 340/20, 625 00 brno, czech republic 3department of pulmonary diseases and tuberculosis, faculty hospital brno, faculty of medicine, masaryk university, jihlavská 340/20, 625 00 brno, czech republic in this work, capillary electrophoresis with contactless conductometric detection (ccd) was used for the analysis of the ionic content of exhaled breath condensate (ebc) to differentiate between healthy individuals and patients with gastroesophageal reflux disease (gerd). the exhaled breath condensate was collected using a miniature sample collection device and the content analyzed using a separation electrolyte composed of 20 mm 2-(n-morpholino)ethanesulfonic acid, 20 mm l-histidine, 2 mm 18-crown-6 and 30 µm cetyltrimethylammonium bromide. the separation of anions took less than 2.5 minutes, while the cations were separated in less than 1.5 minutes. the most significantly elevated ions in the group of patients suffering from gastroesophageal reflux disease were chloride, nitrate, propionate and butyrate. although the number of subjects was too small to draw definite conclusions with regard to the discriminatory power of these ions, the pilot data are promising for ebc as a useful non-invasive alternative for other methods used in the diagnosis of gastroesophageal reflux disease. keywords: capillary electrophoresis, exhaled breath condensate, ionic analysis, diagnosis, gastroesophageal reflux disease 1. introduction capillary electrophoresis is an attractive separation technique that is particularly suitable for the analysis of biological samples. non-invasive sampling and the analysis of alternative biofluids are gaining scientific attention as these samples are acquired easily, can be obtained repeatedly without any particular stress to the patient, and often are formed of a simple matrix. one such sample is exhaled breath condensate (ebc). ebc is obtained by cooling exhaled breath using suitable pieces of cooling equipment and apparatus. ebc is the aqueous part of the exhaled breath that mainly contains condensed water from breath and volatile compounds that are soluble in water, in addition to small respiratory droplets that provide information concerning the condition, inflammation and oxidative/nitrosative stress of the lungs. ebc was first used as a diagnostic sample by sidorenko in the 1980s [1] and since then numerous articles on ebc have been published, including some re*correspondence: petr.kuban@gmail.com cent reviews [2, 3]. ebc is attractive not only in terms of studying the condition of the lungs [4, 5], but possibly in the identification of other applications, for instance, in the assessment of inflammatory conditions of the trachea and esophagus. the latter is of particular importance because gastroesophageal reflux disease (gerd) is one of the most common diseases in the western world. between 20 and 30% of the general population in europe and usa will suffer from gerd [6] and about 60% of the adult population will experience some type of gerd during their lifespan. gerd is often diagnosed using invasive instruments such as 24-hour multichannel intraluminal impedance and ph monitoring (mii-ph) [7], during which the patient is required to continuously wear a narrow catheter in the esophagus. this device measures the spread and volume of gases, liquids as well as solids through the esophagus and evaluates the composition of refluxate. the data are eventually used to evaluate whether the person is suffering from the disease based on the number of recorded reflux episodes and the demeester score [8] which describes the severity of reflux. hungarian journal of industry and chemistry vol. 46(1) pp. 29-33 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0007 study of various parameters that influence the content of exhaled breath condensate used in the diagnosis of gastroesophageal reflux disease michal greguš ∗1,2, pavol ďurč1,2, júlia lačná1,2, františek foret1,3, and petr kubáň1,2,3 1department of bioanalytical instrumentation, ceitec masaryk university, veveří 97, 602 00 brno, czech republic 2department of chemistry, masaryk university, kotlářská 267/2, 611 37 brno, czech republic 3department of bioanalytical instrumentation, institute of analytical chemistry of the czech academy of sciences, v.v.i., veveří 97, 602 00 brno, czech republic in this work, various parameters that influence the ionic content and ph of exhaled breath condensate in terms of the noninvasive diagnosis of gastroesophageal reflux disease were studied. exhaled breath condensate samples were collected using a miniature and inexpensive sampling device. capillary electrophoresis with contactless conductometric detection was used to monitor the ionic content of exhaled breath condensate. background electrolyte composed of 20 mm of 2-(n-morpholino)ethanesulfonic acid, 20 mm of l-histidine, 2 mm of 18-crown-6 and 30 µm of cetyltrimethylammonium bromide facilitated the rapid separation of anions and cations, both in less than 2 minutes. the possibility of contamination of the exhaled breath condensate by saliva is discussed in detail. the day-to-day repeatability (n=5) of the ionic content and ph of the exhaled breath condensate was studied and was satisfactory, reflecting mainly the physiological variability. keywords: capillary electrophoresis, exhaled breath condensate, ionic analysis, ph, gastroesophageal reflux disease 1. introduction gastroesophageal reflux disease (gerd) is a disease caused by the backflow of gastric contents into the esophagus due to the failure of physiological antireflux mechanisms and can lead to symptoms such as a chronic cough, globus sensation, laryngitis, pharyngitis, rhinosinusitis, otitis media, bronchial asthma, chronic obstructive pulmonary disease, sleep apnea and noncardiac chest pain [1, 2]. currently, no suitable, non-invasive diagnostic method for gerd is applicable in clinical practice. nowadays, the gold standard with regard to the diagnosis of gerd is a 24-hour multichannel intraluminal impedance-ph technique (mii-ph) that is rather invasive [3]. non-invasive sampling is becoming more important. exhaled breath condensate (ebc) as one of several noninvasive samples can be easily obtained by the cooling and subsequent condensation of exhaled breath. the ebc is composed mainly of water, however, it also contains volatile and non-volatile compounds (inorganic ions, organic acids) that can be useful as biomarkers of various diseases [4]. the identification of ions in ebc samples is easily achieved by capillary electrophoresis (ce). the main ad∗correspondence: gregus@mail.muni.cz vantage of this method is that it is able to cope with a minute volume of samples and analyses are often very rapid. another parameter that is often used to diagnose gerd is ph, measured by a conventional mii-ph probe, which is both invasive and costly. the ph can also be measured in collected samples of ebc [5] which is noninvasive and cheaper. monitoring various parameters of ebc in patients suffering from symptoms of extraesophageal/gastroesophageal reflux disease is an attractive, simple and non-invasive approach that could be used as a surrogate for other, more invasive diagnostic methods. however, to obtain relevant results, various parameters that can affect the results such as sampling procedures, effects of food and drinks and the intraday variability of individuals have to be studied prior to the use of ebc sampling in diagnostics. 2. experimental 2.1 instrumentation a purpose-built ce instrument was used for all ce analyses. the separation voltage was provided by a highvoltage power-supply unit (dx250, emco high voltage, sutter creek, ca, usa). a custom-made contactless conductivity detector (c4d, version 5.06, admet 30 greguš, ďurč, lačná, foret and kubáň 10 cm 2 ml syringe straw hollow aluminum cylinderseptum figure 1: the photo of the components used to build a miniature ebc sampling device. s.r.o., prague, czech republic) operating at a frequency of 1.8432 mhz and a voltage of 50 vp−p using a 24-bit a/d converter (orca 2800, ecom s.r.o., prague, czech republic) was used to detect separated analytes and collect data. ce analyses were performed in fused-silica capillaries (inner diameter (id) of 50 µm, outer diameter (od) of 375 µm, total length of 40 cm, effective length of 17 cm, microquartz gmbh, munich, germany). injection of a standard solution and samples was performed hydrodynamically. two pt wires (od of 0.5 mm, length of 3 cm, advent research materials ltd., eynsham, england) were inserted into the electrolyte vials to serve as electrodes. all ce experiments were performed at ambient temperature. to measure the ph of the ebc samples, co2 present in these samples was removed by a stream of n2 gas (nitrogen generator, rp-ze-n2l3000). the ph was measured using a ph microelectrode (mi-410 microcombination ph probe, microelectrodes, inc., bedford, new hampshire, usa) and ph-meter (orion startm a111 ph benchtop meter, thermo fisher scientific, waltham, massachusetts, usa). ebc samples were collected from the volunteers using an ebc sampler previously developed by our group [6,7]. briefly, the sampler for collection of ebc was constructed from a 2-ml syringe (b. braun melsungen ag, melsungen, germany) and a 5 cm-long hollow aluminum cylinder (see fig. 1) with an outer diameter (od) of 2.5 cm and an inner diameter (id) precisely matching the outer diameter of the syringe to facilitate efficient cooling of the walls. the cylinder was kept in a deep freezer at -17◦c and an insulation sleeve was used during collection to maintain the temperature for the whole duration of the sampling procedure. another aim of this insulation sleeve was to prevent frostbite during collection of the sample. straw (purchased from a local store) with an od of 6 mm and wall thickness of 0.2 mm was used to exhale the air through the sampler. the end of the syringe was enclosed with a parafilm septum to avoid ebc loss. 2.2 chemicals all chemicals were of reagent grade, and deionized (di) water was used for preparation and dilution of the stock solution. stock solutions (10 mm) consisting of inorganic anions and cations were prepared from their sodium and chloride salts (nacl, nano3, nano2, na2so4, kcl, cacl2, mgcl2) with the exception of ammonium, the stock solution of which was prepared from ammonium fluoride (all from pliva-lachema, brno, czech republic). the stock solutions of anions from organic acids were prepared from lithium acetate dihydrate, lithium lactate, propionic acid and butyric acid (all from sigmaaldrich, steinheim, germany). the background electrolyte (bge) for ce measurements was prepared daily by diluting 100 mm stock solutions of 2-(n-morpholino)ethanesulfonic acid (mes), l-histidine (his) and 100 mm 18-crown6 (all sigma–aldrich) to the required concentration. hexadecyltrimethylammonium bromide (ctab, sigma–aldrich) was prepared as 10 mm stock solution in 5 % acetonitrile and was added to the bge to yield the final concentration of 30 µm. 2.3 capillary conditioning prior to its first use, the separation capillary was preconditioned by flushing it with 0.1 m naoh for 30 mins, di water for 30 mins and bge solution for 20 mins. between two successive injections, the capillary was flushed with bge solution for 1 min. at the end of a working day, the capillaries were washed with di water for 15 mins and stored in di water overnight. 3. results and analysis 3.1 ebc sampling procedure the collection of ebc consists of several steps: deep exhalation until the lungs were as empty as possible, followed by rapid inhalation (1-2 s) and finally gradual complete exhalation into the sampling device (8-10 s). this procedure was suggested by almstrand et al. [8] and yielded the highest concentration of respiratory droplets and, therefore, the highest concentrations of non-volatile substances present in ebc. the volunteer was asked to exhale three times into the sampling device according to the proposed procedure. after the ebc sampling had been completed, the condensate from the syringe walls was wiped with the plunger of the syringe as far as the tip of the syringe and transferred to the sample vial for ce analysis. often, only one exhalation (30 µl of the sample) was sufficient to obtain a sizable amount of ebc for ce analysis. during the wiping procedure, the condensate collected from the walls is naturally mixed and hungarian journal of industry and chemistry hungarian journal of industry and chemistry vol. 46(1) pp. 35-38 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0008 analysis and identification of polyphenolic compounds in green foods using a combination of hplc-esi-it-tof-ms/ms pavel škvára ∗1, júlia kezmanová1, csilla mišl’anová1, and andrea vojs staňová1 1department of analytical chemistry, faculty of natural sciences, comenius university, ilkovičova 6, bratislava, sk-842 15, slovakia the beneficial effects of green foods on human health are well known. these benefits are mainly due to polyphenol content. the aim of this work was the development and utilization of an advanced mass spectrometry (ms) technique combined with high-performance liquid chromatography (hplc) for the analysis and identification of polyphenolic compounds in green foods. hplc-esi-ms/ms analyses of selected extracts prepared from various types of green food (urtica dioica l. and allium ursinum l.) and their polyphenolic profiles were performed by an lcms-it-tof analyzer equipped with electrospray ionization. hplc separation was conducted by a kinetex xb-c18 column (100×2.1 mm; 2.6 µm) using gradient elution (water + 0.1% formic acid: acetonitrile + 0.1% formic acid) with a flow rate of 0.2 ml/min. the ms1-ms3 analyses were performed within a 50-1000 m/z range in both positive and negative ionization modes. the total analysis time was 20 minutes and injected volumes were 2 µl and 5 µl, respectively. keywords: polyphenolic compounds, green food, hplc-ms analysis, identification 1. introduction from a chemical point of view, antioxidants are phenolic compounds derived from simple phenols up to complex polyphenols. an antioxidant is a substance whose molecules limit the activity of oxygenated compounds, namely reduce their likelihood or convert them into a less reactive state. antioxidants limit the oxidation process in the body or in the mixtures in which they are found. in food, they extend their expiration date. in the body, they reduce the likelihood of certain types of diseases [1]. the main reason for monitoring the presence and activity of antioxidants is their beneficial effect on the human organism. their health benefits include antioxidant, antibacterial, anticarcinogenic, anti-allergenic and anti-inflammatory properties [2–4]. antioxidants in green foods belong to a group of low-molecular-weight natural antioxidants whose scientific name is phenolic compounds [5]. green foods are characterized into four basic groups: herbs and spices, fruits, vegetables and nuts. despite the fact that numerous polyphenolic compounds have been detected in green food, there is still a need for new reliable analytical methods. the most common procedures for the identification and determination of polyphenolic compounds in green food are based on sample pretreatment by liquid-liquid extraction followed by separation and identification using high-performance liquid chromatography coupled with tandem mass spec∗correspondence: skvara1@uniba.sk trometry (hplc–ms/ms) [6]. several authors are concerned with the identification and characterization of phenolic compounds in green foods using a combination of high-performance liquid chromatography and mass spectrometry with electrospray ionization (hplc-esi-ms) and atmospheric pressure chemical ionization (hplcapci-ms). for example, hplc-esi-ms was used to separate and identify phenolic acids in custard apples [7], tannins in chestnut samples [8], phenolic compounds in groundnuts [9], tomatoes [10], spinach [11], and gingerol-related species (gingerols and shogaols) in ginger [12]. the hplc-apci-ms/ms method was used to identify carotenoids in samples of mango and citruses [13]. the hplc-esi-ms method was also used to analyze samples of nettles [14] and bear’s garlic [15]. the aim of this work was to analyze and identify polyphenolic compounds in selected samples of green food using a combination of high-performance liquid chromatography and high-resolution mass spectrometry techniques. 2. experimental 2.1 instrumentation all hplc-esi-ms/ms analyses were performed by using a shimadzu lcms-it-toftm mass spectrometer (shimadzu, kyoto, japan). this mass spectrometer combines an electrospray ionization (esi), a 3d quadrupole ion trap (it) and an orthogonal acceleration time-of-flight 36 škvára, kezmanová , mišlanová, and vojs staňová analyzer (tof) to provide both a high degree of sensitivity and resolution of ions. the hplc part consisted of an autosampler (sil-20a), high pressure pumps (lc20ad), a thermostat (cto-20a), a diode array detector (spd-m20a), a degasser together with a mixing system (dgu-20a5) and system controller (cbm-20a). lcms solutions v. 3.5.1 (shimadzu) software was used for data acquisition and evaluation. chromatographic separation of the polyphenolic compounds was performed on a kinetex xb-c18 column (100 × 2.1 mm; 2.6 µm) (phenomenex, torrance, ca, usa). acidified water and acetonitrile (both with an addition of 0.1 % or 10 mmol/l of formic acid) were used as mobile phases. gradient elution of the mobile phase was used. the flow rate of the mobile phase was 0.2 ml/min. the gradient program was 0 min.: 5% b; 3 min.: 10% b; 8 min.: 40% b; 10 min.: 60% b; 11 min.: 90% b; 12 min.: 90% b; 12.1 min.: 5% b; and 20 min.: 5% b. the chromatographic column was thermostated at 40 ◦c. all ms analyses were performed in both positive and negative ionization modes. the voltages at the esi capillaries were +4.5 kv and −3.5 kv. the range of recorded values was set at 50 − 1000 m/z. the temperatures of the curved desolvation line (cdl) capillary and heat block were set at 200 ◦c. the injected volume of the sample was 2 µl and 5 µl, respectively. 2.2 chemicals the following chemicals were used to prepare the solutions and mobile phases: water for lc-ms, acetonitrile for lc-ms (both from lichrosolv, merck, darmstadt, germany), and formic acid for lc-ms (sigma-aldrich, steinheim, germany). standard selected polyphenolic compounds were obtained from sigma-aldrich. 2.3 sampling and sample preparation the samples of nettle (urtica dioica l.) were collected in march 2017 in the geographical area of hruštín, after which they were dried and stored in a dry and dark place. samples of bear’s garlic (allium ursinum l.) were collected in march 2017 in the geographical area of bratislava, after which they were dried and stored in a dry and dark place. prior to the analysis, the extracts of each sample were prepared as follows: approximately 0.5 g of each was weighed and 50 ml of water was poured onto them at 97 ◦c. the extraction times were 5, 10 and 15 mins. the extracts were then filtered through filter paper and cooled to room temperature. after cooling, the samples were filtered through a syringe microfilter (pvdf with pore size 0.22 µm) and then analyzed using hplcesi-ms/ms or stored in a refrigerator at 4 ◦c for a maximum of 24 hours. 3. results and discussion the first part of the experimental work focused on the optimization of conditions for the chromatographic separation of phenolic compounds in selected extracts prepared figure 1: hplc-esi-ms analysis of the nettle extract (5 min extraction) with the addition of 10 mmol/l formic acid to the mobile phases. tic (total ion current) in the positive mode – top: tic in the negative mode – bottom and middle: eic (extracted ion chromatogram) records of identified phenolic compounds included. figure 2: hplc-esi-ms analysis of the nettle extract (5 min extraction) with the addition of 0.1% formic acid to the mobile phases. tic in the positive mode – top: tic in the negative mode – bottom and middle: eic records of identified phenolic compounds included. from different plant species. after hplc separation, optimization with regard to the composition of the mobile phase in terms of the ionization of the analytes was performed. to confirm the effect with regard to the composition of the mobile phase on the resulting ms signal, a simple experiment was proposed. hplc-esi-ms/ms analysis of the bear’s garlic and nettle extracts used mobile phases, which varied according to only the concentration of the added formic acid. gradient elution utilized the following mobile phases with the addition of different concentrations of formic acid: 0.1% formic acid in water (a) / 0.1% formic acid in acetonitrile (b), and 10 mmol/l formic acid in water (a) / 10 mmol/l formic acid in acetonitrile (b). for illustrative purposes, figs. 1 and 2 show the results from the hplc-esi-ms analysis of the 5-minutelong extraction of nettles. after comparing these results with the results of measuring a 5-minutelong extraction of nettles with the addition of 0.1% (26.5 mmol/l) formic acid to the mobile phases, it is clear that the use of a higher concentration of formic acid is more appropriate for the analysis of nettle extracts (promoting the protonation of molecules). a similar procedure was used to select the appropriate composition of the mobile phases for hplc-esims analysis of the garlic extract. the results of the 15minute-long extraction of bear’s garlic with the addition of 0.1% formic acid to the mobile phases can be seen in fig. 3. the results of the 15-minute-long extraction of garlic with the addition of 10 mmol/l formic acid are recorded in fig. 4 and suggest this is preferable for the hungarian journal of industry and chemistry analysis and identification of polyphenolic compounds in green foods 37 figure 3: hplc-esi-ms analysis of the garlic extract (15 min extraction) with the addition of 0.1% formic acid to the mobile phases. tic in the positive mode – top: tic in the negative mode – bottom and middle: eic records of identified phenolic compounds included. figure 4: hplc-esi-ms analysis of the bear’s garlic extract (15 min extraction) with the addition of 10 mmol/l formic acid to the mobile phases. tic in the positive mode – top: tic in the negative mode – bottom and middle: eic records of identified phenolic compounds included. analysis of the garlic samples. the final conditions for chromatographic separation and mass spectrometric detection are described in detail in the experimental section. on the basis of the data gathered from hplc-esims analyses, it is possible to obtain a better overview of the composition of individual extracts prepared from different plant species as well as information on the nature and structure of the phenolic compounds contained therein. the characterization and identification of individual polyphenolic compounds in plant extracts was performed by the analysis of the ms1-ms2 spectra that were recorded. the ms1 and ms2 spectra of the coumaric acid in the sample of the nettle extract can be seen in fig. 5. in the ms1 spectrum an ion with m/z 163.0471 related to the coumarone [m-h]− ion is observed. in the ms2 spectrum obtained by the fragmentation of coumaric acid, the ion with m/z 119.0612, which was formed by cleaving the carboxyl group from the coumaric acid molecule, is visible. another analyte found in the nettle sample was figure 5: ms1 and ms2 spectra corresponding to coumaric acid obtained by hplc-esi-ms/ms analysis of the nettle extract (15 min extraction) in the negative ionization mode. figure 6: ms1 and ms2 spectra of the corresponding chlorogenic acid obtained by hplc-esi-ms/ms analysis of the nettle extract (15 min extraction) in the negative ionization mode. chlorogenic acid, the presence of which was confirmed by the ms1 and ms2 spectra shown in fig. 6. the ms1 spectrum is dominated by the ion with m/z 353.0780 corresponding to the [m-h]− ion of chlorogenic acid. in the ms2 spectrum obtained by the fragmentation of the ion with m/z 353.0780, the ion with m/z 191.0557, which was obtained by cleaving -c9o3h7 from the chlorogenic acid molecule, is identified. in this spectrum another ion with m/z 179.0378, which was formed by cleaving -c7o5h6 from the chlorogenic acid molecule, is observed. in the ms2 spectrum an ion with m/z 173.0451 is also seen, which corresponds to this cleavage. an ion with m/z 135.0459 in ms2 seen in the chlorogenic acid spectrum was probably generated by cleaving the carboxyl group from the ion m/z 179.0378. as in the case of the hplc-esi-hrms analysis of nettle extracts, tandem mass spectrometry was used to identify polyphenolic substances in garlic extracts. as an illustration, the ms1 and ms2 chlorogenic acid spectra are presented in fig. 7. in the ms1 spectrum the molecular ion [m-h]− with m/z 353.0844, which is associated with chlorogenic acid, in a sample of the garlic extract is seen. in the ms2 spectrum the ions with m/z 191.0496 and 179.0298, which were formed from the precursor ion (m/z 353.0844) and belong to the illustrated chlorogenic acid fragments, are observed. the identification of each polyphenolic compound was possible by recording the retention time as well as mass spectra of samples and authentic standards. figure 7: ms and ms/ms spectra corresponding to chloroformic acid obtained by hplc-esi-ms/ms analysis of the bear’s garlic extract (10 min extraction) in the negative ionization mode. 46(1) pp. 35-38 (2018) hungarian journal of industry and chemistry vol. 46(1) pp. 39-42 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0009 silica monolithic capillary columns for hilic separations dana moravcová∗1 and josef planeta1 1institute of analytical chemistry of the czech academy of sciences, veveri 97, 602 00 brno, czech republic the monolithic capillary columns (0.1 mm × 150 mm) prepared by the acidic hydrolysis of tetramethoxysilane (tmos) in the presence of polyethylene glycol (peg) and urea were modified by zwitterionic stationary phases and evaluated under hilic separation conditions by employing a mixture containing nucleosides and nucleotides. the polymeric layer of zwitterions did not affect the high separation efficiency of the original silica monolith. the prepared zwitterionic columns exhibited high separation efficiencies in a range 61,000–289,000 theoretical plates/m for a 2methacryloyloxyethyl phosphorylcholine-based stationary phase and in a range 59,000–135,000 theoretical plates/m for a [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide-based stationary phase under optimal separation conditions. the grafted layer of zwitterions on the silica monolithic surface also significantly improved the separation selectivity to compounds of interest. keywords: hilic, silica monolith, nucleoside, nucleotide, capillary chromatography 1. introduction silica-based monolithic columns were developed by nakanishi and co-workers in the early 1990s [1, 2]. the preparation procedure of the columns has been improved over the years [3]. the unique structure of silica-based monoliths facilitates a high degree of permeability of separation beds and good mass transfer kinetics leading to a high separation efficiency. thus, liquid chromatography has been identified as an alternative to particle packed columns. while silica-based monolithic columns dedicated to reversed-phase separations are well established, the new stationary phases of hydrophilic interaction chromatography (hilic) separation are still a focus of research. concerning the published papers, the preparation of silicabased monoliths via the so-called “one-pot” process prevails. on the other hand, the chemical modification of preformed silica monoliths offers a well-defined silica skeleton of almost the same permeability and separation efficiency for all designed stationary phases. this contribution presents a characterization of silica-based monolithic capillary columns prepared by employing the second approach. the zwitterionic monomers [2-(methacryloyloxy)ethyl]dimethyl-(3sulfopropyl)ammonium hydroxide (medsa) and 2methacryloyloxyethyl phosphorylcholine (mepc) were used to prepare the desired stationary phases. the prepared columns were evaluated under hilic separation ∗correspondence: moravcova@iach.cz conditions by employing a mixture containing nucleosides and nucleotides. 2. experimental 2.1 material and instrumentation medsa and mepc monolithic capillary columns were prepared following a protocol outlined in our previous study [4]. in order to obtain a stable polymeric layer of mepc on the silica-based monolith, the polymerization time was prolonged to 6 hours. toluene, adenosine, uridine, cytidine and nucleotides – adenosine monophosphate (amp), adenosine diphosphate (adp), adenosine triphosphate (atp), cytidine monophosphate (cmp), cytidine diphosphate (cdp), uridine monophosphate (ump), and uridine diphosphate (udp) – were purchased from sigma–aldrich (prague, czech republic). acetic acid, ammonium hydroxide and acetonitrile (acn) (chromasolv, hplc gradient grade) were obtained from riedel-de haën (seelze, germany). high-performance liquid chromatography (hplc) equipment consisted of two identical syringe pumps (100dm model with a d-series controller, teledyne isco, lincoln, nebraska, usa) directly connected to a static nano mixer (60 nl volume) (upchurch scientific, oak harbor, washington, usa). the injection was performed by an electrically actuated e90-220 injection valve with a 60 nl internal loop (valco instruments, houston, texas, usa) and a t-splitter with a restrictor (fused hungarian journal of industry and chemistry vol. 46(1) pp. 43-46 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0010 determination of homocysteine in urine and saliva by microchip electrophoresis peter troška ∗1, anna mandžáková1, jasna hradski1, juraj ševčík2, and marián masár1 1department of analytical chemistry, faculty of natural sciences, comenius university in bratislava, mlynská dolina ch-2, ilkovičova 6, sk-84215 bratislava, slovak republic 2department of analytical chemistry, faculty of science, palacký university olomouc, 17. listopadu 12, cz-77146 olomouc, czech republic an online combination of isotachophoresis (itp) and capillary zone electrophoresis (cze) was employed on a microchip with a column-coupling technology for the determination of homocysteine in various body fluids. itp with its high concentration ability was used as a sample pretreatment and injection technique for cze, which facilitated the rapid and sensitive determination of homocysteine. the resolution of the analyte from other constituents present in real complex samples was enhanced by discrete spacers, which were added to the injected sample. a solid-phase microextraction (spme) pretreatment technique based on silverand barium-form resins was used prior to the itp-cze analysis to remove high concentrations of chloride and sulfate naturally present in the analyzed samples. the combination of the micropretreatment and microelectrophoresis techniques facilitated the determination of trace concentrations of homocysteine in samples of urine and saliva. keywords: homocysteine, body fluids, microchip electrophoresis, solid-phase microextraction 1. introduction homocysteine (hcy) is a non-proteinogenic sulfurcontaining amino acid whose metabolism is at the intersection of two metabolic pathways: remethylation and transsulfuration. in remethylation, hcy acquires a methyl group from n5-methyltetrahydrofolate or from betaine to form methionine. the reaction with n5methyltetrahydrofolate occurs in all tissues and is vitamin b12-dependent, whereas the reaction with betaine is confined mainly to the liver and is vitamin b12-independent. a considerable proportion of methionine is then activated by atp to form s-adenosylmethionine [1]. increased concentration levels of hcy in body fluids are considered to be an important risk factor or marker of various diseases, particularly cardiovascular ones [2]. in review papers [3–5], individual methods of determining hcy in biological samples are summarized. analytical methods using high-performance liquid chromatography (hplc) to separate hcy are some of the most commonly used. hplc methods for the quantification of hcy utilize derivatization procedures as well as procedures with non-derivatized hcy by electrochemical detection (ecd). the growing interest in clinical analyses has generated increased attention due to the rapid determination of hcy using automated methods. for this reason, the immunoas∗correspondence: peter.troska@uniba.sk say of hcy in plasma has become a preferred analytical approach [5]. recently several procedures have been published for the determination of hcy by capillary electrophoresis (ce). ce compared to hplc is more advantageous in terms of the need for a very small sample volume, good resolution, short analysis time, simplicity of automation and elimination of various (toxic) solvents. this is evidenced by many of the works that have dealt with the determination of hcy in body fluids, e.g. in plasma [6–18], serum [13] or urine [16, 19]. most of them dealt with the use of laser-induced fluorescence (lif) as a detection technique, however, uv detection was also used. a miniaturized form of ce, microchip electrophoresis (mce), was used for the separation and detection of hcy and glutathione. the analysis time on the glass microchip using amperometric detection was less than 80 s [6]. a polydimethylsiloxane (pdms) microchip produced by a simple photolithographic technique facilitated the rapid separation of hcy and cysteine [20]. mce analyses are more favorable than ce because they are considerably shorter, achieve higher degrees of separation efficiency and, in particular, reduce overall costs associated with chemical consumption and waste production. this paper deals with the development of a new method for the determination of hcy in various body fluids on a microchip with coupled-channels (cc). the page 1 page 2 page 3 page 4 page 5 page 6 page 7 page 8 page 9 page 10 page 11 page 12 page 13 page 14 page 15 page 16 page 17 page 18 page 19 page 20 page 21 page 22 page 23 page 24 page 25 page 26 page 27 page 28 page 29 page 30 page 31 page 32 page 33 page 34 page 35 page 36 page 37 page 38 page 39 page 40 page 41 page 42 page 43 page 44 page 45 page 46 page 47 page 48 page 49 page 50 page 51 page 52 page 53 page 54 page 55 page 56 page 57 page 58 page 59 page 60 page 61 page 62 page 63 page 64 page 65 page 66 page 67 page 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hungary 2biogas plant, magyar cukor zrt., pécsi u. 10, kaposvár, 7400, hungary residence time distribution (rtd) measurement-based analysis of mixing conditions on an industrial-scale (13, 000 m3) anaerobic digester of pressed sugar-beet slices at kaposvár sugar factory of magyar cukor zrt. was studied. the lithium salt tracing technique was applied, while the quantity of the lithium chloride tracer and the sampling of the effluent were designed by a preliminarily studied simulation model of mixing. the lithium concentration at the outlet was analysed by inductively coupled plasma–optical emission spectroscopy (icp-oes). taking into account the geometrical arrangement, the biogas flow produced and the cyclically changing recycle flow, various mixing models were generated with different compartmentalization and flow structures by applying the method of programmable process structures. the simulation-based approximate identification of the mixing model was accomplished by a heuristic approach that took into consideration multiple structures with changing mixing flows. a model with an advantageously small number of compartments and parameters was sought which satisfies the measured rtd. the results suggest the intensive mixing of upper levels with a poorly mixed lower level, which contributes to the long tail in the rtd. the actual set-up supports a good horizontal distribution of the sugar-beet slices and the microbial biomass, while the limited degree of vertical mixing helps to avoid the elutriation of the useful microbiome. the suggested mixing model will be combined with the formerly elaborated model involving 9 bacterial groups. keywords: anaerobic digestion, mixing of digester, residence time distribution, lithium tracing, programmable process structures 1. introduction the mixing of anaerobic digesters is a critical issue because it should support the uniform distribution of raw materials to be digested and the bacterial biomass along the cross-section of the unit. moreover, the excessive sedimentation of the solid (bacterial) phase at the bottom of the digester should be avoided. however, an unnecessarily high degree of mixing may elutriate the bacterial biomass that decreases the effectiveness of transformations and may cause surplus environmental load. the computational modelling of anaerobic digesters was developed from the modelling of wastewater treatment and degradation [1, 2] and from the adm models designed by iwa [3, 4]. a comprehensive review from 2013 is available [5]. knowledge about mixing in large biogas digesters is still in its infancy, so the objective of this study is to broaden this by determining the minimum retention time of substrates fed into anaerobic digesters and estimate the distribution time of substrates before being extracted from the investigated digester. *correspondence: varga.monika@ke.hu over the last century, compartmentalized models were successfully used given the lack of computational fluid dynamics (cfd) models available, e.g. for studying an interesting scale-up problem, where the partially mixed pilot performed better than the perfectly mixed laboratory unit [6]. moreover, at that time, a review comparing compartmentalization with cfd was published [7] which concluded that cfd is the most scale–independent method for mixing and scale-up studies, however, it is hampered by limitations such as high computational demands and the inadequacy of submodel consideration, e.g. biokinetics. in a recently published detailed review [8], the authors concluded that “compartmental models allow multi-scale modelling with low computational time compared to a full coupled model (e.g. reactive numerical simulations). thanks to these main characteristics, compartmental models are able to model complex full-size industrial systems. an effective compartment model could handle multiple, multiphysics phenomenological models (detailed kinetic reaction scheme, complex heat and mass transfer model, population balance, etc.) that could not be included in cfd analysis. observed deviation between https://doi.org/10.33927/hjic-2019-19 mailto:varga.monika@ke.hu 44 tankovics, takács, szendefy, csukás, and varga fully detailed cfd model and compartment model show very small results deviation despite of very significant reduction in calculation time (3 orders of magnitude).” an interesting new example of a hypothesis-driven compartmental model is given in [9]. two full-scale digesters from a biogas plant (2, 000 m3 and 1, 500 m3) equipped with different mixing systems and filled with different substrates were investigated by kamarad et al. [10]. to characterize the substrate distribution, solutions of lithium hydroxide monohydrate were used in tracer tests at concentrations of 45− 50 mg li+/kg ts in digesters. the tracer concentration in the effluent of the digester was measured. although the data calculated by cfd methods were in very good agreement with the results, a full comparison was not made kaposvár sugar factory of magyar cukor zrt. developed an internationally straightforward anaerobic fermentation technology to generate onsite used and surplus energy with a reduced amount of waste emitted by producing fuel gas of high methane content from the pressed sugar beet slices. in a former phd thesis [11], a detailed simulation model was developed and validated for an approximately perfectly mixed pilot unit that took into consideration 9 pseudogroups of bacteria by applying the available earlier version of direct computer mappingbased modelling methodology. the scaling up of the model to an industrial scale [12] requires more detailed knowledge about the hydrodynamic conditions of the appropriately compartmentalized volume. the objective of this work was to measure and analyse the residence time distribution of a large industrial unit by a lithium tracer technique. the final goal of this analysis was to embed the formerly developed detailed digestion model into the compartmentalized mixing model to enhance the investigated fermenter. 2. experimental work the industrial digester (see fig. 1) was a cylindrical unit with a diameter of 25 m and height of 28 m. the effluent was removed from a volume of approximately 13, 000 m3 at a level of 20 m. spatially uniform feeding and appropriate mixing was ensured by the recycle flow from a level 20 m in height from the base of the unit and fed into the annularly placed 6 subsequent bottom segments with a prescribed cyclic change of the flow. the pressed sugar beet slices were also fed into this recycle flow via a screw feeder. mixing was enhanced significantly by the increasing upward flow of the generated biogas. moreover, three small mechanical mixers ensured the raw materials and bacteria were uniformly distributed in the lower third of the unit. the slowly accumulating inorganic residue could be removed from the middle of the bottom of the digester by means of a slowly rotating agitator. figure 1: schematic diagram of the industrial-scale fermenter of 13, 000 m3 in volume 2.1 tracing and measurement technique for the tracing of the flow, 40 kg of lithium chloride p.a. was dissolved in 150 litres of tap water. considering the contamination of sugar beet slices with many ions, lithium was chosen given the sensitivity of its measurements. a blank sample was tested and a calibration prepared by adding known amounts of lithium chloride to the blank solution of realistic composition. this amount was added to the sludge flow of fresh sugar beet slices at a rate of 43 m3/h on average. the duration of tracing was 150 seconds, while the main recycle flow was switched off during this time. before and after the tracer inlet, the recycle flow was maintained at 200 m3/h. differing from the geometrically arranged order of annular segments 1-2-3-4-5-6, the actually applied order of feeding was 1-2-(3)-6-4-5, while during the experiments the inlet to segment #3 was closed (because of a malfunctioning valve). accordingly, the cyclic feeding sequence was changed to 1-2-6-4-5 over 360 seconds. the tracer was fed into segment 4, while the samples were taken from the effluent and discharged from segment 5 at a height of 20 m. the draft samples of 1-2 litres in volume were filtered before being analysed. the concentration of li+ was measured by the icpoes spectrometer at kaposvár university. 2.2 modelling and simulation methodology for the modelling and simulation of the flow structure of the fermenter, the methodology of programmable process structures (pps) was applied [9, 10]. in pps (see fig. 2), the locally programmable structure of process models could be generated from two general meta-prototypes and from the standardized description of the actual process network automatically, resulting in the dynamic structure of unified state and transition hungarian journal of industry and chemistry residence time distribution-based analysis 45 figure 2: schematic diagram of the generation of the process model by the method of programmable process structures elements. the prototype elements, which describe the functionalities of the model, could also be derived from the general meta-prototypes. the freely editable, actual prototype programs contain symbolic input, parameter and output variables as well as a locally executable program code. in various applications, many state and transition elements can be modelled with the same or similar, reusable local programs (referred to as actual prototypes). the state and transition elements of the actual model can be parameterized and initialized concerning their casespecific prototypes. its execution, namely connectionbased communication between the state and transition elements of the programmed structure, is solved by the general-purpose kernel program of the method. during the simulation, the actual elements are initialized by initial conditions and parameters, moreover, the output values are recalculated stepwise by taking into consideration input and parameter data according to the associated local program prototype. the identified input and output connections of the extensive/intensive properties and signals make the combined execution of the balance-based and signal-based functionalities possible. 3. results and analysis 3.1 experiments the quantity of the lithium chloride tracer (40 kg) and the sampling of the effluent during the measurement of the rtd were designed by some preliminarily studied, approximate mixing models. the concentration of lithium chloride in the effluent was measured every 0.5−2 hours during the first period and daily or even less frequently over the following 23 days (when production slowed down by ending campaign). the data are summarized in table 1 and in fig. 3. 3.2 possible flow structures and parameters by taking into consideration the geometrical layout, the produced biogas flow and cyclically changing recycle flow, various mixing models with different compartmentalization and flow structures were generated by applying the method of programmable process structures. table 1: measured concentrations of lithium chloride in the effluent sample id date time, hours li+, mg/l 0 blind 0 <0.100 1 2018.12.18 0.5 <0.100 2 2018.12.18 1 0.226 3 2018.12.18 2 0.347 4 2018.12.18 4 0.311 5 2018.12.18 6 0.237 7 2018.12.18 8 0.811 8 2018.12.19 26 0.627 9 2018.12.19 38 0.538 10 2018.12.20 48 0.625 11 2018.12.22 96 0.536 12 2018.12.24 144 0.401 12b 2018.12.26 192 0.516 13 2018.12.28 240 0.423 14 2019.01.02 360 0.325 15 2019.01.04 408 0.361 16 2019.01.07 480 0.384 17 2019.01.10 552 0.323 the most detailed compartmentalization (d1) is shown in fig. 4. here the sludge zone of the process unit was divided into three vertical layers which were divided further into an inner cylinder, surrounded by an annulus that was divided into six parts. the mixing flows between the 21 (approximately perfectly mixed) compartments are as follows: circflowmix: cyclically changing recycle flow, superposed by a bidirectional mixing flow between the annular slices above each other; gasflowmix: bidirectional mixing flow, induced by the upward biogas flow between the compartments above 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0 5000 10000 15000 20000 25000 30000 35000 40000 c o n ce n tr a ti o n , m g /l time, hour measured tracer concentration in effluent figure 3: measured tracer concentration of li+ in the effluent of the industrial-scale fermenter (40 kg of lithium chloride dissolved in 150 litres of tap water was added to a sludge of sugar beet slices that entered segment #4 at a flow rate of 43 m3/h for 150 seconds). 47(2) pp. 43–51 (2019) 46 tankovics, takács, szendefy, csukás, and varga figure 4: the most detailed schematic diagram of the fermenter (scheme d1). each other (for practical considerations, circflowmix and gasflowmix can be integrated into a single flowmix); permix: peripheral bidirectional mixing flow between the subsequent annular slices of the same layer , horizontally; radmix: radial bidirectional mixing flow between the annular slices and the inner cylinder of the same layer, horizontally. the flow rate of the biogas increased as the height of the unit increased. accordingly, gasflowmix was higher between layers 2 and 3 than between 1 and 2. it is worth mentioning that the outflow rate of the effluent was considerably less than the inflow rate of the sludge composed of pressed sugar beet slices because a significant proportion of the raw material was converted into biogas that escaped through the upper gas dome. in scheme d2 (fig. 5 which was finally proven to be the best solution), the inner cylinder and the related vertical and horizontal mixing flows were removed because they slowed down the mixing in scheme d1 by an unfeasible degree. as a further simplification, the upper layer was not decomposed at all. it should be noted that an interaction between the changes in the structures and their parameters exists. as an example, scheme d3 (fig. 6) behaved in a similar way to d2 with the highest horizontal mixing flows in the upper layer. planned future research will focus on using less compartments which might also be advantageous in terms of embedding the detailed dynamic model of anaerobic digestion into the flow structure. accordingly, scheme d4 (fig. 7) was also tested, where only the lower layer was decomposed. as a marginal solution, the case of scheme d5 (fig. 8) was also studied with only vertical decomposition of the process unit. figure 5: schematic diagram of the best performing fermenter (scheme d2). 3.3 generation of the simulation models the process network of the various schemes can be defined by a general declarative program. a characteristic part of the definitions of scheme d2 is as follows: states([c11],[sludge]). states([c12,[sludge]). ... states([c36,[sludge]). states([env,[sludge,feed]). transitions([c11],[flowmix,permix]). transitions([c12],[flowmix,permix]). ... transitions([c26],[flowmix,permix]). transitions([c31],[permix]). transitions([c32],[permix]). figure 6: simplified schematic diagram of the fermenter without decomposition of the upper layer (scheme d3). hungarian journal of industry and chemistry residence time distribution-based analysis 47 figure 7: a more simplified schematic diagram of the fermenter (scheme d4). figure 8: trial in the absence of horizontal compartmentalization (scheme d5). ... transitions([c35],[permix, feeding\_recirc]). transitions([c36],[permix]). dcode(sludge,[li]). dcode(feed,[li]). where states and transitions are declared by the state and transition elements in the given compartments, respectively. meanwhile, the lowest level components of the state elements are described by the dcode() predicates. the transition-based representation of the flow structure is defined by the facts of predicate: trans(transitionname,compartment, inputcomponents,inputsigns, outputcomponents,outputsigns). for example, trans(flowmix,[c13], [n([c13],[sludge]), n([c23],[sludge])], [n([c13],[sludge]), n([c23],[sludge])],[],[]). generates bidirectional connections for mixing flows between compartments [c13] and [c23] of the first and second layers, respectively. similarly, trans(permix,[c32], [n([c32],[sludge]), n([c33],[sludge])], [n([c32],[sludge]), n([c33],[sludge])],[],[]). generates peripheral flows between compartments [c32] and [c33] in the third layer. the initial concentrations and parameters of the various state and transition elements were recorded in an ms excel file from where they were transformed into a textual form of declarative predicates. according to fig. 2, the automatic generation of the programmable process structures was conducted: • from the two general prototypes [9, 10], • from the textual description of the actual process network, and • from the textual declaration of initial values and parameters. the automatically generated structural model of scheme d2 is illustrated in fig. 9. 3.4 local programming of the generated process structure the functionalities of the flow-structure models can be represented by locally executable programs embedded in the prototype elements. the prototype elements can be prepared from the copies of the meta-prototypes, e.g. the local program for the calculation of flowmix is presented below: figure 9: programmable process structure of scheme d2. 47(2) pp. 43–51 (2019) 48 tankovics, takács, szendefy, csukás, and varga { program ( ’ p e r m u t a t i o n ( inpconcs , [ d ( [ coord1 , s ludge , l i ] , [ c1 ] , g_m3 ) , d ( [ coord2 , s ludge , l i ] , [ c2 ] , g_m3 ) ] ) , p e r m u t a t i o n ( p a r a m e t e r s , [ d ( vgas , [ vgas ] , m3_h ) , d ( v c i r c , [ v c i r c ] , m3_h ) ] ) , g ( dt , dt) , p l u s f l o w ( coord1 , vci rc , vplus ) , dm1 i s ( vgas+vplus ) / 6 0 * ( c2−c1 )*dt, dm2 i s ( vgas+vplus ) / 6 0 * ( c1−c2 )*dt, outcomps = [ d ( [ coord1 , s ludge , l i ] , [dm1] , g ) , d ( [ coord2 , s ludge , l i ] , [dm2] , g ) ] , ou ts igns = [ ] , re po r t = [ ] . p l u s f l o w ( [ coord1 ] , vci rc , vplus ) :− sub_atom ( coord1 , 2 , 1 , 0 , column ) , g ( s e l e c t e d , column ) , ! . p l u s f l o w ( _ , _ , 0 ) . ’ ) } this program illustrates how the input, parameter and output data are represented by the unified d(identifier,list_of_values,dimension) triplets. the input data for calculations originated from the respective compartments coord1 and coord2. the parameters define the vgas mixing flow associated with the gas flow and the vplus mixing flow generated by the recycle upflow between the given vertical segments. the actually active segment was determined by the integer value of column in the g(selected,column) global predicate (which was actualized by another local program, responsible for the cyclic switching of the recycle flow). the auxiliary clause plusflow() considers mixing flow vcirc only if the recirculation is actually associated with the given compartments, otherwise the surplus mixing is equal to zero. the outcomps output of the program forwarded the changes in the amount of tracing component dm1 and dm2 in the compartments coord1 and coord2, respectively. 3.5 evaluation of the rtd measurements the mass flow of the produced biogas was calculated from the measured total volumetric flow rate of the three parallel operating digesters, divided according to the individually measured loads of sugar beet slices of the parallel lines whilst taking into consideration the measured composition of the biogas. the slightly changing output 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0 1000 2000 3000 4000 5000 6000 c o n ce n tr a ti o n , p p m time, min characteristic part of shemes d1 and d5 measured values d1 scheme d5 scheme figure 10: initial period of scheme d1 that was insufficiently mixed and scheme d5 that was overmixed. flow of the effluent was calculated from the changing load and biogas mass flows. regarding the identification and validation of the multiple structure, it must be emphasized that this task was underdetermined. considering the multiple interactions between the structures and parameters, instead of a rigorous optimization procedure, a heuristic trial and error approach was applied, controlled by the main features first and then the values of the normalized root mean square error (nrmse) in the refinement. the evaluation was effectively aided by monitoring the change in concentrations in each compartment. first, d1 (being insufficiently mixed) and d5 (being overmixed) were excluded as can be seen in fig. 10. afterwards, d2-4 were studied and based on the calculated nrmse values, d3 and d4 were stepwise rejected. finally, the parameters of d2 were refined. the simulated and measured data are illustrated in figs. figs. 11–14 in addition to the calculated nrmse values. fig. 10 (and many trials using other parameters) showed that even schemes d3-5 were unable to model the evident initial peaks of the measurements. 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0 5000 10000 15000 20000 25000 30000 35000 c o n ce n tr a ti o n , p p m time, min simulated effluent concentration for scheme d3 simulated measured figure 11: trial using horizontal compartmentalization in two lower layers only (scheme d3, nrmse = 12.10 %). hungarian journal of industry and chemistry residence time distribution-based analysis 49 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0 5000 10000 15000 20000 25000 30000 35000 c o n ce n tr a ti o n , p p m time, min simulated effluent concentration for scheme d2 simulated measured figure 12: trial using horizontal compartmentalization in three layers (scheme d2, nrmse = 12.08 %). the horizontal decomposition in all layers (without an inner tube) is able to express the main features using many parameters (an example is shown in fig. 11). decomposition scheme d2 (compartment volume is 685.3 m3) with improved parameterization describes the measured data better (see fig. 12). the change in the concentration in the various compartments (except for the traced bottom and output top ones) is shown in fig. 13. this shows that because of the changing input bottom compartment of the recycle flow, the initial peak in concentration does not appear in each compartment. the long tail is partly a consequence of the great difference between the input feed and output effluent flows as well as of the limited degree of mixing between the layers and annular zones (especially in the bottom layer). it is also worth noticing the constant difference in concentration in the compartments. unfortunately, the continuation of measurements was limited by the closing end of the campaign. moreover, were they to continue, the sensitivity of the concentration measurements would decrease far below 0.3 ppm. the computation time, depending on the number of 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0 5000 10000 15000 20000 25000 30000 35000 c o n ce n tr a ti o n , p p m time, min effluent concentration for scheme d2 (modified parameters) calculated measured figure 13: scheme d2 with a feasible parameter set (nrmse = 21 %). 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 0 5000 10000 15000 20000 25000 30000 35000 c o n ce n tr a ti o n , p p m time, min calculated concentrations in the compartments of scheme d2 sludge [c22] li sludge [c23] li sludge [c24] li sludge [c25] li sludge [c26] li sludge [c21] li sludge [c32] li sludge [c33] li sludge [c35] li sludge [c34] li sludge [c11] li sludge [c12] li sludge [c13] li sludge [c15] li sludge [c16] li sludge [c36] li sludge [c31] li figure 14: change in concentration in the various compartments of the experiment shown in fig. 12. compartments and the flow structure, was between 2 and 90 minutes but was typically less than 10 minutes. a large difference in the volume of the compartments leads to an increase in computational efforts, while an equidistant volume distribution accelerates computation. 4. discussion the results prove that the fermenter is thoroughly mixed but by no means perfectly mixed. accordingly, detailed modelling needs to take into consideration hydrodynamics, e.g. by using mixing flows between the compartments of the volume. it should be emphasized that an interaction between the fermentation model and mixing exists because mixing is considerably enhanced by the produced biogas. in due course, this coupling has to be taken into consideration in the final implementation of the model. it is a specific feature of the residence time distribution of anaerobic digesters that the output liquid effluent flow is much less than the input load of the fresh sugar beet sludge (because of the production of biogas). this contributes to the slowly decreasing long tail of the rtd. by considering the approximately identified parameters, the mixing conditions can be characterized by the following features: • in the bottom layer, no bidirectional, horizontal mixing flow occurs between the annular segments. the horizontal mixing flow between the annular segments can also be neglected in the middle layer. however, in the intensively bubbling upper layer, significant mixing occurs characterized by a flow rate of 200 m3/h between the adjacent segments. • regardless of the very limited horizontal mixing in the bottom and middle layers, the appropriate distribution of the fluid and solid phases is achieved by the frequent change in location of the recycle flow (and feed) between the bottom segments. 47(2) pp. 43–51 (2019) 50 tankovics, takács, szendefy, csukás, and varga • the estimated mixing flow rate of the vertical sludge, generated by the upward biogas flow, was 150 m3/h and 300 m3/h between the bottom & middle and middle & upper layers, respectively. • the estimated vertical mixing flow rate in the changing active sites, generated by the recycle flow, was 200 m3/h between the vertically connected segments (i.e. the mixing ratio was 0.5). 5. conclusions the kaposvár sugar factory of magyar cukor zrt. has developed an internationally straightforward anaerobic fermentation technology to generate onsite used and surplus energy with decreased emissions of waste by producing fuel gas of high methane content from pressed sugar beet slices. the development of an improved computer model as well as the analysis-based development of the technology required more detailed knowledge of the hydrodynamic conditions found within the process unit. the objective of this work was to measure and analyse the rtd of the appropriately compartmentalized industrial unit of 13, 000 m3 in volume. spatially uniform feeding and appropriate mixing was ensured by the recycle flow, fed into the annularly placed six subsequent bottom segments with cyclic changes in location. the pressed sugar beet slices were also fed into this recycle flow via a screw feeder. mixing was enhanced significantly by the upward increasing upstream flow of generated biogas and three mechanical agitators. by considering the geometrical arrangement, produced biogas flow and cyclically changing recycle flow, various mixing models were generated with different compartmentalization and flow structures via the method of programmable process structures. a lithium salt-based tracer technique was applied, while the quantity of the lithium chloride tracer and the sampling of the effluent during the measurement of the residence time distribution were designed by some preliminarily studied simulation models of mixing. the lithium chloride concentration at the outlet was initially measured every 2 hours and daily or less frequently during longer periods. the lithium chloride concentration was analyzed by icp-oes. for the simulation-based approximate identification of the mixing model, a heuristic approach was used that took into consideration multiple structures with changing mixing flows. a model of an advantageously smaller number of compartments and parameters was sought which satisfies the measured residence time distribution. the results suggest the intensive mixing of upper levels with a limitedly mixed lower part that contributes to the long tail of the rtd. the applied arrangement supports the horizontal distribution of the sugar beet slices to be digested and the multiple groups of bacteria. moreover, limited vertical mixing helps to avoid the elutriation of the bacteria and undigested organic materials into the environment. the suggested mixing model will be combined with the formerly elaborated model of the anaerobic fermentation process that consists of 9 groups of bacteria in our future work. abbreviations adm anaerobic digestion model cfd computational fluid dynamics icp-oes inductively coupled plasma optical emission spectroscopy iwa international water association nrmse normalized root mean square error pps programmable process structures rtd residence time distribution ts total solid content acknowledgement the authors are grateful for the financial support from the project efop-3.6.1-16-2016-00007. references [1] batstone, d.j.; keller, j.; newell, r.b.; newland, m.: modelling anaerobic degradation of complex wastewater. i: model development. bioresour. technol., 2000, 75, 67–74, doi: 10.1016/s09608524(00)00018-3 [2] batstone, d.j.; keller, j.; newell, r.b.; newland, m.: modelling anaerobic degradation of complex wastewater. ii: parameter estimation and validation using slaughterhouse effluent. bioresour. technol., 2000, 75, 75–85, doi: 10.1016/s0960-8524(00)00019-5 [3] blumensaat, f.; keller, j.: modelling of two-stage anaerobic digestion using the iwa anaerobic digestion model no. 1 (adm1). water res., 2005, 39, 171–183, doi: 10.1016/j.watres.2004.07.024 [4] fezzani, b.; cheikh, r.b.: modelling of the mesophilic anaerobic co-digestion of olive mill wastewater with olive mill solid waste using anaerobic digestion model no. 1 (adm1). bioresour. technol., 2008, 99, 6565–6577, doi: 10.1016/j.biortech.2007.11.035 [5] lauwers, j.; appels, l.; thompson, i.p.; degrčve, j.; impe, j.f.v.; dewil, r.: mathematical modelling of anaerobic digestion of biomass and waste: power and limitations. prog. energ. combust., 2013, 39, 383–402, doi: 10.1016/j.pecs.2013.03.003 [6] csukás, b.; balogh, s.: combining genetic programming with generic simulation models in evolutionary synthesis. computers in industry, 1998, 36, 181–197, doi: 10.1016/s0166-3615(98)00071-2 hungarian journal of industry and chemistry https://doi.org/10.1016/s0960-8524(00)00018-3 https://doi.org/10.1016/s0960-8524(00)00018-3 https://doi.org/10.1016/s0960-8524(00)00019-5 https://doi.org/10.1016/j.watres.2004.07.024 https://doi.org/10.1016/j.biortech.2007.11.035 https://doi.org/10.1016/j.biortech.2007.11.035 https://doi.org/10.1016/j.pecs.2013.03.003 https://doi.org/10.1016/s0166-3615(98)00071-2 residence time distribution-based analysis 51 [7] guillard, f.; tragardh, c.: modeling of the performance of industrial bioreactors with a dynamic microenvironmental approach: a critical review. chem. eng. technol., 1999, 22, 187– 195, doi: 10.1002/(sici)1521-4125(199903)22:3<187::aidceat187>3.0.co;2-9 [8] jourdan, n. et al.: compartmental modelling in chemical engineering: a critical review. chem. eng. sci., 2019, 210, 115–196, doi: doi.org/10.1016/j.ces.2019.115196 [9] norregaard, a. et al.: hypothesis-driven compartment model for stirred bioreactors utilizing computational fluid dynamics and multiple ph sensors, chem. eng. j., 2019, 356, 161–169, doi: 10.1016/j.cej.2018.08.191 [10] kamarad, l.; pohn, s.; bochmann, g.; harasek, m.: determination of mixing quality in biogas plant digesters using tracer tests and computational fluid dynamics. acta univ. agric. silvic. mendelianae brun., 2013, 61(5), 1269–1278, doi: 10.11118/actaun201361051269 [11] varga, m.: economic optimization of sustainable complex processes (model based optimization under uncertain cost parameters for industrial scale anaerobic fermentation of sugar beet slice). phd thesis, kaposvár university 2009, (in hungarian) [12] csukás, b.; varga, m.: préselt répaszelet anaerob fermentációján alapuló biogáz előállítás számítógépi modellezésének előzetes vizsgálata. 2008. témajelentés. folyamatinformatika kutató – fejlesztő bt., kaposvár (in hungarian) 47(2) pp. 43–51 (2019) https://doi.org/10.1002/(sici)1521-4125(199903)22:3<187::aid-ceat187>3.0.co;2-9 https://doi.org/10.1002/(sici)1521-4125(199903)22:3<187::aid-ceat187>3.0.co;2-9 https://doi.org/doi.org/10.1016/j.ces.2019.115196 https://doi.org/doi.org/10.1016/j.ces.2019.115196 https://doi.org/10.1016/j.cej.2018.08.191 https://doi.org/10.1016/j.cej.2018.08.191 https://doi.org/10.11118/actaun201361051269 https://doi.org/10.11118/actaun201361051269 introduction experimental work tracing and measurement technique modelling and simulation methodology results and analysis experiments possible flow structures and parameters generation of the simulation models local programming of the generated process structure evaluation of the rtd measurements discussion conclusions hungarian journal of industrial chemistry veszprem vol. 30. pp. 181185 (2002) equivalent system method applied to multivariable cascade control of industrial tubular furnace a. g. abilov, 0. tuzunali', z. tela tar and h. g. ilk (department of electronics engineering, faculty of engineering, ankara university, 06100-tandogan, ankara!i'urkey) received: july 3, 2002 the purpose of this paper is to apply and improve a multi variable advanced control structure on the basis of equivalent system teclmique for two-flow tubular furnace, which has widespread application in industrial fumace plants. after analyzing the dynamic properties of furnaces, it was concluded that these furnaces are symmetric mimo processes, having two inputs and two outputs. there are a numerous reciprocal interactions between input and output variables. for this reason, equivalent system method was employed to investigate and develop advanced control structures for these furnaces. according to this method, symmetric mimo system was divided into two equivalent separate systems. finally, the equivalent model control design of combined feedback/feedforward multivariable cascade system is given and the results are presented. keywords: industrial furnace plant, symmetric mlmo systems, combined feedback/feedforward control structure introduction furnaces are the basic and most important industrial units of petroleum refineries and petrochemical processes. the furnaces can have single or multiple flows according to their technological structures. they are made up from the regions of convection and radiation_ the heat exchange between chimney gasses and petroleum flows is realized in the regions of convection and radiation. sufficient quantity of oxygen, required for the control of the burning process in these regions, is obtained from the air. in addition, an optimum amount of air is desired for the economical and ecological sound burning in furnaces. there appeared many studies in literature about controlling the burning process [l-7]. these studies have shown that furnaces are multivariable, distributed, complex dynamic control systems. in multiple flow furnaces, there are also large delays in their dynamic channels and cross relationships between the control parameters. in most applications, a linear model was used to present the dynamic behaviour of the process (impulse/step response function, transfer function, state­ space model). due of these complexities, it is necessary to investigate the more effective multivariable advanced control structures working on the basis of equivalent system technique [8]. the following steps are carried out in the study of the equivalent system method: transformation of the system to the equivalent method. constructing the control algorithms of the system according to equivalent model. application of the control algorithms to separate systems working under different conditions. performance evaluation. in this paper, an advanced multivariable cascade equivalent control system has been developed for two flow industrial petroleum refinery furnaces. the following sections present the proposed algorithm in detail. the simulation results are given. finally, discussion and conclusion are presented. process description in the industrial furnace plant, crude oil is passed through two spiral pipes and divided into two flows and then it enters into the burning chambers in the convection and radiation sections. firstly, the petroleum contact information: e-mail: abilov@science.ankara.edu.tr; tuzunalp@ science.ankara.edu.tr; telatar@science.ankara.edu.tr; iik@science.ankara.edu.tr 182 fig.l schematic diagram of tubular furnace. fc: the feed control, pc: control of pressure, rc: ratio control, tc1: temperature control of the chimney gasses, tc2: the outlet temperature of the petroleum · flow is heated by chimney gasses, and then at the outlet, two flows are combined by the flame in the burning chamber. the unit operates between 700 and 900 °c intervals with a duty to bring the outlet crude oil to 320 °c, and to leave the stack gases at 750 °c. the outlet temperature of the petroleum in the left and right pipeline is obtained by supplying sufficient quantity of oxygen and natural gas to the right and the left fuel chambers. this creates reciprocal relations between these parallel transfer channels. when these properties of the furnace are considered, it is quite important to develop and apply new temperature control algorithms. in a burning process, the oxygen/fuel ratio must be omms:o~max· so, the complete combustion affecting the concentration in the chimney gases that pollute the environment is achieved by adjusting the vacuum required for the furnace. on the other hand, the complete combustion is evaluated by the concentration of the oxygen in the chimney gasse-s. besides, the temperature of the combustion depends significantly on the quantity of the used air. the schematic diagram of an industrial petrol refinery furnace is illustrated in fig.l. transfer function of the process our industrial research on the dynamic characteristics of furnaces reveal that furnaces consist of a mimo system with two inputs and two outputs and that there are symmetric reciprocal interactions between the input­ output ''ariables. a block diagram showing the dynamic channels is given in fig.2. where x." x:;, xr, y,.y,::. y~tl and yt~ are the consumption of natural gas. given to the left and light fuel chambers the consumption of the pettoleum flow given to furnace. the outlet temperatures of the pettoleum in the left and right sides and the temperature of the chimney gases which enter the left and right sections of the convection chamber, respectively. · the transfer function of the dynamic channels was determined from the reaction curve of the process fig.2 block diagram of the dynamic channels fig.3 block diagram of the symmetric control systems with two inputs-outputs obtained by ± step disturbances to the fuel inlet of the furnace. since the furnace with two flows is a symmetric process, the transfer functions are as follows. w11 (s)=w22 (s), w12 (s)=w2/s), kn(s)=k22 (s) (1) the laplace domain transfer function of the symmetric multivariable system is: w. (s)"' 5 ·10 2 · e·180s 11 356·106 s3 +7.96·104 s 2 +4.71·102 s+l oc i % max. fuel consumption (2) "' ( ) 4·102 -!80s rr12 s e 8.74 ·106 s3 + 10.9 · hr' s 2 + 5.31·102 s + 1 °c i% max. fuel consumption (3) 1.6·102 ·180s e 5.22·106 s3 +8.68·104 s2 +4.88·102s+ 1 "c i% max. fuel consumption (4) k ( ~10·102 ·30• u s, e 3680s2 + 280s + 1 "c i% max. fuel consumption {5) symmetric multivariable control system of the p:i:'ocess block diagram of symmetric conttol system with two input.-output for two flow furnaces is given in fig.3. x,(s) w,,,(s)= w<(s) ± wl(s) y•(•) + x,(-'-s)'---fvr_,...t-_w._:'',(.:..:s)_·_w._l(:.:._•)_±w----'-',(s)'-->..j-+~~~~y,(s) + fig.4 block diagram of control of the equivalent transfer function :xt(s) y•qv(s) fig.5 block diagram of multi variable cascade equivalent seperate system the differential equations of this system can be formulated as follows. here, w0 (s) is the transfer function of the main control channel; w; (s) is the transfer function of the inside cross dynamic channel and wa~ )is the transfer function of the petroleum flow as a disturbance. since the system is symmetric. w0 (s)=wu(s)=w22 (s) , w1(s)=w12(s)=w21(s) , wft(s)=w1,(s) (8) due to the symmetry of the system, the transfer function of the main and cross channels are identical and in accordance with the other. differential equation of the controller system is: u1 (s) = wr(s) [xj (s)-y1 (s)j, uz (s)== wr(s) fxz (s)-yz (s)] the form of transfer function matrices (9) y(s) = [w0 (s)e+ w;(s)a]u(s)+was)e f(s) {10) where, a=jo ii e=ll 0 i f(s)==lft(s)~ it 0 0 1 f2 (s~ 183 fig.6 combined feedforward/feedback equivalent separate system equivalent decoupled control system equivalent block diagram of the relevant control system is given in fig.4. in this system, because the transfer function of the equivalent channels is symmetric, it is identified as, equivalent multivariable cascade control system a block diagram of the multi variable cascade control of the equivalent system is shown in fig.5. in this separated system, the object of the control was also divided into two stages. the transfer function of the internal chimney gas is k11(s) and the transfer function of the equivalent channel is weq(s). in this system, the same controller could be used for both of two control loops [l-4}. the main feature of the system is that the optimum parameters of the stabilizator and the regulator controller are found in two control loops with different frequencies. for this purpose, firstly the parameters of the stabilizator loop are calculated and then the parameters of the regulatpr are evaluated within the framework of the calculated optimum parameters. in this stage, for the evaluation of the parameters of the regulator loop, a transfer function is obtained by the combination of the transfer function of the closed loop stabilizator and the transfer function of the equivalent channel. so the transfer function of the controller qbject can be written as follows; (l3) combined feedback/feed forward control system in equivalent multivarlable cascade as known, these systems consist of two loops. one of them is open loop based on compensating the exterior effects {disturbances) and the other is dosed loop based u(s)= wr(s )ef,x(s)y(s)} (11) on the feedback control principle 18*101. combined 184 table i the optimum pi parameters of the control systems in furnace control loop of loop of loop of systems regulaton stabilization compensation kx104 tx104 kxl04 tx104 kxl04 tx104 forwu(s) -5.85 0.05 for weqv(s) 44 0.01 multi variable cascade 5.5 0.013 70 1.12 control combined multi variable 5.5 0.013 70 1.12 0.1 20 cascade open and closed loop multivariable cascade control structure of the furnace is given in fig.6. u(s) = x1 (s)-wri (s)u * (s); (14) (15) h(s) = wf (s )x/1 (s); (16) yeqv(s)= yeqv 1 (s)+h(s); (17) ycgl (s) = k 11 (s )u(s); (18) the transfer function of the whole system between the inputs (xh xn) and the output (y*eqv) are described as follows, * w.qvl(s) y,qvl (s) 1 + w, 4 • 1 (s )vri (s )wr 2 (y )+ wr 1 (s )k11 (s (• + (20) [ wf,(s)+wr,(s)kll(s)wf,(s) { 'ur f)~ + w () +wrii,sjy•,i_s xfl(s) e-q~rl s from this statement, according to provision of the absolute invariant, the transfer function of the compensator is defined as follows. wc(s) ==[w.fl(s) + wrj(s)kn(s) wil(s)] i (21) mostly, in this type of systems, because the transfer function detennined by the principle of the absolute invariant consists of a higher degree of fraction, realization of this statement can be difficult. this feature can practically be expressed by showing the compensatory as a simplified differential block, wc(s) = k{ tsi(ts+ 1)] (22} naturally, the compensator block expressed in this way cannot completely compensate the external disturbances. but, by selecting the appropriate parameters of the k and t, the outlet value of y;tp·l 15.0 1-w11 (s) 2-weqv(s) 3-cascade control ~ 10.0 ofweqv(s) ~4-k 11 (s) <i 5.0 0.0 0.0 600 1200 1800 2400 3000 3600 4200 4800 5400 time (second) fig.7responses of pi control to the 1-w11(s), 2-weqv(s), 3· cascade control of weqv(s) and 4k11(s) could be made independently from the external disturbance. since the block of the compensatory cannot affect the stability of the system there is more freedom to determine its parameters. when the system was designed, optimum parameters of the closed loop system were selected and the parameters of the compensator were calculated in a way to reduce the dynamic deviations to minimum. application results in this section the results are presented obtained from application of the combined multivariable cascade advanced equivalent control structure in industrial tubular furnace. the responses wn(s), .weqv(s) and k11(s) of pi controller in these systems and combined multivariable cascade controllers were performed in fig.7 and their optimal parameters were listed .in table 1 [5]. fig. 7 presents the control performance of output temperature of petroleum on w11(s) main dynamic channel, control performance of output temperature on weq(s) equivalent channel of the system, performance value of the multivariable cascade equivalent control and control performance of chimney gases on k11(s) intermadiate channel, respectively. discussion and conclusion in this paper, the application was investigated of the multivariable cascade advanced equivalent control structure for an industrial furnace plant. in this respect, equivalent system model of the process was determined by considering ail the disturbance effects of the input-output variables on all dynamic channels of the furnace with two flows. finally, experimental tests of the control of temperature in industrial furnace plant using multivariable cascade equivalent control system has also verified the conclusion that equivalent system technique has considerable control performance. a e fc ft k kn(s) kzz(s) pc rc tci tcz 't t u wu(s) wzz(s) wrz(s) xz symbols unit matrix of the process unit matrix of the error the feed control temperature of feed the gain value of the compensator the transfer function of the interval channel in left side. the transfer function of the interval channel in right side. control of pressure ratio control temperature control of the chimney gasses. the outlet temperature of the petroleum dead time time constant control vector. the transfer function of the main channel in left side. the transfer functions of the inside cross dynamic channel of the furnace the transfer function of the main channel in right side. the transfer function of the compensator the transfer function of the controller object for equivalent channel; the transfer function of the petroleum, given to the left side as a disturbance the transfer function of the petroleum flow in right side as a disturbance. the transfer function of the pi control block. the transfer function of the pi control block in cascade control of furnace. the transfer function of the pi control block in cascade control of furnace. manipulated variable. consumption of the natural gas/air ratio, given to the left chambers. consumption of the natural gas/air ratio, given to the right chambers. consumption of the petroleum flow, given to the right chambers consumption of the petroleum flow, given to the right chambers 185 the outlet temperature of the petroleum in left side. yz the outlet temperature of the petroleum in right side. ycgl the temperature of the chimney gasses in left side. yc8z the temperature of the chimney gasses in right side. yeqv * output of the equivalent channel which is independent of the external disturbance. references 1. abilov a. g., optimal parameter design of an autonom and combined system of temperature regimes in atmospheric tubular furnace, applied inva.rlant control science, academic press, moscow, russia, 261-270, 1970 2. abilov a. g., journal of technical progress, 1972, 5, 10-15 3. ussr pat. 1373717 (1987) 4. abilov a. g., computer control of combustion process and technological regimes in petroleum industrial furnace, third combustion symposium, istanbul, 319-329, 1993 5. abilov a. g., process modeling, optimization and control systems in petrochemical engineering. ankara university facu1ty of science publishers. 200, 1994 6. gough n. g., dimirowski g. m., ting i. h. and sadaoui n., robust multivariable control systems designed for a furnace based on characteristic patterns, ehalley ed., application of multivariable systems techniques,elsevier sciences-london, 145152, 1990 7. turkish pat. 91085 (2000) 8. sobolev 0. s., research methods of linear multivariable systems, energy publishers, moscow, 1985 9. zhu y. c. and backx a. c. p. m., identification of mu1tivariable industrial processes: for simulation, diagnosis and control, springer-verlag, london,1993 10. lundstrom p., lee j. h., morari m. and skogestad s., camp. chern. eng., 1995, 19(4), 409-420 page 184 page 185 page 186 page 187 page 188 hungarian journal of industry and chemistry vol. 45(1) pp. 37–48 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0007 improvement possibilities of heterogeneous photocatalysis with the aim of in-field use orsolya fónagy, 1 péter hegedűs, 1 erzsébet szabó-bárdos, 1 annamária dobrádi, 2 and ottó horváth 1* 1 department of general and inorganic chemistry, university of pannonia, egyetem u. 10., h-8200 veszprém, hungary 2 institute of materials engineering, university of pannonia, egyetem u. 10., h-8200 veszprém, hungary heterogeneous photocatalysis can be successfully applied for the degradation of organic pollutants, although the efficiency of this method is insufficient. it can be increased by modification of the catalyst with precious metals (e.g. silver) or heterogeneous catalysis can be combined with other oxidative procedures such as ozonation. another obstacle to the infield use of the method is that separating the catalyst from the liquid phase is difficult. this problem can be eliminated by the immobilization of the catalyst. the poly(vinyl alcohol)-tio2 immobilized catalyst has been prepared for this purpose. during tio2-based photocatalysis, active oxygen species such as the hydroxyl radical, superoxide radical and hydrogen peroxide are produced. the formation rate of the oxidative •oh radicals was also determined in the case of the previously mentioned techniques. as a scavenger of this radical, coumarin was added. keywords: tio2-based photocatalysis; triton x-100; benzenesulfonic acid; silver-deposited tio2; immobilization; thermal decomposition of pva 1. introduction nowadays, a great proportion of anthropogenic pollutants cannot be mineralized by traditional biological and physicochemical wastewater treatment procedures. therefore, important developments in chemical wastewater treatment technologies and in their utilizations are required. for economic, technological and healthcare reasons, in terms of both type and quantity, it is important to use as few chemical additives as possible. their applicability against remarkably different pollutants using minimal levels of energy consumption is even more important. advanced oxidation processes satisfy these challenges [1]. a common characteristic of these processes is the generation of oxidative radicals, predominantly hydroxyl radicals, using solar radiation or other kinds of energy. hydroxyl radicals are able to oxidize a great variety of organic compounds, therefore, heterogeneous photocatalysis has become an intensively studied field of research. in the pharmaceutical industry, benzenesulfonic acid is mostly used for producing other speciality chemicals. a variety of pharmaceutical drugs are prepared as salts of benzenesulfonic acid, known as besilates. triton x-100 *correspondence: horvath.otto@mk.uni-pannon.hu with an average n ≈ 9.5 is one of the most widely applied man-made non-ionic surfactants. non-ionic surfactants are more stable than ionic tensides and not sensitive to ph and electrolytes. besides the hydrophilic polyethoxy chain, it also contains a hydrophobic octylphenyl group. both compounds can hardly be degraded by biological treatments [2–4]. hence, a more efficient degradation method like heterogeneous photocatalysis is indispensable for the total mineralization of these pollutants. 1.1. photodegradation of model compounds the titanium dioxide-mediated photocatalyzed degradation of benzenesulfonic acid (later abbreviated as bs) was investigated by monitoring the absorption and emission spectral changes, sulfate concentration, ph, as well as the total organic carbon (later abbreviated as toc) content in both argon-saturated and aerated systems. during the degradation of benzenesulfonic acid, a characteristic change in the π→π* transition (typical of aromatic systems) in the absorption spectrum of bs (λmax=262 nm, ε=439 m–1 cm–1) can be observed. at first, there is a slight increase in the 260-270 nm range, while two new shoulders appear at around 280 and 300 nm and as the period of irradiation progresses the level of absorbance decreases. the reason for the increase in absorbance observed in the spectrum of this aromatic surfactant is that the absorbances of the intermediates fónagy,hegedűs,szabó-bárdos,dobrádi, and horváth hungarian journal of industry and chemistry 38 formed in the initial period of the process are higher than that of the starting compound. on the basis of the characteristic molar absorbances of 4hydroxybenzenesulfonic acid (4-hbs) (λmax=277 nm, ε=868 m–1 cm–1) and 2,5-dihydroxybenzenesulfonic acid (λmax=302 nm, ε=3300 m–1 cm–1) as commercially available standards, the appearance of a shoulder at 280300 nm suggests the formation of hydroxylated intermediates. the results indicate that the initial step of the degradation is hydroxylation of the starting surfactant, resulting in the production of hydroxyand dihydroxybenzenesulfonates [5–7]. therefore, liquid chromatography-mass spectrometry analysis was utilized for the detection of intermediates. the sulfonate group of the substrate to be degraded can easily be oxidized by oxygen-containing reactants generated in these systems. sulfate ions were detected in the irradiated reaction mixtures, which means that the hydroxylation reactions were accompanied by desulfonation. the initial rate of this process was lower in each case than that for the transformation (i.e. hydroxylation) of the starting compound (bs). these results indicate that the first step of mineralization is hydroxylation; desulfonation takes place afterwards. during the photocatalytic oxidation of bs, especially in the first 180 min, a continuous decrease of ph was observed in both the argon-saturated and the aerated systems, i.e. strong acidification occurred. probably, there is a direct correlation between the formations of hydrogen and sulfate ions, due to the following reaction (eq.(1)), which can take place between the sulfonate group and hydroxyl radical, the main oxidizing agent in these systems: •rsohr•hsooh•rso 2 443   (1) the hydroxy species did not decay during the irradiation in the absence of dissolved oxygen. in the aerated system desulfonation and hydroxylation was much more efficient, moreover, a significant decrease in toc took place during the initial stage. further hydroxylation resulted in the cleavage of the aromatic system, through the formation of polyhydroxy derivatives, followed by ring-opening, which led to the production of aldehydes and carboxylic acids. total mineralization was realized by the end of the photocatalysis. it has been proved that in this photocatalytic procedure the presence of dissolved oxygen is indispensable for the cleavage of the aromatic ring because hydroxyl radicals photochemically formed in the deaerated system alone are not able to break the c-c bond [5]. the degradation mechanism of triton x-100 was also investigated [8]. in the case of this surfactant, hydroxyl radicals can attack in three ways; on the ethoxy chain, on the aromatic ring or on the alkyl chain. according to the absorption spectrum (no shift in the longer wavelength (275 nm) band and no new shoulders), no hydroxylation of the aromatic ring took place during the photocatalytic degradation. after the total disappearance of the starting surfactant (after approx. 60 min), an appreciable degree of absorbance arose at 275 nm, which indicates that aromatic intermediates were formed during the first hour. in liquid chromatographic experiments, triton x-100 produced a multiple-peaked chromatogram. the retention time of these non-ionic surfactant components is in strong correlation with the length of the ethoxy chain. intermediates formed from various lengths of ethoxy chains and others with aromatic rings were detected in the reaction mixture after irradiation started. the concentration of the shorter-chain molecules increased during the initial stage (in the first 10 min) of the irradiation, indicating that the fragmentation of the longer polyethoxy chains of the starting components initially increased the concentration of those with shorter ones, which was followed by a gradual decay. the component with a relative molecular weight of 206 dalton could be clearly identified. based on its structure, it was identified as the alkyl phenol part of the original triton x-100. its concentration peaked at around the 50th minute of irradiation. this is the result of the total cleavage of the polyethoxy chains without any oxidation of the rest of the original tenside molecules. based on the results so far, it can be stated that hydroxyl radicals attack the ethoxy side-chain and subsequently the alkyl group, afterwards, the ring opens. 1.2. challenges of heterogeneous photocatalysis the obstacle to the practical application of heterogeneous photocatalysis is that its efficiency is relatively low. fortunately there are several ways to improve its mineralization effect: by the combination of heterogeneous catalysis with other oxidative procedures such as ozonation [6, 9-10] or by the modification of the catalyst with precious metals. the latter solution helps promote charge separation by accumulating the electrons on the surface of the silver particles [11-12]. the other obstacle is that the catalyst is in a suspended form, therefore, its separation from the liquid phase is difficult and makes the technology more expensive. this problem can be eliminated if the catalyst is immobilized. there are several methods for immobilization, for example, the catalyst particles can be fixed directly into polymers. between a polymer and the catalyst usually a physical contact is formed, but in some cases, such as with poly(vinyl alcohol), a chemical bond can be formed. unfortunately, this method is not free of disadvantages. the fact that immobilization decreases the active surface area of the catalyst has to be taken into consideration, thus, it will become less efficient [13–16]. irradiation in the near uv range generates electron-hole pairs in the tio2 nanoparticles. under aerobic conditions the electrons in the conduction band are scavenged by adsorbed oxygen molecules with a relatively high quantum yield, producing o2• – ions, which are readily protonated in acidic media. beides, improvement possibilities of heterogeneous photocatalysis 45(1) pp. 37–48 (2017) 39 the holes, in the absence of reducing species, oxidize the surface-adsorbed water or hydroxide ions to hydroxyl radicals. the •oh radical can also be formed by thermal reactions following the primary electron transfer processes that occur at the surface of semiconductor particles or in the liquid phase [13,17]. the hydroxyl radical is often assumed to be the major reactant responsible for the photooxidation of various organic molecules. the first step of the mineralization of benzenesulfonic acid is hydroxylation of the aromatic ring, while the degradation of triton x100 is initialized by hydroxyl radicals, which attack the ethoxyl side chain (fig.1). due to the high reactivity and short lifetime of •oh, the direct detection of this species is difficult. appropriate methods such as steady-state fluorescence were applied to measure the quantity of scavenged hydroxyl radicals. recent studies have proved that several nonor weakly luminescent test molecules, such as coumarin, produce strongly luminescent compounds (7-hydroxycoumarin) with hydroxyl radicals. thus, these molecules can be utilized for detecting and measuring •oh radicals produced by uv excitation of tio2 particles in heterogeneous systems [18-19]. the main goal of our work was to investigate the effect of silver doping and immobilization of the catalyst applied for photocatalytic degradations. in this work, coumarin was used as a scavenger to determine the formation rate of hydroxyl radicals under various circumstances. 2. experimental section 2.1. materials for the experiments, the following materials were used: benzenesulfonic acid (c6h5o3s alfa aesar), 4hydroxybenzenesulfonic acid (c6h4(oh)o3s alfa aesar), silver nitrate (agno3 aldrich), degussa p25 tio2: 25±5% rutile, 75±5% anatase with a specific surface area of 50 m2 g–1 (now called evonik aeroxide® tio2 p25), coumarin (c9h6o2 vwr), triton x-100 (c14h22o(c2h4o)9.5 alfa aesar), and poly(vinyl alcohol) ((later abbreviated as pva) m=146000-186000 g mol–1, hydrolysis: 99+% aldrich). the materials used for the hplc and ic measurements were the following: methanol (ch3oh sigma-aldrich), tetra-n-butylammonium bromide ((ch3ch2ch2ch2)4nbr sigma-aldrich), sodium sulfate (na2so4 vwr), 37% cc. hydrochloric acid (hcl vwr) and sodium hydroxide (naoh vwr). high purity water, used in this study as a solvent, was double distilled and then purified using a milli-q system. 2.2. analytics for the analysis, 4 cm3 samples were taken, the solid phase was removed by filtration using millipore millexlcr ptfe 0.45 m filters. the absorption spectral changes of the reaction mixtures irradiated were followed using a perkinelmer lambda 25 uv-vis spectrophotometer, while the emission spectra were recorded using a perkinelmer ls 50b spectrofluorometer. both measurements were carried out in 1 cm quartz cuvettes. mineralization was followed by measuring the total organic carbon (toc) concentration, utilizing a thermo electron corporation toc tn 1200 apparatus. the ph of the aqueous phase of the reaction mixture was determined by a sp10t electrode connected to a consort c561 instrument. hplc analyses of the benzenesulfonic acid samples were carried out using an agilent 1100 instrument. a water:methanol (in a volume ratio of 95:5) solvent mixture containing 0.1 % (v/v) formic acid was the mobile phase with a flow rate of 1 cm3 min–1. during the experiments a 100×2 mm synergi hydro-rp c18 (phenomenex, torrance, ca, usa) column packed with 2.5 m particles was used. the column was thermostated at 30°c. the sample volume injected was 1 μl, photometric detection was applied at wavelengths of 262, 277 and 302 nm. degradation of triton x-100 was followed by the 1290 infinity uhplc system (agilent technologies inc., santa clara, ca, usa). the mobile phase was 65:35 methanol:water for five minutes of analysis, then it was gradually increased to 75:25 over the following five minutes. the signal was detected with a dad detector. the column used during the experiments was a 100×2 mm synergi hydro-rp c18 (phenomenex, torrance, ca, usa) column packed with 2.5 μm particles. the column was thermostated at 50 °c. the flow rate of the eluent was 1 cm3 min−1. during the study of the degradation mechanism an agilent 6890n gas chromatograph with an agilent db5ms ultra inert column (30 m×0.25 mm×250 μm) was used for the separation. as a detector, an agilent 5973 n-type mass spectrometer was used. the surface of immobilized catalysts was tested using a philips/fei xl30 scanning electron microscope at an accelerating voltage of 20 kv, using backscattered electron imaging. the composition was measured by an edax genesis energy dispersive x-ray analyzer. prior to testing, the samples were sputter coated by a 10 nm figure 1. the role of •oh radicals in the degradation of the model compounds. fónagy,hegedűs,szabó-bárdos,dobrádi, and horváth hungarian journal of industry and chemistry 40 thick layer of gold. elements of the qualitative composition do not overlap with the gold, therefore, the gold coating did not disturb the analysis. 2.3. experimental circumstances the concentration of benzenesulfonic acid to be degraded was 10–3 m in each experiment, while that of the catalyst was 1 g dm–3 in all cases. for homogenization, the suspension was stirred for 20 minutes in the reactor before irradiation. the silverdeposited tio2 was prepared by photoreduction from a mixture initially containing 10−4 m agno3 and 1 g dm–3 tio2 as a photocatalyst. after 1 hour of photoreduction the catalyst, brown in color, was separated by vacuum filtration then dried at room temperature. to re-suspend the catalyst powder before each experiment an ultrasonic bath was applied in order to achieve a dispersion of particles sufficiently small in size. during subsequent ultrasonic treatment, the substrate to be degraded was added to the system only after a period of time, so that the •oh radicals generated during the sonication could recombine and not tamper with the experimental results. a detailed description of the production of immobilized catalyst can be found in our previous article [20]. the pva-tio2 catalyst was prepared by using a pva with a molecular weight of 146 000-186 000 and a 99+% degree of hydrolysis and degussa p-25 tio2. immobilization was carried out using a solutioncasting method [21]. the pva-tio2 mixture was stirred at 90 then 60°c, subsequently a viscous solution was obtained, which was then poured into a petri dish and dried. the average weight of the immobilized catalyst was 0.47 g with a pva content of 40%. before its use, it was subjected to a 2 hour-long thermal treatment in an argon atmosphere to increase its stability. the triton x100 concentration was 2∙10–4 m with 1.5 g dm−3 tio2. it is important to note that when comparing the efficiencies of the catalyst in various forms, the amount of tio2 immobilized in pva (0.3 g) and used as a suspension in 200 cm3 of reaction mixture were both 1.5 g dm−3. photochemical experiments were carried out using two different reactors and light-source setups. one was a laboratory-scale reactor with an effective volume of 2.5 dm3, equipped with a 40 w light tube located in the middle of the reactor. it emitted most of its energy at wavelengths exceeding 300 nm (λmax=350 nm, i.e. within the uva range) [5]. the photon flux of the light source was i0 = 4.3∙10-6 mol photon dm–3 s–1, which was measured by the actinometry of trisoxalatoferrate(iii). the heterogeneous reaction mixture was circulated by using a peristaltic pump through the reactor and a buffer vessel. compressed air was bubbled through the reaction mixtures from gas bottles, to facilitate stirring and (with its o2 content) as an electron acceptor. o3 was produced by a lab2b ozone generator, and introduced into the same airstream. the ozone concentration was determined by iodometry, using sodium iodide as a reagent and sodium thiosulfate for the titration of the iodine formed. the ozone dosage was estimated to be 0.35 mm min–1. the other setup consisted of one small reactor made of borosilicate glass (its volume was 250 cm3) [20]. the catalyst film was placed on a perforated glass platform (foil holder) standing on a glass frit, through which compressed air was bubbled from a gas bottle at a flow rate of 10 dm3 h−1, ensuring a constant oxygen concentration. the 200 cm3 reaction mixture (triton x100 solution or distilled water in the case of pretreatment) was circulated by a magnetic stirrer. it was irradiated from above using an oriel lcs-100 solar simulator resulting in a light intensity of 72 mw cm–2 on the surface of the reaction mixture. fig.2 shows the change in toc during the photodegradation of benzenesulfonic acid under various experimental conditions. the band-gap energy of tio2 is 3.2 ev, indicating that the catalyst can be excited by light of 360 nm in wavelength. the difference between the two light sources used is clearly visible. the radiation intensity of the solar simulator in the uv range is very low, so the total organic carbon content of the initial solution decreased by only 10 mg over 360 minutes, while total mineralization was achieved using the uv lamp within this period. 3. results 3.1. increase in photocatalytic efficiency using various methods as mentioned previously, the efficiency of heterogeneous photocatalysis can be increased in multiple ways: by combination with other oxidative procedures such as ozonation and by modification of the catalyst surface using noble metals. since the first reaction in the mechanism of photocatalytic oxidative degradation of benzenesulfonic figure 2. change in the toc concentration in the case of two different light sources used for irradiation. c(bs)0=10-3 m, air: 40 dm3 h-1, c(tio2)=1 g dm-3 – air+tio2+solar simulator  – air+tio2+uv lamp improvement possibilities of heterogeneous photocatalysis 45(1) pp. 37–48 (2017) 41 acid is hydroxylation of the aromatic ring, the determination of the rates of formation of hydroxyl radicals as the main oxidant in these systems was indispensable as far as the elucidation of the mechanism under various circumstances was concerned. coumarin was used as an •oh scavenger. an intensive band at 278 nm and a shoulder at around 300 nm is visible in the absorption spectrum of coumarin. the level of absorbance quickly decreased under irradiation (fig.s1), while the concentration of the fluorescent 7-hydroxycoumarin rapidly increased during the initial period, and subsequently decreased gradually, i.e. degraded (fig.s2). by depicting the intensity of the emission line at 453 nm as functions of the irradiation time, the initial rate of formation of 7hydroxycoumarin, which is proportional to that of the hydroxyl radicals formed, can be determined from the initial gradients of the increasing sections, so it is easy to compare the ability of each process to generate hydroxyl radicals [18]. before measuring the formation of 7hydroxycoumarin in the photocatalytic oxidative systems that apply ozone, blind probes were used (fig.3). the reaction between coumarin and ozone in the dark (at 10–4 m coumarin and 0.35 mm min-1 ozone concentrations) yielded a negligible spectral change after 2 hours. although ozone itself is a strong oxidant, a very low rate of formation of 7-hydroxycoumarin (0.32 int min–1) was observed under these experimental conditions. upon uv irradiation of this probe, the rate of formation slightly increased (to 1.84 int min–1). ozone can be absorbed over a wide range, from infrared to vacuum uv, but is optimal at 254 nm. the light source applied in this work emits most of its radiation in the 300-380 nm range, where the molar absorbances of o3 are rather low. thus, it can poorly promote the dissociation of ozone via the homolytic cleavage of a bond. contrary to the blind probe with ozone, significant spectral changes were observed in irradiated reaction mixtures containing catalysts. the surface of the catalyst was also modified with silver and combined with ozonation, then the difference between the effects of the two methods of improvement was investigated by determining the rate of formation of oxidative •oh radicals (fig.4). the combination of heterogeneous photocatalysis with ozonation resulted in a 2.5 fold increase in the rate of formation (from 7.42 int min–1 to 19.4 int min–1). a further increase was achieved by the application of surface-modified (silver-deposited) titanium dioxide (to 21.9 int min–1). these results are in accordance with the fact that silver deposited on the surface of the catalyst diminishes the probability of the recombination of the photogenerated electron-hole pair, i.e. promotes charge separation [11]. 3.1.1. degradation of benzenesulfonic acid our research group has been studying the combination figure 3. change in the luminescence intensity of 7-hydroxycoumarin formed (λexc=332 nm). c(coumarin)0=10-4 mol dm-3, air: 40 dm3 h-1, c(o3)=0.35 mm, ℓ=1 cm  – o3  – o3+uv figure 4. change in the luminescence intensity of 7-hydroxycoumarin produced (λexc=332 nm) (a) and rates of formation of •oh radicals under various circumstances (b). c(coumarin)0=10–4 mol dm–3, air: 40 dm3 h–1, c(o3)=0.35 mm, c(catalyst)=1 g dm–3, ℓ=1 cm ♦ – air+tio2+uv ● – o3+tio2+uv ▲ – air+ag-tio2+uv a b fónagy,hegedűs,szabó-bárdos,dobrádi, and horváth hungarian journal of industry and chemistry 42 of heterogeneous photocatalysis and ozonation in detail. it has been established that a joint application of these procedures results in synergic effects [6]. another possibility of enhancing the efficiency of photocatalysis is the modification of the catalyst surface by the deposition of silver. our results in this work are compared with previous observations [17]. the spectral changes during the irradiations of suspensions containing ag-tio2 agree with earlier results. the degree of light absorption increases during the initial period (until the 50th minute), then it decreases (fig.s3). the fine-band structure gradually disappears, while new bands arise at longer wavelengths (277 and 302 nm), suggesting the formation of isomers of hydroxyand dihydroxybenzenesulfonic acid [6]. characteristic changes can also be observed in the emission spectra of the samples in these experiments: an increase in the intensity of luminescence for 60 minutes, then a decrease accompanied by a red-shift of the 290 nm band (characteristic of the starting compound) and the appearance of a new emission band at about 330 nm (fig.s4). the band-shift becomes considerable (46.5 nm) after the first hour of irradiation: from 286 nm to 333 nm. this finding also confirms the formation of hydroxy and dihydroxy intermediates with em.max.=305 nm and 352 nm, respectively. the changes in the concentrations of benzenesulfonic acid and the hydroxylated intermediates were followed by hplc analyses (fig.5). of the three possible hydroxy isomers, the absolute concentration could only be determined for the commercially available 4-hydroxybenzenesulfonic acid (4-hbs, rt=0.86 min). although the concentration of the substrate gradually decreases, the content of the benzenesulfonic acid in the reaction mixture is practically zero by the 180th minute of irradiation. on the basis of the concentration vs. time plot, the rate of decay of the model compound was determined by polynomial fit: 2.1∙10–2 mm min–1. regarding the heterogeneous catalytic experiments (untreated tio2 catalyst), 8∙10–3 mm min–1 was the degradation rate of the starting surfactant, while 1.4∙10–2 mm min–1 was measured in the case of combination with ozonation (table 1) [6]. mineralization of the model compound was followed by toc (total organic carbon content) measurements. taking the difference between the toc value of the reaction mixture (toc of the solution) and that of the benzenesulfonic acid (toc of bs, calculated from its actual concentration), the toc value regarding the intermediates in the solution can be obtained (fig.6).this figure also displays the toc values belonging to 4-hbs (calculated from its actual concentrations, see fig.5) the concentration of the starting material and its toc value rapidly decrease in the heterogeneous photocatalytic experiments involving silver-modified tio2, while the amount of intermediates (predominantly hydroxy and dihydroxy derivatives) gradually increases. the initial rate of decrease in toc for the reaction mixture was 1.58∙10–1 mg dm–3 min–1. the first step of the degradation of the model compound is hydroxylation. the highest initial rate of decay of bs was observed in the case of the system containing the silver-modified catalyst (fig.7, table 1). these results are in good agreement with those obtained for the experiments using coumarin, an efficient scavenger of •oh. the highest initial rate of formation of hydroxyl radicals was obtained on the ag-tio2 catalyst. table 1. comparison of the initial rates*. toc benzenesulfonic acid [mg dm-3 min-1] [mm min-1] air+ ag-tio2+uv 1.58∙10-1 2.3∙10-2 air+tio2+uv 2.24∙10-1 6.5∙10-3 o3+tio2+uv 5.92∙10-1 1.3∙10-2 *the error of the rate determinations is ±10%. figure 5. transformation of the initial compound and change in concentration of the 4-hbs intermediate. c(bs)0=10-3 m, air: 40 dm3 h-1, c(ag-tio2)=1 g dm-3 figure 6. change in toc contents during the treatment. c(bs)0=10-3 m, air: 40 dm3 h-1, c(ag-tio2)=1 g dm-3  – toc of the solution (measured)  – toc of bs (calculated)  – toc of intermediates (calculated)  – toc of 4-hbs (calculated) improvement possibilities of heterogeneous photocatalysis 45(1) pp. 37–48 (2017) 43 the cleavage of the aromatic ring is indispensable in terms of the mineralization of the model compound, besides the fragmentation of the hydrocarbon chain. szabó-bárdos et al. rendered it probable that ringopening takes place in the reaction of hydroxylated intermediates with reactive oxygen-containing species (o2• –/ho2•, o2( 1g)) [5]. deviating from the decrease in the bs concentration, the lowest rate of the decrease in toc, an indicator of mineralization, was observed in the case of the silver-modified catalyst, while the highest value (3.7 times higher than the previous one) was obtained for the combined procedure (fig.7, table 1). based on our results, the application of heterogeneous photocatalysis with silver-modified tio2 only accelerates the formation of hydroxyl radicals, while its combination with ozonation also increases the amount of other oxidative radicals (o2• –/ho2•, o2( 1g)). 3.2. immobilization of the catalyst with poly(vinyl alcohol) the thermal treatment of the immobilized catalysts, the preparation of which was thoroughly described in section 2.3, resulted in significant physical and chemical changes; on the one hand, their thickness varied (fig.8), on the other hand, their color turned from their original white to brown (fig.9). song et al. described similar results [22]. the thickness of the foils prepared was tested by scanning electron microscopy prior to and after the thermal treatment. following the treatment, the average thickness decreased from about 75.6 µm to about 69.6 µm (fig.8). the shrinkage of about 6 µm can be attributed to the evaporation of water content. it has been established in our earlier studies that during the thermal treatment the polymer underwent dehydroxylation and cracking processes; compounds containing double and triple bonds as well as aromatic rings appeared on the surface of the foil, increasing its degree of light absorption [20]. irradiation of the immobilized catalysts in the absence of the model compound led to the dissolution of the side-products of the cracking processes, and they also underwent heterogeneous photocatalytic degradation due to the presence of tio2. accordingly, stearic acid and its derivatives containing double bonds such as linoleic acid (9,12-octadecadienoic acid (z,z)and oleic acid (9octadecanoic acid) were detected by gc-ms analysis of figure 7. change in concentrations of bs (a) and toc (b) under various circumstances. c(bs)0=10-3 m, air: 40 dm3 h-1, c(o3)=0.35 mm, c(catalyst)= 1 g dm-3 ♦ – air+tio2+uv ● – o3+tio2+uv ▲ – air+ag-tio2+uv a figure 8. cross sections of scanning electron micrographs of pva-tio2 foils before (a) and after (b) thermal treatment. a b b fónagy,hegedűs,szabó-bárdos,dobrádi, and horváth hungarian journal of industry and chemistry 44 the liquid phase. during the photocatalytic degradation, organic acids with shorter hydrocarbon chains were also produced, e.g. tetradecanoic acid (c14), caprylic acid (c8) and malic acid (c4) [20]. although thermal treatment improves the stability of the foil, it restricts its efficiency because a considerable proportion of the oxidative radicals formed during photocatalysis are consumed in the reactions with the pollutants produced during the thermal treatment. taking all these factors into consideration, how the temperature of the thermal treatment affects the stability of the immobilized catalyst was also studied. the foils heated at different temperatures were submersed in 200 cm3 of distilled water, then irradiated for 8 hours. the change in toc of the liquid phase is shown in fig.10/a, while the reductions in the foil masses are displayed in fig.10/b. for the interpretation of the results, the increase in the temperature of the solution due to irradiation also has to be taken into account, because it enhances the solubility of poly(vinyl alcohol), i.e. the amount of the dissolved pva, which increases the actual toc value. the organic materials (pva and the products of the thermal treatment) dissolved off the foil which also underwent photocatalytic degradation in the presence of tio2. both processes determine the change in toc in the liquid phase, along with the mass reduction of the foil. the stability of the foils treated at lower temperatures (e.g. at 60oc) is rather modest, the pva is dissolved in water, the toc value of the liquid phase increased to 130 mg dm–3 by the end of the experiment, and the mass of the foil decreases considerably. the stability of the foils treated at higher temperatures (e.g. at 140oc or 200oc) significantly increased, while the toc value of the liquid phase only grew slightly (to 34 mg dm–3 at 140°c, to 18 mg dm–3 at 200oc), in a similar fashion to the weight loss of the foils (140°c m=93 mg, 200oc m=24 mg). the results clearly indicate that by increasing the temperature of the thermal treatment, the stability of the foil is gradually improved, due to efficient crosslinking [21]. the thermally treated immobilized catalysts cannot be applied for photocatalytic purposes, because they undergo degradation themselves during the irradiation, increasing the toc value of the solution phase. besides, the brownish organic compounds formed in the cracking processes diminish the catalytic efficiency because they occupy the active sites on the catalyst surface. hence, a compromise has to be made between stability and efficiency. efforts were made to mineralize the products of cracking during a pretreatment. before the photocatalytic experiments, the thermally treated foils were cleaned by three sequential 8-hour-long pre-treatments, to remove the pollutants formed during the cracking processes. since the pollutants formed whilst heated at the higher temperature (200oc) were rather difficult to remove, 140°c was applied for the thermal treatment of the foils in further experiments of ours [20]. 3.2.1. efficiency of •oh production during pretreatments of immobilized catalysts to detect the hydroxyl radicals formed during the irradiation of tio2 particles embedded in the polymer, 10-4 m of coumarin as a scavenger was applied. following the thermal treatment to enhance the stability of the foils, the undesirable products of this procedure have to be removed. in the first cycle of this process, when the foil is yet brown, the immobilized photocatalyst starts to work upon irradiation, but oxidative radicals formed in this process are mostly involved in the degradation of the products of cracking. the initial rate for the formation of 7-hydroxycoumarin just slightly exceeds the value observed in blind experiments (in the absence of a catalyst); 3∙10–2 int min–1 (blind), 4∙10–2 int min–1 (1st cycle) (fig.11). figure 9. immobilized catalysts before and after heat treatment. figure 10. change in the toc content of the liquid phase after various heat treatments (a) and the weight loss of foils after 8 hours of irradiation (b) 200 cm3 distilled water, air: 10 dm3 h-1,-c(tio2)=1.5 g dm-3 improvement possibilities of heterogeneous photocatalysis 45(1) pp. 37–48 (2017) 45 the rate of formation of the hydroxyl radicals significantly increases during the 2nd cycle; the emission intensity at the end of this cycle (v0=10–1 int min–1) is more than twice as high as in the previous one. the results obtained during the 3rd cycle are similar to those during the 2nd one. practically, during the three sequential 8-hour-long periods of irradiation, the polluting compounds that originate from the thermal treatment are totally degraded, hence, the active sites on the surface of the catalyst become more accessible, resulting in a much higher rate for the formation of oxidative radicals (in the 4th cycle v0=2.5-2.8∙10–1 int min–1, see fig.11). in other applications, the radical producing efficiency of the catalyst does not change significantly, i.e. the foil can be applied at constant efficacy. the lower value determined during the 7th cycle suggests a slow rate of degradation of the immobilized catalyst, which has to be taken into consideration during its application. 3.2.2. degradation of the model compound the photocatalytic degradation of the model compound was investigated following the cleaning procedure. the average degree of degradation of triton x-100 in three sequential cycles was 62%; the deviations might originate from measurement errors (fig.12). this value is significantly lower than that observed in the case of the suspended catalyst (90%). although the catalyst concentrations with regard to the volume of solution were equal (1.5 g dm–3), immobilization considerably diminished the specific surface of the catalyst, leading to a substantial decrease in its efficiency. mineralization of triton x-100 takes place via cleavage-producing intermediates. the cleavage of the alkyl-phenyl part of the starting components of triton x-100 took place from the beginning of the irradiation period. as completive intermediates originated from such a cleavage, ethylene glycol and dioxolane derivatives were detected by gc-ms. at the beginning of the irradiation the edge of the starting molecules or the initially generated intermediates mineralize to co2. therefore, the decrease in toc is much less than expected from the concentration change. the concentration changes of triton x-100 components and the typical intermediates are in accordance with our previous results using a similar system that applied a suspended catalyst (see section 1.1). remarkably, gcms analyses did not detect any intermediates which might derive from the pva support. this suggested that three pre-treatment cycles of irradiation and rinsing were sufficient for a satisfactory level of removal of the derivatives formed during the thermal treatment. 3.2.3. surface morphology of foils sem analysis the behavior of the active surface of immobilized photocatalysts after repeated use raises an important issue. the surfaces of titanium dioxide containing pva before and after thermal treatment are shown in figs.13/a and 13/b, respectively. some tio2-rich islands (fig.14) are not fully covered by the pva film, these are visible on the surface. otherwise, no significant changes are observed after the thermal treatment. however, simulated solar radiation (repeated usage) induces visible changes in the morphology of the b figure 11. change in the intensity of luminescence of 7-hydroxycoumarin formed. c(coumarin)0=10-4 m, air: 10 dm3 h-1, λexc=332 nm figure 12. change in concentration change of triton x-100 during the irradiation. c(tx-100)0=2∙10-4 m, air: 10 dm3 h-1, c(tio2)=1.5 g dm-3 fónagy,hegedűs,szabó-bárdos,dobrádi, and horváth hungarian journal of industry and chemistry 46 surface. such a period of radiation partially or totally removes the pva layer covering the tio2 agglomerates. this process is enhanced after prolonged use: after four cycles the homogeneously distributed particles are already visible (fig.13/c). extended use seven cycles will enhance grain boundaries by removing more of the pva matrix, indeed some of the particles become loosely bounded to the rest of the agglomerate (fig.13/d). the observed changes in thickness strongly correlate with the degradation of films (fig.15). after four cycles, a significant decrease in thickness can be observed: the foil thickness decreases to about 58.5 µm (from 69.6 µm). this corresponds to a decrease of about 2.7 µm / cycle. as for the thickness measured after seven cycles, the last three cycles only represent a decrease of about 0.9 µm/cycle. these observations imply a more intense degree of degradation during the initial stage. 4. conclusion heterogeneous photocatalytic procedures are widely applied for the degradation of organic pollutants. the degradation of benzenesulfonic acid and triton x-100 by heterogeneous photocatalysis was investigated under various circumstances. the formation of hydroxyl radicals as one of the major reactants responsible for the photooxidation of these molecules was also measured in the case of both setups of the catalyst. silver deposition on the surface of the tio2 catalyst significantly increased the initial degradation (hydroxylation) rate of bs, due to the hindered recombination of the photogenerated electron-hole pairs, increasing the rate of •oh production. however, mineralization of the intermediates was not accelerated by this method, deviating from the combination of the tio2-based photocatalysis with ozonation. the degradation efficiency in the latter procedure indicated a synergic effect on the mineralization rate as a consequence of the enhanced production of oxidative agents other than •oh radicals [6]. these reactive oxidants play key roles in the ring-opening processes needed for the mineralization of aromatic intermediates. quantitative determinations of such reactants (e.g. o2• – and o2( 1g)) to gain a deeper understanding of the mineralization mechanism are in progress. our results indicate that the methods applied for the enhancement of the degradation efficiency in heterogeneous photocatalysis affect the generation of the oxidizing agents in different ways, which ought to be taken into consideration in further studies. in general, suspensions of the photocatalyst are used in these procedures. thus, at the end of these processes the semiconductor particles have to be separated from the cleaned solution. this operation can be taken out by immobilization of the catalyst, which was achieved by using poly(vinyl alcohol) in this work. figure 13. scanning electron micrographs of foil surfaces. a) before and b) after thermal treatment c) after 4 irradiation cycles d) after 7 cycles of irradiation a b c d figure 14. energy dispersive x-ray spectra of the tio2 island. in te ns it y / au improvement possibilities of heterogeneous photocatalysis 45(1) pp. 37–48 (2017) 47 the stability of the pva support proved to be too low for practical use. the stability of the pva-based foils could be considerably improved by thermal treatment. however, before photocatalytic application the watersoluble products of the heating process had to be removed from the surface of the pva-tio2 foil. according to the efficiency of •oh formation, three cycles of irradiation and rinsing proved to be sufficient for this purpose. the foil pre-treated by this method could be applied for the photocatalytic degradation of a frequently used non-ionic detergent, triton x-100. when using the immobilized catalyst, it should be noted that the foil catalyst is degraded, its thickness decreases and the catalyst particles become more and more accessible on the surface. acknowledgements this work was supported by széchenyi 2020 under the projects ginop-2.3.2-15-2016-00016 and efop-3.6.116-2016-00015. references [1] dewil, r.; mantzavinos, d.; poulios, i.; rodrigo, m. a.: new perspectives for advanced oxidation processes, j. environ. manage., 2017 195 93–99 doi: 10.1016/j.jenvman.2017.04.010 [2] hack, n.; reinwand, c.; abbt-braun, g.; horn, h.; frimmel, f. h.: biodegradation of phenol, salicylic acid, benzenesulfonic acid, and iomeprol by pseudomonas fluorescens in the capillary fringe, j. contam. hydrol., 2015 183 40–54 doi: 10.1016/j.jconhyd.2015.10.005 [3] mohan, p. k.; nakhla, g.; yanful, e. k.: biokinetics of biodegradation of surfactants under aerobic, anoxic and anaerobic conditions, water res., 2006 40(3) 533–540 doi: 10.1016/j.watres.2005.11.030 [4] wyrwas, b.; dymaczewski, z.; zgołagrześkowiak, a.; szymański, a.; frańska, m.; kruszelnicka, i.; ginter-kramarczyk, d.; cyplik, p.; ławniczak, ł.; chrzanowski, ł.: biodegradation of triton x-100 and its primary metabolites by a bacterial community isolated from activated sludge, j. environ. manage., 2013 128 292–299 doi: 10.1016/j.jenvman.2013.05.028 [5] szabó-bárdos, e.; markovics, o.; horváth, o.; törő, n.; kiss, g.: photocatalytic degradation of benzenesulfonate on colloidal titanium dioxide, water res., 2011 45(4) 1617–1628 doi: 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wang, f.; gao, x.; ding, y.; zhang, s.; zhao, j.; liu, s.; yang, m.: immobilization of tio2 nanoparticles in polymeric substrates by chemical bonding for multi-cycle photodegradation of organic pollutants, j. hazard. mater., 2012 227–228 185–194 doi:10.1016/j.jhazmat.2012.05.029 [22] song, y.; zhang, j.; yang, h.; xu, s.; jiang, l.; dan, y.: preparation and visible light-induced photo-catalytic activity of h-pva/tio2 composite loaded on glass via sol-gel method, appl. surf. sci., 2014 292 978–985 doi: 10.1016/j.apsusc.2013.12.090 hungarian journal of industry and chemistry vol. 47(1) pp. 11–16 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-03 evaluation of resource optimization based on quantum search sara el gaily *1 1department of networked systems and services, budapest university of technology and economics, műegyetem rkp. 3-9, budapest, 1111, hungary quantum computing and communications try to identify more efficient solutions to the most challenging classical problems such as optimization, secure information transfer, etc. this paper will describe a new quantum method for the distribution of resources in computing platforms that consist of a large number of computing units. furthermore, a simulation environment was developed and the performance of the new method compared to a classical reference strategy will be demonstrated. moreover, it will be proven that the proposed solution tackles the problems of computational complexity, computing units that are time-consuming and slow to process, as well as the accuracy in determining the optimum result. keywords: quantum computing, quantum existence testing, finding extreme values in an unsorted database, resource management distribution, exhaustive algorithm, heuristic algorithm, computational complexity 1. introduction nowadays, resource management and especially the distribution of resources is one of the most discussed and fundamental issues, for example, the problem considers a large amount of distributed energy resources including electric vehicles with gridable capacity [1], and the rapid progress of cloud computing, i.e. the growing number of video providers that have deployed their streaming services onto multiple distributed data centers [2]. this greatest demand on efficient resource distribution motivated us to search for new approaches and solutions. the majority of operational processes require an amount of computational resources and their wide availability, namely the amount of computing units, is not the present issue, rather the utilization of resources and usage of the units are [3]. thus, this challenge was tackled by introducing a new strategy which aims to optimize the computational load of the resources that handle the problems of computational complexity, time, speed and accuracy. as is common knowledge, the primary aim of quantum computing and communications is to reduce computational complexity and achieve optimum and efficient results with regard to the requirements of the given problem [4]. in order to exploit the power of quantum computing in terms of resource distribution, a quantum extreme value searching algorithm was used [5], which will be *correspondence: elgaily@hit.bme.hu combined with an appropriately designed classical framework. 2. modelling our novel model deals with the classical problem of resource distribution and contains three components. the first one generates tasks to be computed in the system denoted by pi and can be characterized as processing time, memory, energy, etc. the actual number of running tasks in the system is referred to as n. these tasks are served by computing units that represent the resources of the system. the number of the units is denoted by c. the computing units may have different theoretical capacities. the theoretical capacity of the jth unit is depicted as sj and its free (unused) capacity is denoted by xj [t] which depends on time t, as depicted in fig. 1. the third block is the decision-making unit which answers the question of how to deploy a new task among the process units in order to optimize the operation of the figure 1: architecture of the model mailto:elgaily@hit.bme.hu 12 el gaily system. there are different metrics to distribute the resources, here uniformly loaded units have been chosen because actually, they are an important aspect of many applications. the overall capacity of the processing units in the system can be calculated as ŝ = c∑ j=1 sj , (1) while the overall free processing capacity is determined according to x̂ = c∑ j=1 xj [t]. (2) the average amount of free capacity per unit is given by the following expression x[t] = 1 c c∑ j=1 xj [t] sj . (3) our purpose is to uniformly distribute the load over the resources. therefore, the variance of the relative free capacities in the system is used. in the case of optimal task distribution, if σ2 tends to zero, then the resources are distributed uniformly, otherwise they are not. the corresponding formula of the relative variance is: σ2 = 1 c c∑ j=1 ( x[t]− xj [t] sj )2 . (4) 2.1 description of the quantum algorithm the optimized solution will be based on the quantum extreme value searching algorithm, a stochastic process which functions on an unsorted database that combines the technique of a classical binary search of a sorted database [6] and quantum existence testing (qet) [4]. the best classical solution requires n queries of the database to determine the optimum result, while in order to solve previous problems the well-known logarithmic (often referred to as binary) search algorithm, which is originally intended to search for a given item in a sorted database with quantum existence testing (a special case of quantum existence testing interested in whether a given entry exists in the database or not rather than in determining the number of existence entries) needed to be combined. the quantum algorithm maintains the efficiency of the binary search while processing an unsorted database [4]. it is hard to classically compute the optimum deployment scenario, therefore, the quantum extreme value searching algorithm [5] is applied as a minimum searching algorithm (msa), which enables the deployment scenario to be identified and results in minimum variance. the msa is a stochastic process that works on an unsorted database. our new approach handles the database 1: we start with s = 0 : σ2 min 1 = σ2 min 0 , σ2 max 1 = σ2 max 0 , and ∆σ2 = σ2 max 0 − σ2 min 0 2: s = s + 1 3: σ2 meds = σ2 mins + [ σ2 maxs−σ 2 mins 2 ] 4: flag = qet ( σ2 meds ) 5: if flag = true then σ2 maxs+1 = σ2 meds 6: else σ2 maxs+1 = σ2 maxs , σ2 mins+1 = σ2 meds 7: if s < log2 ( ∆σ2 α ) then goto 2 8: else yopt = σ2 meds stop as a function, i.e. the variance. the proposed algorithm is now given in detail: the algorithm will stop once the following step s < log2 ( ∆σ2 α ) has been fulfilled where α denotes the smallest sub-region between two possible results in a database and is explained in more detail in section 2.3. 2.2 description of the randomized, exhaustive and sequence-searching algorithms the randomized, exhaustive and sequentialsearching algorithms are generally viewed as references and the cornerstone with regard to finding solutions. they are considered as three different methods [7]. firstly, the randomized approach anticipates the solution guided by given knowledge and is not perceived as an optimal solution because it randomly searches for one solution in one step from the space in which the duration of time may be less reasonable [8]. on the other hand, the exhaustive algorithm examines every possible solution and leads to an optimal result, it checks all the o(d) steps which is time-consuming and yields an accurate result. a large number of iterations are required when compared to the number of queries, hence, its time-consuming nature. furthermore, the sequence method exhibits a similar degree of computational complexity to the randomized method, using o(const) or o(1). 2.3 evaluation of the algorithms our purpose is to provide a concrete comparison of solving distribution problems via heuristic ‘random’, exhaustive or sequence as well as quantum algorithms, hence, the difference in terms of the computational complexity applied and the minimum variance computed by each method was measured leading to the optimum distribution uniformity of the system. hungarian journal of industry and chemistry evaluation of resource optimization based on quantum search 13 figure 2: quantum existing testing device (qft: quantum fourier transform). comparison according to computational complexity by comparing the computational complexity of the quantum, randomized, exhaustive and sequence solutions, the quantum solution requires only √ log2(t ) log3 2 (√ d ) steps, where d refers to the number of different possible deployment scenarios and t denotes the number of subregions given by all the possible outcomes of the different deployments. the exhaustive solution, on the other hand, needs o(d). with regard to the randomized solution, it uses fewer steps so is faster than the three former solutions, which means that the computational complexity of the random method is less than for the other ones. moreover, it does not determine the optimum solution since the computational complexity of the sequence method is similar to the randomized algorithm. in contrast, the exhaustive and quantum solutions require more computation steps, but the quantum solution always is preferred because it requires significantly less computation than the exhaustive method. as was mentioned previously, the quantum extreme value searching algorithm uses the binary search and quantum existing testing methods. as the quantum phase estimation algorithm is the core of qet, as can be seen in fig. 2, it outperforms the other counterpart’s algorithms, thus, its physical implementation is highly constrained with the required number of bits k. in fact, the number of bits k depends on the application of the system, as is illustrated in fig. 2. this remains hard to realize, for example, if the error probability pε of the application is neglected and the classical specification considered, which is of accuracy a, the number of steps needed is o ( log2(t ) log3 2 (√ d )) and the number of bits will be influenced only by one factor, namely the accuracy a, as presented in k = a− 1 (5) in addition, the relationship between the maximum relative variance and the number of sub-regions given t according to all the possible outcomes of the different deployments is given by t = σ2 max α (6) where α denotes the smallest sub-region between two possible results in a database (eq. 7). α is illustrated in figure 3: functional representation of the database fig. 3: α = min ∀ i,j ∣∣(σ2 i − σ2 j )∣∣ (7) on the other hand, if two factors, namely the accuracy a and probability of error pε [4], are taken into consideration, this assumption will influence the second term of the computational complexity log3 2 (√ d ) , it will be transformed intoo ( log2 (t ) log3 2 ( 2 p 2 √ d )) and the number of bits will be expressed by k = a− 1 + ⌈ log2(2π) + log2 ( 3 + 1 p̌ε )⌉ ︸ ︷︷ ︸ p , (8) where p̌ε is the maximally allowed quantum uncertainty (probability of error) and p is the number of qbit which controls the quantum uncertainty. the computational complexity of the classical (exhaustive) and quantum solutions is compared. the number of computational steps to yield the desired results with regard to the number of different deployment scenarios is in accordance with function o(d), while the quantum solution only requires o ( log2 (t ) log3 2 (√ d )) . furthermore, the quantum method derives its stochastic behavior from the quantum phase estimation algorithm which heightens the degree of accuracy and speed in computation. in the light of what has been shown, in fig. 4, the classical strategy for identifying the deployment scenario which leads to the minimum variance needs more computational computing, while the quantum solution requires significantly less computation, which reduces the complexity and duration necessary to determine the optimum deployment scenario of resource distribution. figure 4: comparison between the computational complexity of the classical and quantum decision-makers 47(1) pp. 11–16 (2019) 14 el gaily figure 5: the simulation architecture comparison of the uniformity in compliance with what has been discussed, the quantum and exhaustive solutions conserve the uniformity of the system, but the proposed quantum solution is the best and most efficient method because it requires less computation and time to determine the optimum deployment scenarios. however, the randomized and sequence algorithms do not ensure the uniformity of task distribution. 3. results and analysis to show the importance of the proposed quantum solution, a simulation environment of optimizer+distributor was constructed. the model of a resource distribution system contains three processing units with different theoretical capacities: twenty, forty and sixty running tasks in parallel. practical systems contain significantly more processing units, however, to observe trends and effects it is worthwhile investigating a small-scale model first. furthermore, a task generator block is present in the system. the tasks are considered to have exponential arrival times. an optimizer+distributor block is considered to be a decision-maker between the different deployment scenarios. the model implemented in the simulation environment is illustrated in fig. 5. 3.1 experiments two factors influence the behavior of the simulation: the mean (intensity) of the exponential distribution with refigure 6: the average load of processing units in the case of the random reference strategy figure 7: average load of the three distribution strategies when the mean (intensity) of the exponential distribution of the arrival times of tasks is equal to 0.6 gard to the arrival times of tasks, and the service time of the tasks in the processing units. the system will be more heavily loaded if the mean value is smaller or the service time of the tasks larger. 3.2 simulations in order to demonstrate the efficiency of the proposed optimization strategy, two other reference strategies were considered which distribute the tasks randomly or sequentially among the processing units. by considering the following simulation parameters, the mean of the exponential arrival times is equal to 0.4 and the service time of the resources is equal to 3. the average load of the processing units in the case of the random reference strategy is presented in fig. 6 with the following simulation parameters: the mean of the exponential arrival times is equal to 0.4 and the service time of the resources is equal to 15. the line graph contains two phases: the transition phase with a duration of 0 to 30 s, and the stationary phase that commences after approximately 30 s, when the system reaches a certain equilibrium. comparing the performance of the three distribution strategies, it can be stated that during the transition phase the variances of the reference systems are approximately stable, but during the stationary phase (normal operation) the variance started to fluctuate dramatically as well as increase. on the other hand, the variance of the proposed quantum solution remained approximately linear and tended to zero, therefore, the quantum system conserves the distribution uniformity. according to fig. 7 and 8 the average load of the different methods remains similar independent of the intensity of the exponential distribution of the arrival times of tasks as well as the decision methods. furthermore, it is clearly noticeable that when the mean of the exponential distribution of the arrival times of tasks is smaller, the tasks are generated faster which leads to an increase in the load of the computing units. hungarian journal of industry and chemistry evaluation of resource optimization based on quantum search 15 figure 8: average load of the three distribution strategies when the mean (intensity) of the exponential distribution of the arrival times of tasks is equal to 0.1 the simulation results concerning the variance of each distribution strategy show that the trends of the randomized and sequence strategies diverge from zero, but the sequence method yields a more uniform variance than the randomized one. in contrast, the optimized (quantum and exhaustive) strategies maintain and conserve the load uniformity of the system. these results are illustrated in fig. 9 and 10. 4. conclusion in this paper, a new strategy for resource distribution based on a quantum searching algorithm was introduced. it was demonstrated that the quantum solution is more efficient by comparing the computational complexity and distribution uniformity of the quantum solution with the randomized, exhaustive and sequence methods. furthermore, the changes applied to the computational complexity when the specification classical requirement depends on the application were demonstrated. to show the importance of the quantum solution, a simulation environment of the proposed optimization of figure 9: variances over time of the optimized (yellow), randomized (blue) and sequence distribution (orange) strategies when the mean (intensity) of the exponential distribution of the arrival times of tasks is equal to 0.1 figure 10: variances over time of the optimized (yellow), randomized (blue) and sequence distribution (orange) strategies when the mean (intensity) of the exponential distribution of the arrival times of tasks is equal to 0.6 a distribution system was constructed and compared to two reference distribution systems which follow the randomized and sequence strategies. the proposed quantum approach is practical in most domains of infocommunication and computer science where resources have to be distributed among a large number of processing units. these are the initial results of this new field of research. obviously, other optimization metrics should be considered in the future. furthermore, tasks can be modelled in a more sophisticated manner: different classes of tasks can be defined following various arrival processes and characterized by more than one resource parameter (processing time, memory, battery requirement). finally, even an individual task can contain more blocks with dependencies among them and different blocks can be distributed among different processing units. the wider future context of our research is to start with a polynomial time problem and progress towards a nondeterministic polynomial time problem. acknowledgement the research was partially supported by the national research development and innovation office of hungary (project no.2017-1.2.1-nkp-2017-00001), by the hungarian scientific research fund -otka k-112125 and in part by bme artificial intelligence fikp grant of emmi (bme fikpmi/sc). the research reported in this paper was supported by the bmeartificial intelligence fikp grant of emmi (bme fikp-mi/sc). references [1] soares, j.; canizes, b.; vale, z; venayagamoorthy, g. k.: benders’ decomposition applied to energy resource management in smart distribution networks, clemson university power systems conference, clemson, sc. march 8, 2016. doi: 10.1109/psc.2016.7462820 47(1) pp. 11–16 (2019) https://doi.org/10.1109/psc.2016.7462820 https://doi.org/10.1109/psc.2016.7462820 16 el gaily [2] zhang, z.; jiang, x.; xi, h.: joint resource allocation and traffic management for cloud video distribution over software-defined networks, 8th ieee international conference on communication software and networks, university of science and technology of china, hefei, china. 2016. doi: 10.1109/iccsn.2016.7586692 [3] keränen, j.; kortelainen, j.; antila, m.: computational resource management system. version 1.0/14.8.2015. https://www.vtt.fi/inf/julkaisut/ muut/2015/vtt-r-01975-15.pdf [4] imre, s.; balázs, f.: quantum 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quantum algorithm description of the randomized, exhaustive and sequence-searching algorithms evaluation of the algorithms comparison according to computational complexity comparison of the uniformity results and analysis experiments simulations conclusion hungarian journal of indus1rial chemis1ry veszprem vol. 29. pp. 79 (2001) polymer-plasticizer interactions: comparison of experimental data with theoretical results a. orban, r. zelk61 , j. dredan1 , s. marton1 and i. ra.cz1 (gedeon richter ltd., gyomr6i street 19-21. budapest h-1103 hungary 1 pharrnaceuticallnstitute, semmelweis university, hogyes e. street 7. budapest h-1092 hungary) received: october 20, 2000 in the course of the formulation of coated dosage forms, selection of the suitable composition of the coating sysrem is essential as regards dosage form, since the systems applied for coating are multicomponent, it is highly important to quantitatively evaluate the possible interactions between 'the components. these interactions determine the physico­ chelnical stability of the formulated dosage form, the drug release process and the formulation parameters, as well. in the present study molar refraction values of polymer dispersions were deterlnined for the quantitative estimation of polymer­ plasticizer interactions. dynamic surface tension measurements, differential scanning calorimetry and x-ray diffraction studies were applied to analyse the possible interactions between the polymer and the selected plasticizer. the results indicate that the calculation of molar refraction values of polymer dispersions containing plasticizer offers useful means for the determination of the optimum concentration of the selected plasticizer. keywords:eudragit aqueous dispersion; polymer-plasticizer interaction; molar refraction; x-ray diffraction; lninimum fjj.m-forming temperature introduction · .• acrylate polymers and their derivatives, collectively known as eudragit polymers, were the first synthetic polymers used in pharmaceutical coatings as aqueous polymeric dispersions. the physical properties of film­ coating dispersions can potentially exert an influence at many stages during the film coating process [1-3j. the coating formulations usually contain many additives in addition to the polymer, therefore it is highly important to prove and quantitatively evaluate the possible interactions between the components. among the additives that are incorporated into aq1,1eous polymeric dispersions, the plasticizer is the · most critical component that dictates proper film formation and quality of the resulting film. incorporation of a plasticizer is recommended for eudragit rijrs 30d formulations due to the high glass transition temperature values of the polymers [4, 5]. for successful formation of an aqueous latex film, the minimum film-forming temperature (mfi') must be determined, since this is the lowest temperature at which a polymer emulsion forms a continuous film. the mff of polymer emulsions have been studied by several authors [4, 6-7]. the eudragit rsirl 30d types possess a minimum film-forming temperature of approximately 50 and 40 °c respectively and require the addition of between 10 and 20 %w/w of plasticizer to bring the minimum film-forming temperature down to a usable value [5]. the aim of the present study was to quantify the extent of interaction between the selected polymer and plasticizer and to confirm the obtained results with other physico-chemical dynamic surface tension, differential scanning calorimetry, x-ray diffraction methods. the selected methods characterize the film­ forming properties of polymer systems which are of importance from the aspect of the coating process. experimental materials eudragit rl 30 d (rohm pharma, germany) aqueous film dispersions and sebacic acid dibutyl ester (dibutyl sebacate (dbs), sigma) selected as plasticizer. 8 methods dynamic surface tension measurements the dynamic surface tension of different eudragit dispersions was determined by the du nouy ring method using a computer-controlled and programmable tensiometer (ksv sigma 70, rbm-r. braumann gmbh, germany) after equilibration at 25-40°c for 1 hour. the temperature was continuously increased in the course of measurements to determine the minimum film formation temperature (mft) of polymer dispersions. measuring parameters were the following: minimum number of cycles: 5; minimum measuring time: 10 min; speed up: 1 mmfmin. the high standard deviations in the surface tension values within the measuring cycles refered to the film formation. the lowest temperature at the film formation started was defined as mft. film preparation approximately 10 g eudragit rl30d dispersions containing dibutyl sebacate of different concentrations were poured on a glass plate and dried in a sealed container above copper sulphate and stored at room temperature for 1 week. the obtained casted films were used for dsc and x-ray analysis. determination of the glass transition temperature of casted polymer films by differential scanning calorimetry approximately 2-5 mg polymer samples were sealed in closed aluminium pans and transferred to the dsc-ceu of perkin-elmer dsc 4 instrument. after a primary cooling to -30°c, the samples were heated to 150°c and the glass transition temperature was determined using peak-analysis from the first derivative of the measured heat flow. the heating and cooling rates were always 20"'cimin. x-ray diffraction (xrdj measuremems xrd patters of casted eudragit films were taken \vith a <:omputer-\:ontrolted diffractometer (philips anal;1ical x~ray, t}-pe: pw1840). the measuring parameters were the following: tube: anode: cu. generator tension: 30 kv. generator current: 30 rna. wavelength alpha!: ts40s6, wavelength .alp~: 1.54439. intensity ratio (alphallalpba i ): o.soo. detr:tmitunicm of tlte refraui~·e lnde.li: of polymer disptrsit.ms without and in the presence of plasticizer were determined at 24 ± 1 °c applying abbe refractometer. preceding the measurements each sample was thoroughly stirred. in spite of the fact that the examined samples were polymer latex dispersions, the sample preparation and the determination of the refractive index were reproducible without any problem. calculation of the molar refraction by the lorenz­ lorenz equation the following equation was used for the determination of molar refraction values (r): (1) where n is the determined refractive index, m is the molecular weight and d is the density of the examined material [8]. the molar refraction is an additive property. due to the additive characteristic of molar refraction, the molar refraction of eudragit dispersions containing dibutyl sebacate can be calculated by adding up the molar refraction values of each component of the system. the difference between the measured and the calculated molar refraction values of the examined polymer-plasticizer systems could refer to the nature and extent of polymer-plasticizer interaction. results and discussion table 1 summarizes the measured (r,j and the calculated (r.,) molar refraction values of eudragit rl 30d dispersions containing dibutyl sebacate of different concentrations. since the molar refraction is an additive property, the molar refraction of eudragit rl 30d coating dispersions was obtained by adding the molar refraction values of eudragit rl 30d and that of the dibutyl sebacate. the obtained results show that along with the increase of dibutyl sebacate concentration, the differences between the measured and calculated molar refraction values also increased. at 20%w/w plasticizer concentration the calcaluted molar refraction difference is higher with a magnitude than that of the difference calculated at l0%w/w plasticizer concentration. the reason of this phenomena could be the immiscibility of dibutyl sebacate with eudragit rl 30d at higher than io<.fw/w concentrations. table 2 illustrates the minimum film formation temperature values of the same systems analysed by dynamic surface tension measurements. the results indicate that the increasing plasticizer concentration decreased the minimum film formation temperature, but above l0%w/w dibutyl sebacate concentraticn no significant mff changes were seen. the obtained mft values leveled out to constant value with the increasing dbs concentration which also refers to the immiscibilily of the selected plasticizer in the polymer table 1 measured (rru) and calculated (rc) molar refraction values of different eudragit rl30d dibutyl sebacate systems (average values, n=6, rsd < 5%) dibutyl sebacate concentration rm rc (r,n-r,)/rru (%w/w) 0 6547.87 5 6554.61 6551.09 0.0001 10 6599.05 656q.43 0.006 20 6860.70 6568.23 0.043 table 2 minimum film-forming temperature values (mff) of eudragit rl30d dispersions containing dibutyl sebacate of different concentrations (average values, n=6, ±s.d.) dibutyl sebacate concentration (%w/w) 0 5 10 20 36.5 ±0.5 34.5 ± 1.0 32.0± 1.0 32.0± 1.0 fig.l x-ray diffi:action pattern ofeudragit rl 30d casted films containing dibutyl sebacate of different concentrations dispersion above 10%w/w plasticizer concentration. the latter is in good compliance with the molar refraction results, calculated by the lorenz-lorenz relationship. authors previous results indicate that not only the mfi' values did not significantly change above 10%w/w plasticizer concentration but the glass transition values of casted polymer films. either [9]. the x-ray diffraction pattern of casted eudragit films (figure 1) shows that in the presence of 10 and 20 %w/w dibutyl sebacate concentration a peak appears indicating the separated plasticizer. 9 conclusions information can be obtained from the calculation of molar refraction values of eudragit dispersions containing plasticizer concerning the extent of interaction between the polymer and the plasticizer. the theoretical results based on the calculation of molar refraction values of the selected polymer-plasticizer system were in good complience with the results of applied physico-chemical methods that characterize the film-forming behaviour of polymers. acknowledgement authors are grateful to dr. karoly pataki for the valuable discussions. references l lehmann k. and dreher d.: drugs made in germany. 1973 19, 126-136 2. mcginity j. w. (ed): aqueous polymeric coatings for pharmaceutical dosage forms, marcel dekker. inc., new york-basel-hong kong, pp. 267-286, 1997 3. musk6 zs., pintye-h6di k., szab6-revesz p., kasa p. jr., eros i. and deak d.: hung. j. ind. chem.,2000,28, 111-115 4. fukumori y., yamaoka y .. ichikawa h., takeuchi y., fukuda t., and 0sako y.: chern. pharm. bull. 1988, 36, 427-493 5. cole g., hogan j. and aulton m.: pharmaceutical coating technology, taylor & francis ltd, t.j. press ltd, padstow, p. 304. 415, 1995 6. brodnyan j. g. and konen t.: j. appl. polym. sci. 1964,8,687-697 7. berthas. l. and ikeda r. m.: j. appt polym. sci. 1971, 15, 105-109 8. neumljller 0. a.: rompps chemie-le:dkon, franckh 'sche vedagshandhmg, kosmos-verlag, stuttgart, 7. auflage, iv. vol., p. 74, 1977 (in hungarian) 9. orban a., zelko r., dmma.n j., balogh e., marton s. and ra.cz i.: investigation of polymer­ plasticizer interactions in relation to drug release from fum-coated pellets. proceedings of the 3m world meeting apviapgi, berlin, 901·902., 2000 page 11 page 12 page 13 20 stiborek, preisler, shekargoftar, kanický, and kelar table 1: ablation parameter settings monitored in addition to the other isotopes of interest. isotope integration time 0.1 s flow rate of the he carrier gas 1.0 l·min−1 flow rate of the ar auxiliary gas 0.6 l·min−1 flow rate of the ar plasma gas 15 l·min−1 laser pulse repetition rate 10 hz laser-beam waist 250 µm laser fluence ∼ 0.75 j·cm−2 ity of the modification are the voltage and frequency of the electromagnetic field, the composition of the gaseous atmosphere, the exposure time and the geometries of the sample and electrodes. 2. experimental in the first experiment, a dcsbd device (rps400roplass plasma system 400 w, roplass, czech republic) was used to increase the surface energy of the pet substrate (bayer materialscience, germany). the substrate surface was modified at 300 w for one, five and ten seconds. subsequently, 1µl of 0.5 mm trisodium citrate (sigma-aldrich, usa) solution was deposited onto ten replicates of the pet substrate as a model biological sample. the contact angles were measured by the instrument (see system e, advex instruments, czech republic) using a technique called “sitting droplet on a solid foundation”. the device consists of a charge-coupled device (ccd) camera placed on a sliding table in front of which a substrate plate is positioned. using a micropipette, a 1µl droplet of the sample is deposited onto the substrate and the see system software calculates the contact angle based on the interpolation of the height and width of the arc that describes the shape of the drop. the size of the contact angle was evaluated immediately after modification of the substrate surface as well as after one, seven and 31 days. based on the previous experiment, where the aging of the modified surface was monitored by varying the contact angle and size of the stain, depending on the dropping time that elapsed from the surface modification, a complementary experiment was performed. 1ml of trisodium citrate sample was mixed with cadmium and indium standards (aqueous calibration solutions, certified reference materials (crm), analytika, czech republic) so that the resulting solution contained 400 ng·l−1 of these standards. five replicates of the 200 nl droplet sample solutions prepared were immediately applied using a micropipette to the surface of the modified pet substrate as well as one, three and six days after the modification. the cd and in standards, chosen because of their similar atomic masses and first ionization energies, were used figure 1: dependence of the contact angle of droplets of 0.5 mm trisodium citrate solution on the pet surface modified by dcsbd after one, five and ten seconds; droplets were deposited immediately as well as one, seven and 31 days after the modification. to correct the intensity of the monitored signals. the purpose of this experiment was to demonstrate whether aging of the substrate affects the intensities of the signals. at the same time, the size of the stains was measured. ideally, the application conditions should be identical to the experiment where aging was observed by measuring contact angles. however, this was not possible due to different sample-volume requirements for the given measuring technique. 1 µl was required to measure contact angles and 0.2 µl for sald icp-ms. the plate with samples was then inserted into the ablation cell (up213 model, new wave research, inc., usa) equipped with a 213-nm pulsed nd:yag laser, 3d positioning system and built-in ccd camera for visual control of the ablated samples. the dry aerosol created during ablation was analysed by the icp mass spectrometer (agilent 7500ce icp-ms, agilent, usa). in order to determine the beginning and end of the ablation process, the 13c isotope was isotope was monitored in addition to the other isotopes of interest. for the ablation of the stains, a “zig-zag” ablation trajectory was selected with a 170 µm ablation line and a 160 µm·s−1 scanning speed. the remaining basic ablation parameters are shown in table 1. 3. results and discussion first, the contact angle formed by 1 µl droplets of 0.5 mm trisodium citrate onto a pet substrate surface was evaluated immediately after modification of the substrate surface as well as after one, seven and 31 days. ten replicates of the substrate surface were modified for one, five and ten seconds. fig. 1 shows that the droplets of 0.5 mm trisodium citrate solution that were applied to the substrate surface of pet modified by dcsbd for one second exhibited the greatest contact angle, hence the least wettability; i.e., a longer duration of dcsbd modification causes a higher degree of wettability. it is also evident from fig. 1, howhungarian journal of industry and chemistry 22 stiborek, preisler, shekargoftar, kanický, and kelar strate surface. however, the disadvantage of this technique is the aging of the treated surface, i.e. the return of the modified physicochemical properties of the substrate surface to their original state prior to the modification. the experiments showed that the integrated signal intensities of the selected analytes, 111cd and 115in, present in the desorbed spots of 0.5 mm trisodium citrate solution, that were deposited onto the substrate surface at various time intervals following its modification differed. also, the repeatability of the analysis of individual samples expressed as rsds changes with deposition time. rsd values were approximately 30% for 0.5 mm trisodium citrate samples. when quantifying the ratio of integrated 115in/111cd signals, it was found that the values did not differ significantly from each other and could be used in quantitative analysis. using internal standards, rsd values were reduced to less than 10% for trisodium citrate samples. acknowledgement we gratefully acknowledge the financial support of the czech science foundation (15-05387s and 18-16583s) and the ministry of education, youth and sports of the czech republic under the project ceitec 2020 (lq1601). references [1] peš, o.; jungová, p.; vyhnánek, r.; vaculovič, t.; kanickı, v.; preisler, j.: off-line coupling of capillary electrophoresis to substrate-assisted laser desorption inductively coupled plasma mass spectrometry. anal. chem. 2008 80(22), 8725–8732 doi: 10.1021/ac801036x [2] navrátilová, j.; jungová, p.; vanhara, p.; preisler, j.; kanickı, v.; šmarda, j.: copper ions regulate cytotoxicity of disulfiram to myeloid leukemia cells. int. j. mol. med. 2009 24(5), 661–670 doi: 10.3892/ijmm_00000277 [3] nehybová, t.; šmarda, j.; daniel, l.; stiborek, m.; kanickı, v.; spasojevič, i.; preisler, j.; damborskı, j.; beneš, p.: wedelolactone acts as proteasome inhibitor in breast cancer cells. int. j. mol. sci. 2017 18(4), 729–742 doi: 10.3390/ijms18040729 [4] černák, m.; černáková, l’.; hudec, i.; kováčik, d.; zahoranová, a.: diffuse coplanar surface barrier discharge and its applications for in-line processing of low-added-value materials. eur. phys. j. appl. phys. 2009 47(2), 1–6 doi: 10.1051/epjap/2009131 [5] štěpánová, v.; kelar, j.; galmiz, o.; zemánek, m.; slavíček, p.; buček, a.; černák, m.: areal homogeneity verification of plasma generated by diffuse coplanar surface barrier discharge in ambient air at atmospheric pressure. contrib. plasm. physic. 2017 57(4), 182–189 doi: 10.1002/ctpp.201600093 [6] prysiazhnyi, v.: atmospheric pressure plasma treatment and following aging effect of chromium surfaces. jsemat 2013 3(2), 138–145 doi: 10.4236/jsemat.2013.32018 hungarian journal of industry and chemistry introduction experimental results and discussion conclusion microsoft word hjic 2015 43(2) 55-101.docx hungarian journal of industry and chemistry vol. 43(2) pp. 73–78 (2015) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2015-0012 comparison of decontamination standards le cong hao,1 mai dinh thuy,2 do trung hieu,3 and zoltán sas4* 1 nuclear techniques laboratory, university of science, vnu-hcmc, ho chi minh city, vietnam 2 school of nuclear engineering and environmental physics, hanoi university of science and technology, ho chi minh city, vietnam 3 faculty of chemistry, university of science, vnu, ho chi minh city, vietnam 4 institute of radiochemistry and radioecology, university of pannonia, veszprém, h-8201, hungary the quality of materials used in nuclear-related facilities is critical, especially the ease of decontamination of different paints and coatings. standards describe different testing methods for classification. nevertheless, compliance with these standards cannot be carried out negligibly from a safety point of view. in this study, a withdrawn hungarian (msz-05 22.7662-83), an international iso (iso 8690:1988), and russian (gost 2514682) decontamination standard were compared. four different paints were tested as part of this survey. the ease of decontamination varied mainly from poor to fair levels in the case of the hungarian standard, while the iso standard exhibited very good level. in the case of the russian standard, only a theoretical comparison was carried out. based on the results, it was found that a special epoxy-based coating can be recommended for isotope laboratories due to being the best material from an ease of decontamination point of view. from comparison of the standards considered here, it was found that the application of iso standard is significantly faster and simpler than the withdrawn hungarian standard. however, in the case of the hungarian standard the data described the ease of decontamination in more details. the use of water or some other cleaning agents can be effective to remove 137cs and 60co contamination right after early identification. isotope 137cs and 60co contamination of a surface can be cleaned quickly and effectively using distilled water for the 137cs isotope removal from the surfaces being several times easier than that of 60co. keywords: surface contamination, decontamination value, iso standard 8690:1988, hungarian standard msz-05 22.7662-83, russian standard gost 25146-82, 60co isotope, 137cs isotope 1. introduction contamination of surfaces with radionuclides can lead to human exposure depending on the type, extent of contamination, and activity of the contaminating isotope. in order to reduce the risk, quick and effective decontamination of the involved area is required. the contamination of different surfaces are common in workplaces that deal with radionuclides e.g. isotope laboratories, nuclear industry related activities, etc.[1,2]. contamination can occur in various ways, but chemical and physical adsorption processes are the most important ones. in the case of chemical adsorption, ions exit from the hydration shell and bind directly to the surface, while in the case of physical adsorption the ions binds to the surface together with the hydration shell. furthermore, the contaminating isotopes can infiltrate into the pores of the surface material via diffusion. to avoid the internal contamination of porous materials special paints and coatings should be applied which inhibits the diffusion of contaminating isotopes into *correspondence: ilozas@almos.uni-pannon.hu pores [3]. the decontamination capacity of surfaces greatly depends on the form of contamination media and the chemical and physical parameters of surfaces. the main influencing parameters that can affect the ease of decontamination are i) surface porosity, ii) surface roughness, iii) surface wettability, iv) chemical reactions between the radionuclide and the surface, and v) adsorption processes on the outer part of the electric double layer of the solid/liquid interface. the efficiency of decontamination expressed by the decontamination factor (df) [3] can be calculated according to the following equation: !" = !"#$%$#& !" !"#$%&' !"#$% !"#$%&'#%$'"# !"#$%$#& !" !"#$%&' !"#$% !"#$%&'()%'&)$% . (1) however, the decontamination efficiency is greatly parameter dependent as mentioned above. standardised protocols are necessary to classify certain paints and coatings from a decontamination point of view, which is informative about their utilisation in isotope laboratories and other relevant workplaces as well. in this study, the comparison of different decontamination standards is presented that includes a hungarian (withdrawn in 2003) standard msz-05 22.7662-83 “testing of painted coatings in laboratory. hao, thuy, hieu, and sas hungarian journal of industry and chemistry 74 determination for ease of decontamination”[3], an international iso 8690:1988 standard “decontamination of radioactively contaminated surfaces – method for testing and assessing the ease of decontamination” [4], and a russian interstate standard gost 25146-82 “radiochemical production and atomic power plant materials. method for determination of decontamination ratio” [5]. 2. experimental 2.1. sample preparation in order to compare the three selected standards, four different types of coatings were used for providing various conditions during the survey. the relevant properties of the applied coatings are shown in table 1. the selected coatings were painted on 4×4 cm aluminium test disks (fig.1) and stored for 24 hours to dry completely. the selected standards require 5 parallel measurements for each type of coating. 2.2. comparison of contamination processes in the case of the russian gost 25146—82 standard, the investigated surfaces are contaminated by natural or artificial β-radiating nuclides. the activity of the samples was distributed on the surface to avoid selfabsorption. the gost standard describes in great detail the measurement conditions and apparatus, which should be enforced to ensure reliable results. the same standard allows for using any types of contamination solution, which provides numerous ways for measuring the ease of decontamination under a wide variety of conditions, while in the case of the iso and msz standards specific conditions have to be maintained. in the case of the withdrawn hungarian msz-05 22.766283 and iso 8690:1988 standards the recommended contaminating isotopes are 137cs and 60co (carrier concentration 10-5 mol dm-3 and ph value of 4) which were prepared in a laboratory before testing. to determine the count rate of the contaminating isotopes a γ-spectrometer was used with a high purity germanium (hpge) semiconductor detector ortec gmx40-76, with 40% efficiency. to obtain counts from 137cs, the 661.6 kev γ-line was measured, while in the case of 60co, the 1173.4 and 1332.5 kev lines were measured. the spectra were recorded by an ortec dspec lf 8196 mca instrument. before contamination the background spectra were recorded, which were extracted from all contaminated and decontaminated spectra. 2.3. hungarian standard msz-05 22.7662-83 for the hungarian standard, the decontamination was investigated in two differentiated ways to obtain relevant information related to physical and chemical links adsorption separately. to investigate the physical adsorption, 0.1 cm3 of contamination solution was dropped onto test samples and dried under an infrared lamp at 40 °c. after drying, the count rates were measured using a hpge detector for 1000 s to obtain the specific count rate of the contamination solution. to investigate chemical origin contamination, a special socketed cylinder-shaped contamination block (fig.2) was used with 0.565 cm3 of the contamination solution, which provides a 10 cm2 contact surface between the solution and test specimens. the contamination block was put onto coated test specimens and filled with the contamination solution for 2 hours. after that period, the contamination solution was removed from the contamination block and the test specimens were gently flushed using ultrapure water. 2.4. iso standard 8690:1988 for the iso standard, only chemical adsorption was investigated. the specific count rate of the contamination solution was determined before contamination of the test specimens. a micropipette was used to put 0.1 cm3 of contamination solution onto glass sheets. the test specimens were inserted between the upper and lower parts of the contamination block for contamination, which was prepared according to the iso standard (fig.3). before filling the upper part with 1 cm3 of contamination solution both parts were fastened together tightly to avoid leakage. after filling the holder, disks were covered to avoid evaporation of the contamination solution for 2 hours. after this contamination process, the contamination solution was pumped out of the holder, and the test specimens inserted into the decontamination unit. table 1. properties of the coatings investigated. id coating type paint colour roughness dc base-modified silicone resin spray grey (fig.1a) slight cv alkyd resin spray painted dark grey (fig.1b) great km enamel paint brush painted brown (fig.1c) glossy nr epoxy resin brush painted beige (fig.1d) semi glossy figure 1. applied coatings on test disks. comparison of decontamination standards 43(2) pp. 73–78 (2015) doi: 10.1515/hjic-2015-0012 75 2.5. decontamination process in the case of the hungarian standard, an immersionbased decontamination method was used over three steps. firstly, upon the completion of count rate measurements, the contaminated surfaces were immersed in ultrapure water for 10 s then pulled out and tilted to allow the residual fluid to trickle down before finally being immersed again in the decontamination solution. the immersion was repeated 15 times (total immersion time: 150 s). thereafter, the test specimens were dried under an infrared lamp and the count rate originating from the residual contaminating isotopes recorded using a γ-ray spectrometer. in the second step, a special decontamination solution was prepared according to the method described as a standard in order to get information about the decontamination efficiency of detergents. the decontamination solution was composed of polyethylene glycol nonylphenyl ether (5 g dm-3), citric acid (4 g cm-3), and edta (4 g cm-3). the test specimens were added to the decontamination cocktail and decontaminated using the same immersion/pull out technique described in the first step. the count rate was measured again after drying. for the final step 1 m hcl was used to get information about more aggressive decontamination fluids, which can cause structural changes in the case of the investigated coating but can also be beneficial from a decontamination point of view to remove isotopes from pores also. the decontamination and the measurement process were repeated for each specimen after the acidic decontamination step. in the case of the iso standard, the test specimens were placed immediately into a special cage-stirrer apparatus (described in the standard) after the contamination process. the apparatus was equipped with a 100 rpm motor. the cage was immersed into a glass beaker filled with ultrapure water and rotated for 150 s. thereafter, the specimens were dried and measured using γ-ray spectrometry to obtain residual count rates. the details of the msz-05 22.7662-83 and iso 8690:1988 decontamination methods are summarised in table 2. 2.6. calculation of df values and classification of specimens the decontamination factors were calculated from recorded spectra. the peak areas corresponding to the presence of 137cs and 60co isotopes were corrected by background measurements. the specific count rates (count-per-seconds cm-3) were calculated for all samples. the decontamination factors of each step for all samples were calculated using the eq.(1). 3. results and discussion 3.1. decontamination factors from the hungarian standard msz-05 22.7662-83 the obtained decontamination factor of each treated surface on the basis of the hungarian standard is shown in fig.4, which compares the physical adsorption between the contaminating isotopes and surfaces. the decontamination factors varied from 2.0 to 196.3 for 137cs and from 1.0 to 30.1 for 60co. the largest variation between the two isotopes was observed for the nr sample, which is an epoxy-based laboratory coating. most of the decontaminated isotopes were removed independently from applied decontamination solutions, while the decontamination of cv-coated (strongly rough alkyd resin) samples seemed unaffected by treatment using any of the solutions. the decontamination of other surface materials was less figure 2. scheme of the contamination block according to the withdrawn hungarian msz-05 22.7662-8 standard. figure 3. scheme of the contamination block according to the iso 8690:1988 standard. table 2. results of decontamination experiments performed in this study. standards steps method agents msz-05 22.7662-83 3 immersed for 150 s then pulled out ultrapure water decontamination solution 1 m hcl msz-05 22.7662-83 adsorption iso 8690:1988 1 immersed stirring cage in water for 150 s ultrapure water hao, thuy, hieu, and sas hungarian journal of industry and chemistry 76 effective than that of the nrs. in the case of km (glossy enamel paint), the decontamination factor was fair for both isotopes. the results for all materials suggest that decontamination efficiency may be independent of the number of attempts, but dependent on the characteristics of the contamination and features of the surface and contaminant media. in all cases, it seemed that the hcl solution improved the efficiency of decontamination for both 137cs and 60co. nevertheless, it is notable that distilled water is also a good nominated agent for the decontamination of less specific radioactive cleaning agents. table 3 presents the assessment of ease of decontamination using 0.1 cm3 of contamination solution. the ease of decontamination was found to vary from poor to fair for dc, km and cv. an acceptable level of efficiency was found for nr. chemical adsorption was investigated by another decontamination experiment using 0.565 cm3 of contamination solution. similar results (fig.5) were observed when compared with the drying method (fig.4). the decontamination factor using distilled water was found to be approximately the same as for the applied cocktail solution. similar phenomena were reported by ruhman et al. [1]. the reason for unacceptable efficiencies in the case of samples with cv coatings can be explained by the roughness of the surface, which allows contamination of inner pores due to diffusion, hence the surface becomes very difficult to clean. surface degradation due to the porosity of the material or by some unknown chemical modification might be another reason. a recommended area for further study is the ease of decontamination in the light of surface changes after years of use [1]. the ease of decontamination was found to vary from poor for cv to fair for dc and km as shown in table 4. an acceptable efficacy was found for nr. the ease of decontamination varied from excellent for km to good for dc and nr. a poor/bad level was found for cv. 3.2. decontamination factors from the iso standard 8690:1988 the decontamination factors using the iso standard method are illustrated in fig.6. the values clearly show that in the case of epoxy-based nr resin the ease of decontamination was efficient. in the case of the km coating, the efficiency was the highest. the worst decontamination capability was found for cv-coated samples. the results using the iso standard clearly show that the ease of decontamination greatly depends on the types of coating. furthermore, the 137cs isotope can be removed more easily than the 60co isotope, which can be explained by the different physical/chemical properties of investigated isotopes. the obtained decontamination factors for each isotope are summarised in table 5. depending on available conditions, the task and specific conditions, the hungarian standard method and the iso standard will be chosen, while the russian standard was studied only for the sake of comparison. it is important to mention that simulation exercises, for both major and minor contamination events, may be essential for coordination and execution of a response [6–12]. table 3. assessment of ease of decontamination using 0.1 cm3 of contaminated solution. samples isotopes df degree of ease dc 137cs 22.5 fair 60co 1.5 poor/bad km 137cs 13.4 fair 60co 12.6 fair cv 137cs 4.0 poor/bad 60co 2.7 poor/bad nr 137cs 196.3 good 60co 30.1 fair figure 5. decontamination factors for msz-05 22.7662-83 using the adsorption method (table 2). figure 4. decontamination factors for msz-05 22.7662-83 (table 2) after drying. comparison of decontamination standards 43(2) pp. 73–78 (2015) doi: 10.1515/hjic-2015-0012 77 3.3. comparison of df values form the iso and hungarian standards although a direct comparison of the results between the hungarian and the iso standards has limited usefulness and relevance due to fundamental differences in the methods used, we found the same experimental phenomena in terms of ease of decontamination. as expected, similar results were observed and measured for higher decontamination factors in all cases. the most different finding, in the case of km was that the most effective method observed was by treatment using distilled water. most of the 137cs contamination was removed more effectively than 60co contamination for dc, km, and nr surfaces. in comparison with the hungarian standard method, the iso standard was used for testing and assessing the ease of decontamination only for chemically adsorbed contaminating isotopes. the experiment was then conducted using 20 contaminated samples of the same type, distilled water as a cleaning agent, and using different decontamination methods. the results are shown in figs.6-7 and table 5. these results are in contrast to our previous observations using the hungarian standard method and the low efficiency for cv sample. the differences can be explained by some unknown chemical bond formation between the surface of the material and the studied isotopes. this research confirms that the use of deionised water or cleaning agents described in standards may be a sufficient means of removing wet 137cs and 60co contamination when identified early. 4. conclusion the aim of this study was to identify some of the best surfaces, which would meet alara and goodmanufacturing-practice requirements to set up protocols to manage contamination in laboratories. the russian standard can provide very specific information about the ease of decontamination for a wide variety of contamination conditions. the fixed measurement parameters in the case of the iso 8690:1988 and hungarian msz-05 22.7662-83 standards provide an opportunity to compare paints and coatings and classify them. using the hungarian and iso standards, the 137cs and 60co contamination on a surface can be cleaned quickly and effectively using distilled water. based on the results obtained after the decontamination procedure for the hungarian and iso standards, nr can be applied to the surface, the walls of the laboratory, and where figure 6. decontamination factors for the iso standard 8690:1988 (table 2). table 5. assessment of ease of decontamination for the iso standard 8690:1988. sample isotopes df degree of ease dc 137cs 684 good 60co 315 good km 137cs 4928 excellent 60co 3444 excellent cv 137cs 13 poor/bad 60co 30 poor/bad nr 137cs 934 excellent 60co 3822 good figure 7. decontamination factors for the iso 8690:1988 (e) and hungarian (adsorption-type contamination) standards. table 4. assessment of ease of decontamination in the case of the adsorption method. samples isotopes df degree of ease dc 137cs 370 fair 60co 158 fair km 137cs 411 fair 60co 257 fair cv 137cs 16 poor/bad 60co 17 poor/bad nr 137cs 6550 excellent 60co 1859 good hao, thuy, hieu, and sas hungarian journal of industry and chemistry 78 radiation is susceptible in nuclear power plants. in the worst case scenario, when there is an accident involving radioactive contamination, the ability of cleansing the decontamination of surfaces covered by nr will be the most efficient. according to our findings, we were able to select the best materials for the floor of our laboratory. acknowledgement the authors thank the ministry of education, vietnam for funding this research, and the institute of radiochemistry and radioecology, university of pannonia for providing experimental conditions. references [1] ruhman, n.; vesper, g.; martin c.: the effectiveness of decontamination products in the nuclear medicine department, j. nucl. med. technol., 2010, 38(4), 191–194 doi: 10.2967/jnmt.110.076919 [2] leonardi, n.m.; tesán, f.c.; zubillaga, m.b.; salgueiro, m.j.: radioactivity decontamination of materials commonly used as surfaces in generalpurpose radioisotope laboratories, j. nucl. med. technol., 2014, 42(4), 292–295 doi: 10.2967/jnmt.114.144303 [3] hungarian standard msz-05 22.7662-83: testing of painted coatings in laboratory. determination for ease of decontamination (hungarian patent office, budapest, 1983 withdrawn in 2003) [4] international iso standard 8690:1988: decontamination of radioactively contaminated surfaces. method for testing and assessing the ease of decontamination (international organization of standardization, switzerland, 1988) www.iso.org/iso/ catalogue_detail.htm?csnumber=16094 [5] russian interstate standard gost 25146-82: radiochemical production and atomic power plant materials. method for determination of decontamination ratio (technormativ llc, 1983 official translation in 2015) http://runorm.com/product/view/2/10771 [6] schleipman, a.r.; gerbaudo, v.h.; castronovo, f.p.: radiation disaster response: preparation and simulation experience at an academic medical center, j. nucl. med. technol., 2004, 32(1), 22–27 pubmedd: 14990671; tech.snmjournals.org/content/ 32/1/22 [7] gurau, d.; deju r.: the use of chemical gel for decontamination during decommissioning of nuclear facilities, rad. phys. chem., 2015, 106, 371–375 doi: 10.1016/j.radphyschem.2014. 08.022 [8] varga, k.; baradlai, p.; hirschberg, g.; nemeth, z.; oravetz, d.; schunk, j.; tilky, p.: corrosion behaviour of stainless steel surfaces formed upon chemical decontamination, electrochim. acta, 2001, 46(24-25), 3783–3790 doi: 10.1016/s00134686(01)00665-x [9] anthofer, a.; lippmann, w.; hurtado, a.: laser decontamination of epoxy painted concrete surfaces in nuclear plants, optics laser technol., 2014, 57, 119–128 doi 10.1016/j.optlastec. 2013.09.034 [10] endo, m.; kakizaki, t.: washing operation of a road surface washing mechanism for decontaminating radioactive substances, robomech j., 2014, 1, 13 doi 10.1186/s40648-014-0013-8 [11] iaea-tecdoc-102 2: new methods and techniques for decontamination in maintenance or decommissioning operations, results of a coordinated research programme 1994–1998 (international atomic energy agency, vienna) 1998 issn 1011-4289; www-pub.iaea.org/mtcd/ publications/pdf/te_1022_web.pdf [12] iaea-tecdoc-24 8: decontamination of operational nuclear power plants (international atomic energy agency, vienna) 1981 wwwpub.iaea.org/mtcd/publications/pdf/te_248_web.pdf phosphoglycolipid profiling of bacterial endotoxins 11 [5] sándor, v.; kilár, a.; kilár, f.; kocsis, b.; dörnyei, á.: characterization of complex, heterogeneous lipid a samples using hplc–ms/ms technique iii. positive-ion mode tandem mass spectrometry to reveal phosphorylation and acylation patterns of lipid a. j. mass spectrom. 2018, 53(2), 146–161. doi: 10.1002/jms.4046 [6] madalinski, g.; fournier, f.; wind, f.l.; afonso, c.; tabet, j.c.: gram-negative bacterial lipid a analysis by negative electrospray ion trap mass spectrometry: stepwise dissociations of deprotonated species under low energy cid conditions. int. j. mass spectrom. 2006, 249–250, 77–92. doi: 10.1016/j.ijms.2005.12.049 46(1) pp. 7-11 (2018) introduction experimental chemicals and reagents bacterial strains and lipid a isolation liquid chromatography – mass spectrometry measurements results and analysis hplc-ms of bacterial lipid a tandem mass spectrometric analysis of lipid a species discussion conclusion microsoft word 16.14 polcz.docx hungarian journal of industry and chemistry vol. 44(2) pp. 113–120 (2016) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2016-0014 computational stability analysis of lotka-volterra systems péter polcz1,∗ and gábor szederkényi1,2 1 faculty of information technology and bionics, pázmány péter catholic university, práter u. 50/a, budapest, 1083, hungary 2 systems and control lab, institute for computer science and control, hungarian academy of sciences, práter u. 50/a., budapest, 1083, hungary this paper concerns the computational stability analysis of locally stable lotka-volterra (lv) systems by searching for appropriate lyapunov functions in a general quadratic form composed of higher order monomial terms. the lyapunov conditions are ensured through the solution of linear matrix inequalities. the stability region is estimated by determining the level set of the lyapunov function within a suitable convex domain. the paper includes interesting computational results and discussion on the stability regions of higher (3,4) dimensional lv models as well as on the monomial selection for constructing the lyapunov functions. finally, the stability region is estimated of an uncertain 2d lv system with an uncertain interior locally stable equilibrium point. keywords: nonlinear systems, lotka-volterra models, stability analysis, linear matrix inequalities, lyapunov function 1. introduction approximating the domain of attraction (doa) is often a fundamental task in the analysis and control of nonlinear systems. the stability properties of dynamical systems are most often studied using lyapunov functions. therefore, extensive literature exists on the computational construction of lyapunov functions [1]. due to their advantageous properties and the availability of efficient numerical solvers, the use of linear matrix inequalities (lmi) and semi-definite programming (sdp) techniques has become popular in the field of system and control theory. important results were announced [2,3] in the context of linear uncertain systems, their stability analysis and control synthesis. recently, an optimization-based method for doa estimation was published [4], where the authors use finsler’s lemma and affine parameter-dependent lmis to compute rational lyapunov functions for a wide class of locally asymptotically stable nonlinear systems. based on these results an improved method was published [5,6], where the transformation of the model to the form required for optimization is done automatically using the linear fraction transformation (lft) and further automatic model simplification steps, which results in the dimension reduction of the optimization task. as the dimensions of the problem are *correspondence: ppolcz@gmail.com reduced, the method is capable of handling more complex models. for example, the doa is successfully estimated for a 3-dimensional rational uncertain system [6] (bioreactor model with an applied proportional and integral substrate feedback law). the dynamical descriptive power of lotkavolterra systems is so extensive that lv models “have the status of canonical format” within the class of smooth nonlinear dynamical systems [7]. besides modelling biological/ecological environments, they are widely used in other scientific fields like neural networks [8] or in economics, where the goodwinlotka-volterra models are applied for modelling the predator-prey mechanism of the technological substitution [9,10]. in order to model the correlation between the employment rate and the share of wages of the working population, the authors of ref. [11] used a stochastic extension of the goodwin model. some important results that make lv models even more attractive are the existing techniques used to represent a general nonlinear system as a multidimensional lv model [12]. the analysis of stability and behaviour of lv systems is extensive in the literature [13]. plank has shown [14] that ndimensional lv systems are hamiltonian if they fulfil certain algebraic properties (theorem 3.1 in ref. [14]). he demonstrated that, when using an appropriate poisson structure, one can obtain the hamiltonian function of the system, which is a key object in determining the system's doa. furthermore, candidates of hamiltonian function were defined in (section iv in ref. [14]). it is important to note that lv systems are polcz and szederkényi hungarian journal of industry and chemistry 114 kinetic in the sense that they can be formally described as chemical reaction networks with mass action kinetics. in this paper, the local stability properties of lv models are analysed by applying the underlying method presented [6]. the stability region is estimated on a few locally stable 2-, 3-, and 4-dimensional benchmark lv systems. the doa of an uncertain 2d system is also estimated by two concentric regions. the main motivation of our work was to evaluate the applicability of the approach [4] on a general polynomial system class consisting of low-degree monomials, and to study the limits of the method as the number of dimensions of the state space increase. 2. background in this section, the basic notions and results on which our computational method is based are presented. 2.1. system class, lyapunov functions, and the domain of attraction. our computational method can handle general nonlinear systems of the form 𝑥 𝑡 = 𝑓(𝑥 𝑡 , δ 𝑡 ) 𝑥 𝑡 ∈ ℝ!, 𝑥! ∈ 𝒳, δ 𝑡 ∈ 𝒟, δ 𝑡 ∈ 𝒟 (1) where 𝒳 ⊂ ℝ! and 𝒟,𝒟 ⊂ ℝ! are given polytopes, x is the state vector function with its initial condition x0 = x(0), and δ is a smooth, bounded vector function of uncertain parameters with a bounded time derivative. the applied method is presented in detail elsewhere [15]. from now on, the time arguments of x and δ will be suppressed as is commonly done in the literature. it is assumed that function 𝑓:ℝ!×𝒟 ↦ ℝ! of eq.(1) is a well-defined smooth rational mapping, with the property f(0, δ) = 0 for all 𝛿 ∈ 𝒟. additionally, it is assumed that x* = 0 ∈ ℝ! is a locally asymptotically stable equilibrium point of eq.(1) for all δ ∈ 𝒟. the set of all initial conditions, from which the solutions converge to x*, is called the domain of attraction (doa). furthermore, it is assumed that function f(x, δ) can be written in a so-called quasi-lpv form f(x, δ) = function a(x, δ) x the aim is to identify an appropriate rational lyapunov function v(x, δ), which satisfies the following conditions: 𝑣! 𝑥 ≤ 𝑉 𝑥, δ ≤ 𝑢! 𝑥 ,∀(𝑥, δ) ∈ 𝒳×𝒟 𝑉 𝑥, δ, δ ≤ −𝑣! 𝑥 ∀(𝑥, δ, δ) ∈ 𝒳×𝒟×𝒟 (2) where vl, ux, vd are continuous positive functions on 𝒳. due to conditions of eq.(2) any closed level set of the lyapunov function contained entirely in 𝒳 bounds an invariant region of the state space. our objective is to find a lyapunov function, which fulfils the conditions of eq.(2) and to determine its maximal invariant level set completely inside 𝒳. 2.2. dynamical system representation a lyapunov function can be computed [4] in the form shown in eq.(3). 𝑉 𝑥, δ = π!! 𝑥, δ 𝑃π! 𝑥, δ ,π! = 𝑥 π (3) where 𝑃 ∈ ℝ!×! is a constant symmetric matrix, not necessarily positive definite, and π:ℝ!×𝒟 ↦ ℝ! is mapping, in which each element is a monomial in (x, δ), or a smooth rational function with a monomial numerator. the arguments of π and πb will be suppressed below. applications of the linear fractional transformation (lft) and further algebraic steps have been proposed [5,6] to transform the system equation 𝑥 = 𝑓 𝑥, δ = 𝐴(𝑥, δ)𝑥 into the desired differential-algebraic representation that was introduced in the same references: 𝑥 = 𝐴 𝑥, δ 𝑥 = 𝐴𝑥 + 𝐵𝜋 𝑥! ∈ 𝒳 0 = 𝒩!! 𝑥, δ π! 𝛿 ∈ 𝒟, 𝛿 ∈ 𝒟 (4) where 𝐴 ∈ ℝ!×! and 𝐵 ∈ ℝ!×! are constant matrices, and 𝒩!! 𝑥, δ ∈ ℝ!×! is an affine matrix function in (x, δ) also known as an “annihilator”. these transformations also result in the dimension reduction of the optimization problem compared to the results presented in ref. [4]. the representation in eq.(4) separates the linear part of the system (x) from its nonlinear part (π). 3. the sdp problem for estimating the doa in this section, how to construct the semi-definite optimization task (sdp) is presented, which will uniquely characterize an appropriate lyapunov function and its maximal invariant level set εα as an estimate of the true domain of attraction. it is assumed that polytopes 𝒳,𝒴, and 𝒟 are already given. using the model representation of eq.(4) and a lyapunov function candidate of the form in eq.(3), sufficient lmis for the lyapunov conditions in eq.(2) can be formulated. according to finsler’s lemma (lemma 2.1 in ref. [4]), if real-valued matrices 𝐿! ∈ ℝ!×! and 𝐿! ∈ ℝ(!!!"!!!!!")×(!"!!!!!") exist ∀ 𝑥, δ ∈ 𝜗 𝒳×𝒟 : 𝑃 + 𝐿!𝒩!! 𝑥, δ +𝒩!! ! 𝑥, δ 𝐿!! > 0 (5) ∀ 𝑥, δ, δ ∈ 𝜗 𝒳×𝒟×𝒟 : 𝑃! + 𝑃!! + 𝐿!𝒩!! 𝑥, δ, δ +𝒩!! ! 𝑥, δ, δ < 0 (6) then the conditions of eq.(2) are satisfied for every (𝑥, δ, δ) ∈ 𝒳×𝒟×𝒟. variables pa and 𝒩!! 𝑥, δ, δ are computational stability analysis of lotka-volterra systems 44(2) pp. 113–120 (2016) doi: 10.1515/hjic-2016-0014 115 defined in eqs.(3.16) and (3.22) of ref. [15], respectively. 𝜗 ∙ denotes the corner points (vertices) of a given polytope. since the lyapunov conditions are satisfied within 𝒳, an attempt is made to identify the maximal α-level set ε! = 𝑥 ∈ 𝒳|𝑉 𝑥 = 𝛼, 1 ≤ 𝛼 , which lies inside 𝒳. that level set will be invariant, in the sense that every trajectory entering this region will never leave it. α ≥ 1is defined, as a free variable of the optimization task, and 𝜀! is constrained inside 𝒳. one can observe that by maximizing α an unbounded feasible solution is obtained, as the function v(x, δ) can be scaled arbitrarily. therefore, as fig.1 illustrates, an auxiliary polytope 𝒴 is defined around the locally stable origin inside 𝒳 , constraining the 1-level set 𝜀! = 𝑥 ∈ 𝒳|𝑉 𝑥 = 1 to be around 𝒴. according to finsler’s lemma, for every 𝑘 = 1,𝑀𝒳 and 𝑙 = 1,𝑀𝒴, if real-valued matrices 𝐿!! , 𝐿!! ∈ ℝ !×!, 𝑀!! ,𝑀!! ∈ ℝ (!!!)×! exit 𝑄!!𝑃!! (!) 𝑥, δ 𝑄! ≥ 0 ∀ 𝑥, δ ∈ 𝜗 ℱ!𝒳×𝒟 (7) 𝑄!!𝑃!! (!) 𝑥, δ 𝑄! ≤ 0 ∀ 𝑥, δ ∈ 𝜗 ℱ! 𝒴×𝒟 (8) then 𝜀! is inside 𝒳 and 𝜀! is around 𝒴. variables 𝑄! , 𝑄! , 𝑃!! (!), and 𝑃!! (!) are defined in eqs.(3.34) and (3.36) of ref. [15], ℱ!𝒳 denotes the kth facet of 𝒳, furthermore, 𝑀𝒳 denotes the number of facets of 𝒳. the lmi conditions of eqs.(5)-(8) are affine parameter-dependent lmis, which can be computationally handled by checking their feasibility at the corner points of the polytopic region, on which the parameters 𝑥, δ, δ are defined. depending on the number of the corner points, a given number of parameter independent lmi conditions (table 1) is obtained. the sdp task can be summarized as follows. in order to find the maximal invariant level set 𝜀! of the lyapunov function, one should maximize α, under the following conditions: eq.(5) 𝑉 𝑥, δ is positive on 𝒳×𝒟 eq.(6) 𝑉 𝑥, δ, δ is negative on 𝒳×𝒟×𝒟 eq.(7) 𝜀! lies inside 𝒳 eq.(8) 𝒴 is inside 𝜀! the number of lmis and their dimensions are given in table 1, furthermore, the free variables of the optimization task are listed in table 2. figure 1. illustration of the conditions regarding 𝒳 and 𝒴 . inside polytope 𝒳 of the lyapunov conditions in eq.(2) are required. the α-level set ε! of the lyapunov function should lie inside polytope 𝒳 (hence it is invariant). the 1-level set ε1 should be around polytope 𝒴. this condition ensures that the problem has a bounded solution. table 2. free variables of the optimization task and the number of (scalar) symbolic decision variables they introduce into the optimization task. matrix variable number of (scalar) independent decision variables appearing in the sdp α 1 p ½ m(m+1) lb mq la (n + 2p + n2 + np)(2q + n2 + nq) 𝐿!!and 𝐿!!! !𝑀𝒳 +𝑀𝒴!×𝑚𝑞 𝑀!!and 𝑀!!! !𝑀𝒳 +𝑀𝒴!×(𝑚 + 1)𝑛 the dimensional parameters are the following: n number of state variables (size of x) p number of elements in π m number of elements in πb (n + p) q number of rows in annihilator 𝒩!!(𝑥, δ) 𝑀𝒳 number of corner points of 𝒳 𝑀𝒴 number of corner points of 𝒴 𝑀𝒟 number of corner points of 𝒟 𝑀𝒟! number of corner points of 𝒟! table 1. number and dimensions of parameter independent lmis of the optimization task. dimension of the lmis no. of lmis eq.(5) m 𝑀𝒳 ∙𝑀𝒟 eq.(6) n + 2p + n2 + np 𝑀𝒳 ∙𝑀𝒟 ∙𝑀𝒟! eq.(7) m + 1 2𝑀𝒳 ∙𝑀𝒟 eq.(8) m + 1 2𝑀𝒴 ∙𝑀𝒟 figure 2. polytope 𝒳 is evaluated through iterations considering the bounding box of the obtained α-level set. polcz and szederkényi hungarian journal of industry and chemistry 116 3.1. finding the most appropriate outer polytope in the case of 2d systems, polytope 𝒳 is evaluated manually through iterations. when having a higherdimensional system (n ≥ 3), the iterative procedure [6] is applied that starts from an initial polytope 𝒳(!), then a new polytope 𝒳(!) is defined by enlarging the axis aligned bounding box of the obtained α-level set ε! (!). during the iterations, 𝒳(!) is constrained to be a rectangular polytope. fig.2 illustrates the operation of a single iteration step. 4. lotka-volterra systems the n-dimensional lv equation has the form 𝑥 = 𝑑𝑖𝑎𝑔 𝑥 + 𝑏 , 𝐴 ∈ ℝ!×!, 𝑏 ∈ ℝ!, (9) where diag(a), 𝑎 ∈ ℝ! denotes an n × n square diagonal matrix with the x1, …, xn on the main diagonal. the system is translated into its, by assumption, unique interior equilibrium point 𝑥∗ = −𝐴!!𝑏 by introducing the centred state vector 𝑥 = 𝑥 − 𝑥∗ . then, an autonomous nonlinear system of the form 𝑥 = 𝒜 𝑥 𝑥 is obtained, where the matrix function 𝒜 can be expressed as: 𝒜 𝑥 = 𝑑𝑖𝑎𝑔 𝑥 + 𝑥∗ 𝐴. by applying the lft and the further algebraic model transformation steps, a model is obtained in the representation of eq.(4), where the entries of π(x) are second order monomials of the state variables. 5. numerical results in this section, the applicability of the approach presented above is illustrated through different locally stable lotkavolterra models. the results presented here have been computed in a matlab environment. for symbolic computations, matlab’s built-in symbolic math toolbox was used based on mupad. for linear fractional transformations (lft), the enhanced lfr-toolbox is used [16, 17]. to model and solve semi-definite optimization (sdp) problems, mosek solver with yalmip was used [18]. 5.1. 2d lotka-volterra system a locally stable lv system is considered with the model matrix: 𝐴 = -2 -3 1.4 1 , with a unique interior equilibrium point x* = [1 1]t. in fig.3, some trajectories of the centred system can be observed from different initial conditions. the red trajectories converge at the equilibrium point, the blue ones do not tend to the equilibrium point. after solving the corresponding sdp, the obtained lyapunov function is 𝑉 𝑥 = π!!𝑃π! (fig.4), where π = 𝑥!! 𝑥!𝑥! 𝑥!! ! , π! = 𝑥 π (10) 𝑃 = 87.39 63.83 -3.45 0 0 63.83 165.26 67.24 100.85 28.76 -3.45 67.24 7.63 0.15 0 0 100.85 0.15 38.78 39.97 0 28.76 0 39.97 15.53 in fig.3, the shape of the manually chosen polytope 𝒳, and the obtained invariant α-level set of the lyapunov function can be seen, which is considered as the estimated doa (filled orange region). areas can be observed, where the lyapunov function's time derivative is positive (green region) can also be observed to be completely outside of 𝒳. fig.5 illustrates how the value of the lyapunov function decreases along the trajectories. figure 3. phase diagram of the 2d locally stable system. red trajectories converge at the origin, the blue ones do not converge at the origin. the estimated doa and the used polytope 𝒳 are illustrated by the orange-filled region and by the grey-dashed polytope, respectively. the green area highlights the subset of the state space where the lyapunov function features a positive time-derivative. figure 4. the obtained lyapunov function in the case of the 2d lv system. computational stability analysis of lotka-volterra systems 44(2) pp. 113–120 (2016) doi: 10.1515/hjic-2016-0014 117 5.2. 3d lotka-volterra system a locally stable 3d lv system has been chosen with the model matrix 𝐴 = 0.06 0.21 0.83 −2.47 −2.10 −3.64 0.06 0.47 −0.45 . similarly to the 2d example, the equilibrium point is set to x* = [ 1 1 1 ]t. the monomial set appearing in πb contains the state variables and every possible 2nd order monomial: π! = 𝑥!! 𝑥!𝑥! 𝑥!𝑥! 𝑥!! 𝑥!𝑥! 𝑥!! (12) matrix p is a 9×9 symmetric matrix. fig.6 illustrates the invariant α-level set of the obtained lyapunov function (3d red volume). in fig.7, one can see the cross-sections of the 3d invariant region from three different viewpoints. some trajectories of the system are shown in red (stable) and blue (unstable). figure 5. in panel a, the obtained invariant level set is shown, furthermore some trajectories x(i)(t) of the system can be seen in different colors with initial conditions 𝑥! (!) close to the boundary of the estimated doa. the values of the lyapunov function along the trajectories (v(i)(t)) are presented in panel b, respectively. figure 7. cross-sectional view of the 3d estimate along the major planes xi,xj and using different values for xk, where (i, j, k) is a permutation of (1, 2, 3). figure 6. estimated doa of the locally stable 3d lotka-volterra system (red mesh) and the corresponding final polytope 𝒳. polcz and szederkényi hungarian journal of industry and chemistry 118 5.3. 4d lotka-volterra system the method was applied to a locally stable 4d lv system with a unique interior equilibrium point: x* = [ 1 1 1 1 ]t . (13) the model matrix of the lv system was chosen to be: 𝐴 = -4.7126 -1.5833 1.5346 2.3230 -9.2461 -3.1634 2.8648 2.7796 -14.258 -4.5477 3.6104 4.6238 -3.1687 -0.8016 1.2287 1.2656 . due to the fact that model matrix a is a “full” matrix, i.e. there are no zero entries in it, every secondorder monomial will appear in the equation of the system. as a consequence, the lft will produce a model eq.(4), in which π will contain every possible second-order monomial. this means that the number of monomials (including the state variables) is mb = (n2 + 3n) / 2 in the case of a “full” model matrix. in table 3, the number and sizes of the lmis have been summarised in the case of n-dimensional lv systems with a “full” model matrix. the exponential factor 2n in table 3 originates from the rectangular shape of polytope 𝒳 possessing 2n corner points. on the other hand, the feasibility of lmi conditions in eqs.(7) and (8) should be checked at each corner point of every facet of the polytope. furthermore, an n-dimensional rectangular polytope has 2n facets with 2n-1 corner points. as can be seen, a rectangular polytope introduces an exponential increase in the dimension of the given problem. however, n-dimensional intervals can be easily handled compared to arbitrarily shaped polytopes defined by (hyper)-triangle meshes. fig.8 illustrates the cross sections of the invariant domain along the different pair of axes. 5.4. 2d uncertain lv system with an uncertain equilibrium point in this section, the same 2-dimensional system is presented that appeared in section 5.1 with the same model parameters but with an additional uncertain term kδ, where k = [1 1]t. it is assumes, that δ ∈ 𝒟 = -0.1, 0.1 is an unknown constant parameter (δ = 0). the equation of the uncertain model is the following: 𝑥 = 𝑑𝑖𝑎𝑔(𝑥) 𝐴𝑥 + 𝐾δ + 𝑏 (15) table 3. number and sizes of the lmis in the case of n-dimensional lv systems. size number description mb × mb 2n positivity of 𝑉(𝑥) ma × ma 2n negativity of �̇�(𝑥) mb × mb n ⋅ 2n ε! ∈ 𝔗𝔫𝔱(𝒳) mb × mb n ⋅ 2n 𝒴 ∈ 𝔗𝔫𝔱(ε!) mb is the size of the lyapunov matrix p, ma = ½ (n3 + 5n2 + 4n) is the size of the matrix pa(p), which appears in the lmi ensuring the negativity of the time derivative of the lyapunov function. figure 8. cross-sectional view of the doa estimate of the 4d lv system. computational stability analysis of lotka-volterra systems 44(2) pp. 113–120 (2016) doi: 10.1515/hjic-2016-0014 119 the equilibrium point of the uncertain system is an affine function of the uncertain parameter δ: 𝑥∗ δ = 𝐴!! −𝐾δ − b = −𝐴!!𝐾δ + 𝑥!∗ , (16) where 𝑥!∗ is the equilibrium point of the system presented in section 5.1, i.e. when δ = 0. eq.(15) is translated into the following form: 𝑥 = 𝑑𝑖𝑎𝑔(𝑥)𝐴 𝑥 − 𝑥∗(δ ) . (17) the centred model of the system around the uncertain equilibrium point x*(δ) can be calculated if the new state vector x = 𝑥 – x*(δ) is introduced. the equation of the centred system is the following: 𝑥 = 𝑑𝑖𝑎𝑔 𝑥 + 𝑥∗ δ 𝐴𝑥 . (18) if the lyapunov function depends on δ, especially when possessing an uncertain equilibrium point, it is not straightforward to determine an invariant region by considering the α-level set of the lyapunov function. however, it is possible to compute a region ℑ, which is “invariant with respect to” a larger region 𝔘 (ℑ ⊂ 𝔘), in the sense that every trajectory with an initial condition from ℑ will not leave 𝔘. in order to compute ℑ and 𝔘, the α-level set ε!(δ) of the obtained lyapunov function v(x, δ) is determined in the coordinates system of the original system and at the corresponding equilibrium point for every δ ∈ 𝒟. the overlining in the notation ε!(δ) means that this level set is translated into the original coordinates system. as fig.9 illustrates, the intersection ℑ and the union 𝔘 of the α-level sets obtained for different values of δ have been computed. it can be stated that every trajectory starting from region ℑ will not leave region 𝔘. 6. conclusion in this work, the lyapunov function of n-dimensional lv systems (n = 2, 3, 4) was successfully computed by using the improved optimization-based method [6, 15]. in the case of each deterministic system, an invariant region was given, as the estimated doa. in the case of an uncertain lv system with an uncertain interior equilibrium point, two regions (ℑ ⊂ 𝔘) were given, which describe the stable regions of the system. symbols 𝑥 denotes the time-derivative of function x(t) lt denotes the transpose of a matrix l 𝜗(∙) denotes the corner points of a polytope diag(x) denotes the diagonal matrix x = x(t) ∈ ℝ! represents the state variables of a dynamical system δ ∈ ℝ! vector of uncertain parameters π ∈ ℝ! vector valued function, which represents the set of monomial and rational nonlinear terms to be considered in the lyapunov function π ∈ ℝ!!!!! auxiliary variable denoting 𝑥𝜋 v(x) denotes the lyapunov function 𝒳 ⊂ ℝ!, 𝒟,𝒟 ⊂ ℝ! bounded polytopes acknowledgement this research was supported by otka nf 104706 references [1] chesi, g.: domain of attraction: analysis and control via sos programming (springer-verlag, london, uk) vol. 415, 2011 doi: 10.1007/978-085729-959-8 [2] boyd, s.; el ghaoui, l.; feron, e., balakrishnan, v.: linear matrix inequalities in system and control theory, in studies in applied mathematics (siam, philadelphia, pa, usa) vol. 15, 1994 doi: 10.1137/1.9781611970777 [3] scherer, c.; weiland, s.: linear matrix inequalities in control, lecture notes (dutch institute for systems and control, delft, the netherlands) 2000 doi: 10.1201/b10384-28 [4] trofino, a.; dezuo, t.j.m.: lmi stability conditions for uncertain rational nonlinear systems, int. j. robust nonlinear control 2013 24(18), 3124–3169 doi: 10.1002/rnc.3047 figure 9. α-level set ε!(δ!) of the lyapunov function in the original coordinates system for some values δi of the uncertain parameter and the corresponding equilibrium point x∗(δi) of the same color. the redfilled region is the intersection of the level sets for every possible value of δ. the black line shows the contour of the union of the level sets. polcz and szederkényi hungarian journal of industry and chemistry 120 [5] polcz, p.; szederkényi, g.; péni, t.: an improved method for estimating the domain of attraction of nonlinear systems containing rational functions, j. physics: conf. ser. 2015 659(1), 012038 doi: 10.1088/1742-6596/659/1/012038 [6] polcz, p.; szederkényi, g.; hangos, k.m.: computational stability analysis of an uncertain bioreactor model, proc. int. symp. stability, vibration, and control of machines and structures (svcs 2016, budapest, hungary) pp. 1-12, 2016 [7] rocha filho, t.m.; gléria, i.m.; figueiredo, a.; brenig, l.: the lotka–volterra canonical format, ecol. mod. 2005 183(1), 95–106 doi: 10.1016/j.ecolmodel.2004.07.023 [8] noonburg, v.w.: a neural network modeled by an adaptive lotka-volterra system, siam j. appl. math. 1989 49(6), 1779–1792 doi: 10.1137/0149109 [9] bhargava, s.: generalized lotka-volterra 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rational systems using linear matrix inequality conditions and sdp optimization, technical report (faculty of inform. techn. and bionics, pázmány péter catholic univ., budapest, hungary), 2016 users.itk.ppke.hu/~polpe/techreport2016apr.pdf [16] �hecker, s.; varga, a.; magni, j.f.: enhanced lfrtoolbox for matlab, proc. ieee int. symp. computer aided control systems design pp. 25– 29, 2004 doi: 10.1109/cacsd.2004.1393845 [17] magni, j.f.: linear fractional representation toolbox (ver. 2.0) for use with matlab, 2006 www.cert. fr/dcsd/idco/perso/~magni [18] loefberg, j.: yalmip: a toolbox for modeling and optimization in matlab, proc. cacsd conference (taipei, taiwan), 2012 users.isy.liu.se/ johanl/yalmip microsoft word 16.12 bálint.docx hungarian journal of industry and chemistry vol. 44(2) pp. 99–104 (2016) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2016-0012 refrigerator optimal scheduling to minimise the cost of operation roland bálint and attila magyar faculty of information technology, university of pannonia, egyetem u. 10, veszprém, 8200, hungary the cost optimal scheduling of a household refrigerator is presented in this work. the fundamental approach is the model predictive control methodology applied to the piecewise affine model of the refrigerator. the optimisation could not be solved using off-the-shelf tools, e.g. multi-parametric toolbox, so a binary treebased optimal scheduling algorithm has been developed for this problem. keywords: optimal scheduling, model predictive control, operating cost minimization, modelling, day-ahead market 1. introduction environmental awareness is trendy in modern societies. policy-makers tend to prefer green energy, e.g. solar, wind, etc. in order to decrease carbon footprints. the demand-and-supply-based nature of the electricity market has led to hourly electricity prices in day-ahead markets [1]. most people seek the cheapest solution by using their appliances during low price periods, however, there are certain devices, e.g. refrigerators work all day long. in this case, the only opportunity lies in the optimal scheduling of the cooling periods. the prescribed inside temperature of the refrigerator makes the problem difficult to solve. *correspondence: balint.roland@virt.uni-pannon.hu 2. problem statement in a day-ahead market, the service provider provides the hourly electricity price for the next day. the problem to be solved is the optimal scheduling of a given refrigerator based on the forthcoming electricity prices. as a constraint, the refrigerator temperature must be kept within given boundary values. 2.1. energy price the service provider provides the electricity price for the next 24 hours (dam: day-ahead market). fig.1 shows the electricity price [2] over a week, each line corresponds to the price of a day. figure 1. electricity price of a day-ahead market over a week [2]. day: monday tuesday wednesday thursday friday saturday sunday bálint and magyar hungarian journal of industry and chemistry 100 2.2. refrigerator model in order to describe the dynamics of the thermal behaviour of the refrigerator, the electric substitution model of fig.2 can be used, where the red voltages correspond to the inner air temperature (uair) and the cooled back wall (uwall). the blue elements are the inputs to the system: the outer air temperature (uout) and the on/off switch (s). the capacitors demonstrate the heat capacity of the back wall (cwall) and the inner air (cair) while the resistors are the heat transfer coefficients between the components. 2.2.1. cooling dynamics the first case is when the switch s is closed, i.e. the refrigerator is cooling. the dynamics of the system can be described by the state-space model of the form outlined in eqs.(1) and (2), where the state and input vectors are given in eqs.(3) and (4). 𝑥 = a x + b u (1) y = c x + d u (2) 𝒙 = 𝑇!"# 𝑇!"## (3) 𝒖 = 𝑇!"#𝑆 (4) the parameters of the state-space model of the cooling dynamics are given as follows: 𝐀!" = − !!!!! !!∙!!∙!!"# ! !!∙!!"# ! !!∙!!"## − ! !!∙!!"## + ! !!""#∙!!"## (5) 𝐁!" = ! !!∙!!"# 0 0 !!""# !!""#∙!!"## (6) 𝐂 = 1 0 0 1 (7) 𝐃 = 0 0 0 0 (8) 2.2.2. reheating dynamics the second case is when the switch s is open, i.e. the refrigerator is reheating to environmental temperature. the system is still linear and time invariant as outlined in eqs.(3) and (4). the parameters of the state-space model are given in eqs.(9)-(12). 𝐀!"" = − !!!!! !!∙!!∙!!"# ! !!∙!!"# ! !!∙!!"## − ! !!∙!!"## (9) 𝐁!"" = ! !!∙!!"# 0 0 0 (10) 𝐂 = 1 0 0 1 (11) 𝐃 = 0 0 0 0 (12) 2.3. control aim the aim of this study is to schedule refrigerator's operation to minimise the operational costs with the following assumptions: • the operational cost is the energy consumption of the refrigerator during the day; • the price of electricity changes hourly; • the energy price is known for 24 hours in advance; • the temperatures must be between the following operating constraints: o the inner air temperature should be between 0.1 ºc and 5.5 ºc; o the cooled back wall temperature should be between -19 ºc and 7 ºc; • the outer air temperature is constant; • the input variable is binary (on/off); • the models should be chosen based on the value of the input. the main objective is to minimize the operational costs, defined as 𝑐𝑜𝑠𝑡 = 𝑝! ∙ 𝑈!!!! !!! (13) where pk is the price of electricity and uk is the input at time ts ⋅ k (ts: sample time). 3. optimal scheduling to find the optimal scheduling of a system the model predictive control approach is used. afterwards a novel heuristic optimisation technique is presented. 3.1. model predictive control of the system for optimization, the multi-parametric toolbox 3.0 (mpt) [3] is used first, because in this matlab toolbox we can find all the necessary options can be found: • ‘piecewise affine’ (pwa) modelling for linear time invariant (lti) systems; • optimal controller design for pwa systems. figure 2. electric substitution model of a refrigerator. s symbolizes the switch of the devices controlled by a thermostat in an ordinary refrigerator. refrigerator optimal scheduling 44(2) pp. 99–104 (2016) doi: 10.1515/hjic-2016-0012 101 the solver uses a cost function as follows: 𝑚𝑖𝑛 | 𝑸!𝒙! |! + | 𝑸!𝒖! |!!!! !!! , (14) where variables xk and uk are the state and input vectors at the kth step of the prediction horizon n. the || · ||p expression is the standard p vector norm, and qx and qu are penalty matrices. the mpt toolbox for the pwa system description uses discrete time models, thus initially the continuous time model must be discretised. however, there are two problems to solve: • the penalty matrices (qx and qu) cannot be changed, so the actual electricity price cannot be used in this form; • the time information of the system, e.g. system time, is unknown. to handle these problems, two supplementary state variables have been introduced. the first counts the time and the second stores the actual energy price. if the refrigerator is switched off the energy price is zero, otherwise it provides the actual price value. one pair of (on/off) systems for every price of each hour needs to be created, during the calculation the model parameters and the price are constants. thus, the choice is based on the state of the binary input and the time value of the state vector. the modified lti state-space models are the following: 𝒙 = 𝑇!"# 𝑇!"## 𝑡 𝑝 (15) u = [ s ] (16) φon= 0.9998 0.0001 0 0 0.0004 0.9977 0 0 0 0 1 0 0 0 0 0 (17) 𝚪on= -0.0024 -0.045 0 𝑝! (18) φoff= 0.9998 0.0001 0 0 0.0010 0.9988 0 0 0 0 1 0 0 0 0 0 (19) 𝚪off= 0 0 0 𝑝! (20) 𝒇 = 0.0022 0.028 1 0 (21) 𝐂 = 1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1 (22) 𝐃 = 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 (23) the hourly changing energy prices are denoted by ph in matrices γ, so there are 24 models with two system dynamics (on and off) in total. the model actually used is chosen based on the input (on and off states) and the third element of the state vector (t: define the model over time so the energy price value). based on the two variables the necessary model is chosen: • if the refrigerator operates, its value is the actual energy price; • if the refrigerator is switched off, it is zero. by the summation of the values of x4 the operational cost is obtained (in €/kwhr) for the operating period. the piecewise affine model of the system is given by eq.(24). 𝒙!!! = 𝚽!"𝒙! + 𝚪!"𝒖! + 𝒇 , if 𝑺 = 1 𝚽!""𝒙! + 𝚪!""𝒖! + 𝒇 , if 𝑺 = 0 (24) the simulation is very sensitive to some design parameters. these parameters are the sampling time (ts), the prediction horizon size, and the cycle number of the simulation horizon. the correlation between horizon size and simulation time is outlined in table 1 (ts = 5 min). if the horizon is bigger than 12 – 15, the simulation will end in deadlock. the sample time value cannot be too large because the change in one step would be too high and the algorithm would not be able to function properly. the multiplication of the sample time and the horizon yields to predicted time horizon. if the sample time and the horizon are small, the algorithm runs quickly, but with a small pre-determined time interval and cannot calculate the forthcoming electricity prices. as nsim increases, the running accelerates. in the pwa system, only the systems of the simulated time interval are present. if nsim is small, the number of models is small so the algorithm must choose from fewer systems but in that case, the cycle has to run repeatedly as the new pwa system is defined. 3.2. heuristic search algorithm using binary tree growing the general optimizer in the mpt is very slow due to several problem-specific assumptions, e.g. binary input, and the horizon size is bounded so another optimisation algorithm is needed that runs faster and uses problemspecific heuristics. table 1. the simulation time in minutes versus horizon size. size of horizon, 8 10 12 13 calculation time, min 2 8 59 111 bálint and magyar hungarian journal of industry and chemistry 102 3.2.1. base of algorithm in order to find the optimal solution, all input combinations need to be counted over time. trivially, this number can be reduced by deleting those combinations where the system exceeds the operating constraints. in this case, in all steps, the states are duplicated and 1 or 0 (on or off) is added to input vectors so the number of combinations grow exponentially and the simulation time of one cycle grows, too (fig.3). without additional heuristics, the running time of the 18th loop was as high as the mpt simulation with a horizon size of 13. model-related heuristics can be applied to decrease the number of combinations. this rule is simple: between any two input combinations, if the corresponding air and wall temperatures are higher and also the operational cost is greater than or equal to one of the examined combinations then this input combination is not optimal, i.e. it can be ignored. the pseudo code of the algorithm is summarized by algorithm 1. with these heuristics, the number of combinations and the running time of the simulation can be reduced. fig.4 shows the running time of the nth cycle with and without this filtering. this figure shows that without the filter, the simulation time of the 20th cycle is more than 30 minutes but with the filter it is a maximum of 1.5 minutes. algorithm 1 heuristic algorithm procedure optimum searching define: x0 ← initial state �bounds ← bounds of temperatures ph ← electricity prices of a day � h = 1 (actual hour of day) � ts ← sample time [hour] � simtime ← simulation time cost = 0 �sys1 ← reheating dt-lti system sys2 ← cooling dt-lti system u0,0 =[] create: � pwa ← pwa system from sys1 and sys2 loop: �for i = 0 : 1 : simtime/ts do ui,all = [ui−1,all; ui−1,all] (duplicate u) n = size(u) (number of combinations) � k ∈ {1, 2, ..., n} �if 1 < k <= n/2 then ui,k = [ui,k, 1]; else ui,k =[ui,k, 0]; xi+1,k = pwa(xi,k,ui,k) cost ← update cost �k ∈ {1, 2, ..., n} �if xi+1,k ∈/ bounds then delete xall,k, xall,k and costk n = size(u) k,l∈{1, 2, ..., n} � if xi+1,k > xi+1,l and costk > costl then delete xall,k, xall,k, costk else if xi+1,l > xi+1,k and costl > costk then delete xall,l, xall,l, costl n = size(u) � k ∈ {1, 2, ..., n} � opt = min(costk) � optimal solution = uall,opt 3.2.2. algorithm with horizon the algorithm of the mpt uses a horizon to reduce the calculation time for fast online implementation. in the investigated problem, the maximum usable horizon available in mpt is too small. the previous algorithm calculates the optimal solution during a whole day, so the horizon is 24 hour, e.g. if the sample time is 5 minutes then the size of the horizon is 288. this large horizon size causes slow simulations. to decrease this simulation time, a horizon as in the mpt algorithm is defined. this step causes a very large reduction in running time. this time is proportional to the horizon size, but if the horizon is too small the solution would not be optimal. the running times and calculated costs are collected in table 2. figure 3. running time and number of combinations vs number of cycles. figure 4. without the heuristic algorithm, the simulation time of the 20th cycle is more than 30 minutes, but with the heuristic algorithm, it has a maximum of 1.5 minutes. refrigerator optimal scheduling 44(2) pp. 99–104 (2016) doi: 10.1515/hjic-2016-0012 103 the running times in table 2 show that by increasing the horizon size the simulation time increases, too. the operating cost increases, but it is uncertain whether a bigger horizon is better. based on this, the suggested heuristic search-based optimization algorithm can be used as a basis for a special model predictive scheduling/control algorithm. 4. results and discussion the model predictive control algorithm in the mpt did not work correctly due to the serious limitations connected to the control task. by increasing the horizon size, the simulation becomes slow with maximum horizon size of 13. the proposed optimization algorithm has been developed to find the optimal scheduling. table 2 shows the difference between simulation times and operating costs if the horizon size is changed. fig.5 shows the calculated optimal scheduling for wednesday. fig.6 shows the energy prices and the number of input combinations of the ith cycle without and without a horizon size of 4 hours. there is a correlation between the monotonous energy price and the number of input combinations. if the price is increased the number opf combinations increases, too. simulations of energy prices for a whole week with and without horizon size of 4 hours (ts = 5 minutes) have also been performed. the results are shown in table 3. the simulation times were reduced by 70-90% while the costs grew only by 1-2%. table 2. the size of horizon, the simulation time in minutes and the cost of best solution. size of horizon running time cost deviation from optimal none (∞) 75.0 0.20235 0% 24 5.7 0.20427 +0.95% 36 12.6 0.20433 +0.98% 48 16.9 0.20394 +0.79% 60 25.9 0.20413 +0.88% 72 31.0 0.20456 +1.09% figure 5. the optimal scheduling for wednesday’s energy prices. figure 6. wednesday energy prices and the number of input combinations of the ith cycle with and without a horizon size of 4 hours. bálint and magyar hungarian journal of industry and chemistry 104 5. conclusion a heuristic search algorithm has been implemented for the optimal scheduling of a refrigerator model. this work was initiated by the fact that the optimization algorithm of the mpt did not work correctly with large horizon sizes for the applied piecewise affine system. the proposed algorithm calculates the optimal input sequence for a whole day with any horizon size but it also works with an infinitely large horizon. the calculation time is fast compared to that of the matlab mpt solver. our own heuristic algorithm is faster without a horizon than the mpt solver with horizon size of 13 hours. i can be run with a larger horizon size, and can yield the absolute optimum without a prediction horizon. the operating cost of the solution is 12 percent less with the aid of a heuristic search. this cost is 25 percent cheaper than the cost of traditional refrigerator control. the suggested heuristic search-based optimization algorithm can be used as a basis of a special model predictive scheduling/control algorithm. the present work is based on an ideal refrigerator model. as a future step, the validation of the model and the scheduling algorithm in an mpc framework will be investigated. testing the control scheme in a real situation with random disturbances, e.g. opening the refrigerator’s door, etc. will also be performed. symbols a state matrix b input matrix c output matrix cair heat capacity of the inside of the refrigerator cwall heat capacity of the back-wall dam day-ahead market dt-lti discrete time linear time invariant f constant input or disturbance φ off off state discrete time state matrix φ on on state discrete time state matrix γ off off state discrete time input matrix γ on on state discrete time input matrix lti linear time invariant mpc model predictive control mpt multi-parametric toolbox pwa piecewise affine qu penalty matrix of u vector in mpt qx penalty matrix of x vector in mpt rcool heat resistance of the back-wall re heat resistance between back-wall and inner air ri insulation of refrigerator s binary state switch tair inner air temperature of refrigerator tout outer room temperature twall cooled back-wall temperature of refrigerator u input vector uk input vector value in kth sample moment in dt uair voltage corresponding to inner air temperature ucool voltage corresponding to minimum reachable back-wall temperature uout voltage corresponding to outer air temperature uwall voltage corresponding to cooled back-wall temperature x state vector xk state vector value in kth sample moment in dt acknowledgement this research is supported by the national research, development and innovation office nkfih through grant no. 115694. a. magyar was supported by the jános bolyai research scholarship of the hungarian academy of sciences. the authors would like to express their gratitude to prof. katalin hangos and dr. gyula simon for useful discussions. references [1] huisman, r.; huurman, c.; mahieu, r.: hourly electricity prices in day-ahead markets, energy econ. 2007 29(2), 240–248� doi 10.1016/j.eneco.2006.08.005 [2] nord pool: elspot prices, www.nordpoolspot.com/ market-data1/elspot/area-prices/all1/hourly, 2016 [3] herceg, m.; kvasnica, m.; jones, c.; morari, m.: multi-parametric toolbox 3.0, proc. eur. control conf., epfl-conf-186265 (zurich, switzerland) 2013 table 3. differences in optimal operating cost and simulation time with and without a horizon. without horizon 4 hour horizon difference in percent day of the week cost, 1/kw time, min cost, 1/kw time, min cost, 1/kw time, min monday 0.20235 75 0.20394 16.9 +0.79 -77.47 tuesday 0.20200 1013.2 0.20650 78.9 +2.23 -92.21 wednesday 0.27748 234 0.28111 48.8 +1.31 -79.18 thursday 0.22255 116.1 0.22739 38.3 +2.17 -67.04 friday 0.23127 267.7 0.23618 32.3 +2.12 -87.93 saturday 0.25819 222.3 0.26281 45.1 +1.79 -79.70 sunday 0.27286 100.4 0.27488 18.7 +0.74 -81.34 hungarian journal of industrial chemistry veszprem vol. 30. pp. 41 45 (2002) liquid-solid heat transfer with the phase-change of solid s. petrescu and a. bacaoanu (department of chemical engineering, the "gh. asachi" technical university of iasi, romania) received: may 14,2001 this paper presents a study of the heat transfer for a singular spherical particle melting in a stagnant liquid phase. the proposed mathematical model allows the calculation of process duration, the radius of melting front and the degree of melting. in order to verify the mathematical model, the degree of melting, the melting rate and the heat transfer coefficient were experimentally determined, using spherical ice particles at 267 k. the melting medium was distilled water at temperatures of288, 298 and 318 k. the experimental results have been compared with those corresponding to relation: nu == 2 + 0.6ra114 pr113 • the agreement isgood. keywords: melting, heat transfer, heat transfer coefficient, melting rate introduction technical literature provides a large onumber of papers regarding the heat transfer in liquid solid systems. part of these papers [1-9] approach theoretically and experimentally the heat transfers at the melting process by direct contact with a liquid phase of a singular particle or assembly of particles. the available studies regard equally to heat transfer by natural and forced convection. thereby, woods [2] presents a review about the dissolution and melting of solids in contact with a melted substance. jochem and koerber [3] studied theoretically the heat and mass transfer of ice, melting in sodium chloride solution and glycerin. using an iterative method based on the newton algorithm; they solved the differential equations of the melting process. fukusako et all [4] approach experimentauy the heat transfer by natural convection at the melting of an ice cylinder in 3.5% saline solution. they determined the local heat transfer coefficient for the range of 274.8292,8 k temperatures. okada et all [5] studied experimentally the melting of a fix bed of spherical ice particles using water as melting medium. gobin and bernard [6] treated the metal melting by natural convection and analyzed the influeoce of prandtl and rayleigh numbers. other investigations [7 .8] approached theoretically and experimentally the heat transfer at the melting of a spherical ice, moving upwards through a column with water. the authors established a mathematical model, which was applied to the determination of temperature distribution, in the inner of the particle, as function of radius and time. also, they determined experimentally the heat transfer coefficient. this paper presents a mathematical model allowing the determination of melting front radius, degree of phase change and process duration at the melting of a singular spherical particle in a stagnant liquid phase. the heat transfer coefficient was experimentally determined. the influence of the liquid phase temperature on the rate melting and heat transfer coefficient was also studied. the proposed model was verified. mathematical formulation the melting process of a solid, being in direct contact with a liquid phase, when the particle temperature is different of that of the melting temperature, has two stages: in the first stage, the heating of the particle takes place until the temperature at the solid-liquid interface becomes equally to the melting temperature. at that moment, the second stage begins, that is, the proper melting. if the initial temperature of the particle is close to the melting temperature value, the duration of the primary stage is short and can be neglected. in the case of the melting of a spherical particle containing a single a component in a solution 42 i i r fig .1 physical model containing also a component, the following three elementary processes are involved: the heat transfer from the solution to the particle surface the proper melting at the solid-liquid interface the mass transfer of the a component from the particle surface to the liquid phase. the physical model is presented in the fig.]. according to the physical model, at the initial moment, the radius of particle is r and decreases as the melted region grows. for a given moment, the radius of the particle is r{}. the temperature· is ti at the solid-liquid interface and r_ in the bulk solution. since the aim of the mathematical modelling is to establish the equation of process duration or the radius of melting front (degree of transformation) in time, one considers the energy equation for the radial direction: ar a. a ( 2 ar) pep-a/= r2 dr r tr the boundary conditions are: t so. r sr5rb t= t ... t > 0, r = ro. (1) (2) (3} ~(rz dt)=o dr dr by integration of the eq.(5) one obtains: dt =_!_c dr r 2 1 c r = _ ___!_ + c 2 r (6) (7) (8) the integration constants, c1 and c2, result from the boundary conditions: (9) (10) from relations (9) and (10) one obtains: t,t~ =at= -c{:, -~~) (11) or: t:..t 1 1 substitution of eq.(l2) into eq.(jo) gives: (12) c2 = t.,., + at(_!__!_)1 (13) rl ro rl also, substitution of the cl constant into (7) gives: dt dr (14) the boundary condition (3) associated with eq.( 14) is: (15) since, 1 1 8 r0 r1 r0 (r0 +s) t= t ... (4) and to simplify the solution of the differential equations, when the temperature is constant on an infinitesimal time, one considers the quasi-steady state. thus, the process can mathematically be described by the equation: (5) or: il -=a 8 eq.( 15) becomes: ciat{r0 +o) (16) the integration of eq.(16), between 0 t and r r0, leads to: 4 6 fig.2 experimental installation. 1 -cylindrical glass vase, 2 43 table 1 the variation of the particle mass with time t=288 k t 103&n (s) (kg) 30 4.5 60 7.5 90 9.4 120 12.0 '150 15.1 12 0,6 0,5 0,4 t=298 k t 103&n (s) (kg) 30 6.0 60 10.8 90 17.2 120 20.3 150 25.7 t=308k t 103&n (s) (kg) 20 6.9 40 12.4 60 17.5 80 21.7 100 27.5 t=318k t 103.8.m (s) (kg) 15 7.6 30 13.6 45 19.3 60 24.0 75 28.8 cover, 3 glass recipient, 4rod, 5 support, 60,3 · semiautomatic scales, 7 control thermometer, 8 agitator (17) for small values of 5, results: (18) the radius (the location) of the melting front can be written as function of the degree of melting, 11: ro = r9 -1})113 replacing (19) into (18) gives: (19) t rpsl.\hm [1-(l-7])113 ] (20) a!lt the relations (18) and (20) allow the calculation of the melting front radius, respectively, the process duration. experimental apparatus and procedure according to fig.2, the experimental arrangement consists of a cylindrical glass vase {1) with a cover (2), a glass recipient (3), rod ( 4}, support {5), semiautomatic scales (6), control thermometer (7). the vase (1) represents the melting chamber, where the melting of particle ice takes place. the vase is provided with a dismountable agitator (8) for the temperature homogenization of the melting medium (distilled water). during of the particles melting, the agitator is removed from the melting · chamber. a thermostat connected to recipient (3) supplies the necessary thermal energy for the temperature homogenization. for investigations, the spherical ice particles have been used. the ice particles have been obtained by freezing of distilled water at 267 k, using a special 0.2 0,1 ot:288k ot:o291 k t. t:308k vt:318k o~-2~0---4~o--ro~--8~0~1~0~0~12~0~1~4~0-t~(~sl~~ fig.3 variation of the degree of melting with time device. the melting medium was distilled water of temperatures of 288, 298, 308 and 318 k. in the experiments, the mass variations function in time has been determined separately, for every particle. results and discussion experimental results for the mass variation of the ice particle in time are presented in table i. these results have been used for the calculation of the melting level, 1], with the following relation: (21) graphically, the fj values are shown in fig.3. as may be seen the degree of melting is increasing with the temperature increase. the medium melting temperature has a positive influence on the melting process: in the following, using the above data and relations: (22) (23) the melting rate (vm) and the heat transfer coefficient (a.} have been determined. the melting rate bas been calculated taking into account the degree of melting 44 0,08 0,06 0,04 0.()2 290 300 310 320 t(k} fig.4 temperature influence on melting rate 500 400 290 300 310 320 t{k) fig.s temperature influence on heat transfer coefficient corresponding to a 60-sec. duration. the diagram in fig.4 shows an increase of the melting rate with the temperature. also, the water temperature has a positive effect on the heat transfer coefficient (fig.5). the temperature increase amplifies the natural circulation of water around the particle ice. consequently, the transferred heat flux from water to ice particle will increase and will amplify the heat transfer coefficient and the melting rate. the proposed mathematical model represented by eq.(20) is verifying. based on the values of the heat transfer coefficient~ using the relation (20), the process duration values have been calculated. for the degree of melting. the values corresponding to the ro..sec. duration have been considered. the obtained results are presented in table 2. according to this table. one may see that the calculated values of the process duration are close to the experimental values (60 sec.). therefore. one may assert that experimental data verify the proposed mathematical model. further on. the experimental data obtained in this study agree with the other authors data. to this purpose .. one considers the dimensionless equation [ 1}: nu = 2+0.6ra114 prll 3 (24) the experimental values of nusselt number have been determined for more values of rayleigh and table 2 verifying of the mathematical model temperature (k) degree of melting experimental time (s) calculated time (s) 6 . 288 0.172 60 59.61 298 0.247 60 59.08 308 0.400 60 58.72 2 --ra 3 318 0.549 60 58.93 fig.6 the dependence of the experimental nusselt numbers with the rayleigh numbers prandtl numbers. these values are graphically represented in fig.6. this figure contains also the calculated values, using eq.(24), for nusselt number. data from fig. 6 indicate small differences between experimental data obtained by our study and those obtained using eq.(24). conclusions in this paper a mathematical model of the heat transfer at melting of a spherical particle by direct contact with a stagnant liquid phase has been established. the model allows determination of the process duration, the melting front radius and the degree o:f melting. the proposed mathematical model has been experimentally verified. for this purpose, the experimental values of the melting rate and the heat transfer coefficient have been determined. the experiments were carried out in a laboratory installation, using spherical ice particles and distilled water at different temperatures, as melting medium. the comparison of the calculated values, based on the proposed model, with those obtained experimentally were in good agreement. the experimental data obtained in this work were also verified with those of other authors. there can be noted a good agreement. based on experimental data, the influence of the melting medium temperature on the melting rate and on the heat transfer coefficient was studied. cp d g symbols specific heat. jkg-1k-1 partic1e diameter~ m gravitation acceleration, ms-2 mo q=vm11hm r s t ti t= vm t1hm l\m ra=grpr pvd re=-a [3 1 1j ).l p ps j.l particle mass at time t=o, kg specific heat flux, wm·2 radial coordinate, m external surface area of particle, m2 time, s temperature at solid -liquid interface, k temperature in the bulk solution, k melting rate, kg m·2 s·1 latent heat of melting, j kg·1 variation of particle mass, kg rayleigh number reynolds number heat transfer coefficient, w m·2 k·1 thermal expansion coefficient, k.1 heat conductivity, wm-1k-1 degree of melting liquid viscosity, nsm·2 density of liquid, kg m·3 density of particle, kg m·3 references 1. blrd b. r., stewart w. e. and lightfoot n. e.: transport phenomena, new york, j. wiley, 1960 45 2. woods a. w.: j.fluid mech., 1992,239,429-438 3. jochem m., koerber c.: waerme·staffuebertrag 1993, 28, 195-204 4. fukusako s., yamada m., horibe a. and watanabe c.: general papers in heat mass transfer, instalation and turbomachinery asme, 1994, 271, 81-87 5. okada m., hashimoto k. and 01ha 1.: proc. asme-jsme therm. eng. conf. 3 rd., 3, 327-333, 1991 6. gobin d. and bernard c.: j. heat transfer, 1992, 114 (2) 1992,521-524 7. fetecau c. and petrescu s.: rev. roum. sci. techn. mec. appl., 1994,39 (1),. 92 -97 8. petrescu s. and lisa c.: bul. chern. comm., 1996, 29 (1), 34-39 9. sun y. and bernard c.: melting of ice in the presence of thermosolutal convection in the melt, fast (univ. of paris vi and xi, cnrs) campus univ. 91405 orsay 10. raznievic k.: termodinamicke tablia i diagrami, skolska kniga, zagreb, 1975 11. pavlov f. k., romankov p.g. and noskov a. a.: processes and apparatus in chemical engineering, bucharest, 1981 page 40 page 41 page 42 page 43 page 44 hungarian journal of industrial chemistry veszprem vol. 30. pp. 27-31 (2002) a chelate sorbent prepared by the modification of lichroprep rp-8 with titan yellow and its application i. sow a, r. kocjan and r. swieboda (department of inorganic and analytical chemistry, medical school, 6 staszica str., 20-081 lublin, poland) received: aprils, 2001 the new chelating sorbent for metal ions was prepared by impregnation of chemically modified silica lichroprep rp-8 with ion pairs composed of cation of aliquat 336 and anion of titan yellow. the hypothetical molecular mechanism of binding this ion pair by the surface of the applied carrier was presented. the sorbent was compared with analogous sorbent with plain silica carrier containing the same ion pairs. higher stability of the new sorbent in comparison to that of the plain silica chelating sorbent was demonstrated. the sorbent obtained was applied for chromatographic separations of some chosen mixtures of metal ions and for additional purification of aqueous solutions of alkali metals from trace amounts of heavy metals. keywords: titan yellow, chelating sorbent, lichroprep rp-8, extraction chromatography, purification of alkali metal salts introduction in the trace analysis of metal ions an important role is played by the chelating sorbents [1]. besides commercial chelating resins used for these purposes, other chelating sorbents have recently found increasing popularity [2], and especially interesting are silica gels modified with various chelating reagents [3]. in analytical chemistry, including trace analysis of metal ions, chemically modified silicas have also found wide applications [4-6]. the chelating sorbents can be obtained in a very simple manner by the impregnation of common silica with ion pairs formed by an alkylammonium cation of a liquid anion exchanger aliquat 336 (methyltrioctylammonium chloride) and the anion of sulfonated chelating reagent [7]. in ref. [8] the application to trace analysis of some metals of a chelating sorbent obtained by impregnation of silica with a mixture of aliquat 336 and titan yell ow. our earlier data indicate the high stability of sorbents formed by impregnation of chemically modified silicarp-8 with mixtures of aliquat 336 and sulfonated chelating reagents [9,10]. therefore we decided to prepare the sorbent by modification of rp-8 with titan yellow (fig.l) and compare this to common unsilanized silica gel modified with titan yellow. the present paper relates the results of the performed investi gatioris. experimental all experiments were performed at room temperature (20±1°c). reagents and solutions lichroprep rp-8 (0.040-0.063 mm) (merck, germany) was used as support for the stationary phase. aliquat 336 methyltrioctylammonium chloride (merck, germany) was purified by shaking a o.lmol r1 solution in chloroform with equal volume of 0.1 mol r 1 hydrochloric acid and subsequently five times with distilled water and then, by filtering the organic phase through a cellulose filter. titan yellow (merck, germany), was purified as described by nyons [ii]. aqueous metal salt solutions were prepared by dilution of titrisol standard metal salt solutions (merck). working solutions were freshly prepared from standard metal salt solution by dilution with doubly distilled water {previously adjusted to an appropriate ph value with 1 mol r1 hydrochloric acid. acetate buffer, or tetraborate buffer). freshly distilled chloroform of analytical grade was used as diluent of ahquat 336. 28 fig.l titan yellow (thiazol yellow g) solutions of hc104 and hcl (suprapur, merck) were used as eluents. apparatus a pye unicam (cambridge, uk) single-beam atomic absorption spectrometer was used for the determination of the metals. all ph measurements were performed with a mera­ elwro n517 (wroclaw, poland) direct-reading ph meter, a glass-silver/silver chloride combination ele-ctrode. a voltammetric analyser upe-2a (radius, gdansk, poland) was used in the determination of trace amounts of ph, cd, cu and zn in kcl by anodic stripping voltammetry. a graphite electrode, impregnated with epoxy resin and coated with a mercury film in situ, was used as a working electrode having a working area of 12.5 mm2 • procedure the impregnating solution was prepared by shaking an appropriate volume of 0,01mol r 1 solution of aliquat 336 in freshly distilled chloroform with 5 volumes of o.,oolmol r1 aqueous solution of titan yellow. after separating the phases, the organic phase was passed through a cellulose filter to remove the residual aqueous phase. lichroprep rp-8 was impregnated with a chloroform solution of a mixture of aliquat 336 and titan yellow in the following manner: amount of 10 g of the sorbent was prepared by mixing a 200 ml portion of the organic solution containing l mmol of titan yellow (0.651 g) and 2 mmol of aliquat 336 (0.884 g) with 8~465 g of lichroprep rp-8. the diluent (chloroform) was then evaporated with the use of a vacuum evaporator on a water bath. l g amount of the chelating sorbent contained 0.1 mmol of titan yellow and 0.2 mmol of aliquat 336. elution of titan yellow from the sorbent with aqueous solutions of mineral acids was performed in the fouowing manner. a 0.1 g amount of the obtained sorbent was shaken for 10 min. with 5 ml of an appropriate acid solution in small tubes. the solution was subsequently centrifuged and the dye was then determined by spectrophotometry at 337 nm with reference to a calibration graph. small polypropylene columns (55 mm x 5 mm) (j. t. baker. phillipsburg, nj~ usa) were packed with 0.1 g of dry sorbent and used to measure the relative capacity of the sorbent towards different metal ions. a 5 ml portion of each solution (previously adjusted to an appropriate ph), containing 0.3 mg of the metal to be determined, was passed through each column for 5 min. each percolate was analysed by aas to determine the residual metal ion concentrations. voltammetric determination of the metals was performed in the following manner. volumes of 10 ml of 0.5 mol r 1 kcl (analytical grade or suprapur grade) to which mercuric nitrate was subsequently added [the concentration of hg(n03)z in the resulting solution was 10-4 mol r 1 ] were passed through the columns packed with 1 g of the sorbent. volumes of 2 jll of standard solutions of cif'+, cd2+, pb2+ and zn2+ ions of 100 ppm concentration were introduced into 10 ml of 0.5 mol r 1 kcl (analytical-reagent grade) (the concentration of each metal ion added in the solution was then 20 ppb). oxygen was removed from the analysed solutions with a stream of argon of special purity. the solutions were electrolysed for 3 min. at -1.3 v. anodic oxidation of the metals was subsequently performed at the following conditions: amplitude 1.2 v; potential change of 10 mvs-1 • results and discussion as discussed in the introduction, chelating sorbents can be obtained in a simple manner by impregnation of silica by ion pairs composed of methyltrioctylammonium cation and sulfonated chelating reagent anion obtained by static extraction process [7). during the preparation of such sorbents, silica gel was impregnated with aliquat 336 and chelating reagents from chloroform solutions in such proportions that the molar concentration of aliquat 336 was twice as large as the concentration of the reagent containing a single sulfo group (or four times for reagents with two sulfo groups, e.g. nitroso-r-salt or titan yellow). it was experimentally found many times that the use of excess amounts of aliquat 336 improved the quality of sorbents so that they became more resistant to elution of the chelating reagent or the whole ion pairs by the aqueous acid solutions. the problem arises how the ion pairs are bound by the silica surface, what is the role of the double excess of aliquat 336 and what is the cause of the increased stability of the sorbents prepared with this excess. hansen et al. [12] in their paper on dynamically modified silica have demonstrated that the branion from the tetraalkylammonium bromide binds the hydrogen ions from the surface silanol groups of silica; the w ions are substituted by the tetraalkylammonium cation. it can be presented those cations of aliquat 336 are bound to silica surface by a similar mechanism (fig.2). the mode of binding of the ion pairs: tetraalkylammonium cation sulfonated chelating :eagent anion, with double molar excess of ajiquat 336 1s probably the following: half amount of aliquat 336 is bound to the silica surface according to fig.2; the \)( h. \1.v ·-0 \ji i t i i i i i i i i ;1;/i1}/;;/}/jll/7j;}i2;1t/?;j/7j/j//; fig.2 silica impregnated with aliquat 336 fig.3 silica impregnated with aliquat 336 and modified witch ion pairs composed of cation of aliquat 336 and anion of titan yellow 1 adsorbent surface is covered by a monomolecular layer of octyl groups from aliquat 336 so that the surface is hydrophobized and it bounds by hydrophobic (and dispersive) interactions the second layer of aliquat cations forming the chelating ion pairs with the sulfonated reagent. in the hydrophobic interactions the octyl groups from both tetraalkylammonium cations are involved. in effect, the carrier surface is isolated from the aqueous bulk phase and the chelating groups are outside the< double layer, capable of binding metal ions in the bulk aqueous solution. the structure of the sorbent containing lichroprep rp-8 can thus be represented as in fig.3. during elution of metal ions bound by sorbent of this type with aqueous solutions of mineral acids, the weaker or stronger accompanying elution of chelating reagents (or even whole ion pairs) is observed so that the properties of the sorbent are changed and its ion exchange capacity is decreased. the anion of chelating reagents are displaced from the ion pairs by the anion of acids used (especially by ci04~ anions which have greatest affinity to the tetraalkylammonium cations). on the other hand, the hydrogen ions from the acids applied in the eluent elute not only metal ions bound by the sorbent (which is advantageous), but also, at higher· concentrations, can displace the whole hydrophobic layer in a process reverse to fig.2 and then the chelating sorbent is decomposed. it happens especially in cases when to elute some metal ions bound by the sorbent aqueous acid solutions of high concentrations (0.51 mol r1 ) are to be used. therefore, we were 29 fig.4 lichroprep rp-8 modified with ion pairs composed of cation of aliquat 336 and anion of titan yell ow 50 45 :a 40 2 35 ~ -e-smcagel -fr-lichroprep rp-8 g 30 hci ~ 25 ;>< = 20 ~ 15 '<!. 10 hcl 5 0 0 2 4 6 8 10 acid cone., mol r1 fig.s percent of titan yellow eluted from silica and lichroprep rp-8 modified with a mixture of ali quat 336 and titan yell ow as a function of concentration of hci04 and hcj acids used as eluents looking for other carriers, which would bind the ion pairs more strongly so that sorbent of higher stability would be obtained. we decided to prepare sorbent on the basis of modified silica rp-8 and the earlier investigated ion pair composed of aliquat 336 and sulfonated chelating reagenttitan yellow. the investigations of such sorbent have shown that in this case the double excess of aliquat 336 (as in the case of plain silica carrier) is not necessary. the alkyl chairs ("brush") on the rp-8 surface bind directly the aliquattitan yellow ion pairs according to fig.4. the chelating sorbent thus prepared is more stable in comparison to those formed on the basis of plain silica. this is illustrated in fig.5 which represent the amounts of eluted titan yellow (in the form of anion or whole ion pairs) plotted against the concentration of the acids applied, the higher stability of sorbent on the basis of rp-8 is explained by the fact that acidic solutions do not displace the ion pairs as in the case of sorbent prepared on plain silica carrier. titan yellow used alone, without aliquat 336, to impregnate rp·8 did not give good results: it was easily eluted from the column by bidistilled water. the ion exchange capacities of the sorbent obtained was comparable with those formed for silica carrier [8]. this is understandable tasking in to account the equal 30 20 10-4 10-3 10"2 16 mg zn co 12 cu e g. g. us 0 25 50 75 100 125 150 v,ml fig.6 separation of metal ion mixtures containing 100 j..tg of each metal ion, on lichroprep rp-8 treated with a mixture of atiquat 336 and titan yellow. column packed with 5 g of sorbent. mean flow rate: lml min1 amounts of chelating reagent (titan yellow) per 1 g of each sorbent. only very small differences in the concentrations of mineral acids (hci04 and hci) necessary to elute the metal ions from the columns were also observed. the sorbent prepared was successfully applied to analytical problems analogous to those described earlier for titan yellow sorbent on the basis of plain silica. figure 6 represents the separation of a synthetic mixture of some metal ions by column extraction chromatography using stepwise gradient elution with solution of chloric(vii) acid. the recovery of the separated metals was in the range of 97 99.5 %. presumably, the practical application of the sorbent described can be found for selective preconcentration of trace amounts of iron (iii) and cuprum(ii). their ions are bound even from acidic solutions (which is not observed in the case of other metals) and rather high concentrations of acids are required for their elution (fe: 0. i mol r1 ; cu: 0.05 mol r1 ). in this way cu and fe can be separated from other ions. on the other hand, the sorbent do not bind in a wide ph range ( 1 ~9) the ions of alkali metals and the ions of calcium and magnesium are bound only at ph 9. while other metals investigated were bound in the ph range 3 6. therefore. the sorbent can be applied to remove trace amounts of heavy metals from aqueous solution of sodium, potassiumt ammonium, calcium and magnesium salts. such trace amounts are present even in reagents of special .. suprapurn quality. figure 7 representing the voltammograms of solutions of kci purified in the described manner confirms the useful properties of the prepared chelating sorbent. as discussed earlier .. the sorbent containing ion pairs titan yellow aliquat 336 deposited on rp-8 is considerably more stable than analogous sorbent on basis of plain silica. it has been demonstrated experimentally that in the cause of the silica sorbent the pb cu zn cd 1 -1.0 -0.5 0.0 v curves: i unpurified solution of analytical grade kcl to which zn, cd, pb, and cu were added (the concentration of each metal ion was 20 ppb ); 2 unpurified solution of analytical grade kci; 3 unpurified solution of suprapur grade; 4 sample 1 after passing through the column packed with lichroprep rp-8 modified with titan yell ow; 5 sample 2 after passing through the column; 6 sample 3 after passing through the column. fig.7 voltammograms for 10 m1 volumes of 0.5 mol r1 kci potassium chloride solutions after 3 min. electrolysis at -1.3v use of a column five times caused that the sorption capacity gradually decreased due to bleeding of titan yellow so that the results were not quite reproducible. on the other hand, sorbent with rp-8 practically did not show under these conditions any changes. solely, during elution of iron ions (at high concentrations of acids) some small amount of titan yellow were eluted. to sum up, it can be said that chelating sorbent with titan yellow on the basis of rp-8 have much better properties and better chances of practical use that the analogous sorbent with silica carrier. ·references l. minczewski j., chwastowska j. and dybczynski r.: separation and preconcentration methods in inorganic trace analysis, horwood ltd, chichester 1982 2. mizuike a.: enrichment techniques for inorganic trace analysis, springer verlag, berlin 1983 3. marshal m. a. and mottola h. a.: anal. chern., 1985,57,729-734 4._ witkiewicz z: the fundamentals of chromatography, wnt, warsaw 1992 (in polish) 5. niwa h., yasui t., lshizuki t., yuchi a., yamada h. and wada h.: talanta, 1997, 45,349354 6. khuha war m. y., channar a. h., lanjwani s. n.: j. chern. soc. pale, 1997, 19, 135-141 31 7. przeszlakowski s., soczewinski e., kocian r., gawecki j. and michno z.: polish patent 128,743, 1985 8. kocjanr.: analyst, 1992,117,741-744 9. kocjan r., swieboda r. and kitlas i.: chern. anal., (warsaw), 1999, 44, 353-372 10. kocjan r. and sowa i.: analyst, 2000, 125, 297300 11. nyons e. c.: reel. trav. chim. pays bas, 1944, 63,248-252 12. hansen h., helboe p. and thomsen m.: j. pharm. biomed. anal., 1984,2, 165-171 page 28 page 29 page 30 page 31 page 32 hungarian journal of industry and chemistry vol. 47(1) pp. 1–1 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-01 editorial preface to the special issue dedicated to the 15th international phd workshop on systems and control attila magyar1 1department of electrical engineering and information systems, university of pannonia, p. o. box 158, veszprém, h-8201, hungary systems and control theory is a scientific area that is constantly developing and a dominant driving force behind key industries and fields of engineering, e.g. process engineering, automotive engineering, bioengineering, the energy sector, etc. the goal of this issue is to provide an overview of the actual research topics pursued by some selected phd students. the papers presented here were chosen from among the contributions at the 15th international phd workshop on systems and control held august 30-31, 2018. the objective of this workshop was to establish an international forum for discussion between young researchers and engineers from the industry and related research fields. the meeting provided opportunities for the participants to present and discuss their latest results and up-to-date applications in systems and control. this issue represents the entire spectrum of systems and control engineering as follows: • process modeling and analysis; control (traditional, intelligent, adaptive, etc.) • system identification and signal processing • electrical transmission systems, smart grids • bioengineering • traffic control • reaction kinetic networks • artificial intelligence • soft computing (neural, genetic, fuzzy algorithms, etc.) • software issues (parallel computing, distributed and network computing, data visualization) • decision making (decision support, data mining) • applications the organizers are grateful to the authors for their contributions. the tradition of the international phd workshop on systems and control continues. you are welcome to participate at the 16th international phd workshop on systems and control in veszprém, 2020. attila magyar guest editor of the issue hungarian journal of indus1rial chemistry veszprem vol. 30. pp. 299 ~ 303 (2002) hydrotreating of full range fcc gasoline j. hancsok, s. magyar and a. lengyel1 (department of hydrocarbon and coal processing, university of veszprem, h-8201 veszprem, p.o. box 158, hungary 1molhungarian oil and gas co., h-2443 szazhalombatta, p.o. box 1, hungary) received: november 20, 2002 sulphur content of engine gasoline must be reduced below 50 ppm in the european union from 2005, and gasoline containing 10 ppm sulphur will have tax allowance [1 ,2]. fcc gasoline is one of the blend stocks being applied in largest amount (about 20-50%). the sulphur content of this is significant (about 50-2000 ppm), therefore 50-95% of the sul~hur species of gasoline originates from this stream. selective hydrotreating of fcc gasoline may be a fav~urable techmque among the numerous new desulphurising methods. achievements of a research work, made for hydrotreating a £?11 r~ge of fcc gasoline, are presented in this paper. the authors were able to find combinations of process parameters bemg smtable to produce gasoline blend stock of 11 ppm sulphur content with only 2 units loss of octane number. keywords: fcc gasoline, desulphurization, olefin saturation, octane loss introduction further reduction of the automotive emission can be achieved effectively with complex development of fuels, engine construction, lubricants and other parts of vehicles (catalytic converter, tyre etc.). currently the sulphur specifications have dominant importance from the point of view of engine gasoline, because combustion products of sulphur species beside air pollutionare poison the vehicle catalysts. thus further significant reduction of sulphur content can be expected (table i) [3]. three main long-run methods are offered for reducing sulphur content of gasoline, each of which results in lower sulphur content of fcc gasoline: reduction by hydrofining of fcc feed, application of new catalysts and catalyst additives in the fcc unit and desulphurisation of fcc gasoline [4, 5]. these strategies can be used either in themselves or in combination. nevertheless, desulphurisation of fcc gasoline cannot generally be avoided to meet ultra low sulphur specifications of engine gasoline. the loss of octane number can be very significant (up to 10-15 units) applying conventional hydrotreating of fcc gasoline. accordingly, this process is not economical from two aspects: partly due to considerable loss of octane number, partly because significant hydrogen consumption. a number of desulphurising processes for fcc gasoline have ~n develope4 which can economically be used to produce low sulphur fcc gasoline with acceptable loss of octane number [6-1_7]. the new desulphurising processes are wldel y diversified in respect of their principle and technical configuration (selective hydrotreating, adsorption. extractive distillation, caustic extraction etc.). options for desulphurisation of fcc gasoline are summarized in table 2 [18]. some of these processes treat full range fcc gasoline, but others accomplish desulphurisation with only a portion of fcc gasoline. it is extremely important in the latter processes tha~ the colun:n for the distillation of gasoline has to be optunally destgned and the cut point well selected [19]. . fig.} illustrates the major optional pathways tor post-treating of fcc gasoline: the main features of the processes indicated on th1s figure . were . a~eady presented in table 2. in some cas~s th~ hght fracuon_ of fcc gasoline is sent to an ethenficatto~ or alkylatl?n unit for boosting the octane number, while the ~ea~1er fraction is hydrotreated. this kind of combmatmn reduces the overall octane loss of tx>shreating. these processes were not indicated on fig.l. during the research, the possibility of desulphurisation of a full. range fc~ gasoline on pt,pdlzeolite has been investigated. the rum of the study was to examine the effect of process parame~ers (primarily temperature and liquid hourly space veloc1ty} on the yield and quality of liquid product and to determine the advantageous process parameters. 300 region, country, state usa california eu japan process naphtha hydrotreating (nht) nht+octane increase selective nht selective nht + octane increase adsorption extractive distillation oxidation alkylation bio processing table 1 actual and planned motor gasoline specifications maximum sulphur content ppm maximum olefin content v n % (actual) (planned) (actual) (planned) 500 30 (2006) 25 no change 30 15 (end of2002) 4 no change 150 50 (2005) 18 still not decided 100 10 (2008?) not specified still not decided table 2 options for the desulphurisation of fcc gasoline key feature industrial application conventional yes zeolite+ isomerisation yes rt-225 yes dual catalyst yes catalytic distillation yes combination yes zn adsorbent yes alumina adsorbent pilot selective solvent sys. yes peroxyacid pilot ultrasou,nd pilot solid acid pilot bio catalysis no h2-consumption octane loss high high high low medium low medium low medium low medium low low low none none none low none low low low low low low low isal i octgaln i prlme-g+i scan fining conventional hydrotratlng i !sal i octgaln i prlm&-g+i name of process various octgain, isal scan fining prime-g+ cd hydro/ cdhds scanfining ii szorb irvad gt-desulf . . ced sulphco oats fig, j major optional pathways for the desu1phurisation of fcc gasoline licensors a number of firms exxonmobil, uop exxonmobil ifp cd tech exxonmobil philips alcoa gtc petro star bechtel bp enchira ~ydrogen, ·-t>~~ m1rogen 1 2 3 31 ~liquid product 301 fig.2 simplified drawing of the test apparatus. notations: 1, 6, 11, 13, 14, 18, 20, 22, 30, 34, 36, 37, 38: closing valves; 2, 8, 31, 39: control valves; 3, 7, 9, 15: manometers, 4: oxygen converter; 5: dryer; 10, 32: gas filter; 12: gas flow meter/controller; 16.23: back valve; 17, 19: liquid feeds burettes; 21: liquid pump; 24: pre-heater; 25: reactor, 26: sampling valve, 27,29: cooler, 28: separator; 33: pressure recorder; 35: pressure controller; 40: wet gas flow meter experimental apparatus desulphurisation of fcc gasoline has been carried out in a high-pressure reactor system (fig.2) at the department of hydrocarbon and coal processing, university of veszprem. this consists of a tubular reactor of 100 cm3 efficient volume and is free of back mixing. it contains the same equipments and devices applied in the reactor system of desulphurising plants (pumps, separators, heat exchangers, as well as regulators of temperature, pressure and gas flow). catalysts the hydrodesulphurising experiments were carried out on pt,pd/zeolite catalyst, applying 80 cm3 of it. feedstock as feedstock of the desulphurising experiments a full boiling range (data of simulated distillation: 6-228 °c) fcc gasoline were used. the major quality features are summarised in table 3. methods compositions of feedstock and liquid products were analysed by gas chromatography (chromocf ane} and the quality characteristics were calculated by a software from these compositions. composition of gas products was determined, by gas chromatography (astm d 5134-90). sulphur content was measured by pyro­ fluorescence method (astm d 5453). the experiments were carried out on catalyst of steady-state activity. by continuous operation. results and discussion process parameters of the experiments (table 4) were selected and based on literature data and on earlier results of the department. from the results of the experiments it can be stated that crack reactions resulting in lighter hydrocarbons have not proceeded in the investigated temperature range, because the yield of liquid products was high (>99.5 %) at every combination of process parameters. the degree of desulphurisation of fcc gasoline depended on the process conditions. sulphur content of the products (fig.3) became lower with increasing temperature and decreasing lhsv. the highest level of desulphurisation (80 %) was reached at 280 oc and irsv = 1.0 (fig.4). under these conditions the product contained 11 ppm sulphur. 302 table 3 main properties of the feedstock density (15,6°c), g/cm3 0.7423 sulphur, ppm 63 nitrogen, ppm 13 research octane number 93.4 motor octane number 81.7 (ron+ mon)/2 87.6 composition. % n-paraffins 4.0 i-paraffins 31.8 ole fins 24.9 aromatics 31.7 naphthenes 7.6 i 35 ~30+---~~~~~~~----------------~ .:r !~+---------~~~~~~~----------~ ~ 20 r-------------=~~...2~~::------~ ~ 15 5+---~--------~--~----~----~--~--~ 220 230 240 250 270 280 tih!lperatuno, •c fig.3 sulphur content of products as function of temperature 100 ~ 90 .: ao ~ ~ 70 i 00 l 50 40 :t: 30 20 220 230 fig.4 hydrodesulphurisation as function oftemperature taking into account the composition of the feedstock and products it can be stated that the olefin content of each product decreased in proportion to the feedstock. the degree of saturation of olefins as function of temperature is shown on fig.5. higher temperature and tower lhsv resulted in higher olefin saturation. the highest olefin saturation (approx. 50%) occwted when desulphurisation was the lowest. ~iainly paraffins have formed from the olefins. but in a less degree also aromatics and naphthenes. evaluating the change of the concentration of paraffins it was stated that more n~paraffins than i~paraffins were formed from the olefins. every product had lower iso/normal paraffin ratio than the feedstock (8.0). this ratio is presented on fig.6 as function of temperature. the ratio was lower at higher temperatures and lower lhsv. this can be attributed to thermodynamic reasons. because higher temperature binders isomerisation. table 4 applied process parameters parameter reaction temperature, oc reaction pressure, bar liquid hourly space velocity, h"1 hzfhydrocarbon ratio, m3/m3 60 50 ;.!: g 40 ~ 30 = c i 20 '6 10 0 220 230 240 250 260 270 property 230-280 30 1,0-3,0 300 280 290 temperature, •c fig.5 olefin saturation as function of temperature 7,0 .2 6,0 'e ~ 5,0 ; ~ .!! 4,0 3,0 220 230 240 250 260 270 280 290 temperatura, •c fig.6 iso/n-paraffin ratio as function of temperature 2,5 ~ z 0 2,0 ~ 0 1,5 !!:. ~ 1,0 . ~ 0,5 8 0,0 220 230 240 250 260 270 280 200 temperatuta, ·c fig.7 loss of octane number as function of temperature the outcome of the mentioned chemical changes was the lower octane number of the products. fig. 7 illustrates the loss of octane number as function of temperature. the largest loss of octane number (2 units in [ron+mon]/2: the average of ron and mon) was observed at 280 °c, lhsv = 1.0 h-1 • sensibility of every product became lower due to saturation of olefins. by desulphurisation to the same degree, the lowest loss of octane number could be reached with the largest lhsv (3.0 n·1 ). removal of the light fraction of fcc gasoline could result in significant reduction of the loss of octane number. or lower sulphur content could be reached with the same loss of octane number. conclusions from the results of the investigation carried out on pt,pd/zeolit catalyst with the use of full range fcc gasoline, having 63 ppm sulphur content it can be stated that at advantageous process conditions (280°c; jo bar; lhsv=l,o; h2/hc = 300) fcc gasoline of 11 ppm sulphur content can be produced with high yield and only 2 units decrease of octane number ([ron+mon]/2: average of ron and mon). about 75 %of the olefins are in the light fraction of the feedstock (below 70 °c). this light fraction may contain very little sulphur, because it was passed through a merox unit in the refinery, which extracts the mercaptans from the light fraction. below 70 oc thiophenes are not present. this means that if we would cut the feedstock at 70 oc and we would only hydrotreat the heavier fraction, significant octane loss reduction could be reached, but only about 2 or 3 ppm of sulphur wou~d bypass the desulphurisation with the light fractron. furthermore, we can raise the temperature of the reactor, and we can reach higher level of desulphurisation without facing further significant octane loss. however, we have to confirm this with further experiments, and this is the aim of our next research work. nevertheless, our results confirm the opinion that hydrodesulphurisation of fcc gasoline can mainly be accmr~plished effectively and economically by expedient refinement of light and heavy fractions gained by fractionation. acronyms fcc fluid catalytic cracking hcn heavy cracked naphtha lcn light cracked naphtha lhsv liquid hourly space velocity mcn medium cracked naphtha mon motor octane number ron research octane number references 1. dixon-decleve s.: world refining, 2001, 12(9), 8 303 2. anon.: oil gas european magazine 2001 27(1) 42-43 ' , ' 3. sweed n. h.: petroleum technology quarterly, autumn, 2001, 6(3), 45-51 4. reidt. a., brevord e. and laan m. n. t.: the challenge of meeting future gasoline specifications: pre-treating vs. post-treating options around the fccu, european catalyst technology conference, antwerp, 2001 5. bavaro v.: world refining, 2000, 10(2), 30-37 6. maple r. e.: hydrocarbon engineering, 2000. 5~,%~2 . 7. burneit p. a., huff g. a., pradhan v. r., glaseit j. a. and hurst p.: bp low gasoline technology oats™, ertc 5th annual meeting, rome,2000 8. gentry j., khanmamedov t., and wytcherley w.: hydrocarbon engineering, 2002, 7(2), 43-44 9. d~buissc~rt q., nocca j.l. and cariou j.p.: pnme-g+ : the key to fcc gasoline desulfurization, proceedings of the interfaces '2002 conference, budapest, 2002 10. upson l. l. and schnaith m. w.: petroleum and coal, 2001, 40(3), 139-146 11. shih s. s., owens p. j., palit s. and tryjanowski d. a.: mobil's octgain™ process: fcc gasoline desulfurization reaches a new performance level, npra 1999 annual meeting, san antonio, texas, 1999 12. stun1z g. f. and plantenga f. l.: new technologies to meet the low sulfur fuel challange. 17th world petroleum congress. block 2:excelling in refining and delivering qualily petrochemicals, rio de janerio, 2002 13. anon.: world refining, 2001, 12(8), 23 14. rock k. l.: cdhydro/cdhds for ultra low gasoline sulfur, ectc 2002, amsterdam. 2002 15. irvine r. l. and varraveto d. m.: petroleum technology quarterly, summer 1999, 37-44 16. gislason j.: hydrocarbon engineering, 2002, 7(2 l 39-42 17. turk b., gupta r. and arena b.. a new continuous catalytic process for desulfurization of syngas and hydrocarbons, 2002 npra annual meeting, san antonio, texas, 2002 18. o'connor p. and mayo s.: division of fuel chemistry preprints, 2001, 46(2), 381-386 19. goldens. w., hanson d., w. and fulton, s. a.: hydrocarbon processing, 2002, 81(2). 67-72 page 300 page 301 page 302 page 303 page 304 hungarian journal of industry and chemistry vol. 47(1) pp. 41–48 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-07 model reference adaptive control for telemanipulation nándor fink *1 1department of mechatronics, optics and engineering informatics, budapest university of technology and economics, bertalan lajos utca 4-6, budapest, 1111, hungary a 1-dof (degree-of-freedom) telemanipulation system is presented in this paper. the paper focuses on disturbance compensation of the haptic force feedback. the master and slave devices are connected via serial ports. the mechanism, which is applied as a human interface device, is subject to perceptible internal friction that must be eliminated. as a result, the operator would only feel the force feedback from the manipulated environment. the main contribution of this paper is the presentation of the telemanipulation device with a model reference adaptive control that compensates for the friction force using a direct model-based sliding mode algorithm. keywords: telemanipulation, friction compensation, sliding mode control 1. introduction in connection with the rapid spread of the internet over the past few years, research about cscw (computersupported cooperative work) technology is being vehemently conducted. it is expected that this network-based technology will make collaboration in connection with human intellectual activities between distantly connected people easier. in the field of cscw technology, the data to be processed are only images, sounds and other data for computers, little attention has been paid to multi-modal collaboration including physical contact. our focus concerns networked multi-modal collaboration especially between those including haptics. a collaboration tool that facilitates a better connection between laboratories, offices and factories in the manufacturing industry has become necessary [1–3]. research into the bilateral control of master-slave manipulators was conducted in 1992. in [4] a 1-dof telemanipulation system was tested. the research covered the dynamics of the human operator as well as the device. three levels of ideal responses were determined, in all cases a force signal to the master arm was the input. the position of the two arms was identical in the first level, whereas the force response of the two arms was identical in the second, and both responses were identical in the third. in [5] a four-channel control architecture was examined. four models were tested on a teleoperation system, namely on an admittance-admittance, impedance-admittance, admittance-impedance and impedance-impedance pair. based on the types of *correspondence: finknandor@mogi.bme.hu model, a one-one suggestion was made for the control architecture in each case, namely position-position, position-force, force-position and force-force. in addition to the basic criteria of stability, the ease of usability becomes increasingly important. to ensure comfortable and ergonomic telemanipulation, the operator should control the slave device more smoothly and precisely. furthermore, the elimination of perturbations in all circumstances is necessary. for this purpose, the design of a model-reference adaptive control with a sliding mode friction compensator is promising. 2. theoretical background of the experiment 2.1 sliding mode-based disturbance elimination the main concept is the design of a reduced-order state observer for a partially perturbed linear system with infinite gain. the traditional roles of the system and observer are exchanged. the system is forced to follow the states of the unperturbed ideal model. infinite gain is ensured by a sliding mode. consider the following partially perturbed linear system that consists of external disturbances and uncertain parameters which satisfy the so-called drazenovic condition, written in the regular form of a state equation, d dt [ x1 x2 ] = [ a11 a12 a21 + ∆a21 a22 + ∆a22 ][ x1 x2 ] + [ 0 b2 + ∆b2 ] u0 + [ 0 e2 ] f(t) (1) mailto:finknandor@mogi.bme.hu 42 fink where x1 ∈ rn−m denotes the vector of non-perturbed state variables, x2 ∈ rm stands for the vector of perturbed state variables, u0 ∈ rm represents the input of the real system, aij(i, j = 1, 2) and b2 are the nominal or desired (ideal) matrices of the system, respectively, ∆a2j(j = 1, 2) and ∆b2 denote the bounded parameter perturbations, and f(t) stands for the bounded external disturbance. the perturbed state variables are estimated by a discontinuous observer [6] d dt x̂2 = a21x1 + a22x̂2 + b2 ( u0 + ν ) (2) where ν denotes the discontinuous term. let us design the following sliding surface: σ = [ i −i ][x2 x̂2 ] = 0 (3) where i ∈ rm×m represents the identity matrix and σ ∈ rm stands for the distance from the surface. σ must tend to zero. let us calculate the elements of the discontinuous term ν in following way: νi = gi sign(σi), (4) where gi is the gain of the sliding mode controller. the implementation of a sliding mode means that the signs of σi = 0 and νi change at an infinitely high frequency [7]. ν can be substituted by its mean value denoted by νeq. by comparing the second line of eq. 1 and eq. 2:( b2 + ∆b2 ) ν = ∆a21x1 + ( a22 + ∆a22 ) x2 −a22x̂2 + ∆b2u 0 + e2f(t) (5) according to eq. 5, ν can be used to estimate the perturbation. as a result, the response of the perturbed system in terms of u − ν will be identical to that of the unperturbed ideal system, u. the main problem concerning the sliding mode is the chattering caused by the infinitely alternating frequency of ν. to avoid uncontrolled resonances of the unmodeled dynamics of the real system, ν is substituted by νeq (the continuous equivalent of ν. in practice, it is impossible to calculate the equivalent control νeq precisely, but it can be estimated by a low-pass filter for ν as shown in fig. 1, where two loops can be seen. figure 1: sliding mode-based disturbance compensation. figure 2: the haptic device. the observer – sliding-mode control loop is calculated by the computer and should be as fast as possible to achieve an ideal sliding mode [8, 9]. since a reduced order observer is used, x2 of the real system is measured in terms of the disturbance compensation. of course, all state variables might be measured in the outer control loop. ν̂eq, the estimation of νeq, is added to the control signal of the outer control loop. 3. application 3.1 tuning the disturbance compensation the master device consists of a dc motor and an arm (fig. 2). the slave device is identical to the master device. their roles are interchangeable. the arm is not rigid since the force is measured by strain gauges. in the case of the ideal telemanipulation model, the master device is not subject to friction nor mass (inertia). of course it is impossible to construct an ideal master device. the goal of the sliding mode-based disturbance compensation is to force the master device to follow a model subject to significantly reduced degrees of friction and inertia. the model of the master and slave devices is shown in fig. 3. the position of the motor is controlled by a simple proportional derivative (pd) controller. the results of three simulations were compared: • pd controller with the parameters of the real motor • pd controller with the parameters of the desired motor • pd controller with the parameters of the real motor which were modified by the addition of slidingmode disturbance compensation. figure 3: model of the master and slave devices. hungarian journal of industry and chemistry model reference adaptive control for telemanipulation 43 figure 4: model of the feedback force. the main goal of this chapter is to tune the disturbance compensation component. if the results of the last two simulations are similar, sliding-mode disturbance compensation can be used in a bilateral telemanipulation system. the parameters used in the model are calculable. a 1-dof telemanipulation system was studied where the effect of the feedback force of the master arm was modelled [10] as follows (fig. 4): ωmot r · fm = 1 s · jl +b +ba (6) ωmot fm = r b+ba s · jl b+ba + 1 = r bm s · t + 1 , (7) where s is a complex variable and t denotes the time constant of the manipulator: t = jl bm (8) jl is calculated according to: jl = jr + jtr2 + ja, (9) and represents the resultant moment of inertia, jr stands for the inertia of the rotor, jtr2 is the transmission inertia and ja denotes the inertia of the arm. bm = b +ba (10) bm represents the resultant damping, b the mechanical damping and ba the damping caused by the armature resistance. ba = k2 fi ra (11) kfi denotes the torque constant of the motor and ra its resistance. ωmot stands for the angular speed of the motor, fm the forceand r the vector of the lever arm with regard to the torque of the motor. in this experiment, the following constants were used for the aforementioned parameters: kfi = 0.1222 [nm/a], ra = 80 [ω], la = 0.0011 [h] and jl = 0.12 [kg m2]. the model of the ideal motor took friction into account (fig. 5), however, the other models accounted for this separately. 3.2 design of the disturbance compensation component in terms of human sensation, the electrical time constant of the system (the inductance of the dc motor) is negligible. two state variables are used: the position of the arm ϕ and the angular speed ω. the system equation must be written in the same form as (eq. 1) where: d dt [ ϕ ω ] = [ 0 1 0 amotor ][ ϕ ω ] + [ 0 bmotor ] u0, (12) amotor and bmotor are the two perturbed parameters. no external disturbance is applied. the observer is designed for the state variable ω. it should be noted that in the case of the ideal system, friction is accounted for in the model. the ideal parameters were selected in terms of friction and inertia. it is important to choose the ideal parameters wisely because these two parameters will determine the trajectory followed by the position signal of the compensated motor. if the values of the ideal parameters are too unrealistic, the compensated signal would not be able to follow the trajectory! in this simulation, the following parameters were used: jl_i = jl 12 bm_i = bm 5 (13) where jl_i denotes the inertia with regard to the model of the ideal motor and bm_i stands for the coefficient of friction concerning the model of the ideal motor. the compensation component consists of the observer with the following transfer function: bmotor s+ amotor (14) where amotor is calculated by: amotor = bm_i jl_i − k2 fi ra · jl_i (15) and bmotor by: bmotor = kfi ra · jl_i (16) then a pd position controller is added to each model of a motor (fig. 5) and the component concerning the slidingmode compensator connected to the first real model of a motor (fig. 6). an estimated value of the velocity is specified in this section which will be compared with that of the actual velocity. this will be the input for the component of the sliding-mode controller that consists of a signum function and a gain block. from here a positive feedback was applied from the output of the sliding-mode controller to the input of the observer, and the output of the slidingmode controller filtered by a 3rd order low-pass filter as the output of the whole compensation component (fig. 6). 47(1) pp. 41–48 (2019) 44 fink figure 5: model of the ideal motor with the application of a pd controller. figure 6: the component with regard to the compensation of friction. 3.3 calibration of the model to specify the parameters of the system, first the aforementioned model must be implemented. in the first case, a position controller was used for tuning (fig. 7). it is worth noting that the position signal of the real motor reaches its final value by oscillation and overshooting, while the graphs of the ideal motor and the compensated motor are smoother. it has to be mentioned that the pd controller is not optimised for a stand-alone task, rather for the compensation. in this experiment the following constants were used for the aforementioned parameters: pidp = 190, pidp = 60 and gainsliding = 30, 000. in the case of a 1-second-long simulation, the difference between the position trajectory of the ideal and compensated motors is visible (fig. 8). in fig. 9 it is visible that the sliding-mode controller is inactive for about 0.2 seconds which is the time necessary for the controller to reach the sliding surface. 0 2 4 6 8 10 12 time [s] 0 10 20 30 40 50 p o s it io n [ in c re m e n t] position control with friction compensation real motor with compensation ideal motor real motor without compensation figure 7: the compensated signal follows the stated trajectory. between −0.04 and +0.04 the active sliding-mode becomes visible (fig. 10). there is a noticeable level of chattering originating from the output signal of the sliding-mode controller (fig. 11). this was eliminated by the 3rd order low-pass filter (fig. 12). 3.4 verification of the model subsequently, the calibration component follows on from verification of the model. the former simulations were run under nearly ideal conditions, but now a relevant coulomb friction will be added to the system as well as an additional step function load. in fig. 13 the supplemented system is shown only for the model of the motor that compensated for friction using real parameters (the models of the ideal and simple real motors were excluded to save space). 0 0.2 0.4 0.6 0.8 1 time [s] 0 5 10 15 20 25 30 35 p o s it io n [ in c re m e n t] position control with friction compensation real motor with compensation ideal motor real motor without compensation figure 8: the difference between the position signals of the ideal and compensated motors. hungarian journal of industry and chemistry model reference adaptive control for telemanipulation 45 0 0.2 0.4 0.6 0.8 1 time [s] -20 -15 -10 -5 0 s ig m a [ -] reaching the sliding surface sigma figure 9: reaching the sliding surface. 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 time [s] -0.04 -0.02 0 0.02 0.04 0.06 s ig m a [ -] reaching the sliding surface sigma figure 10: after reaching the sliding surface, the sliding mode becomes active. 0 0.2 0.4 0.6 0.8 1 time [s] -3 -2 -1 0 1 2 3 c o n tr o l s ig n a l [] #104 chattering of the unfiltered control signal control signal figure 11: chattering originating from the output of the sliding-mode controller. 0 0.2 0.4 0.6 0.8 1 time [s] -3 -2 -1 0 1 2 c o n tr o l s ig n a l [] #104 the filtered control signal control signal figure 12: the filtered signal of the sliding-mode controller. figure 13: full model of the compensated motor subjected to calibration. 47(1) pp. 41–48 (2019) 46 fink 0 0.5 1 1.5 2 2.5 3 time [s] 0 5 10 15 20 25 30 35 p o s it io n [ in c re m e n t] comparison of the behavior of the models real motor with compensation ideal motor real motor without compensation figure 14: position signals after coulomb friction was accounted for in the system. 0 0.5 1 1.5 2 2.5 3 time [s] -80 -60 -40 -20 0 20 40 p o s it io n [ in c re m e n t] comparison of the behavior of the models real motor with compensation ideal motor real motor without compensation figure 15: an additional load added to the system. figure 16: bilateral control model. 0 0.5 1 1.5 2 2.5 3 time [s] 0 0.2 0.4 0.6 0.8 1 p o s it io n [ in c re m e n t] position following of the slave arm master arm slave arm (with compensation) slave arm (without compensation) figure 17: the same parameters applied to the slave arm failed to yield results. 0 0.5 1 1.5 2 2.5 3 time [s] 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 p o s it io n [ in c re m e n t] position following of the slave arm master arm slave arm (with compensation) slave arm (without compensation) figure 18: position signal following of the bilateral system. hungarian journal of industry and chemistry model reference adaptive control for telemanipulation 47 0 0.5 1 1.5 2 2.5 3 time [s] -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 f o rc e [ n ] force input for the bilateral control master arm figure 19: force input to the bilateral control. in fig. 14 the position signals are shown after the addition of the coulomb friction to the system. this new component has a stabilizing effect on the oscillation of the real motor which is greater than can be compensated for without the introduction of a permanent error. however, the behaviour of the motor compensated for by friction remains unchanged. the values of the coulomb friction and viscous friction used in this experiment were 2, 200 and 0.3, respectively. then after 2 seconds an additional load was added to the system (fig. 15). it was noticeable that when the position signal of the normal motor started to rapidly decrease, the model compensated for by friction adapted to the new circumstances. the value of the load added after 2 s was 42. 4. results and discussion 4.1 final model finally, bilateral haptic control was realized (fig. 16). the model of the two force cells on the real-life device was added to the system by applying the same logic as used on the real. each model of the motor was extended by a leftand right-force block. in terms of bilateral control, the difference between the force blocks of each joystick was compared, which was also the input of the force controller of the master arm. subsequently, the position of the master arm was compared to that of the slave arm, which was the input of the position controller of the slave arm (fig. 16). it would be illogical to apply the same parameters to the position controller as to the one that accounts for compensation because without the component of compensation the friction force would prevent the proper position from being reached (fig. 17). nevertheless, if an individually tuned proportional– integral–derivative (pid) controller is connected to the component responsible for position control of the system, the signal that results would be visible (fig. 18). in this case, the input signal was applied to the right force cell of the master arm in a shape as is shown in fig. 19. it is impossible to eliminate the entire effects of friction and inertia on the mechanical construction, but they can be reduced significantly. the magnitude of the friction force exceeded the limit suitable for a smooth, comfortable operation. compensation aims to make the system behave like an ideal model subject to a minimal level of friction. due to the compensation, the operator can move the master joystick with ease. over a series of experiments, classical and sliding mode-based model reference adaptive control methods were compared. the applications of these methods with regard to compensation for friction are published in [11, 12]. it is crucial to identify an optimal adaptation parameter which facilitates rapid adaptation but avoids overcompensation. in the event of overcompensation, the joystick moves randomly even in the absence of reference torque because of the measurement noise. as the size of the adaptation parameter increases, adaptation occurs more rapidly, however, the likelihood of random movements rises. 5. conclusion an experimental telemanipulation system was presented in this paper. the master device was a serial linked levertype haptic interface with force feedback. even though it is impossible to eliminate the entire effects of friction and inertia on the mechanical construction, a reference model that accounts for minor levels of friction was designed. the system was forced to follow the reference model. in other words, the original dynamics of the master device were replaced by a virtual version which ensures a comfortable degree of manipulation for the operator. references [1] arai, f.; sugiyama, t.; fukuda, t.; iwata, h.; itoigawa k.: micro tri-axial force sensor for 3d bio-micromanipulation, 1999 ieee international conference on robotics and automation, 1999 4, pp. 2744–2749 isbn: 0-7803-5180-0 doi: 10.1109/robot.1999.774012 [2] kwon, d-s.; woo, k. y.; cho, h. s.: haptic control of the master hand controller for a microsurgical telerobot system, 1999 ieee international conference on robotics and automation, 1999 3, pp. 1722–1727 isbn: 0-7803-5180-0 doi: 10.1109/robot.1999.770357 [3] n. ando, m. ohta, h. hashimoto: “micro teleoperation with haptic interface”, proceedings of the 2000 ieee int. conf. on industrial electronics, control and instrumentation, pp. 13-18, 2000, 10.1109/iecon.2000.973119 [4] yokokohji, y.; yoshikawa, t.: bilateral control of master-slave manipulators for ideal kinesthetic coupling-formulation and experiment, ieee t. robotics autom., 1994 10(5), 849–858 doi: 10.1109/70.326566 47(1) pp. 41–48 (2019) https://doi.org/10.1109/robot.1999.774012 https://doi.org/10.1109/robot.1999.774012 https://doi.org/10.1109/robot.1999.770357 https://doi.org/10.1109/robot.1999.770357 https://doi.org/10.1109/70.326566 https://doi.org/10.1109/70.326566 48 fink [5] hashtrudi-zaad, k.; salcudean, s. e.: analysis of control architectures for teleoperation systems with impedance/admittance master and slave manipulators, int. j. robotics res., 2001 20(6), 419–445 doi: 10.1177/02783640122067471 [6] korondi, p.; young, k. d.; hashimoto, h.: sliding mode based disturbance observer for motion control in: proceedings of the 37th ieee conference on decision and control, (ieee press, new york, usa) 1998, pp. 1926–1927 isbn: 0-7803-4394-8 doi: 10.1109/cdc.1998.758595 [7] v. i. utkin: sliding modes in control and optimization, springer –verlag, 1992, isbn: 978-3-642-84379-2 doi: 10.1007/978-3-642-84379-2 [8] ando, n.; korondi, p.; hashimoto, h.: development of micromanipulator and haptic interface for networked micromanipulation, ieee/asme t. mechat., 2001 6(4), 417–427 doi: 10.1109/3516.974855 [9] korondi, p.; young, k-k. d.; hashimoto, h.: discrete-time sliding mode based feedback compensation for motion control, 1996 ieee international workshop on variable structure systems, 1996, pp. 237–242 isbn: 0-7803-3718-2 doi: 10.1109/vss.1996.578577 [10] lukács p.: 1 degree of freedom haptic device for telemanipulation, master’s thesis, 2015 [11] ando, n.; ohta, m.; hashimoto, h.: micro teleoperation with parallel manipulator, 2000 ieee/rsj international conference on intelligent robots and systems, 2000 1, pp. 677–682 isbn: 0-7803-6348-5 doi: 10.1109/iros.2000.894682 [12] korondi, p.; szemes, p. t.; hashimoto, h.: sliding mode friction compensation for a 20 dof sensor glove, j. dyn. sys., meas., control , 2000 122(4) 611–615 doi: 10.1115/1.1317232 hungarian journal of industry and chemistry https://doi.org/10.1177/02783640122067471 https://doi.org/10.1177/02783640122067471 https://doi.org/10.1109/cdc.1998.758595 https://doi.org/10.1109/cdc.1998.758595 https://doi.org/10.1007/978-3-642-84379-2 https://doi.org/10.1109/3516.974855 https://doi.org/10.1109/vss.1996.578577 https://doi.org/10.1109/vss.1996.578577 https://doi.org/10.1109/iros.2000.894682 https://doi.org/10.1115/1.1317232 introduction theoretical background of the experiment sliding mode-based disturbance elimination application tuning the disturbance compensation design of the disturbance compensation component calibration of the model verification of the model results and discussion final model conclusion hungarian journal of industry and chemistry vol. 47(2) pp. 63–70 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-21 investigation of mixing in tanks of a special geometry bálint levente tarcsay*1, attila egedy1, janka bobek2, and dóra rippel-pethő2 1department of process engineering, university of pannonia, egyetem u. 10, veszprém, 8200, hungary 2department of chem. eng. sci.s, university of pannonia, egyetem u. 10, veszprém, 8200, hungary mixing is one of the most crucial processes in the chemical industry. homogeneity is a requirement for all feedstocks and industrial products. the degree of mixing depends on the hydrodynamic properties of the fluid in the units. the residence time distribution (rtd) was investigated in a tank of a special geometry. mixing was investigated using various geometries of the tank by applying the heaviside function in step-response experiments. after obtaining experimental results, the rtd function was calculated. the flow structure in the tank was approximated by fitting black-box transfer function models onto the rtd function of the system. two general model structures were defined and their fitness compared. by evaluating the fitted models, a relationship was established between the flow structure in the tank and its geometry. keywords: tanks with of special geometry, mixing, flow pattern, transfer function model 1. introduction in industrial processes, the thorough homogeneity of materials is a necessity to ensure the quality of the finished products and the safety of the production process. therefore, various industrial-scale techniques for the homogenisation of materials of various densities and phases have been developed over the years. in the case of fluids, homogenization can be achieved through the application of mixers in a device. the optimal type and geometry of these stirred tanks can be approximated by specific models which take the properties of the materials to be mixed and the desired degree of homogeneity into consideration [1]. in the case of the homogenisation of large volumes of liquids (petrochemical and radiochemical industries), external recirculation can be more advantageous since it is considerably more inexpensive in terms of both installation and operation. the operation of stirred tanks has been thoroughly investigated by using mathematical and experimental methods, however, research on mixing achieved by external recirculation is lacking [2]. optimization of the mixing process to achieve the most homogenous product possible in an external recirculation tank can only be achieved after the flow structure of the unit is known. the aim of this research was to analyze the flow structure in a tank of special geometry, moreover, to determine the connection between the flow structure and geometry of the tank. this research forms the basis for future investigations where the flow structure and homogenization in a tank will be tested through an external recirculation mixing *correspondence: tarcsaybalint95@gmail.com process. mixing in stirred tanks can traditionally be analyzed by step-response experiments. step-response experiments are a widely accepted and simple way of determining the flow structure of process units [3]. during these experiments, the input of the system is a tracer fed according to the heaviside function. the time evolution of the tracer concentration in the output of the tank holds information regarding the flow and mixing properties of the system. the heaviside function is the integral of the dirac delta function δ(t): s(t) = ∫ ∞ −∞ δ(t)dt = { 0 if t < t∗ 1 if t ≥ t∗ (1) used as an input in pulse-response experiments [4]. the heaviside function, s(t), as a function of time takes on a value of 0 if the investigated time t is less than the time of the tracer feed t∗ and a value of 1 during and after being fed. after experimental data was collected on the response function of the system, the residence time distribution function (rtd) could be calculated. the rtd function approximates the probability that the residence time of the fed tracer agent is less than a specified residence time [4]. the rtd function, f , was calculated from f (t) = rt −rt−1 rsteady −r0 , (2) wherersteady andr0 are the values of the response function in the steady state and at the beginning of the experiment, respectively. by analyzing the rtd curve in the studied unit, mixing and flow can be characterised and compared to the https://doi.org/10.33927/hjic-2019-21 mailto:tarcsaybalint95@gmail.com 64 tarcsay, bobek, egedy, and rippel-pethő figure 1: response functions of various ideal flow models [3]. flow structure of ideal hydrodynamic models [5, 6]. in this study, the ideal hydrodynamic models, which were used to describe the response, include the plug flow reactor (pfr) and tanks-in-series (tis) model. the pfr model is useful for modelling systems with a continuous flow of cylindrical geometry. it works under the assumption that the flow through a pfr is perfectly mixed in the radial direction but not in the axial direction. it is also assumed that the residence time of each fluid unit within the system is equal to the mean residence time, τ . because of these conditions, the step response function of a system with pfr tendencies is identical to the step function which was used as an input but with a time delay equal to the mean residence time in the unit. an altered version of the pfr model is the laminar flow reactor (lfr) model. the lfr model assumes a laminar flow structure within the system. therefore, the residence time of the fluid phase within the system has a distribution. this causes the shape of the response function to become slightly altered compared to the step function. the tis model is an extension of the continuous stirred tank reactor model (cstr) which defines a system that is perfectly mixed and, therefore, homogeneous. upon entering the unit, the tracer is dispersed throughout the whole tank, therefore, it immediately appears in the output without a time delay. the tis model examines a series of cstr units. the rtd function in this model is dependent on the number of tanks that have been linked. the rtd function of the tis model converges towards the pfr model as the number of units increases and towards the cstr distribution as the number of units decreases. one tank returns the rtd function of a cstr and as the number of tanks in series approaches infinity, the rtd function converges towards the pfr model. the characteristic rtd curves of the aforementioned ideal flow models are shown in fig. 1 [3]. in this figure, t∗ denotes the duration of tracer injection and dt represents the time delay when the tracer appears in the outlet. in this investigation, black-box models were used to approximate the behavior of the tank. blackand whitebox modelling are two distinct modelling techniques to describe the traits of various systems. white-box models utilize well-known physical and chemical laws to characterize a system. these laws come in the form of differential equations, algebraic equations, etc. the model defines the internal functioning of the system and calculates the specific output from the input by taking these into consideration. generally in the case of complex mixing problems, computational fluid dynamics (cfd) simulators are utilized to solve the white-box model of the system [7,8]. cfd simulations can determine the flow field in various units [9]. these simulators can be used to solve scientific problems from a diverse spectrum of disciplines, e.g. aerodynamics, hydrodynamics, ocean engineering, chemical engineering, etc. [10]. to solve these problems, various numerical methods have been invented over the years among which the finite element method (fem) is one of the more frequently applied approaches [11]. however, in cases where the fem is insufficiently advanced, alternative numerical methods can also be implemented, e.g. the spectral element method (sem) [12]. their disadvantage is, however, that since they model the systems so thoroughly, they require considerable computational power and computation time. through these methods, it is possible to analyze processes which are more complex or require long experimentation times to be dissected. despite this, these methods also require experimental data for validation. black-box models, on the other hand, provide generalized means for the modelling of various problems [13]. they often employ empirical methods to calculate the output of a system from the input without thoroughly describing the internal properties of the system [14]. the relationship between the input and output can be modelled using various techniques with the most popular being neural networks as well as state-space and transfer function models [15]. in this study, the transfer function model was utilized to approximate the behavior of a tank of special geometry. 2. experimental and the modelling process the geometry of the investigated tank is shown in fig. 2. the tank consists of 5 cylindrical units integrated with each other. a removable wall was implemented which makes it possible to create the desired number of cylinders from the main tank. therefore, the number of cylindrical units can be varied between 1 and 5. during the investigation, geometries consisting of 1, 3 and 5 cylindrical units were investigated. the residence time, calculated from the inlet volume flow rate and volume of the liquid, was 3 h for all geometries. therefore, the inlet volume flow rate changed as the volume of liquid and number of cylindrical units varied. to obtain the response function of the system, a heaviside function was used. the utilized tracer was a borax solution of low concentration (6.24 gl−1). the tracer was fed into the tank which hungarian journal of industry and chemistry mixing in tanks of a special geometry 65 figure 2: the investigated tank. was filled with a high concentration of borax solution (29.16 gl−1). conductivity measurements were used to monitor the change in concentration and obtain the response function. the experimental equipment is shown in fig. 3. the experimental conditions for the feed and residence time are shown in table 1. the positions of the inlet and outlet during the experiments are shown in table 2. the (0, 0, 0) coordinates of the system were defined as the bottom of the tank at the position of the outlet. the coordinates x, y and z correspond to the longitudinal, vertical and horizontal distances, respectively. the rtd curves of the three different geometries of the tank were investigated. after experimentally obtaining the data from the rtd curves, transfer function models were fitted to the experimental results. two types of fitted functions were investigated. both were black-box convolution models of the pfr and tis. however, one contained only serial links between the perfectly mixed units, the other assumed parallel connections as well. differential equations describe the change in concentration of the output of the tank as a function of the input. in various ideal flow models, these equations were converted into algebraic equations by using the laplace transform. after this the transfer function of the ideal flow modfigure 3: setup of the experimental equipment (1– experimental tank, 2–tracer containment tank, 3– peristaltic pump, 4–buffer unit, 5–rotameter, 6–output containment tank). table 1: experimental parameters. number of cylinders τ (h) b (lh−1) 1 0.4 3 3 1.1 5 1.7 table 2: inlet and outlet positions. number of cylinders inlet position outlet position x (mm) y (mm) z (mm) x (mm) y (mm) z (mm) 1 75 100 0 0 2 0 3 225 100 0 0 2 0 5 375 100 0 0 2 0 els was defined as the ratio of the output (the laplace transformed response function) to the input of the system (the step function of the tracer injection). if the product of multiple elementary transfer functions is computed, a tis model can be generated. a general model structure for this network can be seen in fig. 4. on the other hand, by combining the elementary transfer functions of ideal flow models, a network of flow models with parallel links can be created. a general model for this structure is shown in fig. 5. in both cases, a pfr unit has been included in the structure, in general this is useful for modelling systems with a time delay. the time delay in the rtd function could point to either pfr tendencies in the flow structure or the presence of dead volumes within the tank. to distinguish which is present, further investigations with a cfd simulator are required. the general form of the transfer function that only uses serial connections is gfitted = a bnsn + bn−1sn−1 + · · ·+ b0s0 e−tds, (3) where n denotes the order of the denominator and bn, a, and td are parameters of the transfer function. in the case of the model containing both parallel and serial links, the general transfer function is gfitted= an−1s n−1 + · · ·+ a0s 0 bnsn + bn−1sn−1 + · · ·+ b0s0 e−tds, (4) where n is the order of the denominator and bn, an, and td are parameters of the transfer function. however, due to the parallel connections, the elementary transfer functions are not just multiplied but totalled. therefore, the figure 4: general model structure involving only serial links [5, 6]. 47(2) pp. 63–70 (2019) 66 tarcsay, bobek, egedy, and rippel-pethő figure 5: general model structure involving both serial and parallel links [5, 6]. nominator also contains a higher order polynomial. the order of this polynomial can be one at most below the order of the denominator for the system to be suitable. in both cases, the fitted rtd curve ffitted was calculated from the step response of the system which was characterized by the transfer function, gfitted. the overall parameters of the transfer function were determined by numerically solving a minimization problem. the minimization problem is expressed in min [e (n, a, b, d)] = ∑ [fexp − ffitted (n, a, b, d)] 2∑ (fexp) 2 (5) where e is a function denoting the sum of the squared difference of the experimental and fitted rtd functions divided by the sum of the square of the experimental rtd curve. as such,e is a function similar to the relative error of the fitting which is dependent on the parameters of the transfer function, gfitted. inversely, the goodness of the fit, i , can be defined as the complementer of the fitting error: i (n, a, b, d) = 1− e (n, a, b, d) . (6) for the minimization of the function, the interior-point method was applied in matlab r2011. constraints were defined for the lower and upper boundaries of the parameters, namely 0 and 100 for all parameters, respectively. the fitting algorithm was modified to favor transfer functions with the smallest possible order and smallest relative error. the algorithm can be seen in fig. 6. the algorithm follows a general route for fitting both parallel and serial models. during the first step, a loworder (first-order) transfer function is created. after that the parameters of this transfer function are identified using the interior point method. after obtaining the parameters, the e function is calculated to evaluate the error of the fitting. if the error is less than a predefined threshold (erropt), then the fitting will stop and the current transfer function be defined as the best possible fit. if the error of the fit exceeds the defined threshold, then the fitting continues. in this case, the order of the denominator is increased and the error of the higher order transfer function evaluated as well. if the error of fitting is less than the lower order transfer function, then the fitting continues until either a transfer function which satisfies the error boundary is identified or the error of the fitting does not decrease significantly even though the order of the denominator increases. in the case of models which include parallel links, this algorithm contains an additional iteration step. during this step, the algorithm investigates the fit of an nth order transfer function (if n ≥ 2) with varying orders of the nominator. to achieve this, the fitting is evaluated by applying increasing orders of the nominator. during this process, either the maximum order of the nominator (n − 1) is reached or a point where the increase in the order of the nominator is identified that does not significantly impact the fitting error. in either case, fitting is stopped and the solution accepted as the best possible fit for a transfer function with order of the denominator, n. to evaluate the proposed fitting algorithm for both models, a custom-defined transfer function was analyzed. this reference transfer function (gref is defined by gref = 1 1.6s2 + 2.6s+ 1 e−5s (7) in the case of the model contains only serial links. the step response function for this transfer function was used as reference data. the extrema of function e were numerically determined by using the devised algorithm. the fitted transfer function is gref = 1 1.58s2 + 2.59s+ 1 e−5s. (8) fig. 7 shows the fitting of the rtd of the identified transfer function to the reference rtd function. the goodness of the fit was 98.2 %. the testing was also conducted in cases where parallel links are present besides serial links. in this case, the reference system is characterized by the transfer function: gref = 8.6s+ 1 s4 + 2.5s3 + 11s2 + 10s+ 1 e−2s. (9) the fitting algorithm was augmented to identify both the optimal orders of the nominator and denominator. the fitted transfer function is gfitted = 8.95s+ 1 s4 + 2.37s3 + 11.14s2 + 10.33s+ 1 e−2s. (10) the results of the fitting are displayed in fig. 8. in this case, the goodness of the fit exceeded 99 %. both fig. 8 and the measurements of the parameters show that the algorithm is capable of precisely fitting both models, therefore, it is suitable for identifying the transfer functions of the system. after validating the fitting hungarian journal of industry and chemistry mixing in tanks of a special geometry 67 figure 6: the general applied fitted algorithm for a model containing both serial and parallel links. figure 7: the results of the algorithm validation for fitting the model containing only serial connections. figure 8: the results of the algorithm validation for fitting the model containing parallel and serial links. method, transfer functions were identified for the tank by using the experimental rtd curves. 3. results and analysis the results of the fittings in the case of the model with only serial connections can be seen in figs. 9–11 for all three geometries of the tank that were investigated. the geometry consisting of 5 cylinders was originally modeled using a second order transfer function that yielded the best fit for the experimental rtd curve (92 %). however, to compare the parameters of the fitting figure 9: results of the fitting of the serial model for 1 cylindrical unit. figure 10: results of the fitting of the serial model for 3 cylindrical units. and characterise the system, it was more favorable to fit a third order transfer function here as well since it describes the other two rtd curves best. in this case, the average goodness of the fit was 91 % with the goodness of the fit in the case of the geometry consisting of 5 cylindrical units (86 %) being the lowest. the numerical parameters of the fit are shown in table 3. the results are as follows: to describe the system in the cases of 1 and 3 cylindrical units, a third order transfer function was used. in the case of 5 cylindrical units, a second order transfer function was optimal. in the case of the model containing both parallel and 47(2) pp. 63–70 (2019) 68 tarcsay, bobek, egedy, and rippel-pethő figure 11: results of the fitting of the serial model for 5 cylindrical units. table 3: fitted parameters for the model containing only serial links. parameters n n a0 b3 b2 b1 b0 td (h) i (%) 1 3 1 0.1 0.3 1.0 1 0.9 93.43 3 3 1 0.2 0.6 1.5 1 0.6 94.00 5 3 1 0.3 0.7 2.0 1 0.7 85.76 5 2 1 0.9 2.3 1 0.7 92.00 serial links, the fitted curves are displayed in figs. 12–14. in the case of the model containing both parallel and serial connections, the tendencies are similar to the results of the fitting conducted using the model consisting of only serial links. however, the goodness of the fit was enhanced compared to the simpler models (over 99 % for all investigated geometries). in this case, the behavior of the tank consisting of 1 cylindrical unit was described by a transfer function where the orders of the nominator and denominator were 4 and 2, respectively. in the case of 3 and 5 cylindrical units, the orders of the denominator and nominator were 3 and 1, respectively. the order of the transfer function (the number of cstr units in the tis model) increases as the number of cylinders decreases. this is evident of an increase in the pfr/lfr tendencies of the functions which can also be seen in the figfigure 12: results of the fitting of the parallel model for 1 cylindrical unit. figure 13: results of the fitting of the parallel model for 3 cylindrical units. figure 14: results of the fitting of the parallel model for 5 cylindrical units. ures. it should also be noted, however, that the fitting in all models was exceedingly high (over 95 % on average). this might suggest that the model algorithm is too precise and the model was also fitted according to the experimental noise remaining in the data. in the absence of the noise, such tendencies might be clearer and the decrease in the order of the nominator between the different geometries more prominent. further investigations carried out by cfd simulations may clarify these concerns. the parameters of the fit are displayed in table 4. 4. conclusion in this paper, the velocity field of a tank of special geometry was investigated. in order to determine the relationship between the flow profile and geometry of the tank, step-response experiments were conducted. the rtd curves of the system were measured by applying various geometries of the tank. by analyzing the experimental rtd curves, a model was proposed to be fitted onto the results. the transfer function of the system was optimized by minimalizing the squared difference of the experimental and fitted rtd curves. the interior-point method was applied to minimalize the difference. the following conclusions were drawn from the fitted rtd curves: hungarian journal of industry and chemistry mixing in tanks of a special geometry 69 table 4: fitted parameters of the model containing both parallel and serial links. parameters n n m a2 a1 a0 b4 b3 b2 b1 b0 td (h) i (%) 1 4 2 6 2.4 1 1 4.3 8 3.12 1 1.2 98.28 3 4 1 − 5.5 1 1 3.4 8.5 7.1 1 0.6 99.77 5 3 1 − 12 1 1 3.5 18 14.4 1 0.5 99.43 in the case of models containing only serial links, 1 and 3 cylindrical units could be optimally described using a third order transfer function. the geometry consisting of 5 cylindrical unitscan be described by a second order transfer function. the average goodness of the fit in this case was 91 %. in the case of the model utilizing parallel links, the rtd function of the tank consisting of 1 cylindrical unit was approximated by a transfer function where the orders of the denominator and nominator were 4 and 2, respectively. in the cases of 3 and 5 cylindrical units, the orders of the denominator and nominator were 3 and 1, respectively. the goodness of fit on average in the case of this model was over 99 %. it can be concluded that all geometries of the tank can be described using fourth order or lower transfer functions with increasing model parameters according to the number of cylinders. further investigations to characterise the reasons for such behavior will be carried out by using cfd methods. simultaneously, different step-response experiments will be conducted to observe the behavior of the system. during these experiments, instead of feeding the solution of lower concentration into that of higher concentration within the tank, a positive step function will be used. as a result, the orders will be reversed with the solution of low concentration being in the tank and that of high concentration in the feed. notations latin letters a nominator parameter of transfer function b denominator parameter of transfer function dt time delay [h] h order of the nominator of transfer function (1,n-1) n order of the denominator of transfer function [-] t time [h] td time delay of transfer function [h] x longitudinal coordinate [mm] y vertical coordinate [mm] z horizontal coordinate [mm] capital letters b volume flow rate [lh−1] e error of fitting [%] f residence time distribution function g transfer function i goodness of fit [%] n number of cylinders r response function [gl−1] s step function [gl−1] greek letters δ dirac delta function τ mean residence time [h] indices ∗ time of tracer injection d delay exp experimental fitted fitted ref reference steady steady 0 initial acknowledgement this research was supported by the project efop-3.6.116-2016-00015 “smart specialisation strategy (s3) comprehensive institutional development program at the university of pannonia to promote sensible individual education and career choices”. references [1] nienow, a. w., edwards, m. f., harnby, n. mixing in the process industries. (elsevier, oxford, united kingdom 1997) isbn: 07506-3760-9 [2] blais, b., lassaigne, m., goniva, c., fradette, l., bertrand, f. development of an unresolved cfd–dem model for the flow of viscous suspensions and its application to solid–liquid mixing. j. comp. phys., 2016, 318, 201-221 doi: 10.1016/j.jcp.2016.05.008 [3] levenspiel, o. chemical reaction engineering. ind. eng. chem. res., 1999, 38(11), 4140–4143 doi: 10.1021/ie990488g [4] danckwerts, p. v. continuous flow systems: distribution of residence times. chem. eng. sci., 1995, 50(24), 3857–3866 doi: 10.1016/0009-2509(96)81811-2 [5] fazli-abukheyli, r., darvishi, p. combination of axial dispersion and velocity profile in parallel tanks-in-series compartment model for prediction of residence time distribution in a wide range of non-ideal laminar flow regimes. chem. eng. sci., 2019, 195, 531–540 doi: 10.1016/j.ces.2018.09.052 [6] haag, j., gentric, c., lemaitre, c., leclerc, j. p. modelling of chemical reactors: from systemic approach to compartmental modelling. int. j. chem. reactor eng., 2018, 16(8), 1–22 doi: 10.1515/ijcre-2017-0172 [7] blazek, j. computational fluid dynamics: principles and applications. (butterworth-heinemann, 47(2) pp. 63–70 (2019) https://doi.org/10.1016/j.jcp.2016.05.008 https://doi.org/10.1016/j.jcp.2016.05.008 https://doi.org/10.1021/ie990488g https://doi.org/10.1021/ie990488g https://doi.org/10.1016/0009-2509(96)81811-2 https://doi.org/10.1016/j.ces.2018.09.052 https://doi.org/10.1515/ijcre-2017-0172 https://doi.org/10.1515/ijcre-2017-0172 70 tarcsay, bobek, egedy, and rippel-pethő oxford, united kingdom 2015) isbn: 978-0-08099995-1 [8] toro, e. f. riemann solvers and numerical methods for fluid dynamics. (springer, heidelberg, germany 1999) isbn: 978-3-662-03492-7 [9] pawlowski, s., nayak, n., meireles, m., portugal, c. a. m., velizarov, s., crespo, j. g. cfd modelling of flow patterns, tortuosity and residence time distribution in monolithic porous columns reconstructed from x-ray tomography data. chem. eng. j., 2018, 350, 757–766 doi: 10.1016/j.cej.2018.06.017 [10] delafosse, a., collignon, m. l., calvo, s., delvigne, f., crine, m., thonart, p., toye, d.: cfd-based compartment model for description of mixing in bioreactors. chem. eng. sci., 2014, 106, 76–85 doi: 10.1016/j.ces.2013.11.033 [11] zienkiewicz, o. c., taylor, r. l., zhu, j. z. the finite element method: its basis and fundamentals. (elsevier, oxford, united kingdom, 2005) isbn: 07506-6320-0 [12] solin, p., segeth, k., dolezel, i. higher-order finite element methods. (chapman and hall/crc, new york, 2003) isbn: 978-0-42-920527-9 [13] witt, c., bux, m., gusew, w., leser, u. predictive performance modeling for distributed batch processing using black box monitoring and machine learning. information systems 2019, 82, 33–52 doi: 10.1016/j.is.2019.01.006 [14] suykens, johan a. k.; vandewalle, joos p. l. (ed.) nonlinear modelling: advanced black-box techniques. (springer science and business media, leuven, 2012) isbn: 978-1-4613-7611-8 [15] bunge, m. a general black box theory. philosophy of science, 1963, 30(4), 346–358 doi: 10.1086/287954 hungarian journal of industry and chemistry https://doi.org/10.1016/j.cej.2018.06.017 https://doi.org/10.1016/j.ces.2013.11.033 https://doi.org/10.1016/j.ces.2013.11.033 https://doi.org/10.1016/j.is.2019.01.006 https://doi.org/10.1016/j.is.2019.01.006 https://doi.org/10.1086/287954 introduction experimental and the modelling process results and analysis conclusion hungarian journal of industry and chemistry vol. 45(2) pp. 45–49 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0020 application of a hydrophobic polymeric membrane for carbon dioxide desorption from an mea-water solution zenon ziobrowski * , adam rotkegel institute of chemical engineering of the polish academy of sciences, ul. balycka 5, 44-100 gliwice, poland carbon dioxide desorption from a monoethanolamine (mea) solution using a hydrophobic polydimethylsiloxane (pdms) tubular membrane on a ceramic support is presented. the effects of operating parameters such as feed temperature, liquid flow rate and mea concentration on mass transfer were examined. the mass transfer of co2 from the liquid to gaseous phase was predicted by a multilayer film model with an accuracy of ±25%. research into new selective materials is needed to develop more efficient and environmentally friendly co2 capture technology keywords: mea, desorption, carbon dioxide, hydrophobic membrane, pdms 1. introduction fossil fuel combustion from power plants is one of the most significant sources of co2 emissions [1]. the separation of carbon dioxide from gases can be realized by processes such as adsorption, absorption, low temperature distillation and membrane separation. the absorption of carbon dioxide in amine based solutions is currently the most widespread method in industry for the post-combustion capture of co2 [2]. the advantage of chemical absorption in amine solutions is the fact that at higher temperatures the chemical reaction can be reversed and the amine recycled. on the other hand, obstacles include a relatively low co2 capture capacity, solvent losses caused by evaporation, thermal stability, highly corrosive characteristics, ecotoxicity and biodegradability in the natural environment [2-4]. it was shown that mea and diethanolamine (dea) might promote potential long-term toxicity effects towards living organisms [5,6]. in addition the regeneration step may increase the total operating costs of the capture plant by up to 70%, especially for primary and tertiary amines where the heat of reaction is quite high [7]. the amine scrubbing processes carried out in packed columns are currently most widely used in industry for the post-combustion capture of co2. limiting factors for the application of this technology are its size and large capital costs. the mass transfer performance of this solution can be reduced by flooding, foaming and entrainment conditions. *correspondence: zenz@iich.gliwice.pl in comparison to the studies on co2 absorption in mea solutions there are only a few concerning co2 desorption, despite the fact that the stripping unit is responsible for most of the separation cost of the process [8]. it is important that materials used in the processes concerning post-combustion capture of co2 exhibit low or no environmental effects. various tubular membranes were operated as catalyst supports [9]. recently a new type of ceramic hollow fiber membrane contactor has been studied [10]. this kind of membrane can be modified to be hydrophobic which enables it to be applied for co2 absorption-desorption in amine solutions. in this study the process of co2 removal from an mea solution using a hydrophobic polydimethylsiloxane (pdms) tubular membrane on a ceramic support was investigated. 2. experimental 2.1. experimental setup the experimental setup shown in fig.1 consisted of a membrane module, reactor vessel, cooling system, as well as circulation and vacuum pumps. the hydrophobic pdms membranes on ceramic support (ceramic tubes with an outer diameter of 0.01 m and length of 0.25 m using a pvm 250 membrane module made by pervatech bv) was studied. the feed was circulated by a pump and the flow rate was controlled by a flowmeter. in all experiments the feed temperature was stabilized by a thermostat (1c). the permeate was condensed and collected in cold traps immersed in liquid nitrogen. the vacuum pump was used to maintain the pressure between 7 and 10 mmhg on the permeate side. the concentration of ziobrowski and rotkegel hungarian journal of industry and chemistry 46 carbon dioxide in the permeate was calculated by measuring the mass of carbon dioxide and water in the analyzed permeate sample. the pressures on the feed and permeate sides were measured by pressure gauges. the temperatures of the feed in the reactor vessel, before and after the membrane module were measured by thermocouples. pure monoethanolamine (mea) and deionised water were used to prepare the liquid-feed solution. afterwards the obtained solution was loaded with co2 by bubbling pure co2 in a magnetically stirred vessel until the required carbonation ratio, , was achieved. in our experiments the carbonation ratio was determined by measuring the mass of absorbed co2 in the amine solution at a given temperature. additionally, independent pervaporation experiments with the same pdms membrane under similar thermal and hydrodynamic conditions for a 2-propanol – water mixture were performed to estimate the membrane resistance (1/km). 2.2. experimental results the performance of the pdms membrane was examined experimentally. the operating temperature was between 323 and 348k (50 and 75°c), liquid flow rate between 20 and 600 l/h and the mea concentrations were 5, 10 and 15 wt%. the effect of liquid flow rate on the co2 mass flux and selectivity is presented in figs.2 and 3 for the temperature of 323k (50°c) and 10% mea concentration. the selectivity of the process is defined as follows: 2 2 2 2 co co co co ( (1 )) ( (1 )) p f w w s w w    (1) the measured fluxes increase with the reynolds number. the highest values were obtained for re>10,000 (turbulent flow). this can be explained by the co2 mass transfer increase in the liquid phase for turbulent regime. the measured selectivities rise with the reynolds number and for turbulent flows reach the value of 10. the operating temperature is an important parameter as far as the efficiency of the membrane is concerned as shown in fig.4. for a given turbulent liquid flow rate the measured co2 mass fluxes rise with the feed temperatures due to the increased driving force in favour of co2 mass transfer. the selectivity does not change significantly with the operating temperature, fig.5. the effect of the mea concentration on mass flux and selectivity is presented in figs.6-7 at an operating temperature of 323k (50°c) and turbulent flow (re of about 40,000). the measured mass fluxes do not change significantly with mea concentration (fig.6), because of the figure 1. the experimental setup: 1 – membrane contactor, 2 – feed tank, 3 – cold traps, 4 – circulation pump, 5 – vacuum pump, 6 – heater figure 3. the effect of re number on selectivity (t = 50°c and wmea = 10 wt%) figure 2. the effect of re number on co2 mass flux (t = 50°c, wmea = 10 wt%) figure 4. the effect of feed temperature on co2 mass flux (wmea = 10 wt%) application of hydrophobic polymeric membrane for co2 desorption ... 45(2) pp. 45–49 (2017) 47 relationship between equilibrium constants of the co2 mea reaction and the co2 solubility in water at a given temperature. the selectivity decreases with mea concentration as a result of the rising amount of co2 absorbed in the mea solution and the constant co2 flux in the permeate, see fig.7. 3. mathematical model and calculation results when co2 is absorbed in aqueous monoethanolamine (mea) solution, the following reactions can be written as [11]: slow 2 2 2co rnh rn h coo  (2) fast 2 2 3rn h coo rnh rnh rnhcoo     (3) the formation of carbamate is well understood and the rate of the forward reaction has been determined as first order with respect to both co2 and rnh2: cf 2 2[co ][rnh ]r k (4) during the desorption process the differences in the concentration of the component and the temperature between the inlet and outlet in the liquid phase are very small. therefore, the desorption rate may be simply calculated using the arithmetic mean value of co2 in the liquid phase. with this assumption we can calculate the mass fluxes of co2 can be calculated as follows: 2 2 2 * lco co co( )n k x x  (5) where nco2 [kmol/s] is the flux of co2 and kl [kmol/m2s] is the overall mass-transfer coefficient of the liquid phase. the overall mass-transfer coefficient for co2 can be evaluated by a resistance-in-series model [12]. the numerical calculations based on model equations were performed and estimated values of membrane resistance (1/km) used. in the calculations the experimental values of the henry’s constant for co2 in water and mea under standard conditions are 1.2456 and 1.5732, respectively [13]. the enhancement factor of the chemical reaction of co2 in the liquid phase, as defined by decoursey [14], was between 20 and 60. the viscosity of the water–mea mixture was calculated according to a grunberg and nissan equation [15]. calculated and experimental values of co2 mass fluxes are figure 5. the effect of feed temperature on selectivity (wmea = 10 wt%) figure 6. the effect of mea concentration on co2 mass flux figure 7. the effect of mea concentration on selectivity figure 8. comparison of calculated values of co2 fluxes with experimental ones ziobrowski and rotkegel hungarian journal of industry and chemistry 48 shown in fig.8. the scattering of calculated and experimental values of co2 mass fluxes was within the range of ±25% . the experimental values of co2 mass fluxes were compared with those obtained from the literature for co2 stripping in a ceramic hollow fiber membrane contactor [10]. in spite of the different types of membrane type and hydrodynamic conditions the measured values of co2 mass fluxes were comparable in both cases. conclusions the application of a membrane in the process of co2 stripping from mea solutions avoids some technical problems that are encountered in industrial practices. the pdms hydrophobic tubular membrane on a ceramic support can be applied for the removal of co2 from mea solutions. in developed turbulent flows the measured co2 mass fluxes and selectivities do not change significantly with re number (figs.2-3). the measured co2 mass fluxes increase as the feed temperature rises (fig.4) and slightly depend on the mea concentration (fig.6). the measured and calculated co2 mass fluxes are in good agreement with each other (fig.8). the ±25% variation in scattering can be explained by the accuracy of the correlations, experimental precision and simplification of the model. 4. symbols c – concentration, kmol m-3 d – diffusion coefficient, m2 s-1 kl – overall mass transfer coefficient, kmol m-2 s-1 km – mass transfer coefficient of the membrane, kmol m-2 s-1 n – mass flux kmol m-2s-1 r – reaction rate, kmol s-1 re – reynolds number s – selectivity t – temperature, k w – mass fraction x – mole fraction of co2 in the liquid phase superscripts * refers to equilibrium subscripts calc – calculation co2 – carbon dioxide exp experimental f – feed g – gaseous phase l – liquid phase p permeate references [1] budzianowski w.m.: single solvents, solvent blends, and advanced solvent systems in co2 capture by absorption: a review, int. j. global warming, 2015 7 (2), 184-225, doi: 10.1504/ijgw.2015.067749 [2] rochelle g.t.: amine scrubbing for co2 capture, science, 2009 325, 1652-1654, doi: 10.1126/science.1176731 [3] zhao b.; sun y.; yuan y.; gao j.; wang s.; zhuo y.; chen c.: study on corrosion in co2 chemical absorption process using amine solution, energy procedia, 2011 4, 93–100, doi: 10.1016/j.egypro.2011.01.028 [4] eide-haugmo i. et al.: environmental impact of amines, energy procedia 2009 1, 1297–1304, doi: 10.1016/j.egypro.2009.01.170 [5] libralato g.; volpi ghirardini a.; avezzù f.: seawater ecotoxicity of monoethanolamine, diethanolamine and triethanolamine, j. hazard. mat., 2010 176, 535–539, doi: 10.1016/j.jhazmat.2009.11.062 [6] ethanolamine compounds (mea, dea, tea and others), online: http://www.safecosmetics.org/getthe-facts/chemicals-of-concern/ethanolaminecompounds/, accessed: 2017-10-05 [7] schäfer b.; mather a.e.; marsh k.n.: enthalpies of solution of carbon dioxide in mixed solvents, fluid phase equilib., 2002 194, 929-935, doi: 10.1016/s0378-3812(01)00722-1 [8] dugas r.; rochelle g.: absorption and desorption rates of carbon dioxide with monoethanolamine and piperazine, energy procedia, 2009 1, 11631169, doi: 10.1016/j.egypro.2009.01.153 [9] keil f. j.; flügge u.: high performance catalytic tubular membrane reactors owing to forced convective flow operation, hung. j. ind. chem.,2005, 32(1-2), 31-42 [10] koonaphapdeelert s.; wu z.; li k.: carbon dioxide stripping in ceramic hollow fibre membrane contactors, chem. eng. sci., 2009 64, 1-8, doi: 10.1016/j.ces.2008.09.010 [11] astarita g.; savage d.w.; bisio a.: gas treating with chemical reaction, john wiley & sons, new york, 1983 [12] kreulen h.; smolders c.a.; versteeg g.f.; van swaaij w.p.m.: microporous hollow fiber membrane module as gas-liquid contactors. part 2: mass transfer with chemical reaction, j. membrane sci., 1993 78, 217-238, doi: 10.1016/03767388(93)80002-f [13] browning g.j.; weiland r.h.: physical solubility of carbon dioxide in aqueous alkanolamine via nitrous oxide analogy, j. chem. eng. data, 1994 39, 817-822, doi: 10.1021/je00016a040 [14] decoursey w.j.: enhancement factors for gas absorption with reversible reaction, chem. eng. sci., 1982 37, 1483-1489, doi: 10.1016/0009-2509(82)800055 application of hydrophobic polymeric membrane for co2 desorption ... 45(2) pp. 45–49 (2017) 49 [15] meng-hui l., yei-chung l.: densities and viscosities of solutions of monoethanolamine + nmethyldiethanolamine + water and monoethanolamine + 2-amino-2-methyl-1-propanol + water, j. chem. eng. data, 1994 39, 444-447, doi: 10.1021/je00015a009 hungarian journal of industrial chemistry veszprem . vol. 30. pp. 211-214 (2002) mathematical model of variable volume diafiltration m. n. tekic, z. zavarg6, d. krstic and m. djuric (faculty of technology, university ofnovi sad, bul. caralazara 1, 21000 novi sad, yugoslavia) received: april11, 2002; revised: august 13, 2002 the use of ultrafiltration as a separation technique is frequently accompanied by a diafiltration step to remove microsolutes. there are different ways to combine ultrafiltration and diafiltration to obtain the desired final concentration of components. variable volume diafiltration is a continuous process in which water is continuously added at a rate jess than the permeate flow rate so that the concentration of macrosolute continuously increases, and the final concentrations of macrosolute and microsolute can be reached simultaneously. in this paper a mathematical model of variable volume diafiltration is proposed. the model includes both initial volume and concentration, rejection coefficients, processing time as well as water volume added during diafiltration. the developed model could be served for design and optimization purposes. keywords: modeling, ultrafiltration, diafiltration introduction over two decades ultrafiltration has been recognized as a separation technique to fractionate species according to their size. this technique has several advantages over other separation techniques such as distillation, evaporation solvent extraction, chromatography, etc. ultrafiltration is widely used as a separation technique in many different fields such as chemical and biochemical engineering, food processing and pharmaceutical industry. in order to achieve macrosolute-microsolute separation different ultrafiltration processes can be used. the concentration of macrosolute by ultrafiltration is frequently accompanied by a diafiltration step to remove microsolute. it consists of a continuous or discontinuous addition of a pure solvent to retentate feed and can be applied to both batch and continuous ultrafiltration processes. both, batch and continuous diafilltration can be performed in different ways. batch diafiltration can be carried out depending on the way the pure solution is added as a continuous or discontinuous batch diafiltration. on the other hand, continuous diafiltration can be performed as a co-current or counter-current [1] process. an interesting process in which a pure solvent is continuously added at a rate less than permeate flow rate so that concentration of macrosolute and the removal of impurities occurs simultaneously. wa:c. proposed by jeffrin and charrier [2]. thi~ way a smgle diafiltration process with a continuou~ly decreasing volume makes possible that the final concentration!'> of components are reached simultaneously. the aim of this work is to develop a process model of a variable volume diafiltration. in the presemed model the initial solution concentration, initial volum\.,. retention, processing time as well as the membrane area are included. this model differs from the approach given by jaffrin and charrier [2] where the rejection coefficient was not included. thus, on the basis of incomplete macrosolute rejection and the constant flux assumption an analytical solution is obtained. model let us consider the diafiltration process schematically presented in fig. i. the equation of continuity is given by: dv -=qo-qf dt (1) here vis the volume of the solution in the tank and ql> and q, are diafiltration water flow rate and filtrate flow rate respectively. the mass balance of the macrosolute can be written as 212 d(vc) = qfc(lr) (2) dt table 1 values of model parameters and coefficients parameter unit value a ? 1 mj m3/m2s 2.5·10-5 vo m3 0.2 r 1 0.9-1 r 1 0-0.1 c/co 1 2-10 cclc1 2-10 pconst variable pvar 1 variable a 1 variable where c is concentration, and r is the macrosolute rejection coefficient. in order to obtain concentrated solution with the final volume \'j the flow rate of diafiltration water must be a constant smaller fraction of qf. qd =aqf a<1 after rearranging eq. (2) becomes 0 ~ ~ j d(lnc) = -jqf(~-r) dtj d(lnv) ~ 0 ~ from the third term of eq. ( 4) it follows v = v0 qf(l-a)t (3) (4) (5) and the first term on. the right hand side of eq.(4) becomes 's' qf<ir) dt = (1r) in[i qf<i-a) t j (6) o v (l-a) yo f by introducing eq.(6) in (4). it follows ln cf = (1-r)ln(lqf(l-a)tf)-ln vi (7) c0 (1-a) v0 v0 from which the relative concentration of macrosolute can be related with time cf (8) z-. r-a · • ( 1(1-a)~0·a-t1 )'"" the processing time necessary to reach the desired final concentration can be calculated as (9) the processing time can be related to microsolute concentrations t 1[ ( c0 j~=:] yo fc.f (1-a)ja water retentate ~ feed tank t permeate (10) fig. i schematic representation of the variable volume diafiltration process where r is the microsolute rejection coefficient which is zero or close to zero. from the last two eqs.(9) and (10) the relation between macrosolute and microsolute concentration can be found :; =( ~; t~ (11) the coefficient a can now be calculated from the above eq.(ll) rln~+rln cf a c.r c0 (12) ln~+ln2 cf co the solution volume added during the diafiltration in this process is vd,var = qdt = aja~ combining with eq.(9) one can get · (13) in the classical (constant volume) diafiltration process the volume ratio is r = vd.const =-1-lns1_ (15) pcoif!st v. l o -r cf where concentration ratio cfc0 can be found from eq.(ll). calculation the calculations of the developed model were carried out on the basis of parameters given in table 1. the influence of the relative concentration of macrosolute on processing time at different retention are given in fig.2. the calculations were carried out for initial feed volume of 0.2m3 , and a= 0.3. as expected, we have the shortest time at higher retention as it is at batch ultrafiltration [3]. 180 170 160 150 140 i130 120 110 100 90 6 10 cf/co 213 conclusions a more realistic model which differs from jaffin and charrier's [2] and includes the rejection coefficient is presented. the model provides the basis for more complex simulations of variable volume diafiltration andean 320r,:=:=:=::::.:;-----------------, 300 r=0.1 280 260 240 c 220 ,~200 180 160 140 --u=0.3 .......... 0.=0.5 '"' .... 0.=0.7 ~---fig.2 processing time vs. macrosolute relative concentration 120 +-~.-~--.-~-r--,--~-~-~~ 900 800 700 600 :s 500 .s 400 300 200 100 0.0 ~ q2 q3 q4 0~ q6 oj q8 0.9 fig.3 processing time vs. retentate dilution fig.3 shows how processing time depends on the ratio of the dilution flow rate to the permeate flow rate, a, at different retention. it can be seen that the processing time increases with increasing a, and that the value of a over 0.7leads to very high processing time. the processing time as the function of the relative dilution of the microsolute at different values of a are shown in fig.4. it should be noted that at a = 0.3 the processing time is almost independent of the relative dilution. with increasing an a the processing, time rises significantly with the relative dilution. a simple way of comparing variable volume and constant volume diafiltration is to compare the amount of the diafiltration solvent used to reach desired the final concentration. the results of the calculation on fig.5 represent the relative volume of the water added during the constant volume and variable volume diafiltration. it is important to note that the variable volume diafiltration requires less diluent water than the constant volume diafiltration. c:l. 6 co/cf 10 fig.4 processing time vs. relative microsolute dilution 2.8 2.6 2.4 2.2 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 2 4 6 co/cf 8 i .---~-1 10 fig.5 relative diafiltration volume vs. microsolute dilution at the process with constant and variable volume diafiltration be useful in analysis of process paramete-rs. the obtained analytical solution enables simple calculations such as processing time, amount of diafiltration solvent, concentration of macrosolute and dilution of microsolute. the calculations also show that variable volume diafiltration needs less diafiltration liquid than the constant volume diafiltration which could be of practical interest. acknowledgement this research was supported by ministry of science, technology and development, republic of serbia, project no. 1362. 214 r v symbols membrane area, !if concentration of macrosolute in any time, wt.% initial concentration of macrosolute , wt.% final concentration of macrosolute wt.% initial concentration of microsolute , wt.% final concentration of microsolute wt.% permeate flux, m3 /m2s water (solution) flow rate added during diafiltration, m3/s filtration flow rate, m3/s macrosolute rejection coefficient microsolute rejection coefficient volume in the tank, m3 vo initial volume, m3 yj final volume, m3 t time, s t.r final time, s a defined by eq.(3) references 1. dutre b. and tragardh g.: dessalination, 1994, 95,227-267 2. jaffrin m. y. and charrier j. ph.: j. membrane sci., 1994, 97, 71-81 3. tek.ic m. n., kujacki j. and v atai gy.: hung. j. ind. chern., 1994,22, 1-3 page 213 page 214 page 215 page 216 hungarian journal of industry and chemistry vol. 48(1) pp. 131–138 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-19 xbrl utilization as an automated industry analysis alex suta*1 and árpád tóth1 1research center of vehicle industry, széchenyi istván university, egyetem tér 1, győr, 9026, hungary in the last two decades, electronic financial reporting went through a significant evolution, where to date, extensible business reporting language (xbrl) has become the leading platform that is already obligatory for listed entities in the united states and was also legislated in the european union from january 1, 2020. the primary objective of this research was to review the us-listed companies’ 2018 quarterly reports. the study generated an automated industry analysis for the automotive industry from the aspect of four main financial item categories as an alternative to statistics-based, manually prepared industry analyses. statistical tests were carried out between two industrial classification methodologies, the securities’ industry identification marks and the reported standard industrial classification (sic) codes. the results showed a significant difference between the industry classification methodologies. automated reporting was more precise with regard to the identification of the listed and reporting entities, however, the data fields of sic codes within the xbrl data set provided an inaccurate classification, which is a potential area of improvement along with additional recommendations outlined in the conclusion. keywords: xbrl, us-listed entities, acl, automated data analytics, industry analysis, sic codes 1. introduction the electronic reporting and automated fundamental reviews in the field of financial reporting is becoming increasingly important considering the difficulties and error-prone procedure of manual analysis from the available source of information. the extensible business reporting language (xbrl) provides a standardized platform for this activity, which supports automated and digitalized reviews compared to the paper-based reports from the previous manual. this electronic reporting platform is already used as the official reporting form in the united states for listed entities, therefore, the application of a proper industry classification is essential. even though xbrl reporting is required by the u.s. securities and exchange commission (sec), research institutions can choose from various generally accepted industry classifications. despite the lack of regulation, it is a primary interest of research institutions to protect their reputations by adequately representing companies from the various industries. the two different approaches might provide different results, which can lead to inaccurate trend projections or unreliable industry comparisons. the validation of the xbrl classification and reports by marketing research firms can only be reconciled and validated to statistical industry reports which identify discrepancies. to date, standard industrial classification (sic) codes are used in the sec’s electronic data gathering, analysis, *correspondence: suta.alex@ga.sze.hu and retrieval (edgar) system to define the type of business of companies. based on its primary activity, each company assigns a four-digit code to itself when registering an initial public offering (ipo) with the sec [1]. the four digits indicate levels of description of the industry classification, e.g. the location hierarchy for car manufacturers is division d manufacturing (codes 2039), code 37: transportation equipment, and code 3711: motor vehicles and passenger car bodies [1]. the objective of this research was to review the us-listed companies, where xbrl reports are already required and implemented. subsequently, through an automated review of the automotive industry, to then identify how these reports can be compared to the european listed entities. this information is crucial for stakeholders and regional policymakers to gain a clear view of the conditions of the target industry. according to the european securities and markets authority (esma), from january 1, 2020 onwards, new requirements on the stock exchange-listed companies in the european union came into effect to provide respective financial statements in a new european single electronic format (esef). this is a significant change to the application of xbrl as companies now have to provide reports in this specific reporting language. the data sets include structured information; for this reason, a new wave of research initiatives is expected in this academic area that could follow on from inconsistent industry classifications, further hindering comparability. https://doi.org/10.33927/hjic-2020-19 mailto:suta.alex@ga.sze.hu 132 suta and tóth 2. literature review 2.1 xbrl utilization in industry-specific data analysis prior literature has documented uses of xbrl in a variety of data analysis environments, generally in the research areas of accounting and financial reporting. systematic financial data provides data analysts and investors with the ability to measure performance and risks, as well as create comparisons, ratings and other value-added products [2]. connected to comparability aspects, several sources have been reviewed that are related to the semantic issue of industrial classification. being a driver of electronic data interchange, xbrl data sets are constructed from multiple identifying tags and numerical data that can be processed by computer software [3]. while the technical background on data-centric analysis is available [4] 2013 [5] 2014, [6], it is uncommon in the industry-specific research literature that xbrl databases are used as the primary source of data. chychyla-leone-meza [7] measured financial reporting complexity by comparing the quantity of text in us generally accepted accounting principles (gaap) and sec regulations of textual data from xbrl filings. in this study, the variation with regard to the data content of different taxonomy versions (denominative tags, labels, documentation) is emphasized. for this reason, the annual changes in published taxonomy updates have to be taken into consideration [8]. despite the existence of the xbrl industry resource group established by the fasb [8], standard industrial classification (sic) codes are not part of taxonomy updates and their current 2007 form seems to be generally accepted for statistical use. felokim-lim [9] observed changes in the information environment of analysts by the overuse of customized tags, creating assumptions based on industrial classification as a factor. zhang-guan-kim [10] proposed an expected investor crash risk model based on financial information gathered from xbrl-based sec databases. in terms of the estimation of the impacts, the industry median of customized tags is generated by 2-digit sic codes as an adjustment tool in the regression model. similarly, industrial classification was taken into account as a dummy variable during the analysis with regard to the xbrl adoption of reductions in audit fees as per shan-troshanirichardson [11]. in other xbrl-based studies, industry-specific assumptions required solutions other than basic sic codes. liu-luo-wang [12] reviewed the effect of xbrl adoption on information asymmetry, where sic was reclassified to identify high-technology industries. 2.2 discrepancies between industrial classification systems since the emergence of the north american industry classification system (naics) in 1997 as a sound replacement of standard industrial classification (sic) codes in u.s. industrial statistics, papers have reviewed the impacts of different frameworks in financial research. effective comparative statistics require the use of a standardized classification system [13]. the u.s. economic census bureau has made regulatory, business and academic purposes of performing economic research on historical data possible. in 1997, the existing framework, the sic, was replaced by the naics [14]. unlike the sic’s mixed production/market system, naics introduced a production-oriented economic concept that supports the examination of industry-specific indicators such as productivity, input-output relationships and capital intensity [15]. the specific rearrangements between industrial classes primarily affected manufacturing industries, where the sic functions as a somewhat outdated alternative. u.s. government departments, namely the bureau of labor statistics (bls), internal revenue service (irs) and social security administration (ssa), alongside the u.s. securities and exchange commission (sec), continue to use the most recent 2007 update of four-digit sic codes. while maintaining a unified classification system is necessary for government departments, the lack of conceptual harmony between industrial classification systems creates a discrepancy with academic research [16]. several papers have been collected that present empirical evidence of disharmonious schemes based on financial statement data sets. kahle-walking [17] observed differences in financial variables gathered from two statistical databases (crsp and compustat) using four-digit sic codes to be substantial, moreover, showed that commonly used methods of industrial classification disagree due to frequent changes in the sic codes of firms. bhojraj-lee-oler reviewed the capital market applications of four broadly available industrial classification schemes and found that a significant degree of variance with regard to the number of companies represented in industry divisions exists. the study argues that the six-digit global industry classification standard (gics), followed by naics, offers better comparability between firms concerning sic in terms of the critical evaluation of financial ratios and that industrial classification is essential in instances of fundamental analysis. while gics reflects the dynamic changes in industry sectors, being a privately available system mainly involved in investment processes, it is unlikely to be suitable in statistical research [18]. kelton-pasquale-rebelein [19] referred to sic codes as outdated in the field of industry cluster analysis and prepared an updated framework using naics. as opposed to classifying establishments according to similar products (sic), the groups are formed from identical production processes (naics). hrazdil-zhang [20] and hrazdil-trottier-zhang [21] published empirical results on the heterogeneity of industry concentration with the use of sic and other classification schemes based on the market shares of sales and financial ratios of companies in the manufacturing sector (sic 2000-3999). according to their findings, the sic system remains inferior to gics and naics in terms of industrial homogeneity. hungarian journal of industry and chemistry xbrl utilization as an automated industry analysis 133 instead of ordinary company databases such as compustat or s&p 1500, papagiannidis et al. proposed an exploratory big data method to gather regional research of industry clusters based in the uk. in this study, keywords connected to business operations were collected from official websites to enhance the level of detail provided by single sic codes, supporting the formation of regional clusters. it is a common conclusion in the reviewed literature that the sole use of sic codes in industry analysis could lead to the loss of information and false estimation of market forces; in this context the potential of xbrl as a primary data source of financial statements has been reviewed. 2.3 the multi-tier supply chain approach one possible outcome of the barriers of traditional statistical classification systems is the addition of extra information to existing schemes. in an industrial analysis, especially in the automotive industry, it is essential to differentiate between operational properties, e.g. their position in the automotive supply chain. the contemporary position of an industry must be judged by the different weights of its market players. assumptions about financial information are heavily affected by the final product, whether it is a part of the interorganizational supply chain, or sold to dealerships or directly to consumers in the form of passenger cars. in terms of a supply chain, manufacturers and suppliers can be classified into multi-tiered groups based on their position in the production chain, as well as the state of raw materials (tier 3 and additional sub-tiers) in addition to finished or semi-finished components (suppliers from tiers 1 and 2) compared to fully finished products (original equipment manufacturers (oems)). concerning the automotive industry, sources from both academia, business and governments [22–24] agree that market players from multi-tier supply chain structures can be ranked as follows: 1. oems: a concentrated group of companies accountable for the main manufacturing, assembly and design processes that possess a large market share and well-known brand names; 2. suppliers from tiers 1 & 2: potentially several hundred large or small companies, accountable for the supply of automotive parts and systems to oems. the range of sold goods is diverse and includes engine components, interior, exterior, transmission as well as cooling and electronic systems. although their role in the supply chain is consistent, suppliers from tiers 1 and 2 vary in their direct/indirect (through other participants) nature of interaction with oems, therefore, from a statistical viewpoint, can be aggregated; 3. tier 3 and sub-tier suppliers: several thousand smaller companies are accountable for the supply of raw materials to suppliers from tiers 1 & 2. in the scientific literature, several utilizations of the multi-tier supply chain approach exist. mena-humphrieschoi [25] reviewed the existing literature at the time on structural arrangements (buyer-supplier-customer) and prepared three cases of theoretical linkage. according to the study, the most typical structure of the automotive industry is the “closed triad”, where the buyer (oem) can insist on certain requirements (either assurance or training function) not only from tier 1 but sub-tier suppliers as well. masoud-mason [26] used the multi-tier system in the automotive industry to simulate cost optimization on a supply-chain level. thomé et al. [27] adopted a similar approach of representing many tiers and their interactions that affect selected flexibility measures (product, responsiveness, sourcing, delivery and postponement). other popular fields of use are sustainability-related questions and green supply chains [28–30]. the available literature clarifies the widespread applicability and general acceptance of tiered levels of suppliers, which supports the methodology examined in the current study. despite its academic use, the application of the well-established oem / tiered system of suppliers in automotive business reports published by major consulting firms [31–33] is common practice. 3. data collection and methods used the sec has published xbrl data sets containing raw aggregate financial statement data quarterly since 2009. at the same time, as a premium service, the sec offers a professional version of its search engine [34] designed specifically to fit the goals of professional financial analytics. however, in line with tendencies identified from the literature review, even a discrepancy on the same platform exists between the standard industrial classification codes current in xbrl data sets and the edgar search tool. to perform an automated industry analysis, a suitable classification is required. in this study, a possible classification using the software program acl (audit command language) robotics professional version 14.1.0.1581 is evaluated. from the listed u.s. entities, those operating in the automotive industry were selected to measure deviance in terms of crucial financial indicators between the two data sources. the specific choice of the automotive industry lies in its accurate definability, while the goal of the study was to provide an industry-independent methodology of data analysis that can be applied to several other fields. the two main platforms of data collection were edgar pro online (2019) operated by the sec, which is equivalent to the quasimanual download process of financial statements, and the obligatory quarterly reports of aggregate data sets in the xbrl format available on the sec website. to avoid existing industrial classification issues, a multi-tier supply chain approach was introduced by grouping companies as oems and suppliers from tiers 1 & 2 (t1&2 s). 48(1) pp. 131–138 (2020) 134 suta and tóth 4. results 4.1 data categorization: number of companies and industries by using the edgar pro online search tool, market segments can be filtered, of which three categories connected to the automotive industry are available. at the same time, in the xbrl data set, companies are provided with much general information, including sic codes that can be used for categorization. according to the list of codes provided by the sec, six four-digit codes cover the automotive industry (and related services with the exception of retail) that were reviewed in the quarterly reports of 2018. a summary of publicly listed entities is presented in table 1. all entities listed on the new york stock exchange (nyse), national association for securities dealers automated quotations (nasdaq) and better alternative trading system (bats) from the entire population are supposedly consistent data sources and regulated by the sec. in addition to the variance in the number of listed entities in the automotive industry, the size of the entire population between the two sources is inconsistent and differs by over 24%. in terms of industrial classification, the taxonomy behind sic codes in xbrl data sets is valid but incomparable to the customary edgar approach in the case of the identification of specific activities. therefore, two additional categories were created to fit the measurement process; oems and suppliers from tiers 1 & 2 (other automotive suppliers). 4.2 errors in terms of the consistency and availability of samples listed entities from both data sources that are unmatched as a result of their supposedly consistent counterparts were found. out of the sample sizes of 103 and 74, 50 companies are common in both which raises concerns over reliability. furthermore, data availability raised concerns in terms of search results from the sec edgar pro online system. out of the strong sample size of 103, 13 annual reports concerning 2018 were unavailable in the electric filing system of the sec, while an additional 10 required data collection from official websites. four financial statement items concerning the wealth and profitability of companies were selected for analysis in order to evaluate the differences between the two industrial classification schemes. the values of total assets, total equity, net sales revenue and profit after-tax are central financial factors of investor decision-making. when necessary, exchange rates of the federal reserve were used according to the asc (accounting standards codification) standards issued by the financial accounting standards board (fasb) [35]. 4.3 comparison of financial information on an industrial level based on the financial statement data, descriptive statistics were calculated on the selected reporting lines. differences were summarized in terms of both absolute values between the two data sources and percent deviations as presented in the tables 2 and 3. a general observation of the data source is that the intervals between the minimum and maximum values are substantial for all four financial statement items. it is likely that – when used as a statistical sample – a normal distribution cannot be assumed. the standard deviation exceeds the mean values in the case of total assets, therefore, the set of values (especially for the financial data of suppliers from tiers 1 & 2) is highly dispersed. a pattern can be observed in the deviation between the two data sources. the total values of oem financial statement items are higher in the xbrl data set, in contrast to data derived from the online sec source, while the opposite is seen in the case of suppliers from tiers 1 & 2, where the total values are dominated by online table 1: industrial specification of data sources sec’s edgar online pro sec’s edgar xbrl data set industrial specification number of companies industry (sic) number of companies o e m s { auto & truck manufacturers 26 3711. motor vehicles & passenger car bodies 20  o e m s su pp lie rs fr om ti er s 1 & 2  automobiles, parts & service retailers 24 3713. truck & bus bodies 2 auto, truck & motorcycle parts 53 3714. motor vehicle parts & accessories 41  su pp lie rs fr om ti er s 1 & 2 3715. truck trailers 1 3716. motor homes 2 3751. motorcycles, bicycles, and parts 8 total 103 total 74 entire population size 5,736 entire population size 7,133 hungarian journal of industry and chemistry xbrl utilization as an automated industry analysis 135 sources. as an attempt to generalize the automotive industry, mean values were calculated where xbrl represents higher values except for the net sales revenues of suppliers. these deviations are partly validated by the amount of incompletely matched samples, but the 103:74 sample-size ratio is not represented by the results. the table 4 summarizes the difference between the results of descriptive statistics in the form of percentages. despite former expectations, oems do not represent the majority of the financial item totals (between 45.1 and 55.9%), total equity (between 31.8 and 48.6%), net sales revenue (44.7 and 57.6%) and profit after-tax (35.452.5%), the differences between data sources can be measured on a scale of 6.7% to 31.9% as seen in table 4. suppliers from tiers 1 & 2 match to an even lesser extent, so percent deviations are typically higher, especially in the case of net sales revenue (56.7%). based on the matrix, the individual averages of companies cannot be used for industry generalization, both in terms of absolute mean values and standard deviations. the deviation “hotspots” are clearly centered around the suppliers from tiers 1 & 2. 4.4 chi-square statistical testing to support our assumptions of statistically significant deviation between data sources, pearson’s chi-squared test was implemented, a full description of the steps is available in appendix a [36, 37]. selected categories of oems and suppliers from tiers 1 & 2 were differentiated along with expected (data derived from online sec-based financial statements) vs. observed (data derived from xbrl data sets) values. based on the performed chi-square test, the results highlighted that the differences between the expected and observed values of financial statement items (total assets, total equity, net sales revenue and profit after-tax) were significant. with a 95% confidence interval (α = 0.05), oems and suppliers from tiers 1 & 2 both exceeded the critical value of 16.92 with 7 degrees of freedom (df = 7). it is important to note the very significant (almost 10 times higher) impact of suppliers from tiers 1 & 2 in terms of the total level of deviance. 5. conclusions xbrl preparation is obligatory, however, the content can include differences from the reported and published financial statements. conclusions can be summarized in the following points: • potential duplication of lines in xbrl sources (e.g. 8 lines of certain financial statement items from china automotive systems, inc.); • lack of standardization in tags: the xbrl platform manages to integrate more financial reporting taxonomy (different annual versions of ifrs and us gaap). due to the different (and potentially customized) tags, the definitions of some financial statement items converge; the structure of financial statements has yet to be fully harmonized between annual reports and xbrl statements; • errors in the reporting period (temporal differences): in some cases, outdated (1 or 2 years prior to table 2: automotive market share of the entire population (%, number) representation % (n) sec’s edgar pro online sec’s edgar xbrl data set entire population 100% (5,736) 100% (7,113) oems 0.45% (26) 0.31% (22) suppliers from tiers 1 & 2 1.34% (77) 0.73% (52) total assets total equity net sales revenue profit after-tax total 1.80% (103) 1.04% (74) oems (matched) 0.28% (16) 0.20% (14) suppliers from tiers 1 & 2 (matched) 0.59% (34) 0.50% (36) total (matched) 0.87% (50) 0.70% (50) table 3: absolute financial data from data sources (left – sec’s edgar pro online / right – sec‘s xbrl data set) (usd in millions) statistics category total assets value total equity attributable to company owners net sales revenues profit after taxes totals oem 783.346 874.139 153.668 221.111 606.225 649.422 23.941 35.125 tier 1&2 s. 953.149 688.812 329.224 234.365 749.694 478.399 43.717 31.834 mean oem 27.012 39.734 5.299 10.050 20.904 29.519 826 1.597 tier 1&2 s. 12.880 13.246 4.449 4.507 10.131 9.200 591 612 st. dev oem 66.884 77.251 11.802 18.956 45.992 52.970 1.875 3.007 tier 1&2 s. 56.749 63.640 21.527 23.684 33.241 34.997 2.971 3.262 48(1) pp. 131–138 (2020) 136 suta and tóth table 4: deviation matrix between data sources (%) statistic category total assets value total equity attributable to company owners net sales revenues profit after taxes totals oem 10.39% 30.50% 6.65% 31.84% t1&2 s. 38.38% 40.48% 56.71% 37.33% mean oem 32.02% 47.28% 29.18% 48.29% t1&2 s. 2.76% 1.29% 10.12% 3.50% st.dev oem 13.42% 37.74% 13.18% 37.65% t1&2 s. 10.83% 9.11% 5.02% 8.93% the current fiscal year) financial information is presented in current filings (e.g. an entity presents information from the 2017 fiscal year in the q4 2018 filing as the most current); • the inability to fully and feasibly automate data analysis in the case of automotive suppliers. mean values are inconsistent between data sources due to the varying sample size of automotive suppliers. to perform a comprehensive industry analysis, error terms need to be defined clearly. otherwise such an analysis would be performed with many predefined assumptions, leading to a decrease in the overall explanatory power and raising concerns about reliability/reproducibility. financial analysts should use xbrl datasets with concern, these points kept in mind. as a currently available best practice, the methodology of the u.s. securities and exchange commission is a precedent for the building of inline xbrl statements into integrated datasets. an emerging challenge of regulatory bodies such as the european securities and markets authorities is the supervision of companies uploading their data to a central system of a similar nature to produce well-structured databases for automated financial analytics. acknowledgements the research presented in this paper was financed by the “research area excellence program – 2019 (tudfo/51757/2019-itm)” and university of győr. references [1] naics association (2019). common sic questions, https://www.naics.com/ frequently-asked-questions/#naicsfaq [2] xbrl international (2019). an introduction to xbrl, https://www.xbrl.org/the-standard/ 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https://doi.org/10.1016/j.jacceco.2018.09.005 https://doi.org/10.1506/n57l-0462-856v-7144 https://doi.org/10.1506/n57l-0462-856v-7144 https://www.msci.com/gics https://doi.org/10.1080/00343400701288316 https://doi.org/10.1080/00343400701288316 https://doi.org/10.1016/j.econlet.2011.10.001 https://doi.org/10.1016/j.econlet.2011.10.001 https://doi.org/10.1016/j.econlet.2012.09.022 https://doi.org/10.1111/jscm.12003 https://doi.org/10.1016/j.cor.2015.08.012 https://doi.org/10.1016/j.ijpe.2014.07.024 https://doi.org/10.1016/j.ijpe.2018.07.022 https://doi.org/10.1016/j.ijpe.2018.07.022 https://doi.org/10.1016/j.ijpe.2018.05.030 https://doi.org/10.1016/j.ijpe.2019.09.014 https://www.autonews.com/assets/pdf/ca116090622.pdf https://www.autonews.com/assets/pdf/ca116090622.pdf https://www.rolandberger.com/it/publications/global-automotive-supplier-study-2018.html https://www.rolandberger.com/it/publications/global-automotive-supplier-study-2018.html https://www.rolandberger.com/it/publications/global-automotive-supplier-study-2018.html https://pro.edgar-online.com/ https://www.federalreserve.gov/releases/h10/hist/ https://www.federalreserve.gov/releases/h10/hist/ 138 suta and tóth appendix a – chi-square test steps 1) contingency table financial statement items oems suppliers from tiers 1 & 2 total assets expected 783,346 953,149 observed 874,139 688,812 total equity attributable to the owners of companies expected 153,668 329,224 observed 221,111 234,365 net sales revenue expected 606,225 749,694 observed 649,422 478,399 profit after-tax expected 23,941 43,717 observed 35,125 31,834 total 3,346,977 3,509,195 2) h0 the financial values of the xbrl data source (observed values) are not significantly different from the values of the online sec edgar pro online data source (expected values). therefore, industry totals from the two sources are consistent. 3) calculated marginal totals for the observed table 4) expected value calculation based on the specific financial statement item’s proportion in the whole population 5) degree of freedom df = (r − 1)(c− 1) df = (8− 1)(2− 1) = 7 6) calculation of chi-square values financial statement items χ2 = n∑ i=1 (oi − ei) 2 ei oems suppliers from tiers 1 & 2 total assets e-o -90,792 264,337 (e-o)2 8,243,257,799 69,874,243,884 total equity attributable to the owners of companies e-o -67,442 94,860 (e-o)2 4,548,480,637 8,998,332,516 net sales revenue e-o -43,197 271,295 (e-o)2 1,865,960,356 73,600,784,685 profit after-tax e-o -11,184 11,883 (e-o)2 125,073,800 141,206,159 chi-square total chi-square 4,417 43,490 47,907 7) determination of significance level and critical value: significance level (alpha) 0.05 critical value 16.92 8) the chi square test result showed as the h0 hypothesis should be rejected with a 95% confidence interval (degree of freedom = 7). the chi-squared test results showed that the hypothesis h0 should be rejected. hungarian journal of industry and chemistry introduction literature review xbrl utilization in industry-specific data analysis discrepancies between industrial classification systems the multi-tier supply chain approach data collection and methods used results data categorization: number of companies and industries errors in terms of the consistency and availability of samples comparison of financial information on an industrial level chi-square statistical testing conclusions page 1 page 2 page 3 page 4 page 5 page 6 page 7 page 8 page 9 page 10 page 11 page 12 page 13 page 14 page 15 page 16 page 17 page 18 page 19 page 20 page 21 page 22 page 23 page 24 page 25 page 26 page 27 page 28 page 29 page 30 page 31 page 32 page 33 page 34 page 35 page 36 page 37 page 38 page 39 page 40 page 41 page 42 page 43 page 44 page 45 page 46 page 47 page 48 page 49 page 50 page 51 page 52 page 53 page 54 page 55 page 56 page 57 page 58 page 59 page 60 page 61 page 62 page 63 page 64 page 65 page 66 page 67 page 68 page 69 page 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page 518 page 519 page 520 page 521 page 522 page 523 page 524 page 525 page 526 page 527 page 528 page 529 page 530 page 531 page 532 page 533 page 534 page 535 page 536 page 537 page 538 page 539 page 540 page 541 page 542 page 543 page 544 page 545 page 546 page 547 page 548 page 549 page 550 page 551 page 552 page 553 page 554 page 555 page 556 page 557 page 558 page 559 page 560 page 561 page 562 page 563 page 564 page 565 page 566 page 567 page 568 page 569 page 570 page 571 page 572 page 573 page 574 page 575 page 576 page 577 page 578 page 579 page 580 page 581 page 582 page 583 page 584 conferenceproceed~gs hungarian journal of ~dustrial chemistry veszprem vol. 2. pp. 21-24 (2000) applying geograpidcal information systems in wetland management in the balaton-highlands national park n. kovats and t. szalay (university of veszprem, school of environmental engineering and chemical teclmology, · egyetem street 10, p.o.box 158, veszprem, h-8200, hungary) this paper was p~esented at the second international conference on environmental engineering, umversity ofveszprem, veszprem. hungary, may 29june 5, 1999 the pecsely-basin is situated in the balaton-highlands national park, which was founded in 1997. the basin is rich in ~etlands. increasing landscape diversity and the aesthetic value of this area. this paper gives a review on how different mformatron s?urces •. e.s~ci~ly remote sensing can be used for inventorying wetlands. by using gis, our basic intention was to establish a dtgttised mventory and database, which can serve in the future as a basis of any nature conservation wotk. in addition, we have investigated what information different layers might provide in wetland management and how it can be interpreted. keywords: wetland inventory; wetland management; geographical information systems introduction wetlands have been considered as wastelands or even nuisance. only recently did we discover their values. wetlands are amongst the most productive environments in the world, and due to the specific components (such as soil, water, plant and animal species) they are capable of performing certain functions, therefore playing an essential role for the health, welfare and safety of people living nearby. as wetlands are non-renewable natural resources, frrst of all it is essential to be aware what we have and to make an inventory of existing wetlands. such an inventory can basically answer such simple questions as "for the selected region, how many and what types of wetlands are there?" (naturally, for answering the second part of the question, the inventory must have some previously defined classification as its basis but wetland classification in general and existing wetland types in hungary are out of scope of this paper. for wetland classification see cowardin et al [11 and davis [2}) an inventory can be made for a geographical or for an administrative region: for a wate:cshed, for a county, for a province or for an entire country. whatever the selected area size is, the nature of the inventory means that on the selected area all wetlands have to be included and surveyed. the use of remote sensing platforms has proved to be an effective way of gathering data for wetland surveys. however, the choice of which platform to use depends on the resolution required, the area to be covered and the costs implied f3). the available data sources can be: remote sensing platforms topographic maps land use maps field survey. the first aim of our study was to review how these data sources can be applied for a selected area of the balaton-highlands national park (hungary), in order to make a comparison amongst them considering information provided. nevertheless, the scope of such wetland inventory can be expanded and other, useful .information on the wetland can be included, considering their status and the degree of degradation. functional loss of wetlands can be caused basically by two factors: loss of area (in other words, the wetland or part of it is transformed into a different land cover or land use not capable of performing the same functions) or degradation, which is the loss of function resulting from a stressor [4}. these stressors can be natural, but many of them are of anthropogenic origin. five important categories of stressors can be distinguished: (1) hydrologic modification, (2) physical alteration, (3) sedimentation, (4) nutrient loading and (5) toxic contaminants {5}. t~e degree of functional loss is sometimes very difficult to determine. first of all, how to find out what 22 fig.] situation of the pecsely-basin area changes a wetland might have undergone in the past? secondly, how to identify potential or actual stressors? therefore the second aim of the study was to investigate tci what extent different existing data sources can be used to answer these questions before a timeand money-consuming field monitoring should start. geographical information systems have become widely used in wetland management [6,7]. there comes the third aim of our study: to create a database of these wetlands in a digitised form which can serve as the basis for any future wetland conservation or restoration work. material and methods study area for study area, we choose a small basin within the national park, called pecsely-basin (fig.l). although the area of the basin is rela~ively small, the vegetation is very heterogeneous. typical natural associations are xerotherm oak forests and steppe vegetation. main wetlands of the basin are shown in fig.2. due to their small extension, these wetlands might not have important hydrological or water punfication functions. however, they support such wetland­ dependent species which are unique in. this relatively dry region and among which rare and protected· species are found (epipactis palustris, dactylorrhiza incarnata, orchis laxiflora, etc.). moreover, these wetlands contribute to the diversity of the whole landscape. according to historical data [8], the basin has been populated for thousand years; today, though several villages are situated here with more or iess stable population, the region is mostly favoured for recreation. the question of conserving landscape diversity has become topical since august 9, 1997 when the pecsely-basin was declared as landscape reserve, and especially since 15th september the same year, when the balaton-highlands national park was established. two remote sensing platforms, namely a landsat -5 imagery and 1700-m altitude aircraft photos were used. of topographic maps available, the 1:10000 scale maps proved to he the most useful for creating a digitised database and for field surveys. however, not only recent topographic maps were used but older ones a~ well. the archives of veszprem county is in the possession of very accurate cadastrial maps from the period of the austrian-hungarian empire, from 1857. these maps delineate wetlands, showing their past extension and surrounding land-use as well. these maps could be transformed into digitised form as well. processing of maps can be considered as a secondary data source. using geographical information systems (arcinfo and arcview), such digitised database was established which contains the following layers: roadmap wetlands and water courses topography land use and past extension of wetland (from the 19th century) (fig.2). results aud discussion wetlands of the basin can be classified as marshes, sedge marshes and seasonally flooded meadows. it turned out that such types of wetlands cannot be detected in satellite imagery. on the one hand, these wetlands are rather small, on the other hand, their vegetation coverage is rather high, and therefore they cannot be distinguished from their environment. this coincides with what american scientists working on the national wetlands inventory reported [9]. they found that several small wetlands, namely prairie potholes were not identified by landsat. on the contrary, colour aircraft photos can be very well used as a data source. although colour-infrared photography might provide the best data source for delineation of wetlands [10-12], such infrared photos were not available for our study area. as our main goal was to investigate the applicability of existing data sources, these 1700-m altitude aircraft photos provided the best fit for our purposes. the scale, as well as the colours, which reflect different land cover types, can provide a good basis for distinguishing the diverse elements of the landscape, including wetlands. practically all wetland types can be detected. however, their identification can be accomplished only combining aircraft photos with field surveys. these photos can be weu used for identifying small (app. 1 ha) wetlands. although tlle 1:10000 scale topographic maps proved to be the most useful of maps available for delineating wetlands, their accuracy is far from being perfect. one wetland type, seasonally flooded meadows normally cannot be distinguished on these maps. for determining the extension of a given wetland and for wetland classification, excessive field survey had to be conducted. it also means that topographic maps cannot be transferred into digitised form without additional field surveys when making a wetland inventory. streams /'-/ wetland (old) """" sotetr~t s /'-/ bar6tin>t b /'-/ landuse -forest -wetland c:jmeadow illii] plough-land &vineyard r inhabited area 23 fig.2 land-use map of the basin. it is a combination of two layers, namely land-use and past extension of wetlands. in this way area loss can be determined of different layers of the digitised map, 19th century extension of the wetlands can give useful information, especially in comparison with recent wetland areas (fig.2). such comparison was made for three wetlands: boz6ti-ret, nagyt6i-ret, sotet-ret. it can be seen that the area of these wetlands has changed to different extent a severe area loss has happened in the case of the boz6ti­ ret, but the nagyt6i-ret has not undergone almost any area loss. although no general trend can be drawn concerning area loss of wetlands in the pecsely-basin, some wetlands have been greatly influenced by this stressor. analysing the water current layer, it can be seen that most of these wetlands are without inlet and outlet. their only water source is the rainfall, the quantity of which has shown great variation in the past few years. data available cannot make it possible to draw long­ term trends but in principle, lack of rainfall in successive years might also pose a big risk to the proper functioning of these wetlands. from the land-use map it becomes obvious that agricultural land which surrounds most of the wetlands can provide excessive nutrient input for them. also, from these lands toxic pollutants such as pesticides might be transferred to the wetland. however, we have to emphasise that these are potential stressors. field surveys are needed in order to determine what actual risk these stressors might pose. conclusions the very first step of wetland conservation is inventorying them. our basic aim was to review how already existing information sources can be used for this purpose before an expensive and lengthy field survey would start. for our model area, the pecsely basin, of the investigated data sources (satellite imagery, aircraft photos, and topographic maps), landsat imageries proved to be completely useless for detecting wetlands. for detection, identification and inventory of such wetlands, 1700-m altitude aircraft photos and 1: 10000 scale topographic maps proved to be the most useful. topographic maps provide the best basis for making a digitised inventory, but they might be not as accurate as they should be. some wetland types (sedge marshes, seasonally flooded meadows) might not appear on these maps or their size might not be delineated properly. on the contrary, diverse patches of the environment, including different wetlands are distinguished on the investigated aircraft photos but exact identification of these patches, especially of non­ woody vegetation can be made only in the field. we have come to the conclusion that however tempting remote sensing platforms might seem, neither of these information sources might be used alone. even for answering such simple question as how big a wetland is, both aircraft photos and topographic maps have to be supplemented with field surveys. relying upon only existing data sources might imply that serious errors would be made and important information would be lost. however, these information sources might be used to some extent in identification of potential stressors posing risk to a given wetland. such stressors might come from agricultural land use (such as toxic contaminants or excessive nutrient input) or from hydrological characteristics of the catchment area. having this preliminary information, our field survey can be much more targeted: it has to be checked whether these potential stressors pose actual risk (risk qualification) and if so, to what extent (risk quantification). 24 we have to emphasise that such digitised inventory might be very helpful in any further conservation or restoration work. perhaps the biggest benefit that it can be easily stored, modified and amplified. wetlands are very vulnerable systems, and once such a database is established, even short-term changes might be followed and documented. references 1. cowardin l:m., carter v., golet f.c. and laroe e.t.: classification of wetlands and deepwater habitates of the united states, fish and wildlife service, us. dept. oflnterior, fws/obs-79/31, 1979 2. davis t.j. (ed.): the ramsar convention manual. ramsar convention bureau, gland, switzerland, 1994 3. mitsch w.j. and gosselink j.g. (eds.): wetlands. van nostrand reinhold, new york, 1986 4. lemownz n., squires l., and baker j.b.: research plan for monitoring wetland ecosystems, epa/600/3911010, us epa corvallis, oregon, 1991 5. baker j.p. (ed.): wetlands research plan fy92-96: an integrated risk-based approach, epa/600/r-92/060, corvallis, 1992 6. hugh-jones m. e.: remote sensing, wetlands and health, in global wetlands, ed.: mrrschw.j., elsevier, 1992 7. domotorfy zs., pomogyip.: gis application in the kis­ balaton water protection system: the kbwps vegetation mapping system (in hungarian). kis balaton conference, keszthely, 1996 8. veress d.cs.: history of the three pecselys (in hungarian). publications of the archives of veszprem county 9. veszprem, 1992 9. nyc r. and brooks p.: national wetlands inventory project: inventorying the nation's wetlands with remote sensing, corp of engineers remote sensing symposium, reston, virginia, 29-31 october, 1979 10. wilen b. 0. and pywell h.r.: the national wetlands inventory, in-place resource inventories: principles and practices a national workshop, orono, maine, august 914, 1981 11. tiner r.w.: wetlands of the united states: current status and recent trends, national wetlands inventory, fish and wildlife service, us. dept. of interior, washington d.c., 1984 12. pomogyi p., szeglet p., and csat6 e.: changes in reed associations in the feneki-pond (kis-balaton water protection system), based on vegetation mapping (in hungarian). kis-balaton conference, keszthely, 1996 page 27 page 28 page 29 page 30 hungarian journal of industrial chemistry veszprem vol. 30. pp. 285-288 (2002) the stability of the low alloy steels in organic systems with succinic and adipic acids d.sutiman (faculty of industrial chemistry, technical university "gh. asachi", d. mangeron, 71a, iasy-6600, romania) received: october 21,2002 the behaviour of three type of steel, with a variable carbon concentration (from 0.20 to 0.40 %) is studied in medium of methanol10% ethylene glycol5% succinic or adipic acids with water concentratio~ varying between 1% t~ 5 %. the weight losses are measured; also the polarisation curves are plotted and the corrosion parameters ar~ esta~hshed. sem visualised the metallic surface. the corrosion compounds are analysed by ir spectroscopy, x-ray diffraction and chemical analysis. keywords: steel corrosion, organic acid medium introduction in organic medium, in which water is present like impurity, the corrosion mechanisms of metals, in general, and iron, in particular, are different than those that occur in aqueous electrolyte solutions. in non­ aqueous medium the formation of oxyhydroxylic layer does not use the hogroups derived from water as it happens in aqueous solutions [1-4}. this is possible only if the number of water moles is higher than the corrosive acid, meaning the ratio water/acid being higher than 411 [5-6). it is known that the h+ ion co­ ordinates 4 water molecules. also, some other impurities contained in organic medium presented a much higher influence over the corrosion process than their presence in aqueous solutions. their influence is shown in changes that appear in the conductivity values and also in the dissociation constant [7-8]. this paper continues the study about the influence of water concentration over steels with different carbon concentration. the steels have the composition situated at the limit between cementite and fe-c solution. the corrosion reagents are organic acids and the medium in methanol with 10% ethylene glycol [9-13]. in this paper, succinic and adipic acids are the corrosion reagents. experimental the steels samples that are used for the corrosion, ol 37, ol 50 and ol 60 have the chemical composition contact information: e-mail: sutiman@ch.tuia.si.ro presented in table 1. the steels samples of 5 cm2 active metallic surface were cut up from a cylindrical bar. they were polished and dyeing protected the surface that should not be corroded. the corrosion system contained methanol, 10% ethylene glycol, 5% succinic or adipic acids, hooc-(ch2)n-cooh, (n = 2 and 4} and the water concentration varied between 1 % and 5 %. karl-fisher method was used to determine the water content. we used merck reagents and the water was hi-distilled having electrical conductivity of 12 j.!s cm-1• also the' ph-variation of the corrosion medium was measured with a hach ph-meter. before introducing the samples in the corrosive system, they were submitted to a degreasing proces~ in boiling benzene for 30 minutes and then degreased m a solution of hydrochloric acid 3 % for 3 minutes. the corrosive system was open, allowing the permanent access of oxygen from the atmosphere. . . for every value of the water concentrat10n, six metallic samples were used and were placed in the same time in the corrosive system, being subsequently taken off from 10 to 10 days, degreased with hydrochloric acid (3 %) for 15 seconds and then were weighed by an analytical balance. from the values of weight losses, the gravimetric figure k (g m"2 h"1 ) and the penetration figure p (mm year·1 ) were calculated. the metallic surfaces were visualised by electron microscopy on a tesla b300 microscope. . for the value of 5 % of water concentration, the polarisation curves were plotted on a digital electrochemical analyser dea 332, made by radiometer. copenhagen. denmark. from the 286 table 1 the composition of the tested steels steel %c %mn %s %si %p ol37 0.20 0.80 0.06 0.40 0.06 ol50 0.30 0.80 0.05 0.40 0.05 ol60 0.40 0.80 0.05 0.40 0.05 table 2 the values of k and p figures in the system methanol10 % ethylene glycol5 % organic dicarboxylic acids ol37 ol50 ol60 kip kip kip succinic adipic succinic adipic succinic adipic acid acid acid acid acid acid 0.296/ 0.093/ 0.286/ 0.088/ 0.273/ 0.078/ 0.27 0.08 0.26 0.08 0.24 0.07 2 0.303/ 0.096/ 0.289/ 0.0901 0.280/ 0.080/ 0.27 0.09 0.26 0.08 0.25 0.07 3 0.311/ 0.0991 0.293/ 0.098/ 0.286/ 0.086/ 0.28 0.09 0.26 0.09 0.26 0.08 4 0.318/ 0.102/ 0.298/ 0.100/ 0.295/ 0.0901 0.29 0.09 0.27 0.09 0.27 0.08 5 0.328/ 0.111/ 0.309/ 0.110/ 0.302/ 0.100/ 0.29 0.10 0.28 0.10 0.27 0.09 shape of the polarisation curves the kinetics parameters ( esh ecor and icor) of the corrosion process were calculated. the corrosion final compounds, for every value of water concentration, were insoluble in the system. they were analysed by x-ray diffraction on a hzg 4c karl zeiss jena diffractomefer using co(kj radiation, by ir spectroscopy on a specord m82. the chemical composition (c~ h. 0 and fe) of the final compounds were also determined. results and discussions the ph-metric study of the system ethylene-glycol 10 % methanol -5 ljt organic acid shows that the influence of water on acid dissociation is significant. the initial value of ph in anhydrous medium is 2.95 for the succinic acid system and 3.12 for the adipic system respectively. if we add water until the system contains 5 % water concentration, the phvalue decreases to 2.83 and 2.94. in table 2. the experimental data for weight losses expressed by k and p figures are presented. from these values. resulted that the corrosion rate increases with the increase of water concentration without reaching an optimal value of it in accomplishing the passive layer. even at molar ratio water/acid of 6.53/l for succinic acid and 8.10/l for adipic acid. the passive layer is not obtained. in corrosive medium of inorganic acids the ratio water/acid necessary for obtaining the passive layer is 411 [5.6]. in organic medium. because of the polar character of the solvent molecules of ethylene glycol and methanol is possible that water is stronger table 3 the values of the kinetic parameters of the corrosion in the system methanol10% ethylene glycol5 %organic · dicarboxylic acids v scorm v icon !lai cm 2 f s5t• m t~~~l~ succinic adipic succinic adipic succinic adipic acid acid acid acid acid acid ol 37 -558 -500 -570 -525 12.38 7.63 ol 50 -520 -491 -550 -520 10.86 7.47 ol 60 -506 -481 -540 -510 9.53 7.35 a b fig.l the metallic surface of ol 60 (a. a*: succinic acid; b, b*: adipic acid; a. b: 60 x; a*, b*: 1200 x) bonded through hydrogen bridges and so it does not participate in passive oxy-hydroxylic layer formation. from experimental data resulted also that the steel with the best behaviour in corrosive medium is ol 60, steel that presents the higher carbon concentration and that the succinic acid is more corrosive than the adipic acid, but the differences are not significant. the metallic surface shown in fig.l presents different aspects for the two systems. it is observed that the succinic acid determines a pitting corrosion being different from the generalized corrosion determined by the adipic acid. in the second type of corrosion, the metal is covered with a layer of corrosion compound but this is not uniform permitting the access of the corrosive agent to the metallic surface. the polarization curves were plotted for 5 % water concentration (fig.2) and the values of the kinetic table 4 the chemical composition of the corrosion products in the system methanol10 % ethylene glycol5 % organic dicarboxylic acids ol37 ol50 ol60 % succinic adipic succinic adipic succinic adipic acid acid acid acid acid acid c 28.37 37.73 29.05 37.83 29.17 38.25 h 3.56 4.79 3.16 4.98 3.48 5.14 0 38.45 33.27 38.18 33.03 39.06 34.05 fe 29.32 24.21 29.61 23.36 28.29 22.56 ~~ 16® l$62 b fig.3 their spectra of the corrosion compounds derived from a: succinic acid and b: adipic acid parameters determined from these curves are presented in table 3. it is also observed that in this case, the succinic acid is more corrosive than the adipic acid and the steel with the best behaviour in the corrosive medium is also ol 60. in order to establish a corrosion mechanism, the corrosion compounds were analysed. these were insoluble in the studied systems and presented a red colour. the x-ray diffraction spectra do not show the existence of crystalline compounds in any of the obtained products at any water concentration. the i.r. spectra are identical for all systems at any water concentration, meaning that they present absorption maximum points at the same wave numbers. the i.r. spectra of the corrosion compounds at 5 % water concentration for the two analysed systems are presented in fig.3. these show primarily the displacement of the absorption frequency of the group cooof the two acids from 1700 to 1685 cm·1 for succinic acid and from 1695 to 1680 cm-1 for adipic acid due to a stronger bonding of oxygen. the bond fe-0 is clearly showed by the two peaks that appear in the i.r. spectra. these are situated at 380 and 360 cm-1 in the i.r. spectra of the compound with succinic acid and at 371 and 352 cm'1 in the spectra of the product with adipic acid. the absorption frequency of this bond is displaced to smaller wave numbers in case of adipic acid because of the greater organic chain determining also stronger covalent and coordinative bonding between fe and oxygen. also. the displacement of the absorption band characteristic for the alcoholic group oh from the value 1080 cm·1 to 1066 cm·1 and ,,, ,, ' \i\ ' i i \\\ill \\111 iiiii/ lui hit vljii ... -1000 -800 -600 -400 -200 e [mv] a 10-4 10-6 -700 -600 -500 -400 s {mvj b 287 fig.2 the polarisation curves (a: succinic acid; b: adipic acid; • ol 37; x ol 50; • ol 60) 1060 cm-1 respectively, shows that the two solvents participate to the coordination bond in the obtained compound. the oh group from water presents two vibration frequencies at 3440 and 2942 cm"1 and 3420 and 2960 cm"1 respectively, fact that is explained by the existence of water bonded in two different ways: a group oh is coordinative bonded and the other in bridge linkage. in both i.r. spectra is a well-defined peak at 17 44 cni1, characteristic to the ester type bond. the other peaks from the i.r spectra are characteristic to the c­ hand c-c bonds.[14,15 ]. the chemical element analysis of the corrosion compounds is presented in table 4. the analysis corresponds to a compound in which the ratio fe/succinic or adipic rest is l/1 with a small surplus of oxygen and hydrogen. this ratio can be explained only in polymer compounds. from the presented data, the following corrosion mechanism is assigned: fe -+ fe2+ + 2 e· 288 h ~l/o~ ~o~l/6~l/ fe "=: c --r--c fe fe /t~o/ ~o/t~o/t' i h a fig a the proposed structures for the polymer compounds; a: linear; b: cyclic nfe(oh)3 + nhooc-r-cooh---+ ---+ [fe(ooc-~-coo)ohjn + 2n h20 the structure of the resulted compound with r derived from succinic or adipic acid with fe(iii) is presented in fig.4. the structure is in both linear and polymer forms. the compounds of fe(iii) with succinic or adipic acid are not presented in the literature. the hexacoordination of fe is accomplished through both water molecules and the solvent ones. also, the polymer chain is extended through ether type bonds. conclusions all steel types are corroded in the studied medium the best behaviour is presented by the steel with the highest carbon concentration (0.4 %). that is due to the existence in the steel structure of the solid fe-c solution that determines a superior stability of the material [16]. water is not used in the passive layer formation even if it is present in molar rates higher than 4/l (when the system contain 5 % water the molar rate water/acid bas the value 6.53/1 for succinic acid and 8.10/l for adipic acid). the fact that water does not participate in anticorrosive protection can be justified by the existence of two groups coo· in the structure of the acid that requires a higher quantity of water in order to accomplish the oxyhydroxilic passive layer formation, using the dissolved 02. the water molecule is possible to be stronger bonded through hydrogen bridges of the organic solvents so it does not participate in passive oxy-hydroxylic layer formation. the corrosion mechanism is a complexing one with formation of insoluble compounds non-adherent on the surface of the corroded metal. these compounds presented an amorphous polymer structure. remarkable is the fact that the succinic acid determines a pitting corrosion process. references 1. loren1z w. j. and geona d.: electrochim. acta, 1975, 20, 273-278 2. loren1z w. j. and helman h.: corrosion, 1979, 27, 101-108 3. larbeer p. and loren1z w. j.: corrosion science, 1980, 20,405-410 4. larbeer p. and loren1z w. j .: electrochim. acta, 1980,25, 375-401 5. banas j. and stypula b: metalurgy and foundry engineering, 1995, 6(2), 112-119 6. stypula b.: coor. resit. alloy, 1965, 1, 252-257 7. kamato 0., saito h. and shibata t.: corrosion science, 1984,24, 807-814 8. loren1z w. j. and heusler k.: anodic dissolution of iron group metals in corrosion mechanism, ed. f.mansfeld, dekker, new york, 1987 9. sutiman d., cioroianu t. and georgescu g. 0: hung. j. ind. chern., 1999,27, 107-110 10. sutiman d. and cailean a.: hung. j. ind. chern., 2001,29, 17-20 11. sutiman d. and cailean a.: hung. j. ind. chern., 2002, 30, 37-39 12. sutiman d. and vizitiu m.: hung. j. ind. chern., 2002, 30, 33-36 13. sutiman d., cretescu i. and nemtoi g.: rev. chim., 1999, 50(10), 766-770 14. avram m.: infrared spectroscopy, ed. tehnica, bucuresti, 1960 (in romanian) 15. the sadler of handbook of infrared spectra, sadler hayden, london, 1978 16. cartis g.: thermal treatments, ed. facia, timisoa.ra, 1882 (in romanian) page 287 page 288 page 289 page 290 microsoft word 00.00 inner cover.docx the hungarian journal of industry and chemistry (hjic) formerly (until 2012) the hungarian journal of industrial chemistry the hjic is an international periodical that focuses on results of fundamental and applied research in the field of • biotechnology • chemical engineering science • chemical processes • energetics • environmental chemistry • environmental engineering & technology • industrial management • material science • mechanical engineering • mechatronics • process & system engineering • recycling in the form of original papers, technical reports, reviews, communications, and conference proceedings written in english. hjic is abstracted by chemical abstracts, indexed by hungarian scientific bibliographic database (mtmt), and archived by real-j repository of the hungarian academy of sciences. editorial board editor-in-chief: róbert k. szilágyi department of chemistry and biochemistry, montana state university, bozeman, mt, u.s.a. mta-elte “lendület” chemical structure/function laboratory, budapest, hungary associate editors: jános abonyi department of process engineering, university of pannonia, veszprém, hungary dezső boda department of physical chemistry, university of pannonia, veszprém, hungary norbert miskolczi mol department of hydrocarbon and coal processing, university of pannonia, veszprém, hungary dóra rippel pethő department of chemical engineering science, university of pannonia, veszprém, hungary editors: katalin bélafi-bakó research institute of bioengineering, membrane technology and energetics, university of pannonia, veszprém, hungary peter czermak institute of bioprocess engineering and pharmaceutical technology, mittelhessen university of applied sciences, giessen, germany dénes fodor institute of mechanical engineering, university of pannonia, veszprém, hungary maria gavrilescu department of environmental engineering and management, gheorghe asachi technical university of iasi, romania dirk gillespie department of molecular biophysics and physiology, rush university medical center, chicago, u.s.a lászló gubicza research institute of bioengineering, membrane technology and energetics, university of pannonia, veszprém, hungary jenő hancsók mol department of hydrocarbon and coal processing, university of pannonia, veszprém, hungary jiří klemeš centre for process integration and intensification, university of pannonia, veszprém, hungary zoltán kovács department of management, university of pannonia, veszprém, hungary jános kristóf department of analytical chemistry, university of pannonia, veszprém, hungary istván szalai institute of physics and mechatronics, university of pannonia, veszprém, hungary jános szépvölgyi research centre for natural sciences, university of pannonia, veszprém, hungary gyula vatai department of food engineering, corvinus university of budapest, hungary gábor veress federation of technical and scientific societies – mtesz budapest, hungary ibolya zsoldos department of material science and technology, széchenyi istván university, győr, hungary editorial office: university of pannonia, p.o. box 158, veszprém, 8201 (hungary) tel.: +36 (88) 624-746, e-mail: hjic@almos.uni-pannon.hu; web: hjic.mk.uni-pannon.hu felelős szerkesztő: dr. szilágyi róbert károly, ph.d. nyelvi lektor: mr. matthew chen kiadja: pannon egyetem, 8200 veszprém, egyetem u. 10. elektronikus terjesztés: de gruyter open (formerly versita), warsaw, poland levélcím: h-8201 veszprém, postafiók 158, tel.: (88) 624-000 felelős kiadó: a pannon egyetem, mérnöki kar dékánja (prof. dr. szalai istván, ph.d.) de gruyter open hung. j. ind. chem., 2016 44(1), 1–70 table of contents review mass action and conservation of current robert s. eisenberg ..................................................................................................... 1–28 doi: 10.1515/hjic-2016-0001 articles separation of process wastewater with extractive heterogeneous-azeotropic distillation andrás józsef tóth, ágnes szanyi, enikő haaz, and péter mizsey .......................... 29–32 doi: 10.1515/hjic-2016-0003 vapour pressure of ethanol and 1-propanol binary mixtures misirkhan talibov and javid safarov ......................................................................... 33–38 doi: 10.1515/hjic-2016-0004 group contribution method-based multi-objective evolutionary molecular design gyula dörgő and jános abonyi .................................................................................. 39–49 doi: 10.1515/hjic-2016-0005 selective hydrogen sulphide removal from acid gas by alkali chemisorption in a jet reactor janka bobek, dóra rippel-pethő, éva molnár, and róbert bocsi ........................... 51–54 doi: 10.1515/hjic-2016-0006 hydrogen sulphide corrosion of carbon and stainless steel alloys immersed in mixtures of renewable fuel sources and tested under co-processing conditions andrás gergely, roland locskai, péter szabó, antal krójer, and tamás kristóf ......................................................................................................................... 55–70 doi: 10.1515/hjic-2016-0007 hungarian journal of industry and chemistry vol. 44(1) pp. 1–28 (2016) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2016-0001 mass action and conservation of current robert s. eisenberg* department of molecular biophysics and physiology, rush university medical center, chicago il 60612, usa the law of mass action does not force a series of chemical reactions to have the same current flow everywhere. interruption of far-away current does not stop current everywhere in a series of chemical reactions (analyzed according to the law of mass action), and so does not obey maxwell’s equations. an additional constraint and equation is needed to enforce global continuity of current. the additional constraint is introduced in this paper in the special case that the chemical reaction describes spatial movement through narrow channels. in that case, a fully consistent treatment is possible using different models of charge movement. the general case must be dealt with by variational methods that enforce consistency of all the physical laws involved. violations of current continuity arise away from equilibrium, when current flows, and the law of mass action is applied to a nonequilibrium situation, different from the systems considered when the law was originally derived. device design in the chemical world is difficult because simple laws are not obeyed in that way. rate constants of the law of mass action are found experimentally to change from one set of conditions to another. the law of mass action is not robust in most cases and cannot serve the same role that circuit models do in our electrical technology. robust models and device designs in the chemical world will not be possible until continuity of current is embedded in a generalization of the law of mass action using a consistent variational model of energy and dissipation. keywords: law of mass action, current continuity, chemical device design, variational methods, ion channels 1. introduction* the law of mass action is used widely, nearly universally, in chemistry to describe chemical reactions. the law of mass action does not automatically conserve current, as is clear from the mathematics of a simple case, chosen to illustrate the issues involved (fig.1). if current is not conserved in a theory, charges accumulate that cannot accumulate in the real world. in the real world, tiny charge accumulation much less than one percent produces forces that change predictions of the theory a great deal. indeed, in the real world tiny charge accumulation produces forces that destroy biological membranes and thus living systems, forces large enough to ionize atoms, creating the ionized plasma of electrons, we call a spark, or lightning, that can destroy laboratory apparatus, if not the laboratory itself. turning to mathematics for proof. readers should distrust a claim of conflict between long established laws and so i turn to mathematics for proof to show the conflict unambiguously, hopefully without argument. consider the chemical reaction x! y! z: the currents in the two reactions x! y and y! z are not the same, ixy ≠ iyz. rather, the difference in current is shown to be ixy iyz = zxkxyf[x] zykyxf[y] zykyzf[y] + zzkzyf[z]. the difference is not *correspondence: beisenbe@rush.edu zero in general circumstances, nor robust. the difference can be zero only under special circumstances (details are in eqs.(6–11) below). the appendix shows that the current imbalance ixy iyz between the reactions quickly produces enormous forces. enormous forces are not observed and we conclude that the law of mass action cannot be generally true, although it can be useful (and true) under special circumstances, as also shown in the appendix, and of course in the special circumstance of equilibrium, when current does not flow. law of mass action is an incomplete truth. the ‘law’ of mass action seems to be an example of an “ … incomplete truth [that] may become ingrained and taken as the whole truth … [thereby confusing] … what is only sometimes true with what is always true…” (slight rewording of richard feynman, p. 15–61 of ref. [1]). the ‘laws’ of science are usually learned early in our careers before we have refereed grants and papers, before our critical skills are honed. these scientific laws figure 1. current flow is not the same in a series of classical reactions. eisenberg hungarian journal of industry and chemistry 2 are honored because of their historical role, as much as their logical importance. the laws are often residues of revolutions that once gave us new knowledge. old ideas can have a life of their own, a momentum that is hard to change when knowledge expands. it is easy to continue to use old ideas uncritically even after they have been overtaken by new knowledge. law of conservation of current is different: it is universal. conservation of current is as universal as any law in science. it is a law that has not aged as the law of mass action has. maxwell’s equations and conservation of current have a present role and validity at least as important as their historical one. they are said to be exact at any single time and over any distance scale that can be observed, from sub-atomic, and much smaller, to interstellar, from times much shorter than those of atomic motion to the years it takes light to travel from stars and nearby galaxies. their daily use in high energy accelerators involving inconceivably small distances and brief times, their use in the microwave and faster devices of modern technology, and their use in interstellar astronomy are convincing practical proofs of the nearly universal validity of these equations of electrodynamics. the role of maxwell’s equations depends on the subtle idea of displacement current in a vacuum, current not carried by the movement of mass, and this idea is easy to lose sight of in chemical applications where other forms of displacement current involving the properties of matter (usually called ‘polarization’ in the chemistry literature, along with quite different phenomena, e.g. charge distribution in a carbonyl bond or peptide linkage) receive more attention. the displacement current needs to be incorporated into chemical models, in my view, if it is to satisfy both conservation of mass and conservation of current. both material displacement current accompanying polarization phenomena, and vacuum displacement current need to be incorporated. on the time-scale of atomic motions, 10-16 s, both displacement currents are substantial, and must be incorporated if conservation of current is to be enforced. an important question is how the law of mass action has produced such useful chemistry, over so many years, if it does not conserve current flow? the answer is that chemistry has not been interested in nonequilibrium systems of molecules with current flow, as much as it has been interested in the molecules themselves. chemists make molecules, not currents, with the notable exception of electrochemists, and there the difficulties in dealing with long-range electric fields have long been recognized [2–4]. in classical biochemistry, the law of mass action has been used in another context, more biological, with less attention to the virtues of consistency and invariant physical parameters [5]. a senior biochemist recently said, “the art of biochemistry is to study enzymes under conditions that give insights into biological function, even if the rate constants do not fit results over a range of conditions. the art is to choose experimental conditions in which biochemical reactions are well behaved and rate constants resemble those in real biological systems, so results are useful in understanding how living systems work.” the law of mass action was developed to deal with isolated systems, originally with perfect gases [6–10], and allowed chemists to deal with molecular and atomic reactions before physicists became convinced that atoms existed. but isolated chemical reactions must contact the outside world to pass signals and interact with it, just as electronic systems contact the outside world and pass signals through inputs and outputs. biological systems contact surrounding solutions and cells through ion channels and transporters. the law of mass action was not designed to contact the outside world. it was designed to help chemists build and understand individual molecules. signals and connections with the outside world almost always involve electricity because charge flows through the contacts that connect chemical reactions with the outside world. the contacts are usually the boundary conditions of mathematical models. engineering deals with systems that are not isolated. its devices contact the world through power supplies and inputs and outputs. devices have outputs that follow inputs according to simple rules, for example, the output of an amplifier follows the input according to the gain. the input-output rules are derived from kirchhoff’s current law, i.e. continuity of current in one dimension, and kirchhoff’s voltage law. biology deals with systems that are not isolated. living systems usually have inputs and outputs and are driven by concentration gradients that are power supplies. biological systems interact with surrounding solutions, cells, and tissues. the law of mass action must be extended to deal with inputs and outputs and flow of electrical current if theories and simulations of nanodevices (technological or biological) are to be useful under more than one set of conditions. ionic solutions satisfy three conservation laws, conservation of mass, conservation of charge, and conservation of current. chemistry uses mass conservation almost everywhere, in the form of the law of mass action [11–13] (see eqs.(6–11) below). physics uses conservation of charge and current whenever it deals with electricity [1, 14–21]. the flow of charge is continuous in maxwell’s equations, without loss in series circuits, ∇⋅ i = 0 (1) the current i is simple in a vacuum and in a vacuum that also contains particles, e.g. electrons in a vacuum tube. in the latter case, the total current is what i call the maxwell current imxw because this is the invariant introduced by maxwell to allow the light waves of his equations to propagate forever through a vacuum. imxw = iparticles +ε0 ∂e ∂t (2) mass action and conservation of current 44(1) pp. 1–28 (2016) doi: 10.1515/hjic-2016-0001 3 current in matter is more complex than in a vacuum tube because it includes complex movements of charged particles (and charge inside particles) as well. the complex movement of particles must be described by coupled field equations because the movements are driven by many forces, e.g. mechanical, convectional, thermal, diffusional, as well as electrical. the issues involved are illustrated in fig.2 [5] and the following extensive discussion. i then advocate using variational treatments of forces and movements because variational methods automatically enforce consistency with the field equations of all the forces. the material displacement current accompanying polarization ipol is customarily treated differently from the rest of the movement of particles in a tradition started by faraday and reinforced by maxwell who did not recognize the existence of permanent, i.e. fixed charge [26]. the polarization of matter is the distortion of the distribution of charge produced by the electric field (roughly analogous with the distortion of the oceans produced by the gravitational field of the moon, that produces tides on our beaches twice a day). material displacement current ipol can be separated from the complex movements of particles in matter by two properties: (1) material displacement current is transient. if an electric field is applied to matter, ipol flows as the spatial distribution of charge changes, i.e. as it polarizes, but eventually, flow ceases and ipol → 0, as t → ∞ even if the local electric field remains constant. (2) if an electric field is applied, and then turned off, the charge qpol = ipol0 ∞ ∫ dt that flows when the field is turned on is equal to the charge that flows when the field is turned off, when measured for long enough time periods. the total displacement current idis is often isolated and identified by these features in experiments involving transients. in experiments involving sinusoidal applied fields, idis is usually recognized by its ninety degree phase shift. i dis = εrε0 ∂e ∂t disi totaldisplacement current ! = ε0 ∂e ∂t vacuum displacement current! + ipol material displacement current! ; ipol material displacement current! = εr −1( ) susceptibility !"# $# ε0 ∂e ∂t (3) the vacuum displacement current is a large fraction (say half) of the displacement current on the time-scale of atomic motions, less than 10-15 s. all current produces a magnetic field, according to maxwell’s extension of ampere’s law ∇×b = µ0i = µ0 imxw + ipol( ) = µ0 iparticles + idis( ) = µ0 iparticles + ε0 ∂e ∂t vacuum displacement current! + εr −1( ) susceptibility !"# $# ε0 ∂e ∂t ⎛ ⎝ ⎜ ⎜ ⎜ ⎜ ⎜ ⎞ ⎠ ⎟ ⎟ ⎟ ⎟ ⎟ (4) the divergence operator ∇⋅ f evaluates the conservation of flow in the vector field f it acts on (as its derivation from integral relations shows nicely [27]) ∇⋅ ∇×b( ) =∇⋅ µ0iparticles +µ0ε0 ∂e ∂t + εr −1( )µ0ε0 ∂e ∂t ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ | = µ0 ∇⋅ imxw +∇⋅ ipol( ) = 0 so ∇⋅ i = 0 (5) where we use the vector identity that the divergence of a curl is always zero. b is the magnetic vector field; µ0 is the magnetic constant, the magnetic ‘permeability’ of a vacuum; and ε0 is the corresponding ‘electrostatic constant’, the permittivity of free space. note that µ0 ε0 = c-2, where c is the velocity of light. magnetism only arises from current flow. it is mysterious that magnetic charges (monopoles) do not exist, i.e. ∇⋅b = 0 . maxwell’s equations eqs.(1) and (5) guarantee that current is exactly the same everywhere in a series of two terminal devices. if parameters or geometry are changed, electrical forces and potentials change automatically to ensure the same current flows everywhere (in a series system involving maxwell’s equations). interruption of current anywhere in a series circuit interrupts current flow everywhere, even signals carried by currents far away from the interruption. the law of mass action needs to be extended to deal with displacement current so it can enforce global continuity of current flow. if a particular chemical reaction is at equilibrium, and no current flows, conservation of charge can be enforced easily on the law of mass action. but current flow presents a different situation because the law of mass action must then be modified to deal with the global properties of the electric field. if we are dealing with technological or biological nanodevices, chemical reactions are connected to the outside world and the law of mass action must be extended to enforce continuity of current flow everywhere under all conditions. biological systems involve both chemical reactions and charge. biological systems are always embedded in ionic solutions, and nearly always involve chemical reactants and enzymes with electrical charge, even if (like water), their net charge is zero. substrates of reactions catalyzed by enzymes are usually charged and are nearly always dissolved in complex solutions containing the ions na+, k+, and cl− and often ca2+. trace concentrations of calcium are often used by biological systems as controls that turn biological function on or off. reactants are almost always charged eisenberg hungarian journal of industry and chemistry 4 in biological systems. reactants almost always flow and carry current in biological systems. equilibrium and death are nearly synonymous in life. biological systems must satisfy conservation of current along with conservation of matter. we face a problem when we try to apply both conservation laws together: the law of mass action does not conserve current. ‘the law of mass action does not conserve current’ seems an unlikely statement and so mathematical proof is needed more than verbal argument. a simple sequence of chemical reactions was examined and the questions “does the law of mass action conserve current? is current the same everywhere in the series of reactions? do the potentials change automatically so current is always the same everywhere in a series circuit?” were asked. the same questions can then be asked of whatever series of reactions are of interest. sometimes the answer will be that current does not flow or does not matter and the law of mass action can be easily modified to conserve current. in some symmetrical reactions, the answer will be that current and mass are both conserved, as shown in the appendix. more often, the answer will be that current and mass are not both conserved, as shown in more detail in the appendix. in that case, the law of mass action must be extended to maintain continuity of current. eq.(6) shows the reactions we use to illustrate the problem: x kxy kyx ! ⇀!!!↽ !!!! y kyz kzy ! ⇀!!!↽ !!!! z (6) the reactions of eq.(6) were chosen to show the problem in the simplest case. we define ‘law of mass action’ for this paper as just eqs.(6) and (9) with the symbols defined below. the rate constants in eqs.(6) and (9) are taken as constants and thus of course are uncorrelated and independent of each other. if the law was robust, the rate constants found experimentally under one set of conditions would be found under another set of conditions. such is sometimes the case, but not very often [5, 28]. generalizations of rate constants are sometimes made but, as discussed below in the section ‘how to extend the law of mass action?’, generalizations in the literature [11, 13] deal with ‘chemical correlations’4 and the non-ideality of some types as opposed to current flow, to the best of my knowledge. they do not allow the law of mass action defined here by eqs.(6) and (9) to globally satisfy the conservation of current eq.(1). the generalizations are well designed to deal with systems close to equilibrium with some types of nonideality, but the generalizations do not discuss current flow, and include little3 or no4 discussion about the nonidealities produced by the ionic atmosphere (in the equilibrium case [29]), and changes of shape of the ionic atmosphere (in the non-equilibrium case [30–37]). current flow is important in most applications of the law of mass action. it is almost always present if the reaction is part of a device that communicates with the outside world. the global nature of the electric field (illustrated in fig.1) allows remote devices and boundary conditions to change local atomic flows, an effect not necessarily present at equilibrium. in a nonequilibrium system, electrical forces and potentials change everywhere automatically as a result of the equations of the electric field to ensure the same current flows in all places (in a series system). indeed, interruption of current in a series of reactions stops current anywhere, even far away. of course, there are special cases in which mass action can by itself conserve current flow exactly and those in fact may be the cases where it has proven most quantitatively useful, particularly when extended to deal with non-ideality [11, 13]. in addition, reactions may conserve current approximately. in other cases, like in eq.(6), the reaction will not conserve current, even approximately. each case needs to be studied separately. the appendix provides more detail. the central fact that applies to any chemical reaction, not just to eqs.(6) and (9) is that the global realities of the electric field need to be embedded in the atomic-scale treatment of the reaction, particularly when current flows. proof the current flow in the reactions of eq.(6) is easily shown to be: ixy = fzx ⋅ kxy x!"# $ %&− fzy ⋅ kyx y ! "# $ %& iyz = fzy ⋅ kyz y!"# $ %&− fzz ⋅ kzy z ! "# $ %& (7) units for net current [38] ixy are (c/dm3)/s = c dm-3 s-1 and (moles/dm3)/s = moles dm-3 s-1 for unidirectional flux jxy. double brackets like [[x]] indicate activities, i.e. the generalization of concentration (number density) needed in biological solutions, as discussed below. units for rate constants are (moles/(dm3 s))/(moles/dm3) = 1/s. the valences, i.e. charges on one molecule of each reactant are zx or zy. f is faraday’s constant. in general, the conservation of current law illustrated in eq.(5) is violated ixy ≠ iyz, (8) for a range of concentrations, rate constants, or charges. the main result of eqs.(7) and (8) and the appendix is simple: the law of mass action itself conserves current only under special symmetric circumstances. the law of mass action does not automatically change the electrical potentials to ensure that the current flow in a series circuit is the same everywhere. mass action and conservation of current 44(1) pp. 1–28 (2016) doi: 10.1515/hjic-2016-0001 5 details of proof. rate equations equivalent to chemical reactions involve net flux like j xy . the chemical reactions in eq.(6) define the net fluxes in units of moles/(dm3 s), j xy = kxy x ! "# $ %&− kyx y ! "# $ %& jyz = kyz y ! "# $ %& − kzy z ! "# $ %& (9) with the definitions of rate constant kxy, for example kxy = j xy x!"# $ %& = j xy − d dt x!"# $ %& j yx= 0 (10) remark. unidirectional fluxes like jxy are conventionally measured by tracers originally radioactive isotopes, now usually fluorescent probes flowing into an acceptor solution in which the concentration of tracer is zero. the concentration in the acceptor solution of the substance is not zero in most cases, although the concentration of the tracer is (nearly) zero. note that the activity [[x]] depends on the concentration of all of the other ions in a significant way in non-ideal solutions [5, 34, 39–65]. in non-ideal solutions, changes in the concentration of one substance [y] change the activity of another substance [[x]] and also change its flow. the proof of eq.(7) is completed by writing net fluxes like j xy = jxy jyz as the difference of unidirectional fluxes. net flux is converted into net current like ixy using the proportionality constant fz (where z is the species in question) between flux and current: ixy = fzx ⋅ kxy x!"# $ %&− fzy ⋅ kyx y ! "# $ %& iyz = fzy ⋅ kyz y!"# $ %&− fzz ⋅ kzy z ! "# $ %& (11) obviously, ixy ≠ iyz. this ends the proof. it seems unlikely that conservation of current and conservation of mass are in conflict in the law of mass action, so mathematics is needed to show that current is not conserved. i treat a simple but widely used case, hoping that this will be more convincing than words and easier to extend to other reaction schemes. the methods used can be applied to any series of reactions to see if they satisfy both conservation of current and conservation of mass. in general, an additional constraint and equation is needed to enforce the global continuity of current flow. the additional constraint is introduced in the special case where the chemical reaction describes spatial movement through narrow channels. in that case, a fully consistent treatment is possible using a variety of models for charge movement. the general case where chemical reactions describe covalent bond changes is not worked out in detail here. in my view, the general case must be dealt with by variational methods that enforce consistency of all the physical laws. energetic variational methods appropriate for this purpose (in dissipative systems like ionic solutions) are described. the appendix shows that charge imbalance predicted by the law of mass action would likely have noticeable effects. a small charge imbalance quickly produces potentials and forces that destroy membranes (~0.3 v), molecules in a liquid (~2 v, h2o, with ag|agcl electrode), molecules in a gas (~480 v for h2o gas), and atoms in a gas (~14 ev for n2). these effects would destroy experiments and are not found in the laboratory, which would also soon be destroyed. we figure 2. a demonstration that current in one physical system being quite different from current in another. charge flow is not simply the physical movement of particles of definite charge (and mass). current in a vacuum capacitor, in an ionic solution, and in a wire are all quite different. current is not just the movement of ions, electrons or protons. note that the electric charge in different devices varies on very different scales from subatomic (in dielectrics) to atomic (in diodes, ionic conductors, etc.) to macroscopic. thus, treatments of charge and current must be multi-scale (redrawn from ref. [5]). eisenberg hungarian journal of industry and chemistry 6 conclude that theories that predict charge imbalance because they do not conserve current flow are not acceptable approximations in the world of experiments or life. 2. current flow in complex systems we now discuss current flow in some detail. as we discuss current flow through salt water, vacuum capacitors, dielectric capacitors, vacuum tube diodes, semiconductor diodes, resistors, wires and batteries we will see the bewildering number of ways in which the electric field changes to ensure that current flow is always continuous. current is an abstraction that is conserved. physicists teach that conservation of charge and current are universally true, exact from very small to very large scales and very small times to very large times [68]. what physicists often do not teach clearly is that charge and current are abstract ideas. many students believe that current is always carried by particles and so conservation of mass (of charged particles) implies conservation of charge and current. this is not true. current is carried between the plates of a vacuum capacitor as a displacement current that does not involve the movement of particles [1, 14–16]. current flow in semiconductors is carried by mathematical fictions called quasi-particles that move according to classical physics [17–21], not involving solutions of schrödinger’s equation. this is an important property of semiconductors [69–70], crucial to their use. an essential idea of electricity and magnetism as explained in textbooks [14–16] is that current is continuous (without loss in a series circuit) no matter what the physical nature of the current. electrical potentials and forces change automatically to guarantee continuity of current flow under all conditions, in experiments and in the equations of electromagnetism. i found saslow’s [14] treatment of continuity of current particularly clear and useful. fig.2 tries to show this idea in a concrete way that is easy to build in a lab. ‘completing the circuit’ implies that current in every device is the same. continuity of current the same as kirchhoff’s current law in a one dimensional sequence of reactions states that timevarying currents are the same in any series of devices even if they exhibit very different physics and different constitutive laws, even if they involve chemical reactions (fig.1 and eq.(6)). ionic conductor. the ionic conductor in fig.2 is a cylinder containing nacl. here, current flow (at a frequency say of 1 hz in a 0.02 m solution) is almost entirely the physical movement of charged particles, of ions, say sodium and chloride ions, and follows simple constitutive laws (when concentrations are < 0.02 m and flows are not large enough and do not last long enough to change concentrations). these ions are hard spheres. the finite size of these spheres is significant in the ionic mixtures found everywhere in biology and in general at concentrations greater than say 0.02 m. the finite size makes constitutive equations (valid at all concentrations of mixtures of different types of ions) much more difficult than the classical constitutive equations for quasi-particles that are points. finite size implies saturation effects space cannot be filled more than once and these imply that ‘everything interacts with everything else’. numerical difficulties in dealing with spheres are substantial. spheres must be computed in three dimensions because spheres do not exist in one and two dimensions. that is to say, objects with a single radius have very different surface to volume ratios in one, two and three dimensions and so fill space very differently. phenomena in which spheres fill a significant fraction of three-dimensional space are not easily approximated in one or two dimensions. computation of the forces that prevent overlap of spheres is difficult because those forces are strong and vary significantly in three dimensions. bottom line: non-ideal solutions remain a challenge, as documented below. vacuum capacitor. let’s move on to a vacuum capacitor, in which the space between the two plates is completely empty of matter (as it would be in outer space, for example). the current flow through this capacitor is just as real as the movement of ions of nacl in the cylinder even though no particles or spheres are present, and no mass moves at all. the displacement current between the plates of the vacuum capacitor is a property of the electric field itself, as explained in textbooks of electricity and magnetism [1, 14–16] and is described by the exact and simple constitutive equation for the vacuum idisplacement = c(∂v/∂t), where the displacement current idisplacement (amps) is strictly proportional to the capacitance c (farads) and the time rate of change ∂v/∂t of the voltage across the vacuum capacitor. unlike other constitutive equations, the constitutive equation for vacuum current is exact, valid to some eighteen significant figures [15]. this displacement current induces a magnetic field just as current carried by ions produces a magnetic field. indeed, without displacement current in a vacuum, maxwell’s equations do not allow sunlight to propagate through the vacuum of space. with this exact expression for displacement current, light propagation is a solution of the maxwell equations, and in fact the speed c of propagation of light can be computed from measurements of electrical and magnetic constants, entirely independent of measurements of light itself, by maxwell’s remarkable formula c =1 µ0ε0 . light propagates according to maxwell’s equations over astronomical distances, so we know that the constitutive equation that calculates that speed must be accurate to many significant figures. dielectric capacitor. in the dielectric capacitor in fig.2 (filled with for example the plastic polytetrafluoroethylene = ptfe = teflon), current flow is more complex, and involves the effect of an applied electric field on the spatial distribution of the electric charge intrinsic to the atoms, molecules, and substances of the dielectric. (‘intrinsic’ here means the distribution mass action and conservation of current 44(1) pp. 1–28 (2016) doi: 10.1515/hjic-2016-0001 7 of charge present when there is no applied electric field). note that the electric charge in a dielectric, an ionic solution, a protein or nucleic acid, for that matter, varies significantly on all scales from subatomic to macroscopic. the properties of dielectrics cannot be described in detail here because they vary so much with material, voltage, and time. but some properties need to be emphasized. intrinsic charges do not move from plate to plate in a real capacitor. the current that flows from plate to plate and within the dielectric is a dielectric displacement current not carried by the movement of mass (any substantial distance). the current in a real capacitor is an abstraction. it is the sum of the vacuum displacement current and the material displacement current ipol (in the dielectric) produced by the distortion of intrinsic charges. the material displacement current describes the movement of a charge on a non-linear time-dependent spring (with damping) that eventually stops moving after being perturbed by an external electric field for a finite time. calculating this material displacement current involves solving a non-equilibrium time-dependent version of the schrödinger equation, a difficult task, involving a macroscopic number of atoms and millisecond timescales in cases of biological interest. ideal dielectrics do not approximate ionic solutions. scientists have avoided the difficulties of solving the schrödinger equation in a macroscopic system like a dielectric, or ionic solution, by using approximations. they discuss an ideal dielectric with properties independent of field strength and independent of time. the approximation over a wide range of electric field strengths is satisfactory in most materials. the approximation of a time-independent ideal dielectric is poor over a wide range of times. for example, most solutions of ions in water need effective dielectric coefficients to describe the polarization charge induced by permanent charges. this dielectric charge changes after a step electric field is applied from about 2 to about 80 as time progresses, from zero to 10-15 sec to say 10-5 sec and the change in dielectric charge depends on the substance [71]. there is not a universal constitutive law or approximation for the time dependence of dielectric properties. a factor of 40 change with time is not small. multi-scale analysis must deal with this multi-scale problem because atomic motion has macroscopic consequences on all timescales. the time dependence of real dielectrics needs to be dealt with in biological applications: ideal dielectrics do not approximate the properties of ionic solutions in which biology occurs. the time dependence of polarization charge in proteins has been extensively studied [72–74] and varies over the whole time-scale from atomic to macroscopic. it often has slow components, 10-3 sec or slower. biology is controlled by atomic structures that move significantly in 10-15 sec but have dramatic effects on biological functions between 10-5 sec and 10 sec later. the time dependence of these induced polarization charges appears in simulations (with atomic resolution) as changes in the orientation and induced polarization of water molecules, and in the distribution of ions, as well as in the distribution in proteins of permanent charges, permanent dipoles, and induced dipoles. atomic-scale simulations must last a long time. atomic-scale simulations seeking agreement with experimental data available for a wide range of solutions [71], and proteins [72–74] must last long enough to account for the discrete charge movements that produce an effective dielectric coefficient of 80, as measured experimentally. otherwise, substantial changes in the electric field will not be seen in the simulation, even if those changes in the electric field have great biological significance. electric fields in biology are strong. a nerve signal is a change in an electric field of the greatest biological significance. information transfer in the nervous system, coordination of contraction in muscle, including the coordination of cardiac contraction that allows the heart to pump blood, are all directly controlled by the action potential, the biological name for the nerve signal. electric fields during a biological action potential are slow (say 10-3 sec), and macroscopic in scale, transmitting 10-3 meters, propagating one meter (in humans), and they are remarkably multi-scale. handfuls of atoms in a channel protein control the macroscopic propagation and the nerve signal itself is current carried by ions (that are single atoms) moving through those proteins. the electric field of the action potential is strong, typically some 0.1 v across a 2×10-9 meter-thick membrane or a 3×10-10 meter-long selectivity filter (eeee group in a calcium channel), 5×107 to 3×108 v/m. these electric fields distort the intrinsic distribution of charge within the dielectric on many scales of time and distance, including electrons inside molecules and atoms. they reorient polar molecules that have an intrinsic asymmetric distribution of charge. charges only move a small amount in dielectrics in response to the applied electric field reminiscent of the sloshing of tides in an ocean and on beaches on earth created by the moon’s gravitational field and they eventually return to their resting position when the field is turned off but those small movements of charge produce large effects because the electric field is so strong. dielectric currents ipol share some of the properties of vacuum displacement currents but they do not follow a universal exact constitutive law, not even approximately. it is important not to confuse dielectric ipol and vacuum displacement currents ε0 ∂e/∂t. it is important to realize dielectric displacement currents can be large and produce large effects in biology, as they do in semiconductors. non-linear components of dielectric current are important in biology. non-linear components of dielectric displacement current have large effects important in biology (e.g. in muscle [75], where they were first discovered, and nerves [76]) where they control the opening and closing of the channels that produce the action potential [77] and some enzyme eisenberg hungarian journal of industry and chemistry 8 functions [78], as well. these non-linear dielectric (i.e. displacement) currents can be recorded as ‘gating’ currents because of the shockley-ramo theorem [79], which is a restatement of continuity of current. the dielectric currents involve a tiny fraction of all the charges in and near to an ionic channel, far less than one percent (see appendix “size of effects” near eq.(28)), but continuity of current and the strength of the electric field make gating currents easily measurable in the hands of skilled experimentalists. any electric field is extraordinarily strong compared to diffusion. tiny displacement currents can be recorded routinely in many laboratories because the electric field is so strong. if it were not so strong, these tiny concerted movements of atoms would be lost amongst the brownian thermal motion. extraordinarily small changes in net charge are enough to guarantee that currents are the same in all elements of a series circuit because the capacitances (ratio of charge to potential) involved are often some 10-17 farads, see appendix. continuity of current flow is guaranteed by changes in electrical forces and potential resulting from very small amounts of charge. concentration effects are very small. on the other hand, a one percent deviation in density of mass has a tiny effect on diffusion and chemical reactions, which is hardly noticeable. diffusion forces are tiny perturbations in the electric force field and energies involved in diffusion are tiny perturbations in the total energy of charged systems. electric forces and energies are not small parts of the total energy and it is not wise to say the least to treat them as perturbations of uncharged systems. small changes in charge distribution produce large changes in flow because flow tends to be an exponential function of the spatial profile (even when the profile does not have a large, single, symmetrical peak [80] of potential energy) and the profile of energy is a sensitive function of permanent and dielectric charge, ionic conditions, etc. [81]. it is not wise [82] to neglect the effect of permanent charges of the channel protein on the shape and size of the electric field as is done in many continua [83–105] and rate models of gating and permeation of ion channels, and most treatments of enzyme function and catalysis. current is indeed an abstraction. in each of the devices in fig.2, charge follows different laws, because it has different physical properties, sometimes carried by charged particles, sometimes produced by the rate of change in electric field (displacement current), sometimes as a result of the ‘movement’ of quasiparticles, and sometimes as a consequence of the ‘movement’ of electrons in a macroscopically delocalized quantum state of a wire. current always flows without loss in each device. this abstract property of current is always true, because the potentials change automatically to ensure continuity of current. however, the ‘laws’ describing current as a function(al) of time and potential (for example) depend on the physical nature of the charge and its movement. different devices have different relationships between current, voltage, and time. these different ‘constitutive’ equations are described in engineering literature in great detail. the different constitutive equations combine with kirchhoff’s current law to describe current flow from one place and one device to another. together, the equations describe the universal fact that interrupting current flow in one chemical reaction (of a series of reactions) will interrupt current flow in every other reaction (in that series) even if the interruption is meters away from a chemical reaction being studied on the atomic scale (scale = 1 å). together the equations describe the experimental fact that electric fields, forces, and potentials automatically rearrange so that kirchhoff’s current law and continuity of current flow are always present exactly on all scales no matter what is ‘carrying’ the current. indeed, the physics of current flow changes to accommodate the continuity of current. one is reminded of the power of the electric field when one unplugs a computer. interruption of a circuit meters away from the diodes of the computer’s power supply stops the flow of quasi-particles holes and semi-electrons across atomic-scale junctions of semiconductor diodes, often of the pn variety. the electric potential changes so strongly in response to the interruption (because the power input of the computer power supply stores a great deal of charge) that the electric field exceeds the dielectric strength of air. the automatic change in the electric field needed to maintain continuity of current flow is enough to ‘change the physics’ of the system. electrons are stripped off the atoms of air resulting in a plasma, a spark. we should be frightened of sparks and their electric fields. sparks start fires, sometimes in upholstery or drapes. vacuum tubes. we consider charge movement in a vacuum tube diode as the next device in fig.2. vacuum tubes control the flow of electron current by changes in their internal electric fields and were called ‘valves’ in the uk for that reason. vacuum tubes, semiconductors and even some open ion channels follow simple constitutive laws of rectifiers, as described in textbooks of electronic devices or ion channels. in vacuum tubes, current is indeed carried by a stream of isolated charged particles, electrons with a definite mass and charge, moving through a vacuum, interacting only through their electric fields. at 1 hz, essentially all the current in a vacuum diode is carried this way. current through a diode is not proportional to the voltage across the diode because the electric fields within the diode change shape, despite the simple physics of conduction. the fields change shape as the voltage across the diode is changed because of screening and shielding. the electric fields within the tube are different at small and large potentials. the different internal electric fields change current flow, creating rectification. the electric field creates a large barrier in one direction so current in that direction is small; the electric field creates a small barrier in the other direction, and current in that other direction is large. mass action and conservation of current 44(1) pp. 1–28 (2016) doi: 10.1515/hjic-2016-0001 9 rectification is of historical interest because vacuum tubes allowed the early detection of radio waves in american homes in the 1920’s, as valves did in the uk. the demand for portable radios led to solidstate diodes, then solid-state ‘triodes’, field effect transistors, integrated circuits, and our modern digital world [106]. vacuum tube diodes had certain difficulties they were big (10-2 m at their smallest), hot, greedy consumers of power, cost about $3 in the 1950’s, and electrically unstable: they drifted continuously. they were quickly replaced with semiconductor diodes that cost less than $10-10 each, do not drift significantly, and can be as small as 10-8 meters nowadays. we turn now to the semiconductor diode that operates on a very different scale from the vacuum diode. the rectification of both diodes that is their function depends on essentially the same physics, namely the shape of the electric field and its change in shape with the direction of current flow. the electric field of charge must be respected on both the scale of vacuum diodes and that of semiconductor 10-2 meters of vacuum tubes, 10-9 meters of semiconductor diodes indeed on all scales because the electric field has such large effects on all scales. the immediate implication is that theory and simulation must calculate the electric field on all scales, using an explicitly multi-scale analysis, since it seems unlikely that any one type of simulation or theory can span atomic to biological to laboratory distances and times, let alone the interstellar scales on which the laws of electricity are known to be valid. semiconductor diodes. current in semiconductor diodes is carried by quasi-particles [70], called holes and ‘electrons’ (better named quasi-electrons, or semielectrons in my view). these quasi-electrons and holes are defined because they interact much more simply than the totality of real electrons and lattice of atoms in semiconductors [21, 70, 107–109]. they simplify the quantum mechanical many-body problem into the much simpler motion of imagined quasi-particles. current is carried in semiconductors by rearrangements of charge in the entire lattice of atoms that make up the semiconductor. fortunately in terms of our technology and daily life, current in germanium and silicon can be approximated by classical theories that deal with one quasi-electron or one quasi-hole at a time as they move in mean fields, without requiring a solution to the schrödinger equation at all [17–21]. as a textbook puts it eloquently (p. 68 of ref. [69]): “electron is a quasi-particle consisting of a real electron and an exchange correlation hole … a cloud of effective charge of opposite sign due to exchange and correlation effects arising from interactions with all other electrons of the system. hole is a quasi-particle, like the electron, but of opposite charge; it corresponds to the absence of an electron from a single particle state that lies just below the fermi level”. the motion of these quasi-particles is described by mean field models, evaluated both by simulations [17, 21] and theories [17– 21], e.g. the poisson drift-diffusion equations [110], often called pnp (for poisson nernst planck) in biophysics and nanotechnology [56, 61, 111–117]. pnp is of particular importance because it is used widely, nearly universally, to design and understand the devices of our semiconductor technology, from transistors to computer chips. pnp is used rather widely in nanotechnology these days and increasingly in membrane biophysics, mathematical biology, and electrochemistry, including battery technology, as well as the technology of cement. rectification in biological membranes. early treatments of rectification in biological membranes, then called ionic conductances, ([83]; appendix of [118]) in fact drew heavily on mott’s (nearly) contemporaneous treatments of rectification in diodes [119], but none of these were consistent: they assumed the electric field, instead of computing it. the charge in the system did not produce the assumed electric field if substituted into poisson’s equation. goldman [83], then a graduate student of k.s. cole, recognized the problem, but did not know how to remedy it, nor did these workers [83, 118] understand that electric fields in diodes or open channels were not constant in any sense, including space (numerous personal communications to me from k.s. cole, 1960–1962, and a.l. hodgkin, 1960–1995). mott soon realized [120] that the change in shape of electric fields was a crucial phenomenon in semiconductor diodes, updating the constant field assumption of his original paper [119]. biophysicists were evidently not aware of the evolution of mott’s understanding [121]. semiconductor physicists understood that consistent treatments produced electric fields that varied greatly with conditions, as the fields change to force continuity of current [122]. indeed, transistor design would not be possible [21, 106, 123–124] if computational electronics had assumed constant fields the way some physicists did early on [119], but not for long [120]. in biophysics, the importance of computing the fields from the charges (so the fields and charges were consistent) was not realized (as far as i know) until much later [81, 111–112]. until then, and even after, nernst-planck equations were used in biophysics without including the ionized acid and base groups of the channel protein, i.e. without including the permanent charge of the protein [85–105, 121]. these ionized groups render polymers into ion exchangers [125]. the equivalent doping profiles convert semiconductors into devices. leaving out ionized groups “is like studying a galaxy without stars”, as a prominent physical chemist once told me. the distribution of permanent charge creates a baseline electric field. changes in shape of the electric field with concentration, amino acid composition of the channel protein, etc. are responsible for many of the important properties of these systems. unfortunately, the importance of changes of shape in the electric field, and of the fixed charges involved, were and still are often ignored. charge carriers in semiconductors can be really quite strange from a physical point of view. charge eisenberg hungarian journal of industry and chemistry 10 carriers in silicon and germanium do not exist outside the lattice of the semiconductor as distinct entities. they do not exist in the same sense that na+ and cl− ions exist, but are mathematical representations, with lifetimes sometimes as short as milliseconds. quasiparticles are the second derivative of a fermi surface of silicon and germanium semiconductors, under particular conditions. they are defined, as mentioned above, to allow easy classical analysis compared to the intractable quantum mechanical many-body problem of a macroscopic semiconductor. much of the success of our semiconductor, digital, and video technology is due to the accuracy of the constitutive pnp equations describing holes and semielectrons. they robustly describe the characteristics of semiconductor devices of many different types, with very different input-output relations, as different as an exponentiator and a logarithmic convertor. pnp is so useful because almost all the devices of our digital technology work under a restricted set of conditions in which flows are crucial but are of the special type, well described by quasi-particles moving in a mean field. treatment of distortions of the electric field of all the atoms in macroscopic devices is not needed. almost all of the devices of electronics use power supplies to maintain different voltages at different locations far from the pn junctions of the device itself (and thus require a global treatment of the electric field). these voltages perturb the distribution of velocities of charged particles so the distribution exhibits net flow [80, 126]. the slight perturbation is enough to imply the pnp equations and those provide enough non-linearity to make amplifiers, switches, and the full set of logical circuits necessary to make a computer [21, 107–109]. in fact, in this case the pnp equations can be solved analytically and exactly to give intuitive, pleasingly simple formulae for current flow, once the shape of the electric field is known [80]. pnp equations describe a wide variety of current voltage relations and devices. the pnp equations are the constitutive laws used to describe semiconductor devices as their current voltage relations change drastically (with voltage, for example) from that of a linear amplifier, to a switch, exponentiator, multiplier or even logarithmic converter [21, 107–109]. non-linear input-output relations, as varied as these, enable a rich variety of devices. non-linear input-output relations as diverse as these are not described easily or described at all for that matter in most areas of physics and chemistry. all the non-linear devices in a computer are actually mathematical solutions of the pnp equations in a complex silicon structure built to have the particular spatial distribution of permanent charge (‘doping’) that produces the desired properties of the device, i.e. the input-output relations. the predictive power of pnp is very important in the design of robust semiconductor devices that do not fail even when used many millions of times a second in computers that contain a trillion transistors. in fact, the intrinsic physical properties of semiconductors are adjusted by their designers so pnp remains a good description [127–130], even though the size of the device has been dramatically decreased. the concentrations of fixed charge dopants, geometries, and recently even dielectric coefficients are adjusted by semiconductor engineers in their successive iterations of moore’s law [131–133], so pnp remained a good description as performance increased by factors of a billion or so, over 50 years. evidently, reliable design is more important than raw performance. it seems more important for the designers (and marketplace) that an equation describes behavior robustly and accurately over a range of conditions than that the device be as fast or small as possible [127–130]. evolutionary selection in biology also seems to choose robustness over efficiency in many cases. devices of nanotechnology need to be similarly robust, i believe, before they will be used extensively. pnp is not enough, however, when ionic solutions are involved. a great deal of effort has been spent applying pnp equations to electrochemical systems [56, 61, 111–117] hoping they might serve as adequate robust constitutive equations, but that is not the case. the non-ideality of ionic solutions, arising in large measure from saturation effects produced by the finite size of ions, demands more powerful mathematics than the partial differential equations of pnp used in computational electronics. resistor. the next device we discuss in fig.2 is a resistor, which in some ways is the easiest to describe because current is proportional to voltage with a single proportionality constant over a wide range of voltages, times, and conditions. a resistor follows ohm’s constitutive law with a resistance independent of potential over a wide range from 10-5 v to say 100 v, and for values of resistance from 10-1 ω to 108 or 109 ω. the range of validity of ohm’s law is an enormous help in circuit design. circuit models involving resistors, capacitors, inductors, and operational amplifiers are transferrable. they behave as real devices behave without changes in parameters. largely for that reason, designs are inexpensive and robust. despite the simplicity of resistors, the actual current carrier in a carbon resistor is unclear, at least to me. no one cares very much i suspect because the device works nearly perfectly. the carrier of charge does not matter very much. what matters is the constitutive law that describes the relation between current, voltage, and time. the constitutive law should satisfy conservation of mass, charge, and current. it is instructive to write the constitutive law for a resistor ohm’s law for only particle current, using a conservation of particle (mass) formulation, and then write it again for particle plus displacement current from one terminal to another. if you apply a step function of current (or potential for that matter) to the purely particle formulation, a paradox arises. the potential changes but the particle current flowing into the resistor from the left is exactly equal to the particle current mass action and conservation of current 44(1) pp. 1–28 (2016) doi: 10.1515/hjic-2016-0001 11 flowing out on the right at all times. why does the potential change if there is no accumulation of charge? the paradox can be resolved in two (nearly) equivalent ways: (1) the constitutive equation of ohm’s law can be used with the extended definition of current that includes the displacement current. in this case, there is continuity of generalized current, but there is not continuity of particle current at all times. the transient accumulation of particle current provides the charge that changes the potential. (2) alternatively, the circuit model of the resistor in fig.2 can be changed to have an explicit capacitor in parallel with it. in this case, the charge accumulates on the capacitor, and the resistor itself can have continuity of flux of particles at all times and follow ohm’s law using the current/flux of particles (and not the displacement current). the charge accumulating on the capacitor creates and changes the electric field. maxwell himself repeatedly used capacitors in this spirit to understand the role and significance of displacement current. sections 102, 125, 199 and chapter 8 are some examples in ref. [134]. we (following the insight and advice of wolfgang nonner) have used capacitors as a low resolution, consistent way to connect permanent charges (specifically, ionized side chains in a channel protein away from the pore) and electrical potentials in the pore of a channel protein, e.g. the potassium channel [135]. current flow in wires can also be strange. the current carriers in a wire are delocalized electrons in the simple case of a single solid conductor of metal, and follow the simplest constitutive law of all over long(ish) time-scales, say times longer than 10-5 sec. nevertheless, most of the electronics in our digital technology operate over time-scales much shorter than that. now we confront the importance of the time variable. the physical nature of current flow depends on time-scales, even in wires [14, 16]. the range of timescales in our technology is enormous, from more than one second to less than 10−9 sec. over shorter timescales (< 10-4 s) the wires that must be used are often twisted pairs [136], each made itself of many very fine wires. without twisting, these pairs of wires do not allow successful connections to the internet because rapidly changing signals are not carried reliably by single wires [137]. over those short time-scales, currents flow outside wires, guided by the conductor, to be sure, but outside the conductor nonetheless [16, 137]. the twisting of wires is a necessity if they are to carry signals robustly and reliably so we can use them in our video devices and smartphones, even in old-fashioned hard-wired telephones [136] that only need to amplify audio signals heard by adult humans (< 10,000 hz). the physical nature of current depends on time-scale. the physical nature of current in almost any system depends on the time-scale, and differs at different times as much as it differs in different devices. constitutive equations depend on time. different devices have different constitutive equations with different time dependences. again, current is an abstraction, a different abstraction at different times in one device, as well as different in different devices. charge movement in batteries. batteries are present in fig.2 both as an isolated device and as the ag||agcl interface between wires and nacl solution in the conducting cylinder previously discussed. i hesitate to describe a constitutive equation for the flow of charge in batteries in general because the flow is so very complex, different in different devices, and important for the practical daily use of batteries [138–139], and its interaction with surface charges is also subtle and important [140]. it is enough to say here that current flow through electrochemical systems is carried by different electrochemical systems differ dramatically and change in dramatically with time, frequency, composition and concentration of ionic solutions, as well as electrical potential, and current flow. over short time-scales, e.g. 10-6 sec that are still long compared to the time-scales important in computers current flow from the ag wire and agcl electrode material into the nacl solution is entirely displacement current lagging behind voltage. however, over the longer time-scales characteristic of biological systems (greater than say 0.1 sec), the current is carried by a complex combination of ag+ and cl− ions with negligible displacement current. we conclude that current is indeed an abstraction with different physical meanings in different systems and over different time-scales. no one can visualize and no one knows at least i do not know anyone who knows why or even how this abstraction can be so perfectly conserved under all conditions and over all scales, from angstroms to meters, from femtoseconds to seconds. it is truly amazing to think of the changes in electric forces needed to accommodate and enforce continuity of current in salt water, vacuum capacitors, dielectric capacitors, vacuum tube diodes, semiconductor diodes, resistors, wires and batteries from atomic time-scale 10-16 sec and distances of 10-11 meters to the biological scales of seconds and meters from inside atoms (pp. 8–9 of ref. [1]) to intercontinental distances (in submarine cables) and interstellar space. 3. general remarks about current flow the discussion of fig.2 leads to some general remarks about current flow. the interplay of conservation of matter and conservation of charge and current is different in each system, according to the constitutive law of the system. the idea of a current flow is an abstraction built to accommodate the physics of each system, while maintaining the main feature of electrodynamics, the exact conservation of current, at any one time, on any scale. conservation of mass is eisenberg hungarian journal of industry and chemistry 12 certainly also followed in these systems, but in a more relaxed way. significant deviations are allowed for a time. mass can accumulate for a time without catastrophic results. accumulation of mass does not have dramatic effects. in the systems considered here, the accumulation of mass does not usually have dramatic effects. a one percent accumulation of mass has a small effect on chemical potentials, although of course exceptions can occur. there is no general law for the accumulation of matter. the effect depends on the constitutive law, and its interplay with conservation of matter, charge, and current. accumulation of charge has dramatic effects. the accumulation of charge is different. a one percent accumulation of charge has a huge effect. as feynman memorably mentions at the very beginning of his textbook [1], one percent excess of charge in a person at arm’s length produces a large enough force to lift the earth! the accumulation of charge follows an exact law: the displacement current is the sum of all the other charge flows and it changes the rate of change of the electric field in a precise way so total current is conserved precisely. continuity of current is obeyed and so such enormous forces do not occur. if continuity of current were not obeyed exactly, enormous forces would soon develop (see appendix). such forces are of course incompatible with life or laboratory experiments. fortunately, accumulated charge is easier to deal with in theory than accumulation of mass: the vacuum displacement current does not depend on constitutive laws, it simply depends on the time derivative of potential and so can be calculated. accumulated charge is much simpler than accumulated mass. accumulated charge has universal properties, independent of the physical nature of the charge. particle and quasi-particle currents that accumulate at a junction change the time derivative of electric potential so the electrical potential carries away a displacement current. this displacement current is exactly equal to the sum of the other currents flowing into the junction without known error, to about one part in 1018. continuity of current is exact independent of constitutive laws if current is re-defined to include displacement current. the displacement current (and equivalently ∂v/∂t ‘take up the slack’ so that kirchhoff’s current law (using the extended definition of current) is exact in one dimensional systems like a sequence of chemical reactions. no charge accumulates at all beyond that defined by the integral of the displacement current. the electrical forces and ∂v/∂t change so the displacement current is exactly equal to the sum of the other currents, and continuity of generalized current is exact. accumulation of charge is special because it is universal. the precise linkage between potential change, charge accumulation, and displacement current is a special feature of electromagnetism because it is universal. it is a property of a vacuum, the constitutive equation of a vacuum, if poetic license is allowed. in this sense charge is more fundamental and universal than mass, a fact which certainly came to me as a surprise [141]. then i learned that charge is constant at all velocities according to the ‘lorentz (relativistically) invariant’, whereas mass is not. mass depends on velocity and charge does not. special relativity seems to make charge a more fundamental physical property than mass. the reader may have difficulty visualizing the interactions that enforce conservation of the abstraction ‘charge/current’ in all these devices with all these properties over the entire time-scale. i certainly do. however, current flow and charge are conserved on and between all scales under all conditions, even if we cannot visualize how that manages to be so. experiments demonstrate that fact. current does flow continuously without loss in a circuit. consider a battery feeding a circuit. if a wire is cut far from the battery, current flow stops everywhere. the chemical reaction in the battery is disrupted on an atomic scale, by the (lack of) current flow meters away. those of us living in colder climates have seen the effects of starting a car with another car’s battery. we have learned to be careful because even a twelve volt battery can produce dangerous sparks in air, even though air has nearly infinite resistance ( > 1011 ω for dry air), and is in that way, nearly a vacuum. abstract current is conserved ‘exactly’ even if we cannot visualize how that happens. science often contains mysteries that cannot be visualized consider maxwell’s attempts to visualize his equations as properties of an ether. science often poses questions that cannot be answered. why is there no magnetic charge? why is the charge on an electron 1.6 ×10−19 c? why is charge independent of velocity in special relativity when mass, distance, and even time are not? why are physical laws invariant when locations s move at constant velocity ∂s/∂t mass, distance, or at constant acceleration ∂2s/∂t2 general relativity but not when other time derivatives of location are constant, like a constant third derivative ∂3s/∂t3 or linear combinations of ∂ns/∂tn, perhaps even fractional derivatives? as practical people, scientists cannot afford to just wait while we wonder about such things. scientists wonder a bit and then move on, hoping our successors can do better than we have. biologists and engineers in particular cannot afford to linger on mysteries they do not understand. so many of those mysteries in biology have turned out to be caused by low resolution of our instruments, unable to resolve crucial structures. think of thomas henry huxley looking at the shortening of the striations of muscle [142] that were not understood until one of his grandsons (andrew huxley) studied them many years later working in cambridge, uk [143]. think of lee de forest using vacuum tubes without understanding how they work. biologists and engineers cannot afford to wait to understand everything. they must isolate the mysteries and move on to study other things. here, we move on to discuss devices and the theories and simulations used to understand them. mass action and conservation of current 44(1) pp. 1–28 (2016) doi: 10.1515/hjic-2016-0001 13 biological implications of continuity of current. it is important to note that the continuity of current law has important biological implications in systems more general than a series of chemical reactions. the continuity of current law implies the cable equations (called the telegrapher’s equations in mathematics literature), see derivation from the three dimensional theory in [144–147] and pp. 218–238 of [148]. the cable equation [149] is the foundation of the hodgkinhuxley model [150–154] of the action potential of nerve and muscle fibers. kirchhoff’s current law links the atomic properties of ions, the molecular properties of ion channels, and the centimeter-scale spread of current and potential that create the propagating action potential in nerve fibers meters in length. in short or round(ish) cells, or in organelles like mitochondria, continuity of current forces coupling between multiple pathways of current crossing membranes, even if the currents are carried by different ions, or by electrons, through different structures nanometers apart in the membrane of the finite cells or organelles. the flux-coupling characteristic of active transport systems including the coupled flows in chemiosmotic systems that perform oxidative phosphorylation or photosynthesis might arise in this manner. coupling of flows of charges, whether electrons or ions, is an unavoidable consequence of the global conservation of charge and current, of kirchhoff’s current law globally enforced in three dimensions, and not a consequence of local chemical interactions, just as coupling of membrane currents with axial currents in a nerve fiber is an unavoidable consequence of kirchhoff’s current law, not of local chemical reactions. it is interesting to compare the incorrect chemical theory of nerve propagation by nobel laureate a.v. hill [155] with the correct electrical theory of the then undergraduate [156–157], later nobel laureate [150– 154], alan hodgkin. kirchhoff’s current law in the form of the cable equation [149] was the key to hodgkin’s understanding. the classical voltage clamp experiments were designed to remove difficult terms and isolate membrane terms in the cable equation personal communication, a.l. hodgkin, 1961 that today we know describe ion channels, opening, closing and conducting [121, 158–159]. the cable equation links movement of atoms inside channel proteins to macroscopic current flow that produces nerve propagation of the macroscopic electrical potential, the nerve signal that spreads meters. macroscopic potentials modify atomic movements involved in gating and conduction. atomic movements create macroscopic electrical potentials. equations of the electric field are true on all scales and so allow a unique linkage between models of atomic motion, protein behavior, and macroscopic propagation of electrical signals. i suspect linkage equations of this type valid on all scales will be needed to make any multi-scale analysis robust and transferrable, if it reaches from atoms to meters, from femtoseconds to minutes as models of nanodevices must. models, devices, effective parameters, and transferrable theories. parameters of models or devices can often be chosen so an incomplete theory or simulation describes a system under one set of conditions but not another. experiments often show that rate constants must be adjusted dramatically as conditions change, and the adjustments can rarely be predicted ahead of time by theory. chemistry and biology are filled with examples of non-transferable models. chemical reactions follow rate equations, but the rates are not constant and not independent of one another as conditions change, even though traditional theory assumes they should be [5]. biology describes enzymes with one set of parameters but finds those change when conditions change and attributes that, somewhat mysteriously, to ‘allosteric effects’ and conformation changes. non-transferable theories have limited use. biology and much of chemistry works under a wide range of conditions and so incomplete theories with effective parameters have limited use. even if sensible or valid, theories (and simulations) with effective parameters like these are not accurate enough to design robust devices. by leaving out something important, those theories or simulations omit an energy term that almost certainly varies with conditions. the resulting effective parameters change in large and unpredictable ways. incomplete theories and simulations are not very useful over a range of experiments and conditions. incomplete theories are not likely to be transferable (from one set of conditions to another) in the language of the chemistry literature. devices designed from incomplete theories or simulations are unlikely to be robust or work well under a range of conditions. biological systems analyzed with non-transferable theories (or simulations) are unlikely to be realistic in general because biological systems usually work in a range of ionic concentrations different from those used in the laboratory. simulations must deal with trace ca2+. biological systems usually work in mixtures with a range of ca2+ concentrations, in which the ca2+ concentration has important practical effects, often turning systems on or off or controlling their rate monotonically. simulations and theories in biology have limited use until they are calibrated so we can be sure they actually are correct under the range of conditions and ca2+ concentrations the biological systems use. simulating ca2+ activity in pure solutions is a challenging problem [160]. simulating ca2+ activity in biological mixtures within the 10-8 to 20 m concentration range that are physiological has not been attempted to date. 10-8 m concentrations of ca2+ are found inside most cells, while 20 m concentrations of ca2+ are found in and near ion channels, nucleic acids, and enzyme active sites, where the chemistry of life is catalyzed and controlled. eisenberg hungarian journal of industry and chemistry 14 biological and chemical sciences will benefit enormously if theories and simulations can be made transferable, using one set of parameters to describe systems under a range of conditions, as many physical and most engineering theories and simulations do. i believe the law of mass action must be extended to conserve current before theories and simulations can be made transferable from condition to condition and from physics to chemistry to biology using only mathematics. how to extend the law of mass action so it conserves current? an obvious way to extend the law of mass action is to include activities and electrical potential in the rate constant to ‘right the rates’ by making them (typically exponential) functions of potential [2–4, 11, 13]. this in fact has been done for a very long time in the study of reactions at the electrodes of electrochemical cells and recently in other ways in the treatment of the formation of concrete [161–163]. the butler-volmer and tafel equations [2] include electrical potential in rate constants in an empirical way with limited [3–4] but real success. success is limited i suspect because difficulties of embedding an electrical potential in rate constants are formidable if current flows. we must ‘fix the fields’ so they are global and depend on current flow everywhere. otherwise, they cannot conserve charge flow and support continuity of current as required by maxwell’s equations: the way to ‘right the rates’ is to fix the fields, everywhere. 4. additional perspectives. some additional general remarks may be helpful: (1) a thermodynamic treatment is clearly impossible since the goal is to calculate large fluxes and currents that do not occur in a thermodynamic system at equilibrium by definition without flows. (2) a rate treatment of the frictional treatment of flux over a large potential barrier is needed. the classical brownian motion problem of kramers [164–165] is a necessary step forward, even if it is inconsistent because it does not compute the potential barrier from the charges in the system. kramers’ treatment need not be restricted to large barriers. a simple expression for rates over any shape barrier is available [80] and needed [166] because so few barriers are both symmetrical and large as required in classical high barrier approximations. (3) the rate constants over one barrier must depend on the electrical potential in distant locations. otherwise, interrupting current flow in a distant location cannot interrupt current locally. this requirement implies that the electrical potential must be determined by a global equation like poisson’s equation, including boundary conditions far from the individual chemical reactions and barriers. the barriers of kramers’ model are variable and not constant as conditions change, including conditions far from the barrier itself. the fields and energy landscapes change and it is indeed their change that allows continuity of current, as illustrated in eq.(1), to be satisfied. (4) the rate constants over one barrier are likely to depend on concentrations in other places because the solutions containing the reactants are not ideal. a general characteristic of non-ideal solutions is that ‘everything depends on everything else’. more specifically, the activity of one reactant (the free energy per mole) depends on the concentrations of other species in practice, as well as in principle. (5) a general theory of all non-equilibrium processes is not likely to be useful: a general theory has to describe too much. a general theory must include hydrodynamic behavior of considerable complexity, since aqueous solutions are fluids satisfying the navier-stokes equations of fluid mechanics. a general theory would also include explosions since they occur with regrettable frequency at electrodes of electrochemical cells, when h2 gas is generated (inadvertently) by an overvoltage. fortunately, non-equilibrium processes in biology and much of technology occur in ionic solutions in which atomic motion is heavily damped. that damping ensures that the distribution of velocities is a displaced maxwellian [126], as it is in semiconductor devices [21, 167–168]. the displaced maxwellian exhibits non-zero mean velocity and so allows flux and current through the system from power supplies to outputs. that flux and current is enough to produce the very nonlinear devices of our digital (semiconductor) technology [17–21], and non-linear phenomena like the propagating signal of the nervous system, the action potential [152–154]. boundary conditions are needed to extend the law of mass action to deal with the outside world. equilibrium statistical mechanics and thermodynamics were designed to avoid the complexities of boundary conditions using the ‘thermodynamic limit’ to allow analysis. but when current flows, interactions with the outside world, are unavoidable the thermodynamic limit is not appropriate, and boundary conditions describing those interactions are needed. it is difficult if not impossible to deal in general with boundary conditions for the laws of mass action, and chemical reactions, because of the wide variety of chemical interactions and physical geometries captured in a phase space of very high dimension. boundary conditions are easier to deal with in three dimensional physical space, where the law of mass action is widely, nearly universally, used to describe ion motion through narrow channels [80, 121, 169–170]. current in channels. current flow through a ‘hole in a (insulating) wall’ is a subject of great significance because the hole in the wall allows for control of the current. holes in proteins, membranes, and channels in field effect transistors are all nanovalves providing essential functions to a large fraction of biology and semiconductor technology, and of great mass action and conservation of current 44(1) pp. 1–28 (2016) doi: 10.1515/hjic-2016-0001 15 interest in electrochemistry. indeed, biological channels are nearly picovalves allowing a handful of atoms to control macroscopic flow. it is hard to imagine a smaller valve that could control macroscopic flow. we consider models of current flow through such holes and show how boundary conditions can be applied to nanovalves and systems of this type. we do not consider simulations here because they do not deal with the essential features of these systems. simulations have considerable difficulties in computing the actual currents through systems controlled by a handful of atoms. the currents are macroscopic phenomena, occurring in the world of milliseconds to minutes, and spatial dimensions from say 10-9 to 1 meter. the currents are controlled by atomic-scale structures in biology and near atomic-scale (10-8 meter) structures in semiconductors and electrochemistry. changing a few atoms changes macroscopic currents as is shown in biophysical experiments (usually involving site directed mutagenesis) every day. the macroscopic currents are driven by chemical and electrochemical potentials involving large numbers (>1015) atoms in most cases. simulations must then compute macroscopic-scale inputs and outputs while preserving atomic-scale spatial resolution of the controlling atoms. these issues must be all dealt with at once, because they all exist at once in the systems of interest, and they must be dealt with accurately, because valves typically depend on the balance of nearly equal forces, e.g. electrostatic and diffusion. each force must be quite accurately calculated because it is the difference that controls function. it will be some time before simulations can surmount these problems and be used to make practical devices [171–173]. meanwhile, we use the mesoscopic approach, which has been so fruitful in computational electronics [18, 21, 122] where atomicscale simulations are rarely if ever used. the key to the mesoscopic approach is the choice and treatment of correlations. not all correlations can be handled (see the infinite series in [174] which of course has not been shown to converge). we consider the poisson equation and use the treatment in barton [175] (p. 168) to illustrate the issues in connecting a nanovalve to the outside three dimensional world. ∇2φ(r) = −ρ(r) (12) an integral (‘kirchhoff’) representation of an equation inside the nanovalve is kvol(r) + ksurf(r), where kvol(r) involves the usual free-space green’s function gfree (r̂ | r) =1 4π (r̂ − r). kvol (r) = dv̂vol vol ∫ ρ(r̂)gfree (r̂ | r) where gfree (r̂ | r) = 1 4π 1 r̂ − r (13) ksurf (r) = dŝsurf surf ∫ ∂nφ(r̂)ĝ free (r̂ | r) − dŝsurf surf ∫ φ(r̂)∂nĝ free (r̂ | r) (14) here we use barton’s notation for the normal derivative ∂nφ(r̂) of the potential (for example) as a function of the location of the source r̂ . inside the nanovalve the volume kvol(r) and surface terms ksurf(r) are combined to give the solution φ(r) of poisson’s equation as shown in eq.(12) kvol (r)+ ksurf (r) = φ(r) r is inside the nanovalve kvol (r)+ ksurf (r) = 0 r is outside the nanovalve (15) the free-space green’s function gfree (r̂ | r) is of course the average of the free-space potential in atomicscale simulations. the special properties of nanovalves depend a great deal on the properties of their surfaces because nanovalves are so small. structural biology determines the surface of the protein nanovalve and the amino acids forming that surface. physics determines the surface green’s function ∂nĝ free (r̂ | r) and thus the surface normal derivative ∂nφ(r̂ | r) and the surface charge. determining these properties is the goal of analysis of specific nanovalves and does not concern us here. it is enough to mention that these properties can be determined from experiments analyzed by the mathematical solution [176] of the appropriate inverse problem. the spatial distribution of structure and permanent structure can be determined from measurements of current-voltage relations under a wide range of ionic conditions, concentrations, and voltages ± 6 kbt/e (150 mv). the large amount of accurate data allows for an accurate solution of the inverse problem. connection of the nanovalve to the external world is what concerns us here. in mathematical language, the problem reduces to the kirchhoff representation of the end of the channel, written from eq.(14) by isolating the surface of the ends from the rest of the structure. kend (r) = dŝend end ∫ ∂nφ(r̂)ĝ free (r̂ | r) − dŝend end ∫ φ(r̂)∂nĝ free (r̂ | r) (16) in general, this problem can be complex involving interactions of all sorts between the interior of the nanovalve or channel and the external world. indeed, in some biological channels (calcium channels) this may be important (although so far little studied). in general, however, nanovalves are devices designed to work reasonably robustly and independently of the world eisenberg hungarian journal of industry and chemistry 16 around them. robust devices need to be transferable from one place to another and so the complex interactions are minimized by the design and evolution of the systems. if we oversimplify to make the point clearly: nanovalves are exceedingly narrow where they allow control but widen dramatically outside that region so ‘resistance’ to flow is concentrated in the narrow region. control is robust, available under a wide range of surrounding conditions. in the nanovalves of semiconductor technology, buffer regions isolate the nanovalve and allow it to have robust properties. the connection to the outside world is through a buffer region of a semiconductor separating the metallic contact from the nanovalve itself. in the nanovalves of biology, the buffer regions are the antechambers of the channel and the surrounding ionic baths between the ag|agcl wire (or salt bridge) and the ion channel. these regions are designed (or evolved) so the current in the buffer region is ‘ohmic’ independent of time during the function of the nanovalve. these regions are designed to minimize the layers of charge of eq.(16) that create undesirable complex behavior not easily controlled by the valve itself. the connection of the nanosystem to the outside world is the current flowing in and out of the channel, and of the potential at the ends of the channel. the charges flowing in and out of the channel is not equal because of transient-charge storage (‘capacitive’ properties, famously voltage-dependent and non-linear), which is large and significant in semiconductor valves [21, 107, 177–179]. in biological channels, voltagedependent charge storage phenomena are present as well, where they are called ‘gating currents’ [75–76, 180]. these non-linear displacement currents flowing in channels and associated structures are small but they are controllers of biological function of great importance, and link the motions of handfuls of atoms to macroscopic function. these currents are small because they are produced by motions of a small number of charges compared to the total number of charges in the system. they can be measured because continuity of current guarantees that charge movements arising in conformation changes must also flow in the electrodes and circuits connected to them [181]. the currents flowing in and out of the nanovalves are the connections to the outside world and need to be included in the analysis of the nanovalve itself. these are the currents that are continuous. the currents are the same everywhere in a series-connected system like those described in eq.(6). the rate constants of mass action models of particle movement can be connected to the external world using a theory that accounts for current flow everywhere, along with diffusion, and perhaps migration as well. rate constants for nanovalves. analytical expressions for the rate constants for movement of charged particles in channel structures can be derived in quite a general way, starting with langevin equations for the thermal motion of ions [80, 126, 182–184]. it is necessary to use the full langevin equation (including second derivatives with respect to location) if the treatment is to allow for two boundary conditions (i.e. electrochemical potential on the inside and also the outside of the channel) and macroscopic flux. (if one uses only the smoluchowski, high-friction version of the langevin equation, with only first order spatial derivatives, the distribution of velocities of particles has mean zero and no net flux). trajectories can be doubly conditioned, allowing separate boundary conditions for the two sides of the channel, and the resulting multiple integrals can be performed analytically, somewhat surprisingly, to give the expressions simulated in ref. [166], derived in ref. [126], as shown in ref. [80]. left kf k b ⎯ →⎯⎯← ⎯⎯⎯ right (17) where jk = l ⋅ k f ⋅ck left( ) unidirectional efflux jout! "## $## − l ⋅ kb ⋅ck right( ) unidirectional influx jin! "## $## (18) the rate constants are conditional probabilities derived using the theory of stochastic processes from the properties of doubly conditioned brownian trajectories [126, 182–184]. jk = ck l( ) source concentration !"# dk l ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟ diffusion velocity ! prob {r | l} conditional probability ! "$$ #$$ unidirectional efflux % &$$$$$$$ '$$$$$$$ −ck r( ) dk l ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟ ↑ channel length prob l r{ } unidirectional influx % &$$$$ '$$$$ (19) or jk = l ⋅ k f ck left( ) unidirectional efflux jout! "## $## − l ⋅ kbck right( ) unidirectional influx jin! "## $## (20) where k f ≡ jout ck left( ) = k right left{ }= dkl2 prob right left{ } = dk l2 exp(zkfvtrans / rt ) 1 l exp(zkfφ(ζ ) / rt )dζ 0 l⌠ ⌡ ; kb ≡ jin ck right( ) = k left right{ }= dkl2 prob left right{ } = dk l2 1 1 l exp(zkfφ(ζ ) / rt )dζ 0 l⌠ ⌡ . (21) mass action and conservation of current 44(1) pp. 1–28 (2016) doi: 10.1515/hjic-2016-0001 17 r is the gas constant, f is faraday’s constant, t is the absolute temperature, and vtrans is the electrical potential across the channel not including potential drops outside the channel. the coupling to the long-range fields and flows is through the expressions for the electrical potential φ(x) because the regions outside the channel are decently ohmic [185–189]. first order dependence on concentration in the bath can be described by changes in the concentrations on the left ck(l) and the right ck(r). the changes in concentration can often be described adequately this way because they are slow and small. the potential is computed in all space (channel and surrounding baths) by a consistent theory, of one flavor or another. pnp [20, 56, 81, 113–114] deals with the motion of point charged particles; envara [190] deals with spherical particles that can diffuse, migrate or flow by convection, steric-pnp [191] is an approximate version much easier to compute, and pnp-fermi [192– 194] deals with finite size by enforcing a fermi distribution that prevents over filling and accounts for saturation of space (by spheres), and no doubt there are many other appropriate models in the vast literature (which includes semiconductor applications, ionic solutions, ion channels, and formation of concrete). these models produce potential profiles that automatically change with conditions so rate constants change and produce currents that are continuous and satisfy maxwell equations. nanovalves are obviously a small subset of the applications of the law of mass action, but it is some comfort to see how consistent analysis can be done in this case so the laws of mass action and continuity of current can both be satisfied. the general case is much harder. it is difficult to grasp all the dimensions of chemical reactions at this stage. one can reach in that direction by studying specific chemical reactions, where simple representations (involving one-dimensional reaction paths) are enough to describe important phenomena. variational methods can extend the law of mass action. if the goal is to build transferable systems, so we can build robust devices, as in electronic technology, we must use mathematics that allows interactions between charges and fields, currents and fluxes and flows of solvent, extending from atomic to macroscopic scales. variational methods are designed to deal with systems with multiple forces and flows in which interactions are unavoidable and complex. in these systems, interactions must be included in all analyses. otherwise, theories have more adjustable parameters than can be determined experimentally and still cannot deal with a range of conditions because interactions change with conditions in ways too complex for ordinary theories. theories of ionic solutions have difficulties. sadly, theories of ionic solutions seem to have these difficulties theories of ionic solutions need a large number of adjustable parameters and still cannot describe biological solutions, for example. the first step of analysis seems to be the identification of properties of single ions from measurements of solutions that always contain at least two types of ions, cation, and anion, because of electrical neutrality. the identification of properties of single ions remains ‘elusive’ even in hünenberger and reif’s [195] six hundred-page paper containing more than two thousand references. hünenberger and reif’s title itself characterizes single ion solvation as elusive even in the infinitely dilute solutions they consider. the ionic solutions needed to sustain life (and used in much of electrochemical technology) are much more concentrated and have many more and stronger interactions among solutes; interactions between solutes and water; and interactions with far-field boundary conditions. they do not resemble infinitely dilute solutions [39–45]. references [34, 39, 41–42, 50–51, 55, 62, 196–198] draw particular attention to the difficulties and remind readers that almost all biology and electrochemistry occurs in solutions more concentrated than 0.1 m, often in solutions much more concentrated. solutions tend to be most concentrated where they are most important, near electrodes (in electrochemistry) and in and near nucleic acids, binding sites of proteins, enzyme active sites [199], ion transporters and ion channels [200–204]. almost all of biology occurs in ionic mixtures and involves flow and so is described particularly poorly by existing theories and simulations [56, 65, 196–197, 205–206]. the sad limitations of our understanding of ionic mixtures, like those in which all of biology occurs, are not widely known, and so embarrassing that many do not want to know of them, as i did not for many years. it is necessary then to document the frustration by quotations from leading workers in that field. the classical text of robinson and stokes [40] is still in print and widely used. it is a book not noted for emotion that still gives a glimpse of its authors’ feelings of frustration (p. 302). “in regard to concentrated solutions, many workers adopt a counsel of despair, confining their interest to concentrations below about 0.02 m,... ” [207]. in a recent comprehensive treatment [51] of nonideal properties of solutions, the editor werner kunz says (p. 11 of [52]): “it is still a fact that over the last decades, it was easier to fly to the moon than to describe the free energy of even the simplest salt solutions beyond a concentration of 0.1 m or so.” new mathematical tools are needed to resolve a stalemate that has existing since the 1920’s. the powerful tools of variational calculus automatically deal with interactions that vary dramatically with conditions. if the mathematics does not deal with interactions, those interactions will not be computed correctly and will wreak havoc with theories that are based on algebraic descriptions of interactions or theories based on the law of mass action with constant rate constants. eisenberg hungarian journal of industry and chemistry 18 energy variational approach. the energy variational approach envara is defined by the eulerlagrange process [208] as generalized by liu, and colleagues, into an energy/dissipation functional. the generalized functional combines two variations yielding a single set of euler-lagrange equations (in eulerian coordinates of the laboratory) using push-back and pullforward changes of variables [190, 209–212]. in this way, envara can deal with dissipation (friction) and ionic solutions. envara describes conserved energy using the classical hamiltonian variational principle of least action described in textbooks of mechanics. it deals with friction using the rayleigh dissipation principle described in textbooks of irreversible thermodynamics. when combined, these principles allow energy to be degraded into entropy as matter and charge flow in frictional materials [213], like electrolyte solutions. ionic solutions experience friction because an ionic solution is a condensed phase essentially without empty space. ice floats on water, so liquid h2o has greater density than solid h2o and presumably less space between its atoms than the solid. atoms and molecules in a condensed phase cannot move without colliding. collisions randomize originally correlated motions and make them into the kind of randomized motion that we call heat [214]. the variance of the displacement is what we call temperature. the macroscopic names for the conversion of translational to randomized zero-mean (nearly) brownian motion, are dissipation and friction. energetic variational methods are particularly useful because they allow multi-scale derivation of partial differential equations (and far-field boundary conditions) from physical principles when multiple fields are involved, like convection, diffusion, steric exclusion, and migration in an electric field. energetic variational principles have recently become available for systems involving friction [209, 211, 215], that is to say, for systems involving ionic solutions [117, 190, 210, 216]. energetic variational principles combine the full power of the navier-stokes equations (a) with either a lennard-jones representation of finite-size ions or (b) with a density functional theory of ionic solutions built from rosenfeld’s density functional theory of liquids [190, 217]. computations must be done in three dimensions because spheres do not exist in one and two dimensions. these theories and their simplifications [191, 218–219] are difficult to compute in three dimensions because of the steeply singular forces used to ensure that atoms do not overlap. overlap must not be permitted because spheres cannot overfill space: space can be saturated with spheres. saturation effects are a main cause of nonideality, particularly in the extremely crowded conditions in and near enzyme active sites, ionic channels, nucleic acids, and the working electrodes of electrochemical cells where twenty molar solutions are not uncommon [199]. (as a rule of thumb, ions are crowded and electric fields are largest [220–222] where they are most important in technology and biology). if saturation is described by a fermi-like distribution as recently derived for spheres of unequal sizes [211, 223] some of these difficulties can be attacked [192–194]. a fourth order partial differential equation can be written [192] which is easily integrated in three dimensions, after it is reduced to a pair of second order partial differential equations (with carefully defined boundary conditions) and computed with appropriate numerical methods. but it is still not clear how best to apply any of these methods to chemical reactions (fig.1) described by the law of mass action with rate constants extended to be functions or functionals and not constants. we now have the tools, and we now see the goal a global treatment combining conservation of mass in chemical reactions described by the law of mass action with conservation of charge flow and current described by kirchhoff’s current law everywhere. coda: our grasp must be sure, but our reach should exceed our grasp, as we do our science. we must grasp both charge/current conservation and mass action before we can produce robust theories (or simulations) of chemical reactions in ionic solutions that successfully use one set of parameters over a range of conditions, and include the global properties of electric fields. correct calculations are needed because there is no engineering without numbers and accurate computations [171–173]. calculations from theories and simulations of electronic-, ionic-, or biologically inspired devices must be checked and calibrated against known results. otherwise devices built from those calculations will not work [56, 65, 196–197, 205–206]. if theories and simulations of electrical devices were not robust, if parameters had to be changed as conditions changed, our electronic technology would be severely limited, to say the least. chemical reactions involving current flow must be within our theoretical grasp before we can develop transferable theories. then we can build devices that perform as expected, as electronic devices usually do. only then can we expect exponential growth in molecular engineering whether biological or technological. it seems no coincidence that exponential growth in electronic technology came after scientists had a secure grasp of global electrostatics and the pnp equations of electrodiffusion in semiconductors. let us hope that energetic variational methods can grasp ions and chemical reactions in water as well and as successfully as pnp has grasped the useful properties of holes and (semi-)electrons in silicon and germanium. 5. conclusion the law of mass action is used widely, nearly universally, in chemistry to describe chemical reactions. mass action and conservation of current 44(1) pp. 1–28 (2016) doi: 10.1515/hjic-2016-0001 19 the law of mass action does not automatically conserve current, as is clear from the mathematics of a simple case, chosen to illustrate the issues involved. if current is not conserved in a theory, charges accumulate that cannot accumulate in the real world. in the real world, tiny charge accumulation much less than one percent produces forces that change predictions of the theory a great deal. indeed, in the real world tiny charge accumulation produces forces large enough to destroy biological membranes and thus living systems, forces large enough to ionize atoms, create a plasma of electrons (like sparks or lightning) and thus make experiments impossible in normal laboratory settings. the mathematics in this paper shows that the law of mass action violates conservation of current when current flows if the rate constants depend only on the potential (chemical and electrical) in one location and its immediate vicinity. the same difficulty arises when rate models of the markov type deal with the movement of charge. the implication is that such models cannot deal with current through an open channel, with the gating properties of channels if the gating mechanism is charged, or with the gating current produced by that mechanism, for example. the essential issue is that rate constants are local functions of potential (at one place or in a small region) so they cannot know about current flow far away or at boundary conditions. if current is interrupted far away, local chemical reactions obviously change, but rate constant models show no change. consider, for example, what happens in a battery when current flow is interrupted far from the battery. these problems can be fixed by computing the potential (chemical and electrical φ(x)) globally and using the neighborhood values of potential that are the result of the global calculation. rate constants in this case have simple physical interpretations and simple expressions involving only one integration, explained in eq.(19). jk = ck l( ) source concentration !"# dk l ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟ diffusion velocity ! prob r l{ } conditional probability ! "$ #$ unidirectional efflux% &$$$$$ '$$$$$ −ck r( ) dk l ⎛ ⎝ ⎜⎜ ⎞ ⎠ ⎟⎟ ↑ channel length prob l r{ } unidirectional influx% &$$$$ '$$$$ prob right left{ }= exp(z k fv trans /rt ) 1 l exp(z k fφ(x)/rt )dx 0 l⌠ ⌡ ⎮ ; prob left right{ }= 1 1 l exp(z k fφ(x)/rt )dx 0 l⌠ ⌡ ⎮ . of course, the rate model and the global potentials interact and must be solved together so they are consistent. variational methods guarantee such consistency. energetic variational methods are needed if the systems are dissipative. ions in water and channels are dissipative systems because they are condensed phases with little empty space. when ions move, they collide with atoms and dissipate energy in the form of heat. acknowledgement fred cohen, eduardo rios, and brian salzberg provided most useful criticisms and suggestions of an earlier version of this paper. many thanks! ardyth eisenberg edited the manuscript with vigor and love, for which i am most grateful, as it motivates me every day. references [1] feynman, r.p.; leighton, r.b.; sands, m.: the feynman lectures on physics, mainly electromagnetism and matter (addison-wesley publishing co., new york) 1963 vol. 2, p. 592 www.feynmanlectures.caltech.edu/ii_toc.html [2] bard, a.j.; faulkner, l.r.: electrochemical methods: fundamentals and applications (2nd ed.; john wiley & sons, new york) 2000 [3] gutman, e.m.: can the tafel equation be derived from first principles? 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discontinuity of current flow. the difference in current in two sequential chemical reactions is shown in eq.(22). the difference is the discontinuity of current, the violation of kirchhoff’s law of continuity of current flow. the difference can be zero only in special circumstances. the difference is not zero in general circumstances, nor robustly. ixy − iyz f = zx ⋅ kxy x⎡⎣ ⎤⎦− zy ⋅ kyx y⎡⎣ ⎤⎦− zy ⋅ kyz y⎡⎣ ⎤⎦+ zz ⋅ kzy z⎡⎣ ⎤⎦ (22) when are both conservation laws satisfied? when ixy iyz = 0 in eqs.(22–25), the law of mass action is consistent with kirchhoff’s current law and conservation of mass and conservation of charge/current are all satisfied. special cases. units of current ixy iyz here are c s-1 dm-3. special case a: if all concentrations are set equal to one, the currents (in the special case with a tilde) equal !ixy − !iyz f ⋅1 mole liter = zx ⋅ kxy − zy ⋅ kyx − zy ⋅ kyz + zz ⋅ kzy ; concentrations = 1 mole liter (23) special case a*: if we also set all charges equal to one, along with concentrations equal to one, î xy − îyz f ⋅1 mole liter = kxy − kyx − kyz + kzy ; concentrations = 1 mole liter ; zx = zy = zz =1 (24) in this special case of eq.(24), labelled a*, asymmetry (net difference) in rate constants determines the discontinuity of current, the violation of kirchhoff’s current law. special case b: alternatively, we can set all rate constants and all concentrations equal to one, ⌢ ixy − ⌢ iyz f ⋅1 mole liter 1 sec = zx − zy − zy + zz ; concentrations = 1 mole liter ; rate constants = 1 1 sec (25) in this special case of eq.(25), labelled b, asymmetry (net difference) of charges (valences) determines the discontinuity of current, the violation of kirchhoff’s current law. asymmetry of parameters violates conservation of charge/current and produces discontinuity in current from device to device, i.e. it produces accumulation of charge, with sizable effects, as shown next and are to be expected, given the strength of the electric field as discussed in the text. size of effects. to estimate the effect on electrical potential v, we need to know the size of the system. imagine a spherical capacitor of radius r. its capacitance to ground or coefficient of the self-energy, if one prefers the phrase in the chemical literature, is c = q/v = 4πεrε0r or numerically 4π×8.85×10-12 [farad/meter] εrr = 1.11×10-10 εrr [farad], where εr is the relative dielectric coefficient, about 80 in water solutions over longish times (say greater than 10-5 s). then, a 1 nm radius capacitor with dielectric coefficient 80 has a capacitance of 8.9 × 10-18 farads. small charges produce large voltages in such a tiny capacitor. even the charge on just one ion (1.6×10-19 c) would produce 18 mv, large enough (compared to the thermal potential of 25 mv) to have a noticeable (~50%) effect in theories and simulations, because exp (−18/25) = 0.49 (components of rates often vary exponentially according to exp(-v/kbt)). a unit discontinuity in current ixy iyz in eqs.(23-25) lasting for a second would produce a voltage of v = q/c = (1/f)/(8.9×10-18) = 1.14×1012 v. eisenberg hungarian journal of industry and chemistry 28 of course, 1 second is a long time for current to flow. if current flowed on a biological time-scale, for 1 ms in a structure 1 nm in radius, with dielectric coefficient 80, the electrical potential would be much less, ‘only’ 109/εr v, somewhat less than 107 v at low frequencies in water. current flow of even a microsecond, would produce nearly ten thousand volts. rate of change of potential. we can also look at the effect on the rate of change of potential. the discontinuity of current is connected to the rate of change of potential by a version of coulomb’s law: ∂v ∂t = 1 c i (26) if we apply this formula to the discontinuity of current in the special case of eq.(24) labelled a*, we can estimate how quickly that discontinuity of current would change the potential: ∂v ∂t = î xy − îyz f ⋅1(mole/liter) ⋅ f c = î xy − îyz f ⋅1(mole/liter) ⋅ f 4πεrε0r = f kxy − kyx − kyz + kzy 4πεrε0r (27) for a capacitor r = 1 nm with εr = 80 and capacitance of 8.9 ×10-18 farads (see above): ∂v ∂t =1.1×1017 ×f kxy − kyx − kyz + kzy( ) in v/s (28) in other words, the breakdown voltage (~ 0.2 v) of membranes and proteins would be reached in 1.1×10-22/(kxy kyx kyz + kzy) seconds. the breakdown voltage for matter in general (say 106 v) would be reached very quickly. we conclude that failure of the law of mass action to conserve current is likely to have noticeable effects. hungarian journal of industry and chemistry vol. 44(1) pp. 29–32 (2016) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2016-0003 separation of process wastewater with extractive heterogeneous-azeotropic distillation andrás józsef tóth,* ágnes szanyi, enikő haaz, and péter mizsey department of chemical and environmental process engineering, budapest university of technology and economics, műegyetem rkp. 3., budapest, 1111, hungary the application of vapour-liquid equilibria-based separation alternatives can be extraordinarily complicated for the treatment of process wastewaters containing heterogeneous-azeotropic. despite dissimilar successfully tested methods for separation, there is possibility to get better distillation method by enabling the separation of more and more specific process wastewater. extractive heterogeneous-azeotropic distillation (ehad) is a new advance in treatment of fine chemical wastewater showing special features to cope with the treatment of highly non-ideal mixtures. this method combines the worth of heterogeneous-azeotropic and extractive distillations in one apparatus without addition of any extra materials. the study of the separations of ternary component process wastewater from the fine chemical industry shows both in the modelled and experimental results that ehad can be successfully applied. the measured and modelled compositions at extreme purities, that is, close to 0 % or 100 %, can be different because of the inaccuracies of the modelling. this highlights the paramount importance of the experiments if special extra-fine chemicals with almost no impurities, e.g. of pharmacopoeial quality are to be produced by special distillation technique. this study expands the application of ehad technique, this new field is the separation of process wastewaters. keywords: process wastewater, non-ideal mixtures, extractive heterogeneous-azeotropic distillation 1. introduction the words of dr. james r. fair are still true: “distillation, king in separation, will remain as the workhorse separation device of the process industries. even though it is old in the art, with a relatively mature technology support base, it attracts research and professional interest. without question, distillation will sail into the future with clear skies and a strong wind. it will remain the key separation method against which alternate methods must be judged” from ref. [1]. the above quote clearly explains why distillation should be investigated continuously [2–4]. in our work, the separation of process wastewater is studied. such mixtures are quite common in pharmaceutical industry, where the treatment of generally azeotropic mixtures and then fine chemical quality should be achieved; while simultaneous, it is challenging to balance the energetic and environmental consequences. corresponding non-ideal process wastewaters commonly include different varieties of aldehydes, alcohols, ethers and esters in aqueous media. these compounds already foretoken these problems may resurrect during vapuor-liquid equilibria-based treatment. the separation of a water, isopropyl acetate, ethyl acetate and ethanol process wastewater from the *correspondence: andras86@kkft.bme.hu pharmaceutical industry [5] has drawn attention to the need for the improvement of the vapour-liquid equilibria-based separation techniques that includes the worth of using different treatment solutions. a new hybrid treatment alternative, the so-called extractive heterogeneous-azeotropic distillation (ehad), has been introduced [6–9] that associates the advantages of heterogeneous-azeotropic and extractive distillations (fig.1). the heterogeneous-azeotropic opportunity presumes that water component is current in the process wastewater and moreover limited immiscibility may exist. heteroazeotropic distillation utilizes deviations in volatility and liquid-liquid phase figure 1. scheme of the ehad technique [9]. tóth, szanyi, haaz, and mizsey hungarian journal of industry and chemistry 30 split by connecting a column and phase separator/decanter [10–12]. ehad differs from heterogeneous-extractive distillation [13] because no new azeotropic mixture is created, videlicet the entrainer is water in the case and it is already current in the process wastewaters to be treated. furthermore, relative volatility changing and extractive effect of entrainer agent is absolutely utilised and there is no rectifying section in the column [9]. the capability of the extractive heterogeneous-azeotropic distillation can be demonstrated with a case study. this was carried out for a separation method of 9 devices, extractors and distillation columns [14]. if fine purity is required, e.g. in biofuel or pharmacopoeial applications further unit operations might be needed, e.g. rectification again. however, it can be observed that within the range of extreme purities (close to 0 % or 100 %) the modelling is not reliable enough and the experiments cannot be omitted. the applicability and effectiveness of extractive heterogeneous distillation has been already tested on many different highly non-ideal mixtures with simulations and experiments verifying the accuracy of modelling [8–9]. the strategy clearly shows that ehad is a forceful method for separation of heterogeneous azeotropic mixtures containing water. 2. experimental in spite of the clear guidelines for the applicability of ehad [8], further application areas are going to be investigated. on the other hand, the separation of actual process wastewater should be interpreted explaining the unit operation and identifying new possible application areas. 2.1. simulations for the sake of our aims, a process wastewater was selected: ethyl acetate (etac), methyl alcohol (meoh) and water (h2o). flowsheet simulations were achieved with chemcad in advance on experiments in order to reduce the necessary number of measurements and to look up promising separation alternatives. moreover, cooling and heating demands, massand waste-flow rates and ideal reflux ratio were also determined. the uniquac equilibrium method is applied [15–18] for the computation of vapour-liquid equilibria of non-ideal mixtures. if binary pairs exist without the availability of uniquac data, the unifac method was applied [19]. liquid-liquid equilibria were also considered in the form of a vapour-liquid-liquid equilibria (vlle) model [20]. unifac and uniquac equilibrium models have vll equilibria options. the flowsheet of ehad and intricacies of process wastewater are demonstrated in fig.2 computed with chemcad. there are one heterogeneous and one homogeneous azeotropes, all in all two binary type [20– 23]. 2.2. experiments to save material (amount of sample) and experimental time, first of all, comprehensive flowsheet simulations should be implemented. the results of computer simulations foretoken and prepare the measurements. the measurements are achieved on the distillation column of laboratorial size demonstrated in fig.3. the major specifications of the distillation apparatus are succeeding: internal width of 2 cm structured packing. the theoretical plates of the column are measured with methyl-alcohol – water mixture, that is 10. the feed (f) is not forewarmed, it is injected on the fifth plate of the apparatus and flow value is kept at 0.06 kg h-1. the entrainer is injected on the tenth plate of the tower and flow value is kept at 0.31 kg h-1. the apparatus warming is directed with a 0.300 kw heating crater. the overhead product, after condensation goes to the decanter, or phase separator. the upper phase is measured and the lower phase is pumped as reflux into the apparatus. the concentration of feed, distillate (d), and waste output (w) were measured using a gc-14b type shimadzu gas chromatographer with cp-sil-5cb capillary column. figure 2. separation of the process wastewater in flowsheet simulator environment. figure 3. scheme of ehad laboratory column. separation of process wastewater 44(1) pp. 29–32 (2016) doi: 10.1515/hjic-2016-0003 31 3. results and analysis we summarise the measured and calculated results in table 1. the comparison also shows the accuracy of ehad in the ternary case selected for the given study. the water addition (xf,water) and the feed content of ternary mixture (xf,solvent) are presented in fig.4, along with the theoretical waste output (xw) and distillate (xd) content as well. the two-phase region is found under the dashed curve. operation of this column is shown by the operating lines. 3.1. modelling of high purity separation the concentrations 0% and 100% are two extreme numbers, since these do not exist in practical separation technology. we can approach these numbers with ever more advanced and expensive technologies, but we can never arrive at them. moreover, the problem of extreme concentrations poses two questions: (i) do we have sophisticated enough analytical techniques to do measurements in such regions, and (ii) can we calculate/model these regions accurately/reliably? positive answers are crucial in the case of high purity distillation. modelling is important since it is used for the reduction of solution space and to find promising alternatives. modelling can therefore be applied to the preparation and selection of the experiment(s). this philosophy is also applied to high purity rectification problems. in our ternary example we arrive at such an extreme concentration range where our analytics is not capable of following the separation. but the modelling shows some promise here. another case studies [6–8] from the fine chemical industry highlights that modelling is not reliable in those regions that are close to the extreme numbers of 0% and/or 100%. a demonstrative example for such a crucial situation is the production of ethanol of pharmacopoeial purity. the ethanol produced of this purity may contain contaminants only in concentrations of a few ppm. there are alternative processes for the production of such extremely pure ethanol involving rectification. however, modelling alone can be misleading and it might show such solution alternatives that prove to be unacceptable if they are experimentally tested. on the other hand, the modelling results are definitely uncertain within such extreme purity ranges. the modelled results in all likelihood cannot be supported by experiments. these examples show that if rectification-based process alternatives are investigated the experiments yield reliable results, since modelling is unreliable at purities close to the extreme concentration ranges. 4. conclusion ehad separation technique improves in the separation of heterogeneous azeotropic mixtures. it opens an alternative solution for distillation specialists. treatment of difficult process wastewaters can be solved costeffective and easily with application of ehad. comparison of modelling techniques and experiments shows good agreement; however, there might be contradictions among measured and modelled data if high purity products are required. our results obtained as a solution to fine chemical industrial and other, e.g. pharmacopoeial purity distillation problems show that close to 0% and/or 100% concentrations the experiments and modelling can provide unreliable results underlining the paramount importance of experiments and proper analytics. symbols b.d.l. below detection limit d distillate ehad extractive heterogeneous-azeotropic distillation etac ethyl acetate f feed meoh methyl-alcohol vle vapour-liquid equilibrium vlle vapour-liquid-liquid equilibria w waste output xf,solvent feed concentration xf,water entrainer concentration xd distillate concentration xw waste output concentration table 1. results of ehad technique: simulated and measured data (in mass percent) f simulation experiment d w d w h2o 4 3.6 94.7 5.3 94.6 meoh 26 0.1 5.2 0.2 5.4 etac 70 96.3 0.1 94.5 b.d.l. figure 4. calculated equilibria and operating lines of ehad. residue curve map, ethyl acetate / methanol /water by uniquac tóth, szanyi, haaz, and mizsey hungarian journal of industry and chemistry 32 acknowledgement the research was supported by the otka 112699 grant. references [1] kister, h.: distillation design (mcgraw-hill education, new york) 1992 [2] szabó, l.; németh, s.; szeifert, f.: separation of multicomponent mixtures, hung. j. ind. chem., 2011 39(2), 295–300 [3] toth, a.j.; gergely, f.; mizsey, p.: physicochemical treatment of pharmaceutical wastewater: distillation and membrane processes, per. pol. chem. eng., 2011 55(2), 59–67 doi 10.3311/pp.ch.2011-2.03 [4] mizsey, p.; toth, a.j.: application of the principles of industrial ecology for the treatment of process waste-waters with physicochemical tools, indust. ecol., 2012 1(1), 101–125 [5] mizsey, p.; szanyi, a.; raab, a.; manczinger, j.; fonyo, z.: intensification of a solvent recovery technology through the use of hybrid equipment, comp. aided chem. eng., 2002 10(1), 121–126 10.1016/s1570-7946(02)80048-7 [6] szanyi, a.; mizsey, p.; fonyo, z.: novel hybrid separation processes for solvent recovery based on positioning the extractive heterogeneousazeotropic distillation, chem. eng. proc., 2004 43(3), 327–338 doi 10.1016/s0255-2701(03)00132-6 [7] szanyi, a.; mizsey, p.; fonyo, z.: optimisation of nonideal separation structures based on extractive heterogeneous azeotropic distillation, ind. 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academic press, aachen, germany) 2014, chapter 8, p. 321 [13] wijesinghe, a.m.j.c.: development of industrial complexes of special rectification techniques for solvent recovery (phd dissertation, lomonosov institute of fine chemical engineering, moscow) 1985 [14] raab, a.: separation of highly non-ideal mixtures for solvent recovery (msc thesis, bme, budapest) 2001 [15] abrams, d.s.; prausnitz, j.m.: statistical thermodynamics of liquid mixtures: a new expression for the excess gibbs energy of partly or completely miscible systems, aiche j., 1975 21(1), 116–128 doi 10.1002/aic.690210115 [16] egner, k.; gaube, j.; pfennig, a.: gequac, an excess gibbs energy model describing associating and non-associating liquid mixtures by a new model concept for functional groups, fluid phase equilib., 1999 158–160, 381–389 doi 10.1016/s03783812(99)00137-5 [17] klamt, a.; krooshof, g.j.p.; taylor, r.: cosmospace: alternative to conventional activity-coefficient models, aiche j., 2002 48(10), 2332–2349 doi 10.1002/aic.690481023 [18] wiśniewska-goclowska, b.; malanowski, s.x.k.: a new modification of the uniquac equation including temperature dependent parameters, fluid phase equilib., 2001 180(1–2), 103–113 doi 10.1016/s0378-3812(00)00514-8 [19] fredenslund, a.; jones, r.l.; prausnitz, j.m.: group-contribution estimation of activity coefficients in non-ideal liquid mixtures, aiche j., 1975 21(6), 1086–1099 doi 10.1002/aic.690210607 [20] akita, k.; yoshida, y.: phase-equilibria in methanol-ethyl acetate-water system, j. chem. eng. data, 1963 8(1), 484–490 doi 10.1021/je60019a003 [21] gmehling, j.; menke, j.; krafczyk, j.; fischer, k.: azeotropic data (wiley-vch verlag gmbh & co. kgaa, weinheim, germany) 1994 [22] gmehling, j.; onken, u.; rarey-nies, j. r.: vaporliquid equilibrium data collection (dechema, virginia, usa) 1978 [23] marsden, c.: solvents and allied substances manual with solubility chart (cleaver-hume and elsevier, london) 1954 hungarian journal of industry and chemistry vol. 44(1) pp. 33–38 (2016) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2016-0004 vapour pressure of ethanol and 1-propanol binary mixtures misirkhan talibov1 and javid safarov1,2 1 department of heat and refrigeration techniques, azerbaijan technical university, h. javid ave. 25, az1073 baku, azerbaijan 2 institute of technical thermodynamics, university of rostock, albert-einstein str. 2, d-18059 rostock, germany the vapour pressure of binary mixtures containing ethanol and 1-propanol were investigated at temperatures ranging from 274.15 to 443.15 k using two different setups with static methods. the measured values were fitted to a clausius-clapeyron type relationship. the heat of evaporation of mixtures was determined from the vapour-liquid equilibria data. keywords: vapour pressure, ethanol, 1-propanol, static method, pressure transmitters, clausiusclapeyron equation 1. introduction investigation of thermodynamic properties of pure liquids and their mixtures is important in various fields of science, chemical engineering, economy and industry. aliphatic alcohols are commonly applied in chemical, biological, and medical uses as solvents for fats, oils, resins, paints, and nitrocellulose with regard to the manufacture of goods from perfumes to brake fluids [1]. in addition, the studied solutions of ethanol (c2h5oh) and 1-propanol (c3h7oh) are also used as heat transfer fluids in heat reservoirs, solar heating systems, oxygenates in fuels, and cryogenic power generation systems [2]. for the design and modelling of such applications, the determination of flow in pipes, heat transfer, and mass transfer operations requires the knowledge of thermophysical properties. density, vapour pressure, speed of sound, viscosity, and heat capacity often need to be defined for these purposes. this work is a continuation of our previous publications in the field of thermophysical properties of alcohol and their solutions [3–6]. hereby, the vapour pressure of binary solutions of (1-x) c2h5oh + x c3h7oh were investigated. the vapour pressure data of binary solutions of ethanol and 1-propanol at different temperatures and concentrations were determined. after the analysis of the literature using “thermolit” from nist, we concluded that only a few vapour pressure values for these systems have been reported to date [7–11]. *correspondence: javid.safarov@uni-rostock.de early studies by parks and schwenk [7] reported the vapour pressure of a (1-x) c2h5oh + x c3h7oh mixture at 298.15 k using glass apparatus and the differential method. a good commercial grade ethanol (w = 99.9 %) and "refined" commercial 1-propanol (w = 99.34 %) were used during the preparation of solutions. later, udovenko and frid [8] investigated the vapour pressure of the same mixture, but within a higher temperature range (323.15 to 353.15 k) using the dynamic method. the vapour liquid equilibria (vle) of these systems were analysed using a refractometer. the activity coefficients γ of both pure components were calculated. a series of studies in the early 90s included the work of zielkiewicz [9], who studied the vapour pressure at 313.15 k using the static method. dried ethanol and 1-propanol were used during the preparation of solutions. the temperature and pressure were controlled within ±0.001 k and ±0.004 kpa, respectively. binary samples were prepared by weighing within an uncertainty of ±0.0005 mole fractions. solution preparations were carried out using the dry nitrogen process. furthermore, pradhan et al. [10] investigated the vapour pressures of ethanol and 1propanol solutions at 303.15 k using the static method. for the fitting of obtained values a modified nrtl equation was used. quite recently, cristino et al. [11] carried out high temperature vle measurements for the system of ethanol and 1-propanol solutions within a temperature range of 403.2 to 423.2 k using a flow apparatus. alcohols used during the preparation of solutions had a confirmed purity greater than 99.9 weight percent. the pressure was controlled using two pressure transducers within ranges of 0 – 0.4 (uncertainty of ±0.0002 mpa) and 0–1.7 mpa (uncertainty of ±0.0009 mpa). the talibov and safarov hungarian journal of industry and chemistry 34 temperature was measured using a platinum resistance thermometer with an uncertainty of ±0.1 k. the statistical associating fluid theory for potentials of variable range (saft-vr) was used to model the systems and found to accurately reproduce the experimental data. using this analytical method the uncertainty of solution preparation was ±0.0001 mole fractions. the outcome of a literature survey summarised in table 1 is that only small temperature, pressure, and concentration intervals were investigated to date in addition to older literature examples decades ago that may have used out-dated measurement techniques. in this work, the vapour pressures of binary (1-x) c2h5oh + x c3h7oh solutions were investigated using two highly accurate, fully automatic static experimental setups and ultrapure merck quality chemicals. 2. experimental 2.1. samples and measurements ultra-pure ethanol emplura® (w = 99.995%, cas no. 71-36-3, art. nr. 8.22262.2500) and 1-propanol analyse emsure® acs, reag. ph eur (w = 99.995%, cas no. 71-23-8, art. nr. 1009971000) were purchased from merck schuchardt ohg, germany. the samples were used without further purification. they were carefully degassed in glass flasks with special vacuum leak-proof valves before measurements were taken. the water content is determined by karl fischer titration and was determined to be less than a mass fraction of 20 ppm. 2.2. experimental procedure the vapour pressure measurements of binary solutions of (1-x) c2h5oh + x c3h7oh were measured using two high-accuracy static experimental seweups [12–14]. the glass cells were used for vapour pressure measurements lower than ambient pressure at temperatures from 274.15 to 323.15 k. the metal cell was used for the higher temperature range of 323.15–433.15 k using the static method [12–14]. the glass cell method consists of absolute and differential parts (if the vapour pressure is smaller than the uncertainty of the absolute cell, 30 pa). the vapour pressure of the solution was always higher than the uncertainty of measurements between 274.15 and 323.15 k. the measurements within this temperature range were carried out only using the absolute cell of installation. the internal volume of the glass cell in absolute measurements is approximately 78.56 cm3, and the volume of steel tube cells is 1 cm3. the glass cell static method consists of a bolted-top cell in a water-bath kept at constant temperature (± 0.01 k) using a thermostat. the vapour pressure was measured using a calibrated high accuracy sensor head [type 615a connected to the signal conditioner type 670a, mks baratron, usa] attached to the top of the cell of various keller pressure transmitters: maximum pressure of 300,000 pa with an uncertainty of δp = ±(400 to 1,500) pa, maximum pressure of 1,000,000 pa with an uncertainty of δp = ±(1,000 to 5,000) pa and maximum pressure of 1,600,000 pa with an uncertainty of δp = ±(2,000 to 8,000) pa. the experimental uncertainty of the pressure in the absolute vapour pressure measurement using the glass cell is ±10–30 pa. the internal volume of the measurement cell is approximately 140 cm3. temperatures were measured using two different platinum resistance thermometers, pt-100. the second platinum resistance thermometer, pt-100, transfers the measured temperature in the computer via an omega pt-104a channel rtd input data acquisition module (omega engineering, inc., usa) for the measuring of temperature, with an accuracy of ±0.001 k. experiments were carried out starting from a low temperature (333.15 k) to a high temperature (433.15 k) at 10 k intervals. before the experiments, the measurement cells were washed with water, methanol and acetone and then all residual fluids were removed. this procedure requires approximately 2 to 3 h or more to reach the table 1. summary of the vapour pressure p literature investigations of a (1-x) c2h5oh + x c3h7oh mixture. reference method properties temperature (t in k) concentration (x mole fraction) uncertainty δp fitted density equation purity source parks [7] 1924 ga p, t, ∆h 298.15 0.0000 to 1.0000 99.9% (et) 99.34% (pr) cs udovenko [8] 1948 dm p, t, γ 323.15 – 353.15 0.0000 to 1.0000 cc arg (et) arg (pr) r zielkiewicz [9] 1993 sm p, t 313.15 0.0436 to 0.9291 ±0.004 kpa poch pradhan [10] 1993 sm p, t 303.15 0.0306 to 0.9700 ±0.001 kpa 99.9% (et) 99.6% (pr) ac cristino [11] 2015 fa p, t, vle 403.20 – 423.20 0.0017 to 0.9993 ±0.0002 – ±0.0009 mpa saft-vr 99.9% (et) 99.9% (pr) p (et) fs (pr) ga, glass apparatus; ∆h, heat of mixing; p, vapour pressure; t, temperature; x, mole fraction; et, ethanol; pr, 1-propanol; cs, commercial sample; dm, dynamic method; γ, activity coefficient; cc, clapeyron-clausius equation; arg, analytical reagent grade; r, reachim, ussr; sm, static method; poch, avantor performance materials poland s.a.; ac, aldrich chemical; fa, flow apparatus; saft-vr, statistical associating fluid theory; vle, vapour-liquid equilibrium; p, panreac; fs, fisher scientific. vapour pressure of ethanol and 1-propanol binary mixtures 44(1) pp. 33–38 (2016) doi: 10.1515/hjic-2016-0004 35 desired minimal pressure (20–30 pa). equilibration of the cells is a rapid process and a constant pressure in the stationary regime is reached within 15 minutes. equilibrium pressure readings are performed in triplicate approximately 10 to 20 min intervals. specific quantities of ethanol and 1-propanol were evacuated, degassed in two separate flasks and connected using an adapter [12]. ethanol flowed into a flask containing 1-propanol and the concentration of the solution was determined using the weight of the flask containing the solution on an electronic scale (sartorius ed224s, germany) with an uncertainty of 0.0001 g. a quantity of the solution was injected into the equilibrium cells up to approximately 50% of their volume. the vapour pressures of the water, methanol, acetone, toluene, 1-butanol, etc. were measured as reference substances for testing both setups [12–14]. the experimental vapour pressure results were assessed to be reliable to within an average uncertainty of ±0.05% according to test measurements. 3. results and discussion the measured experimental vapour pressures for an ethanol/1-propanol mixture within the temperature range of 274.15 to 433.15 k are listed in table 2, and are also shown in fig.1. the vapour pressures of pure alcohols were taken from refs. [15–16]. the experimental vapour pressure results, p in pa of investigated solutions were fit to the antoine equation: ln (p) = aa – ba / ( t/k + ca ) (1) table 2. experimental mole fraction x of 1-propanol, and vapour pressure p (in pa) of a solution of (1-x)c2h5oh + x c3h7oh a temperature mole fraction of 1-propanol (x) (k) 0.0000b 0.0989 0.1918 0.4034 0.5935 0.7971 0.9038 1.0000c 274.15 1684 1490 1374 1116 897 672 530 515 278.15 2248 1980 1843 1498 1219 902 739 697 283.15 3155 2810 2620 2149 1761 1330 1102 1008 293.15 5842 5390 5023 4186 3442 2670 2260 2034 303.15 10458 9762 9180 7780 6521 5150 4402 3854 313.15 18054 16872 15880 13558 11502 9260 8030 7048 323.15 29356 27918 26430 22909 19560 15890 13873 12273 333.15 46796 44590 42200 36700 31777 26000 22992 20472 343.15 71902 68812 65321 57200 49784 41400 36903 32867 353.15 108174 103196 98000 86256 75504 63400 56954 50997 363.15 157911 150535 143157 126500 111128 94202 85257 76746 373.15 224798 214272 203797 180800 159521 136296 123958 113402 383.15 313786 298327 284000 252345 223518 192294 176009 161109 393.15 429264 407124 387678 345105 306612 265259 244002 223982 403.15 576481 545340 519543 462803 412430 358865 331402 305477 413.15 759512 718454 684376 610504 545107 476594 441754 408702 423.15 982342 932045 887923 792004 708954 622271 578714 539077 433.15 1254038 1191945 1135123 1012845 907984 800473 746309 702376 443.15 1582042 1505202 1432927 1278187 1147706 1015139 949123 893968 a standard uncertainties u are u(t) = 0.01 k and u(x) = 0.0001 mole fractions and the combined expanded uncertainties uc are uc(p) = 30 pa for p < 0.1 mpa, uc(p) = 1500 pa for p < 3 mpa, and uc(p) = 8000 pa for p < 16 mpa (level of confidence = 0.95); b the vapour pressure values of ethanol were taken from ref. [15]; c the vapour pressure values of 1propanol were taken from ref. [16]. figure 1. plot of vapour pressure p (in kpa) of a (1-x) c2h5oh + x c3h7oh solution mixture as a function of 1-propanol mole fraction x. ¿, 274.15 k; ¢, 278.15 k; ▲, 283.15 k; �, 293.15 k; ▼, 303.15 k; ò, 313.15 k; ì, 323.15 k; ¯, 333.15 k; £, 343.15 k; r, 353.15 k; �, 363.15 k; s, 373.15 k; °, 383.15 k; ⊕, 393.15 k; «, 403.15 k; ¶, 413.15 k, ◐, 423.15 k; x, 433.15 k; �, 443.15 k; lines fit to eqs.(3) and (4). talibov and safarov hungarian journal of industry and chemistry 36 the fitted constants aa, ba, and ca for the investigated solutions are summarised in table 3 with the standard mean deviation defined as follows: δp/p =100/n ⋅ (pexp. − pcal. )/pexp.⎡⎣ ⎤⎦ i=1 n ∑ (2) from table 3, it can be seen that coefficients aa, ba, and ca exhibit non-trivial dependence from the mole fraction of 1-propanol. fitting of these coefficients was a challenging task. thus, we also used a clausius– clapeyron-type equation to obtain the vapour pressure results of the investigated solutions from mole fractions of 1-propanol: ln p = acc + bcc t +ccc lnt +dcct , (3) where p is vapour pressure in pa; t is the temperature in k; and acc, bcc, ccc, and dcc are the coefficients of the equation, depending on the mole fraction of the solvent as follows: acc = aix j bcc = bix j i=0 3 ∑ ccc = cix j dcc = dix j i=0 3 ∑ i=0 3 ∑ i=0 3 ∑ (4) the coefficients ai, bi, ci, and di for the investigated ethanol/1-propanol mixtures are tabulated in table 4. the uncertainty of fitting was approximately ur(δp/p) = 0.7678. the plots of deviation of experimental pexp and calculated pcal vapour pressure values as a function of figure 2. deviation of experimental pexp and calculated pcal vapour pressure values versus pressure p using eqs.(3) and (4) at various temperatures and mole fractions. figure 3. deviation of experimental pexp and calculated pcal vapour pressure values versus temperature t using eqs.(3) and (4) at various pressures p and mole fractions. figure 4. deviation of experimental pexp and calculated pcal vapour pressure values versus mole fraction x using eqs.(3) and (4) at various pressures p and temperatures t. table 4. clausius clapeyron equation fitting parameters ai, bi, ci, and di from eqs.(3) and (4). ai bi ci di a0 = 103.156 b0 = -7994.80 c0 = -12.3406 d0 = 0.0098481 a1 = 251.788 b1 = -8366.78 c1 = -42.1398 d1 = 0.0527419 a2 = 222.344 b2 = -7727.52 c2 = -36.8168 d2 = 0.0438405 a3 = -446.740 b3 = 14403.70 c3 = 74.8888 d3 = -0.0951465 table 3. antoine parameters aa, ba, ca and percent deviations (δp/p in %) as a function of 1-propanol mole fraction. mole fraction aa ba ca δp/p 0.0000a 23.1773 3461.23 -54.3818 0.6234 0.0989 22.8524 3275.81 -63.4603 0.0742 0.1918 22.7353 3228.33 -65.9886 0.0689 0.4034 22.4745 3118.11 -72.4808 0.1652 0.5935 22.3425 3077.68 -76.1926 0.2204 0.7971 22.2692 3064.56 -79.8646 0.3263 0.9038 22.1582 3009.02 -84.6711 0.1983 1.0000b 22.7515 3373.18 -70.0769 0.8270 a from ref. [15]; b from ref. [16]. vapour pressure of ethanol and 1-propanol binary mixtures 44(1) pp. 33–38 (2016) doi: 10.1515/hjic-2016-0004 37 pressure, temperature, and mole fraction using eqs.(3) and (4) are shown in figs.2-4, respectively. the enthalpies of vaporisation, δhvap in j mol-1, for the (1-x) c2h5oh + x c3h7oh mixture at the four middle temperatures (293.15, 333.15, 373.15, and 423.15 within temperature ranges of 274.15–313.15 k, 313.15–353.15 k, 353.15–393.15 k, and 373.15–443.15 k, respectively) were defined using eq.(5) from ref. [12]: d ln p d 1 t ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ = − δhv r (5) if we plot ln(p) as a function of 1/t, we can define δhv from the gradient of the line: δhv = −r ⋅ d ln p d 1 t ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ . (6) after the integration of eq.(6) we can find ln p = − δhv r ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ 1 t ⎛ ⎝ ⎜ ⎞ ⎠ ⎟+ intercept (7) δhv = rt (intercept − ln p) (8) the calculated enthalpy of vaporisations δhv in j mol-1 for the (1-x)c2h5oh + x c3h7oh mixture within the temperature range of 274.15–443.15 k are listed in table 5 and compared to the available literature results [7–11] shown in fig.5. when the measured values by parks [7] at t = 298.15 k are compared to our values, we obtain ∆p = ±242 pa or ∆p/p = ±5.24 % deviations. the maximum deviation is ∆p = 394 pa at x = 0.759 mole fractions of 1-propanol. the parks’ values [7] are higher than our results and the vapour pressures of ethanol exhibit small deviations compared to ours and all other literature values presented in ref. [15]. the vapour pressure of 1propanol published in ref. [7] exhibits a large deviation from ours and all other literature values presented in ref. [16]. we hypothesise that the vapour pressure values of 1-propanol with high deviation from the literature were used during the analysis of concentration dependence in ref. [7]. the 44 data points of udovenko and frid [8] measured within the range of 323.15 – 353.15 k are mostly higher than our values. the average deviations of both sources are ∆p = ±242 pa and ∆p/p = ±5.24% with maximum deviations of ∆p = 2952 pa at t = 343.15 k and x = 0.5 mole fractions of 1-propanol. the 11 data points of zielkiewicz [9] at t = 313.15 k exhibit small deviations from our results with ∆p = ±33 pa and ∆p/p = ±0.2631% mean deviation. the maximum obtained deviation in ∆p = -59 pa at x = 0.2793 mole fractions of 1-propanol. the next 22 data points of pradhan et al. [10] are mostly higher than our values. the average mean deviation of this comparison is ∆p = ±143 pa and ∆p/p = ±2.2378 %. the maximum obtained deviation in ∆p = 209 pa and ∆p/p = ±3.5182 % at t = 303.15 k and x = 0.7002 mole fractions of 1-propanol. the last 18 experimental values from the recent work of cristino et al. [11] measured at high vapour pressure intervals of 304.2–967.4 kpa also exhibit small differences from our values as the mean deviation between two experimental sources is ∆p = ±5698 pa and ∆p/p = ±0.9227 %. the maximum deviation of this comparison is ∆p = -21134 pa at t = 413.2 k and x = 0.0002 mole fractions of 1-propanol. 4. conclusion vapour pressure measurements for the binary mixture of ethanol and 1-propanol over a wide range of temperatures from 274.15 k to 468.15 k were studied. the antoine and clausius–clapeyron equations were used to fit the experimental results. the enthalpies of vaporisation at four various temperatures were calculated. the available literature values were compared with measured values and small deviations were observed. figure 5. deviation of experimental pexp and literature plit vapour pressure values for the ethanol/1-propanol mixture versus 1-propanol mole fraction using eqs.(3) and (4) at various pressures p and temperatures t. table 5. enthalpy of vaporisation, δhv in kj mol-1 for a (1-x) c2h5oh + x c3h7oh mixture at various temperatures. x 293.15 k 333.15 k 373.15 k 423.15 k 0.0000 43.245 41.210 39.579 37.457 0.1574 43.905 41.300 39.542 37.576 0.2876 44.499 41.416 39.425 37.553 0.5351 45.768 41.989 39.707 37.718 0.7130 46.768 42.811 40.157 38.002 0.8699 47.809 43.815 40.965 38.613 0.9411 47.887 44.441 41.546 39.125 1.0000 47.908 45.052 42.330 39.963 talibov and safarov hungarian journal of industry and chemistry 38 acknowledgement the research was supported by university of rostock and azerbaijan technical university references [1] cano-gómez, j.j.; iglesias-silva, c.a.; ramosestrada, m.; hall, k.r.: densities and viscosities for binary liquid mixtures of ethanol + 1-propanol, 1-butanol, and 1-pentanol from 293.15 to 328.15 k at 0.1 mpa, j. chem. engng. data, 2012 57, 2560−2567 doi 10.1021/je300632p [2] kumagai, a.; yokoyama, c.: liquid viscosity of binary mixtures of methanol with ethanol and 1propanol from 273.15 k to 333.15, int. j. thermophys., 1998 19, 3−13 [3] aliyev, f.sh.; safarov, j.t.; talibov, m.a.; shahverdiyev, a.n.: temperature and pressure dependence of density of the methanol and 1propanol solutions, j. fundam. sci. azerbaijan technical uni., 2008 7(3), 55–61 [4] abdulagatov, i.m.; aliyev, f.sh.; safarov, j.t.; talibov, m.a.; shahverdiyev, a.n.; hassel, e.: high-pressure densities and derived volumetric properties (excess and partial molar volumes, vapour-pressures) of binary methanol + ethanol mixtures, thermochimica acta, 2008 476(1-2), 51– 62 doi 10.1016/j.tca.2008.07.011 [5] aliyev, f.sh.; safarov, j.t.; talibov, m.a.; shahverdiyev, a.n.: (p,ρ,t) properties of ethanol and 1-propanol solutions, j. fundam. sci. azerbaijan technical uni., 2008 7(1), 35–39 [6] safarov, j.t.; aliyev, f.sh.; talibov, m.a.; shahverdiyev, a.n.: experimental densities of methanol + 1-propanol at temperatures from 298.15 to 423.15 k and at pressures up to 40 mpa, proc. 18th eu. conf. thermophysical prop. 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kul, i.; talibov, m.a.; shahverdiyev, a.n.; hassel, e.: vapour pressures and activity coefficients of methanol in binary mixtures with 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, j. chem. engng. data, 2015 60(6), 1648–1663 doi 10.1021/je501033z [13] talibov, m.a.; safarov, j.t.; shahverdiyev, a.n.; hassel, e.: vapour pressure of geothermal and mineral waters of yardimli district of azerbaijan, herald kazan state technol. uni., 2014 17(2), 114–118 [14] safarov, j.t.; ahmadov, b.; mirzayev, s.; shahverdiyev, a.n.; hassel, e.: vapour pressures of 1-butanol over wide range of temperatures, chemistry, bulgarian j. sci. ed., 2015 24(2), 226– 246 [15] talibov, m.a.; safarov, j.t.; shahverdiyev, a.n.; hassel, e.: vapour pressure of ethanol in a wide range of temperature, azerbaijan nat. acad. sci., ser. phys. math. techn. sci., 2015 2, 61–71 [16] talibov, m.a.; safarov, j.t.: vapour pressure of 1propanol in a wide range of temperature, azerbaijan nat. acad. sci., ser. phys. math. techn. sci., 2016 2, in press hjhungarian journal of industry and chemistry vol. 44(1) pp. 39–49 (2016) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2016-0005 group contribution method-based multi-objective evolutionary molecular design gyula dörgő1 and jános abonyi* 1,2 1 department of process engineering, university of pannonia, egyetem str. 10, veszprém, h-8200, hungary 2 institute of advanced studies kőszeg, chernel str. 14, kőszeg, h-9730, hungary the search for compounds exhibiting desired physical and chemical properties is an essential, yet complex problem in the chemical, petrochemical, and pharmaceutical industries. during the formulation of this optimization-based design problem two tasks must be taken into consideration: the automated generation of feasible molecular structures and the estimation of macroscopic properties based on the resultant structures. for this structural characteristic-based property prediction task numerous methods are available. however, the inverse problem, the design of a chemical compound exhibiting a set of desired properties from a given set of fragments is not so well studied. since in general design problems molecular structures exhibiting several and sometimes conflicting properties should be optimized, we proposed a methodology based on the modification of the multi-objective non-dominated sorting genetic algorithm-ii (nsga-ii). the originally huge chemical search space is conveniently described by the joback estimation method. the efficiency of the algorithm was enhanced by soft and hard structural constraints, which expedite the search for feasible molecules. these constraints are related to the number of available groups (fragments), the octet rule and the validity of the branches in the molecule. these constraints are also used to introduce a special genetic operator that improves the individuals of the populations to ensure the estimation of the properties is based on only reliable structures. the applicability of the proposed method is tested on several benchmark problems. keywords: computer-aided molecular design, multi-objective optimization, evolutionary algorithm, the joback method, soft constraints 1. introduction the search for compounds exhibiting the desired physical and chemical properties is of significant industrial importance in the search for different chemicals and materials such as polymers [1, 2], blends [3], coatings, solvents, inert agents, heat transfer media [4], and drugs [5]. in the well-known technologies of the chemical, petrochemical, and pharmaceutical industries, the used medium for the given tasks has been developed via practical experience. for the improvement of these technologies or the design of a new process, every hypothetical molecule must be synthesized and tested to check the fulfillment of the design properties. this ‘trial and error’-type method for the search of the appropriate agent with the defined properties is slow, inefficient and expensive, thus infeasible in the modern chemical industry and research. however, the problem is complex; the algorithmization can be carried out extensively with the use of property estimation methods and molecular structural feasibility operators. algorithmic problems can be efficiently solved with the tools of process engineering. over recent decades, the search for new compounds has *correspondence: janos@abonyilab.com resulted in a new area of process engineering, namely computer-aided molecular design (camd) [6]. the original task of the design of molecules is formulated as follows: given a set of desired properties, design a product that satisfies these needs. with the use of camd tools, the algorithmic approach to the same problem determines the search place: given a set of available structural groups for the satisfaction of desired properties, formulate a product from these sub-units that satisfies the targets. during the decomposition of a camd-based problem, two separate tasks can be derived. as can be seen in fig.1, it can be divided into a forward problem, the prediction of a given property, based on the structural characteristics of a molecule; and a ‘reverse’ problem, the identification of a molecular structure for the satisfaction of target properties. figure 1. molecular design is a ‘reverse’ property estimation task. dörgő and abonyi hungarian journal of industry and chemistry 40 the forward problem, the estimation of properties, can be carried out by different methods; for example, polymers [1], solvents [7], surfactant solutions [8], refrigerants [9] and ionic liquids [10]. the limitations of any computer-aided molecular design techniques are closely related to the limitations of the property model being used [11]. the prediction of properties can be carried out with numerous types of methods, including group contribution methods (gc), quantitative structure-activity/property relationship methods (qsar and qspr), molecular modeling, empirical modeling and correlations, black box models like neural networks (nn) and the combination of these tools [12]. a novel method for property estimation is the cosmo-rs theory published by klamt et al. that combines quantum chemistry and thermodynamics [13]. the ‘reverse’ problem, the design of candidate molecules with a given set of properties from a set of molecular sub-units is hardly diversified; the existing techniques were developed for specific molecules and applications. the known methods can be divided into two major groups [14]. the huge chemical search space is further complicated by the often competing target properties of the design process. a genetic algorithm is a promising method for the generation of new candidate molecules. multi-objective optimization algorithms generate a set of optimal solutions. the pareto fronts of these solutions simultaneously consider several design aspects. since when solving the problem multiple target properties must be taken into consideration at the same time; the problem has been implemented in a well-established genetic algorithm-based multi-objective optimization environment, the non-dominated sorting genetic algorithm-ii (nsga-ii). the search space is conveniently described by the occurrence of each fragment from a given set of available types of groups, and the “distance” of the properties from the target values is estimated by the joback method. the feasibility of the molecule is tested by feasibility constraints for branching and the octet rule. these constraints are also used to introduce a special genetic operator that improves the individuals of the populations to ensure the estimation of the properties is based on only reliable structures. thus as the result, an evolutionary approach for solving molecular design problems with descriptors of varying dimensionality has been developed, that moves effectively towards the pareto optimal front. in the present work the definition of the design problem is followed by a theoretical overview of the used property estimation method and of the nature of genetic algorithms paying special attention to nsgaii. after the description of the different algorithms, proposed for the solution of the design task, the efficiencies of these approaches are examined through several benchmark problems, and the results are discussed extensively to determine improvements in the applicability of these algorithms. 2. methodology 2.1. problem formulation in the first class, numerous candidate molecules are created randomly from a given set of groups. the number of candidate molecules that can be generated by selecting n groups from a set of k groups, allowing repetition and ignoring the order of selection can be determined by eq.(1). !! !,! = !!!!! ! !!(!!!) (1) the total number of candidate molecules that can be selected from a set of k groups is the sum of the results of eq.(1) from n1 until nmax as is given by eq.(2) (n1 is practically equal to at least 2, as no molecules consist of only one fragment). the sum of candidates is equal to !! !,!!!"# !! = !!!!! ! !!(!!!) !!"# !! (2) according to eq.(2) the total number of candidate molecules can undergo a combinatorial explosion as can be seen in fig.2. in the second class for the solution of the ‘reverse’ problem, this increased number of candidates must be eliminated by some objective function that expresses the ‘distance’ from the target. an example of this approach can be a tree structure to mimic the chain of a molecule and reach feasible structures as was carried out in refs. [12] and [14]. as in the literature, the proposed methods for the design of molecules are highly diversified. lin et al. studied the design of metal catalysts [15], numerous articles can be found for the design of drugs [5, 16-18], perdomo et al. designed and improved biodiesel fuel blends [3] and kasat et al. summarized the applications of genetic algorithms in polymer science including polymer design [2]. to solve the design problem, several computational strategies have been used. genetic algorithms (ga) are used in several publications [15, 19, 20], a combination of neural networks and genetic algorithms is used in [21] and linear programming is used in [12, 14]. figure 2. the combinatorics of group selection. multi-objective molecular design 44(1) pp. 39–49 (2016) doi: 10.1515/hjic-2016-0005 41 2.2. theoretical methodologies the definition of a chemical product design problem is based on the description of design constraints. a set of properties is specified as constraints with specified values with lower and/or upper boundaries. these properties are the explicit property constraints as their values can be determined directly by the application of some model calculation or experimentally. in the case of camd problems, explicit constraints are evaluated through property estimation methods, these can be, for example, critical properties, solubility indexes, normal boiling points, etc. however, property estimation methods have been significantly improved, there are products, for example, food, fragrances, health and safety products, and aesthetics that cannot be calculated with the use of these models, as these properties are based on subjective opinions or existing knowledge. in the case of these implicit property constraints (e.g. taste, aroma, color and health effects of products) the use of databases or the opinion of the designer can be implemented during the evaluation stage. during the basic camd process explicit constraints are taken into consideration, these relate mainly to physical properties, and implicit considerations are taken into account during the selection of available molecule fragments or compounds (e.g. no aromatic compounds are taken into consideration, or no halogens or cyanides are available) [6]. to understand the formulation of the solution to this explicit property constraint-based problem, the following information must be taken into consideration as the input information of the molecule design task (according to [12, 14]): 1. set g of nmax groups of which the designed molecule can be composed 2. the boundaries for the specified properties to be satisfied: !!" ! ’s for the lower boundaries and !!" ! ’s for the upper boundaries, where ! = 1, 2,… ,!, the specified properties 3. the lower ( !!!! ) and upper limits ( !!"! ), for the number of appearances of group i in the designed molecule (! = 1, 2,… , !) 4. the property k can be estimated via a property estimation method as function !! (! = 1, 2,… ,!), in the case of group contribution methods !! can be written as !!(!!, !!,… , !!) (where !!, !!,… , !! are the numbers of group types #1, #2, …, #n respectively). the problem using the expressions above can be formulated as follows: i groups can be chosen from a given set of molecular subunits (g) considering the limits of !!!! and !!"! , to find all the possible molecular structures, while the property constraints given in eq.(3) are satisfied (where ! = 1, 2,… ,!). !!" ! ≤ ! ! !!, !!,… , !! ≤ !!" ! (3) during the solution of the above-defined camd task, the generation and test method can seem to be inefficient as an enormous number of candidate molecules are created which finally turn out to be infeasible molecular structures. as is familiar among financial and industrial problems, some properties need to be minimized and others maximized between the constraint values, while others need to be close to a specified value. this results in a multiple-objective optimization task with concurring targets. our purpose is not to find a single solution, but a set of candidate molecules from the pareto front. pareto optimal solutions are those for which improvement in terms of one objective can only take place with the worsening of at least one other objective function. pareto-ranking is the process of determining the rank of each solution through identifying the number of other solutions that dominate it (the number of solutions that are better than it in terms of every objective) [22]. a pareto front can be seen in fig.3. in the present work feasibility constraints are implemented in the algorithm to filterout the resultant molecular structures in terms of feasibility. as in this approach the candidates are still filtered out after the property evaluation, the efficiency of the search can still seem to be inefficient. as the solution to this contradiction, a special genetic operator has been introduced that improves the individuals of the populations to ensure the estimation of the properties is based on only reliable structures, and the property evaluation is carried out on solely feasible molecules. 2.3. property estimation as the new molecules created in the ‘reverse’ problem are evaluated via property estimation methods to verify the satisfaction of properties, the success of camd tasks depends on, to a large extent, the reliability of the estimation method being used. from the point of view of precision, the highly improved, detailed models seem to be tempting in terms of the application. however, the computational complexity of these models is increased figure 3. a pareto front (the label of each solution refers to the number of other solutions that dominate them, non-dominating solutions are labeled with zero) [22]. dörgő and abonyi hungarian journal of industry and chemistry 42 as well. in terms of precision and complexity, group contribution methods are promising solutions, as the equation for estimation assumes a linear additivity dependence as presented in eq.(4), where !! ! is the group contribution value of group i for property j, !!! is the offset value of property j and !!"#! is the estimated property value. !!"#! (!) = !!! + !!!!! + !!!!! + …+ !!!!! (4) the joback method, also known as the joback/reid method, is proposed to estimate eleven important physical properties of pure materials. during the determination of group contribution values, a common set of structural groups was employed in the regression process. to obtain the minimum values, the minimization of the sum of the absolute errors found from the estimated and the experimental values was carried out. as not the square values, but the absolute values were minimized, the method provides an improved estimation for the majority of the cases, but estimates slightly higher error values for outliers [23]. the systematic deviations of the joback method in the case of normal boiling points can be seen in fig.4, where experimental data is taken from the dortmund data bank. the joback method uses eqs.(5-15) to predict the specific properties as follows: normal boiling point: !! ! = 198 + !!,!!! (5) melting point: !! ! = 122.5 + !!,!!! (6) critical temperature: !! ! = !! ! !.!"#!!.!"# !!,!!!! !!,!!! ! (7) critical pressure (na is the number of atoms in the molecular structure): !! bar = 0.113 + 0.0032 ∙ !! − !!,!!! !! (8) critical volume: !! cm!/mol = 17.5 + !!,!x! (9) heat of formation (ideal gas, 298 k): !! kj/mol = 68.29 + !!!!! (10) gibbs free energy of formation (ideal gas, 298 k): !! kj/mol = 53.88 + !!!!! (11) heat capacity (ideal gas, parameters are valid from 273 k to approximately 1000 k): !! ! !"#$ = !!x! − 37.93 + !!!! + 0.210 ∙ ! + + !!!! − 3.91 ∙ 10!! ∙ !! + + !!!! + 2.06 ∙ 10!! ∙ !! (12) heat of vaporization at normal boiling point: ∆!!"# kj/mol = 15.30 + !!"#,!!! (13) heat of fusion: ∆!!"# kj/mol = −0.88 + !!"#,!!! (14) liquid dynamic viscosity (mw is the molecular weight, the parameters are valid from the melting point up to 0.7 of the critical temperature): !! pa ∙ s = !! ∙ exp !!,!!! − 597.82 /! + + !!,!!! − 11.202 (15) 2.4. a promising approach for the solution of the design task: genetic algorithms genetic algorithms (gas) are stochastic optimization methods that imitate natural selection. gas provide not a single optimal solution to a problem, but several nearoptimal solutions, which is the main advantage of evolutionary algorithms in the field of camd, because near-optimal solutions can be further processed later by the designer and the most promising ones can be selected for synthesis. during the operation of a ga, a population of candidate solutions competes for survival, based on their resemblance to the target values. this resemblance is described by a normalized distance value between 0 and 1 and called the fitness. candidate molecules are usually described by strings, and the components of these strings represent the ‘genes’ of the individual. the evaluation of the population is carried out therefore by figure 4. deviations between predicted boiling points and experimental data [24]. normal boiling point estimations by the joback method (aliphatic hydrocarbons) multi-objective molecular design 44(1) pp. 39–49 (2016) doi: 10.1515/hjic-2016-0005 43 the calculation of fitness and the surviving members have the chance to reproduce and propagate their genes, thus forming the next generation. this propagation is dependent on the genetic operators applied by the specific algorithm being used, the most common are crossover and mutation. the creation of next generations is continued until convergence is obtained (no considerable improvement is observed), or the maximum number of generations set by the user is reached [21]. 2.4.1. the non-dominated sorting genetic algorithm-ii (nsga-ii) for the description of the nsga-ii algorithm, three innovations of the algorithm must be described first: the fast non-dominated sorting procedure, a fast crowded distance estimation method, and the crowded comparison operator [25, 26]. the fast non-dominated sorting approach of the nsga-ii is based on the calculation of three entities: the domination count, the number of solution, which dominates the given solution, and the set of solutions that the given solution dominates. in the first nondominated front the domination count of all solutions is zero. after the determination of the first non-dominated front, each of the solutions dominated by its members is visited and his or her domination count is reduced by one. if the domination count of a solution becomes 0, then it becomes a member of the second non-dominated front. this algorithm is repeated until all fronts are determined. along with convergence to the pareto optimal set of solutions, the maintenance of a healthy spread of solutions is required to avoid the problem of getting stuck in the area of a local pareto optimum. to prevent this issue, the parameter of crowding distance is introduced. during the calculation of this parameter, the average distance between two points on either side of a particular solution along each objective is calculated. the overall crowding distance value is the sum of the individual crowding distance values along each objective. with the use of this parameter, the “density” of solutions in the search place can be calculated. a solution with a higher crowding distance value is less crowded by other solutions, in other words, the outlier solutions can be identified. thus, the parameter is applicable for the maintenance of diversity. the crowding distance computation for two objectives is illustrated in fig.5. the goal of the genetic algorithm, to obtain a uniformly spread pareto-optimal front, is reached with the help of the crowded-comparison operator. the operator guides the selection between two possible solutions as follows: 1. if the non-domination ranks of two solutions differ, the solution which dominates the other is preferred, in other words, whose domination index is less. 2. if the non-domination ranks of two solutions are equal (the two solutions are from the same front), then the solution of the less crowded region is preferred. the main loop of the nsga-ii can be explained by understanding the operators described above. the randomly created initial parent population (with n members) is sorted based on the non-domination rank. the crossover eqs.(16-17) and mutation eqs.(18-19) operators are applied to create the next generation (with n members) [27]. the algorithm applies to the intermediate crossover, which creates two children from two parents: parent1 and parent2 (child and parent are vectors, ! , containing the results of the specific problems), !ℎ!"#1 = !"#$%&1 + !"#$ ∙ !"#$% ∙ (!"#$%&2 − −!"#$%&1) (16) !ℎ!"#2 = !"#$%&2 − !"#$ ∙ !"#$% ∙ (!"#$%&2 − −!"#$%&1) (17) where ratio is a scalar between 0 and 1, and rand stands for a random number, the applied gaussian mutation adds a normally distributed random number to each variable, !ℎ!"# = !"#$%& + ! ∙ !"#$ ∙ (!" − !") (18) ! = !"#$% ∙ 1 − !ℎ!"#$ ∙ !"##$%&!"#$%& (19) where scale is a scalar, that determines the standard deviation of the random number generated and shrink is a scalar between 0 and 1. as the optimization progresses, this shrink parameter decreases the mutation range. currgen and maxgen are the numbers of the current and maximal generations, respectively. since elitism is introduced, the creation of the first population differs from the creation of a subsequent one. the algorithm is described for the tth generation. a combined population (rt) (with 2n members) is created by the summation of the parent population (pt) and the population obtained by the use of crossover and mutation operators (qt). the population rt is sorted according to non-domination and as all previous and current population members are included, elitism is ensured. now solutions belonging to the first non figure 5. the crowding distance of the ith solution is the average side length of the cuboid (the front is marked with solid circles) [25]. dörgő and abonyi hungarian journal of industry and chemistry 44 dominated front (f1) are chosen for the next generation (pt+1) (if the size of f1 is smaller than n). this selection for the next generation is continued until the number of members from f1 to fi is larger than n. in these cases fi is sorted based on the crowded-comparison operator and the best solutions are chosen to fill the empty slots of the new population. the nsga-ii procedure is illustrated in fig.6. 2.5. description of the proposed algorithm the developed algorithm therefore needs to solve effectively the camd tasks based on the needs of the industrial and research work. by taking into consideration these needs, the optimal properties of the desired molecules can be defined, and this chemical information is essential for the defining of input parameters for the genetic algorithm. this schematic algorithm of the design process can be seen in fig.7. the standard genetic algorithm was modified according to the task of the design of molecules. the chemical information is converted into input parameters. thus, the type, minimum and a maximum number of available groups, the property and structural targets (e.g. acyclic, monocyclic, bicyclic structures), and the property and feasibility constraints (octet rule and a rule for branching) are defined. the algorithm of nsga-ii can be seen in fig.8. the efficiency of five different types of algorithm was tested in the present work. all the algorithms were implemented in matlab. 2.5.1. the ‘base case’ algorithm 1 only the type, the minimum and a maximum number of available groups, the target properties and the property constraints are defined. no structural targets or feasibility evaluations are implemented. 2.5.2. the ‘octet rule’ algorithm 2 besides the objectives and constraints of algorithm 1, the octet rule is defined as target parameter. the octet rule is described in eq.(20), 2 − !! !! = 2!! (20) where xi, vi are the number and valency, respectively, of groups of type i and m = 1, 0 or -1 for acyclic, monocyclic and bicyclic groups, respectively [28]. the valency parameter in this context means the number of available bonds on a group (thus the valency of double bonds counts as a single valency in this context). 2.5.3. the ‘octet rule as a soft constraint’ algorithm 3 besides the structure of algorithm 2, the algorithm contains the octet rule (eq.(20)) as a soft constraint to aspire the program to reach a feasible structure according to the octet rule. the soft constraint was defined as a curve similar to a reverse gaussian distribution according to eq.(21), where !"#.!"#. is the result of the octet rule reordered to give 0 when the constraint is satisfied. figure 7. the algorithm of the design process. figure 6. graphical illustration of the nsga-ii procedure [25]. figure 8. the algorithm of the genetic algorithm (the steps in dashed box are only implemented in algorithm 5). multi-objective molecular design 44(1) pp. 39–49 (2016) doi: 10.1515/hjic-2016-0005 45 ! !"#.!"#. = ! ∙ (1 − !! (!"#.!"#.)! !!! ) (21) as can be seen in fig.9, the curve of this function has a descending value near the !"#.!"#. = 0 value, and is equal to 0 at exactly x = 0. the parameter w shows the ‘weight’, the constant value far from !"#.!"#. = 0, and σ stands for the ‘width’ (thus the ‘sharpness’) of the function. a sharp function type (w = 1, σ = 0.1) was chosen as structural feasibility is not satisfied with mild ones. 2.5.4. the ‘octet and branching rule’ algorithm 4 only the octet rule cannot describe the structural feasibility. two adjacent groups cannot be linked by more than one bond. the valency parameter in this context still means the number of available bonds on a group, as defined in the description of algorithm 2. given xj groups of type j with valency vj, a total of !! !! − 2 + 2 attachments are available for bonding [28]. !!!!! ≥ !! !! − 2 + 2 (22) !!! ≥ !! !! − 1 + 2 (23) 2.5.5. the ‘healing function’ algorithm 5 the genetic algorithm is further improved with the introduction of a novel genetic operator called the healing function. the function is implemented in the algorithm at two points, after the initialization of the first population and after the selection, mutation and crossover steps are conducted in each generation. this function serves the population entities to be feasible with the help of the branching rule described in eq.(23). if the equation is not fulfilled then the difference from the optimal value shows the bonds needed in the molecule to reach the feasible structure. using this value, the algorithm chooses as many available groups with one bond as needed for feasibility and completes the molecule with these groups. during the definition of the input parameters the number of available groups with one bond in the molecule is increased to ensure the availability of these groups. the number of branches and the groups with 3 or more bonds, must be significantly less than the ones with one bond available, e.g. 4 and 20 respectively, thus the termination of every chain in the molecule is ensured. 2.6. the evaluation of the results as the purpose of the current work is the development of an effective algorithm for the design of molecules obtaining target properties, the comparison of the results is an essential task to check the improvement. this efficiency inspection is carried out over two steps. first a visual evaluation was carried out as the matlab implementation of the nsga-ii algorithm plots every generation as the script runs. the plot window of nsga-ii can be seen in fig.10. then the number of solutions is counted and, as the feasible structure is not ensured in every algorithm, the feasible ones based on the octet and branching rules are counted as well. the last generation in which the population of the pareto front was changed was also determined. 3. results and discussion the effect of the various user determined input parameters was examined and presented in several benchmark problems for the identification of different chemicals having the desired physical and chemical properties, as estimated by the multi-dimensional property model. the genetic algorithm worked with 250 generations containing 100 population members each. the effectivity of the different algorithms is compared through these design tasks. 3.1. checking the effectivity through the search for predefined molecules first the effectivity and applicability of the different algorithms were tested in terms of the search for different, predefined molecules. the properties of simple molecules were calculated via the joback method and these values were set as targets to avoid the inaccuracy of the estimation method. the property constraints were set around these target values as given figure 9. the curve of the used soft constraint. figure 10. the plot window of nsga-ii. dörgő and abonyi hungarian journal of industry and chemistry 46 below. the search for two simple molecules, acetone, as its structure is quite simple, and n-octane were carried out to validate the algorithms. 3.1.1. acetone the structure of acetone can be represented by two methyl (blue circles) and one ketone (red circle) groups using the groups of the joback method as can be seen in fig. 11. the experimental and estimated boiling and melting points are presented in table 1. the input parameters for the design task were as follows: available groups: -ch3, -ch2-, >ch-, >c<, -f and >c=o number of available groups: 0–4 for all the available groups (in the case of algorithm 5, the -ch3, and -f numbers were set to 20 to allow healing) target properties: tm = 173.50 k, tb = 321.91 k (estimated values) property constraints: 150 k < tm < 200 k, 300 k < tb < 350 k target molecule structure: acyclic. the results of different algorithms are presented in table 2. next to the number of solutions, the number of feasible solutions is presented in brackets and the value ngen,change stands for the last generation that changed the population of the pareto front. the last row of the table shows if acetone is among the resultant structures. algorithm 5 seemed to be less effective in the light of the unsuccessful search for the structure of acetone, but if we consider that this algorithm could use up to 20 pieces of -ch3 and -f groups, we can understand that the search place is significantly bigger than in the case of algorithms 1-4. 3.1.2. n-octane the structure of n-octane can be represented by 2 methyl (blue circles) and 6 methylene (green circles) groups using the groups of the joback method as can be seen in fig.12. the experimental and estimated boiling and melting points are presented in table 3. the input parameters for the design task were as follows: available groups: -ch3, -ch2-, >ch-, >c<, -f and >c=o number of available groups: 0–6 for all the available groups (in the case of algorithm 5, the -ch3, and -f numbers were set to 20 to allow healing) target properties: tm = 179.92 k, tb = 382.44 k (estimated values) property constraints: 150 k < tm < 250 k, 350 k < tb < 450 k target molecule structure: acyclic. the results of different algorithms are presented in table 4, where the last row shows if n-octane is among the resultant structures. as in the case of the search for acetone, algorithm 5 had a significantly bigger search place than algorithms 1-4; thus, it could not find the structure of n-octane. table 1. the boiling and melting points of acetone. experimental values estimated values tm [k] 178.25 173.50 tb [k] 329.45 321.91 table 2. the results of the search for acetone. algorithm 1 2 3 4 5 solutions (feasible) 2 (1) 2 (1) 1 (0) 1 (1) 2 (2) ngen,change 95 10 8 9 127 acetone yes yes yes figure 12. the structure of n-octane fragmented according to the groups of the joback method. table 3. the boiling and melting points of octane. experimental values estimated values tm [k] 216 179.92 tb [k] 398 382.44 table 4. the results of the search for n-octane. algorithm 1 2 3 4 5 solutions (feasible) 10 (2) 5 (1) 1 (0) 1 (1) 5 (5) ngen,change 191 58 17 207 47 n-octane yes yes figure 11. the structure of acetone fragmented according to the groups of the joback method. multi-objective molecular design 44(1) pp. 39–49 (2016) doi: 10.1515/hjic-2016-0005 47 3.2. examples for testing the algorithms in the following examples the effectivity of the proposed algorithms is tested via two benchmark problems. as concurring minimum and maximum search objectives are set as target variables, a pareto front can be obtained, which represents the applicability of the genetic algorithms to solve camd tasks. 3.2.1. case study 1. the input parameters for the design task were as follows: available groups: -ch3, -ch2-, >ch-, >c<, -f and >c=o number of available groups: 0–4 for all the available groups (in the case of algorithm 5, the -ch3 and -f numbers were set to 20 to allow healing) target properties: max(tc), min(tb, tm) property constraints: 500 k < tc < 600 k 350 k < tb < 450 k 100 k < tm < 200 k target molecule structure: acyclic. the results of case study 1 can be seen in table 5. as the number of the last generation which changed the composition of the population is relatively high (250 is the maximum number of generations), the algorithms seem to evolve effectively towards the pareto front. in the case of algorithms 1 and 2, many of the found solutions proved to be infeasible, as expected since no feasibility constraints were involved in algorithm 1 and no constraint for branching was available in algorithm 2. the soft constraint of algorithm 3 seemed to be ineffective. algorithm 4 found only 2 feasible solutions, but these solutions were all feasible ones and they were close to the target properties. algorithm 5 was very effective, although the search place was significantly bigger than in the case of algorithms 1-4. the pareto front of algorithm 1 can be seen in figure 13. 3.2.2. case study 2. the input parameters for the design task were as follows: available groups: -ch3, -ch2-, >ch-, >c<, -f, -cl, -br, -i, -oh, >c=o number of available groups: 0–6 for all the available groups (in the case of algorithm 5, the -ch3, -f, -cl, -br, -i, and -oh numbers were set to 20 to allow healing) target properties: max(tc), min(tb, tm, pc) property constraints: 500 k < tc < 600 k 350 k < tb < 450 k 100 k < tm < 200 k 10 bar < pc < 30 bar target molecule structure: acyclic. table 5. the results of case study 1. algorithm 1 2 3 4 5 solutions (feasible) 89 (14) 88 (14) 1 (0) 2 (2) 42 (42) ngen,change 250 250 219 186 250 figure 13. the pareto front of algorithm 1 in case study 1. table 6. the results of case study 2. algorithm 1 2 3 4 5 solutions (feasible) 75 (0) 95 (5) 2 (0) 2 (2) 74 (74) ngen,change 250 250 223 197 250 figure 14. the results of algorithm 5 in case study 2. candidate molecules are represented by blue lines. dörgő and abonyi hungarian journal of industry and chemistry 48 in the case of case study 2 (table 6), a wider searching range was available for the design task: 10 types of available groups with a maximum of six pieces of each (except for algorithm 5, see the targets and constraints) and another target property was set, the minimization of critical pressure between the property constraints. the results were similar to case study 1, algorithms 1 and 2 fundnd several infeasible results with the appropriate properties; algorithm 3 seemed to be ineffective, algorithms 4 and 5 provided reliable results, although algorithm 5 still found more results according to the more pieces of available chainterminating groups (groups with 1 valency). as can be seen from the results the improvement of the algorithms increases the number of feasible solutions significantly. the results of algorithm 5 in case study 2 can be seen in figure 14. 4. conclusion the design of molecules with specified properties has an increasing importance in the modern chemical industry. we proposed a multi-objective evolutionary optimization-based approach to take into account several objectives and constraints (e.g. financial aspects, toxicity). the algorithms generate a set of molecules arranged in a pareto front related to the conflicting design targets calculated by the joback method. to get reliable molecular structures we defined soft constraints based on the octet rule. the branching of the molecules was also tested and a healing function was designed to provide reliable results. the application of the proposed algorithms can be useful in the industry. in the future, we are going to improve the algorithms with problem-specific genetic operators. these modifications seem to be promising for the significant increase in the search efficiency. symbols !! !,! selection of n groups from a set of k groups g the set of n groups from which the designed molecule can be composed nmax the available groups of the specified design task x the number of appearances of the specified group ! a specified property value !!"# estimated property value !!"# experimental property value plb the lower boundary of the specified property value pub the upper boundary of the specified property value lll the lower limit for the number of appearances of the specified group lul the upper limit for the number of appearances of the specified group x1, …, xn the number of group type #1, …, #n, resp. !! ! is the group contribution value of group i for property j !! normal boiling point !! normal melting point !! critical temperature !! critical pressure !! critical volume !! heat of formation !! gibbs free energy of formation !! heat capacity ∆!!"# heat of vaporization ∆!!"# heat of fusion !! liquid dynamic viscosity ratio a scalar between 0 and 1 rand a generated random number currgen the number of the current generation maxgen the number of the maximal generation scale a scalar, that determines the standard deviation of the random number generated shrink scalar between 0 and 1. as the optimization progresses this parameter decreases the mutation range rt a combined population (with 2n members) pt parent population qt the population obtained by the use of crossover and mutation operators f the non-dominated front ! the valency of the specified group. the valency parameter in this context means the number of available bonds on a group (thus the valency of double bonds counts as a single valency in this context). m the type of the designed molecule (m = 1, 0 or -1 for acyclic, monocyclic and bicyclic groups, respectively) w the ‘weight’ of the soft constraint curve (the constant value far from x = 0) σ the ‘width’ (the ‘sharpness’) of the soft constraint function curve acknowledgement the research of j.a. has been supported by the national research, development and innovation office (nkfih), project # otka 116674 entitled “process mining and deep learning in the natural sciences and process development”. g.d. was supported by the “a pannon egyetem tudományos műhelyeinek támogatása” támop-4.2.2.b-15/1/konv-2015-0004 project. references [1] camarda, 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novel method for optimal solvent selection, fluid phase equil., 1993 82, 47– 54 doi: 10.1016/0378-3812(93)87127-m hungarian journal of industry and chemistry vol. 44(1) pp. 51–54 (2016) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2016-0006 selective hydrogen sulphide removal from acid gas by alkali chemisorption in a jet reactor janka bobek,* dóra rippel-pethő, éva molnár, and róbert bocsi department of chemical engineering science, university of pannonia, egyetem str. 10, veszprém, 8200, hungary natural gas is a primary energy source that contains a number of light paraffins. it also contains several undesirable components, such as water, ammonia, hydrogen sulphide, etc. in our study, a selective hydrogen sulphide removal process was achieved by alkali chemisorption in a custom-designed jet reactor. several model gas compositions (co2-h2s-n2) were evaluated to find parameters that enable h2s absorption instead of co2. the negative effect of the presence of co2 in the raw gas on the efficiency of h2s removal was observed. the beneficial effect of the low residence time (less than 1 s) on the efficiency of h2s removal was recognized. optimal operational parameters were defined to reach at least a 50% efficiency of h2s removal and minimal alkali consumption. keywords: acid gas, h2s selective removal, co2, competition with h2s, chemisorption 1. introduction natural gas is one of our primary energy sources, which contains mainly methane. however, it us comprised of several undesirable components like carbon dioxide (co2), hydrogen sulphide (h2s), ammonia (nh3), water (h2o), etc. [1]. table 1 shows a typical composition of natural gas [2]; however, the content significantly depends on locality. in most cases, natural gas contains h2s in various quantities between 10 to 20,000 ppm [1]. the gases with a measurable amount of h2s are called sour gases. the acid gases are defined as gases containing some acidic component such as co2 or h2s [3]. the h2s containing hydrocarbon gases causes problems during the delivery, processing, and storage. h2s is converted into so2 during combustion, which poses a health hazard and causes acid rain, smog. in the presence of water, acid components cause corrosion in pipelines and containers. consequently, h2s removal from natural gas is absolutely necessary [3]. there are several methods for reducing the h2s content of natural gas. membrane techniques also exist, but the adsorption and absorption processes are the most widespread. in the adsorption process, the fixed bed construction is the most common. the adsorber is usually filled with metal ions (iron, copper, zinc, cobalt, etc.) and an impregnated solid host (zeolite, activatedcarbon, etc.). the disadvantage of this technique is the huge energy demand of adsorber regeneration. in the absorption process, one of the main points is the high ph value of the medium due to h2s dissociation. there *correspondence: bobekj@almos.uni-pannon.hu are numerous solvents for absorbing h2s, namely alcanol-amines (mea, dea, dipa, tea, mdea, etc.), alkali-hydroxides (koh, naoh), water, and ammonia. the alcanol-amines and the alkali-hydroxides are the most efficient. the alcanol-amines are widely used in h2s removal, but their selectivity can be problematic and foaming appears during the process [4]. the use of alkali-hydroxides seems to be the most efficient process. by choosing the correct parameters, such as residence time, ph, solvent concentration, and intake, the procedure can be h2s selective. in an alkalihydroxide medium competitive chemisorption takes place between co2 and h2s. although co2 is a stronger acid than h2s, it is a slower adsorber, thus h2s absorption can be achieved over a short residence time. intensive phase connection and fast phase separation afterwards are essential steps to facilitate a h2s selective process [2]. the spray technique is a widespread method for the intensification of the reaction between the reactants. the pneumatic nozzles act as two-phase sprayers, because the gas at high speed breaks up the liquid into little droplets [5]. table 1. a typical composition of natural gas [2]. component concentration (%, m3/m3) methane (ch4) 97 nitrogen (n2) 0.936 ethane (c2h6) 0.919 carbon dioxide (co2) 0.527 propane (c3h8) 0.363 butane (c4h10) 0.162 oxygen (o2) 0-0.800 noble gases (ar, he, ne) trace other (e.g. h2s) 0-0.001 bobek, rippel-pethő, molnár, and bocsi hungarian journal of industry and chemistry 52 2. experimental the aim of our research is selective hydrogen sulphide removal from model gases that also contain co2. our goal is to achieve the highest h2s removal efficiency with the lowest alkali specificity as defined by the ratio of naoh and h2s expressed in moles. to find the parameters that support h2s removal several experiments were carried out in a custom-designed jet reactor (fig.1). owing to the construction of the reactor, the gas pressure, gas flow, alkali inlet flow, and alkali concentration were variable. all experiments were carried out at 30 bar total pressure. the absorbent was an aqueous naoh solution of different concentrations, such as 0.5, 1.5, and 2.5% (g/g). the model gas mixtures (table 2) were produced in an acid-proof gas mixing bridge. for the first set of samples the h2s content of the model gas mixtures was kept approximately constant; thus, the effect of co2 could be studied. for the last three samples, the co2 content was kept approximately constant; thus, the sensitivity of the process with regards to the variation of h2s concentration could be investigated. 3. results and analysis first, the effect of naoh concentration, naoh inlet flow, gas flow (residence time), and co2 concentration were investigated on the efficiency of h2s removal. 3.1. effect of residence time to observe the effect of residence time on the efficiency of h2s removal, the gas flow rate as a single parameter was varied. by increasing the gas flow rate, the residence time decreased. the gas flow rates were 3.9, 3.2, 2.4, and 1.6 n m3 h-1, which correspond to residence time rates of 0.05, 0.06, 0.09, and 0.13 s, respectively. fig.2 shows the effect of decreasing residence time. at a constant specific alkali value, the efficiency of h2s removal increased as a result of a decrease in residence time. furthermore, fig.2 also shows that the alkali specificity values decreased by raising the gas flow rate under a constant efficiency of h2s removal. 3.2. effect of naoh concentration the value of alkali specificity depends on the h2s content of the raw gas, the concentration and the flow rate of the absorbent. by increasing the concentration and the flow rate of the absorbent, the efficiency of h2s removal is increased. however, the efficiency could not be improved after a point by the absorbent concentration or flow rate, because the efficiency reached a nearly constant value while the alkali specificity continued to increase (fig.3). 3.3. effect of co2 concentration model gases of different co2 concentrations were used to study the effect of co2 concentration on the efficiency of h2s removal. the difference in h2s concentrations of model gases is a result of non-exact gas mixing, but this does not affect the comparability of the results. fig.4 shows that the efficiency of h2s removal is decreased by increasing co2 content. the competition between h2s and co2 in alkali absorbents is documented. figure 1. experimental device equipped with a 1. gas cylinder, 2. gas inlet, 3. alkali vessel, 4. chemical feeder pump, 5. alkali inlet, 6. reactor space, 7. nozzle, 8. separation space, 9. wastewater removal, 10. drop catcher, 11. outlet of purified gas, 12. gas sampling, and 13. gas analyzer. figure 2. effect of different residence times on the efficiency of h2s removal (gas mixture 4, 30 bar, 2.5% (g/g) naoh). table 2. composition of the tested model gas mixture samples. samples co2 % (m3/m3) h2s ppmv n2 % (m3/m3) 1 0 100 99.999 2 23 90 76.999 3 41 80 58.999 4 60 80 39.999 5 76 85 23.999 6 72 520 27.999 selective hydrogen sulphide removal 44(1) pp. 51–54 (2016) doi: 10.1515/hjic-2016-0006 53 3.4. effect of h2s concentration the influence of h2s concentration on the efficiency of h2s removal was investigated under a nearly constant co2 level (76 and 72% (m3/m3)) and greatly differing h2s (85 and 520 ppmv) containing model gases. when the 85 ppmv h2s containing gas was compared to the 520 ppmv h2s sample, the alkali specificity value measured was five times less (fig.5). on the other hand, fig.5 shows that the efficiency of h2s removal does not depend on the h2s concentration in this process. the alkali hydroxide absorbent technique shows little sensitivity to the changes in the h2s content of the inlet gas. 3.5. optimization of operational parameters based on the above-mentioned results, our aim was to find the optimal operational parameters for model gases of any composition in order to achieve an h2s removal efficiency of at least 50%, while applying the minimal amount of alkali specificity. this efficiency of h2s removal can be achieved by increasing the naoh concentration. a low alkali specificity value can be achieved by adopting a low residence time. as shown in table 3, when the co2 content is below 50% (m3/m3), 1.5% (g/g) naoh absorbent is enough to achieve an h2s removal efficiency of 50% in the given type of reactor at a pressure of 30 bar. a gas flow rate of 2.5 nm3 h-1 with a 0.08 s residence time is needed. when the co2 content is above 50% (m3/m3), 2.5% (g/g) naoh is necessary to achieve a removal efficiency of 50%. the applied gas flow rate needs to be 3.8 nm3 h-1 corresponding to 0.05 s residence time in the given type of reactor at a pressure of 30 bar. 4. discussion in this study, model gases with different h2s-co2-n2 contents were investigated in a custom-designed jet reactor. our aim was to achieve a h2s removal efficiency of at least 50% with minimal alkali consumption. the effect of the naoh, co2, and h2s concentrations, and the residence time on the efficiency of h2s removal was studied. during our experiments co2 absorption was not investigated because the dräger x-am 7000 analyser we used is only able to measure the co2 concentration in percent magnitude. a positive effect of low residence time on h2s removal was observed. by increasing the gas flow rate, the efficiency of h2s removal was increased under constant alkali specificity. if the efficiency of h2s removal is constant, the alkali specificity can be reduced by decreasing the residence time. by increasing the naoh concentration and flow rate, the efficiency of h2s removal was improved until a point after which it nearly remained constant while the alkali specificity was still rising. to study the effect of different co2 concentrations on the efficiency of h2s removal, several co2 concentrations were investigated under nearly the same h2s levels. the removal efficiency was reduced radically by increasing the co2 concentration. when comparing the model gases that contain different h2s concentrations, a reduction in the alkali specificity was observed. the alkali specificity value decreased as the h2s content increased. the removal efficiency remained constant irrespective of the h2s concentration of the model gases, which improves the efficiency of the alkali absorption process in terms of selective removal of h2s. figure 4. effect of different co2 concentrations on the efficiency of h2s removal (gas mixtures 0-5, 30 bar, 0.08 s residence time, 0.5% g/g naoh). figure 3. effect of different naoh concentrations on the efficiency of h2s removal (gas mixture 2, 30 bar, 0.2 s residence time). figure 5. effect of different h2s concentrations on the efficiency of h2s removal (gas mixtures 5-6, 30 bar, 0.09 s residence time, 1.5% (g/g) naoh). bobek, rippel-pethő, molnár, and bocsi hungarian journal of industry and chemistry 54 we observed that when the co2 concentration was less than 50% (m3/m3), a 1.5% (g/g) naoh concentration and 0.08 s residence time is necessary to achieve an h2s removal efficiency of 50% at a pressure of 30 bar under the given experimental conditions. when the co2 concentration was above 50% (m3/m3), we found that this is sufficient to provide a naoh concentration of 2.5% (g/g) over a residence time of 0.05 s at a pressure of 30 bar. based on our experiments a high efficiency of h2s selective removal can be achieved by naoh absorption. references [1] balogh, k.: sedimentology iii (akadémia kiadó, budapest, hungary), 1992 (in hungarian) [2] vágó, á.; rippel-pethő, d.; horváth, g.; tóth, i.; oláh, k.: removal of hydrogen sulphide from natural gas, a motor vehicle fuel, hung. j. ind. chem., 2011, 39(2) 283–287 [3] wu, y.; caroll, j.j.; zhu, w.: sour gas and related technologies (scrivener publishing llc, beverly, ma, usa) 2012 pp. xiv–xvii [4] kohl, a.l.; nielsen, r.b.: gas purification (gulf publishing company, houston, tx, usa) 1997 pp. 40–466 [5] tuba, j.: carburators (műszaki könyvkiadó, budapest, hungary), 1976 pp. 23–24 (in hungarian) table 3. the best operational parameters of the tested model gases at a pressure of 30 bar. co2 content, % (m3/m3) naoh concentration, % (g/g) alkali specificity, mol naoh (mol h2s)-1 h2s removal efficiency, % residence time, s gas flow rate, nm3 h-1 23 0.5 15 44 0.20 1.0 1.5 14 51 0.08 2.5 2.5 19 51 0.10 2.0 41 0.5 12 44 0.20 1.0 1.5 15 50 0.08 2.5 2.5 20 50 0.10 2.0 60 0.5 6 27 0.06 3.0 1.5 24 41 0.09 2.3 2.5 24 55 0.05 3.8 76 0.5 6 20 0.07 3.0 1.5 16 47 0.05 3.8 2.5 22 56 0.05 3.8 hungarian journal of industry and chemistry vol. 44(1) pp. 55–70 (2016) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2016-0007 hydrogen sulphide corrosion of carbon and stainless steel alloys immersed in mixtures of renewable fuel sources and tested under co-processing conditions andrás gergely,* 1 roland locskai,1 péter szabó,2 antal krójer,3 and tamás kristóf1 1 department of physical chemistry, institute of chemistry, university of pannonia, egyetem u. 10, veszprém, 8200, hungary 2 department of general and inorganic chemistry, institute of chemistry, university of pannonia, egyetem u. 10, veszprém, 8200, hungary 3 department of inspection and maintenance, mol co., olajmunkás u. 2, százhalombatta, 2443, hungary in accordance with modern regulations and directives, the use of renewable biomass materials as precursors for the production of fuels for transportation purposes is to be strictly followed. even though, there are problems related to processing, storage and handling in wide range of subsequent uses, since there must be a limit to the ratio of biofuels mixed with mineral raw materials. as a key factor with regards to these biomass sources pose a great risk of causing multiple forms of corrosion both to metallic and non-metallic structural materials. to assess the degree of corrosion risk to a variety of engineering alloys like low-carbon and stainless steels widely used as structural metals, this work is dedicated to investigating corrosion rates of economically reasonable engineering steel alloys in mixtures of raw gas oil and renewable biomass fuel sources under typical coprocessing conditions. to model a desulphurising refining process, corrosion tests were carried out with raw mineral gasoline and its mixture with used cooking oil and animal waste lard in relative quantities of 10% (g/g). co-processing was simulated by batch-reactor laboratory experiments. experiments were performed at temperatures between 200 and 300 ºc and a pressure in the gas phase of 90 bar containing 2% (m3/m3) hydrogen sulphide. the time span of individual tests were varied between 1 and 21 days so that we can conclude about changes in the reaction rates against time exposure of and extrapolate for longer periods of exposure. initial and integral corrosion rates were defined by a weight loss method on standard size of coupons of all sorts of steel alloys. corrosion rates of carbon steels indicated a linear increase with temperature and little variation with composition of the biomass fuel sources. apparent activation energies over the first 24-hour period remained moderate, varying between 35.5 and 50.3 kj mol-1. scales developed on carbon steels at higher temperatures were less susceptible to spall and detach. nonetheless, moderate deceleration of corrosion rates as a function of time are due to the less coherent, frequently spalling and low compactness, higher porosity of the scales evolved at lower and higher temperatures, respectively. on the surface of high alloy steels, sulphide scales of an enhanced barrier nature formed during the induction periods and the layer formation mechanism was found to be assisted by the increasing temperature as initial reaction rates considerably decreased over time. nevertheless, corrosion-related sulphide conversion of metals and mass loss of the high alloys are strongly affected by the composition of the biomass fuel sources especially animal waste lard. thermal activation in the first 24 hours decreased from 68.9 to 35.2 kj mol-1. a greater degree of failure to develop protective sulphide scales was experienced by changing to composition of the biomass fuel sources than the impact of thermal activation between a narrow temperature range at around 100 ºc. in accordance with the literature, high free fatty acid contents lead to high corrosion rates accounted for direct corrosion of high alloy steels and assisted solubilisation of corrosion products. in addition, the pronounced acceleration of sulphide corrosion is connected to the diminishing inhibition effect of the sulphide scales. keywords: hydrogen sulphide corrosion, gas phase corrosion, carbon and high alloy steels, renewable biofuels, used cooking oil, animal waste lard 1. introduction in an increasing power-hungry society coupled with the age of unprecedented global warming, the relevance of the substitution of fossil fuels from mineral sources and their mixtures with materials obtained from renewable biomass sources in the highest possible proportions is *correspondence: gergelyandras432@gmail.com one of the most urgent priorities for current and future generations to observe. sustainable biomass resources, vegetable oils, and waste lard are renewable feedstocks for partial substitution of mineral oils in production of biofuels. although their availability is limited at present, there are clear benefits of biofuel production, namely meeting local consumption demands, reduced emissions of greenhouse gases during transportation over long distances in supply chains. in addition, the lower dependence on fossil fuels unequivocally contributes to increased national security. by 2010, the gergely, locskai, szabó, krójer, and kristóf hungarian journal of industry and chemistry 56 european commission set a goal that eu biofuels must account for 5.75% of transportation fuels. biodiesel as a mono-alkyl ester of vegetable oils and waste lard [1-3] is distinguished from second-generation type renewable feedstocks of inedible oils and algae. using vegetable oils, composed of a majority of natural triacylglycerols in similar to waste lard, biodiesel production involves processing by either trans-esterification with methanol or ethanol besides production of glycerol or catalytic hydrocracking. the latter is an economically more feasible option given the absence of investment costs [4, 5] as no dedicated facility is required [6]. cracking, pyrolysis, catalytic hydrodesulphurisation (hds), deoxygenation [7], and the saturation of olefins and aromatics favour the production of ultra-low sulphur petrodiesel [8, 9]. the fuel derived from lipid feedstock of biological sources emulating the composition of petro-diesel is renewable diesel. several crops such as rapeseed, soybean, palm, sunflower, etc. are excellent renewable oil sources recycled for energy storage and production lines, currently maize is the most frequently used feedstock for biofuel production primarily due to its high profitability. however, when the profit margin is a priority, used cooking oil trumps virgin vegetable oils, since it is around three times cheaper. as for the chemical stability aspects, fossil fuels containing methyl esters of fatty acids are less oxidation-resistant and more hygroscopic, so their long-term storage is not recommended. to process biomass in conventional oil refineries, vegetable oil and vacuum gas oil mixtures are preferred for quality diesel production [10, 11] as hydrotreating the latter along with heavy gas oil results in normal alkanes of c15-c18 [12]. moderate reaction temperatures yield diesel, while higher temperatures lead to gasoline production. technological parameters of hydroprocessing under mild conditions [13] generally mean temperatures of 320–430 ºc and pressures of 3.5– 5.5 mpa with a relative quantity of the biomass source of ~5.5%. high isoparaffin content is obtained by catalytic hydrogenation of triglycerides stemming from waste lard [14]. nevertheless, there are vegetable oils (tall oil) that have high fatty acid contents [15-19] similar to waste lard. if they are not processed properly, they will be corrosive in nature in subsequent applications. their conversion to liquid hydrocarbons by catalytic hydrocracking seems a viable option. nevertheless, aside from indispensable processes relating to biomass-based fuel production, all sorts of sources including biofuels are to be refined to decrease heteroatom content, such as sulphur, nitrogen and phosphorous, which might be potential sources of pollutants. to preserve safety and profitability one should consider possible corrosion risks of coprocessing of renewable fuel sources to metallic structures from which equipment of existing petroleum refineries has been built and used for decades. industrial methods and technological means to protect oil production equipment were reviewed in terms of corrosion protection [20]. in relation to highly corrosive effects caused by waste lard, it depends on the quantity and composition of free fatty acids as a way of dissolution of metal-acid complexes coupled with reduction of a depolarisator. some fatty acids, such as stearic, palmitic, myristic and lauric acid, are even used for heat storage systems and their corrosivity is enhanced by thermal cycling [21]. acceptable resistance of the 304l stainless steel (1.4307) and an aluminium alloy with passive oxide layers on their surfaces was pointed out. the kinetics of naphthenic acid and sulphide corrosion and their interactions with q235 and 5cr1/2mo steel alloys were investigated at 270 ºc in oil with naphthenic acid and sulphur contents of up to 1.0% (g/g) as synthetic refining media [22]. in the liquid phase with naphthenic acids at 230 ºc, the low alloy and carbon steels indicate nearly the same naphthenic corrosion rates but above 230 ºc the former gave higher rates. this is attributed to its higher activation energy (63 kj mol-1) compared to that of carbon steel (54 kj mol-1) leading to greater acceleration with increasing temperature. in dimethyl disulphide containing oil, sulphide corrosion follows parabolic kinetics. film growth was faster on carbon steel than on low alloy steel. in oil containing naphthenic acids and dimethyl disulphide, low alloy steel showed lower corrosion rates than carbon steel; thus, sulphide corrosion proved to be rate-governed by pseudo-passive films. different resistance of the alloys was connected to the chromium sulphide (cr5s8) in the pseudo-passive film formed on low alloy steel, in contrast with pyrrhotite (fe7s8) and troilite (fes) films obtained on carbon steel. at oil refineries, especially in the hds streamline part, the rate of metal loss either in the form of general or local corrosion is one of the highest. thus, to achieve an optimal balance between production, inspection and maintenance careful planning is required. aside from works on corrosion risks of biofuels at low temperatures without the presence of hydrogen sulphide rather for the automotive than refining industry, to our best knowledge, there is a rather limited number of studies in the literature to date, giving insights into either the corrosion rates of engineering alloys or the integrity risk assessment of plant equipment regarding the hds co-processing of renewable fuel sources such as used cooking oil and waste lard in low proportion mixtures with raw gas oils in refining plants originally designed to withstand mineral oils. therefore, the aim of this work is to investigate corrosion rates of inexpensive engineering alloys, two types of carbon steels (1.0425 and st35.8) and a low alloy steel sample (1.7335), which are all basic materials of heat-resistant tube and pipe systems. in addition, for the purpose of making a comparison, as structural materials of absorbers, strippers, and overlays in reactors, three high alloy steel samples (1.4541, 1.4571, 1.4401) were selected for hydrogen sulphide corrosion, tested at a pressure of 90 bar and temperatures between 200 and 300 ºc. under the aforementioned parameters, hydrogen sulphide and naphthenic acid corrosion of steel alloys are investigated focusing on the dependence of corrosion rates on temperature and time. sulphide corrosion of steel alloys immersed in renewable biomass sources 44(1) pp. 55–70 (2016) doi: 10.1515/hjic-2016-0007 57 2. experimental in processing technology before the hydrotreating reactor is heated to ~420 ºc, generally the high proportions of unsaturated and saturated free fatty acids cause the main corrosion problem, after that hydrogen sulphide is usually responsible for most of the corrosion risks. therefore, experiments were planned to satisfy the goals of investigating the corrosion rates of engineering steel alloys representative of materials in hds plants caused by the evolution of hydrogen sulphide during processes, combined with the increased risks exerted by the mixture of used cooking oils and animal fats that should all be co-processed in the same plant altogether under the same conditions. batch type experiments were carried out in two reactors with a wall thickness of 25 mm (manufactured by lampart vegyipari gépgyár zrt) having internal sizes of 2 and 4 litres. the temperature was measured inside the reactors through a stainless steel tube casing leading from the head into the core of the inner volume, with platinum100 resistive thermometers and adjusted with haga kd481dd controllers within ±6 ºc after auto-tuning refining with liquidand gas-filled reactors at pressure targets. heating of the reactors was performed with 6 resistance-heating wires, which were evenly distributed around the encasings wrapped in a 4 cm thick thermo-insulation layer of glass wool lined inside steel scaffolds. the apparent effective performance of the heating systems with power consumptions of 3.7 and 6 kw at 3*380 v and drew currents of 4.5 and 7.2 a to the small and large reactors, respectively. heat ramp and cooling down phases of batch-type experiments were carried out as rapidly as possible especially in the cases of the 24and 72-hour tests. fast temperature ramp ups were achieved by providing the highest laboratory temperature and the close location of the nearby working reactor to utilise its dissipated heat (initial pressure was corrected for fillups). during cooling down phases at the end of corrosion tests, reactor encasings were removed from scaffolds. the inside pressure was slowly reduced by letting the gas slowly out of the reactor through pressure valves so that gas phase reactions were frozen within the shortest possible period. the time when the temperature decreased to 200 ºc and/or the gas pressure dropped to at least 70% of its initial target was regarded as the end time of reactor experiments. short stainless steel tubes (outerand inner-diameters of 6 and 4 mm) were employed for fill-ups and long ones for the evacuation of reactor gases. for safety reasons, used reactor gases still containing about 2% (m3/m3) hydrogen sulphide were led over several steps through erlenmeyer flasks containing an aqueous solution of sodium bicarbonate with a moderately high ph to work as alkaline absorbers. coupons of steel alloys of a standard size (32 mm outerand 10.5 mm inner-diameters with a thickness of 2 mm) were used for the experiments. all coupons were grated and polished with silicon carbide emery papers (#400 and #600) soaked in water to remove rust and stain spots. then they were ultrasonicated twice for 5 minutes in isopropanol and acetone. the cleaning process obeyed and adapted principles of the astm g1 standard (‘standard practice for preparing, cleaning, and evaluating corrosion test specimens’). after drying, mass of the coupons was measured with an analytical balance. compositions of the investigated steel alloys are summarised in table 1. with proper engravings, coupons were assembled on glass rods, each with annular glass cylinders (8 mm long) for proper spacing. then glass rods with steel alloys were inserted into large glass tubes holding the media of raw or refined gas oil and its mixture with used cooking oil (uco in 10% (g/g)) or waste lard (wl in 10% (g/g)). the composition of gas oil and renewable sources, supplied by the department of analytics and the institute of biotechnology, and bay zoltán non-profit ltd. for applied research, are summarised in table 2. animal waste lard was one of the most corrosive types available in the region owing to its high free fatty acid content. all materials were supplied by mol co., hungary. glass tubes accommodated five coupons (parallel samples) four times (according to the four different chemical compositions of steel alloys). when integral corrosion rates were defined for a time period by weight loss measurements, the standard deviation was also assessed by the 5 parallel specimens. error bars in figures based on gathered data are directly related to the standard deviation of population samples of the experiments obtained by five coupons in one autoclave test. the level of the fluids was set well above the upper coupons. to minimize loss of the fluids owing to evaporation especially around 300 ºc despite the high pressure, inner and outer glass caps were employed for each glass tube. glass caps with an appropriate figure did not hinder efficient gas diffusion into sample holder glass tubes, ensuring good access to the fluids and steel coupons. table 1. chemical compositions of autoclave experiment-tested steel alloys in weight percent (fe in balance). alloys c cu si p s mn cr ni mo n ti 1.0425 ≤0.20 ≤0.30 ≤0.40 ≤0.025 ≤0.015 ≤0.80-1.40 ≤0.30 ≤0.30 ≤0.08 ≤0.012 ≤0.03 st35.8 0.10-0.35 ≤0.04 ≤0.04 0.40-0.80 1.7335 ≤0.08-0.18 ≤0.30 ≤0.35 ≤0.025 ≤0.01 0.4-1.0 0.70-1.15 0.5 0.012 1.4541 ≤0.06 ≤0.75 ≤0.04 ≤0.015 ≤2.0 17.0-19.0 9.0-11.0 5*c-0.70 1.4571 ≤0.08 ≤1.0 ≤0.045 ≤0.015 ≤2.0 16.5-18.5 10.5-13.5 2.5 5*c≤0.70 1.4401 ≤0.07 ≤1.0 ≤0.045 ≤0.03 ≤2.0 16.5-18.5 10.0-13.0 2.5 ≤0.1 gergely, locskai, szabó, krójer, and kristóf hungarian journal of industry and chemistry 58 for the experiments, bottled hydrogen gas (2.5ip, with a purity of 99.5%) with an initial pressure of 150 bar (provided by messer hungarogáz kft.) was used as received to fill up reactors at around room temperature (or the temperature when the experiment started). initial fill-up pressures were calculated according to the pressure of hydrogen refining at the target temperature according to the p-v-t database [23]. there were pressure increments almost in all experiments, which were caused by the varying volatility of raw and refining gas oil phases. hence real pressure of reactor gas phases was recorded during the experiments. the mixtures of gas oil and used cooking oil or animal fats were not so volatile as pure gas oil so pressure increases were less pronounced with those materials. at the time of filling up, the gas pressure inside the reactors was measured both by a reductor (200/200, supplied by messer hungarogáz kft.) and pressure gauges (merrkfm prlt s91, pressure measuring was calibrated before and after experiments) nested in reactor heads. for practical and safety reasons, hydrogen sulphide of stoichiometric quantity was in situ produced from elemental sulphur. the quantity of hydrogen sulphide was calculated to be ~2 percent by volume in all autoclave experiments at the target pressure, but the overall pressure was greater because of the changing volatility of the organic fluid phases. thus, the pressure in autoclave experiments was higher than the hydrogen table 2. basic characteristics of the renewable biomass fuel sources and distillation data of raw gas oil. fuel source distillation data of raw gas oil used cooking oil animal waste lard boiling point of fractions proportion of fractions organic acids (c1-c4, mg kg-1) 136.4 initial citric acid 1.90 187.2 5 lactic acid 32.69 197.3 10 formic acid 8.46 214.1 20 acetic acid 64.43 94.13 227.6 30 isobutyric acid 0.00 30.83 241.8 40 butyric acid 27.69 175.58 258.2 50 organic acids (c8-c20, mg kg-1) 274.2 60 caprylic acid 1 1.5 291.5 70 capric acid 1 310.9 80 lauric acid 2 1 331.9 90 myristic acid 3 11 347.3 95 palmitoleic acid 2.5 18 recovery 96.7 heptadecanoic acid 3.5 residue 1.5 γ-linoleic acid 0.6 5 loss 1.8 arachidic acid 3.5 gondoic acid 7.5 nervonic acid 1 palmitic acid 100 165 stearic acid 25 95 oleic acid 285 310 linoleic acid 190 65 extractable petroleum hydrocarbons (c10-c40, mg kg-1) c36 1.15 0.30 c37 0.10 c38 0.15 0.24 c39 0.12 iodine number (10-2 mg g-1) 96 65 total acid number (koh mg g-1) 6 74 alcohol components (mg kg-1) glycerol 7014.05 methanol 100.33 ethanol 11.12 6.35 water content (mg kg-1) 611 1171 metals & other elements as impurities al 0.02 0.016 fe 0.001 0.004 na 0.005 0.740 p 0.021 s 0.038 k 0.021 ca 0.036 amino acids (in % g/g) -less than 0.3 sulphide corrosion of steel alloys immersed in renewable biomass sources 44(1) pp. 55–70 (2016) doi: 10.1515/hjic-2016-0007 59 sulphide contents would have been lower with a maximum of 15%, but stoichiometric quantities were initially set with an excess of 10% in the experiments so the concentration of 2% (m3/m3) was considered to be assured. before the series of autoclave experiments, blind tests were performed to validate the proportion of hydrogen sulphide of the gas phase (2 volume percent) after an induction time of one hour at a temperature of 250 ºc and at least 40 bar of pressure. the reactor gas was diluted by 100 times with a nitrogen stream then the mixture was entrained into a draeger x-am 5600 h2s detector to validate the hydrogen sulphide contents of the reactors. after continuous decompression at the end of the autoclave experiments, reactor heads were removed then glass tube holders (made of stainless steel) with the fluid and steel samples were gathered. depending on the kind of alloy, the heavy oil and greasy residue of steel coupons were removed with paper towels then purification was performed three times for 10 minutes each using ultrasonication to eliminate traces of organic phases. sulphide corrosion scale was removed by careful polishing, while continuously monitoring the surface for intact metallic steel. the use of clark’s solution was attempted to use but it proved to be inefficient in cleaning metal sulphides first rather than attacking some of the remaining metallic parts of steel coupons near the surface. the masses of the coupons were measured on the same analytical balance as before the tests then by relying on the weight loss method corrosion rates were assessed for the measured periods. in almost all experiments, high mass changes were obtained with low relative variance of data. corrosion tested coupons were not investigated for internal penetration forms of corrosion products deep inside the bulk lattice and the corrosion of grain boundaries, only external corrosion scale products were analysed. although the temperature highly impacts the efficiency of hydroprocessing of biomass sources and composition of diesel fuels [24] at the proposed target temperature of 420 ºc and pressure of 100 bar to reproduce original conditions, severe limitations were faced because of the rapid coke formation from the mixture of raw gas oil with used cooking oil and animal fat, yield complete conversion within less than 24 hours. this made it impossible to carry out experiments at such a high temperature. therefore, the temperature rage had to be compromised and balanced with the dwelling time of the samples. then, all experiments could be carried out without any noticeable loss of the organic fluid phase caused by evaporation or cock deposition. 2.1. x-ray diffraction after reactor testing, spalled layers were crushed. the powdered and low adhering sulphide scales were scrubbed, gathered, and purified twice over 10 minutes each using ultrasonication in isopropanol. xrd analysis was performed using a philips pw 3710 type powder diffractometer equipped with a pw 3020 vertical goniometer and curved graphite diffracted beam monochromator. the radiation applied was cukα from a broad-focus cu tube, operating at 50 kv and 40 ma. samples were measured in a continuous scan mode with a 0.02° s-1 scanning rate. data collections and evaluations were carried out with x’pert data collector and x’pert high score plus software. 2.2. scanning electron microscopy and energy dispersive spectroscopy at the end of reactor testing, steel coupons containing multiple layers of low-adhering sulphide scales and powders gathered from removed surface scales were purified twice over 10 minutes each using ultrasonication in isopropanol. the morphology of corroded steel coupons was measured with a scanning electron microscope (sem, philips xl31 esem) in the secondary electron mode with an accelerating voltage of 20 kv and recording images produced by back-scattered electrons, as well. for rough elemental analysis, energydispersive x-ray spectroscopy (eds) was also carried out. 2.3. micro-raman spectroscopy after gathering the metal coupons from fuel mixtures and removing the traces of organic phases twice of over 5 minutes each using ultrasonication both in isopropanol and acetone, sulphide scales were probed five times at different spots on the surface. raman measurements were performed at atmospheric pressure and gas composition. a bruker senterra raman microscope was used to analyse samples. the source was a green semiconductor laser with a diameter of 532 nm and a maximum power of 10 mw. for the microscope, a 10x objective was used. raman signals were collected with a thermoelectrically-cooled charge-coupled device detector and recorded for typically 15 scans. the typical integration time to record raman spectra was 15 s on average with a spectral resolution of 4 cm-1. 3. results and analysis 3.1. reactor experiments temperature dependence of the corrosion rates of steel alloys immersed in raw gas oil and its mixtures with renewable biomass sources are presented in fig.1. over a narrow temperature range of 100 ºc, the 1.0425 carbon steel indicated saturation of sulphidation rates at 275 ºc in all organic fluids. corrosion rates in raw gas oil at 300 ºc remained similarly high but in used cooking oil and waste lard mixtures decreased beyond a random scatter of data. the st35.8 carbon steel indicated a similar trend. in case of the 1.7335 carbon steel, the highest corrosion rates were obtained with almost linear relationship between the reaction rate and temperature. reaction rates over the entire temperature range were the least affected by the types of organic fluids. as expected, the 1.4541 high alloy steel gave the gergely, locskai, szabó, krójer, and kristóf hungarian journal of industry and chemistry 60 lowest sulphidation rates in all experiments. the higher corrosion resistance of this alloy is well reflected by the almost levelled rates up to 225 ºc, although its markedly different behaviour can be observed by the steeply increasing sulphidation rates above 250 ºc. this temperature range is associated with the evolution of adherent sulphide scale in appreciable amounts. the special behaviour of this alloy is also underscored by the high sensitivity to composition of the organic phase, i.e. waste lard, showing various corrosion rates even around 200 ºc which remained decisive over the entire temperature range. corrosion rates were heavily dependent on fluid phase composition with biomass sources mixed in 10% (g/g) than on variation of the temperature up to 250 ºc. generally, sulphidation rates of metals should be similarly more temperature dependent than hydrotreating and desulphurising conversion of the hydrocarbons [25]. in addition, according to the literature, corrosion rates of the 18/8 stainless steels are 10–50 μm year-1 between 250 and 300 ºc in the presence of hydrogen sulphide at 2% (m3/m3). in our case, carbon steels indicated much greater sulphidation rates than the advisable as maximum of 0.25 mm year-1, which should be acceptable up to 390 ºc under a pressure of 34 atm with 10% (m3/m3) of hydrogen sulphide [26]. logarithmic corrosion rates as a function of reciprocal absolute temperature were used to evaluate thermodynamic activation. as results over a short timescale characterise thermodynamics of the sulphide corroding alloys immersed in various organic fluid phases, long-term results are much more dependent on inherent kinetic controls such as barrier effect of the scales. therefore, reaction rates were both evaluated over the first 24 h and the entire 504 h periods. estimated activation energies are assumed to be closely related to the overall free energy change of the reactions, as presented in tables 3 and 4. over a short time period, the highest activation energy of the 1.4541 was ascertained to be in raw gas oil and its mixture with used cooking oil. nevertheless, about half of the energy was required for the activation in the waste lard mixture of gas oil. this tendency was found to be reversed over long periods when activation was the lowest in gas oil and the highest in the waste lard mixture. this result might only be interpreted as acid corrosion of the 1.4541 taking place over short time periods and sulphidic corrosion occurring over longer periods in parallel with the hydrodesulphurisation gas oil. adsorption of the fluid phase components and dissolution of the ionized metals are probably inhibited by the firm and adherent sulphide scales. the 1.0425 and st35.8 carbon steels indicated lower activation energies in the short term almost independent of the composition of the organic fluid phase, although the st35.8 might yield some increase with the presence of biomass sources. over longer periods, except for the st35.8 in gas oil, lower activation with regards to sulphide corrosion manifested, which leads to the recognition that corrosion of these alloys is primarily governed by the hydrogen sulphide. furthermore, if activation of the interfacial reactions changes it almost certainly decreases over time, which is anticipated in many metal sulphide forming reactions. the 1.7335 low alloy experienced high reaction rates featuring low thermal activation irrespective of the nature of the organic phase and time exposure. similarly to carbon steels, activation tends to decrease over time, suggesting a catalysed reaction by the scales of precipitating corrosion products, which were porous, susceptible to spalling and semiconductors. this behaviour reveals an insignificant difference between the rates of sulphidic and acidic corrosion, whereas an inefficient barrier effect of the sulphide scale. in short term experiments, figure 1. integral corrosion rates over 504 hours of test period (as a function of temperature) of steel alloys immersed in raw gas oil (go) and its mixtures with used cooking oil (uco) and animal waste lard (awl) at an overall pressure of 90 bar in the presence of 2% (m3/m3) hydrogen sulphide, as well as the integral corrosion rates for test periods of 24 hours for the alloys of (b) 1.0425, (c) st35.8, (d) 1.7335, and (e) 1.4541. table 4. temperature dependence of logarithmic integral corrosion rates (in mm m-2 year-1) expressed in activation energies (δ!!⋕ in kj mol-1) of steel alloys over 21 days. all other parameters are the same as detailed in table 2. steel alloys in organic fluids raw go go-uco go-wl δ!!⋕ δ!!⋕ δ!!⋕ 1.0425 30.5 41.1 36.7 st35.8 78.8 46.5 43.1 1.7335 30.3 30.3 33.3 1.4541 30.3 41.6 53.3 table 3. temperature dependence of logarithmic corrosion rates of steel alloys (in mol m2 s-1) expressed in activation energies (δ!!⋕ in kj mol-1) over the first 24 hours tested at a pressure of 90 bar in the presence of 2% (m3/m3) hydrogen sulphide. steel alloys in organic fluids raw go go-uco go-wl δ!!⋕ δ!!⋕ δ!!⋕ 1.0425 50.3 45.8 52.0 st35.8 45.4 53.3 63.1 1.7335 35.5 31.0 45.6 1.4541 68.9 67.8 35.2 sulphide corrosion of steel alloys immersed in renewable biomass sources 44(1) pp. 55–70 (2016) doi: 10.1515/hjic-2016-0007 61 higher activation energy of the 1.4541 for sulphide corrosion is due to the formation of metal sulphides with the chromium and nickel alloying elements. in contrast, over long time exposures the lower activation energy barrier is partly related to the increased thermodynamic preference in complete balance of the reaction between hydrogen sulphide and iron [27]. furthermore, the activation of surface processes such as adsorption and dissociation is more attributed to a less preferable free energy balance increasing with the organic materials of used cooking oil and animal fat having a greater absorption abilities. in this regard, the 1.4541 high alloy steel proved to be more sensitive exhibiting more than 2 orders of magnitude changes depending on composition of the organic phase, rather than that of carbon steel alloys indicating changes within a magnitude of 3 times or less. consequently, the reaction mechanism leading to sulphide corrosion should partly be impacted by adsorption and accelerated by saturated free fatty acids composing a considerable proportion of waste lard. moreover, the increasing temperature is known to play a vital role in governing the mechanism of naphthenic acid corrosion either by chemical or electrochemical mechanisms [28]. the latter is more dependent on thermal activation as a greater rate of dissociation of the weak acids occurs at elevated temperatures [29]. electrochemical acceleration may lead to local corrosion and pit formation, whereas chemical naphthenic acid corrosion at lower temperatures results in general processes. pearlite as an interpenetrating bicrystal phase composed of ferrite and cementite in plain carbon steels is a relatively good cathodic area due to the effective depolarisation for hydrogen ion discharge [23]. in our case, selective corrosion like pitting on specimens of the steel alloys was not observed as a function of temperature between 200 and 300 ºc except for the 1.0425 carbon steel exhibiting pitting corrosion of metal lattice regardless of the organic fluid phase. process of the latter must be governed by the hydrogen sulphide which with its increasing concentration after a threshold enhances the rate of local process around metal crystal boundaries and sulphide inclusions. as a blind experiment to probe the effects of an hds plant using a batch reactor experiment, alloys were tested under the same conditions as for temperature dependence at 250 ºc and the results are presented in fig.2 and table 5. the corrosion rates of carbon steels (1.0425, st35.8 and 1.7335) were greater with low variances of data compared to the ones measured for the 1.4541, 1.4571 and 1.4401 high alloy steels that exhibited reaction rates an order of magnitude lower with high variances, except for the 1.4541. thus, the firm corrosion resistivity of the 1.4541 alloy was observed, which is primarily connected to its high chromium [30] and moderate nickel contents and the absence of molybdenum. nickel and molybdenum are of high and moderate concentrations in tested steel alloys causing somewhat decreasing sulphation resistance [31, 32]. furthermore, from the results of an independent experiment, a less favourable activation of metal sulphide formation is suspected due to the inefficient adsorption and dissociation of hydrogen sulphide from the gas phase besides the absence of dissolved small molecule acids in the fluid phase. thus, corrosion rates of steel alloys might be the least affected by the adsorption of species from the organic phase only the gaseous phase, such as hydrogen and rather the hydrogen sulphide. the difference between the medium sulphidation resistivity of the 1.4571 and 1.4401 high alloy steels at low temperatures can be explained. on the other hand, by comparing the results of the blind experiment with that obtained in raw gas oil, the corrosion rates were roughly the same or somewhat greater, since the refining of the raw gas oil and the desulphurisation of the raw gas oil content should not have a notable effect on the resistivity of investigated alloys and their observed corrosion rates at least up to 250 ºc. the timespan, over which parabolic corrosion rates appear after a short term linear reaction rate decrease in the induction period is related to development of thick sulphide scales. therefore, the time dependence of integral corrosion rates is presented in figs.3a-3d. the 1.0425 and st35.8 carbon steels indicated parabolic or even more intense decay of corrosion rates over time periods above 250 ºc in all organic fluids but especially in waste lard mixture (figs.3a and 3b). the only exception was the st35.8 at 275 ºc that exhibited a less pronounced decay of sulphidation rates over time. this figure 2. corrosion rate of steel alloys immersed in refined gas oil tested in a blind experiment for 504 hours at a pressure of 90 bar and temperature of 250 ºc in the presence of 2% (m3/m3) hydrogen sulphide. table 5. general corrosion rates of steel alloys (in mm year-1) immersed in raw and refined gas oils, tested at 250oc over 21 days under a pressure of 90 bar in the presence of 2% (m3/m3) hydrogen sulphide. steel alloys raw gas oil refined gas oil 1.0425 0.10 – 0.50 0.55 st35.8 0.10 – 0.50 0.60 1.7335 0.30 – 1.00 0.55 1.4541 0.01 – 0.10 0.05 1.4401 0.10 1.4571 0.10 gergely, locskai, szabó, krójer, and kristóf hungarian journal of industry and chemistry 62 may be attributed to the partially incorrect experimental data owing to the lack of a large number of samples and parallel experiments to provide a more reliable prediction of the most probable corrosion rates with the least scattering of the mean values as possible. below 250 ºc, a less remarkable decay of reaction rates was ascertained for both metals. the 1.7335 low and 1.4541 high alloys exhibited moderately intense parabolic figure 3. integral sulphide corrosion rates of steel alloys over time at various temperatures: (a) 1.0425, (b) st35.8(a38), (c) 1.7335, (d) 1.4541, parameters as defined in fig.1. figure 4. gradients (in terms of absolute value) of logarithms of integral corrosion rates over 21 days in raw gas oil (go) and its mixtures with used cooking oil (uco) and waste lard (wl) as a function of temperature: (a) 1.0425, (b) st35.8, (c) 1.7335, (d) 1.4541, parameters as defined in fig.1. sulphide corrosion of steel alloys immersed in renewable biomass sources 44(1) pp. 55–70 (2016) doi: 10.1515/hjic-2016-0007 63 decreases of reaction rates over time. nevertheless, the gradients of decay of the reaction rates were lower (greater in absolute value) at higher temperatures than quadratic rate decreases at and under 250 ºc as a function of time (figs.3c and 3). the 1.7335 yielded gave almost constant corrosion rates at 250 ºc between 3 and 21 days of exposure (fig.3c). its induction period seemed to be restrained to the first 24 h term in the mixture of used cooking oil. the 1.4541 steel experienced the lowest corrosion rates in the used cooking oil mixture over the parameter space (fig.3d), which exhibited a rather linear dependence as a function of temperature. overall, all steel alloys indicated the most severe corrosion-type integrity loss in the waste lard mixture of gas oil. the absolute values of the gradients obtained by linear fitting to the logarithms of the integral corrosion rates measured over 21 days is presented in figs.4a-4d. sulphidation rates of the 1.0425 and st35.8 carbon steels exhibited the highest temperature dependence in the waste lard mixture (a 5 times increase), whereas the lower gradients probably indicate that a less sensitive thermal activation occurs in raw gas oil and the used cooking oil mixture (enhanced by around 3 times, figs.4a and 4b). as for the 1.7335 low and the 1.4541 high alloy steels, the low and the lowest gradients with restrained enhancement of around two times were obtained as a function of temperature (figs.4c and 4d). this signifies a less pivotal role of thermal activation in the interfacial sulphidic corrosion of the latter two alloys but in all cases waste lard was the fluid phase that was proven to be the most susceptible to open thermally-allowed reaction mechanism leading in some cases to the highest corrosion rates by far. among all steels, only the 1.4541 exhibited low thermal rate dependence in used cooking oil compared to the results obtained in other phases. as a general impression, either the most intense dependence of thermal activation on sulphidation or the highest magnitudes of reaction rates occurred in the waste lard mixture of gas oil. thus, not only sulphidation takes place by the hydrogen sulphide, but also acidic corrosion occurs and competes with the former at a rate of the latter becoming higher by increasing temperatures. this finding may also point out that the contributing role of free fatty acids in parts of the corrosion processes could be adsorption of mercapto compounds assisted by possible chelating effect and thermally favoured dissociation of the anchoring functional groups. the greater oxidation ability of the organic compounds than hydrogen sulphide, and their more positive redox potentials are due to their stronger electron withdrawing ability boosted by conjugated electron systems of various extents. the desorption of corrosion products is promoted by the proper dissolution of metal ions with lipophilic complexes, and diffusion through porous, cracked or spalled scales, allowing a less hindered access of the steel surface to the species taking part in subsequent processes. in the case of the exclusive hydrogen sulphide corrosion, effective desorption and diffusion from the surface can only be realised by high porosity, cracking or spalling, and failure of the scales as observed with many of the carbon and low alloy steels but it should not happen to high alloy steels developing quasi-passivating, coherent and adherent sulphide scales. in the latter case, fluid phases with improved wettability based on the closer surface energy of the solid phases and tension of the fluid phases compared to that of the raw gas oil and steel combination is beneficial as less hindered interfacial reactions result. 3.2. x-ray diffraction in fig.5a, diffraction pattern of troilite, a 1:1 stoichiometric ratio of iron sulphide (fes) was identified on the whole in the powder of the spalled scales of the 1.0425 steel tested in raw gas oil at 250 ºc. low crystallinity metallic iron fe(0) with high magnetic susceptibility formed the majority of the rest phase. figure 5. xrd patterns of the (a) 1.0425 carbon steel immersed in raw gas oil and (b) refined gas oil tested at 250 ºc, (c) 1.7335 low alloy steel immersed in a gas oil mixture with waste lard (10% g/g) tested at 300 ºc, all for 21 days at a pressure of 90 bar. gergely, locskai, szabó, krójer, and kristóf hungarian journal of industry and chemistry 64 because typical high intensity reflections at 2θ values of 12º, 15º, and 19º [33] and 40º, 50º, and 59º [34] were not measured, the low intensity reflections gained at 2θ values of 17.5º and 30º might not be connected to mackinawite. the absence of its phase in metal sulphides in the long-term tested samples is attributed to its formation during the early reaction phase and rapid transformation to more stable pyrrhotite, the sub-phase of troilite. the reflections together at 2θ values of 30º and 53º may not be related to greigite as its stability region is above the h+/h2 equilibrium line. troilite is more stable in weakly acidic aqueous solutions under reducing conditions, i.e. below the h+/h2 equilibrium line [35]. the intense reflection at 2θ value of 44º cannot unanimously be attributed to pyrrhotite [36], as it undoubtedly overlaps with one of the main reflections of polycrystalline iron [37]. in fig.7b, a different diffraction pattern of the corrosion scale can be identified by the varied intensity ratios of reflections at 43º and 53º. this is due to a composition change of the scale leading to metallic iron fe0 and crystalline troilite formation (fes) in molar ratio of about a 2:1. thus, a considerable amount of metallic iron segregated over the course of high rates of sulphide corrosion, but its amorphous phase did not result in its conversion to sulphide by either hydrogen sulphide or naphthenic acids in refined gas oil subjected to testing over 21 days at 250 ºc and 90 bar. as expected, long-term medium temperature exposure resulted in high sulphide conversion of metallic iron and the formation of iron sulphide crystals in raw gas oil of a high sulphur content. on the other hand, roughly the same reaction rates resulted in the evolution of a similar amount of sulphide scales in refined gas oil, which proved to be more brittle. thus, high proportions of the scale detached and rapid disintegration of the metallic phase occurred, resulting in corrosion products with far lower ratio of the elements than stoichiometry. the lower sulphur content of the refined (hydrodesulphurised) gas oil is accountable for this finding because of the lower plasticity of the more compact sulphide scale. an xrd investigation of the sulphide scale formed on the 1.7335 low alloy steel coupons yielded a similar diffraction pattern (fig.5c) to that of the 1.0425 carbon steel (fig.5b) tested under the same conditions. nevertheless, in this case the massive amount of highly porous corrosion scale formed with a low spalling ability (high coherence and adherence) should mean less frequent occasions of the surface to renew by spalling or detachment resulting in further hydrogen sulphide attack but lower diffusion hindrance to accessing the metallic surface by sulphide species. 3.3. sem and edx analyses morphology of the sulphide scales gathered from the bottom of the glass tubes and removed from the surface of the 1.0425 carbon steel specimens is presented in table 6. sem-eds composition (in atomic %) of the corrosion product of sulphide corrosion scales removed from the surface of carbon steel coupons (1.0425) immersed in raw gas oil tested at a temperature of 250 °c and pressure of 90 bar. elements spot 1 spot 2 c (k) 0.00 6.95 o (k) 6.02 7.42 si (k) 0.00 0.38 s (k) 36.58 35.77 mn (k) 1.06 1.02 fe (k) 56.33 48.00 figure 6. sem image of (a) the powdered form of sulphide scale removed from the surface of the 1.0425 carbon steel coupons immersed in raw gas oil and tested at a temperature of 250 ºc and pressure of 90 bar; (b and c) the elemental composition of the scale removed from surface of the coupons obtained by eds analysis of spots 1 and 2 marked by arrows, respectively. sulphide corrosion of steel alloys immersed in renewable biomass sources 44(1) pp. 55–70 (2016) doi: 10.1515/hjic-2016-0007 65 fig.6a. the multiple layers of sulphide scale were moderately easy to detach, brittle, and highly porous. spalled and detached scales were of a lateral size of about 500 μm and a thickness of 40 μm. the spots of 1 and 2 (arrowed in the image) were analysed to identify the elemental composition of the scale and the semeds results (figs.6b and 6c) is presented in table 6. the molar ratios of the iron sulphide (surmised to be 1:1 stoichiometric ratio of fes) and metallic iron (fe0) were 3:1 and 1.8:1 at spots 1 and 2, respectively. this is in acceptable agreement with and supplementary to xrd results. 3.4. micro-raman spectroscopy the raman spectra of the sulphide scales gathered from the surface of the steel coupons (tested at 250 ºc over various time exposures) are presented in fig.7. similar spectra were obtained for the st35.8 carbon (b) and 1.7335 low alloy (c) steels. the 1.4541 high alloy steel (d) indicated a strong feature in the wavenumber region of 550-800 cm-1. in the low wavenumber range, a similar raman spectrum was detected to that of the 1.0425 carbon steel (a). because raman spectra depend strongly on the intensity and wavelength of the incident beam, based on the weak feature of the spectra around the main raman characteristic wavenumbers, it is thought that small proportion of troilite in the crystalline phase [38] should probably have formed after the chemical conversion of the initial metal sulphide on the st35.8 and 1.7335 (lines at 289 and 290 cm-1) over a short time period. metal sulphides, detected in a somewhat greater proportion of crystallinity (yielding a relatively low amount of scale) formed on the slower corroding 1.4541, resulting in to the more pronounced features in the wavenumbers between 550 and 800 cm-1. corrosion scales of st35.8, 1.7335, and 1.4541 alloys yielded intense broad and weak features at 1292 and 218 cm-1 as a result of the troilite phase. these characteristic wavenumbers were only found in the spectra in accordance with the literature [40]. this reveals that the low crystallinity of corrosion scales evolved within 24 hours. other raman features of troilite, a weak intensity peak at 456 cm-1 and the sharp ones at 600, 398, and 283 cm-1 [41], and 400 and 295 cm-1 [38] were not found. on the other hand, iron sulphide in a form close to mackinawite [42] might keep evolving in the early stages on 1.0425, st35.8 and 1.4541 as wavenumbers of moderate intensity at 321, 317, and 315 cm-1, respectively, were detected. they usually appear as intense overlapping peaks between 310 and 320 cm-1 depending on the degree of crystallinity [43]. thus, this seems to concur with greater reaction rates leading to a lower proportion of crystallinity in the product as the rate of nucleation overtakes to a level of far beyond orientation and growth. insignificant raman intensities in the regions of 280-360 cm-1 (at 206, 257, and 296 cm-1 and at 256, 312, and 355 cm-1) are generally connected to mackinawite (fe(ii)s1-x and fe(ii-iii)s1-x) and iron-rich mackinawite, and greigite, respectively [44]. in the 1.4541, the very low raman intensity at 240 cm-1 is probably due to the presence of chromium-rich troilite whereas the low intensity features at 255 (290) and 365 cm-1 are partly connected to daubrelite (fecr2s4 and fecr2s3). nonetheless, these phases should have been present in negligible quantity, because none of the supporting xrd results could confirm the presence of such crystals, besides theoretical thermodynamic calculations of stable regions of iron sulphides (see discussion). in all cases, the low crystallinity of the corrosion products is attributed to the short time-scales and low temperatures of the experiments. it should also be noted that amorphous iron sulphide scales, which evolved in the induction periods were far less coherent, more crystalline, and more susceptible to spalling and detaching than the ones formed in slower reactions. thus to explain this phenomenon, lower mechanical stress might have accumulated over time in scales generated by slower and decreasing rates of reactions. as a result, the induction time of sulphide scale formation should be very low at a pressure as low as 20 bar but crystallisation must occur over longer periods. therefore, time constants in terms of spalling, and the failure of the scales to detach might be related to relaxation of accumulated stresses, probably at a rate faster than the crystallisation of iron sulphides. for troilite, it must be longer than 8 hours, but much less than 21 days at 250 ºc and a pressure of 90 bar. in fact [45], due to kinetic reasons in connection with the highest reaction rate of scale growing without diffusiontype mass transport control [46], it has been stated that [47] generally mackinawite is expected to form rapidly first almost regardless of reaction conditions. for thermodynamic reasons, if metastable cubic fes formed, it should have also transformed into pyrrhotite and troilite over the weeks the experiment was undertaken at a moderate temperature and pressure both in the presence [48] and absence of chloride [49]. phase transformation of metal sulphides to troilite takes place in days or even hours as was found in our case. the evolution of pyrrhotite might occur over a couple of figure 7. micro-raman survey spectra of steel alloys tested under specified conditions as stated: a) 1.0425 (250 ºc/20 bar, 8 h), b) st.35.8 (250 ºc/50 bar, 24 h), c) 1.7335 (250 ºc/20 bar, 8 h) and d) 1.4541 (250 ºc/50 bar, 24 h). gergely, locskai, szabó, krójer, and kristóf hungarian journal of industry and chemistry 66 days so its detection in samples tested over at least 3 days can be anticipated. not exactly in line with the location of the pyrrhotite-troilite transition boundary [50, 51], in our case elevated temperatures favoured the formation of troilite rather than pyrrhotite under less than 2 bar of partial pressure of the hydrogen sulphide. 4. discussion the hypothetical growth in thickness of the sulphide scales over selected time periods based on the mass changes of the coupons is given in figs.8a-8d. the 1.0425 at 225 ºc exhibited thicker scale development in biomass mixtures with lower reductions in rate over time than in neat gas oil (fig.8a). at 250 ºc, all corrosion rates exhibit proportional growth as time of exposure increases. such linear rates of sulphidation started to decelerate as a function of time above 250 ºc. the lowest variation of corrosion rates over time manifested in the used cooking oil mixture. the st35.8 exhibited similar sulphidation resistance behaviour up to 275 ºc but at 300 ºc a higher drop in corrosion rates was observed in mixed organic environment of the biomass and a smaller reduction in neat gas oil over time (fig.8b). the 1.7335 experienced increasing corrosion rates in all fluids as a function of temperature, without any notable decrease related to barrier effects over longer time periods (fig.9c). depending on the type of the organic phase, moderate drops and increases in the corrosion rates over intermittent periods were observed at 74, 168, and 168 h for 1.0425, st35.8 and 1.7335 steels, respectively. according to our experience, the growth rate in the thickness of stable scales on carbon steels never exceeded 10 µm over the first 3 days. up to 250 ºc, the 1.0425 exhibited a higher and the st35.8 a somewhat lower susceptibility of the sulphide layers to spalling and detachment. the 1.7335 manifested the development of more coherent scales that were not susceptible to spalling or failure over time especially at and above 275 ºc. a less frequent variation in time of reaction rates along with the observed quantity of detached scales in the form of a sediment at the bottom of the glass tubes led to the conclusion that the about low compactness, and high porosity of the sulphide scales are the primary reasons for the longlasting high sulphidation rate of this alloy. nonprotective scales exhibit linear growth and a mass change over time similar to that of the 1.733. this is typical for porous or cracked films, which facilitate the less hindered transport of reactants and access to the metallic phase at faster rates than at which the chemical reaction proceeds. as far as the 1.0425 and st35.8 carbon steels are concerned, due to the high barrier nature of the sulphide scales at elevated temperatures, variations in the time needed to renew the surface almost to the metallic phase were necessary to maintain the high reaction rates over long periods of time. scale failures should have been caused by the accumulation of high internal stresses along with high growth rates taking place on polycrystalline surfaces. such failures do not occur within scales at the scale/metal interface since it is cohesive in nature due to the high electrostatic forces that exceed the yield strength of the scales [52]. figure 8. hypothetical differential metal-sulphide scale thicknesses developed over time periods based on the mass change of the coupons of steel alloys immersed in refined gas oil (go) and its mixtures with used cooking oil (uco) or waste lard (wl) tested at a pressure of 90 bar in the presence of 2% (m3/m3) hydrogen sulphide. sulphide corrosion of steel alloys immersed in renewable biomass sources 44(1) pp. 55–70 (2016) doi: 10.1515/hjic-2016-0007 67 thus, hypothetically speaking, further scale growth as a solid-state reaction must trigger the breakdown of scales [53]. this is basically in line with the literature [54] as the corrosion resistances of carbon and low alloy steels are approximately equal. the low chromium alloys of up to 5% (g/g) warrant little or no advantages over carbon steels in terms of resistance to reactions with hydrogen sulphide. nonetheless, the 18cr-8ni stainless steels feature acceptable resistances over a wide range of pressures, temperatures, and hydrogen sulphide concentrations, except under severe conditions [55]. in other aspects, the protection potential of sulphide scales for carbon steels is usually questionable when well adsorbing species or compounds are in fluid media. after the first phase of mackinawite growth, corrosion rates can accelerate because the tarnish is not a uniform film, but rather composed of discrete crystallites that are highly permeable [56]. if the electrochemical mechanism of sulphide corrosion occurs and cathodic depolarisation is efficient, pyrrhotite formation becomes anodically controlled by cation diffusion that takes place through sulphides, which are in part limited by maximum reaction rates. thus, as thermodynamic simulations delineated the region of stability of troilite [57], in our experiment the electrode potential of the steel coupons should have been between -0.4 and -0.65 v versus standard hydrogen electrode (she), which is a narrow stability region in neutral media. at 250 ºc, the 1.4541 showed slight variations in sulphidation over time regardless of the fluid phase (fig.8d). the scale structure was less compact and easily removable from the surface. at 250 ºc, the highest decrease in reaction rate was obverserved over moderate periods of time that could only be accounted for by the greater initial sulphidation rates, increased compactness, and packing of the corrosion film, resulting in the metallic surface becoming more rapidly blocked, thus preventing subsequent reactions leading to less hindered ionic diffusion. as the temperature increased to 275 ºc and above, time variations in the reaction rates became less remarkable as a function of time with similar changes in all organic fluids. this may suggested as the factors of utmost importace that determines the type of sulphide scales that could grow on the specimens, which slows down further metal sulphide forming reactions. as recognised first by wagner [58], some metals develop oxide scales exhibiting excellent protection characteristics as a result of the decreasing diffusion rate of ions through compact scales. such quasi-passivating behaviour was found in the sulphide corrosion of the 1.4541 under the experimental conditions, as mass changes obeyed the parabolic law as a function of time. this is in accordance with the nature of chromium, which is considered to be present in relatively high amounts as the most significant alloying element that increases sulphidation resistance. in some instances, the logarithmic rate of sulphide conversion by mass change was also observed in the initial phases of the reactions. the induction periods in the formation of metal sulphides were intense probably because of the lack of mass transport hindrances at the interfaces which evidently evolved to various extents in later phases of the experiments as thermal activation between 200 and 300 ºc is inefficient to maintain high ion fluxes through the lattice of scales of moderate thicknesses and compactnesses. thermodynamic calculations based on gibbs free energy changes of the reactions of sulphide corrosion processes do not justify remarkable changes in reaction rates as a function of temperature. therefore, kinetic factors are likely to play a pivotal role in the enhancement of reaction rates in all cases. as a comparison of the protection performances provided by sulphide scales on different sorts of steel alloys, corrosion layers on the 1.4541 and the st35.8 evolved better barrier characteristics at higher temperatures than under 250 ºc, which is generally in agreement with the terms of scaling tendency [59]. more coherent and adherent scales of metal sulphides formed at greater rates as corrosion products were not as solubile in go and uco compared to the wl mixture. so precipitates shrank and became more compact, which is partly is accounted to their mediocre thermal activations. in waste lard mixtures, corrosion through both chemical and electrochemical mechanisms assisting each other resulted in a pronounced efficiency of thermal activation was experienced along with the impact of acids relegating protective function of the chromium-, nickel-, and molybdenum-alloying elements. aside from the 1.7335 exhibiting good mechanical protection characteristics independent of temperature, the 1.0425 yielded rapidly increasing sulphidic corrosion with temperature. the former is attributed to high porosity of the sulphide film and the latter is explained by detachment of the layers thereof regularity depends on the corrosion rate and surface structure, orientation of the metallic crystallites, affecting the rate of stress accumulation in the corrosion products. the pronounced sensitivity of corrosion resistance in the 1.4541 regarding composition of the organic fluid phase resulted in high reaction rates especially in waste lard mixtures not only in the short run, but over longer periods, suggests the existence of an altered microstructure, lower compactness and increased solubility of metals and sulphide scales in acid containing fluid than in neat gas oils. this is in agreement with the literature [60] as naphthenic acids are most accountable for the highly corrosive nature oils [61-64]. the high corrosion rate of the st35.8 at low temperatures probably is a result of diffusion along short-circuit paths at grain boundaries or dislocations rather than of lattice diffusion, as thermal activation is high compared to over long periods when kinetic control of barrier effects besides the seldom failure of scales. slow growing scales proved to be more coherent and protective, exerting better mass transport control on during subsequent reactions. the gibbs free energy change of the metal sulphide reactions is inferior to diffusion activation in the solid state. the growth mechanism of metal sulphide scales takes place via outward diffusion of cations which leads to lower rate of stress accumulation in the layer. in carbon steel gergely, locskai, szabó, krójer, and kristóf hungarian journal of industry and chemistry 68 samples, spalling and scale failure were experienced over the first 24 hours as one of the four types of stressrelief mechanisms. in the case of thin scales, maximumstress affects metal/scale interface. the imperfections of the flat surface and the geometry of the coupons is also partially connected to the detachment of sulphide scales [65] especially at the inner and outer edges as flat interfaces are less susceptible to spalling compared to the ones with small radii, high curvatures [66]. low film ductility at low temperatures and high corrosion rates might inevitably lead to spalling, undermining and detachment. 5. conclusion the corrosion rates of carbon steels yielded an almost linear dependence as a function of temperature between 200 and 300 ºc regardless of the biomass fuel sources. although carbon steels developed less spalling and detaching sulphide scales with increasing temperature, the porous layers did not contribute to the higher protection of the metallic phase as a result of their enhanced barrier natures. in contrast, on the surface of high alloy steels sulphide scales with excellent protection characteristics evolved during the induction period and the layer formation is assisted by temperature. integrity loss of the high alloys can severely be affected by biomass fuel sources such as animal waste lard when they are used in high proportions along with raw gas oil. free fatty acids play probably a dominant role in the corrosion mechanism. the higher corrosion rates observed than reported in the literature lead us to conclude that the proportion of the biomass sources used, especially those the ones having high free fatty acid contents, should preferably be kept low to prevent rapid losses in integrity of steel alloys, ensuring long and safe life cycles of the equipment used in hds refining plants. acknowledgement the authors are indebted to ferenc molnár, corrosion research group, department of physical chemistry, institute of chemistry, university of pannonia, for his invaluable discussions and advice on planning experiments and evaluating results. bence nagy, mol co., is gratefully acknowledged for his mediation and help in the procurement of precursors for the experiments. the authors are indebted to róbert bocsi, department of chemical processing, institute of chemical and process engineering, university of pannonia, for his instruction, laboratory work and help in detecting and measuring the concentrations of hydrogen sulphide during reactor experiments. the authors are grateful to csaba tóth, department of mol hydrocarbon and coal processing, institute of chemical and process engineering, university of pannonia, for his variety of contributions to the experimental work, and to margit balázs for her analytical results of the biomass fuel sources. references [1] knothe, g.: biodiesel and renewable diesel: a comparison, prog. energy combus. sci., 2010 36(3), 364–373 doi: 10.1016/j.pecs.2009.11.004 [2] astm d6751-15ce1, standard specification for biodiesel fuel blend stock (b100) for middle 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word 16.13 neukirchner.docx hungarian journal of industry and chemistry vol. 44(2) pp. 105–111 (2016) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2016-0013 modelling a three-phase current source inverter lászló neukirchner* and attila magyar department of information technology, university of pannonia, egyetem u. 10, veszprém, 8200, hungary a current source inverter model has been developed in the given paper that is constructed from six lti models for the different switching modes. the overall model is in a piecewise affine form that supports the use of model predictive control. the model has been verified against engineering expectations and its open-loop performance shows that it is a promising basis of model predictive control structures. keywords: model predictive control, current source inverter, space vector modulation, modelling, simulation 1. introduction in industrial applications power electronic converters are divided into two major classes, namely voltage source (vsi) and current source inverters (csi). as a vsi employs modulating the voltage wave through the inverter’s legs, its counterpart relies on modulated current waveforms. to operate a vsi the inverter’s switching devices should operate in a specified alternating modulation to avoid shorting the inverter’s legs, while its current source counterpart could embed this operation into the modulation. thyristor rectifiers suffer from several drawbacks, e.g. high-input current harmonic distortion or a low power factor. pulse width modulated current-source inverters, on the other hand, are free from the above-mentioned drawbacks. in such cases, a smoothing lc filter is placed on the ac side and a choke inductor dc side to reduce the harmonic injection resulting from the current modulating pwm operation. in the case of sinusoidal supply voltages, an input power factor with unit value can be achieved if both requirements are met. in conventional control structures, pwm-csr is usually operated by off-line patterns and look-up tables like in trapezoidal modulation and selective harmonic elimination. the use of these techniques simplifies the calculation of the gate control signals with the special requirements of applied switches like igbts. input filtering, on the other hand, may result in oscillatory transient behaviour. this can be attenuated by adding damping resistive elements, but using them also reduces the overall efficiency. space vector modulation (svm) has proven to result in a high voltage gain, reduced switching frequency and low *correspondence: neukirchner.laszlo@uni-pannon.hu current harmonic distortion, and could be straightforwardly implemented in digital systems [1]. in the second section, the structure of the investigated inverter is presented. in the next section, a detailed open-loop model is presented, and in the fourth section a predictive strategy is chosen for controlling svm. 2. inverter structure the current source inverter normally requires threephase inductive and capacitive filtering (lf and cf, respectively), improving the load current and voltage waveform’s harmonic distortion, and in thermistor appliances assisting the commutation of the switching devices. the legs of the device should include protective diodes, otherwise the absence of a current path introduces a high-voltage spike, causing damage to the switching devices [2]: • the switching devices used are symmetrical, they do not require freewheeling diodes. • the current source inverter produces a threephase pulse-width modulated current instead of a pulse-width modulated voltage. as such, a capacitor needs to be installed on the output for filtering purposes. the high voltage derivative is associated with the vsi. • the rate at which the dc current rises is limited by the dc choke, allowing sufficient time for the protection circuit to function in the case of a short circuit at the inverter output terminals. • as a restraint, the dc link current cannot be instantaneously changed, which resulted in a reduction in dynamic performance. neukirchner and magyar hungarian journal of industry and chemistry 106 3. open-loop switched model with space vector modulation 3.1. space vector formulation the switched model of the three-phase csi supplying a three-phase load through an lc filter and rl load is shown in fig.1. the lc filter is a low-pass filter included with the three-phase csi to decrease the thd by eliminating higher order harmonics. the implemented lc filter includes a resistor rf in series with a capacitor cf. this resistor provides a passive damping solution and it was recommended to be within the range of 0.5 to 1 ω. moreover, the resistor rdc represents any start-up pre-charging resistance or any resistance in series with the dc voltage source vdc. for constructing the model the following assumptions are made: • the lc filter and the rl load’s circuit components are symmetric. • only a continuous conduction mode is assumed. • each time, the switch state index s is known. • the switching devices used for modulation are assumed �to be ideal, with zero losses and switching is consid �ered to be instant. • no external disturbance is assumed. • no magnetic coupling between the inductances is �assumed. with the above assumptions, the equation system of the inverter, filter and load for all the switching states can be created, as different state-space models [3, 4]. under the above-mentioned constraints, the three-phase current source inverter has nine switching states as can be seen in table 1. these switching states can be classified as zero switching states (i0) and active switching states (i1, ..., i6). in addition, there are three zero states which implies vertical conduction of the inverter leg. this implies that the source is shorted, leading to ia = ib = i c = 0. this operating mode is often referred to as the bypass operation. assuming that the operation of the inverter is three-phase balanced then eq.(1) applies ia + ib + ic = 0 (1) according to fig.2, the five active vectors can be expressed as: 𝑰! = ! ! 𝐼!"e ! !!! ! !! ! ! , k = 1, 2, …, 6 (2) the active and zero vectors are assumed to be stationary, on the contrary, the current reference vector iref in fig.2 rotates with an angular velocity ω = 2πf, and θ 𝑡 = ω 𝑡 𝑑𝑡 + θ 0 ,! ! where f is the fundamental frequency of the inverter output current and θ is the angular displacement. a desired vectorial length and angle, iref can be calculated from the neighbouring space figure 1. current source inverter with an lc filter and rl load. table 1. switching states of svpwm modulated csi. active switches ia ib ic space vector zero states s1, s4 0 0 0 i0 s2, s5 s3, s6 active states s6, s1 idc -idc 0 i1 s1, s2 idc 0 -idc i2 s2, s3 0 idc -idc i3 s3, s4 -idc idc 0 i4 s4, s5 -idc 0 idc i5 s5, s6 0 -idc idc i6 modelling a three-phase current source inverter 44(2) pp. 105–111 (2016) doi: 10.1515/hjic-2016-0013 107 vectors (fig.3), based on the switching pattern and frequency of the inverter. as iref passes through the vectorial spaces, different switch sets are applied to formulate the desired output. as a result, when iref rotates one revolution, the output continues for one cycle based on the fundamental frequency. 3.2. calculating dwell-time the dwell time for stationary vectors represents the time that space vectors spend in a sector during ts. the basic method used for dwell-time calculations is the so-called ampere-second balancing principle. the main idea behind it is that the product of the sampling period ts and the reference vector iref is equal to the sum of the current vectors multiplied by the time interval of chosen space vectors. with small enough ts, iref can be assumed as constant over a period. with this notion, the reference current is approximated from the neighbouring vectors corresponding to the actual sector and from the zero vector for adjusting the length. the ampere-second balancing principle is given by 𝑰!"#𝑇! = 𝑰!𝑇! + 𝑰!𝑇! + 𝑰!𝑇! 𝑇! = 𝑇! + 𝑇! + 𝑇! (3) where t0, t1, and t2 denote the dwell times of the vectors i0, i1, and i2. from eq.(2), the individual values of space vectors in sector i are defined in eq.(4): 𝑰!𝑇! = ! ! 𝐼!"e !!!! 𝑰!𝑇! = ! ! 𝐼!"e !!! 𝑰!𝑇! = 0 (4) projecting the resulting complex vector onto the real and imaginary axes leads to: 𝑰!"# cos θ 𝑇! = 𝐼!"(𝑇! + 𝑇!) 𝑰!"# sin θ 𝑇! = ! ! 𝐼!" −𝑇! + 𝑇! . (5) solving eqs.(3) and (5) yields the dwell times t0, t1, and t2 at any given θ angle as shown in eq.(6): 𝑇! = 𝑚! sin (! ! − θ)𝑇! 𝑇! = 𝑚! sin (! ! + θ)𝑇! 𝑇! = 𝑇! − 𝑇!−𝑇! for − ! ! ≤ θ ≤ ! ! , (6) where ma = | iref | / idc is the modulation index in the domain: ma ∈ [0, 1]. when iref is inside of other sectors a multiple of π/3 is subtracted from θ so that the modified angle σ happens to fall within the range of − ! ! ≤ θ ≤ ! ! for use in eq.(7): σ = θ − (𝑘 − 1) ! ! 𝑠 = 1, 2,… , 6 for − ! ! ≤ θ ≤ ! ! , (7) where s is the sector index. this method save sthe need for implementing unnecessary calculations and code capacities. 3.3. switching sequence as far as designing the switching pattern of the svm for the csi a few notions should be specified for switching loss reduction: • the state transition should involve the least amount of switches (one switch is desired). • minimum amount of switches should be involved as iref transits from the current to the next state. figure 2. a typical space vector diagram for the csi. i1, ..., i6 are the active vectors, i0 is the zero vector, ω is the angular velocity, θ is the angular displacement and the cartesian coordinate system represents the imaginary and real axes. the active vectors form a symmetric hexagon with six identical sectors, while the zero vector i0 lies at the center of the hexagon. figure 3. calculation of iref in sector i, where the cartesian coordinate system represents the imaginary and real axes. neukirchner and magyar hungarian journal of industry and chemistry 108 the typical sequence can be observed in table 2. iref is created by i1, i2, and i0 with the mentioned dwell time rule 6. ts can be divided into three or more segments (t0, t1, and t2) according to the desired thd value of the output current. from the above, a continuous switching sequence for the svpwm modulation can be obtained by eq.(8): 𝑰!, 𝑰!!!, 𝑰! 𝑘 = 1, 2,… , 5 𝑰!, 𝑰!, 𝑰! 𝑘 = 6 , (8) where k is the sector index. 3.4. obtaining open-loop ‘piecewise affine’ model with every state vector i0, i1, ..., i6 a different switch configuration and a different circuit configuration is present at a given time. for every case the circuit’s state equations can be written in continuous state-space form: 𝒙(𝑡) = 𝐀!𝒙 𝑡 + 𝐁!𝒖(𝑡) 𝒚(𝑡) = 𝐂!𝒙(𝑡) s = 0, 1,… , 6 , (9) where as is the sth state matrix, bs is the sth input matrix, cs is the sth output matrix, x(t) and u(t) are space vectors, and s represents the space vector index with s = 0 as the zero state and s = 1, 2, …, 6 as the active states. since all the equation systems have the same input (bs) and output (cs) matrices they will be referred to as b and c matrices. any linear circuit can be represented by a number of differential equations equal to the number of energy storage units in the circuit. however, in three-phase balanced circuits, the number of equations can be reduced by a third factor because any three-phase quantity can be expressed in terms of the other two phase quantities. therefore, since currents flowing through lf and ll and voltages across cf are three-phase balanced quantities only four linear differential equations representing the ac side and one linear differential equation representing dc current across ldc are needed. hence, linear differential equations for the state variable x = 𝑖!"𝑉!! !"𝑉!! !"𝑖!𝑖! ! , input variable u = vdc and output variable y = [ir is]t can be derived using kvl and kcl. arranging the expressions for the aforementioned state variables and recognizing vdc as the input of the system, yields the following state-space matrices for the zero switching state as shown in eqs.(10)-(12): 𝐀𝟎 = − !!" !!" 0 0 0 0 0 − ! !! 0 − ! !! ! !! 0 0 − ! !! − ! !! − !! !! 0 !! !! ! !! !! !! 0 0 ! !! ! !! 0 !! !! (10) 𝐁 = − ! !!" 0 0 0 0 ! (11) 𝐂 = 0 0 0 1 0 0 0 0 0 1 , (12) where qa = c(3r + rf), qb = rrf + 3rrl + rfrl and qc =(3r + rf)(lf + ll). 3.5. open-loop performance as csi exhibits different lti regions for different state matrices a0, a1, ..., a6 according to the used space vector i0, i1, ..., i6 in the corresponding dwell time, the piecewise affine approach (pwa) can be used to describe the overall dynamics. the discrete time piecewise affine model can be obtained by discrediting the set of continuous affine models in the form of eq.(13) 𝒙!!! = φ!𝒙! + 𝚪 𝒖! , if 𝒖! 𝒙! ∈ 𝑃! ⋮ φ!𝒙! + 𝚪 𝒖! if 𝒖! 𝒙! ∈ 𝑃! (13) such systems are composed of s local affine models whose parameters in (φs) change according to which polyhedron pk contains the state vector. � the simulated waveforms for vdc = 400 v dc link with pre-charge resistance rdc = 1 ω and choke inductance ldc = 2e−1 h using the space vector modulation as shown in fig.5, where ia denotes the pwm current of the inverter and ir stands for the phase current through the load. the inverter operates at a fundamental frequency of f = 50 hz. the filter capacitor c f = 20e−6 f, the filter inductance lf = 10e−3 h with filter resistance rf = 1 ω and r = 1 ω representing losses. the inverter consists of three-phase balanced inductive load ll = 2e−3 and resistive load rl = 5 ω. the open-loop performance can be observed in fig.4 and the modulation and pwm formulation in fig.5. table 2. typical switching sequence for sector i. the sequence was repeated twice to achieve a smoother output signal. in this case, the sampling period ts is one 12th of the fundamental time period. the active switch pairs are s6, s1 and s1, s2 for space vectors i1 and i2. the chosen zero state (with switches s1, s4) is chosen for i0 such that the minimum switching loss requirement is met. vectors i1 i2 i0 i1 i2 i0 s1 x x x x x x s2 x x s3 s4 x s5 s6 x x x dwell time t1 t2 t0 t1 t2 t0 ts ts modelling a three-phase current source inverter 44(2) pp. 105–111 (2016) doi: 10.1515/hjic-2016-0013 109 4. mpc assisted svpwm the aim of the previous sections was to develop a model for the inverter that describes the switching behaviour of the dynamics. the obtained piecewise affine model gives a good basis for the model predictive control technique that is advantageous from two points of view: the possibility of introducing constraints to the state and input variables and the fact that optimal control problems can be formulated within it. the aim is to find the optimal space vectors in such a way that the error between the predicted states of the inverter and the chosen reference values are minimized with respect to constraints. previously, the method of model predictive control was reserved only for applications with relatively slow time scales, like plants and chemical processes. the reason for this is that mpc requires an optimization problem to be solved at each sampling instant in order to obtain the control input. over the past decade, more and more applications use fast mpc applications, thanks to the advances in computer technology. the optimization problem is often np hard, and finding a solution is taxing in terms of the calculation time of the control device, thus limiting the rate at which the control could intervene with the application. in particular, model predictive control has been applied in the field of power electronics, where the control frequency ranges from a few hundred hz up to a few mhz [5,6]. the main challenge of implementing mpc consists of solving the associated optimization problem in a bounded time. the predicted values are assumed to be constant after time k. then, the control problem can be formulated as follows: min j (x[k]) �s.t. x[k] = x[k|k] �j(x[k]) = ||𝑄(𝒙 𝑘 + 𝑗 𝑘]! !!! − xref ([k]))||2 (14) where x[k + j | k] denotes the prediction of the state at time k + j based on the information available at time k, n is the prediction horizon, q is the constant weighting. the optimal state-finding algorithm follows: optimalerror = inf for s = 1 : 7 do 𝑥(1) 𝑥(2) … 𝑥(𝑁) ! = 𝐵! 0 ⋯ 0 𝐴! 𝐵! ⋯ 0 ⋮ ⋮ ⋱ ⋮ 𝐴!!!!𝐵! 𝐴!!!!𝐵! ⋯ 𝐵! ∙ 𝑢 0 𝑢 1 ⋮ 𝑢 𝑁 + 𝐴! 𝐴!! ⋮ 𝐴!! 𝑥(0) figure 5. comparison of the inverter output current ia and the filtered load current ir with ts = t /36 and ma = 0.9. the background s’s value indicates the corresponding affine state of the model at a given time. figure 4. three-phase sinusoidal waveform of the csi output currents ia, ib, and ic with a sample period of ts = t/36 and a modulation index of ma = 0.9. the output wave can be smoothened by adding higher filter parameters or further reducing the sampling period. neukirchner and magyar hungarian journal of industry and chemistry 110 errors = js(x) �if errors < optimalerror then optimalerror = errors optimal_s = s where optimalerror represents the minimal error value, error_s is the actual error value in each iteration, and optimal_s is the optimal state. the algorithm uses a parallel implicit mpc scheme for every state. since there are only seven states, with a low horizon the algorithm can be feasibly implemented. when f = 50hz, 𝐼 = 37.5a, and n = 2, deviations from the optimal trajectory are present during optimization as shown in fig.6, but they are still acceptable in terms of harmonic distortion. the performance observed in fig.7 can be compared to the open-loop solution. it can be stated that due to the rigid structure of the open-loop modulation’s rigid structure the dynamical properties of the mpcassisted system exhibit better performance in terms of time response and signal shape. 5. conclusion a current source inverter model has been developed in this paper that is constructed from six lti models for the different switching modes using svpwm modulation. the obtained overall model is in a piecewise affine form that supports the use of model predictive control in the future. the model has been verified against engineering expectations and its openloop performance shows that it is a promising basis of further work in terms of identification and control. as the next step, a model predictive control synthesis was performed based on the technology-driven optimality criteria to assist the open-loop svpwm modulated system. due to the implicit mpc-assisted modulation the optimal space vector could be found and utilized in each state over an acceptable timescale due to the low horizon. as such a significantly lower time response and better signal shape was achieved. symbols a state matrix b input matrix c output matrix � cf filter capacitance f fundamental frequency φ discrete state matrix � γ discrete input matrix i0,i1,..., i6 space vector � ia, ib, ic inverter output currents per phase figure 6. mpc reference tracking with f = 50hz, �̂� = 37.5a, and n = 2. in order to create the simplest implicit mpc for a finite state pwa environment, every affine state was tested with the according horizon in every iteration. figure 7. comparison of classic svpwm and mpc on the same system. the svpwm is applied with a modulation index of 0.9, and the mpc reference tracking with f = 50hz, �̂� = 37.5a, and n = 2. modelling a three-phase current source inverter 44(2) pp. 105–111 (2016) doi: 10.1515/hjic-2016-0013 111 idc dc link current ir, is, it load currents per phase iref reference current value k sector index lf filter inductance ll load inductance � lti linear time invariant ma modulation index mpc model predictive control νcr triangular carrier wave for tpwm νm modular wave for tpwm p discrete time index p space vector containing polyhedron pwa ‘piecewise affine �’ current source inverter (csi) pwm pulse width modulation r loss resistance rdc dc link start-up pre-charging resistance rf filter resistance rl load resistance s space vector index s1, s2,..., s6 switching devices σ modified angle she selective harmonic elimination svpwm space vector pulse width modulation t fundamental cycle time �tk dwell time of corresponding space vectors �ts sampling period tpwm trapezoidal pulse width modulation θ angular displacement u input vector � vdc dc link voltage source value 𝑉!! !", 𝑉!! !",𝑉!! !" filter capacitance’s voltage x state vector y output matrix � ω angular velocity acknowledgement this research is supported by the national research development and innovation office (nkfih) through grant no.115694. a. magyar was supported by the jános bolyai research scholarship of the hungarian academy of sciences. references [1] espelage, p.; nowak, j.m.; walker, l.h.: symmetrical gto current source inverter for wide speed range control of 2300 to 4160 v, 350 to 7000 hp induction motors, ieee ind. appl. soc. conf. (ias) 1988 1, 302–307 doi 10.1109/ias.1988.25079 [2] wu, b.: high-power converters and ac drives (wiley-ieee press, new jersey, usa) 2006 [3] ma, j.; wu, b.; rizzo, s.: a space vector modulated csi-based ac drive for multi-motor applications, ieee trans. power electron., 1999 16(4), 535–544 doi: 10.1109/apec.1999.750460 [4] wiseman, j.; wu, b.; castle, g.s.p.: a pwm cur �rent source rectifier with active damping for high power medium voltage applications, ieee power electron. spec. conf. (pesc) 2002 1, 1930–1934 doi: 10.1109/psec.2002.1023096 [5] mariéthoz, s.; morari, m.: explicit modelpredictive control of a pwm inverter with an lcl filter, ieee trans. ind. electron. 2008 56(2), 389– 399 doi: 10.1109/tie.2008.2008793 [6] mariéthoz, s.; almér, s.; baja, m.; beccuti, a.g.; patino, d.; wernrud, a.; buisson, j.; cormerais, h.; geyer, t.; fujioka, h.; jonsson, u.t.; kao, c.y; morari, m.; papafotiou, g.; rantzer, a.; riedinger, p.: comparison of hybrid control techniques for buck and boost dc-dc converters, ieee trans. control syst. technol. 2010 18(5), 1126–1145 doi: 10.1109/tcst.2009.2035306 hungarian journal of industry and chemistry vol. 49(2) pp. 47–52 (2021) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2021-21 comparative analysis of burrs in ud-cfrp composites using advanced hole machining technologies anna nikoletta helle1, csongor pereszlai1, andrás gödri1, and norbert geier*1 1department of manufacturing science and engineering, budapest university of technology and economics, műegyetem rkp. 3, budapest, 1111, hungary machining of carbon fibre reinforced polymer (cfrp) composites is challenging due to their inhomogeneous and anisotropic structure as well as the strong effect of the carbon fibres on wear. burrs are critical machining-induced macro-geometrical defects in the case of the machining of cfrp composites, which may lead to assembly difficulties. nowadays, although novel hole-machining technologies reduce the likelihood of burrs occurring, these technologies are often more costly and require longer machining times. the current experimental study focuses on the analysis of burrs induced by advanced hole machining technologies (helical milling, tilted helical milling and wobble milling) and comparison with a conventional one (conventional drilling). a total of 32 experiments were carried out in a vhtc 5-axis machining centre using uncoated solid carbide end mills. furthermore, these technologies are compared and discussed based on the burrs experienced and average material removal rate (amrr). experimental results show that conventional drilling caused the lowest amount of burrs, followed by wobble milling, tilted helical milling and helical milling. even though wobble milling is one of the most advantageous technologies in terms of burrs, the amrr of conventional drilling is twenty times larger than that of wobble milling, therefore, the further development of wobble milling is recommended. keywords: carbon fibre reinforced polymer, exit burr, drilling, digital image processing 1. introduction nowadays, the demand for fibre reinforced polymer composites is increasing and their key role in industry is undeniable. carbon fibre reinforced polymer (cfrp) composites are no exception. according to a market report made in 2018 by m. sauer and m. kühnel [1], their demand by 2017 has more than doubled (114k tons) compared to that of 2010 (51k tons). the reason for this increasing trend lies behind the outstanding material and specific mechanical properties of these composites. cfrps possess larger strength-to-weight ratios compared to metals, making them exceptionally suitable for parts built into assemblies connected to the aviation, aerospace and automotive industries, reducing fuel consumption [2, 3]. they also exhibit good levels of corrosion resistance and are very strong as well as stiff. however, to be a part of an assembly, these composites must be machinable, that is, can be drilled or milled. cfrps are difficult to machine, since the carbon fibres significantly contribute to tool wear as well as make the material anisotropic and inhomogeneous. these aspects lead to several difficulties such as delamination, burrs, matrix degradation, microcracks or fibre pullouts [3, 4]. since the present of burrs renders post-machining almost inevitable, in order to reduce the resources necessary for further manufacturing *correspondence: geier.norbert@gpk.bme.hu and achieve the quality that the aviation and automotive industries require, novel technologies have been introduced. in the current study, the most frequently used and promising novel ud-cfrp machining technologies are compared, namely conventional drilling, helical milling, tilted helical milling and wobble milling. the kinematics of these technologies are illustrated in fig. 1. the kinematics of conventional drilling (fig. 1a) is the simplest of the four technologies investigated: the axis of the tool is coincident to the axis of the hole along which the tool is moving downwards while rotating around this axis. therefore, the diameter of the hole is determined by the diameter of the tool [2,5]. this simplicity renders machining the least time-consuming and results in a large material removal rate (mrr), however, in the case of drilling, it is highly likely that the surface will be damaged when the tool enters and exits the composite, leading to separation of the laminated layers. this phenomenon is referred to as delamination, which can render parts unsuitable for further assemblies. to prevent such outcomes, a novel technology, namely helical milling (fig. 1b) has been introduced. this technology is also known as orbital drilling [6], since the tool is moving on a helical path while rotating around its own axis, which is shifted from the axis of the hole. the kinematics can be carried out by circular interhttps://doi.org/10.33927/hjic-2021-21 mailto:geier.norbert@gpk.bme.hu 48 helle, pereszlai, gödri, geier figure 1: the examined technologies: a) conventional drilling, b) helical milling, c) wobble milling, d) tilted helical milling [3] polation even with a tool with a smaller diameter to the hole being machined. according to denkena et al. [5], although smaller forces and tool wear occur during machining, the drawback of this technology is that the effective cutting speed can reduce to zero [7]. to avoid an effective cutting speed of zero, further novel technologies have been introduced, which require a 5-axis machining centre or an industrial robot to be executed. one of them is tilted helical milling (fig. 1d), during which the tool moves along a helical path while being tilted to the axis of the hole with an angle of ∆ [7]. the surface of the hole becomes threaded, which leads to a high incremental increase of surface roughness compared to the other technologies. the novel technology, wobble milling (fig. 1c), is also based on the principle of tilted axes. the tool chamfers the top and bottom sides of the composite while the axes of both the hole and the tool enclose an angle of ∆. this tilted motion compresses the layers of the composite, before the material is eliminated between the chamfers. the advantage of this process is that the surface is less likely to delaminate. in the case of technologies that can only be executed on the 5-axis machining centres or using industrial robots, since the time required for machining is higher than needed for drilling, a novel characteristic factor shall be introduced for their comparison, namely the average material removal rate (amrr), which gives the average amount of material that is removed over a unit of time [3]. 2. experimental and theoretical methods this chapter is comprised of three subchapters. the first summarizes the information about the workpieces, tools and machines required for the experiments. in the second, details regarding the methods applied during the experiment and analysis are provided such as the experimental design, measurements of burrs, amrr and analysis of variance (anova). 2.1 experimental setup the workpieces of the present study were composed of ud-cfrp composite plates containing a vinyl ester matrix and long carbon fibres to provide reinforcement. the plates were cut by a water-jet cutting machine into cylindrical parts with a diameter of d = 40 mm and thickness of h = 5 mm. the experiments were executed on a vhtc-130m5ht 5-axis cnc machining centre with a tilting head. two cutting tools were used for the machining: both tools were uncoated solid carbide end mills with only one cutting edge and a helix angle of λ = 25◦. for conventional drilling and milling technologies, a tool with a diameter of d1 = 6 mm (tivoly 82329710600) and of d2 = 4 mm (tivoly 82329710400) were used, respectively. a nilfisk gb733 industrial vacuum cleaner was used to eliminate chips from the working environment. no coolant was applied during the experiment. 2.2 methods full factorial experimental design by focusing on the impact of the technologies (category factor) and feed rate (continuous factor) on the burrs and amrr, an experimental design was needed that can be applied in the case of category factors as well. in this study, a full factorial experimental design [8] was applied, hungarian journal of industry and chemistry comparative analysis of burrs in ud-cfrp composites 49 table 1: parameters and their levels feed rate (mm/min) technologies (-) levels 50 100 150 t1 t2 t3 t4 figure 2: digital photo capturing moreover, the impact of the feed rate on the burrs and amrr was examined in the case of the following technologies: conventional drilling (t1), helical milling (t2), tilted helical milling (t3) and wobble milling (t4). during the experiment, a constant cutting speed of vc = 120 m/min was set, thus the spindle speeds of the tools with diameters of d1 = 6 mm and d2 = 4 mm were n1 = 6,366 rpm and n2 = 9,549 rpm, respectively. the feed rate was set at the following three levels: vf,1 = 50 mm/min, vf,2 = 100 mm/mi and vf,3 = 150 mm/min. at least one of the settings was repeated five times for each technology to ensure the experiment was reproducible. in order to eliminate the hidden errors, the 32 experimental settings were randomized. the parameters and their levels are summarized in table 1. evaluating burrs a dino-lite am0413mt digital microscope was used with a 50x magnification and dinocapture 2.0 software installed to examine the burrs. the photos were taken from the top and bottom sides of the composites which, being denoted by their individual numbers written on top, were identified with ease. a light source was placed beneath the composites to illuminate them, thereby enhancing the view of the uncut fibres as presented in fig. 2. in order to create as clear photos as possible, the distance between the composites and the microscope varied at each setting. as a result, since the holes in the photos were of different sizes, a universal evaluation method was needed to eliminate any errors when compared. this was achieved by creating an image of an ideal hole (not containing any black pixels where the white circle and black square meet) before segmenting it and calculating the number of black and white pixels found. the photos of the machined holes, after being segmented, were cropped given the absence of any black pixels at each side of the square and circular meeting point, as is shown in fig. 3. then the number of pixels was determined using the program wolfram mathematica, before being listed in microsoft excel and used for further calculations in minitab. the burrs resulting from different technologies were compared based on a burr ratio factor (fbr) and the length of the longest burr of the holes (lb). the burr ratio factor fbr = 100 1 − wi ti wid tid  (1) is based on the quotient of the ratio wi (the number of white pixels of the given hole) to ti (total number of pixels of the given hole) and the ratio of wid (the number of white pixels of the ideal hole) to tid (total number of pixels of the ideal hole). the larger fbr is, the more burrs found in the hole. by following this method, since the difference in the size of the photos does not affect the results, the comparison of holes does not depend on the distance set between the microscope and the composites. the length of the longest burr in the case of each setting examined was determined using autocad 2022 by measuring their lengths based on the photos created by dinocapture 2.0 (fig. 3a). on the one hand, measurements were made by connecting the endpoint of the longest uncut fibre to the edge of the hole with a straight line and determining the distance between them three times before calculating their mean according to lb = 1 3 3∑ j=1 lj (2) where lj (µm) denotes the measured length of the longest burr andlb (µm) represents the average length of a given burr used for comparison. on the other hand, a corrected burr length (lb,corr) was calculated by measuring the length of the burr via the creation of a polyline: the five break points of these polylines were nearly equidistant from each other and each hole was measured three times. the lengths of the polylines were calculated by lb,corr = 1 3 1 5 3∑ j=1 5∑ i=1 lij (3) where lij (µm) denotes a segment of the polyline of the longest burr and lb,corr (µm) represents the length of the burr used for comparison. average material removal rate the amrr (mm3/min), which gives the average amount of material removed, was calculated using amrr = hd2π ∆t (4) 49(2) pp. 47–52 (2021) 50 helle, pereszlai, gödri, geier figure 3: digital image processing: a) photo captured by the digital microscope, b) segmented image, c) cropping the image, d) image used for the analysis figure 4: burr ratio factor – feed rate diagram by measuring the required time for machining. in eq. 4, h = 5 mm is the height of the composite, d = 6 mm is the diameter of the holes, and ∆t (min) denotes the time required for machining. furthermore, assuming the holes have the same geometry at each setting, the average material removal rate could be determined. since the tool follows a longer path without machining in the case of 5d technologies, material is removed over a longer period of time. therefore, the average material removal rate is needed to precisely compare these technologies. analysis of variance in this study, the impact of technologies on burrs was investigated by anova. the null hypothesis states that the technologies have no significant effect on the burrs at a significance level of α = 0.05. 3. results and discussion 3.1 analysis of burrs the results show that the holes machined by conventional drilling and wobble milling are the most burr-free compared to the ideal hole, whereas the holes machined by figure 5: main effect of the technologies on the burr ratio factor at vf = 100 mm/min. tilted helical milling and helical milling contain a larger number of burrs as is shown in fig. 4. helical milling resulted in the greatest amount of burrs, contradictory to the statements made by denkena et al. [5] as well as eguti and trabasso [7] that helical milling can yield less burrs compared to conventional drilling. given the main effect of technologies shown in fig. 5, the null hypothesis was rejected, that is, these technologies have a significant impact on the burr ratio factor. there is a significant difference between the length of burrs achieved by different technologies as can be seen in fig. 6. the length of burrs was less than 1 mm for holes machined by conventional drilling and wobble milling, while the length of burrs in holes machined by tilted helical milling exceeded 2 mm at all settings. the longest burrs were produced by tilted helical milling and conventional helical milling, the latter resulted in burrs that were more than four times as long compared to conventional drilling and wobble milling at the greatest examined feed rate. wobble milling, causing short burrs and a low burr ratio factor, yielded outstanding results compared to technologies based on helical milling. analysis of variance showed that with a significance level of α = 0.05 the null hypothesis was rejected, thus hungarian journal of industry and chemistry comparative analysis of burrs in ud-cfrp composites 51 figure 6: length of burrs – feed rate the technologies have a significant effect on the length of burrs. 3.2 analysis of amrr amrr was greatest in the case of conventional drilling. the amrrs resulting from milling technologies were lower but similar. as is illustrated with the second axis of the diagram in fig. 7, the amrrs of the milling technologies are far greater than that of the drilling technology (4−5% of the amrr). the amrr values are shown in fig. 7 with a feed rate of vf = 50 mm/min. 4. conclusions in this study, 32 holes were machined by conventional drilling, helical milling, tilted helical milling and wobble milling technologies using solid carbide end mills. the conclusions are summarized as follows. • the experimental results show that the hole machining technology has a significant effect on the burr ratio factor defined at the exit of the holes. • it was observed that holes machined by conventional drilling and wobble milling are characterized by the smallest amount of burrs compared to the other examined technologies. since the burr ratio factors of holes machined by tilted helical milling and helical milling were larger, these holes contain a larger amount of burrs. holes machined by helical milling are the least ideal of the four technologies examined concerning burrs. • anova results show that the technologies have a significant effect on the length of burrs in the holes. • the length of burrs was the longest in the case of holes machined by helical milling, followed by tilted helical milling. however, with a feed rate of vf = 50 mm/min, holes machined by tilted helical milling contained the longest burrs. holes machined figure 7: amrr of the technologies compared to conventional drilling by conventional drilling and wobble milling contained shorter burrs compared to the other milling technologies. burrs of holes machined by wobble milling were the shortest, independent of the feed rate. • the amrr of conventional drilling is the largest due to the simplicity of its kinematics and the amrr of the milling technologies is around 4−5% of that of drilling for the parameter set applied during the experiment. • although wobble milling is a promising novel hole machining technology, further development is required to increase its material removal rate. acknowledgement the research reported in this paper and carried out at bme was partly supported by the national research, development and innovation office (nkfih) no. otkapd20-134430, the nrdi fund (tkp2020 nc, grant no. bme-nc) based on the charter of bolster issued by the nrdi office under the auspices of the ministry for innovation and technology and the project “centre of excellence in production informatics and control” (epic) no. eu h2020-widespread-01-20162017-teamingphase2-739592. the authors acknowledge the assistance of dániel istván poór in their experimental work. references [1] composites market report 2018. https://www.avk-tv.de download date: 2021 [2] boccarusso, l.; fazio, d.d.; durante, m.; langella, a.; capece minutolo, f.m.: cfrps drilling: comparison among holes produced by different drilling strategies. procedia cirp, 2019, 79, 325–330 doi: 10.1016/j.procir.2019.02.075 [3] geier, n.; davim, j. p.; szalay, t.: advanced cutting tools and technologies for drilling carbon fibre reinforced polymer (cfrp) composites: a review. compos. a appl. sci. 2019, 125, 105552 doi: 10.1016/j.compositesa.2019.105552 49(2) pp. 47–52 (2021) https://www.avk-tv.de/files/20181115_avk_ccev_market_report_2018_final.pdf https://doi.org/10.1016/j.procir.2019.02.075 https://doi.org/10.1016/j.procir.2019.02.075 https://doi.org/10.1016/j.compositesa.2019.105552 https://doi.org/10.1016/j.compositesa.2019.105552 52 helle, pereszlai, gödri, geier [4] poór, d. i.; geier, n.; pereszlai, c.; xu, j.: a critical review of the drilling of cfrp composites: burr formation, characterisation and challenges. compos. b eng. 2021, 223, 109155 doi: 10.1016/j.compositesb.2021.109155 [5] denkena, b.; boehnke, d.; dege, j. h.: helical milling of cfrp–titanium layer compounds. cirp j. manuf. sci. technol., 2008, 1(2), 64–69 doi: 10.1016/j.cirpj.2008.09.009 [6] pereira, r. b. d.; brandăo, l. c.; de paiva, a. p.; ferreira, j. r.; davim, j. p.: a review of helical milling process. int. j. mach. tools manuf. 2017, 120, 27–48 doi: 10.1016/j.ijmachtools.2017.05.002 [7] wang, q.; wu, y.; bitou, t.; nomura, m.; fujii, t.: proposal of a tilted helical milling technique for high quality hole drilling of cfrp: kinetic analysis of hole formation and material removal. int. j. adv. manuf. technol. 2018, 94(9–12), 4221–4235 doi: 10.1007/s00170-017-1106-3 [8] full factorial design an overview. sciencedirect topics. 2018 https://www.sciencedirect.com hungarian journal of industry and chemistry https://doi.org/10.1016/j.compositesb.2021.109155 https://doi.org/10.1016/j.compositesb.2021.109155 https://doi.org/10.1016/j.cirpj.2008.09.009 https://doi.org/10.1016/j.cirpj.2008.09.009 https://doi.org/10.1016/j.ijmachtools.2017.05.002 https://doi.org/10.1007/s00170-017-1106-3 https://www.sciencedirect.com/topics/engineering/full-factorial-design introduction experimental and theoretical methods experimental setup methods full factorial experimental design evaluating burrs average material removal rate analysis of variance results and discussion analysis of burrs analysis of amrr conclusions hungarian journal of industry and chemistry vol. 50 pp. 33–43 (2022) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2022-07 unraveling the novel bacterial assisted biodegradation pathway of morpholine rupak kumar*1, suman kapur2, and srinivasa rao vulichi2,3 1central drugs standard control organization, new delhi, india 2birla institute of technology and science – pilani, hyderabad campus, hyderabad, india 3svu college of pharmaceutical sciences, sri venkateswara university, tirupati, india most xenobiotics are biodegradable, persistent or recalcitrant in nature. morpholine, a typical xenobiotic, was initially regarded as recalcitrant, however, later proved to be biodegradable by bacterial species like mycobacterium and pseudomonas in particular. however, establishing the metabolic pathways involved for the successful biodegradation of morpholine is challenging because of its extreme level of water solubility that affects various analytical procedures. in addition, to date, no suitable analytical methods have been reported to directly estimate morpholine and its degradable products or intermediates. nevertheless, methods, especially optical density, gas chromatography and mass spectrophotometric analysis, could indirectly estimate the degradation product(s) of morpholine formed as a result of its biotransformation. in the present study, the degradation pathway of morpholine was ascertained by selected bacterial isolates by measuring their capacity to degrade morpholine. based on this analysis of culture filtrates, it was determined that the novel isolate is the genus halobacillus blutaparonensis which follows the diglycolic acid route from the metabolic degradation pathway of morpholine to induce one of two branches of the morpholine biodegradation pathway. in the presence of concentration of morpholine, out of two branches of morpholine degradation one branch is induced, while the other branch is inhibited. whatever the branches with regard to the degradation pathway of morpholine exhibited by bacteria are, ammonia is the final end product of degradation which might be biochemically utilized by the isolate. keywords: morpholine, xenobiotic, recalcitrant, glycolic acid route, ammonia 1. introduction environmental pollution has become a global problem. due to the indiscriminate and frequent release of xenobiotics as a result of different anthropogenic activities, each and every day our environment becomes increasingly devastated by the pollutants. morpholine (1-oxa4-azacyclohexane) is one such heterocyclic xenobiotic organic chemical with different versatile applications in various processes in the rubber, paper, iron, textile, personal care, pharmaceutical and agricultural industries amongst others. as a consequence of its vast operational usage, a significant amount of this chemical is released into the environment through the differential process of discharging at both microand macro-concentrations. therefore, it is necessary to mention that anthropogenic environmental pollutants, even at low concentrations, often produce deleterious effects on organisms, which are recieved: 1 march 2022; revised: 20 april 2022; accepted: 26 april 2022 *correspondence: rupakraman@gmail.com difficult to predict because measurable effects are expressed only after prolonged exposure. in the environment, the majority of exposure to morpholine originates from water and leads to the formation of the carcinogen n-nitrosomorpholine (nmor) by the process of natural nitrosation [1] (fig. 1). furthermore, it is pertinent to mention that this process of nitrosation may occur in biological systems when directly consumed, ingested, inhaled and applied to the skin. in addition, nmor is known as a mediator of various debilitating cancers associated with organs like the digestive tract, respiratory tract, kidneys and liver, which is eventually biomagnified through different trophic levels of biota by its application or the intake of polluted water leading to this carcinogen entering the food chain. in figure 1: formation of nmor https://doi.org/10.33927/hjic-2022-07 mailto:rupakraman@gmail.com 34 kumar, kapur, and vulichi this regard, it would be best to provide a solution for its efficient discharge or effective removal by different physical and chemical processes. recently, photocatalysis using catalysts irradiated by ultraviolet or visible light has been applied for the mineralization of toxic organic dyes in water and carbon dioxide [2, 3]. however, a costeffective, environmentally-friendly biological tool powered by microbes has been widely used as an ancient core concept for the purpose of conserving the natural environment and resources to curb the negative impacts on biotic components. therefore, a sustainable solution driven by microbes must be explored to elucidate the degradation pathway and measure how potent microbes are for the purposes of decontaminating a wide range of pollutants and their mitigation. in general, most pollutants are organic and may be biodegradable (transformed by biological mechanisms which might lead to mineralization), persistent (fail to undergo bioremediation in the environment or under a specific set of experimental conditions) or recalcitrant (inherently resistant to biodegradation) in nature. biogenic or naturally occurring compounds are biodegradable while man-made (anthropogenic) compounds may be biodegradable, persistent or recalcitrant. in terms of xenobiotics that are man-made, the microbial communities present in the environment may not have evolved suitable mechanisms for their degradation. many possible mechanisms exist which differ from one xenobiotic to another. one common mechanism is the binding of enzymes analogous to their natural substrates which contain xenobiotic functional groups, assuming these do not greatly alter or change the active site which catalyzes a reaction with the xenobiotic. the success of this enzymatic reaction (as a biodegradation mechanism) also depends on other factors such as the ability of the xenobiotic as an inducer or inhibitor and the nature of the product/intermediate formed. specific to morpholine, the metabolic degradation pathway has been very difficult to establish because of the aforementioned technical limitation. 1.1 sustainable remediation of morpholine and its degradation pathway although morpholine was previously thought to be recalcitrant, several microbes have proven to metabolically degrade it. the majority of studies showed that the species mycobacterium and pseudomonas are the two potential bacterial isolates that utilize morpholine as their sole source of carbon and nitrogen, thereby undergoing degradation [4–7]. a few studies have been carried out to understand the biodegradation of morpholine and its regulation [8–10]. later a hypothetical pathway was proposed for the complete mineralization of morpholine that could proceed via 2-(2-aminoethoxy)acetate to produce its diglycolate salt and/or ethanolamine [5, 11, 12]. these two different routes of degradation are called the ethanolamine/monoethanolamine pathway (pathway 1) (a) (b) figure 2: (a) hypothetical pathway of morpholine degradation where x = 2-(2-aminoethoxy)acetaldehyde, y = 2(2-aminoethoxy)acetate and a, b, c indicate the position of carbon atoms in the ring. (b) postulation of the morpholine degradation pathway after 1h-nmr and ion spectroscopic analyses where 1 = 2-(2-aminoethoxy)acetate, 2 = diglycolic acid and 3 = glycolic acid. and diglycolic acid/glycolate pathway (pathway 2), respectively (fig. 2a). the illustrated degradation pathway might start with the cleavage of the c-n bond, leading to the formation of an intermediary amino acid which is followed by deamination and oxidation of this amino acid to form a diacid [11, 12]. the degradation of morpholine via the ethanolamine or glycolate pathways has been described in the presence of mycobacterium chelonae and m. aurum mo1 [8, 9] (fig. 2a). the degradation of morpholine is likely to begin with the breakage of a bond between a heteroatom and an adjacent carbon atom by the enzyme morpholine monooxygenase, which is responsible for the ring cleavage. morpholine monooxygenase is an important enzyme in the degradation of morpholine as it catalyzes the biotransformation of morpholine to form 2(2-aminoethoxy)acetic acid and contains a catalytic subunit of cytochrome p450 [1, 10]. morpholine could serve as a substrate for flavin-containing monooxygenases or cytochromes p450 which is associated with oxygen consumption [13]. further inhibitory effects of metyrapone on the degradation of the mycobacterium strain rp1 have been attributed to the involvement of cytochromes p450 hungarian journal of industry and chemistry bacterial assisted biodegradation pathway of morpholine 35 in the biodegradation of morpholine [5]. depending on the concentration of morpholine in the culture medium, one pathway could be expressed while the other might be inhibited [11]. recently, a new approach was applied in which the culture filtrate was analyzed by 1h-nmr spectroscopy and ion spectroscopy to identify the metabolic intermediates of morpholine degradation by m. aurum mo1 [11, 12] (fig. 2). although many different species of mycobacterium have been shown to degrade morpholine via this shared group of degradation reactions, little information is known about the enzymes involved (fig. 2b). furthermore, the byproducts of the microbial processes can be indicative of a successful bioremediation process. consequently, since only hypothetical pathways have been proposed, limited interpretations of various experimental designs can be made to establish the degradation pathway that follows the route of degradation pathway that follows the route of pathway 1 and /or pathway 2 via the shared formation of 2-(2aminoethoxy)acetate. 2. materials and methods 2.1 environmental samples the sample used in the present degradation study was collected from natural sources (soil) in and around durgapur steel plant, west bengal, india. the site is located in durgapur at a latitude of 51◦50’43.8” north and a longitude of 8◦16’35.8” west in the state of west bengal, india. soil samples consisted of blackish fine-to-medium sub-angular gravel in the upper surface, including fine sand and a high content of iron flecks. samples were collected in a clean, sterile plastic container before being transferred to the laboratory and stored at room temperature until used for further analysis. 2.2 chemicals and reagents all chemicals and reagents were of analytical grade and used as received without any further purification. even though milli-q water (elix essential 3 water purification system with a conductance of 0.12 siemens) was used to prepare an aqueous solution of reagents, autoclaved double distilled water was used because of the microbial cultures. 2.3 screening, characterization and sequence accession of the morpholinedegrading isolate for the initial isolation and cultivation of bacteria, tenfold serial diluted samples were spread onto nutrient agar plates, which were prepared according to the manufacturer’s instructions. the specific colonies obtained were subcultured further to isolate the pure bacterial strain. the selected pure bacterial isolate was identified based on morphological, biochemical and molecular characterization. morphological characterization was achieved by visually observing colonies in terms of their appearance, shape, color, arrangement, optical nature, margin, texture and elevation. however, the biochemical tests were performed as per standard methods [14]. furthermore, the pure colony was then identified by 16s rrna gene sequence analysis. in order to verify the phylogenetic affiliation of the selected isolate, a single colony was collected for the purpose of dna isolation (instagenetm matrix genomic dna isolation kit (bio-rad catalog # 7326030) as per the kit instructions and procedures) and subjected to polymeric chain reaction (pcr) analysis using primers targeting two 16s rrna genes [27f (5’-agagtttgatcmtggctcag-3’) and 1492r (5’tacggytaccttgttacgactt-3’-). a pcr reaction (20 µl) was performed containing 8 µl of taq dna polymerase master mix, 1 µl of both 10 µm stock 27f/1492r primers, 9 µl of double distilled water and 1 µl of a dna template. the pcr (mj research ptc200 peltier thermal cycler; bio-rad ptc-200) reaction was conducted using specified conditions from the literature [15]. dna was denatured at 94◦c for 5 mins, followed by 35 cycles of amplification, each consisting of the following components: 94◦c for 45 secs (denaturation), 55◦c for 60 secs (annealing), 72◦c for 60 secs, (extension) followed by 72◦c for 10 mins (final extension). the pcr product was sequenced by yaazh xenomics, chennai, tamil nadu, india. the 16s rrna gene was sequenced using the national center for biotechnology information’s basic local alignment search tool (blast). the phylogenetic analysis of the sequence using the closely related sequence of blast results was performed by multiple sequence alignment. the program muscle 3.7 was used for multiple sequence alignments [16]. the resulting aligned sequences were filtered using the program gblocks 0.91b, which eliminates poorly aligned positions and divergent regions, that is, removes alignment noise [17]. finally, the program phyml 3.0 alrt was used for phylogenetic analysis and hky85 as a substitution model. the nucleotide sequence of the isolated bacterium was included in ncbi’s genbank and assigned an accession number consisting of 2 letters and 6 numbers [18]. 2.4 cultivation and acclimatization of the isolate: microbial adaptation against morpholine bacterial inocula were prepared by aseptically transferring the selected identified pure colonies to 10 ml of an enriched media called knapp buffer. alternatively, a mineral salt solution (mss) comprised of 100 mg of kh2po4, 100 mg of k2hpo4, 4 mg of mgso4.7h2o and 0.2 mg of fecl3 was used as previously described by the author supplemented with 0.1% v/v morpholine as previously described by the author [19]. cultures were incubated at 37oc as well as 150 rpm for 1−2 weeks and 50 pp. 33–43 (2022) 36 kumar, kapur, and vulichi table 1: gc parameters for the estimation of the monoethanolamine concentration parameters specificity column and its configuration rtx-35 30 mm × 0.32 mm × 1 µm oven/column temperature initial temp.: 60 ◦c hold: 1 min ramp rate: 30 ◦c/min final temp.: 240 ◦c maintained for 3 mins linear velocity: 37.6 cm/sec (for nitrogen) injection port temp.: 200 ◦c split ratio: 30:1 injection volume: 1 µl carrier gases (mobile phase) column gas flow rate: 2 ml/min purge gas flow rate: 1 ml/min hydrogen gas flow rate: 40 ml/min zero air flow rate: 400 ml/min nitrogen gas flow rate: 15 ml/min stationary phase 60% dimethylpolysiloxane and 35% diphenyl polysiloxane detector flame ionization detector at 300 ◦c analysis time 10 mins software gc solution workstation windows 8 their absorbance at 600 nm was taken regularly as a measure of growth. based on their growth, when an optical density of 0.5 was reached (data not shown), the culture was diluted to 1 : 100 before being further spread onto mss-agar plates (treated with 2% agar + 0.1% morpholine) to confirm the acclimatization of the isolate against morpholine stress. furthermore, the growing culture was centrifuged at 6500 rpm for 10 mins and the pellet was resuspended in the mss medium while gradually increasing the concentration of morpholine to 0.2% which was referred to as a seeded acclimatized bacterial inoculum. for each increased acclimatization study, the tested bacteria were grown in an mss broth supplemented with an increased concentration of morpholine and a respective mss-agar plate with the same concentration of morpholine to confirm the said acclimatization. the acclimatized inoculum was later grown in the presence of an intermediate degradation product of morpholine to explore whether this particular isolate follows pathway 1 or 2. this was further validated by performing in-vitro chemical and analytical assay(s) with the availability of intermediate product of morpholine degradation in the culture filtrate. lastly, estimation of the ammoniacal nitrogen (measure of the amount of ammonia) in the culture filtrate revealed the complete degradation of morpholine by this isolate following the concerned pathway. 2.5 growth on different hypothetical degradation intermediate compounds the growth of the isolate on various substrates (degradation intermediate compounds) was investigated by adding the corresponding compounds (0.15%) to the mss. the ph of the media was adjusted to 7 and growth carried out at 37◦c as well as 150 rpm for 48 hours. at regular time intervals, the absorbance was measured in terms of optical density to establish whether these degradation products might have been formed to facilitate the growth of the isolated bacteria. 2.6 chemical tests of intermediate(s) in the degradation pathway chemical tests on degradation products, mainly monoethanolamine (primary amine) and morpholine (secondary amine), were carried out by the standard simon test 1 (rimini test) and simon test 2 (modified rimini test) on the culture filtrate to determine the presence of primary and secondary amines [20]. the amine undergoes a nucleophilic addition reaction with nitroprusside ions in the presence of acetaldehyde or a ketone to yield the characteristic color of primary amines (blue) or secondary amines (violet). 2.7 gas chromatography (gc) studies of degradation intermediate(s) a gc system (shimadzu gc-2010) equipped with a standard oven for temperature ramping, split condition, injection ports, a flame ionization detector and a rtx-35 amine column (30 mm × 0.32 mm × 1µm film thickness) in the presence of nitrogen as a carrier gas by the direct injection method was used for the analysis of monoethanolamine (mea). the analytical parameters for the analysis of mea are summarized in table 1, as per the method (by modifying the column and its parameters) reported in the literature [21]. hungarian journal of industry and chemistry bacterial assisted biodegradation pathway of morpholine 37 table 2: ms operating parameters for intermediate(s) parameter specificity ionization electrospray ionization needle voltage = 4.5 kv interface temperature 350 ◦c temperature of heating block 200 ◦c sheath/drying gas flow rate 15 l/min nebulizer gas flow rate 1.5 l/min acquisition time 2 mins acquisition mode positive/negative scan m/z 50− 200 scan speed = 52 units/sec sampling acquisition time = 1.56 hz (640 msec) detector electron multiplier software lab solutions workstation windows 7 a standard solution of 0.125 to 0.5% v/v mea (corresponding to ppm and prepared in methanol) was injected along with the processed culture supernatant (1:10, filtrate volume of 1 and 9 volumes of methanol), as per the method described above. gc of the test samples was run against blank media using positive controls to quantify or estimate the presence of mea in the culture filtrate by analyzing the area under the curve (auc) calculated by the machine. 2.8 mass spectrometry studies of degradation intermediate(s) the mass spectrometry (ms) system of an integrated liquid chromatography-mass spectrometry instrument (shimadzu lcms-2020) equipped with an inlet interface, ion source, mass analyzer and detector was used to analyze the degradation products of morpholine. the analytical parameters for ascertain the morpholine degradation products are summarized in table 2. the sample for injection was prepared without using a solvent, as per the method reported in the literature [12]. the culture sample (5 ml) was centrifuged at 10,000 rpm for 10 mins before the supernatant was filtered through a nylon filter with a pore size of 0.22 µm (axiva sichem biotech, india) to remove any bacterial cells. 1 ml of neat filtrate was injected directly into the ms instrument. 2.9 estimation of the ammonia concentration the presence of ammonia in the culture supernatant was estimated by the standard nessler’s method [22], which involves coupling of ammonium to the nessler’s reagent figure 3: estimation of the ammoniacal nitrogen concentration by nessler’s method to produce a yellow color under strongly alkaline conditions (fig. 3). the resulting yellow color was formed in proportion to the ammonium (nh+ 4 ) concentration and was measured at a wavelength of 405 nm using an elisa reader (elx50/8ms biotek india) against a reagent blank. the ammonia level in terms of ammoniacal nitrogen was expressed in mg/l (ppm). a standard solution of 10 ppm of nh+ 4 −n was prepared by dissolving 4.773 mg of ammonium chloride in 125 ml of doubledistilled water and further diluted to make solutions of 1− 5 ppm nh+ 4 −n. a calibration curve was plotted and is presented in the results section. 3. results and discussion 3.1 morphological, biochemical and molecular identification morphologically, the isolate was found to be white in color with a dull opaque appearance, rod-shaped, have a smooth texture and grow as a convex elevation colony. standard staining reported it to be a gram-negative bacterium with high motility which also showed signs of growth on a selective medium, namely hicrome uti agar m1353. the primary sequence of the 16s rrna from the present bacterial isolate was determined. the program phyml 3.0 alrt for phylogenetic analysis and hky85 as a substitution model on the 16s rrna gene sequences determined the phylogenetic position of said isolate to be a species closely related to the genus halobacillus blutaparonensis with a sequence representative of e. coli (fig. 4). nucleotide sequence accession was assigned by genbank, ncbi and an accession number of kc345029 was figure 4: molecular phylogeny of the 16s rrna gene sequence and sequences from identified bacteria in the database. the sequence of e. coli served as the outgroup for rooting the tree. 50 pp. 33–43 (2022) 38 kumar, kapur, and vulichi figure 5: growth of the isolate in the presence of intermediates of morpholine degradation figure 6: gc (rtx-35)flame ionization detector chromatogram of mea assigned to this bacterial isolate of genus halobacillus blutaparonensis. 3.2 growth on intermediates the isolate grew in the presence of morpholine and the intermediate, namely aminoethoxy ethanol (reduced product of aminoethoxy acetate) by consuming it as a source of carbon and nitrogen. however, no growth was recorded in the presence of ethanolamine in the culture media shown in fig. 5. the count of bacterial cells was adjusted to 1×108 cells/ml (1 unit of absorbance = 5×108 cells) by varying the incubation periods up to 48 hours. 3.3 chemical assay of intermediate(s) based on simon tests 1 and 2 [20], the presence of mea and morpholine in the culture filtrate is shown in table 3. 3.4 gc studies of mea in the culture supernatant gc of the culture supernatant was run at different concentrations (ppm) of a standard mea solution. table 4 and fig. 6 indicate a retention time of mea equal to 2.2 mins which was absent in the diluted culture supernatant. gc analysis revealed that no mea was present in the culture supernatant suggesting that bacteria might prefer the diglycolic route (pathway 2) of morpholine degradation which was later confirmed by ms analysis. 3.5 ms studies of the culture filtrate ms was run directly with a neat culture filtrate. each sample was analyzed separately in both the positive and negative ion modes (table 5 and fig. 7). it was observed that the m/z peak of the neat culture filtrate (fig. 7) indicates the presence of 2-(2aminoethoxy)acetate (c4h9no3, molecular weight = 119.119 and m/z = 120 as [m+h]+) and an anion of diglycolic acid (c4h6o5, molecular weight = 134.09 and m/z = 133 as [m-h]–) which supports the fact that this particular isolate prefers the degradation pathway of diglycolic acid (pathway 2), similar to a strain of mycobacterium reported earlier by conducting electrospray ionization mass spectrometry on the culture filtrate [12]. further ms analysis supports the gc findings that mea is not present in the culture filtrate because it might have an inhibitory effect on the bacteria. therefore, the said bacterial isolate prefers the diglycolic acid route of the metabolic pathway given the fact that in the presence of morpholine, one of the two branches of morpholine biodegradation was induced while the other was inhibited. the illustrated degradation pathway might start with the cleavage of c-n bond, leading to the formation of an intermediary amino acid followed by deamination and oxidation of this amino acid to form a diacid as is shown in fig. 2b. 3.6 ammonia release: as the end product of morpholine degradation morpholine can be degraded by bacteria which releases ammonia. whichever degradation pathway of morpholine is followed, ammonia is produced as an end product. the concentration of ammoniacal nitrogen produced by the isolate was calculated (table 6 and fig. 8) by the regression equation of a standard curve (y = 0.137x with r2 = 0.98) and found to be present at a concentration of 5.2 ppm based on nessler’s quantification. the initial morpholine concentration in the culture supernatant (before degradation) was reported to be 2000 ppm. the molar ratio with regard to the conversion of morpholine into ammonia was found to be 1 : 0.014. furthermore, it was shown that the final ph of the media throughout the experiment did not change, supporting the fact that a low concentration of ammonia was released as an end product of morpholine degradation. hungarian journal of industry and chemistry bacterial assisted biodegradation pathway of morpholine 39 table 3: simon tests for the presence of the primary amine mea and secondary amine morpholine in the culture supernatant sample test feature remark result morpholine simon 1 characteristic blue color of the secondary amine morpholine positive mea simon 2 characteristic violet color of the primary amine mea positive culture media simon 1 no characteristic blue color morpholine negative simon 2 no characteristic violet color mea negative culture supernatant (filtrate) simon 1 no characteristic blue color morpholine negative simon 2 no characteristic violet color mea negative 50 pp. 33–43 (2022) 40 kumar, kapur, and vulichi table 4: gc analysis of the diluted culture filtrate vial retention time (mins) auc interpretation (compound) methanol 1.331 378534920.9 methanol 5000 ppm mea 1.333 2.218 366649701.7 2748948.5 methanol mea 2500 ppm mea 1.331 2.216 374551161.2 2397300.9 methanol mea 1250 ppm mea 1.331 2.211 378803557.4 1149593.1 methanol mea culture supernatant (1:10) 1.334 2.331 310947764.4 92353.6 methanol no/negligible mea table 5: expected intermediate according to the ms analysis of the culture filtrate. sample m/z positive mode m/z negative mode remark neat culture filtrate 120 [m+h] + 2,2 aminoethoxy acetate 133 [m-h] – anion of diglycolic acid figure 7: electrospray ionization ms spectra recorded under positive and negative ionization of the neat culture filtrate. hungarian journal of industry and chemistry bacterial assisted biodegradation pathway of morpholine 41 table 6: estimation of ammoniacal nitrogen concentration by nessler’s reagent well 10 ppm stock nh4-n+ (µl) milli-q water (µl) culture media (µl) 50% na-k tartrate (µl) nessler’s reagent (µl) net absorbance at 405 nm 1 ppm 25 225 — 5 5 0.091 2 ppm 50 200 — 5 5 0.284 3 ppm 75 175 — 5 5 0.353 4 ppm 100 150 — 5 5 0.552 5 ppm 125 125 — 5 5 0.725 culture supernatant 250 — 5 5 0.725 figure 8: standard curve of ammoniacal nitrogen concentration by nessler’s reagent 4. discussion based on the results summarized, it has been reported that the isolate prefers to undergo the diglycolic acid route of degradation instead of the ethanolamine pathway, which might be an inhibitory effect on bacterial growth. the illustrated degradation pathway starts with cleavage of the c-n bond, leading to the formation of an intermediary amino acid which is followed by deamination and oxidation to form the diacid (fig. 9). this diacid, namely diglycolate, later participates in intermediate metabolism and is converted indirectly into tca by the krebs cycle, which is beyond the scope of the present article. moreover, the presence of degradation intermediate compounds in culture filtrate also favors this finding with the conclusion that the diglycolic acid route of biodegradation might be a common degradation mechanism, which is also shown by other strains of bacteria, proceeding via 2-(2-aminoethoxy)acetate. the said investigation to reveal the degradation pathway of morpholine is supported by similar findings published by other authors [5, 10–12]. furthermore, whatever the degradation pathway exhibited by the bacterial isolate, the end product, that is, ammonia, will be biochemically produced and used. our studies confirm the presence of ammonia as an end product in a molar conversion ratio of morpholine to ammonia of 1 : 0.014. due to the low concentration of ammonia produced, the ph of the culture medium did not change throughout the experiment. however, a higher molar ratio of morpholine to ammonia brought about an inhibitory effect on the growth of bacteria by increasing the ph of the medium and making it more alkaline. the molar ratio of morpholine to ammonia was found to be different for different strains of bacteria as viz., namely 1 : 0.5 for mycobacterium sp. he5 [6], 1 : 0.89 for mycobacterium sp. [7] and 1 : 0.82 for mycobacterium sp. mo1 [9]. 5. conclusions the large scale industrial applications of morpholine and its known carcinogenic effect thus have an environmental interest for its biodegradation and exploring the degradative pathway so that unrevertable damage to the natural environment and biota can be minimized. along with the mycobacterium and pseudomonas sp. another potential isolate namely halobacillus blutaparonensis has been investigated for its ability to removal of morpholine by adopting the diglycolate degradation pathway. hence, sustainable remediation practice by utilizing effective microbes should be applied to bring the environmental cleanup or facilitate the existing system of effluent treatment mechanism incorporation with biological approaches to minimize the impact of xenobiotic pollutants in the anthropocentric epoch. conflicts of interest the authors confirm no conflicts of interest with regard to the results derived from this study on the sustainable remediation of morpholine and its micro-scale degradation pathway. references [1] sielaff, b.; andreesen, j. r.; schräder, t. a.: cytochrome p450 and a ferredoxin isolated from mycobacterium sp. strain he5 after growth on morpholine. appl. microbiol. biotechnol., 2001, 56(3-4), 458–464 doi: 10.1007/s002530100634 [2] dhiwahar, a. t.; maruthamuthu, s.; marnadu, r.; sundararajan, m.; manthrammel, m. a.; shkir, m.; sakthivel, p.; reddy, v. r. m.: improved photocatalytic degradation of rhodamine b under visible light and magnetic properties using microwave 50 pp. 33–43 (2022) https://doi.org/10.1007/s002530100634 42 kumar, kapur, and vulichi figure 9: the complete illustration of a possible degradation pathway of morpholine. the isolate, namely halobacillus blutaparonensis, prefers pathway 2 for the successful removal of morpholine. abbreviations used tca: tricarboxylic acid; atp: adenosine triphosphate; adp: adenosine diphosphate; h+: hydrogen atom; e-: free electron; o2: oxygen molecule; 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10.1016/j.jinorgbio.2008.08.013 [11] combourieu, b.; besse, p.; sancelme, m.; verschambre, h.; delort, a. m.; poupin, p.; truffaut, n.: morpholine degradation pathway of mycobacterium aurum mo1: direct evidence of intermediates by in situ 1h nuclear magnetic resonance. appl. environ. microbiol., 1998, 64(1), 153–158 doi: 10.1128/aem.64.1.153-158.1998 [12] combourieu, b.; besse, p.; sancelme, m.; godin, j.-p.; monteil, a.; veschambre, h.; delort, a.m.: common degradative pathways of morpholine, thiomorpholine, and piperidine by mycobacterium aurum mo1: evidence from 1h-nuclear magnetic resonance and ionspray mass spectrometry performed directly on the incubation medium. appl. environ. microbiol., 2000, 66(8), 3187–3193 doi: 10.1128/aem.66.8.3187-3193.2000 hungarian journal of industry and chemistry https://doi.org/10.1016/j.solidstatesciences.2021.106542 https://doi.org/10.33927/hjic-2021-02 https://doi.org/10.1023/a:1008855912907 https://doi.org/10.1128/aem.64.1.159-165.1998 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k.; plateel, g.; charrière, n.; vernez, d.: a simple gas chromatography method for the analysis of monoethanolamine in air. j. sep. sci., 2012, 35(17), 2249–2255 doi: 10.1002/jssc.201200196 [22] crosby, n. t.: determination of ammonia by the nessler method in waters containing hydrazine. analyst, 1986, 93(1107), 406–408 doi: 10.1039/an9689300406 50 pp. 33–43 (2022) https://doi.org/10.1111/j.1472-765x.1996.tb00202.x https://doi.org/10.1111/j.1472-765x.1996.tb00202.x https://www.wjpr.net/abstract_show/2951 https://doi.org/10.1093/nar/gkh340 https://doi.org/10.1093/nar/gkh340 https://doi.org/10.1080/10635150701472164 https://doi.org/10.1080/10635150701472164 https://www.ncbi.nlm.nih.gov/genbank https://www.unodc.org/pdf/scientific/scitec20-fin.pdf https://doi.org/10.1002/jssc.201200196 https://doi.org/10.1039/an9689300406 https://doi.org/10.1039/an9689300406 introduction sustainable remediation of morpholine and its degradation pathway materials and methods environmental samples chemicals and reagents screening, characterization and sequence accession of the morpholine-degrading isolate cultivation and acclimatization of the isolate: microbial adaptation against morpholine growth on different hypothetical degradation intermediate compounds chemical tests of intermediate(s) in the degradation pathway gas chromatography (gc) studies of degradation intermediate(s) mass spectrometry studies of degradation intermediate(s) estimation of the ammonia concentration results and discussion morphological, biochemical and molecular identification growth on intermediates chemical assay of intermediate(s) gc studies of mea in the culture supernatant ms studies of the culture filtrate ammonia release: as the end product of morpholine degradation discussion conclusions microsoft word inner cover.docx the hungarian journal of industry and chemistry (hjic) formerly (until 2012) the hungarian journal of industrial chemistry the hjic is an international periodicals that focuses on results of fundamental and applied research in the field of • biotechnology • chemical engineering science • chemical processes • energetics • environmental chemistry • environmental engineering & technology • industrial management • material science • mechanical engineering • mechatronics • process & system engineering • recycling in the form of original papers, reviews, short communications, and conference proceedings written in english. editorial board editor-in-chief: róbert k. szilágyi department of chemistry and biochemistry, montana state university, bozeman, mt, u.s.a. honorary senior editor: géza horváth department of chemical engineering science, university of pannonia, veszprém, hungary associate editors: jános abonyi department of process engineering, university of pannonia, veszprém, hungary dezső boda department of physical chemistry, university of pannonia, veszprém, hungary norbert miskolczi mol department of hydrocarbon and coal processing, university of pannonia, veszprém, hungary dóra rippel pethő department of chemical engineering science, university of pannonia, veszprém, hungary editors: lászló bartha mol department of hydrocarbon and coal processing, university of pannonia, veszprém, hungary katalin bélafi-bakó research institute of bioengineering, membrane technology and energetics, university of pannonia, veszprém, hungary peter czermak institute of bioprocess engineering and pharmaceutical technology, mittelhessen university of applied sciences, giessen, germany dénes fodor institute of mechanical engineering, university of pannonia, veszprém, hungary maria gavrilescu department of environmental engineering and management, gheorghe asachi technical university of iasi, romania lászló gubicza research institute of bioengineering, membrane technology and energetics, university of pannonia, veszprém, hungary jenő hancsók mol department of hydrocarbon and coal processing, university of pannonia, veszprém, hungary jiří klemeš centre for process integration and intensification, university of pannonia, veszprém, hungary zoltán kovács department of management, university of pannonia, veszprém, hungary jános kristóf department of analytical chemistry, university of pannonia, veszprém, hungary istván szalai institute of physics and mechatronics, university of pannonia, veszprém, hungary ferenc szeifert department of process engineering, university of pannonia, veszprém, hungary jános szépvölgyi research centre for natural sciences, university of pannonia, veszprém, hungary imre tímár institute of mechanical engineering, university of pannonia, veszprém, hungary gyula vatai department of food engineering, corvinus university of budapest, hungary gábor veress federation of technical and scientific societies – mtesz budapest, hungary ibolya zsoldos department of material science and technology, széchenyi istván university, győr, hungary editorial office: university of pannonia, p.o. box 158, veszprém, 8201 (hungary) tel.: +36 (88) 624-746, e-mail: hjic@almos.uni-pannon.hu; web: hjic.mk.uni-pannon.hu felelős szerkesztő: szilágyi róbert károly nyelvi lektor: matthew chen kiadja: pannon egyetem, 8200 veszprém, egyetem u. 10. levélcím: h-8201 veszprém, postafiók 158, tel.: (88) 624-000 felelős kiadó: a pannon egyetem, mérnöki kar dékánja hung. j. ind. & chem. 2014, vol. 42(2), pp. 57-113 table of contents a comparison of advanced non-linear state estimation techniques for ground vehicles györgy max, béla lantos ...................................................................................................... 57-64 telemedical heart rate measurement for lifestyle counselling mario salai, gergely tuboly, istván vassányi, istván kósa .......................................... 65-70 the application of unknown input estimators to damp load oscillations of overhead cranes bálint patartics, bálint kiss ................................................................................................. 71-77 challenges of enterprise policy compliance with smartphone enablement or an alternative solution based on behaviour-based user identification sándor dobos, attila kovács ................................................................................................ 79-84 measurement-based modelling and simulation of a hydrogen-generating dry cell for complex domestic renewable energy systems attila göllei, péter görbe, attila magyar, lászló neukirchner ................................. 85-89 quasi-polynomial representation-based control of mechanical systems lászló neukirchner, attila magyar .................................................................................... 91-95 a network model for simulating the dynamic behaviour of an energy distribution network levente bálint, tibor dulai, ágnes stark-werner, gergely apostol, ádám tompos ........................................................................................................................... 97-101 on the parametric uncertainty of weakly reversible realizations of kinetic systems györgy lipták, gábor szederkényi, katalin m. hangos .............................................. 103-107 stability and parameter sensitivity analyses of an induction motor attila fodor, roland bálint, attila magyar, gábor szederkényi ........................... 109-113 editorial preface systems and control theory is a constantly evolving scientific area and the dominant driving force in key industries and engineering fields e.g. process engineering, automotive engineering, bioengineering, and the energy industry. the aim of the current issue (volume 42, number 2) is to provide an overview of research topics pursued by selected phd students. the papers presented here were selected from contributions at the 13th international phd workshop on systems and control conference held on august 25, 2014 (virt.uni-pannon.hu/phdws2014). the objective of the conference was to establish an international forum for young researchers. the meeting provided opportunities for the participants to present and discuss the latest results and up-to-date applications in systems and control. this issue represents the entire spectrum of systems and control engineering as follows: • process modelling and analysis • control (traditional, intelligent, adaptive, etc.) • process monitoring and supervision • system identification and signal processing • bioengineering • traffic control • reaction kinetic networks • modelling of complex systems (classical, hierarchical, bayesian, fuzzy, networks) • image processing and pattern recognition • artificial intelligence • soft computing (neural, genetic, fuzzy algorithms, etc.) • software (parallel computing, distributed and network computing, data visualization) • decision making (decision support, data mining) • applications of systems and control theory the organizers are grateful for the contributions of the authors. the tradition of the international phd workshop continues. you are invited to participate at the 14th international phd workshop in veszprém in 2015! attila magyar university of pannonia, veszprém, hungary guest editor hungarian journal of industry and chemistry veszprém vol. 42(2) pp. 57–64 (2014) a comparison of advanced non-linear state estimation techniques for ground vehicles györgy max! and béla lantos 1 department of control engineering and informatics, budapest university of technology and economics, magyar tudósok körútja 2, budapest, 1117, hungary !email: max@iit.bme.hu this paper presents a comparative examination of state-of-the-art non-linear state estimation techniques. first, the sigmapoint (spkf) stochastic estimators are investigated on the basis of the unscented transformation. this is followed by the technique of non-linear symmetry-preserving observers for non-linear dynamics on the basis of symmetrical lie groups. the variety of the deterministic and stochastic state estimation algorithms is studied the kinematics of ground vehicles. two cases are described that deal with the reliability of path tracking, the convergence and speed of off-line calibration. keywords: state estimation, invariant observers, unscented kalman filter, vehicle kinematics introduction vehicles are indispensable in modern society, and vehicle safety is consequently of importance in everyday life. a lack of information about the state of vehicle and parameters presents a major obstacle for the development of vehicle control systems. the effectiveness of vehicle stability control largely depends on the accuracy of the vehicle state parameters that are measured by appropriate sensors. unfortunately, measurements from these sensors contain bias, as well as electrical noise, and can drift with temperature changes. however, the state estimation method is also able to dramatically reduce errors introduced by measurement and process noise contained in the signal. the focus of this work is the non-linear state estimation techniques. firstly, the ‘sigma-point kalman filter family’ (spkf) is discussed on the basis of the ‘unscented transformation’ (ut) and sterling’s interpolation [3, 5, 6]. secondly, the symmetry-preserving observer is presented [15, 16, 18], which is based on lie-transformation of invariant frames. the various state estimation procedures are then examined and compared through an illustrative nonlinear example of vehicle kinematics. sigma-point kalman filters sigma-point kalman filter [2, 4, 7] is a collective name for derivativeless kalman filters that employs the deterministic sampling based sigma-point approach to calculate the optimal terms of the state estimation. common methods use the scaled unscented transformation [4] and sterling’s polynomial interpolation. the former replaces the original set of sigma-points with a transformed set in order to minimize the errors of higher order terms, the latter approximates the derivation of the divided difference filter [10, 11] and central difference filter in [12]. the scaled unscented transformation the scaled unscented transformation (sut) has two steps. first, a fixed number of sigma points is chosen to capture the desired moments (at least mean and covariance) of the original distribution. then the sigma points are propagated through the non-linear function and the moments of the transformed variables are estimated. the advantage of sut over the taylor series based approximation is that sut is better at capturing the higher order moments caused by the non-linear transformation, as discussed in [1, 8-10]. consider a non-linear function y = g(x) and assume x has mean x and covariance xp . the first two moments of y are calculated by the following two steps: 1) weighted sigma-point selection: x0 = x xi = x + (l +λ)px( )i=1…l xi = x − (l +λ)px( )i=l+1…2l (1) with weights w0 m = λ l+λ w0 c = λ l+λ + (1−α2 +β ) wi m = wi c = λ 2(l+λ ) (2) 58 where wi m, and wi c are associated with the ith sigmapoint such that 1 2 0 =∑ = l i iw . symbols λ, α, and β denote scaling parameters and ( ) ixpl )( λ+ is the ith column of the matrix square root of the weighted xpl )( λ+ covariance matrix. 2) propagation: )( ii xgy = y ≈ wi myi i=0 2l ∑ py ≈ wi c(yi − y )(yi − y )t i=0 2l ∑ pxy ≈ wi c(xi − x )(yi − y )t i=0 2l ∑ (3) where y , yp , and xyp are the approximated mean, covariance and cross-covariance respectively. the unscented kalman filter (ukf) the algorithm of the ukf according to refs. [3, 7, 8] consists of the following steps: 1) initialization: x̂0 = e x0[ ] , px0 = e (x0 − x0 )(x0 − x0 ) t" # $ % (4) x̂0 a = e x̂0 a! " # $= x̂0 t v0 t n0 t! "% # $& t (5) p0 a = px0 0 0 0 rv 0 0 0 rn ! " # # # # $ % & & & & (6) 2) state estimation for ∞= …1k : a) calculate sigma-points: xk−1 a = x̂k−1 a x̂k−1 a +γ pk−1 a x̂k−1 a −γ pk−1 a" # $ % & ' (7) b) time-update: xi,k|k−1 x = f (xi,k−1 x ,xk−1 v ,uk−1), i = 0,…, 2l x̂k − = wi mxi,k|k−1 x i=0 2l ∑ pxk − = wi c(xi,k|k−1 x − x̂k −)(xi,k|k−1 x − x̂k −)t i=0 2l ∑ (8) c) measurement-update: yi,k|k−1 = h(xi,k|k−1 x ,xk−1 n ), i = 0,…, 2l ŷk − = wi myi,k|k−1 i=0 2l ∑ pŷk = wi c(yi,k|k−1 − ŷk −)(yi,k|k−1 − ŷk −)t i=0 2l ∑ pxkyk = wi c(xi,k|k−1 x − x̂k −)(yi,k|k−1 − ŷk −) i=0 2l ∑ (9) kk = pxkyk pŷk −1 x̂k = x̂k − +kk (yk − ŷk −) pxk = pxk − −kkpŷkkk t (10) where xk a = xk t vk t nk t! "# $ %& t and xk a = (xk x )t (xk v )t (xk n )t! "# $ %& t are the l dimension vectors of the augmented states and sigma-points respectively, vr and nr are the covariances of the process and measurement noise respectively, λγ += l , λ = α2(l+κ)+l, α = 10-3, κ = 0, β = 2, and wi is the weighting parameter defined in eq.(2). the central-difference kalman filter this approach is based on sterling’s polynomial interpolation, which was used in the derivations of divided difference filter [10, 11] and central difference filter in ref. [12]. the result of this approximation can be used for sigma-point approach as in the case of sut. the algorithm consists of the following steps: 1) weighted sigma-point selection: x0 = x xi = x + h px( )i=1…l xi = x − h px( )i=l+1…2l (11) with weights w0 m = h2−l h2 , wi m = 1 2h2 , wi c1 = 1 4h2 , wi c2 = h2−1 4h2 , (12) where wi m, and wi c are associated with i = 1, …, 2l sigma-point. 2) initialization: the same as defined in eqs.(4-6) 3) state estimation for k = 1, …, ∞: a) sigma-points for time-update: x̂k−1 av = x̂k−1 v" # $ % , pk−1 av = pxk−1 0 0 rv " # $ $ % & ' ' (13) xk−1 av = x̂k−1 av x̂k−1 av + h pk−1 av x̂k−1 av − h pk−1 av " # $ % & ' (14) b) time-update: xi,k|k−1 x = f (xi,k−1 x ,xk−1 v ,uk−1), i = 0,…, 2l x̂k − = wi mxi,k|k−1 x i=0 2l ∑ pxk − = wi c1 (xi,k|k−1 x − xl+i,k|k−1 x )2 + i=1 l ∑ wi c2 (xi,k|k−1 x + xl+i,k|k−1 x − 2x0,k|k−1 x )2 i=1 l ∑ (15) 59 c) sigma-points for measurement-update: x̂k−1 an = x̂k − n" #$ % &' , pk|k−1 an = pxk − 0 0 rn " # $ $ % & ' ' (16) xk|k−1 an = x̂k|k−1 an x̂k|k−1 an + h pk|k−1 an x̂k|k−1 an − h pk|k−1 an " # $ % & ' (17) d) measurement-update: yi,k|k−1 = h(xi,k|k−1 x ,xk|k−1 n ), i = 0,…, 2l ŷk − = wi myi,k|k−1 i=0 2l ∑ pŷk = wi c1 (yi,k|k−1 −yl+i,k|k−1)2 i=0 2l ∑ + wi c2 (yi,k|k−1 +yl+i,k|k−1 − 2y0,k|k−1)2 i=0 2l ∑ pxkyk = w1 c1pxk − (y1:l,k|k−1 −yl+1:2l,k|k−1)t kk = pxkyk pŷk −1 x̂k = x̂k − +kk (yk − ŷk −) pxk = pxk − −kkpŷkkk t (18) symmetry-preserving observers among many problems in control theory, the symmetric nature of the system can be utilized, such as in the case of optimal control for feedback or regulations. the symmetry properties can also be used in the design of observers. symmetry-preserving observers are also known as invariant observers that are based on the differential geometric background of abstract liegroups [15, 16, 18]. the constructive algorithm can be defined for designing invariant observers, which is based on the group transformation of symmetry. the aim is to produce invariant frames and invariant output errors to transform a locally asymptotically convergent observer around an equilibrium point into an invariant one, retaining its first-order approximation. the method in refs. [16, 18] benefits from the fact that the error equations and the first-order approximation can be calculated explicitly and the relationships can be defined globally. in addition, the invariant error equations make stability issues easier to deal with [1921]. assumptions suppose g is a lie-group with identity e on manifold σ. the group transformation (ϕg )g∈g on σ is a smooth mapping (g,ξ )∈g ×σ→ϕg(ξ )∈ σ (19) such that ϕe(ξ ) = ξ and ϕg2 (ϕg1 (ξ )) =ϕg2g1 (ξ ) for ζ, g1, and g2. the transformation group is local if ϕg(ξ ) is defined only when g lies sufficiently near to e. we consider only local transformations. invariant observers are designed for the smooth nonlinear system d dt x = f (x,u) , y = h(x,u) (20) where x, u, and y belong to the open subsets x ⊂ ℝn, ⊂u ℝm, and ⊂y ℝp respectively and p ≤ n . let r ≤ n be the dimension of the lie-group. we assume that for each x the mapping x→φg(x) is full rank. time functions u(t) and y(t) are known. invariant pre-observer for the differential geometric description of the symmetric observers [14], the following definitions and theorems should be introduced: definition 1. the group of local transformation on manifold ux× is expressed by (x,u) = (φg(x),ψg(u)) (21) where φg(x),ψg(u) is local diffeomorphism and g ∈g definition 2. system d dt x = f (x,u) is g-invariant, if f (φg(x),ψg(u)) = dφg(x) ⋅ f (x,u) for g, x, u. thus, the system remains unchanged for the local transformation, !x = f (x,u) . definition 3. the output y = h(x,u) is g-equivariant, if there exists ρg transformation on y, such that g ∈g and h(φg(x),ψg(u)) = ρg(h(x,u)) for g, x, u. thus, the output remains unchanged for the local transformation, y = h(x,u) . definition 4. the vector field w is g-invariant on manifold x, if d dt x = w(x) is invariant to the transformation, i.e. w(φg(x)) = dφg(x) ⋅w(x) for g, x. definition 5. an invariant frame (w1, w2, …, w3) consists of n linearly point-wise independent ginvariant vector fields on x thus (w1(x),w2(x),…,wn (x)) is a basis of the tangent space tx(x) . lemma 1. the invariant frame can be constructed from the canonical basis of x. the vector field defined by wi(x) = (dφγ (x) ) −1 ⋅ ∂∂xi (22) for i = 1, …, n forms an invariant frame. definition 6. the system d dt x̂ = f(x̂,u, y) is a preobserver, if f(x,u,h(x,u)) = f (x,u) is satisfied for x and u. furthermore, if lim x̂(t) = x(t) as t→∞ , then the pre-observer is asymptotic. 60 definition 7. the pre-observer is g-invariant, if ),,ˆ()ˆ())(),(),ˆ(( yuxfxdyuxf gggg ⋅= ϕρψϕ (23) is satisfied for g, x̂ , u, and y i.e. the observer remains unchanged for the group transformation on yu,,x . thus, x = φg(x) , u =ψg(u) , y = ρg(y) , and d dt x̂ = f(x̂,u,y ) . an invariant observer is an asymptotic g-invariant pre-observer. moreover, if the pre-observer is ginvariant and rank (f) = dim y , then the output map y is g-equivariant. definition 8. smooth map (x̂,u, y)→ e(x̂,u, y)∈ ℝp is an invariant output error if a) y→ e(x̂,u, y) is invertible for x̂ , u, and y b) e(x̂,u,h(x̂,u)) = 0 for x̂ and u c) e(φg(x̂),ψg(u),ρg(y)) = e(x̂,u, y) for x̂ , u, and y. the first two properties mean e is an output error, the third expresses the invariance. the introduction of the invariant error is necessary, because the output error ŷ− y does not usually preserve the geometry of the system [21]. the following three theorems [15, 16] support the construction of the symmetry-preserving observers. theorem 1. the observer d dt x̂ = f(x̂,u, y) is a ginvariant pre-observer for the g-invariant non-linear eq.(20) with a g-equivariant output if and only if f(x̂,u, y) = f (x̂,u)+ li(i(x̂,u),e(x,u, y)) i=1 n ∑ wi(x̂) (24) where e is an invariant output error, (x̂,u)→ i(x̂,u)∈ ℝn+m&r is a full rank function, li is a smooth function, such that li(i(x̂,u), 0) = 0 and (w1,w2,…,wn ) is an invariant frame. since li(i,e) = li(i,e)e li(i,e)wi i=1 n ∑ = wi(li(i,e) i=1 n ∑ e) = w1 … wn( ) l1(i,e) ! ln (i,e) " # $ $ $ $ % & ' ' ' ' e (25) the observer can be written as follows f(x̂,u, y) = f (x̂,u)+w (x̂)l(i(x̂,u),e(x̂,u, y))e(x̂,u, y). (26) theorem 2. the following statements are valid: • (x̂,u, y)→ e(x̂,u, y) invariant output error exists, • there is a (x̂,u)→ i(x̂,u)∈ℝn+m&r invariant function, • every other invariant output error has the form of !e(x̂,u, y) = l(i(x̂,u),e(x̂,u, y)) (27) where l is a smooth function such that l(i, 0) = 0 and e →l(i,e) is invertible. theorem 3. consider the equilibrium of a non-linear system f (x,u ) = 0 and y = h(x,u ) assume that the linearized system a,b,c,d around this equilibrium is observable, where a = ∂f ∂x (x,u ) , b = ∂f ∂u (x,u ) ,c = ∂h ∂x (x,u ) , a = ∂h ∂u (x,u ) and let l be such that a+ lc is a stable matrix. from the locally asymptotically convergent observer d dt x̂ = f (x̂,u)+ l(ŷ− y) , ŷ = h(x̂,u) (28) an invariant observer can be constructed by the same linear approximation d dt x̂ = f (x̂,u)+w (x̂)l(i(x̂,u),e(x̂,u, y))e(x̂,u, y) (29) where l = −w (x)−1lv−1 and v = ∂e ∂y(x,u,y ) is an invertible matrix of pp× dimensions. there is no general algorithm for designing the li gain functions of theorem 1. however, if we consider the following invariant state error η(x, x̂) = φγ (x)(x̂)−φγ (x)(x) (30) instead of the xx −ˆ state error, where )(xγ is the solution of φg a (x) = c (31) with respect to g, then the invariant error will only depend on the i(x,u) trajectories. constructive algorithm consider an invariant system, i.e. unchanged by transformation eq.(21) with an equivariant output (definition 3). the non-linear observer design for nonlinear dynamic systems [10, 11] can be divided into the following steps: a) choose a g lie-group and a group transformation taking into account the symmetrical properties of the system. b) solve the normalization eq.(31). build an invariant error e and the complete set of scalar invariants i. c) construct the invariant frame eq.(22). d) determine the pre-observer eq.(25). e) linearize the system f (x,u ) = 0 around the equilibrium and obtain a,b,c,d matrices. check the observability and design an invariant observer from the chosen linear observer by using theorem 3. choose an appropriate l . f) choose the parameters of the linearized error equations, based on the invariant state-errors η, such that the invariant system will be asymptotically stable. 61 then the non-linear symmetry-preserving observer is asymptotically stable, and converges locally and exponentially along all system trajectories. case study: a non-holonomic vehicle in this section, the previously introduced state estimation procedures are employed for an example of a non-holonomic vehicle tracking control. the wellknown model in the robotics of the simplified vehicle kinematics is considered. the tracking is maintained by satisfying the kinematic constraints with the appropriate choice of reference signals. kinematic model the simplified kinematic model of the vehicle can be written in the following form !x !y !θ ! " # # # $ % & & & = ucosθ usinθ uv ! " # # # $ % & & & , h(x, y,θ ) = (x, y) (32) where u is the velocity, v is the curvature, i.e. a function of the steering angle and h is the measured output. all signals contain additive gaussian noise. the model assumes that the contact point of the wheel and the ground does not slip. notice, that the linearized system is not observable. tracking for path tracking the control signals are set to satisfy the kinematic constraints, thus u and v are calculated as follows: u(t) = !xr 2(t)+ !yr 2(t) and v(t) = !!yr (t) !xr (t)− !xr (t)!!yr (t) u3(t) (33) where xr(t) and yr(t) are time functions of the reference signal. the initial conditions for tracking control is θr (0) = tan −1 !yr (0) !xr (0) " # $ % & ' . (34) hence, the reference signals for the vehicle velocity and steering function can be calculated. in the simulations, sinusoidal path tracking is implemented using the reference signals xr (t) = t, and yr (t) = asin(ωt). invariant observer design group transformation eq.(32) is independent of the origin and of the orientation of the frame chosen, i.e. it is invariant with regards to the group of rotations and translations. we chose the lie-group g = se(2) and defined the group transformation as follows: φ(xg,yg,θg )(x, y,θ ) = xg yg θg ! " # # # # $ % & & & & ⋅ x y θ ! " # # # $ % & & & = = x cosθg − ysinθg + xg xsinθg + ycosθg + yg θ +θg ! " # # # # $ % & & & & (35) ψ(xg,yg,θg )(u,v) = u v ! " # $ % & ρ(xg,yg,θg )(x, y) = x cosθg − ysinθg + xg xsinθg + ycosθg + yg ! " # # $ % & & one can check that eq.(32) is invariant to the transformations ϕ, and ψ in terms of definition 1 and the output is equivariant to transformation ρ in terms of definition 3. invariant output errors the normalization eq.(31) for :0=c 0 = x cosθγ − ysinθγ + xγ 0 = xsinθγ + ycosθγ + yγ 0 =θ +θγ (36) the solution of eq.(36), the scalar invariants and output errors can be written as follows respectively xγ yγ θγ ! " # # # # $ % & & & & = x y θ ! " # # # $ % & & & −1 = −x cosθ − ysinθ xsinθ − ycosθ −θ ! " # # ## $ % & & && = γ x y θ ! " # # # $ % & & & (37) i(x, y,θ,u,v) =ψγ (x,y,θ )(u,v) = u v ! " # $ % & (38) e = ρ(xγ ,yγ ,θγ )(x̂, ŷ)− ρ(xγ ,yγ ,θγ )(x, y) = cosθ̂ sinθ̂ −sinθ̂ cosθ̂ " # $ $ % & ' ' x̂ − x ŷ− y " # $$ % & '' (39) invariant frame w = (dφγ (x,y,θ )(x, y,θ )) −1 ∂ ∂(x,y,θ ) = = dφγ (x,y,θ )(x, y,θ ) = cosθ −sinθ 0 sinθ cosθ 0 0 0 1 # $ % % % & ' ( ( ( . (40) 62 invariant pre-observer d dt x̂ ŷ θ̂ ! " # # # $ % & & & = ucosθ̂ usinθ̂ uv ! " # # # # $ % & & & & + cosθ̂ −sinθ̂ 0 sinθ̂ cosθ̂ 0 0 0 1 ! " # # # # $ % & & & & l × cosθ̂ sinθ̂ −sinθ̂ cosθ̂ ! " # # $ % & & x̂ − x ŷ− y ! " ## $ % && (41) where l is a smooth 23× gain matrix, whose elements depend on the invariant error e and the invariants i. error equations and error dynamics η = ηx ηy ηθ ! " # # # # $ % & & & & = γ (x̂, ŷ,θ̂ ) x̂ ŷ θ̂ ! " # # # $ % & & & −γ (x̂, ŷ,θ̂ ) x y θ ! " # # # $ % & & & = = (x̂ − x)cosθ̂ + (ŷ− y)sinθ̂ −(x̂ − x)sinθ̂ + (ŷ− y)cosθ̂ (θ̂ −θ ) ! " # # # # $ % & & & & (42) !ηx !ηy !ηθ ! " # # # # $ % & & & & = u(1− cosηθ )+ (uv+ l31ηx + l32ηy )ηy usinηθ − (uv+ l31ηx + l32ηy )ηx 0 ! " # # # # $ % & & & & + +l ηx ηy ! " # # $ % & & (43) it can be seen that the invariant error equations are independent of the trajectory and only depend on the relative quantities ηx, ηy, and ηθ and the i invariants. stability and convergence the weighting matrix is defined as follows l = − |u | a ubey −uv uv−ubey − |u | c 0 −ub " # $ $ $ $ % & ' ' ' ' , (44) where a and b are care positive scalars and ey = ηy. the invariant error dynamics can be made locally asymptotically stable. furthermore, the resulting symmetry-preserving observer is almost globally asymptotically convergent, i.e. it converges any initial condition except for one as described in refs. [15-16]. simulation results the state estimation techniques are illustrated in two tracking examples. for comparative purposes, the following algorithms have been implemented: extended kalman filter (ekf), central difference and unscented kalman filter (ckf, ukf) and the symmetry preserving observer (sym) discretized by the sample time of the sigma-point estimators. the reference paths are xr (t) = t, and yr (t) = asin(ωt) , where a = 3 m and ω = π/5 rad s-1. zero mean additive gaussian noise is assumed with standard deviations of 0.01 and 0.005 for the process noise and 0.02 for the measurement noise. the sampling time is ts = 0.1 s. the initial values are x0 est = y0 est =θ0 est =1 , and x0 = y0 = 0 . example 1 the vehicle starts from the origin of the xy-plane with large initial estimation error and tracks a sinusoidal path. fig.1 shows the estimated output positions of the vehicle using sigma-point kalman filters and symmetry-preserving observers. the estimation errors of different algorithms can be seen in figs.2 and 3. the errors are smaller and show smoother signals in the case of the spkf estimators, which was expected, since the sym observer is deterministic. large errors appear at the peak values of the reference signals; however, both estimation techniques achieved the same satisfactory results in spite of the relatively small sampling frequency. figure 2: estimation errors of the sigma-point and extended kalman filters from example 1 63 root-mean-square errors can be seen in table 1. we can conclude that among the processes of state estimation techniques the sym observer is competitive with spkf estimators. example 2 in this example the vehicle performs an off-line estimation before movement starts, followed by an online estimation along a sinusoidal path. it is notable that in the stationary state the velocity is zero and at the beginning of movement the velocity changes to a nonzero value abruptly, see eq.(33). figs.4-7 illustrate the estimated output positions and the measurement errors for the sigma-point estimators and the invariant observers respectively the error signals show a quick convergence in the case of the symmetry-preserving observer. the speed of convergence depends on the parameters set in the l matrix; however, high gains can cause the observer to be divergent and make larger errors. since there are no u and δ signals in the stationary position and the orientation is not directly measured, the orientation can only be estimated after the vehicle starts moving. the error signal oscillates around zero in a similar way to example 1. due to calibration, smaller errors appear. the invariant observer and sigma-point estimators have the same magnitude of error components. the root-mean-square errors of the simulation can be seen in table 2. figure 3: estimation errors of the symmetry-preserving observer (sym) from example 1 figure 6: estimation errors of the sigma-point and the extended kalman filters from example 2 figure 4: estimated output position of the vehicle using sigma-point state estimation (ukf, ckf) and extended kalman filter (ekf) from example 2 figure 5: estimated output position of the vehicle using symmetry-preserving observer (sym) from example 2 figure 7: estimation errors of the symmetrypreserving observer (sym) from example 2 table 1: root-mean-squared errors of the estimated signals from example 1 rmse x, m y, m θ, rad ukf 0.1368 0.1587 0.0338 ckf 0.1366 0.1577 0.0336 ekf 0.1371 0.1551 0.0352 sym 0.1371 0.1628 0.0455 table 2: root-mean-square errors of the estimated signals from example 2 rmse x, m y, m θ, rad ukf 0.0998 0.1180 0.0627 ckf 0.0993 0.1175 0.0628 ekf 0.1013 0.1165 0.0648 sym 0.1264 0.1453 0.0760 64 conclusion in this paper we presented a comparison of two different recently developed state estimation techniques. the sigma-point (spkf) stochastic estimator is based on the unscented transformation and the non-linear symmetry-preserving observers are based on the group transformation of symmetrical lie groups and invariant frames. two examples are considered for the estimation of vehicle kinematics: the first example deals with the path tracking reliability of the vehicle; the second example examines the convergence and the speed of the off-line calibration followed by path tracking. the examples illustrate that for non-linear systems in noisy environments the use of stochastic stateestimators is needed. moreover the sigma-point approach provides more accurate estimation results than the commonly used non-linear ekf state estimators. the symmetry preserving observers for non-linear systems benefit from their constructive design method, which provides local asymptotic convergence. this method can be utilized by non-linear applications in which the physical and mechanical symmetry properties of the system can be exploited. references [1] bar-shalom y., li x.-r., kirubarajan t.: estimation with applications to tracking and navigationm, wiley interscience, new york, ny, u.s.a., 2001 [2] särkkä s.: recursive bayesian inference on stochastic differential equations, phd thesis, helsinki university of technology, helsinki, finland, 2006 [3] julier s.j., uhlmann j.k.: unscented filtering and nonlinear estimation, proc. ieee, 2004, 92(3), 401–422 [4] van der merwe r., wan e.a., julier s.: sigma-point kalman filters for nonlinear estimation and sensorfusion: applications to integrated navigation, proc. aiaa guidance, navigation & control conference (gnc), providence, ri, u.s.a. 2004 [5] van der merwe r.: sigma-point kalman filters for probabilistic inference in dynamic state-space models, phd thesis, oregon health & science university, eugene, or, u.s.a., 2004 [6] julier s.j., uhlmann j.k.: corrections to unscented filtering and non-linear estimation, proc. ieee, 2004, 92(12), 1958–1958 [7] julier s.j., uhlmann j.k.: unscented filtering and nonlinear estimation, proc. ieee, 2004, 92(3), 401–422 [8] wan e.a., van der merwe r.: the 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3–15 [21] collon c., rudolph j., woittennek f.: invariant feedback design for control systems with liesymmetries – a kinematic car example, discrete cont. dyn. sys. 2011, 2(11), 312–321 hungarian journal of industry and chemistry veszprém vol. 42(2) pp. 65–70 (2014) telemedical heart rate measurements for lifestyle counselling mario salai,! gergely tuboly, istván vassányi, and istván kósa faculty of information technology, university of pannonia, egyetem u. 10.,veszprém, 8200, hungary !email: mario.salai@gmail.com in this paper we analyse a low-cost commercial chest belt to be integrated into a lifestyle counselling system as a source of heart rate data. we compared data from a schiller ecg holter device, which serves as a reference to a cardiosport device. due to missing data in the cardiosport device caused by loss of contact with the body, the creation of special algorithms was necessary for synchronization and data validation. the results show that when using our synchronization algorithms the average absolute percentage error between the two signals was 2% with correlation of more than 99%. using a data validation algorithm, we were able to get on average more than 70% of the signal with an absolute percentage error of 3% and a high average correlation of 99%. the mean rr interval values and standard deviation of rr intervals are very close to those of the reference device using both the synchronization and data validation algorithms. when using the data validation algorithm, the reference measurements produced only slightly better results with regard to false detections of atrial defibrillation than the cardiosport device. in conclusion, we found that with a simple preprocessing algorithm, cardiosport as a low-cost device can be safely integrated into a lifestyle support system as a telemedical solution. keywords: telemedicine, lifestyle counselling, heart rate monitor introduction low-cost telemedical sensors are often used in modern ambient assisted living (aal) telemonitoring and selfmanagement systems for providing inputs to medical intelligence algorithms [1]. such systems extend the scope of traditional health care that is based purely on data measurement. however, the proper interpretation and reliability of the results depends on the reliability of the measured data and the sensor itself. nevertheless, there are still surprisingly few reviews reported in the literature to date on the validation of the information content of such low-cost sensors compared to the clinically accepted reference device. an example of a device that was tested for validity is the sensewear hr armband [2]. in this study, they used the reference device simultaneously with the tested device as a way of validating data. however, most of the compared devices are expensive high-end devices, which present an obstacle for their wide use in telemedicine. in this proof-of-concept paper, we analyse a simple commercial chest belt chosen to be integrated into the lavinia lifestyle mirror system [3] as a source of heart rate (hr) data. in the lavinia system, the hr signal of the patient will be used to (i) estimate the calories burnt by physical activity, (ii) calculate the heart rate variability (hrv) in order to detect periods of mental or emotional stress, and (iii) analyse arrhythmia patterns (poincare plots) for atrial fibrillation detection. our approach involves the comparison of the hrv and poincare plots computed from the filtered chest belt signal, with those parameters computed from a reference holter device. methods measurements two devices were used simultaneously by a healthy volunteer over a 24 hour period. a schiller mt101/mt-200 holter device was our reference device designed for clinical use. the chest belt was a cardiosport tp3 heart rate transmitter device. since this device does not have its own memory for storing data, we used a nexus 7 tablet with android version 4.4.2 to connect the device via the bluetooth 4.0 protocol and store the measured data on the tablet. although both devices were worn by volunteers for 24 hours, only 12 hours of the overall signal were used for analysis due to frequent detachments of the device from the body during nighttime. the measurements of 12 hours were repeated on 4 additional healthy male subjects. signal analysis the direct comparison of measured data was not possible due to the different designs of the reference and the telemedical devices. however, we wanted to 66 compare signals directly in terms of time and also to develop a data validation algorithm for removing the noisy parts of the cardiosport device measurements reliably without using the reference data. the problem was that the chest belt was not firmly attached to the body and sudden movements of the device caused signal loss. therefore, we needed to create a software module for synchronization and data validation before any analysis. data validation means removing obviously bad data (artefacts) and keeping only ‘good’ data segments of sufficient length, because, as a rule of thumb, both hrv and poincare plot computations require data chunks of at least 5 minutes. even though the data validation algorithm removed a considerable amount of data from the original signal, we still had enough useful data for analysis from the daytime. the synchronization algorithm our simple algorithm for signal synchronization uses a sliding window that passes from the beginning of the chest belt signal to the end and calculates the absolute error between the two signals. when sliding finishes, the location of the sliding window with the minimum absolute error is considered as the point where the two signals should be synchronized. this applies only if the correlation of the data in the sliding window and the same amount of data from the reference device are higher than a minimum set by the user. if these conditions are met, the algorithm copies data from the sliding window into a newly generated third signal, which represents the chest belt signal fully synchronized with the reference signal. if conditions are not met, the third signal is filled with zeros. finally, the algorithm extracts all the highly correlated segments from the third signal ignoring zero values. also, a file with all the merged segments is generated for general analysis. the algorithm uses the following 5 main parameters that can be set up by the user: 1. window size: amount of data copied from the signal into the sliding window (default: 200), 2. window shift step: the number of samples by which we shift the sliding window in each iteration (default: 50), 3. absolute error window: amount of data used for calculating the minimum absolute error (default: 200), 4. maximum error distance: the number of samples by which we shift the absolute error window in order to find the minimum absolute error (default: 1000), 5. minimum correlation: minimum correlation, expressed as a percentage, required for the two signals to consider data in the chest belt signal as accurate (default: 97%). each parameter’s default value was determined empirically. after running the synchronization process, we obtained segments of highly correlated data. fig.1 shows the distribution of the lengths of signal segments. we can see that most segments are 3 to 18 minutes long. the longest highly correlated segment with the reference data is 110 minutes long. the default parameter settings minimize the number of overly short (< 5 min) segments. most of the bad segments (fig.2) are shorter than one minute, and only one bad segment was 60 minutes long. data validation algorithm another type of algorithm was used in the real telemedical scenario for finding good parts of the signal without relying on reference data. this implies finding gaps and abnormal values and omitting them. first, we compared the timestamp of each data point with the timestamp of the previous one. if the difference between the timestamps was longer than 3 seconds, we marked this as a ‘gap’. the 3-second gap detection was enabled by the chest belt’s buffering system that can tolerate short detachments of the device from the body. in the second step we identified abnormal values in the signal that were treated as gaps. the abnormal values are identified by observing the mean value of 20 neighbouring data points (10 before and 10 after a given point). if the mean value differs from the value of the figure 1: the distribution of strongly correlated segment lengths for all subjects figure 2: the distribution of weakly correlated segment lengths for all subjects 67 current sample by more than 300 units, we consider it invalid and mark it as a gap/error in the signal. finally, we extract the good segments from the signal with a length of more than 5 minutes. we implemented the above algorithm in a simple software tool (fig.3). on the left-hand side we can load the two signals and set the parameter values as well as the amount of data to be analysed. the graph shows two signals after the synchronization process was completed. the user can examine signals by clicking the previous and next buttons. general statistics are shown in the middle part of the screen, while in the lower part, we can see the histogram, and save the histogram and results as a file. two tabs in the top left-hand corner allow the user to switch between synchronization and data validation algorithms. statistical analysis time and frequency domain analyses, correlation comparisons, mean absolute percentage errors, and the slopes of scatter plot diagrams were compared between two measurements for hrv analysis. the specificities of a self-developed atrial fibrillation detector algorithm were compared for atrial fibrillation analysis. the latter algorithm is based on the k-means clustering of poincaré plots (consisting of rr intervals) the time and frequency domain analyses for hrv were performed using kubios hrv analysis software, while the rest of the analysis for hrv and atrial fibrillation was performed in microsoft excel. atrial fibrillation detection was done using the matlab environment and the results were saved as microsoft excel workbooks. results and analysis heart rate variability after the synchronization process, we got strongly correlated (greater than 97%) synchronized data segments of various durations. table 1 summarizes the duration of signals analysed. table 2 shows results in the time domain for schiller and cardiosport devices after using the algorithm for the synchronization of signals. time domain analysis shows similar values for mean rr values and standard deviation (std rr in eq.(1)). the average mean rr values for the schiller and cardiosport devices are 851 and 871 respectively. the average std rr for the schiller device is 108 and 110 for the cardiosport device. figure 3: synchronization and data validation software table 1: signal duration after the synchronization process subject duration (h:m:s) #1 10:53:28 #2 8:45:40 #3 10:30:17 #4 7:46:56 68 !"#!!! = ! !!! (!!! − !!)!! !!! (1) the frequency domain analysis for the synchronization process is presented in table 3. the absolute power was compared for very low frequencies (vlf: 0-0.04 hz), low frequencies (lf: 0.04-0.15 hz), high frequencies (hf: 0.15-0.4 hz) and ratios between low frequencies and high frequencies (lf/hf). results show no significant difference between schiller and cardiosport device values. the average mean absolute percentage error (mape) between two signals is 2% with a high average correlation of close to 100%. using the data validation algorithm, we extracted data points from the collected signals. the duration of the resulting signal is shown in table 4. it is important to note that due to the noise on schiller device recordings, we had to remove noisy parts from the original signal. therefore, even though the signal was recorded continuously for 12 hours, overall duration is much less. calculations show that in the worst scenario only 45% of the signal can be used for analysis using this data validation method, while in the best scenario this number reaches 95%. this leads to a conclusion that results are rather subject dependent. the results of data analysis in the time domain after the removal of bad parts using the validation algorithm can be seen in table 5. the mean rr intervals for schiller and cardiosport devices are 851 and 871 and standard deviations are 104 and 106, respectively. the cardiosport device has slightly greater values, but these are practically identical. the frequency domain analysis for the data validation process is presented in table 6. the absolute power was compared for very low frequencies (vlf: 00.04 hz), low frequencies (lf: 0.04-0.15 hz), high frequencies (hf: 0.15-0.4 hz), and ratios between low frequencies and high frequencies (lf/hf). as in the synchronization process, the results show no significant difference between the schiller and cardiosport device values. the minimum, maximum and average percentage errors on whole signals were calculated using 5 minute long sliding windows with one minute long shift steps (table 7). only one subject had a high maximum error value of 34%. by visual examination, it was determined that the cause of such a high error was the artefact of the schiller device. in spite of that, the average error remained low (2%). table 2: time domain analysis after synchronization mean rr (ms) a std rr (ms) b subject schiller cardiosport schiller cardiosport #1 738 755 123 125 #2 704 720 91 93 #3 908 929 90 93 #4 855 875 145 148 #5 937 959 107 109 average 851 871 108 111 a with 2% error, b with 1-3% error table 3: frequency domain analysis after synchronization schiller cardiosport error subject absolute power (ms2) absolute power (ms2) % % % % vlf lf hf lf/hf vlf lf hf lf/hf vlf lf hf lf/hf #1 7937.6 3086 1578 1.956 8444 3224 1330 2.4235 6 4 19 19 #2 5431.5 626.6 245 2.557 5723 659.3 250.9 2.6281 5 5 2 3 #3 4251.2 1927 494.4 3.898 4543 2055 538.8 3.8146 6 6 8 2 #4 12682 1790 636.5 2.813 13514 1869 621.5 3.0077 6 4 2 6 #5 6139.8 1212 476.7 2.542 6465 1274 481.4 2.6459 5 5 1 4 table 4: signal duration after data validation subject duration (h:m:s) #1 1:28:10 #2 11:20:03 #3 6:15:38 #4 9:27:07 #5 4:29:44 table 5: time-domain analysis after data validation mean rr (ms) a std rr (ms) b subject schiller cardiosport schiller cardiosport #1 701 724 136 139 #2 700 717 91 93 #3 899 921 100 100 #4 846 866 139 142 #5 958 981 88 90 average 851 871 105 106 a with 2% error, b with 0-2% error table 6: frequency domain analysis after data validation schiller cardiosport error subject absolute power (ms2) absolute power (ms2) % % % % vlf lf hf lf/hf vlf lf hf lf/hf vlf lf hf lf/hf #1 10414 2297 1171 1.96 10847 2442 1004 2.43 4 6 17 19 #2 5446 631 245 2.57 5718 654 245 2.67 5 3 1 4 #3 5163 1990 523 3.80 5424 2054 540 3.80 5 3 3 0 #4 11683 1769 616 2.87 12149 1831 594 3.08 4 3 4 7 #5 4356 1235 317 3.89 4522 1303 330 3.95 4 5 4 1 69 fig.4 represents a typical relationship between cardiosport and schiller devices. all gradient values are close to 1. the lowest slope value is 0.98 while the highest value is 1.02. the average mean absolute percentage error (mape) between two signals was 3% with a strong average correlation of 99%. atrial fibrillation we carried out the detection of atrial fibrillation (afib) by analysing poincaré plots consisting of 30 rr intervals. we considered 30 rr intervals per iteration and in each iteration after constructing the poincaré plot we calculated the dispersion around the diagonal line and used k-means based cluster analysis to determine the number of the clusters. if the dispersion was too high (greater than 0.06) and the number of clusters was 1, or the number of clusters was more than 9; we assigned “afib” to that series of rr intervals, otherwise to “non-afib”. the details of the algorithm can be seen in our previous study [16]. since our data set did not contain real afib cases, only specificity could be calculated with regard to the efficiency of detection. the evaluation of atrial fibrillation detection results for synchronized data validation can be seen in tables 8 and 9. conclusion even though the cardiosport device may suffer from signal loss due to its design, we managed to determine that it can be safely used for telemedical purposes of measuring hrv and atrial fibrillation. we found only a few usable data segments that were less than 5 minutes long. with our algorithm that detects gaps and errors in table 7: the minimum, maximum and average percentage errors subject minimum error maximum error average error #1 0.1% 3.5% 1.5% #2 0.0% 7.7% 2.1% #3 0.0% 33.9% 3.2% #4 0.1% 6.7% 1.9% #5 0.1% 5.1% 2.2% average 0.1% 13.4% 2.4% figure 4: comparison of the cardiosport and schiller devices after data validation table 8: results from the synchronized data related to atrial fibrillation detection subject number of iterations schiller mt-101/mt-200 system cardiosport tp3 heart rate transmitter afib cases non-afib cases afib cases non-afib cases #1 331 26 8% 305 92% 31 9% 300 91% #2 1796 9 1% 1787 99% 3 >1% 1793 ~100% #3 1120 7 1% 1113 99% 5 1% 1115 99% #4 1427 11 1% 1416 99% 16 1% 1411 99% #5 964 46 5% 918 95% 45 5 919 95% min 1% 92% >1% 91% max 8% 99% 9% ~100% mean 3% 97% 3% 97% std 3% 3% 4% 4% table 9: results from the data validation process related to atrial fibrillation detection patient number of iterations schiller mt-101/mt-200 system cardiosport tp3 heart rate transmitter afib cases non-afib cases afib cases non-afib cases #1 241 3 1% 238 99% 8 3% 233 97% #2 1879 29 2% 1850 98% 2 >1% 1877 ~100% #3 808 15 2% 793 98% 3 >1% 805 ~100% #4 1296 10 1% 1286 99% 20 2% 1276 98% #5 544 6 1% 538 99% 7 1% 537 99% min 1% 99% >1% 97% max 2% 99% 3% ~100% mean 1% 99% 1% 99% std >1% >1% 1% 11% 70 the signal and removes them with an average effectiveness of more than 70%, which translates into having enough data to calculate hrv and atrial fibrillation from daytime measurements. regarding atrial fibrillation detection, we can conclude that by using the developed data validation algorithm the reference schiller mt-101/mt-200 measurements produced only slightly better results with regard to false detections than the cardiosport tp3 heart rate transmitter. in two cases the cardiosport measurements proved to be even better than schiller records, which implies that some relatively simple heart rate recorders are equivalent to some holter devices after signal processing using the data validation algorithm. we have to emphasize; however, that we have not performed any measurements on actual atrial fibrillating patients yet. therefore, the investigation of the sensitivity of our atrial fibrillation detection algorithm under the presented circumstances could be the subject of further studies. in summary, the cardiosport as a low-cost device can easily be integrated into a lifestyle support system as a telemedical solution. acknowledgments this research was supported by the european union and co-funded by the european social fund “telemedicinefocused research activities in the field of mathematics, informatics and medical sciences” támop-4.2.2.a11/1/konv-2012-0073. references [1] patel s., park h., bonato p., chan l., rodgers m.: a review of wearable sensors and systems with application in rehabilitation, j. neuroengng. rehab., 2012, 9(21), 1–17 [2] kristiansen j., korshøj m., skotte j.h., jespersen t., søgaard k., mortensen o.s., holtermann a.: comparison of two systems for long-term heart rate variability monitoring in freeliving conditions a pilot study, biomed eng. online, 2011, 10(27), 1–14 [3] kósa i., vassányi i., nemes m., kálmánné k.h., pintér b., kohut l.: a fast, android based dietary logging application to support the lifestyle change of cardio-metabolic patients, global telemedicine and ehealth updates: knowledge resources, eds.: m. jordanova, f. lievens, 2014, 7, 553–556 [4] salai m., tuboly g., vassanyi i., kosa i.: reliability of telemedical heart rate meters, ime j., 2014, 8(5), 49–55 hungarian journal of industry and chemistry veszprém vol. 42(2) pp. 71–77 (2014) the application of unknown input estimators to damp load oscillations of overhead cranes bálint patarticsb and bálint kiss department of control engineering and information technology, budapest university of technology and economics, magyar tudósok krt. 2, budapest, 1111, hungary be-mail: patarticsbalint@gmail.com this paper focuses on the development of state estimation methods for mechanical systems with uncertain frictional parameters. the goal of the study is to provide reliable angle estimation for state-feedback-based crane control solutions, designed to reduce load sway. cranes are underactuated systems, usually unequipped with the sensors necessary to measure the swinging angle, therefore the damping of their oscillatory behaviour is a challenging task. two estimators are proposed for the calculation of the unmeasured states. one is based on an ’unknown input kalman filter’ (uikf), the other applies the ’unscented kalman filter’ (ukf) with load prediction. simulation results are provided to demonstrate the accuracy of the algorithms. keywords: overhead crane, state estimation, nonlinear systems, unknown inputs, kalman filter introduction the sway of the load carried by cranes is an unwanted phenomenon. friction may decouple load motion from the remaining crane mechanism. this causes difficulty for inexperienced operators, especially when they try to land the cargo. the friction present in the crane mechanism makes the reduction of the swinging particularly demanding. therefore the goal of the design of crane control systems is often to ensure minimal swinging along a specified trajectory [1–6]. there are numerous algorithms available in the literature for the solution to this problem. the design of such a control system can be addressed using soft computing methods such as fuzzy logic and neural network with genetic algorithm. these solutions require however the measurement of the load position, which is often based on workspace visualization [1]. hard commuting techniques are also widely applied for sway reduction. an h2 optimal solution is described in ref.[2], which also relies on image processing for the measurement of the load coordinates. there are a variety of algorithms taking advantage of the flatness property (or exact linearizability) of overhead cranes [7]. the control systems in refs.[3] and [4] consider all the states measurable, however an estimator is proposed in ref.[3] for the computation of the uncertain parameters. in the case of navy cranes, local asymptotic stability can be achieved without the measurement of the swinging angle, if trajectory planning exploits the flatness property of the system [6]. there is also a tracking control algorithm specifically designed for overhead cranes, that is capable of effectively reducing the sway despite the friction [5]. for the calculation of the unmeasured states, this controller uses a linear observer. in this paper we propose new methods of state observation for systems that take into account friction, and are applicable to overhead cranes. these estimators can replace the linear observer in ref.[5] or the need to measure the load coordinates in any other state-feedback-based method to enhance the precision of the control. our estimation methods are based on the assumption that the effect of the friction on the inputs can be reduced. this is true for most mechanical systems (including overhead cranes), where the actuating signals are usually forces and torques. in the following section, the modelling of lagrangian mechanical systems is overviewed, and it is shown how the friction can be handled as an input disturbance. in the next section the state estimation techniques are presented based on the possible approaches of interpreting the friction. the next section describes the results of the application of these methods to the state estimation problem of overhead cranes and presents the simulation results. lagrangian-based models of mechanical systems the nonlinear dynamics of the controlled system can be obtained using the euler-lagrange equations. if the generalized coordinates are q = � q1 q2 . . . qn �t and the generalized forces are ⌧ = � ⌧1 ⌧2 . . . ⌧n �t , the eulerlagrange equations read d dt @l @q̇i � @l @qi = ⌧i, (1) 72 where l is the so-called lagrangian, the difference between the kinetic and potential energy of the system, q̇i = dqi dt and i = 1, 2, . . . n. using these equations, under some conditions the controlled system’s model can be written in the form h(q)q̈ + h(q, q̇) + hs(s) = ⌧, (2) where h(q) is the inertia matrix, h(q, q̇) comprises the centrifugal, coriolis and gravitational terms, and hs(s) is the frictional term with s being the vector of the frictional forces. in this form hs(s) can be reorganized to the right-hand-side of the equation. introducing the disturbance torques as ⌧̃ = ⌧ � hs(s), eq.(2) yields h(q)q̈ + h(q, q̇) = ⌧̃ . (3) the state-space representation of the model is ẋ = f(x, u) y = g(x), (4) where x is the state, u is the input, y is the output of the system, and f and g are nonlinear functions. this form can be obtained from eq.(5) assuming that xt =� qt q̇t � , and the output is not directly dependent on the torques. the state-space equations read ẋ = ✓ q̇ �h�1 (q)h(q, q̇) ◆ + ✓ 0 h�1 (q) ◆ ⌧̃ y = g(x). (5) the inputs of mechanical systems are usually forces and torques, consequently they are only dependent on ⌧̃ . this means, that the effect of the friction can be reduced to the actuated degrees of freedom of the system. if it is necessary for the design of the control system, the nonlinear dynamics can be approximated by a first order taylor series expansion around a setpoint (x0, u0). the linear model then becomes �ẋ = a�x+b�u �y = c�x, (6) where the quantities prefixed with � mean the distance from the setpoint, e.g. �x = x� x0, and the matrices are jacobians [8]. state estimation methods since the friction can be interpreted in our setup as an input disturbance, we consider two ways for its compensation in the state estimation. either all input variables can be disregarded, or the additive disturbance can be estimated using a load predictor. these ideas form the basis of the two estimator design techniques described as follows. the computations of the controllers implemented in embedded systems are based on sampled signals. hence the design of the estimators is done in discrete-time. unknown input approach consider the discrete-time linear stochastic system model x[k + 1] = �x[k] + �dd[k] + ![k] z[k] = cx[k] + v[k], (7) where x is the state, d is the unknown input (disturbance) of the system and z is the measurement of the output y[k] = cx[k]. � and �d are obtained from the matrices of eq.(6) in the form of � = eats , �d = z ts 0 eatb dt, (8) where ts is the sample time. the measurement and process noise v and ! are assumed to be additive, white, and gaussian with mean of zero. notice, that in eq.(7), all of the system inputs are considered to be disturbances. the state and the unknown input of such a system can be estimated using an ’unknown input kalman filter’ (uikf) [9], if the system satisfies the conditions dim{d}  dim{y} (9) rank{c} = dim{y} (10) rank{�d} = dim{d} (11) rank{c�d} = dim{d} . (12) additive disturbance approach in the case of input disturbances, load prediction is often applied. let us introduce the discrete-time nonlinear model of a system in the form x[k + 1] = �(x[k], ũ[k]) + ![k] z[k] = g(x[k]) + v[k], (13) where ũ is the disturbed input of the system, and � and g are nonlinear functions. we will follow the assumption, that the disturbance is additive to the input, thus ũ[k] = u[k] + ⇤d[k], where u is the vector of actuating signals, and ⇤ is a constant matrix. we also assume a constant disturbance model with process noise !d, d[k + 1] = d[k] + !d[k], resulting in the model x̃[k + 1] = ˜�(x̃[k], u[k]) + !̃[k] z[k] = g̃(x̃[k]) + v[k]. (14) in eq.(14) x̃t = � xt dt � is the extended state and !̃t = � !t !t d � is the extended process noise. the extended nonlinear mappings of the system are given by g̃(x̃[k]) = g(x[k]) and ˜�(x̃[k], u[k]) = ✓ �(x[k], u[k] + ⇤d[k]) d[k] ◆ . (15) in most cases the continuous-time differential equation of the observed system is available, in the form 73 m uf uc r ` ✓ j ⇢ cartwinch m load rail figure 1: the two-dimensional ovearhead crane of eq.(4). the discrete-time state-transition equation can then be obtained by �(x[k], u[k]) = x[k] + (k+1)tsz kts f(x, u[k]) dt, (16) where the input is piecewise constant and u[k] = u(kts). if the integral in eq.(16) cannot be given in closed form and ts is sufficiently small, the left rectangle rule approximation (k+1)tsz kts f(x, u[k]) dt ⇡ tsf(x[k], u[k]). (17) can be used. substituting this into eq.(15), the expression reads ˜�(x̃[k], u[k]) = ✓ x[k] + tsf(x[k], u[k] + ⇤d[k]) d[k] ◆ . (18) for the observation of the system described by eq.(14) and eq.(18) the ’unscented kalman filter’ (ukf) [10] is applicable. we chose one of the implementation variants of this filter from ref.[10]. application of the methods to overhead cranes system dynamics we will now consider the state estimation problem of the two-dimensional overhead crane (fig.1). let us denote the horizontal displacement of the cart by `, the length of the rope by r and the angle between the vertical and the rope by ✓. the generalized coordinates of the system are chosen to be q = � ` r ✓ �t , and the state is x = � ` r ✓ ˙` ṙ ˙✓ �t . based on the sensors available, the output is y = � ` r ˙` ṙ �t . overhead cranes is a typical example of underactuated systems. it is actuated by two motors, one applying the force uf on the cart, and another delivering the estimated system s ⇤ + + u u system model s = ⌘(x, ẋ, u) ẋ = f(x, ũ) y = g(x) ũ y r ẋ x figure 2: dynamics of the estimated system torque uc to the winch. the system input consists of these, u = � uf uc �t . the parameters of the system are the mass of the cart m , the mass of the load m, the moment of inertia of the winch j and the radius of the winch ⇢. the acceleration in the gravitational field is denoted by g. the following assumptions are made of the system. • the rope connecting the load to the winch is massless and behaves as a rigid rod during the motion. • the load is a point mass. • m , m, j and ⇢ are known. • in the initial state of the system the unmeasured states are zero: ✓ = 0 rad and ˙✓ = 0 rad/s. • the effect of the aerodynamic resistance is negligible. the lagrangian of overhead cranes reads l = 1 2 (m +m) ˙`2 + 1 2 j ⇢2 ṙ2 ++ 1 2 m ⇣ ṙ2 + r2 ˙✓2 ⌘ +m ˙lṙ sin ✓ +m ˙lr ˙✓ cos ✓ +mgr cos ✓. (19) using eq.(1), the model can be written in the form of eq.(2), where the expressions become h(q) = 0 b@ � m +m sin 2 ✓ � m sin ✓ 0 m sin ✓ ⇣ j ⇢2 +m ⌘ 0 cos ✓ 0 r 1 ca , (20) h(q, q̇) = � 0 @ m(r ˙✓2 + g cos ✓) sin ✓ mr ˙✓2 +mg cos ✓ �2ṙ ˙✓ � g sin ✓ 1 a , (21) hs(s) = � 0 @ sf sc 0 1 a , ⌧ = 0 @ uf �uc ⇢ 0 1 a , (22) where sf is the frictional force between the cart and the rail and sc is the frictional force applied to the winch. the continuous-time linear model of the crane is computed around the setpoint x0 = � 0 r0 0 0 0 0 �t , u0 = � 0 mg⇢ �t , and sf = sc = 0 is substituted 74 table 1: numeric values of the parameters value unit m 5 kg m 0.05 kg j 3.802 · 10�4 kg m 2 ⇢ 0.02 m g 9.81 m s �2 ts 1 ms r0 0.47 m `d 0.5 m into eq.(5). the resulting jacobians are a = 0 bbbbbb@ 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 m m g 0 0 0 0 0 0 0 0 0 0 0 �m+m mr0 g 0 0 0 1 cccccca , b = 0 bbbbbb@ 0 0 0 0 0 0 1 m 0 0 � ⇢ m⇢2+j � 1 mr0 0 1 cccccca , c = 0 bb@ 1 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0 1 cca . (23) substituting eq.(22), the disturbance torque term in eq.(3) reads ⌧̃ = 0 @ uf + sf � 1 ⇢ (uc � ⇢sc) 0 1 a . (24) eq.(24) shows, that the disturbed input of the system can be introduced in the form ũ = u+ ⇤s, where ⇤ = ✓ 1 0 0 �⇢ ◆ . (25) the frictional forces usually depend on the actuating signals, state variables, and the derivative of the state as well. the general characteristics of the friction reads as s = ⌘(x, ẋ, u). the block diagram of the dynamics of the system is illustrated in fig.2. only the system model block is used for estimator design, which is eq.(5) if the effect of the friction is disregarded, hs(s) = 0. proposition 1. the discrete-time linear crane model obtained from the matrices in eq.(23) and using eq.(8) satisfies the design conditions of the uikf in eq.(9-12). proof. it is clear that dim{y} = 4, dim{d} = 2 and rank{c} = 4, thus eq.(9) and (10) are satisfied. using eq.(8) and the numerical values in table 1, �d = 10 �2 0 bbbbbb@ 0.0001 0 0 �0.025 �0.0002 0 0.2 0 0 �49.975 �0.4255 0 1 cccccca , c�d = 10 �2 0 bb@ 0.0001 0 0 �0.025 0.2 0 0 �49.975 1 cca . (26) we obtain rank{�d} = 2 and rank{c�d} = 2, which are both equal to the number of unknown inputs. this satisfies eqs.(11) and (12). the continuity argument holds for the rank of the matrices in eq.(26), therefore there exists a neighbourhood around our parameter set where the design conditions are still satisfied. simulation the estimation results were obtained by simulation of overhead cranes in a closed-loop scenario using a simple discrete-time pole-placement-based linear controller. the simulation also took into account friction. there are various models of the friction phenomenon, ours included coulomb, stribeck, viscous friction, and stiction [11]. the numerical values of the parameters used in the simulation are given in table 1. because of friction, but mainly stiction, the position of the crane can not be accurately controlled without integrators in the controller. consequently we included the integral of the measurable positions in the controller design as proposed on page 309 of ref. [8]. the outputs to be integrated are yi = � ` r �t . integrals of these quantities are approximated by the left rectangle rule as xi [k+1] = xi [k] +tsyi [k] = xi [k] +tscix[k], (27) where ci is defined so that yi [k] = cix[k]. in our case ci is the first two rows of c in eq.(23). using eq.(27) and eq.(7) a new system model is introduced in the form x̃[k + 1] = ˜ �x̃[k] + ˜ �u[k] y[k] = ˜cx̃[k]. (28) where the expanded state is x̃t = � xt xt i � and the matrices are ˜ � = ✓ � 0 tsci i ◆ , ˜ � = ✓ �d 0 ◆ , and ˜c = � c 0 � . (29) for the controller design the process and measurement noises are omitted. 75 r dac system in fig. 2 adc ukf k ki u[k] y y[k]u u0 + ++ yid + xd adc x[k] x yi [k] = (`[k] r[k])t y[k] yi [k] x̂[k] ŝ[k] uikf x̂[k] ˆ̃ u[k] u[k] ckf x̂[k] figure 3: closed-loop estimation setup used in the simulation 0 1 2 3 4 5 6 7 time [s] �10 0 10 20 30 40 50 60 u f , ˆ̃ u f , [n ] uf uikf ukf 0 1 2 3 4 5 6 7 time [s] �1.0 �0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 u c , ˆ̃ u c , [n m ] uc uikf ukf figure 4: actuating signals and the estimated inputs of the system we want the state-feedback controller to output u[k] = � ˜kx̃[k] = �kx[k] � kixi [k]. the gain ˜k can be computed using the eigenvalue placement method implemented in matlab’s place algorithm: ˜k = place(˜�, ˜�, �), where � contains the chosen eigenvalues of the closed-loop system. in continuous time they are �1 + 0.5j, �1� 0.5j, �5.1, �5.2, �5.3 �5.4, �5.5, and �5.6. the controller gains are k = 0 bbbbbb@ 100.594 �0.1273 0.6011 �1.6765 �185.407 0.0458 81.4011 �0.0558 0.0562 �0.3166 �4.2257 �0.0195 1 cccccca t , and ki = ✓ 46.641 1.6026 �0.074 �2.955 ◆ . (30) the closed-loop setup is illustrated in fig.3. here the integration is done using the left rectangle rule, and the 0 1 2 3 4 5 6 7 time [s] �0.1 0.0 0.1 0.2 0.3 0.4 0.5 m ea su re d st at es [m , m /s ] � r �̇ ṙ 0 1 2 3 4 5 6 7 time [s] �0.4 �0.3 �0.2 �0.1 0.0 0.1 0.2 u n m ea su re d st at es [r ad , ra d /s ] � �̇ figure 5: state evolution of the controlled crane using the true states as feedback adc and dac blocks are analogue-digital and digitalanalogue converters respectively. the dac uses the zeroorder hold method for signal reconstruction. the desired state of the system is xd = � `d r0 0 0 0 0 �t , `d is the desired position of the cart and yid = cixd. since we only want to demonstrate the results of the state estimation, first the real states are fed back to the controller. to compare the accuracy of our methods to a traditional solution, the classical kalman filter (ckf) [12] is also implemented. as a result, the kalman filters compute the estimated state of the system x̂[k], and they also provide information about the input. the uikf estimates the friction loaded actuating signals directly, while the ukf estimates the frictional forces superposed to the actuating signals. the actuating signals along with the estimates of the real inputs provided by the filters can be seen in fig.4. here, the estimated input of the ukf is computed as ˆũ = u[k]+⇤ŝ[k]. because of friction, the real inputs are estimated to be 76 0 1 2 3 4 5 6 7 time [s] 0.00000 0.00005 0.00010 0.00015 0.00020 0.00025 0.00030 0.00035 ` � ˆ̀ [m ] uikf ukf 0 1 2 3 4 5 6 7 time [s] �0.001 0.000 0.001 0.002 0.003 0.004 0.005 ˙̀ � ˆ̇̀ [m /s ] uikf ukf figure 6: error of the position and velocity estimations much less than the actuating signals. the large offset in fig.4 is a consequence of the stiction, the cart will not move until uf becomes greater than a certain value (in our case about 28 n). when the cart finally stops moving, the fluctuation of uf tries to counter the load sway, during which the measured states do not change. this is the reason why the estimators find the input to be zero. fig.5 shows the transient of the states in a closedloop. results show that the controller can bring the system into the desired state, but friction prevents it from stopping the low amplitude swinging of the load, because it makes quick, short motions impossible. error estimates are illustrated by figs. 6 and 7. in all cases, the error becomes zero when the crane reaches the desired state. this is not true for the angle and its derivative in fig.8. the error decreases at the end of the state transient, but does not become zero. when the cart stops and the load swings, the measurements are all constant thus they carry no information regarding ✓ and ˙✓. in these situations the cart and winch are usually also motionless due to friction. consequently, the estimation error of these quantities never becomes zero. it is possible to decrease the estimation error using two laser slot sensors. with the help of such devices, ✓ can be measured accurately in two positions and through the application of proper sensor fusion techniques the estimation of the angle can become more precise in between the chosen positions as well. in fig.9 the estimation error of ✓ and ˙✓ is illustrated using ckf. the filter was designed for the dynamics given by eq.(7) except that it does not consider the inputs unknown. the results show that the error is substantially higher than in the case of the uikf or ukf. 0 1 2 3 4 5 6 7 time [s] �0.00005 0.00000 0.00005 0.00010 0.00015 r � r̂ [m ] uikf ukf 0 1 2 3 4 5 6 7 time [s] �0.0010 �0.0005 0.0000 0.0005 0.0010 0.0015 0.0020 0.0025 0.0030 0.0035 ṙ � ˆ̇ r [m /s ] uikf ukf figure 7: error of the rope length and hoisting velocity estimations 0 1 2 3 4 5 6 7 time [s] �0.003 �0.002 �0.001 0.000 0.001 0.002 0.003 0.004 0.005 � � �̂ [r ad ] uikf ukf 0 1 2 3 4 5 6 7 time [s] �0.020 �0.015 �0.010 �0.005 0.000 0.005 0.010 0.015 0.020 0.025 �̇ � ˆ̇ � [r ad /s ] uikf ukf figure 8: error of the angle and angular velocity estimations fig.8 shows the estimation error of the ukf to be less. we applied this estimator in a closed-loop scenario identical to the one presented in fig.3, but instead of x[k] the x̂[k] of the ukf was used in the feedback loop. the state evolution of the crane in this simulation is illustrated in fig.10. the system’s behaviour is only slightly different from the case when the actual states were used in the feedback control in fig.5. 77 0 1 2 3 4 5 6 7 time [s] �0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 � � �̂ [r ad ] 0 1 2 3 4 5 6 7 time [s] �5 �4 �3 �2 �1 0 1 2 3 �̇ � ˆ̇ � [r ad /s ] figure 9: error of the angle and angular velocity estimations using ckf conclusion it was shown that in most mechanical systems the disturbing effect of friction can be reduced to the actuating signals. based on this statement, two estimation methods were provided for the computation of the unmeasured states. one of these techniques considers the inputs completely unknown and uses uikf for the estimation. the other algorithm treats the inputs as distorted by an additive disturbance, and applies ukf with a load predictor extension. simulation results in a closed-loop controlled scenario were provided to prove the applicability of the concepts. it was also pointed out, that the precision of the estimators could be improved using laser slot sensors. this will be the subject of a forthcoming paper. references [1] hyla p.: the crane control systems: a survey, proc. 17th int. conf. methods and models in automation and robotics (mmar), 2012, 505–509 [2] schindele d., menn i., aschemann h.: nonlinear optimal control of an overhead travelling crane, proc. 18th ieee int. conf. control applications, 2009, 1045–1050 [3] boustany f., d’andrea novel b.: adaptive control of an overhead crane using dynamic feedback linearization and estimation design, proc. ieee int. con. robotics and automation, 1992, 1963–1968 0 1 2 3 4 5 6 7 time [s] �0.1 0.0 0.1 0.2 0.3 0.4 0.5 m ea su re d st at es [m , m /s ] � r �̇ ṙ 0 1 2 3 4 5 6 7 time [s] �0.4 �0.3 �0.2 �0.1 0.0 0.1 0.2 u n m ea su re d st at es [r ad , ra d /s ] � �̇ figure 10: state evolution of the controlled crane using the ukf’s estimated states as feedback [4] neupert j., hildebrandt a., sawodny o., schneider k.: trajectory tracking for boom cranes using a flatness based approach, proc. int. joint conf. sice-icase, 2006, 1812–1816 [5] rózsa t., kiss b.: tracking control for towdimensional overhead crane, proc. 8th int. conf. informatics in control, automation, and robotics, icinco, 2011, 1, 427–432 [6] kiss b., levine j., mullhaupt p.: a simple output feedback pd controller for nonlinear cranes, proc. 39th ieee conference on decision and control, 2000, 5, 5097–5101 [7] kiss b., lévine j., müllhaupt p.: modelling, flatness and simulation of a class of cranes, electrical engineering, 1999, 43, 215–225 [8] lantos b.: theory and design of control systems i., akadémia kiadó, 2001 (in hungarian) [9] darouach m., zasadzinski m., onana a.b., nowakowski s.: kalman filtering with unknown inputs via optimal state estimation of singular systems, int. j. sys. sci., 1995, 26(10), 2015–2028 [10] haykin s.s.: kalman filtering and neural networks, john wiley & sons, inc., 2001 [11] armstrong-hélouvry b., dupont p., de wit c.c.: a survey of models, analysis tools and compensation methods for the control of machines with friction, automatica, 1994, 30, 1083–1138 [12] kalman r.e.: a new approach to linear filtering and prediction problems, journal of basic engineering, 1960, 82, 35–45 advertise upcoming meetings, conferences, workshops, new products or services; make public announcements, introduce your research laboratory on the pages of the hungarian journal of industry and chemistry please contact us if interested! editorial office: university of pannonia p.o. box 158, veszprém h-8201 (hungary) tel.: +36 (88) 624-746, e-mail: hjic@almos.uni-pannon.hu; web: hjic.mk.uni-pannon.hu felelős szerkesztő: szilágyi róbert károly, phd kiadja: pannon egyetem, 8200 veszprém, egyetem u. 10. levélcím: h-8201 veszprém, postafiók 158, tel.: (88) 624-000 felelős kiadó: a pannon egyetem, mérnöki kar dékánja hungarian journal of industry and chemistry veszprém vol. 42(2) pp. 79–84 (2014) challenges of enterprise policy compliance with smartphone enablement or an alternative solution based on behaviour-based user identification sándor dobos! and attila kovács department of information technology, elte university budapest, budapest, 1117, hungary !email: sandor.dobos@hu.ibm.com current trends show the intense growth in the role and importance of mobile technology (smartphones, tablets, etc.) in business due to economic, social and technological reasons. the social element drives a powerful convenience expectation called “bring your own device” (byod) for taking notes and accessing internal and external network resources. apparently, the future is leading toward a more extensive enablement of smartphones and tablets with their enterprise applications. internal security standards along with applicable regulatory ones to achieve ‘policy enforcement’ as types of solutions and controls; however, this allows for merely one aspect of compliance. an alternative solution could be behaviour-based analysis to identify the user, attacker or even a malicious program accessing resources on phone or internal networks. complex networks can be defined by graphs, such as connections to resources on smartphones and serve as a blueprint. in case the motif is different from the user’s actual behaviour, the company can initiate specific actions to avoid potential security violations. this document reviews the it security challenges related to smartphones as well as the concept of graph-based user identification. the challenges of the latter are the identification of motif, selection of search algorithm and defining rules for what is considered a good or bad behaviour. keywords: mobile device security, “bring your own device” (byod) management, secure data communication, behaviour-based identification of threat, graph-based user identification introduction enterprise policy enforcement with current mobile technology management tools (mobile device management (mdm), virus detection, and other necessary modules) ensure only the compliance of piece of equipment. within enterprise, mdm servers initiate the compliant actions, if the smartphone client fails the access privilege is taken away; however, this has an immediate impact on revenue through operational efficiency affecting the business. the enterprise compliance of the smartphone device is only a validated response, which can be altered by understanding the mobile technology, such as the application structures or the way mdm technology works. hackers are heavily attacking smart devices with malicious software (malware). these can be viruses, spyware, adware, and other types of attacks. a specific example is the “obad.a trojan”, which is now being distributed via mobile botnets. the trojans are occupying a larger space and becoming more complex, which shows the need for it security to find new ways to detect them. the secure enterprise environment is crucial for organizations to ensure the business strategy and continuity of operation, irrespective of its environment being production, service delivery, or customer support related. companies are following the trend to ensure efficiency and simplify service accessibility for their customers, business partners or employees. it is an essential element of the it security strategy to be aligned with the business strategy due to (i) the intense growth of mobile technology and (ii) pressure from enterprise that has transformed business operations. forrester research from the q2 foresights security survey shows (fig.1) that mobile security is of primary concern amongst enterprise leaders. ceos are concerned about the risk of data loss, particularly due to device loss or theft. another worry regards data protection or data leak prevention usually in connection with data related to finance and innovation. figure 1: degree of concern of ceos from forrester research, foresights security survey 80 current challenges within today’s economic environment, profit-driven organizations are challenged from revenue, growth or profit target perspectives. in order to meet such expectations, organizations are under high pressure to offer innovative products (services) within newly identified channels and more accessible yet-to-bepenetrated markets to a demanding customer base, especially in the area of providing smartphone solutions. on the other hand, regulatory bodies are alarmed at mobile enablement and organizations in general striving to protect critical financial systems better, in particular via identity and access management. at the same time, organizations need to maintain operational resiliency and perform risk management assessments as an integrated part of day-to-day operations. the cost perspective is an important factor for customers facing the task of achieving a lower total cost of ownership (tco) although, by this shift in paradigm, they move from reactive protection to proactive value creation mode. the alignment of the current it strategy to business strategy is a challenge for corporations as it is a service provider within an enterprise also offering business enablement leads. companies need to manage security policy at the corporate level, assess the security health of the heterogeneous it environment, monitor the security weakness(es) in processes and systems and, of course, meet the plethora of banking laws, regulations and standards including sox, basel iii, glba, and pci compliance. with the adaptation of the byod concept in business practices, mobile technology itself contributes to additional and more complex challenges. enterprises are not the owners of those smart devices with access to enterprise networks and their data. fig.2 illustrates how smartphones with applications developed by unknown sources could be a threat to enterprise’s sensitive data. business drivers for change as introduced above an active need is emerging for more effective mobile solutions. it is not only a reflection of the compliance requirements but a real protective solution against mobile threats without any restrictions on financial growth or cutbacks on efficiency initiatives. there are compelling reasons to act and change now including data potentially at risk, pressure from regulatory bodies and audit firms to be compliant with the applicable data handling regulations, and the implementation of mobile security into an existing security structure. highlights of a political-economic-social-technology (pest) analysis politicians are setting high standards for data management regardless of platforms, even if they are related to mobile devices or mobile applications. these regulations mostly focus on the handling of financial data such as the sarbanes–oxley act of 2002 (sox). there are new developments regarding data (pictures, text, etc.) ownership such as the stop online privacy act (sopa). the preventing real online threats to economic creativity and theft of intellectual property act or in short protect ip act (pipa) will have an even more rigorous norm for enterprises who need to meet these regulations in order to obtain permission to operate in a certain field or market (market player). the economic situation puts more pressure on businesses as the trend still shows stagnancy on a macro level while in some segments it is still in decline. firms have high demands for business achievements measured by revenue and profit perspectives to meet shareholder expectations. one way to do so is to improve cost structures with mobile enablement (particularly byod). society wants to live more comfortably by searching for easily accessible services, such as online mobileenabled bank transfers or online mobile retail orders. companies aim to reach their customers via mobile applications that are more easily accessible through user-friendly interfaces, such as social network platforms. as usual, this trend is typical for major market areas, such as north america or, western europe; however, other regions are expected to follow. the trend in technology continues to be more vivid from a computing power and portability perspective. internet service providers are granting access to higher bandwidth networks for new applications and online content. policy enforcement and its weaknesses to manage the various types of mobile devices in an enterprise, a solution was introduced in 2008 by stricklen, mchale, caminetsky and reddy based on pattern definition for mobile device management (mdm). mdm is the most common approach how mobile devices (including smartphones, tablets) are managed within the enterprise as a management tool for monitoring and policy enforcement. even though this technology is available and wide-spread, according to abi research, mobile threats grew by 261% just in the figure 2: graphical illustration of mobile phone technology security threats 81 last quarter of 2012; however, mdm technology is not growing at a comparable rate to the number of vulnerabilities and attacks. one of the components of mdm is the registration module, which is responsible for identifying mobile devices within the enterprise network, where the identifier indicates the platform of each mobile device, e.g. smartphone and tablet. the other significant element is the management module. its job is to receive a management function definition performed on mobile devices using identifiers from mobile devices. the management module is responsible for instructions for the first platform to perform the management tasks and provides instructions for the other modules specific to the second platform to perform the management task on at least the second device. however, mdm is not the ultimate solution for mobile device security within the enterprise environment due to some concerns regarding the verifiable device integrity. there are attempts at identifying mdm solutions to detect modifications of the underlying platform, but since the mdm agent has limited privileges and was susceptible to compromise by malicious privileged software, these stand little chance of detecting a targeted attack. the us national security agency (nsa) describes an immutable cryptography, as the ‘root of trust’ on a specific platform, to be available for leveraging by mdm or other software, providing a means of countering this type of threats. encryption enables devices to attest their integrity on an enterprise and carry out any local policy decisions. the availability of this ‘root of trust’ to other software can vigorously complement a chain of trust that begins when booting and extends into the system runtime. an additional benefit of an immutable root of trust is that it allows a company to bind the unique identifier of that device together with other credentials to restrict company access to only those devices. in effect, the device itself can become one of the factors of a multi-factor access. in summary, mdm’s current capabilities support the byod and enterprise-owned use of mobile devices with certain gaps for high-security issues. management capabilities are limited to those provided for mdm products by the underlying mobile os (ios, android, and other platforms), and therefore, these capability gaps cannot be closed by mdm providers alone. ongoing cooperation between enterprise customers, os vendors, and mdm vendors is critical to the continued advancement of enterprise-level security for mobile devices. closing stated holes will enable the deployment of commercially available mobile devices to tackle high-security use issues common in sensitive industrial and governmental environments. secure data networks need to guarantee integrity, confidentiality and availability; this is when security is fulfilled. policy enforcement with the mdm can be too liberal, but then there is no real need for mdm or strictly constraining users thus limiting the value-add. the proposed solution is to identify the user based on behaviour and compare behaviour changes. behaviour analysis and challenges growing recognition drove the importance of network science related to the behaviour of sophisticated systems that is shaped by relations among their constituent elements. the rising availability and tractability of large and high quality data sets on a wide range of complex systems [1-3] have led to a primary insight: substantially diverse complex systems often share core key organizational principles. these can be quantitatively characterized by the same parameters, which means that they show remarkably similar macroscopic behaviour despite reflective differences in the low-level details of the components of each system or their mechanisms of interaction. the behaviour as described above can be modelled by mathematical graphs, where the graphs are defined simply as a set of nodes called vertices linked together in direct or indirect ways by connections (edges). from a mathematical point of view, g(v, e) are canonical graphs as the vertices and edges are labelled. in network science, methodological advances permit research to quantify other topological properties of complex systems, such as modularity [4], hierarchy [5], centrality [6] and the distribution of network hubs [7,8]. there have also been significant efforts to form the development or evolution of complex networks [9], to link network topology to network dynamics, and to explore network robustness and vulnerability. these topics are likely to become more relevant in relation to behavioural studies. structural and functional behaviour maps can be created using graph theory through the following four steps: 1. define the network nodes. 2. estimate a continuous measure of association between nodes. 3. generate an association model by compiling all pairs of associations between nodes and usually apply a threshold to each element of this model to produce a binary adjacency matrix or undirected graph. 4. calculate the network parameters of interest in this graphical model of the behaviour network and evaluate them against the equivalent parameters of a population of random networks. the elements such as defined network nodes, relationship of nodes, generated association matrix and network parameters give the basis of the behaviour type of “blueprint” of a user. a mobile user can be defined as an identity based on certain features of this behavioural “blueprint” as the key points of a fingerprint within the enterprise company. in fig.3 the darker highlighted edges could be the essential elements for the identifier. access to resource driven networks is defined in the graph theory as a set of nodes or vertices and the edges or lines, plus the connections between them. the graph topology can be quantitatively captured by a wide variety of measures used to generate the key points of the blueprint. the most important measurement is the node degree. the degree of a node is the number of 82 connections it links to the rest of the network. based on this definition, it is the most elementary network measure, and most other measures are ultimately linked to the node degree. the degrees of all the network’s nodes identified form a degree distribution [10]. in randomly selected networks all of the connections are equally probable, i.e. the result is a gaussian distribution. however, complex networks in general have non-gaussian distributions, often with a long tail towards higher degrees. the degree distributions of the scale-free networks follow a power law [11]. this landmark study [11] was the first to describe the scalefree organization of many complex networks and proposed a simple growth rule for their formation. the number of connections could give a large graph network that could be used for usability needs to define clustering, coefficients, and motifs. if the nearest neighbours of a node are also directly linked to each other, they form a cluster, and the clustering coefficient quantifies the number of connections that subsist between the nearest neighbours of a node as a quantity of the maximum number of possible connections [12]. the randomly selected networks exhibit low average clustering, whereas compound networks displays high clustering. interactions between neighbouring nodes can also be counted by counting the occurrence of small motifs of interconnected nodes [13]. the distribution of different motif classes (nodes efl and kmj in fig.3) in a network provides information about the types of local interactions that the network can support [14]. the numbers of reachable nodes and hops needed for connectivity are defined by the path length and efficiency. the path length is the minimum number of edges that must be passed through to start moving from one node to another. random, complex networks have short mean path lengths; they exhibit high global efficiency of parallel information transfer, whereas regular patterns exhibit long mean path lengths. efficiency is inversely related to path length. nevertheless it is numerically easier to estimate topological distances between elements of disconnected graphs. moreover, the link density or cost of the route provides further description. the connection density is the actual number of the network edges in the graph as a proportion of the total number of possible edges and is the simplest estimator of the physical cost of the network. hubs are nodes of high degree, where the centrality of a node measures how many of the shortest paths exist between all other node pairs in the network passing through it. it can be asserted that nodes with high centrality are thus crucial to efficient communication [15]. the importance of an individual node to network effectiveness can be assessed by deleting it and estimating the efficiency of the severed network. the robustness property refers either to the structural integrity of the network following the deletion of nodes, edges or effects of perturbations on local or global network states. finally, modularity is the property that has significant influence on the “blueprint” of the behaviour. there are algorithms that estimate the modularity of the network on the basis of hierarchical clustering [16]. each module contains several densely interconnected nodes, and there are relatively few connections between these nodes in different modules. airline hubs described this as a function of their roles in community structure [17]. provincial hubs are connected mainly to nodes in their modules where the connector hubs are connected to nodes in other modules. graph based analysis of smartphone usage previously, the challenges of using mobile devices in the enterprise environment were discussed. it is important to identify the activities on the device in order to take either preventive or corrective actions. g(v, e) used for the behaviour identification and description graphs. vertices are defined as applications, more precisely, vertices within the device or network addresses and sites. edges are the connections between the vertices applications called websites, network addresses, useror process-initiated connections. • network nodes can be defined as the resource access, i.e. applications, programs, and device elements access initiated by the user or application calls. • association between network nodes could be defined as the connections of the applications (calls, connections, as web access), usually resources are connecting together. • based on the above elements, network nodes and associations provide the details to calculate the association matrix. • the following steps include network parameter analysis calculated from the above. the question is not whether mobile activity can be defined as a complex network and describable by graph, but whether the process identies a user by a motif. however, before this question can be answered certain challenges need to be faced: • identify motifs as maximum independent set, • search motif in the complex network, • define „approved behaviours” according to the identification of user behaviour. figure 3: an example of a mobile user’s identity on the basis of a “blueprint” network 83 identification of the motif in the graph the task is to find the maximum independent set (mis) of a particular graph as was defined by garey and johnson [18] as np-complete and remains so even for bounded degree graphs. according to feige et al. [19] mis cannot be approximated even within a factor of |v|1 − o(1) in polynomial time. the greedy algorithm (gmis) can provide a solution for the identification of the maximum independence set. the algorithm selects a vertex of minimum degree, deletes that vertex and all of its neighbours from the graph, and repeats this process until the graph becomes empty. a recent detailed analysis of the gmis algorithm has shown that it produces reasonably good approximations of the mis for boundedand lowdegree graphs defined by halldorsson and radhakrishnan [20]. in particular, for a graph g with a maximum degree δ and an average degree !, the size |i| of the mis satisfies eq.(1). |!| ≤ min! ∆!! ! |gmis ! |, !!!! |gmis ! | (1) where |gmis(g)| is the size of the approximate mis found by the gmis algorithm. eq.(1) provides an upper-bound of the number of edge-disjoint embeddings of a particular sub-graph, and will use this bound to obtain a computationally tractable problem formulation that is guaranteed not to miss any sub-graphs that can potentially be frequent. searching for a discover motif in the graph the grochow-kellis method [21] can be used to find all examples of sub-graphs of a given size, similar to exhaustive methods. in the background, all nonisomorphic graphs are generated of a particular size using mckay’s tools [22]. then for each graph, the method evaluates its significance. due to symmetries, a set sub-graph of g may be mapped to a set query graph h multiple times. therefore, a simple mapping-based search for a query graph will locate every case of the query graph as many times as the graph has symmetries. to avoid this, the method computes and enforces several symmetry-breaking conditions, which ensure that there is an exclusive map from the query graph h for each case of h in g, so that the search only spends time finding each instance once isomorphicextensions (f,h,g[,c(h)]: finds all isomorphic extensions of partial map f : h → g [satisfying c(h)] start with an empty list of isomorphism. let d be the domain of f. if d=h, return a list consisting solely of f. (or write to disk.) let m be the most constrained neighbour of any d � d (constrained by degree, neighbours mapped) for each neighbour n of f (d) if there is a neighbour d � d of m such that n is not neighbours with f(d), or if there is a non-neighbour d � d of m such that n is neighbours with f(d) [or if assigning f (m)=n would violate a symmetrybreaking condition in c (h)], then continue with the next n. otherwise, let f=f on d, and f (m)=n. find all isomorphic extensions of f. append these maps to the list of isomorphism. return the list of isomorphism the symmetries of a graph h equals automorphism (self-isomorphism). the collection of automorphism of h is indicated by aut(h). for a set a of automorphism, two nodes are stated to be “a-equivalent” if there is some automorphism in a which maps one to the other, or just “equivalent” if a =aut(h). given a set of conditions c, α preserves the conditions c if, given a labelling l1 of h which satisfies c, the corresponding labelling l2: h → z given by l2(n) = l1(α(n)) also satisfies c. we are thus searching for setting c, such that the only automorphism preserving c is the identity. this ensures exactly one map from h onto each of its instances in g to satisfy the conditions. to find these conditions, an aut(h)-equivalence class {n0, ..., nk} of nodes of h, and the condition l(n0) < min (l(n1), ..., l(nk)) imposed. any automorphism must send n0 to one of the ni, since these are all of the nodes equivalent to n0. however to preserve this state, an automorphism must send n0 to itself. then the process continues recursively, replacing aut(h) with set a of automorphisms that send n0 to itself. because findsubgraphinstances starts with a particular node that node can be considered already fixed. the main reasons for the selection of the grochow and kellis method are summarized as follows: • capable of finding more significant motifs by enabling exhaustive discovery of motifs up to seven nodes. to find even larger motifs, the method samples a connected subgraph, and then finds all its occurrences and assesses their significance using this method. this practice has enabled the algorithm to find motifs of up to fifteen nodes and examine subgraphs of up to thirty-one nodes; • capable of quering a particular subgraph by querying whether a particular subgraph is significant; • capable exploring motif clustering; because the algorithm finds all occurrences of a given subgraph, it can be used to examine how these cases cluster together to form larger structures; • time and space applied to all subgraphs of a set size, takes exponentially a smaller amount of time than previous methods, even when implementing the previous method with the hashing scheme. conclusions apparently the current policy enforcement solutions are not sufficient because they mainly focus on policy compliance based on the response of the device. the installation of malicious applications could alter the mobile devices response (jailbreak on ios or android 84 and software imitating a response to the mdm server) taking to more serious security issues. similarly to the recently identified malware oldboot.b, which can install malicious applications in the background, it can inject malicious modules into the system process that prevents malware applications from uninstalling. oldboot.b can change the browser setup (set a new and unwanted home page), and it also can uninstall or disable installed mobile antivirus software, and even steal data such as credit card information or any other critical data. this malware is especially dangerous as it implements evasion techniques to stay undetected. in order to optimize current threat detection, which is also in line with business requirements, additional and different methodologies are required such as user identification based on the blueprint of the behaviour of the user. to create a working model of the graph-based user identification, several tasks await completion. the running tasks are the edges started by the system or user defined as the connections between them. once the complex network and graph are set up the motif can be identified with a greedy algorithm and search of the global graph with the grochow-kellis algorithm. in order to have a behaviour-based decision making system, all of the above algorithms will be tested to further develop the behaviour-based system. references [1] amaral l.a.n., scala a., barthelemy m., stanley h.e.: classes of small-world networks, proc. natl acad. sci. usa 2000, 97, 11149–11152 [2] amaral l.a.n., ottino j.m.: complex networks. augmenting the framework for the study of complex systems, eur. phys. j. b 2004, 38, 147– 162 [3] barabási a.l., oltvai z.n.: network biology: understanding the cell’s functional organization, nature rev. genet. 2004, 5, 101–113 [4] girvan m., newman m.e.j.: community structure in social and biological networks. proc. natl acad. sci. usa 2002, 99, 7821–7826 [5] ravasz e., barabási a.l.: hierarchical organization in complex networks, phys. rev. e stat. nonlin. soft matter phys. 2003, 67, 026112 [6] barthélemy m.: betweenness centrality in large complex networks, eur. phys. j. b 2004, 38, 163– 168 [7] guimera r., amaral l.a.n.: functional cartography of complex metabolic networks, nature 2005, 433, 895–900 [8] guimera r., mossa s., turtschi a., amaral l.a.: the worldwide air transportation network: anomalous centrality, community structure and cities’ global roles, proc. natl acad. sci. usa 2005, 102, 7794–7799 [9] kashtan n., alon u.: spontaneous evolution of modularity and network motifs, proc. natl acad. sci. usa 2005, 102, 13773–13778 [10] amaral l.a.n., scala a., barthelemy m., stanley h.e.: classes of small-world networks, proc. natl acad. sci. usa 2000, 97, 11149–11152 [11] barabási a.l., albert r.: emergence of scaling in random networks, science 1999, 286, 509–512 [12] watts d.j., strogatz s.h.: collective dynamics of “small-world” networks, nature 1998, 393, 440–442 [13] amaral l.a.n., ottino j.m.: complex networks. augmenting the framework for the study of complex systems, eur. phys. j. b 2004, 38, 147– 162 [14] barabási a.l., oltvai z.n.: network biology: understanding the cell’s functional organization. nature rev. genet. 2004, 5, 101–113 [15] freeman l.c.: a set of measures of centrality based on betweenness, sociometry 1977, 40, 35– 41 [16] girvan m., newman m.e.j.: community structure in social and biological networks. proc. natl acad. sci. usa 2002, 99, 7821–7826 [17] guimerà r., mossa s., turtschi a., amaral l.a.: the worldwide air transportation network: anomalous centrality, community structure and cities’ global roles. proc. natl acad. sci. usa 2005, 102, 7794–7799 [18] garey m.r., johnson d.s.: computers and intractability: a guide to the theory of npcompleteness. new york: w. h. freeman and company, 1979 [19] feige u., goldwasser s., lovasz l., safra s., szegedy m.: approximating clique is almost np complete, proc. 32nd ieee symposium on foundations of computer science (focs), 1991, 2–12 [20] halldorsson m.m., radhakrishnan j.: greed is good: approximating independent sets in sparse and bounded-degree graphs, algorithmica, 1997, 18(1), 145–163 [21] grochow j.a., kellis m.: network motif discovery using subgraph enumeration and symmetry-breaking, computer science and ai laboratory, m.i.t. broad institute of m.i.t. and harvard, 2007 [22] mckay b.d.: isomorph-free exhaustive generation, j. algorithms, 1998, 26, 306–324 hungarian journal of industry and chemistry veszprém vol. 42(2) pp. 85–89 (2014) measurement-based modelling and simulation of a hydrogen generating dry cell for complex domestic renewable energy systems attila göllei,! péter görbe, attila magyar, and lászló neukirchner department of electrical engineering and information systems, university of pannonia, egyetem u. 10., veszprém, 8200, hungary !e-mail: golleia@almos.uni-pannon.hu nowadays, the growing need for energy from renewable sources and growing revulsion towards fossil and nuclear fuels puts sustainable and green energy in the limelight. producing (electrical) energy in domestic power plants from renewable sources (mainly solar and wind) hardly results in difficulties, but the storage of energy not consumed immediately is a great engineering challenge. in the present paper a complex model has been developed by investigating renewable energy sources, the surplus energy not actually consumed and stored in electrical vehicle (ev) batteries, the conversion to hydrogen for storage purposes and how the main grid is fed. a measurement-based model of a hydrogen generating cell developed for the simulation of complex energetic systems. the parameter estimation of the static model was based on the collected measurement data coming from the detailed examination of a built demonstration cell. the novel element of this work is the matlab simulink model for the hydrogen generation cell. using this model, a dynamic simulator of a complex domestic power plant is made available using renewable energy sources and hydrogen generation cells. hydrogen generation enables the lossless long-term storage of surplus electric energy collected, but not consumed or injected into the low voltage grid. the generated hydrogen can be consumed for transportation purposes in suitable vehicles or it can be applied in fuel cells generating direct electrical energy for energy-deficient low voltage network situations. energetic situations potentially occurring in practice were simulated in our complex model. simulations showed that the presented model is suitable for domestic scale low voltage complex energetic systems. keywords: hydrogen generation, renewable energy sources, domestic power plants, modelling and simulation, measurement-based modelling introduction producing hydrogen gas (h2) from excess energy is not a new idea. this is an alternative way to store and convert renewable energy for further utilization. the produced hydrogen can be stored or used in power cells to be converted back to electric energy or in vehicles for hydrogen propulsion [1]. although the described procedure is efficient and able to produce a high quantity of h2 it is not suitable for application in combination with domestic power plants. the most relevant from of h2 production is when the energy consumption and quantity of produced h2 are controlled. when power consumption and generation are continuous (and not necessarily deterministic) functions of time, the h2 production depends solely on the excess energy of the grid. the best solution is the usage of supervisory control and data acquisition systems (scada) of management [2]. the domestic applicability of this technology in the future depends on the cost of scada system installation. producing hydrogen and oxygen gases from water using electricity in a laboratory is a simple electrochemical process that can be performed easily and in a very demonstrative way. producing hydrogen on a large scale or in industrial quantities calls for an optimized or near-optimized cell model. in an energy demanding process only a few percent of variance in efficiency could mean a significant energy surplus or shortage [3]. the electrochemical parameters of a dry cell (fig.1) that are used here are discussed to simulate hydrogen and oxygen gas production. compared to wet oxyhydrogen (hho) cells where the entire unit is underwater, the plates of dry cells are separated with rubber seals. these seals stop the water from leaking from the cell. the electrical connections and edges of figure 1: the theoretical setup of a dry hho block 86 the plates do not touch the electrolyte. these parts of the unit stay dry, thus the name dry cell. to make sure the gas made from the electrolyte gets out of the cell and the solution flows between the plates, there are holes on the top (for the gas) and bottom (for the electrolyte) on the metal slats (fig.1). the application of dry hho units has two main advantages. the surface of the dry cell plates enables one to use smaller amounts of electrolyte compared to with wet cells; therefore, the volume and weight of the cell is smaller. furthermore, the connectors of dry cells remain dry, i.e. they do not corrode unlike to wet cells, where the connectors are underwater therefore their surface slowly corrodes [4]. electrochemical foundations electrochemical cells can be considered as galvanic batteries where the electrochemical reactions are supported by an external current supply. they are composed of two electrodes and a conductive electrolyte fluid. if the electrode material does not participate directly in the electrode reaction, it is called an indifferent electrode (e.g. graphite). during electrolysis, if there is more than one possible type of electrochemical reaction, then a simple anion will detach from the positive anode (e.g. chloride), without this anion, howill be created by water splitting. the dissolution voltage of water is 1.23 v at 25 °c, the temperature coefficient is -0.85 mv/k, which means that at 100 °c this voltage decreases to 1.17 v. therefore, in the light of these data, the specific energy demand to make hydrogen via electrolysis at 25°c can be calculated from eqs.(1–4). the amount of charge needed to evolve 1 kg of h2 gas is q = zfm = 2⋅96487⋅0.5 = 96487 a s mol-1 = = 26801 ah kg-1 (1) wh2 = qemf = 26801⋅1.23 = 32966 wh kg-1 (2) since the volume of 1 kg of standard state h2 is 12474 dm3, the amount of energy required to produce 1 dm3 of h2 gas is: wh2 = 32966 12474 = 2.64 wh dm−3 (3) to generate 1 dm3 of hydrogen gas, 1.5 dm3 of hho gas is needed and thus the energy demand of producing 1 ldm3 of hho gas (0.667 dm3 h2) is: wh2(hho) = 0.667⋅2.64 = 1.76 wh dm-3 (4) the unit has been measured at 10 different electrolyte concentrations, using different currents. at the same time, the voltage on the plates and amount of gas produced by electrolysis has also been measured. the hho cell unit the setup of one block of the unit is shown in fig.2. usually five cells make up one block giving one gasproducing block. the block’s electrical connections are on the ends of two plates (fig.1). four of the six electrode plates are neutral electrodes, as there is no voltage connected to them. the potential is divided between the neutral plates according to voltage division in series connections. it means that the voltage between two electrodes is one fifth of the voltage on one whole block. in the experiment, a unit with three blocks connected in parallel has been used. besides the hho cell, a water reserve tank to infuse the electrolyte into the cell was necessary. a tube between the gas outlet and the tank has also been installed since due to bubbling, electrolyte comes out of the tube that needs to be recycled back into the system. then, as the electrolyte drips back into the tank, the gas can escape into the bottle through another hose. the produced h2 volume and the production speed are measured with this bottle. a power supply (manson sps9600) has been connected to the electrical connections of the hho unit, in this way the input current was controlled (table 1). matlab model of the dry cell the model of the dry cell considered was implemented in matlab simulink using the simpowersystems toolbox. two unknown functional relationships between the generated h2 volume, the cell current and the koh concentration and between cell voltage, cell current and koh concentration were approximated using fourth and third order polynomials, respectively figure 2: the setup of a hho gas generator cell block table 1: experimental results electrolyte concentration, g dm-3 mmwa, cm3 min-1 w-1 gas production, dm3 min-1 power of unit, w 1 2.13 0.20 10.8 2 2.66 0.75 34.4 3 2.66 1.37 55.8 4 2.59 1.51 82.2 5 2.72 1.90 90.6 6 2.63 2.52 119.5 7 2.67 2.96 140.0 8 2.65 2.76 125.0 9 2.46 2.28 105.6 10 1.82 2.15 103.2 a millilitres per minute per watt 87 using the matlab surface fitting tool. as the fitted polynomials do not have a physical connection to the given device, the model is applicable to any similar electrochemical h2 generation device with an electric two-pole system. in the different linear and non-linear physical and chemical models different coefficients become dominant. the voltage relationship is given by eq.(5), where icell denotes the cell current and ckoh stands for the koh concentration. parameters can be found in table 2. ucell(icell,ckoh) = p00 + p10 icell + p01 ckoh + p20 icell 2 + p11 icellckoh + p02ckoh 2 + p30icell 3 + p21icell 2 ckoh (5) the volume of the generated h2 is given by eq.(6). h2 (icell,ckoh ) = p00 + p10 icell + p01 ckoh + p20 icell 2 + p11 icellckoh + p02 ckoh 2 + p30 icell 3 + p21 icell 2 ckoh + p12 icellckoh 2 + p03 ckoh 3 + p40 icell 4 + p31 icell 3 ckoh +p22 icell 2 ckoh 2 + p13 icellckoh 3 (6) table 3 and figs.3-4 show representative results for the model. as expected, the h2 generation speed decreases and the cell finally stops working as the amount of water decreases and the koh concentration increases. a simulink block scheme of the cell model is depicted in fig.5. this simulink model was validated by considering a system with the same parameters as the layout of the experimental cell. in this layout, we ran a simulation for 24 h using this model, decreasing water and increasing koh concentrations. the results of this simulation can be seen in fig.6. it can be seen that the hydrogen gas generated is reduced because of the rising koh concentration. the exact values are in good agreement with our measurements. dry cell model in complex energetic systems the model for h2 generating cells described in the previous section was investigated in the matlab simulink simulation environment that studies the energy flow conditions of a complex energetic system consisting of a renewable source with a gridtable 2: coefficients of the polynomial relationship describing the cell voltage value value value p00 1.429 p10 0.2548 p01 -0.1226 p20 -0.008571 p11 -0.01191 p02 0.008257 p30 0.0001141 p21 -8.76e-05 p12 0.0009697 table 3: coefficients of the polynomial relationship for the generated h2 gas value value value p00 -0.1695 p10 0.1687 p01 -0.01765 p20 -0.007486 p11 -0.03234 p02 0.03446 p30 -0.0001077 p21 0.00412 p12 -0.004094 p03 -0.004061 p40 -4.269e-06 p13 6.169e-05 p22 -0.0005518 p13 0.0009544 figure 3: simulation of the cell model with a constant current of 5 a for 1 day figure 4: generated h2 as a function of koh concentration and dry cell current figure 5: matlab simulink model of the hho cell. the functional blocks implementing eqs.(5) and (6) are denoted by different background colours figure 6: simulation of a cell model with a constant current of 5 a for 1 day 88 synchronized inverter, a low voltage grid, an intermediate voltage controller [3,5] and a lithium ion battery. we replaced the lithium ion battery in this cell model, which reduces the potential energy flow modes, because this cell can only adsorb current for storing energy in hydrogen production. it cannot reverse the electrochemical process for electrical energy generation from hydrogen gas. the structure of the system can be seen in fig.7, where it is apparent that the cell model is connected directly only to the grid-synchronized inverter module of the system. the system depicted in fig.7 operates in different discrete states according to the energy flow direction. four cases can be defined: • normal inverter mode: the energy flows from the renewable source to the grid only (fig.8a). • normal inverter and hydrogen generation mode: the energy flows from the renewable source to both the dry cell and the grid (fig.8b). • hydrogen generation only mode: the energy flows from the grid to the dry cell only (fig.8c). • distortion reduction only mode: the energy flows from the grid into the intermediate capacitance and from the intermediate capacitance into the grid. the energy balance is zero for a period, and the active power is zero (fig.8d). model verification was performed by changing the energy flow modes in subsequent time intervals, and this was implemented by changing the energy balance of the system with outer current loads (iouter load). the different values for the simulations as parameters can be figure 7: simulink model of a complex energetic system with an hho cell model inside figure 8: complex energetic system energy flow modes: a: normal inverter mode, b: inverter and hydrogen generator mode, c: hydrogen generation only mode, d: distortion reduction only mode 89 seen in table 4. the simulation results are shown in fig.9, where uconn is the effective value of the voltage at the connection point, ihho is the current value of the dry cell, vh2 is the volume of generated hydrogen gas, ckoh is the koh concentration of the electrolyte and vwater is the volume of water inside the cell system. these values are plotted as a function of time. the results of the simulation show that the behaviour of the simulated electronic two-pole system is identical to that of the measured database. conclusion we developed a complex model to investigate renewable energy sources, for the conversion of surplus energy to hydrogen gas for storage and to represent how a main grid is fed. we built a measurement-based model of a hydrogen-generating cell for the simulation of complex energy systems in matlab simulink environment. we estimated the parameters of the model based on measurements collected during the detailed examination of a demonstration cell. we carried out a series of experiments on a hho gas producing dry cell to find the optimal electrolyte concentration, current value, etc. or change the setup by altering the distance between the plates with koh electrolyte solution. we monitored the experimental setup in several regards, for example cell voltage, and gas production. the novel element is the temperature and concentration dependent matlab simulink model of the hydrogen generation cell, which was found to be suitable for simulation purposes. we tested it in a simulation of a complex domestic power plant using a renewable energy source and hydrogen generation cell. hydrogen generation enables the long-term storage of surplus electrical energy collected, but not consumed or injected into the low voltage grid. the generated hydrogen can be consumed by vehicles for transportation purposes or it can be applied in fuel cells generating direct electrical energy for energy-deficient low voltage network situations. we simulated all the potential energetic situations in this complex model of an energetic system. the simulations showed that the presented model of a hydrogengenerating cell performed well. acknowledgement we acknowledge the financial support of this work by the hungarian state and the european union under the tamop-4.2.2.a-11/1/ konv-2012-0072 project. references [1] koutsonikolasa d.e., kaldisa, s.p., pantoleontosb, g.t., zaspalisac, v.t., sakellaropoulosc, g.p.: techno-economic assessment of polymeric, ceramic and metallic membranes integration in an advanced igcc process for h2 production and co2 capture, chem. engng. trans. 2013, 35, 715-720 [2] ziogoua c., elmasidesb c., papadopoulouca s., voutetakisa s.: supervisory control and unattended operation of an off-grid hybrid power generation station with hydrogen storage chem. engng. trans. 2013, 35, 529-534 [3] görbe p., magyar a., hangos k.m.: line conditioning with grid synchronized inverter's power injection of renewable sources in nonlinear distorted mains, proc. 10th international phd workshop on systems and control, 2009, 978-980 [4] al-rousan a.a.: reduction of fuel consumption in gasoline engines by introducing hho gas into intake manifold, int. j. hydrogen energy, 2010, 35, 12930-12935 [5] görbe p., magyar a., hangos k.m.: thd reduction with grid synchronized inverter’s power injection of renewable sources, proc. 20th int. symp. power electronics, electrical drives, automation and motion (speedam) 2010, 13811386 figure 9: simulation results of a complex energetic system using a cell model short time range (5 sec) advertise upcoming meetings, conferences, workshops, new products or services; make public announcements, introduce your research laboratory on the pages of the hungarian journal of industry and chemistry please contact us if interested! editorial office: university of pannonia p.o. box 158, veszprém h-8201 (hungary) tel.: +36 (88) 624-746, e-mail: hjic@almos.uni-pannon.hu; web: hjic.mk.uni-pannon.hu felelős szerkesztő: szilágyi róbert károly, phd kiadja: pannon egyetem, 8200 veszprém, egyetem u. 10. levélcím: h-8201 veszprém, postafiók 158, tel.: (88) 624-000 felelős kiadó: a pannon egyetem, mérnöki kar dékánja hungarian journal of industry and chemistry veszprém vol. 42(2) pp. 91–95 (2014) quasi-polynomial representation-based control of mechanical systems lászló neukirchnerb and attila magyar department of electrical engineering and information systems, university of pannonia, egyetem u. 10., veszprém, 8200, hungary be-mail: neu.groszber@gmail.com a simple kinematic model of a differential steering mobile robot is investigated using a nonlinear technique based on the quasi-polynomial representation of the dynamical model. dynamical systems can be embedded in the generalized lotka-volterrs (or quasi-polynomial) form under mild conditions. quasi-polynomial systems are good candidates for a general nonlinear system representation, since their global stability analysis is equivalent to the feasibility of a linear matrix inequality. the stabilizing quasi-polynomial state feedback controller design problem is equivalent to the feasibility of a bilinear matrix inequality. the classical stabilizing state feedback problem for quasi-polynomial systems was extended with the ability of tracking time-dependent reference signals. it is shown that the stabilizing quasi-polynomial controller design is equivalent to a bilinear matrix inequality. the results are applied to the model of the differential steering mobile robot. the goal reaching quasi-polynomial controller is shown to be a special kind of proportional state feedback. keywords: quasi-polynomial, robotics, differential drive robot, control systems, kinematics, lotka-volterra system introduction trajectory and goal tracking of mobile robots is an intensively studied field of modern robotics as well as modern control theory. several papers deal with an adaptive output feedback approach [1]. on the other hand some groups try to apply neural network-based methods for the task [2]. another direction is to describe the problem as an optimal control problem and apply optimal control results for it [3]. the class of quasi-polynomial (qp) systems plays an important role in the theory of nonlinear dynamical systems because nonlinear systems with smooth nonlinearities can be transformed into quasipolynomial form ref.[4]. this means, that any applicable method for quasi-polynomial systems can be regarded as a general technique for nonlinear systems [5]. the aim of this work is to widen the applicability of the quasipolynomial representation-based methods to the class of mechanical systems, more precisely to mobile robots. the goal reaching problem of a differential steering mobile robot is reformulated as a globally stabilizing feedback design problem in the quasi-polynomial framework. basic notions differential drive mobile robot kinematics the chosen mechanical system is the kinematic model of a two wheeled differential drive mobile robot eq.(1). the model deals with the geometric relationships that govern the system. it calculates the motion without considering the affecting forces. the system’s states are the cartesian coordinates x, and y and the orientation ✓ of the mobile robot. the basic kinematic model of the differential drive robot is given by ˙✓ = r 2a (!left � !right) ẋ = r 2 cos(✓)(!left + !right) ẏ = r 2 sin(✓)(!left + !right), (1) where a is half the shaft’s diameter, r is the radius of the wheels and ! is the angular velocity of the right or left wheel. to order the robot to reach a specific goal, it is acceptable to design a proportional controller to govern the expected trajectory eq.(2) [6] . in this case, the model is modified to calculate the state errors between the ordered and the present value. the new error model with proportional gain is ẋ = kv(edis cos(✓)� x(t)) ẏ = kv(edis sin(✓)� y(t)) ˙✓ = kh(eang � ✓(t)) edis = q (xg � x(t))2 + (yg � y(t))2 eang = arctan ✓ 2 yg � y(t) xg � x(t) ◆ , (2) where kv is the velocity control gain, kh is the rotational velocity control gain, edis is the distance error, eang is the 92 angular error, and xg, yg are the cartesian coordinates to reach. quasi-polynomial representation of nonlinear systems some basic notions of quasi-polynomial and lotkavolterra systems are summarised in this section. generalised lotka-volterra form representing an ode in generalised lotka-volterra (glv) form can increase the structural simplicity in exchange for increasing its dimension. the glv or quasipolynomial (qp) form: ẋ i = x i ✓ � i + mp i=1 a ij · nq k=1 x bij k ◆ , i = 1, . . . , n, m � n (3) where a and b are n ⇥ m, m ⇥ n real matrices, and � 2 rn is a vector. the set of non-linear odes can be embedded into qp form if it meets two requirements: (i) the non-linear odes should follow this form: ẋ s = p is1...isn,js a is1...isn,jsx is1 1 . . . xisn n f(x̄)js , x s (t0) = x0 s , s = 1 . . . n (4) where a is1...isn,js✏r, s = 1 . . . n, and f(x̄) is some scalar function which cannot be reduced to quasy-monomial form. (ii) the partial derivatives of the system eq.(4) should fulfil: @f @x s = p es1...esn,es b es1...esn,esx es1 1 . . . xesn n f(x̄)es , (5) where b es1...esn,es✏r, s = 1 . . . n. by embedding, we introduce the new auxiliary variable: y = fq nq s=1 xps s . q 6= 0 (6) differentiating the new, substituted equations we get the qp representation of the original equation eq.(4): ẋ s = x s 2 4 x is1...isn,js ⇣ a is1...isnjsy js/q ny k=1 xisk��sk�jspk/q !# , s = 1 . . . n (7) where � sk = 1 if s = k and 0 otherwise. a new additional dimension appears as the ode of the new variable y: ẏ = y " x is1...isn,js ✓ p s x�1 s ẋ s + + x is↵,js es↵,es a is↵,jsbis↵,jsqy (es+js�1)/q ⇥ ⇥ ny k=1 x isk+esk+(1�es�js)pk k ◆# . ↵ = 1 . . . n (8) it is important to mention that the new ode is not unique because we can choose the parameters p s and q. the quasi-monomial transformation is defined as: x i = nq k=1 xcik k , i = 1 . . . n (9) where c is an arbitrary invertible matrix. the matrices of glv can be modified as ˆb = b · c, ˆa = c�1 · a, and ˆ� = c�1 ·�, and the transformed set is also in glv form. lotka-volterra models the above family of models is split into classes of equivalence according to the values of the products m = ba and n = bl. the lotka-volterra form gives the representative elements of these classes of equivalence. if rank(b) = n, then the set of odes in eq.(3) can be embedded into the following m-dimensional set of equations, the so-called lotka-volterra model: ż j = z j n j + mx i=1 m ji z i ! , j = 1, . . . ,m (10) where m = ba, n = bl, and each z j represents a so-called quasi-monomial: z j = ny k=1 y bjk k , j = 1, . . . ,m. (11) input-affine qp model the well known input-affine model of nonlinear systems is given in the following state space model: ẋ = f(x)+ pp j=1 gj(x)uj where f 2 rn ! rn, and gj 2 rn ! rn are qp functions and the input variable u is p-dimensional. in 93 figure 1: membership functions for angular error this case we need a qp form with the matrices from the glv form ode set: ẋ i = x i 0 @� i + mx j=1 a0 ij ny k=1 x bjk k 1 a + + px l=1 x i 0 @µ li + mx j=1 c lij ny k=1 x bjk k 1 au l . i = 1 . . . n (12) it can be proven that if u = h(x) state feedback is in qp form, the closed-loop system remains in qp form as well, but the quasi-monomials of the system will be greater, than the system’s without the feedback. global stability analysis global equilibrium points can be obtained by finding a lyapunov function v (·). for lv systems there is a well known lyapunov function family: v (z) = mx i=1 c i ✓ z i � z⇤ i � ln z i z⇤ i ◆ , c i � 0, i = 1 . . .m (13) and the time derivative: ˙v z = @v (z) @z · @z @t = = 1 2 (z � z ⇤ )(c m +m t c)(z � z ⇤ ), (14) where z ⇤ = (z⇤1 . . . z ⇤ m ) t is the unique positive equilibrium point, c = diag(c1, . . . , cm) and m is the invariant coefficient matrix of the lv form. if cm t +m c is negative semi-definite then z ⇤ is stable and if negative definite then z ⇤ is asymptotically stable. the global stability analysis is thus equivalent to the linear matrix inequality cm t +m c  0 c > 0. (15) the presented lyapunov function eq.(13) can be extended to glv systems by embedding the system using the lv coefficient matrix m = ba. it is necessary to solve the lmi system eq.(15) for the stability analysis of the qp and lv system: ✓ c 0 0 �cm t �m c ◆ > 0 (16) controller design in quasi-polynomial representation the globally stabilizing qp state feedback design problem for qp systems can be formulated as follows [7]. consider arbitrary quasi-polynomial inputs in the form: u l = rx i=1 k il q̂ i , l = 1 . . . , p (17) where q̂ i = q̂ i (y1, . . . , yn), i = 1, . . . , r are arbitrary quasi-monomial functions of the state variables of the system and k il is the constant gain of the quasi-monomial function q̂ i in the l-th input u l . the closed-loop system will also be a qp system furthermore, the closed-loop lv coefficient matrix m̂ can also be expressed in the form m̂ = b̂ â = m0 + px l=1 rx i=1 k il mil. (18) then the global stability analysis of the closed-loop system with unknown feedback gains k il leads to the following bilinear matrix inequality m̂ t c +cm̂ = m0 t c +cm0+ px l=1 rx i=1 k il ⇣ mil t c +cmil ⌘  0. (19) the variables of the bmi are the p ⇥ r k il feedback gain parameters and the c j , j = 1, ..,m parameters of the lyapunov function. if the bmi above is feasible then there exists a globally stabilizing feedback with the selected structure. quasi-polynomial control of a differential drive mobile robot quasi-polynomial representation of the kinematic model with the given differential drive robot model eq.(1) and the explained error model eq.(2) the qp representation can be built. the fist step as mentioned, is to find the new auxiliary variables, that help to eliminate the non-qp expressions. the newly chosen auxiliary variables are: ↵ = cos(✓), � = sin(✓), � = arctan ✓ 2 yg � y xg � x ◆ , � = (xg � x)2 + (yg � y)2, and ✏ = p � + (xg � x). (20) 94 �2 0 2 4 6 0 2 4 6 start finish x [m] y [ m ] pid qp fuzzy figure 2: comparison of different controllers by substituting them into the original system eq.(2) and performing the differentiation of the new equations eq.(20): ẋ = x kv p �↵ x �kv ! ẏ = y kv p �� y �kv ! ˙✓ = ✓ ✓ kh� ✓ �kh ◆ ↵̇ = ↵ ✓ �� ↵ ◆ ˙� = � ✓ ↵ � ◆ (21) �̇ = �· ⇣ � 2kv� p � �✏ + kvy �✏ �kvxg� �✏ + kvx� �✏ + kvxgy �✏ p � �kvxy �✏ p � + kvyg↵ �✏ �kvy↵ �✏ �kvygx �✏ p � + kvxy �✏ p � ⌘ (22) ˙� = � ⇣ � 2kvxg↵p � + 2kvxgx � + 2kvx↵p � � 2kvx 2 � � 2kvyg�p � + 2kvygy � + 2kvy�p � � 2kvy 2 � ⌘ (23) ✏̇ = ✏ ⇣ �kvxg↵ ✏ + kvx↵ ✏ + kvxgx ✏ p � �kvx 2 ✏ p � �kvyg� ✏ + kvy� ✏ + kvygy ✏ p � �kvy 2 ✏ p � + kv↵ ✏ �kvx ✏ p � ⌘ (24) figure 3: membership functions for distance error the closed-loop qp system eq.(21-24) has 29 quasimonomials. x : ↵ p �x�1 y : � p �y�1 ✓ : �✓�1 ↵ : �↵�1 � : ↵��1 � : � p ���1✏�1, y��1✏�1, ���1✏�1, x���1✏�1, y��1��1/2✏�1, ↵��1✏�1, y↵��1✏�1, x��1��1/2✏�1 � : ↵��1/2, x��1, x↵��1/2, x2��1, ���1/2, y��1, y���1/2, y2��1 ✏ : ↵✏�1, x↵✏�1, x✏�1��1/2, x2✏�1��1/2, �✏�1, y�✏�1, y✏�1��1/2, y2✏�1��1/2, (25) the qp system eq.(21-24) can obtain the glv form invariants with the help of monomials. these matrices are: a the coefficient matrix, b the exponential matrix and � the constant’s matrix. the invariant matrix product ba results in the lv coefficient matrix m , which is necessary for the global stability analysis. controller design as the original model eq.(2) already contains the proportional controller parameters kh and kv, they naturally appear in the qp and lotka-volterra forms, respectively. the closed-loop lotka-volterra coefficient matrix m contains the proportional gains in a linear manner eq.(26) [7] m = m0 +kh mh +kv mv, (26) where m 2 r29⇥29. this means, that the globally stabilizing feedback design bmi can be formulated, and checked for feasibility. the controller design is practically solved as a control-lyapunov function-based state feedback. the prescribed lyapunov function parameters are c1,2,3 = 0.1, c4,5 = 1 and c6�29 = 0. the control gains are obtained by solving an lmi version of the feedback design bmi by substituting c into eq.(19). the obtained values are kh = 2.78 and kv = 0.8. 95 table 1: rules for the fuzzy controller ^ ^ eang edis !left !right zero zero ) zero zero pos zero pos neg zero neg pos zero pos pos pos pos pos pos zero pos zero pos comparison of results for different controller types the first and most basic method was the proportional controller approach. this was explained in the second chapter. this is a more systematic approach, but with the increasing non-linearities it is becoming a more difficult method to solve. fig.3 shows that the robot moves on a significantly wider curve compared to the other two designs. secondly a fuzzy controller was designed to compare the original design to. this is a much more intuitive approach, the physical nonlinearities were easily implementable with the cost of inaccuracy. this can be seen in fig.3, where the robot travels on a much smaller curve. table 1 shows the definition of the rules. the membership functions follow simple triangular shapes according to the acceptable rate of angular and velocity changes. the qp controller performance can be seen in fig.3. where a classical pid controller and a fuzzy logic controller are also shown. it is apparent, that the qp controller performs well by means of the length of the trajectory. conclusions a quasi-polynomial representation-based nonlinear control design method has been applied to the kinematics of a differential steering mobile robot in this work. it has been shown, that the quasi-polynomial model of the mobile robot’s kinematics extended with the tracking error dynamics has 29 quasi-monomials, i.e. the sizes of matrices appearing in the bilinear matrix inequality that should be solved for a globally stabilizing feedback controller acknowledgement this research was supported by the european union and the state of hungary, co-financed by the european social are reasonably great. the resulting controller and the trajectory were compared to the trajectories of a reference pid controller and a fuzzy logic controller. it can be seen that the controller performs satisfactorily. possible future directions include the application of the lmi and /or bmi cost function to introduce some optimality measure to the problem to be minimised. a next step would be the application of a time dependent goal position (i.e. a trajectory). fund in the framework of the támop 4.2.4. a/2-11-12012-0001 ’national excellence programme’. references [1] huang j., wen c., wang w., jiang z.-p.: adaptive output feedback tracking control of a nonholonomic mobile robot, automatica, 2004, 50(3), 821– 831 [2] mohareri o., dhaouadi r., rad a.b.: indirect adaptive tracking control of a nonholonomic mobile robot via neural networks, neurocomputing, 2012, 88, 54–66 [3] li j., guo x., li z., chen w.: stochastic adaptive optimal control of under-actuated robots using neural networks, neurocomputing, 2014, 142, 190-200 [4] hernández-bermejo b., fairén v.: nonpolynomial vector fields under the lotka-volterra normal form, phys. lett. a, 1995, 206, 31–37 [5] magyar a., fodor a.: quasi-polynomial control of a synchronous generator, hung. j. ind. chem., 2013, 41(1), 55–61 [6] tzafestas s.g.: mobile robot control i: the lyapunov-based method, in introduction to mobile robot control (tzafestas s.g., ed.) elsevier, oxford, 2014, 137–183 [7] magyar a., szederkényi g., hangos k. m.: globally stabilizing feedback control of process systems in generalized lotka-volterra form, j. proc. contr., 2008, 18(1), 80–91 advertise upcoming meetings, conferences, workshops, new products or services; make public announcements, introduce your research laboratory on the pages of the hungarian journal of industry and chemistry please contact us if interested! editorial office: university of pannonia p.o. box 158, veszprém h-8201 (hungary) tel.: +36 (88) 624-746, e-mail: hjic@almos.uni-pannon.hu; web: hjic.mk.uni-pannon.hu felelős szerkesztő: szilágyi róbert károly, phd kiadja: pannon egyetem, 8200 veszprém, egyetem u. 10. levélcím: h-8201 veszprém, postafiók 158, tel.: (88) 624-000 felelős kiadó: a pannon egyetem, mérnöki kar dékánja hungarian journal of industry and chemistry veszprém vol. 42(2) pp. 97–101 (2014) a network model for simulating the dynamic behaviour of an energy distribution network levente bálint,1! tibor dulai,2 ágnes stark-werner,2 gergely apostol,1 and ádám tompos1 1 faculty of information technology, university of pannonia, egyetem u. 10., veszprém, 8200 hungary !e-mail: balintlevente.z@gmail.com 2 department of electrical engineering and information systems, faculty of information technology, university of pannonia, egyetem u. 10., veszprém, 8200 hungary the aim of this paper is to present the planning and implementation of a network model for an energy distribution network for simulating its dynamical behaviour. the model includes different types of energy sources, distribution centres and consumers. the prepared simulation environment makes it possible to add/remove/modify any type of node – to/form/in the model. other actions that may be carried out are the initiation/termination of an energy source or change to its production level. the main goal of the simulation is to investigate the effect of an immediate event (such as a power plant failure, decreased production, etc.) on the network and search for the most appropriate substitute possible. the search may happen either on cost bases or time bases. the system created is based on web technology, any user is able to create/save/load his own model and do simulations on it. this work serves as a basis for further work, which involves more complex electrical knowledge and possibilities regarding the network. keywords: energy distribution network, energy sources, dynamical behaviour, network model, simulation introduction energy efficiency has an increasing importance due to costand environment-related factors. at the same time, the customer demands have to be satisfied. these circumstances result in a largely heterogeneous energy producing and distributing environment. renewable energy is applied to a considerable degree in addition to the electricity produced by traditional power plants [1]. this resulted in a system, where different types of energy sources – with different properties, like cost, response time, etc. – are applied in a mixed way. it is a non-trivial task to decide, which sources to apply even in the case of pre-determined demands. moreover, in practice the amount of the demand appears only when needed. earlier efforts implemented simulation environments for analysing the effect of the hybrid manner of an electric network [2, 3]. however, the problem becomes more complex when an immediate negative event happens, e.g. an energy source becomes unavailable or has to decrease its output suddenly. the optimal answer depends on many factors: e.g. how quickly a new energy source can be applied or how much it will cost. moreover, some types of energy sources are only able to produce discrete levels of output power. this paper describes a web-based system, which makes it possible to create and modify an energy distribution network (including different types of energy sources and customers, too) with the goal of simulating different immediate events. the requirements to be collected and the network model and its elements are introduced, followed by details of the implementation and simulation. requirements: the desired properties of the system functional requirements include mainly the creation and manipulation of network models and simulations. fig.1 presents the possible applications of the system. the interface contains a tree graph-based model whose root is the power source, the inner nodes are the network stations and the leaves are the consumers. the graph’s edges are the connections between the components. there are multiple projects in the system, each project contains a model. the main functions of the system are available through the modeling and simulation interfaces. during the simulation the components can be switched on and off. after two hours of simulation a statistic diagram can be viewed for each component of the model, showing its consumption or production. information about components can be edited while the system is not simulating. next to the functional requirements, the system-related requirements are that: • the system has to be web-based, • no user authentication is needed, • the reaction time is less than 1 s, even if there are 100 users, and • any system or communication failure has to be presented by an unambiguous alert to the user. 98 the interface the interface of the system contains four important elements. on the upper edge is the modelling control bar with the component adding buttons, background theme switcher and save/load buttons. by pressing the load button, the system opens the project selector. the save button must be pressed before loading another project in order to save the current one. under the right side of the control bar, there is the simulation control panel. there are buttons on it for editing corporate and residential priority orders, and sliders for the importance of certain properties while calculating the priority order of the power sources. there are buttons for starting, stopping, and restarting simulation time. the simulation time begins at 6:00 am and the step time can be set from 1 to 60 minutes. in the bottom left-hand corner, the event-log is located, which indicates the basic events like start/stop simulation, add/remove components in black and important events like system failure or insufficient power in red. all events have a time-stamp. while hovering the mouse over a component, the system shows the detailed properties of the element. double clicking selects a component or deletes a connection. while a component is selected, the edit, delete and diagram buttons appear in the modelling control bar. the diagram button works only after a minimum of two hours of simulation. in simulation mode the modelling control bar is hidden and double clicking switches a component on/off. the network model and its elements as the system’s main potential is in handling different types of network nodes and making the investigation of a heterogeneous energy producing and distribution system possible, the elements of the network models and their properties have a huge role. the network nodes can be classified as follows. energy sources the system considers renewable energy sources (water, bio, wind, solar, and geo), non-renewable energy sources (natural gas, petrol, coal, nuclear), and quick start-up energy sources (gas turbines) when the energy provided by power plants is insufficient for consumers. each energy source has a unique name and a maximum output, which defines an upper limit for the source (fig.2). a minimum output is defined as a lower limit, below that the operation is not profitable. start-up cost is the cost needed to switch on the source, and starttime is the time required to start producing energy. the operational cost is a financial value which is needed for one hour of operation. power sources have an environmental multiplier. this multiplier is 1 for renewable sources, 0.2 for non-renewable ones and 0.1 for quick start-up sources by default, but it can be edited any time during the modelling. larger values are better, the maximum is 1 but the value cannot be 0. the system calculates an order between sources from their start-up cost, operational cost and environmental multiplier. this order can be modified by the user before starting the simulation. distributing elements distributing elements for the system are power plant stations that distribute the energy to multiple network stations that further distribute the energy to retail stations directly transmit the energy to consumers. distributing stations have only two properties (fig.3). they have a unique name to identify them and a maximum throughput, which is the maximum power that the station can distribute to lower stations or consumers. if that limit is reached the station will not pick up more power even if the consumers need more. figure 1: example uses of the prepared system figure 3: edit station properties (név: name or location, teljesítmény: power) figure 2: edit power source properties (név: name or location, bekapcsolási költség: cost of starting up, indítási idő: start-up time, üzemköltség: operational cost, környezeti szorzó: environmental factor, optimális sorrend: optimal order) 99 consumers the residential consumers are linked to the model through homes, while corporate consumers include factories, public institutions, etc. consumers have a rate of consumption that describes their maximum required power. current consumption is estimated during the daytime in the simulation. consumers also have an order of priority that can be modified by the user but corporate consumers always have priority over residential consumers (fig.4). connections connections have a length property, which will be used for calculating the loss, dissipated by the cables resistance. networks can be built up by the previously introduced network nodes by connecting them appropriately. the order of connectivity is as follows: • power sources, • power plant distribution station, • network distribution station, • retail distribution station, and • consumer. connections can be established only in this order regardless of the performance of individual components. database and implementation details properties of the network model elements and the network formed are stored in an associative array that can be used directly by the system. at each time it is saved, this array is stored in javascript object notation (json) format in a text file for each project separately. the database array contains an entry for all components of the model. every component has an id, a name, a type and position on the modelled field. energy sources also have a fuel type, start-up time, start-up cost, running cost, environmental factor, and minimum and maximum performance level attributes. stations have a defined maximum tolerance. for consumers, there is a stored average consumption rate, which dynamically changes over time. each object has a sub-array, which stores the id of any other components that are connected to the current one. consumer objects have priority numbers that define the relevance of the consumer. if the power source cannot produce enough energy to satisfy all needs, then the consumer that has the highest priority number will be switched off from the network. the priority order equals the order of creation of components, but the corporate consumers always have preference. the order can be changed by the user any time in modelling mode and during the simulation. implementation details the program is implemented in javascript language with plug-ins like jquery and jsplumb. the plug-in jquery is the most popular extension of the javascript language. it makes it easier to select, move, remove or modify the elements on the interface by selecting the element by its id and modifying its properties. the system uses an in-house jquery plug-in, windows.js. this plug-in creates free movable small windows on the interface and fills them with appropriate content defined by the programmer. the jsplumb plug-in is an opensource plug-in for javascript, created to visually connect elements on the interface with straight lines or bezier curves. the database is stored in json format text files, created and edited by hypertext preprocessor (php) functions and called asynchronously by javascript’s asynchronous javascript and xml (ajax) protocol. php is a server-side scripting language, but in our case its only function is to properly save and load database files to the server computer. the whole software can be started in a browser on the user’s computer and it connects to the server only while loading or saving the project. the interface is fully interactive, in modelling mode the objects can be moved or removed, in simulating mode switched on and off. simulation possibilities the system was created for simulating immediate events during the operation of a modelled energy distribution network. after forming the network, the software makes it possible to cause different immediate events. these severe a connection or switch on/off sources, stations and/or consumers. all of these events can be carried out on the graphical interface of the software (fig.5). the simulation is daytime-based. it starts at 6:00 am. users can set the step time from 1 min or sec to 60 min or sec. at the beginning the system distributes the energy produced by the power plant(s) to all consumers in a user defined order. if a power plant does not produce enough power then the last consumer will be switched off and so on. the electricity-related behaviour will be implemented in the future into the software. a possible solution is to build an ideal flow model as a cooperative game over a graph with the sources and consumers located at the nodes, each described by a maximum supply or desired demand and the power lines figure 4: edit consumer properties (név: name or location, fogyasztás: consumption, prioritás: priority) 100 represented by the edges, each with a given power transmission capacity and admittance value describing their ability to transmit electricity. [4] the user is able to initiate immediate events and the system reacts to them in real-time and recalculates the distribution. calculation of the consumption rate is based on the hungarian average with a small random factor. an example for a simulation let us assume that we have a power plant with a maximum power of 100 kw. the model has one of each type of stations, three households (10-10 kw maximum) and a factory (80 kw maximum) (fig.6). normally, all of the consumers are satisfied, but in the peak times, when the factory and the houses also approach their maximum consumption, the power will not be enough for every consumer, so the system switches off the retail consumer that is last in the priority order. there will not be a consumption reduction, but a complete shutdown. subsequently, the plant will have to produce 95% of the maximum power. in this example all of the stations can transfer the maximum of 100 kw, but if a station cannot transfer this, then the consumer with the largest priority number connected to this station will be switched off, regardless of the current level of the power source. if the consumption is too high, it is possible that complete distribution stations are switched off. further developments the current system can model and simulate a fictional power network with components and connections, but the main goal of the project is to create a simulating software that can model and simulate a real electrical network. it is important to emphasize that the unit of the power of the sources and the consumption are now only kw. we need to include that the voltage of connection cables depends on the length of the connection and the diameter of the cable that are required to calculate the amperage from the resistance of the cable. international connections transmit 750 kv, and the main network in hungary transmits 400 kv starting from the power plants (fig.7). the distribution stations transform and divide it to lower values until the voltage reaches the necessary 250 v for retail and 360 v (or more) for corporate consumers. during the transformations, the system needs to use kirchhoff’s current law that states that at any node in an electrical circuit, the sum of currents flowing into that node is equal to the sum of currents flowing out of that node. that means that the system has to calculate amperages for every incoming and outgoing connection of the distribution stations based on the consumption of the consumers and the target voltage of the cables. the biggest problem of power distribution networks in reality is to satisfy all consumers at all the time, even if the load is very low, without making large changes to the output of the power sources everyday. the current solution in hungary is nighttime power. households using electric water heaters have nighttime electric meters, when the consumption of corporate consumers is drastically reduced. this solution slightly optimizes the operation of power plants. figure 5: the graphical interface of the software (új erőmű: new powerplant, új fogyasztó: new consumer, új állomás: new station, új kapcsolat: new connection, mentés: save, betöltés: load, lakossági sorrend: order of households, céges sorrend: order of companies, maxköltség: maximum cost, környezet: environment, bekaps: start-up, indulás: begin, indítás: start, leállítás: stop, újraindítás: restart figure 6: the model of our example (méter: distance in m) 101 conclusion this paper presented the planning phase and implementation of a web-based system that makes it possible to construct an energy distribution network together with different types of energy sources and consumers. the simulations are carried out to determine the most effective response to different immediate events (e.g. a sudden network problem or failure of an energy source). the simulation takes into account both cost-related and time-related properties, too. the present state of the software provides a basis for further works, which intend to add deeper electricity-related properties and behaviour to the system. acknowledgement the authors are thankful for scientific guidance by prof. katalin m. hangos from the computer and automation research institute. we acknowledge the financial support of the hungarian state and the european union under the tamop-4.2.2.a11/1/konv-2012-0072 project. references [1] breitner m.h.: modeling the transformation of the german energy system until 2050: a multi-criteria, long term optimization problem with many constraints, operations res. proc. 2012, 369-374 [2] geysen d., booiy p., warmer c.: a framework for simulation and control of hybrid energy networks, proc. energycon 2014, dubrovnik, croatia, 2014 [3] padulles j., ault g.w., mcdonald j.r.: an integrated sofc plant dynamic model for power systems simulation, int. j. power sources 2000, 86, 495-500 [4] csercsik d., kóczy l.á.: externalities in the games over electrical power transmission networks, iehas discussion papers, 2011, no 1125 figure 7: the hungarian transmission network advertise upcoming meetings, conferences, workshops, new products or services; make public announcements, introduce your research laboratory on the pages of the hungarian journal of industry and chemistry please contact us if interested! editorial office: university of pannonia p.o. box 158, veszprém h-8201 (hungary) tel.: +36 (88) 624-746, e-mail: hjic@almos.uni-pannon.hu; web: hjic.mk.uni-pannon.hu felelős szerkesztő: szilágyi róbert károly, phd kiadja: pannon egyetem, 8200 veszprém, egyetem u. 10. levélcím: h-8201 veszprém, postafiók 158, tel.: (88) 624-000 felelős kiadó: a pannon egyetem, mérnöki kar dékánja hungarian journal of industry and chemistry veszprém vol. 42(2) pp. 103–107 (2014) on the parametric uncertainty of weakly reversible realizations of kinetic systems györgy lipták b1, gábor szederkényi1,2 and katalin m. hangos1,3 1process control research group, mta sztaki, kende u. 13-17, budapest, 1111, hungary 2faculty of information technology, péter pázmány catholic university, práter u. 50/a, budapest, 1083, hungary 3department of electrical engineering and information systems, university of pannonia, egyetem u. 10, veszprém, 8200, hungary be-mail: lipgyorgy@gmail.com the existence of weakly reversible realizations within a given convex domain is investigated. it is shown that the domain of weakly reversible realizations is convex in the parameter space. a lp-based method of testing if every element of a convex domain admits weakly reversible realizations is proposed. a linear programming method is also presented to compute a stabilizing kinetic feedback controller for polynomial systems with parametric uncertainty. the proposed methods are illustrated using simple examples. keywords: parametric uncertainty; computational methods; optimization; kinetic systems introduction the notion of parametric robustness is well-known and central in linear and nonlinear systems and control theory [1]. it is used for ensuring a desirable property, such as stability, in a given domain in the parameter space around a nominal realization having the desired property. the aim of the paper is to extend the notions and tools of parametric robustness for a class of positive polynomial systems, namely a class of kinetic systems. only the very first steps are reported here that offer a computationally efficient method for checking one of the many important properties of kinetic systems, their weak reversibility. basic notions and methods the basic notions and tools related to reaction kinetic systems and their realizations are briefly summarized in this section. kinetic systems, their dynamics and structure deterministic kinetic systems with mass action kinetics or simply chemical reaction networks (crns) form a wide class of non-negative polynomial systems, that are able to produce all the important qualitative phenomena (e.g. stable/unstable equilibria, oscillations, limit cycles, multiplicity of equilibrium points and even chaotic behaviour) present in the dynamics of nonlinear processes [2]. the general form of dynamic models studied in this paper is the following ẋ = m · (x), (1) where x 2 rn is the state variable and m 2 rn⇥m. the monomial vector function : rn ! rm is defined as j(x) = ny i=1 x yij i , j = 1, . . . ,m (2) where y 2 nn⇥m 0 . the system eq.(1) is kinetic if and only if the matrix m has a factorization m = y ·ak. (3) the kirchhoff-matrix ak has non-positive diagonal and non-negative off-diagonal elements and zero column sums. the matrix pair (y,ak) is called the realization of the system eq.(1). the chemically originated notions: the chemically originated notions of kinetic systems are as follows: the species of the system are denoted by x1, . . . , xn, and the concentrations of the species are the state variables of eq.(1), i.e. xi = [xi] � 0 for i = 1, . . . , n. the structure of kinetic systems is given in terms of its complexes ci, i = 1, . . . ,m that are non-negative linear combinations of the species i.e. ci = pn j=1[y ]jixj for i = 1, . . . ,m, and therefore y is also called the complex composition matrix. the reaction graph: the weighted directed graph (or reaction graph) of kinetic systems is g = (v,e), where 104 v = {c1, c2, . . . , cm} and e denote the set of vertices and directed edges, respectively. the directed edge (ci, cj) (also denoted by ci ! cj) belongs to the reaction graph if and only if [ak]j,i > 0. in this case, the weight assigned to the directed edge is ci ! cj is [ak]j,i. stoichiometric subspace: stoichiometric subspace s is given by the span of the reaction vectors s = {[y ]·i � [y ]·j | [ak]ij > 0}. (4) the stoichiometric compatibility classes of a kinetic system are the affine translations of the stoichiometric subspace: (x0 + s) \ rn �0. structural properties and dynamical behaviour it is possible to utilize certain structural properties of kinetic systems that enable us to effectively analyze the stability of the system. deficiency: there are several equivalent ways to define deficiency. we will use the following definition � = dim(ker(y ) \ im(bg)), (5) where bg is the incidence matrix of the reaction graph. it is easy to see that deficiency is zero if ker(y ) = {0} or equivalently rank(y ) = m. weak reversibility: a crn is called weakly reversible if whenever there exists a directed path from ci to cj in its reaction graph, then there exists a directed path from cj to ci. in graph theoretic terms, this means that all components of the reaction graph are strongly connected components. deficiency zero theorem: a weakly reversible kinetic system with zero deficiency has precisely one equilibrium point in each positive stoichiometric compatibility class that is locally asymptotically stable (conjecture: globally asymptotically stable). computing weakly reversible realizations formulated as an optimization problem in this section, first a method for computing weakly reversible realization based on ref.[3] is briefly presented. we assume that we have a kinetic polynomial system of the form eq.(1). we use the fact known from the literature that a realization of a crn is weakly reversible if and only if there exists a vector with strictly positive elements in the kernel of ak, i.e. there exists b 2 rn + such that ak · b = 0 [4]. since b is unknown, too, this condition in this form is not linear. therefore, we introduce a scaled matrix ãk ãk = ak · diag(b) (6) where diag(b) is a diagonal matrix with elements of b. it is clear from eq.(6) that ãk is also a kirchhoff matrix and that 1 2 rm (the m-dimensional vector containing only ones) lies in kernel of ãk. moreover, it is easy to see that ãk defines a weakly reversible network if and only if ak corresponds to a weakly reversible network. then, the weak reversibility and the kirchhoff property of ãk can be expressed using the following linear constraints mx i=1 h ãk i ij = 0, j = 1, . . . ,m mx i=1 h ãk i ji = 0, j = 1, . . . ,m h ãk i ij � 0, i, j = 1, . . . ,m, i 6= j h ãk i ii  0, i = 1, . . . ,m. (7) moreover, the equation eq.(3) is transformed by diag(b) (we can do this, because diag(b) is invertible): m · diag(b) = y ·ak · diag(b)| {z } ãk (8) finally, by choosing an arbitrary linear objective function of the decision variables ãk and b, weakly reversible realizations of the studied kinetic system can be computed (if any exist) in a lp framework using the linear constraints eq.(7) and (8). weakly reversible crn realizations in this section, first the convexity of the weakly reversible kirchhoff matrix will be shown. after that the practical benefits of this property will be demonstrated in the field of system analysis and robust feedback design. convexity of the weak reversibility in the parameter space theorem 1. let a (1) k and a (2) k be m ⇥ m weakly reversible kirchhoff matrices. then the convex combination of the two matrices remains weakly reversible. proof. the idea behind the proof is based on ref.[5]. a kirchhoff matrix is weakly reversible if and only if there is a strictly positive vector in its kernel. therefore strictly positive vectors p1, p2 exist such as a(1) k · p1 = 0 and a (2) k · p2 = 0. let us define the following scaled kirchhoff matrix: â(1) k = a (1) k · diag(p1) and â (2) k = a (2) k · diag(p2). these scaled matrices have identical structures to the original ones. moreover, â(1) k ·1(m) = 0 and â (2) k ·1(m) = 0 where the vector 1(m) denotes the m dimensional column vector composed of ones. for that (�â(1) k + (1� �)â(2) k ) · 1(m) = 0. (9) for any � 2 [0, 1]. therefore the convex combination of the original two realizations has to be weakly reversible. 105 (a) (b) (c) figure 1: a weakly reversible reaction graphs of the three realizations (y,a(1) k ), (y,a(2) k ) and (y,a(3) k ) weak reversibility of crn realizations with parametric uncertainty we assume that a crn with parametric uncertainty is given as ẋ = m · (x), (10) where x 2 rn is the state variable, 2 rn ! rm contains the monomials and the matrix m 2 rn⇥m is an element of the following set m = � lx i=1 ↵imi | (8i : ↵i � 0) ^ lx i=1 ↵i = 1 . (11) the goal is to find a method for checking the weak reversibility of the system eq.(10) for all matrices m 2 m. when all vertices mi have a weakly reversible realization (y,a(i) k ) then any element of the set m has a realization (y,ak) such that ak is the convex combination of the kirchhoff matrices a (i) k . the obtained realization ak will be weakly reversible due to theorem 1. therefore, it is enough to compute a weakly reversible realization for each matrix mi by using the previously presented lp-based method. a simple example let us consider the following polynomial system  ẋ1 ẋ2 � = m · 2 4 x1 x2 x1x2 3 5 , (12) where m is an arbitrary convex combination of the following three matrices m1 =  0 1 �1 1 �1 0 � , m2 =  �1 1 0 1 �1 0 � , and m3 =  0 1 �1 0 0 0 � . figure 2: a weakly reversible realization of the convex combination m = 0.2m1 + 0.4m2 + 0.4m3 in order to show weak reversibility for all possible convex combinations, we have to find a weakly reversible realization for each matrix m1, m2 and m3. the resulting weakly reversible reaction graphs are depicted in fig.1, while fig.2 illustrates an inner point realization which is weakly reversible too. computing kinetic feedback for a polynomial system with parametric uncertainty besides the possible application of the above described lp-based method for robust stability analysis, it can also be used for stabilizing feedback controller design. for this purpose, a generalized version of our preliminary work on kinetic feedback computation for polynomial systems to achieve weak reversibility and minimal deficiency [6] is used here. the feedback design problem we assume that the equation of the open-loop polynomial system with linear constant parameter input structure is given as ẋ = m · (x) +bu, (13) where x 2 rn is the state vector, u 2 rp is the input and 2 rn ! rm contains the monomials of the open-loop system. the input matrix is b 2 rn⇥p, the corresponding complex composition matrix is y with rank m, and m 2 rn⇥m is an element of the following set m = ( lx i=1 ↵imi | (8i : ↵i � 0) ^ lx i=1 ↵i = 1 ) . (14) moreover, a positive vector x 2 rn >0 being the desired equilibrium point is given as a design parameter. note that the above polynomial system is not necessarily kinetic, i.e. not necessarily positive, and may not have a positive equilibrium point at all. 106 the aim of the feedback is to set a region in the state space r ✓ rn �0 where x is (at least) a locally asymptotically stable equilibrium point of the closed-loop system for all m 2 m. for this purpose we are looking for a feedback in the form u = k (x) (15) which transforms the open-loop system into a weakly reversible kinetic system with zero deficiency for all m 2 m with the given equilibrium point x. feedback computation similarly to the realization computation, the matrix k will be determined by solving an lp problem. the convexity result shows that it is enough to compute one weakly reversible realization (y,a(r) k ) in each vertex mr to ensure weak reversibility for all possible closed-loop systems. all realizations will have zero deficiency, because of the rank condition rank(y ) = m [7]. first we note, that the realization (y,a(r) k ) that corresponds to the closed-loop system is mr +b ·k = y ·a(r) k . (16) where the matrix a (r) k should be kirchhoff mx i=1 [ãk]ij = 0, j = 1, . . . ,m [ãk]ij � 0, i, j = 1, . . . ,m, i 6= j [ãk]ii  0, i = 1, . . . ,m. (17) in order to obtain a weakly reversible closed-loop system with an equilibrium point x, the matrix a (r) k should be weakly reversible and has to have the vector (x) in its right kernel, i.e. a (r) k · (x) = 0. (18) finally, by choosing an arbitrary linear objective function of the decision variables a (1) k , . . . , a (l) k and k, the feedback gain k can be computed (if it exists) in a lp framework using the linear constraints eqs.(16-18). with the resulting feedback gain k, the point x will be an equilibrium point of all possible closed-loop systems, and x will be locally asymptotically stable in the region s = (x+s)\rn �0, where s is the stoichiometric subspace of the closed-loop system. example let the open-loop system be given as ẋ = m 2 4 x1x2 x2x3 x1 3 5+ 2 4 0 1 0 3 5 u (19) figure 3: weakly reversible realization of the closed-loop system, where m = 0.6m1 + 0.2m2 + 0.2m3 where m is an arbitrary convex combination of the following three matrices: m1 = 2 4 �1 1 0 2 1 2 1 �1 0 3 5 , m2 = 2 4 0 0 0 1 1 3 0 0 0 3 5 , and m3 = 2 4 0 1 �1 2 0 3 0 �1 1 3 5 . the desired equilibrium point x = [1 1 1]t . we are looking for a feedback law with gain k which transforms the matrices mi into weakly reversible kinetic systems with the given equilibrium point. by solving the feedback design lp optimization problem using the linear constraints eqs.(16-18), the computed feedback is in the following form: u = ⇥ 2 1 2 ⇤ (x). (20) fig.3 depicts a weakly reversible realization of the closed-loop system. the obtained closed-loop system in an inner point of the convex set m has the following stoichiometric subspace: s = span 0 @ 2 4 1 1 0 3 5� 2 4 0 1 1 3 5 , 2 4 1 1 0 3 5� 2 4 1 0 0 3 5 1 a . (21) therefore, the equilibrium point x will be asymptotically stable with the region s = (x+s)\rn �0. note, that one should choose the initial value of the state variables from s . fig.4 shows the time dependent behaviour of the closed-loop solutions started from different initial points in s . 107 figure 4: time-domain simulation of the closed-loop system conclusion it is shown in this paper that the domain of weakly reversible realizations is convex in the parameter space. this property is utilized for developing methods in system analysis and robust control design. an lp-based optimization method is proposed for testing if every element of a convex domain given by its extremal matrices admits a weakly reversible realization. an lp-based feedback design method is also proposed that guarantees stability with a desired equilibrium point. the proposed methods are illustrated with simple examples. references [1] siljak d.: parameter space methods for robust control design: a guided tour, aut. contr., ieee transactions on, 1989, 34(7), 674–688 [2] angeli d.: a tutorial on chemical network dynamics, eur. j. contr., 2009, 15, 398–406 [3] szederkényi g., hangos k. m., tuza z.: finding weakly reversible realizations of chemical reaction networks using optimization, match commun. math. comp. chem., 2012, 67, 193–212 [4] feinberg m., horn f.: chemical mechanism structure and the coincidence of the stoichiometric and kinetic subspaces, arch. rational mechanics and analysis, 1977, 66(1), 83–97 [5] rudan j., szederkényi g., hangos k.m., péni t.: polynomial time algorithms to determine weakly reversible realizations of chemical reaction networks, j. math. chem., 2014, 52(5), 1386–1404 [6] lipták g., szederkényi g., hangos k.m.: kinetic feedback computation for polynomial systems to achieve weak reversibility and minimal deficiency, 13th eur. control conf. ecc, strasbourg, france, 2014, 2691–2696 [7] angeli d., lenhee, p.d., sontag e.d.: on the structural monotonicity of chemical reaction networks, proc. 45th ieee conf. decision and control, 2006, 7–12 advertise upcoming meetings, conferences, workshops, new products or services; make public announcements, introduce your research laboratory on the pages of the hungarian journal of industry and chemistry please contact us if interested! editorial office: university of pannonia p.o. box 158, veszprém h-8201 (hungary) tel.: +36 (88) 624-746, e-mail: hjic@almos.uni-pannon.hu; web: hjic.mk.uni-pannon.hu felelős szerkesztő: szilágyi róbert károly, phd kiadja: pannon egyetem, 8200 veszprém, egyetem u. 10. levélcím: h-8201 veszprém, postafiók 158, tel.: (88) 624-000 felelős kiadó: a pannon egyetem, mérnöki kar dékánja hungarian journal of industry and chemistry veszprém vol. 42(2) pp. 109–113 (2014) stability and parameter sensitivity analyses of an induction motor attila fodor1, roland bálintb1, attila magyar1, and gábor szederkényi2 1department of electrical engineering and information systems, university of pannonia, egyetem u. 10., veszprém, 8200, hungary 2pazmány péter catholic university, práter u. 50/a, budapest, 1083, hungary be-mail: balint.roland27@gmail.com a simple dynamical model of an induction motor is derived and analyzed in this paper based on engineering principles that describe the mechanical phenomena together with the electrical model. the used state space model consists of nonlinear state equations. the model has been verified under the usual controlled operating conditions when the speed is controlled. the effect of load on the controlled induction motor has been analyzed by simulation. the sensitivity analysis of the induction motor has been applied to determine the model parameters to be estimated. keywords: induction motor, stability analysis, sensitivity analysis introduction induction motors (im) are the most commonly used electrical rotating machines in several industrial applications. irrespective of size and the application area, these motors share the most important dynamical properties, and their dynamical models have a similar structure. because of the specialties and great practical importance of ims in industrial applications, their modelling for control purposes is well investigated in the literature. besides basic textbooks [1-3], there are several papers that describe the modelling and use the developed models for the design of different types of controllers: vector control [1, 4], sensorless vector control [5] and direct torque control (dtc) [6]. the aim of this paper is to build a simple dynamical model of the im and to perform its parameter sensitivity analysis. the results of this analysis will be the basis of the next step since the final aim of our study is to estimate the parameters of the im and design a controller that can control the speed and torque of the im. the state space model has been implemented in the matlab/simulink environment which enables us to analyze the parametric sensitivity based on simulation experiments. nonlinear model of an induction motor in this section a state space model of an induction motor (im) is presented. the model development is largely based on refs.[1, 8-10]. for constructing the im model, the following modelling assumptions are made: 1. a symmetrical triphase stator winding system is assumed, 2. the flux density is radial in the air gap, 3. the copper loss and the slots in the machine can be neglected, 4. the spatial distribution of the stator fluxes and apertures wave are considered to be sinusoidal, 5. stator and rotor permeability are assumed to be infinite with linear magnetic properties. according to the above modelling conditions the mathematical description of the im is developed through the space-vector theory. if the voltage of the stator is presumed to be the input excitation of the machine, then the spatial distribution along the stator of the x phase voltage can be described by the complex vector v sx (t). we can determine the orientation of the voltage vector v s , the direction of the respective phase axis and the voltage polarity. i s (t) = 2 3 � a0 · i sa (t) + a1 · i sb (t) + a2 · i sc (t) � = p 2 · i e↵ (t) · ej!0t+⇡ 2 +' i , (1) where a is the ej120 o vector and i sa , i sb and i sc are the following: i sa (t) = re(a0 · i s (t)) = re(i s (t)), i sb (t) = re(a2 · i s (t)), and i sc (t) = re(a1 · i s (t)). in eq.(1), 2/3 is the normalizing factor. the flux density distribution can be obtained by integrating the current density wave along the cylinder of the stator. the flux linkage wave is a system variable, because it contains detailed information about the winding geometry. 110 figure 1: the equivalent circuit of the im the rotating flux density wave induces voltages in the individual stator windings. thus stator voltage v s (t) can be represented as the overall distributed voltages in all phase windings: v s (t) = 2 3 � a0 · v sa (t) + a1 · v sb (t) + a2 · v sc (t) � = p 2 · v e↵ (t) · ej!0t+⇡ 2 +' u , (2) where a is the ej120 o vector and i sa , i sb and i sc are the following: v sa (t) = re(a0 · u s (t)) = re(u s (t)), v sb (t) = re(a2 · u s (t)), and v sc (t) = re(a1 · u s (t)). considering the stator of the im as the primer side of the transformer, then using kirchoff’s voltage law the following equation can be written (fig.1): v s (t) = i s (t) ·r s + d� s (t) dt . (3) as for the secondary side of the transformer, it can be deduced that the same relationship is true for the rotor side space vectors: v r (t) = ir(t) ·rr + d� r (t) dt = 0. (4) eqs.(3) and (4) describe the electromagnetic interaction as the connection of first order dynamical subsystems: � s (t) = i s (t) · l s + i r (t) · l m , and (5) � r (t) = i s (t) · l m + i r (t) · l r . (6) since four complex variables (i s (t) , i r (t) , � s (t) , and � r (t)) are presented in eqs.(5) and (6), flux equations are needed to complete the relationship between them. the mechanical power (p mech (t)) of the im can be defined as: p mech (t) = w mech (t) dt , (7) where the mechanical energy (p mech (t)) in the rotating system can be given by the following expression: p mech (t) = w mech (t) dt = t mech (t) · ! r , (8) where t e (t) is the torque and ! r is the angular velocity of the im. afterwards the energy balance of the im is as follows: w e = w mech +w r +w field , (9) figure 2: the equivalent circuit of the d-axis of the im figure 3: the equivalent circuit of the q-axis of the im where p e = w e (t) dt = 3 2 re (u s · i s + u r · i r ) (10) is the input electrical power, p r = w r (t) dt = 3 2 re � r s · |i s |2 +r r · |i r |2 � (11) represents the resistive power losses and p field = w field (t) dt = 3 2 re ✓ d� s dt i s + d� r dt i r ◆ (12) is the air gap power. using eqs.(8-12), p mech (t) = t mech (t) · ! r = 3 2 · lm l r · � s (t)⇥ i s (t), and (13) t e = 1.5p · (� ds i qs � � qs i ds ). (14) the equivalent circuit of the im can be decomposed to direct axis and quadratic axis components by park’s transformation as shown in figs.2 and 3. the actual terminal voltage v of the windings can be written in the form v = ± jx j=1 (rj ij)± jx j=1 ✓ d�j dt ◆ , (15) where ij are the currents, rj are the winding resistances, and �j are the flux linkages. the positive directions of the stator currents point out of the im terminals. by composing the d and q axes of the im the following equations can be written: v qs = r s · i qs + � qs dt + ! · � ds , (16) v ds = r s · i ds + � ds dt � ! · � qs , (17) v qr = r0 r · i0 ds + �0 dr dt + (! � ! r ) · �0 dr , and (18) v dr = r0 r · i0 dr + �0 dr dt � (! � ! r ) · �0 qr . (19) 111 figure 4: response to the step change of the speed-controlled im d! m dt = 1 2h (t e � f · ! m � t mech ) (20) where ! is the reference frame angular velocity, ! r is the electrical angular velocity, � qs = l s · i qs + l m i0 qr , (21) � ds = l s · i ds + l m i0 dr , (22) � qr = l r · i0 qr + l m i0 qs , and (23) � dr = l r · i0 dr + l m i0 ds . (24) the above model can be written in state space form by expressing the time derivative of the fluxes and ! from the voltage and swing equations eqs.(21-24). the nonlinear state space model of the im is given by eqs.(25-29): d� qs dt = �r s l s � l2 m l0 r · � qs r s · l m l0 r (l s � l2 m l0 r ) · �0 qr � ! · � ds + v qs , (25) d� ds dt = �r s l s � l2 m l0 r · � ds + r s · l m l0 r (l s � l2 m l0 r ) · �0 dr � ! · � qs + v ds , (26) d�0 qr dt = �r0 r l m � l0 r·ls lm · � qs + �r0 r · l s l m · (l m � l0 r·ls lm ) · �0 qr � ! · �0 dr + ! r · �0 dr + v qr , (27) d�0 dr dt = �r0 r l m � l0 r·ls lm · � ds + �r0 r · l s l m · (l m � l0 r·ls lm ) · �0 dr + ! · �0 qr � ! r · �0 qr + v dr , and (28) d! r dt = 1 2h · 1.5 · p · l m l m · (l s � l2 m l0 r ) · �0 dr · � qs � 1 2h · 1.5 · p · l m l m · (l s � l2 m l0 r ) · �0 qr · � ds � f 2h · ! r � t m 2h . (29) the state vector of the above model is x=[� qs , � ds , �0 qr , �0 dr , ! r ]t 2 r5, and the input variables are organized in terms of the the input vector u=[v q , v d , �t mech ]t 2 r3. it is assumed that all the state variables can be measured i.e. y = x. model validation the dynamical properties of the im have been investigated. the response of the speed-controlled motor has been tested under step-like changes. the simulation results are shown in fig.4, where the fluxes (� qs , � ds , �0 qr , and �0 dr ) and the angular velocity (!) are shown. model analysis the above model eqs.(21-24) has been verified by simulation against engineering intuition. local stability analysis as the final aim of our research is to estimate the parameters of a particular grundfos im, first of all the resistances (r s and r r ) of the im were measured. afterwards the values of the inductances (l ls , l lr and l m ) and the mechanical parameters (h and f ) of a similar im with similar r s and r r found in the literature have been used. the parameters used during the model and the sensitivity analyses are the following: r s = 0.196 ohm r r = 0.0191 ohm l ls = 0.0397 h l lr = 0.0397 h l m = 1.354 h h = 0.095 f = 0.0548 p = 1 (30) 112 figure 5: the model state variables for a ±50% change of l m it can easily be seen that the im model is nonlinear since there are products of two state variables in the following equations: • eq.(27): �0 dr is multiplied by ! r • eq.(28): �0 qr is multiplied by ! r • eq.(29): �0 dr is multiplied by � qs • eq.(29): �0 qr is multiplied by �0 ds for the local stability analysis we have to calculate the eigenvalues of the system. the examined equilibrium point is � qs = �0.744 vs � ds = 1.0287 vs �0 qr = �0.174 vs (31) �0 dr = �0.087 vs ! r = 48.477 s�1 the numerical value of the jacobian of the nonlinear model (i.e. the state matrix of the locally linearized model) is as follows: 2 66664 �2.504 �50 2.4328 0 0 50 �2.504 0 2.4328 0 0.2370 0 �0.244 �1.522 0 0 0.2370 1.5222 �0.244 0 �8.617 17.077 0 0 �0.288 3 77775 . (32) the eigenvalues of the state matrix of the linearized systems are: � 1,2 = �2.504 ± j49.98, � 3,4 = �0.243 ± j1.534, and � 5 = �0.288 (33) figure 6: the model state variables for a ±50% change in r s it is apparent that the real parts of the eigenvalues are negative with small magnitudes. parameter sensitivity analysis the sensitivity of the nonlinear model to the mutual inductance has been investigated. the steady state value of the system variables does not change (as is apparent in fig.5) even for a considerably large change in l m . sensitivity analysis of the inductances l lr , l ls of the stator and rotor, resistances of the stator r s and the damping constant f has also been investigated. in this investigation it can be seen that the values of the state variables were changed a bit, as shown in fig.6. the analysis of the resistances of the rotor r0 r and the inertia h of the rotor showed that every value of the state variables changed significantly, as shown in fig.7. as a final result of the sensitivity analysis, we can define the following groups of parameters: • not sensitive: mutual inductance l m . since the state space model of interest is insensitive in this respect, the values of this parameter cannot be reliably determined from measurement data using any parameter estimation method. • sensitive: these sensitive parameters are candidates for parameter estimation. – less: inductances l lr and l ls , resistance of the stator r s and the damping constant f . – more: resistances of the rotor r0 r and the inertia h of the rotor. • critically sensitive: none. 113 figure 7: the model state variables for a ±50% change in h conclusion the simple nonlinear dynamical model of an im has been investigated in this paper. it has been shown that the model is locally asymptotically stable with regards to a physically meaningful equilibrium state. the effect of the controlled generator has been analyzed by simulation using a traditional pi controller. it has been found that the controlled system is stable and can follow the set-point changes. seven parameters of the model were selected for sensitivity analysis, and the sensitivity of the state variables has been investigated. as a result, the parameters were partitioned into three groups. based on the results presented here, a future aim is to estimate the parameters of the model for a real system from measurements. the sensitivity analysis enables us to select the candidates for estimation that are inductances l lr and l ls , resistances r s and r r , the damping constant f and the inertia h . an additional future aim is to develop a model for control purposes and investigate different controllers before applying them on real systems. acknowledgement we acknowledge the financial support of this work by the hungarian state and the european union under the tamop-4.2.2.a-11/1/konv-2012-0072 project. we acknowledge also the investigated im of grundfos hungary producer ltd. symbols c 1 , c 2 , c 3 constant f damping constant � qs and � ds q and d components of the stator flux �0 qr and �0 dr q and d components of the reduced rotor flux h inertia constant i qs and i ds q and d components of the stator current i0 qr and i0 dr q and d components of the reduced rotor current l m mutual inductance p number of pole pairs r r and l r rotor resistance and inductance r0 r and l0 r reduced value of rotor resistance and inductance r s and l s stator resistance and inductance v d and v q q and d components of the stator voltage ! angular velocity of the magnetic field ! r angular velocity of the rotor t mech mechanical torque references [1] vas p.: artifical-intelligence-based electrical machines and drives, oxford university press, 1999 [2] vas p.: sensorless vector and direct torque control. oxford university press, 1998. [3] zheng l., fletcher j.e., williams b.w. he x.: dual-plane vector control of a five-phase induction machine for an improved flux pattern, ieee transac. ind. elec., 2008, 55(5), 1996–2005 [4] levi e.: impact of iron loss on behavior of vector controlled induction machines, ieee transac. ind. appl., 1995, 31(6), 1287–1296 [5] hasegawa m., matsui k.: robust adaptive full-order observer design with novel adaptive scheme for speed sensorless vector controlled induction motors, proc. 28th annual conf. industrial electronics society, ieee 2002, 2002, 1, 83–88 [6] geyer t., papafotiou g., morari m.: model predictive direct torque control-part i: concept, algorithm, and analysis, ieee transac. ind. elec., 2009, 56(6), 1894–1905 [7] krause p.c., wasynczuk o., sudhoff s.d.: analysis of electric machinery, ieee press, new york, 1995 [8] mohan n., undeland t.m., robbins w.p.: power electronics: converters, applications, and design, john wiley & sons inc., new york, 1995 [9] hatos p., fodor, a., magyar a.: parameter sensitivity analysis of an induction motor, hung. j. ind. chem., 2011, 39(1), 157–161 advertise upcoming meetings, conferences, workshops, new products or services; make public announcements, introduce your research laboratory on the pages of the hungarian journal of industry and chemistry please contact us if interested! editorial office: university of pannonia p.o. box 158, veszprém h-8201 (hungary) tel.: +36 (88) 624-746, e-mail: hjic@almos.uni-pannon.hu; web: hjic.mk.uni-pannon.hu felelős szerkesztő: szilágyi róbert károly, phd kiadja: pannon egyetem, 8200 veszprém, egyetem u. 10. levélcím: h-8201 veszprém, postafiók 158, tel.: (88) 624-000 felelős kiadó: a pannon egyetem, mérnöki kar dékánja hungarian journal of industry and chemistry vol. 46(2) pp. 55–62 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0019 worker movement diagram based stochastic model of open paced conveyors tamás ruppert1 and jános abonyi *1 1mta-pe lendület complex systems monitoring research group, department of process engineering, university of pannonia, egyetem u. 10, veszprém, h-8200, hungary human resources are still utilized in many manufacturing systems, so the development of these processes should also focus on the performance of the operators. the optimization of production systems requires accurate and reliable models. due to the complexity and uncertainty of the human behavior, the modeling of the operators is a challenging task. our goal is to develop a worker movement diagram based model that considers the stochastic nature of paced open conveyors. the problem is challenging as the simulator has to handle the open nature of the workstations, which means that the operators can work ahead or try to work off their backlog, and due to the increased flexibility of the moving patterns the possible crossings which could lead to the stopping of the conveyor should also be modeled. the risk of such micro-stoppings is calculated by monte-carlo simulation. the applicability of the simulator is demonstrated by a well-documented benchmark problem of a wire-harness production process. keywords: industry 4.0, operator 4.0, monte-carlo simulation, process development, line balancing, wire-harness assembly 1. introduction conveyor lines are more productive than regular assembly lines [1]; therefore there are more prevalent in the automotive industry [2]. the movement of these conveyors mostly has paced and cyclic characteristic where at the beginning of the cycle, every station moves to the next position [3]. it can happen that the operator cannot finish his/her work before the product leaves the workstation. there are two alternative approaches for completing the unfinished work. we speak about close station production when the operator must stop the conveyor even in case of a minor delay [4]. such processes are typical in japan. in u.s.-type production systems, the operator does not have to finish his or her job, he or she can move with the product to the next station to work off the backlog. in these open stations the operators can work ahead or can be delayed [5], and the production stops only when the delay exceeds a critical limit. these open workstations reduce capacity loss by decreasing the risk of stopping the conveyor, but the modeling and optimization of these processes is much more challenging as the model has to handle idle and delay times [6]. worker movement diagrams are widely used to model the work of operators at conveyor belts [7]. such models can be used to reduce the risk of conveyor stoppage [8] and optimize production sequence [9], since the optimal distribution of the products can also reduce the probability of critical backlogs [10]. *correspondence: researcher@abonyilab.com worker movement diagrams focus only one station. in open paced conveyors the operators effect on each other; therefore the model should handle the interactions between the workstations, especially for the prediction of the conveyor stoppage. our goal is to develop a worker movement diagram based model for open paced conveyors, which model considers the stochastic nature of production and recognizes the meeting point of operators and analyzes the idle times due to working in the same zones and risk of stopping the production in case of unmanageable backlogs. we introduce stochastic variables into the movement diagram representation based model and apply monte-carlo simulation to evaluate the risk of conveyor stoppage and give robust estimates of the effects of different parameter settings. the simulator is developed in python environment. the applicability of the proposed model and simulator is demonstrated by a well-documented benchmark problem of a wire-harness production process. section 2 describes the worker movement diagram and the sections defined based on the relative position of the operators and the conveyor. the model of the paced conveyor is based on equations that represent the movement of the operators in these sections. based on these equations we calculate when the conveyor should be stopped. section 3 describes the applicability of the developed simulator in a wire harness production system. mailto:researcher@abonyilab.com 56 ruppert and abonyi 2. model of the paced conveyor 2.1 problem definition the most widespread paced open station conveyors are used to produce wire harnesses in the automobile industry. the optimization and cost estimation of these processes are an economically significant problem [11]. these modular assembly lines consist of manual workstations (tables) shown in fig. 1. human operators work at the tables that are moving similarly as a conveyor belt (see fig. 2). these tables move with a fixed speed which is determined based on the tact time, tc. after the cycle, every table moves to the next station. the modeling the relative position of the operators and the tables can be represented by worker movement diagrams that will be presented in the next section. 2.2 movement diagram of an open station the paced conveyor has k, k = 1, . . . ,k is number of workstations that moves in every n = 1, . . . , n cycle. the speed of the conveyor is vc, and the walking speed of operator is vw. the tc is the tact time determines the assembly speed: vkn = l tkπ(n−k) (1) where l represents the length o the workstation, the tkπ(n−k) the assembly time which is dependent on the produced product. the sequence of the products is represented by a π vector of the labels of the types, so π(k) = pj states that type product pj started to be produced during the k-th production cycle. the modeling of the paced conveyor is complex task as the conveyor moves only for a tcm < tc period of the time, which defines several sections of the tack time according to the speed and position of the table and the operators. as it is depicted in figs. 3 and 4, the worker movement diagram is divided for six sections (s = 1, . . . , 6) . 1. the operator moves to the starting point of the table figure 1: an example assembly table in wire harness manufacturing. the dashed line with an arrow represents the worker motion at the table. the operator works on the table from left to right. the assembly speed is vkn. figure 2: the most widely used open station paced conveyors are used in wire harness assembly, where the operators are working at tables that moving in every cycle of the production [12]. 2. the operator works before the new cycle 3. the operator and the table move together 4. the operator works and the table stays 5. the operator and the table move together after the end of tact time 6. the operator works and the table stays after the end of tact time in the first section, s = 1, the operator walks to the left side of the table, f (1)kn. after reaching this position the operator starts the assembly process and moves with the conveyor till the conveyor moves to its next workspace. after this f (3)kn position the operator works at the standing table with a vkn speed. when the job is finished, the operator reaches the end of the table, f (4)kn = kl, as it is shown at fig. 5). the second, fifth and sixth sections happen when operator deviates from this normal case (work ahead or delayed). in the following, we present a model that describes how the positions of the table and the operators are changing in time. in the model f (s)kn denotes the position of kth operator at nth cycle step in sth section of diagram, where the positions are measured from the starting point of the first table. section 1. the operator moves to the starting point of the table at the beginning of the cycle, the operator moves the starting point of the next table which is 2l far from its actual position. the f (1)kn position when the kth operator reaches the staring point of table should be calculated as f (1)kn = f (6)kn−1 − t (1)knvw (2) t (1)kn = nwt+dwt+cdwt+ iwt (3) where f (6)kn−1 is the kth operator finishing position in the previous cycle step (n− 1), while the t (1)kn required hungarian journal of industry and chemistry worker movement diagram based model of open paced conveyors 57 figure 3: worker movement diagram of the sections when the operator works ahead. lines with arrow represent the motion of the operator, while dashed lines represent movement of the table. figure 4: worker movement diagram of the sections when the operator has a backlog. lines with arrow represent the motion of the operator, while dashed lines represent movement of the table. figure 5: worker movement diagram of one station. the first meeting point with the table and the operator is f (1)kn. f (3)kn and f (4)kn are the positions at the end of the second and third sections. when there is no delay or the operator does not work ahead f (4)kn = f (6)kn, where f (6)kn is the finishing position. 46(2) pp. 55–62 (2018) 58 ruppert and abonyi time can be decomposed into four components, which will be modeled in the following subsections: • nwt normal walking time • dwt delayed walking time • cdwt critically delayed walking time • iwt idle walking time nwt: normal walking time in the normal case, the operator and the conveyor move together at the beginning of the cycle with vc+vw relative speed. the effect of the akn−1 idle time and the lkn−1 late time of the previous cycle is represented by the nwta and nwtb variables that are used to calculate the nwt walking time: nwt = max[min(nwta; nwtb); 0] (4) nwta = max ( 2l− akn−1vw vc + vw ; 0 ) (5) nwtb = min ( tcm − lkn−1, 2l vc + vw ) , (6) where akn−1vw represents the walking distance of operator at the end of the previous cycle. when tcm − lkn−1 is less than zero, then operator does not have to walk, because he or she still works on the last (n− 1) product (in this case we should calculate dwt). dwt: delayed walking time when the assembly time in the previous cycle exceeds tc, dwt is equal to the time which necessary for the reaching the table after tc. dwt = if [tcm − lkn−1 > 0 or lkn−1 = 0]; (7) then dwth; else 0 dwth = (8) max [ 2l vc + vw −max ( tcm − lkn−1; 0 ) ; 0 ] vcw where vcw = vc+vw vw is the walking speed of operator, when the conveyor is moving. cdwt: critically delayed walking time when lkn−1 is more than tcm, the operator moves to the beginning of the table when the conveyor is standing. cdwt = if [tcm − lkn−1 <= 0 (9) or lkn−1 = 0]; then 2l vw ; else 0 iwt: idle walking time when the conveyor does not move and akn−1 is bigger than the necessary walking time, 2l vw , then iwt = min ( akn−1, 2l vw ) (10) section 2. the operator works before the new cycle thef (2)kn staring position and t (2)kn duration of the the second section is calculated as: f (2)kn = f (1)kn + t (2)knv k n (11) t (2)kn = max ( akn−1 − 2l vw ; 0 ) (12) where vkn is the average speed of the assembly. section 3. the operator and table move together in this section, operator and the conveyor are moving together for a time period shorter than tcm, so they will meet at: f (3)kn = f (2)kn + t (3)kn(vc + vkn) (13) t (3)kn = min ( max [ (n− 1)tc + tcm − t k; 0 ] ; tcm ) (14) where (n− 1)tc + tcm describes the time instant the section will finish. in normal situation t (3)kn equals to tcm, while in extreme case the operator has as significant idle time as he or she finishes his or her job before the end of this section. section 4. the operator works and table stays in this section the operator works with vkn linear speed until the conveyor does not move, so this section finishes at: f (4)kn = f (3)kn + t (4)knv k n (15) t (4)kn = min{max[ntc − t ; 0]; (16) l vkn − t (2)kn − t (3)kn} , where l vkn −t (2)kn−t (3)kn defines the remaining assembly time before the end of the tact time. the idle and delay times at the end of the cycles the akn idle or lkn delay time is calculated as: lkn = max ( l vkn + t (1)kn − akn−1 + lkn−1 − tc; 0 ) (17) akn = max ( tc − l vkn − t (1)kn + akn−1 − lkn−1; 0 ) (18) the prediction of conveyor stoppage is the most important ability of the model which will be calculated based on the delay time as it will be presented in the following subsection. hungarian journal of industry and chemistry worker movement diagram based model of open paced conveyors 59 section 5. the operator and the table move together after the end of tact time this section can be considered as the modification of the third section with the delay of the operator. as we already know lkn and the operator can work in this section maximum till tcm, the calculation is straightforward: f (5)kn = f (4)kn + t (5)kn(vc + vkn) (19) t (5)kn = min ( lkn, tcm ) (20) section 6. the operator works and the conveyor stays after the end of tact time as the duration of this section is limited as tc − tcm, the variables that define the end of the section are calculated as: f (6)kn = f (5)kn + t (6)knv k n (21) t (6)kn = min [ max ( lkn − tcm; 0 ) ; tc − tcm ] (22) calculation of the stoppage and the idle time the open station type operation of the paced conveyor has increased flexibility as the conveyor has to be stopped only when the delay of the kth operator is as significant as it disturbs the work of the neighboring k−1th operator. we define this situation as: t k + t (1)kn <= t k−1 + t (1)k−1 n−1 + tc 4 (23) in this case the idle ikn time has to be modified by t (1)kn and reset the value of akn to zero. ikn = (n− 1)tc − t (1)kn (24) when the lkn − t (6)kn is smaller than tcm, the operator stops the conveyor. the lkn is reset and the stoppage time is: skn = max(lkn − t (6)kn − tcm; 0) (25) 2.3 kpis and the developed simulator the developed simulator handles the stochastic and open nature of the conveyor, simulates all workstations, the interactions between the operators and predicts stoppage. the worker movement diagram representation helps in the stoppages prediction (see fig. 6). production planners can use the developed simulator to try sequencing strategies and analyze a new production lines capability. the following key performance indicators (kpis) calculated based on monte-carlo simulation gives a realistic picture about the production. • the balance of conveyor line is depended on the maximum of the late times of operators, lk = [lk1 , l k 2 , . . . , l k n]: b = k∑ k=1 max(lk) k 1 tc (26) • the efficiency of production is calculated based on to the sum of the l vkn assembly times divided by the maximum of the t(6) k = t (6)k1 , t (6) k 2 , . . . , t (6) k n) finishing times and the sum of stoppage times multiplied by the number of workstations. p = k∑ k=1 l vkn {max[t(6) k ] + n∑ n=1 k∑ k=1 skn}k (27) • the sum of the s stoppage times (eq. 25). • the mean of the assembly times. the simulator and the movement diagram are developed in python environment. d the developed simulator and the related dataset is freely and fully available on the website of authors: www.abonyilab.com. 3. application to wire harness production to demonstrate the applicability of the simulator three typical types of production sequencing strategies were analyzed. in the first case, the sequence follows the random customer demand which case often happens in just in time (jit) production. batch production is a more efficient sequencing strategy. in this case, batches of lower and higher complexity products are following each other. one of the best solutions is the π = m1,m2,m1, . . . high/low sequencing strategy because it utilizes the open station nature of the conveyor. the studied conveyor contains k = 5 workstations. the number of manufactured products is n = 100, and two different group of products (m = 2) are produced. the assembly times are represented by a normal distribution, which is t1 = n (250, 30) for the lower complexity product and t2 = n (310, 30) for the higher complexity product. the tact time of the conveyor is constant and set to tc = 280s which is the average assembly time of the products. fig. 7 shows the results of 1,000 simulations of the three sequence types. this scatter matrix plot shows the main kpis, the balance, the number of the manufactured products, the number of stoppages, and the average assembly times. the green dots represent the high/low, the blues the batched, and the red the random sequences. as shown in fig. 7, the difference between the random (blue) and high/low (green) sequences is significant on all kpis. the batched sequence (red) has similar performance to the high/low sequence, but many times this batch production is not manageable because of the high variance of the products and the short delivery times. 4. conclusions as human resources are still necessary for many manufacturing systems, the development of production process should also focus on the performance of operators. 46(2) pp. 55–62 (2018) www.abonyilab.com 60 ruppert and abonyi −5 0 5 10 15 20 25 30 distance [m] 0 1000 2000 3000 4000 5000 6000 ti m e [s ] figure 6: the developed worker movement diagram of five stations and 18 cycle steps. the distance begins at −5 m to represent the previous workstation. figure 7: the result of a monte-caro simulation of three different sequencing strategies. the scatter plot shows all of kpis. the high/low sequence is denoted by green, the batch by red, and the random by blue dots. the difference between the random and high/low sequences is significant on all kpis. hungarian journal of industry and chemistry worker movement diagram based model of open paced conveyors 61 according to the digital twin concept, this development should be based on the model of the production system, which necessaries the development of simulators that can handle uncertainties related to the human nature of the operators. the developed worker movement diagram based model handles the paced and open workstations of the conveyors and the stochastic nature of production. the worker movement representation helps in the analysis of the operators which is needed to predict production stoppages. the introduction of stochastic variables and the monte-carlo simulation-based evaluation of the key performance indicators provide a realistic picture about the production. the applicability of the simulator in the analysis of the effect of production sequencing is demonstrated by a well-documented benchmark problem of a wire-harness production process. the developed simulator is not specialized to the studied wire harness production; it can be used to model all of the types of paced conveyors even open or closed workstations. acknowledgement this research was supported by the national research, development and innovation office nkfih, through the project otka-116674 (process mining and deep learning in the natural sciences and process development) and the efop-3.6.116-201600015 smart specialization strategy (s3) comprehensive institutional development program. notations kpi key performance indicator nwt normal walking time dwt delayed walking time cdwt critically delayed walking time iwt idle walking time k index of workstation k = 1, . . . ,k k number of workstations n index of cycle step n = 1, . . . , n n number of cycle steps s index of section s=1, . . . , 6 vkn assembly speed of th operator [ms ] vw walking speed of the operator [ms ] vc speed of the conveyor [ms ] vcw walking speed of the operator when the conveyor is moving [ms ] tc tact time [s] tcm conveyor movement time [s] tk(π(n) assembly time of actual the product at kth operator [s] t (s)kn duration of the actual s section in nth cycle step a kth workstation [s] t(6)k finishing times of the kth operator [s] akn work ahead time in nth cycle step at kth operator [s] lkn late time in nth cycle step at kth operator [s] lk late times of kth operator [s] t actual simulated time [s] ikn final idle time in nth cycle step at kth workstation [s] skn stoppage time in nth cycle step at kth workstation [m] f (s)kn position of operator at the actual s section in nth cycle step a kth workstation [m] tablekn table position in nth cycle step at kth operator [m] π(n) sequence of products [−] l length of the workstation [m] t kn position of the tables [m] references [1] estrada, f., villalobos, j.r., roderick, l., estrada, f., villalobos, j.r., roderick, l.: evaluation of justin-time alternatives in the electric wire-harness industry, taylor and francis, 1997 35(7), 1993–2008, doi: 10.1080/002075497195038 [2] lodewijks, g.: two decades dynamics of belt conveyor systems bulk solids handling, 2002 22(2), 1–2 [3] xiaobo, z., zhou, z., asres, a.: note on toyota’s goal of sequencing mixed models on an assembly line, computers and industrial engineering, 1999 36(1), doi: 10.1016/s0360-8352(98)00113-2, 57–65 [4] sarker, b.r., pan, h.: designing a mixed-model, open-station assembly line using mixed-integer programming, the journal of the operational research society palgrave macmillan journals, 2001 52(52), 545–558 doi: 10.1057/palgrave.jors.2601118 [5] bukchin, j., tzur, m.: design of flexible assembly line to minimize equipment cost, iie transactions (institute of industrial engineers), 2000 32(7), 585– 598 doi: 10.1080/07408170008967418 [6] bautista, j., cano, j.: minimizing work overload in mixed-model assembly lines, international journal of production economics, 2008 112(1), 177–191 doi: 10.1016/j.ijpe.2006.08.019 [7] xiaobo, z., ohno, k.: algorithms for sequencing mixed models on an assembly line in a jit production system, computers ind. engng, 1997 32(1), 47–56 doi: 10.1016/s0360-8352(96)00193-3 [8] xiaobo, z., ohno, k.: properties of a sequencing problem for a mixed model assembly line with conveyor stoppages, european journal of operational research, 2000 124(3), 560–570 doi: 10.1016/s03772217(99)00198-8 [9] fattahi, p., salehi, m.: sequencing the mixed-model assembly line to minimize the total utility and idle costs with variable launching interval, international journal of advanced manufacturing technology, 2009 45(9-10), 987 doi: 10.1007/s00170-009-2020-0 46(2) pp. 55–62 (2018) https://doi.org/10.1080/002075497195038 https://doi.org/10.1016/s0360-8352(98)00113-2 https://doi.org/10.1057/palgrave.jors.2601118 https://doi.org/10.1080/07408170008967418 https://doi.org/10.1016/j.ijpe.2006.08.019 https://doi.org/10.1016/s0360-8352(96)00193-3 https://doi.org/10.1016/s0377-2217(99)00198-8 https://doi.org/10.1016/s0377-2217(99)00198-8 https://doi.org/10.1007/s00170-009-2020-0 62 ruppert and abonyi [10] tsai, l.h.: mixed-model sequencing to minimize utility work and the risk of conveyor stoppage mixed-model sequencing to minimize utility work and the risk of conveyor stoppage, source: management science, 1995 41(3), 485–495 doi: 10.1287/mnsc.41.3.485 [11] ong, n.s., boothroyd, g.: assembly times for electrical connections and wire harnesses, the international journal of advanced manufacturing technology, 1991 6(2), 155–179 doi: 10.1007/bf02601438 [12] assembly line conveyor systems, 2015, https: //www.pacline.com/photos/photos-by-solution/ assembly-line-conveyors/ hungarian journal of industry and chemistry https://doi.org/10.1287/mnsc.41.3.485 https://doi.org/10.1287/mnsc.41.3.485 https://doi.org/10.1007/bf02601438 https://www.pacline.com/photos/photos-by-solution/assembly-line-conveyors/ https://www.pacline.com/photos/photos-by-solution/assembly-line-conveyors/ https://www.pacline.com/photos/photos-by-solution/assembly-line-conveyors/ introduction model of the paced conveyor problem definition movement diagram of an open station section 1. the operator moves to the starting point of the table nwt: normal walking time dwt: delayed walking time cdwt: critically delayed walking time iwt: idle walking time section 2. the operator works before the new cycle section 3. the operator and table move together section 4. the operator works and table stays the idle and delay times section 5. the operator and the table move together after the end of tact time section 6. the operator works and the conveyor stays after the end of tact time calculation of the stoppage and the idle time kpis and the developed simulator application to wire harness production conclusions hungar~journal of jndustrial chemistry veszprem vol. 29. pp. 15 (2001) refractive indices, densities and derived excess properties of binary and ternary systems with dimethyl sulfoxide, water and 1,4-dioxane l. m. omota, 0. iul~ and c. mateescu (department of applied physical chemistry & electrochemistry, faculty of industrial chemistry, university "politehnica", 313, splaiul independentei, bucharest, 77206, romania) received; august 9, 2000 refractive indices and densities for binary dimethyl sulfoxide+ water, dimethyl sulfoxide+ 1,4-dioxane systems and ternary dimethyl sulfoxide+water+1,4-dioxane system have been measured at 298.15 k, over the entire mole fraction scale of the mixture. changes on molar volume, partial molar volume and molar refraction have been calculated. the experimental data were used to test several mixing rules for estimation of the refractive index. keywords: binary and ternary systems with dimethyl sulfoxide, excess properties introduction the properties of liquid mixtures have attracted much attention in the literature from both theoretical and practical viewpoints. the properties of dimethyl sulfoxide (dmso) and its mixtures have been the subject of considerable interest because of its versatility as a solvent and a plasticizer. in addition to our studies on the physico-chemical properties of binary and ternary liquid mixtures containing dmso, 1,4-dioxane and water {1-4], we report in this paper the measurement of refractive indices for binary dmso+water, dms0+1,4-dioxane and ternary dmso+water+1,4-dioxane mixtures. we present the experimental values of refractive indices and calculated changes of molar refraction on mixing over the entire mole fraction range at 298.15 k and at atmospheric pressure. moreover, experimental data were used to test several mixing rules for refractive indices. the densities, reported earlier [5], were used here to present the calculated excess molar volumes and excess partial molar volumes. the results are discussed in terms of the molecular interactions between the water and organic molecules. there are less data available concerning the refractive indices for the binary dmso+water system [6,7]; we mention that refractive indices for the binary dms0+1,4-dioxane and ternary water+1,4dioxane+dmso systems were not found in the literature. experimental apparatus and procedure refractive indices values for the sodium d-line were measured with a thermostated abbe refractometer with a precision of± 0.0001. temperature is accurate to ± 0.05 k. density of pure liquids and mixtures was measured using a calibrated pycnometer with an internal diameter of 1 mm. an average of duplicate measurements was considered and these are accurate to ± 0.0002 g cm-3• . materials the used substances were purified by distillation. dmso was distilled under vacuum of 0.8-0.9 kpa at 338.65 k. the analytical-reagent-grade 1,4-dioxane from merck was distilled at 374.35 k. the water was bidistillated. the impurities were found by gc. a comparison of refractive index and density values of pure liquids with the literature findings is given in table 1. the mixtures were prepared favimetrically using a balance with precision of 0.1·10· kg. the experimental uncertainties are: o(xj = 0.0001, a(p)lkg n{' = 0.2 and o(vsj!l0-9m3mor1 = 10. 2 table 1 densities and refractive indices of pure components at 298.15 k p , w-3-kg m·3 compound exptl literature 0.99704&,9 0.9971 water 0.9970510 1.0957 1.095378 dmso 1.0954712 1.0281 1.027978 1,4-dioxane 1.0280213 1.0278314,15 exptl 1.3325 1.4768 1.4198 nv literature 1.3324-'>·11 1.33146 1.33258 1.476812 1.47695 1.47758 1.41945 table 2 densities, excess molar volumes and excess partial molar volumes. binary systems at t= 298.15 k 1.0000 0.9085 0.8287 -0.7585 0.6962 0.6406 0.5205 0.4331 0.3459 0.2979 0.2158 0.1363 0.0782 0.0351 0.0000 1.0000 0.9581 0.8938 0.7829 0.6906 0.5950 0.5459 0.4959 0.3929 0.2861 0.1750 0.0888 0.0470 o.oooo dmso(l)+water(2) 1.0957 0.0000 0.0000 1.0966 -0.2035 0.0267 1.0979 -0.4032 -0.0010 1.0989 -0.5626 -0.0509 1.0997 -0.6938 -0.1310 1.1001 -0.7921 -0.2297 1.0996 -0.9411 -0.5664 1.0973 -0.9826 -0.9415 1.0922 -0.9526 -1.4441 1.0876 -0.9000 -1.7810 1.()756 -0.7466 -2.4697 1.0563 -0.5145 -3.2856 1.0361 -0.3079 -4.0031 1.0166 -0.1406 -4.6136 0.9971 0.0000 -5.1674 dmso(l)+ 1,4-dioxane(2) 1.0957 0.0000 0.0000 1.0934 -o.o708 -0.0115 1.0895 -0.1504 -0.0276 1.0825 -0.2547 -0.0937 1.0764 -0.3074 -0.1755 1.0699 -0.3335 -0.2816 1.0665 -0.3361 -0.3421 1.0630 -0.3313 -0.4066 1.0558 -0.3069 -0.5527 1.0482 -0.2493 -0.7016 1.0403 -0.1650 -0.8520 1.0343 -0.0924 -0.9670 1.0313 -0.0443 -1.0095 1.0281 0.0000 -1.0658 results and discussion binary systems -2.5890 -2.4893 -2.3487 -2.1698 -1.9836 -1.7945 -1.3479 -1.0140 -0.6927 -0.5263 -0.2724 -0.0772 0.0056 0.0221 0.0000 -1.5916 -1.4273 -1.1845 -0.8353 -0.6017 -0.4099 -0.3288 -0.2571 -0.1478 -0.0680 -0.0193 -0.0072 0.0033 0.0000 tables 2 and 3 list the measured densities ( p ) and refractive indices ( n0 ) together with the calculated values of excess molar volumes ( ye ), excess partial -£-£ molar volumes of the components ( v, , v 2 ) and, respectively. changes of molar refraction on mixing ( m ). table 3 includes also the results of prediction of table 3 refractive indices, changes of molar refraction on mixing and refractive indices deviations calculated with several mixing rules. binary systems at t=298.15 k 1.0000 0.9085 0.8287 0.7585 0.6962 0.6406 0.5205 0.4331 0.3459 0.2979 0.2158 0.1363 0.0782 0.0351 0.0000 1.0000 0.9581 0.8938 0.7829 0.6906 0.5950 0.5459 0.4959 0.3929 0.2861 0.1750 0.0888 0.0470 0.0000 l!r, 10·6 linv nv m3mor1 l-l g-d a-b edw dms0(1)+water(2) 1.4768 0.0000 0.0000 0.0000 0.0000 0.0000 1.4739 -0.0272 -0.0008 -0.0008 -0.0038 -0.0011 1.4713 -0.0474 -0.0015 -0.0014 -0.0079 -0.0021 1.4685 -0.0661 -0.0022 -0.0020 -0.0118 -0.0031 1.4658 -0.0767 -0.0028 -0.0025 -0.0152 -0.0038 1.4630 -0.0833 -0.0032 -0.0029 -0.0183 -0.0044 1.4552 -0.0915 -0.0040 -0.0037 -0.0246 -0.0056 1.4475 -0.0892 -0.0043 -0.0041 -0.0285 -0.0060 1.4371 -0.0821 -0.0044 -0.0044 -0.0312 -0.0060 1.4298 -0.0754 -0.0044 -0.0045 -0.0317 -0.0058 1.4135 -0.0634 -0.0042 -0.0046 -0,0305 -0.0051 1.3914 -0.0494 -0.0037 -0.0044 -0.0251 -0.0040 1.3701 -0.0352 -0.0029 -0.0037 -0.0177 -0.0028 1.3505 -0.0225 -0.0020 -0.0026 -0.0096 -0 .. 0018 1.3325 0.0000 0.0000 0.0000 0.0000 o:oooo dms0(1)+ 1,4-dioxane(2) 1.4768 0.0000 0.0000 0.0000 0.0000 0.0000 . 1.4741 -0.0124 -0.0003 -0.0003 -0.0013 -0.0004 1.4698 -0.0324 -0.0009 -0.0008 -0.0029 -0.0011 1.4628 -0.0519 -0.0014 -0.0013 -0.0048 -0.0016 1.4572 -0.0593 -0.0015 -0.0015 -0.0056 -0.0018 1.4515 -0.0641 -0.0016 -0.0016 -0.0059 -0.0019 1.4487 -0.0619 -0.0015 -0.0015 -0.0059 -0.0019 1.4458 -0.0621 -0.0015 -0.0015 -0.0058 -0.0018 1.4401 -0.0549 -0.0013 -0.0013 -0.0052 -0.0016 1.4343 -0.0449 -0.0011 -0.0011 -0.0041 -0.0012 1.4284 -0.0337 -0.0008 -0.0008 -0.0028 -0.0009 1.4241 -0.0188 -0.0004 -0.0004 -0.0015 -0.0005 1.4220 -0.0113 -0.0003 -0.0003 -0.0008 -0.0003 1.4198 0.0000 0.0000 0.0000 0.0000 0.0000 refractive indices by various mixing rules: lorentz­ lorenz (l-l), gladstone-dale (g-d), arago-biot (a­ b), edwards (edw). the deviations between experimental and predicted values of the refractive indices were represented by 1m . excess molar volumes and changes of molar refraction on mixing were calculated from: · ve = 'l.x;m;~-l-pt) (1) m=rlx1r1 (2) r=v n~-1 n~+2 (3) where x 1 is the mole fraction of component i; p and r are the density and molar refraction of the mixture, respectively; m 1 , p1° and r1 are the molar mass, density and molar refraction of pure components. the molar refractions were calculated from the lorentz­ lorenz equation (eq.3), vbeing the molar volume. ve and ar for the binary systems were fitted with redlich-kister polynomials [16j to derive the binary coefficients, ak, and standard deviation, n, between the observed and calculated quantities: 3 table 4 coefficients and standard deviations for excess molar volumes and changes of molar refraction on mixing. binary systems at t=29s.15 k dmso+water dmso+ 1,4-dioxane dmso+water+ + 1,4-dioxane coefficients ve, ve, ve, m, m, m., 10'6m3mor1 10'6m3mor1 10.6m3mor1 10·6m3mor1 10·6m3mor1 10.6m3mor1 ao -3.8264 -0.3679 al 1.3438 -0.0305 a2 0.1426 0.0815 a3 -0.3202 0.1833 a4 0.7828 -0.2069 a5 a6 a7 as a9 cr, 10'6m3mor1 0.0013 0.0013 -0.20 + dmso+water ,.. dms0+1,4-dioxane -1.00 -1.20 +----.---~----.----~-------1 0.00 0.20 0.40 0.60 0.80 1.00 x, a) 1.00.--------------------, dmso+water ~ dms0+1,4-dioxane -0.00 +-----.---~~--...,-------,.----! o.oo 0.20 o.4o o.ro 0.80 1.00 x, b) fig.l excess molar volume (a) and excess partial molar volume (b) vs. mole fraction of dmso. binary systems at t=298.l5k. -1.3339 -0.2449 -0.2614 -0.0821 0.0079 -0.0611 0.0015 0.0366 -0.0746 -0.1443 0.0024 0.0009 1.4a 1.46 1.44 1 .$ 1.42 ~ ! 1.40 1.38 1.36 1.34 -22.8351 -7.7350 -2.3061 5.4136 -39.8483 -20.1031 -69.6860 -84.2652 -74.7347 4.6162 0.0945 -1.9693 -0.4168 -2.0049 2.8996 -2.3964 -2.9990 -5.1973 0.0186 -o.o1 -002 ;, a ·c03 ~ -0.09 1.32 +---~--~----.---------+..010 0.00 0.20 0.40 x, 0.60 0 60 1.00 fig.2 refractive indices and changes of molar refraction on mixing vs. mole fraction ofdmso. binary systems at t=298.15k. z=x;xilak(2x; -lr-1 k (4) (5} where z represents the experimental and calculated excess values (ve' or ilr). nexp is the number of experimental data and npar is the number of parameters. no significant better standard deviation was obtained by trying various models to correlate the excess values. the parameters of the fitting equation (4) and the corresponding standard deviations are presented in table4. we have also calculated excess partial molar -e volumes, v; , as follows: (6) 4 table 5 refractive indices, changes of molar refraction on mixing and refractive indices deviations calculated with several mixing rules. ternary system at t=298.15 k x1 xz p 103, llr 106 , llnv k ni3 nv m3mor1 l-l g-d a-b edw 0.0999 0.8001 1.0376 1.4242 -0.0208 -0.0005 -0.0004 -0.0043 -0.0008 0.1000 0.5998 1.0535 1.4358 -0.0433 -0.0011 -0.0010 -0.0075 -0.0016 0.0998 0.4001 1.0691 1.4480 -0.0548 -0.0015 -0.0014 -0.0091 -0.0021 0.1000 0.1999 1.0838 1.4602 -0.0686 -0.0020 -0.0018 -0.0088 -0.0026 0.1997 o.6000 1.0490 1.4300 -0.0238 -0.0007 -0.0005 -0.0088 -0.0013 0.1998 0.4020 1.0662 1.4420 -0.0721 -0.0021 -0.0019 -0.0123 -0.0029 0.2000 0.2001 1.0835 1.4572 -0.0371 -0.0011 -0.0009 -0.0118 -0.0021 0.1998 0.1000 1.0927 1.4632 -0.0876 -0.0028 -0.0025 -0.0136 -0.0038 0.3002 0.5999 1.0442 1.4220 -0.0518 -0.0016 -0.0013 -0.0121 -0.0025 0.3000 oaooo 1.0627 1.4364 -0.0459 -0.0015 -0.0012 -0.0143 -0.0025 0.3000 0.2000 1.0835 1.4508 -0.0947 -0.0032 -0.0028 -0.0187 -0.0046 0.2999 0.1002 1.0918 1.4582 -0.0908 -0.0032 -0.0028 -0.0175 -0.0044 0.3997 0.5001 1.0465 1.4200 -0.0526 -0.0018 -0.0015 -0.0149 -0.0028 0.4000 0.4002 1.0573 1.4275 -0.0659 -0.0023 -0.0020 -0.0173 -0.0035 0.4002 0.1998 1.0812 1.4436 -0.1085 -0.0040 -0.0036 -0.0233 -0.0057 0.3998 0.1002 1.0911 1.4522 -0.0979 -0.0038 -0.0034 -0.0226 -0.0054 0.5000 0.4001 1.0503 1.4170 -0.0744 -0.0028 -0.0025 -0.0201 -0.0042 0.5001 0.3000 1.0629 1.4256 -0.0863 -0.0034 -0.0031 -0.0231 -0.0049 0.5002 0.1998 1.0751 1.4348 -0.0850 -0.0035 .{).0032 -0.0246 -0.0051 0.4998 0.1002 1.0884 1.4440 -0.1030 -0.0044 -0.0040 -0.0272 -0.0062 0.5997 0.3002 1.0528 1.4130 -0.0728 -0.0032 -0.0029 -0.0236 -0.0047 0.6001 0.1997 1.0685 1.4232 -0.0857 -0.0039 -0.0036 -0.0281 -0.0057 0.6000 0.1000 1.0826 1.4352 -0.0529 -0.0025 -0.0023 -0.0282 -0.0044 0.7000 0.2001 1.0564 1.4082 -0.0582 -0.0030 -0.0027 -0.0278 -0.0047 0.6998 0.1000 1.0734 1.4200 -0.0590 -0.0032 -0.0030 -0.0310 -0.0050 0.8001 0.1500 1.0466 1.3928 -0.0388 -0.0024 -0.0022 -0.0269 -0.0039 0.7990 0.0500 1.0645 1.4042 -0.0569 -0.0037 -0.0039 -0.0299 -0.0049 0.9000 0.0500 1.0366 1.3732 -0.0377 -0.0029 -0.0031 -0.0223 -0.0036 0.9000 0.0250 1.0407 1.3765 -0.0331 -0.0026 -0.0031 -0.0213 -0.0030 where v; represents the partial molar volumes and '1';0 the molar volumes of the pure components. the curves of excess molar volumes (eq.l), of excess partial molar volumes and of changes of molar refraction on mixing (eq.2) are given in figs. i and 2; fig.2 contants also the refractive index as function of mole fraction. the values of v e are negative for both binary systems, the magnitude of minimum value of ve observed in the case of dmso+water is approximately three times larger than that observed in dmso+l.4-dioxane mixture. the excess partial molar volumes of components are mostly negative and decrease with xi, for· both systems. negative excess volumes are characteristic of polar nonelectrolyte mixtures. intermolecular interactions. the main effect in dmso+water system is the strong h-bonding between dmso and water, reflected by the negative values of v:. smaller negative values of ye for dms0+1,4dioxane are due to unlike dipole-dipole interactions between so groups of dmso and 0 group of 1,4dioxane. the addition of 1,4-dioxane (dipole moment p = 0.4 d) to the dmso (p = 4.06 d) tends to destroy the strong polar type interaction between dmso molecules. the negative m values for binary systems vary almost identically throughout the composition scale with the values of y£. the ilr for dmso+water system is greater than ar for dmso+l,4-dioxane -e: system. more negative v.e. v, and ar observed for dmso+water mixture compared to those for dmso+ t4·dioxane is supported by the published results refering to 11£ and ge of the mixtures {2-4}. e -£ negative values of v , v, and .:jr suggest the presence of specific interactions between the mixing components. because of three distinctive functional ~ps. dmso is capable to exhibit intra and our studies agree with other studies in the literature [6] for dmso+water system. several methods to predict refractive indices of mixtures were applied to test their validity in high polar mixtures. the refractive indices were predicted by mixing rules proposed in literature [17,18]. the results are presented in table 3. it can be seen from this table that for these binary systems, the lorentz-lorenz mixing rule was the most suitable; the arago-biot mixing rule gave in both cases poor predictions of the refractive index. a close similarity was observed between the lorentz-lorenz and gladstone-dale relations. ternary systems experimental densities, refractive indices and changes of molar refraction of mixing are given in table 5. excess molar volumes and changes of molar refraction of mixing were fitted using equation (7): z = x 1xzxjao +a1(x1x 2 )+az(xl -x3)+ +a3 (x 2 -x3 )+a.,(x1 -x2 y +a5 (x1 -x3y + (7) +a6 (x 2 -x3 y + ..... ] where z represents v' or l1r. the results of fitting equation (7), parameters and standard deviations, are given in table 4. the values of ar are negative over the entire composition range. the binary mixtures dmso+water, dms0+1,4-dioxane present negative ar values with a minimum of -0.09 cm3mor1 and -0.064 cm3mol'\ respectively. the ar values of ternary system are also negative with a minimum of0.136 cm3mor1 • the values of ternary v', reported previously [5], are likewise negative for all compositions. the predictive mixing rules for the refractive indices were used. the differencies between the experimental and calculated values (ann in table 5) show that the better results were obtained by lorentz-lorenz and gladstone-dale equations. conclusion excess values of molar volumes, partial molar volumes and molar refraction supported by earlier reported properties indicate the presence· of molecular interactions in binary and ternary studied systems. lorentz-lorenz and gladstone-dale mixing rules for refractive indices lead to the best results. acknowledgements this work was financed by cncsis (national council . for academic scientific research romania) grant. symbols ak coefficients in redlich-kister equation ge excess gibbs free energy k degree of the redlich-kister polynomials mt molar mass of component i nexp number of experimental points npar number of parameters in redlich-kister equation nv refractive index r; molar refractivity of component i r molar refractivity of mixture ar changes of molar refractivity on mixing ¥;0 molar volume of the pure components i ve excess molar volume v. partial molar volume of component i -e v; v x; z excess partial molar volume of component i molar volume of mixture mole fraction of component i 5 experimental and calculated excess values for v' orar greek letters p? density of pure component i p density of mixture · 1je excess viscosity j-l dipole moment a standard deviation references 1. julian 0., jinescu g., iliuta m. and hamplea l., hung.j.ind.chem., 1994, 22(2), 95-100 2. lulian 0., mateescu c. and iliuta m.: rev.roum.chim., 1995, 40(3), 235-239 3. lulian 0., hamplea l. and jjnescu g., hung.j.ind.chem.: 1997, 25(4), 249-253 4. landauer 0., mateescu c., julian 0., iliuta m., 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(bucharest), 1993, 44, 26-30 5. iliuta m., iulian 0. and omota l.m., eldata: intelectron.j.phys.-chem.data, 1998,4, 121-128 6. aminabhavi t.m. and gopalakrishna b.: j.chem.eng.data, 1995,40, 856-861 7. le bel r.g. and goring d.a.: j.chem.eng.data, 1962,7,100-101 8. riddick j.a., bunger w.b. and sakano t.k.: techniques of chemistry, vol. ii, organic solvents, 4th ed. john wiley & sons, new york, 1986 9. arce a., ageitos j.m., mendoza j. and sota a.: j.chem.eng.data, 1995,40,647-649 10. lide d.r.: crc handbook of physics and chemistry, 78th ed. crc press, florida, 1997 11. arce a., blanco a., soto a. and vidal i.: j.chem.eng.data, 1993, 38, 336-340 12. aralaguppi m., aminabhavi t.m., haroooppad s.b. and baujndg! r.h.: j~chem.eng.data, 1992, 37,298-303 13. t!emermans j.: physico-chemical constants of pure organic compounds, elsevier, amsterdam, 1950 14. sakurai m.: j.chem.eng.data, 1992, 37, 492496 15. acevedo i.j., pedrosa g.c. and katz m.: can.j.chem., 1991, 69, 1906-1910 16. redlich 0. and kls'll!r a.t.: ind.eng.chem., 1948,40,345-348 17. tasic a.z., djordjevic b.d. and grozdanic d.k.: j.cbem.eng.data, 1992,31,310..313 18. 18. boti'cher c.j.f.: theory of electric polarization, elsevier, amsterdam, 1952 page 5 page 6 page 7 page 8 page 9 hungarian journal of industrial chemistry veszprem vol. 29. pp. 87-90 (2001) estimation of steady states number of one-route catalytic reactions e. s. patmar, b. v. alexeev, n. i. koltsov and f. j. keil1 (~epartment of physic~ chemi~try o! chuvash state university, moskovskii prospekt 15, 428015 cheboksary, russia department of chemical engmeenng, technical university ofhamburg-harburg, eissendorfer strasse 38, d-21073 hamburg, germany) received: december 28, 2000 for one-route catalytic reactions the relationship between the number of reversible steps and the number of internal steady states (iss) is i~vestigated. ~or r~actions having trimolecular steps, among which there is only one reversible stage, the number iss mcreases to mfimty together with the increase of the number of intermediate substances. the ~o~el.of a reaction with 2n intermediate substances for which the iss number is equal to n-1 is described. if there are no hmitatwns. in the number of reversible ~teps in ~ reaction mechanism, then the number of iss grows exponentially toget~er with the growth ~f ~umber of mtermed1ate substances. the model of a bimolecular homogeous reaction (a reaction whose steps have similar molecularity) with 3n intermediate substances is given. it can have 211 iss. keywords: catalytic reaction, internal steady states, intermediate substances, mechanism introduction one of the important problems . of catalytic reaction kinetics is to find out the reasons for the occurrence and the number of steady states (ss). if there are some ss under the same conditions of reaction, then the reaction rates in these ss are different. therefore, the investigation of the possibility of existance of ss is a topical problem. determining a ss which has the highest rate of reaction allows one to solve optimization probems. the classification of types of ss is given in [ lj. according to this classification both internal (iss) and boundary (bss) steady states are determined. in these steady states the number of intermediate substances with zero concentrations is equal or not equal to zero, respectively. some papers [2-41 were devoted to the investigation problems of multiplicity (mss) of ss. the necessary conditions of mss is the existence of interaction steps of different intermediate substances in a reaction mechanism [2]. the sufficient conditions of unique occurrence of iss in catalytic reactions are presented in [3]. however~ the results described in [2] and [3] do not have both necessary and sufficient conditions of multiplicity, that is they are not criteria for mss. for the first time, the multiplicity criterion was described in [4]. later on this criterion was presented in an algorithmic form and a computer program [51. however, this criterion does not allow to determine the number of iss. some estimates of the number of iss for several classes of catalytic reactions were obtained [68]. for one-route reactions of which the steps are irreversible and have arbitrary molecularity the iss number does not exceed two [6]. some reaction models with two intermediate substances of which iss number can be infinite are presented in [7]. however, these reactions have a high molecularity of steps. for obvious reasons one may ask the question: are there any classes of reactions with low molecularity allowing an unlimited increase of the number of iss? the answer is given in [8]. the reaction models with n intermediate substances of which the number of iss is not less than n+ 1 are given in this paper. this means that with the help of these reaction models steady regimes can be obtained, which are characterized by a large number of iss. the reactions investigated in [8] are multi-route, therefore, the possibility of the unlimited increase of the number of iss for one-route reactions with a low molecularity of each of their steps has not yet been studied. this paper gives new results obtained by the authors on the investigation of iss for different classes of catalytic reactions. for one-route reactions proceeding according to inhomogeneous schemes and having trimolecular steps we have proved the possibility of an unlimited increase of iss accompanied by an increase of the 88 number of steps. this means that the existence of one reversible step in reaction schemes having a great number of iss is not only a necessary [6] but also a sufficient condition. additionally, the exponential increase of the number of iss under the condition of increasing the number of steps for one-route reactions proceeding via homogeneous bimolecular schemes is demonstrated. results and discussion let us describe the reaction a=> b proceeding via the scheme which contains 2n inhomogeneous (different molecularity) steps, one of which is reversible: t.a+x1 =x2 2.2x1 +x3 -7x4 +2x2 3.x~ +x5 --=>x6 +x2 (n+l).x1 +x2 -72x3 ; (n+2).x3 +x4 +x2 -72x5 +x1 (n+3).x5 +x6 +x2 -72x1 +x4 (n-2).x2,_.. + x2•-~' -7 x:bo-4 +x2 (2n-2).x2._5 + x2 ...... + x2 -72x2._3 + xz...,; (n-1). xz.-1 + xz-3 -7 2xz._2 (2n -1). x2._3 + x2,_2 + x2 -7 2x2._1 + x2.-4 n. xz._2 + xz...1 -7 2x2• 2n. xz._1 + 2x2• -7 3x1 + b (1) where a and bare reactants, x1 are catalytic centers, xi are intermediate substances (i=2, ... ,2n). this reaction is one-route because it proceeds via 2n steps in which 2n-1 independent intermediate substances take part. according to the theory of stationary reactions [9] under isothermal conditions of a gradientless differential reactor for scheme (1) the stationary equations have the following form: k2x~x3 = r k3x4x5 = r kn+zxzx3x4 = r kn+3xzxsx6 = r kn-2x2n-6x2n-5 = r kzn-zxzxzn-sxzn-4 = r kn-tx2n-4xzn-3 = r kzn-!xzx2n-3xzn-2 = t knxzn-zxzn-1 :;:;: r kznxzn-lxin == t (2) where ki = const are stage rate constants, ca is the concentration of a, x; are concentrations of intermediate substances xi ~ r is the reaction rate. let us introduce new variables x = c1x2 ,y = c2x21 x1 ~ where cpc;: must be in such a form that the first two equations of scheme (2) after substituting r. lead to the equation x + y = l . further, let us mark au xi by x and \' .;• x3 = p3y; xs = psy·x; xz = pzx x4 = p4xl y2 x6 = p6/ yz x2n-3 = p2n-3y. xn-3 ; x2n-z = p2nx-n+ 4 i y 2 xzn-1 = p2n-1y. xn-z; x2n = p2nx-nl2+2 i y where the pi are determined by the equations k_l kl pt=k,p2=k, n+l n+l kn+t ( kt )j-ttij-t km+n . 2 pzj-1 ----, ]= , ... ,n, k_l kn+l m=l km+l (3) p2i = (~)2( kn+i )j-1 it~. j = 2, ... ,n -1 ' kn+l kl m=z km+n pzn = (!sj...)2( kn+i )n-2 it~ kn+l kl m=z km+n the numbers pi can have any positive values by changing the rate constants ki . look at the relations p1pz 3 -~:....:::...-kn+l' j = , ... ,n, p2i-4p2i-3 k _ ptpz k 2n2 n+l • pzn-tpzn this note is necessary in order to work with such values of numbers pi. thus, let us mark all xi by x and y, and reduce scheme (2) to one equation: p3y + psy·x+ ... + p2n.-ry·xn-2 -1+ + ptxly+ p2x+ p4xi y2 + p61y2 + ... , (4) where y=1-x. let us consider the function <p(x) = p3y+ psy·x+ ... + p2n_1y·xn-2 -1 and show that the number of different roots qj(x) lying in the interval (0.1) is equal to n-1 for the corresponding selection of numbers p3 , p5 , ••• , p 211_1 • the function l{j(x) can be represented in the form: 1p3 + (p3 ps )x + · ·· + (pzn-3 p2n-1 )x"2 + n-l + pzn-lxll-i = pzn-iti(x-xi) i=l hence we obtain (5) jr-i pz • .-~n cr-x,)= pz~~-l(x"-1 -s1x"-2 + ... +(-lt1s1d) (6) t4 where the si are symmetrical root functions in xi , whereby the parameters p;, according to relations (5), n-1 can be written in the form p 21_1 == 1l ( -1)i si , i=n-j+l j = 2, . .. ,n. by choosing different small positive roots xi the symmetrical functions will be also small positive numbers and the p21_1 values will be close to 1. selecting the corresponding ppp2 ,p4 , ••••• ,p2n constants, the number of roots of equations (4) lying in the interval (0,1) is also equal to n-1. in fact, if we make the constants p1, p 2 , p 4 , ... , pzn small, then this results from the theorem on the continuous dependence of the roots on coefficients [10]. thus, scheme (1) has n-1 iss at some sets of rate constants. in order to show the exponential increase of the number of iss for an increasing number of steps, let us consider the reaction a=>b, proceeding via the following steps l.a+.:t2 +~ =:bi 1'.4 +.:t2 -?2xs 2.xs +4; =2x4 2'.x4 +xs-?2xs r".2xj_ =2.x.,; :t'.2x4 =2x6; (7) the stationary equations are written in the following form: is· xi k_t•.xi = dl.r k2.x; k_2.~ = d2-r k.x:m-t.:13.. -k-nxin-z =d.r k.·.:l3..-zajn-l =d •• r k.·xi.-z -k_ •• c8 :x;,. =d •• r }:x;=l i=l . .jij (8) dividing the first three equations of system (8) in the first line by x[ and substituting r we get two equations with two unknown values y2 =x2 /x1,y3 =~lx1 • we continue the same procedure with three equations, then with four ones and so on. further, let us select rate constants for these equations in such a way that the equations obtained could have two different solutions (for example, use the iss multiplicity criterion for one­ route reactions [5]). then for these systems the solutions have the following form ~j-l = uiix3j-z ;x:j1 = u~x3j-l i1 e [1,2], j = l..n (9) using these solutions we can exclude x3i-px:ji, mark then x3i-z, and reduce 3j-l equations of systems (8) to the following form: cix-;1_2 = dlr i1 e [1,2], j = l..n (10) further, let us substitute r and mark x3i_2 by x1 • using relations (9), let us denote all x1 by x1 • on the basis of the last equation of system {8) we calculate x1 and then determine xi • knowing the data for uj 1 , u;; • the solutions of system (9) can be simply found. this 89 r, $-1 0.415 0.3!5 0.40 0.45 0.50 ca • aibitraryunits fig.] dependence of rate on concentration o a for reaction proceeding via scheme (7) at k 1 = luu, k 2 == 4:l, k 3 = :>u, k_1 =k_2 =k_3 =11.0, kr =k2, =ky =:ll, _ 1 k1• = k2• = k3• = 106, k_1• = k_2• = k_3• = 169 ( s ) means that the unique solution of system (9) corresponds to just one vector out of a set of 2n vectors. we want to show that all the solutions are different. if it is not so, then all numbers coincide for two different u/ sets. this is impossible because these sets differ at least in one of the coordinates. scheme (7) is constructed on the base of scheme (1) in table 1 of paper [11]. if we take any other scheme in tables 1 and 2 of paper [11] or their combination, we can construct schemes having the exponential increase of the number of iss. the kinetic dependence in fig.l illustrates the number of iss for schemes (7). this dependence has the following interesting peculiarity: all the roots appear simultaneously (in a general case two solutions appear). this peculiarity is connected with system (8) by splitting the system into independent equation subsystems. this property of system (8) leads to this unusual type of kinetic dependence. schemes (7) can be used as test for the efficiency of computer programs which determine the number of iss. the absent of solutions at some c a (fig.l) is connected with the presence of boundary steady states [1] for scheme (7). ·conclusion the presence of reversible steps in mechanisms of one­ route catalytic reactions is a necessary and sufficient condition of an unlimited iss number. if there are no limitations in the number of reversible steps. the number of iss increases exponentially together with the number of intermediate substances. 90 references 1. koltsov n. i., fedotov v. kh. and alexeev b. v.: zhurn. phys. chern., 1988, 62, 1973-1975 (in russian) 2. slin'ko m. g., bykov v. i., yablonski! g. s. and akramov t. a.: dokl. akad. nauk sssr, 1976, 226, 87 6-879 (in russian) 3. !vanova a. n. kinet. katal., 1979, 20, 1019-1028 (in russian) 4. fedotov v. kh., alekseev b. v., koltsov n. i. and kiperman s. l.: react. kinet. catal. lett., 1984,26,25-29 5. alekseev b. v., kozhevnikov i. v. and koltsov n. i.: cornput. chern., 1999,23,69-74 6. koltsov n. i., fedotov v. kh. and alekseev b. v.: dokl. akad. nauk sssr, 1991, 318, 1179-1183 (in russian) 7. fedotov v. kh. and koltsov n. i.: dokl. akad. nauk, 1995, 343, 493-495 (in russian) 8. alekseev b. v. and koltsov n. 1.: mendel. commun., 1998,8, 116-117 9. temkin m. i.: dokl. akad. nauk sssr, 1963, 152, 156-159 (in russian) 10. kostrikin a. i.: introduction to algebra. fundarn of algebra, fizrnatlit, moscow, 1994 11. koltsov n. i., alekseev b. v., kozhevnikov i. v. and fedotov v. kh.: zhurn. phis. chern. 1997, 71, 769-772 (in russian) page 91 page 92 page 93 page 94 microsoft word 16.16 halmagyi.docx hungarian journal of industry and chemistry vol. 44(2) pp. 135–139 (2016) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2016-0017 characterisation of cements from dominantly volcanic raw materials of the carpathian bend zone timea halmagyi,1 emilia mosonyi,2 józsef fazekas,2* maria spataru1 and firuta goga2 1 s.c. valdek impex srl, sfantu gheorghe str. 1 decembrie 1918, bl. 15, sc. e, et. 3, ap. 9., judetul covasna, romania 2 “babes-bolyai” university, kogalniceanu str. 1, 400082 cluj-napoca, romania this paper presents the results of laboratory investigations regarding the production of cements from local raw materials, such as limestone from varghis, gypsum from nucsoara, basaltic scoria from racosul de jos, volcanic tuff from racosul de sus, diatomite from filia, and red mud from oradea. the raw mixtures, based on modified bogue calculations, contain limestone, gypsum, and one or two of the above-mentioned materials. the cements resulted from clinker grinding in a laboratory gas furnace at 1260–1300 ºc, with one hour at the peak temperatures, and were characterised for blaine specific surface area, specific density, and mineral phases. physico-mechanical properties, such as water content for normal consistency, setting time, soundness, and compressive strength were also determined. results show that these cements contain belite, ferrite, calcium sulphoaluminate, anhydrite, and some minor compounds. keywords: experimental cement, varghis limestone, racosul de sus volcanic tuff, setting time, mechanical properties 1. introduction manufacturing of portland cement is energy consuming, globally accounting for 2% of primary energy and 5% of industrial energy consumption. moreover, portland cement production contributes significantly to greenhouse gas emission in the order of 5% of the global co2 emissions due to anthropogenic sources [1]. new civil engineering requirements impose the production of a new type of cement, which is of good quality, environmentally friendly, and requires low energy utilization. low-energy cement manufacturing is economically and ecologically preferable. these cements could be used in places where high early strength or expansion compensation and also increased durability are required. in cement chemistry, notation of oxides are abbreviated by their first capital letters: c=cao, s=sio2, a=al2o3, f=fe2o3, cs=so3, and h=h2o. lowenergy cements comprise those that belong to the caosio2-al2o3-fe2o3cs system. they are mainly sulphoaluminate belitic and sulphoferroaluminate belitic cements [2]. these can be produced from both natural raw materials or raw material mixtures, containing byproducts or industrial waste, by firing at lower temperatures than for portland cement clinkers. a large variety of cements was developed in china based on the *correspondence: chemiceramic@gmail.com composition c4a3s . these were standardized and named as “third cement series” [3]. these cements have special features such as quick setting time, good impermeability, and rapid strength development even at low temperatures. there are numerous investigations on the laboratory-scale production of sulphoaluminate belite (sab) cement [4–18]. sab cement can be classified into three major categories according to the content and proportions of the phase compositions. the tentative naming and some basic properties are summarized below: 1. calcium sulphoaluminate-rich belite cement: they are mostly composed of only two main phases of sab cement, the major components being c4a3s (around 55–75 (g/g)%) and c2s. this type of cement is typically used for applications requiring rapid setting and high early strength [4, 6, 8, 9, 19, 20]. 2. expansive belite-rich calcium sulphoaluminate cements: besides the main components of the sab cements they contain free lime up to 10 (g/g)% which promotes expansion. this type of cement can be used in restricted areas requiring shrinkage-resistant and self-stressing cements [4, 12, 16, 20, 21]. 3. non-expansive belite-rich calcium sulphoaluminate cements: these cements have higher belite, lower calcium sulphoaluminate, and much lower or completely deficient of free lime content than those of commercially produced sab cements. industrial by-products with high sulphate content can be used in high halmagyi, mosonyi, fazekas, maria, and firuta hungarian journal of industry and chemistry 136 percentages in production. this type of cement shows high mechanical strength both at early and late ages comparable to ordinary portland cement and has the potential to replace it [4, 6, 8, 14, 16]. there is no commercial production of the beliterich calcium sulphoaluminate-type of cement. mehta [18] produced sab cements containing no free cao, but large amounts of belite rich in caco3, silicic acid, hydrated alumina, iron oxide, and gypsum. the clinkers were obtained by heating the raw materials in an electric muffle furnace at 1200 ºc for about 1 hour. clinkers were ground to a blaine specific surface area of about 400 m2 kg-1. microstructure examinations of the clinkers showed that c4a3s appears as cubic crystals whereas belite appears as large rounded grains. the clinkers were very easy to grind due to their brittleness [4]. sahu et alia [12] produced cements of types 2 and 3 from limestone, fly ash and gypsum at 1200 ºc, for a bearing time of 30 minutes and cooled by fresh air. kasselouri et alia [17] in 1995 obtained cement of type 3 at 1280 ºc from limestone, gypsum, bauxite, silica sand, and iron-rich industrial by-products. cements composed from a mixture of baghouse dust, f-class fly ash, and scrubber sludge, sintered at 1175–1250 ºc for bearing times of 30, 45, and 60 minutes, and cooled by natural air were obtained according to arjunan et alia [10]. mixtures composed of limestone, bottom ash, baghouse filter ash, bauxite, and gypsum fired at 1250 and 1300 ºc, for a bearing time of 60 minutes, lead to sab cement of c4a3s – ye’elimite, c2s-larnite (belite), c4af-brownmillerite, and csanhydrite compositions [4]. the absence of tricalcium aluminate (c3a) in these cements indicates that the decomposition of the desired mineral c4a3s does not take place at these temperatures. the presence of the desired minerals and the absence of c5s2s confirmed the formation of the sab cement at 1250 ºc and 1300 ºc after 1 hour. this article presents our study on the cement series sintered using local raw materials, such as volcanic tuffs from racosul de sus, basaltic scoria from racosul de jos, and diatomite from filia (all in the carpathian orocline), and red mud. 2. experimental the raw materials used for the cement experiments carried out as part of this study are natural (varghis) limestone, bodoc clay, nucsoara gypsum, racosul de jos basaltic scoria, racosul de sus volcanic tuff, filia diatomite, and artificial industrial waste (oradea red mud). the selected raw materials were investigated for chemical compositions. the chemical compositions of the limestone, red mud, diatomite, and basaltic scoria were analysed by sem/edax. the volcanic tuff and gypsum analyses were performed by wet chemical methods, according to the sr en 192-2 (table 1). the theoretically estimated mineralogical, chemical compositions based on modified bogue calculations [1, 4, 22] are given in table 2. the compositions of the raw material mixtures are presented in table 3. the raw material mixtures were obtained by grinding them in a laboratory ballmill up to a sieve residue of 90 µm about 12%. afterwards, the raw material mixtures underwent a process of briquetting and drying followed by firing in a laboratory gas oven for one hour at a constant temperature of 1260–1300 ºc. the inside temperatures of the furnace were estimated with a thermocouple thermometer. fast cooling was achieved in the air. the obtained cements from grinded clinkers (five hours in a mill, balls:clinkers ratio of 2:1) were tested. mineralogical table 1. chemical compositions of the raw materials in (g/g) %. oxides varghis limestone oradea red mud racosul de jos basaltic scoria racosul de sus volcanic tuff filia diatomite nucsoara gypsum cao 89.61 12.71 10.38 2.88 0.71 28.31 sio2 4.01 8.93 46.10 64.53 92.52 9.83 al2o3 5.16 17.04 18.78 11.80 3.24 2.73 fe2o3 48.37 9.93 2.57 2.18 1.07 na2o 3.68 3.23 1.89 0.15 k2o 1.69 2.75 0.46 0.55 mgo 1.30 7.21 0.45 0.39 tio2 6.80 1.61 0.27 0.13 v2o5 0.19 0.04 p2o5 1.22 0.98 1.07 0.04 so3 0.89 37.08 mn2o3 0.02 p.c. 12.40 19.90 table 2. theoretical mineralogical and chemical compositions of the cements in (g/g) %. sample mineral composition oxidic compositions c2s c4a3s! c4af cs! cao fe2o3 sio2 al2o3 so3 c1, c2, c3 56 12 22 10 55.15 7.23 19.53 10.63 7.46 c4 50 18 15 17 53.11 4.93 17.44 12.17 12.36 c5 43 28 23 6 51.38 7.56 15.00 18.86 7.20 characterisation of cements from dominantly volcanic raw materials 44(2) pp. 135–139 (2016) doi: 10.1515/hjic-2016-0017 137 compositions of cements made by xrd analyses with a panalytical-philips cubix pro x-ray spectrometer, according to il lab 41 proceedings are presented in table 4. experimental laboratory-produced cements were tested in conditions provided by the romanian crh cement s.a. plant in hoghiz (brasov county). the blaine specific surface area, specific density, heat of hydration (table 5), volume of water for normal consistency, setting time, soundness, and compressive strength (table 6) have been determined. identification of mineral phases formed during the burning of clinkers was carried out by means of the cubix pro spectrometer. 3. results and discussions the mineralogical compositions of the experimental cements are summarized in table 4. all cement samples contain belite, ferrite, anhydrite, and many other phases in small amounts. the largest amount of belite found in a cement sample is in the raw mixture containing diatomite (sample c2 with c2s = 69.1%), followed by the sample prepared with volcanic tuff (sample c3 with c2s = 65.9%). soner et alia reported [4] that the mineral c4a3s is stable between 1250–1350 ºc, but probably it can decompose during cooling. furthermore, it was demonstrated that aluminium could be substituted by iron in the ye’elimite structure forming c4a3-xfxs [23– 26]. the experimental cement samples were characterized with regards to specific density and fineness, representing the blaine specific surface area [27]. the heat of hydration according was also determined to the sr en 196-9/2006 method [28]. the physical properties of experimental cements are presented in table 5. the experimental blaine fineness data are characterised by large specific surface areas. the biggest blaine specific surface area was found in sample c2 (with diatomite) followed of sample c3 sample (with volcanic tuff). these samples have the smallest specific densities in the same order. the binding behaviour of the cements was estimated by measuring the setting time, volume of water for normal consistency, soundness, and compressive strengths (after second and twenty-eighth days). to determine the table 5. physical properties of cement samples c1-c5. sample blaine specific surface area, cm2 g-1 heat of hydration, j g-1 specific density, g cm-3 c1 7367 29 3.17 c2 8745 123 3.04 c3 7963 32 3.07 c4 6501 44 3.14 c5 7553 110 3.26 table 3. the compositions of raw material mixtures in (g/g) %. samples varghis limestone oradea red mud racosul de jos basaltic scoria racosul de sus volcanic tuff filia diatomite nucsoara gypsum cement 1 48.90 36.67 14.43 cement 2 54.08 13.70 32.22 cement 3 54.35 23.37 22.28 cement 4 54.66 0.98 31.53 12.83 cement 5 47.45 1.19 20.66 30.70 table 6. physico–mechanical properties of cement samples c1-c5. sample water for normal consistency, cm3 setting time, hour : minutes soundness, mm compressive strength, n mm-2 early final 2 days 28 days c1 135 0:44 1:44 2.75 0.24 0.42 c2 225 0:13 0:35 0.50 4.12 26.67 c3 124 3:35 4:29 3.00 0.23 8.42 c4 185 1:57 > 10 hour 1.00 0.53 0.72 c5 178 0:05 0:15 2.00 1.44 2.28 figure 1. early and final setting times of the cement samples in minutes. table 4. mineral compositions in (g/g) % of the cement samples c1-c5 according to the il-lab-41 testing method. minerals c1 c2 c3 c4 c5 belite 24.2 69.1 65.9 52.7 58.4 ferrite 7.5 13.1 8.5 24.6 20.8 cubic aluminate 8.5 0.4 0.0 0.2 4.7 orthorhombic aluminate 20.5 0.0 0.0 1.5 0.0 free lime 1.4 0.5 1.7 0.6 0.1 anhydrite 2.1 6.8 3.8 1.5 5.3 halmagyi, mosonyi, fazekas, maria, and firuta hungarian journal of industry and chemistry 138 setting times, the quantity of water required to form cement paste of standard (normal) consistency was determined previously [29]. the water data for standard consistency are presented in table 6. the setting time for the paste with standard consistency was measured using a vicat device. the initial and final setting data of the investigated cements are also shown in table 6 and fig.1. the compressive strengths have been determined according to the sn en-1/2006 method [30] and the data are shown in fig.2. the investigated cements exhibited different mechanical strengths, as a function of their mineral compositions. the strength of sab cements depends mainly on the mineral ye’elimite (ca4al6o12so4 or c4a3s ) during the initial minutes up to hours of hydration [31, 32]. yeʼelimite is almost entirely responsible for the hydration reactions at early ages of csa-type cements [23]. the presence of belite was found to be responsible for compressive strength at late ages. the compositions of raw material mixtures for these experimental cements influenced their mineral contents. taking into consideration these, the initial strengths are better for the cements containing diatomite (sample c2), volcanic tuff (sample c3), basaltic scoria (sample c4), and red mud (sample c5). a higher content of red mud is favoured over sample c4 (see tables 3 and 4, fig.2). a good evolution of mechanical strength over time is shown for samples c5 and especially for the c2 cements. c3 cement sample is also notable, but with lower initial strength, which is an important characteristic for a favourable evolution of specific surface area. this is clearly the largest value for cement sample c3. the cements containing basaltic scoria generally developed lower mechanical strengths in comparison to those containing diatomite or volcanic tuff. the cement containing diatomite is noticeable due to its very high initial strength (table 6). for this cement, the compressive strength, after two days increased, which may be a consequence of the increased specific surface area. in terms of practical applications, the development of cement of good mechanical strength and workability depending on the setting time is of importance. the setting time of investigated cements was decisively influenced by the content of raw material mixtures (see table 3). in the order of c4→c3→c1→c2→c5, the setting time becomes shorter. for the cement samples containing 1.2% red mud, 20.7% basaltic scoria (c5) and 13.7 % diatomite (c2), the setting time is quick. this is a consequence of rapid hydration processes. because of this, these latter samples can be considered for practical applications only as retarding admixtures or super-plasticizers due to their set-retarding effect. soundness shows reasonable values, which is required to be less than 10 mm for portland cement. 4. conclusion based on investigations into cement samples in the laboratory of the hoghiz plant, it can be concluded that from all raw material mixtures, heated at temperatures of between 1260 and 1300 ºc, resultant clinkers contain more belite, ferrite, and anhydrite. physico-mechanical properties show good compressive strength at early ages, good soundness, the biggest blaine specific surface area (ssp = 8745 cm2 g-1) for cement containing limestone, diatomite, and gypsum, as well as belite and anhydrite. the use of the local raw materials from the carpathian orocline area, e.g. varghis limestones, bodoc clays, nucsoara gypsum, volcanic tuffs from racosul de sus, basaltic scoria from racosul de jos, and filia diatomite, facilitated the formation of cements that are more belitical than sulphoaluminate. acknowledgement the authors are grateful to chemi ceramic srl in sfantu gheorghe where the specific experimental cements were manufactured and to the hoghiz plant where their physico-mechanical characteristics were tested. references [1] chen, i.a.: synthesis of portland cement and calcium sulfoaluminate-belite cement for sustainable development and performance, ph.d. dissertation, the university of texas at austin, 2009 www.lib.utexas.edu/etd/d/2009/cheni55279 [2] jun-an, d.; de-dong, l.; mu-zhen, s.; jan-mon, w.: a study of mineral composition of cement in the quinary system cao-sio2-al2o3-fe2o3-so3, j. chin. ceram. soc. 1982 article no. 4 en.cnki.com.cn/article_en/cjfdtotalgxyb198204000 [3] zhang, l.; su, m.; wang, y.: development and use of sulphoand ferro-aluminate cements in china, adv. chem. res. 1999 1, 15–21 doi: 10.1680/adcr.1999.11.1.15 figure 2. compressive strength of cement samples after 2 and 28 days in mpa. characterisation of cements from dominantly volcanic raw materials 44(2) pp. 135–139 (2016) doi: 10.1515/hjic-2016-0017 139 [4] soner, i.: utilization of fluidized bed combustion ashes as raw material in the production of a special cement, m.sc. dissertation, middle east technical university, haziran, turkey, june 2009 www.osti.gov/scitech/biblio/5635811 [5] majling, j.; roy, m.d.: the potential of fly ash for cement manufacture, am. ceram. soc. bull. 1993 72(10), 77–81 www.osti.gov/scitech/biblio/5635811 [6] gartner, e.: industrially interesting approaches to “low-co2” cements, cement concrete res. 2004 34, 1489–1498 doi: 10.1016/j.cemconres.2004.01.021 [7] quillin, k.: performance of belite-sulfoaluminate cements, cement concrete res. 2001 31, 1341– 1349 doi: 10.1016/s0008-8846(01)00543-9 [8] phair, w.j.: green chemistry for sustainable cement production and use, green chem. 2006 8, 763–780 doi: 10.1039/b603997a [9] zhou, q.; milestone, b.n.; hayes, m.: an alternative to portland cement for waste encapsulation the calcium sulfoaluminate cement system, j. 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determination of setting time and le chatelier soundness, 2006 tpm.fsv.cvut.cz/student/ documents/files/bum1/chapter12.pdf [30] sr en standard 196-1: method of testing cement part 1: determination of strength, 2006 [31] zhang, l.; su, m.; wang, y.: development and use of sulfoand ferro-aluminate cements in china, adv. cement res. 1999 1, 15–21 doi: 10.1680/adcr.1999.11.1.15 [32] winnefeld, f.; barlag, s.: calorimetric and thermogravimetric study on the influence of calcium sulfate on the hydration of yeʼelimite, j. therm. anal. calorimet. 2009 101(3), 949–957 doi: 10.1007/s10973-009-0582-6 hungarian journal of industry and chemistry vol. 48(1) pp. 71–75 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-11 design and construction of a vibration data acquisition system for road vehicles roland nagy*1 and istván szalai1 1institute of mechatronics engineering and research, university of pannonia, gasparich márk utca 18/a, zalaegerszeg, 8900, hungary this article describes the design of a vibration data acquisition system which can be mounted on the undercarriage of a vehicle to acquire information about the quality of and defects in road surfaces. it is important to be able to deduce the condition of a road section from its data. for practical reasons, a microcontroller-based control unit was used and a separate power supply created. bumps in the road were detected by a piezoelectric accelerometer. once the system was completed, different measurements were made and the results analyzed. according to the results, it can be stated that the whole system worked well since they are identical to reality. the bumps in the road were clearly visible on the diagrams. it was concluded that the completed vibration data acquisition system is more than capable of detecting bumps in roads. the advantage of the system is that it can be easily mounted on any car which does not need to be driven at low speeds. keywords: road vehicle, vibration, data acquisition, microcontroller, accelerometer 1. introduction road vehicles are continuously subjected to vibrations which have very important and serious consequences. these vibrations should be dampened as they have a detrimental effect on both mechanical properties and vehicle occupants. vibrations can significantly reduce the lifetime of mechanical and electrical components. the effects of degradation are greatly increased if the frequency of the vibration is identical to that of a component. these resonances cause health issues for passengers in the car, e.g. back pain is a frequent complaint. vibrational frequencies of between 4 and 8 hz are the most dangerous for the human body [1]. such vibrations can be caused by poor road surfaces and the engine of a car. the former reason is more significant, so this issue will be tackled. due to the important role of vibrations that can occur in road vehicles, it is important to know the condition and characteristics of a road network. in hungary, the measurement of road quality is based almost exclusively on visual observations and manual data recording. inspectors observe the roads and record any defects in a database. even though hardly any automated survey equipment is used, these vehicles have the advantage of faster assessment and more objective evaluation. the purchase of one of these automated measurement systems could cost hundreds of millions of hungar*correspondence: nagy.roland@mk.uni-pannon.hu ian forints [2]. our goal is to design and build a vibration data acquisition system that can be used on road vehicles. the system should easily be mountable on any vehicle and measurements recorded at any speed. the system should be simple, but the measurement results must contain information about the quality of the road section [3]. 2. experimental 2.1 tools of implementation first, a design analysis was carried out and the structure of the system designed accordingly. a compact and light design is important, moreover, the housing should be sufficiently massive. reliability and a constant sampling rate are also crucial. a block diagram of the system is shown in fig. 1. the system is based on an atmega328p microcontroller. the device is optimal for the control task as it supports several communication standards to connect the units to each other as well as possesses an inner a/d converter, pwm channels and several digital pins. the main microcontroller is responsible for managing communication between the individual units and handles the input data. a 16 mhz external oscillator ic is necessary to generate the clock signal and the supply voltage has to be stabilized at 5 v. as the microcontroller possesses a watchdog timer, a reset button is unnecessary. along https://doi.org/10.33927/hjic-2020-11 mailto:nagy.roland@mk.uni-pannon.hu 72 nagy and szalai figure 1: the structure of the system with it, due to stable and robust operation, a pull-up resistor was placed in connection with the microcontroller’s reset pin. in addition, an ftdi connector is placed near the microcontroller which enables it to be programmed in the programming language c++. the wiring diagram of the atmega328p microcontroller is shown in fig. 2. vibrations caused by road defects were detected by a 805m1-0020 piezoelectric accelerometer. the sensitivity of the sensor is 100 mv/g with an offset voltage of 2.5 v. previous studies suggest that accelerations of up to 2 g are expected, and because the analog-to-digital converter has a measuring range of 0 − 5 v, a voltage gain of approximately 16 db was necessary to ensure the analog signal fill the measuring range. for this purpose, an ina128p instrumentation amplifier was used, where the voltage gain was determined by the external resistor rg between pins 1 and 8. the measuring amplifier amplified the potential difference between the two inputs. in this case, due to the 2.5 v offset voltage of the acceleration sensor, a voltage reference ic that provided 2.5 v was used. this voltage reference was connected to the figure 2: a wiring diagram of the atmega328p microcontroller figure 3: a wiring diagram of the amplifier section inverter input of the amplifier, which caused the amplification to change linearly under different accelerations. an ad580 voltage reference ic was used. the output of the instrumentation amplifier is referred to as the output reference terminal. with 2.5 v connected to this pin, the offset voltage of the analog signal was in the middle of the measuring range. a wiring diagram of the amplifying section is shown in fig. 3. following the amplifying section, the analog signal was digitized. due to the increase in resolution, the voltage resolution was 5000/4096, therefore, a change in voltage of 1.22 mv was detected instead of the previous 5 mv. the max186 is a successive-approximation converter with 8-channel single-ended or 4-channel differential inputs. the single-ended input mode was used, so the input signal voltages are referred to as agnd. it should be noted that the device worked in unipolar mode, therefore, an analog input signal of between 0 v and vref could be converted. vref was 5 v in our application [4]. firstly, in terms of programming the max186 process, the parameters were set with the first 8 input bits. these bits were expected to shift synchronously with the clock signal. once set up, the bits of digitized signal could be read out. the read-out process consisted of a 12times repetitive ‘for cycle’, which reads out the digitized value bit by bit. it can be seen that the microcontroller obtains the value of the most significant bit (msb) first. all the input bits have to shift left and must connect to each other with a logical or connection to yield the original measurement of the accelerometer. eventually, the conversion process ends with the a/d converter chip select pin level changing to logic high. a wiring diagram of the max186 is shown in fig. 4. in addition to the accelerations, the gps coordinates were also collected to help identify road humps and potholes that were detected by the accelerometer. for this task, a neo-6m gps module was used that provides momentary velocity and altitude data in addition to longitudinal and latitudinal coordinates. to control this gps module, another atmega microcontroller was installed which was necessary as a debugging process associated with the gps communication was present. its purpose was to verify the adequacy of the data and the connection with the satellites. as a result, the running time and sampling rate of the program cycle became quite slow. hungarian journal of industry and chemistry design and construction of a vibration data acquisition system 73 figure 4: a wiring diagram of the analog-to-digital converter following the installation of a second microcontroller, the program could be run synchronously, which a single atmega328p microcontroller would have been unable to do. as a result, the main microcontroller could be defined as the master and the controller that controls the gps as the slave. the gps unit communicated with the slave controller by using a standard universal asynchronous receiver-transmitter (uart). the two microcontrollers were connected by a bus system, using the i2c protocol which could only handle 8 bits of data in one cycle that corresponded to a number between 0 and 255 in the decimal system. as the gps coordinates had to be transferred, which were 16 bits long in the binary system, these needed to be converted into 3 bit arrays that each contained 8 bits of data. the c++ program of the slave controller handled these numbers in the binary system. first, it executed the right shift by a 16bit command, which was followed by the bitwise and command, masked by 0xff, the hexadecimal number ff. in this way, the first array was obtained, followed by the second array with a right shift using an 8-bit command and finally the last array by masking only. no conversion was needed for data concerning speed and elevation, because these values were only 8 bits long. the master controller decoded the input arrays to the original 16-bitlong data. the data from the first input array had to left shift by 8 bits then perform a bitwise or operation using the 8 bits of the following array to yield the original 16-bit-long data. therefore, the gps data from the slave controller immediately became available, resulting in a much faster sampling frequency. figure 5: a wiring diagram of the power supply unit throughout the measurement process, the acceleration and gps data were collected on an sd card using an arm-mcu sd card module slot socket reader, which communicated with the master controller by applying a standard spi interface. the master controller’s c++ program specified the sampling frequency of the accelerometer, i.e. 60 hz, but is only suitable up to 30 hz according to shannon’s law. the power supply of the system was provided by its own integrated power supply. a maximum of 35 v could be connected to the power input connection of the power supply, thus, the system could be connected to the car’s cigarette lighter. a nee 78h05asc voltage regulator converted 5 v from the input voltage. as ±12 v needed to be supplied to the instrumentation amplifier, an ad941 dc-dc converter was used to convert 5 v into ±12 v. furthermore, 5 v was available from the output of the power supply unit to supply the microcontrollers, other units and sensors. a wiring diagram of the power supply unit is shown in fig. 5. 2.2 construction of the system after designing the system and circuit diagrams, a printed circuit board was planned. given the complexity of the panels, a double-sided pcb was designed. all of the integrated circuits (ics) were used with the housing of the dual inline package (dip). the design rules were set for a cnc machine as the pcbs were handled using an engraving needle. the width of the wiring track was 0.9 mm at 5 v and 1.3 mm at 12 v. the clearance between the wiring tracks and solder pads was 1 mm and 0.4 mm, respectively. by taking into account insulation against electrical noise, larger copper surfaces were left on both sides of the pcb and placed on ground potential. the pcb was designed using eagle cad software. after the design process, the cam programs were generated from cad files. pcb panels were made by an isel icp 4030 3-axes cnc-milling machine. all parts of the system were placed in an ip-protection box. two switches were placed on one side of the box, enabling the 48(1) pp. 71–75 (2020) 74 nagy and szalai figure 6: the completed data acquisition system system to be turned on and the data acquisition process started. the complete system is shown in fig. 6. to check the output signal waveform in the relevant frequency bandwidth, a frequency response function of the amplifier unit was applied. the input signal was in the form of a sine wave within the frequency bandwidth of 10 hz to 3 mhz with an amplitude of 40 mv. the data obtained is shown in fig. 7. the natural frequency was approximately 700 khz, so the frequency response function of the system performed well in the relevant frequency bandwidth. furthermore, amplification of the instrumentation amplifier was checked. the frequency of the input signal was 5 hz with an amplitude of 400 mvpp and an offset voltage of 2.5 v. the amplification factor was set at 6.5 v/v. the data obtained is shown in fig. 8. by plotting the data, the difference between the amplified and original signals can be seen. the waveform of the amplified signal was unchanged and by reading the amplitudes it can be seen that the voltage gain (g) was preset to 6.5 v/v. 3. results and analysis following inspections, the sensor was placed in a car and fixed to the rear control arm to avoid the presence of any damping object between the wheel and sensor [5]. after figure 7: the frequency response function of the amplifier unit, where ω0 = 1 hz figure 8: the amplified and original output signals at 5 hz installing the data acquisition system, several measurements were carried out by vehicle-to-record data on different road surfaces. the results of the measurements are as follows: the first measurement was taken in the vicinity of zalaegerszeg on a 5.5 km stretch of road. the data was saved on an sd card as a txt file and plotted. the gps coordinates helped to analyze the data, through which the exact location of each acceleration value was determined. the voltage gain was set at 16 db (6.5 v/v) [6] and the data from the accelerometer was visible on the diagram without amplification. from the first route, whilst driving in a populated area at the beginning of the measurement period, it can be concluded that the quality of the road surface was generally good with only a few significant potholes and cracks. later, while leaving the town, the poorer quality of the road became immediately obvious given the increase in amplitudes. the road surface consisted of flange grooves and creases. according to the diagram, road defects continued to increase since the highest accelerations occurred towards the end of the measurement period. the acceleration data from the first measurement period is shown in fig. 9. the conditions of the second set of measurements were the same as those of the first. the initial section of this measurement period was identical to that of the first set of measurements (fig. 10). the quality of the road surface was initially quite good as only accelerations of 1 g were recorded, but after leaving the populated area, the quality of the road surface also deteriorated. at the end of the route, several wearing courses, bonding layers and spotting errors were identified on the road surface. the third stretch of road was 3 km long. compared to the other measurements, the quality of the road surface here, which was covered in potholes, patches and surface sinks, was the worst. consequently, in fig. 11, almost all the accelerations reached the limit of 1 g, moreover, for a moment, accelerations of 2 g were also recorded. the right side of the diagram shows that when arriving in a populated area, the amplitudes reduced significantly as the quality of the road substantially improved. only minor cracks were visible on the surface. a small degree of asymmetry can be observed in the graphs, which is caused by the car’s shock absorbers. as hungarian journal of industry and chemistry design and construction of a vibration data acquisition system 75 figure 9: the acceleration of the first set of measurements plotted as a function of time figure 10: the acceleration of the second set of measurements plotted as a function of time figure 11: the acceleration of the third set of measurements plotted as a function of time the damping force of the shock absorbers is less in the negative direction, higher accelerations might occur than in the positive direction. this is also supported by the characteristics of the shock absorbers. 4. conclusion the aim of our research was to design, build and program a vibration data acquisition system suitable for measuring the quality of a motor vehicle. this task involved numerous requirements: the measuring system had to function reliably, withstand the car’s load and be easily installed, moreover, the data had to be produced and recorded as required. in the light of the results, the system worked well; it detected road defects as expected. after measurements were taken, the data was illustrated in charts and the results were identical. the poorest road surface could be detected by the largest amplitudes and was identified according to the gps coordinates when each measurement was made. the advantages of the system are that it can be easily mounted on any model of car and does not require driving at low speeds. acknowledgements this research was supported by the european union and co-financed by the european social fund under the project efop-3.6.2-16-2017-00002. references [1] souissi, h.; hamaoui, a.: effect of human exposure to whole-body vibration in transport, neuroergonomics, 2018, 229 doi: 10.1016/b978-0-12811926-6.00049-x [2] szántó, m.: közúti adatbázisok valós idejű frissítése közösségi megoldás alkalmazásával, útügyi lapok, 2017, 5(1), 13-19 http://utugyilapok.hu/ wp-content/uploads/2017/06/ul_5_c2_szm.pdf [3] brown, j. c.; robertson, a. j.; serpento, s. t.: motor vehicle structures (butterworth-heinemann) 2001, 4–84 isbn: 978-0-7506-5134-9 [4] william, b.: programmable logic controllers, (elsevier books) 2015 isbn 01-28-0-2929-3 [5] bidgoli, m. a.; golroo, a.; nadjar, h. s.; rashidabad, a. g.; ganji, m. r.: road roughness measurement using a cost-effective sensor-based monitoring system, automat. constr., 2019, 104, 140–152 doi: 10.1016/j.autcon.2019.04.007 [6] kennedy, j.; oakley, c.; sumon, s.; parry, i.; wilkinson, e.; brown, j.: impact of road humps on vehicles and their occupants, trl report, 2004, 614, 3–16 https://trl.co.uk/sites/default/files/ trl614%281%29.pdf 48(1) pp. 71–75 (2020) https://doi.org/10.1016/b978-0-12-811926-6.00049-x https://doi.org/10.1016/b978-0-12-811926-6.00049-x http://utugyilapok.hu/wp-content/uploads/2017/06/ul_5_c2_szm.pdf http://utugyilapok.hu/wp-content/uploads/2017/06/ul_5_c2_szm.pdf https://doi.org/10.1016/j.autcon.2019.04.007 https://doi.org/10.1016/j.autcon.2019.04.007 https://trl.co.uk/sites/default/files/trl614%281%29.pdf https://trl.co.uk/sites/default/files/trl614%281%29.pdf introduction experimental tools of implementation construction of the system results and analysis conclusion hungar~journal of industrial chemistry veszprem vol. 29. pp. 113-117 (2001) optimization of pipeline network for oil transport a. jokic andz. zavargo (faculty oftechnolgy, university ofnovi sad, bul caralazara 1, 21000 novi sad, yu) received: june 18,2001 in this work the pipeline network for oil transport has been optimized. the network layout has already been given, the flow rates are specified and the inlet and outlet pressures are defined. the capital cost of such a network has been minimized. from many feasible combinations of section diameter distributions the aim was to find the optimal one. the problem has been solved by applying nonlinear programming. keywords: pipeline network, oil transport, capital cost, optimization, nonlinear programming introduction the total head loss is h =a~l+l£ l 2g d (1) (2) there are many works dealing with the solution of fluid network problems [1-3, 6, 8, 9]. there are also numerous algorithms for pipeline network optimization by minimizing some cost functions [6, 4]. the network which has to be optimized is the network for oil transport (fig.l). the network consists of nodes, sections and paths. a pipe section is a pipeline with a constant diameter and no branching. a node is defined as the branching point or the point of inlet or outlet from the section. finally, a path is defined as the sequence of pipe sections between an inlet (source) and outlet (consumer) from the network. thus, each section has two nodes, one at each end. each path has at least one section. the configuration of the network is given so are the flows through each section as well as the inlet and outlets pressures. while the inlet and outlet pressures are fixed, the other node pressures are unknown and subject to change via d. this problem has many feasible solutions. the goal was to find that one which minimizes the capital cost. where a is the darcy friction factor, while l and le are pipe length and equivalent length respectively. for a long distance pipeline the effect of le can be neglected. for hydraulically smooth pipes the friction factor depends only on reynolds number. in that case blasius correlation [5] can be used a. =0.3164re-0 ' 25 combining eq. ( 1) and (2) with continuity equation 4q v= dk (3) (4) it follows for the case when blasius eq. (3) can be used kd-4·15 :::; -ap -i::jjpg pipe section flow where the oil that flows through the network can be k = 0.242qt75 p 0 · 75 p 0·25 l considered as isothermal and incompressible. as the network is in the ground the temperature variances are and l1p = p2p1: &1. = h2h1. negligible. having in mind that the section diameter is constant, the section velocity is also constant. the bernoulli equation for each pipe section in that case is (5) (6) 114 node 1 2 3 4 5 6 7 8 9 10 11 12 13 table 1 pipeline network nodes data h[m] 942 p[kpa].l0-5 147.1 unknown unknown unknown 4.9 unknown 4.9 4.9 unknown unknown unknown 4.9 4.9 most of the pipes in the engineering practice have rough boundaries. in that case the equation of altshul [5] can be used { 68 ) 0 · 25 a= 0.1 .e_+d re (7) where e is the pipe surface roughnes. in this case the d cannot be explicitly expressed as it can be in blasius eq. (3). the eqs. (5) and (6) have now the following form k* n-s = -ap-mpg (8) (9) note that k isn't a true constant because it depends on d,. since a depends on d. pipe cost function the weight per unit length of the pipe is assumed to be an exponential function of the diameter w=adp (10) the total weight of the pipe section will be wl [kg] and the price of such a pipe can be easily calculated knowing the price of the pipe per unit weight. it is a well knov..n fact that the ratio &d (pipe wall thickness/pipe diameter) depends upon pressure. eq. (10) is usually correlated with a given pressure (pcorr)· in the case of a pipe network it is usually a maximum expected pressure in the network. the higher pressure demands larger q and consequently a larger weight of the pipe. when the pressure in the pipe (p) differs from pressure (pcorr) for which eq. ( 10) was correlated, the following relation is proposed [7]. {11) table 2 pipeline network sections data section input, output node l[m] q[m3s-l] sl 1,2 12,000 1.2688 s2 2,3 18,000 1.2688 s3 3,4 150,000 1.2688 s4 4,5 5,000 0.2985 s5 4,6 110,000 0.4478 s6 6,7 65,000 0.0746 s7 6,8 5,000 0.3732 s8 4,9 141,000 0.5224 s9 9,10 5,000 0.1866 slo 9,11 161,000 0.3358 s11 11,12 5,000 0.1119 s12 11,13 85,000 0.2239 pipe network optimization for a pipe network that consists of n pipe section there is ann eqs.(8) i =l,n (12) with 2n unknown variables (di and l1pi). to reduce the number of the equations as well as the number of the unknown variables the alternative system of equations can be formulated. for each path we have ±k;di-4.75:=.-i)mj,-llh;pg)=apj-mzjpg j=l,m (13) i=l i=l where k corresponds to the number of the section that belongs to path j, while m represents the number of paths. in such a way the unknown pressure drops l1pt are excluded recall that the paths pressure drops jj.pj, from the source to the sink, are fixed. the capital cost function which has to be minimized is n n n wn = l ~l1 == laltdf == l.cidf i=l i=l i=l· (14) by introducing new variables into the eqs.(l3) and (14), in the case when blasisus relation can be used, i= l,n we have the following nonlinear cost function (min) wn = i cix;n·ztosp i=l subject to linear constrains k ~ k.x. = t}.p. ah .p,ru .l.j ll j jo i=l where ci = ali. j=l,m (15) (16) (17) for rough pipes the following variables are introduced i=l,n {18) eqs. (14) and(l3) are now path p1 p2 p3 p4 p5 p6 table 3 pipeline network paths data sections s1,s2,s3,s8,sl0,sl2 s1,s2,s3,s8,s10,s11 s1,s2,s3,s8,s9 s1,s2,s3,s4 s1,s2,s3,s5,s6 s 1 ,s2,s3 ,s5 ,s7 3 input, output node 1,13 1,12 1,10 1,5 1,7 1,8 fig. i pipeline network layout n (min)wn = lci(x;)-02 tl i=l subject to 14.22 14.22 14.22 14.22 14.22 14.22 (19) table 4 initial values for smooth pipes section s1 s2 s3 s4 s5 s6 s7 s8 s9 s10 sll sl2 d[m] 1.0 1.0 1.0 0.3 0.6 0.5 0.4 0.7 0.3 0.7 0.3 0.6 k 10'6 0.463 0.694 5.782 0.015 0.685 0.018 0.023 1.150 0.007 0.606 0.003 0.157 table 5 optimization results for smooth pipes section sl s2 s3 s4 s5 s6 s7 s8 s9 slo sll s12 d[m] 1.025 1.025 1.025 0.268 0.624 0.393 0.414 0.790 0.255 0.706 0.272 0.638 115 (20) are: a= 1412.15 and f3 =2. the initial guess values f0r d as well as k are given in table 4 while the optimization results are presented in table 5. experimental the layout of the pipeline network for oil transport is shown in fig.l. the data necessary for the calculations are given in tables 1, 2 and 3 [7]. hydraulically smooth pipes for such systems the linear constrains are eqs. ( 17) ktxt + k2x 2 + k3x3 + k8:xg + k10x10 + k12x12 = 14,220,000 klxl + k 2x 2 + k 3x3 + k 8x8 + k10x10 + k 11xu = 14,220,000 ktxt + k2x2 + k3~ + k8:xg + k9~ = 14,220,000 (21) k1x1 + kzx2 + k3~ + k4x4 = 14,220,000 ktxt + kzx2 + k3xs + k5x5 + k6x6 = 14,220,000 ktxt + kzx2 + k3x3 + k5x5 + k1x., = 14,220,000 and the objective function is n (min) wn = l cix-:2105 p i=l thus we have a nonlinear objective function with linear constrains. eq. ( 11) has been correlated for pr:orr = 159.105 [pa] and the obtained values for coefficients pipes with rough boundaries in this case the linear constrains are given by eqs. ('2(}} k~x; + k;x; + k;x; + k;x; + k~0x;0 + k;2x:z = 14,220,000 k; x; + k;x; + k;x; + k;_x; + k1~x:0 + k;1x:1 = 14.220.000 k; x~ + k;x; + k;x; + k;x; + k;x; = 14,220,000 (22) k; x; + k;x; + k;x; + k;x; = 14,220,000 k~x; + k;x; + k;x; + k;x; + k;x; = 14,220.000 k;x; + k;x; + k;x; + k;x; + k;x; = 14.220,000 with the following objective function (min) wn = !c;(x)-c.lp i=l the initial guess values for d and k"" are presented in table 6 while the optimization results are given in table 7. the value for £ :::: 0.2 is taken from literaure [llj. since k* values depend on d (see eqs. 9 and 7) the optimization results cannot be achieved in one step. this means that on the base of the first optimum d values we have to recalculate k* values and repeat the optimization procedure. as it can be seen (table 5 and table 6 initial valurs for rough pipes 116 section d[m] k*jo-6 s1 1 0.464 s2 1 0.696 s3 1 5.803 s4 0.268 0.011 s5 0.62 0.613 s6 0.47 0.015 s7 0.5 0.019 s8 0.79 1.085 s9 0.26 0.005 s10 0.72 0.560 sll 0.3 0.021 s12 0.7 0.144 table 7) the optimization results are practically the same as in the case of smooth pipes. conclusion in this work the capital cost of pipeline network for oil transport has been minimized. the configuration of the network was fixed, so were the flow rates through each section as well as the pressure drops in each path. the fluid that flows through the network assumed to be isothermal and incompressible. the objective function which has to be minimized was the equation for the weight of the pipeline network as the function of section diameter d, while the constrains were equations for the pressure drop for each path. diameter d of each section has been adjusted in sucl~ a way that it could give a minimum weight under the given constrains. the originally nonlinear constrains, with respect to d, were linearized introducing new variables. the objective function remains nonlinear .. the linearly constrained nonlinear objective function has been solved by nonlinear programming. two relations for darcy friction factor a, have been used. blasius formula for hydraulically smooth pipes, eq. (3), and altshul correlation for rough pipes, eq. (7). in the latter, due to the fact that a. is function of d and k is function of a., k has to be recalculated in each step of the procedure. symbols c coefficient in eq. ( 16) d pipe diameter, m g acceleration due to gravity, kgm-2 h height~ m llh height difference\ m hl head loss~ m .index. for pipe network sections j index. for pipe network paths lc number of sections in a given path l node height, m l~ equivalent height, m table 7 optimization results for rough pipes section s1 s2 s3 s4 s5 s6 s7 s8 s9 s10 sll s12 d[m] 1.025 1.025 1.025 0.268 0.624 0.393 0.414 0.79 0.255 0.706 0.272 0.638 m number of pipe network paths n number of pipe network sections p pressure, kpa lip pressure drop, kpa k'io-6 0.467 0.701 5.838 0.011 0.614 0.014 0.018 1.085 0.005 0.557 0.020 0.141 pcorr pressure for which eq. ( 11) has been correlated, kpa q flow rate, m3s-1 re reynolds dimensionless number w weight per unit length, kgm-1 ws one section weight, kg wn whole network weight, kg x variable defined by eq. ( 15) x* variable defined by eq. (18) greek symbols a coefficient in eq. (10), kg /3 coefficient in eq. ( 10) 8 pipe wall thickness, m a. darcy friction factor abbreviations pl, p2, ... path 1, 2, ... sl, s2, ... section 1, 2, .. references 1. bending m. j. and hutchison h. p.: chem.engng.sci., 1973,28, 1851-1864 2. bullard l. g. and biegler l. t.: comput.chem.engng., 1991, 15,239-254 3. gay b. and middleton p.: chem.engn.sci., 1971, 26, 109-123 4. dragutinovic g.: m. s. thesis, faculty of technical science, novi sad, 1991 5. guliani b. b. and agaurwal c. p.: ptq, autumn 2(}()(), 129-131 6. murtagh b. a.: chem.engng.sci., 1972,27, 11211141 7. pejak m.: b.s. thesis, faculty of technology, novi sad.t 1979 8. preece p. e. and hwei chen ti: the chem,engng.j., 1989,40, 1-6 9. shacman m. and mah r. s. h.: comput.chem.engng., 1978, 2, 64-66 117 10. welty j. r., wicks e. e. and wilson r. e.: fundamentals of momentum, heat and mass transfer, john wiley & sons, new york, 210-211, 1976 11. sasic m.: b. s. thesis, faculty of mechanical science, beograd, 1990 page 116 page 117 page 118 page 119 page 120 hungarian journal of industrial chemistry veszprem vol. 30. pp. 275-280 (2002) surface properties and tissue compatibility of nh3-plasma modified pol yethylenterephtalat :membranes ernstitute of chemistry, gkss research centre, kantstrasse 55, d-145613 teltow, germany 2institute of chemical engineering, university ofveszprem, egyetem u. 10, h-8200 veszprem, hungary) received: october 14, 2002 microwave surface plasma treatment was used to improve the tissue compatibility of.polymeric me~branes. chang~s of surface properties, adhesion and spreading of human skin fibroblasts were studied on ammoma-plasr_na modtfied polyethylentetephtalat (pet) membranes. the variation of the microwave (mw)-plasr_na par~eters -_duration, f~ed-gas composition (ar/nh3) and microwave powercaused a significant change of t~e physicocheffilcal surface properties .. an enhanced cell-surface interaction was observed based on the number of adhenng fibroblasts, but also on morphological criteria including overall cell morphology. it was found that fibroblasts adsorbed better on plasma modified hydrophilic surfaces with a relatively high amine content than on the original membrane. keywords: nh3-plasma, surface functionalisation, wettability, tissue compatibility, cell morphology introduction polymeric membranes play a crucial role for the development of biohybrid organs in tissue engineering and also in biotechnological.applications. in addition to specific bulk characteristics like permeability and selectivity they must possess an excellent biocompatibility. substitutes for cell cultures have to support cell attachment and proliferation as well as to assure the delivery of nutrients and oxygen and the removal of metabolites [1, 2, 3]. there are several polymeric materials available for the production of synthetic membranes with diverse mechanical properties and permeation characteristic according to special needs, but most of them possess poor characteristics regarding to cellular interaction and function f4]. attachment, spreading, and proliferation of anchorage dependent cells are highly dependent on the physicochemical properties of the biomaterial surface [5]. several authors have already reported on enhanced cell adhesion on hydrophilic surfaces [1, 6, 7]. the presence of certain functional groups (eg. amines) [8, 9], or immobilised adhesive proteins [10], surface charge [11], and morphology [12] were also found to regulate cell adhesion. a number of physical and chemical techniques have already been applied for the modification of the topmost layer of polymeric materials ranging from methods of contact information: e-mail: thomas.weigel@gkss.de conventional wet chemistry to novel methods of plasma chemistry [13]. in the last decade techniques using electromagnetic irradiation to induce chemical reactions are getting even more frequent. such methods like plasma treatment, plasma polymerisation, and ion irradiation, are very attractive, and favourable in modifying samples with a chemically resistive surface or complex shape [6, 14, 15]. if a surface is exposed to a non-polymer forming plasma reactive plasma-species interact with the polymer surfaces and new functional groups are formed. as a result, such impl.antation reactions lead to remarkable changes of physical and chemical surface properties, and are frequently used to improve adhesion properties and wettability. ammonia plasma treatment of polymeric. s.urfaces leads to . the incorporation of nitrogen contatmng groups amme, amide, imin etc. resulting a hydrophilic surface and supports cell adhesion and growth [9, 16, 17]. in frames of our present work polyethylene­ terephtalate (pet) track-etched membrane~ were modified by low-temperature nh3-plasma to tmprove the ceu adhesive properties. polyesters are widely used in the biomedical praxis for catheters) vascular grafts {15] or for joint protheses {18]. because of the relatively low production costs, mechanical properties. uniform pore size distribution track--etch~ pet -me~bra~s could be very attractive for tissue engmeermg applications such as the production of biohybrid organs. we investigated the influence of different process 276 parameters on the amine concentration of polyester surfaces. samples having the highest amine concentration were further characterised by means of x­ ray photoelectron spectroscopy (xps), and fluorescence labelling. the wettability of samples chosen for biocompatibility tests was also investigated by water-air contact angle (captive bubble) measurements. biocompatibility was evaluated by studying adhesion and proliferation of human skin fibroblasts on modified pet surfaces. cell adhesion was further characterised studying the overall cell morphology of adhering cells. methods and materials pet-membrane pet track-etched microfiltration membranes with an effective thickness of 20 f.!m and nominal pore diameter of 1 f.!m were purchased from oxyphem (groj3erkmannsdorf, germany). all membranes were cleaned ultrasonically for 5 min in pure ethanol bath and dried in an exsiccator for 15 min before every treatment. mw-plasma treatment the plasma treatment was performed in a flow type cylindrical mw -plasma reactor operating at 2.45 ghz (modified plaslan 500, je plasmaconsult, wuppertal, germany) [19]. samples were placed in the post discharge region, 6 em downstream from the plasma chamber. the reactor was evacuated down to the base pressure of 1 o-3 bar for 10 minutes, followed by a purge with ar for 10 other minutes. the flow rate of the arinhrmixture was then adjusted and the plasma ignited. surface chemical characterisation the chemical composition of the sample surfaces was determined by x-ray photoelectron spectroscopy (xps) [20]. the total amine (primary, secondary. and ternary) concentration of surfaces was determined by colorimetric staining with acid orange ii (ao) [21] and primary amines were labelled with fluram® to obtain relative concentrations [22]. surface physical characterisation wettability was determined by water air contact angle measurements using the captive bubble meth<xi as described elsewhere {3j pore size distribution of pet­ micro--filtration membranes was characterized by bubble point technique using a coulter porometer ii (beckman & coulter electronics. uk) and porofil (coulter) as displacement liquid [3]. -.--------· ...-----···---... , ....... "-·--····~····--... ······--·----~---··;·--····---···-·-·--:-·--·~-··-···--·--: 20 40 60 com]losition of process gases (vol% nh3) 80 100 fig .i the int1uence of process gas composition on amine concentration. samples were treated for 60 seconds. + pmw:::: 1.2 kw; + pmw:::: 0.8 kw; ~ pmw= 0.4kw tissue compatibility human skin fibroblasts were obtained from cell lining gmbh, (berlin, germany) and used up to the ninth passage. cells were cultivated in dulbecco's modified eagle medium (dmem) containing l 0 % fetal bovine serum (fbs; sigma, taufenkirchen, germany) in a humidified incubator with 5 % c02 at 37.5 °c. samples with a diameter of 13 mm were placed in 24-well tissue culture plates a cell suspension with 2.5xl04 cells/ml was filled into each well, and the samples were incubated at 37 oc for times indicated. for the quantitative determination of cell proliferation ldh (lactate dehydrogenase, boehringer mannheim, penzberg, germany) tests were carried out, using the commercial pet as reference material. to accomplish biocompatibility studies overall cell morphology was studied by vital staining with fluorescein diacetate (fda) (sigma). 5 pl fda stock solution (5 mg fda dissolved in 1 m1 acetone) was added to the samples with cells and incubated for 2 min at 37 °c, then the samples were washed twice with phosphate-buffered saline (pbs) fixed on a microscope slide and observed by a confocal laser scanning microscope lsm 510 (carl zeiss, jena, germany) with an excitation at 440 .. .480 nm and emission at max. 520nm. results and discussion surface chemical characterisation treatment time and chemical composition of the plasma are the most important factors to determine the result of plasma processes [6, 14]. first the effect of process gas table 1 chemical composition of samples obtained by colorimetric staining, fluorescent labelling and xps. pet1 was treated with nh3:ar (1:5) plasma, at a mw-power of 0.4 kw for 600 sec; pet2 with pure nh3-plasma, at a mw­ power of 0.8 kw for 420 sec; pet3 with nh3-plasma at a mw power of 1.2 kw, for 240 sec c 0 n c . c . * camind cp-umind cp-amind unum: p-umme n n camine sample pet petj pet2 pet3 ccat% nmol/ . 2 rel mt. em 72.1 27.9 85.0 13.6 1.4 14.2 135.1 85.8 12.3 1.9 15.7 100.8 84.9 11.5 3.6 15.7 81.5 10.1 96.4 9.5 8.3 53.1 6.4 4.4 22.6 5.2 * p-amine contents obtained by fluorescent labelling are only relative values 18 16 ~ 14 ~ 0 e 12 ..s 2 0 oto 0 200 400 600 800 treatment time (sec) 1000 fig.2 effect oftreatment time on amine concentration ofnh3 treated pet-membrane surfaces. process parameters were + pmw= 1.2 kw; tvnh3= 300 seem+ pmw= 0.8 kw; %rn3= 300 seem and a pmw= 0.4 kw; 41nid= 50 seem <i>ar= 250 seem respectively. deviation within 10% composition on the amine concentration of the polymer surface was studied. it was observed that at high mw­ power (1.2 kw) the amine concentration increased proportionally to the nh3 content in the process gas. the highest concentration was reached using a pure nhrplasma. in this case the coupled energy was high enough to assure an appropriate ion density and energy of the reactive gas ammonia, in the plasma. on the contrary at low (0.4 kw) energies when plasma was operated with pure ammonia the coupled energy might not have been enough for an adequate ionisation of the reactive gas, indicated by the relatively low amine concentrations obtained. the mixing of 160 °0 -0 140 ·;; & 120 .s = .s ~ -~ 80 q.l ~ 60 t,, ~ 40 ~ = ~ 20 0 -'----o-t·. 0 r-oo .. ,..."~--.. -277 420 440 460 480 500 520 540 560 580 600 emission wavelength (nm) fig.3 fluorescence emission spectra of plasma modified pet membranes with fluram® labelling of primary amines (excitation at 335 nm, emission at 467 nm) argon to the process gas up to 80 % promoted the implantation of amine functionalities possibly resulted by a higher ion density in the plasma (fig. i). treatment time dependency of amine concentration is depicted in fig.2. already after a short treatment amine groups were incorporated in the samples, and parallel with a longer treatment time an increase of the amine concentration was observed. it is clearly shown that iitespective of the plasma composition (mw­ power, and process gas composition) a maximum (15 ± 0.8 nm/cm2 ) concentration was reached. thisc occurred however earlier when samples were treated with high energetic plasma (1.2 kw) containing more high energetic reactive species than modified al "milder" conditions (0.4 kw). nevertheless a further increase of the treatment time led to a loss of amine functionalities. surface modification by low-pressure plasma can be described as a dynamic equilibrium 1.)f competing functionalisation and degradation processc:~ [14]. our results indicate that after a longer treatmem surface degradation, while in the initial phase implantation was predominant. samples (petl, pet2 and pet3) treated under different plasma conditions having a relatively high amine concentration were further characterised regarding their primary amine content (fig.3) and elemental composition. the highest p-amine concentration was found on sample pet l, modified at 0.4 kw whereas treatments at higher energies led to a considerably lower p-amine content (table 1). results of xps-measurements are shown in table 1 ° after exposure to high energetic plasma a relativel~ high amount of nitrogen was found on pet3 (3.6 at%) and only 1.4 at% on sample petl (table/). oxygen abstraction was also observed. the total oxygen content decreased drastically in all cases. from 28 at% of the m1treated sample it was reduced to i 1.4 at% on pet3 and to 13.6 at% on petl. it is well known when ammonia is exposed to a plasma. fragmentation, ionisation, excitation and radical 278 70 60 ·~50 q; ~ ~ 40 t:>j) = <n t 30 .a = 0 u 20 10 0 oreceeding. !;lhysteresis pet petl pet2 pet3 pet4 fig.4 contact angle measurement of untreated pet, and samples peti, pet2 pet3, and pet4 (pet4 was exposed to the same plasma as petl, treated however only for 300 sec and had an amine concentration of9.45 nmollcm2 ). deviation was ±2.5 o generation occurs. in general the fragmentation; ion density and energy of heavy ions is higher at higher energy input than at lower energies. as a consequence a variety of nitrogen containing groups could form depending on process parameters [23]. the higher p­ amine concentration on pet 1 could be described by the lower fragmentation of ammonia which means that more nh3 +, nh:t or nh2 * were available in the plasma, thus the possibility to form -nh2 functionality was also higher in contrast with pet3. also the differences in plasma composition and ion energy could explain the observation that though amine concentrations were almost the same nitrogen content of pet3~ and pet2 was higher than that of pet 1. this means as indicated also from results presented in table 1 that a bigger part of nitrogen was involved to form n-containing groups other than amines on pet2 and pet3 than on petl. suiface physical characterisation fig.4 shows results of water contact-angle measurements of plain pet and differently modified membranes chosen for biocompatibility tests (pet 1-4). it is dearly shown that the functional groups introduced by plasma treatment increased the wettability of the surfaces. sample petl were found to be the most hydrophilic than the other samples. but the differences in contact angles between modified ones were only marginaj. these results correlated with the results obtained from xps and colorimetric measurements. despite of the same amine concentration measured on 3 ,••o•'~ .. •••nu..,._ouooooooo .. oouun••-•<oooooo .. .,.u .. ooo·-·•--"'•--••'''-'"''''' .. ..._..'~"''u-~~.._...-.. ,,_,~•-~1 •lduy 03day q6day ~ e. 1,5 . 0,5 pet petl pet2 pet3 pet4 fig.5 cell proliferation of human fibroblasts adsorbed on plain pet and plasma modified pet-membranes. results obtained by ldh-test petl-3, the degradation of surface polymer and the loss of oxygen of pet2 and pet3 was higher, what could explain the observed deviation in wettability. pet4 was the most hydrophobic of all modified samples. there were no considerable differences in contact angle­ hysteresis between the modified polymers, however there is a slight difference in comparison to the unmodified membrane. this could be explained by a change of roughness and/or by the heterogeneity of the samples [7]. no significant changes in permeation characteristics were observed after membrane characterisation. for the unmodified membrane the nrflux obtained was 7247 m3/hm2bar, the average pore size diameter (d(50)) 1.4 ~m. and the cut-off (d(loo)) 1.51 ~m, while for pet3 7338 m31hm2bar, 1.37 ~m, and 1.51 jlm respectively. cell proliferation metabolic activity and growth of adhering fibroblasts on plain and differently modified pet membranes were evaluated over a cultivation period of 6 days by ldh­ assay. shown in fig.s. in early cultures the number of adhered cells on modified membranes was only slightly higher than on plain pet. after 6 days however this effect became significant (p < 0.05), while no significant difference were observed between the differently modified membranes (petl-4) over the entire cultivation period. the improved cell adhesivity of ammonia plasma modified membranes can be explained due to their hydrophilic character and the presence of nitrogen-containing functional groups [24]. cell morphology to supplement studies on cell proliferation, investigations studying the morphology of adhering fig.6 overall cell morphology of fibroblasts adhering on plain pet (a, b) and pet3 (c, d) membranes; 4 h of cultivation (a, c), 24 h of cultivation (b, d) fibroblasts were carried out. for cells from connective tissue extensive cell spreading on the foreign substrata indicates generally good cell-contacting properties, while rounding up of cells is a sign of weak cell­ material interaction, which could be followed by cell death [1]. overall cell morphology was studied by staining with fda after 4h and 24 h of cell contact with the surface. pictures obtained from plasma modified membranes were very similar thus we present only pictures made from pet3. a higher cell density was observed on modified surfaces, compared to plain pet. furthermore after 4h cultivation the attached cells on the unmodified pet -surfaces were mostly round and only some spread. on the contrary better fibroblast adhesion and spreading was seen on modified surfaces where many cells were flattened and spread (fig.6/a,c). after 24 h cells were spread on both plain pet and modified pet surfaces showing typical fibroblast like morphology. the higher density of fibroblasts however was obvious on pet3 (fig.6/b,d). conclusions polyethyleneterephtalat membranes were modified by low temperature ammonia plasma with the objective to ~ouple amine functional-groups on the surface and to improve their biocompatibility. it was shown that nh3plasma treatment can be effectively used to change the chemical and physical properties of pet membranes. amine functionalities were coupled onto the membrane surfaces and a saturated stage seemed to exist. in this case the amine concentration was almost the same for all samples but the maximum was reached earlier for high energetic plasma. a high variety of n-containing functional groups were formed above all on pet3 as a result of fragmentation of ammonia caused by high 279 plasma energy. all modified membranes become hydrophilic due to the presence of amine groups and wettability seemed to correlate with the primary amine content. permeation characteristics remained unchanged after membranes were exposed to the plasma. cell proliferation on plasma treated surfaces was almost 125 % of the original membrane after 6 day of cultivation. in the initial stage of attachment more intensive cell spreading was also observed on modified membranes. hence modified membranes provide better starting conditions for the immobilisation of cells and could be also easily modified by simple wet chemistry. on the other hand based on quantitative and qualitative measurements we presume that differences in plasma conditions (mw-power gas composition) did not influence substantially the adhesive properties of the treated samples. no significant connection between the kinrt of amine functionalities and biocompatibility was found. besides tissue culture a wide range of possible applications for amine containing hydrophilic membranes are imaginable. for instance enzymes or adhesive proteins can be immobilised on amine functionalities [7], blood compatibility can be improved by immobilisation of heparin [25], or anti-fouling properties can be improved by grafting of peg on amine groups [26]. acknowledgements we are very grateful to dr. barbara seifert, and ruth hesse from the gkss research centre, institute for chemistry, teltow (germany), for advice and technical support for biocompatibility measurements, moreover to dr. katalin josepovits 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dörgő1 and jános abonyi* 1,2 1 department of process engineering, university of pannonia, egyetem str. 10, veszprém, h-8200, hungary 2 institute of advanced studies kőszeg, chernel str. 14, kőszeg, h-9730, hungary the search for compounds exhibiting desired physical and chemical properties is an essential, yet complex problem in the chemical, petrochemical, and pharmaceutical industries. during the formulation of this optimization-based design problem two tasks must be taken into consideration: the automated generation of feasible molecular structures and the estimation of macroscopic properties based on the resultant structures. for this structural characteristic-based property prediction task numerous methods are available. however, the inverse problem, the design of a chemical compound exhibiting a set of desired properties from a given set of fragments is not so well studied. since in general design problems molecular structures exhibiting several and sometimes conflicting properties should be optimized, we proposed a methodology based on the modification of the multi-objective non-dominated sorting genetic algorithm-ii (nsga-ii). the originally huge chemical search space is conveniently described by the joback estimation method. the efficiency of the algorithm was enhanced by soft and hard structural constraints, which expedite the search for feasible molecules. these constraints are related to the number of available groups (fragments), the octet rule and the validity of the branches in the molecule. these constraints are also used to introduce a special genetic operator that improves the individuals of the populations to ensure the estimation of the properties is based on only reliable structures. the applicability of the proposed method is tested on several benchmark problems. keywords: computer-aided molecular design, multi-objective optimization, evolutionary algorithm, the joback method, soft constraints 1. introduction the search for compounds exhibiting the desired physical and chemical properties is of significant industrial importance in the search for different chemicals and materials such as polymers [1, 2], blends [3], coatings, solvents, inert agents, heat transfer media [4], and drugs [5]. in the well-known technologies of the chemical, petrochemical, and pharmaceutical industries, the used medium for the given tasks has been developed via practical experience. for the improvement of these technologies or the design of a new process, every hypothetical molecule must be synthesized and tested to check the fulfillment of the design properties. this ‘trial and error’-type method for the search of the appropriate agent with the defined properties is slow, inefficient and expensive, thus infeasible in the modern chemical industry and research. however, the problem is complex; the algorithmization can be carried out extensively with the use of property estimation methods and molecular structural feasibility operators. algorithmic problems can be efficiently solved with the tools of process engineering. over recent decades, the search for new compounds has *correspondence: janos@abonyilab.com resulted in a new area of process engineering, namely computer-aided molecular design (camd) [6]. the original task of the design of molecules is formulated as follows: given a set of desired properties, design a product that satisfies these needs. with the use of camd tools, the algorithmic approach to the same problem determines the search place: given a set of available structural groups for the satisfaction of desired properties, formulate a product from these sub-units that satisfies the targets. during the decomposition of a camd-based problem, two separate tasks can be derived. as can be seen in fig.1, it can be divided into a forward problem, the prediction of a given property, based on the structural characteristics of a molecule; and a ‘reverse’ problem, the identification of a molecular structure for the satisfaction of target properties. figure 1. molecular design is a ‘reverse’ property estimation task. dörgő and abonyi hungarian journal of industry and chemistry 40 the forward problem, the estimation of properties, can be carried out by different methods; for example, polymers [1], solvents [7], surfactant solutions [8], refrigerants [9] and ionic liquids [10]. the limitations of any computer-aided molecular design techniques are closely related to the limitations of the property model being used [11]. the prediction of properties can be carried out with numerous types of methods, including group contribution methods (gc), quantitative structure-activity/property relationship methods (qsar and qspr), molecular modeling, empirical modeling and correlations, black box models like neural networks (nn) and the combination of these tools [12]. a novel method for property estimation is the cosmo-rs theory published by klamt et al. that combines quantum chemistry and thermodynamics [13]. the ‘reverse’ problem, the design of candidate molecules with a given set of properties from a set of molecular sub-units is hardly diversified; the existing techniques were developed for specific molecules and applications. the known methods can be divided into two major groups [14]. the huge chemical search space is further complicated by the often competing target properties of the design process. a genetic algorithm is a promising method for the generation of new candidate molecules. multi-objective optimization algorithms generate a set of optimal solutions. the pareto fronts of these solutions simultaneously consider several design aspects. since when solving the problem multiple target properties must be taken into consideration at the same time; the problem has been implemented in a well-established genetic algorithm-based multi-objective optimization environment, the non-dominated sorting genetic algorithm-ii (nsga-ii). the search space is conveniently described by the occurrence of each fragment from a given set of available types of groups, and the “distance” of the properties from the target values is estimated by the joback method. the feasibility of the molecule is tested by feasibility constraints for branching and the octet rule. these constraints are also used to introduce a special genetic operator that improves the individuals of the populations to ensure the estimation of the properties is based on only reliable structures. thus as the result, an evolutionary approach for solving molecular design problems with descriptors of varying dimensionality has been developed, that moves effectively towards the pareto optimal front. in the present work the definition of the design problem is followed by a theoretical overview of the used property estimation method and of the nature of genetic algorithms paying special attention to nsgaii. after the description of the different algorithms, proposed for the solution of the design task, the efficiencies of these approaches are examined through several benchmark problems, and the results are discussed extensively to determine improvements in the applicability of these algorithms. 2. methodology 2.1. problem formulation in the first class, numerous candidate molecules are created randomly from a given set of groups. the number of candidate molecules that can be generated by selecting n groups from a set of k groups, allowing repetition and ignoring the order of selection can be determined by eq.(1). 𝐶! 𝐾,𝑁 = !!!!! ! !!(!!!) (1) the total number of candidate molecules that can be selected from a set of k groups is the sum of the results of eq.(1) from n1 until nmax as is given by eq.(2) (n1 is practically equal to at least 2, as no molecules consist of only one fragment). the sum of candidates is equal to 𝐶! 𝐾,𝑁!!"# !! = !!!!! ! !!(!!!) !!"# !! (2) according to eq.(2) the total number of candidate molecules can undergo a combinatorial explosion as can be seen in fig.2. in the second class for the solution of the ‘reverse’ problem, this increased number of candidates must be eliminated by some objective function that expresses the ‘distance’ from the target. an example of this approach can be a tree structure to mimic the chain of a molecule and reach feasible structures as was carried out in refs. [12] and [14]. as in the literature, the proposed methods for the design of molecules are highly diversified. lin et al. studied the design of metal catalysts [15], numerous articles can be found for the design of drugs [5, 16-18], perdomo et al. designed and improved biodiesel fuel blends [3] and kasat et al. summarized the applications of genetic algorithms in polymer science including polymer design [2]. to solve the design problem, several computational strategies have been used. genetic algorithms (ga) are used in several publications [15, 19, 20], a combination of neural networks and genetic algorithms is used in [21] and linear programming is used in [12, 14]. figure 2. the combinatorics of group selection. multi-objective molecular design 44(1) pp. 39–49 (2016) doi: 10.1515/hjic-2016-0005 41 2.2. theoretical methodologies the definition of a chemical product design problem is based on the description of design constraints. a set of properties is specified as constraints with specified values with lower and/or upper boundaries. these properties are the explicit property constraints as their values can be determined directly by the application of some model calculation or experimentally. in the case of camd problems, explicit constraints are evaluated through property estimation methods, these can be, for example, critical properties, solubility indexes, normal boiling points, etc. however, property estimation methods have been significantly improved, there are products, for example, food, fragrances, health and safety products, and aesthetics that cannot be calculated with the use of these models, as these properties are based on subjective opinions or existing knowledge. in the case of these implicit property constraints (e.g. taste, aroma, color and health effects of products) the use of databases or the opinion of the designer can be implemented during the evaluation stage. during the basic camd process explicit constraints are taken into consideration, these relate mainly to physical properties, and implicit considerations are taken into account during the selection of available molecule fragments or compounds (e.g. no aromatic compounds are taken into consideration, or no halogens or cyanides are available) [6]. to understand the formulation of the solution to this explicit property constraint-based problem, the following information must be taken into consideration as the input information of the molecule design task (according to [12, 14]): 1. set g of nmax groups of which the designed molecule can be composed 2. the boundaries for the specified properties to be satisfied: 𝑃!" ! ’s for the lower boundaries and 𝑃!" ! ’s for the upper boundaries, where 𝑗 = 1, 2,… ,𝑚, the specified properties 3. the lower ( 𝑙!!! ) and upper limits ( 𝑙!"! ), for the number of appearances of group i in the designed molecule (𝑖 = 1, 2,… , 𝑛) 4. the property k can be estimated via a property estimation method as function 𝑓! (𝑓 = 1, 2,… ,𝑚), in the case of group contribution methods 𝑓! can be written as 𝑓!(𝑥!, 𝑥!,… , 𝑥!) (where 𝑥!, 𝑥!,… , 𝑥! are the numbers of group types #1, #2, …, #n respectively). the problem using the expressions above can be formulated as follows: i groups can be chosen from a given set of molecular subunits (g) considering the limits of 𝑙!!! and 𝑙!"! , to find all the possible molecular structures, while the property constraints given in eq.(3) are satisfied (where 𝑗 = 1, 2,… ,𝑚). 𝑃!" ! ≤ 𝑓 ! 𝑥!, 𝑥!,… , 𝑥! ≤ 𝑃!" ! (3) during the solution of the above-defined camd task, the generation and test method can seem to be inefficient as an enormous number of candidate molecules are created which finally turn out to be infeasible molecular structures. as is familiar among financial and industrial problems, some properties need to be minimized and others maximized between the constraint values, while others need to be close to a specified value. this results in a multiple-objective optimization task with concurring targets. our purpose is not to find a single solution, but a set of candidate molecules from the pareto front. pareto optimal solutions are those for which improvement in terms of one objective can only take place with the worsening of at least one other objective function. pareto-ranking is the process of determining the rank of each solution through identifying the number of other solutions that dominate it (the number of solutions that are better than it in terms of every objective) [22]. a pareto front can be seen in fig.3. in the present work feasibility constraints are implemented in the algorithm to filterout the resultant molecular structures in terms of feasibility. as in this approach the candidates are still filtered out after the property evaluation, the efficiency of the search can still seem to be inefficient. as the solution to this contradiction, a special genetic operator has been introduced that improves the individuals of the populations to ensure the estimation of the properties is based on only reliable structures, and the property evaluation is carried out on solely feasible molecules. 2.3. property estimation as the new molecules created in the ‘reverse’ problem are evaluated via property estimation methods to verify the satisfaction of properties, the success of camd tasks depends on, to a large extent, the reliability of the estimation method being used. from the point of view of precision, the highly improved, detailed models seem to be tempting in terms of the application. however, the computational complexity of these models is increased figure 3. a pareto front (the label of each solution refers to the number of other solutions that dominate them, non-dominating solutions are labeled with zero) [22]. dörgő and abonyi hungarian journal of industry and chemistry 42 as well. in terms of precision and complexity, group contribution methods are promising solutions, as the equation for estimation assumes a linear additivity dependence as presented in eq.(4), where 𝜃! ! is the group contribution value of group i for property j, 𝜃! ! is the offset value of property j and 𝑃!"# ! is the estimated property value. 𝑃!"# ! (𝑥) = 𝜃! ! + 𝑥!𝜃! ! + 𝑥!𝜃! ! + …+ 𝑥!𝜃! ! (4) the joback method, also known as the joback/reid method, is proposed to estimate eleven important physical properties of pure materials. during the determination of group contribution values, a common set of structural groups was employed in the regression process. to obtain the minimum values, the minimization of the sum of the absolute errors found from the estimated and the experimental values was carried out. as not the square values, but the absolute values were minimized, the method provides an improved estimation for the majority of the cases, but estimates slightly higher error values for outliers [23]. the systematic deviations of the joback method in the case of normal boiling points can be seen in fig.4, where experimental data is taken from the dortmund data bank. the joback method uses eqs.(5-15) to predict the specific properties as follows: normal boiling point: 𝑇! 𝐾 = 198 + 𝑇!,!𝑥! (5) melting point: 𝑇! 𝐾 = 122.5 + 𝑇!,!𝑥! (6) critical temperature: 𝑇! 𝐾 = 𝑇! ! !.!"#!!.!"# !!,!!!! !!,!!! ! (7) critical pressure (na is the number of atoms in the molecular structure): 𝑃! bar = 0.113 + 0.0032 ∙ 𝑁! − 𝑃!,!𝑥! !! (8) critical volume: 𝑉! cm!/mol = 17.5 + 𝑉!,!x! (9) heat of formation (ideal gas, 298 k): 𝐻! kj/mol = 68.29 + 𝐻!!𝑥! (10) gibbs free energy of formation (ideal gas, 298 k): 𝐺! kj/mol = 53.88 + 𝐺!!𝑥! (11) heat capacity (ideal gas, parameters are valid from 273 k to approximately 1000 k): 𝐶! ! !"#$ = 𝑎!x! − 37.93 + 𝑏!𝑥! + 0.210 ∙ 𝑇 + + 𝑐!𝑥! − 3.91 ∙ 10!! ∙ 𝑇! + + 𝑑!𝑥! + 2.06 ∙ 10!! ∙ 𝑇! (12) heat of vaporization at normal boiling point: ∆𝐻!"# kj/mol = 15.30 + 𝐻!"#,!𝑥! (13) heat of fusion: ∆𝐻!"# kj/mol = −0.88 + 𝐻!"#,!𝑥! (14) liquid dynamic viscosity (mw is the molecular weight, the parameters are valid from the melting point up to 0.7 of the critical temperature): 𝜂! pa ∙ s = 𝑀! ∙ exp 𝜂!,!𝑥! − 597.82 /𝑇 + + 𝜂!,!𝑥! − 11.202 (15) 2.4. a promising approach for the solution of the design task: genetic algorithms genetic algorithms (gas) are stochastic optimization methods that imitate natural selection. gas provide not a single optimal solution to a problem, but several nearoptimal solutions, which is the main advantage of evolutionary algorithms in the field of camd, because near-optimal solutions can be further processed later by the designer and the most promising ones can be selected for synthesis. during the operation of a ga, a population of candidate solutions competes for survival, based on their resemblance to the target values. this resemblance is described by a normalized distance value between 0 and 1 and called the fitness. candidate molecules are usually described by strings, and the components of these strings represent the ‘genes’ of the individual. the evaluation of the population is carried out therefore by figure 4. deviations between predicted boiling points and experimental data [24]. normal boiling point estimations by the joback method (aliphatic hydrocarbons) multi-objective molecular design 44(1) pp. 39–49 (2016) doi: 10.1515/hjic-2016-0005 43 the calculation of fitness and the surviving members have the chance to reproduce and propagate their genes, thus forming the next generation. this propagation is dependent on the genetic operators applied by the specific algorithm being used, the most common are crossover and mutation. the creation of next generations is continued until convergence is obtained (no considerable improvement is observed), or the maximum number of generations set by the user is reached [21]. 2.4.1. the non-dominated sorting genetic algorithm-ii (nsga-ii) for the description of the nsga-ii algorithm, three innovations of the algorithm must be described first: the fast non-dominated sorting procedure, a fast crowded distance estimation method, and the crowded comparison operator [25, 26]. the fast non-dominated sorting approach of the nsga-ii is based on the calculation of three entities: the domination count, the number of solution, which dominates the given solution, and the set of solutions that the given solution dominates. in the first nondominated front the domination count of all solutions is zero. after the determination of the first non-dominated front, each of the solutions dominated by its members is visited and his or her domination count is reduced by one. if the domination count of a solution becomes 0, then it becomes a member of the second non-dominated front. this algorithm is repeated until all fronts are determined. along with convergence to the pareto optimal set of solutions, the maintenance of a healthy spread of solutions is required to avoid the problem of getting stuck in the area of a local pareto optimum. to prevent this issue, the parameter of crowding distance is introduced. during the calculation of this parameter, the average distance between two points on either side of a particular solution along each objective is calculated. the overall crowding distance value is the sum of the individual crowding distance values along each objective. with the use of this parameter, the “density” of solutions in the search place can be calculated. a solution with a higher crowding distance value is less crowded by other solutions, in other words, the outlier solutions can be identified. thus, the parameter is applicable for the maintenance of diversity. the crowding distance computation for two objectives is illustrated in fig.5. the goal of the genetic algorithm, to obtain a uniformly spread pareto-optimal front, is reached with the help of the crowded-comparison operator. the operator guides the selection between two possible solutions as follows: 1. if the non-domination ranks of two solutions differ, the solution which dominates the other is preferred, in other words, whose domination index is less. 2. if the non-domination ranks of two solutions are equal (the two solutions are from the same front), then the solution of the less crowded region is preferred. the main loop of the nsga-ii can be explained by understanding the operators described above. the randomly created initial parent population (with n members) is sorted based on the non-domination rank. the crossover eqs.(16-17) and mutation eqs.(18-19) operators are applied to create the next generation (with n members) [27]. the algorithm applies to the intermediate crossover, which creates two children from two parents: parent1 and parent2 (child and parent are vectors, 𝑥 , containing the results of the specific problems), 𝑐ℎ𝑖𝑙𝑑1 = 𝑝𝑎𝑟𝑒𝑛𝑡1 + 𝑟𝑎𝑛𝑑 ∙ 𝑟𝑎𝑡𝑖𝑜 ∙ (𝑝𝑎𝑟𝑒𝑛𝑡2 − −𝑝𝑎𝑟𝑒𝑛𝑡1) (16) 𝑐ℎ𝑖𝑙𝑑2 = 𝑝𝑎𝑟𝑒𝑛𝑡2 − 𝑟𝑎𝑛𝑑 ∙ 𝑟𝑎𝑡𝑖𝑜 ∙ (𝑝𝑎𝑟𝑒𝑛𝑡2 − −𝑝𝑎𝑟𝑒𝑛𝑡1) (17) where ratio is a scalar between 0 and 1, and rand stands for a random number, the applied gaussian mutation adds a normally distributed random number to each variable, 𝑐ℎ𝑖𝑙𝑑 = 𝑝𝑎𝑟𝑒𝑛𝑡 + 𝑆 ∙ 𝑟𝑎𝑛𝑑 ∙ (𝑢𝑏 − 𝑙𝑏) (18) 𝑆 = 𝑠𝑐𝑎𝑙𝑒 ∙ 1 − 𝑠ℎ𝑟𝑖𝑛𝑘 ∙ !"##$%& !"#$%& (19) where scale is a scalar, that determines the standard deviation of the random number generated and shrink is a scalar between 0 and 1. as the optimization progresses, this shrink parameter decreases the mutation range. currgen and maxgen are the numbers of the current and maximal generations, respectively. since elitism is introduced, the creation of the first population differs from the creation of a subsequent one. the algorithm is described for the tth generation. a combined population (rt) (with 2n members) is created by the summation of the parent population (pt) and the population obtained by the use of crossover and mutation operators (qt). the population rt is sorted according to non-domination and as all previous and current population members are included, elitism is ensured. now solutions belonging to the first non figure 5. the crowding distance of the ith solution is the average side length of the cuboid (the front is marked with solid circles) [25]. dörgő and abonyi hungarian journal of industry and chemistry 44 dominated front (f1) are chosen for the next generation (pt+1) (if the size of f1 is smaller than n). this selection for the next generation is continued until the number of members from f1 to fi is larger than n. in these cases fi is sorted based on the crowded-comparison operator and the best solutions are chosen to fill the empty slots of the new population. the nsga-ii procedure is illustrated in fig.6. 2.5. description of the proposed algorithm the developed algorithm therefore needs to solve effectively the camd tasks based on the needs of the industrial and research work. by taking into consideration these needs, the optimal properties of the desired molecules can be defined, and this chemical information is essential for the defining of input parameters for the genetic algorithm. this schematic algorithm of the design process can be seen in fig.7. the standard genetic algorithm was modified according to the task of the design of molecules. the chemical information is converted into input parameters. thus, the type, minimum and a maximum number of available groups, the property and structural targets (e.g. acyclic, monocyclic, bicyclic structures), and the property and feasibility constraints (octet rule and a rule for branching) are defined. the algorithm of nsga-ii can be seen in fig.8. the efficiency of five different types of algorithm was tested in the present work. all the algorithms were implemented in matlab. 2.5.1. the ‘base case’ algorithm 1 only the type, the minimum and a maximum number of available groups, the target properties and the property constraints are defined. no structural targets or feasibility evaluations are implemented. 2.5.2. the ‘octet rule’ algorithm 2 besides the objectives and constraints of algorithm 1, the octet rule is defined as target parameter. the octet rule is described in eq.(20), 2 − 𝑣! 𝑥! = 2𝑚! (20) where xi, vi are the number and valency, respectively, of groups of type i and m = 1, 0 or -1 for acyclic, monocyclic and bicyclic groups, respectively [28]. the valency parameter in this context means the number of available bonds on a group (thus the valency of double bonds counts as a single valency in this context). 2.5.3. the ‘octet rule as a soft constraint’ algorithm 3 besides the structure of algorithm 2, the algorithm contains the octet rule (eq.(20)) as a soft constraint to aspire the program to reach a feasible structure according to the octet rule. the soft constraint was defined as a curve similar to a reverse gaussian distribution according to eq.(21), where 𝑅𝑒𝑠.𝑂𝑐𝑡. is the result of the octet rule reordered to give 0 when the constraint is satisfied. figure 7. the algorithm of the design process. figure 6. graphical illustration of the nsga-ii procedure [25]. figure 8. the algorithm of the genetic algorithm (the steps in dashed box are only implemented in algorithm 5). multi-objective molecular design 44(1) pp. 39–49 (2016) doi: 10.1515/hjic-2016-0005 45 𝑓 𝑅𝑒𝑠.𝑂𝑐𝑡. = 𝑤 ∙ (1 − 𝑒! (!"#.!"#.)! !!! ) (21) as can be seen in fig.9, the curve of this function has a descending value near the 𝑅𝑒𝑠.𝑂𝑐𝑡. = 0 value, and is equal to 0 at exactly x = 0. the parameter w shows the ‘weight’, the constant value far from 𝑅𝑒𝑠.𝑂𝑐𝑡. = 0, and σ stands for the ‘width’ (thus the ‘sharpness’) of the function. a sharp function type (w = 1, σ = 0.1) was chosen as structural feasibility is not satisfied with mild ones. 2.5.4. the ‘octet and branching rule’ algorithm 4 only the octet rule cannot describe the structural feasibility. two adjacent groups cannot be linked by more than one bond. the valency parameter in this context still means the number of available bonds on a group, as defined in the description of algorithm 2. given xj groups of type j with valency vj, a total of 𝑥! 𝑣! − 2 + 2 attachments are available for bonding [28]. 𝑥!!!! ≥ 𝑥! 𝑣! − 2 + 2 (22) 𝑥!! ≥ 𝑥! 𝑣! − 1 + 2 (23) 2.5.5. the ‘healing function’ algorithm 5 the genetic algorithm is further improved with the introduction of a novel genetic operator called the healing function. the function is implemented in the algorithm at two points, after the initialization of the first population and after the selection, mutation and crossover steps are conducted in each generation. this function serves the population entities to be feasible with the help of the branching rule described in eq.(23). if the equation is not fulfilled then the difference from the optimal value shows the bonds needed in the molecule to reach the feasible structure. using this value, the algorithm chooses as many available groups with one bond as needed for feasibility and completes the molecule with these groups. during the definition of the input parameters the number of available groups with one bond in the molecule is increased to ensure the availability of these groups. the number of branches and the groups with 3 or more bonds, must be significantly less than the ones with one bond available, e.g. 4 and 20 respectively, thus the termination of every chain in the molecule is ensured. 2.6. the evaluation of the results as the purpose of the current work is the development of an effective algorithm for the design of molecules obtaining target properties, the comparison of the results is an essential task to check the improvement. this efficiency inspection is carried out over two steps. first a visual evaluation was carried out as the matlab implementation of the nsga-ii algorithm plots every generation as the script runs. the plot window of nsga-ii can be seen in fig.10. then the number of solutions is counted and, as the feasible structure is not ensured in every algorithm, the feasible ones based on the octet and branching rules are counted as well. the last generation in which the population of the pareto front was changed was also determined. 3. results and discussion the effect of the various user determined input parameters was examined and presented in several benchmark problems for the identification of different chemicals having the desired physical and chemical properties, as estimated by the multi-dimensional property model. the genetic algorithm worked with 250 generations containing 100 population members each. the effectivity of the different algorithms is compared through these design tasks. 3.1. checking the effectivity through the search for predefined molecules first the effectivity and applicability of the different algorithms were tested in terms of the search for different, predefined molecules. the properties of simple molecules were calculated via the joback method and these values were set as targets to avoid the inaccuracy of the estimation method. the property constraints were set around these target values as given figure 9. the curve of the used soft constraint. figure 10. the plot window of nsga-ii. dörgő and abonyi hungarian journal of industry and chemistry 46 below. the search for two simple molecules, acetone, as its structure is quite simple, and n-octane were carried out to validate the algorithms. 3.1.1. acetone the structure of acetone can be represented by two methyl (blue circles) and one ketone (red circle) groups using the groups of the joback method as can be seen in fig. 11. the experimental and estimated boiling and melting points are presented in table 1. the input parameters for the design task were as follows: available groups: -ch3, -ch2-, >ch-, >c<, -f and >c=o number of available groups: 0–4 for all the available groups (in the case of algorithm 5, the -ch3, and -f numbers were set to 20 to allow healing) target properties: tm = 173.50 k, tb = 321.91 k (estimated values) property constraints: 150 k < tm < 200 k, 300 k < tb < 350 k target molecule structure: acyclic. the results of different algorithms are presented in table 2. next to the number of solutions, the number of feasible solutions is presented in brackets and the value ngen,change stands for the last generation that changed the population of the pareto front. the last row of the table shows if acetone is among the resultant structures. algorithm 5 seemed to be less effective in the light of the unsuccessful search for the structure of acetone, but if we consider that this algorithm could use up to 20 pieces of -ch3 and -f groups, we can understand that the search place is significantly bigger than in the case of algorithms 1-4. 3.1.2. n-octane the structure of n-octane can be represented by 2 methyl (blue circles) and 6 methylene (green circles) groups using the groups of the joback method as can be seen in fig.12. the experimental and estimated boiling and melting points are presented in table 3. the input parameters for the design task were as follows: available groups: -ch3, -ch2-, >ch-, >c<, -f and >c=o number of available groups: 0–6 for all the available groups (in the case of algorithm 5, the -ch3, and -f numbers were set to 20 to allow healing) target properties: tm = 179.92 k, tb = 382.44 k (estimated values) property constraints: 150 k < tm < 250 k, 350 k < tb < 450 k target molecule structure: acyclic. the results of different algorithms are presented in table 4, where the last row shows if n-octane is among the resultant structures. as in the case of the search for acetone, algorithm 5 had a significantly bigger search place than algorithms 1-4; thus, it could not find the structure of n-octane. table 1. the boiling and melting points of acetone. experimental values estimated values tm [k] 178.25 173.50 tb [k] 329.45 321.91 table 2. the results of the search for acetone. algorithm 1 2 3 4 5 solutions (feasible) 2 (1) 2 (1) 1 (0) 1 (1) 2 (2) ngen,change 95 10 8 9 127 acetone yes yes yes figure 12. the structure of n-octane fragmented according to the groups of the joback method. table 3. the boiling and melting points of octane. experimental values estimated values tm [k] 216 179.92 tb [k] 398 382.44 table 4. the results of the search for n-octane. algorithm 1 2 3 4 5 solutions (feasible) 10 (2) 5 (1) 1 (0) 1 (1) 5 (5) ngen,change 191 58 17 207 47 n-octane yes yes figure 11. the structure of acetone fragmented according to the groups of the joback method. multi-objective molecular design 44(1) pp. 39–49 (2016) doi: 10.1515/hjic-2016-0005 47 3.2. examples for testing the algorithms in the following examples the effectivity of the proposed algorithms is tested via two benchmark problems. as concurring minimum and maximum search objectives are set as target variables, a pareto front can be obtained, which represents the applicability of the genetic algorithms to solve camd tasks. 3.2.1. case study 1. the input parameters for the design task were as follows: available groups: -ch3, -ch2-, >ch-, >c<, -f and >c=o number of available groups: 0–4 for all the available groups (in the case of algorithm 5, the -ch3 and -f numbers were set to 20 to allow healing) target properties: max(tc), min(tb, tm) property constraints: 500 k < tc < 600 k 350 k < tb < 450 k 100 k < tm < 200 k target molecule structure: acyclic. the results of case study 1 can be seen in table 5. as the number of the last generation which changed the composition of the population is relatively high (250 is the maximum number of generations), the algorithms seem to evolve effectively towards the pareto front. in the case of algorithms 1 and 2, many of the found solutions proved to be infeasible, as expected since no feasibility constraints were involved in algorithm 1 and no constraint for branching was available in algorithm 2. the soft constraint of algorithm 3 seemed to be ineffective. algorithm 4 found only 2 feasible solutions, but these solutions were all feasible ones and they were close to the target properties. algorithm 5 was very effective, although the search place was significantly bigger than in the case of algorithms 1-4. the pareto front of algorithm 1 can be seen in figure 13. 3.2.2. case study 2. the input parameters for the design task were as follows: available groups: -ch3, -ch2-, >ch-, >c<, -f, -cl, -br, -i, -oh, >c=o number of available groups: 0–6 for all the available groups (in the case of algorithm 5, the -ch3, -f, -cl, -br, -i, and -oh numbers were set to 20 to allow healing) target properties: max(tc), min(tb, tm, pc) property constraints: 500 k < tc < 600 k 350 k < tb < 450 k 100 k < tm < 200 k 10 bar < pc < 30 bar target molecule structure: acyclic. table 5. the results of case study 1. algorithm 1 2 3 4 5 solutions (feasible) 89 (14) 88 (14) 1 (0) 2 (2) 42 (42) ngen,change 250 250 219 186 250 figure 13. the pareto front of algorithm 1 in case study 1. table 6. the results of case study 2. algorithm 1 2 3 4 5 solutions (feasible) 75 (0) 95 (5) 2 (0) 2 (2) 74 (74) ngen,change 250 250 223 197 250 figure 14. the results of algorithm 5 in case study 2. candidate molecules are represented by blue lines. dörgő and abonyi hungarian journal of industry and chemistry 48 in the case of case study 2 (table 6), a wider searching range was available for the design task: 10 types of available groups with a maximum of six pieces of each (except for algorithm 5, see the targets and constraints) and another target property was set, the minimization of critical pressure between the property constraints. the results were similar to case study 1, algorithms 1 and 2 fundnd several infeasible results with the appropriate properties; algorithm 3 seemed to be ineffective, algorithms 4 and 5 provided reliable results, although algorithm 5 still found more results according to the more pieces of available chainterminating groups (groups with 1 valency). as can be seen from the results the improvement of the algorithms increases the number of feasible solutions significantly. the results of algorithm 5 in case study 2 can be seen in figure 14. 4. conclusion the design of molecules with specified properties has an increasing importance in the modern chemical industry. we proposed a multi-objective evolutionary optimization-based approach to take into account several objectives and constraints (e.g. financial aspects, toxicity). the algorithms generate a set of molecules arranged in a pareto front related to the conflicting design targets calculated by the joback method. to get reliable molecular structures we defined soft constraints based on the octet rule. the branching of the molecules was also tested and a healing function was designed to provide reliable results. the application of the proposed algorithms can be useful in the industry. in the future, we are going to improve the algorithms with problem-specific genetic operators. these modifications seem to be promising for the significant increase in the search efficiency. symbols 𝐶! 𝐾,𝑁 selection of n groups from a set of k groups g the set of n groups from which the designed molecule can be composed nmax the available groups of the specified design task x the number of appearances of the specified group 𝑃 a specified property value 𝑃!"# estimated property value 𝑃!"# experimental property value plb the lower boundary of the specified property value pub the upper boundary of the specified property value lll the lower limit for the number of appearances of the specified group lul the upper limit for the number of appearances of the specified group x1, …, xn the number of group type #1, …, #n, resp. 𝑎! ! is the group contribution value of group i for property j 𝑇! normal boiling point 𝑇! normal melting point 𝑇! critical temperature 𝑃! critical pressure 𝑉! critical volume 𝐻! heat of formation 𝐺! gibbs free energy of formation 𝐶! heat capacity ∆𝐻!"# heat of vaporization ∆𝐻!"# heat of fusion 𝜂! liquid dynamic viscosity ratio a scalar between 0 and 1 rand a generated random number currgen the number of the current generation maxgen the number of the maximal generation scale a scalar, that determines the standard deviation of the random number generated shrink scalar between 0 and 1. as the optimization progresses this parameter decreases the mutation range rt a combined population (with 2n members) pt parent population qt the population obtained by the use of crossover and mutation operators f the non-dominated front 𝑣 the valency of the specified group. the valency parameter in this context means the number of available bonds on a group (thus the valency of double bonds counts as a single valency in this context). m the type of the designed molecule (m = 1, 0 or -1 for acyclic, monocyclic and bicyclic groups, respectively) w the ‘weight’ of the soft constraint curve (the constant value far from x = 0) σ the ‘width’ (the ‘sharpness’) of the soft constraint function curve acknowledgement the research of j.a. has been supported by the national research, development and innovation office (nkfih), project # otka 116674 entitled “process mining and deep learning in the natural sciences and process development”. g.d. was supported by the “a pannon egyetem tudományos műhelyeinek támogatása” támop-4.2.2.b-15/1/konv-2015-0004 project. references [1] camarda, k.v.; maranas, c.d.: optimization in polymer design using connectivity indices, ind. engng. chem. res., 1999 38(5), 1884–1892 doi: 10.1021/ie980682n [2] kasat, r.b.; ray, a.k.; gupta, s.k.: applications of genetic algorithms in polymer science and engineering, mat. manufact. proc., 2003 18(3), 523–532 doi: 10.1081/amp-120022026 multi-objective molecular design 44(1) pp. 39–49 (2016) doi: 10.1515/hjic-2016-0005 49 [3] perdomo, f.a.; perdomo, l.; millán, b.m.; aragón, j.l.: design and improvement of biodiesel fuel blends by optimization of their molecular structures and compositions, chem. engng. res. design, 2014 92(8), 1482–1494 doi: 10.1016/j.cherd.2014.02.011 [4] joback, k.g.: computer aided molecular design (camd): designing better chemical products. 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333 page 334 microsoft word 2012_dr_bodor_endre_hjic.doc hungarian journal of industrial chemistry veszprém vol. 39(3) 437-445 (2011) flow pattern within hydrocyclone j. németh, s. verdes university of pannonia, institute of mechanical engineering 8200 veszprém, egyetem u 10., hungary e-mail: verdess@almos.vein.hu the paper deals with the measurement methods of tangential, radial, axial velocities evolving in hydrocyclone and the characteristics of the velocity distributions defined in the course of the experiments. the definition of the cut-size diameter based on the so-called equilibrium model requires a review according to the authors. in the sense of the model there are only twoo forces acting on a unique particle settling: the centrifugal force and the one, opposite of the motion, resistance strength, and it does not take into consideration, that liquid flows in hydrocyclon. in the hydrocyclone the medium flowing inwards from the tapered cloak wall has a transport velocity and so an effect on the settling onto a particle may not be apart from attention to let. in the hydrocyclone the phenomenon of an air core taking shape in his axis line was explained by means of the basis equations of the hydrostatics till now. the authors demonstrated that the development of the air core is justifiable also with the necessities of the rotating bowls on an actual example. keywords: hydrocylone, flow, application, working principle introduction considering the construction of hydrocyclone it is one of the simplest separation machines working continuously in centrifugal field. a liquid rotation around the axis of the apparatus comes into existence as a result of liquid flow introduced tangentially under a pressure. based on the phases to be sparated one may distinguish liquid-solid hydrocyclons, where the liquid usually is water, as well as hydrocyclons for separation of liquids consisting of two ones not mingling in each other, e.g. when operation aim is separation of oil with water. in the following we deal with the relations of flow of liquid belonging to the first group. as regards the characteristics of the second group refer to the literature [1, 2]. the first patent announcement concerning hydrocyclone has happened more than 100 years ago /bretney, 1891/, despite this industrial application of hydrocyclones has really begun only after the second world war. the first publications in hungary also appeared at this time, in the field of coal and ore preparation [3-5], as well as in the building material industry [6, 7]. the benefits of hydrocyclones – they do not have moving component, simple structural forming, small place for installation etc. – and their disadvantages – do not give sharp separation, danger of erosion in case of hard grains etc. – practically are the same as it is for gas cyclones [8]. the fact that the the density of the liquid cannot be neglected compared to density of solid material means a considerable difference. in the hydrocyclones the driving force of particle settling is only close to half of the driving force in the gas cyclones. mode of operation fig. 1 shows a typical cylindrical-conical classifier hydrocyclone. figure 1: schematic drawing of a typical cylindrical-conical hydrocyclone 438 according to the practice for hydrocyclones it is well that other sizes are given with ratio to diameter of the cylindrical shell, dc. the suspension enters in tangentially on the upper part of the cylindrical cloak and streams curling downwards, overwhelmingly beside the exterior wall of the apparatus. the bigger and/or the heavier particles are concentrated at the wall and then get into the lower outflow in the form of thick slurry. the smaller or easier particles in big dilution are transported upwards by streaming liquid into the upper outflow on the middle of the cyclone through the vortex finder pipe. the flow curling downwards beside the wall changes direction on a certain level of the cone and starts to move upwards with an identical twist. the ratio of the two volume-flows (the leaving one, qu, on the bottom, through the so-called apex, and leaving one from above, qo) is the split: s = qu / qo. (1) if we relate the qu to the entry volume-flow, qi, we get the ratio of the partial current proportion, rf, (flow ratio). it is simply justifiable, that rf = s / (1+s). (2) according to the experience the single part of massflow under the lid of the apparatus on a short road under the vortex finder pipe lower his edge cross – unclassified – leaves through the upper slot. yeah, the so-called short circuit flow for qi value 10–15% may attain it. this loss can be reduced by a constructional road [8], eg. with double introduction, or introductory pipe of evolvens shape. in the same time these solutions reduce the appearance of whirl /eddy flow/ between the vortex finder and the cylindrical cloak, mainly if the velocity of the entry liquid is equal to the tangential velocity occuring in the cylindrical part, what is the condition of striking-free flow. bradley in the monograph about the hydrocyclones [9] suggested the next experimental formula for s value if outflows from the cyclone are free or regulated with choking: s = c(du / do) xqi -y, (3) where c ≈ 5, if the measure for qi is imp.gal/min; x is between 1.75 and 4.4, while y changes between 0.75 and 0.44. the smaller exponents are recommended for hydrocyclones with small diameter, while the bigger ones concern evidently the cyclones of bigger diameter. the usual parameters for the operation are the following: dc = 0.01–2.5 m, the limit cut-size dh = 5–300 µm, qi = 0.1–340 m3/h and the solid material concentration at feeding is ci = 10–60%. at the top overflow the concentration is 5–30%, while at the bottom outflow it is 50–70%. bigger volume flows – similarly to the gas cyclone – could be achieved by several units put together paralelly, called multi-cyclones. simultaneously only one of the compositions for the top or lower outflow – fitted to the operation purpose with the right value of s – is designable. the prescribed composition for both outlet could only be achieved by units connected in series. the peculiarity of a function in hydrocyclones – which is not properly cleared up until now – is the phenomenon of the air core taking shape in the axis line of the cyclone. in the hydrocyclone an air core arises, if even the top or the lower outflow is in contact with the atmosphere. since near the axis the flow velocity of the liquid rotating in the cyclone attains a value to which – in the sense of the hydrostatics equations – belongs a pressure decrease already yielding vacuum. the measure of the vacuum may expand from some kpa to 10–20 kpa, according to literature [10]. however air core may occur in locked systems, joining into tanks, and in this case the air core is filled with steam released from the liquid or gas. we yet return to this debatable question later ones. the diameter of the air core along the full height of the hydrocyclone, on an irregular manner, is constant, its value is (0.06–0.33) dc. the bigger value belongs to the bigger rotation velocities. it may occur if the diameter of the air core is big that it covers the lower outflow slot. in this case the lower outflow may cease. this state is actually observable in case of clear water flow, but rarely with suspensions, because the settling particles accumulate on the bottom of the cone and decrease the velocity of the rotating motion. to smaller rotating motion on the other hand belongs an air core with smaller diameter, which does not cover the lower outlet slot. examination of flow-pattern it is clear from the previously ourlined description of the function manner that the flow-pattern of the simple structured classifier hydrocyclone and running simply is complicated. the hydrodynamic complexity increases, because 3d whirlpool motion evolving in the hydrocyclone /both in the free vortec and the forced one, as well as below cap of the hydrocyclone resultant of the feeding /eddy flow/ is not izotrop, it is not completely axially symmetric, even though, because of the recessionary motion of the air core forming it changes even in the time. in case of bigger solid concentrations the conditions of free settling are not fulfilled. in such a case the characteristics of the granular bulks, e.g. the free voidage factor must be considered in the calculation. the interactive effect of particles settling down onto the motion of the liquid also put questions to be cleared up. in the latter years increasingly more scientists undertook [11-15] onto the modeling of the sketched complex current picture and his theoretical treatment, consequently of the development in computational fluid dynamics (cfd). when doing numerical treatment of the turbulent flows, however, the validation of the applied models is always necessary. to this modern measurement technique is need which is used for the systematic and carefully carried out experiments. since the starting works of kelsall [16] and rietema [17] even recently most of the publications [18-20] deal with the clarification of a complex picture took shape in the hydrocyclone. the lectures of international conferences about hydrocyclone and organised four yearly since 1984 439 confirm also the previous statement [10, 21]. it could be made clear from the publications until now, that for the measurement of flow situations in the hydrocyclones the application of indirect methods which do not disturb the flow is preferable. such a technique is for eaxample photography of motion /cinematography/ where the isokineticallly injected coloured liquid or the very fine and light particles moving together with the liquid as trace materials can be detected by a microscope with rotating objective /kelsall, 1952/ or by cinematography of big velocity /knowles, 1973/. with the development of the electronics and computer science (for example picture recogniser programs) the laser methods are spreading. here can be listed lda /laser doppler anemometer/ [22], ldv /laser doppler velocimeter/ [19] with the two beams or the pdpa /phase doppler particle analyser/ applied also in the research institute of technical chemistry (mükki), veszprém, by which the velocity distribution of a secunder flow was possible to check in a twisted static mixer element [23]. the velocity measurement method based on the demonstration of the flow, piv (particle image velocimetry) [24] is a quickly developing one. the piv method applied for velocity distribution in plane beside the research work on the department of fluid mechanics at technical university of budapest serves also the practical training of students [25]. the microholographie is also a multy way applicable method. the combination of he–ne laser beam of continuous radius used in the holographic laboratory of mükki and the q-switch rubin laser with its holograms of short flash of nanosecond order in magnitude the movement of the traced particles in 3d are measurable. it is promissing although costly the newly developed tomography method: eit (electrical impedance tomography) as well as ert (electrical resistance tomography) [26, 27]. williams [28] examined the dynamics of the motion of the air core with ert technique. at the given experiments in hydrocyclones water, or transparent liquid streamed. the suspensions optically are not transparent, so there is not yet a measurement technique uniformly accepted for examination of the flow velocity distribution of suspensions containing particles. only qualitative statement can be made about the fact that the presence of the particles decreases the velocities in clean water. velocity distribution in hydrocyclone gusztáv tarján in a coursebook [5] written together with gábor fejes summarized his own results and the ones of researchers known until that time. he presented the velocity of medium introduced tangentially into the hydrocyclone by three components shown on fig. 2. the figure on the left shows the change of tangential velocity through the longitudinal section of the hydrocyclone, the middle one concerns the axial velocity and the figure on the right is for the change of the radial velocity. it is clear from the length segments that the places of isotangential velocities are coaxial cylinder surfaces, the place of isoaxial velocities are close to coaxial conical surfaces with an identical apex, while the places of isoradial velocities in the conical space part are roughly conical surfaces with a common vortex angle. in both latter cases the velocity distributions of the cylindrical space parts were influenced by whirling (eddy flow) caused by the feeding on a manner shown on the figure. figure 2: velocity distributions in hydrocyclone on the middle figure the dashed line marks the va = 0 dots (loci of zero vertical velocity). on the right from this line the direction of the axial velocity is downwards while on the section close to the axis it is directed upwards. on the dashed line the forces acting on the settling particles are in a dynamic equilibrium. more authors, e.g. kelsall [16], bradley [9] or tarján [5] based on this phenomenon the so-called equilibrium model which makes possible to define the cut size diameter. we shall return yet onto the assessment of this model. none of the distribution curves along the radius starts from r = 0 which can be seen below on fig. 2 because of the air core. the velocities along the radius was first determined by kelsall [16] (see fig. 3). on the figure we have shown distributions of the velocities (tangential vt; axial va and radial vr) converted them into metric measurement system. we note that the author was able to measure only the vt and va velocities with the help of a microscope supplied with rotating objectives, the vr values were defined by calculation with respect of the continuity equation. the diameter of the experimental hydrocyclone was 75 mm and its cone angle was 20°. the vortex finder with length of 100 mm /on the figure indicated with hatching/ reached the conic part of the cyclone. the author wished to insure with this non usual solution the stability of the flow and its symmetry around the axis. for the greatness of the single velocities the scales give guidance. it is seen that vr is much smaller than vt or va. according to fig. 3 the tangential velocity increased from the wall of the cone towards the axis, then reaching the maximum, it steeply decreased. the maximum values with a good approach fall on a line of r = 5 mm = constant. we note that the diameter of vortex finder, do was 12.7 mm, while the diameter of the air core was 5 mm. 440 figure 3: velocity distributions according to kelsall a) vt – tangential, b) va – axial, c) vr – radial velocity distributions the left part of fig. 4 shows the change of the tangential velocity on a log-log diagram figure 4: the diagram of the tangential velocity (log-log plot) and schematic drawing explaining the equilibrium the changing parameter was the pressure of the feeding. the breakpoint of the lines corresponds to the maximum value of the vt. on the left from the breakpoint in the expression vtrn = constant which desribes the line for the exponent n = –1 is good approximation, that is vt = rω, where ω is the steady rotational angular velocity. this expression is equal to the equation characterise the rotation of the rigid bodies with a constant revolution. kelsall called this section forced vortex. for the exponent of vtrn = constant valid for the longer line being on the right from the breakpoint on the basis of measurements offered n = 0.77, that is vtr0.77 = constant. in the sense of fig. 2 the tangential velocity, vt is only function of the radius, the liquid parts may only rotate around an axis perpendicular onto the plane, in our case around the axis of hydrocyclone. the velocity of a potential whirl can be described by the equation of v = k / r [25], that is, the velocity distribution of vtr0.77 = constant forming in the hydrocyclone, can be well approached by one of the potential whirl, similarly to dust-precipitator gas cyclones. by that way the free vortex term suggested by kelsall for this current flow pattern in hydrocyclone indicates a potential whirl as regards the flow dynamics. based on relevant publications of hydrocyclones it can be said about the change of exponent n the following: n increases when dc, do, or di, as well as the cone angle, θ of the hydrocyclone increases. the interval of the change is from 0.4 to 0.9 otherwise. the value of n was n ≈ +1 only when the hydrocyclone was without cone, it consisted of only cylindric part [9]. the knowledge of the tangential velocity is important for designing of hydrocyclone including the definition of the cut-size, dp as well as the size taken as separation average size. kelsall, according to the right sketch of fig. 4, indicated the intersection of the line described by relation va = 0 and the plane belonging to the the lower edge of of the vortex finder at 2.3do. the radial velocity at point k on the surface of the cone defined by the basic plane with diameter of 2.3do and the vax = 0 dots and generatrix l is given by o rk o qv = . 2.3 d l /2π (4) taking into consideration the value of s according to expression qo = qi / (s+1) instead of qo in eq.4. qi can be written. the researchers using the equilibrium model assume that in the point k one can write the following: vrk = wo. (5) if the stokes-law for settling is valid, the settling velocity of the particle is 2 2 p s l tk o k d ( ) vw = , 18µ r ρ ρ (6) where vtk is the tangential velocity belonging to point k. 441 if vrk = wo, then the particle of size dp is orbitting on a circles of radius rk. if vrk > wo, then the circling particle moves away into the direction of the axis, while if vrk < wo, then the particle moves towards the wall of the cone. the validity of stokes law exists when re ≤ 1. in clear water (ν = 0.01 cm2/s) and in case of re = 1 to radial velocities of 5, 10 and 20 cm/s, the dp values belong of 20, 10 and 5 µm. the dh, the value of a separation average size is understood as the average of dp values got by different k points on va = 0 line. the length l, with a good approach is l = dc / (2tgθ). after replacing and arrangement we get 1/ 2 i h * c t qtg 6 d = d / 2 s l v μβ π ρ ρ ⎡ ⎤θ ⎢ ⎥−⎣ ⎦ . (7) in the previous expression vt * means the average of tangential velocities belonging to the line of va=0. romankov and kurocskina in their book [30] published other nine equations for the definition of the dp cut size particle. all of the authors of the equations started from the equilibrium model outlined previously. the diversity of the equations reflects that a uniform computational method for the definition of dp and dh did not developed yet. the reason of this is on one hand that the authors deducing the equations started out from different hypotheses. e.g. the validity of the stokes law for suspensions was presupposed which is valid only till 2.5 volume percentage of particles. apart from this at bigger solid concentrations the particles settling to the the wall displace the liquid being there, which is obliged to flow towards the inside of the hydrocyclone. forming so drag, the free settling velocity, w0 decreases. because of this the validity of the stokes law is debatable. an additional difference follows if the sizes or structural arrangemnet of hydrocyclone are different from kelsall’s one. in that case the so-called diameter of a basis circle may be different from the kelsall’s one, which was 2.3 d0 for him. the average residential time in hydrocyclones is short, for example the average residential time in a hydrocyclone of diameter of 100 mm with a performance of 8 m3/h is altogether 0.55 s. for this reason it is uncertain whether the velocity of a given particle in the suspension with size dp might be able to reache its quilibrium on the line va = 0 suiting to it. at the same time this is a prerequisite for adaptability of the equilibrium model. the authors of the present paper on the other hand take the force-balance for settling particle misguided. according to the authors of the equilibrium model in a coordinate system co-rotating with the liquid there acts only two forces on a particle settling down: the centrifugal force and the drag force, that are in balance at the places of va = 0, that is they are equal. the authors of the present paper consider this notion a wrong one. this equality is only true for settling happening in a medium of rest. in a streaming medium, so in a hydrocyclone, too, it is necessary to take into consideration transport velocity, u of the liquid that, acconding to bloor-ingham [18] actually is commensurable with the movement or drift velocity of the particle. so, fluidmechanically correctly, beside the centrifugal force and the one of flow resistance it is necessary to take into consideration an other force, namely the force which can be defined by the product of mass of the particle and the acceleration, du/dt. implicitly so the vectorial equation is: 3 3 2 p p p0 d d ( ) 3µd w. 6 6 t s s l vdu dt rr ρ ρ ρ= − + (8) in eq. (8) w = vr – u is the relative velocity related to the particle, where vr is the radial velocity of the liquid, ro the radial unit vector. writing this equation we presupposed that the velocity of the moving particle became steady-state. for hydrocyclones this is generally allowed, because a particle of 100 μm size and of density ρs = 2700 kg/m3 in 0.006 s attains the the accelerationfree, steady-stae velocity, the so-called terminal velocity. in case of known velocity vt and vr the balance equation modified by us is numerically solvable. we previously showed (see fig. 4) that the decrease of the tangential velocity in the hydrocyclone near to its axis can be given by expression of vtr–1 = constant. we also referred to that this expression – according to the researchers' uniform opinion – is analogous with vt = rω, peripheral speed of rigid bodies circulating with constant angular velocity, ω. until now, according to the knowledge of the authors of the present paper, nobody in the literature has examined the possibility, that the flow pattern in the hydrocyclone in the environment of its axis, with the air core in it could not be characterised with the flow properties of the rotating bowls? it is known [25] that in rotating vessels, e.g. in a centrifugal clarifying drum, the surface of the liquid is equipotential surface which is described by a rotatory paraboloid of second degree. as a result of the rotation in the bowl the middle of the originally horizontal surface is sinking down, and at the same time it rises up beside the wall of the vessel. it can be justified on the basis of fluid mechanics, that the largest sinking in the axis line of the paraboloid and the largest rise at the wall of the vessel is equal: δh = r2ω2/4g. (9) taking the measurement data of kelsall as a basis the radius of the rotating vessel is founded bought r=5 mm, what is the radius of hydrocyclone giving the maximum tangential velocities. the maximum tangential velocity is 15 m/s, the angular velocity belonging to this is 3000 s-1. with these data it comes out that δh = 1.15 m. the whole height of the experimental hydrocyclone is smaller than 0.3 m, so the peak of the rotatory paraboloid gets under the outlet slot /apex/ of the hydrocyclone. if at the time of starting the water in standstill fills the hydrocyclone, that is in our case the height of the water column is h ≈ 0,3 m, then it can be seen that h < δh, but on the other hand, in this case, according to the necessity of the rotating vessels, the liquid layer in the drum of the centrifuges is nearly parallel to the vessels wall. the liquid flowing out from the drum of the centrifugal clarifyer is prevented with flange (rim) arranged above. in the hydrocyclone because of the continuous operation, ring road of thickness δr is forming and the water 442 circulates in it. its volume flow is equal to the outflow from the hydrocyclone on the top, qo. inside the ring there is air with an atmospheric pressure. taking kelsall measurements as a starting point the thickness of the ring δr = 3.85 mm and the diameter of the air column is around 5 mm. based on the previous lines we consider possible that in the hydrocyclone for the development of the air core, not exactly cleared up completely, not only the vacuum is responsible, the reason should also be the centrifugation of the fluid as a layer next to the inside wall of the bowl, typically characteristic for rotating vessels! our opinion is supported by experiments of smyth and thew [10], too. the researchers of southampton university have tested in a vortoil-f type hydrocyclone with diameter of 70 mm that what kind of measure expands the carbon dioxide from the liquid saturated with the co2 due to the vacuum reigning in the air core, as a surprise it was experienced that negligibly few gas bubbles freed from the saturated liquid, far not so much, than for as much would have been needed due to the pressure decrease to expand. the english researchers tried to explain this unexpected phenomenon by the rotating flow caused over-saturation. in our opinion this explanation is a forced one because of the flow mechanical doctrines concerning equipotential surfaces. since it is known that in force fields the equipotential surfaces coincide with the surfaces with a constant pressure. it follows from this, that the force fields do not cause pressure increase on their own equipotential surface. if there is no pressure increase, then over-saturation neither may occur. with the data of the previous example the centrifugal acceleration of rotating liquid mass as rigid body, surrounded the air core, is 4587 times bigger than the gravitational acceleration field, g, belonging to of the earth, for this reason pressure increase of the inertial force increasing proportionally by the water depth is negligible. the above described usage of data from kelsall of 1952 brings up the question how sound they are in the mirror of the newer experiments. based the velocity distributions measured by modern measurementtechniques and presented on the following figures (see figs. 5-8) it can be stated that in the conical part the distributions of the tangential and axial velocity are of identical character, which means that the use of these data of kelsall based on the newer experiments can be said legitimate. but, opposite this, the radial velocity distribution defined with calculation of kelsall is debatable. only in the lane beside the conical wall can be considered valid the vr = va tg(θ/2) (10) expression. on fig. 5, from left to right, data of a tangential velocity distribution are seen from knowles et al. (1973), kelsall (1952) and ohasi and maeda (1958). figure 5: tangential velocity distributions in all the three cases the diameters of the hydrocyclones, the quantity of input liquid flow, its velocity and pressure were near identical. there was a slight difference in cone angle, in the manner shown on the figure (11.3°, 20° and 15.2°). knowles and his colleagues [29] worked with a hydrocyclone of the optimal geometry size assessed by rietema [17]. in their experiments they injected coloured liquid of density of 0.99327 kg/litres into the water, and they checked the velocity distribution by cinematography with high speed (20000 frame-quarters in a second). because of their shorter vortex finder they waited for bigger velocity fluctuation as compared to kelsall’s measurements and despite of this the velocity distributions were commensurable. compairing the three hydrocyclones the most significant difference appeared in the air core. ohasi and maeda were choking the lower outflow beside the free upper outflow, because of this they have got other aircore diameter than kelsall. knowles and his colleagues hintered the development of the air core, but despite of this the character of the distributions is similar. figure 6: velocity distributions measured with ldv method 443 fig. 6 shows experimental data of quian et al. from year 1989 [19]. in their experiments the authors used ldv measurement technique. on the figure from left to right we can see velocity distributions for tangential, axial and radial velocities. in the cylindrical section the tangential and radial velocities are small, the axial ones here are around 0.5 m/s. the distributions of the tangential and axial velocity in the cylindrical space part are different of character as compared to distributions in the conical space part because of the effect of the feeding. the tangential velocity in the conical section was describable with expression of vtrn = constant, discussed already at kelsall, although here the vtmax = 4 m/s was smaller in this case. the change in the radial velocity compared to the calculated one of kelsall shows different character. the velocity of -4 m/s close to the air core seemed particularly big. but on the other hand it counts nearly as a novelty that the authors were able to measure the rotation of the air core with a diameter of 8 mm and it was found 10300 rotations per minute. finally, it is worthy to analyse the experiments of hsieh and rajamani [11] which used ldv technique, too, from the year of 1991 (see figs 7 and 8). figure 7: velocity distributions measured by hsieh and rajamani the authors used silicone carbide particles of 1.5 μm as marked substance. the diameter of the hydrocyclone in this case was 75 mm, the full length was 244 mm and the cone angle 20°. the tangential velocity was 200–800 cm/s, the one of axial 0–400 cm/s, while the radial one changed between values of 0 and 80 cm/s. because of the fluctuation of the air core the scattering of the tangential velocity was 20–50 cm/s. for this reason the reliability of the measurement of radial velocity values which are similar order in magnitude is questionable. on the figures one can see that the asymmetry appearing in the cylindrical section of the hydrocyclone practically disappeared in the conical section. the distribution of the tangential velocity as regards it tendency is in good agreement of one discussed at kelsall’ result. the axial velocity changes its direction twice in the cylindrical section, but in the conical part the already discussed traditional distribution is characterictic with thel inear line of va = 0 dots. the big jump sign in the radial velocity distribution under the vortex finder is unusual. on fig. 8 distributions of the tangential velocity can be seen, but the viscosity of the streaming medium was changing on the figure. in case of [a] the steaming medium was clear water, while in case of the [b] it was mixture of water and glycerine, of which the viscosity was 1.4 pa s. the distribution curves in the two figure parts are practically identical, so an increase in viscosity indicated above had no effect onto the tangential velocity. figure 8: tangential velocity distribution in case of a fluid with different viscosity theoretically it was only to be expected, because neither in the whirl rotating as a rigid body neither in the potential whirl the viscosity does not play a role. the authors wrote down the balance of forces acting on moving particle in the classifier hydrocyclones, in radial and axial direction. in both cases two forces were taken into consideration, in radial direction the centrifugal force and the drag force being effective against it, while in axial direction the gravity and the resistance force against it. the balance of radial forces was expressed by the following equation 3 22 p p2 d d d1( ) c 6 2 4 t s m l r v v r π π ρ ρ ρ− = , (11) from which the radial velocity of the particle is 444 1/ 2 2 p d d( )4 . 3 c s m t r l vv r ρ ρ ρ ⎡ ⎤− = ⎢ ⎥ ⎢ ⎥⎣ ⎦ (12) the authors gave the force-balances in axial direction by similar way: 3 2 p p2 d d d1( ) c , 6 2 4s m l ag v π π ρ ρ ρ− = (13) from which the axial velocity of the particle is 1/ 2 p d d( )4 . 3 c s m a l v gρ ρ ρ ⎡ ⎤− = ⎢ ⎥ ⎢ ⎥⎣ ⎦ (14) in the equations ρm is the density of the suspension and cd = f(re), the drag coefficient. hsieh and rajamani, similarly to kelsall – according to our opinion – do unduly not take into consideration the radial as well as axial components of the absolute transport velocity of spirally streaming water in the hydrocyclone about the velocity distributions given previously the following can be said as a summary: the distribution of the tangential velocity along radius is of the same character at most of the authors. near the axis the velocity distribution of the forced vortex can be written as it is for the velocity of the rigid bodies running with constant angular velocity. the maximum tangential velocities can be find in parallel with the axis on the line of r = constant. from this value towards the wall of the hydrocyclone the tangential velocity decreases and as a free vortex with vtrn = constant can be well approached by flow pattern of the potential whirl. the distribution of axial velocities presented here shows already more differences, mainly in the cylindrical space part of the hydrocyclone. in the distributions it is common, that the va in the conic part of the hydrocyclone next to the wall points down, though near the axis line points upwards. in the so-called equilibrium models using va = 0 dots user, in our opinion, when writing up the force balance the transport velocity of the streaming medium was neglected. the measurement of the radial velocity is the largest difficulty currently. in the direct measurements until now the difference of the values of the vr is considerable. the validation of numerical flow dynamics /cfd/ calculations being based on different models by measurements can be said uncertain. we justified with an actual example, that the development of the air core could be explained not only with the arising of vacuum, but also by relationships describing fluid flow in rotating vessels. acknowledgements the authors owe honest thanks to dr. tamás lajos university professor, for his useful councels and generous collaboration. symbols ci initial particle concentration dp grain size, cut size dh average cut size diameter g gravitational acceleration δh change of liquid surface r radius of hydrocyclone u velocity of transportation vt, va, vr tangential, axial and radial liquid velocity w relative velocity wo settling velocity cd drag coefficient dc the diameter of the hydrocyclone cylindrical part di, do, du diameter of input, the upper and lower leading out pipes l the length of the surface cone qi, qo, qu the volume flow-rate of feeding, upper and lower downstream r radius rf flow ratio re reynolds number s volume split ρs, ρl, ρm density of particlee, liquid and suspension μ dynamic viscosity factor ν kinematical viscosity factor θ cone angle of the hydrocyclone ω angular velocity references 1 j. németh, a. ujhidy, gy. bucsky, j. katona: mol scientific magazine, 2011, no. 1, 48–54, part 1 2 j. németh, a. ujhidy, gy. bucsky, j. katona: mol scientific magazine, 2011, no. 2, 58–66, part 2 3 g. tarján: acta technica hung. 7, 1953, 389–411 4 g. tarján: aufbereitungstechnik, 12, 1961, 477–483 5 g.fejes, g.tarján: chemical machines and unit operations (in hungarian), budapest, tankönyvkiadó, 1979. 6 l. demeter: the practical application of the hydrocyclone (in hungarian), bme mt intézet, 1954. 7 gy. bréda: doctor thesis (in hungarian), bme 1963. 8 j. németh, s. verdes: building material, xxx, 2011 (in press) 9 d. bradleys: the hydrocyclone, oxford, pergamon press, 1965. 10 d. claxton, l. svarovsky, m. thew (eds.): hydrocyclones 96, london, mech. eng, publ. 1996. 11 k. t. hsieh, r. k. rajamani: aiche journal, 37, 1991, 735–746 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(in hungarian), budapest, műegyetem k. 2004, 151–159, 503–506 26 j. bonds, j. c. cullivan, n. climpson, t. djakowski: 1st world congress on industrial process tomography, buxton, greater manchester, apr. 14-17, 1999 27 j. c. cullivan, r. a. williams, c. r. cross: particulate science and technology, 21, 2003, 83–103 28 r. a. williams, o. m. ilyas, f. j. djakowski: chem. eng. j. biochem. eng. j. 56, 1995, 135–141 29 s. r. knowles, d. r. woods, i. a. feuerstein: the canadian j. of chem. eng. 51, 1973, 263–271 30 p. g. romankov, m. i. kurocskina: hydromechanical processes in the chemical technology /in russian/, chimia, leningrad, 1974 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice hungarian journal of industry and chemistry vol. 48(1) pp. 67–70 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-10 vibration generator device based on industrial vibrators péter decsi *1 and istván szalai1 1institute of mechatronics engineering and research, university of pannonia, gasparich márk utca 18/a, zalaegerszeg, 8900, hungary a low-cost vibration generator device based on industrial vibrators was designed. the control software was implemented in labview environment. the device is able to generate an oscillating force of 8 kn and an amplitude of up to 4 mm at a frequency of 50 hz to model low-amplitude, high-frequency vehicle vibrations. a national instruments myrio device was responsible for data acquisition, with which a signal of a piezoelectric accelerometer was detected. the test results show that the device is able to generate a sinusoidal harmonic acceleration. keywords: industrial vibrator, vibration generator, test equipment 1. introduction the suspension of a car acts as a connector between the chassis and the road. it provides a comfortable ride for passengers while maintaining maneuverability. nowadays, comfort is a prerequisite so car manufacturers have started developing new technologies for isolating vibrations [1, 2]. the vibration can be dampened or converted into electrical energy [3]. electro[4] and magnetorheological dampers [5, 6] are filled with a special fluid. small ferromagnetic particles are dispersed in a carrier fluid, usually silicone oil. the diameters of the particles fall within the microand nanometre ranges. when subjected to an electric or magnetic field, the particles form chains. these chains provide an elevated level of resistance against shear stress, therefore, the apparent viscosity of the fluid rises [7, 8]. using adjustable shock absorbers, the natural frequency of the suspension can be altered. the damping coefficient can be varied depending on the road conditions or the driver’s preference. the reaction time of these fluids is very short (approximately 10ms), so the technology can be used in systems where short reaction times are required [9]. suspension-testing equipment is crucial during the development phase. the acquisition cost of appliances for this task is very high. our goal was to develop a low-cost piece of equipment for testing shock absorbers that is capable of generating high frequencies (within an acceptable range for vehicles) and vibrations of low amplitude. *correspondence: decsi.peter@mk.uni-pannon.hu 𝑥1 𝑥2 𝑚1 𝑚2 𝑘1 𝑏1 𝑘2 𝑏2 𝑥𝑟 (a) structure model 𝑚2 𝑚1 𝑘1 𝑘2 𝑏1 𝑏2 𝑥 1 𝑥 2 𝑥 𝑟 𝑥 𝑟 (b) structure graph figure 1: quarter-car model 2. modeling the vehicle several options of modeling the suspension of vehicles are available; quarter-, halfand full-car models can be used to describe the system, which is chosen depends on the aim of the study. the quarter-car model was chosen for this study due to its simplicity. industrial vibrators are able to generate vibrations of constant amplitude. to change the generated force and amplitude, it is necessary to stop the device and mechanically set the eccentricity, therefore, the roll, pitch and yaw of the vehicle is hard to model with such a device. fig. 1 shows a quarter-car model. the system has two degrees of freedom (dof), m1 denotes the mass of the chassis, m2 represents the mass of the wheel, which is usually referred to as the unsprung mass. the related displacements are labelled as x1 https://doi.org/10.33927/hjic-2020-10 mailto:decsi.peter@mk.uni-pannon.hu 68 decsi and szalai and x2, spring stiffnesses as k and viscous damping coefficients as b. the wheel and chassis are connected through a spring k1 and a damper b1. the wheel and the road are connected through a spring and damper (elastic tire with damping loss) k2, b2. based on the structure graph, the equilibrium equations can be written in the form: m1ẍ1 = −b1(ẋ1 − ẋ2)− k1(x1 − x2) m2ẍ2 = b1(ẋ1 − ẋ2) + k1(x1 − x2)+ +b2(ẋr − ẋ2) + k2(xr − x2). (1) based on fig. 1 and eq. 1, it is clear that the system has a cross-variable source, namely speed. 3. modeling the proposed system this research presents an equivalent model based on industrial vibrators. industrial vibrators are traditional asynchronous motors with a dual shaft on which eccentric masses are mounted. fc = mrω2 (2) where m denotes the eccentric mass, r represents the eccentricity, which is the distance between the axis center point and the center of gravity of the eccentric mass, and ω stands for the rotational speed. due to the eccentricity, a centrifugal force is generated because of the rotation (eq. 2). if two motors of opposite rotational directions are mounted together, lateral forces cancel each other out, therefore, a one-axis oscillation is created. a system with two degrees of freedom was designed using industrial vibrators. the model of the system is depicted in fig. 2: the differential equations of this system are: m1ẍ1 + k1(x1 − x2) + + b1(ẋ1 − ẋ2) + fin = 0 m2ẍ2 − k1(x1 − x2)− − b1(ẋ1 − ẋ2) + k2x2 + ẋ2b2 = 0 (3) x1 xr = s2b1b2 + s(k2b1 + b2k1) + k1k2 s4m1m2 + s3(m1(b1 + b2) +m2b1) + s2(m1(k1 + k2) +m2k1 + b1b2) + s(k1b2 + k2b1) + k1k2 (4) x1 f = s2m2 + s(b1 + b2) + k1 + k2 s4m1m2 + s3(m1(b1 + b2) +m2b1) + s2(m1(k1 + k2) +m2k1 + b1b2) + s(k1b2 + k2b1) + k1k2 (5) according to the impedance network of the quartercar model shown in fig. 3, the transfer function can be written in the form eq. 4. the impedance network of the proposed system is shown in fig. 4 and contains the transfer function of eq. 5: it can be seen that the transfer function x1/xr of the quarter-car model (eq. 4) is similar to that of the transfer 𝑓𝑐 ω 𝑥1 𝑥2 𝑚1 𝑘1 𝑏1 𝑘2 𝑏2 (a) structure model 𝑥 1 𝑥 2 𝑘1 𝑘2 𝑏1 𝑏2 𝑚1 𝑚2 𝑓𝑖𝑛 (b) structure graph figure 2: vibrator model 𝑠 𝑘2 𝑠 𝑘1 1 𝑏1 1 𝑠𝑚1 1 𝑏2 𝑣𝑟 1 𝑠𝑚2 𝑥 1 𝑥 2 figure 3: impedance network of the quarter-car model 𝑠 𝑘2 1 𝑏2 1 𝑠𝑚2 𝑠 𝑘1 1 𝑏1 1 𝑠𝑚1 𝑓𝑖𝑛 𝑥 1 𝑥 2 figure 4: impedance network of the vibrator model hungarian journal of industry and chemistry vibration generator device based on industrial vibrators 69 function x1/f of the proposed system (eq. 5). the characteristic polynomials, i.e. the denominators, are identical as the two systems differ only in terms of the excitation source. the numerators are of the same degree, therefore, the characteristics of the system response are similar, that is to say the dynamics of the two systems are not significantly different. the breakpoints in terms of the frequency response are expected to be shifted. 4. implementation after deriving the differential equations, a simulink model was created to choose the optimal combinations of parameters (mass, spring stiffness and damping coefficients). according to the simulations, the connection between the chassis and the ground should be as stiff as possible in order to focus the force on the shock absorbers. it should not be too rigid, otherwise the force acting on the ground would be excessive and affect the building too significantly. the moving mass, where the motors are mounted, should be small to achieve the maximum possible exciting force, therefore, more force can be used to accelerate the payload. during the design process, models with two or three degrees of freedom were examined. the motion became chaotic with three independent masses, that is 3 dofs, so the spring stiffness available was insufficient to produce a stable and predictable shape of sinusoidal motion. it was concluded that a system with 2 dofs generates a stable sinusoidal oscillation with multiple frequency components in terms of the shape of motion. the device, shown in fig. 5, consists of two threephase asynchronous two-pole industrial vibrators each figure 5: the implemented vibration generator with a nominal performance of 300w. the centrifugal force can be incrementally set up to 4070n at a frequency of 50hz on one motor. the motors are operated with frequency converters, thus the frequency can be set. if the motors operate in opposite rotational directions and a suitable arrangement is applied, the lateral forces cancel each other out, thereby creating a one-axis oscillation. the frequency converters are controlled with analogue signals generated by a national instruments myrio device. a piezoelectric accelerometer was mounted on the sheet holding the vibrating motors. a high-pass filter with a cutoff frequency of 1hz was installed to cancel out the bias voltage of the accelerometer. data was acquired by the field-programmable gate array (fpga) module of the myrio device on analogue channels. the ac signal was coupled to a high-pass filter with a cutoff frequency of 1hz. the sensitivity of the accelerometer was 100mv/g and the analogue input of the myrio device was ±10v. an instrumentation amplifier with an amplification of 7.08 was built to utilize the full range of the a/d converter. the fpga module takes a sample according to the previously set sampling frequency, which can be set up to 100 khz. the data is stored temporarily in the first in first out (fifo) memory on the myrio device. a second virtual instrument (vi), which displays and stores the data in technical data management streaming (.tdms) file format, was run on the controlling pc. the vi read out data from the fifo memory in batches. these batches were stored in the tdms file, creating a reliable data acquisition. meanwhile, following the application of a fast fourier transform algorithm, a frequency spectrum was displayed on the controlling pc. 5. test results a test measurement was taken after the implementation. for test purposes, the frequency converters were set at 16hz. fig. 6 shows a long-term test and fig. 7 shows the measurement of a short-term acceleration. it can be seen that the acceleration is approximately sinusoidal and consists of two main frequency components. fig. 6 shows that the acceleration was stable over an extended period of time with several protrusions. fig. 8 shows that the set 20 30 40 50 60 70 80 90 100 time [s] -6 -4 -2 0 2 4 6 a c c e le ra ti o n [ m /s 2 ] figure 6: test measurement, long duration 48(1) pp. 67–70 (2020) 70 decsi and szalai 30 30.2 30.4 30.6 30.8 31 time [s] -4 -3 -2 -1 0 1 2 3 a c c e le ra ti o n [ m /s 2 ] figure 7: test measurement, short duration 0 10 20 30 40 50 60 70 80 90 100 frequency (hz) -40 -30 -20 -10 0 10 p ow er s pe ct ru m ( db ) figure 8: frequency spectrum of the test measurement frequency was present in the spectrum alongside multiple frequency components. 6. conclusion according to our experience and the aforementioned results, it can be concluded that a cost-effective vibration generator was designed and produced. the device is able to generate an amplitude of vibration equal to 4mm with a frequency of up to 50hz. the total centrifugal force was as high as 8 kn, of which 7500n could be focused on the examined sample. the frequency can be set between 1hz and 50hz, however, as shown in eq. 2, the centrifugal force depends on the rotational speed. the amplitude cannot be set, and when the natural frequency of the system, namely 1.3 hz, is exceeded, the amplitude becomes constant. at this frequency, the centrifugal force is low so resonance can be avoided. the excitation force can be set between 0 and 100% by modifying the eccentricity of the motors. to set the eccentricity, the motors must be powered down and the side covers removed. the vibration generators that are typically used (electrodynamic and hydraulic) are able to create higher amplitudes and higher vibrational frequencies, but these devices belong to a different cost category. acknowledgement the project has been supported by the european union, co-financed by the european social fund. efop-3.6.216-2017-00002 references [1] qin, y.; tang, x.; jia, t.; duan, z.; zhang, j.; li, y.; zheng, l.: noise and vibration suppression in hybrid electric vehicles: state of the art and challenges, renew. sustain. energy rev., 2020, 124, doi: 10.1016/j.rser.2020.109782 [2] ning, d.; sun, s.; du, h.; li, w.; li, w.: control of a multiple-dof vehicle seat suspension with roll and vertical vibration, j. sound vib., 2018, 435, 170–191, doi: 10.1016/j.jsv.2018.08.005 [3] zhang, z.; xiang, h.; shi, z.; zhan, j.: experimental investigation on piezoelectric energy harvesting from vehicle-bridge coupling vibration, energy convers. manag., 2018, 163, 169–179, doi: 10.1016/j.enconman.2018.02.054 [4] holzmann, k.; kemmetmüller, w.; kugi, a.; stork, m.: design, mathematical modeling and control of an assymetrical electrorheological damper, ifac proceedings volumes, 2006, 39(16), 372–377, doi: 10.3182/20060912-3-de-2911.00066 [5] graczykowski, c.; pawłowski, p.: exact physical model of magnetorheological damper, appl. math. model., 2017, 47, 400–424, doi: 10.1016/j.apm.2017.02.035 [6] yao, g.z.; yap, f.f.; chen, g.; li, w.h.; yeo, s.h.: mr damper and its application for semiactive control of vehicle suspension system, mechatronics, 2002, 12(7), 963–973, doi: 10.1016/s09574158(01)00032-0 [7] carlson, j.d.: what makes a good mr fluid?, j. intel. mat. syst. str., 2002, 13(7-8), 431–435, doi: 10.1106/104538902028221 [8] rankin, p.j.; ginder, j.m.; klingenberg, d.j.: electroand magneto-rheology, curr. opin. colloid interface sci., 1998, 3(4), 373–381, doi: 10.1016/s1359-0294(98)80052-6 [9] olabi, a.; grunwald, a.: design and application of magneto-rheological fluid, mater. des., 2007, 28(10), 2658–2664, doi: 10.1016/j.matdes.2006.10.009 hungarian journal of industry and chemistry https://doi.org/10.1016/j.rser.2020.109782 https://doi.org/10.1016/j.rser.2020.109782 https://doi.org/10.1016/j.jsv.2018.08.005 https://doi.org/10.1016/j.enconman.2018.02.054 https://doi.org/10.1016/j.enconman.2018.02.054 https://doi.org/10.3182/20060912-3-de-2911.00066 https://doi.org/10.3182/20060912-3-de-2911.00066 https://doi.org/10.1016/j.apm.2017.02.035 https://doi.org/10.1016/j.apm.2017.02.035 https://doi.org/10.1016/s0957-4158(01)00032-0 https://doi.org/10.1016/s0957-4158(01)00032-0 https://doi.org/10.1106/104538902028221 https://doi.org/10.1106/104538902028221 https://doi.org/10.1016/s1359-0294(98)80052-6 https://doi.org/10.1016/s1359-0294(98)80052-6 https://doi.org/10.1016/j.matdes.2006.10.009 introduction modeling the vehicle modeling the proposed system implementation test results conclusion page 1 page 2 page 3 page 4 page 5 page 6 page 7 page 8 page 9 page 10 page 11 page 12 page 13 page 14 page 15 page 16 page 17 page 18 page 19 page 20 page 21 page 22 page 23 page 24 page 25 page 26 page 27 page 28 page 29 page 30 page 31 page 32 page 33 page 34 page 35 page 36 page 37 page 38 page 39 page 40 page 41 page 42 page 43 page 44 page 45 page 46 page 47 page 48 page 49 page 50 page 51 page 52 page 53 page 54 page 55 page 56 page 57 page 58 page 59 page 60 page 61 page 62 page 63 page 64 page 65 page 66 page 67 page 68 page 69 page 70 page 71 page 72 page 73 page 74 page 75 page 76 page 77 page 78 page 79 page 80 page 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527 page 528 page 529 page 530 page 531 page 532 page 533 page 534 page 535 page 536 page 537 page 538 page 539 page 540 page 541 page 542 page 543 page 544 page 545 page 546 page 547 page 548 page 549 page 550 page 551 page 552 page 553 page 554 page 555 page 556 page 557 page 558 page 559 page 560 page 561 page 562 page 563 page 564 page 565 page 566 page 567 page 568 page 569 page 570 page 571 page 572 page 573 page 574 page 575 page 576 page 577 page 578 page 579 page 580 page 581 page 582 page 583 page 584 hungarian journal of industry and chemistry vol. 53(1) pp. 17–25 (2025) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2025-03 development of a natural cream additive containing an extract of aronia melanocarpa berries and a probiotic to inhibit microbial development and increase solar protection ali saglam1 and meltem asan-ozusaglam1* 1 department of molecular biology and genetics, faculty of arts and sciences, aksaray university, bahçesaray district, aksaray, 68100, turkey natural products have been used in cosmetics for centuries for skincare purposes. one of the most effective ways to protect skin flora and keep the skin healthy is to use plant extracts in cosmetic products. this study aimed to investigate the biological activities of an aronia berries ethanol extract (abee) obtained from aronia melanocarpa (aronia) as well as determine its potential use in the cosmetic and pharmaceutical industries. in the study, disc diffusion, minimum inhibitory concentration (mic) and minimum fungicidal or bactericidal concentration (mfc or mbc) tests were applied to evaluate the antimicrobial potential of abee. next, the antimicrobial activity of abee was accurately determined by counting live cells against staphylococcus aureus atcc 25923 using the macrodilution method. the sun protection factor (spf) of abee and abee + commercial cream mixtures was obtained in vitro. finally, cream formulations containing abee and a probiotic were developed for the treatment and prevention of clinical infections. in this context, the antimicrobial activities of the developed cream mixtures were determined using the well diffusion test. the inhibition zone diameter of abee against test microorganisms was measured to be between 8.32 and 14.49 mm. mic and mbc or mfc values of the extract were measured to be within 12.5-50.0 µg/µl. abee exhibited the best antimicrobial activity against s. aureus atcc 25923. at an abee concentration of 50 mg/ml, a significant decrease in the number of viable cells of s. aureus atcc 25923 was observed compared to the control. an abee concentration of 100 mg/ml inhibited all bacterial growth. the spf value of abee determined in vitro was high (25) and those of the cream mixtures also increased as the abee concentration increased. abee and probiotic-containing cream mixtures exhibited high antimicrobial activities on the tested microorganisms. with the synergistic effect of the extract and probiotic, the highest antimicrobial activity was determined against escherichia coli o157:h7 with an inhibition zone diameter of 25.40 mm. abee may be used as a natural antimicrobial agent to prevent or treat clinical infections in the pharmaceutical industry and as a natural ingredient in sunscreen in the cosmetic industry. keywords: aronia, extract, living cell, sun protection factor, antimicrobial cream 1. introduction humans have used various plants for thousands of years to cure diseases [1]. natural products, especially plants, exhibit important pharmacological effects and form the basis of modern medicines [2]. herbal medicines use the fruit, seeds, leaves, roots, flowers or bark of plants for medicinal purposes [3]. natural extracts obtained from plants are used in many areas such as the pharmaceutical [4], agricultural [5] and food industries [6] for their various biological activities. aronia melanocarpa (aronia) is a shrub belonging to the rosaceae family [7]. aronia is widely consumed as a fresh fruit and used for various purposes, for example, as a herbal medicine and food colorant [8]-[9]. the presence of bioactive compounds such as received: 28 nov 2024; revised: 9 dec 2024; accepted: 9 dec 2024 *correspondence: meltemozusaglam@gmail.com polyphenolic compounds, minerals and vitamins in aronia berries has many beneficial effects on our health, e.g. anti-aging, antimicrobial, anticancer and antiinflammatory [10]-[12]. aronia extracts improve the health of the liver, intestines and brain [13]-[14]. probiotics are defined as non-pathogenic live microorganisms that are administered to improve the microbial balance in the body, especially in the gastrointestinal tract and skin [15]. probiotics also increase immune response, strengthen the epithelial barrier, degrade toxins and exhibit antimicrobial effects [16]. limosilactobacillus fermentum, an important probiotic bacterium for human health, has antimicrobial, antioxidant and anti-photoaging activities by improving skin health and flora [17]-[18]. the skin, the largest organ of the human body, is exposed to environmental effects. the skin ages https://doi.org/10.33927/hjic-2025-03 mailto:meltemozusaglam@gmail.com saglam and asan-ozusaglam hungarian journal of industry and chemistry 18 depending on chronological events and external factors. in addition, sunscreen products should be used to provide protection against the harmful effects of the sun [19]-[20]. creams developed using chemical additives remain on the skin for a long time causing unwanted penetration into its epidermis, potentially negatively affecting skin biology [21]. sunscreens containing herbal additives are known to exhibit more photoprotective activities with fewer or no side effects compared to sunscreens containing chemical additives [22]. infections in the skin and soft tissues are common conditions that cause serious morbidity caused by yeasts and bacteria [23]. topical creams with antimicrobial properties are used to treat superficial skin infections. topical treatments are based on administering drugs in appropriate concentrations to the desired area [24]. for skin infections, new antimicrobial agents containing natural ingredients should be used instead of existing antibiotics [25]. the ability to select antimicrobial agents containing natural ingredients suitable for developing topical creams is highly advantageous [26]-[27]. creams developed with plant extracts can be used to treat different skin disorders caused by microbial infections [28]. protecting the skin from prolonged exposure to direct sunlight and applying sunscreen topically when exposed protects the skin from sunburn and photoaging as well as reduces the risk of developing skin cancer [29]. sunscreen applied topically before or after sun exposure may help increase dna repair, regulate dna transcription, reduce inflammation and play an important role in skin cancer prevention [30]. this study aimed to determine the potential of aronia berries as a natural bioactive compound in the pharmaceutical and cosmetic industries. for this reason, the antimicrobial effect of an ethanol extract obtained from aronia berries (abee) on various test microorganisms was investigated. in addition, the antibacterial activity of this extract on s. aureus atcc 25923 was examined in more detail by determining the viable cell count. the sun protection factor (spf) values of abee and abee + commercial cream mixtures were measured to evaluate their potential as safer and cheaper alternatives to the harmful chemicals used in sunscreens. the antimicrobial activities of creams containing a mixture of abee and probiotic l. fermentum were investigated on test microorganisms for pharmaceutical purposes. 2. experimental 2.1. preparation of extracts aronia were purchased as fresh berries from chokeberry food and health i.c (yalova, turkey) before being rinsed first with tap water and then distilled water. the berries were dried in an airy environment then ground using a blender manufactured by waring laboratory science. the extraction was carried out with ethanol (99.9%) using a sonicator (amplitude of 100%; cycle of 1). after the solvent was evaporated, the extract was dissolved in dimethyl sulfoxide and then sterilized using a 0.45 µm syringe filter. 2.2. test microorganisms the antimicrobial activity of abee was tested against 5 test microorganisms. candida albicans atcc 10231 was cultured at 30 °c in yeast peptone dextrose medium for 24 hours. pseudomonas aeruginosa atcc 27853, escherichia coli o157:h7, staphylococcus epidermidis atcc 12228 and staphylococcus aureus atcc 25923 were grown at 37 °c for 24 hours. 2.3. bioactivity of abee 2.3.1. disc diffusion method the antimicrobial activity of abee on test microorganisms was investigated using the disc diffusion method. the active cultures of the microorganisms were prepared as microbial suspensions at a density of a 0.5 mcfarland standard (1.5x108 cfu/ml). the sterile discs, 6 mm in diameter, were placed on an agar medium and inoculated with a suspension equal to 0.5 mcfarland standard before 20 µl of the extract (2 mg/disc) was dripped onto them. as a positive control, standard ampicillin antibiotic (am: 10 µg/disc), kanamycin (k: 30 µg/disc) and fluconazole (fca: 25 µg/disc) discs were used. the discs were left to allow the test microorganisms to incubate at appropriate temperatures for 24 hours before the diameter of the inhibition zones were measured and recorded with a digital caliper. this method was repeated three times to obtain the means and standard deviations of the inhibition zone diameters of the abee. 2.3.2. microdilution method the minimum inhibitory (mic) and minimum fungicidal or bactericidal (mfc or mbc) concentrations on the test microorganisms of abee were determined using the two-fold dilution method. at the first concentration (100 µg/µl), the broth medium and extract were added to the tube and homogenized before the other tubes containing the broth medium were subjected to two-fold dilutions. finally, the suspension equal to 0.5 mcfarland standard was added to the diluted tubes separately and incubated. the concentration of the extract at which no microbial growth occurred after incubation was determined to be the mic. next, the samples taken from the tubes were inoculated sequentially onto the solid medium and incubated for 24 hours. the abee concentration at which no microbial growth occurred in the solid medium after incubation was denoted as the mbc or mfc. 2.3.3. macrodilution method the biological activity of abee on clinically sourced s. aureus atcc 25923 pathogenic bacteria was determined using the macrodilution method. a suspension of s. aureus atcc 25923 equal to 0.5 mcfarland was prepared and added to the mixture of natural cream additive with an extract containing aronia melanocarpa berries 53(1) pp. 17–25 (2025) 19 abee (50 and 100 mg/ml) and the growth medium. the control consisted of the broth without the extract. the test groups were incubated over 48 hours at the appropriate temperature for the bacteria. samples were taken after 0, 24 and 48 hours before being diluted and then cultured on solid media. at the end of each incubation period, the number of viable cells was determined and this value recorded in cfu/ml. 2.4. calculating the sun protection factor (spf) the sun protection factor of abee was determined by a spectrophotometric analysis [31]. the abee was homogenized in ethanol (96%) at a concentration of 2 µg/μl. 3 replicates of the mixture were measured by a uv-b spectrophotometer (beckman coulter inc., usa) at 5 nm intervals between 290 and 320 nm before using the mansur equation [32]. the spf values of the mixtures developed with abee and a commercial cream were determined spectrophotometrically with some modifications [33]. the abee (5% w/v) was mixed with the commercial cream (10% w/v) and increased to its final volume by adding distilled water. ethanol (10 ml, 40% v/v) was added to 0.1 g of the sample taken from the mixture. next, the sample was sonicated (amplitude of 100%, cycle of 1) with an ultrasonicator (hielscher up100h) for 5 minutes. the mixtures of 2.5, 5.0 and 10.0 ml in volume were measured on the spectrophotometer as mentioned above. the mansur equation was used to determine the spfs of the abee and cream mixtures [32]: 𝑆𝑃𝐹 = 𝐶𝐹 х ∑ 𝐸𝐸(𝜆)х 𝐼(𝜆)х 𝐴𝑏𝑠(𝜆) 320 290 (1), where cf: correction factor (=10); ee(𝜆): erythemal effect spectrum; i(𝜆): intensity of sunlight at wavelength 𝜆; abs(𝜆): od value of abee at uv-b wavelength 𝜆; ee(𝜆) x i(𝜆): a constant specified by sayre et al. [34]. 2.5. determining the antimicrobial activity of the cream developed with abee and l. fermentum ma-7 groups of antimicrobial creams developed with abee and/or l. fermentum ma-7 in commercial creams were prepared by the methods used in the studies by handali et al. [35] and chen et al. [36]. the content of the groups of creams developed consisted of 10% commercial cream (w/v) and 20% abee (w/v). the volume of the groups with and without probiotic l. fermentum ma-7 were increased to their final volumes with a live culture (od600nm = 1.6) and distilled water, respectively. the negative control group of creams did not contain the extract nor l. fermentum ma-7 which were sterilized using a 0.45 μm syringe filter. the cream formulations were stored at 4 °c under dry conditions until used. the antimicrobial activities of the developed groups of creams were tested on the tested microorganisms using the well diffusion method. the microbial suspensions at a concentration of 0.5 mcfarland standard were dripped onto 100 µl of the solid media and spread. the cream formulations, 100 µl in volume, were inoculated into wells 6 mm in diameter. after incubation, the clean areas around the wells were measured and recorded with a digital caliper. this method was replicated three times to obtain the means and standard deviations of the inhibition zone diameter of the extract. 2.6. statistical analysis all data in the current study are reported as the mean and standard deviation (sd) of three different evaluation results. the data were analyzed using the gnu pspp program and statistical significance was confirmed by the one-way analysis of variance (anova) with tukey's post-hoc test. the difference between the values was considered statistically significant when p<0.05. 3. results and discussion excessive use and inappropriate selection of antibiotics is causing an increase in antimicrobial resistance in healthcare [37]. it is difficult to treat antibiotic-resistant microorganisms in bacterial infections [38]. wounds and hospital-acquired infections often prolong healing and cause implant failure as well as lead to other serious health problems, even death [39]. safe bioactive compounds that can control and inhibit the development of pathogenic microorganisms need to be developed. an alternative way to ensure a microbial balance in hospital services and cosmetic products is to use herbal extracts that are antimicrobially active [40]. an alternative to chemical preservatives in the cosmetic industry is the combination of herbal extracts and probiotics, increasing the number of properties exhibited by cosmetic products [41]-[42]. 3.1. biological activity of the extract the biological activity of abee on test microorganisms is presented in table 1. the results show that the largest inhibition zone diameter of abee was 14.49 mm on s. aureus atcc 25923. the results show that the difference between the antimicrobial activity of the extract on c. albicans atcc 10231 (8.32 mm in diameter) and s. epidermidis atcc 12228 (8.66 mm in diameter) was not statistically significant (p>0.05). for other test microorganisms, the statistical difference between the means of c. albicans atcc 10231 and s. epidermidis atcc 12228 was significant (p<0.05). saglam and asan-ozusaglam hungarian journal of industry and chemistry 20 a study measured the antimicrobial activities of aronia berry extracts (96% ethanol, 50% ethanol and water) using the disc diffusion method. although the extracts did not create an inhibition zone on e. coli jm109, the 50% ethanol extract did create an inhibition zone of 10.20 mm in diameter on b. cereus 407 according to bräunlich et al. [43]. in another study, the ethanol extract prepared using aronia berries exhibited inhibition zones of 7.00 and 8.66 mm in diameter on c. albicans atcc 10231 and e. coli atcc 25922, respectively [44]. compared with these studies, in the present study, abee exhibited good levels of antimicrobial activity on e. coli o157:h7 and c. albicans atcc 10231 by forming inhibition zones of 12.10 and 8.32 mm in diameter, respectively. the minimum inhibitory concentration of an antimicrobial that can inhibit the microorganism was determined using the microdilution method. the lowest concentration at which the extract inhibited the microorganism was denoted as the mic of the extract and the lowest concentration at which the growth of a microorganism on solid media was completely inhibited was denoted as the mbc or mfc of the extract (figure 1). the mic and mfc of the extract on c. albicans atcc 10231 was recorded to be 50 µg/µl. among the bacteria, the lowest mic and mbc of the extract were recorded as 12.5 µg/µl on s. aureus atcc 25923. the most resistant microorganisms to the extract were c. albicans atcc 10231 and s. epidermidis atcc 12228. in a study, deng et al. [45] extracted anthocyanin (75% ethanol) from aronia berries. the mic of anthocyanin on e. coli o157:h7 was determined to be 0.625 µg/µl and the mbc was 1.25 µg/µl. in another study, a hydrophilic ethanol extract was obtained from aronia branches using 96 and 50% ethanol. it was determined that the 96% ethanol extract yielded both mic and mbc of 0.20 and 0.39 µg/µl on e. coli and s. aureus, respectively. the 50% ethanol extract showed 0.20 µg/µl mic and 0.39 µg/µl mbc for e. coli and 0.20 µg/µl mic and 0.20 µg/µl mbc for s. aureus. in addition, both 96% and 50% ethanol extracts resulted in mic and mbc values of 0.39 µg/µl and 0.78 µg/µl, respectively, for p. aeruginosa. [46]. according to the disc diffusion test results, the abee did not exhibit the highest inhibitory activity among the test microorganisms on s. aureus atcc 25923 by producing an inhibition zone diameter of table 1: antimicrobial activity of abee inhibition zone diameter (mm±sd) test microorganisms abee (2 mg/µl) antibiotics am k fca c. albicans atcc 10231 8.32±0.82a -a -a 21.85±0.14 p. aeruginosa atcc 27853 13.09±0.59b 23.53±0.20b 20.37±0.32b e. coli o157:h7 12.10±0.86b,c 17.76±0.03c 19.33±0.40c s. epidermidis atcc 12228 8.66±0.31a 20.52±0.09d 14.35±0.37d s. aureus atcc 25923 14.49±0.35b 21.04±0.11e 19.91±0.30b,c *abee: aronia berry ethanol extract, am: ampicillin, k: kanamycin, fca: fluconazole, na: no activity *different superscript values in the columns indicate significant differences (p<0.05) according to the one-way anova followed by tukey's post-hoc test. f(54.945) sig.(0.000) for abee, f(21729.569) sig.(0.000) for am, f(2216.392) sig.(0.000) for k figure 1: mic and mbc or mfc of abee 0 10 20 30 40 50 60 mic ( µg/µl) mbc or mfc ( µg/µl) c. albicans atcc 10231 p. aeruginosa atcc 27853 e.coli o157:h7 s. epidermidis atcc 12228 s. aureus atcc 25923 natural cream additive with an extract containing aronia melanocarpa berries 53(1) pp. 17–25 (2025) 21 14.49 mm, moreover, the lowest mic and mbc of 12.5 µg/µl were determined. these results indicated that s. aureus atcc 25923 was the most sensitive microorganism against abee since an abee concentration of 100 mg/ml inhibited the growth of this strain throughout the experiment with no live cells. the concentration of 50 mg/ml abee (4.81 cfu/ml) exhibited a 1 log reduction compared to the control (5.92 cfu/ml) initially (p<0.05). after 24 and 48 hours, 50 mg/ml of abee inhibited the growth of bacteria as the number of viable cells significantly decreased compared to the control (p<0.05), as presented in figure 2. in a study conducted by tamkutė et al. [47], the aronia pomace ethanol extract exhibited a higher antimicrobial activity than the water extract equivalent. the extracts were reported to be very effective on l. monocytogenes in pig slurry and burgers stored in a refrigerator for 16 days. they suggested that extracts from aronia pomace could be used as natural antimicrobial agents when added to meat. 3.2. spf of abee-cream mixtures prolonged exposure to uv rays increases the risk of various skin diseases such as cancer and photoallergic reactions [48]. in recent years, plants have become regarded as potential additives in cosmetics due to their ability to absorb uv rays and protect skin from the sun's harmful rays [49]-[50]. the ability of sunscreens to protect the skin against uv-b radiation is referred to as the spf [51]. sunscreen provides protection against the negative effects of the sun and uv rays [52]. since the spf of abee determined by spectrophotometry is high, that is, 25 (table 2), abee may be a potential natural additive in sun cream. in our study, the spfs of the cream mixtures prepared with various amounts of abee, namely 2.5, 5.0 and 10.0 ml, and commercial creams are given in figure 3. as the abee amount increased, the spf of the cream mixtures increased proportionally (p<0.05). the figure 2: macrodilution results of abee on s. aureus atcc 25923 *f(668692.000) sig.(0.000) after 0 h, f(2123403.250) sig.(0.000) after 24 h, f(1583247.077) sig.(0.000) after 48 h 0.h 24.h 48.h control 5,92 11,21 16,51 50 mg/ml 4,81 5,87 3,34 100 mg/ml 0 0 0 a a a b b b c c c 0 2 4 6 8 10 12 14 16 18 20 colony-forming unit/ml table 2: spf of abee λ (nm) abs cf x ee(λ) x i(λ) x abs(λ) 290 2.52 0.37 295 2.64 2.15 300 2.58 7.43 305 2.48 8.15 310 2.41 4.49 315 2.34 1.95 320 2.31 0.41 spf value = 25.00±0.09 figure 3: spf of abee and cream mixtures *f(397248.800) sig.(0.000) for control, f(37408.505) sig.(0.000) for cream+extract 0,07 0,44 4,94 0,22 1,77 16,84 0 2 4 6 8 10 12 14 16 18 20 2.5 ml 5ml 10ml 2.5 ml 5ml 10ml c (control) abee spf of abee and cream mixtures saglam and asan-ozusaglam hungarian journal of industry and chemistry 22 highest spf among the cream mixtures was determined to be 16.84 in 10 ml. in one study, the protective effect of the water extract obtained from aronia berries against uv-binduced photodamage was investigated on the dorsal skin of mice. the extract was applied topically once a day for 7 days to the skin of mice exposed to uv-b radiation. it was reported that the topical application of the extract protected against skin damage by reducing collagen degradation of the skin after uv-b irradiation [53]. in another study, oral supplementation of the aronia extract improved the antioxidant status of human skin [54] and the consumption of fresh aronia berries increased radical scavenging rates of the skin by 22-23% [55]. in addition, according to the literature, abee and cream mixtures can be potential sources for preventing skin damage with their high spfs. 3.3. antimicrobial activity of cream developed with abee and l. fermentum ma-7 nowadays, the demand for chemical preservative-free cosmetic products is increasing. an alternative way to ensure a microbial balance in cosmetic products is to use herbal extracts that do not contain chemical preservatives but are also antimicrobially active [40]. herbal extracts and probiotics are used as natural additives as an alternative to synthetic preservatives in the cosmetic industry, thereby providing extra properties to cosmetic products [41]. the biological activities of the developed groups of creams on clinical microorganisms using a well diffusion assay are presented in table 3. the control, namely cream, exhibited no antimicrobial activity on test microorganisms except for p. aeruginosa atcc 27853 with an inhibition zone diameter of 2.44 mm. the c-abee group exhibited the two highest antimicrobial activities on e. coli o157:h7 and p. aeruginosa atcc 27853 with inhibition zone diameters of 11.75 and 11.55 mm, respectively. c-p created a large inhibition zone diameters on s. epidermidis atcc 12228 and s. aureus atcc 25923 of 10.43 and 10.80 mm, respectively. the c-abee-p group yielded the largest inhibition zone diameter among the test microorganisms of 25.40 mm on e. coli o157:h7. among the groups of creams, the highest antimicrobial activity was detected in the c-abee-p group on all test bacteria, possibly due to the synergistic antimicrobial activity of abee and l. fermentum ma-7 on the microorganisms tested. in another study, it was determined that the topical application of water extracts obtained using aronia berries reduced deterioration in the function of types i and iii collagen in photodamaged mouse skin induced by uv-b radiation [53]. aronia berry extract has been reported to reduce the activity of matrix metalloproteinases 1 and 3, which are associated with the delayed healing of chronic wounds [56], moreover, the main polyphenols found in aronia berry extracts can inhibit reactive oxygen species, including chlorogenic acid, rutin and hydroxyl radicals [57]. in addition, a study reported that an important interaction occurs between the skin and the fermentation of lactic acid bacteria (lab), moreover, that the lactate and amino acids in the supernatant of lab help moisturize the skin [58]. 4. conclusions abee exhibited antimicrobial and antifungal activities against pathogen microorganisms and abee as well as cream mixtures yielded high spfs. therefore, it was determined that abee could add extra features to commercial creams as an additive. abee, which was combined with both probiotics and commercial creams, exhibited high levels of antimicrobial activity against pathogen microorganisms. therefore, the ethanol extract obtained from aronia berries may be a promising in the cosmetic and pharmaceutical industries as a natural additive against infections and to protect the skin. references [1] jamal, a.: embracing nature's therapeutic potential: 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of environmental engineering, university oi' kocaeli,41300, izmit-turkey) received: july 26, 2002 alkylation of biphenyl with 1-hexen by using a catalyst was investigated experimentally in this study. ((al + c3h7cl) + c2h4) was used as catalyst and mono-, diand polyalkylbiphenyls were formed at the end of alkylation. the influences of temperature, mol ratio of biphenyl to 1-hexen, reaction time and catalyst concentration on alkylation process were investigated. also the influences of these parameters on the formation of the obtained alkylbiphenyls were observed. experiments show that alkylbiphenyl concentration in alkylat increases with temperature. it was observed that the selectivity of rnonohexylbiphenyl increases by increasing of reaction time and catalyst concentrations. experiments showed that the selectivity of monohexylbiphenyls reached to its maximum value at a ratio of biphenyl to 1-hexen of 1: l on the basis of these results, optimum conditions were determined for mono-, diand polyhexylbiphenyls. key words: alkylation, biphenyl, 1-hexen, ((al + c3h7cl) + c2h4) catalyst, selectivity introduction aromatic hydrocarbons are a proper raw material for the processes of petro-chemical syntheses. as a simple compound of bicyclic aromatic hydrocarbons, biphenyl has both the properties of polycyclic compounds (high thermodynamic stability) and the properties of aromatic compounds (high reaction formation). alkylation of biphenyl by using different catalysts have been widely discussed in the literature [1-3}. especially the investigations of alkylation of biphenyl by olefins [1-7] and alcohols [8-9] have played the most important role to understand many problems in catalyst chemistry and chemical industry. the aim of this paper is to investigate alkylation of biphenyl with 1-hexen by using a catalyst ((ai + c3h7cl) + c2f4). at the experiment, biphenyl and 1-hexen at 99.9% purity were used. experimental results showed that biphenyl is alkylated with 1-hexen easily and different alkyl derivatives of biphenyl are formed. the effects of some parameters (temperature, molar ratio of biphenyl to 1-hexen, reaction time and catalyst concentration) on the process and on the formation of alkylbiphenyls were investigated. contact infonnation: e .. mail: sevilv@kou.edu.tr experimental materials ((ai+ c3h7cl) + c2h4) was used as catalyst in the experiment. biphenyl and 1-hexen (with 99 % purity) were used as raw matter. boiling point, density and index of refraction of 1-hexen were 62-63 °c. 0.673 g/cm3 and 1.388, respectively. 99 % pure ethylene and pure nitrogen were also used. catalytic reaction is as follows: c2h4 + 4c3h7cl + 2al = 2al(c3h1hcl + c2~ch experiment alkylation of biphenyl with 1-hexen was carried out in a laboratory device (fig.!). it consists of a reactor of 1.51 (l) and a flowmeter (5) connecting liquid monometers with the reactor. reactor was equipped with a mixer (2), a heater (6), manometer (3), 208 6 fig.l scheme of the laboratory device (1-reactor, 2-mixer, 3i 80 ~ii 60 40 ~ • .... .... .... .... .... ... ill 20 0 0 20 40 60 80 100 temperature oc fig.2 the effect of temperature on the variation of the biphenyl conversion and selectivities of alkylbiphenyls ; !­ biphenyl conversion, iiselectivity ofmonohexylbiphenyl, iii­ selectivities of diand polyhexylbiphenyls. reaction conditions: reaction time 60 min., molar ratio of biphenyl to 1hexen 1:1, mass ratio of catalyst to biphenyl1,5% manometer, 4-1-hexen cup, 5-difmonometer, 6-heater, 71 00 thermocouple channel) thermocouple channel (7) and inlet and outlet valves. flowmeters and reactor are made of stainless steel for the experiment, catalyst and biphenyl at certain amounts were added to reactor. air in the reactor was removed by nitrogen. then reactor was heated and, started to be mixed when biphenyl was liquefied. after that, nitrogen application was continued and by the time reaction conditions was reached, 1-hexen at sufficient amounts was added into the reactor by flowmeter (5) under nitrogen pressure. alkylation was carried out by continuous mixing. at this time temperature was lowered by water bath. after the reaction was completed, the reactor was cooled by water bath to room temperature and opened. finally samples were taken and prepared for alkyl biphenyl analyzis. results and discussion biphenyl is alkylated by different compounds. the alkylation process of biphenyl with olefins is one traditional methods to produce alkylbiphenyls. therefore alkylation of biphenyl with 1-hexen in the presence of a catalyst has a high importance. effect of reaction temperature results showed that temperature is one of the main factors affecting the reaction rate. its effect on the alkylation was observed between 20-80 °c. it was observed that the conversion of biphenyl increases with temperature. in this case~ the amounts of mono-, diand polyhexylbiphenyls obtained were also increased. the results of the experiment were shown in fig.2. 80 '*60 40 20 0 0,5 1,5 2 biphenyl/1-hexen (mol ratio) fig.3 the effect of molar ratio of biphenyl to 1-hexen on the variation of biphenyl conversion and the amounts of obtained alkyl biphenyls; i-biphenyl conversion, iiamount of monohexyl biphenyl, iiiamounts of diand polyhexyl biphenyls. reaction conditions: reaction temperature 60 °c, reaction time 60 min., ratio of catalyst to biphenyl 1,5 % effect of molar ratios the effect of molar ratios of biphenyl to 1-hexen was observed at the ratios of 115; 1/1 and 1.8/l. experiments showed that molar ratios of monomers have a significant effect on alkylation process. as the molar ratio of biphenyl to 1-hexen increases, conversion of biphenyl decreases. at the same time, selectivity of monohexyl biphenyl increases while the amounts of di­ and polyhexylbiphenyls decreases. experimental results are shown in fig.3. as shown in fig.3, maximum amounts of monohexyl biphenyl was observed at the 1:1 molar ratio of monomers. increasing the biphenyl ratio in the process caused biphenyl conversion to decrease. simultaneously the concentration of monohexyl biphenyls increased, while the other alkylbiphenyls decreased. according to these results~ it is suggested that as the biphenyl concentration in the process increases, the 0+-------~-------.--------~----~ 0 20 40 60 80 time (minute) fig.4 the effect of reaction time on the variation of biphenyl conversion and the amounts of obtained alkyl biphenyls; !­ biphenyl conversion , iiamount of monohexyl biphenyl, iii­ amounts of diand polyhexyl biphenyls. reaction conditions: reaction temperature 60 °c, ratio of catalyst to biphenyl1,5 %, molar ratio of biphenyl to 1-hexen 1:1 bounding of one 1-hexen molecule to biphenyl molecule separately occurs easier than the bounding of two 1hexen molecules to one biphenyl molecule. on the other hand, since all biphenyl molecules could not be alkylated, the amount of biphenyl molecules that are not reacted, increase and therefore the biphenyl conversion decreases. effect of reaction time the effect of reaction time on the alkylation process was examined between 20-60 minutes. the effect of reaction time on the process is shown in fig.4. as shown in fig.4, biphenyl conversion and monohexyl biphenyl concentration in alkylat increases as the reaction time increases, while di~ and polyhexyl biphenyl concentrations decrease. these results suggest that as the reaction time increases, the dealkylation reaction, parallel reaction of alkylation, accelerates. this leads to a decrease in the diand polyhexyl biphenyl amount in alkylat, as well as an increase in the amount of monohexyl biphenyl. effect of catalyst concentration the rate of alkylation reaction also depends on the catalyst concentration as all reactions do. the effect of catalyst was examined at three ratios of catalyst used to biphenyll,s %, 4 % and 6,5 %. fig.5 shows the results of the experiment. as shown in the fig.5, as the catalyst concentration increases, alkylation reaction accelerates and then, conversion of biphenyl and amounts of obtained monohexyl biphenyl increase while amounts of diand polyhexyl biphenyls decrease. the decreasing of di-, and polyhexyl biphenyls is explained that the catalyst used was a catalyst of both alkylation and dealkylation. therefore, as the catalyst concentration increases, dealkylation also increases and diand polyhexyl biphenyls are transformed to monohexyl biphenyl by 40 20. 0 0 209 ~ill 2 4 6 8 catalyst concentrations(%} fig.5 the effect of catalyst concentration on variation of the of biphenyl conversion and the amounts of obtained alkyl biphenyls; !-biphenyl conversion , iiamount of monohexyl biphenyl, iiiamounts of diand polyhexyl biphenyls. reaction conditions: reaction temperature 60 °c, reaction time 60 min., molar ratio of biphenyl to 1-hexen 1:1 dealkylation. as a result, the ratio of monohexyl biphenyls to alkyl biphenyls increases. the experiments showed the high activity of the catalyst used in alkylation of biphenyl with 1-hexen. that activity causes the alkyl biphenyls to be formed with a higher selectivities as compared to other catalysts. consequently, after examining the effects of these parameters on the process, the optimum conditions for the formation of mono, diand polyhexyl biphenyls can be determined. optimum conditions for the formation of monohexyl biphenyls were found a5 follows: reaction temperature reaction time molar ratio of biphenyl to 1-hexen ratio of catalyst to biphenyl 60''c 60min 1:1 6.5% on the other hand, optimum conditions for the formation of diand polyhexyl biphenyls were determined to be as follows: reaction temperature reaction time molar ratio of biphenyl to l-hexen ratio of catalyst to biphenyl conclusions 60°c 20min 1:1 1.5% the alkylation of biphenyl with 1-hexen by a catalyst produces alkyl biphenyls with high efficiency and selectivity. activity of the catalyst was studied in different intervals of temperature, molar ratio, reaction time and catalyst concentration. it was showed that increasing the temperature accelerates the process and leads to an increase in the amount of alkyl biphenyls obtained. additionally, optimum conditions for the production of monoand dialkyl biphenyls were determined. 210 acknowledgement the author wishes to express his thanks to prof. dr. asker htiseyinov for the helpful discussions and suggestions. references 1. matsuda t., urata t. and kikuchi e.: appl.catal.a-gen., 1995, 123,205-215 2. matsuda t., urata t., saito u. and kikuchi e.: appl.catal.a-gen., 1995, 131,215-224 3. butruille j. r. and pinna v aia t. j.: propene alkylation of biphenyl catalyzed by alumina pillared clays and related acidic oxides, 1992, 12, 187-192 4. sugi y., matsuzaki t., hanaoka t., kubota y., kim j. h., tu x. and matsumoto m.: catal.let., 1994,26,181-187 5. matsuda t., kimura t., herawati e., kobayashi c. and kikuchi e.: appl.catal.a-gen., 1996, 136, 19-28 6. vergani d., prins r. and kouwenhoven h. w.: appl.catal.a-gen., 1997, 163,71-81 7. aguilar j., corma a., melo f. v. and saste e.: catal.tod., 2000, 55, 225-232 8. aguilar j., melo f. v. and sastre e.: appl.catal.a-gen., 1998, 175, 181-189 9. horniakova j., mravec d., fabokova s., hronec m. and moreau p.: appl.catal.a-gen., 2000, 203,47-53 page 209 page 210 page 211 page 212 hungarian journal of industry and chemistry vol. 46(2) pp. 43–46 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0017 recovery of itaconic acid by electrodialysis veronika varga1, katalin bélafi-bakó1, dávid vozik1, and nándor nemestóthy *1 1research institute of bioengineering, membrane technology and energetics, university of pannonia, egyetem u. 10, veszprém, 8200, hungary itaconic acid is an organic acid produced mainly for non-food purposes. it can be manufactured by biotechnological synthesis using various strains which results in the salt form of the acid. in this work, the separation of sodium itaconate by electrodialysis was studied. homopolar cationand anion-selective membranes were applied and the module was operated under a constant voltage. the transport of the acid was followed by on-line ultraviolet and visible absorption spectroscopy, where the detector was installed in the system. the experiments with models of aqueous solutions confirmed that the technique is suitable for the effective recovery of itaconic acid. keywords: ultraviolet and visible absorption spectroscopy, on-line detection, monopolar membranes 1. introduction itaconic acid was discovered by baup in 1837 as the coproduct resulting from the degradation of citric acid [1]. itaconic acid (2-methylene,1,4-butanedioic acid) is an unsaturated dicarboxylic acid, a rather reactive compound due to its conjugated double bond and two carboxyl groups. therefore, it can easily participate in polymerisation reactions. itaconic acid – unlike citric acid – is applied exclusively for non-food purposes [2]. it is used mainly in the production of synthetic fibres and ion-exchange resins as well as in the pulp and paper industry. itaconic acid can be synthesized biotechnologically. kinoshita was first to describe the process in 1932 when it was isolated from the broth of aspergillus itaconicus [3]. later a similar strain, aspergillus terreus, was found to produce itaconic acid. other microbes suitable for the fermentation of itaconic acid are listed in table 1. the main problem with downstream processing is that several similar organic acids are present in the broth, thus, recovery of itaconic acid is difficult. separation of itaconic acid can be conducted by filtration with the aid of activated carbon and crystallisation (consecutive steps) or adsorption by strong anion-exchange resins, like purolite a-500 p or pfa-300 [10]. the efficiency of the separation depends mainly on the temperature, ph and concentration. an application of electrodialysis (ed) as a membrane process is the separation of organic acids [11–14]. malic acid and galacturonic acid amongst others can be separated by ed using monopolar and bipolar membranes by *correspondence: nemesn@almos.uni-pannon.hu table 1: biotechnological synthesis of itaconic acid strain reference aspergillus itaconicus kinoshita et al. (1932) [3] ustilago maydis steiger et al. (2013) [4] pseudozyma antarctica levinson et al. (2006) [5] yarrowia lipolytica kuenz et al. (2018) [6] synechocystis cyanobacteria heidorn et al. (2011) [7] chin et al. (2015) [8] aspergillus terreus karaffa et al. (2015) [9] implementing batch and continuous modes of operation. the majority of these acids are produced as a salt, thus, the aim of the separation by ed is to transport the organic acid through the anion-selective membrane, while the cation should pass through the cation-selective membrane. the other neutral components remain in the feed solution. usually the mobility of the acid is sufficient for effective transport, hence both the acid and cation can be recovered by ed. the aim of this paper was to study the possibility of applying ed for the recovery of sodium itaconate. 2. experimental itaconic acid, sodium sulphate, sulphuric acid, sodium hydroxide and all the other chemicals used were of anmailto: nemesn@almos.uni-pannon.hu 44 varga, bélafi-bakó, vozik, and nemestóthy table 2: features of the membranes feature fumasep faa fumasep fks selectivity >92 % >96 % electrical resistance <2 ωcm2 <8 ωcm2 ph stability in acidic media 5-13 thickness 0.13-0.15 mm 0.11-0.13 mm ion-exchange capacity >1.2 meq/g >1.0 meq/g conductivity >8 ms/cm >5 ms/cm alytical grade and purchased from sigma-aldrich. the anionand cation-selective membranes were fumasep faa and fks membranes, respectively. the main features of the membranes are summarized in table 2. the membranes were activated by sodium chloride and sulphuric acid before usage. for analytical purposes a young lin instrument co., ltd. (yl9100-type) high-performance liquid chromatography (hplc) system (including a yl9109 vacuum degasser, yl9110 quaternary pump and yl9150 automatic sample dispenser) was used to determine the concentration of itaconic acid with a hamilton hplc column (15 cm in length, 4.6 mm inner diameter, 5 µm particle size) and a yl9120 uv/vis detector. the luff-schoorl method was used to determine the glucose concentration which is based on the reduction of cupric (cu(ii)) cations in a boiling alkaline solution of cuprous (cu(i)) oxide [15]. the surplus of cu(ii) was measured by iodometry using a titration with sodium thiosulfate. the conductivity of the solutions was measured by a radelkis ok-102/1 conductivity meter equipped with a radelkis ok-9023 bell electrode using a cell constant of 0.7 cm−1. data concerning the voltage and current were measured by a national instruments usb-600866009 device. all the experimental data were collected online using labview software. an electrodialysis module was constructed from 2 anionand 2 cation-selective membranes using spacers between them. the electrode solution was an aqueous solution of sodium sulphate. electrodialysis measurements were conducted using diluted (aqueous) model solutions of sodium itaconate and sodium itaconate mixed with glucose. the module was operated under a constant voltage. 3. results in this project, the final aim was to connect the ed device to the fermentation of itaconic acid in order to set up an integrated system. for this purpose, firstly the operation of ed was investigated by using model solutions of sodium itaconate and a simple ed device with monopolar figure 1: percentages of the four distinct forms of itaconic acid. ion-exchange membranes. the transport of the itaconic acid through the anion-selective membranes was the focus of the study to follow the process, it was important to determine the exact concentration of itaconic acid. if the acid is the only compound in the solution, measuring the conductivity is a simple method for detection. however, if any other charged compound is present, it will disturb such measurements. in this case, hplc is suggested for the analysis [9]. itaconic acid is a dicarboxylic acid (consisting of three different ionic forms) and its dissociated forms and ionic strengths vary according to the ph. thus, four distinct peaks over different retention times can be detected in hplc chromatograms. the percentages of the four distinct forms as a function of ph were determined and are presented in fig. 1. since it is quite difficult to measure the actual concentration of itaconic acid, another method was chosen. itaconic acid has a uv absorption maximum at 243 nm which can be used for detection. this method seemed sufficiently sensitive for our purposes. in our work, a loop was constructed from the solution (recirculated in the ed module) to the uv detector. thus, online detection was applied to follow the concentration figure 2: calibration curve for the determination of itaconic acid concentration by uv detection hungarian journal of industry and chemistry recovery of itaconic acid by electrodialysis 45 figure 3: polarization curves of itaconic acid as a function of operating time. firstly, a calibration curve was recorded (fig. 2) over the concentration range of itaconic acid that was planned to be used. the data measured by the online uv system were checked by hplc. to test the ed module, polarization curves were taken using a potentiostat by applying a range of voltages from 0 to 10 v (fig. 3). the current data were recorded as a function of the voltage data. the measurements were repeated in various electrode solutions. it seems that beyond a sodium sulphate concentration of 0.125 m, the ed operated properly. experiments were conducted in the ed module by using aqueous model solutions of itaconic acid (with an initial concentration of 3-3 g/l). the electrode solution was a 0.16 m na2so4 solution. the experiments were conducted under a constant voltage (10 v) and the current intensity varied between 0.11 and 0.15 a. subsequently, the conductivity in the diluate solution was measured. the concentration of the acid decreased gradually to half its initial value after an operating time of 70 mins as can be seen in fig. 4. this means that itaconic acid was able to pass through the anion-selective membrane, while sodium ions were able to diffuse across the cation-selective membrane. therefore, the measurements confirmed that the mobility of this acid is sufficient to separate it by ed. figure 4: conductivity data of the diluate of ed figure 5: concentration of itaconic acid in the diluate solution in the next series of experiments, glucose was added to the acid (4 g/l) to investigate whether the ed module was able to separate the two compounds. the concentration of itaconic acid in the diluate was followed online by the uv detector installed in the loop. the concentration of the glucose was determined by the luff-schoorl method. the concentration of the acid decreased from 3.0 to 1.5 g/l during the experiment (fig. 5), while the glucose concentration was monitored in all three streams. in the diluate (originally feed) solution, a slight decrease in glucose concentration was observed (to 3.52 g/l), its concentration was negligible (0.20 g/l) in the electrode solution, while in the concentrate solution 0.59 g/l glucose was measured probably due to its diffusion from the feed solution. 4. conclusion the measurements provided a definite answer to the original question, namely whether ed is a suitable technique for the recovery of itaconic acid. the results of the experiments using model solutions (sodium itaconate on its own as well as a mixture of sodium itaconate and glucose) confirmed that ed is an effective method for the separation of itaconic acid. based on these results, further experiments are being planned using more complex model solutions, similar to the composition of the fermentation broth. subsequently, it is our intention to connect the ed module to the fermentation process. acknowledgements this research was supported by the national research, development and innovation fund project otka k 119940 entitled “study on the electrochemical effects of bioproduct separation by electrodialysis” and by the financial support of széchenyi 2020 within project efop3.6.1-16-2016-00015. 46(2) pp. 43–46 (2018) 46 varga, bélafi-bakó, vozik, and nemestóthy references [1] baup, s.: über eine neue pyrogencitronensäure, und über benennung der pyrogen säure überhaupt, ann. chim. phys., 1837 9, 29–38 doi: 10.1002/jlac.18360190107 [2] delidovich, i.; hausoul, p. j.; deng, l.; pfutzenreuter, r.; rose, m.; palkovits, r.: alternative monomers based on lignocellulose and their use for polymer production, chem. rev., 2016 116(3), 1540–1599 doi: 10.1021/acs.chemrev.5b00354 [3] kinoshita, k.: über die produktion von itaconsäure und mannit durch einen neuen schimmelpilz, aspergillus itaconicus, acta phytochimica, 1932 5, 271–287 [4] steiger, m.; blumhoff, g.; marzena, l.; mattanovich, d.; sauer, m.: biochemistry of microbial itaconic acid production, front. microbiol., 2013 4(23), 1–5 doi: 10.3389/fmicb.2013.00023 [5] levinson, w. e.; kurtzman, c. p.; kuo, t. m.: production of itaconic acid by pseudozyma antarctica nrrl y-7808 under nitrogen-limited growth conditions, enzyme microb. technol., 2006 39 (4), 824– 827 doi: 10.1016/j.enzmictec.2006.01.005 [6] kuenz, a.; krull, s.: biotechnological production of itaconic acid—things you have to know, appl. microbiol. biotechnol., 2018 102(9), 3901–3914 doi: 10.1007/s00253-018-8895-7 [7] heidorn, t.; camsund, d.; huang, h.; lindberg, p.; oliveria, p.; stensjo, k.; lindblad, p.: synthetic biology in cyanobacteria: engineering and analyzing novel functions, methods enzymol., 2011 497, 539–579 doi: 10.1016/b978-0-12-385075-1.00024-x [8] chin, t.; sano, m.; takahashi, t.; ohara, h.; aso, y.: photosynthetic production of itaconic acid in synechocystis sp. pcc6803, j. biotechnol., 2015 195, 43–45 doi: 10.1016/j.jbiotec.2014.12.016 [9] karaffa, l.; diaz, r.; papp, b.; fekete, e.; sandor, e.; kubicek, c. p.: a deficiency of manganese ions in the presence of high sugar concentrations is the critical parameter for achieving high yields of itaconic acid by aspergillus terreus, appl. microbiol. biotechnol., 2015 99(19), 7937–7944 doi: 10.1007/s00253-015-6735-6 [10] magalhăes, a. i.; de carvalho, j. c.; ramírez, e. n. m.; medina, j. d. c.; soccol, c. r.: separation of itaconic acid from aqueous solution onto ionexchange resins, j. chem. eng. data, 2016 61 (1), 430–437 doi: 10.1021/acs.jced.5b00620 [11] lameloise, m. l.; matinier, h.; fargues, c.: concentration and purification of malate ion from a beverage industry waste water using electrodialysis with homopolar membranes, j. membr. sci., 2009 343(1-2), 73–81 doi: 10.1016/j.memsci.2009.07.013 [12] molnár, e.; nemestóthy, n.; bélafi-bakó, k.: galacturonic acid recovery from pectin rich agrowastes by electrodialysis with bipolar membranes, hung. j. ind. chem., 2008 36, 95–99 doi: 10.1515/186 [13] stodollick, j.; femmer, r.; gloede, m.; melin, t.; wessling, m.: electrodialysis of itaconic acid: a short-cut model quantifying the electrical resistance in the overlimiting current density region, j. membr. sci., 2014 453, 275–281 doi: 10.1016/j.memsci.2013.11.008 [14] bélafi-bakó, k.; molnár, e.; csanádi, z.; nemestóthy, n.: comparative study on electrodialysis systems for galacturonic acid recovery, hung. j. ind. chem., 2012 40, 65–67 doi: 10.1515/343 [15] koutinas, a.; bélafi-bakó, k.; kabiri-badr, a.; tóth, a.; gubicza, l.; webb, c.: enzymatic hydrolysis of polysaccharides: hydrolysis of starch by an enzyme complex from fermentation by aspergillus awamori, food bioprod. process., 2001 79, 41–45 doi: 10.1205/09603080151123353 hungarian journal of industry and chemistry https://doi.org/10.1002/jlac.18360190107 https://doi.org/10.1002/jlac.18360190107 https://doi.org/10.1021/acs.chemrev.5b00354 https://doi.org/10.3389/fmicb.2013.00023 https://doi.org/10.1016/j.enzmictec.2006.01.005 https://doi.org/10.1007/s00253-018-8895-7 https://doi.org/10.1016/b978-0-12-385075-1.00024-x https://doi.org/10.1016/j.jbiotec.2014.12.016 https://doi.org/10.1007/s00253-015-6735-6 https://doi.org/10.1007/s00253-015-6735-6 https://doi.org/10.1021/acs.jced.5b00620 https://doi.org/10.1016/j.memsci.2009.07.013 https://doi.org/10.1515/186 https://doi.org/10.1016/j.memsci.2013.11.008 https://doi.org/10.1016/j.memsci.2013.11.008 https://doi.org/10.1515/343 https://doi.org/10.1205/09603080151123353 introduction experimental results conclusion hungarian journal of industry and chemistry vol. 47(2) pp. 25–30 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-17 multistage gravity beneficiation of rutile in a tar-free sand residue rukayat akande*1 and abraham adeleke1 1department of materials science and engineering, obafemi awolowo university, ile-ife, nigeria this study reports on the concentration of rutile in the sand recovered from tar sand in ondo state in nigeria. the tar-free sand residue, approximately 90 % of which passes through a sieve with a pore size of 355 µm, was subjected to sieve analysis as well as sequences of panning gravity pre-concentration and shaking-table concentration at a slurry density of 25 % solids to improve the rutile content. the sand residue recovered in addition to the panned pre-concentrate and shaking table concentrates were also subjected to reflected light microscopy as well as transmitted light microscopy, counting using imagej software and x-ray fluorescence spectroscopy. the micrographs obtained showed that the samples contain rutile, dark-brown in color, interlocked with the major silica content and the content of rutile estimated by imagej software increased in the pre-concentrate from 7.90 % to 19.23 % in the final concentrate. x-ray fluorescence spectroscopy also showed that the rutile content increased in the pre-concentrate from 1.43 % to 31.02 % in the final concentrate. therefore, the rutile content was successfully increased by the cheap gravity techniques of panning and shaking tables. keywords: tar sand, rutile, panning, shaking table, pre-concentrate, concentrate 1. introduction tar sands, also known as oil sands, are a combination of clay, sand and water saturated in a dense and extremely viscous form of petroleum technically referred to as bitumen. tar sands are impregnated sands that yield mixtures of liquid hydrocarbons, which require further processing other than mechanical blending before becoming finished petroleum products. tar sand deposits are found in various parts of the world including canada, madagascar, venezuela, russia, the united states and nigeria [1]. tar sand is exceedingly rich in oil as well as other valuable minerals and metals in varying proportions [2]. tar sand deposits are composed primarily of quartz sand, silt, clay, water and bitumen along with trace amounts of metallic minerals such as rutile, pyrite, zircon and gemstones like tourmaline. rutile is a major source of the element titanium and it is industrially used as a white pigment for paint, a ceramic glaze and in optical equipment [3, 4]. it is also used in sunscreen products due to its ability to reflect ultraviolet light [5]. nigeria has a large deposit of natural bituminous tar sand, which is estimated to be the fourth largest in the world after canada, russia and venezuela [6]. it is estimated that about 34 to 45 billion barrels of heavy oil is trapped in tar sand deposits in ondo state in southwestern nigeria alone, with more reserves in edo and ogun states. the reserve of tar sand in ondo state alone is es*correspondence: akanderukayat2@gmail.com timated to be 31 billion metric tons [7]. the tar sand here is located in the eastern part of the dahomey basin, a coastal sedimentary basin that extends from the ghanaivory coast border through togo and the republic of benin to western nigeria [8]. adeleke et al. [9] leached tar sand from ondo state using sodium hydroxide and sodium carbonate to strip off bitumen from the admixture of sand and also conducted a solubility test on the tar sand using toluene. sodium hydroxide was found to yield a higher percent recovery of bitumen than sodium carbonate over the same leach contact time. adebiyi et al.[10] determined the elemental composition of oil sand from southwestern nigeria by total reflection x-ray fluorescence and detected twelve elements, namely k, ca, ti, v, cr, mn, fe, ni, cu, zn, as and pb. ignasiak [11] reported that a nigerian deposit of bitumen-free sand residue contains only 0.06 wt% tio2. gravity beneficiation techniques make use of the difference in the specific gravity of minerals to separate them. therefore, heavy minerals such as rutile can be separated from the associated lighter minerals like silica. in the gravity method of shaking tables, a flowing film of water effectively separates coarse light particles from small dense particles [12]. mixed rutile and ilmenite ores were subjected to coarse concentration using a mineral jig [13]. in this research, the lean content of the mineral rutile in a residue of tar sand from ondo was increased over a sequence of gravity beneficiation by panning and shaking https://doi.org/10.33927/hjic-2019-17 mailto:akanderukayat2@gmail.com 26 akande and adeleke tables. 2. materials and methods 2.1 the collection of samples the basic raw materials used in this work were lumps of bituminous tar sand obtained from ondo state, nigeria. lumps of the semi-solid black tar sand of about 50 kg in weight were collected from the villages of agbabu and loda in the local government area of irele in ondo state. the local government area of irele is situated to the east of the local government area of okitipupa which lies at 40° 3” in longitude east of the greenwich meridian and at 50° 45” and 80° 15” in latitude north of the equator. the samples were collected from two open pits at a depth of about 3 feet. after field sampling, the lumps of tar sand extracted were stored in large plastic bags. 2.2 sample preparation the black lumps of tar sand were crushed and ground thoroughly with a steel rod. the ground tar sand was then homogenized in a mortar by pounding it with a pestle. the resultant mass of tar sand was composed of a finer mixture of particles and bitumen. 2.3 stripping of bitumen by leaching whilst being stirred the tar sand was leached on a magnetic hotplate stirrer using a 32 factorial design, that is, at three different temperatures and by applying variables concerning the concentration process. the 250 ml beaker reactor containing the slurry of tar sand and 25 ml of 0.5 m sodium hydroxide at a pulp density of approximately 40 g/l was initially homogenized for 5 minutes. the beaker was placed on a stuart magnetic hotplate stirrer, model number r000101019, which was set to 50 °c and 90 rpm to yield the t1c1 test combination. the magnetic stirrer was switched on and the pulp of tar sand allowed to react with the leachant, sodium hydroxide, for 30 minutes. after 30 minutes, the concentrate of bitumen was skimmed off and the leachant filtered to remove the remaining bitumen. the procedure was repeated for combinations t1c2, t1c3, t2c1, t2c2, t2c3, t3c1, t3c2, and t3c3. 2.4 stripping of bitumen by leaching in the absence of stirring a slurry of tar sand with a pulp density of approximately 40 g/litre was prepared by mixing 25 ml of 1.5 m sodium hydroxide and 1 g of tar sand in a 500 ml beaker. the beaker containing the slurry of tar sand was then placed on a hp-11electric hot plate. the slurry was stirred continuously for 30 minutes with a glass rod to agitate it to facilitate the recovery of bitumen from the tar sand. subsequently, the bitumen was decanted off and the residue washed with water to remove the bitumen. the residue was washed again with toluene to dissolve traces of bitumen in the tailings. the residue was then dried at 70 °c in an oven and the procedure repeated using 20, 3, 4, 5, 6, 7, 8, 9, and 10 g of tar sand which resulted in pulp densities of approximately 80, 120, 160, 200, 240, 280, 320, 360, and 400 g/l, respectively. the same procedure was repeated using 30 g of tar sand and the slurry prepared by mixing 300 ml of 1.5 m sodium hydroxide and 30 g of tar sand in a 500 ml beaker. the procedure was repeated several times until 7 kg of tar-free sand was recovered. a blank test was conducted using 25 ml of distilled water and 1 g of tar sand in a 500 ml beaker reactor. the beaker containing the slurry of tar sand was then placed on the hp-11 electric hot plate. the slurry was stirred continuously with a glass rod to agitate it to facilitate the recovery of bitumen from the tar sand. 2.5 panning of the tar-free sand about 50 g of the sample was thoroughly mixed and agitated with 50 ml of water in a 500 ml plastic bowl. the panning process caused the lighter mineral particles to float while the denser particles sank. the floating light particles were decanted off while the denser residue was dried and weighed. the procedure was repeated but with 100, 150, 200, 250, 300, and 350 ml of water. following preliminary panning, the remaining sample that weighed 36.25 g was subjected to further panning using the same 350 ml of water. the procedure was repeated ten more times by weighing the wet residue together with a content of 4.02 g after each panning. the same procedure was employed for the shaking tabling of approximately 138 g of the sample. 966 ml of water was used for panning the 138 g of tar-free sand ten times and the final product weighed and dried before proceeding to the shaking table. 2.6 determination of the specific gravity of tar-free sand a density bottle was washed, dried and its weight, m1, measured. subsequently, 5 g of tar-free sand residue was placed inside the dried bottle and its weight, m2, determined. then, 50 ml of distilled water was poured into a measuring cylinder and weighed to give m4. lastly, distilled water was added to the tar-free sand in a covered bottle and shaken very well for thorough mixing, moreover, additional distilled water was added to increase the volume to 50 ml and then weighed to give m3. to determine the specific gravity, thsese values were inserted into equation [12] g = m2 −m1 (m4 −m1)− (m3 −m2) (1) where m1 is the mass of empty bottle, m2 is the mass of bottle + dry soil, m3 is the mass of bottle + dry soil + hungarian journal of industry and chemistry multistage gravity beneficiation of rutile 27 figure 1: weight percentage of tar sand recovered following stripping on an electric hot plate. water, and m4 is the mass of bottle filled with water only. after deriving the specific gravity, the ratio of solids to water required to make the slurry was also determined as the feed should be composed of about 25 % solids by weight. 2.7 shaking tabling a slurry composed of 25 % solids by weight was produced by mixing 108 g of the panned sample in 324 ml of water which was introduced via the feed box of a shaking table, model number ed808148566q. the slurry was distributed evenly over the table, wash water was dispersed along the balance length of the feed launder. the table was then vibrated longitudinally using a slow forward stroke and a rapid return strike which caused the mineral particles to ‘crawl’ along the deck parallel to the direction of motion. as a result, the minerals were subjected to two forces, one due to the motion of the table and the other at right angles to it due to the flowing film of water. consequently, the particles moved diagonally across the deck from the feed end and fanned out on the table – the smaller, denser particles rode on top towards the concentrate launder at the far end. the larger lighter particles were washed into the tailings launder, which runs along the length of the table. an adjustable splitter at the concentrate launder was used to separate the product into three fractions, namely a high-grade concentrate and two medium-grade fractions. the concentrate continued to be shaken nine more times and the products weighed wet after every shaking. the final products were dried separately and then weighed [12]. 2.8 particle size analysis using a sieving method the eight sieves with pore sizes of between 850 and 63 µm were chosen based on the square root of two rule. the weights of the empty sieves were recorded and stacked on top of each other with the coarsest sieve with a pore size of 850 µm on the top and the finest of 63 µm at the bottom. a fitting receiver was placed below the bottom sieve to collect any undersized particles and a lid placed on top of the coarsest sieve to prevent the sample from escaping. fig. 1 shows the sieving machine and the setup of the sieves. a 300 g sample of the recovered tar-free sand was poured onto the uppermost, coarsest sieve, and the nest of sieves placed in an endecotts test sieve shaker, model number 9205. the nest of sieves was vibrated in a vertical plane. the period of shaking was set to 30 mins using an automatic timer. during the shaking, the undersized material dropped through successive sieves until it was retained on a sieve with a pore size slightly smaller than the diameter of the particles. in this way, the sample was separated into size fractions. after the required time, the nest of sieves was dismantled and the amount of material retained on each sieve weighed [12]. 2.9 reflected light microscopy the sample was deposited on a slide which was placed on the stage of an accu-scope microscope, serial number 0524011. the diaphragm was then used to vary the intensity and size of the cone of light that was projected upwards through the slide. the microscope was connected to a laptop to capture the plane section of the image which was captured using image capture software on a laptop as soon as a clear image was obtained. reflected light microscopy was used to view the raw sample, panned sample, samples obtained from the particle size analysis and those from the shaking table. imagej was used to analyze the images obtained from reflected light microscopy. 2.10 thin section microscopy the sample was impregnated since it was a loose sample by mixing equal amounts of araldite (resin and hardener) and sample together which was placed on a glass slide. the glass slide was placed on a hot plate for 5 mins and left to cool overnight. the cooled glass slide was ground by a lapping machine, transferred to a lapping plate for further grinding and viewed intermittently several times under the microscope till it became thin enough for light to penetrate through. the glass slide was dried on the hot plate, covered in araldite and viewed under a brunel petrographic microscope, model no. 1287599. 2.11 x-ray fluorescence spectroscopy a 3 g sample was pulverized into a fine homogenous mass and pelletized. an x-ray fluorescence spectrometer, model no. edx3600b, was used to analyze the sample. the desired method was selected on the measuring instrument and the sample carefully placed onto the instrument according to the set-up of its benchtop measurement position. the compartment containing the sample was covered to prevent x-ray radiation from being scattered. the measurement conditions were set, the details of the sample entered and the complete spectrum recorded which 47(2) pp. 25–30 (2019) 28 akande and adeleke table 1: screened distribution of sand recovered from tar sand. pore-size range of sieve (µm) weight of sieve fraction (g) weight of sieve fraction (%) nominal aperture size (µm) cumulative undersize distribution (%) cumulative oversize distribution (%) +850 1.02 0.37 850 99.63 0.37 850 to +500 0.92 0.33 500 99.26 0.74 500 to +355 5.05 1.84 355 97.45 2.55 355 to +212 20.44 7.45 212 89.97 10.03 212 to +150 178.7 65.14 150 24.86 75.14 150 to +125 50.51 18.41 125 6.45 93.55 125 to +90 16.62 6.06 90 0.39 99.61 90 to +63 0.96 0.35 63 0.04 99.96 < 63 0.11 0.04 lasted 60 to 120 seconds per sample, moreover, all detectable elements were measured simultaneously. raw quantitative spectra and quantified results were acquired and saved. 3. results and discussion it can be seen from fig. 1 that the weight percent of recovered tar-free sand reduces as the mass of the tar sand increases which indicates that the percent recovery decreases as the pulp density increases. therefore, pulp density is one of the factors that affects leaching, hence the laboratory-scale leaching of about 40 g/l was conducted. the decrease in the leaching rate as the pulp density increases is due to increased particle crowding and a lower concentration of leachant available per unit volume of the slurry [14]. it was observed that the smallest bitumen recovery of 55 % obtained from stirred leaching on the magnetic stirrer hotplate was greater than the highest recovery of 45 % for the unstirred leaching on the ordinary hotplate. this confirms that slurry stirring is an important process variable in the hydrometallurgical approach to leaching [14]. the sieve analysis showed that the majority of the sample was found within the 212 to 150 µm pore-size range, namely 65.14 % of the sample. the results obtained suggest that the residue of the tar sand is fairly coarse as the fraction smaller than 63 µm is insignificant. coarse-sized ores are preferred for gravity concentration as they are more efficiently treated than finer ones [12]. the results are presented in table 1. the lighter minerals from the 350 ml volume of water were further reduced following nine sequential pannings. the residue obtained after ten sequential pannings was found to contain many of the denser minerals given that the majority of the lighter minerals had been previously removed as shown in table 2. this table shows that the mass of the denser sand residue obtained after panning generally decreased as the volume of water used for panning increased. the results obtained suggest that panning efficiency increases as the volume of water increases. this may be due to the fact that by increasing table 2: the recovery of denser materials as a function of the volume of water used during panning. volume (ml) residue (g) mass recovered (%) 50 47.43 94.86 100 45.42 90.84 150 45.38 90.76 200 44.01 88.02 250 40.18 80.36 300 38.63 77.26 350 36.25 72.5 the water content, a more dilute slurry subject to less particle crowding, a better degree of free flow and settling of mineral particles is produced, thus enhancing the separation of lighter particles from denser ones. fig. 2 indicates that generally the mass of denser residues decreased as the sequence of panning stages progressed. the results suggest that as the sequence of panning advances, the minerals composed of denser particles are progressively concentrated into the concentrates of denser residues [12]. it was observed from fig. 3 that the more the shaking table charge was subjected to a sequence of shaking tabling, the greater the proportion of denser rutile that was separated from the lighter silica mineral. the weight of the dry concentrates and tailings obtained after the sefigure 2: residue obtained after panning the sand residue with various volumes of water. hungarian journal of industry and chemistry multistage gravity beneficiation of rutile 29 table 3: summary of the numbers of total and rutile counts as well as the estimated percentage of the raw and panned samples in addition to the concentrates and tailings from the shaking table obtained from the xrf spectroscopy of each sample. type of sample total count rutile count imagej estimated % of rutile the % of rutile by xrf spectroscopy raw sand residue 1265 192 7.9 1.43 panned sand residue 913 192 10.04 17.5 shaking table concentrate of sand residue 1061 204 19.23 31.02 shaking table tailings of sand residue 2041 99 4.85 5.01 quence of ten shaking tablings of the charge were 10.55 and 48.29 g, respectively. this figure shows that the mass of the concentrates of denser particles recovered generally decreased while that of the tailings increased with some minor exceptions. the results obtained confirm the concentration of rutile in the concentrate increased as the sequence advanced. the sequential stages of shaking progressively improved the grade of the concentrates in terms of denser minerals. the plane-polarized and cross-polarized images obtained from reflected light microscopy and thin section microscopy of the raw and panned samples, in addition to the concentrate and tailings from the shaking table were analyzed. according to francis [15], rutile was translucent and dark red-brown in color, while silica was transparent and whitish in color under a thin section microscope. further observations showed that pure crystalline rutile was not abundant in the sample as most of the rutile under cross-polarized light was observed to be interlocked with silica. the plates further indicated that the rutile content of the concentrate on the shaking table exceeded that of the panned concentrate. a summary of the number of total and rutile counts as well as the percent distribution estimated for the raw and panned samples in addition to the concentrates and tailings of the shaking table is shown in table 3. imagej counting estimated the rutile content in the recovered sand residue as well as in the concentrates of the shaking table and following panfigure 3: recovered masses of concentrates and tailings from ten sequential shaking tables. ning as 7.9, 19.23 and 10.04 %, respectively. fig. 4 shows the results from the x-ray fluorescence spectroscopy of the recovered and panned sand residues in addition to the concentrates from the shaking table. the percentage of silica in the recovered sand residue was reduced from 49.9 % to 47.6 % in the panned preconcentrate and further to 41.4 % in the concentrate of the shaking table. moreover, the titanium content of the recovered sand residue was enhanced from 0.86 % to 10.6 % in the panned pre-concentrate, while that of the concentrate from the shaking table in the panned preconcentrate was further improved to 18.3 %. therefore, the results obtained showed that the rutile content of the recovered sand residue was enhanced from 1.43 % to 17.50 % in the panned concentrate and finally to 31.02 % in the concentrate from the shaking table. the decrease in the silica content and increase in the titanium content strongly suggest that the panning and shaking table were efficient methods to improve the rutile content of the residue of tar sand. the results obtained from imagej counting also compare favorably with that of xrf spectroscopy except for the sample as received where both appeared to be significantly different. the flow diagram of the beneficiation process is shown in fig. 5. figure 4: percent recoveries of the elements ti, si, fe, sn and al in the concentrates. 47(2) pp. 25–30 (2019) 30 akande and adeleke figure 5: flow diagram of the bench-scale beneficiation of tar sand from ondo. 4. conclusions the rutile content of the tar-free residue obtained from tar sand extracted from ondo was successfully improved by gravity beneficiation of the sand residue. the results obtained show that a sequence of panning preconcentrations followed by a sequence of shaking tabling improved the rutile content from 1.43 % to 31.02 %. references [1] falebita, o. a.; koul, s.: sustainable development of oil sands and host communities: preliminary system dynamics assessment. (managing intellectual capital and innovation for sustainable and inclusive society: proceedings of the makelearn and tiim joint international conference 2, toknowpress, 2015), pp. 2095–2109 [2] allen, c.: mineralogy of tar sand in the upper part of the green river formation in the eastern utah basin, utah. u.s. geological survey open-file report 76-381, pp. 27. [3] erdogan, l. dielectric properties of oil sands at 2.45 ghz determined with rectangular cavity resonator. m.sc. thesis, université de montréal, montréal, qc, canada. https://publications.polymtl.ca/732/1/2011_leventerdogan.pdf retrieved on 12 november 2019 [4] lavat, a. e.; gayo, g. x.: new environmental friendly yellow ceramic pigments of the type (fe111mv)-ti02. j. chem. chem. eng. 2014 8: 1026–1035 doi: 10.17265/1934-7375/2014.11.003 [5] reddy, k. m.; manorama, s. v.; reddy, a. r.: bandgap studies on anatase titanium dioxide nanoparticles. mat. chem. phys. 2003 78(1): 239– 245 doi: 10.1016/s0254-0584(02)00343-7 [6] adegoke, o. s.; ako, b. d.; enu, e. i.: geotechnical investigations of the ondo state bituminous sands, geology and reserves estimate. unpublished manuscript. department of geology, obafemi awolowo university, ile-ife, nigeria. [7] emmanuel, e.; ajibade, o. m.: elemental composition and geochemistry of heavy oil in parts of eastern dahomey basin, southwestern nigeria. j. env. earth sci. 2014 4(12): 18–25 [8] enu, e. i.: textual characteristics of the nigeria tar sands. sedimentary geology, 44: 65–81. doi: 10.1016/0037-0738(85)90032-6 [9] adeleke, a. a.; ibitoye, s. a.; oladokun, c. b.; oluwasegun, k. m.: an evaluation of the hot aqueous caustic leaching of nigerian ondo tar sand. petroleum and coal, 2011 53(4): 320–323 [10] adebiyi, f. m.; asubiojo, o. i.; ajayi, t. r.; obiajunwa, e. i.: trace element and physico-chemical characteristics of the sand and water fractions of nigerian bituminous sands. chemistry and ecology, 2005 21(5): 369–380 doi: 10.1080/02757540500291725 [11] ignasiak, a. k.: microscopic structure of athabasca oil sand. can. j. chem. eng., 0982 60(4): 538–545 doi: 10.1002/cjce.5450600416 [12] wills, b. a., napier-munn, t.: mineral processing technology (elsevier, 2015) isbn: 978-0-08-097053-0 [13] 911 metallurgist. metallurgists & mineral processing engineers. https://www.911metallurgist.com retrieved on 25 august 2018 [14] ghosh, a.; ray, h. s.: principles of extractive metallurgy. (new age international, 1991) isbn: 9788122403220 [15] francis, c.: characterization and upgrading of a rutile concentrate produced from the oil sands tailings. m.sc. thesis, university of alberta, edmonton, ab, canada, pp. 95-96. https://era.library.ualberta.ca/items/79044641-a67d410f-b072-4bf5b4cadb0d/view/f051e5bd-3406-4262-abc8dd479e66f11a/mq81377.pdf retrieved on 12 november 2019 hungarian journal of industry and chemistry https://publications.polymtl.ca/732/1/2011_leventerdogan.pdf https://doi.org/10.17265/1934-7375/2014.11.003 https://doi.org/10.1016{/}s0254-0584(02)00343-7 https://doi.org/10.1016/0037-0738(85)90032-6 https://doi.org/10.1016/0037-0738(85)90032-6 https://doi.org/10.1080/02757540500291725 https://doi.org/10.1002/cjce.5450600416 https://www.911metallurgist.com https://era.library.ualberta.ca/items/79044641-a67d-410f-b072-4bf5b4cadb0d/view/f051e5bd-3406-4262-abc8-dd479e66f11a/mq81377.pdf https://era.library.ualberta.ca/items/79044641-a67d-410f-b072-4bf5b4cadb0d/view/f051e5bd-3406-4262-abc8-dd479e66f11a/mq81377.pdf https://era.library.ualberta.ca/items/79044641-a67d-410f-b072-4bf5b4cadb0d/view/f051e5bd-3406-4262-abc8-dd479e66f11a/mq81377.pdf introduction materials and methods the collection of samples sample preparation stripping of bitumen by leaching whilst being stirred stripping of bitumen by leaching in the absence of stirring panning of the tar-free sand determination of the specific gravity of tar-free sand shaking tabling particle size analysis using a sieving method reflected light microscopy thin section microscopy x-ray fluorescence spectroscopy results and discussion conclusions conferenceproceed~gs hungarian journal of ~dustrial chemistry veszprem vol. 2. pp. 1215 (2000) data organisation and modelling experiences in budapest air quality management a. gyovai and i. kiss (dasydecision and systems management ltd., pob 446, budapest, h-1537, hungary) 'this paper was presented at the second international conference on environmental engineering, university of veszprem, veszprem, hungary, may 29 -june 5, 1999 in the budapest air quality management system programme the british atmospheric dispersion modelling system (adms-urban) is to be used. the integrated database demanded consists of different emission sources with their co­ ordinates, meteorological data and surface data. special pre-processing is needed in case of traffic emission where a traffic flow model and a set of emission factors are used. in case the number of sources exceeds 1500, a simplified approach is used by 1 xl km grids. a combination of grid and individual source impact assessment is also possible. as general schemes are known in this field, the presentation puts emphasis on some major methodological considerations especially in data organisation. keywords: air quality; dispersion modelling; budapest case study; emission inventory introduction the budapest air quality management system is under development it is supported by a management toolkit consisting of a dispersion model, an integrated database and a digitised map of budapest. the project is financed by the municipality, the ministry of environment, the national committee for technological development and technical assistance is provided by the british environmental know how fund. the project is co-. ordinated by the authors. the participating institutions from hungary are as follow: institute of public health officer service (antsz}, transport ltd., norg ltd., clean air protection ltd., institute of atmospheric physics and dasy ltd. two departments are acting on behalf of the municipality namely that of the environment management and transport management. air quality management is intrinsically a multi~ disciplinary and holistic activity. accordingly, a strong and multi~skilled uk team has been assembled for this project: this comprises international experts :from aea technology's national environmental technology centre (netcen). together with corresponding specialists :from cambridge environmental research consultants ltd. (cerc) and the london research centre. [l] within the british team the iilla technology is responsible for the overall project management, and for ensuring that the technical input on monitoring, modelling and inventories is effectively co-ordinated and quality assured. lrc is responsible for ensuring inventory compilation and for inventory linkage to the selected adms modelling package. cerc is supplying the advanced adms-urban model to· be used in budapest's air quality management system. it will also adapt and optimise the model to local circumstances and validate using data from the budapest air monitoring networks. a conceptual scheme of the system is shown in fig.l. considering that the adms-urban is the core of the planned toolkit, it is introduced briefly below. fig.l conceptual outline of air quality management system in budapest outline ofthe adms-urbau [2,5] adms is an advanced "new generation" dispersion model, using the most up-to-date understanding of boundary layer physics to model dispersion of pollutants for industrial sources, traffic and other sources such as domestic heating. the model incorporates a semi-empirical photochemical scheme for nox reactions and links easily to an emissions inventory database. adms-urban, a version of the atmospheric dispersion modelling system (adms), is a pc-based model of dispersion in the atmosphere of pollutants released from industrial, domestic and road traffic sources in urban areas. adms-urban models these using point, line, area and volume source models. it is designed to allow consideration of dispersion problems ranging from the simplest (e.g. a single isolated point source or a single road) to the most complex urban problems (e.g. multiple industrial, domestic and road traffic emissions over a large urban area). amds-urban can be used as a stand-alone program, or in conjunction with arc view, esri' s desktop geographical information system (gis), with which it is fully integrated. it is recommended to use the two programs together, as this allows the user to set-up problems visually using digital map data, cad drawings and/or aerial photographs, and create output such as contour plots and produce hard-copy presentation layouts. a significant difference between adms-urban and other models used for air dispersion modelling in urban areas is that adms-urban applies up-to-date physics using parameterisations of the boundary layer structure based on the monin-obukhov length, and the boundary layer height. other models characterise the boundary layer imprecisely in terms of the pasquill stability parameter. in the up-to-date approach, the boundary layer structure is defined in terms of measurable physical parameters, which allow for a realistic representation of the changing characteristic of dispersion with height. the result is generally a more accurate and soundly based prediction of the concentrations of pollutants. some principal features of adms-urban: a meteorologtcal pre-processor which calculates the boundary layer parameters from a variety of input data: e.g. wind speed, day, time, cloud cover or, wind speed, surface heat flux and boundary layer height. meteorological data may be raw, hourly averaged or statistically analysed. advanced dispersion model in which the boundary layer structure is characterised by the height of the boundary layer and the monin­ obukhov length, a length scale dependent on the friction velocity and the heat flux at the surface. a non-gaussian vertical profile of concentration in convective conditions, which allows for the skewed nature of turbulence within the atmospheric boundary layer that can lead to high toolkit arc view fig.2 block diagram of the toolkit surface concentrations near the source. an easy to use interactive graphical interface. 13 a direct link to an emissions inventory database. integration with a commercial gis. an integrated street canyon model. the modelling of chemical reactions involving no, n02 and ozone. the calculation of emissions from traffic count data, using a database of emission factors. the realistic calculation of flow and dispersion over complex terrain and around buildings. the toolkit to be applied is shown in fig.2. a pre-requisite to use any numerical modelling as a powerful tool is to compile an appropriate input dataset that is an emissions inventory to the model hence some methodological questions related to emission inventories have to be considered. emissions inventory and data pre-processing [4,5] there are two sets of data to be used in the model. one is describing the air quality on monitoring, the other is the emissions inventory. while monitoring data show air quality near the given monitoring station, model results can provide more detailed but estimated/calculated data for areas not covered by monitoring stations. emission inventories form a means by which local sources can be identified and quantified as an input to models providing these "missing" data. an air pollution emissions inventory is a schedule of the sources of an air pollutant or pollutants within a particular geographical area. the inventory usually includes information on the amount of the pollutant released from major industrial sources, average figures for the emissions from smaller sources, and from transport throughout the area. emission inventories are mi essential tool in the management of local air quality. whilst monitoring shows the concentration of air pollution, emission inventories identify the sources and help "in preparing abatement strategies. compilation of an emissions inventory is a complex task involving diverse inputs from many different participating organisations. in case of budapest these data are provided by authorities {anrsz, kdv~kf and omsz) and calculated by others like transport ltd. providing traffic flow data as well. a complete inventory for a city wiu need to include emissions from: 14 point sources, primarily industrial, area sources such as domestic emissions, mobile (mostly traffic) sourcessometimes referred to as line sources. the purpose of an emissions inventory is to quantify and organise data describing emissions from identifiable sources across the study area. such an inventory can then be used: (a) in general terms, to examine the main causes of observed poor air quality and to develop remediation measures, or (b) in a more specific sense as one of the basic inputs to an atmospheric dispersion model, such as the adms model being used for the budapest air quality management system. for the purpose of air quality management, sources of emissions are typically categorised into the following main types: line or mobile sources.are emissions occurring along line-of-route, primarily from road traffic but also other transport-related sources such as -aircraft flight paths, ra~lway lines or shipping routes. point or stationary sources are emissions occurring at a discrete point in space, typically a factory chimney, and therefore mainly relating to industrial, power generation or incineration activity. diffuse, low-level or area-sources are emissions arising from low-intensity activities across areas of varying sizes, such as domestic fuel combustion, industrial solvent use, and waste disposal. · of these listed emissions from mobile sources that means the calculation of line sources is the most critical in the case of urban emission inventories. the most significant source of emissions for urban pollutants is traffic on major roads. two primary sources of road traffic data are currently in use for preparing urban emission inventories: traffic surveys and transportation models. information from traffic surveys is attractive because it relates to real traffic on real roads whereas transportation models are a computerised reflection of the actual conditions. however, traffic surveys have the disadvantage that they only provide information relating to the specific survey points, rather than area wide information. on the other hand, transportation models are available for most of the main urban areas and are comprehensive. {in budapest the emme-2 model is used by the transport ltd.) in order to estimate the annual fuel use and emissions aiong each link and within each grid square, it is necessary to know the proportion of the links within a particular grid square. the link lengths, the annual flows, speed, and the composition of the traffic (heavy goods vehicles, light goods vehicles, buses and cars). the model does not contain an the information required, for example. on the composition of the traffic flows on the individual links in the road network. traffic surveys carried out in budapest provide information on four categories of heavy goods vehicles, light goods vehicles, buses and cars. using these data, a traffic fleet composition can be ascribed to each link: in the road network. the proportions of the vehicle fleet within each of these categories, which are petrol, and diesel engines, and the proportion of cars fitted with catalytic converters, are estimated from the vehicle licensing records. the total annual vehicle kilometres travelled for each category of vehicle can then be combined with emission factors in order to calculate the total emissions for each linlc these can then be aggregated for each grid square. in addition to the method outlined above and used in the case of the main roads,. minor road traffic has to be considered as well but in a simplified way, namely treating it as area emission sources. it has to be mentioned here that a line source emission is calculated on the base of the traffic outlined and the vehicle emission factors of the given composition of vehicles. the emission sources are geocoded, hence an emissions inventory is usually held in a geographical information system (gis), to allow normalisation of the different geographies involved (usually in the form of 1 kilometre grid squares), and to allow easy data retrieval and manipulation. outputs of the emissions inventory can then be fed into a dispersion model quality assurance/quality control the quality of the data in the emissions inventory is fundamental to the overall performance of the air quality management system. it is also one of the most difficult elements of the system to compile accurately. this is because of the sheer range of input data required, which is compiled by originators to different levels of space, time and quality (accuracy). it is also a product of the basic methodology used, which relies · on the application of emissions factors to some measure of the activity giving rise to the emission (e.g. emissions from domestic combustion would be estimated with reference to statistics of fuel consumption). some specific reasons constraints to the development of an accurate inventory include [2]: lack of ability to obtain measurement of actual emissions (e.g. it is not possible to monitor every vehicle travelling on the roads) and reliance on secondary or surrogate data {activity data and emissions factor) to arrive at an emissions estimate. use of emissions factors which have a large measure of uncertainty associated with them, either through being based on observations of inappropriate or obsolete technologies or on a small, possibly statistically non-robust, number of observations. short-period measurements being used to estimate long-term averages, such as weekday peak hour traffic flows extrapolated to daily or annual totals. fig.3 the steps involved in manipulating raw source and emissions data into an adms-urban file inability to obtain the ideal range and depth of activity data required for using the most accurate emissions factors (such as speed of traffic flows, type and efficiency of combustion unit). uncertainties in the geographical resolution at which activity data is available: for instance, data only available at the level of the · city administrative unit, or even pertaining to the entire city, province or country. uncertainties associated with primary activity data, including: errors associated with traffic model vehicle flow estimates, under-reporting in fuel sales data, specific deficiencies in the reporting of emissions data from industrial processes. sources and emissions data thus must be in a specific format for entering the emissions inventory, the adms-urban. three excel templates are supplied with adms­ urban. these illustrate the format that the raw data must be in before it can be entered the access emissions inventory. the first is therefore to manipulate the raw data in excel so that it is in the form of the excel templates. each worksheet corresponds to a particular table in the access emissions inventory. fig.3 shows how raw data are processed to be made applicable by the model. [ 5] preliminary results during the inception phase of the baqms programme it was realised that the dataset required is sparse, fragmented and maintained by different organisations furthermore some (traffic) data are not even available. therefore it was recommended and generally accepted that a spatial subset of data has to be produced and enter into the "pilot" inventory. for this approach, a representative pilot area was selected. (the area is shown in figa). based on the guidelines given in the frame of the know how fund technical assistance the frrst version of 15 o~~~iiiiiiiiiiiiiiiiiiiilii10 kilometers fig.4 pilot area for modelling budapest (dark solid line: district, light solid line: road network, shaded area: study area) fig.s budapest pilot area for modelling. emission of oxides of nitrogen from road traffic the inventory for the study area was compiled (fig.5 shows a sample of database on a map). during the conference, the first results of modelling are being presented as well. acknowledgement the authors greatly acknowledge the help having received from the british expert team, especially from charles buckingham of lrc, which has made this work possible. references 1. bower j., buckingham c. and mchugh c.: budapest air quality management system: inception report, aea teclmology, culham, 1998 2. bower j., w allace-plews j., buckingham c., mchugh c., carruthers d. and e. simon.: budapest air quality management system: first progress report, aea teclmology, culham, 1998 3. mchugh c., carruthers d. and edmunds h.: adms· urban: an air quality management system for traffic, domestic and industrial pollution, cerc, cambridge, 1997 4. hutchinson d. and clewl.by l.: west midland atmospheric emissions inventory. lrc, london, 1996 5. adms·urban user guide, cerc, cambridge, 1998 page 18 page 19 page 20 page 21 hungarian journal of industry and chemistry vol. 48(2) pp. 51–53 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-27 considerations to approach membrane biofouling in microbial fuel cells szabolcs szakács *1 and péter bakonyi1 1research institute on bioengineering, membrane technology and energetics, university of pannonia, egyetem u. 10, 8200 veszprém, hungary among bioelectrochemical systems, those referred to as microbial fuel cells (mfcs) are widely implemented for wastewater management and simultaneous recovery of electrical energy. mfcs are fundamentally assisted by bacterial populations, mostly mixed cultures to be more exact that, after oxidizing the substrate, are capable of facilitating the passage of electrons to an electron acceptor, usually the anode. however, certain undesired bacterial strains often colonize not only the electrode but the membrane separator over time and cause severe biofouling. the membrane is an architectural element of many mfcs and determines the efficiency of the system. in this paper, this issue is overviewed briefly and some considerations concerning how to approach the problem are presented. keywords: microbial fuel cell, membrane, oxygen mass transfer, biofouling 1. introduction bioelectrochemical systems, including microbial fuel cells (mfcs), are often installed with a physical separator such as a membrane as illustrated in fig. 1 [1]. the membrane, which separates the anode from the cathode, should enable the adequate migration of ions (in this case, cations such as protons) between the electrodes to ensure the mfc continues to produce electricity [2]. furthermore, the membrane should function as a barrier against the crossover effect of substances to avoid the loss of the substrate (which normally is injected into the anode chamber in order to feed the species of electroactive bacteria shown in table 1 living on a biofilm on the electrically-conductive anode surface) and penetration of dissolved oxygen from the aerated cathode chamber to the anaerobic anode chamber [3]. in addition to these requirements which are associated with the physical and chemical properties of the material, the membranes should be relatively affordable. another point that needs to be addressed is the stability of the membrane, which can be influenced by the complex chemical environment of the bulk phases (anolyte in the anode chamber, catholyte in the cathode chamber) in an mfc and microbiological phenomena [5]. altogether, these effects may cause fouling of the membrane during its operation, moreover, when the underlying mechanism is associated with the metabolism and/or growth of microorganisms, the term “biofouling” is more appropriate [6]. in summary, various membranes can be evaluated *correspondence: szakacs.szabolcs@mk.uni-pannon.hu figure 1: scheme of an mfc and ranked based on the characteristics of the membrane materials (typically but not exclusively fabricated from polymers) and their observed behavior during mfc operation which can be monitored by various electrochemical measurements, e.g., recording the cell voltage, as presented in fig. 2. 2. membranes and biofouling in mfcs – the potential role of oxygen mass transfer in accordance with the previous section, the membrane separator divides the anaerobic anode chamber from the aerobic cathode chamber [7]. therefore, it is reasonable to assume that the actual microbial communities developing on the anode and the membrane have completely different structures and relationships with gaseous oxygen. from the literature, it can be concluded with a good degree of certainty that the electrochemically active bacteria https://doi.org/10.33927/hjic-2020-27 mailto:szakacs.szabolcs@mk.uni-pannon.hu 52 szakács, and bakonyi table 1: electroactive species of bacteria and their oxygen tolerance [4] species oxygen tolerance e. coli facultatively anaerobic https://bacdive.dsmz.de/strain/4907 shewanella oneidensis facultatively anaerobic https://img.jgi.doe.gov/cgi-bin/m/main.cgi?section= taxondetail&page=taxondetail&taxon_oid=637000258 geobacter sulfurreducens strict anaerobe https://bacdive.dsmz.de/strain/5792 geobacter metallireducens strict anaerobe https://bacdive.dsmz.de/strain/5791 desulfobulbus propionicus strict anaerobe https://bacdive.dsmz.de/strain/4004 geothrix fermentans strict anaerobe https://bacdive.dsmz.de/strain/17672 paracoccus pantotrophus facultatively anaerobic https://bacdive.dsmz.de/strain/13703 rhodopseudomonas palustris dx-1 strict anaerobe https://bacdive.dsmz.de/strain/1819 on the anode are either strict or facultative anaerobes as shown in table 1 [4]. however, a considerable knowledge gap seems to exist concerning the populations attached to the surface of the membrane and the occurrence of biofouling. in contrast, it is reasonable to suppose that these membrane-bound colonies and biofilms are more tolerant of dissolved oxygen due to the technically direct and long-lasting contact with this substance. in general, the oxygen flux across a membrane in mfcs is described by the oxygen transfer coefficient which can be calculated by [8, 9] ko = − v at ln [ (c0 − c) c0 ] (1) where ko denotes the oxygen transfer coefficient (cm3/cm2s), v stands for the volume of liquid (cm3), a represents the surface area of the membrane (cm2), c0 refers to the saturation oxygen concentration (mol/dm3), c is the actual oxygen concentration measured (mol/dm3) and t denotes the time of the measurement (s); and ko = do l (2) where do stands for the oxygen diffusion coefficient (cm2/s) and l represents the thickness of the membrane (cm). figure 2: schematic diagram of the mfc therefore, it is worth examining which strains colonize the membrane and how these mixed communities vary depending on ko. even though some previous papers have demonstrated the use of various microscopic imaging techniques based on visual observations to study these biofouling layers on the surface of membranes [10–12], qualitative and quantitative feedback to highlight “what type of” and “how many” microbes can coexist is scarce. as a result, experimental methodology involving the apparatus of modern molecular biology, e.g. dna-based identification, should be encouraged and implemented to answer such questions [13]. 3. conclusions the capability of membranes to permeate dissolved oxygen in microbial fuel cells is key. on the one hand, reduced oxygen transport membranes (otms) are likely to maintain the typically less oxygen tolerant, electroactive bacteria located on the surface of the anode in a good condition. on the other hand, oxygen mass transfer through the membrane is expected to affect the biofouling of the separator and thus, how microbial communities respond to changes in material properties, in particular ko, needs to be understood. the assessment of membranes with different values of ko should be carried out relative to nafion, which is by far the most broadly employed polymer for benchmarking studies [14]. acknowledgement this work was supported by the national research, development and innovation office (nkfih, hungary) under grant number fk 131409 and ginop-2.3.2-15-201600016 excellence of strategic r+d workshops, entitled “development of modular, mobile water treatment systems and waste water treatment technologies based on university of pannonia to enhance growing dynamic export of hungary” (2016-2020) hungarian journal of industry and chemistry https://bacdive.dsmz.de/strain/4907 https://img.jgi.doe.gov/cgi-bin/m/main.cgi?section=taxondetail&page=taxondetail&taxon_oid=637000258 https://img.jgi.doe.gov/cgi-bin/m/main.cgi?section=taxondetail&page=taxondetail&taxon_oid=637000258 https://bacdive.dsmz.de/strain/5792 https://bacdive.dsmz.de/strain/5791 https://bacdive.dsmz.de/strain/4004 https://bacdive.dsmz.de/strain/17672 https://bacdive.dsmz.de/strain/13703 https://bacdive.dsmz.de/strain/1819 membrane biofouling in microbial fuel cells 53 references [1] leong, j. x.; daud, w. r. w.; ghasemi, m.; liew, k. b.; ismail, m.: ion exchange membranes separators in microbial fuel cells for bioenergy conversion: a comprehensive review. renew. sustain. energy rev., 2013, 28, 575–587 doi: 10.1016/j.rser.2013.08.052 [2] daud, s. m.; kim, b. h.; ghasemi, m.; daud, w. r. w.: separators used in microbial electrochemical technologies: current status and future prospects. bioresour. technol., 2015, 195, 170–179 doi: 10.1016/j.biortech.2015.06.105 [3] bakonyi, p.; koók, l.; kumar, 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membranes and biofouling in mfcs – the potential role of oxygen mass transfer conclusions hungarian journal of industry and chemistry vol. 50 pp. 45–55 (2022) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2022-08 enzyme reaction engineering as a tool to investigate the potential application of enzyme reaction systems nevena milčić 1, ivana ćevid1, mehmet mervan çakar1, martina sudar1, and zvjezdana findrik blažević *1 1faculty of chemical engineering and technology, university of zagreb, marulićev trg 19, zagreb, hr-10000, croatia it is widely recognized and accepted that although biocatalysis is an exquisite tool to synthesize natural and unnatural compounds under mild process conditions, much can be done to better understand these processes as well as detect resulting bottlenecks and help to resolve them. this is the precise purpose of enzyme reaction engineering, a scientific discipline that focuses on investigating enzyme reactions with the goal of facilitating their implementation on an industrial scale. even though reaction schemes of enzyme reactions often seem simple, in practice, the interdependence of different variables is unknown, very complex and may prevent further applications. therefore, in this work, important aspects of the implementation of enzyme reactions are discussed using simple and complex examples, along with principles of mathematical modelling that provide explanations for why some reactions do not proceed as planned. keywords: enzyme kinetics, modelling, reaction optimisation 1. setting up the reaction conditions for an enzyme reaction in each reaction system, first a proper buffer must be selected and the ph dependence of the enzyme activity determined in order to identify the optimal working conditions [1]. although the impact of temperature on enzyme activity is also important, it should be remembered that the temperature at which the enzyme exhibits the highest level of activity is not necessarily that at which the enzyme stability is optimal. at higher temperatures, the enzyme activity is often increased but at the cost of progressive and irreversible denaturation due to poor thermal stability [2,3]. when multiple enzymes are present in the reaction system and are supposed to operate in the same reactor, as is the case in cascade reactions, the optimal conditions can seldom be chosen for all of them. usually, a compromise must be reached whereby the selection of the reaction conditions depends on the enzyme activity required to catalyse the reaction [4, 5]. after selecting the buffer, temperature and ph for the studied reaction system, it must be analysed in detail, starting from the reaction scheme. even though the reaction scheme usually clearly depicts the reaction, it should be noted that recieved: 4 april 2022; revised: 10 april 2022; accepted: 11 april 2022 *correspondence: zfindrik@fkit.hr issues beyond the reaction scheme of the enzymatic reaction need to be discussed and analysed. in many cases, unwanted but insignificant side reactions may take place that sometimes also have a detrimental effect on the outcome of the reaction. although this may not be so important on the laboratory scale as far as screening for enzyme activities is concerned, given that the concentrations applied on that scale fall within the range of a few mm, it must be noted that the rate of chemical reactions increases as the concentration of reactants increases, e.g. firstand second-order reactions. therefore, further analyses to determine the effect of increasing the scale of the reaction by hundreds of mm are required. the same applies to the chemical stability of compounds present in the reactor. in this case, engineering methodology is priceless for the purpose of exploring the possibility of slowly feeding the reactive compound into the reactor. alternatively, if an intermediate is reactive, the reaction rate in the reactor may be tuned to ensure its concentration is always minimal. for example, in the case of epoxides that are substrates of halohydrin dehalogenases [6], it is known that their stability is poor [7,8]. as a result, in these reactions, a prochiral substrate is often used to start the reaction [9,10]. the same is true in this case whereby an epoxide intermediate is formed in situ and immediately spent in the subsequent reaction with the same or a different enzyme such as the one presented in scheme 1. additionally, since both epoxides and their correhttps://doi.org/10.33927/hjic-2022-08 mailto:zfindrik@fkit.hr 46 milčić, ćevid, çakar, sudar and findrik blažević scheme 1: synthesis of (r)-γ-chloro-β-hydroxybutyronitrile from an achiral substrate scheme 2: synthesis of l-homoserine in a cascade reaction sponding nucleophiles can inhibit the catalytic activity of an enzyme [11], the selection of their concentrations in the reactor is crucial in facilitating a successful reaction [12]. clearly, these are very complex reaction systems and the suitable set up of a reactor as well as reaction conditions determined by the model-aided approach can be vital [13]. multi-step reactions cannot always be performed simultaneously in one pot due to complex relationships between the process variables [14, 18]. in a study of an innovative reaction scheme for the preparation of the atorvastatin side-chain precursor, it was found that the two reaction steps consisting of aldol addition and the oxidation of the corresponding product amino lactol could not be performed simultaneously [14]. this was mostly due to the fact that acetaldehyde as the substrate in the first reaction step interferes with the oxidoreduction and coenzyme regeneration by acting as a substrate for the oxidoreductase or as an inhibitor as well as deactivator of both oxidoreductase and nadh oxidase. it is important to determine if all the reaction steps are compatible with each other before deciding how to develop the reaction. although this might suggest a significant amount of experimental work, this can be considerably reduced by evaluating the enzyme kinetics [13, 19, 20]. forming the reaction model enables a vast variable space to be explored in silico. apart from that, combining the kinetic model with mass balances in different reactors enables different types of reactors to be explored in each system. this was found to be crucial with regard to improving the process metrics in the synthesis of lhomoserine [21], a system governed by the unfavourable equilibrium of the transaminase-catalysed reaction and aided by the pyruvate recycling system catalysed by aldolase (scheme 2). the application of model-based optimization techniques led to a doubling of the product concentration (up to 80 gl−1) and an 18% increase in the volumetric productivity (up to 3.2 gl−1h−1) in comparison with a previously published work [22]. in this system, it was crucial that both reactions were carried out simultaneously to improve the position of the equilibrium. formaldehyde was gradually added to the system by using a pump due to its reactivity and inhibiting effect on enzyme activity. additionally, pyruvate and l-alanine were added sequentially once the pyruvate had been consumed in several doses, which, according to calculations, was found to work in silico experiments (fig. 1 a-b) and subsequently proved experimentally (fig. 1 c-d). 2. side reactions and their effect on the reaction scheme. when studying a complex reaction system, possible side reactions must be taken into account. these can be caused by the instability of reactants, products or intermediates; by chemical reactions between the compounds present in the reaction mixture; as well as by the side reactions hungarian journal of industry and chemistry enzyme reaction engineering as a tool 47 (a) (b) (c) (d) figure 1: cascade synthesis of l-homoserine [20] in a fed-batch bioreactor by gradually adding formaldehyde via a pump as well as sequentially adding pyruvate and l-alanine incrementally once the pyruvate had been consumed. (a) (black line – l-alanine, dashed line – pyruvate, dotted line – formaldehyde), (b) (grey line – l-homoserine, grey dashed line – aldol intermediate). in silico experiments, (c) experimental validation (black triangles – l-alanine, white squares – pyruvate, blue diamonds – formaldehyde), and (d) experimental validation (red circles – l-homoserine, grey stars – aldol intermediate). scheme 3: synthesis of the aldol product (3s,4r)-6-[(benzyloxycarbonyl)amino]-5,6-dideoxyhex-2-ulose in a cascade reaction 50 pp. 45–55 (2022) 48 milčić, ćevid, çakar, sudar and findrik blažević caused by the catalytic enzymes due to their low purity or ability to catalyse more than one reaction [8, 23, 24]. reactions are often carried out with a crude enzyme extract or whole cells in order to reduce the costs of synthesising the protein by avoiding the necessity for purification. although such systems often offer an additional advantage in terms of enhancing the operational stability of the desired enzyme within the protein mixture or cell compartment, other enzymes in these systems can also catalyse undesirable enzymatic reactions [23]. all of these aforementioned reactions can lower the concentration of the target product as well as decrease the reaction yield, moreover, in some cases, even prevent the formation of the target product. one example of such an event is the oxidation of an alcohol to form an aldehyde catalysed by horse liver alcohol dehydrogenase that reacts further by oxidizing the aldehyde to form the corresponding acid as a side product. in the cascade synthesis of (3s,4r)-6[(benzyloxycarbonyl)amino]-5,6-dideoxyhex-2-ulose (scheme 3), n-cbz-3-aminopropanoic acid was the dominant main product following our first attempt, with only 2% of the target product being formed [25, 26]. considering the complexity of the system, reaction engineering methodology was applied to determine the reason behind this. a statistical model implied the occurrence of this side reaction [25] which was later confirmed by kinetic studies [26]. not only did the aforementioned studies reveal the reasons for the poor yield but also determined how to improve it to between 79 and 92%, respectively. in many cases, although commercial compounds that contain small quantities of certain additives are purchased for research purposes, these additives can also frequently act as enzyme inhibitors, such as in the case of 4methoxyphenol as a stabilizer of acrylonitrile that was used as a substrate in one of the reactions studied by us [27]. in fact, this was one of the crucial reasons why it was not possible to obtain significant amounts of product in any reactor. 3. investigation of the kinetics of the enzyme-catalysed reaction to formally identify the system, the effect of all the compounds present in the reaction mixture on the enzyme activity / reaction rate can be evaluated. during these measurements, the effects of all the compounds on the enzyme activity can be measured and, in many cases, substrate, intermediate and product inhibition can be detected, which subsequently help with regard to decisionmaking and selection of the reactor mode to be used for the reaction. some examples of reactor designs that can be applied, according to the properties of the studied reaction and desired outcome, are given in fig. 2. in theory, it is known that the fed-batch bioreactor is a favourable choice for reactions subjected to substrate inhibition to increase the concentration of the obtained product [31]. (a) (b) (c) figure 2: schemes of different reactors applied in biocatalysis: (a) batch reactor, (b) fed-batch bioreactor, (c) continuous stirred tank reactor for product-inhibited reactions, a continuous stirred tank reactor operating at the maximum concentration of the product is not recommended and, therefore, the resultant enzyme activity is unsatisfactory [32, 33]. in practice, reactions are rarely inhibited by a single compound, moreover, in many cases, several important inhibitions and/or side reactions take place. therefore, the reactor mode cannot be easily set by viewing the results of the effect of substrates on the reaction rate. in these cases, kinetic models help simulate different scenarios and enable the best choice for the studied reaction system to be made [13]. the simulations of a relatively simple doublesubstrate reaction in which the kinetics can be described by double michaelis-menten kinetics with both substrate and product inhibition are presented in fig. 3. the impact of reaction conditions on substrate conversion and volumetric productivity in the batch reactor is presented in figs. 3a and 3b, while 3c and 3d show the same for the continuous stirred tank reactor (cstr). substrate conversion is governed by the enzyme concentration as well as the reaction time and residence time in the batch reactor and cstr, respectively. the main difference that can be hungarian journal of industry and chemistry enzyme reaction engineering as a tool 49 (a) (b) (c) (d) figure 3: model simulations demonstrating the impact of the reaction conditions on the conversion and volumetric productivity in the batch and continuous stirred tank reactors observed is in terms of volumetric productivity, which explains why continuous processes are currently in the spotlight. in this simulation, the maximum volumetric productivity of the cstr is fourfold greater than that of the batch reactor. nevertheless, it must be noted that the operational stability of the enzyme is important and that the enzyme activity was assumed to be constant. in practice, since the enzyme activity inevitably drops over time and, therefore, enzymes must be stabilized by a form of immobilization, ensuring the continuous process functions is not a straightforward task. the first step to investigate enzyme kinetics is to find an appropriate method that will result in the rapid collection of enzyme kinetic data. this can be done by applying a spectrophotometric enzyme assay and microtiter plate reader, however, should these methods be unavailable, this can also be achieved in a traditional manner by determining the initial reaction rates from hplc or gc data with regard to the concentrations of substrates and products [13]. given that data collection must be accurate and reliable, analytics is the foundation of the research. data must be reproducible and trustworthy to be used for modelling. an example of kinetic data is presented in fig. 4 where the grey line denotes the experiment where the enzyme concentration was too high. furthermore, even though the linear dependence of absorbance over time is obvious in the initial part of the curve, the error of such measurements can be high and depends on the individual measuring. on the other hand, the black line clearly figure 4: the impact of enzyme concentration on the quality of the experimental data 50 pp. 45–55 (2022) 50 milčić, ćevid, çakar, sudar and findrik blažević (a) (b) (c) (d) figure 5: estimation of kinetic parameters for a two-substrate reaction by applying linear (a and b) and nonlinear regression (c and d) analyses represents linear data with a relatively small gradient, indicating that the measurements were made properly and the dependence is undoubtedly linear within that range. a series of such experiments performed at different concentrations of substrates, products and intermediates is required to obtain one set of experimental data to be subsequently used for the estimation of kinetic parameters. based on the kinetic data, the kinetic parameters can be estimated by using nonlinear regression analysis, which is far better than the still commonly used linear regression analysis [34]. this can be illustrated by the example presented in fig. 5 whereby a double-substrate reaction was considered and the kinetic data concerning the dependence of the specific enzyme activity on the concentration of the reactants measured. by measuring the initial reaction rate (conversion less than 10%), the effect of product inhibition or enzyme deactivation could be minimized [35]. this example will be used to illustrate the differences between the values of the estimated kinetic parameters when various methods of estimation are applied. in the first case, linear regression analysis was applied by using a lineweaver-burk plot (figs. 5a-5b). the data show discrepancies and, in the case of 5b, two points needed to be removed from the analysis as they were outliers. the estimated kinetic parameters are presented in table 1. in the second case, the kinetic parameters were estimated by using singlesubstrate michaelis-menten kinetics, which in all likelihood is frequently used in practice. the estimated kinetic parameters presented in table 1 are very different from the ones obtained following linear regression analysis. furthermore, since the maximum reaction rates differ for each substrate, the measurements in all probability were not made in the area of substrate saturation. michaelis constants estimated by using double-substrate michaelis-menten kinetics strongly resemble the values estimated by using single-substrate michaelis-menten kinetics. however, when the maximum reaction rates are compared, a significant discrepancy between them can still be observed. estimating the maximum reaction rate by using double-substrate michaelis-menten kinetics is the optimum solution offering a unique value of vm and taking into consideration the case when the non-varying substrate was not saturated. therefore, in the case when both substrates are saturated, single-substrate michaelismenten kinetics and nonlinear regression analysis offer a suitable solution to estimate the kinetic parameters. 4. investigation of the operational stability of the enzyme enzyme activity inevitably decreases in the reactor over time, which means that the operational stability reduces as well [28–30]. this also needs to be quantified from the hungarian journal of industry and chemistry enzyme reaction engineering as a tool 51 parameter linear regression analysis 1 r = 1 vm + km vm 1 c nonlinear regression analysis – single-substrate kinetics r = vmc km + c nonlinear regression analysis – double-substrate kinetics r = vmc1c2 (km1 + c1) (km2 + c2) vm [u/mg] 0.743 (3.539) 1.448 (2.119) 4.177 km1 [mmol/dm3] 2.56 8.2 9.09 km2 [mmol/dm3] 46.366 7.726 9.191 table 1: comparison between different methods to estimate the values of kinetic parameters in an enzymatic reaction experimental data [29] and incorporated into the kinetic model. in many cases, the enzyme activity can be followed by an independent enzyme assay. in other cases, it can be estimated by using the kinetic model and other experiments. the operational stability of enzymes is an important topic not only in terms of research but also with regard to their applications. understanding and describing quantitatively as well as qualitatively how enzyme function and structure change during conversion in a bioreactor is of crucial importance [28, 36]. in their work, börner et al. investigated the mechanistic reasons for the poor operational stability of amine transaminases along with the influence of quaternary structure, cofactors and substrates. through their kinetic and thermodynamic experiments, they were able to identify the structural domain that appears to confer stability. the study revealed that the enzyme is significantly more stable when at rest than in its operational state, moreover, its operational stability was lower and experiments suggested a mechanism that brought about substrate-induced deactivation [28]. in many reports to date, it has been stated that the presence of substrates and their concentrations can have both positive [37] and negative [30] effects on enzyme stability. in a study by česnik et al. [30], formaldehyde as a substrate was found to have a negative effect on enzyme activity during experiments (fig. 6a). subsequently, it was found that this could be correlated with the operational stability of the enzyme (fig. 6b). considering the reactivity of formaldehyde and the size of this molecule, chemical damage to the protein may occur in its presence, as reported in other studies. in a study involving the dehalogenation of 1,3-dichloro2-propanol (1,3-dcp) catalysed by halohydrin dehalogenases (hhdhs), it was found that the substrate 1,3-dcp causes enzyme deactivation during incubation, moreover, as observed in the previously described case, the substrate concentration has a significant effect on enzyme activity (unpublished data, fig. 6c). experiments conducted in batch reactors corroborated that the operational stability decay rate constant can be directly correlated to the substrate concentration (unpublished data, fig. 6d). these are not the only examples of this behaviour. in a study by vasić-rački et al., it was also shown that glycolaldehyde caused operational stability decay in the reactor, the rate of which was dependent on its concentration [38]. in all of these cases, the quantification of the operational stability decay rate constant and the modelling approach improved the outcome of the reaction and increased process metrics values. another example of the effect of a substrate on enzyme activity can be demonstrated by different oxidases. in one study, the operational stability of d-amino acid oxidase was investigated in the presence and absence of aeration [40]. the enzyme operational stability decay rate of d-amino acid oxidase from porcine kidneys was reduced by increasing the oxygen concentration in the reaction solution and the enzyme activity decreased more rapidly. similar conclusions were drawn in a later study on glucose oxidase [40]. this can be related to the oxidation of protein residues in the presence of oxygen and requires some sort of quantification to enable development of the reaction by focusing on resolving bottlenecks. if operational stability is considered in a very simple reaction with only a basic michaelis-menten model, its effect during dynamic simulations can be observed (fig. 7a). when the enzyme activity reduces in the batch reactor, the shape of the curve changes slightly. to the untrained eye, this can also resemble the result of reaching equilibrium or product inhibition. therefore, if the kinetics of the reaction are completely unknown, it is very difficult to draw the right conclusion. the situation is quite different if the continuous stirred tank reactor is used, since this reactor ideally works at a stationary state and, therefore, no changes in enzyme activity nor in stationary concentrations of reactants and products occur. hence, enzyme operational stability decay in cstrs results in the stationary state being lost and the clearly visible shape of the curve caused by the reduction in enzyme activity (fig. 7b). a third type of reactor often applied in biocatalysis due to substrate inhibition are fed-batch bioreactors. although enzyme operational stability decay can be observed from the shape of the curve (fig. 7c), here, like in the case of the batch reactor, it is more difficult to clearly define the reason for this trend. the answer that is suggested here concerns quantification of enzyme activity during the reaction. 5. choosing the best enzyme variant for the reaction techniques for genetically modifying enzymes have advanced greatly over recent years and can be applied to produce industrially suitable catalysts more quickly and 50 pp. 45–55 (2022) 52 milčić, ćevid, çakar, sudar and findrik blažević (a) (b) (c) (d) figure 6: (a)the influence of the initial concentration of formaldehyde on the enzyme activity of fsad6q during incubation; (b) dependence of the operational stability decay rate constants of fsad6q on the initial concentration of formaldehyde; (c) the influence of the initial concentration of 1,3-dcp on the enzyme activity of hhdh during incubation; (d) dependence of the operational stability decay rate constants of hhdh on the initial concentration of 1,3-dcp (a) (b) (c) figure 7: the effect of operational stability decay on model curves in different types of reactors: (a) batch reactor, (b) continuous stirred tank reactor, (c) fed-batch bioreactor parameter unit enzyme 1 enzyme 2 enzyme 3 vm u/mg 3.42± 0.05 1.74± 0.11 0.74± 0.03 km mm 102.24 ± 4.01 67.52 ± 7.22 36.33 ± 8.82 ki mm 679.94 ± 38.81 183.19 ± 29.25 377.28 ± 68.70 table 2: estimated kinetic parameters for the three enzyme variants cost-effectively. however, in order for new biocatalysts to be worthy of industrial large-scale production, reliable and comprehensive methods for the initial kinetic characterization of possible enzyme variants are necessary. in search of an optimal enzyme variant, the enzyme with the highest activity (highest vm value) or highest affinity for the substrate (lowest km value) is often sought [41]. this is only valid when michaelis-menten kinetics are applied, however, in practice, the situation is rarely that simple. for example, this is not so in the case hungarian journal of industry and chemistry enzyme reaction engineering as a tool 53 (a) (b) 5(c) figure 8: comparison between the three enzyme variants which exhibit substrate inhibition at different levels of michaelis-menten kinetics with substrate inhibition, when the substrate concentration used during screening is critical. given that screening seems to only be conducted at one concentration, accurate data of enzyme activity is not provided, considering that the shape of the michaelismenten curve is unknown. since variants of the same enzyme differ with regard to the estimated values of their kinetic constants, combinations of the relevant kinetic parameters (vm, km, ki) were obtained for each variant (table 2). although it may be assumed that the enzyme with the minimum michaelis constant and highest activity is most suitable, in practice, this enzyme may exhibit a higher level of substrate inhibition as a result. three enzyme variants were kinetically characterized and the dependence of their specific enzyme activities on the substrate concentration is presented in fig. 8, while the kinetic parameters are shown in table 2. the best applied variant was found to be enzyme 1, written in bold, in table 2 because the level of substrate inhibition it is subjected to is by far the least pronounced. in practice, this means a broader substrate concentration area in which the highest enzyme activities can be obtained in the reactor (fig. 8a) and enhanced stability of the reactor’s operating conditions. simulations presented in fig. 8 also show that when screening the enzyme variants, it is important to not only evaluate their activities but also estimate all their kinetic parameters. in further stages of process development, the application of reaction engineering to identify process bottlenecks is required to exploit the full potential of novel enzymes. to develop novel green routes in biocatalysis and scale them up, it is crucial to adopt a multidisciplinary approach by combining the fields of chemistry, biology and chemical engineering. 6. conclusions enzyme reaction engineering can provide explanations for and give answers to different phenomena that occur in bioreactors. this is of particular importance when it comes to multienzyme systems which are very important in terms of sustainable development and green synthesis. many obstacles to their development must be overcome, for example, adjusting enzyme activities, choosing suitable enzyme variants, selecting the best reactor and determining the optimal reaction conditions while considering the side reactions that may occur. therefore, a combined effort and multidisciplinary approach are required to prepare complex enzyme reaction systems for industrial applications. acknowledgement authors would like to thank the croatian science foundation for the phd scholarship of n. milčić. this work was partly supported by the project cat pharma (kk.01.1.1.04.0013) co-financed by the croatian government and the european union through the european regional development fund the competitiveness and cohesion operational programme (i. ćevid). we acknowledge the funding from eu h2020-msca-itn2020 project c-c top under the grant agreement no. 956631 (m. m. çakar). references [1] burgess, r.r.; 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revised: 22 aug 2023; accepted: 23 aug 2023 *correspondence: k_wasewar@rediffmail.com tartaric acid is derived from potassium acid tartrate, a byproduct of the wine industry consisting of fermented and partially fermented press cakes of grape juice [4]. it can be produced through a variety of processes, including chemical synthesis and natural extraction from plant sources such as grapes. the basic stages of each technique are as follows: the precursor chemicals, including glucose and fructose, are derived from renewable resources, or synthesized from other compounds. using a catalyst, typically a metal catalyst, and other chemical reactions, the precursor compounds are oxidized to produce tartaric acid. the resultant tartaric acid is then purified through crystallization, filtration, or chromatography to remove impurities and obtain high-quality tartaric acid. germany, spain, france, and italy are among the leading nations worldwide in terms of ta production. from 2018 to 2026, the demand for ta is projected to increase at a compound annual growth rate of 5.54% [5]. the wine industry generates a substantial amount of environmentally damaging waste streams during production where tartaric acid is readily available. before being released, their environmental impact must be reduced [6]. ta is separated by precipitation in the form of calcium or potassium tartrate, which can be recovered https://doi.org/10.33927/hjic-2023-13 mailto:k_wasewar@rediffmail.com bhanot, kumar, shende and wasewar hungarian journal of industry and chemistry 16 through filtration and sulfuric acid treatment. although this method is effective, it is extremely complicated, costly, laborious and environmentally damaging as large quantities of sulfate residue are generated [7]-[8]. tartaric acid can be extracted from winery waste and effluent, which are generated by the winemaking industry. it is one of the primary acids present, moreover, is used as a sour flavor enhancer and antioxidant in other foods. tartaric acid is found in three different chiral structures: dextro tartaric acid or l(+) tartaric acid, levo tartaric acid or d(-) tartaric acid and meso tartaric acid. kontogiannopoulos et al. (2017) recovered 42.6 g/l of ta from wine residue using a nanofiltration membrane [9]. several authors [10]-[12] have also utilized ion exchange and adsorption to recover ta. although liquid membranes are a new promising method for the separation of carboxylic acids [13], they also exhibit fouling problems. however, since the membrane process is expensive and plagued with contamination issues, industries require a simple and cost-effective method for extracting ta from winery wastewater. the literature indicates that liquid-liquid extraction is a proven method for extracting carboxylic acids from fermentation fluids and water streams. in this procedure, a water-immiscible extractant is introduced into a solution and the solute is extracted based on the relative solubility of the solute molecules in the two media. solvent selection is central in the liquid-liquid extraction method [14]. several authors [15]-[18] have studied the solvent extraction method for extracting ta using kerosene, 1-decanol, 1-octanol and n-heptane as chemical solvents. in this study, ta was separated from the aqueous phase using chemical and organic solvents such as groundnut oil, petroleum, mustard oil, octanol and mibk (methyl isobutyl ketone). to reduce toxicity and create an environmentally favorable method for separating ta from the aqueous phase, organic solvents were utilized. this experimental study was defined using several extraction parameters such as extraction efficiency (e%) and distribution coefficient (kd). 2. experimental 2.1. samples and measurements tartaric acid was purchased from himedia laboratories, while solvents like groundnut oil, mustard oil, octanol, mibk and kerosene were procured from patanjali ayurved ltd., loba chemie, spectrochem and a local store (table 1). sodium hydroxide pellets were procured from merck india private limited for the titration, while oxalic acid was acquired from s d finechem ltd. (india). to normalize the naoh solution, oxalic acid was utilized. every time a new 0.01 m solution of naoh was prepared for titration in the study, all the chemicals used were not purified or pre-treated beforehand. 2.2. experimental procedure aqueous solutions of varying concentrations (0.0406 mol/l–0.1960 mol/l) of ta were prepared by dissolving different amounts of ta in distilled water. the initial concentrations of the samples were measured between ph 2.91 and 3.85 using an ika® ets-d ph meter (table 2). the range of initial concentrations of the acid was in line with its industrial concentrations in winery waste streams [19]. various solvents like groundnut oil, mustard oil, kerosene, octanol and mibk were used individually as solvents in the organic phase. table 1: list of the chemicals used and their properties without any pretreatment in the present study chemicals mw (g/mol) swater (g/l) density (kg/m3) supplier tartaric acid 150 1.33 1760 himedia laboratories groundnut oil _ immiscible 912 patanjali ayurved ltd. mustard oil 99.15 immiscible 920 patanjali ayurved ltd. kerosene 170 immiscible 820 local store octanol 130.23 immiscible 824 loba chemie pvt. ltd. mibk 100.16 0.19 802 spectrochem pvt. ltd. table 2: list of instruments used in the present study instruments conditions model orbital shaking incubator t=25°c, rpm=200 s-24, remi india bench top centrifuge t=25°c, rpm=4000 r-4c, remi india ph meter t=25°c ika® ets-d6, india extraction of the food additive tartaric acid 51(2) pp. 15–20 (2023) 17 both the organic and aqueous phases were prepared in a conical flask at a volumetric ratio of 1:1. until equilibrium was reached, the samples were kept in a remi orbital shaking incubator at 298 ± 1 k for 5 hours and shaken at 200 rpm before the samples were centrifuged for 5 mins at 4000 rpm (remi r-4c, india) to clearly separate the aqueous and organic phases (table 2). having been separated, the ph was measured in the aqueous samples and titrated against a freshly prepared 0.1 m naoh solution to determine the concentration of ta in the aqueous phase. mass balance equations were used to calculate the concentration of the ta organic phase. the change in volume of both phases after separation was checked and found to be negligible. 3. results and analysis the separation of ta from the aqueous phase using various solvents such as groundnut oil, mustard oil, kerosene, octanol and mibk was experimentally investigated (table 3). the following equations define the experiments: [𝑇𝐴]𝑖𝑛 + [𝑆]𝑜𝑟𝑔 ↔ [𝑇𝐴]𝑜𝑟𝑔 . [𝑆]𝑜𝑟𝑔 (1) where [ta]in denotes the initial concentration of tartaric acid; [ta]org stands for the concentration of tartaric acid in the organic phase and [s]org represents the concentration of the solvent in the organic phase. using the concentrations in the aqueous phase, mass balancing was used to determine those in the organic phase: [𝑇𝐴]𝑖𝑛 − [𝑇𝐴]𝑜𝑟𝑔 = [𝑇𝐴]𝑎𝑞 (2) to achieve accurate results, each experiment was repeated three times. the experimental data concerning the separation of ta was defined by the distribution coefficient (kd) and extraction efficiency (e%). the ratio of the organic phase to the aqueous one under equilibrium conditions is known as the distribution coefficient and can be defined as follows: 𝐾𝐷 = [𝑇𝐴]𝑜𝑟𝑔 [𝑇𝐴]𝑎𝑞 (3) where [ta]org and [ta]aq denote the tartaric acid concentrations in the organic and aqueous phases, respectively, in mol/l. in terms of the distribution coefficient, the extraction efficiency can be defined as: 𝐸% = 𝐾𝐷 1 + 𝐾𝐷 × 100 (4) table 3: separation of tartaric acid using various organic and conventional solvents at 298±1k solvents [ta]in (mol/l) [ta]aq (mol/l) [ta]org (mol/l) kd e% groundnut oil 0.0406 0.0400 0.0006 0.015 1.48 0.0798 0.0768 0.0030 0.039 3.76 0.1212 0.1130 0.0082 0.073 6.77 0.1540 0.1366 0.0174 0.127 11.30 0.1960 0.1680 0.0280 0.167 14.29 mustard oil 0.0406 0.0384 0.0022 0.057 5.42 0.0798 0.0720 0.0078 0.108 9.77 0.1212 0.1050 0.0162 0.154 13.37 0.1540 0.1300 0.0240 0.185 15.58 0.1960 0.1650 0.0310 0.188 15.82 kerosene 0.0406 0.0392 0.0015 0.037 3.57 0.0798 0.0740 0.0058 0.078 7.27 0.1212 0.1056 0.0156 0.148 12.87 0.1540 0.1296 0.0244 0.188 15.84 0.1960 0.1632 0.0328 0.201 16.73 octanol 0.0406 0.0318 0.0088 0.276 21.63 0.0798 0.0625 0.0173 0.276 21.64 0.1212 0.0945 0.0267 0.283 22.03 0.1540 0.1154 0.0386 0.334 25.04 0.1960 0.1458 0.0502 0.344 25.62 mibk 0.0406 0.0330 0.0076 0.230 18.71 0.0798 0.0592 0.0206 0.348 25.81 0.1212 0.0735 0.0477 0.649 39.34 0.1540 0.0867 0.0673 0.776 43.68 0.1960 0.0999 0.0961 0.961 49.01 bhanot, kumar, shende and wasewar hungarian journal of industry and chemistry 18 4. discussion the extraction data under equilibrium conditions indicate that molecules of tartaric acid are perpetually relatively soluble in the organic phase, while the concentration of ta in the aqueous phase increases (figure 1). the experimental results depicted the highest distribution coefficient values of 0.961, 0.344, 0.201, 0.188 and 0.167 with mibk, octanol, kerosene, mustard oil and groundnut oil, respectively, at a concentration of 0.1960 mol/l of ta (figure 2). the distribution coefficient was influenced by the initial concentrations of the ta. as the initial concentration increased, the distribution coefficient also rose when all the solvents were used. a higher distribution coefficient was observed when mibk was used with 0.1960 mol/l of ta. according to figure 2, conventional solvents like mibk and octanol exhibit higher distribution coefficients compared to organic solvents like mustard oil, groundnut oil and kerosene because these solvents are immiscible in the aqueous phase, moreover, cannot form free hydrogen bonds due to their high viscosity and density [20]. these solvents have low kd values. since the organic phase cannot dissolve in the aqueous one, these solvents form a barrier between aqueous and organic phases, resulting in oils yielding lower distribution coefficients [21]. the distribution coefficient of an acid rises as its molecular weight increases because the distribution coefficient is influenced by the molecular weight and solubility [22]. the extraction efficiency also increased by increasing the initial concentration of ta using all solvents (figure 3). according to the experimental study, the maximum extraction efficiency of 49.01% was observed using mibk, while the lowest of 14.29% was measured in groundnut oil. due to the non-polar nature and long fatty acids in organic solvents, their extraction efficiency is poorer than chemical solvents. since the organic solvents have no dipole moment, they were unable to form complexes with the acid in the organic phase with free electrons nor serve as a hydrogen donor in solvents other than octanol and mibk. the extraction efficiency when using mibk was higher than with octanol because mibk is a positively charged polar solvent. therefore, it dissolves more easily in tartaric acid in the organic phase, resulting in a higher extraction efficiency. in contrast, octanol is a non-polar solvent due to the large hydrophobic group it contains, limiting mass transfer from the aqueous to the organic phase when compared to mibk [23]. the maximum extraction efficiencies were 49.01, 25.62, 16.73, 15.82 and 14.29% when mibk, octanol, kerosene, mustard oil, and groundnut oil were used, respectively, with 0.1960 mol/l of tartaric acid. since the extraction efficiencies of organic solvents were less than conventional ones, they can be used with various extractants like tributylphosphate, trioctylamine, aliquat 336, etc. to increase the extraction efficiency of ta. figure 1: equilibrium data for the separation of tartaric acid using various solvents at 298±1 k figure 2: variation in the distribution coefficient against the initial concentrations of tartaric acid at 298±1 k figure 3: variation in the extraction efficiency against the initial concentrations of tartaric acid at 298±1k extraction of the food additive tartaric acid 51(2) pp. 15–20 (2023) 19 5. conclusion tartaric acid was separated by an extraction process from the aqueous phase using groundnut oil, mustard oil, kerosene, octanol and mibk as solvents. when mibk was used, higher values for the distribution coefficient (0.961) and extraction efficiency (49.01%) were recorded, the latter was measured at a ta concentration of 0.1960 mol/l in the case of all the solvents. since the extraction efficiencies of the organic solvents were lower than their chemical counterparts, the former can be used with extractants and in a closed loop with the mixersettler reactor during the next step to improve the extraction efficiency of ta. when organic solvents are applied, the toxic nature of using an extractant can be avoided, thereby preventing the organic phase coming into contact with the organism and providing an environmentally-friendly process for extracting the ta. symbols mw molecular weight swater solubility in water kd distribution coefficient e% extraction efficiency [ta]in initial concentration of tartaric acid [ta]aq concentration of tartaric acid in the aqueous phase [ta]org concentration of tartaric acid in the organic phase [s]org concentration of the solvent in the organic phase acknowledgement the authors are thankful for all the administrative and infrastructural support provided by the director of visvesvaraya national institute of technology in nagpur, maharashtra, india. references [1] markets and markets: tartaric acid market, 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(elsevier), 2014, 491–534, doi: 10.1016/c2013-014256-0 https://doi.org/10.1016/s0009-2509(99)00416-9 https://doi.org/10.1016/s0009-2509(99)00416-9 https://doi.org/10.1021/ie050159q https://doi.org/10.1016/j.cdc.2020.100417 https://doi.org/10.1002/jctb.7265 https://pubchem.ncbi.nlm.nih.gov/compound/tartaric-acid https://doi.org/10.1016/c2013-0-14256-0 https://doi.org/10.1016/c2013-0-14256-0 page 1 page 2 page 3 page 4 page 5 page 6 page 7 page 8 page 9 page 10 page 11 page 12 page 13 page 14 page 15 page 16 page 17 page 18 page 19 page 20 page 21 page 22 page 23 page 24 page 25 page 26 page 27 page 28 page 29 page 30 page 31 page 32 page 33 page 34 page 35 page 36 page 37 page 38 page 39 page 40 page 41 page 42 page 43 page 44 page 45 page 46 page 47 page 48 page 49 page 50 page 51 page 52 page 53 page 54 page 55 page 56 page 57 page 58 page 59 page 60 page 61 page 62 page 63 page 64 page 65 page 66 page 67 page 68 page 69 page 70 page 71 page 72 page 73 page 74 page 75 page 76 page 77 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material science • mechanical engineering • mechatronics • process & system engineering • recycling in the form of original papers, technical reports, reviews, communications, and conference proceedings written in english. hjic is abstracted by chemical abstracts, indexed by hungarian scientific bibliographic database (mtmt), and archived by real-j repository of the hungarian academy of sciences. editorial board editor-in-chief: róbert k. szilágyi department of chemistry and biochemistry, montana state university, bozeman, mt, u.s.a. mta-elte “lendület” chemical structure/function laboratory, budapest, hungary associate editors: jános abonyi department of process engineering, university of pannonia, veszprém, hungary dezső boda department of physical chemistry, university of pannonia, veszprém, hungary norbert miskolczi mol department of hydrocarbon and coal processing, university of pannonia, veszprém, hungary dóra rippel pethő department of chemical engineering science, university of pannonia, veszprém, hungary editors: katalin bélafi-bakó research institute of bioengineering, membrane technology and energetics, university of pannonia, veszprém, hungary peter czermak institute of bioprocess engineering and pharmaceutical technology, mittelhessen university of applied sciences, giessen, germany dénes fodor institute of mechanical engineering, university of pannonia, veszprém, hungary maria gavrilescu department of environmental engineering and management, gheorghe asachi technical university of iasi, romania dirk gillespie department of molecular biophysics and physiology, rush university medical center, chicago, u.s.a lászló gubicza research institute of bioengineering, membrane technology and energetics, university of pannonia, veszprém, hungary jenő hancsók mol department of hydrocarbon and coal processing, university of pannonia, veszprém, hungary jiří klemeš centre for process integration and intensification, university of pannonia, veszprém, hungary zoltán kovács department of management, university of pannonia, veszprém, hungary jános kristóf department of analytical chemistry, university of pannonia, veszprém, hungary istván szalai institute of physics and mechatronics, university of pannonia, veszprém, hungary jános szépvölgyi research centre for natural sciences, university of pannonia, veszprém, hungary gyula vatai department of food engineering, corvinus university of budapest, hungary gábor veress federation of technical and scientific societies – mtesz budapest, hungary ibolya zsoldos department of material science and technology, széchenyi istván university, győr, hungary editorial office: university of pannonia, p.o. box 158, veszprém, 8201 (hungary) tel.: +36 (88) 624-746, e-mail: hjic@almos.uni-pannon.hu; web: hjic.mk.uni-pannon.hu felelős szerkesztő: szilágyi róbert károly nyelvi lektor: matthew chen kiadja: pannon egyetem, 8200 veszprém, egyetem u. 10. elektronikus terjesztés: de gruyter open (formerly versita), warsaw, poland levélcím: h-8201 veszprém, postafiók 158, tel.: (88) 624-000 felelős kiadó: a pannon egyetem, mérnöki kar dékánja (prof. dr. szalai istván, ph.d.) de gruyter open hung. j. ind. chem., 2015 43(2), 55–101 table of contents review some analytic expressions for the capacitance and profiles of the electrical double layer formed by ions near an electrode douglas henderson .................................................................................................... 55–66 doi: 10.1515/hjic-2015-0010 articles comparison of two variable interpolation methods for predicting the vapour pressure of aqueous glycerol solutions istván szalkai, attila sebestyén, b. della-vecchia, tamás kristóf, lászló kótai, ferenc bódi ................................................................................................................. 67-71 doi: 10.1515/hjic-2015-0011 comparison of decontamination standards le cong hao, mai dihn thuy, do trung hieu, zoltán sas ......................................... 73–78 doi: 10.1515/hjic-2015-0012 a study of the adsorption characteristics of cobalt and caesium from a solution by using vietnamese bentonite le phuoc cuong, pham hoang giang, bui dang hanh, gergő bátor ....................... 79–83 doi: 10.1515/hjic-2015-0013 application of ionic liquids in the utilization of the agricultural wastes: towards the one-step pre-treatment and cellulose hydrolysis gábor megyeri, nándor nemestóthy, milan polakovic, katalin bélafi-bakó, lászló gubicza ............................................................................................................ 85–89 doi: 10.1515/hjic-2015-0014 mineral matter in nigerian coals and tar sand and their implications in binary blend formulation/co-carbonisation solomon a. ryemshak, aliyu jauro, istifanus y. chindo, eno o. ekanem ................ 91–95 doi: 10.1515/hjic-2015-0015 comparative study of advanced oxidation processes to treat petroleum wastewater dheeaa al deen atallah aljubourya, puganeshwary palaniandy, hamidi bin abdul aziz, shaik feroz ........................................................................... 97–101 doi: 10.1515/hjic-2015-0016 hungarian journal of industry and chemistry vol. 43(2) pp. 55-66 (2015) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2015-0010 some analytic expressions for the capacitance and profiles of the electric double layer formed by ions near an electrode douglas henderson ⇤ department of chemistry and biochemistry, brigham young university, provo, utah 84602, usa the electric double layer, which is of practical importance, is described. two theories that yield analytic results, the venerable poisson-boltzmann or gouy-chapman-stern theory and the more recent mean spherical approximation, are discussed. the gouy-chapman-stern theory fails to account for the size of the ions nor for correlations amoung the ions. the mean spherical approximation overcomes, to some extent, these deficiencies but is applicable only for small electrode charge. a hybrid description that overcomes some of these problems is presented. while not perfect, it gives results for the differential capacitance that are typical of those of an ionic liquid. in particular, the differential capacitance can pass from having a double hump at low concentrations to a single hump at high concentrations. keywords: electric double layer, capacitance, gouy-chapman-stern theory, mean spherical approximation, density functional theory, computer simulation 1. introduction a double layer (dl) or an electric double layer (edl) is formed when charged particles are attracted to a charged surface. the most obvious case is an electrolyte near a charged electrode (as in a battery). however, dna can play a role that is analogous to the electrode. ions can be attracted to membranes. a membrane can be thought of as a pseudo electrode. ions are absorbed (often selectively) into physiological channels in membranes. such channels permit the transport of nutrients into the cell and the removal of waste from the cell and are essential to the functioning of cells and life. the reader’s attention is drawn to some recent reviews of edls [1–3]. it is the case of an electrolyte near a charged flat surface that is considered here. this is the simplest case; it is an interesting and important application of statistical mechanical theory. the theory of the dl is important to our understanding of batteries. it can be used in the analysis of experimental electrochemical data and in analytical chemistry. in the model dl that is presented here, the electrode is approximated as a smooth flat charged surface located at x = 0. this surface is impenetrable and the ions are confined to the region x > 0. the charge of the electrode is located on the surface. there is no charge inside the electrode (x < 0). the electric field does not penetrate the surface. the electrode is a classical metal. obviously, this is an approximation but there has been very ⇤author for correspondence: doug@chem.byu.edu little work that takes into account the electronic structure of the electrode. the electrode charge is presumed to be uniform; the charge density of the electrode is � and has the units of c/m2. ions in the electrolyte near an electrode that have a charge opposite to that of the electrode are attracted to the electrode and form a layer whose net charge is equal in magnitude, but opposite in electric sign, to the charge of the electrode. the electrode and the attracted charge are together called an edl. the charge in the edl of the electrolyte can be spread over an extended region, usually called the diffuse layer, and need not consist solely of counterions whose charge is opposite to the electrode charge. the counterions can bring some coions with them. there may be regions of alternating charge where the coions predominate. however, the net charge of the attracted charged region in the electrolyte is equal in magnitude but opposite in sign to that of the electrode. otherwise, the electric field would not vanish far from the electrode. for simplicity, the model electrolyte that is employed here is a fluid of charged hard spheres of diameter d. in this study, the electrolyte is assumed to be binary. for additional simplicity, the ions are assumed in this article to be symmetric both in the magnitude of their charge and diameter. the value of the charge of an ion of species i is z i e, where z i is the ion valence and has the sign of the ion charge. the magnitude of the elementary charge is e. because the ions are symmetric, |z i | = z. in the bulk, the density of the ions of species i is ⇢ i = n i /v, where n i is the number of ions of species i in the bulk henderson 56 and v is the volume of the system. electrical neutrality requires that n1 = n2 or ⇢1 = ⇢2 or p z i ⇢ i = 0. the solvent (usually water) of the electrolyte is characterized by a dielectric constant, ✏. any change of the dielectric constant with a change of ion concentration is ignored. this model electrolyte is appropriately called the primitive model (pm). in the particular case considered here, where the ions all have the same diameter, this model is called the restricted primitive model (rpm). in this model, the interaction between a pair of ions, whose centers are separated by the distance r, is given by u ij (r) = 8 < : 1 for r < d z i z j e 2 4⇡✏0✏r for r � d , (1) where ✏0 is the permittivity of free space, and the interaction of an ion with the surface is given by uwi (x) = ( 1 for x < d/2 ��z i ex ✏0✏ for x � d/2 , (2) where x is the distance between the center of the ion and the surface. our task is to determine the density profile, ⇢ i (x), of the ions, or equivalently, g i (x) = ⇢ i (x)/⇢ i . note that ⇢ i (1) = ⇢ i , so that g i (1) = 1. once, the g i (x) are known, the charge profile (c/m2), for x > d/2, is given by q(x) = e x i z i ⇢ i h i (x), (3) where h i (x) = g i (x) � 1. in writing eq. 3, the global charge neutrality condition p z i ⇢ i = 0 has been invoked. the charge density on the electrode is given by � = �e x i z i ⇢ i z 1 d/2 h i (t)dt. (4) there is no point including the region 0 < t < d/2 in the integral since p h i (t) = 0 in this region. the potential profile (in volts) is given by �(x) = � e ✏✏0 x i z i ⇢ i z 1 x (t� x)h i (t)dt. (5) in particular, the potential (volts) of the electrode is given by v = �(0) = � e ✏✏0 x i z i ⇢ i z 1 0 th i (t)dt. (6) note that these equations satisfy poisson’s equation d 2 �(x) dx 2 = �q(x) ✏✏0 . (7) indeed, eqs. 3 and 5 are obtained by integrating poisson’s equation. an alternative procedure for computing the potential profile has been proposed by boda and gillespie [4] for simulation purposes. it is often convenient to use dimensionless, or reduced, values that are denoted by an asterisk. for a system whose temperature (k) is t , the reduced temperature is t ⇤ = 4⇡✏✏0dkt/z 2 e 2. the reduced density is ⇢ ⇤ i = ⇢ i d 3, the reduced electrode charge density is � ⇤ = �d 2 /e, and the reduced potential is � ⇤ = �e�, where � = 1/kt , with k being the boltzmann constant (the gas constant per particle). 2. poisson–boltzmann or gouy–chapman–stern theory: comparison with simulations the classic theory of the edl was developed by gouy [5], chapman [6], and stern [7] (gcs) a century ago. the theory is based on poisson’s equation together with the boltzmann formula, g i (x) = ⇢ 0 x < d/2 exp[��z i e�(x)] x � d/2 . (8) in electrostatics, poisson’s equation is exact and is equivalent to one of maxwell’s equations. the boltzmann formula is approximate and neglects ion size and correlations between the ions. eq. 8 states that g i (x) for the coions is the reciprocal of g i (x) for the counterions. this is not true, in general [8]. equation 8, when inserted into poisson’s equation, yields what may be called the poisson-boltzmann (pb) or gcs approximation. this approximation is also employed in the debye-hückel (dh) theory for bulk electrolytes that was developed some years later. however, because of the three dimensional geometry of the dh theory, the nonlinear pb equation cannot be solved analytically and the pb equations in the dh theory are usually linearized. in the gcs theory, the resultant pb equation is a nonlinear second order differential equation. as has been pointed out, such equations generally do not yield analytic solutions. however, for the one dimensional geometry of the planar dl that is considered here, an analytic solution is possible in the case of the gcs theory. the resulting pb/gcs potential is �ze�(x) 2 = ln ( 1 + b/2 1 + p 1 + b 2 /4 exp[�y] ) � ln ( 1� b/2 1 + p 1 + b 2 /4 exp[�y] ) , (9) where y = x� d/2 > 0 and b = �ze� ✏✏0 , (10) where  is the debye screening parameter that is given by  = s �z 2 e 2 ⇢ ✏✏0 (11) hungarian journal of industry and chemistry 57 double layers near an electrode with ⇢ = p ⇢ i . the parameter b is another dimensionless measure of the electrode charge density. however, it is not as fundamental a quantity as �⇤ since it arises from a theory. the parameter  is a screening parameter; it is an inverse measure of the distance over which the profiles reach their asymptotic values within the gcs and dh theories. in the gcs theory the relationship between the potential difference and electrode charge density is given by sinh  �ze� d/2 2 � = b 2 , (12) where � d/2 = �(d/2) is often called the diffuse layer potential. some relations that are equivalent to eq. 12 are cosh  �ze� d/2 2 � = p 1 + b 2 /4, (13) tanh  �ze� d/2 2 � = b/2p 1 + b 2 /4 , (14) and tanh  �ze� d/2 4 � = b/2 1 + p 1 + b 2 /4 . (15) the equivalence of eqs. 12–15 is a result of identities among the hyperbolic functions. thus, eq. 9 can be written as �ze�(x) 2 = ln ⇢ 1 + tanh  �ze� d/2 4 � exp(�y) � � ln ⇢ 1� tanh  �ze� d/2 4 � exp(�y) � . (16) alternative forms of eqs. 9 and 16 are tanh  �ze�(x) 4 � = tanh  �ze� d/2 4 � exp(�y) (17) or tanh  �ze�(x) 4 � = b/2 1 + p 1 + b 2 /4 exp(�y). (18) in the gcs theory, the potential difference across the edl is v = � ze ✏✏0 x i ⇢ i z 1 0 th i (t)dt = �d 2✏✏0 + � d/2, (19) where � d/2 is given by eq. 12. thus, the capacitance, c = �/v , of the edl is 1 c = d 2✏✏0 + 2 sinh �1 (b/2) ✏✏0b (20) and the differential capacitance, cd = @�/@v , of the edl is given by 1 cd = d 2✏✏0 + 1 ✏✏0 p 1 + b 2 /4 . (21) equations 20 and 21 are formally identical to a diffuse layer capacitor with capacitance, c dl = ✏✏0 b/2 sinh �1 (b/2) , (22) or differential capacitance c dl d = ✏✏0 p 1 + b 2 /4 (23) in series with an inner–layer parallel plate capacitor with capacitance (or differential capacitance), c il = c il d = 2✏✏0 d . (24) at contact, g i (d/2) = exp[�z i e� d/2] = 1 + b 2 2 � z i z b r 1 + b 2 4 , (25) so that gsum(d/2) = 1 2 [g1(d/2)+g2(d/2)] is, in the gcs theory, given by gsum(d/2) = 1 + b 2 2 . (26) this is to be compared with the exact result (for the restricted pm) due to henderson and blum [9] and henderson, blum, and lebowitz [10], gsum(d/2) = p ⇢kt + b 2 2 , (27) where p is the osmotic pressure of the electrolyte. the second term in the above equation is just the maxwell electrostatic stress. thus, eq. 27 is just a force balance condition where the momentum transfer to the electrode is equal to the sum of the osmotic term and the maxwell stress. the gcs theory deals with the electrostatic term correctly but replaces the osmotic pressure with the ideal gas result p = ⇢kt because of the neglect of the ion diameters. for comparison with the mean spherical approximation (msa), which is a linear response theory that will be considered in the next section, it is worthwhile to give the linearized gcs theory results, obtained for the case of small electrode charge. in this case, g i (x) = ⇢ 0 for x < d/2 1� �z i e�(x) for x � d/2 , (28) or g i (x) = 8 < : 0 for x < d/2 1 + �z i e� ✏✏0 exp (�y) for x � d/2 . (29) the potential profile in the diffuse layer is given by �(x) = � d/2 exp(�y) (30) with � d/2 given by � d/2 = � ✏✏0 . (31) 43(2) pp. 55-66 (2015) doi: 10.1515/hjic-2015-0010 henderson 58 0.00 0.01 0.02 0.03 0.04 (c d dl ) -1 [cm 2 /µf] 0.02 0.03 0.04 0.05 0.06 0.07 c d -1 [ cm 2 /µ f ] -8 -4 -2 0 2 4 8 figure 1: experimental values of the inverse differential capacitance, cd, of an aqueous solution of nah2po4 at 25 �c near a hanging drop mercury electrode as a function of the inverse diffuse layer capacitance, cdl d , obtained from eq. 23. the points are the experimental results of parsons and zobel. the light straight lines of unit slope give the results of the gcs theory but with the experimental inner layer capacitance obtained empiricially. the numbers at the low concentration end of the lines give the electrode charges in units of µccm�2. the heavy solid curve gives the results of the msa using a dipolar hard sphere model for the solvent together with an estimate of the contribution of the electronic structure of the electrode and is intended only as an aid to the eye. this figure has been reproduced, with permission, from ref. [1]. the potential difference across the edl is v = �d 2✏✏0 + � ✏✏0 (32) and the capacitance (and differential capacitance) of the edl is given by 1 c = d 2✏✏0 + 1 ✏✏0 . (33) in the gcs theory, in the limit of large  (high concentration) or large b (high electrode charge), the diffuse layer capacitance is large and, as a result, the inner layer capacitance dominates, due to the reciprocal or series additivity of eqs. 20 and 21. hence, in the gcs theory, c = 2✏✏0/d is the limiting (maximum) value of c or cd at large concentrations or large electrode charges. further, the differential capacitance at low concentrations looks something like a parabola but flattens out at large �. at high concentrations, the differential capacitance is constant. any additional shape in the experimental differential capacitance is added by an empirical fit of the inner layer capacitance to the experimental results. however, the diffuse layer capacitance is presumed to be given adequately by the gcs theory. parsons and zobel (pz) [11] have plotted their experimental results for the inverse of the differential capacitance as a function of the inverse of the diffuse layer differential capacitance, given by eq. 23. such a plot is often called a parsons-zobel plot. if the gcs theory were correct, this should result in a straight line. the extrapolation of the straight line to 1/c dl d = 0 (high concentration and/or high electrode charge density) should, if the gcs theory were correct, yield the reciprocal of the inner layer capacitance. as is seen in fig. 1, at first sight the experimental results of pz (the points) do seem to follow a straight line and, conventionally, are presumed to provide an experimental verification of the gcs theory. in fig. 1, the light straight lines are the gcs results. the solid curve is the result of the msa that has not yet been discussed. for the moment the solid line can be considered to be an aid to the eye in following the trend of the experimental results. in the conventional gcs picture, the inner layer capacitance might not be given by eq. 24 but might differ because of the presumed effect of the presence and nature of the solvent molecules and the electronic structure of the electrode that are beyond the gcs theory. possible solvent effects might be a lower dielectric constant due to the alignment of the solvent molecules because of the strength of the electrode charge. the important point is that, in the gcs theory, such solvent effects are presumed to be confined only to the inner layer. the gcs theory is conventionally considered to provide an adequate description of the diffuse layer where the ions are present. also, it is thought to provide a description of the edl when combined with some treatment of the solvent molecules in the inner layer, or even an empirical fit. indeed, the extrapolation of the straight lines to 1/c dl d = 0 is one method of obtaining presumed “experimental” values of c il d . however, a careful examination of the pz experimental results in fig. 1 indicates that the experimental differential capacitance does not follow eq. 21 at high concentrations (the left side of the figure) but rises above the extrapolated intercept, possibly without limit. until recently, most experimentalists have ignored this point and did not concern themselves with this issue because ions are not soluble in water when their concentration is large and it is difficult to obtain results with other solvents. additionally, experimental results are difficult to obtain at high electrode charges for conventional electrolytes. however, as we shall see, dls in ionic liquids can be formed at high concentrations and the deficiencies of the gcs theory become quite apparent. given that experiments on aqueous systems are difficult in regimes where problems with the gcs theory become apparent, it is useful to consider computer simulations. one simulation technique is the monte carlo (mc) method. until recently, it has been the most common simulation tool in dl studies. in mc simulations the ions undergo a random walk and the profiles and other properties of interest are obtained by averages over this random walk. a simple random walk would take forever before useful results could be obtained. however, meaningful results can be obtained by means of a biased random walk that confines the ions to regions in which they hungarian journal of industry and chemistry 59 double layers near an electrode 0 5 10 15 b 0 2 4 6 βe φ( d/ 2) a 0.0 0.1 0.2 σd2/e 0 2 4 6 βe φ( d/ 2) b figure 2: diffuse layer potential of a 1:1 electrolyte (d = 3 å) at room temperature as a function of b (part a) and � (part b). the curves are, from top to bottom, for 0.01, 0.1, and 1 m solutions. the symbols give the simulation results. the solid curve in part a gives the gcs results. the dotted lines connect the mc results for easier visualization. the lines in part b give the gcs results. part a is reproduced, with permission, from ref. [1]. have a high probability of residing. the simulation cell consists of a parallelopiped with a charged wall (the electrode) at x = 0 and another wall (charged or uncharged) at x = l, where l is so large that the two walls do not interfere. periodic boundary conditions are used in the other two directions. the size of the cell is chosen to be large enough that electrostatic screening eliminates the effects of the periodic image cells. the number of ions of each species is chosen so that the system is electroneutral. the first use of mc simulations for the study of the edl was that of torrie and valleau [12, 13]. after their seminal studies, there was a hiatus in simulation studies of the edl. however in recent years, there has been a renewed interest in simulations of the edl that includes the work of bhuiyan et al. [8], boda et al. [14, 15], and lamperski et al. [16, 17]. another simulation technique is the molecular dynamics (md) method in which the equations of motion are solved and the properties of the system of interest are obtained by averaging over the positions and velocities of the ions. a simulation cell that is similar to that used 0 1 2 3 4 5 g i (x ) a 0 1 2 3 4 5 x/d 0 1 2 3 4 5 g i (x ) b figure 3: normalized density profiles, gi(x), of a 1:1 electrolyte (d = 3 å) at 1 m and room temperature for the state for which the mc values are �d 2 /e = 0.1685 and �e�(d/2) = 2.6. the points give the simulation results and the curves give the gcs results. the comparison is made at the same charge density (part a) and the same diffuse layer potential (part b). in mc simulations is employed. in recent years, there has been an interest in md simulations of the edl, especially for ionic liquids. some representative studies are those of vatamanu et al. [18, 19], hu et al. [20], and feng [21] et al.. a comparison with simulation gives an unambiguous test of the gcs theory since uncertainties resulting from empirical fits of the diffuse layer capacitance cannot arise. the gcs theory and simulations both use the same model and interaction parameters that are defined in eqs. 1 and 2. additionally, simulations and theory give results for the density profiles, g i (x), that cannot be obtained by present experimental methods. the simulations plotted in figs. 2–5 are those of boda et al. [22]. in fig. 2a, the electrostatic potential �e�(d/2) for a 1:1 electrolyte is plotted as a function of b for three concentrations (0.01m, 0.1m, and 1m). if the gcs theory were correct, these curves would be identical and independent of concentration. hence, there can be only one gcs curve in fig. 2a. as is seen, �(d/2) as a function of b actually decreases with increasing concentration. in fig. 2b, �(d/2) is plotted as a function of �d 2 /e. the cgs curves are greater than the simulation results, espe43(2) pp. 55-66 (2015) doi: 10.1515/hjic-2015-0010 henderson 60 -0.2 -0.1 0.0 0.1 0.2 σd2/e -4 -2 0 2 4 6 βe φ( d/ 2) figure 4: diffuse layer potential of a 2:1 electrolyte (d = 3 å) at room temperature as a function of �. the curves are, from top to bottom, for 0.01, 0.1, and 1 m for positive � and the reverse for negative �. the symbols give the simulation results. the curves give the gcs results. cially as the concentration increases. the density profiles for a 1:1 electrolyte are plotted in fig. 3. the comparison is made at the same value of � in part a and the same value of �(d/2) in part b. in principle, there is no reason to choose whether the comparison should be made at the same �, the same �(d/2), or the same �(0). it was natural for torrie and valleau to make their comparisons at the same � because � is the input variable in their method. however, � is the natural variable in the gcs theory. in any case, the gcs theory looks best when � is used as the input variable. torrie and valleau overstated things when they said that the gcs theory was reasonable for a 1:1 electrolyte. their statement is most applicable if the comparison is made at the same value of �. the value of the counterion profile would be in poor agreement at x = d/2 if �(d/2) or �(0) were used as the input variable. a similar comparison is made for a 2:1 electrolyte in figs. 4 and 5. the agreement of the gcs theory with simulations is much poorer. the electrostatic interactions are stronger because of the presence of the divalent ions. when the divalent ions are the counterions, the potential, �(d/2) has a maximum and then decreases with increasing electrode charge. this is not seen in the gcs results which are monotonic. further, the simulation profiles are not monotonic whereas the gcs results are monotonic. the simulation profiles have oscillations. the edl can consist of regions where counterions or coions predominate. when the coions predominate, this phenomenon is known as charge inversion. of course, the net charge in the diffuse layer is still equal in magnitude, but opposite in sign, to that of the electrode charge. this is required to screen the electrode charge and potential far from the electrode. generally, experimentalists have been content to ignore the discrepancies in the results of the gcs theory and state that these differences are unimportant since they occur at high electrode charges or high concentrations 0 1 2 3 4 5 g i (x ) a 0 1 2 3 4 5 x/d 0 1 2 3 g i (x ) b figure 5: normalized density profiles, gi(x) of a 2:1 electrolyte (d = 3 å) at 1 m and room temperature for the state for which the mc values are �d 2 /e = �0.1685 and �e�(d/2) = �0.15. the points give the simulation results and curves give the gcs results. the comparison is made at the same charge density (part a) and the same diffuse layer potential (part b). or for high valence electrolytes or nonaqueous systems, where experimental results are difficult to obtain. however, this is short-sighted. as scientists, one of our goals is to understand what is happening. this cannot be done with an inaccurate theory even with curve fitting. in the remainder of this article, attention is directed to more accurate, but still analytic, theories. 3. mean spherical approximation the mean spherical approximation (msa) is a natural extension of the linearized gcs theory in which the size of the ions is taken into account. it was first applied to the edl by blum [23]. the gcs is usually obtained by means of the solution of a differential equation whereas the msa is obtained from the solution of an integral equation. at first sight, the connection between the gcs and msa theories is unclear. however, henderson and blum [24] demonstrated that the gcs theory could also be obtained from an integral equation. in fact, the linearized gcs integral equation is just the msa integral equation with the effect of ion size ignored. actually, henderson and blum proved a more general result. they showed that the gcs theory followed from the hungarian journal of industry and chemistry 61 double layers near an electrode hypernetted–chain approximation (hnca) when ion size was neglected. the msa can be regarded as a linearized version of the hnca and, because of this, the stated relation of the linearized gcs theory to the msa follows. in this article, the hnca is not considered because it does not yield analytic results and has severe problems when � is large [25]. also, the emphasis in this article is upon analytic, or at least explicit, results that can be valuable in practical calculations. the msa result that is analogous to eq. 29 is g i (x) = 8 < : 0 for x < d/2 g0(x)� �z i e� ✏✏0 f(y) for x � d/2 , (34) where g0(x) is the percus-yevick (py) profile for hard spheres near a hard surface. earlier, henderson, abraham, and barker (hab) [26] obtained an integral equation for g0(x). the second term gives the electrostatic part of the profile for charged hard spheres near a charged hard surface. blum [23] did not obtain a result for f(y) but he did obtain an analytic result for the laplace transform of f(y), z 1 0 exp(�sy)f(y)dy = = s s 2 + 2(��)s+ 2(��) 2 (1� exp[�s]) , (35) where 2� is a renormalized screening parameter that is related to  by  = 2�(1 + ��) or 2�� = p 1 + 2�1. note that for small  (small concentrations), 2�� = ��(�) 2 /2+···. thus, the msa screening parameter is smaller than the gcs screening parameter. this suggests that the msa edl is wider than that of the gcs theory. this agrees with the simulation results. the notation of blum has been followed. however, it might have been preferable if he had incorporated the factor of 2 into the definition of � so that � became  at low concentrations. note that at low concentrations, the laplace transform of f(y) becomes 1/s(1 + s). this means that f(y) = exp(�y), (36) in the limit of low concentrations. also, g0(x) = 1 in this limit. thus, at low concentrations, the msa becomes the gcs theory. blum did not invert the laplace transform of f(y). however, he did obtain the contact value of f(y) by examining the laplace transform of f(y) at large s. he showed that f(0) = 1. using the earlier result of hab for g0(d/2), the contact value of g i (x) is g i (d/2) = 1 + 2⌘ (1� ⌘) 2 � �z i e� ✏✏0 , (37) where ⌘ = ⇡⇢d 3 /6. the msa contact value is an improvement over the gcs result that contains only the ideal gas term. however, the osmotic pressure should have both a hard sphere term and an electrostatic term. additionally, the hard sphere term is accurate only for low values of ⇢. equation 37 does not contain the quadratic term b 2 of eq. 27. this is because the msa is a linearized theory. a better expression for the osmotic term is p ⇢kt = 1 + ⌘ + ⌘ 2 � ⌘ 3 (1� ⌘) 3 � � 3 3⇡⇢ , (38) where � is the renormalized screening parameter that has been defined above. this result is obtained from the application of the msa to bulk electrolytes. the msa, as is the case for most theories, is not fully self-consistent. henderson et al. [27] have compared this expression with their simulations (see their fig. 1) and found it to be very accurate. despite these problems, the msa contact value given in eq. 37 does represent an advance. by expansion of the laplace transform of f(y), it is easy to show that the msa edl satisfies electroneutrality. that is, the charge in the edl is equal in magnitude, but opposite in sign, to the electrode charge. again, by expanding the laplace transform, the msa expressions for the total and diffuse layer potentials of the edl are found to be v = � ✏✏0(2�) (39) and � d/2 = � ✏✏0 [1� (�d) 2 ]. (40) thus, in the msa, the capacitance (and differential capacitance) of the edl is 1 c = 1 ✏✏0(2�) . (41) expanding the expression that defines �, 2� = �  2 d/2 +  3 d 2 /2 + · · ·. (42) therefore, 1 c = 1 ✏✏0 + d 2✏✏0 � d 2 4✏✏0 + · · · . (43) the msa capacitance does not reach a maximum at 2✏✏0/d but continues to increase, as is indicated in fig. 1. the msa (solid) curve in fig. 1 was not calculated from eq. 41 but from a more sophisticated version of the msa, that is not discussed in detail here, which includes the contribution resulting from explicit solvent molecules and the electronic structure of the metal [28–30]. however, the results of eq. 41 are qualitatively similar to the more sophisticated results. in this paper, the solid curve serves to guide the eye. the inner layer capacitance continues to be 2✏✏0/d but it is simply the electrode charge divided by potential difference across the inner layer and not a ‘catch all’ for the deficiencies of the gcs theory. the diffuse capacitance is the electrode charge divided by the potential difference from the distance of closest approach to the bulk electrolyte and contains correction terms to the gcs theory. this is the reverse of the usual interpretation of the gcs theory where the gcs expressions are assumed to be accurate for the diffuse layer 43(2) pp. 55-66 (2015) doi: 10.1515/hjic-2015-0010 henderson 62 0.14 0.16 0.18 0.2 0.22 0.24 ρ* 1.4 1.6 1.8 2 2.2 2.4 c /f m -2 mc msa gcs figure 6: double layer capacitance, c, as a function of the reduced density, ⇢⇤ = ⇢d 3, at the reduced temperature t ⇤ = 0.08. the circles are the mc data of henderson et al. [27] and the lines are the msa and gcs results. the line through the circles is given as a guide to the eye. because the msa is a linearized theory, the mc, msa, and gcs capacitances are for � = 0. capacitance and everything else is ‘lumped’ into the inner layer capacitance. in the more sophisticated version msa, the contributions due to the solvent molecules appear in both the diffuse and inner layer potentials. the solvent molecule profile is as diffuse as that of the ions. the effect of the molecular nature of the solvent is not confined to the inner layer. the initial slope of the �(d/2) vs. � curves in figs. 2 and 4 is just the inverse of the diffuse portion of the capacitance. it is seen that the initial slope of the mc curves is well described by the gcs theory at low concentrations but increasingly falls below the gcs initial slope (the inverse of the differential capacitance) with increasing concentration as was seen in the experimental results in fig. 1. henderson et al. [27] compared the gcs and msa differential capacitances with their simulation results for a broad range of densities and at a temperature that was meant to be qualitatively representative of an ionic liquid. as is seen in figs. 6 and 7, the msa results are considerably improved over the gcs results. the comparison with the mc results is made for a small value of � because the msa is a linearized theory that is applicable only for small �. although an analytic expression for f(y) is not available, henderson and smith [31] were able to obtain a zonal expansion for f(y). they showed that f(x) = 1x n=1 f n (z)u(z), (44) where z = t�n+1, t = x/d, u(z) is the heaviside step function that is zero for z < 0 and one for z � 0 and f n (z) = exp(�µ) µ n (n� 1)! [j n�2(µ)� j n�1(µ)] (45) with µ = (�d)z. the function j m (µ) is the spherical x / d 0.5 1.0 1.5 2.0 2.5 0 1 2 3 4 g (x /d ) 0 1 2 3 4 5 counterions co-ions counterions co-ions (a) (b) figure 7: the electrode-ion normalized density profiles, gi(x/d), at the reduced density ⇢ ⇤ = ⇢d 3 = 0.5 for the reduced temperature t ⇤ = 0.8 and surface charge density, � = 0.05 c/m2, is small enough that the msa is applicable. the circles are the mc results of henderson et al. [26] and the dashed line gives the msa result. the line through the circles is given as a guide to the eye. this figure is reproduced, with permission, from ref. [26]. bessel function that is easily calculated using the recurrence formula for this function. hundreds of j m (µ) can be calculated without difficulty, even with a laptop computer. henderson and smith [31] also obtained a zonal expansion for g0(x). their result is g0(x) = 1x n=1 g n 0 (z)u(z), (46) where z is again given by z = t � n + 1 with t = x/d. the expressions for the g n 0 (x) are rather complex. however, henderson and smith gave results for n  5. the formulae for g0(x) and f(x) are not quite analytic since they involve infinite series. however, these results are explicit and easily used. fortran programs to obtain g0(x) and f(x) are given in supplementary material. note that the program for g0(x) consists of two parts. one part calculates those parameters that depend only on the state of the electrolyte and the other subroutine in each code calculates profiles for a given x. the user should resist the temptation to combine the two parts into one. mcquarrie [32] did this in an appendix to his excellent book and produced an inefficient, and probably incorrect, code that he referred to as ‘henderson’s code’. fortunately, his code hungarian journal of industry and chemistry 63 double layers near an electrode is illegible in the later printing of his book. if the reader does combine the codes, the reader is on his/her own and should not refer to the combined, or otherwise modified, code as ‘henderson’s code’. the functions g0(x) and f(x) are oscillatory, in accord with the simulations. they are improvements, qualitative and quantitative, to the monotonic functions of the gcs theory. 4. a useful hybrid description as has been mentioned, the deficiencies of the gcs theory could, until recently, be dismissed as appearing mainly under conditions that are of limited experimental interest. however, there has been considerable recent interest in edls formed by ionic liquids. ionic liquids can be thought of as room–temperature molten salts. because there is no solvent, the ions do not become insoluble in some solvent and experimental results can be obtained at high concentrations. the fact that they exist at room temperature is a great experimental convenience. kornyshev [33] has drawn attention to these electrochemical systems and aptly suggested that they provide a paradigm change in electrochemistry. he modestly ends the title of his important paper with a question mark. an exclamation mark might have been more appropriate. as well as exposing the deficiencies of the gcs theory, edls in ionic liquids are important in green technologies, the design of novel energy storage devices, such as high-tech batteries and super-capacitors [34]. ionic liquid dls have attracted recent experimental [35, 36] and theoretical interest [18–21, 37–39]. the differential capacitance, as determined by mc simulations, of a simple model [38] of an ionic salt in which t ⇤ = 0.8 and d = 8 å is given in fig. 8 for ⇢⇤ = 0.04, 0.14 and 0.24. at low concentrations, the differential capacitance is parabolic-like, as the gcs theory suggests. however, cd does not become flat at large electrode charges. at higher concentrations, cd at small electrode charges continues to increase with increasing concentration. this has been seen in fig. 6. at high electrode charges, the capacitance decreases. the nature of this decrease seems to be independent of the concentration. this is similar to the gcs theory except that the capacitance is not flat at high electrode charges but decreases. the decrease is due to the fact that the ions are not point charges but occupy space and cannot sit on top of each other. the diffuse layer must become thicker and the capacitance decreases as the electrode charge increases. this is not because the distance of closest approach of the ions increases. strong secondary peaks in the counterion profile appear [37]. the beginnings of this trend were first observed by torrie and valleau [12] and seem to be quite universal. the gcs theory satisfies eq. 27 at high electrode charges but fails at low electrode charges whereas the msa gives reasonable results at small electrode charges. this implies that a repair of the gcs so that it gives the msa results in the regime of the low electrode charges -2 -1 0 1 2 σ∗ 3 4 5 6 7 8 9 c df * 0.24 0.04 0.14 figure 8: differential capacitance, c⇤ df = cdd/4⇡✏0, obtained from mc simulation for the edl of a model ionic liquid with d = 4 å and t ⇤ = 0.8. the curves are, from bottom to top, for ⇢⇤ = 0.04, 0.14, and 0.24. this figure has been reproduced, with permission, from ref. [40]. but leaves the high electrode charge part unchanged might be useful. likely, there is no way to accomplish this in a fundamental way. additionally, there are probably several semi-empirical ways in which this could be done. henderson and lamperski [40] have presented one procedure. because it is not based on any fundamental ideas, it is not a theory. it would be more appropriate to refer to their procedure as a description. they proposed that the differential capacitance for a symmetric salt could usefully be written as 1 cd = d 0 2✏✏0 + d 0 2✏✏0 p 1 + b 2 /4 ✓ 1 �d 0 � 1 ◆ . (47) the parameter d 0 is an adjustable parameter and represents the effective thickness of the diffuse layer. at small b (small electrode charge), eq. 47 yields 1 c d = 1 2�✏✏0 , (48) which is the msa result. at large b (large electrode charge), eq. 47 yields 1 c d = d 0 2✏✏0 . (49) the results of eq. 47, using d 0 = 2d for the system that lamperski et al. simulated, were given by henderson and lamperski. qualitatively, the results are very similar to the simulation results shown in fig. 8. better agreement could be obtained by making d 0 increase with electrode charge. figure 2 of henderson and lamperski suggests that cd is proportional to 1/� ⇤ at large � ⇤ (electrode charge) with the proportionality constant being independent of concentration. this behavior was first predicted by kornyshev [33] on the basis of a lattice theory and seems to be universal. as well as the simulations of henderson and lamperski, it has been seen experimentally 43(2) pp. 55-66 (2015) doi: 10.1515/hjic-2015-0010 henderson 64 -1.5 -1 -0.5 0 0.5 1 1.5 σ* 4 6 8 10 c * d 0.24 0.14 0.04 figure 9: differential capacitance, c⇤ d = cdd/4⇡✏0, obtained from the hybrid description of the edl of a model ionic liquid with d = 4 å and t ⇤ = 0.8. the curves are, from bottom to top, for ⇢⇤ = 0.04, 0.14, and 0.24. the solid and broken curves give the results of the hybrid approach and gcs theory, respectively. by islam et al. [35]. something of the nature of d 0 = d1 + d2|�⇤| (50) would give the desired decrease of cd at large � ⇤. equation 50 is sensible because it is consistent with the diffuse layer becoming thicker as the electrode charge increases. the results of this ansatz with d1 = 2d and d2 = d are given in fig. 9. the results are similar to the simulation results in fig. 8. this hybrid approach is capable of yielding a capacitance with a double hump at low concentrations and a single hump at high concentrations. this behavior is predicted by simulations and all the good theories of the dl of ionic liquids. a hybrid treatment of the profiles, g i (x), is possible. one could start with the msa expression for g i (x) and add to this g gcs i (x; b) � g gcs i (x; b = 0). however, it must be realized that the msa expressions for the profiles are less accurate than the msa expressions for the potential and capacitance. the potential and capacitance are integrals and tend to average out any inaccuracies in the profiles. 5. conclusion the study of the electric dl is an important application of statistical mechanics that is of experimental and applied interest. the gcs theory is popular with experimentalists because it is intuitively simple and easy to use in the routine analysis of experiments. however, the gcs theory has deficiencies. its use leads to the idea that any problems with the gcs theory can be ‘swept under the carpet’ by placing all of these problems into an empirical treatment of the inner layer. in reality, the deficiencies of the gcs theory lie with the gcs treatment of the diffuse layer. admittedly, it is difficult to observe this in aqueous systems. however, it is not impossible. the departure from linearity in the parsons-zobel plot (fig. 1) is real and should not be ignored. the important field of ionic liquid electrochemistry requires something more adequate than the gcs theory. the best theories of the edl are the modified poisson-boltzmann theory [41] and the density functional theory [42]. however, both theories are numerical and require an iterative numerical solution of a fairly large set of equations and may not be appealing in an experimental analysis. a hybrid description, such as that explored here, preserves the advantage of an analytic treatment of the capacitance and is no more cumbersome than the gcs theory. supplementary information fortran programs to calculate g0(x) and f(x�d/2) using msa. the codes can be downloaded free of charge from http://tinyurl.com/hjic-2015-0010-suppl. acknowledgement professor dezső boda assisted with the preparation of this paper. professor lutful bari bhuiyan read the manuscript prior to submission and suggested several important modifications. the author is grateful to both colleagues for their continuing wise advice. references [1] henderson, d., boda, d.: insights from theory and simulation on the electrical double layer, phys. chem. chem. phys., 2009 11(20), 3822–3830 10.1039/b815946g [2] 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materials and environmental chemistry, research centre for natural sciences, hungarian academy of sciences, po box 17, budapest, 1525, hungary 6 faculty of engineering, university of pannonia, veszprém, 8201, hungary several general mathematical methods for approximating two variable functions are applied for the study of the relationships between the temperature, concentration, and vapour pressure of aqueous glycerol solutions. the general properties of each of the applied methods are discussed in respect of possible alternative applications. keywords: vapour-pressure approximation, splines, glycerol, aqueous solutions, multi-dimensional interpolation 1. introduction recently, the evaporation of aqueous solutions with low glycerol concentrations from the combined processes of ion-exchange and chemisorption of diluted solutions is preferred instead of the expensive purification of concentrated glycerol solutions. these processes are important in the cosmetic industry [1–3]. during the atmospheric evaporation of highly concentrated glycerol solutions, glycerol molecules condense by losing water and convert into acrolein or polyglycerols. thus, the control of the appropriate temperature and pressure limits is of great importance in industrial processes. in the present work, mathematical relationships with regard to concentration, vapour pressure, boiling point, and temperature data are studied for aqueous glycerol solutions. the possibilities for data interpolation using several two variable splineinterpolation methods are investigated with the aim of calculating low pressure evaporation conditions and upper temperature limits for aqueous glycerol solutions with given concentrations as a continuation of our previous work [4, 5]. *correspondence: szalkai@almos.uni-pannon.hu †deceased in 2001. 2. data and methods we use the data shown in table 1 that were taken from ref. [6]. the dataset is graphically presented in fig.1. approximating a two valued function means that we are given the measured values zi, j ∈ r at the measured points pi, j = (xi, yj) for 1 < i < m, 1 < j < n and we want to construct a smooth function s: r2 → r such that s(xi, yj) = zi, j for 1 < i < m, 1 < j < n. in the present paper we considered the following general approximation methods: • iterated one-dimensional (1d) cubic splines [8], • hermite type, two-dimensional (2d) interpolation, improved by lénárd in three versions [10-12], and • shepard’s generalised method for a scattered dataset with certain parameters in two versions [15, 17]. these methods are general approximation methods that are applicable not only to the present problem. when discussing the errors in computer outputs, we differentiate between general mathematical and chemical (material) specific reasons. in order to test the practical applicability of these methods we used every second column of the original dataset (table 1, pressures of 5.3, 20.2, ..., 101.3 kpa) as inputs, then we computed the approximations for the omitted columns, and finally we compared the computed values to the measured data from table 1 in the omitted columns (13.3, 26.6, ..., 93.3). these szalkai, sebestyén, della-vecchia, kristóf, kótai, and bódi hungarian journal of industry and chemistry 68 approximations and comparisons are shown in table s1 (not included in the paper due to its size) and are graphically summarised in figs.2–6. we did not consider specific semi-empirical relationships such as those in ref. [7]: ln(p) = a(c) ⋅ ta(c), where p, c, and t stand for pressure (mpa), concentration (%), and temperature (ºc), respectively. 2.1. iterated one-dimensional interpolations in refs. [8] and [9], one finds the well-known method of two variable spline interpolations, which repeatedly uses 1d spline interpolations. the details can be found in ref. [2] as well. this method requires that the domain of the function we are approximating is rectangular [a, b] × [c, d]. furthermore, the measured points pi, j lie on lines ℓj parallel to the ordinate axis for 1 < j < n. for calculating s(x, y) at each inner point (x, y) ∈ [a, b] × [c, d] we follow a two-step calculation. first, we use 1d splines sj in each horizontal line ℓj to compute the values ℓj(x, yj) = sj(x) for 1 < j < n. next, we use another 1d spline along the vertical line crossing the point (x, y). then, we calculate the value s(x, y) using the numbers ℓj(x, yj) for 1 < j < n and a 1d spline on them. in practice we can compute all the formulae of the splines sj in advance, so later the values of sj(x) can be obtained by an easy substitution. in our computations, we used cubic splines as described in refs. [2], [8] and [9]. the approximating function s(x, y) for our glycerol data is plotted in fig.2, detailed numeric values can be found in table s1. the similarity between figs.1 and 2 shows the small error of iterated 1d spline interpolation, while magnification can reveal some differences. the advantages of this method include that the 1d approximation is widely known, no equidistance tabulated (measured) points yj or xi are needed, and only the parallel lines ℓj are assumed. the method also gives an approximation at the margins of the closed rectangle [a, b]×[c, d] and it can be easily generalised for higher dimensions. a disadvantage of this method is the repeated use of the final spline approximation (“vertical step”) for getting s(x, y) at each point (x, y), which makes the computation slightly slower. we repeatedly have to build up and solve a tridiagonal n×n size system of linear equations. 2.2. direct two-dimensional interpolations in ref. [10], one can find simple, but general direct 2d methods for constructing directly a 2d spline interpolation of minimal degree of hermite type, invented by lénárd. she investigated 2d and higher dimensional methods as discussed also in refs. [2], [11], and [12]. this method requires that the dataset (measured data points) form a rectangular grid, i.e. each quadruple of table 1. the measured boiling points (in ºc) of aqueous glycerol solutions as a function of pressure (kpa) and concentration (mass percent, g g-1) as in table 44 of ref. [6]. conc. pressure 5.3 13.3 20.2 26.6 33.3 39.9 46.6 53.3 59.9 66.6 73.3 79.9 86.6 93.3 101.3 0% 34.0 51.6 60.1 66.4 71.6 75.9 79.6 82.9 85.9 88.7 91.2 93.5 95.7 97.7 100.0 10% 34.4 52.1 60.7 67.0 72.3 76.6 80.3 83.7 86.7 89.5 92.0 94.3 96.6 98.6 100.9 20% 34.9 52.7 61.3 67.7 73.0 77.3 81.1 84.4 87.5 90.3 92.9 95.2 97.4 99.5 101.8 30% 35.5 53.4 62.1 68.6 73.8 78.2 82.0 85.3 88.4 91.3 93.8 96.2 98.4 100.4 102.8 40% 36.5 54.4 63.1 69.5 74.9 79.3 83.1 86.4 89.5 92.4 95.0 97.3 99.6 101.7 104.0 50% 37.5 55.7 64.5 71.1 76.4 80.9 84.8 88.2 91.3 94.2 96.8 99.2 101.5 103.6 106.0 60% 39.5 58.0 66.9 73.5 79.0 83.5 87.4 90.9 94.1 97.0 99.7 102.1 104.4 106.0 109.0 70% 43.0 61.7 70.8 77.6 83.1 87.7 91.7 95.2 98.4 101.4 104.1 106.6 109.0 111.1 113.6 80% 49.1 68.2 77.4 84.3 90.0 94.6 98.7 102.3 105.6 108.7 111.4 113.9 116.3 118.5 121.0 90% 59.5 80.2 90.3 97.7 103.9 109.1 113.5 117.4 121.0 124.4 127.4 130.2 132.8 135.2 138.0 figure 1. the original dataset from table 1. figure 2. estimated boiling points from iterated 1d splines. interpolation methods for predicting vapour pressure 43(2) pp. 67–71 (2015) doi: 10.1515/hjic-2015-0011 69 { (xi, yj), (xi+1, yj), (xi, yj+1), (xi+1, yj+1) } (1) forms a rectangle, but not necessarily of the same size. ref. [11] requires equidistant grids. the problem associated with this is discussed in ref. [2]. the method we currently use is from ref. [10] that gives us separate formulae for each rectangle in eq.(1) as s(x, y) = si, j(x, y) if (x, y) ∈ [xi, xi+1] × [yj, yj+1] (2) such that finally a) s is twice continuously partially differentiable in both variables on its whole domain [a, b]×[c, d], b) si, j values are polynomials in both variables of minimal degree and their degrees, as two variable polynomials, are minimal, too. moreover, lénárd provided three different formulae for points a) and b) with the details described in eqs.(1,3), (2,3), and (3,3) of ref. [10]. the implementation of each of these three methods with numeric values can be found in table s1. the differences among the approximated results using these methods are not so significant, so we present here the plot only for the results of the first method in fig.3. the similarity between figs.1 and 3 shows the small error of lénárd’s hermite-type interpolation. an advantage of this method is that although the precomputation of the higher dimensional arrays takes some time, s(x, y) can then be computed as a polynomial at any point (x, y), making the computation fast. furthermore, the method can be easily generalised for higher dimensions as described in ref. [12]. one disadvantage of this method is that we ultimately need rectangular tabulated, measured data points, pi, j = (xi, yj). if required, the data points can be transformed to form an equidistant grid, i.e. the rectangles in eq.(1) would become congruent as in ref.[2], for example. furthermore, the method gives no approximation at certain margins of the rectangle [a, b]×[c, d], since we cannot compute the finite partial differences of higher order at the margins. 2.3. shepard’s method in ref.[13], shepard presented a more general method for continuous approximation in any dimension as was also discussed in refs. [14–17]. this method does not require any special assumption on the positions of the data points pi, j∈rn as it works for arbitrary distribution as well. this method can be introduced as follows: let the arbitrary measured data points p1, p2, ..., pm ∈rn and the corresponding values f1, f2, ..., fm ∈r be given. then the formula for each p∈rn u (p) = fi ⋅σ d(p,pi )( ) i=1 m ∑ σ d(p,pi )( ) i=1 m ∑ (3) gives a continuous and exact approximation: u(pi) = fi for any i≤m (4) where d(p, pi) is the euclidean distance of the points p and pi and the positive “weight function” σ:r→r+ satisfies lim d→0+ σ d( ) = +∞ and lim d→+∞ σ d( ) = 0+ . (5) in other words, u(p) is a weighted arithmetic mean of the measured values fi with weights, which are “inverses” of the distances of points pi from point p. the closer pi is to p, the greater weight f has in eq.(3). theoretical and practical considerations in refs. [15] and [17] suggest σ to be chosen as figure 3. estimated boiling points from lénárd’s hermite-type interpolation. figure 4. estimated boiling points from shepard’s method. szalkai, sebestyén, della-vecchia, kristóf, kótai, and bódi hungarian journal of industry and chemistry 70 σ d( ) = d−α ⋅e−λd (6) for some "appropriate" α, λ ≥ 1, usually 1 ≤ α, λ ≤ 2 are satisfactory in practice. this problem is discussed in detail in refs. [14–17]. in our present calculations, we used the values α = λ = 1. the approximating function u(p) of shepard’s method is shown in fig.4, detailed numeric values can be found in table s1. it is worth noting that the wave-like patterns on the surface in fig.4 show the unique property of shepard's interpolation (see references [15] and [17] for details). the main advantage of shepard’s method is the simplicity of eq.(3), which makes both theoretical investigations and practical computations easy. furthermore, the measured points p1, p2, ..., pm ∈ rn can be chosen totally arbitrarily, which may be of great assistance during measurements. however, an important disadvantage of this method is that σ and thus u are sensitive to the measurement units, mpa or kpa in our case. though u is always continuous and eq.(4) is valid for any σ, which satisfies eq.(5), the “shape” of u is the best when the distribution of the data points pi is “nearly” uniform in a region of rn (see ref. [17]). to improve our approximation we used data expressed in kpa in table 1. moreover, larger data sets slow down the processing of eq.(3) greatly, even when m ≈ 150 the computational time can be several minutes. a workaround for managing this problem is to deal only with the data points pi closest to p. in our example with aqueous glycerol solutions, we used 4×4 matrices of data points againts pressure and concentration, respectively, surrounding the requested approximated point. this approximation greatly speeded up the execution times. the continuity property of u in this variant is discussed in refs. [15] and [16]. 3. discussion for an alternative comparison of the methods considered in this paper, we present figs.5 and 6. in fig.5, we displayed the boiling points for different fixed concentrations. in fig.6, the pressure is examined. iterated 1d splines are the dashed-dotted lines, lénárd’s hermite-type 2d spline is the dashed line, and shepard’s method is shown in dotted lines. as can be seen, lénárd’s and iterated splines are practically undistinguishable. it seems that shepard’s method works less well than the other two methods. we can see this from the 3d plot (fig.4) with the effect of the flattening being evident. also it is evident from the 2d plot (fig.6) with constant concentration, where estimation in the middle (supposed missing) points is poor (plotted as squares). the flattening effect is again evident from the 2d plot (fig.5) with constant pressure. 4. conclusion we conclude that although shepard’s method represented by eqs.(3) and (4) is an easy approximating method for the measured data, it is extremely sensitive for the large and small distances among the data points. for data sets situated in a rectangular grid (as in table 1), spline methods are more accurate. symbols zi, j measured values in 2d fi measured values in ‘n’-dimension pi, j measured points in 2d pi measured points in ‘n’-dimension s approximating function in 2d u approximating function in ‘n’-dimension σ weight function in shepard’s method figure 6. boiling point dependence on glycerol vapour pressure as a function of concentration. figure 5. boiling point dependence on glycerol concentration as a function of vapour pressure. interpolation methods for predicting vapour pressure 43(2) pp. 67–71 (2015) doi: 10.1515/hjic-2015-0011 71 acknowledgement the research is supported by the european union and co-funded by the european social fund, “telemedicinefocused research activities in the field of mathematics, informatics and medical sciences”, project number: támop-4.2.2.a-11/1/konv-2012-0073. supporting information table s1 can be downloaded free of charge from math.uni-pannon.hu/~szalkai/hjic-16-table2-150110.xls. references [1] isahak, w.n.r.w.; ramli, z.a.c.; ismail, m.; jahim, j.m.; yarmo, m.a.: recovery and purification of crude glycerol from vegetable oil trans-esterification, sep. purif. rev., 2015, 44(3), 250–267 doi:10.1080/15422119.2013.851696 [2] ardi, m.s.; aroua, m.k.; hashim, n.a.: progress, prospect and challenges in glycerol purification process: a review, renewable sustainable ene. rev., 2015, 42, 1164–1173 doi: 10.1016/j.rser.2014.10.091 [3] hunsom, m.; autthanit, c.: adsorptive purification of crude glycerol by sewage sludge-derived activated carbon prepared by chemical activation with h3po4, k2co3 and koh, chem. eng. j., 2013, 229, 334–343 doi: 10.1016/j.cej.2013.05.120 [4] szalkai, i.; sebestyén, a.; kótai, l.; bódi, f.: comparison of interpolation methods for predicting the vapour pressure of aqueous glycerol solutions, proc. 42nd annual conf. canadian soc. chem. engng., toronto, canada, 1992, pp. 279– 280 math.uni-pannon.hu/~szalkai/szalkai-1992c-konftor.pdf [5] szalkai, i.; sebestyén, a.; kótai, l.; bódi, f.: comparison of interpolation methods for predicting the vapour pressure of aqueous glycerol solutions, preprint no. 036 (university of veszprém, veszprém, hungary) 1995 math.unipannon.hu/~szalkai/szalkai-1995preprint-glic.pdf [6] kiss b.: plants oil industry and household tables (mezőgazdasági kiadó, budapest, hungary) 1988 (in hungarian) [7] saburov, a.g.; vasilienec, i.m.; postolov, j.m.; klibov, n.p.: numerical formulae for thermodynamic properties of aqueous glycerol solutions, mashlo-khim. promusl., 1987, 21–22 (in russian) [8] djuric, m.; ranogajec, j.; marinkov-neducin, r.: predicting of floor tiles behaviour by using twodimensional spline interpolation, hung. j. ind. chem., 1992, 20(1), 39–44 [9] press, w.h.; flannery, b.p.; teukolsky, b.p.; vetterling, w.t.: numerical recipes the art of scientific computing (cambridge univ. press, cambridge, uk) 1985 [10] lénárd m.: on the two-dimensional spline interpolation of hermite-type, colloquia math. soc. j. bolyai, 1985, 49, 531–541 [11] lénárd m.: spline interpolation in two variables, studia sci. math. hung., 1985, 20, 145–154 [12] lénárd m.: on an n-dimensional quadratic spline approximation, j. approx. theory, 1992, 68(2), 113–135 doi: 10.1016/0021-9045(92)90088-6 [13] shepard d.: a two dimensional interpolation function for irregularly spaced data, proc. 23rd acm nat. conf., new york, ny, usa, 1968, pp. 517–524 doi: 10.1145/800186.810616 [14] gordon, w.j.; wixon j.a.: shepard’s method of "metric interpolation" to bivariate and multivariate interpolation, math. comp., 1978, 32(141), 253– 264 doi: 10.1090/s0025-5718-1978-0458027-6 [15] szalkai i. : scattered data interpolation via improved shepard’s method, preprint no. 76. (university of veszprém, veszprém, hungary) 1999 math.unipannon.hu/~szalkai/szalkai-1999preprint-shepard.pdf [16] allasia g.: a class of interpolating positive linear operators: theoretical and computational aspects, in approximation theory, wavelets and approximation, (ed.: singh s.p., kluwer publ., dordrecht, the netherlands) 1995, pp. 1–36 doi: 10.1007/978-94-015-8577-4 [17] della-vecchia, b.; szalkai i.: finding better weight functions for generalised shepard’s operator on infinite intervals, int. j. comp. math., 2011, 88(13), 2838–2851 doi: 10.1080/00207160.2011.559542 hungarian journal of industry and chemistry vol. 43(2) pp. 73–78 (2015) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2015-0012 comparison of decontamination standards le cong hao,1 mai dinh thuy,2 do trung hieu,3 and zoltán sas4* 1 nuclear techniques laboratory, university of science, vnu-hcmc, ho chi minh city, vietnam 2 school of nuclear engineering and environmental physics, hanoi university of science and technology, ho chi minh city, vietnam 3 faculty of chemistry, university of science, vnu, ho chi minh city, vietnam 4 institute of radiochemistry and radioecology, university of pannonia, veszprém, h-8201, hungary the quality of materials used in nuclear-related facilities is critical, especially the ease of decontamination of different paints and coatings. standards describe different testing methods for classification. nevertheless, compliance with these standards cannot be carried out negligibly from a safety point of view. in this study, a withdrawn hungarian (msz-05 22.7662-83), an international iso (iso 8690:1988), and russian (gost 2514682) decontamination standard were compared. four different paints were tested as part of this survey. the ease of decontamination varied mainly from poor to fair levels in the case of the hungarian standard, while the iso standard exhibited very good level. in the case of the russian standard, only a theoretical comparison was carried out. based on the results, it was found that a special epoxy-based coating can be recommended for isotope laboratories due to being the best material from an ease of decontamination point of view. from comparison of the standards considered here, it was found that the application of iso standard is significantly faster and simpler than the withdrawn hungarian standard. however, in the case of the hungarian standard the data described the ease of decontamination in more details. the use of water or some other cleaning agents can be effective to remove 137cs and 60co contamination right after early identification. isotope 137cs and 60co contamination of a surface can be cleaned quickly and effectively using distilled water for the 137cs isotope removal from the surfaces being several times easier than that of 60co. keywords: surface contamination, decontamination value, iso standard 8690:1988, hungarian standard msz-05 22.7662-83, russian standard gost 25146-82, 60co isotope, 137cs isotope 1. introduction contamination of surfaces with radionuclides can lead to human exposure depending on the type, extent of contamination, and activity of the contaminating isotope. in order to reduce the risk, quick and effective decontamination of the involved area is required. the contamination of different surfaces are common in workplaces that deal with radionuclides e.g. isotope laboratories, nuclear industry related activities, etc.[1,2]. contamination can occur in various ways, but chemical and physical adsorption processes are the most important ones. in the case of chemical adsorption, ions exit from the hydration shell and bind directly to the surface, while in the case of physical adsorption the ions binds to the surface together with the hydration shell. furthermore, the contaminating isotopes can infiltrate into the pores of the surface material via diffusion. to avoid the internal contamination of porous materials special paints and coatings should be applied which inhibits the diffusion of contaminating isotopes into *correspondence: ilozas@almos.uni-pannon.hu pores [3]. the decontamination capacity of surfaces greatly depends on the form of contamination media and the chemical and physical parameters of surfaces. the main influencing parameters that can affect the ease of decontamination are i) surface porosity, ii) surface roughness, iii) surface wettability, iv) chemical reactions between the radionuclide and the surface, and v) adsorption processes on the outer part of the electric double layer of the solid/liquid interface. the efficiency of decontamination expressed by the decontamination factor (df) [3] can be calculated according to the following equation: !" = !"#$%$#& !" !"#$%&' !"#$% !"#$%&'#%$'"# !"#$%$#& !" !"#$%&' !"#$% !"#$%&'()%'&)$% . (1) however, the decontamination efficiency is greatly parameter dependent as mentioned above. standardised protocols are necessary to classify certain paints and coatings from a decontamination point of view, which is informative about their utilisation in isotope laboratories and other relevant workplaces as well. in this study, the comparison of different decontamination standards is presented that includes a hungarian (withdrawn in 2003) standard msz-05 22.7662-83 “testing of painted coatings in laboratory. hao, thuy, hieu, and sas hungarian journal of industry and chemistry 74 determination for ease of decontamination”[3], an international iso 8690:1988 standard “decontamination of radioactively contaminated surfaces – method for testing and assessing the ease of decontamination” [4], and a russian interstate standard gost 25146-82 “radiochemical production and atomic power plant materials. method for determination of decontamination ratio” [5]. 2. experimental 2.1. sample preparation in order to compare the three selected standards, four different types of coatings were used for providing various conditions during the survey. the relevant properties of the applied coatings are shown in table 1. the selected coatings were painted on 4×4 cm aluminium test disks (fig.1) and stored for 24 hours to dry completely. the selected standards require 5 parallel measurements for each type of coating. 2.2. comparison of contamination processes in the case of the russian gost 25146—82 standard, the investigated surfaces are contaminated by natural or artificial β-radiating nuclides. the activity of the samples was distributed on the surface to avoid selfabsorption. the gost standard describes in great detail the measurement conditions and apparatus, which should be enforced to ensure reliable results. the same standard allows for using any types of contamination solution, which provides numerous ways for measuring the ease of decontamination under a wide variety of conditions, while in the case of the iso and msz standards specific conditions have to be maintained. in the case of the withdrawn hungarian msz-05 22.766283 and iso 8690:1988 standards the recommended contaminating isotopes are 137cs and 60co (carrier concentration 10-5 mol dm-3 and ph value of 4) which were prepared in a laboratory before testing. to determine the count rate of the contaminating isotopes a γ-spectrometer was used with a high purity germanium (hpge) semiconductor detector ortec gmx40-76, with 40% efficiency. to obtain counts from 137cs, the 661.6 kev γ-line was measured, while in the case of 60co, the 1173.4 and 1332.5 kev lines were measured. the spectra were recorded by an ortec dspec lf 8196 mca instrument. before contamination the background spectra were recorded, which were extracted from all contaminated and decontaminated spectra. 2.3. hungarian standard msz-05 22.7662-83 for the hungarian standard, the decontamination was investigated in two differentiated ways to obtain relevant information related to physical and chemical links adsorption separately. to investigate the physical adsorption, 0.1 cm3 of contamination solution was dropped onto test samples and dried under an infrared lamp at 40 °c. after drying, the count rates were measured using a hpge detector for 1000 s to obtain the specific count rate of the contamination solution. to investigate chemical origin contamination, a special socketed cylinder-shaped contamination block (fig.2) was used with 0.565 cm3 of the contamination solution, which provides a 10 cm2 contact surface between the solution and test specimens. the contamination block was put onto coated test specimens and filled with the contamination solution for 2 hours. after that period, the contamination solution was removed from the contamination block and the test specimens were gently flushed using ultrapure water. 2.4. iso standard 8690:1988 for the iso standard, only chemical adsorption was investigated. the specific count rate of the contamination solution was determined before contamination of the test specimens. a micropipette was used to put 0.1 cm3 of contamination solution onto glass sheets. the test specimens were inserted between the upper and lower parts of the contamination block for contamination, which was prepared according to the iso standard (fig.3). before filling the upper part with 1 cm3 of contamination solution both parts were fastened together tightly to avoid leakage. after filling the holder, disks were covered to avoid evaporation of the contamination solution for 2 hours. after this contamination process, the contamination solution was pumped out of the holder, and the test specimens inserted into the decontamination unit. table 1. properties of the coatings investigated. id coating type paint colour roughness dc base-modified silicone resin spray grey (fig.1a) slight cv alkyd resin spray painted dark grey (fig.1b) great km enamel paint brush painted brown (fig.1c) glossy nr epoxy resin brush painted beige (fig.1d) semi glossy figure 1. applied coatings on test disks. comparison of decontamination standards 43(2) pp. 73–78 (2015) doi: 10.1515/hjic-2015-0012 75 2.5. decontamination process in the case of the hungarian standard, an immersionbased decontamination method was used over three steps. firstly, upon the completion of count rate measurements, the contaminated surfaces were immersed in ultrapure water for 10 s then pulled out and tilted to allow the residual fluid to trickle down before finally being immersed again in the decontamination solution. the immersion was repeated 15 times (total immersion time: 150 s). thereafter, the test specimens were dried under an infrared lamp and the count rate originating from the residual contaminating isotopes recorded using a γ-ray spectrometer. in the second step, a special decontamination solution was prepared according to the method described as a standard in order to get information about the decontamination efficiency of detergents. the decontamination solution was composed of polyethylene glycol nonylphenyl ether (5 g dm-3), citric acid (4 g cm-3), and edta (4 g cm-3). the test specimens were added to the decontamination cocktail and decontaminated using the same immersion/pull out technique described in the first step. the count rate was measured again after drying. for the final step 1 m hcl was used to get information about more aggressive decontamination fluids, which can cause structural changes in the case of the investigated coating but can also be beneficial from a decontamination point of view to remove isotopes from pores also. the decontamination and the measurement process were repeated for each specimen after the acidic decontamination step. in the case of the iso standard, the test specimens were placed immediately into a special cage-stirrer apparatus (described in the standard) after the contamination process. the apparatus was equipped with a 100 rpm motor. the cage was immersed into a glass beaker filled with ultrapure water and rotated for 150 s. thereafter, the specimens were dried and measured using γ-ray spectrometry to obtain residual count rates. the details of the msz-05 22.7662-83 and iso 8690:1988 decontamination methods are summarised in table 2. 2.6. calculation of df values and classification of specimens the decontamination factors were calculated from recorded spectra. the peak areas corresponding to the presence of 137cs and 60co isotopes were corrected by background measurements. the specific count rates (count-per-seconds cm-3) were calculated for all samples. the decontamination factors of each step for all samples were calculated using the eq.(1). 3. results and discussion 3.1. decontamination factors from the hungarian standard msz-05 22.7662-83 the obtained decontamination factor of each treated surface on the basis of the hungarian standard is shown in fig.4, which compares the physical adsorption between the contaminating isotopes and surfaces. the decontamination factors varied from 2.0 to 196.3 for 137cs and from 1.0 to 30.1 for 60co. the largest variation between the two isotopes was observed for the nr sample, which is an epoxy-based laboratory coating. most of the decontaminated isotopes were removed independently from applied decontamination solutions, while the decontamination of cv-coated (strongly rough alkyd resin) samples seemed unaffected by treatment using any of the solutions. the decontamination of other surface materials was less figure 2. scheme of the contamination block according to the withdrawn hungarian msz-05 22.7662-8 standard. figure 3. scheme of the contamination block according to the iso 8690:1988 standard. table 2. results of decontamination experiments performed in this study. standards steps method agents msz-05 22.7662-83 3 immersed for 150 s then pulled out ultrapure water decontamination solution 1 m hcl msz-05 22.7662-83 adsorption iso 8690:1988 1 immersed stirring cage in water for 150 s ultrapure water hao, thuy, hieu, and sas hungarian journal of industry and chemistry 76 effective than that of the nrs. in the case of km (glossy enamel paint), the decontamination factor was fair for both isotopes. the results for all materials suggest that decontamination efficiency may be independent of the number of attempts, but dependent on the characteristics of the contamination and features of the surface and contaminant media. in all cases, it seemed that the hcl solution improved the efficiency of decontamination for both 137cs and 60co. nevertheless, it is notable that distilled water is also a good nominated agent for the decontamination of less specific radioactive cleaning agents. table 3 presents the assessment of ease of decontamination using 0.1 cm3 of contamination solution. the ease of decontamination was found to vary from poor to fair for dc, km and cv. an acceptable level of efficiency was found for nr. chemical adsorption was investigated by another decontamination experiment using 0.565 cm3 of contamination solution. similar results (fig.5) were observed when compared with the drying method (fig.4). the decontamination factor using distilled water was found to be approximately the same as for the applied cocktail solution. similar phenomena were reported by ruhman et al. [1]. the reason for unacceptable efficiencies in the case of samples with cv coatings can be explained by the roughness of the surface, which allows contamination of inner pores due to diffusion, hence the surface becomes very difficult to clean. surface degradation due to the porosity of the material or by some unknown chemical modification might be another reason. a recommended area for further study is the ease of decontamination in the light of surface changes after years of use [1]. the ease of decontamination was found to vary from poor for cv to fair for dc and km as shown in table 4. an acceptable efficacy was found for nr. the ease of decontamination varied from excellent for km to good for dc and nr. a poor/bad level was found for cv. 3.2. decontamination factors from the iso standard 8690:1988 the decontamination factors using the iso standard method are illustrated in fig.6. the values clearly show that in the case of epoxy-based nr resin the ease of decontamination was efficient. in the case of the km coating, the efficiency was the highest. the worst decontamination capability was found for cv-coated samples. the results using the iso standard clearly show that the ease of decontamination greatly depends on the types of coating. furthermore, the 137cs isotope can be removed more easily than the 60co isotope, which can be explained by the different physical/chemical properties of investigated isotopes. the obtained decontamination factors for each isotope are summarised in table 5. depending on available conditions, the task and specific conditions, the hungarian standard method and the iso standard will be chosen, while the russian standard was studied only for the sake of comparison. it is important to mention that simulation exercises, for both major and minor contamination events, may be essential for coordination and execution of a response [6–12]. table 3. assessment of ease of decontamination using 0.1 cm3 of contaminated solution. samples isotopes df degree of ease dc 137cs 22.5 fair 60co 1.5 poor/bad km 137cs 13.4 fair 60co 12.6 fair cv 137cs 4.0 poor/bad 60co 2.7 poor/bad nr 137cs 196.3 good 60co 30.1 fair figure 5. decontamination factors for msz-05 22.7662-83 using the adsorption method (table 2). figure 4. decontamination factors for msz-05 22.7662-83 (table 2) after drying. comparison of decontamination standards 43(2) pp. 73–78 (2015) doi: 10.1515/hjic-2015-0012 77 3.3. comparison of df values form the iso and hungarian standards although a direct comparison of the results between the hungarian and the iso standards has limited usefulness and relevance due to fundamental differences in the methods used, we found the same experimental phenomena in terms of ease of decontamination. as expected, similar results were observed and measured for higher decontamination factors in all cases. the most different finding, in the case of km was that the most effective method observed was by treatment using distilled water. most of the 137cs contamination was removed more effectively than 60co contamination for dc, km, and nr surfaces. in comparison with the hungarian standard method, the iso standard was used for testing and assessing the ease of decontamination only for chemically adsorbed contaminating isotopes. the experiment was then conducted using 20 contaminated samples of the same type, distilled water as a cleaning agent, and using different decontamination methods. the results are shown in figs.6-7 and table 5. these results are in contrast to our previous observations using the hungarian standard method and the low efficiency for cv sample. the differences can be explained by some unknown chemical bond formation between the surface of the material and the studied isotopes. this research confirms that the use of deionised water or cleaning agents described in standards may be a sufficient means of removing wet 137cs and 60co contamination when identified early. 4. conclusion the aim of this study was to identify some of the best surfaces, which would meet alara and goodmanufacturing-practice requirements to set up protocols to manage contamination in laboratories. the russian standard can provide very specific information about the ease of decontamination for a wide variety of contamination conditions. the fixed measurement parameters in the case of the iso 8690:1988 and hungarian msz-05 22.7662-83 standards provide an opportunity to compare paints and coatings and classify them. using the hungarian and iso standards, the 137cs and 60co contamination on a surface can be cleaned quickly and effectively using distilled water. based on the results obtained after the decontamination procedure for the hungarian and iso standards, nr can be applied to the surface, the walls of the laboratory, and where figure 6. decontamination factors for the iso standard 8690:1988 (table 2). table 5. assessment of ease of decontamination for the iso standard 8690:1988. sample isotopes df degree of ease dc 137cs 684 good 60co 315 good km 137cs 4928 excellent 60co 3444 excellent cv 137cs 13 poor/bad 60co 30 poor/bad nr 137cs 934 excellent 60co 3822 good figure 7. decontamination factors for the iso 8690:1988 (e) and hungarian (adsorption-type contamination) standards. table 4. assessment of ease of decontamination in the case of the adsorption method. samples isotopes df degree of ease dc 137cs 370 fair 60co 158 fair km 137cs 411 fair 60co 257 fair cv 137cs 16 poor/bad 60co 17 poor/bad nr 137cs 6550 excellent 60co 1859 good hao, thuy, hieu, and sas hungarian journal of industry and chemistry 78 radiation is susceptible in nuclear power plants. in the worst case scenario, when there is an accident involving radioactive contamination, the ability of cleansing the decontamination of surfaces covered by nr will be the most efficient. according to our findings, we were able to select the best materials for the floor of our laboratory. acknowledgement the authors thank the ministry of education, vietnam for funding this research, and the institute of radiochemistry and radioecology, university of pannonia for providing experimental conditions. references [1] ruhman, n.; vesper, g.; martin c.: the effectiveness of decontamination products in the nuclear medicine department, j. nucl. med. technol., 2010, 38(4), 191–194 doi: 10.2967/jnmt.110.076919 [2] leonardi, n.m.; tesán, f.c.; zubillaga, m.b.; salgueiro, m.j.: radioactivity decontamination of materials commonly used as surfaces in generalpurpose radioisotope laboratories, j. nucl. med. technol., 2014, 42(4), 292–295 doi: 10.2967/jnmt.114.144303 [3] hungarian standard msz-05 22.7662-83: testing of painted coatings in laboratory. determination for ease of decontamination (hungarian patent office, budapest, 1983 withdrawn in 2003) [4] international iso standard 8690:1988: decontamination of radioactively contaminated surfaces. method for testing and assessing the ease of decontamination (international organization of standardization, switzerland, 1988) www.iso.org/iso/ catalogue_detail.htm?csnumber=16094 [5] russian interstate standard gost 25146-82: radiochemical production and atomic power plant materials. method for determination of decontamination ratio (technormativ llc, 1983 official translation in 2015) http://runorm.com/product/view/2/10771 [6] schleipman, a.r.; gerbaudo, v.h.; castronovo, f.p.: radiation disaster response: preparation and simulation experience at an academic medical center, j. nucl. med. technol., 2004, 32(1), 22–27 pubmedd: 14990671; tech.snmjournals.org/content/ 32/1/22 [7] gurau, d.; deju r.: the use of chemical gel for decontamination during decommissioning of nuclear facilities, rad. phys. chem., 2015, 106, 371–375 doi: 10.1016/j.radphyschem.2014. 08.022 [8] varga, k.; baradlai, p.; hirschberg, g.; nemeth, z.; oravetz, d.; schunk, j.; tilky, p.: corrosion behaviour of stainless steel surfaces formed upon chemical decontamination, electrochim. acta, 2001, 46(24-25), 3783–3790 doi: 10.1016/s00134686(01)00665-x [9] anthofer, a.; lippmann, w.; hurtado, a.: laser decontamination of epoxy painted concrete surfaces in nuclear plants, optics laser technol., 2014, 57, 119–128 doi 10.1016/j.optlastec. 2013.09.034 [10] endo, m.; kakizaki, t.: washing operation of a road surface washing mechanism for decontaminating radioactive substances, robomech j., 2014, 1, 13 doi 10.1186/s40648-014-0013-8 [11] iaea-tecdoc-102 2: new methods and techniques for decontamination in maintenance or decommissioning operations, results of a coordinated research programme 1994–1998 (international atomic energy agency, vienna) 1998 issn 1011-4289; www-pub.iaea.org/mtcd/ publications/pdf/te_1022_web.pdf [12] iaea-tecdoc-24 8: decontamination of operational nuclear power plants (international atomic energy agency, vienna) 1981 wwwpub.iaea.org/mtcd/publications/pdf/te_248_web.pdf hungarian journal of industry and chemistry vol. 43(2) pp. 79–83 (2015) hjic.mk.uni-pannon.hu doi: 10.1515//hjic-2015-0013 a study of the adsorption characteristics of cobalt and caesium from a solution by using vietnamese bentonite le phuoc cuong,1 pham hoang giang,2 bui dang hanh,3 and gergő bátor4* 1 the university of danang-university of science and technology, danang, vietnam 2 vnu university of science, hanoi, vietnam 3 vietnam atomic energy institute (vinatom), hanoi, vietnam 4 institute of radiochemistry and radioecology, university of pannonia, veszprém, h-8201, hungary the radioactive waste produced from the construction of a nuclear power plant is a controversial topic. the resulting radioactive waste contains 60co and 137cs isotopes that are the most difficult to remove. bentonite is widely used as an adsorbent for heavy metals. an important factor is the safe operation of waste management at a nuclear power plant to be built in vietnam. therefore, a method of degrading complexes of radionuclides and the adsorption of radionuclides onto vietnamese bentonite was implemented in this study. in current literature, uv radiation and heating with oxidising substances are used in general for degrading complexes of radionuclides. the experimental results for the adsorption of co(ii) and cs+ onto vnb suggest that vnb can be used in the future for large-scale liquid waste treatment due to its low cost, high efficiency, and environmentally friendliness. keywords: radionuclides; vietnamese bentonite; adsorption; uv radiation; hydrogen peroxide 1. introduction during operation, a nuclear power plant (npp) releases a large quantity of liquid waste containing radionuclides. the sources of liquid waste include contaminated boric acid solutions, liquid that has leaked from the primary circuit, a solution used to decontaminate the equipment of the primary circuit, and other waste sources. radionuclides that exist in liquid waste include 137cs, 60co, 59fe, 51cr, 54mn, etc. [1–4]. in all types of nuclear reactors, the solutions that are used to decontaminate equipment containing chemicals are for example, alkalis, kmno4, edta, etc. [4] in order to oxidise or to form complexes with radionuclides. these complexes are highly soluble in reactor solutions. liquid waste containing radionuclides has to be stored for a certain period of time to decay. radionuclides with short half-lives decay during this storage time. the longer-lasting radionuclides such as 60co and 137cs are still present in concentrations above the discharge limit of 1 kbq dm-3. thus, they are not allowed to be discharged into the environment even after several years of storage [5–10]. one of the most effective methods for the treatment of radioactive waste is on the basis of ion exchange and adsorption processes using inorganic ion exchangers. the desirable characteristics of high *correspondence: kt@almos.uni-pannon.hu exchange capacity and favourable selectivity for some radioisotopes made certain zeolites useful in the treatment of radioactive waste. natural zeolites considered for radioactive waste treatment include mordenite, erionite, chabazite, clinoptilolite, and bentonite. among these, bentonite has received much attention due to its widespread usage, large surface area, and high selectivity for some radiotoxic metals [4, 11]. bentonite consists predominantly of the mineral montmorillonite, an aluminium hydrosilicate. its crystal structure shows distinct layers forming a lattice (fig.1). the term “bentonite” was first used by knight in 1889 following the discovery of highly colloidal plastic clay near fort benton in the cretaceous bed of wyoming. bentonite is a naturally occurring cationic clay, which can be processed or modified to tailor its properties, so it is suitable for various applications and uses. in its pure form or with some chemical additives or modifications, bentonite can be used as a rotary mud, an anticaking agent for certain granular fertilisers, a binding agent in the agglomeration of cattle feed, in pesticides or mineral oil, for filling, oil deodrising, palletising or bleaching, and in civil construction, foundries, and the alkylation of phenols [4, 6–8]. the aim of this study was the identification of degrading and mineralising complex compounds of co(ii) and cs+ by using uv radiation and heating with oxidation substances. in addition, we also determined the adsorption efficiency of these radioactive isotopes onto vnb. phuoc cuong, hoang giang, dang hanh, and bátor hungarian journal of industry and chemistry 80 2. experimental 2.1. objectives in order to extract 60co and 137cs from radioactive liquid waste, a combined treatment method was used. this method includes two stages. in the first stage, the edta complexed radionuclides were degraded and mineralised by uv radiation and heating with oxidising substances and then in the second stage radionuclides ions were removed by adsorption using vnb. in order to prepare the model solutions for this study, the activity concentrations of the radioactive isotopes of 137cs and 60co in a typical liquid radioactive waste sample were determined by standard γ spectrometry using a gamma műszaki zrt scintillation (nai) detector. table 1 shows measurements taken from the liquid waste radioactive sample. 2.2. research methodology the concentrations of radioactive elements were determined by using an ice 3000 atomic absorption spectrometer (aas, thermo scientific, usa) with an air-c2h2 flame at a flow rate of 0.9 dm3 min-1. the chemicals used as analytical standards were all reagent grade or better. ethylenediaminetetraacetic acid (edta), h3bo3, naoh, h2o2, coso4, and cscl were purchased from merck (germany). all glassware and polyethylene bottles were thoroughly washed and then rinsed using ultrapure water before use. 2.2.1. degradation of complex compounds by heating with an oxidant in the heated system (fig.2), the degradation of complex edta, coso4, and h3bo3 was investigated under two sets of conditions at 60 and 70 ºc both with and without h2o2 in 30 mg dm-3 concentration. each experiment lasted 1 hr for three solutions with various concentrations of coso4 (10, 20, and 40 mg dm-3). aliqots of samples were taken at regular intervals, such as 10, 30, and 60 min. these solutions were centrifuged and stirred with vnb for 1 hr. after that, the solution samples, with and without vnb, were analysed to determine the co(ii) concentration. 2.2.2. degradation of complexes by uv radiation and oxidizers aspects of photocatalytic degradation of complexes with edta, coso4, and h3bo3 were investigated. degradation efficiencies were studied in detail using a uv radiation system within the range of 280–315 nm and at 0.15 w m-2 (fig.3) under the following conditions: 1. only with uv light; 2. uv and o2 with flow rate of 70 dm3 h-1); 3. uv, o2, and h2o2 in 3 mg dm-3 concentration; 4. uv, o2, and tio2; 5. uv, o2, tio2 and h2o2. figure 1. structure of bentonite [6]. figure 2. the experimental set-up of the heating system. table 1. typical radioactive liquid waste sample (3/2/2015 measurements). radionuclides activity concentration, bq dm-3 ph dry matter, g dm-3 boric acid, g dm-3 edta, g dm-3 60co 1.23×104 12.5 85.23 120 4 137cs 2.51×105 figure 3. the experimental set-up for uv radation system. adsorption characteristics of cobalt and caesium 43(2) pp. 79–83 (2015) doi: 10.1515/hjic-2015-0013 81 each experiment lasted for 2 hr for the three solutions using various concentrations of coso4 (10, 20, and 40 mg dm-3). samples were taken at regular intervals of 10, 30, 60, and 120 min. the solutions were centrifuged and stirred with vnb for 1 hr. after that, the solution samples, with and without vnb, were analysed to determine the co(ii) concentration. 2.2.3. adsorption of radioactive elements onto vnb experiments on the adsorption of co(ii) and cs+ onto bentonite were performed in batches to determine their adsorption time and equilibrium isotherms. a volume of 30 cm3 of radioactive solution at various initial concentrations for coso4 (10, 20, and 40 mg dm-3); and cscl (60 and 120 mg dm-3) was stirred with bentonite for 1 hr within a ph range of 12 to 13, depending on the initial concentrations of edta and h3bo3 in the model solution. samples were taken at regular intervals, centrifuged, and the concentration of co(ii) and cs+ ions were measured. 2.2.4. adsorption isotherms to evaluate the adsorption ability of ions onto bentonite, the langmuir and freundlich isotherm models were employed. on the basis of experimental data, the typical parameters of the adsorption process were determined by using the linear regression method. the langmuir equation is given by: qe = qmkace/(1+kace) . (1) its linear form is ce/qe = (1/qm)ce + 1/(kaqm) (2) where qe is the amount of ions adsorbed (mg g-1) at equilibrium; ce is the equilibrium concentration (mg dm-3); qm is the maximum adsorption capacity (mg g-1); and ka is the adsorption equilibrium constant. a plot of ce/qe against ce expected to give a straight line with a gradient of 1/qm and an intercept of 1/(kaqm). the freundlich equation is given by: qe = kfce 1/n . (3) its linear form is: ln qe = ln kf + (1/n) ln ce (4) where kf and n are constants. 3. results and discussion 3.1. efficiency of the adsorption of radioactive elements onto vnb for the estimation of the adsorption ability of co(ii) onto vnb, 0.1 g of vnb was stirred with 50 cm3 of co(ii) solution (8–200 mg dm-3). after equilibrium was achieved, the residual concentration of co(ii) was measured using an ice 3000 aas (atomic absorption spectrometer). the effect of initial concentrations on the adsorption of co(ii) by vnb can be seen in fig.4. when the initial co(ii) concentration was increased from 8 to 200 mg dm-3 the absolute amount of co(ii) adsorbed per unit weight of vnb increased from 2.31 mg g-1 (96.5%) to 6.95 mg g-1 (11.8%). however, the percentage adsorption decreased with increasing initial concentration. the results showed that at higher initial concentrations, the number of available adsorption sites decreased and hence, the removal of co(ii) ions depends upon the initial concentration. to determine the optimal reaction time in order to achieve an equilibrium state, flasks containing a mix of solutions (cscl, naoh, h3bo3) with vnb were stirred for different periods of time (10, 30, 60, and 120 min). the concentrations of cs+ ions in the solutions were measured using an atomic absorption spectrometer. the reaction time required to achieve an equilibrium state was defined between the start of stirring and when the analyte concentration remained constant. fig.5 describes the cs+ content in the solution after different periods of time. according to fig.5, a period of 100 min can be considered optimal reaction time to achieve equilibrium. this optimal time was implemented for the experiments on the adsorption of cs+ ions onto vnb. 3.2. study of the kinetics of the adsorption of radionuclides onto bentonite 3.2.1. adsorption isotherms of co(ii) fig.6 shows the adsorption isotherms of co(ii) onto vnb, which can be described by the langmuir model with a correlation coefficient (r2) of 0.9791 and a maximum adsorption capacity of 8.15 mg g-1. the equilibrium data also corresponded to the freundlich isotherm with a correlation coefficient (r2) of 0.9640. figure 4. the effect of the initial concentration on the adsorption of co(ii) onto vnb. figure 5. cs+ content in the solution after different periods of time. phuoc cuong, hoang giang, dang hanh, and bátor hungarian journal of industry and chemistry 82 regarding the four experiments with heating, only exp. 4 with reaction at 90 ºc and 30 mg dm-3 of h2o2 could reduce the concentration of co(ii) otherwise the co(ii) concentration remained unchanged or showed no significant change. fig.7 shows that the concentration of co(ii) decreased as time increased within 30 minutes, but after that, it practically remained constant. moreover, initial concentrations also affected the efficiency of removing co(ii) with initial concentrations of 10, 20, and 40 mg dm-3. the corresponding efficiency values for removing co(ii) were 22.2%, 31.5% and 61.7%, respectively for samples that were not stirred with vnb, and 22.7%, 43.3%, and 67.7% for samples that were stirred with vnb. thus, the experimental adsorption capacity of vnb indicate that it can adsorb co(ii) at the highest value of adsorption capacity of 8.15 mg g-1, but in the four experiments with heating, the efficiency of removing co(ii) with vnb did not show significant differences without vnb. previous research [2, 4, 6] showed that bentonite exhibits good adsorption capacities toward organic matter. however, these results showed that the adsorption ability of edta onto bentonite is low, and co(ii) still remains complexed with edta. it is removed only when edta is completely degraded. with regard to the uv system, the results from all experiments show that the outcome of this method was not affected by decreasing co(ii) concentration. rekab et al. showed [2] that the efficiencies of uv/tio2 and uv/h2o2 treatments are 67% and 42%, respectively at low ph. on the other hand, the degradation efficiency was greater under acidic ph conditions, likely due to the dissociation of h2o2 into ho2 at alkaline ph, and the photolytic generation of oh• radicals is therefore hindered. the amine functional groups in edta is dominantly converted to ammonia, which forms a complex compound with co(ii) [2]. 3.3. adsorption isotherms of cs fig.8 shows that the adsorption isotherm of cs+ onto vnb could be described by both the langmuir and freundlich models with correlation coefficients (r2) of 0.98 for both respectively. on the basis of both of these models, the highest value of adsorption capacity was 1.15 mg g-1 showing that vnb can adsorb cs. 4. conclusion vnb was tested as an adsorbent material for the removal of cobalt and caesium ions from sulphate and chloride waste solutions. the adsorption of co(ii) ions figure 6. adsorption isotherms of co(ii) onto vnb. figure 7. degradation of co(ii) over different time periods (ex. 4) using solution 1: 40 mg dm-3 co(ii); solution 2: 20 mg dm-3 co(ii); and solution 3: 10 mg dm-3 co(ii). figure 8. adsorption isotherms of cs+ onto vnb. adsorption characteristics of cobalt and caesium 43(2) pp. 79–83 (2015) doi: 10.1515/hjic-2015-0013 83 onto vnb followed the pseudo-second order rate model. the adsorption isotherm of co(ii) was described by the langmuir and freundlich models. these show that radioactive isotopes can be highly efficiently adsorbed onto vnb. the adsorption isotherm of cs+ corresponded to both the freundlich and langmuir models with high correlation coefficients. in the presence of edta in radioactive waste solution, radioactive isotopes could not be adsorbed onto vnb due to forming stronger complexes with edta therefore, in this study two pre-treatment systems were implemented to remove edta from the liquid waste. heating achieves an efficiency of 67% while the uv radiation did not exhibit satisfactory improvement of treatment efficiency. we are planntng to scale up the uv system to include the optimisation of ph values and the effect of ammonium converted from edta in order to apply these findings to radioactive solution waste on a large scale. acknowledgement the authors would like to thank the ministry of education and training, vietnam for funding this research, and the institute of radiochemistry and radioecology at the university of pannonia for providing the experimental conditions. references [1] manohar, d.; noeline, b.; anirudhan, t.: adsorption performance of al-pillared bentonite clay for the removal of cobalt(ii) from aqueous phase, applied clay science, 2006, 31(3-4), 194– 206 doi: 10.1016/j.clay.2005.08.008 [2] rekab, k.; lepeytre, c.; dunand, m.: h2o2 and/or photocatalysis under uv-c irradiation for the removal of edta, a chelating agent present in nuclear waste waters, appl. cat. a: general, 2014, 488(11), 103–110 doi: 10.1016/j.apcata.2014.09.036 [3] omar, h.; arida, h.; daifullah, a.: adsorption of 60co radionuclides from aqueous solution by raw and modified bentonite, appl. clay sci., 2009, 44(1), 21–26 doi: 10.1016/j.clay.2008.12.013 [4] egamediev, s.kh.; nurbaeva, d.a.; tashtemirova, n.g.: modified bentonite as adsorbents for radionuclides: adsorption of carrier-free radiocobalt-57 on acid modified and calcined bentonite, proc. int. conf. “nuclear science and its application”, samarkand, uzbekistan, september 25-28, 2012, pp. 345–346 inis: rn:44129011 [5] iaea: modified combined methods for liquid radioactive waste treatment, final report (int. atomic energy agency, tecdoc-1336) 1997– 2001 issn: 1011–4289 [6] dale ortego, j.; kowalska, m.; cocke, d.: interactions of montmorillonite with organic compounds adsorptive and catalytic properties, chemosphere, 1991, 22(8), 769–798 doi: 10.1016/0045-6535(91)90052-f [7] milyuin, v.v.; kononenko, o.a.: sorption of caesium on finely dispersed composite ferrocyanide sorbents, radiochem., 2010, 52(3), 281–283 doi: 10.1134/s1066362210030100 [8] tofalvi, r.; sepsey, a.; horvath, k.; hajos, p.: environmental significance and identification of metal-chelate complexes using ion chromatography, hung. j. ind. chem., 2011, 39(1), 95–99 [9] frerich, j.k., flugge, u.: high performance catalytic tubular membrane reactors owing to forced convective flow operation, hung. j. ind. chem., 2005, 33(1–2), 31–42 [10] varga, k.; hirschberg, g.: accumulation of radioactive corrosion products on steel surface of vver-type nuclear reactors. ii. 60co, j. nucl. mater., 2001, 298(3), 231–238 doi: 10.1016/s00223115(01)00658-4 [11] kolics, a.; varga, k.: study of cobalt sorption on polyethylene, j. colloid interface sci., 1994, 168(2), 451–457 doi: 10.1006/jcis.1994.1441 hungarian journal of industry and chemistry vol. 43(2) pp. 85–89 (2015) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2015-0014 application of ionic liquids in the utilization of the agricultural wastes: towards the one-step pre-treatment and cellulose hydrolysis gábor megyeri,1 nándor nemestóthy,1 milan polakovic,2 katalin bélafi-bakó,1 lászló gubicza1,* 1 membrane technology and energetics, research institute of bioengineering, faculty of engineering, university of pannonia, egyetem u. 10., veszprém, 8200, hungary 2 department of chemical and biochemical engineering, institute of chemical and environmental engineering, faculty of chemical and food technology, slovak university of technology, radlinského 9., bratislava, 81237, slovakia cheap, renewable lignocellulosic materials are relevant to the future of biofuel production. wood and agricultural wastes (e.g. straw, corn stover) provide a raw material source that cannot be used for human consumption, thus biofuels from such sources do not threaten the food supply. the aim of the work was to carry out the pre-treatment and hydrolysis of lignocellulosic material in the same ionic liquid solvent (1-n-butyl-3methyl-imidazolium-chloride, [bmim]cl), using ground wheat straw and a mixture of corn (zea mays) leaf and stover, as substrates. our measurements show that it is possible to achieve an acceptable glucose content from the cellulose by applying cellic® ctec2 and cellic® htec2 enzyme complexes. keywords: ionic liquid, enzyme, hydrolysis, glucose, agricultural waste, lignocellulose 1. introduction nowadays, lignocellulosic plant biomass is considered as a renewable and cheap natural source of energy for second-generation alcohol production and a source of other platform compounds [1]. the main components of plant biomass are cellulose, hemicellulose, and lignin, which form a quite complex molecular structure [2]. among these substances, the glucose content of cellulose is desirable, which can be obtained in an enzymatic hydrolysis process. however, it is a difficult process, since cellulose is barely soluble in water [3] and thus various pre-treatment methods are required. physical, chemical, physic-chemical, and biological pretreatments can be used [4], such as steam explosion [5], dilute and concentrated acids [6], etc. these techniques may liberate certain inhibitory compounds that are not desirable, because they can significantly hinder enzymatic hydrolysis. some ionic liquids, on the other hand, are able to dissolve cellulose selectively making it accessible to the enzymes while unwanted components are not formed. ionic liquids are salts with low melting points [7, 8]. they are considered as green solvents [9] due to their negligible surface tension. a large number of anions and cations are available in countless variations for forming ionic liquids [10]. the asymmetric organic *correspondence: gubiczal@almos.uni-pannon.hu cation causes the low melting point, because it reduces the lattice energy in 1-alkyl-3-methyl-imidazolium salts [11]. according to literature examples [12, 13], the ionic liquid (il) formed from 1-butyl-3-methyl-imidazolium chloride salt ([bmim]cl) was used to dissolve cellulose. this is the most effective ionic liquid in cellulose pretreatment, but some have found that it could cause the deactivation of the enzymes. hydrolysis cellulase enzyme complexes can be used including endocellulases, (ec 3.2.1.4), exo-cellulases (ec 3.2.1.91) and cellobiases or β-glucosidases (ec 3.2.1.21). the aims of this work were i) to study these two key steps (pre-treatment and enzymatic hydrolysis) using pure cellulose, ii) to decide if it is possible to carry out the two steps in the same il solvent, and iii) to study the processes by using real agricultural waste materials. 2. materials and methods the ionic liquid 1-butyl-3-methyl-imidazolium chloride ([bmim]cl) was provided by io-li-tec (heilbronn, germany). the enzymes celluclast 1.5l, cellic htec2, and cellic ctec2 were supplied by novozymes (bagsvaerd, denmark). a description of the enzyme (mixtures) can be found on the websites of the producers as in the case of the chemicals. cellic ctec2 is a brown liquid with a density of 1.15 g cm-3 and a slightly fermented odour that contains cellulase (iub: megyeri, nemestóthy, polakovic, bélafi-bakó, gubicza hungarian journal of industry and chemistry 86 3.2.1.4) and xylanase. cellic htec2 is a yellow liquid with a density of 1.09 g cm-3 and lightly fermented odour that contains xilanase (endo-1,4 derivative, iub: 3.2.1.8). the optimal temperature and ph for both enzymes are 45–50 ºc and 5.0–5.5, respectively. the enzymatic reaction was followed by measuring either the glucose content using a god glucose kit (sigma-aldrich, budapest, hungary) or the reducing sugar concentration by the ortho-toluidine (sigma-aldrich) spectrophotometric method (hacklange dr 3800 spectrophotometer). sodium acetate buffer (ph = 5) was used in the hydrolysis experiments with a mixture of acetic acid from scharlau (debrecen, hungary) and naoh from spektrum 3d (debrecen, hungary). purified cellulose powder (macherey-nagel, düren, germany), grounded corn leaf and stover (cls), and wheat straw from local (veszprém) farmers were used as substrates. the ash contents of the cls and wheat straw were 7.7% and 7.3%, respectively, while the maximum obtained reducing sugar yield (rdmax) was 44.9% and 29.6% in the cases of cls and wheat straw, respectively. for the pre-treatment, a specified amount of lignocellulosic substance was dissolved in 0.5 g of ionic liquid in a glass reactor then mixed slowly (50 rpm) for 10 minutes in a 100 ºc oil bath. afterwards some buffer and 0.015 cm-3 enzyme preparation were added to the mixture. then hydrolysis was carried out for 2 hours in a 50 ºc water bath with vigorous mixing (650 rpm). when the hydrolysis finished, the samples were centrifuged in eppendorf tubes. after that the reducing sugar content was measured using ortho-toluidine. 3. results and discussion the first set of experiments was carried out using pure cellulose to study the effectiveness of the pre-treatment as well as enzymatic hydrolysis. then ground corn stover and leaf, and finally wheat straw were used as substrates. 3.1. pure cellulose for the pre-treatment, 25 mg of cellulose (5%) was added into 0.5 cm3 of ionic liquid. following the description of sample preparation in ref. [14], the highly viscous mixture was incubated at 100 ºc for 10 min, and stirred slowly. pictures were taken under a microscope to follow changes during the pre-treatment. the pictures of the pure cellulose particles dispersed in il before and after the 10 min pre-treatment are shown in figs.1-2. on the basis of these photos, it seems that a 10 min pre-treatment time is enough for the cellulose to dissolve into the il. for the hydrolysis acetate buffer (ph = 5) and enzyme were added to the mixture. on the basis of our preliminary experiments 3.5 cm3 of buffer and 0.015 cm3 of cellic ctec2 enzyme seemed to be suitable amounts for the reaction. since the total amount of the mixture is still quite small, the glucose concentration of only the final sample was determined by using the god glucose kit. a reaction time of 2 hours was selected on the basis of preliminary measurements. the glucose content was measured in the reaction mixture right after the pre-treatment as well. no glucose was found in the pre-treated mixture, but 9.6 mg of glucose was detected in the reaction mixture after the enzymatic hydrolysis, which corresponds to approximately 35% conversion. this indicates that the enzyme was able to function in il inspite of literature data [15-17] suggesting that il may inhibit enzymatic function. thus, our experiment confirmed that it was possible to carry out the pretreatment and enzymatic hydrolysis in the same il without needing to separate il from the reaction mixture before the degradation of cellulose. figure 1. cellulose in il before pre-treatment (scale in mm is shown below the picture). figure 2. cellulose in il after pre-treatment. table 1. the glucose content after 2 hr of hydrolysis of pure cellulose. enzyme glucose content (mg) celluclast 1.5 l 0.7 cellic htec2 8.4 cellic ctec2 9.6 application of ionic liquids in cellulose hydrolysis 43(2) pp. 85–89 (2015) doi: 10.1515/hjic-2015-0014 87 as follow-up measurements, similar conditions were applied, but the other two enzymes were employed. the glucose content was determined by using the simpler ortho-toluidine reducing sugar method rather than the expensive god glucose kit. the results are shown in table 1. it can be seen from table 1 that the celluclast 1.5l enzyme was practically ineffective, while the performance of cellic ctec2 was similar to the cellic htec2 enzyme. hence, it was decided to use the two cellic enzymes in our further experiments. in the next set of measurements, a higher substrate concentration of at least 20% was applied, although, according to the literature [10], the solubility of cellulose in a similar il is only 5%. however, in industry it is not practical to use excessively diluted cellulose solutions. cellulose of 0.1 g was added to 0.5 cm3 of il (20%) and the mixture was treated as described above. the higher initial substrate concentration caused difficulties in stirring the mixture. its viscosity was extremely high and the texture was rather tacky. elevated stirring was necessary for complete mixing. after the pre-treatment, the mixtures were treated using buffers and enzymes for the hydrolysis. firstly, the same conditions were applied as earlier, then the amount of buffer was varied from 1 to 7 cm3. the corresponding results are shown in table 2. on the basis of data in table 2, it was concluded that 1 cm3 of buffer seems to be insufficient for the hydrolysis. a larger buffer amount, however, does not necessarily result in a higher conversion rate; rather it dilutes the samples considerably. therefore the 3.5 cm3 buffer amount was used in further experiments, which corresponds to a 1:7 ratio of il solution to buffer. this ratio is similar to the literature data found beneficial for the hydrolysis [17]. the conversion rates of the hydrolysis seem quite high especially in the case of the cellic ctec2 enzyme (64.5–76.2%), but these results can be attributed to the usage of pure cellulose and the higher activity enzymes developed lately. 3.2. corn leaf and stover after the successful experiments using the model substrate: pure cellulose, measurements using ground corn leaf and stover were carried out applying the conditions found suitable earlier: 0.5 cm3 il, 100 ºc, and 10 min pre-treatment time. the initial amounts of the substrate were chosen to be 0.750, 0.100, and 0.125 g corresponding to 15, 20, and 25%, respectively. the process was followed again by taking pictures under a microscope (figs.3-4). the higher initial substrate concentration (25%) also caused difficulties in stirring the mixture, but finally the increased stirring applied was enough to achieve complete mixing. it seems, however, that 25% of substrate poses a physical limit for the process. the pictures proved that the biomass dissolved in the il during the pre-treatment. enzymatic hydrolysis was carried out in the pretreated cls by adding buffer (3.5 cm3) and either enzymes cellic ctec2 or cellic htec2 (0.015 cm3). after the degradation (2 hours of reaction time) sufficiently high amounts of glucose were found in the figure 4. corn leaf and stover in il after pretreatment (scale in mm is shown below the picture). table 3. amount of reducing sugar (mg) in the corn leaf and stover samples. amount of substrate (mg) cellic htec2 cellic ctec2 0.075 6.99 10.06 0.100 13.82 11.61 0.125 9.11 11.14 table 2. the amount of reducing sugar (mg) in the various samples. amount of buffer (cm3) cellic htec2 cellic ctec2 1.0 3.5 7.0 7.16 9.36 33.10 64.48 32.84 76.19 figure 3. corn leaf and stover in il before pretreatment (scale in mm is shown below the picture). megyeri, nemestóthy, polakovic, bélafi-bakó, gubicza hungarian journal of industry and chemistry 88 mixture (table 3), though these values are lower than the ones in the case of pure cellulose. from the data in table 3, it can be seen that both enzymes were able to degrade the cellulose content of the biomass, and a quite high amount of glucose was produced. it seems that the differences between the glucose concentrations obtained are not too high, which means that we are approaching the substrate saturation limit, where increased substrate content does not result in a higher amount of glucose production. the conversion data obtained in the range of 7.2– 14% indicate that the cellulose content of this biomass is rather difficult for the enzyme to access, thus the hydrolysis is less effective than in the case of pure cellulose. the hydrolytic effectiveness of the enzyme cellic ctec2 was similar to that of cellic htec2. 3.3. wheat straw in the final set of experiments, wheat straw was ground and processed in a similar way to other sources used as a substrate in the experiments by applying similar conditions as mentioned earlier. the initial substrate concentration was 25%, which means that 0.125 g of wheat straw was added to 0.5 cm3 of il. the results are summarized in table 4. it can be seen that it is possible to carry out the bioconversion processes using wheat straw as a substrate, but the conversion rate is even lower than for in the case of cls. 4. conclusion it can be stated that the pre-treatment and enzymatic hydrolysis of the cellulose content of various types of plant biomass can be carried out using the same ionic liquid, 1-butyl-3-methyl-imidazolium-chloride. our experiments have proven that acceptable conversion rates could be achieved. thus, this technique is considered as a chemically feasible approach for the utilisation of the cellulose content of agricultural waste materials for energetic and other purposes. acknowledgement this work was supported by the projects támop4.2.2.b-15/1/konv-2015-0004 and slovakianhungarian cooperation sk-hu-2013-0008. references [1] abels, c.; thimm, k.; wulfhorst, h.; spiess, a.c.; wessling, m.: membrane-based recovery of glucose from enzymatic hydrolysis of ionic liquid pretreated cellulose, biores. technol., 2013, 149, 58–64 doi: 10.1016/j.biortech.2013.09.012 [2] ha, s.h.; mai, n.l.; an, g.; koo, y.m.: microwave-assisted pre-treatment of cellulose in ionic liquid for accelerated enzymatic hydrolysis, biores. technol., 2011, 102(2), 1214–1219 doi: 10.1016/j.biortech.2010.07.108 [3] iguchi, m.; aida, t.m.; watanabe, m.; smith, r.l.: dissolution and recovery of cellulose from 1butyl-3-methylimidazolium chloride in presence of water, carbohydrate polymers, 2013, 92(1), 651– 658 doi: 10.1016/j.carbpol.2012.09.021 [4] chandra, r.; bura, r.; mabee, w.; berlin, a.; pan, x.; saddler, j.: substrate pre-treatment: the key to effective enzymatic hydrolysis of lignocellulosic, adv. biochem. engng./biotechnol., 2007, 108, 67– 93 doi: 10.1007/10_2007_064 [5] van eylen, d.; van dongen, f.; kabel, m.; de bont, j.: corn fiber, cobs and stover: enzymeaided saccharification and co-fermentation after dilute acid pre-treatment, biores. technol., 2011, 102(10), 5995–6004 doi: 10.1016/j.biortech.2011.02.049 [6] lozano, p.; bernal, b.; jara, a.g.; belleville, m.p.: enzymatic membrane reactor for full saccharification of ionic liquid-pretreated microcrystalline cellulose, biores. technol., 2014, 151, 159–165 doi: 10.1016/j.biortech.2013.10.067 [7] wang, y.; radosevich, m.; hayes, d.; labbé, n.: compatible ionic liquid-cellulase system for hydrolysis of lignocellulosic biomass, biotechnol. bioengng., 2010, 108(10), 1042–1048 doi: 10.1002/ bit.23045 [8] pinkert, a.; marsh, k.n.; pang, s.; strainger, m.p.: ionic liquids and their interaction with cellulose, chem. rev., 2009, 109(12), 6712–6728 doi: 10.1021/ cr9001947 [9] zhu, s.; wu, y.; chen, q.; yu, z.; wang, c.; jin, s.: dissolution of cellulose with ionic liquids and its application: a mini-review, green chem., 2006, 84(4), 325–327 doi: 10.1039/b601395c [10] fehér, e.; major, b.; bélafi-bakó, k.; gubicza, l.: on the background of enhanced stability and reusability of enzymes in ionic liquids, biochem. soc. trans., 2007, 35(6), 1624–1627 doi: 10.1042/ bst0351624 [11] łuczak, j.; hupka, j.; thöming, j.; jungnickel c.: self-organization of imidazolium ionic liquids in aqueous solution, colloids surf. a: physicochem. engng. aspects, 2008, 329(3), 125–133 doi: 10.1016/ j.colsurfa.2008.07.012 [12] swatloski, r.p.; spear, s.k.; holbrey, j.d.; rogers, r.d.: dissolution of cellulose with ionic liquids, j. am. chem. soc., 2002, 124(18), 4974– 4975 doi: 10.1021/ja025790m table 4. amount of reducing sugar (mg) in the hydrolysed wheat straw samples. enzyme amount of reducing sugar (mg) cellic htec2 7.07 cellic ctec2 8.89 application of ionic liquids in cellulose hydrolysis 43(2) pp. 85–89 (2015) doi: 10.1515/hjic-2015-0014 89 [13] lozano, p.; bernal, b.; bernal, j.m.; pucheault, m.; vaultier, m.: stabilizing immobilized cellulase by ionic liquids for saccharification of cellulose solutions in 1-butyl-3-methylimidazolium chloride, green chem., 2011, 13(6), 1406–1410 doi: 10.1039/ c1gc15294g [14] auxenfans, t.; buchoux, s.; djellab, k.; avondo, c.; husson, e.; sarazin, c.: mild pre-treatment and enzymatic saccharification of cellulose with recycled ionic liquids towards one-batch process, carbohydrate polymers, 2012, 90(2), 805–813 doi: 10.1016/j.carbpol.2012.05.101 [15] turner, m.b.; spear, s.k.; huddleston, j.g.; holbrey, j.d.; rogers, r.d.: ionic liquid saltinduced inactivation and unfolding of cellulase from trichoderma reesei, green chem., 2003, 5(4), 443–447 doi: 10.1039/b302570e [16] salvador, â.c.; santos, m. da c.; saraiva, j.a.: effect of the ionic liquid [bmim]cl and high pressure on the activity of cellulase, green chem., 2010, 12(4), 632–635 doi: 10.1039/b918879g [17] kamiya, n.; matsushita, y.; hanaki, m.; nakashima, k.; narita, m.; goto, m.; takahashi, h.: enzymatic in situ saccharification of cellulose in aqueous-ionic liquid media, biotechnol. lett., 2008, 30(6), 1037–1040 doi: 10.1007/s10529-008-9638-0 hungarian journal of industry and chemistry vol. 43(2) pp. 91–95 (2015) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2015-0015 mineral matter in nigerian coals and tar sand and their implications in binary blend formulation and co-carbonisation solomon a. ryemshak,1,2 aliyu jauro,1* istifanus y. chindo,1 and eno o. ekanem1 1 department of chemistry, abubakar tafawa balewa university, p.m.b. 0248, bauchi, bauchi state, 740003, nigeria 2 fuels and energy division, national metallurgical development centre (nmdc), p.m.b. 2116, jos, plateau state, 930001, nigeria in blend simulation for metallurgical applications, the knowledge of the type and amount of mineral matter in coal and other additives, as well as their derivatives as a result of combustion is important in assessing the coke quality and blast furnace efficiency. x-ray diffraction (xrd) and x-ray fluorescence (xrf) techniques were used in assessing the mineral matter contents and oxides produced up on combustion of the following nigerian coals: afuze (afz), garin-maiganga (gmg), lamza (lmz), shankodi-jangwa (skj), and chikila (chk) in addition to a tar sand from ondo (ots). coal samples from afuze (afz) and chikila (chk) were found to contain quartz, hematite, and anhydride as the dominant minerals. the garin-maiganga coal sample (gmg) was found to contain quartz, magnetite, anhydride, and magnesite. quartz and hematite were dominant in lamza coal (lmz), while shankodi-jangwa coal (skj) is associated with dolomite and quartz. the bitumen was found to contain quartz, kaolinite, and rutile. the xrf analysis revealed the presence of sixteen elemental oxides: the most abundant being silicon dioxide, ferric oxide, aluminium oxide, sulphur trioxide, calcium oxide, and titanium oxide. amongst the coal samples, chk, afz and gmg coals have low acidic/basic and basic/acidic ratios, which indicate that cokes originating from them may form the least slag with the best blast furnace efficiency. keywords: coke, mineral content, slag formation, fouling, flux, iron extraction 1. introduction mineral matter and ash resulting from decomposition processes are some of the main determining factors that produce straight carbonisation and develop blend coking technology for metallurgical coke production in the iron and steel industries. the mineral matter of coal is commonly, but incorrectly termed as ash content. coals contain mineral matter, but not ash. the latter is the solid residue, different from the mineral matter in both amount and composition that is obtained during the combustion of coal. mineral matter has negative and positive effects on coal resource utilisation and disposal. therefore, the characterisation of minerals in coal is essential in order to assess the beneficial and detrimental effects, which a given mineral matter may have both on the combustion process and on ultimate application. for example, even though phosphorousbearing minerals are often minor constituents of coal, they can be transferred from coal to coke and interact with iron ore, providing difficulties in steel production [1]. consequently, coke containing a maximum value of 0.2% phosphorus is required for iron and steel production [2]. *correspondence: ajauro@atbu.edu.ng compositional analysis of coal and coke ash is useful in the total coal quality description. knowledge of the ash composition is useful in predicting the slagging and fouling characteristics of combustible materials in combustion chambers, as well as the potential utilisation of ash by-products, and environmental pollution [3]. it is well known that ash deposition on heat transfer surfaces during coal combustion is a common concern for all coal-firing boilers [4]. it is difficult to quantify the mineral matter content of a coal used in high-temperature operations (combustion and coking processes), because the minerals in coal react with organic particles. on combustion, some of the original minerals decompose and the residual substance may recombine or interact with other derivatives of the coal ash. this may lead to abrasion, corrosion, and clogging as well as fouling of the catalyst and slag formation. the ash, being inevitably a heterogeneous mixture leftover after combustion, is therefore not a true measure of the nature or amount of mineral matter originally present in the sample [5]. this paper assesses the mineral matter contents of nigerian coals and ondo tar sand and their implications in binary-blend formulation for coke production. ryemshak, jauro, chindo, ekanem hungarian journal of industry and chemistry 92 2. experimental 2.1. samples and sample preparation coal samples were collected from the following coal fields: garin-maiganga (gmg), chikila (chk), lamza (lmz), shankodi-jangwa (skj) and afuze (afz). tar sand was obtained from ondo (ondo tar sand, ots). the coal samples were shade dried for three days to remove the free moisture (external or primary moisture fraction). the samples were then ground, and sieved through a 250 micron (0.25 mm) mesh. 2.2. methodologies 2.2.1. xrd analysis the powdered samples were placed into a sample holder and pressed with a piston. they were then loaded into the xrd spectrometer to determine the ore mineral contents of the samples. copper kα radiation was used as the source. the spectrometer was operated at 40 kv and 30 ma using continuous scan mode from 2 to 80 degrees. 2.2.2. xrf analysis coal samples were ashed at a temperature of 825 oc for 1 hour in a muffle furnace. 5.00 g of the ash was mixed with a binder (cellulose flakes) in a ratio of 5:1 g/g and pelletised at a pressure of about 15 ton inch-2 in a pelletising machine. the prepared samples were run on an energy-dispersed x-ray fluorescence (ed-xrf) machine by appropriating programmes for various elements, and the various oxides present detected as percentages. 3. results and discussion 3.1. sample description previously published data show that with the exception of shankodi-jangwa coal that is bituminous in rank, all other samples (afz, lmz, and chk) are of subbituminous rank [6–9]. 3.2. mineral matter results from the xrd analysis of the major mineral matter in the coal samples and the ondo tar sand (ots) are shown in figs.1 and 2. the xrd results of the coal samples and the tar sand (ots) revealed that quartz is dominant in all the samples, with the exception of afz, where hematite content is slightly higher than quartz (fig.1). apart from quartz, halide, and anhydride were also detected in chk (fig.1); anhydride, magnetite and magnesite in gmg (fig.1); hematite in lmz (fig.2); dolomite in skj (fig.2); kaolinite and rutile in ots (fig.2). the observed minerals are commonly reported in coal samples worldwide [10]. a mineral is an inorganic substance that affects both the processing and utilisation of an organic material. xrd analysis is a useful tool in the study of the effects of mineral matter on coal industrial applications like gasification, and liquefaction. knowledge of the mineral matter can also be used to evaluate the behaviour of a particular coal in different utilisation processes, including to control the characteristics of fly ash, slag and other combustion byproducts [11]. coal and tar sand occur in association with mineral matters, and have different mineral compositions depending on their origins. based on the association, there are excluded minerals (minerals that are separate from the macerals) and included minerals (minerals closely associated with the organic matter) [12]. the common major minerals identified in coals are quartz, kaolinite, illite, calcite, pyrite, plagioclase, feldspar and gypsum, and occasionally dolomite, ankerite, siderite, iron-oxyhydroxides and sulphates [10]. the amount, mode of occurrence, and composition of the mineral matter in coal are factors of great practical importance in determining its marketability and economic value. the yield and quality of the product obtained by the use of coal also depends upon the characteristics of its mineral matter. consequently, the quality of the coke figure 1. x-ray diffractogram of ash from a) afz coal (quartz 38%, hematite 41%, anhydrite 21%); b) chk coal (quartz 63%, halite 13%, anhydrite 25%); c) gmg coal (quartz 56%, magnetite 12%, anhydrite 18%, magnesite 14%). c co un ts b co un ts a co un ts mineral matter in nigerian coals and tar sand 43(2) pp. 91–95 (2015) doi: 10.1515/hjic-2015-0015 93 also depends heavily on the type and quantity of mineral matter present in the coke after carbonisation. minerals in coals have different technological problems in metallurgy. for example, clay minerals reduce the calorific value of coal [13]. excluded quartz and pyrite could result in the abrasion and wearing of grinding equipment [14] and pyrite could lead to slagging and fouling. however, these challenges can be mitigated by understanding coal composition, its mineralogical association and abundance. the xrd analysis results of these samples (coals and tar sand) showed that both the coal and tar sand samples contain mineral matter impurities such as quartz and anhydride, commonly found associated with coal deposits (fig.3). the minerals in these samples such as kaolinite, hematite, anhydrite, etc., are potential sources of raw materials of chemical industries. some of the minerals in these coal samples, such as silica, dolomite (calcium magnesium carbonate) or calcium and aluminium are acidic, basic and neutral fluxes respectively, and are useful when combined with other impurities in the formation of slag in iron production [15]. 3.3. mineral matter and ash content during combustion some mineral matter is naturally harmful, and some can decompose to form compounds or combine with other organic components to form other derivatives during combustion. alkali and alkali earth metals such as li, na, k, and ca, mg, respectively, at high temperatures disturb the regularity of blast furnace operation by inducing major furnace incidents like frozen hearth and burnt tuyers that cause inconsistency in iron quality. these metals also interact with other elements resulting in problems, such as clinkering, fouling, slagging and corrosion [16–17]. alkali metals also cause lines of fracture by insertion in the carbon mass of the coke. generally, alkaline elements were found to have a serious impact on coke production by causing decreased burden permeability and low yields [18]. the alkaline vapour sometimes acts as a glue in binding impacting ash particles together and enhancing fouling at high temperatures [19]. ash is the inorganic residue that remains after ignition of the combustible substance, and a reduction in ash content improves the coking quality. the ash in coke is of great significance in metallurgy. according to tivo et al. original coal ash contains various kinds of minerals, coexisting as crystal and non-crystal minerals at different temperatures [20]. coke ash affects the operation of blast furnaces and cupolas due to both its amount and chemical composition. industrial experience indicates that a weight percent increase of ash in the coke reduces metal production by 2 or 3 weight percent [21]. the disposal of ash is also a big problem that increases operational costs and poses some environmental challenges [22]. ash content of less than 10% is recommended for a good coking coal [23]. 3.4. slag formation and blast furnace efficiency coal particles can behave differently particularly in terms of carbon conversion, mineral transformation, char fragmentation, and ash formation depending on the association of the organic (maceral) and inorganic (mineral) matter when fed into a gasifier or boiler [12]. this behaviour, which affects the efficiency of the boiler, can be predicted using the data from the xrf analysis of the samples. table 1 shows the xrf analysis results of ash from the coals and tar samples. figure 2. x-ray diffractograms of ash from a) lmz coal (quartz 72%, hematite 28%); b) skj coal (quartz 80%, dolomite 20%); c) ots sample (quartz 86%, kaolinite 6%, and rutile 8%). figure 3. mineral distribution in coal samples and the tar sand. a b c co un ts co un ts co un ts ryemshak, jauro, chindo, ekanem hungarian journal of industry and chemistry 94 a total of 16 elemental oxides were detected in the ashes resulting from combustion, but the most prominent ones are sio2, fe2o3, al2o3, and cao. even though the results of the oxides (ash composition) fall within the acceptable limit for iron production with the exception of silicon dioxide in ots, which is above the maximum limit of 64% [2]. the ratio of acidic-to-basic (a/b) oxides (al2o3+sio2 versus fe2o3+cao+mgo) characterises the ash with respect to refractoriness. the a/b ratio indicates the ash fusion temperature and blast furnace efficiency, a high ratio leads to a high fusion temperature resulting in a high slag volume and low blast furnace efficiency [24]. the basic constituents are iron, alkali earth metals (ca, mg) and the alkali metals (na, k). the acidic constituents are si, al, and ti. for instance, the coke from skj coal (fig.4), which has the highest a/b ratio is expected to exhibit the highest fusion temperature and the lowest efficiency during blast furnace operation, while the one from chk coal would guarantee the highest efficiency of the furnace. considering the high a/b ratio value of 12 for the ots sample (fig.4), a small quantity of its bitumen may be good for blend formulation with the coal samples. the ratio of basic-to-acidic oxides (b’/a’ calculated from fe2o3+cao+mgo+k2o+na2o content versus sio2+al2o3+tio2 content [25]), corresponds to the slagging tendency of the coal; the higher the ratio the lower the slag formation [25]. ash with a high b’/a’ ratio, generally exhibits high ash fusion and melting temperatures. however, ash with a medium b’/a’ ratio, tends to exhibit low fusion and melting temperatures, hence high slag volume. ash with a low fusion temperature can cause problems during combustion. the melting and viscosity behaviour has been described as a function of the composition of the coal ash in terms of acids and bases. therefore it is expected that chk and afz coals with high b’/a’ ratios (fig.5), would generate coke that may exhibit the least slag formation, closely followed by gmg coal. the highest slag volume is expected in ots and skj coal. overall, the parallel values of a/b and b’/a’ ratios for chk, afz, and gmg coals in fig.6 indicate that cokes produced from them may form the least slag and therefore the best blast furnace efficiency. excessive ash in metallurgical coke gives rise to high slag volume and low blast furnace efficiency. 4. conclusion the relatively low ash contents of these coal samples suggest that they can safely form part of blend formulation for the production of both domestic and industrial cokes without any or significant adverse effects on fouling and slagging, and minimal corrosion and clogging tendencies. the high a/b and low b’/a’ ratios of the tar sand (ots), suggest that a small amount of bitumen may be beneficial for binary blend formulation with the coals, for coke production. based on the oxide ratios, chk, afz and gmg coals may produce cokes by coking technology that may create the least slag with the best blast furnace efficiency. acknowledgement we acknowledge the department of chemistry atbu in bauchi and the national metallurgical research and development centre in jos for the use of their laboratories. the publication of this article was table 1. chemical composition (% oxide content) of the coals and tar sand ashes from xrf measurements. oxide afz chk gmg lmz skj ots sio2 24.61 29.41 38.60 46.40 57.36 70.39 tio2 1.87 1.90 2.40 4.46 2.32 1.62 al2o3 7.31 8.93 7.19 15.81 16.20 14.33 fe2o3 23.97 18.28 16.26 22.53 19.30 5.31 so3 13.70 14.70 11.00 6.20 1.10 0.09 cao 11.20 25.00 21.10 1.64 1.36 1.26 mgo 0.35 0.31 1.96 0.11 0.20 0.49 na2o 0.07 0.15 0.10 0.05 0.33 0.30 k2o 0.04 0.87 0.07 0.30 1.46 0.96 mno 0.40 0.04 0.41 0.04 0.06 v2o5 0.07 0.10 0.08 0.23 0.14 0.07 cr2o3 0.03 0.03 0.02 0.04 0.04 0.03 cuo 0.08 0.07 0.03 0.20 0.08 0.03 bao 0.30 0.17 0.77 0.13 zno 0.04 0.07 nio 0.04 0.02 0.04 0.03 0.02 figure 4. blast furnace efficiencies of the coal samples. figure 5. slag formation tendencies of the coal and tar sand samples. figure 6. slag formation tendencies and blast furnace efficiencies. mineral matter in nigerian coals and tar sand 43(2) pp. 91–95 (2015) doi: 10.1515/hjic-2015-0015 95 supported by professor jános szépvölgyi (hungarian academy of science, research centre for natural sciences), professor jude onwudili (university of leeds) and dr. biswajit ruj (csir-central mechanical engineering research institute). references [1] ward, c.r.; corcoran, j.f.; saxby, j.d.; read, h.w.: occurrence of phosphorous mineral in australian coal seams, int. j. coal geol., 1996, 30(3), 185–210 doi: 10.1016/0166-5162(95)00055-0 [2] astm: petroleum products, lubricants and fossil fuels (annual book of astm standard, easton, md, u.s.a.) 1992 [3] shimogori, m.; ooyatsu, n.; takarayama, n.; mine, t.: ash deposition characteristics determined 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[4] reported that the combination of tio2 photocatalysis and the fenton-like reaction synergistically increased the degradation of organic compounds at around neutral ph (6.5–7.5) by the increased production of reactive oxidants and their improved reactivity. however, it has not been clearly addressed whether the integration of the uv/tio2 and fe2+/h2o2 systems exhibits synergistic results with respect to the degradation of contaminants. little data are available on the role of fe2+ ions in the uv/fe2+/tio2 system at neutral ph, where the fe2+/h2o2 or uv/fe2+/h2o2 system alone is not effective for oxidant production and pollutant oxidation due to the low aqueous iron solubility and h2o2 decomposition via a non-radical mechanism without hydroxyl radical generation [1,4,5]. zarei et al. [6] showed that the removal efficiency of phenol was 69% after 150 min using photoelectro-fenton (pef)/mn2+/tio2 nanoparticles for the removal of phenol from aqueous solutions. nogueira [7] showed that the role of fe2+ ions and h2o2 are much more important than that of tio2 in the photodegradation of both 4-chloro-phenol (4cp) and dichloro-acetic acid (dca) under solar irradiation [7]. aljubourya, palaniandy, aziz, and feroz hungarian journal of industry and chemistry 98 the aims of the given study are as follows: (i) comparison of the homogenous (solar photo-fenton) and heterogeneous photocatalytic systems (solar photocatalysis by tio2 and solar photocatalysis using combined tio2/fenton processes) by central composite design (ccd) with response surface methodology (rsm) on the basis of their performances with regard to the chemical oxygen demand (cod) and total organic carbon (toc) in petroleum wastewater and (ii) assessment of treatment efficiencies and the main factors with regard to these methods by ccd and rsm. to our knowledge there are no reports in the literature of a similar comparison by a central composite design (ccd) with response surface methodology (rsm) applied to the homogeneous and heterogeneous photocatalytic systems for treatment of petroleum wastewater as shown in table 1. 2. materials and methods 2.1. wastewater characterisation the physicochemical characteristics of the petroleum wastewater from sor are summarised in table 2. samples of the petroleum wastewater were collected on different days. samples were transferred to the laboratory and stored in a refrigerator at 4 ºc until use. samples were characterised before the analysis for their chemical and physical properties. the petroleum wastewater was characterised by the quantification of ph and chemical oxygen demand (cod) according to the standard methods for the examination of wastewater methodology [12]. 2.2. materials the catalyst used was tio2 aeroxide p-25 manufactured by evonik industries co., germany. hydrogen peroxide (h2o2) (35% dm3 dm-3) and iron sulphate hydrate (feso4⋅xh2o) were supplied by emprove exp. (usa). sulphuric acid and sodium hydroxide were used to set the desired ph values. 2.3. analytical procedures a shimadzu toc analyser (lcsh/csn) was used to measure the total organic content (toc). chemical oxygen demand (cod) was measured by a cod photometer (manufactured by chemetrics). the ph levels were monitored by using a digital ph meter. toc and cod were determined before and after treatment. before each analysis, samples were filtered by using a 0.22 µm millipore durapore membrane (40 ashless, diameter 150 mm) filter paper. 2.4. experimental procedure the solar photocatalytic equipment used is shown schematically in fig.1 consisting of a stirred glass recirculation tank (1.5 dm3). the tubular solar reactor contained four tubes 50 cm in length × 2 cm in inner diameter × 0.1 cm in thickness. the solution was recirculated through the reactor at a flow rate of 1.5 dm3 min-1 using a peristaltic pump. natural sunlight was used as a light source. the added materials and their concentrations such as tio2, h2o2, and fe2+ were varied according to a central composite design (ccd) with response surface methodology (rsm) to determine the cod and toc removal efficiencies under the optimum operational conditions. table 1. overview of research done in the area of fenton/tio2 processes in recent years. no. wastewater method material removed ref. 1 aqueous imidacloprid photocatalysis by tio2 photo-fenton imidacloprid [1] 2 milli-q water tio2/fenton-like/solar 2,4-dinitrophenyl hydrazine (dnph) [4] 3 aqueous solutions tio2/photoelectro-fenton/mn2+/uv phenol [6] 4 aqueous media tio2/fenton-like/solar 4-chloro-phenol (4cp) and dichloroacetic acid (dca) [7] 5 oil-water emulsions tio2/h2o2/fe2+/uv tio2/h2o2/fe2+/uv/air zno/h2o2/fe2+/uv organics measured by reduction in cod value [9] 6 dye polluted water tio2/h2o2/fe2+/uv tio2/h2o2/fe2+/solar azo dye basic blue 4 [11] 7 petroleum wastewater tio2/h2o2/fe2+/solar solar photocatalysis by tio2 solar photo-fenton organics measured by reduction in cod and toc values this study table 2. characteristics of petroleum wastewater from sohar oil refinery (sor). parameters units ranges of concentration in petroleum wastewater average concentration standard discharge limit ph 6–8 7 6–9 conductivity µs cm-1 2600–3950 3275 2000–2700 tds ppm(mg dm-3) 1200–1500 1350 1500–2000 toc ppm (mg dm-3) 220–265 243 50–75 cod ppm(mg dm-3) 550–1600 1075 150–200 comparative study of advanced oxidation processes 43(2) pp. 97–101 (2015) doi: 10.1515/hjic-2015-0016 99 3. results and analysis 3.1. effect of ph there are two types of advanced oxidation processes (aops) depending on the reaction medium: a homogeneous process such as the solar photo-fenton process, a heterogeneous process such as solar tio2 photocatalysis, and their combined processes. according to previous results [13], the solar photofenton process is more efficient for petroleum wastewater treatment than solar tio2 photocatalysis under acidic conditions. by comparing solar photocatalysis using combined tio2/fenton processes with the solar photo-fenton process under the same ph values, the toc and cod removal efficiencies improved from 16% to 23% and from 27% to 38%, respectively at ph 7 as shown in table 3. this enhancement is attributed to increased hydroxyl radical (•oh) production by the presence of tio2. as shown in fig.2, solar photocatalysis using combined tio2/fenton processes improves performance at neutral ph for petroleum wastewater. therefore, there is no need to adjust the ph during this treatment. by comparing these results with previous studies, the results of this work are in agreement with some studies. ardhendu et al. [2] reported that the greatest toc reduction took place under photo-fenton process (pfp). it was found to be more efficient than uv/tio2 photocatalysis (uvpc) under acidic conditions. gbandi et al. [3] found that photocatalysis of tio2 was independent of the ph of the solution, while under fenton photocatalysis, the degradation rate of orange ii increases as the ph decreases. duran et al. [8] found that the tio2 concentration and ph were the main factors for the tio2/fenton/sunlight method for the degradation of the “blue 4” dye. kim et al. [4] showed that the synergistic removal of benzoic acid by the uv/tio2/fe3+/h2o2 system was very efficient between the ph values of 4 and 7. but, at higher ph values (ph>7), the addition of fe3+ and h2o2 to the uv/tio2 system caused negative effects. however, tony et al. [9] reported that the neutral ph of the oil-water solution was the optimum ph value for the degradation of cod by the fenton/tio2/uv system. 3.2. effect of fenton reagent and tio2 concentration the degradation of organic matter monitored by toc and cod for solar tio2 photocatalysis is significantly improved by using a fenton reagent in combination with solar photocatalysis as shown in fig.2 for the tio2/fenton system. the excess iron has a negative effect because it reacts with hydroxyl radicals reducing the degradation rate of the pollutant [6]. also, the excess amount of hydrogen peroxide can cause the auto decomposition of h2o2 to oxygen and water, and the recombination of hydroxyl radicals. therefore, decreasing the concentration of hydroxyl radicals and table 3. comparing the removal efficiencies (%) for three degradation processes expressed by toc and cod under acidic ph range between 5.5 and 7 of petroleum wastewater. removal (%) ph tio2/ solara fenton/ solarb tio2/fenton/ solarc toc 5.5 9 17 26 7.0 15 16 23 cod 5.5 6 39 61 7.0 24 27 38 experimental conditions: a1 g dm-3 tio2 and 180 min (rt); b1 g dm-3 h2o2, 0.04 g dm-3 fe2+ and 180 min (rt); c1 g dm-3 tio2, 1 g dm-3 h2o2, 0.02 g dm-3 fe2+ and 180 min (rt). figure 2. the three processess of toc (a) and cod (b) under different ph figure 1. schematic view of the experimental setup for solar photo-fenton, solar tio2 photocatalysis and solar photocatalysis using combined tio2/fenton processes. a b aljubourya, palaniandy, aziz, and feroz hungarian journal of industry and chemistry 100 reagents reduces efficiency [9]. the degradation rate measured by cod and toc increases as the tio2 concentration increases up to the optimum tio2 dosage in solar tio2 photocatalysis and solar photocatalysis using combined tio2/fenton processes, which were l g dm-3 and 0.66 g dm-3, respectively. however, tio2 dosages greater than the maximum value have a negative effect on these processes since the excess tio2 particles increase the turbidity of the solution that decreases the penetration of light into the solution resulting in a reduction in production of hydroxyl radicals (•oh) at the tio2 surface [10]. 3.3. treatment efficiency to assess the interactive relationships between the independent variables and the responses of certain models, 3d surface response plots were created by design expert 6.0.7. as shown in figs.3 and 4, the tio2 dosage and ph were the two main factors that improved the toc and cod values after removal under solar photocatalysis using the combined tio2/fenton and solar tio2 photocatalysis processes, while the ph and h2o2 concentration were the two main factors in the solar photo-fenton method. the greater removal rates from toc and cod values under acidic conditions for solar photocatalysis using the combined tio2/fenton and solar photo-fenton methods were achieved with ph values of 3.6 and 4.2, respectively. however, they were under alkaline conditions (ph 8) for solar tio2 photocatalysis. the fenton ratio and fe2+ concentration were the essential variables for solar photocatalysis using the combined tio2/fenton and solar photo-fenton methods, respectively. figure 4. figure 3. response surface models for toc removal efficiencies for . a a b b c c tio2 tio2 ph ph ph ph ph ph tio2 tio2 h2o2 h2o2 comparative study of advanced oxidation processes 43(2) pp. 97–101 (2015) doi: 10.1515/hjic-2015-0016 101 4. conclusion the given study evaluated the performance of advanced oxidation processes for the treatment of petroleum wastewater by a central composite design with response surface methodology. these processes include solar photo-fenton catalysis, solar tio2 photocatalysis, and solar photocatalysis using the combined tio2/fenton processes. the decomposition of organic matter was monitored by chemical oxygen demand and total organic carbon content. we obtained experimental evidence for the superior performance of solar photocatalysis using the combined tio2/fenton methods over using tio2 only in the case of petroleum wastewater at neutral ph. under acidic conditions, solar photo-fenton process was found to be more efficient than solar tio2 photocatalysis. however, it was less efficient than the solar tio2 photocatalysis under alkaline conditions. the tio2 dosage and ph can be used to improve the toc and cod values for solar photocatalysis using the combined tio2/fenton processes and solar tio2 photocatalysis only. the ph and h2o2 concentration are the two main factors that influence the efficiency of the solar photo-fenton process. references [1] giri, a.s.; 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[13] aljuboury, d.d.a.; palaniandy, p.; abdul aziz, h.b.; feroz, s.: treatment of petroleum wastewater using combination of solar photo-two catalyst tio2 and photo-fenton process, j. environ. chem. engng., 2015, 3(2), 1117–1124 doi 10.1016/j.jece.2015.04.012 guide for authors 1. electronic copies of manuscripts should be uploaded to the author’s pages at hjic.mk.uni-pannon.hu or emailed directly to hjic@almos.uni-pannon.hu. − please visit the journal’s website for downloading a word or latex template and follow closely the suggested layout for the text, figures, tables, and references. manuscripts without the recommended structure and formatting for publication will be returned without a review. − the use of template is highly desired in order to avoid imposing any article processing charges (apcs), page fees, or article submission charges. 2. in a brief letter attached to each manuscripts, authors must declare that their work is original and has not previously been published elsewhere. the editorial board requests an originality evaluation score to be below 10% according to crosscheck/ithenticate excluding quotes, references, and three-word expressions. if originality of a given manuscript is between 10-20% the authors are kindly requested to rewrite the overlapping sections. nothing above 20% similarity will be accepted for publication and will not be sent out for review. 3. for the purposes of correspondence, the authors are asked to give their current address, telephone, professional website (if applicable), and regularly accessed e-mail address. 4. authors are requested to adhere to the rules given below and follow the examples: − the layout of manuscripts should be a4 page size (21 cm × 29.7 cm) with double columns, single-spaced (approximately 45 characters per line, 55 lines per page), and numbered pages. the text of the papers should be concise, and not exceed twelve pages; 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(lewis, boca raton, fl, usa) 1988 d) patents: u.s. pat. 3,425,442 (1984) e) published lectures, conference proceedings: hih, s.; hhu, c.; leech, w.j.: a discrete method to heat conduction problems, proc. 5th int. heat transfer conf., tokyo, japan, pp. 2.4, 1975. citations of conference presentations are strongly discouraged and should be avoided unless the talk was made available electronically. f) papers that are unpublished, but have been submitted to a journal may be cited with the journal’s name, followed by “submitted for publication” or “in press”. this will be accepted if the author uploads the submitted manuscript as ‘editorial’ material. no reference to “unpublished work” or “personal communication” will be accepted. g) all references must be provided with a digitial object identifier (doi). please provide the editorial office with a rationale for any citations without doi numbers and explain why these references are necessary. 6. authors receive galley proofs, which they are to be corrected and returned as soon as possible, but no later than 1 week after receipt. no new material may be inserted into the text at the time of proofreading. 7. authors who are less practiced with written english are urged to have their manuscripts checked by scientists who are working in the author’s respective field and proficient in english. editorial board of the hungarian journal of industry and chemistry hungar~journal of industrial chemistry veszprem vol. 30. pp. 19-25 (2002) possible substrates for acetone-butanol and ethanol fermentation based on organic by-products e. varga, z. kadar, k. c. schuster1 , j. r. gapes 1 , z. szengyel and k. reczey* (department of agricultural chemical technology, budapest university of technology and economics, szt.gellert ter 4, budapest, h-1521, hungary 1institute for chemical engineering, fuel and environmental technology, vienna university of technology, getreidemarkt 91159 vienn<t, a-1060, austria) received: february 27, 2001 an assessment study was carried out on available biomass by-products in hungary, and also several fruit juice wastes were evaluated for their accessibility to enzymatic hydrolysis. among the fruit juice residue samples examined the best results were obtained with apple, peach, apricot and tomato. it can be shown that using intensive stirring, higher conversions can be reached. highest conversion of 98 % based on carbohydrate content was obtained with frozen and thawed apple residues. abe fermentation of apple pulp hydrolysate supplemented with glucose yielded high solvent concentrations up to 22.5 gil. for growth and solvent production supplementation by additional nutrients was not essential, however, this accelerated the process. ethanol fermentation by baker's yeast was carried out on apple pulp hydrolysate supplemented with glucose. this also gave reasonable yields of about 90 % based on glucose consumption. keywords: hydrolysis, biomass, fruit pulp, alternative substrate of abe fermentation introduction the problem of environmental change caused by greenhouse gas emissions mainly from fossil fuels has motivated research in the utilisation of renewable energy sources. biomass of various origins is a great resource for energy carriers, not only by direct combustion, but . also by biological conversion such as biogas production, ethanol fermentation, and acetonebutanol (abe) fermentation [7]. in the traditional abe process, the high cost of conventional "starch" (maize, wheat, millet, rye, etc.) or sugar (molasses) substrates was a major factor affecting the economic viability of the process [7]. abe fermentation, following its success in the 40's and 50's, and its nearly complete disappearance in the 60's once again became of interest in the 70's after the first oil crisis, when much emphasis was placed on the use of renewable raw materials. this interest and the ability of sugar-fermenting clostridia to utilise many different carbohydrates have stimulated research into the use of alternative cheaper substrates [7]. the use of whey and whey permeate has been studied successfully [8]. prescott and dunn [14] have used a number of non-cellulosic, starch-based materials (including potato, rice, jawari, bajra) as substrates with varying success. cheap low-grade potatoes have been used in the ethanol industry for a long time and proved to be an excellent substrate for batch abe fermentation after minor pretreatment with starch-liquefying enzyme [3, 12], and could also be used in a continuous process [17]. as early as 1922, robinson [15] studied the fermentation on various carbohydrates for the production of acetone and butanol. he reported that glucose, fructose, mannose, sucrose, lactose, dextrin, and starch were completely consumed, while galactose, xylose, and arabinose were partially utilised, and glycerol was not fermented. however, nakhmanichov and kochkina [ll] showed that xylose and arabinose could be fermented completely by most abe bacteria. ounine et at. [13] reported a relatively high yield of conversion into solvents of 28 % for xylose, close to the maximal value of 32 % for glucose. wiley et al. [22] investigated sulphite waste liquids from the pulp and paper industry <;ontaining glucose, xyloset and arabinose as alternative substrates for abe fermentation. they showed that good yields of solvents were obtained when sulphur dioxide, lignin, and excess calcium were removed from the sulphite liquid. voget et al. [211 *corresponding author: fax: (36)-1463-25-89. e-mail: reczey@chem.bme.hu 20 investigated the use of apple pomace for butanol production and found that 80 % to 84 % of soluble sugars (about 10% of the dry weight) were consumed. the residue remaining after butanol separation could be used as animal feed. lignocellulosics are, however, the most abundant renewable resources [6] and ~are recognised as having great potential as substrates for fermentation, provided that the hemicellulose and cellulose components can be degraded and utilised cheaply and efficiently. fermentation can be performed by yeasts to ethanol [16] or to acetone-butanol by clostridia [7]. the abe fermentation by clostridia holds further potential as the butyric acid bacteria are capable of utilising all of the prevalent pentose and hexose sugars present in hemicellulose and cellulose in contrast to conventional baker's yeast saccharomyces cerevisiae used for ethanol fermentation. lignocellulosic biomass contains hemicellulose in a range of about 20 to 40 % [19] 'yhich means that the overall substrate utilisation is higher depending on the content of hemicellulose in the biomass, however, the (hemi)cellulose must be hydrolysed prior to fermentation. substrates with high lignin content can usually be hydrolysed only after pretreatment under harsh conditions [16], often leading to high levels of substances inhibitory to the fermentation, and to loss of less thermally stable sugars like xylose. this combination of problems leads to poor economic prospects for the saccharification process starting from lignin-rich substrates like wood [5]. these problems have motivated this. survey of potentially "easier•• substrates which can be readily hydrolysed and are available locally in hungary. selected substrates should also be tested in practical hydrolysis and fermentation experiments. sun·ey of a\·ailabfe by-products from agriculture and food industry in hungary hungarian agriculture produces large amount of plant biomass every year. a part of this biomass is a by­ product or waste, and its efficient utilisation is not yet solved. the aim of this survey in the agriculture and food industries was to identify potential substrates for abe fermentation, which should be easy to hydrolyse and available in sufficiently large quantities. a.fjricultural b.\·~products crop residues considered for collection are from corn. small grains. and grass. they are harvested by combines that leave stubble~ and the straw or stalks are returned to the field after harvest [23}. this is a rather large amount 1.20e+07 com-stow!lr ..._ l,ooe+07 .. ~ 8,00e+06 ;q = .. 6,00e+06 c. wneatstraw ..... .. ';:; 4,00e+06 ~ ~ r csidncs of fr~itjuicc processing 2,00e+06 o,ooe+oo mm • • t • !llllli::~al wheat barley com-stalk com-cob residues of extracted soil waste straw straw frul juke sugar-beet in processilg si:e budapest fig.l amounts of various agricultural and food industry wastes in hungary according to the survey performed in this study (in million tons per year) of biomass. the amount of corn stalk is tenfold more than the municipal solid waste of budapest in a year (fig. i). by-products from the food industry • cheese whey has attracted interest as an alternative substrate for abe fermentation because of its disposal problem, lactose content, and availability in many countries. after the precipitation and removal of casein, whey filtrate contains a relatively low sugar content and is unsuitable for most fermentation processes without prior concentration steps, but it is suitable for abe fermentation [7]. maddox et al. [8] reported successful utilisation of whey permeate after removal of valuable proteins. in hungary 435*106 1itres of whey is produced annually and only 10% of this is dried and utilised as animal feed. the abe fermentation could be a good alternative for ~e remainder. • in hungary, one of the largest companies in the fruit juice processing industry is rauch hungary ltd., which produces annually 10,000 t apple residues (from juice and pulp processing) and apple pomace (from washing and sorting) and 1,500-2,000 t of other fruit waste. expansion of the production facilities is anticipated. • at the canning factories there is no problem with wastes yet, because the entire quantity is used as animal feed or is composted. • according to information from breweries, their by­ products are sold as animal feed. however, with the concentration process going on in this industry as in many others, it might become difficult to distribute in large quantities. experbnentalprocedure substrates for hydrolysis experiments industrial residues from the fruit processing industry for use in the comparison experiments were obtained from rauch hungary. the comparison experiments were performed with fresh residues in the factory without any treatment or preservation. peach residue for the assessment effect of re-freezing was stored at -20 °c, thawed and hydrolysed. a portion was refrozen and hydrolysed after the second freeze-thaw cycle. enzymatic hydrolysis hydrolysis of fruit pulp for the substrate comparison was performed at 3 % dry material in a 0.05 m citrate buffer solution (ph 4.8) supplemented with pulpzyme hc, 24.7 fpu (filter paper unit) and novozym 188, 121.7 cbu (cellobiase unit) per g dried substrate. hydrolysis was performed at 50 oc for 5 h in 1 ooml shake flasks. samples were collected each hour, centrifuged at 10,000 rpm for 3 minutes and analysed for reducing sugar content by the dns method. enzyme preparations used pulpzyme hc is an enzyme preparation with a cellulase and xylanase activityproduced in submerged fermentation with a genetically modified bacillus strain (novo nordisk, denmark). novozym 188 is a cellobiase enzyme preparation obtained by submerged fermentation with aspergillus niger (novo nordisk, denmark). organism, culture maintenance, and growth media the organism utilised was clostridium acetobutylicum atcc 824 maintained in spore stock suspension according to gapes et al. [2]. the composition of the medium used for strain maintenance was 60 gil glucose, 5 gil yeast extract, 1 g/1 k2hpoih20, 1 g/1 khzp04, 1 gil mgs047h20, 0.5 g/1 fes047h20, 0.01 gil p-amino­ benzoic acid, 3 g/1 ammonium acetate. abe fermentation previously hydrolysed apple pulp was used for the abe fermentation experiments, supplemented by nutrients of the standard semisynthetic medium for the maintenance of the c. acetobutylicum atcc 824 strain according to gapes et al. [2], or for the comparison experiment without supplementation. the sugar concentration was increased to 60 gil by adding glucose. the experiments 21 were performed in 300 ml sealable glass bottles filled with 150 m1 of medium. to ensure anaerobic conditions nitrogen was blown through the solutions for 10 min to remove oxygen from the headspace. following sterilisation at 121 oc for 16 min the medium was inoculated with 10 ml of a culture of vegetative cells of c. acetobutylicum atcc 824 grown in continuous cultivation in a wheat medium as described by nimcevic et al. [12]. the fermentation experiments were performed at 35 °c. ethanol fermentation the conditions of the experiment were identical to those of the abe fermentation experiments except for the microorganism used. commercially available baker's yeast (saccharomyces cerevisiae) was used for the ethanol fermentation. an inoculum culture was grown on semisynthetic medium for 24 hours, and 6 m1 of this culture was used to inoculate the apple pulp medium. assays for analysis of the biomass, the first step was an acidic lignin extraction performed according to hagglund ( 4 ]. the sugar content of this acidic supernatant was determined by the phenol-sulphuric acid method [1] and total available carbohydrate concentration was calculated from this. the reducing sugar concentration during enzymatic hydrolysis was estimated calorimetrically using a dinitrosalicylic acid reagent [10]. glucose concentration was analysed by hplc or estimated by reflex photometry with reflolux (boehringer mannheim i roche diagnostics, mannheim, germany). results comparative hydrolysis experiments with various fruit juice processing by-products the purpose of these experiments was to identify those by-products of fruit juice processing, which are suitable for abe fermentation with regard to their sugar and convertible carbohydrate content. the hydrolysis was performed with 12 types of fruit substrates (apple pulp, peach and apricot pulp, juice and pulp processing by­ products, black and red currant, raspberry, blackberry, and elder pomaces) in 100 m1 shake flasks, using the enzymes pulpyzime and novozym. since a portion of the sugars in fruit processing residues is soluble, the water-soluble sugars were first removed from the samples by cold and hot water washing, followed by filtering. the amounts of dissolved sugars in the filtered table 1 soluble sugar and acid-soluble carbohydrate content of residues from fruit processing by-products 22 samples peach* peach** apricot* apricot** apple pomace apple pulp red currant raspberry blackcurrant elder tomato blackberry soluble sugar (g/100 g substrate dw) 9.4 0.9 10 2.6 7.1 12 1.7 2.1 2.1 1.4 7.6 0.5 * residues from pulp production ** residues from juice production acid soluble carbohydrate (g/100 g washed substrate dw) 39 28 38 30 40 38 35 38 31 21 28 34 water were determined by the phenol-sulphuric acid method.. the results, based on 100 g dry weight, are shown in table 1. together with the carbohydrate · contents the dry matter contents were also determined for each sample. the hydrolysis of the samples was performed in 5 h, in suspensions containing 3 % dry weight. previous experiments [20] have shown that the amount of sugar obtained in 24 h enzyme conversions is approximately 10 % higher than when the hydrolysis is stopped after 5 h.. however, since our goal was the identification of easily convertible wastes, this time period was sufficient and informative enough for making the desired determinations. the conversion yields reached with enzymatic hydrolysis based on the samples' carbohydrate contents (table 2) proved to be low (~20 %) in the cases of the so-called coloured fruits (red and black currant, blackberry, raspberry,. and elder). among two types of peach and apricot processing wastes, the pressed waste (the remnant of fruit juice processing) is apparently largely composed of stone-seeds, which are difficult to hydrolyse, resulting in a rather low conversion yield. data from the literature [9] show that the most efficient handling of stone-seeds is combustion. the conversion yields of the by-products of pulping are promising. and these wastes could be useful for fermentation, however, the amounts available are rather smau (below 1,000 t/a). the conversion yield of tomato pulp is comparable to those of the apricot and peach and in this case the water­ soluble sugar content is rather important as its quantity is similar to that resulting from hydrolysis. the results are quite promising with the apple residues. the apple pulp~ as weu as the pulp preparation residues from peach and apricot. these by-products are also available in significant quantities above 10j)00 tons per year. therefore1 further hydrolysis experiments were carried out with this group of fruit by-products. table 2 conversion of insoluble carbohydrate to soluble reducing sugar by enzymatic hydrolysis of washed fruit residues. given as the ratio (in percent) of reducing sugar after hydrolysis to total available carbohydrate content examined residues conversion (% l peach* 47 peach** 21 apricot* 46 apricot** 23 apple pomace 63 apple pulp 73 red currant 16 raspberry 21 blackcurrant 17 elder 30 tomato 46 blackberry 28 * residues from pulp production ** residues·from juice production, containing the stones hydrolysis experiments in a stirred system, with the most readily convertible fruit processing by-products these 250 m1 experiments were performed at 50 °c with 3 6 9 and 12 % dry weight content suspensions , ' ' • -1 • under mild stirring (100-150 mm ) for 24 hours m order to determine the maximum amount of sugar that can be reached, which is an important factor for further experiments. the more efficient stirring increased the effectiveness of the hydrolysis. by increasing the initial amount of substrate, the maximum sugar concentration reached also increased (table 3). in the case of suspensions containing 12 % dry weight, the highest sugar concentration, 46 g/1, was obtained from apple residues, while the lowest, 9 g/1, from tomato juice processing by-products. at the same time, with the increase in the amounts of sugar obtained, the conversion values decreased. however, the decrease between the 3% and the 12% samples was less than 10 % (table 4). among the conversion values obtained with the 5 h and the 24 h hydrolysis, even with the mixtures containing larger amounts of initial matter, the difference was smaller than 10 % (fig.2), thus in future abe fermentation experiments it would be practical to inoculate the hydrolysate after 5 hour hydrolysis. statistical tests showed no significant difference at a 95 % confidence level in the total amount of sugar extracted when the original, unwashed sample is directly hydrolysed, when the sample is first washed and only then hydrolysed. the amount of extractable sugar also does not change when using fresh, dried, or powdered samples. freezing and thawing of the samples does not spoil the degradability, moreover it shows a positive effect on the enzymatic hydrolysis. (table 5). [ 5 ~ §! c 0 1.) table 3 reducing sugar concentrations of enzymatic hydrolysates starting from substrates at varied dry matter contents -sugar concentration (g/1) examined residues 3% 6% 9% 12% apple pulp 12 24 36 46 apricot pulp 8.3 16 24 33 peach pulp 9.0 16 25 32 tomato 3.0 5.3 7.6 9.3 table 4 conversions efficiency of enzymatic hydrolysis starting from substrates at varied dry matter contents conversion of carbohydrate (%) examined residues 3% 6% 9% 12% apple pulp 98 96 94 91 apricot pulp 67 65 65 63 peach pulp 70 64 64 62 tomato 45 42 40 38 95 85 75 65 i"" j "":' i"" ] i. ffti1' ftrt11t55 tt--11t-. 45 h i 0 2 3 4 5 24 time[h] 03 (m/m)% ~6 (m/m)% d9(m/m)% d12(m/m)% fig.2 conversion of insoluble carbohydrate to soluble reducing sugar in hydrolysis of apple pulp, in relation to initial dry matter content of the substrate (in mass percent). conversion is calculated as in table 2 abe fermentation on hydrolysed apple pulp abe fermentation experiments were performed on enzymatically hydrolysed apple pulp. the apple pulp was supplemented with glucose to elevate its sugar concentration to 60 gil, which was necessary because the abe bacteria used require a minimal sugar concentration to initiate solvent production. in addition to the glucose, the medium was also supplemented with nutrients as used in the semisynthetic glucose media [2]. a comparative experiment with an unsupplemented medium was done without adding the nutrients. the fermentation was inoculated with vegetative cells grown in continuous cultivation on a starch medium. the maximum average product concentrations during the fermentation are presented in table 6. on the supplemented medium the sugar was almost completely consumed within 42 h, its concentration decreasing from 60 gil to 1,2-3,7 gil. coupled with the decrease in table 5 effect of refreezing of peach residue on conversion effectivity of enzymatic hydrolysis starting from varied dry matter contents in the substrate sugar concentration [gil} 23 time (h) s=3% s=3% s=12% s=12% refreezing refreezing 0 1.8 3.0 3.5 18 1 9.6 12 31 41 2 10 14 32 42 3 11 15 32 45 4 13 17 37 50 5 14 17 5 14 17 39 54 24 17 18 48 56 table 6 results of abe fermentation using enzymatically hydrolysed apple pulp and effect of medium supplementation on performance maximum product maximum product product, substrate concentration at concentration at not completed medium completed medium (gil) (gil) butanol 11 9.6 ethanol 3.0 1.0 acetone 6.6 4.8 butyric acid 0.02 0.13 acetic acid 1.4 1.3 remaining sugar 2.3 20 start of solvent formation: before 18 h for supplemented medium; after 24 h for unsupplemented medium. max. solvent concentration was reachedat 42 h for supplemented medium; at 66 h for unsupplemented medium. the sugar, the products (acetone, butanol, ethanon appeared in the broth and reached their maximum concentrations after just 42 h when the sugar was almost completely consumed (95 % of the initial glucose). on the uncompleted medium, the maximum product concentrations were somewhat lower (table 6). glucose was not consumed completely only about 70 % was consumed. the fermentation proceeded more slowly. solvent formation started later and maximum product concentrations were reached later. ethanol fermentation experiments on apple pulp with saccharomyces cerevisiae the fermentation experiments were also performed on hydrolysed apple pulp with commercially available baker's yeast. in order to run both fermentation experiments under comparable conditions~ the solutions were supplemented with enough glucose to reach the sugar concentration of 60 gil. as in the abe experiments the medium contained au the necessary nutrients. following sterilisation, the media was inoculated for one night with a saccharomyces cerevisiae inoculum and the fermentation was performed at 35 oc for 46 h. the sugar ~oncentration gradually decreased from the initial value of 60 gil and was completely consumed by the 46th hour. at which point the maximum ethanol concentration was reached as well 24 (24.4, 24.8 and 28.3 gil in three parallel experiments). this is close to the theoretical maximum yield (0.51 gig glucose). conclusions there is large quantity of agricultural and food industrial by-product, which could be potential substrates for abe fermentation. among the 12 different fruit processing residues there are 4 different by-products (apple, apricot, peach and tomato) which are worth further examination. the conversion yields of the apple processing by-products are the most promising, and the nearly 100 % conversion of the technological wastes is especially noteworthy. the experiments also show that in the case of apple residues the amount of sugar obtainable by washing is also significant. in these cases significantly better conversions are obtained, when the apple wastes are initially washed with water, which can be explained by product inhibition ({3-glucosidase). apple processing by­ products are promising both in the ethanol and the abe fermentation experiments. the results showed that the previously hydrolysed apple pulp contain no inhibitors that could interfere with or block the activities of the microorganisms. supplementation of the hydrolysate with additional nutrients is not essential for growth and solvent production, however, it accelerates the fermentation process. the strain examined is able to utilise up to 96 % of the sugar extracted during the hydrolysis and during the anaerobic fermentation it is able to produce the desired products acetone, butanol, and ethanol in amounts close to the theoretical yields. yeast ethanol fermentation on the hydrolysates is also possible. and the yields are reasonable (ca. 90 % based on glucose). ... the pomaces of the berries, blackberry, red and black currant, raspberry. and elder were not easily accessible to enzymatic hydrolysis. their conversion values are low~ therefore they cannot be recommended as abe fermentation substrates based on these results despite their potentially high carbohydrate contents. acknowledgement the research fund of the ministry of education (fkfp)~ osterreichische austauschdienst (oad) national research fund of hungary (otka) and rauch hungary ltd. are gratefully acknowledged for their financial support~ and the novo nordisk for the enzyme preparations. references i. dubois m.,. gn..les k. a., hamu..ton j. k .• rebers p. a. and smith f.: anal. chern .• 1956 .• 28. 350 2. gapes j. r., nimcevic d. and friedl a.: applied and environmental microbiology 1996, 62, 32103219 3. gutierrez n. a., maddox i. s., swoboda h., schuster k. c. and gapes j. r.: bioresource technology 1998, 66,263-265 4. hagglund e.: acad. press, new york 5. hayn m., steiner w., klinger r., steinmueller h., sinner m. and esterbauer h.: in: bioconversion of forest and agricultural plant residues. j. saddler, ed., cab international, wallingford-uk., pp. 33-72, 1993 6. johansson t. b., kelly h., reddy a. k., n. and williams r. h .. : 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forest and agricultural plant residues. cab international wallingford-uk, 1993 ' 17. schuster k. c., swoboda h., nimcevic d., thayer r., gapes j. r. and maddox i.: effects of heat shocking and mixed substrate utilisation on the abe fermentation, clostridium v 5th international workshop on regulation of metabolism, genetics and development of the solventand acid forming clostridia, toulouse, france, 25.-27. june 1998 ' 18. tearce f.: a vibig eghajlata: megerett az ido a cselekvesre, wwf fiizetek 13, 1998 19. timell t. e: wood sci. technol.l967, 1, 45-70 20. veinperl i.: examination of different pectinase and cellulase enzymes preparation in proceeding of apple . pulp. phd thesis, faculty of agricultural chemical technology. technical university of budapest, 1990 21. v~et c. e., mignone c. f. and ertola r. j.: btotechnol. lett. 1985.7,4346 22. wiley a. s., johnson m. j., mccoy e. imd peterson w. h.: ind. eng. chern. 1941, 35, 606610 25 23. wisegoles a., tyson s. and johnson d.: biomass feedstock resources and composition. handbook on bioethanol. (chapter.6), 1996 page 21 page 22 page 23 page 24 page 25 page 26 page 27 hungarian journal of industrial chemistry veszprem vol. 30. pp. 193198 (2002) comparative study and modelling of rutin extraction from hyperici herba and hippophaes fructus a. i. galaction and d. cascav al 1 (dept. of biotechnology, faculty of medical bioengineering, university of medicine and pharmacy of iasi, n. gane 30, 6600iasi, romania 1dept. of biochemical engineering, faculty oflndustrial chemistry, technical university of iasi, d. mangeron 71, 6600 iasi, romania) received: july 12, 2002 the study on rutin extraction from autochthonous hyperici herba andhippophaesfructus with methanol, ethanol and!­ propanol at different concentrations, temperatures and duration indicated that the most efficient solvent is !-propanol, its optimum concentration being determined by the amount and type of the natural compounds from the two plants. using the statistical analyzis and a factorial experiment of second order, two mathematical correlations between the rutin extraction degree and the main parameters influencing the process (!-propanol concentration, temperature, duration) have been established. for both extraction systems, the considered variables control the extraction process in a 99.2-99.5% extent, the solvent concentration exhibiting the most imp01tant influence, especially for rutin extraction from hippophaes fructus. keywords: rutin, extraction, methanol, ethanol, 1-propanol, statistical analyzis introduction flavonoids have been generally considered as secondary metabolites) compounds not absolutely essential to the life of individual cells of plants or even to the plant as a whole. these compounds are found in the higher plants like angiosperms, gymnosperms, but also in some green algae, in the bryophytes, in all tracheophytes and in some insects (flavonoids are currently involved in attracting pollination vectors) [1]. these compounds could assume several roles as subtle mediators of complex processes, from plant growth and development until. sparing of easily oxidizable metabolites, broadly effective enzyme inhibitors, and intervention like pesticides or light screens. both of the mentioned characteristics and the reported efficiency of some flavonoids in improving capillary strength and controlling erythrocyte aggregation are of pharmacological interest [1-6]. the structures of these constituents are derived from flavone (2-phenylbenzopyran) or, sometimes, isoflavone (3-phenylbenzopyran). depending on the oxidation extent, as well as on the position and nature of the various substitutes, the flavonoids could be flavonosides~ biflavonosides, chalcones, aurones, isofla~ones, anthocyanosides and 3-, 4-flavonols [6-8]. the presence of active phenolic and carbonyl groups in their molecule determines the variety of pharmacological properties. among them, the maintaining or restoring of normal capillary resistance could be underlined, this property is claimed b~ rutin. rutin is one of the most used flavonoids in the pharmaceutical practice, being an active compound in capillary tonic and vein tonic medicines. which is included in the complex therapy of toxicosis, thrombosis, and atherosclerosis. from chemical point of view, rutin is 4h-1-benzopyran-4-one,3-[[6-0( 6~deoxy-a-l-mannopyranozyl )-ft-d-glucopyrano zyl]oxy]2 (3,4-dihydro:xyphenyl)5,7dihydroxy, or tetrahydro:xyflavonol-5.7.3 ',4 '-ramnoglucozide, a solid, yellow and crystalline substance [7 ,8]. the most common combinations of rutin are with ascorbic acid and dipyridamol. the medical effectiveness of rutin consists in beneficial effects to the capillaries by: a) chelating metals and thus sparing ascorbate from oxidation, b) prolonging epinephrine action by inhibiting o­ methyltransferase, c) stimulating the pituitary-adrenal axis. and contact infonnation: e-mail: galact@mail.dntis.ro; dancasca@ch.tuiasi.ro 194 45 0 70 ~ 77~ /"' ~ 40 ~ 60 0 0 --methanol • ~ 35 ~50 --e-ethanol ~~ '~-1 0) '----..,._ !-propanol ~ 30 0) q) 40 --methanol '"0 c: --e-ethanol c 0 25 0 ~._/?/ u /' ----..,._ !-propanol += 30 ~ 20 0 a:s '.-:;::::; x ....... 20 lu x 15 w ------· 10 0 20 40 60 80 100 0 20 40 60 80 100 concentration,% val. concentration, 0/o val. fig.] influence of nature and solvent concentration on rutin extraction degree from hyperici herba {a) and hippophaesfructus (b) d) reducing the aggregation of erythrocytes and in retarding the loss of fluids from the capillary and lymphatic system under stress condition. rutin can be found in a proportion of 12-20 % in the flower buds of sophora japonica, the classically raw material for industrial production. in smaller amounts, rutin can be also found in fagopyri herba (5-8%), polygoni hydropiperis herba (3.5 % ), hyperici herba and hippophaes fructus (1 ,3, 7 ,8]. because the sophora japonica is not an available raw material, the aim of this paper is the study on rutin extraction from the last two raw vegetable materials which are autochthonous and easily accessible. ' the experiments were carried out in two steps. the former one consists on a comparatively study of rutin extrac~on from hyperici herba and hippophaes fructus, respectively. for this purpose, methanol, ethanol and !­ propanol have been used as solvents. the separation being performed at different alcohol concentrations temperatures and extraction time. ' in second step of experiments, using the statistical analyzis, respectively the factorial experiment of second order, a mathematical model that describs the rutin extraction from hyperici herba and hippophaes fructus with the most efficient solvent was established. the proposed model takes into account the cumulated influences of solvent concentrationt temperature and the duration of extraction process on the rutin extraction degree. experimental part the rutin extraction was carried out in a glass vessel of 0.3 i volume. provided with jacket heated by water maintalped at the prescribed temperature by means of a thermostat. back~flow condenser and two blade stirrers rotated at 300 rpm. rutin was extracted from hyperici herba and hippophaes fructus. each extraction has been carried out using ig dried and finely cutted material and 50 m1 solvent in the first step of experiments three alcohols were used as solvent: methanol, ethanol and !-propanol. the solvent concentration was varied between 10 and 90 % vol.. the extraction temperature was maintained in the domain of 2060 °c for methanol, respectively, 20 70 oc for ethanol and !-propanol. the process duration was of 5 60 minutes. in the second step of the experiments, the correlation between rutin extraction yield and the main factors influencing the extraction process (solvent concentration, temperature and duration) has been established by means of the results obtained using the adequate experimental matrix. the extraction yield, y, was calculated as the ratio between the rutin concentration in the extract phase and the total amount of rutin in the vegetable material. the total amount of rutin for hyperici herba and hippophaes fructus has been determined by total rutin extraction with methanol in a soxhlet extractor during 4 hours. the rutin dosage in the extract phase was made by spectrophotometric method .[8]. results and discussion rutin extraction from hyperici herba and hippophaes fructus the analyzis of the effect of solvent nature and concentration on rutin extraction from the two vegetable materials indicated that in both cases 1propanol is the solvent that offers the highest extraction degree (fig. i). but~ as it can be observed from fig.l~ the optimum concentration of l-propanol depends on the type of used plant. thus, the maximum extraction yield of rutin from hyperici herba was reached for a solvent concentration of 50 % vol.~ respectively 90 % vol. for extraction from hippophaes fructus. this difference could be the result of the difference between the nature and amount of the natural compounds from the two plants. and consequently of the different capacity of 54 ~52 0 30 40 50 60 70 temperature, °c 70 (]) ~ 60 0) (]) '"'0 c: .q 50 0 cts !::; tij 40 195 --methanol -e--ethanol _._ 1-propanol ~ ·---· ·------;;l-• • ----·-----· • 30 40 50 60 70 tern perature, °c fig.2 influence of temperature on rutin extraction degree from hyperici herba (a) and hippophaesfructus (b) 52 ~ 50 0 cd48 cd ..... ~ 46 "c c44 0 :;:; ~ 42 ..... -x 40 w --methanol90% --e-ethanol 70 % -.a.1-propanol50% 38+-~~~~~~~~~~~~~ 0 10 )0 30 40 50 60 time, min. 70 ~ ---· eft 60 cd~ 50 cd "c c 40 0 +:; ~ 30 '--x w 20 0 __...._._.._.::::::::======.. • .~ ~· . ------· ./ --------.-. ...--/i ·; --methanol 90% --ethanol90% _._ 1-propanol 90% ./ 10 20 30 40 50 60 time, min. fig.3 influence of process duration on rutin extraction degree from hyperici herba (a) and hippophaes fructus (b) solvent to wet and soak the vegetable material. owing to the high content of hydrophobic compounds in hippophaes fructus (12-14% wt. glycerides of oleic, palmitic, linolic and linoleic acids) the wetting and the soaking of the vegetable material, which allow the osmosis and diffusion of the active compound from solid phase to solvent, are possible only with concentrated 1-propanol. this conclusion is sustained by the fact that, contrarily to the extraction from hyperici herba, the maximum rutin extraction yield from hippophaes fructus is reached in a concentration level of 90 % vol. for all used solvents, the presence of water reducing the extraction efficiency. the study on temperature effect was carried out for the solvents concentration values that allow to reach the maximum extraction yield and indicates an increase of extraction yield with temperature increase (fig.2). as in earlier experiments, the extraction with 1propanol was the most efficiently, too. using the previous data, the following extraction conditions have been chosen for analyzing the influence of process duration: • hyperici herba: methanol 90 % voi., 60 °c ethanol 70 % vol., 70 °c !-propanol 50 % vol., 70 1,c • hippophaes fructus: methanol 90 % vol., 60 °c ethanol 90 % vol., 60 °c !-propanol 90 % vol.. 60 °c from fig.3 it can be observed that the rutin extraction degree significantly increases in the time domain of 0 20 minutes, indifferent of the studied extraction system, then the increase becoms slower. the extraction of rutin from hippophaes fructus with 90 % vol. !-propanol is the exception, because the extraction degree reaches a high value after 5 minutes from the process beginning, remaining then at a constant level. as it was above mentioned, this variation can be explained by the high capacity of !-propanol to wet and soak the vegetable material, thus intensifying the rutin diffusion to solvent phase. modelling of rutin extraction from hyperici herba and hippophaes fructus the mathematical model that describes the influences of solvent concentration, temperature and extraction 196 table 1 the limits and coding of process variables for rutin extraction variable code variable level -1 0 +1 hyperici herba solvent concentration,% vol. xi 10 30 50 temperature, °c xz 30 50 70 duration, min. x3 5 10 15 hippophaes fructus solvent concentration, % vol. xt 10 50 90 temperature, °c x2 20 40 60 duration, min. x3 5 10 15 table 2 the experimental matrix no. exp. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. -1 1 -1 -1 1 -1 1 -1 0 0 0 0 0 0 0 0 -1 -1 1 1 -1 -1 1 0 0 -1 1 0 0 0 0 0 -1 -1 -1 -1 1 1 1 1 0 0 0 0 -1 0 0 0 step 20 20 5 40 20 5 dumtion on rutin extraction efficiency was established by statistical analyzis. in this purpose, a factorial experiment of second order has been used. thus, the real values of the process variables were chosen arbitrarily, their limits and coding are given in table 1. in order to settle the correlation between the rutin extraction degree and the above mentioned parameters the following model of polynomial equation type is proposed: y = b0 + b1 • x1 + b2 • x2 + b3 • x3 + +b12 ·x1 ·x2 +b13 ·x1 ·x3 +b23 ·x2 ·x3 + (l) + bn · x~ + b22 • xi + b33 ·xi where bo, ... , b33 are the regression coefficients. the plan of the factorial experiment of second order is given in table 2. because the highest rutin extraction yield was obtained for 1 ~propanol, both the extraction from hyperici herba and hippophalis fructus were carried out using this solvent. by means of the obtained data, the table 3 the values of regression coefficients for rutin extraction from hyperici herba regression coefficient value bo 46.93 bl 11.67 bz 3.58 b3 1.15 bl2 1.11 bl3 0.3875 b23 0.0625 bu -8.07 b22 -0.65 b33 -2.19 regression coefficients bj were calculated using the following relations [9]: 15 l,xji·r: b. =..::.i=_::.i __ j 15 l,xji2 i=l (2) i = 1. .. 15 number of experiments, j = 1...3 number of variables. initially the rutin extraction from hyperici herba was mathematically modelled. the obtained values of regression coefficients are listed in table 3. for checking the normal results obtained in the program center the q test was used. thus, the calculated q value is [9]: (3) where: a1 the uncertain value (47.1 %); az the closest to the uncertain value ( 46.9 % ); a the amplitude (difference between the most distant values, 0.3). for a certain threshold of 0.05, q = 0.77 was found in literature [9]. since the calculated value of 0.66 is lower than the tabulated one, it could be concluded that the uncertain value of 47.1 % is also a normal value. consequently, all of the three obtained values for rutin extraction yields were taken in calculation. hence, the regression equation can be written as: y=46.93+1l.67·x1 +3.58·x2 + +1.l5·x3 +l.ll·x1 ·x2 +0.39·x1 ·x3 + (4) +0.062·x2 ·x3 -8.07 ·xj -0.65·xi -2.19·x; the experimental and calculated values of the rutin extraction yields from hyperici herba were tabulated in table4. table 4 the experimental, yexp• and calculated values, ycalc• for rutin extraction yield from hyperici herba no. exp. yexp•% ycalco% 1. 21.6 21.2 2. 42.1 41.82 3. 26 25.6 4. 51 50.8 5. 22.9 22.9 6. 45 44.8 7. 27.6 28 8. 54.1 54 9. 23.6 27.2 10. 46.2 50.5 11. 42.8 42.7 12. 51.5 49.9 13. 43.3 43.6 14. 45.9 45.89 15. 46.9 16. 47.1 46.93 17. 46.8 the limits between which these values, calculated with the regression equation, oscillate around the experimental value are determined with the relation [9]: (5) the standard deviation sy/ was calculated using the following relationship [9]: 8 l ~xp; ycalc; 1 i=l =0,202 n-(k+l) (6) where n is the number of experiments and k the number of variables taken into account. -the t values are to be found in the tables for student distribution [9], for a confidence threshold of 0.05 and 15 experiments, namely: t=2.131 and ycalci = yexp; ± 0.95 • % (7) the individual influence of the factors under consideration is estimated by means of the value of the correlation coefficient, ryx [9]: (8) which describes the nature of dependence between the process variables and the extraction yield. the detennination coefficient, which represents the square of correlation coefficient, indicates the fraction of rutin extraction yield that can be explained by variable xi variation. in this case7 the calculated values of determination coefficient are: r~ = 0.898 rixz = 0.083 rix, = 0.0 ll 197 table 5 the values of regression coefficients for rutin extraction from hippophaes fructus regression coefficient value bo 24.18 bl 26.15 bz 3.10 b3 0.68 bl2 1.90 bl3 0.35 bz3 0.225 bu 11.40 bzz 3.43 b33 4.16 table 6 the experimental, yexp• and calculated values, ycalc• for rutin extraction yield from hippophaes fructus no. exp. yexp•% ycalc•% 1. 15.5 15.7 2. 63.3 63.5 3. 18.1 17.8 4. 72.8 73.0 5. 16.1 15.9 6. 64.6 64.8 7. 18.9 18.8 8. 75.7 75.6 9. 17.7 16.4 10. 71.4 68.7 11. 28.9 26.5 12. 33.9 32.7 13 32 30.7 14 33.2 33.02 15 24.3 16 24.1 24.18 17 24.15 these values suggest that the considered parameters influence the efficiency of rutin extraction from hyperici herba in a 99.2 % extent, the solvent concentration is the most important factor. the rest of 0.8 % can be attributed to the effect of other factors. namely: ratio between alcohol and plant quantityl mixing intensity. the mathematical modeling of rutin extraction process from hippophaes fructus with 1-propanol was similarly established, using the previous statistical analyzis method. therefore, the real values of the process variables and their limits and coding are given in table 1 and the experimental matrix in table 2. the regression coefficients bj have been calculated using the relations (2), their values are given in tables. for these e1.periments, q = 0. 77 was found. this value is inferior to those given in literature for a certain threshold of 0.05 (q = 0.77) [9]. consequently, it was confinned the accuracy of the used experimental method. 198 fig.4 surface given by eq.(4) plotted for x3 = 0 thus, the correlation between rutin extraction yield from hippophaes fructus and the main parameters that influence the process (solvent concentration, temperature and extraction duration) can be written as follows: y=24.18+26.15·x1 +3.10·x2 + +0.68·x3 +1.90·x1 ·x2 +0.35·x1 ·x3 + (9) +0.225·x2 ·x3 +11.40·xf +3.43·xi +4.16-x; the experimental and calculated values for rutin extraction yield from hippophaes fructus were tabulated in table6. the limits, between the calculated values oscillate around the experimental value~ are: (10) the standard deviation syx2 is 0.0775 the values of determination coefficient for the considered extraction system are: r~, =0.980 r~~ =0.014 in this case, the considered parameters influence the efficiency of rutin extraction from hippophaes fructus in a 99.46% extent, the solvent concentration exhibiting a stronger influence compared with the extraction from hyperici herba. the rest of 0.54 % could be attributed to the effect of the secondary factors earlier mentioned. the graphical representation of the obtained regression eqs.(4) and (9) are given in figs.4 and 5~ for a constant level of process duration (x3). conclusions the experimental results of the study on rutin extraction from h,}perici herba and hippophaes fructus indicated that the most efficient solvent is l-propanol, fig.5 surface given by eq.(9) plotted for x3 = 0 the amount and type of the natural compounds from the two plants determining the concentration of used solvent. by means of the statistical analyzis and using a factorial experiment of second order, the rutin extraction with 1-propanol from the two plants was modeled. thus, two mathematical correlations between the extraction degree and the main parameters influencing the rutin extraction (solvent concentration, temperature, duration) have been established. for both cases, the considered variables control the extraction process in a 99.2 99.5% extent the solvent concentration exhibiting the most important influence, especially for rutin extraction from hippophaes fmctus. references 1. bu'lock j. d.: the biosynthesis of natural products an introduction to secondary metabolism, mcgraw-hill ltd., london, pp. 345352, 1965 2. brolis m.: j. chromatography, 1998,825,9-16 3. hassan h. n. a.: j. pharm. biomed. anal., 1999, 20,315-320 4. swatsitang p.: anal. chim. acta, 2000,417,231240 5. toker g.: j. pharm. biomed. anal., 2001, 26, 111121 6. escarpa a. and gonzalez m. c.: anal. chim. acta, 200 i, 427, 119-127 7. mmca s. s.: j.serb.chem.soc., 2001, 66(3), 205211 8. oniscu c., alexandrescu g., holerca m. and holerca c.: rev. chim.,l993, 44(9), 54-61 9. balaban c.: experimental design and analysis of experimental data, e. a., bucharest, pp. 94, 1993 page 195 page 196 page 197 page 198 page 199 page 200 untitled hungarian journal of industry and chemistry vol. 52(1) pp. 71–77 (2024) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2024-09 formaldehyde resin as a solid fuel and activated carbon azrul nurfaiz mohd faizal1 and muhammad abbas ahmad zaini1,2* 1 faculty of chemical & energy engineering, universiti teknologi malaysia (utm), johor bahru, johor state, 81310, malaysia 2 centre of lipids engineering and applied research (clear), ibnu sina institute for scientific and industrial research (isi-sir), utm, johor bahru, johor state, 81310, malaysia this work was aimed to assess the potential of formaldehyde resin residue as a solid fuel and activated carbon. the resin materials were characterized in terms of calorific value, elemental composition, thermal stability, specific surface area, surface side groups, flame retardancy, flue gas and the toxicity characteristic leaching procedure (tclp). meanwhile, the hardened resin was chemically activated using potassium hydroxide and phosphoric acid to remove methylene blue. the tclp shows that resins are stable with minimal leaching of minerals. the resins are composed primarily of carbon with 3.1 % ash content with the high calorific values. the koh-activated carbon exhibits a maximum dye adsorption capacity of 388 mg/g, surpassing that of h3po4-activated carbon by only 21.2 mg/g. the analysis of hardened resins has revealed its versatility as a solid fuel and activated carbon, thereby supporting sustainability efforts. keywords: activated carbon, calorific value, formaldehyde resin, solid fuel 1. introduction formaldehyde naturally exists as a colorless and flammable gas with a strong smell as well as a boiling point of -19 °c. it is highly soluble in water and commercially available at a concentration of 36 %. nowadays, solutions of formaldehyde are widely used in making resins as adhesives, paints, lacquers and coatings, essential for manufacturing composite and engineered wood products of household furnishings and structures [1]. in these manufacturing processes, the production of by-products is typically inevitable. one of the most challenging waste management issues concerns the handling of formaldehyde (polymer) resin residue, a byproduct of these processes. the material is normally classified as scheduled waste (sw 320) since formaldehyde may remain in the residue, necessitating special disposal by incineration [2]. as the environment worldwide is becoming more sustainable, potential utilizations of this by-product are sought to stimulate a circular economy via a zero waste strategy. therefore, the present work sought to investigate the physicochemical characteristics of formaldehyde resin residue as a solid fuel and activated carbon, hopefully leading to broad applications in briquette technology and pollution control. received: 8 feb 2024; revised: 26 feb 2024; accepted: 29 feb 2024 *correspondence: abbas@cheme.utm.my 2. experimental two formaldehyde resin materials, namely film resin and hardened resin, were supplied by sf-pg, malaysia. methylene blue, potassium hydroxide and phosphoric acid were purchased from hmbg chemicals (germany), all of which are of analytical grade. 2.1. physicochemical characteristics the calorific value was measured using a bomb calorimeter (ika c3000) and calculated based on the rise in temperature and the known heat capacity of the calorimeter [3]. the elemental composition of carbon, hydrogen, nitrogen and sulfur in resin materials was measured by an elementar vario micro cube (germany). the hardened resin was dried in an oven at 110 °c for 4 h to determine the moisture content. the thermal stability and ash content were determined by heating the resin materials at 300 and 850 °c in a muffle furnace for 2 to 24 h before the changes in weight were recorded [4]. the thermal decomposition profiles of resin materials were obtained using a thermogravimetric analyzer (perkinelmer tga 4000) under a flow of n2 at a rate of 10 ºc/min from room temperature to 900 ºc. https://doi.org/10.33927/hjic-2024-09 mailto:abbas@cheme.utm.my faizal and zaini hungarian journal of industry and chemistry 72 the resins materials were scanned for surface functional groups using a fourier transform infrared spectrometer (spectrum one) from 4000 to 400 cm-1 [5]. the toxicity characteristic leaching procedure (tclp) is a chemical technique to identify hazardous elements present in a material. first, the sample was oven-dried at 60 °c and ground to pass through a 9.5 mm sieve. the extraction solution was determined based on the ph. 1.5 g of material was weighed and mixed with 30 ml of extraction fluid. the mixture was agitated for 18 ± 2 h before filtering the extract and preserving it at ph < 2 by adding drops of concentrated hno3 prior to taking icp measurements [6]. 2.2. activated carbon and performance the hardened resin was subjected to chemical activation to evaluate its viability as a source of activated carbon for treating dye wastewater. two commonly used activators, namely potassium hydroxide (koh) and phosphoric acid (h3po4), were employed at a fixed mass ratio of 1:1. activation was performed under an anoxic environment in a muffle furnace at 600 °c for 2 h. the activated carbon was characterized for textural properties using a micromeritics tristar ii plus at 77 k, the temperature of liquid n2. the brunauer-emmettteller (bet) method was used to compute the specific area, mesopore volume and microporosity. the performance of activated carbon was evaluated by the adsorption of methylene blue. 50 mg of activated carbon was added to 50 ml of methylene blue solution at varying concentrations before being allowed to equilibrate over 5 days. afterwards, the residual concentration was measured using a visible spectrophotometer at a wavelength of 600 nm. the amount of dye adsorbed was calculated by a mass balance. 2.3. flame retardancy and flue gas analysis the resin materials were exposed to a direct fire source for 44 s and the images of flame retardancy captured using a photron fastcam mini ux50 high-speed camera. flue gas analysis was carried out using a testo 350 flue gas analyzer. the resin material was added in a muffle furnace heated under anoxic conditions at 428 °c. 3. results and discussion 3.1. physicochemical characteristics the calorific values of resin materials are summarized in table 1, which range from 23.6 to 29.3 mj/kg, comparable with typical solid fuels such as anthracite coal and dried firewood with values of 32.5 and 21.7 mj/kg, respectively. in general, the calorific value increased following heat treatment at 300 °c with some weight loss, indicating the removal of light volatiles (oxygen, hydrogen, etc.). at which point, the carbon content increased, thereby increasing their energy content. adding h3po4 as a binder (at 10% by weight) decreased the calorific value. a suitable binder containing a sufficient amount of carbon that grips strongly could be sought to maintain the calorific value. a considerable weight loss was recorded when the resin materials were heated at high temperatures. the film resin exhibited a greater weight loss due to its brittle structure and highly exposed area compared to the rigid structure of hardened resin. at 300 °c, the weight loss was mainly due to light volatiles, while at 850 °c, was due to fixed carbon and heavy volatiles. the hardened resin is thermally stable with a yield of 12% at 850 °c, suggesting the presence of carbon black. the ash content for both resin samples was 2% after being heated at 850 °c for 24 h. images of the ash are shown in figure 1 and its reddish color indicates that it is rich in iron (fe). analyzing the solubility of hardened resin in solutions helps to determine its chemical interactions as well as make informed decisions regarding environmental and waste management practices [7]. the moisture content of hardened resin is 7.5%, which is stable in water with no significant weight loss. nonetheless, some weight loss was detected in koh (4.3%) and h3po4 (8.2%) solutions during the impregnation process, showing that the light volatiles are soluble in acids and alkalis, thereby vaporizing with water at 110 °c. however, these proportions are relatively small when compared to its moisture content. table 1: calorific values of resin materials material calorific value (mj/kg) hardened resin 23.6 film resin 23.7 heat-treated hardened resin (300 °c) 28.1 heat-treated film resin (300 °c) 29.3 with h3po4 binder hardened resin 20.8 film resin 20.0 heat-treated hardened resin 23.8 heat-treated film resin 22.2 (a) (b) figure 1: images of the ash from (a) hardened resin and (b) film resin formaldehyde resin 52(1) pp. 71–77 (2024) 73 the trend in the weight loss of resin materials when heated is shown in figure 2. the as-received hardened resin exhibited a gradual weight loss as the temperature increased and the remaining weight was 40% of its initial value at 900 °c. several dtg peaks at 200 °c are attributed to light volatiles, while those between 430 and 500 °c correspond to heavy volatiles [8]. the heattreated sample is thermally stable up to 430 °c before declining to 50% by 900 °c. using a simple mass balance, the proportion of light volatiles in hardened resin is about 10%. a sharp peak at 487 °c was attributed to the release of heavy volatiles. the as-received resin and activated samples exhibit a common peak between 80 and 100 °c attributed to the release of moisture. the moisture content of the koh-activated carbon is greater because of its well-developed porous structure that entraps more moisture from the surroundings [9]. likewise, it is more susceptible to degrade at high temperatures because of the collapse of its porous structure. from figure 2c, the mass of the as-received film resin gradually decreases with a yield of 29% at 900 °c. three dtg peaks at 90, 320 and 400-500 °c denote the release of moisture as well as light and heavy volatiles, respectively [10]. furthermore, no peaks associated with light volatiles are found regarding the heat-treated resin which exhibited a yield of 46% at 900 °c. the proportion of light volatiles in film resin is estimated to be 17%. the elemental compositions measured are summarized in table 2. both as-received resin materials contain high carbon contents of about 60% which increased following heat treatment at 300 °c, suggesting the release of light volatiles such as co and co2 as a result of combustion [11]. accordingly, the calorific value increased. for the samples of activated carbon, the liberation of hydrogen is prevalent, implying the creation of aromatic-graphitic structures. the ftir spectra of resin materials are shown in figure 3. all the samples demonstrate similar peaks that correspond to surface functionalities, even after heat treatment (300 °c) and activation (600 °c). the liberation of light volatiles during heat treatment as well as light and heavy ones during activation does not significantly influence the presence of functional groups. except for koh-activated carbon, the spectra become simpler as the peak intensities reduce, indicating partial decomposition of functional groups during the activation process [12]. the as-received hardened resin was originally in liquid form but solidified as a result of gelation and as it aged, resembling the resorcinol-formaldehyde (rf) carbon gel process [13]. resorcinol reacts with formaldehyde to form a hierarchical porous network composed of aggregated particles in the presence of the catalyst k2co3. this reaction is irreversible and the solid formed is thermally stable. the hardened formaldehyde resin used in this work contains both light and heavy volatiles, moreover, can be easily activated using koh to form porous materials unlike rf carbon gel [13]. the results regarding the leaching of metal elements from hardened resin evaluated by tclp and xrf are summarized in table 3. the metal elements measured by xrf in the hardened resin and the derived activated carbons are consistent. all samples are rich in fe displaying elemental compositions of about 90%, except for h3po4-activated carbon that contains 76.7% fe and a (a) (b) (c) figure 2: (a) tga and (b) dtg profiles of hardened resin materials as well as (c) tga and dtg profiles of film resin materials table 2: elemental composition of resin materials n c h s o* hardened resin 1.1 60.8 5.2 0.3 32.6 hardened resin (pre-treatment) 0.6 66.2 3.9 0.3 29.0 film resin 0.3 57.8 5.7 0.3 35.9 film resin (pre-treatment) 0.4 73.7 4.5 0.5 20.9 koh-activated carbon 0.3 60.2 1.0 0.2 38.3 h3po4-activated carbon 0.5 64.7 1.5 0.2 33.1 *calculated by difference faizal and zaini hungarian journal of industry and chemistry 74 considerable proportion of p deposits, that is, 12.9%, following the use of an activator. all the metals in these samples are naturally occurring or originate from substances used in their production. according to tclp analysis, the hardened resin is stable as practically no metals leached out from the solid matrix, only 0.01%. 3.2. activated carbon and the adsorption of dyes the textural characteristics of types of activated carbon derived from hardened resin and other sources from the literature are summarized in table 4 [13]-[14]. the burnout of organic components from resin during pyrolysis resulted in a reduction in mass to 46.8% for koh-activated carbon and 35.7% for h3po4-activated carbon, usually resulting in a porous structure with altered surface chemistry [13]. the koh-activated carbon exhibits a greater microporosity of 84%, signifying the effectiveness of koh as a strong dehydrating agent for pore formation. images of the activated carbon of hardened resin are presented in figure 4. the effects of pore formation, namely surface cracks, crevices and multiple open pores, are evident in koh-activated carbon, while the development of pore channels is not apparent in h3po4activated carbon. (a) (b) figure 3: the ftir spectra of (a) film resin and (b) hardened resin materials table 3: metal elements in hardened resin materials determined by xrf and their leaching characteristics (tclp) element (ppm) kohactivated h3po4activated hardened resin tclp (hardened resin) al 2700 11200 13200 108 si 15400 67900 33800 134 s 2030 623 2530 6.7 cl 86 76 332 0 k 12700 0 2050 0 ca 32000 972 15200 69.4 ti 3820 1480 12400 0 fe 905000 767000 882000 0 zn 8160 4050 1450 0 sr 87 0 0 0 zr 7020 7550 10400 587 sn 28 46 52 0 eu 1380 0 481 0 gd 1040 0 0 0 tb 6420 9020 7910 0 p 0 129000 0 0 pb 0 170 0 0 rn 0 42 0 0 as 0 0 43.4 0 rb 0 0 181 0 nb 0 0 46.7 0 au 0 0 284 0 table 4: textural characteristics of the different sources of activated carbon kohactivated carbon h3po4activated carbon rf carbon gel [13] commercial ac [14] yield (%) 46.8 35.7 ph 8.8 4.8 8.8 bet surface area (m2/g) 661 140 433 909 methylene blue capacity (mg/g) 388 21.2 135 344 micropore area (m2/g) 626 119 358 748 mesopore area (m2/g) 35.2 21.3 75 161 micropore volume (cm3/g) 0.302 0.06 0.17 0.347 mesopore volume (cm3/g) 0.056 0.035 0.09 0.095 total pore volume (cm3/g) 0.358 0.095 0.26 0.442 average pore diameter (nm) 2.2 2.7 2.4 1.9 micropore content (%) 84 63 65 79 formaldehyde resin 52(1) pp. 71–77 (2024) 75 the initial concentration is one of the critical parameters in the dye adsorption process. the adsorption isotherm of methylene blue onto the activated carbon of hardened resins is shown in figure 5. koh-activated carbon demonstrates a strong intensity (steep gradient) at low concentrations, signifying a favorable degree of dye removal. its higher surface area of 661 m2/g offers more active sites to interact with dye molecules. accordingly, the maximum capacity of 388 mg/g for koh-activated carbon is greater than 21 mg/g for h3po4-activated carbon, moreover, the dye adsorption of koh-activated carbon is superior when compared to rf carbon gel [13] and commercial activated carbon [14]. 3.3. flame retardancy and flue gas analysis the resin materials were exposed to a direct fire source for 44 s. images captured using a photron fastcam mini ux50 high speed camera are shown in figure 6. 14.9 mg of hardened resin was used and a reduction in mass of 13% recorded after heating with no significant changes in its physical appearance. these findings are supported by the tga profiles at 300 °c in figure 2. meanwhile, the reduction of mass regarding the film resin of 64% was bigger due to the glowing fire which readily ignites and exhibits a poor flame retardancy due to its sheet-like texture, exposing it more to the heat source. a flue gas analyzer measures and analyzes the composition of gases emitted following combustion, which is essential for monitoring and optimizing the efficiency of combustion to ensure full compliance with environmental regulations [15]-[16]. the results are summarized in table 5. the concentration of co is high due to an insufficient amount of oxygen for complete combustion inside the furnace. the presence of so2 in flue gas is likely because the resin material originally contains 0.3% sulfur (table 2). if applied as a solid fuel, a scrubber can be introduced before exhaust gas from burning the formaldehyde resin is released into the surroundings. the metal elements in flue gas are presented in table 6. although iron is a major mineral in resin materials, only trace amounts of it and other metals are detected in flue gas, implying the stability of metals in the resin matrix, which is consistent with the findings from xrf and tclp in table 3. (a) (b) figure 4: images of (a) h3po4-activated carbon and (b) koh-activated carbon figure 5: methylene blue adsorption onto the activated carbon of hardened resins 0 50 100 150 200 250 300 350 400 450 0 100 200 300 c a p a ci ty ( m g /g ) equilibrium concentration (mg/l) koh activated resin h3po4 activated resin (a) (b) (c) (d) figure 6: flame retardancy images of hardened resin ((a) and (b)) and film resin ((c) and (d)); ((a) and (c)) and ((b) and (d)) are images taken before and after heating, respectively table 5: flue gas composition flue gas (ppm) film resin hardened resin co 13678 12476 no 12 6 no2 1.7 0.3 nox 1.7 6.3 so2 245 170 faizal and zaini hungarian journal of industry and chemistry 76 4. conclusions the tclp test shows that the hardened resin is a stable material and the metals it contains hardly leach from the solid matrix, moreover, are hardly found in the exhaust stream according to the analysis of the flue gas. the calorific value improves as the carbon content increases following facile heat treatment at 300 °c. when compared with the film resin, the hardened counterpart exhibits promising characteristics as a solid fuel with an energy content of 23.6 mj/kg as well as activated carbon with a specific surface area of 661 m2/g and dye capacity of 388 mg/g. the valorization of formaldehyde resin residue will improve waste management, thereby rendering the environment more sustainable. acknowledgement this research was supported by the utm zamalah scholarship no. 00n08. references [1] kristak, l.; antov, p.; bekhta, p.; lubis, m.a.r.; iswanto, a.h.; reh, r.; sedliacik, j.; savov, v.; taghiyari, h.r.; papadopoulos, a.n.; pizzi, a.; hejna, a.: recent progress in ultra-low formaldehyde emitting adhesive systems and formaldehyde scavengers in wood-based panels: a review, wood mater. sci. eng., 2023, 18(2), 763– 782, doi: 10.1080/17480272.2022.2056080 [2] noor artika, h.; yusof, m.z.; nor faiza, m.t.: an overview of scheduled wastes management in malaysia, j. waste biomass manage., 2019, 1(2), 1–4, doi: 10.26480/jwbm.02.2019.01.04 [3] hossain, n.; zaini, j.; mahlia, t.m.i.; azad, a.k.: elemental, morphological and thermal analysis of mixed microalgae species from drain water, renew. energy, 2019, 131, 617–624, doi: 10.1016/j.renene.2018.07.082 [4] ojo, a.; enujiugha, v.n.; ayo-omogie, h.n.; abiodun, o.a.: comparative study on the effect of thaumatococcus daniellii (benn) benth sweetener on the physicochemical and sensory properties of sorghum based kunun-zaki drink, j. appl. sci. environ. manage., 2017, 21(6), 1073–1078, doi: 10.4314/jasem.v21i6.13 [5] faizal, a.n.m.; halim, m.h.a.; zaini, m.a.a.: kinetics and dynamic adsorption of methylene blue by co2-activated resorcinol formaldehyde carbon gels, carbon lett., 2019, 29(4), 319–326, doi: 10.1007/s42823-019-00046-8 [6] chen, c.-w.; chen, c.-f.; hung, c.-m.; dong, c.-d.: evaluating the leachable metals in kaohsiung harbor sediment using the toxicity characteristic leaching procedure (tclp), desalin. water treat., 2015, 54(4-5), 1260–1269, doi: 10.1080/19443994.2014.950337 [7] nicholson, s.r.; rorrer, j. e.; singh, a.; konev, m.o.; rorrer, n.a.; carpenter, a.c.; jacobsen, a.j.; román-leshkov, y.; beckham, g.t.: the critical role of process analysis in chemical recycling and upcycling of waste plastics, annu. rev. chem. biomol. eng., 2022, 13, 301–324, doi: 10.1146/annurev-chembioeng-100521-085846 [8] wang, z.; burra, k.g.; lei, t.; gupta, a.k.: copyrolysis of waste plastic and solid biomass for synergistic production of biofuels and chemicals a review, prog. energy combust. sci., 2021, 84, 100899, doi: 10.1016/j.pecs.2020.100899 [9] gan, y.x.: activated carbon from biomass sustainable sources, c – j. carb. res., 2021, 7(2), 39, doi: 10.3390/c7020039 [10] escalante, j.; chen, w.-h.; tabatabaei, m.; hoang, a.t.; kwon, e.e.; andrew-lin, k.-y.; saravanakumar, a.: pyrolysis of lignocellulosic, algal, plastic, and other biomass wastes for biofuel production and circular bioeconomy: a review of thermogravimetric analysis (tga) approach, renew. sust. energy rev., 2022, 169, 112914, doi: 10.1016/j.rser.2022.112914 [11] ren, s.-j.; wang, c.-p.; xiao, y.; deng, j.; tian, y.; song, j.-j.; cheng, x.-j.; sun, g.-f.: thermal properties of coal during low temperature oxidation using a grey correlation method, fuel, 2020, 260, 116287, doi: 10.1016/j.fuel.2019.116287 [12] heidarinejad, z.; rahmanian, o.; fazlzadeh, m.; heidari, m.: enhancement of methylene blue adsorption onto activated carbon prepared from date press cake by low frequency ultrasound, j. mol. liq., 2018, 264, 591–599, doi: 10.1016/j.molliq.2018.05.100 [13] mohd faizal, a.n.; ahmad zaini, m.a.: dyes adsorption properties of koh-activated resorcinolformaldehyde carbon gels -kinetic, isotherm and dynamic studies, toxin rev., 2022, 41(1), 186–197, doi: 10.1080/15569543.2020.1857773 [14] zaini, m.a.a.; mohamad, n.: activated charcoal for oral medicinal purposes: is it really activated?, j. appl. pharm. sci., 2015, 5(10), 157–159, doi: 10.7324/japs.2015.501028 table 6: metal elements in flue gas metal (mg/m3) film resin hardened resin aluminum 0.43 0.17 calcium 15.34 17.17 copper 1.37 3.18 iron 0.32 0.42 lead 0.09 0.11 magnesium 1.26 1.31 nickel 0.09 0.05 zinc 1.54 2.77 https://doi.org/10.1080/17480272.2022.2056080 https://doi.org/10.26480/jwbm.02.2019.01.04 https://doi.org/10.1016/j.renene.2018.07.082 https://doi.org/10.4314/jasem.v21i6.13 https://doi.org/10.1007/s42823-019-00046-8 https://doi.org/10.1080/19443994.2014.950337 https://doi.org/10.1146/annurev-chembioeng-100521-085846 https://doi.org/10.1016/j.pecs.2020.100899 https://doi.org/10.3390/c7020039 https://doi.org/10.1016/j.rser.2022.112914 https://doi.org/10.1016/j.fuel.2019.116287 https://doi.org/10.1016/j.molliq.2018.05.100 https://doi.org/10.1080/15569543.2020.1857773 https://doi.org/10.7324/japs.2015.501028 formaldehyde resin 52(1) pp. 71–77 (2024) 77 [15] kákonyi, m.; bárkányi, á.; chován, t.; németh, s.: modelling of the pyrolysis zone of a downdraft gasification reactor, hung. j. ind. chem., 2021, 49(1), 71–76, doi: 10.33927/hjic-2021-09 [16] singh, h.m.; kothari, r.; gupta, r.; tyagi, v.v.: bio-fixation of flue gas from thermal power plants with algal biomass: overview and research perspectives, j. environ. manage., 2019, 245, 519– 539, doi: 10.1016/j.jenvman.2019.01.043 https://doi.org/10.33927/hjic-2021-09 https://doi.org/10.1016/j.jenvman.2019.01.043 hungarian journal of industrial chemistry veszprem vol. 29. pp. 53-56 (2001) synthesis of iminodiacetic acid in a cascade reactor l. gulyas, g. deak\ s. kejd, r. horvath andm. zsuga1 (department of chemical engineering, faculty of technical engineering, university of debrecen p.o. box 40, debrecen h-4028 hungary 1department of applied chemistry, university ofdebrecen p.o. box 1, debrecen 10, h-4010 hungary) received; december 28, 2000; revised: april 9, 2001 the present paper deals with the modernization of the manufacturing of iminodiacetic acid, enhancing the conversion and the reactor-intensity, as well as with the elaboration of a procedure permitting continuous production. during the investigation of the industrial synthesis of iminodiacetic acid our important recognition is that glycine, produced together with the desired iminodiacetic acid, can be converted with monochloroacetic acid to iminodiacetic acid after removal of the excess of ammonia from the reaction mixture. for utilization of glycine, an industrial procedure has been elaborated. according to this, production of iminodiacetic acid is carried out in a quadrate cascade reactor, so that the reaction mixture leaving the second reactor element is freed from annnonia, concentrated, and then reacted with an equivalent of monochloroacetic acid calculated on the basis of the glycine-content. in this way, iminodiacetic acid is obtained in the laboratory-scale experimental reactor with a 91 % yield, based on monochloroacetic acid. calculations for the optimization of the reactor-cascade are also presented. these clearly prove that the required new investment is reimbursed upon manufacturing on an industrial scale. keywords: iminodiacetic acid, reactor-cascade, optimization. introduction the industrial production of iminodiacetic acid can be realized in two ways. one is the reaction which proceeds between monochloroacetic acid, ammonia and calcium hydroxide in water solution, which ensures 6065 % of the product, but leaves ca. 20-27 % of glycine in the system, thus decreasing the effective conversion of monochloroacetic acid [1]. the second route is the reaction of glycine with monochloroacetic acid. according to our investigations, for reactor­ technological reasons the latter reaction could be the more convenient choice for production of irninodiacetic acid. namely, in this system the effective conversion of monochloroacetic acid is higher. as the whole process, following the reaction between monochloroacetic acid, ammonia and calcium hydroxide in water, ammonia should be removed from the system, and then glycine should be reacted with monochloroacetic acid, to be introduced into the system, to produce a further amount of iminodiacetic acid. during this latter reaction no damage of the formerly produced iminodiacetic acid occurs. the present paper deals with the modernization of the manufacturing of iminodiacetic acid, enhancing the conversion and the reactor-intensity, as well as with the elaboration of a procedure permitting continuous production. experimental materials monochloroacetic acid, ammonia solution and ca(ohh were purchased from aldrich (germany) and were used as received. instruments the concentration of imda of the solutions was determined with a beckman acta m iv. spectrophotometer. the cr ion concentration of the solution was determined with an o'p-c1~7u3-d type chloride-ion selective electrode (radelkis, budapest, hungary). 54 the intensity of the spot of glycine and iminodiacetic acid on the tlc plates was determined at 510 nm with a cs-20 type videodenzitometer (shimadzu, japan) thin layer chromatography (tlc) the quantitative determination of glycine (rp0.56) and iminodiacetic acid (rp0.85) was performed on fixion-50x8-type cation-exchange thin-layer plates using citrate buffer (ph=3.28) as the mobil phase and and phenylalanine (rp0.14) as the internal standard. the spots were visualized with ninhydrin. results and discussions investigation of the formation ofiminodiacetic acid in a laboratory cascade reactor the reaction was carried out in a quadrate cascade reactor built up from elements of equal volume. a schematic line diagram of the reactor is depicted in figure 1. n2 fig. 1 laboratory cascade reactor iminodiacetic acid (imda) and (gly) glycine is produced in the first two elements of the reactor cascade in the reaction of monochloroacetic acid (mca) ammonia and calcium hydroxide in water solution. as the increase of the concentration is favoured, this reaction is carried out in a relatively concentrated solution, containing 2 molefdm3 of the calcium salt of monochloroacetic acid and 8 mole/dm3 of ammonia. such a large concentration of ammonia was selected to avoid the formation of glycolic acid. concerning the reaction rates and the rate constants in this system, the following cascade model can be concluded for the frrst two elements of the reactor­ cascade [1-5]: (2) where tn in equations (1) and (2) means the average residence time of the reactants in the first and the second elements of the cascade. cmca and cjmda represent the concentration ofmca and imda, and the 0 subscript means the initial concentration of the materials. with this mathematical model one can calculate that the conversion of monochloroacetic acid is almost complete at 1;.1 = 190 min average resi+dence time at 60 °c. in the reaction mixture leaving the second element of the cascade the conversion of monochloroacetic acid into iminodiacetic acid is 67 % and into glycine is 31 %. when the glycine-content of the mixture is utilized by the discussed subsequent conversion, the effective conversion of monochloroacetic acid into iminodiacetic acid can be enhanced. this mixture, possessing a high ammonia concentration, is led to a desorber kept at 105 °c, and freed from ammonia to ensure a 10-15 % increase in the concentration. as previous experimental data have shown, the conversion into iminodiacetic acid can be raised by increasing the concentration of glycine (and at the same time, each of the proportion of formation of glycolic acid and the reaction time is decreasing), an amount of concentrated aqueous solution of the calcium salt of monochloroacetic acid equal with the glycine­ content is added to the mixture, which has been previously freed from ammonia. the resulting system consisting of monochloroacetic acid, calcium hydroxide, glycine and water is allowed to react in the second two elements of the reactor cascade, and the changes in concentration can be described by the following cascade model [2-5]: (3) ( ) 2 cgly 1 co,gly = 1 + k21 . cgly. ti2 (4) where 4z means the average residence time of the reactants in the third and fourth elements of the reactor cascade and caly is the concentration of glycine. in these experiments the conversion of the residual glycine is 82 %, and the overall yield of iminodiacetic acid is 91 %, based on monochloroacetic acid. from this mixture the crystalline hydrochloric acid salt of iminodiacetic acid is isolated in 86% yield, which is better by 26-30 % than that of the currently employed industrial process. this value of conversion may be further enhanced by optimization of certain technological parameters, including the flow-rate, administration of the reactants, the reaction time and concentration, as well as by improving the technique of the isolation of the product. optimization of the reactor cascade realization of a continuous reaction on an industrial scale calls for the knowledge of relations, with the aid of which the desired product can be manufactured with the lowest possible investment and production expenses. for economic reasons, a technological system constructed from standardized elements is much more preferable than that built up from individually produced components. a cascade reactor can be built from lamp art autoclaves. concerning the economical aspects, for the determination of the optimum cascade number we must know the volume-price relation [ 6]. supposing that the price of the autoclave units p [hungarian forint, huf], is in an exponential relation with their volume v [ dm3 ]. (5) the exponent b and the b0 constant can be determined by linearization of equation (5) to obtain: lnp =lnb0 +blnv (6) for the lamp art reactors the volume-price relation is 55 ( 1 jn x-11+k·t; (8) the average residence time is the ratio of the volume of the reactor and the volumetric flow of the reactant: v t. =...2.. ' b (9) by substituting the average residence time (8) into equation (9), and by expressing the volume, it comes that (10) and substituting equation (10) into equation (7) we obtain: (11) shown in figure 2. and by transposing equation (11) we get the relation: :1' 3.5 ~ 3 ]. 2.5 " ... ·c 2 "' .... q 1.5 e is ·~:: ., ~ ... 0.5 0 5 6 7 9 10 11 logarithm of volume [dm3 ] fig.2 volumeprice relation of lamp art reactors according to the data of figure 2, b0 = 10.7451 and b = 0.427, and the corrected correlation coefficient r* = 0.99 for the linearized equation, which proves that equation (5) is correct. the price of a cascade reactor built from n number of elements is (7) according to the cascade model, the value of the desired conversion in a ftrst-order reaction is (12) by denoting the left side of the equation (which contains only constants) with q, it comes: [ 1 j !. q(n);:: ~-xt~ -1 nb (13) the extreme value of the q(n) expense-function can be calculated with a non-linear optimization method [7-8]. in figure 3 the optimum cascade-number versus conversion correlations for cascade systems built up from lamp art autoclaves are summarized. by analysing the curve, the optimum cascade number with which the reaction proceeds with the desired extent of conversion (independently of the rate constant of the reaction), and with the lowest investment costs can be determined. in the knowledge of the cascade number and the rate of the reaction, the average residence time can be determined according to equation (8). the volume of the built~in reactors is determined by the desired daily production, in accordance with the ratio of conversion and the average residence time. 56 g. = 2.5 .:~ 2 l 1.5 ~ a = a 0.5 "' 5 0 80 90 100 conversion [%] fig.3 optimum cascade number versus conversion of lamp art reactors in most cases the desired extent of conversion does not require an integer number of reactors as the optimum. in such cases the most economic number_ of the operational ·units should be calculated by rounding up or down, depending on the price of the product and the investment expenses. concerning the investigated present reaction system, it was an essential starting condition that the overall conversion of monochloroacetic acid must be nearly complete, i.e., at least 98 %. the reaction was conducted at 60 °c, which was considered as an optimum parameter. the diagram shows that an llopt = 2 optimum cascade number belongs to such an extent of conversion, and according to equation (7, 11) the costs of investment of building the cascade reactor system can be simply calculated: (14) conclusion for utilization of glycine, and industrial procedure was elaborated. according to this, production of iminodiacetic acid was carried out in a quadrate cascade reactor, so that the reaction mixture leaving the second reactor element was freed from ammonia, concentrated, and then reacted with an equivalent of monochloroacetic acid calculated on the basis of the • glycine-content. this way, iminodiacetic acid was obtained in the laboratory-scale experimental reactor with a 91 %yield, based on monochloroacetic acid. calculations for the optimization of the reactor-cascade was also presented. these clearly prove that the required new investment were reimbursed upon manufacturing on an industrial scale. acknowledgement this work was financially supported by the grants nos. t 019508, t 025379, t 025269, t 030519, m 2~36~, f 019376 given by otka (national found for sc1ent1fic research development, hungary), and by the grant no. fkfp 04441/1997. c b dar k n t ti t p q x w symbols concentration, mol/dm3 constant first damkohler number rate constant, min-1 number of cascade time, min average residence time, min temperature, k price of lamp art reactor, huf expense-function conversion volumetric flow, dm3 min"1 references 1. gulyas l.,keki s.,deak g.,horv ath r. and zsuga m.: hung. j. ind. chem., 2001, 29, 45 2. gulyas l.: magyar kemikusok lapja, 1983, 38, 60-62 3. benedek p., laszl6 a.: a vegyeszmemoki tudomany alapjai, miiszaki konyvkiad6, budapest, pp. 233-35, 1964 4. himmelblau. d.m.: hibafelmeres vegyi uzemekben, miiszaki konyvkiad6, budapest, 1984 5. himmelblau .d.m and bischoff k.b.: process analysis and simulation, john wiley, new york, pp. 322-23, 1978 6. catalog and price-list, lampart ltd. budapest, 2000 7. kafarov v.: cybernetic methods in chemistry and chemical engineering, mir publishers, moscow,pp.284-87, 1976 8. bojarinov a. i. and kafarov v. v.: optimalizalas a vegyiparban, miiszaki konyvkiad6, budapest, pp. 240-43, 1973 page 52 page 53 page 54 page 55 hungarian journal of industry and chemistry vol. 49(2) pp. 97–100 (2021) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2021-29 building a reusable data model to support systematic layout planning with discrete event simulation of flexible manufacturing systems zsolt molnár*1, péter tamás1, and béla illés1 1institute of logistics, university of miskolc, egyetemváros, miskolc, 3515, hungary manufacturing has undergone a greater change in recent years than it has over almost the entire past century. due to the variety of products, shortening delivery times and changing customer habits, the covid-19 pandemic has demanded greater flexibility from manufacturing companies than ever before. one of the fundamental parts of manufacturing flexibility is the design of manufacturing layouts, which has so far not followed automation and methodological developments with regard to technological areas of manufacturing. in this article, a new method for supporting traditional factory design methods with digital manufacturing tools is introduced. keywords: flexible manufacturing, simulation, layout design, systematic layout planning 1. introduction very few complete methodologies cover and support the entire process of designing manufacturing layouts. when the designing of a layout is considered, what are the most important parameters? the space available and the complexity of the manufacturing process of the product, which is directly proportional to the material flow and the costs, immediately come to mind. our goal was to design an extendable method to be supported by digital manufacturing tools for the purposes of improving as well as speeding up the design and evaluation of future manufacturing layouts. in terms of project planning, the study by schenk et al. [1] comprehensively covers the design of factories and production lines but deals relatively little with the specific challenges of implementation. their 0+5+x method is much more of a project planning and management method. the study by wiendahlet al. [2] presents many more concrete design methods. in addition to examining workplace design, including the connection between layout elements, it handles the workplace, work area, building and site design separately, albeit only to a limited extent, for the purpose of integrating these aspects into a complete system. to the best of our knowledge, the systematic layout planning (slp) methodology by muther and hales [3] is the most comprehensive methodology to date. it addresses the data requirements of layout design and creates *correspondence: zsolt.molnar.zsolt@outlook.com production layouts by following a top-down approach. the design methodology takes into consideration relationships, space and adjustments. as this methodology also contains practical examples, templates and formulae for the steps of layout designs, this method is best suited for use with digital tools. in its current state, this method mainly focuses on traditional manufacturing processes and does not include specific methods for the design of flexible manufacturing systems (fms) [4] or reconfigurable manufacturing systems (rms). since this method was developed in the 1970s, it was mainly designed for paper-based workflows used to design classic dedicated manufacturing lines. given the advancement of fmss, understanding to what extent slp can be supported by digital manufacturing as well as simulation tools and thus to what degree it can be used to design fms’s is a current research topic. during the research, the siemens plant simulation was used as a platform for the digital twin. the siemens plant simulation is a discrete event-based piece of simulation software that takes into account a wide range of factory objects, e.g. material flow and logistics, as well as customization possibilities via its built-in programming environment [5, 6]. another advantage of the system is that since the table component it contains is very versatile, it is also suitable for handling tabular and matrix data [7]. 2. digital twin the digital twin has now become a basic tool for the development of production processes. a digital twin is https://doi.org/10.33927/hjic-2021-29 mailto:zsolt.molnar.zsolt@outlook.com 98 molnár, tamás, and illés table 1: products and bill of materials product component qty operation number a b 3 20 c b 2 10 a d 1 10 table 2: a typical product routing product operation number activity point a 10 m1 or m2 20 m3 the mapping of production in a digital model to develop the production process within the framework of the digital model. the depth of formation of the digital twin is determined in each case by the development goal [8]. process development in the digital model is typically cheaper, providing more what-if analysis possibilities than an analysis or trial of a real-life production system [9]. during the current research, the first steps to digitalize the slp method and make it available to use for the design of flexible manufacturing lines were taken. 3. data model slp works according to 5 elements: product, quantity, routing, supporting service and timing. the implications of these 5 groups of data on flexible manufacturing systems is outlined below. in the case of products, the main purpose of flexible manufacturing systems is to facilitate the production of several products as a result of their flexibility. fms’s always try to implement high-mix and low volume production. the product data should include the related bill of materials along with information outlining which operation refers to the related necessary quantity of a part that is assembled or used to build the product. example product data with information concerning the bill of materials is shown in table 1 in terms of fms lines, the most important parameter is routing, which determines the flexibility of the line itself. a typical product route with the order of operations and the machines (activity points) that are capable of executing the process step is shown in table 2. an activity point is a location where something happens to a product. details of this definition will be provided and expanded on later. although the order of operations is usually fixed (or hardly modifiable), most of these lines include a machine to substitute bottleneck resources to make routing more flexible. the routing data should include the product data and process steps, including the alternative routings which are very common in flexible manufacturing cells. a typical product routing is presented below. in the case of flexible manufacturing, the data model should be able to handle the alternative routings. for the table 3: first alternative routing of product a product operation number activity point a 10 m1 or m2 20 m3 table 4: second alternative routing of product a product operation number activity point a 10 m3 20 m1 or m2 sake of clarity, each alternative routing was stored separately along with the full routing data, thereby ensuring that it can be handled faster and more easily with a route search algorithm. tables 3 and 4 show alternative routings for the same product. given the routing tables, the question may arise as to where to store product-dependent parameters during the simulation, e.g., how long should the production time of product a be on machines m1 and m2? the data model follows the industry 4.0 philosophy of storing data where data-related decisions are made, that is, on machines. in this case, machine m1 knows how much time product a spends on it and this information can be made available to other elements of the production system at any time. the most important areas of the supporting services are maintenance and raw material supply. both are critical to the operation of the line. although the supply of raw materials influences the design and layout at a basic level, maintenance is vital to ensure a functional operation. since operational services are mostly machinerelated, they must be handled by the machine (activity point). repair and rework are special supporting services. if quality control and repair take place within the machine, the necessary time can be regarded as the duration of a process step. if quality control is carried out elsewhere, it should be treated and mapped as part of the routing. the time-based parameter of the slp design process can determine when items will be produced. usually, the number of pieces and product mix over a given period, e.g. monthly, are available here. based on this, orders can be generated in the simulation, the distribution of which corresponds to the given data. the relationship between the slp layout design process and the simulation is shown in fig. 1. apparently, the steps of the design process can be mapped to the steps of building a simulation model. 4. activity points during a manufacturing process, a part could be subjected to six activities: 1. can be processed (assembled, disassembled or manufactured in any way) 2. can be moved or transported hungarian journal of industry and chemistry building a reusable data model to support systematic layout planning 99 figure 1: slp steps in relation to the simulation process [1] 3. can be handled to support processing (change in orientation, placed in a tool, etc.) 4. can be handled to enhance quality (inspected, tested, counted, repaired or reworked) 5. can be forced to wait due to technological reasons (to cool down, etc.) or for the rest of the batch to catch up 6. can be stored to manage activities uniformly, the concept of an activity point was introduced, which is a generic object that can handle the aforementioned six activities in one object depending on the settings specified. a manufacturing object, e.g., an activity point, can be a milling machine, 3d printer or even a buffer as shown in fig. 2. the main attributes of an activity point are: • object type (processing, handling, transferring, buffering, quality handling, storage) • processing type • processing time (product-dependent) • setup parameters • capacity • 3d block size parameters (x, y, z) • logic of supporting services with the help of activity points, the simulation model can be easily built and modified. figure 2: an activity point can represent different types of process objects figure 3: material flow visualization depending on how comprehensive the analysis is, an activity point could be planned by a department or a single processing machine. 5. simulation results the simulation model is suitable for generating the results required for the further steps of the slp analysis. the simulation automatically creates a sankey (or spaghetti) diagram characterizing the material flow intensity between each activity point (fig. 3). the most important result is the so-called travel chart that shows how much material has moved between each activity point. the upper diagonal of the table shows the amount of material that has moved forwards, while the quantity that has moved backwards, e.g. a loop in progress or returned for repair, is depicted below the diagonal. on the diagonal, all values are, by definition, zero. based on the data table, the material movement (or flow) between two activity points can be calculated, which is defined as: mij = material flow from activity i to activity j (1) due to the possible backward material flow, the total material movement between two activity points can be calculated by this formula: mij = mij +mji, for all i > j (2) slp uses an rel (relationship) chart to visualize the importance of how close the different departments are to each other. the rel chart replaces the numbers in the travel chart with a closeness category. six categories are defined to represent the level of importance [3]: • a – absolutely necessary • e – very important • i – important • o – fairly important • u – unimportant • x – undesirable table 5: travel chart (from-to chart) m1 m2 m3 m1 0 m12 m13 m2 m21 0 m21 m3 m31 m32 0 49(2) pp. 97–100 (2021) 100 molnár, tamás, and illés figure 4: simple chart depicting the importance of how close each activity is to each other table 6: summarized travel chart m1 m2 m3 m1 0 m12 m13 m2 − 0 m21 m3 − − 0 table 7: chart depicting the importance of the proximity of the activity points to each other m1 m2 m3 m1 0 o e m2 0 a m3 0 in the example (fig. 4), 3 departments (activity points) are present to evaluate our layout. the intersections denoted by letters depict the importance of how close the departments are to each other. from the simulation model, the results of the travel chart can be transformed into a full travel chart (table 6) which includes the total material flow between the activity points. by taking the largest and smallest values from the table as well as dividing the range into 6 parts, six categories can be created to determine the importance of the proximity of the activity points to each other. the content of the resulting table is identical to the chart depicting how important the proximity between activity points is which is required to evaluate the slp methodology (table 7). based on the table, decisions can be made as to which departments and machines should be placed close to each other as well as how the layout elements should be designed. 6. summary and further research supporting and further developing traditional factory design methods with digital manufacturing and simulation tools is a new approach to design better production lines and shorten design processes. as the aforementioned method is rather generic, that is, applicable to many scenarios, it does not completely fulfill the special requirements of the production lines in fms’s or rms’s. the next phase of this research will strive to include the product mix, namely the variety of processes, in the model. another important field of this research is how to evaluate an automation level of the production lines and determine which automation level is optimal by taking into consideration the material flow as well as technical and investment parameters. references [1] schenk, m.; wirth, s.; müller, e.: factory planning manual, springer-verlag berlin heidelberg, 2010 isbn: 978-3-642-03634-7, doi: 10.1007/978-3-642-03635-4 [2] wiendahl, h. p.; reichardt, j.; nyhuis, p.: handbook of factory planning and design, springer heidelberg new york dordrecht london, 2015 isbn: 978-3-662-46390-1, doi: 10.1007/978-3-662-46391-8 [3] muther, r.; hales, l.: systematic layout planning, marietta, ga: management & industrial research publications, 2015, isbn 978-0-933684-06-5 [4] koštál, p.; velíšek, k.: flexible manufacturing system, zenodo, 2011 doi: 10.5281/zenodo.1075605 [5] erdélyi, f.; tóth, t.; kulcsár, g. y.; mileff, p.; hornyák, o.; nehéz, k.; körei, a.: new models and methods for increasing the efficiency of customized mass production, j. mach. manuf., 2009, 49, 11–17 [6] tamás, p.; illés, b.; tollár, s.: simulation of a flexible manufacturing system, adv. logist. syst. 2012, 6(1), 25–32 [7] bratley, p.; fox, b. l.; schrage, l. e.: a guide to simulation, 2nd ed., springer: new york, ny, usa, 1987 isbn: 978-1-4612-6457-6. [8] cselényi, j.; illés, b.: planning and controlling of material flow systems (textbook), miskolc, hungary: miskolci egyetemi kiadó, 2006 [9] dörgő, g.; abonyi, j.: group contribution methodbased multi-objective evolutionary molecular design. hung. j. ind. chem., 2016, 44(1), 39–49 doi: 10.1515/hjic-2016-00056 hungarian journal of industry and chemistry https://doi.org/10.1007/978-3-642-03635-4 https://doi.org/10.1007/978-3-662-46391-8 https://doi.org/10.5281/zenodo.1075605 https://doi.org/10.1515/hjic-2016-0005 https://doi.org/10.1515/hjic-2016-0005 introduction digital twin data model activity points simulation results summary and further research hungarian journal of industry and chemistry vol. 50 pp. 29–32 (2022) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2022-06 production and characterization of sand-plastic composite floor tiles alexander asanja jock*1, messiah luke akpan1, and francis asokogene oluwadayo2 1department of chemical and petroleum engineering, university of uyo, uyo, nigeria 2department of chemical engineering technology, auchi polytechnic, auchi, edo, nigeria the amount of plastic waste generated in developing nations like nigeria is increasing day by day, which is nonbiodegradable and causes environmental pollution. among the plastics used, low-density polyethylene is abundant. these plastics can be removed from the environment and recycled into useful products. in this study, low-density polyethylene plastic waste was utilized in the manufacture of floor tiles to curb its generation. the tiles were produced by mixing fine sand with molten plastic waste in different proportions. the physical and mechanical properties of the floor tiles such as water absorption, density, tensile and compressive tests, modulus of elasticity as well as impact strength and friction tests were investigated. the water absorption ranged from 0.02 − 0.38 %(m/m), while the density varied between 998.5 and 1289 kg/m3. the tensile strength and modulus of elasticity fell within the range of 0.050 to 0.232 mpa and 0.924 to 2.806 mpa, respectively. this result proved the applicability of recycled plastic waste in the formulation of floor tiles. keywords: plastic waste, floor tiles, low-density polyethylene, pollution, properties 1. introduction plastic waste is now a global problem and one that must be addressed in order to solve worldwide problems concerning resources and energy. plastics are a generic group of synthetic or natural materials consisting of highmolecular-weight chains composed predominantly if not entirely of carbon. they are classified into two categories, namely thermoplastics and thermosetting plastics, moreover, are found in different forms, e.g. as bags, furniture, cups, basins, drinking and food containers, etc. [1]. the increasing consumption of plastic products in various fields generates a significant amount of waste products, equating to more than 12% of municipal solid waste. since plastics are non-biodegradable, that is, cannot easily reenter the natural carbon cycle, the life cycle of plastic materials ends at solid waste disposal facilities and in water bodies. however, the full extent of plastic pollution goes far beyond macroplastic litter. microplastics can contain additives, which have the potential to leach into the surrounding environment, resulting in toxicity to organisms, including carcinogenesis and disruption of the endocrine system in humans [2]. there are several methods for disposing of municipal and industrial plastic waste such as landfill, incineration, recieved: 23 january 2022; revised: 7 february 2022; accepted: 9 february 2022 *correspondence: alsanja@gmail.com true material recycling and chemical recovery. treating plastic waste suitably is crucial to waste management and important in terms of energetic, environmental, economic and political viewpoints. some plastics can safely be recycled, while others cannot so litter the environment [3]. a large and increasing amount of household plastic waste is being produced. the composition of waste varies from country to country, since it is affected by socioeconomic characteristics, consumption patterns and waste management programmes. nevertheless, generally speaking, the proportion of plastics concerning the composition of waste is high. the largest component of plastic waste is polyethylene, followed by polypropylene, polyethylene terephthalate and polystyrene [4]. polyethylene is the most common plastic and can be classified into several different categories based mainly on its density and branching. important grades pf polyethylene are high-density polyethylene (hdpe), linear low-density polyethylene (lldpe) and low-density polyethylene (ldpe). plastic is recycled worldwide since it reduces environmental impacts associated with the improper disposal of plastic waste. therefore, this study focused on the production of floor tiles by mixing sand and plastic waste in different proportions. the characterization of the tiles will provide some insight into the suitability of applying sand-plastic composites in building constructions. https://doi.org/10.33927/hjic-2022-06 mailto:alsanja@gmail.com 30 jock, akpan, and oluwadayo (a) shredded ldpe (b) fine sand figure 1: formulation samples 2. materials and methods 2.1 sample collection and preparation the plastic waste was collected from the university of uyo water company landfill site in uyo, south-south nigeria. the ldpe plastic waste was washed with water to remove dust and other impurities. the washed sample was sun dried for 48 h and shredded into smaller pieces (fig. 1a). a clay-free sample of fine sand (fig. 1b) was obtained from ifiayoung stream in uyo, sun dried for 24 h, then oven dried at 105 ◦c for 4 h before being sieved through a 125 µm mesh. 2.2 formulation and production of floor tiles 35 g of plastic waste was continuously introduced into a fabricated melting pot made of stainless steel and heated to a temperature of 160 ◦c , whilst being stirred continuously to ensure homogeneous melting. 105 g of fine sand was then added to the melted plastic waste before being well mixed. the mixture was transferred into a stainlesssteel mould with the dimensions of 10.0 × 10.0 × 1.5 cm coated with a lubricating oil to facilitate demoulding. the mixture in the mould was compressed by applying figure 2: samples of floor tiles a force before being cooled in a water bath for 5 mins. the resulting tile was then removed from the mould. the production process was repeated by varying the proportions of plastic waste and fine sand. the samples of tiles produced using different formulations are shown in fig. 2. 2.3 characterization of floor tiles water absorption water absorption tests were carried out in accordance with the astm-c373 standard test method. each sample was oven dried at 110 ◦c to constant weight (wo) before being immersed in distilled water at room temperature (25 ◦c) for 24 h. the samples were removed from the distilled water, cleaned with a cotton fabric and weighed (wt). the amount of water absorbed (wa) by each sample was calculated using %wa = (wt −wo) wo × 100 (1) density the density of each sample was calculated using density = mass of sample sample volume (2) impact strength impact strength was measured using a jbs-300n model charpy impact testing machine and determined according to the astm d6110-18 standard test method. a standard sample was prepared with the dimensions 1×8 cm while maintaining the original thickness before being placed on the plate of the impact testing machine, wherein the jack handle was carefully released to allow the load to strike the sample of the ceiling board. the energy of the impact was recorded and the impact strength calculated by hungarian journal of industry and chemistry production and characterization of sand-plastic composite floor tiles 31 impact strength = absorbed energy cross-sectional area (3) tensile strength this was determined using the mohan brothers tensile testing machine cap, 500kgf iso9001 model. the samples were prepared for this test according to the astm c1185 standard test method (type ii). each sample was carefully placed in the tensile testing machine and clamped at both ends. the machine was turned on and the load at which each sample fractured recorded. the tensile strength was calculated by tensile strength = maximum load original cross-sectional area (4) young’s modulus of elasticity young’s modulus of elasticity (y ) is a measure of stress per unit strain and was calculated using y = stress strain (5) friction test a friction test was conducted using the cussons friction test device graduated from 0 − 90° and was performed based on the astm d1037-94 standard test method. the sample was placed on an inclined plane of the piece of equipment and the angle at which the specimen slid freely down the surface was recorded. the coefficient of friction was calculated by: coefficient of friction = tan θ (6) where θ denotes the angle of repose. compressive strength a compressive strength test was carried out using a universal testing machine and performed based on the astm d790 standard test method. the specimens with dimensions of 20 by 20 mm were prepared and tested on a support span of 130 mm in length as per the standard test method. the load at which each sample was compressed as a result of the force applied on it by the machine was recorded. the compressive strength was calculated using compressive strength = maximum load cross-sectional area (7) table 1: composition and physical properties of floor tiles sample composition (%(m/m)) water density ldpe fine sand absorption (kg/m3) (%(m/m)) a 25 75 0.38 1289.6 b 35 65 0.04 1269.5 c 50 50 0.02 1168.2 d 65 35 0.24 1015.6 e 75 25 0.3 998.5 3. results and discussion 3.1 physical properties of floor tiles the physical properties of floor tiles are presented in table 1. water absorption is the ability of a bisque tile to absorb water or moisture. the calculated water absorption of the floor tiles was between 0.02 and 0.38%(m/m). the lowest water absorption (0.02%(m/m)) was obtained in batch c with a composition of 50%(m/m) ldpe and 50%(m/m) fine sand. the amount of water absorbed closely resembled that of ceramic tiles of 0.03%(m/m). generally, tiles with a high level of water absorption have a low resistance to chloride and sulphate as well as to water penetration [5]. the density of the tiles ranged from 998.5 kg/m3 to 1289.6 kg/m3 as is shown in table 1. the lowest density, calculated in batch e, was due to the large quantity of ldpe in the formulation. the density decreased as the proportion of ldpe increased. a rise in the density resulted in an increase in the compressive strength and a decrease in water absorption by the tile [6]. 3.2 mechanical properties of the formulated tiles the mechanical properties of the batches are shown in table 2. the tensile strength of the floor tiles was between 0.050 and 0.232 mpa. the tensile strength of a material is a measure of the force required to pull a material to the point where it breaks. batches a and e exhibited the lowest and highest tensile strengths, respectively, possibly due to the amount of ldpe used as a binding agent in their formulations. the young’s modulus of elasticity with regard to the batches of tiles ranged from 0.924 to 2.810 mpa as depicted in table 2. the young’s modulus of elasticity is a measure of the stiffness of an elastic material and it is an important parameter in evaluating the deformation of materials subjected to a working load. the lowest young’s modulus of elasticity that was calculated in batch a may result in a lower stiffness compared to that of batch e that yielded the highest. the compressive strength of the tiles presented in table 2 was between 91.7 and 133.0 mpa. batches d and b 50 pp. 29–32 (2022) 32 jock, akpan, and oluwadayo table 2: mechanical properties of floor tiles sample tensile young’s modulus compressive impact strength coefficient strength (mpa) of elasticity (mpa) strength (mpa) (kj/m2) of friction a 0.05 0.924 116.7 1912 0.6 b 0.067 0.975 91.7 1883 0.53 c 0.083 2.666 118 1955 0.51 d 0.082 2.653 133 2346 0.58 e 0.232 2.806 115 1933 0.58 exhibited the highest and lowest compressive strengths, that is, 133.0 mpa and 91.7 mpa, respectively. this implies that the impact strength of batch d to compressive loading will be greater than that of batch b. impact strength is the resistance of a material to fracture by being hit, expressed in terms of the amount of energy absorbed before the fracture. the impact strength of the batches ranged from 819.05 to 1720 kj/m2. since batches d and b exhibited the highest and lowest impact strengths, respectively, batch b will easily be fractured. table 2 shows that the coefficient of friction of the floor tiles is between 0.51 and 0.60. however, given that these values are similar, all the floor tiles responded similarly to sliding freely over the same surface. the coefficient of friction depends on the surface finish of the floor tiles and the values obtained are in good agreement with the acceptable value of 0.5 outlined by the astm standard test method [7]. 4. conclusion floor tiles were successfully developed from plastic waste and fine sand. although the physical and mechanical properties of batch d yielded the best results, this recycled plastic waste can be used to produce some industrial products like floor tiles which are resistant to highly corrosive environments like offshore platforms. competing interests the authors declare that there are no competing interests. references [1] osarumwense, o.j.; salokun, o.; okundaye, o.a.: utilization of low-density polyethylene (ldpe) plastic wastes in the production of paving tiles, j. mater. environ. sci., 2020, 11(12), 2052–2060 https://www.jmaterenvironsci.com [2] bishop, g.; styles, d.; lens, n.l.p.: recycling of european plastic is a pathway for plastic debris in the ocean environ. int., 2020, 142, 105893 doi: 10.1016/j.envint.2020.105893 [3] puttaraj, m.h.; basavaraj, p.; gagan, m.s.; shivu, s.; manjunath, s.h.: reuse of plastics waste for the production of floor tiles, j. seybold report, 2020, 15(8), 1633–1639 [4] alla, m.m.g.; ahmed, a.i.; abdalla, b.k.: conversion of plastic waste to liquid fuel, int. j. tech. res. appl., 2014, 2(3), 29–31 https://www.ijtra.com [5] namarak, c.; bumrungsri, c.; tangchrirapat, w.; jaturapitakkul, c.: development of concrete paving blocks prepared from waste materials without portland cement, mater. sci., 2018, 24(1), 92–99 doi: 10.5755/j01.ms.24.1.17566 [6] yalley, p.p.; kwan, a.: use of waste and low energy materials in building block construction. int. refereed j. eng. technol., 2013, 2(1), 1–5 https://www.irjes.com [7] american society for testing and materials (astm c1028) (2008) standard test method for coefficient of friction for manufactured tiles. hungarian journal of industry and chemistry https://www.jmaterenvironsci.com/document/vol11/vol11_n12/jmes-2020-11175-osarumwense.pdf https://doi.org/10.1016/j.envint.2020.105893 https://doi.org/10.1016/j.envint.2020.105893 https://www.ijtra.com/download.php?paper=conversion-of-plastic-waste-to-liquid-fuel https://doi.org/10.5755/j01.ms.24.1.17566 https://doi.org/10.5755/j01.ms.24.1.17566 https://www.irjes.com/papers/vol2-issue11/a02110105.pdf introduction materials and methods sample collection and preparation formulation and production of floor tiles characterization of floor tiles water absorption density impact strength tensile strength young's modulus of elasticity friction test compressive strength results and discussion physical properties of floor tiles mechanical properties of the formulated tiles conclusion hungarian journal of industry and chemistry vol. 50(2) pp. 11–15 (2022) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2022-12 the rhizosphere of petrosimonia triandra may possess growthinducing and salinity-tolerance potential gyöngyi székely1,2,3*, norbert zsolt szígyártó1,2, andrás tóth1,2 and csengele barta4 1 hungarian department of biology and ecology, faculty of biology and geology, babeș -bolyai university, 5-7 clinicilor st., cluj-napoca, 400006, romania 2 institute for research-development-innovation in applied natural sciences, babeș-bolyai university, 30 fântânele st., cluj-napoca, 400294, romania 3 centre for systems biology, biodiversity and bioresources (3b), babeș -bolyai university, 5-7 clinicilor st., cluj-napoca, 400006, romania 4 department of biology, missouri western state university, 4525 downs drive, agensteinremington halls, st. joseph, mo 64507, usa the root microbiome of halotolerant plants can represent a great source of salt-tolerant plant growth-promoting rhizobacteria (st-pgpr) with a wide range of beneficial effects on plants growth, development and productivity. the better understanding of the variety of complex salt tolerance and adaptive mechanisms of haloph ytes can contribute to improve salt tolerance in crops, and as a result, a better and increased use of saline areas worldwide. in addition, reclaiming saline areas for agricultural use may be able to alleviate the global threat of progressive soil salinization. keywords: st-pgpr, molecular analysis, saline soil 1. introduction although the threat of the continuous expansion of areas of saline soil exhibiting enhanced levels of salinity has a negative effect on soil structure, fertility and plant health, by progressively constraining plants in narrower habitats, they can grow and develop optimally without experiencing the negative, stressful impacts of saline conditions. habitat narrowing is expected to decrease biodiversity and have negative impacts on the usability of land for agricultural practices. one of the most damaging abiotic stress factors for plants is the excessive accumulation of salt in their natural habitats caused by soil salinization. soil salinity is most often defined by its electrical conductivity (ec) with values above 4 dsm−1 indicative of saline soils [1]. soil salinity can be determined by the occurrence of a variety of salts such as nacl, na2so4, na2co3, mgso4, mgcl2, kcl and caso4. all of these salts have the potential to induce salinity stress in plants. from among the aforementioned salts, the accumulation of nacl is the most frequent in soils. the adverse effects of nacl stress on plants has been extensively documented [2-4]. saline soils represent a substantial limiting factor for the development and propagation of the majority of plant species belonging to the group of non-halophytes (also referred to as glycophytes). only halophytes, that is, received: 20 sept 2022; revised: 27 sept 2022; accepted: 27 sept 2022 *correspondence: gyongyi.szekely@ubbcluj.ro plants adapted to and capable of achieving optimal development in saline environments, can persist in saline soils. to counteract salinity stress, salt-tolerant species have developed a wide range of tolerance traits such as osmotic adjustment, ion sequestration, ion exclusion, adaptations of the membrane transport system and protection enhanced by the synthesis of a variety of macromolecules with osmolytic properties, e.g. glycine betaine, proline, etc. [5]. petrosimonia triandra is a halophyte able to complete its life cycle under moderate saline conditions (ec: 4.45 dsm−1) native to the saline area of cojocna in cluj county, romania (fig.1) [6]. while the salt tolerance mechanisms of p. triandra are currently poorly understood, podar et al. (2019) documented several adaptive mechanisms in this species that can withstand soil salinity such as morphological, physiological and biochemical adaptations, e.g. the development of efficient photosynthetic and antioxidative systems as well as the accumulation of the protective osmolyte proline. similar salt tolerance mechanisms have also been documented in other halophyte species [7-8]. another strategy of halophyte plant species to improve their range of salt tolerance is co-habitation with groups of rhizosphere-specific bacteria called plant growth-promoting rhizobacteria (pgpr), which live in the immediate vicinity of plants’ root systems (also referred to as the rhizosphere) as well as exert a positive https://doi.org/10.33927/hjic-2022-12 mailto:gyongyi.szekely@ubbcluj.ro székely, szígyártó, tóth and barta hungarian journal of industry and chemistry 12 effect on plant growth and development. these effects are underpinned by diverse mechanisms such as the addition of essential nutrients (n, k, zn, fe, po4); production of 1-aminocyclopropane-1-carboxylate (acc) deaminase, volatile organic compounds and phytohormones; as well as the facilitation of favorable plant-microbe interactions, antifungal effects, etc. [9-10]. some pgpr species have been found to be salt tolerant, namely st-pgpr, and successfully used over recent decades to enhance crop yield and improve soil fertility. most recently, ayub et al. (2020) clearly emphasized the role of pgprs in the salt tolerance of halophytes. in addition, nowadays, st-pgprs are also used as bioinoculants to improve crop productivity and provide protection from phytopathogens [11-12]. therefore, stpgprs are promising tools to enhance the salinity tolerance of plants. the goal of the current study was to identify stpgpr species from the rhizosphere of p. triandra. a better understanding of the rhizobial community contributing to the enhancement of salt tolerance in species adapted to and native to saline areas is expected to lead to valuable applications, thereby enhancing the tolerance of high-value crops and other species of horticultural use as well as provide technologies to expand land-use practices for agricultural purposes to underutilized, highly saline areas [13]. 2. experimental 2.1. soil sampling site soil samples were collected from the rhizosphere of the halophyte p. triandra, native to the saline zone of cojocna in cluj county, romania (gps coordinates n46.74328 e23.84295, fig.1). the salinity of this site is characterized by ec = 4.45 dsm-1, which corresponds to moderate saline soil [1]. the specific physicochemical characteristics of the soil at the sampling site have been described in our former study [6]. 2.2. isolation of bacterial species from the rhizosphere of p. triandra p. triandra plants were carefully dug up and removed from the soil before gently shaking their roots to remove the excess soil. the soil that was directly adhered to the roots was collected and transported back to the laboratory for analysis where it was transferred into a flask containing 99 ml of sterilized distilled water. after shaking the flask for 15 minutes, the soil samples were subjected to a 10-fold serial dilution and 100 µl of the solution was spread on plates containing nutrient agar (na) media (merck, germany) supplemented with 2, 4, 6, 8, 10, 11, 11.5, 12, 12.5 and 13% nacl, respectively. the plate containing na without external nacl was used as the control sample. the plates were incubated at room figure 1. a: location of the study zone in cojocna, romania; b: the habitat of p. triandra in cojocna; c: young p. triandra plants temperature with colonies appearing 3-4 days after inoculation. 2.3. identification of salt-tolerant rhizobacteria using a 16s rrna gene sequence to identify the rhizosphere of bacterial species, strains exhibiting the highest salt tolerance were selected, namely 11.5, 12 and 12.5% nacl. thirty colonies were selected for dna isolation, pcr and gene sequencing of their 16s rrna gene. having extracted the total genomic dna (qiagen, germany), a fragment of the 16s rrna gene was amplified by pcr using the 16s rrna universal primers (27f: 5′agagtttgatcctggctcag-3′ and 1492r: 5′ggttaccttgttacgactt-3′). the pcrs were mixed using a bioline pcr kit with the polymerase mytaq red mix (bioline, meridian bioscience, memphis, tn) in a final volume of 50 µl. the pcrs were performed using a multigene optimax thermal cycler (labnet, cary, nc) under the following cycling conditions: 5 mins. at 95°c, followed by 30 cycles lasting rhizosphere of petrosimonia triandra 50(2) pp. 11–15 (2022) 13 table 1. identified rhizosphere bacteria and the salt concentration facilitating their optimum growth no. pgpr name nacl tolerance (%) 1. bacillus hwajinpoensis fjat-46935 12.5 2. bacillus sp. ls-x7 12.5 3. bacillus sp. ebw4 12.0 4. bacillus sp. ytm5 11.5 30s each at 94°c, 30s each at 55°c and 1.5 mins. each at 72°c followed by a final extension step at 72°c for 7 mins. 5 μl aliquots of each reaction were analyzed on 1% (w/v) agarose gel in tbe buffer, stained with midori green advance nucleic acid staining solution (nippon genetics europe, düren, germany). the resulting ~1500 bp pcr product was purified using an agarose gel extraction kit (jena bioscience, jena, germany) according to the manufacturer’s protocol and sent for sequencing at the genomic sequencing service provider macrogen (south korea, http://dna.macrogen.com/eng). blast analysis and gene sequencing were also performed by macrogen. 3. results and discussion 3.1. determination of the nacl tolerance of the rhizobacteria p. triandra rhizobacteria isolated in close proximity to the roots of p. triandra could survive in a media supplemented with up to 12.5% nacl (fig.2). 46 bacterial colonies were able to grow in the presence of salinities as high as 11.5, 12 and 12.5% nacl. the number of bacterial colonies grown in saline media decreased as the nacl concentration increased. a total number of 26, 12 and 8 bacterial isolates survived in salinities of 11.5, 12 and 12.5% nacl, respectively. the 8 most salt-tolerant bacterial isolates survived in the presence of 12.5% nacl. based on their highest level of salt tolerance and diverse morphology, 30 isolates were selected for molecular identification. 3.2. identification of salt-tolerant rhizobacteria the bacterial 16s rrna gene sequence analysis determined that of the 30 selected isolates, 26 belonged to the bacillus genus (bacillus sp. strains ebw4, ls-x7, ytm5) with one of them identified as the b. hwajinpoensis strain fjat-46935. the other four isolates could not be identified. the names of the isolates and their highest salinity tolerance are presented in table 1. the important role of some of the identified p. triandra rhizobacteria in enhancing plant growth, yield and salt tolerance has been described previously [14]. a plant growth-promoting effect of the rhizosphere bacterial strain bacillus sp. ebw4 was reported by utkhede and smith in 1992 [15], who highlighted an figure 2. bacterial isolates growing on na media supplemented with 12.5% nacl increase in the growth of apple trees and fruit yield after applying bacillus sp. ebw4. another pgpr identified is b. hwajinpoensis, which was also characterized as a halotolerant rhizobacterial species with plant growthpromoting traits by ferreira et al. (2021) [16]. furthermore, many other bacillus sp. strains were also described as st-pgprs. experiments with several plant species proved that a diverse range of bacillus strains such as b. pumilus, b. paramycoides and b. amyloliquefaciens exhibit elevated salinity tolerance following the induction of a series of salt-tolerance mechanisms in plants, e.g. enhance antioxidant enzyme activity and reduce lipid peroxidation [16-19]. ferreira et al. (2021) described the plant growth-promoting characteristics of salt-tolerant bacillus sp., e.g. production of indole-3-acetic acid (iaa) and siderophores, enhanced 1-aminocyclopropane-1carboxylic acid (acc) deaminase activity as well as phosphate solubilization [16]. moreover, nawaz et al. (2020) studied the individual or synergistic effects of stpgprs on wheat growth as well as yield under saline conditions and found that these bacteria may be used as bioinoculants to enhance crop yield in saline environments [20]. our findings regarding the bacillus sp. strains lsx7 and ytm5 in the rhizosphere of the salt-tolerant p. triandra populated by numerous st-pgpr species are novel, moreover, it is hypothesized that these strains are also potential candidates for st-pgpr activity along with the other described species and bacillus strains. the potential st-pgpr function of the aforementioned strains requires further investigation, namely analysis of their acc deaminase activity, phytohormone production and plant-microbe interactions, which are the goals of our future studies. in summary, based on our results and prior findings, the root microbiome of the halophyte p. triandra is likely to be a useful source for the isolation, discovery and characterization of yet unknown st-pgprs providing tools with further applications with regard to inducing halotolerance in plants of high economic value. therefore, understanding the salt tolerance mechanisms of halotolerant plants in general, e.g. that of p. triandra in our study, may ultimately facilitate the exploitation of székely, szígyártó, tóth and barta hungarian journal of industry and chemistry 14 saline areas for agricultural purposes, especially in the carpathian basin. 4. conclusions p. triandra, similarly to a series of other halophyte species, has evolved various morphological, physiological and biochemical salt adaptation mechanisms to counteract the harmful effects of elevated salinity [6]. the isolation of halotolerant bacteria from the rhizosphere of this species indicates that plantmicrobe cohabitation may influence the adaptive strategy of the plant. although further investigations are necessary to characterize the novel identified bacterial strains and demonstrate their pgpr ability, our results are promising. therefore, the identified st-pgpr species from the rhizosphere of p. triandra could possibly be used to improve the salinity tolerance of nonhalophyte species such as many common crops threatened by the salinization of arable land worldwide. acknowledgements this research was supported by a grant from the romanian national authority for scientific research and innovation uefiscdi under project number pn-iiru-te-2014-4-0831. references [1] shrivastava, p.; kumar, r.: soil salinity: a serious environmental issue and plant growth promoting bacteria as one of the tools for its alleviation, saudi j. biol. sci., 2015 22(2), 123–131, doi: 10.1016/j.sjbs.2014.12.001 [2] rengasamy, p.: transient salinity and subsoil constraints to dryland farming in australian sodic soils: an overview, anim. prod. sci., 2002 42(3), 351–361, doi: 10.1071/ea01111 [3] munns, r.; tester, m.: mechanisms of salinity tolerance, annu. rev. plant biol., 2008 59(1), 651– 681, doi: 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plant growth-promoting mechanisms of bacillus strains in elevating rice growth and its interaction with salt stress, front. plant sci., 2022 13, 994902, doi: 10.3389/fpls.2022.994902 [20] nawaz, a.; shahbaz, m.; asadullah; imran, a.; marghoob, m.u.; imtiaz, m.; mubeen, f.: potential of salt tolerant pgpr in growth and yield augmentation of wheat (triticum aestivum l.) under saline conditions, front. microbiol., 2020 11, 2019, doi: 10.3389/fmicb.2020.02019 https://doi.org/10.1186/s43141-021-00186-3 https://doi.org/10.1186/s43141-021-00186-3 https://doi.org/10.3389/fpls.2022.994902 https://doi.org/10.3389/fpls.2022.994902 https://doi.org/10.3389/fmicb.2020.02019 page 1 page 2 page 3 page 4 page 5 page 6 page 7 page 8 page 9 page 10 page 11 page 12 page 13 page 14 page 15 page 16 page 17 page 18 page 19 page 20 page 21 page 22 page 23 page 24 page 25 page 26 page 27 page 28 page 29 page 30 page 31 page 32 page 33 page 34 page 35 page 36 page 37 page 38 page 39 page 40 page 41 page 42 page 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page 494 page 495 page 496 page 497 page 498 page 499 page 500 page 501 page 502 page 503 page 504 page 505 page 506 page 507 page 508 page 509 page 510 page 511 page 512 page 513 page 514 page 515 page 516 page 517 page 518 page 519 page 520 page 521 page 522 page 523 page 524 page 525 page 526 page 527 page 528 page 529 page 530 page 531 page 532 page 533 page 534 page 535 page 536 page 537 page 538 page 539 page 540 page 541 page 542 page 543 page 544 page 545 page 546 page 547 page 548 page 549 page 550 page 551 page 552 page 553 page 554 page 555 page 556 page 557 page 558 page 559 page 560 page 561 page 562 page 563 page 564 page 565 page 566 page 567 page 568 page 569 page 570 page 571 page 572 page 573 page 574 page 575 page 576 page 577 page 578 page 579 page 580 page 581 page 582 page 583 page 584 hungar~journal of indus1rial chemis1ry veszprem vol. 29. pp. 8186 (2001) computer construction of chemical reaction mechanisms b. v. alexeev, n. i. koltsov and f. j. kell 1 (department of physical chemistry of chuvash state university, moskovskii prospekt 15, 428015 cheboksruy, russia 1department of chemical engineering, technical university of hrunburg-harburg, eissendorfer strasse 38, d-21073 hrunburg, germany) received: decernoer 28, 2000 a computer progrrun was developed which permits the design of all possible mechanisms of a certain class of chemical reactions proceeding according to a step scheme via intermediate components and a brutto-reaction. the application of the progrrun for concrete reactions is described. keywords: chemical reaction, reaction mechanism, algorithm, intermidiate substances, maple progrrun introduction it is of great importance to find a mechanism of a chemical reaction in accordance with measurements. the solution of this problem is based on the formulation of all possible step schemes describing the experimental peculiarities of the reaction. it is based also on choosing a mechanism consisting of intermediate components in the various steps which is confirmed by the corresponding physico-chemical methods. in the publications [1-3] the systematization of all possible threeand four-step mechanisms of catalytic reactions is carried out. for these mechanisms the relaxation time [1] and autooscillations [2,3] were investigated. as a base for generating these mechanisms, transient steps of intermediate components on a catalyst surface are taken without referring to special chemical reactants. in the present paper a program for the automatic generation of stoichiometric factors of a certain class of reactions will be presented. the algorithm and the program the computer program which allows the design of step schemes of chemical reactions like (1) (i = l, ... ,sa; l = l, ... ,na), is described in this paper. they proceed via the following steps l,.a;x i = l,.aijx i , d,; j (i = l, ... ,sx, j == l, ... ,nx; r = l, ... ,q ), (2) where a1 , x j are reactants and intermediate substances; na, nx are the numbers of reactants and intermediate substances; sa, sx are the number of brutto-reactions (1) and steps (2) in the mechanism, respectively; a; 2 0 and c: 2 0 are stoichiometric coefficients; d,; > 0 are stoichiometric numbers of the i-th step in the r-th route (a route is a linear combination of elementary steps which lead to the final brutto reaction of the reactants); q is the number of routes. the goal of the program is to determine all possible mechanisms of step scheme (2) in the form 2);a1 + l,.a;x j "'l:h;a1 + l,.a;;x j (3) l j l j taking into account brutto-reactions of eq. (1). it is worth noting that the scheme {2) is supposed to be given and the program provides the selection of basic substances for this scheme. the program searches not only for the stoichiometric coefficients b1i , but also guarantees the satisfaction of the laws of conservation 82 table 1 the block diagram of algorithm of the program defining of stage scheme a*x=a_ *x and brutto-scheme c* a=c_ *a by lists of stages, written in a form of linear equations, connecting the symbols of intermediates and basic substances, respectively . • calculating the matrix of stoichiometric numbers a-a_ and the vector of intermediates x on a stage scheme given. • calculating the number and basis of conservation laws alpha of stage scheme, defined from the property, that they belong to right kernel of the matrix of stoichiometric numbers . • calculating the number and basis of routes d of stage scheme, defined from the property, that they belong to left kernel of the matrix of stoichiometric numbers . • calculating the matrix of stoichiometric numbers c-c_ and the vector of basic substances a by the given brutto-scheme. • calculating the number and basis of conservation laws beta of brutto-scheme, defined from the property, that they belong to right kernel of the matrix of stoichiometric numbers. t calculating the number and basis of routes r of brutto-scheme, defined from the property, that they belong to left kernel of the matrix of stoichiometric numbers. t finding the matrix of stoichiometric coefficients b-b_ from the matrix equation d*{b-b_)=u*(c-c_). usually, the solution is not unique, and may possess some arbitrary parameters v in addition to parameters u. as separate determinion of matrices of stoichiometric numbers b and b_ is impossible under approach .exploited here, the coefficients of the matrix b could be considered as arbitrary. when matrices u, v and b are selected, matrix b_ could be calculated uniquely. t calculating the molecularities matrix gamma from the matrix equation {a-a_)*gamma=-{b-b_)*beta, this constitutes the second condition mentioned above. the solution might be non-unique, wich may cause the appearing of another arbitrary matrix w. t printing the problem solution in a form of stages b*a+a*x=b_ *a+a_ *x of a mechanism and chemical formulas of intermediates lnx=alpha *lnz+gamma *lnp and the basic substances lna=beta*lnp. t for reactants and intermediate substances and the chemical formulas of the species xi and reactants a1 • (5) the algorithm is as follows. the chemical formulas of intermediates x 1 are written in the form x1 =fiz:"'*llp!", where ai* are numbers of adsorption sites of catalyst atoms of type z" where the intermediates x. are j (4) k k where zt and lk are the types of catalyst and types of reactant atoms. the chemical formulas of the reactants "'* have the following form adsorbed; f3 ik are numbers of adsorbing reactants of type lk on the adsorbing sites zk ; r lk are the numbers which connect of numbers a jk , fj j< and the stoichiometric coefficients by the following relations l(a1; -aij)aik =0; j :l<bt; -b~7)y,k =o, l ldr/b; -bij)fjjl =0, i,j :lee; -c~)y1k +:lea; -aij)/3jk = o. l j (6) the solution of these linear equations (unknown values are a ik , f3 ik , y1k_, b1; and b11 ) results in the mechanism (3) which is in accordance with the step scheme (2) and the brutto-reactions (l). this algorithm is realized in a program written in maple programming language. the problem that this program solves is summarized below: given: l step scheme a*x==a_ *x 2. routes d*(a-a_}=o 3. conservation laws (a-a_)*alpha=o 4. chemical formulas inx=alpha*inz 5. brutto-reaction c*a=c_*a 6. routes r*(c-c.j=o 7. conservation laws (c-c_)*beta=o 8. chemical formulas lna=beta*jnp the following set of linear equations has to be solved to find alpha, beta, gamma, b and b_. find b, b_, alpha, beta, gamma such that: 1. mechanism is b* a +a*x=b_ *a +a_ *x, 2. chemical formulas are inx=alpha*lnz+gannna*inp, and the following conditions are fullfilled: a) on routes: d*(b-b_)*beta=o b) on conservation laws: (b-b_)*beta+(a-a_)*gamma=o here a and a_ are matrices of stoichiometric coefficients of the intermediates in eq. (2); c, c_ and b, b_ are matrices of stoichiometric .coefficients of the reactants in eqs. (1) and (3), respectively; dis the matrix of stoichiometric numbers of steps in different routes (see eq.{2)); alpha, beta, gamma are matrices of coefficients aik, f3it, ylk (see eqs. (4),(5)); a, x, z, p are vectors of a,, xi, zk, lk (see eqs.(4), (5)). brief comments on the algorithm will be given. the first condition represents equality of all d-routes of the mechanism (i.e. routes, obtained using stoichiometric coefficients of matrix d) to the set of steps of the brutto-scheme. we mean an equality with respect to linear combinations of steps, i.e. equality of linear spans of vectors of stoichiometric numbers of steps. this condition could be written also in a form d*(b-b.j=n*{c-c_), where n is an arbitrary matrix of the corresponding size. it follows from the orthogonality of matrices d*(b·bj and c-c_ to the same matrix beta. 83 the second condition describes the balance of each step of the mechanism of atoms p of reactants (the balance on atoms x of intermediates is satisfied automatically). the main steps of the program are given in a block scheme (see table 1). application of the program let us analyze the applications of the program for concrete chemical reactions. for example, the reaction 2co + 0 2 = 2c02 proceeds yia a four-step scheme 1. 2x1 =2x2 , 2. x 1 =x3 , 3. x 2 +x3 ==2x1 , 4. x 2 ==x1 • the initial data will look like stepscheme:=£2 *xi =2*x2,xl =x3,x2 +x3=2 *xl,x2==xl ]; bruttoscheme:=[2 *c0+02=2 *c02 ]; the step scheme in mechanism set (9) given below in the appendix becomes the simplest one if the parameter values are the following b12 =b2! =b4l =1, b11 = b13 = hzz = b23 = b3i = b32 = b33 = b42 = b43 ""0, u11 = v11 = w11 = 1, v31 = v32 = -1, u21 = vzi = v12 = vzz == wzi = 0 · the following mechanism is the simplest: 1. 0 2 +2k=2ko, 2. co+k=kco, 3. ko+kc0=2k +c02 , 4. co+ko=k+c02 , (7) which corresponds to a two-route scheme of carbon monoxide oxidation on platinum catalysts (4]. this model is important because mechanism (7) has two routes which are characterized by a similar brutto~ reaction ( 2co + 0 2 = 2c02 ). if a three-step mechanism 1. 2x1 =x2 +x3 , 2. x 2 =x1 , 3. x 3 =x2 , is supposed to be realized for the reaction 2co + 2no = 2c02 + n 2 , the initial data for the program will be as follows: stepscheme:=[2*xl=x2+x3,x2=xl,x3=x2]; bruttoscheme:=[2*c0+2*n0=2*c02+n2]. the program gives not one, but a set of mechanisms (10) which is characterized by the parameters 84 b;p wii, vii, uii. the selection of fixed values of these parameters like b13 = bzl = b33 = 1 ' b11 = h12 = b14 = bzz = bz3 = bz4 = h31 = h32 = b34 = 0 ' uu = vu = v32 = 1, vzt = v4z = -1, v31 =v41 =v12 =vzz =wn =wzl =w31 =0 allows one to write down a mechanism and chemical formulas of reactants and intermediate substances in the following form n0+2x1 = x 2 +x3 , co+x2 = = c02 + x 1 , no+x3 =n2 +x 2 , x 1 =zp x 2 =z1p2p31 , x 3 =z1jl-pz1~, co=p3 ,c02 =p2,no=~,n2 =~2p2-2~2 • this is a mechanism l.n0+2k =ko+kn, 2. co+ ko = k + c02 , 3.no+kn=ko+n2 • (8) it coincides with the known mechanism [5] of carbon monoxide interaction with nitrogen oxide on platinum catalysts. conclusion it is known that the structure of a mechanism to determine the dependence of the reaction rate as a function of concentration of reactants or time [6]. reactions proceeding via linear mechanisms are characterized by monotonous dependences of stationary rates vs. initially taken substance concentrations. reactions proceeding via nonlinear mechanisms are characterized by critical phenomena like multiplicity of stationary states (mss) and autoosciuations. there are papers in which step schemes describing autooscillations [3] and mss [6] are published. thus, if a given reaction proceeds in an autooscillation regime, its mechanism can be established by the step schemes which are given in the paper [3]. for each scheme it is possible with the aid of our program to determine the chemical structure of intermediate components and the amount of reactants in each step. some other schemes are formed in the same manner. as a result, a set of mechanisms is formed. in the end that mechanism containing intermediate components must be chosen, which is confirmed by experimental methods. thus~ the developed program enables one to construct mechanisms of chemical reactions with the aid of a computer. this program gives the ability to search for chemical formulas of reactants and intermediate components in each step of a reaction mechanism. the program can be used for the solution of the step scheme identification problem, which is connected with a unique mechanism determination of a reaction which is characterized by a definite kinetic beha'<1ior. references 1. alexeev b. v., fedotov v. kh. and koltsov n. i.: chern. phys., 1982, 1, 776-779 (in russian) 2. fedotov v. kh., alexeev b. v. and koltsov n. i.: izv. vuzov. chemistry and chern. technology, 1985,28, 66-68 (in russian) 3. koltsov n. i., alexeev b. v. and fedotov v. kh.: dokl. akad. nauk sssr, 1994, 337, 761-764 (in russian) 4. ivanov v. p., ewkhin v.i., yablonski! g. s., savchenko v. i. and tataurov v. l.: kinet. katal., 1981, 22, 1040-1042 (in russian) 5. druzhinin d. l., ivanova a. n. and furman g. a.: chern. phys., 1986, 5, 1410-1412 (in russian) 6. koltsov n. i., fedotov v. kh. and alexeev b. v.: kinet. katal., 1995, 36,42-46 (in russian) appendix the program written in maple and examples program with(linalg): # stepl step scheme a*x=a_ *x & brutto-scheme c* a=c_ *a # stepscheme:=[xl=x2,x2=x3,2*xl +x3=3*xl]; # stepscheme:=[2*xl=2*x2,xl=x3,x2+x3=2*xl,x2=xl]; # bruttoscheme:=[2*c0+02=2*c02]; # 02+2k=2ko, ko+kc0=2k+c02, co+k=kco, co+ko=k+c02 # stepscheme:=[2*xl=x2+x3,x2=xl,x3=x2]; bruttoscheme:=[2*c0+2*n0=2*c02+n2]; # n0+2k=ko+kn, co+ko=k+c02, no+kn=ko+n2 stepscheme:=[xl=x2,x2=x3,x3=xl]; bruttoscheme:=[2*c0+2*n0=2*c02+n2]; #n0+2k=ko+kn,co+ko=k+c02,~0+kn=ko+n2 #step 2 stoichiometric matrix a-a_ & vector x steps:=nups(stepscheme): lprint('intermediate reaction step scheme given' ,stepscheme ); intermediates vector:=transpose(matrix([[ op(indets(stepsche me))]])): intermediates:=rowdim(intermediates vector): lprint('steps founded' ,steps); if steps=o then error(' at least one step must be given') fi; !print(' intermediates founded' ,intermediates): i print(' intermediates vector'): print(intermediates vector): if intermediates=() then error(' at least one intermediate must be founded') fi; a:=matrix(steps,intermediates,['['coeff( op(l,stepscheme[i]}, intermediates vector[j, 1 ]}'$'j'= ! . .intermediates ]'$'i'=l .. steps ]): a....:=matrix(steps,intermediates,['['coeff( op(2,stepscheme[i]), intermediatesvector[j,l])'$t=l .. intermediates]'$'i'=l .. steps]): 'a-a_ ":=matadd(a,a_, 1,-1 ): iprint('stoichiometric matrices of intermediate reaction step scheme,a,a_,a-a_ "}; print(a,a_.'a-a_ ')~ # step 3 conservation laws alpha alpha:=transpose(matrix([op{kernel('a-a_ ')) ])): l...aws:=coldim(alpha): lprint('intermediates conservation laws founded' ,laws); if laws=o then error(' at least one conservation law must exist') else lprint('intermediates conservation laws matrix, alpha'); print( alpha); # step 4 routes d d:=matrix([op(kemel(transpose('a-a_ ')))]): routes:=rowdim( d): lprint('routes founded' ,routes); ifroutes>o then lprint('routes matrix, d'); print(d); fi fi: # step 5 matrix c-c_ & vector a lprint('brutto reaction step scheme given',bruttoscheme); brutos:=nops(bruttoscheme ): i print(' steps founded',brutos); species v ector:=transpose(matrix([[ op(indets(bruttoscheme))] ])): species:=rowdim(speciesvector): lprint('species founded',species): lprint('species vector'): print( species vector): if ( { op(intermediates vector)} intersect { op(speciesvector) })<>{} then error('intermediates vector' ,intermediates vector, 'of step scheme', stepscheme, 'and species vector',species vector,' ofbrutto reaction' ,brutto, 'must have zero intersection', { op(intermediates vector)} intersect { op(species vector)}) fi; 'c-c_':=njatrix(brutos,species,[seq([seq(coeff(op(l, bruttoscheme[i])-op(2,bruttoscheme[i]), speciesvector[j,l]),j=l .. species)],i=l .. brutos)]): lprint('stoichiometric matrix ofbrutto reaction step scheme, c-c_ '); print('c-c_ '); # step 6 conservation laws beta beta:=transpose(matrix([op(kernel('c-c_'))])): bruttolaws:=coldim(beta): lprint('brutto conservation laws founded' ,bruttolaws ); if bruttolaws>o then !print(' conservation laws matrix, beta'); print(beta) fi: # step 7 routes r r:=matrix([op(kernel(transpose('c-c_ ')))]): bruttoroutes:=rowdim(r): lprint('brutto routes founded', bruttoroutes); if bruttoroutes>o then lprint('brutto routes matrix'); print(r) fi; # step 8 stoichiometric matrix b-b_ rowsp:=matrix([ op(rowspan(' c-c_ ')) ]): u:=array(l .. routes, l .. rowdim(rowsp) ): mu:=multiply(u,rowsp )~ 'b-b_ ':=linsolve( d,mu,'r','v'): lprint('matrix b-b_ '): print('b-b_ '): !print(' verification: matrix expression d*(b-b_)*beta'): 'd*(b-b_)*beta':=evalm(d &* 'b-b_' &* beta); print(' d*(b-b_)*beta '): i print(' must be zero matrix'): ifiszero('d*(b-b_)*beta') then lprint('verification passed') else error(' matrix expression d*(b-b_)*beta must be zero matrix') fi; b:=array(l..steps,l..species): lprint('matrix b'): print(b): b_:=matadd(b,'b-b_ ',1,-1): lprint('matrix b_ '): print(b_): #step 9 matrix gamma gama:=linsolve('a-a_ ',evalm(-'b-b_" & * beta),'r2' ,'w'): i print(' stoichiometric matrix, gama '); print(gama); iprint('verification: matrix expression (a-a_)*gama+(b­ b_)*beta'); '(a-a_)*gama+(b-b_)*beta':=evalm('a-a_' &* gama+'b-b_' &*beta): print('(a-a_)*gama+(b-b_)*beta'); lprint('must be zero matrix'); if iszero('(a-a_}*gama+(b-b_)*beta ') then lprint('verification passed') else error('matrix expression (a-a_)*gama+(b­ b_)*beta must be zero matrix') fi; # step 10 print the solution lprint("intennediates step scheme'): print(stepscheme): lprint('brutto step scheme'): print(bruttoscheme ): z:=['z.i'$'i'=l..laws]: p:=['p .i'$'i'= i .. bruttolaws ]: m:=evalm(b &*species vector+ a&* intermediates vector): m_:=evalm(b_ &*species vector+ a_&* intermediates vector): eqs:=array(['['m[i.j]=m_[i,j]'$'i'= l .. rowdim(m) ]'$)'=i .. coidim( m_)j): lprint('reaction mechanism'):print(eqs): m3:=evalm(alpha &* z + gama &* p): ln:=[seq(intermediatesvector[i,l]=m3[i],i=l . .intennediates)]: lprint('chemical formulas of intermediates~): print(in): m4:=evalm(beta &* p): sp:=[seq(speciesvector[i,l]=m4[i],i=l .. species)]: lprint('chemical fonnulas of species'); print(sp): example 1. 85 for the reaction 2co + 0 2 = 2c02 , proceeding in a four-step scheme 1. 2x1 = 2x2, 2. x 1 = x 3 , 3. x2 +x3 =2x1 , 4. x2 =x1 , initial data was entered in a form stepscheme:=[2*x1=2 *x2,xl=x3,x2+x3=2*xl,x2=x 1]; bruttoscheme:=[2*c0+02=2 *c02]; the set of mechanisms of a reaction of carbon monoxide oxidation, which is found by the program, has the following form 1. b11co + b120 2 + bi3c02 + 2x1 = =(b11 -4u 21 -2u11 +2v11)co+ +(blz -2uzl-ul! +2vzr)02 + +(b13 +2u11 +4u21 +2v31 )c02 +2x2, 2. b21co + b220 2 + h23c02 + xl = = (b21 +2u21 +v12 -v11)c0+ +(b2i2 +u21 +vzz -vzi)oz + +(b23 -2uzt +v32 -v31)c0z +x3, 3. b:11co + b320 2 + b33c02 + x 2 + x 3 = = (b31 -vtz)co+(b32 -vzz)oz + +(b33 -v3z)coz +2xl, 4. b41co+b420 2 +b43c02 +x2 = =(b41 -vn)co+(b42 -vzt)oz + + (b43v31) coz + xp (9) where bu, uu, v u are free parameters. the chemical formulas of intermediate substances are determined by the relations where z1 are free centres on a catalyst surface, ~ and p2 are atoms or atom complexes out of which the basic substances are fonned. w11 , w21 are free parameters. the chemical formulas of basic substances are determined by the program as co= f;, 0 2 = f;-2 p2 2 , c02 = p-:.. 86 li and ~ complexes in this model form oxide and brutto step scheme carbon dioxide respectively. 2co + 2no = 2c02 + n2 reaction mechanism example 2. 1. b11co +b12c02 +b13 no +b14n2 + 2x1 = three-step mechanism 1. 2x1 = x 2 + x3 , 2. x 2 =x1 , is supposed to be realized for the reaction 2co + 2no = 2c02 + n 2 . the initial data for the program will be stepscheme:=[2*xl=x2+x3,x2=xl ,x3=x2]; bruttoscheme:=[2*c0+2*n0=2*c02+n2]; the part of the program output is given below. intermediates step scheme 2x1 = x2 +x3, x2 = x1, x3 = x2 = (b11 2u11 + 2v11 + v12 )co+ + (b12 + 2u11 + 2v21 + v22 )c02 + + (b13 2u11 + 2v31 + v32 )no+ + (b14 + uu + 2v 41 + v 42 )n 2 + x 2 + x 3' 2. h21co +h22c02 +h23 no +b24n2 + x 2 = = (b21 v11 )co + (b22 v21 )c02 + (10) + (b23 -v31 )no + (b24 v41 )n2 + xp 3. b31co+b32c02 +b33 no+b34 nz +x3 = = (b31 v12 )co+ (b32 v22 )c02 + + (b33 -v3z)no + (b34v42)n2 + xz chemical formulas of intermediates x z p. wn p. w21 p. w31 i1 i 2 3 ' x _ z p.-v31-2v41+wn p_-v2i+2v4i+w2t r-vu-2v4i +w3i 2i 1 2 3 ' x -z v-v32 -2v42 -2v4i-v3i +wu p -vzz-v2t+2v4t+2v42+w2t 3tlj ? .p-vt2-2v42 -vu-2v4i +w3i 3 chemical formulas of species co=?:,, c02 = p2 , no= .fi, n 2 = li2 p22 p3 2 • page 85 page 86 page 87 page 88 page 89 page 90 hungarian journal of industrial chemistry veszprem vol. 29. pp. 27-34 (2001) multiplicity of steady states and the shapes of its exidbiting in catalytic reactions kinetics n. i. koltsov and f. j. ke1l1 (department of physical chemistry of chuvash state university, moskovskii prospekt 15, 428015 cheboksary, russia 1 department of chemical engineering, technical university of hamburg­ harburg, eissendorfer strasse 38, d-21073 hamburg, germany) received: december 28, 2000 the purpose of the presented review is the analysis of the existing approaches and mathematical methods for the investigation of the critical phenomena of a type of multiple steady states in kinetics of catalytic reactions keywords: multiplicity; steady state; hysteresis; self-crossing; breakdown; isola; mushroom; catalytic reaction; kinetics; step scheme. introduction one of the current problems in kinetics is the investigation of the multiplicity of steady states (mss) and the shapes of the phase portraits in catalytic reactions. their existence was proved by extensive research, and the results were published in many papers and at conferences. thefollowing sections review the development of mathematical methods and the research of mss in catalytic processes. well-known are ya. zeldovich's papers on the uniqueness of the equilibrium point [1] and the anomalous types of critical effects [2]; i. prigozhin brussel's school publications [3,4]; monographs by g. jablonskii, v. bykov, v. elokhin, a. gorban [5-81; and also the research work carried out at the g. boreskov institute of catalysis sd ras, at then. zelinsky organic chemistry institute, at the n. semyonov chemical physics institute,. and at some other institutions are of great importance for the development of this branch of science. at the beginning of the investigation of critical phenomena like mss the experimental data on their existence in concrete heterogeneous catalytic reactions were collected: hydrogen oxidation [9-10], of carbon monooxide oxidation [11-13], ammonia synthesis [17] on platinum metals and others. then researchers·tried to describe these phenomena taking into account thermal and diffusional effects [18, 19]; phase transitions [20]; changes of the catalyst surface structure [21] under the influence of components which take part in a reaction, ramified-chain [22, 23] or homogeneous-heterogeneous [24] character of reactions. discovering mss in the kinetic region [25, 26] for some reactions led to the third step in which mss is described by simple model mechanisms [5-8]. the modern fourth step is characterized by the development of the theoretical methods investigation of mss and different forms of its catalytic reaction kinetics. some important results in this field of research is reviewed in this paper. theory to describe existing approaches of investigation of mss and their various shapes let us regard a general one-route catalytic reaction acting through steps + r; :~:>;;a1 + :la;x 1 <=} lhiia1 + :la;x1 • d1 (2) l j ,.,i j l i,j = l, ... ,s; l = l, ... ,m, 28 where a1 and x; are basic substances and intermediates; a;, b~ ;;:::: 0 are the stoichiometric coefficients ( '2tat = l«ii ); d1 > 0 are the j j stoichiometric numbers of steps, ( i = 1, ... , s ); r/ and rj are directions: rates of i~th step in forward and reverse (3) mi and m; are the frequencies of steps in forward and reverse directions, x1 are the concentrations of intermediates x 1 , c1 are the concentrations of basic substances a1 , k( are rate constants of the steps .. under isothermal conditions in a gradientless differential reactor the scheme (2) describes the changes of concentrations of the reactants ( ~ ) and intermediate substances ( x 1 ) by the following system of the stationary equations (4) l(hi:" -ht,j<r;-r_i)+lcg -qck =0, (5) i where q0 and q are reactor inlet and outlet flows of a reaction mixture, c~ and ck are the concentrations of r a r b parameter,c :r r d e the k th reactants at inlet and outlet of the reactor. the scheme (2) is characterized by the conservation law of the number of centers per unit of a catalyst surface (6) corresponding to the constant total quantity (or concentration) of active centers on the unit of the catalyst surface. under stationary conditions, the rates of the reaction steps (i) are given by (7) we will first discuss the shapes of the kinetic curves which reveal multiplicity. mss of reaction rates are investigated as a function of one parameter (concentration of one reactant, temperature, flow rate of one reactant etc.). these dependencies are characterized by the existence of some different stable regimes of reaction proceeding under the same conditions. the typical shapes of kinetic phase planes which are characterized by mss [271 are given in fij. l. results and d~cussion s·shaped hysteresis first the kinetic dependencies in the form of s-shaped hysteresis are considered which were often detected in experiments (fig. la, lb). the peculiarity of this hysteresis is, as a rule, the existence of two (solid lines) and one unstable (a broken line) branches. only stable branches are observed experimentally. the hysteresis is parameter, c parameter, c r parameter, c parameter, c parameter, c fig. 1. multiplicity shapes of steady states: a"anticlockwise" hysteresis, b"clockwise" hysteresis, cself­ crossing ("loop"), dbreakdown , eisola, fmushroom (solid lines-steady stationary states, broken lines­ unsteady stationary states) shnwn by the arrows in fig ta. fur example, when the hysteresis is antic!ockwise, the parameter c leads to an increase of the reaction rate along the low branch until the critical point u is reached csee fig.!). a further change of reaction rate r takes place along the upper branch of the s·shaped curve. decreasing the parameter c along the upper branch. a sudden jump to the lower branch takes place at the critical pnint a. mss of heterogeneous catalytic reactions in the form of s·shaped hysteresis were observed for the oxidation of hydrogen, carbon monoxide, ammonia, ethylene. benzene, propylene and ammonia synthesis processes. in must cases. for the description of hysteresis in the above-mentioned reactions. mechanisms characterized by interaction of adsorbed components on a catalyst surface were used. a rea~:tion of carbon mtmoxide oxidatilm on the metals of the platinum group as a fun~.:tion of temperature "nnticiock.wise" h;ystt'resis (fig. la} (also concentratimt "clockwise" and "anticlockwise" hystereses) was described, for example. by the following reaction llcheme (281: l 0~+ 2k= 20k, 3. cok + ok-? 2k + coj, 2. co+ k = cok. 4. co+ ok -?k + coz, where k. ok, cok are free, occupied by oxygen or by carbon monoxide catalyst surface centers, respectively. the most effective approach of detecting mss is the mathematical criterion presented in the papers {29, 30j. the t.:riteritm allows, un the basis of the stoichit~metric matrix of intermediate components of n step scheme of reaction, ttl detect definitely the existence of mss, and also to define a set of steps ensuring mss of catalytic reactions as a function of the concentration of intermediate components. this criterion will be formulated. it is obvious that mss can only occur in case that at least two stationary states are possible under the same reaction conditions. this statement is the basis for the mss criterion formulation in paper [30]. the criterion includes the necessary conditions of existence of mss like these: ( w-~a~1v1 ~):kuk} { ~kj -azjrj + ~(bi:k -b;j,pk )>o (8) for ro_i ¢ 0 29 3i.j: v; <0<v1 • <101 in general the criterion of mss is formulated as foll<>ws: if for a reaction scheme of the corresponding relations {8} (or (9) ), ( lo) and { ll) are satisfied then the examined reaction is characterized by multiplicity. otherwise there is only one stationary state. the values v1, u~~: and w at which mss is realized can be applied for the determination of concentration of the reactants and intermediate substances [30}. let us illustrate an application of the criterion of existence of multiplicity in a catalytic reaction of carbon monoxide oxidation 2co + 0 2 = 2co~ on platinum !.31 j proceeding according to the scheme 1. o:j+2k==2ko, 2. co+ko+k~c02+2k. (12) in the beginning we shall write down the criterion of mss for this scheme in isothermal gradientless differential reactors nt constam concentration "* th..t reactants ck , when nil components of a vectm· l.j ar~:: equal to zero. with respect to relations (8) and (9) mss will occur under the following conditions: where the parameters v; and v2 correspond to substances k and ko. a simple analysis reveals that the inequalities (13) are only satisfied if all the vector components v have the same signs. in this case equation (10) is not satisfied. it specifies the impossibility of the description of mss by the scheme (12) in the given reaction. if one takes into account changes of concentration the relations (8), (9) for reactants, the criteria take the form of the relations obtained are carried out, for example, at w=2, v;::::6, v2 =-2, u1 =-13, u 2 =-2 (the w = l:>~f1 + })t.uk,forw_1 ::::0 j k ~ the sufficient conditions ofmss are (9) parameters u1 and u2 correspond to the concentrations of 0 2 and co). the given values satisfy a component of vectors v and u also the inequalities (10), (11). in fig. 2 the dependence r = f(cr0 ) is given which demonstrate mss as a s-shaped "counter-clockwise" hysteresis curve. hence the scheme (12) can be used for 30 the description of mss in the catalytic reaction of carbon monoxide oxidation under isothermal conditions with respect to the change of concentration of the reactants. -1 r.3 4~----~=----------------3 2 1 fig.2. dependence of rate on concentration of carbon monooxide for reaction of carbon monooxide oxidation proceeding on the scheme (12) at: , , (s-1) the criterion developed was used for the investigation of both known and new mechanisms of catalytic hydrogen oxidation and carbon monoxide reactions. the most simple schemes of these reactions describing mss in the form of s-shaped hysteresises are the following: h2 oxidation: 1. 0 2 + 2k == 2ko, 2. h 2 +ko+k-+2k+h20, co oxidation: 1. 0 2 + 2k == 2ko, 2. co+k0-+k+c02 , 3. co+k == kco. self-crossing another shape of mss is a kinetic curve with self­ crossing (fig. lc). this critical phenomenon is characterized by the fact that the graph of reaction rate as a function of a parameter intersects at one point. this leads to a kinetic "loop". fig. lc shows that changing the parameter c from left to right and vice versa in the region of the loop self-crossing, kinetic dependence is realized in the form of a hysteresis "eight" (see the direction of rate change along the cbdac curve). it is worth noting that at the intersection point, which is characterized by various values of intermediate species concentrations on a catalyst surface, the reaction rate has the same value. this property was the basis for the mechanisms which describe self-crossing. as was shown in the papers [32, 33] in an isothermal gradientfess differential reactor at constant concentration of the basic substances (when all components of a vector u are equal to zero) any one­ route~reaction consisting of steps of a kind (2) in a point of self--crossing can be characterized by the following equations between rates ( (2) i r(l) == rc2 l, w == in :<1l ) == 0 (14) and for concentrations of intermediate substances one obtains: :::j j. . (1) "'" (2) j. -1 n ::::1 • x1 -r x1 , , .•• , (15) in various steady states. the equations of mss criteria (8), (9) in case of self-crossing will be written down for reversible and irreversible steps accordingly in the following way: (17) in the case a two-step reaction consisting of steps of a type (2) it is possible if there stoichiometric coefficients satisfy relations: hence the criterion of existence of a loop for two-step reactions is that all four inequalites (18) are fulfilled. the simplest mechanism satisfying this criterion for ar {:::} a2 reaction is 1. a1 +x 1 +x 2 == 2x 1 + a2 , 2. x1 +2x2 =3x2 • (19) fig. 3a illustrates kinetic dependence self-crossing for this reaction. breakdown the kinetic dependencies with self-crossing or breakdown are shown in fig. lc and ld. as can be observed, under certain conditions points a and b in fig.lc with self-crossing can exist very close to each other, which leads to a kinetic curve with breakdown. the kinetic behavior of this form was obtained for reactions of carbon monoxide oxidation on palladium {34, 35} and a1so hydrogen oxidation on platinum [36]. besides these examples the occurrence like breakdown were obtained at joint oxidation of carbon monoxide and nitrogen oxide [37]. r, s-1 31 a b 0.3 0.2 0.2 0.1 +""'"-~~-~-~-~-~cone. ca c 0 os cm~ a . 1.2 0 0.3 0.6 fig. 3. kinetic dependence r(ca1) for reaction a1 {::::} a2 proceeding via scheme (19): a)k 1 = 2, (1)_ 1 = 1/7, mz == 804/343, m_2 == 60/343; b)k1 = 10, 11)_1 = 2.495, m2 = 0.668, m_2 = 0.131 (s-1) 2 1.5 1 0 o~------~~~1~--~~--~2 cone. cb cone. c 8 fig. 4. kinetic dependencies for scheme (20) at k1 = 4, k2 "" 1~5 , k_2 =54 (s-1 ): a)monotonous branch with anisolated "specialpoint(k_1 =.!.)"; b)-isola(k_1 =0.51) 2 the treatment of breakdowns as a function of kinetic parameters for reactions of oxidation of hydrogen, carbon monoxide, ammonia on platinum on the basis of multipathway mechanisms was presented in [37, 38] for the frrst time. it was supposed that for these reactions the rate constant of interaction between adsorbed particles on a catalyst surface is rather strong, also the occupation of the catalyst by oxidizing substances is small [38]. the same approach is presented in [39] for the reaction of carbon monoxide oxidation on platinum. the breakdown of kinetic dependence was interpreted within the framework of the scheme az+2k=2ak, b+k=bk, ak + bk-+ 2k + ab as a limiting case of the kinetic curve at k3 -+ oo • the same explanation of the occurrence of breakdowns can be found in papers {4042] for the reaction of oxidation of hydrogen on monocrystals of platinum. in papers [43461 the criterion of occurrence of a breakdown is offered at the finite values of rate constants. it is shown that the criteria relations of a breakdown are equivalent to the basic criteria of self­ crossing of kinetic curves. this research shows that kinetic dependencies with self-crossing and with a breakdown are determined by an identical reaction stoichiometry, although they display different forms of the critical phenomena. therefore, for describing breakdown it is quite enough to have reaction schemes giving self-crossing of kinetic curves. fig. 3b illustrates breakdown for scheme (19). breakdown and "loop" are two evolutional mss forms. the simplest schemes of catalytic hydrogen oxidation and carbon monoxide reactions describing mss in the form of breakdown (or with self-crossing) of kinetic curves are the following: h2 oxidation: 1. 0 2 + 2k ""2ko, 2. h2 +k=kh2 , 3. ko+kh2 -+2k +hzo, co oxidation: 1. ko + kco = 2k + c02 , 2. co+k+kc0=2kco. 3. 0 2 +2k=2ko. isola isola is a closed isolated branch of a stationary kinetic curve (fig. ld). the existence conditions of this shape for a non~isothermal reaction of the first order are 32 formulated in paper [2].the basic cause of appearance of isola is a process of "rolling unrolling" of a mushroom curve in fig. lf. it is described in papers [47, 48}. the isola in the graph of r(c) can be obtained from a kinetic curve having "a speciaf point" (ref. £2, 49]). if one of the parameters changes slightly, this point becomes an isola. the simplest model of a kinetic curve with isola realization is a a¢=> d reaction proceeding via an intermediate, b, according to the following scheme l.a+2b+x1 =x2 +3b, 2.b+3x1+x;. =4x1+d' (20) for which at some parameter values cb, r(cb) shows "a special point" (fig. 4a). if the k.1 parameter slightly increases the point turns into an isola (fig. 4b). mushroom mushroom behavior (fig. lf) can be considered as a monoparameter kinetic curve which consists of two s­ shaped hysteresis branches. this mss shape rarely appears. there are a few papers in which this critical phenomenon is experimentaliy described. the kinetic behavior according to the mushroom type were experimentally reproduced in benzene [so] and carbon monoxide [sl} oxidation on platinum catalysts. the mushroom shape. is a transitional one between isolated and self-crossing kinetic curves. the mushroom shape is connected with the existence of "a special point". the investigation of stoichiometric conditions of the existence of a "special point" showed some interesting results. for example, the b2 ¢=> 2b1 reaction proceeding via the following scheme 20 " b \ 1 ~+x1= x2+4, 2x2=x3+4, 3. 2x1+ x3=3x1 (21) describes the kinetics with isola under certain conditions (fig. sa). if the conditions change, approaching and blending of the isola with a monotonous branch takes place. thus, self-crossing appears (fig. sb), which finally tnrns into a mushroom form (fig. sc). the above-mentioned examples show that kinetic dependencies with self-crossing, breakdown, isola and mushroom are variable forms of mss curves, they can turn into one another if the conditions of reaction change. conclusion for all kinetic dependencies except breakdown (fig. 1) there is a general property, namely the existence of two different steady states, which are characterized by different values of concentrations of intermediate components and reactants and also rates under the same conditions. this statement is the basis for mss criteria [30]. the criteria developed were used for the investigation of both known and unknown mechanisms of catalytic hydrogen oxidation and carbon monoxide reactions which reveal mss in the form of s-shape, self-crossing, breakdown kinetic dependencies, respectively. these data are given in ref. [5256]. the conditions of occurrence of kinetics with isola and mushroom are given in ref. [57, 58] in which the schemes of models and concrete catalytic reactions characterized by these kinetic dependencies are investigated in detail. the conditions and criteria of mss and its different shapes are mathematical relations ·which contain stoichiometry (molecularity of basic and intermediate components in each step of the investigated reaction mechanism). concentrations of components taking part c '\ 1 ····----·~:-· --­ ' l i j 6.4 0.8 u g £1.4 u 1.2 eooc .. ca cmc. cn fig. 5. lsola (a}. sclf..-cmssing (b} and mushroom (c) for scheme (21) at: kj =405. k.~ ::.iu \:>'1):a)11 =43;bl ~ k1 =50.3; c)· k1 :=50.33 {s"1) 0 0.4 ' ' cone.• k_, =12, "7. =180, "-2 =144. in a reaction and kinetic parameters (rate constants and step activation energies). the solution of these algebraic equations for catalytic reactions, which proceed via two or three steps, is not difficult; it can be done by hand. however, for multiple step reactions with a great number of intermediate compounds this analysis is practically impossible without applying computers. the algorithms and computer programs which can be used by chemists are described in ref. 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mixtures using zeolite naa tamás kristóf* department of physical chemistry, institute of chemistry, university of pannonia, egyetem u. 10., veszprém, h-8200, hungary hydrogen sulphide removal from simple gas mixtures using a highly polar zeolite was studied by molecular simulation. the equilibrium adsorption properties of hydrogen sulphide, hydrogen, methane and their mixtures on dehydrated zeolite naa were computed by grand canonical monte carlo simulations. existing all-atom intermolecular potential models were optimized to reproduce the adsorption isotherms of the pure substances. the adsorption results of the mixture, also confirmed by iast calculations, showed very high selectivities of hydrogen sulphide to the investigated non-polar gases, predicting an outstanding performance of zeolite naa in technological applications that target hydrogen sulphide capture. keywords: hydrogen sulphide, zeolite, selectivity, gas mixture, molecular simulation 1. introduction hydrogen sulphide is a highly toxic, acidic and corrosive substance. it is present naturally in landfills, natural and biogases, as well as in several synthesis gases. one of its main anthropogenic sources is the processing of crude oil in industrial refineries, where hydrodesulfurization (hds) of a variety of streams (e.g. engine fuels) produces hydrogen sulphide-containing gas mixtures, which need to be purified. the economic removal of hydrogen sulphide is a long-standing task of the oil and gas industry. adsorptive separation involves the use of solid substrates with a specific affinity with particular compounds of the mixture. zeolites have been applied as catalysts in the petrochemical industry for a relatively long time and these materials can also be used for purification/separation purposes. zeolites are crystalline aluminosilicates consisting of a threedimensional framework of sio4 and alo4 tetrahedra of a highly regular porous structure [1]. the typical size of zeolitic micropores is similar to that of many small molecules. in contrast to various other adsorbents, zeolites generally endure high temperatures and pressures well, and can tolerate harsh chemical environments. the si/al ratio is a key factor in the application of zeolites. zeolites with lower si/al ratios are more hydrophilic, whereas high-silica zeolites often possess fewer structural defects. these latter adsorbents are preferred in the separation of non-polar gases. zeolite naa is a synthetic microporous zeolite which accommodates extraframework na+ ions. it exhibits an especially high affinity with small polar *correspondence: kristoft@almos.uni-pannon.hu molecules such as water. the adsorption and separation properties of zeolite naa have already been examined in several experimental [2-6] and theoretical/simulation [7-16] works. in our laboratories, the adsorption characteristics of zeolite naa and its performance as a drying agent by classical atomistic simulations [10, 1214] were studied, and new intermolecular potential models for this zeolite [12-14] proposed. our models were optimized for the study of the selective adsorption of water from its mixtures with less polar or non-polar molecules like simple alcohols, carbon monoxide, hydrogen and methane. in this paper, the selective removal of hydrogen sulphide by zeolite naa is investigated. molecular simulation predictions for mixture adsorption from two and three-component gas mixtures containing hydrogen sulphide (h2s), hydrogen (h2) and methane (ch4) are presented. 2. models and simulation details zeolite naa [17-18] is of lta framework type, the structure of which belongs to the fm-3c space group with a lattice parameter of 2.4555 nm. the threedimensional cubic arrangement of its framework atoms is comprised of three kinds of rings with four (4r), six (6r) or eight (8r) oxygen atoms. the interconnection of 4r and 6r rings forms nearly spherical cages (sodalite cages) and these cages are linked by oxygen bridges, shaping straight channels of supercages with a maximum diameter of about 1.2 nm. the standard type of zeolite naa has a si/al ratio of 1. in the present study, the unit-cell composition of the standard type of zeolite naa was chosen: it consists kristóf hungarian journal of industry and chemistry 10 of 576 framework atoms, namely 96 silicon, 96 aluminium and 384 oxygen atoms. the framework atoms were fixed at the atomic positions measured in xray diffraction experiments [17] and the 96 nonframework na+ ions were allowed to move. according to the löwenstein rule that prohibits aloal linkages, each alo4 tetrahedron of this framework is connected to a sio4 tetrahedron. realistic and rigid all-atom intermolecular potential models, consisting of lennard-jones and coulombic interaction sites, were used in the simulations. in these models, the interaction sites were fixed at their experimental atomic positions and assigned their lennard-jones energy (ε) and size (σ) parameters, as well as point charges (q). for zeolite naa, the model that was developed earlier was modified slightly [14] by adding weak lennard-jones interaction sites with realistic size parameters [16, 19] to the (originally) pure coulombic silicon and aluminium atoms, thus preserving the dominant role of oxygen atoms in the dispersion interactions of the framework. for hydrogen sulphide, a rigid four-site model proposed recently by shah et al. [20] was adopted, in which the location of the charge parameter of the sulphur atom is offset on the hsh angle bisector towards the hydrogen atoms. an opls-aa model [21] was used for the methane molecules, and its lennard-jones h parameters were also applied to the h2 molecules, with partial charges on the atomic sites and on the molecular centre of mass [22]. table 1 lists the potential parameters of the above models. instead of the generally accepted lorentz-berthelot combining rule, the unlike lennard-jones interactions were computed by the combining rule proposed by waldman and hagler [23]. this combining rule links the behaviour of the unlike energy parameter εij to the relative sizes of atoms i and j and yields somewhat smaller values for the parameters εij and ij when ii≠jj. song et al. [24] found that the experimental thermodynamic properties of pure methane can be reproduced more accurately using the waldman-hagler combining rule. gas adsorption simulations were carried out by the standard grand canonical monte carlo methodology [25]. total pressure p and partial pressures in the gas phase were specified by the chemical potentials of the components; in a diluted gas, these can be calculated from the ideal gas law [12]. the long-range coulomb interactions were treated with the wolf method [26-27] using a convergence parameter of  = 2/rc and cutoff radius of rc = l/2 (l is the length of the simulation box). the simulations involved an equilibration period of 5×107 monte carlo moves and an averaging period of 2×108 moves, consisting of 70% molecular insertion/deletion and 30% molecular translation steps. since the random insertion of molecules is unable to take into account the inaccessibility of the sodalite cages by multiatomic molecules (the physical diffusion pathways to them), creation of h2s and ch4 molecules inside these cages was blocked artificially by placing repulsive dummy atoms at the centres of the cages. as h2 molecules are sufficiently small to pass through the windows of the sodalite cages, the insertion of h2 molecules into these cages was permitted. in either case, the transition of molecules into sodalite cages via translational trial moves was not artificially prevented. in addition to the adsorption loading, the isosteric heat of adsorption was calculated using the equation: tv a a tp b b n u n h q ,,                       , (1) where hb and ua stand for the residual enthalpy and residual internal energy, respectively, n is the number of moles of the substance in the adsorbed (a) or bulk (b) phases. in the grand canonical ensemble, the second part of the equation can be determined from the particle number fluctuations of the simulation and the crosscorrelation of potential energy and particle number fluctuations [28-29]. assuming the ideal gas adsorbates, the first part of the equation is equal to rt, where r is the gas constant and t is the temperature. predictions for mixture adsorption were also made using the ideal adsorbed solution theory (iast) [30-31], which is an analogue of the ideal raoult’s law. using iast, mixture adsorption loadings at a given t can be obtained from single-component adsorption loadings by determining the bulk pressure of each component po at the same spreading pressure  of the adsorbed phase: )(/ o i b i a i ppyy  . (2) table 1. lennard-jones energy (ε), size parameters (σ) and partial charges (q) for the models used in this work (d is the bond length, k is the boltzmann constant). interaction site σ / nm (ε/k ) / k q / electron charge position in the structure/molecule na+ (naa) 0.250 100 0.60 random positions in supercages si (naa) 0.230 22.0 2.40 experimental atomic positions [17] al (naa) 0.240 16.5 1.80 experimental atomic positions [17] o (naa) 0.330 190 -1.20 experimental atomic positions [17] s (h2s) 0.360 122 ds-h = 0.134 nm h (h2s) 0.250 50.0 0.21 hsh angle: 92° xs (h2s)* -0.42 ds-x = 0.03 nm c (ch4) 0.350 33.21 -0.24 dc-h = 0.109 nm h (ch4) 0.250 15.1 0.06 hch angle: 109.47° h (h2) 0.250 15.1 0.4829 dh-h = 0.0741 nm centre of mass (h2) -0.9658 geometric centre of the linear h2 molecule *off-atom site on the h–s–h angle bisector towards the hydrogen atoms selective removal of hydrogen sulphide using zeolite 45(1) pp. 9–15 (2017) 11 here, y i is the mole fraction of component i, and )(o ip is given implicitly by:  o 0 o ln)()( ip a ii pdpn a rt p , (3) where a is the surface area of the adsorbent. 3. results and discussion the intermolecular potential models were tested by determining equilibrium adsorption isotherms for pure h2s, h2 and ch4 on zeolite naa. experimental data at 298 k are available for h2s [32] and h2 [8] and nearly room-temperature (t = 283 k) data for ch4 were taken from [33]. fig.1 shows that the models are largely able to reproduce the experimental adsorption data for these substances. the reproduction of the experimental isotherm is quite good for h2s and h2. in the case of ch4, the extent of overestimation of the experimental results at 283 k is considered acceptable, given that the availability of transferable zeolite models that are appropriate as far as adsorption predictions are concerned for both polar and non-polar compounds is rather limited [16]. furthermore, it is expected that the observed discrepancies between simulation and experimental results for this non-polar component are unable to cause significant errors in terms of mixture adsorption data, where the ch4 content of the gas phase is low and the adsorption of h2s is dominant. the calculated isosteric heat of adsorption data together with available experimental results for h2 and ch4 [5] are also plotted in fig.1. the pressuredependence of these data is weak. the general order of qh2s > qch4 > qh2 is in line with expectations, bearing in mind that the isosteric heat of adsorption at low loadings proves the strength of interaction between the zeolite framework and the adsorbate molecules. q values are considerably higher for polar h2s than for non-polar substances and the order of magnitude of the former indicates the significance of electrostatic interactions. the relation of qch4 > qh2 can be attributed to the greater polarizability of ch4 molecules (this is implicitly included in the attracting lennard-jones terms of the potential model), and to that the explicitly modelled real quadrupole moment of h2 molecules is very weak. considering the greater uncertainties of these simulation results and that the experimental data for h2 and ch4 were obtained for zero coverage within a given temperature range, these simulation results also confirm the suitability of the models used in this study. equilibrium adsorption selectivities were predicted for typical hydrodesulfurization stream outlets of petroleum refinery units separated by zeolite naa at near-atmospheric pressures. the studied gas streams were comprised of between 1 and 2% h2s and ~95% h2; the remaining hydrocarbon content (low alkanes) was represented by the presence of ch4 in the model mixtures. for comparison, other compositions including very low and reasonably high h2s contents, as well as low pressure ranges were also investigated. the raw simulation results for the h2s-h2 mixtures in comparison with iast predictions shown in fig.2 illustrate well the dissimilar levels of adsorption of the two substances, with the exception of the nearly zero h2s contents of the bulk mixture. the iast calculations underestimate the simulation results for h2 at higher pressures and on the whole overestimate the simulation results for h2s at lower pressures (for visual reasons, data obtained within the very low pressure range are not presented in this figure). the most accurate estimations were achieved at 10 kpa, which is an impractical parameter for the present applications. strictly speaking, the hypothesis of iast which states that the different adsorbate molecules have access to the same adsorbent surface cannot be applied to microporous adsorbents such as zeolite naa, where the accessible surface area depends on the size of the adsorbate. in light of this, the iast predictions can be considered to be remarkably accurate. a b c figure 1. equilibrium adsorption loading (n) and isosteric heat of adsorption (q) as a function of the bulk-gas pressure for pure hydrogen sulphide (a), hydrogen (b) and methane (c) on zeolite naa at the temperatures indicated. the statistical uncertainties of the simulations results do not exceed the size of the symbols. the lines connecting simulation data at 298 k are only drawn to guide the eyes. sim.: simulation data; exp.: experimental data. kristóf hungarian journal of industry and chemistry 12 the calculated equilibrium selectivities are defined as: b j b a j a nn nn s / / sh sh 2 2 , (4) where nj stands for the equilibrium number of moles of h2 in the investigated two-component mixtures or the sum of the equilibrium numbers of moles of h2 and ch4 in the three-component mixtures, as plotted in fig.3. on the whole, this zeolite exhibits an exceptional level of selectivity of h2s to the other substances; this is not surprising given the significant differences between the equilibrium adsorption loadings of the pure components (cf. fig.1). in the case of the two-component gas mixtures, the tendency of the data satisfies the criterion that at the low-pressure limit the selectivity as defined here should be independent of the composition of the bulk-gas mixture (it is the quotient of the ratio of the single-particle partition function of the two substances in the adsorbed phase and the ratio of their free-particle partition functions [34-35]). because of technical reasons, at lower pressures the uncertainties of the selectivity data are relatively large as these data are calculated from simulation results at very low zeolite loadings. at higher pressures the separation efficiency of this zeolite is somewhat weaker. this and the fact that the change with pressure is less intense at lower h2s contents suggest the existence of a ‘crowding’ effect, which inhibits more strongly the sorption of the larger molecule, h2s. in the case of the investigated three-component mixtures, the overall picture is similar, but the selectivity values are smaller. this makes sense since the competitive effect of the additional component, ch4, for the adsorption sites is stronger. yet, the values far in excess of 1000 obtained for the typical hydrodesulfurization streams (1-2% h2s and ~95% h2) are compelling. from the mixture adsorption data, once again it was verified that electrostatic effects control the adsorbent-adsorbate interactions with this zeolite, which implies that the amount of adsorption of pure h2 and ch4 should always be small. adsorbed mole number data showed that the presence of the non-polar components does not affect the sorption of h2s in the adsorbed phase. this conclusion is also supported by the heat of adsorption data (not presented) calculated by assuming one-component mixtures (i.e. using eq.(1)). these data turned out to be simply the amount-weighted average of the q values of pure components and are very close to qh2s at the given pressure. on the other hand, the degree of adsorption of the non-polar substances is reduced by the presence of h2s. selectivities under real conditions (at 50, 100 and 200 kpa and with realistic h2s contents; 1, 2 and 5%) shown in fig.4 make this fact obvious. here, s values obtained from mixture adsorption simulations significantly exceed their counterparts calculated for an ideal case of independent adsorption (i.e. by substituting into eq.(4) the purecomponent adsorption loadings determined at pressures that are equal to the partial pressures of the mixture components). extensive non-ideality in the adsorbed phase can also be seen from the comparative failure of iast (which utilizes the assumption that the adsorbed mixture is an ideal solution) to predict the simulation results accurately at near-atmospheric pressures. it is remarkable that the selectivity of h2s to the two non-polar substances decreases as the temperature and partial pressure of h2s in the bulk gas increase. as the adsorption loading of the zeolite rises, steric hindrance plays an increasingly important role, and sorption of the larger h2s molecules reduces to a greater extent. the impact of an increase in temperature is as expected, e.g. from the higher qh2s values, but the magnitude of decrease in selectivity with temperature changes significantly as a function of the partial pressure of h2s. data lines at the two investigated temperatures seem to converge to similar values at higher partial pressures, because the drop in the sorption of h2s as the temperature increases already becomes figure 2. comparison of the iast predictions with simulation data for hydrogen sulphide (black) and hydrogen (blue). equilibrium adsorption loading (n) as a function of the mole fraction of hydrogen sulphide (yh2s) in the binary gas phase mixture on zeolite naa at 298 k and at the pressures indicated. the statistical uncertainties of the simulation results do not exceed the size of the symbols. (for interpretation of the references to colour in this figure, the reader is advised to refer to the online version of this article.) a b figure 3. equilibrium adsorption selectivity (s) on zeolite naa at 298 k as a function of the bulk-gas pressure for binary (a) and ternary (b) gas mixtures with the compositions indicated. selective removal of hydrogen sulphide using zeolite 45(1) pp. 9–15 (2017) 13 less significant at higher loadings. the two panels of fig.4 also illustrate the above-mentioned difference between the data of the binary (a) and ternary (b) mixtures, i.e. the numerical values are smaller for the ternary mixtures. besides this, the scatter of the points is larger in panel b, because the ratio of nh2 to nch4 in the bulk gas unavoidably changes as the partial pressure of h2s increases (for compositions, see fig.3). finally, panel c in fig.4 illustrates the influence of adsorbateadsorbate attraction on the adsorption characteristics. it was simulated by eliminating the coulomb potential and the attractive part of the lennard-jones potential, but retaining its soft-sphere repulsion potential component, when calculating the instantaneous adsorbate-adsorbate pair interactions in the adsorbed phase. the observed reduction in nh2s and selectivity is sizable enough to establish that like-like attraction is an important factor in the adsorption of h2s. 4. conclusion in this work, molecular simulation predictions for the adsorption of h2s from simple non-polar gas mixtures of technological interest (hydrodesulfurization stream outlets in petroleum refinery units) on zeolite naa were presented. the realistic all-atom intermolecular potential models adopted for the computations were validated by comparing the calculated isotherms of the pure substances with available experimental adsorption data. what is especially noticeable here is the matching of the experimental and simulated adsorption loadings for h2s that was achieved. the investigated zeolite exhibited a remarkable ability to capture h2s, from either binary or ternary mixtures with non-polar gases, namely h2 and ch4. the interactions between the polar h2s molecules and the hydrophilic zeolite framework were found to be particularly favourable, and the mixture-adsorption loadings for h2s essentially agreed with the corresponding pure component loadings (with the exception of the very low h2s contents of the bulkgas mixture). the reverse is true when considering the adsorption of the non-polar gaseous components under technological conditions (at near-atmospheric pressures and with a small proportion of h2s in the bulk); their bindings to the inner surface sites of the zeolite were suppressed by h2s. these results can be of practical importance in terms of selectivity. selectivities of h2s to the non-polar substances were generally higher at lower h2s partial pressures in the bulk gas, and well over 1000 for the range of h2s contents of the typical hydrodesulfurization streams. the obtained order of magnitude of the isosteric heat of adsorption data and the large decrease in selectivity with increasing temperature suggest that electrostatic interactions play a more pronounced role in the selective removal of h2s by zeolite naa and the effect of size has only a limited impact. in association with this, it was also revealed that h2s-h2s attraction contributes to the preferred adsorption of this substance. acknowledgement present article was published in the frame of the project ginop-2.3.2-15-2016-00053 (“development of engine fuels with high hydrogen content in their molecular structures (contribution to sustainable mobility)”). we gratefully acknowledge the financial support of the hungarian national research fund (otka k124353). the author would like to thank tamás kovács and zoltán ható (department of physical chemistry, institute of chemistry, university of pannonia) for their assistance in terms of data analysis. references [1] auerbach, s.m.; carrado, k.a.; dutta, p.k. 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[2], un-noor et al. stated that the development of electric vehicles is immensely beneficial to our environment since this will lead to a reduction in the adverse effects of greenhouse gas emissions. after reviewing the literature on electric vehicles (ev), they drew up different design and development processes in terms of vehicle modelling, ev configurations, battery management and electrical machine drives. in evs, ice propulsion has been replaced by electric propulsion, consisting of electric motor drives, energy sources and other auxiliaries. therefore, a reasonable amount of effort has been made in the field of industrial automation to make the transition from vehicles powered by traditional ices to those driven by evs [3]. however, shariff et al. [4] stated that ‘greenhouse gas *correspondence: aminubabangida24@gmail.com emission and the increased cost of petroleum products are the major factors that need a shift from internal combustion engines to electric vehicles.” electric vehicles are solutions to this problem [5]. in this paper, a volkswagen crafter with a 2.0 diesel tdi cr engine manufactured in 2020 is examined by focusing on the replacement of its ice with rear-wheel-driven electric motor propulsion. according to our literature review, numerous papers have focused on electric vehicles, e.g., wahono et al. [6] who compared three forms of range extender engines for electric cars based on simulations to overcome some disadvantages (such as the weight) of evs over conventional vehicles driven by ices. a further study by marmaras et al. [7] simulated the driver behaviour of evs in road transport networks and electrical grids. the ev studied was modelled to investigate its integration in both the electrical grid and road transport networks. although a multi-agent platform was used to model driver behaviour, a fleet of 1000 evs were used as a case study where known and unknown profiles were chosen to explore the results. the cars were considered to be typical smart mechatronics systems. new trends in smart systems are summarised in ref. [8]. since it is difficult to formulate the exact dynamic equations of a car, aracil et al. [9] proposed the hardware-in-the-loop simulation as an optihttps://doi.org/10.33927/hjic-2021-06 mailto:aminubabangida24@gmail.com 38 babangida and szemes figure 1: battery electric vehicle mal solution. they discovered that electric vehicles have direct and indirect implications on road transport networks and electrical grids. another study [10] presented a “ride comfort performance evaluation on ev conversion via simulations.” this study aimed to investigate the ride comfort of a vehicle before being converted into an electric vehicle. the study considered a full car model with 7 degrees of freedom (dof). the two results were validated by evaluating the performance of the vehicle before and after replacing its conventional ice with an electric motor. 2. electric powertrain the electric powertrain of a battery electric vehicle (bev) consists of two components, namely the electrical and mechanical parts. a schematic diagram of the general layout of the electric powertrain of a bev is depicted in fig. 1 where m denotes the electric motor, while the thin and thick lines represent the electrical and mechanical parts, respectively. 2.1 electrical parts the electrical parts consist of the battery, dc-dc converter, inverter and the controller of the electrical machine, which all depend on the electrical machine applied as the ev. 2.2 mechanical parts the mechanical parts of the electric powertrain consist of the transmission system, axles, wheels and chassis. in this paper, a three-phase permanent magnet synchronous motor (pmsm) was applied in a simplified energy-equivalent pmsm model that makes use of the losses resulting from the detailed pmsm model. 3. simulation of the dynamic system of the electric powertrain a simplified closed-loop representation of the electric powertrain applied in our electric crafter (e-crafter) is presented in fig. 2, which consists of a nissan leaf battery as well as the pmsm drives, transmission and chassis subsystems adapted from refs. [11] and [12], where vref denotes the speed reference and vehspd stands for the vehicle speed. figure 2: simplified ev powertrain figure 3: transmission system [1] 3.1 vehicle transmission system a single-speed transmission system consists of various elements such as the gearbox, torque converter and the final drive. as is described in ref. [1], the torque converter couples the gearbox to the vehicle and the gearbox contains the appropriate gear ratios, where u denotes the velocity required and v represents the actual velocity as a result of the final drive. however, fig. 3 shows a simplified single speed transmission used in modeling our electric vehicle. the presence of the torque converter in the transmission system of fig. 3 clearly indicates that it is automatic transmission. 3.2 vehicle modelling vehicle dynamics is the study of the motion of a vehicle and is comprised of three categories, that is, longitudinal, lateral and vertical dynamics. in this paper, the longitudinal dynamics of the car are modelled in a matlab/simscape/simulink environment. “in practical terms, a vehicle not only travels on a level road but also up and down the slope of a roadway as well as around corners.” [13] a simplified model and more detailed description of dynamical behaviour can be found in ref. [8]. to model the vehicle dynamics, it is necessary to describe the forces acting on the vehicle using a free body diagram as shown in fig. 4. the tractive force acting on the chassis can be described by [3, 14] ft = fad + frr + fhc + fa, (1) where fad denotes the wind resistance, which depends on the density of air ρ, surface area of the front of the vehicle af , drag coefficient cd and its speed v , calculated from fad = 0.5ρcdafv 2. (2) the rolling resistance frr depends on the weight of the vehicle w (w = mg), rolling resistance coefficient crr and the angle of inclination α: frr = wcrr cosα. (3) hungarian journal of industry and chemistry electric vehicle modelling and simulation 39 figure 4: vehicle dynamics [3] table 1: vehicle specifications parameters specifications vehicle mass 3500 kg centre of gravity 0.254 m front axle 1 m rear axle 1.346 m rolling resistance 0.013 drag coefficient 0.3 air density 1.225 kg/m3 gravity 9.81 m/s2 the forces resulting from the grade resistance and resistance to acceleration are given as fhc = w sinα, (4) fa = 1.04ma, (5) where m denotes the mass of the vehicle in kg, 1.04 is its inertia and a stands for its acceleration. the tractive power and energy needed to propel the vehicle are given by the following equations: p = fv, (6) e = pt, (7) where f denotes the tractive force in newtons and t represents the time in seconds. however, the vehicle dynamics system was simulated using the parameters as specified in table 1. 3.3 tyre dynamics using the magic formula “the tire-road interaction (magic formula) block models the longitudinal forces at the tire-road contact patch using the magic formula of pacejka.” [25] in this paper, both the tyres attached to the front and rear axles of the vehicle were modelled using the magic formula. the tyre coefficients used were b, c, d and e. the values of these coefficients, adapted from ref. [25], are shown in table 2. table 2: tyre specifications [25] surfaces constant coefficients b c d e dry tarmac 10 1.9 1 0.97 wet tarmac 12 2.3 0.82 1 snow 5 2 0.3 1 ice 4 2 0.1 1 figure 5: control loop by applying a pi controller 3.4 speed controller a pi controller was developed to control the speed of both the motor and vehicle. this pi controller was implemented in the energy-equivalent model of our pmsm. pid controllers are used in many industrial applications because of their simple structure and robustness [15]. since noise is a measured parameter, the derivative part is not usually used [15]. the general representation of the pi controller is presented in fig. 5. 3.5 integral performance criteria “criteria based on disturbance rejection and system robustness are proposed to assess the performance of pid controllers.” [16] “a two-block structured singular value measures the robustness, and the disturbance rejection is measured by the minimum singular value of the integral gain matrix.” [16] in this paper, five criteria used in a closed-loop control system are employed to assess the performance of our pi controller. they are customarily calculated for different control setpoints such as step input and ramp input. in this research, the performance of our controller was assessed using various test inputs. “it is well-known that a well-designed control system should meet the disturbance attenuation, setpoint tracking, robust stability, and robust performance.” [16] “the first two requirements are traditionally referred to as ’performance’ and the third, ’robustness’ of a control system.” [16] the following are the criteria stated in ref. [16]: iae = ∫ ∞ 0 |e(t)| dt, (8) itae = ∫ ∞ 0 t |e(t)| dt, (9) ise = ∫ ∞ 0 e2(t) dt, (10) 49(1) pp. 37–46 (2021) 40 babangida and szemes figure 6: structure of the pmsm [17] itse = ∫ ∞ 0 te2(t) dt, (11) where iae stands for the integral absolute error, itae the integral time absolute error, ise the integral square error, and itse the integral time squared absolute error [16]. these performance indexes were used to tune our pid controller. 4. permanent magnet synchronous motor a pmsm, which is widely used to overcome the disadvantages of a brushless dc motor (bldc) [17], is proposed in this research. virani et al. employed the fieldoriented control (foc) approach to control the speed and torque of the pmsm of an electric car [17]. moreover, espina et al. in their review of speed anti-windup pi strategies for field-oriented control of permanent magnet synchronous motors emphasized that pmsms are gaining popularity when compared to other ac motors due to their higher efficiency, lower inertia as well as reduction in weight and volume [18]. this study suggests pmsm has advantages in ev applications over other types of electric motors. the general structure of the pmsm motor is presented as shown in fig. 6. the rotor having a permanent magnet mounted on it creates a rotating magnetic field, which in turn produces a sinusoidal electromagnetic field. 4.1 pmsm mathematical model the modelling of a pmsm was carried out based on the following assumptions [17, 26]: 1. there is distribution of the sinusoidal magnetomotive force (mmf) in the air gap. 2. restriction in the saliency according to the rotor position. 3. ignoring the hysteresis and saturation. 4. assuming a balanced 3-phase supply voltage. 5. assuming that the back emf (electromotive force) is sinusoidal. the 3-phase supply voltage is given by [17] va = pψa + iars , (12) vb = pψb + ibrs , (13) vc = pψc + icrs , (14) where ia, ib and ic denote the phase currents, va, vb , and vc represent the phase voltages, ψa, ψb and ψc stand for the flux linkages, and rs and p are the phase resistance and "derivative operator," respectively [17]. however, using the reference frame dq , the model of the pmsm can be represented in the rotating reference frame dq as vq = rsiq + ωrλd + pλp, (15) vd = rsid − ωrλp + pλq, (16) λq = lqiq and λd = ldid + λr, (17) vq = rsiq + ωr (ldid + λr) + plqiq, (18) vd = rsid − ωrlqiq + p (ldid + λr), (19) therefore, the torque developed by the pmsm is given by te = 3 2 p 2 (ψriq + (ld − lq)idiq) , (20) where p denotes the number of poles of the machine [17]: the electric torque derived in eq. 20 is divided into two components, namely the “mutual reactance torque” [17] and “reluctance torque”, the latter results from the difference in reluctance between the qand d-axes [17]. however, for the pmsm, when lq = ld = ls , the torque generated by the pmsm is [17] te = 3 2 p 2 (ψriq) . (21) the three-phase voltages of the detailed pmsm model are presented in fig. 7. since it can be seen that the simulation runs with a stop time of 0.2 s, which is very slow, it runs more slowly than in real time. to resolve this issue, a methodology was adapted using this detailed model of the pmsm to obtain the electrical losses of an energyequivalent model. the corresponding 3-phase currents obtained by simulating the detailed three-phase pmsm are shown in fig. 8. in this model, the torque induced by the structure of the chassis is not included in the modelling process, namely the cogging torque [19]. flux harmonics are also present since the magnet in the pmsm is composed of “neodymium, iron and boron”. [19] therefore, its magnetic flux density is usually affected by variations in temperature. [19] similarly, there parametric uncertainties are present due to mechanical and electrical parameters. in terms hungarian journal of industry and chemistry electric vehicle modelling and simulation 41 figure 7: three-phase voltages figure 8: three-phase currents of mechanical ones, the inertia of the pmsm is uncertain due to its changing behaviour under different operating conditions. regarding electrical ones, the stator resistance, which is a function of the temperature, influences the control of the current loop performance [19]. the electrical losses resulting from the simulation of the pmsm are presented in table 3. these losses were obtained by using the corresponding torque and speed vectors, moreover, this method was adopted from ref. [11]. 4.2 simplified pmsm model in this paper, a three-phase model of the pmsm designed was converted into an equivalent energy model based table 3: pmsm electrical losses speed torque experimental electrical losses (kw) [rpm] [nm] 99 9 0.0811 0.321 0.943 2.146 4.379 454 45 0.0621 0.299 0.925 2.191 4.567 803 80 0.0454 0.281 0.9 2.217 4.796 1149 114 0.0298 0.262 0.858 2.217 4.950 1499 149 0.016 0.251 0.873 2.23 4.998 figure 9: pmsm equivalent energy model table 4: motor specifications parameters specifications maximum power 80 kw maximum torque 280 nm time constant 0.02 s series resistance 0 rotor inertia 3.9×10−4 kg m2 rotor damping 10−5 nm/(rad/s) on the electrical losses obtained from the detailed threephase model of the pmsm. the motor parameters used during the simulation are presented in table 4. from fig. 9, the transfer function from tl to ω is given by g(s) = 1 sj +b , (22) h(s) = ω ωr = f (s)g(s) 1 + f (s)g(s) = α/s 1 + α/s , (23) where tl denotes the load torque, ω represents the achieved speed, ωr refers to the reference speed, j stands for the total of the moments of inertia,b is the coefficient of viscosity and α denotes the bandwidth of the speed control [20] f (s) = α s ( 1 sj +b ) . (24) transforming eq. 3 into the pi form [14] yields f (s) = αj + αb s = kp + ki s . (25) therefore, in the case of the simplified equivalent pmsm model, only the outer loop was analysed, which uses a pi controller to control the speed of the motor. generally, a three-phase pmsm, using the foc (field-oriented control) strategy, consists of two control loops with two pis in the inner loop to control the current vectors. the pi controller can be mathematically represented as u(t) = kpe(t) + ki ∫ e(t) dt, (26) where kp and ki denote the proportional and integral coefficients, respectively and e(t) represents the error between the reference and the feedback signal [21]. 49(1) pp. 37–46 (2021) 42 babangida and szemes table 5: battery parameters [13] chemistry symbol cell voltage specific energy cycle life specific power self-discharge (v) (wh/kg) (w/kg) (per month) lead-acid pba 2 35 ≈ 500 250− 500 5 nickel-metal hydride nimh 1.2 30− 100 > 1000 200− 600 > 10 lithium-ion li-ion 3.8 80− 160 > 1000 250− 600 < 2 lithium-titanate lto 2.5 50− 100 > 20, 000 n/a n/a alkaline znmno2 1.5 110 n/a n/a < 0.3 table 6: battery specifications parameters specifications battery nominal voltage 360 v battery capacity 24 kwh battery charge 66.2 ah energy density 140 wh/kg power density 2.5 kw/kg battery power 90 kw 5. nissan leaf battery in this research, a nissan leaf battery manufactured in 2011 was used to design the electric vehicle. the battery has a nominal voltage of 360 v and a capacity of 24 kwh [13]. it consists of 48 modules and 4 cells (2 in parallel, 2 in series), amounting to 192 cells [14]. the total voltage of the battery pack is approximately 403.2 v. the possible arrangement of the cells in a battery pack has been studied in general by emadi [22]. table 5 shows the batteries available along with their chemistries. in this paper, a lithium-ion battery was used. the specific energy defines the energy stored in the battery per unit of weight. the cell voltage is 4.2 v when fully charged and 2.5 v when discharged. while the battery specifications for a nissan leaf manufactured in 2011 are detailed in table 6, this paper used a model of a built-in battery simulated using simulink based on these specifications to simulate our traction battery. 5.1 battery modelling generally, our battery was analysed using an equivalent circuit model from the literature to study its behaviour mathematically. this equivalent circuit was modelled based on a nissan leaf to carry out the analysis before being compared with the built-in battery simulated using matlab. the cell voltage of the battery as studied in ref. [23] is given by vb = v 0 r − rt nf lnqr, (27) where r denotes the ideal gas constant, t represents the temperature and qr stands for the reaction quotient, which is a function of the concentrations of the reactants. figure 10: battery equivalent circuit model however, since each battery is associated with an ohmic drop [23], the equation can be modified as vb = v 0 r − rt nf lnqr −rbib. (28) the above equation can then be modified to include the battery capacity as vb (ib, y) = v 0 r −a ln (by)−ky−feg(y−y3)−rbib, (29) where y denotes a variable that can be related to the capacity, dod (depth of discharge), soc (state of charge) or the cell energy, y3 represents the value at which the exponential decay begins, and a, b, k, f and g stand for values determined by curve fitting [23]. the above equation can be expressed in terms of the dod as vb(ib,dod) = v 0 r −a ln(b dod)− −k dod− feg(dod−dod3) −rbib (30) in terms of the no-load, the ohmic drop can be expressed as vb(nl)(dod) = v 0 r −a ln(b dod)−feg (dod−dod3). (31) the aforementioned equations can be modelled to represent the equivalent circuit shown in fig. 10. therefore, the above mathematical model of the battery can be represented by the simplified battery model presented in fig. 10 based on the already built-in simulink model. 5.2 battery parameters the design considerations of a battery ensure it functions safely and reliably. therefore, the battery management hungarian journal of industry and chemistry electric vehicle modelling and simulation 43 figure 11: simulink model of the ev system takes into account three parameters, namely the total voltage of the battery pack, the total temperature of an individual cell in the pack and the total current, before calculating the state of charge (soc), state of health (soh), safe operating envelope (soe) and faults. the soc, which is expressed as a percentage, determines the amount of voltage also as a percentage. in this paper, the soc was found to be 99%, that is, almost fully charged. a friction brake was used to stop our vehicle. the battery was naturally recharged due to regenerative braking. the soh represents the battery’s capacity relative to its capacity when initially installed. finally, the soe shows the amount of current that can be charged or discharged at any given time. 6. matlab model the complete model of our electric vehicle simulated in a simulink environment is depicted in fig. 11. the model consists of the nissan leaf battery, the pmsm drives, the transmission systems and the vehicle subsystems. 7. results the "new european driving cycle (nedc)" used in this research to test our vehicle and other driving cycles to comply with energy consumption and emissions reduction targets is presented in fig. 12. in this paper, only three cycles of 200 seconds in duration were used in the "nedc." other driving cycles such as the "urban dynamometer driving schedule (udds)," were used to test our electric vehicle. the nedc, adopted from the literature, is mainly used to determine the consumption of electric vehicles, gas emissions, etc. the reference speed and the speed achieved by the vehicle over 200 seconds are both represented in fig. 13. the power consumption of the battery in kilowatts is shown in fig. 14. the nissan leaf can provide over 90 kw of power, 50 kw of which was consumed by our electric vehicle. the energy consumption of the battery in kwh is presented in fig. 15. given that the soc achieved by our battery was 99%, i.e., it was almost fully charged, the operating temperature used by our battery management system was nefigure 12: nedc driving cycle figure 13: speed achieved by the vehicle figure 14: power consumption of the battery figure 15: energy consumption of the battery 49(1) pp. 37–46 (2021) 44 babangida and szemes figure 16: battery current figure 17: battery soc figure 18: achieved motor speed figure 19: motor torque figure 20: power consumption of the motor figure 21: energy consumption of the motor and battery glected. in a future study, a complete battery management system will be implemented to determine and ensure safe operating conditions for our battery system. the battery current is represented in fig. 16. the battery draws a maximum current of 75 a when the vehicle is accelerating and a minimum current of −55 a when decelerating. the soc of the battery as a percentage, which is approximately maintained at 99% due to natural regenerative braking, is presented in fig. 17: the reference speed of the motor was 4250 rpm, which accurately tracks the actual rate, and is shown in fig. 18. the maximum torque of 280 nm, as seen in table 4 of the motor specifications, is shown in fig. 19, while the power consumption of the motor, which is approximately 49 kw, is presented in fig. 20. the losses can be analysed in terms of the energy transmitted from the storage system, namely from the battery to the wheels of the vehicle. the energy consumption of both the battery and motor are plotted in fig. 21. the difference between the plots in fig. 21 is the energy lost when transmitting from the energy supply system, that is, from the battery to our pmsm. it can be seen that: if eb = 0.3305 kwh is the energy consumed by our nissan leaf battery andem = 0.2599 kwh is the energy consumed by our pmsm, then the energy efficiency, η = em/eb = 78.63 %. therefore, our electric vehicle is approximately 19% hungarian journal of industry and chemistry electric vehicle modelling and simulation 45 table 7: pi controller parameters gains performance indices kp ki iae ise itae itse 60 60 4.1141× 10−6 1.0935× 10−12 2.8676× 10−5 5.1996× 10−12 60 40 1.353× 10−4 1.0372× 10−9 0.0011 6.3622× 10−9 5 20 7.9202× 10−10 3.1365× 10−20 7.9202× 10−9 3.1363× 10−19 more efficient than conventional vehicles. however, du et al. determined that an ev can be up to approximately 15% more efficient than conventional vehicles driven by ices in terms of fuel consumption (fuel economy) [24]. the speed of the vehicle when tested by a ramp input is depicted in fig. 22. in this case, the vehicle accelerates from rest to a final speed of 5.55 m/s (20 km/hr). the pmsm implemented as a result of a ramp test signal is presented in fig. 23 below. the consumption of vehicles was less during this test to prove the performance of our motor and electric vehicle under these ideal conditions. 7.1 settings of the pi controller based on the performance matrix the settings of the pi controller based on the performance matrix obtained by conducting several experiments until optimized gains had been achieved is presented in table figure 22: speed of the vehicle due to a ramp input figure 23: speed of the motor due to a ramp input 7. it can be seen from this table that minimum values of these performance indices were required to obtain these optimal gains. moreover, the system is stable and the controller somewhat reliable. however, a future study may propose intelligent tuning techniques to achieve a realistic level of performance by accurately taking into consideration the model uncertainties and parameter variations due to operating conditions, e.g., temperature and humidity amongst other considerable factors. 8. conclusions the modelling and simulation of an electric powertrain based on the pmsm motor of a light commercial vehicle, a vw crafter manufactured in 2020, has been presented. a pi-based classical control algorithm of the outer control loop of the pmsm was used to control the speed of the vehicle and motor. pmsm-based electrical-rear-wheel-driven traction of a vw crafter manufactured in 2020 was modelled. this motor was chosen due to its high degree of efficiency over other electrical traction machines. this motor propelled the vehicle during its motoring action and while recharging the battery when acting as a generator. a nissan leaf battery with a rating of 360 v manufactured in 2011 and an energy supply to the system of 24 kwh was used. the battery was used to supply energy to propel the vehicle. this research determined that the fuel consumption decreased by a significant percentage by replacing conventional vehicles driven by ices with electric vehicles. acknowledgments this research work is supported by tkp2020-nka-04. project no. tkp2020-nka-04 has been implemented with the support provided from the national research, development and innovation fund of hungary, financed under the 2020-4.1.1-tkp2020 funding scheme. references [1] ehsani, m.; gao, y.; longo, s.; ebrahimi, k.m.: modern electric, hybrid electric, and fuel cell vehicles, third ed. 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fodor, d.; kohlrusz, g.: modeling of slotless surface-mounted pm synchronous motor for sensorless applications, 2014 ieee international electric vehicle conference (ievc), 2014, 1– 5 doi: 10.1109/ievc.2014.7056198 hungarian journal of industry and chemistry https://doi.org/10.3390/en10081217 https://doi.org/10.3390/en10081217 https://doi.org/10.15282/jmes.8.2015.6.0128 https://doi.org/10.1088/1757-899x/561/1/012103 https://doi.org/10.1088/1757-899x/252/1/012060 https://doi.org/10.15282/jmes.10.1.2016.5.0173 https://doi.org/10.15282/jmes.10.1.2016.5.0173 https://doi.org/10.1016/j.trc.2017.05.004 https://doi.org/10.1016/j.trc.2017.05.004 https://doi.org/10.1109/epepemc.2014.6980683 https://doi.org/10.1109/mie.2020.3042171 http://www.arpnjournals.com/jeas/research_papers/rp_2015/jeas_0915_2643.pdf https://github.com/mathworks/simscape-battery-electric-vehicle-model/releases/tag/1.0.0 https://www.mathworks.com/matlabcentral/fileexchange/52631-student-competitions-physical-modeling-training https://doi.org/10.1007/s40435-013-0032-y https://doi.org/10.1007/s40435-013-0032-y https://doi.org/10.1109/icomet48670.2020.9073845 https://doi.org/10.1109/icomet48670.2020.9073845 https://doi.org/10.1016/j.ifacol.2018.06.124 https://doi.org/10.2316/journal.201.2004.3.201-1309 https://doi.org/10.2316/journal.201.2004.3.201-1309 https://doi.org/10.2139/ssrn.3442515 https://doi.org/10.2139/ssrn.3442515 https://doi.org/10.1109/cpe.2009.5156047 https://doi.org/10.1109/tie.2016.2583412 https://doi.org/10.1109/tie.2016.2583412 https://publications.lib.chalmers.se/records/fulltext/253368/253368.pdf https://doi.org/10.1016/j.cja.2014.10.019 https://doi.org/10.1016/j.cja.2014.10.019 https://doi.org/10.1109/tvt.2018.2884812 https://doi.org/10.1109/ievc.2014.7056198 introduction electric powertrain electrical parts mechanical parts simulation of the dynamic system of the electric powertrain vehicle transmission system vehicle modelling tyre dynamics using the magic formula speed controller integral performance criteria permanent magnet synchronous motor pmsm mathematical model simplified pmsm model nissan leaf battery battery modelling battery parameters matlab model results settings of the pi controller based on the performance matrix conclusions untitled hungarian journal of industry and chemistry vol. 53(1) pp. 39–42 (2025) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2025-05 enantioselective catalytic three-component synthesis of optically active propargyl amino ethers gulahmad mirahmad talybov 1* 1 azerbaijan technical university, javid avenue 25, baku, az 1073, azerbaijan catalytic enantioselective three-component aminomethylation of benzaldehyde as well as its methoxy-substituted derivatives and propargyl ethers with aniline in the presence of a chiral catalyst – pseudoephedrine – yielded previously unknown optically active propargyl amino ethers with high yields and a high degree of enantioselectivity. this reaction can also be used to form both c-c and c-n bonds. keywords: enantioselective aminomethylation, enantioselectivity, asymmetric catalysis, threecomponent reaction 1. introduction optically active propargylamines are important synthetic intermediates for the preparation of various natural products [1],[2] and biologically active compounds [3]-[5]. many mannich bases have a number of useful pharmacological properties, for example, antimicrobial, cytotoxic, antitumor and analgesic activity [6],[7]. propargyl-containing chiral organic compounds can act as synthons for the targeted synthesis of many natural nitrogen-containing compounds as well as optically active drugs [8]-[11]. to achieve this goal, the catalytic asymmetric mannich reaction is carried out efficiently. this is one of the most convenient methods for synthesizing chiral nitrogen-containing compounds [12]. although three-component syntheses of amino ethers involving various compounds are found in the literature [11], the synthesis of novel compounds no. 1-7 is the first time that propargyl ethers have been used. enantioselective reactions using pseudoephedrine as a chiral catalyst also exist [12],[13]. 2. experimental the general methodology for synthesizing target compounds was as follows: a mixture of 0.1 mmol of aromatic aldehyde, 0.3 mmol of propargyl ether, 0.1 mmol of aniline as well as 1.5 mg of pseudoephedrine and 0.8 mg of cucl in 18 ml of dry ch2cl2 was stirred at 25°c before being heated for 4 hours at 80-90°c. next, 3 ml of isopropyl alcohol was added before the received: 27 nov 2024; revised: 7 febr 2025; accepted: 7 febr 2025 *correspondence: gtalibov61@gmail.com precipitate was filtered off then washed with water (3 ml) and isopropyl alcohol (3 ml). the purity of the compounds obtained was monitored by tlc on silufol uv-254 plates with a 1:1 ratio of eluent acetone to hexane. their melting points were determined using a melting point m-565 instrument. the specific optical rotation [α]d20 was measured using a perkin elmer-341 polarimeter. hplc was performed by a thermo scientific tsq quantum access™ instrument with a zorbax cb-c18 (150mm x 2.1mm, 1.8 µm) designed to carry out reversed phase hplc. 1h and 13c nmr spectra of the resulting compounds in a solution of cdcl3 were recorded by a bruker sf-300 spectrometer with operating frequencies of 300 (1h) and 75 mhz (13c) as well as an internal standard hmds.the data of 1h nmr, 13c nmr (cdcl3) and ir spectra can be found in the supplement. in the synthesis described, the following novel compounds were obtained: no. 1: n-[(1r,4r)-4-phenoxy-1-phenylpent-2-yn-1-yl]-aniline yield: 45%. light yellow powder, m.p.: 156–157°с (with decomposition), [α]d22 +55.4 (with 0.1, chcl3). observed composition (%): c 84.32; h 6.51; n 4.22 с23н21no. calculated composition (%): c 84.37; h 6.46; n 4.28. no. 2: n-[(1r,5r)-4-phenoxy-1-phenylhex-2-yn-1-yl]-aniline yield: 54%. light yellow powder, m.p.: 158–159°с (with decomposition), [α]d22 +56.8 (with 0.1, chcl3). observed composition (%): c 84.32; h 7.11; n 3.84 https://doi.org/10.33927/hjic-2025-05 mailto:gtalibov61@gmail.com talybov hungarian journal of industry and chemistry 40 с25н25no. calculated composition (%): c 84.47; h 7.09; n 3.94. no. 3: n-[(1r)-4-(cyclohexyloxy)-1-phenylbut-2-yn-1-yl]aniline yield: 51%. light yellow powder, m.p.: 124–125°с (with decomposition), [α]d22 +36.4 (with 0.1, chcl3). observed composition (%): c 82.22; h 8.14; n 4.51 с21н25no. calculated composition (%): c 82.04; h 8.20; n 4.56. no. 4: n-[(1r)-4-(cyclopentyloxy)-1-phenylbut-2-yn-1-yl]aniline yield: 56%. light yellow powder, m.p.: 121–122°с (with decomposition), [α]d22 +34.9 (with 0.1, chcl3). observed composition (%): c 81.23; h 8.21; n 4.87 с19н23no. calculated composition (%): c 81.10; h 8.24; n 4.98. no. 5: n-[(1r,4r)-4-phenoxy-1-(2-(methoxy-phenylpent-2in-1-yl]-aniline yield: 53%. light yellow powder, m.p.: 161–162°с (with decomposition), [α]d22 +66.8 (with 0.1, chcl3). observed composition (%): c 83.87; h 7.21; n 4.21 с24н25no. calculated composition (%): c 83.93; h 7.34; n 4.08. no. 6: n-[(1r,4r)-4-phenoxy-1-(3-(methoxy-phenylpent-2yn-1-yl]-aniline yield: 56%. light yellow powder, m.p.: 160–161°с (with decomposition), [α]d22 +64.8 (with 0.1, chcl3). observed composition (%): c 83.66; h 7.14; n 4.14 с24н25no. calculated composition (%): c 83.93; h 7.34; n 4.08. no. 7: n-[(1r,4r)-4-phenoxy-1-(4-(methoxy-phenylpent-2yn-1-yl]-aniline yield: 50%. light yellow powder, m.p.: 158–159°с (with decomposition), [α]d22 +61.8 (with 0.1, chcl3). observed composition (%): c 83.83; h 7.17; n 4.11 с24н25no. calculated composition (%): c 83.93; h 7.34; n 4.08. 3. results and analysis for the first time, the highly enantioselective threecomponent reaction of aldehydes, aniline and propargyl ethers was investigated using the chiral catalyst pseudoephedrine, where the degree of diastereomeric excess (de) was as high as 96 % (figure 1). the starting propargyl ethers were obtained in advance [14]. since the methylene protons in compound no. 2 are diastereotopic, they exhibit different singlet signals at 3.46 d (1h, och2, j=9.4 hz), 3.75 d (1h, och2, j=9.4 hz). in the case of r2=me for compounds no. 1-2 and 5-7, diastereomers were obtained. the ratio of these diastereomeric isomers was determined by 1h nmr spectroscopy after the reaction had finished and a thermodynamic equilibrium between the diastereoisomers (before chromatography) established according to the ratio of the integration of doublet signals of methine protons 1-2 and 5-7 at 3.46-3.75 ppm. to determine the absolute configuration of amino ethers 1-2 and 5-7, the polarimetric method was used whereby similar compounds had previously been studied [15],[16]. therefore, the measured positive optical rotation of the synthesized diastereoisomers indicates their (r,r)-absolute configuration. reactions of benzaldehyde as well as its methoxysubstituted derivatives and propargyl ethers with aniline in the presence of a chiral catalyst – pseudoephedrine – proceeded smoothly to produce the corresponding figure 1: reaction scheme enantioselective synthesis of optically active propargyl amino ethers 53(1) pp. 39–42 (2025) 41 products in yields of 45-56% and with enantioselectivities of 90-96% (table 1). the protons of pseudoephedrine interact with the hydrogen bonds of propargyl amino ethers, leading to its activation (figure 2). the structure and composition of the obtained target compounds no. 1-7 were confirmed by 1h and 13c nmr spectroscopy as well as elemental analysis (the spectra can be found in the supplementary information, available in the editorial office.). 4. conclusions based on the experimental results, the catalytic enantioselective three-component synthesis of benzaldehyde as well as its methoxy-substituted derivatives and propargyl ethers with aniline in the presence of a chiral catalyst with high yields and a high degree of enantioselectivity was achieved. references [1] trost, b.m.; 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furutachi, m.; yamatsugu, k.; kumagai, n.; watanabe, t.; shibasaki, m.: two approaches toward the formal total synthesis of oseltamivir phosphate (tamiflu): catalytic enantioselective three-component reaction strategy and l-glutamic acid strategy, j. org. chem., 2013, 78(8), 4019–4026, doi: 10.1021/jo400360j [10] ramirez, m.; vece, v.; hanessian, s.; houk, k.n.: computational and further experimental explorations of the competing cascades following claisen rearrangements of aryl propargyl ethers: substituent effects on reactivity and regioselectivity, j. org. chem., 2021, 86(24), 17955–17964, doi: 10.1021/acs.joc.1c02296 n h ch3 ho ch3 nh r 1 o r r 2 n figure 2: scheme of how the protons of pseudoephedrine interact with the hydrogen bonds of propargyl amino ethers table 1: enantioselective reactions of benzaldehyde as well as its methoxy-substituted derivatives and propargyl ethers with aniline in the presence of a chiral catalyst – pseudoephedrine entry time (h) yield (%) de (%) 1 1 45 93 2 1 54 94 3 1 51 90 4 1 56 95 5 1 53 94 6 1 56 94 7 1 50 96 https://doi.org/10.1002/ange.200460058 https://doi.org/10.1021/ol049630m https://doi.org/10.33927/hjic-2022-05 https://doi.org/10.1134/s1070428023060155 https://doi.org/10.1134/s1070428024030254 https://pubs.acs.org/doi/10.1021/jm0604528 https://pubs.acs.org/doi/10.1021/jm0604528 https://pubs.acs.org/doi/10.1021/jm0604528 https://pubs.acs.org/doi/10.1021/jm0604528 https://doi.org/10.1021/jm0604528 https://doi.org/10.1021/acs.jmedchem.9b01886 https://doi.org/10.1021/acssuschemeng.7b00900 https://pubs.acs.org/doi/10.1021/jo400360j https://pubs.acs.org/doi/10.1021/jo400360j https://pubs.acs.org/doi/10.1021/jo400360j https://pubs.acs.org/doi/10.1021/jo400360j https://pubs.acs.org/doi/10.1021/jo400360j https://doi.org/10.1021/jo400360j https://doi.org/10.1021/acs.joc.1c02296 talybov hungarian journal of industry and chemistry 42 [11] mammadbayli, e.h.; 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bakhmutov, v.i.; vitt, s.v.; batsanov, a.s.; struchkov, y.t.; belikov, v.m.: general method for the asymmetric synthesis of antidiastereoisomers of β-substituted l-2aminobutanoic acids via chiral nickel(ii) schiff's base complexes of dehydroaminobutanoic acid. xray crystal and molecular structure of the nickel(ii) complex of the schiff's base from [(benzylprolyl)amino]benzophenone and dehydroaminobutanoic acid, j. chem. soc., perkin trans. 1, 1990, 1(8), 2301–2310, doi: 10.1039/p19900002301 http://doi.org/10.1134/s1070363218100298 http://doi.org/10.1021/ol0268788 http://doi.org/10.1021/ol006614q https://doi.org/10.1134/s107042802211015x https://doi.org/10.1039/p19900002301 hungarian journal of industry and chemistry vol. 49(2) pp. 1–1 (2021) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2021-12 editorial preface to the special issue dedicated to the manufacturing_2021 conference istván gyurika1 1research centre for engineering sciences, university of pannonia, egyetem u. 10, veszprém, 8200, hungary the association of mechanical engineers in hungary, “gte”, has a long tradition in organizing a nation-wide, scientific-technical conference devoted to manufacturing. during the 29-30th october 2021, the university of pannonia offered to host the 24th gte manufacturing conference, where almost 50 presentations were delivered by engineering students with phd or post-doc level. participants from industry had also a good opportunity to present their new products and services, thus a fruitful collaboration platform had taken place at the premises of the university of pannonia. the highly appreciated hungarian journal of industry and chemistry is an excellent medium to convey the novelties and new scientific-technical achievements demonstrated during the conference. the phd students are also grateful to hjic for the chances to generate high-level publications at international level. the presentations were mainly offered in english language, giving additional opportunities for phd students to practice oral presentations of their scientific work and achieved results. all of the topics address one or more of the offered areas of manufacturing, including prodcorrespondence: gyurika@almos.uni-pannon.hu ucts, production, logistics, sensor-, monitoring-, roboticsthematic areas, as well as economic and human aspects, e.g., operator cooperation with robots. the review committee generated detailed feedback to the authors to show higher level of articulation of their ideas and results, and to maintain the scientific high level of the hjic journal. the selected papers are included in this special issue of hjic. the gte association will continue to offer its members opportunities to share up-to-date technical and scientific information and build a reliable social-technical network in the new ecosystem needed for the transition from indutry 4.0 to industry 5.0. we are looking ahead and inviting for the quad-centenarian, 25th jubilee manufacturing conference. istván gyurika chairman of gte’s division of manufacturing systems on behalf of the manufacturing: 2021 organising committee. https://doi.org/10.33927/hjic-2021-12 mailto:gyurika@almos.uni-pannon.hu hungarian journal of industry and chemistry vol. 49(2) pp. 53–58 (2021) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2021-22 experimental implementation of a resource-constrained multi-project scheduling problem solver krisztián mihály*1, mónika kulcsárné forrai1, and gyula kulcsár1 1department of information engineering, university of miskolc, egyetemváros, miskolc, 3515, hungary nowadays, project-based planning and execution are becoming more and more important in product life cycles; from the conceptual idea and its design to manufacturing and maintenance. companies execute several projects simultaneously and these projects usually share the same resources resulting in conflicting situations. since all projects have different requirements, constraints and goals that need to be achieved, the creation of a company-wide optimal schedule is difficult if all the aspects of each project are to be taken into consideration. our paper presents an extended model and a scheduling problem-solving approach for resource-constrained, multi-project scheduling problems. in addition to defining the theoretical solution, its experimental implementation and results are presented. keywords: resource-constrained, multi-project, advanced project scheduling, abap 1. introduction research into project scheduling has a solid and extensive background, moreover, it is still an active research area because – by not taking special cases into consideration – it belongs to the np-hard (non-polynomial) problems [1]. detailed reviews of project scheduling can be found in refs. [2] and [3]. scheduling problems concerning manufacturing optimization is an active research area [4]. np-hardness renders any brute force-based calculation for practical problem sizes unrealistic and heuristic or search-based approaches are required to identify a quasioptimal solution. in our work, an extended model for a resource-constrained multi-project scheduling problem has been developed with an advanced solver concept. the solver is based on a deterministic, rule-based, constructive schedule generation and is combined with search as well as simulation-based methods. 2. resource-constrained project scheduling problem our extended model is based on the well-known resource–constrained project scheduling problem (rcpsp). first of all, the rcpsp is presented. in this paper, the following formulation is used to describe the rcpsp. a given set of tasks (activities, operations) must be executed. the full set of tasks is denoted by t = {1, 2, 3, . . . , n}. there is a given set of resource types k = {1, 2, 3, . . . ,m}. practically speaking, a resource *correspondence: altmihaly@uni-miskolc.hu type can represent machines, people or executors. the capacity of any resource type is known, limited and constant in the time horizon. the capacity of a resource type is denoted by rk, k ∈ k. resource types are renewable, that is, after the execution of a given task, all blocked capacity becomes available again and can be used to execute a different task. there is no decreasing or increasing effect on the capacity of the task execution process (amortization). a deterministic method can be used to calculate the capacity of the resource type at any future time based on the initial state and actual scheduling. tasks are executed on the required resources. task execution on the assigned resource types cannot be stopped or broken; once the execution has been started, the task must be completed. pre-emption is not allowed. the processing time of each task is given. a virtual task can be defined, which does not require any resources. the definition of the scheduling problem is subjected to two constraints: precedence constraints, that is, the prerequisite relation between tasks, and resource constraints. if the task j (j ∈ t ) has immediate predecessor tasks defined by set pj , then all tasks i (i ∈ pj) must be completed before task j executed. it is forbidden for any circle to be located in the precedence graph. if task j (j ∈ t ) requires one or more resources, they are defined by a set of pairs (rj,k). it is forbidden to exceed the maximum available capacity of the resource type for any given resource need (rj,k) ≤ rk, ∀k ∈ k, j ∈ t . let fj denote the completion time of task j (j ∈ t ). a feasible solution can be described as a vector, in which the completion time of each task is given by the correhttps://doi.org/10.33927/hjic-2021-22 mailto:altmihaly@uni-miskolc.hu 54 mihály, forrai, and kulcsár sponding fj . let a(t) = {j ∈ t |fj − pj ≤ t ≤ fj} denote the set of tasks that are being processed at time t. the objective of the rcpsp is to assign a feasible completion time for each task such that the makespan of the project is minimized, while the precedence and resource constraints are met. 3. multi-project scheduling problems the allocation of resources and scheduling tasks for multiple projects are np hard problems that are more difficult than scheduling a single project [1]. in the literature, different classical optimization methods have been used to solve multi-project scheduling problems. a zero-one programming approach has been proposed [2] and an integer programming problem for generating the schedule as well as a simulation method for testing heuristic rules to choose the best schedule introduced [3]. deckro et al. formulated the multi-project scheduling problem as a general integer programming model and presented a decomposition approach to solve large problems [5]. jolayemi proposed an integer programming approach for multi-project scheduling problems and considered a special penalty function [6]. these outlined studies provide good solutions to small problems by using traditional optimization approaches. if the size of a problem is medium or large, then the classical methods cannot solve the problems within a reasonable execution time. in the literature, several heuristic and metaheuristic methods can be found to solve multi-project scheduling problems. researchers have developed many effective algorithms to generate feasible solutions to multiproject scheduling problems [7]. the goals of these developments were to increase the efficiency of the heuristic methods, extend the scope of the problems with new methods and reduce the computation time. many researchers have applied artificial intelligence methods to solve multi-project resource-constrained scheduling problems. for example, kim et al. proposed a combined genetic algorithm to create a schedule [8] in order to minimize the project completion time. kumanan et al. applied a genetic algorithm-based approach for generating the schedule of multi-project scheduling problems [9]. the objective function of the optimization was also to minimize the project completion time. furthermore, damak et al. proposed a variant of a genetic algorithm using a local search strategy to solve the problem by regarding the minimization of any project delays as the optimization goal [10]. after reviewing the related literature, it can be concluded that efficient and flexible methods need to be developed to improve the quality and robustness of the solutions of resource-constrained multi-project scheduling problems. 4. an extended model the rcpsp describes a project along with its tasks and boundary conditions. as an extension of this problem, a case when different shared resources need to be assigned not only to individual projects but also to a set of projects executed in parallel has to be modelled. in our model, tasks that belong to many projects simultaneously are permitted. the projects can be differentiated from each other. on the one hand, the composition and constraints of each project can be unique, but on the other hand, projects can also have individually defined goals (objective functions). in our model, a model transformation technique can be used. the essence of this possible transformation is that two new virtual tasks can be added to the set of tasks in the following way: 1. a new virtual task can be created as the starting task of the global project gs ∈ t . the gs task is defined as a predecessor task to all the tasks which did not have a predecessor task in the original problem. 2. another new virtual task can also be added to the model. this task becomes the finalizing task of the global project gt ∈ t . all the tasks, which have no successor tasks in the original problem, become predecessor tasks for gt. by applying this model transformation, the problem of projects executed in parallel is reduced to a single project scheduling problem. however, due to the different objective functions of individual projects, a new structure of objective functions has to be defined. this modelling approach is usually hard to construct in practice. instead of reducing the problem to a single rcpsp, the basic entities were reused in the extended problem and additional defining parameters as well as constraints introduced. the resource types can be defined independently from the projects. one resource type can be described by its identifier and available capacity function. in the current implementation, each resource type can only have a constant basic capacity function, but the designed architecture is capable of defining capacity constraints that change over time. the tasks, the required capacity with regard to the execution of tasks for each resource type and the precedence relations of tasks can be defined at the task level. when creating a project, the project identification data and the task assignments can be defined. furthermore, the weight of assigned project goals (objective functions) can also be specified. although the list of possible objective functions in the current implementation is fixed, the applied software architecture is capable of extending and implementing further objective functions. 5. problem-solving approach the applied scheduling algorithm has two main components: the first is the project scheduler based on schedule hungarian journal of industry and chemistry experimental implementation of a multi-project scheduling problem solver 55 figure 1: problem-solving approach generation schemes and the second is the search engine based on heuristics. the main principle of the schedule generation scheme-based project scheduler starts with an empty schedule and during each iteration a suitable task can be selected from the set of non-scheduled tasks before being added to the schedule. in the iteration, when the next task is selected, all the given constraints are taken into consideration, which means that all prerequisite tasks are scheduled and all resource requests can be completed simultaneously. a differentiation is made between serial and parallel schedule generation schemes based on the method used to select the next executable task. the serial schedule generation scheme predominantly checks that the prerequisite tasks have been completed. the decision set contains tasks whose prerequisite tasks have all been completed. from this set of tasks, the task with the highest priority value, namely the best candidate, is selected. this task is scheduled in a way that it is added to the schedule as soon as possible, that is, when the required resource capacity can be fulfilled at the same time. the parallel schedule generation scheme focuses mainly on the earliest starting time. in an intermediate state, the decision set contains the earliest executable tasks. in comparison with the serial schedule generation scheme, not all executable tasks form the basis for selecting tasks. from the decision set, the same priority-based technique is used to select a candidate like in the serial schedule generation scheme. if more than one task meets the selection criteria, that is, they have the same priority, the schedule generation scheme randomly selects one of them. in our approach, instead of making a random selection, a deterministic selection was applied, e.g. minimal slack, latest finish time, etc. instead of only using one heuristic method, many task-selection heuristics are combined where the importance weighting of a heuristic component can be defined by the user. the schedule generation scheme can be influenced by parameters defined by a user or any consumer. using the schedule generation scheme as a simulation module, a heuristic search was implemented where the search engine alters the task-selection behavior using heuristic weights. the main flow of this problem-solving approach is depicted in fig. 1. in the first step, the problem set is loaded into the internal data model. the user can alter the project goal (objective functions) if the problem set needs to be changed. the user can alter the parameters of the default search module before the scheduler is started. based on the given parameters, the search module executes simulations using the selected schedule generation scheme. the generated schedule is evaluated based on the defined goal (objective functions) and the search module can decide to reit49(2) pp. 53–58 (2021) 56 mihály, forrai, and kulcsár figure 2: aps system agents erate or exit. among the simulations, the behavior of the schedule generation scheme is altered via selection rules. 6. implementation enterprise resource planning (erp) systems are predominantly used to manage all resources in an enterprise. an erp system consists of a set of different modules responsible for coupled, separated and integrated application areas, e.g., manufacturing, finance, project management, etc. although our study focused on a systems applications and products (sap) erp system, our conceptual model can be used by other erp vendors as well, after adjusting the implemented artefacts to suit the vendorspecific platform. as with all standard project management (pm) systems, the sap erp pm supports the management of project-related entities such as the creation of projects, definition of tasks and dependencies, as well as definition of resources and their task assignments. in the execution phase of the project, execution reporting and collaboration with external parties are covered. in sap erp, this module is referred to as pm or project portfolio management (ppm) [11, 12]. a standalone advanced project scheduling (aps) component on the sap netweaver platform was implemented. this high-level concept is presented in fig. 2. the user accesses the aps user interface via the sap gui (graphical user interface). in this graphical user interface, the user can select the data set, decide where the projects can be selected and calibrate the scheduling parameters. when the project scheduler is started, the actual data is read from the data source, the detected scheduling algorithms are executed, and the scheduling results are stored via the scheduling result manager. the scheduling result is displayed in the aps user interface. the main component of the system is the project scheduling agent. the internal structure of this component is depicted in fig. 3. the scheduler consists of two disjoint sets of entities; one is visible to aps consumers, while the other is not. the aim of separating the disjoint sets is to provide a stable interface to code against it and allow the implementation used to be changed. the external interface consists of the defining interfaces of the supported project scheduling problem (cpm, rcpsp), the reading interface of the resource manager and a solver factory. rcpsps in the absence of resource constraints can be solved using the critical path method (cpm) algorithm. the cpm result may be an import parameter to calculate a dynamic priority rule, therefore, the rcpsp may require a cpm solver and the cpm is modelled as an individual solver entity. the rcpsp solver has different implementation alternatives which can be changed at any time. the reason for this flexibility is that the implementation alternatives can be analyzed without consuming system artefacts. the implemented solution realizes the schedule generation-based solvers (serial sgs and parallel sgs) and extended schedule generation-based solvers such as the rcpsp heuristic solver and the multi-objective search-based solver. the resource manager is responsible for checking the feasibility of the schedules provided by the scheduling algorithms. 7. results the extended model and the designed scheduler have been implemented in our own sap netweaver 7.5 developmental test environment. since the model and algorithm do not contain sap-specific elements, both can be mapped to suit any object-oriented programming language. the main reason for this decision is to enhance integration later using the sap pm module directly on the sap platform. the implemented solution was tested on known basic problems and our numerical results compared with the known results of the test problems by applying two methodologies. in the first case, problems were mapped using special boundary conditions onto the extended model, for which optimal scheduling algorithms are provided. it is hungarian journal of industry and chemistry experimental implementation of a multi-project scheduling problem solver 57 figure 3: project scheduler entities known that johnson’s algorithm yields the optimal solution for permutation flow-shop scheduling problems with a makespan objective function [13]. in most cases (> 95%), our heuristic-based solver identified the optimal solution to small problems (consisting of up to 20 jobs). in the second case, the basic rcpsp was mapped onto the extended model and the results with regard to the objective function concerning the completion time of the project (cmax) were compared with the best published results [4, 14]. our results were compared with the best results from benchmark problems. it was observed that for small problems (consisting of up to 30 jobs), in most cases (> 70%), the best known solution was identified by the scheduler. 8. conclusions our research focused on modelling and solving an extended variant of resource-constrained, multi-objective, multi-project scheduling problems. the execution environment of the modelled project includes different resource types and their capacities, many projects with individual objective functions and precedence constraints, task-dependent individual processing times and resource requirements, tasks belonging to many projects, as well as project-dependent due dates. during the research, new scheduling algorithms were developed that can flexibly solve problems while meeting all constraints. to generate detailed schedules, a predictive search algorithm was developed that includes an advanced simulation concerning the execution of the project. multi-priority rule-based constructive algorithms were also developed by using schedule generation schemes embedded in the scheduling engine. to solve the extended problem, a new approach based on the combined usage of search and constructive methods was proposed. in this paper, the proposed model of the investigated problem, the solution method and the key features of its implementation were described. the effectiveness of the proposed algorithms is demonstrated by presenting two validation methods. the results show that the proposed approach is efficient and flexible. the developed model of the extended problem was formulated in such a way that the individual requirements of tasks and projects can also be taken into account. by considering several aspects simultaneously, vital practical requirements can be incorporated into the model. the management strategy as well as tactical and operational control policies can be implemented, moreover, logical decisions made by modifying the weights of aspects concerning decision-making, namely objective functions and rules. acknowledgements this research was supported by the european union and the hungarian state, cofinanced by the european regional development fund within the framework of the ginop-2.3.4-15-2016-00004 project to promote cooperation between higher education and the industry. references [1] garey, m. r.; johnson, d. s.: computers and intractability: a guide to the theory of npcompleteness. (w. h. freeman and company, 1979) doi: 10.1137/1024022 49(2) pp. 53–58 (2021) https://doi.org/10.1137/1024022 58 mihály, forrai, and kulcsár [2] pritsker, a.; allan, b.; watters, l. j.; wolfe, p. m.: multiproject scheduling with limited resources: a zero-one programmingapproach. manage. sci., 1969, 16, 93–108 doi: 10.1287/mnsc.16.1.93 [3] mohanthy, r. p.; siddiq, m. k.; multiple projects multiple resources-constrained scheduling: some studies. int. j. prod. res. 1989, 27, 261–280 doi: 10.1080/00207548908942546 [4] bálint, r.; magyar, a.: refrigerator optimal scheduling to minimize the cost of operation. hung. j. ind. chem. 2016, 44(2), 99–104 doi: 10.1515/hjic-2016-0012 [5] deckro, r. f.; winkofsky, e. p.; hebert, j. e.; gagnon, r.: a decomposition approach to multiproject scheduling. eur. j. oper. res. 1991, 51, 110– 118 doi: 10.1016/0377-2217(91)90150-t [6] jolayemi, j. k.: scheduling of projects under penalty and reward arrangements: a mixed integer programming model and its variants.acad. inf. manag. sci. j. 2012, 15, 29–52 issn: 1524-7252 [7] gawiejnowicz, s.; lin, b. m. t.: scheduling time-dependent jobs under mixed deterioration. appl. math. comp. 2010, 216, 438–447 doi: 10.1016/j.amc.2010.01.037 [8] kim, k. w.; yun, y. s.; yoon, j. m.; gend, m.; yamazaki, g.: hybrid genetic algorithm with adaptive abilities for resource-constrained multiple project scheduling. comp. ind. eng. 2005, 56, 143–160 doi: 10.1016/j.compind.2004.06.006 [9] kumanan, s.; jegan, j. g.; raja, k.: multi-project scheduling using a heuristic and a genetic algorithm. int. j. adv. manuf. techn. 2006, 31, 360–366 doi: 10.1007/s00170-005-0199-2 [10] damak, n. j. b.; siarry, p.; loukil, t.: differential evolution for solving multi-mode resource constraint scheduling problems. comp. oper. res. 2009, 36, 2653–2659 doi: 10.1016/j.cor.2008.11.010 [11] sap se, sap project and portfolio management 2015 https://help.sap.com [12] sap se, sap s/4hana 1709 fps01, project system (ps) documentation 2018 https://help.sap.com [13] johnson, d. b.: efficient algorithms for shortest paths in sparse networks. j. acm, 1977, 24(1), 1– 13 doi: 10.1145/321992.321993 [14] kolisch, r.; sprecher, a.: psplib a project scheduling problem library: or software orsep operations research software exchange program. eur. j. oper. res. 1996, 96(1), 205–216 doi: 10.1016/s0377-2217(96)00170-1 hungarian journal of industry and chemistry https://doi.org/10.1287/mnsc.16.1.93 https://doi.org/10.1080/00207548908942546 https://doi.org/10.1080/00207548908942546 https://doi.org/10.1515/hjic-2016-0012 https://doi.org/10.1515/hjic-2016-0012 https://doi.org/10.1016/0377-2217(91)90150-t https://doi.org/10.1016/j.amc.2010.01.037 https://doi.org/10.1016/j.amc.2010.01.037 https://doi.org/10.1016/j.compind.2004.06.006 https://doi.org/10.1007/s00170-005-0199-2 https://doi.org/10.1016/j.cor.2008.11.010 https://help.sap.com/doc/saphelp_ppm400/4.0.24/en-us/02/4b1a417c4bf423e10000000a155106/frameset.htm https://help.sap.com/viewer/4dd8cb7b1c484b4b93af84d00f60fdb8/1709%20001/en-us/1ad4b65334e6b54ce10000000a174cb4.html https://doi.org/10.1145/321992.321993 https://doi.org/10.1016/s0377-2217(96)00170-1 https://doi.org/10.1016/s0377-2217(96)00170-1 introduction resource-constrained project scheduling problem multi-project scheduling problems an extended model problem-solving approach implementation results conclusions hungarian journal of industry and chemistry vol. 48(2) pp. 37–43 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-25 the effect of ph on biosurfactant production by bacillus subtilis dsm10 réka czinkóczky1 and áron németh *1 1department of applied biotechnology and food science, budapest university of technology and economics, műegyetem rkp. 3, budapest, 1111, hungary the genus bacillus has long been known for its ability to produce many industrially useful products. these bacteria mostly produce extracellular products like organic acids, enzymes and biosurfactants. in this paper, the production of surfactin using the bacillus subtilis strain dsm10 is investigated. biosurfactant was produced in a lab-scale 1-liter fermenter. ph control using different bases (nh4oh and naoh) was compared to observe whether the amount of produced biosurfactant or the quality of the product was influenced. the formation of the product was followed by measuring the surface tension, and the product formed was analyzed by reversed-phase chromatography. the investigation of the effect of ph control showed that it can be omitted during the fermentation of the biosurfactant. the highest concentration of surfactin (5 g/l) was achieved without ph control in contrast with when the ph was kept constant (ph = 7). keywords: biosurfactant, surfactin, fermentation, purification, bacillus subtilis 1. introduction in recent years, the microbial production of tensio-active molecules with various properties, e.g. emulsifying, wetting, foaming, detergency, solubilizing and dispersing, has been gaining interest [1]. biosurfactants are amphiphilic compounds produced by a variety of microbial communities. natural surfactants are of great importance in the pharmaceutical, cosmetic, agricultural and food industries due to their beneficial properties including low toxicity, biodegradability, high selectivity and activity under extreme environmental conditions [2, 3]. the market of bio-based surfactants is predicted to be worth $5.52 billion by 2022 [4]. this is unsurprising given our high degree of dependency on kinds of hygiene products, the majority of which include surfactants or emulsifiers. biosurfactants are classified based on their chemical structure into the following groups: glycolipids, lipopeptides, fatty acids and lipids, as well as polymeric and particulate biosurfactants [3, 5]. one of the most effective biosurfactants is surfactin. this lipopeptide-type surfactant contains a cyclic peptide linked to a fatty acid chain (fig. 1) [6]. bóka et al. reported that the molecular weights of surfactins range from 993 da to 1049 da [7]. several gram-positive bacillus species naturally produce surfactins, which help the bacteria to stabilize their cell membranes and adhere to a surface [8, 9]. the biosynthesis of surfactin occurs through different mechanisms: the conversion of glucose or glycerol as a substrate *correspondence: naron@f-labor.mkt.bme.hu to glucose 6-phosphate through the glycolytic pathway, providing the main precursor of carbohydrates located in the hydrophilic part and the oxidation of glucose to pyruvate then to acetyl-coa, which serves as a precursor for the synthesis of lipids and amino acids (asp, glu, leu, val). however, if the substrate is a hydrocarbon, the metabolism is shifted towards the lipolytic pathway (βoxidation into acetyl-coa) and gluconeogenesis (acetylcoa involved in the synthesis of the precursor glucose 6-phosphate) [1]. the effectiveness of surfactants is defined by their ability to reduce the surface tension (st), defined as the cohesive force between molecules which is proportional to the concentration of surfactant in the solution [2]. their efficiency is measured by the critical micelle concentration (cmc) [1,11]. above the cmc, surfactants form micellar structures, but below it, the aggregates dissociate into monomers. lipopeptides from b. subtilis are particularly compelling because their surface activity has been reported to be strong [6,12,13]. powerful surfactants can decrease the surface tension of water (72 mn/m at 20 ◦c) to less than 30 mn/m [14]. the emulsifying capacity can be monitored by calculating the emulsification index (ei, %) and emulsion stability. as the ph decreases, surfactin becomes less soluble in water because the carboxyl group is protonated [12]. under neutral or basic conditions, the carboxyl group is in the ionic form, thus its solubility and emulsification capability increases [15]. moro et al. evaluated the influence of the ph on the stability of the surfactants produced by species of b. subtilis, b. gibsonii and b. https://doi.org/10.33927/hjic-2020-25 mailto:naron@f-labor.mkt.bme.hu 38 czinkóczky and németh figure 1: chemical structure of surfactin: peptide loop of amino acids: five l-amino acids (val, asp, leu, glu and leu) two d-amino acids (leu and leu), and a α, βhydroxy c13-c15 fatty acid chain [10] amyloliquefaciens [9]. all isolates exhibited surface tensions below 30 mn/m. in strongly acidic conditions, the emulsifying activity significantly decreased for both b. subtilis odw02 and b. subtilis odw15. as the ph was increased from 7 to 12, the stability of the surfactant produced by b. subtilis odw02 decreased even further, but the one by b. subtilis odw15 remained stable. in the case of b. amyloliquefaciens mo13, a significant increase was observed both under acidic and basic conditions. this different ph-responsive behavior makes surfactin applicable in a variety of industrial fields. the choice of fermentation cultivation media (i.e. of average composition, carbon source, nitrogen source and trace elements) as well as fermentation strategies (i.e. temperature, ph, aeration and agitation) also need to be considered in relation to the type of applications. based on a literature review, the best combination among the fermentation conditions was 1.5 vvm at 300 rpm, resulting in a maximum yield of surfactin of 6.45 g/l [16]. b. subtilis atcc 21332 was grown on an iron-enriched minimal salt (msi) medium including glucose (40 g/l). in a recent study, yang et al. used nanoparticles (nps) to improve the total yield of surfactin. 5 g/l of fe nps were added to the fermentation medium of b. amyloliquefaciens mt45, which increased the titer of surfactin from 5.94 to 9.18 g/l. modifying the biosynthesis of surfactin with metabolic engineering tools can further increase production and titers of surfactin in b. subtilis, as demonstrated by wu et al. (12.8 g/l) [17]. few studies have focused on individual characteristics and relative amounts of surfactin variants in the extracts of lipopeptides. many surfactin variants exist with various lengths of fatty acid chains and different amino acid sequences [5]. akpa et al. analyzed the replacement of l-glutamic acid with four other amino acids, namely l-leucine, l-valine, lisoleucine and l-threonine, in the culture medium. the presence of thr was found to be favorable for the synthesis of longer (c15-c16) fatty acid chains in b. subtilis s499 [18]. supplementation with mn2+, cu2+ and ni2+ ions can also promote the production of novel variants of surfactin with different components of fatty acids (c16c18) and amino acids (central aspartic acid methyl ester residue instead of aspartate) [19]. this approach can be useful for studying specific biological activities. the objectives of our study were to explore the effect of ph control on the production of biosurfactants (i.e. on titers and productivity) by the b. subtilis strain dsm10 and evaluate the properties of biosurfactants, i.e. type, surface tension reduction and emulsifying activity. 2. materials and methods 2.1 cultivation conditions bacillus subtilis dsm10 (ncaim b.02624t) was used for biosurfactant fermentation in this study. cultivation was performed at 37 ◦c in 250 ml erlenmeyer flasks containing 100 ml of an inorganic medium based on the composition used by joshi et al. (2013): 34 g glucose, 1.0 g nh4no3, 6.0 g kh2po4, 2.7 g na2hpo4, 0.1 g mgso4•7 h2o, 1.2·10−3 g cacl2•2 h2o, 1.65·10−3 g feso4•7 h2o, 1.5·10−3 g mnso4•4 h2o and 2.2·10−3 g na-edta [20]. the experiments were carried out in a 1 l benchtop bioreactor, with a working volume of 0.8 l (biostat q fermenter, b. braun biotech international, germany) and a 10% v/v inoculum. for biosurfactant production, the temperature was adjusted to 37 ◦c with an agitation speed of 300 rpm and an aeration rate of 0.25 vvm. the ph was controlled by 25% h2so4 and two different bases, namely 25% nh4oh and 25% naoh. biosurfactant fermentation without external ph control served as a controlled experiment. a cyclone separator for reducing foam was connected to the outlet airstream of the fermenter (fig. 2). the foam could overflow from the fermenter via the air outlet, through the cyclone separator to the collector flask. 2.2 analysis of biomass bacterial growth was monitored by measuring the optical density of the fermentation broth at 600 nm using a pharmacia lkb ultrospec plus spectrophotometer in comparison with that of the centrifuged supernatant of the sample. the biomass concentration (g cell dry weight/l) was determined by using a calibration curve (r2 = 1): biomass [g/l] = 0.4283 · od600 + 1.4568 (1) the sampled broth was centrifuged at 6, 000 rpm for 15 mins. the cell pellets were collected and dried at 105 ◦c to constant weight by a sartorius ma35 moisture analyzer to measure the cell dry weight. hungarian journal of industry and chemistry the effect of ph on biosurfactant production by bacillus subtilis dsm10 39 figure 2: fermentation setup with foam-separating glass cyclone 2.3 analysis of glucose consumption glucose consumption was determined using the waters breeze 2 hplc system. the mobile phase was 5 mm h2so4 and the rate of elution was 0.5 ml/min. a biorad aminex hpx-87h (300 × 7.8 mm, 9 µm) column (65 ◦c) was applied with a refractive index detector (40 ◦c). the glucose concentration was calculated from the peak area by the following calibration curve equation (r2 = 1): glucose [g/l] = 4 · 10−6 · peakarea + 0.0147 (2) 2.4 analysis of biosurfactants surface tension measurement the surface activities of biosurfactants produced by the bacterial strains were determined by measuring the surface tension of the samples of cell-free broth using the stalagmometric method with a traube stalagmometer (2.5 ml, wilmad-labglass lg-5050-102 stalagmometer tube for samples of low viscosity) at room temperature (25 ◦c). to increase the accuracy of the surface tension measurements, the averages of triplicates were used in this report. the surface tension can be determined based on the number of drops that fall per unit volume, the density of the sample and the surface tension of a liquid reference, e.g. deionized water. the actual number of drops was calculated using n = n0 + x− y c (3) where n denotes the number of drops of the sample calculated to the nearest tenth of a drop;n0 represents an integer of drops counted between capillary-scale readings x and y; x and y stand for capillary-scale readings based on the maximum data point as 0 and the minimum data point as 40; x and y refer to the distances in millimeters from the beginning of each scale; and c is the capillary-scale calibration in millimeters per drop. the surface tension (st in mn/m) was calculated according to st = stw ·nw ·d n ·dw (4) where stw denotes the surface tension of water at 25 ◦c (72 mn/m);nw represents the number of water drops (20 drops); d stands for the density of the sample in g/ml; n refers to the number of drops of sample, and dw is the density of water at 25 ◦c. emulsifying activity the emulsifying activity was determined by the addition of 2 ml of sunflower oil to the same volume of cellfree sample or surfactin solution in a test tube, which was vortex-mixed vigorously for 2 mins. [21]. the tubes were incubated at 25 ◦c and the emulsification index (ei) determined after 24 hours according to: eit = ( he ht ) 100 (5) where he and ht are the height of emulsion and total height of the liquid in the tube, respectively. to study the emulsion stability, the same protocol was used. the emulsification index (ei, %) was determined after 1 h and the ei measured after 24 h (ei24, %), the tubes were incubated at 25 ◦c. the emulsion stability was expressed as a function of the changes in ei over the 24 h. high-performance liquid chromatography (hplc) the surfactin concentration was measured by hplc using a waters alliance 2695 separations module, which is a high-performance liquid chromatographic system equipped with a waters 2996 photodiode array detector, at 205 nm and a symmetry c18 column (4.6 × 150 mm, 5 µm waters, ireland). the mobile phase consisted of 20% v/v trifluoroacetic acid (tfa) (3.8 mm) and 80% v/v acetonitrile. the elution rate was 1 ml/min at 25 ◦c and the sample volume was 10 µl. the purified surfactin was identified by using commercially available surfactin (wako chemicals) as the authentic compound [22]. 2.5 isolation of the biosurfactant the method for purifying the biosurfactant was adapted from the one outlined by joshi et al. (2008) [23]. the cell-free broth was obtained by centrifuging the fermentation broth at 4, 000 rpm for 20 mins. at 4 ◦c using a janetzki mlw k23d centrifuge. the cell-free broth was used for further purification steps. the biosurfactant was recovered from the supernatant by acid precipitation: the 48(2) pp. 37–43 (2020) 40 czinkóczky and németh table 1: summary of the results of the fermentations without ph control 25% nh4oh 25% naoh biomass yield [g/g] 0.06±0.02 0.06±0.02 0.08 biosurfactant yield [g/g] 0.120±0.04 0.073±0.07 0.123 glucose conversion [%] 78.90±22 71.40±4 58.35 final biosurfactant concentration [g/l] 3.36±2.3 2.00±1.5 2.34 minimum surface tension [mn/m] 51.1±1 54.3±17 68.4 biomass productivity [g/l·h] 0.060±0.03 0.089±0.05 0.064 biosurfactant productivity [g/l·h] 0.100±0.05 0.034±0.02 0.064 ph was adjusted to 2.0 using 6 n hcl and kept at 4 ◦c overnight. the precipitate was collected by centrifugation at 4, 000 rpm for 20 mins. at 4 ◦c, then resuspended in distilled water. the ph was adjusted to 7.0 using 6 n naoh and the solution lyophilized by a christ alpha 2-4 lsc freeze dryer. the concentration of biosurfactant was determined gravimetrically from the resulting yellowish white powder. the concentration of biosurfactant was determined gravimetrically from the lyophilized powder. the identity of the purified biosurfactant was checked by hplc. 2.6 calculation of fermentation parameters to compare the results of the fermentation, the following parameters were determined. substrate (glucose) conversion was calculated according to: ∆s % = s0 − sf s0 (6) where s0 and sf denote the initial substrate and final glucose concentrations, respectively. the biomass yield on glucose (y x s , g/g) was defined by: y x s = xf − x0 s0 − sf (7) where xf and x0 are the final and initial biomass concentrations, respectively. the biosurfactant yield on glucose (yp s , g/g) was defined by: yp s = pf − p0 sf − s0 (8) where pf and p0 are the final and initial biosurfactant concentrations, respectively. the volumetric productivities jx = xmax txmax (9) and jp = pmax tpmax (10) (g/l · h) were calculated as the quotients of the maximum biomass concentration (xmax, g/l) or the maximum biosurfactant concentration (pmax, g/l) and the fermentation time (txmax or tpmax , h) when the maximum concentration was achieved, respectively. 3. results and discussion to evaluate the effect of ph on surfactin production, a series of batch fermentations were performed either with or without ph control. the biosurfactant solution was analysed quantitatively and qualitatively using the hplc method reported by mubarak et al. [24]. an overview of the calculated parameters of the batch runs can be seen in table 1. in the absence of ph control, the maximum biomass concentration achieved was 4.00 g/l after 35 h (fig. 3). without ph control, the increased acidity of the medium inhibited further growth at ph 4.4. the maximum biosurfactant concentration was 4.99 g/l, which resulted in the surface tension decreasing to 50.1 mn/m. in ph-controlled fermentations, the biomass yields (0.06 and 0.08 g/g ph adjusted with 25% nh4oh and 25% naoh to 7.0, respectively) were similar to that in the absence of ph control (0.06 g/g) (table 1), while the production of biosurfactants was unable, with a few exceptions, to reduce the surface tension significantly (66.5 mn/m with 25% nh4oh, table 1; figs. 4 and 5). this may account for the presence of residual glucose concentrations of 8 to 12 g/l (figs. 4 and 5). the maximum surfactant concentrations were 3.50 and 2.34 g/l by adjusting the ph using nh4oh and naoh, respectively. although these results are similar to the average yield of surfactants (3.36 g/l) in the absence of ph control, a significant drop in productivity of approxifigure 3: fermentation of surfactin without external ph control hungarian journal of industry and chemistry the effect of ph on biosurfactant production by bacillus subtilis dsm10 41 figure 4: a) hpl chromatogram of a 1.25 g/l surfactin standard, b) hplc chromatogram of the isolated biosurfactant fraction from the foam out sample figure 5: fermentation of surfactin ph controlled by 25% nh4oh. mately 50% was observed (table 1). the highest value of the emulsifying activity (ei24) was in excess of 70% at the end of the exponential phase of the growth curve (at 35 h, fig. 3). the ei24 values obtained from samples extracted from ph-controlled experiments increased from 45 to 55% (figs. 5 and 6, respectively). these inconsistencies can be explained in part by the fact that different bacillus species and strains are capable of producing numerous surfactin variants with distinct properties. it is highly likely that the production of surfactants is independent of cell growth as ei24 decreased and st increased during the stationary phase perhaps as a result of degradation by enzymatic hydrolysis or uptake under substrate-limiting conditions [25, 26]. since the spectrum of lipopeptide-type biosurfactants is broad, the profiles of the extracts obtained after the purification process were compared to the surfactin standard. fig. 4 presents two representative chromatograms: figure 6: fermentation of surfactin ph controlled by 25% naoh (a) surfactin standard and (b) purified culture broth of b. subtilis dsm10. comparatively speaking, the samples from our study exhibited similar peaks (number of peaks, retention time). the intense peak at the beginning of the chromatogram indicates the presence of some nonretained impurities, namely contaminants and inorganic salts such as nh4no3, which are often co-extracted with the targeted biosurfactant, that may need to be separated. overall, based on the separation of peaks and retention time, the isolated biosurfactant was identified as surfactin. the surfactin titer of b. subtilis dsm10 was compared with the results from relevant studies (table 2). even though the fermentation strategies differ to some extent, the surfactin concentration from our work compares well with the values previously reported in the literature. 4. conclusion the aim of this study was to assess the biosurfactantproducing capability of bacillus subtilis dsm10 and establish an economically feasible fermentative process. this paper investigated the effect of ph control on the amount of biosurfactant production. the maximum amount of biosurfactant (approximately 5 g/l) was recovered from fermentation experiments in the absence of ph control at 37 ◦c. furthermore, a preliminary characterization of the surface-active compounds produced during fermentation was conducted. hplc analysis confirmed the presence of surfactin in the purified product. table 2: surfactin production by bacillus species strain surfactin titer [g/l] ref. b. subtilis atcc 21332 6.45 [16] b. subtilis 2.00 [27] b. subtilis spb1 4.92 [28] b. subtilis dsm10t 3.99 [29] b. subtilis #573 4.80 [6] b. subtilis cn2 7.15 [30] b. subtilis dsm10 4.99 this work 48(2) pp. 37–43 (2020) 42 czinkóczky and németh the minimum surface tension was 50 mn/m. the emulsifying activity achieved using sunflower oil was approximately 70%. these results represent an initial step towards large-scale production of this biosurfactant. from a technical and economic standpoint, the fermentative process of surfactin carried out in the absence of ph control in a mineral salt medium using glucose as the sole carbon source seems to be an effective strategy for pilotand industrial-scale production. acknowledgment the research was supported by the gedeon richter’s talentum foundation, founded by gedeon richter plc. 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the biosurfactant calculation of fermentation parameters results and discussion conclusion microsoft word a_61_szoboszlai_r.doc hungarian journal of industrial chemistry veszprém vol. 39(1) pp. 117-120 (2011) investigation of kinetics of hydroisomerization of c5/c6 and c6/c7 alkanes and their binary mixtures zs. szoboszlai , j. hancsók university of pannonia, department of mol hydrocarbon and coal processing 8200, veszprém egyetem u. 10, hungary e-mail: szzsolt@almos.uni-pannon.hu modern gasoline quality requirements globally became stricter. these specifications parallel with the applied developments of vehicle technologies contributing to the cleaner environment. nowadays only the concentration of cycloand isoparaffins are not limited in gasoline, because they burn cleaner, have high octane number, lower sensibility and better combustion properties than aromatic or olefinic hydrocarbons. in the last decade because of the applied refinery investments both sulfur and aromatic content of gasolines decreased, but the octane mass of the gasoline pool significantly decreased against the increment of octane number requirement of spark ignition engines. importance of isomerization of light paraffins has been publicized in many papers. however few of them investigated, studied and explained the individual hydrocarbons (c5/c6/c7) interaction with each other in multicomponent mixtures practically in similar to industrial hydrocarbon feedstocks. binary and multicomponent hydrocarbon mixture investigations can contribute to the understanding the results of isomerization of real, feedstocks from multiple sources; which contain higher boiling point hydrocarbons (cycloparaffins, benzene, and heptanes). further these results can help to operate with higher flexibility, safety and economically a light naphtha isomerization units. the hydroisomerization of n-pentane (n-c5), n-hexane (n-c6), cyclohexane (c-c6) and n-heptane (n-c7) and their binary mixture were studied on pt/sulfated zirconia catalyst at temperature 150–170 °c, total pressure 20 bar, 1:1 h2-hydrocarbon molar ratio. the apparent activation energies of all individual components, further the reaction rates individually and in different composition binary mixtures were specified. results of our experiments concluded that the rate of reaction of the higher carbon number hydrocarbon or in case of the same carbon number the cycloparaffins (lower volatility component) increased with increasing the concentration in the binary mixtures, while the rate of reaction of higher volatility component decreasing. keywords: isomerization, light naphtha introduction nowadays the fractions rich in isoparaffin are the most important blending components of the gasolines because they have high octane number, low sensibility, they are practically free from sulphur, olefin, and aromatics, they have low toxicity, and undesired molecules are not generated under controlled combustion [1-4]. the continuous demands for the application of isoparaffin rich hydrocarbon fractions are the followings: from 2000 – low benzene and decreased aromatic concentration (research octane number and octane number distribution) – reducing the research octane number give away – supplementation of the octane number decrease of the deep desulphurization of cracked naphthas – regulation of the application of mtbe – balancing the boiling range shifting in case of heavier ether (etbe, tame) application in high concentration from 2005 – further deep desulphurization – further reduced aromatic and benzene content figure 1: constructed refinery investments in the eu for high quality gasoline production until 2005 to fulfill the 2005 gasoline regulations the simultaneous reduction of the sulphur and aromatic content significantly decreased the octane number of the gasoline pool against the increasing octane number requirements of the otto engines (higher compression ratio → higher octane number → higher volumetric efficiency and specific power with lower emission). 118 the importance of isoparaffin rich fractions is presented in fig. 1 which shows what the most important investments are in the refineries to satisfy the demands and meet the new specifications [1-4]. it can be clearly seen that the highest investments in the refinery were the light paraffin isomerization processes (though the application of light paraffins was slightly reduced by the bioethanol blending, in spite of the significant effect of the ethanol on the gasoline physical-chemical application properties the etherification and alkylation capacity can be significantly increased by taking advance of the isomerization capacity), but the alkylation unit installation and revamping was also important. the possible ways to produce industrial economically isoparaffin rich fractions are the following: ● the proper naphtha fraction separation to isoand normal paraffin fractions ● alkylation of isobutane with c3-c5 olefins (direct alkylation) ● dimerization of c3-c5 fractions rich in olefins (indirect alkylation) after hydrogenation ● isomerization of c5-c7 fractions rich in n-paraffins o isomerization of benzene containing fractions two-steps → two reactors and different catalysts one step • isomerization of benzene containing fractions (the saturation of benzene and isomerization of the n-paraffins is done in the same reactor and on the catalyst) [5-6] • in the same reactor with segmented beds with different catalysts [4] the specifications of the benzene concentration of the naphtha fraction can be ensured by adequate preand post-treating so the feed of reformation does not contain benzene precursor or after the reformation they have to be fractionated (if the reformation is gasoline purpose) from the product and saturated in the isomerization plant. the feedstock of both of the etherification and alkylation technologies are the c4-c5 isoparaffins consequently the light paraffin isomerization will be one of the key processes just partly producing internal components/feeds for other technologies. experimental aim of our experimental work was the investigation of isomerization of hydrocarbons with different volatility and their binary mixtures. we investigated that the isomerization effects/rate on each other further how influenced the individual hydrocarbon the other in laboratory scale reactor on steady state activity catalyst. the inspiration of this research work was the absent of large scale, long term catalytic studies with near industrially parameters [7-14]. experimental eqipment the applied catalytic system contains a 100 cm3 vertical reactor and every instrument which can be found in a commercial scale light naphtha isomerization unit. the catalytic system contains a gas regulator/control and pretreatment system and an on-line gas chromatograph. materials we applied 60cm3 of in situ dried and activated pt/sulphated-zirconia (extrudated, d: 1.5mm) catalyst and the empty space was filled with raschig rings. the feedstocks were analytical grade, sulphur free npentane, n-hexane, cyclohexane and n-heptane. the concentration of components was varied between 0–100% (0, 25, 50, 75 and 100% theoretically) in binary mixtures. the practically sulfur free hydrocarbons continuous demoisturising was done with linde 4a molecule sieve. catalyst and test methods the applied catalyst was pt/sulfated-zirconia. main properties of the catalyst were shown by table 1. table 1: the main characteristics of applied catalysts properties values pt-content, % 0.415 pt-dispersion, % 69 acidity, mmolnh3/g 0.56 sametalic (metal (pt) surface on the catalyst), m2/g metal 25.91 smetal (specific metal surface), m2 metal/g cat. 0.108 aps (average particle size of the metal), nm 2.0 specific acidity, mmolnh3/m2 cat. 0.0043 bet surface, m2/g 130 microporous surface, m2/g 12.2 microporous volume, cm3/g 0.0045 mezoporous volume, cm3/g 0.2874 mezo-/microporous volume ratio 63.9 average pore size, nm(å) 8.5(85) standard measurements methods were used. pt content of the catalyst was measured by uop-274 standard. bet surface area and total acidity of the catalyst was measured by nh3 sorption according to astm d3663 and d4824 standards, while pore size distribution and pore volume was measured by mercury intrusion porosimetry method according to astm d4284 and d6761 standards respectively. the feeds and products composition was measured with gas chromatograph according to astmd5134 standard. the sulphur content of all feeds and products (greenlab ltd./analytik-jena multi ea 3100-type device) with en iso 20846 (2003), water content (greenlab ltd./kem mka-610-type device) with iso 12937:2001 standard was determined. 119 process parameters experiments were measured on steady state activity catalyst. based on preliminary results the experiments was taken on 20 bar total pressure, 1.0–4.0 lhsvs, h2/hc molar ratio was 1.0:1.0. fine changes of the parameter combination kept measuring where the low conversion rates (5–15%) of the individual hydrocarbon were not inhibited by the products. results and discussion near low conversion rates the individual hydrocarbons initial reaction rates were measured then the logarithmized values were presented versus the inverse of temperature. these methods were applied to determine the apparent activation energies of hydrocarbons. based on the given data they had relatively high deviation, and these values can be given with relatively high inaccuracy. our values and the publicized values are relevated well (table 2) but the most of them were determined in different catalytic system and with different parameter combinations [11-15]. for example in case of the cyclohexane the measured values are well correlated with publicized data (100–150 kj/mol). table 2: the apparent activation energies of individual hydrocarbons hydrocarbon n-pentane n-hexane n-heptane cyclohexane eapparent, measured values, kj/mol 130–170 99–107 149–163 113–146 eapparent, publicized values, kj/mol 145–153 120 109–135 100–150 the targeted quantity was added to n-hexane and above 20% concentration it caused significantly lower reaction rate. so the reaction rate of the main component decreased causing lower effectiveness under isomerization consequently the adequate composition of the feed(s) has to be kept assured! based on our measurement the reactivity of the individual hydrocarbons were the following: c-c6>n-c7>n-c6>n-c5, the main cause was that the adsorption energies of cycloparaffins is higher than the same carbon number linear paraffins on strongly acidic catalysts so in their mixtures increasing the individual component reaction rate change with different degree with the concentration interdependently (fig. 2-4). in the hexane the other component concentration more than 20–30% the n-hexane reaction rate was approximately halved and its component reaction rate was comparable/similar to the other individual component reaction rate. in case of cycloparaffin isomerization the lower h2 pressure was beneficial though it increased the selectivity of ring opening reaction. on stricter parameter combinations the ring isomerization selectivity becomes higher and near the equilibrium concentration (cyclohexane↔methylcyclopentane) the cracking reaction come to front that ascribe to methylcyclopentane. in the examination of the gas phase composition it was observed that the c2/c4 molar ratio was very low so the isomerization and cracking reaction probably to take place through c12-c8 intermediate products. 0 5 10 15 20 0 20 40 60 80 100 r ea ct io n ra te , 1 0-8 m ol /s. g c at . n-pentane concentration in binary mixture, % reaction rate of n-hexane reaction rate of n-pentane figure 2: changes in reaction rate of individual components in the binary mixture (t: 150 °c, lhsv: 1.5 h-1, p: 20 bar) 0 5 10 15 20 25 30 35 0 20 40 60 80 100 r ea ct io n ra te , 1 0-8 m ol /s. g c at . n-heptane concentration in binary mixture, % reaction rate of n‐heptane reaction rate of n‐hexane figure 3: changes in reaction rate of individual components in the binary mixture (t: 150 °c, lhsv: 1.5 h-1, p: 20 bar) 0 10 20 30 40 50 60 70 80 0 20 40 60 80 100 r ea ct io n ra te , 1 0-8 m ol /s. g c at . cyclohexane concentration in binary mixture, % reaction rate of cyclohexane  reaction rate of n‐hexane figure 4.: changes in reaction rate of individual components in the binary mixture (t: 150 °c, lhsv: 1.5 h-1, p: 20bar) 120 conclusions the individual component reaction rates were lower in every case than in their binary mixtures. the reaction rates were significantly decreased in the mixtures with increasing the concentration of individual paraffin hydrocarbons. based on the measured and calculated values it was concluded that in case of the non-adequate feed or in case of non-adapted isomerization catalyst – where accordingly to the demands the changes of process parameters have not indicated any opportunity – influence of some component on the isomerization efficiency become significant degree hereby the main linear chain components with low octane number reactions rate of isomerization was interfered. acknowledgment we acknowledge the financial support of this work by the hungarian state and the european union under the tamop-4.2.1/b-09/1/konv-2010-0003 project. references 1. u. szalkowska: fuel quality global overview, 7th international colloquium on fuels 2009, tae, stuttgart/ostfildern (germany) 2. h. weyda, e. köhler: modern refining concepts an update on naphtha-isomerization to modern gasoline manufacture, catalysis today, 81(1), (2003), 51–55 3. sz. magyar, j. hancsók, a. holló: key factors in the production of modern engine gasolines, 6th international colloquim, fuels 2007, germany, esslingen, 2007, in proceedings (isbn 3-92481367-1), 273–284 4. j. hancsók, sz. magyar, zs. szoboszlai, d. kalló: investigation of energy and feedstock saving production of gasoline blending components free of benzene, fuel processing technology, 88(4), (2008), 393–399 5. j. hancsók, sz. magyar, k. v. s. nguyen, zs. szoboszlai, d. kalló, a. holló, gy. szauer: simultaneous desulphurization, isomerization and benzene saturation of n-hexane fraction on pth/mor, studies in surface science and catalysis (isbn 0 444 52083 x), porous materials in environmentally friendly processes 158, (2005), 1717–1724 6. zs. szoboszlai, j. hancsók, sz. magyar: upgrading of benzene containing hexane feeds by simultaneous isomerization at low temperature and saturation of benzene, 6th international colloquium, fuels 2007, germany, esslingen, 2007, in proceedings (isbn 3-924813-67-1), 293–302 7. g. d. yadav, j. j. nair: sulfated zirconia and its modified versions as promising catalysts for industrial processes, microporous and mesoporous materials 33, (1999), 1–48 8. j. m. serra, a. chica, a. corma: development of a low temperature light paraffin isomerization catalysts with improved resistance to water and sulphur by combinatorial methods, applied catalysis a: general, 239(1-2), (2003), 35–42 9. w. takemi, m. hiromi: reaction of linear, branched, and cyclic alkanes catalyzed by brönsted and lewis acids on h-mordenite, h-beta, and sulfated zirconia. journal of molecular catalysis a. 239, (2005), 32–40 10. j. c. duchet, d. guillaume, a. monnier, c. dujardin, j. p. gilson, j. van gestel, g. szabo, p. nascimento: isomerization of n-hexane over sulfated zirconia:influence of hydrogen and platinum, journal of catalysis 198, (2001), 328–337 11. a. holló, j. hancsók, d. kalló: kinetics of hydroisomerization of c5-c7 alkanes and their mixtures over platinum containing mordenite, applied catalysis a: general, 229(1-2), (2002), 93–102 12. t. løften, e. a. blekkan: isomerisation of nhexane over sulphated zirconia modified by noble metals, applied catalysis a: general 299, (2006), 250–257 13. m. guisnet, v. fouche: isomerization of n-hexane on platinum dealuminated mordenite catalysts, ii. kinetic study, appl. catal, 71, (1991), 295–306 14. h. liu, g.d. lei, w. m. h. sachtler: alkane isomerization over solid acid catalysts. effects of one-dimensional micropores, appl. catal., 137(1), (1996), 167–177 15. c.-l. li, l. shi, g-x. huang, r.-y. wang: scaleup for alkane isomerization, chem. eng. comm., 121, (1993), 1–8 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 /colorconversionstrategy /cmyk /dothumbnails false /embedallfonts true /embedopentype false /parseiccprofilesincomments true /embedjoboptions true /dscreportinglevel 0 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice hungarian journal of industry and chemistry vol. 48(1) pp. 81–85 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-13 optimizing the planning and manufacturing processes of electromagnetic energy harvesting equipment lászló móricz*1 and istván szalai1 1institute of mechatronics engineering and research, faculty of engineering, university of pannonia, gasparich márk u. 18/a, zalaegerszeg, 8900, hungary the main aim of this paper is to create an energy harvesting system, which can convert vibrational energy into electrical energy efficiently. our research was carried out in the field of electromagnetic energy conversion using the principles of linear generator construction for both low and high frequency vibrations. energy can be recovered efficiently. during the measurements, how the induced voltage is dependent on the impulsive frequency and the amplitude of impulses was investigated. keywords: energy harvesting, induced voltage, vibration, linear generator, energy 1. introduction many forms of energy sources exist (vibrational, thermal, wind) in the environment which can be converted into electrical energy with a good degree of efficiency. the harvesting of this energy from the environment has the potential to reduce the rate of depletion of non-renewable energy sources [1] and can be converted by using electromagnetic [2,3], electrostatic [4,5] and piezoelectric [6,7] energy conversion processes. our research was conducted in the field of electromagnetic energy conversion for both low and high frequency vibrations. numerous energy harvesting mechanisms are based on the damped driven harmonic oscillator (ddho) [8]. the essence of the process is to create relative displacement between a permanent magnet and a coil [9]. electric power (energy) is induced in the coil due to changes in magnetic flux. to achieve the relative displacement, the magnet and leading house must come into physical contact which can be achieved mechanically or magnetically [10]. each mechanical system has a mechanical damping factor. if the damping of the system is too low, the device exhibits no resistance to harmonic motion. however, if the value becomes too high, the resistance of the device to motion increases dramatically, thus no relative displacement of the device occurs. both the damping force and relative displacement are essential to convert energy efficiently into the system [11]. one of the most difficult tasks of the design process is to define the appropriate degree of damping that maximizes the extractable efficiency. an important aspect of *correspondence: moricz.laszlo@mk.uni-pannon.hu the design process is the tuning of the natural frequency of the structure. if the impulsive frequency deviates from the resonant frequency, a loss of power can be detected. one possibility is that the bandwidth of operation is enhanced which results in the value of the “quality (q) factor” decreasing and diminishes the amount of extractable energy [5]. to achieve a good degree of efficiency of the system, the harvesting of very low frequency vibrations must be taken into account. regarding energy harvesting systems for low frequency applications, the possibilities of frequency upconversion are introduced and achieved in different ways. ashraf et al. [11] optimized the mechanical design of the system by applying the finite element method to broaden the low frequency range. haroun et al. [9] tried to keep the natural frequency of their system, namely ceh, low. they concluded that if the spring is not fixed to the moving frame (fieh), then the natural frequency of the system is lower than that of the fixed spring system (ceh). 2. design process and evolution of the structure there are two types of generator-based energy harvesting systems: • system 1: based on linear movement • system 2: based on rotational movement the linear generator converts the mechanical movement directly into electrical energy. several basic construction solutions can achieve this, e.g. the linear motors can https://doi.org/10.33927/hjic-2020-13 mailto:moricz.laszlo@mk.uni-pannon.hu 82 móricz and szalai figure 1: mechanical structure of the eh system be straightened versions of permanent magnet motors. the structure chosen is presented in fig. 1. the energy harvesting model was made using solidworks 2016 software. the assembled system is shown in fig. 2. the structure consists of two main parts; the stationary part possesses a coil holder and the moving part was produced from a square section slip. four horseshoe neodymium magnets were mounted on the moving part. the horseshoe magnets consisted of two iron plates and a square neodymium magnet. the thickness of the two iron plates was equal to that of the square neodymium magnet. it is important that the iron plate contains less alloys. the best solution from the options available was to use an iron core of a transformer. to determine the optimum layout of the magnets, the direction of the current vectors (e) must be identical. as the direction of movement of the structure was definite (v), according to the right-hand rule the direction of the magnetic induction vectors (b) must point to the center as shown in fig. 3. figure 2: the assembled system figure 3: optimum layout of the magnets figure 4: schematic structure of the loop test 3. structure of the loop test the equipment for the loop test was provided by the institute of mechatronics engineering and research of the university of pannonia in zalaegerszeg. the schematic structure of the loop test is shown in fig. 4. energy harvesting was executed by a type of labworks et-139 electrodynamic shaker. the induced voltage was displayed by an agilent dso5054a digital oscilloscope. the examined parameters were changed by a function generator, which was connected to a labworks pa-138 amplifier on a vibration table as illustrated in fig. 5. 4. results and analysis 4.1 based on experiments throughout the experiments, the following attributes were examined: figure 5: the set-up of the loop test hungarian journal of industry and chemistry optimizing electromagnetic energy harvesting equipment 83 figure 6: energy-harvesting circuit diagram • maximum induced voltage without load • power without load • load on the power • the impact of the number of coils on the induced voltage and power the examined energy-harvesting circuit diagram is shown in fig. 6. the structure consists of an internal resistance rb and an external resistance rt (load). ptotal = u2 ind rtotal = u2 ind rb + rt (1) um = uind rt rt + rb (2) as a result of the impulsive frequency and amplitude of impulses, electrical energy was induced. the induced voltage was equal to the measured voltage in the absence of external resistance. measured and induced voltages differed when the system was subjected to an external resistance. the relationship between them is described in eq. 2. the maximum power can be determined from eq. 1. 4.2 results initially, the device was tested with 100 turns of the coil. the internal resistance of the coil was 3.1 ω. the impulsive frequency was set between 1 and 20 hz and the amplitude of impulses between 2.5 and 15 mm. during figure 7: induced voltage by applying 100 turns of the coil in the absence of external resistance figure 8: induced voltage by applying 100 turns of the coil in the presence of an external resistance the experiment, a decrease in the induced voltage was observed above 20 hz. thus, the investigated bandwidth was maximized at 20 hz, whereas the trend was still visible in terms of the change in the curves, so 20 measurement points were examined during the experiments. the results are summarized in fig. 7. the maximum induced voltage and power were 986 mv and 322 mw, respectively. during the experiments below, an internal resistance equal to the external resistance was applied to the structure. the applied external resistance was 3.4 ω. the results are summarized in fig. 8. the maximum voltage measured was 520 mv. given the values of the external and internal resistances, the induced voltage was 994 mv based on eq. 2. the maximum power was calculated to be 152 mw from eq. 1. the impact of the external resistance on the power during the experiment, a constant excitation amplitude of 15 mm was applied, while the impact of the resistance on the power was examined. the resistances applied were 1, 3.4, 10, 22, 47 and 74 ω. the relationship between the changes in resistance and power are summarized in fig. 9. as is shown in fig. 9, an exponential decrease in power was observed as the resistance increased. based on previous studies, an external resistance that is smaller figure 9: the relationship between the resistance and power 48(1) pp. 81–85 (2020) 84 móricz and szalai figure 10: induced voltage by applying 240 turns of the coil in the absence of an external resistance than the internal resistance is impractical. ideally, the external resistance would be equal to the internal resistance of the coil. next, the number of turns of the coil was increased from 100 to 240. the other aforementioned variables remained unchanged. the results are summarized in fig. 10. as shown in fig. 11, the maximum induced voltage without a load and the maximum power were 2020 mv and 559 mw, respectively. following the aforementioned procedures, the loaded system was analyzed. the external resistance applied was 8 ω. the maximum voltage measured was 1060 mv. by taking into account the values of the external and internal resistances, the induced voltage was 2020 mv based on eq. 2. based on eq. 1, the maximum power calculated was 268 mw. both the induced voltage and power of the system were doubled by increasing the number of turns of the coil by 60 %, the induced voltage increased from 994 mv to 2020 mv and the maximum power rose from 152 mw to 268 mw to be exact. 5. discussion the aim of the research was based on the principles of linear generator construction and manufacturing. at this stage of the process, it was important that the structure was free of mechanical damping. during the experiment, the structure was examined by means of changing the load resistance and number of turns of the coil in addition to the specified amplitude and frequency. an exponential decrease in the efficiency was observed as the resistance increased. ideally, the external resistance would be equal to the internal resistance of the coil. the induced voltage and the power of the system were doubled by increasing the number of turns of the coil by 60 %. as a result, by increasing the number of turns of the coil by 60 %, the efficiency of the system also increased by approximately 57 %. however, a deeper understanding of the relationship between the efficiency of the structure and variables figure 11: induced voltage by applying 240 turns of the coil in the presence of an external resistance requires further investigation. after doubling the number of turns of the coil, the maximum power generated was 1 w. one advantage of this system in particular is that the neodymium magnets are cheap to produce. applying a series connection to this system results in a sufficient degree of efficiency to operate the electronic devices in cars. 6. conclusion in the aforementioned experiments, the maximum induced voltage and power achieved by applying 240 turns of the coil were 2020 mv and 559 mw, respectively. during the experiments in the presence of a load resistance, the best value of the power was calculated when the external resistance was equal to the internal resistance of the coil. the efficiency of this energy harvesting system can be further enhanced by increasing the number of turns of the coil and the strength of the neodymium magnet. symbols uind induced voltage um measured voltage ptotal power rb internal resistance rt external resistance acknowledgements the project was supported by the european union and co-financed by the european social fund through the project efop-3.6.2-16-2017-00002. references [1] elmes, j.; gaydarzhiev, v.; mensah, a.; rustom, k.; shen, j.; batarseh, i.: maximum energy harvesting control for oscillating energy harvesting systems, 2007 ieee power electronics specialists conference, 2007 doi: 10.1109/pesc.2007.4342461 hungarian journal of industry and chemistry https://doi.org/10.1109/pesc.2007.4342461 optimizing electromagnetic energy harvesting equipment 85 [2] von büren, t.; tröster, g.: design and optimization of a linear vibration-driven electromagnetic micropower generator, sensor actuat. a-phys., 2007, 135(2), 765–775 doi: 10.1016/j.sna.2006.08.009 [3] beeby, s.p.; torah, r.n.; tudor, m.j.; glynnejones, p.; o’donnell, t.; saha, c.r.; roy, s.: micro electromagnetic generator for vibration energy harvesting, j. micromech. microeng., 2007, 117(7), 1257–1265 doi: 10.1088/0960-1317/17/7/007 [4] mitcheson, p.d.; green, t.c.: maximum effectiveness of electrostatic energy harvesters when coupled to interface circuits, ieee t. circuits-i, 2012,59(12), 3098–3111 doi: 10.1109/tcsi.2012.2206432 [5] kiziroglou, m.e.; he, c.; yeatman, e.m.: electrostatic energy harvester with external proof mass, proceedings of powermems, 2007, 117–120 [6] marzencki, m.; basrour, s.; charlot, b.; spirkovich, s.; clin, m.: amems piezoelectric vibration energy harvesting device, proceedings of powermems, 2005, 45–48 [7] isarakorn, d.; briand, d.; janphuang, p.; sambri, a.; gariglio, s.; tricone, j. m.; guy, f.; reiner, j. w.; ahn, c.h.; de rooij, n. f.: energy harvesting mems device based on an epitaxial pzt thin film: fabrication and characterization, technical digest of powermems, 2010, 203–206 [8] niu, p.; chapman, p.: design and performance of linear biomechanical energy conversion devices, (power electronics specialists conference, 2006. pesc ’06. 37th ieee), 2006, 1–6 doi: 10.1109/pesc.2006.1711996 [9] haroun, a.; yamada,i.; warisawa, s.: study of electromagnetic vibration energy harvesting with free/impact motion for low frequency operation, j. sound vib., 2015, 349, 389–402 doi: 10.1016/j.jsv.2015.03.048 [10] móricz, l.; szalai, i.: mágneses lebegtetés elvén működő vibrációs energiaátalakító tervezése és építése, (ogét 2019 xxvii. nemzetközi gépészeti konferencia, nagyvárad, románia), 2019, 352–355 [11] ashraf, k.; md khir, m.h.; dennis, j.o.; baharudin, z.: improved energy harvesting from low frequency vibrations by resonance amplification at multiple frequencies, sensor actuat. a-phys., 2013, 195, 123–132 doi: 10.1016/j.sna.2013.03.026 48(1) pp. 81–85 (2020) https://doi.org/10.1016/j.sna.2006.08.009 https://doi.org/10.1088/0960-1317/17/7/007 https://doi.org/10.1109/tcsi.2012.2206432 https://doi.org/10.1109/pesc.2006.1711996 https://doi.org/10.1109/pesc.2006.1711996 https://doi.org/10.1016/j.jsv.2015.03.048 https://doi.org/10.1016/j.jsv.2015.03.048 https://doi.org/10.1016/j.sna.2013.03.026 introduction design process and evolution of the structure structure of the loop test results and analysis based on experiments results discussion conclusion hungarian journal of industry and chemistry vol. 49(1) pp. 83–88 (2021) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2021-11 influence of mineral composition in natural granite rocks on microhardness eszter kelemen-cserta*1 and istván gábor gyurika1 1research centre for engineering sciences, university of pannonia, egyetem u. 10, 8200 veszprém, hungary granites are becoming increasingly popular and, as a result, their areas of use are expanding. in addition to their colour and particle size, the surface roughness of the machined material is becoming an important aspect of their application. in order to create a suitable surface roughness, the type of rocks located on the surface, elemental composition and microhardness of the minerals are important, because knowledge of these characteristics can be used to determine the machining parameters. microhardness is affected by the atomic percentage values of si, al and na. in addition, for some minerals, a correlation can also be established between the si, al and na components. keywords: natural rocks, granite, microhardness, surface roughness 1. introduction granites are one of the most commonly used natural rocks due to their beautiful appearance and the fact that many variations in their colour can be found. their appearance is special since the grains of the constituent minerals found in granite are nicely outlined and clearly visible with the naked eye, therefore, are also preferred architecturally. zhao et al. [1] studied the effect of weathering on samples of granite. for this purpose, the samples were soaked in different concentrations of na2so4 and mgso4 before the wetting–drying cycles. it was found that the increase in wetting–drying cycles greatly influences the physical parameters, namely weight, colour, surface roughness and hardness. in addition, the effect of na2so4 on the specimens was greater than that of mgso4 and the higher salt concentration accelerated weathering of the rock. although the spectacular grain structure of granite is advantageous in terms of appearance, it is disadvantageous in terms of machinability. the particles are composed of different minerals that result in a heterogeneous structure. this heterogeneous property makes machining difficult. ramnath et al. [2] have developed epoxy granite composites (egcs) as a novel alternative material, which exhibit several positive properties, e.g., are stable and lighter, but due to their heterogeneous structure, machining was critical. according to experiments, it was shown that 600 rpm is the optimal spindle speed and 0.09 m/min is the optimal feed rate for machining this material. this *correspondence: kelemen.cserta.eszter@mk.uni-pannon.hu value can even be used for natural granite rocks. in collaboration with us, many researchers have studied the formation, change and effect of surface roughness. sanmartín et al. [3] studied the effect of surface treatment on roughness, surface gloss and colour. it was found that the colour of granite affects the gloss of the surface differently for smooth and rough surfaces. the change in luminosity also depends on the mineral composition of the rock. shen et al. [4] studied concrete and granite by investigating the relationship between surface roughness and hydrophilicity. in their experiments, it was observed that the bonding strength always increases with the joint roughness coefficient (jrc). furthermore, the relationship between surface roughness and hydrophilicity was determined as well as the importance of knowing the effect of surface adhesion and surface characteristics evaluated. aydin et al. [5] machined the surface of granite rocks with diamond saw blades and examined their surface roughness. they concluded that instead of mechanical properties, mineral properties affect surface roughness. among the mineralogical properties, the particle size was chosen as the primary aspect of surface roughness. others have studied the hardness of granite from different perspectives. prikryl [6] cut thin sections of the rock samples in which the size, distribution, shape, orientation and mineral composition of the grains were analysed. it was found that as the particle size of minerals decreases, their strength increases. rajpurohit et al. [7] investigated a statistical relationship between the cerchar hardness index and this diahttps://doi.org/10.33927/hjic-2021-11 mailto:kelemen.cserta.eszter@mk.uni-pannon.hu 84 kelemen-cserta and gyurika mond tool. it was concluded that the hardness of the rock greatly influences the wear of the tool. a similar result was obtained by delgado et al. [8] who studied the sawability of granite as well as determined that its hardness strongly influences the sawability and wear of diamond tools. the vickers hardness of minerals was measured experimentally and it was determined that a small increase in hardness leads to a large decrease in the sawing speed. a similar result was obtained by dong et al. [9] who developed an innovative method for sawing hard rocks and demonstrated that the sawing force correlates with the properties of the rock. a similar experiment was performed by yilmaz [10], who examined the wear of diamond tools as a function of the hardness of the minerals that granite is composed of. the rock hardness index of the specimens was used to determine the hardness according to the percentage occurrence of the constituent minerals. the results showed that the rock hardness index correlated with the sawblade wear rate (swr) of the tool. even though previous studies have attributed the percentage occurrence of quartz to the main reason for sawblade wear, yilmaz’s results showed that other minerals also influence tool wear. in another study, where yilmaz et al. [11] conducted experiments on natural granite, they found that the maximum particle size of quartz, orthoclase and microcline had the greatest effect on swr. li et al. [12] studied how the mineral content of rock affects its properties. for this purpose, the mineral content, particle size, abrasion resistance and hardness of 96 samples from 10 provinces in china were measured. the test results showed that the wear and hardness of the rock can be accurately determined based on the type of rock, mineral content and particle size. diamond is extremely hard, tough and thermally conductive, making it an excellent material for the purpose of cutting rocks. the abrasion resistance of rocks varies, so it is important to provide the right metal matrix in which the diamond grains can be placed. during the experiment, 2 materials were investigated, that is, the coand febased metal matrices. the results showed that the cobased metal matrix is suitable for cutting granites, while the fe-based one is suitable for cutting marbles [13]. this theory is also supported according to a study by gupta and pratap [14]. they also studied the metal matrix of the tool and found that the metal matrix composite (mmc) influences the efficiency and service life of the tool. yan et al. [15] also searched for a way of modifying the machining tool to ensure granite surfaces are properly machined. an ultrahard polycrystalline diamond (uhpcd) tool was compared to a polycrystalline diamond (pcd) one. the hardness of uhpcd was 105-115 gpa, while that of pcd was 53-57 gpa. the results showed that the lifetime of uhpcd bits was 132.33 m and that of pcd ones was 83.76 m. using a hammer, adebayo and okewale [16] determined the rebound values of the specimens as a function of hardness as well as the mineral compositions of the samples. it was concluded that the sample with the highest quartz content resulted in the highest vickers hardness number. a document published by the university of kiel [17] contains a table presenting the vickers hardness number of several materials, in which the vickers hardness number of granite is hvgranite = 850 and that of quartz is hvquartz = 1200. yusupov and co-researchers [18] studied the hardness of minerals in terms of grindability. it was concluded that the presence of quartz increases the grinding time by 1.52 times. to optimize the process and reduce the amount of energy required, they proposed a method in which the minerals are machined separately. xie and tamaki [19] investigated the effect of the micro-hardness distribution in granite on the efficiency of abrasive machining. in their research, it was determined that the efficiency of abrasive machining increases as the microhardness of granite decreases. from the literature, it is also clear that researchers have considered the types of minerals when studying natural rocks. in contrast, in the present paper, the mineral constituents are examined to observe how these affect the hardness of specimens and thus their machinability. our goal is to draw up a prediction system based on complex analysis to facilitate the specification of the parameters required for surface machining. alternatively, the parameters can be modified according to the types of minerals present on the surface or the quality of the surface to be created. 2. materials and methods the granites used in the experiments differ in terms of colour (pink, yellowish, orange, greyish, black and white), grain size (fine, medium and coarse) and composition. 4 of the 5 samples come from brazil and 1 from the hungarian mine in süttő. during the experiment, an experimental process was developed to investigate the composition, formation and hardness of the rock. it was determined that although all granite samples contained the minerals quartz, feldspar and biotite, the difference was in the type of feldspar minerals. 2.1 rock working the surface of the slabs composed of natural rock was machined by a cnc machine manufactured in italy (fig. 1). the used equipment was an italian prussiani golden plus-type cnc machine with a maximum power consumption of 15 kw. the machining cutting depth was 1 mm, the cutting width was 40 mm and the feed speed was 0.1 mm/tooth. the cutting speed used during machining was 37.7 m/min. the machining tool in the cnc machine consisted of 22 segments and the face mill was 100 mm in diameter. although the elemental composition of the face-mill matrix is not specified by the manufacturers, hungarian journal of industry and chemistry influence of mineral composition in natural granite rocks on microhardness 85 figure 1: the cnc equipment and various tools figure 2: one of the granite samples (orange) scanning electron microscopy (sem) of the tool showed that co, cu, sn and ag were also present. 2.2 hardness measurements samples with approximate dimensions of 5 mm × 5 mm (fig. 2) were cut from the machined rock slabs to ensure that they could be easily placed on the tables of various measuring devices. the minerals were separated based on their appearance. biotite, which could be identified by its characteristic dark/black colour, was the first to be examined, followed by feldspar and quartz. in the case of the latter two, even though it was more difficult to distinguish them from each other, in the following examination of mineral composition, it was possible to make an accurate distinction between them. the hardness of minerals is usually given according to the mohs scale. this does not provide an exact value, rather only reflects the relative hardness of the different minerals. secondly, it is worth mentioning the methods used to measure the hardness of metals, which despite yielding accurate values, are greatly influenced by different compositions of minerals. table 1: parameters of the wolpert group hardness tester eyepiece magnification 10× resolution 0.1 µm objective magnification factor 10×, 20×, 40×, 50×, 60× total magnification 400× (for measurements) 100× (for observations) measuring range 200 µm hardness value 5-digit maximum specimen height 85 mm xy stage dimensions 100× 100 mm operating temperature range: 10 to 38 ◦c (50 to 100 °f) figure 3: imprint of the 136° square-based diamond pyramid measurements were performed on a wolpert w group micro vickers digital auto turret 402mvd-type hardness tester, the parameters of which are shown in table 1. when measurements were taken, a specimen was placed on the measuring table and then the 136° squarebased diamond pyramid for measuring the vickers hardness was placed over the relevant mineral. after starting to take the measurements, the pyramid was pressed into the surface of the mineral where it left an imprint (fig. 3). the peaks of the imprint were marked using a microscope, before the machine evaluated the results. 2.3 sem the chemical composition can be determined by scanning electron microscopy (sem). a thermo fischer scientific aprea sem, fei/philips xl-30 esem were used to examine the elemental composition of the sample’s surface in a low vacuum at a resolution of 20å. during the evaluation, the equipment took a photo of the surface before evaluating the compositions of the selected areas. given that the results were given in percentage composition, the types of constituent minerals present could be deduced (fig. 4). 49(1) pp. 83–88 (2021) 86 kelemen-cserta and gyurika figure 4: elemental composition of biotite figure 5: effect of mg, al, si and k constituents on vickers hardness 3. results during this study, the minerals biotite, feldspar and quartz were examined on the surfaces of 5 different specimens. firstly, biotite was placed under the diamond pyramid of the hardness tester. it is known that the content of sio2 and grain size greatly influence the hardness as well as machinability of the specimens. however, it has not yet been studied whether and how the atomic percentage composition of the particles affects the hardness. given that the hardness of granites is related to their quartz content, it was examined whether the hardness varies as a function of the si content. our measurements showed no correlation between the values. for biotite, no correlation was found between si content and vickers hardness. additional measurements also showed that the atomic percentage composition of biotite did not correlate with the vickers hardness (hv). during the evaluation, the constituent elements (mg, al, k) were examined separately, but no correlation (r2 mg = 0.315, r2 al = 0.028, r2 si = 0.3689, r2 k = 0.6127 where r2 denotes the coefficient of determination) was found between changes in any of these constituents and hardness. it is also clear from the diagram (fig. 5) that the individual constituents do not affect the vickers hardness. the next group of minerals studied were feldspars. after evaluating the measurements, several correlations were observed. given that as the si content increases, the total content of na and al decreases (fig. 6), it can be stated that a decrease in the si content leads to an increase figure 6: the correlation between na+al and si contents figure 7: the correlation between hv and na+al content in the na+al content in the case of feldspars (r2 al+na = 0.8445). it also greatly affects the vickers hardness. the change in vickers hardness is inversely proportional to an increase in na+al content (fig. 7). as the na+al content in the mineral increases, the vickers hardness decreases (r2 hv = 0.9551). the results of our measurements are illustrated in the diagram fig. 7. in the case of the mineral quartz, the results do not exhibit such a correlation r2 hv = 0.2646). in uncontaminated quartz, where no impurities (c, k, ca, fe) were detected, large variations in hardness were observed (fig. 8), presumably due to the crystallization of quartz. for minerals where other constituents are present in addition to quartz, neither were clear correlations between the changes in vickers hardness and elemental composition observed. given the results, changes in the constituents of quartz do not affect the vickers hardness. figure 8: the correlation between hv and si content hungarian journal of industry and chemistry influence of mineral composition in natural granite rocks on microhardness 87 4. conclusions an important aspect when machining natural rocks is the hardness of the minerals they are composed of, because the hardness of the rock surface greatly influences machinability. based on preliminary measurements, the surface composition of feldspars was examined in order to predict their hardness. with the knowledge obtained during the present study, the parameters of the processing equipment can be adjusted according to the mineral composition on the given surface. in the case of the minerals biotite and quartz, clear values for machining could not be provided, since increasing the si content of either mineral has no effect on the vickers hardness. our results suggest that na+al constituents do not affect either the change in hardness or the si content. in the case of feldspars, on the other hand, it was observed that both the hardness and si content are inversely proportional to the na+al content. as granites constitute several types 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https://doi.org/10.1007/s10913-007-0046-y https://doi.org/10.1016/j.jmatprotec.2006.12.041 https://doi.org/10.1016/j.jmatprotec.2006.12.041 introduction materials and methods rock working hardness measurements sem results conclusions hungarian journal of industrial chemistry veszprem vol. 29. pp. 39-43 (2001) drying process and resolution of alkali silicate powders m. hasznos·nezdei wj.d e. p allai-v arsanyi (university of kaposvar, research institute of chemical and process engineering, veszprem, egyetem u. 2., p.o.box 125, veszpremh-8201 (hungary) received: february 1, 2001 methods and conditions of dehydration of sodium silicate solutions were investigated in mechanically circulated spouted bed dryer with inert packing. the used commercial silicate solutions were set to a definite mole ratio. the qualification of the powderlike dried products was done using different analytical methods and also the resolution properties were determined. keywords: inert particles, msb-dryer, silicate ratio, thermal treatment, water-glass. introduction alkali silicate solutions are used for many purposes, as basic materials or·. auxiliary products. taking into account the volume of their industrial applications, sodium silicates are more important as potassium silicate solutions. for special use other soluble silicates (e.g. lithium silicate, etc.). are also produced. the use of sodium silicate solutions (water-glass) is important in the manufacture of detergents and cleaning agents utilizing their favourable colloidal and dirt binding properties as well as their corrosion reducing effect. sodium water-glass solutions are processed also in the rubber and dye industries, that is in the production of ingredients and extenders (precipitated silicic acids and silicates), furthermore in manufacturing of synthetic zeolites having catalytic and ion-exchange characteristics. moreover, sodium silicate solutions are used in the formation process of foundry moulds and of acidand heat resistant putties, in the flotation process, as well as to accelerate the setting process of cements [l-3j. potassium water-glass solutions are mostly used for the coating of welding electrodes, in the production of video tubes as binders, furthermore in silicate base paints employed for handling of external plasters. in certain special cases water-glass powders are used instead of water-glass solutiotls. the powderlike products are made by different drying processes from the appropriate solutions [4-7]. the moisture content of the obtained dried product is generally of 15-25% depending on the siozfalkali oxide ratio and on the applied drying conditions. on effect of heating the dried powderlike product dissolves in water, and the obtained solution keeping likewise its colloidal properties can be used advantageously. the composition of alkali silicate solutions, that is these special colloidal systems are in general not strictly stoichiometric [1-3]. the characteristic si02falkali oxide mole or mass ratio, the amount of the dissolved material vary. between definite limits depending on the composition of the solid water-glass basic material and on the method of the dissolution process as well. the water-glass solutions are produced from commercial solid water-glasses by hydrothermal method. the characteristics of the commercial (henkel) solid water-glasses are shown in table 1. table 1. characteristics of solid commercial water­ glasses [2] type sioz/alkali oxide mole ratio l. mass ratio sodium water-glass sio;/nazo high silicic acid 3,9-4,1 4,0-4,2 content neutral 3,3-3,5 3,4-3,6 alkaline 2,0-2,2 2,1-2,3 potassium water-glass sio;ik20 3,3-3,5 l 4,1-4,3 2.6-2,7 40 experimental in our experimental work both commercial and silicate solutions were applied where the module was set to a definite value by industrial processes. our aim was to investigate the possible methods and conditions of dehydration of alkali silicate solutions in mechanically circulated spouted bed dryer with inert packing and to qualify the obtained hydrated powderlike dried products. for this reason different analytical methods were used and also the resolution properties were determined. the most important characteristics of the used sodium silicate solutions are summarized in table 2. in fig. l the na20-si02-h20 ternary diagram is represented with the phase areas of the water-glass solution and of the hydrated powderlike dried water­ glass product at temperatures under 100°c. the compositions related to a and b solid (anhydrous) water­ glasses, furthermore the composition of the crystalline anhydrous sodiummetasilicate na2si02 (na20.sioz) are given too. detailed presentation of further phase areas can be found in the monograph of vail [3]. by the areas indicated in the ternary diagram it is demonstrated that the phase areas of sodium silicate solutions are localised by the si02/na20 ratio. the water content of the solutions is different (45-70%) depending on the conditions of their production. the hydrated water-glass powders of given moisture content are produced by different drying processes. the dried products are dissolved in water to different degrees depending on the final moisture content and on the sio-;/ na20 module value. the less is the moisture content, the less is the resolution ability. the compositions a and b correspond to the state of total dehydration. experiments to investigate dehydration conditions of water-glass solutions were performed in a mechanically circulated spouted bed dryer (msb-dryer) with inert packing of big laboratory scale (fig. 2. ). intensive, well controlled heat and mass transfer can be carried out in the msb-dryer which is developed to improve the operation conditions of the traditional spouted beds. the characteristic particle circulation is provided in this new-type dryer by a houseless screw conveyor that works in the vertical axis of the bed. the hot air entering the bottom of the dryer through slots at high velocity in tangential direction causes intensive gas-solid contact. the spouted bed of circulating inert particles consists of three zones which are separate and differ significantly in their flow characteristics, that is: the zone characterised by turbulent particle and gas flow, enables intensive gas-solid contact in the vicinity of the gas inlet; the zone of particles transported vertically upward by the screw-conveyor is concurrent to the drying air flow; the dense annular part sliding downward is countercurrent to the air flow. for drying materials of high moisture content inert particles can be applied advantageously. na20 a b si02 fig. 1. ternary systemna20-si02-h20 aalkaline character, b -solid water-glass of high silicic acid content fig. 2. msb-dryer with inert particles 1 -drying column; 2inert particles; 3 housless srew; 4 air heater; 5 electric valve; 6 bag filter; 7 pump; 8 fan; 9 aid converter and pc table 2. characteristics of the sodium silicate solutions applied in the drying experiments mark of concentration of solution. w% sioz/nazo density** viscosity* * samples nazo si02 :esolid mass ratio glcm3 mpa.s swg-1* 14,18 28,94 43,12 2,04 1,542 351,0 swg-3* 11,22 26,35 37,57 2,35 1,456 104,9 swg-2* 8,34 25,57 33,91 3,06 1,370 87,8 * · water·€1ass solutions of different t;-pes, ** the values of density and of viscosity are related to 25°c. the principle of drying on inert particles is that pastes, pulps or suspensions of high moisture content are fed into the bed of inert particles (plastic, ceramic, glass, etc. spheres) circulated by the inner conveyor screw. in this way, an almost uniform, film-like coating is formed on the surface of the particles. the thickness is in optimum case 2 ... 4 times higher (d = 20 . ..40mm) than that of the primary particle size of the material to be dried. since the inert particles have a large specific surface, the wet solid dries in a short time even at relatively low bulb temperature. due to the intensive friction inside the screw conveyor, the dried coating wears off the particles and the fine dried product is carried out by the air stream leaving the dryer. from the point of view of drying, the following partial processes are of basic importance: formation of coating (in the annular part of sliding down inert particles); drying of coating (in the inlet air area, that is in the conical bottom part of the dryer, in a bed height of a few (6 ... 8) centimetres; wearing of coating (in the rotation area of the conveyor screw transporting the inert particles upward in the dryer). there is no significant particle mixing between the zone of the sliding down annular layer and that of the vertical particle transport. due to the ,mechanical particle circulation", the characteristic spouted bed movement is independent of the air flow rate thus, the latter can be set to an optimum from the point of view of drying. taking into account the advantages of this well controllable drying system, the water-glass solutions were dehydrated in msb-dryer with inert packing. the drying parameters are summarized in table 3. results and discussion according to the results of x-ray diffraction measurements the dried water-glass powders are of amorphous structure. this could be attributed first of all to the fact that the ratio of the solid components (sioz and na20) of water-glass solutions are not stoichiometric. dehydration of water-glass solutions dehydration of water-glass solutions is a rather complex process deriving from its colloidal nature. the 41 solid material content corresponding to the composition of the water-glass colloidal system is present in sol-form in the very alkaline dispersion medium. the sol particles consist of polysilicate anions which are built of si04-4 tetrahedrons. the polysilicate anions are connected to one another by h-bridge bonds. one part of the na-ions is inside the sol particles, another part is outside the associated polysilicate anions which are in the solutions. the water-glass solution itself is a colloidal system of metastable state. the kinetic changes that happen in this colloidal system point to the direction of gelation. the dimension (molar mass) of the poiysilicate anions depends considerably on the module of the water-glass solution and on the type of cations being in the solution. the molar mass values of polysilicate particles being in water-glass solutions of different modulus were published by nauman and debye [8]. they were determined by light diffraction measurements and vary between 90-500 in sodium water-glass solutions and between 1150-1538 in potassium silicate solutions. the mole mass values measured in potassium water-glass solutions are considerably larger than of those measured in sodium water-glass solution. at drying in spouted bed dryer with inert packing the water-glass solution fed into the dryer forms a filmlike layer (coating) on the surface of inert particles (ceramic spheres). the dehydration process proceeds in this coating in several steps. at first the water content leaves from the disperse phase and as a consequence of the moisture content decrease, the coating becomes gelatinous. as a result of the intensive heat transfer existing in the drying zone, further dehydration occurs, the continuous gel-structure breaks up and in the thin water-glass coating small dehydrated gel-fragments appear. on effect of the hot air flowing through the circulating inert bed the dehydration process continues until the moisture content achieves the required value necessary to wear off the inert particle surface, or until attainment of a final moisture content required from other technological point of view. the final moisture content can be adjusted by the temperature and velocity of the drying air, furthermore by setting the appropriate particle circulation velocity and by the feeding rate that determines the residence time of the water-glass coating. table 3. drying of water-glass solutions. process parameters. volumetric flow rate temperature of temperature of water~glass samples of drying air (20°c) inlet air outlet air feeding rate m3/h oc oc glmin swg-1 65,0 155 120 10,5 swg-3 70,0 145 105 21,7 swg-2 70,0 150 110 19.4 fuert packingceramic particles with diameter of 7mm. 42 table 4. characteristics of hydrated water-glass powders dried in msb-dryer with inert packing sample n p particle fractions by screening thermal dehydration % code m.r.** kg/dm3 swg-ld* 1,98 0,874 swg-3d* 2,28 0,880 swg-2d* 2,96 0,898 * dried water-glass products, ** m.r. mole ratio. <loo!lijl 100-250j.lm 74,2 19,5 59,1 30,7 63,5 29,0 fig. 3. shows the scanning electron microscopic picture of a dried water-glass sample. it can be seen that the particle size distribution is unequal, the product consists of fragmentary, broken particles of irregular shape. the particle size distribution was determined by vibration screening in a dry state. 60-70% of the particles are smaller than loomm, the bulk density is rather high (0.87-0.90kg/dm3) and do not depend on the si02/na20 module of the initial solution. the final moisture content of the dried hydrated product (18.8%27.3%) changes with the composition of the water-glass solution and with the drying conditions (see table 4.). fig. 3. sem picture of the hydrated water-glass powder dried in msb-dryer with inert packing the powderlike dried water-glass samples were tested by thermoanalytical method to examine the bonding characteristics of the water molecules remaining in the dried products. experimental data were obtained on the basis of dehydration processes carried ont after the spouted bed drying process are summarized in table 4. it can be seen that the fmai moisture content of the dried, alkaline products (sample code: swg-1 and swg-3) is rather high {24.3% and 27.3%). on effect of further beat -treatment the greatest part of the moisture content is removed at temperatures below 400"c. the water part that could be removed during the thermal dehydration at temperatures below 200"c does not appear in the thermal-analytical pictures. the small water content that remains still at 400"c in the water­ glass powders could be removed between 600-700"c indicating its stronger bonding in the water-glass structure. the swg-2d samples is less alkaline water-glass product. at the thermo-analytical measurements it can be proved that the moisture removal proceeds in three >250j.lm :lh20 <200°c l200-400oc 600-700°c i 6,3 24,3 23,7 0,6 10,2 27,3 26,4 0,9 7,5 18,8 11,o i 5,5 2,3 phases. below 200°c about 60% of the final moisture content departs, 30% between 200-400°c, and the rest water content similarly to the alkaline samples (swg­ ld and swg-3d)is removed between 600-700°c. on the basis of differential thermal analytical measurements the dehydration process of hydrated water-glass powders proceeds similarly to that of insoluble silicates, such as e.g. precipitated silicic acid [9]. this similarity is getting more end more expressed with the increase of the silicate module. during the differential thermal analytical measurements the water-glass samples of low module values show a characteristic increase in their volume. namely, the diffusion of the water content remaining after drying is hindered by the dried gelatinous structure. on effect of the heating process vapor is originated that tightening (increasing) the structure leaves the water-glass product. this effect appears at the swg-1 sample to the greatest extent, while the increase in volume at sample swg-3 is already less, and it is scarcely observable at the swg-2 samples. products of a structure being increased on effect of heat treatment can be used as isolators. application of such sodium water-glass powders is patented [10]. resolution of amorphous sodium water-glass powders hydrated water-glass powders of amorphous structure are produced by different drying processes. the obtained powderlike products dissolve in different degree depending on the water content and on its module value. by this special property 'it becomes possible to utilise the favourable characteristics of water-glass solutions by employing a drying method even in such cases when the direct use of water-glass solutions meets with difficulties. before the use of powderlike water-glass products it is necessary to investigate both the conditions and the degree of resolution. by setting the best drying parameters it is possible to control the final moisture content of the dried product. it can be seen in table 5. that by the increase of the final moisture content increases the degree of resolution. the solubility of the hydrated amorphous products dried in msb-dryer with inert packing was investigated in distilled water depending on the temperature and on the duration of the dissolution process. at resolution solutions of 20-25% solid content were prepared, that is from the investigated samples 40-sog amounts were dissolved in 150-ioog hot water by mixing under constant temperature and the degree of the solubility was determined. 43 table 5. resolution of the hydrated amorphous water-glass powders samples degree of concentration of the solution sioz/na20 density viscosity resol.**% na20 si02 swg-lr* 98,6 7,65 14,69 swg-3r* 89,3 5,15 11,78 swg-2r* 83,4 3,93 12,30 * solution obtamed by resolution of the dried water -glass powders ** time of dissolution in hot water was one hour. at the end of the measurements the obtained solutions were filtered by a filter-paper of type mn 640w and the amount of the dissolved material, as well as the density and dynamical viscosity were determined from the filtered solution. the sample swg-ld dissolved in hot water quickly and the degree of resolution decreases by the increase of the silicate module. the considerable resolution ability of the hydrated amorphous water-glass powders indicates that during the drying process of water-glass solutions of low module values (2.0-2.5) does not occur, or only in a small measure irreversible changes in the course of the sol-gel transformation. the decrease of the resolution degree of the hydrated powderlike amorphous sample swg-2r relates to the fact that during the drying process of the water-glass solution on effect of the high drying temperature and the not very much alkaline surrounding partial dehydration of polysilicate anions and also its association take place. that means that a part of the sol particles is transformed into insoluble polysilicate anions of silicic acid. these latter anions already do not redissolve. increasing the drying temperature, the final moisture content of the powderlike product obtained by drying of the water­ glass solution of samplecode swg-2r decreases quickly, while the proportion of the fraction that can not be resoluted increases in parallel. the results of experiments carried out in order to dry water-glass solutions proved that the hydrated amorphous water-glass powders produced under suitable chosen drying conditions, are of considerable resolution ability. this is due to their successful use in more special fields, e.g. as additives (water softener, dirt binding component) in solid detergent compositions. conclusions water-glass ·solutions of different modulus values were dried in a so-called ,,mechanically spouted bed" -dryer (msb-dryer) with inert particles. in this way, hydrated amorphous powderlike products were obtained with a final moisture content depending on the composition of the solutions and on the drying conditions. to examine the dehydrated powderlike products thermoanalysis were applied. it was found that the dehydration process of alkaline water-glass powders differs from that of water-glass powders of less alkaline character. :£solid mass% g/crrf mpa.s 22,34' 1,92 1,215 3,3 16,93 2,29 1,158 2,1 16,23 3,13 1,146 2,0 the investigated hydrated water-glass powders dissolve well in hot water. the degree of resolution depends on the silicate-modulus. acknowledgement the financial support from national scientific research fund (otka t 019719) is gratefully acknowledged. references 1. heinertii e.: alkalisilikate in ullmann's encyklopadie der technischen chemie, 4.aufl. bd.21, weinheim, verlag chemie, pp. 409-414, 1982. 2. cbristophliemk p.: glastech. ber. 1985, 58(11), 308-314 3. vail j.g.: soluble silicates vol. i-ii., acs monograph, no. 116., reinhold publ. corp., new york, 1952. 4. u.s. pat. 3,796,777 (1974) 5. u.s. pat. 4,022,704 (1977) 6. u.s. pat. 4,157,978 (1979) 7. masters k.: spray drying handbook, wiley, new york, pp. 563-564, 1984. 8. nauman r. v. and debye p.: l phys. chern., 1951,55,1-8 9. precipitated silicas and alumino-silicates (direction de la communication), rhone-poulenc chimie, organic and inorganic intermediates sector, courbevoie, dec. 1991. 10. u.s. pat. 3,926,905 (1975) page 40 page 41 page 42 page 43 page 44 hungarian journal of industry and chemistry vol. 49(2) pp. 3–7 (2021) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2021-13 3d scanning and model error distribution-based characterisation of welding defects jános hegedűs-kuti *1,2, józsef szőlősi1, dániel varga1, gábor farkas1, tamás ruppert2, jános abonyi2, and mátyás andó1 1savaria institute of technology, eötvös loránd university, károlyi gáspár tér 4, szombathely, 9700, hungary 2complex systems monitoring research group, research centre for biochemical, environmental and chemical engineering, university of pannonia, egyetem u. 10, veszprém, 8200, hungary the inspection of welded structures requires particular attention due to many aspects that define the quality of the product. deciding on the suitability of welds is a complex process. this work aims to propose a method that can support this qualification. this paper presents a state-of-the-art data-driven evaluation method and its application in the quality assessment of welds. image processing and cad modelling software was applied to generate a reference using the iterative closest point algorithm that can be used to generate datasets which represent the model errors. the results demonstrate that the distribution of these variables characterises the typical welding defects. based on the automated analysis of these distributions, it is possible to reduce the turnaround time of testing, thereby improving the productivity of welding processes. keywords: industry 4.0, welding technology, 3d scanner, iterative closest point, defect analysis 1. introduction during the fourth industrial revolution, more modern industrial processes and tools, e.g., various testing instruments, are present in many technological fields. advanced industrial tools are used in these technological environments [1, 2]. in addition to this new economic approach, the implementation of welding with a higher degree of automation has been a technological facilitation [3], while the complexity of the system has required the involvement of new disciplines such as applied informatics. the need to achieve autonomous production also means that quality control of the welding task carried out is also a significant concern [4]. in the meantime, human workers are also utilized [5]. the issues of compliance and standards of quality have become more prominent following adoption of the quality management principle [6]. the standard includes three distinct quality categories as well as indicates acceptability by the terms “not permitted” and “permitted”. the acceptability of a welded joint is based on the visible absence of defects in the weld and the adequacy of all the types of tests described in the relevant standard test procedure [4]. the basic physical principle of the various non-contact inspection tools, *correspondence: hj@inf.elte.hu which are successfully used in many industrial applications to detect quality non-conformities, relies on image recognition and image processing research. the futureoriented results of this research have also appeared in new fields such as face recognition by comparing threedimensional objects or even in the development of image processing systems for self-driving cars [7, 8]. these applications have opened up new dimensions in the context of digitalisation, making industrial processes faster as well as easier and, therefore, more efficient [9]. advanced image processing technologies are available in materials testing laboratories, helping researchers to study changes in material structures [10]. these methodological developments support the basic idea of digitisation, as they provide alternatives to the manual analysis of the past. structured light scanners work in a similar manner to laser scanners, but the light source is a high-resolution projector that projects a raster mesh onto the surface of the object. the optics measure both the reticle distortion and intensity of the reflected light, providing a much more accurate result than variants based on lasers with a resolution of up to 10 microns. one possible solution for processing images from structured light scanners is to use the iterative closest point (icp) algorithm, which is used to create pairwise correspondences between two https://doi.org/10.33927/hjic-2021-13 mailto:hj@inf.elte.hu 4 hegedűs-kuti, szőlősi, varga, farkas, ruppert, abonyi, and andó figure 1: the steps of the proposed weld defect analysis method cloud points. the method was developed in studies from the early 1990s by besl and mckay [11] as well as yang and medioni [12]. this iterative algorithm is known in the field of matching three-dimensional shapes, a process in which the points of the source point cloud are matched to the points of the target point cloud (also known as the reference cloud). the matching is based on the root mean square error method, where originally a point-point metric was to be used, while other techniques use a pointplane metric [7]. in the following, the method is presented in section 2, where sampling, point cloud generation, the use of the fast global registration and icp algorithm as well as the root mean square error is described. finally, section 3 presents the results of the developed framework. 2. the proposed cad model–based method of the generation and analysis of error distributions the proposed framework starts by scanning with a 3d scanner before reducing the number of points in the resulting point clouds. this is followed by a coarse and then a fine fitting, which uses a histogram containing a general comparison of the points and a colour map visualization. its applicability in a specific technological field has been demonstrated. the objective is to investigate the weld geometry of selected welded samples using the available imaging tool to detect discrepancies. a point cloud is generated on the cad models and the welded seams prepared using a camera system. the technique of matching point clouds by fast global registration is presented. an iterative closest point algorithm and a histogram of point features are used to perform the refined transformation. the comparison is carried out within a python framework to solve the problem of matching the evaluation method to a neural network in topic processing. finally, the deviations resulting from the comparison are evaluated in the light of the relevant standard. the test method is illustrated in detail in fig. 1. the test starts by generating a reference point cloud, that is, a scanned point cloud of a welded workpiece (or a point cloud of a part created by cad software), which is considered to be flawless. for the purpose of defect detection, the principle is to fit the original point cloud to the point cloud to be inspected, the geometry of which is nearly identical. as a second step, cad models were created for which a single defect was modelled [13]. these defect modes were compared to the flawless cad model. the analysis aims to obtain the deviations from the point cloud comparison in terms of the specific deviations and explore their correlations. the scanning process is as follows: • when calibrating the tray, the grid is projected by the projector; • background scanning, after inserting a turntable; • positioning of the workpiece at the centre of the turntable; • start the scanning process; • create the three-dimensional model from the images; • fusion process from the image fragments can be exported in other (.stl/.obj) formats. for optimal point matching, distance-based density distribution (sampling) is required. this is important because of the selected order of magnitude (250, 000 points). the differences between the point clouds can be detected. an approximate feature-based registration, fgr (fast global registration), is first performed based on the paired points to compare the two point clouds. this corresponds to an approximate estimate, which looks for similar corners, points and parts before pairing them. although the approach used is faster than icp, it still requires a local refinement algorithm. since the performance is only flawless on a heavily sampled point cloud, a more accurate fitting procedure is also used to further refine the fitting. the icp algorithm is a refined transformation that more closely aligns the two point clouds, hungarian journal of industry and chemistry 3d scanning and characterisation of welding defects 5 which usually iterates over two steps. first, a match is searched for from the target point cloud and then the transformation is updated by minimizing the objective function defined by the correspondence set. the normal vector of a plane is the unit vector perpendicular to its plane and the normal vector is the vector perpendicular to the surface at a point on the surface. calculating the normal vector of the point of detection involves a solution method based on the surface grid and a solution method based on the distribution of points in the surrounding neighbourhood. the axis, on which the normal vector is located, is the most dispersed direction of the neighbourhood distribution. a final geometric feature is computed using the point feature histogram (pfh), which is obtained by calculating the variation ratio between all pairs of points in the neighbourhood of the points. this high-dimensional space provides useful feature representations as well as can cope with different sampling densities and noise levels of neighbours. the pfh stores these variables together with the euclidean distance between points and generates a histogram after computing all the pairs. the final descriptor is the sum of the histograms of each variable. then, after selecting a percentage value (in this case 97%), a colour scale-based (green-near; red-distant) notation is applied according to the location of the pairs of points within a pixel distance of each other. the deviation from the reference area is detected using the mean square deviation formula. the recommended setup parameters observed during the study and the results are detailed in the next section. 3. results a telwin inverpulse 320 welding machine was used to create welded samples. 8 − 8 specimens, 50 mm long with a5 welds (dimension of the height dimension of the triangle enclosing the corner weld), were t-welded. one side of the test specimens had a good weld configuration, while the other side had an unsatisfactory weld configuration. the welded samples were scanned using a hp 3d structured light scanner 5 pro edition (software version 5.2.0.790) and the resulting point clouds compared to the point cloud of the reference part. it is important to note a few details about the 3d scanning process: • environmental preparation (from the projector light, from the harsh light in the room); • system preparation (position the camera 6-8 cm to the left of the projector, adjust the camera angle to 10-12◦ from the guide rail perpendicular to the projector); • tripod adjustment up to 30◦ top view of the object. in the second step of the test series, cad models using the solid edge academic edition (version 221.00.00.00.114) were created for which a single defect was generated and compared to the flawless cad model. an algorithm running in python (version 3.7.7) and using the open3d (version 21.1.3) visualization interface was used to create a framework for the comparison. the study aims to determine the deviations from the point cloud comparison and to write correlations between them. the analysis method is similar to the first process step, but here no scanning process is required. the pfh in fig. 2 indicates whether the points can be grouped according to their distribution or identified by their location. the histogram shows the distances of the deviations. the typical distance values from the histogram data are expected to be close to the calculated deviation limits. a significant achievement in welding quality management is the application of the standard iso 5817 : 2014, which lists surface and volume deviations with the display of defect categories and codes. the standard includes limits in three quality categories or indicates acceptability by the terms not permitted and permitted. the acceptability of a welded joint is based on the visible absence of defects in the weld and the adequacy of all the types of tests described in the relevant test procedure standard. the quality assessment of a welded joint is, therefore, a complex task. as shown in fig. 2, the evaluation is defined with different marginal deviations in each of the three quality categories (b, c, d). by progressing down to bcd, the standard becomes more permissive; for example, the height of the excessive convexity can be up to 3 mm for category b, up to 4 mm for category c and up to 5 mm for category d. the summary results for each of the three root sizes are as follows: • 1. crack: no borderline deviation is allowed in any category. however, for the test, a "brick body cavity" of 0.5 mm × 0.2 mm × 0.1 mm was created in the cad model. the deviation could not be detected by the algorithm used; • 2. cavities: modelled as a 2 mm deep cone-shaped material void in category d and a 1 mm deep coneshaped material void in category c. no deviation is allowed in category b. the deviation cannot be detected even by the most sensitive adjustments; • 3. solid inclusion: 1 mm in category d, 0.5 mm in categories c and b. the algorithm detects special distributions. 4. summary an image and data analyses-based method for the qualification of welding defects was developed. the corner welded joints were studied and the quality deviations of such welded joints observed, these deviations being defects that can be detected by visual inspection. for the detection of volumetric defects, the industry has practically and consistently used x-ray and ultrasonic testing. a results-oriented approach to the cad visualisation of 49(2) pp. 3–7 (2021) 6 hegedűs-kuti, szőlősi, varga, farkas, ruppert, abonyi, and andó figure 2: exemplary distributions, cad models of welding deviations . defects has been adopted. since several defects can occur on a real welded part, it can be said that by including cad models of each deviation in the analysis, the deviations could be kept under control. even though this tool alone cannot be used to perform a comprehensive analysis of a weld, when complemented with other procedures, the steps of the welding process analysis can be accelerated. our investigations have led to the conclusion that, apart from defective joints, all the other categories of defects listed can be detected with certain limitations. the results, treated as differences between components of point clouds, can be subsequently identified and grouped. references [1] mishra, d.; pal, s.k.; chakravarty, d.: industry 4.0 in welding. welding technology, 2021, 253–298 doi: 10.1007/978-3-030-63986-0 [2] farkas, a.: impact of industry 4.0 on robotic welding, xxiii international conference on manufacturing (manufacturing 2018), iop conf. ser.: mater. sci. eng., 2018, 448, 012034 doi: 10.1088/1757-899x/448/1/012034 [3] frolov, a.: automation the welding trajectory control. 2020 international multi-conference on industrial engineering and modern technologies (fareastcon) (ieee), 1–5 doi: 10.1109/fareastcon50210.2020.9271607 [4] stavridis, j.; papacharalampopoulos, a.; stavropoulos, p.: quality assessment in laser welding: a critical review. int. j. adv. manuf. tech., 2018, 94(5), 1825–1847 doi: 10.1007/s00170-017-0461-4 [5] ruppert, t.; abonyi, j.: worker movement diagram based stochastic model of open paced conveyors. hung. j. ind. chem., 2018, 46(2), 55–62 doi: 10.1515/hjic-2018-0019 [6] lászló, s.: hegesztés és rokon technológiák. gépipari tudományos egyesület, budapest, 2007 , 191– 204 [7] zhang, z.: iterative point matching for registration of free-form curves and surfaces. int. j. comput. vis., 1994, 13(2), 119–152 doi: 10.1007/bf01427149 [8] lee, m.: an analysis of the effects of artificial intelligence on electric vehicle technology innovation using patent data. world pat. inf., 2020, 63, 102002 doi: 10.1016/j.wpi.2020.102002 [9] urminsky, j.; marônek, m.; jǎna, m.; morovič, l.: analysis of weld joint deformations by optical 3d scanning. acta polytech. 2016, 56(1), 76–80 doi: 10.14311/app.2016.56.0076 hungarian journal of industry and chemistry https://doi.org/10.1007/978-3-030-63986-0 https://doi.org/10.1088/1757-899x/448/1/012034 https://doi.org/10.1088/1757-899x/448/1/012034 https://doi.org/10.1109/fareastcon50210.2020.9271607 https://doi.org/10.1109/fareastcon50210.2020.9271607 https://doi.org/10.1007/s00170-017-0461-4 https://doi.org/10.1515/hjic-2018-0019 https://doi.org/10.1515/hjic-2018-0019 https://doi.org/10.1007/bf01427149 https://doi.org/10.1016/j.wpi.2020.102002 https://doi.org/10.14311/app.2016.56.0076 https://doi.org/10.14311/app.2016.56.0076 3d scanning and characterisation of welding defects 7 [10] dastres, r.; soori, m.: advanced image processing systems. int. j. imaging robot., 2021, 21(1), 27–44 https://hal.archives-ouvertes.fr/hal-03168963 [11] wold, s.; esbensen, k.; geladi, p.: principal component analysis, chemometr. intell. lab. syst., 1987, 2(1-3), 37–52 doi: 10.1016/0169-7439(87)80084-9 [12] chen, y.; medioni, g.: object modelling by registration of multiple range images. image vis. comput., 1992, 10(3), 145–155 doi: 10.1016/02628856(92)90066-c [13] bęczkowski, r.; gucwa, m.: defects appearing in the surfacing layers of abrasion resistant. arch. foundry eng., 2016, 16(4), 23–28 doi: 10.1515/afe2016-0077 49(2) pp. 3–7 (2021) https://hal.archives-ouvertes.fr/hal-03168963 https://doi.org/10.1016/0169-7439(87)80084-9 https://doi.org/10.1016/0262-8856(92)90066-c https://doi.org/10.1016/0262-8856(92)90066-c https://doi.org/10.1515/afe-2016-0077 https://doi.org/10.1515/afe-2016-0077 introduction the proposed cad model–based method of the generation and analysis of error distributions results summary untitled hungarian journal of industry and chemistry vol. 52(1) pp. 45–53 (2024) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2024-07 towards a circular economy – changing needs and solutions for waste management systems attila sarkady1*, attila egedy2, róbert kurdi3 and eliza tóth3 1 circular economy sustainability competence center, university of pannonia, egyetem u. 10, veszprém, 8200, hungary 2 department of process engineering, university of pannonia, egyetem u. 10, veszprém, 8200, hungary 3 sustainability solutions research laboratory, research centre for biochemical, environmental and chemical engineering; faculty of engineering, university of pannonia, egyetem u. 10, veszprém, 8200, hungary in recent years, the circular economy has become an important element of sustainable development. products become waste at the end of their life cycles. this problem is accompanied by a parallel decline in the availability of certain critical raw materials. it is obvious that the materials that become waste should be recycled and their components reintroduced into the economy, recovering the necessary raw materials and energy. the issues concerning the practical implementation of this are technical, economic and legal. over the last decade, significant progress has been made in terms of how waste can be treated and recovered. meanwhile, both the quality and quantity of collected waste have changed. to ensure that waste management systems can continue to oper ate properly under these changing conditions, it is necessary to examine the impact of such recent changes. furthermore, it is important to provide feedback to decision-makers with regard to how much their efforts have contributed to the principles of a circular economy in the eu member states. in this work, the regulatory framework of the two main periods, namely before and after 2010, will be reviewed while examining the evolution of wastesorting technologies by especially focusing on the mixed and selectively collected municipal solid waste streams. to reduce the amount of landfill, mechanical biological treatment plants had already been developed and packaging materials sorted before 2010, but it is crucial to examine how regulations and technological possibilities are evolving step by step as well as how they affect each other. predictions are also made concerning upcoming trends in and the future of waste management. keywords: circular economy, waste regulation, epr, drs, mbt, selective sorting plant 1. introduction the state of our environment has become an increasingly important issue in our daily lives, whereas previously this was regarded as more of a localized problem, it has now become a global concern. in recent years, although the importance of environmental awareness has become part of public consciousness, it is not only deemed as a problem but has also encouraged measures to be taken. however, objectives have had to be followed by regulations. a significant proportion of global environmental problems can be traced back to the issues of waste generation, collection, disposal and recovery, or lack thereof. the legislative framework in this area also reflects the goal to achieve a circular economy. as the impact of these has already become global, regulations and possible solutions should also be implemented worldwide. received: 4 jan 2024; revised: 23 jan 2024; accepted: 23 jan 2024 *correspondence: attila.sarkady@uni-pannon.hu in parallel to the legal framework, the technical possibilities of waste management and treatment have evolved significantly over the last 10-15 years. the development of collection systems, pre-sorting and sorting technologies as well as the increasing number of recovery options may facilitate a reduction in the amount of waste produced as well as primary raw materials and fossil fuels consumed. to achieve the goals of a circular economy, it is necessary to periodically review the regulatory frameworks already in force to compare them with the originally set goals. it is important to conduct a study on the applied waste-sorting technologies that have been implemented in the past to be able to optimize and modify them in the present and future, respectively, as well as meet needs using sophisticated tools. the development of sensor-based sorting techniques to identify new applications in waste management must also https://doi.org/10.33927/hjic-2024-07 mailto:attila.sarkady@uni-pannon.hu sarkady, egedy, kurdi and tóth hungarian journal of industry and chemistry 46 be taken into consideration. our aim is to review the changes to legislation over recent decades as well as estimate the resulting changes to the quantity and quality of household waste streams with regard to both mixed household waste and separately collected waste. another closely related objective of this study is to introduce new waste management technologies for these two main waste streams in order to determine whether the goals set in accordance with regulations can be reached by applying existing practices and equipment. 2. methodology to achieve our goals outlined in the introduction, a comprehensive study on legislation was written based on available documents found mainly on the official online database of eu law amongst other articles, whilst for the technical overview, mainly related articles were chosen. the aforementioined two periods were selected to informatively and comprehensively examine the changes as well as draw comparisons. the year 2010, especially in central europe, was chosen as a boundary as in this epoque significant changes took place over a relatively short period of time. obviously, this not only applies to 2010 but represents a wider period of 2-3 years. during this epoque, strategic changes took place that affected legislation, meanwhile new financial resources were offered by the eu through cohesion funds to realize previously planned investments. legislative goals also required financial resources, facilitating new quantitative goals to be set that could contribute to the principles of a circular economy. most of these changes and a rapid increase in the number of new investments were witnessed around this time mainly in the less developed central and east european region. the use of eu funds at this time culminated in the realisation of new, modern regional waste management systems. focusing on a comparative investigation of the legal environment and the evolution of available technologies, how closely related the needs and possibilities were and are was examined. our goal was also to draw conclusions about the expected legal and technical development trends in coming years. 3. overview of legislative changes – the regulatory environment 3.1. up to the 2010s as an autonomous international legal entity, the european economic community, which was created by the treaty of rome (1957) [1] and established after the maastricht treaty (1992) [2] has been shaping the legal framework for waste management for more than four decades. figure 1 shows the hierarchy in waste management that sets strategies regarding legislation. eu waste management is based on directive 2006/12/ec [3] of the european parliament and of the council consolidating council directive 75/442/eec [4] as well as its amendments, which set out principles in addition to technical and institutional elements, as well as on council resolution 97/c 76/01 [5] on a community strategy for waste management. a further major overhaul was brought about by directive 2008/98/ec of the european parliament and of the council (waste framework directive) [6]. directive 2008/98/ec compared to the previous framework directive, substantial changes were enforced in directive 2008/98/ec in order to integrate horizontal legislation. its key areas are as follows: article 8 on extended producer responsibility as well as article 16 on the application of the principles of self-sufficiency and proximity. the purpose of these provisions is that all member states should ensure the recovery and disposal of waste. the directive extended the previous three-tier hierarchy to five tiers which is referred to as the waste hierarchy pyramid, so that re-use is linked to prevention leading to waste reduction, while preparation for reuse, recycling and other forms of recovery, e.g. energy recovery, now encompass a single tier within waste recovery. ensuring competitive neutrality. establish equivalent environmental requirements for the treatment of different types of waste. to this end, a register of waste has been introduced (commission decision 2000/532/ec) [7]. "biowaste" has become a separate material stream. article 22 of the directive deals with general issues concerning biowaste management to better process waste for its reuse and recycling. article 6 of sets out the criteria under which a substance or fraction ceases to be waste, namely is no longer considered waste. figure 1: the waste framework directive defines a hierarchy in waste management source: https://chesse.org (retrieved on 20/10/2023) https://chesse.org/ towards a circular economy 52(1) pp. 45–53 (2024) 47 other regulations related to directive 2008/98/ec it was important for the eu to standardize the classification of types of waste. a list of types of waste was implemented by commission decision 2000/532/ec consolidating the previous lists of hazardous and nonhazardous waste. this decision has been amended several times since its adoption. the main objective of directive 2000/76/ec [8] of the european parliament and of the council is to prevent and limit the negative effects on the environment from the incineration and co-incineration of waste. since 12 july 2006, the transboundary movement of waste has been subjected to various procedures and controls in accordance with regulation (ec) no 1013/2006 of the european parliament and of the council [9]. council directive 1999/31/ec on the landfill of waste [10] which contains provisions for measures, procedures and guidelines to prevent or reduce the negative impacts on the environment was published before directive 2006/12/ec. a coherent framework for waste management was followed at the european community level until 2010. definitions were clarified and the main orientations of the legislation set. tasks, responsibilities and institutional expectations of member states were defined. 3.2. from the 2010s to 2020s the objectives of directive 2008/98/ec set out specific future obligations for the member states. they were obliged to finalise their national waste prevention programme by 12 december 2013. meanwhile, directive 2008/98/ec has been amended several times, namely on 01/06/2015, 31/07/2015 and 05/07/2018, and the followings targets set: by 2015, the separate collection of paper, metal, plastic and glass had to be introduced. by 2020, the weight of paper, metal, plastic and glass from households (amongst other sources that produce waste similar to households) that is reused and recycled should be increased by at least 50%. by 2020, the weight of non-hazardous construction and demolition waste, including backfilling using waste as a substitute for other materials, that can be reused and recycled amongst other forms of material recovery should be increased by at least 70%. following these changes, directive 2008/98/ec continues to define european waste management with revised and modified objectives that reflect the growing volumes of waste. the obligations concerning the collection and recovery of waste streams have been refined. for example, 55% of household waste must be recycled by 2025 and less than 10% of the weight of municipal waste can be dumped in landfill sites by 2035 in accordance with directive (eu) 2018/850 that amends directive 1999/31/ec, which is ambitious as targets of 35 and 49% were set for hungary in these fields, respectively, during 2022. the eu has also proposed a new environment action programme to 2020 [10] entitled "living well, within the limits of our planet", which aims to enhance europe's ecological resilience and transform the eu into a sustainable, green organisation. circular economy the legislative changes have made the objectives of waste management more specific. the circular economy and the management of scarce materials have become priorities [12]. the recovery of materials from waste (collection, manual and mechanical sorting, etc.) and the use of recycled materials in production have been focused on and become obligations. in the circular economy model, non-renewable materials remain in a closed loop. to meet these requirements, the aforementioned principles must be taken into consideration even as early on as when a product is designed. products should be durable so that they become waste as late as possible and then, fulfilling the aim, waste will be a thing of the past in the framework of a “circular economy” [13]. using selective waste collection materials is an essential component of recycling to ensure their transition into raw materials. the european commission has published a communication "towards a circular economy: a zero waste programme for europe" [14] and proposed amendments to key eu waste legislation to achieve its goals in 2014, but the proposal was withdrawn by the new european commission (set up after the european parliament elections later that year) with the intention of presenting a new, more comprehensive proposal in 2015, focusing not only on the waste phase of the life cycle of a product but on it as a whole. the european commission published its new package of proposals on a circular economy in 2015. the package consisted of two main parts: a new communication entitled "closing the loop an eu action plan for the circular economy" and proposals for legislative changes [15]. in this action plan, the commission outlined the measures it intends to take, including legislation and funding from eu funding programmes. as a first action within the action plan, the commission published its proposal for modifying eu waste legislation, especially the waste framework directive, landfill directive, packaging and packaging waste directive, end-of-life vehicles directive, waste electrical and electronic equipment directive as well as the battery directive. in addition to the compulsory collection of paper, metal, plastic and glass fractions since 2015, the new rules will also extend separate collection to biowaste from the beginning of 2024 onwards as well as to textile waste and hazardous waste from households by the beginning of 2025. sarkady, egedy, kurdi and tóth hungarian journal of industry and chemistry 48 the legislation clarifies how producers must take responsibility for managing waste from their products enforced by new rules called extended producer responsibility (epr) policies. the european parliament and the council have also amended directive 94/62/ec [16] of the european parliament and of the council on packaging and packaging waste by directive (eu) 2018/852 [17]. the directive describes the deposit-return scheme (drs) to increase the amount of the selectively collected waste and remove mainly packaging materials from mixed household waste [18]. it is also expected that the selectively collected materials will be less contaminated. the goal of the member states is to collect 77% by 2025 and 90% by 2029. in the future, it is expected that cleaner and larger quantities of selective waste streams will be recovered contributing to the circular economy that has also been established in all the member states, including hungary [19]. the new goals are ambitious as significant percentages of recycled waste are targeted as illustrated in table 1 [20]. as an outcome of the regulatory changes, strategic directions are refined in the latest “environment action programme to 2030” [21] from which the current waste collection targets and methods can be predicted, thereby significantly changing the inputs of the existing waste handling and sorting technologies within the upcoming few years. it is expected that cleaner and larger quantities of selective waste streams will have to be treated, sorted and recovered. during this period by relying on the existing legal frameworks, clarifications and quantifications were the main objectives, moreover, the establishment of a circular economy became a new strategy. 4. overview of technological changes and directions for development 4.1. municipal solid waste (msw) mixed fraction the disposal of mixed household waste by landfilling is still significant. the landfilling of organic waste has a negative impact on the environment and public health [22]. firstly, the problem of landfilling was addressed as even new regulated landfill sites still exhibit significant effects on the surrounding environment. to reduce the fractions of solid waste at landfill sites, two approaches have emerged in europe: mechanical biological treatment (mbt) waste incineration 4.1.1. until the 2010s since the 2000s, thanks to eu landfill regulations and financing, several investments have been made to divert waste from landfills. the first simple mbt plants were established in germany in the 1970s [23]. while mbt plants have become widespread in, for example, germany, austria and italy, scandinavian countries and others like switzerland have opted for incineration. mbt focuses on the pre-sorting of waste and seeks to minimise the biodegradable fraction of residues at the end of the process, rather than treating the entire waste stream in one step, unlike incineration [24]. with this integrated and complex treatment, the objective of waste management is to prevent the generation of landfill waste and maximize utilization by the separation of valuable fractions. in some cases, not only is the production of alternative fuels like refuse derived fuel (rdf) sought but leachates of biofractions can also be a potential source of energy [25]. eu funds were available to member states, including hungary, for the planning and implementation table 1: recycling target values recycling target value derogation options by 31 december 2025 by 31 december 2030 plastic 50% 55% the derogation may be a maximum of 15% or divided between two subgoals. the recycling rate for each target value cannot fall below 30%. for glass and paper, the target number cannot be less than 60%. wood 25% 30% ferrous metal 70% 80% aluminum 50% 60% glass 70% 76% paper and cardboard 75% 85% packaging waste sum 65% 70% towards a circular economy 52(1) pp. 45–53 (2024) 49 of mbt plants with financial support from ispa (instrument for structural policies for pre-accession) and cohesion funds [26]-[27]. for instance, in hungary, in order to establish new regional systems, the national waste management plan predicted the amount of waste to increase from 4.7 to 5.2 million tons [28]. mbt plants, in line with directive 1999/31/ec, aimed to achieve the following goals: to separate by mechanical means the fractions that can still be recovered (as material or energetically); to reduce the amount of the biologically active fraction by biostabilization; to improve the quality of the biologically active fraction by making it less hazardous, thereby activating, biostabilizing and recovering a cover material for landfill sites. 4.1.2. from the 2010s to 2020s in hungary, for example, the first mbt plants were built between 2005 and 2012 with eu funding by the new széchenyi plan 2007-2013 [29]. subsequently, a significant increase in the number of technologies both in hungary and europe has been seen. in the case of hungary, in 2017, already 27 mbt and mechanical treatment (mt) plants were in operation with a cumulative input capacity of 1.62 million tons of msw, that is, approximately 55% of the total mixed municipal waste collected [30] and this figure is still growing. the estimated capacity in europe by 2025 is 65 million tonnes of mixed waste, which will be processed in 690 plants according to a research report by ecoprog in 2017 [31]. according to figure 2, a decrease in landfilling between the two examined decades can be observed. despite the realized regional mbt plants and the technological progress made over the last 10 years, numerous eu member states still fall very short of achieving landfill minimization targets. it should be noted that these targets must be reached within a very short timeframe, that is, by 2030 (or 2035 in the case of derogation). due to unclear specifications and a lack of mbt regulations, which had been planned several times before but were not finalized, these systems were implemented in a variety of ways. the applied technologies ranged from a simple mobile equipment system to complex technologies capable of selecting multiple material flows, which makes it difficult to compare these systems. in many cases, analysis of the output material streams was required. simple systems were useable for more or less stable inputs, whilst robust systems could produce stable output material with changing inputs, e.g. due to seasonal variations. simple technology by applying simple technologies like those illustrated in figure 3, weaker quality can be ensured with the same input material compared to more complex technologies, and the simple technology is more sensitive to impurities in the incoming waste. figure 2: municipal waste landfill rates in europe by country source: european environment agency https://www.eea.europa.eu/data-and-maps/figures/municipalwaste-landfill-rates-in-1 figure 3: mbt simple technology https://www.eea.europa.eu/data-and-maps/figures/municipal-waste-landfill-rates-in-1 https://www.eea.europa.eu/data-and-maps/figures/municipal-waste-landfill-rates-in-1 sarkady, egedy, kurdi and tóth hungarian journal of industry and chemistry 50 complex technology a complex technology is usually more robust and can create more recyclable material streams to produce alternative fuels. a good example is shown in figure 4 about northbalaton regional mbt plant in királyszentistván, hungary. here different quality products can also be made parallelly [32]-[33]. in more complex systems, the outputs can be assured and protective steps installed mainly for the mechanical protection of sensitive units. in these systems, sensor-based sorters are already used for negative or positive sorting in order to extract impurities, e.g. chlorine or pet, respectively, as desired. a lack of homogeneous technologies and the absence of certain regulatory elements make it difficult to compare technologies in terms of both their operation and potential. according to the local input materials, the optimisation of mbt plants had to also be addressed to ensure the operational parameters are achieved in order to produce the desired quality of outputs [34]. in the light of the aforementioned reasons, it is beneficial to compare the existing technologies, model operational and functional alternatives as well as simulate them for the purpose of further analysis. 4.2. municipal solid waste (msw) separately collected fraction (packaging materials) 4.2.1. up to the 2010s separately collected “waste” streams have already played an important role following the world wars as important raw materials for rebuilding [35]. afterwards, the existing deposit scheme in europe focused on refilling empty glass bottles, moreover, metals and paper were recovered at specialized locations. although normal waste collection started to expand as a result of sanitation activities in settlements, no separate collection facilities were available to the public in public areas nor through special containers at households for packaging or other forms of selected waste. during this period in hungary, the percentage of selectively collected waste was only 2-3% of the whole amount of collected waste compared to 15-20% in western european countries, even 25-30% was achieved in some countries, e.g. austria, germany, holland, switzerland and sweden [28]. to reduce the amount of mixed household waste, a separate collection system for glass, metal, plastic and paper waste from households (selective collection) was established between 2010 and 2015 based on the legal provisions. after the establishment of this collection system, the waste streams needed to be cleaned in order to be processed further in industry as raw materials. numerous manual sorting facilities for this purpose are located in europe. simple technology – manual sorting manual sorting, even of relatively "clean" material streams, is typically of low quality due to the low pay and prestige of the work, high turnover and scarcity of motivational tools. a typical sorting facility is shown in figure 5. as a result, materials present at the time of collection can be 'lost' in this operation, making it difficult to achieve recovery targets. figure 4: mbt complex technology figure 5: basic hand-sorting facility towards a circular economy 52(1) pp. 45–53 (2024) 51 manual sorting is complex and flexible. even though changes to selected materials amongst other parameters can be easily enforced, it has significant shortcomings. how workers are trained is crucial. setting the right size of workforce can be cost-effective. this process was used in countries where the cost of labour is relatively low and the amount of handled material was less compared to after 2010 due to a lack of selective collection systems. 4.2.2. from the 2010s to 2020s to fulfil the requirements of changes to legislation, more and more packaging waste started to be collected. larger quantities and problems associated with manual sorting encouraged the development of sensor-based techniques to meet higher demands. in addition to simple manual sorting, new hybrid systems were developed to supplement existing ones alongside novel complex automated systems. complex technology – optical machine sorting line in complex technologies, the most valuable components are selected by near-infrared optical sorting machines. the operation is continuous requiring a minimal human workforce to maintain the line. the setup can be configured to meet needs. for the configuration, a mathematical modelling system can contribute towards identifying the most cost-effective arrangement, an example of which is presented in figure 6. 5. trends trends in waste regulations and available technologies are evolving mutually. new, e.g. sensor-based, technologies, let decision-makers set higher expectations that also facilitate technical developments. in line with new legislation, the development of waste-focused consumer products and the setting of ambitious targets with regard to recycling should be sought. in the upcoming years, more waste streams are planned to be selectively collected or capable of being sorted by modern equipment to inject new energy sources and raw materials into the economy. in the case of municipal packaging waste, it is expected that drs systems and optical separation will become widespread. these sophisticated automated sorting plants can contain numerous optical sorting units to increase their capacity and reduce the degree of necessary human factors. instead of the realisation of new mbt plants, additional upgrading of existing one is likely to reduce landfilling [36]. for this purpose, the modelling of waste treatment technologies such as mbt and packaging waste sorting plants might be beneficial for cost optimisation as well as enable changes in the outputs of such technologies to be predicted should inputs vary, for instance, as a result of new drs systems. 6. conclusions in terms of legislation, the new regulations demand that specific waste management targets be met in the upcoming years in accordance with the goals of a circular economy. in the regulatory environment, the relevant directions, strategies and legal framework were established in the 2000s. the implementation of specific instruments and targets was strengthened from around 2010 onwards to significantly reduce waste and reintroduce material streams back into the economy as raw materials, energy sources or nutritive substances. with the introduction of drs, epr as well as the collection of new waste streams such as biological waste and "green" product requirements, it is hoped that not only more raw materials will be produced but crucial scarce materials preserved for modern industry. from a technological point of view, techniques are available to reduce landfilling. from the 1970s onwards, mixed household waste began to be pre-treated for this reason. the use of mechanical and biological technologies, which were mainly designed before 2010 and are still effective today, has led to a reduction in landfilling. since the realised mbt technologies are very different, their outputs differ despite having almost identical inputs. it is questionable how such installations will cope with changing input waste streams due to legislative changes and whether they will be economically viable. the sorting of selectively collected (packaging) waste is necessary following regulatory figure 6: complex sensor-based sorting facility sarkady, egedy, kurdi and tóth hungarian journal of industry and chemistry 52 changes. human factors, e.g. knowledge, motivation and capacity, must be addressed when manual sorting. although automated or hybrid (mechanical and manual) sorting is expected to become widespread, the proper planning of yield and flexibility is essential to meet future goals. in general, current technologies are suitable to realise set goals in line with legislation. since their scaling and modelling can ensure their costeffectiveness, legislators may be given an impetus to set further directions and ambitious goals. meanwhile, experiences concerning selection must also be incorporated into the design phase of products in accordance with the principles of a circular economy. references [1] treaty of rome (eec) https://www.europarl.europa.eu/about-parliament/en/in-thepast/the-parliament-and-the-treaties/treaty-of-rome [2] treaty on european union (teu) / maastricht treaty https://www.europarl.europa.eu/about-parliament/en/in-thepast/the-parliament-and-the-treaties/maastricht-treaty [3] directive 2006/12/ec of the european parliament and of the council of 5 april 2006 https://eur-lex.europa.eu/eli/dir/2006/12/oj [4] council directive 75/442/eec of 15 july 1975 on waste https://eur-lex.europa.eu/eli/dir/1975/442/oj [5] council resolution of 24 february 1997 on a community strategy for waste management 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https://nhkv.hu/wp-content/uploads/2013/12/ohkt_felulvizsgalat_2017_nhkv.pdf?dl=1 https://ecoprog.com/publications/report-market-for-mbt-plants-in-europe-2017 https://ecoprog.com/publications/report-market-for-mbt-plants-in-europe-2017 https://doi.org/10.2495/ess140251 https://doi.org/10.30638/eemj.2013.204 https://doi.org/10.2495/ess140271 https://doi.org/10.2495/ess140271 https://doi.org/10.33927/hjic-2023-09 hungarian journal of industry and chemistry vol. 51(2) pp. 43–49 (2023) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2023-17 the role of raising awareness in ensuring the resilience of cities ben rjiba iskander1, viktor sebestyén1,2 and georgina tóth-nagy1* 1 sustainability solutions research lab, university of pannonia, egyetem u. 10, veszprém, 8200, hungary 2 elkh-pe complex systems monitoring research group, university of pannonia, egyetem u. 10, veszprém, 8200, hungary this paper explores the significant role of raising awareness in ensuring the resilience of cities towards climate change. climate change is an imminent threat to urban development and its adverse effects can only be mitigated with the collective efforts of city dwellers. by evaluating the level of awareness and relating it to the greenhouse gas emissions emitted by three selected countries namely germany, brazil and kenya this study highlights the need for awareness-raising campaigns and community-engagement initiatives centered around the risks of climate change and its potential impact on cities. the findings suggest that raising awareness, through several social action campaigns, can enhance the public understanding of climate change and facilitate the adoption of sustainable behaviors to reduce greenhouse gas emissions. furthermore, raising the awareness of a population will make their participation in the decision-making processes of the different adaptation plans more effective. the paper concludes that raising awareness by enhancing public understanding and ensuring their participation in combating climate change is a crucial step in building resilience to climate change. keywords: climate change, raising awareness, social action plans, greenhouse gases, emissions, adaptation, resilience 1. introduction although government policies and plans are key components when facing challenges, they are insufficient in themselves. the public needs to be made aware of the risks, acquire knowledge about the options that are available in response and be empowered to take their own actions [1]. even though numerous cities aim to mitigate their contribution towards climate change and provide a liveable environment in the context of sustainable development [2], nowadays, cities are facing a growing array of threats and challenges ranging from natural disasters to social and economic crises. to effectively manage these risks and ensure their resilience, it is essential to raise awareness among citizens as well as stakeholders about these potential threats and their impacts. by educating individuals and communities about the risks, encouraging them to take action in response as well as informing them that in the decisionmaking process they should always choose the sustainable and low risk initiatives for the environment [3], cities can build a culture of resilience that is better equipped to withstand and recover from adverse shocks and stresses. as a result, raising awareness has becom e an increasingly important aspect of urban planning and received: 5 sept 2023; revised: 20 sept 2023; accepted: 21 sept 2023 *correspondence: toth-nagy.georgina@mk.uni-pannon.hu management [4]. raising population awareness through surveys, advertisements and mini games [5] has positive impacts on several aspects of life such as our health by making people better prepared to make decisions when unwell [6]. as an example, a campaign to raise public awareness of persistent coughs as a symptom of lung cancer was launched in england in 2014, which had a positive impact by increasing the percentage of patients diagnosed early with lung cancer in the country [7]. furthermore, thanks to various actions aiming to raise awareness in several countries, the general public is more familiar with how to preserve biodiversity [8]. public awareness can also play a critical role in the waste management sector since waste is produced by human activities and everyone needs to have a good understanding of issues related to it, without which the success of even the best conceived waste management plan is questionable [9]. the main objective of this paper is to study how effective raising awareness about reducing the effects of climate change and ensuring the resilience of cities is. climate change is one of the most significant global challenges facing our world today. it is also a critical issue for our cities [10]. global warming throughout the https://doi.org/10.33927/hjic-2023-17 mailto:toth-nagy.georgina@mk.uni-pannon.hu iskander, sebestyén and tóth-nagy hungarian journal of industry and chemistry 44 21st century is projected to be considerably greater than over the previous century. the average global temperature since 1900 has risen by about 1.5 °c. by 2100, it is projected to rise by another 2 to 11.5 °c [11]. cities play a key role in developing and implementing initiatives to combat climate change because they are at the crossroads between local action, climate change adaptation on national as well as international levels, and mitigation commitments [12]. consequently, cities have started drawing up strong strategies to improve local air quality and enhance their resilience, which has become widely regarded as a key goal for both adaptation and mitigation efforts in cities as well as urban regions [13]. in 2008, the european commission (ec) launched the covenant of mayors (com) whereby local and regional authorities are brought together to voluntarily develop and implement a sustainable energy and climate action plan (secap) [14]. in order to reduce their energyrelated greenhouse gas (ghg) emissions, a voluntary agreement was made under which local authorities were committed to reducing co2 emissions by at least 20% within 2020 [15], then they focused on the active role of local authorities and increased its targets in 2016, through the secaps in terms of ghg from 20% to 40% by 2030 [16]. furthermore, an ambitious target has been set to achieve climate neutrality by 2050 [17]. based on the action plans listed on the com website, one of the most common strategies applied recently by several cities is to create tools that include different layers of society (adults, researchers, students, stakeholders) in order to raise awareness of the current situation as well as provide a platform to share their opinions on how to tackle climate change. our goal in this paper is to identify the impacts of applying such a strategy as well as determine how basic education and awareness can affect the trend of greenhouse gas emissions by evaluating the trend in emissions in three countries with different levels of awareness. 2. experimental the aim of this study is to evaluate the effectiveness of raising public awareness as an adaptation strategy to safeguard the resilience and sustainability of cities. consequently, the concept, presented in figure 1, consists of three selected case studies (countries) before extracting and analyzing the maximum values of awareness indicators from each state. finally, the relationship between the analysis results and emission levels is determined in order to compare and deduce the impact of the level of public awareness on tackling the effects of climate change. 2.1. selected case studies selecting the three countries is key to maximize the relationship between public awareness and air quality. consequently, they must be located in different climate zones as well as belong to various educational and awareness levels. in this study, the three countries selected are germany, brazil and kenya. germany is situated in a temperate, rainy climate zone of the midlatitudes [18]. the difference in annual mean temperature between sylt (an island in northern germany) and the zugspitze (the highest peak in germany) from 1961 to 1990 was 8.2 °c. the education system in germany is ranked third / globally and fourth among the countries with the most educated populations (table 1). brazilians experience equatorial, tropical as well as subtropical climates [19]. the annual average temperature in the region is 22 to 26 °c with little variation between the warmest and coldest months. the education system in brazil is ranked 36 in the education ranking of 2023 (table 1). kenya is subjected to three types of climate: a temperate subtropical climate in the west and southwest highlands (where nairobi is located), a hot and humid one along the coast, as well as hot and dry weather in the north and east [20]. the education system in kenya is ranked 68 in the education ranking of 2023 (table 1). 2.2. secondary data collection this step consists of collecting useful data, namely visualizing the level of awareness and the air quality in each country selected. in addition to the education ranking, other education indexes were collected such as the percentage of students admitted to tertiary and upper secondary education. surveys were conducted in germany and kenya in order to determine the level of figure 1: work methodology table 1: main climatic and educational characteristics of germany, brazil and kenya country population climatic zone global education ranking (2023) germany 83,294,633 temperate, rainy 3 brazil 216,422,446 equatorial 36 kenya 55,100,586 hot, temperate subtropical 68 the role of raising awareness in ensuring the resilience of cities 51(2) pp. 43–49 (2023) 45 awareness related to some climatic issues. these data will be crucial when comparing the level of awareness between these two countries. the adaptation plans will be collected and specified from the carbon disclosure project website in order to check whether these countries are taking into consideration social action in their strategies or not. the main data collected evaluating the air quality in germany, brazil and kenya are the annual co2 emissions, the contribution of each country towards the rise in temperature and the level of harm resulting from the ghg emissions. 2.3. public awareness – air quality this step consists of analyzing awareness indexes extracted and linking them to the emissions in each case study in order to compare the emissions of these three countries with their different climatic zones and education levels, thereby deducting the impact of public awareness on air quality and improving the resilience of each country. 2.4. data sources collecting the maximum amount of useful data is key. the data sources used in this study are presented in figure 2: the “our world in data” website a huge amount of data is being added by researchers on this website to tackle the most significant problems worldwide. this website was accessed to collect several emission levels and education indexes. cdp (carbon disclosure project) a more transparent mixed record has been produced [21]. in fact, the large amount of data extracted from this website was key when initiating this study to evaluate the environmental situation in the different case studies and analyze the adaptation plans of germany, brazil and kenya. copernicus it is a program dedicated to monitoring earth’s atmosphere for the benefit of all european citizens [22], in our case, to visualize the climate zones worldwide. 3. results 3.1. evaluation of the educational situation as mentioned in table 1, germany is rated the best (3rd) in the education ranking among the case studies followed by brazil (36th) and finally kenya (68th). the extraction and analysis of the other education indexes (table 2) confirm this ranking. in 2021, only 81.53% of individuals 15 years of age and older were literate. although this rate is higher in brazil (93.23%), it is still less than germany’s where the adult literacy rate is close to 100%. germany has the highest average years of schooling among the 3 countries, while the lowest is kenya with 10.7 years. should the number of years of schooling be too low, students will not be thoroughly trained which can affect their awareness about several topics related to climate change and environmental challenges in general. over 99% of primary school students complete their schooling in the three countries. however, only 3.4, 20.1 and 31.3% complete their tertiary education in kenya, brazil and germany, respectively. the resilience of cities impacts of climate change and different ways of improving the air quality are all topics that can be mentioned, mainly in upper secondary and tertiary education. in the event that the percentage of students who complete these levels is low, the knowledge of the upcoming generation will be lacking in these areas (table 3). figure 2: data sources table 2: education indexes of germany, brazil and kenya [23] country adult literacy rate (2021) average years of schooling (2021) public spending on education as a share of gdp (2018) germany >99% 17.01 4.99% brazil 93.23% 15.60 6.09% kenya 81.53% 10.70 5.08% table 3: completion rate of the different educational levels in germany, brazil and kenya in 2021 [23] country tertiary education upper secondary education primary education germany 31.30% 54.90% 99.02% brazil 20.10% 36.90% 99.00% kenya 3.40% 21.15% 99.68% iskander, sebestyén and tóth-nagy hungarian journal of industry and chemistry 46 3.2. adaptation plans and public awareness adaptation plans play a crucial role in ensuring the resilience of communities as well as ecosystems in the face of climate change and other environmental challenges. by anticipating and preparing for the potential impacts of climate change e.g. rise in sea level, extreme weather events as well as changes in temperature and precipitation patterns adaptation plans can help to reduce the number of vulnerabilities, moreover, increase the capacity of communities and ecosystems to adapt. adaptation plans can also help to identify and prioritize actions that can be taken to mitigate the impacts of climate change such as reducing ghg emissions, conserving natural resources as well as improving infrastructure and land use practices. furthermore, adaptation planning can be an important tool for promoting equity and social justice by ensuring that vulnerable and marginalized communities have a voice in decision-making and are included in the planning process. ultimately, adaptation planning is essential for building more sustainable as well as resilient communities and ecosystems that can withstand the impacts of climate change amongst other environmental challenges. in 2017, 366 action plans were announced by different brazilian cities. only 6.3% of these intend to include the society in their adaptation strategies by raising awareness (figure 3). out of 7, only one social adaptation plan was published in kenya. despite the low number of action plans announced by german cities that year, 22.22% of them have social and educative targets to encourage citizens to act in order to tackle the impacts of climate change. two sub-categories of social adaptation strategies are applied as action plans in the three countries: educative actions to improve the knowledge of citizens with regard to future challenges and the targets of its cities; and another type of social actions encouraging public engagement in decision-making through surveys and websites. a survey conducted in 2020 aimed to evaluate the level of awareness related to specific environmental impacts in several countries. the results of the survey show that the citizens and politicians in kenya are totally unaware of the influence of the layout of cities on the urban climate. 9.09% of german citizens are aware of this influence, while 36.36% of their politicians have been informed about the topic. 45.45% of citizens and 40% of politicians in kenya are aware of the influence of vegetation on the urban climate. 36.36% of german citizens and 90.9% of its politicians are aware of or wellinformed about this influence [24]. 3.3. greenhouse gas emissions and climatic hazards data presented in the document entitled "brazil’s initial national communication" indicated that the country is one of the highest ghg emitters worldwide. the vast majority of brazil’s ghg emissions originate from deforestation of the amazon biome to create agricultural land on which to raise livestock [25]. sub-saharan african countries such as kenya are having to face deteriorating air quality in their cities due to the high urbanization rates [26]. the annual co2 emissions decreased in germany from 1 billion tons in 1990 to 674 million tons in 2021. however, in brazil, this parameter increased from 218 million tons in 1990 to 488 million tons in 2021, while in kenya, from 5 million tons in 1990 to 20 million tons in 2021 (figure 4). the air quality index is good in all three countries: highest in germany at 25, followed by 24 in brazil and just 10 in kenya. the influence of air pollution on the death rate is significant in kenya, reaching 124 deaths per 100,000 people compared to 27 and 14 in brazil and germany, respectively [27]. in kenya, 24% of this death rate, equating to 29 deaths per 100,000 people, is caused by particulate matter, the main pollutant in the country, compared to 70% in brazil and 86% in germany [28]. 43% of climatic hazards caused by kenyan citizens are extremely harmful. 86% of those caused by brazilians are either serious or extremely serious. although no hazards occurred in germany are extremely damaging, 80% of its emissions are classified as harmful (figure 5). while germany isn't facing the most extreme weather events, climate change still poses a serious threat, with a staggering 80% of climate hazards classified as serious. figure 3: classification of adaptation plans in 2017 figure 4: annual co2 emissions in germany, brazil and kenya and their contribution towards global warming the role of raising awareness in ensuring the resilience of cities 51(2) pp. 43–49 (2023) 47 3.4. awareness level – ghg emissions as is shown in figure 3, 22.22% of german adaptation plans published in 2017 seek to involve the society, which is higher than in brazil (despite the large number of action plans drawn up there) and kenya. a calculation made intending to link this factor to the air quality index on a figure covering multiple dimensions confirms a correlation between these two parameters (figure 6). despite the high quantity of adaptation plans applied in several brazilian cities, the co2 emissions increased between 2017 and 2021 (figure 4). in fact, applying various categories of action plans, depending on the situations affecting the cities and related issues, can be more effective than focusing on the quantity of them. the low percentage of social actions applied in brazilian cities from 2017 to 2021 could be a reason for the rising trend in emissions in the country. the adult literacy rate and average years of schooling are two of several educational indexes that can have a direct impact on the level of public awareness. a regression calculation was conducted to identify a correlation between the adult literacy rate and annual co2 emissions in brazil and kenya alone because the level of adult literacy has been stable throughout almost the whole of germany over the last decade. the results show a strong correlation between these two parameters in both countries, that is, a low adult literacy rate can cause greater emissions (figures 7 and 8). the adult literacy rate and the years of schooling are higher in germany than in brazil and kenya (table 2), moreover, correlate with the nature of the climatic hazards occurred in each country. the kenyan population has a low literacy rate and causes a high percentage of extremely serious climatic hazards which can be explained by their lack of knowledge with regard to the impacts of emitting such components, which is not the case in germany (figure 5). since the percentages of those who complete tertiary education are low in brazil and kenya, the main social actors, namely politicians and citizens, are unaware of several topics related to the urban climate. this lack of awareness could lead to breaches in the decision-making procedure and increase ghg emissions. 4. conclusions public awareness has become essential to achieve the targets of cities in several fields such as agriculture, waste management, health and air quality. many case studies have confirmed the effectiveness of engaging the community with the decision-making procedure on figure 5: climatic hazards classification in germany, brazil and kenya figure 6: multidimensional scale figure linking the air quality index with the percentage of social adaptation plans in germany, brazil and kenya figure 7: the correlation between the adult literacy rate and co2 emissions in brazil figure 8: the correlation between the adult literacy rate and co2 emissions in kenya iskander, sebestyén and tóth-nagy hungarian journal of industry and chemistry 48 achieving set targets and this would not be possible without raising their awareness of them. raising the awareness of a population has become one of the main categories of adaptation plans published by several countries to ensure resilience and sustainability due to their positive impacts. an analysis of the action plans listed on the covenant of mayors website shows that approximately 25% of these actions seek to raise the level of public awareness and engage them with the challenge of tackling climate change. evaluating the education level by extracting several education indexes is key to measuring and visualizing the level of awareness of the population. the results of this study show a high, medium and low education level in germany, brazil and kenya, respectively, which correlate with the level of awareness of the environmentrelated topics measured in these three countries. the results show a correlation between ghg emissions in germany, brazil as well as kenya and the levels of education and awareness in these countries. co2 emissions are decreasing in germany as a result of the adaptation plans set by the country. references [1] khatibi, f.s.; dedekorkut-howes, a.; howes, m.; torabi, e.: can public awareness, knowledge and engagement improve climate change adaptation policies?, discov. sustain., 2021, 2, 18, doi: 10.1007/s43621-021-00024-z [2] sebestyén, v.; somogyi, v.; szőke, s.; utasi, a.: adapting the sdewes index to two hungarian cities, hung. j. ind. chem., 2017, 45(1), 49–59, doi: 10.1515/hjic-2017-0008 [3] rózsenberszki, t.; koók, l.; bakonyi, p.; nemestóthy, n.; bélafi-bakó, k.: comparative study on anaerobic degradation processes of 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https://doi.org/10.1016/j.uclim.2020.100705 https://doi.org/10.1590/s0103-90162009000600017 https://doi.org/10.1016/j.puhe.2015.07.014 https://doi.org/10.1016/j.puhe.2015.07.014 https://ourworldindata.org/air-pollution https://ourworldindata.org/outdoor-air-pollution hungarian journal of industry and chemistry vol. 51(2) pp. 35–41 (2023) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2023-16 evaluation of the effect of castor oil-based experimental additives on pla/starch foils bianka nagy1, norbert miskolczi1* and zoltán eller2 1 department of mol hydrocarbon and coal processing, university of pannonia, egyetem u. 10, veszprém, 8200, hungary 2 refinery product development and technical service, mol plc., olajmunkás út 2, százhalombatta, 2440, hungary biodegradable packaging materials are attracting more and more interest nowadays, the primary driving force of which is the generation of enormous amounts of plastic packaging waste. the aim of this study was to investigate the effect of two castor oil-based experimental additives on the properties of foils made from incompatible biodegradable polylactic acid (pla) and native starch (10-50 wt%). differential scanning calorimetry (dsc) measurements and tensile tests were used. it was found that increasing the starch content affected the crystallization of pla in the blends. furthermore, since the additives did not significantly change the glass transition temperatures, the additives did not affect the mobility of pla chains. regarding the tensile tests, the tensile strength of the 60:40 pla:starch longitudinal sample could be increased by approximately 10 and 6 mpa at 25 and -25 °c, respectively, when additives were introduced. keywords: biopolymers, starch, polylactic acid, castor oil, pla/starch foils 1. introduction as a result of the widespread use of plastics, plastic pollution is becoming a growing problem [1]. in 2021, the amount of plastic produced globally was estimated to be 390.7 million tons, a significant proportion of which originated from fossil-based sources (90.2%) [2]. approximately 40% of this was utilized in the packaging industry, while the food packaging market is growing exponentially in developing countries [3]-[4]. in 2020, the amount of packaging waste generated per inhabitant in the eu was estimated to be 177.9 kg, of which 19.4% was plastics [5]. less than 30% of plastic waste in the eu is recycled, some of which is exported to non-eu countries to be treated [6]. although there is no effective way to recycle and reuse food waste mixed with synthetic plastics, plastic packaging is indispensable as the increase in the amount of food waste as a result of eliminating the packaging could be more environmentally threatening than the plastic packaging itself. furthermore, being light, it is more energy efficient to transport plastic packaging than food waste[3],[7]. in november 2022, new packaging regulations were proposed throughout the eu, e.g. clear labelling, promoting reuse and recycling, as well as switching to bio-based, biodegradable and compostable plastics [8]. received: 14 aug 2023; revised: 21 oct 2023; accepted: 22 oct 2023 *correspondence: miskolczi.norbert@mk.uni-pannon.hu although the global production of plastics is dominated by non-degradable, fossil-based polymers [9], bioplastics can potentially provide a green solution in light of the negative environmental impacts, strict environmental protection regulations as well as increasingly important ecologically supportive monetary policies and capital investments [10]-[13]. due to their stable carbon-hydrogen bonds and complex polymer structure, fossil-based plastic waste is not biodegradable, it only breaks down into pieces over a long period of time, resulting in many negative consequences [14]-[15]. in order to protect the ecosystem, in addition to introducing proper waste management, the complete or partial replacement of traditional food packaging with bioplastics is crucial, however, many obstacles have to be overcome [3-4, 15]. nevertheless, concerns about waste disposal and the increasing costs of crude oil extraction have made biodegradable polymers economically attractive [9]. in 2020, 2.1 million tons of bioplastics were produced worldwide, 47% of which were used for packaging [7]. the basic role of packaging materials is to protect food or packaged products from external influences and damage [16]. although the demand for biodegradable packaging materials is basically driven by its biodegradable nature, the packaging material must exhibit suitable mechanical and thermal properties as well as processability in addition to protect products by inhibiting the diffusion of water https://doi.org/10.33927/hjic-2023-16 mailto:miskolczi.norbert@mk.uni-pannon.hu nagy, miskolczi and eller hungarian journal of industry and chemistry 36 vapor, atmospheric gases and lipids which can change the properties of the packaged products (taste, color, nutritional content) [3-4, 17-19]. because of their hydrolyzable ester bonds, polyesters play a dominant role as biodegradable plastics [9]. among others, biopolyesters like polylactide, polyhydroxyalkanoates and polycaprolactone can function as biodegradable packaging [3]. polylactic acid (pla), which can be easily processed by traditional methods, e.g. thermoforming or injection molding, has a high molecular weight and exhibits favorable mechanical, thermal and barrier properties, which can be further enhanced by blending it with plasticizers or other polymers [4,18,20]. pla is an aliphatic polyester, pseudoplastic and non-newtonian fluid that behaves as a classical flexible polymer chain in all compositions above its melting point [4],[20]. it is brittle with a tensile strength of approximately 32 mpa, a young's modulus of 2.3 gpa and an elongation at break of about 5% [4]. the rigidity of pla as well as its poor thermal resistance, limited gas barrier properties and high expense are bottlenecks in the packaging industry [9]. pla is often blended with starch to increase its biodegradability and reduce feedstock costs [9]. starch is a renewable polysaccharide that is attractive given its biodegradability and abundance [4,15,18]. however, as a packaging material, it can only be used in its natural state to a limited extent since its poor solubility, thermal decomposition, high retrogradation, moisture sensitivity, hydrophilic nature and unfavorable mechanical properties have to be compensated for by softening, chemical modifications or mixing it with other polymers [4,7,14,18]. 2. experimental the aim of the experiment was to produce foils from pla and starch with suitable tensile properties (figure 1). however, due to the limited miscibility between starch and pla, it was necessary to improve their mechanical properties. as a result, the synthesis of additives was required to process blends. castor oil was added to maleic anhydride in the presence of the initiator di-tertbutyl peroxide with and without xylene as a solvent. the main properties and reaction parameters of our vegetable oil-based additives were presented in one of our previous papers [22]. it was found that the optimal temperature for the reaction was 140 °c and high acid number values were measured regardless of whether a solvent or solvent-free technique was applied. over the course of this work, an impact assessment of 2 castor oil-based additives was performed. the difference between them was that one additive was synthesized in the presence of a solvent while the other was not. therefore, in this study, the main goal was to compare the effect of the two additives based on differential scanning calorimetry (dsc) measurements and tensile properties of pla/starch composites. to carry out the impact assessments, pla/starch films were produced with the following compositions: 90/10, 80/20, 70/30, 60/40 and 50/50. additive-free pla/starch foils were examined as references. the temperature profile of 180-160 °c and an extrusion screw speed of 125 1/min were used during foil production. afterwards, 10 x 2 cm test specimens were cut out and 5 parallel measurements taken. 2.1. materials ingeotm biopolymer 4043d-type commercial pla was supplied by natureworks llc (usa), while the corn starch was provided by hungrana bioeconomy company (hungary). the vegetable oil used to synthesize the additives was castor oil with a molecular weight of 933 g/mol supplied by alfa aesar (usa). 2.2. methods dsc is effective for monitoring the physical and chemical changes resulting from the phase transformation of substances as well as exothermic and endothermic phenomena [23]. to analyze changes in the behavior of films made of pla and starch, dsc measurements were taken using a dsc 214 polyma instrument. 10 mg samples were weighed into an aluminum crucible and the measurements made in a nitrogen atmosphere with a heating/cooling rate of 10 °c/min. the measurements were taken over the following four stages: heating the specimens from 20 to 200 °c, tempering them at 200 °c for 3 min, cooling them down to 20 °c and finally reheating them to 200 °c, the second heating stage. the tensile properties of pla/starch films were followed by an instron 3345 universal tensile testing machine at a crosshead speed of 75 mm/min and three parallel measurements were taken at both 25 and -25 °c. 3. results and analysis 3.1. dsc evaluation the second heating stage was taken into account, since the first one was used to eliminate the thermal history of the sample [23]. the main properties, e.g. the glass transition temperature (tg), cold crystallization temperature (tcc) and melting point (tm) were determined by integrating the individual peak areas into enthalpies of cold crystallization and melting. figure 1: sample production the effect of castor oil additives on pla/starch foils 51(2) pp. 35–41 (2023) 37 the degree of crystallinity (xc) was calculated by the following equation [24]: 𝑋𝑐 = ∆𝐻𝑚−∆𝐻𝑐𝑐 𝜔∙∆𝐻𝑚 0 ∗ 100 (1) where ω denotes the weight fraction of pla in the blends, ∆𝐻𝑚 is the enthalpy of melting, ∆𝐻𝑐𝑐 is the enthalpy of cold crystallization and ∆𝐻𝑚 0 is the enthalpy of fusion of 100 % pla taken into account with a value of 93 j/g [24]. dsc is excellent for determining polymer compatibility if the glass transition temperatures of the pure components can be sufficiently differentiated [25]. in heterogeneous systems, the sample exhibits two tg values, i.e. two phases [26]. the miscibility and compatibility of polymer blends are best determined by examining the glass transition temperature, which can vary widely depending on the composition of the compatible system but is always somewhere between the tg values of the pure components [25],[27]. the thermograms of the second heating stages of the reference pla/starch foils can be found in figure 2. the relevant tg values and degrees of crystallinity are presented in table 1. the glass transition temperature of virgin pla was 59.9 °c, and those of the blends containing starch were very similar, between 58.4 and 60.2 °c to be exact, so the incorporation of starch into the pla matrix did not have a significant effect on tg. furthermore, a single tg value on the dsc curve is an indirect indication that the components are compatible [28]-[30]. however, as a result of molecular complexity, certain nanostructures may have a locally heterogeneous composition and a certain degree of segregation or partitioning can be experienced, in which case tg appears as a single broad transition [27]. in light of the cold crystallization, the composites composed of 10 and 50% starch exhibited elongated cold crystallization peaks, perhaps caused by the slow and weak crystallization behavior. the melting points are also relevant if the polymers are partially crystalline [30]. tm values fell within the range of 148.8-152.8 °c, while that of virgin pla was 151.1 °c, so the starch had almost no influence on tm. by comparing the degree of crystallinity of additive-free films in table 1, it can be established that xc value rises by increasing the starch content, so starch affects the crystallization process of pla in blends [28]. figure 3 shows the effect of the additives on the dsc results, which was examined using five types of films with differing starch contents of 10-50%. in the case of samples containing 10 and 20 % starch, tg decreased slightly in the presence of both types of additives (table 1). however, taking into account all the tested samples, no notable changes were observed, so the additives did not influence the chain mobility of pla. larger differences were observed in the cold crystallization peaks. in almost all cases, the tcc values increased compared to the additive-free reference samples. regarding the degrees of crystallinity, no clear correlation could be established with the presence of the additives. only in the case of samples containing 30 and 40% starch increased xc in the presence of either additive; in the case of the samples containing different proportions of starch, this parameter depended on the type of additive present. the degree of crystallinity figure 2: thermograms of additive-free pla/starch films table 1: glass transition temperatures and degrees of crystallinity of pla/starch blends compositions of pla/starch blends tg, (°c) xc, (%) pla/10% starch 59.8 2.35 pla/10% starch/co-ma140/xylene 58.7 2.22 pla/10% starch/co-ma-140/no xylene 58.3 3.01 pla/20% starch 60.2 2.92 pla/20% starch/co-ma140/xylene 60.0 4.37 pla/20% starch/co-ma-140/no xylene 58.1 1.90 pla/30% starch 59.5 2.95 pla/30% starch/co-ma140/xylene 60.1 4.01 pla/30% starch/co-ma-140/no xylene 59.2 3.06 pla/40% starch 59.8 3.39 pla/40% starch/co-ma140/xylene 59.2 3.57 pla/40% starch/co-ma-140/no xylene 59.0 3.49 pla/50% starch 58.4 3.44 pla/50% starch/co-ma140/xylene 59.5 3.10 pla/50% starch/co-ma-140/no xylene 59.0 1.98 pla 59.9 2.16 nagy, miskolczi and eller hungarian journal of industry and chemistry 38 increased in the presence of the solvent-free additive with the exception of the 80/20 and 50/50 blends, while in the case of the other additive, xc increased apart from when the 90/10 and 50/50 blends were used. figure 4 shows how the degree of crystallinity changed in the case of all the tested samples. comparing the results, it can be observed that the additive in the presence of the solvent (highlighted in brown) had the greatest effect on the xc for samples with 80/20 and 70/30 pla/starch compositions. 3.2. tensile tests the tensile tests (tensile strength and elongation at break) of foil samples were studied on both longitudinal and transverse samples. the samples were tested at both 25 and -25 °c. the tensile strength values at 25 °c and -25 °c in both directions can be seen in figure 5, which in almost all cases decreased as a result of using additives regardless of the temperature and direction. considering the longitudinal samples, the tensile strength increased at both temperatures in the case of the 80/20 and 60/40 pla/starch compositions containing additives synthesized by the solvent technique, but the increase was not significant. in the case of the 60/40 composition, compared to the reference sample, the tensile strength of the longitudinal specimen increased by approximately 10 and nearly 6 mpa at 25 and -25 °c, respectively, after the additive was added. examining the transverse samples, it was observed that at room temperature, the additives slightly increased the tensile strength of the samples containing 40 and 50% starch but not at -25 °c. the decrease in tensile strength could be the result of the plasticizing effect of the additives. figure 6 shows the elongation at break values at 25 and -25 °c in the longitudinal and transverse directions. regarding the longitudinal samples, at both temperatures the elongation at break values decreased as a result of using additives except for the 90/10 specimen. taking into account the effect of the starch content, it can be concluded that the foils with 80/20 and 70/30 compositions exhibited the highest elongation at break values in both directions. overall, based on the results, it is clear that the elongation at break was not increased due to the presence of additives, except for in a few cases where this increase was insignificant. a) 90/10 pla/starch foils b) 80/20 pla/starch foils c) 70/30 pla/starch foils d) 60/40 pla/starch foils e) 50/50 pla/starch foils figure 3: thermograms of 90/10 (a), 80/20 (b), 70/30 (c), 60/40 (d) and 50/50 (e) pla/starch foils in the presence and absence of castor oil-based additives figure 4: comparison of the degrees of crystallinity between the different pla/starch compositions the effect of castor oil additives on pla/starch foils 51(2) pp. 35–41 (2023) 39 figure 5: tensile strength of pla/starch foils at 25 and -25 °c figure 6: elongation at break of pla/starch foils at 25 and -25 °c nagy, miskolczi and eller hungarian journal of industry and chemistry 40 4. conclusions the aim of the study was to investigate the effect of castor oil-based additives produced using two techniques on the properties of pla/starch films. the impact tests were studied through tensile tests and dsc analysis. based on the dsc tests, it was established that as the starch concentration was increased, the degree of crystallinity of pla in the blends also increased. considering the glass transition temperatures of the doped and non-doped reference samples, no significant changes could be measured, which led us to conclude that the additives had no effect on the chain mobility of pla. based on the results of the tensile tests, it was established that, with the exception of a few cases, both the tensile strength and elongation at break decreased in the presence of the additives. references [1] jock, a.a.; akpan, m.l.; oluwadayo, f.a.: production and characterization of sand-plastic composite floor tiles, hung. j. ind. chem., 2022, 50(1), 29–32, 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(chemtec publishing, toronto), 2017, pp. 135–164, doi: 10.1016/b978-1895198-97-3.50008-1 [27] espíndola, s.p.; norder, b.; koper, g.j.m.; picken, s.j.: the glass transition temperature of heterogeneous biopolymer systems, biomacromolecules, 2023, 24(4), 1627–1637, doi: 10.1021/acs.biomac.2c01356 [28] li, d.; luo, c.; zhou, j.; dong, l.; chen, y.; liu, g.; qiao, s.: the role of the interface of pla with thermoplastic starch in the nonisothermal crystallization behavior of pla in pla/thermoplastic starch/sio2 composites, polymers, 2023, 15(6), 1579, doi: 10.3390/polym15061579 [29] askadskii, a.a.; matseevich, t.; popova, m.; kondrashchenko, v.i.; qi, s.c.: calculation method for predicting polymer compatibility: estimation of microphase compositions from glass transition temperatures, adv. mat. res., 2014, 1033-1034, 948–953, doi: 10.4028/www.scientific.net/amr.10331034.948 [30] brostow, w.; chiu, r.; kalogeras, i.m.; vassilikoudova, a.: prediction of glass transition temperatures: 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process g. gulyás , á. kárpáti university of pannonia, institute of environmental engineering, egyetem street 10, hungary e-mail: g.gulyas.up@gmail.com during my work i analyzed a wastewater purification plant, which clears mostly industrial wastewater. the experimental reactor i planed and created was similar to the purification plant regarding basic parameters and the wastewater i would clean regularly came from the purification plant. my purpose was to develop a purification process, achieving minimal pollution components in the wastewater. keywords: wastewater, sequencing batch reactor, active sludge, cod, nitrogen introduction after joining the eu regulations on most economic areas have been tightened up. one of their most important purposes is to raise level of environmental protection as well as to improve human standard of living. in accordance with these regulations strict quality assurance and environmental protection rules have been introduced; their negligence or default in production and service branches are punished with serious fines or even closure by the authorities. it certainly refers to the companies which deal with collecting and processing animal waste. there are also tight regulations both for finished products quality and for treating waste coming from processing, and their making harmless, too. in hungary most people make a grimace when those cargos are mentioned which carry animal carcass. they are considered stinky and slow going vehicles and if you meet them you should take over or follow them far. now give it a second thought. these vehicles serve to protect inhabitants and environment. without them animal waste could not be placed and processed safely since carcass pits do not give proper and safe solution to the problem. drivers of these vehicles are liable to the smell, moreover they have to pass special driving exams, and their duty is to collect and transport animal waste to a processing plant. during process of animal waste other harmful waste arise which needs special treatment. in my study i am examining the waste water purification in laboratory, which originates from a hungarian animal waste salvage unit. this waste water contains high amount of organic substance and nitrogen; their disposal is substantial for the recipients’ interest. i examined the removal of these components at different temperatures in order to find the optimal condition which gives the best result in purification. experimental reactors the system is built up of four, separated reactors (number 1, 2, 3, 4). their construction is the same, the only one difference is the temperature inside the reactors. these reactors are all sbr systems, so they function fractionally. extraction of organic substances, nitrification and denitrification as well as remove of biological phosphorus is in progress in one space (but certainly not at the same time). intake waste water is in the vessel among the reactors, in which sample material is continuously stirred in order to keep it homogenous. purification process in the reactors is controlled by a central unit, which changes intake, anoxic and oxic circumstances, decantation and pumping at preset times. figure 1: purification reactors the complete process does not only consist of one intake, stirring, airing, decantation and pumping. each case after waste water intake there is a 30 minutes 202 stirring followed by 10 minutes airing. these three steps are repeated 3 times, followed by approximately 60 minutes decantation. it means that a complete purification process takes 8 hours including intake and pumping purified water. the suitable stirring and airing is provided by magnetic stirrers and air diffusers placed at the bottom of the reactors. waste water intake and purified water pumping is done by the pumps, their operation is also controlled by a central unit. altogether there are 14 pumps, 4 of them are responsible for intake and pumping, also 1 pump by reactor feeds alkali. the other two pumps belong to reactors 2 and 3. at the beginning their task was to add needed amount of acid to keep optimal ph level. later we took them out of the system. collecting purified water we have conical flasks with a cork. every reactor has its own ph level and temperature controlling system. temperature is set 20 °c, 25 °c, 30 °c, 35 °c. in case of the first reactor we need cooling, as the laboratory temperature is higher than the set one in the reactor. in case of the other three reactors we need heating to reach the wanted temperature. there are two controllers for the other 4 reactors. each reactor has its own ph sensor, which sends signs to the controllers. according to the signs the pumps, taking the right amount of acid or alkali, is operated. remove organic substances from wastewater it is essential to remove organic substances from waste water, otherwise they would cause lack of oxygen at the recepients’ side and it could kill living organism. remove organic substances is shown in fig. 2. there were problems with the purification efficiency in reactor 1 due to technical faults, in most cases exchange of sludge was needed. the problem was caused by the starter inoculation sludge originated from mátyás-domb wastewater purification plant, where the operational conditions are a bit different, so the sludge needed to adapt. after a while cod measure decreased because we repeated sludge exchange in the reactor. we decided on this action because the amount of organic substances did not decrease after a month of regular operation (30th, september). that is why i did not evaluate the performance in reactor 1 and it is not shown in fig. 2. new sludge arrived, again from the above mentioned mátyás-domb, some weeks later i still did not notice decrease in purification efficiency. it suggests that only the period after sludge exchange is interesting for us. after this action data give clear picture about the 20 °c reactor real purifying performance. the graphs show that after restore the reactor cod in let off water never went over 100 mg/l. time figure 2: chemical oxygen demand (cod) changes in pumped purified water in contrast with reactor 1 the other three reactors operated properly both before and after the exchange. it can be seen that cod rate in purified water varies within a narrow range, there is no extreme case. the most stable and the least changing results are from reactors 3 and 4, while reactor 2 shows bigger fluctuation. only on the ground of measured rate it cannot be identified whether 20°c, 25°c, 30°c, 35°c gives higher level of organic substance remove as cod rates are rather close to each other. comparing the results we cannot find big differences in the efficiency of the reactors’ organic substance remove performance depending on operational temperature. on the base of my experiences i cannot make ranking since there were cases when one of the reactors purified better. however i have to note that it is possible to purify water under limit rate at any temperature, positive load and proper sludge. on the score of bibliography we expected the highest performance from reactor 4 whereas the lowest one from reactor 1. but at such low level load we had different result. supposedly ~100mg/l cod amount is hard to split biologically, so it cannot be removed from waste water even longer period of time. 2nd reactor 3rd reactor 4th reactor c o d (m g/ l) 203 changes of nitrogen forms concentrations waste water arriving at purification plant contains high amount of ammonium ions and organic nitrogen forms. fig. 3 shows measured ammonium concentration in purified water. it can be seen that the most stable results are shown in reactors 3 and 4. it is interesting to observe that reactors operating at 20 °c and 25 °c temperature higher increase in let off ammonium concentration. since all the circumstances, such intake water quality and quantity was the same, differences must be due to different temperatures. the higher the temperature is, the more intensive the functioning of the nitrificating microorganism is. it makes their reproductive ability faster and their amount is more significant. their regular time of hydraulic stay in the system is 12.3 days (due to little intake water), that is why any changes in the system’s operation or let off water quality develops later (2-3 days). supposedly nitrification in reactor 1 capsiced due to increased load (rough waste water content changed) as ammonium concentration was 120 mg/l till then, after that it became more than double. autotrophic volume in the reactor could not oxydate the whole amount of ammonium during time of stay. because of this nitrification stopped after a while, let off water ammonium concentration level was almost the same as intake rough waste water’s nitrate concentration content in purified water went down to zero as well. time figure 3: changes of ammonium concentration level in let off water time figure 4: changes of ammonium concentration level in let off water later i experienced the same situation in reactor 2 as well. only the fall in performance happened later. supposedly the cause is that the higher temperature may be more favourable for autotrophic, so proper rate nitrification went on and ammonium oxygenation stopped only after a while following ammonium load. purifying goes on easier if more microorganisms meets the same amount of nutrients during the same purifying time. in an optimal case when part of nitrogen is taken out from waste water, nitrogen gas develops while the rest is concentrated in the sludge, because nitrogen has an essential role in building of cells. during nitrification ammonium becomes nitrite, then nitrate; during denitrification nitrate develops into nitrogen gas. that explains why it is important to take nitrite and nitrate concentration in purified samples into consideration to evaluate rightly ammonium transformation. improper denitrification might have two causes. one of them is the too short time for anoxic process, the other is the lack of easily splitting nutrients. as it was mentioned above, the optimal cod/tn rate is 10, here it is only 4-5. besides long time of stay helps remove biologically splitting organic substances under oxic circumstances. since organic components rate 1st reactor 2nd reactor 3rd reactor 4th reactor 1st reactor 2nd reactor 3rd reactor 4th reactor n itr at e (m g/ l) a m m on iu m (m g/ l) 204 is low comparing to nitrogen compounds and most of easily splitting organic substances are transformed during airing, denitrification would not happen because of missing nutrients. more load of rough waste water does not help either, since all happens during anoxic phase, in oxygen-free circumstances. except for reactor 3 let off nitrogen concentration from other reactors show the tendency which we could conclude from the amount of ammonium. that is, if ammonium concentration level decreases in purified water, the nitrate content grows. reactor 3 showed the most stable nitrification. during the experiment this reactor let off purified water contained minimum amount of ammonium in each case, while its nitrate content moves within wide ranges. its reason could be the different content cod and n of intake waste water. in practice measuring nitrite concentration is given little interest. although nitrite in purified water also gives important information. considering nitrite reactor 1 showed high rates. if we compare it with nitrogen results it can be seen that nitrification was limited at the beginning of examined period (from 7th to 30th, september), while ammonium was high. nitrification was partial because let off water contained 200–300 mg no3 -–n. according to bibliography high nitrite concentration hinders nitrification so it could have happened so. if we examine let off water organic substance content we can see that filtered cod level was also high so we may suppose that high nitrite concentration strikes on the functioning of heterotrophic organic oxidants. in the other reactors the nitrite concentration was not so high usually under 10-100mg/l. further examination showed that nitrite concentration and cod are related in case nitrite concentration is over 50 mg/l. certainly differences were not very big, they showed only some 10 mg/l cod increase. however, we measured filtered samples, that is why we cannot have false measure due to floating substances. furthermore all 3 high nitrite concentration paralleled with high let off cod than before it suggests positive conclusion. it should be examined during further experiments. references 1. l. l. blackall, g. a. ekema, p. c. griffiths, á. kárpáti, h. kroiss, k. c. limdrea, e. morgenroth, r. j. seviour, k. svardal, m. c. wentzel, p. a. vilderer – szerk. dr. kárpáti á.: eleveniszapos szennyvíztisztító rendszerek és ellenőrzése, ismeretgyűjtemény no.2, veszprémi egyetem, környezetmérnöki és kémiai technológiai tanszék, veszprém, 2002 2. i. illés: ipari szennyvíztisztítás: ipari szennyvizek keletkezése és tisztítása, tankönyvkiadó, budapest, 1972 3. l. hartmann, n. jardin, r. kaiser, g. schön – szerk. dr. kárpáti á.: a szennyvíztisztítás fejlődése a xx. században, az eleveniszapos szennyvíztisztítás fejlesztési irányelvei, ismeretgyűjtemény no.1, veszprémi egyetem környezetmérnöki és kémiai technológia tanszék, veszprém, 2001 4. w. fresenius, w. schneider: waste water technology, origin, collection, treatment and analysis of waste water; berlin, london, paris, tokyo, new york, 1989, isbn 0387174508 microsoft word 2012_dr_bodor_endre_hjic.doc hungarian journal of industrial chemistry veszprém vol. 39(3) pp. 401-406 (2011) influence of cooling profile on the product properties in cooling crystallizers a. borsos , b. g. lakatos university of pannonia, department of process engineering, h-8200 egyetem street 10, hungary e-mail: borsosa@fmt.uni-pannon.hu batch cooling crystallization process is investigated using different cooling procedures through mathematical modelling and computer simulation. the main element of the mathematical model is the population balance equation which contains both process and kinetic parameters. in the mathematical model of crystallizer the population balance equation is completed with the ordinary differential equations governing the mass balances of solute and solvent, as well as the heat balances of the crystalline suspension and the cooling medium. from the population balance model a set of differential equations was obtained for the first four moments of the size variable of crystals and the mass and heat balances, and the resulted equation system was solved in matlab environment. the dynamic properties and behaviour of the crystallizer depending on the cooling procedures was studied by numerical experimentation the results of which are presented and analysed. keywords: cooling crystallization, population balance model, moment method, cooling method, simulation. introduction crystallization is an important unit operation of chemical and process industry and it is a suitable method for formulation of solid particles, and separation and purification of chemical components. in industrial practice there exist special demands for well-designed crystalline products what requires developing more precise operation methods. batch cooling crystallization is an often used method in industry, especially in the pharmaceutical industry hence well designed and operated batch processes seem to have great advantage in producing appropriately tailored crystalline products. naturally, the detailed knowledge of these processes provides an elementary requirement for success. investigation by properly constructed mathematical models is a feasible tool for process design of crystallization. the balance equations which contain process and kinetic parameters as constitutive expressions are coming into view by development of computer science and technology. in the case of crystallization the fundamental balance equation describes the behaviour of crystal population by means of which the size distribution of crystals and dynamics of crystallizer can be investigated [1-5]. the population balance equation is often solved by applying the moment method [6-8]. the moment equations of low order moments describe some important properties of crystals such as the number of crystalline particles, the total crystal volume in solution, the size distribution and mean crystal size of the product. a well designed moment equation model beside the properties of crystalline population involves information also on the mass and heat balance and dynamics of crystallizer. the aim of this paper is to investigate the effects of cooling procedures of a batch cooling crystallizer on the properties of crystalline product by using a suitable model. the population balance equation is completed with the mass and energy balances and is converted into the set of moment equations for the first four moments having physical meaning. the properties of the crystalline product and dynamic behaviour of the crystallizer, obtained by numerical experimentation carried out by using a computer program in matlab environment are presented and analysed. population balance model the population balance equation which describes the kinetic and transport processes in a perfectly mixed crystallizer is written in the following form: ( ) ( ) ( ) ( ) ( )[ ] ( )s in s cclb tlntln v q l tlncclg t tln ,, ,,,,,, 0+ −= ∂ ∂ + ∂ ∂ (1) where g denotes the growth rate of crystals, n is the population density function, l stands for the crystal size, and c and cs are, respectively, the concentration of solution and the equilibrium solubility concentration. further, in eq. (1) q is the volumetric flow rate, v means the volume of suspension, and the variable b describes the nucleation process. 402 ( ) ( ) ( )sbbspps cclbecclbecclb ,,,,,, 000 += (2) where l0 denotes the size of nuclei, bp and bb are the primary and secondary nucleation rates while ep and eb are binary existence variables by means of which the primary and secondary nucleation rates, depending on the actual process conditions can be selected . the mass and energy balance equations are part of the mathematical model. these equations are required to complete the population balance equation to obtain a full crystallizer model for determining and calculating the cooling profiles. the mass balance of solute is governed by the following equation ( )[ ] ( )[ ] ( )[ ]c cininin c c v q c v q dt cd ρεε ρεε ρεε −+− −+= −+ 1 1 1 (3) where ε is the volumetric ratio of solution, ρ is the density. the mass balance equation of solvent is ( ) ( )svinsvin sv cc v q dt cd εε ε += , (4) while the heat balance consists two equation. one of those is the heat balance of suspension ( ) ( )[ ] ( ) ( )[ ] ( ) ( )[ ] ( ) ( ) mcch cccsvsv inccinincinsvsvin cccsvsv rhttua tccccc v q tccccc v q dt tcccccd δ ρεε ρεε ρεε −+−− −++− −++= −++ 1 1 1 , (5) where parameters c are the heat capacities of crystals and solvent, t is the temperature of suspension and u is the overall heat transfer coefficient. the second equation expresses the heats balance of fluid in the cooling jacket: ( ) ( ) ( )h h hinh h h hh hhh tt v uavtt v q c dt tcd −+−= ,ρ ρ (6) the volumetric ratio of solution ε is related to the total volume of crystals in a unit volume of suspension as ( )∫ ∞ −= 0 ),(1)( dltlnlvt cε (7) where vc(l) denotes the volume of a single crystal having linear size l expressed as ( ) 3lklv vc ⋅= (8) where kv denotes the volume shape factor. the mathematical model of the crystallizer consists of the partial differential equation (1) and the set of ordinary differential equations. (3)-(6). it can be solved by using the boundary conditions 0,0),(),,(lim 0 ≥= → ttlnlccg sll (9a) 0,0),(lim ≥= ∞→ ttln l (9b) and the appropriately specified initial conditions. bc (9a) denotes that there is no crystal flux through l=0, while the bc (9b) assures the absence of too large crystals. moment equation model the properties of crystalline particles in the crystallization process and behaviour of the crystallizer are determined by the population balance model (1)-(7). numerical solution of the population balance equation (1) is a complex time consuming procedure but the moment method provides an alternative way of treatment of problem. this method is widely used in modelling of disperse systems. the moment method is a suitable one for computing and investigating the behaviour of a number of parameters characterizing the crystal size distribution such as the particle number, mean crystal size and dispersion of the crystal population. besides, this method provides also a way for approximating the crystal size distribution. the moments of the crystal size variable l weighted by the population density function are given as ...2,1,0,),()( 0 == ∫ ∞ kdltlnlt k kμ (10) where k=0,1,2,3,… denotes the order of moment. taking eq. (8) into consideration the total volume of crystals in a unit volume of suspension is expressed by means of the third order moment μ3 as ∫ ∞ == 0 3 3 ),()()( dltlnlktktv vvc μ (11) therefore the mass and heat balances can be formulated by means of the third order moment of the linear crystal size using the relation (7). the third order moment can be determined from the following infinite hierarchy of moment equations ( ) bbppin bebe v q dt d ++−= 0,0 0 μμμ (12a) ( ) ...3,2,1,1, =+−= − kkg v q dt d kkink k μμμμ (12b) using the sequence of equations for moments μ0, μ1, μ2 in turn. as a consequence, the ordinary differential equations for moments μ0, μ1, μ2 and μ3 together with the mass and heat balance equations (3)-(7) provide a closed model consisting only of ordinary differential equations, representing, in principle, a dynamic system governing the behaviour of continuous cooling crystallizers. this system of equations involves also the models of batch cooling crystallizers taking the volumetric flow rate zero in all differential equations, i.e. q=0. then the 403 whole process is determined by the initial conditions and the cooling rate controlled by eq. (8). scaling the moment equation model needs scaling of variables for numerical solution since there are differences of several orders of magnitude between the kinetic rates of nucleation and crystal growth and, consequently, between the values of moments. the rates of temporal changes of the moments can be reduced to similar orders of magnitude by defining suitable scaling factors [8]. applying these scale factors g ctgv sskks 333 00 6: −−= , g ctgv sskks 222 01 6: −−= g ctgv sskks −−= 1 02 3: , vks =:3 , }max{ 1: c sc = { }t st max 1:= , v sv 1 = , {}tst max 1 = where st, sc, st and sv can be chosen arbitrary, we introduce the following set of dimensionless variables vsvtstsztsz csycsycsymsx vththt scscsvcsvmmm ==== ===== ,,, ,,,3,2,1,0, ξ μ and scaled parameters ccsρα = , g ctgpvap sskkkd 343 006 −−= bg ctgb j vab sskkkd −−−−= 343 00 16 , r se tg g =β r se tp p =β , r se tb b =β , 00 asb c= , t c s asb 1 1 = 2 2 2 t c s asb = , ht c cs uas =κ , h ct c hs δγ −= ( ) 331 x c cy c cy c cx h c h c sv h sv αφ +⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ +−= by means of which the scaled mathematical model of the batch cooling crystallizer is as follows. moment equations: bbpp ee d dx θ+θ= ξ 0 (13) 0 1 x d dx gθ= ξ (14) 1 2 x d dx gθ= ξ (15) 2 3 x d dx gθ= ξ (16) mass balance for solute: 2 31 x x y d dy gθα ξ − − −= (17) mass balance for solvent: ( ) 2 31 x x y d dy g svsv θ ξ − = (18) heat balance for the crystalline suspension: ( ) g s sg h y yy z xzz d dz ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ − ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −+−−= β φ αγ φ κ ξ exp2 (19) heat balance for the cooling medium: ( ) ( )h hh hinh h h zz v zz d dz −+−= α κν ξξ , 1 (20) in eqs. (13)-(20) the scaled rate expressions of growth, primary and secondary nucleation are: ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ − =θ zy yy g g s s g β exp (21) ⎟ ⎟ ⎟ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎜ ⎜ ⎜ ⎝ ⎛ ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −−⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −=θ s ep app y y kx z d 2 3 ln exp)1(exp β (22) j b s sb abb x y yy z d 3exp ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ − ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ −=θ β (23) the dependence of saturation concentration on the temperature is described by the expression 2 210)( zbzbbzys ++= (24) simulation numerical solution of the set of scaled differential equations (13)-(20) was carried out in matlab environment using the ode solvers. in numerical experiments the temporal temperature profile was simulated using the function [9] ( ) startendstart bn endc bn c prof ttt t t t +− ⎟⎟ ⎟ ⎟ ⎠ ⎞ ⎜⎜ ⎜ ⎜ ⎝ ⎛ + − = 11 , 1 (25) where when fixing the start and end values the shape of the profile was controlled by changing the parameter bn. for illustration some examples of temperature profiles are shown in fig. 1 as a function of the parameter bn. here, for the sake of making possible real comparisons, the profile marked by bn=1.655 was used in all simulation runs. this profile has been chosen optimal when the goal function in optimizing experiments was the mean size value of crystals. further, also for the sake of real 404 comparisons, identical initial conditions were used in all simulation runs given in turn of eqs. (13)-(20): 1.2e-1, 6.2e-2, 3.2e-2, 1.8e-2, 0.1, 8.1, 1.0, 0.2. figure 1: temperature profiles depending on the parameter bn of function (25) the effects of four cooling procedures were studied by applying the temperature profile given by eq. (25) at different places of the thermal system as controlled temperature programs. these are as follows. a this program is called perfect cooling of crystallizer. in this case the temperature of the crystalline suspension was controlled following the cooling profile. b in this case the temperature of the cooling medium in the jacket, assumed to be perfectly mixed, was changed in accordance of the cooling profile. c the inlet temperature of the cooling medium was controlled following the cooling profile. d in this case the inlet temperature of the cooling medium was kept constant temperature 18 °c. the process and kinetic parameters used in numerical experimentation are listed in tables 1 and 2. table 1: process parameters used simulation v=10 m3 vh=3 m3 qin=1.1e-3 m3 s-1 cin=221 kg m-3 qh=1 m3 s-1 csvin=870 kg m-3 tin=95 °c th=20 °c ua=2.1e4 j m-2 s-1 k-1 table 2: kinetic parameters used simulation kg0=4.0e-2 ms-1 g=1, b=3 b0=1.448 kp0=1.6e30 #m-3s-1 ke=5 b1=-0.666 kb0=2.0e25 #m-3s-1 δhc=-4.5e4 j kg-1 b2=0.5548 ρc=1760 kg m-3 ρsv=1000 kg m-3 ρh=1000 kg m-3 eg=3.2e4 j mol-1 ep=1.0e5 j mol-1 eb=6.5e5 j mol-1 fig. 2 shows how the temperature of crystalline suspension depends on the cooling methods (b)-(d). large differences are seen between those. since the properties of the crystalline product and behaviour of kinetic processes, i.e. nucleation and growth of crystals strongly depend on evolution of the temperature of suspension these processes produce products of different quality. figure 2: evolution of the temperature of crystalline suspension for different cooling methods fig. 2 shows that the cooling capacities in the case of cooling methods b) and c) prove to be insufficient to eliminate the temperature rise induced by primary nucleation. fig. 3 presents temporal evolutions of the temperature of cooling medium in the jacket when using the cooling methods (c) and (d). the plots in fig. 3 illustrates well that in the case of method (c) the temperature of the cooling medium achieves practically that of the crystalline suspension increasing rather sharply. this figure gives evidence of that in the case of method c) the heat capacity of the cooling medium is insufficient to cool the system monotonously, i.e. such a method appears to be strongly inadequate. figure 3: temperature histories of cooling medium in the case of the (c) and (d) cooling methods evolutions of the zero order moment μ0 are presented in fig. 4 for different cooling methods. this moment, in principle, provides the total number of crystals in a unit volume of suspension. it is seen well that the method (c) produces about one order of magnitude more crystals than the other methods. histories of the third order moment μ3 which is related to the total volume of crystals in a unit volume of suspension is shown in fig. 5. here significant differences are observed in the transients produced by the cooling methods applied while the final volume of 405 the crystalline product becomes of nearly the same value at the end of the process. figure 4: evolution of the zero order moment μ0, i.e. the total number of crystals in a unit volume of suspension for different cooling methods figure 5: evolution of the third order moment μ3 relating to the total volume of crystals in a unit volume of suspension for different cooling methods fig. 5 shows clearly that in the case of cooling programs a), b) and c) the total amount of crystals in the crystallizer is decreased through some period of time. this phenomenon is the result of the initial condition that the initial temperature of the crystallizer was too high compared with the solute concentration. as a consequence, a part of crystals being initially in the crystallizer dissolve before the crystallization process starts. temporal evolutions of the mean size of crystals l̄23, defined as 2 3 23 μ μ =l (26) are presented in fig. 6. this variable was computed using the actual values of the third order and second order moments. the graphs in fig. 6 illustrate well that the temporal evolutions of the mean crystal size exhibit significant differences in transients in accordance with the changes in time shown in figs 4 and 5. the constant temperature cooling method, i.e. method (d) produced the smallest final mean crystal size of the crystalline product as it was expected. using this processing method nucleation of crystals has become very intensive as it is illustrated by the results in fig. 4. at the same time, the largest mean crystal size was obtained using the method (c) although its advantage over the method (b) proves to be rather small. figure 6: temporal evolutions of the mean crystal size for different cooling methods conclusions a population balance model was developed and applied for a detailed study of batch cooling crystallization. using the population balance equation a moment equation model was obtained for the first four moments of crystal size variable weighted by the population density function. these equations coupled with the mass and heat balances of the crystalline suspension and cooling medium form a suitable model for investigating both the dynamic and steady state behaviour of cooling processes of either continuous or batch crystallizers. for making possible real comparisons of the cooling methods studied well defined cooling profiles were applied in all simulation runs but changing their placing in the thermal processes of crystallizer. the effects of these methods were compared also with those of the natural cooling method keeping the temperature of cooling feedstock constant. the results of numerical experimentation revealed that significant differences could be observed between the numbers of crystals produced by means of the cooling methods studied while the final volumes of crystals have become practically of the same value. this means that nucleation of crystals was the dominant process in the case of all cooling methods. analysing the simulation results presented allows concluding that the product properties can be predicted well computer experimentation the mathematical and computer models developed make possible also of optimizing the system and choosing the optimal cooling profiles for producing crystalline products having the required product properties. 406 acknowledgement this work was supported by the hungarian scientific research fund under grant k 77955 what is gratefully acknowledged. also, the financial support from the tamop-4.2.2-08/1/2008-0018 project is acknowledged. symbols a surface area of heat transfer, m2 b nucleation rate, # m-3 s-1 b kinetic parameter bn optimization variable c heat capacity, j kg-1 k-1 c concentration, kg m-3 da dimensionless parameter e energy, j mol-1 e binary existence variable g growth rate, m s-1 δh crystallization heat, j kg-1 k kinetic coefficient kv volume shape factor l size variable, m l0 size of nuclei, m n population density function, # m-4 q volumetric flow rate, m3 s-1 rmc rate of crystallization, kg s-1 s scale factor sc scale factor of concentration t temperature, k t time, s u heat transfer coefficient, j m-2 s-1 k-1 v volume, m3 xk dimensionless kth order moment y dimensionless concentration z dimensionless temperature greek symbols α dimensionless parameter β dimensionless parameter ε volumetric ratio of solution κ dimensionless parameter γ dimensionless parameter θ scaled (dimensionless) growth rate μk kth order moment ξ dimensionless time ρ density, kg m-3 indices b secondary nucleation c crystal g growth h cooling phase in inlet p primary nucleation s equilibrium saturation concentration sv solvent references 1. a. d. randolph, m. a. larson: theory of particulate processes, academic press, new york (1988) 2. n. s. tavare: industrial crystallization. process simulation, analysis and design. plenum press, new york (1995) 3. mersmann a. (ed.): crystallization technology handbook, marcel dekker, new york (2001) 4. d. ramkrishna: population balances, theory and applications to particulate systems in engineering, academic press, san diego (2000) 5. b. g. lakatos, cs. mihálykó, t. bickle: modelling of interactive populations of disperse systems, chemical engineering science 61 (2006) 54–62 6. b. g. lakatos: population balance modelling of crystallization processes, hungarian journal of industrial chemistry 35 (2007) 7–17 7. zs. ulbert: investigation and modelling of dynamic processes of crystallizers (in hungarian). phd thesis, university of veszprém, veszprém (2002) 8. b. g. lakatos, t. j. sapundzhiev, j. garside: stability and dynamics of isothermal cmsmpr crystallizers. chemical engineering science, 62 (2007) 4348–4364 9. á. borsos: modelling and optimizing cooling crystallizers (in hungarian), msc thesis, university of pannonia, veszprém (2010). << /ascii85encodepages false /allowtransparency false 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice untitled hungarian journal of industry and chemistry vol. 53(1) pp. 67–72 (2025) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2025-08 preliminary evaluation of diclofenac gel and emulgel formulated using bentonite as a gelling agent amal ouamrouche1*, abdelbaki benmounah1 and khaled benyounes2 1 research unit: materials, processes and environment, faculty of technology, m'hamed bougara university of boumerdes, frantz fanon city, boumerdes, 35000, algeria 2 laboratoire génie physique des hydrocarbures, faculty of hydrocarbons and chemistry, m’hamed bouguara university of boumerdes, avenue de l’indépendance, boumerdes, 35000, algeria in this work, a bentonite from maghnia (northwestern algeria) was used as a gelling agent in gel and emulgel formulations. the percentage of na-bentonite in the formulations was fixed at 5%. the physical appearance of the formulated gel and emulgel was characterized before determining their ph, viscosity and swelling index. a rheological analysis demonstrated the characteristic shear thinning and viscoelastic behavior of the formulations using thixotropy. stability studies showed that the physical appearance and rheological properties of the prepared gel and emulgel remained unchanged having been stored for 3 months. an ftir study proved that the drug and excipients are compatible with each other. the prepared formulations exhibited acceptable physical properties as well as levels of homogeneity, consistency and viscosity. the ph fell within an acceptable range of 6.40-6.80. keywords: bentonite, formulation, gel, emulgel, rheology, diclofenac 1. introduction bentonites, formed by the weathering of volcanic tuff and ash, consist mainly of montmorillonite, containing varying amounts of other minerals like quartz, calcium and sodium feldspar. they are a type of clay mineral that is composed mainly of montmorillonite, which is a layered silicate mineral and its chemical formula is (na,ca)0.33(al,mg)2si4o10(oh)2 x nh2o [1]. in general, bentonites are classified into two types: na-bentonite, which has a high swelling capacity, and ca-bentonite, which is a non-swelling clay and forms a colloid very quickly in water [2]. due to their exceptional rheological properties, bentonite suspensions are widely used in different industrial applications such as in pharmaceuticals [3]-[5]. this mineral also contains small amounts of other minerals such as feldspar, quartz and calcite. the composition of bentonite varies depending on the location and geological environment where it is found [2],[5]. bentonite exhibits several unique properties that make it an attractive material in various applications. some of the important properties of bentonite are as follows: • swelling: bentonite can absorb water and swell up to several times its original size. this property is due to the presence of interlayer cations, which are exchanged with water molecules [1]. received: 24 march 2025; revised: 7 apr 2025; accepted: 8 apr 2025 *correspondence: a.ouamrouche@univ-boumerdes.dz • cation exchange capacity (cec): bentonite has a high cec, which is a measure of its ability to exchange cations. this property makes it useful for removing impurities and contaminants from water as well as other liquids [1]. • rheological properties: bentonite exhibits thixotropic and plastic behavior, making it useful as a thickening agent and binder in various applications [1],[6]. bentonite also exhibits good adsorption properties, rendering it useful for removing impurities and contaminants from pharmaceutical products. furthermore, this mineral has several applications in the pharmaceutical industry. it is used as a more environmentally sustainable and inexpensive material. in recent years, based on its high retention capacity as well as swelling and colloidal properties, bentonite has been proposed as a useful material to modify drug delivery. because of their swelling potential, clay minerals can be effectively used to delay (extended-release systems) drug release or even improve drug solubility. zheng et al. investigated the interaction between ibuprofen and montmorillonite clay [4], while park et al. studied the intercalation of donepezil, a well-known drug for treating alzheimer's disease, in montmorillonite [7]. other examples of drugs effectively carried by clays include nicotine and timolol [8]. compared to all the clay https://doi.org/10.33927/hjic-2025-08 mailto:a.ouamrouche@univ-boumerdes.dz ouamrouche, benmounah and benyounes hungarian journal of industry and chemistry 68 minerals, montmorillonite has been extensively used in the pharmaceutical field [9]. gels for dermatological use exhibit several favorable properties such as being thixotropic, greaseless, easily spreadable, easily removable, emollient, nonstaining, compatible with several excipients and soluble or miscible in water. emulgels are emulsions, with either oil-in-water or water-in-oil high patient acceptability since they possess the previously mentioned advantages of both emulsions and gels. therefore, they have been recently used to deliver various drugs to the skin [10]. the aim of this work was to create a gel and emulgel formulation using a bentonite modified in algeria [5] as a gelling agent with a low quantity of carbopol 940. the stability of this type of gelling agent was studied from the prepared gel, that is, an emulgel. their organoleptic properties were investigated by visual aspect and microscopic analysis as well as the rheological properties of the prepared gel and emulgel evaluated over 3 months. 2. experimental 2.1. materials and methods bentonite was collected from hammam boughrara (algeria) and provided by bentol; benzoic acid, propylene glycol (pg) as well as diclofenac were purchased from sigma-aldrich; while carbopol 940 and liquid paraffin were obtained from clcm labs. 2.2. preparation of na-bentonite and semisolid formulations bentonite was activated using 4% na2co3 [5]. the semisolid formulations were prepared with diclofenac sodium. adequate preformulation studies were conducted in order to optimize the concentration of the excipients based on visual changes in their appearance, microscopic evaluations and any alterations to their physical characteristics prior to manufacturing the final formulations. the compositions of the final optimized formulations are shown in table 1. 2.3. manufacturing process of emulgel the drug was dissolved in pg before being added to the aqueous phase. the oily phase was added to the aqueous phase and homogenized at 6000 rpm using a high shear homogenizer (hr-500d, faithful). the formulation was then cooled to room temperature while mixing continuously to form a smooth emulsion [10]. in addition, the gel portion was prepared by dispersing 5% bentonite in water at room temperature and mixing until a homogeneous dispersion was obtained before carbopol 940 (0.25%) was added. the emulsion was then gently mixed with the gel in a 1:1 ratio to obtain the emulgel. 2.4. manufacturing process of the gel the gel formulation was made by slowly dispersing bentonite in water while stirring continuously and allowing the dispersion to hydrate for 60 minutes before adding carbopol 940 to form an ameliorate texture. the drug was dissolved in a suitable amount of pg before being transferred to the container and continuously stirred until a homogenous gel was produced [11]. 2.5. microscopic evaluation a microscopic evaluation by polarized light microscopy was used to evaluate the formulations. a small amount of each product was placed on a glass slide and spread evenly using a coverslip. the formulations were observed under a bright-field microscope using a 40× objective and photomicrographs recorded using a hund microscope (h 600 wilo-prax pl bino). 2.6. ph measurements a ph meter (hi 2210 ph meter, hanna, france) was calibrated using buffered standards of ph 4, 7 and 10. approximately 10 g of each formulation was placed in a suitable container and tapped to remove entrapped air. the ph of all the formulations was recorded before washing the probe with deionized water and 70% v/v ethanol after each measurement. 2.7. fourier-transform infrared analysis the spectroscopic analysis was conducted using an iraffinity-1s fourier-transform infrared spectrometer (ftir) equipped with a shimadzu dlatgs (deuterated l-alanine doped triglycine sulfate)-type detector within the range of 4000-400cm-1 and a diamond cell to allow direct analysis. 2.8. rheological characterization the rheological behavior of the different formulations was evaluated by using a stress-controlled rheometer (haake rheostress 1). the equipment consisted of a table 1: composition of the two formulations gel and emulgel ingredients emulgel (%w/w) gel (%w/w) diclofenac sodium 1.00 1.00 propylene glycol 5.00 5.00 bentonite (4% na) 5.00 5.00 carbopol 940 0.25 0.25 liquid paraffin 7.50 benzoic acid 0.25 0.25 purified water q.s. to100% q.s. to100% preliminary evaluation of diclofenac gel and emulgel 53(1) pp. 67–72 (2025) 69 multi-stage peltier module and a 25 mm sandblasted parallel plate. in order to maintain the temperature of the formulations during the experiments at 32± 0.1 °c and prevent any possible evaporation, the measuring system was equipped with a standard tr9 spindle and a thermo haake p5 ultrathermostat to simulate skin temperature. all measurements were triplicated. for each test, approximately 0.5 g of a sample was placed on the lower plate before slowly lowering the upper plate to achieve the preset gap of 100 microns. in order to characterize their rheological behavior, each sample was subjected to a steady-state flow method (0.1–100 s−1) to characterize their flow properties and obtain viscosity values at low (2.0 s−1), medium (20.0 s−1) and high (75.0 s−1) shear rates. in addition, dynamic oscillatory tests can be used to evaluate the microstructure of a viscoelastic material. after identifying the linear viscoelastic region (lvr) by using the strain sweep for each formulation, a frequency sweep was performed over an angular frequency range of 0.1–100 rad/s in order to understand the viscoelastic nature of the formulations. in order to determine the degree of water absorption, the samples were immersed in water at 37 °c. at scheduled time intervals, the samples were removed and weighed. water absorption was calculated using the following equation: 𝑊𝑎𝑡𝑒𝑟 𝑎 𝑟 𝑡 = (𝑊 − 𝑊 )/𝑊 (1), where wt (g) denotes the weight of the swollen sample at the immersion time 𝑡 and 𝑊 (g) represents the weight of the dry sample (initial sample). the measurements of all the samples were triplicated (figure 1). 3. results and discussion 3.1. visual evaluation and ph measurement of the semi-solid formulations the formulations shown in table 1 were evaluated based on their visual appearance (table 2). the gel formulation was clear and homogenous, while its emulgel counterpart was translucent and homogenous in appearance (figure 2 and 3). the ph of the gel-like emulgel fell within the range of 6.40–6.80 which is considered acceptable to prevent any irritation when applied to the skin [9],[10],[12]. 3.2. microscopic evaluation the two formulations were evaluated under a microscope using a 40× objective. the microscopic pictures (figure 4) of the gel formulation show that diclofenac was dissolved and no crystals of api visible. in the case of the emulgel formulation, typical globules were visible under the microscope but no crystals of the drug were present. 3.3. rheological characterization understanding the rheology of the semi-solid formulation is important because it may have an impact figure 2: gel figure 3: emulgel table 2: visual aspect of the gel and emulgel formulations formulation emulgel gel aspect homogenous homogenous microscopic examination stable stable ph 6.40 6.80 viscosity (cp) 42.454 35.121 figure 1: water absorption of the gel and emulgel ouamrouche, benmounah and benyounes hungarian journal of industry and chemistry 70 on the way the therapeutic agent is applied and delivered. therefore, research was conducted to determine how different processing parameters or stressors affected the rheological characteristics of the semi-solid formulations [10],[13]. flow curve (viscosity vs. shear rate) as seen in table 3, the viscosity of the emulgel was found to be higher. the two semi-solid formulations were found to be characteristically shear thinning and nonnewtonian as the shear rate increased. therefore, at low shear rates, the formulations were highly viscous, representing its initial physical stability/firmness before use. as the shear rate was increased, the viscosity of the formulation quickly decreased, indicating its ease of spreadability upon application of the formulation topically [10]. linear viscoelastic response figure 5 shows that the gel and emulgel formulations exhibited similar viscoelastic behavior when subjected to increasing strain with the storage modulus (g’) greater than the loss modulus (g’’). this shows that cohesive forces were heavily predominant in the microstructure of the formulations, facilitating easy application on the skin without any dripping off. thixotropy figures 6 and 7 show the entire rheograms (shear stress vs. shear rate) of the gel and emulgel formulations. as seen in the figures, the gel and emulgel formulations exhibited shear-thinning behavior since the viscosity (the gradient of the curve) decreased as the shear rate increased. as the shear stress increases, the normally disordered molecules of the gelling material align their long axes in the direction of flow. such an orientation reduces the internal resistance of the material, thereby decreasing the viscosity. the figures also indicate thixotropic behavior where the down curve was displaced with regard to the up curve, showing that at any shear rate on the down curve, a lower shear stress was observed than on the up curve. therefore, a hysteresis loop formed between the two curves. thixotropy, or time-dependent flow, occurs because the gel or emulgel formulations require a finite time to rebuild their original structures that break down as a result of continuous shear measurements. it is noteworthy that thixotropy is a desirable characteristic in pharmaceutical preparations, both in terms of engineering design and consumer application, in order to deliver an initially thick product figure 4: microstructure of the gel (a) and emulgel (b) figure 6: rheogram of the gel formulation figure 7: rheogram of the emulgel formulation table 3: flow of the gel and emulgel formulations at low, medium and high shear rates shear rate (s-1) viscosity (cp) emulgel gel low at 2.0 42.352 29.188 medium at 20.0 12.997 3430 high at 75.0 4352 1320 0,1 1 10 100 10 0 10 1 10 2 10 3 10 4 10 5 g ' e t g " g' emulgel g" emulgel g' gel g" gel frequence angulaire (rad/s) pa figure 5: linear viscoelastic response preliminary evaluation of diclofenac gel and emulgel 53(1) pp. 67–72 (2025) 71 as a thinner, easily spreadable material. these findings are in agreement with mohamed magdy who prepared a chlorphenesin emulgel using two types of the gel forming materials [12]. 3.4. stability of the studied formulations the prepared formulations were found to be stable after having been stored for 3 months, during which no change was observed in their physical appearance, ph or rheological properties. the swelling of the formulations was studied at ph 7.2 at room temperature. all the formulations exhibit almost 100% swelling. although the gel swells slightly more than the emulgel, the difference is insignificant. 3.5. ftir analysis the ftir spectra of the gel and emulgel formulations are shown in figure 8. ftir spectroscopy revealed that the various vibrations between the functional groups of the different bonds in the two formulations are similar. all the characteristic peaks exhibit vibrations due to varying functional groups that represent common components of the two formulations and indicate the absence of any overlap between the peaks. the ftir spectra of the formulations show a large peak at 3400 cm-1, which is associated with the stretching of the o–h groups as well as hydrogen bonding. the peaks at 2933 and 2850 cm-1 can be attributed to ch–(17) stretching. the peak at 1730 cm-1 corresponds to c=o stretching. therefore, the excipient and drug are compatible with each other in both formulations, moreover, the gel and emulgel formulations are stable [9]. 4. conclusions by developing and evaluating emulgel and gel formulations, it was concluded that activated bentonite is a good vehicle for semi-solid formulations. organoleptic and sensory analyses were performed with visual verification of their color, odor, appearance and texture. the averages of the results were calculated to determine the ph of the formulations. it was observed that the ph of the gel and emulgel formulations were within a range suitable for skin application. a rheological study revealed the thixotropic behavior of the gel and emulgel formulations. the semi-solid formulations with diclofenac sodium prepared in this study were found to be stable and exhibited characteristic rheological behavior, which was found to be favorable for topical application. in addition, bentonite modified in algeria exhibited acceptable gelling properties and is a more environmentally sustainable as well as inexpensive material. references [1] berillo, d.; ermukhambetova. a.: the review of oral adsorbents and their properties, adsorption, 2024, 30(6), 1505–1527, doi: 10.1007/s10450-02400515-1 [2] hassan, m.s.; abdel-khalek, n.a.: beneficiation and applications of an egyptian bentonite, appl. clay sci., 1998, 13(2), 99–115, doi: 10.1016/s01691317(98)00021-0 [3] aguzzi, c.; cerezo, p.; viseras, c.; caramella, c.: use of clays as drug delivery systems: possibilities and limitations, appl. clay sci., 2007, 36(1-3), 22–36, doi: 10.1016/j.clay.2006.06.015 [4] zheng, j.p.; luan, l.; wang, h.y.; xi, l.f.; yao, k.d.: study on ibuprofen/montmorillonite intercalation composites as drug release system, appl. clay sci., 2007, 36(4), 297–301, doi: 10.1016/j.clay.2007.01.012 [5] ouamrouche, a.; benyounes, k.; benmounah, a.: adaptation and conversion of an algerian bentonite for specific use, alg. j. env. sci. technol., 2023, 9(4), 3407–3413 [6] viseras, c.; aguzzi, c; cerezo, p; lopez-galindo, a.: uses of clay minerals in semisolid health care and therapeutic products, appl. clay sci., 2007, 36(1-3), 37–50, doi: 10.1016/j.clay.2006.07.006 [7] park, j.-h.; shin, h.-j.; kim, m.h.; kim, j.-s.; kang, n.; lee, j.-y.; kim, k.-t.; lee, j.i.; kim, d.d.: application of montmorillonite in bentonite as a pharmaceutical excipient in drug delivery systems, j. pharm. investig., 2016, 46(4), 363–375, doi: 10.1007/s40005-016-0258-8 [8] joshi g.v.; kevadiya, b.d.; patel, h.a.; bajaj, h.c.; jasra, r.v.: montmorillonite as a drug delivery system: intercalation and in vitro release of timolol maleate, int. j. pharm., 2009; 374(1-2), 53–57, doi: 10.1016/j.ijpharm.2 009.03.004 4000 3500 3000 2500 2000 1500 1000 500 0 20 40 60 80 100 t (% ) cm-1 gel emulgel figure 8: ftir spectra of the gel and emulgel formulations https://doi.org/10.1007/s10450-024-00515-1 https://doi.org/10.1007/s10450-024-00515-1 https://doi.org/10.1016/s0169-1317(98)00021-0 https://doi.org/10.1016/s0169-1317(98)00021-0 https://doi.org/10.1016/j.clay.2006.06.015 https://doi.org/10.1016/j.clay.2007.01.012 https://doi.org/10.1016/j.clay.2006.07.006 https://doi.org/10.1007/s40005-016-0258-8 https://doi.org/10.1016/j.ijpharm.2009.03.004 ouamrouche, benmounah and benyounes hungarian journal of industry and chemistry 72 [9] kaur, m.; datta, m.: diclofenac sodium adsorption onto montmorillonite: adsorption equilibrium studies and drug release kinetics, adsorpt. sci. technol., 2014, 32(5), 365–388, doi: 10.1260/02636174.32.5.365 [10] manian, m.; jain, p.; vora, d.; banga, a.k.: formulation and evaluation of the in vitro performance of topical dermatological products containing diclofenac sodium, pharmaceutics, 2022, 14(9), 1892, doi: 10.3390/pharmaceutics14091892 [11] pakhare, a.v.; deshmane, s.v.; deshmane, s.s.; biyani, k.r.: design and development of emulgel preparation containing diclofenac potassium, asian j. pharm., 2017, 11(4), s712–s716, doi: 10.22377/ajp.v11i04.1699 [12] mohamed, m.i.: optimization of chlorphenesin emulgel formulation, aaps j., 2004, 6(3), 26, doi: 10.1208/aapsj060326 [13] ramachandran, s.; chen, s.; etzler, f.: rheological characterization of hydroxypropylcellulose gels, drug dev. ind. pharm., 1999, 25(2), 153–161, doi: 10.1081/ddc-100102155 [14] hidalgo, j.; galambos, i.; turdean, g.; hidalgo, l.: a review of the determination of diclofenac sodium with electrochemically modified sensors in various biological, pharmaceutical and water sources, hung. j. ind. chem., 2024, 52(1), 79–88, doi: 10.33927/hjic-2024-10 https://doi.org/10.1260/0263-6174.32.5.365 https://doi.org/10.1260/0263-6174.32.5.365 https://doi.org/10.3390/pharmaceutics14091892 https://doi.org/10.22377/ajp.v11i04.1699 https://doi.org/10.1208/aapsj060326 https://doi.org/10.1081/ddc-100102155 https://doi.org/10.33927/hjic-2024-10 conferenceproceedr{gs hungarian journal of ll{dustrial chemistry veszprem vol. 2. pp. 711 (2000) going for zero g. gwehenberger, b. erler and h. schnitzer (zeria, zero emissions research in austria, institute of chemical engineering, fundamentals and plant design, graz technical university, inffeldgasse 25, a8010 graz, austria) this paper was presented at the second international conference on environmental engineering, university ofveszprem, veszprem, hungary, may 29june 5, 1999 in this work, we are looking for possibilities to put a zero emission program into action in austria; we present four case studies carried out at austrian companies. a short discussion of the case studies follows: steel production: this enterprise produces steel out of scrap metal. we propose a solution to reuse the waste heat of the smelter exhaust gases for the production of electricity. coating of vehicle bodies: here we are looking for possibilities to close the water cycles of different coating baths and rinses, because the company wants to reduce the chemical oxygen demand (cod) of its waste water. · production of medical infusion solutions: the main emission is waste water in drinking water quality at a temperature of about 40°c. we were able to show that this waste water can be reused as cooling water in a closed loop. mobile dish washer: in the city of graz it is obliged to rent a mobile dish washer at large open air events requiring an official approval. we found a solution to close the water cycle of the "dishmobile". therefore, it can operate a few days without any fresh water supply. keywords: zero emission; cleaner production zero emission research this project is inspired by zeri, the zero emission research initiative at the united nations university unu founded by gunther pauu [1}. the aim of this initiative is the reduction of all industrial emissions to zero. we would like to initiate a zero emission program in austria. in general, waste is nothing more than previously bought raw materials intended for products causing enormous costs. in extension of cleaner production measures we are searchipg for the reasons of this ineffective usage of raw materials and we try to reduce these emissions to zero. definition of zero in zero emissions during our work, we discovered that zero must not be interpreted as zero in a chemical analytical sense. if the concentration and the total mass flow of a substance in an emission are smaller than natural fluctuations in geogenic flows, we will assume that there is not any impact on the environment. we call these emissions "zeroemissions". the input of any process has to be considered as well. the usage of renewable resources must not exceed the natural rate of replenishment. if non-renewable resources are used, the yearly exploitation must not exceed a quantity, which guarantees future generations further chances of development. for further considerations a way to measure zero has to be found. a possibility to measure the potential impact of an emission on the environment is the calculation of the sustainable process index (spi) (2}. the spi concept considers everything leaving a process as an emission, in this sense a product is just an emission later. using the spi, you become aware of typical problems connected with indicators. the problem with the spi, as with all other environmental indicators, is that the available data on dissipation and degradation of substances in nature are still very few and little is known about accumulation factors. now we are mainly interested to establish a zero emission program in austria. in the following case studies we tried to make companies interested in the zero emission concept, we looked for the reasons why there are still emissions and we looked for an approach to zero etnissions within the existing industrial structure in austria. 8 methods our work is based on mass and energy flow analyses [3]. we are comparing all input and output streams of every single process step and the energy and mass streams through the production are followed. the quality of our research depends directly on the completeness and accuracy of the data, so a lot of time has been spent acquiring and crosschecking all available information. a lot of the data we need for carrying out thorough mass and energy flow analyses is not readily available in the companies, especially if they have little to do with product quality, purchasing, sold products or waste disposal. acquiring the data will be even more difficult if third party companies are involved. with the information gathered we carry out mass and energy flow analyses. based on these information we are able to determine where, when and why certain substances become an unwanted emission. with the help of the companies we analyse this information and try to determine where the introduction of cleaner production measures will reduce the usage of raw materials and/or energy. case studies the enterprises in our case studies are all long-standing partners in pollution prevention programs [4j. they already have introduced all easily realisable methods of pollution prevention in their processes. besides technical problems in the realisation of zero emissions, we were confronted with financial, political and legal questions. we were able to propose technical and organisational changes that reduce water and energy consumption. a discussion of the case studies follows. steel and rolling mill marienhiitte gesmbh this enterprise produces steel out of 100% scrap iron. the scrap is molten in an electric arc furnace and auoying ingredients are added, then the molten steel is continuously cast into steel bars. two thirds of the production is manufactured into high grade reinforcing steel using the tempcore heat-treating process in an adjoining rolling mill, the rest is sold as raw material for other steei manufacturers in styria. why is this case study interesting for 'zerla? thete are several reasons why this plant is of special interest to a zero emission program. the most successful zero emissions projects to date are implemented at food and agriculture enterprises [1]. this is a heavy industry plant. we are searching for possibilities to introduce the zero emission concepts into this industrial sector. one of the concepts to archive zero emission is the clustering of industries, where the waste of one factory is sold as raw material to another factory. in this plant. table 1 simplified input/output table of a steel mill output: steel waste water used air solid waste partially sold, reused and recycled input: %out %out %out %out of% of% of% of% scrap iron 85 0 0 15 100 100 100 . 100 water 0 9 90 100 100 100 100 alloying 100 0 0 0 ingredients 100 100 100 100 natural gas 0 0 100 0 100 100 100 100 packaging 0 0 0 100 100 100 100 100 steel is produced out of 100% scrap metal. such a refining process is a necessary step in any clustering of industries. the smelting and refining of steel uses a lot of energy and water. only a very small part of the energy (recrystallization energy) and water can not be found in the final product, but over 85% of all other input materials go into the steel bars and rods. this is an example that energy and input materials must be considered as well for a sustainable industry (see table 1). a very small part of the energy is used as thermal energy for the heating of offices and flats. most of the water is evaporated or decomposed by heat, the rest is reconditioned and reused in the rolling mill. the reconditioning process itself produces a relative small amount of wastewater, which is discharged into the sewerage. results of this case study this is a working plant and changes in the· production process itself are out of the question. the main work was acquiring and evaluating the information necessary for conducting a thorough material and energy flow analysis. on our way to zero emissions, we concentrated our efforts on the reduction of the wastewater and we looked for methods to reuse more of the wasted thermal energy. we were not able to improve the wastewater treatment process with more effective technologies without excessive costs, but we propose a solution to reuse the waste heat of the smelter exhaust gases for the production of electricity. a heat exchanger is installed directly after the cyclone and produces superheated steam at 550°c. this steam drives a turbine to produce electricity. the smelter works as a batch process, this means that the temperature of the exhaust gases changes cyclically. if the smelter is in stand by mode, a gas burner will be used for keeping the exhaust gases at a temperature of typically 650°c. see table 2 and fig.j for more detail. au calculations are based on formula of the vdi warmeadas [.sj, sheet gfl ff. f 17 18~ fig.l apparatus for the reuse of thermal energy (flows: 1 fresh water supply; 2 cooling water; 3 outlet from condenser; 4 to pump (25°c, 0,032 bar); 5 from pump (2soc, 50 bar); 6 from boiler (550°c, 50 bar); 7 from turbine to condenser; 8 air from building; 9 exhaust from heat exchanger (120°c); 10 exhaust to filter (60°l20°c); 11 exhaust to chimney (60°­ l200c); 12 exhaust burner; 13 exhaust from electric arc furnace after cyclone; 14 dust from cyclone; 15 dust from filter; 16 exhaust electric arc furnace (200°l200°c); 17 natural gas supply; 18 air supply processes: c condenser; g generator; w water supply and purification; t turbine; s boiler; b gas burner; m mixing chamber; z cyclone; a water cooling; 0 electric arc furnace; f filter; d deposit for dust) vehicle body coating at chrysler eurostar graz eurostar is a joint venture between "chrysler austria" and "steyer daimler puch fahrzeugtechnik ag & co. kg". eurostar is an automobile manufacturer and many problems implied here are typical for the modern industry. analysis of -the whole emission situation would have been too much, so in agreement with the company the water emissions were investigated. that includes particularly the areas of phosphate coating, cathodic electrodeposition · (ced) and the water treatment plant. why is this case study interesting for zeria? our targets are to find out further possibilities to close the various water cycles within the production areas mentioned above in order to avoid emission. the company was mainly interested in finding out the source of rather high chemical oxygen demand (cod) values and to find a solution to lower them. we were confronted with a lot of very typical problems. data are mainly collected in the view of running the process and production quality. because of this, much information is not available that would be necessary to close the cycles. a large part of the knowledge about the processes is held by the chemical suppliers, this kind of know how in general is sensitive and they hardly provide it. many'substances appearing within the process have their origin in the production of raw materials which were bought. in our case, those are different types of oils and drawing greases. table 2 calculated data for heat exchanger at a steel mill medium input temperature (0c) output temperature (0c) volumetric flow rate (m3 h.j) theoretical possible heat exchange (k:w) turbine power (k:w) cooling load (k:w) mechanical load (kw) exhaust of electric steam arc furnace air 650* 120 139.300 (20°c, 1 bar) -24400 process water 25 550 25,2 +24400 7800 15800 800 9 * '1'o stabilise this temperature the gas burner is necessary, without gas burner the temperature changes cyclically between 200°and 950°c the automotive industry is a very competitive branch, e.g. the payback period prescribed by the major concern of our partner company is half a year, so projects where higher investments are necessary cannot be realised. results of this case study a very detailed mass-flow analysis was carried out. as a result we found that cod-source is the acetic acid separated in ced and an organic solvent used there. the binder in the coating process is a caustic polymer dissolved in acetic acid. the body is immersed in a ced bath, where the paint particles are deposited on the steel surface by means of an electric current. this process releases the acetic acid which must be brought out of the process. this small organic mass flow causes the main part of the cod. most "state of the art" technologies to reduce the organic substances causing cod are realised, like ultra filtration of the ced bath, rinses with filtrate etc. [6]. therefore, any further closing of cycles to reduce the wastewater would increase the cod concentration even if the total amount of wastewater was decreasing, because the amount of acetic acid is a fixed percentage of the used binder. thus, only a complete reengineering of the ced paint and process could reduce the cod within the process. the second possibility to reduce the cod rate in the wastewater would be .an end of pipe treatment. usually bio chemical processes are used to achieve that. however, our partner company releases their wastewater after the chemical water treatment to the sewerage system of the city of oraz, where a public wastewater treatment plant is installed. braun medical, infusion solutions this factory produces medical infusion solutions. the main ingredient of these infusions is desalinated and distilled water, but the largest amount of water is used for cooling purposes. 10 .fig.2 vehicle body preparation (flows: kl-kl3 water goes off with the bodies; dl-dl2 evaporation; 100,5,16,241nput water; 18,19,25,26/46,54/65no input desalinated water; ms,38b,12ab,38a sludges; all other waste water; al-a 7 rinses from other processes. processes: 001,002 cleaning; 003 rinse after cleaning unit; 004 activating process; 005 phosphate coating; 006/007 rinse with desalinated water; 008 chromate passivation; 009-011 rinse; os oil separator; ced cathodic electrodeposition; svl storage vessel) 2 fig.3 simplified water flows (sankey) without cooling pond (for a description of flows and vessels see fig a) why is this case study interesting for zeria? the main emission of this enterprise is wastewater with the quality of drinking water at temperatures of about 40°c. without further measures this temperature is too hot to be discharged into the environment, it is too hot to be used in a closed water cycle and the usable thermal energy is too low to be used in industrial processes. this situation can be found quite often in industries. therefore, we were looking for a way either to reuse the water or the thermal energy in this plant or to use the warm water in other enterprises. results of this case study if we are able to cool the waste water of the autoclave to about 35°c it will be capable of being reused as cooling water in a closed loop without exceeding the time limit for cooling set by the other processes in this company. the fire brigade of the community maria enzersdorf where this enterprise is located would like to have a water pond as a water source in the case of fire. we propose to meet both needs with a cooling pond near the company. fig.3 shows the simplified water flows for the process, fig.4 shows the flow sheet after the changes proposed. in fig.5 the calculated results for the cooling time are given. all calculations were carried out with formulas of the vdi warmeatlas [5], sheet ec9 ff. and ghl and perry's chemical engineers' handbook [7]. mobile dish washer . in the city of graz, it is obligatory to rent a mobile dishwasher at large open-air events requiring an official approval. this "dish-mobile" is a trailer with two industrial dishwashers, one for glasses and tableware and one for kettles, pans etc. the use of glasses and tableware eliminates the need for throw away plates, cutlery and plastic or paper cups. why is this case study interesting for zeria? the idea of washing and reusing used tableware and cutlery for drinking and eating at open-air festivals is a great step towards the reduction of waste. a zero emissions "dish-mobile" would be a great opportunity to bring the idea of zero emissions to the public, our aim is the construction of a "dish mobile" independent of water and mains supply. the practical problems are typical for dosing the water cycle: if water is cycled in a closed loop, the concentration of foreign substances rises. a "r==i] 9-1....:.._1--.11 b fig.4 flow sheet w/o cooling pond (alb resp.) flows: 1 fresh water; 2 demineralised water; 3 recirculated steam; 4 steam; 5 distilled water; 6 product; 7 finished product; 8 waste water; 9 to cooling pond (40°c); 10 from cooling pond (30°c); 11 overflow. processes: a demineralisation; b steam boiler; c distiller; d mixing process; e autoclave; f cooling pond in this case, we were also confronted with questions relating to hygiene and health and with legal problems in case the wash is reused several times after purification. results of this case study in this feasibility study, we found a solution to close the water cycle of the "dish mobile". this solution uses industrial standard units. this "dish mobile" could operate 18 hours continuously at a throughput of 800 plates per hour without any fresh water supply. in addition, a diesel power generator could be used to ensure the independence of a mains supply, the heat of exhaust gases would be used for preheating the wash water. however, this solution was rejected because at nearly every event you will have music and therefore electricity. more details can be seen in fig.6 conclusions and further steps to zero emission improvements in environmental protection will only be possible if the ongoing processes and all mass and energy flows are known. most companies collect a great amount of data for process and quality control, but only a small part of these are usable for carrying out energy and mass flow analyses. a lot of the data necessary for mass and energy flow analyses is not available, either because nobody has asked for it before or because it is sensible information held by third party companies. the main part and the indispensable first step in any energy and mass flow analysis is the collection and evaluation of data. based on this data it is possible to fmd the weak points. we try to eliminate thein with ecological sound solutions as a first step towards zero emission. in some cases, we are not able to improve process steps with more efficient technologies without excessive costs, in other cases other technologies or methods do not exist. 11 90 •··" "' --...small botlle, glass -a-large bottle, glass 70 -xsmall botlle, pe eo -<>-large bottle. pe 150 :."40 lso !max. permissible cooling 20 10 10 20 so 40 50 60 70 cooling water inlet temperatur-.tjmjtai"c fig.5 result of calculation of cooling time &'f1bu·-w gy wg .. 9-~ + fig.6 dishmobile (flows: 1 fresh water from tank; 2 waste water from dishwasher; 3,4,5,6, 7,8 circulated water; 9 reconditioned water in drinking water quality; 10 oil and fat sludge; 11 suspended matter; 12 concentrate; 13, 14, 15 concentrate is used for preliminary washing of dishes. processes: a dishwasher; b plate precipitator; c flotation; d reverse osmosis; e ion exchanger; f activated charcoal absorber; g uv sterilisation; h fresh water tank; i waste water tank) by this way, we are able to determine which areas need further research and development. the most important areas are closing of water cycles, usage of low temperature waste heat, substitution of toxic or indecomposeable substances with renewable and degradable materials. acknowledgement this work is financed by the austrian federal ministry for science and transport austrian federal ministry for the environment, youth and family affairs. references 1. for further information see http://www. zeri. org 2. k:rotschek c. and narodosla wsky m.: ecological engineering, 1996,6,241-258 3. schnitzer h.: chemie jngenieur technik, 1998, 70(1 +2), 64-73 4. sage j.: okoprofit graz 1997, abschlubbericht, stenum, graz, 1998 5. verein deutscher ingenieure: vdi warmeatlas, berechnungsblatter :fl.ir den wlirmeiibergang, vdi verlagsgesellschaft verfahrenstechnik und chemieingenieure, 5. auflage, dusseldorf, 1988 6. gra.f (ed.): abwassertechnik in der produktion, weka augsburg, februar 1998 7. perry h. and green d.: perry's chemical engineers' handbook, 7th edition, mcgrawhill, 1998 page 13 page 14 page 15 page 16 page 17 hungarian journal of jndus1rial chemistry veszprem vol 29. pp. 21-25 (2001) arsenic, zinc and magnesium ion removal from water by nanofiltration, modelling of rejections s. gergely, gy. vatai, e. bekassy-molnar (szent istvan university, faculty of food science, department of food engineering menesi street 44, budapest, h-1118 hungary) received: jun 27, 2000; revised: december 12, 2000 the drinking water sources in some parts of hungary are highly contaminated with arsenic. the recent arsenic removal technologies use chemical treatment combined with filtration, adsorption etc. nanofiltration, which is a relatively new area of membrane filtration, could be suitable for removing arsenic from well water, and in addition it does not require chemical pretreatment. the nanofiltration membranes remove the bivalent ions, therefore the removal of trivalent and pentavalent forms of arsenic could be presumed too. in our measurements the possibility of the nanofiltration of typical bivalent ions (zn, mg) and as (triand pentavalent forms) were examined and compared using model solutions. because of the surprisingly low rejection of as(iti) two oxidation agents (kmn04 and h202) were applied to gain removable as(v). on the base of measurements regression equations were developed to calculate the individual ion rejection. the experimental investigations proved that additive ions in the solution do not influence the individual rejection of a metal ion in this range of concentrations. the joint removal of zn, mg, as(iii) and as(v) ions from south hungarian well water could be well estimated on the base of our regression equations. keywords: arsenic removal, bivalent ion removal, membrane filtration, mmofiltration introduction nanofiltration is a relatively new membrane filtration procedure. at the end of the last decade eriksson [1] wrote that an interesting hybrid membrane area was found, which was suitable to retain multivalent ion and it is s:i:inilar to both ultraftltration and reverse osmosis. even in the middle of the 90's the nanofiltration was not categorised obviously, it was not mentioned at all (bilstad [2}), or referred by another name (ujang and anderson in 1996 called it as membrane softener [3]). the recently valid hungarian standard relating to drinking water (msz 450/1-1989) permits maximum 50 mg/1 arsenic. most of the arsenic-contaminated wells of southern hungary contain four times higher arsenic as it is permitted in the standard. in fact it is not only a hungarian problem. it causes also great difficulties in the vojvodina region (yugoslavia) and concerning this problem janie at al carried out measurements [4}. directives of the european community dealing with drinking water (98/83/ec) valid from 1998 allows 10 mg/1 arsenic. as a condition yf accession to european union. hungarian authority should apply this value too. wayapa [5} made measurements on membrane filtration of arsenic, but he rather examined reverse osmosis. brandhuber and gary f6j carried out pilot plant experiments with nanofiltration of arsenic from drinking water. hagmeyer and gimbel [7] modelled the salt rejection of nanofiltration membranes. cherles (8] removed as(v) ions by different nanofiltration membranes with high efficiency. on the basis of the results of measurements a full scale nanofiltration equipment was established in paris for water treatment (ventesque et al. [9]). numerous researches have studied the arsenic, as the source of soiling material spreading in water and ground, as well. chen et al. [10] have investigated the consequences of illness caused by arsenic species in taiwan. the different kind of the species of arsenic are poisonous in different levels. mester, woller and fodor [11, 12] studied the possibilities of measuring the arsenic species. experimental nanofiltration equipment used for the measurements is shown in fig. 1. the model solution (distilled water with metal ions) was poured into the feeding vessel (1). a high pressure piston pump (2) circulated the liquid on the surface of the membrane (3). in some cases the permeate was led back to the feeding vessel, in other cases it was discharged from the system. the retentate remained in the feeding vessel. the recirculation flow rate was set up by an adjusting-device, which was on the 22 pump cabinet (5), the values were measured by rotameter (7). the pressure was regulated by a setting valve (4). the temperature of the solution was kept constant by using a built-in water cooler (10). a ph meter (type ill 8314) controlled the ph of the solution. 9. ~ 3. 6. 5. ~ 2. fig. 1. laboratory nanofiltration apparatus 1. feed vessel, 2. pump, 3. membrane modul, 4. pressure valve, 5, recycle valve, 6. pressure gauge, 7. rotameter, 8. stopcock, 9. sampling, 10. heat exchanger, 11. thermometer, 12. ph meter. before and after the experiments the equipment was rinsed over by circulating distilled water for 10-10 minutes. the clean water flux and the salt rejection of the membrane were checked after each cleaning procedure. round shaped flat .sheet membranes were used with an active surface of 2xl80 cm2. the parameters of the chosen membranes are collected in table 1. in the model-experiments the concentration of the as, or zn, or mg ions of the feed solution were equal with that of the average well-water doses. the concentrations are shown in table 2. ion as zn mg table 2. amounts of the dosed metals concentration 0,2mg!l 0,6mg/l 60mg/l form the as in the well water appears mostly in as{iti) and partly in as(v) form. using oxidating agent in a proper excess all the as ions can be regarded as as(v) ions. as oxidising agent potassium permanganate and hydrogen peroxide were used. the experiments were carried out under different temperatures, pressures and ph values (table 3). the concentration of as, zn and mg ions in the feed, permeate and concentrate was measured by icp (inductive coupled plasma) method. table 3. operational parameters and levels operational parameters 10 °c temperature 20 oc 30 oc transmembrane pressure drop 5bar lobar 15 bar ph results 5,00 7,00 9,00 results on utc-60 membrane and models the rejection of different ions did not depend on the pressure in the measured range. an increase in the temperature decreased while in the ph increased the rejection. rejection of arsenic in functions of temperature and ph are plotted in fig. 2 and 3, as examples. the comparison of the two figures-shows that the rejection of the arsenic without oxidation is 2 3 times lower than that of the oxidised form. rejection of mg on utc-60 membrane (p=10bar) rejection{%) t(oc) fig. 2. rejection of as (iii) on utc-60 membrane arsenic without oxidation is four times more sensitive to a change in the operation parameters than that of oxidized arsenic. decreasing the hydrogen ion concentration with one unit the rejection of as(ill) increases by 4%, and that of oxidised arsenic, the as(v), by 1 %. considering the influence of the temperature the same difference can be observed: the temperature coefficient of as(iii) in the regression equations is four table 1. characteristics of the examined membranes membrane membrane nacl pure water operational parameters tyjx: producer rejection [%j flux (u:nilh} p (bar] t[ocj ph utc-60 toray/ropur 55 55 15 35 3-11 desal-5 desalination so 58 41 50 4-11 systems times bi her than that of the oxidised arsenic. rejection of zn on utc-60 membrane (jl"10bar) rejection (%) t(oc) ph fig. 3. rejection of as (v) on utc-60 membrane dependence of the rejection of an individual ion on ph and temperature can be well described with a linear regression equation: r =a+ b x t + c x ph, % coefficients of the equations are summarised in table 4. a validity domain of the formula is the measured domain: t = 10 .-. 300c, ph = 5 9, and feed concentration according to table 2. table 4. coefficients of regression functions fit onto the rejections of utc 60 membrane name of ion afconstant as(iii) as(v) zn mg 15,140 85,601 87,880 94,362 b/temperature -0,865 -0,185 -0,263 -0,142 c/ph 4,060 1,060 1,474 0,499 0,937 0,988 0,978 0,996 results on desai d 5 membrane and models on desai d5 membrane similar results were obtained as on utc-60 membrane. rejection of zn and mg ions is shown in fig. 4. and 5, as examples. rejection of as(v) on utc-60 membrane (p=10ber) 100 rejection{%) 30 fig. 4. rejection ofzn on dt:sal d5 membrane experiments carried out with arsenic, zn and mg ions show the same influence of operational parameters {pressure, ph and temperature) on the rejection. values of rejection in the case of mg ion exceed 90% at all adjustment of experimental parameters. rejection of zn 23 depends more sensitively on temperature and ph than that of mg. when the decrease of mg is undesivable, the hardness of water can be increased b additive m salts. rejection of as(lll) on utc..60 membrane (p=10 bar) so rejection(%) 20 30 9 ph fig. 5. rejection of mg on desai d5 membrane dependence of the rejection of individual ions on the ph and temperature could be described with a linear regression equation: r=d+ext+fxph,% coefficients of the equations are summarised in table 5. the validity domain of the formula is the measured domain: t = 10 300c, ph = 5 9, and feed concentration according to table 2. table 5. coefficients of regression functions fit onto the rejections of desai d5 membrane ion d/constant fjtemperature f/ph r::: as (ill) 15,170 -0,818 4,296 0,986 as(v) 93,169 -0,097 0,625 0,988 zn 86,440 -0,230 1,784 0.957 mg 94,980 -0,218 0,694 0,996 model of permeate flux the permeate flux was slightly influenced by the ion content in the measured low concentration range. measured fluxes are shown in fig. 6. flux (llm2h) flux of desai os membram (p=10bar) 10 5 ph fig. 6. permeate flux of desai d5 membrane the permeate flux can be described as a ratio of transmembrane pressure drop and the sum of resistance of the membrane and the boundary layer. in case of model solution the boundary layer can be neglected. 24 therefore the flux is: on the base of the measured data, the resistance of membranes was described by a two-variable linear equation: rm = g + h · t + k · ph the coefficients are summarised in taole 6. the validity of the expression is the measured range: t = 10. -.300c, ph= 5 9 and feed concentration according to table 2. table 6. coefficients of regression functions fit onto the membrane resistance membrane g/constant h/temperature utc 60 0,199 -0,00435 desai d5 0,193 -0,00458 k/ph 0,0055 0,0110 0,947 0,976 if there is an increase in the temperature, the membrane resistance decreases, and consequently, the flux increases. similar influence of the temperature was observed by bilstad [2] in the case of ultrafiltration. the influence of the ph is the opposite on the above parameters. joint retention of ions from well water measurements with model solutions indicated that the retention of a metal ion in "the measured range was not influenced by the presence of another ion or ions. table 7. ion content in well water from south hungary ion as zn mg concentration 214 jlg/l 0,6mg/l 15,8 mgil these results made possible the estimation of the retention of the investigated metal ions using well water. the referring data of the well water are shown in table 7. ion retention calculated from the regression equation was compared with measured retention on desai d5 membrane using well water. the results are collected in table 8. the deviations from the measured results are very low, we think it is supposed that there was no component/material in the well water which could significantly influence the individual retention of the investigated metal ions. the diverse rejection behaviour of as(ill) and as(v) was observed in case of well water too. without oxidation only 25 -30 % of arsenic ions could be filtered out, which show the high proportion of as(ill) besides as(v). after oxidation the as(v) was very wen rejected as it was observed using other nanofiltration membranes. too (gergely et ai [13], bekassy~molnar et al [14]). table 8. measured and calculated rejections using well water, desai d5 membrane ion t[0c] ph rejection% measured calculated as without 20 6,5 47,0 oxidation as after oxidation 20 6,5 94,82 95,29 bykmn04 zn 20 6,5 91,16 93,43 mg 20 6,5 93,86 95,13 conclusions the utc-60 and the desai d5 nanofiltration membranes rejected from model solutions the bivalent zn and mg ions with a high efficiency: 85 95 %. the rejection of non-oxidized as (mostly trivalent ions) was surprisingly low: 15 35 %. the oxidized as, which is in as(v) form could be filtered out with very high efficiency: 80 95 %. there was no influence of oxidising agent on the rejection of arsenic. the influence of transmembrane pressure drop on the rejection could be neglected in the measured range, while the temperature and ph had an influence on the rejection. the membrane resistance slightly decreased with an increase in the temperature, while it slightly increased with an increase in the ph. the individual rejection of zn, mg and as ions and the membrane resistance were described by linear regressions in function of temperature and ph. experimental results proved that additive ion/s in the solution did not influence the individual rejection in the measured range, therefore as, zn, and mg rejection from well water could be estimated on the base of regression equations. even if the well water has very high as concentration (200 mg!l) with proper membrane and operation parameters (low temperature, neutral ph) the ec regulation relating to as concentration in drinking water ( £ 10 mg/l) could be reached in one nanofiltration step. in case of need, the total hardness of the filtered water can be increased by additive lime. acknowledgement the authors express their gratitude to prof. peter fodor, szent istvan university budapest, for the analysis and to the otka foundation (t 026140) for the financial support. a,b,c,d,e,f,g,h,k cp cr symbols constants ion concentration permeate, mg/l ion concentration retente, mg!l in the in the j permeate flux, l/(m2 h) r rejection, r = (cr -cp)/cr x 100,% rm resistance of membrane, l/(m2h bar) r2 square of correlation coefficient dp transmembrane pressure drop, bar t temperature, oc references 1. eriksson p. : nanofiltration extends the range of membrane filtration. environmental progress 7 (1) 1988. 2. bilstad t.: water sci. techn., 1977, 36 [2-3], 17 3. ujang z., anderson gk.: water sci. techn., 1996, 34 [9], 247 4. janic j., conkic l., kinski j., benak j.: water res., 1997, 31 [3], 419 5. wayapa j. j.: arsenic removal by ro and nf membranes. american water works association 89 (10) 102, 1997 6. brandhuber p., gary a. : alternative methods for membrane filtration of arsenic from drinking water. desalination 117, 1-10, 1998. 7. hagmeyer g., gimbel r. : modelling the salt 25 rejection of nanofiltration membranes for ternary ion mixtures and for single salts at different ph values. desalination 117,247-256, 1998. 8. charles p.: elimination de certains micropollutans relargues par les sediments. proceedings of 79. congres assotiation generale des hygienistes & techniciens municipaux (aghtm), budapest, 275289,1999. 9. ventesque c., turner g., babwn g.: nanofiltration from prototype to full scale a ww a 89 (10) 65, 1997 10. chen s-l. dzeng, s.r. yang, m-h. chlu, k.h. shleh, g.-m. wal, c.m.: env. sci. techn., 1994, 28 (5) 877 11. mester z., woller a., fodor p. microchem. j., 1996, 54, 184 12. mesterz., fodc?rp.: j. chrom. a., 1996,756,292 13. gergely s., bekassy-molnar e., vatai gy., biacs p.: membrane filtration as a promising technology for arsenic and heavy metal ion removal from drinking water sources proceedings of the international symposium on energy and food industry, budapest,. 206-211, 1998. 14. bekassy-molnar e., vatai gy., biacs p., godek f.: nanofiltration of drinking water: arsenic and bivalent cation removal. proceedings 8. world filtration congress, brighton, 643-643, 2000. page 23 page 24 page 25 page 26 page 27 hungarian journal of industry and chemistry vol. 52(2) pp. 1–9 (2024) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2024-13 efficiency improvements of solar collectors by turbulence promoters abdelkader lahcene1, nabil benamara1, mohamed benguediab1* and abdelilah benazza1 1 laboratory of materials and reactive systems, department of mechanical engineering, faculty of technology, universite djillali liabes de sidi bel abbes, sidi bel abbes, 22000, algeria due to their sustainability and availability, solar thermal collectors are frequently employed to heat homes. this technique has the advantage of being non-polluting and efficient. the poor thermal efficiency of classic solar air heaters is caused by the low convective heat transfer coefficient between the absorber plate and the circulating fluid. the aim of this research is to determine the optimal configuration of flow d isruptors including their shape, size and distribution in order to streamline the efficiency of the solar collector while maintaining affordable costs. keywords: efficiency, solar collectors, improved turbulence promoters, optimization 1. introduction studies have highlighted the importance of solar thermal collectors for heating homes due to their efficiency and non-polluting nature. the efficiency of solar receivers for thermal applications, like home heating, relies on optimizing the solar angle of incidence as well as convective heat transfer coefficients between the absorber plate and heat transfer fluid [1]-[2]. creating a laminated sublayer on the lower side of the absorber plate can help increase convective heat transfer coefficients and improve the overall performance of solar air heaters [3]-[4]. to tackle this problem, previous research has suggested installing turbulence promoters on the bottom of the absorber plate. this approach aims to disrupt the formation of the viscous sublayer to enhance the thermal efficiency of solar collectors [5]-[9]. previous studies [10]-[12] extensively investigated the effectiveness and feasibility of harnessing solar energy. these studies examined various techniques and advancements to optimize the utilization of this renewable energy source. their findings have significantly contributed to the enhancement of solar technologies as well as led to a deeper comprehension of their performance and practical application. in conclusion, solar thermal collectors are an efficient and environmentally-friendly solution for heating homes. by incorporating turbulence promoters into the absorber plate, the thermal efficiency of solar collectors can be improved as they disrupt the viscous sublayer. received: 3 apr 2024; revised: 22 apr 2024; accepted: 24 apr 2024 *correspondence: benguediabm@gmail.com previous research has played a significant role in the optimization of solar energy utilization, making valuable contributions to its advancement and broader acceptance. a study on improving thermal efficiency in hungary examined home heating using only solar power, including the heat output, storage capacity and cycle timing. it offers ideas for district heating and power generation as well as a workable strategy for heat storage [13]. another study introduced a new sensible heat storage system designed for solar energy using a spiral flow-path layout to improve efficiency. results show superior levels of efficiency compared to traditional systems [14]. a study proposed the use of inclined baffles at the top of a flat solar collector [15]. a heat transfer analysis was conducted using the rng k-ε model and fluent software. the results showed that the best level of heat transmission occurs when the baffles are placed at the bottom of the collector. this configuration makes it possible to optimize the efficiency of the flat-plate solar air collector. using comsol multiphysics 5.4, a performance simulation of a flat-plate solar air collector with rectangular baffles was performed [16]. the intent of this sensor was to heat both air and water. this approach makes it possible to exploit solar energy for different thermal needs. an experimental study conducted by chabane [17] in biskra, algeria focused on the reduction of direct heat losses from a solar air collector. the experimental model included double glazing and enlarged the space between https://doi.org/10.33927/hjic-2024-13 mailto:benguediabm@gmail.com lahcene, benamara, benguediab and benazza hungarian journal of industry and chemistry 2 the double glazing to reduce such losses. experimental results indicated that a reduction in the forward thermal loss of the solar air collector is achieved with the integration of additional glazing. these investigations highlight different approaches to improve the efficiency and reduce the thermal losses of flat-plate solar air collectors. in order to make better use of solar energy in air and water heating, the use of baffles and double glazing are techniques that are often used. in a study conducted by amraoui [18], the solar collector was modeled using computational fluid dynamics (cfd) software to better understand its heat transfer capabilities. ansys workbench was used to model the air intake and manifold in three dimensions, while ansys icem was used to generate the grille. abdi [19] used the finite volume method to investigate the flat-plate solar air collector and used the ansys fluent cfd simulation to solve the system of equations in the computational and thermal analysis of the collector. kumar et al. [20] explored the addition of cylindrical baffles perpendicular to the dynamic airflow between the absorber and the insulation of the flat-plate solar air collector. this configuration aims to increase the convective heat transfer coefficient between the air and absorber, thereby improving the efficiency of the sensor. to enhance the efficiency of flat-plate solar air collectors, an original concept of artificial roughness was introduced to optimize heat transfer by incorporating roughness into the surface of the absorber [21]. in a separate study, trials were conducted to quantify the rate of heat transfer in an airflow channel with different baffle shapes, including triangular, wedge and rectangular designs [22]. this study showed that a triangular baffle offers a significant thermal improvement compared to the other baffles studied. these studies highlight different approaches and techniques such as cfd modeling, the addition of baffles as well as the use of artificial roughness models to enhance the efficiency and heat transfer of flat-plate solar air collectors. an investigation was conducted on the heat exchange characteristics of a fluid flowing in a rectangular conduit equipped with different shapes of baffles such as rectangular, triangular, circular and trapezoidal. the findings showed that raising the height of the baffle contributes to an increase in the nusselt number, indicating an improvement in heat exchange [23]. furthermore, a research investigation was conducted [24] to analyze the thermal-hydraulic properties of a channel fitted with a v-shaped deflector, wherein the angle of inclination varied in relation to the horizon. they found that the highest level of heat exchange is achieved when the baffle is tilted at an angle of 45°. another study on heat exchange in turbulent airflow through a container equipped with one or more baffles was conducted [25]. two baffles were tilted at an angle of 45° in this study, showing that by placing them in opposite positions, the rate of heat exchange increases by up to 6%. other studies have also examined the impact of obstacles and baffles on heat transfer. these studies were conducted both numerically and experimentally, analyzing laminar and turbulent flows. some studies are limited to two-dimensional cases. the objective of these researches is to rationalize the geometric forms of the baffles and understand their effect on heat transfer with regard to the absorber. these researches seek to improve the design of flatplate solar air collectors by employing turbulence promoters and barriers to optimize the efficiency of heat transfer and contribute to a better understanding and optimization of these systems for a more efficient use of solar energy. 2. cfd simulation cfd is employed to examine a two-dimensional solar air heater conduit featuring artificially roughened ribs. the resolution of the conservation equations of mass, momentum and energy is conducted using the finite volume method with the ansys fluent 16.0 software. the analysis is based on several hypotheses: 1. the flow is assumed to be stable, twodimensional and turbulent. 2. the flow through the conduit is considered to be single-phase. 3. the surfaces in contact with the fluid are the walls, which are subjected to a no-slip boundary condition. 4. the fluid within the operating range of the solar heater unit is assumed to be incompressible as variations in density along its width and height are negligible. 5. the air and aluminum absorber plates are assumed to exhibit constant thermophysical properties throughout the analysis (table 1). 6. minor radiant heat losses and other losses are taken into account in this analysis. these assumptions help simplify the problem and focus on the key aspects of flow and heat transfer within the solar heater unit conduit. the simulation results will provide valuable insights into the performance of the system and enable the optimization of the rib design to enhance heat transfer efficiency. table 1: thermophysical properties properties al absorber plate fluid/air ρ (kg/ m3) 2719 1.225 λ (w/m k) 202.4 0.0242 cp (j/kg k) 871 1006.43 μ (n.s/ m2) 1.7894e-05 improvement of solar collectors 52(2) pp. 1–9 (2024) 3 2.1. geometric model a rectangular duct as a calculation domain for the solar heater unit is presented in this study. the dimensions of the duct (figure 1) are its height (h) = 20 mm, width (w) = 100 mm and total length (l) which is divided into three sections: an inlet section (l1), a second test section (l2) and a third outlet section (l3). figure 2 shows three different types of rib shape (triangular, square, semicircular). the influence of the relative roughness height (e/d), relative roughness pitch (p/e) and the reynolds number (re) range of 3500 to 18000 on the system is presented. by choosing these parameters, different configurations are explored and a wide range of operating conditions for solar heaters covered in this study. the objective is to assess how the relative roughness height, relative roughness pitch and reynolds number impact the performance of the system, ultimately optimizing the design of the solar heater unit in order to enhance its heat transfer efficiency. the absorber plate is heated with a constant heat flux (q) of 1000 w/m2 in this study. the geometric dimensions and operating conditions are summarized in table 2. 2.2. mesh generation the accuracy of the results obtained in the numerical simulation essentially depends on the mesh. in this study, the numerical solutions are obtained using a non-uniform mesh structure generated by applying ansys 16.0 software. for the analysis, a grid containing 300,665 cells was adopted after careful verification of the values of the nusselt number and the friction factors. the non-uniform mesh structure of the solar air heating conduit is illustrated in figure 3. a non-uniform grid enhances the resolution of velocity and temperature gradients through the duct, leading to more accurate results. this approach also reduces the computational time required to obtain a convergent solution. the nonuniform mesh structure used in this study will provide reliable and accurate results for heat exchange in the solar air heating duct. 2.3. mesh sensitivity the impact of the mesh size on variations in the nusselt number (nu) and coefficient of friction (fr) are illustrated table 2: geometric dimensions and operating conditions geometric parameters interval duct inlet section: l1 (mm) 245 duct outlet section: l3 (mm) 115 test section of duct: l2 (mm) 280 thickness: e (mm) 1.00 1.14 hydraulic diameter of conduit: d (mm) 33.33 rib pitch: p (mm) 20 10 ratio p/e 14.28 17.14 ratio e/d 0.042 0.030 figure 1: proposed 3d diagram of sah (a) (b) (c) figure 2: proposed sah with three shapes of ribs: a) triangular, b) square, c) semi-circular figure 3: non-uniform wire mesh of the pipe of the solar air heater lahcene, benamara, benguediab and benazza hungarian journal of industry and chemistry 4 in table 3 to demonstrate their sensitivity. it was found that when the grid number (element number) was larger, the relative error of the nusselt number and coefficient of friction was almost zero. 3. governing equations the problem of convective heat transfer in a solar collector, which is equipped with an absorber plate that is artificially rough, is solved using the equations that govern continuity, conservation of momentum and energy. these equations are well-established and can be expressed in the two-dimensional cartesian coordinate system as follows. the flow in the system is considered to be twodimensional and stable, moreover, the fluid is incompressible. additionally, the radiation heat transfer from the conduit into the environment is assumed to be negligible. the continuity equation governing the system is expressed as follows: 𝜕𝑢 𝜕𝑥 + 𝜕𝑣 𝜕𝑦 = 0 (1) the equations governing momentum in the system are provided below: 𝑢 𝜕𝑢 𝜕𝑥 + 𝑣 𝜕𝑢 𝜕𝑦 = − 1 𝜌 𝜕𝑝 𝜕𝑥 + 𝑣 ( 𝜕2𝑢 𝑑𝑥2 + 𝜕2𝑢 𝜕𝑦2 ) (2) 𝑢 𝜕𝑣 𝜕𝑥 + 𝑣 𝜕𝑣 𝜕𝑦 = − 1 𝜌 𝜕𝑝 𝜕𝑦 + 𝑣 ( 𝜕2𝑣 𝑑𝑥2 + 𝜕2𝑣 𝜕𝑦2 ) (3) the energy equation is given by: 𝑢 𝜕𝑇 𝜕𝑥 + 𝑣 𝜕𝑇 𝜕𝑦 = 𝛼 ( 𝜕2𝑇 𝜕𝑥2 + 𝜕2𝑇 𝜕𝑦2 ) (4) 3.1. performance of the solar air heater (sah) by analyzing the thermal and hydraulic parameters, the design of the solar thermal unit can be optimized. 3.1.1. thermal performance using the hottel-whillier-bliss equation described by duffie and beckman [3], the thermal performance of the solar heater units by taking into consideration the heat transfer process within the collector can be evaluated: 𝑄𝑢 = 𝐴𝑐𝐹𝑅[𝐼(𝜏𝛼)𝑒 − 𝑈𝐿(𝑇𝑖 − 𝑇𝑎)] (5) this equation can be written as follows: 𝑞𝑢 = 𝑄𝑢 𝐴𝑐 = 𝐹𝑅[𝐼(𝜏𝛼)𝑒 − 𝑈𝐿(𝑇𝑖 − 𝑇𝑎)] (6) the valuable heat transfer rate resulting from the circulation of air through the duct of a solar heater unit can be determined the following equation: 𝑄𝑢 = 𝑚𝐶𝑝(𝑇0 − 𝑇𝑖) = ℎ𝐴𝑐(𝑇𝑝𝑚 − 𝑇𝑎𝑚) (7) the heat transfer coefficient (h) can be enhanced by implementing various active and passive augmentation techniques that increase its value. this enhancement can be quantified using a non-dimensional form called the nusselt number: 𝑁𝑢𝑟 = ℎ𝐷 𝑘 (8) where 𝐷 = 4(𝐻𝑥𝑊) 𝑝 (9) for a slick (smooth wall) conduit of a solar heater unit, the nusselt number can be determined using the dittus-boelter equation [26]: 𝑁𝑢𝑠 = 0.023𝑅𝑒0.8𝑃𝑟0.4 (10) 3.1.2. hydraulic performance the drop in pressure (δp) indicates the energy consumption of the fan necessary to propel the air across the conduit and is related to the hydraulic performance of a solar heater unit. for a fully developed turbulent flow in a pipe where re = 50,000, the drop in pressure can be calculated as: 𝑓𝑟 = (∆𝑃/𝐿)𝐷 2𝜌𝑣𝑈2 (11) for a slick conduit of a solar heater unit, the friction factor can be determined using the blasius equation [27]: 𝑓𝑠 = 0.0791𝑅𝑒−0.25 (12) 3.1.3. thermal and hydraulic effectiveness when assessing the efficiency of a solar air heater, it is essential to consider the energy expended to propel air and enhance the amount of heat gained. the concept of a solar air heater must be optimized in such a way as to maximize the transfer of thermal energy to the heat transfer fluid while minimizing the electrical consumption of the fan. to analyze the overall performance of a solar air heater, it is necessary to simultaneously evaluate the thermal and hydraulic characteristics of the collector, facilitating the complete evaluation of its thermal-hydraulic performance. the thermal-hydraulic performance parameter (thpp) is an important criterion used to evaluate thermal-hydraulic performance by comparing the heat transfer of an artificially rough pipe to that of a slick pipe when subjected to constant ventilation power stresses. this parameter is defined by webb and eckert [28] as follows: 𝑇𝐻𝑃𝑃 = 𝑁𝑢𝑟/𝑁𝑢𝑠 (𝑓𝑟/𝑓𝑠) 1/3 (13) table 3: mesh sensitivity number of elements elements size nu δp (pa) fr relative error of nu (%) relative error of fr (%) 51710 0.50 34.486 1.1989 0.0324 -- 79997 0.40 36.455 1.0935 0.0296 1.9690 0.0028 103095 0.35 37.457 1.3766 0.0372 1.0018 0.0076 167657 0.27 37.952 1.3487 0.0365 0.4946 0.0007 300665 0.15 37.895 1.4804 0.0401 0.0057 0.0036 improvement of solar collectors 52(2) pp. 1–9 (2024) 5 the effectiveness of an enrichment device can be determined by obtaining a value greater than one, allowing different devices to be compared and the most efficient one identified. thpp, based on a constant ventilation power, is a commonly utilized metric in the literature to assess the relative efficiency of different rib geometries in terms of enhancing heat transfer when ventilation conditions are stable. 4. analysis of the results 4.1. model validation the fluent code is utilized to simulate the slick conduit using the rng k-ε turbulence model where the absorber plate is considered to exhibit no artificial roughness. the findings of the nusselt numbers and friction coefficients obtained are compared with the outcomes taken from the theoretical correlations given in the literature (see figures 4 and 5). the numerical results obtained from the nusselt numbers and the friction coefficients are in good agreement with the dittus-boelter and blasius correlations, respectively, whose minimum errors were less than 0.6% and the maximum ones did not exceed 5% (see figures 4 and 5). indeed, the turbulence model used is validated for this type of flow. 4.2. analysis of heat transfer 4.2.1. effect of the relative roughness step the influence of the reynolds number on the mean nusselt number with a fixed e/d ratio of 0.042 and varying p/e ratio is depicted in figure 6. the results demonstrate that as the reynolds number and height ratio rise, the average nusselt number also increases, which can be attributed to the transition of the flow field from a laminar sublayer to a turbulent flow near the wall. compared to a slick duct, maximum improvements in the average nusselt number of approximately 53.4% for the triangular, 45.7% for the semi-circular and 25.0% for the square shapes are recorded for a reynolds number of 18000 in the case of an artificially rough conduit. the design and enhancement of the heat transfer in a solar heater unit is heavily dependent on the incorporation of differently shaped artificially rough elements. 4.2.2. influence of the relative roughness height on the flow characteristics the influence of the reynolds number on the nusselt number when the fin pitch-to-height ratio is fixed (p/e = 14.28) and the ratios of fin thickness to hydraulic diameter varies is illustrated in figure 7. it is observed that simultaneously increasing the reynolds number and the relative roughness height leads to an increase in the nusselt number. this phenomenon arises from the figure 4: validation of the nusselt number calculations figure 5: validation of the friction factor calculations figure 6: relationship between the nusselt number and reynolds number (e/d = 0.042 and p/e varies) 0 5000 10000 15000 20000 0 20 40 60 80 100 120 triangular (p/e = 7.14) triangular (p/e = 14.28) bow (p/e = 7.14) bow (p/e = 14.28) square (p/e = 7.14) square (p/e = 14.28) smooth wall n u s s e lt n u m b e r n u number of reynolds re figure 7: relationship between the nusselt number and reynolds number (p/e = 14.28 and e/d varies) 0 5000 10000 15000 20000 0 20 40 60 80 100 120 triangular (e/d =0.042) triangular (pe/d =0.030) bow (e/d =0.042) bow (e/d =0.030) square (e/d =0.042) square (e/d =0.030) smooth wall n u s s e lt n u m b e r n u number of reynolds re lahcene, benamara, benguediab and benazza hungarian journal of industry and chemistry 6 generation of turbulence in localized regions, resulting in the mixing of airflows and the formation of vigorous secondary flows. the detachment and reattachment of the free shear layer in the boundary layer, intensified by an increase in the e/d ratio, contribute to this flow mechanism. as a result, both local and average heat transfer rates are enhanced. in other words, increasing the reynolds number and e/d ratio causes turbulence, which improves the heat transfer rate. 4.3. friction factor calculation 4.3.1. impact of the relative roughness-pitch on the friction factor the impact of the relative roughness pitch on the friction factor when e/d is kept constant at 0.042 is illustrated in figure 8. the findings demonstrate that as the reynolds number increases, the friction factor decreases. the highest values of the friction factor are obtained when the p/e ratio is at its maximum value of 14.28. in this scenario, introducing artificial roughness impacts the primary flow and alters the structure of the turbulent boundary layer, leading to the creation of detachment and reattachment regions in the viscous sublayer as well as an increase in the friction, that is, the flow resistance. in other words, the friction increases by introducing artificial roughness, which can impact the overall efficiency of the enrichment device. 4.3.2. impact of the relative roughness height on the friction factor the change in the friction factor with regards to the reynolds number when the spacing pitch is fixed (p/e = 14.28) and e/d varies is illustrated in figure 9. the results obtained show that when the reynolds number increases, the friction factor decreases. when e/d is highest at 0.042, the maximum friction factors are obtained due to the increased flow resistance of the rough wall. 4.4. improvement of the thermal coefficient variations in the thpp as a function of the reynolds number at different e/d ratios and p/e ratios are shown in figures 10 and 11. it was found that in both cases considered, the thpp is optimal when the reynolds number is equal to 5000. at a fixed e/d ratio of 0.042, the best thpp for improving thermal performance is obtained when the p/e ratio for triangular ribs is 7.14 (see figure 10). when the p/e ratio is fixed at 14.28, the triangular ribs yield the optimal thpp at a maximum e/d ratio equal to 0.042 (figure 11). figure 8: evolution of the friction factor with regards to the reynolds number (e/d = 0.042 and p/e varies) 0 5000 10000 15000 20000 0,00 0,01 0,02 0,03 0,04 0,05 triangular (p/e =7.14) triangular (p/e =14.28) bow (p/e =7.14) bow (p/e =14.28) square (p/e =7.14) square (p/e =14.28) smooth wall f ri c ti o n f a c to r f r number of reynolds re figure 9: friction factor vs. reynolds number (p/e = 14.28 and e/d varies) 0 5000 10000 15000 20000 0,00 0,01 0,02 0,03 0,04 0,05 triangular (e/d =0.042) triangular (pe/d =0.030) bow (e/d =0.042) bow (e/d =0.030) square (e/d =0.042) square (e/d =0.030) smooth wall f ri c ti o n f a c to r f r number of reynolds re figure 10: thpp vs. reynolds number (e/d = 0.042 and p/e varies) 0 5000 10000 15000 20000 0,9 1,2 1,5 1,8 2,1 2,4 2,7 3,0 3,3 triangular (p/e =7.14) triangular (p/e =14.28) bow (p/e =7.14) bow (p/e =14.28) square (p/e =7.14) square (p/e =14.28) t h e rm a l e n h a n c e m e n t fa c to r t h p p number of reynolds re figure 11: thpp vs. reynolds number (p/e = 14.28 and e/d varies) 0 5000 10000 15000 20000 0,9 1,2 1,5 1,8 2,1 2,4 2,7 3,0 triangular (e/d =0.042) triangular (pe/d =0.030) bow (e/d =0.042) bow (e/d =0.030) square (e/d =0.042) square (e/d =0.030) t h e rm a l e n h a n c e m e n t fa c to r t h p p number of reynolds re improvement of solar collectors 52(2) pp. 1–9 (2024) 7 4.5. effects of the geometric shape of the ribs in this section, the influence of changing the shape of the ribs on enhancing the motion transfer in a thermal sensor when the fin pitch-to-height ratio is constant is compared. it is noted that the triangular ribs significantly improve the convective heat transfer compared to the slick case and the other geometric shapes of ribs considered (see figure 12). due to its aerodynamic appearance and in the absence of acute angles, triangular ribs record the greatest energy gain (see figures 13 and 14). 4.6. distribution of the turbulent kinetic energy and turbulence intensity the improved performance of sahs is highly dependent on the presence of the roughness of the triangular ribs compared to the slick, square and semi-circular sahs. the presence of artificial asperities disturbs the main flow and intensifies turbulent mixing in the inter-rib space as determined by analyzing the kinetic energy and turbulence intensity. the contours of the turbulent kinetic energy (k) and the turbulence intensity (i) are illustrated in figures 15 and 16, respectively, when e/d is kept constant at 0.042, p/e = 14.28 and a wide range of reynolds numbers (3500 ≤ re ≤ 18000) used. figure 14: thpp vs. reynolds number (p/e = 14.28 and e/d = 0.042) 0 5000 10000 15000 20000 0,9 1,2 1,5 1,8 2,1 2,4 2,7 3,0 triangular bow (p/e =7.14) square t h e rm a l e n h a n c e m e n t fa c to r t h p p number of reynolds re figure 15: visualization of the contours of the turbulent kinetic energy at different reynolds numbers (e/d = 0.042 and p/e = 14.28) figure 16: visualization of the contours of the turbulence intensity when the reynolds numbers varies (e/d = 0.042 and p/e = 14.28) figure 17: static temperature contours when the reynolds number varies (e/d = 0.042 and p/e = 14.28) figure 13: friction factor vs. reynolds number (e/d = 0.042 and p/e = 14.28) 0 5000 10000 15000 20000 0,00 0,01 0,02 0,03 0,04 0,05 triangular bow (p/e =7.14) square smooth wall f ri c ti o n f a c to r f r number of reynolds re figure 12: relationship between the nusselt number and reynolds number (e/d = 0.042 and p/e = 14.28) 0 5000 10000 15000 20000 0 20 40 60 80 100 120 traingular bow square smooth wall n u s s e lt n u m b e r n u number of reynolds re lahcene, benamara, benguediab and benazza hungarian journal of industry and chemistry 8 4.7. temperature distribution a qualitative comparison of the temperature distribution along the sensor is presented in this section. the temperature contours when the reynolds number varies but the pitch and rib height ratios are fixed (e/d = 0.042; p/e = 14.28) is illustrated in figure 17. it was observed that the gradient of the static temperature near the ribbed section de creases as the reynolds number increases, which can be attributed to the increased flow rate of fresh air from the inlet. this reduces the difference between the temperature of the air mass and that of the wall, thereby increasing the nusselt number. the presence of the ribs disturbs the main flow and intensifies the convective heat transfer as the reynolds number increases. 5. conclusions this numerical study investigates the thermal-hydraulic properties of a fully developed turbulent flow in a rectangular duct equipped with transverse ribs of varying geometric shapes. in the light of this study, the subsequent conclusions can be drawn: 1. the rng-based k-ε turbulence model adopted in this analysis yields good results and is recommended in this kind of convective heat transfer study. 2. the presence of the ribs irrespective of their geometric shape intensifies turbulent convective heat transfer and improves the thermal performance of the sensor. 3. the nusselt number increases as the reynolds number and relative roughness pitch increase due to the modification of the laminar sublayer of a turbulent flow in the near-wall region. 4. the maximum improvement in the nusselt number recorded compared to the slick conduit is 53.4, 45.7 and 25.0% for the triangular, semicircular and square ribs, respectively, when the reynolds number was equal to 18000. 5. in all cases examined, the thermal-hydraulic performance parameter was optimal at a reynolds number equal to 5000. 6. the improvement of the thermal-hydraulic performance parameter brought about by the presence of the triangular transverse ribs is the most important when compared to their semicircular and square equivalents with a relative roughness pitch of 14.28 and a relative roughness height of 0.042. nomenclature nu nusselt number nus nusselt number for slick conduit nur nusselt number for artificially rough conduit re reynolds number pr prandtl number e fin thickness (mm) dh hydraulic diameter of the duct (mm) p pitch (mm) e/d relative roughness height p/e relative roughness pitch h height of the duct (mm) w width of the duct (mm) l length of the duct (mm) q heat flux (w/m2) f friction factor fs friction factor for slick conduit fr friction factor for artificially rough conduit δp drop in pressure (pa) u air flow velocity in the x-direction (m/s) v air flow velocity in the y-direction (m/s) x distance from start of test section (m) y non-dimensional duct wall coordinate t air temperature (k) p pressure (pa) α thermal diffusivity (m2/s) ρ density of air (kg/m3) qu heat transfer rate (w) qu heat flux (w/m2) fr collector heat removal factor ac gross collector area i incident heat flow (τα)e effective transmittance-absorptance product ul overall heat loss coefficient t0 outlet temperature ti inlet temperature ta air temperature tpm average wall temperature tam average air temperature m flow rates cp specific 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doi: 10.33927/hjic-2020-18 new hybrid wavelet and cnn-based indirect tire-pressure monitoring system for autonomous vehicles zoltán márton*1 and dénes fodor1 1research institute of automotive mechatronics and automation, university of pannonia, egyetem u. 10, veszprém, 8200, hungary since the tire pressure has a significant influence on driving safety, even self-driving vehicles need to be aware of their current tire pressures. two major types of methods for estimating tire pressures exist: direct and indirect methods. in spite of recent advancements in direct tire pressure monitoring systems (tpmss), indirect pressure monitoring systems still play a significant role due to their low costs. indirect systems rely on the processing of signals from wheel speed sensors. in most cases, a transformation is applied to generate a frequency spectrum from which the tire pressure-dependent eigenfrequency can be extracted. the most accurate methods apply the fourier transform, but these require the highest computational power. after the spectrum of signals from the wheel speed sensor is created, the eigenfrequency must be extracted. several methods are available to extract significant frequency components. one of the easiest methods is peak searching, however, it is susceptible to noise. on the other hand, more accurate methods that are less sensitive to noise require more computational power. if a transform that consumes less computational power can be applied, then the freed resources can be used by a better eigenfrequency identification method. in this paper, a hybrid wavelet-fourier transform and convolutional neural network-based method is presented, which exhibits a promising level of noise tolerance. keywords: tpms, eigenfrequency, hybrid wavelet-fourier transform, convolutional neural networks, autonomous vehicles 1. introduction the development and spread of autonomous and electric vehicles is about to change everything with regard to the internal structure and operation of cars. however, vehicles will always make contact with the road through tires so tires will continue to play an important role in terms of vehicle safety. the condition of tires is not only dependent on abrasion but on current tire pressures as well. furthermore, tire pressures influence abrasion in addition to fuel or power consumption [1]. as a result, both the eu and usa have legislated that all new vehicles are equipped with tire pressure monitoring systems (tpms) as standard. to achieve safe autonomous driving, the performance parameters of the vehicles must be in accordance with the conditions of the tires, e.g. the driving logic needs to know the current pressure of each tire. nowadays, research is being done with regard to active tires which are capable of adapting to weather and road conditions by changing their own tire pressures according to the requirements [2]. on the other hand, active tires are extortionate compared to their passive counterparts, even those equipped with tpms. an active tire must also include a compressor and be able to transmit the compressed air into the tires, which increases not only their *correspondence: marton.zoltan@mk.uni-pannon.hu cost but also their energy requirements. active tire systems will only be available for high-end vehicles or military applications. mainstream and more cost-effective vehicles will continue to use regular tires and be equipped with tpms. two major types of tpms are available: direct tpms, which includes a pressure sensor in the tires themselves, and indirect tpms, which uses wheel speed sensors (wss) required by the anti-lock braking system (abs), electronic stability program (esp) and other driving safety systems. the indirect tpms (itpms) can be accomplished by following two techniques. the simplest way is to compare the wheel speed signals from three different pairs, the bigger the tire pressure the bigger the radius of the tire will be. these systems are capable of detecting relative pressure changes and require the results to be filtered in such a way that the driving conditions and maneuvers do not affect the system. since tires have different radii, these systems require a learning process to be implemented should any of the tires be changed [3]. nowadays, comparable systems were replaced by signal processing-based systems and research is being done on model-based systems. both approaches are based on the fact that a tire is like a complex system made of springs and masses, where each spring-mass pair has its own eigenfrequencies. one of the springs correhttps://doi.org/10.33927/hjic-2020-18 mailto:marton.zoltan@mk.uni-pannon.hu 124 márton and fodor figure 1: the system architecture of itpms sponds to the air pressure inside the tire, therefore, one eigenfrequency is dependent on the tire pressure [3]. signal processing-based itpmss consist of two major wellseparated steps (fig. 1). the first step is to transform the signal from the time domain into the frequency or a frequency-related domain. these transforms can be fourier [4], cosine [5] or hybrid wavelet-fourier (hwft). the received frequency spectrum of the signal from the wheel speed sensor contains different eigenfrequencies as well as noises originating from the road surface, combustion engine and transmission. the second step is to detect and isolate the pressure-dependent eigenfrequency. different algorithms are available to identify a specific eigenfrequency. each algorithm is only performed on a given bandwidth. the simplest and fastest is the peak search (ps) algorithm. another method is the so-called center of gravity (cog) algorithm which can virtually increase the frequency resolution. although it is more resilient towards noise, noise still may cause the detected eigenfrequency to be shifted. this was subsequently observed in the results presented in table 1. since each eigenfrequency found in the spectrum of the wss exhibits a unique pattern, a pattern-recognition method can also be applied to identify the eigenfrequency in a given bandwidth. one of the most popular and reliable pattern-recognition methods are the deep convolutional neural networks (cnns). deep cnns can learn to recognize and classify patterns through a process called deep learning. in this paper, a novel itpms algorithm is proposed which consists of the hwft and, as an alternative to the cog algorithm, a cnn is used to detect the eigenfrequency. 2. transforms related to itpms the first major step in signal processing-based itpms is always a transform of the wss or other sensor signals from a time into a frequency or frequency-equivalent domain. since one of the major aims of this paper is to compare different transforms and eigenfrequency-detecting methods, a short description will be given of the fourier, cosine and hybrid wavelet-fourier transforms. for the itpms, a “new” hwft will be proposed in this paper. 2.1 fourier transform one of the most mainstream transforms in frequency analysis is the fourier transform, which transforms the time-domain signals directly into the frequency domain [6]. the signals in the frequency domain contain information concerning frequencies, amplitudes and phases. three major varieties of the fourier transform exist depending on the nature of the signal and the number of samples. the continuous fourier transform (cft) is predominantly used in stability and control theory, signal processing theory, symbolic mathematics, electrical engineering, etc. if a continuous signal is sampled, i.e. a discrete signal, by using the integral approximation to the sum, the discrete fourier transform (dft) can be obtained as x [k] = 1√ n n−1∑ n=0 x [n] e−i2πkn/n , (1) where k represents the discrete frequency, x[n] denotes the sampled signal, n stands for the number of samples, x[k] refers to the transformed discrete signal and i is the imaginary unit. unlike the cft, the dft has many practical applications. a special case of dft is when the number of samples can be expressed as a power of two. in this case, dft can be factorized using a divide and conquer approach. hence the factorization of this transform requires less computational power and is referred to as the fast fourier transform (fft), it is the most widespread in signal processing and computer science. 2.2 cosine transform the cosine transform (ct) originates from the fourier transform by removing the imaginary components. unlike the fourier transform, where the phases are encoded in the complex amplitudes, the ct stores the phase information over the entire frequency spectrum if the signal cannot be synthesized entirely from a finite set of cosine functions [7]. ct also consists of three major variants: continuous (cct), discrete (dct) and fast (fct). in practice, fct is predominantly used in the compression of lossy audio, images and motion pictures. dct and fct consist of four different variations, in our case, the so-called dct or fct ii was implemented: x [k] = n−1∑ n=0 x [n] cos [ π ( k + 1 2 ) n n ] . (2) in this paper, fct was examined as an alternative to fft. 2.3 wavelet transform the wavelet transform (wt) can be seen as a transform which transforms a given signal from the time domain into the frequency-time domain. like ft and ct, hungarian journal of industry and chemistry new hybrid wavelet and cnn-based indirect tire-pressure monitoring system 125 table 1: test results of different combinations of transformand eigenfrequency detection methods. test type ref. freq. [hz] transform eigenf. det. average [hz] deviation [hz] correctness [%] sim. 47 fft peak search 46.181 3.808 75.475 fct 46.41 2.515 48.636 hwft-64 46.359 2.493 66.182 fft cog 46.682 0.828 79.986 fct 46.78 0.835 78.616 hwft-64 46.613 0.84 78.029 fft cnn 46.995 0.132 99.853 fct 46.94 0.606 95.724 hwft-64 46.994 0.174 99.347 sim. 43 fft peak search 42.997 4.717 99.539 fct 43.255 0.865 57.852 hwft-64 43.174 0.438 82.529 fft cog 43.73 0.144 99.214 fct 43.806 0.424 89.367 hwft-64 43.886 0.2 79.345 fft cnn 43.011 0.18 99.414 fct 43.446 1.19 82.38 hwft-64 43.092 0.322 91.363 real 45.58 fft peak search 45.21 7.224 the reference frequency was given in the metadata provided by the measurements and it was calculated by a closed source software in off-line processing. hence, there is no guarantee that the reference frequency is always correct. the correctness values are omitted. fct 46.013 5.172 hwft-64 45.775 4.29 fft cog 46.59 1.387 fct 46.671 1.394 hwft-64 47.225 1.407 fft cnn 45.202 3.186 fct 45.254 3.249 hwft-64 45.487 2.831 real 47.03 fft peak search 46.949 3.814 fct 47.374 4.897 hwft-64 46.901 4.53 fft cog 47.339 1.683 fct 47.259 1.584 hwft-64 47.695 1.521 fft cnn 46.711 2.571 fct 46.817 2.406 hwft-64 47.103 2.194 wt also consists of three variants, namely continuous (cwt): x (t, s) = 1√ s ∫ ∞ −∞ x (t)ψ ( τ − t s ) dt, (3) discrete (dwt): x [m, k] = 1√ ck0 n−1∑ n=0 x [n]ψ [( n ck0 −m ) t ] , (4) and fast (fwt), but unlike the aforementioned transforms, wt is not just a transformation, it resembles a whole family of transformations. in the above equations, where ψ(t) is the so-called mother wavelet function, x(t) denotes the continuous input signal or function, and x(t, s) represents the wt. cwt can be discretized. this process requires a scaling base c0 and a time unit of the mother wavelet, t , to be defined: x [m, k] = 1√ ck0 n−1∑ n=0 x [n]ψ [( n ck0 −m ) t ] (5) if the scaling base is two and the total number of samples can be expressed as a power of two, the previously obtained dwt can be factorized. the obtained fwt can be implemented as a cascade of low pass filters (lpf), high pass filters (hpf) and downsampler banks [8]. depending on the mother wavelet function, different wts can be defined. these wts share common properties, e.g. the frequency and time resolutions of the transform are dependent on each other, they can be viewed as bands where both resolutions are in logarithmic steps. their other properties depend on which mother wavelet is selected. the most widespread wts are the mexican hat wavelet, haar (wavelet) transform and cohen48(1) pp. 123–130 (2020) 126 márton and fodor daubechies-feauveau (cdf) wavelets. wts are applied in data compression, e.g. jpeg2000, djvu, cineform, etc., and transient analysis. 2.4 hybrid wavelet-fourier transform while wt was applied in signal processing for transient and fourier transforms in frequency spectrum analysis, demand for both grew simultaneously. one of the solutions to meet this requirement was hwft. the basic idea behind it was that the wt decomposes the signal of the time domain into bandwidths. inside a bandwidth, characteristic information concerning the time domain in the given bandwidth can be found. therefore, it is possible to perform fts on each bandwidth [9]. unlike the continuous hwft: x (f, s) = 1√ s ∫ ∞ −∞ x (t)π ( τ − t s ) dt, (6) which is scarcely applied, the discrete hwft: x [f, k] = n−1∑ m=0 e−i2πfm/n√ nck0 n−1∑ n=0 x [n]ψ [( n ck0 −m ) t ] (7) has some applications in biometry [10]. fast hwft (fhwft) can be synthesised by applying fft to the output of each bandwidth of the fwt. from the perspective of our research, fhwft is suitable to calculate a frequency spectrum of a wss signal for itpms applications. furthermore, fhwft has a special property which can be exploited to reduce the computational complexity by only performing the fft on those bandwidths that are significant with regard to the given application. this property allows it to be used as a lightweight alternative to the traditional fft. however, since the filter banks of the fwt are imperfect, a phenomenon known as spectral leakage can be observed (fig. 2). spectral leakage essentially means that frequency components from one bandwidth also appear in the neighboring bandwidths [9]. this causes additional disturbances in the spectrum necessitating further investigation into how much the detection of eigenfrequencies in an itpms is affected. for this reason, fhwft is compared with fft and fct using different eigenfrequency detection methods in this paper. 3. eigenfrequency detection methods the most important step in an itpms is eigenfrequency detection because this identifies the frequency component inner pressure dependent. several methods are capable of identifying or detecting peaks in a given frequency spectrum. the sensitivity, ability to handle multiple peaks, noise susceptibility, etc. of these methods differ. figure 2: spectral leakage of the hwft demonstrated on a 100 hz signal 3.1 peak search algorithm one of the simplest methods is the peak search (ps) algorithm. in the first step, a bandwidth must be determined in which the interesting and/or important eigenfrequencies can be present. in this bandwidth, a search is performed to identify the frequency which exhibits the maximum amplitude. this simple algorithm is presented in fp = { f ∈ i ∣∣∣max i |s(i)| = |s(f)| } , (8) where fp denotes the set of peaks, i represents the interval of interest, and s(f) stands for the frequency spectrum of a signal. under certain circumstances, multiple frequency components can be found. depending on the application, mostly vibration analysis, error detection as well as searching for local maxima and multiple peaks is required. in such applications, usually a minimum value ε is also defined to restrict the number of possible peaks: fp = {f ∈ i ||s(f)| >ε and ||s(f)| is local max} (9) if noise or disturbances are present, the ps algorithm might identify the wrong peaks. to reduce the impact of the noise, a sliding-window median filter might be applied. if the ps algorithm in eq. 9 is used, then it is more resilient to noise than the global maximum method (eq. 8), but a priori information is required to identify the correct eigenfrequency. neither of the ps methods are as accurate in such systems as the itpms because pressures about 30 % lower than the optimum shift the pressure-dependent eigenfrequency by only approximately 3 − 4 hz. due to disturbances originating from the road surface and transmission, multiple peaks might be present in the interval of interest. 3.2 center of gravity algorithm a more noise-resistant method is the center of gravity (cog) algorithm since it involves weighted averaging. hungarian journal of industry and chemistry new hybrid wavelet and cnn-based indirect tire-pressure monitoring system 127 figure 3: the pressure-dependent eigenfrequency of a tire in the spectrum of the wss signal unlike the ps, cog always yields only one frequency, therefore, this eliminates the problems that originate from multiple peaks present in the interval of interest. furthermore, the eigenfrequency theoretically has a higher resolution than would have resulted from the sampling frequency and sampling time. this theoretically increased frequency resolution can only be achieved in the presence of an error and only in that case when exactly one frequency component is present in the interval of interest. the cog can be calculated by fc = ∫ i f |s(f)|p df∫ i |s(f)|p df , (10) where fc denotes the center frequency and p represents an exponent whose value, depending on the application, is usually between 2 and 3. although this method is more robust than ps, it is still susceptible to noise. 3.3 convolutional neural networks the eigenfrequency of the tire exhibits a very distinct pattern in the frequency spectrum of the wss signal (fig. 3) which facilitates its detection using pattern-matching algorithms. one of the most popular pattern-matching algorithms involves deep (multilayered) cnns. our research focused on developing an algorithm for eigenfrequency detection using cnn. on the downside, cnns demand much more computational power and memory than ps or cog. to compensate for the higher computational power, a fhwft was strictly developed to carry out the transform in the bandwidth where the tire pressuredependent eigenfrequency is located (hwft-64). the artificial neural networks (anns), e.g., cnn, mimic the structure and supposed operation of neurons and neural systems found in living beings. the differences concern the actual operation of neurons and, unlike the central nervous system of a living being, anns often structure artificial neurons (ans) into layers. since in most cases one layer of neurons is insufficient for most figure 4: the structure of a simple image classification cnn [12]. applications, multilayer anns are often constructed. ans often have multiple inputs, each of which has a unique weight assigned to it. unlike living neurons, the inputs and outputs of ans can be vector-valued. anns store the recognizable patterns in the weight values of their ans. the analytical determination of the correct weight values is taxing but like the central nervous system of a living being, anns can learn the desired patterns. the layers of an ann can have different functions. in the case of cnns, at least one of those layers implement spatial discrete convolution, hence the name convolutional neural networks. the structure of a layer depends on its function as well as the connection between the given layers and the previous layer. each an in the layer has a layer-specific activation function (af) which acts as the output function of the an. depending on the function of the layer, the following types of layers can be distinguished: input, convolutional, polling and fully connected layer. since ans can have vector output values, each layer can be regarded as if each component of the output vector has its own parallel layer with its own weights, which are grouped together as matrices. the only thing in common would be the af associated with these virtual parallel layers [11]. pattern recognition that applies cnns usually consists of four different types of an layers: input, convolutional, polling and fully connected (fig. 4) [12]. the simplest layer is the input layer. it has no input weights, moreover, its af is the identity function and serves as a buffer layer. in the case of convolutional layers, each an shares the same input weights matrices which are referred to as convolution kernels. these layers are applied for noise reduction, filtered downsampling, upsampling and feature extraction. the polling layer is used for downsampling or dimension reduction of data. like the input layer, it has no input weights but a kernel radius and step distance. its specific afs are average, minimum and maximum functions. the fully connected (fc) layer is the most important part of an ann-based classifier. the number of ans must be identical to the number of classes the ann has to distinguish. its name originates from the fact that each of its neurons are connected to each of the neurons in the previous layer and each connection has a unique weight assigned to it. the ans in this layer also have a so-called class index attached to them. during the classification, the neurons contain the possibility of their attached classes. this decision can be 48(1) pp. 123–130 (2020) 128 márton and fodor figure 5: the frequency spectrum of a wss signal produced by fft (a) and fhwft (b) after reordering influenced by the chosen af, from which different functions are available. the most commonly used is the socalled softmax function [11]. 4. our new itpms algorithm 4.1 cnn-based determination of eigenfrequencies since similar results can be achieved to fft using fhwft, it can be concluded that fhwft can be safely used as an alternative to fft in itpmss (fig. 5). the eigenfrequency, depending on the tire pressure, is between 42 and 48 hz. using this information, a fhwft can be optimized which only calculates the fft within the bandwidth of 32–63 hz. if the sampling rate is 1024 samples per second, the fft has to be performed on only 64 samples. this fhwft optimized for tpms was labeled by us as hwft-64. the computational power requirements of hwft-64 are about four times less than in the case of a fft with a sampling rate of 1024 (fig. 6). the freed up resources make it possible to use more advanced eigenfrequency detection methods than ps or cog algorithms. since the cnn can learn different patterns, it is possible to construct such learning patterns which include various frequency disturbances. naturally, the cnn must also be constructed in such a way that such patterns could be learnt correctly. furthermore, the cnn should be as simple as possible. as the first step of the design using the a priori information and by taking the available free and open-source cnn software tool into consideration, an interval of 16 hz was selected as the interval of interest with 47 hz (the figure 6: computational complexity of fft and hwft64 eigenfrequency of the non-deflated tire) at the center. one of the goals of this research was to create a better eigenfrequency detection method than ps. this meant that 16 classes had to be and were specified, thus the last layer of the cnn had to be a fully connected layer that consisted of 16 neurons with a softmax function. since the input interval is comprised of 16 elements, the input layer also had to consist of 16 neurons. the structure of the pattern recognition-based eigenfrequency-detecting cnn can be even simpler than the simple image classifier shown in fig. 4 since much less input data is used. the first attempt just applied a two-layer approach, with an input and an fc layer. this design could not be validated during the learning process. to enhance the capabilities of the cnn, an additional layer had to be inserted. the new layer was a convolutional layer consisting of four neurons and a 3x3 convolution kernel. the outputs were 16d vectors (fig. 7). the resulting cnn was capable of passing the validation tests and robust against the simulated disturbances. implementation of the cnn had to be capable of running on an ecu which meant no opencl, compute unified device architecture (cuda), compute shaders or multiprocessor-based implementation could be used. the mojo-cnn was chosen, which is an open-source implementation with different built in solving algorithms such as adam, sgd and adagrad [13]. only the adam solving algorithm was used. the learning samples were created by frequency shifting of the spectrum of a non-deflated tire (fig. 3). additional learning samples were created by injecting a spike at 54 hz because, in most cases, disturbances would occur at this frequency. to prevent overfitting, data augmentation was used. the validation samples were slightly altered versions of learning samples. the amplitude was altered to such a degree of different frequency components that the location of the peaks remained unchanged. hungarian journal of industry and chemistry new hybrid wavelet and cnn-based indirect tire-pressure monitoring system 129 figure 7: structure of eigenfrequency-detecting cnn after the design of the cnn, the new algorithm was tested. for the tests, fft, fct and hwft-64 were selected as the transforms. the eigenfrequency identification algorithms were ps, cog and our new cnn-based pattern recognition. the test data used consisted of both artificial, referred to as “simulated”, and real measurement data. 4.2 simulations and measurements the first sample tests were conducted in such a way to facilitate a known eigenfrequency. this was accomplished by taking real measurement data, which were filtered by a non-ideal band-stop filter (bsf). the bsf being nonideal makes it possible for the original frequency components to be still present but attenuated and, therefore, act as disturbances. following filtration by the bsf, known frequency components were injected (47 hz and 43 hz for the non-deflated and deflated tires, respectively). as previously stated, the other set of test data were unmodified measurement data. the data was provided by continental ag and the expected eigenfrequency was used as a reference frequency. two “simulated” and two unmodified measurement sets of test data were used for the tests. during the tests, the average frequency deviation and accuracy were evaluated. the accuracy was defined as how many times the algorithm would yield the reference frequency compared to the number of times the algorithm was executed. this could only be determined on the “simulated” data set, since on real measurements, the eigenfrequency cannot be guaranteed to be always the same as given in the metadata sheet. the noises and disturbances were uncontrolled and originated from the road surface, transmission and combustion engine. 5. results and discussion the results can be seen in table 1. as can be observed, the cnn yields better results with regard to approaching the reference frequency more appropriately and with less deviation than ps and comparable results to cog in the case of both “simulated” and real measurement data. figure 8: computational complexity of different combinations of transformand eigenfrequency-detecting methods, when the number of samples was 1024 and the interval of interest consisted of 16 frequency spectral amplitudes the most significant improvement of the cnn-based pattern recognition method can be observed in the results from the fct during the “simulated” data tests. however, except for the first test on the 47 hz “simulated” data, the cog yielded the smallest deviations, the differences between the average frequencies of cog and reference frequencies are bigger than in the case of ps or cnn-based pattern recognition methods. in the case of the cnn-based method, the deviation was about 50 % greater than in the case of cog. this is most likely due to the fact that the output of the cnn-based method yielded a lower frequency resolution than cog. on the other hand, the hwft-64 with cnn shows promising and comparable results using just less than half of the computational power required by fft and cog. 6. conclusion in this paper, a new pattern recognition-based eigenfrequency detection algorithm for itpms was presented. by combining this new algorithm with an optimized fhwft, the resulting system is of lower computational complexity, moreover, the reliability and accuracy is almost the same as that of the currently industrial mainstream fft and cog combination (fig. 8). the computational complexity was calculated by how often simple mathematical operations supported natively by the cpu/fpu were used in the implementation and how those embedded in iterations were affected by the input data size. in this case, the input data size was 1024 samples. the cog can also work with the hwft-64 but is slightly less reliable (table 1). since more free resources are still available, when using this new transform optimized for itpms, further improvements or more complex eigenfrequency detection methods can be used without exceeding the computational complexity of the fft. 48(1) pp. 123–130 (2020) 130 márton and fodor acknowledgements the research was supported by efop-3.6.2-16-201700002 programme of the hungarian national government. references [1] national highway traffic safety administration, federal motor vehicle safety standards, tire pressure monitoring systems, controls and displays, march 2009, http://www.nhtsa.dot.gov/cars/rules/ rulings/tirepresfinal/tpmsfinalrule.pdf [2] schoettle, b.; sivak, m.: the importance of active and intelligent tires for autonomous vehicles, the university of michigan sustainable worldwide transportation report, 2017, report no. swt-2017-2 http://umich.edu/~umtriswt/ pdf/swt-2017-2.pdf [3] silva, a.; sánchez, j. r.; granados, g. e.; tudonmartinez, j. c.; lozoya-santos, j. j.: comparative analysis in indirect tire pressure monitoring systems in vehicles, ifac-papersonline, 2019, 52(5), 54–59 doi: 10.1016/j.ifacol.2019.09.009 [4] gustafsson, f.; drevo, m.; forssell, u.; lofgrën, m.; persson, n.; quicklund, h.: virtual sensors of tire pressure and road friction, sae technical paper series, 2001. doi: 10.4271/2001-01-0796 [5] márton, z.; fodor, d.; enisz, k.; nagy, k.: frequency analysis based tire pressure monitoring, 2014 ieee international electric vehicle conference (ievc) doi: 10.1109/ievc.2014.7056187 [6] oberst, u.: the fast fourier transform, siam journal on control and optimization, 2007, 46(2), 496– 540 doi: 10.1137/060658242 [7] strang, g.: the discrete cosine transform, siam review, 1999, 41(1), 135–147 doi: 10.1137/s0036144598336745 [8] goswami, j. c.; chan, a. k.: fundamentals of wavelets, john wiley & sons, inc., 2011 doi: 10.1002/9780470926994 [9] tarasiuk, t.: hybrid wavelet-fourier spectrum analysis, ieee transactions on power delivery, 2004, 19(3), 957–964 doi: 10.1109/tpwrd.2004.824398 [10] ziółko, b.; kozłowski, w.; ziółko, m.; samborski, r.; sierra, d.; gałka, j.: hybrid wavelet-fourierhmm speaker recognition, international journal of hybrid information technology, 2011, 4(4), 25– 41 [11] albawi, s.; mohammed, t. a.; al-zawi, s.: understanding of a convolutional neural network, 2017 international conference on engineering and technology (icet), 2017. doi: 10.1109/icengtechnol.2017.8308186 [12] hijazi, s.; kumar, r.; rowen, c.: using convolutional neural networks for image recognition, ip group, cadence, 2015. https://ip.cadence.com/ uploads/901/cnn/ [13] https://github.com/gnawice/mojo-cnn/wiki hungarian journal of industry and chemistry http://www.nhtsa.dot.gov/cars/rules/rulings/tirepresfinal/tpmsfinalrule.pdf http://www.nhtsa.dot.gov/cars/rules/rulings/tirepresfinal/tpmsfinalrule.pdf http://umich.edu/~umtriswt/pdf/swt-2017-2.pdf http://umich.edu/~umtriswt/pdf/swt-2017-2.pdf https://doi.org/10.1016/j.ifacol.2019.09.009 https://doi.org/10.4271/2001-01-0796 https://doi.org/10.1109/ievc.2014.7056187 https://doi.org/10.1137/060658242 https://doi.org/10.1137/s0036144598336745 https://doi.org/10.1137/s0036144598336745 https://doi.org/10.1002/9780470926994 https://doi.org/10.1002/9780470926994 https://doi.org/10.1109/tpwrd.2004.824398 https://doi.org/10.1109/icengtechnol.2017.8308186 https://doi.org/10.1109/icengtechnol.2017.8308186 https://ip.cadence.com/uploads/901/cnn/ https://ip.cadence.com/uploads/901/cnn/ https://github.com/gnawice/mojo-cnn/wiki introduction transforms related to itpms fourier transform cosine transform wavelet transform hybrid wavelet-fourier transform eigenfrequency detection methods peak search algorithm center of gravity algorithm convolutional neural networks our new itpms algorithm cnn-based determination of eigenfrequencies simulations and measurements results and discussion conclusion microsoft word 00.00 inner cover.docx editorial preface in addition to food and energy, access to water is a strategic issue influencing everyday life of over 7 billion people worldwide. although water is available in vast quantities on earth, the amount of fresh water is only approximately 3% of the total. about 68% of fresh water is captured in polar ice caps and glaciers, and 30% is present in the soil as ground water. the amount of surface water in lakes, rivers, and swamps is only 0.3%. currently humans consume 54% of the renewable fresh water. this figure is predicted to increase to 70% by 2025. it is anticipated that by 2050 the fresh water demand will increase by an additional 70%. thus, the shortage of water will be very soon a critical issue leading to local and even global geopolitical conflicts unless effective measures are taken. the inefficient use of or simply wasting water in the developed countries makes this delicate issue even more complicated. in a modern household, 60% of good quality water is used to flush toilettes and for washing, while only 20% is utilised in the kitchen, and another 20% in the bathroom. the desired “green growth with blue sustainability” requires immediate actions for handling the consequences of climate change (floods, droughts) and environmental pollution. wastewater should be considered as “water wasted”. thus, a good water management must find balance between economy, society, and environment via a series of actions, such as analysis, monitoring, and implementation. since approximately 80% of water discharged worldwide is polluted, there is a need for resource-oriented science and technology that encourages green innovation. this must be done by simultaneously keeping in mind development in engineering, financial resources, and social acceptance. the growing demand of industry for water can only be handled with the introduction of closed loop technologies, where water is reused and recycled. the water issue is more and more in the mainstream of politics as exemplified by the budapest water summit in 2013 and international conferences since then. there is a chance now for making radical and innovative actions with the proper combination of governance, technology, and finance for eliminating imbalance in water use. the university of pannonia in veszprém, hungary was the first to introduce environmental engineering education in hungary. it took the leading role in environmental monitoring and in the development of expert systems for wastewater treatment. in june 2014 the „first national conference on water chemistry and technology” was held in veszprém in the frame of the támop-4.1.1.c-12/1/konv-2012-0015 project supported by the european union and co-financed by the european social fund. in this thematic issue of the hungarian journal of industry and chemistry, selected papers are presented from the conference program that represent some of the important topics of the water sector: e.g. heavy metal removal from waste water and monitoring the bioavailability of heavy metals in river catchment areas; nitrogen removal from municipal waste water; mineralisation of herbicides in water; equilibrium calculations to solve complex aqueous speciation problems; photocatalytic remediation of pesticide-contaminated ground water; purification of dairy-food waste water via biofilms, and novel plasma spectroscopic methods in the analysis of aqueous solution. we do hope that these topics will be of interest to the broad scientific community. veszprém, june 2015 prof. dr. jános kristóf, d.sc. guest editor of the thematic issue project leader dr. viola somogyi, ph.d. guest editor of the thematic issue conference organiser hungarian journalof industry and chemistry vol. 51(1) pp. 15–21 (2023) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2023-03 annealing effect on copper-doped sodium borate glasses (na2o.4b2o3) djamila aboutaleb1* and brahim safi1 1 materials, processes and environment research unit (urmpe), faculty of technology, m’hamed bougara university of boumerdes, frantz fanon city, boumerdes, 35000, algeria the annealing effect of an alkali borate type glass below its softening point was investigated according to the na2o-b2o3 binary system. the samples were doped by introducing different amounts of copper oxide (cuo). the properties of elaborate glasses before and after annealing were studied. x-ray diffraction (xrd) as well as optical and infrared spectroscopy were used in this study. the results obtained show that annealing, that is, a heat treatment process, affects the structure of this type of glass by redistributing its structural units and partially correcting any defects, thereby reinforcing the structure. it was noticed that the bo3 units were reformed while the number of bo4 ones decreased, leading to an increase in the coefficient of thermal expansion, a decrease in both the refractive index and optical dispersion, the weakening of mechanical properties as well as a reduction in thermal conductivity and electric permittivity. keywords: alkali borate glass; sodium borate glass; annealing heat treatment; copper oxide; x-ray diffraction (xrd); optical spectroscopy and infrared spectroscopy 1. introduction although types of glass containing the usual network modifiers are usually completely colorless in the visible region of the spectrum, this is not the case if they also contain elements from the transition metals; cu, ti, v, cr, mn, fe, co and ni being the most important [1]-[3]. regarding these elements, the excited state of electrons changes as a result of the absorption of electromagnetic radiation, even when exposed to low-energy light, so coloration of the glass in the visible range occurs. the observed color depends firstly on the electronic configuration and, therefore, on the nature of the element as well as its environment, that is, the proximity of oxygen ions. among the theories that explain this phenomenon of staining, the ligand field theory by hartmann predicts that the coloring of glass by the "3d" transition metals is due to electronic transitions between the degenerate energy levels of the electrons orbiting free ions in the absence of an electromagnetic field. the "3d" electronic levels are identical in energy, but when a transition metal ion is surrounded by a few anions called "ligands", the interaction between the electric fields causes some perturbations in the energy levels whose amplitudes are a function of the electromagnetic fields as well as the number and geometric arrangement of the neighboring anions [4]. the number of different levels received: 24 feb 2023; revised: 18 march 2023; accepted: 20 march 2023 *correspondence: aboutalebdjamila@univ-boumerdes.dz formed is a function of the electronic configuration and coordination number of the cation. the absorption of photons as a result of electronic transitions between the "3d" levels gives rise to coloration of the glass in the visible spectrum. given that most metal ions of "3d" electronic transitions occur as a result of tetrahedral or octahedral coordination in the oxide glass, the coordination number will change as a result of differences in energy, depending on the number of "3d" electrons present. it is also evident that the color is affected by the concentration of the colored cation: as absorption by the coloring species increases, the effects of changes in the network of ions that are formed or modified are due to alterations to the distance between the bands as well as the electrostatic attraction between the coloring ions and the ligands surrounding them [5]-[12]. industrially, glass is always manufactured by annealing glasses, which is important and necessary to eliminate thermal stress. in this work, the annealing effect of an alkali borate type glass below its softening point was studied according to the na2o-b2o3 binary system [1, 10-16]. doping of the samples was achieved by introducing different amounts of copper oxide (cuo). the properties of elaborate types of glass before and after annealing were studied. x-ray diffraction (xrd) as well as optical and infrared spectroscopy were used in this study. https://doi.org/10.33927/hjic-2023-03 mailto:aboutalebdjamila@univ-boumerdes.dz aboutaleb and safi hungarian journal of industry and chemistry 16 2. experimental 2.1. preparation of the studied samples of glass a mixture of sodium carbonate (na2co3), boric acid (h3bo3) and pure copper oxide (cuo) was used. five variants (nb1 to nb5) were selected according to table 1. well-homogenized mixtures of raw materials were slowly heated to 675 °c for three hours, before increasing the temperature to and maintaining it at 1000 °c for one hour [17]-[19]. the fusions were made in air in stainless steel molds heated to 250 °c. 2.2. test methods differential thermal analysis (dta) and thermogravimetric analysis the piece of apparatus used was a netzsch sta 449c jupiter simultaneous thermal analyzer, which can measure the differential variations in temperatures as well as changes in weight and enthalpy. it works in a high-temperature furnace with protective tubing and in the presence of al2o3 within the temperature range of 25 to 1550 °c. a pt:pt-rh thermocouple was used. the glass transition (tg) and crystallization temperatures (tc) were determined from the second endothermic peak and first exothermic peak of the dta curve. dilatometric analysis the expansion curves of the samples were determined using a netzsch dil 402c dilatometer (urmpe university of boumerdes, algeria) at an average heating rate of 5 kmin-1. the samples were rectangular in shape, 8 mm wide and 20-25 mm long. tg was determined from the expansion curve by calculating the intercept, whereas the softening points (ts) were determined to be the maximum temperature of the expansion curve. density and molar volume measurements the densities were determined using the archimedes’ method by immersing the samples in liquid xylene. the relative error in these measurements was about ± 0.03 gcm-3 and the molar volume (vm) was calculated from the molecular weight (m) and density () according to the following equation: 𝑉𝑚 = 𝑀/ (1) 3. results and discussion 3.1. appearance of the samples the elaborate types of glass are shown in figure 1, where their blue color becomes darker and darker each time cuo is added. 3.2. theoretical calculations of properties the different components make a definite contribution to the effect of certain properties and the structure of types of glass. therefore, from their composition, these properties can be calculated by using additive formulae. however, this conclusion is only valid within a restricted range of compositions because how the ions interact with each other must be taken into account [18]-[21]. according to appen [18], within the temperature range of 20 400 °c between the nb1 and nb2 variants, a decrease in the coefficient of expansion (α) was observed, probably due to the increase in bo4 following the addition of small quantities of cuo; the non-bridging oxygen atoms of b2o3 in the binary glass na2o-b2o3 binded with those reintroduced by cuo to form bridging oxygen atoms (bo4), hence the strengthening of the structure (conversion of bo3 units into bo4). however, regarding the nb3 variant, since α increases in a progressive manner, it is assumed that the introduction of more cuo (greater than 0.77 mol%) increases the coefficient between 20 and 400 °c, leading to the reformation of non-bridging oxygen atoms. the densities of silica glass and boric glass measured show that the [sio4] tetrahedra bonded to each other or the [bo3] trihedra predominantly contain large voids, which influence the density of binary glasses of alkali silicates. if an alkali oxide is introduced into silica glass, the added oxygen ion contributes to the stacking of the oxygen ions, while the cations fill the empty spaces. as a result, the total space filled becomes larger and the density increases [1]-[3] as opposed to alkali borate types of glass where their density decreases as modifiers are added [22]-[23]. however, in our case, an increase in density is observed as the na2o content decreases as a result of the increase in the cuo content. the cu2+ ion, which has a relatively large atomic mass, was inserted between boron tetrahedra or trihedra by filling progressively more voids, table 1. chemical compositions of the variants samples composition [mol%] na2o b2o3 cuo nb1 20.00 80.00 nb2 19.97 79.95 0.075 nb3 19.84 79.38 0.770 nb4 19.68 78.77 1.550 nb5 19.21 76.88 3.900 figure 1. appearance of the elaborate samples annealing effect on copper-doped glasses 51(1) pp. 15–21 (2023) 17 thereby increasing the mass per unit volume of the samples. the properties of the studied types of glass are summarized in table 2. the refractive index (nd) increases in proportion to the content of alkali oxides because of the polarizability of the ions, namely as the polarizability increases, so does the refractive index. in our case, a remarkable decrease in the refractive index as the na2o content reduced and the cuo content increased was observed. the addition of cu2+ ions contributes significantly to the decrease in the refractive index, because it becomes less polarizable and allows the glass to be colored by the effect of ligand fields. the average degree of dispersion (d) also decreases as cuo is added for the same reasons that resulted in the refractive index decreasing. the relatively open structure of b2o3 glass explains its low modulus of elasticity (e) of only 175 kbar. as the na2o content in binary borate glasses increases, their structure becomes more rigid and the modulus of elasticity increases rapidly. according to narsimha [5], at 28.5 mol% of na2o, the modulus of elasticity has already risen to 565 kbar. as the na2o content decreases, a reduction in the modulus of elasticity is observed. in terms of the shear modulus (g), changes in this parameter as a function of its composition are similar to those of the modulus of elasticity albeit smaller. since the values of poisson’s ration (μ) measured are relatively high, a large transverse contraction occurred, however, by adding cuo, the values gradually decreased. given that the mechanical strength of the samples was low, their structures are not sufficiently rigid. as non-bridging oxygen atoms were added, both the mechanical tensile and compressive strengths (σt and σc) decreased. the thermal conductivity (λc) was calculated, the values of which did not change much according to the variants studied (λc ≈ 0.877 w/mk). this value is larger than that for silicate glasses (λc = 0.850 w/mk) [22]-[24]. by adding cuo, the thermal conductivity progressively decreased as cu2 + ions impede the transfer of heat inside the glass. this permittivity effect is caused by the fact that shifts in charge occur in the presence of an electric field. the electronic envelope in an ion may be deformed, the ions themselves may move slightly or they may change sites. the first possibility is all the more important as the polarizability of the ion under consideration is greater. therefore, the permittivity depends on the refractive index, which is also significantly influenced by the polarizability. at very high frequencies in glass, the oxygen ion is most easily polarized [7]. as has been seen with the reduction in the refractive index as a function of a decrease in the na2o content, the same phenomenon is observed by decreasing the electric permittivity (ε). 3.3. annealing effect certain properties of the samples were determined before and after annealing. annealed samples were marked as nb1-a, nb2-a, nb3-a, nb4-a, nb5-a; their nonannealed counterparts were marked as nb1-na, nb2na, nb3-na, nb4-na, nb5-na. a) practical determination of density the measured densities are given in table 3. the densities of the samples that were and were not annealed are different, namely annealed samples were denser than non-annealed ones. since annealing influenced the structure of the types of glasses, the change in their densities was due to structural changes [25]-[28]. it has been shown that the structure of glass after annealing is more compact than beforehand. to confirm this observation, it is necessary to structurally analyze table 2. calculated properties of elaborate types of glass samples α (10-6/k)  (g/cm3) nd d e (kbar) g (kbar) μ σt (mn/m2) σc (mn/m2) λc (w/mk) ε nb1 6.336 1.998 1.4940 0.00812 331.90 155.00 0.3107 56.81 739.84 0.8778 7.92 nb2 6.335 2.000 1.4928 0.00810 331.58 154.39 0.3104 56.76 739.20 0.8780 7.91 nb3 6.346 2.016 1.4823 0.00800 328.93 153.32 0.3079 56.29 733.14 0.8779 7.85 nb4 6.353 2.035 1.4708 0.00790 325.89 152.12 0.3051 55.78 726.45 0.8778 7.79 nb5 6.381 2.092 1.4356 0.00770 316.91 148.48 0.2967 54.24 706.37 0.8778 7.61 table 3. the measured densities of glass samples samples  (g/cm3) nb1-na 1.857 nb2-na 1.988 nb3-na 2.100 nb4-na 2.219 nb5-na 2.250 nb1-a 2.134 nb2-a 2.170 nb3-a 2.200 nb4-a 2.220 nb5-a 2.261 aboutaleb and safi hungarian journal of industry and chemistry 18 their structures before and after annealing by, for example, xrd (figure 2). as defects in their structure before annealing were corrected, the densities of the annealed samples increased [27]. b) structural diffraction analysis (xrd) the diffraction of sample nb1 before annealing (figure 2a) suggests an amorphous structure, while that after annealing (figure 2b) exhibits some peaks (impurities) but the structure remains unchanged. if the spectra of nb1 samples before annealing (a) and after annealing (b) are compared, it is observed that the last diffraction pattern, which can almost be superimposed on the first one, is less intense. therefore, annealing affects the structure of sodium borate glass by redistributing its structural units, partially correcting any defects and reinforcing its structure. c) practical determination of the refractive index the refractive indices measured for the different types of glass are presented in table 4. the refractive index always reduces as the amount of alkali oxides decreases and cuo is added. although the refractive indices of samples nb1 and nb2 decrease after annealing, those of nb3 remain the same before and after annealing. as a result, the structure influences the refractive index of the nb2 sample which contains little cuo and variant nb1 which does not contain any cuo because annealing decreases the number of defects in their structures (figure 3). for samples containing high levels of cuo (0.77, 1.55 and 3.90 mol%), annealing has no influence on nd, which remains constant for each variant. d) practical determination of vickers microhardness (hv) hardness is a property that characterizes the strength of the glass surface vis-à-vis its concentrated mechanical load, which is referred to as microhardness. the microhardnesses of the samples were measured using an equotip durometer. according to our results (table 5), it was observed that the microhardness increased as the na2o content (network modifiers) decreased and cuo was added. the annealed samples represent a strong degree of pickup, which is explained by the reinforcement of their structures and the release of structural stress. e) determination of chemical attack the etching test is based on the determination of the mass loss of the glass samples before and after three hours of chemical attack in chemical solutions (acids, bases and figure 2. diffraction spectra (xrd) of the nb1 samples (a): before annealing and (b): after annealing table 4. measured refractive indices of the samples of glass samples nd nb1-na 1.4930 nb2-na 1.4885 nb3-na 1.4820 nb4-na 1.4815 nb5-na 1.4800 nb1-a 1.4910 nb2-a 1.4830 nb3-a 1.4820 nb4-a 1.4815 nb5-a 1.4800 figure 3. refractive indices of the studied samples of glass before and after annealing table 5. vickers microhardness of the measured samples samples hv.107 (n/m2) nb1-na 122.2 nb2-na 144.0 nb3-na 216.0 nb4-na 229.0 nb5-na 289.6 nb1-a 190.0 nb2-a 200.0 nb3-a 221.0 nb4-a 233.0 nb5-a 426.2 annealing effect on copper-doped glasses 51(1) pp. 15–21 (2023) 19 neutral ones). in the three environments, since it was initially observed that the chemical attack was less severe for the annealed samples, annealing also improved their chemical resistance. in light of the values recorded (table 6), these samples of glass are unstable in the aqueous solutions used; the reactions that take place are complex and depend on the nature (composition) of the glass studied. investigation of the ir bands leads to an explanation for this phenomenon. generally, borate glasses are soluble in chemical solutions because of their weak structure composed of borate units. the chemical resistance of these samples of glass and the density of their structure increase by adding cuo compared to their basic chemical compositions without cuo [25]-[26]. f) optical spectroscopy of the samples (nb) the absorption spectra of samples nb1 and nb2 were recorded before and after annealing (figure 4). regarding sample nb1-na, some absorption bands of low intensity were observed and after sample nb1-a had been annealed, their intensities became even lower. annealing is believed to have reduced structural defects within the glass, thereby increasing transmission and decreasing the absorption of light. for sample nb2, to which cuo was added, the sample turned light blue in color due to the existence of divalent cu2+ ions resulting from the effect of ligand fields. by adding cuo, its color became even darker (figure 1). in the absorption spectrum of the nb2-na sample, absorption bands between 300 and 400 nm were observed, which are characteristic of the tetrahedral coordination of cu2. however, after annealing (nb2-a), the absorption band was observed between 600 and 700 nm, moreover, its intensity decreased [27]. the positions of this band are characteristic of cu2 + ions with octahedral coordination in the complex [cu(h2o)]2+ [22]. therefore, annealing influences the coordination of cu2 + ions which are transformed from tetrahedral to octahedral coordination. formation of the octahedral complex is indicated by the polarization of the transition metal ion bonded to the oxygen atom. this effect is weak for bo3 (due to the counter-polar effect of the two bridging atoms bound to bridging oxygen atoms) and strong for bo4 (or the bridging oxygen atoms are more weakly counterpolarized), the latter favors octahedral coordination. table 6. the results of samples in different chemical environments samples neutral solution (distilled water) acid solution (hcl) basic solution (naoh+na2co3) m0 (g) m1 (g) 𝑀1 − 𝑀0 𝑀0 (%) m0 (g) m1 (g) 𝑀1 − 𝑀0 𝑀0 (%) m0 (g) m1 (g) 𝑀1 − 𝑀0 𝑀0 (%) nb1-na 2.583 0.010 99.61 1.808 0.01 99.44 2.076 0.102 95.08 nb2-na 2.593 0.254 90.20 0.536 0.01 98.13 4.313 1.861 56.85 nb3-na 3.680 0.549 85.08 1.670 0.01 99.40 3.592 0.199 94.45 nb4-na 4.429 1.246 71.86 3.090 0.009 3 96.99 3.172 0.402 87.32 nb5-na 2.553 0.965 62.20 4.138 0.009 5 97.70 1.243 0.382 69.26 nb1-a 3.649 0.481 86.81 1.117 0.229 79.49 2.040 0.558 72.64 nb2-a 1.908 0.450 76.41 3.273 0.179 94.53 1.586 0.272 82.84 nb3-a 3.259 0.819 74.86 1.222 0.01 99.18 3.772 0.350 90.72 nb4-a 3.345 1.078 67.77 6.334 1.657 73.83 1.348 0.242 82.04 nb5-a 2.150 1.118 48.00 1.567 0.053 96.61 3.240 1.337 58.73 figure 4. absorption spectra of 6mm-thick samples (a) nb1-na, (b) nb1-a, (c) nb2-na, (d) nb2-a aboutaleb and safi hungarian journal of industry and chemistry 20 g) infrared transmission the absorption of light in the ultraviolet and visible regions of the spectrum is due to electronic transitions, while some low-energy electronic transitions are observed in the infrared region of the spectrum due to vibrational transitions. the frequency (ν) of a vibrational absorption in a diatomic molecule is given by the following formula [16-17,28]: 𝜈 = ( 1 2𝜋 ) √ 𝐹 𝜇 (2) where f denotes the binding constant and μ the reduced mass of the molecule, which is calculated by the formula below: 𝜇 = 𝑚1 · 𝑚2 𝑚1 + 𝑚2 (3) where m1 and m2 denote the atomic masses of the two atoms which form the molecule. due to the complexity of the infrared spectra, which is related to the great diversity of structural groupings present in the borate glasses, their interpretation is difficult. the ir spectra of samples nb1 and nb2 (without annealing) are shown in figure 5, the interpretations of which are based on data from the literature of some types of glass and borate phases [19-20,28]. it is known that the absorption bands in the vibrational spectrum of boric glass fall between 1270 and 700 cm-1 due to the bo3 groups which form the boroxol groups. the vibrational modes of the borate network in binary m2o (mo) b2o glasses are mainly active in the following three regions of the infrared spectrum: • 1500-1200 cm-1 (b-o vibrational band of trihedral bo3 units) • 1200-850 cm-1 (b-o vibrational band of tetrahedral bo4 units) • 800-600 cm-1 (asymmetric vibrational band of borates) bo3 and bo4 form structural units such as diborate, triborate and pentaborate, in which the ratio of b3 to b4 varies. absorption in the high frequency regions of the spectrum is given by the vibrational band of the hydroxyl groups forming the hydrogen bonds. the bands between 3700 and 3200 cm-1 are attributed to the vibrations of the o-h linking groups which prove the presence of dissolved water in these glasses. according to the ir transmittance curves of the samples, almost the same band at about 3443.09 cm-1 was observed, which is characteristic of the o-h bond. when cuo was introduced, a change in intensity was observed. it can be concluded that the addition of cuo to the network seems to progressively transform rigid tetrahedra (bo4) into more flexible trihedra (bo2o-) [27]-[28]. 4. conclusion by adding small amounts of cuo (0.075 mol%) to a sodium borate glass, the bo3 units were transformed into bo4 ones. however, following the addition of 0.770 mol% of cuo, it was noticed that the bo3 units reformed and the quantity of bo4 ones decreased, leading to an increase in the coefficient of thermal expansion, a decrease in the refractive index and optical dispersion as well as a reduction in the mechanical properties, thermal conductivity and electric permittivity. in contrast, an increase in density, microhardness and chemical resistance was observed by adding cuo. the oxygen added following the addition of cuo became a nonbridging oxygen atom and created trihedral bo3 units, which released its glassy structure. however, the insertion of cu atoms in the structure increased the density, microhardness and resistance to chemical attack of the glasses. it can be concluded that the addition of cuo to the network seems to progressively transform rigid tetrahedra (bo4) into more flexible trihedra (bo2o-) with non-bridging oxygen 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of mechatronics, optics and mechanical engineering informatics, budapest university of technology and economics, bertalan lajos u. 4-6, budapest, 1111, hungary this paper deals with an instantaneous feedback controlled inverter using sliding mode control. the theoretical contribution of this paper is that a common state-space-based sliding surface design method is extended for follow-up control. starting from the basic theory of sliding mode control, the trajectory of the error signal is modelled. the practical contribution of this paper is the relationship between the trajectory of the error signal and the total harmonic distortion (thd) of the output voltage signal. the conditions of the sliding mode control using an uninterruptible power supply (ups) are discussed. a rectifier as a non-linear load is simulated. experimentally validated simulation results are presented. keywords: sliding mode control, hysteresis control, second order system, ups 1. introduction power electronics equipment that produces alternating voltage and current impulses is typical of variable structure systems (vsss). a vss usually consists of a state when it is insensitive to variations in parameters and load disturbances. this state is referred to as the sliding mode. the cost of insensitivity is an infinitely high switching frequency. due to the limits with regard to switching delays and frequencies of controlled switches, an ideal sliding mode does not exist. however, the ideal sliding mode can be approximated with an acceptable degree of accuracy. the theory of variable structure systems and sliding mode control was developed decades ago in the soviet union, mainly by vadim i. utkin [1] and david k. young [2]. according to the theory, sliding mode control should be robust but experiments have shown that it is subject to serious limitations. the main problem with applying the sliding mode is the high frequency of oscillation around the sliding surface, referred to as chattering, which strongly reduces the performance of the control. very few have managed to put the robust behavior predicted by the theory into practice. many have concluded that the presence of chattering makes the sliding mode control a good game theory, which is not applicable in practice. over the following period, researchers invested most of their energy in chattering-free applications, leading to the development of numerous solutions like the discrete-time sliding mode [3], sector sliding mode [4], adaptive sliding mode [5] and terminal sliding mode [6]. *author for correspondence: domonkos@mogi.bme.hu sliding modes can also be used for feedback compensation [7]. the design of a sliding mode controller consists of three main steps. the first is the design of the sliding surface, the second step is the design of the control law which holds the system trajectory on the sliding surface, and the third and key step is implementation of the chattering-free sliding mode control. the systematic sliding manifold design for linear systems was proposed by utkin [1]. this method was extended in several ways and optimal sliding manifold designs proposed, e.g. frequency-shaped sliding mode control (fssmc) [8] surface design based on h∞ control theory [9, 10] and tensor product model transformation-based sliding surface design [11]. the reference signal was constant in all the aforementioned papers. recently, the application of predictive control has become popular [12]. the new element in this paper is that the original method was extended for follow-up control. according to refs. [13] and [14], uninterruptible power supplies (upss) are being broadly adopted for the protection of sensitive loads, e.g. pcs, air traffic control systems, life care medical equipment, etc., against line failures or other perturbations in ac mains. ideally, an ups should be able to deliver: 1) a sinusoidal output voltage with low total harmonic distortion during normal operation, even when feeding nonlinear loads (particularly rectified loads); 2) the voltage dip and recovery time due to a change in load step must be kept as small as possible, that is, provide a fast dynamic response; 3) the steadystate error between the sinusoidal reference and load regulation must be zero. to achieve these, a proportional inhttps://doi.org/10.33927/hjic-2020-23 mailto:domonkos@mogi.bme.hu 14 domonkos and fink tegral (pi) controller is usually used [15], moreover, issues concerning robust stability and controller robustness are discussed in [16]. however, the system using the pi controller subject to a variable load rather than the nominal ones cannot produce a fast and stable output voltage response. in the literature, some hybrid solutions to overcome this problem can be found [17,18]. the principle of pulse width modulation (pwm) plays a very important role in power electronics [19]. in the field of inverter technology, which produces a sinusoidal voltage, a great number of "optimized pwm" techniques have been proposed in the literature. these types of pwm inverters have very good steady-state characteristics, but for the voltage regulator to respond to a sudden change in the load takes a few cycles and nonlinear loads can cause high "load harmonics". this is unacceptable in ups applications for which instantaneous feedback is preferred [20, 21]. the sliding mode control of power electronic inverters is suggested in refs. [22] and [23]. on the one hand the main advantage of the sliding mode-based method proposed in this paper is the direct control of the transistor switches, but on the other hand uncontrolled thd results. that is why the thd is the focus of this paper. the structure of this paper is as follows. after the introduction, section 2 presents the problem statement, describes the system configuration and summarizes the design of the sliding mode control. section 3 describes the equations of the system and shows how the mathematical foundations are applied to a practical example. following the main steps of sliding mode design, namely the surface design, a control law is selected by taking into consideration the reduced chattering. section 4 presents the simulation results, which are validated by experimental measurements of a 10 kva ups. finally, in section 5, the presented results are analyzed. 2. problem statement 2.1 system configuration a simplified diagram of the inverter and filter is shown in fig. 1 vb denotes the battery voltage and vi stands for the input voltage of the system, which is a filter with a load. the input signal consists of three different values (vb, −vb and 0) depending on the switching states of the transistors. the goal is that the transistors must be switched in such a way that vo, the output voltage of the system, follows the sinusoidal reference signal. ls in fig.1 denotes the leakage inductance of the transformer, which has a special structure to increase and set the value of ls. the main field inductance lp cannot be ignored from the point of view of the resonance circuit. the loss of the transformer is modelled by an increased load. vo(t) = √ 2 · 230 cos (2π50t) (1) figure 1: simplified figure of the inverter and filter 2.2 sliding mode control a single-input single-output (siso) system is given in state-space controllable canonical form. ẋ(t) = ax(t) + bu(t) (2) y(t) = cx(t) (3) where x(t) ∈ rn, a ∈ rn×n, b ∈ rn×1, c ∈ r1×n and u(t), y(t) ∈ r. y(t), the output variable of the controlled plant, can be described by a n-th order differential equation supposing that the reference signal yr(t) can be differentiated at least n times. the goal is given in yr(t) = y(t) if t > tc (4) where tc denotes the control period. the system error, ey(t), is given by ey(t) = yr(t)− y(t) (5) thus the error signal, ey(t), can also be differentiated at least n times, so the n − 1-th derivative must exist and is continuous. due to the latter property, when trying to eliminate the error, it is also useful to control its derivatives (including the n − 1-th derivative). otherwise, because of the system inertia, an oscillation with a large amplitude could arise. the essence of sliding mode control could be summarized as follows: in order to eliminate the error in the n-th dimensional phase space, a continuous error trajectory running into the origin has been designed. whilst planning, the physical limits should be taken into account. by implementing our very own transient, the ideal system follows the reference signal without any errors. the control signal is designed so that the hungarian journal of industry and chemistry follow-up control of a second order system in sliding mode 15 trajectory realized does not deviate from the prescribed one or once the origin has been reached, it remains at rest. usually σ, a scalar variable, can be defined as a positive or negative distance between the desired and actual trajectories, or each trajectory sector can be prescribed by a single scalar variable. the task of the controller is to ensure this scalar variable remains zero. in the classical method of sliding mode control, this scalar variable is calculated as a linear combination of the error and its derivatives [1]. when n = 2, the scalar variable can be defined by the following equation: σ(t) = ey(t) + τ ėy(t) (6) where τ denotes a time constant-type control parameter chosen by us. in sliding mode control: σ = 0 (7) and the trajectory is described by the following equation: ey(t) = −τ ėy(t) (8) that corresponds to a −1/τ gradient in the phase plane. this is usually referred to as the sliding line or sliding surface in multidimensional phase space. the solution of eq. 8 is an exponential function with a negative exponent: ey(t) = e0e − t τ t ≥ 0 (9) where e0 = ey(0). consequently, the error will decrease according to the chosen time constant, τ , independently from the system parameters, e.g. load. after an exponential transient process, yr(t) = y(t). to ensure that the system moves in all cases towards the sliding mode (i.e. towards σ(t) = 0), the following condition is necessary: σ(t)σ̇(t) ≤ 0 (10) the design of a sliding mode controller does not require accurate modelling, it is sufficient to only know the boundaries of the model parameters and the disturbance. during sliding mode control, the only task is to switch the control signal so that eq. 10 is valid in every instance. no other information concerning the controlled plant and the disturbances is needed. it is sufficient to determine whether eq. 10 holds or not. in simple cases (or within a range of errors and its derivatives), the signs of the control signal and σ̇(t) are opposite. thus it is often satisfactory to use a relay controller, which switches the control signal according to the sign of the parameter σ(t). 2.3 follow-up control since yr(t) is not constant, wyr,u(s), the transfer function from u(t) (vi(t)) to yr(t) (vo(t)), must be calculated. according to eq. 4, it is the inverse of the transfer function with regard to the inverted system: y(s) = wu,y(s)u(s) (11) wyr,u(s) = w−1u,y(s) (12) usually, the inverse of wu, y(s) cannot be realized. in our case, yr(t) is sinusoidal: yr(t) = √ 2vr cos (ωrt) (13) only two parameters must be calculated, namely the gain (gr) and phase shift (ϕr) of the transfer function of the system at the reference angular frequency (ωr). the definition of the error (eq. 5) must be modified: ey(t) = √ 2 gr vr cos (ωrt− ϕr)− y(t) (14) 3. equations of the system 3.1 filter and load using the notation of fig. 1, the equation for the currents is: ii(t) = io(t) + ip(t) + ic(t) (15) by assuming resistive load rl: io(t) = 1 rl vo(t) (16) the equation of the input voltage is vi(t) = ls dii(t) dt + vo(t) (17) by substituting eqs. 15 and 16 into eq. 17, the filter circuit with a resistive load can be described by the following differential equation: vi(t) = lscpv̈o(t) + ls rl v̇o(t) + 1 g vo(t) (18) where g = lp ls + lp (19) the transfer function from u(t) (vi(t)) to yr(t) (vo(t)) (including the effect of the resistive load) can be calculated from the laplace transformed form of eq. 18: vo(s) = g glscps2 + gls rl s+ 1 vi(s) = w (s)vi(s) (20) 3.2 the states of the state-space equation since the inverter and load are handled separately, the system has two inputs, namely ui and io. since the input current must be calculated, three state variables are selected for the three storage elements, even if they are not independent and the rank of the system matrix is only 2. using the notation of fig. 1, the three state variables are ii(t), ip(t) and vc(t): x(t) =  ii(t)ip(t) vo(t)  (21) 48(2) pp. 13–21 (2020) 16 domonkos and fink the load is connected in parallel to the inverter capacitor cp. the load current includes the effect of transformer losses. the system has three outputs since vo(t) = vc(t) as well as its derivative are necessary to calculate the scalar variable and ii(t) is visualised. in the real system, the current of the capacitor is measured instead of v̇o(t). according to eqs. 15, 16, and 17, the matrices of the system are: a =  0 0 − 1 ls 0 0 1 lp 1 cp − 1 cp 0  b =  0 − 1 ls 0 0 − 1 cp 0  c = 1 0 0 0 1 0 0 0 1  d = 0 0 0 0 0 0  (22) 3.3 error trajectory to calculate the error defined by eq. 14, gr and ϕr must first be calculated. according to eq. 20: w (jωr) = g glscp(jωr)2 + gls rl jωr + 1 (23) gr and ϕr can be calculated from eq. 23, where w (jωr) denotes a simple complex number: gr = |w (jωr)| (24) ϕr = angle(w (jωr)) (25) since the filter must be inductive, ϕr must be negative. therefore, the reference signal must lead to vo(t), which is the controlled signal in eq. 14: y(t) = vo(t) (26) the derivative of the error is: ėy(t) = −ωr √ 2 gr vr sin (ωrt− ϕr)− v̇o(t) (27) the scalar variable of the sliding mode control is calculated by eq. 6. 3.4 control law three different control laws were examined. all of them can directly control the switching of the transistors. this is the main advantage of sliding mode control in the field of power electronics. more advanced controllers can be found in ref. [24]. simple relay the input voltage on the filter is switched according to the sign of σ(t): vi(t) = vbsign(σ(t)) (28) from a practical point of view, the main problems of eq. 28 are • the inverter has a zero state, which is not applied; • the switching frequency is uncontrolled. figure 2: double relay with dead zone and hysteresis double relay the solution to the first problem is the usage of two relays: vi(t) = vb 2 sign(σ(t)) + vb 2 sign(cos (ωrt− ϕr)) (29) vb and 0 are switched in the positive half period, while −vb and 0 are switched in the negative half period. however, eq. 29 does not solve the second problem. double relay with dead zone and hysteresis both problems can be solved by a double relay with dead zone and hysteresis. this control law is shown in fig. 2. 3.5 stability analysis using a simple relay controller, whether or not eq. 10 holds can be verified. first, σ̇(t) must be expressed: σ̇(t) = ėy(t) + τ ëy(t) (30) according to eq. 27: ëy(t) = −ω2 r √ 2 gr vr cos (ωrt− ϕr)− v̈o(t) (31) v̈o(t) can be expressed from eq. 18: v̈o(t) = 1 lscp vi(t)− 1 rlcp v̇o(t)− 1 glscp vo(t) (32) by substituting eq. 28 into eq. 32: v̈o(t) = vbsign(σ(t)) lscp − v̇o(t) rlcp − vo(t) glscp (33) according to eqs. 30 and 31, if the value of v̈o(t) is sufficiently large and the system operates in an area which is close enough to the sliding mode, then the sign of v̈o(t) is the opposite to that of σ̇(t). from eq. 33, it is clear that if the value of vb is sufficiently large and the system operates in an area which is close enough to the sliding mode, then the sign of v̈o(t) is the same as that of σ(t). in conclusion, if the value of vb is sufficiently large and the hungarian journal of industry and chemistry follow-up control of a second order system in sliding mode 17 system operates in an area which is close enough to the sliding mode, then the sign of σ(t) is the opposite to that of σ̇(t). similar analyses can be conducted for all control laws. in practice, the simulations proved that by substituting the actual parameters of the system, all the control laws examined fulfil the condition (eq. 10) during normal operations. 4. simulation matlab-simulink simulations were carried out. 4.1 matlab-simulink model the main elements of the matlab-simulink model are shown in figs. 3–6. even if the structure of the controller shown in fig. 6 is quite simple, its performance is quite robust. 4.2 model validation the simulation results were compared to previous results measured by [25] as shown in fig. 7. the nominal power of the inverter is 10 va. all parameters of (14) and (22) in addition to the values of dead zone and hysteresis shown in fig. 2 are known from ref. [25]. like in real systems, where σ is tuned manually to set the number of switches per period, σ is changed to achieve a similar result in the simulation as in real systems. the simulation result is shown in fig. 8 after the value of σ was set. the first problem faced in the simulation was the steady state. when the real system was measured, the screen of the oscilloscope seemed to be frozen for most settings of σ. therefore, the error trajectory was a closed curve during a period in a steady state. using the default settings of simulink, a quasi-steadystate period of the error trajectory of the simulation resulted as is shown in fig. 9. the consequent periods are slightly different, which causes subharmonics that are crucial from a practical point of view. the main question is whether these subharmonics are an immanent property of the applied switching method or a result of an insufficiently precise simulation. several simulations were carried out using different model configuration parameters in simulink. it is concluded that the precise calculation of the switching instant is key to simulating proper steady states. the ode113(adam) method is the most suitable integral method for switched systems. (the equation solvers for ups are compared in ref. [26]). 4.3 analysis of the simulation results the main advantage of the pwm technique is that the filter can be smaller resulting in a smaller no-load current. the parameters of the filter are given in ls = 3.5mh, lp = 32mh, cp = 320µf (34) figure 3: the whole system. figure 4: subsystem for calculating scalar variables. figure 5: subsystem for the load. figure 6: subsystem for the relay controller of the dead zone and hysteresis τ , the gradient of the switching line in the sliding mode, has been changed. the value of the nominal load is rl = 5.3ω. the relationship between the gradient of the switching line and the number of switches is shown in fig. 10. the larger the value of τ , the smaller the gradient of the switching line and the greater the number of switches per period. on the other hand, the bigger the value of τ , the longer the transient according to eq. 9. the optimum must be calculated. the number of switches per period and the total harmonic distortion (thd) are shown in fig. 11 as a function of τ . the first one is staggered. the larger the num48(2) pp. 13–21 (2020) 18 domonkos and fink figure 7: reference measurement result figure 8: reference simulation result figure 9: error trajectory during a quasi-steady-state period ber of switches is, the greater the switching loss and the smaller the thd are. the optimum is approximately 52 switches, therefore, 13 pulses per period, as is shown in fig.7 and fig. 8. the step concerning the optimal number of switches is magnified in fig. 12. a local minimum of thd is located at the middle of a staircase (in fig. 12) when the transient between the positive and negative half periods is smooth as is shown in fig. 13. by increasing τ , the transients change slightly. first, a v shape appears (see fig. 14). by further increasing τ , the v shape transforms into a loop (see fig. 15) and the last pulses in all half periods have the opposite signs when compared to the reference signal (see fig. 16) which increases the thd. finally, the number of switches per period is increased by 4 and the figure 10: the effect of τ on the number of switches figure 11: number of switches and thd as a function of the gradient of the switching line figure 12: the optimal number of switches and its thd transients are in the form of vs and loops once more (see fig. 17), which disappear at the middle of the staircase. 4.4 non-linear load the most challenging load is the rectifier [27], since its current is not sinusoidal and the value of its peak is relatively large. a rectifier resembling a load is simulated, which has approximately the same root mean square (rms) value of the current as that of the nominal current. the time functions of the output voltage and current in addition to the input current are shown in fig. 18. the rms value of the input no-load current is zero at the beginning of the period, when the output current is zero. since the load current is continuous and the reaction of the sliding mode controller is practically instantaneous as a result, this type of non-linear load has no significant efhungarian journal of industry and chemistry follow-up control of a second order system in sliding mode 19 figure 13: smooth transient of error trajectory figure 14: v-shaped transient of error trajectory figure 15: loop-shaped transient of error trajectory fect on the output voltage the thd depends on the shape of the error trajectory, which is shown in fig. 19: 4.5 switching on the load a nominal resistive load is assumed and the load is switched on at the peak value of the output voltage. the time functions of the voltage and current are shown in fig. 20. since the current is discontinuous, a transient is figure 16: control signal figure 17: transient of error trajectory after the number of switches is increased present, which is recognizable in terms of the shape of the error trajectory in fig. 21. the length of the transient depends on the value of τ , that is, 0.22 ms. the transient caused by any step change in the load occurs extremely quickly and only lasts approximately 1 ms. 5. conclusions this paper introduced a follow-up control method with a sinusoidal reference signal for the design of a sliding surface and the performance of a double relay controller with a dead zone and hysteresis operating in a sliding mode was analysed. the simulation of variable structure systems is very sensitive to the integral method of simulation. the zero-crossing must be detected. even a relatively simple controller, which can be implemented by an analogue operational amplifier, also performs very well with a non-linear load. the positive and negative half periods can be separated by a dead zone and the switching frequency limited by hysteresis. the actual number of switches can be set by the gradient of the sliding line. the value of the thd depends on the shape of the error phase trajectory. a non-linear load with a continuous output current has no significant effect on the output voltage because of the instantaneous behavior of the sliding mode controller. 48(2) pp. 13–21 (2020) 20 domonkos and fink figure 18: output voltage as well as input and output currents with a rectifier-like load figure 19: error trajectory of the non-linear rectifier-like load acknowledgement the research reported in this paper and carried out at the budapest university of technology and economics has been supported by the national research development and innovation fund (tkp2020 institution excellence subprogram, grant no. bme-ie-mifm) based on the charter of bolster issued by the national research development and innovation office under the auspices of the ministry for innovation and technology. references [1] utkin, v. i.: variable structure control optimization (springer-verlag), 1992 doi: 10.1007/978-3-642-84379-2 [2] young, k.: controller design for manipulator using theory of variable structure systems, ieee trans. syst. man cybern. syst., 1978, 8(2), 101–109 doi: 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https://doi.org/10.1109/tia.1984.4504486 https://doi.org/10.1109/tia.1984.4504486 https://doi.org/10.1016/j.rser.2015.12.335 https://doi.org/10.1016/j.rser.2015.12.335 https://doi.org/10.1007/bfb0109978 https://doi.org/10.1142/s0218126695000424 https://doi.org/10.3390/en11102544 https://doi.org/10.12700/aph.11.03.2014.03.6 https://doi.org/10.12700/aph.11.03.2014.03.6 https://doi.org/10.1016/j.ifacol.2017.08.1169 https://doi.org/10.1016/j.ifacol.2017.08.1169 https://doi.org/10.3390/en12040581 introduction problem statement system configuration sliding mode control follow-up control equations of the system filter and load the states of the state-space equation error trajectory control law simple relay double relay double relay with dead zone and hysteresis stability analysis simulation matlab-simulink model model validation analysis of the simulation results non-linear load switching on the load conclusions untitled hungarian journal of industry and chemistry vol. 52(1) pp. 93–96 (2024) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2024-12 assessement of the surface roughness of cellulose ionogel membranes using atomic force microscopy péter bakonyi1* 1 research group on bioengineering, membrane technology and energetics, university of pannonia, egyetem u. 10., veszprém, 8200, hungary nowadays, ionogels are widely researched materials as they can be easily designed and varied as well as have a wide range of applications. being composed of an ionic liquid and cellulose, they are biodegradable with properties dictated by the ionic liquid such as high conductivity and ion transport capabilities. sometimes they are used in the aqueous phase, making their analysis very difficult due to the conditions surrounding them. the porosity and surface roughness of membranes are important properties. atomic force microscopy is capable of avoiding the aforementioned difficulties and providing such essential data while providing images of the examined surface as well. the purpose of this work is to examine this novel material and how specific data can be recorded by atomic force microscopy. keywords: cellulose, ionic liquid, ionogel, afm, surface roughness 1. introduction ionic liquids are organic solvents which are nonflammable, thermally stable and good conductors at extremely low vapour pressures capable of carrying out ion exchange. being environmentally-friendly solvents composed of an organic cation and an organic or inorganic anion, they are designable and offer a versatile range of applications. the majority of them are liquid below 100 °c and are referred to as room-temperature ionic liquids (rtils) [1]. one of the most commonly used groups of rtils are based on an imidazolium cation (figure 1) usually with a halide anion, the most commonly used and researched being 1-butyl-3-methylimidazolium chloride ([bmim][cl]). in order to utilize the ionic liquid [bmim][cl] as a membrane, it must be immobilized since it cannot maintain the typical conformation of a cylindrical membrane. one method is to make an ionogel from a mixture of an ionic liquid and microcrystalline cellulose [2]. in doing so, the ionic liquid will become part of the grid structure of cellulose which acts as a matrix for the ionic liquid. this novel gel-like material, that is, ionogel, is biodegradable and cheap as cellulose is the most abundant organic material on earth. once spread, the fabricated ionogel can be used as a membrane, for example, in a microbial fuel cell (mfc) that may be subjected to microbial fouling due to certain strains attaching to its surface. a mfc is a galvanic cell in which the anode chamber is filled with electrochemically active received: 5 march 2024; revised: 18 march 2024; accepted: 20 march 2024 *correspondence: bakonyi.peter@mk.uni-pannon.hu anaerobic microorganisms that catalyse the oxidation of organic matter, leading to the conversion of hydrogen ions and electrons [3]. the protons migrate to the aerobic cathode chamber, where the oxygen on the cathode is reduced by the electrons released thus closing the circuit. during this process, these electrons can be harnessed and utilized. since the anode chamber of the fuel cells is filled with a mixed culture, the membrane suffers from the formation of an inevitable layer of organic mass called biofouling which is affected by the composition of the microbial culture of the seeds and the properties of membranes such as surface roughness [4]. as a result of the aforementioned property, it is crucial to study the surface of the membrane. in the mfc, the membrane is in its wetted state, so in order to gain representative data it is necessary to also carry out an analysis of the membrane in its wetted form, which is impossible using certain analytical techniques such as scanning electron microscopy, the most common surface-imaging method for membranes. other techniques, such as stylus instruments or optical methods like diffuse reflection or figure 1: imidazolium cation https://doi.org/10.33927/hjic-2024-12 mailto:bakonyi.peter@mk.uni-pannon.hu bakonyi hungarian journal of industry and chemistry 94 taper sectioning [5], are also unsuitable, because the surface of the samples is not conductive, cannot tolerate vacuums and is relatively easily damaged. on the other hand, atomic force microscopy (afm) is a technique that is capable of providing information about the surface of the examined material, even in its wetted state since a vacuum is not required for the analysis unlike for scanning electron microscopy. 2. experimental 2.1. fabrication of the ionogel 5 grams of ionogel was fabricated by stirring 13 m/m % of microcrystalline cellulose (molar chemicals kft., hungary) and 87 m/m % of [bmim][cl] (iolitec-ionic liquids technologies gmbh, germany) together in a porcelain mortar until the product became a liquid of low viscosity. next, it was poured onto a glass plate and spread to achieve the necessary thickness of 750 µm before being cured at 100 °c for an hour. during the heat treatment, the ionic liquid breaks the h-bonds between two glucose units before it is presumably wedged between them, forming a colloidal solution with the cellulose [6]. this process is not yet fully understood and remains a subject of research. the suspected mechanism whereby the h-bonds are broken can be seen in figure 2. after curing, the glass plate the mixture was submerged in distilled water for an hour. during that time, gelation took place resulting in the formation of an ionogel. subsequently, the necessary shape needs to be cut out and can be used as can be seen on figure 3. 2.2. afm imaging afm is an imaging technique in where the surface topography of a solid sample is investigated by a probe consisting of a sharp tip attached to an elastic cantilever which moves over the surface of the sample. the interaction between the probe and this surface creates a morphological and topographic image by monitoring the changes in the vertical position of the probe as the sample is moved. other than the surface morphology, afm is able to investigate other aspects of the sample based on the tip-surface interactions such as adhesive forces, young’s modulus, electrical conduction, charge distribution and inhomogeneity [7]. the change in the position of the afm probe vertically during imaging is shown in figure 4. in general, the surface of the sample must be flat with inclines that the cantilever can handle, that is, usually less than 10 µm, to prevent it from getting damaged. the surface of the sample must also be clean so a suitable degree of chemical purging is preferable [8]. in this study, the afm imaging of ionogel membrane samples was carried out with the support of dr. zbynek pientka from the institute of macromolecular chemistry at the czech academy of sciences. figure 2: mechanism of cellulose dissolution [6] figure 3: ionogel membrane figure 4: interaction between the sample surface and the afm probe cellulose ionogel membrane 52(1) pp. 93–96 (2024) 95 3. results and analysis the samples were examined in their wetted state. a scanning probe microscope bruker dimension icon pt was used to observe the samples in peakforce qnm tapping mode in water providing both i) the topography of the surface depicted and ii) local elastic/adhesive properties of the sample. silicon nitride afm cantilevers and a scanasyst-fluid+ probe (bruker) with a typical tip-apex distance of 2 nm (max 10 nm) were used. no damage to the samples caused by the scanning probe was observed. the resulting images were not processed further, except to compensate for tilt. an examined spot on the surface of the membrane is shown in figure 5 (side a). a 3x3 µm wide area was observed at a magnification suitable for observing distances 350 nm across. darker spots indicate pores on average 200 nm in diameter on the surface of the membrane. the porosity could not be calculated precisely from these images. the average surface roughness ra was 428 nm. in figure 6, side b of the membrane was observed using the same method and parameters as for side a, revealing the same features except that the average surface roughness was no more than 222 nm due to the glass plate being in contact with the membrane during curing. 4. conclusions wetted ionogel membranes were observed using afm. the surface of one of the membranes was very corrugated, while the other was smooth. local mechanic properties (adhesivity) did not reveal any material heterogeneity. the difference in surface roughness (428 vs. 222 nm) originates from the fact that one side was in contact with a glass plate which held the material during heat treatment, thereby making it smoother. although the images revealed signs of pores, this method was not able to determine if they penetrate through the main bulk of the membrane nor provide information about their porosity. nevertheless, it was able to determine their size which varied between 200 nm and 1-2 µm, sometimes even forming valleys. knowing how difficult it is to analyse such materials, afm has proven to be a useful method for gaining information directly about a gel-like material which usually requires pretreatment that alters the material, thereby altering the results. acknowledgements this research was supported by the projects 2023-1.2.1era_net-2023-00012 and otka k 138232 as well as by the national research, development and innovation office (nkfih) of hungary. the author would like to acknowledge the support provided by dr. zbynek pientka from the institute of macromolecular chemistry at the czech academy of sciences, prague regarding afm imaging of the ionogel membrane samples. references [1] ghandi, k.: a review of ionic liquids, their limits and applications, green sustain. chem., 2014, 4(1), 44–53, doi: 10.4236/gsc.2014.41008 [2] kadokawa, j.-i.; murakami, m.-a.; kaneko, y.: a facile preparation of gel materials from a solution of cellulose in ionic liquid, carbohydr. res., 2008, 343(4), 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(ed) (crc press, boca raton), 2000, pp. 62–63, isbn: 9780849384035 [6] liu, z.; wang, h.; li, z.; lu, x.; zhang, x.; zhang, s.; zhou, k.: characterization of the regenerated cellulose films in ionic liquids and rheological properties of the solutions, mater. chem. phys., 2011, 128(1–2), 220–227, doi: 10.1016/j.matchemphys.2011.02.062 [7] johnson, d.; hilal, n.: characterization and quantification of membrane surface properties using atomic force microscopy: a comprehensive review, desalination, 2015, 356, 149–164, doi: 10.1016/j.desal.2014.08.019 [8] kosareva, e.k.; pivkina, a.n.; muravyev, n.v.: atomic force microscopy in energetic materials research: a review, energ. mater. front., 2022, 3(4), 290–302, doi: 10.1016/j.enmf.2022.05.004 https://doi.org/10.1016/j.matchemphys.2011.02.062 https://doi.org/10.1016/j.desal.2014.08.019 https://doi.org/10.1016/j.enmf.2022.05.004 hungarian journal of industry and chemistry vol. 47(1) pp. 1–83 (2019) hjic.mk.uni-pannon.hu contents editorial preface to the special issue dedicated to the 15th international phd workshop on systems and control attila magyar 1-1 non-technical loss diagnosis in electrical networks with a radial layout anna i. pózna, attila fodor, and katalin m. hangos 3–9 evaluation of resource optimization based on quantum search sara el gaily 11–16 simulation of color afterimages: an approach to computing virtual color perception lőrinc garai and andrás horváth 17–24 thermal model development for a cubesat nawar al hemeary, maciej jaworski, jan kindracki, and gábor szederkényi 25–32 automated labeling process for unknown images in an open-world scenario dávid papp and gábor szűcs 33–39 model reference adaptive control for telemanipulation nándor fink 41–48 simulation of a balanced low-voltage electrical grid using a simplified network model márton greber and attila fodor 49–56 modeling and calculation of the global solar irradiance on slopes roland bálint, attila fodor, istván szalkai, zsófia szalkai, and attila magyar 57–63 aggregation of heterogeneous flexibility resources providing services for system operators and the market participants istván balázs, attila fodor, and attila magyar 65–70 comparison of the approximation methods for time-delay systems: application to multi-agent systems áron fehér and lőrinc márton 71–77 rule-base formulation for clips-based work ergonomic assessment benedek szakonyi, tamás lőrincz, ágnes lipovits, and istván vassányi 79–83 hungarian journal of industry and chemistry vol. 47(1) pp. 1–1 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-01 editorial preface to the special issue dedicated to the 15th international phd workshop on systems and control attila magyar1 1department of electrical engineering and information systems, university of pannonia, p. o. box 158, veszprém, h-8201, hungary systems and control theory is a scientific area that is constantly developing and a dominant driving force behind key industries and fields of engineering, e.g. process engineering, automotive engineering, bioengineering, the energy sector, etc. the goal of this issue is to provide an overview of the actual research topics pursued by some selected phd students. the papers presented here were chosen from among the contributions at the 15th international phd workshop on systems and control held august 30-31, 2018. the objective of this workshop was to establish an international forum for discussion between young researchers and engineers from the industry and related research fields. the meeting provided opportunities for the participants to present and discuss their latest results and up-to-date applications in systems and control. this issue represents the entire spectrum of systems and control engineering as follows: • process modeling and analysis; control (traditional, intelligent, adaptive, etc.) • system identification and signal processing • electrical transmission systems, smart grids • bioengineering • traffic control • reaction kinetic networks • artificial intelligence • soft computing (neural, genetic, fuzzy algorithms, etc.) • software issues (parallel computing, distributed and network computing, data visualization) • decision making (decision support, data mining) • applications the organizers are grateful to the authors for their contributions. the tradition of the international phd workshop on systems and control continues. you are welcome to participate at the 16th international phd workshop on systems and control in veszprém, 2020. attila magyar guest editor of the issue hungarian journal of industry and chemistry vol. 47(1) pp. 3–9 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-02 non-technical loss diagnosis in electrical networks with a radial layout anna i. pózna *1, attila fodor1, and katalin m. hangos2 1department of electrical engineering and information systems, university of pannonia, p. o. box 158, veszprém, 8201, hungary 2institute for computer science and control, hungarian academy of sciences, p. o. box 63, budapest, 1518, hungary a network-oriented non-technical loss detection and localization methodology is presented in this paper. the basic idea behind the proposed methodology is the deviation of the measured voltages from their nominal values. the operation of the algorithm was investigated by simulation experiments using an (ieee) european low voltage test feeder benchmark network. the simulation results show that the proposed method is able to detect and localize multiple occurrences of nontechnical losses caused by fraudulent meters. keywords: power network, diagnosis, non-technical loss, load-flow 1. introduction the demand for electrical energy is continuously increasing on a global scale. electrical energy is generated by power plants or renewable energy sources and is transmitted from the source of generation to consumers through distribution stations and power lines. during transmission, technical losses, that originate from dissipation in conductors, transmission lines and substation transformers as well as magnetic losses in transformers, reduce the efficiency of power delivery. the proportion of technical losses is about 20 % of the total energy transmitted. besides the technical losses, non-technical losses (ntls) may be present as well. these are unnecessary losses which are not expected and cannot be anticipated. the ntls are usually related to energy theft and fraudulent consumption behavior. energy theft has been a widespread and major issue for many years and various techniques of energy theft are present from unregistered users to hacking meters [1]. following this unwanted phenomena, several methods of non-technical loss detection have appeared in the literature. it can be stated that no golden rule exists for detecting energy theft, rather, several different approaches are available [2]. papers [3] and [4] provide very good reviews on the most frequently used methods in this field. the majority of solutions available in the literature are based on the analysis of consumption data using some statistical or machine-learning methods, for example, the authors of [5] used a linear regression-based pro*correspondence: pozna.anna@virt.uni-pannon.hu cedure that not only detects energy theft but defects of smart meters as well. a probabilistic neural networkbased classification approach is presented in [6] where the levenberg-marquardt method is used for training the network. a support-vector machine-based solution is given in [7], where a parallel computer architecture was proposed in order to enhance computation. another approach to non-technical loss detection is based on network topology, such network-oriented methods use readings from grid sensors and smart meters. in [8], the authors proposed state estimation with a kalman filter to identify currents and biases in a microgrid network. the currents and biases are estimated separately using two different filters. if the estimated bias of a customer exceeds the predefined threshold, then this user has committed fraud. the authors of [9] suggest a probabilistic power flow approach to ntl detection. the output of the algorithm is a probability distribution of ntls in the subnetwork. besides the above classes, other methods of localizing illegal electricity usage exist, e.g. in [10] a power lines inspection robot was applied to find ntls. the approach followed in the present work belongs to the network-oriented class and it is based on analyzing the differences between the measured and nominal voltages. the uncertainty in the model parameters together with the measurement uncertainties are taken into account to ensure the approach is applicable to real-world cases. the structure of the paper is as follows. the basic notions and problems are introduced in section 2. section 3 mailto:pozna.anna@virt.uni-pannon.hu 4 pózna, fodor, and hangos contains the main contribution of the paper and presents the proposed novel diagnostic method in detail. afterwards, the proposed method is subject to simulationbased analysis in section 4. 2. problem statement 2.1 non-technical losses according to a source non-technical losses (ntls) can be classified as follows [11]: before meter: illegal tapping of distribution lines or feeders meter: inaccurate power readings due to a meter being faulty (e.g. changes to the calibration), reversed, disconnected or bypassed billing: non-payment of electricity bills, inaccurate billing, faulty operation of the billing system, a cyber attack against the billing system, etc. ntls caused by companies in the us were estimated to cost between 0.5 % and 3.5 % of annual gross revenues. the ntls may account for more than 15 % of the generated power in some countries [2] and [12]. in the remaining part of the paper only the following type of non-technical loss is examined that belongs to the first class above: • fraud committed by tampering with the meter (reversing or hacking the hardware or software, or calibration of the meter), • bypassing the meter. 2.2 detection and localization in general, two main parts of the diagnostic procedure exist: fault detection and fault identification. the aim of detection is to decide if any fault has occurred in the system. the exact type and localization of the occurred fault is determined in the identification phase. in the case of non-technical loss diagnosis, detection and localization are defined as follows: detection of non-technical loss means that the loss is acknowledged. localization means that the fraudulent user is identified if the illegal consumption of power occurs at the meter. in the case of multiple ntls, every fraudulent meter is to be identified by the method. illegal load is a load that originates from a fraudulent meter, i.e. the consumer uses illegal power. 2.3 basic assumptions during development of the non-technical loss detection and localization method, the following assumptions were made: • the electrical network is represented by its static linear model. the known parameters of the model are the resistances of the transmission lines, the current and voltage of the feeding point (transformer), and the currents of the loads. • the structure of the electrical network is radial (for more details see section 3.2). • every load has a smart meter that measures the current, voltage and power consumption of the load. • at least one illegal load may be present in the network. if more than one illegal load exists then each is located in a different part of the network (see section 3.2 for more details). 2.4 uncertainties and measurement errors the main uncertainties that affect the voltages and currents in a public electrical grid can be classified as follows: • uncertainties about the parameters of the transmission lines the resistance of the transmission lines is the main source of uncertainty. this resistance can be computed from its diameter, curvature and length, which are functions of temperature. the function is approximately linear in the domain −50 ◦c to 100 ◦c: ρ = ρ0(1 + α(t − t0)), (1) where ρ and t stand for the values of resistance and temperature, respectively, while ρ0 and t0 denote the nominal resistance and temperature, respectively, and finally α represents the temperature modulus. the main uncertainty over the line is the small difference between the planned and installed transmission line. the losses, which are justifiable given these technical reasons, contribute to approximately 2–3 %. • measurement errors the presence of smart meters in our electrical network is assumed. the precision of smart meters varies from ±0.2 % to ±2 % depending on their precision and the percentage of nominal power, see international standards iec 62051, iec 62052-11, iec 62052-21 and iec 62052-31. in this paper the effects of the harmonic currents [13] are not investigated, rather, it is assumed that the voltages and currents are sinusoidal. the effects of asymmetrical loads [14] are also not investigated because a single-phase grid is assumed. a three-phase grid can be assembled from three single-phase grids with one n line. hungarian journal of industry and chemistry non-technical loss diagnosis in electrical networks with a radial layout 5 ut i1 i2 i3 in it iw1 r1 iw2 r2 iw3 r3 iwn rn figure 1: single-feeder layout 3. diagnostic method the proposed diagnostic method uses the topology and electrical parameters of the network together with the nominal and measured voltages as well as current values to detect and localize the illegal loads. the nominal voltage and current values are generated from the topology and the parameters of the network determined by solving its linear time-invariant model using the known feeder voltage and current values [15]. input data it is assumed that the model of the network is present together with the nominal values of its elements. current and voltage readings with measurement errors are available from smart meters of all loads. detection the proposed diagnostic method is based on analyzing the difference between the measured and nominal voltages. it is assumed that the currents measured are the nominal currents of the network. the presence of an illegal load is detected if a difference between the sum of the measured currents ( ĩi, i = 1, . . . , n ) and the measured current of the transformer (it) exists. n∑ i=1 ĩi − it > ε (2) localization the localization method starts with the simulation of the network assuming the nominal current values. during the simulation, the voltages of the loads are computed. the simulated voltages are considered to be the nominal voltages. subsequently the nominal voltages are compared to the measured voltages. localization is based on the evaluation of deviations in voltage from the nominal values. the measurement error is taken into account in such a way that only deviations that fall outside the maximum measurement error are considered during the diagnosis. 3.1 single-feeder layout the single-feeder layout is the simplest topology of electrical networks. it contains a single feeding point with several loads connected to it along a transmission line (fig. 1). the difference between the nominal and measured voltage levels is computed as: ∆ui = ũi − ui, i = 1, ..., n, (3) where ũi and ui are the measured and nominal voltages of the ith load, respectively. larger drops in voltage than the nominal ones are caused by illegal loads. therefore, ut it i1 in im1 imnm i11 i1n1 iw1 r1 iwn rn iw11 r11 iwm1 rm1 ug r1n1 iw1n1 rmnm iwmnm figure 2: radial feeder layout the value of ∆ui is negative. if the illegal load is in the kth load, differences in voltage of subsequent loads are equal to the kth load. this difference is proportional to the magnitude of the illegal current and the resistance of the transmission line: ∆ui = iill ∑i j=1rj , if i < k iill ∑k j=1rj , if i ≥ k (4) if, by starting from a certain load, the voltage differences of the loads are equal, then the load in question consumes power illegally. in practice two differences in voltage are considered to be equal if the difference between them is less than the measurement error. therefore, localization of the illegal load is quite straightforward in a singlefeeder layout: the load in question needs to be identified and from this the differences in voltage start to become equal. this method can be generalised if more than one illegal load in a single-feeder network is present. in this case, sections in the sequence of voltage differences where consecutive voltage differences are equal exist. the illegal loads are located at the start of these sections. 3.2 radial layout the radial-feeder layout is commonly used in lowvoltage networks. the general structure of a radial-feeder network can be seen in fig. 2. this type of network can be decomposed into single-feeder subnetworks by identifying and cutting off the branches (for further details see [16]). the loads are considered to be part of the same subnetwork if they are connected to the same bus. after decomposition, a set of disjoint single-feeder networks is formed which can be processed in parallel. from a diagnostic point of view, two types of subnetworks should be distinguished. the first type is when the subnetwork contains more than one load (referred to as multiple load subnetwork hereinafter). the structure of this subnetwork is similar to the single-feeder layout (fig. 1). the second type of subnetworks is the special case when the subnetwork contains only one load (referred to as single load subnetwork hereinafter). one illegal load in a multiple load subnetwork if only one illegal load is present in the whole network and it is 47(1) pp. 3–9 (2019) 6 pózna, fodor, and hangos located in a subnetwork with several loads, then it can be clearly localized using the diagnostic method described in section 3.1. one illegal load in a single load subnetwork in the case when the subnetwork contains only one load, the voltage difference cannot be compared to any other voltage difference within this subnetwork. therefore, the diagnostic procedure in section 3.1 cannot be used. in this case, the voltage deviations need to be analyzed globally. the increased consumption causes the biggest deviation in the voltage at the location of the illegal load. in this case, the diagnostic procedure to determine the minimum voltage difference is identical. more illegal loads in multiple load subnetworks if more than one illegal load is present and are located in different multiple load subnetworks, then their locations can be determined independently of each other. more illegal loads in single load subnetworks in this case, local minima in the voltage differences indicate the locations of the illegal loads. the local minima are determined in such a way that the voltage differences of the single loads can be compared to the voltage differences of their two nearest neighbors. if the voltage difference of the single load is smaller than that of its neighbors, then an illegal load is present at the single load. 3.3 diagnostic algorithm the four aforementioned cases in the radial layout can be merged into one algorithm, the flowchart of which can be seen in fig. 3. during the diagnosis the illegal loads identified are collected in a set calledntl. at the beginning of the diagnostic algorithm, the set ntl is empty. the diagnostic algorithm searches for illegal loads in different parts of the network. the algorithm consists of three main parts: searching in multiple load subnetworks, searching for one illegal load in single load subnetworks, and searching for more illegal loads in single load subnetworks. detection the inputs of the combined algorithm are the measured currents and voltages as well as the network structure. first, to detect the illegal consumption, the inequality in eq. 2 is checked. if the difference between the sum of the measured currents and the transformer current exceeds a predefined threshold, then illegal consumption occurs in the network, otherwise the network operates normally. if illegal loads are detected, then the algorithm tries to determine their locations. to do this, the network is simulated using the measured current to obtain the nominal voltage values. isolation ntls in multiple load subnetworks this algorithm starts to search for illegal loads in the multiple load subnetworks using the method described in section 3.1. the illegal loads identified are added to the set ntl. in this step, all of the illegal loads in the multiple load subnetworks are localized. measurement data: ĩ , ũ , it ∑ ĩ−it > ε initialize: ntl = ∅ simulate network with ĩ normal operation search in multiple load subnetworks ntl = ∅ find minimum of ∆u in single load subnetworks is new load found? ntl = ∅ illegal load is not found calculate illegal currents (iill) ∑ (ĩ+iill)− it > ε find local minimum of ∆u in single load networks calculate illegal currents (iill) ∑ (ĩ+iill)− it > ε calculate illegal currents (iill) ∑ (ĩ+iill)− it > ε not all illegal loads are found set of illegal loads: ntl yes no yes no no yes yes no yes no no yes yes no figure 3: flowchart of the diagnostic procedure hungarian journal of industry and chemistry non-technical loss diagnosis in electrical networks with a radial layout 7 figure 4: structure of the ieee 2015 european low voltage test feeder network before proceeding, the algorithm checks if any illegal loads have been identified in the multiple load subnetworks. if the setntl is empty, then no illegal loads were found, therefore, they should be located in the single load subnetworks. if at least one illegal load is identified in the multiple load subnetworks, then their illegal currents are calculated using eq. 4. the currents of the illegal loads are substituted by the calculated currents and the inequality of eq. 2 is checked. if the inequality is false, then all of the illegal loads are localized and the algorithm stops. if the inequality is true, then at least one illegal load is still present in the single load subnetworks. ntl in a single load subnetwork to identify the illegal load in single load subnetworks, the algorithm searches for the minima of the voltage differences. the illegal load possesses the minimum voltage difference. if during this step no new illegal loads are identified, then two scenarios are possible: (i) if set ntl is still empty, then the illegal load has not been found and the algorithm proceeds to the second search in the single load networks. (ii) if the set ntl is not empty, then the illegal currents are calculated and the inequality of currents checked. if no significant difference is present, then all illegal loads have been identified and the algorithm stops. if the inequality is true, then a second search of the single load networks is performed. more ntls in single load subnetworks during this step, the voltage difference of the single loads is compared to the voltage difference of their two nearest (left and right) neighbors. if the voltage difference of the single load is minimal between the three differences, then the single load is an illegal load. after this search the inequality of the currents is verified again. if a difference is still present, then not all the illegal loads have been identified, otherwise all of the illegal loads have been found and the algorithm stops. figure 5: loads in phase a 4. case study the diagnostic algorithm was tested on the ieee 2015 european low voltage test feeder [17] which is a benchmark provided by the power system analysis, computing & economics (psace) committee. it is a threephase radial distribution feeder with one feeding point. the network contains 1 transformer, 55 loads and 905 lines. the structure of the network can be seen in fig. 4. the algorithm was tested by only taking into consideration one phase (namely phase a) of the system. 21 loads are present in this phase which are displayed in fig. 5 along with their identifiers. at the time of the test, the minimum and maximum power consumed by these loads was 35 w and 64.9 w, respectively. during the diagnosis, the measurement error was set at 0.2 % of the measured currents. the network belonging to phase a can be decomposed into 13 subnetworks, 5 of which are single load networks and 8 are multiple load networks consisting of 2 loads each. the decomposition and diagnostic algorithm was implemented in matlab. the simulation of the network was also performed in matlab [18] using the method of nodal potentials. 4.1 case 1: one illegal load at first, it is assumed that only one illegal load is present in the network, more specifically in a single or multiple load subnetwork. let us consider the subnetwork that contains the loads no. 25 and 30. load no. 25 increases its consumption by 80 % of its nominal value but deceives the current meter, therefore, the registered current value is not suspicious. the network is simulated using the nominal current values. the difference between the nominal and measured voltages is presented in fig. 6. it can be seen that the voltage differences are equal in the multiple load subnetworks, e.g. loads 1 and 3 as well as 20 and 22, except for the subnetwork of loads 25 and 30. since the absolute voltage deviation at load no. 25 exceeds that at load no. 30, the illegal consumption is located at load no. 25. 47(1) pp. 3–9 (2019) 8 pózna, fodor, and hangos figure 6: voltage differences of the loads in case 1 4.2 case 2: more illegal loads in different subnetworks in the second case, it is assumed that two illegal loads are present in different subnetworks. the first illegal load is no. 46 which is located in a single load subnetwork. the power consumption of load no. 46 is 50 % more than its nominal value. the second illegal load is load no. 54 which is located in a multiple load subnetwork along with load no. 51. the consumption of load no. 54 is increased by 80 % of its nominal value. the difference between the simulated and measured voltages can be seen in fig. 7. at first the diagnostic algorithm searches for illegal loads in the multiple load subnetworks. in the subnetwork of loads no. 51 and 54, the voltage deviation of load no. 54 exceeds the voltage deviation of load no. 51, therefore, load no. 54 is identified as an illegal load. the illegal current is calculated using eq. 4. in the other multiple load subnetworks, the voltage differences of the loads within a subnetwork are equal, therefore, it can be stated that no illegal loads are present in these subnetworks. the algorithm checks if some remaining illegal currents are present thereafter. a difference between the current of the transformer and the sum of the measured currents is still present which is indicative of at least one illegal load that is yet to be identified. these illegal loads should be located in single load networks. the minimum of the voltage differences is located at load no. 46, therefore, it is an illegal load. after calculating the illegal current of load no. 46 and checking the inequality in eq. 2, it can be stated that no additional illegal loads are present in the network. 5. conclusions and future work a novel diagnostic method for detecting and locating illegal loads in electrical radial networks is proposed in this figure 7: voltage differences between the loads in case 2 paper that utilizes the topology of the network and is capable of taking the uncertainties and measurement errors into account. a preprocessing step decomposes the radial layout of single-feeder subnetworks with single or multiple loads, and the method is capable of locating the illegal load(s) in the subnetworks in parallel. the proposed method can detect and locate multiple independent illegal loads under certain conditions. future work will include the extension of the diagnostic methods to general, not necessarily radial, topology and to develop the computational model of a network to handle the uncertainties related to network parameters (resistances). furthermore, the effect of the uncertainties and measurement errors on the diagnostic accuracy should also be investigated. acknowledgement we acknowledge the financial support of széchenyi 2020 under the efop-3.6.1-16-2016-00015. we acknowledge the financial support of széchenyi 2020 under the ginop-2.2.1-15-2017-00038. this research is partially supported by the national research, development and innovation office nkfih through grant no. 115694. references [1] ahmad, t.; chen, 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evaluation of resource optimization based on quantum search sara el gaily *1 1department of networked systems and services, budapest university of technology and economics, műegyetem rkp. 3-9, budapest, 1111, hungary quantum computing and communications try to identify more efficient solutions to the most challenging classical problems such as optimization, secure information transfer, etc. this paper will describe a new quantum method for the distribution of resources in computing platforms that consist of a large number of computing units. furthermore, a simulation environment was developed and the performance of the new method compared to a classical reference strategy will be demonstrated. moreover, it will be proven that the proposed solution tackles the problems of computational complexity, computing units that are time-consuming and slow to process, as well as the accuracy in determining the optimum result. keywords: quantum computing, quantum existence testing, finding extreme values in an unsorted database, resource management distribution, exhaustive algorithm, heuristic algorithm, computational complexity 1. introduction nowadays, resource management and especially the distribution of resources is one of the most discussed and fundamental issues, for example, the problem considers a large amount of distributed energy resources including electric vehicles with gridable capacity [1], and the rapid progress of cloud computing, i.e. the growing number of video providers that have deployed their streaming services onto multiple distributed data centers [2]. this greatest demand on efficient resource distribution motivated us to search for new approaches and solutions. the majority of operational processes require an amount of computational resources and their wide availability, namely the amount of computing units, is not the present issue, rather the utilization of resources and usage of the units are [3]. thus, this challenge was tackled by introducing a new strategy which aims to optimize the computational load of the resources that handle the problems of computational complexity, time, speed and accuracy. as is common knowledge, the primary aim of quantum computing and communications is to reduce computational complexity and achieve optimum and efficient results with regard to the requirements of the given problem [4]. in order to exploit the power of quantum computing in terms of resource distribution, a quantum extreme value searching algorithm was used [5], which will be *correspondence: elgaily@hit.bme.hu combined with an appropriately designed classical framework. 2. modelling our novel model deals with the classical problem of resource distribution and contains three components. the first one generates tasks to be computed in the system denoted by pi and can be characterized as processing time, memory, energy, etc. the actual number of running tasks in the system is referred to as n. these tasks are served by computing units that represent the resources of the system. the number of the units is denoted by c. the computing units may have different theoretical capacities. the theoretical capacity of the jth unit is depicted as sj and its free (unused) capacity is denoted by xj [t] which depends on time t, as depicted in fig. 1. the third block is the decision-making unit which answers the question of how to deploy a new task among the process units in order to optimize the operation of the figure 1: architecture of the model mailto:elgaily@hit.bme.hu 12 el gaily system. there are different metrics to distribute the resources, here uniformly loaded units have been chosen because actually, they are an important aspect of many applications. the overall capacity of the processing units in the system can be calculated as ŝ = c∑ j=1 sj , (1) while the overall free processing capacity is determined according to x̂ = c∑ j=1 xj [t]. (2) the average amount of free capacity per unit is given by the following expression x[t] = 1 c c∑ j=1 xj [t] sj . (3) our purpose is to uniformly distribute the load over the resources. therefore, the variance of the relative free capacities in the system is used. in the case of optimal task distribution, if σ2 tends to zero, then the resources are distributed uniformly, otherwise they are not. the corresponding formula of the relative variance is: σ2 = 1 c c∑ j=1 ( x[t]− xj [t] sj )2 . (4) 2.1 description of the quantum algorithm the optimized solution will be based on the quantum extreme value searching algorithm, a stochastic process which functions on an unsorted database that combines the technique of a classical binary search of a sorted database [6] and quantum existence testing (qet) [4]. the best classical solution requires n queries of the database to determine the optimum result, while in order to solve previous problems the well-known logarithmic (often referred to as binary) search algorithm, which is originally intended to search for a given item in a sorted database with quantum existence testing (a special case of quantum existence testing interested in whether a given entry exists in the database or not rather than in determining the number of existence entries) needed to be combined. the quantum algorithm maintains the efficiency of the binary search while processing an unsorted database [4]. it is hard to classically compute the optimum deployment scenario, therefore, the quantum extreme value searching algorithm [5] is applied as a minimum searching algorithm (msa), which enables the deployment scenario to be identified and results in minimum variance. the msa is a stochastic process that works on an unsorted database. our new approach handles the database 1: we start with s = 0 : σ2 min 1 = σ2 min 0 , σ2 max 1 = σ2 max 0 , and ∆σ2 = σ2 max 0 − σ2 min 0 2: s = s + 1 3: σ2 meds = σ2 mins + [ σ2 maxs−σ 2 mins 2 ] 4: flag = qet ( σ2 meds ) 5: if flag = true then σ2 maxs+1 = σ2 meds 6: else σ2 maxs+1 = σ2 maxs , σ2 mins+1 = σ2 meds 7: if s < log2 ( ∆σ2 α ) then goto 2 8: else yopt = σ2 meds stop as a function, i.e. the variance. the proposed algorithm is now given in detail: the algorithm will stop once the following step s < log2 ( ∆σ2 α ) has been fulfilled where α denotes the smallest sub-region between two possible results in a database and is explained in more detail in section 2.3. 2.2 description of the randomized, exhaustive and sequence-searching algorithms the randomized, exhaustive and sequentialsearching algorithms are generally viewed as references and the cornerstone with regard to finding solutions. they are considered as three different methods [7]. firstly, the randomized approach anticipates the solution guided by given knowledge and is not perceived as an optimal solution because it randomly searches for one solution in one step from the space in which the duration of time may be less reasonable [8]. on the other hand, the exhaustive algorithm examines every possible solution and leads to an optimal result, it checks all the o(d) steps which is time-consuming and yields an accurate result. a large number of iterations are required when compared to the number of queries, hence, its time-consuming nature. furthermore, the sequence method exhibits a similar degree of computational complexity to the randomized method, using o(const) or o(1). 2.3 evaluation of the algorithms our purpose is to provide a concrete comparison of solving distribution problems via heuristic ‘random’, exhaustive or sequence as well as quantum algorithms, hence, the difference in terms of the computational complexity applied and the minimum variance computed by each method was measured leading to the optimum distribution uniformity of the system. hungarian journal of industry and chemistry evaluation of resource optimization based on quantum search 13 figure 2: quantum existing testing device (qft: quantum fourier transform). comparison according to computational complexity by comparing the computational complexity of the quantum, randomized, exhaustive and sequence solutions, the quantum solution requires only √ log2(t ) log3 2 (√ d ) steps, where d refers to the number of different possible deployment scenarios and t denotes the number of subregions given by all the possible outcomes of the different deployments. the exhaustive solution, on the other hand, needs o(d). with regard to the randomized solution, it uses fewer steps so is faster than the three former solutions, which means that the computational complexity of the random method is less than for the other ones. moreover, it does not determine the optimum solution since the computational complexity of the sequence method is similar to the randomized algorithm. in contrast, the exhaustive and quantum solutions require more computation steps, but the quantum solution always is preferred because it requires significantly less computation than the exhaustive method. as was mentioned previously, the quantum extreme value searching algorithm uses the binary search and quantum existing testing methods. as the quantum phase estimation algorithm is the core of qet, as can be seen in fig. 2, it outperforms the other counterpart’s algorithms, thus, its physical implementation is highly constrained with the required number of bits k. in fact, the number of bits k depends on the application of the system, as is illustrated in fig. 2. this remains hard to realize, for example, if the error probability pε of the application is neglected and the classical specification considered, which is of accuracy a, the number of steps needed is o ( log2(t ) log3 2 (√ d )) and the number of bits will be influenced only by one factor, namely the accuracy a, as presented in k = a− 1 (5) in addition, the relationship between the maximum relative variance and the number of sub-regions given t according to all the possible outcomes of the different deployments is given by t = σ2 max α (6) where α denotes the smallest sub-region between two possible results in a database (eq. 7). α is illustrated in figure 3: functional representation of the database fig. 3: α = min ∀ i,j ∣∣(σ2 i − σ2 j )∣∣ (7) on the other hand, if two factors, namely the accuracy a and probability of error pε [4], are taken into consideration, this assumption will influence the second term of the computational complexity log3 2 (√ d ) , it will be transformed intoo ( log2 (t ) log3 2 ( 2 p 2 √ d )) and the number of bits will be expressed by k = a− 1 + ⌈ log2(2π) + log2 ( 3 + 1 p̌ε )⌉ ︸ ︷︷ ︸ p , (8) where p̌ε is the maximally allowed quantum uncertainty (probability of error) and p is the number of qbit which controls the quantum uncertainty. the computational complexity of the classical (exhaustive) and quantum solutions is compared. the number of computational steps to yield the desired results with regard to the number of different deployment scenarios is in accordance with function o(d), while the quantum solution only requires o ( log2 (t ) log3 2 (√ d )) . furthermore, the quantum method derives its stochastic behavior from the quantum phase estimation algorithm which heightens the degree of accuracy and speed in computation. in the light of what has been shown, in fig. 4, the classical strategy for identifying the deployment scenario which leads to the minimum variance needs more computational computing, while the quantum solution requires significantly less computation, which reduces the complexity and duration necessary to determine the optimum deployment scenario of resource distribution. figure 4: comparison between the computational complexity of the classical and quantum decision-makers 47(1) pp. 11–16 (2019) 14 el gaily figure 5: the simulation architecture comparison of the uniformity in compliance with what has been discussed, the quantum and exhaustive solutions conserve the uniformity of the system, but the proposed quantum solution is the best and most efficient method because it requires less computation and time to determine the optimum deployment scenarios. however, the randomized and sequence algorithms do not ensure the uniformity of task distribution. 3. results and analysis to show the importance of the proposed quantum solution, a simulation environment of optimizer+distributor was constructed. the model of a resource distribution system contains three processing units with different theoretical capacities: twenty, forty and sixty running tasks in parallel. practical systems contain significantly more processing units, however, to observe trends and effects it is worthwhile investigating a small-scale model first. furthermore, a task generator block is present in the system. the tasks are considered to have exponential arrival times. an optimizer+distributor block is considered to be a decision-maker between the different deployment scenarios. the model implemented in the simulation environment is illustrated in fig. 5. 3.1 experiments two factors influence the behavior of the simulation: the mean (intensity) of the exponential distribution with refigure 6: the average load of processing units in the case of the random reference strategy figure 7: average load of the three distribution strategies when the mean (intensity) of the exponential distribution of the arrival times of tasks is equal to 0.6 gard to the arrival times of tasks, and the service time of the tasks in the processing units. the system will be more heavily loaded if the mean value is smaller or the service time of the tasks larger. 3.2 simulations in order to demonstrate the efficiency of the proposed optimization strategy, two other reference strategies were considered which distribute the tasks randomly or sequentially among the processing units. by considering the following simulation parameters, the mean of the exponential arrival times is equal to 0.4 and the service time of the resources is equal to 3. the average load of the processing units in the case of the random reference strategy is presented in fig. 6 with the following simulation parameters: the mean of the exponential arrival times is equal to 0.4 and the service time of the resources is equal to 15. the line graph contains two phases: the transition phase with a duration of 0 to 30 s, and the stationary phase that commences after approximately 30 s, when the system reaches a certain equilibrium. comparing the performance of the three distribution strategies, it can be stated that during the transition phase the variances of the reference systems are approximately stable, but during the stationary phase (normal operation) the variance started to fluctuate dramatically as well as increase. on the other hand, the variance of the proposed quantum solution remained approximately linear and tended to zero, therefore, the quantum system conserves the distribution uniformity. according to fig. 7 and 8 the average load of the different methods remains similar independent of the intensity of the exponential distribution of the arrival times of tasks as well as the decision methods. furthermore, it is clearly noticeable that when the mean of the exponential distribution of the arrival times of tasks is smaller, the tasks are generated faster which leads to an increase in the load of the computing units. hungarian journal of industry and chemistry evaluation of resource optimization based on quantum search 15 figure 8: average load of the three distribution strategies when the mean (intensity) of the exponential distribution of the arrival times of tasks is equal to 0.1 the simulation results concerning the variance of each distribution strategy show that the trends of the randomized and sequence strategies diverge from zero, but the sequence method yields a more uniform variance than the randomized one. in contrast, the optimized (quantum and exhaustive) strategies maintain and conserve the load uniformity of the system. these results are illustrated in fig. 9 and 10. 4. conclusion in this paper, a new strategy for resource distribution based on a quantum searching algorithm was introduced. it was demonstrated that the quantum solution is more efficient by comparing the computational complexity and distribution uniformity of the quantum solution with the randomized, exhaustive and sequence methods. furthermore, the changes applied to the computational complexity when the specification classical requirement depends on the application were demonstrated. to show the importance of the quantum solution, a simulation environment of the proposed optimization of figure 9: variances over time of the optimized (yellow), randomized (blue) and sequence distribution (orange) strategies when the mean (intensity) of the exponential distribution of the arrival times of tasks is equal to 0.1 figure 10: variances over time of the optimized (yellow), randomized (blue) and sequence distribution (orange) strategies when the mean (intensity) of the exponential distribution of the arrival times of tasks is equal to 0.6 a distribution system was constructed and compared to two reference distribution systems which follow the randomized and sequence strategies. the proposed quantum approach is practical in most domains of infocommunication and computer science where resources have to be distributed among a large number of processing units. these are the initial results of this new field of research. obviously, other optimization metrics should be considered in the future. furthermore, tasks can be modelled in a more sophisticated manner: different classes of tasks can be defined following various arrival processes and characterized by more than one resource parameter (processing time, memory, battery requirement). finally, even an individual task can contain more blocks with dependencies among them and different blocks can be distributed among different processing units. the wider future context of our research is to start with a polynomial time problem and progress towards a nondeterministic polynomial time problem. acknowledgement the research was partially supported by the national research development and innovation office of hungary (project no.2017-1.2.1-nkp-2017-00001), by the hungarian scientific research fund -otka k-112125 and in part by bme artificial intelligence fikp grant of emmi (bme fikpmi/sc). the research reported in this paper was supported by the bmeartificial intelligence fikp grant of emmi (bme fikp-mi/sc). references [1] soares, j.; canizes, b.; vale, z; venayagamoorthy, g. k.: benders’ decomposition applied to energy resource management in smart distribution networks, clemson university power systems conference, clemson, sc. march 8, 2016. doi: 10.1109/psc.2016.7462820 47(1) pp. 11–16 (2019) https://doi.org/10.1109/psc.2016.7462820 https://doi.org/10.1109/psc.2016.7462820 16 el gaily [2] zhang, z.; jiang, x.; xi, h.: joint resource allocation and traffic management for cloud video distribution over software-defined networks, 8th ieee international conference on communication software and networks, university of science and technology of china, hefei, china. 2016. doi: 10.1109/iccsn.2016.7586692 [3] keränen, j.; kortelainen, j.; antila, m.: computational resource management system. version 1.0/14.8.2015. https://www.vtt.fi/inf/julkaisut/ muut/2015/vtt-r-01975-15.pdf [4] imre, s.; balázs, f.: quantum computing and communications: an engineering approach (wiley, chichester, uk) 2005 isbn 0-470-86902-x, doi: 10.1002/9780470869048 [5] imre, s.: extreme value searching in unsorted databases based on quantum computing, int. j. quantum inf., 2005 3(1), 171–176 doi: 10.1142/s0219749905000700 [6] knuth, d. e.: sorting and searching in the art of computer programming vol. 3 (2nd ed.) (addisonwesley, reading, ma, usa) 1998 isbn 978-0-20189685-5 [7] zin, n. a. m.; abdullah, s. n. h. s; zainal, n. f. a.; ismail, e.: a comparison of exhaustive, heuristic and genetic algorithm for travelling salesman problem in prolog, int. j. adv. sci. eng. inf. technol., 2012 2(6), 459–463 doi: 10.18517/ijaseit.2.6.244 [8] hooker, j. n.: toward unification of exact and heuristic optimization methods, int. t. oper. res., 2013 22, 19–48 doi: 10.1111/itor.12020 hungarian journal of industry and chemistry https://doi.org/10.1109/iccsn.2016.7586692 https://doi.org/10.1109/iccsn.2016.7586692 https://www.vtt.fi/inf/julkaisut/muut/2015/vtt-r-01975-15.pdf https://www.vtt.fi/inf/julkaisut/muut/2015/vtt-r-01975-15.pdf https://doi.org/10.1002/9780470869048 https://doi.org/10.1002/9780470869048 https://doi.org/10.1142/s0219749905000700 https://doi.org/10.1142/s0219749905000700 https://doi.org/10.18517/ijaseit.2.6.244 https://doi.org/10.1111/itor.12020 hungarian journal of industry and chemistry vol. 47(1) pp. 17–23 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-04 simulation of color afterimages: an approach to computing virtual color perception lőrinc garai *1 and andrás horváth2 1doctoral school of multidisciplinary engineering sciences (mmtdi), széchenyi istván university, egyetem tér 1, győr, 9026, hungary 2department of physics and chemistry, széchenyi istván university, egyetem tér 1., győr, 9026, hungary afterimages are a common and frequent perceptual phenomenon of everyday life. when looking into a high-intensity light source and suddenly turning away from it, a temporary “ghost” of the light source remains visible, for a while. the computer-graphics simulation of afterimages is based on biophysical and mathematical models as published in the literature. a subordinate of afterimages defined in our research is virtual color perception, that is in our interpretation an unusual and intense temporary color perception provoked by a rapid change in the color of the incident light. in research, the modelling of virtual color perception is a field that is by and large untouched. our publication presents a kinetic model established to characterize the intensity and duration of virtual color perception as a function of rapid changes in the color of the incident light. keywords: afterimage, rod and cone photoreceptors, photopigment, kinetics 1. introduction in our vision, an afterimage is an illusionary image that appears after having been exposed to a prior one. color afterimages are experienced in everyday life, for example, when driving at night the headlights of oncoming cars are so bright that when the driver looks away from them, the illusion of bright headlights still remains in perception [1]. when photorealistic images are rendered [1–4], some papers reported simulations of color afterimages by combining mathematical models [5–9]. a subordinate of afterimages defined in our research is virtual color perception, a phenomenon that originates from chromatic adaptation in photoreceptors influenced by environmental color interactions, and based on the sensitivity to light and adaptibility of each cone receptor. the physiological background of virtual color perception in brief is as follows: human photopic (daylight) color vision is a combined response of type l (long wavelengths), m (medium wavelengths) and s (short wavelengths) cone receptors to adequate stimuli of light. the photopigment rhodopsin plays a key role in the process; the equilibrium of its relative concentration is achieved by the opposing processes of rapid cleavage when exposed to light and slow resynthesis in darkness [10, 11]. adaptations of cone receptors to changes in the color of the incident light is time-consuming [12, 13], hence, a *correspondence: garailorinc@garailorinc.hu rapid change in the color of the incident light facilitates unusual and intense temporary color perception, the socalled virtual color perception. for example, when exposed to red light the sensitivity of l cone receptors is low and in this case is accompanied by the high sensitivity of m and s cone receptors. following a rapid change in color from red to blue in the incident light, the sensitivity of s cone receptors remains temporarily high, resulting in perception of the color bright blue that transforms into common blue after a short period of time during which the relative concentration of photopigment is equilibrated (restored), i.e. this is the duration of virtual color perception. the purpose of our work is to develop a computational kinetic model capable of simulating and quantifying virtual color perception. in our research chromaticity diagrams are used. note that changes in the xy coordinates [14] are not proportional to human color perception. to overcome this distortion, several chromaticity coordinates were defined, for example, cie u′v′ [15]. the gamut of a device is the complete subset of colors it can produce. usually, in an rgb (red, green, blue) device, it consists of a color triangle with two-dimensional chromaticity coordinates. a gamut is characteristic of the given display (screen) currently in use, for example, modern rgb led displays are characterized by wider gamuts compared to old-fashioned cold cathode fluoresmailto:garailorinc@garailorinc.hu 18 garai and horváth table 1: gamut points ccfl rgb led gamut point x y x y b 0.2091 0.2218 0.1563 0.0307 b3r1 0.2753 0.2518 0.2837 0.1056 b2r2 0.3415 0.2817 0.4111 0.2181 b1r3 0.4077 0.3115 0.5385 0.3024 r 0.4739 0.3415 0.6658 0.3305 r3g1 0.4420 0.3837 0.5687 0.4236 r2g2 0.4101 0.4239 0.4717 0.5632 r1g3 0.3783 0.4652 0.3746 0.6679 g 0.3464 0.5064 0.2775 0.7028 g3b1 0.3121 0.4353 0.2472 0.5348 g2b2 0.2778 0.3641 0.2169 0.2827 g1b3 0.2434 0.2930 0.1866 0.0937 cent lamp (ccfl) displays that were frequently used about 10 years ago. in our work, gamuts characteristic of ccfl and rgb led desktop monitors were measured first. following this, the simulation of virtual color perception obtained by gamut data as a result of a rapid change in the color of the incident light was conducted. finally, preliminary validation tests were run on the aforementioned rgb led desktop monitor in use [16]. 2. experimental 2.1 measurement of the gamuts of the displays used in our experiments and key parameters of our model the spectral power distribution of the red, green and blue primaries of two displays was measured by a spectroradiometer (a flame miniature spectrometer by ocean optics, inc. calibrated 12 strong lines of he, ne, ar and h2 flashtubes). one of the displays used was that of an old notebook using a ccfl as a backlight and the other was a more modern one (hp zr2440w) with a display using rgb leds as a backlight. based on the spectral power distributions measured, the cie 1931 (x, y) chromaticity coordinates were calculated for all three primaries of both displays, using a color matching function (cmf) of 10° at a resolution of 1 nm between the wavelengths of 360 nm and 830 nm. intermediate gamut point coordinates were calculated by interpolation. gamut point numbers in table 1 and fig. 1 were further referred to as colors of incident light. in our kinetic model, actual color perception is compiled from the generally known mathematical relations [8, 9, 17] shown below. the actual color perception j of a single (l, m or s) cone receptor can be calculated by the formula j = dep, (1) where d denotes a conversion constant between the cleavage of rhodopsin and neural impulses and here is figure 1: chromaticity diagram of gamut points: an old ccfl display of a notebook (inner gamut) and an hp zr2440w display (outer gamut) equal to 1. the variable e represents the intensity of incident light expressed in trolands (td). during the calculations a maximum luminance of the monitor of 300 cd/m2 was used and a diameter of the pupil of 5 mm assumed. therefore, the maximum retinal illuminance was equal to 5890 td. the variable p denotes the relative concentration of photopigment (between 0 and 1). the time differential of p determined from the rate of photopigment synthesis (qs), spontaneous photopigment cleavage (qc) and photoinduced cleavage (qi) is calculated by dp dt = qs −qc −qi. (2) the variables of eq. 2 are calculated by qs = 1 τ , (3) qc = p τ , (4) and qi = e e0 p τ , (5) where the time constant τ = 99 1/s and e0 = 20, 000 are used [13]. the following differential equation is composed from eqs. 2–5: dp dt = 1 τ − p τ − e e0 p τ . (6) the solution of eq. 6 yields the actual relative concentration of photopigment: p(t) = 1 b [1 − (1 − p0b)] e −tb/τ, (7) where p0 denotes the initial relative concentration of photopigment. hungarian journal of industry and chemistry biophysical model of color afterimages 19 finally, the equilibrium with regard to the relative concentration of photopigment pe and percentage of photopigment cleaved b are related as follows: pe = 1 b = e0 e + e0 . (8) 2.2 simulation formula in accordance with cie 1931 [18, 19], the actual coordinates of color perception x(t), y(t) and z(t) are calculated from the color coordinates of incident light xi, yi and zi by equations eqs. 9–24. in the equations below, variables indexed with l, m and s apply to cone receptors l, m and s, respectively. el = emultip ·m1,1-3 × [xi, yi, zi] (9) em = emultip ·m2,1-3 × [xi, yi, zi] (10) es = emultip ·m3,1-3 × [xi, yi, zi] (11) bl = bm = bs = 1 + emultip e0 (12) emultip, which is equal to 6, 000, denotes the light intensity of the display. the actual relative concentration of photopigment is calculated from the initial relative concentrations of photopigment p0l, p0m and p0s: pl(t) = 1 bl (1 − (1 − p0lb))e −tb/τ (13) pm(t) = 1 bm (1 − (1 − p0mb))e−tb/τ (14) ps(t) = 1 bs (1 − (1 − p0sb))e −tb/τ (15) for the purposes of iteration in simulations, the initial relative concentration of photopigment p0 was equal to 0.1. from the actual relative concentrations of photopigment eqs. 13–15, the color perception coordinates are as follows jl(t) = d · pl · el, (16) jm(t) = d · pm · em, (17) js(t) = d · ps · es, (18) where jl, jm and js denote the cone receptors of long, medium and short wavelengths, respectively. to obtain more accurate color perception coordinates, tristimulus values were calculated: x(t) = m−11,1-3 × [jl, jm, js], (19) y (t) = m−12,1-3 × [jl, jm, js], (20) z(t) = m−13,1-3 × [jl, jm, js], (21) figure 2: an example of fast color change leading to virtual color perception. color point yellow shows primary color perception. color points bright blue show virtual color perception as reflected by the tendency to reach equilibrium in photopigment relative concentration. where m denotes a transformation matrix between tristimulus values x , y and z, and the actual color perception j . the actual color perception coordinates x(t), y(t), z(t) are calculated by the following equations: x(t) = x(t) x(t) + y (t) + z(t) , (22) y(t) = y (t) x(t) + y (t) + z(t) , (23) z(t) = 1 − x(t) − y(t). (24) in accordance with the cieluv (1976) chromaticity diagram, the actual color perception coordinates x(t), y(t) and z(t) are transformed into coordinates u′(t) and v′(t) by an easy-to-compute method [19] : u′(t) = 4x(t) 12y(t) − 2x(t) + 3 , (25) v′(t) = 6y(t) 12y(t) − 2x(t) + 3 . (26) the intensity of the actual virtual color perception is determined by ∆c = √ (u′(t) − u′e) 2 + (v′(t) − v′e) 2 , (27) where u′e and v′e denote color coordinates at equilibrium following restoration from virtual color perception (see restoration to the equilibrium in fig. 2). a summary of variables and parameters is shown in notations at the end of this paper. 2.3 simulation to understand the calculations, a graphical approach is shown in fig. 2. gamut color point 1 stands for the primary perception of the actual incident light, which is yellow here. with a rapid change in color from yellow to 47(1) pp. 17–23 (2019) 20 garai and horváth table 2: example of iteration t(s) xi yi u′(t) v′(t) ∆c 0.0 0.4250 0.56875 – – – 10.0 0.4250 0.56875 0.1893 0.3802 – 20.0 0.4250 0.56875 0.1892 0.3802 – 30.0 0.4250 0.56875 0.1891 0.3802 – 30.1 0.1400 0.05000 0.1748 0.0836 0.02075 30.2 0.1400 0.05000 0.1748 0.0837 0.02066 30.3 0.1400 0.05000 0.1747 0.0838 0.02057 30.4 0.1400 0.05000 0.1747 0.0838 0.02048 30.5 0.1400 0.05000 0.1746 0.0839 0.02039 30.6 0.1400 0.05000 0.1745 0.0840 0.02031 30.7 0.1400 0.05000 0.1745 0.0840 0.02022 30.8 0.1400 0.05000 0.1744 0.0841 0.02013 30.9 0.1400 0.05000 0.1744 0.0842 0.02004 31.0 0.1400 0.05000 0.1743 0.0842 0.01995 31.1 0.1400 0.05000 0.1743 0.0843 0.01987 31.2 0.1400 0.05000 0.1742 0.0844 0.01978 . . . . . . . . . . . . . . . . . . 63.9 0.1400 0.05000 0.1611 0.0991 0.000126 64.0 0.1400 0.05000 0.1611 0.0991 0.000101 64.1 0.1400 0.05000 0.1611 0.0992 0.000092 64.2 0.1400 0.05000 0.1611 0.0992 0.000102 blue, a bright blue color appears in perception that transforms into common blue after a short period of time necessary for the restoration of the equilibrium in terms of the relative concentration of photopigment, which is the time period required for virtual color perception, namely for the perception of bright blue (fig. 2). our kinetic simulation model (section 2.2) is illustrated in table 2. the first five lines in the first four columns show the same values of the color coordinates of incident light xi, yi, zi, against time (0 − 30 seconds). figure 3: photopigment relative concentration values in the iteration in table 2 over this 30 second-long period, the u′(t) and v′(t) values of color perception are quasi identical. however, after 30 seconds, a rapid change in color of the incident light from red to blue results in virtual color perception, as demonstrated by line 6 and column 5. the values of ∆c in column 7 concern the intensity of virtual color perception. (∆c)max denotes the peak intensity in virtual color perception and the minimum ∆c stands for the duration of virtual color perception (tvirtcol). actual relative concentrations of photopigment of cone receptors l, m and s are shown in the diagram in fig. 3. in terms of simulating virtual color perception, rapid changes in the color of incident light were indicated on ccfl and rgb led monitors by the assignment of defined gamut points to each other (fig. 1). altogether, 24 changes in color were simulated. 2.4 validation of the simulation our kinetic model was validated by a test that consisted of 20 subjects involving an in-house piece of software run in a python environment. accordingly, a homogeneous solid colored circle is displayed on a homogeneous background of a different color for 30 seconds (fig. 4), then the circle disappears (fig. 5) and the intensity and duration of virtual color perception is determined by the key inputs of the user. further details concerning the test are found below: • first, the test subject looked at a white screen for 30 seconds. figure 4: second screen of validation test. figure 5: third screen of validation test: circle removed. hungarian journal of industry and chemistry biophysical model of color afterimages 21 table 3: comparison of virtual color perception intensity in model situations and in validation test results ranking in model ranking category ranking in validation test results id rank id median of ranking correlation r → g 1 high b → g 1.00 no g2b2 → r 2 b2r2 → g 2.00 yes g1b3 → r 3 r → g 3.00 yes b2r2 → g 4 b → r2g2 4.00 no r → g2b2 5 medium r → g2b2 4.00 yes r2g2 → b 6 low g1b3 → r 4.50 no g → b2r2 7 g2b2 → r 5.00 no b → g 8 g → b2r2 5.00 yes b → r2g2 9 r2g2 → b 7.00 yes matching percentage between model and validation test results: 56% table 4: comparison of virtual color perception time period in model situations and in validation test results ranking in model ranking category ranking in validation test results id rank id median of ranking correlation r → g2b2 1 high b → g 1.00 no r → g 2 g1b3 → r 2.00 no g → b2r2 3 b → r2g2 3.00 no b2r2 → g 4 r → g2b2 4.00 yes r2g2 → b 5 medium g2b2 → r 4.00 no g2b2 → r 6 low g → b2r2 4.50 no b → r2g2 7 b2r2 → g 5.00 no g1b3 → r 8 r → g 5.00 no b → g 9 r2g2 → b 7.00 no matching percentage between model and validation test results: 11% • second, the eyes of the subject were fixed on a circle at the center of the subsequent colored image (fig. 4) for 30 seconds. according to our definition, the color of the central circle represents the first gamut point, while the color of the background represents the second gamut point. altogether, 9 assignments of gamut points have been validated so far. • third, the central circle suddenly disappeared (fig. 5) and the subject responded according to the intensity and duration of virtual color perception experienced. • the intensity of virtual color perception was rated on a four-grade scale, where zero stands for the absence of virtual color perception and 4 denotes its highest intensity. the duration of virtual color perception was indicated by the subject pressing a key as the perception faded away. first, the assignments of gamut points for each test subject were ranked according to the intensity (table 3) and duration (table 4) of virtual color perception induced. then, the median of the rank order with regard to the intensity and duration of virtual color perception was calculated. table 5: intensity and time period of virtual color perception related to gamut points assignments (∆c)max tvirtcol(s) color point 1 color point 2 ccfl rgb led ccfl rgb led b r3g1 0.00792 0.01212 30.9 24.5 b r2g2 0.00553 0.00513 36.3 27.5 b r1g3 0.00339 0.00197 41.9 16.0 r3g1 b 0.00794 0.01210 33.5 29.5 r2g2 b 0.00852 0.01367 34.9 32.2 r1g3 b 0.00953 0.01523 37.2 34.6 g3b1 r 0.00931 0.02381 27.1 29.3 g2b2 r 0.00958 0.02187 27.5 27.6 g1b3 r 0.00994 0.01989 28.1 25.8 r g3b1 0.00920 0.02298 46.9 44.2 r g2b2 0.00821 0.01686 51.2 52.8 r g1b3 0.00735 0.01260 50.2 38.2 g b3r1 0.00807 0.01789 48.2 41.1 g b2r2 0.00648 0.01362 45.8 42.2 g b1r3 0.00693 0.01722 30.5 31.0 b3r1 g 0.00324 0.01337 25.0 27.8 b2r2 g 0.00524 0.01799 33.7 33.7 b1r3 g 0.00749 0.02256 41.4 38.7 b r 0.01036 0.01786 28.8 23.8 r b 0.00788 0.01053 33.3 26.6 r g 0.00980 0.02707 48.2 43.1 g r 0.00915 0.02571 26.7 30.8 g b 0.01084 0.01677 40.1 37.0 b g 0.00234 0.00868 17.8 20.5 since the number of test subjects was limited, the results could not be divided according to their age and gender. further tests are needed to ensue virtual color perception with regard to gender and age. 3. results and discussion in table 5, the maximum (∆c)max for the ccfl and rgb led displays were identified during the rapid change in the color of incident light from gamut point g to b (from green to blue) and r to g (from red to green), respectively. when compared to the ccfl display, the rgb led display appears to yield higher (∆c)max values with the exception of rapid changes in the color of the incident light from gamut point b to r2g2 (from blue to orange). with regard to our results, the duration of virtual color perception seems to be platform-free, i.e. tvirtcol displayed on both the ccfl and rgb led monitors was identical. however, rapid changes in the color of the incident light from gamut point b to r1g3 (from blue to yellowish green) was an exception with regard to the values of tvirtcol. as is shown in table 5, tvirtcol computed on the ccfl display has doubled in value compared to that computed on the rgb led display. the kinetic simulation results so far point to the likelihood of the appearance of virtual color perception on all 47(1) pp. 17–23 (2019) 22 garai and horváth display platforms. as for our preliminary tests performed on 20 test subjects so far as well as the parameters (∆c)max and tvirtcol, a correlation between model situations (simulations) and the results of a validation test cannot be confirmed at present. further tests, statistical evaluations and the introduction of additional parameters are also necessary to achieve more accurate conclusions. 4. conclusion photopic human color vision is a combined response to the stimulation from light of red, green and blue cone receptors. cone receptors adapt individually to the actual color of the incident light. since the adaptation of cone receptors is time-consuming, virtual color perception can be achieved in the meantime by rapid changes in the color of the incident light. our kinetic model developed for individual cone receptors is based on mathematical correlations that simulate the intensity and duration of virtual color perception which result from rapid changes in color. according to our model, virtual color perception can result from both ccfl and rgb displays. our preliminary validations are yet to confirm a correlation between model situations (simulations) and the results of a validation test. some refinements to the simulation by the introduction of additional parameters as well as further validation tests with regard to the gender and age of participants are indispensable to reach more accurate conclusions. acknowledgement this research would not have been possible without the participation of volunteers from széchenyi istván university as test subjects. notations symbol meaning unit j in actual color perception: jl = red cone receptors specific for long wavelength jm = green cone receptors specific for medium wavelength js = blue cone receptors specific for short wavelength dimensionless p relative photopigment concentration dimensionless (range:0 . . . 1) d conversion constant between rhodopsin cleavage and neural impulses dimensionless (value: 1) e incident light intensity troland qs synthesis of photopigment dimensionless qc spontaneous cleavage of photopigment dimensionless qi light induced cleavage of photopigment dimensionless τ time constant in rhodopsin synthesis seconds symbol meaning unit p0 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doi: 10.1002/9780470175637 47(1) pp. 17–23 (2019) https://doi.org/10.18136/pe.2016.642 http://konyvtar.uni-pannon.hu/doktori/2016/csuti_peter_dissertation.pdf http://konyvtar.uni-pannon.hu/doktori/2016/csuti_peter_dissertation.pdf https://doi.org/10.1088/1475-4878/33/3/301 https://doi.org/10.1088/1475-4878/33/3/301 https://doi.org/10.1002/9780470175637 https://doi.org/10.1002/9780470175637 hungarian journal of industry and chemistry vol. 47(1) pp. 25–32 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-05 thermal model development for a cubesat nawar al hemeary *1,2, maciej jaworski3, jan kindracki3, and gábor szederkényi1 1faculty of information technology and bionics, pázmány péter catholic university, práter u. 50/a, budapest, 1083, hungary 2electromechanical engineering department, university of technology, al senaha st., baghdad, 10066, iraq 3faculty of power and aeronautical engineering, warsaw university of technology, nowowiejska 24, warszawa, 00-665, poland cubesats provide a cost-effective means of several functions of satellites due to their small size, mass, relative simplicity and short development time. therefore, cubesat technologies have been widely studied and developed by space organizations, companies and educational institutions all over the world. these satellites have certain drawbacks. small surface areas are a consequence of their small size which often imply thermal and power constraints. a novel development of cubesats known as pw-sat has been developed by warsaw university of technology. a control-oriented lumped thermal model of this satellite containing a fuel tank in the form of nonlinear ordinary differential equations is proposed in this paper. the model is able to simulate the thermal behavior of the surface and fuel tank of the satellite in its orbit. for the pw-sat to operate reliably, the temperature of the fuel tank has to be maintained within given safety limits. because of the limited power, passive thermal control is assumed in this case. several simulation results are presented for different surface compositions to determine whether they are able to guarantee the prescribed temperature range throughout the entire orbit or not. keywords: pw-sat, tmm, thermal behavior, propellant tank, dynamical modeling 1. introduction in recent years, interest in cube-satellites (cubesats) has grown tremendously within the space community from space agencies as well as in industry and academia. two factors have influenced this spurt of interest, namely the low-cost nature of access to space and the utilization of commercial off-the-shelf (cots) technologies in the design architecture. these two factors have led to a significantly low overall cost of a cubesat mission [1]. a cubesat is cubic in form with edges 10 cm in length and a mass of up to 1.33 kg. the pw-sat is a cubesat that has been in development for more than a year by different teams at warsaw university of technology [2, 3]. at present, pw-sat has never been flown with an onboard propulsion system. due to the significant and growing interest in cubesat mission capabilities, several propulsion systems have been rapidly developed for use in cubesats such as cold gas propulsion systems, solar sails, electric propulsion systems and chemical propulsion systems [4, 5]. cold gas propulsion systems are relatively simple solutions in cubesats. gas from a high-pressure gas cylinder is simply vented through a valve and nozzle to produce thrust [6, 7]. *correspondence: al.hemeary@itk.ppke.hu the goal of this paper is to propose a lumped dynamical model of temperatures during orbital motion in the main parts of a cubesat that contains a fuel tank. the model is built in the form of nonlinear ordinary differential equations (odes). although advanced thermal simulation tools exist that utilize detailed distributed mathematical models, this simple form of a model has been chosen since it is intended to be used in the model of temperature control design. the overwhelming majority of control design techniques require models in the form of ordinary differential equations [8]. moreover, in the case of nonlinear models such as the cubesat system studied, a low dimensional model is preferred due to the computational complexity of control design. this approach is also supported by control theory and practice, namely that in general such simple models are sufficient for controller design [9]. as a first step in terms of the regulation of temperature, passive control in the form of the appropriate composition of materials covering the surfaces of the satellite is used. during the construction of the model, the standard principles of thermal modeling [10, 11] and their application in aerospace engineering are followed [12, 13]. relevant results can be found in the literature concerning the thermal modeling and analysis of small satelmailto:al.hemeary@itk.ppke.hu 26 al-hemeary, jaworski, kindracki, and szederkényi lites in the form of odes. in [14] a simple thermal dynamical model of a cubesat containing two differential equations is presented. the two lumped balance volumes are the surface and internal parts of the satellite, respectively. it is shown that the problem is mathematically analogous to the forced vibration of a damped mechanical system. in [9], new theoretical results on the qualitative behavior of spacecraft thermal models are provided that contain several nodes (compartments). it is proven that such models exhibit a unique asymptotically stable equilibrium in the positive orthant with constant external disturbance inputs which leads to a stable limit cycle during orbital motion. the analysis concerning the frequency domain of a multi-compartmental model of a satellite is conducted in [15]. the odes are linearized around the equilibrium points which permit the use of fourier analysis. the structure of the paper is as follows: the description starts with the derivation of a simple mathematical model to simulate the transient thermal behavior of the fuel tank as well as the satellite faces in orbit. then, by changing either the optical properties of the surface of the pw-sat or the solar cell ratio of the satellite surface, several simulations are presented to illustrate how different configurations satisfy the given temperature limits. 2. system description and assumptions the intended use of the model developed in this paper is twofold: 1) to study the effect of different surface compositions (including solar cells) on temperature, 2) to evaluate the possibility of installing a propellant tank in the cubesat. with regard to the modeling, the following assumptions are made: 2.1 structural assumption pw-sat is a cubic structural bus with a total mass of 1 kg composed of six faces as walls. the basic structure of these faces is composed of the aluminum alloy 6061-t6 with various optical surface properties. these properties are based on uncoated surfaces for one experiment and coated with a magnesium oxide-aluminum oxide paint for the others. the nitrogen fuel tank, made of stainless steel with a diameter of 5 cm, is planned to be installed in the center of this satellite as shown in fig. 1a and is assumed to contain an internal gas subject to 100 bars of pressure at an initial temperature of 298 k. the solar cells will be attached to sides 1, 2 and 4 of the pw-sat, as shown schematically in fig. 1b, because these faces will be exposed to solar radiation due to the assumed orbit of this satellite. 2.2 orbital assumption the pw-sat is designed for a circular low earth orbit (leo). the total orbital period (p ) is 1.5 h. however, (a) (b) figure 1: pw-sat structure ((a) pw-sat spherical fuel tank set, (b) pw-sat solar cell arrangements). the motion of pw-sat is assumed to be identical when exposed to solar radiation and during shadow passage at an altitude of 300 km and an inclination of zero. face 3 is directed towards the earth throughout its orbit. faces 1, 2 and 4 are exposed to the sun with regard to the orbital motion of the satellite. finally, faces 5 and 6 are directed towards the space along the satellite orbit as shown in fig. 2. 2.3 thermal assumption the six faces of the pw-sat are considered to have a uniform temperature distribution. the conductive heat transfer between the fuel tank and satellite is ignored to simplify the thermal modeling calculations. only face 3 is exposed to infrared radiation from the earth in this orbit and the albedo during the luminous orbit intervals figure 2: pw-sat orbital motion. hungarian journal of industry and chemistry thermal mathematical model 27 [14, 16]. the thermal rate of power dissipation generated from the operation of elements from the satellite is assumed to be 2 w. the thermal limits of the fuel tank are 228 k and 338 k, and for the surface area of the satellite are 173 k and 373 k. 3. thermal mathematical model (tmm) the problem concerns the formulation of the model, which is on the one hand simple enough to limit the expenditure, on the other hand, detailed enough to present an adequate description of the physical surroundings [17]. the main purpose of these calculations is to divide the periodic motion of the satellite (with period p ) into three intervals (parts) as shown in fig. 2. the first interval (p1) starts with an initial time of t = 0 s when face 1 faces the sun and ends at a time of t = 1350 s when face 4 faces the sun. the second interval (p2) is an eclipse interval between t = 1351 s and t = 4050 s. the third interval (p3) starts at t = 4051 s when face 2 faces the sun and ends at the end of the satellite period at t = 5399 s. 3.1 first interval equations interval p1 : t = 0→ t = p 4 (1) the satellite spends a quarter of its orbital period in this luminous part. during this time interval, the surface of the satellite receives direct solar and albedo radiation depending on the position of the satellite due to its motion and the satellite emits thermal ir radiation into space; however, only face 3 receives additional infrared radiation from earth because it faces the earth [18]. the rate of heat transfer between face 1, the external environment and the spherical fuel tank during the first interval can be described by (mal cp +msc c sc p ) dt1 dt = gsa al-sc s a cos ( 2πt p ) + q̇+ q̇f1 − εal-sc ir σat 4 1 (2) where mal denotes the mass of aluminum, cp stands for the specific heat of aluminum (980 j/(kg·k)), msc represents the mass of the solar cell , csc p is the specific heat of the solar cell (1600 j/(kg·k)), t1 denotes the temperature of face 1, gs stands for the solar constant (1367 w/m2), and aal-sc s represents the average solar absorptance of aluminum and the solar cell which is calculated as (al %·aal s +sc %·ascs ), where al % and sc % denote the percentages of aluminum and solar cells in the cover, respectively. a stands for the surface area of the face (0.01 m2), q̇ represents the thermal rate of power dissipation, q̇f1 denotes the radiative heat transfer between face 1 and the tank, εal-sc ir is the average infrared emissivity of al and sc which is calculated as (al %·εal+sc %·εsc) and σ stands for the stefan-boltzmann constant (5.669 · 10−8w/m2 k4) [6]. the rate of heat transfer between face 2, the external environment and the spherical fuel tank during the first interval can be described by (mal cp +msc c sc p ) dt2 dt = q̇+ q̇f2 − εal-sc ir σat 4 2 (3) where t2 denotes the temperature of face 2 and q̇f2 stands for the radiative heat transfer between face 2 and the tank. the rate of heat transfer between face 3, the external environment and spherical fuel tank during the first interval can be described by mcp dt3 dt = af ·gsa al s fsea cos ( 2πt p ) + q̇+ q̇f3 + aal irσat 4 e − εal irσat 4 3 (4) where m denotes the mass of the face (0.04 kg), fse stands for the view factor between the face of the satellite and the earth which is almost one [18], t3 represents the temperature of face 3, q̇f3 is the radiative heat transfer between face 3 and the tank, af denotes the factor on the albedo (0.28), aal s stands for the solar absorptivity of aluminum, aal ir represents the infrared absorptivity of aluminum, te is the reference temperature of the earth (255 k) and εal ir denotes the infrared emissivity of aluminum. the rate of heat transfer between face 4, the external environment and the spherical fuel tank during the first interval can be modeled as( mal cp +msc c sc p ) dt4 dt = gsa al-sc s a sin ( 2πt p ) + q̇+ q̇f4 − εal irσat 4 4 (5) where t4 denotes the temperature of face 4 and q̇f4 stands for the radiative heat transfer between face 4 and the tank. the rate of heat transfer between face 5, the external environment and the spherical fuel tank during the first interval can be described as mcp dt5 dt = q̇+ q̇f5 − εal irσat 4 5 (6) where t5 denotes the temperature of face 4 and q̇f5 stands for the radiative heat transfer between face 5 and the tank. the rate of heat transfer between face 6, the external environment and the spherical fuel tank during the first interval can be described as mcp dt6 dt = q̇+ q̇f6 − εal irσat 4 6 (7) where t6 denotes the temperature of face 6 and q̇f6 stands for the radiative heat transfer between face 6 and the tank. 47(1) pp. 25–32 (2019) 28 al-hemeary, jaworski, kindracki, and szederkényi 3.2 second interval equations interval p2 : t = p 4 → t = 3 4 p (8) these concern the duration of an eclipse. the satellite spends half of its orbital period in an eclipse. during this interval, the surface of the satellite receives neither direct solar nor albedo radiation, whilst face 3 still receives ir radiation from the earth because it faces it. the satellite emits thermal ir radiation into space. therefore, the rates of heat transfer of the faces of the satellite (1, 3 and 4) have slightly changed in their equations compared to the first interval. the rate of heat transfer between faces 1, 3 and 4 as well as the external environment during the second interval can be described by the following equations (mal cp+msc c sc p ) dt1 dt = q̇+q̇f1 −εal-sc ir σat 4 1 (9) mcp dt3 dt = q̇+ q̇f3 + aal irσat 4 e − εal irσat 4 3 (10) (mal cp +msc c sc p ) dt4 dt = q̇+ q̇f4 − εal-sc ir σat 4 4 (11) 3.3 third interval equations interval p3 : t = 3 4 p → t = p (12) the satellite spends a quarter of its orbital period in this second luminous part. during this time interval, the surface of the satellite receives and emits thermal radiation in a similar manner to during interval 1 with only a slight change in the equation of face 2. the rate of heat transfer between this face, the external environment and the spherical fuel tank during the third interval can be modeled as (mal cp +msc c sc p ) dt2 dt = gsa al-sc s a ∣∣∣∣sin(2πt p )∣∣∣∣+ q̇+ q̇f2 − εal−sc ir σat 4 2 (13) 3.4 the transient heat transfer of the spherical propellant tank the rate of heat transfer between the faces of the satellite and the fuel tank can be described by the following equation (ms c s p +mgcv ) dtt dt = − 6∑ 1 q̇fn (14) table 1: material properties of pw-sat. al 6061-t6 uncoated al 6061-t6 coated solar cells specific heat [j/(kg·k)] 980 980 1600 emissivity (thermal) 0.08 0.92 0.85 absorptivity (solar) 0.379 0.09 0.92 table 2: material properties of fuel tank. stainless steel nitrogen specific heat [j/(kg·k)] 504 743 mass [kg] 0.0926 0.0074 table 3: average of optical surface properties of partially covered surfaces. cube face ε a coverage 1,2 and 4 0.89 0.33 70 % al, 30 % sc 0.87 0.67 30 % al, 70 % sc 3,5 and 6 0.92 0.09 al painted where ms denotes the mass of stainless steel, cs p stands for the specific heat of stainless steel (504 j/(kg·k)), mg represents the mass and cv the specific heat of nitrogen (743 j/(kg·k)), and tt is the temperature of the tank. the radiative heat transfer between each face and the tank q̇fn , depending on which face it applies to, can be described as q̇fn = fftεσa(t 4 t − t 4 n) (15) the view factor between the face in question and the fuel tank is given by fft = 1 (1+h)2 (see, e.g. [10, 11]), where h denotes the ratio of the distance between the spherical surface of the tank to the surface of the internal face (h = 0.025 m) in terms of the radius (r = 0.025 m), which is expressed as h = h r . the mass of the solar cell msc per unit area is on average 850 g/m2, thus, the mass of the solar cell as a proportion of the total mass of the face is determined by the equation (msc = 850 g/m2 · a · sc %). the total mass of the tank mt is assumed to be 0.1 kg, so the mass of nitrogen gas was calculated by assuming the initial temperature and total pressure of the tank. the optical surface properties are shown in table 1, and the masses of both nitrogen gas and the tank are shown in table 2. hence, it is necessary to calculate the properties of the average materials to conduct a thermal analysis. the emissivity of infrared radiation from these faces can be calculated as the average of the emissivity of infrared radiation from aluminum and the emissivity of infrared radiation from the solar cell in addition to the absorptivity of these faces as shown in table 3. hungarian journal of industry and chemistry thermal mathematical model 29 (a) (b) figure 3: the thermal behavior using 100 % al during one orbital period ((a) temperatures of the faces and fuel tank, (b) temperature of the fuel tank) (t1, . . . , t6) refers to the temperatures of faces 1, . . ., 6, respectively, and (tt) denotes the temperature of the tank. 4. computational results in this section, the faces and investigations into the thermal behavior of the tank are presented for several cases based on: uncoated surfaces, surfaces coated with magnesium oxide-aluminum oxide paint and different feasible options of the ratios of solar cells from the pw-sat to simulate the temperature of the fuel tank with different optical properties of the surface materials and solar cell ratios. 4.1 the pw-sat faces composed of 100 % uncoated aluminum in this case, the thermal simulations of the faces and fuel tank were conducted according to the assumption that the faces of the satellite are composed of the aluminum alloy 6061-t6. starting with the equations of the intervals and by using the ode45 solver in matlab (the simulation time step was 1 s), the thermal behavior during the orbital motion of the satellite was computed. 1 the thermal simulation of the faces and spherical fuel tank during one orbital period (time span from 0 s to 5399 s) is shown in fig. 3a and the simulation of the temperature of the tank during this orbital period is shown in fig. 3b. it can be seen that the predefined temperature limits are not adhered to in this case, since the minimum (a) (b) figure 4: thermal behaviors using 100 % al during 8 orbital periods ((a) temperatures of the faces and fuel tank, (b) temperature of the fuel tank). temperatures of the faces of the satellite and fuel tank exceed 460 k during its orbital period. 2 the thermal simulation of the faces and spherical fuel tank during several orbits (8 orbital periods with a time span of 12 h to illustrate long-term operations) is shown in fig. 4a, and the simulation of the temperature of the tank during these orbital periods is shown in fig. 4b. 4.2 the faces of the pw-sat are composed of 100 %-coated aluminum the thermal simulations of the faces and fuel tank were conducted according to the assumption that the surface of the satellite was composed of aluminum coated with magnesium oxide-aluminum oxide paint. by using the assumed time span of each interval, the results are shown below: 1 the thermal simulations of the faces and spherical fuel tank during one orbital period (time span from 0 s to 5399 s) are shown in fig. 5a, and the simulation of the temperature of the tank during this orbital period is shown in fig. 5b. it can be seen that all the defined temperature limits are adhered to in this case. 2 the thermal simulation of the faces and spherical fuel tank over 8 orbital periods (time span of 12 h) is shown in fig. 6a, and the simulation of the temperature of the tank during these orbital periods is shown in fig. 6b. 47(1) pp. 25–32 (2019) 30 al-hemeary, jaworski, kindracki, and szederkényi (a) (b) figure 5: thermal behaviors using coated al during one orbital period ((a) temperatures of the faces and fuel tank, (b) temperature of the fuel tank). 4.3 the faces of the satellite exposed to the sun during its orbit are covered with 70 % aluminum and 30 % solar cells in this case, these three sides of the pw-sat are assumed to be composed of 70 % aluminum and 30 % solar cells and the other faces are coated with magnesium oxidealuminum oxide paint. the simulation results are as follows: 1 the thermal simulation of the faces and spherical fuel tank during one orbital period (time span of 0 s to 5399 s) is shown in fig. 7a and the simulation of the temperature of the tank during this orbital period is also shown separately in fig. 7b. the results show that the temperature of the tank varied between a maximum of 281.9 k and a minimum of 265.4 k, while the temperatures of the faces also remained within the given temperature limits. 2 the thermal simulation of the faces and spherical fuel tank over 8 orbital periods (time span of 12 h) is shown in fig. 8a, and the simulation of the temperature of the tank during these orbital periods is shown in fig. 8b. (a) (b) figure 6: thermal behaviors using coated al over 8 orbital periods ((a) temperatures of the faces and fuel tank, (b) temperature of the fuel tank). 4.4 the faces of the satellite exposed to the sun during its orbit are covered with 30 % aluminum and 70 % solar cells the results, according to the assumption that three sides of the pw-sat are composed of 30 % aluminum and 70 % solar cells while the rest of them are coated with magnesium oxide-aluminum oxide paint, are shown below: 1 the thermal simulation of the faces and spherical fuel tank during one orbital period (time span from 0 s to 5399 s) is shown in fig. 9a, while simulation of the temperature of the tank during this orbital period is shown in fig. 9b. the results show that the temperature of the tank varied between a maximum of 302.4 k and a minimum of 270.6 k, while the temperatures of the faces were within thermal limits. 2 the thermal simulation of the faces and spherical fuel tank over 8 orbital periods (time span of 12 h) is shown in fig. 10a, while the simulation of the temperature of the tank during these orbital periods is shown in fig. 10b. 5. conclusion a thermal mathematical model was constructed and studied to compute the temperatures of the surfaces and fuel tank of the pw-sat. several cases were presented using various surface compositions and the results show that the proposed tmm is able to calculate the radiative heat hungarian journal of industry and chemistry thermal mathematical model 31 (a) (b) figure 7: thermal behaviors with 30 % sc during one orbital period ((a) temperatures of the faces and fuel tank, (b) temperature of the fuel tank). (a) (b) figure 8: thermal behaviors with 30 % sc over 8 orbital periods ((a) temperatures of the faces and fuel tank, (b) temperature of the fuel tank). (a) (b) figure 9: thermal behaviors with 70 % sc during one orbital period ((a) temperatures of the faces and fuel tank,(b) temperature of the fuel tank). (a) (b) figure 10: thermal behaviors with 70 % sc over 8 orbital periods ((a) temperatures of the faces and fuel tank, (b) temperature of the fuel tank). 47(1) pp. 25–32 (2019) 32 al-hemeary, jaworski, kindracki, and szederkényi that the pw-sat would encounter during its assumed orbit. initially, the surfaces of the pw-sat were assumed to be composed of 100 % of the aluminum alloy 6061-t6. the corresponding results suggest that the temperatures of the surfaces and fuel tank would be too high. therefore, additional finishes applied to the surfaces were taken into consideration. the first choice of finish was to coat the entire surface of the satellite with magnesium oxidealuminum oxide paint. the obtained results show that the temperatures of the surfaces and fuel tank dropped because of the increasing emissivity and decreasing absorptivity of the surfaces. further simulations were performed of cases in which the faces were exposed to the sun when partially covered with solar cells. the results indicate that the case described in subsection 4.4, which delivers the most electrical power due to the highest percentage of solar cells, still satisfies the temperature limits of the fuel tank and surfaces of the satellite. the results also suggest that it is possible to install a fuel tank inside the pw-sat which could be the first step required to add a propulsion system that can generate thrust for this cubesat. future works will include validation of the model using advanced thermal simulation tools as well as active control design to precisely regulate the temperature of the fuel tank. acknowledgement this work has been partially supported by the european union, co-financed by the european social fund through the grant efop-3.6.3-vekop-16-2017-00002. the support of the university of technology of baghdad and warsaw university of technology is also acknowledged. references [1] tummala, a. r.; dutta, a.: an overview of cube-satellite propulsion technology and trends, aerospace, 2017 4(4), 58. doi: 10.3390/aerospace4040058 [2] mehrparvar, a.: cubesat design specification rev. 13, the cubesat program, cal poly slo, 2015. http://www.cubesat.org/resources [3] pw-sat description (cubesat warsaw university of technology). https://directory.eoportal.org/web/ eoportal/satellite-missions/p/pw-sat [4] lemmer, k.: propulsion for cubesats, acta astronaut., 2017 134, 231–243. doi: 10.1016/j.actaastro.2017.01.048 [5] gaite, j.: nonlinear analysis of spacecraft thermal models, nonlinear dyn. 2011 65, 283–300. doi: 10.1007/s11071-010-9890-4 [6] sutton, g. p.; biblarz, o.: rocket propulsion elements, seventh edition (wiley, new york, usa) 2001. isbn 0-471-32642-9 [7] mueller, j.; hofer, r.; parker, m.; ziemer, j.: survey of propulsion options for cubesats, 57th jannaf propulsion meeting (colorado) 2010 jannaf1425 1–56. https://trs.jpl.nasa.gov/bitstream/ handle/2014/41627/10-1646.pdf [8] isidori, a.: nonlinear control systems (springer, london, uk) 1999. isbn 978-1-84628-615-5 [9] hangos, k. m.; bokor, j.; szederkényi, g.: analysis and control of nonlinear process systems (springer, london, uk) 2004. isbn 978-1-85233-861-9 [10] modest, m. f.: radiative heat transfer, third edition (academic press, oxford, uk) 2013. isbn 9780123869906 [11] sala, a.: radiation heat transfer (in polish) (wnt, scientific and technical publications, warsaw, poland) 1982. isbn 8320403677 [12] gilmore, d. g.: spacecraft thermal control handbook, second edition, vol. 1. (the aerospace press, el segundo, usa) 2002. isbn 1-884989-11-x [13] diaz-aguado, m. f.; greenbaum, j.; fowler, w. t.; lightsey, e. g.: small satellite thermal design, test, and analysis, modeling, simulation, and verification of space-based systems iii, proc. spie, 2006 6221, 622109. doi: 10.1117/12.666177 [14] grande, i. p.; andres, a. s.; guerra, c.; alonso, g.: analytical study of the thermal behaviour and stability of a small satellite, appl. therm. eng., 2009 29(11-12), 2567–2573. doi: 10.1016/j.applthermaleng.2008.12.038 [15] farrahi, a.; pérez-grande, i.: simplified analysis of the thermal behavior of a spinning satellite flying over sun-synchronous orbits, appl. therm. eng. 2017 125, 1146–1156. doi: 10.1016/j.applthermaleng.2017.07.033 [16] jaxa: design standard, spacecraft thermal control system, jerg-2-310 (japan aerospace exploration agency, tsukuba, japan) 2009. http://sma.jaxa.jp/ en/techdoc/docs/e_jaxa-jerg-2-310_08_re.pdf [17] fortoscue, p.; stark, j.; swinerd, g. (eds): spacecraft systems engineering, fourth edition (wiley, chichester, uk) 2011. isbn 978-0-470-75012-4 [18] vanoutryve, c. b.: a thermal analysis and design tool for small spacecraft, master’s thesis, 2008. https://scholarworks.sjsu.edu/etd_theses/3619 hungarian journal of industry and chemistry https://doi.org/10.3390/aerospace4040058 https://doi.org/10.3390/aerospace4040058 http://www.cubesat.org/resources https://directory.eoportal.org/web/eoportal/satellite-missions/p/pw-sat https://directory.eoportal.org/web/eoportal/satellite-missions/p/pw-sat https://doi.org/10.1016/j.actaastro.2017.01.048 https://doi.org/10.1016/j.actaastro.2017.01.048 https://doi.org/10.1007/s11071-010-9890-4 https://doi.org/10.1007/s11071-010-9890-4 https://trs.jpl.nasa.gov/bitstream/handle/2014/41627/10-1646.pdf https://trs.jpl.nasa.gov/bitstream/handle/2014/41627/10-1646.pdf https://doi.org/10.1117/12.666177 https://doi.org/10.1016/j.applthermaleng.2008.12.038 https://doi.org/10.1016/j.applthermaleng.2008.12.038 https://doi.org/10.1016/j.applthermaleng.2017.07.033 https://doi.org/10.1016/j.applthermaleng.2017.07.033 http://sma.jaxa.jp/en/techdoc/docs/e_jaxa-jerg-2-310_08_re.pdf http://sma.jaxa.jp/en/techdoc/docs/e_jaxa-jerg-2-310_08_re.pdf https://scholarworks.sjsu.edu/etd_theses/3619 hungarian journal of industry and chemistry vol. 47(1) pp. 33–39 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-06 automated labeling process for unknown images in an open-world scenario dávid papp *1 and gábor szűcs1 1department of telecommunications and media informatics, budapest university of technology and economics, magyar tudósok krt. 2., h-1117 budapest, hungary most of the recognition systems presume a controlled, well-defined research setting, where all possible classes that can appear during a test are known a priori. this environment is referred to as the “closed-world” model, while the “open-world” model implies that unknown classes can be incorporated into a recognition algorithm whilst being predicted. therefore, recognition systems that operate in the real world have to deal with these unknown categories. our objective was not only to detect data that originate from categories unseen during training, but to identify similarities between pieces of unknown data and then form new classes by automatically labeling them. our double probability model was extended by an image clustering algorithm, in which kernel k-means was used. a new procedure, namely the cluster classification algorithm for the detection of unknowns and automated labeling, is proposed. these approaches facilitate the transition from openset recognition to an open-world problem. the fisher vector (fv) was used for the mathematical representation of the images and then a support vector machine introduced as a classifier. the measurement of similarity was based on the fv representations. experiments were conducted on the caltech101 and caltech256 datasets of images and the rand index was evaluated over the unknown data. the results showed that our proposed cluster classification algorithm was able to yield almost the same rand index, even though the number of unknown categories increased. keywords: open-world problem, cluster classification, image classification, open-set recognition, image clustering 1. introduction in scenarios in the real world, the size of the available dataset continues to increase, therefore, any machine learning algorithm that operates in such an environment has to be capable of preventing growth. this is especially true in the case of image classification, because the growing dataset of tests can pose many difficulties, e.g. it is possible that some of the test images originate from categories that are unseen during training. recognition systems should detect these unknown images and handle them in an appropriate way. in the rest of the paper the terms "unknown class or category" represent classes or categories that are unseen during training, and “unknown image” denotes images that originate from unknown classes or categories. one way of handling detected unknown images is to measure their similarities and identify new categories. subsequently, these new categories can be added to the set of known classes. based on this, three modules are required to solve such problems in the real world, namely a recognition system equipped with an unknown detector, a labeling process and an incremental learning process. *correspondence: pappd@tmit.bme.hu let us assume that there are k known classes (c1, c2, . . . ck) and u unknown classes in the test set at any given moment, where sk and su denote the sets of known and unknown classes, respectively. few distinguishable cases depend on the value of u : 1. u = 0, 2. u = 1, 3. u > 1. furthermore, a few more cases depend on the amount and type of available information concerning su : (a) training images, (b) set of attributes, (c) number of unknown categories (u ), (d) nothing. the cases that include 1 or a (e.g. 1a, 2a, 1b, 1c) produce the general multiclass classification because all categories are known a priori and positive-negative samples are available for each category during training. when mailto:pappd@tmit.bme.hu 34 papp and szűcs u = 1, the task is only to identify the unknown images because they originate from the same category, therefore, the similarity measurement is unnecessary. in this paper, the situation when u > 1 is considered. as has been mentioned, 3a represents the traditional multiclass classification. 3b+3c is referred to as transfer learning or zero-shot learning [1], whereas according to the literature the case of 3c+3d is known as open set recognition [2,3] or the open-world problem [4]. the former refers to the detection of images that originate from unknown classes, and the latter includes the detection of unknown images and a labeling process to identify new classes, followed by the incremental learning of these new categories. our goal was to tackle the open-world problem as well as develop an algorithm that is able to detect the unknown images and then introduce new classes by automatically labeling the unknown data using unsupervised learning. previously an algorithm referred to as the double probability model (dpm) [5] was proposed, which is suitable as an unknown detector in an open-set environment. there are several works that use a variant of support vector machine (svm) to solve the unknown detection problem, such as the support vector data description [6], one-class svm [7, 8], reject option svm (ro-svm) [9] and the novel weibull-calibrated svm (w-svm) [3]. the latter one was developed to operate under the compact abating probability model, where the probability of class membership decreases (abates) as points move from known data towards unknown space. scheirer et al. claim that w-svm outperforms their previous solutions, namely the 1-vs-set machine training algorithm [2] and the pi-svm [10]. on the other hand, it was shown that dpm outperforms w-svm [5], therefore, in this paper the dpm was used for unknown detection. bendale and boult defined open world recognition and presented the nearest non-outlier algorithm in [4], which adds object categories incrementally while detecting outliers and managing open space risk. they defined open world recognition in the form of three sequential steps: a multiclass open set recognition function with a novelty detector, a labeling process and an incremental learning algorithm. although all of these steps should be automated, they presumed labels were obtained by human labeling. the main objective of our work and this paper is to propose an automated labeling process, the so-called cluster classification (cc). in the next section, the dpm and image clustering methods are reviewed, subsequently, a baseline method is suggested for an open-world problem and finally our proposed algorithm, the cc, is presented. the third section contains experimental results and in the last section our conclusion is discussed. 2. proposed open-world recognition system 2.1 double probability model the dpm [5] is based on the likelihood of a classifier and can be used with any kind of classifier that provides class membership probabilities for the images. as a result, after training the classifier, it is capable of making predictions with reliability values (scores) for each class, i.e. decision vectors. the range of the scores depends on the type of classifier (sometimes it is from 0 to 1 but it can be over any range. only one condition is required, namely the larger score for class ci should represent the higher likelihood of being a member of class ci. in the training set or a validation set, the instances with corresponding scores are investigated in each class. the ground truth is known for this set, so the positive elements can be selected from each class. in order to calculate the conditional probability that a new instance belongs to class ci according to its score, the cumulative distribution function (cdf) of positive scores should be determined, therefore, a reverse cdf of negative scores was created: fpi (x) = p (ci|score < x) , (1) fni (x) = p (¬ci|score > x) , (2) where pi and ni denote the positive and negative elements, respectively. note that the sum of these probabilities is not always equal to 1 (this is not a requirement). a dpm was constructed based on the cdf and reverse cdf functions. during testing, the focus is on the likelihood of the occurrence of an unknown class compared with any of the known classes. before the comparison, the probabilities of the known classes should be calculated. scores (scorei for class ci) for a new instance are obtained as outputs from the original classifier, and based on them the probability of class ci occurring can be expressed as described in pci = fpi (scorei) k∏ j=1,j 6=i fnj (scorej). (3) an expression for the probability of class ck+1 is pck+1 = k∏ j=1 fnj (scorej). (4) if the probability of being a member of class ck+1 is higher than for any other (known) class, then the new instance will be a member of the unknown class. otherwise the prediction is based on the original classifier, i.e. the class with the largest score will be selected. the decision with regard to the prediction of test instance j is formalized as dj = { ck+1 | pck+1 > maxi {pci } argmaxj {scorej} | otherwise (5) hungarian journal of industry and chemistry automated labeling process for unknown images 35 at this point the algorithm is able to make a decision about test data if it originates from an unknown category. also, should it originate from a known category, then based on the output of the classifier its known category can be determined. 2.2 unknown image clustering the image representations were created according to the bag-of-words [11, 12] model. based on their visual content, each image was represented by a single high dimensional vector. in order to create these high-level descriptors, the local attributes of the images were investigated by calculating the low-level scale invariant feature transform (sift) [13] descriptor. next, the gaussian mixture model (gmm) [14–16] was used to define the visual code words and the fisher vectors [17, 18] to encode the low-level descriptors into high-level descriptors based on the visual code words. the fisher vectors were the final representations (image descriptors) of the images and were used as the input data for the clustering algorithm. after the final clusters of fisher vectors were formed, the image clusters could be produced by substituting the fisher vectors for the corresponding images. the basis of our clustering approach is the wellknown k-means clustering algorithm [19] which consists of two important inputs, namely the initial cluster centers and the number of clusters. the k-means clustering algorithm aims to minimize the sum of squared distances from all points to their cluster centers: e = min ( k∑ l=1 ∑ xi∈cl ‖xi − zl‖2 ) , (6) where k denotes the number of clusters, xi represents a member of cluster cl and zl stands for the center of it. however, the fisher vector consists of 65,791 dimensions, and the basic k-means clustering algorithm performs less efficiently when the clusters are non-linearly separable or the data contains arbitrarily shaped clusters of different densities. therefore, an upgraded version of the k-means clustering algorithm was applied in the recognition system referred to as kernel k-means [20–22]. the objective function of kernel k-means is still to minimize the sum of squared distances, but it uses the kernel trick to transform the data points into infinite feature space xi → ϑ (xi), as can be seen in e = min  k∑ l=1 ∑ xi∈cl ∥∥∥∥∥∥∥ϑ (xi)− ∑ xj∈cl ϑ (xj) nl ∥∥∥∥∥∥∥ 2 , (7) where nl denotes the number of images in cluster cl. the trick here is that explicit calculations in the feature space are never required, since transformed data points are only present as part of an inner product. therefore, they can be substituted for their kernel representatives (the gaussian kernel was implemented here). in order to reduce the randomness of final clusters, the plusplus cluster center initialization algorithm was used before the iterative steps, which was proposed by d. arthur and s. vassilvitskii [23]. this approach aims to spread out the initial cluster centers and accelerate their convergence. the first cluster center is randomly selected from the data points, after that each subsequent cluster center is chosen from the data points with a probability proportional to its squared distance from the closest existing cluster center. in the following sub-sections, the usage of the presented methods is discussed. 2.3 baseline method in this section, a baseline method of open world recognition is presented. first, at training time the classifier of the training data is trained with k known classes, then, at testing time classification of the test data (k+u classes) is performed. the dpm is applied to the output of the classifier to detect unknown images udpm: udpm = nu⋃ j=1 {ij |dj = ck+1} (8) where ij represents test instance j, nu denotes the number of test instances in the test data, dj stands for the decision of the dpm, and ⋃ {. . . } is the operation of union. now, let us assume that information concerning u was provided (as in the case 3c), and u was used as the number of clusters. the kernel k-means plusplus cluster center initialization algorithm (kk++) was performed on udpm with k = u clusters (which is the input parameter for the kk++), and then the appropriate labels were assigned to the unknown images: lj = ck+i|i = out ( kk++ ) j = 1 . . .m, i = 1 . . . u (9) where m represents the number of unknown images; lj and ci denote the label of unknown image udpm j and cluster identity, respectively. this concludes the baseline method for automated labeling. at this point the classifier can be retrained based on the previously known and new labels, and then the new test data classified. 2.4 cluster classification in this section our proposed cc approach is presented, which is suitable for unknown detection and automated labeling. this algorithm contains extended training and testing phases. in training time, a classifier of the training data is trained with k known classes, then a pseudocluster is also created based on the k known categories. this means that the ground truth class labels are implemented rather than a clustering algorithm (to determine the final clusters), i.e. each category is a cluster. subsequently, the images are substituted for their fisher vector 47(1) pp. 33–39 (2019) 36 papp and szűcs representations and the cluster centers calculated which will be used in the testing phase. let us assume t categories are found in the testing phase, and that t > k. the test data is classified into the k known categories and a dpm applied based on the decision vectors to detect the unknown images udpm. the next step is to form clusters using the kernel k-means clustering algorithm starting from the k cluster centers that were calculated at training time from the pseudocluster. afterwards, the remaining t -k cluster centers are determined following the plusplus initiation protocol. furthermore, the training and test datasets were used together as the input data. basically, with these modifications it was possible to guide the clustering algorithm, therefore, create more accurate clusters. the following step of the testing phase is to classify the clusters {ci} by weighted majority voting of the members of the cluster. the vote is based on the class membership probabilities (pci ; i = 1 . . .k + 1) calculated in eqs. 3–4. as was seen in section 1, the definition of problem 3c assumes that the number of unknown categories exceeds 1. nonetheless, the output of the dpm only yields k + 1 alternatives instead of t . in spite of this, the classification of clusters that depend on {pci} can increase the number of alternatives to t as will be seen later. in section 1, a differentiation was made between known and unknown images, and now this differentiation is broken down even more. the training data contains only known images, because each of them belongs to one of the set of known categories (sk). from now on, the union of known images of the training data will be denoted by kgt as can be seen in: kgt = nk⋃ j=1 {ij} (10) where nk stands for the number of images in the training data. on the other hand, the test data contains both known and unknown images. furthermore, based on the output of dpm, the test data can be divided into two different subsets, namely predicted known images (kdpm) and predicted unknown images (udpm), as can be seen in eqs. 11 and 8, respectively. kdpm = nu⋃ j=1 {ij |dj 6= ck+1} (11) the weight of the images can be calculated based on the cluster coherence. the coherence of a cluster can be determined by comparing the number of known images to the number of predicted unknown images inside that given cluster. it should be noted that known images inside the clusters either originate from kgt or kdpm, while the predicted unknown images are all part of udpm. if the number of known images exceeds the number of unknown images it is implied that a cluster exhibits “known coherence” (kc), and “unknown coherence” (uc) vice versa, as described in: ccoh = { kc | ∥∥{kgt ∪kdpm }∥∥ ≥ ∥∥udpm ∥∥ uc | ∥∥{kgt ∪kdpm }∥∥ < ∥∥udpm ∥∥ (12) where ‖x‖ represents the number of elements in x , and the superscript coh indicates the coherence of cluster c. the weights can be calculated as described in eqs. 13 and 14. intuitively, if an image is known and located inside cluster uc, then it is “punished” by assigning a lower weight to it; and vice versa, an unknown image is given a lower weight inside cluster kc. moreover, the larger the difference between the numbers of known and unknown images implies a more severe punishment with regard to the value of weights. wkc j =  1 + (#known−#unknown) (#known+#unknown) | ij /∈ udpm 1− (#known−#unknown) (#known+#unknown) | ij ∈ udpm (13) wuc j =  1 + (#known−#unknown) (#known+#unknown) | ij ∈ udpm 1− (#known−#unknown) (#known+#unknown) | ij /∈ udpm (14) thereafter the final decision vector of cluster ci can be calculated as: vi = 1 ni ni∑ j=1 wj × dj (15) where ni denotes the number of images in cluster ci, wj represents the weight and dj stands for the decision vector ({pci }) of image j. note that dj possesses k + 1 elements (+1 from dpm), therefore, vector vi also possesses k + 1 elements. consequently, the element with the maximum value of vi determines the category of cluster ci. the classification of cluster ci is formalized in: di = { new class | vk+1 = maxj{vj} argmaxi{vi} | otherwise (16) the results of the classification of the clusters can be considered as a labeling proposal, i.e. label each image inside cluster ci according to di. when decision di for cluster ci is that it is part of a known category, then each image inside ci gets labeled with the same category. on the other hand, when di = a new class, a new category is created and each image in ci gets labeled with the new category. basically, the cc algorithm follows this labeling proposal. 3. experimental results in order to measure the efficiency of the labeling process, experiments were conducted on the caltech101 [24] and hungarian journal of industry and chemistry automated labeling process for unknown images 37 figure 1: example images from the caltech101 and caltech256 datasets. the airplane, butterfly and windmill categories are represented by the left, middle and right columns, respectively. caltech256 [25] datasets. example images from these datasets are shown in fig. 1. the former consists of 101 categories and 8, 677 images, while the latter is composed of 30, 607 images from 256 different classes. to create an open-world environment, 50 known and 50 unknown categories were randomly selected from the caltech101 dataset, and 100 of both categories from the caltech256 dataset. these ranfigure 2: averaged results of the 5-5 different test datasets that were randomly selected from the caltech101 and caltech256 datasets. the ri is plotted against the number of unknown categories. the diagrams compare the labeling performance of the dpm with kernel k-means (dpm+kk) against the cc. table 1: summary of the results obtained from the test data with the baseline (dpm+kk) and cc methods using the caltech101 and caltech256 datasets. the baseline column contains the ri values evaluated which depend on the number of unknown categories (un. cat.), and the cc column presents the improvements that result from cc as a percentage. caltech101 caltech256 un. cat. base-line cc (%) un. cat. base-line cc (%) 5 0.629 6 10 0.514 1 10 0.594 13 20 0.489 9 15 0.567 15 30 0.484 6 20 0.561 16 40 0.478 9 25 0.550 17 50 0.452 13 30 0.514 28 60 0.448 13 35 0.536 18 70 0.433 19 40 0.522 23 80 0.426 17 45 0.505 24 90 0.412 22 50 0.497 25 100 0.397 21 dom selections were repeated 5 times in order to calculate the average of the results of each experiment to obtain a more comprehensive overview of the efficiency of the cc algorithm with regard to these datasets. all of the known categories were available from the beginning of the tests, but the unknown categories were added incrementally over 10 steps, and in each step the rand index (ri), ri = tp + tn tp+ fp + tn+ fn , (17) was evaluated over the unknown images, where tp, tn, fp, and fn denote the number of true positive, true negative, false positive and false negative decisions, respectively. the ri measures the similarity between the ground truth and predicted labels of the unknown images, in other words, the percentage of correct decisions. two methods were assessed and compared, namely the baseline method (dpm+kk) and the cc, which were discussed in section 2.3 and 2.4, respectively. both procedures used fisher vectors to mathematically represent the images encoded from 128 dimensional sift descriptors using a gmm consisting of 256 code words; a svm equipped with a radial basis function (rbf) kernel was applied as a classifier. the results can be seen in fig. 2 and table 1. the first diagram shows the results obtained from the caltech101 dataset and the second from the caltech256 dataset. the dpm with kernel k-means and the cc are represented by dashed and solid lines, respectively. in both experiments, the cc algorithm yielded a higher ri, although during the first step the difference between the two methods was minimal. it can be seen that the ri of dpm+kk starts to decrease as the number of unknown categories increases, while the cc remains by and large unchanged. 47(1) pp. 33–39 (2019) 38 papp and szűcs 4. conclusion in this paper, the problem of open world recognition was reviewed and the possible cases were differentiated based on our prior knowledge and actual information about the test data and, thus, the unknown space. the dpm and kernel k-means algorithm were also reviewed in brief, followed by the presentation of two approaches, which perform multi-class classification, automatically detect unknown images and propose a labeling for them. the first method is a baseline technique where dpm was sequentially applied followed by kernel k-means with a plusplus cluster center initialization algorithm. however, our proposed cc is a complex method of combining the unknown detector and clustering algorithm that seeks to determine the identity of formed clusters, while refining the decisions made by the classifier and unknown detector. the cc algorithm constructs a specific weight system to reward or punish images which were placed into a category that is presumably unsuitable for their estimated identity. multiple experiments were conducted on two large datasets (caltech101 and caltech256), and the ri evaluated with regard to the unknown images. the results 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pp. 41–48 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-07 model reference adaptive control for telemanipulation nándor fink *1 1department of mechatronics, optics and engineering informatics, budapest university of technology and economics, bertalan lajos utca 4-6, budapest, 1111, hungary a 1-dof (degree-of-freedom) telemanipulation system is presented in this paper. the paper focuses on disturbance compensation of the haptic force feedback. the master and slave devices are connected via serial ports. the mechanism, which is applied as a human interface device, is subject to perceptible internal friction that must be eliminated. as a result, the operator would only feel the force feedback from the manipulated environment. the main contribution of this paper is the presentation of the telemanipulation device with a model reference adaptive control that compensates for the friction force using a direct model-based sliding mode algorithm. keywords: telemanipulation, friction compensation, sliding mode control 1. introduction in connection with the rapid spread of the internet over the past few years, research about cscw (computersupported cooperative work) technology is being vehemently conducted. it is expected that this network-based technology will make collaboration in connection with human intellectual activities between distantly connected people easier. in the field of cscw technology, the data to be processed are only images, sounds and other data for computers, little attention has been paid to multi-modal collaboration including physical contact. our focus concerns networked multi-modal collaboration especially between those including haptics. a collaboration tool that facilitates a better connection between laboratories, offices and factories in the manufacturing industry has become necessary [1–3]. research into the bilateral control of master-slave manipulators was conducted in 1992. in [4] a 1-dof telemanipulation system was tested. the research covered the dynamics of the human operator as well as the device. three levels of ideal responses were determined, in all cases a force signal to the master arm was the input. the position of the two arms was identical in the first level, whereas the force response of the two arms was identical in the second, and both responses were identical in the third. in [5] a four-channel control architecture was examined. four models were tested on a teleoperation system, namely on an admittance-admittance, impedance-admittance, admittance-impedance and impedance-impedance pair. based on the types of *correspondence: finknandor@mogi.bme.hu model, a one-one suggestion was made for the control architecture in each case, namely position-position, position-force, force-position and force-force. in addition to the basic criteria of stability, the ease of usability becomes increasingly important. to ensure comfortable and ergonomic telemanipulation, the operator should control the slave device more smoothly and precisely. furthermore, the elimination of perturbations in all circumstances is necessary. for this purpose, the design of a model-reference adaptive control with a sliding mode friction compensator is promising. 2. theoretical background of the experiment 2.1 sliding mode-based disturbance elimination the main concept is the design of a reduced-order state observer for a partially perturbed linear system with infinite gain. the traditional roles of the system and observer are exchanged. the system is forced to follow the states of the unperturbed ideal model. infinite gain is ensured by a sliding mode. consider the following partially perturbed linear system that consists of external disturbances and uncertain parameters which satisfy the so-called drazenovic condition, written in the regular form of a state equation, d dt [ x1 x2 ] = [ a11 a12 a21 + ∆a21 a22 + ∆a22 ][ x1 x2 ] + [ 0 b2 + ∆b2 ] u0 + [ 0 e2 ] f(t) (1) mailto:finknandor@mogi.bme.hu 42 fink where x1 ∈ rn−m denotes the vector of non-perturbed state variables, x2 ∈ rm stands for the vector of perturbed state variables, u0 ∈ rm represents the input of the real system, aij(i, j = 1, 2) and b2 are the nominal or desired (ideal) matrices of the system, respectively, ∆a2j(j = 1, 2) and ∆b2 denote the bounded parameter perturbations, and f(t) stands for the bounded external disturbance. the perturbed state variables are estimated by a discontinuous observer [6] d dt x̂2 = a21x1 + a22x̂2 + b2 ( u0 + ν ) (2) where ν denotes the discontinuous term. let us design the following sliding surface: σ = [ i −i ][x2 x̂2 ] = 0 (3) where i ∈ rm×m represents the identity matrix and σ ∈ rm stands for the distance from the surface. σ must tend to zero. let us calculate the elements of the discontinuous term ν in following way: νi = gi sign(σi), (4) where gi is the gain of the sliding mode controller. the implementation of a sliding mode means that the signs of σi = 0 and νi change at an infinitely high frequency [7]. ν can be substituted by its mean value denoted by νeq. by comparing the second line of eq. 1 and eq. 2:( b2 + ∆b2 ) ν = ∆a21x1 + ( a22 + ∆a22 ) x2 −a22x̂2 + ∆b2u 0 + e2f(t) (5) according to eq. 5, ν can be used to estimate the perturbation. as a result, the response of the perturbed system in terms of u − ν will be identical to that of the unperturbed ideal system, u. the main problem concerning the sliding mode is the chattering caused by the infinitely alternating frequency of ν. to avoid uncontrolled resonances of the unmodeled dynamics of the real system, ν is substituted by νeq (the continuous equivalent of ν. in practice, it is impossible to calculate the equivalent control νeq precisely, but it can be estimated by a low-pass filter for ν as shown in fig. 1, where two loops can be seen. figure 1: sliding mode-based disturbance compensation. figure 2: the haptic device. the observer – sliding-mode control loop is calculated by the computer and should be as fast as possible to achieve an ideal sliding mode [8, 9]. since a reduced order observer is used, x2 of the real system is measured in terms of the disturbance compensation. of course, all state variables might be measured in the outer control loop. ν̂eq, the estimation of νeq, is added to the control signal of the outer control loop. 3. application 3.1 tuning the disturbance compensation the master device consists of a dc motor and an arm (fig. 2). the slave device is identical to the master device. their roles are interchangeable. the arm is not rigid since the force is measured by strain gauges. in the case of the ideal telemanipulation model, the master device is not subject to friction nor mass (inertia). of course it is impossible to construct an ideal master device. the goal of the sliding mode-based disturbance compensation is to force the master device to follow a model subject to significantly reduced degrees of friction and inertia. the model of the master and slave devices is shown in fig. 3. the position of the motor is controlled by a simple proportional derivative (pd) controller. the results of three simulations were compared: • pd controller with the parameters of the real motor • pd controller with the parameters of the desired motor • pd controller with the parameters of the real motor which were modified by the addition of slidingmode disturbance compensation. figure 3: model of the master and slave devices. hungarian journal of industry and chemistry model reference adaptive control for telemanipulation 43 figure 4: model of the feedback force. the main goal of this chapter is to tune the disturbance compensation component. if the results of the last two simulations are similar, sliding-mode disturbance compensation can be used in a bilateral telemanipulation system. the parameters used in the model are calculable. a 1-dof telemanipulation system was studied where the effect of the feedback force of the master arm was modelled [10] as follows (fig. 4): ωmot r · fm = 1 s · jl +b +ba (6) ωmot fm = r b+ba s · jl b+ba + 1 = r bm s · t + 1 , (7) where s is a complex variable and t denotes the time constant of the manipulator: t = jl bm (8) jl is calculated according to: jl = jr + jtr2 + ja, (9) and represents the resultant moment of inertia, jr stands for the inertia of the rotor, jtr2 is the transmission inertia and ja denotes the inertia of the arm. bm = b +ba (10) bm represents the resultant damping, b the mechanical damping and ba the damping caused by the armature resistance. ba = k2 fi ra (11) kfi denotes the torque constant of the motor and ra its resistance. ωmot stands for the angular speed of the motor, fm the forceand r the vector of the lever arm with regard to the torque of the motor. in this experiment, the following constants were used for the aforementioned parameters: kfi = 0.1222 [nm/a], ra = 80 [ω], la = 0.0011 [h] and jl = 0.12 [kg m2]. the model of the ideal motor took friction into account (fig. 5), however, the other models accounted for this separately. 3.2 design of the disturbance compensation component in terms of human sensation, the electrical time constant of the system (the inductance of the dc motor) is negligible. two state variables are used: the position of the arm ϕ and the angular speed ω. the system equation must be written in the same form as (eq. 1) where: d dt [ ϕ ω ] = [ 0 1 0 amotor ][ ϕ ω ] + [ 0 bmotor ] u0, (12) amotor and bmotor are the two perturbed parameters. no external disturbance is applied. the observer is designed for the state variable ω. it should be noted that in the case of the ideal system, friction is accounted for in the model. the ideal parameters were selected in terms of friction and inertia. it is important to choose the ideal parameters wisely because these two parameters will determine the trajectory followed by the position signal of the compensated motor. if the values of the ideal parameters are too unrealistic, the compensated signal would not be able to follow the trajectory! in this simulation, the following parameters were used: jl_i = jl 12 bm_i = bm 5 (13) where jl_i denotes the inertia with regard to the model of the ideal motor and bm_i stands for the coefficient of friction concerning the model of the ideal motor. the compensation component consists of the observer with the following transfer function: bmotor s+ amotor (14) where amotor is calculated by: amotor = bm_i jl_i − k2 fi ra · jl_i (15) and bmotor by: bmotor = kfi ra · jl_i (16) then a pd position controller is added to each model of a motor (fig. 5) and the component concerning the slidingmode compensator connected to the first real model of a motor (fig. 6). an estimated value of the velocity is specified in this section which will be compared with that of the actual velocity. this will be the input for the component of the sliding-mode controller that consists of a signum function and a gain block. from here a positive feedback was applied from the output of the sliding-mode controller to the input of the observer, and the output of the slidingmode controller filtered by a 3rd order low-pass filter as the output of the whole compensation component (fig. 6). 47(1) pp. 41–48 (2019) 44 fink figure 5: model of the ideal motor with the application of a pd controller. figure 6: the component with regard to the compensation of friction. 3.3 calibration of the model to specify the parameters of the system, first the aforementioned model must be implemented. in the first case, a position controller was used for tuning (fig. 7). it is worth noting that the position signal of the real motor reaches its final value by oscillation and overshooting, while the graphs of the ideal motor and the compensated motor are smoother. it has to be mentioned that the pd controller is not optimised for a stand-alone task, rather for the compensation. in this experiment the following constants were used for the aforementioned parameters: pidp = 190, pidp = 60 and gainsliding = 30, 000. in the case of a 1-second-long simulation, the difference between the position trajectory of the ideal and compensated motors is visible (fig. 8). in fig. 9 it is visible that the sliding-mode controller is inactive for about 0.2 seconds which is the time necessary for the controller to reach the sliding surface. 0 2 4 6 8 10 12 time [s] 0 10 20 30 40 50 p o s it io n [ in c re m e n t] position control with friction compensation real motor with compensation ideal motor real motor without compensation figure 7: the compensated signal follows the stated trajectory. between −0.04 and +0.04 the active sliding-mode becomes visible (fig. 10). there is a noticeable level of chattering originating from the output signal of the sliding-mode controller (fig. 11). this was eliminated by the 3rd order low-pass filter (fig. 12). 3.4 verification of the model subsequently, the calibration component follows on from verification of the model. the former simulations were run under nearly ideal conditions, but now a relevant coulomb friction will be added to the system as well as an additional step function load. in fig. 13 the supplemented system is shown only for the model of the motor that compensated for friction using real parameters (the models of the ideal and simple real motors were excluded to save space). 0 0.2 0.4 0.6 0.8 1 time [s] 0 5 10 15 20 25 30 35 p o s it io n [ in c re m e n t] position control with friction compensation real motor with compensation ideal motor real motor without compensation figure 8: the difference between the position signals of the ideal and compensated motors. hungarian journal of industry and chemistry model reference adaptive control for telemanipulation 45 0 0.2 0.4 0.6 0.8 1 time [s] -20 -15 -10 -5 0 s ig m a [ -] reaching the sliding surface sigma figure 9: reaching the sliding surface. 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 time [s] -0.04 -0.02 0 0.02 0.04 0.06 s ig m a [ -] reaching the sliding surface sigma figure 10: after reaching the sliding surface, the sliding mode becomes active. 0 0.2 0.4 0.6 0.8 1 time [s] -3 -2 -1 0 1 2 3 c o n tr o l s ig n a l [] #104 chattering of the unfiltered control signal control signal figure 11: chattering originating from the output of the sliding-mode controller. 0 0.2 0.4 0.6 0.8 1 time [s] -3 -2 -1 0 1 2 c o n tr o l s ig n a l [] #104 the filtered control signal control signal figure 12: the filtered signal of the sliding-mode controller. figure 13: full model of the compensated motor subjected to calibration. 47(1) pp. 41–48 (2019) 46 fink 0 0.5 1 1.5 2 2.5 3 time [s] 0 5 10 15 20 25 30 35 p o s it io n [ in c re m e n t] comparison of the behavior of the models real motor with compensation ideal motor real motor without compensation figure 14: position signals after coulomb friction was accounted for in the system. 0 0.5 1 1.5 2 2.5 3 time [s] -80 -60 -40 -20 0 20 40 p o s it io n [ in c re m e n t] comparison of the behavior of the models real motor with compensation ideal motor real motor without compensation figure 15: an additional load added to the system. figure 16: bilateral control model. 0 0.5 1 1.5 2 2.5 3 time [s] 0 0.2 0.4 0.6 0.8 1 p o s it io n [ in c re m e n t] position following of the slave arm master arm slave arm (with compensation) slave arm (without compensation) figure 17: the same parameters applied to the slave arm failed to yield results. 0 0.5 1 1.5 2 2.5 3 time [s] 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 p o s it io n [ in c re m e n t] position following of the slave arm master arm slave arm (with compensation) slave arm (without compensation) figure 18: position signal following of the bilateral system. hungarian journal of industry and chemistry model reference adaptive control for telemanipulation 47 0 0.5 1 1.5 2 2.5 3 time [s] -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 f o rc e [ n ] force input for the bilateral control master arm figure 19: force input to the bilateral control. in fig. 14 the position signals are shown after the addition of the coulomb friction to the system. this new component has a stabilizing effect on the oscillation of the real motor which is greater than can be compensated for without the introduction of a permanent error. however, the behaviour of the motor compensated for by friction remains unchanged. the values of the coulomb friction and viscous friction used in this experiment were 2, 200 and 0.3, respectively. then after 2 seconds an additional load was added to the system (fig. 15). it was noticeable that when the position signal of the normal motor started to rapidly decrease, the model compensated for by friction adapted to the new circumstances. the value of the load added after 2 s was 42. 4. results and discussion 4.1 final model finally, bilateral haptic control was realized (fig. 16). the model of the two force cells on the real-life device was added to the system by applying the same logic as used on the real. each model of the motor was extended by a leftand right-force block. in terms of bilateral control, the difference between the force blocks of each joystick was compared, which was also the input of the force controller of the master arm. subsequently, the position of the master arm was compared to that of the slave arm, which was the input of the position controller of the slave arm (fig. 16). it would be illogical to apply the same parameters to the position controller as to the one that accounts for compensation because without the component of compensation the friction force would prevent the proper position from being reached (fig. 17). nevertheless, if an individually tuned proportional– integral–derivative (pid) controller is connected to the component responsible for position control of the system, the signal that results would be visible (fig. 18). in this case, the input signal was applied to the right force cell of the master arm in a shape as is shown in fig. 19. it is impossible to eliminate the entire effects of friction and inertia on the mechanical construction, but they can be reduced significantly. the magnitude of the friction force exceeded the limit suitable for a smooth, comfortable operation. compensation aims to make the system behave like an ideal model subject to a minimal level of friction. due to the compensation, the operator can move the master joystick with ease. over a series of experiments, classical and sliding mode-based model reference adaptive control methods were compared. the applications of these methods with regard to compensation for friction are published in [11, 12]. it is crucial to identify an optimal adaptation parameter which facilitates rapid adaptation but avoids overcompensation. in the event of overcompensation, the joystick moves randomly even in the absence of reference torque because of the measurement noise. as the size of the adaptation parameter increases, adaptation occurs more rapidly, however, the likelihood of random movements rises. 5. conclusion an experimental telemanipulation system was presented in this paper. the master device was a serial linked levertype haptic interface with force feedback. even though it is impossible to eliminate the entire effects of friction and inertia on the mechanical construction, a reference model that accounts for minor levels of friction was designed. the system was forced to follow the reference model. in other words, the original dynamics of the master device were replaced by a virtual version which ensures a comfortable degree of manipulation for the operator. references [1] arai, f.; sugiyama, t.; fukuda, t.; iwata, h.; itoigawa k.: micro tri-axial force sensor for 3d bio-micromanipulation, 1999 ieee international conference on robotics and automation, 1999 4, pp. 2744–2749 isbn: 0-7803-5180-0 doi: 10.1109/robot.1999.774012 [2] kwon, d-s.; woo, k. y.; cho, h. s.: haptic control of the master hand controller for a microsurgical telerobot system, 1999 ieee international conference on robotics and automation, 1999 3, pp. 1722–1727 isbn: 0-7803-5180-0 doi: 10.1109/robot.1999.770357 [3] n. ando, m. ohta, h. hashimoto: “micro teleoperation with haptic interface”, proceedings of the 2000 ieee int. conf. on industrial electronics, control and instrumentation, pp. 13-18, 2000, 10.1109/iecon.2000.973119 [4] yokokohji, y.; yoshikawa, t.: bilateral control of master-slave manipulators for ideal kinesthetic coupling-formulation and experiment, ieee t. robotics autom., 1994 10(5), 849–858 doi: 10.1109/70.326566 47(1) pp. 41–48 (2019) https://doi.org/10.1109/robot.1999.774012 https://doi.org/10.1109/robot.1999.774012 https://doi.org/10.1109/robot.1999.770357 https://doi.org/10.1109/robot.1999.770357 https://doi.org/10.1109/70.326566 https://doi.org/10.1109/70.326566 48 fink [5] hashtrudi-zaad, k.; salcudean, s. e.: analysis of control architectures for teleoperation systems with impedance/admittance master and slave manipulators, int. j. robotics res., 2001 20(6), 419–445 doi: 10.1177/02783640122067471 [6] korondi, p.; young, k. d.; hashimoto, h.: sliding mode based disturbance observer for motion control in: proceedings of the 37th ieee conference on decision and control, (ieee press, new york, usa) 1998, pp. 1926–1927 isbn: 0-7803-4394-8 doi: 10.1109/cdc.1998.758595 [7] v. i. utkin: sliding modes in control and optimization, springer –verlag, 1992, isbn: 978-3-642-84379-2 doi: 10.1007/978-3-642-84379-2 [8] ando, n.; korondi, p.; hashimoto, h.: development of micromanipulator and haptic interface for networked micromanipulation, ieee/asme t. mechat., 2001 6(4), 417–427 doi: 10.1109/3516.974855 [9] korondi, p.; young, k-k. d.; hashimoto, h.: discrete-time sliding mode based feedback compensation for motion control, 1996 ieee international workshop on variable structure systems, 1996, pp. 237–242 isbn: 0-7803-3718-2 doi: 10.1109/vss.1996.578577 [10] lukács p.: 1 degree of freedom haptic device for telemanipulation, master’s thesis, 2015 [11] ando, n.; ohta, m.; hashimoto, h.: micro teleoperation with parallel manipulator, 2000 ieee/rsj international conference on intelligent robots and systems, 2000 1, pp. 677–682 isbn: 0-7803-6348-5 doi: 10.1109/iros.2000.894682 [12] korondi, p.; szemes, p. t.; hashimoto, h.: sliding mode friction compensation for a 20 dof sensor glove, j. dyn. sys., meas., control , 2000 122(4) 611–615 doi: 10.1115/1.1317232 hungarian journal of industry and chemistry https://doi.org/10.1177/02783640122067471 https://doi.org/10.1177/02783640122067471 https://doi.org/10.1109/cdc.1998.758595 https://doi.org/10.1109/cdc.1998.758595 https://doi.org/10.1007/978-3-642-84379-2 https://doi.org/10.1109/3516.974855 https://doi.org/10.1109/vss.1996.578577 https://doi.org/10.1109/vss.1996.578577 https://doi.org/10.1109/iros.2000.894682 https://doi.org/10.1115/1.1317232 hungarian journal of industry and chemistry vol. 47(1) pp. 49–56 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-08 simulation of a balanced low-voltage electrical grid using a simplified network model márton greber *1 and attila fodor1 1department of electrical engineering and information systems, faculty of information technology, university of pannonia, egyetem u. 10., veszprém, h-8200, hungary a simulation method for low-voltage balanced distribution networks is proposed in this article. the novel method of node powers is based on the general calculation technique of node voltages. by researching only balanced networks, singlephase equivalents of the three-phase system are applicable. for the description of power lines, various parameters and matrices are available. in this work a simplified model is applied by using a purely resistive one. the active power results are solved through an iterative process. a main accomplishment is that the number of iterations needed is independent of the size of the network, and the process rapidly converges. validation of the method is performed on the ieee european low-voltage test feeder network. the simulation results confirm the achievements described in this paper. keywords: low-voltage distribution system, grid simulation, smart grid, method of node voltages, ieee european low-voltage test feeder 1. introduction in recent years a lot of research has been conducted and progress made in the field of smart grid applications. therefore, the demand for cloud-based systems with integrated simulation capabilities has increased. the calculation of the voltages, currents and powers of the components of the electrical (smart) grid is not easily achieved. this has resulted in the development of custom calculation methods which have the benefit of being fine-tuned for a particular application. one of the fundamental network calculation methods in a general sense is the node voltages method. from a mathematical perspective, this method is based on solving a system of linear equations. as a result, this method can be implemented through various frameworks. one proposed solution revolves around using an open source discrete event simulator called omnet++ [1]. the models for electrical components need to be constructeda and the simulation is conducted via message handling. another approach used coloured petri nets to model electrical networks [2]. a network model needs to be constructed for the simulation, which consists of a propagation process. a solution is presented for basic network types, while complex ones are calculated through decomposition. both of these methods offer solutions but the method of node voltages regards currents as an input. the more common approach to calculations of distribution systems calculation is via the method of power *correspondence: greber.marton@virt.uni-pannon.hu flow. this uses complex numbers to distinguish between active and reactive power. for the given nodes, both active and reactive power, voltage and phase angle are required to formulate the solution [3]. this poses a nonlinear problem, furthermore, the system of equations consists of real and imaginary subsets. over the years, several pieces of research have dealt with this subject and the method known as dc power flow developed. by restricting the parameters the calculation was simplified, namely the voltage angles as well as generated and consumed active powers. this method assumes small differences in voltage angle and lossless lines [4]. the biggest downside of the method is that it cannot be used to calculate line losses because of the assumptions, although efforts are being made to overcome this obstacle [5]. by taking into account the extent of a given power system, different parameters of the power line model become dominant [6]. in low-voltage systems the distance between adjacent nodes is smaller than in high-voltage systems. by using this information a new set of restrictions is proposed, inspired by the dc power flow. it can be regarded as a complementary method since the line reactances are neglected. utilising a resistive transmission line model offers the possibility to calculate distribution losses. this method has been developed from the method of node voltages. in this article the issues of harmonic currents [7] and unbalanced networks [8] are not examined, it is assumed that the currents as well as voltages are sinusoidal and the grid is balanced with balanced three-phase loads. the mailto:greber.marton@virt.uni-pannon.hu 50 greber and fodor r7 uv7 φ3 r5 φ2 r2φ1 r1 uv1 φ0 ia4 r3 uv6 r6 figure 1: example network neutral wire can be omitted by restricting the set of networks in balanced low-voltage systems. this enables the application of a one-line equivalent circuit. 2. method of node voltages in distribution network calculations the main emphasis is on power flow. that means the voltages and angles are calculable when the generated and consumed powers are given [9]. the known formula for calculating the active power in a dc network is the following: p = ui, (1) but the observed systems operate on alternating currents, hence the notion of ac power needs to be introduced [10]. since voltages and currents are time-varying quantities, these are expressed as complex numbers, namely u and i . the complex power is calculated by multiplying the conjugate of i by the voltage s = u i ∗ . (2) the phase angle of the complex power is defined by the difference between the angles of voltage and current: ϕ = arg(u)− arg(i). (3) by observing the real and imaginary parts of the complex number, the active (p ) and reactive powers (q) are obtained: p = re(s), q = im(s). (4) a known method for the analysis of electrical networks is the method of node voltages. the component values, e.g. the sources of resistance, voltage and current are given, the unknown variables are the node voltages. the calculation steps are best explained through an example network as shown in fig. 1. one key component of the process is the definition of a directed graph for the example network shown in fig. 2. the reference directions in the graph are arbitrary. φ1 φ2 φ3 φ0 2 7 5 1 6 43 figure 2: the reference directed graph by using the graph in addition to kirchoff’s first law, the nodal equations can be written in the following form: i1 − i2 − i7 = 0 i2 − i3 + i4 + i5 = 0 i7 − i5 + i6 = 0 (5) after that, ohm’s law is used to express the edge currents with regard to the nodal voltages: i1 = −g1(φ1 − uv1) i2 = g2(φ1 − φ2) i3 = g3φ2 i4 = ia4 i5 = g5(φ3 − φ2) i6 = −g6(φ3 + uv6) i7 = g7(φ1 + uv7 − φ3) (6) where the conductance of the arm of the network is denoted by g. if these steps are followed, the system of equations must be rearranged. the final form can be obtained by substituting the currents into eq. (5) and rearranging it to determine the nodal voltages [11]: φ = g−1e ie (7) the notation represents the dimensions of the elements it contains: the node voltage vector is obviously denoted by φ, the nodal admittance matrix by ge and the excitation vector by ie. at first sight, this equation does not account for the voltage sources in the branches. since these elements can be described in terms of current dimensions, the excitation vector takes the following form: ie = −g1uv1 +g7uv7 −ia4 −g7uv7 +g6uv6  . (8) 2.1 the generalized nodal equations the above-mentioned method describes the working principle of the technique, but it is not suitable for algorithmic applications. a generalized approach is needed. one has to define column vectors for the voltage sources: u>v = [ uv1 uv2 . . . uvn ] , (9) hungarian journal of industry and chemistry simulation of low-voltage electrical grid 51 current sources: i>a = [ ia1 ia2 . . . ian ] , (10) and admittances: y > = [ y1 y2 . . . yn ] , (11) where y refers to the complex conductance known as the admittance. each scalar of the vectors contains the aforementioned properties of a particular edge. for the representation of the graph, an incidence matrix (a) is used of (m − 1) × n dimensions, and describes connections between nodes and edges: ai,j =  0, if j is not connected to i 1, if j is pointing away from i −1, if j is pointing towards i , (12) where i = 1, 2, . . . ,m − 1 represents the nodes of the graph and j = 1, 2, . . . , n denotes the edge index set. as with the direction of the graph, the reference of a is also arbitrary, it is only manifested when multiplied by (−1). these matrices can be constructed algorithmically and facilitate the use of the following equation [12]: φ = y −1a a ( diag(y ) uv − ia ) , (13) where: ya = a diag(y )a>. (14) a method which can be used to compute node voltages by defining a graph represented by the incidence matrix that includes the electrical properties of the edges is proposed as a result. 3. network model in order to reduce the amount of computational power that is needed for simulations, a simplified network model is used. the feeder points of low-voltage grids are transformer substations which convert forward the desired power from the medium voltage side into the base voltage, therefore, can be represented as voltage sources. power flows from the feeder points to the customers via transmission lines. compared to mediumor high-voltage lines, the length between consecutive nodes is smaller. as a result, these can be modelled as series resistances. customers are represented as current sources with consumer references of course. the computationally demanding part of the method of node voltages is to invert ya. in the case of complex analyses, the system of equations is separated into real and imaginary parts. through one iteration cycle, two inverse calculations are needed. if voltages and currents are calculated as root mean square (rms) values, the simulation method only requires real numbers. therefore, the effort and time to calculate one cycle is halved. 2. bus 3 phase 10-35kv/0.4kv 1. bus 3. bus 4. bus figure 3: low-voltage distribution system 3.1 topology verification in the structure of a low-voltage distribution network, some rules are noticeable. the transmission line forms a power rail to which the consumers can connect, as is shown in fig. 3. these mainly consist of households with single-phase connections, i.e. one phase and the neutral wire are used [13]. the method of node voltages can be applied to general circuits, on the other hand, the proposed method of node powers can be applied to distribution networks. these form a tighter set, therefore, the topology needs to be checked to ensure it works properly. if a network contains m nodes, m node equations can be obtained. on the other hand, only m− 1 equations are linearly independent. therefore, one node can be omitted, namely the 0 v node is omitted in the proposed methods. if an edge is connected to this point, it will have a nonzero column sum. if it is not connected to this point, it will have a column sum of zero. using this, the criteria for the validation of topology can be formulated. the column sum for an arbitrary edge containing a current source in a cannot be equal to zero: ∀iaj 6= 0, j ∈ {1, . . . , n} → m−1∑ i=1 ai,j 6= 0. (15) similarly, the column sum for an arbitrary edge containing a voltage source ina cannot be equal to zero: ∀uvj 6= 0, j ∈ {1, . . . , n} → m−1∑ i=1 ai,j 6= 0. (16) in the case of an edge that possesses admittance, the column sum ina must be zero: ∀yj 6= 0, j ∈ {1, . . . , n} → m−1∑ i=1 ai,j = 0. (17) in algorithm 1, a pseudo code is shown that implements the above-mentioned criteria. it returns a boolean value and is only true if the network topology is appropriate. 47(1) pp. 49–56 (2019) 52 greber and fodor algorithm 1 topology verification input:a, y , ia, uv output: isvalidtopology 1: isvalidtopology= 1 2: n = numberofcolumns(a) 3: for i = 1 to n do 4: s = 0 5: if ia(i) != 0 then 6: s = sum(a(:, i)) 7: if s == 0 then 8: isvalidtopology= 0 9: end if 10: end if 11: if uv(i) != 0 then 12: s = sum(a(:, i)) 13: if s == 0 then 14: isvalidtopology= 0 15: end if 16: end if 17: if y (i) != 0 then 18: s = sum(a(:, i)) 19: if s != 0 then 20: isvalidtopology= 0 21: end if 22: end if 23: end for 4. method of node powers since the simulated households are single-phase consumers, the corresponding active power can be calculated as follows: p = u i cos(ϕ). (18) let us define the power factor (pf ) and current-source active power (pa) vectors for further matrix calculations. single elements in both of these describe properties with regard to a single edge. pf> = [ cos(ϕ1) cos(ϕ2) . . . cos(ϕn) ] , (19) p>a = [ pa1 pa2 . . . pan ] . (20) voltage can be expressed as the electric potential difference between two points. if the incidence matrix represents node-edge relations, transposing it will describe edge-node relations. multiplying it with the node voltages column vector will result in edge voltages: u = a>φ. (21) by determining these notations and definitions, the basic equation of node voltage can be extended: φ = y −1a a ( diag(y ) uv − ia ) pa = diag(pf )diag(a>φ)ia , (22) in the case of the method of node voltages, the node voltages are calculated using the given current consumption. however, in the case of the method of node powers, the node voltages must be calculated with regard to the consumption, given in terms of the active power. eq. 22 opens up the possibility of finding a solution following a trial and error procedure. in other words, if only one current source in this system of equations is changed, all the node voltages will also be changed. let us consider the case where the current of one particular customer is changed until its active power becomes equal to its actual value. nonetheless, if a second consumer is to be set in the same fashion, the first one will be ruined. through positive changes in current to the second source, a net drop in voltage will occur. since power is the product of current and voltage, the current was untouched so the active power will be less. therefore, it is also clear that if the second current source is decreased, the active power of the first source will exceed its actual value. 4.1 constant iteration current in the aforementioned problem, the solution is acquired through an iterative process to build up the unknown currents of the system gradually, instead of trying to determine them individually. it is necessary to choose a value of the current for the iterations: iiter. in the first step, every element of the current vector is zero, however, if an edge contains a consumer, its value will be set as the iteration current. the problem, namely that by changing one current, all the node voltages will also change, still exists. however, if the iteration current is sufficiently small, the ability to build up the parameters from the ground is viable. to select a source for the actual iteration, a new variable was defined: dpp = p sim a pa . (23) this can be calculated for all consumer edges per iteration and provides information about how similar the simulated active power is to its desired value. it is obvious that the edge with the smallest dpp requires the highest degree of correction, therefore, it is incremented by iiter. consequently, in every iteration the branch with the minimum dpp needs to be identified, using a simple minimum search. after appropriate incrementation, the node voltages must be calculated in order to determine the new values of power. this procedure can be observed in algorithm 2. in an ideal case, the algorithm converges into the desired power vector and the following expression will be true: ∀i ∈ {1, . . . , k} → dppi = 1, (24) where k denotes the number of consumers in the grid. it is clear that the rate of convergence and the accuracy of the algorithm are heavily influenced by iiter. if this rate is particularly small, the results will be precise (dpp = 1). however, in this case the number of iteration cycles will be enormous because the function described is analogous hungarian journal of industry and chemistry simulation of low-voltage electrical grid 53 algorithm 2 constant iteration current input:a, y , pa, uv, pf , iiter, m, n output: φ, ia 1: ia = zeros(n, 1) 2: for i = 1 to n do 3: if pa(i) != 0 then 4: ia(i) = iiter 5: end if 6: end for 7: φ = calculatenodevoltages(a,y ,uv, ia) 8: p sim a = diag(diag(a> · φ) · ia) · pf 9: [dpp, index] = min(p sim a /pa) 10: while dpp < ε do 11: ia(index) = ia(index) + iiter 12: φ = calculatenodevoltages(a,y ,uv, ia) 13: p sim a = diag(diag(a> · φ) · ia) · pf 14: [dpp, index] = min(p sim a /pa) 15: end while to 1 x . this can be observed by determining the actual number of iterations needed for the process: k∑ i=1 iai iiter (25) as the desired current will consist of portions of iiter on every edge. according to how the desired current is divided by the iteration current, overshoots are possible. therefore, a value of ε is needed in order to secure a suitable exit condition for the loop. basically the blue plot represents a function similar to f(x) = c mod x, where c denotes a given number. in the case of the method described, c stands for a desired load current and x represents possible iteration currents used in the algorithm. according to how the desired current is divided by the actual iteration current, false values can be calculated. the periodic increase in the error is a property of the modulo operation, since the remainder increases until an integer multiple of x is identified. then the error is equal to zero but begins to increase again. the red line represents the number of iterations needed to converge into a final solution. if x << c, the maximum "overshoot" by the modulo operator is relatively small, on the other hand, if x < c, more significant errors can occur. it is clear that in the first case many more iterations are necessary than in the second. since c cannot be determined beforehand, unnecessarily large errors can occur which represents the weakness of the algorithm. it is clear that a compromise must be made between the run-time and precision, as illustrated in fig. 4. 4.2 dynamic iteration current to fix the weaknesses of the algorithm elaborated on in the previous chapter, an advanced version was developed. the first aspect, in which there is room for improvement, is to obtain reasonable initial values of ia. the process 0 0.5 1 1.5 2 iiter 1 1.05 1.1 1.15 m in (d p p ) 0 2000 4000 6000 8000 10000 n u m b e r o f it e ra ti o n s figure 4: minimum error number of iterations does not have to originate from iai = 0, consequently, a considerable amount of cycles can be skipped. in distribution networks the deviation from the nominal voltage (un) is always regulated by standards, for example, in hungary it is approximately ±7.5%. using this restriction, a general estimation can be made for the nodes. the following min() and max() operators relate to the values of the given function. the possible interval between current values can be formulated as follows: min(ia) = pai un cos(ϕi) max(ia) = pai (1−d)un cos(ϕi) , (26) where d is the aforementioned deviation value. this means overestimating the voltage results in the minimum value of the current. setting the starting values of the currents according to the minimum approximation is adequate. to calculate the maximal remaining error, the minimum value of dppi needs to be calculated: dppi = un(1−d) pai un cos(ϕi) cos(ϕi) pai = 1−d. (27) the logic behind this equation is as follows: the fraction in the numerator is the minimum current estimation the un(1−d), on the other hand, is the worst case scenario in terms of the voltage. the deviation is defined by d, so under no circumstances can the voltage drop below un(1 − d), once the initial value has been set. because d is small, this approach alone solves a huge part of the problem, since by taking the hungarian voltage levels as an example, a dpp value greater or equal to 0.925 is achieved! since the initial value problem has been solved, the remaining iterations can also be improved by taking the aforementioned method one step further. in order to take the absolute error in the active power into account, the following variable is introduced: dp = pa − p sim a . (28) 47(1) pp. 49–56 (2019) 54 greber and fodor which can also be formulated using the relative error: dp = pa(1− dpp ). (29) since the whole algorithm is founded on an iterative method, it would be suitable to use the minimum estimation process of the worst-case scenario in the following iterations. the idea in theory, however, is similar to the power value that is being approximated changes. only the remaining error component needs to be recalculated. therefore, the approximation will take the given dpi into consideration instead of the whole pai. un can still be used for this, but is not ideal. once the initial values are set, a node voltage calculation is performed, thus the new node voltages can be used. as a result, the new values must be used as the upper limit of the voltage. finally, the current generated for a particular consumer can be represented by the following series: iai = 1 cos(ϕi) ( pai un︸︷︷︸ j=1 + dp ′i φ′i︸︷︷︸ j=2 + dp ′′i φ′′i︸︷︷︸ j=3 + . . . ) , (30) where j = 1, 2, . . . denotes the number of iterations. if j → ∞, the simulated values approach the desired active powers. in theory this would mean that an infinite number of iterations would be necessary. the maximum error or minimum dpp can be calculated as shown before not only for the initial values but also for the upcoming iteration currents. since in every consequent cycle the absolute error from the previous cycle is corrected, the remaining dp will be corrected by a minimum dpp equal to (1−d). since the fitted values are multiplied, the minimum value of the j-th iteration can be calculated as follows: dppmin = 1−dj . (31) the process of the method of dynamic node powers is shown in algorithm 3. in the literature review, the algorithm 3 dynamic iteration current input: un,a, y , pa, uv, pf output: φ, ia 1: φ = ones(m, 1) · un 2: ia = pa/ ( (a> · φ) · pf ) , if 0 0 : iai → 0 3: φ = calculatenodevoltages(a,y ,uv, ia) 4: p sim a = diag(diag(a> · φ) · ia) · pf 5: dpp = min(p sim a /pa) 6: while dpp < ε do 7: iiter = (pa − p sim a )/(u · pf ), if 0 0 : iai → 0 8: ia = ia + iiter 9: φ = calculatenodevoltages(a,y ,uv, ia) 10: p sim a = diag(diag(a> · φ) · ia) · pf 11: dpp = min(p sim a /pa) 12: end while newton-raphson method was examined in more detail which uses the mismatch in power by incorporating the jacobian matrix in order to achieve convergence. the proposed error recalculation method was developed whilst taking that process into consideration. another possible solution to the calculation of powers could be an algorithm, in which the total power is recalculated rather than the power mismatch. the explicit expression for convergence was determined first, and the total power recalculation method did not suggest better results. although through simulation and observation, it was noted that both require the same amount of iterations. using the monte carlo method, a large number of random networks were created in order to monitor the run-time. results showed the presence of slight deviations with regard to each other. nevertheless, the two methods require almost the same amount of computational time, as is shown in fig. 5. 0 30 0.002 0.004 100 0.006 r u n ti m e [s ] 20 0.008 error recalculation algorithm number of streets ~ network size 0.01 unique simulations 0.012 5010 0 0 0 30 0.002 0.004 100 0.006 r u n ti m e [s ] 20 0.008 whole power recalculation algorithm number of streets ~ network size 0.01 unique simulations 0.012 5010 0 0 figure 5: monte carlo simulation hungarian journal of industry and chemistry simulation of low-voltage electrical grid 55 figure 6: the topology of the test network 5. simulation results in order to verify the proposed method properly, a reference network with available simulation data was required. for verification purposes the ieee european low-voltage test feeder network [14] was used. the simulation process consisted of the implementation of the stated algorithm and importation of network data using matlab. the topology of the test grid is shown in fig. 6. some of the important network parameters are the following: it consists of 906 nodes which are connected by 927 edges that supply 55 single-phase consumers. previous runs have shown that approximately 2 iterations are sufficient for engineering purposes. for the sake of accuracy, a limit was set for dpp , therefore ε is still shown in algorithm 3. the minimum estimations of dpp predicted that the error should rapidly converge to zero. the simulation verified this statement, the rapid decrease in the absolute error can be seen in tables 1 3. it can be clearly observed that in the case of a network of such a size, the maximum voltage difference can be maintained under 10 mv (table 4). the results of the simulation can be seen in fig. 7 which represents the bus voltages of a single phase. note that the y axis is divided into increments of 50 mv. table 1: convergence of dp in phase ‘a’ iteration max (dp ) 0. 0.052137599675 w 1. 0.000041085202 w 2. 0.000000032240 w table 2: convergence of dp in phase ‘b’ iteration max (dp ) 0. 0.042119472811 w 1. 0.000029088116 w 2. 0.000000019550 w table 3: convergence of dp in phase ‘c’ iteration max (dp ) 0. 0.043952897250 w 1. 0.000025174297 w 2. 0.000000014771 w table 4: maximum voltage differences phase ‘a’ phase ‘b’ phase ‘c’ 0.056859 v 0.036058 v 0.023649 v since the active power values are reached with an excellent degree of precision, one would expect that the voltage differences would be smaller. however, this effect does not originate from the algorithm, rather from the simplified network model. this facilitates the possibility of achieving small simulation times. since the introduction of the method of dynamic iteration currents, the number of iterations is independent of the size of the network. the computationally heavy component is the calculation of the inverse of ya. the topology of the network remains unchanged during the iterations. therefore, the steady state simulation of a three-phase network requires, independen of the network size, only three matrix inversions. the duration of the simulation of this network was 2.29 s at a particular instant. 0 100 200 300 400 500 600 700 800 900 1000 bus id 251.9 251.95 252 252.05 252.1 252.15 252.2 v o lt a g e [ v ] ieee reference simulation figure 7: simulation results for phase ‘a’ 47(1) pp. 49–56 (2019) 56 greber and fodor 6. conclusion a novel simulation method for low-voltage distribution networks is proposed in this paper. the existing method of node voltages is further developed in order to handle active power calculations in low-voltage grids. these systems consist of a unique topology to which the process was fitted. the verification criteria for the network structure was formulated. a solution was proposed in which the number of iterations is independent of the size of the network and the simulation error decreases exponentially. the method was tested and verified on the ieee european low-voltage test feeder network. this confirmed the statements about the algorithm. insignificant errors appeared in the test results but these were the effect of the simplified network model. in the future, the algorithm could be improved to handle unbalanced distribution networks. with the aid of appropriate modifications, distributed generation could be taken into consideration that accounts for not only power consumption but also generation. the algorithm can serve as a foundation of network diagnostics by using it to detect faults as well as technical or non-technical losses. acknowledgement we acknowledge the financial support of széchenyi 2020 under the efop-3.6.1-16-2016-00015. we acknowledge the financial support of széchenyi 2020 under the ginop-2.2.1-15-2017-00038. notations φ node-voltage vector ie excitation vector uv voltage-source vector ia current-source vector a incidence matrix y admittance matrix ya nodal admittance matrix m number of nodes n number of edges cos(ϕ) power factor pf power factor vector pa current-source active-power vector u branch voltage vector dpp delta power percentage iiter iteration current dp delta power d voltage level deviation p sim a simulated power vector s complex power p active power q reactive power ϕ phase angle g conductance ε threshold value for iteration references [1] sőrés, m.; fodor, a.: simulation of electrical grid with omnet++ open source discrete event system simulator, hung. j. ind. chem., 2016 44(2), 85–91, doi: 10.1515/hjic-2016-0010 [2] pózna, a.i.; fodor, a.; gerzson, m.; hangos, k.m.: colored petri net model of electrical networks for diagnostic purposes, ifac-papersonline, 2018 51(2), 260–265, doi: 10.1016/j.ifacol.2018.03.045 [3] stagg, g.; el-abiad, a.h.: computer methods in power system analysis (mcgraw-hill), interntaional student edn., 1968 [4] hertem, d.v.; verboomen, j.; purchala, k.; belmans, r.; kling, w.l.: usefulness of dc power flow for active power flow analysis, the 8th iee international conference on ac and dc power transmission, 2006 1, doi: 10.1049/cp:20060013 [5] stott, b.; jardim, j.; alsac, o.: dc power flow revisited, ieee t. power syst., 2009 24(3), 1290–1300, doi: 10.1109/tpwrs.2009.2021235 [6] das, j.c.: load flow optimazitaion and optimal power flow (crc press), 2017 [7] görbe, p.; magyar, a.; hangos, k.m.: thd reduction with grid synchronized inverter’s power injection of renewable sources, in 2010 international symposium on power electronics electrical drives automation and motion (speedam) (ieee), 1381–1386, doi: 10.1109/speedam.2010.5545079 [8] neukirchner, l.; görbe, p.; magyar, a.: voltage unbalance reduction in the domestic distribution area using asymmetric inverters, j. clean. prod., 2017 142, 1710–1720, doi: 10.1109/59.575728 [9] kersting, w.h.: distribution system modeling and analysis (crc press), 2016, isbn: 9781439856475 [10] bird, j.: electrical circuit theory and technology (taylor & francis), 4th edn., 2010, isbn: 185617770x [11] wang, x.f.; song, y.; irving, m.: modern power system analysis (springer), 2008, doi: 10.1007/978-0387-72853-7 [12] zhang, f.; cheng, c.s.: a modified newton method for radial distribution system power flow analysis, ieee t. power syst., 1997 12(1), 389 – 397, doi: 10.1109/59.575728 [13] westinghouse electric corporation, electrical transmission and distribution reference book (east pittsburgh, pa), 1964 [14] schneider, k.p.; mather, b.a.; pal, b.c.; ten, c.w.; shirek, g.j.; zhu, h.; fuller, j.c.; pereira, j.l.r.; ochoa, l.f.; de araujo, l.r.; dugan, r.c.; matthias, s.; paudyal, s.; mcdermott, t.e.; kersting, w.: analytic considerations and design basis for the ieee distribution test feeders, ieee t. power syst., 2017 33(3), 3181–3188, doi: 10.1109/tpwrs.2017.2760011 hungarian journal of industry and chemistry https://doi.org/10.1515/hjic-2016-0010 https://doi.org/10.1016/j.ifacol.2018.03.045 https://doi.org/10.1049/cp:20060013 https://doi.org/10.1109/tpwrs.2009.2021235 https://doi.org/10.1109/speedam.2010.5545079 https://doi.org/10.1109/59.575728 https://doi.org/10.1007/978-0-387-72853-7 https://doi.org/10.1007/978-0-387-72853-7 https://doi.org/10.1109/59.575728 https://doi.org/10.1109/59.575728 https://doi.org/10.1109/tpwrs.2017.2760011 https://doi.org/10.1109/tpwrs.2017.2760011 hungarian journal of industry and chemistry vol. 47(1) pp. 57–63 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-09 modeling and calculation of the global solar irradiance on slopes roland bálint *1, attila fodor1, istván szalkai2, zsófia szalkai3, and attila magyar1 1department of electrical engineering and information systems, faculty of information technology, university of pannonia, egyetem u. 10, veszprém, 8200, hungary 2department of mathematics, faculty of information technology, university of pannonia, egyetem u. 10, veszprém, 8200, hungary 3eötvös loránd university, egyetem tér 1-3, budapest, 1053, hungary the first step with regard to a simple model of a photovoltaic power plant is developed in this paper based on astronomical and engineering principles. a solar irradiance model is presented in this paper that can be used to forecast the solar energy a surface on earth is exposed to. the obtained model is verified against engineering expectations. the developed model can serve as a basis for forecasting the power of solar energy. keywords: solar irradiance, modeling, solar geometry, inclined surface 1. introduction as sustainable development is becoming highly important all over the world, the power production forecast of photovoltaic power plants (pvpps) is becoming ever more necessary. the sun is the greatest potential energy source available. the thermal energy it emits can be transformed into electrical energy, or its irradiance can be converted into electricity by solar panels. the amount of energy produced by both of the solutions above is directly dependent on the solar irradiance. several works have focused on the determination or forecast of this energy and its dependence on the geometrical parameters of the surface. a general model of the angle of incidence of solar irradiance with regard to the azimuth is derived in ref. [1] that is used for both fixed and tracking surfaces. in ref. [2], a simple spectral model is given that is applicable to inclined surfaces and clear skies. a very good comparative study was proposed in refs. [3] and [4] where different area-specific models were analysed with regard to the optimal tilt angle. unfortunately, the hungarian region is not covered by the models used in this study. a semi-empirical method for short-term (hourly) solar irradiance forecasting was proposed in ref. [5] founded on the widely used ångströmprescott model. the aim of this work is to propose a model that is not only able to handle clear-sky conditions but clouds as *correspondence: balazs.istvan@virt.uni-pannon.hu well. the computational complexity of the model is also a key factor which should be kept to a minimum. the organization of this paper is as follows: section 2 introduces the problem at hand and also presents the motivation of the paper. afterwards, the elementary astronomical relationships are collected and the proposed model is developed in section 3. the mathematical model is verified against basic engineering expectations in section 4. finally, some concluding remarks are presented. 2. problem statement the produced energy forecast of the renewable energy sources is one of the main problems of the distributed energy resource management system. the operators of the electrical grids need precise mathematical models of renewable power plants, e.g. pvpps, wind farms or hydroelectric power plants. the first step to develop a simple model of a pvpp is presented in this paper based on first astronomical then engineering principles. the energy production of a pvpp is a function of the following: • parameters of the pvpp, • weather (cloud, temperature, wind), • quality of the atmosphere (dust, relative humidity), • activity of the sun (11-year solar cycle). the parameters of the pvpps are the following: • position, mailto:balazs.istvan@virt.uni-pannon.hu 58 bálint, fodor, szalkai, szalkai, and magyar • orientation of the pv solar panels, – tilt angle, – azimuth angle, • surface area (or the number of pv solar panels), • nominal power of the pv solar panels, • efficiency of the solar inverter. by using the first four parameters, the solar energy can be calculated by the developed solar irradiance model which is presented in this paper. 3. astronomical relationships sun-earth geometries to estimate the solar irradiance from the sun, some astronomical (geometrical) calculations to define the position of the sun relative to the local horizontal surface need to be conducted. many different equations are found in the literature to calculate the same parameter. the size of these equations, in addition to the frequency of measurements, vary significantly. in this section some equations are compared. 3.1 comparison of the available solar geometry models due to the elliptic orbit of the earth around the sun, some parameters exist with a 1-year cycle. these parameters can be calculated with different equations and the difference between values of these equations varies due to discrepancies in the description of the method. the calculations regard a year as consisting of 365 days. most of the results were obtained from ref. [6] and references therein. relative sun-earth distance the first parameter is the reciprocal of the square of the sun-earth distance during the year. the elliptic orbit of the earth causes this to change in value. this relative distance can be calculated from equations e0 = (r0 r )2 = 1.000110+ + 0.034221 cos ( 2π dn − 1 365 ) + + 0.001280 sin ( 2π dn − 1 365 ) + + 0.000719 cos ( 4π dn − 1 365 ) + + 0.000077 sin ( 4π dn − 1 365 ) (1) and e0 = (r0 r )2 = 1 + 0.033 cos ( 2π dn 365 ) (2) 0 50 100 150 200 250 300 350 0.96 0.98 1 1.02 1.04 3 january 4 april 4 july 5 october the day of the year e 0 eq. 1 eq. 2 figure 1: the calculated value of the reciprocal of the square of the sun-earth distance (e0) using eqs. 1 and 2 eqs. 1 and 2 are from refs. [6] and [7]. e0 denotes the reciprocal of the square of the sun-earth distance, r0 represents the mean sun-earth distance (1 au) and r stands for the sun-earth distance on the dnth day of the year. values of e0 using various equations are shown in fig. 1. this change will change the solar constant too. the solar constant, i0, yields the following solar irradiance value (in w/m2) at the edge of the earth’s atmosphere. this constant value is 1367 w/m2 if the earth is a distance of 1 au (astronomical unit) from the sun. this value is greater at perihelion (minimum sun-earth distance ≈ 0.983 au on 3 january) and less at aphelion (maximum sun-earth distance ≈ 1.017 au on 4 july). since the irradiance is proportional to the surface area, which is inversely proportional to the square of the distance, the corrected solar irradiance can be calculated from in = i0e0. (3) solar declination the declination of the sun, δ, yields the latitude above which the path of the sun follows. therefore, the zenith angle is zero at local noon. this value can be calculated from the following equations [6]: δ = ( 0.006918− − 0.399912 cos ( 2π dn − 1 365 ) + + 0.070257 sin ( 2π dn − 1 365 ) − − 0.006758 cos ( 4π dn − 1 365 ) + + 0.000907 sin ( 4π dn − 1 365 ) − − 0.002697 cos ( 6π dn − 1 365 ) + + 0.00148 sin ( 6π dn − 1 365 )) 180° π (4) hungarian journal of industry and chemistry modeling and calculation of the global solar irradiance on slopes 59 0 50 100 150 200 250 300 350 −23.5° −10° 0° 10° 23.5° 20/21 march 21/22 june 22/23 september 21/22 december the day of the year δ eq. 4 eq. 5 eq. 6 eq. 7 figure 2: the calculated value of the declination of the sun (δ) using eqs. 4–7 δ = arcsin ( 0.4 sin ( 360 365 (dn − 82) )) (5) δ = 23.45° sin ( 2π 365 (dn + 284) ) (6) and δ = arcsin ( 0.39779 sin ( 4.8888 + 0.017214dn+ + 0.033 sin(0.017214dn) )) (7) the results of different equations that calculate the declination of the sun are shown in fig. 2. the sun is above the equator on 20/21 march (vernal equinox) and 22/23 september (autumnal equinox), moreover, the winter solstice is on 21/22 december and the summer solstice on 21/22 june. the difference between the equations in fig. 2 is minimal. the maximum change in the declination when calculated on a daily basis is less than 0.5° (|δ(dn+1)− δ(dn)|). equation of time a solar day varies in length throughout the year. a day on earth is 24 hours long and is based on the rotation of the earth around its polar axis. a solar day is based on the rotation of the earth around its polar axis and on its motion around the sun. the elliptic orbit of the earth causes a difference between the time of day and the solar time of day (astronomical). this means that noon in local and astronomical times (the sun is in the southern hemisphere) differ. this time difference can be calculated from the following equations [6]: et = [ 0.000075 + 0.001868 cos ( 2π dn − 1 365 ) − − 0.032077 sin ( 2π dn − 1 365 ) − − 0.014615 cos ( 4π dn − 1 365 ) − −0.04089 sin ( 4π dn − 1 365 )] 229.18 (8) 0 50 100 150 200 250 300 350 −20 −10 0 10 20 the day of the year e t [m in ] eq. 8 eq. 9 eq. 10 data series † figure 3: the values of the equation of time over a year using eqs. 8–10 and a series for the year 2018 et = [ 0.043 sin ( 2 ( 4.8888 + 0.017214dn+ + 0.033 sin(0.017214dn) )) − − 0.03342 sin(0.017214dn)+ + 0.2618tutc − π ] 229.18 (9) and et =− 7.655 sin ( 2π dn 365 ) + + 9.873 sin ( 4π dn 365 + 3.588 ) . (10) eqs. 8 and 9 yield et in radians and the constant 229.18 converts this into minutes. this constant can be calculated from 229.18 = 360° 2π 360° 24 · 60 min 16 min (11) fig. 3 shows the results according to eqs. 8–10 over a whole year, together with astronomical data for the year 2018. the largest difference was calculated by eq. 10 when compared with the other data. 3.2 solar beam equations using the equations in section 3.1, the position and angles of the sun at a local (geological) position can be calculated with the gps coordinates φlat and φlong. fig. 4 shows the path of the sun and the angles of the actual position of the sun. the nomenclature is as follows: • α: solar altitude angle • θz: solar zenith angle • ψ: solar azimuth angle since the altitude (α) and zenith angles (θz) are complementary angles, α+ θz = 90°, (12) the local solar hour angle can be calculated from [6] †http://www.ppowers.com/eot.htm 47(1) pp. 57–63 (2019) 60 bálint, fodor, szalkai, szalkai, and magyar s n e w zenith sunset sunrise α ψ θz ψ < 0 ψ > 0 geological position path of sun path of sun projection of figure 4: the local position of the sun with important angles h = 180°− 15° ( tutc + et 60 ) − φlong, (13) where tutc is the local time in time zone +0 in hours and φlong is the local longitudinal position in degrees. the cosine of the solar zenith angle can be calculated by using the solar declination, local latitudinal position and solar hour angle. according to eq. 12, cos(θz) = sin(δ) sin(φlat)+ + cos(δ) cos(φlat) cos(h), (14) and cos(θz) = sin(α), (15) (eq. 14 is from ref. [6]) the solar azimuth angle (ψ) can be calculated from cos(ψ) = sin(α) sin(φlat)− sin(δ) cos(α) cos(φlat) (16) and sin(ψ) = cos(δ) sin(h) cos(α) . (17) 3.3 global solar irradiance the solar irradiance can be calculated in a simple form: i = inq tmz sin(α), (18) where q denotes the clear sky transmissivity through a thickness of one atmosphere, tm represents the linke turbidity factor of the air and z stands for the relative path length of the solar beam through the atmosphere. parameter q is a constant with a value of 0.93 (when the sky is dry and clear and the zenith angle is equal to zero). the value of tm determines how many clear atmospheres should be stacked to achieve the actual spectral transmittance. this value depends on the amount of water vapor, dust, smog, etc. in the eu, tm is between 1.8 and 4. the suggested formula for the calculation of parameter z is z = latm rearth − rearth , (19) where latm denotes the path length of the solar beam through the atmosphere, rearth represents the mean radius of the earth’s surface and rearth stands for the radius of the earth when the atmosphere is included (rearth− rearth is the thickness of the atmosphere). the value of latm depends on the solar altitude and can be calculated using the law of cosines which yields l2atm−2 rearth latm cos(α+ 90°)+ + (r2earth −r2 earth) = 0. (20) the correct value of latm is the positive root of eq. 20. eq. 18 yields the solar irradiance under ideal conditions. however, aerosols in the atmosphere cause diffuse scattering and absorb a proportion of the solar irradiance. furthermore, clouds also have an effect on the irradiance. some models divide the global solar irradiance into two parts: • direct solar irradiance • diffuse solar irradiance irradiance on a horizontal surface various models exist to calculate the global solar irradiance on a horizontal surface, e.g., a hungarian model [8] is presented in g = ( in sin(α) + a )( 1 + b1n b2 ) , (21) where in denotes the corrected solar constant, n represents the cloudy parameter between 0 and 1 (0 when clear, 1 when overcast). a is a local correction value (a negative constant in w/m2, and b1 as well as b2 are locally constant in terms of the cloud correction. this hungarian model [8] takes the cloud cover into consideration but not the transparency of the atmosphere (q, tm and latm). a german model [9] accounts for atmospheric conditions. equation g = in sin(α)ad e −bdtmz(1− adn bd) (22) shows the global solar irradiance and equation s = in sin(α)ad q tmz(1−n bd) (23) presents the direct solar irradiance formula. the parameters ad, bd, ad and bd are place-dependent values. a typical parameter set is ad = 0.72, bd = 3.2, ad = 0.7 and bd = 0.027. the diffuse solar irradiance can be calculated by a simple subtraction. d = g− s (24) the calculated global solar irradiance is shown in fig. 5 over a year with weekly resolutions during clear sky conditions in veszprém, hungary. the red curve tracks the maximum values of the astronomical noons on each curve (analemma curve). this curve shows the effect of hungarian journal of industry and chemistry modeling and calculation of the global solar irradiance on slopes 61 5 10 15 20 0 200 400 600 800 hour g [w / m 2 ] global irradinace analemma curve figure 5: calculated global solar irradiance on a horizontal surface over the year in veszprém according to weekly resolutions and the analemma curve (astronomical noon times) the et, the duration of which is approximately 11 hours because the longitudinal position of veszprém is 17.9° and this causes a delay of about 1 hour (the local time zone is +1). fig. 5 clearly illustrates the difference in irradiance between the winter and summer periods. irradiance on the slope for the sake of simplicity the cartesian coordinate system is used, the axes of which are s (south), w (west) and z (zenith). the azimuth angle ψ in the direction sw-n-e-s and the altitude of the sun α have been calculated, so the normed vector that points towards the sun is −→ os = [cos(α) cos(ψ), cos(α) sin(ψ), sin(α)]>. if the surface σ exhibits an angle of inclination of β to the horizon and an orientation of γ, which defines γ as negative, positive or zero if and only if the surface faces se, sw or s, respectively, then the normed vector of the surface (contained within the same half-space as the sun) is −→n and exhibits the altitude ν = 90o − β so −→n = [cos(ν) cos(γ), cos(ν) sin(γ), sin(ν)]>. the angle between −→ os and −→n is θsurf = arccos ( cos(α) cos(ψ) cos(ν) cos(γ)+ + cos(α) sin(ψ) cos(ν) sin(γ)+ + sin(α) sin(ν) ) = arccos ( cos(α) cos(ν) ( cos(ψ) cos(γ)+ + sin(ψ) sin(γ) ) + sin(α) sin(ν) ) , (25) since −→ os and−→n are normed. so −→ os meets σ at the angle αsurf = 90o − θsurf . eq. 23 yields the direct solar irradiance on a horizontal surface with solar altitude angle α. the solar altitude s n e w zenith α ψ γ βo p q surface θsurf figure 6: the angle of the solar beam and the zenith angle between the surface and the slope β and orientation γ angle on the slope is αsurf . to calculate the corrected direct solar irradiance, equation ssurf = s sin(αsurf) sin(α) (26) must be used. calculation of the diffuse solar irradiance is far from trivial. if the diffuse solar irradiance is consistent with the all-sky, equation dsurf = d 1 + cos(β) 2 (27) can be used to estimate the value of the irradiance. the global solar irradiance of the slope is the sum of the direct and diffuse solar irradiances: gsurf = ssurf +dsurf . (28) 4. model verification the aim of this section is to verify the solar irradiance model proposed in the previous section against basic engineering expectations. figs. 7 and 8 show the results of the implemented model on 1 march (dn = 60) and 1 july (dn = 121) and the geographical position of veszprém, hungary. both figures present the value of the solar irradiance for various orientations as well as the tilt and azimuth angles. 6 8 10 12 14 16 0 200 400 600 800 hour g [w /m 2 ] horizontal β = 10°; γ = 0° β = 30°; γ = 0° β = 45°; γ = 0° β = 30°; γ = −45° figure 7: calculated global solar irradiance on sloping terrain of various orientations on 1 march in veszprém, hungary 47(1) pp. 57–63 (2019) 62 bálint, fodor, szalkai, szalkai, and magyar 5 10 15 20 0 200 400 600 800 hour g [w /m 2 ] horizontal β = 10°; γ = 0° β = 30°; γ = 0° β = 45°; γ = 0° β = 30°; γ = −45° figure 8: calculated global solar irradiance on sloping terrain of various orientations on 1 july in veszprém, hungary irradiance on a horizontal surface is denoted by a blue solid line. the other curves show the value of the solar power with a non-zero tilt angle: 10° (magenta dotted line), 30° (orange dashed line with an azimuth angle of zero, purple dashed dotted line with an azimuth angle of −45° (south-east)) and 45° (green dashed dotted line). the peak values of the curves in fig. 7 correlate with the tilt angle (β). as the tilt angle increases, so does the irradiance when the azimuth angle is constant (γ = 0°). as the azimuth angle changes towards the southeast, the peak of the curve shifts towards the sunrise. the effect of the tilt angle is somewhat different in fig. 8. on 1 july, the absolute peak can be observed for cases β = 10° and β = 30° but the irradiance for the whole day is higher if the tilt angle is smaller. this effect is caused by the angle of the solar altitude (smaller zenith angle). if the tilt angle is greater than the minimum horizontal zenith angle, the solar irradiance will decrease on the slope. on 1 march the maximum angle of the solar altitude did not reach 45°. in other words, a greater tilt angle generates more power on sloping terrain. the effect of the azimuth angle can be seen in fig. 7. 5. conclusions a solar irradiance model is presented in this work that can be used for forecasting the solar energy absorbed by an inclined surface, e.g. a pvpp. the developed model is preliminary in nature and serves as a basis for further developments, e.g. forecasting the power of the solar energy under cloudy conditions. the novel element of the model is that the relative path length of the solar beam in the atmosphere can be calculated more accurately. the calculated irradiance an inclined surface is exposed to is another novel element. the proposed model has been verified against engineering expectations and the results show that it works well. the next step will be the validation of the model using real measured parameters and meteorological data. by extending the model with an electrical power module, it will also be possible to forecast the amount of electrical energy produced. acknowledgement we acknowledge the financial support of széchenyi 2020 under the efop-3.6.1-16-2016-00015. we acknowledge the financial support of széchenyi 2020 under the ginop-2.2.1-15-2017-00038. a. magyar was supported by the jános bolyai research scholarship of the hungarian academy of sciences. references [1] braun, j.e.; mitchell, j.c.: solar geometry for fixed and tracking surfaces, sol. energy, 1983 31(5), 439– 444, doi: 10.1016/0038-092x(83)90046-4 [2] bird, r.e.; riordan, c.: simple solar spectral model for direct and diffuse irradiance on horizontal and tilted planes at the earth’s surface for cloudless atmospheres, j. clim. appl. meteorol., 1986 25(1), 87–97, doi: 10.1175/15200450(1986)025%3c0087:sssmfd%3e2.0.co;2 [3] danandeh, m.a.; mousavi g., s.m.: solar irradiance estimation models and optimum tilt angle approaches: a comparative study, renew. sust. energy rev., 2018 92, 319–330, doi: 10.1016/j.rser.2018.05.004 [4] li, d.h.w.; chau, t.c.; wan, k.k.w.: a review of the cie general sky classification approaches, renew. sust. energy rev., 2014 31, 563–574, doi: 10.1016/j.rser.2013.12.018 [5] akarslan, e.; hocaoglu, f.o.; edizkan, r.: novel short term solar irradiance forecasting models, renew. energy, 2018 123, 58–66, doi: 10.1016/j.renene.2018.02.048 [6] iqbal, m.: an introduction to solar radiation (academic press, london, uk), 1st edn., 1983, doi: 10.1016/b978-0-12-373750-2.x5001-0, isbn: 978-0-12373750-2 [7] duffie, j.a.; beckman, w.a.: solar engineering of thermal processes (john wiley & sons, new jersey, usa), 2013, doi: 10.1002/9781118671603 isbn:978-0-47087366-3 [8] práger, t.; ács, f.; baranka, g.; feketéné nárai, k.; mészáros, r.; szepesi, d.; weidinger, t.: a légszennyezõ anyagok transzmissziós szabványainak korszerũsítése iii. fázis részjelentés 2., 1999 [9] kasten, f.: strahlungsaustausch zwischen oberflächen und atmosphäre, vdi-bericht, 1989 (nr. 721. s.), 131–158 hungarian journal of industry and chemistry https://doi.org/10.1016/0038-092x(83)90046-4 https://doi.org/10.1175/1520-0450(1986)025%3c0087:sssmfd%3e2.0.co;2 https://doi.org/10.1175/1520-0450(1986)025%3c0087:sssmfd%3e2.0.co;2 https://doi.org/10.1016/j.rser.2018.05.004 https://doi.org/10.1016/j.rser.2013.12.018 https://doi.org/10.1016/j.rser.2013.12.018 https://doi.org/10.1016/j.renene.2018.02.048 https://doi.org/10.1016/j.renene.2018.02.048 https://doi.org/10.1016/b978-0-12-373750-2.x5001-0 https://doi.org/10.1002/9781118671603 modeling and calculation of the global solar irradiance on slopes 63 appendix: nomenclature symbol description value/dimension e0 reciprocal of the relative sun-earth squared distance (r0/r) 2 r0 mean sun-earth distance (astronomical unit: [au]) 1 au r actual sun-earth distance in au [au] dn the day of the year 1-365 i0 solar constant 1367 w/m2 in corrected solar constant i0e0 δ sun’s declination ±23.5° et equation of time ∼ ±15 min tutc the time in utc 0-24 φlat geographic latitude ±90° φlong geographic longitude ±180° α the angle of the solar altitude 0°-90° θz solar zenith angle 90°− α ψ solar azimuth angle ± 180° h the solar hour angle 0°-360° q clear sky transmissivity 0.93 tm linke turbidity factor 1.8-4 in central eu z relative solar beam length in the atmosphere latm length of the path of the solar beam through the atmosphere [km] rearth median radius of the earth including the atmosphere ∼ 6470 km rearth median radius of the earth from the ground ∼ 6370 km g global solar irradiance [w/m2] n cloudy parameter 0-1 ad place-dependent constant bd place-dependent constant ad place-dependent constant bd place-dependent constant d diffuse solar irradiance [w/m2] s direct solar irradiance [w/m2] β angle above the surface from the horizontal position 0°–90° γ surface azimuth angle ±90° θsurf the solar zenith angle on the surface 90°− αsurf αsurf the angle of the solar altitude on the surface 0°-90° ssurf direct solar irradiance on the surface [w/m2] dsurf diffuse solar irradiance on the surface [w/m2] gsurf global solar irradiance on the surface [w/m2] 47(1) pp. 57–63 (2019) hungarian journal of industry and chemistry vol. 47(1) pp. 65–70 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-10 aggregation of heterogeneous flexibility resources providing services for system operators and the market participants istván balázs *1, attila fodor1, and attila magyar1 1department of electrical engineering and information systems, faculty of information technology, university of pannonia, egyetem u. 10, veszprém, 8200, hungary power systems characterized by large, centralized generation sources and the typical flow of energy from the transmission grid to the distribution grid towards consumers are evolving. the increasing penetration of intermittent and distributed renewable energy generation is forcing system operators to increase the volume of balancing capabilities and procure flexibility services at the distribution grid level that must be supported by the aggregation of small-scale resources connected at the distribution grid. this paper suggests an aggregator framework that provides services for both operators of transmission and distribution systems while optimizes its portfolio to perform on wholesale energy trading markets too. overlaying phases of multi-period optimization runs are proposed that incorporate stochastic renewable energy generation as well as load forecasts and, moreover, the continuously changing business context while enabling cooperation between optimization phases throughout the business process. keywords: generation aggregator, optimization, distributed energy resources, tso-dso coordination, smart grid 1. introduction conventional power systems are characterized by large generation sources that inject power into the transmission grid, which is transported to distribution networks before being delivered to the end users. power flows one way from the high-voltage transmission grid to the end user at low-voltage networks. centralized, dispatchable and predictable generation provides flexibility at the transmission level to the electricity system to balance generation and demand. the increasing amount of distributed and renewable generation (from around 21% of total net electricity generation in 2010 to 44% in 2030 [1]) has transformed generation into a more variable and intermittent source of energy. demand has become more active, emphasizing the engagement of consumers. distributed generation (dg), demand response (dr) and storage facilities will become important components of power systems in the future. these resources are connected to lowand medium-voltage networks, thus, making the distribution grid a crucial element of the electricity sector. the increasing penetration of intermittent generation and distributed energy resources has already forced tsos (transmission system operator) to increase the volume of balancing capabilities and start procuring services for *correspondence: balazsistvan08@protonmail.com system balancing not only from the transmission grids but also from distribution grids. an important concept is flexibility, that is the modification of generation injection and/or consumption patterns in reaction to an external signal (price signal or activation), in order to provide a service within the energy system [2]. it is the active management of an asset that can impact the balance of a system or power flows to the grid on a short-term basis. the proper management of available flexibility, both in terms of generation and demand, can help to compensate for the lack of certainty with regard to renewable sources. on the other hand, dsos (distribution system operator) have started to manage congestion actively in their distribution grids and consider procurement of flexibility services to redispatch the system at the distribution level. as a result, the same flexibility resources could also be potentially used for congestion management and voltage control by the tso and dso [3]. conflicts of interest may arise between the tso and dso that must be managed by suitable coordination schemes [4], but this also provides an opportunity for players on the distribution grids to offer flexibility capabilities to multiple customers resulting in higher demand. an aggregator, that is a new market agent, will play a central role in collecting resources on the distribution grid and involving them in markets that are unavailable for them individually. usef (universal smart energy mailto:balazsistvan08@protonmail.com 66 balázs, fodor, and magyar framework) foundation’s aggregator workstream analyzed the different topics related to the role of the aggregator whilst paying particular attention to demandresponse aggregation as well as the relationship between an aggregator and the brp (balance responsible party)/supplier. seven different models to implement aggregation were identified, and advantages as well as limitations evaluated [5]. flexibility resources were investigated in detail and an information model set up by smartnet d1.2 [6] that contains a mathematical description of the dynamic behaviour of the resource, its constraints in terms of flexibility provision, and a formulation of the different components of costs needed to provide flexibility. the research project bestres (best practices and implementation of innovative business models for renewable energies aggregators) [7] explored different ways in which an aggregator can create value, and categorized services that are provided into internal (own balancing) as well as external reasons (wholesale, retail, reserve capacity mechanisms). an aggregation function manages distributed energy resources, the optimization of dispatch by taking into consideration the states of a time-variant system is a core capability. with regard to isolated microgrids, olivares et al. [8] proposes a stochastic-predictive control approach. the uncertainty of an isolated grid for a single purpose (generation and load balancing) is addressed, a two-stage stochastic receding horizon approach is presented that can be generalized to develop formulations for marketconnected multi-purpose optimization scenarios. the objective of this study is to develop a framework for an aggregator that implements the aggregator role of heterogeneous distributed energy resource management, complies with the typical electricity market model, follows its business processes, and operates in both wholesale energy and electricity balancing markets. the present paper provides novelties in terms of aggregator roles. it is based on a centralized approach where a new market agent, the aggregator, manages the flexibilities of a portfolio and offers services to tso, dso and external brps. in addition, it participates in wholesale energy trading activities and co-optimizes resource portfolios for both energy trading as well as flexibility services. the building blocks of such an aggregator have been determined: 3 phases of an overlaying optimization process are recommended, optimization requirements are defined and input/output parameters determined to enable cooperation between optimization phases throughout the business process. section 1 introduced challenges that concern the energy sector, defined a problem statement and presented current research as well as implementations. section 2 describes the architecture of an aggregator extending the virtual power plant concept with heterogeneous resources of flexibility and the optimization module. differences between typical aggregator definitions and functions proposed in this paper are highlighted. an architecture is planned where optimization is separated from the generator control module as it has to solve a much more complex problem than regular, built-in dispatch functions face. the business context is presented that assumes a complex optimization approach as introduced in section 3. here optimization requirements are collected to fulfil the objectives of previous sections and to optimize process phases, data exchange between phases is determined. 2. aggregator framework the flexibility center (fc) is introduced in this paper as an entity that implements the role of the aggregator. it is a framework of tools and functions that enable the aggregation of distributed, heterogeneous flexibility resources and provide services in wholesale markets. components of the fc will be presented as well as its operating environment in order to provide a framework for optimization of heterogeneous energy resources. 2.1 aggregator role according to the definition derived from the universal smart energy framework (usef) [9], an aggregator is responsible for acquiring flexibility from prosumers, aggregating it into a portfolio, creating services that draw on the accumulated flexibility, and offering these flexibility services to different markets that serve various market players. in return, the aggregator receives the value it creates on these markets and shares it with the prosumer as an incentive to shift its load. in the definition above, usef only restricts the scope of the aggregator for prosumers by limiting the activities of the aggregator with regard to demand response aggregation. the eu commission proposal for the recast of the e-directive [2] defines the aggregator as a market participant that combines multiple customer loads or generated electricity for sale, purchase or auction in any organised energy market. in this study the commission’s definition is used that incorporates aggregation of all types of decentralized energy resources. the objective of the research is to identify optimization use cases of an aggregator, so assumptions have to be made to simplify the market environment the aggregator operates in. to be able to ignore challenges concerning the dissociation of energy supply / wholesale energy trading and flexibility activation, which is a significant change to current market models, the fc implements the role of the aggregator using an integrated aggregator model [5]. following the integrated model, the roles of the supplier/trader and aggregator are combined into one market party, both of which are part of the same balancing group, contracted by the same brp. since compensation for imbalances and the open supply position are unnecessary, portfolio optimization efforts rather than market issues remain the primary focus. definitions and implementations of an aggregator, as referenced in section 1, outline a model aggregator as a hungarian journal of industry and chemistry aggregation of heterogeneous flexibility resources 67 service provider that responds to external requirements. in this study, the role of the aggregator is extended to operate on the wholesale energy markets as well, in cooperation with its brp/energy trader. it is proposed that the flexibility center should both fulfil external requests and participate in energy trading to optimize economic gain. 2.2 architecture the proposed flexibility center contains individual modules that cooperate to implement the roles of aggregation. the scada (supervisory control and data acquisition) system is responsible for data acquisition and control. it can be considered as a low-level interface to the controlled resources. standard building block. the aglc (automatic generator loading control) module controls power levels concerning elements of the portfolio using scada services based on the expected optimized dispatch. standard building block. the forecast module provides forecasts with regard to generation, consumption volumes and market prices. generation and consumption is forecast as a standard function for any implementations that control intermittent resources. however, price forecasting is an additional function required by the trading responsibility of the flexibility center. the proposed architecture of the aggregator defines optimization as an individual module. according to the proposed architecture, it has an extended responsibility, enabling the flexibility center to control a diverse portfolio of distributed resources and optimize their capacities in order to both participate in wholesale energy markets and fulfil external requests for flexibility activation. 2.3 services offered and customers the flexibility center provides services for its customers in terms of aggregating the flexibility capabilities of distributed resources. in terms of the fc, the reason why a customer requested flexibility is irrelevant. however, to prepare high-quality services that meet the technical requirements of the customer and are profitable for the fc, a set of offered services has to be defined. fig. 1 presents connections between flexibility providers, the flexibility center and customers. the flexibility center provides services to potential customers: internal brp: fc provides optimal dispatch of the portfolio and trading recommendations to maximize profit on the day-ahead and intraday energy markets. fc can use the portfolio of its own balancing group to minimize imbalance costs of providing such a service for the balance responsible party (brp) of the balancing group near the delivery time. tso: tso procures balancing reserves to ensure resources for load-frequency control. fc can bid on both balancing capacity and balancing the energy market by offering frequency restoration reserves (frr). tso dso internal brp external brp scada flexibility center optimization forecast aglc distributed generation demand response energy strorage c u st o m e rs fl ex ib ili ty p ro vi d e rs a gg re ga to r 1 2 4 3 nondispatchable load figure 1: flexibility center services and operational context dso: dso’s will be empowered to actively purchase local flexibility capabilities to mitigate voltage and grid congestion problems due to the increasing penetration of intermittent and distributed energy resources in the distribution system. fc can bid on future local flexibility markets by offering services for congestion management in the distribution network [9]. voltage / reactive power controls may also be a positive use case, but these are not considered in this study. external brp: similarly to the internal brp service, it is also economically worthwhile to balance an external brp portfolio [10]. 2.4 flexibility resources distributed generation refers to power generation facilities connected to the distribution grid. it may consist of predictable, dispatchable and intermittent generation. demand response is defined as the changes in energy use by end users (domestic and industrial) from their current/normal consumption patterns in response to market signals. energy storage can be used to store an excess of energy during high generation periods and transform it back into electricity during periods of high demand or to balance the power system. a non-dispatchable load is the consumption of an end user that does not participate in demand response programs. 3. optimization phases markets, in which the fc operates, change over time during the same delivery period. information on the market, assets of the portfolio, contractual commitments and weather conditions all change over time and the fc optimization function has to reflect such changes. an optimization approach is proposed that takes into consideration the changing objectives and status of the optimization phases. 47(1) pp. 65–70 (2019) 68 balázs, fodor, and magyar 0 3 6 9 12 15 18 21 0 3 6 9 12 15 18 21 day: d-1 day: d da: d d ay ah ea d in tr ad ay id: d / h 00:00 id: d / h 01:00 id: d-1 / h 23:00 id: d-1 / h 10:00 id: d-1 / h 09:00 … … id: d / h 18:00 id: d / h 18:00 period 1 results period 2 results 18:00 18:10 18:20 18:30 18:40 18:50 19:00 20:0019:10 19:20 19:30 19:40 19:50 g&l 18:00 g&l 18:05 g en er at io n & lo ad d is p at ch … g&l 18:40 g&l 19:20 … … figure 2: examples of optimization phases and look-ahead windows 3 phases are identified that are built upon each other. each phase shares the same primary objective to maximize profit, but the objective function, set of variables, parameters and constraints may differ as the time of delivery approaches and former calculations/forecasts become reality. in order to prepare a consistent optimization framework for the fc, optimization phases are identified and descriptions provided. fig. 2 depicts an example of overlaying optimization runs. day-ahead planning is run once a day, intraday planning is initiated every hour, and generation and load dispatch is executed every 5 minutes. once initiated, all optimization runs have to update optimization parameters so they can provide progressively more precise results. 3.1 requirements of optimization requirements of wholesale energy and flexibility activation call for a complex optimization approach. in this paper, common optimization requirements are identified, however, detailed formulations will be developed as part of future research. the flexibility center as an aggregator manages distributed resources that use the grid but does not operate the grid. it is not responsible for nor able to perform network monitoring and control, thus, the grid is not modeled, rather an economic dispatch problem is solved by fc optimization. due to uncertainties concerning consumption and intermittent renewable generation, a stochastic optimization function has to manage multiple, probability-weighted load and generation scenarios. energy storage, ramping and unit commitment considerations require a multi-period planning horizon. objective functions are formulated to maximize profit and optimization phases share execution results, but they all solve a different optimization problem. variables, parameters, cost functions and constraints must be aligned accordingly. contractual commitments have no cancellation value, these are obligatory constraints. orders from contracted customers (tso, dso, brp) must be superposed to fulfil expectations and incorporated into the portfolio optimization model. 3.2 day-ahead planning the goal of the day-ahead planning phase is to provide portfolio dispatch for schedule nominations containing make-or-buy recommendations based on market price forecasts. since this is performed on a daily basis, the run time is not critical. multi-stage stochastic unit commitment and economic dispatch optimization are recommended to mitigate generation and load uncertainties. periods of 15 minutes in duration are necessary to meet the requirements of the nomination process. input parameters for day-ahead planning are reserved flexibility capacities, contractual commitments (e.g. reserved capacities, commercial contracts), the state of the system at the beginning of day d according to the previous intraday run, technical and price parameters with regard to the assets of the portfolio, the generation forecast of intermittent resources, the consumption forecast of loads, and the day-ahead spot price forecast. the outhungarian journal of industry and chemistry aggregation of heterogeneous flexibility resources 69 table 1: timeframes of phases phase interval number of runs periods da 1 calendar day 1 / day 96× 15 min periods id 24 hours 24 / day 96× 15 min periods g&l 60−5 mins 12 / hour 12−1× 5 min periods put contains the power dispatch of the portfolio including binary unit commitment decisions and day-ahead trading recommendations. table 1 summarizes optimization intervals and the duration of each phase. the results of day-ahead optimization are inputted into schedule nominations and dayahead trading so a calendar day is covered but executed according to nomination schedules from the middle of the previous day. 3.3 intraday operation the primary objective of the intraday run is to determine the system state at the end of the first hour which is then used by generation and load dispatch as a target state (19:00 according to the example in fig. 2). it can also be used to fine-tune day-ahead results and produce inputs for intraday trading and schedule modifications. intraday optimization takes into consideration unit commitment decisions, nominated day-ahead as well as intraday schedules, reserved capacities, more precise weather as well as price forecasts, portfolio parameters and the current state of the system provided by the scada module, price parameters of the assets from the portfolio, and activation orders from customers. it is executed hourly by applying a 24-hour look-ahead window. the run-time is critical and the unit commitment is not revised, but probability-weighted generation and load scenarios still need to be generated for stochastic optimization. multi-period stochastic optimization is recommended. the duration of periods is 15 minutes to support intraday trading. 3.4 direct generation and load dispatch intraday optimization performs a 24-hour run and determines a target system state for a direct generation and load dispatch run to calculate optimized dispatch for the automatic generator loading control module. here the optimization interval is 1 hour and the duration of calculations is 5 minutes. the result of the first period is used by the aglc to directly control the assets of the portfolio. the initial parameter set is the actual system state provided by the scada module, the target state is determined by the intraday run. it also follows the shrinking horizon model by being executed every 5 minutes and performing calculations up until the hourly target. results must be sent to aglc to control assets since the run-time is extremely critical. a deterministic optimization linear programming formulation is proposed. 4. conclusion in this paper, an aggregator framework was presented that aims to manage distributed energy resources, provide services for system operators, support brps to minimize imbalances in the balancing group, and determine energy trading volumes in day-ahead and intraday markets. 3 phases of overlaying process optimization were recommended in line with a regular marketing process. a. appendix: acronyms abbr. description aglc automatic generator loading control brp balance responsible party bsp balancing service provider dg distributed generation dr demand response dso distribution system operator fc flexibility center scada supervisory control and data acquisition tso transmission system operator b. appendix: definitions balancing group: a group of market participants (consumers, producers, traders) who optimize costs by netting deviations (imbalances) and reduce overall deviations between the projected and reported electricity usage. balance responsible party: a chosen representative of a balancing group who is responsible for the imbalance of the group. balancing service provider: a market participant providing balancing services to the tso. balancing services: (1) balancing energy is energy used by tso to perform balancing and (2) balancing capacity, namely a volume of capacity that a bsp has agreed to hold to and in respect of to which the bsp has agreed to submit bids for a corresponding volume of balancing energy to the tso. balancing: balancing encompasses all actions and processes through which tso ensures the system frequency is within a predefined stability range and complies with the amount of reserves needed with respect to the required quality. 47(1) pp. 65–70 (2019) 70 balázs, fodor, and magyar distribution system operator: responsible for providing and operating low-, mediumand high-voltage networks for the regional distribution of electricity as well as for the supply of lower-level distribution systems and directly connected customers. transmission system operator: responsible for providing and operating highand extra high-voltage networks for the long-distance transmission of electricity as well as for the supply of lower-level regional distribution systems and directly connected customers. prosumer / active customer: customers who consume, store or sell electricity generated on their premises, or participate in demand response or energy efficiency schemes provided that these activities do not constitute their primary commercial or professional activity. demand response: the change of electricity load by final customers from their normal or current consumption patterns in response to market signals, including timevariable electricity prices or incentive payments, or in response to acceptance of the final customer’s bid. references [1] merino, j.; gómez, i.; turienzo, e.; madina, c.: ancillary service provision by res and dsm connected at distribution level in the future power system, tech. rep., smartnet project d, 2016, http://smartnet-project.eu/wp-content/ uploads/2016/12/d1-1_20161220_v1.0.pdf [2] european commission: proposal for a directive of the european parliament and of the council on common rules for the internal market in electricity, 2017 [3] de jong, g.; franz, o.; hermans, p.; lallemand, m.: tso-dso data management report, tech. rep., cedec, edso, entso-e, eurelectric, geode, 2016 [4] gerard, h.; rivero, e.; six, d.: basic schemes for tso-dso coordination and ancillary services provision, tech. rep., smartnet project d, 2016, http://smartnet-project.eu/wp-content/ uploads/2016/12/d1.3_20161202_v1.0.pdf [5] de heer, h.; van der laan, m.: recommended practices and key considerations for a regulatory framework and market design on explicit demand response, tech. rep., universal smart energy framework, 2017 [6] le baut, j.; leclerq, g.; viganò, g.; degefa, m.z.: characterization of flexibility resources and distribution networks, tech. rep., smartnet project d, 2017, http://smartnet-project.eu/wp-content/ uploads/2017/05/d1.2_20170522_v1.1.pdf [7] verhaegen, r.; dierckxsens, c.: existing business models for renewable energy aggregators, 2016 , 2689723 http: //bestres.eu/wp-content/uploads/2016/08/bestres_ existing-business-models-for-re-aggregators.pdf [8] olivares, d.e.; lara, j.d.; cañizares, c.a.; kazerani, m.: stochastic-predictive energy management system for isolated microgrids, ieee transactions on smart grid, 2015 6(6), 2681–2693, doi: 10.1109/tsg.2015.2469631 [9] framework, u.s.e.: usef: the framework explained, tech. rep., universal smart energy framework, 2015 [10] olivella-rosell, p.; lloret-gallego, p.; munnécollado, i.; villafafila-robles, r.; sumper, a.; ottessen, s.ø.; rajasekharan, j.; bremdal, b.a.: local flexibility market design for aggregators providing multiple flexibility services at distribution network level, energies, 2018 11(4), 822, doi: 10.3390/en11040822 hungarian journal of industry and chemistry http://smartnet-project.eu/wp-content/uploads/2016/12/d1-1_20161220_v1.0.pdf http://smartnet-project.eu/wp-content/uploads/2016/12/d1-1_20161220_v1.0.pdf http://smartnet-project.eu/wp-content/uploads/2016/12/d1.3_20161202_v1.0.pdf http://smartnet-project.eu/wp-content/uploads/2016/12/d1.3_20161202_v1.0.pdf http://smartnet-project.eu/wp-content/uploads/2017/05/d1.2_20170522_v1.1.pdf http://smartnet-project.eu/wp-content/uploads/2017/05/d1.2_20170522_v1.1.pdf http://bestres.eu/wp-content/uploads/2016/08/bestres_existing-business-models-for-re-aggregators.pdf http://bestres.eu/wp-content/uploads/2016/08/bestres_existing-business-models-for-re-aggregators.pdf http://bestres.eu/wp-content/uploads/2016/08/bestres_existing-business-models-for-re-aggregators.pdf https://doi.org/10.1109/tsg.2015.2469631 https://doi.org/10.1109/tsg.2015.2469631 https://doi.org/10.3390/en11040822 https://doi.org/10.3390/en11040822 hungarian journal of industry and chemistry vol. 47(1) pp. 71–77 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-11 comparison of the approximation methods for time-delay systems: application to multi-agent systems áron fehér *1,2 and lőrinc márton1 1department of electrical engineering, sapientia hungarian university of transylvania, c.1., târgu mureş, 547367, romania 2department of mathematics, university of pannonia, egyetem u. 10, veszprém, 8200, hungary this paper presents a review of dominant pole and model-approximation algorithms for delayed systems that can be applied to multi-agent systems. a novel algorithm is proposed to determine an approximation method for multi-agent systems in the platoon configuration with a communication delay. simulations are presented to show the applicability of the proposed algorithm. keywords: time delay, differential equations, asymptotic properties, multi-agent systems 1. introduction a multi-agent system (mas) consists of multiple active agents (e.g. vehicles), passive agents (e.g. obstacles), in addition to cognitive agents and their environment [1]. every active agent is at least partially autonomous and uses a distributed control algorithm [2]. the agents can communicate with each other. this communication structure is defined by a graph, where each vertex corresponds to one agent and each edge to a communication direction. a platoon is a special mas configuration, with a linear communication graph. the leading (first) agent implements a reference tracking algorithm. every other agent implements a consensus with the adjacent agents [3]. with the increase in the number of agents and the physical distance between the agents, the communication delay cannot be neglected. while the stability of such systems is ensured by the consensus protocol [4], the delay will influence the transient behavior of the mas [5]. the goal of this paper is to compare the existing approximation methods for the transient behavior analysis of mas with communication delays and present a novel analysis method which can be applied to any mas system which satisfies a smallness delay condition. 2. modelling of mas a mas is considered with agents that exhibit singleintegrator dynamics [6]. the state-space model of an agent becomes ẋi(t) = ui(t), where xi ∈ r denotes *correspondence: fehera@ms.sapientia.ro the state of the ith agent and ui ∈ r represents the input, i = 1, 2, . . . , n. a mas has an underlying communication graph, in which the vertex is an agent and the edge a communication path [7], so the agent ith in the system is the vertex vi. let ni be the set of neighbors of vi, so that ni contains all vertices that are connected to vi. consensus algorithm the consensus problem of a mas is the procedure of gathering every state from the initial condition to a common steady-state. if the communication graph is connected, the consensus with regard to an agent can be reached with the input (consensus protocol) ui(t) = ∑ j∈ni (xj(t)− xi(t)) . (1) the adjacency matrix a = (aij) ∈ rn×n of a graph with n nodes is defined as aij := { 1, if i 6= j and vi are adjacent to vj 0, otherwise . (2) the degree matrix d = (dij) ∈ rn×n of a graph with n nodes shows the number of neighbors for each vertex and can be defined as dij := { deg(vi), if i = j 0, otherwise , (3) where deg(vi) denotes the degree or the number of edges incident to vertex i. mailto:fehera@ms.sapientia.ro 72 fehér and márton figure 1: the communication topology of a vehicle platoon system consisting of n vehicles with time delay τ in the communication graph. the dashed line symbolizes more nodes in between, while the dotted line represents the reference input of the nodes. with this notation the dynamics of the mas with the consensus protocol is given by ẋ(t) = −lx(t), x(0) = x0, (4) where l denotes the laplacian matrix [8] which is constructed as l = d − a, d stands for the degree matrix, a represents the adjacency matrix of the graph, x = ( x1 x2 . . . xn )> ∈ rn denotes the state vector consisting of the n states of the mas, and x0 ∈ rn is a constant vector of the initial states. according to [9] the eigenvalues of a mas consisting of n agents with a connected communication graph can be ordered as 0 = λ1 > λ2 ≥ · · · ≥ λn. (5) the steady states (equilibria) of the mas xss are the elements of the null space of l. given, according to the definition of the laplacian matrix, ∑ j∈ni lij = 0 [6] for every solution x of (eq. 4): lim t→∞ x(t) = xss = 1 n ∑n i=1 xi(0)1, where 1 = ( 1 1 . . . 1 )> ∈ rn. mas with delayed communication in the case of delayed communication, the consensus protocol is of the form ui(t) = ∑ j∈ni (xj(t− τ)− xi(t)) , (6) where τ ≥ 0 denotes the constant communication delay which is present among adjacent agents. according to refs. [4] and [10], the mas with communication delay (also referred to as multi-agent system with delays (dmas)) is ẋ(t) = −dx(t) +ax(t− τ) +r, (7) x(θ) = x0 ∈ rn, θ ∈ [−τ, 0], 3. platoon of vehicles a platoon of vehicles is a special class of mas with a communication topology shown in fig. 1. the kinematic model of a vehicle can be written as ẋi(t) = ui(t), (8) where xi(t) denotes the position of the vehicle and ui(t) represents the control signal in the form{ u1(t)=kp1(r−x1(t)) ui(t)=ξi(xi−1(t−τ)−d−xi(t)),∀i = 2, ..., n (9) where i ∈ (1, n), n ∈ n, n > 1, d denotes the prescribed inter-vehicle distance, ξi > 0, and kpi > 0 are constant control gains. r is the position reference of the first vehicle. eqs. 8 and 9 can be written as a system of differential equations with delay: ẋ(t) = −φx(t) + γx(t− τ) + f 1 r − f 2 d, (10) where φ = diag{ ( kp1 ξ2 . . . ξn−1 ξn ) } (11) denotes the degree matrix with the state feedback, γ =  0 0 0 . . . 0 0 0 ξ2 0 0 . . . 0 0 0 ... ... ... . . . ... ... ... 0 0 0 . . . ξn−1 0 0 0 0 0 . . . 0 ξn 0  (12) represents the adjacency matrix, and f 1 = ( kp1 0 . . . 0 )> , (13) f 2 = ( 0 ξ2 . . . (n− 1)ξn )> . (14) the homogeneous part of the relation in eq. 10 is of the same form as the relation in eq. 7, and the term f 1 r−f 2 d represents the reference as well as inter-vehicle distance induced inflows. 4. existing methods for the approximation of time-delay systems in this section, the various current approximation methods for time-delay systems are reviewed. the form of the studied systems is shown by the following relation: ẋ(t) = −φx(t) + γx(t− τ), x(h) = x0, (15) which is the homogeneous part of eq. 10, where θ(h) denotes the initial condition with h ∈ [−τ, 0], and has a quasi-polynomial characteristic equation: λin + φ− γe−τλ = 0, (16) where the delay component induces an exponential term. the roots of eq. 16 determine the transient behaviour of the system in eq. 15. as eq. 15 possesses an infinite number of solutions, it is important to develop such an equivalent system which has a finite number of eigenvalues and is a good approximation of the original system in eq. 15. if a good delay-free approximation is available, it hungarian journal of industry and chemistry approximation of multi-agent systems with delays 73 could be applied to the transient behaviour analysis and control design for delayed systems. let a special solution be denoted by x̃, which is uniquely determined by the value x̃(0), and independent of θ(h), h ∈ [−τ, 0), thus forming an n parameter family. in a linear autonomous system, this corresponds to the eigensolution generated by exactly n characteristic roots (multiplicities included) which lies in the half-plane reλ > −1/τ , see ref. [11]. theorem 1. [11] consider a delay differential equation (dde) system of the form shown in relation eq. 15 with a lipschitz criterion of: (‖φ‖+ ‖γ‖)τe < 1, (17) further noted as smallness condition, for every solution x of eq. 15 a globally defined solution x̃ : r→ rn exists that satisfies the growth condition supt≤0 ‖x̃(t)‖et/τ < ∞ such that ‖x(t)− x̃(t)‖ → 0 exponentially as t→∞. for further related discussions, see refs. [12] and [13]. the aforementioned theorem yields n dominant eigenvalues which can accurately represent a dde system. the system shown in the relation in eq. 15 uses the consensus protocol, which ensures that the eigenvalues are located in the left half-plane in the complex region. the final location of the dominant eigenvalues is created as a semicircle with origin 0, radius 1/τ , and a negative real part. 4.1 the modified chain approximation the modified chain approximation method creates an approximating system directly from the state-space representation of the delayed system [14]. for a dde in the form of eq. 15, the modified chain approximation method yields an approximating linear system in the form of ẏ 0 (t) = −φy 0 (t) + m τ inym(t) ẏ 1 (t) = γy 0 (t)− m τ iny1 (t) (18) ... ẏ k (t) = m τ inyk−1 (t)− m τ inyk(t), 2 ≤ k ≤ m the output vector z = y 0 represents the approximation of the solution x of the relation in eq. 15. the approximating system in the form of a matrix is shown in ẏ(t) = gy(t) (19) with g =  −φ 0n 0n · · · 0n m τ in γ −mτ in 0n · · · 0n 0n 0n m τ in −mτ in · · · 0n 0n ... ... ... . . . ... ... 0n 0n 0n · · · m τ in −mτ in  (20) where y ∈ rmn denotes the state vector, g ∈ r(m+1)n×(m+1)n represents the matrices of the system, 0n ∈ rn×n stands for the zero matrix, n is the number of agents and m denotes the number of approximating equations. according to ref. [14] the output of the system (eq. 19) defined as z(t) = y 0 (t) linearly converges into the solution of the original dde system such that c > 0 and supt≥0‖x(t)− z(t)‖ ≤ c m . 4.2 the lambert w function the lambert w function can be used to find the dominant eigenvalues of a quasi-polynomial equation (eq. 16). every w (s) function that satisfies w (s)ew (s) = s (21) by definition is referred to as a lambert w function [15], where s is either a scalar or matrix complex number function. the lambert w function has multiple branches denoted as wk(s) with k = 0,±1,±2, . . . ,±∞ . example 4.1. if a scalar dde is present in the form of ẋ(t) = ax(t) + bx(t− τ) + cu(t), (22) with a, b, c, θ ∈ r, x(h) = θ(h) for h ∈ [−τ, 0], the quasi-polynomial of the homogeneous part can be written as (λ− a)eτλ = b. (23) if both sides are multiplied by τe−aτ , then (λ− a)τeτ(λ−a) = bτe−aτ , (24) which satisfies eq. 21 with w (bτe−aτ ) = (λ− a)τ , and the eigenvalues can be calculated using the branches of the lambert w function as λk = 1 τ wk(bτe−aτ ) + a. (25) in our case, in terms of the relation in eq. 15, the aforementioned solution is generalized as λk = 1 τ wk(γτqk)− φ, (26) 47(1) pp. 71–77 (2019) 74 fehér and márton where qk can be calculated by solving the equation numerically wk(γτqk)ewk(γτqk)−φτ = γτ (27) for qk [16]. although many numerical solvers provide native support for the solution of the scalar lambert w function, the general case requires additional solver tools. therefore, the lambertwdde toolbox [17] was created. the function find_sk assumes τ , γ and−φ. the returned values are the eigenvalues λk and the qk parameters for a given k branch. the toolbox can create the approximating solution for the given system as x̃(t) = m2∑ k=m1 eλktcik , (28) where x̃ is the approximating solution of the original delay system and the parameter cik can be computed with the help of find_ci for a given m1 < k < m2 branch. in the scalar case, cik takes the form of cik = x0 + be−λkτ ∫ τ 0 θ(t− τ)dt 1 + bτe−λkτ . (29) 4.3 the quasi-polynomial root-finder algorithm the quasi-polynomial root-finder algorithm calculates the dominant eigenvalues of a system based directly on the quasi-polynomial equation in eq. 16. the quasi-polynomial equation of the system in eq. 16 can be written as: p (λ) = n∑ k=0 qk(λ)e−αkτλ, (30) whereqk is a polynomial with real coefficients and αk ∈ r. the objective is to compute the spectrum in the region of the complex plane d ⊂ c with boundaries βmin < re(d) < βmax and ωmin < im(d) < ωmax. let the surfaces defined by the real and imaginary parts of p (λ) be: re(p (β, ω)) = 0 (31) im(p (β, ω)) = 0 (32) the eigenvalues can be located at the points of intersection of the zero-level curves of the surfaces re(p (β, ω)) = 0 and im(p (β, ω)) = 0 as shown in ref. [18]. the accuracy of the algorithm is increased by newton’s method and by adapting the grid density of d as shown in ref. [16]. the quasi-polynomial root-finder algorithm (qpmr) [19] is implemented in matlab. the function expects the region of interest [βmin, βmax, ωmin, ωmax] to be in the complex plane of the polynomial coefficient matrix of the quasi-polynomial where one row corresponds to one polynomial multiplied by the same exponential term. the delay vector, computational accuracy and grid step are also required. in our case this translates into a region of interest [− 1 τ , 0,− 1 τ , 1 τ ] if the smallness condition (eq. 17) is satisfied. the first row of the matrix of polynomial coefficients contains the coefficients of the delay-free part so that the delay vector is of the form [0, τ, 2τ, ...]. the algorithm covers the given region with a mesh grid, then evaluates the quasi-polynomial at each point of the grid by splitting it into a real and an imaginary part. the zero-level curves are then mapped with the help of the contour plotting algorithm. the computational error is checked and if it is too large, the algorithm is restarted using a modified grid density as described in ref. [16]. if the computational error is smaller than the given level of tolerance, the computed dominant eigenvalues are returned. 5. explicit matrix approximation method an approximation method was devised where the convergence rate is exponential, the degree of the resulting system in the form of eq. 4 matches exactly the degree of the delayed mas given in eq. 15, and the same properties are exhibited in specific cases. the banach fixed-point theorem was used as discussed in ref. [20] to explicitly find a linear system of the form of eq. 4 which approximates the homogeneous part of the system in eq. 10. if an (x, f) metric space is present and t : b → b is a contraction with a bounded set b ⊂ x , and q < 1 such that f(t (x), t (y)) ≤ qf(x, y) (33) by definition t admits a unique fixed point x̃ such as t (x̃) = x̃, and this fixed point can be found by starting from an arbitrary element x0 ∈ b with the sequence xn = t (xn−1), (34) where xn → x̃. a dde system is defined in eq. 15 by the corresponding smallness condition of eq. 16. since all normed spaces are metric spaces, the metric space x = rn×n is set with f as the induced matrix norm. the contraction t : b → b is present such that t (λ) = −φ + γe−λτ , (35) and b = {λ ∈ rn×n|‖λ‖ ≤ (‖φ‖ + ‖γ‖)e}. the relation in eq. 33 holds true for (‖φ‖+ ‖γ‖)τe < 1. let λ1,λ2 ∈ b such that ‖λ1‖ > ‖λ2‖. the left side of the inequality in eq. 33 can be written as ‖t (λ1)− t (λ2)‖ = ‖γ‖‖e−λ1τ − e−λ1τ‖. it is evident that ‖γ‖ ≤ ‖γ‖ + ‖φ‖ and the maximum norm can be used as ‖e−λ1τ − e−λ1τ‖ ≤ τ‖λ1 − λ2‖eτ max{‖λ1‖,‖λ2|}. hungarian journal of industry and chemistry approximation of multi-agent systems with delays 75 it can be seen that ‖t (λ1)−t (λ2)‖ ≤ τ‖λ1−λ2‖(‖γ‖+‖φ‖)eτ(‖γ‖+‖φ‖)e and by applying the smallness condition ‖γ‖ + ‖φ‖ ≤ 1/(τe) (eq. 17), ‖t (λ1)− t (λ2)‖ ≤ ‖λ1 − λ2‖ is obtained, which proves that t : b → b is a contraction. this shows that by solving λ = −φ + γe−λτ (36) for the λ matrix, a system is created dx̃ dt = λx̃, (37) which approximates the dde system of eq. 15. as a result of the proposed iterative method, the eigenvalues and eigenvectors of eq. 37 approximate, with a given degree of precision, the dominant eigenvalues of eq. 14. 5.1 comparison with the existing methods • chain approximation: + the result is an approximating system with known system matrices (both eigenvalues and eigenvectors are known). the resulting system is of a higher degree than the delay system. the convergence rate of the algorithm is linear. • lambert w function: + the result is a trajectory approximation. + the convergence rate of the algorithm is exponential. the algorithm requires numerical solvers for an exponential matrix equation. multiple branches of the lambert w function must be used to create an accurate approximation, and the number of eigenvalues in a branch cannot be predetermined generally. • qpmr algorithm: + the algorithm determines the exact number of eigenvalues in the given complex domain, with the given computational error. + the convergence rate of the algorithm is exponential. the algorithm uses the quasi-polynomial equation, thus, will not contain any information on the eigenvectors. the algorithm uses numerical solvers to compute the zeros of the zero-level curves created from the quasi-polynomial equation. • approximation of an explicit matrix: + the result is an approximating system. + the resulting system is of the same degree as the approximating system. the algorithm calculates a matrix exponential numerically, which is a compute-intensive task. 6. simulations and results let us consider two cases: a mas consisting of five and twenty-five agents, respectively, with first-order dynamics in a platoon configuration as shown in the relation of eq. 10, with the constant initial condition θ(h) = x0. for the comparisons, a 6th order chain approximation was used. in the case of the lambert w function, the initial matrix q0 = ( 1 1 1 1 ) and the branches k = −2,−1, 0, 1 were used. for the quasi-polynomial rootfinder algorithm (qpmr), a symbolic calculation to find the characteristic quasi-polynomial equation of the system was used, and the plane of the search was set to [−τ, 0]× [−τj, τj]. the algorithm for explicit matrix approximation was used with the initial matrix λ0 = 0n×n. the error threshold 1e−7 was used in every iterative algorithm. the dominant eigenvalues of the system consisting of five agents, with minor differences, was identified by every approximation method. in the case of the larger system, the chain and explicit matrix approximations could generate a result, while the quasi-polynomial root-finder algorithm and the lambert w function were determined by numerical calculations. as such, the smaller system was chosen as a point of comparison for the algorithms. tables 1 and 2 contain a comparative summary of the four aforementioned algorithms: the number of iterations, the overall computation time and the dominant eigenvalues identified for a platoon consisting of five agents as shown in fig. 2. fig. 3 shows that the linear system is generated by the explicit matrix approximation in just twelve steps for the dmas that consists of twenty-five agents. fig. 4 shows that the resultant approximating system exhibits the same steady-state and transient behavior as the original delayed system using the same initial conditions. since the initial position falls within the range of table 1: the number of iterations and the overall computation time for the algorithms. name of algorithm no. of cycles computation time chain approximation 1 0.02 s lambert w function 35 7.5 min qpmr algorithm 12 17.18 s explicit algorithm 4 0.03 s 47(1) pp. 71–77 (2019) 76 fehér and márton table 2: the eigenvalues returned by the studied algorithms. name of algorithm eigenvalues chain approximation -0.1080, -0.9471, -1, -2.4736, -4.2511 lambert w function -0.1081, -0.9482, -1, -2.4658, -4.1603 qpmr algorithm -0.1081, -0.9481, -1, -2.4661, -4.1603 explicit algorithm -0.1080, -0.9481, -1, -2.4661, -4.1603 -4.5 -4 -3.5 -3 -2.5 -2 -1.5 -1 -0.5 0 re( ) -1 -0.5 0 0.5 1 im ( ) figure 2: dominant poles of the dmas consisting of five agents. 0 20 40 60 80 100 120 number of iterations (1) -60 -50 -40 -30 -20 -10 0 10 20 30 tr ( n ) tr( n ) |tr(| n )-tr( n-1 )|=1e-6 figure 3: the explicit matrix approximation returns a valid system after 12 iterations for 25 agents. 0 to 100 m, the error of the approximating system is 8 cm in the transient domain and 5 mm under steady-state conditions, as shown in fig. 5. 7. conclusions an iterative algorithm was proposed and tested based on which a degree-preserving approximation model can be created for a class of mas in a platoon formation consisting of agents that exhibit first-order dynamics in the presence of a small communication delay. the algorithm uses methods of numerical computation. the obtained mas is of the same degree and steady state as the delayed mas, moreover, it correctly approximates the transient behavior. the algorithm was compared with existing methods for approximating eigenvalues and systems. simulations show that the presented algorithm is suitable for the analysis of complex mas. 0 50 100 150 200 250 300 350 400 450 500 time (s) 0 10 20 30 40 50 60 70 80 90 d is ta n c e ( m ) figure 4: the trajectories of the platoon of the delayed mas compared to the platoon of the approximated mas created by the explicit matrix approximation. 0 10 20 30 40 50 60 70 80 90 100 time (s) -0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08 d is ta n c e ( m ) figure 5: the trajectory of the approximation error. acknowledgement the authors would like to express their gratitude to dr. mihály pituk (university of pannonia, hungary) for his useful comments. references [1] kubera, y.; mathieu, p.; picault, s.: everything can be agent!, in proceedings of the ninth international joint conference on autonomous agents and multi-agent systems (aamas’2010) (w. van der hoek, g.a. kaminka, y. lespérance, m. luck, s. sen, eds.) 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https://doi.org/10.1007/978-3-319-01586-6_2 hungarian journal of industry and chemistry vol. 47(1) pp. 79–83 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-12 rule-base formulation for clips-based work ergonomic assessment benedek szakonyi *1, tamás lőrincz1, ágnes lipovits2, and istván vassányi1 1department of electrical engineering and information systems, university of pannonia, egyetem u. 10, veszprém, 8200, hungary 1department of mathematics, university of pannonia, egyetem u. 10, veszprém, 8200, hungary modern societies are dominated by computer-based work. as a result, people tend to be seated for most of their working life. prolonged sedentariness is known to significantly increase the risk of developing unwanted conditions. this paper presents the development of a rule-based expert system module using clips that provides ergonomic assessment. the system was validated by evaluating pre-recorded user logs from real-life office environments. the tests showed that the system is able to perform the required basic assessment functionality, thus, the implementation of more complex features to advance its development is viable. keywords: expert system, clips, work ergonomics 1. introduction civilization-related diseases have become more widespread over time, although small improvements to our lifestyle could effectively reduce both their severity and number of sufferers. as adults spend a significant proportion of time working, which for the vast majority involves sitting in front of a computer [1], under what conditions this time is spent is very much relevant. thanks to tools of information technology and ergonomics experts, it is possible to provide automated solutions, in terms of monitoring and assessing user behaviour, to help more employees avoid the adoption of undesirable and harmful postures whilst at work. research has already shown that providing such real-time feedback to users can promote this, thus, reducing the impact of related negative effects [2, 3]. but in these cases, wearable sensors were used to track user motion, which can be considered problematic to be applied in real life applications. a possible solution to this might be microsoft’s kinect sensor [4] that, being a good value-formoney motion capture device, has already been used in similar cases [5, 6]. in spite of this, just as in numerous other papers that concern work-related assessment [7–10], considerably more focus is placed on manual labour where “blue-collar workers” are subject to physically demanding conditions (e.g. production lines, agricultural or construction work, etc.). even though these fields are of equal importance, such conditions cannot be applied to office environments, where “white-” and *correspondence: benedek.szakonyi@virt.uni-pannon.hu “pink-collar workers” spend most of their time, as here the majority of problems does not originate from incorrect movement (e.g. bad techniques when lifting heavy items) but rather from the (utter) lack of movement itself and prolonged sedentariness. the aim of this research was to develop an expert system module for ergonomic assessment (based on a previously created lifestyle coach framework [11] as shown in fig. 1 with an emphasis placed on the formulated work ergonomics-based rule set, and to investigate if such a system is capable of properly evaluating user behaviour in office environments. 2. experimental 2.1 the framework used the lifestyle coach framework used in the development process is a rule-based expert system framework using clips (c language integrated production system) [12]. the main reason for using a rule-based solution (instead of neural networks, fuzzy logic, etc.) is the fact that most healthcare experts can express their knowledge using simple if-then-like statements, which is exactly how rule-based systems work. the clips runtime is responsible for providing the basic functionality of evaluating the current state of the system and deducing the most suitable response and reactions. the statements that describe the current state and different events are called facts, while rules convey the relevant information concerning what actions to take in mailto:benedek.szakonyi@virt.uni-pannon.hu 80 szakonyi, lőrincz, lipovits, and vassányi figure 1: the components of the framework used. the event (or absence) of such facts, in the form of “simple” if-then expressions. the majority of these components are neither predefined nor hardcoded in the framework itself (except for those that are automatically generated) but are to be defined in light of the specific topic and task at hand in the form of a rule set. hence the framework can be applied in different fields as long as the problem is interpretable as the evaluation of a log of successive events. these events are transmitted to the system via the protobuf interface (that uses google protobuf [13]), which also serves as a tool to receive the corresponding responses. the messages of which can be categorized into two types, namely control and event. the former is used to manage the expert system itself, e.g. to signal that a unit of time has passed and re-evaluation of the state of the system should be commenced. the latter serves as a way of inserting new facts (incoming data) and handling consequences (outgoing reactions). how such messages are interpreted and forwarded is the responsibility of the event dispatcher. apart from bridging the gap between the interface and clips runtime, it is also connected to a database that is used to initialize (i.e. it stores the rulebase used), record system behaviour and act as a backup should anything fail. 2.2 work ergonomics to create the rule base required for ergonomic evaluation, methods used to estimate the risks of developing musculoskeletal disorders (msds) were analysed, with the help of ergonomics experts. the most popular and widely accepted tools used for such tasks are rula (rapid upper limb assessment) [14], reba (rapid entire body assessment) [15], owas (ovako working posture analysis system) [16] and harm (hand arm risk-assessment method) [17]. rula applies a scoring method for measuring the physical load that workers are subjected to when adopting specific postures by taking into consideration six main body regions: neck, trunk, legs, upper arms, forearms and wrists. reba works in a similar fashion by using scores but takes into consideration the whole body when such postures are adopted. owas uses a 4-digit score for each posture where the digits describe the back, arms, legs and load. harm accounts for the head, neck, arms and wrists as well as the forces that are applied and the duration over which each posture is adopted. however, these methods cannot be used directly for the matter at hand as originally none of them were intended to be used in regular office environments: rula was developed to assess work in the textile industry, reba in healthcare, owas in the steel industry, and harm in hand-intensive professions (e.g. barbers, product assembly/disassembly, woodwork, etc.). based on these tools, a basic method of postural assessment was derived as presented in table 1. it is important to note that when subject to these constraints, the values used were chosen as initial limits as a proof of concept in light of the fact that they may need to be updated. for each body part, the relevant axes of movement were selected and for each axis, ranges were defined. a range can be characterised into three types: appropriate, incorrect and harmful. appropriate ranges define the desired position the user should take, while harmful ones represent postures that should be avoided or even prohibited. incorrect ones fall somewhere between the other two categories, when, as far as is feasible, a posture should be prevented since it is considered unhealthy, however, when adopted for short intervals of time it is still acceptable. for the ranges of the inappropriate postures, a frequency is given, that describes that in one work hour, how much time spent in them (in total) is still considered as tolerable. apart from evaluating specific body parts based on their position, the time the user spends sitting was also selected to be taken into account, as a general aspect. 2.3 rule-base formulation the formulation of the constraints introduced in table 1 that are applied to a clips-based rule set could have been determined using numerous different approaches. the one that was selected, builds on the fact that the implementation of these aspects has the same general structure: 1. there are numerical measurement values to be evaluated over each time interval 2. there is a constraint that the measured values are compared to when evaluated 3. there is a frequency that, if exceeded, should trigger a warning to be sent. therefore, instead of creating multiple rules for each aspect, one main rule can be defined and applied during the evaluation which can make use of an “aspect template” to check if the related conditions have been adhered to or not. to achieve this, as rules in clips are governed by facts, the aspects are to be in the form of facts. in fig. 2 the template used for defining aspects is shown. the aspect_type serves as a name/identifier for the aspect, while measurement_type defines which measurements hungarian journal of industry and chemistry rule-base formulation for clips-based work ergonomic assessment 81 table 1: the advised constraints to be used in the formulated rule base. for each body part, separate ranges were used for the different planes of movement. the acceptable duration within each range was defined (as % of 1 working hour). body part axis range frequency head/neck sagittal < 0 < 20% 0 < < 10 10 < < 30 < 40% 30 < < 20% horizontal < ±10 ±10 < < ±30 < 40% ±30 < < 20% frontal < ±5 ±5 < < ±10 < 40% ±10 < < 20% trunk sagittal < 0 < 40% 0 < < 15 15 < < 25 < 40% 25 < < 20% horizontal < ±5 ±5 < < ±10 < 40% ±10 < < 20% frontal < ±5 ±5 < < ±10 < 40% ±10 < < 20% upper arm sagittal < −10 < 20% −10 < < 0 < 40% 0 < < 10 10 < < 45 < 40% 45 < < 20% frontal < 10 10 < < 20 < 40% 20 < < 20% forearm sagittal < 60 < 20% 60 < < 80 < 40% 80 < < 100 100 < < 110 < 40% 110 < < 20% should be inspected. in spite of some axes, where ranges of constraints are “evenly distributed” or “symmetrical” (e.g. head frontal, trunk sagittal), the relation between the measured data and the constraint must be provided in the constraint_type template, as for other cases, the ranges are “uneven”. this type can be either smaller than or equal to, or greater than or equal to, followed by the value to use in the value_constraint. the horizon_minute slot is used to determine the duration of measurement that is to be examined (e.g. the last 60 minutes). as cases may occur when, despite being warned, users continue to follow their unhealthy lifestyle, a feature that permits repeated warnings of increasing severity (or even more extensive interventions such as turning off the computer screen) could be useful. in the logic developed, checking whether the user has taken the advice given or not is considered to takes less time than the original evaluation interval (this will have an impact on the main evaluating rule, that is detailed later on). with regard to this feature, apart from the first_occurrence_constraint that corresponds to the frequency in table 1 and the first_reaction_event_code that defines what actions to take if the limit has been reached, (deftemplateaspect_to_monitor (slot aspect_type (type symbol)(default ?none)) (slot measurement_type (type symbol)(default ?none)) (slot constraint_type (type symbol)(default ?none)) (slot value_constraint (type number)(default ?none)) (slot horizon_minute (type number)(default ?none)) (slot first_occurrence_constraint (type number)(default ?none)) (slot first_reaction_event_code (type number)(default ?none)) (slot repeated_occurrence_constraint (type number)) (slot repeated_reaction_event_code (type number)) (slot repeated_feedback_horizon (type number)) ) figure 2: the clips fact template used for describing the structure of ergonomic aspects. optional repeated_ slots can be used for this purpose in the template. as the evaluating clips rule is lengthy, only a short explanation of the logic behind it is provided here. over each evaluation interval, the number of measurements that exceed the given constraints during the corresponding time horizon is counted, and if this value is above the acceptable limit, a request to send feedback is made and the related measurements are labelled as evaluated (according to the current aspect). if only a few “bad” measurements are identified, the evaluation is considered to be finished, unless repeated feedback is received with regard to the current aspect. in that case, it must be determined if a “first feedback” was given recently, and if it was, the number of measurements that exceed the limit must be compared to the occurrence constraint of the second feedback. if this is exceeded, a second feedback is sent. 2.4 experiments for rule-base validation as the aim of the research was to provide feedback for users concerning their postures by using a rule base consisting of ergonomic rules, a method for recording and identifying their postures was needed. to accomplish this, a microsoft kinect v2 sensor was used. as it is an easy-to-use and relatively small device, it was possible to insert it into the real working setups of the willing participants, with only slight modifications in their environments. the general setup that was created for all users was the following: each user was seated at a desk with a personal computer that consisted of 1 or 3 displays, a keyboard, a mouse and a landline telephone. the sensor was placed on a tripod behind and slightly above the “main” screen (i.e. the one in front of the user). the kinect was tilted forward in order to ensure as much of the participant as possible was in view (from the top of the head down to the waist/hips). users were monitored according to two different “behaviour modes”, one being general “everyday” attitude where they completed their daily computer-based tasks as usual. as this inherently meant that users might have had to leave their desks, long measurement sessions were recorded (up to 8 hours in duration) where logging was 47(1) pp. 79–83 (2019) 82 szakonyi, lőrincz, lipovits, and vassányi suspended once the absence of the participant was detected until their return, when it was resumed (such “gaps”, of course, were then taken into account as part of the evaluation). in the other “mode”, where considerably shorter measurement intervals were used in order to ensure sessions that definitely consisted of unsuitable behaviour, the users were asked to adopt some evidently inappropriate postures. as the framework used offers a customisable time unit for defining when an interval stops (i.e. it can last for an hour, a minute, a second, etc.), it was possible to load and evaluate the logs gathered using this method quickly. 3. results and discussion based on the evaluation method suggested by the ergonomist experts, a total of 11 aspects have been formulated (by using 34 facts), 9 for the positions of the body parts (one for each axis using the constraints shown in table 1) and 2 regarding sedentariness, where the acceptable duration of continuous sitting was chosen to not exceed 60 minutes (the first aspect was related to sending a warning once this limit had been reached, the second was used to alert when a participant had been sitting continuously for 3 hours). subsequently the recorded user logs were evaluated, for the majority of aspects used (10 out of 11) the expected functionality was achieved. however, in the case of the facts responsible for assessing head positions, considerably more warnings were sent by the system than was acceptable. as for manually created input (simulated user postures), this behaviour had not emerged again, examination of the monitoring software developed have begun. upon inspection of the logs created, it was found that this error was a result of improper calibration: the inaccuracy of the sensor itself was higher than anticipated and the distortions that resulted meant that even when the user evidently adopted a suitable posture, the logged value exceeded the threshold defined as acceptable. based on this information, the related constraints were adjusted accordingly and this undesirable behaviour of the system was successfully removed. this source of inconvenience, however, highlights the possible sensitivity and dependency of the system, i.e. the reliability of the measurement data received. still, its significance might be diminished by utilizing methods developed for improving the accuracy and error tolerance of kinect, such as the ones proposed in [18–20]. in general, it can be said that the system developed and the initial rule set created are capable of providing the required functionality. however, there is still room for improvement as the constraints involved could be fine-tuned and additional or more precise aspects implemented. moreover, a more complex system capable of adapting to user behaviour could also be created, the main goal of which would be to assist users, without being too rigorous or repetitive, by changing how frequently and in what manner its responses are displayed. this could help to maintain the motivation of workers to break bad habits concerning improper postures whilst seated. even though the number of participants in the experiments conducted was sufficient to validate the initial version of the expert system, further investigations with considerably larger user groups are desirable as they would provide a more thorough validation and may yield additional insight into what other aspects the system could provide assistance to users. additionally, while the recording sessions, on average of 5-6 hours in duration, implemented so far have been useful, by extending these to a few days or even a couple of weeks, more complex behavioural patterns could be identified and analysed. furthermore, by providing real-time assessment over much longer periods, the effects caused by this intervention could be investigated and subsequently the methods used to assist users improved. nevertheless, from the results that have already been logged, it can be clearly seen that the global tendency of users to be seated for longer periods of time than is advisable was also exhibited by the cases investigated. most participants reported that over such prolonged sessions whilst seated, a need to change position is common, however, usually a better alternative cannot be found. a solution to this problem could be to provide workers with electric height adjustable desks, which may facilitate the ability to switch easily between sitting and standing working postures and customise the height of desks to match the anthropometric features of the individual. moreover, such furniture could enable the expert system itself to “take action”, when needed, to raise the desk when users fail to heed previous warnings. it should be noted that, when asked, most of the participants considered such a monitoring and assessment system to be useful, however, some, while welcoming the idea of an adjustable desk, expressed concerns about personal security and were reluctant to be “continuously monitored”. this reveals that if such a system enters the market, apart from providing the necessary security measures, assuring users that their personal data is safe would also be necessary. 4. conclusion in this research a proof-of-concept clips-based rulebase for an expert system was created to facilitate ergonomic evaluation of users in office environments. it has been shown that such a system is capable of thoroughly evaluating user behaviour, thus, implementing interventions 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https://doi.org/10.1016/j.promfg.2015.07.591 https://doi.org/10.1080/10803548.2017.1306960 https://doi.org/10.1139/cjce-2015-0143 https://doi.org/10.5334/bbe http:\www.clipsrules.net/?q=aboutclips http:\developers.google.com/protocol-buffers http:\developers.google.com/protocol-buffers https://doi.org/10.1016/s0003-6870(99)00039-3 https://doi.org/10.1016/0003-6870(77)90164-8 https://doi.org/10.1016/j.ergon.2013.09.003 https://doi.org/10.1016/j.ergon.2013.09.003 https://doi.org/10.1007/s11042-016-3546-4 https://doi.org/10.1007/s11042-016-3546-4 https://doi.org/10.1109/tcyb.2013.2275945 https://doi.org/10.1145/2671015.2671021 introduction problem statement non-technical losses detection and localization basic assumptions uncertainties and measurement errors diagnostic method single-feeder layout radial layout diagnostic algorithm case study case 1: one illegal load case 2: more illegal loads in different subnetworks conclusions and future work introduction modelling description of the quantum algorithm description of the randomized, exhaustive and sequence-searching algorithms evaluation of the algorithms comparison according to computational complexity comparison of the uniformity results and analysis experiments simulations conclusion introduction experimental measurement of the gamuts of the displays used in our experiments and key parameters of our model simulation formula simulation validation of the simulation results and discussion conclusion introduction system description and assumptions structural assumption orbital assumption thermal assumption thermal mathematical model (tmm) first interval equations second interval equations third interval equations the transient heat transfer of the spherical propellant tank computational results the pw-sat faces composed of 100 % uncoated aluminum the faces of the pw-sat are composed of 100 %-coated aluminum the faces of the satellite exposed to the sun during its orbit are covered with 70 % aluminum and 30 % solar cells the faces of the satellite exposed to the sun during its orbit are covered with 30 % aluminum and 70 % solar cells conclusion introduction proposed open-world recognition system double probability model unknown image clustering baseline method cluster classification experimental results conclusion introduction theoretical background of the experiment sliding mode-based disturbance elimination application tuning the disturbance compensation design of the disturbance compensation component calibration of the model verification of the model results and discussion final model conclusion introduction method of node voltages the generalized nodal equations network model topology verification method of node powers constant iteration current dynamic iteration current simulation results conclusion introduction problem statement astronomical relationships sun-earth geometries comparison of the available solar geometry models relative sun-earth distance solar declination equation of time solar beam equations global solar irradiance irradiance on a horizontal surface irradiance on the slope model verification conclusions introduction aggregator framework aggregator role architecture services offered and customers flexibility resources optimization phases requirements of optimization day-ahead planning intraday operation direct generation and load dispatch conclusion appendix: acronyms appendix: definitions introduction modelling of mas platoon of vehicles existing methods for the approximation of time-delay systems the modified chain approximation the lambert w function the quasi-polynomial root-finder algorithm explicit matrix approximation method comparison with the existing methods simulations and results conclusions introduction experimental the framework used work ergonomics rule-base formulation experiments for rule-base validation results and discussion conclusion hungarian journal of industry and chemistry vol. 49(2) pp. 65–70 (2021) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2021-24 using finite element analysis in the 3d printing of metals hussein alzyod*1 and péter ficzere1 1department of railway vehicles and vehicle system analysis, budapest university of technology and economics, műegyetem rkp. 3, budapest, 1111, hungary over the last few years, additive manufacturing, or as it is sometimes known, 3d printing, has become a significant research field for researchers worldwide. the necessity to increase the strength of materials and minimize their weight in the automotive and aviation industries has urged engineers and scientists to conduct more investigations and identify manufacturing methods to replace the classical ones. additive manufacturing involves building a geometry layer by layer from a wide range of materials, which helps to utilize materials efficiently while minimizing the amount of waste produced as well as build complex, large geometries and light-weight components. furthermore, it minimizes fabrication and processing times. in this paper, three different alloys were printed (tial6v4, alsi10mg and 316l) using msc simufact software to investigate the effect of changing machines on the effective stress and surface deviation. furthermore, thermal analysis as well as mechanical, thermal and thermomechanical calibrations were carried out to determine a parameter set consisting of the laser power, inherent strains, fraction of exposure energy and volumetric expansion factor. keywords: additive manufacturing, 3d printing, simufact additive. 1. introduction over the last three decades, research into printing technology/additive manufacturing (am) has progressed from fast prototyping to industry 4.0 [1,2]. the third industrial revolution took place in 1987 with the commercial exploitation of the first stereolithography (sla) machine, which was developed by 3d systems and named sla-1. after many editions of sla machines in the early 90s, new am principle technologies were launched, namely solid ground curing, fused deposition modeling and laminated object manufacturing [3, 4]. this development was followed by many years of continuous improvement in am technology, from resin to metal powders and from non-functional molding applications to the fabrication of medical implants [5]. am methods have been characterized in the literature based on a variety of parameters, including direct or indirect process technology, the state of the raw materials, and the materials used. the state of the raw materials is the most commonly used as illustrated in fig. 1. am is a revolutionary manufacturing technique proliferating as major industries transition from conventional to advanced production methods. threedimensional printing is used in am to convert engineering design files into fully functional and durable structures. after the components in the first layer have been bonded together using glue or heat, the second layer *correspondence: hussein.alzyod@edu.bme.hu is constructed and the bonding procedure repeated, enabling the construction of previously unimaginable geometries. am creates samples of products quickly, which is crucial since it reduces the traditional trial-and-error process, allowing novel ideas to enter the market more quickly. it may also be used to rapidly create bespoke metal items to replace old or broken industrial parts. 1.1 part-building technology metal am can be classified into four main categories as shown in fig. 2: directed energy deposition, powder bed fusion, sheet lamination and binder jetting. table 1 shows the thickness of layers in each process [6]. 1.2 fields of application metal 3d printing is the fastest-growing sector. metal am is increasingly being utilized to create final products table 1: the thickness of layers in the metal am process [6]. processing the thickness of layers (mm) directed energy deposition 0.089 − 0.203 powder bed fusion 0.08 − 0.15 sheet lamination 0.1 − 0.19 binder jetting 0.089 − 0.203 https://doi.org/10.33927/hjic-2021-24 mailto:hussein.alzyod@edu.bme.hu 66 alzyod and ficzere figure 1: types of additive manufacturing processes based on the state of raw materials [1]. figure 2: classification of metal additive manufacturing technologies [5]. in many sectors like in the aviation, automotive, medical implants, material handling robotics as well as lifestyle and sport industries. the aviation industry companies in this sector are among the most well-known early investors of am technology since they were among the first to upgrade from modest research projects to large-scale production runs. norsk titanium, airbus, alcoa and ge amongst others have begun serial production or are planning to invest in significant manufacturing operations within am [7]. the automotive industry for many years, the automotive industry has utilized 3d printing to rapidly prototype single test components or entire visualization models. leading companies are experimenting with am. small series or customized production may be the first sectors to adopt this technology [7]. 1.3 modeling approach in simufact many commercial companies, e.g., autodesk, general electric (via geonx), msc software, ansys, etc., provide am simulation, which enables designers to understand where the critical zones in a particular geometry are located and produce approximate first findings within a few hours. with this information, designers can iteratively develop their concept by taking all aspects into consideration using simulation software rather than wasting time and money on the actual manufacture of a possibly unsuitable design. simufact is a piece of software hungarian journal of industry and chemistry brownian dynamics simulation of chain formation 67 figure 3: additive manufacturing workflow [own edition]. that uses finite element analysis to simulate metal am by focusing on powder bed fusion processes. the difficulties with metal powder bed fusion am can be addressed and analyzed by simulations [8]. as is shown in fig. 3, the am workflow to date has been one of the best traditional manufacturing technologies. the revision of am goes through those processes to select the best predicted design parameters, build orientation, removal cutting, supporting structure, etc. [9]. three-dimensional objects are constructed from several thin layers, each of which with a pattern defined by a computer-aided design (cad) that is exposed using a scanning laser for stereolithography or a pattern in the absence of a mask. manufacturing information is obtained from cad or other design software before being sliced into individual layers using the standard tessellation language [10]. sometimes, the building fails due to many reasons, e.g. supporting structures or a high degree of distortion. once the best predicted design parameters have been chosen, construction commences and an inspection is made. if any defects are observed, the component is subjected to a process of trial and error to achieve the desired part. alternatively, as illustrated in fig. 4, a virtual model can be built to minimize the number of required physical builds figure 4: am simulation workflow [own edition]. in the am simulation workflow. in this virtual model, different approaches can be applied, e.g. various parameters, changing supporting structures, building orientation, and keeping treatment cutting and support removal to achieve the desired product free from any adverse effects of the process the first time it is constructed. since a feedback loop is included in the simulation, the results of the process simulation can impact topology optimization. the significant benefits of this are that the formation of some of these parts may cost thousands of dollars and the trialand-error approach is quite undesirable. 2. design methodology and simulation given that am depends on many factors to determine the required parameter set to produce the desired part, e.g., laser power, fraction of exposure energy and volumetric expansion factor, experimental tests should be conducted to measure these parameters. 2.1 sample selection as is shown in fig. 5 of the simulation, an aircraft component was chosen because of the complexity of its geometry and the importance of am in the aerospace industry, 49(2) pp. 65–70 (2021) 68 alzyod and ficzere figure 5: an aircraft component [9]. e.g., in increasing asset uptime, reducing costs, manufacturing lighter parts, enhancing durability and improving customer satisfaction. 2.2 material selection three alloys (tial6v4, alsi10mg and 316l) were chosen with different properties to construct the sample for the purpose of investigating the effect of each material on the surface (shape) deviation with respect to the original sample. 2.3 machine selection different types of 3d printing machines are available using this piece of software, e.g. two kinds of electro optical systems (eos) have been used, namely m280 and m400, the size and power of both differ. 2.4 thermal analysis the laser power has to be adjusted, moreover, the printing temperature has to be greater than the melting point of each alloy but less than its boiling point. 2.5 mechanical calibration the purely mechanical, macro-scale analysis approach of simufact additive requires the input of the so-called inherent strain values before the simulation. as is shown in fig. 6, the inherent strain values are produced during the construction process as a result of plastic strain, thermal strain and phase transformations as shown in εinherent = εth + εpl + εph. (1) moreover, they depend on material properties and process parameters. these strains can be calibrated from experiments, e.g. by measuring the degree of distortion after cutting a printed cantilever beam and running simulations to match the experimental distortion values that should be less than 3%, or estimated based on the process. this paper used the empirical calibration by printing two cantilevers on the xand y -axis as is shown in fig. 7 that are 72 mm figure 6: inherent strain [9]. figure 7: printing two cantilevers [9]. in length, 12 mm in width, and 9 mm high. afterwards, the cantilevers are cut in the middle of the teeth, so a particular part of them remains on the base plate. finally, the maximum observed distortion in the z-axis was measured as shown in fig. 8. three values of strains are inputted into the build stage dialogue (εxx, εyy, εzz). these values are dimensionless and defined in three directions, x , y , and z. default values will be shown in the dialogue [9]: εxx = −008, εyy = −0.003, εzz = −0.030. (2) the mechanical calibration was carried out for the three alloys, namely tial6v4, alsi10mg and 316l, to calculate the inherent strains. 2.6 thermomechanical calibration the thermomechanical analysis requires that the fraction of the exposure energy and the volumetric expansion factor have been calculated before the simulation is started. figure 8: measuring the distortion in the z-axis [9]. hungarian journal of industry and chemistry brownian dynamics simulation of chain formation 69 figure 9: thermal calibration since these values depend on material properties and machine parameters, they need to be carefully calibrated, which should be done experimentally. 2.7 fractions of exposure energy the fraction of exposure energy is a term that is responsible for the peak temperature of the process. during the exposure time, the energy predominantly (but not only) melts the powder. the rest of the powder reheats the solid material after the exposure time. for the purpose of thermomechanical calibration, it is recommended to carry out the thermal calibration first to determine the optimized exposure energy and then conduct the thermomechanical calibration with the optimized fraction of the exposure energy to calibrate the volumetric expansion factor. the calibration was carried out using a specimen of a cantilever. the peak temperature has to be measured during the process to determine the maximum degree of distortion in thez-axis after cutting, as is shown in fig. 8. the measured point was chosen on the upper surface because the temperature is the highest there and the average will be recorded between the two surfaces. thermal calibration of the three alloys, that is, tial6v4, alsi10mg and 316l, was carried out to determine the fraction of exposure energy. the thermal calibration of tial6v4 is shown in fig. 9. 2.8 volumetric expansion factor the volumetric expansion factor accounts for the thermal expansion and shrinkage effects caused by the modelling approach, that is, by combining multiple powder layers and repeated heating of the heat source in one element layer. the volumetric expansion factor can either be set to isotropic in all directions or anisotropic for each individual order and scales the thermal expansion factor of the material. volumetric expansion is the change in the volume of a given mass with temperature. the thermal expansion factor is a measure of the change in volume in three dimensions as is shown in eq. ??: v = 3αvo∆t (3) this equation is usually written as: v = βvo∆t, (4) where β = 3α denotes the volumetric expansion factor, vo represents the original volume and ∆t stands for the change in temperature. 3. results different machines and materials were used to print an aircraft component. as illustrated in table 2, changing the machine does not have any effect on the design or features of the sample. the effective stress in msc simufact was implemented once the printed aircraft component had been compared to calculations regarding residual stresses using stoney’s equation. the effective stress of both the m280 and m400 machines is identical. for the alloys tial6v4, alsi10mg and 316l, the stresses were 1260 mpa, 370 mpa and 680 mpa, respectively. when the m280 machine was used, the surface deviation, representing the difference between the designed and printed samples, of all three alloys did not change. however, when the m400 machine was used, the surface deviation in each alloy varied. the laser power of the machine, which is responsible for fusing the powder, is one of the most crucial elements to modify. as a result, the printing temperature of a material, which is roughly twice as high as its melting point, must be higher than its melting point but lower than its boiling point. for each alloy, the changes in laser power as well as the measured temperature are shown in table 3. for tial6v4, 200 w is a suitable power, while the optimal laser power for alsi10mg and 316l is 100 w. the mechanical calibration was carried out to identify the inherent stresses. for measuring the distortion in 49(2) pp. 65–70 (2021) 70 alzyod and ficzere table 2: the effects of the machines and alloys. material eos effective surface used machine stress [mpa] deviation [mm] max min tial6v4 m280 1262.03 0.17 −0.16 m400 1288.13 0.88 −0.93 alsi10mg m280 370.01 0.13 −0.12 m400 370.02 0.36 0.26 316l m280 683.19 0.17 −0.16 m400 680.65 0.16 −0.15 table 3: adjusting the laser power. alloy used melting laser printing point (c°) power (w) temperature (c°) tial6v4 1600 200 2650 alsi10mg 660 200 4220 150 3098 100 2084 316l 1400 200 4454 150 3500 100 2463 the beam, two points on the cantilever were chosen at heights of 3.09 and 2.01 mm. the simulation repeatedly printed the specimen until the permissible distortion error became less than 3%. the sample was printed seven times to achieve an acceptable degree of distortion. table 4 shows the inherent strains of the three alloys. since the volumetric expansion factor is a crucial parameter in 3d printing, the simulation carried out the thermomechanical calibration to determine the volumetric expansion factor, as is shown in table 5. 4. conclusion the simulation tool simufact was used to print a component of an airplane out of different alloys using am technology to determine the specified parameter and carry out virtual printing. as indicated in table 3, since the laser power has a massive effect on the printing temperature, it should be regulated carefully. furthermore, as indicated in tables 4 and 5, in order to determine the inherent strains and volumetric expansion factor, the component must be printed multiple times. references [1] hernandez korner, m.e.; lambán, m.p.; albajez, j.a.; santolaria, j.; ng corrales, l.d.c.; royo, j.: systematic literature review: integration of additive manufacturing and industry 4.0. metals, 2020. 10(8),1061 doi: 10.3390/met10081061 [2] alex, s.; árpád, t.: xbrl utilization as an automated industry analysis. hung. j. ind. chem., 2020, 48(1), 131–138 doi: 10.33927/hjic-2020-19 table 4: inherent strains of tial6v4, alsi10mg and 316l. metal εxx εyy εzz ns tial6v4 -0.00488099 -0.0022865 -0.3 7 alsi10mg -0.00637062 -0.0016680 -0.3 18 316l -0.0198353 -0.0025170 -0.3 3 ns: number of samples printed table 5: volumetric expansion factors for tial6v4, alsi10mg and 316l. metal volumetric expansion factor number of steps tial6v4 0.821869 18 alsi10mg 0.60999 2 316l 0.307238 24 [3] attaran, m.: the rise of 3-d printing: the advantages of additive manufacturing over traditional manufacturing. bus. horiz., 2017, 60(5), 677–688 doi: 10.1016/j.bushor.2017.05.011 [4] gábora, a.; varga, t. a.; kozma, i.; beke, s.; mankovits, t.: 3d geometrical reconstruction of closed-cell aluminum foam using ct images. in incell 2019: book of abstracts of the international conference on multifunctional cellular materials (ua editora universidade de aveiro.), page 74 isbn: 978-972-789-611-0 https://ria.ua.pt [5] li, j.z.; alkahari, m.r.; rosli, n.a.b.; hasan, r.; sudin, m.n.; ramli, f.r.: review of wire arc additive manufacturing for 3d metal printing, int. j. autom. technol., 2019, 13(3), 346–353 doi: 10.20965/ijat.2019.p0346 [6] loughborough, u.: the 7 categories of additive manufacturing, 2019, https://www.lboro.ac.uk [7] software solutions, s.s.s.a.s.: additive manufacturing technology, 2017, https://www.simufact.com [8] mankovits, t.: numerical analysis of unit cell models for orthopedic applications, iop conf. ser.: mater. sci. eng., 393, 012019 doi: 10.1088/1757899x/393/1/012019 [9] software solutions, s.s.s.a.s.: english webinar on the entire portfolio of msc software for additive manufacturing, 2017, https://www.simufact.com [10] rasiya, g.; shukla, a.; saran, k.: additive manufacturing-a review, mater. today: proc., 2021, 47(1), 6896–6901 doi: 10.1016/j.matpr.2021.05.181 [11] schelhorn, l.; gosch, m.; debeugny, l.; schroter, p.; schwarz, w.; soller, s.: optimal design and process simulation for additive manufacturing, in 8th european conference for aeronautics and space sciences, eucass2019-fp0354, madrid, spain, 1–15 doi: 10.13009/eucass2019-354 hungarian journal of industry and chemistry https://doi.org/10.3390/met10081061 https://doi.org/10.33927/hjic-2020-19 https://doi.org/10.1016/j.bushor.2017.05.011 https://ria.ua.pt/bitstream/10773/26710/1/abstractbook-incell2019.pdf https://doi.org/10.20965/ijat.2019.p0346 https://doi.org/10.20965/ijat.2019.p0346 https://www.lboro.ac.uk/research/amrg/about/the7categoriesofadditivemanufacturing/ https://www.simufact.com/additive-manufacturing.html#challenges-in-metal-am https://doi.org/10.1088/1757-899x/393/1/012019 https://doi.org/10.1088/1757-899x/393/1/012019 https://www.simufact.com/simufact-additive.html https://doi.org/10.1016/j.matpr.2021.05.181 https://doi.org/10.1016/j.matpr.2021.05.181 https://doi.org/10.13009/eucass2019-354 introduction part-building technology fields of application modeling approach in simufact design methodology and simulation sample selection material selection machine selection thermal analysis mechanical calibration thermomechanical calibration fractions of exposure energy volumetric expansion factor results conclusion page 1 page 2 page 3 page 4 page 5 page 6 page 7 page 8 page 9 page 10 page 11 page 12 page 13 page 14 page 15 page 16 page 17 page 18 page 19 page 20 page 21 page 22 page 23 page 24 page 25 page 26 page 27 page 28 page 29 page 30 page 31 page 32 page 33 page 34 page 35 page 36 page 37 page 38 page 39 page 40 page 41 page 42 page 43 page 44 page 45 page 46 page 47 page 48 page 49 page 50 page 51 page 52 page 53 page 54 page 55 page 56 page 57 page 58 page 59 page 60 page 61 page 62 page 63 page 64 page 65 page 66 page 67 page 68 page 69 page 70 page 71 page 72 page 73 page 74 page 75 page 76 page 77 page 78 page 79 page 80 page 81 page 82 page 83 page 84 page 85 page 86 page 87 page 88 page 89 page 90 page 91 page 92 page 93 page 94 page 95 page 96 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541 page 542 page 543 page 544 page 545 page 546 page 547 page 548 page 549 page 550 page 551 page 552 page 553 page 554 page 555 page 556 page 557 page 558 page 559 page 560 page 561 page 562 page 563 page 564 page 565 page 566 page 567 page 568 page 569 page 570 page 571 page 572 page 573 page 574 page 575 page 576 page 577 page 578 page 579 page 580 page 581 page 582 page 583 page 584 hungarian journal of industry and chemistry vol. 49(2) pp. 39–45 (2021) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2021-20 mechanical deburring of drilling-induced exit burrs in carbon fibre reinforced polymer composites andrás gödri1, anna nikoletta helle1, and norbert geier*1 1department of manufacturing science and engineering, budapest university of technology and economics, műegyetem rkp. 3, budapest, 1111, hungary carbon fibre reinforced polymer (cfrp) composites have excellent specific mechanical properties, which have contributed to the replacement of metallic structural components in high-tech sectors. however, the anisotropic and inhomogeneous properties of cfrps render them difficult to cut. burr is one of the main machining-induced macro-geometrical defects in cfrps. even though burr does not weaken the resultant strength of the composites (unlike delamination), its removal is time-consuming and costly. the main aim of the present paper is to investigate the efficiency of the mechanical deburring method. deburring experiments were carried out on unidirectional cfrp, based on a full factorial experimental design using a special solid carbide cutting tool. the effects of feed and cutting speed were analysed using digital image processing and visual evaluation of high-resolution images. the experimental results show that the examined factors seem to have no significant effect on the results over the applied parameter range, because the exit burrs were successfully removed at each parameter setting. furthermore, during the deburring process, the formation of a significant amount of chamfers was observed. since the size of the chamfers depends on the size of delamination-induced material deformation and process control, it should be either compensated for or monitored in the future to develop a more reliable deburring process. keywords: deburring, carbon fibre reinforced polymer, exit burr, drilling, digital image processing 1. introduction nowadays, carbon fibre reinforced polymer (cfrp) composites make up a significant proportion of materials used in the automotive, defence, aerospace, marine and space technology industries where it is almost indispensable [?]. the reason for their popularity is due to the fact that they have excellent mechanical properties, however, their anisotropic and inhomogeneous properties cause major problems like delamination, microcracks and burrs which have to be solved in machining. the main machininginduced defects in terms of machining cfrps are delamination and burrs which bring about inaccuracies and also damage the structure of the workpiece [?]. although the formation of burrs in quasihomogeneous materials like metals has been studied for decades, research into burr formation in fibrous composites is not that extensive. in fibre reinforced polymer composites, the burr formation mechanism strongly depends on the following five key factors: the material to be machined, the fibre cutting angle (θ), the machining direction, the supporting plate in use and the cutting edge radius (rβ). four types of chip-removal mechanisms are associated with machining unidirectional cfrps when the rake angle (γ) is positive and the cutting edge radius *correspondence: geier.norbert@gpk.bme.hu (rβ) is small: type i: θ = 0◦/180◦, type ii: θ = 45◦, type iii: θ = 90◦, and type iv: θ = 135◦. the fibre cutting angle has a significant effect on the texture of the machined surface as well as on the burr formation mechanism [?]. jia et al. [?] examined the effect of the machining direction at the working point. they observed that in the absence of an external supporting plate, the machining is bending-dominated and the probability of uncut fibres and burrs forming increased. however, if the fibre is supported by either a plate or a material, the machining is fracture-dominated and the possibility of surface damage is minimal. fuji et al. [?] investigated the effect of the cutting edge radius and fibre cutting angle on surface defects after machining and found that if rβ is relatively small, machining will occur with fracture-dominated fibre cutting. however, should rβ be too large, bending-dominated thread cutting takes place, where there is no guarantee that cutting will be successful. they also studied burr formation during drilling and observed that the area around the hole can be divided into four separate regions, where the boundaries of the regions were chosen based on the fibre cutting angles. these four regions are symmetrical in pairs and the same processes take place in them, as can be seen in fig. ??. if the fibre cutting angle is within the https://doi.org/10.33927/hjic-2021-20 mailto:geier.norbert@gpk.bme.hu 40 gödri, helle, and geier figure 1: surface damage as a result of drilling cfrp laminates using a worn tool [?] range of 90 ◦ < θ < 180 ◦, the material is machined under favourable conditions. this range is not characterized by burr formation but fibre pull-out occurs more frequently (depicted by the green range in the figure). if the fibre cutting angle is within 0 ◦ < θ < 90 ◦ (illustrated by the red range in fig. ??), the tool will machine the material under adverse conditions. within this interval, if the tool edge radius is large, burrs will always form here. xu et al. [?] examined burr formation, tearing and delamination with a digital microscope and an ultrasonic c-scan technique using three tools with different geometries. they observed that the feed has a significant effect on the extent of drilling defects. they also noted that while the cutting performance of brad and spur drills is the best during drilling, the dagger drill was the least satisfactory. the primary purpose of machining is to produce clear as well as burrand damage-free geometrical features. several suggestions have been made for the parameter set and the use of special cutting tools to ensure damage-free machining. yu et al. [?] investigated a new tool geometry for cfrp drilling. the double-pointed tool had an extragrooved helical cutting edge, which was significant due to the removal of burrs formed during drilling. the experiment was also performed with a conventional drill as a reference and later compared to the two results which showed that no burrs occurred at the exit point of the holes, even after more than 100 drilling operations had been performed. in the case of the improper selection of a machining technology and parameters, the remaining burrs can be reduced by deburring methods. islam et al. [?, ?] investigated the effectiveness of deburring strategies using electrical discharge machining (edm) and observed that the material removal rate increased for the negatively charged tool and as the capacity increased, the voltage and gas pressure also rose during both solid-state dielectric edm processes. in addition, compared to conventional oily edm, oxygen caused the material removal rate to almost triple and that of air to nearly double. based on these results, it was stated that dry edm is much more effective than oily edm with regard to the deburring of cfrp. park et al. [?] investigated a hybrid cryogenic method for deburring. they compared four setups and established that the final setup was the most effective with a burr removal rate of 100%. even though the aforementioned deburring technologies are suitable to remove cfrp burrs, their material removal rate is not as good as the mechanical equivalent. a relatively wide range of cutting tools can be used for mechanical deburring [?], e.g., compact tools that can remove both the entrance and exit burrs (like spiral slot drills) as well as those that can only remove burrs on one side of the composite (like tapered countersink drills). however, since the number of studies examining their effectiveness is relatively low in the field of cfrp deburring, the main aim of the present study is to analyse the mechanical deburring of drilling-induced burrs in unidirectional cfrp composites. 2. experimental setups the deburring experiments were examined on a predrilled vinyl ester-based unidirectional carbon fibre reinforced polymer (ud-cfrp) plate. the main mechanical properties of the ud-cfrp plate at different fibre orientation angles (φ: angle between the fibre direction and load directions of the mechanical tests) are listed in table ??. the pre-drilled composite can be seen in fig. ??. the diameter of the pre-drilled holes was d = 10 mm. given that the performance of the mechanical deburring was tested on the exit burrs, the entrance burrs were removed by a sheet of sandpaper to prevent them from influencing the evaluation. the deburring experiments were conducted on a kondia b640 3-axis machining centre. a nilfisk gb733 industrial vacuum cleaner was used to remove the carbon fibres from the machining zone. a fraisa 20340.450 uncoated, solid carbide compression end mill with coarse teeth was used with a diameter of d = 10 mm and a point angle of σ = 135◦. the schematic diagram of the table 1: main mechanical properties of the applied ud-cfrp mechanical properties φ = 0◦ φ = 30◦ φ = 60◦ φ = 90◦ tensile strength (mpa) 547.85 ± 45.78 61.22 ± 5.15 17.36 ± 1.31 19.01 ± 1.83 charpy impact strength (kj/m2) 263.17 ± 24.76 26.83 ± 2.24 9.35 ± 1.16 5.28 ± 0.20 average shore d hardness (-) 88.2 ± 0.4 average interlayer shear strength (mpa) 21.77 ± 0.70 hungarian journal of industry and chemistry mechanical deburring of drilling-induced exit burrs in cfrp composites 41 table 2: the values of the parameters at different levels parameters levels 1 2 3 cutting speed (vc m/min) 20 60 100 feed (f mm/rev) 0.05 0.075 0.1 deburring cycle is illustrated in fig. ??. the applied deburring cycle was a rolling circular interpolation motion, where the cutting point of the tool was at the middle of the main cutting edge at the point denoted by t in the absence of a cooling fluid. the experiments were designed by the full factorial method. the parameter set was chosen based on previous works [?, ?] and suggestions from tool producers. the parameter sets can be seen in table ??. the set values of the parameters are interpreted at the t position of the cutting tool. each experimental setting was repeated five times and their order was randomized to eliminate hidden errors during the experiment. a dinolite premier ad7013mzt digital handheld microscope was applied for image capturing before and after deburring. the drilled and deburred holes were captured by the microscope from the top side while they were illuminated from the bottom side by an led source to improve the contrast of the images. the digital images taken before and after deburring were processed to determine the burr area (ab). the main steps of the digital image processing are illustrated in fig. ??. firstly, the original image was taken, before being filtered and segmented in the second step. finally, the image was cut to form a particular shape figure 2: drilling-induced exit burrs at the edges of the pre-drilled holes in the cfrp composite figure 3: the rolling circular interpolation motion and the t cutting point of the tool 49(2) pp. 39–45 (2021) 42 gödri, helle, and geier figure 4: main steps of the digital image processing method: (a) original image, (b) filtered and segmented image, (c) cut around hole in order to determine the burred area parameter by pixel counting and transformation. the ab0 parameters, which are listed in table ??, were determined before the deburring experiments. 3. results and discussion the efficiency of mechanical deburring was examined in this study on drilling-induced exit burrs by comparing the parameters ab0 and ab. each parameter was determined by a digital image processing method of images taken before and after deburring. the digital image processed holes – before and after deburring – are summarised in fig. ??. as can be seen, the holes contained a significant amount of burr before deburring, which was radically reduced by the applied deburring cycle. it can be stated that the deburring experiment was successfully completed. in addition, based on the images, the examined parameters seem to have no significant effect on the results because the exit burrs were totally removed under all experimental conditions. furthermore, some remaining burrs can be seen on the post-deburring photos. these errors could be the result of the following three main issues: (i) an error in terms of the digital image processing method could distort the filtered and segmented photos, (ii) the inner surface of the holes can reflect light or contain some uncut fibre which can also distort the photos, and (iii) if the entrance side of the hole contour contains burrs or uncut fibres, these will be visible on images as well as disfigure the filtered and segmented photos. the ab parameters were also determined by the digital image processing method. in fig. ??, the parametersab0 and ab were both depicted so they can be easily compared. these ab values were consistent with the photos. it can be seen on the diagram that the deburring cycle minimized the average amount of burr (ab = 2.496 mm2), where the standard deviation was relatively low (s(ab) = 0.422 mm2). in addition to the analysis of the burred area, the deburred workpiece was quantitatively evaluated by taking a high-resolution photo of each hole which were then visually evaluated by searching for machining-induced surface defects, e.g., uncut fibres, fragmentation, delamination, burr formation and burnout. these enlarged images of the holes present all the macro-type errors which could be observed and identified (fig. ??a-h). the properties of the critical holes can be seen in table ??. it was observed that the macro-type errors were characteristically uncut fibres. it can also be noticed that the defects mostly appeared symmetrically on the chamfers as a result of the directional dependence of the unidirectional cfrp plate, as was also observed by fuji et al. [?]. it can be seen that 4 out of the 5 repetitions with the parameters vc = 20 m/min and f = 0.1 mm/rev contained macro-type errors, so this parameter set can be identified as the most unfavourable setup and the set vc = 60 m/min and f = 0.1 mm/rev with 3 out of the 5 repetitions containing such areas as the second least table 3: burr areas before deburring (ab0) no. ab0 (mm2) no. ab0 (mm2) no. ab0 (mm2) no. ab0 (mm2) no. ab0 (mm2) 1 22.0168 10 15.9655 19 17.1038 28 12.7630 37 15.5607 2 16.3193 11 12.5244 20 11.7950 29 13.7123 38 17.7133 3 17.6914 12 12.1362 21 11.8991 30 27.4602 39 14.9731 4 15.9935 13 10.3192 22 22.1512 31 18.0514 40 25.4493 5 14.1156 14 23.8615 23 16.8891 32 19.2630 41 17.4130 6 16.0116 15 14.4638 24 13.9843 33 12.6162 42 14.4501 7 13.0983 16 11.1045 25 11.8457 34 14.7083 43 22.6858 8 16.6144 17 13.7582 26 12.8019 35 33.3027 44 14.4981 9 20.3942 18 12.2648 27 15.2845 36 14.7146 45 12.4184 hungarian journal of industry and chemistry mechanical deburring of drilling-induced exit burrs in cfrp composites 43 figure 5: the digital image processed holes – before and after deburring favourable. only 1 out of the 5 repetitions for the parameter set vc = 20 m/min and f = 0.01 mm/rev consisted of macro-type errors, possibly as a result of a random influential effect. no macro-type errors were visible by the naked eye in the other holes. by taking into account that each experimental setup analysed resulted in efficient deburring, the maximum vc = 100 m/min and f = 0.1 mm/rev is recommended to achieve the maximum material removal rate (mrr). although the present experimental results show that the developed mechanical deburring technology is efficient over the whole analysed parameter range of vc = 20 − 100 m/min and f = 0.05 − 1 mm/rev, a significant degree of chamfer formation was observed. since the size of these chamfers probably depends on the size of delamination-induced material deformations and process control, this should be compensated for or monitored in the future. 49(2) pp. 39–45 (2021) 44 gödri, helle, and geier figure 6: comparison of burr areas before (ab0) and after (ab) the applied deburring cycle 8 figure 7: the holes with observed macro-type errors: a) burrs, b) uncut fibres and rough surface roughness, c) burrs and uncut fibres, d) uncut fibres and rough surface roughness, e) rough surface roughness, f) uncut fibres, g) burrs and uncut fibres, h) rough surface roughness and delamination hungarian journal of industry and chemistry mechanical deburring of drilling-induced exit burrs in cfrp composites 45 table 4: properties of the holes containing macro-type errors presented applied parameters picture no. of hole during deburring vc (m/min) f (mm/rev) a) 4 20 0.1 b) 5 20 0.1 c) 13 20 0.01 d) 15 60 0.1 e) 17 60 0.1 f) 20 20 0.1 g) 39 20 0.1 h) 45 60 0.1 4. conclusions in the present study, the influence of the cutting speed (vc) and feed (f ) on the efficiency of mechanical deburring was experimentally analysed. the efficiency of mechanical deburring was examined by digital image processing. according to the present study, the following conclusions can be drawn: • the applied mechanical deburring technology successfully removed all cfrp burrs in each experimental setup. • the experimental results show that neither the feed nor the cutting speed have a significant influence on deburring over the analysed parameter range. • according to the quantitative evaluation, the observed holes with macro-type errors show that the parameters vc = 20 m/min and f = 0.1 mm/rev can be identified as the most unfavourable setup, followed by the parameter set vc = 60 m/min and f = 0.1 mm/rev. • as the mechanical deburring was successful when implementing each parameter set, it is recommended that the maximum parameters vc = 100 m/min and f = 0.1 mm/rev be applied in order to maximise the material removal rate (mrr). • during the deburring process, a significant degree of chamfer formation was observed. since the size of these chamfers depends on the size of the delamination-induced material deformations and process control, this should be compensated for or monitored in the future. acknowledgements this research reported in this paper and carried out at bme was partly supported by the national research, development and innovation office (nkfih) no. otkapd20-134430, the nrdi fund (tkp2020 nc, grant no. bme-nc) based on the charter of bolster issued by the nrdi office under the auspices of the ministry for innovation and technology, and the project “centre of excellence in production informatics and control” (epic) no. eu h2020-widespread-01-2016-2017teamingphase2-739592. the authors acknowledge the support of csongor pereszlai and dániel istván poór in their experimental work. references [1] poór, d. i.; 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[1] for example, on the basis of dexterity, how much it can grip and how much it can open. gripper fingers are applied less than small jaws which are preferred because of their flexible elements. one of the significant advantages of collaborative robots, which are currently emerging in industry, is that they can be used to conduct multiple tasks with the need for minimal modifications. in the past, installed and enclosed industrial robots were usually purchased as well as prepared for a single purpose, typically to be operated in a production cell. currently, collaborative robots often perform a range of tasks in collaboration with humans [2], partly because if a robot is no longer needed at one workstation, it can be used on another line at another workstation. as a result, the amount of reassembly and installation work that maintenance and line engineers are required to do is minimal. 2. gripper selection it is recommended to choose a solution for the robot effector that is best suited to such a general manufacturing environment. although grippers are available in a variety of sizes, it is also worth considering their cost. in general, a more expensive gripper can handle multiple tasks, *correspondence: boleraczki.miklos@mk.uni-pannon.hu while a cheaper version may be less capable of adapting to the task at hand. the gripper is a mechanical interface between the robot and its environment [3]. without it, the robot cannot perform its task, e.g. packing or assembling. the cited article introduces various designs of grippers. the first group of gripper fingers include several notches in the gripping surfaces, which make it possible to grip workpieces of different shapes. this is usually only suitable for workpieces of a similar size and weight. even though they are simple to make and low-cost, the number of notches that can be cut is limited. since the number of notches required for all workpieces must be specified, the design time may be longer. programming the robot can also be a lengthy process because the gripper must be correctly oriented to the workpieces. another method is to change the fingers of the gripper so that differently shaped workpieces can be handled by changing the gripper fingers. the fingers are stored on a rack and the robot knows the exact position of each finger. a reliable mechanical device to accurately clamp and unclamp the fingers is essential in this case, moreover, their replacement time should be minimized. therefore, the gripper and robot will be able to handle a wide range of workpieces and easily adapt to other applications. this method is more flexible than the previous one, which is more application-specific. the third technique is to replace grippers. for this purpose, complete tool changer grippers can be purchased, which are expensive but precise and allow grippers to be quickly replaced. they are used when a gripper cannot handle the differences in size, geometry and weight between workpieces. therefore, several griphttps://doi.org/10.33927/hjic-2021-28 mailto:boleraczki.miklos@mk.uni-pannon.hu 92 boleraczki, gyurika, and fodor pers are needed to cover a range of workpieces. the robot must be provided with precise information about each gripper and its position, which usually also requires a power supply and sensors. in general, this gripper changeover can be used for different types of grippers, e.g. mechanical, vacuum, magnetic, etc. as the changeover time increases the downtime, it should be kept to a minimum. although modern tool changers are equipped with a number of energy transfers (air and electrical connections), they are expensive. a fourth solution is to attach several grippers to the robot simultaneously in a revolving or linear arrangement. in the simplest case, two grippers are mounted for loading/unloading operations, which significantly speeds up the service time of the machine. the fifth option presented in this article are active and passive universal grippers. grippers that can adapt to the workpiece, e.g. in an elastic manner, with a passive (non-actuated) degree of freedom can be considered as passive universal grippers. they are characterized by the fact that they do not provide a precise position of the workpiece in the coordinate system of the robot. they are well-suited for simple pick-and-place tasks where a high degree of precision is not required. active universal grippers mimic the universal gripping ability of human hands. even though such experiments have been conducted in the past, nowadays, with the addition of 3d printing, some open source projects include such active universal robotic hands. at the time of writing that article, these robotic hands were expensive and unreliable so inapplicable on an industrial scale, which is still true today. although they are constantly being improved and better products are being developed, their real applications are in the service robotics market rather than in industrial manufacturing despite research being carried out in this field as well [4]. zubair et al. have developed [5] an attachable core gripper for a collaborative robot that can be operated without the robot using its own power source, which is an uncommon solution in the market. detachable robotic grippers not only work as a fully functional gripper when attached to the robot but also once detached. in terms of their physical design, 4 electromagnets are located on the side which is attached to the robot, while on the other side, 4 fingers grasp objects. the whole device is located in a 3d-printed housing. the usability of their gripper has also been tested by 12 participants. the development solution is predominantly intended to be used in a nonindustrial environment. long et al. designed a multifunctional gripper for grasping general objects [6] because many places, e.g. warehouses, require simple pick-and-place tasks and the level of automation is increasing due to rising costs of manpower. underactuated grippers consist of two fingers, each of which has three degrees of freedom with a fivebar mechanism actuated by two motors. experience has shown that the gripper, which combines two types, is versatile and reliable for the purpose of manipulating a wide range of objects. in terms of workpieces, it is easiest to categorize the many different products into families, thereby simplifying and economizing the process required to select grippers. according to a survey of 1,000 workpieces, the most necessary requirements for a gripper are an inexpensive rugged type of jaw with a stroke of 50 mm and a clamping force of less than 100 n. 3. promising attempts current conventional robotic grippers have a number of drawbacks, namely their large volume, high weight as well as energy consumption and significant cost. a promising trend is the exploration of shape memory alloy-actuated grippers. shape memory alloys (smas) can change their shape under stress [7]. the gripper presented in this research is powered by 9 100 mm-long sma wires with a diameter of 0.4 mm. the wires are tied together sequentially so that their displacement is added and the opening of the stroke gripper is long. conventional grippers have servo or stepper motors and pneumatic or hydraulic actuators, rendering the gripper heavy and expensive as well as requiring a high power consumption. in contrast, smas as actuators are characterized by their high energy density, low energy consumption, quick response and repetitive actuation. another special feature of the gripper presented in this article is that it has four parallel jaws on one finger. the outer two are rigid, while the inner two are flexible. at the time of writing, the gripper also has some defects, the most critical of which is that since the sma wire is cooled naturally, the time required for the finger to close is more than 5 seconds. horacio leon et al. are developing a robotic hand that consists of 5 fingers, with an extra thumb instead of a little finger [8]. the thumb is important for two reasons, namely for precision grip and power grip. the thumb is particularly critical because it increases the functionality of the hand by 60 %. in the article, the concept dfam (design for additive manufacturing) was used to develop the object quickly and cheaply by building it layer by layer using a variety of materials, that is, plastic, ceramic, metal or even concrete and glass. the method is based on reducing the amount of resources, print time, weight and cost. it also brings about quality enhancement like strength and functionality. a common practice is referred to as “remixing,”that is, a 3-dimensional design refers to other designs that are used. eight different versions of remixing have been created, the first of which is the open inmoov robotic hand, which consists of 36 parts and 17 degrees of freedom, namely its parameters are identicalto those of the human hand. the first remix version, “parloma hand,” has 22 degrees of freedom. the article also gives an important account of the methodology, which consists of three main parts: inspiration, ideation and implementation. by its very nature, remixing is an iterative process, which is also reflected in the methodology. finally, a gripper was developed that has two thumbs, one hungarian journal of industry and chemistry gripper finger design for special purpose applications 93 on both the right and left side of the hand, with three fingers in between them. the hand called “kool” is composed of 33 components and has 19 degrees of freedom, moreover, its weight, cost and printing time has been reduced compared to the original hand. since the thumb can also grip more firmly, it is also more secure and, therefore, more functional. based on the aforementioned classification, the types of grippers created in the context of soft robotics can be considered as active universal grippers, which do not essentially have rigid articulated links but can be described by continuous kinematics. developers expect these to be more effective in everyday life because they better replicate the structure of living beings, i.e. given that most of them are made of soft materials rather than rigid ones, they are more adaptable to changes in the environment. although some connect rigid members with hinges, other studies have experimented with grippers made of a material that is truly continuously soft. an example of this is the printed soft gripper [9] presented in the article by slesarenko et al. their method involved inserting wires and inserts into a polymer gel in various ways to create a more controllable as well as deformable shape and even reduce the actuating force required. the basic principle of a hollow polymeric fuselage thread was used and the shape as well as internal design of the fuselage varied by sectioning it, stiffening it in certain places and weaking it in others. the resulting gripper is suitable for manipulating small objects. the recommended strategy can be applied to other types of soft actuators. based on the presented gripper, it would be worthwhile to investigate how these grippers can be combined with conventional ones. nowadays, the greatest need is for a gripping system that can quickly adapt to the task. robotic head exchange systems are available that typically consist of two parts, one to be placed on the robot and the other on the gripper, which can then be connected together. more than one gripper can be used to adapt the robot to suit different tasks. this system requires several grippers and the tool changer must be purchased as well as integrated. another problem is the weight of the head exchanger, which is grooved according to the payload of the robot. typically, this is undesirable for companies wishing to use collaborative robots for multiple tasks. a better solution might be to attempt to use the gripper for each significantly different task by changing the finger itself. these fingers can be precisely fitted to the gripper, moreover, are relatively simple to manufacture and replace. additive manufacturing can be used to reduce production time and costs. 4. methods to design fingers of the gripper according to the design methodologies, the easiest solution would be to use a given template. by following a series of well-established steps, a finger can be obtained that is suitable for the current gripper and task. by following these steps, the design time is also significantly reduced because it is unnecessary to intuitively guess a solution, which can take an uncertain amount of time. the easiest way to proceed is to create a spreadsheet or flowchart in which the following questions can be answered to achieve the required outcome: 1. what type of gripper is used? 2. what product is to be gripped? 3. how accurate is our robot? 4. what material are the gripper fingers composed of? the proposed methodology shown in fig. 1 builds on the main elements outlined above with a more detailed description as follows. firstly, which component (or families of components) are to be manipulated needs to be determined. its size, weight, geometry, surface quality and material need to be taken into consideration. furthermore, the robot gripper must be analyzed to determine the type and size of its opening as well as how the gripper fingers can be connected to it. the next step is to start the design process, which requires knowledge of the manufacturing technologies available in the factory, namely the 3d printing machines themselves, their characteristics and the type of materials used. the design process should be carried out by bearing in mind the aspects discussed above with a focus on good printability. finally, based on the design, the 3d printing of the fingers results in physical parts. the solution to the problem is then tested by mounting the gripper fingers on the robot. replicating the grip and timing of the fingers is sought. for this purpose, the quickest and most efficient manufacturing solution is 3d printing. since numerous excellent review articles on 3d printing have been published, researchers are easily provided with an up-to-date overview of the technology [10]. the article presents a comparative analysis of the available technologies and materials. as various additive manufacturing machines are becoming available in more and more factories , it is important to understand the manufacturing requirements that need to be met in the design [11]. by taking into consideration the most common fdm (fused deposition modeling) machines, it is recommended that the printed finger has a flat surface which can be placed on the print bed. by maintaining an angle of 45◦ when designing upwardly extending gripper fingers, the finger can extend the gripper’s field of application by increasing its maximum opening width. it can also be adapted to suit more precise gripping tasks by designing shaped fingers. universal grippers can also meet specific needs. other design considerations are: 1. the fingers should consist of one or more pieces; 2. the fingers should be composed of at least one material and produced by at least one technology. 3. in 3d printing, composite materials, both continuous and short fiber-reinforced, are also commonly used [12]. the design should take into consideration both sides, one of which is the surface of the workpiece. between the two 49(2) pp. 91–95 (2021) 94 boleraczki, gyurika, and fodor figure 1: methods of designing and manufacturing fingers main components, a form that can be printed easily must be fitted. the available 3d printing processes must be assessed and the one that best suits the task selected. pla (polylactide), abs (acrylonitrile butadiene styrene) and nylon are the most common materials used by fdm machines. 5. example design of a finger based on the aforementioned methodology, two examples are presented in fig. 2. firstly, in order to grip a cylindrical workpiece, it is necessary to extend the opening width. besides, the finger has a prismatic shape, which renders the gripping concentrical. in this case, the limitation of this printing technology , namely the 45◦ overhang, must be taken into consideration. in the second image, a small pcb (printed circuit board) must be moved by fingers, which include notches to guide their orientation against the short gripping surface. in this finger design, the 45◦ overhang is not important because of its small dimensions. the gripper is an rg2-type universal gripper with an electric motor. 3d printing can be used to produce a rapid prototype for the purpose of experiments, which is advantageous due to its rapid nature and as the fingers can be produced very cheaply. 6. summary and future work choosing a suitable gripper is important in terms of its application and once selected, it must be implemented as effectively as possible. the present paper aimed to provide guidance on how this can be achieved by extending its range of uses with custom-designed fingers. in the future, it is expected that composite 3d printers will become more widespread in the industrial environment, furfigure 2: cylindrically shaped workpiece and pcbgripping fingers hungarian journal of industry and chemistry gripper finger design for special purpose applications 95 ther expanding the application areas covered by 3d printing. a similarly exciting topic would be the integration of mobile robots into the manufacturing environment, for which additive manufacturing could also be used. 7. acknowledgment this work was supported by the tkp2020-nka-10 project financed under the 2020-4.1.1-tkp2020 thematic excellence programme by the national research, development and innovation fund of hungary. references [1] pham, d. t.; yeo, s. h.: a knowledge-based system, for robot gripper selection: criteria for choosing grippers and surfaces for gripping. int. j. mach. tools manuf. 1988, 28(4), 301–313 doi: 10.1016/08906955(88)90045-4 [2] azima, m.s.; lobov, a.; pastukhov, a.: methodology for implementing universal gripping solution for robot application. proc. eston. acad. sci. 2019, 68(4), 413–420 doi: 10.3176/proc.2019.4.11 [3] pham, d. t.; yeo, s. h.: strategies for gripper design and selection in robotic assembly. int. j. prod. res. 1991, 29(2), 303-316 doi: 10.1080/00207549108930072 [4] staretu, i.: robotic arms with anthropomorphic grippers robotic technological processes. proceedings, 2021, 63(1), 77 doi: 10.3390/proceedings2020063077 [5] iqbal, z.; pozzi, m.; prattichizzo, d.; salvietti, g.: detachable robotic grippers for human-robot collaboration. front. robot. ai, 2021, 8, 644532 doi: 10.3389/frobt.2021.644532 [6] kang, l.; seo, j.-t.; kim, s.-h.; kim, w.-j.; yi, b.j.: design and implementation of a multi-function gripper for grasping general objects. appl. sci., 2019, 9(24), 5266 doi: 10.3390/app9245266 [7] lu, y.; xie, z.; wang, j.; yue, h.; wu, m.; liu, y.: a novel design of a parallel gripper actuated by a large-stroke shape memory alloy actuator. int. j. mech. sci. 2019, 159, 74–80 doi: 10.1016/j.ijmecsci.2019.05.041 [8] león, h.: design for additive manufacturing of a robotic hand with two thumbs. in: gonzález díaz c. et al. (eds.) viii latin american conference on biomedical engineering and xlii national conference on biomedical engineering. claib 2019. ifmbe proceedings, vol 75. springer, cham. doi: 10.1007/978-3-030-30648-9_133 [9] slesarenko, v.; engelkemier, s.; galich, p.i.; vladimirsky, d.; klein, g.; rudykh, s.: strategies to control performance of 3d-printed, cabledriven soft polymer actuators: from simple architectures to gripper prototype. polymers, 2018, 10(8), 846 doi: 10.3390/polym10080846 [10] krajangsawasdi, n.; blok, l.g.; hamerton, i.; longana, m.l.; woods, b.k.s.; ivanov, d.s.: fused deposition modelling of fibre reinforced polymer composites: a parametric review. j. compos. sci., 2021, 5(1), 29 doi: 10.3390/jcs5010029 [11] diegel, o.; nordin, a.; motte, d.: a practical guide to design for additive manufacturing, springer, 2020 doi: 10.1007/978-981-13-8281-9 [12] wang, k.; li, s.; rao, y.; wu, y.; peng, y.; yao, s.; zhang, h.; ahzi, s.: flexure behaviors of absbased composites containing carbon and kevlar fibers by material extrusion 3d printing. polymers, 2019, 11(11), 1878 doi: 10.3390/polym11111878 49(2) pp. 91–95 (2021) https://doi.org/10.1016/0890-6955(88)90045-4 https://doi.org/10.1016/0890-6955(88)90045-4 https://doi.org/10.3176/proc.2019.4.11 https://doi.org/10.1080/00207549108930072 https://doi.org/10.1080/00207549108930072 https://doi.org/10.3390/proceedings2020063077 https://doi.org/10.3390/proceedings2020063077 https://doi.org/10.3389/frobt.2021.644532 https://doi.org/10.3390/app9245266 https://doi.org/10.1016/j.ijmecsci.2019.05.041 https://doi.org/10.1016/j.ijmecsci.2019.05.041 https://doi.org/10.1007/978-3-030-30648-9_133 https://doi.org/10.1007/978-3-030-30648-9_133 https://doi.org/10.3390/polym10080846 https://doi.org/10.3390/jcs5010029 https://doi.org/10.1007/978-981-13-8281-9 https://doi.org/10.3390/polym11111878 introduction gripper selection promising attempts methods to design fingers of the gripper example design of a finger summary and future work acknowledgment hungarian journal of industrial chemistry veszprem vol. 29. pp. 123127 (2001) obtaining quantitative information on the fluctuation of the active ingredient content in drugswhat \vould the customer find a. dregelyi-kiss ands. kemeny (department of chemical engineering, budapest university of technology and economics, h-1521 budapest, hungary) received: october 8, 2001 this paper was presented at the 7th international workshop on chemical engineering mathematics, bad honnef, germany, august 12-17, 2001 the active ingredient content of tablets is not uniform due to inhomogeneity and the fluctuation of the process circumstances. moreover, the measured data are subject to measurement (analytical) error. both the consumer and the producer should be aware of the possible range of active ingredient content of the tablets. the analysis of variance technique was used in the context of nested designs. several variance components and their confidence ranges were calculated utilising the satterthwaite-approximation. the customers may also control the product quality. our purpose is to study the measurement process, as the customer would perform it, raising the question on the range in which the customer finds the amount of the key compound in a tablet purchased at a pharmacy. various cases are compared concerning the measurement precision and way of chemical analysis performed by the customer, calculating the ranges in which the active ingredient content could be tnund with 95% probability. the width of these ranges may be affected by the bias of the satterthwaite-approximation. keywords: nested design, satterthwaite-approximation, confidence intervals, variance components, drug analysis introduction in pharmaceutical industries there are strict guidelines to check the manufacturing processes in order to assure the steadiness of quality. the companies have to elaborate their own specifications related to the processes, chemical analysis, etc. these guidelines contain the appropriate design of experiments, where it can be seen how to perform the measures and statistical methods to appraise the results, for instance giving the confidence interval for the expected value in a 3x3 design. in this paper we examine the relevant guidelines and ask some questions from the customer's point of view. data source table 1 contains data obtained from a real manufacturing process in the course of the current guideline and process validation of the factory. durmg the batch-wise production of drugs these tablets were collected in lose-boxes. tablets of one batch of the finished products are collected to 13 or 141ose-box. the first five boxes are called the beginning of the batch (first fraction), the 6-9/loth boxes are the middle and the 1 0/11-13/14th boxes are the end of the batch. in order to control the process the active ingredient contents have to be measured in drugs. during the sampling 2-3 tablets were taken from the three different fractions of three batches, they were pulverized and powder fractions (altogether 9) were analysed three times each. the analytical procedure was high-temperature hplc with low-wavelength detection. these data are shown in table 1. the declared active ingredient content of the tablets calculated for the average ma:,s of tablet is 2.5 mg ±5%, i.e. 2.375 mg 2.625 mg. thus these samples have met this requirement. contact information: e-mail: cj:regelyi. vmt@chem.bme.hu. kemeny. vmt@chem.bme.hu 124 table 1 the active ingredient content of drugs in several batches, from different fractions of batches and with repeated chemical analysis batch sampling mass [mg] batch sampling mass [mg] batch sampling mass [mg] fraction fraction fraction first 2.60 2 first 2.58 3 first 2.55 1 first 2.59 2 first 2.57 3 first 2.56 1 first 2.60 2 first 2.56 3 first 2.58 1 middle 2.62 2 middle 2.58 3 middle 2.56 1 middle 2.60 2 middle 2.58 3 middle 2.60 1 middle 2.62 2 middle 2.58 3 middle 2.57 1 end 2.57 2 end 1 end 2.57 2 end 1 end 2.58 2 end anova and variance components model the measured data were processed using analysis of variance technique (anov a) and the statistica for windows software was used for calculations. the experimental design contains batch as random factor with 3 levels (1, 2t 3}, sampling fraction as random factor with 3 levels (first, middle, end), and analysis repeated three times as repetition. the sampling fraction factor is nested within batches. the factors are: a: batch (r:=3 levels) {j(a): fraction within a batch (q=3ievels) thus the measurements are assumed to follow the nested-random-effects model: (1) i = i, ... ,r;j =l, ...• q;k = l, ... ,p where j1 is the expected value. £xi is the random effect of the l 1 batch, p.im is the random effect of the / 1 fraction within the ,4h batch, and eijt is the random noise for the kth measurement taken from the ,.m fraction of the fh batch. certain assumptions have to be fulfilled when calculating anov a. assume that a;.. fj.ftu and eut are independent and identically distributed variables with normal distribution, mean 0 and variance a! , aital and o} .. respectively. the nun hypotheses: h: :a~ = 0. i.e. there is no batch effect. h: :a~(aj :::=0, i.e. the sampling fractions are not different (there is no inhomogeneity}. the theoretical anov a table is found as table 2 with the calculated and expected mean squares. the terms used for f-tests to check the nuil~hypotheses. 2.59 3 end 2.57 2.59 3 end 2.56 2.57 3 end 2.57 results of anova calculations the homoscedasticity and normality requirements are checked with positive results. the analysis of variance results are shown in table 3. there is no significant difference between batches, but the inhomogeneity is significant at 0.05 level. as in the f test the batch mean square is compared with the mean square of the sampling fraction, the large value of the latter may cover the otherwise important effect of batches. this was checked by calculating the probability of the error of second kind ({3) for a fixed probability of the error of first kind, a=0.05 . the alternative hypothesis considered for the calculation is the value of variance found as point estimate: (2) this means that the question is the probability of not detecting a variance of the size really .estimated (a! =1.13·10-4, see later). the probability of not detecting is: (3) degrees of freedom for calculating the fa critical value are: vnumeratrva=2, and vdeoominator=ya=6. the critical value itself is f0.05=5.14. thus the probability of the error of second kind is: fj = j f <5.14 s·l0-4 3 )= p(f <1.696)=0.74 &l 1.515·10the chance that the difference between batches remains unobserved is /3=0.74 with a=0.05 . this risk is very high. thus it is advisable to keep the batch effect in the model instead of neglecting it. 125 table 2 the theoretical anov a-table for two-way nested-random-effects model effect sum of squares df mean squares expectedms fo s l()2 2 sa 2 a r-1 qpa~ + pa~ +a; sa a -qp yi··y ... sa=--2i r-1 sb(a) sb(a) = p ~(.yij.-y; .. ) 2 2 sb(a) ') b(a) r(q-1) ') ) sb(a) 1 sb(a) = r(q -1) po"n +a; s2 r error sr = lll(yijk.vij.r rq(p-1) s~ = sr (j2 i j k rq(p-1) e table 3 the anova table: numerical evaluation effect df mean squares a: batch 2 0.001515 b(a): sampling fraction 6 0.000500 error 18 0.000126 it is important to estimate variance components ( <j~, ai(a) and cr;) in order to split the variance of the process into different parts. its usual way is the method of moments or anov a method, where the estimates are obtained using the terms of expected mean squares in table 2: ~2 (ja s! -s~(a) 1.13-10-4 (4.a) qp 2 2 ~2 sb(a) -sr =1.25 ·10-4 (4.b) (jb(a) p a-;= s~ = 1.26·10-4 (4.c) the estimated variances are obviously of the same order of magnitude, thus neglecting the between-batch variation is not justified. computation of the content range relevant for the customer model two questions arise: • what is the range for the active ingredient content of the tablet purchased by the customer at a pharmacy? • what is the range in which the customer would find the content analysing a tablet? in the first case (range for the true content) the error of the analysis does not affect the result, this is achieved by assuming an infinite number of repetitions ( p' -7 oo ). the interval in which the customer at 95% probability would measure the active ingredient content of a tablet expectedms fa p 9a! +3a~<al +a; 3.030 0.123 3ai<a> +a; 3.970 0.011 u? depends on the precision of her own measurement system and on the number of repetitions in chemical analysis. the statistical treatment is common for the two cases. student's t distribution is used to calculate the range for the content on the customer's side. a deviation variable (d) is introduced: d=y.-y ... (5} where y. is the average value measured by the customer, y ... is the grand average measured by the manufacturer (calculated from table 1, y ... =2.580). the expected value of this d deviation is e(d) = 0 . its variance is a sum of two terms: var(d)= var(y.)+ var(y ... ) {6) the two variances are added, because the error of the measurements by the manufacturer is independent from that at the customer. these variances are expressed in terms of the variance components: ( -) 2 z a•; vary. =o'a +ab(.aj +­ p* (7) where cr'; is the variance of measurement error obtained by the customer. p' is the customer's number of repetition, 11 () 1 2 1 z a; vary ... =-a a +-o"b,m +r rq rqp (8) it may well be assumed that the analytical method and the measurement apparatus of the 'u))tomer is analogous to the system used by tht~ analytical laboratory of the manufacturer, thus the un~ertainty of their ~easurements is equal ( a;:! = a; ). the number of repetitions may not be the same, however. upon 126 table 4 the dependence of customer's 95% range on the number of repetitions i width of the 95% intervalw.a. width of the p' 95% intervals to.975, w.a. d to.97s,s interval intervalw.a. 4.20·10'4 2.413 2.531 <y<2.630 0.099 3.370 2.511<y<2.649 0.138 3 3.36·10'4 2.742 2.530<y.<2.631 0.100 3.688 2.513<jl. <2.648 0.135 5 3.19·10'4 2.858 2.529<jl. <2.631 0.102 3.772 2.513<j/.<2.648 0.135 10 3.06·10"4 2.966 2.529<j7. <2.632 0.104 3.841 2.513<j7. <2.648 0.134 20 3.00·10"4 3.029 2.528<j7. <2.633 0.105 3.877 2.513<j7. <2:648 0.134 00 2.94·10-4 3.098 2.527<y<2.634 0.106 3.915 2.513<y<2.647 0.134 prescribed 2.375<y <2.625 0.250 subscripts: s means calculating with satterthwaite method, w.a. means using weighted average method substitution the resulting variance for the d deviation variable is var(d)=(1+.!. k! +(1+_!_ ki<a> +(_!_+1-k; (9) r r rq r p' rqp r as the variance components ( cr~ , ai<a> , a;) are not known, they are estimated from the experimental data: s~ =(1+.!_ 'k! +(1+...!_ 'k,i<al +(..!..+-1-k; (10) r r rq r . p' rqp r upon substituting eqs.(4.a)-(4.c) for the estimates of variance components the following expression is obtained: z r+l 2 q-1 z ( 1 1) 2 sd =--sa +--sb(a) + --+sr rqp qp p p' (11) the interval. where the customer would find the average active ingredient content of a tablet at e.g. 95% probability~ is calculated as: the main difficulty of the further calculation lies in the fact that the estimator for the resulting variance, as a linear combination of mean squares, does not follow 2 2 x ad distribution~ thus the range above is only v approximate. according to the satterthwaite approximation [ 11 the l ais; linear combination of i 2 2 mean squares is treated as if it were x u 11 , with v degrees of freedom expressed as: {13) where s,2 is the 1-m mean square. v; its degrees of freedom~ a, is the coefficient of the ;th mean square in the linear combination. another method [2] suggests calculating t1-an;v as a weighted average of the appropriate t critical values related to the calculated mean squares and degrees of freedom: tl-al2,v (14) results and discussion eq. (11) gives the following expression for s~ if r=3, q=3 and p=3 is substituted for the number of batches, number of sampling fractions and number of repetitions, respectively: 2 4 2 2 2 ( 1 1) 2 sd =-sa +-sb(a) + --+sr 27 9 3 p' (1l.a) the degrees of freedom using satterthwaite's approximation is given as (13.a) the other method, averaging the critical, t values takes the following form: (14.a) several p' values were taken for calculations, including p' -7 oo , the latter stands for the case of no analysis on the customert s side, giving the range for the true content. the results for the 95% intervals are given in table 4. it is well seen that neither the true content nor the values to be obtained by the customer upon chemical analysis at 95% probability are within the required range. there is a clear overage. at the same time the range of uncertainty is much narrower than it would be allowed. the uncertainty here means not only the measurement error but also batch differences and inhomogeneity within batches, as the tablet purchased by the customer may come from any batch and from any sampling fraction of a batch. what is surprising in table 4 is, that the width of the 95% range obtained using satterthwaite approximation is increasing with p' . that means the more precise is the measurement due to more repetitions, the wider is the interval. the reason comes from eq. (13.a): increasing the number of repetitions ( p') the numerator decreases, while the denominator is almost unchanged. this gives smaller degrees of freedom and larger critical t value at larger p' . this over-compensates the reduction of s~ and slightly broadens the interval. this anomaly is the error of the approximation, but the numerical consequence is not serious. the weighted average method results in wider intervals. conclusion in pharmaceutical industry there are strict guidelines regarding e.g. active ingredient content. the problem is that the prescribed interval is related to the average measured by a laboratory near the process or the average measured by the "customer" (this could be even the next laboratory). if we take 'the customer's uncertainty into consideration, the interval for the average may be evaluated. there are two methods to construct this interval; _ the first one uses the satterthwaite-approximation, the second one calculates the average of critical t-values weighted by mean squares. due to the bias of the approximation, the larger is the number of repetition, the broader is the width of the interval. the second method gives broader interval for the average. in spite of the fact that all tablets analysed, individually conform to the specifications, the interval in which values may occur is partly outside the specifications. acknowledgement the authors wish to express their gratitude to dr. k. kollar-hunek (department of chemical informatics, budapest university of technology and economics bute). the work has been supported by the hungarian national research foundation otka under contract number t0033005 and varga jozsef foundation of the chemical engineering faculty of the btjte. symbols d deviation vatiable f fisher test statistic 127 h hypothesis p number of repetitions in the producer's laboratory p' number of repetitions performed by the customer q number of levels of the fraction factor r number of levels of the batch factor i mean square ta. v critical value of student-distribution for a probability and v degrees of freedom yiik the measured value y. the average value measured by the customer y... the average value measured by the laboratory of the manufacturer greek symbols a the probability of the error of first kind at · the effect of the batch {3 the probability of the error of second kind {3j(ij the effect of the fraction within the batch gjk the random noise v degrees of freedom j1 the expected value cj variance component subscript/superscript related to the customer a related to the factor of the batch b related to the factor of the fraction d related to the deviation variable r related to the error r related to the error references 1. saiterthwaite f. e.: biometrics bull, 1946, 2(6), 110-114 2. paark k. and burdick r. k.: commun. statist.­ theory meth., 1998, 27(11). 2807-2825 3. box g. e. p., hunter w. g., hunter j. s.: statistics for experimenters, j. wiley and sons. 1978 4. lorenzen t. j., anderson v. l.: design of experiments. a no-name approach, marcel dekker, 1993 5. kameny s., deak a.: design of experiments, miiszaki konyvkiad6, budapest, 2000 {in hungarian) page 125 page 126 page 127 page 128 page 129 hungarian journal of industry and chemistry vol. 53(2) pp. 49–53 (2025) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2025-17 diastereoselective alkylation of 4-methyl-5-oxo-2-phenyl-1,3-oxazolidine-3-carboxylate and 2-chloromethyl-isoindole-1,3-dione odey bsharat1* 1 department of chemistry, faculty of sciences, an-najah national university, nablus, p.o. box 7, palestine asymmetric synthesis, that is, diastereoselective alkylation of a chiral auxiliary, is an important tool in organic synthesis. in this work, an α-methyl, non-natural amino acid (nnaa) building block equipped with a phthalimide group tail was prepared. this work describes the generation of the lithium enolate for an oxazolidin-2-one chiral auxiliary derived from a nnaa followed by quenching this enolate with 2-chloromethyl-isoindole-1,3-dione to provide an α-methyl nnaa building block equipped with a phthalimide group in good yield through a multistep synthesis with no signs of any minor diastereomers. the identity of this compound was confirmed by 1h nmr (proton nuclear magnetic resonance) and 13c nmr (carbon-13 nuclear magnetic resonance) spectroscopy. with the availability of this building block, peptides can be produced and evaluated over a variety of therapeutic areas in drug discovery. keywords: asymmetric synthesis, diastereoselective alkylation, chiral auxiliary 1. introduction asymmetric synthesis, namely assembling complex molecules as single enantiomers from relatively simple and readily available starting materials, is an important tool in modern organic chemistry synthesis [1]. in the pharmaceutical industry, these single enantiomers play an important rule in drug discovery since almost all newly introduced chiral drugs are marketed as single enantiomers [2]. one of the most common methods for asymmetric synthesis is the use of a chiral auxiliary. in order for the application of chiral auxiliaries to be beneficial, three important conditions must be met: first, they should mediate a highly diastereoselective transformation; second, they must be easily removed without racemization of the newly created stereogenic center(s); third, they need to be readily attached in their enantiomerically pure form to the substrate. in the literature, several chiral auxiliaries that meet these requirements have been developed [3], however, the class of chiral oxazolidinones developed by david evans have proven to be the gold standard [4]. these chiral auxiliaries have successfully directed many diastereoselective alkylations, α-aminations, aldol additions, diels–alder cycloadditions and michael additions. most importantly, the products of these reactions can be transformed into useful enantiopure intermediates that can be used in industry to prepare received: 14 june 2025; revised: 2 aug 2025; accepted: 8 aug 2025 *correspondence: obsharat@najah.edu drugs. compounds with an oxazolidine ring are of great importance due to their presence in several biologically active synthetic products, for example, linezolid, an oxazolidin-2-one, which is considered to set a new antimicrobial class developed over the past 30 years (figure 1) [5]. chiral auxiliaries were first discovered and introduced by e. j. corey in 1975 [6] using chiral 8-phenylmenthol and followed by the discovery of chiral mandelic acid by b. m. trost [7]. as menthol is difficult to synthesize, trans-2-phenyl-1-cyclohexanol was introduced by j. k. whitesell in 1985 as an alternative [8]. undoubtedly, the most efficient and frequently used chiral auxiliaries with prevalent applications are the chiral oxazolidinones developed and reported by david evans. oxazolidinones are a class of compounds containing 2-oxazolidone, which is a heterocyclic compound containing both nitrogen and oxygen in a 5-membered ring usually prepared from chiral natural amino acids [9]-[15]. figure 1: the structure of linezoid https://doi.org/10.33927/hjic-2025-17 mailto:obsharat@najah.edu bsharat hungarian journal of industry and chemistry 50 one of the most effective and popular reactions of acylated evans’ oxazolidinones is diastereoselective alkylation. in spite of the advantages realized for asymmetric catalysis, organic synthetic chemists frequently turn to evans’ methodology, especially when optically pure carboxylic acid derivatives are required as final products or as intermediates. although it is not as graceful as asymmetric catalysis, chiral auxiliaries continue to be very significant and frequently used for asymmetric synthesis. in this regard, the total synthesis of cytovaricin by evans et al. is considered as a classic application of oxazolidinones as chiral auxiliaries for one asymmetric alkylation and four asymmetric aldol reactions required to bring about the absolute configuration of nine stereogenic centers present in the aforementioned natural products [16]. therapeutic programs based on peptides have closed the gap on those focused on small molecules in pharma. one modification that has extended the lifetime of peptides is backbone modification, including α-methylation using non-natural amino acids (nnaas) [17]-[19]. however, there are very few commercially available α-methyl amino acids, and they are extremely expensive. the development of a general synthetic strategy to approach a wide variety of α-methyl nnaas would provide a significant step forward for drug discovery by employing peptide-based candidates. herein, a new protocol for the introduction and diastereoselective alkylation of the evans chiral auxiliary, namely 4-methyl-5-oxo-2-phenyl-1,3oxazolidine-3-carboxylate with 2-chloromethylisoindole-1,3-dione, is presented. 2. experimental 2.1. synthesis of 2-chloromethyl-isoindole-1,3dione (compound (3)) compound (3), that is, 2-chloromethyl-isoindole-1,3dione, was prepared according to a method found in the literature [20]. a solution of phthalimide (1) and formaldehyde (40% m/v aqueous solution) in water (40 ml) was stirred at 100 °c for 4 h. the mixture was cooled to room temperature and filtered. the precipitate was washed several times with water and pentane before being dried to provide a quantitative yield of 2-hydroxymethyl-isoindole-1,3-dione (2). in the next step, compound (2) and thionyl chloride (socl2) were stirred under argon at 75 °c for 4 h before the mixture was cooled to room temperature. thionyl chloride was removed under reduced pressure. the residue was diluted with dichloromethane (dcm) and the solvent evaporated off under reduced pressure. this procedure was repeated 5 times to afford a quantitative yield of 2-chloromethylisoindole-1,3-dione (3). 2.2. synthesis of (2r,4r)-4-methyl-5-oxo-2phenyl-1,3-oxazolidine-3-carboxylate (compound (6)) legend: compound (6), namely (2r,4r)-4-methyl-5oxo-2-phenyl-1,3-oxazolidine-3-carboxylate, was synthesized according to a method found in the literature [21]. cyclization of benzyloxycarbonyl (cbz)-protected (d) alanine (4) with benzaldehyde dimethyl acetal (5) provided compound (6) as a single isomer by slowly adding hexane over 6 hours to crash out the product. more specifically, in a dry flask under n2, cbz-d-alanine (4) (1.000 equiv.) and compound (5) (1.025 equiv.) were dissolved in dry tetrahydrofuran (thf) before being cooled to 0 °c. socl2 (1.100 equiv.) was added dropwise and after having been stirred for 10 mins. zncl2 (1.100 equiv.) was added then the solution further stirred for 4 h at 0°c. the reaction was quenched with the dropwise addition of ice water, followed by the addition of sodium bicarbonate (nahco3) solution until the ph became equal to 4. the mixture was diluted in water and extracted with ether three times before the organic layers were washed with brine, dried over anhydrous sodium sulphate (na2so4) and evaporated to dryness in vacuo. the crude product was dissolved in the minimum volume of ether, cooled to room temperature and the product precipitated by the dropwise addition of hexane over 6 hours resulting in a yield of 56%. 2.3. asymmetric alkylation between compound (6) and compound (3) to offer produce compound (7) below the synthesis of compound (7) is described. in a dry flask under n2, compound (6) (9.2 g, 29.6 mmol, 1.000 equiv.) was dissolved in dry thf (144 ml) and n-methyl-2-pyrrolidone (nmp) (24 ml) before the solution was cooled to -78°c. lithium bis(trimethylsilyl)amide (lihmds) (1.0 m) in thf (30.8 ml, 30.8 mmol, 1.300 equiv.) was added dropwise to the solution and having been stirred for 10 mins., compound (3) (13.9 g, 71.1 mmol, 3.000 equiv.) was added dropwise. the reaction was allowed to warm up gradually to room temperature over 18 h and quenched with an ammonium chloride (nh4cl) solution before being diluted with h2o and extracted with dcm (3x). the organic layers were combined, washed with brine, dried over anhydrous na2so4 and evaporated to dryness in vacuo. the residue was purified by column chromatography with a gradient of 0-30% ethyl acetate in hexanes (v/v) to produce 9.5 g (20.1 mmol) with a 68% yield of compound (7) as a white solid. https://www.google.com/search?sca_esv=813765718ccf2407&rlz=1c1rxqr_enca1001ca1001&cs=0&q=benzyloxycarbonyl&sa=x&ved=2ahukewinqpfx3oanaxu7tkqehthmiqeqxccnegqibbab&mstk=autexfcfe_lr7lxateue6lqwmounmoxgp4pgdi8y34ia97hrzds1pbob_hm6hhsgduhndbi_xuxehsds8tpkwbv5othu1hjqq5ba_krgitmo3sawmdlsjtzi2gh0himnqemgvtq&csui=3 diastereoselective alkylation 53(2) pp. 49–53 (2025) 51 3. results and discussion the purpose of this article is to report a new procedure regarding evans’ diastereoselective alkylation of (2r,4r)-4-methyl-5-oxo-2-phenyl-1,3-oxazolidine-3carboxylate (6) with 2-chloromethyl-isoindole-1,3-dione (3). this alkylation is the last stage of the multistep synthesis to produce a 68% yield of compound (7) as a white solid as shown in figure 2. in summary, in the first case, a starting substance that was available in both its enantiomeric form and chiral as well as optically pure was envisioned. the cyclization of cbz-protected (d) alanine with benzaldehyde dimethyl acetal yielded compound (6) after recrystallization as a single isomer. after the lithium enolate of compound (6) was generated and quenched with compound (3), chirality transfer was accomplished, yielding compound (7) with no indication of any minor diastereomers [22]. the identity of the α-methyl, non-natural amino acid (nnaa) building block equipped with a phthalimide moiety, that is, compound (7), was confirmed by 500mhz nmr and hrms spectroscopy. the experiments were carried out in dimethyl sulfoxided6 (dmso-d6) at 100 °c. 1h nmr (500 mhz, dmso-d6, 100 °c): δ 8.02 – 7.78 (m, 4h), 7.52 – 7.34 (m, 5h), 7.34 – 6.93 (m, 5h), 6.40 (s, 1h), 5.05 (s, 2h), 4.38 (d, j = 14.4 hz, 1h), 4.16 (d, j = 14.4 hz, 1h), 1.87 (s, 3h) 13c nmr (126 mhz, dmso-d6, 100 °c) δ 172.05, 168.02, 151.96, 137.40, 136.04, 135.13, 131.90, 130.15, 129.06, 128.64, 128.28, 127.90, 127.22, 123.81, 89.15, 67.44, 61.88, 22.66 hrms (esi): calcd. for c26h20n2o6 [m+na]+: 479.1219. the peak at 479.1219 was identified as shown in figure 3. in summary, an α-methyl nnaa building block equipped with a phthalimide group tail, namely compound (7), was prepared in good yield in a multistep synthesis by the generation of the lithium enolate for (2r,4r)-4-methyl-5-oxo-2-phenyl-1,3-oxazolidine3-carboxylate and quenching with 2-chloromethylisoindole-1,3-dione, to achieve chirality transfer, thereby providing compound (7) with no sign of any minor diastereomers. the α-methyl nnaa building block can figure 2: asymmetric alkylation between (2r,4r)-4-methyl-5-oxo-2-phenyl-1,3-oxazolidine-3-carboxylate (6) and 2-chloromethyl-isoindole-1,3-dione (3) to produce compound (7) (a) 1h-nmr spectra of compound (7) in dmso-d6 at 100°c (b) 13c-nmr spectra of compound (7) in dmso-d6 at 100°c (c) hrms spectra of compound (7) figure 3: characterization of compound (7) bsharat hungarian journal of industry and chemistry 52 be used in the preparation of peptide and drug discovery processes [23]-[30]. 4. conclusions a multistep synthesis pathway was developed to prepare an α-methyl, non-natural amino acid building block equipped with a phthalimide group tail, namely compound (7), in good yield with no sign of any minor diastereomers. the power of chiral auxiliaries in asymmetric synthesis was demonstrated using the highly utilized and well-understood evans oxazolidinone system. this α-methyl, non-natural amino acid building block could be used in the preparation of peptide and drug discovery processes in the future. symbols nnaa: non-natural amino acid 1h nmr: proton nuclear magnetic resonance 13c nmr: carbon-13 nuclear magnetic resonance nmr: nuclear magnetic resonance dcm: dichloromethane cbz: benzyloxycarbonyl socl2: 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https://doi.org/10.1007/s10967-025-10073-7 https://doi.org/10.33927/hjic-2025-05 https://doi.org/10.1371/journal.pone.0327632 https://doi.org/10.1186/s40538-025-00772-4 https://doi.org/10.1016/j.molstruc.2019.02.109 hungarian journal of industry and chemistry vol. 48(2) pp. 59–64 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-29 temperature and electric field dependence of the viscosity of electrorheological (er) fluids: warming up of an electrorheological clutch sándor mester1 and istván szalai *1 1institute of mechatronics engineering and research, university of pannonia, gasparich márk u. 18/a, zalaegerszeg, 8900, hungary cognition of the temperature-dependence of intelligent fluids, e.g. electrorheological (er) and magnetorheological (mr) fluids, is critical for their application. in this paper, the dependence of the viscosity of er fluids on temperature and electric field strength is examined. a new correlation equation is presented to describe the dependence of the viscosity on temperature by extending the andrade equation. considering the dependence of viscosity on the electric field strength and temperature, that equation is used to model the warming up of an er clutch. keywords: electrorheological fluid, viscosity, heat effect in er fluids, er clutch 1. introduction electrorheological (er) fluids are suspensions made by dispersing micron-sized solid particles with a relative permittivity of εp into a carrier fluid with a smaller relative permittivity of εf [1–3]. normally, small concentrations of stabilizers are also used to avoid sedimentation. the structure and, therefore, the rheological properties are altered by applying an external electric field. the dispersed particles, guided by the electric field, form chain-like structures [4]. these structures impair the motion of the suspended particles resulting in an increase in the apparent viscosity. using silicone oil as the carrier fluid is common, although other oils such as transformer oil have also been examined. the dispersed phase can consist of oxides, carbides, etc. er and magnetorheological (mr) fluids are used in various applications, e.g. couplings, shock dampers, [5, 6] ultra-smooth polishing materials, etc. [7]. most of the applications require the viscosity to be precisely adjusted, however, the viscosity alters as the temperature changes. [8,9] this disadvantage greatly limits its industrial use, as a change can impair fine-tuned systems by creating stern operating conditions. apart from the need to measure the temperature, the dependence of the parameters of the er fluids on temperature ought to be considered as well. in addition to the er effect, an er fluid is also affected by the thermal motion of particles. this motion works against the er effect, as it disrupts the chain-like structure [10, 11]. *correspondence: szalai@almos.uni-pannon.hu 2. experimental the dependence of the viscosity of fluids on the temperature is characterized by a law proposed by andrade: η = a e b t , (1) where η denotes the dynamic viscosity of the fluid, t stands for the temperature, whilea andb represent characteristic constants of the fluid. the constants are experimentally defined for each fluid. for er fluids, this equation is inadequate because their dependency on the electric field strength is not addressed. in the following chapters, the dependence on the electric field in eq. 1 is introduced. 2.1 samples and viscosity measurements to study the thermal and field effects, an anton paar physica mcr 301 rotational rheometer was used to measure the viscosity. different measuring equipment can be used for mr and er fluids, moreover, the samples can also be thermostated. the usage of a cylindrical probe is shown schematically in fig. 1. the length of the probe was l = 40.046 mm, the radius of the probe was ri = 13.33 mm and the inner radius of the chamber was re = 14.46 mm. for the measurements, a self-prepared er fluid was used. the carrier fluid was silicone oil with a viscosity of 1000 mpas at 298 k. the dispersed phase was silica powder of 0.5 − 10 µm in diameter (as the manufacturer https://doi.org/10.33927/hjic-2020-29 mailto:szalai@almos.uni-pannon.hu 60 mester and szalai figure 1: schematic representation of the probe claims that 80% of the particles have diameters of between 1 and 5 µm). as a result, three different concentrations of particles were investigated, namely 10, 20 and 30 wt%. the samples were prepared through a multi-step procedure: after stirring by hand, the fluid was placed in an ultrasonic bath for 15 minutes to mix further. to ensure an air bubble-free er fluid, the sample was exposed to a vacuum for 10 minutes before being placed in the rheometer. the samples were measured at six different temperatures at increments of 10 k ranging from 293 k to 343 k. considering the 1.13 mm gap at the measuring probe, the used voltages resulted in the following electrical field strengths: 0, 0.442, 0.885, 1.327 and 1.769 mv/m. the samples were constantly stirred in the rheometer. a two-minute-long stirring cycle in the absence of an electric field came after setting the temperature. a tenminute-long measuring cycle with an electric field was applied and another one-minute-long stirring cycle followed in the absence of an external electric field. the two mixing cycles at the beginning and end ensured that no residual particle arrangements from the previous measurements were present. the viscosity was measured per second. 3. measurement results and analysis 3.1 temperature dependence of the viscosity as an example, the measurement results of an 30 wt% er fluid at a temperature of 293 k are shown in fig. 2: after an initial rise (while the chain-like structure was forming), the viscosity became roughly constant. the anomalies in the figure were caused by external interferences. for the analysis, the results of a specific mixing ratio, electric field strength and temperature were averaged into figure 2: viscosity measurements under various electric field strengths, c = 30%, t = 295 k figure 3: experimental results and fitted curves (eq. 2) of viscosity at c = 10% under various electric field strengths a single value. the expected tendencies are as follows: as the electric field strength increases, so does the viscosity, while a rise in temperature is inversely proportional to the viscosity. it was found that eq. 1 is inappropriate for the exact representation of the dependence of er viscosity data on temperature, therefore, in terms of the pre-exponential factor, a further temperature dependence was proposed: η = (a0 +a1t ) e b t , (2) where a0, a1 and b denote constants derived by fitting eq. 2 to measurement data. figs. 3–5 demonstrate the fitted curves of the different concentrations of er fluid. the extended formula (eq. 2) correlates well with the measurements: the worst coefficient of determination for the fittings is r2 = 97.3 %. eq. 2 can be used to describe the viscosity of electrorheological fluids as a function of the temperature. hungarian journal of industry and chemistry temperature and electric field dependence of the viscosity of er fluids 61 figure 4: experimental results and fitted curves (eq. 2) of viscosity at c = 20% under various electric field strengths figure 5: experimental results and fitted curves (eq. 2) of viscosity at c = 30% under various electric field strengths 3.2 electric field strength dependence of viscosity the introduced formula does not concern how the viscosity depends on the electric field strength. in the case of many practical applications, the electric field changes, therefore, the temperature-dependent description of viscosity alone is insufficient. eq. 2 can be extended by making the pre-exponential factor dependent on the electric field strength as well. this expansion is carried out via the square of the electric field, indicating that the direction of the field is reversible: η = [ a0 +a1e 2 + ( a2 +a3e 2 ) t ] e b t (3) where a0, a1, a2, a3 and b denote constants, while e stands for the electric field strength. eq. 3 fitted to the measurement data can be seen in figs. 6–8. here the viscosity is represented as a function of the electric field strength and temperature. the coefficients of determination for the fittings are r2 10% = 99.62%, r2 20% = 98.62% and r2 30% = 99.06%. fitting parameters are summarized in table 1. figure 6: viscosity measurement data (•) and the fitted surface (eq. 3) at c = 10% figure 7: viscosity measurement data (•) and the fitted surface (eq. 3) at c = 20% figure 8: viscosity measurement data (•) and the fitted surface (eq. 3) at c = 30% 48(2) pp. 59–64 (2020) 62 mester and szalai table 1: fitted coefficients of eq. 3 at different er fluid concentrations concentration [m/m] 10% 20% 30% a0 -2.17623e-4 0.12252 3.82564 a1 2.47298e-16 2.2336e-14 5.10306e-13 a2 9.7734e-6 -2.32975e-4 -9.89e-3 a3 -6.84985e-19 -5.8753e-17 -1.2747e-15 b 1831.25188 1017.00608 3.82564 figure 9: cylindrical er clutch model for the dissipation of viscous energy 4. temperature rise in an er clutch 4.1 er clutch model a schematic diagram of a simple cylindrical electrorheological clutch is shown in fig. 9. nakamura et al. [12] described the temperature rise of similar clutches: their model consisted of several cylinders with gaps between them with radii from r(i) to r(i+1), where i = 1, 2 . . . n denotes the number of gaps which are filled with er fluid with a viscosity of η. according to the model, assuming the clutch is insulated, the dissipation of the viscous energy per second in the gap i is dei = ∂(τarω) ∂r dr, (4) where a denotes the surface of the cylinder, τ stands for the shear stress and ω represents the rotational speed. by utilizing the attributes of the cylinders and integrating the formula, the following equation can be derived: t (t+ ∆t) = 1 c { n∑ i=1 2πhη(t )ω2r(i) 3 s ∆t } + t (t) , (5) where t denotes the temperature, s stands for the gap, c represents the heat capacity of the fluid, ω refers to the relative rotational speed and h is the height of the cylinder. in our system, only one gap is examined so eq. 5 can be simplified to a differential equation: dt dt = 2πhω2r3 sc η(t ). (6) 4.2 viscous energy dissipation in the clutch using the model of the er clutch (eq. 6), the viscous energy dissipation was calculated by inserting the formula of the viscosity (eq.3): 1 [a0 +a1e2 + (a2 +a3e2)t ] e b t dt = 2πhω2r3 sc dt. (7) the integration of the left-hand side of the equation can be solved numerically using mathematical software. analytical integration requires the expansion of the exponential term into a taylor series:∫ e − b t [a0 +a1e2 + (a2 +a3e2)t ] dt = = ∫ 1 − b t + 1 2! b2 t 2 − 1 3! b3 t 3 + [a0 +a1 · e2 + (a2 +a3e2)t ] dt (8) eq. 7 can be integrated following the expansion into a taylor series resulting in the following expression: t2∫ t1 1 [a0 +a1e2 + (a2 +a3e2)t ] e b t dt = (−1) 0 b0 0! 1 a0 [ 1 c ln (1 + ct ) ]t2 t1 + + (−1) 1 b1 1! 1 a0 [ c1−1(−1) 1 ln 1 + ct t ]t2 t1 + + ∞∑ i=2 (−1) i bi i! 1 a0 ci−1(−1) i ln 1 + ct t + i∑ j=2 (−1) i−j+1 ci−j (j − 1)t j−1 t2 t1 , (9) hungarian journal of industry and chemistry temperature and electric field dependence of the viscosity of er fluids 63 figure 10: heating of an er clutch model as a function of the number of addends, c = 30%, e = 1.327 mv/m and t = 295 k figure 11: heating of an er clutch model over time, c = 10% where a0 = a0 +a1e 2 and c = a2 +a3e 2 a0 . the expression in eq. 9 can be used to calculate the time needed for the clutch to be heated to a given temperature. the closed formula, a double infinite sum, yields varying results depending on how many terms are used. in the present calculation, the following parameters are used: h = 0.04 m, r = 0.0133 m, s = 0.0113 m, ω = 4.057 rad/s and c = 0.05 j/k. the temperature as a function of the number of addends n is shown in fig. 10. after the 5th addend, the numerical and analytical solutions are almost identical. to calculate the amount of heating, the physical properties of the anton paar probe and the calculated parameters (a0, a1, etc.) of the examined er fluids were used. figs. 11–13 show the heating results using three different concentrations of er fluids. as can be observed, as the electric field strength and concentration increase, the temperature also rises faster due to the internal friction. figure 12: heating of an er clutch model over time, c = 20% figure 13: heating of an er clutch model over time, c = 30% 5. conclusion in our paper, a new correlation equation was proposed to describe the dependence of the viscosity of er fluids on temperature and electric field strength. the proposed equation describes the measurement results with a correspondingly small deviation. the temperature rise of the model system examined by using the aforementioned equations can also form the basis for the description of real systems. the applied model can be further refined, e.g. by taking into account the dependence of heat capacities on temperature. acknowledgement this research was supported by the european union and co-financed by the european social fund under project efop-3.6.2-16-2017-00002. references [1] shin, k.; kim, d.; cho, j.-c.; lim, h. s.; kim, j. w.; suh, k. d.: monodisperse conducting colloidal dipoles with symmetric dimer structure for enhancing electrorheology properties, j. coll. interf. sci., 2012, 374(1), 18–24 doi: 10.1016/j.jcis.2012.01.055 48(2) pp. 59–64 (2020) https://doi.org/10.1016/j.jcis.2012.01.055 64 mester and szalai [2] wu, j.; xu, g.; cheng, y.; liu, f.; guo, j.; cui, p.: the influence of high dielectric constant core on the activity of core–shell structure electrorheological fluid, j. coll. interf. sci., 2012, 378(1), 36–43 doi: 10.1016/j.jcis.2012.04.044 [3] rankin, p. j.; ginder, j. m.; klingenberg, d. j.: electroand magneto-rheology, curr. op. coll. interf. sci., 1998, 3(4), 373–381 doi: 10.1016/s13590294(98)80052-6 [4] sanchis, a.; sancho, m.; martínez, g.; sebastián, j.; muñoz, s.: interparticle forces in electrorheological fluids: effects of polydispersity and shape, colloid surf. a, 2004, 249(1-3), 119–122 doi: 10.1016/j.colsurfa.2004.08.061 [5] olabi, a. g; grunwald, a.: design and application of magneto-rheological fluid, mat. design, 2007, 28(10), 2658–2664 doi: 10.1016/j.matdes.2006.10.009 [6] bucchi, f.; forte, p.; frendo, f.; musolino, a.; rizzo, r.: a fail-safe magnetorheological clutch excited by permanent magnets for the disengagement of automotive auxiliaries, j. int. mat. sys. struc., 2014, 25(16), 2102–2114 doi: 10.1177/1045389x13517313 [7] peng, w.; li, s.; guan, c.; li, y.; hu, x.: ultraprecision optical surface fabricated by hydrodynamic effect polishing combined with magnetorheological finishing, optik, 2018, 156, 374–383 doi: 10.1016/j.ijleo.2017.11.055 [8] ayani, m.; hosseini, l.: the effect of temperature and electric field on the behavior of electrorheological fluids, in 4th annual (international) mechanical engineering conference (isfahan university of technology, isfahan, iran) [9] mokeev, a. a.; gubarev, s. a.; korobko, e. v.; bedik, n. a.: microconvection heat transfer in electrorheological fluids in rotating electric field, j. phys.: conf. ser., 2013, 412, 012008 doi: 10.1088/1742-6596/412/1/012008 [10] spaggiari, a.: properties and applications of magnetorheological fluids, frattura ed integrità strutturale, 2012, 7(23), 48–61 doi: 10.3221/igf-esis.23.06 [11] wang, r.; wang, y.c.; feng, c.q.; zhou, f.: experimental research on the heat transfer characteristics of electrorheological fluid shock absorber, in advances in industrial and civil engineering, advanced materials research, 2012, 594– 597 (trans tech publications ltd), 2836–2839 doi: 10.4028/www.scientific.net/amr.594-597.2836 [12] nakamura, t.; saga, n.; nakazawa, m.: thermal effects of a homogeneous er fluid device, j. int. mat. sys. struct., 2003, 14(2), 87–91 doi: 10.1177/1045389x03014002003 hungarian journal of industry and chemistry https://doi.org/10.1016/j.jcis.2012.04.044 https://doi.org/10.1016/s1359-0294(98)80052-6 https://doi.org/10.1016/s1359-0294(98)80052-6 https://doi.org/10.1016/j.colsurfa.2004.08.061 https://doi.org/10.1016/j.colsurfa.2004.08.061 https://doi.org/10.1016/j.matdes.2006.10.009 https://doi.org/10.1177/1045389x13517313 https://doi.org/10.1177/1045389x13517313 https://doi.org/10.1016/j.ijleo.2017.11.055 https://doi.org/10.1016/j.ijleo.2017.11.055 https://doi.org/10.1088/1742-6596/412/1/012008 https://doi.org/10.1088/1742-6596/412/1/012008 https://doi.org/10.3221/igf-esis.23.06 https://doi.org/10.4028/www.scientific.net/amr.594-597.2836 https://doi.org/10.4028/www.scientific.net/amr.594-597.2836 https://doi.org/10.1177/1045389x03014002003 https://doi.org/10.1177/1045389x03014002003 introduction experimental samples and viscosity measurements measurement results and analysis temperature dependence of the viscosity electric field strength dependence of viscosity temperature rise in an er clutch er clutch model viscous energy dissipation in the clutch conclusion hungar~journal of industrial chemistry veszprem vol. 30. pp. 219-227 (2002) a new procedure of phosphogypsum purification in order to diminish the content of radionuclides m. b. rajkovic and d. toskovic1 (institute of food technology and bioschemistry, faculty of agriculture, university of belgrade, p.o.box 127, yu-11081 belgrade-zemun, yugoslavia 1faculty of technology, zvornik, university of serbian saraevo, republic of srpska) received: october 7, 2002 phosphogypsum obtained by "wet procedure" for phosphoric acid production is actually calcium-sulphate dihydrate, cas04 • 2h20, which contains a high percent of impurities as well as radionuclides, originating from the basic raw material. technology of phosphoric acid production by "wet process" intends for phosphogypsum to be a •·sponge" that absorbs all impurities from phosphoric acid (except uranium) and to be left in deposits as an unnecessary burden. as an enormous amount of phosphogypsum results from phosphoric acid production (the ratio is 5:1), phosphogypsum deposits are a burden per se, from the view of environmental protection, because they occupy large areas and may contaminate the air, ground water, but also surface water that receive phosphogypsum in the form of dilute suspension. by the proposed procedure, phospho gypsum is transformed into hemihydrate, cas04 • y2h20. im the proces<> of removing radionuclides with barium-sulphate, 22~a isotope content decreases below the peimitted concentration, but this process is directly dependent on the type of the phosphate utilized in phosphoric acid production. keywords: phosphogypsum, scanning electron microscopy (sem), x-ray diffraction analysis, gammaspectrometric analysis, thermogravimetric analysis introduction phosphogypsum is the by-product of the phosphate fertilizer which is produced in large quantities world­ wide [1,2]. the "wet" prosphoric acid process is th.e most common one, used to produce phosphoric acid, it can be shown by the following reaction equation: [3] ca10(p04)~2 + 10h2s04 + 20h20 -4 -4 6h3p04 + 10cas04 • 2h20 + 2hf e.g. by scheme on fig.l [8]. as it may be seen in fig.l, phosphogypsum is separated on filters from phosphoric acid, which is then concentrated and subsequently utilized for fertilizer production. the phosphogypsum is disposed (fig.2) [5], in the areas intended for this purpose (mines, opencasts) or is (temporarily) discarded as a very diluted (2 wt.%) slurry into natural water streems. phosphogypsum represents a great problem for phosphoric acid producers. the problem of phosphogypsum arised at the moment as the frrst plant of phosphoric acid was established. working with .. wet process" technology, and the final solution of this problem could not be found yet. namely, caoip20~ ratio in the phosphates used for phosphoric acid production, is 1,35-1,65, which means that the mass of dried phosphogypsum per 1 t of obtained p10~. ts between 4 and 5 t. this means that phosphogypsum, and not phosphoric acid, is the main product of the plant [ 6}. phosphogypsum mainly consists of gypsum (cas04 • 2h20), but it also contains small quantities of impurities, that may influence unfavourably the environment, as eg. heavy metals [7] and natural radionuclides [8}. the presence of impurities in phosphogypsum. especially of radionudides, may prevent its further utilization. thus. its additional purification is necessary before any application (9.10). the components of phosphogypsum. originally present in raw phosphate, but are absent in na.tural gypsum, pollute the soil (as well as ground waters) and natural water streems [5]. insoluble particles, sooner or later. are sedimented along the banks and shallows of the river bed, forming bigger accumulations. lessening the isolation of the bottom of the river and covering river flora and fauna with a thin layer of sediment besides occupying large areas and preventing further development of flora and fauna, phosphogypsum. due to 220 amlliloniated triplesiij:l"r• ploojpbafe * phosphate rock" * radioactive fig.l the production of phosphate fertilizers fig.2 appearance of a phosphogypsum deposit "white dead sea" the radionuclides which originate from phosphates, represents also a further source of radionuclides and their radioactive daughters, which may additionaly contaminate the environment [11]. for _that re?son, there are investigations in progress worldwide wtth the objective of exploitation of phosphogypsum as a raw material in construction industry this is represented schematically (optionally) in the fig.j. all these were reasons to undertake investigations in order ~~ purify phosphogypsum and bring its composition. closer to natural gypsum. to achieve the given objective. a new method was applied in phosphogypsum purification. and testing the quality. chemical composition and physico-chemical analyses were performed using standard silicate analyses. as the method of alkaline melting, x-ray diffraction and thermo-gravimetric analysis. to compare the structure of natural gypsum with phosphogypsum, obtained immediately after filter separation in the plant of phosphoric acid production. as well _as after application of purification procedure. scannmg electron microscopy was applied. as the raw material ~ natural phosphates contain radionudides (fig./). they are also found in the phosphogypsum. for that reason. gamma spectrometric analysis of phosphogypsum ~vas performed. before and fig.3 scheme of application of phosphoric acid and optionally of phospho gypsum after the purification, and an equation is given for calculating the coefficient of radon liberation from phospho gypsum. materials and methods all investigations were performed with phosphogypsum, obtained from chemical plant in ihp prahovo by a technological procedure in which raw ph~spha~es are treated with h2s04• phosphogypsum pw:lficat~on w~s carried out by the new procedure, whtch will be dtscussed in further part of this paper. gamma spectrometric analysis of phosphogypsum samples was performed as follows: phosphogypsum samples w~re homogenised, dried at 105°c (for 6 hours) and put. mto a container (marinelli) of appropriate geometnc shape and kept closed airtight (30 days) in order to achieve radioactive equilibrium. gamma spectrometric measurements were performed by three pure germanium detectors manufactured by eg&g ··ortec'\ germany~ with the efficiency of 25-30% and energy resolution 1,75-1,95 kev. the detectors were connected to a multi-channel analyser by the same ma~ufacturer and to corresponding computer eqmpment. energy calibration, as well as calibration of detector efficiency were performed by radioactive standard supplied by amersham. the measurement time for one sample was 60.000 to l 00.000 s and the basic radiation was measured after 250.000 s. • 100 .---------------onatural gypsum c ['/o] -+phosphogypsum .95 90 c55 200 300 400 500 toe fig.4 thermogravimetric analysis of phosphogypsum samples measurements of total activity were performed by ~;l3 anticoincidental proportional gas counter ( countermaster") with basic radiation of 1 imp/min. planchet radius was 2.3 em. counter efficiency amounted to 24 % and was determined by a standard of 90sr. phosphogypsum and natural gypsum samples were analysed using scanning electron microscopy sem, jsm-840a, jeol, japan. x-ray diffraction analysis was carried out using the diffractometer for powder siemens d-500 with ni­ filtered cuk... radiation. identification of crystalline phases in recorded samples was carried out by position and intensity comparison of diffraction profiles with jc pds data. thermogravimetric analysis of phosphogypsum w~re performed on dermatograph stanton, england, with speed of heating up to 7 °c/min in air stream in mixture with alz03. samples were analysed in ceramic crucible, on temperature up to 500°c. results and discussion thermogravimetric analysis of phosphogypsum samples were performed in air stream with speed of heating of 7°c/rnin, and the obtained results are ?resented at fig.4, showing the change of sample mass m wt.% in dependence on temperature. the mass loss for phospho gypsum is 17.53 wt.% (gypsum loses 2 moi~ule of water), that would correspond to gypsmn portion of 84 wt.% in sample. for natural gypsum, which is hernihydrate (cas04 • y.ili20) the mass loss is 5.75 wt.% that would corresponds to gypsum portion of 93 wt.%. temperature oc 80 60 40 20 40 611 region ill cas04 stable 221 caso 4 · t/2 h2o l!nstable region! cas04 ·h2s04 stable the procedure of phosphogypsum purification is based on enhanced temperature. the conditions, temperature around 90°c and sulphuric acid concentration of 28 wt. %, were necessary for phospho gypsum (cas04 • 2h20 dihydrate) to be transformed into a hemihydrate cas04 • ~20, that corresponds to natural gypsum this is represented in fig.5, the state diagram of calcium sulphate. from fig.5 it can be seen that only under these conditions phosphogypsum is situated within region ii, where the form cas04 • %120 is dominant over cas04 • 2h20. phosphogypsum purification was carried out by solution of h2s04, with concentration of 28 wt. %. which was heated up to 90°c. phosphogypsum was added to the solution and an emulsion was made with intensive stirring. after the addition of phosphogypsum, barium sulphate was added also with continuous stirring, until the temperature reached 85°c. then the mixture was cooled. after cooling, it was filtered through a special buchner funnel, separating the solid from the liquid phase. after drying and calcination. the grinding of the purified phosphogypsum was carried out by laboratory mixer. until the particle size reached 100 to 200 j.uu, only 12 % of the particles were bigger than 200 fltil. the results of analyss of chemical and mineralogic composition of natural gypsum. phosphogypsum taken from filter from the process of phosphoric acid production by "wet proceduren and previously processed and purified phosphogypsum by the new procedure, are presented in table 1. from table 1 it can be seen that phosphogypsum is in the form of dihydrate. immediately after separation from filters (74.16 wt.%). while the natural gypsum is hemihydrate in essence (81.34 wt.% cas04·y.zh20). by the proposed purifying procedure, phosphogypsum is tranformed into hemihydrate (77 .26 wt.% 222 table 1 chemical and mineralogical composition of natural gypsum, phosphogypsum taken from plant's pipe and purified phospho gypsum natural gypsum phosphogypsurn taken from purified phosphogypsum plant's pipe chemical composition cas04·2h20 cas04·v2h20 cas04, anyhidride bonded (fixed) water, h20 cas04, total free cao so3 free water, at 45°c calcination loss si02+insoluble residue mgc03 na20 k20 al20 3+fe20 3 mgo cac03 p20s sum: sum: total: (in wt.%) 81.34 6.16 5.38 82.12 excess: 0.70 88.20 impurties: 1.30 0.98 4.15 0.06 5.09 11.58 99.78 fig.6 sem photograph of crystalline structure of natural gypsum (x500) cas04·~ 0) and all the remaining parameter are far clo er to natural gyp urn than to phosphogypsum. to establish morphological compo ition and tru ·ture, their homogen ity and the pre ence of faults in the tru ture, an inspe 6on wa performed by anning electronic micros opy (sem) of the natural gyp urn and arious pho phogypsum samples and the photograph are repre ented in figs.6 to 9. se photographs of natural gyp urn and phosphogyp urn show that th e two material regardle s of having the same chemical composition have different structures: natural gyp urn has poorly expres ed cry tal tructure and pho phogypsurn ha a marked cry tal tru ture mo tly of rhombi and he agonal forms hich indicate it more complex compo ition than that of the natura} gyp urn. thi ha al o been confirmed by pre iou in estigation [1-,l ). (in wt.%) (in wt.%) 74.16 11 .54 77.26 18.02 7.21 56.14 81.59 0.77 0.29 74.93 89.09 0.34 1.03 2.18 0.60 21.75 4.55 0.04 0.17 4.48 0.84 0.09 25.15 10.92 100.08 100.01 fig. 7 sem photograph of crystalline structure of phosphogypsum taken from plant's pipe (xl,ooo) x-ray diffraction analysis of natural gypsum and phosphogypsum indicated the presence of impurities in phosphogypsum. the results confirm that the two materials are the same, but that phosphogypsum contains ingredients being absent in natural gypsum. the x-ray diffractograms obtained for natural gypsum and phosphogypsum are presented in figs.jo and 11. x-ray diffraction analy is was carried out by comparing the position and intensity of diffraction profiles \-vith jc pds data. the following crystalline phases were identified: for natural gypsum cas04·~h20 (33-3 10) identification number from standard· for phosphogypsum: cas04·2h20 (33-311)· cas04·yzh20 (33-310) spectra corresponded to natural gyp urn, cahp04 (90) or cahp04·2h20 (9-77) pe tra al o corre ponded to natural gyp urn [14]. fig.8 sem photograph of crystalline structure of purified phosphogypsurn(x300) fig.9 sem photograph of crystalline structure of mixture of 75 wt.% natural gypsum and 25 wt.% phosphogypsurn (x500) the main difference between natural gypsum and phosphogypsum lies in their radionuclide content, although this content is variable, because it depends on the initial raw materialphosphate. namely, phosphates formed from sediment phosphates (florida, marocco, tunisia, senegal) contain uranium in higher concentrations, while phosphates of volcanic origin (cola, caratau) either contain radionuclides in traces, or do not contain them at all. during technological processing of phosphates by wet procedure, due to degradation with h2s04, 14 wt.% of uranium from phosphates pass into phosphogypsum (and the residue into h3p04), while almost 80 wt.% od the present radium from the phosphate passes into phosphogypsum. uranium in phosphate is in equilibrium with radium. radium quantity may be calculated according to the equation: nj4,u = nrj!ln,ra where: n = number of atoms submitted to radioactive degradation; ln = half-life of radioactive isotope. oxidation state of uranium in phosphates and the mode of ore treatment determine uranium distribution between acid and phosphogypsum. passage of uranium from phosphoric acid i in proportion with the use of p20 if ore dissolution is performed under oxidation condition [15]. in phosphates from florida which contain u(iv) 223 fig.jo characteristic x-ray diffractogram of natural gypsum fig.ll characteristic x -ray diffractograrn of phospho gypsum fprm as uranium dominant form at normal conditions of processing by "wet process", between 60 and 80 wt.% uranium passes into the acid, and the residue into phospho gypsum, while for phosphate~ of african origin, where uranium is mostly in the form of u(vi . its participation in the acid may be almost 90 t.% [16). process of uranium removal from phosphog psum in the available literature there are presented variou procedures for decreasing of radionuclide conte t in phosphogypsum [17-20], but no one could rem e completely that main "fault ' of phosphogyp urn in comparision with natural gypsum, because it is variable and is in direct relation with the type of pho ph ate u. ed as raw material [7]. the process for reducing radionuclide contamination in phosphogypsum, applied in this paper it is a primary object of our idea. it is a further object of this idea to provide a cour e purified gypsum product from phosphogyp urn containing radioactive contaminants it has now been discovered that the foregoing objects are accomplished for reducing the radioacti e contamination (radionuclide ) in phosphogyp urn in a process which comprise : • admixing pho phogyp urn ontaining radionu jide with dilute ulphuric acid ~ontaining barium sulphate at an elevated temperat...l e t ~ rm an acidic lurry having a olid omponem compri ed of fin fra tion and a coar e fra tion and • separating the aid fine fracti n f ohd from the coar e fraction, 224 table 2 gamma-spectrometry results of samples unpurified and purified phosphogypsum by new process [21] radioactivity (bq/kg) radionuclides activity of unpurified phospho gypsum activity of purified phospho gypsum 439±20 379±20 8.7±0.5 7.1±0.5 radionuclides artificial origin • whereby said fine fraction predominates in said barium sulphate and said radionuclides, and • whereby the coarse fraction predominates in phosphogypsum of reduced radioactive contamination. in the first step of purifying the phospho gypsum the termal decomposition of the phosphogypsum, from dihydrate to hemihydrate (in accordance with fig.5), may generally be accomplished by dry kettle calcination of atmospheric pressure and temperatures about 1151600c or be dilute acid thermal dehydration such as in about an aqueous sulphuric acid solution having a concentration of 28 wt. %. at atmospheric pressure and temperature about 90°c, which is used to digest the phospho gypsum. in the second step of this process, sufficient barium sulphate is added to the slurry of phosphogypsum and sulphuric acid to provide a barium sulphate concentration in the resulting slurry. excess barium sulphate may be employed, but it is generally unnecessary, since such an excess adds to the cost of carrying out the process without significantly improving the reduction of radioactive contamination (radionuclides). barium sulphate is preferably added to a concentrated sulphuric acid solution containing from about 0.10 to 10 wt.% by weight of barium sulphate. fuming sulphuric acid may be employed to dissolve the barium sulphate, if desired. phosphogypsum was agitated with the solution of sulphuric acid and barium sulphate for a period of 12 minutes. while maintaining the temperature of the resulting slurry at about 85°c. after the desired elevated temperature is obtained. the slurry is agitated for a sufficient period to effect solubilization of the radioactive contaminations (radionuclides), followed by absorption and/or co-precipitation of radium sulphate crystals with barium sulphate crystals in fine divided fonn. this digestion period ranges from 5 to 250 minutes. after the reaction of the acid slurry was completed, the slurry is preferably cooled, at a temperature of 30350c and then filtered. if desired. the hot acid slurry can be washed without a separate cooling step. the acidic slurry with or without prior cooling is subjected to a solid-liquid separation step, such as filtration or cyclone separationt and the clarified acid is recovered. it may be recycled, after reconstruction. for use in reacting with additional imp¥fe phosphogypsum or used in other parts of the fertilizer process. the filter cake was washed with water and the solids were dried at a temperature of 60°c. the dried solids < 8.7 7.8±0.5 < 1.0 < 1.1 was slurried with water and then wet screened on a 100 micron screen. the solid phosphogypsum retained on the 100 micron was collected and dried at 60°c. the results of gamma spectrometric analysis of natural gypsum and phosphogypsum purified by the proposed procedure are represented in the table 2. as it can be seen from the table 2, activity of phosphogypsum purified by this procedure is decreased by approx. 10 wt.% in comparison with raw phosphogypsum. it is necessary to stress that the original raw material phosphate determines much the content of radionuclides, which should be primarily taken into consideration when choosing the phosphate. the obtained results of radionuclide content analysis in raw phosphogypsum are in accordance with literature data obtained by investigation of 2~a isotope contents in various types of phosphogypsum, which range from 430 to 790 bq/kg. the presence of thorium, as well as of the products of degradation of thorium sequence is not of any importance, because the activity originating from thorium is not high. . the presence of 226ra isotope is dangerous because of liberation of (the only) radioactive gas radon (isotope-222), which is a daughter of radium degradation sequence (table 3). the daughter product of 22~a, 222rn, having a half-life of 3.82 days, and the extent to which this escapes from any biological system in which 22~a is deposited profoundly affects the dose. radiation danger at the contact of human organism with radon is connected with its radioactive "short-lived radon· escendents": 218 po 214 pb 214 bi and 214po which mostly 84 , 82 ' 83 84 ' damage the lungs. a disintegration product later in series is rad e10pb) with a half-life of 21 years; this element and those derived from it will not reach equilibrium amount in the life-time of a man but, for example, may be present in a person who has acquired an accidental body burden of 22~a. determination of 222rn emanition coefficient [22] after the 30 days equilibrium period, the total activity of 222rn in secular equilibrium with 22~a. the activity of the total gaseous 222rn in phosphogypsum (or sample} was calculated~ taking into consideration the volume of the vessel in which sample exist, the porosity of the phosphogypsum, and the volume removed during sampling. porosity (p)~ fraction of total phosphogypsum was calculated by: 225 table 3 radioisotopes in the radium series radioisotope element half-time particle energiesa y-ray energies (mev) (historical name) (mev) radium ra 1620 years a, 4.78 (94.3 %) 0.187 (5.7 %) a, 4.59 (5,7 %) radon 222rn 3.82 days a, 5.49 (99+%) 0.51 (0.075) a, 4.98 (<0,1 %) raa 21sp0 3.05 min a, 6.00 (99+%) rab 214pb 26.8 min ~-. 0,67-1,03 0.053-0.352 rae 214bi 19.7 min ~-. (99+%) 0.4-3.18 a, (0.04 %) ~c·(ls)l 214p 0 160 ?sec a, 7.68 i rac" (o.j %) 21171 1.32 min ~-. 1.96 0.32-2.36 rk 210pb 21.4 years ~-. 0.017 (85 %) 0.047 (85 %) ~-, 0.064 (15 %) rae 210bi 5.0 days ~-. 1.16 (99+%) raf zwp0 138.4 days a, 5.30 (99+%) rag 206pb stable a where the ~or yspectra contain many lines, only ranges of energy without abundances are given rag unradioactive lead (isotope 206pb) or (radium's lead or rag) where db is bulk density (g!cm3 , phospho gypsum (solids+porosity) and dp is particle densitl of phospho gypsum was assumed to be 2.32 g/cm , the value fos cas04·2h20 [23]. the efficiencies of the scintillation cells were determined with a calibrated 222rn source, which quantitatively delivered 3 bq in an unspecified volume. the 222rn emanation coeficient (c) was calculated by: total activity (bq) of 222rn in the gas phase £= ·100% total activity (bq) of 226ra in the sample radioactivity is investigated as the contents of three radioactive isotopes: k--40, ra-226 and th-232. biologically harmful evaluation of these three isotopes has the following relations: 40k: 22~a: 23zrh = 1: 12,5: 16,50 which is not the case with phosphogypsum, because several times higher radioactivity originates from 22~a isotope, than from other isotopes {table 2). from the table 2, it rna~ be noticed that by the proposed procedure, isotope 2~a activity is decreased below tha maximal permitted concentration ( 400 bq/kg) [24]. upper permitted limits of radioactivity are calculated according to so-called summary formula which has been formulated by national commission for protection from radiation in former ussr, and according to our currently valid regulations it has the following form [24]: 226 ra (bq/kg) index for interiors = + 200 232 th (bq/kg) + .. 4(j k(bq/kg) + v interiors (bq/kg) = l 300 3000 4000 index for exteriors = 226 ra (bq/kg) + 400 232 th (bqjkg) 40 k(bqjkg) v~xteriors (bq/kg) ___ __:::_-=.;.... + _ ___:_.........;:.:--=:..:... + = 1 300 5000 4000 index for roads 226 ra (bq/kg) ::: 700 + 232th (bq/kg) + 40 k(bq/kg) + vrorroatls<bq/kg) = l 500 8000 2000 in the opinion of the majority of experts, there is no negligible level of radioactive rays; only one radioactive disintegration is enough to cause mutagenic change, that is, appearance of cancer cells. lowering of the dose only brings about the lowering of the probability of the illness appearance. the obtained results of the investigation of radionuclide content indicate a significant presence of ra-226 isotope of 439 bq/kg. this fact is in accordance with literature data on the values of ra-226 isotope content in various forms of phosphogypsurn. which range between 430 and 790 bq/kg. the presence of ra-226 isotope is dangerous because of the liberation of radioactive gas radon rn-222 isotope. radon, which is produced by radium degradation and the half-life of which is 3.8 days. gets accumulated in the atmosphere of closed rooms. radon is a-emitter and induces much more serious damage to living tissue when it is inhaled and the radioactive products of its decay are deposited in lungs. at radioactivity equilibrium, l g of ra corresponds to 3,7·1010 bq. during decay. radon yields at first a sequence of solid radioactive particles which emit a.-, f3-partides and y-quant ... radiation danger at the contact of human organism with radon is connected with its radioactive "short-lived radon descendents": 218po 214 pb 214 bi and 214po which mostly 84 ~ 82 ' 83 84 ' damage the lungs. these isotopes are called~ which are 226 responsible for the dose of radiation received by human lungs. radon is inhaled and expired by people, it does not remain in breathing system, but the products of its radioactive decay adhere to all materials, and even to air particles. when they are inhaled, they remain in lungs and constantly emit the radiation. there is no a generally accepted scientific view on how small quantities of radon affect human health, but one thing is sure: radon in high quantities is certainly harmful, but for the small ones, there are no valid data. this is one fundamental scientific problem that has not still been solved. it actually amounts to the question on the risk from "small doses". it is an old scientific controversy: according to some authors each dose is harmful, even the smallest received dose may have disastrous consequences. with the lowering of the dose, the probability of a harmful effect decreases, but does not disappear, until the dose decreases down to zero. conclusions phosphogypsum obtained by "wet procedure" for phosphoric acid production is actually calcium-sulphate dihydrate, cas04·2h20, which contains a high percent of impurities as well as radionuclides originating from the basic raw material for the productionphosphate. technology of phosphoric acid production by "wet procedure" intends for phosphogypsum to be a "sponge" that absorbs all impurities from phosphoric acid (except uranium) and to . be left in deposits as an unnecessary burden. as enormous amounts of phosphogypsum result from phosphoric acid production (the ratio is 5:1), phosphogypsum deposits are a problem per se, from the aspect of environmental protection, because they occupy large areas and may contaminate the air, underground waters, but also water flows that receive phosphogypsum in the form of 2 wt.% suspension. by the proposed procedure, phosphogypsum is transformed into hemihydrate, cas04·y.ill20, which corresponds to natural gypsum, and the present impurities are in accordance with natural gypsum composition. by process of removing radionuclides with barium-sulphate, 2~a isotope content decreases below the maximal permitted concentration, but this process is directly dependent on the type of the phosphate utilized in phosphoric acid production. acknowledgements the work from our laboratory was supported by the ministry for science~ technology and development of serbia (project 1941}. the authors are grateful to the ministry for science~ technology and development for partial financial support. references 1. ferguson f.: phosphogypsum, 2nd international symposium on phosphogypsum, miami, fl: florida institute of phosphate research, 1988, 1, 117-130 2. slack a. v.: phosphoric acid, part ii, marcel dekker inc., new york, p. 766, 1968 3. beallj. v: min. eng., 1966, 18,80-99 4. habashi f.: the recovery of uranium from · nd phosphate rock. progress and problems, 2 international congress on phosphorus compounds, boston, 1980,629-660 5. ra.jkovic m. b. and vladisavljevic g. t.: ecologica, 1999, 21(1), 9-15 (in serbian) 6. phosphorus&potassium: geting rid of phosphogypsum i. can technology provide the answer to a mountainous waste problem?, 1977, 87, p.37 7. ra.jkovic m. b., blagojevic s.d., jakovljevic m. d. and todorovic m. m.: j. agricul. sci., 2000, 45(2), 155-164 8. becker p.: phosphates and phosphoric acid: raw materials, technology and economics of the process, 2nd edition, marcel dekker inc., new york, 1989 9. ra.jkovic m. b., hadzic v. and molnar i.: otpadni fosfogips iz hemijske industrije pojam, primena, perspektiva -, institut za ratarstvo i povrtarstvo, novi sad, 117, 1995 (in serbian) 10. raikovich m. b., karlikovich-raich k. and chirich i.: russ. j. appl. chern., 1994, 67(3) 454456 11. rajkovic m. b.: zastita prirode, 1993-1994, 4647, 87-92 (in serbian) 12. ra.jkovic m. b. and mitrovic m. m.: phosphogypsum surface characterisation using scanning electron microscopy, 5th international conference on fundamental and applied aspects of physical chemistry, belgrade, 2000, 453--455 13. ra.jkovic m. b., simovic d. and vladisavljevic g. t .: experiences in the chemical gypsum phosphogypsum preparation from the triad "synthesis-structure-properties" viewpoint". in the book: advanced science and technology of sintering. editors: biljana d.stojanovic, valery v.skorokohd, and maria vesna nikolic, kluwer academic/plenum publishers~ new york, 323-328, 1999 14. rajkovic m. b., stevanovic r., ka.rljikovic­ raiic k. and vladisa vuevic g.: the application of different instrumental techniques for characterization of phosphogypsum. 12th international congress of chemical and process engineering, chisa'96, praha, 1996, p5.84 [19] 15. hurst f. j. and posez f. a.: long term potential of uranium recovery from phosphoric acid in sulphuric/phosphoric acid plant operations, a.i.ch.e., new york7 pp. 184-194, 1982 16. rajkovic m. b. and karuikovic-rajic k.: arh. farm., 1995, 45(1-2), 31-35 (in serbian) 17. lange p. h.: u.s. pat.. 4,146,568 (1979) 18. krempffr.: u.s. pat., 3,951,675 (1976) 19. palmer j. w. and gaynor j. c.: u.s. pat., 4,388,292 (1983) 20. palmer j. w.: u.s. pat., 4,421,731 (1983) 21. rajkovic m. b. and toskovic d.: acta periodica technologica, 2001, 32(1-172), 79-88 22. rutherford p. m., dudas m. j. and arocena j. m.: health physics, 1995, 69(4), 513-520 227 23. weast r. c.: crc handbook of chemistry and physics, 66th edition, boca raton, fl: crc press, inc.; 1985 24. sluzbeni list sfrj: pravilnik o maksimalnim granicama radioaktivne kontaminacije covekove sredine 0 vrsenju dekontaminacije, 8, pp. 226-246, 1987 (in serbian) page 221 page 222 page 223 page 224 page 225 page 226 page 227 page 228 page 229 untitled hungarian journal of industry and chemistry vol. 52(1) pp. 89–92 (2024) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2024-11 ultrafiltration membranes for microdialysis zbynek pientka1* and zuzana doubkova1 1 institute of macromolecular chemistry as cr, v.v.i., heyrovského nám. 2, prague, 162 06, czech republic porous asymmetric polysulfone ultrafiltrat ion membranes were prepared via the nonsolvent-induced phase separation process. the composition of the casting solution was optimized to achieve the required transport properties before membranes in the form of hollow fibers were prepared and characterized. the microdialysis probes were fabricated to extract samples from complex media like living tissues. keywords: membrane, ultrafiltration, hollow fiber, microdialysis 1. introduction microdialysis enables highly complex samples such as blood or living tissues to be sampled. this technique relies on the selective transfer of analytes through a dialysis membrane into an acceptor solution (dialysate). the selectivity of this transfer is primarily determined by factors such as the material the membrane is composed of, its pore size (cut-off) and the composition of the acceptor solution [1]. the functional part of the microdialysis probe is an ultrafiltration (uf) membrane in this case polysulfone (psu) with suitable surface properties, which is widely used in industrial and laboratory uf membranes, wastewater treatment [2] as well as hemodialysis modules. psu can also be chemically modified. the membranes are prepared by the nonsolvent-induced phase separation (nips) process resulting in an asymmetric porous structure [3]. the porosity of the membrane and thus its permeance can be influenced by the concentration of psu in the solvent, that is, the higher the concentration, the less permeable the resulting membrane will be. as the permeance of polysulfone uf membranes is limited, their porosity can be increased by additives, e.g. the nonsolvent-soluble polymer polyvinylpyrrolidone (pvp) [4]-[5]. in addition, pvp enhances hemocompatibility and prevents fouling [6]. the study commenced with membranes in the form of flat films to optimize the casting conditions as well as regulate porosity and other properties. once the optimum conditions had been determined, probes for microdialysis were developed and prepared. received: 28 march 2024; revised: 9 apr 2024; accepted: 10 apr 2024 *correspondence: pientka@imc.cas.cz 2. experimental 2.1. materials polysulfone from aldrich mn 22000 from aldrich, pvp (k90) from aldrich as well as dextrans from pharmacia with average molecular weights of 9.9 (dextran t10), 35.6 (t40), 74.3 (t70) and 486 kda (t500). 2.2. preparation of membranes the membranes were prepared by the method of controlled coagulation nips. casting solutions of the desired composition were prepared from a stock solution of psu in n-methylpyrrolidone by diluting it further and adding a weighed amount of pvp while accelerating the process by heating to about 60 °c and stirring. within a few hours, the solutions appeared to be homogeneous. this method of preparation is faster, the time the solutions are exposed to humid air is shorter and the measurements more reproducible than when a weighed amount of psu and pvp in n-methylpyrrolidone was dissolved. this was particularly evident during a series of measurements when one of the parameters was changed. the casting solution that was cooled to room temperature and free of air bubbles was poured onto a glass plate and spread into a uniform film using a doctor blade with a 350µm slot. having been exposed to air for 10 seconds, the glass with the polymer film was immersed in water as a nonsolvent. the polymer, which was insoluble in water, precipitated in the form of an asymmetric microporous membrane before being washed in water for several hours. https://doi.org/10.33927/hjic-2024-11 mailto:pientka@imc.cas.cz pientka and doubkova hungarian journal of industry and chemistry 90 the membranes for a microdialysis probe are in the form of hollow fibers with one closed end. a special extrusion device was developed to form these membranes. as the support, a glass fiber 0.90 mm in diameter was used, forming a film of the required thickness on the glass surface. using the optimized composition of the casting solution, tiny membranes were prepared with an outer diameter of 1.10 mm and 15 to 30 mm in length. to fabricate the microdialysis probe, the hollow fiber membranes were adjusted on the tip of a pipette with a capillary to insert the acceptor solution (figure 1). 2.3. measurement of transport properties the properties of the prepared flat sheet membranes were studied on an amicon stirred cell, which was pressurized with argon to a working overpressure of 2.0 ± 0.1 bar. the total area of the measured membrane was 13.8 cm² and the amount of permeate that flowed through was determined by weighing. the properties of the prepared microdialysis probes were measured by a device made in the laboratory. the probes were submerged in a stirred vessel containing a measured volume of liquid. the permeate was collected in the tip of a pipette while a negative pressure of 150 mbar was applied to the tip. the amount of permeate was measured on a calibrated scale. the concentrations of the dextran solutions used in the measurement of the retention coefficients were determined refractometrically using a mettler toledo mybrix refractometer with an accuracy of 0.4 g/1. the retention coefficient (r) of a given membrane for a given dextran solution describing the relative amount of retained molecules is defined as follows: 𝑅 = 1 − 𝑐𝑃𝑐𝑅 (1) where cr denotes the concentration of dextran in the solution above the membrane and cp represents its concentration in the permeate. the retention properties of the given membrane were determined for a series of dextran solutions, that is, t10, t40, t70 and t500, each with a starting concentration of 10 g/1. the experiment progressed from the dextran with the lowest molecular weight to the one with the highest. the permeabilities of water and the individual dextran solutions were measured. 3. results and discussion 3.1. experiments changes to the permeation properties of a membrane in the form of a flat film were measured by altering the concentration of psu and pvp in the casting solution. the dependence on the psu concentration while the pvp concentration was kept constant at 4 % was studied in detail as shown in figure 2 and table 1. as expected, the permeability decreases by increasing the psu concentration, while retention coefficients for individual dextrans increased. from table 1, it is also possible to determine the optimal concentration of psu for the separation of a certain mixture of dextrans or molecules of similar size. for some concentrations of psu, up to 6 membranes were prepared in order to verify the reproducibility of the preparation process. the accuracy of the permeance measurements and retention coefficients was in excess of 5 %, while the reproducibility was about 10 %. next, the dependence of the transport properties on the concentration of pvp in the casting solution was figure 1: microdialysis probe (22 mm in length) made of polysulfone uf membrane table 1: dependence of the retention coefficients (r) for dextrans on the concentration of psu in the casting solution (the membranes are identical to those in figure 2) psu (%) t10 t70 t500 12 20 60 99 16 0 70 95 20 5 90 99 figure 2: dependence of the membrane permeance (p) during the ultrafiltration of pure water and aqueous solutions of dextrans on the concentration of psu in the casting solution (pvp concentration: 4 %) ultrafiltration membranes for microdialysis 52(1) pp. 89–92 (2024) 91 measured while the psu concentration was kept constant at 16%, as presented in figure 3 and table 2. for pvp concentrations lower than 2 %, the permeabilities were very low, in fact only dextrans t10 and t70 passed through the membranes. when the pvp concentration was increased to 4 %, the permeability rose sharply. however, as the pvp concentration increased further, this dependence decreased. by washing water-soluble pvp with a molecular weight of 300,000 out of the membrane, it should become more porous. the nitrogen contents in the membrane samples, determined by elemental analysis (table 3), show that part of the added pvp is not removed from the membrane, even when washed with pressurized water in the cell for as long as 100 mins. for example, for a membrane from a casting solution containing 2 % pvp, one third of the added pvp is trapped in its entire profile. however, it is unknown how much of it is captured in the upper "skin" layer directly affecting the permeation properties of the membrane. the transport properties of microdialysis probes are shown in figure 4 and table 4 whereby their dependence on the psu concentration at a constant pvp concentration of 4 % was measured. permeabilities are higher than in the case of flat sheet membranes. although hollow fiber membranes are 60 % thinner, in general, both exhibit similar properties. table 2: dependence of the retention coefficients (r) for dextrans on the concentration of pvp in the casting solution (the membranes and conditions are identical to those in figure 3) pvp (%) t10 t70 t500 0 30 80 99 2 20 70 99 4 2 70 95 6 10 20 90 8 19 85 99 figure 3: dependence of membrane permeance (p) during the ultrafiltration of pure water and aqueous solutions of dextrans on the concentration of pvp in the casting solution (psu concentration: 16 %) table 3: elemental analysis of the prepared dried uf membranes casting solution washed dried membrane pvp (%) psu (%) n (%) pvp (%) 0 16 0 0 2 16 0.52 4.2 4 16 0.41 3.2 8 16 0.88 7.0 table 4: dependence of the retention coefficients (r) for dextrans on the concentration of psu in the casting solution (the microdialysis probes are identical to those in figure 4) psu (%) t40 t500 12 23 97 16 74 99 figure 4: dependence of the permeance of the microdialysis probe (p) during the ultrafiltration of pure water and aqueous solutions of dextrans on the concentration of polysulfone in the casting solution (pvp concentration: 4 %) -0,50 0,00 0,50 1,00 1,50 2,00 2,50 3,00 3,50 4,00 10 12 14 16 18 20 p [ m l/ (c m 2 .m in .b a r) ] c(psu) % h2o t40 t500 pientka and doubkova hungarian journal of industry and chemistry 92 4. conclusions porous asymmetric polysulfone ultrafiltration membranes were prepared by the nonsolvent-induced phase separation process. the addition of a certain amount of polyvinylpyrrolidone to the polysulfone casting solution significantly improves the permeation properties of the resulting membranes. the optimized composition consists of 12 to 16 % polysulfone and 4 to 6 % polyvinylpyrrolidone. using the optimized composition of the casting solution, tiny membranes in the form of hollow fibers were prepared and characterized before the microdialysis probes were fabricated. acknowledgements the authors are grateful for the financial support provided by the czech science foundation (22-22398s) and would like to especially thank jan schauer for introducing them to membrane science. references [1] tůma, p.: steady state microdialysis of microliter volumes of body fluids for monitoring of amino acids by capillary electrophoresis with contactless conductivity detection, anal. chim. acta, 2024, 1287, 342113, doi: 10.1016/j.aca.2023.342113 [2] komáromy, p.; bélafi-bakó, k.; hülber-beyer, éva; nemestóthy, n.: enhancement of oxygen transfer through membranes in bioprocesses, hung. j. ind. chem., 2020, 48(2), 5–8, doi: 10.33927/hjic2020-21 [3] guillen, g.r.; pan, y.; li, m.; hoek, e.m.v.: preparation and characterization of membranes formed by nonsolvent induced phase separation: a review, ind. eng. chem. res., 2011, 50(7), 3798–3817, doi: 10.1021/ie101928r [4] tang, y.; lin, y.; ford, d.m.; qian, x.; cervellere, m.r.; millett, p.c.; wang, x.: a review on models and simulations of membrane formation via phase inversion processes, j. membr. sci., 2021, 640, 119810, doi: 10.1016/j.memsci.2021.119810 [5] schauer, j.; albrecht, w.; weigel, t.; kůdela, v.; pientka, z.: microporous membranes prepared from blends of polysulfone and sulfonated poly(2,6dimethyl-1,4-phenylene oxide), j. appl. polym. sci., 2001, 81(1), 134–142, doi: 10.1002/app.1423 [6] abdelrasoul, a.; shoker, a.: wcn23-0021 polyvinylpyrrolidone (pvp) enhances the hemocompatibility of polyethersulfone (pes) hemodialysis membranes, kidney int. rep., 2023, 8(3 suppl.), s303, doi: 10.1016/j.ekir.2023.02.680 https://doi.org/10.1016/j.aca.2023.342113 https://doi.org/10.33927/hjic-2020-21 https://doi.org/10.33927/hjic-2020-21 https://doi.org/10.1021/ie101928r https://doi.org/10.1016/j.memsci.2021.119810 https://doi.org/10.1002/app.1423 https://doi.org/10.1016/j.ekir.2023.02.680 hungarian journal of industrial chemistry veszprem vol. 29. pp. 139141 (2001) possibilities of the application of polyisobutenyl succinic anhydride derivatives of v arlo us molecular structures z. kocsis, j. baladincz, l. bartha1 and j. hancs6k1 (mol co.ltd., lubricants business unit, komarom refinery, komarom, hungary 1university ofveszprem, veszprem, p. 0. box 158, h-8201, hungary) received: october 10, 2001 detergent-dispersant (dd) effect is one of the most important properties of lubricants and fuels. to ensure these properties various types of additives are used in increasing amount in the performance additive packages. among them ashless types and mostly polyalkenyl succinic anhydride derivatives are applied in high volumes. in this paper the main advantages of the ashless additives are presented showing the dependence of their properties on the molecule structure (monosuccinimides, bissuccinimides, mixtures thereof and polysuccinimide). additionally, the interactions with other additives are shown which can determine the main tribological properties of the lubricants. keywords: ashless dispersants, detergents, polyisobutenyl succinic anhydride derivatives, interactions of additives introduction the first innovations about polyalkenyl succtmc anhydride derivatives, used as ashless dd additives in engine oils, were published in the 60's. since, more than thousand patents have dealt with the alternatives of these additives and their syntheses. a wide group of them: the polyalkenyl succinimides and their derivatives are mainly used in engine oils and in fuels as detergent­ dispersant additives. a classification of polyalkenyl succinimides of various molecular structures, based on their polyalkenyl chain, is the following: polyisobutylene (pib) based • monosuccinimides, • bissuccinimides, • high molecular weight succinimides (mnpm>iooo), • modified versions of the aboves, • ester, amide and imide derivatives of succinic acid, • polysuccinimides based on maleic anhydride (ma) polyisobutylene copolymer (1] mapib a-olefin terpolymer [2] macomonomer copolymer grafted on pib [3]. a-olefin copolymer based • ethylene propylene copolymer based succinimides [4] and other succinic anhydride derivatives • ethylene ma a-olefin terpolymer i·"' j based succinimides • ma methyl methacrylate copolymer grafted on ethylenepropylene copolymer (6]. in this paper the pib based succinic anhydride derivatives are presented. the first step of the synthesis of polyisobutenyl succinimides is usually the production of polyisobutenyl succinic anhydride (pibsa or pibbsa depending on the number of succinic anhydride groups in one pib chain). the synthesis can be carried out in different ways. initiating the process thermally, catalytically or radically. the quality of the pib used for the synthesis (the percentage of terminal double bonds, average molecular weights etc.), the technological parameters, the active material content and the molecular structure of intermediate product can be different. these factors basically determine the molecular structure and performance of the end products in engine oils and fuels. the main types of the developed and studied polyisobutenyl succinimides are shown in fig.j. new engine designs require high quality lubricating oils in order to maximally utilise their economical benefits in fuel efficiency (reduced consumption). in longer drain intervals and in lower emissiom.. therefore the understanding of the properties and interactions of the additives working together in lubricating oils is of increasing importance. 140 0 r-ch-c.r 1 ~n-(c~-c~-nh)n-h chz-c ~0 polyisobutenyl monosuccinimide (msi) lp 0~ r-ch-c, 1c-cha /n-(chzchz-nh)mchzchz-n, i cha-c c-ch-r ~0 ~ 0 polyisobutenyl bisuccinimide (bsi) (chch)n -(y) i i c c -1' ..... / -::::0 n 0 i (u)tt i p general molecule structure of the polysuccinimide (psi) where: msit bsi: r=polyisobutenyl group ( nln = 300-30000)· n, m 2:: 1 (integer); ' psi: r= polyolefin chain; u= -ch2-chz-(nh-ch2-ch2-)"; n,p,g,r 2:: 1: y= bifunctional hydrocarbon chain; x, m ~ 0. fig.] polyisobutenyl succinimides experimental the interactions between performance additives were studied extensively [7]. the studies showed that the interactions are able to modify dd, extreme pressure and anti wear (ep/ a w) properties of individual additives. in order to examine the ability of interaction of the developed additives'. polyisobutenyl succinimides were synthesised having the main properties listed in table 1. to investigate the properties of these succinimides in various mixtures containina performance additive, the blends represented in table 2 were prepared (dispersant content 3.5<kmlm as active material. detergents 5.wmlm and znddp l.o%mlm). the dd effects were examined by using the testing methods of washing efficiency (we). detergent index (di) and potential-detergent~dispersant~efficiency {pdde) f 8]. 'the data of table 2 represent that interactions between ~ormance additives enhance the \ve significantly in mtxtures of bsi and calcium sulphonate. au blends show unchanged or increased pdde values. other important measurements were done to determine the rheo~ogk?l p~operties (~hange of relative viscosity and of vtscosjty mdex) whtch results are characterised bv figs.2 and j. these show the strength of interaction~ betw~n detergent_ additives and succinimide dispersants regardmg rheologtcal properties which is in the order of calcium sajicyl?tc: >.calcium pht!nate > calcium sulphonate. the polysucctmmtde sh:o\\"s the most significant vi table 1 the properties of the synthesised polyisobutenyl succinimides t_xee of additive msi mbsi* bsi psi pib molecular weight 1000 1000 1000 2300 kinematic viscosity at 230 70 50 510 100 oc, mm2 /s tbn, mgkoh/g 82 44 26 19 nitrogen content, %rnlm 3.2 1.7 1.3 1.0 base oil content, %rnlm 45 45 45 45 * blend of mono-and bissucinimide table 2 dd effects of performance additive blends washing efficiency (we) msi+znddp 0 + ca-salycilate 0 +ca-phenate 0 +ca-sulphonate ++ mbsi+znddp 0 + ca-salycilate 0 +ca-phenate 0 +ca-sulphonate ++ bsl+znddp 0 + ca-salycilate + +ca-phenate 0 +ca-sulphonate +++ psi+znddp ++ + ca-salycilate +++ +ca-phenate +++ +ca-sulphonate +++ ---... 0 ... +++: strength of significance detergent index (di) 0 0 0 0 0 pdde 0 0 0 + 0 0 0 + 0 + 0 +++ 0 ++ ++ ++ increasing effect with calcium salicylate. in order to examine another very important effect of the interactions of these additives, polysuccinimide was used for me~s~ring the changes of ep/ a w property of the addtttve blends. table 3 contains the main results of the standardised four ball tests (astm d 2783). as it can be seen in table 3, polysuccinimide itself has ep/ a w effect and the best result was obtained when c~icium salicylate or calcium phenate was used together with polysuccinimide and znddp additive. taking into consideration the presented results~ the synergy of the additives can be utilised in the formulation of engine oil compositions of high perform?nce leve~ with polysuccinimide, utilising its outstandmg dd, viscosity and viscosity index improving and ep/ a w effect whilst reducing the cost of formulation by reducing the conventionally required amount of rheological and ep/ a w additives. the formulation [9] meets the requirements of api sj/cf, acea a-3/98, ccmc g5/cd2 and other oem's (ford, gm. rover) specifications. summary various types of polyisobutenyl succinimides were examined regarding their properties and the effects of 141 table 3 data of four ball tests of different additive blends scar diameter, mm load,n base oil sn-150 +psi +psi+ +psi+zndd +psi+znddp+ +psi+znddp+ p+ca-znddp salicilate ca-phenate ca-sulphonate 1.965 2.637 2.800 welding 1.941 2.398 2.564 3.186 welding 0.341 0.735 2.278 2.413 0.312 0.311 0.312 0.728 0.394 0.379 2.106 2.047 2.226 2.294 2.275 2.240 600 800 1000 1260 1400 2000 2400 2.611 2.605 2.630 welding welding welding welding 18~·-··-··------... ---···--·-·-·~--···~-·--------·----·-------~ 016+-------------~------------~ ~14+-------------~~~----------i_ ~12+--------=~--~~~~r-------il ~10+-------1-r-~r-r ·~ 8 +---------l-\;;;;;:;---1-t--­ c 6 +----------+~ : ++--ihej...d----t0 -1-l---'"'"~~_j...._ ca-sulphonate ca-salicilate ca-phenate zrtddp fig.2 relative changes of kinematic viscosity at 40 oc by the interactions of the additives interactions, blended with performance additives of lubricating oils. detergent-dispersant, extreme pressure/antiwear and rheological properties were shown which demonstrate that utilising the synergy among the additives, lubricants of the highest performance level can be formulated and the costs of formulation can be reduced. references 1. pct wo pat. 90/03359 2. mach h. and rath p.: highly reactive polyisobutene as a composition element for a new 130 +-----------------tl=!l---!l'oca-sulphonate ~ 120 tm ca-salicilate > l!l1l ca-phenate l•znddp 100 msi mbsi bsi psi· fig.3 changes ofviscosityindexes (vlex) of the additive blends generation of lubricant and fuel additives. additives '97 conference, sopron, 52-66, 1997 3. hu pat. 206,390, hu 214,439, ep 658,572, fp 677,572 and pct wo 95/28460 4. us pat. 4,089,794 and ep 0400866 5. us pat. 5,205,949 6. us pat. 4,161,452 7. ramakumar s. s. v., aggarwal n. and rao m.: lubrication science, 1994, 7(1), 25-38 8. bartha l. and deak gy.: hung. j. ind. chern 1979 (7), 359-366 9. ep pat. 0789069 page 140 page 141 page 142 hungarian journal of industry and chemistry vol. 48(2) pp. 23–36 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-24 informative environment qualifying index anett utasi *1, viktor sebestyén1, and ákos rédey1 1sustainability solutions research lab, university of pannonia, egyetem u. 10, veszprém, 8200, hungary improvement in the quality of the environment and, as a result, in the quality of life, including environmental impact assessments and environmental management, play an important role in the practical implementation of environmental regulations. the goal of this paper is to develop a new type of quantitative environmental impact assessment method to describe changes in environmental elements as well as the environment in an objective and reliable manner for various projects, investments, plans and proposals. an easily adaptable method was sought which provides a clear and well-interpretable result on the condition of and foreseeable changes in the environment. the algorithm operates using the limit values of environmental elements set forth by national regulations. the evaluation is independent of the number of environmental parameters chosen as it was included in the informativity rates of the method. the process results in an aggregated index for qualifying the total environment but, nonetheless, the affected environmental elements and measured environmental parameters can be analysed independently. the informative environment qualifying index evaluates the environmental parameters in proportion to the strictness of the limit values. the final assessment of the total environment is performed by using varying intervals, therefore, the different cases can be compared to each other. experts interpret the results as well as explain the changes in the state of the environment and, therefore, identify the cause-effect relationships. keywords: environmental impact assessment, quantitative methods, informative environment qualifying index, environmental pollution 1. introduction the state of the environment has been changing drastically in an unfavourable direction due to economic development, rapid population growth, as well as increases in the rates of production and consumption resulting in extremely severe levels of environmental pollution amongst several other consequences. the european union itself is committed to introduce actions and measures in order to take preventive steps to protect the environment. regarding immediate actions to be implemented, environmental protection is an essential objective. the environmental impact assessment (eia) and sustainability planning are intertwined. both approaches aim to optimize future activities in an environmentally sound way and support decision-makers with appropriate, scientifically based evidence. analyses must provide quantified information as well as easily understandable and comparable results, therefore, the aggregation of quantitative methods is widespread. the aim of this work is to develop an informative environment qualifying index. in addition to indexing based on immission limits, it is important to evaluate the sustainability of cities, for *correspondence: utasi.anett@uni-pannon.hu which the sdewes index is an excellent approach [1]. this method has been implemented in southeast european cities [2] and adapted for hungarian cities [3]. toro et al. developed a qualitative methodology for environmental impact assessment (eia) processes, which uses a double matrix to identify the impacts and assign quantitative values to the categories of quality [4]. pavlickova and vyskupova elaborated on a cumulative method for the evaluation of landscape vulnerability by taking this as well as ecological stability and the ratio of different measures of stability into account [5]. herva and roca reviewed the combined approaches and multicriteria analysis for the purposes of evaluating corporate environmental performance. it was suggested to use the multi-criteria decision-making (mcdm) techniques in the industrial sector, decision-making in energy projects, waste management and wastewater treatment [6]. a possible method is the environmental impact assessment, which comprises 25 different eia methods as well as uses a quantitative framework and standard classification method as an optimal technique for the actual evaluation [7]. an integrated weight of evidence approach for environmental risk assessment proposed by caeiro et al. https://doi.org/10.33927/hjic-2020-24 mailto:utasi.anett@uni-pannon.hu 24 utasi, sebestyén and rédey where anthropogenic pollution, the impacts on human health, the exposition of polluted wells and agricultural soils as well as pollutants in sediments are combined with 14 categories of absolute conditions [8]. phillips used an enhanced rapid impact assessment matrix (riam) method to evaluate quantitatively the potential impacts of an onshore wind farm during its construction and operation [9], as well as for the sustainability evaluation of municipal solid waste management [10]. the riam approach was successfully used by brindusa et al. to evaluate the environmental impacts resulting from heavy metal pollution on the southern coast of the romanian black sea [11]. sun and wang developed a comprehensive eia system for shale-gas exploration, which includes the evaluation systems of influence with regard to the natural and macro environments. the algorithm includes social, policy and economic impacts, therefore, it can be adapted to other fields of environmental analysis [12]. robu et al. analysed the impacts and risks of heavy metal pollutants in bodies of surface water. the basis of such evaluations was the measured concentrations of the environmental parameters, therefore, the method is more objective [13]. the reliability of the different quantitative and qualitative methods may be increased by integrating the technical background of environmental risk assessment [14]. an environmental evaluation system (ees) that incorporates relationships between environmental parameters and environmental quality was developed by battelle columbus laboratories [15] and implemented for water resources planning by ferreira et al. [16]. a review of aquatic environmental assessment methods was published by foden et al. in which a new classification system is suggested that differentiates between static and dynamic links [17]. yu et al. developed a universal calibrated model for the evaluation of bodies of surfaceand groundwater. the main advantage of this algorithm is that it works with any combination of water quality indicators. it was developed in accordance with chinese legislation, therefore, must be adapted for international applications [18]. on the basis of the literature review on eia, it can be concluded that the aforementioned methods have several benefits, however, their limits should be taken into consideration. the main advantage of such methods is their suitability to compare different project alternatives. however, in light of its practical applications, two main issues need to be addressed. namely, the assessment is based on the limit values of environmental parameters, measured/calculated values as well as the ranking/weighting/scaling of the environmental parameters and elements. in addition to these, it can also be concluded that the methods in the literature are less sensitive to extreme values, namely to discharges above the limit values. in addition to environmental impacts, risk assessment is important for decision-makers. wu et al. proposed a quantitative environmental risk assessment for the iron and steel industrial symbiosis network, which provides an aggregate index value and is able to identify the most important driving forces [19]. risks were identified in a chemical plant in zhejiang province in china, where an index-based approach with the analytic hierarchy process (ahp) and fuzzy operators was used for the evaluation [20]. the objective of this paper is to develop a new, easily adaptable, objective and reliable quantitative eia method which provides an unambiguous outcome in the case of projects, investments, plants and proposals in comparison with the methods given in the literature. environmental impacts should be identified during the early design phases [21] in order to avoid unlawful and polluting activities. a widely usable, target-oriented, objective and comprehensive new type of quantitative eia technique was sought and its applicability verified. the environmental impacts were linked to human activities in order to explore the cause-and-effect relationships, therefore, systems thinking is crucial in the case of an eia. rocha et al. developed a multiple indicatorbased approach for environmental quality assessment in urban areas [22]. the proposed iieq method is suitable for tracking environmental changes which can be linked to different human activities. 2. results: methodology the informative environment qualifying index (iieq) method was developed in accordance with legal and other relevant stipulations. the iieq characterizing the total environment can be determined as depicted in fig. 1. the environmental assessment of alternatives to the project begins with screening the projects according to the applicable laws and regulations. the preparation of a reference databased bepends on the scope of the analysis. firstly, the relevant environmental elements must be selected and their limit values determined. following the preparation of the database, the algorithm is expanded by defining the environmental parameters studied for the selected environmental elements and the weighting of these parameters determined. the workflow of the method has been developed in such a way that it can be used to study an individual environmental element or complex cases, e.g. where several environmental elements are considered simultaneously. by analysing the environmental parameters (the second block in fig. 1 which qualify the given environmental element, it is possible to plan the optimal mitigation strategy for that element. therefore, the driving forces/drivers in the quality of the element are identified. the analysis with regard to the level of the environmental element provides a comprehensive picture of the state of the studied elements and important information in the evaluation of the environmental impacts of the projects. the environmental analysis (the last block in fig. 1) ensures a basis for the comparison of the different cases investigated. the iieq value helps decision-makers to determine the optimal measure or project alternative. hungarian journal of industry and chemistry informative environment qualifying index 25 figure 1: methodology of the informative environment qualifying index the method is suitable for multilevel analysis. the levels are represented by different colours in fig. 1. the final outcome of the method is the determination of the iieq. these steps are discussed in the following section. 2.1 reference database laws and regulations pertaining to the investigation the basis for the method is the set-up of the environmental reference database according to hungarian stipulations. when used in other countries, the reference database should be adjusted to pertain to the legal regulations of the country in question. the environmental elements are studied in the present paper in light of the hungarian law on the environment. the following environmental elements were taken into consideration: 1. surface water: water flows (w) 2. surface water: lakes (l) 3. groundwater (g) 4. soil (s) 5. air (a) some eia techniques, which were developed for the analyses of specific environmental elements, e.g. németh et al. provided a quantitative tool for bodies of surface water [23] to show changes in water quality of lake balaton, the largest natural shallow lake in central europe [24, 25]. in the case of air pollution, the air quality index (aqi) is a useful tool to improve public understanding and participation [26]. calculations of aqi can be supported by the two-phase decomposition technique and machine learning [27]. indoor environmental quality (ieq) can also be taken into consideration as this was analysed in a university building [28]. the eia techniques can be sector-specific as well, e.g. sanz et al. developed a new well-being index to describe the environmental quality of renewable energy sources and nuclear power [29]. one of the most important goals during the development of the iieq was to provide a tool that facilitates the public understanding of environmental impacts in a simple, clear way, which includes more graphical representations of the impacts and is capable of describing changes in the state of the environment across an aggregated index value. determination of the environmental parameters for the environmental elements studied lists of environmental parameters are collected for every environmental element which is to be evaluated according to the pertaining stipulations. the database includes the names of the environmental parameters as well as their limit values and validity. the list for surface water is based on gd 2010 [31], the water framework directive. the lists for soil as well as groundwater are based on gd 2006 [32], and the one for the environmental parameters of air can be defined on the basis of gd 2011 [33]. environmental parameters for which no limit values are specified can be studied as well, since the numerical target for the environmental parameters should be determined by specialists and such values are to be included in the list of environmental parameters. weight of environmental parameters generally speaking, the objectivity of the eia is compromised or questionable when a specialist defines the weighted preferences for the environmental parameters. in order to solve this problem, the authors have developed a weighting procedure based solely on environmental regulations and specifications. the hypothesis assumes that legislators took the risks and impacts of the environmental parameters into account whilst defining the limit values. the iieq weighting procedure defines different categories of importance with regard to the environmental elements on the basis of the order of magnitude of the limit values. to determine the confined values of the intervals, the lowest (most severe) and highest (mildest) limit values should be sought in the specifications and classified in the appropriate categories of magnitude. the other limit values should be ranked between those two 48(2) pp. 23–36 (2020) 26 utasi, sebestyén and rédey figure 2: weights of the various environmental elements predefined confined values. the environmental parameters are classified by fitting a natural logarithmic curve as can be seen in fig. 2, where the x and y axes indicate the magnitude and weight of the environmental parameters, respectively. weights of 1 and 0.01 represent the most severe and mildest situations, respectively. the equations of the aligned curves are given in fig. 2 by taking into consideration environmental elements (according to hungarian regulations, the same magnitudes are assigned to certain environmental elements). fig. 2 presents the relationship between the air, bodies of surface water, soil and groundwater. using the equations given in fig. 2, weights, presented in table 1, can be generated for the given environmental parameters. in the case of surface water, the limit value of po4-p is 200µg/l, which belongs to the order of magnitude of 102, therefore, its value is 0.122. in the case of mercury, the limit value is 0.05µg/l, which can be assigned to the order of magnitude of 10−2, therefore, its value is 0.505. table 1: weights according to orders of magnitude orders of magnitude of the environmental parameters studied exponent of 10 wa ww&s wg&l 0.000001 -6 1 *o.r. *o.r. 0.00001 -5 0.714 *o.r. *o.r. 0.0001 -4 0.546 1 1 0.001 -3 0.427 0.687 0.714 0.01 -2 0.335 0.505 0.546 0.1 -1 0.26 0.375 0.427 1 0 0.196 0.274 0.335 10 1 0.141 0.192 0.26 100 2 0.093 0.122 0.196 1,000 3 0.049 0.062 0.141 10,000 4 0.010 0.010 0.093 100,000 5 *o.r. *o.r. 0.01 *o.r.: outside the range of interpretation figure 3: the qualifying diagram of an environmental element on the basis of the quality factor (fpi), quality index (ipi) and quality indicator (∆pi) of the environmental parameter 2.2 analysis of parameters in order to better understand the status of environmental elements, a visualization technique has been developed where the pollution/environmental load of an environmental element is represented by circles of defined radii and areas (fig. 3). as a result, the parameters describing the environmental elements can be represented by segments of a circle (hereinafter referred to as “segment”). the following basic considerations were taken into consideration: the radii of the different segments are the ratios of the measured parameters to limit values expressed as percentages, referred to as the so-called environmental parameter quality index. environmental parameter quality index (ipi) the environmental parameter quality index (ipi) specifies the relationship between the immission concentration and limit values defined by the environmental specifications. ipi is determined by ipi = mvi lvi 100 (1) where ipi is the environmental parameter quality index for parameter i, mvi is the measured value of environmental parameter i, and lvi is the limit value of environmental parameter i. if the value of ipi changes between 0 and 100%, the environmental parameter meets the legal specifications. however, if it exceeds 100%, the limit value is exceeded and mitigation measures must be considered. environmental parameter quality factor (fpi) the environmental parameter quality factor (pi) is determined on the basis of the weight. the central angles (fp1, fp2, fp3) of the circle as depicted in fig. 3 are calculated by fpi = wi 360∑npj l=1 wl (2) hungarian journal of industry and chemistry informative environment qualifying index 27 figure 4: immission analysis as a function of the environmental parameter quality index and factor where fpi is the environmental parameter quality factor for environmental parameter i,wl is the weight of the examined environmental parameter, and npj is the number of environmental parameters in the case of environmental element i. environmental parameter quality indicator (∆pi) the environmental parameter quality indicator (∆pi) is given by ∆pi = (ipi) 2 π fpi 360 (3) where ∆pi is the environmental parameter quality indicator for environmental parameter i, ipi is the environmental parameter quality index for environmental parameter i (according to eq. 1), and fpi is the environmental parameter quality factor for environmental parameter i (according to eq. 2). the environmental parameter quality index for environmental parameter i is of square/quadratic form to emphasize the importance of the measured concentration of the parameter. according to this interpretation, the different parameters with different units can be compared to each other so the environmental parameters can be easily qualified whether they exceed the limit values or fall within them. the central angles of the segments (fp1, fp2, fp3) represent the importance of the environmental parameter in question which is expressed as the environmental parameter quality factor as defined by eq. 2 . regarding fig. 3, the expression of the environmental parameter quality indicator is introduced based on the area of the segment (eq. 3), which represents the extent to which the environmental parameter has an impact on the environmental element. immission analysis the environmental parameters defined above can be illustrated in a three-dimensional system, therefore, the key parameters of the studied impact area identified. fig. 4 illustrates the environmental parameter quality indicators (∆pi) as a function of the environmental parameter quality factor (fpi) and the environmental parameter quality index (ipi). fig. 4 shows the environmental parameters, their risks and the environmental damage caused should their values be extreme. according to the informative environment qualifying index method, the risk is a function of the specified limit value or target. the following conclusions can be drawn on the basis of fig. 4. the area (xmin; ymin; zmin) represents the group of environmental parameters for which the limit values are mildest and present in low concentrations, therefore, their negative impact on the environment is minimal. the point (xmax; ymax; zmax) represents the group of environmental parameters for which the limit values are most severe and present in high concentrations, therefore, their negative impact on the environment is maximal. according to the protocol defined here, the key factors can be identified on the basis of a system-oriented method and the outcome of the analysis used for plan48(2) pp. 23–36 (2020) 28 utasi, sebestyén and rédey figure 5: the relationship between the load of the environmental element and the reference areas ning the environmental mitigation measures. 2.3 analysis of the environmental element level the analysis of the environmental element level provides information to specialists about the cumulative impact of the environmental parameters on the environmental element in question. load of environmental elements (elj) the cumulative environmental impacts of the environmental elements can be determined by totalling the environmental parameter quality indicators (∆pi), which are equal to the sum of the areas of the segments. the environmental element can be interpreted as a circle and the total levels of pollution stemming from the environmental parameters are represented by circles with different radii (fig. 5). in fig. 4, the circle with r = 100 represents the case when the load of the environmental element is equal to the total limit load of the environmental parameters. qualification of environmental elements for the numerical evaluation of an environmental element, the relationships required are defined in table 2. on the basis of the outcome of case studies and professional experience, 10 categories were defined for the environmental evaluation: 10-30-50-70-90-100-110-150200-300. in fig. 5, blue-coloured zones mark the acceptable categories (categories in table 2: 10, 30 and 50), the green-coloured zones represent maximum environmental quality with regard to immission limit values (categories 70, 80 and 100), and the orangeas well as yellowcoloured zones represent situations when the level of pollution exceeds the limit value (categories 110, 150, 200 and 300). given these defined categories, the relative radius can be calculated from which, after working out the area of the circle (as = r2π), the corresponding area can be determined (as). this corresponding area can be interrelated to the load of the environmental parameters studied, that is to the total area of the segments (elj) representing the environmental parameters. from the load of the environmental parameters, the total area can be calculated by a numerical evaluation. the qualification/level of pollution of the environmental element can be determined from table 2. the interval when the load of the environmental element (elj) is less than the reference area (as) needs to be determined. table 2 can be used generally to evaluate all environmental elements and is independent from the number of environmental parameters with regard to the environmental elements since the environmental parameter quality factors (flip) are normalized for 360◦. the values of the environmental parameter quality factors depend on the number of environmental parameters and their weights. theoretical number of environmental parameters (ntj) the theoretical numbers of environmental parameters define the number of environmental parameters to be measured as well as monitored according to the stipulations and are based on the reference database. they are summarized in table 3: practical number of environmental parameters (npj) during the environmental impact assessment, specialists define the environmental elements to be studied and the scope of the environmental parameters. the set of environmental parameters can be different in the case of a natural environment, post-disaster situation or artificial environment. the method puts a special emphasis on the determination of the uncertainties. element quality index (iej) the element quality index determines how the immission concentrations are related to the pollutants to be theoretically released into the environment: iej = √ elj π (4) where iej is the element quality index for environmental element j and elj is the environmental load of environmental element j. element quality factor (fej) the element quality factor (fej) specifies the weight of the environmental element during the evaluation process. the goal of this factor is to take the number of environmental parameters into consideration (eq. 7): fej = npj360∑m k=1 ntk (5) hungarian journal of industry and chemistry informative environment qualifying index 29 table 2: the qualification system for evaluating the different environmental elements reference radius (r) reference area (as) evaluation 300 282743 the environmental element is seriously damaged which the ecosystem cannot tolerate. 200 125664 natural regeneration is impossible because the environmental element is seriously damaged. 150 70686 natural regeneration is inhibited because the environmental element is damaged. 110 38013 the concentrations of the environmental parameters defining the environmental element exceed the limit value. 100 31416 the concentrations of the environmental parameters defining the environmental element are equal to the limit values. 90 25447 the concentrations of the environmental parameters defining the environmental element are close to the limit value. 70 15394 the environmental element with environmental parameters below the limit value or influenced by anthropogenic impacts. 50 7854 the environmental element with minimal disturbances. 30 2827 the natural environmental element with indirect or direct anthropogenic impacts. 10 314 the natural environmental element free of anthropogenic impacts. where fej is the element quality factor for environmental element j, npj is the practical number of environmental parameters in the case of environmental element j, ntk is the theoretical number of environmental parameters in the case of environmental element j (table 3), and m is the number of environmental elements. environmental element informativity rate (fij) the environmental element informativity rate (fij) represents the ratio of the number of theoretical environmental parameters (ntk) for which legal requirements are in effect to the number of investigated environmental parameters. the ideal value of the environmental element informativity rate is equal to when all parameters set forth by the legal stipulations are involved in the investigation: fij = npj ntk (6) where fij is the environmental element informativity rate for environmental element j, npj is the practical number of environmental parameters in the case of environmental element j, and ntk is the theoretical number of environmental parameters in the case of environmental element k (table 3). 2.4 environmental analysis the next step to be undertaken, following the investigation of the environmental parameters and elements, is the comprehensive analysis of the whole environment. the whole environmental system should be evaluated by taking the human, health, social, economic and cultural astable 3: the theoretical numbers of environmental parameters (ntk) for different environmental elements environmental element theoretical number of environmental parameters (pcs) surface water: water flow 59 surface water: lake 59 groundwater 58 soil 52 air 33 pects into consideration in an integrated way. it is insufficient to solely focus on the natural or artificial environment. the usability of a given project area depends on several factors, not only on the excellence of one environmental element. therefore, a holistic approach is adopted during the evaluation. element quality indicator (∆ej) the element quality indicator (∆ej) enables the environmental element to be taken into consideration in light of the weights of the environmental parameters that describe the environmental element. those environmental elements which are monitored less contribute to a lesser extent with regard to the characterization of the environment. during the analysis, the cumulative load of the environmental elements is taken into account: ∆ej = i2ejπ fej 360 (7) where ∆ej is the element quality indicator for environmental element j, iej is the element quality index for environmental element j (according to eq. 4), and fej is the element quality factor for environmental element j (according to eq. 5). total environmental load (tl) the total environmental load (tl) represents the proportional pollution of the whole environment, which can be generated by the summation of the element quality indicators (∆eqj). the environmental load is regarded as the most important issue during the calculation of the informative environment qualifying index (iieq) as defined by tl = m∑ j=1 ∆ej (8) where tl is the total environmental load, ∆ej is the element quality indicator for environmental element j (according to eq. 7), and m is the number of environmental elements. 48(2) pp. 23–36 (2020) 30 utasi, sebestyén and rédey table 4: evaluation table of the whole environment reference radius (r) dynamical reference area (ad) evaluation 300 3002πfenv.i degraded area which the ecosystems cannot accommodate. 200 2002πfenv.i the natural regeneration of the environment is impossible because the area is severely damaged. 150 1502πfenv.i natural regeneration is inhibited because of the damaged area. 110 1102πfenv.i the concentration of the environmental parameters exceeds the limit value. 100 1002πfenv.i the concentration of the environmental parameters is equal to the limit value. 90 902πfenv.i the concentration of the environmental parameters is similar to the limit value. 70 702πfenv.i the environment is influenced by levels of pollution under the limit value and directly influenced by anthropogenic impacts. 50 502πfenv.i the environment closely resembles the natural conditions or with minimal disturbances. 30 302πfenv.i the natural environment with direct or indirect anthropogenic impacts. 10 102πfenv.i the natural environment free of anthropogenic impacts. qualification of the total environment table 4 is used to evaluate the total environment, which is based on dynamical reference areas as calculated from ad = r2πfenv.i (9) where ad is the dynamical reference area (the level of the whole environment), r is the reference radius (table 4), and fenv.i is the environment informativity rate (eq. 10). the basis of the dynamical reference area is the reference radius (fig. 5 and table 2) by which 10 different categories of quality were defined. the dynamical reference area depends on the ratio of the studied environmental parameters to the theoretical number of environmental parameters (informativity defined in the method). the numerical assessment of the whole environment results in the element quality indices from the environmental load stemming from the total environmental parameters for the environmental elements. the evaluation of table 4 concerns the results in terms of quality/pollution during the interval, in which case the value of the total environmental load (tl) is less than the dynamical reference area (ad). environment informativity rate (fenv.i) the environment informativity rate (fenv.i) shows the depth of monitoring with regard to the environmental elements during the environmental evaluation: fenv.i = ∑m j=1 npj∑m k=1 ntk (10) where fenv.i is the environment informativity rate, npj is the practical number of environmental parameters in the case of environmental element j, ntk is the theoretical number of environmental parameters in the case of environmental element k, (table 3), and m is the number of environmental elements. the environment informativity rate (fenv.i) indicates the coverage of the environmental parameters used in the investigation compared to the specified environmental parameters. the environmental impact assessment is more informative if the scope of the environmental parameters is larger. lim npj→ntk (fenv.i) = 1 (11) according to eq. 11, the value of fenv.i approaches 1 if the practical number of environmental parameters (npj) closely resembles the theoretical number of parameters (ntk). informative environment qualifying index (iieq) the final outcome of the method that is elaborated on is the informative environment qualifying index, which is a complex indicator (eq. 12). the status of the environment is determined on the basis of the load of the different environmental elements and the informativity. its value depends on the actual load of the environmental elements as well as the practical and theoretical numbers of environmental parameters. from the reference radius of table 4 during the evaluation, iieq determines the accurate radius of the area derived from the actual load of the environmental elements: iieq = √ tl πfenv.i (12) where iieq is the informative environment qualifying index, tl is the total environmental load (eq. 8), and fenv.i is the environment informativity rate (eq. 10). the application of the informative environment qualifying index provides a solid basis to compare the outcomes of different environmental evaluations since certain cases can differ from each other regarding the parameter sets. iieq includes all these variables. the method can be expediently used to evaluate the environment before and after a disaster (e.g. the red mud disaster of devecser), and the outcomes of the studies can be evaluated as a function of time. the method provides an opportunity to compare different cases (industrial parks, settlements, the natural environment) as well as provides a systemized and comprehensive approach to the evaluation. 2.5 a case study zirc is a small city in the heart of the bakony mountains in western hungary. the city and its surroundings is a distinguished touristic area in hungary with several natural attractions. an arboretum and national parks are situated in the direct vicinity of the city. the water quality of the cuha stream which flows through the city is influenced hungarian journal of industry and chemistry informative environment qualifying index 31 table 5: the measured parameters of zirc on june 13, 2016 the basic data of surface water environmental parameters measured value limit value electrical conductivity (µs/cm) 985 1,000 codcr (µg/l) 3,300 30,000 no3-n (µg/l) 1,497.24 2,000 nh4-n (µg/l) 50 400 po4-p (µg/l) 169 200 the basic data of air environmental parameters measured value limit value no (µg/m3) 3.708 100 nox (µg/m3) 8.406 200 co (µg/m3) 278.77 10,000 o3 (µg/m3) 80.77 120 benzene (µg/m3) 0.331 10 pm10 (µg/m3) 16 50 by the wastewater treatment plant located here. the population of zirc is 7, 106 and the main economic activity in the region is agriculture. during the field studies in the summer of 2016, two environmental elements were measured, namely surface water and air. the location of the measurement points is shown in fig. 6. in the case of surface water and air, the environmental parameters as defined in table 5 were measured. the weights as well as quality indices, quality factors and quality indicators of parameters were determined and are summarized in tables 6 and 7. fpi in the last rows of tables 6 and 7 are used as a control since their total value must be equal to 360. values of elj , as defined in table 2, constitute the basis of the numerical evaluation. the value of the parameter quality index for the environmental parameter po4-p calculated on the basis of eq. 1 is illustrated below. the measured value of the parameter po4-p was 169 mg/l and the limit value pertained to it was 200 mg/l [30]. ippo4−p = 169(mg l ) 200(mg l ) 100 = 84.5 the parameter quality factor for the environmental parameter po4-p is determined on the basis of eq. 2. the weight of po4-p is 0.12 and the five numbers in the denominator include the weight of the five environmental parameters of water. fppo4−p = 0.12 · 360 0.06+0.01+0.06+0.12+0.12 = 116.22 the values of ipi and fpi calculated for the environmental parameters listed in tables 6 and 7 constitute the basis of the calculation. parts a and b of fig. 7 refer to the surface water and air, respectively. on the basis of the parametric analysis of surface water, it can be concluded that the maximum limit value is defined for po4-p. therefore, in the following steps, the maximum weight (fpi = max) is assigned to po4-p. the electrical conductivity is close to the limit value and the parameter quality index of no3-n is ∼ 75%. these parameters are key to improve the water quality in zirc and are represented by circles in fig. 7. a similar analysis of air was also carried out. for the environmental parameter po4-p, the parameter quality indicator is based on eq. 2 using the parameter quality index (84.50) and parameter quality factor (116.22): ∆ppo4−p = 84.52 · 3.14 · 116.22 360 = 7, 241.59 the quantitative analysis of the environmental elements of surface water and air is depicted in fig. 8. parts a and b of fig. 8 refer to the surface water and air, respectively. the weights of the environmental parameters can be seen in fig. 8 during the evaluation procedure (the total of the interior angles of the segments is equal to fpi). the radii of the sectors are identical to the values of ipi which provide information on the quality. the load of the environmental element (elw) of the surface water is equal to 15, 296. the qualification system for evaluation of the different environmental elements (table 2) functions by substitution. an assignment in the category of r = 50 (environmental element with minimal disturbances, table 2 is obtained. it can be concluded that the water quality of the cuha stream was disturbed to a minimal extent. nevertheless, the ecosystem can tolerate this level of pollution. by applying eq. 4, the values of the environmental quality index express the actual loads of the environmental elements. on the basis of measurements in zirc, the five parameters for surface water represent an area, iew, equal to r = 69.78, while the six environmental parameters for air represent an area, iea, of r = 31.58: iew = √ 15, 295.6 3.14 = 69.78 iea = √ 3, 132.57 3.14 = 31.58 following these steps, the aforementioned algorithm was followed. the element quality factors for water and air, few and fea, were calculated according to the theoretical number of environmental parameters, altogether 92 parameters are to be monitored according to the specifications of gd 2010 [30] and gd 2011 [32]. in the case studies for surface water and air, five and six environmental parameters were investigated, respectively. few = 5 · 360 92 = 19.57 fea = 6 · 360 92 = 23.48 next, the environmental element informativity rate was determined. the environmental element informativity rates for surface water and air are 0.08 and 48(2) pp. 23–36 (2020) 32 utasi, sebestyén and rédey figure 6: the measuring points and location of zirc in hungary table 6: the results of the calculations (eqs. 1-3) for all measured parameters in the case of surface water from cuha stream, zirc parameter (unit) measured value limit value wi ipi fpi ∆pi electrical conductivity (µs/cm) 985 1,000 0.06 98.5 59.03 4,998.33 cod (mg/l) 3,300 30,000 0.01 11 9.5 10.03 no3-n (mg/l) 1,497.24 2,000 0.06 74.86 59.03 2,887.19 nh4-n (mg/l) 50 400 0.12 12.5 116.22 158.47 po4-p (mg/l) 169 200 0.12 84.5 116.22 7,241.59 total *n/a *n/a *n/a *n/a 360 elw = 15, 296.6 *n/a: not applicable table 7: the results of the calculations (eqs. 1-3) for all measured environmental parameters in the case of air in the vicinity of the mayor’s office, zirc parameter (unit) measured value limit value wi ipi fpi ∆pi no2 (µg/nm3) 3.71 100 0.09 3.71 58.45 7.01 nox (µg/nm3) 8.41 200 0.09 4.2 58.45 9.01 co (µg/nm3) 278.77 10,000 0.01 2.79 6.32 0.43 o3 (µg/nm3) 80.77 120 0.09 67.31 58.45 2,310.77 benzene (µg/nm3) 0.33 10 0.14 3.31 89.17 8.53 pm10 (µg/nm3) 16 50 0.14 32 89.17 796.83 total *n/a *n/a *n/a *n/a 360 ela = 3, 132.57 *n/a: not applicable hungarian journal of industry and chemistry informative environment qualifying index 33 figure 7: immission analysis of the surface water (left-hand side, part a) and air (right-hand side, part b) figure 8: the quantitative analysis of the environmental elements (left-hand side: water, part a; right-hand side: air, part b) 0.18, respectively. it should be noted that the total of feqw/feiw = 19.57/0.08 = 230.87) and feqa/feia = 23.48/0.18 = 129.13) is equal to 360. fiw = 5 59 = 0.08 fia = 6 33 = 0.18 on the basis of eq. 7, the load of the whole environment (∆ej) can be calculated using the actual load of the environmental elements. the actual load is substituted into the equation in the square/quadratic form, while npj/ntj for the informativity is linear. ∆ew = 69.782 · 3.14 · 19.57 360 = 831.28 ∆ea = 31.582 · 3.14 · 23.48 360 = 204.3 the total load of the environment is equal to the total of the summarized loads of the environmental elements (eq. 8). in the case of zirc, the larger proportion of environmental load stems from the surface-water pollution and the load of the air pollution represents roughly 20%. tl = 831.28 + 204.3 = 1, 035.58 the whole environment can be evaluated by the dynamical reference areas as given by eq. 9 and table 4. by substituting tl into table 4, it can be stated that the parameters describing the status of the environment are close to the concentrations of limit values. the radius assigned to the environmental quality of the city is equal to r = 50. a50 = 502 · 3.14 · 0.12 = 939 in the aforementioned formula, the radius is equal to 50, representing the worst category of quality. the environmental element informativity rate is 0.12 (eq. 10) which provides information on the number of environmental parameters in the study. fenv.i = 5 + 6 59 + 33 = 0.12 the informative environment qualifying index (iieq) is calculated on the basis of eq. 12: iieq = √ 1, 035.58 3.14 · 0.12 =52.51 iieq of zirc is 52.51. by substituting this value into table 4, it can be seen that the environmental parameters 48(2) pp. 23–36 (2020) 34 utasi, sebestyén and rédey describing the status of the environment closely resemble the natural conditions with minimal disturbances. specialists agree with the results, which are supported by the outcome of the field study. 3. conclusion the novelty of the informative environment qualifying index method is that the maximum environmental loads of the environmental parameters as stipulated in the legal specifications and the actually measured/calculated levels of pollution are taken into consideration when compared to the methods published in the literature. during the evaluation, the algorithm is applied at different levels, namely at the levels of environmental parameters, environmental elements and the total environment, to expediently elaborate on the planning of environmental mitigation measures. the quantitative methods used in the environmental impact assessment procedure include several subjective components during the weighting/ranking/scaling which could result in different interpretations with regard to the outcome of the evaluation. the informative environment qualifying index method is based on the specifications of national regulations, while the weight of the environmental elements depends on their status and the number of environmental parameters included in the study. the informative environment qualifying index method is suitable for following up and monitoring the status of the environment in the cases of protected areas, national parks, urban areas, disasters, etc. the applicability of the method was demonstrated in the case of zirc, a small city in the heart of the bakony mountains in western hungary. the scope of the evaluation ranges from the category “environment close to the natural conditions or with minimal disturbances” to “natural environmental elements with indirect or direct anthropogenic impacts”. the method casts light on the significant environmental impacts without concealing extreme situations nor distorting the final conclusions. acknowledgement the financial support of széchenyi 2020 under project ginop-2.3.2-15-2016-00016 is acknowledged. the financial support of széchenyi 2020 under the project efop-3.6.1-16-2016-00015 is acknowledged. nomenclature ∆ej quality indicator for environmental element j ∆pi quality indicator for environmental parameter i a subscript, air ad dynamical reference area (level of the total environment) as reference area (level of the environmental elements) elj environmental element load of environmental element j fej quality factor for environmental element j fenv.i informativity rate of total environment fij informativity rate of environmental element j fpi quality factor for environmental element i g subscript, groundwater iej quality index for environmental element j iieq informative environment qualifying index ipi quality index for environmental element i l subscript, surface water: lake lvi limit value of environmental parameter i m number of environmental elements mvi measured value of environmental parameter i npj practical number of parameters in the case of element j ntk theoretical number of parameters in the case of element k r reference radius s subscript, soil tl total environmental load w subscript, surface water: water flow wi, wl weights of environmental parameters i and l references [1] kılkış, ş.: composite index for benchmarking local energy systems of mediterranean port 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(viii. 18.) of ministry of rural development (vm) defining the rules for establishment and use of water pollution limits of surface water (in hungarian) [32] gd (2006) joint government decree no. 6/2009. (iv. 14.) of ministry of health and ministry of agriculture and rural development (kvvm-eümfvm) from the limit values and the measurement of pollutants for the protection from pollution of soil and groundwater (in hungarian) [33] gd (2011) government decree no. 4/2011. (i. 14.) of ministry of rural development (vm) from the ambient air quality limit values and the emission limit values of stationary point sources of air pollutants (in hungarian) hungarian journal of industry and chemistry https://doi.org/10.1016/j.scitotenv.2016.12.018 https://doi.org/10.1016/j.scitotenv.2016.12.018 https://doi.org/10.1016/j.buildenv.2018.05.001 https://doi.org/10.1504/ijgw.2016.075448 https://doi.org/10.1504/ijgw.2016.075448 https://doi.org/10.1515/hjic-2017-0008 https://doi.org/10.1515/hjic-2017-0008 introduction results: methodology reference database laws and regulations pertaining to the investigation determination of the environmental parameters for the environmental elements studied weight of environmental parameters analysis of parameters environmental parameter quality indicator (pi) immission analysis analysis of the environmental element level load of environmental elements (elj) qualification of environmental elements theoretical number of environmental parameters (ntj) practical number of environmental parameters (npj) element quality index (iej) element quality factor (fej) environmental element informativity rate (fij) environmental analysis element quality indicator (ej) total environmental load (tl) qualification of the total environment environment informativity rate (fenv.i) informative environment qualifying index (iieq) a case study conclusion hungarian journal of industrial chemistry veszprem vol. 29. pp. 129134 (2001) identification of nonlinear systems using gaussian mixture of local models j. abonyi, t. chovan and f. szeifbrt (department of process engineering, university ofveszprem, p.o. box 158, h-8201, hungary) received: october 8, 2001 identification of operating regime based models of nonlinear dynamic systems is addressed. the operating regimes and the parameters of the local linear models are identified directly and simultaneously based on the expectation maximization (em) identification of gaussian mixture model (gmm). the proposed technique is demonstrated by means of the identification of a neutralization reaction in a continuously stirred tank reactor. keywords: operating regime based model, expectation maximization, takagi-sugeno fuzzy model, nonlinear system, neutralization reaction introduction the problem of a successful model based control application arises from difficulties in system modeling [1, 2]. this difficulty stems from lack of knowledge or understanding of the process to be controlled [3]. while it may not be possible to find process information that is universally applicable, .it would certainly be worthwhile to examine what types of process-knowledge would be most relevant for specific operating points of the process. this type of local understanding, in fact, will be a key to identifying reliable local models with a limited amount of data. the model that has a range of validity less than the operating regime of the process is called local model, as opposed to a global model that is valid in the full range of operation. global modeling is a complicated task because of the need to describe the interactions between a large number of phenomena that appear globally. local modeling, on the other hand, may be considerably simpler, because locally there may be a smaller number of phenomena that are relevant, and their interactions are simpler [4]. the modeling framework that is based on combining a number of local models. where each local model has a predefined operating region in which the local model is valid is called operating regime based model [5], where the local models are combined into a global model using an interpolation technique as it is illustrated in fig. i. the main advantage of this framework is its transparency. both the concept of operating regimes and the model structure are easy to understand. this is important, since the model structure can be interpreted in terms of operating regimes, but also quantitatively in terms of individual local models. the operating regime of the local models can be also represented by fuzzy sets [6]. this representation is appealing, since many systems change behaviors smoothly as a function of the operating point, and the soft transition between the regimes introduced by the fuzzy set representation captures this feature in an elegant fashion. fuzzy modeling and identification proved to be effective tools for the approximation of uncertain nonlinear systems because of the ability to combine expert knowledge and measured data. fuzzy models use if-then rules to describe the process through a collection of locally valid relationships. the antecedents (if-parts) of the rules divide the input space into several fuzzy subspaces, while the consequents (then-parts) describe the local behavior of the system in these fuzzy subspaces [7]. in this paper the local models are linear. the contribution of this paper is two-fold: • a new method for the identification of operating regime based models is proposed based on em identification of gaussian mixtures model. • method to transform the obtained mt1del imo takagi-sugeno fuzzy model is presented. the paper is organized as follows. section 2 pre~ents the structure of the operating regime based model along with the methods for its transformation into a fuzzy model. in section 3, the identification algorithm of the 130 y(k) where the l/j;(xk) function describes the operating regime of the i -th local linear model defined by the ei =[a; ,bi r parameter vector. the operating regime of the local models can also be represented by fuzzy sets [6]. hence, the entire global model eq.(3) can be conveniently represented by takagi-sugeno fuzzy rules: r;: if xk is a;(xk) then yk =a; xk +hi' i = l, ... ,c (4) u(k) where a; (xk) represents the multi variable membership function that describes the fuzzy set a; while a; and fig. i example for an operating regime based model. the operating region defined by the current input u(k) and output y(k) of the system is decomposed into four regimes. · model is proposed. an application example the identification of a ph process is given in section 3. conclusions are given in section 4. operating regime based modeling of dynamical system nonlinear dynamic systems are often represented in the nonlinear autoregressive with exogenous input (narx) model form, which establishes a nonlinear relationship between the past inputs and outputs and the predicted output: y(k +1) = f(y(k) •.•. ,y(k -ny),u(~-nd), .•. ,u(k -n")) (1) here, n.,. and n 11 denote the maximum lags considered for the output, and input terms, respectively, nd <nil is the discrete dead time, and f represents the mapping of the narx model. the aim of this paper is to develop an algorithm for the identification of a transparent and easily interpretable model (2) based on some available training pattern y1 and x4 = [tu ~ .... .xd y t where k = 1~ ... ~ n denotes the index: of the k .. th data that can be used for identification. when eq.(2) is used to represent a narx modet the training pattern is formed to have a model that gives one-step-ahead prediction: yt = y(k +ll, xt = [v(k) •... ~y(k -n~),u(k -nj)• ...• u(k -n,.,).f. the operating regime based model of the system given by eq.(2j is formulated as: r 5,., = l9i(x,) (al xh +hi) (3) l=l bi are the parameters of the local linear model. usually, the antecedent proposition "xk is a;(xk)" is expressed as a logical combination of simple propositions with univariate fuzzy sets defined for the individual components of xk , often in a conjunction form: r1• : if x 1 k is a1• 1 (x1 k) and ... and xn k is a; n (xn k) , , , , ' ' (5) then yk =a; xk +h; in this case, the degree of fulfillment of a rule is calculated as the product of the degree of fulfillment of the fuzzy sets in the rule /3;(xk) = a;(xk) = ii: ai,j(xj,k) (6) j=l' the rules of the fuzzy model are aggregated using the fuzzy mean formula c l wi /3;(xk)(a;xk +b) yk=~~~~---c----------(7) lw; f3;(xk) i=l where w; = [0,1] is the weight of the rule that represents the desired impact of the rule. the value of w; is often chosen by the designer of the fuzzy system based on his or her belief in the goodness and accuracy of the i -th rule. when such knowledge is not available w; is set as w; = 1, \;fj. as eq.(7) and eq.(3) show, fuzzy models are identical to operating regime based models as the operating region of the local linear models are defined by the normalized rule fulfillments: w; {3i(xk) r (8) l:wi /3;(xa) i=l to represent the ai.i(xu) fuzzy set, in this paper gaussian membership function is used (9) where v,. . represents the center and a,~ . the. variance of ,j ,) the gaussian function. the use of gaussian membership functions allows the compact formulation of eq.(6): ,b;(x,) ~ a;(x,) ~exp( -~(x,-v;l (f;'t' (x,vj)) (10) where v~ = [ v1,j' ... , v n) represents the center of the i th multivariate gaussian and (f:xf1 stands for the inverse of a diagonal matrix that contains the variances: [a~; 0 xx 0 2 fi = : (j2,i 0 0 1] (11) this compact formulation of the operating regime based model suggests that the model is not only equivalent to a ts fuzzy model but it is functionally identical to generalized radial basis function network (gbfn) [8]. when there is a correlation among input variables of the model, f;xx is not a diagonal matrix as it was shown in eq.(ll). in this case the decomposition of ai(xk) to ~./xj,k) fuzzy sets by a ( ii n ( ) iin ( 1 (xj,k -zvi,jl) (12) i xk) = i=l ~.i xi,k = i=l exp 2 ai,j is not possible directly. the proposed method to solve this problem is based on the eigenvector projection [9] or transformed input-domain approach [10]. the approach is based on the calculation of the eigenvalues ali and the eigenvectors t~ , of the ~xx matrix, where j = l, ... ,n. using the eigenvalues and the eigenvectors the following fuzzy model that has no correlation in its transformed input space can be obtained: r; : if (t~)t xk is a;,1 and ... and (t~)r xk is a;,n ( 13 ) then yk =a; xk + b1 where the gaussian membership functions are defined as h _ ( i )t _ ( i t x d -2 _ ( 11 )2 were x ... t. x .. , v.,t.) v. an 0'; 1 ·a 1· }." j " l,j j l , denote the transformed input variable, the cluster center and variance, respectively. the aim of the remaining part of the paper is to propose a new identification technique for the identification of the model presented above. 131 em algorithm for identification of mixture of gaussians model the expectation maximization (em) algorithm is an iterative algorithm for the computation of maximum likelihood parameter estimates when the observations can be viewed as incomplete data. the em algorithm is widely used for parameter estimation of the mixture of models, in particular the mixture of gaussians model [11]. the basics of em are the following. suppose we know the observed values of a random variable z and we wish to model the density of z using a model parameterized by rj . each observation consists of n + 1 measured variables, grouped into an n +!-dimensional column vector z k = [zl,k' ... 'zn+l,k r . a set of n observations is denoted by z and represented as a matrix: [ z,,, zr,z z,,n l z = zz,l zz,z zz,n (15) zn:i,l zn+l,2 zn:!.n as the identification is performed on the available identification data, z is divided into a regression data matrix x and a regression vector y (16) (17) in the pattern recognition terminology, the columns of z called patterns or objects, the rows are called the features or attributes, and z is called the pattern matrix. em obtains parameter estimates fj which maximize the likelihood l(rj) = p(z~) of the data. the em assumes that this estimation is intractable and the values of a missing or hidden random variable h would make the problem more tractable. let p(z,h~) denote the joint probability of z and h parameterized by 11 • it is assumed that z and h are such that maximizing the complete data likelihood lr(rj) = p(z,hjr]) is more tractable than maximizing l(q). however, the values of h are not known. the em algorithm tackles this problem by iteratively generating a probability over ~he values h and estimating the parameters whtch maximize the expected value of l< vj) with respect to b. the mixture of gaussians model represents the p(z~) probability density function that b e\panded in a sum over the c clusters 132 c c p(z~) = l p(z,1ji) = lp<zl1]j)p(1ji) next we compute the remaining parameters of the (18) cluster, the mean i=l i=l where 1j is the set of the parameters 1j = {1j;ii = l, ... ,c} of the model and p(1j;) denotes the unconditioned cluster probabilities normalized to satisfy :l;=l p(1j;);:::: 1. the p(zj1ji) distribution generated by the i -th cluster is represented by gaussian like p(z~-) 1 exp(-.!.(z-v.l (f.f1 (z-v.)) (19) i ( 27c ff .jifj 2 l i l where 1j; represents the parameters of the i -th cluster, 1]; ={v;,fzli=l, ... ,c}. as each data point zk is generated by one and only one of the component gaussians, the hidden random variable hk for the em algorithm it is the label of the component gaussian to which z k belongs. based on this assumption, the em algorithm for maximum likelihood parameter estimation is the following. the algorithm starts with an initial guess 11'0' of the parameters and repeatedly applies the following two steps to generate successively better parameter estimates: initialization: initialize the means v; to randomly picked data points from z and the covariance matrices fj to unit matrices.' set p(1ji) = 1/ c for all i. expectation (e) step: in the e-step we assume the current cluster parameter to be correct and evaluate the posterior probabilities that relate each data point in the conditional probability p (rjtjz). these posterior probabilities can be interpreted as the probability that a particular piece of data was generated by a particular cluster. by using bayes theorem, (. ·lz>= p(zj1j;) p(1j;) p y/, ' ( ) p z {21) maximization (m) step: in the m-step we assume the current data distribution to be correct and find the parameters of the clusters that maximize the likelihood of the data. according to this~ the unconditional probabilities are calculated as f f p (1jijz) v. = zp(z~-)dz= z--p(z)dz i i p(1ji) (23) and in a similar way the cluster weighted covariance matrices n l(zk -v)(zk -v;l p(1jijzk) k=l (24) in the above it has been shown that the gaussian mixture model models the p(z) = p(x, y) joint density of the response variable yk and the regressors xk as a mixture of c multivariate n + 1 dimensional gaussian functions. the conditional density p(yjx) is also a mixture of gaussians model and the regression e[yjx] is i j i j y p(y,x)dy j y p(y,x)dy e[yx]= y p(yx)dy p(x) j p(x,y)dy (25) = i. [xr 1]8; ]p(~1j;) p(1j;) i. p (1j;ix) [xr 1]8;] i=l p(x) i=l where ei denotes the parameter vector of the local model and p(1j;jx) denotes the probability that the i -th gaussian component generated the regression vector x : p (tl;) exp(-.!(xv':)t (f:"t1 (x -·v':) l (21r )'2 .jiif4 2 ' ' ' j (26) :t p(ij;) exp(-.!(x-v':l (f.""'f1 (x-v':)l i=l (21r )'2 .jiif4 2 ' l ' j where the ~xx is obtained by the partitioning of the f; covariance matrix f -[· ft fty] i~]x f/y (27) the optimal ei parameter vector of the local models can be obtained as: a1 = {fjxx t f;xy b; =v( -afv: or in a more compact form: (j = l.!"~lf.t.t \-1 ,y -f'j'x{fxx \-1 xj t l.i'i \ i } ~ li i \ i j v; (28) (29) ph fig.2 the considered continuous stirred tank reactor. 526 524 522 520 j518 516 514 512 6.5 7.5 8.5 9 9.5 10 10.5 11 ph(k) fig.3 orientation of the identified clusters. this is identical to the weighted, also called local, parameter estimation approach that does not estimate all parameters simultaneously, because the parameters of the local models are estimated separately using a set of local estimation criteria where xe denotes the extended regression matrix obtained by adding a unitary column to x, xe = [x 1], and <pi denote a diagonal matrix having membership degrees in its diagonal elements. [ f.li,l 0 ((). = 0 j.li,2 l : : 0 0 (31) the weighted least-squares estimate of the consequent rule parameters is given by (32) note that the resulted gaussian mixture of local models defined by eq.(25) is identical to the operating regime based model given by eq.(3) when the 133 6.5 "o 200 400 600 800 ~000 time [time-step=0.2 min] fig.4 free-run test of the model on the validation data. weighting function is chosen as ¢i(x) = p(1j;jx). furthermore, the model is also identical to ts fuzzy models, when the membership functions are identified as it was shown in section 2. application to the identification of a ph process the identification of the ph (the concentration of hydrogen ions) in a continuous stirred tank reactor (cstr) is a well-known benchmark problem. the cstr depicted in fig.2. has two input streams: sodium hydroxide and acetic acid. the dynamic model for the ph in the tank is given in the appendix. po, collection of the data, a sampling interval of 0.2 min was used. as the process can be modeled as a first !jrder dynamic system [12], the fuzzy model consisu, uf the following rules: ri : if (ph(k), fnaoh (k)] is a (33) then ph (k + 1) = a1,1 ·ph (k) + a1•2 • f nuoil {k) + b, by using transformed input variables: ri: if ~:.1 • ph(k)+t{,2 ·fnaou(k)j is as.t and &~.1 • ph(k)+t~.2 • fnuoil(k)] is a1.z (34} then ph(k + 1) = ai,t' ph(k)+a,,2 • f,.a011 (k) + b, four local models were identified. the number of local models were determined by cross-validation. the operating region (the orientation of ft matrices) of these models are shown in fig.3. the identified model was tested with a validation data set. the model was used for one-step-ahead and simulation {infinite-step~ahead) prediction of the ph. the later experiments is depicted in fig.4. the results were compared with the performance of models obtained by using fuzzy model ldentl tkation toolbox [9]. as table 1 shows, the propo'\ed method shows superior performance over this adv~mced tool developed for identification of nonline;1r dynamic systems. 134 table 1 comparison of model performances (mean squares of prediction errors). method one-ste simulation fmid [9] proposed 0.0241 0.009 conclusions 0.2835 0.0956 a new algorithm for the identification of nonlinear systems is proposed that is based on the expectation maximization identification of gaussian mixtures model. a method to extract takagi-sugeno fuzzy models from gaussian mixtures model is presented. the resulted fuzzy models are based on the transformed input-domain approach, which allows the effective partition of the input space and enables the interpretability of the model. the performance of the proposed modeling technique was demonstrated in the identification of the a ph process. acknowledgement the financial support of the hungarian ministry of culture and education (fkfp-0023/2000, fkfp0073/200 1) and the hungarian science foundation (t023157} is greatly acknowledged. janos abonyi is grateful for the financial support of the janos bolyai research fellowship of the hungarian academy of science. tibor chovan is supported by the hans pape foundation. model of the ph process a dynamic model of the ph in a tank can be obtained by considering the material balances on [na+] and the total acetate [hac+ ac-] and assuming that acid-base equilibrium and electroneutrality relationships hold [12]. f e.~tc • [haclin ( f hac + fnuoh) ·[hac+ ac-] = =vd[hac+ac-] dt sodium ion balance: f,.,itoh ·[naoh},,-(fnm: + fl..,uoh )·[na+]= v d[~;+j hac equilibrium: [ac"}·[h .. ] ----=k {hac] " water equilibrium: [h .. l·[oh-1= k)! electroneutra1ity: {na.,.}+[h""j=[oh-}+[ac-1 the ph can be calculated from the previous equations as table 2 parameters used in the simulations. parameter fnaoh [naoh!n [hacjn [na+] description volume of the tank flow rate of acetic acid flow rate of naoh inlet concentration of naoh nominal value 1000 [1] 81 [1/min] 515 [1/min] 0.05 [molll] inlet concentration of acetic 0.32 [mol/1] acid initial concentration of 0.0432 [molll] sodium in the cstr r -] initial concentration of acetate 0 0432 [mol!l] lhac + ac in the cstr . ka acid equilibrium constant 1.753 ·10-5 water equilibrium constant [h+]3 + [h+] 2 (ka + [na+]) + [h+]([na+]ka -[hac+ac-]ka -k.,.)-kwka =0 ph== log[h+] the parameters used in our simulations are taken from [12] and are given in table 2. references 1. leitch r.: comput. control eng. j., 1992, july, 153-163 2. coit b. j., durham r. g. and sullivan g. r.: comput. chern. eng., 1989, 13,973-984 3. sjoberg j., zhang q., ljung l., benveniste a., deywn b., gwrennec p-y., hjalmarsson h. and juditsky a.: automatica, 1995,31, 1691-1724 4. murray-smith r.: a local model network approach to nonlinear modelling, phd thesis, university of strathclyde, computer science department, 1994 5. murray-smith r. and johansen t. a. (ed): multiple model approaches to nonlinear modeling and control, taylor & francis, london, uk, 1997 6. babuska r. and verbruggen h. b.: fuzzy set methods for local modeling and identification, in multiple model approaches to nonlinear modeling and control (ed. murray-smith r., johansen, t. a.), taylor & francis. london, uk, 75-100, 1997 7. takagi t. and sugeno m.: ieee trans. syst. man cybem.,l985, 15(1), 116-132 8. hunt k.j., haas r. and murray-smith r.: ieee trans. neural netw., 1996, 7(3), 776-781 9. babuska r.: fuzzy modeling for control, kluwer academic publishers, boston, ma, 1998 10. kim e., park m., kim s. and park m.: ieee trans. fuzzy syst., 1998, 6, 596-604 11. schoner b.: probabilistic cheracterization and synthesis of complex driven systems, ph.d. thesis~ massachusetts institute of technology, 2000 12. brat n. v. and mcavoy t. j.: comput. chern. eng., 1992, 16,271-281 page 130 page 131 page 132 page 133 page 134 page 135 hungarian journal of industry and chemistry vol. 45(2) pp. 35–39 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0018 effect of chain length and order of the alcohol on enzyme activity during enzymatic esterification in organic media zsófia márkus, katalin bélafi-bakó, gábor tóth, nándor nemestóthy and lászló gubicza* research institute on bioengineering, membrane technology and energetics, university of pannonia, egyetem u. 10, veszprém, 8200, hungary esters of short chain acids and alcohols are found in nature as compounds of flavors. lately the method for their manufacture has been the enzymatic esterification in non-conventional media. although several reactions have been studied in various media (organic solvents, ionic liquids, supercritical fluids, solvent-free systems), there has been no systematic investigation to clarify the effects of chain length and order of alcohols on the activity of the enzyme. in this work acetic acid was used as an acyl donor and the roles of the linear and branched chains of c2-c8 primary, secondary and tertiary alcohols on the activity of novozym 435, the widely used lipase preparation were studied. both the length of the carbon chain and the order of the alcohol were found to strongly influence the activity of the enzyme using the same operational parameters for the reactions. as a result of this project general conclusions were made with regard to the characters of alcohols affecting the reaction rates, which can be applied to other similar reactions. keywords: enzymatic esterification, non-conventional media, effect of alcohol chain lengths, lipase activity 1. introduction enzyme technology provides a promising solution for the biosynthesis of natural flavor esters, since several enzymes are able to catalyze the synthesis of aroma compounds from precursor molecules [1]. nowadays most flavor compounds are manufactured by conventional methods: chemical synthesis or recovery from natural sources. esters produced chemically are quite common, but their method of production is not considered environmentally safe and cannot be classed as “natural”. recently interest has been growing in the production of these components by biotransformation, that is the manufacture of natural flavor esters by using natural raw materials. lipases belong to the most diverse class of enzymes, they catalyze various reactions due to their wide spectrum of industrial applications. lipase enzymes have been applied in many industrial sectors, e.g. the food and pharmaceutical industries, in the production of biological detergents (esters of carbohydrates), moreover in the manufacture of certain cosmetics and fragrances. recently interest has grown in the production of natural flavor esters by the biosynthesis of short chain acids and alcohols [2,3]. several similar reactions have been studied, most of which focused on the synthesis of acetates, like ethyl *correspondence: gubiczal@almos.uni-pannon.hu [4], butyl [5], hexyl [3], cinnamyl [6], and benzyl [7] acetates. during the investigation of the reactions‘ parameters the roles of temperature, the molar ratio of acid to alcohol and the amount of enzyme were described in almost every paper. from these data the optimal values of these parameters could be estimated. numerous reactions were carried out in organic solvents [8, 9], ionic liquids [10, 11], supercritical fluids (mainly in supercritical carbon dioxide) [12], solvent-free systems [13], in addition to in the gas phase [14]. since these reactions can be conducted in non-aqueous media, the water content, to be more precise the water activity of the reaction mixture plays an extremely important role in terms of the reaction rate. for the operation of the enzyme lipase it is necessary to provide a minimal amount of water. on the other hand it is an equilibrium reaction, thus the greater excess of water shifts the reaction towards hydrolysis, decreasing the conversion rate significantly. the investigation of the effect of water content, or at least an intention to adjust the initial water content by a constant value is missing in several papers. the water content during the reaction continuously changes due to the production of water in the esterification. this effect can be neglected during the investigation of the initial reaction rates, but in terms of the development of continuous production it should be taken into account. a number of methods are known to maintain water content/activity. from a practical point of view membrane separation processes, like pervaporation provide attractive procedures [15]. márkus, bélafi-bakó, tóth, nemestóthy and gubicza hungarian journal of industry and chemistry 36 beyond the parameters mentioned and the water content, only a limited attention was paid to the role of substrates present in the reaction. as pointed out earlier, acetic acid was the acidic component used in most cases. the alcohols applied, however, were much more diverse: linear and branched chains, aromatic and different orders of alcohols were investigated. nevertheless our group has not found a single study in the literature where systematic research was conducted to assess the role of alcohols on enzyme activity. the effect of the chain length of various alcohols was investigated in reactions catalyzed by enzymes in non-conventional media. romero and colleagues conducted experiments in supercritical carbon dioxide using four different alcohols: propanol, butanol, pentanol and octanol. it was found that higher degrees of conversion could be obtained by applying longer chain alcohols. enzymes have a higher affinity towards longer chain alcohols, the difference, however, was small [16]. in another paper romero used butyric acid as an acyl donor and the enzyme novozym 435. an insignificant difference was observed in terms of the reaction rate or conversion during esterification when the four primary alcohols (propanol, butanol, hexanol and octanol) were applied. applying secondary alcohols, e.g. 2-hexanol, however, yielded higher reaction rate and conversion than was the case with 2-butanol [17]. pan et al. studied how the chain length of alcohol compounds can influence the resolution reaction of mandelic acid. using methanol, ethanol, butanol, heptanol and octanol it was found that the highest degree of enantioselectivity could be obtained by ethanol. moreover the reaction was described as following michaelismenten kinetics in all cases and the inhibition constant increased as the carbon chain go longer [18]. varma and madras investigated the esterification of propionic acid and three different alcohols by the enzyme novozym 435 in supercritical carbon dioxide. primary (isobutanol, isoamyl alcohol) and secondary alcohols (isopropyl alcohol) were used, as well. based on the measurements, it was concluded that enzymatic esterification was faster with primary alcohols than with secondary alcohols, moreover a greater degree of conversion was achieved with isobutanol than with isoamyl alcohol [19]. therefore the aim of this paper was to study the role of alcohols by the preparation of a given enzyme whilst maintaining the operation parameters as constants. the esterification primary, secondary and tertiary alcohols of c2-c8 carbon chain lengths were investigated to be able to draw general conclusions concerning the role of alcohol structure on reaction rate. for the measurements a popular immobilized lipase enzyme preparation, novozym 435®, was used. 2. experimental 2.1. chemicals and enzymes all chemicals: acetic acid, ethanol, 1-propanol. 1butanol and n-hexane (merck), 1-pentanol, 2-pentanol tert-butanol (2-methylpropan-2-ol) and 1-hexanol (sigma-aldrich); 1-heptanol (bdh chemicals); 1-octanol and isobutanol (2-methylpropan-1-ol) (spektrum-3d); isoamyl alcohol (3-methylbutan-1-ol) (molar chemicals); and 2-propanol, 2-butanol, tert-amyl alcohol (2methylbutan-2-ol) and toluene (reanal) were of analytical grade. the water content of the chemicals varied greatly, that is why they were dewatered over a 3å molecular sieve in the form of beads (sigma-aldrich). the enzyme used was novozym 435® from candida antarctica lipase b, immobilized on a macroporous acrylic resin with a water content of 1-2% w/w, which was kindly provided as a gift by novo nordisk a/s, denmark. according to their commercial product manual, its catalytic activity was 7000 plu/g (propyl laurate units/gram). 2.2. reaction and analysis reactions were carried out in 50 ml erlenmeyer flasks on a laboratory incubator shaker (ika incubator shaker, ks 4000i) at 150 rpm and 50 oc. the typical reaction mixture contained acetic acid (0.5 mmol), alcohol (3.0 mmol), novozym 435® lipase (60 mg) and n-hexane (20 ml). the reaction was commenced by adding the enzyme. the gas chromatography (gc) analyses for the determination of ester concentrations were conducted by a hp 5890 a gas chromatograph, with an hp-ffap column (macherey-nagel), split: 70 kpa, n2: 19 cm3/min, using a flame ionization detector (fid). toluene was used as an internal standard, the changes in ester yield were followed during the reaction. samples were taken after reaction times of 0.5, 1.0, 2.0 4.0 and 6.0 min. the water contents of the reaction mixtures were determined by a mettler dl35 karl fisher titrator. 3. results and discussion although several publications have presented results on the production of flavor esters, the optimal initial conditions suggested were quite different and a high degree of deviation was found among data in the literature. firstly the average of the literature data was used for our preliminary experiments. based on these figures the following initial parameters were applied: in the reaction mixture the molar ratio of acetic acid to alcohol was 1:6, and 20 ml of n-hexane, 20 mmol of toluene and 60 mg of the enzyme novozym 435 were added to it. enzymatic esterification 45(2) pp. 35–39 (2017) 37 3.1. the effect of water content experiments had to be conducted to determine the correct water content since it could not be found in the literature. the esterification of acetic acid and isoamyl alcohol – a reaction that has been quite frequently studied – was investigated under the conditions mentioned earlier. during the measurements completely dried reaction mixtures (0 % w/w water content) were used and others adjusted the initial water content to the levels of 0.3, 0.5 and 0.7 % w/w by adding water. as can be seen from the data of table 1, the reaction was extremely slow in the case of completely dried solvents and reagents – as was expected. the reaction rate began to rise when the water content grew slowly (and approached the optimal value) due to the water forming in the reaction. based on the experimental results an initial water content of 0.3 % w/w was applied to further measurements since this water concentration provided the highest yield. the yields of esterification after a reaction time of 4 h were presented in fig.1, where the measurements were taken under the conditions given earlier, with an adjusted and the same initial water contents. the yields of esterification were sufficiently high to observe the differences caused by the different structures of alcohols, but saturation levels were not reached and the distinct amounts of water formed during the reaction did not affect such a tendency either. 3.2. primary alcohols our study involved linear and branched alcohols with a chain length of c2-c8. as can be seen from fig.1 for primary alcohols, the yield increased as the length of the carbon chain grew. the effect of chain length was investigated by romero using propanol, butanol, hexanol as well as octanol and a similar conclusion was drawn: acetic acid conversion was greater with alcohols of longer chain lengths, thus the yields of esterification were higher, as well [16]. as far as branched primary alcohols were concerned, the opposite trend was observed: the yield of esterification decreased as the chain length increased. at the beginning of the reactions the differences were only minor: only a difference of 3 % was observed in the yields in the cases of alcohols consisting of a carbon chain of 4 or 5. the behavior of isooctanol was especially interesting, because a significant drop in yield was observed compared to the other linear, 8-carbonchain alcohols – a far smaller amount of ester was formed in the reaction mixture. 3.3. secondary alcohols in this work three secondary alcohols: 2-propanol, 2-butanol and 2-pentanol were used. as presented in table 2, an increase in ester yields was observed as the carbon chain length of secondary alcohols grew, as well. the values, however were not as high as for primary alcohols. neji et al. observed a similar behavior when butanol and 2-butanol were used in the esterification reaction [20]. although both alcohols could perform esterification, yields of esterification were 50 % lower for secondary alcohols. 3.4. tertiary alcohols among tertiary alcohols tert-amyl alcohol and tertbutanol were used, however, the enzyme was not able to convert them into esters using acetic acid. from the literature, stavarache et al. applied tertiary alcohols for transesterification in the production of biodiesel [21]. similarly no activity was observed during their experiments, not even when using ultrasonic radiation. 3.5. discussion of the experimental results although our experimental results did not reveal entirely general conclusions, which are valid in all cases, obvious relationships could be formulated for certain figure 1. ester yields during the reactions of acetic acid and primary alcohols after a reaction time of 4 h 31,4 37,3 46,2 76,1 49,6 73,6 53,9 63,2 76,4 7,2 0 10 20 30 40 50 60 70 80 90 yi e ld [ % ] table 1. the effect of water content on ester yield in the esterification of acetic acid and isoamyl alcohol time (h) 0.0% 0.3% 0.5% 0.7% ester yield (%) 0 0.0 0.0 0.0 0.0 0.5 3.2 16.7 18.5 20.5 1 8.3 28.8 33.4 30.7 2 15.8 50.2 48.3 46.7 4 24.2 73.5 68.2 60.3 6 33.1 85.4 79.7 68.5 table 2. ester yields using secondary alcohols secondary alcohol ester yield after 4 h (%) 2-propanol 2-butanol 35.8 44.8 2-pentanol 50.5 márkus, bélafi-bakó, tóth, nemestóthy and gubicza hungarian journal of industry and chemistry 38 groups of alcohols. it is certain that for alcohols with a linear carbon chain of c2-c8 in length, the conversion rate increases proportionally to the lengthening of the carbon chains. as for branched alcohols, the opposite tendency can be observed: yields were found to decrease as the carbon chain grew. the relationship is more obvious when the order of alcohols is taken into consideration. yields of esterification decreased in the following order: primary alcohol > secondary alcohol > tertiary alcohol (noting that tertiary alcohols did not react at all under the conditions used by novozym 435). by applying other enzymes, e.g. carboxylesterase from bacillus licheniformis, small degrees of conversion were measured, but remained close to the limit of detection [22]. in an attempt to justify such behavior, it can be assumed that access of the hydroxyl group of the alcohol to the active centre of the enzyme is severely sterically hindered in the case of secondary and especially tertiary alcohols, which cause enzyme activity to decline or even cease. 4. conclusion the expected reaction rate produced by a given enzyme can be predicted according to characteristics of the alcohol used, namely carbon chain length, linear or branched, and the order in production of flavor esters by enzymatic esterification of natural acids and alcohols. the expected ester yield of the esterification reaction using acetic acid as an acyl donor depends on certain characteristics of the alcohol according to a welldefined tendency. it can be assumed that a similar tendency (though distinct in terms of rate) could be observed for other enzymes regarding the effect of the alcohol. this should be studied separately to decide whether a similar tendency could be detected if various acids are used with the same alcohol. references [1] bommarius, a.s.; riebel, b.r. biocatalysis (wiley-vch verlag gmbh & co. kgaa, weinheim, germany) 2004 pp. 339-372 doi: 10.1002/aoc.651 [2] yan, h-d.; zhang, q.; wang, z.: biocatalytic synthesis of short-chain flavor esters with high substrate loading by a whole-cell lipase from aspergillus oryzae, catal. commun., 2014 45, 59–62 doi: 10.1016/j.catcom.2013.10.018 [3] almeida, a.g.; de meneses, a.c.; de araújo, p.h.; de oliveira, d.: a review on enzymatic synthesis of aromatic esters used as flavor ingredients for food, cosmetics and pharmaceuticals industries, trends food sci. tech., 2017 69, 95–105 doi: 10.1016/j.tifs.2017.09.004 [4] xu, y.; wang, d.; mu, x.y.; zhao, g.a.; zhang, k.c.: biosynthesis of ethyl esters of short-chain fatty acids using whole-cell lipase from rhizopus chinesis cctcc m201021 in non-aqueous phase, j. mol. cat. b-enzym., 2002 18, 29–37 doi: 10.1016/s1381-1177(02)00056-5 [5] martins, a.b.; schein, m.f.; friedrich, j.l.; fernandez-lafuente, r.; ayub, m.a.; rodrigues, r.c.: ultrasound-assisted butyl acetate synthesis catalyzed by novozym 435: enhanced activity and operational stability, ultrason. sonochem., 2013 20(5), 1155–1160 doi: 10.1016/j.ultsonch. 2013.01.018 [6] tomke, p.d.; rathod, v.k.: ultrasound assisted lipase catalyzed synthesis of cinnamyl acetate via transesterification reaction in a solvent free medium, ultrason. sonochem., 2015 27, 241–246 doi: 10.1016/j.ultsonch.2015.04.022 [7] mcginty, d.; vitale, d.; letizia, c.s.; api, a.m.: fragrance material review on benzyl acetate, food chem. toxycol., 2012 50, s363–s384 doi: 10.1016/j.fct.2012.02.057 [8] gubicza, l.; kabiri-badr, a.; keoves, e.; belafibako, k.: large-scale enzymatic production of natural flavour esters in organic solvent with continuous water removal, j. biotechnol., 2000 84, 193–196 doi: 10.1016/s0168-1656(00)00352-7 [9] doukyu, n.; ogino, h.: organic solvent-tolerant enzymes, biochem. eng. j., 2010 48, 270–282 doi: 10.1016/j.bej.2009.09.009 [10] de los ríos, a.p.; hernández-fernández, f.j.; tomás-alonso, f.; gómez, d.; víllora g.: synthesis of flavour esters using free candida antarctica lipase b in ionic liquids, flavour frag. j., 2008 23, 319–322 doi: 10.1002/ffj.1884 [11] major, b.; nemestóthy, n.; bélafi-bakó, k.; gubicza, l.: enzymatic esterification of lactic acid under microwave conditions in ionic liquids, hung. j. ind. chem., 2008 36, 77–81 [12] dos santos, p.; meireles, m.a.; martínez, j.: production of isoamyl acetate by enzymatic reactions in batch and packed bed reactors with supercritical co2, j. supercrit. fluids, 2017 127, 71–80 doi: 10.1016/j.supflu. 2017.03.019 [13] sun, j.; yu, b.; curran, p.; liu, s.q.: lipasecatalysed ester synthesis in solvent-free oil system: is it esterification or transesterification?, food chem., 2013 141, 2828–2832 doi: 10.1016/j.foodchem.2013.05.109 [14] csanádi, z.; kurdi, r.; bélafi-bakó, k.: ethylacetate synthesis in gas phase by immobilized lipase, hung. j. ind. chem., 2012 40, 39–44 [15] findrik, z.; nemeth, g.; vasic-racki, d.; belafibako, k.; csanadi, z.; gubicza, l.: pervaporationaided enzymatic esterifications in non-conventional media, process biochem., 2012 47, 1715–1722 doi: 10.1016/j.procbio.2012.08.003 [16] romero, m.; calvo, l.,; alba, c.; habulin, m.; primozic, m.; knez, z.: enzymatic synthesis of isoamyl acetate with immobilized candida antarctica lipase in supercritical carbon dioxide, j. supercrit. fluids, 2005 33, 77-84 doi: 10.1016/j.supflu.2004.05.004 enzymatic esterification 45(2) pp. 35–39 (2017) 39 [17] romero, m.d.; gómez, j.m.; díaz-suelto, b.; garcía-sanz, a.: study of the influence of alcohols in the synthesis of short chain esters, chem. eng. trans., 2011 24, 37-42 doi: 10.3303/cet1124007 [18] pan, y.; tang, k.v.; he, c.; yi, w.; zhu, w.; liu, y.: effect of alcohol chain length on the enzymatic resolution of racemic mandelic acid and kinetic study, biotechnol. appl. biochem., 2014 61(3), 274-279 doi: 10.1002/bab.1170 [19] kumar, r.; modak, j.; madras, g.: effect of chain length of alcohol on the lipase-catalyzed esterification of propionic acid in supercritical carbon dioxide, appl. biochem. biotechnol. 2010 160, 2342-2354 doi: 10.1016/j.bej.2005.01.007 [20] neji, s.b.; trabelsi, m.; frikha, m.h.: esterification of fatty acids with short-chain alcohols over commercial acid clays in a semicontinuous reactor, energies, 2009 2, 1107-1117 doi: 10.3390/en20401107 [21] stavarache, c.; vinatoru, m.; nishimura, r.,; maeda, y.: fatty acids methyl esters from vegetable oil by means of ultrasonic energy, ultrason. sonochem., 2005 12, 367-372 doi: 10.1016/j.ultsonch.2004.04.001 [22] berger, r.g.: biotechnology as a source of natural volatile flavors, curr. opin. food sci., 2011 1(2), 38–43 doi: 10.1016/j.cofs.2014.09.003 hungarian journal of industrial chemistry veszprem vol. 30. pp. 33 36 (2002) the influence of water concentration on the corrosion of low alloy steels in the system methanolethylene glycol­ acetic acid d. sutiman and m. vizitiu (faculty oflndustrial chemistry, technical university "gh.asachi", d.mange10n 71a, iasi-6600, romania) received: aprillo, 2001 the behaviour of three types of steel with a variable carbon content (from 0.2 to 0.4%) is studied in medium of methanol 10% ethylene glycol 5% acetic acid with water concentration between 1% to 5%. the weight losses are measured; also the polarisation anodic curves are plotted, and the corrosion parameters are established. ir spectroscopy, x-ray diffraction and chemical analysis are the methods used for analysing the corrosion compounds. with the obtained data, a corrosion mechanism is assigned. an optimum ratio between water and acid is established in order to obtain the passive oxyhydroxylic layer. introduction in the aqueous electrolyte solutions, water molecules are active participants both in the oxidation process of metals and in the passive layer formation. a lot of authors that had studied this process, as lorentz [1-4], sato and cohen [5], okamoto [6-7] had shown that water molecules participate in a polynuclear structure achievement with bonds depending on the value of the anodic potential. at the value noted as the passivation potential, a partial water elimination of the film, together with a decomposition of the groups hoin oxygen, take places. in non-aqueous medium, the nature and the concentration of the presented impurities play an important role [8]. these impurities determine a change of some organic medium properties such as, conductivity or the dissociation constant. the main impurity in organic solvents is represented by water that has a strong influence on the equilibrium of the solution, determining changes both in the process of ions solving and in the values of the dissociation constants in the electrolyte dissociation. this paper represents a continuation of a study which deals with water influence on corrosion of three types of low alloy steels in organic medium of ethylene glycol and/or methanol at variable water concentration, corrosion reagents being monoand di-carboxyl saturated acids [9-11]. these organic mediums represent important corrosion reagents for the ethylene glycol recuperation in installations for obtaining synthetic fibers. experimental part the steel samples that are used for corrosion are: ol 37, ol 50 and ol 60. they have the chemical composition presented in table i. the steel samples of 5 cm2 active metallic surface were cut up from a cylindrical bar. they were polished, and dyeing protected the surface that should not be corroded. the corrosion system contained methanol, 10% ethylene glycol and 5% acetic acid. the water concentration varied between 1% and 5%. karl-fisher method was used to determine the water content. we used merck reagents and the water was bidistilled, having electrical conductivity of 12 j!s cm·1 • also the ph-variation of the corrosion medium was measured with a hach ph-meter. before introducing the sample in the corrosive system, they were submitted to a degreasing process in boiling benzene for 30 minutes and then degreased in a solution of hydrochloric acid 3% for 3 minutes. the corrosive system was open, allowing the permanent access of oxygen from the atmosphere. for every value of the water concentration, six metallic samples were used and were placed in the same time in the corrosive system, being subsequently taken 34 table 1 the composition of steels used for corrosion steel ol37 olso ol60 %c 0.20 0.30 0.40 %mn 0.80 0.80 0.80 %s 0.06 0.05 0.05 %si 0.40 0.40 0.40 %p 0.06 0.05 0.05 table 2 the values of indices k and p for the studies steels 1 2 3 4 5 ol37 kip 1.115/1.00 1.437/1.29 1.654/1.39 1.332/1.12 0.816/0.73 olso kjip 0.983/0.88 1.117/1.00 1.228/1.10 0.993/0.89 0.719/0.64 ol60 kip 0.773/0.69 0.928/0.83 1.118/1.01 0.886/0.79 0.627/0.56 fig.] a fig.l b fig.l c fig.] the metallic surface of samples in the system methanol-10% ethylene glycol-s% acetic acid-5%water (x1200). a-ol 37; b­ ol 50; c-ol 60 off from 10 to 10 days, degreased with hydrochloric acid (3%) for 15 seconds and then were weighted by an analytical balance. from the values of weight losses, the gravimetric figure k (g·m-2·h-1 ) and the penetration p (mm·m2·year-1 ) were calculated. the metallic surfaces were visualised by electron microscopy on a tesla b300 microscope. for the values 1%, 3% and 5% of water concentration, the anodic polarisation curves were plotted on a t acussel s8r potentiometer with input impedance of 1012 fl. from the shape of the polarisation curves the kinetic parameters (est• ecor and icor) of the corrosion process were calculated. the corrosion final compounds. for every value of water concentration. were insoluble in the system. they were analysed by x-ray diffraction on a hzg 4c karl zeiss jena diffractometer using co (kj radiation, by 1r spectroscopy on a specord m82. the chemical composition (c~ h, 0 and fe) of the final compounds also were determined. results and discussion studying the ph -values variation • it was observed that for the anhydrous system~ the ph value is 2.12 and when water is added • the ph decreases significantly till the value 2.03. this behaviour can be justified by acid dissociation that has a maxim value in organic solvents, and when water is introduced in the system it determines a modifying of proton coordination: ch3cooh + ch30h ~ ch3coo+ ch30h; ( 1) ch3cooh + c2h4(0h)z ¢::> ch3coo+ c2l4(0h)2h+ (2) ch30h; + h20 ~ ch30h + h30+ (3) c2f4(0h)2h+ + h20 ~ c2l4(0hh + h30+ ( 4) the values of weight losses converted into k and p figures are presented in table 2. from these figures, it can be observed that the corrosion rate increases until the water concentration is 3%, than decreases. the metallic surface, visualized by electron microscopy has the same aspect for a steel type in all the systems with variable water concentration. in fig.l, the aspect of metallic surface, magnified by 1200 times, of all steel types in the system with 3% h20 is presented. for ol 37 and ol 50 it was observed that metallic surface is covered with an non-uniform layer of corrosion product and also, the obtaining of a filiform polymer compound. for ol 60 steel, the surface is also covered with a corrosion compound, but its distribution is more uniform than in other steel types. tab/~ 3 the values of the corrusion parameters in the system methanol i 0% ethylene glycol acetic acid water types bst> mv bcon mv icon jla/cm2 of 1% 3% 5% 1% 3% 5% 1% 3% 5% steels hzo hzo hzo h20 h20 h20 h20 h20 h20 ol 37 -540 -550 -593 -547 -560 -600 14.18 28.26 7.94 ol 50 -520 -530 -560 -535 -542 -580 11.65 25.87 7.03 ol 60 -488 -503 -542 -510 -526 -555 9.12 23.69 6.36 lgi !lafcnf fig.2 the polarisation curves in the system methanol-10% ethylene glycol-s% acetic acid-5%water. •ol 37; x-ol 50;o­ ol60 the polarization curves were plotted for the values of 1%, 3% and 5% water concentration. for the values 1% and 3% water concentration, passivation was not observed. for 5% h20 (figure 2) a slight tendency of passivation is observed after the value -200 mv. the values of the corrosion parameters calculated from these curves are presented in table 3. from the data regarding the density of the corrosion current, it was observed that after 3% h20, the corrosion rate decreases, being in concordance with weight losses. the corrosion final compounds from all the systems were insoluble and did not present x -ray spectra. the lr-spectra are the same for all. comoounds derived from every steel type and in all the syste~s with variable water concentration, presenting peaks at the same wave numbers. in fig.3, the ir spectrum of the c~rrosion compound resulted from ol 60 in the system with 5% h20, is presented. the presence of two peaks at 368 cm·1 and 382 cm·1, characteristic for fe-0 bond, shows the two different bonding of oxygen are, a coordinative bond and a simple covalent one. the characteristic peak of the coo· group from acetic acid is displaced from the value 1718 cm·1 to 1586 cm·i, where a shoulder exists. this explains the coordinative and covalent bonding of oxygen from coo· group, is stronger than in free acid. the presence of three peaks characteristics for ho groups from alcohols, displaced from 1080 cm1 to 1056 cm'1 shows table 4 the chemical composition of the corrosion compounds in the system methanol 10% ethylene glycol 5% acetic acid 3% water ol37 olso ol60 35 c 29.06 28.87 29.32 h 4.87 4.95 5.57 0 38.45 38.12 37.66 fe 27.62 28.06 27.35 cm-l fig.3 their spectrum of the corrosion compounds in the system methanol-10% ethylene glycol-s% acetic acid5%water fig.4 the structure of the fe(iii) poliacetate that oxygen from this group participates to stronger bonding with heavier atoms, for instance iron [12-13]. also, the presence of a double peak around the value of 2800 cm·1 , shows that hogroups from water participate in bridge linkage ~oh[12]. the chemical elemental composition of the corrosion compounds is also similar for the different steel types and systems with variable water concentration. in table 4, the chemical composition of the corrosion compounds from the system with 5% h20 is presented. from these data, the ratio between iron and acetate radical from the corrosion compounds is ~ with a little deficiency in iron. from the presented observations, the following corrosion mechanism is proposed: fe -7 fe2+ +2e· hz0+~0z+2e· -7 2ho· 2 fe2+ + ho· + ~ oz + hzo -7 2 fe(ohh n fe(ohh + 2n ch:£00h -7 [fe(ch3coo}z0hla + 2n hzo the structure of this polymeric acetate is presented in fig.4. the hexacoordination of iron and the final chain molecules are accomplished by water molecules or by oxygen coordination from organic sol vents. 36 conclusion • the molar ratio water/acid, where water can participate in oxyhydroxylic passive layer formation is 2/1, is smaller than the ratio indicated by literature [14-15]. the smaller value of this ratio is due to the proton coordination (proton resulted from the acid) to the organic solvents molecules, fact that determines a decreasing of water quantity necessary for the protective layer formation. • the steel having the highest stability is ol 60, which has the highest carbon content. this high value of the stability may be connected to the existence in the steel's structure of a solid solution of iron-carbon, formed where the carbon concentration is over 0.3% [16]. • the corrosion mechanism is a complex one that involves the dissolved oxygen. references 1. loren1z w. j. and geona d.: electrochim. acta, 1975, 20, 273-278 2. loren1z w. j. and heiman h.: corrosion, 1979, 27~ 101-108 3. larbeer p. and loren'iz w. j.: corrosion science, 1980,20, 405-410 4. larbeer p and lorentz w. j.: electrochim. acta, 1980,25,375-401 5. sato n. and cohen m.: j. electrochim. soc: 1964, 111,512-518 6. heusler k. e.: z. electrochem, 1958,62,582-587 7. kamato 0., saito h. and shibata t.: corrosion science, 1984,24, 807-814 8. loren1z w. j. and heusler k. e.: anodic dissolution of iron group metals in corrosion mechanism, ed. f. mansfeld, de kker, new york, 1987 9. sutiman d.: bul. i.pj., 1999, xlv 3-4, 19-23 10. sutiman d. and cretescu i.: rev. de chim.1999, 10, 50, 766-770 11. sutiman d., georgescu 0. and cioroianu t.: hung. j. ind. chern., 1999,27,107-110 12. avram m.: infrared spectroscopy, ed. tehnica, bucuresti, 1960 (in romanian) 13. the sadler of handbook of infrared spectra, sadler hayden, london, 1978 14. stypula b.: corr. resit. alloy, 1965, l, 252-257 15. banas j. and stypula b.: metallurgy and foundry engineering, 1995, 6, 2, 112-119 16. cartis g.: thermal treatments, ed. facia, timisoara, 1982 (in romanian) page 33 page 34 page 35 page 36 microsoft word 2012_dr_bodor_endre_hjic.doc hungarian journal of industrial chemistry veszprém vol. 39(3) pp. 359-362 (2011) experiments for d-lactic acid production with fermentation á. németh , á. kiss, b. sevella budapest university of technology and economics, department of applied biotechnology and food science 1111 budapest szt gellért tér 4., hungary e-mail: naron@f-labor.mkt.bme.hu lactic acid is one of the oldest known chiral chemicals. its l-enantiomer is widely produced and used both in the nature and in human society. the renaissance of the l-lactic acid production was forced by the biodegradable plastic production on lactic acid basis which produces pla. this polymer has good biodegradability, but poor mechanic properties, thus its characteristic is under strong improvements. during this investigations it was established that the stereocomplex polymers from l and d enantiomers has higher melting point resulting in broader application. unfortunately the production of d-lactic acid was not solved since it is not the natural form of lactic acid. for this reason we wanted to examine the possibilities for d-lactic acid fermentation with lactobacillus coryniformis. we adapted a new technique for cultivation in microtiterplates. first we successfully optimized the media composition in term of carbon source (glucose) and nitrogen source (yeast extract) and obtained an optimal glucose=67.5 g/l and ye=27 g/l concentration by gauss-surface fitting. next we noticed (on observation that the final product titer never surpassed 65 g/l but a lot of glucose remained) that this fermentation is under strong product inhibition. we also examined the inhibitory effect of different form of product lactate (i.e. with na+, ca2+ and nh4 +). we obtained that all the examined products cause total inhibition on cell growth at 90–120 g/l concentration but they differ in their effect between 30–60 g/l: the strongest inhibition occurred at nh4-la (both 30 and 60 g/l), the na-la has lower inhibition range, but its effect is also equal at 30 and 60 g/l and finally ca-la showed hardly inhibition at 30 g/l but strong inhibition at 60 g/l keywords: d-lactic acid, lactobacillus coryniformis, product inhibition, microtiter fermentation introduction lactic acid is one of the basic molecules in chiral chemistry. four different ligands are connected onto its central carbon atom, of which ligands’ stereoscopic orientation results in two isomers, which are of reflected by mirror form of each other. in the nature the presence of the l-form is universal starting from simple organism (like prokaryotes) to higher order organisms (like humans). furthermore it is also produced industrially and used in large scale mostly by the food industry. the real massproduction demand on lactic acid arised in the ‘90s, when the price of crude oil dramatic increased, resulting also in the price elevation of oil based polymers, beside the upcoming of their environmental-toxic effect. although lactic acid can also be produced synthetically (resulting in racemic mixture of the d and l form) in large scale, but the fermentative production has been most widespread since early of the last century. the homopoylmers resulted by the polymerisation of the l-enantiomer is easily biodegradable, but its mechanic properties are disadvantageous from application point of view (brittle and easy to break). the situation was quite the same in case of polymerisation of d-enantiomer. the poor polymer characteristics were investigated with different additives, meanwhile it became clear, that with simultaneous polymerisation of the two isomers at appropriate polymerisation conditions a stereocomplex polymer can be formed, which has higher melting point, thus the application possibilities were widened [1]. however the industrial production of d-lactic acid has not been solved yet, thus the bottleneck of a widely applicable and at the same time easily biodegradable polymer manufacture is the production of the d-lactic acid. although in nature the l-form is common, but between microbes it is possible to find also d or racemic (d, l) lactic acid producers. the chirality of the microbiologically produced lactic acid is depending on the stereospecifity of lactate dehydrogenase (ldh, ec 1.1.1.27) of the producer strain. in our research group fermentative production of lactic acid and related researches have quite long history [3-6], in the frame of which recently we investigate also the technology of a biorefinery realizing in hungary. in a biorefinery (that is a complex raw material processing bio-combinate) it would be possible to utilize different non-food grade crops (wheat (also with fusarium infections), corn or sweet sorghum) for both l-lactic acid and d-lactic acid production, which latter has higher price (value) causing benefits for the investment of the biorefinery. on the basis of these, our goal in the present work was to establish pre-experiments for d-lactic acid fermentation, and to compare these results with the outputs of l-isomer fermentation. during these experiments we adapted a 360 new high throughput method, which made it possible to carry out simultaneously high number of experiments on microtiterplates (mtp’s). materials and methods we used lactobacillus coryniformis dsm20007 strain previously described in the literature [2] as d-lactic acid producer. for strain maintenance mrs agar slants specially developed for lactobacilli were used. for fermentation we used mrs broth with different yeast extract (ye) and glucose content both in shaking flasks and in round lowwell (24 cells) microtiter plates (mtp). the applied temperature was 37 °c, whereas 150 rpm shaking was used, and the ph was adjusted to 5.8 twice on every day with 12% ammonium-hydroxide with the help of phelectodes in the case of shaking flasks (from sample) and with ph-indicator strips in case of mtp cells. for shaking mtps in a rotary shaker incubator we used ‘system duetz’ from enzyscreen, which consisted of a fixing adapter (clamp) and a ‘sandwich cover’ that is crucial for aerobic fermentation. the latter one has little holes above filter cloth for gas exchange, and on the other hand it can prevent the individual mtp cells from (cross)contaminations [7]. the glucose and lactic acid content of fermentation broths were analysed on biorad aminex hpx-87h column at 65 °c with 0.5 ml/min 5 mm h2so4 eluent and ri detection in a waters breeze hplc system. in case of shaking flasks biomass growth was followed with od600 photometric measurements, while in the mtp’s cells we determined cell density with scanning the transparent mtp, and the obtained grayscale images were evaluated with the calibration curve on fig. 1. y = 0,1568x r² = 0,9284 0 1 2 3 4 5 6 7 8 9 10 0 10 20 30 40 50 60 cell dry weight (g/l) gray scale figure 1: calibration curve for cell dry weight determination on the basis of grayscale to obtain the above calibration curve we drove fermentation in shaking flask, and samples was measured both with photometer (od600), and after placing them into mtp cells with scanner (epson stylus sx-600fw). for image evaluation we used bell microimage analyser software, with which we were able to determine the gray grade of the sample between 0 and 256 (0-black, no lactobacillus cells, 256-white, full light reflection). results and evaluation in the first shaking flask experiments the culture grew well beside 20 g/l glucose in 24 h and the decreasing ph also indicated the produced lactic acid. on the basis of this, in the first experiment on mtp we examined the more economical higher substrate concentration (30-6090-120 g/l), which may cause substrate inhibition or according to the resulted higher amount of lactic acid product inhibition can also occur. each different substrate concentration was tested with different ye (i.e. nitrogensource) supplementations (5-15-25-35 g/l) which resulted 16 experimental set up. beside these we designed a central point with 75 g/l glucose and 20 g/l ye running with three repeats and furthermore three “central point’s” were also created, but not inoculated to test (cross)contamination. to evaluate the obtained results we defined a combined parameter (objective function) (q) to find the optimal media composition with smaller amount of remaining glucose and higher amount of lactic acid yield simultaneously. this was necessary, since the final lactic acid titer could be correlated with the different starting amount of substrate making impossible to compare them. the obtained q = yla/gluremained values are presented on fig. 2 as the function of glucose and ye concentrations. 0 2 4 6 8 10 12 14 16 18 20 40 60 80 100 120 5 10 15 20 25 30 35 q glu co se (g /l ) ye (g/l) figure 2: examination of the media composition on the effectiveness of lactic acid fermentation onto the calculated q values obtained from the experiment we fitted a gauss-surface (r2=0.98) with sigma plot 2001 software, and from the fitted constants of the function the location of the maximal q can be established as follows: glucose = 67.5 g/l and ye = 27 g/l. it have to be remarked, that we never found higher lactic acid concentration than 65 g/l, although the obtained more than 90% product yield at lower substrate concentration (for example 30 g/l) predicted very high lactic acid titer at 90 or 120 g/l starting glucose concentration. the problem is clearly demonstrated on fig. 3, indicating product inhibition, since the final glucose remains around zero up to ca 60 g/l of final la 361 titer, but above it the final remaining glucose concentration breaks out. 0 10 20 30 40 50 60 0 20 40 60 80 remaining glucose (g/l) final la titer (g/l) figure 3: coming up the question of product inhibition to examine the product inhibition more detailed a new mtp experiment was designed as follows: 30-6090-120 g/l initial concentration of different (na+, ca2+, nh4 +) lactates were applied before inoculation with two replicates of every experiental set up. becauuse in the existing la technologies these alkali (naoh, nh4oh, caco3) are applied for ph controlling during fermentation, we wanted to examine the effects of these. in the cases of 90 and 120 g/l initial lactates we never found any cell growth, indicating full product inhibition. the 30 and 60 g/l cases can be compared on fig. 4. time (h) 0 20 40 60 80 100 cell dry weight (g/l) 0 1 2 3 4 5 6 nh-la (r2=0,98) na-la (r2=0,99) ca-la (r2=0,99) figure 4: comparing the different kind of 30 g/l initial lactates if the two profiles on fig. 4 and 5. are compared it can be obtained, that ammonium-lactate (nh-la) has the strongest inhibitory effect and there is no difference between the levels of 30 and 60 g/l, thus already 30 g/l can dramatic decrease in the cell growth of l. coryniformis. the inhibitory effect of sodium-lactate (na-la) was lower, but also the same at 30 and 60 g/l concentrations. finally, ca-la can hardly inhibit in 30 g/l amount, but it has strong inhibitory effect at 60 g/l concentration. time (h) 0 20 40 60 80 100 cell dry weight (g/l) 0 1 2 3 4 nh4-la (r2=0,95) ca-la (r2=1) na-la (r2=0,99) figure 5: comparing the different kind of 60 g/l initial lactates conclusions our preliminary results clearly show, that the lactic acid fermentation of l. coryniformis has high yield (>90 %) when applying lower substrate concentration, but the industrially acceptable level of substrate causes product inhibition. on the basis of our experiments we can start to build kinetic approaches to obtain inhibition constants in order to describe the lactic acid fermentation performance with this strain. however, most probably to introduce it to an industrial technology it needs thorough strain improvements. acknowledgements this work is connected to the scientific program of the “development of quality-oriented and harmonized r+d+i strategy and functional model at bme” project. this project is supported by the new hungary development plan (project id: támop-4.2.1/b-09/1/kmr-2010-0002). references 1. c. lee: production of d-lactic acid by bacterial fermentation of rice, fibers and polymers 8 (1) (2007) 571–578 2. r. yáñez, a. b. moldes, j. l. alonso, j. c. parajó: production of d(-)-lactic acid from cellulose by simultaneous saccharification and fermentation using lactobacillus coryniformis subsp. torquens, biotechnology letters 25 (2003) 1161–1164 3. k. hetényi, á. németh, b. sevella: use of sweet sorghum juice for lactic acid fermentation: preliminary steps in a process optimization, journal of chemical technology 85 (2010) 872–877 362 4. k. hetényi, á. németh, b. sevella: optimization of wheat flour based medium for lactic acid fermentation, chemical and biochemical engineering quarterly 24(2) (2010) 195–201 5. t. tábi, á. németh, a. selmeczi, f. szalay: keményítővel és cellulózzal töltött politejsavból előállított fröccsöntött lebomló polimer termékek laboratóriumi lebontásának és komposztálásának vizsgálata, biohulladék 5(2-3) (2010) 30–34 6. k. hetényi, á. németh, b. sevella, p. kovács, zs. bodnár: eljárás haszonnövények fermentációs felhasználására tejsav és származékainak előállítása 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice conferenceproceed~gs hungarian journal of ~dustrial chemistry veszprem vol. 2. pp. 65-70 (2000) new waste management system in zirc area a. vony6, l. tamaska and a. redby (department of environmental engineering and chemical technology, university ofveszprem) this paper was presented at the second international conference on environmental engineering, university ofveszprem, veszprem, hungary, iviay 29june 5, 1999 the amount of generated solid wastes increases from year to year in the whole world. one of the causes of this fact is the incr~asin~ popul~ti?n, but. the change of the standard of living plays an extremely important role, too. the enterprise ?eal1ng ":lth mumc1pal sohd ;vaste (they are also responsible for the waste collection in some of the surrounding villages) 1s collectmg about 95-105 m of compacted waste every week from the area of the town. as far as waste management is concerned, zircas smaller hungarian settlements can be characterised with disposal in a landfill site. however, the necessity of a new waste management system is connected with the drinking water supply of the town. the different possible waste disposal methods were evaluated mostly from environmental and social acceptance viewpoints, a brief waste reduction plan was recommended. the digitised map of the surrounding area was created, as far as land usage, contour lines, surface waters, topsoil types, geological formations, artificial facilities are concerned. with the help of the electronic processing of these data, two possibly suitable areas were found for a new municipal waste landfill site. keywords: waste; management; environment introduction the contribution of packaging materials and goods having short life cycle to the increasing amount of solid waste is very significant.. during the last two decades, the amount of annually produced municipal solid wastes (msw) in hungary has doubled from roughly 10 million m3 to about 20 million m3 • its composition has also changed to a great extent. in case of industrial waste generation a continuous growth could be observed that ended with the political and consequently, economical changes in the late 1980's and early 1990's [1-6]. while in the large majority of western european countries significant achievements can be observed as far as prevention of waste generation, reuse, and recycling of solid wastes are concerned, the case in hungary is quite different. the country's waste management policy and practice is characterised mostly by different disposal methods, i.e. disposal in landfills and incineration. however, most of our existing and operating landfill sites are not meeting the national standards and in the large majority of our settlements there are no financial possibilities to build a new landfill and remedy the outmoded old one. almost every hungarian settlement has its own problem connected with solid wastes. these problems are ranging fi:om the relatively harmless uncontrnlled disposal of msw and littering to very serious tases causing extremely bad consequences like large areas polluted with chlorinated hydrocarbons. in the first part of the complete version of this report the general state of municipal and industrial waste management in hungary is discussed. then tile problem of zirc is specified, the data collection techniques and progress and the calculations are described. finally, conclusions are drawn in the form of presenting suggestion. in the shortened version only the detailed zirc case is discussed, followed by the conclusions and suggestions and where necessary, some calculated data are mentioned [7,11,12]. the zirc case general description of the town zirc is a small town in the mountains of bakony that can be found in transdanubia, north from the lake balaton and about 20 km from the capital of veszprem county, veszprem. the citizens of the town often refers to their settlement as the capital of mountains bakony. zirc has a population of about 8500 citizens. though the town is in the so called northwest-southeast industrial centreline established mainly at the beginning 66 of the 1950s, it has no remarkable industrial activity. there are only three small industrial plants. one of them is the sawmill belonging to the forestry of zirc, the second one is a newly established company dealing with treatment of painting tools contaminated with paint residues. the third company deals with the construction . of agricultural machinery. the main activities connected to the area are agriculture and forestry. the tourism is not significant and it has a transit character, nevertheless the representatives of the local government would like to develop this financial source in the future. the only green movement in the town is a small group of civilian activists forming the "sziget" (island) organisation. the organisation has 18 members and was formed at the end of 1995. their main goal is to prohibit the operation of the paint-waste incineration plant mentioned above. as they are arguing, the wastes treated by the plant are qualified as hazardous wastes and during the location of the plant the laws having reference to construction of hazardous waste treating facilities were not taken into consideration. to achieve their main goal they have gathered about 2500 autographs from the population of the town among the citizens having the right to vote. nevertheless, the plant's test operation has taken place already and emission measurements proved that the plant met the current emission standards described by the law [29]. waste management in zirc the cause of demand for a new waste management system as far as waste management is concerned, zirc as most of the smaller hungarian settlements can be characterised with disposal in a landfill site. however, the necessity of a new waste management system is connected with the drinking water supply of the town. the drinking water supply of zirc was based on consuming the water content of a nearby aquifer. however, a new housing estate without sewage system was built above the aquifer used as the main water source. the houses were provided with cesspools which (vv"ith proper insulation and operation) could prevent the pollution of the aquifer. nevertheless, part of the citizens in a rather inadmissible way have followed the very characteristic hungarian practice, namely they have ruined or have not installed the insulation system of the cesspools in order to let the liquid fraction of their domestic liquid wastes infiltrate to the soil. in this way they could reduce the fee to be paid for transport and disposal of these wastes. the pollution derived from the cesspools has reached the aquifer already, causing a nitrate concentration in the water supply higher than the allowable threshold limit in the hungarian national standards [13-17]. after that the pollution has become obvious the local firm providing the drinking \vater supply service decided to use the karstic water to mix with the \vater deriving from the aquifer, thus diluting its nitrate content below the threshold limit. however, the old landfill site of the town was located in an abandoned sand pit in the border of the town. this landfill site does not have any insulation system, fencing, leachate or landfill gas control, etc. a small intermittent water flow connects the landfill site with the rivulet cuha flowing near the town. in this way the leachate can get to the rivulet. according to some estimations about one-third part of the water flowing in the watercourse of cuha gets to the karstic system under the town. so, it is very possible that sooner or later the pollution will appear in the karstic water used to provide healthy drinking water for the city. because of these facts, there is no possibility of disposing any wastes in the old landfill site of zirc from may 1, 1996. from that time the large majority of municipal solid wastes is disposed in a nearby village's landfill site at dudar. the amount, composition, and collection of waste in zirc the two most important non-domestic waste generation facilities of the town zirc are the waste water treatment plant operated by the local government and the sawmill belonging to the forestry of zirc. the largest proportion of the technological wastes produced in the sawmill is sawdust. a significant part of it is burned in-site and the produced heat is used up in the dryers of the mill. the remains are sold to different companies (brick. works, caloric centres, etc.). besides the sawdust, the metal wastes are sold to the scrap yard. moreover, a large container (5m3 volume) is filled with municipal-like wastes in every two weeks that is hauled by the firm responsible for the collection and transportation of municipal solid wastes in the town. the waste water treatment plant produces roughly 500 kg sludge every day. this sludge is delivered to the local farmers' co-operative and after chemical analysis proved its suitability, it is used as a fertiliser. besides these, the "altalanos fogyasztasi es ertekesftesi szovetkezet" i.e. afesz (general co­ operative society) produces a large amount of paper and cardboard wastes that is gathered selectively and carried to the landfill. the rest of waste generated in the town is municipal solid waste. the enterprise dealing with municipal solid waste (they are also responsible for the waste collection in some of the surrounding villages) is collecting about 95105 m3 of compacted waste every week from the area of the town. they are using a collection-transporting vehicle having 7 m3 volume and a compaction ratio of about 4.5. this vehicle is collecting the municipal solid waste generated in households and the publicly owned areas of the town and is capable of loading from standardised 110 i volume containers. besides this, there are 17 large (5 m3 ) containers for construction and demolition wastes, and every winter the local government is providing 30 containers (also 5 m3) for the collection of slag and ash generated during the heating period (15th nov. ~ 15th apr.). however, due to the installation of natural gas pipeline system into the town, the amount of these materials will decrease drastically in the future and their generation should not be taken into consideration from the next year. the fee for collecting and transporting of solid waste is 300 huf/month/household, regardless the amount of waste generated during one month in the household in question [25,7,8,10]. the overall amount of waste disposed in landfill is 23 500m3/year (uncompacted) the seasonal variation in the amount of municipal solid waste is not significant, mostly because of the transit character of the tourism. nevertheless, if the projects aiming to develop the tourism in the region will start, the increase of waste generation rate during the summer season is very likely. the determination of the composition of municipal solid waste transported to the landfill site of dudar has been fulfilled personally. the measured data, however, are valid only in the vegetational period (june-august). the composition of the solid waste produced during the winter is unknown. it is likely, however, that the amount of compostable constituents are much lower than in summertime. taking into consideration other facts and data, the composition of zirc's waste (by weight) was estimated as follows: paper and cardboard = · 3 %; inorganic matter (without metals) = 20 %; plastics= 8 %; metals = 4 %; textile and rubber = 2.5 %; compostable organics= 62.5 %. present waste disposal practice in zirc waste disposal methods other than the disposal in landfill sites (i.e. composting, controlled incineration, reuse and recycling) are not typical in the region. the high amount of compostable organic materials reveals that composting is not a widespread practice. the open burning of combustible waste components can not be regarded as an environmentally friendly method. the only recycling facility in the town is a scrap yard that is accepting only metal wastes. the annual amount of metal wastes delivered over there is about 500 t, 30% of it is delivered by individuals, the rest is transported by different companies. the wastes are cut up, sorted, and then transported to the danube ironworks for reprocessing. after the closure of the zirc's own landfill, the municipal solid wastes of the town is transported to a nearby village (dudar) for landfllling. that landfill site is one of the few acceptable examples in the country, however, some imperfections have been found during the visit [24]. conclusions and suggestions in order to create a complete waste management strategy, all of the techniques evaluated fully in the complete version of this report have to be examined from environmental, economic, and social viewpoints. 67 new landfill site establishing of a new landfill site is included in the long-range plans of the local government. the map of preferred areas (see at the end of this document) that was created electronically, is a good help for them to select an appropriate area for a new landfill site in the proximity of the town. the red spots in the southern edge of that map are too far from zirc, the distance on road between the town and the area is only slightly shorter than that of between zirc and the landfill site of dudar. the same is true for the smaller areas signed with red in the eastern edge of the examined quadrangle. the red specks very close to zirc are too small for constructing a landfill site, though the combination of green and red areas (positioned at about 1.5 km northwest from zirc) is worth being investigated because of its medium-poor water conductivity, size and closeness. the most promising site, however, can be found on the mid-western margin of the "preferred areas" map. this area is near the palinkahazpuszta farmer's co­ operative, and its preferability is supported by the following facts: its characterising geological formation is tes clay marl formation; the water conductivity of geologic~l formations of the adjacent areas is middling; roughly half of it is under cultivation, the other half is grassland; the size of it is about 0.126 km2 , and the combined area of poor and medium water conductivity is 0.306 km2 ; the gradient of the area is about 6%; and the distance on road from zirc is about 3 km. however, there are large areas southeast from zirc within twenty kilometres (out of the borders of the digitised area), where the characteristic geological formation is the so called gyulaflrat6t formation. the main constituents of this formation are clay, bentonite, gravel, and some calcareous clay, lignite, lime silt and tuff. if further studies and measurements prove the suitability of these areas, it would be worth taking into the consideration the construction of a regional municipal solid waste landfill site there possibly together with the government of veszprem, since this large city's landfill was located above very sensitive karstic systems and limestone formations [26-28}. incineration the building of a waste incinerator is not advisable. though the volume and weight reduction of that method is very good (94 and 81 %, respectively) and according the enthalpy balance calculations, zirc's waste could be incinerated without auxiliary fuel, it has several disadvantages, namely: high investment cost. this investment cost •viu be even higher if the generated amount of \vaste increases due to the growth of tourism in d1e 68 area. this is, because the amount of waste to be burned is quite close to the 1000 kg/hour limit (the present amount to be burned is about 800 kg/h), above which the continuous monitoring of flue gas constituents is ordered by law. the presumption of the necessity of the implementation of an exhaust gas scrubber system is very high and this also increases the investment costs of the incinerator (the sulphur­ dioxide content of the exhaust gases under almost every but extreme operational conditions exceeds the allowable threshold limit of 200 mg/nm3 ). the solid residues of incineration have to be regarded as ii class hazardous wastes and their disposal is possible only in landfill site belonging to the third building category, their usage as a covered material is allowed only in landfills provided with artificial insulation system. the acceptance of deployment of an incinerator by the citizens is uncertain. the public opposition against such facilities can be observed world-wide. with incineration, the valuable secondary raw materials (recyclables and compostablesr in the waste perish forever. though the energy content of the waste can be recovered in the form of heat, this fact is not a good argument for the sake of building an incinerator if one considers the implementation of the relatively cheap and environmentally friendly natural gas to the town proceeding in our days [18-22]. composting in a central facility composting is a very effective way to reduce the overall volume and weight of waste to be disposed in landfills (the estimated annual percentage of compostables in zirc's waste is about 60 % by weight). it has several advantages. a valuable product is produced that can be used to improve topsoil structure and prevent soil destruction by erosion, for land reclamation, and for daily cover in landfill sites; removing the compostable materials from the municipal solid waste decreases the generated amount of landfill gas and leachate, the possibility of mobilisation of heavy metal ions in the landfilled waste will also decrease. the composting process is natural and very simple, special equipment is not needed unless in-vessel technique is applied. among the disadvantages, the high land requirement (800 3150 m2 depending on the applied technique) and the possible odour generation can be mentioned. also, there is a chance of ground water pollution, if the infiltration of the produced leachate is not prevented with some kind of insulation system. the two potential organisations that may be interested in composting in tbe town are the forestry and the local farmers' co-operative. the local government should make contact with them in order to determine their willingness to start an experimental project. for the selective collection of compostable materials from households, the 5 m3 containers could be used that were applied to collect the slag and ash generated in the heating period. the containers could be positioned in the same points where they used to be, and the citizens should transport their compostables to them. in this case, a hauled container system could be used. on the other hand, since almost every households have two 110 1 containers, one of them also could be used to collect the organic materials selectively. in this case, containers of organic matter . have to · be distinguished clearly for example with a colour code, and one of the collector-compactor vehicles should be appointed exclusively to fulfil the collection of compostable materials. since its · amount varies during the year, and the biological reactions taking place in the organic materials are much quicker in summer than in wintertime, a varying collection frequency should be applied. also, because of taking away one collection­ compaction vehicle from the fleet, the whole collection route system should be redesigned, even in the nearby villages. thus, the favourable reception of the fixed container system is questionable [25]. source reduction source reduction would be the most favourable way to resolve most of the town's problems connected to waste management. this technique requires a combination of composting, recycling, a new waste fee system with arousing public interest towards the waste related problems, and very broad social co-operation. source reduction has multitude advantages: backyard composting has the same advantages as were enumerated in the previous chapter. this option has the lowest investment costs. due to the reduced amount of landfilled waste, the life-span of a landflll site can be expanded, the necessity of constructing a new one may arise later. citizens may become more environmentally conscious behaving more environmentally friendly every day. due to the labour-intensiveness of the activities, new jobs can be created. however, the timing of the different steps to be accomplished is crucial, otherwise the program can come to a halt, fail or even can worsen the situation [1213}. meeting of interested parties the very first step is to summon a meeting of the representatives of parties interested in the issue, namely the local government, the potential receivers of the recyclable materials (forestry, farmers' co-operative, scrap yard, the by-product and waste trading company of veszprem, companies dealing with hazardous waste treatment from dorog and budapest, etc.) and the representatives of citizens. it is extremely important to invite the members of island organisation since they have a very strong influence and public opinion forming ability as it has been proved in the past already. the whole problem should be discussed and the receiving willingness and capacity of the potential recyclable material processing companies have to be determined. the acceptability of the different waste treatment options (incineration, composting at central facilities, inspiring of backyard composting" amongst the dtizens, locating containers for recyclable materials at frequently visited facilities i.e. at shopping centres for glass and plastics, at kiosks for newsprints, in schools for dry cells and small batteries, etc.) and a combination of these possibilities should be got across to every parties [1315]. new waste fee system the implementation of a new waste fee system also has to be discussed in this meeting, mainly with the owner of the company responsible for the collection and transport of solid waste. the reason of this is that if the project aiming to reduce the amount of wastes to be disposed in landfills has a great success, the profit of this firm will decrease unless the owner is willing to take part in the collection and transport of recyclable materials. instead of the present flat rate, a per container fee system should be sugge'sted. in order to implement this system, the record of the number of monthly emptied containers pel' every single households is inevitable. this can be fulfilled with simple forms containing the date, the addresses of household served on that day and the number of centainers emptied in reality. the forms can be 'printed in advance, and only the number of containers should be written by hand. at the end of each months, the waste fee has to be calculated individually for every household. the amount of per container waste fee is crucial. if it is too low, there is no economic incentive that forces the citizens to exploit the waste reducing possibilities. if it is too high, the illegal waste disposal affairs will be more frequent and the cost of eliminating the results of uncontrolled littering will be quite high. perhaps a fee between 200 and 300 huf/container is reasonable and can help the program to a success [9]. informing the population before starting the program, informing the citizens is very important. a short leaflet is the best way that contains the problems of the town connected to its solid waste, the harmful effects (dioxin, solid particles, halogen emissions) of uncontrolled burning of waste components, the possibilities of the decision-makers, the plarmed arrangements to be made, and the possible 69 actions that each citizen can do to reduce the amount of waste produced in his or her household (description of composting, using the recycling opportunities, location of recyclable collection containers, buying products that have recyclable packaging, etc.), consequently, the amount of money he or she has to pay for waste disposal. it is very important that all the participants of the first meeting should sign the document, preferably with a few lines in which they are stressing the advantages and importance of the agreement and the action plan. a simple questionnaire also should be attached to the leaflet, inquiring information about the citizens' opinion. the result of the survey with the possible modifications of the preliminary program plan concerning the public opinion should also be published together with the agreement of all the interested parties. an informational phone line preferably free of charge should also be provided for answering the questions in connection with the program [12-15]. starting and maintenance of the source reduction program the best time to start a program is in the spring, when the percentage of compostable materials in municipal solid waste starts to grow due to the beginning of vegetational period. it is very important that at flrst the waste reducing facilities (containers for recyclables, information leaflet about composting, 5 m3 containers for compostable materials, small containers !or dry cells and batteries, etc. depending on the accepted action plan) have to be located in publicly accessible ;ncas. a brief article about the action plan and the positive effects expected can be placed into a local or regional newspaper at the same time. it has to be emphasised that only those special containers may be placed into public areas, whose content really will be reused and recycled (in case of recyclables) or treated properly (for example in case of household hazardous wastes). if the selectively collected waste components are transported to the landfill site, people may lose their trust toward the program. a few weeks after that, the implementation of the new waste fee system can be started. if the time interval between the two action is too short, the citizens can not discover and get used to the new waste reducing possibilities, consequently, their waste fee will grow, so there is a very high possibility that uncontrolled disposal and littering can spread in the area of the town. if the time is too long, however, those who follow the program and act properly, will pay the same amount of money for waste disposal that the other part of the population whose response time is longer. this can cause disappointment amongst the citizens with stronger willingness to follow :he program and can defeat the success of the action plan. if the timing is good, the economic advances connected to waste reducing activities become obvious and there will be a greater chance for the success of the program to proceed. 70 starting the program is not enough. the method of its maintenance has an equal importance. the necessary modifications of the program regardless whether they were decided by the policy-makers or were born with the help of the citizens' suggestions have to be implemented. the success and problems of the program have to be published regularly, for example decline of actually landfilled amount of waste in the past few months, impairment of the special containers, realisable ideas of public origin (preferably with mentioning their author), impurities in the selectively collected materials, etc. [i2.29]. results within the confines of the complete version of this report, the following results were obtained: the amount, composition, physical and chemical properties of zirc's municipal solid waste were estimated, the present waste . disposal practices were identified. the different possible waste disposal methods were evaluated mostly from environmental and social acceptance viewpoints, a brief waste reduction plan was recommended. the digitised map of the surrounding area was created, as far as land usage, contour lines, surface waters, topsoil types, geological formations, artificial facilities are concerned. with the help of the electronic processing of these data, two possibly suitable areas were found for a new municipal waste landfill site. a database was created containing the data of hungarian companies dealing with waste recycling, treatment and disposal, this database was made available on the internet. references 1. barotfi i.: environmental technical handbook, kornyezet-technika szolgaitat6 kft., budapest, 1991 (in hungarian) 2. arval j.: waste management handbook, miiszaki konyvkiad6, budapest, 1993 (in hungarian} 3. indexes of the state of hungary's environment, ministcy of environment and regional policy, budapest, 1994 4. st\nnta a.: environmental management, nemzeti tankonyvkiad6, budapest, 1993 (in hungarian) 5. state of hazardous wastes in hungary. ministry of environment and regiorud policy, budapest, 1994 6. gulyas f., szili kov.-\cs t. and anton a.: agrochemical and biological evaluation of compost gained by processing garden wastes from the public areas in the capital, 2nd environmental protection conference, veszprem, 30 may ~ l june 1995 1. hungary's national report to united nations conference on environment and development, budapest, 1997 8. state t1f the environment in huntmrv, ministtv of environment and regional policy, budapest, j~uary 1997 't waste fee in budapest, heti vitliggazdasag, 4 november 1995 {in hungarian) 10. vo:-<y6 a.: \vaste collection and disposal in hungary, warmer bulletin49, may 1996 11. vony6 a. and magosanyi zs.: hungarian waste management related laws, under publication, warmer bulletin 51, october 1996 12. vony6 a and foldenyi r.: the waste in hungary solid waste management in hungary, environmental excellence magazine, september, 1996 13. tchobanoglous g., theisen h. and vigil s.: futegrated solid waste management, mcgrow-hill book company, new york,1993 14. environmental and building affairs bulletin official paper of ministry of environment and regional policy, budapest, july 21, 1995 15. erdey gy.: full collection of environmental related laws napra-forg6 joginformatika es kiad6 kft., budapest, 1994 16. scavenger quarterly press of the· waste work association, gyor, spring 1996 17. szenes e.: environmental protection in the small and middle-sized food processing plants, futegra-project kft., budapest, appendix 7. pp 215-218, 1995 18. hungarian statistic annual, 1994, central statistical office, budapest, 1995 19. 11/1991. (v.16) k1m enactment about the determination of technological emission threshold limits of waste incineration and about the rules concerning their application, comprehensive collection of environmental laws, napra-forg6 joginformatika es kiad6 kft., budapest, p 124, 1994(in hungarian) 20. cheremisinoff p.n.: waste incineration handbook, butterworth-heinemann ltd., oxford, p 15, 1992 21. raznjevic k.: calorific tables, muszaki konyvkiad6, budapest, pp 286-288, 1964 (in hungarian) · 22. pungor e.: handbook of analysts, mftszaki konyvkiad6, budapest, p 31, 1987 (in hungarian) 23. 102/1996. (vii.12.) korm. r. law about hazardous wastes, hungarian bulletin 57., official paper of the hungarian government, budapest, pp 3578 3653 (in hungarian) 24. stefanovrrs p.: soil research, mezogazdasagi kiad6, budapest, p 253, 1975 (in hungarian) 25. o'leary p., w als p. and rzvi a: solid waste composting, study-aid, university of wisconsin· madison, p 7, 1990 26. pule l. and magyar i.:geo-informatic evaluation of the surroundings of balaton:ffizffi with environmental aspects, fustitut :fitr technische okosystemanalyse montanuniversitat leoben, 1994 27. malone sz6nyi j.:vulnerability survey of \vater holding systems, theory and practice, eotvos l6nind technical university, department of applied and environmental geology, budapest, 1995 28. geology of bakony mountains, explanation of the uncovered geological maps of the bakony mountains, hungarian nationalgeological fustitute, budapest, 1990 29. personal communication with b:er..a kasz.as, representative of the local government of zirc with vilmos ma.r, owner of x-ion ltd, the firm collecting and transporting municipal solid waste of zirc with uszl6 hegedos, operator of landfill site of the village dudar with zoltk'i horvarn, owner of the scrap yard of zirc with istvan galambos, member of the local non-governmental green organisation sziget of zirc with gyorgy polgar, manager of the sawmill of zirc forestry with laszlo ft'i.e, professor's assistant at department of environmental engineering and chemical technology, university ofveszprem page 71 page 72 page 73 page 74 page 75 page 76 hungarian journal of industry and chemistry vol. 51(1) pp. 23–27 (2023) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2023-04 laboratory measurement of rolling resistance coefficient under different conditions sándor guba1*, péter kocsor1, bálint vörös1, barnabás horváth1 and istván szalai1,2 1 mechatronics and measurement techniques research group, research centre for engineering sciences, university of pannonia, egyetem u. 10, veszprém, 8200, hungary 2 institute of mechatronics engineering and research, university of pannonia, gasparich márk u. 18/a, zalaegerszeg, 8900, hungary the aim of our research was to design and construct a measuring device that can determine the rolling resistance coefficient (rrc) under laboratory conditions. the measuring device has a drum arrangement and the rrc was measured on two different model surfaces. the deceleration method was used to investigate t he dependence of the rrc on the compression force, velocity and surface temperature on steel as well as rubber surfaces. the measured rrc values (0.010–0.025) were similar in magnitude to those characteristic of asphalt roads. by increasing the model road surface temperature up to t = 60 ºc the rrc dropped by ∼13% compared to the equivalent values at t = 22 ºc keywords: rolling resistance coefficient, deceleration measurement, temperature change, drum measurement, measuring device 1. introduction the motion of wheeled vehicles is hampered by the rolling resistance force (frr), which occurs when an object rolls on another due to the interaction between a wheel and the track it is running on. this force is characterized by the rolling resistance coefficient (rrc), which is one of the most important factors in today’s automotive industry. the first study of losses as a result of rolling friction was carried out by coulomb in 1785, while the first experimental method for determining the rolling resistance of vehicle wheels was drawn up by holt and wormeley [1]. in vehicles, one way to save energy is to reduce the rolling friction [2]. manufacturers use different materials and pattern designs to create tires that exhibit better rolling friction properties, thereby further reducing the fuel consumption of vehicles and the greenhouse gases they emit. research has shown that a 10% reduction in the rrc results in a 1 2% reduction in fuel consumption [2]-[3]. the frr results from deformation of the rolling body (and surface) as shown in figure 1. in the case of a body rolling at an angular velocity ω, deformation occurs on the contact surface between the body and surface. a consequence of such deformation to the body is that forces act on it to work against the deformation. fm represents the cumulative resultant force of the system acting on the contact surface. the resultant force can be received: 18 jan 2023; revised: 9 march 2023; accepted: 10 march 2023 *correspondence: guba.sandor@mk.uni-pannon.hu split into a vertical and a perpendicular component, which – at a constant angular velocity – are in equilibrium with the other components. fv contributes towards keeping the wheel in motion, which is balanced by the horizontal component of fm. the vertical component of fm is balanced by the force g′, which results from the mass of the rolling body. since the rolling resistance can be interpreted as a force [4], the rrc is a dimensionless physical constant figure 1. motion of the wheel at a constant speed on a non-deformable road surface https://doi.org/10.33927/hjic-2023-04 mailto:guba.sandor@mk.uni-pannon.hu guba, kocsor, vörös, horváth and szalai hungarian journal of industry and chemistry 24 derived from the quotient of the horizontal and vertical components of fm: 𝑅𝑅𝐶 = 𝐹𝑅𝑅/𝐺′ (1) the magnitude of the rrc (which typically varies between 0.001 and 0.400) depends on the ratio and magnitude concerning the deformation of the road surface as well as tire. the degree of deformation depends on the material properties as well as roughness of the tire and the pavement, in addition to the diameter, pressure and rotational speed of the wheel amongst other factors like temperature that influence these parameters [5]. our aim was to study the dependence of the rrc on various measurement conditions such as velocity, compression force and surface temperature on different surfaces. for this purpose, a laboratory-scale device was designed and constructed by us which can measure the rrc of a model tire on two different model surfaces in the event of various conditions. 2. experimental 2.1. measurement system in industry, the methods and conditions for measuring the rrc are specified in the standards iso 18164:2005 and iso 28580:2018. in practice, the most common currently used measurement setups are trailer measurements, the coast-down method, measurements based on fuel consumption and drum measurements [6]. however, these all measure the value of the frr indirectly and infer the value of the coefficient. each measurement method has different advantages and disadvantages, moreover, none of them can be used to carry out a complete study. the appropriate measurement method must be chosen according to the situation and opportunities presented by it. the drum measurement method is the most widely used technique for determining the frr and rrc under laboratory conditions [6]. the measuring device designed by us is based on this principle. our apparatus consists of a drum with a large diameter on which the model road surfaces are mounted, a drive chain, a test wheel, a mechanism that presses the wheel and drum together as well as sensors needed to make the measurements (figure 2). from the values of the frr and compression force measured, the rrc can be obtained using the parameters of the drum and wheel. in the drum measurement method, the curvature of the model road surface causes an error, but this can be corrected according to the following equation: 𝐹𝑅𝑅 = 𝐹𝑅𝑅,𝑚𝑒𝑎𝑠𝑢𝑟𝑒𝑑√ 𝑟𝑑𝑟𝑢𝑚 𝑟𝑑𝑟𝑢𝑚+ 𝑟𝑤ℎ𝑒𝑒𝑙 (2) where rdrum and rwheel are the radii of the drum and wheel, respectively. using this arrangement, the rolling friction force can be determined by direct force measurements. in this case, the force acting on the axis of the wheel (or drum) is measured by applying a given compression force. furthermore, the frr can be determined indirectly by measuring the torque, power or angular deceleration. when measuring the power, the rolling friction force and its coefficient are determined from the difference between the amount of power required to drive the freely rotating drum and the power that is needed when the wheel is pressed against it (∆p). due to the differential measurement, the bearing and aerodynamic losses do not affect the result. one disadvantage is that the power consumption changes as the driving motor heats up and could lead to an error. the deceleration method is similar to the one based on power measurements, however, instead of ∆p, the difference in the deceleration of the drum is measured. since this is also a differential method, the aforementioned sources of errors are not present. an additional advantage of measuring the deceleration rather than the power is that heating of the driving motor is also cancelled out. our equipment can determine the rrc on two different model surfaces, namely rubber and steel, by measuring the force, power and deceleration. the temperature of the surfaces can be controlled by heating blankets mounted on the inner surface of the drum. the blankets consist of a resistance heating wire embedded in silicone rubber and are powered by a high-performance hp 6030a power supply. using the blankets, the surface temperature was set between room temperature and 60 ± 2 ºc. figure 3 shows that the heat distribution on the surfaces of the drum was uniform, a small difference figure 2. schematic diagram of the measurement system figure 3. heat map of the drum at 10 km/h measurement of rolling resistance coefficient 51(1) pp. 23–27 (2023) 25 of ∼2 ºc between the temperature of the rubber and model steel surfaces was observed. the drum is driven by a 0.28 kw robax asynchronous motor controlled by a siemens sinamics cu240e-2 pn-f control unit connected to a sinamics pm340 power module. the rotational speed and, therefore, the deceleration of the drum are measured by a custom-made inductive rotary encoder based on a balluff bes 516-360-s4-c inductive sensor. the wheel is positioned by two linear units, which are perpendicular to each other. control functions and data acquisition are provided by a python program running on a raspberry pi singleboard computer described in [7]. 2.2. measurement method taking into account the advantages and disadvantages of the applicable methods concerning the drum setup, the measurements were made using the deceleration method. firstly, the drum was accelerated to a constant angular velocity before the driving motor was disengaged, causing the drum to decelerate. the rate of deceleration was measured in the form of angular deceleration (β) and this measurement repeated by pressing the measuring drum and wheel together by applying a given force. together, the rate of deceleration of the drum and wheel was greater due to losses resulting from their interaction caused by the frr, which can be calculated by the moments of inertia of the drum (idrum) and wheel (iwheel) according to the following equation: 𝐹𝑅𝑅 = 𝛽𝑑𝑟𝑢𝑚 𝐼𝑑𝑟𝑢𝑚 𝑟𝑑𝑟𝑢𝑚 + 𝛽𝑑𝑟𝑢𝑚 𝐼𝑤ℎ𝑒𝑒𝑙𝑟𝑑𝑟𝑢𝑚 𝑟𝑤ℎ𝑒𝑒𝑙 2 − 𝛽𝑙.𝑤ℎ𝑒𝑒𝑙 𝐼𝑤ℎ𝑒𝑒𝑙 𝑟𝑤ℎ𝑒𝑒𝑙 − 𝛽𝑙.𝑑𝑟𝑢𝑚 𝐼𝑑𝑟𝑢𝑚 𝑟𝑑𝑟𝑢𝑚 (3) where βl.drum and βl.wheel denote the angular deceleration of the compressed drum and wheel, respectively, and βdrum stands for the angular deceleration of the freely decelerating drum. 3. results and discussion the measurements were carried out at an initial tire pressure of ∼2 bars. the compression force was changed between 30 n and 60 n, moreover, the circumferential speed was varied between 5 km/h and 20 km/h. the surface temperature of the drum was adjusted by changing the feeding current of the heating blankets. a minimum of three data points were measured under each set of conditions before their averages and standard deviations were calculated. the standard deviations of the compression force and surface temperature were also calculated. error bars x and y were generated using these standard deviations. the value of the rrc on the rubber surface was higher than on the steel one in most cases. 3.1. measurements when different compression forces were applied according to the literature, the rrc does not depend on the magnitude of the compression force. our measurement data, which is presented in figure 4, show that the rrc increases as the compression force rises. the reason for this disagreement may have occurred as the tire pressure of the model wheel, which depends on the compression force applied, was set in the unloaded state. increasing the tire pressure can either increase or decrease the rrc depending on the surface it is in contact with [5]. with the current measuring device, the tire pressure cannot be changed during the measurement. this could be an option for future development. it is worth mentioning that the standard deviation of the data in the case of the rubber surface is higher than in that of the steel surface. 3.2. measurements at different velocities the dependence of the rrc on the circumferential velocity of the drum was measured between 5 km/h and 20 km/h at an initial tire pressure of ∼2 bars while subjected to a compression force of 40 n. the measured values (figure 5) show an increasing trend, which is consistent with data in the literature [5], [8] from which large changes in the rrc are only expected above 50 km/h. figure 4. measurements when different compression forces were applied with an initial tire pressure of ∼2 bars and a velocity of 10 km/h in the case of the steel (a) and rubber (b) surfaces guba, kocsor, vörös, horváth and szalai hungarian journal of industry and chemistry 26 3.3. measurements at different model roadsurface temperatures the effect of the road-surface temperature on the rrc was investigated by adjusting the temperature of the drum, thereby modelling driving on a hot road surface. the surface temperature was set at constant values between 20 °c and 60 ºc. in all cases, the drop in temperature due to rotation of the wheel was below 2 ºc. it should be noted that the temperature of the model wheel was below the surface temperature throughout the experiment. the rrc decreased linearly between 0.024 and 0.021 as the temperature increased (figure 6), therefore the following equation was fitted to the measurement points to determine the temperature (t) dependence of the rrc: 𝑅𝑅𝐶 = 𝑅𝐶𝐶0 − 𝑎𝑇 (4) where rrc0 denotes the extrapolated value of rrc when t = 0 ºc and a stands for the slope of the regression line. the parameters of the linear regression are shown in table 1. in our experimental setup, the small change of the rrc with the temperature shows that the temperature of our model wheel remained less than that of the surface. based on the literature [9], it is expected that the decrease in the rrc would be greater if the temperature of the surface and wheel were identical. an additional possible research direction could be the use of a closed system in which the temperature of the drum and wheel can be adjusted simultaneously by means of the built-in heating blankets. 4. conclusions in our work, a laboratory device to measure the rrc based on the drum measurement method was designed and constructed, which is able to determine the rrc on two different model surfaces at various temperatures. the dependence of the rrc on the compression force, velocity as well as the temperatures of the two surfaces, namely steel and rubber was determined based on the deceleration method. the measured rrc values (0.010– 0.025) were similar in magnitude to those characteristic of asphalt roads. figure 6. measurements at different surface temperatures with an initial tire pressure of ∼2 bars by applying a compression force of 40 n and at a velocity of 10 km/h in the case of steel (a) and rubber (b) surfaces (the red line denotes the linear regression.) figure 5. measurements at different circumferential velocities with an initial tire pressure of ∼2 bars and by applying a compression force of 40 n in the case of the steel (a) and rubber (b) surfaces table 1. the parameters of the fitted curve rrc0 a (ºc-1) steel 0.024 -4.15·10-5 rubber 0.027 -7.28·10-5 measurement of rolling resistance coefficient 51(1) pp. 23–27 (2023) 27 • the rrc increased as the compression force rose. since the rrc is independent of the compression force, this discrepancy may have resulted from changes to the tire pressure that affected the measurements. a possible solution to this problem is to continuously adjust the tire pressure as the compression force changes. • the dependence of the rrc on the velocity was investigated at three different speeds, that is, 5 km/h, 10 km/h and 20 km/h. the data shows an increasing trend, which is consistent with the literature. • the dependence of the rrc on temperature was also tested. by increasing the temperature of the model road surface up to t = 60 ºc, only a slight decrease (∼13%) in the measured rrc was observed. acknowledgement this work was supported by the tkp2020-nka-10 project financed under the 2020-4.1.1-tkp2020 thematic excellence programme by the national research, development and innovation fund of hungary. references [1] kumar, p.; sarkar, d.k.; gupta, s.c.: rolling resistance of elastic wheels on flat surfaces, wear, 1988, 126(2), 117–129, doi: 10.1016/00431648(88)90133-0 [2] alternative fuels and advanced vehicle technologies for improved environmental performance: towards zero carbon transportation (2nd edition), folkson, r.; sapsford, s. (eds.) (elsevier science and technology, san diego), 2022, doi: 10.1016/c2020-002395-9 [3] wiratkasem, k.; pattana, s.: the effect of motorcycle tyre rolling resistance coefficient on the saving of fuel consumption, energy rep., 2021, 7, 248–252, doi: 10.1016/j.egyr.2021.06.042 [4] ehsani, m.; gao, y.; gay, e.s.; emadi, a.: modern electric, hybrid electric, and fuel cell vehicles: fundamentals, theory, and design (power electronics and applications series), (crc press, boca raton), 2005, isbn: 9780849331541 [5] gillespie, t.d.: fundamentals of vehicle dynamics (society of automotive engineers, warrendale, pa), 1992, isbn: 9781560911999 [6] andersen, l.g.; larsen, j.k.; fraser, e.s.; schmidt, b.; dyre, j.c.: rolling resistance measurement and model development, j. transp. eng., 2015, 141(2), 04014075, doi: 10.1061/(asce)te.1943-5436.0000673 [7] decsi, p.; bors, á.; kocsor, p.; vörös, b.; horváth, b.; guba, s.; gugolya, z.; mester, s.; szalai, i.: a framework for demonstration devices used in distance-learning environments, hung. j. ind. chem., 2021, 49(1), 17–21, doi: 10.33927/hjic-2021-03 [8] wiegand, b.p.: estimation of the rolling resistance of tires, sae tech. pap., 2016, april, doi: 10.4271/2016-01-0445 [9] ejsmont, j.; taryma, s.; ronowski, g.; swieczkozurek, b.: influence of temperature on the tyre rolling resistance, int. j. automot. technol., 2018, 19(1), 45–54, doi: 10.1007/s12239-018-0005-4 https://doi.org/10.1016/0043-1648(88)90133-0 https://doi.org/10.1016/0043-1648(88)90133-0 https://doi.org/10.1016/c2020-0-02395-9 https://doi.org/10.1016/c2020-0-02395-9 https://doi.org/10.1016/j.egyr.2021.06.042 https://doi.org/10.1061/(asce)te.1943-5436.0000673 https://doi.org/10.33927/hjic-2021-03 https://doi.org/10.4271/2016-01-0445 https://doi.org/10.4271/2016-01-0445 https://doi.org/10.1007/s12239-018-0005-4 hungarian journal of industry and chemistry vol. 50 pp. 57–65 (2022) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2022-09 developing plant models of reduced complexity by chemical process engineering way of thinking mónika varga1 1hungarian university of agriculture and life sciences, kaposvár campus, guba sándor u. 40, kaposvár, 7400, hungary given the increasing complexity of agricultural systems within the broader context of the bio-based circular economy, simplified and unified plant models are needed that represent the primary biomass production by solar-driven carbondioxide sequestration. utilizing experiences from process systems engineering, which was originally inspired by chemical engineering, a suitable plant model is proposed. the structure of the model is generated from the process net of the underlying state and transition elements. two special-state elements are introduced for the short-term storage of the supplied biomass to be distributed and of the uptake of nutrient-containing water, necessary for evapotranspiration and photosynthesis. the transition-oriented description of functionalities follows the essential causalities and balances of natural self-control. implementation of the model is illustrated by a simple example. keywords: plant model, reduced complexity, stoichiometric processes, process network, supply/demand logistics, natural self-control 1. introduction the bio-based circular economy is crucial to secure the supply of food and materials for mankind given the burden of depleting non-renewable resources and finite reservoirs. the replacement of open process systems with circular ones needs conscious engineering planning and operations while systemically overviewing the underlying processes. multisectoral process networks require the coupling of sub-models from various disciplines on different scales. in the bio-based circular economy, the photosynthetic biosystems (plants) represent biomass production from solar energy, i.e. from the only external, unlimited energy resource for our planet. accordingly, the model-based analysis, planning and operation of cultivated and natural plants plays an important role. recently, motivated also by the increasingly integrated engineering of natural and man-made systems, intensive bidirectional learning has commenced between the computational modeling of natural and man-made processes whereby: • the principles of more sustainable and resilient natural ecosystems can be applied in the design and control of man-made systems on the one hand, while recieved: 26 may 2022; revised: 7 june 2022; accepted: 7 june 2022 correspondence: varga.monika@uni-mate.hu • the experiences of industrial systems designed by engineers can be taken into account with regard to the model-based analysis, planning and operation of agricultural cultivation on the other. although systems of chemical process engineering played a unique role in this knowledge transfer because the underlying multidisciplinary processes were complex enough to represent various features, they were not too complex for the application of formerly applied computational tools. the lessons learnt from chemical process systems are still clearly important in terms of the rapidly developing model-supported problem-solving of complex agri-food and agro-environmental process systems. this paper shows how chemical process engineering can be used to develop plant (crop) models of limited complexity. first, some available plant models will be overviewed in brief. two different approaches are available, namely (i) empirical (statistical) models to calculate various specific sources of biomass production and (ii) the mechanistic (biophysical) models that describe the underlying physical, chemical and biological processes, representing causalities and balances. this overview focuses on the mechanistic crop models. physiological models are important to further our understanding of metabolism, growth and how plants respond to environmental conditions, e.g. climate change [1]. the detailed dynamic modeling of physiological processes is not a novel endeavor, in fact it was https://doi.org/10.33927/hjic-2022-09 mailto:varga.monika@uni-mate.hu 58 varga already applied at the end of the previous century [2–5]. however, because of the increasing complexity of waterenergy-food-ecosystems nexus [6–8], besides detailed biophysical models, the systemic coupling of these biophysical models from various disciplines is also necessary, which also requires flexible models to couple economic considerations [9]. regarding the level of detail, the improved understanding of physiological characteristics and the expected response to environmental changes require mechanistic models at both the cellular and organ level [10]. however, their practical applicability, considering the available data and knowledge, also requires the development of advanced coupling models. various complex crop models are available. in a recent paper, eight kinds of crop models are classified and compared [11], the most important of which are as follows: agricultural production systems simulator (apsim) is an actively evolving tool for the modeling and simulation of a wide range of agricultural systems, including plants, animals and soil, which also takes into consideration management actions and climatic effects [12]. the crop-related parts contain the detailed biophysical description concerning the phenology, biomass accumulation and distribution of newly synthesized biomass as well as the uptake of water and components by taking into account the related limitations and dependencies on environmental conditions. stics is a detailed biophysical modeling tool that considers water, carbon as well as thermal and radiation energy balances for many (ca. 20) different crops ([13, 14]). it also clearly represents the phenological stages and the most important biophysical processes, e.g. light interception, transpiration, uptake of water and nutrients, etc. cropping systems simulation model [15] is also a frequently used simulation model that takes into consideration the soil water budget, soil-plant nitrogen budget, crop-canopy and root growth, dry matter production, yield, residue production and decomposition as well as several management options, e.g. cultivar selection, crop rotation, irrigation, fertilization, tillage operations, residue management, etc. recently, the rediscovery of advantages regarding the coupling of tree and crop systems by combining their models has also come to the fore. both apsim and stics follow this direction. a few validated tree models are available that are integrated in apsim to be used in combination with plants [12]. on the other hand, a stics crop model is embedded in the hi-safe agroforestry tool [16]. 2. challenges and objective plant models for well-defined important crops and trees are available. these detailed, specific models require a considerable set of parameters to be identified, moreover, the increasing design space of the bio-based circular economy needs simplified, approximate, unified, flexible, extensible and connectible plant models. the objective of this paper is to introduce the conceptual framework and experimental implementation of a unified plant model of reduced complexity. to develop the model, the following chemical process engineeringbased principles were applied: • generalized unit operations; • specific stoichiometric composition of pseudocomponents and other entities; • stoichiometric conservation processes based on the model-specific conservation laws, e.g. conservation of atoms in chemistry; and • demand-supply chain-like representation of material flows driven by the underlying push or pull logistics. 3. materials and methods 3.1 data and calculation formulae for a typical example of a plant to be modelled as an illustrative example of a man-made and operational plant ecosystem, a cultivated field of maize was modeled, where 9600 individual plants were cultivated over an area of 1600 m2. the maize-related specific data were derived from the literature [17–19]. within the contours of the outlined system, this cultivated field was associated with the connected layers of soil and the compartment of air. the environmental conditions were taken into consideration in accordance with the data from the respective meteorological database. the initial data of the plants refer to the stage following the sowing of the seeds when the initial biomass of the plants is contained within the seeds and sprouting has not yet occurred. the initial conditions of the seed biomass (based on estimations by experts) and its components [20, 21] are the following: biomass = 0.0003 kg/plant c = 0.03747 kmol/kg h = 0.06999 kmol/kg o = 0.02846 kmol/kg n = 0.00154 kmol/kg p = 0.00011 kmol/kg x = 0 kmol/kg h2o = 0.118 kmol/kg o2 = 0.00066 kmol/kg germination is an event-driven process that occurs after the time-driven sowing. sowing, which is a management process, is modelled by putting the seeds into downflow material storage. afterwards, in the event of the appropriate environmental (meteorological and hydrological) conditions, the seeds germinate resulting in the release of these stored materials in accordance with the following parameters (based on estimations by experts): seed biomass = 0.0001 kg/pc hungarian journal of industry and chemistry developing plant models of reduced complexity 59 seed rate = 6.579 × 10−7 kg/h proportion of leaves = 0.853 proportion of roots = 0.147 surface area ratio of leaves = 6.667 m2/kg surface area ratio of roots = 3.003 m2/kg in our example model, the germination period is from april 20th until may 9th. after the leaves and roots appear, resulting from the event-driven process of germination, the life processes of plants, that is, photosynthesis, growth, respiration, evapotranspiration and uptake, start. the rate of photosynthesis is calculated by the following simplified equations [19]: ∆biomassdry = num rad ft et ρ dt (1) where ∆biomassdry = biomass produced, kg, num = number of plants, pc. rad = radiation, w/mj2 ft = proportion of radiation absorbed by the plants et = radiation-use efficiency, kgdry matter/wabsorbed radiation ρ = density, number of plants/m2, where ft = 1 − e−ktlaiact (2) laiact = leavessurf num aact (3) aact = lairatio landsurf (4) ρ = num aact (5) landsurf = surface area of land, m2 lairatio = 1 m2 area of leaf / m2 area of land kt = 0.8 light extinction coefficient [19] et = 0.01409 kg/mj, radiation-use efficiency [19] the process of evapotranspiration is calculated from the reference evapotranspiration (et0, mm/day), determined from meteorological data according to the wellknown penman-monteith combination equation [22]. based on this equation, the evaporation from the land and plants during a time step are calculated separately based on the following equations: etland = ke etm landsurf dt (6) etplants = kcb etm surf num dt (7) where etm = reference evapotranspiration, recalculated from et0 / kmol/h etland = land-related evapotranspiration, kmol etplant = plant-related evapotranspiration, kmol landsurf = surface area of the land, m2 surf = surface area of the leaves, m2 num = number of plants, pc ke = 1 m−2, soil-related part of the dual crop coefficient [22] kcb = 1 m−2, basal plant-related part of the dual crop coefficient [22] dt = the time step in hours, distinguished for the changing actual daylight or night period growth is calculated after germination and is interpreted as the distribution of the photosynthetic biomass between the parts of the plants. before the timeor eventdriven appearance of the product, the following ratios are applied in line with estimations by experts: proportion of leaves = 0.853, proportion of roots = 0.147. afterwards: proportion of leaves = 0.637, proportion of products = 0.253, proportion of roots = 0.110. respiration is calculated for the individual parts of the plants. for all the parts, two kinds of respiration is simulated: one as a given proportion of the biomass synthesized and the other as a given proportion of the already existing biomass. the applied equations are the following: rleaves = k dmleaves + c mleaves num dt (8) rprod = k dmprod + c mprod num dt (9) rroot = k dmroots + c mroots num dt (10) where rleaves = respired biomass of leaves, kg rprod = respired biomass of product, kg rroot = respired biomass of roots, kg dmleaves = synthesized biomass of leaves, kg dmprod = synthesized biomass of product, kg dmroots = synthesized biomass of roots, kg mleaves = existing biomass of leaves, kg mprod = existing biomass of product, kg mroots = existing biomass of roots, kg k = the constant of 0.1 h−1 [22] c = the constant of 0.0001 h−1 [22] num = number of plants, pc. dt = the time step in hours, distinguished for the changing actual daylight or night period the uptake of water, nitrogen and phosphorus (or of other optional elements) is calculated as the minimum amount: • required for evapotranspiration and photosynthesis together and • available in the soil. 50 pp. 57–65 (2022) 60 varga 3.2 non-conventional methodology of programmable process structures programmable process structures (pps, [23–26]) have developed from its antecedent, that is, direct computer mapping [27]. pps offers automatic generation of easily extensible, connectible and combined dynamic balanceand rule-based models for the analysis, planning and operation of complex process systems, even beyond industries that apply cim (chemical integrated manufacturing). these models consist of unified state and transition elements, transition-oriented representations of structures as well as locally programmable functional prototypes. the main sources of inspiration behind pps are: 1) the general functional definition of process systems in kalman’s state space model [28]; 2) the structural representation of general net theory [29]; 3) the concept of communicating autonomous programs in terms of agentbased modeling [30]. accordingly, pps models are derived from two general (state and transition) "meta-agents," namely the structure of the generated state and transition elements form a net structure, moreover, the locally programmed state and transition prototypes represent the distributed functionalities in terms of kalman’s model. in addition, pps can consciously make a distinction between modelspecific conservation laws based on additive measures and signals. in fact, pps models can be generated from two general meta-prototypes and from the corresponding description of the process net. the local program containing prototype elements (that are responsible for the casespecific calculations), are also derived from the same meta-prototypes. the simulation can be executed according to the connections between the actual state and transition elements, accompanied by the data transfer between the actual elements and their calculated prototypes. this architecture and its ai programming language-based (swi-prolog to be exact) implementation strongly support the integration of various fieldand task-specific models. 4. results and discussion 4.1 chemical process engineering-inspired principles and hypotheses of plant models natural and cultivated plants, including crops, vegetables, herbs, grasses and bushes, trees, etc. in a broader context, cover a wide variety of biological species embedded in a naturally occurring and partly human-controlled process system. since many different species exist, at first glance this resembles the early stages of chemical engineering when individual technologies were interpreted as a system of various case-specific reactors, separators, etc. the essential invariant elements were later generalized according to the concept of unit operations. similarly, the unified, essential features of agricultural models can be formulated as “biological engineering unit operations” within the complex system of the connected agrotechnological, ecological and environmental systems. considering the need for unified and simplified biological, ecological and environmental engineering process units, these systems must be represented by the necessary and sufficient types as well as numbers of state and transition elements calculated by a limited set of generally usable program prototypes. the coherent and connectible set of the underlying ‘first principles’-based mechanistic (physical, chemical and biological) models must be based on causally correct, model-specific conservation laws-based material and energy balances. considering the numerous biochemical compounds and biological objects, that is, organs, etc., synthesized from these compounds, the various typical biological units can be characterized by their specific stoichiometric composition that facilitates the representation of balances in accordance with the conservation of atoms and in line with chemical principles. besides the conservation-based balances, the causally determined (driving force-based) transformations and transportations are the second pillar of process engineering models. in this regard, plant-like biological process units represent a special case because the major driving force is solar radiation originating from beyond the contours of the system. this feature determines the unique position of plants in the bio-based circular carbon economy. in fact, solar radiation-driven photosynthesis produces a stoichiometric composition of biomass that supplies biomass in the various state elements of plants through downflow transporting short-term storage. moreover, the forces of solar radiation-driven evapotranspiration result in the uptake of water and dissolved nutrients through upflow transporting short-term storage that supplies the additional resources required for photosynthesis as well as removes the by-products of the energyproducing respiration. accordingly, the essential self-control of plant life is organized by the solar radiation-driven push logistics of downflow as well as by the solar radiation-driven pull logistics of upflow. the daily and seasonal changes in plant behavior are determined by the temporally changing environmental functionalities, while human intervention can be taken into consideration by the respective managerial events. the hypotheses for the simplified and unified plant model can be summarized as follows: • the state elements are described by the specific biomass (or mass); the stoichiometric amounts of c, h, o, n, p and optional x atoms; as well as those originating from h2o, o2 and co2. • the transition elements, e.g. photosynthesis, growth, respiration, evapotranspiration, uptake, etc., determine the functionalities resulting in stoichiometric changes in the aforementioned sources hungarian journal of industry and chemistry https://www.swi-prolog.org/ developing plant models of reduced complexity 61 of biomass, mass, atoms and components in the respective state elements. • the life processes of plants as self-controlled living systems can be characterized by (i) the supply logistics of the photosynthesis-driven utilization of co2 from air and h2o, n, p, etc. (from top soil) to produce o2 which is emitted into the atmosphere in addition to stoichiometric pools of c, h, o, n and p that is incorporated into downflow material storage, as well as by (ii) the demand logistics of the solar energy-driven evapotranspiration-controlled uptake of h2o, n and p from the soil and the emission of co2 and h2o into the air. 4.2 structure of the investigated process system the process net structure of the simplified plant model, embedded in its natural environment and extended with human managerial interventions, is illustrated in fig. 1. in the net model, the dots and bars represent the state and transition elements, respectively. the state and transition elements of the simplified plant model are the following: plant-related model elements: • state elements: – roots (responsible for the water uptake, transportation of dissolved nutrients and long-term biomass storage that is also capable of generating useful products); – leaves (including stems which are responsible for solar radiation-driven photosynthesis and evapotranspiration); – products (which facilitate the storage of biomass for reproduction that also generates useful products); – downflow of material (short-term storage of photosynthesized biomass to be distributed amongst the roots, leaves and products); – upflow of material (short-term storage of uptaken water and nutrients as well as of respired components to be distributed between evapotranspiration and photosynthesis). • transition elements: – photosynthesis: utilizes solar radiation to synthesize biomass from atmospheric carbon dioxide, uptaken water and dissolved components, e.g. nitrogen, phosphorus, etc.; – growth: distributes the photosynthesized biomass between the parts of the plant according to the phenological phase-specific stoichiometry; – respiration: creates energy to synthesize tissues from already synthesized biomass and in part maintain existing plant biomass; – evapotranspiration: which is determined by the atmospheric conditions, i.e. level of solar energy, generates the driving force for the uptake of water and dissolved nutrients from the soil as well as releases the co2 and h2o produced by respiration; – uptake: supplies the necessary water and dissolved nutrients from the soil. soil-related model elements: • state elements: – residue (only in the topsoil): contains organic residues, e.g. from leaf littering or the ploughing of roots; – humus (only in the topsoil): transformed organic biomass in the soil; – solution containing water and dissolved components; – inorganic solid phase. • transition elements: – transform (only in the topsoil): describes the production of humus and dissolved nutrients from the residues; – air_land (only in the topsoil): calculates the levels of precipitation and nitrogen fixation from the atmosphere into the soil as well as those of evaporation and co2 emission from the soil into the atmosphere; – miner_deminer: determines the degrees of mineralization and demineralization of dissolved components in the soil; – seepage: calculates the vertical downflow of water and dissolved components between the layers of soil. human interventions in terms of cultivation: • typical state elements: manure, seeds, harvested products, etc. • typical timeand/or event-driven transition elements: manuring, sowing, harvesting, ploughing, etc. other environmental state elements: the atmosphere (air), solar radiation-related meteorology, ground layer below the soil that absorbs water and nutrients. 4.3 solar radiation-driven “natural supply logistics” of plant biomass generation the essential functionalities of the investigated process system can be represented as solar energy-driven as well as predominantly self-regulated, natural supply-anddemand logistics. moreover, the respective supply-anddemand processes are causally connected that establish a natural (basically cooperative) feedback between each other. solar radiation facilitates the synthesis of biomass, the latter is calculated according to eqs. 1-5. the related subprocesses of the plant model are denoted in green lines in fig. 1. the synthesis of biomass is driven by solar radiation but limited by the available amounts of water, nitrogen and phosphorus with regard to the upflow material to be 50 pp. 57–65 (2022) 62 varga figure 1: process network of the simplified plant model stored. the rate of photosynthesis also depends on the surface area of the leaves and stem. controlled by these conditions and limitations, the synthesis sequestrates the calculated amount of the practically unlimited supply of atmospheric co2 in the biomass. simultaneously, photosynthesis emits o2 into the atmosphere as a result of the oxidation of uptaken water, while the associated hydrogen is incorporated into the synthesized biomass. the photosynthesized biomass supplies the downflow of material to be stored according to the plant-specific atomic stoichiometry. in the case of the studied maize, the stoichiometry of the synthesized dry matter was as follows [20, 21]: [c, h, o, n, p, x] = [0.037, 0.062, 0.029, 0.00087, 4.8 × 10−5, 0] the dry matter is supplied by an additional amount of h2o, according to the average water content of the plant (in our case 0.682). the synthesized biomass is divided between the leaves, roots and product state elements of the plant, according to the plant-specific ratios that also depend on the phenological condition of the model. furthermore, different stoichiometries can be used by the various parts of the plant. in addition to the increase in the amount of synthesized biomass, a given proportion of that which is stored in the short term is utilized to meet the energy demand supplied by respiration for the synthesis of plant biomass according to eqs. 8-10. 4.4 solar energy-driven “natural demand logistics” of water and nutrient uptake considering the “natural demand logistics,” the solar energy facilitates the uptake of water and dissolved nutrients from the soil as well as of h2o and co2, the byproducts of respiration. the respective evapotranspiration is calculated according to the penman-monteith combination equation [22] as well by eqs. 6-7. the related subprocesses of the plant model are denoted in red lines in fig. 1. depending on the meteorological conditions, the h2o and co2 content of the uptaken material to be stored is emitted into the atmosphere by the process of evapotranspiration. simultaneously, the by-products of respiration, namely h2o and co2, accumulate here, moreover, the necessary amounts of h2o as well as of dissolved nitrogen and phosphorus are utilized for photosynthesis from this store. in the knowledge of the resultant actual conditions with regard to the uptaken material to be stored, the uptake is controlled by demand-determined pull actions according to the concentration bounds and uptake rules as follows: lower and upper bounds for h2o as well as n and p atoms are known. the rule that is applied is the following: if actual ≤ lower, then demand = min((upper-actual), available), otherwise demand = 0, where actual = actual amount of uptaken material to be stored, lower = lower bound, hungarian journal of industry and chemistry developing plant models of reduced complexity 63 upper = upper bound, demand = quantity to be uptaken, available = available amount in the topsoil. 4.5 generation and simulation of the pps model the files describing the respective model are found in the “plant” directory of a mendeley database [31]. the process network of the example model is defined in the text file named plant_n.pl. the initial conditions (mass, biomass, components, etc.) and parameters (coefficients of equations, bounds, etc.) are described in the text file entitled plant_d.pl, which was derived using an appropriately configured ms excel spreadsheet. starting from these case-specific files and the general definition of state and transition meta-prototypes, the general-purpose kernel program generates the editable graphical model plant_g.graphml. in parallel, by utilizing the meta-prototypes-based templates, modeling experts have to prepare the local programs for the respective elements of the prototypes. the locally executable programs of the prototypes are described in the file entitled plant_g_prot.graphml. in the knowledge of the prototype elements, the second generating algorithm of the pps kernel prepares the dynamic databases of the simulation, namely • plant_exp.pl containing the declaration of the prolog clauses describing the local programs; and • plant_use.pl containing the declaration of the prolog facts describing the case-specific elements of the model along with their initial values and parameters. the actually selected simulation results are saved in the file named plant_out.csv, while the data can be visualized using a case-specific ms excel spreadsheet. some examples of the simulated results are illustrated in figs. 2-5. fig. 2 shows the change in the total amount of biomass produced over one hectare during consecutive half days in the simulation. time = 0 indicates when the land was sowed. biomass begins to be produced following germination and stops at the end of the vegetation period. fluctuations in biomass production indicate that its rate is higher during the daytime compared to at nighttime. in fig. 3, water that evaporated from the plant (blue) and from the land (red) are illustrated. evaporation from the land follows the weather conditions much more closely and dominates during the early stages of the growing season, particularly when the leaves develop. similarly to the production of biomass, evaporation rates are also higher in this simulation during the daytime. in fig. 4, the biomass of the parts of one plant (leaves, stem, roots, products) can be seen. the leaves, stem and roots begin to develop at the point of germination, while products appear later on. although the leaves, stem and products are removed at harvest time, the roots are transformed into residues as a result of ploughing. of course, figure 2: total amount of photosynthesized biomass per hectare figure 3: dynamic changes in the evaporation rate of h2o from plants and the surface of the land figure 4: biomass of plant parts throughout the growing season the stepwise increase in biomass is insignificant in this integrated illustration. fig. 5 shows the sequestrated co2 over one hectare during consecutive half days of the simulation. the negative values refer to the reduction in its concentration in the surrounding atmosphere. 5. conclusion although detailed plant models for well-defined important crops are available that require hundreds of parame50 pp. 57–65 (2022) 64 varga figure 5: amount of sequestrated co2 ters to be identified, the increasing complexity of agricultural systems within the broader context of the bio-based circular carbon economy requires simplified and unified plant models, which can describe the primary production of biomass. the suggested conceptual framework and its experimental implementation show how the chemical process engineering principles of process units, stoichiometric conservational processes, process networks, driving force-controlled functionalities and supply/demand processes can result in a reduced, unified plant model. the structure of the model can be generated from the process net of the underlying state and transition elements. the model contains two special state elements for the short-term storage of the synthesized biomass to be distributed amongst the state elements of the plant as well as for the short-term storage of the uptaken aqueous nutrients required for evapotranspiration and photosynthesis. these two forms of logistical storage used represent the roles of phloem and xylem in detailed biophysical models. the transition-related dynamic models follow the essential causalities and balances of natural self-control. solar radiation-driven photosynthesis produces a stoichiometric composition of biomass that, as a result of the downflow of products to be stored in the short term, increases the biomass in the various plant elements. moreover, solar radiation-driven evapotranspiration forces water and dissolved nutrients to be uptaken through the upflow of products to be stored in the short term, which increases the amount of water and the additional resources for photosynthesis required, as well as removes the by-products of energy-producing respiration. the natural self-control of plant life is organized by the solar radiation-driven push logistics of downflow as well as by the solar radiation-driven pull logistics of upflow. the suggested stoichiometric approach underlines the increasing importance of elemental analysis with regard to agriculture-related raw materials and products. the experimental pps implementation of a simple example model 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https://doi.org/10.1016/j.biosystems.2016.12.005 https://doi.org/10.1016/j.ecolmodel.2017.09.014 https://doi.org/10.1016/j.aquaeng.2020.102073 https://doi.org/10.1016/j.envsoft.2020.104755 https://doi.org/10.1016/j.envsoft.2020.104755 https://doi.org/10.1007/3-540-10001-6_21 https://doi.org/10.1016/j.cosrev.2017.03.001 https://doi.org/10.1016/j.cosrev.2017.03.001 https://doi.org/10.17632/nw3cjv75j5.1 introduction challenges and objective materials and methods data and calculation formulae for a typical example of a plant to be modelled non-conventional methodology of programmable process structures results and discussion chemical process engineering-inspired principles and hypotheses of plant models structure of the investigated process system solar radiation-driven ``natural supply logistics'' of plant biomass generation solar energy-driven ``natural demand logistics'' of water and nutrient uptake generation and simulation of the pps model conclusion hungarian journal of industry and chemistry vol. 51(2) pp. 7–14 (2023) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2023-12 effect of heat treatment on the structure of selfassembled undecenyl phosphonic acid layers developed on different stainless steel surfaces éva kocsisné pfeifer1, jános mink2, istván gábor gyurika1 and judit telegdi2,3* 1 institute of materials and mechanical engineering, university of pannonia, egyetem u. 10, veszprém, 8200, hungary 2 institute of materials and environmental chemistry, research centre for natural sciences, magyar tudósok körútja 2, budapest, 1117, hungary 3 faculty of light industry and environmental engineering, óbuda university, doberdó út 6, budapest, 1034, hungary deterioration caused by corrosion is well known, which can destroy metallic and non-metallic materials alike. dissolved inhibitors of bionic microand nanocoatings can decrease the degree of undesirable corrosion in various ways. in this paper, a self-assembled molecular layer formed from undecenyl phosphonic acid developed on two different steel surfaces was the subject of our experiments. the influence of the metal composition, layer-forming conditions and postheat treatment was documented by wettability measurements as well as surface roughness parameters; the change in surface morphology caused by the formation of a layer in addition to post-heat treatment was visualized by an atomic force microscope (afm); and infrared spectroscopy elucidated the bindings of the amphiphilic molecules involved in the self-assembled layer to the metal surface as well as to each other. over the course of the self-assembling process, the – p(o)(oh)2 head groups can fix the amphiphilic molecule to the solid surface through the metal oxide-hydroxide layer. the hydrophobic alkenyl chains remain together as a result of special forces, namely hydrogen bonds and van der waals forces, between them. the double bond at the end of the alkenyl chain disturbs how well the layer is ordered. to improve the homogeneity of the molecular layer and increase its level of compactness, the self-assembled molecular (sam) layer was heat treated to achieve a more compact molecular film that can perfectly cover the metal surface. keywords: alkenyl phosphonic acid, self-assembled layer, wettability, surface morphology, atomic force microscope, infrared spectroscopy 1. introduction since corrosion is a major problem, the development of effective corrosion inhibitors in many industrial sectors is important. the use of organic inhibitors has been extensively studied and several classes of inhibitors developed for different metals as well as in various environments. among the various types of corrosion inhibitors, organic compounds with heteroatoms such as oxygen, nitrogen, phosphorous and/or sulfur are commonly used due to their high adsorption capability on a metal surface, which is mainly due to the lone pairs of electrons on the heteroatoms [1]-[2]. for the corrosion inhibition of iron, phosphonic acid derivatives are applied in different aqueous and oily environments, not only in dissolved form but as additives in coatings, concrete, etc. these molecules are stable as the covalent bond between the phosphorous and carbon atoms stabilizes the molecule, so these molecules are not nutrients for microand macroorganisms, that is, they do not increase the degree of eutrophication of natural received: 22 july 2023; revised: 14 august 2023; accepted: 14 august 2023 *correspondence: telegdi.judit@ttk.hu waters. alkyl and aralkyl phosphonic acids as well as their substituted derivatives form an effective class of organic inhibitors applied in both neutral or acidic media. numerous studies have reported the effectiveness of alkyl phosphonic acids as corrosion inhibitors of various metals, including steel, aluminum, copper and zinc. for example, a very good review article summarizes the usefulness of phosphonic acids as inhibitors to control the corrosion of mild steel in acidic environments by providing information about the enhanced inhibition efficiency at increased concentrations attributed to the adsorption of the inhibitor molecules [3]. similarly, a good review article on the inhibition of copper corrosion by alkyl phosphonic acids attributed to the adsorption of inhibitor molecules to the copper surface has been published [4]. alternatively, phosphonates [5] or phosphonic acid inhibitors can be used when they are embedded in nanolayers as several publications have demonstrated, e.g. on aluminum [6], iron [7] or titanium [8] and copper alloys [9]-[10] amongst other possible applications. https://doi.org/10.33927/hjic-2023-12 mailto:telegdi.judit@ttk.hu pfeifer, mink, gyurika and telegdi hungarian journal of industry and chemistry 8 the adsorption behavior of alkyl phosphonic acids on metal surfaces has been investigated using various techniques, including electrochemical impedance spectroscopy, atomic force microscopy and x-ray photoelectron spectroscopy. these studies demonstrated that the molecules of alkyl phosphonic acid adsorb onto the metal surface through a combination of chemisorption and physisorption mechanisms. the chemisorption mechanism involves the formation of a covalent bond between the inhibitor molecule and the metal surface, while the physisorption mechanism involves weak van der waals forces between the inhibitor molecule and the metal surface. it is important to emphasize that although the head group of these amphiphilic molecules is bound to the solid surface, the metal oxide layer is never bound directly to the pure metal. the effect of the alkyl chain length on the inhibition efficiency of alkyl phosphonic acids has also been studied. it has been reported that the inhibition efficiency rises as the alkyl chain length increases up to a certain point after which it starts to decrease. even though it is not easy for a shorter amphiphile to form a homogenous nanolayer, molecules with longer hydrophobic chains form compact molecular films over a shorter period of time, which is attributed to stronger hydrophobic interactions between the alkyl/aralkyl chains. a homogenous, compact nanolayer can better control the corrosion processes as the aggressive ions cannot get close to the metal surface [10]-[12]. in addition to the anticorrosion activity, alkyl phosphonic acids exhibit other useful properties such as surfactant behavior and the ability to form stable lamellar structures in aqueous media that are advantageous in various applications such as when synthesizing nanocomposites. one method of increasing the compactness of selfassembled molecular layers (sams) is by heat treating those that have already formed on different solids to help remove water molecules that have formed during the adsorption of phosphonic acid functional groups as well as eliminate the residual solvent. as a result, the van der waals forces and hydrogen bonding between the alkyl/alkenyl chains increase. in the case of the double bond in the hydrophobic side chain, heat treatment could facilitate the polymerization of amphiphilic molecules involved in the sam layer. the proximity of the unsaturated bonds in the nanofilm allows polymerization to take place in the absence of any other additives/catalysts. it is important to take into consideration the heat sensitivity of the molecules that are found in the sam film. several examples are found in the literature of when the positive influence of heat treatment not only influences layer formation but confirms the structure of the nanolayer, e.g. in the case of a copper alloy [9] and on mica [13]. in all cases, the aim was to reduce the number of pores formed in phosphonic acid layers by changing their conformation. these examples in the literature prove the effectiveness of alkyl/aralkyl phosphonic acid nanolayers on a wide range of metals. in this paper, the nanolayer formation of undecenyl phosphonic acid on two different iron alloys is demonstrated and the possibility of improving the effectiveness of this special alkenyl phosphonic acid in the formation of compact nanolayers addressed. the questions raised were: 1) how can the alloying metal components influence the formation of self-assembled molecular layers?; and 2) will the compactness of the nanolayer be improved by posttreatment or not? furthermore, layer formation was analyzed by infrared spectroscopy [5]. 2. experimental 2.1. solid supports in our experiments, two types of stainless steel were used with the following compositions: 1) 1.4841: elements [%]: cr: 25, c: 0.2, si: 2, mn: 2, p: 0.045, s: 0.045, balance fe; 2) 1.4571: elements [%]: cr: 17, c: 0.08, si: 1, mn: 2, p: 0.045, s: 0.045, mo: 2, ni: 12, ti: 0.7, balance fe. the metal samples (10x10x1 mm) were smoothened with emery paper (200, 400, 800, 1200 mesh) and polished with diamond pastes (grain size: 15, 12, 9, 6 and 3 m). all polishing treatments were followed by sonicating the coupons as well as washing them in water and finally with methanol. 2.2. amphiphile in all the experiments, undecenyl phosphonic acid (ch=ch-[ch2]9-po(oh)2, mw: 234) (specific polymers, castries, france) was used to form the sam layer. a solution of 5x10-3 m amphiphile was prepared by dissolving it in methanol. 2.3. self-assembled molecular layer (sam) preparation the metal coupons were immersed in the solution of undecenyl phosphonic acid at 23oc for different periods of time, namely 4, 24 and 48 hours. following immersion, the metal samples were rinsed in pure methanol to remove the excess of amphiphilic solution before being dried in air. all layers formed at 23oc, while the post-treatment was performed at 50oc for 5 hours. the method used in this study is easily reproducible. 2.4. characterization of the nanolayers 2.4.1. water wettability study the water repellency of the metal surfaces in the presence or absence of nanolayers was characterized by the static contact angle measured by milli-q water sessile drops at 20°c using a motorized syringe [14]. effect of heat treatment on self-assembled layers 51(2) pp. 7-14 (2023) 9 2.4.2. surface visualization by atomic force microscopy the bare and coated metal surfaces were visualized by an atomic force microscope (nanoscope iii, digital instrument, contact operation, height and deflection mode, tip: si3n4). the surface morphology was presented in 2d and 3d modes, while the three surface roughness parameters calculated by the software of the instrument were checked at three or more different places (measurement error was less than 1%). 2.4.3. surface roughness parameters measured on the coated or uncoated surfaces of the sam layer three surface roughness parameters were calculated by the software of the atomic force microscope to characterize the solid surfaces with or without nanocoatings: ra: the arithmetic average height that shows the absolute deviation of the irregularities to characterize the height variation; rq: the root mean square roughness that represents the standard deviation of the surface height distribution, while the roughness is described by a statistical method; rmax: sensitive to the deep valleys and high peaks; it analyzes the profile and shows the vertical distance between the lowest valley and the highest peak [15]. 2.4.4. infrared spectroscopy ft-ir (fourier transform infrared) spectra were recorded on a jasco ft/ir-4600 spectrometer equipped with a jasco multi-reflection atr (5 reflections), znse atr crystal (incident angle 45°) and a dtgs (deuteratedtriglycine sulfate) detector used within the 4000–400 cm– 1 range. a resolution of 4 cm–1 and co-addition of 128 individual spectra were applied. an atr correction was performed on the raw spectra. 3. results and discussion 3.1. results of the wettability measurements changes in the wettability data measured on the steels with and without sam layers are summarized in tables 1 and 2. for the sake of comparison, the water contact angles measured on pure iron (armco iron) are also included in tables 1 and 2. the alloying metals slightly increase the wettability of the metal samples. the presence of mn and mo, even at low percentages (2%), together with a lower cr content (17%), renders this metal sample less wettable than the other one, which contains more cr (25%) and 2% mn. the differences are visible in the receding contact angle values on the alloys. interestingly, the molecular layer deposition over a short period of time alters the wettability of the lower alloy steel more significantly than the other one. however, heat treatment in both cases results in the surfaces becoming more hydrophobic. a longer layer deposition time (24 h) increases the contact angles on both steels, moreover, post-heat treatment increases the surface hydrophobicity, however, the wettability does not change significantly. it is important to mention that the differences between the advancing and receding contact angles are much less in the presence of 25% cr and 2% mn. this means that the compactness of the layer is much more enhanced by the post-heat treatment on this alloy, a consequence of the increased surface coverage due to differences in the surface oxide composition. table 1: static wettability data measured on 1.4571 metal surfaces in the presence and absence of undecenyl phosphonic acid sam layers before and after heat treatment solid surface treatment water contact angle (o) (advancing) water contact angle (°) (receding) armco iron 68.4 44.1 1.4571 steel 65.6 62.1 +4 h sam (23°c) 66.9 36.7 +4 h sam (23°c) 50°c, 5h 76.5 43.3 +24 h sam (23°c) 72.4 43.1 +24 h sam (23°c) 50°c, 5h 86.1 75.6 +48 h sam (23°c) 79.5 47.9 table 2: static wettability data measured on 1.4841 metal surfaces in the presence and absence of undecenyl phosphonic acid sam layers before and after heat treatment solid surface treatment water contact angle (°) (advancing) water contact angle (°) (receding) armco iron 68.4 44.1 1.4841 steel 60.2 57.2 +4 h sam (23°c) 70.5 35.5 +4 h sam (23°c) 50°c, 5h 73.3 45.1 +24 h sam (23°c) 81.1 75.5 +24 h sam (23°c) 50°c, 5h 85.5 78.3 pfeifer, mink, gyurika and telegdi hungarian journal of industry and chemistry 10 3.2. surface visualization by an atomic force microscope in the afm images taken of the 1.4841 steel samples shown in figures 1 and 2, it can be observed that a fourhour-long immersion time in the udp solution produces a thin layer that covers the metal surface loosely given the low receding contact angle. increasing the immersion time results in a well-ordered layer on the metal surface that produced a special surface image. after heat treatment, the pattern on the surface does not change significantly, just the layer is more compact. by increasing the immersion time to 48 hours, the nice pattern formed earlier on the surface is still evident, but an additional layer is visible, proving that 24 h is sufficient to achieve a compact, well-ordered monomolecular sam layer that properly covers the steel surface. these afm images clearly show that on this steel sample a four-hour-long immersion time and post-heat treatment produce a sam layer with a special pattern. the pattern on the layer is not altered by increasing the immersion time, however, the layer seems to be more compact. on this steel sample, the long immersion time does not result in the formation of a second layer. however, heat treatment facilitated the formation of more compact sam layers. 3.3. surface roughness parameters the surface roughness parameters derived from the afm images taken on coated as well as uncoated steel surfaces are summarized in tables 3 and 4. the surface roughness data demonstrate well that the layer deposition – even after shorter film formation times – decreases the surface roughness. post-heat treatment causes a small increase in these values. a visible difference in the surface roughness caused by the difference in the steel compositions is observed. more alloying components enhance the surface roughness after shorter as well as longer layer deposition times and even after heat table 3: surface roughness parameters measured on uncoated and sam layer coated surfaces of the 1.4571 alloy; ra: arithmetic average height; rq: root mean square roughness; rmax: maximum height of the profile solid surface post-heat treatment rq [nm] ra [nm] rmax [nm] armco iron 3.21 2.34 46.2 1.4571 steel 7.14 5.46 58.3 +4 h sam (23°c) 4.03 3.10 37.1 +4 h sam (23°c) 50°c, 5h 5.52 4.14 49.0 +24 h sam (23°c) 4.85 3.90 52.3 +24 h sam (23°c) 50°c, 5h 5.41 4.09 63.7 +48 h sam (23°c) 3.89 3.06 43.0 figure 1: afm images (taken in contact mode, visualization in deflection mode) of the starting 1.4841 steel surface and the steel with sam nanolayers of undecenyl phosphonic acid (udp); sam: formed in a 5x10-3m undecenyl phosphonic acid solution at 23°c; layer formation time: 4 and 24 h figure 2: afm images (taken in contact mode, visualization in deflection mode) of the starting steel surface and 1.4841 steel with self-assembled nanolayers of undecenyl phosphonic acid (udp); sam: formed in a 5x10-3m undecenyl phosphonic acid solution at 23oc; layer formation time: 24 and 48 h; post-heat treatment: 5 h at 50oc figure 3: afm images (taken in contact mode, visualization in deflection and 3d modes) of the 1.4571 steel surface as well as of the metal surface with selfassembled udp nanolayers; sam: formed in a 5x10-3m udp solution at 23oc; layer formation time: 4, 24 and 48 h; post-treatment: 5 h at 50oc effect of heat treatment on self-assembled layers 51(2) pp. 7-14 (2023) 11 treatment. this may be a consequence of the formation of a more compact molecular film demonstrated by the contact angles. 3.4. infrared spectroscopy ft-ir spectroscopy was used to analyze the alkyl chain ordering and bonding mode of the molecules to the surface. on the polished, that is, cleaned stainless steel substrates, no sign of organic deposition was observed from their spectra. in the spectra of sam layer deposited substrates, the reference peaks determine that the organization of sams was defined by the c-h stretching vibrations of the methylene group. the c-h stretching possesses two typical stretching vibrations: antisymmetric represented by a peak at 2850 cm-1 and asymmetric stretching represented by a peak at 2918 cm-1. the frequency of these two wavenumbers becomes either higher or lower depending on the conformation of the alkyl chain. when the peaks are centered at wavenumbers that are shifted to higher frequencies (asymch2 > 2918 cm-1), a disordered monolayer with gauche defects in the alkyl chain is suggested. conversely, if the wavenumbers shift to lower frequencies, the monolayer is considered to be ordered (asymch2 < 2918 cm-1) with all-trans c-c bonds. in this study, the peaks corresponding to ch2 were positioned at asymch2 = 2917.7 and symch2 = 2850.5 cm-1, while those concerning undecenyl phosphonic acid were shifted to 2920.3 and 2850.1 cm-1 in the spectrum of its sam layer on the 1.4841 steel surface. the 2.6 cm upshift of the antisymmetric ch2 stretching band indicates the formation of a slightly disordered surface structure with some gauche conformations in the alkyl chain (figure 4). meanwhile, an insignificant 0.4 cm-1 downshift of the symmetric ch2 stretching band was observed. besides these effects, it was observed that the band broadened slightly. the two ch2 stretching bands exhibit 21 and 14 cm-1 half band half widths in the spectrum of undecenyl phosphonic acid, which were slightly broadened to 23 and 16 cm-1 for antisymmetric and symmetric ch2 stretching bands in the sam layer, respectively. additional information regarding the bonding of the head group to the substrate can be obtained by analyzing the position of the ir absorption bands in the fingerprint region. figure 5 and table 5 show the selected ir bands important for structural and compositional characterization of the formed sam layer. the assignment of fingerprint regions is especially difficult due to the appearance of various deformation modes of ch2 groups, namely scissoring, wagging, twisting and rocking modes, as well as the alkyl chain cc stretching modes. table 4: surface roughness parameters measured on uncoated and sam layer -coated surfaces of the 1.4841 alloy; ra: arithmetic average height; rq: root mean square roughness; rmax: maximum height of the profile solid surface post-heat treatment rq [nm] ra [nm] rmax [nm] 1.4841 steel 5.22 4.17 55.6 +4 h sam (23°c) 3.55 2.39 48.12 +4 h sam (23°c) 50°c, 5h 4.71 3.36 54.9 +24 h sam (23°c) 5.75 4.23 53.01 +24 h sam (23°c) 50°c, 5h 6.50 4.73 63.1 +48 h sam (23°c) 6.89 4.95 63.19 +48 h sam (23°c) 50°c, 5h 7.79 5.54 78.0 figure 4: ir spectra of undecenyl phosphonic acid (lower trace) and its sam layer on the 1.4841 steel surface in the ch2 stretching band (upper trace). the precise positions of the bands were obtained by calculating their second derivatives asymch2 = 2920.3 and symch2 = 2850.1 cm-1, indicating the presence of a strongly bound and ordered film pfeifer, mink, gyurika and telegdi hungarian journal of industry and chemistry 12 two extra bands were detected at 1702 and 1560 cm-1 assigned to partial oxidation of the product, that is, ketones and antisymmetric stretching of the carboxylate group vibrational mode, respectively. two weak bands result from symmetric coostretching at 1388 and 1360 cm-1. all four characteristic bands of olefinic end groups, namely c=c stretching, =ch2 scissoring, =ch2 wagging and =ch2 rocking, can be seen in the ir spectrum of the sam layer. insignificant frequency shifts were observed in symmetric (spoh) and antisymmetric (apoh) p-o-h in-plane bending modes. the dpu exhibits bands at 1136 and 1116 cm-1, while the studied sam layer yields bands at 1130 and 1119cm-1. a very similar effect was observed in the case of out-of-plane p-o-h deformations. the symmetric (spoh) and antisymmetric (apoh) out-ofplane deformation bands appeared at 779 and 718 cm-1 in the ir spectrum of udp, moreover, these features only slightly shifted in the case of heated sams, e.g., to 786 and 715 cm-1. from these experimental results, it can be concluded that the –p(oh)2 side of the phosphoryl group did not strongly interact with the metal surface. additional information regarding the bonding of the head group to the substrate can be obtained by analyzing the position of the ir absorption bands in the p=o stretching region (1000-1200 cm-1) for phosphonic acids. although the interpretation of the peaks within this region is hindered by their broadness and complexity, the substantial variations observed provide compelling evidence for the existence of a robust interaction between the phosphonate head group and the oxidized metal surface. the difference between the starting spectrum of undecenyl phosphonic acid and those of the films on the metal surface is very significant. the most significant difference is observed in the intense valence vibrations of the phosphoryl group. a major effect of surface bounding was that the unbounded p=o stretching at 1179 cm-1 downshifted to 1046 cm-1. in contrast to the p-o single bond stretching of –p(oh)2, strong bands of the udp– p=o(oh)2 end group at 938 and 908 cm-1 correspond to the -po2 asymmetric and -po2 symmetric stretching vibrations, respectively, which are only slightly upshifted in the ir spectrum of sam layer on the 1.4841 steel surface to 960 and 918 cm-1. according to these relatively small shifts in p-o stretching bands in agreement with the little shifts of the p-o-h deformation features, it can be concluded that in the –p=o(oh)2 end group, the –p(oh)2 site weakly interacts with the metal surface. contact with the metal surface is most significant at the –p=o site of the –p=o(oh)2 end group exhibiting about a 130 cm-1 downshift on the metal surface. besides the aforementioned experimental observations, some weak features among the aliphatic ch2 deformation modes can be assigned to the partial presence of gauche conformers in the long chain (see table 5). to summarize the infrared spectroscopic results, the precise analysis of spectra taken in udp in bulk and in nanolayer forms proved that the amphiphilic monomers in sam layers yield different spectra from the bulk one. additionally, the detailed analysis of the fingerprint region of the spectra demonstrated clearly how the head group of the amphiphile (-p(o)(oh)2) is bound to the metal/metal oxide surface (mostly through the metal oxide layers) as well as demonstrated the interaction between the hydrophobic chains. similar results were observed on the heat-treated udp in bulk and nanolayer forms. 4. conclusion the alloying metals slightly increase the wettability of the metal samples. the presence of mn and mo, even at low percentages (2%), together with a lower cr content (17%) results in similar contact angles to the other steel, figure 5: ir spectra of undecenyl phosphonic acid (upper trace) and the sam layer on the 1.4841 steel surface (lower trace) in the fingerprint region effect of heat treatment on self-assembled layers 51(2) pp. 7-14 (2023) 13 which contains cr at a higher concentration (25%) as well as 2% mn. the differences are not significant. the heat treatment causes a significant increase in the contact angles. the increased level of compactness is proved by the smaller differences in the advancing and receding contact angles. a longer layer deposition time (24 h) increases the water contact angles on both steels, even before and after post-heat treatment. the metal surfaces, with and without selfassembled molecular layers imaged by a atomic force microscope, showed that the formation of nanolayers changes the surface morphology significantly. the surface roughness parameters demonstrate that layer deposition – even after shorter film formation times – decreases the surface roughness. post-heat treatment causes a small increase in these values. a visible difference in the surface roughness caused by the difference in the steel compositions is observed. more alloying components enhance the surface roughness over shorter and longer layer deposition times as well as after heat treatment, which may be a consequence of the differences in the layer compositions of the oxide surface. differences between spectra of undecenyl phosphonic acid measured on the bulk material and involved in nanolayers were proven by infrared spectroscopic measurements. furthermore, bonding between the phosphonic acid head groups and the solid surface (mainly via the metal oxides) as well as hydrophobic interactions between the alkenyl groups were clearly demonstrated. experiments on the layer thickness by spectroscopic ellipsometry as well as the determination of the composition of the oxide surface by xps are in progress. acknowledgements the authors are grateful for the experimental support provided by lászló trif (research centre for natural sciences) and péter márton (budapest university of technology and economics). table 5: comparison of selected infrared bands from atr spectra of the h2c=ch-(ch2)9 po(oh)2 molecule of the original powdered sample and heat-treated sam layer sample after 24 hours of heating at 50°c. bulk powder at 25°c sam layer at 50°c for 24h assignments remarks 2917.7 vs (a) 2920.3 vs (b) ach2 2850.5 s 2850.1 vs 1702 w,b 1560 w sch2 c=o acoo oxidation products 1642 m 1401 m,w 993 vs 638 w 1642 m 1403 w 994 s 659 w c=c  = ch2  = ch2 + p=o  = ch (vinyl) +  = ch 1470 m,s ch2 (trans) 1462 m,s 1468 s ch2 (gauche) 1388 vw / 1360 vw scoooxidation products 1136 w,sh 1130 w spoh 1116 m 1119 w apoh 1179 vs 1188 m p=o (unbounded) 1046 m p=o (surface bounded) 1141 vw tch2 (gauche) 938 s (doublet) 960 s apo 908 s 918 s spo 821 vw ch2 + spoh (gauche) 779 s 718 s 786 s 715 m spoh apoh remarks: a abbreviations used to describe the intensity and shape of bands: vs = very strong; s = strong; m = moderate; w = weak; vw = very weak; b = broad; and sh = shoulder. b the proposed assignments were taken from dft calculations [16] and the following notations used for different vibrational modes:  = stretching;  = deformation or scissoring;  = wagging; t = twisting;  = rocking;  = in-plane deformation; and  = out-of-plane deformation modes. https://doktori.hu/index.php?menuid=190&lang=en&i_id=3 https://doktori.hu/index.php?menuid=190&lang=en&i_id=3 pfeifer, mink, gyurika and telegdi hungarian journal of industry and chemistry 14 references [1] dhaundiyal, p.; bashir, s.; sharma, v.; kumar, a.: an investigation on mitigation of corrosion of mildsteel by origanum vulgare in acidic medium, bull. chem. soc. ethiop., 2019, 33(1), 1, doi: 10.4314/bcse.v33i1.16 [2] mouden, o.i.e.; ahmed, b.; bammou, l.; belkhaouda, m.; anejjar, a.; salghi, r.: zygophyllum qatarense extract as corrosion inhibitor for mild steel in acidic medium, appl. j. environ. eng. sci., 2021, 7(1), 114–124, doi: 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journal of industrial chemistry veszprem vol. 29. pp. 57-60 (2001) advantageous and disadvantageous properties of diesel fuels of low sulphur and reduced aromatic content j. hancsok, z. varga, l. szirmai1 (department of hydrocarbon and coal processir.g, university ofveszprem, p.o. box 158, veszpremh-8201 hungary 1mol, hungarian oil & gas co., danube refinery, department of research and development, p.o. box 1, szazhalombattah-2443 hungary) received: aprillo, 2001 in the paper the different quality grades of diesel fuels of low sulphur and reduced aromatic content are summarized (on the base of various degrees of reduction in sulphur and aromatic content). the effects of reduction in sulphur and aromatic content on exhaust gas emissions, fuel consumption and wear of fuel pump and other parts of engine are presented. the possibilities for reducing and eliminating the disadvantageous properties (wear of the fuel pump and injection system, excess fuel consumption, etc.) by using different types of additives (cetane number improver, lubricity improver, etc.) are discussed. the improvement in lubricity of reformulated and additive containing diesel fuels is presented on the base of results of high frequency reciprocating rig (hfrr) test. keywords: diesel fuel, hydrotreating, lubricity, biodiesel introduction to achieve the requirements of the more and more stricter exhaust gas emission standards of diesel engines is only possible by combining improvement of fuel quality, enhancements of in-engine performance (for example: improvement of fuel injection systems, redesign of the combustion chamber, control of charge air temperatury, etc.), and development of more effective exhaust gas treating systems (for example: particulate filter, lean nox catalyst, lean nox traps, etc). this paper only deals with the fuel quality improvements and their advantages and disadvantages. the present (year 2000) and expected (years 2005 and 20 10) diesel fuel quality requirements are summarized in table 1 (1). advantages and disadvantages of reformulated diesel fuels the advantages of the application of diesel fuels of low sulphur and aromatic content can be summarized in the following manner [1 9): • reduction in the emission of acid rain precursor substances (s02, noj and particulates • reduction in the rate of the decrease in the total basic number of lubricating oil by lowering the amount of combustion products of nitrogen and sulphur compounds having acid character • reduction in the rate of increasing the viscosity by lowering the formation of particulates which can get into the lubricating oil • longer lubricating oil drain intervals are possible because of the lower solids formation and by reserving the base content of the lubricating oil for an extended period • by applying diesel fuels of low sulphur content, the total base number (tbn) of the lubricating oil can be reduced, consequently ash containing detergent· dispersant additives may be applied in lower level and the lower ash level contributes to operating of the exhaust treating catalysts and particulate filters more effectively and for a longer period • the lubricity improver additives are applied to diesel fuels not merely for reducing the wear of the fuel pump but it results in the same effects on different parts of the combustion chamber increasing the lifetime of the engine • the reduction in the no" content of exhaust gases contributes to decreasing the ozone problems in the upper air (where the problem is the ozone depletion} 58 table i the present and the future quality requirements of diesel fuels en-590: requirements in the european community properties ec ep eca ec density at l5°c, kglm3, max. distillation 85 vol.% point, °c, max. 95 vol.% point, °c, max. cetane number, min. sulphur content, ppm, max. total aromatic content,%, max. 2000 820-845 350 360 51 350 845 350 53 200 polyaromatic content, %, max. 11 8 2005 january 2010 825 825 340 58 50 1 d d 50 d 330 58 50 1 ec: european council, ep: european parliament, e ca: eu conciliation agreement on fuels and vehicles, d: debated and in the near ground air (where the problem is the ozone content increasing) • the lower sulphur content leads to keeping the activity of catalysts used in the exhaust gas treating system for extended period, which contributes to lower emission of harmful substances • reduction in the corrosion of different parts of engine and of exhaust gas system. however, beside the many advances of application of reformulated diesel fuels their use causes some disadvantages, too. some examples are summarized in the following: • the sulphur containing compounds are generally considered as components providing some anti-wear properties, and the reduction of their amount and that of other compounds providing lubricity results in numerous problems in fuel pumps of diesel engines • aromatic compounds have higher heat of combustion than paraffin hydrocarbons having same carbon numbers, so if their portion is decreased, the energy content of the diesel fuel will decrease, too, increasing the fuel consumption • reduction in the aromatic content of the diesel fuel its density will be lower, too, and this leads to higher fuel consumption and higher emission • the formation of gel and sediments in the type of in­ line fuel injection pumps lubricated by the crankcase oil, causes interactions between the lubricity improver additives of diesel fuel and of crankcase lubricants, and this leads to wear in the fuel pump, contributing to worse driveability, blocking of fuel filters, unsteady fuel pumping, and increase in regulated emission. the objective of this study was the production of gas oils having different sulphur and aromatic contents. the disadvantageous effects of the reduction in sulphur and aromatic content of the products on the lubricity were investigated, and the possibilities of reducing this negative effects were summarized. experimental the hydrodesulphurization and hydrodearomatization experiments were carried out at the university of veszprem, department of hydrocarbon and coal processing. the experiments were carried out in a high pressure twin reactor system. this system consists of a tubular reactor free of back mixing and having 100 cm3 efficient volume, as well as equipments and devices applied in the reactor system of hydrotreating plants (pumps, separators, heat exchangers, temperature and pressure regulators, gas flow regulators). the experiments were carried out on catalysts of constant activity level and by continuous operation. the repeatability of the experimental results was higher than 95% considering the ensemble errors of both the technological experiments and the test methods. the hydrodesulphurization (hds) experiments were carried out on co-mo/support catalyst and the hydrodearomatization (hda) experiments on metals/support catalyst. the applied operating conditions are summarized in table 2. the properties of the feedstock and products were determined by standard test methods which are summarized in table 3. results and discussion the results of hds experiments are summarized in table 4. these data display well that reduction in the sulphur content of the products causes decrease in lubricity, shown by the hfrr test results. however, the product having the lowest sulphur content also satisfies the requirements of the en 590 standard (scar diameter max. 460mm). the results of hda experiments are summarized in table 5. we applied a product of hds experiment as feed for hda experiment. these data display that both the sulphur and the aromatic content of the products were reduced. so, it cannot be established whether the reduction in the aromatic content of the products is table 2 the applied operating conditions parameter temperature, oc pressure, bar liquid hourly space velocity, h-1 h2-to-hydrocarbon volume ratio, m3/m3 hds hda experiment 300-330 280-320 40 50-80 1,5-3,0 1,0-1,5 200 800 table 4 the main properties of feedstock and products of hds experiments property feed experiments all a/2 a/3 a/4 density, kglm3 859 857 856 855 855 sulphur cnt., ppm 188 118 64 45 24 total aromatic 37,7 37,1 36,8 36,5 36,2 cnt.,% nitrogen cnt., ppm 193 77 49 45 38 lubricity, hfrr, 323 381 387 410 413 at60°c, )..tm contributed to reducing of the lubricity, and how it is influenced by such an effect if it exists at all. the data of table 5 show that on the examined catalyst within the applied process parameters not only the saturation of aromatic compounds occurred in considerable level but also the reduction of the sulphur content. the maximum of hds activity is about 54% which shows that the red~ction of the sulphur content is not the main function of the examined catalyst. accordingly, the hydrodesulphurization of sulphur compounds having the lowest reactivity (e.g. dialkyl dibenzothiophenes) presumably did not take place on the applied catalyst of given composition. the maximum of hda activity is about 75%, but higher aromatic saturation level was not obtainable probably owing to the sulphur content of the feed which reduced the efficiency of the relatively low sulphurtolerant catalyst. the lubricity of products of the hda experiments does not satisfy the specified limit. in order to meet the requirements of the standard, 1% biodiesel, the properties of which meet the requirements of the standard (din 51606), or 400 ppm commercially available lubricity improver additive were added to the products, and the hfrr tests were repeated. the new lubricity data of the products were less than 300 mm. the data of table 4 and table 5 also show that the lubricity highly depends on the type of the gas oil fraction applied as feedstock in the experiments. 59 table 3 the applied test methods properties standards density, at l5°c msz en iso 12185 sulphur content astm d2622-98 aromatic content by hplc* ip 391:1995 distillation data astm d86-97 lubricity (hfrr **), at60°c, j..tm msz iso 12156-1 * hplc: high performance liquid chromatography **hfrr: high frequency reciprocating rig table 5 the main properties of feedstock and products of the hda experiments property feed experiments b/1 b/2 b/3 b/4 density, kglm3 855 828 822 818 812 sulphur cnt., ppm 24 21 17 12 11 total aromatic 36,2 16,8 14,8 12,3 9,3 cnt.,% lubricity, hfrr, 413 520 573 595 615 at60°c, )..tm hds activity,% 12,5 29,1 50,0 54,2 hda activity,% 53,6 59,1 66,0 74,3 conclusion the application of diesel fuel of low sulphur and aromatic content has many advantages and also disadvantages. the advantages mainly arise from the aspects of the environmental protection (lower exhaust gas emission) and the disadvantages from the reduced lubricity of the diesel fuel. however, the disadvantages can be eliminated relatively easily by applying additives even in low level. the results of the experiments of the study confirmed that reduction in the sulphur content of the gas oils causes loss in lubricity. ~he ~efinite answ~r concerning the effect of the reduction m the a:omattc content on the lubricity can be given by carrymg out further experiments. the results also confirmed that application of additives or ?ie!lding ";ith_ biodiesel can give satisfying solution to ehmmate tht~ ~lsadvantage. this paper also displayed that iubnc1ty became one of the most important specifications of reformulated diesel fuels. references 1. hancs6k j.: fuels for engines and jet engines, 2nd part: diesel fuels, veszprem university press, veszprem, 1999 2. hancs6k j., bartha l., auer j. and baladlnczd j.: interactions between modem lubricants an motor fuels, ,interfaces 99" conference, sopron, pp. 29-36, 1999 3. ishii m.: the influence of the fuel sulfur for n40~ storage-reduction catalyst (nsr catalyst), tu 60 annual world fuels conference focusing on refining, vehicle technology and fuel quality, brussels, 1999 4. peckham j.: world refining, 1999, 9(1), 86 5. hancsok j., lakatos i. and valasek i.: fuels and their applications, tribotechnik ltd., budapest, 1998 6. peckham j.: diesel fuel news, 1999, 3(16), 3 7. peckham j.: diesel fuel news, 1999, 3(16), 10 8. peckham j.: world refining, 2000, 10(5), s-3 9. walendziewski, j., grzechowiak, j. and pniak, b.: erdol erdgas kohle, 2000, 116(6), 297 page 56 page 57 page 58 page 59 conference proceedings hungar~journal of industrial chemistry veszprbm vol. 2. pp. 48-52 (2000) production of environmentally friendly diesel fuels z. varga, j. hancsok and f. kovacs (department of hydrocarbon and coal processing, university ofveszprem, p. 0. box 158, veszprem, h-8201, hungary) this paper was presented at the second international conference on environmental engineering, university of veszprem, veszprem, hungary, may 29 -june 5, 1999 this paper examines options for reducing emissions by improving fuel quality. in the scope, the importance of deep hydrodesulphurization and hydrodenitrogenation is discussed which reduce the formation of acid :rains and sulphate particles. the experimental results of the hydrotreating of a gas oil on ni-mo/ a}zo.;fpromoter catalyst are presented. the effect of the key process parameters (temperature, pressure, lhsv, hydrogen/hydrocarbon volume ratio) on the yield and quality of products are discussed. based on experimental results, the advantageous process parameters were determined for producing diesel fuel blending components of 500, 400, 300, 200, 150 and 50 ppm sulphur content. the possible applications of the obtained diesel fuel blending components in themselves or together with others are examined to satisfy the standard specifications of commercial products. keywords: hydrodesulphurization; diesel fuel; emission reduction introduction the exhaust gases of diesel engines pollute the environment to a significant extent due to containing co, coz, no", s02 and particulates. therefore, these contribute to the formation of acid rains, green house effect and the reduction of ozone level in the higher atmosphere, which may damage both the environment and human health [1-3]. the emissions of diesel engines which may cause cancers, are 25-35 times higher as compared to gasoline engines. the particles of smallest size are especially harmful; the effects of these were investigated by epidemology and breathing studies, and established to cause asthma, allergies and lung cancer [4]. for this reasons the sulphur and aromatic, mainly polyaromatic, content of automotive diesel fuels was tightened all over the world. for example sulphur content limit of 350 ppm will come into force in the european union in the year 2000 and 50 ppm in the year 2005, respectively (table 1) [5-8]. the emissions of diesel engines can be reduced partly by developing engine constructions, improving the quality of fuels and using exhaust gas treating systems (oxidising catalysts, particle filters, nox~trap) [9-13}. the aim of the present study was to identify and quantify the key process parameters for the hydrotreating of a gas oil to produce diesel fuel blending components of various sulphur contents which meet the requirements of the year of 2000 and the following years. table 1 diesel fuel quality requirements at present and in the future msz· requirements in the european community properties en-590 1627 ec ep eca et ep eca et january 2000 janu~2005 2010 density at l5°c, kg m3, max. 820-860 850-860 845 845 845 845 825 825 distillation 85 vol.% point, oc, max. 350 350 95 vol.% point, oc, max. 370 350 350 360 350 340 d 330 cetan number, min. 49 48 51 51 51 53 58 d 58 sulphur content, ppm, max. 500 500 350 200 350 200 50 50 50 total aromatic content, %, max. polycyclic aromatic content, %, max. 11 11 11 8 1 d 1 ec: european council; ep: european parliament; e ca: eu conciliation agreement on fuels and vehicles; et: european community amendment; d: debated <f! ~ :>-< 98 97 96 lhsv,h"1 -+-1 95 -1,3 ....,._1,6 ~2 94"1"-~-320 330 340 350 360 temperature, oc fig.j effect of temperature and lhsv on the yield of the stabilized liquid product we also studied the rate of hydrodenitrogenation (hdn) reactions, taking place parallel to the deep hydrodesulphurization (hds). we considered this particularly important because only little information is available in the literature about the connection between the change of sulphur and nitrogen contents of the gas oil under the conditions of deep hds, when the sulphur content of the products is 50-500 ppm [14·18]. however, from environmental aspects the reduction of the nitrogen content of diesel fuels is similarly important, because nitrogen oxides, which are also formed during the burning of the organonitrogen compounds, may cause pollution of the environment (acid rains, ozone formation), corrosion in the parts of the engine and its exhaust system, furthermore they decrease the base content of the engine oil. experimental the experiments were carried out in the high pressure twin reactor system at our department. this system consists of a tubular reactor of 100 cm3 efficient volume, as well as equipments and devices applied in the reactor system of hydrodesulphurization plants (pumps, separators, heat exchangers, temperature and pressure regulators, gas flow regulators). the feedstock was a heavy gas oil fraction having sulphur content of 9300 ppm, nitrogen content of 217 ppm and total aromatic content of 27.5%. its detailed properties are given later together with those of the products obtained in the case of using advantageous process conditions. the experiments were carried out on a ni­ mo/alzoipromotor type catalyst, which was available in presulphided form. the temperature range of the experiments was 3203600c, the pressure 40 bars; the liquid hourly space velocity (lhsv) varied between 1.0 h"1 and 2.0 h-1 and the volume ratio of hydrogen-to-hydrocarbon was 200 dm3 dm"3• 49 1400 1200 ~ 1000 1f ~ 800 <.> 600 ] ,9< :::1 400 --+-1 !;/) • 1,3 200 ... 1,6 • 2 0 320 330 340 350 360 temperature, °c fig.2 effect of temperature and lhsv on the reduction of the sulphur content the properties of the feedstock and products were determined by standard tests methods: sulphur content by x-ray fluorescence spectrometry, aromatic content by hplc (msz 10907/1998) and nitrogen content by the astm d 4629 method. the experiments were carried out on catalyst of permanent activity and by continuous operation. the repeatability of the experimental results was higher than 95% considering the ensemble errors of the technological experiments and tests methods. results and discussion we plotted the yields of the stabilised liquid product as a function of temperature and lhsv. fig.] demonstrates that both the increase in temperature and decrease in lhsv results in the reduction of the yields of liquid products. the effect of the change in temperature is more significant than that of lhsv. the decrease of the yield can be explained therewith that the rate of lids, hdn and hydrocracking reactions increases with stricter process parameters. above 340°c, the yield loss can be placed mainly to the account of the hydrocracking reactions. this is supported by the fact that the amounts of the gas and the gasoline fraction (boiling point < 200°c) increase above this temperature. fig.2 displays the change of the sulphur content of the products as a function of temperature and lhsv. this demonstrates that both increase in temperature and decrease in lhsv reduces the sulphur content of the products. the effect of the change in temperature is in this regard, too, more significant than that of lhsv. in the case of lhsv values of 1.6 h-1 and 2.0 h-1 the sulphur content decreases exponentially in the temperature range of 320-350°c and gradually above this. applying lhsv values of 1.0 h-1 and 1.3 h"1 the rate of sulphur content decreases nearly exponentially with increasing temperature. 50 table 2 process parameters for producing products of various sulphur contents process parameters sulphur content, ppm temperature, oc lhsv, h-1 <500 <400 <300 <200 <100 <50 340 1.0 and 1.3 350 1.0; 1.3 and 1.6 360 1.0; 1.3; 1.6 and 2.0 340 1.0 350 1.0 and 1.3 360 1.0; 1.3 and 1.6 350 1.0 and 1.3 360 1.0; 1.3 and 1.6 350 1.0 360 1.0 and 1.3 360 1.0 and 1.3 360 1.0 140,----------------------------, 120 s 100 ·g; 1 80 <=:: g ~ ~ :: ]~r-:-~:_.¥_s_,, -+-1 20 ---1,3 lj --lr--1,6 0 ll--*-2 'i 320 330 340 temperature, °c i 350 360 fig.3 effect of temperature and lhsv on the reduction of the nitrogen content products having sulphur content of max. 350 ppm (ec limit in 2000) can be obtained only above 340°c. the possible key process parameters for producing products of various sulphur contents are summarised in table2. we also studied the change of nitrogen content of the products as a function of temperature and lhsv. the results are plotted in fig.3, which displays that in contrast to the change of sulphur content that of the nitrogen content has a minimum point. the nitrogen content of the products decreases with rising temperature to 340-350"c, then it increases gradually. one explanation for this can be that the nitrogen content of the gas oil fraction is present in aromatic compounds, and the saturation of the rings occurs in the first step of the hdn reaction, before the nitrogen splits from the molecule 'in the second one. from the point of view of kinetics, the increase of temperature is advantageous for the saturation of the rings until a point where thermodynamic hindrance begins to exert a significant effect on the rate of reaction. consequently, the rate of the hdn reactions is detennined by the rate of the saturation of the rings. table 3 summary of the results of the advantageous experiments properties feed experiment stock vz/1 vz/2 vz/3 vz/4 vz/5 process conditions temp., oc 340 350 350 360 360 press., bar 40 40 40 40 40 lhsv, h-1 1.0 1.3 1.0 1.3 1.0 h2/hc, dm3 dm-3 200 200 200 200 200 yield,% gas 1.6 2.2 3.2 3.8 5.3 liquid <200°c both 0.7 1.4 3.3 4.9 >200°c 98.4 97.1 95.4 92.9 89.8 density, kg rri3 product quality 860 850 855 853 848 846 sulphur cnt., ppm 9300 350 260 150 80 40 nitrogen cnt., ppm 217 11 33 12 53 32 aromatics, % mono 16.9 20.5 22.6 23.1 23.4 di 8.1 6.6 6.1 5.5 5.2 poly 2.4 1.6 1.4 l3 1.2 total 27.5 28.7 30.1 29.9 30.0 assay ibp. 188 180 193 188 186 191 lovol.% 284 268 274 272 269 267 30vol.% 309 303 307 305 301 299 50 vol.% 324 320 322 321 319 322 70vol.% 336 333 335 335 331 334 90vol.% 354 351 352 353 351 350 fbp., 369 362 363 365 362 361 flash point, oc 70 58 79 70 62 66 cetanindex 55 56 56 56 61 61 cfpp,oc 0 2 2 2 1 1 from the aspect of the environmental protection the reduction of both the sulphur and the nitrogen content of diesel fuels is very important. therefore, we plotted the hds and hdn activity in one diagram to determine the optimal process parameters for producing diesel fuel blending components of low sulphur and nitrogen contents (figa). however, we assessed that the optimal process parameters for the hds and hdn reactions differ from each other. in consequence. a compromise is necessary concerning the sulphur and nitrogen content of the products. for the time being only the sulphur content of diesel fuels is limited, we determined the process parameters for obtaining products, which can meet the present and the expected requirements. the results of the advantageous experiments are summarised in table 3. these data display that the properties of the products meet the demands of en 590 and msz 1627 standards, except cfpp. however, the cfpp requirements can be satisfied by blending the improper products with light gas oil or/and applying flow improving additives. the data concerning the distribution of the aromatic content support that saturation of aromatics also takes place parallel with the hds and hdn reactions, though not to a considerable extent. we estimated jhe emissions of the products of the experiments. the equations approved by the epefe ·were used to determine the potential of emitting co, table 4 emission potential of the products and feedstock emission, feed experiment gkm"1 stock vz/1 vz/3 vz/4 vz/5 co 1.341 1.312 1.322 1.307 1.301 hc 0.093 0.083 0.086 0.066 0.065 nox 0.943 0.942 0.942 0.942 0.942 pm 0.159 0.060 0.060 0.0582 0.057 hydrocarbon (hc), nox and particulate matter (pm) [19]. co (g km"1 ) = -1.3250726 + 0.003037d0.025643cpa0.015856cn + 0.0001706t95 (1) hc (g ~-1) = -0.293192 + 0.0006759d0.0007306cpa 0.0032733cn0.000038t95 (2) nox (g km"1 ) = 1.00397260.0003113d + 0.027263cpa 51 100 100 90 90 80 80 ~ ~ :t 70 70 -~ ·e g g (/) 60 60 s @ lhsv,h-1 :r: 50 ......,._ 1 50 ---*--1 40 --1,3 40 ---1,3 30 30 320 330 340 350 360 370 temperature, oc fig 4 effect oftemperature and lhsv on the hds and hdn activities 0.0000883cn0.0005805t9s pm (g km-1 ) = [-0.3879873 + 0.0004677d + (3) products that contributes to the reduction of particulate emission of diesel engines. 0.0004488cpa + 0.0004098cn + 0.0000788t95] · · [1 0.00016(450cs)] (4) where ddensity, kg m·3; cpapolyaromatic content, %; cncetan number; t95 back-end volatility, °c; cs sulphur content, ppm. the data concerning the products and the feedstock are summarised in table 4. based on these data we established that reduction of the sulphur content significantly contributes to the decrease of the particulate matter emission. however, the values of the other emissions change little or not at all. conclusions we were able to produce diesel fuel blending components on the applied catalyst which satisfy the present (year 2000) and the expected (year 2005) requirements. the sulphur content of the feedstock can be reduced in one step to a great extent, and this decreases significantly the emission of s02 and sulphate particles of the diesel engine, in addition the products are less poisonous for the oxidising and nox converting catalysts used in the exhaust gas system that leads to further reduction of diesel engine emissions. the optimal process parameters of the hdn and hds reactions do not coincide, so the products of low sulphur content have relatively high nitrogen content and this may result in emission problems in the future. the obtained product is applicable as diesel fuel blending component in itself or together with others in order to suit.the standard specifications of commercial symbols lhsv liquid hourly space velocity hds hydrodesulphurization hdn hydrodenitrogenation cfpp cold filter plugging point hc hydrocarbon pm particulate matter d density cpa polyaromatic content cs sulphur content, ppm cn cetan number t9s back-end volatility references 1. knoche a.: air quality and fuel specifications, the 1997 european oil refining conference and exhibition, cascais (portugal), 1997 2. perera p.: future air quality strategies and integrated assessment post-2000, 3rd annual world fuels conference, brussels, 1-19, 1998 3. rainbow l.j.: european programme on emissions, fuels and engine technologies (epefe) gasoline and diesel test fuels blending and analytical data, sae technical paper series, nr 961066, 1996 4. jungbluth h. and richter b.: regeneration von partikeifiltem mit additiven, 2nj international colloquium on fuels, esslingen, 9.4, 1999 5. aama, acea, jama: proposed world-wide fuel charter, 1998 6. buchsbaum a.: modem fuels for automotive engines • the european point of view, 15'h world petroleum congress, peking, 12-16., 3{1), 1-9, 1997 7. anon.: hart's european fuels news, 1998. 2(13), 1-3 8. heckel t.: hart's fuel technology and !\>i:magement. 1998, 8(4), 35-40 52 9. halbert t.h.: meeting the challenge of deep diesel desulphurization, 15th world petroleum congress, peking, 9(2), 1-13, 1997 10. signer m.: fuel quality influence on engine performance and emissions, 3rd annual world fuels conference, brussels, 1998 11. martindale d.c.: sulphur, nitrogen and aromatics removal from fuels: comparison of processing options, npra, am-97-25, 1997 12. hannerup p.n. and cooper b: oil gas european magazine, 1995, (1), 25-29 13. tock r.w.: world refining, 1999, 9(2), 53-62 14. pierru a.: petroleum technology quarterly, 1997, 39-43 15. skripek m.: petroleum and coal, 1995, 37(2), 4-13 16. nakai k.: hydrocarbon engineering, 1997, 2(4), 20-22 17. van loou f.: applied catalysis a: general, 1998, 170, 1-12 18. ho t.c.: preprints, a.c.s., div. petr. chern., 1992, (37)3, 729-733 19. macklnven r. and mcarragher j.s.: review of the european auto/oil programme and epefe, 1 '' international colloquium on fuels, esslingen, 1.3, 1997 page 54 page 55 page 56 page 57 page 58 hungarian journal of industry and chemistry vol. 53(2) pp. 79–84 (2025) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2025-21 s-polarized light-induced uv-vis plasmonics in al-ag dimers: a theoretical perspective raju devika1, aiswarya satheesh1, pearl augustine2, manoj parameswaran2 and ranjini radhakrishnan1* 1 department of physics, kuriakose elias college, mannanam, kottayam, kerala, 686 561, india 2 department of chemistry, st. michael’s college, cherthala, alappuzha, kerala, 688 539, india the interaction of light with metallic nanoparticle dimers has gained significant attention due to the enhanced local electric fields generated within the nanogap region. in this study, a detailed theoretical investigation of plasmonic homodimers and heterodimers composed of al and ag, covering the deep ultraviolet to visib le spectral range, is undertaken. simulations are carried out using comsol multiphysics version 5.6 to examine the effects of dimer composition, gap width and particle size on far-field optical responses. the localized surface plasmon resonance (lspr) behavior with the systematic variation of dimer radii and interparticle spacing to explore their influence on resonance characteristics is focused on in particular. the results reveal a redshift in lspr peaks as particle size increases, while a reduction in gap width induces a blueshift. furthermore, the lspr wavelength of the al -ag heterodimer consistently falls between those of the respective homodimers. these findings demonstrate that the plasmonic response of such dimers can be effectively tuned by adjusting geometric and material parameters, offering potential for tailored nanophotonic applications. keywords: dimers, plasmons, nanoparticles, simulation, localized surface plasmon resonance 1. introduction the collective oscillatory movements of the conduction band electrons on the metal-dielectric interface when irradiated with light give rise to two pivotal phenomena, surface plasmon resonance (spr) and localized surface plasmon resonance (lspr) [1],[2]. both phenomena arise from the electromagnetic excitation of free electrons in the conduction band of the metal surface. surface plasmons (sps) are coherent delocalized electron oscillations that occur at the metal/dielectric interface. in contrast, localized surface plasmons (lsps) are formed when surface plasmons become confined within nanoparticles whose size is comparable to or smaller than the wavelength of the incident light used to excite the plasmons. plasmon resonance occurs when the electromagnetic field of the incident light aligns with the energy of the oscillating electrons on the surface of the nanometallic particles/nanometallic surface, fulfilling the resonance condition. an in-depth knowledge of these systems will greatly benefit the development of various applications, including surface-enhanced raman spectroscopy (sers) [3],[4], biological sensing [5], solar cell design [6], photocatalysis [7],[8], pesticide received: 21 july 2025; revised: 5 aug 2025; accepted: 15 aug 2025 *correspondence: ranjinimanoj@kecollege.ac.in detection [9],[10], toxin monitoring [11],[12] as well as gas and vapor sensing [13],[14]. noble metallic nanoparticles (nps) are the widely utilized plasmonic nanomaterials that, upon interaction with incident light, unlock diverse applications known for their reliable performance [15]. moreover, when two metallic nanoparticles are placed in close proximity to each other (forming a dimer), plasmons in their individual nanostructures couple, leading to plasmon hybridization. the examination of metallic dimers, consisting of two closely spaced metallic nanoparticles, is of great importance in the field of nanoplasmonics [16]. these systems showcase distinctive optical properties because of the robust electromagnetic interplay between the individual nanoparticles. understanding metallic dimers is vital to implement their potential applications in surface-enhanced spectroscopy, nano-optics and photonic devices. plasmon hybridization can be used to understand the multifeatured plasmonic response of complex structures [17]. plasmonic metallic dimers are interesting candidates for a variety of optical and sensing applications as they exhibit a significant degree of plasmonic interaction between two closely spaced nanoparticles [18]. extensive research has sought to comprehend the mechanisms that govern electromagnetic interactions within metallic dimer systems. the interaction between https://doi.org/10.33927/hjic-2025-21 mailto:ranjinimanoj@kecollege.ac.in devika, satheesh, augustine, parameswaran and radhakrishnan hungarian journal of industry and chemistry 80 light and metal in addition to further effects which arise because of this interaction is always an interesting topic for scientists. although the plasmonic properties of noble metals such as silver (ag) and gold (au) have been well studied, aluminum (al) remains the least explored and can be regarded as a viable alternative due to its affordability, abundance and strong plasmonic response in the ultraviolet (uv) spectrum. however, a thorough investigation into the field intensity distribution and hot spot formation in al nanostructures within the visible region has yet to be comprehensively conducted. in this study, a theoretical investigation of aluminum and silver homodimers is performed followed by an analysis of al-ag heterodimers to explore how their plasmonic properties can be tuned. by simulating their response under different conditions, our aim is to understand the impact of material composition on plasmonic resonance behavior. this comparative analysis provides insights into the potential of hybrid plasmonic systems for applications in uv-vis plasmonics such as sensing and photonic devices. plasmonic coupling resonances of ag and al homodimers as well as ag-al heterodimers are evaluated using the simulation software comsol multiphysics version 5.6. the study focuses on how dimer size and the interparticle gap influence the plasmonic resonance wavelength. 2. computational methods numerical simulations of homoand heterodimers were carried out using comsol multiphysics version 5.6 which is a powerful simulation software that enables multiphysics modelling and analysis of complex engineering and scientific problems through finite element methods in a user-friendly, integrated environment [19]. the simulation was conducted by solving the frequency domain form of maxwell’s equations. an s-polarized wave represented by the following wave equation was used: 𝑒𝑥𝑝(−𝑗∗𝑒𝑤𝑓𝑑. 𝑘0∗𝑧) (1), where k0 denotes the propagation constant. aluminum and silver were selected as representative materials for this study as these metals are promising candidates for supporting plasmons. the material data were selected from the comsol database [al: rakić 1995: 0.00012399-200 µm and ag: werner et al. 2009: n, k 0.01759-2.480 µm]. spherical nanospheres of identical radius were designed and electromagnetic radiation with an electric field polarized perpendicular to the dimer’s axis (s-polarized wave) applied. air was designated as the surrounding medium for the dimer system and a perfectly matched layer (pml) was implemented to mitigate the backscattering effect. triangular meshing elements were employed to discretize the external pml surface and the remaining surfaces were discretized using tetrahedral meshing elements, thereby enhancing the degree of accuracy. the far-field extinction cross sections were determined through integrating the timeaveraged poynting vector (sext) over a surface encompassing the dimer as given in the equation below: 𝜎𝑒𝑥𝑡 = ∬−𝑆𝑒𝑥𝑡 𝑑𝑠 𝐼0 ⁄ (2), the expression represents the power flow per unit area of the incident light. e0 = 1 v/m denotes the amplitude of the incident electric field, ϵ0 represents the vacuum permittivity and c is the velocity of light. simulations involved changing the dimer radius while keeping the gap size constant and vice versa. a minimum sub-np separation of 2 nm was set in this model to avoid quantum tunnelling and non-local effects [20],[21]. 3. results and analysis the extinction, absorption and scattering cross-sections of the dimer for an s-polarized light wave were analyzed to understand the plasmonic coupling effect. the extinction cross-section of a plasmonic dimer is the sum of its scattering and absorption cross-sections, representing the far-field plasmonic resonance. the scattering, absorption and extinction cross-sections of al with a radius of 30 nm and a 2 nm gap are depicted in figure 1. the resonance peak of the extinction crosssection was observed at 310 nm within the uv region as already reported in the literature [22]. furthermore, according to the figure, scattering was more prominent while absorption was minimal. furthermore, simulations were conducted by keeping the gap size of the dimer fixed at 2 nm and changing the radius from 30 to 60 nm as presented in figure 2. a redshift of the resonance peak (extinction spectra) was observed upon increasing the radius of the dimer. for a gap of 2 nm and a radius of 30 nm, the resonance wavelength was observed to be 310 nm but shifted to 560 nm as the radius increased to 60 nm. in all al homodimers, the spectrum was dominated by a pronounced peak of the bonding dipole plasmon mode (bdp). starting from a radius of 40 nm, the emergence 2 000 2 1 eci = figure 1: far field spectra of the al dimer with a gap size of 2 nm and a radius of 30 nm 200 300 400 500 600 700 800 0 1×10−14 2×10−14 3×10−14 4×10−14 c ro s s s e c ti o n ( m ^ 2 ) wavelength (nm) scattering absorption extinction s-polarized light-induced uv-vis plasmonics 53(2) pp. 79–84 (2025) 81 of a second peak at shorter wavelengths was observed. as the dimer size increased, this peak became more pronounced due to the quadrupole plasmon mode (qdp). it was also observed that the intensity of both the bdp and qdp modes increased as the radii increased. bdp, the fundamental mode in a dimer, exhibits a higher extinction cross-section at longer wavelengths compared to other higher order modes that occur at shorter wavelengths. the results show that the plasmonic response of the metallic nanodimer is highly sensitive to its radius. a comparison of the extinction cross-section of various al homodimers is represented in figure 2. in this study, the extinction cross-sections were compared as they quantify the proportion of incident light that is either scattered or absorbed by the nanodimers. the local electric field distribution near the bdp mode at the resonance peak for al dimers is illustrated in figure 3. the extinction spectra of the al homodimer with a fixed radius of 60 nm and a gap increased from 2 to 8 nm is shown in figure 4. similar to earlier results, prominent peaks in the bdp mode at longer wavelengths and in the qdp mode at shorter wavelengths were observed. as the gap size was increased, the intensity of the bdp mode decreased, while the qdp mode intensity increased. both modes were blue shifted as the gap size of the homodimer was increased. it was observed that the corresponding shift in the quadrupole mode was less when compared to the shift in the bdp mode, clearly demonstrating the dependence of the dimer radius and gap size on the plasmonic response of the dimer system to the spolarized electromagnetic wave. similarly, ag nanodimers were analyzed, yielding far-field extinction spectra for various radii and gap sizes (figure 5a). a redshift was observed when increasing the size of the dimer, similar to the behavior seen in al dimers at the resonance peaks in the prominent bdp mode. in contrast to the al homodimers, several higher multipole peaks were detected at shorter wavelengths, however, these higher modes were less pronounced. for the dimer with a radius of 30 nm, only a single higherorder mode was observed in the bdp mode. as the radius increased, more higher modes became apparent, with three higher modes identified for the dimer with a radius of 60 nm. the formation of a hot spot in the gap of a silver (ag) dimer with a radius of 60 nm at the resonance wavelength is shown in figure 5b. the far-field spectra regarding different gap sizes for ag dimers were also computed and presented in figure 6. when the gap size of the dimer was reduced, a blueshift was observed at the resonance peaks in the prominent bdp mode. unlike the behavior seen with al homodimers, no shift was detected in the other higher modes, which tended to overlap. to analyze the impact of material properties on the resonance wavelength, the optical plasmonic properties of the al-ag heterodimer were also simulated. the far-field optical spectra of the al-ag heterodimer are presented in figure 7a. following the approach of earlier studies, the gap was fixed at 2 nm and the effect of the radius evaluated by increasing it from 30 to 60 nm. at 30 nm, the dominant peak identified as the bdp mode exhibited a significant redshift as the radius increased. a higher-order mode was also observed for the dimer with a radius of 30 nm at shorter wavelengths in the near-uv region, however, became less pronounced as the radius increased. as the particle figure 2: the dependence of the far-field resonance peak on the radius of the al dimer with a fixed gap size of 2 nm. the far-field extinction spectra exhibit a strong redshift as the radius increases 200 300 400 500 600 700 800 0.0 2.0×10−14 4.0×10−14 6.0×10−14 8.0×10−14 1.0×10−13 1.2×10−13 e x ti n c ti o n c ro s s s e c ti o n ( m ^ 2 ) wavelength (nm) 30nm 40nm 50nm 60nm figure 3: the hot spot formation in the gap of the al dimer with a radius of 60 nm at a resonance wavelength of 560 nm figure 4: dependence of the resonance peak on the gap size, that is, 2, 4, 6 and 8 nm, of the al dimer with a fixed radius of 60 nm 200 300 400 500 600 700 800 4.0×10−14 8.0×10−14 1.2×10−13 e x ti n c ti o n c ro s s s e c ti o n ( m ^ 2 ) wavelength (nm) 2nm 4nm 6nm 8nm devika, satheesh, augustine, parameswaran and radhakrishnan hungarian journal of industry and chemistry 82 size grew, the dipole resonance became more dominant due to the larger scattering cross-section. the far-field optical spectra of the al-ag heterodimer with a fixed radius of 60 nm is illustrated in figure 7b. the impact of the gap was assessed by increasing it from 2 to 6 nm, revealing a blueshift at the resonance peaks in the extinction spectra of the prominent bdp mode while only a slight blueshift in the higher order mode was observed. the relationship between the radii and gap sizes of nanoparticles with their resonance wavelengths for three different dimers, namely the al-ag heterodimer as well as al and ag homodimers, is illustrated in figure 8. it was observed that as the radius of the nanoparticles increased, the resonance wavelength (corresponding to the bdp mode) also increased. the resonance wavelength of the heterodimer was found to lie between those of the al and ag dimers, as shown in figure 8. consequently, the bdp mode of the heterodimer closely resembled an overlap between the bdp modes of al and ag. furthermore, the bdp modes of the heterodimer tend to align more closely with silver, suggesting that the properties of the heterodimer may more closely resemble a silver homodimer. among the three materials considered, the ag nanoparticle dimer exhibited the longest resonance wavelength followed by the al-ag dimer with the al dimer yielding the shortest. this suggests that ag nanoparticles possess the longest resonance wavelength while al provides the shortest across the examined wavelength range for any given gap size. the strong (a) (b) figure 5: (a) the dependence of the resonance peak on the radius of the ag dimer with a fixed gap size of 2 nm. the intensity of the redshift increases as the radius increases; (b) hot spot formation in the gap of the ag dimer with a radius of 60 nm 200 300 400 500 600 700 800 0.0 4.0×10−14 8.0×10−14 1.2×10−13 1.6×10−13 e x ti n c ti o n c ro s s s e c ti o n ( m ^ 2 ) wavelength (nm) 30nm 40nm 50nm 60nm (a) (b) figure 7: (a) the dependence of the resonance peak on the size of the al-ag dimer with a fixed gap of 2 nm. a strong redshift was observed when the radius increased; (b) the dependence of the resonance peak on the gap of the heterodimer with a fixed radius of 60 nm 200 300 400 500 600 700 800 0.0 4.0×10−14 8.0×10−14 1.2×10−13 1.6×10−13 e x ti n c ti o n c ro s s s e c ti o n ( m ^ 2 ) wavelength (nm) 30 nm 40 nm 50 nm 60 nm 200 300 400 500 600 700 800 4.0×10−14 8.0×10−14 1.2×10−13 1.6×10−13 e x ti n c ti o n c ro s s s e c ti o n ( m ^ 2 ) wavelength(nm) 2 nm 4 nm 6 nm 8 nm figure 6: the dependence of the resonance peak on the gap of the ag dimer with a fixed radius of 60 nm 200 300 400 500 600 700 800 4.0×10−14 8.0×10−14 1.2×10−13 1.6×10−13 e x ti n c ti o n c ro s s s e c ti o n (m ^ 2 ) wavelength (nm) 2nm 4nm 6nm 8nm s-polarized light-induced uv-vis plasmonics 53(2) pp. 79–84 (2025) 83 plasmonic response of ag resulted in higher resonance wavelengths, while the combination of aluminum and silver modifies the plasmonic properties, leading to intermediate resonance wavelengths. al exhibited the shortest resonance wavelengths due to its distinct properties compared to those of silver. 4. conclusions a more profound understanding of light-matter interactions has paved the way for "plasmonics" to develop into a rapidly advancing field with a wide range of innovative applications. plasmonic coupling in al and ag homodimers as well as in the al-ag heterodimer was analyzed using comsol multiphysics version 5.6 simulation software with the incident light polarized along the dimer axis using various radii and gap sizes. a redshift as the radii increased and blueshift as the gap size increased was observed in all configurations of dimer. regarding ag and al-ag dimers, a larger particle size potentially diminished the quadrupole peak while the opposite effect occurred in the al homodimer. for nearly all configurations of dimers, multipole peaks were observed in the qdp and bdp modes towards the lower and longer wavelengths, respectively. in aluminum homodimers, as the particle size increased, a prominent peak appeared in the near-uv range, suggesting the presence of strong quadrupole modes. in the case of the heterodimer, multipole peaks appeared only at radii of 30 and 40 nm but disappeared at larger radii accompanied by a broadening in the bdp mode. concerning the relationship of the radii and gap size of nanoparticles with their resonance wavelengths with regard to three different dimers, it was found that the resonance wavelength of the heterodimer fell between al and ag in both cases. the strong plasmonic response of ag results in longer resonance wavelengths, while the combination of aluminum and silver modifies the plasmonic properties, leading to intermediate resonance wavelengths. al exhibits shorter plasmonic resonance wavelengths due to its distinct properties compared to those of silver. this study shows how the interaction between light and nanoparticles can be controlled or modified based on their arrangement. this means that by modifying the configuration of nanoparticles (dimers), optical properties such as scattering, absorption, or resonance behavior can be fine-tuned. theoretical studies show that al stands out as one of the rare metals capable of achieving plasmonic resonance across a wide spectral range from near-ultraviolet to visible simply by adjusting the particle size and interparticle distance. this is significant in nanophotonics, perhaps leading to more precise control over light-matter interactions for applications in sensing, imaging and the development of other optical devices. acknowledgements the authors are grateful for the financial support provided by the department of science and technology science and engineering research board (serb/sb/s1/pc-42/2012), the dst-fist program by the indian government as well as i-stem for providing access to the comsol multiphysics version 5.6 simulation software. references [1] ritchie, r.h.: plasma losses by fast electrons in thin films, phys. rev., 1957, 106(5), 874–881, doi: 10.1103/physrev.106.874 [2] kelly, k.l.; coronado, e.; zhao, l.l.; schatz, g.c.: the optical properties of metal nanoparticles: the influence of size, shape, and dielectric environment, j. phys. chem. b, 2003, 107(3), 668–677, doi: 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aluminum nanoparticles and nanorods, j. appl. phys., 2008, 104(8), 083107, doi: 10.1063/1.2999370 https://doi.org/10.1016/s1369-7021(12)70017-2 https://doi.org/10.1038/natrevmats.2016.21 https://doi.org/10.1021/acsphotonics.6b00062 https://doi.org/10.1038/nmat2629 https://doi.org/10.1016/j.apcatb.2016.02.002 https://doi.org/10.1016/j.apsusc.2015.11.016 https://doi.org/10.1016/j.bios.2006.05.007 https://doi.org/10.1016/j.snb.2021.130977 https://doi.org/10.1021/acsami.9b14980 https://doi.org/10.1016/j.teac.2021.e00117 https://doi.org/10.1021/ac102127p https://doi.org/10.1021/ja1074272 https://doi.org/10.1016/j.matchemphys.2022.127255 https://doi.org/10.1364/oe.18.003187 https://doi.org/10.1126/science.1089171 https://doi.org/10.7716/aem.v7i2.563 https://doi.org/10.33927/hjic-2024-13 https://doi.org/10.1021/nl803811g https://doi.org/10.1038/ncomms6228 https://doi.org/10.1063/1.2999370 hungarian journal of industrial chemistry veszprem vol. 29. pp. 61-65 (2001) toward global optimization of a difficult optimal control problem r.luus (department of chemical engineering, university of toronto, toronto, on m5s 3e5, canada) received: july 5, 2001 the optimal control problem introduced in 1980 by yeo [1] exhibits numerous local optima which have not been reported in the literature. when 50 time stages of equal length are used, there are only two local optima. when so time stages are taken, there are over 50 local optima. it was found that there are at least 15 local optima which are better than the one reported in the literature as the global optimum. with the use of 100 time stages of equal length, the number of local optima is increased substantially to over 150. with 100 time stages of equal length, the global optimum solution found with iterative dynamic progranuning (idp) gives i= 0.119044. this value of the performance index is 0.2% better than the value that had been accepted in the literature as the global optimum. idp provides a good means of getting the global optimum solution for this problem, but numerous runs are necessary due to the presence of a large number of local optima. keywords: optimal singular control, iterative dynamic progranuning, idp, global optimization, sensitivity introduction yeo's optimal control problem establishing the optimal control policy for nonlinear control problems is usually quite difficult, especially when the system exhibits low sensitivity of the performance index to a. change in the control policy. when the number of time stages is small, then the optimal control policy can usually be readily obtained either by iterative dynamic programming [2,3) or with the lj optimization procedure [4}. for many problems a small number of flexible stage lengths, where the stage lengths are incorporated into optimization, can be used to give very accurate results by enabling the optimal switching times to be accurately determined. however, there are some problems where the structure of the optimal control policy changes quite substantially when the number of time stages is increased. this is especially true with the system introduced by yeo [1]. the goal of this paper is to illustrate the interesting features presented by this system and to show how the optimal control policy can be established in a reliable way. one of the earliest examples tried with iterative dynamic programming [5,6], is the optimal control problem used by yeo fl] to illustrate the use of quasilinearization to solve nonlinear singular control problems. the system is described by dxl -=xz dt dx _3_::::u dt dxs =1 dt {2) {3) (5) 62 with x(o) = [ 0 -1 .j5 0 0 f, and final time t.f = 1. the constraints on the control are -4::::; u $10 (6) it is required to find the control policy that minimizes the performance index (7) this system was used for global optimization by rosen and luus [7] with the introduction of a line search into sequential quadratic programming (sqp). with the use of p = 80 time stages of equal length they obtained i= 0.119258, and concluded by extrapolation that the minimum value for the performance index for the continuous case (infinite number of stages) should be i= 0.11923. this system was recently investigated by esposito and floudas [8], with p = 10 time stages, who found two local optima as was found by luus [3]. the differential equations are well behaved, but to get six figure accuracy for the performance index, it was necessary to use double precision and to use a tight local error tolerance of 10·8 in the subroutine dverk [9]. the optimal value of the performance index depends very much on the number of time stages that are used. the goal here is to illustrate the nature of the optimal solution when the. number of time stages of equal length is increased. table i affect of the number of time stages p on the value of the performance index after 50 passes, each consisting of 20 iterations number of time staaes p 10 20 40 50 60 80 100 performance index i 0.120114 0.119438 0.119292 0.119277 0.119272 0.119134 0.119085 results and discussion cpu time seconds 5.9 9.0 28.9 47.1 61.1 110.5 180.7 in using iterative dynamic programming (idp), we used the multi~pass approach as outlined by luus [3, p. 106], using 20 iterations per pass. the region contraction factor was chosen as r= 0.95 and the region restoration factor 17 = 0.85. a single grid point was used at each time stage, and 3 candidates for control, chosen as o. ±r were used at each grid point. the initial value for control was chosen as 7.0 and the initial region size r = 4 was used. the computational results carried out on a pentiumiy400 personal computer in double precision after 50 passes for different number of time stages p are given in table i. it is noted that idp yields the optimum substantially faster than the global optimization procedure of esposito and floudas [8]. even with p = 100 the computation time is almost negligible. the use of p = 60 provides a very small refinement to the control policy obtained with p = 40 and p == 50 for which the optimal control policy is shown in fig.]. e "e 0 (.) 0.0 0.4 time,t 0.8 fig.l optimal control policy for p = 50 giving i = 0.119277 0.0 m time,t 0.8 fig.2 optimal control policy for p = 80, giving i ::: 0.1191325 ~ "c .e 8 c: til e .g c]) a. 0.11912 l---1---l..----jl--'--l----jl-_[__l__j 72 76 position of dip, stage number fig.3 local optima asa function of the location of the dip in the control pro.le for p = 80 e 'e 8 0.0 0.4 time, t 0.8 fig.4 control pro.le for a local optimum for p = 80, giving i= 0.1191603 since there is a significant improvement in the performance index for p = 80 stages, the run was repeated, using 40 iterations per pass and allowing 100 passes. the performance index was marginally decreased to i= 0.119133. as is shown in fig.2, the use of p = 80 yields a totally different optimal control policy. by using a greater number of time stages, the ~hotter stage lengths allow sudden changes to be made ill the control policy. these abrupt changes in the control policy here improve the performance index quite significantly. ::::. ~ 0 (.) -4 0.4 time,t 63 0.8 fig.5 control pro.le for local optimum for p = 100 giving i= 0.119250 e 'e 0 (.) -4 0.4 time,t 0.8 fig.6 control pro.le for local optimum for p = 100, giving i = 0.119092 there is a dip in the control policy to -4 at stage 59. and in the time interval (0.8, 1.0) there is a dip to -4 at stage 75, with a significant improvement in the resulting performance index over the value of 0.119258, where there are no dips to the minimum value of control as is shown in fig.3, the position of the latter dip affects the performance index. with p = 80 we can also get local optima with two dips in the time interval (0.8, 1.0}, as is shown in fig a, where the dips at stages 70 and 76 give a performance index i= 0.119160. 64 0.1190580 85 90 95 100 position of dip, stage number fig.7 local optima asa function of the location of a single dip in the control pro.le with p = 100 0.0 0.4 time,t 0.8 fig.8 control pro.le for a local optimum with p = 100. giving l = 0.119045 the gk1bal optimum for p = 80 with 1 = o.h91325 occurs with a single dip at stage 75. with the use of p = 100 time stages of equal length the number of local optima is quite large. the local optimum control policy in which there are no dips, yielding i= 0.119250 is shown in fig.s. the best local optimum with a single dip at stage 94, giving i = o.hooij2 is shown in fig.6. as is shown in fig.7. the position of the single dip affects the value of the performance index. as cae be seen 14 local optima with a sin,e!je dip give a better value for the performam:e index than the local tlptimum wiu!out any dips. 0.0 0.4 time, t fig.9 optimal control policy for p = 100 giving i= 0.1190437 0.0 0.4 time,t fig.jo control policy for p = 150, giving i = o.h8977 what makes this problem challenging is the existence of double dips in the time interval (0.8, 1.0), many of which give better values for the performance index. in fact, the best local optimum with dips at stages 88 and 95, giving 1 = 0.119045, is shown in fig.8. further improvement to 1 = 0.1190437 is obtained with the control policy shown in fig.9. where there are additional 3 dips in the time interval (0.2, 0.8). there are over 150 local optima for this system with p = 100 stages of equal length. here. with ldp only the most likely candidates for global optimum were scanned to yield the global optimum of l = 0.119044. 0.0 0.4 time, t 0.8 fig.ll state trajectories corresponding to the 65 this example illustrates the difficulty in determining with absolute certainty the global optimum of some nonlinear systems. idp proved to be an effective tool in the establishment of local optima. through the interpretation of the results obtained for the local optima, the global optimum for 100 time stages was readily obtained. however, the complexity of the problem is realized, so the results obtained here provide only a step toward obtaining the global optimum to the problem for which we could conceptually use an infinite number of time stages. acknowledgement financial support from the natural sciences and engineering research council of canada is gratefully appreciated. symbols control policy in x figure 10 i performance index to be minimized number of time stages of equal length the question of what happens when the number of time stages is further increased arises. it is obvious that the number of local optima will increase. in fact, a run was performed with p = 150, yielding i = 0.118977$, with the control policy shown in fig.jo. this result was obtained with the conditions used for table 1, so this result is expected to be close to the global optimum. it is interesting to note that now there are three dips in the time interval (0.8, 1.0). the corresponding trajectories for the first three state variables is given in fig.ll. there is no doubt that further noticeable improvement of the performance index can be obtained by using even a larger number of time stages, such as 200. alternatively, one could use time stages of varying length to refine the results obtained here. research in this area is continuing. conclusions by increasing the number of time stages to solve the optimal control problem presented by yeo [1], some very interesting features about this system were noted. with the use of 80 time stages numerous local optima, that had been observed for the frrst time, were found. a large number of these local optima were better than the best local optimum that was obtained by sqp. the use of 100 time stages yielded even a larger number of local optima. by scanning numerous local optima, the global optimum with 100 stages of equal length was determined as i= 0.119044. this value is 0.2% better than the best value reported in the literature. with the use of 150 stages, the performance index was further improved to 0.118977, showing that further increases in the number of time stages, or the use of stages of varying length should yield even better values for the performance index.. p r region size t time f_t final time u control variable x1 ith state variable x state vector greek letters y region contraction factor by which the 1 egion size is reduced after every iteration 1j restoration factor by which the region size is restored after every pass abbreviations idp iterative dynamic programming sqp sequential quadratic programming references 1. yeob.p.: int. j. control, 1980, 32, 723~730. 2. luus r.: control and intelligent systems, 1998, 26, 1~8. 3. luus r.: iterative dynamic programming, chapman & hall crc, london, uk, 2000. 4. luus r. and hennessy d.: ind. eng. chern. res., 1999,38, 1948·1955. 5. luus r.: hung. j, ind. chem., 1989, 17, 523~543. 6. luus r.: int. j. control1990, 19, 995~ 1013. 7. rosen 0. and luus r.: j. optimization theory & applk., 1992, 73, 547--562. 8. esposito w.r. 'lnd floudas c.a.: j. global optimization, 2()()(), 17.97-126. 9. hull t.e., enright w .d. and jackson k.r.: u5er guide to dverk •• a subroutine for solving nonstiff ode's, report 100. 1976, department of computer science, university tjff(.'fnnto, canada page 60 page 61 page 62 page 63 page 64 conferenceproceed~gs hungarian journal of ~ustrial chemistry veszprem vol. 2. pp. 30-35 (2000) improving eco-efficiency by auditing steam and condensate systems j. pejekandp. glavic (university of maribor, faculty of chemistry and chemical engineering, smetanova 17, sl0-2000 maribor, slovenia) tills paper was presented at the second international conference on environmental engineering, university ofveszprem, veszprem, hungary, may 29june 5, 1999 several assessments of steam and condensate systems have been carried out (in textile plants, an animal food production plant, in processing of waste from a slaughterhouse, in the boiler house). the methodology of the assessment includes flowsheet, mass and energy balances of the process and boiler house, identifying all steam consumers, the flowsheet of steam and condensate systems, studying pressure and temperature levels, determining the database of pressure reducing valves and steam traps, producing rational steam consumption and effective steam production options, and making technical, economic and environmental assessments. only the most beneficial options should be proposed and implemented. the analyses show that several options can improve the eco-efficiency of a plant. efficiency of boilers can be improved by heat recovery from blowdown, from flue gas and deaerating gasses, control of the combustion process, etc. the steam should be efficiently consumed, all steam traps should be correctly selected and installed in the process. the staff should regularly check the operating of the steam and condensate armatures, seek for leaks, etc. the results show that it is possible to reduce the production of flue gas emissions by more than 10 %, wastewater by 5 %, fuel by 8 % and waste heat up to 20 %. payback periods of the proposed options reach up to 1.1 years. keywords: cleaner production; eco-efficiency; steam and condensate systems introduction the concept of eco-efficiency was first introduced in 1992 by the business council for sustainable development (bcsd) in its landmark report, changing course. in november 1993 it was finally defined at the frrst antwerp workshop on bee-efficiency. it involves the delivery of competitively priced goods and services that satisfy human needs and bring qnality of life, while progressively reducing ecological impacts and resource intensity throughout the life cycle, to a level at least in line with the earth's estimated carrying capacity {11. seven success factors for eco-efficiency have been identified: to reduce the material intensity of goods and services; to reduce the energy intensity of goods and services; to reduce toxic dispersion; to enhance material recyclability; to maximise sustainable use of renewable sources; to reduce material durability; to increase the service intensity of goods and services. a similar concept, which has been promoted elsewhere, especially through the united nations environmental programme (unep), is cleaner production. eco-efficiency embraces cleaner production concepts such as efficient use of raw materials, pollution prevention, source reduction, waste minimisation and internal recycling and reuse. but it emphasises value creation for businesses and the society by improving competitiveness of the companies, their products and services. cleaner production is a continuous application of an integrated environmental strategy applied to processes, products, and services to increase eco-efficiency and reduce risks for humans and the environment. there are numerous cleaner production and eco-efficiency projects, which are successfully being introduced in industry. a common feature of ali of them is that an integral approach was used. the latter consists of several steps, which should be gradually adopted in order to find large waste producers and energy consumers. part of this approach could be the analysis of the steam generation, 31 fig.l a typical steam and condensate system (1 feedtank:; 2 steam generator; 3 condensate receiver with electric powered pumps; 4 deaerator; 5 steam injection and temperature control system; 6 direct acting pressure reduction valves; 7 level control; 8 auto tds system; 9 safety valves; 10 steam separator; 11 steam meter; 12 steam traps; 13 steam trap monitors; 14 stop valves; 15 separators; 16 flash vessel; 17 pressure gauges; 18 pneumatic pressure control system; 19 compressed air regulator; 20 pilot actuated pressure reducing valve; 21 air vents; 22 check valves) distribution, utilisation, and condensate recovery [2]. another well-known approach is energy auditing. it consists of a detailed examination of how the facility uses energy, how much the facility pays for the energy, and finally a recommended program for changes in the operating practice or in energy-consuming equipment that will cost-effectively save money for energy [3]. all kinds of energy and energy carriers are included, e.g. electricity, fuels, heat carriers {hot water, steam or other heat transfer fluids), cooling agents, and compressed air. steam and condensate system analysis should be part of the auditing of the complete company's utility and energy system. steam and condensate system steam has been used since the 18th century to supply power and heat to industrial and commercial organisations. it is one of the most abundant, least expensive, and most effective heat-transfer medium obtainable. steam can transfer large amounts of energy compared to water systems, which can be transferred without additional power at a constant temperature. it can be accurately determined by controlling the steam pressure. {t is clean, non-toxic, non-flammable and comes from water, which is an abundant resource. fig. i shows a typical steam and condensate system. it consists of a steam boiler, steam distribution system, steam users, and a condensate recovery system. the boiler installed in a boiler house is supplied by feed water, which is a mixture of make-up water, and the condensate returned from the steam users. feed water requires a proper treatment to prevent boiler corrosion and to reduce water carry-over due to foaming. it has to be physically and/or chemically treated . to reduce ·dissolved solids, i.e. primarily hardness; dissolved gasses, i.e. primarily oxygen and carbon dioxide must be removed by deaeration. the boiler produces steam at the highest pressure and temperature required by the process. the steam is distributed through large steam mains to the process and then through transfer lines to each piece of equipment. the steam distribution system has to be properly designed, therefore steam pipes should be correctly sized for flow according to pressure drop or steam velocity, a separator should be installed for removing water droplets and condensate in order to improve steam dryness and prevent water hammer. steam lines should slope down so that condensate can drain by gravity, and at the end of the steam mains steam traps and air vents should be installed. steam should be taken from the top of the steam main because the driest steam is there. if some processes require lower steam temperature, steam is throttled to lower pressure through a pressure­ reducing valve. steam is used in different kinds of equipment for heating purpose [4]. the type of equipment used depends on the type of processes, but usually there are several kinds of heaters, reactors, ovens, sterilisers, retorts, digesters, vulcanisers, evaporators, calandrias, reboilers, dryers, ironers, tumblers etc. the condensate produced in the heating spaces has to be correctly removed in order to prevent drainage and corrosion so that efficient heat transfer is maintained [5]. it is discharged into the condensate system through steam traps (thermostatic, mechanical or thermodynamic}. traps operate at different pressures, which is why check valves should be installed to prevent condensate backflow. condensate mains should be designed for 32 two-phase flows and should slope downhill to the receiver. the flash steam is the best way of decreasing the condensate pressure and preventing backpressure in the condensate system. the use of low pressure steam can substantially improve the efficiency of the steam and condensate system. the condensate, collected in the receiver, has to be pumped to a higher point usually to the boiler feed tank. there are two kinds of pumps to be used: the electric-driven centrifugal pump or the pressure powered automatic pump. it sometimes is useful to install condensate contamination detectors to prevent the contaminated condensate from being pumped into the boiler [6]. ref.[3) represents a checklist of energy conservation opportunities in steam and condensate system: 1. review the operation of long steam lines to remote single-service application. relocate remote equipment. 2. review the operation of steam systems used only for occasional services. use temperature controlled valves to assure system to be used when needed. 3. implement regular steam leak survey and repair programs. 4. establish a regular steam-use monitoring program to track the progress in the reduction of steam consumption. 5. consider the revision of plant-wide steam balance in multipressure systems to eliminate venting of low-pressure steam. 6. check the actual steam usage of the equipment against the theoretical or design requirements to find disparities, determine the cause and correct it. 7. review the pressure-level requirements of the steam-driven mechanical equipment to evaluate feasibility of using lower pressure levels. 8. review the pressure requirements in the process and reduce the temperatures to the minimum acceptable level. 9. evaluate the production scheduling of batch operations and revise it if possible to minimise start-ups and shutdowns. 10. implement a regular steam trap survey and maintenance program. h. check the sizing of all steam traps to make sure they are adequately rated for proper condensate drainage. 12. review the types of traps in various services to assure that the most efficient trap is used for each application. 13. survey the condensate sources presently being discharged to waste drains for feasibility condensate recovery. l4. consider the opportunities for flash steam utilisation in low-temperature processes. 15. consider pressuring · atmospheric condensate return systems to minimise flash losses. 16. review the mechanical drive standby turbines presently left in the idling mode and consider the feasibility of shutting down standby turbines. 17. implement a steam turbine performance testing program and clean the turbine on a regular basis to maximise efficiency. 18. evaluate the potential for cogeneration in multipressure steam systems presently using large pressure reducing valves. 19. survey the insulation of the equipment and piping to locate areas of insulation deterioration. maintain insulation on a regular basis. 20. insulate all uninsulated lines, fittings, valves, flanges and small lines. auditing steam and condensate systems in the last two years several steam and condensate systems have been analysed in animal food production, meat processing and textile industry. in the following paragraphs, some interesting results will be described. animal food production steam was used primarily for the sterilising and keeping of proper water content in the pellets. therefore the steam was mixed with the product which made the returning of the condensate impossible. since the older steam boiler was damaged the company invested in a new one together with boiler feed water treatment. instead of deaerating feed water they used chemicals for oxygen removal because dissolved gases were not efficiently removed from the feed water, corrosion of the heating coil occurred which was why it had to be changed every two years. the consumption of heating oil was 66 t y-1 and of process steam 900 t y"1 • 31 000 t of animal feed pellets were produced, 1 380 t y"1 of flue gas, 60 t y·1 of waste water from blowdown, 28 kw of waste heat, while 204 t y·1 of condensate were lost with 45 kw heat· content released into the environment. the analysis of the whole steam and condensate system showed that the production and distribution of the steam were inefficient and formed condensate in the distribution system which due to heat losses was not returned into the steam boiler. several options were proposed to improve efficiency of the system and to cut the costs: 1. deaeration of the feed water. the investment demanded a new feedtank, a deaerator and armatures (stop valves, pressure reduction valve, a self acting temperature control system and feedwater pump); 2. condensate recovery. due to heat losses the formed condensate should be returned into the feedtank. the investment demanded pipes and insulation. 3. replacing of inefficient and broken steam traps. from table 1 it is evident that the payback period was approximately 16 months, while table 2 shows the reduction of waste water and waste heat. flue gas emissions. savings of fuel and chemicals. table 1 investment and savings of the suggested rational steam production and consumption in animal feed production alternative 1 2 3 total investment (us d) 14300 1800 500 16600 savings (usdt1 ) 11500 600 300 12400 hot wo.ter to the process payback period (year) 1.2 3.0 1.7 1.3 table 2 reduction of effluents, fuels and chemicals chemicals (l y-1) water (m3'y-1) fuel (kg y-1) flue gas emissions (t y-1 ) waste heat (kw) reduction 130 204 3 200 67 9 fraction(%) 100 23 5 5 4 33 ~================~ by-po.ss co tel soft wo. ter from the system .. ==========~ fig.2 flash steam recovery retrofitting of steam and condensate system in the plant where the waste from broilers slaughterhouse is treated waste meat, blood and plumage from the broiler slaughterhouse were processed into useful products (fat, bone meal and plumage meal) and currently used in the production of animal feed. waste is decomposed into five reactors heated by steam. two air heaters, two fat tanks and a filter press are also iristalled. the annual production of heme meal reached 1 770 t, of plumage meal 1 280 t and of fat 1 250 t. steam consumption amounted up to 15 000 t y·1• the audit of the steam and condensate system involved a flowsheet, a mass and energy balance, a datasheet of all steam traps, reducing, safety, regulating and stop valves, separators and other armatures, proposed alternatives for rational steam distribution, consumption and condensate recovery. three ways of improving the steam and condensate system were proposed: 1. eliminating of steam and condensate leaks, maintaining insulation, retrofitting steam and condensate pipes, replacing inefficient and broken stop and reducing valves. 2. replacing of inefficient and broken steam traps. 29 steam traps were monitored, all types of traps were reviewed and the most efficient traps for every application installed. 19 steam traps were found inefficient or broken. 3. flash steam recovery. flash st~am produced at passing through steam traps at substantial pressure drop js used for heating process and cleaning water (fig.2). after the implementation of the proposed measures, steam consumption was reduced by 5 % and condensate saved by 8 %. savings reached 15 000 usd y1 at investment costs of 16 000 usd. the payback period was approximately 1.1 year. designing of an optimal condensate system the meat processing company installed new equipment for treating sausages. the production of sausages demands sterilising, cooking, washing and treating in smoking chambers. high pressure steam was needed for heating the air in the chambers and low pressure steam for cooking. the equipment producer designed a steam system and proposed the collecting of condensate in an aerated tank and the pumping of it into the boiler house by an electric-driven pump. after studying the possibilities for an optimal condensate recovery system, several options were suggested. three of them are: the drainage of high pressure condensate under pressure into a receiver, the collecting of condensate into an aerated· receiver and the pumping of it by an electric-driven pump, and the flash steam recovery with pumping low pressure condensate into the condensate receiver by a pressure powered pump. technical and economical assessments showed that the last option was the best of the three. flash steam produced from high pressure condensate was used for cooking sausages, while low pressure condensate was collected in a receiver and pumped by a steam powered pump into the condensate tank (flg.3). 34 table 3 savings, investment and operating costs of the proposed two options investment (usd) operating costs (usd y·1 ) losses (usd y"1) savings (usd y·1) payback period (year) option2 17 500 300 1200 option3 12500 3 000 5 000 6.2 table 5 reduction of flue gas emission, waste water and waste heat flue gas (t y· ) waste water (m3 y·1 ) waste heat (mw y·1) reduction 1483 43 91 mass fraction of total (%) 16 16 16 table 4 investment, savings and payback periods investment costs savings payback period alternative (usd) (usd tt) (year) 1 7 000 17 000 0.4 2 19 000 20 000 0.9 total 26 000 37 000 0.7 table 6 dependence of payback period and specific savings process pellets production waste treatment payback savings period (year) (usd r 1 ) 1.3 0.4 1.0 3.5 threads and bands production 0.7 117.1 inpvt of low pressure codenso.te "fr outi(iut of lo'lo' pressure condensate input of ¢1 high .pressure steq.m q output of \ow pre-ssure flo.sh steo.l'l fig.3 flash steamrecovery,"collecting and pumping oflow pressure condensate table 3 shows the savings, the investment and operating costs of the second and third option, which were technically feasible. the third option has lower investment and higher operating costs (steam for driving the pump), and substantial savings of condensate and steam compared with the second option. integration of a steam boiler into the threads and yam production proces:1 a thread and yarn producing company was being supplied with steam and hot water for heating by a nearby company. as the costs of steam and hot water kept rising they decided to invest in their own ooilerbouse. the external designer proposed a ooilerhouse with two steam boilers of 4.92 mw. together with the company experts we carried out an assessment of the production, distribution, utilisation of steam and condensate recovery in order to decrease investment costs. in the frrst phase of research a flows'heet was produced, mass and energy balances were carried out. some options for rational energy consumption were proposed in the second phase. renovation of the steam and condensate system. it included steam leaks prevention, replacing of inefficient pressure reduction valves and broken steam traps. recycling of cooling water and heat recovery from waste water. warm water produced at the temperature of over 60 °c could be reused for the preparation of process solutions and for warm rinsing of threads. the investment demanded a warm water tank, pipes, valves and pumps. investment, savings of steam, water and payback periods are presented in table 4. the total savings amount to 37 000 usd y-1 , the payback period is less than 9 months. based on the results of mass and energy balance and of the proposed options, the company invested in one steam boiler with 1,97 mw instead in two with 4,92 mw. the free capacity of this boiler was further assessed and the possibilities for heating production buildings by hot water investigated. it was concluded that the capacity of the installed steam boiler satisfied the demands for the production process and heating of buildings. at the annual steam consumption of 6 500 t, 1 070 t were saved (which is approximately 16 %). proposing a minimum steam capacity resulted in an additional45% reduction of depreciation costs (218 000 usd). the reduction of flue gas emissions, waste water and heat losses are presented in table 5. after installing the steam boilerhouse, additional possibilities of fuel savings were investigated. waste heat recovery from flue gas and deaerating waste flow from the feedtank and by flash of a boiler blowdown were proposed. it was concluded that the proposed options could lead to an 0.8 % improvement of the boiler efficiency and the boilerhouse by 4 %. the payback period of the proposed options was 4 years. it should be possible to decrease fuel consumption by 8 %, boiler water consumption by 2.5 % and flue gas emissions by 10 %. conclusions auditing of the steam and condensate system is a useful procedure for saving fuel, steam, water and for reducing effluents into the environment and therefore for improving the eco-efficiency of the company especially where the reduction of the energy intensity of goods and services is concerned. savings depend on the size, and the conditions of steam and condensate system as well as on efficiency of using steam in the process. in table 6 payback periods of the proposed options are presented and specific savings per product are shown. besides the above mentioned energy conservation opportunities there are also other energy conservation possibilities for improving eco-efficiency in steam and condensate systems: 35 design of an optimal steam and condensate system after the steam demand in the process is established. considering the possibility of pumping low pressure condensate with a pressure-powered pump instead an electric-driven one. considering the possibility for heat recovery from flue gas, deaerating waste flow, boiler and bottom blowdown. installing a total dissolved solids (tds) control system for boiler blowdown and a time programmed bottom blowdown system. considering the possibility of waste heat recovery from process waste streams in order to decrease steam usage for heating. references 1. eco-efficiency and cleaner production, charting course to sustainability, wbcsd, geneva, unep, paris, 1996 2. petek j. and glavic p.: res.con. and rec., 1996, 17, 169-188 3. turner c.w.: energy management handbook, the fairmont press, lilburn, pp. 7, 1993 4. spirax sarco: steam distribution, cheltenham, 1990, pp. 1-37 5. spirax sarco: practical steam trapping, charlton house, cheltenham, 1990 6. sp!rax sarco: condensate and steam flash recovery, charlton house, cheltenham, pp. 1-38, 1990 page 36 page 37 page 38 page 39 page 40 page 41 microsoft word 00.00 inner cover.docx the hungarian journal of industry and chemistry (hjic) formerly (until 2012) the hungarian journal of industrial chemistry the hjic is an international periodical that focuses on results of fundamental and applied research in the fields of • biotechnology • chemical engineering science • chemical processes • energetics • environmental chemistry • environmental engineering & technology • industrial management • materials science • mechanical engineering • mechatronics • process & systems engineering • recycling in the form of original papers, technical reports, reviews, communications, and conference proceedings written in english. hjic is abstracted by chemical abstracts, indexed by the hungarian scientific bibliography database (mtmt), and archived by the real-j repository of the hungarian academy of sciences. editorial board editor-in-chief: róbert k. szilágyi department of chemistry and biochemistry, montana state university, bozeman, mt, u.s.a. mta-elte “lendület” chemical structure/function laboratory, budapest, hungary associate editors: jános abonyi department of process engineering, university of pannonia, veszprém, hungary dezső boda department of physical chemistry, university of pannonia, veszprém, hungary norbert miskolczi mol department of hydrocarbon and coal processing, university of pannonia, veszprém, hungary dóra rippel pethő department of chemical engineering science, university of pannonia, veszprém, hungary editors: katalin bélafi-bakó research institute of bioengineering, membrane technology and energetics, university of pannonia, veszprém, hungary peter czermak institute of bioprocess engineering and pharmaceutical technology, mittelhessen university of applied sciences, giessen, germany dénes fodor institute of mechanical engineering, university of pannonia, veszprém, hungary maria gavrilescu department of environmental engineering and management, gheorghe asachi technical university of iasi, romania dirk gillespie department of molecular biophysics and physiology, rush university medical center, chicago, u.s.a. lászló gubicza research institute of bioengineering, membrane technology and energetics, university of pannonia, veszprém, hungary jenő hancsók mol department of hydrocarbon and coal processing, university of pannonia, veszprém, hungary jiří klemeš centre for process integration and intensification, university of pannonia, veszprém, hungary zoltán kovács department of management, university of pannonia, veszprém, hungary jános kristóf department of analytical chemistry, university of pannonia, veszprém, hungary istván szalai institute of physics and mechatronics, university of pannonia, veszprém, hungary jános szépvölgyi research centre for natural sciences, university of pannonia, veszprém, hungary gyula vatai department of food engineering, corvinus university of budapest, hungary gábor veress federation of technical and scientific societies – mtesz budapest, hungary ibolya zsoldos department of materials science and technology, széchenyi istván university, győr, hungary editorial office: university of pannonia, p.o. box 158, veszprém, 8201 (hungary) tel.: +36 (88) 624-746, e-mail: hjic@almos.uni-pannon.hu; web: hjic.mk.uni-pannon.hu felelős szerkesztő: szilágyi róbert károly nyelvi lektor: matthew chen kiadja: pannon egyetem, 8200 veszprém, egyetem u. 10. elektronikus terjesztés: de gruyter open (formerly versita), warsaw, poland levélcím: h-8201 veszprém, postafiók 158, tel.: +36 (88) 624-000 felelős kiadó: a pannon egyetem, mérnöki kar dékánja (prof. dr. szalai istván, ph.d.) de gruyter open hung. j. ind. chem. 2016 44(2), 71–139 table of contents articles of the thematic issue route planning based on urban mobility management tamás mátrai, jános tóth, and márton tamás horváth ........................................... 71–79 doi: 10.1515/hjic-2016-0008 cloud-based application for smart grid simulation szabolcs tar and attila fodor ................................................................................. 81–83 doi: 10.1515/hjic-2016-0009 simulation of electrical grid with omnet++ open source discrete event system simulator milán sőrés and attila fodor .................................................................................... 85–91 doi: 10.1515/hjic-2016-0010 mobile data synchronization methods miklós pál and gábor láner ....................................................................................... 93–98 doi: 10.1515/hjic-2016-0011 refrigerator optimal scheduling to minimize the cost of operation roland bálint and attila magyar ............................................................................. 99–104 doi: 10.1515/hjic-2016-0012 modelling a three-phase current source inverter lászló neukirchner and attila magyar ................................................................. 105–111 doi: 10.1515/hjic-2016-0013 computational stability analysis of lotka-volterra systems péter polcz and gábor szederkényi ..................................................................... 113–120 doi: 10.1515/hjic-2016-0014 diagnosis of technological systems based on the structural decomposition of their coloured petri net model anna i. pózna, miklós gerzson, adrien leitold, and katalin m. hangos ............. 121 –128 doi: 10.1515/hjic-2016-0015 regular articles metal chloride-activated empty fruit-bunch carbons for rhodamine b removal muhammad abbas ahmad zaini and mohd shafiq mohd shaid ................................ 129–133 doi: 10.1515/hjic-2016-0016 characterisation of cements from dominantly volcanic raw materials of the carpathian bend zone tímea halmagyi, emília mosonyi, józsef fazekas, spataru maria, and goga firuta ............................................................................................................ 135 –139 doi: 10.1515/hjic-2016-0017 editorial preface systems and control theory is a constantly developing scientific area and a dominant driving force behind key industries and engineering fields, e.g. process engineering, automotive engineering, bioengineering, the energy industry, etc. the aim of the current issue (volume 44, number 2) is to overview the actual research topics pursued by some selected ph.d. students. the papers presented in this thematic issue were selected from contributions at the 14th international ph.d. workshop on systems and control engineering held on august 25, 2016. the objective of the conference was to establish an international forum for young researchers and young engineers from industry and academia. the meeting provided opportunities for the participants to present and discuss the latest results and up-to-date applications in systems and control engineering. this issue represents the entire spectrum of systems and control engineering as follows: • process modeling and analysis; • control (traditional, intelligent, adaptive, etc.); • system identification and signal processing; • electrical transmission systems and smart grids; • bioengineering; • traffic control; • reaction kinetic networks; • artificial intelligence; • soft computing (neural, genetic, fuzzy algorithms, etc.); • software issues (parallel computing, distributed and network computing, data; visualization); • decision making (decision support, data mining); • applications. the organizers are grateful to the authors for their contributions. the tradition of the international ph.d. workshop on systems and control engineering continues. you are invited to participate at the 15th international ph.d. workshop in veszprém in 2018! attila magyar university of pannonia, veszprém, hungary guest editor hungarian journal of industry and chemistry vol. 44(2) pp. 71–79 (2016) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2016-0008 route planning based on urban mobility management tamás mátrai,1* jános tóth,1 and márton tamás horváth2 1 department of transport technology and economics, budapest university of technology and economics, műegyetem rkp. 3, budapest, 1111, hungary 2 department of control for transportation and vehicle systems, budapest university of technology and economics, műegyetem rkp. 3, budapest, 1111, hungary mobility management centres play a significant role in urban transport, taking into account several factors that have an effect on the flow of vehicles. in the present paper a mobility management centre equipped with necessary information and information technologies for travellers is presented that can provide route plans. a route guidance methodology is described that combines current transportation demands with the results of the traditional four-step model. keywords: mobility management, route planning, urban mobility, demand management 1. introduction the mobility management centre (mmc) as an organization helps to realize and manage mobility demand. the centre controls both private and public transport modes, as well as the provision of information for individual users with the aim of optimizing the entire transport network. the main goal is to provide safe and quick transportation for everyone. during the optimization process the system satisfies the mobility demands with the best available transport modes and routes, the 4r-s principles can be used (reduce, retime, reroute, revise mode) [1]. fig.1 shows the main tasks of the mobility management centre. usually in an urban environment, private transport users are supported by the traffic lights from the mobility management centres. the centres can control all traffic lights in the city based on network level principles. additionally, dynamic parking management can be developed, where the free spaces are displayed on variable message signs and in a further developed version individuals can be guided towards free spaces. private users can be informed about the actual transport situation and weather conditions via various channels. nowadays the most used channels are internet-based mobile applications, but there are also radio-based solutions like rds-tmc services or roadside infrastructure like variable message signs. if the individual users expect a response and guidance from the mmc for their route choices and do not decide their routes individually, then these centres can optimize the demand on the level of transport network system. in this case they can manage the *correspondence: tamas.matrai@mail.bme.hu demand to avoid congestion – the overuse of certain routes – during peak hours, in other words, they can distribute the demand in terms of a network evenly. currently these solutions have not yet been developed enough, due to the lack of communication among centres and users. currently only a very small proportion of vehicles receive dynamic information from the centre. it should be mentioned here that the slow but steady shift towards shared vehicles and ondemand modes has become an emerging trend, especially in conjunction with public transport. ideally, these services would be integrated together to provide a sustainable and equally convenient alternative to private cars for door-to-door mobility. the realisation of such figure 1. tasks of the mobility management centre. mátrai,tóth, and horváth hungarian journal of industry and chemistry 72 an alternative has set in motion the development of a new mobility concept known as the mobility-as-aservice (maas), which is a user-centric, digital and intelligent mobility distribution model in which the major transport needs of users are met via a single platform and are offered by a single service provider [2]. there is a strong connection between short-term traffic forecasts and route planning. users would like to receive route suggestions not only based on the current situation but also the forecasted one. either they are preparing the route on their own device or they are obtaining a plan from the centre. therefore, an efficient and acceptable level of prediction is essential. automatic vehicle location (avl) is one of the key elements in the accurate running of public transport systems in urban areas. as soon as the dispatchers identify any deviation from the predefined schedule, they initiate certain actions based on a pre-defined rulebook. one action from this rulebook can be to provide priority for those vehicles that are late, this priority provision can be achieved via certain junctions which are equipped with the necessary functions. the traffic lights at these junctions can change their signal plan dynamically in order to provide a green signal to the late public transport vehicles. other main task of the mmc is the provision of information concerning both static timetables and current traffic situations of public transport, which can be achieved through different channels. different information is necessary on different channels before a journey commences (e.g. internet-based route planning services, mobile applications) and during the trip (e.g. at the public transport stop, on the vehicle). the users are expecting to get not only information, but also suggestions especially from the integrated services (e.g. connections, local public transport, railway services, coach services) based on their individual preferences [3]. the most advanced version of this approach is a dynamic multimodal journey planner which provides the ability to adjust to a variety of anomalies (i.e. network disruptions, high capacity usage, etc.) concerning the transport network and evaluates the most efficient routes to get from a to b allowing for efficient traffic management [2]. it has to be mentioned here, that a feedback loop is essential; in order to continuously fine-tune the algorithm in the background, it needs to be determined if the users are really heeding the advice of the route planner. in functional urban areas, such as agglomerations with high levels of connectivity between urban centres and hinterland, one of the main goals is to promote the shift in mode of the commuters from private cars to more sustainable modes of transport. therefore, the provision of information with regards to other services such as p+r facilities and their saturation is vital. in this regard, the transfers should be seamless and the information beforehand should be sufficient to help make the right decision. there are different options to ease the level of inconvenience of the transfers, e.g. visual aids of the location of the p+r, information regarding available free spaces, guidance concerning public transport services at the parking facilities, and on-the-spot information about public transport schedule. 2. database of mobility management centres all the aforementioned tasks are feasible if the mmc is based on complex data collection. from these data, the mmc can create the information necessary to manage mobility demands and give information to travellers. fig.2 shows such a possible database. there are several public transport providers with their own data, which must be integrated into a joint database. thus, the timetable, network, real-time data, travel conditions and services at stops or interchange points are available. connecting timetables is particularly important when trips are satisfied by several transport modes. the intermodal hub cannot function without it. the public transport network itself is an integrated network because more public transport companies use the same routes, stops, or stations. dynamism of data is essential for real-time services (e.g. disturbances on a network). the accurate information is sent according to the current position and status of vehicles. vehicles equipped with a tracking system are necessary for fleet management. tariff is an integral part of travel conditions; the passengers must be informed about prices (e.g. is there a transport association selling common tickets) and fares for different passenger groups, etc. the data concerning fares and travel conditions remain unchanged for long periods of time; they are static or semi-dynamic data. information systems often figure 2. schematic overview of an integrated transport database [4] (sp = service provider). route planning based on urban mobility management 44(2) pp. 71–79 (2016) doi: 10.1515/hjic-2016-0008 73 lack such services at stops or stations. it could be helpful for passengers to spend time whilst waiting constructively. the database of private transport consists of network data, traffic data (presenting the actual situation on the network and also including historical data), weather conditions, parking data, and data regarding environmental effects, and other services. the network data are static, but sometimes include semi-dynamic or dynamic data (e.g. shortor long-term road construction). traffic data shows accidents, traffic jams, traffic volumes, etc. on the network in real-time and historically. the historical data are very important for traffic forecasting. numerous methods are based on the comparative examination of present and past situations. parking data can be static (location and capacity of parking area) or dynamic (parking occupation). advanced parking systems help to find a free parking place. p+r plays an outstanding role in encouraging drivers to change their modes transport. more and more travellers are sensitive to the environment. they are easily encouraged to use environmentally friendly modes of transport. therefore, the importance of the data of environmental effects is more accentuated. data regarding other services includes all the data concerning available services during trips. 2.1. mobility management centre solutions according to the needs of modern society, online planning software plays an increasingly important role in optimizing the flow of traffic, and utilizing the capacity of dynamic network traffic models that are strongly connected with real-time traffic management systems. several models developed for a city may not easily be applied to other cities. the rapid development of it equipment and the efforts to standardise protocol have facilitated the development of design software for traffic management purposes. the main aim of such software is to support decision made by dispatchers based on actual traffic situations. 2.1.1. sydney coordinated adaptive traffic system (scats) scats is a fully adaptive urban traffic control system that optimises traffic flow. the basic goal is to coordinate traffic lights at junctions in order to improve traffic flow and to reduce travel and waiting times. the main advantage of the system is its ability to adapt to changes in traffic conditions with the modification of the programming of traffic lights. fig.3 shows the daily changes of the cycle length of traffic light. the red borderline represents the previous period (before scats), the light blue area is the cycle length optimized by scats, and the dark blue area is the time saved. different travel demands have different goals: • low traffic demand: minimising the number of stops; • normal traffic demand: minimising the waiting time; • heavy traffic: maximising the throughput capacity. the system can prioritise public transport. in cooperation with trips (traffic modelling) software, traffic forecasting is also feasible (fig.4). 2.1.2. helsinki – helutc, finland this mobility management system in helsinki controls traffic lights, parking and public transport management systems. the concept of controlling traffic lights involves choosing a suitable cycle length according to traffic conditions. there are 10-12 different programmes for each junction. the coordinated intersections have identical cycle lengths. the system can prioritise public transport. variable message signs are applied to show parking information. it is very simple: are there any free spaces (fig.5). the public transport management figure 3. changing cycle length in the scats system (source: www.scats.com.au). figure 4. estimating the expected travel time using scats. figure 5. variable message signs for parking as part of the helutc system. mátrai,tóth, and horváth hungarian journal of industry and chemistry 74 system provides passengers with dynamic information at stops, in vehicles and pre-trips via an internet home page or mobile application. fig.6 shows a diagram for the system. 2.1.3. 5t system in turin, italy the name of the system is “telematic technologies for transport and traffic in torino”. fig.7 shows an overview of the system. the main goals of the system are to change the travel behaviour of passengers, increase the utilisation of public transport, and optimise travel time, energy consumption, and emissions. subsystems of 5t consist of traffic control, public transport management including vehicle priority, environmental control, information for travellers (via variable message signs, the internet, mobile applications), and parking management. every subsystem has its own management centre, but on the city management level all the information required for coordinating the subsystems is concentrated. the general strategy aims to avoid the overloading of network. the centre consists of seven modules as follows: • status monitoring module (treating subsystem information); • origin-destination estimation module; • modal split module (demand estimation for private and public transport); • traffic assignment module; • management module (cooperation with subsystems); • operator interface module (creating a connection between the operator and system); • database module (handling and storing the data of the operating system). in order to decrease travel time public transport has priority at junctions, and individual drivers are informed about the status of the network and the shortest route for their trip. all the public transport vehicles equipped with avl (automatic vehicle location) to give real-time information at stops and on vehicles, via the internet and mobile applications. the parking management subsystem uses vms to show the number of free spaces. the subsystem considers historical data to account for the filling up process of the parking area. the goal is to provide information about the supposed status of the parking lot in the near future, i.e. when the vehicle arrives at the entrance. 2.1.4. split cycle offset optimisation technique (scoot) the scoot system was developed by the transport research laboratory (trl) in the uk in order to manage and control traffic lights in cities by taking into account real traffic flows. this system is used in several cities around the globe such as london, santiago and beijing. since scoot is designed to update automatically to compensate for the effect of incidents. scoot achieved an average reduction of delays of about 25%, when compared with up-to-date fixed-time plans in nijmegen, the netherlands [5]. the system also offers additional opportunities: • providing priority to buses as part of the pt system; • providing gate effects; • incident detection; • online density measurements; • traffic flow estimation. all static data, e.g. the physical parameters of the transport network and traffic lights are stored in the scoot database. as an adaptive system, scoot requires good quality traffic data, so that it can respond to changes in flow. the system should calculate traffic volumes in every section of the controlled network. detectors are normally required at every link. their location is important and they are usually positioned at the upstream end of the approach link. inductive loops are normally used, but other methods are also available. for the schematics of data collection and processing see fig.8. when vehicles pass the detector, scoot receives the information and converts the data into its internal units in order to construct "cyclic flow profiles" for figure 6. diagram of the public transport management system in helsinki. figure 7. overview of the 5t system. route planning based on urban mobility management 44(2) pp. 71–79 (2016) doi: 10.1515/hjic-2016-0008 75 each link. the sample profile shown in the diagram is colour coded green and red according to the state of the traffic lights when vehicles arrive at the stop line at normal cruise speed. vehicles are modelled down the link at cruise speed and join the back of the queue (if present). whilst green, vehicles depart from the stop line at the validated saturation flow rate. the data from the model is then used by scoot in three optimisers, which are continuously adapting to three key traffic control parameters the number of green lights for each approach (split), the time between adjacent signals (offset) and the time allowed for all approaches to a signalised intersection (cycle time). these three optimisers are used to continuously adapt these parameters to all intersections in the scoot controlled area, minimising wasted green time at intersections and reducing stops and delays by synchronising adjacent sets of signals. this means that signal timings evolve as the traffic situation changes without the inconvenience of changing fixed time plans of more traditional urban traffic control systems (see fig.9). the combination of these optimisers provides the necessary solution to deal with the fluctuation in different traffic scenarios, and maintain the stability of different interventions. the split module is optimizing every status change, offset module optimizes the duration of every phase of the signalling system, while the cycle time module optimizes the length of the signal cycle in a certain region of the network. providing bus priority happens on three levels, namely (i) equal priority for all buses, (ii) different level of priority for punctual and delayed buses, and (iii) extra priority. priority provision and intervention are independent from the detection of the buses. in order to detect pt vehicles, the cities usually develop automatic vehicle location systems (avl), in some cities selective vehicle detection is applied. vehicle location monitoring is conducted at the avl centre. these location data are then incorporated into the selective priority algorithm. as it can be programmed to calculate the length of delays, the vehicle with the longest delay should receive the highest priority. it is possible to provide local priorities under the supervision of scoot. a schematic of an example system in london can be seen in fig.10 [6]. 2.1.5. mobility management in budapest in budapest the following mobility management tasks are in service: • public transport management and control (futár) o fleet management o vehicle priority o provision of information o route planning • private transport management and control o traffic management o provision of information o route planning o police monitoring centre • other services o bike sharing figure 9. illustration of the operation of the scoot model [6]. figure 8. data collection and analysis in scoot [6]. figure 10. schematic of the london bus scoot system [6]. mátrai,tóth, and horváth hungarian journal of industry and chemistry 76 these tasks are centralized in the same building, but there are three different management systems for the main tasks. they are connected, but there is no common supervisory system. the information flows, although not seamlessly, among them but traffic incidents are managed independently. the aim of project futár was to completely renew the provision of information and traffic management system at bkv zrt. this renewal only concentrated on the surface transport network: trams, buses, and trolley buses. the project consisted of four main steps. the first one was the development of the dispatcher centre and the main central server system. this consists of 32 dispatcher workplaces and all the connecting software and hardware developments. every dispatcher can view the location of all vehicles in the network in real time and are able to intervene in order to maintain schedules especially when some incidents occur. the second step was the developments of invehicle unit. budapest has one of the largest surface transport vehicle fleets in europe. therefore, equipping these vehicles with the necessary on-board units, communication devices, and vehicle location systems was a long and demanding task. this system has been installed in 2295 vehicles and some of them have also received new displays (2024). the third step was the deployment of roadside equipment. all over the capital 257 new displays have been deployed. these displays contain information concerning the route number of the next vehicle, while it terminate and the waiting time for this vehicle. additionally, these displays can provide information remotely through their loudspeakers for visually impaired persons. the last step was the introduction of the radio system. this is an integrated part of the network, which connects the dispatchers to the drivers. moreover, the system is capable of providing priority for public transport vehicles at 30 different intersections. fig.11 shows a schematic of the futár system. budapest also has a private transport management centre, which in 2012 started to use a new itraffic version 1.6 developed by siemens. the new system replaced the old and outdated migra central system, which was installed in 2002. one of the main reasons for the changes was that support for the operation system required by migra was no longer provided. this meant that the replacement of hardware element was hardly possible. of course, not only operating systems, hardware, or communication possibilities but also traffic management systems have evolved over the past 10 years. the new version of the centre possesses several new features. the communication systems have been replaced with a modern ip-based system: open communication interface for road traffic control systems (ocit) and canto. this wireless technology has also been integrated into the system (gprs at intersections), which is able to use any network topology or data transfer media. all the control devices which use the old befa 12, 15 or 16 communication systems can be supported by the new system, either as a sub-centre or as an outstation access point. the software has also been upgraded. it has received a new clear gui, some statistical analysis tools and further developed motion logistics. some new variable message signs have also been integrated into this system. 3. a pilot system in budapest the aim of the pilot system presented in this paper is to demonstrate how a mobility management centre equipped with the necessary information and information systems can provide tailor-made multimodal route advice to individual users by not only taking into account the average state of the transport network, but incorporating the current demand, too. this solution can be more elaborate than already existing private services such as waze application, for the following reasons: • this pilot system uses o-d matrices; • the continuous monitoring of the network is not required; therefore, the number of loop detectors, floating cars or other devices can be reduced; • it provides real multimodal alternatives before trips in order to choose the best transport mode for the current trip; • it uses already existing services; therefore, it does not require any major investment; • it is a module-based system; therefore, easily configurable to match local needs. the distribution of the demand on the network cannot be estimated without a transport model, which assigns the demand to the available transport network. fig.12 shows the proposed concept of this pilot system. the main concept behind this approach is to use the conventional, static demand matrices for the first iteration of the network load, but later on these matrices will be fine-tuned based on current demands. during the route planning phase, actual road traffic disturbances, e.g. road construction, accident; dynamic information from the avl system; and the current availability of other services like bikes at the nearest bike sharing station, are taken into account. based on the combination of this information and predefined user preferences, the system provides a tailor-made route for the user that is compared with at least two alternatives. figure 11. illustration of the operation of the futár model. route planning based on urban mobility management 44(2) pp. 71–79 (2016) doi: 10.1515/hjic-2016-0008 77 the system will use time intervals of 15 minutes to calculate the average situation, based on pre-defined static demand matrices (sdm) for each 15 minute-long time interval of the day, starting from midnight. the current demand, which is the sum of the number of queries concerning a specific route between distinct points of the network, is recorded in an actual demand matrix (adm). in order to obtain the current state of the network the sum of the sdm and adm is necessary. however, sdm already indirectly contains the demands of the adm. however, only as a static estimation from which the real state, represented by the adm, can differ. therefore, the adm cannot be added directly to the sdm, so the system will use a complex method to create a dynamic demand matrix (ddm), which correctly incorporates the actual demand. the static demand matrix is reduced proportionally by the corner sum of the actual demand matrix. then the adm and sdm are added together resulting in the new matrix (ddm) for the next 15 minute period. route suggestions will be provided based on the current state of the transport network. 4. discussion as described in the methodology chapter, the concept of the pilot project has already been elaborated. the existing matrix of the budapest macroscopic transport model [5] will be used as a daily static matrix and create matrices for each 15 minute interval of the day. demand matrices will be created for every mode individually (4 freight categories, car, bike, public transport). however, only car and bike matrices will be updated with the current demand. the averaging method described in the previous chapter is valid until the sum of the actual demand matrix corner sum reaches 30% of the static demand. over this scale, the averaging might yield false results and a different method will need to be applied. an important assumption is that the sum of the corner of the average daily matrix is fixed, in other words, each day the same number of trips is conducted on the network. a public transport model will not be developed in this pilot case, since an online journey planner exists which is based on real-time data and can make queries. alternatively, the existing interface of the futár system will be used to provide public transport route suggestions. for car and bike users, a search for the shortest route will be based on the results of traffic assignments obtained by visum software. disturbance to the road network will be added as changes in link or node capacity occur. in this case, a simple approach can be formulated, but in the end it represents the real disruption to the network. a description of the entire procedure is shown in fig.13. the entire procedure consists of two main phases: the preparation and elaboration periods. the preparation period can be done any time before the system starts. the elaboration period can be divided into 15 minute intervals that are represented in the figure by time periods of between 1 and t. time period 0 is an initialising period that differs slightly from the others, since there are no measurements beforehand. the indexing of time periods and time are the following: τ represents the time when a routing request arrives in the system, (t-1) and (t) are the start and end times of t, t is the time period when τ occurs. during the preparation period the 15 minute-long matrices are created for each mode and the basic static equilibrium assignment sta[prep] has to be run. these assignments run for roughly 45 minutes for each time period on an average pc using visum. the results of these assignments are the basic loads of the network. time period 0 is the initial period, there is no routing request that is filled before that period. therefore, disruptions only exist for the average state. the routing can be drawn from this state and the requests are collected in an actual demand matrix. in this period a traffic assignment sta[0] runs which incorporates the traffic disturbance reported at the beginning (period -1) of the period and the static demand matrix for the next period (period 1). this assignment usually runs for 8-10 minutes on an average pc running visum. figure 12. concept overview of the pilot system introduced in budapest. mátrai,tóth, and horváth hungarian journal of industry and chemistry 78 time period t is the current period, when current routing requests arrive and are collected in an actual demand matrix. an all-or-nothing assignment dta[t] is run using the dynamic matrix t-1 and the corrected capacity based on road traffic disturbances in (t-1). this assignment usually runs for less than 5 seconds. sta[t] is the same type of assignment as sta[0], but with the relevant data. the routing algorithm uses an average level of disturbance from sta[t-1] and dta[t] to determine the shortest route for car and bike users. time period t can represent any subsequent period as well, where the procedure is identical. 5. conclusion this paper introduces the concept of mobility management centres. it provides an overview of the tasks, responsibilities and opportunities of mobility management centres together with some international best practices. later an innovative pilot system is described in detail that will be elaborated in budapest. certainly, as this is a pilot system, it has several limitations and points for further research have been identified. some of the limitations arise from the required run times of the transport model, e.g. a shorter time interval than 15 minutes cannot be used. from the description of the process, it is evident that it includes averaging in several instances. this system assumes that all the planned journeys will be made; however, under real circumstances there are more planned than actual journeys. this can be one area of further research, since a good approach can be used to determine the proportion of planned journeys that are actually made. as suggested, a model like this should provide feedback, but this will not be developed during the pilot study. the validation of the proposed system is important. it can be validated by data from inductive loops and floating cars, but the above mentioned feedback loop would be an asset. there is another validation step, which should be done regarding the capacity reduction of the road traffic disturbance. the current system operates with some educated guesses, but appropriate values can be calculated with actual data. the planned approach for this is to collect incident data from the road network and at the same time collect data from loop detectors in close proximity to the incidents. the current pilot system is based on a series of static equilibrium assignments, but such a system should use dynamic user equilibria or dynamic stochastic assignments. the authors are currently analysing the possibilities of this approach, but it might require greater computing demands as well as more input data, which are currently not available in budapest. nevertheless, this is one of the most important research steps. figure 13. list of processes of the pilot system introduced in budapest. route planning based on urban mobility management 44(2) pp. 71–79 (2016) doi: 10.1515/hjic-2016-0008 79 acknowledgement we acknowledge the financial support of this work by the hungarian state under the vksz_12-1-2013-0088 project. the authors are grateful for the comments from colleagues at the bme department of transport technology and economics. references [1] juhász, m.; mátrai, t.; gál, g.; kerényi, l.s.: mobility management survey for the 2012 olympic games on the basis of published data for "transport for london", közlekedéstudományi szemle 2013 2, 11–19 (in hungarian) [2] kamargianni, m.; matyas, m.; li, w.; schäfer, a.: feasibility study for ‘mobility as a service’ concept in london, ucl energy institute, dept. transp. 2015, 1–82 doi: 10.13140/rg.2.1.3808.1124 [3] esztergár-kiss, d.; csiszár, c.: evaluation of multimodal journey planners and definition of service levels, int. j. intel. transp. syst. res. 2015 13(3), 154–165 doi: 10.1007/s13177-014-0093-0 [4] tóth, j.: its international trends, proc. xi. current issues of urban transport: organisations, innovation, quality service (közlekedéstudományi egyesület, balatonfenyves, hungary) 2011 (in hungarian) [5] mátrai, t.; ábel, m.; kerényi, l.s.: how can a transport model be integrated to the strategic transport planning approach: a case study from budapest, proc. 2015 int. conf. model. technol. intel. transp. syst. pp. 192–199, 2015 doi: 10.1109/mtits.2015.7223256 [6] scoot advice leaflet 1: the "scoot" urban traffic control system, available at scootutc.com/documents/1_scoot-utc.pdf. hungarian journal of industry and chemistry vol. 44(2) pp. 81–83 (2016) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2016-0009 cloud-based application for smart grid simulation szabolcs tar1* and attila fodor2 1 delta-group holding zrt., szentendrei út 39-53, budapest, 1033, hungary 2 department of electrical engineering and information systems, university of pannonia, egyetem út 10, veszprém, 8200, hungary this study provides an overview of the content of an r&d project for increasing the efficiency of smart grids to analyse the energy market, consumption, generation, and renewable energy usage. the new energy participants, for example decentralized generation, dynamic consumption, and weather-dependent power plants, are facing challenges. this project offers solutions to these challenges: modelling of distribution networks, forecasts of renewable energy sources distributed generation (res-dg), micro-grid management and responses to demand in new, complex solutions. a hardware device is being developed for smart grids and security modules to enhance it security. keywords: renewable energy, smart grid, demand response, cyber-security, network assets 1. introduction the main objective of our project is to utilize the opportunities in smart grids based on smart grid data and remote control to improve energy and cost efficiency. the service package is composed in a way that our solutions are put into use either as a whole or for the fulfilment of subtasks. the services and hardware devices are being developed like one intelligent cloud-based service. the rationale of these solutions is supported by several aspects of the energy market. the vastly proliferating renewable energy sources distributed generation producers (res-dg) are affecting every player in the energy market. the number and built-in power of such power stations are expected to exhibit a rising tendency in the near future according to various energy tenders, see tables 1 and 2. 2. experimental data grid operators should find a solution for operating grids with more entry points replacing the ones utilizing one directional power flow, where the direction of power flow changes over time and is influenced mainly by the performance of weather-dependent power plants. fig.1 shows the electricity consumption of hungary, which displays both domestic generation and importation, as well as planned and actual values of power transmissions from or to neighbouring countries. the prime cost of the electricity and the volume of the consumption set the actual, base, and peak prices of *correspondence: szabolcs.tar@delta.hu table 1. number of (pc.) and power generation (kw/mw) of res-dg producers over recent years in hungary [1]. 2008 2014 2015* pc. kw pc. mw pc. mw solar 107 363 8.8k 68 11k 84 wind 1 10 56 0.5 56 0.5 hydro 1 16 3 0.06 3 0.06 * based on estimated data table 2. use of renewable energy in hungary [2]. available capacity in mid. 2014 (mw) electricity consumption plan for 2020 (gwhr) hydroelectric 66 238 under 1mw 6 12 1 – 10mw 22 67 above 10mw 39 158 geothermal 57 410 solar 63 81 wind 750 1545 biomass 600 3324 steady 500 2688 biogas 100 636 total 1537 5597 figure 1. electricity consumption, export, and import of hungary as of september 25, 2016 (at 5 p.m.) [1]. tar and fodor hungarian journal of industry and chemistry 82 electrical energy. fig.2 shows the hourly average price of the electrical energy in 2015 in hungary. as solar and wind renewable energy sources are somewhat uncontrollable, the integration of renewable sources is a big challenge for transmission operators. as a solution, our group implemented a calculation model of the grid that takes into account parameters of the grid elements and details of network measurements. details about grids are provided by smart measurement and points of consumption defined in the remote reading circuit. measurement data are generated over periods of at least 15 minute in length at these measurement points. 3. simulations the spread of decentralised energy producers based on table 1, cause time-dependent power flows in grid sections. figs.3-5 show the load of a radial grid examined at various times. the lines on the left side of the graphs start from the contact bar of a transformer, the specific points show the power of grid lead-downs. positive values indicate a flow of power from a transformer towards an endpoint of the grid, while negative values illustrate a flow of power from an endpoint of the grid towards a transformer. 4. results and discussion it is reasonable according to the graphs that the built-in power is insufficient but the trends of consumption and production should be taken into account and a mathematical model created to know the exact operating states as well as for the integration requirement of the new production unit. in order to be able to model the integration of new res-dg efficiently and safely over a specific section, new forecast services need to be impremented. our service concept is mainly based on mass useage of solar cells in accordance with table 1. external environmental aspects were taken into account that affect the operation of renewable energy source power stations such as clouds, the temperature, humidity, global isolation as well as characteristics of power stations, such as orientation, tilt angle, integrated power, type and efficiency. the sources of data are defined, e.g. online satellite images and analytics, which in a complex fashion, can be used to create forecasts based on factual measurement data. for microgrid operators, e.g. lowand mediumvoltage operators, private grid operators, industrial parks, multiple household buildings, balancing groups, etc., a complex energy service concept was outlined. in which an opportunity for intervention was provided to facilitate a more efficient operation examining the production and consumption habits involved in the given microgrid. if the green energy produced is to be used as widely as possible, it should be identified where and to what extent the available green energy was consumed. by utilizing storage capacities, energy market transactions should be performed that are regarded as new nowadays, e.g. electrical energy is sold and thermal and hydrogen energy sources, vehicle charging, or other services purchased. our group has proposed a support application service for this. furthermore, settlement and cost allocation becomes more efficient and clearer based on details for operators. meters and sensors as well as intervention devices allow microgrid operators to modify the image of a grid proactively based on up-to-date information reducing service outage, which is highly relevant not only for consumers but also producers and trade licence holders too, as an outage location impacting both consumption plan and production plans. an outage location leads to figure 2. hourly average price of electrical energy in hungary (2015). figure 4. consumption of the electricity network of consumers (power versus 15 minute long sample times). figure 5. consumption on the electricity networof consumers (power versus 15 minute long sample times). figure 3. consumption on the electricity network of consumers only (power versus number of 15 minute sample times). cloud-based application for smart grid simulation 44(2) pp. 81–83 (2016) doi: 10.1515/hjic-2016-0009 83 unplanned resource withdrawal due to the spread of res-dg power stations. microgrid providers can initiate interventions to influence the expected production and consumption, providing basic parameters of energy usage. this basic signal can be a plan or request to balance out deviation in the plan. the controller is a decision logics based on the deviation of measurements and basic signals that issues a command within the available limits, which is based on a complex logics by transferring this to the energy use and consumption process in order to achieve the desired result. the consumer and equipment of the consumer are parts of the energy-use and -production processes (hereinafter referred as to process), respectively. this equipment is connected to smart grids among others via smart home devices. to allow the consumer to interact, a service shall be developed that is users demand. when intervention in the process does not take place automatically, the consumer is provided with detailed and aggregated information via various solutions in which the result of his/her intervention is displayed as well as the decrease or rise in energy use or costs. the means of automatic intervention or interaction are dynamic tariffs, which also require smart grids that provide detailed and instantly available data. this allows for the service provider supplying dynamic tariffs to make an offer that reaches the user in a timely manner, which will be either reviewed or accepted by the user or just received as information, as it is possible to intervene remotely and automatically in processes. the goal of our service is to make this information available on a platform based on priorities, irrespective of service providers, ensuring the opportunity to change of energy provider and the access previous data. we provide information to consumers as well as producers by connecting the initiator of an intervention securely via processes about which information, states, and backtesting are also generated by us to providers. to ensure the overall security of smart grids and services included in smart grids, the situation of cyber security and its expectations shall be mapped. smart grids are regarded as an extended electronic information system, whose endpoints can be accessed and managed remotely. however, they are less verified and have partial physically protection. the main requirements considered are • act. cxii of 2011 on the right of information selfdetermination and information liberty; • act. clxvi of 2012 on the identification, designation and protection of essential systems and facilities; • act. l of 2013 on the electronic information security of stateand local government-owned organisations; • directive 95/46/ec of the european parliament and of the council • relevant provisions of energy legislation • information methodologies and recommendations a hardware development has been implemented to enhance information security and a universal communication device has likewise been developed in the framework of hardware development offering a solution that facilitates efficient communication between various devices of smart grids. 5. conclusion these services and hardware devices reduce the costs for the participants in the energy sector from generation to consumption via distribution networks, and provide more secure itc infrastructure. to manage and forecast generation and consumption, new implementations of res-dg can be easily installed in the current distribution network, without the need for extra investment. the service package is flexible. anyone can choose whether to use services in the future or logged date. the system will be extended to include other new services. such services generate data requirements. further complex analytics provide useful results for the value chain actors, e.g. to improve the reliability of the distribution network. a source of irregular consumption is unchecked loads on the network, which leads to the overload of built-in elements of infrastructure, premature aging and damage. the simulation engine analyses the data and generate alerts concerning the status of network elements. before a failure occurs, the system can take various actions to reduce its duration and damage caused in order to expand cloud-based services for industrial consumers to dynamically control consumption for the network balancing. as far as the value chain is concerned, actors provide further bonuses to reduce energy costs. the devices and services in smart grids, like in telecommunications or it infrastructure create an opportunity for the further integration of sensors and surveillance camera networks. this integration into the management systems of cities is currently being tested. acknowledgement we acknowledge the financial support of this work by the hungarian state under the vksz_12-1-2013-0088 project. references [1] hungarian energy and public utility regulatory authority (mekh), 2015 www.mekh.hu/nemengedelykoteles-kiseromuvek-es-haztartasi-meretukiseromuvek-adatai-2008-2015-villamos-energia [2] hungarian independent transmission operator company ltd. (mavir) analysis of the hungarian electricity network, 2015 www.mavir.hu/documents/ 10258/15461/forr%c3%a1selemz%c3%a9s_2015.pdf [3] hungarian power exchange ltd. (hupx): www.hupx.hu hungarian journal of industry and chemistry vol. 44(2) pp. 85–91 (2016) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2016-0010 simulation of electrical grid with omnet++ open source discrete event system simulator milán sőrés and attila fodor* department of electrical engineering and information systems, university of pannonia, egyetem út 10., veszprém, 8200, hungary the simulation of electrical networks is very important before development and servicing of electrical networks and grids can occur. there are software that can simulate the behaviour of electrical grids under different operating conditions, but these simulation environments cannot be used in a single cloud-based project, because they are not gnu-licensed software products. in this paper, an integrated framework was proposed that models and simulates communication networks. the design and operation of the simulation environment are investigated and a model of electrical components is proposed. after simulation, the simulation results were compared to manual computed results. keywords: energy transmission, electrical networks simulation, distributed energy systems 1. introduction the simulation of electrical networks is important before network planning, development, servicing, etc. is conducted. there are many planning and simulation software solutions on the market, which can simulate electrical networks and grids, e.g. matlab, eplan, wscad. the problem with commercial simulation software is that such software packages cannot be ported to a new system. for example, if the development of a cloudbased electrical network and grid simulation system is required, standard simulation software products and methods cannot be used. to solve this problem, a simulation engine was used, which possesses a gnu licence. the omnet++ discrete event simulator (des) [1] was chosen. mets et alia [2] have previously used the omnet++ simulator environment. omnet++ is an extensible, modular, componentbased c++ simulation library and framework, primarily for building network simulators. omnet++ is not supported directly by the simulation of an electrical grid. to solve this incompetency, a model of the most important electrical components was constructed and as a result, the general simulation engine can be used for cloud-based electrical grid simulation. two methods were implemented in our omnet++ software, which investigated their mathematical foundations, as well. *correspondence: fodor.attila@virt.uni-pannon.hu 2. simulated network according to load distribution the electrical distribution system can be classified as: • fed at one end with one load at the other end; • fed at one end with more loads; • fed at both ends; • radial; • ring; • the distribution system. to test the omnet++ and model of the developed components, a network architecture was chosen, which is convenient and compatible with normal methods for planning of electrical networks. a system has been simulated, which is fed at both ends and consists of three loads (fig.1). of course, this omnet++ simulation project can simulate any distribution systems, though exact values will only be calculated in this case. to simplify our calculations, the wire parameters shown in table 1 were figure 1. distribution system fed at both ends with three loads. table 1. wire parameters ρ 1.85⋅10-8 ωm q 1 mm2 l1 27.027 m l2 54.027 m l3 27.027 m l4 27.027 m sőrés and fodor hungarian journal of industry and chemistry 86 considered. the resistances of all sections of wire are computable using eq.(1). the calculated resistances of the sections of wire are r1 = r3 = r4 = 1 ω and r2 = 2 ω, which were used in the omnet++ simulation. r = 2 ρ l / q (1) the selected resistance values are far from the resistance of wire used in real distribution systems, but the calculations are simplified and the illustration of the results more obvious. the values of current loads for each load were i1 = 10 a, i2 = 16 a, and i3 = 5 a. 2.1. classical method of calculating the voltage drop first, the voltage drop of a distribution system was simulated, in order to calculate the voltage drops using the classical method. our system consists of three loads and it is fed from both ends. the current of the first and second feeding points should be ii and iii, respectively. by applying kirchhoff’s law, eq.(2) is defined as: ii + iii = i1 + i2 + i3 . (2) the total length of the wire is calculated as: σ l = l1 + l2 + l3 + l4 . (3) if ii and iii are known and the load currents are subtracted from one of them, a load that is fed by both ends is identified [4, 5]. afterwards, the electrical network can be separated to obtain two networks fed at one end. the method of calculating, for example, ii is as follows: ii σ l = i3 l1 + i2 (l2 + l3) + i1 (l4 + l3 + l2) . (4) using eqs.(2) and (3), the results of the calculations of the total current, currents of feeding points, and the length of the wire are i1 + i2 + i3 = 31 a, ii = 15.4 a and iii = 15.6 a, and σ l = 135 m, respectively. from ii and iii, it can be determined that the voltage drops accotding to ohm’s law. the voltages of the loads are u1 = 214.6 v, u2 = 203.8 v, and u3 = 214.4 v. 2.2. a method of calculating the voltage drop based on the node-potentials the previously presented method can be easily used to calculate networks consisting of topology fed at one end as well as at both ends. however, our electrical grids are obviously not that simple, see fig.2 or they can even be more complex. furthermore, in this kind of method implemented using omnet++ the presence of a small solar plant on a rooftop is hard to handle. another method of calculating the voltage drops and currents was identified. using the node-potential method, any parameter of an electrical network can be calculated. to apply such a method, the feeding points with voltage sources, the loads with current sources, and the wires with resistances were modelled (fig.3). with this method the feeding points are modelled with voltage sources exhibiting constant voltages, which results in a crucial consequence for more complex networks. if another feeding point is added to the system, some part of it or even the whole network will be parallel to the new feeding point, as it is directly connected to the ground. that would make the investigation of the system and the handling of complex grids easier. of course this is only a theoretical method with many limitations and conditions, but it can be a good basis on which to start our investigation, plus the method can be developed. later new elements, both linear and non-linear, can be added to the network. although the focus of this paper was linear timeinvariant systems. the electrical circuit can be transformed into a directed graph, where the direction of the edges is the same as the direction of the current in calculations. in this case our network possesses six potentials. two potentials of the feeding points, three potentials of the current sources and the ground potential (fig. 4). the index of the nodes is identical to the index of potentials. if we apply kirchhoff’s first law to all nodes, six equations and in ordinary cases five unknown variable potentials from 1 to 5 (the ground potential is 0 figure 2. a more complex electrical network than shown in fig.1. figure 3. the network fed at both ends modelled with electrical elements. figure 4. directed graph of the modelled circuit. simulation of electrical grid with omnet++ 44(2) pp. 85–91 (2016) doi: 10.1515/hjic-2016-0010 87 v) will results so the linear equation system can be solved. they can be arranged them into a vector φ. φ = !! !! ⋮ !! (5) from the potential, voltages can be calculated from eq.(6). u = φi – φi+1 (6) obviously the voltages can be arranged into a vector u, similarly to vector φ. from the resistances, a resistance matrix r or conductance matrix g can be can created. for the node-potential method, a special matrix was used. once again, the central concept is kirchhoff’s first law. the first row of the matrix contains the conductances associated with the first node. the direction of the voltage (likewise the direction of the current) will determine their sign. ! = −!! !! 0 … 0 !! −(!! + !!) !! … 0 ⋮ ⋮ ⋮ ⋱ ⋮ 0 0 0 … −!! (7) the potential vector can be reduced by omitting φ0 thus yielding a reduced potential vector φr. of course the current matrix labeled i can be used. ! = !! !! ⋮ !!! (8) ohm’s law helps to calculate the unknown values of the network based on eq.(9). i = g × φ r (9) in the method of node-potentials, the potentials are considered to be unknown, while the other parameters are given. as a result, matrix φr contains all parameters that should be calculated. in the present situation the two potentials of the feeding points are considered to be known, 230 v and the ground potential is 0 v. each current value of the loads is known, but the currents of the feeding points are unknown. therefore, the matrices should be modified so that all unknown variables will be present in one matrix, x, and all known parameters in another one, c, a constant matrix. the g matrix must be used as well and denoted by gm. ! = !! !! !! !! !!! (10) ! = !!!! −!!!! + !! !! −!!!! + !! !!!! (11) !! = !! 0 0 1 0 −(!! + !!) !! 0 0 0 !! −(!! + !!) !! 0 0 0 !! −(!! + !!) 0 0 0 0 !! 0 1 (12) by arranging the three matrices into one equation, we get c = gm × x (13) eq.(13) was solved using gauss-jordan elimination method and the same results presented earlier for i1 + i2 + i3, ii and iii, σ l, u1, u2, and u3 were obtained. to make use of the gauss-jordan elimination method, the modified conductance matrix with the constant matrix had to be extended. with the help of a newly created matrix ge, the elimination process yielded the values for vector x directly. the extended conductance matrix (ge) is as follows: !! 0 0 1 0 !!!! − !! + !! !! 0 0 0 −!!!! + !! !! − !! + !! !! 0 0 !! 0 !! − !! + !! 0 0 −!!!! + !! 0 0 !! 0 1 !!!! (14) 2.3. comparison of the two methods although both calculations yield exactly the same results, in our opinion the second one is preferred. the structure of the matrices indicates that it can be applied to even more complex grids, e.g. in radial topology. another advantage of the node-potential-based method is that the direction of the load currents is irrelevant. for example, even a small solar plant on a rooftop can be simulated. 3. simulation with omnet++ the omnet++ 4.x integrated development environment is based on the eclipse platform, which has been extended with new editors, views, wizards, and additional functionality. although omnet++ is not a network simulator in itself, it has gained widespread recognition as a network simulation platform in the scientific community as well as in industrial settings, and has built up a large community of users. the most common area of application of omnet++ is the simulation of telecommunication networks. the simulator itself is message-based, so our electrical distribution system had to “communicate” via sőrés and fodor hungarian journal of industry and chemistry 88 messages, which is rather unusual in terms of physics or electrical engineering. omnet++ provides component architecture for models. components (modules) are programmed in c++, then assembled into larger components and models using a high-level language (ned). omnet++ simulation comprises three different files, which are (i) source code (cpp), (ii) network file (ned), and (iii) configuration file (ini). in omnet++ modules are defined, which can communicate via messages. both modules and messages are special c++ objects. in the source code, we can specialize our modules, and define their tasks precisely. the network file contains the actual topology of the network system, and the position and names of the used modules as well as their connections. with the aid of the configuration file, other network settings can be specified, though none were used in our simulations. all modules have four functions, which can be defined by users. in our simulation, only two of them were used; the initialize() and handlemessage() functions. in the initialize function the initial parameters of the modules can be set, in the handlemessage() function the action in case of an incoming message can be declared. with these functions, completely different modules can be developed. the main idea was to show the current or energy flow via messages in our system. it worked quite well in the case of a system fed at one end. although because of the message and handling of messages inclinations of omnet++ in systems fed at both ends, the energy flow was not so easy to show. 3.1. implementing the distribution system in omnet++ the distribution system shown in fig.1 had to be implemented. it is obvious that we have at least three different types of modules exist in this network as follows: (i) feeding point, (ii) load, and (iii) connection between them. the implemented electrical distribution network is shown in fig.5. by analysing the topology more closely, we could identify another module could be identified, connecting two wires and a load, the node. nodes are important parts not only of grids with their topology, but also of radial grids. the previously used module is not shown in fig.1 but there should be a ground point to make our simulation easier and clearer. this ground point module is the most important as it carries out the main calculations and connects the loads to the producers. table 2 shows the modules and the names used in our source code and files. 3.2. modules and messages the class of messages possesses several variables, including a void-type pointer called contextptr, which is a user-defined pointer. in our simulation, this pointer was used to send data to modules. it points to a class, which contains the used variables such as voltage, current, effective power, reactive power, resistance, etc. of course, some of the variables are used in only one module (e.g. the resistance in wire module), and some in all of the modules (e.g. voltage, current). in the constructor, all variables were set to zero. the simulation consists of cycles. each cycle begins with the producers sending messages, and ends when they receive their messages from ground modules. in simulations, the event logging (ev) function can be used to log the parameters or result(s) of the calculations. there are two feeding points in all simulations, though loads are user-defined (n) in preprocessor instruction where both twoand three-pointloaded networks can also be considered. the first module is called producer. it exhibits a constant voltage value set in pre-processor instruction #define ut 230. in advanced simulations, it should be a user-defined value, and it is not necessarily constant. it could be a function as well, but in this simple simulation, it will remain constant throughout the whole process. at the start of the simulation, only the voltage of the producer is known, but the current and power are unknown parameters until the end of the turn. thus, these values are set to -1 at the beginning. all three parameters are set in the initialize() function. the next stage of the module is handling an incoming message. the incoming message is actually a pointer to the message. at first, in all modules, the values of the pointer were stored as local variables were identified. this is very useful as during simulation some memory allocation problems. the message contains information only about the currents (the voltage remains constant). the current of the producers is set to the value from the message. the power is calculated from the current and voltage values. the module is connected to the ground and one-wire modules. the producer module logs the voltage, current, and power. figure 5. the schematic of the network using omnet++. table 2. summary of modules used in omnet++ simulations. parts of the system module names feeding point producer load consumer connections wire node node ground point ground simulation of electrical grid with omnet++ 44(2) pp. 85–91 (2016) doi: 10.1515/hjic-2016-0010 89 the second module simulates the load and referred to as consumer. it exhibits a constant current and power factor. both users are defined. current values are the same as discussed above in section 2. from these and the voltage from the incoming message, the module calculates the power and reactive power. this block sends the current value to the ground block for further calculations. consumer modules are connected to one node and the ground module, which logs voltage, current, power, reactive power, and the power factor. in real networks, the connecting wires exhibit resistances as well, causing a voltage drop in the system. in our example, this is desirable, almost 1 ohm, but our calculations are simple. in the initialize() function, the lengths from table 1 and r1 to r4 resistances from section 2 are set. the wire module calculates the voltage drop simply with ohm’s law. obviously, it shows a useful value from the second cycle, as the current is negative until that turn. wires are connected to one producer and one node or between two nodes. wires log the voltage drop, current, resistance and length. the node module is especially useful in radial topology, but also implemented here as well. the aim of this module is to distribute current by applying kirchhoff’s first law to our network. it works only after the first ‘initial stage’. the module is connected to two wires and one consumer module. it shows the value of currents. the ground module conducts the main calculations of the simulation. it determines the exact current values for each producer module. the calculations are based upon eqs.(2) and (3). the module takes into consideration the length of each wire and the currents from the consumer modules and distributes them. the ground module is connected to all consumer and producer modules in addition to logging the sum of currents and the currents for each producer. 3.3. simulation as stated before, this omnet++ simulation can be divided into three different stages. at first, the omnet++ simulation engines build the network with the user-defined values for each module. this is referred to as stage 0, and there is no logging occurs here. in other simulations, logging is possible here as well, but in this case this opportunity is omitted. the next stage, or the first cycle, starts when the producers send their first message, and ends when they get their message from the ground module. this part is not necessary in other kinds of simulations. in this part all modules have their own user-defined values, but they do not have any effect on the other modules, e.g. producers exhibit their own voltages, but their current and power are both -1 or the voltage and current of wires are both unknown (-1), as shown in figs.6 and 7. at this stage, the voltage of the consumers is 230 v, and its powers are calculated with this voltage, shown in fig.8. the first cycle of the simulation is examined in fig.9. currents are “delivered” between the modules throughout the whole network system. however, at the end of the initializing stage, the ground module calculates the sum of currents of the consumers and the currents of each feeding point (fig.10). thus, the producers receive their currents, and the correct calculated values, e.g. voltages, powers, etc. will be obtained without any unknown parameters (fig.11). figure 8. consumer logging during the first cycle. figure 9. the first cycle of the omnet++ simulation. figure 10. current distribution. figure 6. wire logging during the first cycle. figure 7. node logging during the first cycle. figure 11. voltage, current and power of the first feeding point. figure 12. logging of wire, node, and consumer modules in the second cycle. sőrés and fodor hungarian journal of industry and chemistry 90 the previously shown modules can be examined and it can be concluded that our voltage and current values are known (fig.12). it could be interesting to see how our nodes work after the first stage, when applying kirchhoff’s first law (fig.13). we have to mention that in the case of node modules iout means the current of the consumer subtracted from iin. 3.4. validation of the simulation results it has been seen that the results of the omnet++ simulation and the results of the classical method of calculating are the same. as an example, the results of the voltage drops are shown in fig.14. 3.5. topology all electric systems have unique topologies the position of the components or element(s) and the wires that connect them. by considering a network fed at both ends with only one node, it conatins one node module and two connecting modules between the feeding points and the node. in the case of a similar network with two loads there are two nodes and three connecting channels, as in the previous case. from this point of view the simulated network can be checked, this one contaists of three loads and four channels. if a gred fed at both ends with n loads (where n is a positive integer) exists then the number of wire modules, w (also a positive integer) can be calculated as follows: w = n + 1 (15) eq.(15) is only true for this type of topology. for example for a topology in which there is only one feeding point, the number of loads obviously is equal to the number of wires (and nodes). a proven formula can be applied to more complex topology variations. the advantage of these formulae are that they automate the creation of ned files either from another piece of software or implemented from omnet++. 4. summary of simulation experiences it can be concluded that our des program works properly as shown in section 3.4. obviously there are some advantages and disadvantages of this method. 4.1. advantages first of all it is an open-source platform, thus it can be modified and developed easily. the use of other auxiliary pieces of software can be added, too. as the program includes a graphical viewer, individual simulation results can be followed. the message direction is the same as the current direction, thus a negative current means failure in the program, or negative values can be defined as unknown parameters. our system can be observed for values of interest. with this definition the model later may be used in transient analysis to consider the reinitialization cycles each time. 4.2. disadvantages on the other hand, as an open-source platform it is still in the development phase. sometimes the program gave us crash reports during the development phase. the message direction is the same as the current direction; however, according to the message sending system of omnet++ extra message(s) can be obtained. another issue is the network description file (ned). each time our network system is modified, the whole code needs to be modified, including the connection definition part, as well as the gate declaration. topology statements are omitted. although the time of the simulation is user-defined, all the steps are to be followed the simulation may be rather lengthy. in this case, the simulation of another type of electrical distribution system was attempted, e.g. for a system fed at only one end, a totally new program has to be written. this program can be solved only if a formula is created for each different type of topology. real electrical grids may be more complex than the situations our des can handle at the present. 5. conclusion the models of the electrical components have been developed in this paper based on engineering principles that are able to describe the behaviour of an electrical grid. it seems that the omnet++ discrete event simulator is suitable for the simulation of electrical grids. at first we need to fix some problems mentioned in section 4.2. a future task would be to implement new electrical network components, e.g. photovoltaic power plants, wind turbines, and different loads, etc. to the simulation environment and subsequently the omnet++ would be suitable to simulate smart grid networks. figure 14. voltage drop of the loads. figure 13. applying kirchhoff’s first law to the node modules. simulation of electrical grid with omnet++ 44(2) pp. 85–91 (2016) doi: 10.1515/hjic-2016-0010 91 symbols des discrete event simulatoion ev event logger i1, i2, i3 currents of the loads ii, iii currents of the feeding points l1, l2, l3, l4 length of the wires connecting loads and feeding points n number of loads w number of wires q diameter of the wire u1, u2, u3 voltages of the loads ut voltage of the feeding point ρ resistivity ned network description file ini initialization file φ potential φ potential vector φr reduced potential vector r resistance matrix g conductance matrix gm modified conductance matrix ge extended conductance matrix i current vector x vector of variables c vector of constants acknowledgement we acknowledge the financial support of this work by the hungarian state under the vksz_12-1-2013-0088 project. references [1] omnet++ discrete event simulator omnetpp.org [2] mets, k.; verschueren, t.; develder, c.; vandoorn, t.l.; vandevelde, l.: integrated simulation of power and communication networks for smart grid applications, proc. ieee 16th int. workshop, computer aided modeling and design of communication links and networks (camad), pp. 61-65, 2011 [3] niemi, r.; lund, p.d.: decentralized electricity system sizing and placement in distribution networks, applied energy 2010 87(6), 1865-1869 doi: 10.1016/j.apenergy.2009.11.002 [4] gonen, t.: electrical power transmission system engineering: analysis and design (crc press, boca raton, fl usa) 2011 [5] jamniczky, á.: electric engines, (university of veszprém press, veszprém, hungary) pp. 31–49, 1994 (in hungarian) hungarian journal of industry and chemistry vol. 44(2) pp. 93–98 (2016) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2016-0011 mobile data synchronization methods miklós pál and gábor láner capture it solutions and consulting, záhony u. 7 building b, budapest, 1031, hungary the study introduces and compares the performance of a classical and two innovative mobile data synchronization methods. a customized test environment will be created for every selected method researched. performance, stability, and other measurement results will be produced from these environments, which will be the major outcome of the study. keywords: mobile synchronization, comparison, performance measurement, data optimization, slow network connections 1. introduction the main goal of mobile workforce management software is to make fieldwork easier and more efficient. this requires all necessary data to be available and in sync with the server databases. this is why the synchronization module is one of the most important parts of mobile workforce management software. during the fieldwork, there are various data connection conditions that the application needs to be conformed with. there are several data objects, e.g. task, user, client, etc., and multipart objects, e.g. document files, images to be synchronized. the usability of an application highly depends on the efficiency of this synchronization. the main problem that synchronization needs to solve is to transfer data between the devices and the data source. the solution begins with the data source and through the communication channel ends with the saved data on the device. three potential implementation methods will be introduced and compared in this article. 2. experimental all three considered solutions have different technical backgrounds. the first one is a soap (simple object access protocol) web service implementation based on xml communication. this is the classical way to transfer data between two different platforms. the protocol originally was designed for microsoft in 1998. the xml-based web service is a widespread solution because it is platform independent and built on industrywide standards. it was one of the first ways to build service-oriented, modular architectures using smaller *correspondence: www.capture.hu applications is by the communication of web services instead of robust, monolithic systems. as the technology was mainly used in enterprise environments, and has been in use for more than 15 years, naturally it consists of an antiquated approach compared to modern, lightweight services. while the technology is based on standard http protocols, the requests and responses travel in objects called envelopes. all of the envelopes have a header and a body part, where the body contains the actual payload, the data that is the main reason of communication. the format of the envelopes is strict, and furthermore, there are several encoding, formatting, and parsing standards that have been created since the birth of the protocol. unfortunately, not all implementations are compatible, it is easy to create a server that cannot digest the client’s request, while both endpoints use valid but different soap formats, even though the raw format of the envelope is an easily readable xml file. the strict format has both benefits and inconveniences. when the service at the server is ready, it is easy to generate a unique description xml, called wsdl (web services description language). this file not only helps the development of the client side, but there are several tools available that can generate almost all of the client-side code, that can be used to connect to the service. overall, it is a strict, old fashioned, but really reliable way to approach services in the modern mobile world. the second tested solution is the restful (representational state transfer) service in the architecture of microservices. rest is also known as restful architectural design, and was represented in 2000 by roy thomas fielding in his dissertation at the university of california, irvine [1]. rest has become the main architectural design for web and mobile development over the last few years. according to ‘programmableweb’, 69% of the newly created apis were using rest while only 22% were using soap in 2014. pál and láner hungarian journal of industry and chemistry 94 there are many advantages of this architectural design. the first is its solid performance, due to the high level approach of the solution. it typically communicates over http (hypertext transfer protocol) using http verbs like get, post and put. rest supports more message formats, e.g. xml, csv (comma-separated values), json (javascript object notation), etc. the primary communication format is json, which is structured text data type. this message format requires significantly less metadata than the xml format, thus greatly increasing the network efficiency as the valuable data can fit in smaller network packages. the spread of the json message format is shown in fig.1. the diagram shows the percentage of json versus xml message formats used by apis in the ‘programmable web directory’ between 2005 and 2013 [2]. another great advantage of restful is its simplicity. it is easy to implement and maintain due to its structure. it clearly separates the client and server implementations. today’s trends point in a direction where developers need to create highly availabile applications exhibiting high level of scalability that are ready to run in cloud environments. microservice architecture is a method of developing software applications as a suite of independently deployable, small, modular services in which each service runs a unique process and communicates through a well-defined, lightweight mechanism to serve a business goal. the most wellknown microservice architecture users are netflix and amazon. applications based on this architecture are easy to understand and modify because of the independent parts. instead of a robust application which contains all functions, logics and millions lines of code, there are many separated services with a focused function. these applications or application modules are able to run on multiple copies of multiple machines which makes them highly scalable, available and capable of running in cloud environments. patterns in programming are reusable solutions to a problem occurring in a particular context. in the world of microservice architecture there are many patterns available to choose from. from the aspect of deployment there are two main patterns: • multiple services per host there is one physical server with all services installed on it. • single service per host in this case, there is a standalone host for each service. the host could be a virtual machine or a container. the communication methods between the clients and servers are described with the api gateway communication pattern. in this pattern the gateway is a service discovery between the client and server. this service is the single entry point. from the aspect of the database there are two main patterns. the shared database pattern uses only one database for all services. the database per service pattern uses a standalone database for every single service. finally, the third solution is a distributed nosql implementation of mobile data synchronization. early versions of nosql databases have existed since the 1960s but the technology started to spread only in the twenty-first century. nosql in other words means nonrelational database. one of the main benefits of these databases is the simplicity in design, because they store data in a key-value structure. the other main benefit is the horizontal scalability with the support of clustered environments and cloud infrastructure. these types of databases are mainly used in big data environments. all three applications have the same functionalities. during the experimental three demonstration applications were created. one separated environment for each featured solution. all the applications have three main modules with the same functionalities: (i) database at the backend side to store test data and (ii) synchronization module to transfer data between the backend and mobile application. mobile applications exist with the capability to connect to the synchronization module and synchronize data to the mobile device. additionally, there are some status checking and logging functionalities on this side. every mobile application was created with its own mobile database to store synchronized records. the data source of solutions was tested, which contains up to 50 thousand historical roadwork items of data from 2011 until 2016. the structure and an example record of the database are shown in table 1. test data is stored in a single table with a sequence number as a primary key. the architecture of soap web service implementation is shown in fig.2. on the database side figure 1. percentage of apis added to the programmableweb directory based on communication types over the years [2]. p er ce ta ge s of a p i t yp es years table 1. data structure used in tests with the field data types and typical contents. column type example id numeric la reference numeric 476483 promoter character vultron street character stonegate road locality character meanwood works type character standard easting numeric 428804 northing numeric 437215 location character opp stainbeck avenue description character vultron ducting for mains cable to display in bus shelter works start date date 19/03/2008 works end date date 08/06/2013 mobile data synchronization methods 44(2) pp. 93–98 (2016) doi: 10.1515/hjic-2016-0011 95 there is a postgresql server (version: "postgresql 9.0.3, compiled by visual c++ build 1500, 64-bit") installed. for the experimental, a separated database was created with pg_default tablespace and utf-8 encoding. inside the database test, tables were created in a public scheme. the application server is a j2ee web application implemented with the springboot framework, which builds a standalone runnable jar application that includes a war web application and also grants an embedded apache tomcat application server. this solution provides a monolithic architecture, which is widely used in the enterprise environment. the core framework of the application server is springboot (version 1.3.6.-release), where the embedded tomcat server version is 8.0.36. the web service itself is provided by spring-ws (version 2.3.0.-release). the getroadworklistrequest web service provides the main query about synchronization logic. this service performs a select * from roadworks query through the persistence layer and returns the whole list of the currently stored roadworks. the response is the xml representation of the data table presented in table 1. as a persistence layer the application uses the eclipsellink jpa provider version 2.5.0. the mobile application of soap implementation was built for the android sdk version 24.0.0. android does not offer any built-in library to handle soap calls. there are several third-party libraries to fill the gap, but one could not be found that could be a fully satisfactory solution to our problem. in the tests, the ksoap2 (version 3.6.1) implementation was used that also has some very uncomfortable limitation, but during the test it was working reliably. the synchronized data is saved into the sqlite database in the mobile device. sqlite is the built-in android database that offers a relational database with functionalities to access and store data. the architecture of the restful service implementation is shown in fig.3. this architecture is a typical microservice architecture where the service itself implements the synchronization functions. the mobile application implements the mobile-device functions like synchronization calls and status reports. a shared database pattern was used by sync service, which means the database used by synchronization service is a database used by other services, too. the same postgresql database was used at the database level in the rest implementation as used before for the soap test application. thus, the database version and database configuration were the same. the service is implemented as a standalone java application supported by jetty (version 9.2.1.v20140609). jetty provides a lightweight embeddable web server and it has support for rest apis of web socket. these features make jetty ideal to use in microservice architecture. sync service provides a rest api for mobile clients to conduct synchronization. the main api is the get /rest/sync/roadworks http/1.1; content-type: application/json service that responds with the whole list of roadworks as a json content type. the roadworks data is accessed with a full table selected from a database over an eclipselink persistence layer. the same jpa provider (eclipselink version 2.5.0) is used for this service as it is for the soap application. the mobile application of the rest implementation was also built for the android sdk version 24.0.0. however, android has its own http client provider, in this article android-async-http (version: 1.4.9) was used for asynchronous http client functionalities at the mobile application level. this is a well-featured and widely used library by top developers like instagram and pinterest [3]. the sqlite database was used to store synchronized data in the mobile device as well as in soap implementation. it was experienced during development that implementing rest api calls in the mobile environments is relatively easy to perform since it is a widely supported method of communication. couchbase was used to build the nosql database because it offers a complete solution with a server-side database (couchbase server), synchronization gateway and mobile-side database (couchbase lite). the architecture of this solution is shown in fig.4. the data layer is a couchbase server (version 4.0.0-4051 community edition (build-4051)). the database has a single server node configured. the server node in couchbase represents an instance of the database. in our test only one instance was run. in production environments, more instances are necessary to improve server availability. the node contains the physical data representation objects, called buckets. a new bucket was configured for the article as a couchbase bucket type with 200 mb of memory allocated per node. the optimization of disk i/o figure 2. the soap based test application’s logical architecture. the communication between the client and server component is based on xml / soap messages. figure 3. the rest based test application’s logical architecture. the communication between the client and server component is based on json / rest messages. pál and láner hungarian journal of industry and chemistry 96 operations was set to default, which means the disk i/o priority is low for this bucket. in this article this is an issue, because there are no other buckets in use. the auto-compaction settings are also set to default which means auto-compaction should run if the fragmentation is above 30%. the sync gateway (version 1.2.1 was installed) is located at the server side as a standalone application. this module implements database read / write functions and solution specific apis to transfer data to and from mobile devices. it has a built-in versioning logic, which adds revision information to the documents stored in the server of the database and handles synchronization metadata like synchronization cycles and user data. the sync gateway is configured. it was created to setup the gateway to sync every document type without any user authorization. in this case every connected device synchronizes every document without restrictions between the client and server. the mobile application of nosql implementation is similar to the previous solutions built for android sdk version 24.0.0. the most significant difference here is the mobile database, which is couchbase lite (version 1.3.0). this is a mobile database created for couchbase and sync gateway. it contains the mobile database engine, the mobile database handler and the synchronization interface implementation. the synchronization supports both push and pull requests with version checking so only modified documents are transferred during a call. 2.1. samples and measurements four types of measurements were performed during the experiment: speed test between server and devices for different numbers of datasets (small 1-10, medium 1,000-10,000 and a large number of records up to 50,000). speed tests were performed during data transfer to and from the devices and with mixed directions. speed and stability tests were performed using text and binary data types with a high amount of data to transfer. during the tests, all data packages and sizes of the packages were monitored, as well as the performance of mobile applications, synchronization gateways and databases. 3. results and analysis 3.1. experiments during the analysis an attempt was made to provide constant conditions with the following hardware infrastructure. an asus k53s notebook with intel® core™ i7-2630qm cpu, 8 gb ram and hdd wdc wd7500bpvt-80hxz was used as the server to run the database, application server, synchronization service and synchronization gateway. a samsung galaxy smg935f (s7 edge) smart phone with android 6.0.1 (build number mmb29k.g935fxxs1apg2) was used as the mobile environment. every test was run on the same local network. the network used a 100 mb/s wifi router. the server was connected to the router with a local area network (lan) cable, the mobile device was connected via a wifi network. this way the network speed during the experiment was constant. during the experiment, six test rounds were run on the three different solutions. the amount of data was raised in every step from 1 row to 50,000 rows. one test round with 100,000 records was also planned, but the tests revealed the limitation of the mobile hardware, for around 30 mb of data, the response could not be parsed in one batch, mainly due to the lack of memory. to achieve realistic conclusions from the measurements, every step was repeated three times. overall, a total of 54 tests were run. measurement results were collected using several methods. in soap and rest implementations, most of the information was collected from the mobile platform. both applications were provided with a logger module that provided log entries in every main step of the synchronization. these steps were the following: • synchronization initialized • synchronization started (request was sent from the mobile device to the server) • synchronization finished (the response came back from the server) • parse start (when the mobile application started to process the response) • parse done (when processing finished and all records from the response were saved in the database of the mobile client) in the case of the nosql solution, the monitoring was a bit different because there was no way to write a custom logger module for the built-in processes. fortunately, the couchbase sync gateway provides a fine-grained log where nearly all equivalent steps can be found that we redefined for the previous tests. the performance and mobile database monitoring was the other main part of the analysis. this part was the same for all solutions including nosql. the performance was monitored continuously with an android debug tool while the database was monitored from the application with a status screen. it was expected that the soap web service implementation would be significantly slower than the restful and nosql solutions mainly because of the larger data packets transferred in xml format. figure 4. the couchbase based test application’s logical architecture. the communication between the client and server component is based on the database standard synchronization gateway. mobile data synchronization methods 44(2) pp. 93–98 (2016) doi: 10.1515/hjic-2016-0011 97 the measured results refuted these expectations. as fig.5 and table 2 show, the average sync times are not just nearly the same but with smaller data amount the soap is even faster than the rest. in this result, the nosql lags behind the other two solutions, but the sync time gets closer as the amount of data increases. the reason for this difference could be the additional versioning features of couchbase. furthermore, nosql is built for working with high amounts of data. the synchronized data amount on the horizontal axis is increasing nearly logarithmically because of this, a logarithmic view of this result set (fig.6) could yield a better understanding. fig.6 shows the key point is at 1,000 rows. here is the point where all solutions start to converge into each other. from this point, increase in the sync time becomes more directly proportional to the increased in the data amount. by taking into consideration the result, numbers and sync time per row values in table 3, is can be seen that the minimum value using soap is at 1,000 records, using rest the minimum value is at 10,000 and using nosql the minimum is above 50,000. the results above were calculated using synchronization and data processing. if data processing is skipped, the results change as shown in table 4. again, the key point here is the limit where the number of records is 1,000. after that point the synchronization using rest increases much faster. as shown in fig.7, the soap sync time rises sharply while the rest sync time rises less rapidly. the size of the messages can only be monitored for the soap and rest implementations. the results of these measurements were the same as expected. due to the strict data format, the xml structure requires larger amount of data transfer packages than json, as shown in table 5. the logarithmic diagram in fig.8 shows that the increase in size is directly proportional to the number of transferred rows. figure 6. the synchronization time required for each test application with different record counts, in seconds, on logarithmic scale. table 3. the time needed to synchronize one record for each test applications in different package sizes. number of rows soap sync time (s/record) rest sync time (s/record) nosql sync time (s/record) 1 0.06533 0.33833 6.67100 10 0.01280 0.03390 0.67633 100 0.00393 0.00621 0.06169 1,000 0.00309 0.00376 0.00817 10,000 0.00341 0.00343 0.00539 50,000 0.00451 0.00433 0.00526 table 4. the synchronization time required for the soap and rest based test applications with different record counts, in seconds, without data parsing and persisting. number of rows soap sync time – without parsing (s) rest sync time – without parsing (s) 1 0.044 0.278 10 0.090 0.239 100 0.134 0.243 1,000 0.815 0.764 10,000 6.842 3.589 50,000 26.540 7.020 figure 7. the synchronization time required for the soap and rest based test applications with different record counts, in seconds, without data parsing and persisting. figure 5. the synchronization time required for each test application with different record counts, in seconds. table 2. the synchronization time required for each test application with different record counts, in seconds. number of rows soap sync time (sec) rest sync time (sec) nosql sync time (sec) 1 0.065 0.338 6.671 10 0.128 0.339 6.763 100 0.393 0.621 6.169 1,000 3.094 3.757 8.169 10,000 34.084 34.324 53.922 50,000 225.444 216.492 262.898 table 5. the size of the data packages using xml and json format, in kilobytes for different record counts. number of rows soap xml size (kb) rest json size (kb) 1 0.727 0.272 10 6.200 3.700 100 55.400 32.900 1,000 554.400 331.600 10,000 5,734.000 3,481.600 50,000 29,286.000 17,920.000 pál and láner hungarian journal of industry and chemistry 98 the last measured value is the size of mobile database after data synchronization. the soap and rest implementations have the same database size because both of them used an sqlite database with the same data. this is the reason why only sqlite and couchbase lite databases were compared in table 6. as shown in table 6 and fig.9, the size of the couchbase lite database is much bigger than that of sqlite. the difference increases as the amount of data rises. 4. conclusion finally, we need to state that soap performed surprisingly well during the experiment performance tests. the biggest limitation with regards to it is the minimal support in mobile development. because in enterprise companies soap is still the most common technique this architecture is still popular. more measurement data confirmed that there is a common key point where there is only a minimal difference between the selected solutions. this point is around 1,000 records per transaction, which is the point where it does not matter which solution is used. this is not the optimal point of performance for all solutions but it could be a good compromise. the best choice is the rest synchronization, if the goal is to quickly implement a customizable, reliable, scalable, and extendable, cloud-ready modern solution. any amount of data is supported from small datasets to big data solutions. the bottleneck of this solution occurs during data processing. the best choice is the soap synchronization if the goal is to create an enterprise-ready highly secure and auditable solution. this solution is not recommended for big data environments, but up to medium amounts of data, it could offer a real alternative to restful service. working with soap has many limitations in mobile development. nosql is the best choice for big data environments where a very large amount of data needs to be processed and there is a limited time for development. acknowledgement we acknowledge the financial support of this work by the hungarian state under the vksz_12-1-2013-0088 project. references [1] fielding, r.t.: architectural styles and the design of network-based software architectures, ph.d. dissertation, university of california, irvine, 2000 [2] duvander, a.: json's eight year convergence with xml, 2013 www.programmableweb.com/ news/jsons-eight-year-convergence-xml/2013/12/26 [3] smith, j.: android asynchronous http client, 2016 loopj.com/android-async-http table 6. the size of the database on the client device using sqlite and couchbase lite databases for different record counts. number of rows sqlite database size (kb) couchbase lite database size (kb) 1 3,993.600 7,168.000 10 4,003.840 7,372.800 100 4,044.800 7,536.640 1,000 4,167.680 8,325.120 10,000 5,457.920 15,656.960 50,000 14,704.640 47,462.400 figure 8. comparison of the size of the data packages between the xml and json format on a logarithmic scale. figure 9. comparison of the size of the databases between the sqlite and couchbase databases. hungarian journal of industry and chemistry vol. 44(2) pp. 99–104 (2016) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2016-0012 refrigerator optimal scheduling to minimise the cost of operation roland bálint and attila magyar faculty of information technology, university of pannonia, egyetem u. 10, veszprém, 8200, hungary the cost optimal scheduling of a household refrigerator is presented in this work. the fundamental approach is the model predictive control methodology applied to the piecewise affine model of the refrigerator. the optimisation could not be solved using off-the-shelf tools, e.g. multi-parametric toolbox, so a binary treebased optimal scheduling algorithm has been developed for this problem. keywords: optimal scheduling, model predictive control, operating cost minimization, modelling, day-ahead market 1. introduction environmental awareness is trendy in modern societies. policy-makers tend to prefer green energy, e.g. solar, wind, etc. in order to decrease carbon footprints. the demand-and-supply-based nature of the electricity market has led to hourly electricity prices in day-ahead markets [1]. most people seek the cheapest solution by using their appliances during low price periods, however, there are certain devices, e.g. refrigerators work all day long. in this case, the only opportunity lies in the optimal scheduling of the cooling periods. the prescribed inside temperature of the refrigerator makes the problem difficult to solve. *correspondence: balint.roland@virt.uni-pannon.hu 2. problem statement in a day-ahead market, the service provider provides the hourly electricity price for the next day. the problem to be solved is the optimal scheduling of a given refrigerator based on the forthcoming electricity prices. as a constraint, the refrigerator temperature must be kept within given boundary values. 2.1. energy price the service provider provides the electricity price for the next 24 hours (dam: day-ahead market). fig.1 shows the electricity price [2] over a week, each line corresponds to the price of a day. figure 1. electricity price of a day-ahead market over a week [2]. day: monday tuesday wednesday thursday friday saturday sunday bálint and magyar hungarian journal of industry and chemistry 100 2.2. refrigerator model in order to describe the dynamics of the thermal behaviour of the refrigerator, the electric substitution model of fig.2 can be used, where the red voltages correspond to the inner air temperature (uair) and the cooled back wall (uwall). the blue elements are the inputs to the system: the outer air temperature (uout) and the on/off switch (s). the capacitors demonstrate the heat capacity of the back wall (cwall) and the inner air (cair) while the resistors are the heat transfer coefficients between the components. 2.2.1. cooling dynamics the first case is when the switch s is closed, i.e. the refrigerator is cooling. the dynamics of the system can be described by the state-space model of the form outlined in eqs.(1) and (2), where the state and input vectors are given in eqs.(3) and (4). ! = a x + b u (1) y = c x + d u (2) ! = !!"# !!"## (3) ! = !!"#! (4) the parameters of the state-space model of the cooling dynamics are given as follows: !!" = − !!!!! !!∙!!∙!!"# ! !!∙!!"# ! !!∙!!"## − ! !!∙!!"## + ! !!""#∙!!"## (5) !!" = ! !!∙!!"# 0 0 !!""# !!""#∙!!"## (6) ! = 1 0 0 1 (7) ! = 0 0 0 0 (8) 2.2.2. reheating dynamics the second case is when the switch s is open, i.e. the refrigerator is reheating to environmental temperature. the system is still linear and time invariant as outlined in eqs.(3) and (4). the parameters of the state-space model are given in eqs.(9)-(12). !!"" = − !!!!! !!∙!!∙!!"# ! !!∙!!"# ! !!∙!!"## − ! !!∙!!"## (9) !!"" = ! !!∙!!"# 0 0 0 (10) ! = 1 0 0 1 (11) ! = 0 0 0 0 (12) 2.3. control aim the aim of this study is to schedule refrigerator's operation to minimise the operational costs with the following assumptions: • the operational cost is the energy consumption of the refrigerator during the day; • the price of electricity changes hourly; • the energy price is known for 24 hours in advance; • the temperatures must be between the following operating constraints: o the inner air temperature should be between 0.1 ºc and 5.5 ºc; o the cooled back wall temperature should be between -19 ºc and 7 ºc; • the outer air temperature is constant; • the input variable is binary (on/off); • the models should be chosen based on the value of the input. the main objective is to minimize the operational costs, defined as !"#$ = !! ∙ !!!!! !!! (13) where pk is the price of electricity and uk is the input at time ts ⋅ k (ts: sample time). 3. optimal scheduling to find the optimal scheduling of a system the model predictive control approach is used. afterwards a novel heuristic optimisation technique is presented. 3.1. model predictive control of the system for optimization, the multi-parametric toolbox 3.0 (mpt) [3] is used first, because in this matlab toolbox we can find all the necessary options can be found: • ‘piecewise affine’ (pwa) modelling for linear time invariant (lti) systems; • optimal controller design for pwa systems. figure 2. electric substitution model of a refrigerator. s symbolizes the switch of the devices controlled by a thermostat in an ordinary refrigerator. refrigerator optimal scheduling 44(2) pp. 99–104 (2016) doi: 10.1515/hjic-2016-0012 101 the solver uses a cost function as follows: !"# | !!!! |! + | !!!! |!!!! !!! , (14) where variables xk and uk are the state and input vectors at the kth step of the prediction horizon n. the || · ��p expression is the standard p vector norm, and qx and qu are penalty matrices. the mpt toolbox for the pwa system description uses discrete time models, thus initially the continuous time model must be discretised. however, there are two problems to solve: • the penalty matrices (qx and qu) cannot be changed, so the actual electricity price cannot be used in this form; • the time information of the system, e.g. system time, is unknown. to handle these problems, two supplementary state variables have been introduced. the first counts the time and the second stores the actual energy price. if the refrigerator is switched off the energy price is zero, otherwise it provides the actual price value. one pair of (on/off) systems for every price of each hour needs to be created, during the calculation the model parameters and the price are constants. thus, the choice is based on the state of the binary input and the time value of the state vector. the modified lti state-space models are the following: ! = !!"# !!"## ! ! (15) u = [ s ] (16) φon= 0.9998 0.0001 0 0 0.0004 0.9977 0 0 0 0 1 0 0 0 0 0 (17) !on= -0.0024 -0.045 0 !! (18) ! off= 0.9998 0.0001 0 0 0.0010 0.9988 0 0 0 0 1 0 0 0 0 0 (19) !off= 0 0 0 !! (20) ! = 0.0022 0.028 1 0 (21) ! = 1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1 (22) ! = 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 (23) the hourly changing energy prices are denoted by ph in matrices γ, so there are 24 models with two system dynamics (on and off) in total. the model actually used is chosen based on the input (on and off states) and the third element of the state vector (t: define the model over time so the energy price value). based on the two variables the necessary model is chosen: • if the refrigerator operates, its value is the actual energy price; • if the refrigerator is switched off, it is zero. by the summation of the values of x4 the operational cost is obtained (in €/kwhr) for the operating period. the piecewise affine model of the system is given by eq.(24). !!!! = !!"!! + !!"!! + ! , if ! = 1 !!""!! + !!""!! + ! , if ! = 0 (24) the simulation is very sensitive to some design parameters. these parameters are the sampling time (ts), the prediction horizon size, and the cycle number of the simulation horizon. the correlation between horizon size and simulation time is outlined in table 1 (ts = 5 min). if the horizon is bigger than 12 – 15, the simulation will end in deadlock. the sample time value cannot be too large because the change in one step would be too high and the algorithm would not be able to function properly. the multiplication of the sample time and the horizon yields to predicted time horizon. if the sample time and the horizon are small, the algorithm runs quickly, but with a small pre-determined time interval and cannot calculate the forthcoming electricity prices. as nsim increases, the running accelerates. in the pwa system, only the systems of the simulated time interval are present. if nsim is small, the number of models is small so the algorithm must choose from fewer systems but in that case, the cycle has to run repeatedly as the new pwa system is defined. 3.2. heuristic search algorithm using binary tree growing the general optimizer in the mpt is very slow due to several problem-specific assumptions, e.g. binary input, and the horizon size is bounded so another optimisation algorithm is needed that runs faster and uses problemspecific heuristics. table 1. the simulation time in minutes versus horizon size. size of horizon, 8 10 12 13 calculation time, min 2 8 59 111 bálint and magyar hungarian journal of industry and chemistry 102 3.2.1. base of algorithm in order to find the optimal solution, all input combinations need to be counted over time. trivially, this number can be reduced by deleting those combinations where the system exceeds the operating constraints. in this case, in all steps, the states are duplicated and 1 or 0 (on or off) is added to input vectors so the number of combinations grow exponentially and the simulation time of one cycle grows, too (fig.3). without additional heuristics, the running time of the 18th loop was as high as the mpt simulation with a horizon size of 13. model-related heuristics can be applied to decrease the number of combinations. this rule is simple: between any two input combinations, if the corresponding air and wall temperatures are higher and also the operational cost is greater than or equal to one of the examined combinations then this input combination is not optimal, i.e. it can be ignored. the pseudo code of the algorithm is summarized by algorithm 1. with these heuristics, the number of combinations and the running time of the simulation can be reduced. fig.4 shows the running time of the nth cycle with and without this filtering. this figure shows that without the filter, the simulation time of the 20th cycle is more than 30 minutes but with the filter it is a maximum of 1.5 minutes. algorithm 1 heuristic algorithm procedure optimum searching define: x0 ← initial state �bounds ← bounds of temperatures ph ← electricity prices of a day � h = 1 (actual hour of day) � ts ← sample time [hour] � simtime ← simulation time cost = 0 �sys1 ← reheating dt-lti system sys2 ← cooling dt-lti system u0,0 =[] create: � pwa ← pwa system from sys1 and sys2 loop: �for i = 0 : 1 : simtime/ts do ui,all = [ui−1,all; ui−1,all] (duplicate u) n = size(u) (number of combinations) � k � {1, 2, ..., n} �if 1 < k <= n/2 then ui,k = [ui,k, 1]; else ui,k =[ui,k, 0]; xi+1,k = pwa(xi,k,ui,k) cost ← update cost �k � {1, 2, ..., n} �if xi+1,k �/ bounds then delete xall,k, xall,k and costk n = size(u) k,l�{1, 2, ..., n} � if xi+1,k > xi+1,l and costk > costl then delete xall,k, xall,k, costk else if xi+1,l > xi+1,k and costl > costk then delete xall,l, xall,l, costl n = size(u) � k � {1, 2, ..., n} � opt = min(costk) � optimal solution = uall,opt 3.2.2. algorithm with horizon the algorithm of the mpt uses a horizon to reduce the calculation time for fast online implementation. in the investigated problem, the maximum usable horizon available in mpt is too small. the previous algorithm calculates the optimal solution during a whole day, so the horizon is 24 hour, e.g. if the sample time is 5 minutes then the size of the horizon is 288. this large horizon size causes slow simulations. to decrease this simulation time, a horizon as in the mpt algorithm is defined. this step causes a very large reduction in running time. this time is proportional to the horizon size, but if the horizon is too small the solution would not be optimal. the running times and calculated costs are collected in table 2. figure 3. running time and number of combinations vs number of cycles. figure 4. without the heuristic algorithm, the simulation time of the 20th cycle is more than 30 minutes, but with the heuristic algorithm, it has a maximum of 1.5 minutes. refrigerator optimal scheduling 44(2) pp. 99–104 (2016) doi: 10.1515/hjic-2016-0012 103 the running times in table 2 show that by increasing the horizon size the simulation time increases, too. the operating cost increases, but it is uncertain whether a bigger horizon is better. based on this, the suggested heuristic search-based optimization algorithm can be used as a basis for a special model predictive scheduling/control algorithm. 4. results and discussion the model predictive control algorithm in the mpt did not work correctly due to the serious limitations connected to the control task. by increasing the horizon size, the simulation becomes slow with maximum horizon size of 13. the proposed optimization algorithm has been developed to find the optimal scheduling. table 2 shows the difference between simulation times and operating costs if the horizon size is changed. fig.5 shows the calculated optimal scheduling for wednesday. fig.6 shows the energy prices and the number of input combinations of the ith cycle without and without a horizon size of 4 hours. there is a correlation between the monotonous energy price and the number of input combinations. if the price is increased the number opf combinations increases, too. simulations of energy prices for a whole week with and without horizon size of 4 hours (ts = 5 minutes) have also been performed. the results are shown in table 3. the simulation times were reduced by 70-90% while the costs grew only by 1-2%. table 2. the size of horizon, the simulation time in minutes and the cost of best solution. size of horizon running time cost deviation from optimal none (∞) 75.0 0.20235 0% 24 5.7 0.20427 +0.95% 36 12.6 0.20433 +0.98% 48 16.9 0.20394 +0.79% 60 25.9 0.20413 +0.88% 72 31.0 0.20456 +1.09% figure 5. the optimal scheduling for wednesday’s energy prices. figure 6. wednesday energy prices and the number of input combinations of the ith cycle with and without a horizon size of 4 hours. bálint and magyar hungarian journal of industry and chemistry 104 5. conclusion a heuristic search algorithm has been implemented for the optimal scheduling of a refrigerator model. this work was initiated by the fact that the optimization algorithm of the mpt did not work correctly with large horizon sizes for the applied piecewise affine system. the proposed algorithm calculates the optimal input sequence for a whole day with any horizon size but it also works with an infinitely large horizon. the calculation time is fast compared to that of the matlab mpt solver. our own heuristic algorithm is faster without a horizon than the mpt solver with horizon size of 13 hours. i can be run with a larger horizon size, and can yield the absolute optimum without a prediction horizon. the operating cost of the solution is 12 percent less with the aid of a heuristic search. this cost is 25 percent cheaper than the cost of traditional refrigerator control. the suggested heuristic search-based optimization algorithm can be used as a basis of a special model predictive scheduling/control algorithm. the present work is based on an ideal refrigerator model. as a future step, the validation of the model and the scheduling algorithm in an mpc framework will be investigated. testing the control scheme in a real situation with random disturbances, e.g. opening the refrigerator’s door, etc. will also be performed. symbols a state matrix b input matrix c output matrix cair heat capacity of the inside of the refrigerator cwall heat capacity of the back-wall dam day-ahead market dt-lti discrete time linear time invariant f constant input or disturbance φ off off state discrete time state matrix φ on on state discrete time state matrix γ off off state discrete time input matrix γ on on state discrete time input matrix lti linear time invariant mpc model predictive control mpt multi-parametric toolbox pwa piecewise affine qu penalty matrix of u vector in mpt qx penalty matrix of x vector in mpt rcool heat resistance of the back-wall re heat resistance between back-wall and inner air ri insulation of refrigerator s binary state switch tair inner air temperature of refrigerator tout outer room temperature twall cooled back-wall temperature of refrigerator u input vector uk input vector value in kth sample moment in dt uair voltage corresponding to inner air temperature ucool voltage corresponding to minimum reachable back-wall temperature uout voltage corresponding to outer air temperature uwall voltage corresponding to cooled back-wall temperature x state vector xk state vector value in kth sample moment in dt acknowledgement this research is supported by the national research, development and innovation office nkfih through grant no. 115694. a. magyar was supported by the jános bolyai research scholarship of the hungarian academy of sciences. the authors would like to express their gratitude to prof. katalin hangos and dr. gyula simon for useful discussions. references [1] huisman, r.; huurman, c.; mahieu, r.: hourly electricity prices in day-ahead markets, energy econ. 2007 29(2), 240–248� doi 10.1016/j.eneco.2006.08.005 [2] nord pool: elspot prices, www.nordpoolspot.com/ market-data1/elspot/area-prices/all1/hourly, 2016 [3] herceg, m.; kvasnica, m.; jones, c.; morari, m.: multi-parametric toolbox 3.0, proc. eur. control conf., epfl-conf-186265 (zurich, switzerland) 2013 table 3. differences in optimal operating cost and simulation time with and without a horizon. without horizon 4 hour horizon difference in percent day of the week cost, 1/kw time, min cost, 1/kw time, min cost, 1/kw time, min monday 0.20235 75 0.20394 16.9 +0.79 -77.47 tuesday 0.20200 1013.2 0.20650 78.9 +2.23 -92.21 wednesday 0.27748 234 0.28111 48.8 +1.31 -79.18 thursday 0.22255 116.1 0.22739 38.3 +2.17 -67.04 friday 0.23127 267.7 0.23618 32.3 +2.12 -87.93 saturday 0.25819 222.3 0.26281 45.1 +1.79 -79.70 sunday 0.27286 100.4 0.27488 18.7 +0.74 -81.34 hungarian journal of industry and chemistry vol. 44(2) pp. 105–111 (2016) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2016-0013 modelling a three-phase current source inverter lászló neukirchner* and attila magyar department of information technology, university of pannonia, egyetem u. 10, veszprém, 8200, hungary a current source inverter model has been developed in the given paper that is constructed from six lti models for the different switching modes. the overall model is in a piecewise affine form that supports the use of model predictive control. the model has been verified against engineering expectations and its open-loop performance shows that it is a promising basis of model predictive control structures. keywords: model predictive control, current source inverter, space vector modulation, modelling, simulation 1. introduction in industrial applications power electronic converters are divided into two major classes, namely voltage source (vsi) and current source inverters (csi). as a vsi employs modulating the voltage wave through the inverter’s legs, its counterpart relies on modulated current waveforms. to operate a vsi the inverter’s switching devices should operate in a specified alternating modulation to avoid shorting the inverter’s legs, while its current source counterpart could embed this operation into the modulation. thyristor rectifiers suffer from several drawbacks, e.g. high-input current harmonic distortion or a low power factor. pulse width modulated current-source inverters, on the other hand, are free from the above-mentioned drawbacks. in such cases, a smoothing lc filter is placed on the ac side and a choke inductor dc side to reduce the harmonic injection resulting from the current modulating pwm operation. in the case of sinusoidal supply voltages, an input power factor with unit value can be achieved if both requirements are met. in conventional control structures, pwm-csr is usually operated by off-line patterns and look-up tables like in trapezoidal modulation and selective harmonic elimination. the use of these techniques simplifies the calculation of the gate control signals with the special requirements of applied switches like igbts. input filtering, on the other hand, may result in oscillatory transient behaviour. this can be attenuated by adding damping resistive elements, but using them also reduces the overall efficiency. space vector modulation (svm) has proven to result in a high voltage gain, reduced switching frequency and low *correspondence: neukirchner.laszlo@uni-pannon.hu current harmonic distortion, and could be straightforwardly implemented in digital systems [1]. in the second section, the structure of the investigated inverter is presented. in the next section, a detailed open-loop model is presented, and in the fourth section a predictive strategy is chosen for controlling svm. 2. inverter structure the current source inverter normally requires threephase inductive and capacitive filtering (lf and cf, respectively), improving the load current and voltage waveform’s harmonic distortion, and in thermistor appliances assisting the commutation of the switching devices. the legs of the device should include protective diodes, otherwise the absence of a current path introduces a high-voltage spike, causing damage to the switching devices [2]: • the switching devices used are symmetrical, they do not require freewheeling diodes. • the current source inverter produces a threephase pulse-width modulated current instead of a pulse-width modulated voltage. as such, a capacitor needs to be installed on the output for filtering purposes. the high voltage derivative is associated with the vsi. • the rate at which the dc current rises is limited by the dc choke, allowing sufficient time for the protection circuit to function in the case of a short circuit at the inverter output terminals. • as a restraint, the dc link current cannot be instantaneously changed, which resulted in a reduction in dynamic performance. neukirchner and magyar hungarian journal of industry and chemistry 106 3. open-loop switched model with space vector modulation 3.1. space vector formulation the switched model of the three-phase csi supplying a three-phase load through an lc filter and rl load is shown in fig.1. the lc filter is a low-pass filter included with the three-phase csi to decrease the thd by eliminating higher order harmonics. the implemented lc filter includes a resistor rf in series with a capacitor cf. this resistor provides a passive damping solution and it was recommended to be within the range of 0.5 to 1 ω. moreover, the resistor rdc represents any start-up pre-charging resistance or any resistance in series with the dc voltage source vdc. for constructing the model the following assumptions are made: • the lc filter and the rl load’s circuit components are symmetric. • only a continuous conduction mode is assumed. • each time, the switch state index s is known. • the switching devices used for modulation are assumed �to be ideal, with zero losses and switching is consid �ered to be instant. • no external disturbance is assumed. • no magnetic coupling between the inductances is �assumed. with the above assumptions, the equation system of the inverter, filter and load for all the switching states can be created, as different state-space models [3, 4]. under the above-mentioned constraints, the three-phase current source inverter has nine switching states as can be seen in table 1. these switching states can be classified as zero switching states (i0) and active switching states (i1, ..., i6). in addition, there are three zero states which implies vertical conduction of the inverter leg. this implies that the source is shorted, leading to ia = ib = i c = 0. this operating mode is often referred to as the bypass operation. assuming that the operation of the inverter is three-phase balanced then eq.(1) applies ia + ib + ic = 0 (1) according to fig.2, the five active vectors can be expressed as: !! = ! ! !!"e ! !!! ! !! ! ! , k = 1, 2, …, 6 (2) the active and zero vectors are assumed to be stationary, on the contrary, the current reference vector iref in fig.2 rotates with an angular velocity ω = 2πf, and θ ! = ω ! !" + θ 0 ,! ! where f is the fundamental frequency of the inverter output current and θ is the angular displacement. a desired vectorial length and angle, iref can be calculated from the neighbouring space figure 1. current source inverter with an lc filter and rl load. table 1. switching states of svpwm modulated csi. active switches ia ib ic space vector zero states s1, s4 0 0 0 i0 s2, s5 s3, s6 active states s6, s1 idc -idc 0 i1 s1, s2 idc 0 -idc i2 s2, s3 0 idc -idc i3 s3, s4 -idc idc 0 i4 s4, s5 -idc 0 idc i5 s5, s6 0 -idc idc i6 modelling a three-phase current source inverter 44(2) pp. 105–111 (2016) doi: 10.1515/hjic-2016-0013 107 vectors (fig.3), based on the switching pattern and frequency of the inverter. as iref passes through the vectorial spaces, different switch sets are applied to formulate the desired output. as a result, when iref rotates one revolution, the output continues for one cycle based on the fundamental frequency. 3.2. calculating dwell-time the dwell time for stationary vectors represents the time that space vectors spend in a sector during ts. the basic method used for dwell-time calculations is the so-called ampere-second balancing principle. the main idea behind it is that the product of the sampling period ts and the reference vector iref is equal to the sum of the current vectors multiplied by the time interval of chosen space vectors. with small enough ts, iref can be assumed as constant over a period. with this notion, the reference current is approximated from the neighbouring vectors corresponding to the actual sector and from the zero vector for adjusting the length. the ampere-second balancing principle is given by !!"#!! = !!!! + !!!! + !!!! !! = !! + !! + !! (3) where t0, t1, and t2 denote the dwell times of the vectors i0, i1, and i2. from eq.(2), the individual values of space vectors in sector i are defined in eq.(4): !!!! = ! ! !!"e !!!! !!!! = ! ! !!"e !!! !!!! = 0 (4) projecting the resulting complex vector onto the real and imaginary axes leads to: !!"# cos θ !! = !!"(!! + !!) !!"# sin θ !! = ! ! !!" −!! + !! . (5) solving eqs.(3) and (5) yields the dwell times t0, t1, and t2 at any given θ angle as shown in eq.(6): !! = !! sin (!! − θ)!! !! = !! sin (!! + θ)!! !! = !! − !!−!! for − ! ! ≤ θ ≤ ! ! , (6) where ma = | iref | / idc is the modulation index in the domain: ma ∈ [0, 1]. when iref is inside of other sectors a multiple of π/3 is subtracted from θ so that the modified angle σ happens to fall within the range of − ! ! ≤ θ ≤ ! ! for use in eq.(7): σ = θ − (! − 1) !! ! = 1, 2,… , 6 for − ! ! ≤ θ ≤ ! ! , (7) where s is the sector index. this method save sthe need for implementing unnecessary calculations and code capacities. 3.3. switching sequence as far as designing the switching pattern of the svm for the csi a few notions should be specified for switching loss reduction: • the state transition should involve the least amount of switches (one switch is desired). • minimum amount of switches should be involved as iref transits from the current to the next state. figure 2. a typical space vector diagram for the csi. i1, ..., i6 are the active vectors, i0 is the zero vector, ω is the angular velocity, θ is the angular displacement and the cartesian coordinate system represents the imaginary and real axes. the active vectors form a symmetric hexagon with six identical sectors, while the zero vector i0 lies at the center of the hexagon. figure 3. calculation of iref in sector i, where the cartesian coordinate system represents the imaginary and real axes. neukirchner and magyar hungarian journal of industry and chemistry 108 the typical sequence can be observed in table 2. iref is created by i1, i2, and i0 with the mentioned dwell time rule 6. ts can be divided into three or more segments (t0, t1, and t2) according to the desired thd value of the output current. from the above, a continuous switching sequence for the svpwm modulation can be obtained by eq.(8): !!, !!!!, !! ! = 1, 2,… , 5 !!, !!, !! ! = 6 , (8) where k is the sector index. 3.4. obtaining open-loop ‘piecewise affine’ model with every state vector i0, i1, ..., i6 a different switch configuration and a different circuit configuration is present at a given time. for every case the circuit’s state equations can be written in continuous state-space form: !(!) = !!! ! + !!!(!) !(!) = !!!(!) s = 0, 1,… , 6 , (9) where as is the sth state matrix, bs is the sth input matrix, cs is the sth output matrix, x(t) and u(t) are space vectors, and s represents the space vector index with s = 0 as the zero state and s = 1, 2, …, 6 as the active states. since all the equation systems have the same input (bs) and output (cs) matrices they will be referred to as b and c matrices. any linear circuit can be represented by a number of differential equations equal to the number of energy storage units in the circuit. however, in three-phase balanced circuits, the number of equations can be reduced by a third factor because any three-phase quantity can be expressed in terms of the other two phase quantities. therefore, since currents flowing through lf and ll and voltages across cf are three-phase balanced quantities only four linear differential equations representing the ac side and one linear differential equation representing dc current across ldc are needed. hence, linear differential equations for the state variable x = !!"!!!!"!!!!"!!!! !, input variable u = vdc and output variable y = [ir is]t can be derived using kvl and kcl. arranging the expressions for the aforementioned state variables and recognizing vdc as the input of the system, yields the following state-space matrices for the zero switching state as shown in eqs.(10)-(12): !! = − !!" !!" 0 0 0 0 0 − ! !! 0 − ! !! ! !! 0 0 − ! !! − ! !! − !! !! 0 !! !! ! !! !! !! 0 0 ! !! ! !! 0 !! !! (10) ! = − ! !!" 0 0 0 0 ! (11) ! = 0 0 0 1 0 0 0 0 0 1 , (12) where qa = c(3r + rf), qb = rrf + 3rrl + rfrl and qc =(3r + rf)(lf + ll). 3.5. open-loop performance as csi exhibits different lti regions for different state matrices a0, a1, ..., a6 according to the used space vector i0, i1, ..., i6 in the corresponding dwell time, the piecewise affine approach (pwa) can be used to describe the overall dynamics. the discrete time piecewise affine model can be obtained by discrediting the set of continuous affine models in the form of eq.(13) !!!! = φ!!! + ! !! , if !! !! ∈ !! ⋮ φ!!! + ! !! if !! !! ∈ !! (13) such systems are composed of s local affine models whose parameters in (φs) change according to which polyhedron pk contains the state vector. � the simulated waveforms for vdc = 400 v dc link with pre-charge resistance rdc = 1 ω and choke inductance ldc = 2e−1 h using the space vector modulation as shown in fig.5, where ia denotes the pwm current of the inverter and ir stands for the phase current through the load. the inverter operates at a fundamental frequency of f = 50 hz. the filter capacitor c f = 20e−6 f, the filter inductance lf = 10e−3 h with filter resistance rf = 1 ω and r = 1 ω representing losses. the inverter consists of three-phase balanced inductive load ll = 2e−3 and resistive load rl = 5 ω. the open-loop performance can be observed in fig.4 and the modulation and pwm formulation in fig.5. table 2. typical switching sequence for sector i. the sequence was repeated twice to achieve a smoother output signal. in this case, the sampling period ts is one 12th of the fundamental time period. the active switch pairs are s6, s1 and s1, s2 for space vectors i1 and i2. the chosen zero state (with switches s1, s4) is chosen for i0 such that the minimum switching loss requirement is met. vectors i1 i2 i0 i1 i2 i0 s1 x x x x x x s2 x x s3 s4 x s5 s6 x x x dwell time t1 t2 t0 t1 t2 t0 ts ts modelling a three-phase current source inverter 44(2) pp. 105–111 (2016) doi: 10.1515/hjic-2016-0013 109 4. mpc assisted svpwm the aim of the previous sections was to develop a model for the inverter that describes the switching behaviour of the dynamics. the obtained piecewise affine model gives a good basis for the model predictive control technique that is advantageous from two points of view: the possibility of introducing constraints to the state and input variables and the fact that optimal control problems can be formulated within it. the aim is to find the optimal space vectors in such a way that the error between the predicted states of the inverter and the chosen reference values are minimized with respect to constraints. previously, the method of model predictive control was reserved only for applications with relatively slow time scales, like plants and chemical processes. the reason for this is that mpc requires an optimization problem to be solved at each sampling instant in order to obtain the control input. over the past decade, more and more applications use fast mpc applications, thanks to the advances in computer technology. the optimization problem is often np hard, and finding a solution is taxing in terms of the calculation time of the control device, thus limiting the rate at which the control could intervene with the application. in particular, model predictive control has been applied in the field of power electronics, where the control frequency ranges from a few hundred hz up to a few mhz [5,6]. the main challenge of implementing mpc consists of solving the associated optimization problem in a bounded time. the predicted values are assumed to be constant after time k. then, the control problem can be formulated as follows: min j (x[k]) �s.t. x[k] = x[k|k] �j(x[k]) = ||!(! ! + ! !]! !!! − xref ([k]))||2 (14) where x[k + j | k] denotes the prediction of the state at time k + j based on the information available at time k, n is the prediction horizon, q is the constant weighting. the optimal state-finding algorithm follows: optimalerror = inf for s = 1 : 7 do !(1) !(2) … !(!) ! = !! 0 ⋯ 0 !! !! ⋯ 0 ⋮ ⋮ ⋱ ⋮ !!!!!!! !!!!!!! ⋯ !! ∙ ! 0 ! 1 ⋮ ! ! + !! !!! ⋮ !!! !(0) figure 5. comparison of the inverter output current ia and the filtered load current ir with ts = t /36 and ma = 0.9. the background s’s value indicates the corresponding affine state of the model at a given time. figure 4. three-phase sinusoidal waveform of the csi output currents ia, ib, and ic with a sample period of ts = t/36 and a modulation index of ma = 0.9. the output wave can be smoothened by adding higher filter parameters or further reducing the sampling period. neukirchner and magyar hungarian journal of industry and chemistry 110 errors = js(x) �if errors < optimalerror then optimalerror = errors optimal_s = s where optimalerror represents the minimal error value, error_s is the actual error value in each iteration, and optimal_s is the optimal state. the algorithm uses a parallel implicit mpc scheme for every state. since there are only seven states, with a low horizon the algorithm can be feasibly implemented. when f = 50hz, ! = 37.5a, and n = 2, deviations from the optimal trajectory are present during optimization as shown in fig.6, but they are still acceptable in terms of harmonic distortion. the performance observed in fig.7 can be compared to the open-loop solution. it can be stated that due to the rigid structure of the open-loop modulation’s rigid structure the dynamical properties of the mpcassisted system exhibit better performance in terms of time response and signal shape. 5. conclusion a current source inverter model has been developed in this paper that is constructed from six lti models for the different switching modes using svpwm modulation. the obtained overall model is in a piecewise affine form that supports the use of model predictive control in the future. the model has been verified against engineering expectations and its openloop performance shows that it is a promising basis of further work in terms of identification and control. as the next step, a model predictive control synthesis was performed based on the technology-driven optimality criteria to assist the open-loop svpwm modulated system. due to the implicit mpc-assisted modulation the optimal space vector could be found and utilized in each state over an acceptable timescale due to the low horizon. as such a significantly lower time response and better signal shape was achieved. symbols a state matrix b input matrix c output matrix � cf filter capacitance f fundamental frequency φ discrete state matrix � γ discrete input matrix i0,i1,..., i6 space vector � ia, ib, ic inverter output currents per phase figure 6. mpc reference tracking with f = 50hz, !̂ = 37.5a, and n = 2. in order to create the simplest implicit mpc for a finite state pwa environment, every affine state was tested with the according horizon in every iteration. figure 7. comparison of classic svpwm and mpc on the same system. the svpwm is applied with a modulation index of 0.9, and the mpc reference tracking with f = 50hz, !̂ = 37.5a, and n = 2. modelling a three-phase current source inverter 44(2) pp. 105–111 (2016) doi: 10.1515/hjic-2016-0013 111 idc dc link current ir, is, it load currents per phase iref reference current value k sector index lf filter inductance ll load inductance � lti linear time invariant ma modulation index mpc model predictive control νcr triangular carrier wave for tpwm νm modular wave for tpwm p discrete time index p space vector containing polyhedron pwa ‘piecewise affine �’ current source inverter (csi) pwm pulse width modulation r loss resistance rdc dc link start-up pre-charging resistance rf filter resistance rl load resistance s space vector index s1, s2,..., s6 switching devices σ modified angle she selective harmonic elimination svpwm space vector pulse width modulation t fundamental cycle time �tk dwell time of corresponding space vectors �ts sampling period tpwm trapezoidal pulse width modulation θ angular displacement u input vector � vdc dc link voltage source value !!!!", !!!!",!!!!" filter capacitance’s voltage x state vector y output matrix � ω angular velocity acknowledgement this research is supported by the national research development and innovation office (nkfih) through grant no.115694. a. magyar was supported by the jános bolyai research scholarship of the hungarian academy of sciences. references [1] espelage, p.; nowak, j.m.; walker, l.h.: symmetrical gto current source inverter for wide speed range control of 2300 to 4160 v, 350 to 7000 hp induction motors, ieee ind. appl. soc. conf. (ias) 1988 1, 302–307 doi 10.1109/ias.1988.25079 [2] wu, b.: high-power converters and ac drives (wiley-ieee press, new jersey, usa) 2006 [3] ma, j.; wu, b.; rizzo, s.: a space vector modulated csi-based ac drive for multi-motor applications, ieee trans. power electron., 1999 16(4), 535–544 doi: 10.1109/apec.1999.750460 [4] wiseman, j.; wu, b.; castle, g.s.p.: a pwm cur �rent source rectifier with active damping for high power medium voltage applications, ieee power electron. spec. conf. (pesc) 2002 1, 1930–1934 doi: 10.1109/psec.2002.1023096 [5] mariéthoz, s.; morari, m.: explicit modelpredictive control of a pwm inverter with an lcl filter, ieee trans. ind. electron. 2008 56(2), 389– 399 doi: 10.1109/tie.2008.2008793 [6] mariéthoz, s.; almér, s.; baja, m.; beccuti, a.g.; patino, d.; wernrud, a.; buisson, j.; cormerais, h.; geyer, t.; fujioka, h.; jonsson, u.t.; kao, c.y; morari, m.; papafotiou, g.; rantzer, a.; riedinger, p.: comparison of hybrid control techniques for buck and boost dc-dc converters, ieee trans. control syst. technol. 2010 18(5), 1126–1145 doi: 10.1109/tcst.2009.2035306 hungarian journal of industry and chemistry vol. 44(2) pp. 113–120 (2016) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2016-0014 computational stability analysis of lotka-volterra systems péter polcz1,∗ and gábor szederkényi1,2 1 faculty of information technology and bionics, pázmány péter catholic university, práter u. 50/a, budapest, 1083, hungary 2 systems and control lab, institute for computer science and control, hungarian academy of sciences, práter u. 50/a., budapest, 1083, hungary this paper concerns the computational stability analysis of locally stable lotka-volterra (lv) systems by searching for appropriate lyapunov functions in a general quadratic form composed of higher order monomial terms. the lyapunov conditions are ensured through the solution of linear matrix inequalities. the stability region is estimated by determining the level set of the lyapunov function within a suitable convex domain. the paper includes interesting computational results and discussion on the stability regions of higher (3,4) dimensional lv models as well as on the monomial selection for constructing the lyapunov functions. finally, the stability region is estimated of an uncertain 2d lv system with an uncertain interior locally stable equilibrium point. keywords: nonlinear systems, lotka-volterra models, stability analysis, linear matrix inequalities, lyapunov function 1. introduction approximating the domain of attraction (doa) is often a fundamental task in the analysis and control of nonlinear systems. the stability properties of dynamical systems are most often studied using lyapunov functions. therefore, extensive literature exists on the computational construction of lyapunov functions [1]. due to their advantageous properties and the availability of efficient numerical solvers, the use of linear matrix inequalities (lmi) and semi-definite programming (sdp) techniques has become popular in the field of system and control theory. important results were announced [2,3] in the context of linear uncertain systems, their stability analysis and control synthesis. recently, an optimization-based method for doa estimation was published [4], where the authors use finsler’s lemma and affine parameter-dependent lmis to compute rational lyapunov functions for a wide class of locally asymptotically stable nonlinear systems. based on these results an improved method was published [5,6], where the transformation of the model to the form required for optimization is done automatically using the linear fraction transformation (lft) and further automatic model simplification steps, which results in the dimension reduction of the optimization task. as the dimensions of the problem are *correspondence: ppolcz@gmail.com reduced, the method is capable of handling more complex models. for example, the doa is successfully estimated for a 3-dimensional rational uncertain system [6] (bioreactor model with an applied proportional and integral substrate feedback law). the dynamical descriptive power of lotkavolterra systems is so extensive that lv models “have the status of canonical format” within the class of smooth nonlinear dynamical systems [7]. besides modelling biological/ecological environments, they are widely used in other scientific fields like neural networks [8] or in economics, where the goodwinlotka-volterra models are applied for modelling the predator-prey mechanism of the technological substitution [9,10]. in order to model the correlation between the employment rate and the share of wages of the working population, the authors of ref. [11] used a stochastic extension of the goodwin model. some important results that make lv models even more attractive are the existing techniques used to represent a general nonlinear system as a multidimensional lv model [12]. the analysis of stability and behaviour of lv systems is extensive in the literature [13]. plank has shown [14] that ndimensional lv systems are hamiltonian if they fulfil certain algebraic properties (theorem 3.1 in ref. [14]). he demonstrated that, when using an appropriate poisson structure, one can obtain the hamiltonian function of the system, which is a key object in determining the system's doa. furthermore, candidates of hamiltonian function were defined in (section iv in ref. [14]). it is important to note that lv systems are polcz and szederkényi hungarian journal of industry and chemistry 114 kinetic in the sense that they can be formally described as chemical reaction networks with mass action kinetics. in this paper, the local stability properties of lv models are analysed by applying the underlying method presented [6]. the stability region is estimated on a few locally stable 2-, 3-, and 4-dimensional benchmark lv systems. the doa of an uncertain 2d system is also estimated by two concentric regions. the main motivation of our work was to evaluate the applicability of the approach [4] on a general polynomial system class consisting of low-degree monomials, and to study the limits of the method as the number of dimensions of the state space increase. 2. background in this section, the basic notions and results on which our computational method is based are presented. 2.1. system class, lyapunov functions, and the domain of attraction. our computational method can handle general nonlinear systems of the form ! ! = !(! ! , δ ! ) ! ! ∈ ℝ!, !! ∈ !, δ ! ∈ !, δ ! ∈ ! (1) where ! ⊂ ℝ! and !,! ⊂ ℝ! are given polytopes, x is the state vector function with its initial condition x0 = x(0), and δ is a smooth, bounded vector function of uncertain parameters with a bounded time derivative. the applied method is presented in detail elsewhere [15]. from now on, the time arguments of x and δ will be suppressed as is commonly done in the literature. it is assumed that function !:ℝ!×! ↦ ℝ! of eq.(1) is a well-defined smooth rational mapping, with the property f(0, δ) = 0 for all ! ∈ !. additionally, it is assumed that x* = 0 ∈ ℝ! is a locally asymptotically stable equilibrium point of eq.(1) for all δ ∈ !. the set of all initial conditions, from which the solutions converge to x*, is called the domain of attraction (doa). furthermore, it is assumed that function f(x, δ) can be written in a so-called quasi-lpv form f(x, δ) = function a(x, δ) x the aim is to identify an appropriate rational lyapunov function v(x, δ), which satisfies the following conditions: !! ! ≤ ! !, δ ≤ !! ! ,∀(!, δ) ∈ !×! ! !, δ, δ ≤ −!! ! ∀(!, δ, δ) ∈ !×!×! (2) where vl, ux, vd are continuous positive functions on !. due to conditions of eq.(2) any closed level set of the lyapunov function contained entirely in ! bounds an invariant region of the state space. our objective is to find a lyapunov function, which fulfils the conditions of eq.(2) and to determine its maximal invariant level set completely inside !. 2.2. dynamical system representation a lyapunov function can be computed [4] in the form shown in eq.(3). ! !, δ = π!! !, δ !π! !, δ ,π! = ! π (3) where ! ∈ ℝ!×! is a constant symmetric matrix, not necessarily positive definite, and π:ℝ!×! ↦ ℝ! is mapping, in which each element is a monomial in (x, δ), or a smooth rational function with a monomial numerator. the arguments of π and πb will be suppressed below. applications of the linear fractional transformation (lft) and further algebraic steps have been proposed [5,6] to transform the system equation ! = ! !, δ = !(!, δ)! into the desired differential-algebraic representation that was introduced in the same references: ! = ! !, δ ! = !" + !" !! ∈ ! 0 = !!! !, δ π! ! ∈ !, ! ∈ ! (4) where ! ∈ ℝ!×! and ! ∈ ℝ!×! are constant matrices, and !!! !, δ ∈ ℝ!×! is an affine matrix function in (x, δ) also known as an “annihilator”. these transformations also result in the dimension reduction of the optimization problem compared to the results presented in ref. [4]. the representation in eq.(4) separates the linear part of the system (x) from its nonlinear part (π). 3. the sdp problem for estimating the doa in this section, how to construct the semi-definite optimization task (sdp) is presented, which will uniquely characterize an appropriate lyapunov function and its maximal invariant level set εα as an estimate of the true domain of attraction. it is assumed that polytopes !,!, and ! are already given. using the model representation of eq.(4) and a lyapunov function candidate of the form in eq.(3), sufficient lmis for the lyapunov conditions in eq.(2) can be formulated. according to finsler’s lemma (lemma 2.1 in ref. [4]), if real-valued matrices !! ∈ ℝ!×! and !! ∈ ℝ(!!!"!!!!!")×(!"!!!!!") exist ∀ !, δ ∈ ! !×! : ! + !!!!! !, δ +!!! ! !, δ !!! > 0 (5) ∀ !, δ, δ ∈ ! !×!×! : !! + !!! + !!!!! !, δ, δ +!!! ! !, δ, δ < 0 (6) then the conditions of eq.(2) are satisfied for every (!, δ, δ) ∈ !×!×!. variables pa and !!! !, δ, δ are computational stability analysis of lotka-volterra systems 44(2) pp. 113–120 (2016) doi: 10.1515/hjic-2016-0014 115 defined in eqs.(3.16) and (3.22) of ref. [15], respectively. ! ∙ denotes the corner points (vertices) of a given polytope. since the lyapunov conditions are satisfied within !, an attempt is made to identify the maximal α-level set ε! = ! ∈ !|! ! = !, 1 ≤ ! , which lies inside !. that level set will be invariant, in the sense that every trajectory entering this region will never leave it. α ≥ 1is defined, as a free variable of the optimization task, and !! is constrained inside !. one can observe that by maximizing α an unbounded feasible solution is obtained, as the function v(x, δ) can be scaled arbitrarily. therefore, as fig.1 illustrates, an auxiliary polytope ! is defined around the locally stable origin inside ! , constraining the 1-level set !! = ! ∈ !|! ! = 1 to be around !. according to finsler’s lemma, for every ! = 1,!! and ! = 1,!!, if real-valued matrices !!! , !!! ∈ ℝ!×!, !!! ,!!! ∈ ℝ(!!!)×! exit !!!!!! (!) !, δ !! ≥ 0 ∀ !, δ ∈ ! ℱ!!×! (7) !!!!!! (!) !, δ !! ≤ 0 ∀ !, δ ∈ ! ℱ! !×! (8) then !! is inside ! and !! is around !. variables !! , !! , !!! (!), and !!! (!) are defined in eqs.(3.34) and (3.36) of ref. [15], ℱ!! denotes the kth facet of !, furthermore, !! denotes the number of facets of !. the lmi conditions of eqs.(5)-(8) are affine parameter-dependent lmis, which can be computationally handled by checking their feasibility at the corner points of the polytopic region, on which the parameters !, δ, δ are defined. depending on the number of the corner points, a given number of parameter independent lmi conditions (table 1) is obtained. the sdp task can be summarized as follows. in order to find the maximal invariant level set !! of the lyapunov function, one should maximize α, under the following conditions: eq.(5) ! !, δ is positive on !×! eq.(6) ! !, δ, δ is negative on !×!×! eq.(7) !! lies inside ! eq.(8) ! is inside !! the number of lmis and their dimensions are given in table 1, furthermore, the free variables of the optimization task are listed in table 2. figure 1. illustration of the conditions regarding ! and ! . inside polytope ! of the lyapunov conditions in eq.(2) are required. the α-level set ε! of the lyapunov function should lie inside polytope ! (hence it is invariant). the 1-level set ε1 should be around polytope !. this condition ensures that the problem has a bounded solution. table 2. free variables of the optimization task and the number of (scalar) symbolic decision variables they introduce into the optimization task. matrix variable number of (scalar) independent decision variables appearing in the sdp α 1 p ½ m(m+1) lb mq la (n + 2p + n2 + np)(2q + n2 + nq) !!!and !!!! !!! +!!!×!" !!!and !!!! !!! +!!!×(! + 1)! the dimensional parameters are the following: n number of state variables (size of x) p number of elements in π m number of elements in πb (n + p) q number of rows in annihilator !!!(!, δ) !! number of corner points of ! !! number of corner points of ! !! number of corner points of ! !!! number of corner points of !! table 1. number and dimensions of parameter independent lmis of the optimization task. dimension of the lmis no. of lmis eq.(5) m !! ∙!! eq.(6) n + 2p + n2 + np !! ∙!! ∙!!! eq.(7) m + 1 2!! ∙!! eq.(8) m + 1 2!! ∙!! figure 2. polytope ! is evaluated through iterations considering the bounding box of the obtained α-level set. polcz and szederkényi hungarian journal of industry and chemistry 116 3.1. finding the most appropriate outer polytope in the case of 2d systems, polytope ! is evaluated manually through iterations. when having a higherdimensional system (n ≥ 3), the iterative procedure [6] is applied that starts from an initial polytope !(!), then a new polytope !(!) is defined by enlarging the axis aligned bounding box of the obtained α-level set ε!(!). during the iterations, !(!) is constrained to be a rectangular polytope. fig.2 illustrates the operation of a single iteration step. 4. lotka-volterra systems the n-dimensional lv equation has the form ! = !"#$ ! + ! , ! ∈ ℝ!×!, ! ∈ ℝ!, (9) where diag(a), ! ∈ ℝ! denotes an n × n square diagonal matrix with the x1, …, xn on the main diagonal. the system is translated into its, by assumption, unique interior equilibrium point !∗ = −!!!! by introducing the centred state vector ! = ! − !∗ . then, an autonomous nonlinear system of the form ! = ! ! ! is obtained, where the matrix function ! can be expressed as: ! ! = !"#$ ! + !∗ !. by applying the lft and the further algebraic model transformation steps, a model is obtained in the representation of eq.(4), where the entries of π(x) are second order monomials of the state variables. 5. numerical results in this section, the applicability of the approach presented above is illustrated through different locally stable lotkavolterra models. the results presented here have been computed in a matlab environment. for symbolic computations, matlab’s built-in symbolic math toolbox was used based on mupad. for linear fractional transformations (lft), the enhanced lfr-toolbox is used [16, 17]. to model and solve semi-definite optimization (sdp) problems, mosek solver with yalmip was used [18]. 5.1. 2d lotka-volterra system a locally stable lv system is considered with the model matrix: ! = -2 -3 1.4 1 , with a unique interior equilibrium point x* = [1 1]t. in fig.3, some trajectories of the centred system can be observed from different initial conditions. the red trajectories converge at the equilibrium point, the blue ones do not tend to the equilibrium point. after solving the corresponding sdp, the obtained lyapunov function is ! ! = π!!!π! (fig.4), where π = !!! !!!! !!! ! , π! = ! π (10) ! = 87.39 63.83 -3.45 0 0 63.83 165.26 67.24 100.85 28.76 -3.45 67.24 7.63 0.15 0 0 100.85 0.15 38.78 39.97 0 28.76 0 39.97 15.53 in fig.3, the shape of the manually chosen polytope !, and the obtained invariant α-level set of the lyapunov function can be seen, which is considered as the estimated doa (filled orange region). areas can be observed, where the lyapunov function's time derivative is positive (green region) can also be observed to be completely outside of !. fig.5 illustrates how the value of the lyapunov function decreases along the trajectories. figure 3. phase diagram of the 2d locally stable system. red trajectories converge at the origin, the blue ones do not converge at the origin. the estimated doa and the used polytope ! are illustrated by the orange-filled region and by the grey-dashed polytope, respectively. the green area highlights the subset of the state space where the lyapunov function features a positive time-derivative. figure 4. the obtained lyapunov function in the case of the 2d lv system. computational stability analysis of lotka-volterra systems 44(2) pp. 113–120 (2016) doi: 10.1515/hjic-2016-0014 117 5.2. 3d lotka-volterra system a locally stable 3d lv system has been chosen with the model matrix ! = 0.06 0.21 0.83 −2.47 −2.10 −3.64 0.06 0.47 −0.45 . similarly to the 2d example, the equilibrium point is set to x* = [ 1 1 1 ]t. the monomial set appearing in πb contains the state variables and every possible 2nd order monomial: π! = !!! !!!! !!!! !!! !!!! !!! (12) matrix p is a 9×9 symmetric matrix. fig.6 illustrates the invariant α-level set of the obtained lyapunov function (3d red volume). in fig.7, one can see the cross-sections of the 3d invariant region from three different viewpoints. some trajectories of the system are shown in red (stable) and blue (unstable). figure 5. in panel a, the obtained invariant level set is shown, furthermore some trajectories x(i)(t) of the system can be seen in different colors with initial conditions !!(!) close to the boundary of the estimated doa. the values of the lyapunov function along the trajectories (v(i)(t)) are presented in panel b, respectively. figure 7. cross-sectional view of the 3d estimate along the major planes xi,xj and using different values for xk, where (i, j, k) is a permutation of (1, 2, 3). figure 6. estimated doa of the locally stable 3d lotka-volterra system (red mesh) and the corresponding final polytope !. polcz and szederkényi hungarian journal of industry and chemistry 118 5.3. 4d lotka-volterra system the method was applied to a locally stable 4d lv system with a unique interior equilibrium point: x* = [ 1 1 1 1 ]t . (13) the model matrix of the lv system was chosen to be: ! = -4.7126 -1.5833 1.5346 2.3230 -9.2461 -3.1634 2.8648 2.7796 -14.258 -4.5477 3.6104 4.6238 -3.1687 -0.8016 1.2287 1.2656 . due to the fact that model matrix a is a “full” matrix, i.e. there are no zero entries in it, every secondorder monomial will appear in the equation of the system. as a consequence, the lft will produce a model eq.(4), in which π will contain every possible second-order monomial. this means that the number of monomials (including the state variables) is mb = (n2 + 3n) / 2 in the case of a “full” model matrix. in table 3, the number and sizes of the lmis have been summarised in the case of n-dimensional lv systems with a “full” model matrix. the exponential factor 2n in table 3 originates from the rectangular shape of polytope ! possessing 2n corner points. on the other hand, the feasibility of lmi conditions in eqs.(7) and (8) should be checked at each corner point of every facet of the polytope. furthermore, an n-dimensional rectangular polytope has 2n facets with 2n-1 corner points. as can be seen, a rectangular polytope introduces an exponential increase in the dimension of the given problem. however, n-dimensional intervals can be easily handled compared to arbitrarily shaped polytopes defined by (hyper)-triangle meshes. fig.8 illustrates the cross sections of the invariant domain along the different pair of axes. 5.4. 2d uncertain lv system with an uncertain equilibrium point in this section, the same 2-dimensional system is presented that appeared in section 5.1 with the same model parameters but with an additional uncertain term kδ, where k = [1 1]t. it is assumes, that δ ∈ ! = -0.1, 0.1 is an unknown constant parameter (δ = 0). the equation of the uncertain model is the following: ! = !"#$(!) !! + !δ + ! (15) table 3. number and sizes of the lmis in the case of n-dimensional lv systems. size number description mb × mb 2n positivity of !(!) ma × ma 2n negativity of !̇(!) mb × mb n ⋅ 2n ε! ∈ !"#(!) mb × mb n ⋅ 2n ! ∈ !"#(ε!) mb is the size of the lyapunov matrix p, ma = ½ (n3 + 5n2 + 4n) is the size of the matrix pa(p), which appears in the lmi ensuring the negativity of the time derivative of the lyapunov function. figure 8. cross-sectional view of the doa estimate of the 4d lv system. computational stability analysis of lotka-volterra systems 44(2) pp. 113–120 (2016) doi: 10.1515/hjic-2016-0014 119 the equilibrium point of the uncertain system is an affine function of the uncertain parameter δ: !∗ δ = !!! −!δ − b = −!!!!δ + !!∗ , (16) where !!∗ is the equilibrium point of the system presented in section 5.1, i.e. when δ = 0. eq.(15) is translated into the following form: ! = !"#$(!)! ! − !∗(δ ) . (17) the centred model of the system around the uncertain equilibrium point x*(δ) can be calculated if the new state vector x = ! – x*(δ) is introduced. the equation of the centred system is the following: ! = !"#$ ! + !∗ δ !" . (18) if the lyapunov function depends on δ, especially when possessing an uncertain equilibrium point, it is not straightforward to determine an invariant region by considering the α-level set of the lyapunov function. however, it is possible to compute a region ℑ, which is “invariant with respect to” a larger region ! (ℑ ⊂ !), in the sense that every trajectory with an initial condition from ℑ will not leave !. in order to compute ℑ and !, the α-level set ε!(δ) of the obtained lyapunov function v(x, δ) is determined in the coordinates system of the original system and at the corresponding equilibrium point for every δ ∈ !. the overlining in the notation ε!(δ) means that this level set is translated into the original coordinates system. as fig.9 illustrates, the intersection ℑ and the union ! of the α-level sets obtained for different values of δ have been computed. it can be stated that every trajectory starting from region ℑ will not leave region !. 6. conclusion in this work, the lyapunov function of n-dimensional lv systems (n = 2, 3, 4) was successfully computed by using the improved optimization-based method [6, 15]. in the case of each deterministic system, an invariant region was given, as the estimated doa. in the case of an uncertain lv system with an uncertain interior equilibrium point, two regions (ℑ ⊂ !) were given, which describe the stable regions of the system. symbols ! denotes the time-derivative of function x(t) lt denotes the transpose of a matrix l !(∙) denotes the corner points of a polytope diag(x) denotes the diagonal matrix x = x(t) ∈ ℝ! represents the state variables of a dynamical system δ ∈ ℝ! vector of uncertain parameters π ∈ ℝ! vector valued function, which represents the set of monomial and rational nonlinear terms to be considered in the lyapunov function π ∈ ℝ!!!!! auxiliary variable denoting !! v(x) denotes the lyapunov function ! ⊂ ℝ!, !,! ⊂ ℝ! bounded polytopes acknowledgement this research was supported by otka nf 104706 references [1] chesi, g.: domain of attraction: analysis and control via sos programming (springer-verlag, london, uk) vol. 415, 2011 doi: 10.1007/978-085729-959-8 [2] boyd, s.; el ghaoui, l.; feron, e., balakrishnan, v.: linear matrix inequalities in system and control theory, in studies in applied mathematics (siam, 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proc. ieee int. symp. computer aided control systems design pp. 25– 29, 2004 doi: 10.1109/cacsd.2004.1393845 [17] magni, j.f.: linear fractional representation toolbox (ver. 2.0) for use with matlab, 2006 www.cert. fr/dcsd/idco/perso/~magni [18] loefberg, j.: yalmip: a toolbox for modeling and optimization in matlab, proc. cacsd conference (taipei, taiwan), 2012 users.isy.liu.se/ johanl/yalmip hungarian journal of industry and chemistry vol. 44(2) pp. 121–128 (2016) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2016-0015 diagnosis of technological systems based on the structural decomposition of their coloured petri net model anna i. pózna,1* miklós gerzson,1 adrien leitold,2 and katalin m. hangos1,3 1 department of electrical engineering and information systems, university of pannonia, po box 158, veszprém, 8201, hungary 2 department of mathematics, university of pannonia, po box 158, veszprém, 8201, hungary 3 institute for computer science and control, hungarian academy of sciences, po box 63, budapest, 1518, hungary diagnosing faults during the operation of a system is an essential task when investigating technological systems. in this paper, a new online fault identification method is proposed which is based on the occurrence graph of the coloured petri net model of the system. the model is able to simulate the normal and faulty operations of the system given in the form of event lists, so called traces. the diagnosis is based on the search for deviations between the traces of the normal and the actual operations. in the case of complex technological systems, the occurrence graph can contain hundreds of nodes; therefore, the computational effort and searching-time increase significantly. our proposed structural decomposition method can manage these demands so it has a crucial impact on the practical application of diagnostic processes. the main idea of our method is that the complex systems can be decomposed into technological units. therefore, the diagnosis can be done by components separately and the diagnostic result of a unit can be used for the diagnosis of the other units connected to it. because of the structural decomposition, the diagnosis has to be performed on much smaller occurrence graphs but the effect of faults in previous units is taken into account. the proposed method is illustrated by a simple case study. keywords: technological system, diagnosis, coloured petri net model, structural decomposition, qualitative model 1. introduction identifying faults and analysing their consequences are important tasks during the investigation of technological systems. a number of diagnostic methods are known in the literature and the model-based methods are very popular among them [1]. petri nets and their different extensions (such as coloured, timed or hierarchical nets) are powerful tools for modelling discrete event systems [2]. for example, coloured petri nets are often used for modelling production lines [3]. it is important that the resultant models describe not only the normal (faultless) operation of the system, but they also take into account different, randomly occurring errors in the system. in many cases, the normal or faulty operations of technological processes can be characterised by a series of events possessing discrete or qualitative valued variables. in this case, the occurring deviations can be generated by the comparison of the normal and actual events. the occurring faults can be detected and identified based on the observed deviations. *correspondence: pozna.anna@virt.uni-pannon.hu discrete event systems are usually modelled by automata. in this case, the diagnosis is usually based on the idea of unobservable events [4]. faults can be modelled as unobservable events, which means only the effects of faults can be noticed. the problem with fault detection is specifying whether any fault has occurred or not in the system. fault isolation is the problem of identifying which fault has occurred exactly. since faulty events are unobservable by assumption, the detection and isolation problem must be solved based on the available information of the observed non-faulty events. the diagnosability of discrete event systems was first investigated [5] using the methods of automata theory. besides automata, petri nets are also frequently used for modelling discrete event systems (des). the structural and mathematical representations of petri nets both can be used for diagnostic purposes. methods include various techniques such as analysis of the occurrence graph, marking estimation, linear algebra, integer linear programming, diagnoser nets, or reverse nets. a simple fault detection method based on the measurement of token quantity is given [6]. it is assumed that the given petri net is conservative, and any change in the token quantity is caused by faults. if the difference between measured and initial token number pózna, gerzson, leitold, and hangos hungarian journal of industry and chemistry 122 exceeds a predefined threshold then a fault has occurred. sensor signals are used for token determination instead of modelling the faulty behaviour of the system. the proposed method is very simple and can be used for early fault detection; however, it is not able to isolate faults. faults can also be modelled as unobservable transitions in petri nets. the set of places can be also observable; therefore, the marking of the petri net has to be estimated. the notion of basis marking [7] (set of markings consistent with the observation) and j-vectors (minimal sequences of unobservable transitions to reach basis markings) are introduced. an online algorithm is developed to detect the occurrence of faults, which uses the basis occurrence graph. the main advantage of the proposed algorithm is that in the case of bounded petri nets the basis occurrence graph can be computed offline. it reduces the computational effort of the online diagnosis. the basis occurrence graph can be used as an online diagnoser. sufficient conditions of diagnosability of faulty transitions are given in the form of a system of inequalities [8]. in this method, the marking of places is observable. authors introduce the notion of g-markings (markings with negative elements) and unobservable explanations (sequences of unobservable transitions, whose firings can explain the negative elements of a gmarking). after an observed event, the g-marking is updated according to the petri net equation. when an observed transition fires it removes tokens from its input places and adds tokens to its output places. if this transition is not enabled under the previous g-marking then the removal of tokens causes negative marking. an online fault detection algorithm has also been developed [9], which is based on solving integer linear programming problems and checking the diagnosability conditions. the integer linear programming approach has also been used [10] to determine if the system behaviour is normal, faulty, or ambiguous. the algorithm has further been improved [11], for a more general situation where different observable transitions can share the same label. firing times of transitions are also considered, which add more constraints to the ilp problem making the fault detection algorithm more accurate. timing characteristics have also been used [12], but with a different meaning: the faults affect the firing speed of the transitions. the fault detection is based on the generation of residuals, which are computed by comparing the markings of observable places with the reference model. a bottom-up modelling methodology has been proposed using interpreted petri nets [13]. in the generated model, the faulty and normal states are represented by places. the authors introduce the definition of input-output diagnosability and also give conditions to test this property. the diagnoser model contains the normal behaviour of the system. an online algorithm based on the difference between the system output and the diagnoser model output is developed for detecting faulty markings. in the case of large systems, the models and associated diagnosers can be extremely large. furthermore, the diagnostic methods are computationally expensive. therefore, it is essential to investigate the possibility of distributed diagnosis. the idea of distributed diagnosis is to divide the system into modules or components then make a local diagnoser for each component. the challenging problem is to ascertain the diagnosis state of the whole system from the results of local diagnosers. it usually requires a distributed algorithm and a communication protocol [14]. coloured petri nets (cpn) have the advantage of making compact information representations. a cpn diagnoser equivalent to the classical diagnoser has been built [15]. in this approach, places represent different hypotheses and colours represent diagnosis results. the advantage of the cpn diagnoser is the simplified graphical representation. on the other hand, the coloured diagnoser is not necessarily smaller than the classical diagnoser. decomposition and methods of modular diagnosis of des are also studied by the authors. backward reachability can also be used for diagnosis purposes. if a marking m is reachable from m0, then m0 is backward reachable from m in a petri net. possible sources of failures for this method can be determined. backward reachability is extended to coloured petri nets [16]. transformation techniques for the inversion of cpn are also presented here. 2. basic concepts a brief description of the basic concepts and notions of our method are given in this section. at first qualitative ranges are introduced to characterise the measured values. after that events, traces, and deviations in a technological system are defined, then the most important parts of the coloured petri net model and its analysis are introduced. finally, the structural decomposition-based diagnosis is described in detail. 2.1. qualitative range spaces in many applications, it is not always necessary to know the exact values of the measured signals. qualitative models can be used in this case and it is enough to know whether the value of a signal belongs to a specified range space or not. for example, the measurement range of a sensor can be divided into the following range spaces: qs = { e0, 0, l, n, h, e1 } (1) where 0, l, n, h denote the zero, low, normal and high measured value, respectively, while e0 and e1 may refer to the extremely low and high values caused by sensor errors. the states of actuators, e.g. valves, switches, etc. can be described similarly. for example, a two-state valve can be represented by diagnosis of technological systems 44(2) pp. 121–128 (2016) doi: 10.1515/hjic-2016-0015 123 qv = { op , cl } (2) qualitative range spaces, where op and cl refer to the open or closed state of the valve. 2.2. events, traces, and deviations considering a technological system as a discrete event system, the state of the system can be characterised with the measured values at a given time. the actions in the system, e.g. interactions by operators, modify the values of input and output variables thus the system state changes. an event is defined as the arranged (qualitative) input and output values of the system at a given time instance τ: eventτ = (τ, in1, …, inm, out1, …, outn) . the course of the system can be described as a sequence of consecutive events, so called trace: trace = (event1, …, eventn). in a technological system the most important types of traces with respect to the diagnosis are the nominal, faulty, and characteristic traces. the nominal trace describes the normal operation of a system. the faulty trace contains the occurring events if a known fault is present while the characteristic trace refers to the actual course of the process. in this paper, it is assumed that only one fault may occur in a process unit of the technological system and this fault evolves before the start of the operation and remains unchanged during the course of the process. if a fault occurs then the trace of the system differs from its nominal trace. as a result, deviations between the nominal trace and the current characteristic trace can be defined. in our diagnosis method the following types of deviations are used: • never happened(eventτ) (abbreviated as h(eventτ): this type of deviation refers to the events of the nominal trace which (eventτ) never occur in the characteristic trace of the process. • chronological deviations: if an event of the nominal trace (eventτ) happens later or earlier in the characteristic trace than time point τ, the deviations lat(eventτ) and ear(eventτ) denote them. • quantitative deviations: this type of deviations is used to denote that the ith output value is greater (denoted by grei(eventτ)) or smaller (smli(eventτ)) in the characteristic event at time τ than in the nominal event while the input values are identical. our diagnosis method is based on the search and comparison of the deviation list on the reachability graph of the cpn model of the technological system. 2.3. coloured petri nets coloured petri nets (cpns) are extensions of the ordinary or low-level petri nets. the main differences with respect to ordinary petri nets are that so-called colours can be assigned to tokens and functions can be assigned to arcs and transitions, too. the detailed formal definition is given in ref.[17], only the special concepts used in our models are presented here. • places of the cpn model of the technological system may have three functions. at first input and output variables are represented by places and the colour of the tokens on them denotes the qualitative value of the variable at the current time. on the other hand, places may refer to the occurred fault and the generated deviations. the colours of tokens in these places denote the type of the fault and the occurring deviations, respectively. • there are three transitions in our model, which have different tasks. transition t1 is responsible for the generation of faulty or normal operations at the beginning of the process and the initialisation of the variables according to the investigated operational mode. the function of transition t2 is the timing of the process. it is assumed that the technological process is time-driven and the values of the variables change at the end of the time steps. therefore, t2 fires until the end of the process. transition t3 is used for the generation of the ‘never happened’-type deviations at the end of the process. • arc functions are assigned to the arcs between places and transitions defining the change in the colours and computing deviations. the structure of the coloured petri net for modelling and diagnosing technological systems can be seen in fig.1. places are represented with ellipses and transitions are represented with rectangles. in a technological system, the consequences of a processing step can be stochastic. for example, the step may be completed in a normal way, or a fault occurs. the probabilistic nature of a transition t associated with a processing step can be modelled in a cpn by a fault function, which is built into its guard function. this figure 1. structure of the coloured petri net model. pózna, gerzson, leitold, and hangos hungarian journal of industry and chemistry 124 fault function returns the logical value true or false with predefined probability, and the token values of the adjacent consequence places of transition t can be controlled by this logical value. this type of transition firing is called a stochastically fired transition. the occurrence graph of the cpn is a graph, which contains all of the system states reachable from a given initial state [17]. assuming that the cpn model of the examined system is given, the occurrence graph can be used for its behavioural analysis. the nodes of the graph refer to system states and the arcs connecting them refer to state transitions, e.g. events. different paths on the occurrence graph refer to different operational modes of the system and they can be used for analysing the causes and consequences of a system state. 2.4. diagnosis with structural decomposition the disadvantage of the occurrence graph-based method is the increasing size of the graph as the size, i.e. number of places, of the cpn model increases. in the case of even a simpler technological system containing three or four units, the occurrence graph of its cpn model can contain hundreds of nodes depending on the number of sensors and actuators. the refinement of the qualitative measuring range of sensors or the application of control valves instead of two-state actuators may also cause the growth of occurrence graphs because their branches will be longer. with the growth in the size of the graph, the computational effort and searching-time also increase. this is the reason why the structural decomposition has a crucial impact on the practical application of the diagnostic process. generally speaking, complex systems can be decomposed into technological units. by taking advantage of this, the diagnosis can be done by components separately, and the diagnostic result of a unit can be used for the diagnosis of the other units connected to it. to perform diagnosis with structural decomposition the full trace of the system should be decomposed, too. to do this, first the time instances belonging to the operation of the investigated units have to be selected. then the variables referring to this unit are picked out from the events belonging to the selected time instances. if the trace is represented in tabular form then specific rows and columns should be selected. afterwards, time is shifted back in the case of every unit such that the initial time step of the first event should be 1 in every sub-trace. this means that every unit has its own relative time-scale. by applying this decomposing process, the trace describing the operation of the entire system is disintegrated into the event lists referring to the operation of simpler technological units. as a next step the deviation list of the given subsystem is generated by comparing the nominal trace of the subsystem with its characteristic trace. then the diagnosis is performed using the cpn model and occurrence graph of the subsystem. the task is to compare the generated deviation list with the token distribution of the terminal nodes on the occurrence graph. if the deviation list corresponds with the token distribution of exactly one terminal node then the fault can be determined based on the token of the fault place. if the deviation list matches the token distribution of more than one terminal node then only the set of possibly occurred faults could be determined. if the deviation list cannot be found in the token distribution of any terminal nodes then an unknown failure occurs in the system. in the case of complex systems, it is necessary to take into account the effect of faults that have occurred in subsystems connected to the diagnosed unit. therefore, the cpn model of the units has to be modified such that the place of the fault has to contain not only the actual operating mode, but the operating modes of previous subsystems, too. to store this information the colour set of this place is extended with an attribute referring to the type of fault and to the place where the fault occurred. let us assume that one fault is diagnosed in the first technological unit. this information is added to the fault place of the next unit as a previous fault. then the occurrence graph of this subsystem is generated based on its cpn model where the fault of the previous unit appears as an initial condition. the resultant occurrence graph now contains those states and deviation lists which can occur in this subsystem if the fault of the previous unit is taken into account. the diagnosis is performed on this graph, the possible fault of this unit is determined based on this investigation, and the result is taken into account during the diagnosis of the following unit. in certain cases, the exact type of fault cannot be determined exactly. if the result of the diagnosis of the unit is a set of possible faults then each element of the set is treated separately. this means that the diagnosis of the next unit has to be performed taking into account every one of the possible previous faults. occurrence graphs of the subsystem are generated according to each fault of the previous subsystem. the result of the diagnosis is the union of the obtained faults. the main advantage of the described method is the smaller size of the occurrence graphs of subsystems. therefore, the search requires less time than in the case of the investigation of the entire technological system. 3. simple case studies a simple case study is presented in this section as a practical illustration of the diagnosis of complex technological systems based on their structural decompositions. 3.1. description of the technological process our simple technological example contains three uniform tanks, ta, tb, and tc, which are serially connected as can be seen in fig.2. each tank has an input valve, an output valve (denoted by vx, where x = a, b, c, and d), and a continuous level sensor (lev_x, x diagnosis of technological systems 44(2) pp. 121–128 (2016) doi: 10.1515/hjic-2016-0015 125 = a, b, and c). the short description of the technological process is as follows: as an initialisation, it is assumed that all the valves are closed. the process starts with the opening of the first valve (va) and then the filling of the first tank (ta) starts. the flow of liquid is considered constant so the control of the filling process is based on time. the role of the level sensors is to measure the actual liquid level only. at time step 3, the filling process of tank ta completes and its output valve (vb) is opened. the second tank tb is filled the same way as described for tank ta. at time step 5, the tb tank is full and its output valve (vc) is opened. the filling process of the third tank (tc) happens the same way. during the filling of the second and third tanks, the first (ta) then the second tank (tb) operates as a continuous unit. after the filling of the third tank (tc) has completed, the technological systems work in continuous mode. it is assumed that five possible faults can occur in each tank: • 2 faults of the level sensor: negative or positive bias error. in this case, the sensor signal is lower or higher with qualitative unit than the actual value of the level. • leaking of the tank: it is assumed that all of the incoming liquid runs out through the hole, i.e. it is a “big” hole. • 2 different faults of the output valves vb, vc, and vd: besides their normal operations, they can stay closed or open only halfway. for the sake of simplicity, only one of these faults can occur with each tank and all of the faults evolve before the filling process of the first tank ta starts. 3.2. cpn model of the system for the diagnostic investigation, a coloured petri netbased (cpn) model of the technological system is developed as follows: the system can be decomposed into three subsystems. each subsystem represents a tank together with its input and output valves. as can be seen from the technological description of the system, all the subsystems (tanks with their input and output valves and sensors) work in a very similar way, so the structure of their cpn models is identical. the cpn models were built using cpn tools 3.4.0. the cpn model of a subsystem can be seen in fig.3. the description of the cpn model is as follows: the locations of the petri nets represent input and output variables, i.e. the state of the input and output valves (denoted by in and out), and measured level value (level), respectively. the qualitative values of these variables are represented by different colour sets. • colour set of valves: qvalve = {cl, op}, which represents the closed or open-state of the twostate valve. • colour set of level sensors: qlevel = { e0, 0, l, n, h, e1 }, where 0, l, n, h denotes that the level is zero, low, normal or high, respectively, and e0, and e1 indicate that the level is below or above the measurement range, respectively. three additional places are needed: one to store the operating mode (place fault), one to collect the deviations (place dev) and one for the list of events that have not occurred until a given simulation time step (place never). the cpn model contains three transitions (t1, t2, t3). t1 is the initialisation transition, it fires only once at the start of the simulation. it generates an operating mode (normal or faulty) and updates the variables according to the generated operating mode. afterwards, transition t2 fires until the end of the process. it updates the values of variables in every simulation step and generates quantitative and chronological deviations except for the ‘never happened’-type. the ‘never happened’-type deviations can be generated after the process has ended. this is done by the firing of transition t3, which removes the events that remain at place never at the end of the simulation and attaches the nh guideword to them. the values of variables at a given time step can be read from the trace files. each trace file contains the list of events that describe the process according to the operating mode. all traces were generated by a matlab script. figure 2. the investigated technological example. figure 3. the coloured petri net model of a tank (for the sake of clarity parts of some inscriptions were omitted). pózna, gerzson, leitold, and hangos hungarian journal of industry and chemistry 126 3.3. diagnosis of the system with structural decomposition according to the general description, the technological system consists of three uniform tanks. because of the same structure and operational mode, all three tanks have the same cpn model. this model can be seen in fig.3. the occurrence graph of the cpn model of a tank can be seen in fig.4. at the time of the generation of this occurrence graph, any fault occurring in a previous technological unit was not taken into account. as can be seen in fig.4, node no. 17 refers to normal operation of the system, while the other terminal nodes (no. 20, 21, 23–25) belong to the five different faulty modes. the nominal trace of the complex technological system can be seen in table 1. the input variables of the first tank (tank ta in fig.2) are the states of valves va and vb, while the output variable is the value of level sensor lev_a. the variables of the second tank are vb, vc, and lev_b, while vc, vd, and lev_c belong to the third tank, respectively. the rows belong to time steps 1, 2, and 3, while columns va, vb, and lev_a compose the trace of the first tank. these cells are framed with a dotted line in table 1. similarly, rows 3, 4, and 5 as well as columns vb, vc, and lev_b define the trace of the second tank (framed with a continuous line) while rows 5, 6, and 7, along with columns vc, vd, and lev_c give the trace of the third tank (framed with a dashed line). consider the characteristic trace of the technological system given in table 2. as a next step, the trace pieces belonging to each individual tank are removed from the characteristic trace of the entire system. the initial time step is shifted to 1 for every unit. the resultant event lists belonging to the three tanks can be seen in table 3. the diagnostic process is started with the first tank. by comparing the nominal trace of the first tank with the characteristic trace (first column of table 3) the deviation list is generated. this deviation list is then searched for among the terminal nodes of the occurrence graph of the first tank. (this occurrence graph can be seen in fig.5). it can be stated that terminal node no. 21 contains the same deviation list and based on the token of the fault place the type of fault can be determined: the level sensor exhibits a positive failure bias in the first tank. the diagnosed fault in the first tank is used during the investigation of the second tank. this fault is added to the place fault as a token (pos_bias, prev1) in the model of the second tank. then the occurrence graph of the second tank is generated which contains those states that can occur in the second tank if the sensor of the first tank exhibits a positive bias error. the resultant graph can be seen in fig.6. the deviation list of the second tank is generated by comparing the second column of table 3 with the characteristic trace of the second tank. by checking the terminal nodes of the occurrence graph in fig.6, it can be stated that terminal node no. 24 exhibits the same deviation list. this means that the fault of the second tank is leakage and it can be identified unambiguously. the diagnosed faults of the first and second tanks are added to the model of the third tank in the form of tokens (pos_bias, prev1) and (leak, prev2) belonging to the fault place. based on this information the occurrence graph of the third tank is generated in accordance with fig.7. the nodes on this occurrence graph refer to the states if a positive failure bias occurs in the first tank and leak in the second tank. figure 4. the occurrence graph of a cpn tank model. table 1. decomposition of the nominal trace. dotted line: first tank, continuous line: second tank, dashed line: third tank. time input variables output variables va vb vc vd lev_a lev_b lev_c 1 op cl cl cl 0 0 0 2 op cl cl cl l 0 0 3 op op cl cl n 0 0 4 op op cl cl n l 0 5 op op op cl n n 0 6 op op op cl n n l 7 op op op op n n n table 3. characteristic traces of the three tanks after decomposition. ta tb tc (1, op, cl, l) (1, op, cl, 0) (1, op, cl, 0) (2, op, cl, n) (2, op, cl, 0) (2, op, cl, 0) (3, op, op, n) (3, op, op, 0) (3, op, op, 0) table 2. decomposition of the characteristic trace. dotted line: first tank, continuous line: second tank, dashed line: third tank. time input variables output variables va vb vc vd lev_a lev_b lev_c 1 op cl cl cl l 0 0 2 op cl cl cl n 0 0 3 op op cl cl n 0 0 4 op op cl cl n 0 0 5 op op op cl n 0 0 6 op op op cl n 0 0 7 op op op op n 0 0 figure 5. the occurrence graph of the first tank. diagnosis of technological systems 44(2) pp. 121–128 (2016) doi: 10.1515/hjic-2016-0015 127 the deviation list based on the trace pieces stemming from the filling process of the third tank (see the third column of table 3) is generated and compared to the terminal node of the occurrence graph. it can be stated that terminal nodes no. 21–24 possesses the same deviation list as the deviation list obtained from the characteristic trace of the third tank. this means that the operating mode of the third tank cannot be unambiguously determined, the set of possible operating modes, i.e. normal, leak, or fault, of valves can be defined. 4. conclusion a novel method for online fault diagnosis in a technological system is described in this paper. the method is based on the structural decomposition of a complex technological system. the process starts with the modelling of the technological system in the form of coloured petri nets. for the characterisation of sensor values and actuator states, qualitative value sets are used in the form of coloured tokens. this modelling method allows for the simulation of both normal and known faulty operations of the system. the diagnosis is performed using the occurrence graph of the basic units of the complex system. by generating the deviation list based on the normal and characteristic traces the fault or the set of possible faults can be determined. as a result of the structural decomposition, the diagnosis has to be performed on much smaller occurrence graphs but the effect of faults in previous units are taken into account. our method reduces the demand of computational efforts and search time. the proposed method was illustrated by a simple case study. acknowledgement the authors acknowledge the financial support of the hungarian research fund through grant no. k-115694. references [1] blanke, m.; kinnaert, m.; lunze, j.; staroswiecki, m.: diagnosis and fault-tolerant control (springerverlag, berlin, germany) 2006 doi: 10.1007/9781-84628-877-7 [2] hrúz, b.; zhou, m.: modeling and control of discrete-event dynamic systems with petri nets and other tool (springer-verlag, london, u.k.) 2007 [3] campos, e.j.; seatzu, c.; xie, x.: formal methods in manufacturing (crc press taylor and francis group, boca raton, usa) 2014 doi: 10.1201/b16529 [4] zaytoon, j.; lafortune, s.: overview of fault diagnosis methods for discrete event systems, ann. rev. control 2013 37(2), 308–320 � doi: 10.1016/j.arcontrol.2013.09.009 [5] sampath, m.; sengupta, r.; lafortune, s.; sin namohideen, k.; teneketzis, d.: diagnosability of discrete-event systems, ieee trans. automat. control 1995 40(9), 1555–1575 �� doi: 10.1109/9.412626 [6] prock, j.: a new technique for fault detection using petri nets, automatica 1991 27(2), 239–245 � doi: 10.1016/0005-1098(91)90074-c [7] cabasino, m.p.; giua, a.; seatzu, c.: fault detection for discrete event systems using petri nets with unobservable transitions, automatica 2010 46(9), 1531–1539 � doi: 10.1016/j.automatica.2010.06.013 [8] basile, f.; chiacchio, p.; tommasi, g.d.: sufficient conditions for diagnosability of petri nets, in proc. 9th int. workshop on discrete event systems, wodes (göteborg, sweden) pp. 370– 375, 2008 � doi: 10.1109/wodes.2008.4605974 [9] basile, f.; chiacchio, p.; tommasi, g.d.: an efficient approach for online diagnosis of discrete event systems, ieee trans. automat. control 2009 54(4), 748–759 � doi: 10.1109/tac.2009.2014932 [10] dotoli, m.; fanti, m.p.; mangini, a.m.; ukovich, w.: online fault detection in discrete event systems by petri nets and integer linear programming, automatica 2009 45(11), 2665–2672 � doi: 10.1016/j.automatica.2009.07.021 [11] fanti, m.p.; mangini, a.m.; ukovich, w.: fault detection by labeled petri nets and time constraints, proc. 3rd int. workshop on dependable control of discrete systems (dcds, saarbrucken, germany) pp. 168–173, 2011 � doi: 10.1109/dcds.2011.5970336 [12] lefebvre, d.; aguayo-lara, e.: initial study for observers application to fault detection � and isolation with continuous timed petri nets, ifacpapersonline 2015 48(7), 97–103 doi: 10.1016/j.ifacol.2015.06.479 figure 6. the occurrence graph of the second tank in the case of a positive failure bias in the first tank. figure 7. the occurrence graph of the third tank in the case of a positive failure bias in the first tank and leak in the second tank. pózna, gerzson, leitold, and hangos hungarian journal of industry and chemistry 128 [13] ramirez-trevino, a.; ruiz-beltran, e.; rivera rangel, i.; lopez-mellado, e.: online fault diagnosis of discrete event systems. a petri netbased approach, ieee trans. automation sci. engng. 2007 4(1), 31–39 doi: 10.1109/tase.2006.872120 [14] genc, s.; lafortune, s.: distributed diagnosis of place-bordered petri nets, ieee trans. automation sci. engng. 2007 4(2), 206–219 doi: 10.1109/tase.2006.879916 [15] pencolé, y.; pichard, r.; fernbach, p.: modular fault diagnosis in discrete-event systems with a cpn diagnoser, ifac-papersonline 2015 48(21), 470–475 doi: 10.1016/j.ifacol.2015.09.571 [16] bouali, m.; barger, p.; schon, w.: backward reachability of colored petri nets for systems diagnosis, reliability engng. system safety 2012 99, 1–14 doi: 10.1016/j.ress.2011.10.003 [17] jensen, k.: coloured petri nets: basic concepts, analysis methods and practical use (springer verlag, berlin, germany) 1997 doi: 10.1007/9783-642-60794-3 hungarian journal of industry and chemistry vol. 44(2) pp. 129–133 (2016) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2016-0016 metal-chloride-activated empty fruit-bunch carbons for rhodamine b removal muhammad abbas ahmad zaini1,2* and mohd shafiq mohd shaid1 1 faculty of chemical & energy engineering, universiti teknologi malaysia, johor bahru, johor, 81310, malaysia 2 centre of lipids engineering & applied research, ibnu sina institute for scientific & industrial research, universiti teknologi malaysia, johor bahru, johor, 81310, malaysia this study aimed to investigate the adsorptive ability of activated carbons derived from empty boil palm fruitbunch carbons through metal-chloride activation. the derived activated carbons were characterized in terms of yield, ph, surface functional groups, and specific surface area. rhodamine b dye was used as a pollutant probe to evaluate the performance of activated carbons. results show that empty, zncl2-activated fruit-bunch carbon exhibits a higher surface area of 866 m2 g-1 and a rhodamine b removal yield of 105 mg g-1. activation at the same temperature of 600 ºc using the recovered fecl2 yields an activated carbon with nearly twice the surface area compared to the fresh one. a direct correlation was obtained between the roles of the specific surface area and removal of rhodamine b. empty fruit-bunch carbon is a promising adsorbent precursor for colour removal from water. keywords: activated carbon, chemical activation, empty fruit-bunch, metal-chloride, rhodamine b 1. introduction malaysia and indonesia are the leading producers worldwide of palm oil. due to the growth in palm oil production and despite the high economic returns, this industry also generates a huge amount of was that has negative implications on the environment. as one of the largest oil palm producers in the world, malaysia generates abundant empty fruit-bunch (efb) residues amounting to 12.4 million tonnes annually [1]. at present, only a small quantity of efb is used as fuel for boilers in the oil palm mills while the remaining large quantity is left to decay in fields or disposed of in landfills. due to the limited area of landfill sites and other associated environmental implications, the quest for the effective utilization of efb has become a subject of significant interest. because efb is rich in carbon and lignin, it has a great potential to be converted into adsorbent or activated carbon for a variety of purification and environmental purposes [2]. nasir et alia [3] reported the selectivity of methylene blue removal over copper(ii) ions by empty fruit-bunch. yet, the uptake capacity was too small (32.3 mg methylene blue per g of efb) to warrant large-scale adsorption operation. in a recent related work, wirasnita et alia [4] reported the preparation of zncl2-activated empty fruit-bunch carbon with a specific surface area of 86.6 m2 g-1. however, the *correspondence: abbas@cheme.utm.my surface area obtained is somewhat small to be regarded as that of activated carbon [5]. there are also reports on the use of co2 and steam to physically activate the efb into activated carbons. however, the surface area is often not controllable and the yield is very low because of high activation temperatures (800 to 900 ºc) [6,7]. our present work aimed to evaluate the adsorptive characteristics of metal-chloride-activated empty fruitbunch carbons. zinc(ii) chloride and iron(ii) chloride were used for the chemical activation of efb. attempts were also made to recover the activator for the second activation. rhodamine b was used as a model pollutant to establish the adsorption data. the activated carbons were characterized and the adsorptive results compared and discussed. 2. experimental oil palm empty fruit-bunch (efb) was obtained from sungei kahang palm oil factory in johore state, malaysia. the material was oven-dried at 110oc overnight to remove moisture. all chemicals used in the preparation of activated carbons and adsorption were of analytical reagent grade. 2.1. preparation of activated carbon empty fruit-bunch was loosened and separately modified with zinc chloride and iron(ii) chloride in the mass ratio (activator : efb) of 3:2. firstly, the activator was dissolved in water, sufficient for the efb to be immersed. next, the efb-activator mixtures were zaini and shaid hungarian journal of industry and chemistry 130 stirred at 90 ºc for 40 minutes. after that, the sample was placed in the oven overnight at 110 ºc for impregnation. the impregnated sample was put in a crucible wrapped in aluminium foil, and heated in a furnace for 1.5 h at 300 ºc and 550 ºc for zinc chloride activation and iron(ii) chloride activation, respectively. the selected activation temperatures are half of the boiling points of the activators. the resultant activated carbon was washed with distilled water, and the washed water was used for the second activation using the same impregnation ratio of 3:2 at 550 ºc for both activators. activated carbons were designated as z1 and f1 for activation using fresh zinc(ii) chloride and iron(ii) chloride, respectively, and z2 and f2 when using recovered activators, respectively. 2.2. characterization of activated carbon the yield of activated carbon was calculated from the mass of the resultant product over that of the dried efb used. the adsorbent ph was determined by soaking 1 g of adsorbent in 100 cm3 of distilled water. the ph was measured using a ph meter (hi 8424, hanna instruments). the specific surface area of activated carbon was measured using a surface area analyser (pulse chemisorb 2705, micromeritics) at the temperature of liquid n2, 77 k. fourier transform infrared spectroscopy (ftir) (ir tracer-100, shimadzu) was used to obtain the peaks of functional groups at specific wave numbers ranging from 400 to 4000 cm-1. 2.3. adsorption of rhodamine b rhodamine b of commercial purity was utilized without further purification. 500 mg of rhodamine b powder was weighed using an analytical balance and then dissolved in 1 dm3 of distilled water in a volumetric flask to make up a stock solution. the dilution of stock solution was needed for preparing the working concentrations for adsorption. adsorption was performed according to the bottlepoint technique. briefly, about 0.5 g of activated carbon was added to 50 cm3 of rhodamine b solution at varying concentrations. the mixture was allowed to equilibrate on an orbital shaker at 120 rpm and room temperature for 72 h. the residual concentration was measured using a spectrophotometer (halo vis-10, dynamica scientific ltd.) at a wavelength of 555 nm (absorption unit = 0.014 × concentration, r2 = 0.99). the adsorption capacity (mg g-1) was calculated by a simple material balance (eq.(1)), and the adsorption data were analysed by general isotherm models, namely langmuir (eq.(2)) and freundlich (eq.(3)). the respective constants were solved by non-linear regression using solver as implemented in ms excel for the smallest sum-of-squared error (sse) and optimum coefficient of determination (r2). !! = (!!!!!) ! ! (1) !! = !"!! !!!!! (2) !! = !!!! ! ! (3) where, qe (mg g-1) is the adsorption capacity of rhodamine b, co and ce (mg dm-3) are the initial and equilibrium concentrations, respectively, m (g) is the mass of activated carbon, and v (dm3) is the volume of rhodamine b solution. constant q (mg g-1) is the maximum monolayer capacity, b (dm3 g-1) is the adsorption intensity, and kf ((mg g-1)(dm3 mg-1)1/n) and 1/n are the freundlich constants related to the adsorption capacity and intensity, respectively. 3. results and analysis 3.1. characteristics of activated carbons chemical activation using freshly prepared metalchlorides was performed at a temperature of about half of the boiling point of each activator. the boiling point of zncl2 and fecl2 are 723 and 1023 ºc, respectively. this is to allow a sufficient amount of activator to be recovered upon activation as it is commonly understood that chemical activators, e.g. zncl2, koh, etc., are prone to intercalate with the matrix material and/or lost when the activation is done close to the boiling point of the activators. in addition, it enables one to evaluate the effectiveness of activated carbon preparation at the selected temperatures. table 1 displays the yield, ph, and specific surface area of metal-chloride-activated empty fruit-bunch carbons. in general, the yield of activated carbons ranges between 38 and 47%. this indicates the underlying role of metal-chlorides as dehydrating agents to enhance the burning off the carbonaceous material. this is also true for zncl2 activation at a temperature of 300 ºc. in addition, it signifies that a significant portion of metalchlorides could be recovered for the subsequent activation. the ph values of activated carbons are in the range of 3.8 to 5.3. the activated carbons are slightly acidic because both metal-chloride activators are lewis acids. the ph values were found to increase when the recovered activators were used in the activation. this could be attributed to the decreased amount of metalchlorides that probably could not be fully recovered after the first activation. from table 1, the developed surface area of z1 upon activation is undeniably small, even smaller than for raw efb (28.4 m2 g-1) [3]. this could be due to the table 1. properties of activated carbons. activator type temp. (°c) yield (%) ph surface area (m2 g-1) zncl2 fresh (z1) 300 44.0 3.8 2.64 recovered (z2) 550 41.2 4.9 866 fecl2 fresh (f1) 550 46.8 4.6 98.4 recovered (f2) 550 37.9 5.3 226 metal-chloride-activated empty fruit-bunch carbons 44(2) pp. 129–133 (2016) doi: 10.1515/hjic-2016-0016 131 blockade of existing pore channels because of the intercalation of zinc cations within the material matrix. intercalation of a chemical activator normally creates new pathways for the porous structure when adequate heat is supplied to the impregnated material. this often results in an increase in pore volume, thus increasing the specific surface area. yet, the activation temperature for z1 (300 ºc) may not be sufficient to initiate the job, consequently the activator becomes lodged inside the rudimentary pores even though burning off decreases the activated carbon yield. therefore, z1 could not be regarded as activated carbon because of its inferior development of surface area. activation using the recovered activators was performed at 550 ºc. there is a tremendous increase in the surface area of z2 using the recovered zncl2 from z1. although the amount of zncl2 in the recovered solution is presumably less than for the fresh one (ratio 3:2), the elevated activation temperature shows a positive effect in increasing the surface area by more than 300 times. this could be related to the fact that more volatiles (nearly 65% weight loss) are liberated from the empty fruit-bunch at 550 ºc [8]. it is suggested that the liberation of volatiles from the material also contributes to creating the pore pathways. these combined effects bring about the development of activated carbon with a high surface area. from table 1, f2 shows a higher surface area than for f1 at the same activation temperature. this could be associated with the optimum impregnation ratio in the preparation of activated carbon. the specific surface area of activated carbon normally increases as the impregnation ratio increases, but decreases when an excessive amount of activator is used. too much activator may result in the collapse of pore textures, thus decreasing the surface area [9]. in other words, fecl2 used in the activation of f1 could have already exceeded the optimum impregnation ratio. however, further experimental works of varying impregnation ratios of fecl2 are needed to establish the optimum surface area of fecl2-activated empty fruit-bunch carbons. nevertheless, f2 demonstrates a 3.8 times lower surface area than z2. this shows that zncl2 is an effective activator for empty oil palm fruit-bunch-based activated carbon. fig.1 shows the ftir spectra of efb and its derived activated carbons. the designated possible functional groups are summarized in table 2. the spectroscopy technique measures the absorption of various wavelengths of infrared light by materials of interest to identify specific organic functional groups on the surface of activated carbon. from fig.1, the efb displays various peaks that correspond to the presence of functional groups. the broad and strong band at 3300 cm-1 is assigned to the stretching vibration of the (–oh) hydroxyl group. the intensity of the peak decreased by the order of efb > z1 > f1 ≈ f2 > z2. the peak completely disappeared in z2 probably due to the stronger dehydrating effect of zncl2 compared to fecl2 in activating the efb at 550 ºc. it also signifies that the activation of z1 remains incomplete because most of the attributes of efb spectra remained unchanged. as the efb is converted into activated carbon, the complicated peaks become simplified indicating the liberation of functional groups in the activated carbons. the absorption peaks at 2930– 2850 cm-1 are attributed to the (c–h) stretching vibration of the (–ch3) group. the peaks between 1400 and 1000 cm-1 are ascribed to (c–o) stretching or (si– o) of silica containing minerals (ash). the peak at 1026 cm-1 in z1 is assigned to the out of plane (c–h) bending. 3.2. adsorption of rhodamine b water polluted with dyes especially from the textile industries has become a subject of great concern because of the disruption to biodiversity and food chains [10]. basic or cationic dyes are very bright dyes that are water-soluble. in this work, rhodamine b (c28h31c1n2o3, mw = 479 g mol-1, solubility in water = 15 g dm3) was chosen as the model dye to evaluate the performance of empty fruit-bunch-based activated carbons. the ph of the rhodamine b solution was not adjusted, and the values were measured as 5.1±0.2 for all concentrations. at equilibrium, the ph values slightly changed as they are measured to be 5.3±0.1. fig.2 illustrates the molecular structure of rhodamine b. figure 1. ftir spectra of efb and activated carbons. table 2. functional groups used in characterizing samples. wave number (cm-1) functional group type sample 3100–3550 a o—h alcohol efb, f1, f2, z1 1000 c—o 2900, 2810 c—h aldehyde efb, z1 1600, 1470 c=c aromatic efb, z1 1600 c=c alkene efb, z1, f1, f2 3300 n—h amine efb 1300 c—n a broad feature zaini and shaid hungarian journal of industry and chemistry 132 fig.3 shows the removal of rhodamine b by efbderived materials. from fig.3, the removal of rhodamine b was found to increase with concentration by the order of z2 > f2 > f1 > z1. activated carbon z2 demonstrates the highest rhodamine b removal of 105 mg g-1. this trend is in agreement with the increase in specific surface area of adsorbents. in general, the concentration of dye in the solution provides a driving force for adsorption if the adsorbent or activated carbon possesses abundant active sites. in this case, the active sites are directly associated with the surface area. fig.4 displays the correlation between the removal of rhodamine b and the surface area. a linear relationship for rhodamine b removal (mg g-1) = 0.124 × specific surface area (m2 g-1), r2 = 0.993 was obtained. a bigger surface area normally provides better interaction probabilities for the rhodamine b molecules to lodge onto the pore channels. in addition, it is presumed that all types of pore play a dominating role in the adsorption especially mesopores [5,11]. the adsorption data were analysed using the langmuir and freundlich models, and the constants are tabulated in table 3. the adsorption data reasonably fitted to both adsorption models with r2 ranging between 0.71 and 0.97, except for z2 according to the langmuir model. the values of langmuir model capacity (q) are in close proximity to the experimental data (qexp). in addition, z2 shows a higher adsorption affinity (b) for rhodamine b when compared with the other counterparts. this signifies a higher removal efficiency (~99%) at concentrations below 80 mg dm-3. similar explanations apply for the freundlich model. the deviation of the lines of the model from the experimental data is shown in fig.3, which indicates that the removal of rhodamine b by efb-based materials is neither a strict monolayer adsorption nor heterogeneous coverage, but could be a blend of the two – monolayer adsorption onto a heterogeneous surface [11]. in a related work, santhi et alia [12] reported a removal capacity of 22.3 mg g-1 of rhodamine b using h2so4-treated a. nilotica leaves. generally, z2 shows a higher dye removal capacity compared to this chemically treated natural adsorbent. this is likely due to the well-developed graphitic structure and surface area of z2 for the effective removal of rhodamine b. figure 2. chemical structure of cationic rhodamine b dye. figure 3. removal of rhodamine b by (a) z1, f1 and f2, and (b) z2. lines were predicted by the langmuir (solid) and freundlich (dashed) models. figure 4. correlation between rhodamine b removal and specific surface area. table 3. parameters of isotherm models. z1 z2 f1 f2 qexp (mg g-1) 2.33 105 14.8 33.4 langmuir model q (mg g-1) 2.85 97.9 18.5 42.2 b (dm3 g-1) 0.166 2.92 0.248 0.187 r2 0.907 0.434 0.857 0.967 sse 0.233 403 23.7 26.3 freundlich model kf (mg g-1)(l mg-1)1/n 0.560 72.5 4.73 8.86 n 2.10 13.4 2.61 2.33 r2 0.882 0.707 0.718 0.869 sse 0.435 209 44.7 94.3 metal-chloride-activated empty fruit-bunch carbons 44(2) pp. 129–133 (2016) doi: 10.1515/hjic-2016-0016 133 4. conclusion oil palm empty fruit-bunch was used in the preparation of activated carbons via metal-chloride activation. zinc chloride is a more effective activating agent for activated carbon than iron(ii) chloride. activation at 500 ºc yields empty fruit-bunch-based activated carbon with a surface area of 866 m2 g-1. a bigger surface area offers greater removal of rhodamine b dye and a higher adsorption affinity at lower dye concentrations. the maximum removal efficiency was recorded as 105 mg g-1. the mechanism could be described as monolayer rhodamine b adsorption onto heterogeneous activated carbon. empty fruit-bunch is a promising alternative to activated carbon precursors for wastewater treatment. acknowledgement the research was supported by universiti teknologi malaysia through tier one research grant #10h42. references [1] tanaka, r.; rosli, w.; magara, k.; ikeda, t.; hosoya, s.: chlorine-free bleaching of kraft pulp from oil palm empty fruit-bunches, jpn. agric. res. 2004 38(4), 275–279 doi: 10.6090/jarq.38.275 [2] duan, x.; peng, j.; srinivasakannan, c.; zhang, l.; xia, h.; yang, k.; zhang, z.: process optimization for the preparation of activated carbon from jatropha hull using response surface methodology, energy sources, part a: recovery util. environ. effect, 2011 33(21), 2005–2017 doi: 10.1080/ 15567030903515047 [3] nasir, n.h.m.; zaini, m.a.a.; setapar, s.h.m.; hassan, h.: removal of methylene blue and copper(ii) by oil palm empty fruit-bunch sorbents, j. teknologi 2015 74(7), 107–110 doi: 10.11113/ jt.v74.4707 [4] wirasnita, r.; hadibarata, t.; yusoff, a.r.m.; lazim, z.m.: preparation and characterization of activated carbon from oil palm empty fruit-bunch wastes using zinc chloride, j. teknologi 2015 74(11), 77–81 doi: 10.11113/jt.v74.4876 [5] ming-twang, s.; lin-zhi, l.; zaini, m.a.a.; zhiyong, q.; pei-yee, a.y.: activated carbon for dyes adsorption in aqueous solution, in: advances in environmental research, ed.: daniels. j.a. (nova science publishers, inc., new york, usa) pp. 217–234, 2015 [6] hidayu, a.r.; mohamad, n.f.; matali, s.; sharifah, a.s.a.k.: characterization of activated carbon prepared from oil palm empty fruit-bunch using bet and ft-ir techniques, proc. engng. 2013 68, 379–384 doi: 10.1016/j.proeng.2013.12.195 [7] alam, m.z.; ameem, e.s.; muyibi, s.a.; kabbashi, n.a.: the factors affecting the performance of activated carbon prepared from oil palm empty fruit-bunches for adsorption of phenol, chem. engng. j. 2009 155(1–2), 191–198 doi: 10.1016/j.cej.2009.07.033 [8] nyakuma, b.b.; johari, a.; ahmad, a.; abdullah, t.a.t.: thermogravimetric analysis of the fuel properties of empty fruit-bunch briquettes, j. teknologi 2014 67(3), 79–82 doi: 10.11113/jt.v67.2768 [9] zaini, m.a.a.; okayama, r.; machida, m.: adsorption of aqueous metal ions on cattlemanure-compost based activated carbons, j. hazard mater. 2009 170(2–3), 1119–1124 doi: 10.1016/j.jhazmat.2009.05.090 [10] ming-twang, s.; zhi-yong, q.; lin-zhi, l.; peiyee, a.y.; zaini, m.a.a.: dyes in water: characteristics, impacts to the environment and human health, and the removal strategies. in: advances in chemistry research, ed.: taylor, j.c. (nova science publishers, inc., new york, usa) vol. 23, pp. 143–156, 2015 [11] zaini, m.a.a.; zakaria, m.; setapar, s.h.m.; yunus, m.a.c.: sludge-adsorbents from palm oil mill effluent for methylene blue removal, j. environ. chem. engng. 2013 1(4), 1091–1098 doi: 10.1016/j.jece.2013.08.026 [12] santhi, t.; prasad, a.l.; manonmani, s.: a comparative study of microwave and chemically treated acacia nilotica leaf as an eco-friendly adsorbent for the removal of rhodamine b dye from aqueous solution, arabian j. chem. 2014 7(4), 494–503 doi: 10.1016/j.arabjc.2010.11.008 hungarian journal of industry and chemistry vol. 44(2) pp. 135–139 (2016) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2016-0017 characterisation of cements from dominantly volcanic raw materials of the carpathian bend zone timea halmagyi,1 emilia mosonyi,2 józsef fazekas,2* maria spataru1 and firuta goga2 1 s.c. valdek impex srl, sfantu gheorghe str. 1 decembrie 1918, bl. 15, sc. e, et. 3, ap. 9., judetul covasna, romania 2 “babes-bolyai” university, kogalniceanu str. 1, 400082 cluj-napoca, romania this paper presents the results of laboratory investigations regarding the production of cements from local raw materials, such as limestone from varghis, gypsum from nucsoara, basaltic scoria from racosul de jos, volcanic tuff from racosul de sus, diatomite from filia, and red mud from oradea. the raw mixtures, based on modified bogue calculations, contain limestone, gypsum, and one or two of the above-mentioned materials. the cements resulted from clinker grinding in a laboratory gas furnace at 1260–1300 ºc, with one hour at the peak temperatures, and were characterised for blaine specific surface area, specific density, and mineral phases. physico-mechanical properties, such as water content for normal consistency, setting time, soundness, and compressive strength were also determined. results show that these cements contain belite, ferrite, calcium sulphoaluminate, anhydrite, and some minor compounds. keywords: experimental cement, varghis limestone, racosul de sus volcanic tuff, setting time, mechanical properties 1. introduction manufacturing of portland cement is energy consuming, globally accounting for 2% of primary energy and 5% of industrial energy consumption. moreover, portland cement production contributes significantly to greenhouse gas emission in the order of 5% of the global co2 emissions due to anthropogenic sources [1]. new civil engineering requirements impose the production of a new type of cement, which is of good quality, environmentally friendly, and requires low energy utilization. low-energy cement manufacturing is economically and ecologically preferable. these cements could be used in places where high early strength or expansion compensation and also increased durability are required. in cement chemistry, notation of oxides are abbreviated by their first capital letters: c=cao, s=sio2, a=al2o3, f=fe2o3, cs=so3, and h=h2o. lowenergy cements comprise those that belong to the caosio2-al2o3-fe2o3cs system. they are mainly sulphoaluminate belitic and sulphoferroaluminate belitic cements [2]. these can be produced from both natural raw materials or raw material mixtures, containing byproducts or industrial waste, by firing at lower temperatures than for portland cement clinkers. a large variety of cements was developed in china based on the *correspondence: chemiceramic@gmail.com composition c4a3s . these were standardized and named as “third cement series” [3]. these cements have special features such as quick setting time, good impermeability, and rapid strength development even at low temperatures. there are numerous investigations on the laboratory-scale production of sulphoaluminate belite (sab) cement [4–18]. sab cement can be classified into three major categories according to the content and proportions of the phase compositions. the tentative naming and some basic properties are summarized below: 1. calcium sulphoaluminate-rich belite cement: they are mostly composed of only two main phases of sab cement, the major components being c4a3s (around 55–75 (g/g)%) and c2s. this type of cement is typically used for applications requiring rapid setting and high early strength [4, 6, 8, 9, 19, 20]. 2. expansive belite-rich calcium sulphoaluminate cements: besides the main components of the sab cements they contain free lime up to 10 (g/g)% which promotes expansion. this type of cement can be used in restricted areas requiring shrinkage-resistant and self-stressing cements [4, 12, 16, 20, 21]. 3. non-expansive belite-rich calcium sulphoaluminate cements: these cements have higher belite, lower calcium sulphoaluminate, and much lower or completely deficient of free lime content than those of commercially produced sab cements. industrial by-products with high sulphate content can be used in high halmagyi, mosonyi, fazekas, maria, and firuta hungarian journal of industry and chemistry 136 percentages in production. this type of cement shows high mechanical strength both at early and late ages comparable to ordinary portland cement and has the potential to replace it [4, 6, 8, 14, 16]. there is no commercial production of the beliterich calcium sulphoaluminate-type of cement. mehta [18] produced sab cements containing no free cao, but large amounts of belite rich in caco3, silicic acid, hydrated alumina, iron oxide, and gypsum. the clinkers were obtained by heating the raw materials in an electric muffle furnace at 1200 ºc for about 1 hour. clinkers were ground to a blaine specific surface area of about 400 m2 kg-1. microstructure examinations of the clinkers showed that c4a3s appears as cubic crystals whereas belite appears as large rounded grains. the clinkers were very easy to grind due to their brittleness [4]. sahu et alia [12] produced cements of types 2 and 3 from limestone, fly ash and gypsum at 1200 ºc, for a bearing time of 30 minutes and cooled by fresh air. kasselouri et alia [17] in 1995 obtained cement of type 3 at 1280 ºc from limestone, gypsum, bauxite, silica sand, and iron-rich industrial by-products. cements composed from a mixture of baghouse dust, f-class fly ash, and scrubber sludge, sintered at 1175–1250 ºc for bearing times of 30, 45, and 60 minutes, and cooled by natural air were obtained according to arjunan et alia [10]. mixtures composed of limestone, bottom ash, baghouse filter ash, bauxite, and gypsum fired at 1250 and 1300 ºc, for a bearing time of 60 minutes, lead to sab cement of c4a3s – ye’elimite, c2s-larnite (belite), c4af-brownmillerite, and csanhydrite compositions [4]. the absence of tricalcium aluminate (c3a) in these cements indicates that the decomposition of the desired mineral c4a3s does not take place at these temperatures. the presence of the desired minerals and the absence of c5s2s confirmed the formation of the sab cement at 1250 ºc and 1300 ºc after 1 hour. this article presents our study on the cement series sintered using local raw materials, such as volcanic tuffs from racosul de sus, basaltic scoria from racosul de jos, and diatomite from filia (all in the carpathian orocline), and red mud. 2. experimental the raw materials used for the cement experiments carried out as part of this study are natural (varghis) limestone, bodoc clay, nucsoara gypsum, racosul de jos basaltic scoria, racosul de sus volcanic tuff, filia diatomite, and artificial industrial waste (oradea red mud). the selected raw materials were investigated for chemical compositions. the chemical compositions of the limestone, red mud, diatomite, and basaltic scoria were analysed by sem/edax. the volcanic tuff and gypsum analyses were performed by wet chemical methods, according to the sr en 192-2 (table 1). the theoretically estimated mineralogical, chemical compositions based on modified bogue calculations [1, 4, 22] are given in table 2. the compositions of the raw material mixtures are presented in table 3. the raw material mixtures were obtained by grinding them in a laboratory ballmill up to a sieve residue of 90 µm about 12%. afterwards, the raw material mixtures underwent a process of briquetting and drying followed by firing in a laboratory gas oven for one hour at a constant temperature of 1260–1300 ºc. the inside temperatures of the furnace were estimated with a thermocouple thermometer. fast cooling was achieved in the air. the obtained cements from grinded clinkers (five hours in a mill, balls:clinkers ratio of 2:1) were tested. mineralogical table 1. chemical compositions of the raw materials in (g/g) %. oxides varghis limestone oradea red mud racosul de jos basaltic scoria racosul de sus volcanic tuff filia diatomite nucsoara gypsum cao 89.61 12.71 10.38 2.88 0.71 28.31 sio2 4.01 8.93 46.10 64.53 92.52 9.83 al2o3 5.16 17.04 18.78 11.80 3.24 2.73 fe2o3 48.37 9.93 2.57 2.18 1.07 na2o 3.68 3.23 1.89 0.15 k2o 1.69 2.75 0.46 0.55 mgo 1.30 7.21 0.45 0.39 tio2 6.80 1.61 0.27 0.13 v2o5 0.19 0.04 p2o5 1.22 0.98 1.07 0.04 so3 0.89 37.08 mn2o3 0.02 p.c. 12.40 19.90 table 2. theoretical mineralogical and chemical compositions of the cements in (g/g) %. sample mineral composition oxidic compositions c2s c4a3s! c4af cs! cao fe2o3 sio2 al2o3 so3 c1, c2, c3 56 12 22 10 55.15 7.23 19.53 10.63 7.46 c4 50 18 15 17 53.11 4.93 17.44 12.17 12.36 c5 43 28 23 6 51.38 7.56 15.00 18.86 7.20 characterisation of cements from dominantly volcanic raw materials 44(2) pp. 135–139 (2016) doi: 10.1515/hjic-2016-0017 137 compositions of cements made by xrd analyses with a panalytical-philips cubix pro x-ray spectrometer, according to il lab 41 proceedings are presented in table 4. experimental laboratory-produced cements were tested in conditions provided by the romanian crh cement s.a. plant in hoghiz (brasov county). the blaine specific surface area, specific density, heat of hydration (table 5), volume of water for normal consistency, setting time, soundness, and compressive strength (table 6) have been determined. identification of mineral phases formed during the burning of clinkers was carried out by means of the cubix pro spectrometer. 3. results and discussions the mineralogical compositions of the experimental cements are summarized in table 4. all cement samples contain belite, ferrite, anhydrite, and many other phases in small amounts. the largest amount of belite found in a cement sample is in the raw mixture containing diatomite (sample c2 with c2s = 69.1%), followed by the sample prepared with volcanic tuff (sample c3 with c2s = 65.9%). soner et alia reported [4] that the mineral c4a3s is stable between 1250–1350 ºc, but probably it can decompose during cooling. furthermore, it was demonstrated that aluminium could be substituted by iron in the ye’elimite structure forming c4a3-xfxs [23– 26]. the experimental cement samples were characterized with regards to specific density and fineness, representing the blaine specific surface area [27]. the heat of hydration according was also determined to the sr en 196-9/2006 method [28]. the physical properties of experimental cements are presented in table 5. the experimental blaine fineness data are characterised by large specific surface areas. the biggest blaine specific surface area was found in sample c2 (with diatomite) followed of sample c3 sample (with volcanic tuff). these samples have the smallest specific densities in the same order. the binding behaviour of the cements was estimated by measuring the setting time, volume of water for normal consistency, soundness, and compressive strengths (after second and twenty-eighth days). to determine the table 5. physical properties of cement samples c1-c5. sample blaine specific surface area, cm2 g-1 heat of hydration, j g-1 specific density, g cm-3 c1 7367 29 3.17 c2 8745 123 3.04 c3 7963 32 3.07 c4 6501 44 3.14 c5 7553 110 3.26 table 3. the compositions of raw material mixtures in (g/g) %. samples varghis limestone oradea red mud racosul de jos basaltic scoria racosul de sus volcanic tuff filia diatomite nucsoara gypsum cement 1 48.90 36.67 14.43 cement 2 54.08 13.70 32.22 cement 3 54.35 23.37 22.28 cement 4 54.66 0.98 31.53 12.83 cement 5 47.45 1.19 20.66 30.70 table 6. physico–mechanical properties of cement samples c1-c5. sample water for normal consistency, cm3 setting time, hour : minutes soundness, mm compressive strength, n mm-2 early final 2 days 28 days c1 135 0:44 1:44 2.75 0.24 0.42 c2 225 0:13 0:35 0.50 4.12 26.67 c3 124 3:35 4:29 3.00 0.23 8.42 c4 185 1:57 > 10 hour 1.00 0.53 0.72 c5 178 0:05 0:15 2.00 1.44 2.28 figure 1. early and final setting times of the cement samples in minutes. table 4. mineral compositions in (g/g) % of the cement samples c1-c5 according to the il-lab-41 testing method. minerals c1 c2 c3 c4 c5 belite 24.2 69.1 65.9 52.7 58.4 ferrite 7.5 13.1 8.5 24.6 20.8 cubic aluminate 8.5 0.4 0.0 0.2 4.7 orthorhombic aluminate 20.5 0.0 0.0 1.5 0.0 free lime 1.4 0.5 1.7 0.6 0.1 anhydrite 2.1 6.8 3.8 1.5 5.3 halmagyi, mosonyi, fazekas, maria, and firuta hungarian journal of industry and chemistry 138 setting times, the quantity of water required to form cement paste of standard (normal) consistency was determined previously [29]. the water data for standard consistency are presented in table 6. the setting time for the paste with standard consistency was measured using a vicat device. the initial and final setting data of the investigated cements are also shown in table 6 and fig.1. the compressive strengths have been determined according to the sn en-1/2006 method [30] and the data are shown in fig.2. the investigated cements exhibited different mechanical strengths, as a function of their mineral compositions. the strength of sab cements depends mainly on the mineral ye’elimite (ca4al6o12so4 or c4a3s ) during the initial minutes up to hours of hydration [31, 32]. yeʼelimite is almost entirely responsible for the hydration reactions at early ages of csa-type cements [23]. the presence of belite was found to be responsible for compressive strength at late ages. the compositions of raw material mixtures for these experimental cements influenced their mineral contents. taking into consideration these, the initial strengths are better for the cements containing diatomite (sample c2), volcanic tuff (sample c3), basaltic scoria (sample c4), and red mud (sample c5). a higher content of red mud is favoured over sample c4 (see tables 3 and 4, fig.2). a good evolution of mechanical strength over time is shown for samples c5 and especially for the c2 cements. c3 cement sample is also notable, but with lower initial strength, which is an important characteristic for a favourable evolution of specific surface area. this is clearly the largest value for cement sample c3. the cements containing basaltic scoria generally developed lower mechanical strengths in comparison to those containing diatomite or volcanic tuff. the cement containing diatomite is noticeable due to its very high initial strength (table 6). for this cement, the compressive strength, after two days increased, which may be a consequence of the increased specific surface area. in terms of practical applications, the development of cement of good mechanical strength and workability depending on the setting time is of importance. the setting time of investigated cements was decisively influenced by the content of raw material mixtures (see table 3). in the order of c4→c3→c1→c2→c5, the setting time becomes shorter. for the cement samples containing 1.2% red mud, 20.7% basaltic scoria (c5) and 13.7 % diatomite (c2), the setting time is quick. this is a consequence of rapid hydration processes. because of this, these latter samples can be considered for practical applications only as retarding admixtures or super-plasticizers due to their set-retarding effect. soundness shows reasonable values, which is required to be less than 10 mm for portland cement. 4. conclusion based on investigations into cement samples in the laboratory of the hoghiz plant, it can be concluded that from all raw material mixtures, heated at temperatures of between 1260 and 1300 ºc, resultant clinkers contain more belite, ferrite, and anhydrite. physico-mechanical properties show good compressive strength at early ages, good soundness, the biggest blaine specific surface area (ssp = 8745 cm2 g-1) for cement containing limestone, diatomite, and gypsum, as well as belite and anhydrite. the use of the local raw materials from the carpathian orocline area, e.g. varghis limestones, bodoc clays, nucsoara gypsum, volcanic tuffs from racosul de sus, basaltic scoria from racosul de jos, and filia diatomite, facilitated the formation of cements that are more belitical than sulphoaluminate. acknowledgement the authors are grateful to chemi ceramic srl in sfantu gheorghe where the specific experimental cements were manufactured and to the hoghiz plant where their physico-mechanical characteristics were tested. references 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10.1016/j.cemconres.2010.02.009 [26] pöllmann, h.; stöber, s.; schmidt, r.: synthesis and characterization of sulfoaluminate (belite) cements from industrial residues, proc. 1st int. conf. on sulphoaluminate cement: mat. engng. technol (wuhan university of technology press, wuhan, china) pp. 366–384, 2013 www.irsm.cas.cz/ materialy/cs_content/2013/ma_cs_2013_0000.pdf [27] sr en standard 196-6: method of testing cement part 6: determination of blaine specific surface area and specific density, 2006 tpm.fsv.cvut.cz/ student/documents/files/bum1/chapter12.pdf [28] sr en standard 196-9: method of testing cement part 9: determination of the heat of hydration, 2006 tpm.fsv.cvut.cz/student/documents/files/bum1/chapter12.pdf [29] sr en standard 196-3: method of testing cement part 3: determination of setting time and le chatelier soundness, 2006 tpm.fsv.cvut.cz/student/ documents/files/bum1/chapter12.pdf [30] sr en standard 196-1: method of testing cement part 1: determination of strength, 2006 [31] zhang, l.; su, m.; wang, y.: development and use of sulfoand ferro-aluminate cements in china, adv. cement res. 1999 1, 15–21 doi: 10.1680/adcr.1999.11.1.15 [32] winnefeld, f.; barlag, s.: calorimetric and thermogravimetric study on the influence of calcium sulfate on the hydration of yeʼelimite, j. therm. anal. calorimet. 2009 101(3), 949–957 doi: 10.1007/s10973-009-0582-6 guide for authors 1. electronic copies of manuscripts should be uploaded to the author’s page at hjic.mk.uni-pannon.hu or emailed directly to hjic@almos.uni-pannon.hu. − please visit the journal’s website to download a word or latex template and follow closely the suggested layout for the text, figures, tables, and references. manuscripts without the recommended structure and formatting for publication will be returned without a review. − the use of the template is required in order to avoid imposing any article processing charges (apcs), page fees, or article submission charges. 2. in a brief letter 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(lewis, boca raton, fl, usa) 1988 d) patents: u.s. pat. 3,425,442 (1984) e) published lectures, conference proceedings: hih, s.; hhu, c.; leech, w.j.: a discrete method to heat conduction problems, proc. 5th int. heat transfer conf., tokyo, japan, pp. 2.4, 1975. citations of conference presentations are strongly discouraged and should be avoided unless the talk was made available electronically. f) papers that are unpublished, but have been submitted to a journal may be cited with the journal’s name, followed by “submitted for publication” or “in press”. this will be accepted if the author uploads the submitted manuscript as ‘editorial’ material. no reference to “unpublished work” or “personal communication” will be accepted. g) all references must be provided with a digitial object identifier (doi). please provide the editorial office with a rationale for any citations without doi numbers and explain why these references are necessary. 6. authors receive galley proofs, which are to be corrected and returned as soon as possible, but no later than 1 week after receipt. no new material may be inserted into the text whilst being proofread. 7. authors who have less experience of written english are urged to have their manuscripts checked by scientists who are working in the author’s respective field and proficient in english. editorial board of the hungarian journal of industry and chemistry hungarian journal of industry and chemistry vol. 50(2) pp. 7–10 (2022) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2022-11 optimization of erythritol fermentation by high-throughput screening assays edina eszterbauer1 and áron németh1* 1 department of applied biotechnology and food science, budapest university of technology and economics, műegyetem rkp. 3, budapest, 1111, hungary in this research, the erythritol-producing ability of three yarrowia lipolytica strains was investigated. the focus of our research was to achieve the highest possible erythritol concentration by examining and optimizing the cultivation conditions of erythritol fermentation. the complex utilization of the produced fermentation broth was also sought, e.g. the ergosterol extraction of yeast cells and isolation of a biodetergent from the foam formed during erythritol fermentation. erythritol is a naturally occurring, widespread sugar alcohol that is gaining popularity, moreover, due to increases in usage, its demand among consumers is rising, which is why the importance of its biological production is becoming all the more critical in the food industry. erythritol is 60 -70% as sweet as sucrose and a low-calorie sweetener. some microorganisms are capable of producing erythritol from glucose, meanwhile yarrowia lipolytica strains have been reported as glycerol-consuming erythritol producers. these two sources of carbon were compared despite being subjected to further conditions like the initial ph, nitrogen sources and some additives. the largest production of erythritol was achieved by y. divulgata resulting in 44g/l on glycerol compared to only 2g/l on glucose. the best supplementation was found to include ammonium nitrate and sodium citrate resulting in a product yield of 33%. keywords: erythritol, fermentation, yarrowia, glycerol, glucose 1. introduction due to the current lifestyle of society, the number of people suffering from diabetes mellitus and obesity is increasing. the desire of consumers to become healthier has created a whole market for sugar-free and zerocalorie foods, an important part of which is the production of sugar alcohols called polyols. erythritol (c4h10o4) is a naturally occurring sugar alcohol. since the synthesis of erythritol is more difficult than those of other polyols, intensive research has been conducted to optimize its production in terms of the erythritol concentration, production rate (productivity) and/or yield [1]. although erythritol is 60-70% as sweet as table sucrose, it is almost calorie-free (0.2 kcal/g), does not affect the blood sugar level nor cause tooth decay [2], has antioxidant effects, binds free radicals, possesses a glycemic index of 0 and increases the ability to absorb fructose [3]. many methods are available to produce erythritol, both chemically and biotechnologically. even though one of the most well-known chemical methods is high-temperature chemical synthesis from dialdehyde starch in the presence of a metal catalyst, namely nickel, which yields equimolar amounts of erythritol and ethylene glycol, this chemical process involves several received: 2 sept 2022; revised: 16 sept 2022; accepted: 20 sept 2022 *correspondence: naron@f-labor.mkt.bme.hu steps [2,4-5]. however, it is not used in industry due to its very low yield and relatively high costs. currently, biotechnological methods are far superior to chemical methods. the large-scale production of erythritol uses microbial fermentation processes with pure glucose, sucrose and glucose syrup from chemically and enzymatically hydrolyzed wheat and corn starches [2]. the main microbiological strains in the synthesis of erythritol are osmophilic yeasts, e.g. moniliella pollinis, trichosporonoides megachiliensis and y. lipolytica, as well as many strains of lactic acid bacteria, e.g. oenococcus oeni, leuconostoc mesenteroides and lactobacillus sanfranciscensis [5]. within the food industry, erythritol is mainly used as a sweetener in finished goods. sugar-free, reduced sugar and calorieor sugar-free alternative foodstuffs can be produced. as a sugar substitute, erythritol can be found as a tabletop sweetener as well as a sweetener in drinks, chewing gum, chocolate, candy and baked goods. polyols are also commonly used in products from the personal care industry such as cosmetics or toiletries. as an additive, it is increasingly included in care products such as toothpastes, mouthwashes, creams, make-up, perfumes or deodorants. due to its properties, erythritol offers good fluidity and stability as an excipient, making it an ideal candidate for active ingredients in sachets and capsules [6]. yarrowia lipolytica is one of the most https://doi.org/10.33927/hjic-2022-11 mailto:naron@f-labor.mkt.bme.hu eszterbauer and németh hungarian journal of industry and chemistry 8 widely studied species of yeast [7]. y. lipolytica exhibits strong proteolytic and lipolytic activity [8-9]. one of its most important products is lipase, an enzyme widely used in various areas of industry. y. lipolytica can produce succinic acid [15] as well as erythritol and mannitol using glycerol as a substrate both in the presence and absence of sodium chloride [10]. erythritol (170 g/l) was produced at ph 3.0 with the acetate-negative strain y. lipolytica wratislavia k1 by fed-batch fermentation [11]. in terms of its industrial use, it is most widespread in the food industry, moreover, is known for both its positive and negative effects [8]. to increase erythritol production, the effects of various additives, including sodium citrate and mannitol, were investigated in order to down-regulate the formation of by-products during erythritol fermentation. furthermore, the supplementation of metal ions provides cofactors for key enyzmes [10], various nitrates [13] and polyethylene glycol (peg) as an osmoticum [12]. 2. experimental the planned experiment in terms of erythritol production was performed by three yarrowia lipolytica strains from the national collection of agricultural and industrial microorganisms (ncaim, hungary), namely ncaim yarrowia lipolytica 00597, ncaim yarrowia lipolytica 00594 and ncaim yarrowia divulgata 1485. during the fermentations, a 24-well deep-well microtiter plate (fig.1) was applied with a sandwich cover by enzyscreen.com (the netherlands) for each strain separately since many small-scale experiments can be conducted at the same time. due to the high osmotic pressure and low ph during erythritol production, cells grow slowly, so a thorough study of many parallel fermentations needs to be performed. using the microtiter plate, 24 experiments in different or even the same media in parallel fermentations were performed simultaneously to provide a comparison. the ability of the strains to produce erythritol and the conditions required for erythritol fermentation were examined in order to increase the efficiency of production and achieve the highest possible erythritol concentration. the effects of the initial ph and c:n ratio were investigated during the fermentation. given that previous studies [12,14] have shown that proper osmolarity has a significant effect on erythritol production, the effect of changing it was also investigated to determine the most appropriate range of osmolarity for erythritol production with these strains. the main consideration was the comparison of two substrates, that is, glycerol and glucose, in terms of erythritol production. after determining the most efficient fermentation conditions, our intention was to scale up the process. in the case of significant erythritol production, extraction of the product from the fermentation medium was sought. our aim was to use the residual cells, e.g. yarrowia lipolytica lysates, to further investigate cosmetic purposes after ultrasonic treatment. all the inoculum medium was contained, that is, glycerol (50 g/l), yeast extract (3 g/l), malt extract (3 g/l) and peptone (5 g/l). the erythritol fermentation medium was also contained, namely glycerol (150 g/l), nh4cl (3 g/l), mgso4*7h2o (1 g/l), kh2po4 (0.2 g/l) and yeast extract (1 g/l) [11]. in order to increase erythritol production, the effects of the following additives was also tested. 20 g/l of both mannitol and sodium citrate were added during the fermentation. metal ion supplementation resulted in the following concentrations of salts in the medium: cuso4*5h2o (2.5 mg/l), feso4*7h2o (10 mg/l), mnso4*7h2o (25 mg/l) and znso4*7h2o (20 mg/l). 100 g/l of the supplement peg (polyethylene glycol) was added, moreover, 4.6 g/l of nitrate supplementation was applied. furthermore, cofermentation was investigated in combination with the two carbon sources, namely glucose and glycerol. the strains were inoculated in 100 ml of inoculum medium in 250 ml flasks and incubated on a rotary shaker (new brunswick innova 40) at 250 rpm for 3 days at 25°c. all wells of the microplate contained 5 ml of fermentation medium and were incubated on a rotary shaker at 250 rpm for at least 20 days at 25°c. the ph was measured by a mettler toledo fiveeasy ph meter and controlled at 3.0 with naoh (6n). the cell density was measured optically at 600 nm by a camspec m501 single beam uv/vis spectrophotometer every other day. fermentation products were determined by a waters breeze isocratic hplc system equipped with a bio-rad aminex hpx87h column at 65°c. an ri detector was applied at 40°c and the eluent was 5mm h2so4 in ultrapure water (simplicity, millipore). to determine the osmotic pressure of the fermentation, 60 µl of fermentation medium was analyzed by measuring the freezing-point depression using an osmometer (gonotec osmomat 3000). figure 1. deep-well microplate erythritol fermentation 50(2) pp. 7–10 (2022) 9 3. results and discussion 3.1. yarrowia lipolytica strain 594 y. lipolytica strain 594 was produced using the least amount of erythritol compared to the other two tested strains. the highest concentration (10.95 g/l) was achieved on the 14th day of the fermentation in the basic fermentation media containing 100 g/l glycerol with 50 g/l glucose supplementation, i.e. co-fermentation. the highest product yield of 14.81% was also recorded using the same experimental setup, where glycerol in the media was completely consumed but not the glucose. in the case of y. lipolytica strain 594, it can be stated that erythritol was not produced when only glucose was used as a substrate together with any of the other supplements. the highest erythritol concentration of 8.65 g/l was achieved when glycerol was used as the substrate supplemented with peg, which is also rather low in comparison to other reports. glucose as a substrate was not useful with regard to erythritol production using y. lipolytica strain 594. 3.2. yarrowia lipolytica strain 597 y. lipolytica strain 597 was able to produce more erythritol than y. lipolytica strain 594. the highest concentration (14.04 g/l) was produced in glycerol containing a medium supplemented with nano3, which was achieved on the 20th day of fermentation and corresponded to a yield of 30.31%. the average osmolarity with a slight decrement was 2243 mosmol/kg, which is twice that of glucose. the maximum osmolarity of the medium containing glucose was approximately 1200 mosmol/kg, which decreased in correlation with the reduction in glucose concentration. this may explain why erythritol was produced in larger quantities in the medium containing glycerol. glycerol was only completely consumed by the end of the fermentation when the media were combined, containing 100 g/l of glucose and 50 g/l of glycerol. on the 14th day, erythritol production had reached its maximum (11.13 g/l), after which its amount began to decrease. although the osmolarity was 1043 mosmol/kg on the 14th day, it was initially 1346 mosmol/kg. in the case of glucose, the highest concentration of erythritol was 2.04 g/l, which was achieved in a medium supplemented with ammonium sulfate and corresponded to a yield of 4.54%. using this setup, even though the average osmolarity was 1165 mosmol/kg, which is very low for erythritol production, 4.24 g/l of mannitol was produced. therefore, when glucose was used as the substrate supplemented with ammonium sulfate, mannitol was produced by y. lipolytica strain 597 instead of erythritol. 3.3 yarrowia divulgata strain 1485 once again, two different substrates, namely glycerol and glucose, were compared. among the tested additives (fig.2a), the largest increase in erythritol concentration was experienced in the case of sodium citrate compared to the control samples. the highest concentration of erythritol (44.38 g/l) was produced by y. divulgata on the 18th day of the fermentation using glycerol as a substrate supplemented with sodium citrate (fig.2b). the glycerol was completely used up in the medium. the highest productivity of 0.1 (g/l)/h and highest yield of 37.86% were achieved with this supplementation. the osmolarity of the medium decreased in correlation with the exhaustion of glycerol from 2371 mosmol/kg initially to 1099 mosmol/kg by the end of the fermentation. in the case of peg and metal supplementation, 32.44 and 8.31g/l of erythritol had been produced by the end of the fermentation, respectively. among the tested nitrogen sources (fig.2c), ammonium nitrate yielded the highest erythritol concentration of 30.75 g/l, corresponding to a yield of 31.11% based on glycerol. compared to the control media, neither of the nitrogen figure 2. results of y. divulgata strain 1485 a) effect of supplements, b) time course of best run, c) effect of n-sources a b c eszterbauer and németh hungarian journal of industry and chemistry 10 sources could significantly increase the erythritol production. by the end of the fermentation supplemented with ammonium nitrate, 5.13 g/l of mannitol had been produced. regarding the fermentations supplemented with ammonium sulfate and sodium nitrate, 27.60 and 23.87 g/l of erythritol had been produced by the end of the fermentation, respectively. in the case of the substrate glucose, the highest production of erythritol (12.95 g/l) was achieved in the medium supplemented with sodium citrate. 4. discussion in the present work, 3 strains of yarrowia species were examined on two carbon sources, namely glycerol and glucose, in terms of erythritol fermentation. glycerol proved to be more usable. among the 3 yarrowia strains tested, y. divulgata was the most productive, achieving 44.38 g/l of erythritol in the media supplemented with sodium citrate during the microplate fermentation. in the case of y. lipolytica strain 594, the highest erythritol concentration of 10.95 g/l was achieved without supplementation but in a medium containing 100 g/l of glycerol supplemented with 50 g/l of glucose on the 14th day of the fermentation. finally, in the case of y. lipolytica strain 597, the highest concentration of erythritol was 14.04 g/l in the medium supplemented with sodium nitrate. the tested supplementations could increase the erythritol concentration from 24.70 to 44.38 g/l, yield from 33.15 to 37.86% and productivity from 0.049 to 0.102. among the reported yarrowia results, although the aforementioned erythritol concentrations achieved are not particularly high, y. divulgata may reach the recently used strains after optimization. in addition to the use of erythritol alone, the complex utilization of the broth for the application of ergosterol and cosmetics may be of greater interest and feasibility. in the future, given the high number of variables influencing erythritol productivity, a neural network will be used to optimize erythritol fermentation for y. divulgata strain 1485, which proved to be the best. additionally, isolation and determination of the ergosterol content of the cells as well as the produced biodetergent will also be investigated references [1] de cock, p.: sweeteners and sugar alternatives in food technology, (wiley-blackwell, chichester, west sussex, uk) 2012, pp. 215–241, isbn: 9781118373941 [2] godswill, a.c.: sugar alcohols: chemistry, production, health concerns and nutritional importance of mannitol, sorbitol, xylitol, and erythritol, int. j. adv. acad. res., 2017, 3(2), 31–66, issn: 2488-9849 [3] martău, g.a.; coman, v.; vodnar, d.c.: recent advances in the biotechnological production of erythritol and mannitol, crit. rev. in biotechnol., 2020, 40(5), 608–622, doi: 10.1080/07388551.2020.1751057 [4] janek, t.; dobrowolski, a.; biegalska, a.; mirończuk, a.m.: characterization of erythrose reductase from yarrowia lipolytica and its influence on erythritol synthesis, microb. cell factories, 2017, 16(1), 1–13, doi: 10.1186/s12934-017-0733-6 [5] rakicka-pustułka, m.; mirończuk, a. m.; celińska, e.; białas, w.; rymowicz, w.: scale-up of the erythritol production technology – process simulation and techno-economic analysis, j. cleaner prod., 2020, 257, 120533, doi: 10.1016/j.jclepro.2020.120533 [6] regnat, k.; mach, r.l.; mach-aigner, a.r.: erythritol as sweetener — wherefrom and whereto? appl. microbiol. biotechnol., 2018, 102(2), 587– 595, doi: 10.1007/s00253-017-8654-1 [7] gonçalves, f.a.g.; colen, g.; takahashi, j.a.: yarrowia lipolytica and its multiple applications in the biotechnological industry, sci. world j., 2014, 476207, doi: 10.1155/2014/476207 [8] nagy, e.s.: biodiversity of food spoilage yarrowia group in different kinds of food. phd theses (in hungarian), (corvinus university, budapest, hungary) 2015, doi: 10.14267/phd.2015033 [9] groenewald, m.; boekhout, t.; neuvéglise, 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https://doi.org/10.1007/s00449-018-2001-5 https://doi.org/10.1007/s00449-018-2001-5 https://doi.org/10.1016/j.jclepro.2016.08.126 https://doi.org/10.1016/j.jclepro.2016.08.126 https://doi.org/10.11648/j.ijmb.20210603.11 https://doi.org/10.33927/hjic-2019-13 hungarian journal of industry and chemistry vol. 51(2) pp. 21–26 (2023) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2023-14 influence of tic on density and microstructure of al2o3 ceramics doped with nb2o5 and lif pedro henrique poubel mendonça da silveira1* and alaelson vieira gomes1 1 department of materials science, military institute of engineering-ime, praça general tibúrcio, 80, urca, rio de janeiro 22290-270, brazil ceramic matrix composites are widely studied in the ballistic sector due to their high hardness, fracture toughness, and improved ballistic performance in multilayer shielding systems. however, the presence of dopants in ceramics can pose challenges during processing and potentially compromise the final properties of the sintered material. this study focused on the ceramic processing of al2o3-based ceramic matrix composites by adding 4 wt.% nb2o5 (niobium oxide), 0.5 wt.% lif (lithium fluoride), and 38.5 wt.% tic (titanium carbide). the composites were produced using cold uniaxial pressing and conventional sintering at 1400 °c for 3 h. the composites were characterized using archimedes’ principle and scanning electron microscopy (sem). the results revealed that the samples to which tic was added exhibited low initial densities, indicating that the applied pressure of 50 mpa during cold pressing was insufficient to adequately densify the green bodies. moreover, the presence of tic led to a significant reduction in densification, making it challenging to apply a conductive coating for sem analysis. adjustments to the intensity of the electron beam were necessary to conduct the analysis successfully . conversely, the samples to which tic was not added exhibited high density values in the green state and yielded consistent results after sintering in line with previous research, indicating a satisfactory degree of sintering in the absence of tic. these findings highlight the importance of carefully considering the addition of tic in ceramic matrix composites during processing, which can have a significant impact on densification and subsequent material properties. the results contribute to the understanding of processing parameters with regard to the production of ceramic composites with desirable characteristics for ballistic applications. keywords: absence of ceramic matrix composites, al2o3, nb2o5, lif, tic, sem, archimedes’ principle 1. introduction the demand for composite materials has grown due to their advantageous properties, e.g. high strength-toweight ratio, elevated resistance and relatively low density compared to other classes of materials. for this reason, composites have been widely adopted in, for example, the aerospace, automotive and military sectors amongst various other fields in recent decades [1]-[2]. one of the main applications of composites is in ballistic protection, where these materials play a crucial role in the military field. due to their low weight, composites are preferred when manufacturing aircraft, tanks, and bulletproof vests [3]-[6]. the ceramic materials used in ballistic armor must be able to fragment the bullet, reducing its velocity and splitting it into small fragments, which are absorbed by the rear layer of the armor composed of a flexible material capable of supporting the ceramic. therefore, it is crucial that the ceramic material exhibits a high modulus of elasticity, as well as high hardness and good fracture toughness [7]-[10]. received: 4 july 2023; revised: 3 aug 2023; accepted: 7 aug 2023 *correspondence: pedroo.poubel@gmail.com the main commercially used ceramic materials in the development of ballistic armor are al2o3, b4c, sic and ceramic matrix composites (cmcs), such as the al2o3-zro2 or al2o3-nb2o5-lif systems. however, the high cost associated with processing restrictions and the difficulties in predicting the ballistic performance of these ceramic materials impede ceramic mechanisms, making it necessary to include other elements to improve their properties and reduce costs [11]-[14]. in this regard, al2o3 exhibits the best benefit-cost ratio among advanced ceramics, with high modulus of elasticity, good refractory performance, high degree of hardness, and relatively lower cost. however, due to its low fracture toughness and flexural strength, the ballistic performance of alumina is inferior to that of sic and b4c [15]-[17]. an important factor to be considered in the processing of ceramics for ballistic armor is the formation of a liquid phase, which enables higher densification of the material accompanied by reduced sintering temperatures without property loss. an example of this is the use of nb2o5, which, when added to alumina https://doi.org/10.33927/hjic-2023-14 mailto:pedroo.poubel@gmail.com da silveira and gomes hungarian journal of industry and chemistry 22 in quantities of 1 to 8 wt.%, provides a considerable reduction in the sintering temperature [18]-[19]. another crucial factor is the addition of carbide to the ceramic matrix. the inclusion of ceramics, such as nbc, sic as well as b4c in the al2o3 matrix enhances the hardness and fracture toughness [20]. regarding the development of cmcs in armor, tic is a material with good properties which is used as an interstitial addition to increase hardness and fracture toughness [20]-[23]. tic is an extremely hard ceramic (mohs hardness scale 9.0-9.5) and has a very high melting point (3260 °c) [24]. however, concerning the processing of al2o3, tic cmcs are challenging as they require techniques such as spark plasma sintering (sps) or hot pressing (hp), which are difficult to implement. although these techniques facilitate faster sintering with densities around 95% of theoretical values, their availability is limited [25]. with the aim simplifying processing and making it more cost-effective, this work aims to process al2o3 matrix cmcs by adding tic using conventional sintering and cold uniaxial pressing as well as sintering additives such as nb2o5 and lif. 2. materials and methods 2.1. raw materials the powders used to manufacture the ceramic bodies were acquired from different sources. the α-al2o3 was obtained from treibacher schleifmittel (brazil) with an average grain size of 3 μm. the nb2o5 was acquired from companhia brasileira de metalurgia e mineração (brazil). the lif used was purchased from vetec (brazil). the tic applied as an additive was produced by sigma-aldrich (usa). the organic binder used to strengthen the green body is polyethylene glycol (peg 300) manufactured by isofar (brazil). in table 1, the compounds used to produce the ceramic compounds are presented along with their densities. the densities of the mixtures (ρ) were determined using the rule of mixtures as described in equation 1: 𝜌 = (𝑚𝑎 ∙ 𝜌𝑎) + (𝑚𝑏 ∙ 𝜌𝑏) (1) the densities of each element in the mixture (ρa, ρb) and their weight fractions (ma, mb) were taken into account, except for peg which was eliminated during sintering. the weight percentages of each element added were 0.5 of lif, 4 of nb2o5, and 38.5 wt.% of tic. the densities of each mixture are shown in table 2. 2.2. ceramic processing the starting materials were placed in an alumina-coated jar. to facilitate homogenization, deionized water along with alumina balls to enhance powder comminution were added in a ratio of 1:1. grinding and mixing were carried out in a ball mill over 8 hours before being dried in an oven at 80 °c for 48 hours. after drying, the resulting ground mixture was deagglomerated using a pestle and mortar before being sieved to obtain the desired particle size. a sieve shaker was applied for 3 minutes using a din 4188 sieve with an aperture of 0.255 mm. green ceramic bodies were prepared by cold uniaxial pressing using a skay press with a capacity of 30 tons. the ceramic discs were prepared molds with a diameter of 20 mm for the purpose of archimedes tests before being pressed over two stages. the first stage involved a preload of 15 mpa for 30 seconds to settle the powders in the mold, while the second involved pressing with a load of 50 mpa to compress the powders and form a pellet. sintering of the samples was carried out conventionally in the absence of a controlled atmosphere. a jung furnace was used in which a maximum temperature of 1400 °c was reached. the sintering route is shown in figure 1. table 1: density of the raw materials of the produced ceramics material density (g/cm3) al2o3 3.98 nb2o5 4.60 lif 2.60 tic 4.93 peg 300 table 2: theoretical density of each sample mixture sample mixture density (g/cm3) al2o3-nb2o5 3.98 al2o3-nb2o5-lif 3.99 al2o3-tic-nb2o5 4.37 al2o3-tic-nb2o5-lif 4.37 figure 1: sintering ramp adopted in this study influence of tic on al2o3 ceramics 51(2) pp. 21–26 (2023) 23 2.3. characterization density of green bodies from the theoretical density value obtained using the rule of mixtures, it was possible to calculate the density and densification of the ceramic bodies in the initial production phase. equation 2 was used to determine the density of the bodies (ρgb) in the initial phase by dividing the mass of the sample (msample) by its volume (vsample). 𝜌𝑔𝑏 = 𝑚𝑠𝑎𝑚𝑝𝑙𝑒 𝑣𝑠𝑎𝑚𝑝𝑙𝑒 (2) densification in the initial phase was calculated by equation 3 based on the percentage difference between the obtained density (ρgb) and theoretical density (ρtheo) values using the rule of mixtures. %𝑇𝐷 = 𝜌𝑔𝑏 𝜌𝑡ℎ𝑒𝑜 ∙ 100% (3) density of sintered samples the density and densification of the sintered ceramic bodies were calculated based on the standard abnt nbr 16667:2017 [26]. the calculation is based on the archimedes’ principle using the data of immersed mass (mi), wet mass (mw) and dry mass (md) to determine the apparent density according to equation 4: 𝜌𝑎𝑝𝑝𝑎𝑟𝑒𝑛𝑡 = ( 𝑚𝑑 𝑚𝑤−𝑚𝑖 ) (4) during the analysis, a beaker containing deionized water was heated up to its boiling point before the samples were placed in this boiling water for 1h to remove any impurities. afterwards, the samples were weighed, and their initial mass mi recorded before carefully removing the excess moisture from the samples using paper and measuring their mass mw. subsequently, the samples were dried in an oven at 120 °c for 2h to remove all the moisture in the sintered samples, thereby enabling their mass md to be measured. from the masses obtained, it was possible to determine the relative density of the ceramic bodies by calculating the difference between the apparent and theoretical densities of each composition (equation 5). 𝑅𝑒𝑙𝑎𝑡𝑖𝑣𝑒 𝐷𝑒𝑛𝑠𝑖𝑡𝑦 = ( 𝜌𝑎𝑝𝑝𝑎𝑟𝑒𝑛𝑡 𝜌𝑡ℎ𝑒𝑜 ) ∙ 100% (5) scanning electron microscopy (sem) the fracture surface of the sintered samples was analyzed using a quanta feg-250 scanning electron microscope. beam power settings of 5, 20 and 25 kv were used with a beam diameter of 5.5 µm as well as magnifications of 500x and 2000x to observe the microstructures. the samples were coated with gold to enable visualization by the sem. 3. results and discussion 3.1. density of the green bodies the density and green densification values of the four sample mixtures before sintering are presented in table 3. based on the values displayed in table 3, it was observed that the samples to which tic was not added yielded satisfactory results regarding green densification. it is important to emphasize that in order for ceramics to achieve satisfactory levels of densification after sintering, the green bodies need to achieve a relative density of between approximately 55 and 65% of the theoretical density. however, the samples to which tic was added exhibited very low densification values, resulting in an unsatisfactory degree of densification of the bodies after sintering. furthermore, another factor that must be considered is how difficult it was to press the bodies to which tic was added due to the presence of lamination and endcapping defects. the high concentration of tic used led to an insufficient level of homogenization, impairing densification of the green bodies. 3.2. density of the sintered samples in table 4, the density and densification values of the sintered ceramic composites are displayed. significant discrepancies were observed between the average densification values of the different sample mixtures. in the al2o3-nb2o5-lif sample mixture, the highest degree of densification was observed compared to the other groups with values close to those obtained in the literature, that is, in excess of 91% of the theoretical density [11-12, 18]. on the other hand, the al2o3-nb2o5 sample mixture exhibited a lower degree of densification, namely approximately 85% of the theoretical density, table 3: density and green densification results of the ceramic green bodies sample mixture density (g/cm3) relative density (%) al2o3-nb2o5 2.02 ± 0.01 50.64 ± 0.44 al2o3-nb2o5-lif 2.12 ± 0.10 53.37 ± 2.57 al2o3-tic-nb2o5 1.48 ± 0.05 33.86 ± 1.21 al2o3-tic-nb2o5-lif 1.44 ± 0.10 33.11 ± 2.31 table 4: density and densification results of the sintered ceramics sample mixture density (g/cm3) relative density (%) al2o3-nb2o5 3.39 ± 0.07 84.88 ± 1.77 al2o3-nb2o5-lif 3.69 ± 0.02 92.71 ± 0.50 al2o3-tic-nb2o5 1.06 ± 0.01 24.22 ± 0.26 al2o3-tic-nb2o5-lif 1.27 ± 0.01 29.19 ±0.58 da silveira and gomes hungarian journal of industry and chemistry 24 due to the formation of only the alnbo4 phase during homogenization [27]. meanwhile, the sample mixture containing lif and nb2o5 showed interaction between these two compounds, resulting in the formation of the linbo3 and nb3o7f phases during sintering [28]. in turn, the two groups containing tic in the composition presented severe reductions in sample densification, with values below 30% of the theoretical density. this low densification can be attributed to the high content of tic used in the composition (38.5 wt.%), which prevents accommodation of the material as an interstitial element in alumina. based on data in the literature, it is possible to assume that in the absence of an inert atmosphere, tic reacts with oxygen, forming tio2, which could promote sintering in the presence of a liquid phase [23],[25]. however, the excessively high concentration of tic, combined with the low level of densification of the ceramic discs during pressing, may have hindered interaction between the samples, resulting in porous and brittle discs. 3.3. microstructure analysis the fracture surfaces of the sintered samples obtained by sem at different magnifications are illustrated in figures 2 and 3. the micrographs in figure 2 generally depict the fracture region of the sintered samples. it can be observed that the samples from the al2o3-nb2o5 and al2o3nb2o5-lif sample mixtures exhibit lower surface porosity, given the high densification achieved during the sintering process in these two sample mixtures. on the other hand, the samples to which tic was added exhibited high degrees of porosity on their surfaces due to low grain interaction during the sintering process. when the samples were coated before sem analysis, it was difficult to deposit gold on the tic samples, as some of the material was deposited in the pores and therefore, removed from the surface. consequently, it was not possible to generate images of these two samples mixtures with the same electron beam power (25 kv) during the analysis. the beam power had to be reduced to 5 kv for the analysis of the al2o3-tic-nb2o5 sample mixture due to excessive light charging in the image, moreover, a beam power of 20 kv was used for the sample mixture containing al2o3-tic-nb2o5-lif. micrographs magnified at 2000x to improve the visualization of grain morphology are presented in figure 3. the micrographs in figure 3 provide a more detailed insight into the grain morphology. the al2o3nb2o5 and al2o3-nb2o5-lif sample mixtures exhibit rounded grains with well-defined necks, indicating good degrees of compaction and sintering. although some pores are present, they are small and uniformly distributed throughout the sample mixtures as a result of effective wetting of the liquid phase during sintering. on the other hand, the two sample mixtures to which tic was added, that is al2o3-tic-nb2o5 and al2o3-tic-nb2o5-lif contain a significant number of pores and grains of various sizes. this could be attributed to poor homogenization during grinding, leading to difficulties in compaction and sintering of the sample mixtures, ultimately resulting in a depleted microstructure. regarding the ballistic applications of al2o3–tic ceramics, in light of the possible addition of nb2o5 and lif, a wide range of parameters must be investigated to obtain dense and very hard ceramics capable of withstanding ballistic impacts. these parameters include figure 2: fracture region micrographs of the sintered samples with a magnification of 500x (a) al2o3-nb2o5; (b) al2o3-nb2o5-lif; (c) al2o3-tic-nb2o5; (d) al2o3-tic-nb2o5-lif figure 3: micrographs of the fracture regions of the sintered samples under 2000x magnification (a) al2o3-nb2o5; (b) al2o3-nb2o5-lif; (c) al2o3-tic-nb2o5; (d) al2o3-tic-nb2o5-lif influence of tic on al2o3 ceramics 51(2) pp. 21–26 (2023) 25 temperature, composition and cold uniaxial pressing load amongst other factors. to date, al2o3 ceramics to which tic was added have not been applicable due to their low degree of densification. however, samples to which tic was not added exhibit high levels of densification and have been reported to possess good ballistic properties [12]. it is worth noting that these ceramics are also applied in other areas such as in cutting tools [29], substrates [30], high-temperature electromagnetic applications [31] and abrasives [32] amongst various others. the development and optimization of these materials would make it possible for the performance across different industries and technological sectors to be significantly improved. 4. conclusions in this study, four distinct sample mixtures of ceramic matrix composites were produced by cold uniaxial pressing and conventional sintering. these sample mixtures were subsequently characterized using the archimedes’ principle and scanning electron microscopy (sem). based on the obtained results, it can be concluded that the samples to which tic was added exhibited low initial densities, indicating that the pressure of 50 mpa was insufficient to achieve an adequate level of densification of the green bodies. furthermore, the presence of tic drastically reduced the degree of densification, making the application of a conductive 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https://doi.org/10.1016/j.materresbull.2017.09.034 https://doi.org/10.1016/j.materresbull.2017.09.034 https://doi.org/10.1016/j.jallcom.2016.11.113 https://doi.org/10.1016/j.jallcom.2016.11.113 https://doi.org/10.3390/met11060882 https://doi.org/10.1016/j.jeurceramsoc.2020.09.063 https://doi.org/10.1016/j.jeurceramsoc.2020.09.063 https://doi.org/10.1016/j.jeurceramsoc.2020.01.036 https://doi.org/10.1016/j.jeurceramsoc.2020.01.036 https://doi.org/10.3390/ceramics6020047 hungarian journal of industry and chemistry vol. 46(2) pp. 1-100 (2018) hjic.mk.uni-pannon.hu contents tribological behaviour of polymers in terms of plasma treatment: a brief review hayder al-maliki and gábor kalácska 1-11 application of 2n design of experiment method for the evaluation of the efficiency and cross-effects of oilfield chemicals zoltán lukács and tamás kristóf 13–17 strong reachability of reactions with reversible steps eszter virágh and bálint kiss 19–25 production of a biolubricant by enzymatic esterification: possible synergism between ionic liquid and enzyme zsófia bedő, katalin bélafi-bakó, nándor nemestóthy, and lászló gubicza 27–31 comparison between static and dynamic analyses of the solid fat content of coconut oil vinod dhaygude, anita soós, ildikó zeke, and lászló somogyi 33–36 monitoring of chemical changes in red lentil seeds during the germination process ildikó szedljak, anikó kovács, gabriella kun-farkas, botond bernhardt, szabina králik, and katalin szántai-kőhegyi 37–42 recovery of itaconic acid by electrodialysis veronika varga, katalin bélafi-bakó, dávid vozik, and nándor nemestóthy 43–46 the initial magnetic susceptibility of dense aggregated dipolar fluids sándor nagy 47–54 worker movement diagram based stochastic model of open paced conveyors tamás ruppert and jános abonyi 55–62 investigations into flour mixes of triticum monococcum and triticum spelta katalin kóczán-manninger and katalin badak-kerti 63–66 formation of glycidyl esters during the deodorization of vegetable oils erzsébet bognár, gabriella hellner, andrea radnóti, lászló somogyi, and zsolt kemény 67–71 effect of algae treatment on stevia rebaudiana growth réka czinkóczky and áron németh 73–77 comparison of particle size distribution models for polymer swelling ádám wirnhardt and tamás varga 79–84 effects of different heat treatments on the chemical and microbiological characteristics of egg-free and quail egg dried pasta ildikó szedljak, viktória tóth, judit tormási, anikó kovács, lászló somogyi, lászló sipos, and gabriella kiskó 85–90 optimal design and operation of buffer tanks under stochastic conditions bálint levente tarcsay, éva mihálykó-orbán, and csaba mihálykó 91–100 hungarian journal of industry and chemistry vol. 46(2) pp. 1-11 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0011 tribological behaviour of polymers in terms of plasma treatment: a brief review hayder al-maliki ∗1 and gábor kalácska1 1faculty of mechanical engineering, mechanical engineering phd school, szent istván university, páter károly utca 1, h-2100 gödöllő, hungary a review to enrich the literature concerning the effect of various plasmas on the tribological behaviour of polymers and monitor the developments of plasma for the modification of polymer surfaces over recent decades using up-to-date data. a comparative study of plasmas was conducted to identify the most useful and efficient ones which facilitate optimal improvements with regard to the characterizations of polymer surfaces and tribological properties. the studies included in this review strongly suggest that (besides plasma-immersion ion implantation, piii) atmospheric plasmas (dielectric barrier discharges, dbd) are an effective technique in terms of modifying the characterizations of polymer surfaces thereby enhancing the tribological behaviour of polymers under different operating conditions that extends the operating life of elements within the machine. keywords: polymer, plasma treatment, surface characterization, tribology 1. introduction the term tribology originates from two greek words, namely τριβω (tribo), a verb which means “i rub”; and the suffix -logy which is derived from λωγια (logia) which can be translated as “study of” or “knowledge of”. this word was introduced by the british scientists bowden, tabor [1] and jost in 1964 [2]. luke mitchell, a professor of lubrication, observed the problems caused by increasing the level of friction exerted on machines [3]. tribology is the science which studies the principles and applications of friction, wear and lubrication [4]. friction and wear are widespread phenomena in our daily lives. processes that result in friction occur when moving surfaces are in contact with each other [5]. friction is a consequence of two main non-interacting components (adhesion and deformation) and can be considered as an approach for all materials including polymers. polymers are nonpolar materials that exhibit unique tribological behaviour, and some of them possess good selflubrication characteristics, examples of which are stated in [6, 7]. the rapid development of industry was accompanied by the urgent need to decrease the size of equipment which in turn leads to a higher degree of friction and enhanced rates of wear to be exerted on the elements of machines. this prompted the evolution of several surfacemodification techniques, in particular for polymers, to diminish the disadvantages of friction and wear. the alteration of surface properties such as hydrophilicity, chemical composition and roughness lead to inevitable changes ∗correspondence: haidrlatif@gmail.com in tribological behaviour which provided an opportunity for researchers to govern such behaviour with regard to polymers. therefore, specific techniques have been developed over the last few years to modify the surfaces of polymers to improve frictional behaviour and adhesive bonding performance. a lot of chemical and physical techniques have been developed to treat the surfaces of polymers. chemical techniques are the processes which deal with wet or chemical reactions on surfaces, for instance, wet etching, grafting, acid-induced oxidation and plasma polymerization. physical techniques deal with the modification of physical surfaces such as corona discharge, ion or electron beams, photon beams, plasma discharge and oxidizing flames [8]. experimentally, the chemical treatments of polymer surfaces exhibit some disadvantages such as localized corrosion and environmental pollution. in contrast, physical treatments have been adapted recently to modify the surface of polymers [9]. one of the most effective techniques to modify the surfaces of polymers are plasmas which facilitate changes in the properties of polymer surfaces by several processes, for instance, cleaning, ablation, crosslinking and surface chemical functionalization [10]. recently, plasma surface treatment was referred to as the most accepted method of modifying the surface of polymeric materials due to its remarkable stability concerning the enhancement of surface properties compared to conventional techniques, in particular, atmospheric plasma treatment which has the ability to operate under ambient atmospheric conditions (in terms of temperature haidrlatif@gmail.com 2 al-maliki and kalácska and humidity) and does not require a vacuum [9,11]. the literature often suggests that plasma treatment may improve the hydrophilicity of polymers [12–16], which has also been demonstrated in our previous works [17–19]. even though plasmas often increase the surface roughness of polymers [15, 20, 21], some studies have proven that a decrease in surface roughness might occur after shorter treatment times [16, 22]. the present study attempts to review the tribological aspects of polymeric materials treated by various plasmas and compared to their pristine surface behaviour by taking into consideration the influence of plasmas on the characteristics of polymer surfaces which vastly governs the tribological behaviour of polymers. finally, plasma types that may currently be recommended to utilize and reinforce the tribological properties of polymers are highlighted. 2. plasma modification of plastic surfaces plasma can be defined as a chemically active media. the composition of plasmas varies depending on the way they are generated and their working power. plasmas produce either low or very high temperatures and according to the heat they generate they can be termed as cold or thermal plasmas. thermal plasmas, especially arc plasmas, were widely industrialized by the aeronautic sector in particular. cold plasma technologies have evolved in the microelectronics industry, but they have a limited use due to their vacuum equipment. there have been many attempts to transpose plasmas to work under atmospheric pressure without the need for a vacuum. the research has led to various sources that are described in [23]. it is known that plasma is the fourth state of matter and it is more or less an ionized gas that constitutes about 99 % of the universe. plasma consists of electrons, ions and neutrons; these constituents may exist in fundamental or excited states. from a laboratory point of view, plasma is electrically neutral. however, it contains some free charge carriers thus is electrically conductive [24, 25]. the degree of plasma ionization can range from small values, e.g. 10−4 − 10−6 for partially ionized gases to 100 % for fully ionized gases. in a laboratory, two types of plasma can be generated; the first are hightemperature plasmas which are also referred to as fusion plasmas, the second are low-temperature plasmas or gas discharges [26]. 2.1 classification of plasmas plasmas can be differentiated into several groups depending on the energy supply and amount of energy transferred to them since the properties of a plasma change depending on electronic density or temperature as presented in fig. 1 [23]. there are two major plasma groups the first are thermal equilibrium plasmas and the second are those not in thermal equilibrium. plasmas that consist of figure 1: 2d classification of plasmas (electron temperature versus electron density) [28]. particles (electrons, ions and neutral species) of uniform temperature are known as thermal equilibrium plasmas, for instance, stars and fusion plasmas. usually they are termed as “local thermodynamic equilibrium plasmas” which is abbreviated to lte. high temperatures typically ranging from 4,000 k to 20,000 k are required to obtain thermal equilibrium plasmas. otherwise, plasmas that are not in thermal equilibrium, abbreviated as non-ltes, will be formed, for example, interstellar plasma matter [25]. lte and non-lte plasmas can be distinguished according to the gas pressure the plasma is subjected to. a high gas pressure is indicative of many collisions in the plasma and it could be argued that just a few collisions occur in the plasma when the gas pressure is low, for example, dielectric-barrier discharge and atmospheric pressure glow discharge plasmas. more details about types, sources and applications of plasmas can be found in [27]. 2.2 influence of plasmas on the surface characteristics of polymers different types of plasma treatments have exhibited potential changes in the physical and chemical surface characteristics of polymers. the variation in wettability is a fundamental parameter that controls adhesion, lubrication and/or interactions with molecules. the formation of polar groups at the surface following plasma treatments, such as carbonyl, carboxyl and hydroxyl groups, enhances the surface energy. the enhancement of wettability following plasma treatment can be a combined effect of surface functionalization and an increase in surface roughness. when surface grafting occurs relatively quickly, an increase in surface roughness has mainly been observed following longer treatment times [21]. depending on the selection of adequate parameters, different types of plasma treatment are used for either enhancing as well as diminishing adhesion or surface hardness. experimentally, tóth et al. [29] observed a significant improvement in the surface hardness of ultra-high molecular weight polyethylene (uhmwpe) following nitrogen plasma ion implantation (npii). the hydrogen plasma hungarian journal of industry and chemistry tribological behaviour of polymers 3 figure 2: f/c atomic ratio vs. voltage. immersion ion implantation (hpiii) treatment of the surface of uhmwpe induces amelioration in terms of the scratch resistance, temperature, mean surface roughness, oxygen content, and surface hardness, while the surface slope and elastic modulus often decreased, but it is possible to enhance these characteristics upon treatment. low values of temperature and mean roughness favour the reduction of the surface slope [30]. in parallel, the nanomechanical, chemical and wear properties of the uhmwpe surface have been significantly enhanced following treatment with helium plasma immersion ion implantation (hepiii). over the ranges of the parameters, the surface hardness increased by up to six times, whereas the loss in volume following multipass decreased by up to about 2.5 times [31]. in a related study, the influence of nitrogen plasma immersion ion implantation (npiii) on the surface of uhmwpe was investigated as well. the results suggested a relative increase in surface hardness, macroscopic temperature and mean surface roughness, while the loss in volume decreased. however, the elastic modulus decreased or maybe even increased depending on the actual parameter set applied in the process. according to the parameter range studied, a reduction in wear rate is strongly dependent on thermal effects [32]. a statistical study by tóth et al. [33] that revised the literature of engineering plastics treated by plasma-based ion implantation (pbii) and plasma-based ion implantation and deposition (pbiid) concluded that there is a rapidly trending in the number of related publications. as a consequence, the effect of nitrogen plasma-based ion implantation (npbii) on poly(tetrafluoroethylene) (ptfe) was discovered by kereszturi et al. [34]. the study observed that the f/c atomic ratio significantly decreased in an inverse relationship with the voltage as shown in fig. 2. meanwhile the surface roughness increased inversely with the voltage and correlated directly with fluence as shown in fig. 3. figure 3: mean surface roughness of ptfe vs. fluence and voltage. although a clear relationship between wear volume and the main process parameters was not observed, in general this was improved following treatment along with an increase in surface roughness and o/c atomic ratio. furthermore, the water contact angle recorded increased under low voltages and high fluences. atmospheric dielectric barrier discharge (dbd) plasmas enhance the wettability and surface roughness of polypropylene (pp) proportionally to an increase in the duration of plasma exposure [35]. also, the surface roughness of pp increases linearly with the exposure time of atmospheric dbd plasma due to degradation of the polymer surface and the formation of nodulelike features. these nodules are shaped by highly oxidized short fragments of polymer which are referred to as low-molecular-weight oxidized materials (lmwoms) in the literature [15]. in a subsequent study, kostov et al. [36] reported that modifications in terms of the surface of different engineering plastics, such as polyethylene terephthalate (pet), polyethylene (pe) and pp could be achieved by atmospheric pressure plasma jets (appj). the primary aim of this research was to identify the optimal treatment conditions as well as compare the effect of appjs on another source of atmospheric pressure plasmas, e.g., dbd on the characteristics of polymer surfaces. as a consequence of appj treatment the surface roughness is increased as shown in fig. 4. however, nodule-like structures were produced as well, but were much smaller compared to those constituted in the previous study when the polymer was treated by dbd. this was attributed to the higher degree of polymer degradation during dbd treatment. the adhesion strength of pp and perfluoroalkoxy alkanes (pfas) has been significantly enhanced due to atmospheric plasma treatment under several gas flows. the characteristics of the surface introduced hydrophilic functional groups where the level 46(2) pp. 1-11 (2018) 4 al-maliki and kalácska figure 4: afm images of pp (a) untreated; (b) 30 s treated; (c) 30 s treated and washed; (d) 60 s treated; (e) 60 s treated and washed. all treatments were conducted with sample reciprocations using a signal amplitude of 10 kv, frequency of 37 khz and ar flow of 1.3 l/min. of improvement changed in proportion to the duration of the treatment as illustrated in fig. 5 [37]. although atmospheric pressure glow (apg) discharge plasma treatment is moderate in terms of energy characteristics, apgderived fluoropolymers exhibit similar surface properties under conventional low-pressure plasmas [38]. treating metals and polymers by a cold arc-plasma jet under atmospheric pressure leads to a superficial improvement in hydrophilicity and a decrease in the water contact angle of these materials as shown in fig. 6 [39]. on the other hand, the literature shows that modifications to the surface of aromatic polymers by dielectric barrier discharge (dbd) can achieve a substantial degree of chemical functionalization on the polymer surface by applying relatively low or intermediate levels of power without suffering severe topographical damage [40]. the surface modification of a pet film by an atmosphericpressure plasma in combination with different gas flows promptly improved its hydrophilicity and was followed by hydrophobic recovery after longer durations [41]. in parallel, significant changes in the morphology and reactivity of pet surfaces have been observed [42,43]. when figure 5: effect of gas blowing on wettability of pfa film. figure 6: water contact angles of various materials after treatment. exposed to air the processing parameters, such as discharge power, processing speed, processing duration, and electrode configurations, affect the nature and scale of changes to the surface. in general, longer durations (low processing speed and a high number of cycles) and high levels of power induced greater changes in the surface wettability of the polymer [44]. among the various environmental gases studied, air and oxygen yielded the highest levels of hydrophilicity, while argon and nitrogen resulted in lower degrees of hydrophilicity of the pet surface [45]. cold atmosphericpressure plasmas (surface dielectric barrier discharge sdbd) improve the oxygen and nitrogen contents of pet [46]. in comparison to pet, the effects of plasma treatment on polyether ether ketone (peek) have been studied less frequently, but also lead to enhanced degrees of hydrophilicity and adhesion [47] due to the incorporation of functional groups and greater surface roughness following dbd [48]. the hydrophilicity, which is governed by the oxygenation of peek following dbd in the air, also recovered after several months through loss of the structurally related functional groups, but it remained more stable than other non-aromatic polymers [49]. nylon 6 (pa6) exhibited a reduction in surface roughness, and an increase in the o/c and n/c ratios due to diffuse coplanar surface barrier discharge (dcsbd) plasma treatment in two different gas flows (nitrogen and oxygen). however, the oxygen dcsbd plasma was more efficient in terms of modifying the surface compared to the nitrogen equivalent [16]. also, plasma treatment enhances the contact angle and alters the surface topography of nylon 66 (pa66) [50]. plasma pre-treatment of the surface of the biopolymer poly l lactic acid (plla) leads to the formation of pits in the crystalline phase accompanied by a mild increase in surface roughness [51]. hungarian journal of industry and chemistry tribological behaviour of polymers 5 3. tribology of plasma-treated polymer surfaces 3.1 friction of polymers many studies have dealt with the tribology of polymers [52, 53]. hardness and the elastic modulus are governed by the penetration depth, maximum load and strain rate [54]. microcuttings are a consequence of ploughing, and they may exacerbate the friction force under specific conditions. friction that results from elastic hysteresis is known as the deformation component [55, 56]. “the mechanical component results from the resistance of the softer material to "ploughing" by asperities of the harder one” [57]. the adhesive bonds generated between the surfaces in the frictional contact are referred to as the adhesion component. the adhesion component is higher than the deformation (mechanical) equivalent [58]. the friction force is equal to the sum of the adhesion and deformation components as shown in eq. 1 [59]. from this, the reason for polymer transferred layers forming on the metal counterface during frictional contact can be determined. the transferred films are an essential factor which must be taken into consideration whilst estimating the tribological behaviour of polymers [53]. the effect of load, sliding velocity and temperature on friction are also important parameters that could influence the tribological behaviour of the polymer: ff=fa+fd [n] (1) where ff represents the friction force, fa the adhesion component, and fd the deformation component of friction. under low loads, ff ≈ fa since fd is far smaller than fa. 3.2 wear of polymers wear is the undesirable removal of layers from the surface of a material. wear occurs when two materials come into contact as a result of movement. mechanical stress, temperature and chemical reactions directly influence the characteristics of the surface layer. polymers are sensitive to these factors due to their particular structure and mechanical behaviour. the interface temperature can be significantly higher than the temperature of the environment. the wear of some polymers, that were examined by lancaster [60] whilst being slid against steel, was found to be influenced by temperature with regard to polymers that the pass is minimum at the characteristic temperature. the accurate classification with regard to the wear of a polymer is not a trivial matter due to the highly diverse nature of such mechanisms [53, 61, 62]. however, abrasion, adhesion and fatigue are the three most common types of polymer wear that occur during the sliding process. figure 7: pin-on-disc tribological test system : 1) base frame, 2) pin holder, 3) loading head, 4) positioning rail, 5) rotating steel disc. 3.3 tribological tests of polymers the tribological behaviour of a specific material is not inherent of its properties as far as strength, elastic modulus, etc., are concerned. the influence of friction and wear on the overall performance of a polymer is strongly dependent on the entire configuration of the test. to evaluate the polymer under operating conditions that occur in actual structures, test configurations have to simulate the main sliding mode as accurately as possible in terms of system pair materials, contact geometry, contact pressure, sliding motion, sliding velocity, environmental conditions, mechanical stiffness, etc. as a consequence, regular basis tribo-test systems are assembled from test apparatus that has yet to be standardized. several parameters should be taken into consideration to select the most favourable test system, i.e. the structure of the material (macroor microstructure), contact conditions (whether the contacting bodies possess the same radii of curvature as in a pin-on-disc test or different radii of curvature as in the ball-on-disc test), and energy dissipation (sliding temperature) [63]. the real tribosystem of the elements of a polymer is considered to be the most dependable test, however, due to its expense and impractical nature the test cannot be conducted regularly. the scale of tribological tests varies from ‘field tests’ that consist of ‘large-scale simulation tests’ on real components to ‘laboratory tests’ on artificial samples which are widespread in the field of the tribological research of polymers due to the small apparatus used and their relatively low cost and versatility with regard to the testing of various materials under different test conditions, e.g. pin-on-disc fig. 7). 3.4 tribological behaviour of the surface of polymers treated by plasmas it is hard to accurately predict the effects of plasma surface treatment on the tribological behaviour of polymers, due to the multitude of mechanisms that govern such processes. it can be expected that functionalization, 46(2) pp. 1-11 (2018) 6 al-maliki and kalácska (a) (b) (c) figure 8: tribological behaviour of pristine and npiii-treated pa6; (a) dry conditions; (b) water lubrication conditions; and (c) run-out lubrication conditions. crosslinking and chain scission will affect their chemical and mechanical surface properties after plasma treatment, which in turn will alter friction and wear characteristics. however, it cannot be confirmed whether such alterations lead to improved tribological properties or not, this can only be ascertained after the treated surface is tested. the tribological behaviour of rubber treated by plasma has been thoroughly investigated, indicating improvements in terms of friction and wear resistance [13]. the pin-on-disc test yields the lower friction coefficient of pc and pp, whereas pe and ps exhibit larger coefficients of friction after atmospheric plasma treatment compared to their pristine surfaces. bismarck et al. [64] attributed the significant decrease with regard to the friction coefficient of pc either to the most substantial reduction in contact angle or the changes in the chemical and simultaneously the physical properties of pc after treatment. on the other hand, the increase in the extent of crosslinking after atmospheric plasma treatment resulted in lower levels of friction and wear of peek composites [65], while argon plasma treatment led to a higher friction coefficient of pet [12]. the effects of nitrogen plasma immersion ion implantation (npiii) on pet indicated improvements with regard to scratch resistance [66]. kalácska et al. [67] demonstrated that the benefits of sliding tribological properties are strongly dependent on the sliding conditions: a lower degree of friction and enhanced wear performance of pet treated by piii only occurred in the presence of low pv factors under dry or water-lubricated sliding conditions. five minutes of atmospheric plasma treatment is sufficient to reduce the coefficient of friction and enhance the wear properties of a uhmw-pe film under a constant pv factor [68]. in contrast, uhmw-pe treated by atmospheric pressure gas plasma does not exhibit a significant change in terms of wear properties after a treatment time of two minutes. since the level of wear reduced by half after longer treatment times, the duration a polymer is exposed to a plasma plays a major role with regard to the tribological properties of the treated surface, in particular for uhmwpe [69]. uhmw-pe treated by a cold argon plasma using dielectric barrier discharge (dbd) supports such a finding since (under dry conditions) an increase in the friction coefficient with treatment time was observed whereas the wear volume reduced over the treatment time due to modifications of its surface. under normal saline (n-saline) lubrication conditions, wear volume and friction were reduced over the treatment time which is indicative of an increase in surface wettability and, therefore, enhanced surface lubrication capability [70]. sagbas [71] reported an increase in friction and improvement in the wear properties of conventional uhmw-pe after plasma treatment, whereas the friction coefficient was unaffected in terms of hungarian journal of industry and chemistry tribological behaviour of polymers 7 figure 9: tribological testing under dry sliding conditions at 0.5; 1; and 2 mpa; including online measurements of coefficients of friction, (specific wear and displacement ∆h), and temperature. vitamin-e-blended uhmw-pe under the same test conditions. however, the wear factor slightly decreased compared to the significant improvement with regard to the wear properties of conventional uhmw-pe as a consequence of the highly cross-linked nature of conventional uhmw-pe. according to the brief review above with regard to the effect of some plasmas on different polymers, the ability of plasmas to alter the surface characterization and thereby the tribological behaviour of polymers is unquestionable. however, the tribological behaviour of the treated surface depends on several factors such as the type of plasma, treatment method, exposure time, operating mechanism and lubrication conditions amongst many other factors. kalácska et al. [72] studied the tribological behaviour of pa6 treated by nitrogen plasma immersion ion implantation (npiii) under different conditions (dry, water and oil lubrication) and various pressure velocity factors (pv). the results show that the friction coefficient and specific wear of treated pa6 are lower than that of the untreated one under dry sliding conditions and low pv factors, while the friction coefficient, specific wear and contact temperature of treated pa6 are higher than the pristine equivalent under high pv factors (fig. 8a). on the other hand, the water lubricant reduces the adhesive component of friction after treatment, which was reflected in the fluctuation of the friction behaviour of the treated surface (fig. 8b). however, under continuous oil lubrication, no difference could be detected between the treated and untreated parameters, therefore, the run-out type was preferred in terms of detecting such a difference. test conditions in terms of run-out oil lubrication exhibit a lower friction coefficient for treated pa6 than the pristine equivalent in the presence of low pv factors as a consequence of an increase in the dispersive component (fig. 8c). in contrast, our last work [73] elaborated on the effect of atmospheric dbd plasma on the tribological behaviour of pet under various test conditions (3 “dry” normal load and “run-out lubrication” constant normal load conditions). the effect of dbd plasma treatment on the characterization of the surface was interpreted as an enhancement of the surface energy and reduction in the surface roughness due to the melting of surface asperities. however, increasing the surface wettability induces higher coefficients of friction according to archard’s theory of friction [74]. the dry tribological test yielded unexpected behaviour where the coefficient of friction of the treated surface was lower than the pristine equivalent under different pv factors. also, the specific wear and the vertical deformation were enhanced. however, the interface temperature of the treated surface was higher than the untreated one (fig. 9). the reduction in the coefficient of friction can be theoretically attributed to the smaller contributions of a deformation component. in a related context, a “run-out” oil lubrication test yielded a lower coefficient of friction for the treated surface due to a rise in the surface energy after treatment, leading to a favourable enhancement with regard to the adsorption of the lubricant as shown in fig. 10. by using the analysis and comparison of the previously reviewed studies, it can be said that atmospheric dbd plasma can be an effective technique nowadays for the treatment of polymer surfaces that aims to reduce friction and improve wear under dry and run-out lubrication conditions under various pv factors, especially under lower ones compared to other techniques, e.g. npiii. 4. conclusion in conclusion, the reviewed research and results have apparently shown the capability of plasmas to modify the 46(2) pp. 1-11 (2018) 8 al-maliki and kalácska figure 10: tribological testing under lubricated sliding and “run-out” conditions at 0.5 mpa. surfaces of polymers which results in a change in the tribological properties of surfaces. however, the effect of plasmas depends on several factors such as the sources of plasmas, vacuum, temperature, pressure, etc. the essential points concerning the tribological behaviour of polymers that are subjected to plasma treatment are summarized below: • plasmas can efficiently alter the characterization of polymer surfaces by utilizing different sources such as appj, piii, apg, pbii and dbd and various vacuums which results in the enhancement of surface wettability and an increase in surface roughness with few exceptions. atmospheric dbd plasma can achieve the optimum surface configuration in a shorter time. • there is a paucity of studies which deal with the tribological behaviour of polymers in terms of plasma treatment. most studies focused on the effect of plasmas on the tribology of engineering polymers especially pet, pa6, and in some cases peek. however, no studies appear to deal with polyolefins, except some studies which investigate the tribology of uhmw-pe for medical applications in particular. • uhmw-pe exhibits a higher coefficient of friction and improvements in specific wear after plasma treatment under dry conditions where cross-linking plays a prominent role in terms of controlling the wear rate upon plasma treatment. however, the lubricated tribological test of uhmw-pe resulted in a lower coefficient of friction due to an increase in wettability. • the comparative investigation of engineering polymers treated by different plasmas under the same conditions (pa6 treated by npiii and pet treated by atmospheric dbd) can explain the remarkable effect of atmospheric dbd plasma on the tribological behaviour of pet under dry conditions where the friction coefficient of pet remained 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https://doi.org/10.1016/j.actbio.2011.12.007 https://doi.org/10.3390/polym8080295 https://doi.org/10.3390/polym8080295 https://doi.org/10.1108/ilt-11-2015-0176 https://doi.org/10.1016/j.wear.2012.05.011 https://doi.org/10.1002/pen.24689 https://doi.org/10.1063/1.1721448 hungarian journal of industry and chemistry vol. 46(2) pp. 13-17 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0012 application of 2n design of experiment method for the evaluation of the efficiency and cross-effects of oilfield chemicals zoltán lukács ∗1 and tamás kristóf1 1department of physical chemistry, institute of chemistry, university of pannonia, egyetem u. 10, veszprém, h-8201, hungary it has been known for a long time that oilfield chemicals used for different purposes (corrosion and scale inhibitors, scavengers, biocides, etc.) can modify the efficiency of each other. these cross-effects can exhibit adverse or beneficial impacts and may modify the overall corrosiveness of the medium to a great extent. however, there is no standard procedure in order to evaluate the cross-effects, i.e. the extent to which the effect of one of the chemicals is modified by the addition of another. the 2n design of experiment (doe) method provides a robust and simple statistical way to evaluate the change in efficiency of oilfield chemicals owing to the addition of other additives. the 2n doe method can also be applied to other systems. in the present work the effects and cross-effects in systems consisting of a corrosion inhibitor, as well as an oxygen and a hydrogen sulphide scavenger are investigated and successfully demonstrated in a typical oilfield corrosion system with electrochemical corrosion monitoring methods. keywords: oilfield chemicals, corrosion inhibitor, design of experiment 1. introduction the chemical treatment of wet oils that are produced is a widely used method for mitigating unfavorable phenomena in the production, transportation and processing of crude oils: corrosion, scaling, emulsion forming, etc. on the way from the oil well to the refinery a variety of oilfield treatment chemicals are added to the oil: corrosion and scale inhibitors, biocides, hydrogen sulfide and oxygen scavengers (typically with wash waters), demulsifiers, anti-foam agents, etc. [1–4]. the effects of these chemicals are typically well defined in themselves, but the cross-effects, i.e. the influence on each other, are rarely discussed and even more rarely investigated, especially in situ. the reason for this is rather complex. from a practical perspective, there is no standard or wellestablished procedure for such testing. from a theoretical standpoint, the evaluation of such tests, if any, is rather problematic because if the effects of factors are strongly correlated (i.e. one or more “cross-effects” are significant in the system) then the evaluation of the effects by usual means (i.e. least square model fitting [5–7]) is subject to a significant error, if not impossible. in order to formulate the problem, let us consider a dependent variable, y, e.g. the corrosion rate, and assume that it is a quantitative function of some other quantitative ∗correspondence: lukacs600131@gmail.com independent variables: y = p1x1 + p2x2 + · · · + pnxn. (1) this is an uncorrelated multilinear model, that is, the (p1, · · · , pn) parameter set, the set of the factor coefficients, is invariant throughout the whole (x1, ·, xn) model variable space. if the (p1, ..., pn) parameter set is dependent on the location in the model variable space then the following correlated multilinear model can be applied: y = p1x1 + p2x2 + · · · + pnxn + (2) +q1,2x1x2 + · · · + qn−1,nxn−1xn, where the q1,2, · · · qn−1,n coefficients represent the cross-effects coefficients (the effect of quadratic and higher order contributions is not discussed here). if the cross-effects are significant in a model, i.e. the coefficients of the cross-effects are comparable to the coefficients of the factors, then severe computational difficulties may occur, especially if a remarkable error (random or systematic) is superimposed on the measurement data. in such cases conventional parameter-fitting procedures generally fail to provide realistic and accurate model coefficients. for the investigation of cross-effects, a viable technique is the so-called 2n design of experiment (doe) method. as this method is not widely used in the field of corrosion science and technology, its basic concepts are outlined in brief here. mailto:lukacs600131@gmail.com 14 lukács and kristóf in the methodology of the design of experiment technique the independent variables are known as factors and the values of the factors are referred to as factor levels. the factor levels are fixed, discrete values (in contrast to the continuous range of the independent variables). the variance in the factor levels, if any, will be transformed into a variance of the dependent variable. the design of experiment methods are typically used in industrial quality assurance testing, where the fixed factor levels correspond to certain standardized levels of the factors that are assumed to influence a quality parameter (i.e. the dependent variable). in oilfield chemical performance tests a fixed value with regard to the factor of the “corrosion inhibitor” can be the concentration recommended by the supplier. apart from the fixing of the factor levels, the general design of experiment schemes and the supporting mathematical apparatus basically do not differ from conventional multilinear parameter fitting. however, a special type of doe, the 2n design of experiment method, possesses some noteworthy mathematical properties that make it especially applicable for studying cross-effects. in the 2n doe method every factor possesses exactly two factor levels and they are normalized to −1 and +1. in some cases, if all the factors are quantitative, a factor level of 0 exists in order to test the linearity of the model. with the normalization of the factor levels to −1 and +1, all the factors and cross-effects are orthogonal, i.e. independently calculable from each other. this is a great advantage, making the method applicable to study cross-effects. on the other hand, the normalization of the factor levels to the arbitrary −1 and +1 levels is costly. the coefficients of the factors and cross-effects, determined after the calculations, do not have any direct physical meaning, they can only be interpreted in terms of a comparison with one another and to the variance of the measurement data. a comparison of the factors and cross-effects with one another can yield a series of more and less significant effects and a comparison to the variance can provide information on the statistical significance of the respective factor/cross-effect. obviously, the value of the obtained factor and cross-effect coefficients is dependent on the chosen spread between the two factor levels, therefore, this choice must be made with careful consideration. for example, if effects and interactions of oilfield chemicals are investigated, then one of the factor levels would be proposed to be “no chemical added” (concentration = 0) and the other factor level would be termed as the chemical added to the fluid within the recommended range. the purpose of this work was to demonstrate the applicability of the 2n doe method for studying the factors and cross-effects of oilfield chemicals in a suitably chosen model system. 2. experimental the model system was chosen as a typical corrosion system, containing a carbon steel electrode in a wellbuffered, slightly acidic electrolyte (0.1 m nahso4 + 0.1 m na2so4), which maintains a nearly constant corrosiveness and reduces the accumulation of solid corrosion products on the surface of the electrode which also improves the reproducibility of the tests. as the aim was to simulate the effects and cross-effects of oilfield chemical treatment additives (corrosion inhibitor, as well as hydrogen sulfide and oxygen scavengers), 1 mm of na2s was added to the solution. the carbon steel plates (three specimens) were applied for three parallel runs in each measurement set. the specimens were abraded with emery paper and then degreased in acetone for one hour. before each run the species were etched in 5 % hcl, degreased in an alkaline degreasing solution and etched in 5 % hcl again (all dippings lasted for a duration of 5 minutes). 600 cm3 of the solution was poured into a cylindrical test cell of 1000 cm3 in volume and a carbon steel plate electrode with a surface area of 17 cm2 was introduced into the cell, equipped with a silver/silver chloride (3.5 m) reference electrode and two mixed metal oxide-coated titanium tube counter electrodes both 3 mm in diameter and 50 mm in length. the solution was not de-aerated and the measurements were conducted at room temperature (25 ◦c). the corrosion rate was determined by impedance measurements carried out at 1 khz and 0.1 hz with a 20 mv p-p amplitude ac signal superimposed on the corrosion potential, which was established to a satisfactorily stationary level (max. 1 mv/min drift) of no more than 10 minutes. the polarization resistance of the electrode was determined by subtracting the high-frequency resistance (solution resistance) from the low-frequency resistance. the measurements were conducted by an electroflex ef430 potentiostat and a picoscope 3403d oscilloscope. the results were cross-checked by a metrohm potentiostat. in order to simulate the components of a typical oilfield chemical treatment procedure, a commercial corrosion inhibitor (bpr 81100, baker hughes, 100 ppm), zinc acetate as a model compound for a hydrogen sulfide scavenger at a concentration of 2 mm, and sodium metabisulfite (na2s2o5) also at a concentration of 2 mm were added. all chemicals were of p.a. quality. the 2n doe scheme is shown in table 1 below. all experimental sets were repeated 3 times with different electrodes. 3. results and discussion the effect of three factors (a corrosion inhibitor, as well as hydrogen sulfide and oxygen scavengers) was studied on the polarization resistance (compensated for by the ohmic drop in the solution, see the previous section) and the corrosion current. the relationship between the pohungarian journal of industry and chemistry application of 2n design of experiment method for oilfield chemicals 15 table 1: levels of factors and cross-effects of factors in the doe sets. factors factor cross effects set # corrosion inhibitor hydrogen sulfide scavenger oxygen scavenger corrosion inhibitor × hydrogen sulfide scavenger corrosion inhibitor × oxygen scavenger hydrogen sulfide scavenger × oxygen scavenger 1 -1 -1 -1 1 1 1 2 -1 -1 1 1 -1 -1 3 -1 1 -1 -1 1 -1 4 -1 1 1 -1 -1 1 5 1 -1 -1 -1 -1 1 6 1 -1 1 -1 1 -1 7 1 1 -1 1 -1 -1 8 1 1 1 1 1 1 larization resistance and the corrosion current was calculated as: j0[a] = 1 2.303 ( b−1 a [v ] + b−1 c [v ] )−1 rp[ω] = 1 2.303 0.04[v ] rp[ω] , (3) with a typical value of ba = 0.06 v/decade and bc = 0.12 v/decade, furthermore,rp is measured in ohms and j0 in amperes. the units of measurement are shown in square brackets. the design of experiment scheme is shown in table 1 the scheme consists of 23 = 8 sets. the levels of interactions (cross-effects) are simply the product of the levels of the respective factors. the original assumption of the work was that the polarization resistance and/or the corrosion current of the test specimen depend on the factors according to the following model: ys = y + ∑ f afef + ∑ i biei, (4) where ys stands for the value of the target function in the respective set (the polarization resistance or corrosion current), y denotes the total average of the same,ef table 2: factors (in diagonal cells), cross-effect coefficients and the variance of the measurement data for the evaluation of polarization resistance values. values larger than the standard deviation are set in bold. factors corrosion inhibitor hydrogen sulfide scavenger oxygen scavenger corrosion inhibitor 3.359 −1.086 −3.319 hydrogen sulfide scavenger 0.022 −0.082 oxygen scavenger −3.087 standard deviation of measurement data 2.125 and ei represent the level of the respective factor/crosseffect in the respective set (−1 or +1), andaf andbi are the values of the respective effect/interaction coefficients. the overall standard deviation of the measurement data was determined via σ(y ) = √√√√ 1 s(j − 1) s∑ s=1 j∑ j=1 ( ys,j − y s )2 , (5) where s = 8 is the number of sets, j = 3 stands for the number of runs per set, ys,j denotes the measurement result (polarization resistance or the corrosion current) and y s represents the average of the latter for a certain set. the results based on the model of eq. 4 are included in tables 2 and 3 for the polarization resistance and corrosion current, respectively. by comparing the coefficients in the tables above it is striking at first sight that – apart from the coefficient of the corrosion inhibitor factor, which possesses the greatest absolute value in both tables – there is great variation in the relative significance of the corresponding values. it could be expected that if a factor/cross-effect is more significant in the model describing the variations of the table 3: factors (in diagonal cells), cross-effect coefficients and the variance of the measurement data for the evaluation of corrosion current values. values larger than the standard deviation are set in bold. factors corrosion inhibitor hydrogen sulfide scavenger oxygen scavenger corrosion inhibitor −9.06 · 10−4 7.39 · 10−4 8.71 · 10−4 hydrogen sulfide scavenger −7.31 · 10−4 7.45 · 10−4 oxygen scavenger −3.98× 10−4 standard deviation of measurement data 4.55 · 10−4 46(2) pp. 13-17 (2018) 16 lukács and kristóf table 4: factors (in diagonal cells), cross-effect coefficients and the variance of the measurement data for the evaluation of the logarithm of the polarization resistance values. values larger than the standard deviation are set in bold. factors corrosion inhibitor hydrogen sulfide scavenger oxygen scavenger corrosion inhibitor 0.275 −0.143 −0.266 hydrogen sulfide scavenger 0.110 −0.117 oxygen scavenger −0.110 standard deviation of measurement data 0.172 polarization resistance, then the same factor/cross-effect will exhibit approximately the same relative significance in the model of the corrosion current. however, in this case great differences exist in terms of the relative significance. the coefficient of the factor concerning the hydrogen sulfide scavenger and its cross-effect with the oxygen scavenger are both negligible in the model of the polarization resistance ( table 2) and much more significant (compared to the standard deviation of the measurement data in table 3). this magnitude of the differences cannot simply be attributed to some changes with regard to the weighing of measurement data due to the reciprocal transformation from the polarization resistance to the corrosion current (cf. eq. 3 and raises doubts suggesting that the model in eq. 4 is invalid. eq. 4 suggests that the contribution of the additives (corrosion inhibitor and the scavengers) to the dependent variable is a linear function of the concentration. however, if it is taken into consideration that the effects of the additives are basically kinetic, then it can be implied that instead of the linear eq. 4 a logarithmic approximation might exist: lnys = lny + ∑ f af lnef + ∑ i bi lnei, (6) which is in agreement with the general experience that the effects (activities) of components are proportional to the logarithm of concentration. by applying eq. 6, the factors and cross-effect coefficients of the models for the polarization resistance and corrosion current will be identical apart from a multiplicator of (−1). the model-fitting results of eq. 6 are shown in table 4 for the polarization resistance data. from the results it can be concluded that the corrosion inhibitor has the greatest effect on the system and it increases the polarization resistance significantly. the hydrogen sulfide scavenger also decreases the corrosion rate in itself, but its application along with the corrosion inhibitor is less favorable. the use of an oxygen scavenger is not at all advisable under these conditions. 4. summary the general aspects of the 2n design of experiment method and also a specific application for a chemical treatment model system were discussed. the effects and interactions of a corrosion inhibitor, as well as hydrogen sulfide and oxygen scavenger model compounds were studied. the linear model for these additives yielded controversial results, namely the fitting of the model on the polarization resistance data provided totally different results to those on the corrosion current data. by applying the logarithmic model, the results are consistent and their interpretation straightforward. it has been proven that – by carefully selecting the appropriate mathematical model – the proposed method is applicable for the investigation of the effects and crosseffects of different oilfield treatment chemicals. acknowledgement present article was published in the frame of the project ginop-2.3.2-15-2016-00053 (“development of engine fuels with high hydrogen content in their molecular structures (contribution to sustainable mobility)”). references [1] rahmani, kh.; jadidian, r.; haghtalabb, s.: evaluation of inhibitors and biocides on the corrosion, scaling and biofouling control of carbon steel and copper–nickel alloys in a power plant cooling water system, desalination, 2016 393(1), 174–185 doi: 10.1016/j.desal.2015.07.026 [2] barmatov, e.; hughes, t.; nagl, m.: efficiency of film-forming corrosion inhibitors in strong hydrochloric acid under laminar and turbulent flow conditions, corr. sci., 2015 92, 85–94 doi: 10.1016/j.corsci.2014.11.038 [3] papavinasam, s.: corrosion control in the oil and gas industry, chapter 7 – mitigation – internal corrosion (elsevier, amsterdam) 2014 p. 361 isbn: 978-0-12-397022-0 [4] song, g.-l.: the grand challenges in electrochemical corrosion research, front. mater., 2014 1(2), 1–3 doi: 10.3389/fmats.2014.00002 [5] giunta, a.a.; wojtkiewicz jr., s.f.; eldred, m.s.: overview of modern design of experiments methods for computational simulations, proceedings of 41st aerospace sciences meeting and exhibit 2003; reno, nv; usa. aiaa 2003-0649 hungarian journal of industry and chemistry https://doi.org/10.1016/j.desal.2015.07.026 https://doi.org/10.1016/j.desal.2015.07.026 https://doi.org/10.1016/j.corsci.2014.11.038 https://doi.org/10.1016/j.corsci.2014.11.038 https://doi.org/10.3389/fmats.2014.00002 https://doi.org/10.3389/fmats.2014.00002 application of 2n design of experiment method for oilfield chemicals 17 [6] garud, s.s.; karimi, i.a.; kraft, m.: design of computer experiments: a review, comput. chem. eng., 2017 106, 71–95 doi: 10.1016/j.compchemeng. 2017.05.010 [7] kemény, s.; deák, a.: kísérletek tervezése és kiértékelése [design and evaluation of experiments, in hungarian] (műszaki könyvkiadó, budapest) 2002 isbn: 978-963-2799-12 46(2) pp. 13-17 (2018) https://doi.org/10.1016/j.compchemeng. 2017.05.010 https://doi.org/10.1016/j.compchemeng. 2017.05.010 hungarian journal of industry and chemistry vol. 46(2) pp. 19-25 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0013 strong reachability of reactions with reversible steps eszter virágh ∗1 and bálint kiss1 1department of control engineering and information technology, budapest university of technology and economics, magyar tudósok krt. 2, budapest, 1117, hungary the controllability of reactions is an important issue in the chemical industry. the control of reactions is of great practical interest in order to ensure the energyand time-efficient production of compounds. this paper studies the dynamical models of some chemical reactions in order to verify their controllability with regard to a candidate input signal, namely the change in the ambient temperature of a reaction. keywords: reversible reaction, strong reachability, controllability, lie algebra 1. introduction chemical reactions are widely applied during the synthesis and transformation processes of organic compounds. the reaction mechanism and resulting products depend mainly on the concentrations of the species, the catalyst used, the ambient temperature, and the ambient pressure. if the values of these parameters are changed, one can obtain different products from the original ones but it is also possible to increase the productivity and energyefficiency of the reaction. hence the application of a proper feedback law to ensure the latter scenario may be envisaged. a study of the local controllability by considering the reaction rate coefficient as an input has been presented in ref. [1]. the authors of ref. [2] have also considered the reaction rate coefficient as an input and extended the results by claiming that global controllability holds. the controllability of another control input, namely the dilution ratio, is studied in ref. [3]. general conditions for strong reachability in the case of a temperature input were reported earlier in ref. [4]. moreover, the conditions of strong reachability for polymer electrolyte membrane fuel cells (pemfc), controlled by concentrations, have also been analysed. the motivation to consider the concentrations and temperature (or their rate of change) as input signals is due to the fact that these quantities can be easily modified efficiently by industrial equipment that is currently in use, thus these results can be used as a basis to establish control laws to stabilize a desired reaction performance without major changes being made to the equipment used in production. the oxidation of acetone with hydroxylamine (the oximation reaction) was investigated by raman spectroscopy [5]. knowing the mecha∗correspondence: viragh.eszter@gmail.hu nism, the controllability is important for this reaction. throughout this paper, the candidate variable for control is the rate of change in the temperature ṫ , i.e. the first time derivative of the ambient temperature. from a practical point of view, this is a simplification since the variable which can be changed externally, denoted by u, is not ṫ but an algebraic expression involving u and other variables of the system as well. for the dynamics considered in this paper it is always possible, however, to obtain the values of u as a function of ṫ and other state variables. the remaining part of this paper is organized as follows. sec. 2 briefly revisits the concepts related to the strong reachability of nonlinear dynamical systems and conditions of strong reachability. the differential equations describing the dynamics of reactions are presented so that the rate of change in temperature is considered as the controlled input in sec. 3. in sec. 4 the strong reachability of the oximation reaction is studied. the systems in the case of acidic medium in subsection 4.1 and in weakly basic medium in subsection 4.2 are analyzed. in ref. [4] a sufficient condition for strong reachability was given for reactions with general dynamics. in sec. 5, the conditions for strong reachability are given, if the reaction also contains reversible steps. in the last section the conclusions of the paper are drawn. 2. study of strong reachability consider the following nonlinear dynamical system, given by the differential equation: ξ̇ = f(ξ) + g(ξ)u, ξ(0) = ξ∗ ∈ rn, (1) where f, g ∈ c∞(rn,rn) are smooth vector fields and u ∈ r is the control-input variable. the vector fields mailto:viragh.eszter@gmail.hu 20 virágh and kiss f and g are often referred to as drift and control vector fields, respectively. for the sake of completeness, let us revisit some definitions used in refs. [4, 6]. definition 1 (reachability set). consider the system given by eq. 1. the set r(ξ∗, t) ⊂ rn is referred to as the reachability set from the point ξ∗ at time t and it is the union of values at t of the solutions to eq. 1 for some admissible input function u with the initial condition ξ(0) = ξ∗. definition 2 (strong reachability). the system eq. 1 is referred to as strongly reachable from the point ξ∗, if the setr(ξ∗, t) has an interior point for all t > 0. definition 3 (lie bracket). suppose that f ∈ c∞(rn,rn) and g ∈ c∞(rn,rn), then the lie bracket of the vector fields f and g is [f, g] = dg f −df g. (2) the operator adng f : c∞(rn,rn) × c∞(rn,rn) → c∞(rn,rn) is defined as: ad0 gf = f, adng f = [g, adn−1g f ]. (3) definition 4 (lie algebra). consider the vector fields f, g ∈ c∞(rn,rn). the lie algebra generated by f and g is denoted by λ = lie(f, g) and is the smallest linear subspace of c∞(rn,rn) that satisfies the following conditions: 1. f , g ∈ λ , 2. for any a, b ∈ λ, [a, b] ∈ λ. it should be noted that λ also defines a distribution. definition 5 (distribution). the distribution ∆ is the operator which assigns a linear subspace of rn to ∀x ∈ rn . definition 6 (controllability distribution). the controllability distribution ∆c of eq. 1 is the smallest distribution which satisfies the following conditions: 1. g ∈ ∆c, 2. ∆c is invariant to the vector field f (∀η ∈ ∆c, [η, f ] ∈ ∆c), 3. ∆c is involutive (∀η1, η2 ∈ ∆c, [η1, η2] ∈ ∆c). the controllability distribution has a subspace spanned by vector fields g and [f, g]. the following theorem is a fundamental result used in ref. [6]. theorem 1 (reachability rank condition). consider the controllability distribution ∆c of eq. 1. the system eq. 1 is strongly reachable at point ξ∗ ∈ rn if dim{∆}c (ξ∗) = n. 3. strong reachability of kinetic equations the active control of chemical processes may be necessary to maximize the amount of target products and minimize the amount of by-products. to achieve such a control objective, a suitable input variable must be selected so that the resulting dynamical system is controllable from that input. to check if this requirement is satisfied, the tools introduced in the previous section will be applied to the equations describing the reaction dynamics. consider a system of r reaction steps and with m species (r,m > 0). by borrowing notational conventions from chemistry, each reaction step can be generally defined by m∑ m=1 α(m, r)x(m) kr−−→ m∑ m=1 β(m, r)x(m), r = 1, 2, . . . , r, (4) where α(·, r) = (α(1, r), α(2, r), . . . , α(m, r))t denotes the reactant complex vector, β(·, r) = (β(1, r), β(2, r), . . . , β(m, r))t represents the product complex vector, x(m) is themth species and kr is the reaction rate coefficient of the rth reaction step. the species on the left-hand side of eq. 4 are referred to as reactant species and reactant complexes refer to their formal linear combinations. similarly, one may find the products and their linear combinations (product complexes) on the right-hand side of the reaction described in eq. 4. let us also define the stoichiometric matrix, denoted by γ. the matrix γ consists of r columns and m rows, such that each column is obtained by γ(·, r) = β(·, r)− α(·, r). (5) eq. 4 defines the reaction but it does not specify its mass action kinetics. however, in order to study the controllability, the differential equations of the reaction dynamics need to be obtained in the form of differential equation eq. 1. these equations are obtained from the heat balance [7–9] of reaction eq. 4 as ẋm = r∑ r=1 γ(m, r)krx α(·, r) m = 1, 2, . . . ,m, (6) ṫ = r∑ r=1 1 βr,0 krx α(·, r) + u, (7) where xm denotes the concentration of species m, t is the temperature, and xα(·, r) = ∏m p=1 x α(p, r) p . recall that the single input u appears in the expression of ṫ . the state vector ξ for the dynamics eqs. 6–7 reads ξ = (x1, x2, . . . , xm, t )t . the reaction rate coefficient kr can be given as kr = kr,0e − er r0t (8) hungarian journal of industry and chemistry strong reachability of reactions with reversible steps 21 where kr,0, er, r0 ∈ r+. to study reachability, one has to determine the number of linearly independent lie brackets spanning the lie algebra generated by the vector fields g and adgf . thanks to the special structure of the reaction dynamics, the linear independence can be examined by factorizing the matrix of lie brackets and checking the rank of the factors. first, let us define the reaction dynamics matrix: definition 7 (reaction dynamics matrix dr). introduce the notation k (i) j := ∂i ∂t i kj i, j ∈ {1, 2, . . . , r} (9) the matrix of sizer×r of the derivatives of the reaction rate coefficient defined as dr =  k (1) 1 k (2) 1 . . . k (r) 1 k (1) 2 k (2) 2 . . . k (r) 2 ... ... . . . ... k (1) r k (2) r . . . k (r) r  (10) is referred to as the reaction dynamics matrix. the following lemma and theorem have been shown in ref. [4]. they are also provided here for completeness. lemma 1. consider a reaction with r steps. suppose that the activation energies e1, e2, . . . , er of the reaction steps are all different and strictly positive, then the reaction dynamics matrix dr is of full rank for every t > 0. theorem 1 cannot be applied directly to the reaction dynamics eq. 6–7, because the right-hand sides (rhs) of some equations in eq. 6 may be linearly dependent. let δ denote the number of linearly dependent rhss in eq. 6. the system of chemical reactions is considered to be strongly reachable from a point ξ∗ ∈ rm+1 if and only if the dimension of the controllability distribution is m − δ+ 1. the additional dimension is due to eq. 7 with the temperature t as an additional variable. using theorem 1, the controllability subspace for particular reactions can be deduced, so the conditions for strong reachability of the reactions can be determined. theorem 2. consider a reaction with m species and r reaction steps. suppose that the activation energies e1, e2, . . . , er of the reaction steps are all different and strictly positive. then the reaction dynamics with the temperature change (ṫ ) as an input variable are strongly reachable if the concentrations of all reactant species are positive. theorem 2 provides a condition for the strong reachability of reactions in a general form. however, for some reactions where the reaction dynamics have additional properties, weaker conditions may be sufficient to ensure strong reachability. in sec. 4, the strong reachability conditions in the case of oximation reactions were investigated. 4. controllability study of the oximation reaction the oxidation of acetone with hydroxylamine was investigated by raman spectroscopy in ref. [5]. the reaction is strongly exothermic and the concentration of the intermediate highly depends on the ph and temperature. the process can be hazardous, however, it is not dangerous to run in a laboratory with low concentrations and in a controlled manner. strong reachability is a necessary condition to be able to control the reaction. 4.1 oximation reaction in acidic medium in oximation reactions, the sequence (number and nature) of reaction steps depends on the ph. the equations of the reaction steps are different in acidic and weakly basic media. in the case of acidic media the reaction takes place over two reaction steps as given by for the sake of notational simplicity, the symbols a, b, c, d, e, and f will denote the species such that the two reaction steps above read: a + b k1−−→ c (11) c + d k2−−→ e + f. (12) let us denote the concentrations of the species by a, b, c, d, e, f ≥ 0. it is assumed that the reaction rate coefficients k1, k2 > 0. theorem 2 implies that the reaction is strongly reachable, provided that the conditions are met. it follows from strong reachability that it is possible to arrive at any concentrations of m − δ species and at any temperatures by suitable manipulation of the input. recall that there is no guarantee that such concentrations and temperatures also define a steady-state for the system. note that theorem 2 only provides a sufficient condition for strong reachability. for chemical reactions, the positivity condition of activation energies is almost always satisfied. considering the reaction steps of the oximation reaction in acidic media the two remaining conditions of strong reachability will be studied: (1) the positivity of the concentration of all reactant species; (2) the distinctness of activation energies. let us now suppose that the system in eqs. 11–12 is strongly reachable. the stoichiometric matrix for the re46(2) pp. 19-25 (2018) 22 virágh and kiss action steps reads: γ =  −1 0 −1 0 1 −1 0 −1 0 1 0 1  (13) and it is easy to verify that δ = 2 in this case. the differential equation of the reaction: ȧ ḃ ċ ḋ ė ḟ ṫ  =  −k1ab −k1ab k1ab− k2cd −k2cd k2cd k2cd k1 β ab+ k2 β cd  +  0 0 0 0 0 0 1  u = = f(ξ) + g(ξ)u (14) is in a form similar to eq. 1, where ξ = (a, b, c, d, e, f, t )t and the vector field g(ξ) is constant. since the rank of the stoichiometric matrix γ is 2 and the temperature is a scalar quantity, theorem 1 implies that the system is strongly reachable if dim{∆}c = 2 + 1 = 3. hence, to study strong reachability, the number of linearly independent vector fields spanning the lie algebra generated by the vector fields adgf and g must be determined. the lie brackets adgf and ad2 gf read: ad(i) g f =  −k(i)1 ab −k(i)1 ab k (i) 1 ab− k(i)2 cd −k(i)2 cd k (i) 2 cd k (i) 2 cd k (i) 1 β ab+ k (i) 2 β cd  , (15) where i ∈ {1, 2}. to study the dimension of the controllability distribution ∆c one has to determine the rank of the matrix whose columns are g, adgf and ad2 gf which reads: ( adgf ad2 gf g ) = =  −k(1)1 ab −k(2)1 ab 0 −k(1)1 ab −k(2)1 ab 0 k (1) 1 ab− k(1)2 cd k (2) 1 ab− k(2)2 cd 0 −k(1)2 cd −k(2)2 cd 0 k (1) 2 cd k (2) 2 cd 0 k (1) 2 cd k (2) 2 cd 0 k (1) 1 β ab+ k (1) 2 β cd k (2) 1 β ab+ k (2) 2 β cd 1  . (16) the last row is linearly independent of all other rows in the matrix of eq. 16, hence, by deleting the last row and column from the matix, the rank will be decreased by 1. the remaining matrix is denoted by θ and defined as θ =  −k(1)1 ab −k(2)1 ab −k(1)1 ab −k(2)1 ab k (1) 1 ab− k(1)2 cd k (2) 1 ab− k(2)2 cd −k(1)2 cd −k(2)2 cd k (1) 2 cd k (2) 2 cd k (1) 2 cd k (2) 2 cd  . (17) it is clear that the condition dim{∆c} = 3 holds true if and only if rank(θ) = 2. it is easy to see that the matrix θ can be factorized as θ =  −ab 0 −ab 0 ab −cd 0 −cd 0 cd 0 cd  ( k (1) 1 k (2) 1 k (1) 2 k (2) 2 ) = a ·d2. (18) the condition of rank(θ) = 2 can hold true if and only if the matrices a and d2 are of full rank according to the multiplication theorem of determinants. matrix a is of full rank (rank(a) = 2) if and only if a 6= 0, b 6= 0, c 6= 0 and d 6= 0. the reaction dynamics matrix d2 is of full rank if and only if there is no constant c ∈ r \ {0} such that k(2)1 = ck (1) 1 and k(2)2 = ck (1) 2 , hence k (2) 1 k (1) 1 = k (2) 2 k (1) 2 (= c) (19) cannot be true. recalling that the reaction rate coefficients are kr = kr,0e − er r0t (kr,0, er, and r0 are positive constants), it is easy to determine the time derivatives: k(1)r = ( er r0t 2 ) kr,0e −er r0t , (20) k(2)r = kr,0 ( e2 r r2 0 t 4 − 2er r0 t 3 ) e −er r0t . (21) the ratios of the firstand second-order time derivatives are obtained as k (2) r k (1) r = kr,0 ( e2 r r2 0 t 4 − 2er r0 t 3 ) e −er r0t( er r0t 2 ) kr,0e −er r0t = er − 2r0t r0t 2 . (22) based on eq. 22, the equality in eq. 19 holds true if and only if e1 = e2. as a result it has been proven that if the reaction dynamics are strongly reachable then the concentrations a, b, c and d are positive and e1 6= e2. thus the conditions of theorem 2 are also necessary for strong reachability in the case of oximation reactions in acidic media. 4.2 oximation reaction in weakly basic medium in the case of weakly basic media the reaction occurs according to the reaction steps given by: hungarian journal of industry and chemistry strong reachability of reactions with reversible steps 23 since the specific chemical compositions of the species are irrelevant to the controllability analysis, the symbols a, b, c, d, e, f, and g will denote the species such that the above reaction steps read: a + b k1−−→ c, (23) c k2−−→ d + e, (24) d + f k3−−⇀↽−−− k−3 g + e. (25) let us denote the concentration of the species by a, b, c, d, e, f , g ≥ 0. it is assumed that the reaction rate coefficients are strictly positive: k1, k2, k3, k−3 > 0. recall that theorem 2 only provides a sufficient condition for strong reachability. by considering oximation reactions in weakly basic media the remaining conditions of strong reachability will be studied. let us suppose now that the system of eqs. 23–25 is strongly reachable. the stoichiometric matrix for the reaction steps reads: γ =  −1 0 0 0 −1 0 0 0 1 −1 0 0 0 1 −1 1 0 1 1 −1 0 0 −1 1 0 0 1 −1  . (26) the differential equation of the reaction ȧ ḃ ċ ḋ ė ḟ ġ ṫ  =  −k1ab −k1ab k1ab− k2c k2c− k3df + k−3ge k2c+ k3df − k−3ge −k3df + k−3ge k3df − k−3ge k1 β ab+ k2 β c+ k3 β df + k−3 β ge  + +  0 0 0 0 0 0 0 1  u = f(ξ) + g(ξ)u (27) is in a form similar to eq. 1, where the vector field g(ξ) is constant and ξ = (a, b, c, d, e, f, g, t )t . since the rank of the stoichiometric matrix γ is 3 and the temperature is a scalar quantity, theorem 1 implies that the system is strongly reachable if dim{∆}c = 3 + 1 = 4. hence, the number of linearly independent vector fields spanning the lie algebra generated by the vector fields adgf and g must be determined. the lie–brackets adgf , ad2 gf and ad3 gf read: adigf =  −k(i)1 ab −k(i)1 ab k (i) 1 ab− k(i)2 c k (i) 2 c− k(i)3 df + k (i) −3ge k (i) 2 c+ k (i) 3 df − k(i)−3ge −k(i)3 df + k (i) −3ge k (i) 3 df − k(i)−3ge k (i) 1 β ab+ k (i) 2 β c+ k (i) 3 β df + k (i) −3 β ge  , (28) where i ∈ {1, 2, 3}. to study the dimensions of the controllability distribution ∆c one has to give the rank of the matrix whose columns are adgf , ad2 gf , ad3 gf , and g:( adgf ad2 gf ad3 gf g ) . (29) the last row is linearly independent of all other rows in matrix eq. 30, hence, by deleting the last row and column from the matrix, the rank will be decreased by 1. the remaining matrix is denoted by θ and defined as θ =   −k(i)1 ab −k(i)1 ab k (i) 1 ab− k(i)2 c k (i) 2 c− k(i)3 df + k (i) −3ge k (i) 2 c+ k (i) 3 df − k(i)−3ge −k(i)3 df + k (i) −3ge k (i) 3 df − k(i)−3ge  i=1,2,3  (30) the condition dim{∆}c = 4 holds true if and only if rank(θ) = 3. it is easy to see that the matrix θ can be factorized as θ = a ·d = −ab 0 0 0 −ab 0 0 0 ab −c 0 0 0 c −df ge 0 c df −ge 0 0 −df ge 0 0 df −ge   k (1) 1 k (2) 1 k (3) 1 k (1) 2 k (2) 2 k (3) 2 k (1) 3 k (2) 3 k (3) 3 k (1) −3 k (2) −3 k (3) −3  (31) the condition rank(θ) = 3 can hold true only if rank(a) ≥ 3 and rank(d) ≥ 3. t he 3rd and 4th columns in matrix a are linearly dependent, thus rank(a) ≤ 3. the condition rank(a) = 3 can hold true only if the concentrations a, b, and c as well as the 46(2) pp. 19-25 (2018) 24 virágh and kiss concentrations d and f , or the concentrations g and e are strictly positive. matrix d is of full rank only if d consists of a 3 × 3 times full-rank matrix. lemma 1 implies that the reaction dynamics matrix d3 is of full rank if the activation energies are different. hence, matrix d is of full rank, if 3 different activation energies exist. the system was proven to be strongly reachable if 3 of the activation energies are all different and concentrations a, b, c and d, f , or g, e are positive. thus a condition for strong reachability coule be given more precisely in the case of oximation reaction in weakly basic media. 5. reversible reaction step for reactions of general types, theorem 2 provides a condition for strong reachability. however, it will be shown that if the reaction contains one or more reversible steps, weaker conditions are sufficient for strong reachability. the concentrations are defined by x1, x2, . . . , xm , as in the previous sections. the notationa is introduced for the matrix describing the effect of concentrations: a := γ diag(xα(· ,1), xα(·, 2), . . . , xα(·, r)), (32) where xα(·,r) = ∏m m=1 x α(m, r) m and γ is the stoichiometric matrix as introduced by eq. 5. the vector k = (k1, k2, . . . , kr)t is composed of the reaction rate coefficients. the notation d is introduced for the following matrix composed of the derivatives of reaction rate coefficients: d := ( k(1) k(2) ... k(rank(γ)) ) . (33) lemma 2. the reaction dynamics in eqs. 6–7 with the input variable ṫ are strongly reachable, if rankγ = rank(ad), where γ is the stoichiometric matrix and a and d are defined as above. proof the differential equation of the reaction reads: ( ẋ ṫ ) =  v r∑ r=1 kr βr,0 xα(·, r) + ( 0 1 ) u, (34) where ẋ = (ẋ1, ẋ2, . . . , ẋm )t , u is the control input and the vector field v stands for the vector composed of the right-hand sides of eq. 6. as in the previous sections, the study of strong reachability means verification of the dimension of the controllability distribution ∆c. the dimension of the controlled input (the dimension of the change in temperature) is 1, thus, theorem 1 implies that the system is strongly reachable if and only if dim{∆}c = rank(γ) + 1. the vector fields spanning the controllability distribution are g and adigf for i > 0. the lie bracket adigf reads: adigf=  v(i) r∑ r=1 k (i) r βr,0 xα(·, r) =  a · k(i) r∑ r=1 k (i) r βr,0 xα(·, r)  (35) for i ∈ {1, 2, . . . , rankγ}. the rank of the controllability distribution is hence the rank of the matrix( adgf ad2 gf . . . adrankγ g f g ) = a · k(1) . . . a · k(rankγ) 0 r∑ r=1 k (1) r βr,0 xα(·, r) . . . r∑ r=1 k(rankγ) βr,0 xα(·, r) 1  (36) the last row in eq. 36 is linearly independent of the others, hence, the same reasoning as earlier is followed and the last row and columns are eliminated, thus, decreasing the rank by one. the resulting matrix is denoted by θ and reads: θ = ( a · k(1) a · k(2) . . . a · k(rankγ) ) = = ad. (37) since the dimension of the controllability distribution is rank(θ) + 1, the reaction dynamics are strongly reachable if rankγ = rankθ or if rankγ = rank(ad). theorem 3. consider the reaction dynamics eqs. 6–7 such that the activation energies e1, e2, . . . , er are positive and different in pairs. suppose that the concentrations of reactant species are positive in the case of oneway reaction steps and at least one of the ways is positive in the case of reversible reaction steps. then, the reaction dynamics controlled by ṫ are strongly reachable. proof if the system does not contain reversible reaction steps, theorem 2 is obtained. without loss of generality, it can be supposed that the system contains one reversible reaction step. this step can be replaced by pairs of irreversible reaction steps, with reaction rate coefficients denoted by ke and k−e. the changes in the concentrations are equal in the reaction step with rate coefficient ke and in the reaction step with rate coefficient k−e, only the direction is different. thus, the two columns in matrix γ for the reversible reaction steps are always linearly dependent. lemma 2 implies that the system is strongly reachable if and only if rankγ = rank(ad). if the activation energies are positive and all different, lemma 1 implies that matrix d is of full rank. the matrix a is defined by eq. 32, thus, the columns for ke and k−e are linearly dependent. the column for ke contains the factor of the concentrations of the reactant species in the transformation step and k−e contains the factor of the concentrations of the reactant species in the transformation step in the opposite direction with the arbitrary sign in the place of non-zero elements. by substituting one of the two vector fields with a zero vector field, the rank of matrix a remains unchanged. thus, in the case of reversible reactions for strong reachability, it is sufficient if the reactant species have positive concentrations only in one of the directions, and the activation energies are positive and all different. hungarian journal of industry and chemistry strong reachability of reactions with reversible steps 25 6. conclusion the reaction dynamics of strong reachability where the control variable is selected as the rate of change in the ambient temperature (ṫ ) have been studied. first, the strong reachability was analyzed in the case of the oximation reaction. since the processes depend on the ph, conditions that facilitate strong reachability in acidic as well as weakly basic media were studied. for our analysis, theorem 2 was used. it provides sufficient conditions to facilitate strong reachability, however, these conditions are not always necessary. it was proven that the conditions in theorem 2 are necessary to facilitate strong reachability of the oximation reaction in the case of acidic media. in weakly basic media, the system contained a reversible reaction step, thus, the conditions of theorem 2 could be determined. strong reachability has also been studied for reaction dynamics of a general type that contain at least one reversible reaction step where the conditions of theorem 2 could also be further refined. for reversible reaction steps it has been shown that positive reactant concentrations are unnecessary to facilitate strong reachability in both directions of the reversible steps, in one direction is sufficient. acknowledgement the chemistry-related comments from zsombor kristóf nagy and györgy marosi at the bme department of organic chemistry and technology are gratefully acknowledged. references [1] farkas, g.: local controllability of reactions, j. math. chem., 1998 24, 1–14 doi: 10.1023/a:1019150014783 [2] drexler, d.a., tóth, j.: global controllability of chemical reactions, j. math. chem., 2016 54, 1327– 1350 doi: 10.1007/s10910-016-0626-7 [3] dochain, d., chen, l.: local observability and controllability of stirred tank reactors, j. math. chem., 1992 2, 139–144 doi: 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19-25 (2018) https://doi.org/10.1023/a:1019150014783 https://doi.org/10.1023/a:1019150014783 https://doi.org/10.1007/s10910-016-0626-7 https://doi.org/10.1016/0959-1524(92)85003-f https://doi.org/10.1016/j.fuel.2017.09.095 https://doi.org/10.1016/j.fuel.2017.09.095 https://doi.org/10.1021/op500015d https://doi.org/10.1007/978-1-84628-615-5 hungarian journal of industry and chemistry vol. 46(2) pp. 27–31 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0014 production of a biolubricant by enzymatic esterification: possible synergism between ionic liquid and enzyme zsófia bedő1, katalin bélafi-bakó1, nándor nemestóthy1, and lászló gubicza *1 1research institute of bioengineering, membrane technology and energetics, university of pannonia, egyetem u. 10, veszprém, 8200, hungary the possible replacement of lubricants with fossil-fuel sources and the manufacture of biolubricants with more beneficial features were studied. oleic acid and isoamyl alcohol were reacted with an enzyme in an ionic liquid. during the reaction conventional as well as microwave heating was applied. after the experimental determination of the optimal reaction parameters, it was unexpectedly found that a synergistic effect occurred by applying ionic-liquid and microwave-heat treatment simultaneously. the enzyme exhibited a much higher level of activity than the value expected based on the measurements carried out separately by using an ionic liquid instead of an organic solvent and microwave-heat treatment or a conventional method. in the experiments with recycled enzyme it was found that ionic liquid maintained the enzyme more effectively, as if it was immobilized by it: the enzyme managed to maintain its activity and recycling ability. keywords: synergistic effect, ionic liquid and microwave heating, biolubricant production, enzyme reuse 1. introduction lubricants from mineral oils have a considerable detrimental effect on the environment due to the aromatic organic compounds within their chemical structures. mineral oils that have leached into water or soil are toxic for living organisms, they substantially decrease the level of dissolved oxygen in the water. these lubricants can hardly be degraded biologically. during their manufacture several by-products form and further additives are needed for the lubricants. hence the demand for biolubricants from plant oils has been growing recently, since they are natural, renewable, non-toxic as well as environmentally-friendly compounds, and often cheaper than synthetic oils. therefore, they are suitable for eliminating the disadvantages of mineral oil, moreover, our dependence on mineral oils and other non-renewable sources might be decreased [1, 2]. the production of synthetic and semi-synthetic lubricants is necessary since now it is not possible to conduct all lubrication tasks by using lubricants derived exclusively from mineral oils. in several cases non-coking lubricants with extremely high degrees of viscosity are able to operate at low temperatures (below -50 °c). biolubricants are used in numerous fields of application, but in all of them it is vital to prevent the contamination (only a negligible level is acceptable) of the product and environment. these provide an alternative to the mineral oilbased lubricants in industrial applications that are used in *correspondence: gubiczal@almos.uni-pannon.hu the automotive industry as hydraulic fluids during metal processing and oils for driving gears [3]. they are not considered as biological hazards in water systems when applied in watercrafts. in biotechnological methods for the manufacture of biolubricants, raw materials with a high oleic acid content are generally used for the transesterification processes. biolubricants are mainly produced from plant oils, e.g. sunflower oil, soybean oil and castor oil [4, 5]. the lifetime of these biolubricants that possess esters is usually longer than those obtained from mineral oils. on the other hand, their widespread industrial usage is hindered by the fact that certain equipment must be converted to run on biolubricants [6]. various esters can be enzymatically produced from acids and alcohols of different chain lengths in nonconventional systems (organic solvents, ionic liquids, supercritical fluids, solvent-free media). thus, the esterification of acids and alcohols of short chain lengths by lipase results in flavour esters [7, 8]. the esterification of fatty acids (acids with carbon numbers of between 12 and 18) and alcohols may yield both biolubricants and biofuels depending on alcohols’ chain lengths [9,10]. biodiesel is obtained when alcohols of short chain lengths are used, while biolubricants can be manufactured by alcohols of long chain lengths. the formation of a biolubricant from oleic acid and isoamyl alcohol in organic solvents has been studied previously [11–13]. the term ‘biolubricant’ may be used since both isoamyl alcohol and oleic acid are considered mailto:gubiczal@almos.uni-pannon.hu 28 bedő, bélafi-bakó, nemestóthy, and gubicza to occur naturally and the reaction is carried out by a naturally-occurring catalyst, an enzyme. koszorz et al. studied the same reaction and stated that the water formed as a by-product of the esterification reaction had a negative effect on the rate of reaction and activity of the enzyme. to enhance the effectiveness of the process, water had to be removed by an integrated system where the reaction was combined with a pervaporation unit [14]. turkish researchers applied fusel oil – a by-product of bioethanol production – containing a significant amount of isoamyl alcohol that was used to synthesize a biolubricant with high yield [15]. in addition to organic solvents, good results were achieved recently using ionic liquids as solvents. in the field of heat treatment microwave irradiation has yielded excellent results in both organic synthetic and enzymatic reactions [16, 17]. in transesterification reactions even a synergy effect was observed between the enzyme and ionic liquid [18–20]. the aim of this paper was twofold: (i) to study the possibility of applying ionic liquids instead of organic solvents; (ii) to investigate the role of microwave irradiation to achieve the highest possible degree of conversion in the minimum amount of time. 2. experimental the reactions were conducted in an incubator shaker and microwave equipment using conventional heating and microwave irradiation, respectively. similar compositions and reaction volumes were used in the measurements to be able to compare the experimental results. 2.1 samples and measurements all chemicals were commercially available and used without further purification. novozym 435 (immobilised candida antarctica lipase b, calb), a triacylglycerol acylhydrolase (e.c. 3.1.1.3.) immobilized on an acrylic resin, was a gift from novozymes (bagsvćrd, denmark). its nominal catalytic activity and water content were 7000 propyl laurate units (plu)/g and 1-2 %, respectively. isoamyl alcohol (98 %) and oleic acid (99 %) were used as received from sigmaaldrich. the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]pf6) (≥98.5 %) was purchased from sigma-aldrich while n-hexane and isooctane (99 %) were acquired from reanal. to follow the yield of the ester, a hp-5890a gas chromatograph (gc) was used. the device was equipped with a split/splitless injector, flame ionization detector (fid), and db-ffap column (length: 10 m, inner diameter: 0.53 mm, film thickness: 1.00 µm). the following heating programme was applied: 130 °c, 3 mins.; temperature ramp up: 10 °c min−1; 240 °c, 5 mins. isooctane was used as an internal standard. for the analysis, a 10 µl sample of the reaction mixture was extracted. reaction mixtures that contain ionic liquids cannot be injected into the gc, since they – as a viscous liquid – form a deposit on the inner side of the column that causes fouling. moreover, they may be degraded due to the high temperature, thus, the precision of the measurements will be affected and undesirable peaks may appear in the chromatograms. during the measurements the components are usually separated from the ionic liquid by extraction and injected into the column. in our measurements – to preserve the gc column – fiberglass and adsorbent material were placed inside the injector, which retained the ionic liquid after injection while the component to be analysed was transferred in a gas phase to the column as a result of the high temperature. in this way extraction of the product from the reaction mixture could be avoided, therefore, the errors that originate from the incomplete extraction (effectiveness) could be eliminated. 2.2 experimental setups two different procedures were used for the production of biolubricants. firstly, by using conventional heating the synthesis of biolubricants was conducted in eppendorf tubes (1.5 ml) at 40 °c rotated at 200 rpm (ika incubator shaker ks 4000i). in a typical experiment 5 cm3 of reaction mixture (22.5 mmol of isoamyl alcohol and 3.75 mmol of oleic acid dissolved in n-hexane or [bmim]pf6) was prepared in a volumetric flask, and the eppendorf tubes were each filled with 1 cm3 of the reaction mixture. the reaction started when 10 mg of the enzyme was added. tests under microwave conditions were performed in a commercial microwave synthesizer (discover series, benchmate model, cem corporation, usa). it was equipped with a magnetic stirrer and a fibre-optic sensor to monitor the temperature, which was set by varying the power of the microwave. for the esterification of biolubricant, 10 w of energy was used to maintain the temperature of the reaction between 40 and 60 °c. the volume and composition of the reaction mixture was identical to under conventional conditions. experiments to study the reusability of enzymes were conducted by separating the enzyme from the reaction mixture and starting a novel reaction with a reaction mixture of the same volume. 3. results and analysis 3.1 experiments certain ionic liquids may catalyse esterification reactions. even though in the case of [bmim]pf6 this phenomenon does not occur according to earlier publications, measurements were conducted in reaction mixtures which did not contain enzymes to be able to exclude this effect. our experiments confirmed previous results from the literature: [bmim]pf6 did not catalyse the reactions. hungarian journal of industry and chemistry production of a biolubricant by enzymatic esterification 29 figure 1: biolubricant production in the organic solvent (dashed lines) and ionic liquid (solid lines) using conventional heating. the experimental conditions were selected according to data from the literature in addition to our earlier observations, and they were checked by preliminary measurements. thus, the molar ratio of isoamyl alcohol to oleic acid was adjusted to 6:1, with a shaking rate of 200 rpm. the measurements were conducted at a temperature of between 30 and 50 °c to follow the eventual changes at various temperatures. it would have been possible to carry out measurements at higher temperatures using the enzyme novozym 435 or the ionic liquid [bmim]pf6, furthermore, changes over longer reaction times could be more suitable to follow and evaluate. 3.2 experiments using conventional heating firstly, measurements under the conditions described in section 2.2 were conducted using conventional heating (fig. 1). as can be seen esters were produced in high yields during the reactions in the ionic liquid as well as expected, and the yield was always higher in the ionic liquid at the same temperature. 3.3 experiments using microwave heating the results of the measurements using microwave irradiation are presented in fig. 2. as can be observed, a much shorter time was necessary to reach equilibrium, and the reaction rate was also faster in the ionic liquid. 3.4 investigation of enzyme reuse the reusability of the enzyme novozym 435 was studied under similar conditions in an ionic liquid (i.e. using conventional and microwave heating). the results indicated figure 2: biolubricant production in the organic solvent (dashed lines) and ionic liquid (solid lines) using microwave irradiation. that the activity of the enzyme declined more rapidly using conventional heating. 4. discussion the results of the experiments conducted in the organic solvent, n-hexane, and in the ionic liquid, [bmim]pf6, under similar conditions provided a good basis to compare the effects of conventional and microwave heating during the production of biolubricants using enzymes since in both cases the same reaction volumes were used. as can be seen in fig. 1, the reaction rate was higher in the ionic liquid (il) than in n-hexane (n-h), the organic solvent that was usually applied. the data in table 1 can be further compared. by comparing the values of c, il/c and n-h (the ratio of enzyme activities in the ionic liquid and n-hexane using conventional (c) heating), it can be seen that the activity of the enzyme increased by a factor of 1.2 (on average) at each temperature due to the presence of the ionic liquid. in the organic solvent the activity of the enzyme was found to be 2.8 times greater as a result of the microwave irradiation at each temperature (data of mw, n-h/c, n-h) compared to the conventional heating. in similar experiments in ionic liquids even more significant increases in the activity of enzymes were observed: microwave irradiation (mw) resulted in a 5.8-fold rise (data of mw, il/c, il). a possible explanation for the significant increase is that the ionic liquid and microwave irradiation have a positive synergistic effect on the activity of the enzyme. previously it was observed that ionic liquids seem to protect the enzyme in a similar way to the immobilising suptable 1: comparison of the activity of the enzyme under various conditions. t / °c activity / µmol·min−1·g−1 conventional heating microwave heating c, il/c, n-h mw, n-h/c, n-h mw, il/c, il n-h il n-h il 30 162 194 475 1120 1.19 2.93 5.77 40 342 444 990 2510 1.29 2.89 5.65 50 575 660 1650 3840 1.15 2.86 5.82 46(2) pp. 27–31 (2018) 30 bedő, bélafi-bakó, nemestóthy, and gubicza figure 3: reusability of the enzyme in the ionic liquid using microwave and conventional heating port of the enzymes. in this work an immobilised enzyme was applied, thus, the synergistic effect simply strengthened the enzyme preparation or stabilised the active site of the enzyme. a similar effect has already been described in transesterification reactions in some papers in the literature [18,20], but not with regard to esterification reactions. the stabilisation effect of the ionic liquid was confirmed by the results presented in fig. 3. by re-using the enzyme 5 times under conventional heating, the activity of the enzyme decreased much more rapidly than in the case of microwave heating. while in the first case 50 % of the original activity of the enzyme was maintained after the fifth application, using microwave irradiation this value was 70 %. 5. conclusion the experiments led to a definite answer to the original question, namely whether microwave irradiation may enhance the effectivity of the enzymatic production of a biolubricant from isoamyl alcohol and oleic acid. it was observed that microwave heating increased the rate of reaction. during the evaluation of the experiments an unexpected effect was discovered: a synergistic effect was observed between microwave irradiation and the ionic liquid. as a result, a significantly greater increase in the activity of the enzyme was achieved during the reaction in the ionic liquid using microwave irradiation than in the organic solvent or according to the value obtained in the ionic liquid using conventional heating. acknowledgement references [1] carrea, g.; riva, s.: organic synthesis with enzymes in non-aqueous media (wiley-vch verlag gmbh & co. kgaa, weinheim, germany) 2008 pp. 169–190 isbn: 978-3-527-31846-9 [2] salimon, j.; salih, n.; yousif, e.: improvement of pour point and oxidative stability of synthetic ester basestocks for biolubricant applications, arab j. chem., 2012 5, 193–200 doi: 10.1016/j.arabjc.2010.09.001 [3] akerman, c.o.; hagström, a.e.v.; mollaahmad, m.a.; karlsson, s.; hatti-kaul, r.: biolubricant synthesis using immobilised lipase: process optimisation of trimethylolpropane oleate production, proc. biochem., 2011 46, 2225–2231 doi: 10.1016/j.procbio.2011.08.006 [4] dossat, v.; combes, d.; marty, a.: lipasecatalysed transesterification of high oleic sunflower oil, enzyme microb. tech., 2002 30, 90–94 doi: s0141-0229(01)00453-7 [5] hajar, m.; vahabzadeh, f.: modeling the kinetics of biolubricant production from castor oil using novozym 435 in a fluidized-bed reactor, ind. crop prod., 2014 59, 252–259 doi: org/10.1016/j.indcrop.2014.05.032 [6] mobarak, h.m.; mohamed, e.n.; masjuki, h.h.; kalam, m.a.; al mahmud, k.a.h.; 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of (r,s)-1phenylethanol by cutinase from novel isolate fusarium ict sac1, biochem. eng. j., 2017 117, 121– 128 doi: 10.1016/j.bej.2016.09.007 46(2) pp. 27–31 (2018) https://doi.org/10.1016/s0011-9164(04)00064-5 https://doi.org/10.1016/s0011-9164(04)00064-5 https://doi.org/10.1016/j.enzmictec.2006.06.010 https://doi.org/10.1016/j.enzmictec.2006.06.010 https://doi.org/10.1016/j.molliq.2016.11.123 https://doi.org/10.1016/j.molliq.2016.11.123 https://doi.org/10.1016/j.biortech.2012.01.030 https://doi.org/10.1016/j.biortech.2012.01.030 https://doi.org/10.1039/c1gc15114b https://doi.org/10.1039/c1gc15114b https://doi.org/10.1016/j.bej.2016.09.007 hungarian journal of industry and chemistry vol. 46(2) pp. 33–36 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0015 comparison between static and dynamic analyses of the solid fat content of coconut oil vinod dhaygude *1, anita soós1, ildikó zeke2, and lászló somogyi1 1department of grain and industrial plant technology, szent istván university, villányi út 29–43, budapest, 1118, hungary 2department of refrigeration and livestock products technology, szent istván university, ménesi út 43-45, budapest, 1118, hungary the objective of this work was to compare the physical and thermal characteristics of two coconut oils and their blends which were observed by the results of differential scanning calorimetry (dsc) and pulsed nuclear magnetic resonance (pnmr). fat blends composed of different ratios (fully hydrogenated coconut oil / non-hydrogenated coconut oil: 25/75, 50/50 and 75/25) were prepared and examined for solid fat content. the solid fat content of samples was determined as a function of temperature by pnmr. the dsc technique determines the solid fat index by measuring the heat of fusion successively at different temperatures. dsc calculates the actual content of solids in fat samples and how it changes throughout the duration of heating or cooling. a characteristic curve is constructed by the correlation of enthalpies. based on our results, it is clear that both dsc and pnmr techniques provide very practical and useful information on the solid fat content of fats. dsc is dynamic and pnmr is static. a difference in the values of the solid fat indexes of samples was observed which may be due to a fundamental difference between the two techniques. these data can be used by food manufacturers to optimize processing conditions for modified coconut oil and food products fortified with coconut oil. keywords: solid fat content, solid fat index, pnmr, dsc, and coconut oil 1. introduction nowadays, a proper understanding of the crystallization and melting properties of coconut oil systems is essential to increase the number of applications in the food industry. coconut oil is considered as a multi-component mixture of various triglycerides which determines the physical properties that affect the structure, stability, flavor as well as sensory and visual characteristics of foods [1]. modification of the properties of solid fat has received much attention in research recently because of its importance during the processing and production of new food products. the crystallization and melting properties of modified fat used as a shortening in bakery products are critical [2]. the crystal networks present in modified fat strongly enhance its texture, stability and acceptance of fatty-food products. an essential aspect of the industrial manufacture of edible oils and fats is the ability to measure the physical and thermal properties of the materials such as melting and crystallisation profiles, solid fat content (sfc), solid fat index (sfi) and enthalpy. nuclear magnetic resonance (nmr) spectroscopy and differential scanning calorimetry (dsc) are easier to implement and faster techniques than dilatometry which is time-consuming and inaccurate *correspondence: vinod.dhaygude05@gmail.com [3]. nmr has been widely used for the analysis of food materials such as dairy products, fats and oils, in addition to wine and beverages. over the past two decades, dsc has been increasingly utilised for the thermodynamic characterisation of edible oils and fats as well as the sfi determination of food fats. considering the significant scientific and practical importance of the physical properties of coconut oil from a few studies, the solid fat content determined by nmr and dsc methods was investigated and the obtained results compared. ultimately, this research study is beneficial to the food industry which continues to reformulate many products. 2. experimental 2.1 materials in this research study, barco coconut oil was used as a source of non-hydrogenated coconut oil (nhco) which was kindly provided by mayer’s kft. in budapest. the fully hydrogenated coconut oil (fhco) was obtained from local industry in hungary. blends of nhco and fhco were mixed in 25:75, 50:50 and 75:25 (w/w) proportions. the blends were melted and maintained at 80 ◦c for 30 mins to erase crystal memory. subsequently, mailto:vinod.dhaygude05@gmail.com 34 dhaygude, soós, zeke, and somogyi table 1: fatty acid composition (%) of nhco, fhco and their blends. fatty acid fhco fhco:nhco nhco (%) 75:25 50:5 25:75 c6:0 0.1 0.225 0.35 0.475 0.6 c8:0 1.9 3.175 4.45 5.725 7 c10:0 2.7 3.4 4.1 4.8 5.5 c12:0 53.3 51.425 49.55 47.675 45.8 c12:1 0.1 0.075 0.05 0.025 − c14:0 21.3 20.675 20.05 19.425 18.8 c16:0 10 10.025 10.05 10.075 10.1 c18:0 10 8.25 6.5 4.75 3 c18:1 trans 0.03 0.0575 0.085 0.1125 0.14 c18:1 cis 0.3 2.0 3.7 5.4 7.1 c18:2 trans − 0.02 0.05 0.08 0.11 c18:2 cis 0.1 0.5 0.9 1.3 1.7 c20 0.1 0.1 0.1 0.1 0.1 other 0.02 0.03 0.05 0.065 0.08 all blends and pure samples of fat were stored in a refrigerator at 10 ◦c until use. 2.2 methodologies static analysis the static analysis of the solid fat content was conducted by pulsed nuclear magnetic resonance (pnmr) apparatus (bruker minispec 300, bruker gmbh, germany) according to the official method cd 16b-93 of the american oil chemists’ society (aocs) [4]. the solid fat content was measured at 5 ◦c, 10 ◦c, 15 ◦c, 20 ◦c, 25 ◦c and 30 ◦c. three parallel measurements were conducted and average values reported (fig. 1). additionally, these sfc values were converted into percentages where the initial value was considered to be 100 %. these percentage sfcs were compared with the sfis. dynamic analysis dynamic analyses of the samples were studied by dfc according to aocs official method cj 1–94 [4]. samples of nearly 20 mg were loaded onto the middle of the aluminum pans using a small spatula and hermetically sealed by an empty pan that served as a reference. samples were cooled to 0 ◦c at a rate of 1 ◦c min−1 and maintained at this temperature for 10 mins. the heating of blends and pure samples of oil was performed until a temperature of 80 ◦c was achieved at the same rate as for the cooling. the samples were maintained at 80 ◦c for 30 mins. the cooling process started after this period and the rate of cooling was 1 ◦c min−1 until the temperature reached −20 ◦c. before being heated again to ambient temperature, the samples were maintained at this temperature for 10 mins. after that, heating commenced once more at a rate of 5 ◦c min−1 up to 20 ◦c at which point calorimetric measurements ended. three parallel measurements were taken and the average thermogram was reported. the sfi of fat is expressed as a function of temperature. the numbers of solids in the samples of oil in relation to the temperature were estimated on the basis of the calorimetric results. areas of the thermograms were figure 1: solid fat content profiles of two coconut oils and their blends. calculated and correlated with the percentage of solids in the samples. 3. results and discussion 3.1 fatty acid composition samples were characterized by their fatty acid composition (see table 1). the dominant fatty acids in the sample of coconut oil were lauric acid (c12:0) 45.8-53.3 % and myristic acid (c18:0) 18.8-21.3 %. the nhco exhibited a higher percentage of medium-chain fatty acids and a lower percentage of unsaturated fatty acids. the fhco was rich in polyunsaturated fatty acids (pufa) and monounsaturated fatty acids (mufa). 3.2 solid fat content according to nmr the composition of fatty acids and triacylglycerols (tag) would contribute to the percentage of solid fat particles in liquid oil at various temperatures. the sfc profiles of the original fats and their blends at temperatures ranging from 5 ◦c to 30 ◦c are presented in fig. 1. the sfc profile of nhco exhibited low values of 81.06 %, 69.70 %, 54.61 %, 34.54 %, 25.86 % and 0.17 % over the temperature range of 5 ◦c – 30 ◦c because of the concentration of fatty acids. in the case of fhco, the solid fat content was high at 90.49 %, 81.28 %, 69.29 %, 54.15 %, 48.30 % and 4.46 % over the same temperature range. the sfc profiles of blends changed following the addition of fhco to nhco. an increase in the maximum values of sfc was also observed by ribeiro et al. following the addition of fully hydrogenated soybean oil to soybean oil [5]. this can be explained by the changes in the composition of triacylglycerols of the blends. at 5 ◦c, the blends exhibited sfcs ranging from 84.94 % to 90.02 %, which decreased non-linearly until melting completely at 30 ◦c. during the blending, the concentration of tags with high melting points increased and subsequently the sfc values of blends were modified. in all blends, the sfc values at 30 ◦c were almost identical to the sfc of the fhco. hungarian journal of industry and chemistry static and dynamic analyses of the solid fat content of coconut oil 35 figure 2: melting profiles of two coconut oils and their blends. table 2: thermal properties of nhco, fhco and their blends. sample max. peak temperature enthalpy (◦c) (j/g) fhco 24.61 80.24 75:25(w/w)fhco:nhco 24.30 76.21 50:50(w/w)fhco:nhco 23.96 63.44 25:75(w/w)fhco:nhco 23.52 55.84 nhco 23.27 46.38 3.3 melting characteristics the melting profiles of nhco in the presence of fully hydrogenated coconut are depicted in fig. 2. the melting behavior of the original oils and blends was characterized by only one endothermic peak. a similar thermal behavior of coconut oil and hydrogenated coconut oil was observed by one major peak in various studies [6, 7]. components with the lowest melting points tend to melt first and represent the most unsaturated triglycerides, while components with higher melting points that represent the most saturated triglycerides melt later. similarly, results showed that nhco started melting first compared to other samples because of its higher content of unsaturated triglycerides. the addition of fhco to nhco did not alter the melting behavior but as the content of fhco was increased, the peaks according to the melting profiles of blends shifted towards the highmelting temperatures (fig. 2). this melting profiles provided an indication of the amount of crystallized fat and the occurrence of polymorphic transitions. the thermal characteristics of the original oils and their blends are shown in table 2. no significant differences were observed between the values of onset temperature (ton) and peak temperature (tp) in addition to the enthalpies of nhco and fhco. ton ranged from 15.60 ◦c to 20.50 ◦c while tp ranged from 23.27 ◦c to 24.61 figure 3: solid fat index profiles of two coconut oils and their blends. ◦c. melting enthalpies of nhco following the addition of fhco increased from 46.38 j/g to 80.24 j/g (see table 2). 3.4 solid fat index (sfi) the solid-liquid ratio in fats expressed as solid fat content is determined from the melting curves that result from dsc by partial integration. the heat flow into or out of samples of fat was measured as they were heated and cooled isothermally. the estimation of the sfis of samples is dependent upon the onset and final temperatures of melting. the sfi profiles of all samples calculated by melting thermographs are shown in fig. 3. nonhydrogenated coconut oil exhibited a characteristic steep slope and a rapid decrease in the percentage of solids at 20 ◦c. this ratio of solids to liquids decreases differently in these blends of fat as the temperature rises and is at its minimum for all blends at around 30 ◦c (see fig. 3). 4. discussion the results obtained from two methods exhibited a wide range of solid fat content values of the same samples. the values of sfc calculated from pnmr results were lower than values of sfi according to dsc where dsc is a dynamic method and nmr is a static method. the values of the percentages of sfc for each blend at 15 ◦c calculated by dsc were 87.55 %, 88.38 % and 95.95 % (see fig. 3) but 68.05 %, 68.83 % and 72.35 % when calculated by pnmr, respectively (see fig. 4). dsc samples exhibited a sharp decline in their sfi or ratio of solids to liquids when heated from 15◦c to 25◦c, however, the sfc of samples according to nmr exhibited a gradual slope. dsc measurements of physical behavior were observed under controlled heating conditions. the results of dsc describe the whole melting process whilst being heated. the nmr results indicate the statistical values of solid fat content. the difference between the two measurements was possibly due to the time-dependent process concerning the development of crystal structure where sfi describes the status of the fat system and sfc 46(2) pp. 33–36 (2018) 36 dhaygude, soós, zeke, and somogyi figure 4: solid fat content (%) of two coconut oils and their blends. the solid status after stabilization. in addition nmr identified state vise crystals at respective temperatures. the difference in values may be due to the method of tempering, the rate of heating or cooling, and the degree of accuracy. 5. conclusion the results revealed that by combining fhco with nhco the melting behavior of blends of coconut oils was modified, leading to significant increments in the melting point and in the maximum solid fat content. these two methods yielded more descriptive and clear information about melting behaviour by determining amounts of solids in the samples of coconut oil in relation to the temperature. static and dynamic analytical methods showed a difference in the solid-to-liquid ratio of samples which may be due to fundamental differences. the blending of fhcos with vegetable oils can produce valuable blends of fat of good consistency and with reduced or even in the absence of trans-isomers of unsaturated fatty acids suitable for margarine. acknowledgement this research was supported by the doctoral school of food sciences at szent istván university. references [1] dayrit, f. m.: the properties of lauric acid and their significance in coconut oil. j. am. oil chem. soc., 2015 92, 1–15 doi: 10.1007/s11746-014-2562-7 [2] o’brien, r. d.: fat and oils formulating and processing for applications boca raton, fl crc/taylor & francis, 2009, usa isbn: 9781420061666 [3] walker, r. c.; bosin, w. a.: comparison of sfi, dsc and nmr methods for determining solidliquid ratios in fats. j. am. oil chem. soc., 1971 48, 50–53. doi: 10.1007/bf02635684 [4] aocs: official method cd 16b-93 solid fat content (sfc) by low-resolution nuclear magnetic resonance; in: firestone, d. (ed.) official methods and recommended practices of the aocs. the american oil chemists society, 2005 , champaign, usa. isbn: 9780935315974 [5] ribeiro, a.; grimaldi, r.; gioielli, l. a.; gonçalves, l.: zero trans fats from soybean oil and fully hydrogenated soybean oil: physicochemical properties and food applications. food research international, 2009 42, 401–410 doi: 10.1016/j.foodres.2009.01.012 [6] tan, c. p.; che man, y. b.: differential scanning calorimetric analysis of palm oil, palm oil based products and coconut oil: effects of scanning rate variation. food chemistry, 2002 76, 89–102 doi: 10.1016/s0308-8146(01)00241-2 [7] shen, z.; birkett, a.; augustin, m. a.; dungey, s.; versteeg, c.: melting behavior of blends of milk fat with hydrogenated coconut and cottonseed oils. j. am. oil chem. soc., 2001 78, 387–394 doi: 10.1007/s11746-001-0273-4 hungarian journal of industry and chemistry https://doi.org/10.1007/s11746-014-2562-7 https://doi.org/10.1007/bf02635684 https://doi.org/10.1016/j.foodres.2009.01.012 https://doi.org/10.1016/j.foodres.2009.01.012 https://doi.org/10.1016/s0308-8146(01)00241-2 https://doi.org/10.1016/s0308-8146(01)00241-2 https://doi.org/10.1007/s11746-001-0273-4 https://doi.org/10.1007/s11746-001-0273-4 hungarian journal of industry and chemistry vol. 46(2) pp. 37–42 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0016 monitoring of chemical changes in red lentil seeds during the germination process ildikó szedljak *1, anikó kovács1, gabriella kun-farkas2, botond bernhardt3, szabina králik1, and katalin szántai-kőhegyi1 1department of grain and industrial plant processing, szent istván university, villányi út 29-43, budapest, 1118, hungary 2department of brewing and distilling, faculty of food science, szent istván university, villányi út 29-43, budapest, 1118, hungary 3department of soil chemistry and turnover, institute for soil sciences and agricultural chemistry, centre for agricultural research, hungarian academy of sciences, herman ottó út 15, budapest, 1022, hungary red lentils are a very important raw material in the food industry due to their high protein content and high level of healthpromoting components. the nutritive value of red lentils is the most important attribute from a research point of view; it can be increased by germination, soaking as well as physical and biochemical processes. the antinutritive materials are reduced or denatured by the germination process and indigestible components become available to the human body. heat treatment was applied to achieve different temperatures and increase the microbiological stability of germinating samples. the effect of heat treatment on the amounts of certain components and the activity of oxidative enzymes was tested during our experiments; the nutritional characteristics (water-soluble total polyphenol content (wstpc), watersoluble protein content (wspc), water-soluble antioxidant capacity, in addition to peroxidase and polyphenol oxidase enzyme activities) of different treatments in red lentil samples were monitored. the wstpc in our samples ranged from 0.726 mg gallic acid equivalent gae/g dw (dw being dry weight) to 1.089 mg gae/g dw, and the wspc varied from 19.078 g / 100g dw to 29.692 g / 100 g dw. results showed that germination led to an increase in the wstpc and wspc. the peroxidase enzyme activity also exhibited an increase during germination which could result in deepening of the colour of the finished products. germination resulted in the water-soluble antioxidant capacity of red lentil samples decreasing. keywords: red lentil, germination, antioxidant activity, protein, enzyme 1. introduction lentils (lens culinaris m.) are bushy annual plants of the legume family. lentils are grown for the high protein content and high nutritive value of their lens-shaped seeds. lentils are primarily a cool-season crop; they are moderately resistant to high temperatures and droughts. lentils are characterized by their high levels of plant protein, complex carbohydrates (resistant starch, slowly digestible starch and oligosaccharides), fibres (soluble and insoluble) as well as very low sodium and fat content. additionally, lentils are rich in b-vitamins, e.g. folate, thiamin and niacin, and key minerals, namely iron, potassium, magnesium and zinc, make them a highly nutritious food. the most common types of lentils are red, green and black of which red and green are the most commonly traded. the cultivation and consumption of red lentils are considerable in asian countries. on the other hand, con*correspondence: ildiko.szedljak@gmail.com sumer demand for red lentils in the western hemisphere is not high [1]. red lentils are a valuable source of macronutrients (proteins, fats, carbohydrates) and other important components (phytochemicals: phytic acid, phenolic acids, flavonols, flavanols and condensed tannins). lentils have demonstrated many health benefits, e.g. lowering the glycemic index and their gluten-free status for people with metabolic disorders. the consumption of lentils can also lead to weight loss, which is recommended for all overweight and obese individuals [2, 3]. the germinated seeds and their compounds are possible components of functional foods. functional foods play an important role in health promotion and disease prevention. different scientific papers suggest that lentils provide protection against chronic diseases through a multitude of biological activities including anticancer, antioxidant and angiotensin-converting enzyme inhibition. lentils also reduce blood lipid levels and the risk of developing cardiovascular diseases [4, 5]. mailto:ildiko.szedljak@gmail.com 38 szedljak, kovács, kun-farkas, bernhardt, králik, szántai-kőhegyi the nutritive value of lentil seeds can be improved by the germination process. germination is a complex metabolic process during which the lipids, carbohydrates and storage proteins within seeds are broken down in order to obtain the necessary energy and amino acids. these changes influence the bioavailability of essential nutrients [6]. the presence of antinutritional factors might be reduced by germination. red lentils have been gaining increasing attention due to their health benefits as part of the human diet and they are considered to be an excellent source of dietary antioxidants largely because of their high level of bioactive phytochemicals [1, 7] in hungary, small-scale (20 seeds) red lentil germination experiments have already been conducted during which the effect of germination on the lectin content was studied [8]. the main purpose of our research was to examine the suitability of the germinated red-lentil grist as a raw material of dry pasta. red lentils were selected for our experiments due to their aforementioned favourable nutritional characteristics. in addition, its flour can be suitable in the development of gluten-free pasta products in the form of enrichment and gluten-free raw materials. the formation of more digestible water-soluble components was conduced by seed germination, but at the same time a loss may be observed due to the heat treatments (drying pasta) used in the manufacture of the products. the same loss may occur during the boiling process. therefore, it is important to check for all kinds of changes that occur during heat treatment. the control of the activity of enzymes which generate oxidation processes is also essential during germination as is technological / kitchen-technological processing from the point of view of the expected quality of the finished products. developing food diversity by incorporating red lentil seeds and its flour into western diets is highly recommended. 2. experimental the aim of our study was to examine the chemical changes in red lentil seeds during the germination process. the effect of different heat treatments on the amount of certain components and the activity of oxidative enzymes were monitored. moreover, a connection between the parameters and the extent to which these variables interact was sought. 2.1 samples and measurements samples 10 kg of raw organic whole red lentil was purchased from biorganik online kft. 3 kg of which was added to the germination device. 500 g of both soaked and sprouting seeds were sampled and heat-treated at three different temperatures. the heat-treated seeds were milled using a hammer grinder and then homogenized. the aqueous extracts were made from the control samples and the heat-treated grists. steeping, germination and heat treatment steeping and germination were performed in a schmidtseeger, kma-a1-2008 micromalting plant. the micromalting plant was controlled by a personal computer with a special controlled by a personal computer with special software. during germination the temperature of the air was regulated and wetted with special jets. during the steeping process compressed air was dispersed in the steeping water. alternate wet and dry periods were implemented during steeping, because during the latter the oxygen uptake of grains is more effective. wet steeping lasted for 3 hours at 20 ◦c with aerations of 6.67 minutes in duration every 8 minutes. this was followed by a 2 hour-long dry period at 22 ◦c with humidification. the second 2-hour-long wet period was performed at 20 ◦c. steeping was stopped when an adequate moisture content was achieved. germination lasted for 96 hours at 22 ◦c with humidification. during the first 48 hours, the germinating seeds were rotated 30 times every two hours, then every three hours. germinating seeds were not sprayed during the process. germinating red lentil samples were taken daily at the same time. heat treatment was applied at different temperatures (60 ◦c, 80 ◦c, 100 ◦c) in order to increase the microbiological stability of germinating samples. the effect of heat treatment on the amount of certain components and the activity of oxidative enzymes was tested during our experiments. chemical analysis the samples were homogenized and 0.10 ml of distilled water was added to each sample. the centrifugation process was conducted after extraction for 10 minutes at 4 ◦c and 10,000 rpm. the watersoluble polyphenolic content was measured by colorimetric analysis using folin & ciocalteu’s phenol reagent [9] and the results were expressed in gallic acid equivalent (gae) (mg gae/g dw – dw being dry weight). the wspc was measured by a method discovered by layne [10]. the water-soluble antioxidant activity was determined using a ferric reducing antioxidant power (frap) assay kit [11]. the polyphenol oxidase (ppo) enzyme activity was measured by using a synthetic substrate, pyrocatechol. the oxidized form of the substrate can be synthesized photometrically at 420 nm by a spectrophotometer [12]. the peroxidase (pod) enzyme activity of the extracts was determined using o-dianisidine as a hydrogen donor in sodium acetate (ph 5.1) [13]. the reagents for the chemical measurements were provided by sigma-aldrich kft. statistical methods all of the measurements were replicated five times. the kruskal-wallis test was applied to calculate the exact p-value (α = 0.05) and dunn’s post hoc pair-wise test was chosen with an adjustment by bonferroni. the relationship between the parameters was determined by spearman’s rank correlation coeffihungarian journal of industry and chemistry chemical changes in red lentil seeds during the germination process 39 figure 1: water-soluble total polyphenol content in red lentil samples. different letters indicate significant differences between treatments (p ≤ 0.05). cient (non-parametric equivalent of pearson’s correlation coefficient) (α = 0.05) using the xlstat-sensory solution software, version 2013.1.01 (addinsoft, 28 west 27th street, suite 503, new york, ny 10001, usa). during the correlation test the correlation between the variables regardless of their units was examined. 3. results and evaluation 3.1 water-soluble total polyphenol content (wstpc) zhang et al. [14] measured the total polyphenol content (soluble and insoluble in water) using folin ciocalteu’s reagent in raw red-lentil extracts (5.04 ± 0.36 mg gae/g dw – 7.02 ± 0.48 mg gae/g dw). according to their data all extracts of lentils cultivated in canada were significantly different from each other. in contrast to this tpc values changed over a very narrow range (from 5.9 ± 0.1 mg gae/g dw to 5.93 mg gae/g dw) in the samples of red-lentil flour tested [15–17]. the results of tpc are shown in fig. 1. the wstpc in our samples ranged from 0.726 mg gae/g dw to 1.089 mg gae/g dw. our wstpc values were 5 to 10 times smaller than in the aforementioned experiments. by comparing the control and soaked samples, it can be observed that the wstpc increased during the soaking process. these values were higher than the measured data from germinated samples (fig. 1). according to our experiments heat treatment at high temperatures (80 ◦c and 100 ◦c) equalized the wstpc values in red lentil samples. furthermore, germination and heat treatments did not effect the wstpc of the seeds. 3.2 water-soluble antioxidant capacity the results of water-soluble antioxidant capacity were measured using a frap assay kit. the values ranged between 0.177 mg ascorbic acid equivalent (aae)/g dw figure 2: water-soluble antioxidant capacity of red lentil samples. different letters indicate significant differences between treatments (p ≤ 0.05). and 0.815 mg aae/g dw. as a result of the germinating process, the antioxidant capacity of the samples was significantly reduced compared to that of the control sample. however, treatment at a high temperature (100 ◦c) led to a further increase in the amount of new water-soluble components with antioxidant capacity. samples that were not dried during the first 3 days were significantly different from the control samples in all of the categories. moreover, they differed from the sample dried at 100 ◦c on the 4th day (fig. 2). the highest water-soluble antioxidant capacities were measured in the control samples, except for the control sample treated at 100 ◦c. by comparing control samples to germinated samples, it is evident that the germinating process did not result in an increase in the water-soluble antioxidant capacity. our results showed that whilst being soaked the water-soluble antioxidant capacity started to decrease. the water-soluble antioxidant capacity in the heattreated sample on the 3rd day of germination at 80 ◦c decreased drastically compared to the control sample. the same change occurred with the samples that were not dried. nevertheless, the significant decrease had already occurred on the 1st day of germination. no correlation was found between the wstpc and water-soluble antioxidant capacity. 3.3 water-soluble protein content (wspc) wspcs, given in fig. 3, ranged from 19.078 g / 100 g dw (dry weight) to 29.692 g / 100 g dw. by comparing the control and soaked samples, it is evident that the wspc increased during the soaking process. in the case of samples that were not dried in addition to those treated at 80 ◦c and 100 ◦c, no significant differences were observed between treatments except for samples treated at 60 ◦c where those soaked and on their 2nd day of germination had significantly higher values compared to the control sample. the highest wspc was 46(2) pp. 37–42 (2018) 40 szedljak, kovács, kun-farkas, bernhardt, králik, szántai-kőhegyi figure 3: water-soluble protein content in red lentil samples. different letters indicate significant differences between treatments (p ≤ 0.05). measured on the 2nd day of germination at 60 ◦c, which was significantly higher than all the heat-treated control samples as well as samples treated at 100 ◦c except for the value on the 1st day of germination. as the germination process advanced – especially on the 3rd and 4th days – the wspc of samples heat-treated at 80 ◦c and 100 ◦c started to decrease compared to the same phenophases of those that were not dried or heattreated at 60 ◦c. this may be explained by the fact that plant proteins are more easily degraded at higher temperatures over prolonged periods of time. a negative correlation was observed between the wspc and water-soluble antioxidant capacity. the total protein content was determined using the dumas method as described by hefnawy [18]. in this study the total protein content was 26.6 ± 0.50 g / 100 g dw and the effect of the heat treatment was insignificant. 3.4 peroxidase (pod) enzyme activity the changes in pod enzyme activity of red-lentil samples are shown in fig. 4. the pod adversely affects the nutritive value, taste, texture and colour of food products. these enzymes are referred to as heat-tolerant enzymes and can regain their activity following heat treatment and storage (fig. 4). pod enzyme activity ranged from 10.815 u/g dw to 215.785 u/g dw with statistically significant differences. the highest value (215.785 u/g dw) was found in the sample dried at 100 ◦c on the 4th day. the samples that were not dried or heat-treated were identical to each other on the same level (control, soaked, 1st-4th day). pod activity progressively increased during the germination process in almost all cases. the pod activity of the sample dried at 100 ◦c was 20-fold higher than that of the control sample. the pod activity of different tempered lentil samples was also measured by pathiratne et al. [19] and their maximum value was 186.4 figure 4: peroxidase enzyme activity of red lentil samples. different letters indicate significant differences between treatments (p ≤ 0.05). u/g protein. however, in another study by świeca et al. [20], the pod activity of germinated lentil samples was much higher than the aforementioned ones, 10.3 ± 0.24 ku/mg protein. elevated temperatures of heat treatment resulted in an increase in the pod activity during the germination process. 3.5 polyphenol oxidase (ppo) enzyme activity ppos and pods are the most studied enzymes in fruit and vegetables. świeca et al. [20] studied the ppo enzyme activity in sprouts of lentils according to the method described by galeazzi et al. [21] and measured 2.24 ± 0.05 ku/mg protein. they reported that enzymatic markers of the stress metabolism of plants, e.g. ppo activities, did not differ significantly between sprouts. in our study a catechol substrate was also used but no ppo enzyme activity was detected in the samples. 4. conclusion of all the parameters studied, the wspc of red lentils strongly correlated with the values of water-soluble antioxidant capacity measured using the frap assay kit (data not shown). the correlation is inversely proportional, hence, the greater the wspc, the lower the watersoluble antioxidant capacity. seed germination is one of the most important stages in the life cycle of plants and germinated seeds may be a useful source of healthy food. germinated seeds are very complex living matrices and it is very difficult to understand the biochemical changes that occur during sprouting. further studies on the germination process of red lentils are needed to help understand and identify the important parameters that are able to describe such changes. functional foods play an important role in terms of consumer acceptance [22], thus, a more suitable approach hungarian journal of industry and chemistry chemical changes in red lentil seeds during the germination process 41 may well be sensory evaluation in the case of our redlentil samples. the latest development methodologies should be used, namely preference mapping methods, just-about-right (jar) scaling and eye-tracking methods [23–25]. references [1] zhang, b.; deng, z.; tang, y.; chen, p.; liu, r.; ramdath, d. d.; liu, q.; hernandez, m.; tsao, r.: fatty acid, carotenoid and tocopherol compositions of 20 canadian lentil cultivars and synergistic contribution to antioxidant activities. food chem., 2014 161, 296–304. doi: 10.1016/j.foodchem.2014.04.014 [2] papanikolaou, y.; fulgoni, v. l.: bean consumption is associated with greater nutrient intake, reduced systolic blood pressure, lower body weight, and a smaller waist circumference in adults: results from the national health and nutrition examination survey 1999–2002. j. am. coll. nutr., 2008 27(5), 569– 576. doi: 10.1080/07315724.2008.10719740 [3] sravanthi, b.; jayas, d. s.; alagusundaram, k.; chelladurai, v.; white, n. d. g.: effect of storage conditions on red lentils. j. stored prod. res. 2013 53, 48–53. doi: 10.1016/j.jspr.2013.01.004 [4] duane, w. c.: effects of legume consumption on serum cholesterol, biliary lipids, and sterol metabolism in humans. j. lipid res., 1997 38(6), 1120–1128. 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tóth, b.; lőrincz, r.; szendi, sz.; gere, a.; kókai, z.; sipos, l.; tömösközi, s: effect of aleurone-rich flour on composition, baking, textural, and sensory properties of bread. lwt food sci. tech., 2016 65, 762–769. doi: 10.1016/j.lwt.2015.08.073 [23] gere, a.; kovács, s.; pásztor-huszár, k.; kókai, z.; sipos, l.: comparison of preference mapping methods: a case study on flavoured kefirs. j. chemom., 2014 28(4), 293–300. doi: 10.1002/cem.2594 [24] gere, a.; sipos, l.; héberger, k.: generalized pairwise correlation and method comparison: impact assessment for jar attributes on overall liking. food qual. prefer., 2015 43, 88–96. doi: 10.1016/j.foodqual.2015.02.017 [25] gere, a.; danner, l.; de antoni, n.; kovács, s.; dürrschmid, k.; sipos, l.: visual attention accompanying food decision process: an alternative approach to choose the best models. food qual. prefer., 2016 51, 1–7. doi: 10.1016/j.foodqual.2016.01.009 hungarian journal of industry and chemistry https://doi.org/10.1016/j.lwt.2015.08.073 https://doi.org/10.1016/j.lwt.2015.08.073 https://doi.org/10.1002/cem.2594 https://doi.org/10.1016/j.foodqual.2015.02.017 https://doi.org/10.1016/j.foodqual.2015.02.017 https://doi.org/10.1016/j.foodqual.2016.01.009 hungarian journal of industry and chemistry vol. 46(2) pp. 43–46 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0017 recovery of itaconic acid by electrodialysis veronika varga1, katalin bélafi-bakó1, dávid vozik1, and nándor nemestóthy *1 1research institute of bioengineering, membrane technology and energetics, university of pannonia, egyetem u. 10, veszprém, 8200, hungary itaconic acid is an organic acid produced mainly for non-food purposes. it can be manufactured by biotechnological synthesis using various strains which results in the salt form of the acid. in this work, the separation of sodium itaconate by electrodialysis was studied. homopolar cationand anion-selective membranes were applied and the module was operated under a constant voltage. the transport of the acid was followed by on-line ultraviolet and visible absorption spectroscopy, where the detector was installed in the system. the experiments with models of aqueous solutions confirmed that the technique is suitable for the effective recovery of itaconic acid. keywords: ultraviolet and visible absorption spectroscopy, on-line detection, monopolar membranes 1. introduction itaconic acid was discovered by baup in 1837 as the coproduct resulting from the degradation of citric acid [1]. itaconic acid (2-methylene,1,4-butanedioic acid) is an unsaturated dicarboxylic acid, a rather reactive compound due to its conjugated double bond and two carboxyl groups. therefore, it can easily participate in polymerisation reactions. itaconic acid – unlike citric acid – is applied exclusively for non-food purposes [2]. it is used mainly in the production of synthetic fibres and ion-exchange resins as well as in the pulp and paper industry. itaconic acid can be synthesized biotechnologically. kinoshita was first to describe the process in 1932 when it was isolated from the broth of aspergillus itaconicus [3]. later a similar strain, aspergillus terreus, was found to produce itaconic acid. other microbes suitable for the fermentation of itaconic acid are listed in table 1. the main problem with downstream processing is that several similar organic acids are present in the broth, thus, recovery of itaconic acid is difficult. separation of itaconic acid can be conducted by filtration with the aid of activated carbon and crystallisation (consecutive steps) or adsorption by strong anion-exchange resins, like purolite a-500 p or pfa-300 [10]. the efficiency of the separation depends mainly on the temperature, ph and concentration. an application of electrodialysis (ed) as a membrane process is the separation of organic acids [11–14]. malic acid and galacturonic acid amongst others can be separated by ed using monopolar and bipolar membranes by *correspondence: nemesn@almos.uni-pannon.hu table 1: biotechnological synthesis of itaconic acid strain reference aspergillus itaconicus kinoshita et al. (1932) [3] ustilago maydis steiger et al. (2013) [4] pseudozyma antarctica levinson et al. (2006) [5] yarrowia lipolytica kuenz et al. (2018) [6] synechocystis cyanobacteria heidorn et al. (2011) [7] chin et al. (2015) [8] aspergillus terreus karaffa et al. (2015) [9] implementing batch and continuous modes of operation. the majority of these acids are produced as a salt, thus, the aim of the separation by ed is to transport the organic acid through the anion-selective membrane, while the cation should pass through the cation-selective membrane. the other neutral components remain in the feed solution. usually the mobility of the acid is sufficient for effective transport, hence both the acid and cation can be recovered by ed. the aim of this paper was to study the possibility of applying ed for the recovery of sodium itaconate. 2. experimental itaconic acid, sodium sulphate, sulphuric acid, sodium hydroxide and all the other chemicals used were of anmailto: nemesn@almos.uni-pannon.hu 44 varga, bélafi-bakó, vozik, and nemestóthy table 2: features of the membranes feature fumasep faa fumasep fks selectivity >92 % >96 % electrical resistance <2 ωcm2 <8 ωcm2 ph stability in acidic media 5-13 thickness 0.13-0.15 mm 0.11-0.13 mm ion-exchange capacity >1.2 meq/g >1.0 meq/g conductivity >8 ms/cm >5 ms/cm alytical grade and purchased from sigma-aldrich. the anionand cation-selective membranes were fumasep faa and fks membranes, respectively. the main features of the membranes are summarized in table 2. the membranes were activated by sodium chloride and sulphuric acid before usage. for analytical purposes a young lin instrument co., ltd. (yl9100-type) high-performance liquid chromatography (hplc) system (including a yl9109 vacuum degasser, yl9110 quaternary pump and yl9150 automatic sample dispenser) was used to determine the concentration of itaconic acid with a hamilton hplc column (15 cm in length, 4.6 mm inner diameter, 5 µm particle size) and a yl9120 uv/vis detector. the luff-schoorl method was used to determine the glucose concentration which is based on the reduction of cupric (cu(ii)) cations in a boiling alkaline solution of cuprous (cu(i)) oxide [15]. the surplus of cu(ii) was measured by iodometry using a titration with sodium thiosulfate. the conductivity of the solutions was measured by a radelkis ok-102/1 conductivity meter equipped with a radelkis ok-9023 bell electrode using a cell constant of 0.7 cm−1. data concerning the voltage and current were measured by a national instruments usb-600866009 device. all the experimental data were collected online using labview software. an electrodialysis module was constructed from 2 anionand 2 cation-selective membranes using spacers between them. the electrode solution was an aqueous solution of sodium sulphate. electrodialysis measurements were conducted using diluted (aqueous) model solutions of sodium itaconate and sodium itaconate mixed with glucose. the module was operated under a constant voltage. 3. results in this project, the final aim was to connect the ed device to the fermentation of itaconic acid in order to set up an integrated system. for this purpose, firstly the operation of ed was investigated by using model solutions of sodium itaconate and a simple ed device with monopolar figure 1: percentages of the four distinct forms of itaconic acid. ion-exchange membranes. the transport of the itaconic acid through the anion-selective membranes was the focus of the study to follow the process, it was important to determine the exact concentration of itaconic acid. if the acid is the only compound in the solution, measuring the conductivity is a simple method for detection. however, if any other charged compound is present, it will disturb such measurements. in this case, hplc is suggested for the analysis [9]. itaconic acid is a dicarboxylic acid (consisting of three different ionic forms) and its dissociated forms and ionic strengths vary according to the ph. thus, four distinct peaks over different retention times can be detected in hplc chromatograms. the percentages of the four distinct forms as a function of ph were determined and are presented in fig. 1. since it is quite difficult to measure the actual concentration of itaconic acid, another method was chosen. itaconic acid has a uv absorption maximum at 243 nm which can be used for detection. this method seemed sufficiently sensitive for our purposes. in our work, a loop was constructed from the solution (recirculated in the ed module) to the uv detector. thus, online detection was applied to follow the concentration figure 2: calibration curve for the determination of itaconic acid concentration by uv detection hungarian journal of industry and chemistry recovery of itaconic acid by electrodialysis 45 figure 3: polarization curves of itaconic acid as a function of operating time. firstly, a calibration curve was recorded (fig. 2) over the concentration range of itaconic acid that was planned to be used. the data measured by the online uv system were checked by hplc. to test the ed module, polarization curves were taken using a potentiostat by applying a range of voltages from 0 to 10 v (fig. 3). the current data were recorded as a function of the voltage data. the measurements were repeated in various electrode solutions. it seems that beyond a sodium sulphate concentration of 0.125 m, the ed operated properly. experiments were conducted in the ed module by using aqueous model solutions of itaconic acid (with an initial concentration of 3-3 g/l). the electrode solution was a 0.16 m na2so4 solution. the experiments were conducted under a constant voltage (10 v) and the current intensity varied between 0.11 and 0.15 a. subsequently, the conductivity in the diluate solution was measured. the concentration of the acid decreased gradually to half its initial value after an operating time of 70 mins as can be seen in fig. 4. this means that itaconic acid was able to pass through the anion-selective membrane, while sodium ions were able to diffuse across the cation-selective membrane. therefore, the measurements confirmed that the mobility of this acid is sufficient to separate it by ed. figure 4: conductivity data of the diluate of ed figure 5: concentration of itaconic acid in the diluate solution in the next series of experiments, glucose was added to the acid (4 g/l) to investigate whether the ed module was able to separate the two compounds. the concentration of itaconic acid in the diluate was followed online by the uv detector installed in the loop. the concentration of the glucose was determined by the luff-schoorl method. the concentration of the acid decreased from 3.0 to 1.5 g/l during the experiment (fig. 5), while the glucose concentration was monitored in all three streams. in the diluate (originally feed) solution, a slight decrease in glucose concentration was observed (to 3.52 g/l), its concentration was negligible (0.20 g/l) in the electrode solution, while in the concentrate solution 0.59 g/l glucose was measured probably due to its diffusion from the feed solution. 4. conclusion the measurements provided a definite answer to the original question, namely whether ed is a suitable technique for the recovery of itaconic acid. the results of the experiments using model solutions (sodium itaconate on its own as well as a mixture of sodium itaconate and glucose) confirmed that ed is an effective method for the separation of itaconic acid. based on these results, further experiments are being planned using more complex model solutions, similar to the composition of the fermentation broth. subsequently, it is our intention to connect the ed module to the fermentation process. acknowledgements this research was supported by the national research, development and innovation fund project otka k 119940 entitled “study on the electrochemical effects of bioproduct separation by electrodialysis” and by the financial support of széchenyi 2020 within project efop3.6.1-16-2016-00015. 46(2) pp. 43–46 (2018) 46 varga, bélafi-bakó, vozik, and nemestóthy references [1] baup, s.: über eine neue pyrogencitronensäure, und über benennung der pyrogen säure überhaupt, ann. chim. phys., 1837 9, 29–38 doi: 10.1002/jlac.18360190107 [2] delidovich, i.; hausoul, p. j.; deng, l.; pfutzenreuter, r.; rose, m.; palkovits, r.: alternative monomers based on lignocellulose and their use for polymer production, chem. rev., 2016 116(3), 1540–1599 doi: 10.1021/acs.chemrev.5b00354 [3] kinoshita, k.: über die produktion von itaconsäure und mannit durch einen neuen schimmelpilz, 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hungary to correlate the dipole moment and density dependence of the initial magnetic susceptibility on the basis of the former related theories and the probability analysis of chain formation, physically based analytical correlation equation was derived. after the local magnetic field strength and the chaining probability between two particle have been determined the chain and particle distributions came from the geometric distribution. the initial magnetic susceptibility was resulted from the summation of langevin initial susceptibility of k-length chains. two particles were considered in a chain if the interaction energy between them was below a certain limit. by varying slightly this energy limit around 70–75 % good agreement has been obtained between the simulation and theoretical data. monte carlo simulations were used to calculate the initial magnetic susceptibility of dipolar hard sphere system at different dipole moments and densities. keywords: dipolar fluids, initial susceptibility, monte carlo simulation 1. introduction the investigation of dipolar fluids has been induced by the evolution of magnetorheology and electrorheology over the last two decades. the viscosity of electrorheological (er) fluids increases dramatically due to an external electric field. er fluids can be obtained by dispersing solid particles with dielectric permittivity εp in a fluid with dielectric permittivity εf , where εp > εf . the dispersed particles are of between 0.1 mm and 100 mm in diameter. the polarized particles are organized into pairs and chains. the magnetic analogy of the phenomenon described above is the magnetorheological (mr) effect. if the magnetic permeabilities of the liquid and dispersed particles differ, then in an external magnetic field the particles are also arranged in chains. the dispersing medium can be water, oil, an organic solvent, etc. while the dispersed particles can be some kind of iron oxide or ferrit. in this paper, the magnetic terminology and centimetregram-second (cgs) system of units are used. in the figures, the reduced quantities are applied. electroand magnetorheological fluids typically exhibit a reduced density of up to ρ∗ = 0.4 (where ρ∗ = ρσ3; ρ and σ are the concentration and diameter of the suspended particles, respectively). the magnetic properties, e.g. magnetization curve and initial magnetic susceptibility, are well described by the various theories within this range of reduced density. the magnetization m can be obtained by summation of the dipole moments in the *correspondence: sata123.sandor@gmail.com unit volume: m = 1 v ∑ i mi. (1) in the absence of any external magnetic field the fluid is isotropic and according to eq. 1 the magnetization is zero. when any external magnetic field is present, the field-oriented components of dipole moments should be summarized as m = ρm 〈cos θ〉 h0 h0 , (2) where h0 = |h0| and 〈cos θ〉 is the ensemble average of the cosine of the angle between mi and h0, and m = |mi|. since the directions of h0 and m are identical, vector notation can be omitted. the initial magnetic susceptibility is equal to the initial gradient of the magnetization curve χ0 = ∂m ∂h0 ∣∣∣∣ h0=0 . (3) in practice, er and mr fluids can be used for the transmission of torque or force, in vibration dampers and braking systems, etc. the magnetic properties generally are calculated from monte carlo simulations because it is not necessary to know the velocity and acceleration of the particles nor the forces between them. the expressions of the related models are listed in table 1. (one line belongs to one theory and the first line is the head of the table, e.g. table 1: 2.4 refers to the 4th cell in the 2nd line within the 1st table.) three different mailto:sata123.sandor@gmail.com 48 nagy table 1: the expressions of the effective magnetic field, the magnetization and the initial magnetic susceptibility of the related theories. model he – effective magnetic field m – magnetization χ0 – initial magnetic susceptibility 1 “langevin” [1] h0 ρml ( mh0 kbt ) ρm2 3kbt = χl 2 “weiss” [2] h0 + 4π 3 m(he) ρml ( mhe kbt ) χl 1− 4π 3 χl 3 “pshenichnikov” [3] h0 + 4π 3 m(h0) ρml ( mhe kbt ) χl ( 1 + 4π 3 χl ) 4 “ivanov” [4] h0 + 4π 3 m(h0) ( 1 + 4π 48 ∂m ∂h0 ) ρml ( mhe kbt ) χl ( 1 + 4π 3 χl + (4π) 2 144 χ2 l ) 5 “tani” and “szalai” [5, 6] m(h0) = ρml+ 4π 3 ρ 2βm3ll ′ + 1 10ρ 2β2m5ζ ′ idd∆ − 16π2 27 ρ3β2m5ll ′ + 1 3ρ 3β2m5ll ′ idd∆ χl ( 1 + 4π 3 χl + (4π)2 144 χ2 lf(ρ) ) magnetic fields will be used. the applied external magnetic field is denoted by h0 and the sum of the external and generated magnetic fields by he. he is always parallel to h0. the third one is the local magnetic field hl which is of chain-parallel orientation and its formation is due to dipole-dipole interactions between the particles. the well-known langevin function is applied from the initial theory [1] in the magnetization formula (table 1: 1.3), where l(α) = cothα − 1/α. the magnetic dipole moment of the particles is denoted by m and the applied external magnetic field by h0, while the boltzmann constant is represented by kb. the expression of magnetic susceptibility can be written as in table 1: 1.4. this is known as langevin susceptibility which is indicated by χl as well. in this approach the effective magnetic field he exerted on the given particle is equal to the external magnetic field (table 1: 1.2). according to the more accurate model by weiss [2] the effective magnetic field is equal to the sum of the external magnetic field and the magnetic field induced by the magnetization (table 1: 2.2). the formula of the magnetization (table 1: 2.3) is similar to the previous one but h0 is substituted by he. due to the iterative nature of the magnetization expression the initial magnetic susceptibility (table 1: 2.4) exhibits divergence at χl = 3/4π, therefore, overestimates the real values. above this initial magnetic susceptibility limit, when χl ≥ 3/4π, the zerofield magnetization is not equal to zero: m(h0) 6→ +0, ifh0 → +0. moreover, in weak external magnetic fields, one h0 value belongs to three equilibrium magnetization values. the effective magnetic field has been substituted for the external magnetic field in the expression of the effective magnetic field (table 1: 3.2) in the theory by pshenichnikov et al. [3]. the magnetization formula (table 1: 3.3) is the same as in weiss’ theory. the initial magnetic susceptibility (table 1: 3.4) is in good agreement with the simulations but underestimates them at higher densities or higher dipole moments. that is why it seems to be a good method to extend the expression of the effective magnetic field (table 1: 4.2) by ivanov et al. [4]. the magnetization formula is once again identical (table 1: 4.3) but a new term is introduced in the initial magnetic susceptibility (table 1: 4.4). although at higher densities it yields higher values than in pshenichnikov’s model, it underestimates the simulation data as well. the factor of the third term is (4π)2/144 = 1.0966 and perhaps it could be higher, but in this case at low densities the initial magnetic susceptibility overestimates the simulations. the perturbation theory by tani et al. [5] is worth mentioning because a density-dependent correction was used to complete the third term of the susceptibility (table 1: 5.4), where f (ρ) = 9idd∆/π 2 − 16, and idd∆ = 17π2 9 [ 1− 0.93952ρ∗ + 0.36714(ρ∗) 2 1− 0.92398ρ∗ + 0.23323(ρ∗) 2 ] . the formula of the magnetization curve for this perturbation theory was calculated by szalai et al. the expressions that are not mentioned in table 1: 5.2 can be found in ref. [6]. the values of the susceptibility more closely resemble the simulation data but still underestimate those. it is worth mentioning the study by huke and lücke [7] who introduced the so-called “dipolar coupling constant” into the second term of the initial magnetic susceptibility, but the third term was ignored in expressions in table 1: 4.4 and 5.4. thereby their theory at higher densities underestimates and at lower densities overestimates the simulation data. furthermore, the theory of mean-spherical approximation (msa) [8–10] should also hungarian journal of industry and chemistry the initial magnetic susceptibility of dense aggregated dipolar fluids 49 be mentioned which provides a formula for initial magnetic susceptibility and magnetization as well, but the validity of these are within the range of up to m∗ < √ 1.5. with regard to the distribution of chain aggregates in ferrofluids [11, 12], it has been found that in the absence of any external magnetic field, the chain size distribution is proportional to pk exp(−ε), where the chain length is denoted by k and the dimensionless energy parameter ε is a function of the maximum dipole interaction energy but independent from the density, therefore, it is a constant here and the probability of bond formation between two adjacent particles in a chain is p. subsequently, the chain size distribution decreases according to an exponential function because pk = exp(−k/k0), where k0 = −1/ ln p. based on some publications [13, 14], in the case of high dipole moments this exponential expression turns into a power law: g(k) ∝ k−ι, with exponent ι ≈ 2.0− 2.5. our investigation was performed in a dipolar hardsphere (dhs) monodisperse system with a permanent magnetic dipole moment and of fixed density. it is supposed that the chains are perfectly straight and parallel to the local magnetic field. furthermore, the average distance between two neighbouring particles in a chain is the same as the distance between two neighbouring parallel chains. the particles interact with each other only by the evolved mean magnetic field and the applied external magnetic field is superimposed on this, thus, the chains influence each other only by this mean magnetic field. 2. theory 2.1 the appearance of probability analysis in the initial magnetic susceptibility the distribution of chains was calculated with the aid of probability analysis in a zero applied magnetic field. as was mentioned in the “introduction”, weiss’ theory states that the effective (now “local”) magnetic field converges to zero when χl < 3/4π and non-zero values when χl ≥ 3/4π. the central and surrounding particles are under the influence of this local magnetic field. the chain is oriented in the same direction as the local magnetic field. let us denote the probability of chain formation between two particles whose direction relative to each other is parallel to the local magnetic field by p. now using this approach the exact distribution of chain length can be calculated because the probability that the chain length ought to be equal to k follows the geometric distribution with parameter q: gk = qpk−1, (4) where q = 1−p and the “chain distribution” is denoted by gk. according to its definition the geometric distribution shows the probability that a kth particle is connected to a chain of length k − 1 thus forming a chain of length k. a geometric sequence is described in eq. 4, where the common ratio is denoted by p and the first term by q. the sum of the terms of a geometric sequence is s∞ = ft 1−cr , thus, ∑∞ k=1 gk = q 1−p = q q = 1. it is also important to calculate the so-called “particle distribution” that implies the number of those particles which are members of the chains of length k: hk = q2kpk−1. (5) the detailed deduction of hk and the sum of hk terms are described in appendix a. the expected value of the geometric distribution with parameter q is 1/q, thus, here the average chain length is 1/q. the number of chains is equal to the number of particles divided by the average chain length: n 1/q = nq, where the number of particles is denoted by n. until now only the local magnetic field which arises from the strength of interaction energies between neighbouring particles and induces spontaneous magnetization in a random direction has been discussed, thus, the total magnetization of the system of volume v is equal to zero. when an infinitesimal external magnetic field h0 is switched on, non-zero total magnetization is formed. since h0 is parallel to m, scalar notations are used in the following. as was observed from pshenichnikov’s model the effective magnetic field is the sum of the external h0 and secondary (4π/3)m(h0) magnetic fields. the question arises why it is legitimate to use the expression of effective magnetic field from “pshenichnikov” (table 1: 3.2) instead of from “weiss” (table 1: 2.2). the answer is because h0 modifies infinitesimally the orientation of the chains but does not align them with its own direction, thus, the average angle between the local and external or even the effective magnetic fields is not equal to zero. when calculating the initial magnetic susceptibility, a chain of length k is considered as a particle with a dipole moment km, thus, in terms of magnetization the argument of the langevin function is kmhe kbt . the langevin function is weighted by the distribution hk, and finally the gradient of magnetization in an infinitesimal external magnetic field is calculated as χ0 = ∂ ∂h0 ∣∣∣∣ h0=0 ρm ∞∑ k=1 hkl ( kmhe kbt ) . (6) an infinitesimally weak external magnetic field can be written as χ0 = 1 + p 1− p χl ( 1 + 4π 3 χl ) , (7) where the following infinite expression is used (|p| < 1): ∞∑ k=1 pk−1k2 = 1 + p (1− p)3 . (8) the detailed derivation of the initial magnetic susceptibility (eq. 7) is given in appendix b. 46(2) pp. 47–54 (2018) 50 nagy figure 1: the rates of the local magnetic field as a function of the density from eq. 9 at three different dipole moments in the absence of any external magnetic field. 2.2 the numerical calculation of the probability of chain formation “p” the main challenge of our approach is the determination of p. the particles form chains because of the local magnetic field even in the absence of any applied external magnetic field. according to weiss’ model when χl ≥ 3/4π this local magnetic field predicts an infinite initial magnetic susceptibility. the problem with this model is that it assumes that the orientation of the local magnetic field is parallel with the external magnetic field. nevertheless, weiss’ model is applicable to predict the extent of the local magnetic field by the expression (when h0 = 0): hl = 4π 3 ρml ( mhl kbt ) . (9) h∗l as a function of the reduced density ρ∗ at three different dipole moments is presented in fig. 1. the definitions of the reduced quantities are h∗ = h √ σ3/kbt ; m∗ = m √ σ3/kbt ; m∗ = m/ √ σ3kbt . all particles are considered to be influenced by this local magnetic field hl, in the absence of any external magnetic field h0 when calculating the initial magnetic susceptibility. as was mentioned before, the most accepted criterion for chaining is to determine an energy level and if the dipolar energy between two given particles is under this level, the particles are in a bound relationship. generally [15–17], this energy level is 70-75 % of the minimum of the dipolar energy, i.e. u∗lim = −0.7 ∗ 2(m∗)2. here the well-known dipolar energy is defined as the interaction between point dipoles: udd ij = −m 2 r3 ij [3 (m̂i · r̂ij) (m̂j · r̂ij)− (m̂i · m̂j)] , (10) where the particles have dipole moments of strength m as well as an orientation given by unit vectors m̂i and figure 2: the feasible location of a particle between two fixed particles. m̂j . furthermore, the distance between the centers of the particles is denoted by rij and r̂ij = rij/rij . as is shown in fig. 2, according to our model particle j can move along the direction of the chain between the two fixed adjacent particles, namely i and the grey one, in the tube with a light blue background. logically, the minimum distance between two particles in a hard sphere system is σ, on a reduced scale d∗min = 1, while for the maximum distance d∗max = 2 〈r∗〉 − 1, where the reduced average distance between two adjacent particles is denoted by 〈r∗〉. obviously the maximum distance between two neighbouring particles could be greater than d∗max but at higher densities in particular the surrounding particles obstruct the movement of the central particle. assuming that the distance distribution is isotropic, it is given by 〈r∗〉 = 3 √ 1/ρ∗. taken all round to calculate p the probability of those states of particle pairs should be totalled when the dipolar interaction energy is less than or equal to the aforementioned energy limit ulim and the interval of integration in distance is [d∗min, d ∗ max], that is p = ∫ udd≤ulim p (θi)dθip (θj)dθjp (φi)dφip (φj)dφj , (11) where 0 ≤ θ < π and 0 ≤ φ < 2π are the usual spherical angles of the dipoles and the probabilities when magnetic field h (here h = hl) is applied in general are p (θ)dθ = exp ( mh kbt cos θ ) sin θdθ ∫ π 0 exp ( mh kbt cos θ ) sin θdθ (12) and p (φ) dφ = dφ/2π. the calculation of p was performed by numerical integration. particles i and j (fig. 2) are under the influence of the local magnetic field independently from each other. for both particles, all possible values of θ, φ, and r are swept and taken into account if the dipolar interaction energy between particles i and j is less than or equal to ulim. this is expressed by eq. 11. for instance, when ρ∗ = 0.8 and m∗ 2 = 3.0 then h∗l = 5.154 and d∗max = 1.154435. the probability of chaining between particles i and j as a function of distance is shown in fig. 3. the requested probability p is hungarian journal of industry and chemistry the initial magnetic susceptibility of dense aggregated dipolar fluids 51 figure 3: an example calculation of p. the parameters are rho∗ = 0.8, (m∗)2 = 3.0, h∗ l = 5.154, d∗max = 1.154435, and u∗ lim = 0.7u∗ min. the requested probability p is the average of this curve in the interval [d∗min, d ∗ max]. the average of this curve from 1 to d∗max, i.e. p = 0.3454, if u∗lim = 0.7u∗min. 3. simulation results and discussion to determine the initial magnetic susceptibility, monte carlo simulations of dhs fluids were performed using a canonical nvt ensemble. boltzmann sampling [18], periodic boundary conditions and the minimum-image convention were applied. in order to take into account the long-range character of the dipolar interaction, the reaction field method under boundary conditions of conduction was used. after 100,000 equilibration cycles, between 1 and 10 million production cycles were conducted involving n = 512 particles. in the absence of an external magnetic field, the initial magnetic susceptibility was obtained from the following fluctuation formula: χ0 = 1 3kbtv (〈 m2 〉 0 − 〈m〉20 ) , (13) where m = ∑n i=1 mi. the exact results of the probability of chain formation from eq. 11 applied to the local magnetic field, given by eq. 9, are shown in table 2. the data associated with the aforementioned dipole moments were rounded to three non-zero decimals. according to fig. 1 at low densities the values of the local magnetic field are zero, nevertheless, the rates of the probability of chaining are not equal to zero. the value of the energy limit was fitted to the best agreement between the simulation data and our theory lines. our theoretical findings (green lines, eq. 7 ) in terms of the initial magnetic susceptibility according to our monte carlo simulation data (blue dots) and the values of ivanov’s theory (grey lines, table 1: 4.4) are compared in figs. 4-6. the variability is not indicated where its magnitude is comparable to the size of the dot. the values of dipole moments in the order m∗ = 1, m∗ = √ 2 and m∗ = √ 3 are shown in figs. 4-6. table 2: the probability of chaining at three different dipole moments. the applied energy limit at m∗ = 1 and m∗ = √ 2 is ulim = 0.77umin and ulim = 0.71umin at m∗ = √ 3. p ρ∗ m∗ = 1 m∗ = √ 2 m∗ = √ 3 0.1 0.000260 0.000263 0.000580 0.2 0.000426 0.000429 0.000943 0.3 0.000615 0.000617 0.00794 0.4 0.000852 0.00292 0.0250 0.5 0.00117 0.0110 0.0521 0.6 0.00164 0.0253 0.0953 0.7 0.00241 0.0515 0.170 0.8 0.0135 0.107 0.320 0.85 0.0269 0.164 0.471 0.9 0.0539 0.273 0.649 0.95 0.101 0.416 0.775 in the case of m∗ = 1 (fig. 4), the energy limit is ulim = 0.77umin. a significant difference was only observed between ivanov’s theory and the simulation data beyond a reduced density of 0.8 and the simulation dots were tracked by our present theory. the maximum relative deviation from the simulation data is |χ0 sim − χ0 th| /χ0 sim = 4.175%. when m∗ = √ 2, the appropriate energy criterion is ulim = 0.77umin as well. up to a reduced density of 0.6 the former theory and simulation are in good agreement (fig. 5), but in the present theory more than double the surplus is shown in the region of high density compared to table 1: 4.4. the maximum relative deviation from the simulation data is 8.024 %. here it is quite conceivable that the simple series expansion of initial magnetic susceptibility as the summation of positive integer powers of langevin susceptibility is unsatisfactory. by increasing the third coefficient in figure 4: initial magnetic susceptibility of dhs fluid as a function of reduced density with dipole moment m∗ = 1. monte carlo simulation results are denoted by symbols and the solid lines correspond to the present (eq. 7) and ivanov’s (table 1: 4.4) theories. 46(2) pp. 47–54 (2018) 52 nagy figure 5: initial magnetic susceptibility of dhs fluid as a function of reduced density with dipole moment m∗ =√ 2. monte carlo simulation results are denoted by symbols and the solid lines correspond to the present (eq. 7) and ivanov’s (table 1: 4.4) theories. figure 6: initial magnetic susceptibility of dhs fluid as a function of reduced density with dipole moment m∗ =√ 3. monte carlo simulation results are denoted by symbols and the solid lines correspond to the present (eq. 7) and ivanov’s (table 1: 4.4) theories. table 1: 4.4, the initial magnetic susceptibility at lower densities is also increased. when m∗ = √ 3 the difference is even more spectacular between the theories (fig. 6). at high densities the uncertainty of initial magnetic susceptibility is quite large with regard to the simulation data. the best fit curve belongs to an energy limit of 71 %, which is very close to the value from references [15–17] of 70 %. the maximum relative deviation from the simulation data is 15.850 %. when m∗ = 1 and ρ∗ = 0.95, with an energy limit of 70 %, the theoretical value of initial magnetic susceptibility is χ0 = 1.042, and if the energy limit is 75 %, χ0 = 0.937. both values are higher than the corresponding simulation data, thus, the energy limit has to be raised to 77 %. the situation is similar when m∗ = √ 2 and ρ∗ = 0.95, namely χ0 = 8.701 when the energy limit is 70 % and χ0 = 6.363 when it is 75 %. probably at lower dipole moments and higher densities the two adjacent particles cannot be considered as a chain even though the interaction energy exceeds an energy limit of 70 % or 75 % for example because the average kinetic energy is closer to this interaction energy than is the case when m∗ = √ 3. therefore, the duration of chain formation is short to draw the particles together. 4. conclusion the initial magnetic susceptibility of dipolar hard sphere fluids was described by the help of the probability variable p supplemented by pshenichnikov’s well-known theory. the validity of the present theory is up to ρ∗ = 0.95 and at leastm∗ = √ 3. in addition to the theoretical work, monte carlo simulations were run to confirm our investigation. at higher densities, especially with higher dipole moments, the former related theories significantly underestimate the simulation data but good results are also provided by the presented theory within this range. by considering the green curves and blue dots in figs. 4-6, it is obvious that the simple quadratic or tertiary polynomial approach is outdated, therefore, the taylor series expansion of (1 + p)/(1− p) contains powers even as high as infinity. 5. appendix 5.1 appendix a the particle distribution can be obtained by dividing the number of particles in chains of length k by the total number of particles: hk = kgk∑ kgk = kqpk−1∑ kqpk−1 = kpk−1∑ kpk−1 = kpk−1 1 + 2p+ 3p2 + · · · = = kpk−1 (1+p+ p2 + · · · ) + (p+ p2 + p3 + · · · ) + (p2 + p3 + p4 + . . .) + · · · = = kpk−1 (1 + p+ p2 + · · · ) + (p+ p2 + p3 + · · · ) + (p2 + p3 + p4 + · · · ) + · · · = = kpk−1 1 1− p + p 1− p + p2 1− p + · · · = qkpk−1 1 + p+ p2 + · · · = qkpk−1 1 1− p = q2kpk−1. (14) hungarian journal of industry and chemistry the initial magnetic susceptibility of dense aggregated dipolar fluids 53 the sum of hk terms must be equal to one: ∞∑ k=1 hk = ∞∑ k=1 q2kpk−1 = q2 ( 1 + 2p+ 3p2 + . . . ) = q2 [( 1 + p+ p2 + · · · ) + ( p+ p2 + p3 · · · ) + · · · ] = = q2 [ 1 1− p + p 1− p + p2 1− p + · · · ] = q [ 1 + p+ p2 + . . . ] = q 1 1− p = 1. (15) 5.2 appendix b χ0 = ∂ ∂h0 ∣∣∣∣ h0=0 ρm ∞∑ k=1 hkl ( kmhe kbt ) = ∂ ∂h0 ∣∣∣∣ h0=0 ρm ∞∑ k=1 q2kpk−1l km ( h0 + 4π 3 ρml ( mh0 kbt )) kbt  = = q2ρm ∂ ∂h0 ∣∣∣∣ h0=0 ∞∑ k=1 kpk−1l kmh0 kbt + 4π 3 kρm2l ( mh0 kbt ) kbt  = = q2ρm ∞∑ k=1 kpk−1 1 3  km kbt + 4π 3 kρm2 1 3 m kbt kbt  = q2 ∞∑ k=1 k2pk−1 ( 1 3 ρm2 kbt + 1 9 4π 3 ρ2m4 k2 bt 2 ) = q2 ( χl + 4π 3 χ2 l ) ∞∑ k=1 k2pk−1 = 1 + p 1− p χl ( 1 + 4π 3 χl ) . 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https://doi.org/10.1103/physreve.51.5962 hungarian journal of industry and chemistry vol. 46(2) pp. 55–62 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0019 worker movement diagram based stochastic model of open paced conveyors tamás ruppert1 and jános abonyi *1 1mta-pe lendület complex systems monitoring research group, department of process engineering, university of pannonia, egyetem u. 10, veszprém, h-8200, hungary human resources are still utilized in many manufacturing systems, so the development of these processes should also focus on the performance of the operators. the optimization of production systems requires accurate and reliable models. due to the complexity and uncertainty of the human behavior, the modeling of the operators is a challenging task. our goal is to develop a worker movement diagram based model that considers the stochastic nature of paced open conveyors. the problem is challenging as the simulator has to handle the open nature of the workstations, which means that the operators can work ahead or try to work off their backlog, and due to the increased flexibility of the moving patterns the possible crossings which could lead to the stopping of the conveyor should also be modeled. the risk of such micro-stoppings is calculated by monte-carlo simulation. the applicability of the simulator is demonstrated by a well-documented benchmark problem of a wire-harness production process. keywords: industry 4.0, operator 4.0, monte-carlo simulation, process development, line balancing, wire-harness assembly 1. introduction conveyor lines are more productive than regular assembly lines [1]; therefore there are more prevalent in the automotive industry [2]. the movement of these conveyors mostly has paced and cyclic characteristic where at the beginning of the cycle, every station moves to the next position [3]. it can happen that the operator cannot finish his/her work before the product leaves the workstation. there are two alternative approaches for completing the unfinished work. we speak about close station production when the operator must stop the conveyor even in case of a minor delay [4]. such processes are typical in japan. in u.s.-type production systems, the operator does not have to finish his or her job, he or she can move with the product to the next station to work off the backlog. in these open stations the operators can work ahead or can be delayed [5], and the production stops only when the delay exceeds a critical limit. these open workstations reduce capacity loss by decreasing the risk of stopping the conveyor, but the modeling and optimization of these processes is much more challenging as the model has to handle idle and delay times [6]. worker movement diagrams are widely used to model the work of operators at conveyor belts [7]. such models can be used to reduce the risk of conveyor stoppage [8] and optimize production sequence [9], since the optimal distribution of the products can also reduce the probability of critical backlogs [10]. *correspondence: researcher@abonyilab.com worker movement diagrams focus only one station. in open paced conveyors the operators effect on each other; therefore the model should handle the interactions between the workstations, especially for the prediction of the conveyor stoppage. our goal is to develop a worker movement diagram based model for open paced conveyors, which model considers the stochastic nature of production and recognizes the meeting point of operators and analyzes the idle times due to working in the same zones and risk of stopping the production in case of unmanageable backlogs. we introduce stochastic variables into the movement diagram representation based model and apply monte-carlo simulation to evaluate the risk of conveyor stoppage and give robust estimates of the effects of different parameter settings. the simulator is developed in python environment. the applicability of the proposed model and simulator is demonstrated by a well-documented benchmark problem of a wire-harness production process. section 2 describes the worker movement diagram and the sections defined based on the relative position of the operators and the conveyor. the model of the paced conveyor is based on equations that represent the movement of the operators in these sections. based on these equations we calculate when the conveyor should be stopped. section 3 describes the applicability of the developed simulator in a wire harness production system. mailto:researcher@abonyilab.com 56 ruppert and abonyi 2. model of the paced conveyor 2.1 problem definition the most widespread paced open station conveyors are used to produce wire harnesses in the automobile industry. the optimization and cost estimation of these processes are an economically significant problem [11]. these modular assembly lines consist of manual workstations (tables) shown in fig. 1. human operators work at the tables that are moving similarly as a conveyor belt (see fig. 2). these tables move with a fixed speed which is determined based on the tact time, tc. after the cycle, every table moves to the next station. the modeling the relative position of the operators and the tables can be represented by worker movement diagrams that will be presented in the next section. 2.2 movement diagram of an open station the paced conveyor has k, k = 1, . . . ,k is number of workstations that moves in every n = 1, . . . , n cycle. the speed of the conveyor is vc, and the walking speed of operator is vw. the tc is the tact time determines the assembly speed: vkn = l tkπ(n−k) (1) where l represents the length o the workstation, the tkπ(n−k) the assembly time which is dependent on the produced product. the sequence of the products is represented by a π vector of the labels of the types, so π(k) = pj states that type product pj started to be produced during the k-th production cycle. the modeling of the paced conveyor is complex task as the conveyor moves only for a tcm < tc period of the time, which defines several sections of the tack time according to the speed and position of the table and the operators. as it is depicted in figs. 3 and 4, the worker movement diagram is divided for six sections (s = 1, . . . , 6) . 1. the operator moves to the starting point of the table figure 1: an example assembly table in wire harness manufacturing. the dashed line with an arrow represents the worker motion at the table. the operator works on the table from left to right. the assembly speed is vkn. figure 2: the most widely used open station paced conveyors are used in wire harness assembly, where the operators are working at tables that moving in every cycle of the production [12]. 2. the operator works before the new cycle 3. the operator and the table move together 4. the operator works and the table stays 5. the operator and the table move together after the end of tact time 6. the operator works and the table stays after the end of tact time in the first section, s = 1, the operator walks to the left side of the table, f (1)kn. after reaching this position the operator starts the assembly process and moves with the conveyor till the conveyor moves to its next workspace. after this f (3)kn position the operator works at the standing table with a vkn speed. when the job is finished, the operator reaches the end of the table, f (4)kn = kl, as it is shown at fig. 5). the second, fifth and sixth sections happen when operator deviates from this normal case (work ahead or delayed). in the following, we present a model that describes how the positions of the table and the operators are changing in time. in the model f (s)kn denotes the position of kth operator at nth cycle step in sth section of diagram, where the positions are measured from the starting point of the first table. section 1. the operator moves to the starting point of the table at the beginning of the cycle, the operator moves the starting point of the next table which is 2l far from its actual position. the f (1)kn position when the kth operator reaches the staring point of table should be calculated as f (1)kn = f (6)kn−1 − t (1)knvw (2) t (1)kn = nwt+dwt+cdwt+ iwt (3) where f (6)kn−1 is the kth operator finishing position in the previous cycle step (n− 1), while the t (1)kn required hungarian journal of industry and chemistry worker movement diagram based model of open paced conveyors 57 figure 3: worker movement diagram of the sections when the operator works ahead. lines with arrow represent the motion of the operator, while dashed lines represent movement of the table. figure 4: worker movement diagram of the sections when the operator has a backlog. lines with arrow represent the motion of the operator, while dashed lines represent movement of the table. figure 5: worker movement diagram of one station. the first meeting point with the table and the operator is f (1)kn. f (3)kn and f (4)kn are the positions at the end of the second and third sections. when there is no delay or the operator does not work ahead f (4)kn = f (6)kn, where f (6)kn is the finishing position. 46(2) pp. 55–62 (2018) 58 ruppert and abonyi time can be decomposed into four components, which will be modeled in the following subsections: • nwt normal walking time • dwt delayed walking time • cdwt critically delayed walking time • iwt idle walking time nwt: normal walking time in the normal case, the operator and the conveyor move together at the beginning of the cycle with vc+vw relative speed. the effect of the akn−1 idle time and the lkn−1 late time of the previous cycle is represented by the nwta and nwtb variables that are used to calculate the nwt walking time: nwt = max[min(nwta; nwtb); 0] (4) nwta = max ( 2l− akn−1vw vc + vw ; 0 ) (5) nwtb = min ( tcm − lkn−1, 2l vc + vw ) , (6) where akn−1vw represents the walking distance of operator at the end of the previous cycle. when tcm − lkn−1 is less than zero, then operator does not have to walk, because he or she still works on the last (n− 1) product (in this case we should calculate dwt). dwt: delayed walking time when the assembly time in the previous cycle exceeds tc, dwt is equal to the time which necessary for the reaching the table after tc. dwt = if [tcm − lkn−1 > 0 or lkn−1 = 0]; (7) then dwth; else 0 dwth = (8) max [ 2l vc + vw −max ( tcm − lkn−1; 0 ) ; 0 ] vcw where vcw = vc+vw vw is the walking speed of operator, when the conveyor is moving. cdwt: critically delayed walking time when lkn−1 is more than tcm, the operator moves to the beginning of the table when the conveyor is standing. cdwt = if [tcm − lkn−1 <= 0 (9) or lkn−1 = 0]; then 2l vw ; else 0 iwt: idle walking time when the conveyor does not move and akn−1 is bigger than the necessary walking time, 2l vw , then iwt = min ( akn−1, 2l vw ) (10) section 2. the operator works before the new cycle thef (2)kn staring position and t (2)kn duration of the the second section is calculated as: f (2)kn = f (1)kn + t (2)knv k n (11) t (2)kn = max ( akn−1 − 2l vw ; 0 ) (12) where vkn is the average speed of the assembly. section 3. the operator and table move together in this section, operator and the conveyor are moving together for a time period shorter than tcm, so they will meet at: f (3)kn = f (2)kn + t (3)kn(vc + vkn) (13) t (3)kn = min ( max [ (n− 1)tc + tcm − t k; 0 ] ; tcm ) (14) where (n− 1)tc + tcm describes the time instant the section will finish. in normal situation t (3)kn equals to tcm, while in extreme case the operator has as significant idle time as he or she finishes his or her job before the end of this section. section 4. the operator works and table stays in this section the operator works with vkn linear speed until the conveyor does not move, so this section finishes at: f (4)kn = f (3)kn + t (4)knv k n (15) t (4)kn = min{max[ntc − t ; 0]; (16) l vkn − t (2)kn − t (3)kn} , where l vkn −t (2)kn−t (3)kn defines the remaining assembly time before the end of the tact time. the idle and delay times at the end of the cycles the akn idle or lkn delay time is calculated as: lkn = max ( l vkn + t (1)kn − akn−1 + lkn−1 − tc; 0 ) (17) akn = max ( tc − l vkn − t (1)kn + akn−1 − lkn−1; 0 ) (18) the prediction of conveyor stoppage is the most important ability of the model which will be calculated based on the delay time as it will be presented in the following subsection. hungarian journal of industry and chemistry worker movement diagram based model of open paced conveyors 59 section 5. the operator and the table move together after the end of tact time this section can be considered as the modification of the third section with the delay of the operator. as we already know lkn and the operator can work in this section maximum till tcm, the calculation is straightforward: f (5)kn = f (4)kn + t (5)kn(vc + vkn) (19) t (5)kn = min ( lkn, tcm ) (20) section 6. the operator works and the conveyor stays after the end of tact time as the duration of this section is limited as tc − tcm, the variables that define the end of the section are calculated as: f (6)kn = f (5)kn + t (6)knv k n (21) t (6)kn = min [ max ( lkn − tcm; 0 ) ; tc − tcm ] (22) calculation of the stoppage and the idle time the open station type operation of the paced conveyor has increased flexibility as the conveyor has to be stopped only when the delay of the kth operator is as significant as it disturbs the work of the neighboring k−1th operator. we define this situation as: t k + t (1)kn <= t k−1 + t (1)k−1 n−1 + tc 4 (23) in this case the idle ikn time has to be modified by t (1)kn and reset the value of akn to zero. ikn = (n− 1)tc − t (1)kn (24) when the lkn − t (6)kn is smaller than tcm, the operator stops the conveyor. the lkn is reset and the stoppage time is: skn = max(lkn − t (6)kn − tcm; 0) (25) 2.3 kpis and the developed simulator the developed simulator handles the stochastic and open nature of the conveyor, simulates all workstations, the interactions between the operators and predicts stoppage. the worker movement diagram representation helps in the stoppages prediction (see fig. 6). production planners can use the developed simulator to try sequencing strategies and analyze a new production lines capability. the following key performance indicators (kpis) calculated based on monte-carlo simulation gives a realistic picture about the production. • the balance of conveyor line is depended on the maximum of the late times of operators, lk = [lk1 , l k 2 , . . . , l k n]: b = k∑ k=1 max(lk) k 1 tc (26) • the efficiency of production is calculated based on to the sum of the l vkn assembly times divided by the maximum of the t(6) k = t (6)k1 , t (6) k 2 , . . . , t (6) k n) finishing times and the sum of stoppage times multiplied by the number of workstations. p = k∑ k=1 l vkn {max[t(6) k ] + n∑ n=1 k∑ k=1 skn}k (27) • the sum of the s stoppage times (eq. 25). • the mean of the assembly times. the simulator and the movement diagram are developed in python environment. d the developed simulator and the related dataset is freely and fully available on the website of authors: www.abonyilab.com. 3. application to wire harness production to demonstrate the applicability of the simulator three typical types of production sequencing strategies were analyzed. in the first case, the sequence follows the random customer demand which case often happens in just in time (jit) production. batch production is a more efficient sequencing strategy. in this case, batches of lower and higher complexity products are following each other. one of the best solutions is the π = m1,m2,m1, . . . high/low sequencing strategy because it utilizes the open station nature of the conveyor. the studied conveyor contains k = 5 workstations. the number of manufactured products is n = 100, and two different group of products (m = 2) are produced. the assembly times are represented by a normal distribution, which is t1 = n (250, 30) for the lower complexity product and t2 = n (310, 30) for the higher complexity product. the tact time of the conveyor is constant and set to tc = 280s which is the average assembly time of the products. fig. 7 shows the results of 1,000 simulations of the three sequence types. this scatter matrix plot shows the main kpis, the balance, the number of the manufactured products, the number of stoppages, and the average assembly times. the green dots represent the high/low, the blues the batched, and the red the random sequences. as shown in fig. 7, the difference between the random (blue) and high/low (green) sequences is significant on all kpis. the batched sequence (red) has similar performance to the high/low sequence, but many times this batch production is not manageable because of the high variance of the products and the short delivery times. 4. conclusions as human resources are still necessary for many manufacturing systems, the development of production process should also focus on the performance of operators. 46(2) pp. 55–62 (2018) www.abonyilab.com 60 ruppert and abonyi −5 0 5 10 15 20 25 30 distance [m] 0 1000 2000 3000 4000 5000 6000 ti m e [s ] figure 6: the developed worker movement diagram of five stations and 18 cycle steps. the distance begins at −5 m to represent the previous workstation. figure 7: the result of a monte-caro simulation of three different sequencing strategies. the scatter plot shows all of kpis. the high/low sequence is denoted by green, the batch by red, and the random by blue dots. the difference between the random and high/low sequences is significant on all kpis. hungarian journal of industry and chemistry worker movement diagram based model of open paced conveyors 61 according to the digital twin concept, this development should be based on the model of the production system, which necessaries the development of simulators that can handle uncertainties related to the human nature of the operators. the developed worker movement diagram based model handles the paced and open workstations of the conveyors and the stochastic nature of production. the worker movement representation helps in the analysis of the operators which is needed to predict production stoppages. the introduction of stochastic variables and the monte-carlo simulation-based evaluation of the key performance indicators provide a realistic picture about the production. the applicability of the simulator in the analysis of the effect of production sequencing is demonstrated by a well-documented benchmark problem of a wire-harness production process. the developed simulator is not specialized to the studied wire harness production; it can be used to model all of the types of paced conveyors even open or closed workstations. acknowledgement this research was supported by the national research, development and innovation office nkfih, through the project otka-116674 (process mining and deep learning in the natural sciences and process development) and the efop-3.6.116-201600015 smart specialization strategy (s3) comprehensive institutional development program. notations kpi key performance indicator nwt normal walking time dwt delayed walking time cdwt critically delayed walking time iwt idle walking time k index of workstation k = 1, . . . ,k k number of workstations n index of cycle step n = 1, . . . , n n number of cycle steps s index of section s=1, . . . , 6 vkn assembly speed of th operator [ms ] vw walking speed of the operator [ms ] vc speed of the conveyor [ms ] vcw walking speed of the operator when the conveyor is moving [ms ] tc tact time [s] tcm conveyor movement time [s] tk(π(n) assembly time of actual the product at kth operator [s] t (s)kn duration of the actual s section in nth cycle step a kth workstation [s] t(6)k finishing times of the kth operator [s] akn work ahead time in nth cycle step at kth operator [s] lkn late time in nth cycle step at kth operator [s] lk late times of kth operator [s] t actual simulated time [s] ikn final idle time in nth cycle step at kth workstation [s] skn stoppage time in nth cycle step at kth workstation [m] f (s)kn position of operator at the actual s section in nth cycle step a kth workstation [m] tablekn table position in nth cycle step at kth operator [m] π(n) sequence of products [−] l length of the workstation [m] t kn position of the tables [m] references [1] estrada, f., villalobos, j.r., roderick, l., estrada, f., villalobos, j.r., roderick, l.: evaluation of justin-time alternatives in the electric wire-harness industry, taylor and francis, 1997 35(7), 1993–2008, doi: 10.1080/002075497195038 [2] lodewijks, g.: two decades dynamics of belt conveyor systems bulk solids handling, 2002 22(2), 1–2 [3] xiaobo, z., zhou, z., asres, a.: note on toyota’s goal of sequencing mixed models on an assembly line, computers and industrial engineering, 1999 36(1), doi: 10.1016/s0360-8352(98)00113-2, 57–65 [4] sarker, b.r., pan, h.: designing a mixed-model, open-station 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harnesses, the international journal of advanced manufacturing technology, 1991 6(2), 155–179 doi: 10.1007/bf02601438 [12] assembly line conveyor systems, 2015, https: //www.pacline.com/photos/photos-by-solution/ assembly-line-conveyors/ hungarian journal of industry and chemistry https://doi.org/10.1287/mnsc.41.3.485 https://doi.org/10.1287/mnsc.41.3.485 https://doi.org/10.1007/bf02601438 https://www.pacline.com/photos/photos-by-solution/assembly-line-conveyors/ https://www.pacline.com/photos/photos-by-solution/assembly-line-conveyors/ https://www.pacline.com/photos/photos-by-solution/assembly-line-conveyors/ hungarian journal of industry and chemistry vol. 46(2) pp. 63–66 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0020 investigations into flour mixes of triticum monococcum and triticum spelta katalin kóczán-manninger *1 and katalin badak-kerti1 1department of grain and industrial plant processing, szent istván university, villányi út 29-43, budapest, 1118, hungary bread samples were made using flour mixes of triticum monococcum (tr. monococcum) and triticum spelta (tr. spelta). they were tested for their rheological behaviour over the first 3 days of storage at room temperature, and for their characteristics based on a hungarian standard. parameters were set such as the volume of the baked product, baking loss, crumb characteristics and elasticity of crumbs. the behaviour of flour from einkorn wheat is different to that of tr. spelta. the properties of the tested flour mixes measured by a farinograph show that tr. spelta produces an acceptable dough, on the other hand, the dough of tr. monococcum develops quickly but is very unstable so weakens within minutes of being kneaded. this also suggests that doughs composed of einkorn wheat flour require a different type of kneading than those of tr. spelta (or tr. aestivum, also referred to as common wheat) flours. breads composed of tr. spelta were comparable with those made with tr. aestivum, the crumb elasticity was above 90 % on the day of baking, which indicates high quality. the tr. monococcum breads, however, were of low grade: the volume of the breads decreased by increasing the ratio of tr. monococcum to tr. spelta and the elasticity reduced to unacceptable levels (less than 60 %). it should be mentioned that the grading was based on breads made purely from tr. aestivum flours. keywords: spelt, einkorn, bread, texture analysis 1. introduction as a result of the increasing number of cases of celiac disease and allergies, as well as the growing popularity of conscious nutrition, interest in older varieties of wheat is once again on the rise. in general, consumers think that these species of wheat are potentially less immunogenic than their modern equivalents. the manufacturing properties of doughs produced from ancient varieties of wheat are much weaker than those of common wheat. in order to obtain good quality bakery products, it may be necessary to use mixtures of flours from different varieties. in our research, the properties of the flour of einkorn and spelt wheats in addition to breads that consist of different proportions of these flours were prepared and investigated. during measurements, attempts were made to determine whether these wheat species – which are in theory suitable for baking bread – could improve the baking performance or whether a significant difference exists between the characteristics of the finished products of various compositions. crossing more modern varieties results in higher yields, greater resistance, more uniform ripening times and higher gluten contents. although these breeding procedures facilitated processing, the genetic diversity and nutritional value decreased significantly which virtually *correspondence: koczan.gyorgyne@etk.szie.hu resulted in the total displacement of indigenous species [1, 2]. one reason for this is that tr. monococcum was consumed primarily as a mush or simply cooked; these methods did not require proofing, which was originally used in ancient egypt during bread baking [3]. bread made from spelt flour is also of lower quality than that of common wheat, both in terms of specific volume and crumb structure [4]. according to previous research, spelt wheat flour produces less stable and elastic but stickier dough than plain flour. due to its sticky and soft nature after kneading, it is difficult to handle [5, 6]. breads made from einkorn flour exhibit a wide range of possible specific volumes, ranging from very low to high. although only a few subtypes are suitable for making breads, most versions are suitable for preparing pasta or biscuits [7], or utilisation for special purposes like fermentation processes [8]. the first phase of the investigations concerned the quality of the gluten, followed by the preparation and testing of loaves of bread. the main question concerned how the blends of flours of these species of wheat influence the quality of the final products. mailto: koczan.gyorgyne@etk.szie.hu 64 kóczán-manninger and badak-kerti 2. experimental 2.1 samples and measurements triticum monococcum (einkorn) and triticum spelta wheat flours were manufactured by szabó hengermalom kft. using conventional technology and contained no additives or bread improvers. for the measurements fine flours were used, i.e. small grain particles with low bran content, to ensure they contained only a negligible amount of outer shell. the determination of wet gluten content was performed according to a standard using the glutomatic system. after gluten washing, a gluten index was also calculated using a gluten centrifuge. the moisture content was determined by a sartorius moisture analyser. the uniformly dispersed sample of 2.5 g was dried at 105 ◦c to a constant weight (which has not changed for 20 seconds more than 1 mg). the change in mass could be deduced from the moisture content of the whole test substance. the determination of water absorption was conducted by a brabender farinograph in accordance with a hungarian standard (msz 6369-6:2013) in duplicates, followed by further experimentation using a baking test (msz 6369-8:1988). the volume of the bread samples was measured by placing a loaf in a container of known volume and pouring in a known quantity of mustard seeds around the loaf until the container was full. by measuring the amount of seeds remaining once the container was full, the volume of the loaf could be calculated. the quality of the bread texture was evaluated by a ta.xtplus texture analyser (stable micro systems, surrey, uk), following a modified american association of cereal chemists (aacc) international approved method (74-09) and expressed as crumb firmness (force, 1/g) and relative elasticity (%). a 40 % compression of a 25 mmthick sample was achieved, following a resting time of 30 seconds (at the same compression depth) and then the measuring head was slowly lifted and the springiness of the sample calculated. thus, it was a “measure of force in compression” test using an aacc 36mm-diameter cylinder probe with radius (p/36r). the analyser was set at a ‘return to start’ cycle with a pre-test speed of 1 mm s−1, a test speed of 0.5mm s−1, a post-test speed of 10 mm s−1 and a pre-defined percentage (40 %) of the original sample height. the relative elasticity was calculated from the difference between the original height and the height to which the sample recovered (after pressing and releasing the pressure). measurements were conducted in triplicates. statistical evaluations were carried out using anova (analysis of variance) tests in excel. bread samples were stored at room temperature in plastic bags. texture measurements were taken on the day of baking after the bread had been cooled to room temperature (day 0) and on the following 2 days, namely days 1 and 2. table 1: composition of the samples (%) 100a 80a 60a 40a 20a 100t tr. monoc. (a) % 100 80 60 40 20 0 tr. spelta (t) % 0 20 40 60 80 100 water % 57 62 64 65.4 65.8 71 yeast % 4 4 4 4 4 4 salt % 1.2 1.2 1.2 1.2 1.2 1.2 the ingredients consisted of 250 g of flour, 10 g of yeast and 3 g of salt, the only variable parameter was the amount of water used to make the dough. initially, the dough consisted of approximately 60 % (150 ml) water based on the weight of the flour, and the amount of water was increased to form a homogeneous dough. the final compositions are shown in table 1. 3. results and discussion 3.1 experiments in the case of the einkorn flour, gluten washing was ineffective as it could not be washed out. after the mixing phase, a yellowish substance remained on the bottom of the washer. in the case of spelt flour, gluten tests could be conducted without any problems. the wet gluten content of the tr. spelta flour was 46.73 %. according to the hungarian regulations bread wheat flours must have a minimum wet gluten content of 28 % and for wheat flours used to improve the baking quality a minimum of 34 %. bakers consider a gluten content in excess of 30 % to be good. the wet gluten content of the spelt flour examined is well above this value, but other factors are also taken into account to determine the quality of flour. the gluten index, a measure of gluten quality, of spelt flour was 45.73 %. a value of between 60 and 90 % is considered to be ideal, below 60 % weak and in excess of 90 % too strong. thus, the gluten quality of the spelt flour was clearly weak. the gluten quality calculated from the results of the farinograph tests for spelt flour was 98 % which is acceptable but does not fully reflect the quality of the flour. although the kneading and stability times of the doughs fell within the range of expected values, the planimetric area was greater due to the degree of softening. thus, the quality score obtained by hankóczy’s evaluation method was smaller. the farinogram of spelt flour more closely resembles a flour of medium quality (fig. 1). this is especially true for the tr. monococcum flour. it reaches its maximum consistency very quickly; the top of the curve barely exceeds the consistency line (500 bu – brabender units). the degree of softening is enormous, as is reflected well by the large planimetric area. the qualitative value assigned to the curve is very low (fig. 2). hungarian journal of industry and chemistry investigations into flour mixes of triticum monococcum and triticum spelta 65 figure 1: farinogram of triticum spelta flour. a direct correlation was identified between the volume of the bread samples and the amount of spelt flour in the flour blend (fig. 3). this is in accordance with the gluten quality of the flour blends, as is seen from the results of the farinograph measurements. the crumb hardness of the bread samples is shown in fig. 4. as the samples started to age the compression force increased. by examining the initial and final forces (measures of crumb hardness), it can be stated that sample 60a showed the best results. in this case, the force increased by 29 % between day 0 and day 2. for samples containing less einkorn flour the crumbs seemed to be softer and the relative increase in hardness during storage less (when values on day 2 were compared to those on day 0). even though sample 80a was initially even softer than 60a, by the end of day 2 it needed 1.7 times the force to compress it. an explanation of this phenomenon can also be given with regard to the different compositions of the starch molecules in einkorn flour compared to those in spelt flour. the staling of bread is related to the crystallization processes of starch molecules. significant differences between samples consisting of 100 % spelt flour and those of 20 % einkorn flour mixed with 80 % spelt flour were shown by the results. the increase in crumb hardness during storage resulted in significant differences in all samples of identical compositions. figure 2: farinogram of triticum monococcum flour figure 3: volume of bread samples (a – einkorn flour, t – spelt flour; the numbers are the percentages of einkorn flour in the flour blend) the elasticity of the bread crumbs increased as the amount of spelt flour increased in the flour blend (fig. 5). this tendency persisted during storage as well. the slight increase in the elasticity of the bread composed of 100 % triticum monococcum flour was probably due to improper handling of the samples, i.e. improper cooling before being packed, although it is questionable whether any moisture originating from the headspace of the packaging could cause such a change. taking into account that the results obtained could be derived from measurement and/or calculation errors, it may be worthwhile to consider the role of the chemical structure of einkorn flour during the baking process, and its effect on the elasticity during further targeted experiments. by using a rating system for the tr. aestivum flours, the bread samples can be classified. although the same judgment about the “marketability” of the bread samples cannot be made for breads based on these special types of flour, trends can clearly be observed. by adding more einkorn flour to the flour blends, the “quality” of the crumb structure decreased. most of the samples did not achieve an elasticity of 80 % meaning that they did not return to 80 % of their original height after compression. with these values, most of the breads fall into the non-marketable category. elasticfigure 4: crumb hardness (force, 1/g) as a function of different flour compositions over 3 days 46(2) pp. 63–66 (2018) 66 kóczán-manninger and badak-kerti figure 5: change in the elasticity of the bread samples during storage at room temperature ities of between 90 and 95 % are indicative of good quality breads. such values were only achieved when 100 % triticum spelta flour was used. after 2 days of storage at room temperature, the crumbs of 100 % spelt flour bread degraded to an average quality. 4. conclusion the purpose of our investigations was to examine the quality of flours from varieties of ancient wheats. gluten could not be washed out of einkorn samples and the wet gluten content of tr. spelta was also very low. farinograph measurements revealed that when only einkorn flour is used, the dough forms very fast but is very soft and almost completely unstable. by mixing einkorn and spelt flours bread can be made, however, an acceptable ratio would not exceed 20 % of einkorn to 80 % of tr. spelta flour. with this flour blend, the resulting bread volume is comparable to the accepted low values of bread composed of 100 % spelt flour. the hardness and elasticity of the bread crumbs already changed significantly at the lowest mixing ratios. further studies on the sensory characteristics of these breads and consumer tests are needed before deciding on the use of flour blends of triticum monococcum and triticum spelta in the absence of any addition of triticum aestivum flour. references [1] draskovics, m. r.: seed plants (spermatophyta) in: turcsányi, g. (ed.) agricultural botany, mezőgazdasági szaktudási kiadó, budapest, hungary, 2000 pp 363-365 isbn: 9633563593 [2] dinu, m.; whittaker, a.; paglia, g.; benedettelli, s.; sofi, f.: ancient wheat species and human health: biochemical and clinical implications. j. nutr. biochem., 2018 52, 1-9 doi: 10.1016/j.jnutbio.2017.09.001 [3] brandolini, a.; hidalgo, a.: chapter 8: einkorn (triticum monococcum) flour and bread in flour and breads and their fortification in: preedy v. r.; watson r. r.; patel v. b.: health and disease prevention, academic press/elsevier, uk, 2011 pp 7988 isbn: 978-0-12-380886-8 [4] abdel-aal, e-s. m.; hucl, p.; sosulski, w.; bhirud, p. r.: kernel, milling and baking properties of spring-type spelt and einkorn wheats. j. cereal sci., 1997 26, 363-370 doi: 10.1006/jcrs.1997.0139 [5] callejo, m. j.; vargas-kostiuk, m. e., rodríguezquijano, m.: selection, training and validation process of a sensory panel for bread analysis: influence of cultivar on the quality of breads made from common wheat and spelt wheat. j. cereal sci., 2015 61, 55-62 doi: 10.1016/ j.jcs.2014.09.008 [6] frakolaki, g.; giannou, v.; topakas, e.; tzia, c.: chemical characterization and breadmaking potential of spelt versus wheat flour. j. cereal sci., 2017 79, 50-56 doi: 10.1016/j.jcs.2014.09.008 [7] hidalgo, a., brandolini, a.: lipoxygenase activity in wholemeal flours from triticum monococcum, triticum turgidum and triticum aestivum. food chem., 2012 131, 1499-1503 doi: 10.1016/j.foodchem.2011.09.132 [8] hetényi, k.; németh, á.; sevella, a.: examination of medium supplementation for lactic acid fermentation. hung. j. ind. chem., 2008 36(1-2) 49-53 hungarian journal of industry and chemistry https://doi.org/10.1016/j.jnutbio.2017.09.001 https://doi.org/10.1016/j.jnutbio.2017.09.001 https://doi.org/10.1006/jcrs.1997.0139 https://doi.org/10.1016/ j.jcs.2014.09.008 https://doi.org/10.1016/j.jcs.2014.09.008 https://doi.org/10.1016/j.foodchem.2011.09.132 https://doi.org/10.1016/j.foodchem.2011.09.132 hungarian journal of industry and chemistry vol. 46(2) pp. 67–71 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0021 formation of glycidyl esters during the deodorization of vegetable oils erzsébet bognár *1, gabriella hellner2, andrea radnóti2, lászló somogyi1, and zsolt kemény2 1department of grain and industrial plant processing, szent istván university, villányi út 29-43, budapest, 1118, hungary 2bemea katalin kővári r&d centre, illatos út 38, budapest, 1097, hungary glycidyl esters are foodborne contaminants formed during the production of fats and oils, especially during the deodorization of palm oil. the hydrolyzed free form of glycidol has been categorized as probably carcinogenic to humans by the world health organization’s international agency for research on cancer. the aim of this research was to study the formation of glycidyl esters during the lab-scale deodorization of the three most widely produced seed oils in the world (sunflower, rapeseed and soybean). the effects of two independent factors – temperature and residence time – were analyzed by a 32 full factorial experimental design and evaluated by response surface methodology. in accordance with findings in the literature, the greatest amount of glycidyl esters was formed in the soybean oil matrix. for all three oils, the effects of both residence time and temperature were significant, while the latter was more so. to reduce the formation of glycidyl esters, milder deodorization is required, which is limited because of the purposes sought by the thermal operation and removal of volatile minor components and contaminants. keywords: glycidyl esters, deodorization, seed oils 1. introduction glycidyl esters (ges) are foodborne contaminants formed in fat-containing food and food ingredients during high-temperature thermal treatment. according to previous studies, glycidol is produced during digestion from the enzymatic hydrolysis of ges [1,2]. the iarc (international agency for research on cancer) has listed glycidol as a group 2a or genotoxic carcinogen [3]. this year, the european commission adopted the commission regulation (eu) 2018/290 that stipulates the maximum level of glycidyl fatty acid esters permitted in vegetable oils and fats, infant formula, follow-on formula and foods for special medical purposes intended for infants and young children. the maximum concentration of glycidyl fatty acid esters is 1 mg/kg in vegetable oils and fats placed on the market for end consumers or for use as an ingredient in food, and 0.5 mg/kg for vegetable oils and fats destined for the production of baby food and processed cereal-based food for infants and young children [4]. ges are formed in vegetable oils during the refining process in the deodorization step, which is conducted at high temperatures (200-275 ◦c) under vacuum (of less than 10 mbar residual pressure) [5, 6]. deodorization is the last step of refining of conventional edible oils and is intended to remove undesirable substances in order to im*correspondence: zsofi.bognar@outlook.hu prove the taste, odor, color and oxidative stability of such oils [7]. according to data from the literature, high levels of ges are primarily measured in refined palm oil and its fractions. destaillats et al. [8] showed in their study that ges are formed from diand monoacylglycerols (dags and mags), but not from triacylglycerols (tags). accordingly, high levels of ge can be traced back to high levels of dags in crude palm oil [8]. the formation of ge starts at about 200 ◦c [8]. analytical methods for the determination of ges can be divided into two main groups: direct and indirect methods [9]. individual ges are determined by direct quantitation methods which are mainly based on liquid chromatography-mass spectrometry (lc-ms), requiring a significant number of reference compounds and internal standards [10, 11]. indirect determination is based on the conversion of ges into glycidol which is then isolated, derivatized, chromatographically separated and quantified. the result is expressed as the amount of glycidol that can be released from ges. these methods require only a small number of internal standards [9]. in our study, the quantity of ges in seed oil during lab-scale deodorization was determined in order to examine the effects of two independent factors – temperature and residence time – on the formation of ges. mailto: zsofi.bognar@outlook.hu 68 bognár, hellner, radnóti, somogyi, and kemény 2. experimental 2.1 samples and measurements bleached sunflower, rapeseed and soybean oils were supplied by bunge limited (bunge zrt. hungary and bunge ibérica, s.a.u.). diethyl ether, ethyl acetate, n-hexane and high-performance liquid chromatography (hplc)grade water were obtained from vwr international kft. (debrecen, hungary). toluene, isohexane, sodium bromide and phenylboronic acid were obtained from merck kft. (budapest, hungary). methanol, sodium hydroxide and anhydrous sodium sulfate were purchased from reanal laborvegyszer kft. (budapest, hungary). the internal standards glycidyl palmitate-d5 and 3-chloro-1,2propanediol-d5 (3-mcpd-d5) were obtained from labstandards (budapest, hungary). all reagents and chemicals were of analytical grade. lab-scale deodorization trials were conducted in 150 g batches at temperatures between 220 and 260 ◦c. the bleached oils (sunflower, rapeseed or soybean) were heated to the target temperature (220, 230, 240, 250 or 260 ◦c) within 10–15 minutes. the process lasted 3 hours at a pressure of 3–4 mbar using nitrogen as a stripping gas. without breaking the vacuum, sampling was conducted after 0, 15, 30, 45, 60, 90, 120 and 150 minutes had elapsed. the quantities of glycidyl esters were determined using the american oil chemists’ society (aocs) official method cd 29b-13, which is based on alkalinecatalyzed ester cleavage and transformation of the released glycidol into monobromopropanediol (mbpd) and derived free diols using phenylboronic acid (pba). these derivatives are measured by the gas chromatography/mass spectrometry (gc/ms) coupled system (agilent 6890 coupled with 5973) in the selected ion monitoring (sim) mode. quantitative determination was based on the deuterated internal standard using characteristic ions for derivatised glycidol-d5 at m/z 150 and 245, and derivatised glycidol at m/z 147 and 240. 2.2 experimental design and statistical analysis the temperature and residence time were studied using response surface methodology (rsm). the results of the 32 full factorial experimental design (see table 1) were evaluated by analysis of variance (anova) models using statistica 13. the center point of the 32 full factorial design (mid temperature 240 ◦c) and mid time 90 minutes) was repeated three times. only the significant effects (of main effects and interactions) were taken into account in the response surface methodology. the generalized polynomial model for describing the response of independent variables is given in y = β0 + β1x1 + β2x 2 1 + β3x2 + + β4x 2 2 + β5x1x2 + β6x1x 2 2 + + β7x 2 1x2 + β8x 2 1x 2 2 (1) table 1: 32 full factorial experimental design independent variables levels -1 0 +1 x1 temperature (◦c) 220 240 260 x2 residence time (min) 0 90 180 dependent variables (yi) glycidyl esters (mg/kg) 3. results and evaluation 3.1 experiments the results of the lab-scale investigation of ge formation are shown in fig. 1. in our experimental design, the greatest amount of ges formed in soybean oil, in which the concentration of ges reached 5.5 mg/kg at 260 ◦c after 180 minutes (fig. 1a). in the sunflower and rapeseed oils, the maximum concentrations of ges reached were 1.6 and 1.5 mg/kg, respectively (figs. 1b and 1c). the ge content of sunflower and rapeseed oils was kept under 1 mg/kg after 120 minutes of deodorization at a temperature of 250 ◦c or less, but for soybean oil this level was obtained at or below 230 ◦c. this demonstrates that the amounts of precursors in the oils strongly influence the formation of ge, and consequently the optimal deodorization temperature. the threshold concentration of figure 1: ges of seed oils during deodorization: a) sunflower oil, b) rapeseed oil, c) soybean oil hungarian journal of industry and chemistry formation of glycidyl esters during the deodorization of vegetable oils 69 figure 2: fitted surfaces for seed oils: a) sunflower oil, b) rapeseed oil, c) soybean oil 0.5 mg/kg permitted for infant food was complied with at 240, 230 and 220 ◦c for rapeseed, sunflower and soybean oils, respectively (after 120 minutes of deodorization). in the applied experimental setup, up to 0.3 mg/kg of ge formed after 10–15 minutes of heating. at lower deodorization temperatures, the effect of time becomes practically insignificant, especially at 220 and 230 ◦c. 3.2 statistical analysis the application of rsm allowed the main effects and interactions to be determined simultaneously. anova shows the significant effects, which can be used for buildtable 2: regression coefficients for intercept (i), linear and quadratic factors, as well as interactions between factors in the fitted models of seed oils sunflower oil rapeseed oil soybean oil i 7.95 7.12 10.32 t −6.72× 10−2 −5.9×10−2 −9.02×10−2 t 2 1.45×10−4 1.23× 10−4 2× 10−4 t 1.17×10−1 2.16×10−1 1.14 t2 n.s. n.s. n.s. tt −1.13× 10−3 −1.96×10−3 −1.01× 10−2 t 2t 3× 10−5 4× 10−5 2.2× 10−5 tt2 n.s. n.s. −2.38× 10−8 n.s.: effect not significant ing the response surface model. the fitted surfaces for sunflower, rapeseed and soybean oils are presented in figs. 2a-c, respectively. the shapes of the surfaces are very similar, the only difference is in their heights. the interactions between the independent variables can be observed from the fitted surfaces, because at lower temperatures the concentrations of ges gradually increased over time, while at higher temperatures a more rapid increase occurred. for all three seed oils the temperature had the largest effect. the interaction between the independent variables and the effect of time were the second and third most significant, but the quadratic components and their interactions with the other factors were noticeable in most cases, as well. the regression coefficients are shown in table 2 coefficients in the case of sunflower and rapeseed oils are very similar so the rsm diagrams of these oils fall within the same range of values (figs. 2a and 2b). 4. discussion according to the data from the literature, the oil that has been studied the most in this respect is palm oil along with its fractions [8, 12]. cheng et al. [13] summarized the data from previous studies and according to this review the highest concentrations of ges in seed oil were found in soybean oil when compared to rapeseed and sunflower oils. this is in agreement with our observations. the higher concentrations of ges that formed during deodorization were due to the higher levels of dags and mags in the raw material. it was found that the critical temperature range is between 220 and 240 ◦c, above which more than 0.5 mg/kg of ges may form, depending on the quality of the raw material. this conclusion is similar to the results of previous investigations. craft et al. [12] concluded that between 230 and 240 ◦c, the formation of ge is extensive, consequently this value should be considered as an upper limit for the deodorization process. de kock et al. [14] suggested conducting deodorization for a longer period 46(2) pp. 67–71 (2018) 70 bognár, hellner, radnóti, somogyi, and kemény of time at temperatures below 240 ◦c, which might also minimize the formation of trans fatty acids. 5. conclusion the present investigation suggests that the formation of ges in seed oils during deodorization is not negligible. the rate of formation can be traced back to the level of dags and mags [15] in the raw material. a simultaneous increase in temperature and time could result in extremely high levels of ges in oils. on an industrial scale, the formation of ges can be controlled in the oils examined, meaning that the upper limit of ges (1 mg/kg) in vegetable oils and fats placed on the market for general consumption can be achieved through preventive measures. the stricter limit imposed on oils destined for the production of food for infants and young children presents greater challenges, and thus requires a combination of high quality raw materials as well as a controlled refining process. acknowledgement funding for this research was provided by the doctoral school of food sciences at szent istván university (budapest) and by the bemea katalin kővári r&d centre. the project is supported by the european union and cofinanced by the european social fund (grant agreement no. efop-3.6.3-vekop-16-2017-00005). symbols β0−8 regression coefficients for intercept, linear and quadratic factors and interactions between factors x1, x2 independent factors t deodorization temperature t deodorization time references [1] appel, k.e.; abraham, k.; berge-preiss, e.; hansen, t.; apel, e.; schuchardt, s.; vogt, c.; bakhiya, n.; creutzenberg, o.; lampen, a.: relative oral bioavailability of glycidol from glycidyl fatty acid esters in rats, arch. toxicol., 2013 87(9), 1649–1659 doi: 10.1007/s00204-013-1061-1 [2] frank, n.; dubois, m.; scholz, g.; seefelder, w.; chuat, j.-y.; schilter, b.: application of gastrointestinal modelling to the study of the digestion and transformation of dietary glycidyl esters, food addit. contam. part a, 2013 30(1), 69–79 doi: 10.1016/j.foodchem.2010.08.036 [3] iarc (international agency for research on cancer): glycidol, in: iarc monographs volume 77. on the evaluation of carcinogenic risks to humans (who press, lyon, france) 2000 pp. 469–486 isbn: 9283212770 [4] official journal of the european union: commission regulation (eu) 2018/290 of 26 february 2018 amending regulation (ec) no 1881/2006 as regards maximum levels of glycidyl fatty acid esters in vegetable oils and fats, infant formula, follow-on formula and foods for special medical purposes intended for infants and young children 2018 [5] carlson, f.k.: deodorization. in: hui, y. h. (ed.) bailey’s industrial oil and fat products. edible oil and fat products: processing technology. 5th edition. volume 4. (john wiley & sons inc., new york, usa) 1996 pp. 411–449 isbn: 9780471594284 [6] o’brien, r.d.: fats and oils formulating and processing for applications. third edition. (crc press taylor & francis group, boca raton, florida, usa) 2009 pp. 153–164 isbn: 9781420061666 [7] sipos, e.f.; szuhaj, b.f.: edible oil processing. in: hui, y.h. (ed.) bailey’s industrial oil and fat products. edible oil and fat products: oils and oilseeds. 5th edition. volume 2. (john wiley & sons inc., new york, usa) 1996 pp. 497–602 isbn: 9780471594260 [8] destaillats, f.; craft, b.d.; dubois, m.; nagy, k.: glycidyl esters in refined palm (elaeis guineensis) oil and related fractions. part i: formation mechanism, food chem., 2012 131(4), 1391–1398 doi: 10.1016/j.foodchem.2011.10.006 [9] ermacora, a.; hrncirik, k.: indirect detection techniques for mcpd esters and glycidyl esters. in: macmahon, s. (ed.) processing contaminants in edible oils mcpd and glycidyl esters (aocs press, urbana, usa) 2014 pp. 57–90 isbn: 9780988856509 [10] thürer, a.; granvogl, m.: direct detection techniques for glycidyl esters. in: macmahon, s. (ed.) processing contaminants in edible oils mcpd and glycidyl esters (aocs press, urbana, usa) 2014 pp. 91–120 isbn: 9780988856509 [11] blumhorst, m.r.; venkitasubramanian, p.; collison, m.w.: direct determination of glycidyl esters of fatty acids in vegetable oils by lc–ms, j. am. oil chem. soc., 2011 88(9), 1275–1283 doi: 10.1007/s11746-011-1873-1 [12] craft, b.d.; nagy, k.; seefelder, w.; dubois, m.; destaillats, f.: glycidyl esters in refined palm (elaeis guineensis) oil and related fractions. part ii: practical recommendations for effective mitigation, food chem., 2012 132(1), 73–79 doi: 10.1016/j.foodchem.2011.10.034 [13] cheng, w.w.; liu, g.q.; wang, l.q.; liu, z.s.: glycidyl fatty acid esters in refined edible oils: a review on formation, occurrence, analysis, and elimination methods, compr. rev. food sci. f., 2017 16(2), 263–281 doi: 10.1111/1541-4337.12251 [14] de kock, j.; papastergiadis, a.; de greyt, w.: technological solutions and developments in edible oil processing to minimize contaminants in various oils and fats. 5th leipzig symposium ‘processing and hungarian journal of industry and chemistry https://doi.org/10.1007/s00204-013-1061-1 https://doi.org/10.1016/j.foodchem.2010.08.036 https://doi.org/10.1016/j.foodchem.2010.08.036 https://doi.org/10.1016/j.foodchem.2011.10.006 https://doi.org/10.1016/j.foodchem.2011.10.006 https://doi.org/10.1007/s11746-011-1873-1 https://doi.org/10.1007/s11746-011-1873-1 https://doi.org/10.1016/j.foodchem.2011.10.034 https://doi.org/10.1016/j.foodchem.2011.10.034 https://doi.org/10.1111/1541-4337.12251 formation of glycidyl esters during the deodorization of vegetable oils 71 analytics: how does co-operation work in practice?’ (9-10 march 2016, leipzig, germany) 2016 [15] csányi, e., bélafi-bakó, k.: semi-continuous fatty acid production by lipase, hung. j. ind. chem., 1999 27(4), 293–295 46(2) pp. 67–71 (2018) hungarian journal of industry and chemistry vol. 46(2) pp. 73–77 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0022 effect of algae treatment on stevia rebaudiana growth réka czinkóczky1 and áron németh *1 1department of applied biotechnology and food science, budapest university of technology and economics, műegyetem rkp. 3, budapest, 1111, hungary stevia rebaudiana bertoni is a small, perennial and herbaceous shrub which originated in paraguay (south america). stevia rebaudiana is not native to hungary but its cultivation and consumption may have many benefits, e.g. to reduce blood pressure and as a non-caloric sweetener. steviol glycosides, mostly stevioside and rebaudioside a, located in the leaves are about 200–300 times sweeter than sucrose. s. rebaudina cultivation in hungary would offer many opportunities in healthcare and the sweet industry. with the aim of achieving good green biomass yields, the effect of macc4 autotrophic and heterotrophic algae strains was investigated by testing them as both leaf and soil fertilizers in the soil of stevia rebaudiana seedlings and in its aqueous rooting experiments. in one of the later set up, the formation of roots was improved by combining the application of red light and algae treatment. keywords: stevia rebaudiana, steviol glycosides, algae treatment, chlorella vulgaris 1. introduction stevia rebaudiana bertoni (fig. 1) is a perennial shrub and a member of the asteraceae family. stevia originated in brazil and paraguay (south america). this plant is widely used by the guaraní indians of south america to sweeten tea [1, 2]. s. rebaudiana was botanically classified in 1899 by moisés santiago bertoni, who described it in more detail. initially called eupatorium rebaudianum, its name changed to s. rebaudiana (bertoni) in 1905. the sweet principle was first isolated in 1909 and only in 1931 was the extract purified to produce stevioside, its chemical structure was established in 1952 as a diterpene glycoside. stevioside (fig. 2) is described as a glycoside comprised of three glucose molecules attached to an aglycone referred to as steviol moiety [3, 4]. s. rebaudiana also has other names like sweet leaf, sweet herb of paraguay, sweet honey leaf and candyleaf. the sweetening components of the plant, i.e. steviol glycosides, were described in 1931 [5]. s. rebaudiana and its extracts have been used for a long time in asia, south america and several countries in europe. s. rebaudiana leaves and highly refined extracts are used as low-calorie sweeteners in korea, japan and brazil [6]. stevioside, one of the steviol glycosides, has been reported to lower the postprandial blood glucose concentration of type ii diabetics and the blood pressure of mildly hypertensive patients [7]. s. rebaudiana is used by diabetics as a diet therapy, and its extracts exhibit pharmacological effects such as anti-insulin resistance, the promotion of insulin secretion, as well as antihypertensive and anti-obesity proper*correspondence: naron@f-labor.mkt.bme.hu figure 1: stevia rebaudiana ties [8]. nowadays, the utilization of alternative sweeteners has become a viable option for producing lowor zero-calorie foods due to the development of the healthy food industry which intends to reduce the sucrose content of food products by the total or partial replacement of sucrose with alternative sweeteners. steviol glycosides are mainly produced in the leaves of the plant. the major components are steviol, stevioside and rebaudioside a. the typical proportions of the major components of the leaves are stevioside (5–10 % of the mailto:naron@f-labor.mkt.bme.hu 74 czinkóczky and németh figure 2: structure of stevioside total dry weight of the leaves), reb a (2–4 %), reb c (1–2 %) and dulcoside a (0.4–0.7 %) [9]. the leaves ofs. rebaudiana are sessile, 3-4 cm in length, elongate-lanceolate or spatulate in shape with blunt-tipped laminae in addition to serrated margins from the middle to the tip and on the entire underside. the upper surface of the leaves is slightly glandular-pubescent. the stem is weak-pubescent at its base and woody. the rhizome has slightly branching roots. flowers are composite surrounded by an involucre of epicalyx. the capitula are in loose, irregular, sympodial cymes. the flowers (fig. 3) are white and pentamerous [5]. this plant can grow up to 1 m tall if it is exposed to sufficient light and receives enough nutrients as well as water. therefore, it is worth considering the examination of crop production due to its wide range of applications. chlorella vulgaris is a eukaryotic unicellular green algae which is one of the fastest growing microalgae. this algae can be used in biodiesel processing following cell cultivation. the economic feasibility of algal biodiesel production highly depends on the biomass productivity and lipid yield [10]. green algae (like chlorella vulgaris) may produce phytohormones which can influence the growth of plants. odgerel et al. used chlorella vulgaris as a biofertilizer on barley and wheat. faheed et al. used c. vulgaris as a biofertilizer on lettuce plants. these results showed that algae treatment yields longer roots and shoots of wheat compared to control [11, 12]. the aim of our work was to test chlorella vulgaris figure 3: stevia rebaudiana flowers figure 4: plant cells macc4 autotrophic and heterotrophic cultures of microalgae to enhance the roots, biomass and stems of s. rebaudiana. 2. materials and methods in our work, the effects of hormones produced by algae on s. rebaudiana were tested. phytohormones may improve its development. the plants were in a phytotron (25±1 ◦c) where they received 16 hours of light per day. each plant was placed in a 4.5 cm × 5.0 cm planting cell (fig. 4). in table 1, the blue background denotes the rootgrowing experiments where seedlings were placed into water as a control and into an aqueous algal suspension for trials. furthermore, the green background indicates the modeling of experiments in land: while seedlings in samples of commercial potting soil were sprinkled with water as a control and an algal suspension as to test changes in biomass, the growth of roots and stems was recorded in terms of weight and length, respectively. cells were replicated three times for each setting. as algal suspensions, chlorella vulgaris macc4 heterotrophic and autotrophic cultivated strains were used. the cell suspension was diluted by up to 300 times with water to achieve a concentration of 5 × 107 colonyforming units (cfu)/ml. from this solution, 2 ml was sprinkled onto each cell every 2 to 3 days. the duration of the experiments was about five weeks. at the end of the fifth week (fig. 5), the mass of the total green biomass and the length of the stem and roots in both water and soil were measured. for the results a statistical evaluation was conducted with minitab 17 statistical software. the statistical analysis consisted of a two-sample table 1: planting cells (h: heterotrophic, a: autotrophic, c: control, green: seedlings in soil, blue: seedlings in water, white: empty cells) hungarian journal of industry and chemistry effect of algae treatment on stevia rebaudiana growth 75 figure 5: s. rebaudiana plants at the end of the experiment t-test where the algae-treatment samples were compared against the controls and each other. 3. results and discussion the two-sample t-test in terms of the growth in biomass observed in the seedlings planted in soil is presented in fig. 6. the p-value shows whether or not the treatment had an effect on biomass growth. the comparison between heterotrophic algae treatment and the control samples is presented in fig. 6a. the p-value was 0.653, i.e. no significant difference exists between the two groups of results that were examined. a figure 6: box plots of two-sample t-tests: biomass growth in soil (a: heterotrophic algae vs. control, b: heterotrophic vs. autotrophic algae, c: autotrophic algae vs. control). iiuv()luv comparison between the heterotrophic and autrotrophic algae cultures is presented in fig. 6b. the p-value was 0.511, i.e. no significant difference exists between them. a contrast is made between the autotrophic algae treatment and the control samples in fig. 6c. the p-value was 0.316, i.e. no significant difference exists between these groups either. from the results it can be seen that algae treatment does not have a positive effect on the growth of the green biomass of s. rebaudiana with regard to model experiments in soil. the two-sample t-tests in terms of stem growth are presented in fig. 7. a comparison between the heterotrophic algae treatment and the control samples is presented in fig. 7a. the p-value was 0.642, i.e. no significant difference exists between them. the results of heterotrophic versus autotrophic algae treatment cultures are shown in fig. 7b. the p-value was 0.055, i.e. once more no significant difference exists between them. a contrast between autotrophic algae treatment and control samples is presented in fig. 7c. the p-value was 0.147, i.e. yet again no significant difference exists between both groups. from these results it can be concluded that no significant improvements were observed in terms of the yield of plant biomass of algae treatments applied to seedlings planted in soil. however, the autotrophic alfigure 7: box plots of two-sample t-tests in terms of stem growth in soil: (a: heterotrophic algae vs. control, b: heterotrophic vs. autotrophic algae, c: autotrophic algae vs. control) 46(2) pp. 73–77 (2018) 76 czinkóczky and németh figure 8: box plots of two-sample t-tests in terms of root growth in land (a: heterotrophic algae vs. control, b: heterotrophic vs. autotrophic algae, c: autotrophic algae vs. control) gae treatment seemed to be the most significant which suggests a weak positive effect in terms of the plant development of s. rebaudiana in soil may occur. the two-sample t-tests in terms of the root growth observed in soil are presented in fig.8. a comparison between heterotrophic algae treatment and the control samples is presented in fig. 8a. the p-value was 0.503, i.e. no significant difference exists between them. a contrast between the heterotrophic and autotrophic algae treatments is shown in fig. 8b. the p-value was 0.357, i.e. no significant difference exists between them either. the difference between autotrophic algae treatment and the control samples is presented in fig. 8c. the p-value was 0.811, i.e. once again no significant difference exists between the examined two groups of results. these results suggest (without significance) that heterotrophic algae cultures maybe preferred for the root development of s. rebaudiana seedlings in soil. the two-sample t-tests in terms of the root growth in water are presented in fig. 9. a comparison between heterotrophic algae treatment and the control samples is shown in fig. 9a. the p-value was 0.012, i.e. a significant difference exists between them and heterotrophic treatment is beneficial. a contrast between heterotrophic figure 9: box plots of two-sample t-tests in terms of root growth in water (a: heterotrophic algae vs. control, b: heterotrophic vs. autotrophic algae, c: autotrophic algae vs. control) and autotrophic algae treatments is presented in fig. 9b. the p-value was 0.003, i.e. a significant difference exists between them and heterotrophic algae treatment is also beneficial. the difference between autotrophic algae treatment and the control samples is shown in fig. 9c. the p-value was 0.128, i.e. no significant difference exists between them. from these results it can be concluded that while heterotrophic algae treatment was found to be significantly advantageous for the root development of s. rebaudiana in water, the effect of autotrophic cultures did not significantly differ from that of the control samples. in soil a lateral-like root was formed, while in water the formation of a thicker root was observed. just like when the root fibers were grown in land, not all the soil could be washed out without damaging the root. therefore, a comparison between the biomass yield in water and soil was not conducted. 4. conclusion the following conclusions can be drawn from the experiments with regard to the growth of s. rebaudiana. neither heterotrophic nor autotrophic algae treatments had any positive effect on the biomass growth in soil. by examining the stem growth, the autotrophic culture seemed hungarian journal of industry and chemistry effect of algae treatment on stevia rebaudiana growth 77 to have a slightly positive effect but was not significant. in terms of root growth in soil, none of the treatments had any significant effect, but heterotrophic cultures seemed to have a slightly positive effect. root growth in water supplemented regularly with heterotrophic algae cultures had a significant positive effect in comparison to the other treatments. probably the positive effect of algae treatment in the case of the experiments on s. rebaudiana seedlings in water can be attributed to the fact that the applied algae provided complex nutrients unlike the pure tap water, while in the case of the experiments on seedlings in soil the additional nutrients provided by the algae treatment was practically negligible in comparison to those offered by the soil. therefore, further studies will be done to separate the effect of algae as a provider of nutrients and as a source of plant hormones. further studies would be necessary to prove whether changes in algae cell concentrations have an effect on the growth of stevia rebaudiana or not, i.e. in soil, experiments on biomass growth should be applied differently in diluted algae suspensions with and without any additional nitrogen sources. moreover, different types of light, e.g. red, blue and white, will be tested. these additional plant studies will be implemented using larger numbers of samples. references [1] geuns, j. m. c.: stevioside. phytochemistry, 2003 64(5), 913–921 doi: 10.1016/s0031-9422(03)00426-6 [2] kaur, g.; pandhair, v.; cheema, g. s.: extraction and characterization of steviol glycosides from stevia rebaudiana bertoni leaves. j. med. plants. stud., 2014 2(5), 41–45 issn: 2320-3862 [3] lemus-mondaca, r.; vega-gálvez, a.; zura-bravo, l.; kong, a. h.: stevia rebaudiana bertoni, source of a high-potency natural sweetener: a comprehensive review on the biochemical, nutritional and functional aspects. food chem., 2012 132(3) 1121– 1132 doi: 10.1016/j.foodchem.2011.11.140 [4] barriocanal, l. a.; palacios, m.; benitez, g.; benitez, s.; jimenez, j. t.; jimenez, n.; rojas, v.: apparent lack of pharmacological effect of steviol glycosides used as sweeteners in humans. a pilot study of repeated exposures in some normotensive and hypotensive individuals and in type 1 and type 2 diabetics. regul. toxicol. pharmacol., 2008 51(1), 37–41 doi: 10.1016/j.yrtph.2008.02.006 [5] madan, s.; ahmad, s.; singh, g. n.; kohli, k.; kumar, y.; singh, r.; garg, m.: stevia rebaudiana (bert.) bertoni – a review. indian j. nat. prod. resour., 2010 1(3), 267–286 isbn: 3216321509, issn: 09760504 [6] kinghorn, a. d. (ed.): stevia the genus stevia in: hardman, r. (ed.) medicinal and aromatic plants – industrial profiles series vol. 19, crc press, taylor & francis, london uk, 2003. isbn: 0-203-16594-2 [7] gregersen, s.; jeppesen, p. b.; holst, j. j.; hermansen, k.: antihyperglycemic effects of stevioside in type 2 diabetic subjects. metabolism, 2004 53(1), 73–76 doi: 10.1016/j.metabol.2003.07.013 [8] dyrskog, s. e. u.; jeppesen, p. b.; colombo, m.; abudula, r.; hermansen, k: preventive effects of a soy-based diet supplemented with stevioside on the development of the metabolic syndrome and type 2 diabetes in zucker diabetic fatty rats. metabolism, 2005 54(9), 1181–1188 doi: 10.1016/j.metabol.2005.03.026 [9] puri, m.; sharma, d.; tiwari, a. k.: downstream processing of stevioside and its potential applications. biotechnol. adv., 2011 29(6), 781–791 doi: 10.1016/j.biotechadv.2011.06.006 [10] kim, j.; lee, j-y.: growth kinetic study of chlorella vulgaris (august 2016), pp. 2–7. 2009. isbn: 9781615679140 [11] odgerel, b.; tserendulam, d.: effect of chlorella as a biofertilizer on germination of wheat and barley grains proc. mong. acad. sci., 2017 56(4) 26 doi: 10.5564/pmas.v56i4.839 [12] faheed, f. a.: effect of chlorella vulgaris as biofertilizer on growth parameters and metabolic aspects of lettuce plant. j. agri. soc. sci., 2008 4(4) 165-169 issn: 1813-2235 46(2) pp. 73–77 (2018) https://doi.org/10.1016/s0031-9422(03)00426-6 https://doi.org/10.1016/j.foodchem.2011.11.140 https://doi.org/10.1016/j.yrtph.2008.02.006 https://doi.org/10.1016/j.metabol.2003.07.013 https://doi.org/10.1016/j.metabol.2005.03.026 https://doi.org/10.1016/j.metabol.2005.03.026 https://doi.org/10.1016/j.biotechadv.2011.06.006 https://doi.org/10.1016/j.biotechadv.2011.06.006 https://doi.org/10.5564/pmas.v56i4.839 https://doi.org/10.5564/pmas.v56i4.839 hungarian journal of industry and chemistry vol. 46(2) pp. 79–84 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0023 comparison of particle size distribution models for polymer swelling ádám wirnhardt *1 and tamás varga1 1department of process engineering, university of pannonia, egyetem u. 10, veszprém h-8200, hungary in polymer technologies, various particle shapes and size distributions can be found. one of these are heterodisperse polymer beads. the capabilities of polymer swelling can be used in industries, e.g in the production of ion-exchange resins, to intensify specific technological steps such as sulphonation in the manufacturing process of ion-exchange resins. according to the literature different approaches can be used to create models for describing the behavior of disperse systems, of which the simplest models are the particle size distribution models for a given state of the solid phase. the aim of our examination was to compare and evaluate these simple models in terms of modeling polymer swelling. hence, most of these models examine how each of the investigated models can be applied to approximately describe growth in a heterodisperse polymer system and how the identified model parameters in each time step could be interpreted. all the models were fitted to generate particle size distributions based on a swelling rate constant. the swelling of a styrene divinylbenzene-based copolymer was chosen as the basis of our examination. a model is proposed that is capable of describing the changes in the size of beads over time in this system. keywords: polymer swelling, particle size distribution, heterodisperse polymer beads, modeling, ion-exchange resin 1. introduction polymer beads are used as raw materials in a wide range of technologies, e.g. in the production of ion-exchange resins. before the chemical modification of polymer beads, they are often swollen with different types of swelling agents such as dichloroethane, dichloromethane, toluene, etc. monodisperse and heterodisperse types of beads are known in polymer technologies. the process of the swelling of monodisperse beads is easily measurable and easily predictable. the production of monodisperse polymers is a more expensive process than the production of heterodisperse beads, which makes heterodisperse polymer beads a more popular form. heterodisperse polymer beads exhibit a closely normal distribution in terms of particle size. the prediction of the swelling of these particle systems is more difficult because the different beads can swell at significantly different rates due to the change in the specific area of each bead. the swelling of the polymer network system has already been a subject of interest. painter and shenoy[1] considered the chemical properties of polymers. schott [2] described the kinetics of polymer swelling. first order and second order kinetics were founded by him. a *correspondence: wirnhardt.adam@fmt.uni-pannon.hu swelling model was formulated by sweijen et al. [3] according to the diffusion properties of components in the polymer matrix. these models are capable of describing the swelling of polymer networks, but because of its complexity they are hard to apply in any kind of optimization process. hence, the simplest particle size distribution (psd) model, which can describe the swelling of polymers over time using the least number of parameters, can be of interest from a process intensification point of view. bayat et al. collected psd models from the last seventy years [4, 5]. thirty-five models were listed. these models describe the cumulative mass fraction of polymers as a function of the diameter of polymer beads. the models contain one, two, three or four unknown parameters, which can be identified with a specific polymer fraction. a hyperbolic tangent distribution [6, 7] psd model composed of four parameters was added to this list by us. this study is the first step in the process of developing this model which focuses on the investigation of the swelling phenomena of the styrene divinylbenzene copolymer system. therefore, our focus is on identifying a simple psd model which is capable of describing the swelling of heterodisperse polymer beads. hence, all the previously mentioned psd models are investigated and compared. our aim was not only to identify a psd model which is capable of describing the distribution of the investigated polymer system but to find a psd model which mailto:wirnhardt.adam@fmt.uni-pannon.hu 80 wirnhardt and varga exhibits a correlation between changes made to parameters and particle size. 2. experimental for the modelling of heterodisperse polymer systems physical experiments with regard to swelling should be performed to obtain the data necessary to validate the model. in our case, with the lack of experiments, the data were generated from a model implemented and solved in matlab. a code was made in matlab for the generation of these distributions. in the developed model, the swelling of polymer beads with a given theoretical rate of growth was calculated. the volume of each bead increased at the same rate. hence, the diameter of the beads does not influence the rate of growth and the tension caused by the swelling process of the polymer beads is neglected in this investigation. the following simplifications were implemented in the model: 1. the shape of the polymer beads is a perfect sphere. 2. the particles swell until they reach a steady state. 3. the swelling rate of particles is constant until a steady state is achieved. 4. the number of particles is constant. 5. the initial psd of the beads is close to normal. to generate the distributions after different durations of swelling an initial unswollen distribution is required. the initial distribution was calculated by matlab from a picture of heterodispersed particles. the varion ks preform styrene divinylbenzene copolymer was used for the zero-time distribution. the polymer beads were identified by a circle detection algorithm and the size distribution of the detected particles was calculated using a reference particle. from the initial state, the size of the polymer particles starts to increase by applying a swelling agent to the system. the size of the particles increases until a steady state is achieved. the steady state in this case means that the size of the particles grows until a state when the amount of infiltration of the swelling agent is equal to the outcome amount. the size of the particles can increase until a maximum is reached because of the internal tension of the polymer. the data are generated using the parameters of the steady state. these parameters are the swelling rate (p [-]) and time required (t [sec]). psds were generated at different times during the swelling process. the next step was to examine the psd models to determine if they were able to describe the distribution in every instant. 2.1 psd models in this study only psd models that are capable of describing cumulative mass fraction distribution were investigated. altogether five models with one parameter, twelve with two, two with three and four with four were examined. they are collected in table 1. the cumulative mass fraction of particles is denoted by p (d), the maxima and minima of the particle size range are represented by dmax and dmin, respectively, and the particle diameter [mm] is denoted by d. the models were fitted to all the distributions collected over time using extreme value problem solver algorithms in matlab. 2.2 theoretical methodologies two types of extreme value problem-solving methods were applied to fit the psd models. one is a local extreme value problem solver known as the nelder-mead simplex algorithm and its function “fminsearch” to implement it in matlab. the other one is a global extreme value problem solver called “nomad” [8]. they are both components of the matlab toolkit. matlab 2011b was applied in all modelling steps. the minimum difference was sought between the generated distribution data and calculated distributions based on each model. the parameters of psd models were the results of this search. in every case, the goodness of fit was measured. for each model, every sample time was considered and the difference examined using the mean absolute difference. the average of the mean absolute difference of the percentage difference was calculated for every function. the extreme value problem solver attempted to find the minimum of the following equation et = ∣∣p (d) ′ t − p (d)t ∣∣ nd (1) where the mean absolute difference between the generated and calculated distribution is et at instant t. the calculated distribution is denoted by p (d) ′ t and the generated distribution by p (d)t at instant t. the number of items of data is represented by nd. 2.3 model selection a selection could be made according to the average percentage differences. the selection was carried out with a criterion. this criterion was an average percentage difference of five percent because under this value the difference is not considerable but over it an unacceptable fit is shown. three different models, namely the rosin-rammler, the exponential-power_pasikatan and the logarithm-zhuang models fitted to the generated data are shown in fig. 1. the goodness of fit for these three models is 1 %, 5 % and 11 %, respectively. as can be seen the differences of 1 % and 5 % are negligible, and are only noticeable at diameters in excess of 0.7 mm. however, a considerable difference can be observed between the models with fits of 5 % and 11 %. it can be seen that a goodness of fit of under 5 % is appropriate. hungarian journal of industry and chemistry comparison of particle size distribution models for polymer swelling 81 table 1: the investigated psd models name model 1 parameter (k1) 1 gaudy-meloy p (d) = 1− (1− d/dmax) k1 2 nesbitt-breytenbach p (d) = 10[(1/(k1 + 1)](d/2)k1+1 +[0.1− 1/(k1 + 1)](d/2)1/[1/(k1+1)−0.1] 3 rosin-rammler p (d) = 1− exp(−k1d) 4 jaky p (d) = exp { − ( 1/k21 ) [ln(d/dmax)] 2 } 5 schumann p (d) = (d/dmax) k1 2 parameters (k1, k2) 6 power lowpaskikatan p (d) = [k1/(1− k2)]d1−k2 7 van genuchten p (d) = [ 1 + (k1/d) k2 ]1/k2−1 8 rosin-rammler p (d) = 1− exp ( −k1dk2 ) 9 fractal p (d) = exp {ln(k2))+[( 3k21 − 13k1 + 14 ) / ( k21 − 5k1 + 4 ) + 1 ] log(d) } 10 power low gimenez p (d) = k1d k2 11 best p (d) = [ 1 + (k1/d) k2 ]2/k2−1 12 bennet p (d) = k1k2d k1−1 exp ( −k2dk1 ) 13 exponential powerpasikatan p (d) = exp ( −k1dk2 ) 14 logarithm-zhuang p (d) = k1 ln(d) + k2 15 log-exp-kolev p (d) = k1 exp [k2 log(d)] 16 weibull-2par p (d) = 1− exp [ −(d/k1)k2 ] 17 lognormalzobeek p (d) = 1/ { k1(2π) 1/2 exp [ −(log(d)− k2)2/(2k21) ]} 3 parameters (k1, k2, k3) 18 s-curve: vipulanandan ozgurel p (d) = 100 exp { −k1 [ k2 ln(d/0.001) d/k3 ]} 19 weibull-3par p (d) = k1 − exp [ −(d/k2)k3 ] 4 parameters (k1, k2, k3, k4) 20 gompertz p (d) = k1 + k2 exp {− exp [−k3(d− k4)]} 21 weibull-4par p (d) = k3 + (1− k3) [ 1− exp ( −k1kk2 4 )] where k4 = (d− dmin)/(dmax − dmin) 22 fredlund p (d) = { 1/ [ ln ( exp(1) + (k1/k2) k2 )]k3 }{ 1− [ln(1 + k4/d)/ ln(1 + k4/0.001)] 7} 23 tanh if 0<k2+k3d then p (d) = { tanh [ (k2 + k3d) k4 ]}k1 otherwise p (d) = 0 46(2) pp. 79–84 (2018) 82 wirnhardt and varga figure 1: the cumulative distribution of the rosinrammler (1 %), exponential-power pasikatan (5 %) and logarithm-zhuang (11 %) models as well as the generated data. 2.4 parameter correlation the next step in the modelling process was the investigation into how the model parameters of each simple psd model can be fitted into a monotonous series over time. based on this experiment, these simple models can be applied to describe the swelling of specific material systems over time. by depicting the parameters of the distribution functions as a function of time, a statement can be made for the models if they were capable of this task. assuming that the correlation is linear for every model parameter, in each psd model it can be calculated as follows: kx = ax +bxt (2) where the parameter of the psd model is denoted by kx, the parameters of the k parameter are a and b, and the time passed is t. it is obvious that there are twice as many unknown model parameters than in the previous step, i.e. every model parameter in each model is defined by eq. 2, however, only one set of parameters is required to describe the swelling process over time. in this examination, the mean absolute difference was also needed to fit the functions to different time instants. in this case the extreme value problem solver determined the minimum for the average of the mean absolute difference: e = ∑nt t=1 et nt (3) where the average of the mean absolute difference is denoted by e and the number of time instants by nt. 3. results and analysis the zero distribution was evaluated by matlab based on a picture taken from a sample of polymer beads. the sample consisted of approximately five hundred beads within the diameter range of 0.2 to 0.9 mm. the probability distribution with regard to the size of the polymer beads is shown in fig. 2. figure 2: the probability distribution with regard to the size of the polymer beads before swelling within the diameter range of 0.2 to 0.9 mm. the parameters for the generated data were p = 2 and t = 1500 s which means the polymer beads doubled their size in 1500 s and the steady-state size of the beads is this rate of growth. psd was calculated twenty-five times between 0 and 1500 s. three of the twenty-five distributions are shown in fig. 3. all 23 models were fitted to all the distributions generated at every instant. altogether twenty-three times twenty-five curve fittings were performed. the parameters were calculated for all the fitted models. for every fitted value a mean absolute difference (et) was determined, the average of which are shown in table 2 according to the values in table 1 a selection of psd models could be made. those models show good agreement with the generated psd, which yields an average mean absolute difference of less than five percent. a difference can be observed between the two methods to find extreme values. the global finder “nomad” has found a better fit for the two-parameter model known as best. in most cases the two search methods give the same results using the same model parameters. in some models, the global optimizer has found a better solution than was expected. eleven of the twenty-three models were found to be able to describe the distribution at all time instants. from figure 3: cumulative distribution functions at three different time instants during the swelling of the polymer beads. hungarian journal of industry and chemistry comparison of particle size distribution models for polymer swelling 83 table 2: the goodness of fit for the different models. psd model id simplex fitting e [%] nomad fitting e [%] 1 15 15 2 39 39 3 24 24 4 2 2 5 10 10 6 12 8 7 3 3 8 1 1 9 19 13 10 8 9 11 39 2 12 5 5 13 5 5 14 12 12 15 8 8 16 1 1 17 30 30 18 35 13 19 0 0 20 2 1 21 1 1 22 37 34 23 1 1 these, the best model was the weibull-3par which is shown in fig. 4. this result does not mean that the model is able to describe polymer growth. a correlation should be present in terms of changing the parameters. by examining the correlation of model parameters in these eleven models, one model called jaky exhibited a correlation as shown in fig. 5 the other models did not show any kind of correlation over time. the jaky model consists of one parameter and it seems to describe properly the growth of heterodisperse polymer systems. the other models did not show any correlation in terms of the changing of the parameter over time. in most cases one parameter was present which did figure 4: the change in the parameter of the weibull-3par model after various durations of swelling. figure 5: the change in the parameter of the jaky model after various durations of swelling. not show any regularity as is shown in fig. 4. the following examination sought to set a correlation between the change in the parameter and time due to the swelling of beads. with linear criteria (see eq. 2) the goodness of fit will definitely deteriorate. the presumption was to find a model which exhibits a goodness of fit of under five percent after setting the criterion. the results collected in table 3 show that two of the eleven selected models produced a goodness of fit of under 5 %, the others were all in excess of 30 %. therefore, the jaky model consisting of one parameter and the rosin-rammler model of two exhibit a linear correlation for their parameters over time. the other nine models did not exhibit a linear correlation in their parameters over time. it would be worthwhile trying other non-linear functions to describe the parameters. 4. conclusion in polymer technologies, one of the steps is the swelling of the polymer beads. several studies were conducted that deal with the swelling of polymer networks. our aim was to examine the swelling of the polymer beads from a different point of view to find out if a simple psd model exists which may be able to describe changes in size of this system. table 3: the goodness of fit of the linear correlation of parameters over time. psd model id simplex fitting e [%] nomad fitting e [%] 4 2 2 7 33 14 8 1 1 11 − 44 12 44 44 13 53 44 16 44 44 19 35 35 20 35 35 21 30 52 23 44 44 46(2) pp. 79–84 (2018) 84 wirnhardt and varga psd models were examined according to their ability to describe the swelling of polymer beads. the results show that two models were present which could be used to describe and predict the behavior with regard to changes in size of the heterodisperse polymer bead systems. in this examination, the copolymer styrene divinylbenzene was used. two extreme value problem solvers were used to identify and confirm psd models that are able to describe changes in size of the copolymer system. two models, namely the one-parameter jaky model and the two-parameter rosin-rammler model, were able to describe the growth in size over time with an error of less than 2 %. the parameters of these models could be interpreted by a linear correlation over time according to the generated data that was produced in this study. based on these working models a prediction can be made with regard to changes in size of a heterodisperse copolymer system over time. symbols et mean absolute difference e average of mean absolute difference p (d) ′ t calculated distribution p (d)t generated distribution nd number of data nt number of time instants kx parameters of models acknowledgment this research was supported by the széchenyi 2020 project ginop 2.2.1-15-2017-00059. references [1] painter, p.c.; shenoy, s.l.: a simple model for the swelling of polymer networks, j. chem. phys., 1993 99(2), 1409-1418 doi: 10.1063/1.465385 [2] schott, h.: swelling kinetics of polymers, j. macromol. sci., part b: physics, 1992 31(1), 1-9 doi: 10.1080/00222349208215453 [3] sweijen, t.; van duijn, c.j.; hassanizadeh, s.m.: a model for diffusion of water into a swelling particle with a free boundary: application to a super absorbent polymer particle, chem. eng. sci., 2017 172, 407-413 doi: 10.1016/j.ces.2017.06.045 [4] bayat, h.; rastgou, m.; nemes, a.; mansourizadeh, m.; zamani, p.: mathematical models for soil particle-size distribution and their overall and fraction-wise fitting to measurements, eur. j. soil sci., 2017 68(3), 345-364 doi: 10.1111/ejss.12423 [5] bayat, h.; rastgo, m.; zadeh, m.m.; vereecken, h.: particle size distribution models, their characteristics and fitting capability, j. hydrology, 2015 529, 872-889 doi: 10.1016/j.jhydrol.2015.08.067 [6] blickle, t.; lakatos, b.g.; ulbert, zs.; mihálykó, cs.: the hyperbolic tangent distribution and its applications-i. mathematical foundations, hung. j. ind. chem., 1998 26, 89-96 [7] blickle, t.; lakatos, b.g.; mihálykó, cs.; ulbert, zs.: the hyperbolic tangent distribution family, powder technology, 1998 97, 100-108 [8] le digabel, s.: algorithm 909: nomad: nonlinear optimization with the mads algorithm, acm trans. math. softw., 2011 37(4), 1–15 doi: 10.1145/1916461.1916468 hungarian journal of industry and chemistry https://doi.org/10.1063/1.465385 https://doi.org/10.1080/00222349208215453 https://doi.org/10.1080/00222349208215453 https://doi.org/10.1016/j.ces.2017.06.045 https://doi.org/10.1111/ejss.12423 https://doi.org/10.1016/j.jhydrol.2015.08.067 https://doi.org/10.1145/1916461.1916468 https://doi.org/10.1145/1916461.1916468 hungarian journal of industry and chemistry vol. 46(2) pp. 85–90 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0024 effects of different heat treatments on the chemical and microbiological characteristics of egg-free and quail egg dried pasta ildikó szedljak *1, viktória tóth1, judit tormási1, anikó kovács1, lászló somogyi1, lászló sipos2, and gabriella kiskó3 1department of grain and industrial plant processing, faculty of food science, szent istván university, villányi út 23, budapest, 1113, hungary 2department of logistics and sensory analysis, faculty of food science, szent istván university, villányi út 23, budapest, 1113, hungary 3department of microbiology and biotechnology, faculty of food science, szent istván university, villányi út 23, budapest, 1113, hungary in hungary, dried pasta products are very popular amongst all groups of society. in recent years the demand for not only dried pasta made from hen eggs (gallus gallus domesticus) but from alternative types of ingredients has increased. however, according to the literature the chemical and microbiological characteristics of this type of pasta have yet to be studied in depth. the effects of the use of quail eggs and heat treatments at different temperatures were studied by chemical and microbiological measurements. the activity of oxidative enzymes and nutritional characteristics (watersoluble total polyphenol content, water-soluble antioxidant capacity, peroxidase enzymatic activity, water-soluble protein content and yellow pigment content) was tested during our experiments. the data were evaluated by relevant statistical methods. significant differences were found both between heat treatments and between the egg content of the dried pasta samples. the peroxidase enzymatic activity and yellow pigment content increased with temperature. however, the usage of quail eggs provides a higher water-soluble protein content and water-soluble antioxidant capacity. the presence of microorganisms is decreased by increasing the drying temperature. the number of all the examined microorganisms was within limits. keywords: dried pasta, quail egg, heat treatment, chemical and microbiological characteristics 1. introduction present-day problems of globalization have led to a need for more diverse, long-lasting and convenient food products of high nutritional value. mindful consumers look for products that have positive physiological effects and have been subject to a minimal degree of processing. in hungary, dried pasta products are popular amongst all groups of society. their position in the global market is safe because these products possess all of the aforementioned qualities and fall within an affordable price range too. the amount of dried pasta products consumed in recent years has elevated [1], therefore, the food industry continuously tries to lower production costs as well as improve profits and their nutritional value [2]. one of the important ingredients of pasta are eggs. for the industrial processing of dried pasta only two kinds of eggs are usable; hen and quail eggs. the most commonly used type of eggs are hen eggs (gallus gallus domesticus). pasta products made from *correspondence: ildiko.szedljak@gmail.com this type of eggs have been well studied. however, recently a need has emerged for more unconventional dried pastas made from alternative ingredients [3]. quail egg pasta (coturnix coturnix) is one of these innovations. quail eggs as an ingredient are of a relatively high nutritional value. when compared to hen eggs they possess more protein but less carbohydrate and fat [4]. chemical changes during processing define the quality of the end product. the most determinative factors are the temperature of the drying process and its changes during the process [5]. significant changes in chemical behavior occur even at lower temperatures. enzymeactivated changes like protein denaturation and pigment oxidation take place below 60 ◦c. at temperatures higher than 80 ◦c the oxidative enzymes deactivate and the maillard reaction occurs, simultaneously the lysine concentration of the pasta decreases [6]. therefore, choosing the most suitable drying temperature is an important step when it comes to the quality of the heat-treated products, especially in the case of dried pastas. when designing and processing products with long mailto:ildiko.szedljak@gmail.com 86 szedljak, tóth, tormási, kovács, somogyi, sipos, kiskó storage and shelf lives, another important concern is the microbiological safety of the product. with the diminished water activity of these kinds of foods, the activity of microorganisms also decreases. the main parameter in this case is the number of microorganisms when processing commences. during drying the microbes deactivate and their numbers decrease [7]. chemical and microbiological properties depend on the nutritional characteristics and drying properties of the pasta. since the chemical and microbiological characteristics of quail egg pasta, according to the literature, have yet to be studied in depth, our goal was to expand this knowledge. studying the properties of this product is beneficial to both advancing the technology and food safety. 2. experimental the aim of our study was to examine and compare the chemical and microbiological characteristics of the eggfree and quail egg dried pasta that had been subjected to different heat treatments. changes caused by the presence of quail eggs were sought. differences made by varying the temperature of heat treatments were examined. moreover, a connection between the microbiome and heat treatments was characterized. materials the wheat flour, triticum aestivum l., used and the quail eggs were bought from commercial sources. the reagents for the chemical and microbiological measurements were provided by reanal laborvegyszer kereskedelmi kft. the bacterial substrates were produced by merck kft. samples the tests were conducted on the samples of egg-free and “four hen egg pasta” doughs using sufficient quantities of quail eggs. all the pastas were made from triticum aestivum l. flour, water and quail eggs for the egg pasta. to improve the heat distribution the pastas were shaped into the form of linguine. the pasta doughs were treated at three different temperatures (40 ◦c, 60 ◦c and 80 ◦c) for twenty-five minutes in an armfield-type fluid bed dryer. the samples were subjected to chemical and microbiological measurements. in preparation for the chemical tests the samples were first grated then 100 mg/ml extracts were taken using distilled water. every analytical method was conducted on five parallel samples. chemical analysis the moisture content was determined by an ma50 sartorius moisture analyzer. the water activity was measured by a novasina ms1 water activity meter. for the measurement of color the konica minolta cr-310 chroma meter with a tristimulant objective in a laboratory coordinate system was used. to measure the ph, the sg23 mettler-toledo sevengo duo ph/conductivity meter was used. the acid values of the extracted samples were titrated with 0.1 m naoh solution in the presence of the indicator phenolphthalein. the determination of ph and acid value was conducted based on hungarian standards [8]. the water-soluble total polyphenol content was measured by folin-ciocalteu reagent [9] and expressed in gallic acid equvalent (gae). water-soluble antioxidant capacity was measured using a frap (ferric reducing antioxidant power) assay kit [10]. the peroxidase enzymatic activity was given by using oda (o-dianisidine) as a hydrogen donor [11] and the data converted into ascorbic acid equivalent (aae). for measuring the watersoluble protein content, a method by layne [12] was used. the yellow pigment content of the samples was determined according to hungarian standards extracted by butanol [13]. microbiological analysis microbiological measurements were conducted given the relevant standards [14– 16]. three parallel measurements were made from each sample. all samples were tested for coliform bacteria, staphylococcus aureus and molds. in addition, the presence of salmonella using a european standard [17] was tested for. statistical evaluation all the measurements were replicated five times using xlstat software [18]. given the parallel samples, non-parametric probes were used. the kruskal-wallis test was applied to calculate the pvalue (α = 0.05) and dunn’s post hoc pair-wise test was used with bonferroni correction on significant results. the correlation between parameters was determined by spearman’s rank correlation coefficient (non-parametric equivalent of pearson’s correlation) (α = 0.05). 3. results and analysis 3.1 chemical analysis moisture content the moisture content of the dried pasta samples decreased as the temperature of heat treatment increased. the moisture content of all the dried pasta products was below the maximum set by hungarian standards [19] of 13 %. when treated at the same temperature the quail egg pastas always contained less moisture than the egg-free samples. however, significant differences were not determined. water activity this parameter is important for determining the initial microbial count and activity of samples during storage. the water activity of the samples decreased as the temperature of the heat treatment increased. in the quail egg pastas, the numbers were higher (aw(80◦c) = 0.6254 ± 0.0313) compared to commercially available pastas (aw < 0.6). thus, at this level of water activity the xerotolerant and xerofil microbes could survive and reproduce. a significant difference was not determined. hungarian journal of industry and chemistry quality features of egg-free and quail egg dried pasta 87 figure 1: water-soluble total polyphenol content of the samples in mg/g gallic acid equivalent. ph the ph also plays a key role in the reproduction and survival of microorganisms as well as in the activity of peroxidase. the ph of the quail egg samples was always lower than the egg-free samples. a significant difference was only measured in the quail egg (3.572 ± 0.128) and egg-free (5.898 ± 0.019) samples treated at 40 ◦c. since the molds are capable of reproducing at a lower ph (ph = 2–4) [20], this value of the quail egg pasta poses a threat from a microbiological point of view. acid value (av) this parameter was always lower in the quail egg samples. in the samples dried at 60 ◦c, significant differences were observed. all the acid values of measured samples were between 3.15 and 3.66 ◦sh, which falls within the codex alimentarius hungaricus’ guidelines [19] (in dried pastas av = maximum of 5 ◦sh). water-soluble total polyphenol content for evaluating the water-soluble total polyphenol content (tpc) of the samples, the data was calibrated with the gallic acid equivalent as shown in fig. 1, which gives the polyphenolic components in mg of gallic acid equivalent found in 1 gram of dried pasta. the presence of the quail eggs resulted in higher water-soluble total polyphenol contents in each case. significant differences based on the coupled comparison’s pvalues were only observed between the samples that were not heat treated. based on the results of the kruskal-wallis test a significant difference is observed between the tpc values of quail egg pastas. among the quail egg samples, based on the comparison of pairwise p-values, a difference is found for at least two samples. this can be detected between the samples that were not heat treated and those treated at 80 ◦c as well as between samples treated at 60 ◦c and at 80 ◦c. based on these results, it can be stated that the tpc may be influenced by heat treatment. figure 2: peroxidase enzyme activity of the samples in u/g ds. peroxidase enzymatic activity the peroxidase enzymatic activity was calculated on the basis of data from the literature and its value was given in terms of dry matter content (björkstén, 1968). the graph in fig. 2 clearly shows the effect of heat treatment. the enzymatic activity decreases as the temperature of the heat treatment increases and is always lower in the quail egg samples. the cause of this difference could be the different ph of the two types of pastas. in both cases a significant difference is observed between the samples treated at 60 ◦c and those not subjected to heat treatment. in the results of the egg-free pastas, the decline is less than in the quail egg samples. water-soluble protein content the water-soluble protein content was always higher in the quail egg samples. significant differences were observed between both the separate and cumulative evaluations. a significant difference was measured in the p-values in terms of the comparison of egg content when heat treated at 40 ◦c. in addition differences were observed between the eggfree samples that were not subjected to heat treatment and those heat treated at 80 ◦c, as well as between the quail egg samples that were not heat treated and those treated at 40 ◦c and 80 ◦c. from these results it can be stated that the examined treatments influence the water-soluble protein content of the samples. water-soluble antioxidant capacity the measurements of the water-soluble antioxidant capacity were converted into ascorbic acid equivalent. the antioxidant capacity of the pastas rose as the temperature of the heat treatments increased, in terms of the egg-free samples, the maximum was observed at 60 ◦c. the statistical evaluation revealed significant differences in every case. the increase in the antioxidant capacity as the temperature of heat treatment rises is common in the literature [21, 22]. 46(2) pp. 85–90 (2018) 88 szedljak, tóth, tormási, kovács, somogyi, sipos, kiskó figure 3: yellow pigment content of samples given in mg carotene/kg ds. yellow pigment content and color measurement the yellow pigment content was only measured on samples of dried pasta. both the egg-free and quail egg pastas exhibited significant differences between samples treated at 40 ◦c and 80 ◦c. as seen in fig. 3 in the case of the quail egg samples, a significant decline in the yellow pigment content was observed as the temperature of heat treatment increased. even so, the noticeable drop in the yellow pigment content of quail egg samples was still higher than in the case of the egg-free samples (except for the decline at 80 ◦c). for the assessment of color the “lab” color chart was used. the l∗ value denotes the lightness and positive rate of the b∗ value which represents the intensity of the color yellow. neither of these two values changed significantly in the presence of the quail eggs. however, the heat treatment resulted in significant changes in both color rates. a significant change in the lightness has already been observed in all the samples treated at 40 ◦c. as shown in fig. 4 the b∗ value increased as the temperature of heat treatment rose, therefore, the pastas became yellower as the temperature increased. in both types of pastas, significant differences were observed between figure 4: yellow color intensity of samples from the cielab color space. figure 5: the results of the microbiological analysis of egg-free pastas. the samples that were not subjected to heat treatment and those treated at higher temperatures (60 ◦c and 80 ◦c). the results of the yellow pigment content and color measurements are controversial in terms of the quail egg samples. the b∗ value – which shows the intensity of the color yellow – increases while the yellow pigment content decreases. the seemingly ambiguous data might be caused by chemical and microbiological changes not examined by us. the yellow pigment content continuously decreases during the drying process, therefore, choosing the most suitable drying temperature is critical. from these results, to retain the maximum amount of yellow pigments in the finished products, heat treatment at 60 ◦c is recommended. 3.2 microbiological measurements the microbiological contamination of egg-free samples remained below the limit (figs. 5 and 6). however, in the case of the quail egg pasta, the coliform bacteria appeared in the samples treated at 40 ◦c. the presence of the coliforms is not surprising since they figure 6: the results of the microbiological analysis of quail egg pastas. hungarian journal of industry and chemistry quality features of egg-free and quail egg dried pasta 89 table 1: spearman correlation matrix of the six studied parameters, “r” values (r = 0 no linear correlation, r = −1 perfect negative correlation, r = 1 perfect positive correlation). variables pox tpc l∗ b∗ antioxidant capacity yellow pigment content peroxidase enzymatic activity 0 0.2283 0.0000 0.0159 0.7815 0.8270 total polyphenol content 0.2283 0 0.0502 0.0009 0.0001 0.0024 l∗ <0.0001 0.0502 0 0.5675 0.6137 0.4238 b∗ 0.0159 0.0009 0.5675 0 0.0016 0.1523 antioxidant capacity 0.7815 0.0001 0.6137 0.0016 0 0.1723 yellow pigment content 0.8270 0.0024 0.4238 0.1523 0.1723 0 values in bold are different from 0 with a significance level α = 0.05 table 2: spearman coefficient determination matrix of the six studied parameters, “p” values variables pox tpc l∗ b∗ antioxidant capacity yellow pigment content peroxidase enzymatic activity 1 0.0512 0.4894 0.1930 0.0028 0.0017 total polyphenol content 0.0512 1 0.1307 0.3397 0.4304 0.2910 l* 0.4894 0.1307 1 0.0117 0.0092 0.0228 b* 0.1930 0.3397 0.0117 1 0.3118 0.0717 antioxidant capacity 0.0028 0.4304 0.0092 0.3118 1 0.0653 yellow pigment content 0.0017 0.2910 0.0228 0.0717 0.0653 1 are found in the feces of warm-blooded animals (bíró, 2014). as a result of the heat treatment the number of microbes decreased in both types of pasta. based on these results it can be clearly seen that heat treatment increases the quality of both types of pasta from a microbiological standpoint. the higher the temperature of the heat treatment, the more microbiologically advantageous it is. 3.3 statistical evaluation in addition to the examination of significant differences between our data, correlation studies were conducted on six selected variables of the evaluated factors: peroxidase enzymatic activity (pox), water-soluble total polyphenol content (tpc), l∗ and b∗ values, yellow pigment content and water-soluble antioxidant capacity. since five parallel measurements were taken, spearman correlations were determined [23], which is the nonparametric equivalent of the pearson’s correlation. based on the obtained “r” and “p” values (tables 1 and 2), two positive and three negative correlations were identified. the positive correlations were between the water-soluble total polyphenol content and yellow pigment content as well as between the water-soluble antioxidant capacity and b∗ values. the negative correlations were identified between the peroxidase enzymatic activity and l∗ value as well as b∗ values, the water-soluble total polyphenol content and b∗ values, in addition to the water-soluble total polyphenol content and water-soluble antioxidant capacity. 4. conclusion the aim of this study was to expand the literature on the chemical and microbiological characteristics of quail-egg dried pastas. with regard to the nutritional value of the pastas almost all of the examined characteristics declined as the temperature of the heat treatment increased except for the water-soluble antioxidant capacity. from our study it was found that 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computing, university of pannonia, egyetem u. 10, veszprém, h-8200, hungary safety regulations demand the elimination of random mistakes and the reliable operation of production units. however, the control and maintenance of batch and semi-continuous processes haalways been difficult. in this paper, a way of preventing malfunctions in batch and semi-continuous processes is presented by using appropriately designed buffer tanks. a stochastic model was investigated in which batch and continuous subsystems were linked by an intermediate storage tank. the main concern was the reliability of the system. reliable operation was defined as neither the exhaustion of raw materials nor the excessive accumulation of them. the counting processes that describe the random batch-input and random batch-output processes are supposed to be independent homogeneous poisson processes with different rates. by introducing a function that describes the material in storage, reliable operation is defined as when this function satisfies two inequalities for a time interval of any duration. by applying probabilistic methods, an integral equation is set up for the the reliability. nevertheless, its analytical solution cannot be determined, hence the values according to a monte carlo simulation are approximated. by applying this method, a link could be identified between the necessary initial buffer and tank capacities that belong to a reliability level. economic investigations were conducted to help determine the optimal initial buffer and tank capacities that satisfy the appointed reliability level. keywords: intermediate storage, stochastic modelling, batch system control, monte carlo simulation, economic optimization 1. introduction during the operations of chemical processes, one often encounters uncertainties. these events can stem from equipment failures, mistakes made by staff managing the process, or bad managerial decisions. these mistakes can often lead to malfunctions which cannot be tolerated in processes using dangerous or very expensive materials. a serious malfunction can cause damage to equipment, force the process to stop, or, in the worst-case scenario, endanger the lives of operators. all of these can cause serious financial damage to a company. since these malfunctions carry considerable risks, some procedures are designed to be able to withstand and mitigate the effects of random events. a good control system with trained operators can be the key to neutralizing malfunctions. however, in batch and semi-continuous processes the implementation of control systems has always been difficult. one of the best ways to manage these processes is the isa-88 standard. isa-88 provides a consistent set of rules as well as terminology for batch control in addition to defining the physical model, procedures and recipes. however, the implementation of a control system which *correspondence: mihalyko@almos.uni-pannon.hu is up to standard is expensive given the costs of equipment, salaries of operators, etc. in the light of these factors, an attempt was made to devise a method for the design and operation of intermediate storages to mitigate the effects of malfunctions and reduce overall costs of equipment and operators in a plant. intermediate storages, also known as buffer tanks, are important units in the chemical industry. throughout the paper the investigated units will be referred to as buffer tanks, intermediate storages or simply as tanks and storages. with these storages the production process can be made safer by creating an emergency reserve to provide raw materials for the operation of other units. the design of buffer tanks is not trivial even when uncertainties are disregarded which are present during the production process [1]. however, to ensure the reliable operation of a device, which is even subject to uncertainties, a more complex approach is required. therefore, it could prove beneficial to use stochastic models for the design of units since with these models all random variables which define the operation process can be taken into account. operating and design parameters of the buffer tank must be chosen so that the amount of material stored is always sufficient to satisfy the demands of customers while also providing mailto:mihalyko@almos.uni-pannon.hu 92 tarcsay, mihálykó-orbán, mihálykó a reserve of the raw material in question in the event that other units malfunction. nowadays, models used to determine these parameters under different operating conditions are a significant focus of research [2–5]. these models are closely related to those applied in insurance mathematics to calculate the amount of capital and insurance prices required to operate an insurance company so that the firm can cover the damages of its clients while still turning a profit. many of the techniques used in that field can be applied following minor adjustments in these cases as well [5, 6]. during the study of chemical processes, infinite intervals of time are often presumed, meanwhile, the probabilities of the material in the tank overflowing or being exhausted are investigated separately. if the process is investigated over an infinite time interval, then the function that defines the reliability of the system can be expressed as a solution of volterraor fredholm-type integral equations. despite being difficult to solve, it must be noted that they are easier to handle than those that define reliability over a finite time interval. the main reason for this, in the case of finite intervals, is that not only the first occurrence but also the time remaining during the time interval contribute to the reliability of the system. in the case of infinite time intervals, this quantity is constant, namely infinity. if only the probability of the raw material in the tank being exhausted is studied as a function of the initial buffer capacity or the probability of it overflowing as a function of the tank capacity, then only the probability of malfunction as a function of one variable need be investigated [5, 6]. solving equations with one variable is simpler than solving integral equations that describe the process as a function of two variables, namely initial buffer and tank capacities, supplemented with the time interval. the economical optimization of similar processes has already been conducted in some simpler cases [7]. in this publication, the focus of interest was on investigating the process over a fixed finite time interval where the reliability of the system was treated as a function of two variables. a chemical process was examined where a raw material was loaded into a buffer tank from a batch reactor. some of this raw material was drained from the tank at randomly chosen intervals for customers as required. moreover, the raw material could be constantly extracted which fed the unit after the tank had been used to separate components of the raw material and accumulate the key component. this differs from popular models which investigate such processes that by and large only deal with a batch feed and continuous extraction of the raw material. to investigate the model, a function was defined to express the reliability of the process as a function of the initial buffer and tank capacities. the integral equation satisfied by the function, however, could not be solved analytically, therefore, a monte carlo simulation was used to approximate the reliability of the process numerically. based on the investigations using one variable, a function was applied to the numerical results whose parameters were identified using the least squares method. by applying this function, the initial buffer and tank capacities required could be calculated to ensure the reliable operation of the unit over the examined finite time interval. however, the required degree of reliability could be achieved by an infinite number of parameter combinations. from among these combinations that ensure a safe operation, the optimal parameter pair was determined using economical optimization by considering the incomes and expenditure of the process. to investigate a process like this based on actual data from a plant, a thorough knowledge of the distribution functions of every random variable present is required. to acquire such data, information about equipment failures or mistakes made by the operators is required which is documented in every chemical plant. should the demand for the raw material vary, data with regard to economic trends from previous years can be used. if the amount of data is sufficiently large, then various methods can be used to compare the sample with a reference probability distribution. in this way a known cumulative distribution function can be used to approximate the empirical distribution function of the sample. in this publication, instead of using authentic data, assumptions about the distribution of the random variables were made, however, the techniques shown in this paper can be applied to different distributions as well and by using our methods an answer to design and operation problems using authentic data can be found. 2. the investigated model the change in mass of a raw material in a buffer tank was studied. the intermediate storage acts as a link between a batch system which feeds the tank and a batch in addition to a semi-continuous processes which both drain material from the tank (fig. 1). the process was studied over the finite time interval of [0, tmax]. over the course of the chemical process, the product is synthesised periodically in a batch reactor (1). then the product, which is a mixture of byproducts, and the key component are fed into the buffer tank (2). the buffer tank, also known as the intermediate storage (2), is linked to a continuously operational unit, e.g. a fractionating column (3), which is responsible for purifying the product by separating the byproducts from the key component. however, as with most processes that produce multiple components, consumer demand is not exclusively focused on the key component but on the raw mixture of products as well. the goal of the plant is to design and operate the intermediate storage in a way which supplies the necessary amount of raw materials for the continuous subsystem whilst satisfying the demands of the clientele. the frequency and volume of consumer demand for the hungarian journal of industry and chemistry optimal design and operation of buffer tanks under stochastic conditions 93 figure 1: illustration of the examined process (1. batch reactor, 2. buffer tank, 3. fractionating column). raw products as well as those of equipment failures and mistakes made by operators within the batch subsystem occur randomly. due to equipment failures or mistakes made by operators, the batch feeds that originate from the reactor (1) can vary in terms of both mass and time of arrival. the varying amounts and schedule of both feeds and drainings can cause two types of malfunctions to occur, the materials in the tank can either overflow or be completely exhausted which will hinder the rate of production in the continuous subsystem and render it impossible to meet consumer demands. in the following, the mathematical assumptions of this problem is discussed. let z0 denote the initial buffer capacity of the intermediate storage, zmax represent the capacity of the tank, and the duration of the time intervals between the consecutive batch feeds be tbi , i = 1, 2, · · · it is assumed that these intervals are independent random variables of the exponential distribution with parameter λl. in the same way, let the duration of the time intervals between consecutive drainings from the intermediate storage be tli, i = 1, 2, · · · which like the feeds are independent random variables of the exponential distribution with parameter λl. the number of feeds over time interval t denoted by nb(t ), and the number of periodic drainings by nl(t ), which, because of our assumptions, are random variables of poisson distribution with parameter λb−t or λlt , respectively. the amount of raw material fed into the intermediate storage during batch i is denoted by yb i , similarly the ith draining from the intermediate storage is represented by yl i. the character c represents the rate at which the raw product was drained from the intermediate storage by the continuous subsystem. the amounts of both the fed and drained batches are assumed to be random variables of identical distribution. the functions gb(y)and gl(y) are their respective probability density functions. it is supposed that the amounts of materials in addition to the durations of feeds and drainings are independent of each other. assuming the material in the intermediate storage was neither exhausted nor overflew throughout the operating time t then equation 0 < z0 + nb(t )∑ i=1 yb i − nl(t )∑ i=1 yl i − ct ≤ zmax (1) must be satisfied by the amount of material currently in the buffer tank. since these inequalities contain random variables, they can only be fulfilled with a certain probability. the mass of material in the intermediate storage can be expressed by equation z(t ) = z0 + nb(t )∑ i=1 yb i − nl(t )∑ i=1 yl i − ct, (2) the reliability of the system, i.e. the probability that the material neither overflows nor is exhausted throughout the time interval [0, tmax], can be defined as shown in equation ψ(z0, zmax, tmax) = p (0 < z(t ) ≤ zmax) for all 0 ≤ t ≤ tmax. (3) conversely, 1−ψ (z0, zmax, tmax) is the probability of a malfunction occurring, also referred to as a failure. both are defined as functions of the initial buffer and tank capacities as well as the operating time. the expectation of z(t ), i.e. e(z(t )), can be expressed by e (z (t )) = e ( yb i ) λbt − e ( yl i ) λlt − ct + z0 (4) if 0 > e (z (t )) − z0, then the process has decreasing tendency in average. if 0 < e (z (t )) − z0, then an overflow can be expected over a large time interval. if 0 = e (z (t ))− z0, then the process is in equilibrium. to evaluate the process, the time the failure first occurred is required during the interval [0, tmax], when the amount of material exceeded the capacity of the tank or was equal to zero. the time of failure is defined as the following function: tf (z0, zmax, tmax) = { inf {t : 0 ≤ t ≤ tmax : z(t ) ≤ 0 or zmax < z(t )} , if such a t value exists ∞, if for all 0 ≤ t ≤ tmax 0 < z(t ) ≤ zmax (5) 46(2) pp. 91–100 (2018) 94 tarcsay, mihálykó-orbán, mihálykó this time point is a random variable too, its expectation,e(tf (z0, zmax, tmax)·1tf (z0,zmax,tmax)<∞), will be denoted by e(tf ) and its standard deviation by d(tf ). they are finite, as 0 ≤ tf (z0, zmax, tmax) · 1tf (z0,zmax,tmax)<∞ ≤ tmax is adhered to. by applying the renewal theory [8], it can be proven that ψ satisfies the integral equations ψ (z0, zmax, tmax) = λl λl+λb  min ( z0 c ,tmax )∫ 0 z0−ct1∫ 0 ψ (z0 − ct1 − y1, zmax, tmax − t1) · λle−λlt1gl(y1)dy1dt1 + e −λltmax + + λb λl+λb  min ( z0 c ,tmax )∫ 0 zmax−(z0−ct2)∫ 0 ψ (z0−ct1+y2, zmax, tmax−t2) · λbe −λbt2gb(y2)dy2dt2+e −λbtmax  , (6) if ctmax ≤ z0 and ψ (z0, zmax, tmax) = λl λl+λb  min ( z0 c ,tmax )∫ 0 z0−ct1∫ 0 ψ (z0−ct1−y1, zmax, tmax−t1) · λle−λlt1gl (y1) dy1dt1 + + λb λl+λb  min ( z0 c ,tmax )∫ 0 zmax−(z0−ct2)∫ 0 ψ (z0−ct2+y2, zmax, tmax−t2) · λbe−λbt2gb(y2)dy2dt2  (7) if z0 < ctmax. to design a buffer tank which is capable of operating with a desired degree of reliability of 1 − α where α denotes the probability of malfunction during the time interval [0, tmax], solutions to equation ψ (z0, zmax, tmax) = 1− α (8) must be found. 3. parameter dependence of the reliability of the process and the expectation of failure time since the integral equation proved to be exceedingly difficult to handle analytically, a monte carlo simulation to approximate the probability values for different parameters was used. monte carlo simulations are more widely accepted tools in dealing with stochastic models [9, 10]. for the simulation environment, matlab r2015a [11] was used. realization of the process when the parameters tmax = 50 h, λl = 0.3 h−1, λb = 0.4 h−1 and c = 5 kgh−1 were chosen is demonstrated in fig. 2. the mean of the input suddenly increased in the function z(t), the withdrawals from the batch caused sudden decreases and continuous withdrawal resulted in a reduction in linear parts. the amounts drained and fed were defined as random variables from the gaussian distribution. the initial buffer capacity was 50 kg and continuous withdrawal resulted in a linear decrease in the amount of material. at t = 1 h, the tank was filled. the amount of material in the tank increased by 3 kg, then the continuous withdrawal resumed. a little bit later a sudden withdrawal occurred. similar events were repeated at random time points with random quantities. at t = 7.8 h a large withdrawal took place and the material became exhausted, therefore, z(t) became negative. the time of failure, in this case the time a shortage was observed, was tf = 7.8 h. although the process was investigated over an interval of time, it is sufficient to compute the values of z(t) only at those points where sudden changes occurred and at the endpoint of the interval. an overflow could only occur if an input was present. both continuous and batch withdrawals can cause shortages. if the amount of material at the time points of batch inputs and outputs is comfigure 2: the change in the mass of material in the buffer tank. hungarian journal of industry and chemistry optimal design and operation of buffer tanks under stochastic conditions 95 figure 3: the probability of a failure as a function of the initial buffer and tank capacities. puted, it can be determined whether or not the continuous withdrawal caused the shortage during the time interval bounded by the last two batch events. if it did, the time point of the shortage can also be computed by solving a linear equation. by applying a monte carlo simulation, the probabilities were approximated by relative frequencies and the expected failure times were estimated by the average times. 10, 000 simulations were conducted which yielded an accuracy 0.01. for example, tmax = 50 h was fixed and the parameters of the process were λl = 8 h−1, λb = 12 h−1 and c = 12 kg h−1. the amounts drained and fed were defined as random variables from the gaussian distribution with a mean of 8 kg and a standard deviation of 2 kg. with the aforementioned parameters, the probability of malfunction was calculated and the following results obtained for the process under the indicated conditions (fig. 3). figure 4: the expected malfunction times as a function of initial buffer and tank capacities. figure 5: a histogram of the malfunction times. in fig. 3 it can be seen that when the tank capacity was fixed, the probability of failure increased as a function of the initial amount of material. this can be explained by the fact that although the likelihood of a shortage decreased, the amount of material in the tank tended to increase, therefore, the free volume of the tank decreased, hence the increase in the probability of overflow. on the other hand, when the initial buffer capacity was fixed, the probability of a failure decreased as a function of the tank capacity. this tendency can be explained by the fact that the probability of overflow decreased and stemmed from the fact that λb was greater than λl meaning that the average time intervals between feeds were smaller than those between drainings. this caused the process to be more prone to malfunction due to overflow. the times of failures (tf ) were investigated as well. expected failure times are shown in fig. 4 as a function of the initial buffer and tank capacities. if no failure occurred, then tf was equal to zero, therefore, the expected tf was close to zero as well. a histogram of the malfunction times is provided in fig. 5 when z0 = 400 kg and zmax = 1500 kg. it demonstrates that no quick failures occurred due to a shortage of material resulting in an increase in the amount of material and the tank overflowing. the distribution of the malfunction time in this case is unimodal and the degree of dispersion is quite large. the dispersion of the malfunction time as a function of the initial buffer and tank capacities can be seen in fig. 6 which demonstrates that when the tank is half full, large standard deviations with regard to the malfunction times were calculated. in the case of large or small capacities, the malfunction time can be accurately predicted as the degree of dispersion is small. 46(2) pp. 91–100 (2018) 96 tarcsay, mihálykó-orbán, mihálykó figure 6: the standard deviation of the malfunction times. 4. design of the tank and initial buffer capacities for a given reliability level during previous research, only models that consisted of a batch feed and continuous drainage in the absence of batch drainage [5–7] were studied. in the papers that deal with these models, it has been published that the integral equation for the reliability of the unit could be solved analytically in special cases where the process over an infinite time interval as a function of one variable is observed. in these special cases the solutions to the equation were mainly exponential in form or the linear combination of exponential functions [5, 6]. consequently, when fitting a function to simulated data, a function was chosen which exhibits similar characteristics. by fixing tmax, seeking ψ is suggested as a function of the initial buffer capacity x and tank capacity y, in the form of equation h (x, y) = 1− ( 1− e(−ax) )c( 1− e(−b(y−x)) )d , (9) where x < y; a, b, c, and d are positive parameters which have to be optimized. numerical values of ψ were computed by a monte carlo simulation for some values of z0 and zmax, and the parametersa–d were determined using the least squares method, by minimizing function s (a,b,c,d) = ∑ r ∑ s (ψ (xr, ys)−h (xr, ys)) 2 (10) this function was minimized numerically. the approximated function exhibited a fit to the original function of 95 % on average which was calculated using a monte carlo simulation. the error of the fitting was inversely proportional to the number of simulations used to model the system as well as the number of points with regard to the tank and initial buffer capacities investigated. since the quality of the fit was high (95 % on average), it can be assumed that even if the minimum identified is a lofigure 7: the relationship between the tank and initial buffer capacities that correspond to different levels of reliability 1− α. cal minimum, the approximation is sufficient for use in further computations. using the fitted function, equation ψ(x, y) ∼ h (x, y) = = 1− ( 1− e−ax )c( 1− e−b(y−x) )d = 1− α. (11) was solved. appropriate initial buffer and tank capacities for the process are provided by the solution to the equation above with a reliability of 1−α over the time interval [0, tmax]. a link between the values of x and y is provided by the solution to the equation, namely equation y = x− ln ( 1− ( 1− α (1− exp(−ax))c )1/d ) b . (12) this relationship, using the parameter set presented in the previous section, is given in fig. 7. the interval of the initial buffer capacity was [100, 500] kg and the step sizes applied were 100 kg. the interval of the tank capacity was [1000, 2500] kg and the step sizes applied were also 100 kg. to eliminate numerical inaccuracies, the values of the time intervals were transformed into the time intervals [0, 100]. by transforming the time intervals into a subset of [0, 100], a = 0.4966, b = 0.12, c = 0.9324, and d = 86.4875 were computed. after the computations, the results were transformed into the original time intervals. the required tank capacities as a function of the initial buffer capacity in the intermediate storage corresponding to the reliabilities 1 − α = 0.95, 0.975, . . . 0.99 can be seen in fig. 7. it can be seen that with some initial values a reliability of 0.99 is infeasible since the likelihood of a shortage itself exceeds level α. the minimum initial amount hungarian journal of industry and chemistry optimal design and operation of buffer tanks under stochastic conditions 97 figure 8: the required initial buffer capacity corresponding to a fixed tank capacity of 1, 900 kg and reliability level of 0.8 as a function of the draining intensity (c) . of material in the intermediate storage with a reliability of 1− α can be expressed by − ln ( 1− (1− α) 1/c ) a < xmin (13) from fig. 7 it can be seen that if the lower limit is used as the initial buffer capacity, the corresponding storage capacity is enormous. the reason for this is the fact that the likelihood of a shortage is equal to α and an overflow is undesirable, therefore, the tank capacity must be very large. according to the results shown in fig. 7, this value is approximately 150 kg. moreover, if z0 exceeds a certain level, the function is by and large linear. it is shown by the linear part of the function that when the initial buffer capacity exceeds 250 kg, the likelihood of a failure due to exhaustion of material is almost zero. the likelihood α of an overflow is provided by the difference between the tank and initial buffer capacities. therefore, to calculate the required tank capacity over this time interval, the volume which can ensure that the likelihood of overflow will remain as α is simply added to the buffer capacity in the intermediate storage. finally, the minimum tank capacity that corresponds to a given level of reliability can be determined by numerically minimizing function y = x− ln 1− ( 1− α (1− exp(−ax)) c )1/d  b (14) for the reliability level 1− α = 0.95, the minimum tank capacity is approximately 1, 820 kg and the required initial buffer capacity approximately 245 kg. by fixing the tank capacity and reliability level, the dependence of the required initial buffer capacity on the withdrawal rate was investigated. the values of the refigure 9: the required drainage intensity corresponding to a fixed tank capacity of 1, 900 kg and a reliability level of 0.8 as a function of the initial buffer capacity. quired initial buffer capacity were determined numerically according to the secant method. the reliability level was 1−α = 0.8 and the tank capacity was 1, 900 kg. the results can be seen in fig. 8. according to this result, by increasing the withdrawal rate, the required initial buffer capacity increases sharply which facilitates control of the process. finally, the required drainage intensity corresponding to the reliability level of 1 − α = 0.8 and fixed tank capacity zmax = 1, 900 kg as a function of the initial buffer capacity was provided (fig. 9). it can be seen that it is also a monotonically increasing function, but the rate of increase is usually less than in the case of fig. 8. 5. economic investigations according to fig. 7, if the minimum required amount of initial buffer capacity is supplied then the required level of reliability of the process can be achieved by an infinite number of combinations of tank and initial buffer capacities. to determine the optimal combination, economic evaluations of the design are recommended. it is assumed that following a possible failure, the process is restarted, however, such a restart is time-consuming and expensive. during the calculations both the income and expenditure associated with each parameter are taken into account. these include the costs of raw materials, the buffer tank, malfunctions and repairs as well as the income generated from sales of both the key component and raw product. to determine the income generated by the process at time t , equation q (t ) = gkey (t ) +graw (t )−kmat (t )− − kshort (t )−krep (t )−ktank (15) was used. the symbols g and k represent the income and expenditure of the process in usd. the profitability of 46(2) pp. 91–100 (2018) 98 tarcsay, mihálykó-orbán, mihálykó the whole process, (q) stems from the income generated from the sales of the key component (gkey) and raw product (graw). the income is reduced by the various expenses of the process, namely the costs of raw materials (kmat), restoring the buffer capacity of the tank in case of exhaustion (kshort), repairs (krep) and the buffer tank itself (ktank). the method of calculating each source of income and expenditure is shown below. the main goal of the process is to produce the key component, which is isolated in the continuous subsystem. to calculate the profit that stems from this, equation gkey (t ) = t − nrep(t )∑ i=1 trep  cβkey (16) was used. in this equation, βkey denotes the sale price of the key component (usd kg−1), t represents the duration of the process throughout which the profit (h), the number of malfunctions (nrep(t )), and the random time of repair (trep) during each malfunction are examined. additionally, the plant secures an income from the sales of the raw product as well as the remaining raw product at the end of the production process, which can be defined as shown in graw (t ) = βraw δ z0 − t − nrep(t )∑ i=1 trep  c + + nb(t )∑ i=1 yb i − nl(t )∑ i=1 yl i + nl(t )∑ i=1 yl i  (17) where βraw denotes the sale price of the raw product (usd kg−1) and δ is a factor which defines the price at which the remaining raw product can be sold following production. among the expenses, it should be mentioned that the cost of raw materials used for the production of the raw product and the cost of the initial raw product in the tank are calculated according to equation kmat(t ) = γmat nb(t)∑ i=1 yb i + z0γmat (18) where γmat is the cost of the raw material (usd kg−1). in the event of its exhaustion, additional raw product is required to restore the initial buffer capacity of the tank and the cost of this is shown in kshort(t ) = nshort(t )z0γmat, (19) where nshort(t ) denotes the number of malfunctions caused by exhaustion during time t . finally, the cost of repairs and installing the intermediate storage itself need to be considered. to determine the installation costs, the installation factor of the tank (f ) and the cost of the tank (γtank in usd) were taken figure 10: mean profit as a function of the initial buffer and tank capacities. into account. to determine the expense of repairs, the parameter γrep was used to represent the cost of repairs (usd h−1) which was calculated according to equations krep(t) = nrep(t)∑ i=1 trepγrep (20) and ktank = f z0.6 max γtank. (21) the cost of installing the buffer tank was calculated according to references found in the literature [12]. the mean of the profit was investigated according to the reliability level of 0.95 ≤ 1 − α using a monte carlo simulation and its optimum was calculated using the grid method. it is shown by the results that if the reliability of the system is high, then the costs of repairs and malfunctions in general are negligible compared to the cost of storage. as a result, the maximum profit was achieved close to the minimum storage capacity which is shown in fig. 10. this value roughly corresponds to the minimum of the investigated boundary, using a reliability of 0.95. to generate this figure the following parameters were used: βkey = 120 usd kg−1, δ = 0.3, γmat = 80 usd kg−1, βraw = 100 usd kg−1, f = 100 usd kg−0.6, γtank = 12, 000 usd, mtrep = 0.5 h, and σtrep = 0.29 h, where repair times were independent random variables of the uniform distribution during the time interval [0, 1]. the maximum profit according to these calculations is 4.76 · 104 usd, which can be achieved by tank and initial buffer capacities of 2, 101 kg and 389 kg, respectively. 6. conclusion in this paper, a stochastic storage model was investigated. random batches as inputs and outputs, as well as continuous withdrawal were allowed. a monte carlo simulation was used for the investigation. an analytic function hungarian journal of industry and chemistry optimal design and operation of buffer tanks under stochastic conditions 99 was fitted to the simulated data, which provided a link between the initial buffer and tank capacities that correspond to a given level of reliability. the results agree with engineering practice. although the data for the research did not stem from authentic sources, by utilizing data from the industry, the distribution of the random variables present during the process could be determined using standard statistical methods. therefore, the method can be a useful supplement during the design phase of a chemical plant and also be utilized to help simplify the overall control of a chemical process. symbols small letters c draining intensity (kg h−1) f installation factor of a tank (kg−0.6) g probability density function (h−1) m expectation x fixed initial buffer capacity (kg) y fixed tank capacity (kg) yb mass of batch fed into the tank (kg) yl mass of batch drained from the tank (kg) z mass of material (kg) capital letters a,b,c,d fixed parameters of the approximated failure probability function g income (usd) e expectation h approximated failure probability function k expenses (usd) n number of events during time interval [0, tmax] p probability q net income (usd) t time (h) tf time of failure (h) greek letters α probability of malfunction β sale price (usd kg−1) γ cost (usd kg−1) δ ratio of decrease in material value λ parameter of exponential distribution (h−1) σ standard deviation ψ function describing the probability of reliable operation during time interval [0, tmax] indices 0 initial b feed i index of event (i = 1, 2, · · · ) rep repair short material exhaustion l draining mat reactant max maximum min minimum r the number of mesh points of the initial buffer capacity s the number of mesh points of the tank capacity t time raw raw material tank tank key key component references [1] towler, g., sinnott, r. k. chemical engineering design: principles, practice and economics of plant and process design. 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(mcgraw-hill, new york) 1968 isbn: 0072392665 hungarian journal of industry and chemistry https://doi.org/10.1007/978-1-4471-4588-2 https://doi.org/10.1109/mcse.2006.34 https://www.mathworks.com/products/matlab.html https://www.mathworks.com/products/matlab.html microsoft word 07-10 1402 voros.docx hungarian journal of industry and chemistry veszprém vol. 41(1) pp. 7–10 (2013) design of a new chemical injection pump system for gas hydrate inhibition csaba vörös1!, viktor füvesi1, and ákos pintér2 1,2research institute of applied earth sciences, university of miskolc, miskolc-egyetemváros, pob 2, h-3515 hungary 1department of research instrumentation and informatics, miskolc-egyetemváros pob 2, h-3515, hungary 2department of reservoir and mining chemical engineering, miskolc-egyetemváros pob 2, h-3515, hungary !e-mail: voros@afki.hu in this study the main feature of chemical injection systems used in gas industry are detailed. the two main energy sources of these systems are air and electric power source. the general structure and main properties of these injection systems are discussed. examples for a pneumatic commercial and a newly developed, electric system are compared. keywords: chemical injection system, hydrate inhibition, solar energy, pneumatic system introduction during the production of gas, a major problem is the formation of hydrate crystals in the pipeline. a considerable amount of hydrate crystal can cause hydrate plugs in the pipeline. the hydrate plug effect lengthens production outages and results in loss of money for the maintainer [1], because elimination of the plug is a time consuming procedure. one of the most widely used traditional solutions to prevent hydrate formation is addition of methanol to the steaming gas. the methanol helps to dehydrate the gas, thus, the growth of hydrate crystal is limited [2]. the methanol can be transported from the gas separator station or gas collection station to the gas wells via a dedicated pipeline. this traditional solution was the most popular practice for a long time in gas industry. this technology is safe, but has several drawbacks, such as the cost of additional pipe to the gas wells, the cost of the methanol regeneration [3], and methanol contamination of the environment. regardless the methanol technologies are still major solutions for hydrate inhibition for the currently operating gas wells. the modern installations use methanol in low concentrations for newly installed gas wells. these bring the need for injecting methanol locally at the site of the gas wells. thus, an injection unit is needed for this purpose. the production-related aspects such as the consumers expecting increased flexibility from gas provider cannot be neglected, because of the habits of the consumers and the appearance of competitive energy-saving technologies. therefore the different injection systems spread noticeably dynamically in recent years. in the first part of the paper, the main features of the commercial injection systems are detailed followed by the introduction of a newly developed injection system. chemical injection systems in gas industry there are two applications, where chemical injection is required. the first one is the above described gas hydrate inhibition technology. the second one is where usage of corrosion prevention chemicals is needed. new chemical injection technology appeared in sophisticated form using a wide service range as a result of a change in gas production and distribution in the last decade. structure of pneumatic chemical injection pump systems the most commonly used chemical injection units in gas industry employ the energy of gas for dosing. these systems are called “operating without auxiliary power systems”. in details, the energy of gas steam in the pipeline is used as a power source in the dosing of hydrate inhibiting chemical pump systems. this method has the major advantage that the gas is always available, or it is not necessary to provide a separate power source for the equipment to operate. big disadvantage of the technique is that gas is required for operation and this gas is emitted to environment, which is a harmful effect, moreover, the cost of it is also not negligible. there are some solutions to utilize the emitted gases, but these methods raise the price of the pump. 8 fig.1 shows a common structure of chemical injection pump systems, which illustrates how the actuated gas gets into the injection system through a gas preparation unit. this unit is typically a special tank, which is filled with methanol. by using this type of conditioning one can be sure that the gas is sufficiently dry, thus, the water does not disturb the operation of the pump. it is needed to avoid the risk of freezing out various components. the gas bubbles through the methanol, so it loses a significant part its water content. the replacement of the methanol is needed at appropriate intervals of time as a technology management. after the gas leaves the conditioning unit, the gas steams through a two-stage pressure regulator. this unit provides the required pressure to the system for operation. the timer unit is responsible for providing appropriate technological demands of the schedule, i.e. sufficient number of strokes is needed to operate the pump. the chemical is injected with the piston of the injection pump. the injection system includes other components, which are essential for the operation, such as check valves, ball valves and other fittings. the hydrate inhibitor compound can be found in the tank. the main task of the control system is the monitoring of the injection system, so several parameters are required to be measured, e.g. the level of chemical in the tank, the pressure of the after the regulator and the ambient temperature. one of the most substantial information about the injection pump is the entry of the inhibitor to the pipeline. to measure these parameters, transducers are needed, which require some solar energy for the operation. fig.2 shows a wellorganized, modern gas well in hungary. the injection system used employs the gas of the well for its operation. injection system from haskel milton roy the haskel milton roy company develops and manufactures various injection systems for special oil and gas applications for many years. chemical injection pump (cip) series is one of the most widely used equipment for gas wells. a pneumatic version of the device is shown in fig.3, as a typical system. the driving gas or air is fed from the regulator to the gasdrying unit. the air is let into the injection pump, which includes the timer unit. the chemical enters the pump through the appropriate valves and filters. the dosage of chemicals can be adjusted through the rate setting gauge unit (typically it is a burette) at, which the quantity of chemical of one injection is displayed. the strokes can be counted by using the flow meter on the system. the check valve prevents the injection pump from the backpressure of the process fluid. the company can deliver the complete unit in different versions according to the quantity of injection, e.g. the given series can be adjusted from 0.27–25.8 dm3 min-1. the range of operation pressure is also wide, typically 120–600 bar. structure of electric injection systems this category includes systems, where the electricity is the only energy source. in general, the site of the gas figure 1: block scheme of chemical injection system figure 2: chemical injection system on a gas well figure 3: pneumatic injection system from haskel milton roy [4] 9 well is not equipped with electric power because of the relatively large distance from the processor (separator station, collector, etc.). thus, these systems are not commonly employed in the gas well applications. most of the electric chemical injection pump systems are based on the principle of displacement pumps. these high-pressure pumps provide the chemical injection by using speed adjustment in a wide range, or with different piston volumes. as shown in fig.4, the electrical injection pump system contains relatively few units. it cannot be ignored that the electric pump does not only include a motor-driven piston with frequency inverter, the controller electronics is also an important part of the system. solar energy can be applied as energy source of this type of system. this source can feed the control electronic besides the main actuator of the system. in-house designed injection system the development of the injection system was a part of a bigger project with the scada ltd, a company from automation industry. the aim of development was to create an injection system, which can be used mainly at hungarian gas wells. thus, the temperature requirement of the system was in the -40 °c to 60 °c range. the system must be capable of working in ‘ex’ environment with high efficiency. the power source of the actuator is solar energy to reach close to zero emission of the system. in the system, corrosive chemical has to be injected, thus, a corrosive resistant is required at critical parts of the equipment e.g. piston, piston space, etc. the maximal working pressure was 160 bars. a wide range of injection volume was also a fundamental requirement. these requirements were the main parameters at the design phase of the equipment. the block scheme of the developed system can be seen in fig.5. the base of the system is an ex class asynchronous motor (table 1), which is assembled with a helical gear unit from nord manufacturer. the base of injection system is a crank mechanism, which transforms the rotary motion to alternating motion. the pump has two pistons to reach higher injection volume and a wellbalanced load of the motor. the main parameters of the mechanics can be found in table 1. the sealing of the mechanism is a critical design point. the relatively high pressure, corrosive fluids, and high stroke number require special solution for sealing. a single acting, spring energized-seal was selected. the application conditions demanded the tight guiding of neck of piston, to avoid the damage of seals during the operation of pump (fig.6). the electromechanical actuator gives the opportunity to smoothly alter the injected volume in continuous or in periodic operation. table 2 shows the injected volume of the pump at different frequency of the inverter in continuous mode. the power source of the system is an array of solar cells. the power of solar energy system was 2 kw to get extended service and short recharge time. the capacity of the accumulators was 800 ah. the developed equipment has a plc-based control system to monitor the main parameters of the technology and to change the behaviour of the injection system. figure 4: block scheme of electric power injection system figure 5: block scheme of new injection system table 1: main parameters of the injection pump designed asynchronous motor nominal voltage 230 v(y) /400 v (d), 50 hz nominal power 0,12 kw ex class ptb 07 atex 1058 x ii2g ex de iic t4 type dex 63k/4k vendor hew helical gear unit gear ratio 41,58 ex class ex ii 2g c iic t4 x type sk02f-iec63 /26-63 s/4 tf/2g vendor nord crank mechanism length of stroke 20 mm ratio of mechanics 7 injection unit diameter of piston 5 mm vendor of seals trelleborg type of seals turcon® variseal® 10 the measured parameters are the pressure of siphon of well, drill pipe, injection pipe; the temperature of pipe of well, soil, chemicals, controller, temperature of inverter; the level of the chemical in the tank; the current and the voltage of the inverter. the frequency of the inverter can be changed in function of the conditions of the well. the injection system is able to communicate wirelessly with a server. by using modern computer technology, the main parameters of the system can be monitored and changed. fig.7 shows the website of the system, which shows, on one hand, the main actual online parameters of the system, on other hand, the trends and history of the parameters on diagrams. the structure of the website is user friendly, simple. a model technology for an actual gas well was set up at the site of the scada ltd. near to hajdúszoboszló (fig.8). at the test site, main parameters like level of the chemical in the tank, process gas pressure, frequency of the inverter, etc. were monitored and measured. after the successful test of the model technology, the equipment was moved to a real gas well at békásmegyer in october 2012. conclusion a new solar energy-based chemical injection pump system was developed with a modern control and computerized support system at university of miskolc, research institute of applied earth sciences. the equipment meets the modern requirements. it is an efficient injection system; it has wide operation range and has user-friendly high-level computer support. in the process automation field of gas industry, the adaptation of new approaches appear slower in consumer or in industrial environments than in other fields of industry. the new, energy efficient, solar supplied, standalone chemical injection systems hopefully can enter in the field and will be utilized more wells in hungary. acknowledgement this work was partially supported by the framework of the centre of excellence of mechatronics and logistics at the university of miskolc. references [1] berecz e., balla-achs m.: gázhidrátok, akadémiai kiadó, budapest, hungary, 1980 (in hungarian) [2] hammerschmidt e.g.: formation of gas hydrates in natural gas transmission lines, ind. eng. chem. 1934, 26(8), 851 [3] lederhos j.p., long j.p., sum a., christiansen r.l., sloan, e.d. jr.: effective kinetic inhibitors for natural gas hydrates, chemical engineering science, 1996, 51(8), 1221–1229 [4] williams chemical metering pumps: www.willamspump.com (last accessed: may 25, 2014) figure 7: website of pump system figure 6: section of injection unit table 2: injected volume of pump at 150 bars frequency of inverter, hz injected volume, dm3 h-1 30 21.71 50 36.19 70 50.67 90 65.14 figure 8: block scheme of chemical injection system conferenceproceedtings hungarian journal of tindustrial chemistry veszprem vol. 2. pp. 59· 64 (2000) description of a pilot plant for the co-composting of the solid residue and wastewaters from the olive oil industry a. g. vlyssides, a.a zorpas*, p.k. karlis and g.a. zorpas (national technical university of athens, department of chemical engineering, 9 heroon polytechniou st., zographou athens, g-15700, greece) this paper was presented at the second international conference on environmental engineering, university of veszprem, veszprem, hungary, may 29june 5, 1999 the co-composting of the solid residue and wastewater from the olive oil production process have been studied as a new method fo~ the treatm~nt of wastewater containing high organic and toxic pollutants. the experimental results for a dem?nstrat10n plant usmg solid residue from olive extraction as bulking material and olive oil processing effluents as continuously fed wastewater are reported. composting temperature was controlled between 45 and 65 °c by air supply and the wastewater addition was fed mainly in order to keep the moisture in the range of 45 to 60% and secondary to replace the carbon substrate. during twenty three days of operation in the thermophilic region, the system was fed with 26~ m3 wastewater in total, which means an average rate of 11.4 m3 day"1 wastewater or 2.9 kg wastewater per kg solid residue. then followed a three months stabilisation period in the mesophilic region until the final product reached ambient temperature. keywords: composting; solid waste residue; oil olive industry introduction olive oil extraction is among the most traditional agricultural industries in greece and it has always been, and is still of primary importance for the national economy, as greece has a share of 15% of world production [1]. the annual olive oii production is in the range of 350.000 ~ 400.000 tons per year resulting in the generation of about 1.500.000 tons of olive mill wastewater, which causes serious environmental problems, mainly due to its high organic content. the quantity and the physico-chemical characteristics of olive mills wastewater, commonly called 'vegetation water', depends on the place, age of growth, harvesting season, yearly changes, olive variety, extraction method, etc. the organic matter of vegetation water contains mainly polyphenols, carbohydrates, polysaccharides, sugars, nitrocompounds, polyalcohols, fats and oil, substances generally worth recovering. a number of vegetation water treatment methods have recently been employed, especially in the mediterranean area, and these can be divided into physico-chemical and biological methods. * author to whom correspondence should be addressed. the physico-chemical methods have the disadvantages of high cost and low efficiency: lime precipitation results in 40% reduction of the organic matter but production of large quantities of sludges. moreover, the effluents after precipitation as well as the chemical-organic sludges that are produced, have all the toxicity of the ii:ritial vegetation water leading to serious disposal problems [2]; reverse osmosis has over 90% efficiency in removing organic matter, but on the other hand high operating cost and sludge disposal problems [2]; incineration (with or without concentration) is reliable but expensive, and complicated by high energy demand and emission of air pollutants; lagooning as a physical method for water evaporation, since a very · limited biological degradation takes place [31 has significant cost disadvantages due to land requirements and the necessity for taking special measures to protect public health [4]. biological methods have certain clear benefits due to their potential for the utilisation of by~products. (compost for fertilising, biogas for energy production, natural colouring substances, proteins for cattle feed enrichment): protein production has low fixed costs but requires additional treatment methods due to the low 60 table 1 composition of the solid residue characteristics total solids (ts), % total carbon content, % of ts total kjeldahl nitrogen, % of ts total phosphorous as p20 5, % of ts fats and oils, % of ts total sugars, % of ts cellulose, % of ts hemicellulose, % of ts ash, %ofts bther extraction substan<;es, % of ts lignin, % of ts potassium as k20, % of ts calcium content, % of ts c/nratio cip ratio specific weight, g cm-3 porosity,% value 86.00 ±3.33 55.45 ±4.48 1.06±0.015 0.11 ±0.008 1.8 ±0.69 2.07±0.025 37.27 ± 0.438 16.57 ± 0.942 3.65 ±0.225 8.38 ±o.q35 21.9 ±0.45 0.83 ±0.07 0.82±0.092 52.14±5.2 1123.79 ± 147 1.09 ±0.02 52.4 ± 5.5 table 2 composition of the vegetation water characteristics total solids (ts), % total volatile solids,% ofts total carbon content, % of ts total kjeldahl nitrogen, % ofts total phosphorous as p20s, % ofts ph bod5,gdm-3 cod,gdm-3 ash, %ofts c/nratio c/pratio specific weight, g cm~3 value 6.33 ± 1.81 90.36 ±3.31 62.71 ± 16.27 1.2 ± 0.173 0.84 ± 0.158 5.00 ± 1 55± 35 130 ± 40 9.64 ± 3.31 53.57 ± 5.4 75 ± 9.8 1.048 ± 0.033 initial removal of organic matter (about 50%}; &naerobic digestion has the benefit of energy production but also relatively low efficiency (80%) compared to the high capital cost of the hightechnology installations and equipment [5,6]; co-composting is the optimum method from the environmental ·point of view as the organic matter is totally recovered. furthermore it has low fixed cost and the final product could be marketable as a high­ quality soil conditioner [7]. for the present work a co-composting demonstration plant was designed and constructed in order to treat the wastewater from an olive oil extraction factory. the design of this plant was based on laboratory scale results obtained previously [7]. the results from the operation of this plant are presented in this work. the fundamental principle of a co-composting system is the biodegradation of the organic matter through exothermic aerobic bioreactions which take place in the thermophilic region with the simultaneous evaporation of the moisture of the wastewater due to the release of thermal energy [8}. in application to wastes from olive oil extraction plants, the critical parameters for the growth of microorganisms and bioreactions are the oxygen demand, the moisture (which must be in the range of 40 tel 60%) the temperature (which must be retained between 45 and 65°c; optimum 60°c) and the carbon/nitrogen (c/n) ratio (which must be kept below 30/1). the solid residue from the olive oil extraction process is used as substrate (bulking material), the vegetation water as supplier of moisture, carbon and nutrients. air is supplied for cooling and oxygen needs. in addition, excess nitrogen, in form of urea, is provided for the system. methods plant description and operation based on the above mentioned principles a wastewater treatment plant was constructed in kouisouras, crete, greece, in order to handle the effluents from an olive oil factory with 250-300 t annual oil production and 10001200 t wastewater. the plant was operated simultaneously with the olive oil factory for 120 days, the common olive oil extraction period in greece, between september 1992 and january 1993. figs. i and 2 illustrate the flow diagram of the plant, which consisted of: an aerobic bioreactor of 18m length,· 6m width and 2.2m height (195m3 active volume) with an agitation system of a travelling bridge with a helical type agitator of 0.90m blade diameter. an aeration system of three fans and nine diffusion pipes installed over the bottom of the bioreactor. a wastewater storage tank of 80 m3 active volume and two dosing pumps. a nutrient preparation and dosing unit, including a preparation tank eqnipped with a mechanical agitator and two dosing pumps. a programmable logical controller {plc) for the control of the plant operation and data collection. the steps followed in the successive periods are described below. start-up period at the start-up of the plant, a quantity of about 91.5 t solid residue, 119 t vegetation water and 1600kg urea (as nutrient source) were fed into the bioreactor. the solid residue was agitated and sprinkled with the vegetation water and urea in order to achieve a· homogenous mixture in the bioreactor. the compositions of the solid residue and vegetation water are reported in tables 1 and 2 respectively. these values were obtained from the analysis of five samples of solid residue and vegetation water and average concentrations are reported. from the analysis, it was indicated that vegetation water did not contain enough nitrogen and so urea was added to cover the needs for this particular nutrient. co-composting period this period got under way when the temperature in the bioreactor came into the thermophilic region due to the 61 fig.] flow diagram of the plant. a: wastewater feeding; b: feed storag~ tank; c: co-composti,ng bioreactor; d: urea feeding system; e:agitator; f: air feeding fans; g: roofto prevent access of rainwater; h:mono-pumpfor wastewater dossing; i: proportional pump feeding of urea solution; k:computer for controlling and data collection; l :travelling ridge for the agitator; m: motors; tc: temperature controller 18.0 m ---,--------fig.2 sectional plan of the bioreactor. c : co-composting bioreactor; e: agitator; f: air feeding fans; l:travelling bridge for the agitator;_m: motors; ----·-······ ··-·-... agitator running; air line increase of the bioreaction rate. during the thermophilic period, oxygen, vegetation water and nutrients were provided for the system. the compost was mixed by a travelling helical agitator as shown in fig.2. one complete mixing period of total bioreactor content was achieved within two hours. the bioreactor was divided into three areas of 6x6 m. in each area one fan and three diffusing pipes were installed (see fig.2). the travelling bridge, with velocity 1 m min "1, entered each area every 20 min. a temperature control system, fixed on the travelling bridge, controlled the operation of each fan in order to maintain the temperature about 60 °c, according to the following principle: minimum air flow (4.6 m3 pert of compost) was provided at low temperature (<30 oq and maximal air flow (56 m3 per t of compost) was provided at high temperature (>60 °c). the minimum airflow should have corresponded to the minimum oxygen demand for the microorganisms and the maximal airflow to meet the needs of air supply for cooling purposes (9]. the vegetation water was sprinkled on the bioreactor surface in the area of agitation (imaginary cylinder) in quantities inversely proportional to the temperature. the feeding rate was calibrated by the following linear equation according to vlyssides et al. (7]: q = 2.228 0.034 t (1) fl 3 h-1 t. where q is the vegetation water ow rate, m ; is the temperature, oc with boundary conditions: q = 1.2 for t:o;30 oc and q = 0 for ~65 oc. urea (15% solution) was fed simultaneously with the vegetation water at a steady rate of 1.34 kg urea per m3 of vegetation water. the air, vegetation water and urea feeding processes were performed automatically and controlled by the plc. stabilisation period after the thermophilic period, in which the organic material was biodegraded, the final product remained in the bioreactor, without any addition of infiuents. this stabilisation step was necessary in order to assure that the compost could be environmentally safe after its disposal the stabilisation period took place in the mesophilic region and it was terminated after three months, when the temperature dropped and reached ambient values. 62 70 60 50 40 30 o tempel>ture pc} --q-m o:is!ws (i; } 20 w~~~~~~~~~-r~~~~~y 10 15 20 25 deys fig 3 temperature and moisture changes during composting 9 days fig.s ph during composting methods of analysis during the plant operation, especially the composting period to which emphasis is given in this work, daily samplings and analyses were performed. every day 36 different core samples of loog weight each were taken from various places and depths of the bioreactor. every sample was homogenised before analysis. the sample moisture was measured according to standard methods [10] and the evaporated water was calculated by mass balance. total organic nitrogen was determined by a macro-kjeldahl method . according [11). total phosphorous was determined according to the chapman method [12]. total organic carbon was determined according to higgins et al. [13]. the ph was determined by the method chang and hudson [14). results and discussion temperature and moisture as shown in fig.3 the temperature rapidly increased to 63°c after 36 hours from the start-up and remained above 60°c (control set point) for 9 days. it was controlled by the air supply for which the flow rate is shown in fig. 4. this indicates an insufficiency of the air supply for cooling the system and the reasons for this are discussed later. other, uncontrolled, parameters that were affecting the temperature were the periodic mixing (one minute mixing time for each point per two hours) of the bulking material, and the wastewater feeding. after 2l days the temperature dropped to 36°c, which meant that the system was operating in the mesophilic region and the bioreactions rate was reduced as shown by the limiting carbon content. it was decided that the composting period was finish~d atler 23 days, when the temperature dropped below 35 c. as was expected the moisture continuously decreased during the tirst ten days unijl it stabilised in 12 3 4 56 7 8 91011121314151617181920212223 fig.4 air flow during the composting 1 2 3 ~ 5 6 7 8 9 d ll ~ d y 6 d ll e b ~ill~~ cl¥; fig.6 water balance during composting the range of 48-52% (fig.3). after the 20th day, the moisture started to increase due to the low energy production related to the low biodegradation rate. as shown in fig.4 the air feeding fluctuated during the first 9 days while the following days, after about 11 days, the air feeding stabilised near to 20000 jtrl day·1 due to the temperature drop. ph ph is a parameter, which greatly affects the composting process. the optimum ph values are 6-7.5 for bacterial development, while fungi prefer an environment in the range of 5.5-8.0 [15]. usually during composting the ph values are initially low because of volatile acids production, then the ph increases and in the final stage of composting a decrease in the ph is expected. this pattern was not followed in the present experiments (fig.5) in the final stage when the ph gradually increased because of excess ammonia production from biodegradation of urea. water balance as shown in fig.6, the water that entered the composting system by wastewater feeding was not in balance with the evaporated water over the entire period. during the first ten days the water evaporation was much higher than the rate of sprinkling of wastewater and the following ten days the sprinkled water rate was higher than the evaporated one, so the overall water balance was not kept stable during the process. it would be difficult to achieve a stable water balance, since there is a need for moisture control by using an on-line moisture probe, which is generally not available in practice. the stabilisation of the water and carbon balance is the main key for successful continuos carbon content ~ m ~ ~ ~ ~ m ~ ~ m ~ ~ ~-~-~nc\1 deys fig. 7 total solids, volatile matter and carbon content changes during composting isis fig.9 active bioreactor volume during composting co-composting process [7], and this was the main target duting the present process. at the end of the composting period, the system had consumed 263 m3 wastewater, which was equal to an average rate of 11.4 m3 day·1, corresponding finally to 2.9 kg wastewater per kg solid residue. these figures indicate that in order to treat the total amount of the wastewater that is produced in the plant (about 1200 m3 annually), four to five similar plants would be required or the plant must be used for successive batches of waste solids. carbon content and carbon balance fig. 7 shows the changes in total carbon content, of solids and liquid, during composting. the daily carbon dioxide that was produced during the composting was calculated by the following relation (ccoz)t == (c)t-i (c)t + cw.w. · cfw.wjt (2) where ( c c02) 1 is the total carbon content of coz produced at day t, kg; ( c)1_1 total carbon content of the bioreactor at a day before day t kg (data from fig.l) (c)r total carbon content of the bioreactor at day t, kg (data from fig.l); cww carbon content of wastewater, kg m· 3 (table i); cfww)r daily flow rate of wastewater at day t, m3 (data from fig.6). the carbon balance is shown in fig.8 and it was stable only between the 13th and 20th day of composting. a significant amount of the solid residue was consumed during the first ten days of the composting process as was observed by the reduction of the volume of the bulking material as shown in fig.9. the minimisation of residue consumption would be beneficial for the wastewater treatment process. 75 25 0~~~~==~~~~~~ l23456789dll~ekbbybhidz~~ devs fig.8 carbon balance during composting 35 800 • 30 700 25 600 500 ~ 20 400 ~ 15 300 10 200 100 10 15 20 25 days fig. i 0 ratio of carbon/nitrogen and carbon/phosphorous variation during composting carbon/nitrogen and carbon/phosphorous 63 as shown in fig. i 0 the c/n ratio steadily decreased due to the continuous urea inflow as well as wastewater feeding. the excess of nitrogen showed that the urea addition was not necessary. this could not be foreseen because it was not known at the beginning how much wastewater was going to be consumed during the process. the c/p ratio rapidly decreased during the first 10 days, when the vegetation water inflow was maximal and afterwards the ratio stabilised at about 80/1. conclusions the plant operated successfully with respect to the wastewater consumption without any hazardous effects to the enviromnent. furthermore, the general design of the plant as well as the selection and the quality of equipment were also successful. . . the short duration of the co-compostmg penod (23 days) with 263 m3 vegetation water consumption indicates that the total wastewater effluent from the particular factory (1200 m3 ) coul~ be treat~d in five similar successive phases of operatton. for th1s purpose, the content of the bioreactor, after the end of thermophilic operation, should be transferred out into a static pile for mesophilic stabilisation in order to start a new phase of thermophilic treatment. it should be stressed that the solid waste required to treat the volume of wastewater produced is sufficient due to the fact that the waste production rate from the olive oil mills is about 1 t of solids per 3 m3 of wastewater. the main issues, which require more investigation and optimisation, are given below: . " . the production of high temperatures (>60 c) during the first 9 days indicates apotential 64 wastewater loading increase, leading to possible efficiency improvement. thus the modification of eq. ( 1) might be advisable. the air feeding process was rather unsuccessful for cooling the bioreactor content at high temperatures. as previously reported the fans operation was controlled by temperature measurements which were taken at one spot of each bioreactor area every 20 minutes, which did not represent the mean area temperature. the optimum solution for this problem would be the instailation of additional temperature probes across the travelling bridge in order to obtain an accurate profile of the real temperature conditions. a possible explanation for the low cooling efficiency could be attributed to the non­ homogeneous air distribution in the bioreactor, due to the high solids concentration (formation of air pathway channels). the accumulation of nitrogen and the final high ph in the system indicates that an excess urea feed was provided. therefore, the application of a flexible and dynamic feeding control formula based on daily analyses is required. references 1. michelakis n. olive oil processing wastewaters managment. proceedings of futernational conference in olive oil processing wastewater treatment methods, hania, crete, greece, 1991 2. fiestas ros a.j.: reuse ·and complete treatment of vegetable water: current situation and prospects in spain. proceedings of international conference in olive oil processing wastewater treatment methods, hania, crete, greece, 1991 3. vlyssides a., loizidou m., bouranis d.l., and karvouni g.: journal, 1995, paper in preparation 4. marinos e.: lagooning concentration of olive oil processing wastewaters. proceedings of international conference in olive oil processing wastewater treatment methods, hania, crete, greece, 1991 5. boar! g., brunetti a., passino r. and rozzi a.: agricultural wastes, 1984, 10, 161-175 6. georgacakis d., kyritsis s., manios b. and vlyssides a.: economic optimization of energy production from olive oil wastewater. proceedings of the ltit. conference on energy from biomass, brescia, italy, 1986 7. vlyssides a., parlavantza m. and balis k.: co­ composting as a system for handling of liquid wastes from olive oil mills. proceedings of the futernational conference in composting, athens, greece, 1989 8. jewell j.w. and kabrick m.r.: j. w.p.c.f, 1980, 52, 3, 512-523 9. f!nstein m.s.: biocycle, 1980,2125-7 10. american public health association (apha), standard methods for the examination of water and wastewater, 17th edn, 1989 11. jackson m.l.: soil chemical analysis. prentice-hall inc., 1962 12. charman h.d. and pratt p.f.: methods of analysis for soils, plants and waters. univ. ofcallifornia, 1961) 13. higgins a.j., kaplovsky a.j. and hunter j.v.: j. w.p.c.f., 1982, 54, 5, 466-473 14. chang y. and hudson h.j.: trans.br.mycol.soc., 1967, 50(4) 649-666 15. kapetanios g.e., loizidou m. and valkanas g. bioresource technology, 1993, 44, 13-16 page 65 page 66 page 67 page 68 page 69 page 70 hungarian journal of industry and chemistry vol. 49(1) pp. 71–76 (2021) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2021-09 modelling of the pyrolysis zone of a downdraft gasification reactor márta kákonyi*1, ágnes bárkányi1, tibor chován1, and sándor németh1 1research centre for biochemical, environmental and chemical engineering, university of pannonia, egyetem u. 10, veszprém, 8200, hungary the increasing amount of municipal solid waste (msw) is a growing challenge that current waste-treatment practices are having to face. therefore, technologies that can prevent waste from ending up in landfill sites have come to the fore. one of the technologies that produces a valuable product from waste, namely synthesis gas, is gasification. the raw material of this technology is the so-called refuse-derived fuel, which is made from msw. three separate zones are located in downdraft gasification reactors: the pyrolysis, oxidation and reduction zones. this work is concerned with the determination of kinetic parameters in the pyrolysis zone. it also discusses the estimation of the product composition of this zone, which defines the raw material of the following zone. keywords: gasification, modelling, waste, refuse-derived fuel 1. introduction management of the increasing quantity of municipal solid waste (msw) is an ongoing issue. the majority of the waste ends up in landfill sites or is incinerated, leading to the emission of significant amounts of greenhouse gases. according to data from the european union’s eurostat database [1], the eu27 countries produce in excess of 200 million tons of waste. the amount disposed of is continuously being reduced by separating recyclable and biodegradable materials. although less and less waste is being dumped as landfill, landfill sites cannot accommodate waste being generated therefore, the quantity of waste ending up in landfill sites is not reducing significantly. in 2019 the eu member states deposited 24 mass % of waste in landfill sites; that quantity was 53 million tons. in hungary, this value was 51 mass %, namely 1.9 million tons (fig. 1). as the waste deposited in landfill sites decomposes, methane is formed and released into the atmosphere as a result of a reduction in its volume through cracks in the soil layer used to cover the landfill. the global warming potential of methane (ch4) is 25 times greater than that of carbon dioxide (co2) [2]. therefore, the development of technologies that can prevent waste from ending up in landfill sites and further reduce greenhouse gas emissions through carbon capture, utilization and storage is justified. one such technology is gasification. different types of gasification reactors are available, namely moving bed, fluidized-bed, entrained-flow, rotary *correspondence: kakonyi.marta@mk.uni-pannon.hu figure 1: generation of municipal solid waste and the amount deposited as landfill [1]. kiln and plasma gasifiers, which have been reviewed in ref.[3,4]. updraft and downdraft reactors are moving bed gasifiers. in the case of the former, the product gas travels in the opposite direction to the feedstock and leaves through the top of the reactor. since the amount of tar contained in the product gas is higher than in the case of downdraft reactors, where the gas and feedstock flow in the same direction, the temperature of the effluent gas is higher. in fluidized-bed gasifiers, a bed material is used for the purpose of heat transfer and the raw material, which is fed into the reactor from the bottom, as well as the bed material are fluidized by air. the product gas contains a higher proportion of particles. the raw material of entrained-flow reactors is powdered, it along with https://doi.org/10.33927/hjic-2021-09 mailto:kakonyi.marta@mk.uni-pannon.hu 72 kákonyi, bárkányi, chován, and németh air is fed into the reactor from the top. rotary kiln gasifiers rotate around their axes to ensure the solid and gas phases mixture. plasma reactors use copper or carbon electrodes and the raw material is decompozed down to the atomic level. downdraft reactors are the most suitable for low tar content with high carbon conversion, as well as high hydrogen (h2) and carbon monoxide (co) content of the product. its operating temperature and residence time meet the requirements of waste, namely its investment and operating costs are low. the feedstock of downdraft reactors is fed from above while the air feed enters through the side of the reactor at a height slightly higher than halfway up the gasifier and is evenly distributed inside. therefore, three separate zones can be formed. at the top, in an oxygen-deficient environment, is the pyrolysis zone, before air is introduced and the raw material partially burned in the oxidation zone to meet the energy demand of the endothermic reactions that take place in the other two zones. by proceeding along the length of the reactor, the reduction processes occur in the reduction zone after passing through the oxidation zone. once the gas has passed through the reduction zone, it is extracted and the slag falls to the bottom of the reactor. the aim of this work is to create a simple model that estimates the amount of gaseous components in the pyrolysis zone as a function of temperature based on the composition of the raw material and the amounts of the gases. furthermore, such a model can be integrated into a model of a more complex gasification reactor. to calculate the amounts of the gases, the kinetic parameters of the pyrolysis zone are required, which were identified. the output of this zone is the raw material for the following oxidation zone. 2. identification of pyrolysis kinetic parameters various models using mainly biomass and cellulose feedstocks have been developed over the years to describe the pyrolysis zone. some of them are suitable for molecular level studies, others are designed for particle-level studies and some are also applied to study equipment. hameed at al. have compiled a detailed overview of them [5]. since the pyrolysis zone is only one component of the reactor model, the less complex model referred to as the one-step kinetic model was chosen, which is written for the mass conversion as [6] dm dt = −km (1− y). (1) here, y is the conversion factor calculated by using the mass of raw material (min), current mass (mactual), and the mass of the solid residue (mfinal) as [7] y = min −mactual min −mfinal . (2) the rate constant of the reaction, k, is defined by the arrhenius equation k = ae −ea rt , (3) from which the unknown parameters a and ea/r can be determined. the amount of gas can be calculated from eq. 1. the parameters for cellulose and lignin (a mixture of paper, cardboard and wood)–hereinafter referred to as cellulose, plastic (a mixture of pe, pp and pet) as well as a 50−50 m% blend of cellulose and plastic were identified separately. the kinetic parameters (a and ea/r) of both kinds of raw materials were unknown. since the search space was smaller when identifying the parameters of pure raw materials, faster and more accurate results were achieved. the parameters were determined using the matlab r2019b program based on experimental data from the literature [8]. the effect of a catalyst on the decomposition of waste was investigated by thermogravimetry and mass spectrometry in a mass spectrometer. the inert atmosphere was composed of argon, while the masses of the samples were between 0.5 and 4 mg. results in the absence of a catalyst are studied in this work. the heating rate of measurements was 20 °c/min. the degradation of cellulose started at approximately 250 °c, while that of plastic commenced at around 400 °c (fig. 2). in order to focus on the portion of the curves where the changes in mass were larger as well as the measured and calculated values deviated more, the temperature range was narrowed from 60−700 °c to 142−552 °c for cellulose and to 369− 531 °c for plastic. the m% of the residue was read from the graph. a global extrema searcher, nomad, was used in matlab to identify the parameters. the differential equation (eq. 1) was solved using ode23s. the objective function to be minimized was the sum of the squares of the difference between the measured and calculated data for each temperature value: min(f) = ∑ t (m%measured-m%calculated) 2. (4) the identified parameters are shown in table 1. once the kinetic parameters of the pure fractions had been identified, the mixture was calculated using these values. the change in total weight is the sum of the change in weight of the cellulose (mc) and plastic (mp) (eq. 5). furthermore, the y-factor (eq. 2), the kinetic rate of the reaction (eq. 3) and the mass conversion (eq. 1) table 1: identified parameters ln(a) ea/r [k] correlation coefficient cellulose 16.83 13 540 0.915 plastic 55.3 43 502 0.765 hungarian journal of industry and chemistry modelling of the pyrolysis zone of a downdraft gasification reactor 73 figure 2: measured [8] and simulated results using the identified parameters: a) cellulose, b) plastic, c) cellulose and plastic 50− 50% mixture; o experimental curve , — fitted curve, — fitted curve with modified ea/r, — degradation start were calculated separately for both components: dm dt = dmc dt + dmp dt (5) the results of the calculation using the applied model are shown in fig. 2. the simulated decomposition curves of plastic (fig. 2a) and cellulose (fig. 2b) follow the experimental results well; the end of the curve deviates to a small extent caused by the decomposition of the lignin [9]. in the case of the mixture (fig. 2c), a higher deviation in excess of 400 °c was observed. the decomposition of the cellulose commenced earlier at 250 °c, while that of the plastic started at 400 °c. the degradation of the plastic component started later. although lignin begins to degrade at 400 °c, which may affect the decomposition of plastic [8,9], the difference was not significant, so the degradation of the lignin was not treated separately from that of the cellulose. since the component of the arrhenius equation corresponding to the activation energy depends on the temperature, the ea/r value had to be modified. from the arrhenius equation (eq. 3), the value of k was calculated along with the parameters before the kinetic parameters were recalculated by retaining the k value. the parameter ea/r of plastic changed, its new value was 44 500 k, the values of the other parameters remained unchanged as is presented in table 1. using this new ea/r number, the recalculated curve (depicted in orange) fitted better. based on the one-step kinetic model, the mass of gas formed in the pyrolysis zone can be calculated. the disadvantage of this model is that it cannot determine the composition of the gas nor the quantities of its components. in the oxidation zone, since the products from the pyrolysis zone are partially oxidized, it is also necessary to quantify each gaseous component. 3. composition of the gas pyrolysis gas consists of different components; the main components are carbon monoxide (co), hydrogen (h2), carbon dioxide (co2), methane (ch4), water (h2o), and tar. the exact molecular formula of tar is unknown, its formula is represented as cahboc. an extrema search was used to determine its composition. 3.1 composition of refuse-derived fuel some waste-treatment plants include mechanical biological treatment plants that produce refuse-derived fuel (rdf) by filtering out and grinding msw. in such plants, glass, metal as well as inert and biodegradable materials are removed, msw is dried whilst being grinded and finally 3 % of its original weight will be equal to the mass of the rdf. as the raw material of the reactor is rdf, the results of studies into the composition of rdf were collected and averaged table 2. [10, 11] 3.2 objective function and constraints based on the composition, the constraints required for the extrema search can be determined. the total masses (mj) of each element, namely c, o, h, cl, s, and n, were determined from eq. 6. the mass of the impurities (mcl, ms and mn) was subtracted from the total gas mass (mgas). the extrema finder searches for the minimum of the objective function, which is the absolute value of the 49(1) pp. 71–76 (2021) 74 kákonyi, bárkányi, chován, and németh table 2: average rdf composition proximate analysis [m%] moisture content 17.55 ash 12.3 volatile matter 63.18 fixed carbon 6.97 ultimate analysis of the dry basis [m%] c 40.83 h 5.36 o 37.08 n 1.18 s 0.29 cl 0.34 ash 14.92 difference between the total mass of the gas and the sum of the mass of each gaseous component according to eq. 7, where ni denotes the moles of gaseous compounds and mi represents the molecular weight. mj = mgas (m%)j 100 (6) min(f) = abs ( mgas−(mcl+ms+mn)− ∑ i mini ) (7) the total weight of each element should be equal to the sum of the weight of the same element in each compound. due to the strength of the constraints, only a minimal error is permissible. the nonlinear constraints are 0.01 ≥ abs [mc−mc(nco+nch4 +nco2 +antar)] mc (8) 0.01 ≥ abs [mo−mo(nco+2nco2+nh2o+cntar)] mo (9) 0.01 ≥ abs [mh−mh(4nch4 +2nh2o+2nh2 +bntar)] mh (10) the limits of the parameters a, b, and c are determined based on the measurement of the tar composition [12,13]. the constraints of these parameters are 12 > a > 6; 24 > b > 6; 6 > c > 0 (11) empirical relationships [14, 15] were applied to the mass ratios of co to co2, and ch4 to co2, which are temperature-dependent: yco/co2 = exp ( 1.8447896+ 7 730 313 t + 5019 898 t ) (12) table 3: lower and upper limits limit co2 h2o h2 cahboc a b c lower [m%] 10 0 0.4 40 9 10 4 upper [m%] 25 10 0.7 95 11 20 6 ych4/co2 = 5× 10−16t 5.06 (13) by measuring the composition of the pyrolysis gas [8,16], the lower and upper limits were determined for the mass percent of components (table 3). the m% limits were calculated from 0 ≥ m%lower 100 − ni mi mgas − (mcl +ms +mn) (14) 0 ≥ ni mi mgas − (mcl +ms +mn) − m%upper 100 (15) using the kinetic parameters identified in the previous section, the batch pyrolysis was simulated for 250 kg of raw material with a moisture content of 17.55 % as well as plastic and cellulose fractions of 50 − 50 %. during the process, the composition of the gas was calculated as a function of temperature based on the aforementioned equations. the heating rate which was used during identification was 20 °c/min. the dry raw material was taken into account in the calculation. to reduce the calculation time, the composition was estimated every 20 s so the total simulation time was 3600 s. in each step, the starting point of the extrema search was the result of the calculation during the previous step. the results of the simulation are shown in fig. 3 and table 4. above 500 °c, the tar began to decompose and the amount of co increased compared to that of co2. 4. conclusions the aim of this work was to develop a relatively simple model of the pyrolysis zone of a downdraft gasification reactor to estimate its kinetic parameters and based on these propose a methodology to determine the amount of gaseous components generated. the kinetic parameters of the pyrolysis zone were determined by an extrema finder and the calculated values fit well with the experimental results found in the literature. with the help of the proposed model, the kinetic parameters can be identified for any new raw material and heating rate. the method applied to determine the composition of gaseous components is suitable for estimating the quantity of components as a function of temperature based on the elemental composition of the raw material. the one-step kinetic model using a simple calculation of the gas composition can be easily applied to describe the pyrolysis zone of the rdf gasification reactor and even integrated into a more complex model of a gasification system because of the low computational capacity required. hungarian journal of industry and chemistry modelling of the pyrolysis zone of a downdraft gasification reactor 75 figure 3: evolution of molar quantity a) and weight percentage b) as a function of temperature table 4: gas composition as a function of temperature temperature [°c] 200 300 400 500 600 700 molar quantity [mol] co2 0 29.2 266.1 406.5 386.5 390.2 co 0 1.2 98.9 499.7 927.7 1361.5 ch4 0 3.6 74.7 229.9 404.6 707.1 h2o 0 21.2 157 499.8 696.8 804.4 h2 0 14 132 304.2 340.3 349.6 tar 0 23.6 211 483.1 489.8 387.1 a 0 9.1 9.2 9 9 9.5 b 0 17.3 18.2 17.3 17.3 18.2 c 0 5.6 5.9 6 5.9 6 mass [m%] co2 0 18.6 17.8 11.8 10 10.1 co 0 0.5 4.2 9.2 15.3 22.4 ch4 0 0.8 1.8 2.4 3.8 6.7 h2o 0 5.5 4.3 5.9 7.4 8.5 h2 0 0.4 0.4 0.4 0.4 0.4 tar 0 74.2 71.5 70.3 63.1 51.9 5. acknowledgements this work was supported by the tkp2020-nka-10 project financed under the 2020-4.1.1-tkp2020 thematic excellence programme by the national research, development and innovation fund of hungary. references [1] eustat-municipal waste by waste management, date of save: 2021. 04. 07. https://ec.europa.eu/eurostat [2] ipcc: fourth assessment report, 2006 [3] molino, a.; chianese, s.; musmarra, d.: biomass gasification technology: the state of the art overview, j. energy chem., 2016, 25(1), 10–25 doi: 10.1016/j.jechem.2015.11.005 [4] kumar, a.; jones, d.d.; hanna, m.a.: thermochemical biomass gasification: a review of the current status of the technology, energies, 2009, 2(3), 556–581 doi: 10.3390/en20300556 [5] hameed, s.; sharma, a.; pareek, v.; wu, h.; yu, y.: a review on biomass pyrolysis models: kinetic, network and mechanistic models, biomass bioenerg., 2019, 123, 104–122 doi: 10.1016/j.biombioe.2019.02.008 [6] varhegyi, g.; jakab, e.; antal jr, m.j.: is the broido-shafizadeh model for cellulose pyrolysis true?, energy fuels, 1994, 8(6), 1345–1352 doi: 10.1021/ef00048a025 [7] faravelli, t.; frassoldati, a.; hemings, e.b.; ranzi, e.: multistep kinetic model of biomass pyrolysis, in cleaner combustion, 2013, 111–139, http://link.springer.com [8] sebestyén, z.; barta-rajnai, e.; bozi, j.; blazsó, m.; jakab, e.; miskolczi, n.; sója, j.; czégény, z.: thermo-catalytic pyrolysis of biomass and plastic mixtures using hzsm-5, appl. energy, 2017, 207, 114–122 doi: 10.1016/j.apenergy.2017.06.032 [9] grammelis, p.; basinas, p.; malliopoulou, a.; sakellaropoulos, g.: pyrolysis kinetics and combustion characteristics of waste recovered fuels, fuel, 2009, 88(1), 195–205 doi: 10.1016/j.fuel.2008.02.002 [10] vounatsos, p.; atsonios, k.; itskos, g.; agraniotis, m.; grammelis, p.; kakaras, e.: classification 49(1) pp. 71–76 (2021) https://ec.europa.eu/eurostat/databrowser/view/env_wasmun/default/table?lang=en. https://doi.org/10.1016/j.jechem.2015.11.005 https://doi.org/10.1016/j.jechem.2015.11.005 https://doi.org/10.3390/en20300556 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gasification (htag) of plastic containing waste, fuel process. technol., 2006, 87(3), 223–233 doi: 10.1016/j.fuproc.2005.08.002 [14] salem, a.m.; paul, m.c.: an integrated kinetic model for downdraft gasifier based on a novel approach that optimises the reduction zone of gasifier, biomass bioenerg., 2018, 109, 172–181 doi: 10.1016/j.biombioe.2017.12.030 [15] sharma, a.k.: modeling and simulation of a downdraft biomass gasifier 1. model development and validation, energy convers. manag., 2011, 52(2), 1386–1396 doi: 10.1016/j.enconman.2010.10.001 [16] efika, e.c.; onwudili, j.a.; williams, p.t.: products from the high temperature pyrolysis of rdf at slow and rapid heating rates, j. anal. appl. pyrolysis, 2015, 112, 14–22 doi: 10.1016/j.jaap.2015.01.004 hungarian journal of industry and chemistry https://doi.org/10.1007/s12649-016-9520-6 https://phyllis.nl/browse/standard/ecn-phyllis#rdf https://doi.org/10.1021/ef300031j https://doi.org/10.1016/j.fuproc.2005.08.002 https://doi.org/10.1016/j.biombioe.2017.12.030 https://doi.org/10.1016/j.biombioe.2017.12.030 https://doi.org/10.1016/j.enconman.2010.10.001 https://doi.org/10.1016/j.jaap.2015.01.004 introduction identification of pyrolysis kinetic parameters composition of the gas composition of refuse-derived fuel objective function and constraints conclusions acknowledgements hungarian journal of industry and chemistry vol. 53(2) pp. 61–71 (2025) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2025-19 degradation of pharmaceuticals from simulated and real hospital wastewater applying the conventional fenton process: optimization conditions and application foffié thiery auguste appia1 and lassiné ouattara1* 1 laboratoire de constitution et réaction de la matière, ufr ssmt, université félix houphouëtboigny de cocody-abidjan, 22 bp 582 abidjan 22, cote d’ivoire this study investigated the treatment of simulated and real hospital wastewater spiked with amoxicillin (amx), ceftriaxone (ctx), and/or telebrix (tlx) using the fenton process. first, the optimal treatment conditions were determined on simulated wastewater by varying the initial concentration of amx, the h₂o₂/fe²⁺ ratio (k), and the initial ph. subsequently, the effects of inorganic ions (cl⁻, no₃⁻, so₄²⁻ and po₄³⁻), considered both individually and in combination, as well as temperature and the different pharmaceutical compounds, were evaluated under the established optimal conditions. finally, experiments were performed on real hospital wastewater. chemical oxygen demand (cod) and spectrophotometric analysis (used to monitor amx concentration) were employed to assess treatment performance. the results showed that the optimal conditions for the fenton process were: 0.5 mm amx, k = 2, and ph 3. the process does not degrade all pharmaceutical compounds with the same efficiency, and its performance decreases at high temperatures and in the presence of inorganic ions. moreover, the fenton process exhibited limited efficiency (37.05% cod removal) when applied to real hospital wastewater due to its high inorganic ion content. however, the successive addition of fenton’s reagent significantly improved cod removal, reaching 88.96% in real wastewater. keywords: fenton process, pharmaceuticals, hospital wastewater, iron, advanced oxidation process 1. introduction the issue of discharging untreated hospital wastewater into nature is a real concern in côte d'ivoire. indeed, most hospitals do not have a functional wastewater treatment plant. this is the case at the treichville university teaching hospital (tht) in abidjan, whose wastewater treatment plant, which was supposed to treat its wastewater, has not been operational since 1975. since then, its effluent has been directly and continuously discharged into ebrié lagoon. it should be noted that fishing, bathing and transportation activities take place there, not to mention the presence of residential areas nearby, thereby endangering both aquatic and human life. according to investigations conducted by sadia et al., wastewater produced at tht contains some inorganic ions such as chlorides, nitrates and phosphates [1]. this survey also revealed that amoxicillin (amx), ceftriaxone (ctx) and telebrix (tlx) were commonly prescribed for inpatients or imaging purposes in this hospital. amx and ctx are antibiotics in the penicillin and cephalosporin families, respectively. tlx is an iodinated contrast medium used for radiological examinations. not all three drugs are biodegradable organic compounds. received: 28 june 2025; revised: 30 july 2025; accepted: 8 aug 2025 *correspondence: ouatlassine@yahoo.fr the majority of antibiotics administered orally to patients are only partially metabolized, while the remaining 25-75% are released from the body into the environment [2],[3]. the continuous and direct discharge of hospital wastewater, which may contain pharmaceuticals, could pose a real risk to aquatic ecosystems and human health. numerous studies have shown the presence of pharmaceuticals such as antibiotics in soil, urban wastewater, groundwater and surface water at very low concentrations [4]-[7]. the persistence of antibiotics such as amx and their residues in ecosystems can lead to drug allergies and toxicological problems [8] as well as the development of antibiotic-resistant bacteria [9],[10]. due to the potential adverse effects of pharmaceuticals on the human body and natural life, it is important to develop effective methods to remove them from contaminated water. conventional wastewater treatment processes, such as biological processes or adsorption, have proven to be ineffective regarding the removal of most pharmaceutical compounds that are not readily biodegradable. in this context, advanced oxidation processes offer an alternative. these processes are based on the in-situ generation of powerful reactive species, in this case, https://doi.org/10.33927/hjic-2025-19 mailto:ouatlassine@yahoo.fr appia and ouattara hungarian journal of industry and chemistry 62 hydroxyl radicals, which are essential for degrading and mineralizing organic compounds. several advanced oxidation processes (aops) exist, including the processes anodic oxidation [11], sono-fenton [12], fenton-like [13], electro-fenton [14],[15], ozonation [16], photo-fenton [17] and fenton [18]-[20]. the classical fenton process involves reactions between fe2+ and h2o2 to produce hydroxyl radicals. the efficiency of the fenton process is strongly dependent on several parameters, including the concentration of h2o2 and fe2+, the molar ratio of h2o2 to fe2+, the properties of the organic matter and the ph of the solution [2, 21-22]. the application of the fenton process for the degradation of organic compounds has been widely researched. for example, li et al. studied the treatment of simulated pharmaceutical wastewater containing nbutanol, ethyl p-nitrobenzoate, 4,7-dichloroquinoline and ethyl acetoacetate by the fenton process [23]. the operational parameters investigated were the initial ph, the molar ratio of h2o2 to fe2+ and h2o2 dosage. their work revealed that, under optimal degradation conditions (initial ph = 2.5, [h2o2]/[fe2+] = 20, h2o2 = 0.6q, where q is the theoretical dosage of the fenton’s reagent, and reaction time = 30 mins), the fenton process was able to remove all the pollutants studied at different rates of efficiency. the highest degradation rate (100%) was obtained with 4,7-dichloroquinoline and the lowest (56%) with n-butanol. similarly, sönmez et al. showed that the optimal concentrations of fenton’s reagent (h2o2 and fe2+) for degradation depend on the organic compounds present [24]. thus, 0.6 mg/l h2o2 and 6-8 mg/l fe2+ are required to completely degrade carbamazepine. for caffeine and paracetamol, higher concentrations are needed to achieve a 100% degradation rate (7.5 mg/l h2o2 and 6 mg/l fe2+ for caffeine compared to 5 mg/l h2o2 and 10 mg/l fe2+ for paracetamol). furthermore, li et al. reported that pharmaceutical species such as acetaminophen, atenolol, carbamazepine, metoprolol, dilantin, diclofenac, pentoxifylline, oxybenzone, caffeine, fluoxetine, gemfibrozil, ibuprofen, naproxen, propranolol, sulfamethoxazole, bisphenol a and trimethoprim were completely degraded by the fenton process at a concentration of 20 mg/l fe2+ and a h2o2 to fe2+ molar ratio of 2.5 [25]. the optimal experimental conditions for the treatment of cosmetic wastewater from car care products determined by cüce and temel are ph 3, concentrations of 300 mg/l fe2+ and 1050 mg/l h2o2 as well as a [h2o2]/[fe2+] molar ratio of 600/300 [26]. the objective of this work was to investigate the efficiency of the fenton process regarding the degradation of pharmaceutical compounds (amx, ctx, and tlx) contained in simulated and real hospital wastewater. the first step involved investigating amoxicillin-doped simulated wastewater to determine the optimal conditions for degradation by optimizing operational parameters such as the concentration of the compound, the [h2o2]/[fe2+] molar ratio and the initial ph of the solution. these optimal conditions were subsequently applied for the degradation of ctx and tlx as well as for the study of the effects of inorganic ions (kcl, kno3, k2so4 and k2hpo4) and the temperature. in the last step, the physicochemical parameters of real hospital wastewater collected at tht were evaluated before being treated under the optimal operational conditions determined for the simulated wastewater. to the best of our knowledge, such a research study has yet to be conducted. this work intends to provide a green and efficient method for the treatment of hospital wastewater. 2. experimental 2.1. reagents amx, ctx and tlx were manufactured by baillycreat, ldp torlan and guerbet, respectively, as well as purchased from pharmacies in the city of abidjan. potassium hydrogen phosphate (k2hpo4), iron(ii) sulfate heptahydrate (feso4*7h2o), potassium sulfate (k2so4) and potassium nitrate (kno3) were obtained from merck. sodium hydroxide (naoh) and hydrogen peroxide (h2o2) were obtained from panreac and scharlau, respectively, while sulfuric acid (h2so4) and potassium chloride (kcl) were obtained from sigmaaldrich. potassium permanganate (kmno4) was purchased from fluka. all the chemicals, except for the pharmaceutical compounds, were of analytical grade. the different solutions were prepared in ultrapure distilled water. 2.2. experimental procedure a 500 ml solution containing the drug was prepared before each experiment in distilled water. in addition, the initial ph of the solution was adjusted to the desired value using 1 m naoh and h2so4. the wastewater treatment experiments were conducted in a 600 ml beaker used as a reactor at room temperature for a duration of 60 mins. the appropriate amounts of feso4*7h2o were added to the reaction medium. the resulting mixture was magnetically stirred to ensure the dissolution of the iron sulfate and homogenization of the solution. finally, hydrogen peroxide was introduced to the reaction mixture to initiate the degradation process. to complex the residual iron and stop the reaction, the collected samples (10 ml) at defined time intervals were added to a beaker containing 1 ml of 1 m naoh. the samples were filtered 3 times with an ordinary filter 250 mm in diameter (lab filter) and placed in a water bath heated to 45°c for 10 minutes to remove the residual amount. the experimental setup is shown in figure 1. 2.3. determination of the cl-, no3 and po4 3 concentrations as well as total suspended solids nitrate and phosphate ion concentrations were determined using nitraver 5 and phosver 3 powders, respectively, as well as measured with a dr6000 uv-vis spectrophotometer at wavelengths of 500 and 800 nm, degradation of pharmaceuticals from hospital wastewater 53(2) pp. 61–71 (2025) 63 respectively, as described by sadia et al. [1]. total suspended solids (tss) were determined by weighing a filter containing total suspended solids having been heated for one hour at 105°c. the chloride content was determined volumetrically by mohr's method in the presence of silver nitrate. the real wastewater was taken from treichville university teaching hospital. 2.4. analytical methods the chemical oxygen demand (cod), a global parameter which corresponds to the amount of oxygen consumed for the complete oxidation of the organic matter and some oxidizable inorganic compounds contained in the sample analyzed, was then determined. during the experiments, 2 ml of the samples were taken at welldefined time intervals and placed in pre-dosed hach tubes which were then heated in a digester at 150 °c for 120 minutes. after cooling, the cod value was read directly using a dr6000 uv-vis spectrophotometer. the cod reduction rate was determined using this formula: ∆(𝐶𝑂𝐷) = 𝐶𝑂𝐷0−𝐶𝑂𝐷𝑡 𝐶𝑂𝐷0 𝑥100 (1), where cod0 and codt denote the initial and final cod (mg o2/l), respectively. the normalized cod (cod*) was calculated as follows: 𝐶𝑂𝐷∗ = 𝐶𝑂𝐷𝑡 𝐶𝑂𝐷0 (2). the change in the hydrogen peroxide concentration was monitored during the experiments by dosing a beaker containing 5 ml of both the sample and h2so4 (1 m) with 0.01 m kmno4 according to the following equation: 2kmno4+3h2so4+5h2o2→ k2so4+2mnso4 + +5o2+8h2o (3). equilibrium was reached when the solution turned a persistent pale pink color [27]. 3. results and discussion in this section, the initial concentration of amoxicillin, [h2o2]/[fe2+] ratio and ph will be investigated in order to identify the optimum treatment conditions which will then be applied. 3.1. determination of the optimal conditions 3.1.1. effect of the initial concentration of amx the effect of the amx concentration on the performance of the fenton process was evaluated at concentrations ranging from 0.395 to 2.37 mm at ph 3 and with a h2o2 to fe2+ molar ratio of 2 ([h2o2] = 60 mm and [fe2+] = 30 mm) over a reaction time of 60 minutes. in figure 2a, all the curves display two distinct parts, namely a very rapid decrease in cod during the first 10 minutes followed by a very slow phase during which the degradation rate of the organic compound remains almost constant over the last 50 minutes of the experiment. in fact, according to lu et al. [28], the first stage is called the fe2+/h2o2 stage when ferrous ions react rapidly with hydrogen peroxide to form hydroxyl radicals which in turn rapidly oxidize the pharmaceutical substance as described by the following equation: fe2++h2o2→fe3++∙oh+ho (4). equation 4 yields a rate constant between 63 and 76 m-1s-1. in the slow stage, the ferric ions produced in the first stage can react with hydrogen peroxide to produce hydroperoxyl radicals (ho2 .) and regenerate ferrous ions: fe3++h2o2→fe2++ho2∙+h+ (5). the reaction in equation 5 occurs with a kinetic constant of 0.01-0.02 m-1s-1 which is much lower than that of equation 4. since the formed hydroperoxyl radicals have a very low oxidation capacity compared to that of hydroxyl radicals, degradation in the second step, referred to as fe3+/h2o2, is very slow [28]. moreover, the degradation rate decreases as the concentration of amx increases possibly due to the formation of reactive intermediates that may compete with the parent compound [29]. in addition, the formation of complexes in the reaction medium as the concentration of the organic compound increases and/or the formation of hydroxyl radicals is limited can also explain the decrease in the cod removal rate as the amx concentration increases. figure 2b shows the time-dependent change in hydrogen peroxide concentration during amx degradation, with initial amx concentrations of 0.395 and 2 mm and 60 mm initial h2o2 concentration. as shown in the figure, the h2o2 concentration decreased very rapidly during the first 10 minutes and then remained nearly constant for the rest of the reaction time. this finding is consistent with the observations presented in figure 2a. furthermore, at the same initial h2o2 concentration, more than 97.5% of the h2o2 was consumed in the 0.395 mm amx system, whereas only 90% was consumed in the 2 mm system after 10 minutes figure 1: experimental setup of the fenton process banté ph meter magnetic stirrer beaker containing the solution covered with aluminum foil appia and ouattara hungarian journal of industry and chemistry 64 of reaction, indicating that an increase in the initial concentration of amx results in an increase in the degradation time. according to figure 2c, the cod removal rates determined after 60 mins were 71.72, 78.86, 74.16, 67.42, 56.85 and 53.15% for amx concentrations of 0.395, 0.500, 1.05, 1.58, 2.00 and 2.37 mm, respectively. the highest degradation efficiency was achieved at 0.500 mm amx. 3.1.2. effect of the h2o2 to fe2+ molar ratio the molar ratio of fenton's reagent (k = [h2o2]/[fe2+]) is one of the parameters that significantly influences how efficient the fenton process is. to determine the optimal ratio, the fe2+ concentration was maintained at 30 mm, while the h2o2 concentration was adjusted between 30 to 300 mm, yielding ratios ranging from 1 and 10. the experimental conditions were set as follows: amx concentration of 0.500 mm; ph 3 and treatment duration of 60 minutes. the degradation efficiency of amoxicillin by the fenton process depends on the [h2o2]/[fe2+] molar ratio as indicated in figure 3. the cod removal rate increased from 59.13 to 78.86% when the [h2o2]/[fe2+] molar ratio increased from 1 to 2, respectively. increasing the molar ratio, that is, the increase in the h2o2 concentration, led to an improvement in the degradation efficiency of amx. on the other hand, a very high concentration of h2o2 (k>2) inhibited the fenton process with regard to the degradation of the model organic compound. when the molar ratio of fenton’s reagent was less than 2, the amount of hydroxyl radicals generated was insufficient to effectively degrade the pharmaceutical compound due to the low amount of h2o2. in contrast, when the molar ratio was greater than 2, an excess of h2o2 could occur, resulting in a generation of a large amount of hydroxyl radicals, thereby triggering competing side reactions that diminish the efficiency of amx degradation. according to our results, the best cod removal rate was obtained when [h2o2]/[fe2+] was 2, which is practically the same as the value in the literature. this is the case for dehghani et al. [30], who found a [h2o2]/[fe2+] molar ratio of 1.5 for the degradation of sulfonamide by the fenton process. similarly, li et al. reported an optimum value of 1.5 for the degradation of pharmaceutical species [25]. cüce and temel reported a [h2o2]/[fe2+] molar ratio of 2, namely 600/300 [26]. in accordance with the literature, the concentrations of iron and hydrogen peroxide are important parameters in the fenton process [30]. an excessive or insufficient amount of either reagent can significantly reduce the efficiency of the process. studies have shown that for figure 2: a) the effect of the amx concentration on the degradation process by the fenton process at ph 3 in a stirred solution of [fe2+]=30 mm and [h2o2]=60 mm at t=25 °c; b) the evolution of the remaining h2o2 concentration during the amx degradation process by the fenton process; c) cod abatement rate at different concentrations of amx after a reaction time of 60 mins figure 3: cod removal rates for different molar ratios of reagents after a reaction time of 60 minutes with 0.500 mm amoxicillin at ph 3 degradation of pharmaceuticals from hospital wastewater 53(2) pp. 61–71 (2025) 65 [h2o2]/[fe2+] ratios greater than 10, an excess of hydrogen peroxide in the solution can lead to the scavenging of hydroxyl radicals according to the following equation [31]: h2o2+∙oh→h2o+∙ho2 (6), and recombination of such radicals to form h2o2 according to the equation below [32]: ∙oh+∙oh→h2o2 (7). these generated species are less reactive than hydroxyl radicals. 3.1.3. effect of the initial ph of the solution the fenton process is strongly dependent on ph, which plays an important role in the mechanism of hydroxyl radical production. in order to determine the optimum ph, five acidic ph values (1.7, 2.0, 3.0, 3.5 and 4.0) were investigated using 0.500 mm amoxicillin, a [h2o2]/[fe2+] molar ratio of 2 and an experimentation duration of 60 mins. numerous studies have indicated that the optimum initial ph is between 2.5 and 4.0 to achieve the best degradation rates of organic compounds [26]. as shown in figure 4a, the degradation rate of amx remained consistent at all initial ph values during the first 10 mins of the experiment. the cod removal rates determined after 60 mins of treatment (figure 4b) increased from 64.72 to 78.86% as the ph increased from 1.7 to 3.0. beyond ph 3, a decrease in the efficiency of the fenton process for the amx treatment was observed, since the rates obtained were lower than those obtained at ph 3 (64.98 and 55.23% at ph 3.5 and 4.0, respectively). the best degradation rate was therefore obtained at an initial ph of 3.0. other authors have also reported the same optimum ph for the degradation of organic compounds [23],[24]. in fact, the ph of the solution is a very sensitive parameter in the fenton process as it governs the formation of hydroxyl radicals, the main oxidative species of organic compounds, in the reaction medium. thus, at high phs (ph˃4), hydroxyl radicals are generated very slowly due to the formation of hydroxoferric complexes and the precipitation of ferric oxyhydroxide (fe(oh)3) [33],[34]. furthermore, h2o2 easily decomposes into o2 and h2o [35]: 2h2o2→02+2h2o (8). when the ph is very acidic (ph˂2), the degradation rate of organic compounds decreases due to the formation of [fe(h2o)6]2+ complex [33],[34], which react more slowly with peroxide than the [fe(oh)(h2o)5]2+ complex, that are formed at ph values between 2 and 3 [33],[34]. in addition, peroxide reacts with h+ protons to form an hydroxyoxidanium ion (h3o2 +), which is very stable and therefore not highly reactive with fe2+ [36]: h2o2+h+→h3o2 + (9). furthermore, excess h+ can react with hydroxyl radicals to form h2o [23]: h++∙oh+e-→h2o (10). under the present experimental conditions, the optimal operating parameters for maximum degradation of amoxicillin were determined to be an amx concentration of 0.500 mm, a ph value of 3, and a molar ratio of [h2o2]/[fe2+] = 2. the influence of inorganic ions, temperature and pharmaceuticals on the efficacy of this technology under the previously determined optimum conditions will be further investigated. next, these optimum conditions will be applied to the treatment of real hospital wastewater. 3.2. investigations under optimal conditions 3.2.1. influence of inorganic ions the influence of chloride, sulfate, nitrate and phosphate ions was investigated during the degradation of amoxicillin (0.500 mm) by the fenton process. the evolution of the cod removal rate as a function of the inorganic ion concentration (200 mm) is displayed in figure 5. the presence of inorganic ions in the reaction medium appeared to have a detrimental effect on the performance of the conventional fenton process. the observation was the same whether a single type of ion or all ions are present simultaneously in the reaction medium. indeed, the degradation rate of amx in the absence of inorganic ions was much higher than that in the presence of inorganic ions. the cod removal rates obtained in the presence of 200 mm cl-, no3 -, so4 2and figure 4: a) the effect of ph on the change in the amx degradation rate as a function of time with a molar ratio of k=2, [amx]=0.500 mm; t=60 mins; b) cod abatement rate at different phs after 60 mins of amoxicillin treatment and a molar ratio of k=2 appia and ouattara hungarian journal of industry and chemistry 66 po4 3were 67.72, 51.31, 50.18 and 46.85%, respectively. the performance of the fenton process decreased further when all the inorganic ions were present in the reaction medium simultaneously. the abatement rate obtained after a reaction time of 60 minutes under these conditions was 44.59%. regarding the results obtained, inorganic ions strongly slow down the degradation rate of amx in the following order of an increasingly negative effect: cl˂ no3 ˂ so4 2˂ po4 3-. de oliveira et al. also showed that sulfate ions inhibited the oxidation of caffeine by the fenton process more than chloride ions [37]. several studies were carried out with different concentrations of inorganic ions (table 1). the results confirmed inhibition of the fenton process by inorganic ions at all concentrations studied. research has shown that the fenton process is very sensitive to inorganic ions present in solution [38]. these ions can form complexes with fe(ii): fe2++cl-→fecl+ (11), fe2++so4 2-→feso4 (12), fe2++h2po4 →feh2po4 + (13), fe2++no3 →feno3 + (14), thereby affecting the distribution and reactivity of free fe2+ ions. the formation of inorganic complexes leads to a reduction in the production of hydroxyl radicals as fe2+ ions are no longer available to react with h2o2. the presence of cl-, no3 -, so4 2and po4 3promotes competition between organic matter and hydroxyl radicals, delaying the oxidation of amoxicillin. inorganic ions react with hydroxyl radicals, leading to the generation of inorganic radicals with less potent oxidizing powers than hydroxyl radicals: cl-+∙oh→cloh∙ k = 4.30x109 lmol-1s-1 (15), hso4 +∙oh→so4 ∙ k = 1.40x107 lmol-1s-1 (16). 3.2.2. the effect of temperature on the degradation of amx temperature is an important parameter in determining the kinetics of the fenton reaction. indeed, according to many studies, increasing the temperature accelerates the rate of consumption of h2o2, indicating better decomposition of h2o2 into iron-catalyzed radicals as the temperature increases. this process improves the percentage of degradation of organic compounds [39]. however, when the temperature surpasses its optimum, the performance of the fenton reaction diminishes because an elevated temperature favors the decomposition of h2o2 into o2 and h2o. the literature presents varying views on the optimal temperature. lin et al. reported that the optimum temperature for the degradation of phenol was 30 °c [40], while guo et al. established in their study that 40 °c yielded the best results for the degradation of amoxicillin [41]. above this temperature, a decrease in the rate of organic degradation was observed. conversely, homem et al. reported that the degradation rate of amoxicillin increased as the temperature increased progressively within the 22-57°c range [20]. figure 5: the effect of inorganic ions on the amx degradation rate as a function of time when ph=3, k=2, [amx]=0.500 mm, [no3 -]=[cl-]=[so4 2-]=[po4 3-]=200 mg/l and t=60 mins figure 6: the effect of temperature on the degradation of amoxicillin at ph 3, [amx]=0.500 mm and k=2 table 1: the effect of inorganic ions on the cod removal rate inorganic ions concentration (mg/l) cod removal ratio (%) no3 10 64.63 74 54.92 cl 13 60.00 35 62.54 70 52.99 so4 2 10 56.83 35 54.55 71 47.01 po4 3 10 44.53 35 48.66 degradation of pharmaceuticals from hospital wastewater 53(2) pp. 61–71 (2025) 67 in this work, the effect of temperature on the degradation of amx was investigated under the optimum conditions defined above. the cod removal rates calculated at four different temperatures (25, 40, 50 and 60 °c) are presented in figure 6, which demonstrates that the cod removal rate declines with increasing temperature. the rates obtained are 78.86, 72.06, 65.07 and 64.31% at 25, 40, 50 and 60 °c, respectively. under our experimental conditions, an increase in temperature has a detrimental effect on the degradation of the pharmaceutical compound. 3.2.3. degradation of pharmaceutical compounds the pharmaceutical compounds amx, ctx and tlx were oxidized by the fenton process under the optimum conditions obtained in the simulated wastewater. the degradation rates of the pharmaceuticals as a function of the reaction time are shown in figure 7a. the results indicate that the fenton process does not degrade pharmaceutical compounds at the same rate. for instance, at an identical concentration, namely [amx] = [ctx] = [tlx] = 0.500 mm, the fenton process achieves fast degradation of amoxicillin (blue line) compared to ceftriaxone (orange line) or telebrix (grey line). the difference in the degradation efficiency is probably related to the molecular structures of the target compound and steric hindrance effects, which may impede the accessibility of certain functional groups to hydroxyl radical attack. in addition, the fenton reaction is further slowed down when the compounds are simultaneously present (yellow line) in the reaction medium. furthermore, the degradation of pharmaceutical antibiotic compounds (amx and ctx) is more favorable than that of the iodinated contrast product (tlx). for example, li et al. reported differences in the reactivity of fenton’s reagent with regard to the degradation of the compounds n-butanol, ethyl pnitrobenzoate, 4,7-dichloroquinoline and ethyl acetoacetate [23]. the cod removal efficiencies of each pharmaceutical compound as a function of the initial concentration (0.500 and 1.00 mm) is displayed in figure 7b. the results reveal that organic compound degradation rates decline with increasing initial concentration. for amoxicillin, the degradation rate ranged from 78.86 to 74.16% when its concentration varied between 0.500 and 1.00 mm, respectively (blue line). for ceftriaxone, the degradation rate ranged from 38.46 to 30.65% when its concentration varied between 0.500 and 1.00 mm, respectively (orange line). for telebrix, the cod removal rate ranged from 25.68 to 15.01% when its concentration varied between 0.500 and 1.00 mm, respectively (grey line). 3.3. application to the treatment of real hospital wastewater physico-chemical parameters of real wastewater from tht were determined and recorded in table 2. the analysis of this wastewater revealed the presence of inorganic ions such as no3 (1.11 mg/l), po4 3 (1.26 mg/l) and cl(29.33 mg/l). the chloride ion concentration was 23.28-fold higher than that of phosphate ions and 26.42-fold higher than that of nitrate ions. figure 7: a) change in the normalized cod removal rate when [amx]=[ctx]=[tlx]=0.500 mm and when amx, ctx and tlx are simultaneously present, ph=3, k=2, t=60 mins; b) cod abatement rate of different pharmaceutical compounds at different concentrations: [amx]=0.500 and 1.00 mm, [ctx]=0.500 and 1.00 mm, and [tlx]=0.500 and 1.00 mm table 2: physico-chemical characteristics of real hospital wastewater at tht parameters (units) values temperature (°c) 24.8 ph 6.71 nitrates (no3 -) (mg/l) 1.11 phosphates (po4 3-) (mg/l) 1.26 chlorides (cl-) (mg/l) 29.33 conductivity (μs/cm) 103 suspended matter (mg/l) 11.5 appia and ouattara hungarian journal of industry and chemistry 68 a comparison of the change in the chemical oxygen demand of the simulated effluent (orange curve) and real effluent from tht (blue curve) is illustrated in figure 8. both types of wastewater were spiked with 0.500 mm amoxicillin. compared to the simulated wastewater, the degradation rate of amx in the real wastewater proceeded considerably more slowly. after a reaction time of 60 mins, the cod removal rate reached 37.05%, approximately 2.13-fold lower than that achieved with the simulated wastewater (78.86%) but close to that calculated in the presence of cl-, no3 -, so4 2and po4 3 ions simultaneously present in the simulated wastewater (44.59%). the effectiveness of the fenton process with regard to breaking down amx in the real wastewater was significantly reduced which is not unexpected, as the presence of inorganic ions in simulated wastewater has been demonstrated to hinder fenton process performance. however, inorganic ions (cl-, no3 and po4 3-) were present in the real effluent from tht investigated in this study. in the case of hospital wastewater spiked with amx, this could partly explain the low cod removal rate obtained. however, the complex composition of the matrix may also explain the poor performance of the fenton process. to improve the efficiency of the fenton process for real wastewater treatment, further investigations were carried out. one of the alternatives was to increase the [h2o2]/[fe2+] molar ratio from 2 to 10 (figure 9a). according to this figure, increasing the molar ratio leads to a decrease in the efficiency of treating the real wastewater with cod removal efficiencies of 37.05 and 25.67% for k=2 and k=10, respectively. the change in the concentration of amoxicillin and cod during the fenton reaction is displayed in figure 9b. in this experiment, the molar ratio was kept constant (k = 2) but the concentrations of the reactants changed. overall, the results demonstrate that high levels of reagents (60 mm [h2o2] and 30 mm [fe2+]) are more effective than low levels (2.50 mm [h2o2] and 1.25 mm [fe2+]) in terms of treating wastewater under our optimum conditions. in the latter case, no sludge was formed in the reaction medium and the coloration at the end of the reaction was green. the amount of reagents used seems to play an important role in the fenton process. in our study, maintaining the molar ratio of fenton’ reagent unchanged while reducing the reagent concentration resulted in a substantial decrease in both the degradation rate and the chemical oxygen demand. furthermore, the amx concentration (represented by yellow and grey curves) decreased faster than the cod (represented by figure 8: cod* evolution curves of simulated and real wastewater containing amoxicillin. operating conditions: [amx]=0.500 mm, ph=3, t=25 °c and k=2 figure 9: a) the effect of the molar ratio of h2o2 to fe2+ on the treatment of real wastewater from treichville university teaching hospital; b) comparison of the change in the amx concentration and cod using different concentrations of fenton’s reagent and a molar ratio of 2; c) the effect of successive additions of fenton’s reagent. operating conditions: [amx]=0.500 mm, ph=3, t=25 °c and k=2 degradation of pharmaceuticals from hospital wastewater 53(2) pp. 61–71 (2025) 69 blue and orange curves) in both cases. the formation of intermediate species during the reaction may explain the observed differences. the concentration of an organic compound is a compound-specific parameter, whereas cod is a global parameter that takes into account all the organic compounds in the reaction medium. additionally, amx degradation rates of 96.0 and 71.9% were obtained at the end of the reaction, whereas cod removal rates of 37.05 and 6.25% were obtained for high ([h2o2] = 60 mm and [fe2+] = 30 mm) and low ([h2o2] = 2.50 mm and [fe2+] = 1.25 mm) concentrations of the reagents, respectively. these values indicate that the degradation rate of amx results in the formation of intermediates in the reaction medium. to improve the performance of the fenton process for the treatment of real hospital effluent containing pharmaceuticals, another alternative was tested. the successive addition of fenton’s reagent to the reaction medium at 20 min intervals after filtration was the method adopted. the process was repeated three times. the cod removal rates of 37.17, 28.95 and 17.84% for stages i, ii and iii, respectively, are shown in figure 9c. after each addition of fenton’s reagent, the efficiency of our technology decreased, possibly because the degradation of amoxicillin using the fenton process produces by-products that can be recalcitrant to degradation such as carboxylic acids [42]. furthermore, the combined action of adding this reagent sequentially led to a clear improvement in the total abatement rate of 88.96%. 4. conclusions the optimal experimental conditions established in the simulated wastewater were a concentration of 0.500 mm amoxicillin, a ph of 3 and k = 2. under these conditions, the cod removal rates were 78.86, 38.46 and 25.68% for amoxicillin, ceftriaxone and telebrix, respectively. a low cod removal rate was observed when all three pharmaceuticals were present in the reaction medium (17.36%). the presence of inorganic ions strongly inhibits the efficiency of the fenton process due to the formation of complexes between iron and these inorganic ions on the one hand and to the trapping of hydroxyl radicals by these ions on the other. ion inhibition occurred in the following descending sequence: cl(67.72%) ˂ no3 (51.31%) ˂ so4 2(50.18%) ˂ po4 3 (46.85%). the inhibitory effect of ions was most pronounced when they were present simultaneously in the reaction medium (44.59%). the efficiency of the fenton process also decreased at higher temperatures. the physicochemical characterization of the tested real wastewater showed that it contains concentrations of cl-, no3 and po4 3of 29.33, 1.11 and 1.26 mg/l, respectively. the ph was 6.71, temperature 24.8 °c, conductivity 103 μs/cm and suspended solids concentration 11.5 mg/l. this work showed that treating real hospital wastewater under optimal fenton treatment conditions is difficult because the cod removal rate (37.05%) is approximately 2.13 times lower than that determined under optimal conditions with simulated wastewater. reducing the reagent concentration by maintaining the molar ratio at 2 and increasing the molar ratio did not improve the efficiency of wastewater treatment. in addition, the subsequent addition of fenton’s reagent at regular intervals resulted in a removal percentage of more than 88% after a reaction time of 60 mins. a comparison of the amoxicillin concentration with cod indicated that reactive compounds were formed during wastewater treatment. acknowledgement this research was funded by swiss national funds under grant iz01z0_146919. references [1] sadia, s.p.; berté, m.; loba, e.m.h.; appia, f.t.a.; gnamba, c.q.-m.; sanogo, i.; ouattara, l.: assessment of the physicochemical and microbiological parameters of a teaching hospital’s wastewaters in abidjan in côte d’ivoire, j. water resour. prot., 2016, 8(13), 1251–1265, doi: 10.4236/jwarp.2016.813096 [2] allahverdiyeva, s.; yardim, y.; şentürk, z.: electrooxidation of tetracycline antibiotic demeclocycline at unmodified boron-doped diamond electrode and its enhancement determination in surfactant-containing media, talanta, 2021, 223, 121695, 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chemistry vol. 53(1) pp. 81–89 (2025) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2025-10 stabilization of acid tars present in oil residue lagoons mihaela nicolae (tita)1, timur chis2*, ion onutu1, daniel tita1, doru bârsan2 1 faculty of petroleum technology and petrochemistry, petroleum-gas university of ploiesti, bucharest boulevard, no. 39, ploiesti, prahova, 100680, romania 2 faculty of oil and gas engineering, petroleum-gas university of ploiesti, bucharest boulevard, no. 39, ploiesti, prahova, 100680, romania having been active for over 100 years, romanian refineries have also produced large amounts of waste resulting from the complex processing of crude oils, most of which is stored in tanks to be processed later. the closure of 9 refineries (out of the existing 13) has also led to the abandonment of this waste treatment. after joining the european union, romania eliminated these acid tar lagoons and returned the decontaminated land to the local communities. however, eliminating these chemical substances ( from acid tars and other waste to oil and petroleum products and chemical substances) is challenging, both because of their multiple physicochemical compositions and mainly given the lack of techniques that reduce ecological destruction (incineration or slow pyrolysis creates other pollutants). acid tars are present in the waste of the crude oil processing industry and originate from the refining of some petroleum fractions (oil, paraffin). this article analyzes acid tars and proposes several solutions for their stabilization and encapsulation. the effects of their encapsulation on the primary pollutants present in acidic waste are also presented. keywords: refinery waste, acid tars, encapsulation, stabilization 1. introduction in terms of refinery, the quantities of solid residual materials resulting from the manufacture of finished petroleum products are within the limits of 3 5 kg/ton of crude oil processed. over 80% of these residues are highly polluting due to the presence of organic toxins and heavy metals [1]. at present, it should be noted that the rational and complex processing of crude oil and its fractions no longer leads to waste production. the losses are minimal and technologically planned, moreover, all the resulting by-products are exploited [2]. unfortunately, crude oil refining in romania before the 1990s was carried out in simple refineries and without hydrorefining processes, leading to large amounts of residual waste such as acid tars, petroleum sludges, sludges containing petroleum products and infested soil, all of which are legally classified as hazardous waste [2] over 861 potentially contaminated sites due to petroleum operations (drilling, extraction, transport, processing) [3]. in refineries worldwide, this residual waste is processed by the following technologies: neutralization by applying calcium oxide directly (producing another pollutant); received: 18 febr 2025; revised: 28 apr 2025; accepted: 29 apr 2025 *correspondence: timur-vasile@upg-ploiesti.ro incineration in specialized equipment, releasing gases containing particulate contaminants; thermal decomposition occurs at temperatures between 260 and 650 ºc, producing free sulfuric acid and particulate pollutants; recovery of sulfonic acids neutralized by calcium oxide to create compounds used to build communal roads; neutralization of various agents; pyrolysis at high temperatures from 800–1200 ºc and decomposition at low temperatures from 150–350 ºc followed by the production of bitumen. this study aims to identify a technology for encapsulating strong acids to be transported and stored under specific environmental conditions in line with legislation and used in the construction materials industry for communal and minor roads. 2. strategy for analyzing and resolving acid tar issues in addition to restructuring, the oil refining industry also faces environmental requirements and restrictive legislation regarding the quality of petroleum products. at present, refineries must comply with the following objectives [4]-[6]: https://doi.org/10.33927/hjic-2025-10 mailto:timur-vasile@upg-ploiesti.ro nicolae (tita), chis, onutu, tita and bârsan hungarian journal of industry and chemistry 82 1) the processing of crude oils with a high content of sulfur and metals, which are increasingly present in the depleted deposits in romania; 2) alignment with the european requirements regarding the continuous improvement of the quality of gasoline and diesel, especially in terms of the drastic reduction in their sulfur content; 3) the need to reduce greenhouse gas emissions and waste from refining; 4) growth in the market of electric and hybrid machines as well as other equipment has decreased the demand for petroleum products. this is precisely why only a small quantity of acid tars are produced from refineries and processed. nevertheless, waste lagoons at closed refineries must be treated and eliminated quickly. acid tars are obtained from treating refined products with sulfuric acid during their synthesis. they are residual materials from the technologies applied from the foundation of the petroleum industry. acid tar appeared at the end of the 19th century as a waste material due to the use of concentrated sulfuric acid to process distillate, motor and other petroleum oils [7]. therefore, unsaturated and aromatic hydrocarbons, sulfur and nitrogen compounds as well as resinous substances, which affected the stability and performance of commercial petroleum oils, were removed by this process. acid tars also result from the refinery of special oils such as those used in alternating current transformers in addition to hydraulic, medicinal and cosmetic oils as well as from the production of flotation reagents on top of the individual sulfonation of some hydrocarbons and petroleum fractions [8]. meanwhile, acid tars are also generated during the alkylation of isobutene with olefins, a technological process necessary to manufacture octane components and stabilize aromatic compounds [9]. acid tars are analytically characterized by how much free sulfuric acid they contain, their total organic matter and their consistency (viscosity) at the end of the process. the presence of acid tars in romania was confirmed as a result of the use of acids in the following industrial processes: a) alkylation of gasoline and the manufacture of detergents acid tars are easily handled liquids that are extremely stable over time; b) oil refining these wastes are viscous, unstable and become more difficult to pump as they age. interestingly, appreciable differences are found between acid tars obtained from paraffinic oils and those from naphthenic oils. the process leading to the generation of acid tar results in an emulsion in which the upper layer contains the acid oil and the lower the acid sludge. the sludge contains products from secondary reactions, namely an excess of sulfuric acid and a small amount of oil/petroleum adsorbed on various solid particles. acid tars exhibit the following physicochemical behavior over time: a) in the production phase, acid tars are obtained in an emulsified form, which is much less stable. b) over time, an upper phase is separated by a lighter emulsion. the continuous phase is the petroleum product and the dispersed phase consists of sulfuric acid and water. a thin film composed of sulfonic acids lies between the two phases. c) the lower phase of acid tars consists of sulfuric acid, water as well as low-molecular-weight sulfonates and sulfates of nitrogen compounds. this phase appears as a cloudy, gray-black solution. d) during their storage in pits, water from precipitation enters the upper layer, diluting the existing sulfuric acid. meanwhile, the organic mass begins to oxidize (due to the uptake of oxygen from the atmosphere and the heating of the tar as a result of the adsorption of solar energy) and the temperature of this waste reaches 80-95 ºc. e) during its oxidation, resinous, asphaltogenic and carcinoid compounds are produced, moreover, the tar matures and becomes a solid mass. the tar releases products into the atmosphere, mainly sulfur oxides, hydrogen sulfide, ammonia, carbonyl sulfide and water vapor. f) after a long period of storage, acid tars age, forming a layer of organic mass similar to bitumen on their surface. the mineral acidity of this layer referred to in f) is relatively low and contains compounds such as heavy sulfonic acids, heavy naphthenic-aromatic acids, metals and resins, asphaltenes, carbides and carbenes formed by polycondensation and polymerization. this layer usually does not contain free hydrocarbons or only trace amounts. the lower layer of aged tars contains acidified water with dissolved compounds such as metal sulfates and sulfides of essential compounds from petroleum products [10],[11]. the transformation of acid tars over time leads to the formation of highly dense and viscous waste. furthermore, over time, acid tars absorb oxygen and other strongly polar components which produce polymerization and polycondensation reactions with the appearance of macromolecular compounds such as resins and asphaltenes. therefore, the tars resemble bitumen that solidifies at the interface with the environment. the processing and/or elimination of acid tars is always topical, moreover, countries with highly developed industries and clear legislation have almost completely solved this problem. 3. scope of this study and procedures the analyses were carried out on stratified and surface samples, 40 in total, collected from 4 storage tanks of acid tars (table 1), originating from the treatment of gasoline (tar 1), lamp oil (tar 2), lubricating oils (tar 3) stabilization of acid tars 53(1) pp. 81–89 (2025) 83 and viscous lubricating oils (tar 4).the results confirm the presence of free sulfuric acid. the analyses carried out on the samples collected from the acid waste storage basins showed that these treatments were helpful with regard to the finished products but presented a real danger to the environment with the highest concentration of residual acid originating from the treatment of gasoline and the lowest from the treatment of oils (which confirms the data from the specialized literature). in romania, the processing of waste such as acid tars was significantly reduced due to a lack of interest at the time of storage, namely the remediation of the generally extensive and heavily contaminated sites where the acid tars were stored was carried out by excavating, transporting and storing this waste in concrete pits that were often ineffectively covered. the research on waste lagoons in romania confirms the impossibility of treating acid tars by classical methods due to their aging, namely incineration, thermal decomposition or neutralization, which are highly expensive and uneconomical techniques. the only effective method is encapsulation followed by the neutralization of acid waste. to create new technologies for encapsulating and treating acid tars, a field study was carried out over 3 years by investigating several acid tar waste storage lagoons related to closed and abandoned romanian refineries. from the 30 oil waste storage lagoons, 300 samples containing acid tar were taken. the samples were collected as follows: a) each lagoon was mapped, filmed and photographed by drone inspection. b) having been mapped, the areas that had been depolluted or excavated (which were decontaminated according to the documents drawn up by the environmental authority) were delimited. c) the polluted areas were delimited with the help of grids with 4 sampling sites from the interface between the pollutant and soil or the protected lagoon and 6 randomly chosen ones depending on the size of the lagoon. d) each sample was collected by drilling and taking cores of the soil-pollutant-acid tar up to 2 m deep to analyze the vertical composition and separation processes of acid tars rather than the amount of pollutant. e) all 300 samples were grouped according to the origin of the acid tar, namely from the treatment of gasoline, diesel and light or heavy lubricating oils. they were easily divided because the storage lagoons were located in the treatment areas of the refined products, that is, gasoline, diesel as well as light and heavy lubricating oils, rather than in areas especially designed for storage. f) all the samples taken were dried with water and evaporated gases analyzed separately. g) afterwards, the samples were crushed and analyzed according to the protocol created for this purpose, determining the main physicochemical properties, the level of contamination in terms of their depth and the average amounts of the analyzed contaminants in particular. h) for each sample analyzed and subsequently for each group of samples as well as each depth interval of pollution, the extreme values, standard deviation and values that do not statistically correctly identify the level of contamination were determined in terms of pollution and its evolution over time. the harvesting method used complies with romanian law according to the procedures and technical norms regarding the identification of damage caused to the environment to determine the level of responsibility for their remediation. it is based on the provisions of articles 36, 42 and 48 of environmental protection law no. 137/1995 as well as the provisions of article 15 paragraph (5) from water law no. 107/1996 [3]. the experimental data was statistically processed using artificial intelligence (data science) to ensure a good prediction regarding the properties of the acid tars from the waste lagoons and the associated leachate. the collected and statistically processed data only eliminated outliers and was handled without plotting a graph of the evolution of acid waste behavior over time. given that the laboratory study analyzed the quality and physicochemical properties of some deposits totaling 80,000 m3 of waste (acid tars, oil residues and acid water) originating from a refinery that ceased to operate in the year 2000, the collected samples were defined as stabilized waste (acid tar). the physicochemical analysis of the acid tar samples is shown in table 2. this study presents only the characteristics necessary to create an additive for the encapsulation/neutralization of this waste. analytical determinations of the collected samples were carried out according to the internationally used standardized methods. to establish a new encapsulation technique, the following research program was agreed [12],[13]: a) sampling of acid tar samples from a bottle and their characterization according to the following indicators: ph, total hydrocarbons as well as metal, cyanide, chloride and sulfates content; b) characterization and determination of indicators from the stabilized acid tar leachate: ph; total hydrocarbons; metal, cyanide, chloride and sulfate content; tds (total dissolved solids); toc (total organic carbon) and doc (dissolved organic carbon); c) identifying, testing and establishing the optimal conditions for stabilizing acid tar; table 1: acid tar of romanian refinery lagoons [5],[6] characteristics acid tar 1 acid tar 2 acid tar 3 acid tar 4 density, kg/m3 1.62±0.1 1.43±0.1 1.33±0.1 1.27±0.1 total acidity, % of mass 55.4±0.1 45.8±0.1 42.8±0.1 18.3±0.1 sulfuric acid, % mass 46.3±0.1 33.2±0.1 39.7±0.1 17.5±0.1 water content, % mass 3.30±0.1 5.6±0.1 7.6±0.1 3.8±0.1 nicolae (tita), chis, onutu, tita and bârsan hungarian journal of industry and chemistry 84 d) characterization of the stabilized acid tar leachate and compliance with the legal provisions; e) capitalizing on laboratory research in the treatment of acid tars by proposing alternative technical solutions applied on a macroscale for the treatment of acid tars in situ and to reduce the impact of acid tars on environmental factors; f) estimating the costs per ton of treated waste, the materials used and the specific levels of consumption associated with the treatment. the treatment technology of acid tar-type waste refers to a composition and a process necessary to achieve in situ physical and chemical stabilization. treating soils contaminated with acid tar needs neutralization, stabilization and encapsulation processes. the encapsulation/neutralization additive recipes and the encapsulation/neutralization process are particularly applied to acid tar with a total hydrocarbon content below 200,000 mg/kg and doc value below 1000 mg/kg in particular whose composition is not uniform. the ph, total petroleum hydrocarbons (tph), heavy metals, toc, doc and sulfate content can vary per meter both in terms of length and depth. since no gas emissions were detected during the collection of the acid tars subjected to analysis and treatment, these aspects were neglected. this is explained by "historical" acid tars in batal from over 20 years ago. worldwide, several technologies have been developed for the treatment of acid waste that results from refining petroleum products. when treated by the method of stabilization/encapsulation chosen and applied to acid resins, the following substances were used as additives and filler materials: cement, sand, calcium oxide, sodium hydroxide, bentonite, an emulsifier, strengthening additives, absorbents and sodium metasilicate (table 3). the remaining mass is represented by acid tar subjected to stabilization. identifying the potentially applicable reagent depends on several factors, including the contaminant to be treated, the concentration of pollutants in the acid tar, the geotechnical and acid tar properties, required performance parameters as well as minimum acceptable performance criteria for the treated acid tar. the identification and selection of the reagents applied in the experiment was based, on the one hand, on the technical literature consulted in the theoretical research and, on the other hand, on the experience of the author in implementing stabilization/encapsulation projects. therefore, several candidate reagents were identified, narrowing down the number of reagents based on lowcost and less time-consuming treatability tests. the selection of candidate reagents was based on the knowledge and analysis of chemical interferences and incompatibilities in the chemical behavior of the metals in the acid tar, but also took into account the cost and history of the process. in the present case, the performance of the technology was measured and composition for the treatment of waste analyzed from bottles, while the stabilization/solidification in situ was investigated through several encapsulation formulae of acid waste. as a result, in the first stage to encapsulate acid tars, the following mixture was used measured in mass % relative to acid tar: a) cement without additives: 25%, b) bentonite: 2.5% (by weight), c) acid tar: 36% (by weight), d) loam soil: 18% (by weight), e) clay: 18% (by weight). the solidification/stabilization treatment applied to the acid tar under these conditions exhibited the following disadvantages: a) the ph of the eluate after mixing acid tar with bentonite, loam soil and clay 1/10 l/s was between 2 and 3 (acidic environment). b) the dissolved components were not chemically bound. table 2: stabilized acid tar characteristics average experimental results organic products, % mass 40 60 58.0 inorganic products, % mass 20 60 27.0 calorific value, kcal/kg 4 900 5 300 4850 water, % mass 15 20 14 acidity, mg koh/g 10 100 38.0 sulphur, % mass 0.5 3 2.0 fe, % mass 0.008 0.4 0.2 ca, % mass 0.1 0.3 0.26 mg, ppm 38 925 400.0 mn, ppm 3.7 15 11.0 ni, ppm 4.0 85 48.0 zn, ppm 35 157 123 pb, ppm 13 237 88.0 cu, ppm 2 11.4 8.8 hydrocarbons, % mass 15 20 17.2 resins, % mass 35 50 37.4 asphaltene, % mass 15 20 17.3 table 3: the composition required for the neutralization, stabilization and encapsulation of acid tar compound (%) cement 3-20 sand 2-5 lime 3-8 sodium hydroxide 1-10 bentonite 1.0-2.8 emulsifier 1-2 strengthening additives 1 stabilization of acid tars 53(1) pp. 81–89 (2025) 85 c) the contaminant particles were not encapsulated in an impermeable cover. d) the hazardous components were not chemically fixed by reducing their solubility. e) the toxicity of the contaminants was not reduced. later, 3 mixtures were established for treating acid tars according to table 4. mixture 1 was applied for acid tars with high ph and low tph values. mixture 3 was used for acid tars with low ph and high tph values. for tars with medium tph values, mixture 2 yielded the best results. it was found that tph and ph values amongst other indicators, including the concentrations of various metals in the initial acid tar, influence the efficiency of the mixture used. if the application of the chosen mixture did not decrease the concentrations below the limits stipulated in law no. 95/2005, the application of the other 2 mixtures was applied. all these attempts were completed by filing 2 patents, one international and the other national. after applying the mixtures accordingly, a significant decrease in the parameters and compliance with the regulations stipulated in law no. 95/2005 was observed. the following chemical compounds were used in the mixtures: sodium metasilicate sodium metasilicate was added comprising 0.3 to 0.8 % mass. as argued in the literature, the final performance of the stabilization/encapsulation technology applied is determined by the quality and intrinsic properties of the additives as well as binders in the mixtures. the added sodium metasilicate exhibits a waterscavenging effect. sodium metasilicate is not a cleaning agent per se but is a strong base that reacts violently with acids. it was added to enhance the mixtures because it maintains the cleaning efficiency of the added emulsifier and absorbent mainly by reducing water hardness. it has also been reported that cu can bind to cement using this agglomerating agent, that is, sodium metasilicate, na2sio3 x 9h2o. ordinary portland cement ordinary portland cement (opc) used in the present study facilitates the immobilization of cr, cu, zn, mn and pb. the addition of cement increases the degree of immobilization and the curing time of the hardened material. this reference is attributed to the pozzolanic and/or hydraulic properties of the cement on the microstructure of the hardened material. additives added to the cement and the hydration reactions in the mixtures favor the formation of the specific microstructure, facilitating the immobilization of dangerous elements. sand sand is used as an additional aggregate that forms a hard layer covering contaminants in the acid tar in the presence of cement and water. calcium oxide calcium oxide (slaked lime, quicklime), presented as a white powder, is used to neutralize the acid tar. in addition to the neutralizing effect, the calcium oxide and emulsifier contributed to the transition of the metals from a volatile to stable phase. the added lime favors immobilization, especially of cd, cu, ni, pb and zn. sodium hydroxide sodium hydroxide neutralizes the tar acid tar and the reaction is strongly exothermic. emulsifier the emulsifier stabilizes the ph and results in a homogeneous mixture of the stabilized acid tar. the presence of the emulsifier leads to a higher degree of encapsulation of the acid tar by breaking the hydrocarbon chains and embedding the compounds faster and deeper. the emulsifier is used quickly to mix and incorporate all the compounds proposed in the mixtures elaborated on in the thesis according to the certificate no. 107443 granted by the state office for inventions and trademarks [12],[13]. bentonite and cement bentonite and cement contribute to the hardening/encapsulation of the acid tar as well as the additional retention of pb. absorbent the absorbent is used to reduce the volume of the treated acid tar. the freshly prepared sample of acid tar is homogenized and binders added to stabilize as well as encapsulate the acid tar. following treatment in the laboratory, the stabilized acid tar is presented as a compacted block. the values of the pollutants identified in its leachate are below the limits permitted according to law no. 95/2005. table 4: mixtures for encapsulating acid tar compound mixture 1 mixture 2 mixture 3 sodium metasilicate, % 0.30 0.50 0.80 emulsifier 1.00 3.50 4.00 calcium oxide 8.00 3.00 7.00 magnesium oxide 0.10 0.20 0.30 bentonite 1.00 2.00 2.80 sand 2.00 5.00 3.00 cement 3.00 5.00 8.00 reinforcing additives 1.00 1.00 1.00 absorbent (oil absorbent) 1.00 1.00 1.00 sodium hydroxide 1.00 1.00 1.00 nicolae (tita), chis, onutu, tita and bârsan hungarian journal of industry and chemistry 86 4. results final processing and verification found that a stabilized and encapsulated material with low degrees of permeability and leachability as well as moderate to high resistance was obtained, meeting all the performance criteria. the volume of the treated acid tar increased by up to 5% of the initial volume of the acid tar before treatment. this aspect is essential in the following valorization stage of the research because it will allow the tar to be treated in situ using only the limited space of the existing pits without the need to dig additional pits to store the surplus resulting from the treatment. since acid tar is a particular waste, its treatment by stabilization/encapsulation had to be carried out carefully as elaborated on in the literature review. firstly, being unstable from a geotechnical point of view, it can exhibit creep effects depending on the type and temperature. secondly, leachates of organic compounds (hydrocarbons) and inorganic compounds (sulfuric acid, metals) can be recorded in the water. after adding and mixing the additives, no significant heating of the neutralized and treated acid tar was observed, leading to the volatilization of specific contaminants. furthermore, no sulfur dioxide emissions were detected since an "old" acid tar was treated. since the treated and stabilized acid tar was not exploited as a construction material, it was not analyzed from a geomechanical point of view in the thesis. once immobilized in the matrix, contaminants do not migrate as long as the integrity of the matrix is maintained. the leachate from the disposal site was analyzed to monitor any contaminant migration. as mentioned, acid tar samples from the field under study were taken, their composition determined and the following indicators measured: ph; tph; metal, cyanide, chloride and sulfate content as well as doc were compared with the limits stipulated by law no. 95/2005. at all locations, the depth from which acid tar samples were taken was approximately 5-30 % of their weight. 5. discussion analysis of the experimental data led to the following conclusions as presented in table 5 [14]. the strongly acidic character intensified the categories of potential waste stored in the studied area (sludge, oil sludge) due to the mixture of these wastes with the acid tar. the highest tph concentration was detected in all acid tar samples but decreased approximately fourfold at a depth of 30 cm. the study of tph concentrations whereby large-scale cement-based stabilization/encapsulation technologies were applied to inorganic waste, including metals, is essential under the conditions reported when organic substances can be easily leached. unfortunately, little information is available on organic leaching from acid tars after applying stabilization/encapsulation technologies or on the effects of organic compounds on complex reactions, which can alter the cement matrix. it was found that the films formed by asphaltenes are resistant to acidic environments (low ph) and become less persistent as the ph increases. the concentrations of the analyzed metals were determined according to the analysis method sr en iso 15586:2004: determination of trace elements by atomic absorption spectroscopy with a graphite furnace and the method for the rapid detection of trace elements. an atomic absorption spectrometer with a graphite furnace and a mobile edxrf device with x-ray detection were used to rapidly detect trace elements. the different and, of course, sometimes high levels of metal concentrations in the untreated acid tar samples can be attributed to the concentrations of such metals in the waste stored in polluted areas and in the additives used in the refining processes, the absorption of metals from the storage tanks and the supply, as well as the natural presence of metals in the parent rock from which the crude oil was extracted and even the materials with which the stabilization/encapsulation is carried out, e.g. cement. as a general finding, the values determined and recorded for the concentrations of the metals pb, cd, cu, cr and as are noted. however, their values in the initial acid tar exceeded the maximum allowed limits. however, in the leachate stabilized for 1 day, low values were recorded, some even below the limit of quantification of the determination methods. the leachates were prepared and analyzed from the treated acid tars according to the leaching procedure sr en 16192:2020 characterization of waste — analysis of eluates. 5.1. ph the eluates were analyzed to determine the acidity according to sr en iso 10523:2012 determination of ph. in general, it was found that increasing the ph from between 0.2 and 5.28 (untreated acid tar) to 8.7 and 10 (in the case of the leachate) was beneficial in increasing table 5: acid tar concentration indicators value minimum value mean value maximum ph 0.20 3.90 5.20 tph in soil, mg/kg dry substances 48,333 477,062 200,000 pb, mg/kg 42 400 478 cd,mg/kg 1 5 126 cu, mg/kg 2.6 100 789 cr, mg/kg 3 70 452 ni, mg/kg 2 40 859 as, mg/kg 1.4 25 589 stabilization of acid tars 53(1) pp. 81–89 (2025) 87 the leaching performance, e.g. in the speciation of metal contaminants. 5.2. tph the tph content of the leachate was determined using the method sr en iso 9377-2:2002 — determination of the hydrocarbon oil index. the stabilization-encapsulation technology applied in the study to treat acid tar confirmed that the organic materials—hydrocarbons—do not react with the inorganic binders from the 3 applied mixtures due to the significant differences in hydrophobicity and polarity between the organic contaminants and the organic binders. this may often lead to ineffective immobilization of hazardous organic hydrocarbon contaminants in the solid matrix and significant leaching of many pollutants. however, the final results of the leaching tests showed a good degree of efficiency in reducing the tph in the leachate. 5.3. metals the concentrations of metals from the pb, cd, cu, cr and as group were also monitored in the leachate and the following was found. the leachate was prepared and analyzed according to sr en 16192:2020 waste characterization analysis of eluates. the leaching of heavy metals is the main reason stored acid tars and managed encapsulated/stabilized products should be classified as hazardous waste. the opc used in the present study contributed to the immobilization of cr, cu, zn, mn and pb in particular. the addition of cement increases the degree of immobilization and the curing time of the hardened material. as a result of the high ph of the cement, the metals are retained in the form of insoluble hydroxide or carbonate-type salts from the hardened structure. in addition to the neutralization effect, the calcium oxide and the emulsifier in the formulated mixtures contributed to the transition of the metals from the volatile to a stable phase. the added lime favors immobilization, especially in cd, cu, ni, pb and zn. studies have shown that lead, copper, zinc, tin and cadmium will likely bind in the matrix by chemical fixation, forming insoluble compounds. meanwhile, mercury is predominantly retained by physical microencapsulation. on the other hand, organic contaminants interfere with the hydration process, reduce the final strength and are not quickly stabilized, delaying the formation of the crystalline structure and resulting in a more amorphous material. incorporating modified and natural clays or sodium silicate into the stabilizing mixture with the cement can reduce the interference of organic contaminants with cement hydration and improve stabilization. the different elements in the formulated mixtures presented different leaching potentials correlated with the curing time, the compositions of the binders as well as the initial and final ph, suggesting that how each metal contaminant is preliminarily released should be considered for the practical immobilization of the contaminated materials. the applied encapsulation technology decreased the mobility of cadmium, copper, chromium, lead, nickel and arsenic in the acid tar. the tracked metal group experienced a drop in concentration of over 95%. therefore, the leaching test results show that the metal concentration is much lower than the pollution limits stipulated by international standards (iso et al.) and romanian standards order 95/2005. as a general finding, also noted in the published literature, the leaching of some heavy metals largely depends on the ph of the liquid, e.g. pb and cr. lead lead (pb) concentrations varied between 0.0003 and 0.0056 mg/kg in all the stabilized samples. it should be noted that the ph of the samples from which the metal concentrations were determined varies from 8.7 at a pb concentration of 0.008 mg/kg to 10.0 at a pb concentration of 0.002 mg/kg. it can be seen that a high ph affects the precipitation of pb. the concentration of pb in the eluate will decrease with increasing ph due to the cement in the mixture used for stabilization/encapsulation. unfortunately, it was found that pb (lead) is difficult to detect in the eluate when the ph is between 9 and 11 due to the formation of insoluble hydroxide. however, it can be detected at ph 12 due to the formation of an amphoteric hydroxide complex. cadmium cadmium (cd) concentrations in the eluate samples varied between 0.0001 and 0.0050 mg/kg. most eluate samples (approx. 87%) are contaminated with less than 0.002 mg/kg cd. the studied acid tar samples subjected to leaching contain a significant amount of cd with an average of approximately 30 mg/kg. cd leaching in all samples showed that the concentrations of this metal varied considerably with values below 0.001 mg/kg for the first 9 samples, a maximum in the case of sample 10 (0.005 mg/kg) and values below 0.002 mg/kg for samples 11-39. furthermore, the solubility of cadmium hydroxide is low at ph 10 over a short solidification time. as mentioned in the literature, cement enhances the immobilization of cd under all conditions. since a reduction in cd migration as the ph increases is probably attributed to cd commonly existing as hydroxide on cementitious materials, higher ph conditions accelerated the formation of the insoluble cd(oh)2 precipitate. copper the copper (cu) concentration detected varied between 0.00083 and 0.01610 mg/kg. the leachate's cu concentrations are approximately 85% lower than 0.008 mg/kg. however, it was found in the literature that the ph is not influenced. nicolae (tita), chis, onutu, tita and bârsan hungarian journal of industry and chemistry 88 in terms of cu elution, which, when leaching the same sample, generally behaved like chromium, the cr concentrations were approximately 5 times higher. the lower cu concentrations in the leachate resulting from the acid tar treated by encapsulation/stabilization can be explained by applying some mixtures in which the agglomeration agent, sodium metasilicate na2sio3.9h2o, was added in larger quantities. chromium chromium (cr) concentrations, known as one of the most toxic metals, measured in the eluate collected after acid tar treatment varied between 0.0010 and 0.0840 mg/kg. as in the case of copper, very high values of cr concentrations were found (over 330 mg/kg) and none of the 3 mixtures could achieve an acceptable reduction in the cr concentration in the eluate. although cr concentrations between 30 and 100 mg/kg can be found in ordinary portland cement which can be added to those found in acid tar, the application of the 3 mixtures formulated and applied in the treatment of acid tar led to values below 0.1 mg/kg of chromium in the leachate. a noticeable trend for all samples can be observed when the cement content increases the cr concentration since cement contains cr6+, as mentioned in the literature. meanwhile, the additional presence of cr6+ increased the initial and final setting times of the cement. it was concluded that the immobilization of cr6+ by the cementbased encapsulation/stabilization technology was achieved due to the formation of a calcium chromate complex (cacro4) of low solubility. the cement hydration process was affected in the presence of cr6+ because a proportion of the ca2+ in the cement reacted with cro4 2–. nickel nickel (ni) concentrations in the eluate varied between 0.0015 and 0.0910 mg/kg of dry substance. the hydroxides of ni and cd are incorporated in the hydrated cement matrices, which gives ni a good immobilization capacity. arsenic arsenic (as) concentrations varied considerably in the untreated acid tar (between 1.4 and 589 mg/kg of dry substance) and eluate (below 0.001 to 0.402 mg/kg). the sample containing 2 % cement yielded a higher as concentration than when 0 and 4 % of cement were used. for 4 % cement with different amounts of rubber chippings, the as concentration also increased significantly, possibly because of the leaching of as upon the formation of ca-as precipitates. therefore, ca-as precipitation increases with the ca concentration in the cement. increasing the ph of the leachate, on the one hand, and adding cao, on the other hand, is more favorable. fixation occurs when the leaching takes place in an alkaline environment. furthermore, high as concentrations were recorded in samples 21 and 24 in which the tph contents in the acid tar were high. 5.4. cyanides to determine the concentration of free cyanides in the eluted water, a uv-vis dr3900 spectrophotometer was used to detect cyanide concentrations between 0.01 and 0.60 mg/l. cyanide concentrations between 0.013 and 0.368 mg/kg s.u. in the untreated acid tar reduced to <0.001 mg/kg in the leachate, which is below the detection limit. 5.5. chlorides, sulfates, doc the concentration of chlorides, sulfates and doc in the leachate reduced with maximum values at sampling point 20 at a depth of 30 cm for doc and sulfates of 2047 and 619 mg/kg, respectively. the doc concentration was between 108 and 2047 mg/kg with 3 measurements above 1000 mg/kg. according to this research, the macroscale application of the process for the stabilization and encapsulation of acid tar with tph values below 200,000 mg/kg would allow the metal concentration from the group considered, that is, pb, cd, cu, cr and as, to decrease below the imposed limits and doc below 1000 mg/kg s.u. the technological flow of the model is based on the following technological phases: supply of the material to be treated, dosing of treatment agents, aeration, homogenization, heating and maintaining a constant treatment temperature, controlling the technological parameters during the treatment process, as well as extracting the treated product. 6. conclusions based on the literature, which was correlated with the practical results, a technology to treat the studied acid tar was sought. the untreated contaminated material was characterized and the performance of the technologies at different stages evaluated. solidification/stabilization technologies are usually used to treat soils and sludges containing heavy metals. the establishment of the rehabilitation technology and its feasibility were evaluated through an analytical study in the laboratory. the treatability tests carried out in the laboratory allowed for the technologies to be evaluated before their selection as well as the proposal of design parameters for the process and subsequent scaling up for implementation on a macroscale in the field. an experimental procedure was applied that took into account representative parameters (type of waste/tar, its specifications, potential air emissions of vocs, dust and odors, necessary materials and binders, etc.). acid tar sampled from lagoons as well as the indicators namely ph, tph in addition to the concentrations of metals from stabilization of acid tars 53(1) pp. 81–89 (2025) 89 the pb, cd, cu, cr, ni and as group, cyanides, chlorides, doc and sulfates were mixed and homogenized. the formulation, preparation and testing of several mixtures for the treatment of acid tar samples taken from the waste lagoon sites highlighted the fact that the composition of the acid tar was not uniform and the values of the leading analyzed indicators were higher than the legal limits. several treatment mixtures were tested, of which three representative mixtures were finally retained. the curing process of the samples was analyzed as a function of time by visual examination. the testing process was stopped for mixtures that did not yield good results. by examining the distribution of additives in the final mixture as well as their mixing ratio in the 3 distinct mixtures, the following was noted: the concentrations of strengthening additives, absorbent and sodium hydroxide (approx. 1.00% each) were constant. variable amounts of emulsifying agents produced by eurototal (1.00, 3.50 and 4.00%, respectively) were used. increase in cement concentration (from 3.00% in mixture 1 to 8.00% in mixture 3); the cement concentration was increased from 3.00% in mixture 1 to 8.00% in mixture 3. the added calcium oxide concentration varied from 8.00% in the case of mixture 1 to 7.00% in mixture 3. the bentonite concentration increased from 1.00% in mixture 1 to 2.80% in mixture 3. a relatively constant increase is sodium metasilicate concentration was noted of 0.30, 0.50 and 0.80% for mixtures 1-3, respectively. it was found that the tph, ph and other indicators, including the concentrations of various metals, influence the effectiveness of the mixture. therefore, if the application of the chosen mixture did not decrease the contaminant concentrations below the limits stipulated in law no. 95/2005, one of the other two mixtures was used. if the second mixture did not yield the expected results, the third mixture was used. after completing the treatment in the laboratory, the stabilized acid tar was presented in the form of a compacted block and the values of the pollutants identified in its leachate were below the maximum values stipulated in law no. 95/2005. the leaching capacity of the pb, cd, cu, cr, ni and as group of metals from the stabilized and encapsulated material was evaluated because the encapsulation of acid tar reduces the mobility of the transported toxic substances. however, it cannot be guaranteed that the stabilized poisonous materials remain within the treated acid tar, especially after the acid tar has been damaged or come into contact with corrosive agents. although it is challenging to establish the effectiveness of the stabilization/encapsulation process applied to acid tar from waste lagoons, this can be evaluated by performing leaching tests in the laboratory. references [1] riazi, m.r.: characterization and properties of pure hydrocarbons, in: characterization and properties of petroleum fractions, riazi, m.r. 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https://apmnt.anpm.ro/-/situri-potential-contaminate https://doi.org/10.3390/chemengineering6030041 https://doi.org/10.1515/hjic-2016-0007 https://doi.org/10.1515/317 https://doi.org/10.1515/317 https://doi.org/10.1016/j.crcon.2019.12.001 https://doi.org/10.1515/509 https://patents.google.com/patent/wo2021221524a1/en https://patentimages.storage.googleapis.com/fd/d6/92/c3b1247266e173/ro134684a0.pdf https://patentimages.storage.googleapis.com/fd/d6/92/c3b1247266e173/ro134684a0.pdf http://www.acidtarlagoons.org.uk/acidtars hungarian journal of industry and chemistry vol. 53(1) pp. 27–37 (2025) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2025-04 comparative analysis of machine model-based sensorless dtc of two parallel connected five-phase induction machines khaled mohammed said benzaoui1*, sifelislam guedida2, ahmed zouhir kouache1 and elakhdar benyoussef1 1 laboratoire lage, faculté des sciences appliquées, université kasdi merbah ouargla, ouargla, 30000, algeria 2 école militaire polytechnique, uer elt, algiers, 16111, algeria in high-performance vector control methods, especially for critical applications, accurate and precise information about the state variables of a machine (speed, flux and torque) is necessary. nevertheless, environmental conditions such as temperature, vibrations and emi affect the performance of sensors. sensorless control is a potential solution to address the aforementioned drawbacks as well as further enhance the reliability and performance of the system, in addition to reducing the cost and the size of the drive. therefore, this work provides a comparative study of three different sensorless approaches of measuring the stator flux and speed estimation for the direct torque control (dtc) of two five-phase induction machines (fpim) connected in parallel to a single two-level inverter based on a model reference adaptive system (mras), sliding mode observer (smo) and highgain observer (hgo). the independent control of such a drive is possible due to the additional degrees of freedom (dof) provided by the five-phase system and the suitable rearrangement of phases. the open-loop estimator used in conventional dtc for estimating flux leads to drift and initial value problems as a result of using the pure integration method. finally, an analytical study of the robustness, stability and effectiveness of the discussed sensorless control schemes is verified in terms of reference command tracking, low-speed operation and disturbance rejection. keywords: sensorless direct torque control (dtc), sliding mode observer (smo), model reference adaptive system (mras), high-gain observer (hgo), two parallel-connected fpims 1. introduction highly reliable and high-power critical applications such as in ship propulsion, electric vehicles and electric aircraft are the most suited applications for five-phase induction machines (fpim) and permanent magnet synchronous machines (pmsm) [1]-[3]. this is due to several advantages that they boast, for instance, reduced current rating per phase, less flux and torque ripples as well as increased torque density on top of their faulttolerant operation and additional degrees of freedom (dof) compared to three-phase induction machines [4],[5]. these dofs can be employed to achieve drive in two independent parallel-connected machines fed by a single inverter where the two machines operate independently under different conditions such as speed and load torque [6]. the direct torque control (dtc) of the fpim is simple compared to field-oriented control and less sensitivity to the parameters of the machine with the received: 19 sept 2024; revised: 6 nov 2024; accepted: 11 nov 2024 *correspondence: benzaoui.khaled@univ-ouargla.dz decoupled control of the flux and torque of the fpim enabling high dynamic performance [7],[8]. the working principle of dtc is based on choosing the optimal voltage vector (vv) to be applied in each sampling period in order to obtain the desired level of performance regarding the stator flux and electromagnetic torque requirements [9]. high-quality speed and flux sensors, such as incremental encoders and the hall effect, are a crucial part of vector control for drive systems like in automotive applications. nevertheless, environmental conditions, costs and the sheer size of the system restrict their application in drive systems. moreover, flux sensors require the machine to be redesigned. as a result, developing a speed and flux sensorless approach is greatly sought. since mechanical sensors are heavy and susceptible to malfunction under demanding conditions, resulting in the degradation of the inherited robustness of the fpim, sensorless technologies can improve the reliability and robustness of the drive system [10]. https://doi.org/10.33927/hjic-2025-04 mailto:benzaoui.khaled@univ-ouargla.dz benzaoui, guedida, kouache and benyoussef hungarian journal of industry and chemistry 28 as mentioned above, sensorless drive systems have attracted considerable attention over the last few years since implementing sensors increases hardware complexity and reduces noise immunity. therefore, numerous methods for estimating the rotor speed and stator flux have been introduced to date classified as signal injections and machine model-based methods [11], as illustrated in figure 1. the first method is the signal injection technique, which can be further classified into high-frequency and low-frequency methods. meanwhile, good performance at low speeds and when stationary as well as reduced parameter sensitivity are achieved. regardless, these methods require additional hardware, resulting in severe skin effects due to the injected signal and noticeable electromagnetic torque ripples. furthermore, the machines need to be redesigned. the state-of-the-art nature of signal injection methods has been reported [11],[12]. the second method is a machine model-based (mm) technique, where the machine model and measured parameters (stator voltages and currents) are used to estimate state variables following a specific structure and direct physical phenomena interpretation. such methods have gained much attention in the literature [10],[11]. estimating the rotor speed using the model reference adaptive system (mras) is based on the error between the output of two models, that is, the reference and adjustable model, which is fed into an adaptive model to estimate the rotor speed. this approach is known for its accuracy, simplicity and ease of implementation [13]. in [14], a sliding mode observer (smo) for the sensorless application of an induction machine was proposed. the smo is comprised of a sliding surface and control law, ensuring the state variables are accurately estimated with reduced sensitivity to parameter variations and a faster dynamic response. the high-gain observer (hgo) can estimate state variables of the system based on the canonical form and reject model uncertainties. furthermore, its simple structure and fast dynamic response have drawn interest concerning the sensorless control application of induction machines [15]. therefore, this manuscript provides a comparative analysis of the three mm-based sensorless solutions, namely mras, smo and hgo. considering the merits and disadvantages of each technique, the structure of this paper is as follows: section 2 describes the modeling of a dual parallel-connected fpim drive. section 3 deals with the dtc of the drive of the two machines. the mmbased sensorless schemes are described in detail in section 4. in section 5, the simulation results are interpreted. finally, in the last section, conclusions are drawn. 2. modelling drive the circuit diagram of the two fpims connected in parallel powered from a single two-level inverter is shown in figure 2. sensorless techniques signal injection methods model-based methods low frequency methods high frequency methods open-loop estimator model reference adaptive system extended kalman filter sliding mode observer high gain observer full and reduced order closed loop observer figure 1: classification of sensorless control techniques 2a s 1a s 2b s 1b s 2c s 1c s 2d s 1d s 2e s 1e s dc v a b c d e fpim 1 fpim 2 figure 2: schematic diagram of two fpim drives connected in parallel comparative analysis of sensorless methods 53(1) pp. 27–37 (2025) 29 the relationship between the inverter and the voltage of both machines is discussed as follows: 1 2 1 2 1 2 1 2 1 2 inv a sa sa inv b sb sc inv c sc se inv sd sbd inv se sde v v v v v v v v v v vv v vv   =      =       ==     =       =   (1). the clarke’s transformation matrix [c] describes the five-phase system in two orthogonal planes, 1 and 2 , as well as in terms of a zero sequence component as follows [16]: 1 cos (2 / 5) cos (4 / 5) cos (6 / 5) cos (8 / 5) 0 sin (2 / 5) sin (4 / 5) sin (6 / 5) sin (8 / 5) 2 1 cos (6 / 5) cos (2 / 5) cos (8 / 5) cos (4 / 5) [ ] 5 0 sin (6 / 5) sin (2 / 5) sin (8 / 5) sin (4 / 5) 1 1 1 1 1 2 2 2 2 2 c                         =           (2). the considered machines consist of five distributed star-connected windings spatially shifted by 72 electrical degrees. the two machines model in the stationary reference frame, described assuming the same simplifying assumption applied in three-phase machines, is given below [17]: 0 sj j sj j sj sj j rj j rj rj j s j sj s j mj rj j sj j sj sj j rj j rj rj j mj sj j rj j rj rj j d v r i dt d r i dt l i l i l i l i l i l i                       = +   = +   = +  =  = +  = (3). the electromagnetic torque is given as: 5 sin j mj emj sj rj j j sj rj p l t l l     = (4), where: j = 1 or 2, sj j v  stator voltages, sj j i  stator currents, s j stator flux linkages, rj j i  rotor currents, r j rotor flux linkages, sr stator resistance, sl stator leakage inductance, ml mutual inductance, rr rotor resistance, rl rotor leakage inductance, emt electromagnetic torque and p pair poles. 3. direct torque control the dtc scheme is based on the direct application of the optimal vv to the drive, which is further explained by equation 4. over a sampling period, the stator flux is assumed to be constant due to the high time constant of the rotor circuit compared to the stator circuit [18]. from equation 3, the stator flux is described as follows in the plane j : ^ ( )sj j sj j sj sj jv r i dt   = − (5). by neglecting the drop in the resistance voltage, equation 5 can be written as: ^ sj j sj jv dt  =  (6). therefore, by applying the optimal vv, the stator flux and electromagnetic torque angle δ are controlled (equation 4) [18]. the implemented dtc for the proposed drive is shown in figure 3. two-level and seven-level hcs are utilized to compare the error between the reference and estimated values of both the flux and torque of the machines, thereby determining the required response, namely to increase or decrease the flux and torque. the obtained output of the hcs and the flux position are exploited to develop look-up table (table 1) in order to select the optimal vv. the vvs of the twolevel inverter are illustrated in figure 4. control of the two-machine drive requires two independent dtc controllers. therefore, one controller is developed in the 1 plane and the other in the 2 plane taking into consideration the phase transposition given in equation 1 and figure 2, resulting in the current components generating torque/flux for one machine but not for the other and vice versa [19]. for further explanation if the stator flux vector of the first fpim is in sector ii and the stator flux needs to be increased ( sj =1) and decreasing the electromagnetic torque ( temj =3). therefore, from figure 4a, the selected vv is vm4 with a switching sequence of 11110. furthermore, if the stator flux of the second fpim is within sector vi and the stator flux must be decreased while increasing the electromagnetic torque ( sj =0, temj =3), the chosen vv is vl5 with a switching sequence of 01110 as shown in figure 4b. table 1: the look-up table temj sj -1 1 3 vl(i+4) vl(i+1) 2 vm(i+4) vm(i+1) 1 vs(i+4) vs(i+1) 0 v0 v0 -1 vs(i+6) vs(i+9) -2 vm(i+6) vm(i+9) -3 vl(i+6) vl(i+9) benzaoui, guedida, kouache and benyoussef hungarian journal of industry and chemistry 30 the logic selection block alternates between the two selected vvs throughout the whole sampling period. for example, when vm4 is applied to the inverter over the first sampling period and vl5 over the second. 4. machine model (mm)-based sensorless methods the basic common schematic structure of the mm-based sensorless methods which consist of the stator flux and/or rotor speed observer are depicted in figure 5. this paper analyzes the principles of three mmbased stator flux and rotor speed observers. 4.1. model reference adaptive system (mras) the mras discussed herein was proposed in [20]. the main objective of this observer is to estimate the rotor’s mechanical speed based on the measured stator voltages and currents. the mras constitutes three models as follows [21]: stator flux and torque estimation logic selection pi pi first fpim second fpim 5 look-up table look-up table 1tem  2tem 2 * em t 1 * em t 1m  2m  2m  * 1m  * dc v 2 2s v  2 2s i  1 1s i  1 1s v  1s 2s 1 * s  2 * s  abcde acebd 1  2 2emt ^ 2s ^ 2s ^ 1emt ^ 1s ^ 1s ^ stator flux and torque estimation 1emt ^ 1s ^ 2emt ^ 2s ^ 2s ^ 1s ^ s acebd s abcde i sabcde i sacebd s abcde s abcde 1 s abcde 2 2m  1m  figure 3: dtc of two fpims connected in parallel vl1 11001 v l 9 v l 8 v l 7 vl5 vl6 vl2 vl10 vm 10 v m 9 v m 8 vm 7 vm6 vm 5 v m 3 v m 4 vm 2 vm1 v s 8 vs10 v s 9 vs7 vs6 vs5 v s 4 v s 3 vs2 vs1 01001 10000 11000 11101 11010 0 1 0 0 0 1 0 1 0 0 1 1 1 1 0 0 1 1 0 1 01110 00100 01010 101100111100110 00111 00010 00101 0 0 0 1 1 1 0 1 1 1 0 1 0 1 1 1 0 0 1 1 0 0 0 0 1 1 0 0 1 0 10001 11011 10101 [i] [viii] [vii] [vi] [v] [iv] [iii] [ii] [x] [ix] v0 11111 00000 (a) 0 0 1 0 1 vl1 1011001001 v l 9 v l 8 v l 7 vl5 vl6 v l 4 v l 3 vl2 vl10 vm 10 v m 9 v m 8 vm 7 vm6 vm 5 v m 3 v m 4 vm 2 vm1 v s 8 vs10 v s 9 vs7 vs6 vs5 v s 4 v s 3 vs2 vs1 01111 1000011001 10100 10111 11100 1 0 1 0 1 0 0 1 0 0 1 0 0 0 1 1 1 1 0 1 0 0 1 1 1 01101 00001 01100 00110 01011 01000 00011 0 1 0 1 0 1 1 0 1 1 0 1 1 1 0 1 1 0 1 0 0 0 0 2 0 1 1 0 0 0 10010 11110 10011 [i] [viii] [vii] [vi] [v] [iv] [iii] [ii] [ix] [x] v0 11111 00000 (b) figure 4: mapping vvs: (a) in the 1 plane, (b) in the 2 plane observer gain fpim model observer observed quantities motor output command vector figure 5: general presentation of the observers comparative analysis of sensorless methods 53(1) pp. 27–37 (2025) 31 the reference model the voltage model of the machine is utilized given the independent nature of the mechanical speed of the rotor as follows: ( )       rj rj sj sj sj j sj sjj j j mj ld v r i l i dt l        = − −        (7). the adaptive model the stator current model of the fpim is implemented, where the estimated mechanical speed of the rotor is integrated into the model to adjust the rotor flux. ^ ^ ^ ^ ^ 1            sj j rj j rj jmj rj r sj jj rj rj rj j rj j ild idt t t     −      = − +                 (8) the adaptation mechanism the error between the estimated values of the rotor flux obtained by the two models is entered into the adaptation mechanism to estimate the mechanical speed of the rotor as described in the following equation: ^ ^ ^ estj rj j rj j rj j rj j rj pj estj ij estjk k dt             = −   = +   (9). the stator flux and electromagnetic torque can be calculated as follows: 2 ^ ^ 2 ^ ^ 2 2^ ^ ^ ^ 1 ^ ^ ^ ^ tan 5 ( ) 2 mj sj rj mj sj j rj sj j rj rj mj sj rj mj sj j rj sj j rj rj sj sj j sj j sj j sj sj j j emj sj j sj j sj j sj j l l l l i l l l l l l i l l p t i i                           −  − = +   − = +    = +      =          = −  (10). the schematic diagram of the mras is illustrated in figure 6. 4.2. sliding mode observer in this control method, the sliding mode control is used to construct the stator flux and speed observer to reconstruct the fpim variables. figure 7 shows the block diagram of the smo. the observer design is based on two aspects, namely the sliding surface and the control law, which control the estimation process. with reference to the fpim model in the j plane, the observer is expressed as follows [22]: ^ ^ ^ ^ ^ 1 6 2 3 1 1 1 2 2 ^ ^ ^ ^ ^ 6 1 3 2 1 3 1 4 2 ^ ^ 4 1 2 21 ^ ^ 4 3 1 4 2 s j s j s j s j s j s j i s i s s j s j s j s j s j s j i s i s s j s j s j s s s j s j s j s s d i a i a i a a bv a i a i dt d i a i a i a a bv a i a i dt d a i v a i a i dt d a i v a i a i dt                              = + + + + + +    = − + + + + + +  = + + + = + + +        (11), where ^ ^ ,s j s ji i  denote the estimated stator currents, ^ ^ ,s j s j   represent the estimated stator flux components, r stands for the estimated rotor speed, ( 1,2,3,4)ixa x = refer to the stator current gains and ( 1,2,3,4)xa x = are the stator flux gains. the sliding surface is defined as: 1 2 ( 1) ( 2) s s s i sign s i i sign s     = =       (12), where: ^ ^ 1 2 s js j s js j s i i s i i    = −   = − (13). rs s jv  s ji  sl rs s jv  s ji  1 rt m r l t 0 kp ki sl r m l l r m l l 1 rt m r l t r j r j ^ r j ^ r j ^ rj figure 6: schematic diagram of the mras rs k sign sjv sji sj s v l 1 sl 1 s rl l figure 7: schematic diagram of the smo benzaoui, guedida, kouache and benyoussef hungarian journal of industry and chemistry 32 the current and flux gains can be selected as follows: 1 2 1 1 2 2 0 0 i i i i a a d a a       =       (14), where r r s r s r r s s r r l l l d r l l l            =   −    (15) and ^ 1 1 1 2 ^ 1 2 1 2 rjrj rj j sj rj rj j sj rj r q l la a a a r q l l               −         =      −  −       (16), where 1 , 2 , 1q and 2q are positive constants. the stability of the observer is related to its convergence onto the sliding surface [22]. a lyapunov function is proposed to solve this problem as follows: 1 2 tv s s= (17). since the stability of the observer is related to the estimated stator flux and their convergence onto the sliding surface, the observation error should be equal to zero. for this to be so, the derivative of the lyapunov function must be strictly negative. . .1 0 2 tv s s=  (18) therefore, the stability of the observer is ensured if the inequality below is verified: 1 2           (19). the stator flux vector and position, in addition to the rotor speed and electromagnetic torque, are computed as follows: 2 2^ ^ ^ ^ ^ 1 ^ ^ ^ ^ ^ ^ ^ ^ ^ tan 1/ ( ( ) ) 5 ( ) 2 sj sj j sj j sj j sj sj j mj j ljsj j sj jj j sj j s j j mj j emj sj j sj jsj j sj j d j p i i t f dt p t i i                       −  = +      =       = − − −   = −  (20). 4.3. high-gain observer (hgo) the hgo technique has attracted much attention for its simple design and ease of tuning. the hgo is designed to directly reconstruct the stator variables of the machine from the measured quantities (stator voltages and currents) [23]. the block diagram of the hgo is illustrated in figure 8. the expression of the observer, based on the fpim model, can be given as: . ^ ^ ^ 1 1 1 ( ) ( ) ( ) m t m m x a x bu v e v e x s c ce − − −   = + +   =  v (21), ^ ^ 0 0 t s j s j s j s j t s j s jm s j s j x i i e i i i i           =       = − −    (22), where x denotes the state variables and me the stator current error. 1 1 2 2 1 2 2 1 1 2 2 1 ( , ) 0 ( ) ( , ) 1 ( , ( )) ( , ( )) diag i i with diag i i diag i kf with diag i f k      − −  =  =    =  =  v v (23) with 1 s k l = , ( ) r s r s r s s r r l l l kf r l l l             =   −    (24), where s represents the peculiar solution of the lyapunov function.  1 1 2 2 2 2 2 2 22 t ts a s sa c c s c c i c i i i−  + + =   = =   (25) replacing ( )mv e in equation 21 yields: sjv sji sjv sji b1 a1/a6 a2/a3 2θ sji ^ sji ^ sji a4 ^ sj ^ sj ^ sj ji sj ji  ^ sj ji sj ji  k k figure 8: schematic diagram of the hgo comparative analysis of sensorless methods 53(1) pp. 27–37 (2025) 33 ^ ^ 1 6 2 3 1 ^ ^ 6 1 3 2 1 ^ ^ ^ 2 2 32 4 2 2 2 2 2 3 2 3 ^ 4 2 ( ) 2 ( ) ( ) ( ) s j s js j s j s j s j s j s j s j s js j s j s j s j s j s j s j s j s js j s j s j s j s j s j d i a i a i a a bv i i dt d i a i a i a a bv i i dt d aa a i v i i i i dt a a a a d a i dt                                 = + + + + + − = − + + + + + − = + + − − − + + = ^ ^ 2 2 2 2 2 2 2 2 3 2 3 3 ( ) ( )s j s js j s j s j aa v i i i i a a a a                   + + − − −  + + (26), where 1 s r s r r a l  + = −    , 2 r s r r a l l = , 3 s a l   = , 4 sa r= − , 6 ra = − , 1 1 s b l = and  is the observer gain. estimation of the speed and torque are achieved based on the following formula: ^ ^ ^ ^ ^ ^ ^ 1/ ( ( ) ) ( ) j s j s jj s j s j l j em s j s jj s j s j d j p i i t f dt t p i i               = − − −   = − (27). 5. simulation results this section uses simulation tests to evaluate the performance of the three mm-based observers in their transient/steady state and at low speeds as well as by taking into consideration implementation complexity and computational burden. the parameters of the two machines are depicted in table 2. 5.1. first test the performance of the three mm-based sensorless methods is evaluated at different speeds, such as low and high, under their rated load torque. the test scenarios are summarized in tables 3 and 4. 5.2. second test this test examines the robustness and disturbance rejection of the three mm-based sensorless methods when the load torque is suddenly changed. the test scenario is described in table 5. 5.3. discussion the discussed mm-based sensorless methods to estimate accuracy using the fpim over a wide range of reference speeds and by varying the load torque is evaluated (figures 9-18). in figures 9 and 14, the rotor speed responses of the two machines are shown. when the drive is operated in its steady and transient states, the speed of the machines table 3: test scenario of the first fpim [ ]time s [ / ]m rad s [ ]lt nm 0 0.1→ 0 20→ 8 0.1 1→ 20 1 1.3→ 20 60→ 1.3 2→ 60 2 2.2→ 60 100→ 2.2 3→ 100 3 4→ 100 100→ − 4 4.5→ 100− table 2: parameters of the machine 1 hp ; 200 v; 50 hz; 1400 rpm 𝑅𝑠 [ω] 10 𝑅𝑟 [ω] 6.3 𝐿𝑠 [ω] 0.4642 𝐿𝑟 [ω] 0.4612 𝐿𝑚 [𝐻] 0.4212 𝐽 [𝐾𝑔. 𝑚2] 0.03 𝑓 [ 𝑁𝑚. 𝑠−1 𝑟𝑎𝑑 ] 0.0001 𝑇𝑒𝑚 [𝑁. 𝑚] 8 𝑝 2 table 4: test scenario of the second fpim [ ]time s [ / ]m rad s [ ]lt nm 0 0.5→ 0 100→− 8 0.5 2→ 100− 2 2.6→ 100 20− → 2.6 3.4→ 20 3.4 3.7→ 20 60→ 3.7 4.2→ 60 4.2 4.4→ 60 100→ 4.4 5→ 100 table 5: second test scenario [ ]time s [ / ]m rad s 1[ ]lt nm 2[ ]lt nm 0 0.5→ 0 100→ 8 -2 0.5 1→ 100 1 2→ 0 8 2 3→ -4 0 benzaoui, guedida, kouache and benyoussef hungarian journal of industry and chemistry 34 (a) (b) (c) (d) figure 9: rotor speed response: (a) dtc, (b) mras, (c) smo and (d) hgo (a) (b) (c) (d) figure 10: electromagnetic torque response: (a) dtc, (b) mras, (c) smo and (d) hgo (a) (b) (c) (d) figure 11: stator flux response: (a) dtc, (b) mras, (c) smo and (d) hgo (a) (b) (c) figure 12: estimated rotor speed: (a) mras, (b) smo and (c) hgo (a) (b) (c) figure 13: estimation error: (a) mras, (b) smo and (c) hgo comparative analysis of sensorless methods 53(1) pp. 27–37 (2025) 35 (a) (b) (c) (d) figure 14: rotor speed response: (a) dtc, (b) mras, (c) smo and (d) hgo (a) (b) (c) (d) figure 15: electromagnetic torque response: (a) dtc, (b) mras, (c) smo and (d) hgo (a) (b) (c) (d) figure 16: stator flux response: (a) dtc, (b) mras, (c) smo and (d) hgo (a) (b) (c) figure 17: estimated rotor speed: (a) mras, (b) smo and (c) hgo (a) (b) (c) figure 18: estimation error: (a) mras, (b) smo and (c) hgo benzaoui, guedida, kouache and benyoussef hungarian journal of industry and chemistry 36 accurately follows reference commands regardless of the loading conditions of both machines with negligible over/undershoot. the estimated rotor speeds for the three observers are illustrated in figures 12 and 17, respectively. these results show that the three methods accurately track the reference speed applied to the drive using different estimation errors, namely 4 rad/s for mras, ±3 rad/s for smo and ±6 rad/s for hgo as presented in figures 13 and 18, respectively. given the electromagnetic torque response shown in figures 10 and 15, it is quickly interpreted that in response to changes in speed and the load torque applied, the electromagnetic torque is precisely and quickly determined corresponding to the load torque in the steady state. the stator flux response exhibiting a circular trajectory following the reference command as well as a good degree of decoupling between the stator flux and electromagnetic torque of the two fpims is depicted in figures 11 and 16. therefore, neither the transient state nor sensorless operation affects the performance of the two-machine drive. the test results are summarized in table 6 where a slight reduction in the torque and flux ripples is due to the accurate estimation of the three observers as opposed to the open-loop estimator used in the conventional method. an analytical comparison is given in table 7 between the discussed sensorless control schemes based on a set of performance criteria. when compared to the smo, the structures of the hgo and mras observers are less complex, only requiring one or two parameters to be tuned. however, the smo performs better during the steady and transient states at high and low speeds with negligible estimation errors. 6. conclusions an analytical study of three machine model-based sensorless schemes for a two-fpim drive connected in parallel is presented where the sensorless operation of this two-machine drive is evaluated over a wide range of operations based on several criteria such as dynamic performance, low-speed operations as well as robustness to external disturbances such as variation in load torque, computational burden and implementation complexity. as illustrated in the simulation results, the three sensorless control schemes, namely the model reference adaptive system (mras), sliding mode observer (smo) and high-gain observer (hgo), perform satisfactorily considering the reference speed and tracking of load torque when disturbances are ignored. however, among these schemes based on the merits and demerits discussed herein, the sliding mode observer (smo) performs better in terms of its estimation error, dynamic 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(eds), lecture notes in networks and systems (springer, cham), 2022, 454, doi: 10.1007/978-3-031-01942-5_78 https://doi.org/10.1109/pedg.2018.8447807 https://doi.org/10.1109/ojies.2021.3072232 https://doi.org/10.59277/rrst-ee.2023.4.2 https://doi.org/10.1109/iicpe.2018.8709603 https://doi.org/10.1016/j.rser.2013.03.051 https://doi.org/10.23919/tems.2018.8326456 https://doi.org/10.1016/j.matpr.2021.03.081 https://theses.hal.science/tel-00117094/ https://doi.org/10.1016/j.jfranklin.2020.06.013 https://doi.org/10.59277/rrst-ee.2024.2.10 https://doi.org/10.1109/tie.2016.2610941 https://doi.org/10.1109/epe.2015.7309400 https://doi.org/10.5370/jeet.2018.13.3.1185 https://doi.org/10.1109/tia.1987.4504905 https://doi.org/10.2478/pead-2024-0005 https://doi.org/10.57647/j.mjee.2024.180348 https://doi.org/10.1007/978-3-031-01942-5_78 hungarian journal of industry and chemistry vol. 46(2) pp. 67–71 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0021 formation of glycidyl esters during the deodorization of vegetable oils erzsébet bognár *1, gabriella hellner2, andrea radnóti2, lászló somogyi1, and zsolt kemény2 1department of grain and industrial plant processing, szent istván university, villányi út 29-43, budapest, 1118, hungary 2bemea katalin kővári r&d centre, illatos út 38, budapest, 1097, hungary glycidyl esters are foodborne contaminants formed during the production of fats and oils, especially during the deodorization of palm oil. the hydrolyzed free form of glycidol has been categorized as probably carcinogenic to humans by the world health organization’s international agency for research on cancer. the aim of this research was to study the formation of glycidyl esters during the lab-scale deodorization of the three most widely produced seed oils in the world (sunflower, rapeseed and soybean). the effects of two independent factors – temperature and residence time – were analyzed by a 32 full factorial experimental design and evaluated by response surface methodology. in accordance with findings in the literature, the greatest amount of glycidyl esters was formed in the soybean oil matrix. for all three oils, the effects of both residence time and temperature were significant, while the latter was more so. to reduce the formation of glycidyl esters, milder deodorization is required, which is limited because of the purposes sought by the thermal operation and removal of volatile minor components and contaminants. keywords: glycidyl esters, deodorization, seed oils 1. introduction glycidyl esters (ges) are foodborne contaminants formed in fat-containing food and food ingredients during high-temperature thermal treatment. according to previous studies, glycidol is produced during digestion from the enzymatic hydrolysis of ges [1,2]. the iarc (international agency for research on cancer) has listed glycidol as a group 2a or genotoxic carcinogen [3]. this year, the european commission adopted the commission regulation (eu) 2018/290 that stipulates the maximum level of glycidyl fatty acid esters permitted in vegetable oils and fats, infant formula, follow-on formula and foods for special medical purposes intended for infants and young children. the maximum concentration of glycidyl fatty acid esters is 1 mg/kg in vegetable oils and fats placed on the market for end consumers or for use as an ingredient in food, and 0.5 mg/kg for vegetable oils and fats destined for the production of baby food and processed cereal-based food for infants and young children [4]. ges are formed in vegetable oils during the refining process in the deodorization step, which is conducted at high temperatures (200-275 ◦c) under vacuum (of less than 10 mbar residual pressure) [5, 6]. deodorization is the last step of refining of conventional edible oils and is intended to remove undesirable substances in order to im*correspondence: zsofi.bognar@outlook.hu prove the taste, odor, color and oxidative stability of such oils [7]. according to data from the literature, high levels of ges are primarily measured in refined palm oil and its fractions. destaillats et al. [8] showed in their study that ges are formed from diand monoacylglycerols (dags and mags), but not from triacylglycerols (tags). accordingly, high levels of ge can be traced back to high levels of dags in crude palm oil [8]. the formation of ge starts at about 200 ◦c [8]. analytical methods for the determination of ges can be divided into two main groups: direct and indirect methods [9]. individual ges are determined by direct quantitation methods which are mainly based on liquid chromatography-mass spectrometry (lc-ms), requiring a significant number of reference compounds and internal standards [10, 11]. indirect determination is based on the conversion of ges into glycidol which is then isolated, derivatized, chromatographically separated and quantified. the result is expressed as the amount of glycidol that can be released from ges. these methods require only a small number of internal standards [9]. in our study, the quantity of ges in seed oil during lab-scale deodorization was determined in order to examine the effects of two independent factors – temperature and residence time – on the formation of ges. mailto: zsofi.bognar@outlook.hu 68 bognár, hellner, radnóti, somogyi, and kemény 2. experimental 2.1 samples and measurements bleached sunflower, rapeseed and soybean oils were supplied by bunge limited (bunge zrt. hungary and bunge ibérica, s.a.u.). diethyl ether, ethyl acetate, n-hexane and high-performance liquid chromatography (hplc)grade water were obtained from vwr international kft. (debrecen, hungary). toluene, isohexane, sodium bromide and phenylboronic acid were obtained from merck kft. (budapest, hungary). methanol, sodium hydroxide and anhydrous sodium sulfate were purchased from reanal laborvegyszer kft. (budapest, hungary). the internal standards glycidyl palmitate-d5 and 3-chloro-1,2propanediol-d5 (3-mcpd-d5) were obtained from labstandards (budapest, hungary). all reagents and chemicals were of analytical grade. lab-scale deodorization trials were conducted in 150 g batches at temperatures between 220 and 260 ◦c. the bleached oils (sunflower, rapeseed or soybean) were heated to the target temperature (220, 230, 240, 250 or 260 ◦c) within 10–15 minutes. the process lasted 3 hours at a pressure of 3–4 mbar using nitrogen as a stripping gas. without breaking the vacuum, sampling was conducted after 0, 15, 30, 45, 60, 90, 120 and 150 minutes had elapsed. the quantities of glycidyl esters were determined using the american oil chemists’ society (aocs) official method cd 29b-13, which is based on alkalinecatalyzed ester cleavage and transformation of the released glycidol into monobromopropanediol (mbpd) and derived free diols using phenylboronic acid (pba). these derivatives are measured by the gas chromatography/mass spectrometry (gc/ms) coupled system (agilent 6890 coupled with 5973) in the selected ion monitoring (sim) mode. quantitative determination was based on the deuterated internal standard using characteristic ions for derivatised glycidol-d5 at m/z 150 and 245, and derivatised glycidol at m/z 147 and 240. 2.2 experimental design and statistical analysis the temperature and residence time were studied using response surface methodology (rsm). the results of the 32 full factorial experimental design (see table 1) were evaluated by analysis of variance (anova) models using statistica 13. the center point of the 32 full factorial design (mid temperature 240 ◦c) and mid time 90 minutes) was repeated three times. only the significant effects (of main effects and interactions) were taken into account in the response surface methodology. the generalized polynomial model for describing the response of independent variables is given in y = β0 + β1x1 + β2x 2 1 + β3x2 + + β4x 2 2 + β5x1x2 + β6x1x 2 2 + + β7x 2 1x2 + β8x 2 1x 2 2 (1) table 1: 32 full factorial experimental design independent variables levels -1 0 +1 x1 temperature (◦c) 220 240 260 x2 residence time (min) 0 90 180 dependent variables (yi) glycidyl esters (mg/kg) 3. results and evaluation 3.1 experiments the results of the lab-scale investigation of ge formation are shown in fig. 1. in our experimental design, the greatest amount of ges formed in soybean oil, in which the concentration of ges reached 5.5 mg/kg at 260 ◦c after 180 minutes (fig. 1a). in the sunflower and rapeseed oils, the maximum concentrations of ges reached were 1.6 and 1.5 mg/kg, respectively (figs. 1b and 1c). the ge content of sunflower and rapeseed oils was kept under 1 mg/kg after 120 minutes of deodorization at a temperature of 250 ◦c or less, but for soybean oil this level was obtained at or below 230 ◦c. this demonstrates that the amounts of precursors in the oils strongly influence the formation of ge, and consequently the optimal deodorization temperature. the threshold concentration of figure 1: ges of seed oils during deodorization: a) sunflower oil, b) rapeseed oil, c) soybean oil hungarian journal of industry and chemistry formation of glycidyl esters during the deodorization of vegetable oils 69 figure 2: fitted surfaces for seed oils: a) sunflower oil, b) rapeseed oil, c) soybean oil 0.5 mg/kg permitted for infant food was complied with at 240, 230 and 220 ◦c for rapeseed, sunflower and soybean oils, respectively (after 120 minutes of deodorization). in the applied experimental setup, up to 0.3 mg/kg of ge formed after 10–15 minutes of heating. at lower deodorization temperatures, the effect of time becomes practically insignificant, especially at 220 and 230 ◦c. 3.2 statistical analysis the application of rsm allowed the main effects and interactions to be determined simultaneously. anova shows the significant effects, which can be used for buildtable 2: regression coefficients for intercept (i), linear and quadratic factors, as well as interactions between factors in the fitted models of seed oils sunflower oil rapeseed oil soybean oil i 7.95 7.12 10.32 t −6.72× 10−2 −5.9×10−2 −9.02×10−2 t 2 1.45×10−4 1.23× 10−4 2× 10−4 t 1.17×10−1 2.16×10−1 1.14 t2 n.s. n.s. n.s. tt −1.13× 10−3 −1.96×10−3 −1.01× 10−2 t 2t 3× 10−5 4× 10−5 2.2× 10−5 tt2 n.s. n.s. −2.38× 10−8 n.s.: effect not significant ing the response surface model. the fitted surfaces for sunflower, rapeseed and soybean oils are presented in figs. 2a-c, respectively. the shapes of the surfaces are very similar, the only difference is in their heights. the interactions between the independent variables can be observed from the fitted surfaces, because at lower temperatures the concentrations of ges gradually increased over time, while at higher temperatures a more rapid increase occurred. for all three seed oils the temperature had the largest effect. the interaction between the independent variables and the effect of time were the second and third most significant, but the quadratic components and their interactions with the other factors were noticeable in most cases, as well. the regression coefficients are shown in table 2 coefficients in the case of sunflower and rapeseed oils are very similar so the rsm diagrams of these oils fall within the same range of values (figs. 2a and 2b). 4. discussion according to the data from the literature, the oil that has been studied the most in this respect is palm oil along with its fractions [8, 12]. cheng et al. [13] summarized the data from previous studies and according to this review the highest concentrations of ges in seed oil were found in soybean oil when compared to rapeseed and sunflower oils. this is in agreement with our observations. the higher concentrations of ges that formed during deodorization were due to the higher levels of dags and mags in the raw material. it was found that the critical temperature range is between 220 and 240 ◦c, above which more than 0.5 mg/kg of ges may form, depending on the quality of the raw material. this conclusion is similar to the results of previous investigations. craft et al. [12] concluded that between 230 and 240 ◦c, the formation of ge is extensive, consequently this value should be considered as an upper limit for the deodorization process. de kock et al. [14] suggested conducting deodorization for a longer period 46(2) pp. 67–71 (2018) 70 bognár, hellner, radnóti, somogyi, and kemény of time at temperatures below 240 ◦c, which might also minimize the formation of trans fatty acids. 5. conclusion the present investigation suggests that the formation of ges in seed oils during deodorization is not negligible. the rate of formation can be traced back to the level of dags and mags [15] in the raw material. a simultaneous increase in temperature and time could result in extremely high levels of ges in oils. on an industrial scale, the formation of ges can be controlled in the oils examined, meaning that the upper limit of ges (1 mg/kg) in vegetable oils and fats placed on the market for general consumption can be achieved through preventive measures. the stricter limit imposed on oils destined for the production of food for infants and young children presents greater challenges, and thus requires a combination of high quality raw materials as well as a controlled refining process. acknowledgement funding for this research was provided by the doctoral school of food sciences at szent istván university (budapest) and by the bemea katalin kővári r&d centre. the project is supported by the european union and cofinanced by the european social fund (grant agreement no. efop-3.6.3-vekop-16-2017-00005). symbols β0−8 regression coefficients for intercept, linear and quadratic factors and interactions between factors x1, x2 independent factors t deodorization temperature t deodorization time references [1] appel, k.e.; abraham, k.; berge-preiss, e.; hansen, t.; apel, e.; schuchardt, s.; vogt, c.; bakhiya, n.; creutzenberg, o.; lampen, a.: relative oral bioavailability of glycidol from glycidyl fatty acid esters in rats, arch. toxicol., 2013 87(9), 1649–1659 doi: 10.1007/s00204-013-1061-1 [2] frank, n.; dubois, m.; scholz, g.; seefelder, w.; chuat, j.-y.; schilter, b.: application of gastrointestinal modelling to the study of the digestion and transformation of dietary glycidyl esters, food addit. contam. part a, 2013 30(1), 69–79 doi: 10.1016/j.foodchem.2010.08.036 [3] iarc (international agency for research on cancer): glycidol, in: iarc monographs volume 77. on the evaluation of carcinogenic risks to humans (who press, lyon, france) 2000 pp. 469–486 isbn: 9283212770 [4] official journal of the european union: commission regulation (eu) 2018/290 of 26 february 2018 amending regulation (ec) no 1881/2006 as regards maximum levels of glycidyl fatty acid esters in vegetable oils and fats, infant formula, follow-on formula and foods for special medical purposes intended for infants and young children 2018 [5] carlson, f.k.: deodorization. in: hui, y. h. (ed.) bailey’s industrial oil and fat products. edible oil and fat products: processing technology. 5th edition. volume 4. (john wiley & sons inc., new york, usa) 1996 pp. 411–449 isbn: 9780471594284 [6] o’brien, r.d.: fats and oils formulating and processing for applications. third edition. (crc press taylor & francis group, boca raton, florida, usa) 2009 pp. 153–164 isbn: 9781420061666 [7] sipos, e.f.; szuhaj, b.f.: edible oil processing. in: hui, y.h. (ed.) bailey’s industrial oil and fat products. edible oil and fat products: oils and oilseeds. 5th edition. volume 2. (john wiley & sons inc., new york, usa) 1996 pp. 497–602 isbn: 9780471594260 [8] destaillats, f.; craft, b.d.; dubois, m.; nagy, k.: glycidyl esters in refined palm (elaeis guineensis) oil and related fractions. part i: formation mechanism, food chem., 2012 131(4), 1391–1398 doi: 10.1016/j.foodchem.2011.10.006 [9] ermacora, a.; hrncirik, k.: indirect detection techniques for mcpd esters and glycidyl esters. in: macmahon, s. (ed.) processing contaminants in edible oils mcpd and glycidyl esters (aocs press, urbana, usa) 2014 pp. 57–90 isbn: 9780988856509 [10] thürer, a.; granvogl, m.: direct detection techniques for glycidyl esters. in: macmahon, s. (ed.) processing contaminants in edible oils mcpd and glycidyl esters (aocs press, urbana, usa) 2014 pp. 91–120 isbn: 9780988856509 [11] blumhorst, m.r.; venkitasubramanian, p.; collison, m.w.: direct determination of glycidyl esters of fatty acids in vegetable oils by lc–ms, j. am. oil chem. soc., 2011 88(9), 1275–1283 doi: 10.1007/s11746-011-1873-1 [12] craft, b.d.; nagy, k.; seefelder, w.; dubois, m.; destaillats, f.: glycidyl esters in refined palm (elaeis guineensis) oil and related fractions. part ii: practical recommendations for effective mitigation, food chem., 2012 132(1), 73–79 doi: 10.1016/j.foodchem.2011.10.034 [13] cheng, w.w.; liu, g.q.; wang, l.q.; liu, z.s.: glycidyl fatty acid esters in refined edible oils: a review on formation, occurrence, analysis, and elimination methods, compr. rev. food sci. f., 2017 16(2), 263–281 doi: 10.1111/1541-4337.12251 [14] de kock, j.; papastergiadis, a.; de greyt, w.: technological solutions and developments in edible oil processing to minimize contaminants in various oils and fats. 5th leipzig symposium ‘processing and hungarian journal of industry and chemistry https://doi.org/10.1007/s00204-013-1061-1 https://doi.org/10.1016/j.foodchem.2010.08.036 https://doi.org/10.1016/j.foodchem.2010.08.036 https://doi.org/10.1016/j.foodchem.2011.10.006 https://doi.org/10.1016/j.foodchem.2011.10.006 https://doi.org/10.1007/s11746-011-1873-1 https://doi.org/10.1007/s11746-011-1873-1 https://doi.org/10.1016/j.foodchem.2011.10.034 https://doi.org/10.1016/j.foodchem.2011.10.034 https://doi.org/10.1111/1541-4337.12251 formation of glycidyl esters during the deodorization of vegetable oils 71 analytics: how does co-operation work in practice?’ (9-10 march 2016, leipzig, germany) 2016 [15] csányi, e., bélafi-bakó, k.: semi-continuous fatty acid production by lipase, hung. j. ind. chem., 1999 27(4), 293–295 46(2) pp. 67–71 (2018) introduction experimental samples and measurements experimental design and statistical analysis results and evaluation experiments statistical analysis discussion conclusion hungarian journal of industry and chemistry vol. 46(2) pp. 91–100 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0025 optimal design and operation of buffer tanks under stochastic conditions bálint levente tarcsay1, éva mihálykó-orbán1, and csaba mihálykó *1 1department of mathematics and computing, university of pannonia, egyetem u. 10, veszprém, h-8200, hungary safety regulations demand the elimination of random mistakes and the reliable operation of production units. however, the control and maintenance of batch and semi-continuous processes haalways been difficult. in this paper, a way of preventing malfunctions in batch and semi-continuous processes is presented by using appropriately designed buffer tanks. a stochastic model was investigated in which batch and continuous subsystems were linked by an intermediate storage tank. the main concern was the reliability of the system. reliable operation was defined as neither the exhaustion of raw materials nor the excessive accumulation of them. the counting processes that describe the random batch-input and random batch-output processes are supposed to be independent homogeneous poisson processes with different rates. by introducing a function that describes the material in storage, reliable operation is defined as when this function satisfies two inequalities for a time interval of any duration. by applying probabilistic methods, an integral equation is set up for the the reliability. nevertheless, its analytical solution cannot be determined, hence the values according to a monte carlo simulation are approximated. by applying this method, a link could be identified between the necessary initial buffer and tank capacities that belong to a reliability level. economic investigations were conducted to help determine the optimal initial buffer and tank capacities that satisfy the appointed reliability level. keywords: intermediate storage, stochastic modelling, batch system control, monte carlo simulation, economic optimization 1. introduction during the operations of chemical processes, one often encounters uncertainties. these events can stem from equipment failures, mistakes made by staff managing the process, or bad managerial decisions. these mistakes can often lead to malfunctions which cannot be tolerated in processes using dangerous or very expensive materials. a serious malfunction can cause damage to equipment, force the process to stop, or, in the worst-case scenario, endanger the lives of operators. all of these can cause serious financial damage to a company. since these malfunctions carry considerable risks, some procedures are designed to be able to withstand and mitigate the effects of random events. a good control system with trained operators can be the key to neutralizing malfunctions. however, in batch and semi-continuous processes the implementation of control systems has always been difficult. one of the best ways to manage these processes is the isa-88 standard. isa-88 provides a consistent set of rules as well as terminology for batch control in addition to defining the physical model, procedures and recipes. however, the implementation of a control system which *correspondence: mihalyko@almos.uni-pannon.hu is up to standard is expensive given the costs of equipment, salaries of operators, etc. in the light of these factors, an attempt was made to devise a method for the design and operation of intermediate storages to mitigate the effects of malfunctions and reduce overall costs of equipment and operators in a plant. intermediate storages, also known as buffer tanks, are important units in the chemical industry. throughout the paper the investigated units will be referred to as buffer tanks, intermediate storages or simply as tanks and storages. with these storages the production process can be made safer by creating an emergency reserve to provide raw materials for the operation of other units. the design of buffer tanks is not trivial even when uncertainties are disregarded which are present during the production process [1]. however, to ensure the reliable operation of a device, which is even subject to uncertainties, a more complex approach is required. therefore, it could prove beneficial to use stochastic models for the design of units since with these models all random variables which define the operation process can be taken into account. operating and design parameters of the buffer tank must be chosen so that the amount of material stored is always sufficient to satisfy the demands of customers while also providing mailto:mihalyko@almos.uni-pannon.hu 92 tarcsay, mihálykó-orbán, mihálykó a reserve of the raw material in question in the event that other units malfunction. nowadays, models used to determine these parameters under different operating conditions are a significant focus of research [2–5]. these models are closely related to those applied in insurance mathematics to calculate the amount of capital and insurance prices required to operate an insurance company so that the firm can cover the damages of its clients while still turning a profit. many of the techniques used in that field can be applied following minor adjustments in these cases as well [5, 6]. during the study of chemical processes, infinite intervals of time are often presumed, meanwhile, the probabilities of the material in the tank overflowing or being exhausted are investigated separately. if the process is investigated over an infinite time interval, then the function that defines the reliability of the system can be expressed as a solution of volterraor fredholm-type integral equations. despite being difficult to solve, it must be noted that they are easier to handle than those that define reliability over a finite time interval. the main reason for this, in the case of finite intervals, is that not only the first occurrence but also the time remaining during the time interval contribute to the reliability of the system. in the case of infinite time intervals, this quantity is constant, namely infinity. if only the probability of the raw material in the tank being exhausted is studied as a function of the initial buffer capacity or the probability of it overflowing as a function of the tank capacity, then only the probability of malfunction as a function of one variable need be investigated [5, 6]. solving equations with one variable is simpler than solving integral equations that describe the process as a function of two variables, namely initial buffer and tank capacities, supplemented with the time interval. the economical optimization of similar processes has already been conducted in some simpler cases [7]. in this publication, the focus of interest was on investigating the process over a fixed finite time interval where the reliability of the system was treated as a function of two variables. a chemical process was examined where a raw material was loaded into a buffer tank from a batch reactor. some of this raw material was drained from the tank at randomly chosen intervals for customers as required. moreover, the raw material could be constantly extracted which fed the unit after the tank had been used to separate components of the raw material and accumulate the key component. this differs from popular models which investigate such processes that by and large only deal with a batch feed and continuous extraction of the raw material. to investigate the model, a function was defined to express the reliability of the process as a function of the initial buffer and tank capacities. the integral equation satisfied by the function, however, could not be solved analytically, therefore, a monte carlo simulation was used to approximate the reliability of the process numerically. based on the investigations using one variable, a function was applied to the numerical results whose parameters were identified using the least squares method. by applying this function, the initial buffer and tank capacities required could be calculated to ensure the reliable operation of the unit over the examined finite time interval. however, the required degree of reliability could be achieved by an infinite number of parameter combinations. from among these combinations that ensure a safe operation, the optimal parameter pair was determined using economical optimization by considering the incomes and expenditure of the process. to investigate a process like this based on actual data from a plant, a thorough knowledge of the distribution functions of every random variable present is required. to acquire such data, information about equipment failures or mistakes made by the operators is required which is documented in every chemical plant. should the demand for the raw material vary, data with regard to economic trends from previous years can be used. if the amount of data is sufficiently large, then various methods can be used to compare the sample with a reference probability distribution. in this way a known cumulative distribution function can be used to approximate the empirical distribution function of the sample. in this publication, instead of using authentic data, assumptions about the distribution of the random variables were made, however, the techniques shown in this paper can be applied to different distributions as well and by using our methods an answer to design and operation problems using authentic data can be found. 2. the investigated model the change in mass of a raw material in a buffer tank was studied. the intermediate storage acts as a link between a batch system which feeds the tank and a batch in addition to a semi-continuous processes which both drain material from the tank (fig. 1). the process was studied over the finite time interval of [0, tmax]. over the course of the chemical process, the product is synthesised periodically in a batch reactor (1). then the product, which is a mixture of byproducts, and the key component are fed into the buffer tank (2). the buffer tank, also known as the intermediate storage (2), is linked to a continuously operational unit, e.g. a fractionating column (3), which is responsible for purifying the product by separating the byproducts from the key component. however, as with most processes that produce multiple components, consumer demand is not exclusively focused on the key component but on the raw mixture of products as well. the goal of the plant is to design and operate the intermediate storage in a way which supplies the necessary amount of raw materials for the continuous subsystem whilst satisfying the demands of the clientele. the frequency and volume of consumer demand for the hungarian journal of industry and chemistry optimal design and operation of buffer tanks under stochastic conditions 93 figure 1: illustration of the examined process (1. batch reactor, 2. buffer tank, 3. fractionating column). raw products as well as those of equipment failures and mistakes made by operators within the batch subsystem occur randomly. due to equipment failures or mistakes made by operators, the batch feeds that originate from the reactor (1) can vary in terms of both mass and time of arrival. the varying amounts and schedule of both feeds and drainings can cause two types of malfunctions to occur, the materials in the tank can either overflow or be completely exhausted which will hinder the rate of production in the continuous subsystem and render it impossible to meet consumer demands. in the following, the mathematical assumptions of this problem is discussed. let z0 denote the initial buffer capacity of the intermediate storage, zmax represent the capacity of the tank, and the duration of the time intervals between the consecutive batch feeds be tbi , i = 1, 2, · · · it is assumed that these intervals are independent random variables of the exponential distribution with parameter λl. in the same way, let the duration of the time intervals between consecutive drainings from the intermediate storage be tli, i = 1, 2, · · · which like the feeds are independent random variables of the exponential distribution with parameter λl. the number of feeds over time interval t denoted by nb(t ), and the number of periodic drainings by nl(t ), which, because of our assumptions, are random variables of poisson distribution with parameter λb−t or λlt , respectively. the amount of raw material fed into the intermediate storage during batch i is denoted by yb i , similarly the ith draining from the intermediate storage is represented by yl i. the character c represents the rate at which the raw product was drained from the intermediate storage by the continuous subsystem. the amounts of both the fed and drained batches are assumed to be random variables of identical distribution. the functions gb(y)and gl(y) are their respective probability density functions. it is supposed that the amounts of materials in addition to the durations of feeds and drainings are independent of each other. assuming the material in the intermediate storage was neither exhausted nor overflew throughout the operating time t then equation 0 < z0 + nb(t )∑ i=1 yb i − nl(t )∑ i=1 yl i − ct ≤ zmax (1) must be satisfied by the amount of material currently in the buffer tank. since these inequalities contain random variables, they can only be fulfilled with a certain probability. the mass of material in the intermediate storage can be expressed by equation z(t ) = z0 + nb(t )∑ i=1 yb i − nl(t )∑ i=1 yl i − ct, (2) the reliability of the system, i.e. the probability that the material neither overflows nor is exhausted throughout the time interval [0, tmax], can be defined as shown in equation ψ(z0, zmax, tmax) = p (0 < z(t ) ≤ zmax) for all 0 ≤ t ≤ tmax. (3) conversely, 1−ψ (z0, zmax, tmax) is the probability of a malfunction occurring, also referred to as a failure. both are defined as functions of the initial buffer and tank capacities as well as the operating time. the expectation of z(t ), i.e. e(z(t )), can be expressed by e (z (t )) = e ( yb i ) λbt − e ( yl i ) λlt − ct + z0 (4) if 0 > e (z (t )) − z0, then the process has decreasing tendency in average. if 0 < e (z (t )) − z0, then an overflow can be expected over a large time interval. if 0 = e (z (t ))− z0, then the process is in equilibrium. to evaluate the process, the time the failure first occurred is required during the interval [0, tmax], when the amount of material exceeded the capacity of the tank or was equal to zero. the time of failure is defined as the following function: tf (z0, zmax, tmax) = { inf {t : 0 ≤ t ≤ tmax : z(t ) ≤ 0 or zmax < z(t )} , if such a t value exists ∞, if for all 0 ≤ t ≤ tmax 0 < z(t ) ≤ zmax (5) 46(2) pp. 91–100 (2018) 94 tarcsay, mihálykó-orbán, mihálykó this time point is a random variable too, its expectation,e(tf (z0, zmax, tmax)·1tf (z0,zmax,tmax)<∞), will be denoted by e(tf ) and its standard deviation by d(tf ). they are finite, as 0 ≤ tf (z0, zmax, tmax) · 1tf (z0,zmax,tmax)<∞ ≤ tmax is adhered to. by applying the renewal theory [8], it can be proven that ψ satisfies the integral equations ψ (z0, zmax, tmax) = λl λl+λb  min ( z0 c ,tmax )∫ 0 z0−ct1∫ 0 ψ (z0 − ct1 − y1, zmax, tmax − t1) · λle−λlt1gl(y1)dy1dt1 + e −λltmax + + λb λl+λb  min ( z0 c ,tmax )∫ 0 zmax−(z0−ct2)∫ 0 ψ (z0−ct1+y2, zmax, tmax−t2) · λbe −λbt2gb(y2)dy2dt2+e −λbtmax  , (6) if ctmax ≤ z0 and ψ (z0, zmax, tmax) = λl λl+λb  min ( z0 c ,tmax )∫ 0 z0−ct1∫ 0 ψ (z0−ct1−y1, zmax, tmax−t1) · λle−λlt1gl (y1) dy1dt1 + + λb λl+λb  min ( z0 c ,tmax )∫ 0 zmax−(z0−ct2)∫ 0 ψ (z0−ct2+y2, zmax, tmax−t2) · λbe−λbt2gb(y2)dy2dt2  (7) if z0 < ctmax. to design a buffer tank which is capable of operating with a desired degree of reliability of 1 − α where α denotes the probability of malfunction during the time interval [0, tmax], solutions to equation ψ (z0, zmax, tmax) = 1− α (8) must be found. 3. parameter dependence of the reliability of the process and the expectation of failure time since the integral equation proved to be exceedingly difficult to handle analytically, a monte carlo simulation to approximate the probability values for different parameters was used. monte carlo simulations are more widely accepted tools in dealing with stochastic models [9, 10]. for the simulation environment, matlab r2015a [11] was used. realization of the process when the parameters tmax = 50 h, λl = 0.3 h−1, λb = 0.4 h−1 and c = 5 kgh−1 were chosen is demonstrated in fig. 2. the mean of the input suddenly increased in the function z(t), the withdrawals from the batch caused sudden decreases and continuous withdrawal resulted in a reduction in linear parts. the amounts drained and fed were defined as random variables from the gaussian distribution. the initial buffer capacity was 50 kg and continuous withdrawal resulted in a linear decrease in the amount of material. at t = 1 h, the tank was filled. the amount of material in the tank increased by 3 kg, then the continuous withdrawal resumed. a little bit later a sudden withdrawal occurred. similar events were repeated at random time points with random quantities. at t = 7.8 h a large withdrawal took place and the material became exhausted, therefore, z(t) became negative. the time of failure, in this case the time a shortage was observed, was tf = 7.8 h. although the process was investigated over an interval of time, it is sufficient to compute the values of z(t) only at those points where sudden changes occurred and at the endpoint of the interval. an overflow could only occur if an input was present. both continuous and batch withdrawals can cause shortages. if the amount of material at the time points of batch inputs and outputs is comfigure 2: the change in the mass of material in the buffer tank. hungarian journal of industry and chemistry optimal design and operation of buffer tanks under stochastic conditions 95 figure 3: the probability of a failure as a function of the initial buffer and tank capacities. puted, it can be determined whether or not the continuous withdrawal caused the shortage during the time interval bounded by the last two batch events. if it did, the time point of the shortage can also be computed by solving a linear equation. by applying a monte carlo simulation, the probabilities were approximated by relative frequencies and the expected failure times were estimated by the average times. 10, 000 simulations were conducted which yielded an accuracy 0.01. for example, tmax = 50 h was fixed and the parameters of the process were λl = 8 h−1, λb = 12 h−1 and c = 12 kg h−1. the amounts drained and fed were defined as random variables from the gaussian distribution with a mean of 8 kg and a standard deviation of 2 kg. with the aforementioned parameters, the probability of malfunction was calculated and the following results obtained for the process under the indicated conditions (fig. 3). figure 4: the expected malfunction times as a function of initial buffer and tank capacities. figure 5: a histogram of the malfunction times. in fig. 3 it can be seen that when the tank capacity was fixed, the probability of failure increased as a function of the initial amount of material. this can be explained by the fact that although the likelihood of a shortage decreased, the amount of material in the tank tended to increase, therefore, the free volume of the tank decreased, hence the increase in the probability of overflow. on the other hand, when the initial buffer capacity was fixed, the probability of a failure decreased as a function of the tank capacity. this tendency can be explained by the fact that the probability of overflow decreased and stemmed from the fact that λb was greater than λl meaning that the average time intervals between feeds were smaller than those between drainings. this caused the process to be more prone to malfunction due to overflow. the times of failures (tf ) were investigated as well. expected failure times are shown in fig. 4 as a function of the initial buffer and tank capacities. if no failure occurred, then tf was equal to zero, therefore, the expected tf was close to zero as well. a histogram of the malfunction times is provided in fig. 5 when z0 = 400 kg and zmax = 1500 kg. it demonstrates that no quick failures occurred due to a shortage of material resulting in an increase in the amount of material and the tank overflowing. the distribution of the malfunction time in this case is unimodal and the degree of dispersion is quite large. the dispersion of the malfunction time as a function of the initial buffer and tank capacities can be seen in fig. 6 which demonstrates that when the tank is half full, large standard deviations with regard to the malfunction times were calculated. in the case of large or small capacities, the malfunction time can be accurately predicted as the degree of dispersion is small. 46(2) pp. 91–100 (2018) 96 tarcsay, mihálykó-orbán, mihálykó figure 6: the standard deviation of the malfunction times. 4. design of the tank and initial buffer capacities for a given reliability level during previous research, only models that consisted of a batch feed and continuous drainage in the absence of batch drainage [5–7] were studied. in the papers that deal with these models, it has been published that the integral equation for the reliability of the unit could be solved analytically in special cases where the process over an infinite time interval as a function of one variable is observed. in these special cases the solutions to the equation were mainly exponential in form or the linear combination of exponential functions [5, 6]. consequently, when fitting a function to simulated data, a function was chosen which exhibits similar characteristics. by fixing tmax, seeking ψ is suggested as a function of the initial buffer capacity x and tank capacity y, in the form of equation h (x, y) = 1− ( 1− e(−ax) )c( 1− e(−b(y−x)) )d , (9) where x < y; a, b, c, and d are positive parameters which have to be optimized. numerical values of ψ were computed by a monte carlo simulation for some values of z0 and zmax, and the parametersa–d were determined using the least squares method, by minimizing function s (a,b,c,d) = ∑ r ∑ s (ψ (xr, ys)−h (xr, ys)) 2 (10) this function was minimized numerically. the approximated function exhibited a fit to the original function of 95 % on average which was calculated using a monte carlo simulation. the error of the fitting was inversely proportional to the number of simulations used to model the system as well as the number of points with regard to the tank and initial buffer capacities investigated. since the quality of the fit was high (95 % on average), it can be assumed that even if the minimum identified is a lofigure 7: the relationship between the tank and initial buffer capacities that correspond to different levels of reliability 1− α. cal minimum, the approximation is sufficient for use in further computations. using the fitted function, equation ψ(x, y) ∼ h (x, y) = = 1− ( 1− e−ax )c( 1− e−b(y−x) )d = 1− α. (11) was solved. appropriate initial buffer and tank capacities for the process are provided by the solution to the equation above with a reliability of 1−α over the time interval [0, tmax]. a link between the values of x and y is provided by the solution to the equation, namely equation y = x− ln ( 1− ( 1− α (1− exp(−ax))c )1/d ) b . (12) this relationship, using the parameter set presented in the previous section, is given in fig. 7. the interval of the initial buffer capacity was [100, 500] kg and the step sizes applied were 100 kg. the interval of the tank capacity was [1000, 2500] kg and the step sizes applied were also 100 kg. to eliminate numerical inaccuracies, the values of the time intervals were transformed into the time intervals [0, 100]. by transforming the time intervals into a subset of [0, 100], a = 0.4966, b = 0.12, c = 0.9324, and d = 86.4875 were computed. after the computations, the results were transformed into the original time intervals. the required tank capacities as a function of the initial buffer capacity in the intermediate storage corresponding to the reliabilities 1 − α = 0.95, 0.975, . . . 0.99 can be seen in fig. 7. it can be seen that with some initial values a reliability of 0.99 is infeasible since the likelihood of a shortage itself exceeds level α. the minimum initial amount hungarian journal of industry and chemistry optimal design and operation of buffer tanks under stochastic conditions 97 figure 8: the required initial buffer capacity corresponding to a fixed tank capacity of 1, 900 kg and reliability level of 0.8 as a function of the draining intensity (c) . of material in the intermediate storage with a reliability of 1− α can be expressed by − ln ( 1− (1− α) 1/c ) a < xmin (13) from fig. 7 it can be seen that if the lower limit is used as the initial buffer capacity, the corresponding storage capacity is enormous. the reason for this is the fact that the likelihood of a shortage is equal to α and an overflow is undesirable, therefore, the tank capacity must be very large. according to the results shown in fig. 7, this value is approximately 150 kg. moreover, if z0 exceeds a certain level, the function is by and large linear. it is shown by the linear part of the function that when the initial buffer capacity exceeds 250 kg, the likelihood of a failure due to exhaustion of material is almost zero. the likelihood α of an overflow is provided by the difference between the tank and initial buffer capacities. therefore, to calculate the required tank capacity over this time interval, the volume which can ensure that the likelihood of overflow will remain as α is simply added to the buffer capacity in the intermediate storage. finally, the minimum tank capacity that corresponds to a given level of reliability can be determined by numerically minimizing function y = x− ln 1− ( 1− α (1− exp(−ax)) c )1/d  b (14) for the reliability level 1− α = 0.95, the minimum tank capacity is approximately 1, 820 kg and the required initial buffer capacity approximately 245 kg. by fixing the tank capacity and reliability level, the dependence of the required initial buffer capacity on the withdrawal rate was investigated. the values of the refigure 9: the required drainage intensity corresponding to a fixed tank capacity of 1, 900 kg and a reliability level of 0.8 as a function of the initial buffer capacity. quired initial buffer capacity were determined numerically according to the secant method. the reliability level was 1−α = 0.8 and the tank capacity was 1, 900 kg. the results can be seen in fig. 8. according to this result, by increasing the withdrawal rate, the required initial buffer capacity increases sharply which facilitates control of the process. finally, the required drainage intensity corresponding to the reliability level of 1 − α = 0.8 and fixed tank capacity zmax = 1, 900 kg as a function of the initial buffer capacity was provided (fig. 9). it can be seen that it is also a monotonically increasing function, but the rate of increase is usually less than in the case of fig. 8. 5. economic investigations according to fig. 7, if the minimum required amount of initial buffer capacity is supplied then the required level of reliability of the process can be achieved by an infinite number of combinations of tank and initial buffer capacities. to determine the optimal combination, economic evaluations of the design are recommended. it is assumed that following a possible failure, the process is restarted, however, such a restart is time-consuming and expensive. during the calculations both the income and expenditure associated with each parameter are taken into account. these include the costs of raw materials, the buffer tank, malfunctions and repairs as well as the income generated from sales of both the key component and raw product. to determine the income generated by the process at time t , equation q (t ) = gkey (t ) +graw (t )−kmat (t )− − kshort (t )−krep (t )−ktank (15) was used. the symbols g and k represent the income and expenditure of the process in usd. the profitability of 46(2) pp. 91–100 (2018) 98 tarcsay, mihálykó-orbán, mihálykó the whole process, (q) stems from the income generated from the sales of the key component (gkey) and raw product (graw). the income is reduced by the various expenses of the process, namely the costs of raw materials (kmat), restoring the buffer capacity of the tank in case of exhaustion (kshort), repairs (krep) and the buffer tank itself (ktank). the method of calculating each source of income and expenditure is shown below. the main goal of the process is to produce the key component, which is isolated in the continuous subsystem. to calculate the profit that stems from this, equation gkey (t ) = t − nrep(t )∑ i=1 trep  cβkey (16) was used. in this equation, βkey denotes the sale price of the key component (usd kg−1), t represents the duration of the process throughout which the profit (h), the number of malfunctions (nrep(t )), and the random time of repair (trep) during each malfunction are examined. additionally, the plant secures an income from the sales of the raw product as well as the remaining raw product at the end of the production process, which can be defined as shown in graw (t ) = βraw δ z0 − t − nrep(t )∑ i=1 trep  c + + nb(t )∑ i=1 yb i − nl(t )∑ i=1 yl i + nl(t )∑ i=1 yl i  (17) where βraw denotes the sale price of the raw product (usd kg−1) and δ is a factor which defines the price at which the remaining raw product can be sold following production. among the expenses, it should be mentioned that the cost of raw materials used for the production of the raw product and the cost of the initial raw product in the tank are calculated according to equation kmat(t ) = γmat nb(t)∑ i=1 yb i + z0γmat (18) where γmat is the cost of the raw material (usd kg−1). in the event of its exhaustion, additional raw product is required to restore the initial buffer capacity of the tank and the cost of this is shown in kshort(t ) = nshort(t )z0γmat, (19) where nshort(t ) denotes the number of malfunctions caused by exhaustion during time t . finally, the cost of repairs and installing the intermediate storage itself need to be considered. to determine the installation costs, the installation factor of the tank (f ) and the cost of the tank (γtank in usd) were taken figure 10: mean profit as a function of the initial buffer and tank capacities. into account. to determine the expense of repairs, the parameter γrep was used to represent the cost of repairs (usd h−1) which was calculated according to equations krep(t) = nrep(t)∑ i=1 trepγrep (20) and ktank = f z0.6 max γtank. (21) the cost of installing the buffer tank was calculated according to references found in the literature [12]. the mean of the profit was investigated according to the reliability level of 0.95 ≤ 1 − α using a monte carlo simulation and its optimum was calculated using the grid method. it is shown by the results that if the reliability of the system is high, then the costs of repairs and malfunctions in general are negligible compared to the cost of storage. as a result, the maximum profit was achieved close to the minimum storage capacity which is shown in fig. 10. this value roughly corresponds to the minimum of the investigated boundary, using a reliability of 0.95. to generate this figure the following parameters were used: βkey = 120 usd kg−1, δ = 0.3, γmat = 80 usd kg−1, βraw = 100 usd kg−1, f = 100 usd kg−0.6, γtank = 12, 000 usd, mtrep = 0.5 h, and σtrep = 0.29 h, where repair times were independent random variables of the uniform distribution during the time interval [0, 1]. the maximum profit according to these calculations is 4.76 · 104 usd, which can be achieved by tank and initial buffer capacities of 2, 101 kg and 389 kg, respectively. 6. conclusion in this paper, a stochastic storage model was investigated. random batches as inputs and outputs, as well as continuous withdrawal were allowed. a monte carlo simulation was used for the investigation. an analytic function hungarian journal of industry and chemistry optimal design and operation of buffer tanks under stochastic conditions 99 was fitted to the simulated data, which provided a link between the initial buffer and tank capacities that correspond to a given level of reliability. the results agree with engineering practice. although the data for the research did not stem from authentic sources, by utilizing data from the industry, the distribution of the random variables present during the process could be determined using standard statistical methods. therefore, the method can be a useful supplement during the design phase of a chemical plant and also be utilized to help simplify the overall control of a chemical process. symbols small letters c draining intensity (kg h−1) f installation factor of a tank (kg−0.6) g probability density function (h−1) m expectation x fixed initial buffer capacity (kg) y fixed tank capacity (kg) yb mass of batch fed into the tank (kg) yl mass of batch drained from the tank (kg) z mass of material (kg) capital letters a,b,c,d fixed parameters of the approximated failure probability function g income (usd) e expectation h approximated failure probability function k expenses (usd) n number of events during time interval [0, tmax] p probability q net income (usd) t time (h) tf time of failure (h) greek letters α probability of malfunction β sale price (usd kg−1) γ cost (usd kg−1) δ ratio of decrease in material value λ parameter of exponential distribution (h−1) σ standard deviation ψ function describing the probability of reliable operation during time interval [0, tmax] indices 0 initial b feed i index of event (i = 1, 2, · · · ) rep repair short material exhaustion l draining mat reactant max maximum min minimum r the number of mesh points of the initial buffer capacity s the number of mesh points of the tank capacity t time raw raw material tank tank key key component references [1] towler, g., sinnott, r. k. chemical engineering design: principles, practice and economics of plant and process design. (elsevier, oxford, uk) 2012, pp. 183. doi: 10.1016/c2009-0-61216-2 [2] browning, c., kumin, h. stochastic reservoir systems with different assumptions for storage losses, am. j. oper. res., 2016 6(5), 414–423 doi: 10.4236/ajor.2016.65038 [3] karacan, c. ö., olea, r. a. stochastic reservoir simulation for the modeling of uncertainty in coal seam degasification, fuel, 2015 148, 87–97 doi: 10.1016/j.fuel.2015.01.046 [4] prabhu, u. u. stochastic storage processes: queues, insurance risk, dams, and data communication. springer science & business media, 2012. 15, 63– 76 isbn: 978-1-4612-1742-8 [5] orbán-mihálykó, é., mihálykó, c. investigation of operation of intermediate storages applying probability density functions satisfying linear differential equation, periodica polytechnica chemical engineering, 2012 56(2), 77–82 doi: 10.3311/pp.ch.20122.05. [6] orbán-mihálykó, é., mihálykó, c. sizing problem of intermediate storages under stochastic operational conditions, periodica polytechnica chemical engineering, 2015 59(3), 236–242 doi: 10.3311/ppch.7598 [7] orbán-mihálykó, é., mihálykó, c., lakatos, b. g., szabó, t., papp, a. profit optimization of batchcontinuous systems under stochastic processing conditions by simulation, hung. j. ind. chem., 2011 39(3), 353–358 46(2) pp. 91–100 (2018) https://doi.org/10.1016/c2009-0-61216-2 https://doi.org/10.4236/ajor.2016.65038 https://doi.org/10.4236/ajor.2016.65038 https://doi.org/10.1016/j.fuel.2015.01.046 https://doi.org/10.1016/j.fuel.2015.01.046 https://doi.org/10.3311/pp.ch.2012-2.05. https://doi.org/10.3311/pp.ch.2012-2.05. https://doi.org/10.3311/ppch.7598 https://doi.org/10.3311/ppch.7598 100 tarcsay, mihálykó-orbán, mihálykó [8] karlin, s., taylor, h. a first course in stochastic processes. (academic press, london, uk) 2014, pp. 113 isbn: 9780123985521 [9] zio, e. the monte carlo simulation method for system reliability and risk analysis. vol. 39. (springer, london, uk) 2013 doi: 10.1007/978-1-4471-4588-2 [10] amar, j. g. the monte carlo method in science and engineering, computing in science & engineering, 2006, 8(2), 9–19 doi: 10.1109/mcse.2006.34 [11] https://www.mathworks.com/products/ matlab.html [12] stone et al. plant design and economics for chemical engineers. (mcgraw-hill, new york) 1968 isbn: 0072392665 hungarian journal of industry and chemistry https://doi.org/10.1007/978-1-4471-4588-2 https://doi.org/10.1109/mcse.2006.34 https://www.mathworks.com/products/matlab.html https://www.mathworks.com/products/matlab.html introduction the investigated model parameter dependence of the reliability of the process and the expectation of failure time design of the tank and initial buffer capacities for a given reliability level economic investigations conclusion hungarian journal of industrial chemistry veszprem vol. 29. pp. 3538 (2001) a novel method for isolation of lipoxygenase-1 isoenzyme from soybean meal a. sz. nemeth, b. szaja.ni1, j. sz. marcz¥ and m. l. s1mon2 (research institute of chemical and process engineering, university of kaposvar p.o. box 125, veszprem, h-8201, hungary 1 ' sato ltd, szel street 4, budapest, hungary 2 department of biochemistry, attila j6zsefuniversity, p.o. box 533, szeged, h-6701, hungary) received: january 30, 2001 a novel method has been elaborated for the isolation of lipoxygenase-1 (lox-1) isoenzyme from soybean meal. the essential step of the procedure is the selective heat treatment of soybean meal extract at 70 "c in a medium of 0.05 ionic strength and ph 5.2 for 5 min. the heat treated extract practically free from lipoxygenase-2 (lox-2) and lipoxygenase-3 (lox-3) isoenzymes was pnrified by deae-cellulose ion exchange chromatography. the resulted lipoxygenase-1 isoenzyme was homogeneous as judged by page. a tenfold purification and a relatively high yield (39 %) was achieved. keywords: soybean; glycine max; lipoxygenase isoenzymes; selective heat treatment introduction soybean seeds contain an iron"containing dioxygenase namely lipoxygenase (linoleate : oxygen oxidoreductase, ec 1.13.11.12) catalyzing the hydroperoxidation of polyunsaturated fatty acids and esters containing a cis,cis-1,4-penta:diene system [1]. the hydroperoxides formed are cleaved by hydroperoxide lyase, resulting in c6 aldehydes in plants. there are at least three lipoxygenase isoenzymes in soybean seeds, named lipoxygenase-1 (lox-1), lipoxygenase-2 (lox-2) and lipoxygenase-3 (lox-3), which exhibit differences in substrate and product specificity, optimum ph for catalytic activity, isoelectric point and thermal stability [2-4]. the levels of the lipoxygenase isoenzymes are influenced to different degrees by both cultivar and climatic effects. the weather conditions can exert a greater effect than the cultivar effect £5]. with linoleic acid as substrate, linoleic acid 13hydroperoxide and 9-hydroperoxide can be formed in the reaction catalyzed by iipoxygenase. the ratio of isomers derived from the reaction depends on the isoenzyme(s) present and the reaction conditions {6]. soybean lipoxygenase can be used to produce flavour compounds, but in some cases the presence of lox-2 and lox-3 isoenzymes is undesirable because of side reactions. a large number of methods have been suggested for separation of the isoenzymes, e.g. ion exchange chromatography £7-9], chromatofocusing [lo­ ll], electrophoresis [12] and isoelectric focusing [7, 10]. we have found [13] that the selective heat treatment of the soybean meal extract makes the elimination of lox-2 and lox-3 isoenzymes possible. based on this finding, a novel method for the isolation of lox-1 isoenzyme has been elaborated. materials and methods reagents linoleic acid, tween 20, deae-cellulose and soybean lipoxygenase (type i-b) were purchased from sigma chemical co. (st. louis, mo, usa). acrylamide, n,n,n' ,n' -tetramethylethylenediamine and coomassie brilliant blue r-250 were supplied by reanal factory of laboratory chemicals (budapest, hungary) and n,n' • methylene-bis(acrylamide) was obtained from fluka a.g. (buchs, switzerland}. the other chemicals were of analytical grade. the sodium linoleate substrate was prepared according to axelrod et al. f14}. 36 apparatus a biochrom 4060 spectrophotometer was used for enzyme activity measurements and a 2117 multiphor ii electrophoresis system for electrophoresis (pharmacia lkb, uppsala, sweden). lipoxygenase assay the method of axelrod et al. [14] as modified by marczy et al. [5] was applied, except that 0.2 m sodium borate buffer was used for lox-1. one unit of activity was defined as the amount of enzyme producing 1 j.llllol of linoleic acid hydroperoxide per min at room temperature at ph 9.0 (lox-1) or 6.8 (lox-2 and lox-3). protein content protein contents were determined according to lowry et al. [15], with bovine serum albumin as standard or by absorbance at 280 nm. electrophoresis polyacrylamide gel electrophoresis (page) was performed in a continuous buffer system of 0.1 m sodium phosphate buffer (ph 7 .5). the total monomer concentration [acrylarnide + n,n'-methylene­ bis(acrylarnide)] in the gel was 5 %, the concentration of n,n' -methylene-bis(acrylarnide) being 2.7% of the total monomer concentration. samples of 15 j.tg protein in 0.01 m sodium phosphate buffer (ph 7 .5) were applied onto a gel slab {12 em x 4 em). electrophoresis was carried out for 2 h at 200 ma at 5 °c. the gel was stained for protein with 0.25 % of coomassie brilliant blue r-250 dissolved in methanol:water:acetic acid (23:23:4). experimental preparation of crude extracts soybean meal was prepared :&om a chandor cultivar harvested in 1993. kindly provided by the cereal research institute (szeged, hungary). ten grams of soybean meal was defatted with 20 cm3 portions of petroleum ether at 0 <>c. defatted meal was extracted with 5 volumes (v/w) of 0.05 m acetic acid by mechanical stirring for 1 h at 4 oc. the suspension was then filtered through cheesecloth and centrifuged at 10,000 g for 20 min. the resulting supernatant was used in the further experiments. selective heat treatment the crude extract was heated to 70 oc in a water bath under continuous stirring and was kept at this temperature for 5 min [13]. immediately after heat treatment the suspension was cooled to room temperature in an ice bath and then was centrifuged at 10,000 g for 20 min at room temperature. ion exchange chromatography anion exchange chromatography of heat treated soybean meal extract was performed according to axelrod et al. [14] and weber et al. [16] with modifications on deae-cellulose. 14.5 cm3 heat treated soybean meal extract was dialyzed against 3 x 500 cm3 0.01 m sodium phosphate buffer (ph 7.0). the enzymatically inactive precipitate was discarded and the supernatant was loaded on a deae-cellulose column (1.85 x 21 em) equilibrated with 0.01 m sodium phosphate buffer (ph 7.0). elution (22.5 cm31h) was performed with a linear gradient formed from equal volumes of 0.01 m and 0.22 m sodium phosphate buffer (ph 7 .0). fractions of 6 cm3 were collected and the protein contents were determined by absorbance at 280 nm. activities were assayed at ph 9.0 (lox-1) and 6.8 (lox-2 + lox-3). the enzymatically active fractions of lox-1 were pooled and concentrated by ultrafiltration. results and discussion· data from a typical lox-1 isoenzyme isolation and purification experiment are summarized in table i. the data show that the selective heat treatment of soybean meal extract at 70 oc is a crucial step in the isolation of lox-1. though the purification of lox-i was less than twofold in respect of specific activity as an effect of heat treatment, the amounts of lox-2 and lox-3 isoenzymes were markedly reduced by this simple method. the anion exchange chromatography makes the removal of further protein impurities possible (fig.l}. tenfold purification and a relatively high yield (39 %) was achieved by the two purification steps. the purified lox-l isoenzyme was electrophoretically homogeneus as judged by page (fig.2). 37 table 1 isolation oflipoxygenase-1 isoenzyme from soybean meal a volume totallox-1 lox-1 total lox-1 purification step (cm3 ) activity yield protein specific activity activity purification (units) (%) (mg) (units/mg erotein) ratio* extraction 17.0 582.6 100.0 317.6 1.83 5.4 1.0 heat treatment 14.5 392.5 67.4 130.8 3.00 20.1 1.6 deae-cellulose 30.0 227.3 39.0 chromatography 11.1 20.48 20.8 11.2 •rn the experiment, 5 g soybean meal was processed *lox-1 activity i (lox-2+lox-3 activity) """ 0.8 12 0.8 ] /"".. 1.0 ~ s -w ! 0.6 _§ l:l "" 0.6 0.8 0 :t:: ~:g <7 § 8 .::: ~ '-' 8 !:l v ~ i !':; 0.6 0 0.4 x 6 0.4 0 !:l ~ 0 .. 0 ....:) ~ 0 ...... .... 0 0.4 ~ ....:) ~ 4 g-i ...... 0.2 ::; 0 ·:~ 0.2 ..0 0 <i) 2 0.2 t;:i .:~ <!! .......... -& "' <!! 0 0 0 0 -o ..0 {:!.. 0 10 20 30 40 50 60 70 80 fig.l deae-cellulose column chromatography of a heat-treated soybean meal extract. column (1.85 x 21 em) was equilibrated with 0.01 m sodium phosphate buffer (ph 7.0). sample (131 mg protein) was applied in the same buffer and was eluated (22.5 cm31h) with a linear gradient formed from equal volumes ofo.ol m and 0.22 m sodium phosphate buffer (ph 7.0). symbols: -e-, lox-2 + lox-3 activity at ph 6.8; --11-, lox-1 activity at ph 9.0; -, absorbance at 280 nm; · · · · · · , concentration of sodium phosphate (m) > 0 ~1 )· * ,;.. .. """' 1 to ' ; ' t lj ,.,.....,. * '-' -+ '-" fig. 2 polyacrylamide gel electrophoretic pattern of purified lox-1 isoenzyme. electrophoresis was carried out in 5 % polyacrylamide gel slab (12 x 4 em) for 2 h with 200 rna at 5 oc. samples 15 vg protein each. a: sigma type i-b iipoxygenase; b: lipoxygenase-lisoenzyme purified with the new method conclusion we have found earlier {17, 181 that the selective heat treatment of aqueous extracts of animal organs as kidney and pancreas could be advantageous in enzyme isolations. it was supposed that this simple method would be useful in the isolation of plant enzymes too. the difference in the heat stability of soybean lipoxygenase isoenzymes {19] and the practical demand on lox-1 isoenzyme make the application of heat treatment obvious. the heat treated soybean mea! extract is practically free from lox-2 and lox-3 isoenzymes. it can be used immediately for the production of linoleic acid 13-hydroperoxide, or it can be stored frozen without deterioration for a long time. in comparison with the known methods [7-12] the proposed novel procedure is more advantageous because it does not require special equipments and chemicals. therefore it is not expensive and is suitable for industrial purposes promoting the biocatalytic production of flavour compounds. references 1. hayashi 0., nozaki m. and abboti m. t.: the enzymes, 3rd ed.. ed.: boyer p.d., acad. press, newyork,pp.ll9-l89,1975 2. christopher. j. p., plstorius e. i{. and axelrod b.: biochim. biophys. acta, 1970, 198, 12-19 3. grosch w. and laskawy g.: j. agtic. food chern. 1975,23,791-794 4. zhuang h., hu..debrand d. f., andersen r. a and hamilton-kemp t. it: j. agric. food chern. 1991.39,1357·1364 5. marcz'l:' simon m. l., m6zs!k l. and szajanib.: j. agric. foodchem.j995,43, 313·315 3-8 6. shibata d., s1eczko j., dixon j. e., hermondson m., y azdanparast r. and axelrod b.: j. bioi. chem.1987, 262, 10080-10085 7. verhue w. m. and francke a.: biochim. biophys. acta 1972, 284,43-53 8. hausknecht e. c. and funk m. 0.: phytochemistry 1984,23, 1535-1539 9. shkarina t. n., kuhn h. and schewe t.: lipids 1992,27, 690-693 10. funk m. 0., whitney m. a., hauscknecht e. c. and o'brien e. m.: anal biochem.1985 ,146, 246251 11. fbiters m. c., veldink g. a. and vljegenthart j. f. g.: biochim. biophys. acta 1987,870,367-371 12. christopher j.p., pistorius e. k. and axelrod b.: biochim. biophys. acta, 1972,284, 54-621 13. nemeth a. sz., szaiani b., marczy j.sz. and simon m. l.: biotech. tech., 1998, 12(5), 389-392 14. axelrod b., cheesbrough t. m. and laakso s.: methods enzymol. 1981, 71, 441-451 15. lowry 0. h., rosebrough n. r., parr a. l. and randallr. j.: j. biol. chem.1951, 193,265-275 16. weber f., laskawy g. and grosch w.: z. lebensm. unters.-forsch.1974, 155, 142-150 17. szaiani b.: acta biochim. biophys. acad. sci. hung. 1980, 15, 287-293 18. dala e., kiss a., sum p. and szaiani b.: acta biochim.biophys. hung. 1986, 21, 327-333 19. 19. matoba t., hidaka h., narita h., kitamura k., kaizuma n. and kito m.: j. agric. food chern. 1985, 33, 852-855 page 36 page 37 page 38 page 39 hungarian journal of industry and chemistry vol. 50(2) pp. 17-21 (2022) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2022-13 investigations into the usage of the mineral alginite fermented with lactobacillus paracasei for cosmetic purposes pál tóth1 and áron németh1* 1 department of applied biotechnology and food science, budapest university of technology and economics, műegyetem rkp. 3, budapest, 1111, hungary a remarkable interplay between the skin and the fermentation of lactic acid bacteria (lab) occurs. the lactate and amino acids in the supernatant of this bacteria help to hydrate the skin. the fermentation broth of lactic acid bacteria, generally referred as "lactic acid bacteria ferment" according to international nomenclature of cosmetic ingredients (inci), has been used to make a variety of cosmetic components. the goal of this study was to evaluate new approaches to assess ferment filtrates (also known as cell-free fermentation broths) that could be used in cosmeceuticals. despite years of research on the production of lactic acid, aesthetic evaluations have not yet been performed. first, the lactobacillus paracasei strain ncaim b.01525 was employed in our research. furthermore, a fermentation broth was produced containing the hungaricum mineral alginite and the impact of hydration on human skin tested. the influence of alginite on the fermentation of lab was also examined. according to the results of the trials, although alginite might double and triple biomass and specific growth rates, respectively, it cannot facilitate hydration of the skin. these results might contribute to the development of more widely accessible, environmentally-friendly cosmetic components in the future. keywords: human skin, dermatoscope, moisturizing effect 1. introduction the use of cosmetics dates back 7,000 years to ancient egypt and were later used in the roman empire, for example, according to some legends, cleopatra bathed in goats' milk to preserve the youthfulness of her skin. later, milk baths became popular in the english royal court, for instance, catherine parr, the last queen of the house of tudor, and later elizabeth i, queen of england, regularly used a milk bath to preserve their beauty. in today's modern world, using natural ingredients in cosmetics has come to the fore again. although our laboratory has been dealing with lactic acid producers for many years, to date, no measurements have been made in terms of cosmetics. the structure of the skin and the composition of the stratum corneum (sc) are shown in fig. 1, including the natural moisturizing factor (nmf). the skin consists of two main layers, namely the dermis and epidermis. the epidermis is further divided into two main layers, that is, the viable epidermis and the stratum corneum (sc), which is the outermost layer mainly consisting of dead cells. the essential function of the sc is to act as a barrier, preventing dehydration caused by water loss from the body. the sc contains 30% nmf, which received: 2 sept 2022; revised: 15 oct 2022; accepted: 15 oct 2022 *correspondence: naron@f-labor.mkt.bme.hu consists of 40% amino acids such as serine, glycine and alanine as well as 12% lactate, which is capable of retaining water in the stratum corneum [2]. on the other hand, lactic acid bacteria (lab) are generally defined as gram-positive, non-spore-forming, catalase-negative, aerotolerant, acid-tolerant, nutrientdemanding and strictly fermentative organisms that lack cytochromes as well as produce lactic acid as the main end product of carbohydrate metabolism [3]. lab contains cell wall-bound proteinase that initiates the transformation of extracellular proteins into oligopeptides [4]. the protease activity as well as figure 1. composition of the skin and its natural moisturizing factor (nmf), where pca is pyrrolidone carboxylic acid [1] https://doi.org/10.33927/hjic-2022-13 mailto:naron@f-labor.mkt.bme.hu tóth and németh hungarian journal of industry and chemistry 18 catabolic production of proteins and peptides enable lab to produce amino acids in the fermentation broth [5]. since many amino acids are contained in various lab-fermented foods such as cheese [6], sausage [7] and even japanese sake [8], a lab-fermented ingredient contains large amounts of lactic acid and amino acids, which together form the nmf. therefore, these ingredients exert a hydration effect when they are applied on the skin. furthermore, a particular combination of a substrate and a strain of lab could provide another beneficial functional impact on the skin. our goal was to investigate how the mineral alginite affects fermentation and moisturization of the skin. another aim of this study was to screen for new methods to evaluate the ferment filtrate, i.e. cell-free broth, in terms of usage in cosmeceuticals. 2. experimental 2.1. fermentation the planned experiment concerning the production of lactobacillus ferment filtrate was performed using a strain of lactobacillus paracasei from the national collection of agricultural and industrial microorganisms (ncaim, hungary), namely ncaim lactobacillus paracasei b.01525. the fermentations were conducted in 250 ml shake flasks and 10 ml bactrac impedance tubes (sy-lab, austria fig. 2) at 37°c. only the shake flasks were shaken at 150 rpm. the fermentations could be monitored online using a sy-lab bactrac 4100 microbiological analyzer due to changes in the impedance of the medium (m%) and on the surface (e%) of the electrodes by following the same method previously reported by áron németh [9]. the measurements were performed using the bactrac analyzer and the results displayed by bacmonitor y 1.39er software. since the bactrac program only shows curves and does not give the corresponding points, these points had to be extracted in a different way. the curves were saved as qrp files, which were converted into jpeg format using smartqrp software. the jpeg files had already been recognised by digitizeit, which made it easy to determine the points associated with the curves. the points were copied into a microsoft excel spreadsheet and curves were fitted to the points using sigmaplot 2001 software for windows version 7.0. the generalized logistic equation by verhulst-pearl was used [10]. the nutrient solution was the following marierogosa-sharpe medium: peptone (10.0 g/l), yeast extract (5.0 g/l), beef extract (10.0 g/l), glucose (20.0 g/l), kh2po4 (2.0 g/l), sodium acetate (5.0 g/l), magnesium sulfate (0.2 g/l), manganese sulfate (0.05 g/l), tween 80 (1.08 g/l) and ammonium citrate (2.0 g/l). the fermentations with alginite were supplemented with 10g/l of alginite. during the fermentation, the changes in glucose and lactic acid concentrations were monitored by a waters breeze hplc system consisting of a bio-rad aminex hpx-87h column, waters 717 plus autosampler and waters 2414 ri detector. after appropriate dilution steps, the samples were mixed with a 0.2 µm-pore-size mixed ester syringe filter (vialab magyarország kft.). the dry matter was measured as follows: the contents of the bactrac tubes, that is, 10 ml of fermentation broth, were loaded into falcon conical centrifuge tubes and centrifuged at 6000 rpm for 10 mins. using a hermle z200a centrifuge. the supernatant was then decanted before the cells were suspended in distilled water and centrifuged once more. the supernatant was decanted again and the biomass poured into the crystallization cup with 2-3 ml of distilled water before being dried relatively quickly using our sartorius ma35 moisture analyzer. 2.2. determination of moisture content the short-term/immediate hydration effect of the ferment filtrates was determined by taking triplicate measurements using a dermatoscope (fig. 3). on the forearm of the subject, three 1 cm2 areas were marked out onto which 20 µl of fermented juice was pipetted. after 5 mins., these areas were wiped with a dry hand towel and then the hydration on that part of the subject’s skin was measured at given intervals with the installed corneometer (capacitance) sensor. in order to establish a basis for comparison, the hydration of the subject’s skin figure 2. bactrac and its vials with electrodes figure 3. measuring with a dermatoscope mineral alginite fermented with lactobacillus paracasei 50(2) pp. 17-21 (2022) 19 was recorded before measurements were taken and the values displayed here corrected according to this value. 3. results and discussion 3.1. bactrac results the effect of alginite on the kinetics of lab fermentation was also investigated. the fermentations were monitored by bactrac online by replicating both setups three times, that is, in the presence and and absence of alginite, supplemented with a noninoculated (blank) reference. the reference bactrac tube contained the medium mrs and 10 g/l of noninoculated alginite. the replicates were compared by excluding outliers from further processing and their curves are presented in fig. 4. the resulting curves clearly show the impedance of lactobacillus paracasei fermentations in the presence of alginite during the declining growth phase is twice as high as that of nonalginite fermentations. furthermore, the specific growth rate was also determined to quantitatively compare the effect of alginite on fermentation kinetics as is presented in fig. 5. the specific growth rates also differ significantly between the normal and alginite fermentations, namely 0.6 and 1.9 l/h, respectively (fig. 5). therefore, the specific growth rate of fermentation with alginite is three times higher than without. the data obtained from dry matter measurements also indicate that alginite fermentations achieved higher yields (fig. 6). 3.2. skin hydration since a lactic acid-producing strain was investigated, firstly the moisturizing effect of solutions of different lactic acid concentrations, namely 5, 10, 15 and 20 g/l of lactic acid in distilled water, was determined by a dermatoscope. how skin hydration changes over time once the given concentration of the lactic acid solution had been reduced is represented in fig. 7. it is clearly visible that the level of hydration rapidly decreases over time but eventually stabilizes after ca. 35 mins. since the initial phase is difficult to quantify, the steady-state values after 30, 35, 40 and 45 minutes were used before being plotted against concentration as presented in fig. 8. the trend is clear, that is, as the concentration of lactic acid increases, so does the moisturizing effect. the effect of the 5g/l lactic acid solution is so minimal that it has a relatively mild dehydration effect on the skin. a trendline was fitted to the points (r^2>0.99) and from the resulting equation, the hydration effect of the fermentation broth was predicted based on its lactic acid content. while our technique for measuring the moisturizing effect is first described and applied here, the lactic acid sting test (last), which also measures capacitance figure 4. lactobacillus paracasei fermentations in bactrac tubes figure 5. specific growth rates of l. paracasei fermentations figure 6. concentration of dry matter in the l. paracasei fermentations figure 7. the moisturizing effect of the lactic acid (la) solutions tóth and németh hungarian journal of industry and chemistry 20 using a corneometer (similarly to our dermatoscope’s corneometer) is highly comparable to it [11]-[13]. the only two differences are that the cited authors applied the ferment filtrates to the facial skin, to nasolabial folds to be exact, where the hydration effect was 6 times higher in contrast to on the forearm in our study, and that they only reported the measured level of hydration after 10 mins., which according to our time profile varies rapidly over time suggesting it may be more reliable. overall, a correlation with regard to the lactic acid solutions is observed between our results and those from the cited studies. the effect on skin hydration of the lactobacillus paracasei fermented broths was also measured and plotted against time (fig. 9). a comparison concerning the steady-state values of the fermentation samples in the presence and absence of alginite is presented in fig. 10. according to the results, the samples containing alginite were less hydrating than the cell-free fermentation broth. this may be due to the higher concentrations of lactic acid produced in the alginite-free fermentation broth, namely 23.8 g/l and 28.8 g/l, respectively. by applying the equation in fig. 5, hydration values of 15.2 and 11.7% were predicted for the alginite-free and alginitecontaining fermentation broths, respectively, based on these lactic acid concentrations. although the measured results in both cases are slightly lower, the difference is insignificant. 4. conclusion the current study investigated the effects of the mineral alginite on the fermentation of lactobacillus paracasei and its moisturizing effects on the skin. this study also aimed to test novel approaches for evaluating ferment filtrates (also known as cell-free fermentation broths) for use in cosmeceuticals. according to studies on the process, alginite increases the specific growth rate and dry matter content during fermentation. while the latter doubled, from 1.6 to 3.3 g/l to be exact, the former tripled from 0.60 to 1.91 l/h. based on these encouraging findings, it was predicted that the hydration effect of the filtrate in the presence of alginite would outweigh that without. however, dermatoscopic measurements provided evidence to the contrary. the measured hydration levels of the alginite-free and alginitecontaining fermentation broths were 13.9 and 8.1%, respectively. our future studies will focus on the effects of fermented broths containing alginite on additional aesthetic aspects such as antioxidants, skin whitening or the inhibition of the enzyme hyaluronidase. references [1] izawa, n.; sone, t.: cosmetic ingredients fermented by lactic acid bacteria, in: microbial production: from genome design to cell engineering, (springer, tokyo) 2014, pp. 233–242, doi: 10.1007/978-4-431-54607-8_20 [2] spier, h.w.; pascher, g.: zur analytischen und funktionellen physiologie der hautoberfl äche (analytical and functional physiology of the skin surface), hautarzt, 1956, 7(2), 55–60, pmid: 13318589 [3] axelsson, l.: lactic acid bacteria: classification and physiology, in: salminen, s.; von wright, a. (eds) lactic acid bacteria: microbiological and functional aspects, (marcel dekker, inc., new york) 1998, pp. 1–71, isbn: 0-8247-5332-1 [4] savijoki, k.; ingmer, h.; varmanen, p.: proteolytic systems of lactic acid bacteria, appl. microbiol. biotechnol., 2006, 71, 394–406, doi: 10.1007/s00253006-0427-1 figure 10. lactobacillus paracasei ferment filtrates moisturizing comparison in steady state figure 8. steady-state moisturizing effects of la solutions figure 9. a comparison of the moisturizing effect of lactobacillus paracasei ferment filtrates https://doi.org/10.1007/978-4-431-54607-8_20 https://doi.org/10.1007/978-4-431-54607-8_20 https://doi.org/10.1007/s00253-006-0427-1 https://doi.org/10.1007/s00253-006-0427-1 mineral alginite fermented with lactobacillus paracasei 50(2) pp. 17-21 (2022) 21 [5] lee, k.; lee, j.; kim, y.h.; moon, s.h.; park, y.h.: unique properties of four lactobacilli in amino acid production and symbiotic mixed culture for lactic acid biosynthesis, curr. 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questionnaire and lactic acid sting test play different role on the assessment of sensitive skin: a cross-sectional study, clin. cosmet. investig. dermatology, 2021, 14, 1215–1225, doi: 10.2147/ccid.s325166 [12] an, s.; lee, e.; kim, s.; nam, g.; lee, h.; moon, s.; chang, i.: comparison and correlation between stinging responses to lactic acid and bioengineering parameters, contact derm., 2007, 57(3), 158–162, doi: 10.1111/j.1600-0536.2007.01182.x [13] wu, y.; wang, x.; zhou, y.; tan, y.; chen, d.; chen, y.; ye, m.: correlation between stinging, tewl and capacitance, skin res. technol., 2003, 9(2), 90–93, doi: 10.1034/j.1600-0846.2003.00026.x https://doi.org/10.1007/s002840010324 https://doi.org/10.3168/jds.s0022-0302(93)77354-3 https://doi.org/10.3168/jds.s0022-0302(93)77354-3 https://doi.org/10.1021/jf980834p https://doi.org/10.6013/jbrewsocjapan1988.99.659 https://doi.org/10.33927/hjic-2019-13 https://doi.org/10.1002/bit.260100208 https://doi.org/10.2147/ccid.s325166 https://doi.org/10.2147/ccid.s325166 https://doi.org/10.1111/j.1600-0536.2007.01182.x https://doi.org/10.1034/j.1600-0846.2003.00026.x hungarian journal of industry and chemistry vol. 47(1) pp. 49–56 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-08 simulation of a balanced low-voltage electrical grid using a simplified network model márton greber *1 and attila fodor1 1department of electrical engineering and information systems, faculty of information technology, university of pannonia, egyetem u. 10., veszprém, h-8200, hungary a simulation method for low-voltage balanced distribution networks is proposed in this article. the novel method of node powers is based on the general calculation technique of node voltages. by researching only balanced networks, singlephase equivalents of the three-phase system are applicable. for the description of power lines, various parameters and matrices are available. in this work a simplified model is applied by using a purely resistive one. the active power results are solved through an iterative process. a main accomplishment is that the number of iterations needed is independent of the size of the network, and the process rapidly converges. validation of the method is performed on the ieee european low-voltage test feeder network. the simulation results confirm the achievements described in this paper. keywords: low-voltage distribution system, grid simulation, smart grid, method of node voltages, ieee european low-voltage test feeder 1. introduction in recent years a lot of research has been conducted and progress made in the field of smart grid applications. therefore, the demand for cloud-based systems with integrated simulation capabilities has increased. the calculation of the voltages, currents and powers of the components of the electrical (smart) grid is not easily achieved. this has resulted in the development of custom calculation methods which have the benefit of being fine-tuned for a particular application. one of the fundamental network calculation methods in a general sense is the node voltages method. from a mathematical perspective, this method is based on solving a system of linear equations. as a result, this method can be implemented through various frameworks. one proposed solution revolves around using an open source discrete event simulator called omnet++ [1]. the models for electrical components need to be constructeda and the simulation is conducted via message handling. another approach used coloured petri nets to model electrical networks [2]. a network model needs to be constructed for the simulation, which consists of a propagation process. a solution is presented for basic network types, while complex ones are calculated through decomposition. both of these methods offer solutions but the method of node voltages regards currents as an input. the more common approach to calculations of distribution systems calculation is via the method of power *correspondence: greber.marton@virt.uni-pannon.hu flow. this uses complex numbers to distinguish between active and reactive power. for the given nodes, both active and reactive power, voltage and phase angle are required to formulate the solution [3]. this poses a nonlinear problem, furthermore, the system of equations consists of real and imaginary subsets. over the years, several pieces of research have dealt with this subject and the method known as dc power flow developed. by restricting the parameters the calculation was simplified, namely the voltage angles as well as generated and consumed active powers. this method assumes small differences in voltage angle and lossless lines [4]. the biggest downside of the method is that it cannot be used to calculate line losses because of the assumptions, although efforts are being made to overcome this obstacle [5]. by taking into account the extent of a given power system, different parameters of the power line model become dominant [6]. in low-voltage systems the distance between adjacent nodes is smaller than in high-voltage systems. by using this information a new set of restrictions is proposed, inspired by the dc power flow. it can be regarded as a complementary method since the line reactances are neglected. utilising a resistive transmission line model offers the possibility to calculate distribution losses. this method has been developed from the method of node voltages. in this article the issues of harmonic currents [7] and unbalanced networks [8] are not examined, it is assumed that the currents as well as voltages are sinusoidal and the grid is balanced with balanced three-phase loads. the mailto:greber.marton@virt.uni-pannon.hu 50 greber and fodor r7 uv7 φ3 r5 φ2 r2φ1 r1 uv1 φ0 ia4 r3 uv6 r6 figure 1: example network neutral wire can be omitted by restricting the set of networks in balanced low-voltage systems. this enables the application of a one-line equivalent circuit. 2. method of node voltages in distribution network calculations the main emphasis is on power flow. that means the voltages and angles are calculable when the generated and consumed powers are given [9]. the known formula for calculating the active power in a dc network is the following: p = ui, (1) but the observed systems operate on alternating currents, hence the notion of ac power needs to be introduced [10]. since voltages and currents are time-varying quantities, these are expressed as complex numbers, namely u and i . the complex power is calculated by multiplying the conjugate of i by the voltage s = u i ∗ . (2) the phase angle of the complex power is defined by the difference between the angles of voltage and current: ϕ = arg(u)− arg(i). (3) by observing the real and imaginary parts of the complex number, the active (p ) and reactive powers (q) are obtained: p = re(s), q = im(s). (4) a known method for the analysis of electrical networks is the method of node voltages. the component values, e.g. the sources of resistance, voltage and current are given, the unknown variables are the node voltages. the calculation steps are best explained through an example network as shown in fig. 1. one key component of the process is the definition of a directed graph for the example network shown in fig. 2. the reference directions in the graph are arbitrary. φ1 φ2 φ3 φ0 2 7 5 1 6 43 figure 2: the reference directed graph by using the graph in addition to kirchoff’s first law, the nodal equations can be written in the following form: i1 − i2 − i7 = 0 i2 − i3 + i4 + i5 = 0 i7 − i5 + i6 = 0 (5) after that, ohm’s law is used to express the edge currents with regard to the nodal voltages: i1 = −g1(φ1 − uv1) i2 = g2(φ1 − φ2) i3 = g3φ2 i4 = ia4 i5 = g5(φ3 − φ2) i6 = −g6(φ3 + uv6) i7 = g7(φ1 + uv7 − φ3) (6) where the conductance of the arm of the network is denoted by g. if these steps are followed, the system of equations must be rearranged. the final form can be obtained by substituting the currents into eq. (5) and rearranging it to determine the nodal voltages [11]: φ = g−1e ie (7) the notation represents the dimensions of the elements it contains: the node voltage vector is obviously denoted by φ, the nodal admittance matrix by ge and the excitation vector by ie. at first sight, this equation does not account for the voltage sources in the branches. since these elements can be described in terms of current dimensions, the excitation vector takes the following form: ie = −g1uv1 +g7uv7 −ia4 −g7uv7 +g6uv6  . (8) 2.1 the generalized nodal equations the above-mentioned method describes the working principle of the technique, but it is not suitable for algorithmic applications. a generalized approach is needed. one has to define column vectors for the voltage sources: u>v = [ uv1 uv2 . . . uvn ] , (9) hungarian journal of industry and chemistry simulation of low-voltage electrical grid 51 current sources: i>a = [ ia1 ia2 . . . ian ] , (10) and admittances: y > = [ y1 y2 . . . yn ] , (11) where y refers to the complex conductance known as the admittance. each scalar of the vectors contains the aforementioned properties of a particular edge. for the representation of the graph, an incidence matrix (a) is used of (m − 1) × n dimensions, and describes connections between nodes and edges: ai,j =  0, if j is not connected to i 1, if j is pointing away from i −1, if j is pointing towards i , (12) where i = 1, 2, . . . ,m − 1 represents the nodes of the graph and j = 1, 2, . . . , n denotes the edge index set. as with the direction of the graph, the reference of a is also arbitrary, it is only manifested when multiplied by (−1). these matrices can be constructed algorithmically and facilitate the use of the following equation [12]: φ = y −1a a ( diag(y ) uv − ia ) , (13) where: ya = a diag(y )a>. (14) a method which can be used to compute node voltages by defining a graph represented by the incidence matrix that includes the electrical properties of the edges is proposed as a result. 3. network model in order to reduce the amount of computational power that is needed for simulations, a simplified network model is used. the feeder points of low-voltage grids are transformer substations which convert forward the desired power from the medium voltage side into the base voltage, therefore, can be represented as voltage sources. power flows from the feeder points to the customers via transmission lines. compared to mediumor high-voltage lines, the length between consecutive nodes is smaller. as a result, these can be modelled as series resistances. customers are represented as current sources with consumer references of course. the computationally demanding part of the method of node voltages is to invert ya. in the case of complex analyses, the system of equations is separated into real and imaginary parts. through one iteration cycle, two inverse calculations are needed. if voltages and currents are calculated as root mean square (rms) values, the simulation method only requires real numbers. therefore, the effort and time to calculate one cycle is halved. 2. bus 3 phase 10-35kv/0.4kv 1. bus 3. bus 4. bus figure 3: low-voltage distribution system 3.1 topology verification in the structure of a low-voltage distribution network, some rules are noticeable. the transmission line forms a power rail to which the consumers can connect, as is shown in fig. 3. these mainly consist of households with single-phase connections, i.e. one phase and the neutral wire are used [13]. the method of node voltages can be applied to general circuits, on the other hand, the proposed method of node powers can be applied to distribution networks. these form a tighter set, therefore, the topology needs to be checked to ensure it works properly. if a network contains m nodes, m node equations can be obtained. on the other hand, only m− 1 equations are linearly independent. therefore, one node can be omitted, namely the 0 v node is omitted in the proposed methods. if an edge is connected to this point, it will have a nonzero column sum. if it is not connected to this point, it will have a column sum of zero. using this, the criteria for the validation of topology can be formulated. the column sum for an arbitrary edge containing a current source in a cannot be equal to zero: ∀iaj 6= 0, j ∈ {1, . . . , n} → m−1∑ i=1 ai,j 6= 0. (15) similarly, the column sum for an arbitrary edge containing a voltage source ina cannot be equal to zero: ∀uvj 6= 0, j ∈ {1, . . . , n} → m−1∑ i=1 ai,j 6= 0. (16) in the case of an edge that possesses admittance, the column sum ina must be zero: ∀yj 6= 0, j ∈ {1, . . . , n} → m−1∑ i=1 ai,j = 0. (17) in algorithm 1, a pseudo code is shown that implements the above-mentioned criteria. it returns a boolean value and is only true if the network topology is appropriate. 47(1) pp. 49–56 (2019) 52 greber and fodor algorithm 1 topology verification input:a, y , ia, uv output: isvalidtopology 1: isvalidtopology= 1 2: n = numberofcolumns(a) 3: for i = 1 to n do 4: s = 0 5: if ia(i) != 0 then 6: s = sum(a(:, i)) 7: if s == 0 then 8: isvalidtopology= 0 9: end if 10: end if 11: if uv(i) != 0 then 12: s = sum(a(:, i)) 13: if s == 0 then 14: isvalidtopology= 0 15: end if 16: end if 17: if y (i) != 0 then 18: s = sum(a(:, i)) 19: if s != 0 then 20: isvalidtopology= 0 21: end if 22: end if 23: end for 4. method of node powers since the simulated households are single-phase consumers, the corresponding active power can be calculated as follows: p = u i cos(ϕ). (18) let us define the power factor (pf ) and current-source active power (pa) vectors for further matrix calculations. single elements in both of these describe properties with regard to a single edge. pf> = [ cos(ϕ1) cos(ϕ2) . . . cos(ϕn) ] , (19) p>a = [ pa1 pa2 . . . pan ] . (20) voltage can be expressed as the electric potential difference between two points. if the incidence matrix represents node-edge relations, transposing it will describe edge-node relations. multiplying it with the node voltages column vector will result in edge voltages: u = a>φ. (21) by determining these notations and definitions, the basic equation of node voltage can be extended: φ = y −1a a ( diag(y ) uv − ia ) pa = diag(pf )diag(a>φ)ia , (22) in the case of the method of node voltages, the node voltages are calculated using the given current consumption. however, in the case of the method of node powers, the node voltages must be calculated with regard to the consumption, given in terms of the active power. eq. 22 opens up the possibility of finding a solution following a trial and error procedure. in other words, if only one current source in this system of equations is changed, all the node voltages will also be changed. let us consider the case where the current of one particular customer is changed until its active power becomes equal to its actual value. nonetheless, if a second consumer is to be set in the same fashion, the first one will be ruined. through positive changes in current to the second source, a net drop in voltage will occur. since power is the product of current and voltage, the current was untouched so the active power will be less. therefore, it is also clear that if the second current source is decreased, the active power of the first source will exceed its actual value. 4.1 constant iteration current in the aforementioned problem, the solution is acquired through an iterative process to build up the unknown currents of the system gradually, instead of trying to determine them individually. it is necessary to choose a value of the current for the iterations: iiter. in the first step, every element of the current vector is zero, however, if an edge contains a consumer, its value will be set as the iteration current. the problem, namely that by changing one current, all the node voltages will also change, still exists. however, if the iteration current is sufficiently small, the ability to build up the parameters from the ground is viable. to select a source for the actual iteration, a new variable was defined: dpp = p sim a pa . (23) this can be calculated for all consumer edges per iteration and provides information about how similar the simulated active power is to its desired value. it is obvious that the edge with the smallest dpp requires the highest degree of correction, therefore, it is incremented by iiter. consequently, in every iteration the branch with the minimum dpp needs to be identified, using a simple minimum search. after appropriate incrementation, the node voltages must be calculated in order to determine the new values of power. this procedure can be observed in algorithm 2. in an ideal case, the algorithm converges into the desired power vector and the following expression will be true: ∀i ∈ {1, . . . , k} → dppi = 1, (24) where k denotes the number of consumers in the grid. it is clear that the rate of convergence and the accuracy of the algorithm are heavily influenced by iiter. if this rate is particularly small, the results will be precise (dpp = 1). however, in this case the number of iteration cycles will be enormous because the function described is analogous hungarian journal of industry and chemistry simulation of low-voltage electrical grid 53 algorithm 2 constant iteration current input:a, y , pa, uv, pf , iiter, m, n output: φ, ia 1: ia = zeros(n, 1) 2: for i = 1 to n do 3: if pa(i) != 0 then 4: ia(i) = iiter 5: end if 6: end for 7: φ = calculatenodevoltages(a,y ,uv, ia) 8: p sim a = diag(diag(a> · φ) · ia) · pf 9: [dpp, index] = min(p sim a /pa) 10: while dpp < ε do 11: ia(index) = ia(index) + iiter 12: φ = calculatenodevoltages(a,y ,uv, ia) 13: p sim a = diag(diag(a> · φ) · ia) · pf 14: [dpp, index] = min(p sim a /pa) 15: end while to 1 x . this can be observed by determining the actual number of iterations needed for the process: k∑ i=1 iai iiter (25) as the desired current will consist of portions of iiter on every edge. according to how the desired current is divided by the iteration current, overshoots are possible. therefore, a value of ε is needed in order to secure a suitable exit condition for the loop. basically the blue plot represents a function similar to f(x) = c mod x, where c denotes a given number. in the case of the method described, c stands for a desired load current and x represents possible iteration currents used in the algorithm. according to how the desired current is divided by the actual iteration current, false values can be calculated. the periodic increase in the error is a property of the modulo operation, since the remainder increases until an integer multiple of x is identified. then the error is equal to zero but begins to increase again. the red line represents the number of iterations needed to converge into a final solution. if x << c, the maximum "overshoot" by the modulo operator is relatively small, on the other hand, if x < c, more significant errors can occur. it is clear that in the first case many more iterations are necessary than in the second. since c cannot be determined beforehand, unnecessarily large errors can occur which represents the weakness of the algorithm. it is clear that a compromise must be made between the run-time and precision, as illustrated in fig. 4. 4.2 dynamic iteration current to fix the weaknesses of the algorithm elaborated on in the previous chapter, an advanced version was developed. the first aspect, in which there is room for improvement, is to obtain reasonable initial values of ia. the process 0 0.5 1 1.5 2 iiter 1 1.05 1.1 1.15 m in (d p p ) 0 2000 4000 6000 8000 10000 n u m b e r o f it e ra ti o n s figure 4: minimum error number of iterations does not have to originate from iai = 0, consequently, a considerable amount of cycles can be skipped. in distribution networks the deviation from the nominal voltage (un) is always regulated by standards, for example, in hungary it is approximately ±7.5%. using this restriction, a general estimation can be made for the nodes. the following min() and max() operators relate to the values of the given function. the possible interval between current values can be formulated as follows: min(ia) = pai un cos(ϕi) max(ia) = pai (1−d)un cos(ϕi) , (26) where d is the aforementioned deviation value. this means overestimating the voltage results in the minimum value of the current. setting the starting values of the currents according to the minimum approximation is adequate. to calculate the maximal remaining error, the minimum value of dppi needs to be calculated: dppi = un(1−d) pai un cos(ϕi) cos(ϕi) pai = 1−d. (27) the logic behind this equation is as follows: the fraction in the numerator is the minimum current estimation the un(1−d), on the other hand, is the worst case scenario in terms of the voltage. the deviation is defined by d, so under no circumstances can the voltage drop below un(1 − d), once the initial value has been set. because d is small, this approach alone solves a huge part of the problem, since by taking the hungarian voltage levels as an example, a dpp value greater or equal to 0.925 is achieved! since the initial value problem has been solved, the remaining iterations can also be improved by taking the aforementioned method one step further. in order to take the absolute error in the active power into account, the following variable is introduced: dp = pa − p sim a . (28) 47(1) pp. 49–56 (2019) 54 greber and fodor which can also be formulated using the relative error: dp = pa(1− dpp ). (29) since the whole algorithm is founded on an iterative method, it would be suitable to use the minimum estimation process of the worst-case scenario in the following iterations. the idea in theory, however, is similar to the power value that is being approximated changes. only the remaining error component needs to be recalculated. therefore, the approximation will take the given dpi into consideration instead of the whole pai. un can still be used for this, but is not ideal. once the initial values are set, a node voltage calculation is performed, thus the new node voltages can be used. as a result, the new values must be used as the upper limit of the voltage. finally, the current generated for a particular consumer can be represented by the following series: iai = 1 cos(ϕi) ( pai un︸︷︷︸ j=1 + dp ′i φ′i︸︷︷︸ j=2 + dp ′′i φ′′i︸︷︷︸ j=3 + . . . ) , (30) where j = 1, 2, . . . denotes the number of iterations. if j → ∞, the simulated values approach the desired active powers. in theory this would mean that an infinite number of iterations would be necessary. the maximum error or minimum dpp can be calculated as shown before not only for the initial values but also for the upcoming iteration currents. since in every consequent cycle the absolute error from the previous cycle is corrected, the remaining dp will be corrected by a minimum dpp equal to (1−d). since the fitted values are multiplied, the minimum value of the j-th iteration can be calculated as follows: dppmin = 1−dj . (31) the process of the method of dynamic node powers is shown in algorithm 3. in the literature review, the algorithm 3 dynamic iteration current input: un,a, y , pa, uv, pf output: φ, ia 1: φ = ones(m, 1) · un 2: ia = pa/ ( (a> · φ) · pf ) , if 0 0 : iai → 0 3: φ = calculatenodevoltages(a,y ,uv, ia) 4: p sim a = diag(diag(a> · φ) · ia) · pf 5: dpp = min(p sim a /pa) 6: while dpp < ε do 7: iiter = (pa − p sim a )/(u · pf ), if 0 0 : iai → 0 8: ia = ia + iiter 9: φ = calculatenodevoltages(a,y ,uv, ia) 10: p sim a = diag(diag(a> · φ) · ia) · pf 11: dpp = min(p sim a /pa) 12: end while newton-raphson method was examined in more detail which uses the mismatch in power by incorporating the jacobian matrix in order to achieve convergence. the proposed error recalculation method was developed whilst taking that process into consideration. another possible solution to the calculation of powers could be an algorithm, in which the total power is recalculated rather than the power mismatch. the explicit expression for convergence was determined first, and the total power recalculation method did not suggest better results. although through simulation and observation, it was noted that both require the same amount of iterations. using the monte carlo method, a large number of random networks were created in order to monitor the run-time. results showed the presence of slight deviations with regard to each other. nevertheless, the two methods require almost the same amount of computational time, as is shown in fig. 5. 0 30 0.002 0.004 100 0.006 r u n ti m e [s ] 20 0.008 error recalculation algorithm number of streets ~ network size 0.01 unique simulations 0.012 5010 0 0 0 30 0.002 0.004 100 0.006 r u n ti m e [s ] 20 0.008 whole power recalculation algorithm number of streets ~ network size 0.01 unique simulations 0.012 5010 0 0 figure 5: monte carlo simulation hungarian journal of industry and chemistry simulation of low-voltage electrical grid 55 figure 6: the topology of the test network 5. simulation results in order to verify the proposed method properly, a reference network with available simulation data was required. for verification purposes the ieee european low-voltage test feeder network [14] was used. the simulation process consisted of the implementation of the stated algorithm and importation of network data using matlab. the topology of the test grid is shown in fig. 6. some of the important network parameters are the following: it consists of 906 nodes which are connected by 927 edges that supply 55 single-phase consumers. previous runs have shown that approximately 2 iterations are sufficient for engineering purposes. for the sake of accuracy, a limit was set for dpp , therefore ε is still shown in algorithm 3. the minimum estimations of dpp predicted that the error should rapidly converge to zero. the simulation verified this statement, the rapid decrease in the absolute error can be seen in tables 1 3. it can be clearly observed that in the case of a network of such a size, the maximum voltage difference can be maintained under 10 mv (table 4). the results of the simulation can be seen in fig. 7 which represents the bus voltages of a single phase. note that the y axis is divided into increments of 50 mv. table 1: convergence of dp in phase ‘a’ iteration max (dp ) 0. 0.052137599675 w 1. 0.000041085202 w 2. 0.000000032240 w table 2: convergence of dp in phase ‘b’ iteration max (dp ) 0. 0.042119472811 w 1. 0.000029088116 w 2. 0.000000019550 w table 3: convergence of dp in phase ‘c’ iteration max (dp ) 0. 0.043952897250 w 1. 0.000025174297 w 2. 0.000000014771 w table 4: maximum voltage differences phase ‘a’ phase ‘b’ phase ‘c’ 0.056859 v 0.036058 v 0.023649 v since the active power values are reached with an excellent degree of precision, one would expect that the voltage differences would be smaller. however, this effect does not originate from the algorithm, rather from the simplified network model. this facilitates the possibility of achieving small simulation times. since the introduction of the method of dynamic iteration currents, the number of iterations is independent of the size of the network. the computationally heavy component is the calculation of the inverse of ya. the topology of the network remains unchanged during the iterations. therefore, the steady state simulation of a three-phase network requires, independen of the network size, only three matrix inversions. the duration of the simulation of this network was 2.29 s at a particular instant. 0 100 200 300 400 500 600 700 800 900 1000 bus id 251.9 251.95 252 252.05 252.1 252.15 252.2 v o lt a g e [ v ] ieee reference simulation figure 7: simulation results for phase ‘a’ 47(1) pp. 49–56 (2019) 56 greber and fodor 6. conclusion a novel simulation method for low-voltage distribution networks is proposed in this paper. the existing method of node voltages is further developed in order to handle active power calculations in low-voltage grids. these systems consist of a unique topology to which the process was fitted. the verification criteria for the network structure was formulated. a solution was proposed in which the number of iterations is independent of the size of the network and the simulation error decreases exponentially. the method was tested and verified on the ieee european low-voltage test feeder network. this confirmed the statements about the algorithm. insignificant errors appeared in the test results but these were the effect of the simplified network model. in the future, the algorithm could be improved to handle unbalanced distribution networks. with the aid of appropriate modifications, distributed generation could be taken into consideration that accounts for not only power consumption but also generation. the algorithm can serve as a foundation of network diagnostics by using it to detect faults as well as technical or non-technical losses. acknowledgement we acknowledge the financial support of széchenyi 2020 under the efop-3.6.1-16-2016-00015. we acknowledge the financial support of széchenyi 2020 under the ginop-2.2.1-15-2017-00038. notations φ node-voltage vector ie excitation vector uv voltage-source vector ia current-source vector a incidence matrix y admittance matrix ya nodal admittance matrix m number of nodes n number of edges cos(ϕ) power factor pf power factor vector pa current-source active-power vector u branch voltage vector dpp delta power percentage iiter iteration current dp delta power d voltage level deviation p sim a simulated power vector s complex power p active power q reactive power ϕ phase angle g conductance ε threshold value for iteration references [1] sőrés, m.; fodor, a.: simulation of electrical grid with omnet++ open source discrete event system simulator, hung. j. ind. chem., 2016 44(2), 85–91, doi: 10.1515/hjic-2016-0010 [2] pózna, a.i.; fodor, a.; gerzson, m.; hangos, k.m.: colored petri net model of electrical networks for diagnostic purposes, ifac-papersonline, 2018 51(2), 260–265, doi: 10.1016/j.ifacol.2018.03.045 [3] stagg, g.; el-abiad, a.h.: computer methods in power system analysis (mcgraw-hill), interntaional student edn., 1968 [4] hertem, d.v.; verboomen, j.; purchala, k.; belmans, r.; kling, w.l.: usefulness of dc power flow for active power flow analysis, the 8th iee international conference on ac and dc power transmission, 2006 1, doi: 10.1049/cp:20060013 [5] stott, b.; jardim, j.; alsac, o.: dc power flow revisited, ieee t. power syst., 2009 24(3), 1290–1300, doi: 10.1109/tpwrs.2009.2021235 [6] das, j.c.: load flow optimazitaion and optimal power flow (crc press), 2017 [7] görbe, p.; magyar, a.; hangos, k.m.: thd reduction with grid synchronized inverter’s power injection of renewable sources, in 2010 international symposium on power electronics electrical drives automation and motion (speedam) (ieee), 1381–1386, doi: 10.1109/speedam.2010.5545079 [8] neukirchner, l.; görbe, p.; magyar, a.: voltage unbalance reduction in the domestic distribution area using asymmetric inverters, j. clean. prod., 2017 142, 1710–1720, doi: 10.1109/59.575728 [9] kersting, w.h.: distribution system modeling and analysis (crc press), 2016, isbn: 9781439856475 [10] bird, j.: electrical circuit theory and technology (taylor & francis), 4th edn., 2010, isbn: 185617770x [11] wang, x.f.; song, y.; irving, m.: modern power system analysis (springer), 2008, doi: 10.1007/978-0387-72853-7 [12] zhang, f.; cheng, c.s.: a modified newton method for radial distribution system power flow analysis, ieee t. power syst., 1997 12(1), 389 – 397, doi: 10.1109/59.575728 [13] westinghouse electric corporation, electrical transmission and distribution reference book (east pittsburgh, pa), 1964 [14] schneider, k.p.; mather, b.a.; pal, b.c.; ten, c.w.; shirek, g.j.; zhu, h.; fuller, j.c.; pereira, j.l.r.; ochoa, l.f.; de araujo, l.r.; dugan, r.c.; matthias, s.; paudyal, s.; mcdermott, t.e.; kersting, w.: analytic considerations and design basis for the ieee distribution test feeders, ieee t. power syst., 2017 33(3), 3181–3188, doi: 10.1109/tpwrs.2017.2760011 hungarian journal of industry and chemistry https://doi.org/10.1515/hjic-2016-0010 https://doi.org/10.1016/j.ifacol.2018.03.045 https://doi.org/10.1049/cp:20060013 https://doi.org/10.1109/tpwrs.2009.2021235 https://doi.org/10.1109/speedam.2010.5545079 https://doi.org/10.1109/59.575728 https://doi.org/10.1007/978-0-387-72853-7 https://doi.org/10.1007/978-0-387-72853-7 https://doi.org/10.1109/59.575728 https://doi.org/10.1109/59.575728 https://doi.org/10.1109/tpwrs.2017.2760011 https://doi.org/10.1109/tpwrs.2017.2760011 introduction method of node voltages the generalized nodal equations network model topology verification method of node powers constant iteration current dynamic iteration current simulation results conclusion hungarian journal of industrial chemistry veszprem vol. 29. pp. 119-122 (2001) new possibilities for thermal water treatment a.ujhidy, g.bucsky and j.nemeth (research institute of chemical and process engineering, kaposvar university, veszprem, hungary) received: september 5, 2001 in the well tube precipitation and scaling occur if the physical-chemical equilibria of the components dissolved in thermal water are disturbed partly due to cooling, but largely to the drop of pressure and subsequent gas evolution. all the known methods for the prevention of scaling have some disadvantages. this paper describes a novel technology which is eco­ nomical and environmentally sound. supersaturated· ca(oh)2 suspension is pressed below the bubble point of the well tube and induces cac03 precipitation. a unique feature of the process is that it takes place in the presence of excess acid since below the bubble point all c02 is dissolved in water. the pilot scale experiments resulted in products of industrial use. keywords: geothermal fluid, bubbling point, prevention of scaling introduction in his recent paper [1] sandor p~p wrote that 45% of incoming solar energy (2,48.102 j/a) is absorbed by oceans, continental and ice surfaces. eva~oration and convection returns 1,28.1024 j/a and 3,2.10 3 j/a energy into the atmosphere. it is interesting to compare these values with the data given in a paper by fanelli and taffi [2] who evaluated the potential utilization of h n geot ermal energy. they stated that about 10 j/a energy was released through the surface of the earth by heat conduction. currently, however, the industrial utilization of geothermal energy is economical only in certain areas, from either liquid reservoirs with temperature in excess of 260°c (e.g. wairakei, new­ zealand) or from geothermal reservoirs of dry or supersaturated vapor (lardello and mt.amiata, italy). hungary does not have such a potential, but it has the second largest resources of low-enthalpy thermal water and a geothermal gradient of 1 °c/15-18 m well above the global average. in about half of its area it is estimated to have thermal water resources of 70-98°c in the depth 1500-2500 m. however, as against the data for 1976 given by balogh and bokfi [31 indicating development, by the turn of the millennia the utilization of geothermal energy in both industry and agriculture declined considerably. the heating of homes with thermal water has raised a number of technical-financial problems, so now only secondary utilization seems to be economical. it follows that instead of primary utilization for energy production the emphasis is to be put on balneological and medical applications. on the basis of their experiments in zalakaros, the authors propose a novel direction of potential development. characterization of thermal waters the definition of mineral and medicinal waters was modified several times in the previous century. the hungarian standard pending from 1995 defines natural mineral water as water from any well or closed spring which originates from subsurface aquifiers. the mineral water is pure by origin, it is microbiologically clean, has nearly constant chemical composition and temperature, has dissolved solid mineral content of at least 1000 mgil, or, alternatively, if its mineral content is between 500 and 1000 mg!l, the concentration of sodium is less than 200 mgil, and at least one of the following constituents of nutritional-physiological importance exceed the following limits: calcium 60 mg!l, magnesium 20 mg/l, fluoride 0,8 mg/l, iodide 0,05 mg/l. if the mineral water is warm at the surface, has an annual mean temperature in excess of 25°c, it is termed thermal water. the thermal water which has proven curative effect is classified as medicinal water. by their origin thermal waters can be classified according to the concentration ratio of mmor ions ( 10). the ratios of sodium (na). calcium (ci+) and 120 table 1 chemical compositions of the medicinal waters of zalakaros and margitsziget zalakaros margitsziget mgdm3 mgdm"3 k+ 58 k+ 43.4 na+ 1810 na+ 91.9 nw 12 lt 0.2 ca2+ 136 nh4 mgz+ 47.5 ca2+ 152.4 fe2+ 0.15 mg2+ 37.3 mn2+ sr2+ 0.4 cr 2420 mn2+ 0.7 bf 6.5 cr 122.9 r 5.4 b{ 0.04 f 1.4 r 0.1 s04121 s04149.3 hco; 1650 hco; 507.5 s"32.9 cos 4.6 p04 0.12 si02 37.4 hboz 155 hzsi03 19 coz 733 coz 398.2 total 7177.97 total 1546.34 zalakaros ugdm-3 ggdm"3 u 1.0 as 2.3 ra226 (bq cm-3 ) 22.1x10-4 rb 15 th 0.5 sr 4500 b 1000 zr 8.1 y 1900 mo 5.2 p 46 cd 2.5 ti 0.8 sn 2.2 v 0.24 sb 2.9 cr 2.7 cs 1.0 co 0.1 ba 1400 ni 5.4 w 3.3 cu 37 hg 0.5 zn 15 pb 2.9 bi 1.3 magnesium (mg2l~ as well as chloride (co~ a sulfate (sol) and bicarbonate (hc03) assign 49 classes of thermal waters. if the mineral water contains a large amount of free carbon dioxide, it is termed acid water. examples for such waters are thennal waters in balf, balatonfiired~ moha and zalakaros. waters rich in sulfide are thermal waters in parad, harkany and margitsziget. aperient waters contain either magnesium sulfate or sodium sulfate (igmandt mira, hunyadi janos). radioactive waters form a distinct category: their low radioactivity is not harmful for human health. on the contrary~ they may be physiologically beneficial: the uranium and radon contents of the thermal water in zalakaros exceed those of the lake in hevfz, they are exceptionally high in the region. the exceptionally high concentrations indicate the presence of a granite strate below or near the mesosoic reservoir. this granite strate of 300 million years is on the surface at the velence mountains in the transdanubia. according to geological and hydrogeological studies the geothermal reservoirs of zalakaros ~ savoly and heviz are on two different furrows in spite of their geographical proximity. the former is an open reservoir with replenishing potential. the chemical compositions of the medicinal waters of zalakaros and margitsziget are compared in table 1. as it can be seen in the table, the water in margitsziget contains carbonyl sulfide. karoly than was the first to identify this compound in medicinal water in 1871. cos is hydrolyzed to hydrogen sulfide and carbon dioxide. the presence of h2s causes corrosion upon further treatment of the water. the medicinal water in zalakaros has a total mineral concentration of nearly 7.2 gil, predominated by sodium, chloride and bicarbonate. it also contains a multitude of trace constituents. the depth of the well under study in zalakaros is 2250 m. the temperature, pressure and total (carbonate) hardness at the bottom of the well is 121 °c, 225 bar, 23.55°, respectively, the ph is 7.12. the temperature at the wellhead is reduced to 99.5°c, the ph is increased to 7.80 and total (carbonate) hardness drops to 10.88°. upon the start of the well the daily output was 600 m3 at a head pressure of 9 bar [ 4]. during our experiments the zero-point pressure was at a depth of 70 m. currently the thermal water is pumped to the surface by the air lift exerted by the evolving gases (carbon dioxide and small amounts of h2s). problems of operation as it was described earlier, if the physical-chemical equilibria of the dissolved constituents are disturbed in the upwelling thermal water, precipitation occurs in the form of macroor microcrystals. the microcrystals remain suspended in solution and pass through the wellhead, whereas the macrocrystals are deposited on the wall of the well tube and form a thickening layer of scale causing malfunctions in the operation of the well. scaling is primarily caused by dissolved calcium and magnesium hydrogen carbonates responstble for the variable hardness of the water which, upon upwelling, are decomposed to insoluble calcium or magnesium carbonates, carbon dioxide and water. it should be noted that the starting point of precipitation is called critical or bubble point and is defined with its depth. recently scaling processes in the well tube was studied in details by erika kalman and her co-workers [5~ 6] in the case of the ternary system of cac03 h20 c:02 .. they dev~loped a computer model to study the kinetics of scalmg. they emphasized that scaling and corrosion are inseparable problems during operation. they found~ in harmony with others in the literature that the langelier saturation index and ryznar stability index can ~ ~sed for the classification of scaling and corroston m thermal waters of various compositions and temperatures. the more the measured ph differs from the sati?'ation ph. the larger the tendency of the water for scahng and corrosion. it is well known that dry and wet carbonic acid is capable of corroding steel and cast iron at higher temperatures, these materials are no longer corrosion­ resistant at 100°c, nor are copper~ lead and most plastics (e.g. pvc~ pe, polystyrene, polyethylene. etc.). the structural material of the wells should be ko 33 stainless steel with austenite (cr 19, ni 9, cmax 0,07), or aisi 304 steel of similar composition, not only because they are highly corrosionand erosion~proof, but also they have favorable temperature-strength characteristics. in addition, they can be connected to metallic and non­ metallic structural materials. several procedures have been tried to prevent scaling in thermal wells. theoretically the ideal solution would be if the thermal well had a head pressure at which no or negligible amount of carbon dioxide was liberated so that precipitation was avoided. such situation, however, rarely occurs in practice. the scale deposited can be removed chemically or mechanically. both methods wear away the structural elements and have considerable cost-implications. besides, temporal closing and restart of the operation may cause malfunctions. inhibitors injected below the bubble point can also prevent scaling, but it is an expensive technology since large amounts of chemicals are needed and treatment of the extracted water may also be necessary. researchers in the usa showed [7] that acidification prevented the precipitation of cac03 and no corrosive products were deposited on the tube wall. in addition to the costs of the acid and its injection into the well a ph-regulator has to be installed. the ph of the water has always to be kept above 4, because at lower ph the rate of corrosion is significantly enhanced. prior to any further utilization of the extracted acidic thermal water neutralization is needed. in the early 80s in zalakaros scaling was prevented by pressing degassed surface water below the bubble point into the well tube [4]. no scaling occurred when the thermal water was diluted by a factor of 2 or 3 with the injected tap water. the balneological use of the medicinal water of about 80°c did not require any further treatment, but large amounts of carbon dioxide were released into the atmosphere. for example, well a had a daily output of water and gas of 800 m3 and 300 m3, respectively, at deep-well b with an output of 600 m 3 /d 15m3 gas was released for each m3 of water. this and the increased cost of tap water called for the development of the system. experimental part the objectives of the development were to ensure the smooth operation of the deep-well in zalakaros, to fix the excess c02 evolving at a mass rate of 150 kg/h, and to produce new products or raw materials which contain dissolved salts in their natural ratio. the experiments were also aimed at determining the concentrations of trace elements in the products. provided that the original trace element composition does not change, the product could be· a potential medication. it was the most straightforward to select ca(oh)z for the fixation of carbon dioxide since cl+ cations were originally present in the thermal water. the absorption of c02 released from the wellhead in ca(oh)2 solution did not give good results. the excess base caused low 121 fig.l flow chart of the new procedure a./ diluent, b./ ca(oh)z, c./ gas, d./ product, e./ filtrate, k./ mixing chamber, 1./ homogenizer, 2./ well, 3./ pump, 4./ mass flow controller, 5./ static mixing tube, 6./ cyclone, 7./ centrifugal filter, 8./ filter press precipitation efficiency and yielded cac03 precipitate of highly variable quality. therefore the calcium hydroxide suspension was injected into a mixing chamber installed below the bubble point. in the chamber all carbon dioxide is in the form of dissolved carbonic acid. thus in the novel procedure quantitative precipitation occurs in the presence of excess acid, unlike precipitation in the presence of excess base. by keeping the proper rate of addition carbonate formation consumed about half of the carbon dioxide dissolved in the thermal water, before gas evolution had been started. at the bubble point the other half of the dissolved carbon dioxide evolved. it did not cause s<.:ahng but it was needed to exert air lift for the extraction of thermal water, i.e. to ensure the operation of the well. the flow chart of the new process can be seen in fig. i. during the preliminary experiments water and ca(oh)2 suspension of technical quality were introduced into homogenizer 1. after the favorable results analytical grade ca(oh)z suspension was used in the further experiments. effective mixing: was accomplished via recirculation driven by pump 3, in which the recycled fluid passed through the static mixing tube 5 [8] into the homogenizer stirred with hydrodynamical jet [9]. the ca(oh)z suspension of 15 m/m % was then pressed into the mixing chamber k of well 2 at a depth of 400 m at a rate controlled by a mass flow controller 4. the gas/liquid system exiting well 2 at a pressure p and temperature t flowed through the hydrocyclones 6. the separated gas was used in balneology, whereas the fluid was pumped through a centrifugal filter then through the framed filter press 8 for further treatment. the filtrate was directly suitable for balneological use, whereas the precipitate from the centrifugal filter and the filter cake served as raw material for the production of new products. 122 lu• 7 ;.: sl 'i'" r~ ~ ..... ....___ 18 198 1boo partiele si:re ~ fig.2 flow sheet of the pressure of the well and the addition ofca(oh)2 results the efficiency of the removal of precipitate by the centrifugal filter was 75-80%. the remaining precipitate of 20-25% was effectively filtered with a framed filter press at low pressure drop and high filtration rate. the filtrate passed the mirror test so it can be returned to the well as a diluent. the degassed filtrate can replace tap water and can stabilize the chemical composition of the fluid in the well tube. the grain size distribution of the filtered carbonate precipitate is shown in fig.2. it can be seen in the figure that the maximum grain size is smaller than 20 jlffi, whereas the average grain size is 4 4,5 j.lm. figure 3 shows an example of variations of the pressure of the well and the addition of ca(oh)2 in time. the drop and increase of the pressure indicate the start and the end of the reaction, respectively. as it can be seen. the pressure was stabilized at a lower value about 10 minutes after the start. the addition of the suspension was ceased at 20 min. the reaction proceeded for some time and the well pressure returned to its initial value after about 30 min. discussion the wet precipitate from the centrifugal filter contained about 50 % moisture by mass~ in which all the ions originally present in the thermal water were dissolved. an interesting feature of the novel technology is that when the fluid was expanded to atmospheric pressure and was evaporated to dryness, then crystallized thermonatrite (sodium carbonate} and halite (sodium chloride) were formed and the calcium carbonate was amorphous. it follows that in the technology the ratio of the trigonal lattice calcite, the orthorombic lattice aragonite and the amorphous calcium carbonate can be adjusted by varying the amount, concentration and temperature of the ca(oh).z suspension injected into the mixing chamber of the well. other products can also be precipitated in various reactions (e.g. with hzs} with the described technology p {bar} ca(oh}2 (dm 3/min) 10 ~ 8 7 \ 6 5 4 3 2 1 0 10 k y 19 i 28 ,..,. 37 t(min) fig.3 grain size distribution of calcite crystals 120 100 80 60 40 20 in reactions with either dissolved ions or gas compo­ nents. the experience gained with this new procedure can be used for economical and environmentally sound treatment of thermal waters from other, currently unexploited geothermal reservoirs. conclusion to the best of our knowledge we were the first to successfully conduct a pilot-scale experiment in which ca(oh)2 reacted with carbon dioxide in the presence of excess carbonic acid. the initial acidity of the carbonate suspension quickly diminished under atmospheric conditions and the cooled precipitate and filtrate was found to be slightly basic. the precipitate recovered from the filters was loosely packed, pure calcium carbonate in the form of calcite microcrystals, containing halite in minor amounts. the adsorbed moisture retained the original ionic composition of the thermal water, except bicarbonate. the reaction with ca(oh)2 did not affect the operation of the thermal well using this' new procedure all constituents of the thermal water can be utilized in an environmentally sound manner. references 1. papp s.: magyar kemikusok lapja, 2001, 56(4), 144-148 2. fanelli m. and taffi l.: revue de l'institut francais du petrole, 1980, 35(3), 429-448 3. balogh j. and bokfi s.: proc. int. congr. thermal waters, athen, 87-99, 1976 4. hung. pat. 181.380 (1981) 5. stahl g.,. pa'izay g. and kalman e.: hung. j. ind. chern., 1999, 27{1), 9-12 6. stahl g., pa'izay g. and kalman e.: magyar kemikusok lapja, 1999, 54(4), 181-186 7. pruce l. m.: power, 1980, 124(7), 84-87 8. hung. pat. 179,046 ( 1979) 9. hung. pat. 190,202 (1983) 10. borszeki b. gy.: asvanyvizek, gy6gyvizek (mineral and medicinal waters, in hungarian). mete kiad6t budapest 1998 page 121 page 122 page 123 page 124 hungarian journal of industry and chemistry vol. 51(1) pp. 35–42 (2023) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2023-06 development of a digital twin for gas mixing in a generator olga shypul 1*, vadym garin1, denys tkachenko1, sergiy plankovskyy2 and oleg tryfonov1 1 national aerospace university “kharkiv aviation institute”, 17 chkalova street, kharkiv, 61070, ukraine 2 o. m. beketov national university of urban economy in kharkiv, 17 marshala bazhanova street, kharkiv, 61002, ukraine the subject of this research is the development of a digital twin for the process of mixing the components of a gas mixture in the mixer of a mixture generator. the problem is motivated by the concept of digitalizing modern production and is considered in relation to the technology in question for generating a gas mixture of a given composition and homogeneity. a gas-dynamic model of an unsteady flow has been constructed and a numerical study carried out using the ansys fluent software. the reduced order model was developed and used in the ansys twin builder platform to build the digital twin. keywords: digital twin, reduced order model, numerical simulation, gas mixer 1. introduction the incentive for developing digital twins (dt) in the process of generating gas mixtures is the digitalization of modern technologies. a dt is a virtual copy of a real system characterized by continuous and automatic synchronization as well as feedback between the real and digital domains. many authors have diversified the typical development process of dts [1]-[8]. all of the aforementioned referenced studies added their own values to define their dt. in almost all of these works, given the large number and variety of systems for which dts can be created, the authors paid special attention to structuring the process of creating a dt. therefore, the authors of [1] presented a five-dimensional model of a dt in which all stages for creating, implementing and monitoring the operation of equipment as well as recording data are accounted for. a more simplified scheme for creating a dt is provided by the authors of [2]-[4] in which the importance of individual aspects of the dt are emphasized. in [2], the authors insist on the importance of the digital component in the creation and implementation of a dt, which depends on the speed of process control and data exchange between elements of the system. in [3], the importance of communication as well as information exchange between a dt and a real system, in addition to monitoring the operation of a system in real time, is considered. a more unusual received: 8 apr 2023; revised: 17 apr 2023; accepted: 19 apr 2023 *correspondence: o.shipul@khai.edu concept was proposed in [4], in which the evolution of the state of the object when creating a dt is considered. furthermore, the peculiarities and relevance of creating duplicates of multiphysics models, which should process large arrays of heterogeneous data, are addressed in [4]. currently, many studies provide a comprehensive theoretical justification for the concept of creating a dt as well as the importance of the stages necessary to create and implement a dt of a real system or process amongst other research objectives. such works are analysed in a review article [5], moreover, a group of practically oriented studies [6]-[9] is provided. in [6], the authors proved the importance of creating a dt when designing a large complex system. they came to the conclusion that a preliminary analysis of the system in a digital format will help to avoid many expensive problems when constructing and adjusting real equipment. in light of this, a new wind turbine controller was created in [7] in which the functional mock-up interface (fmi) was used to combine the cfx and maxwell 3d models as well as the capabilities of the ansys twin builder platform applied to create a dt. lastly, an exemplary example of combining a real braking device with its dt into one system is given in which data exchange took place in real time [8]. within the framework of this work, a dt to form a fuel mixture in the system in which it is generated is developed, which should automatically provide the required composition of components in the mixture and the degree of its homogeneity. https://doi.org/10.33927/hjic-2023-06 mailto:o.shipul@khai.edu shypul, garin, tkachenko, plankovskyy and tryfonov hungarian journal of industry and chemistry 36 2. problem statement international standards [9]-[12] have been developed on the basis of state-of-the-art research into the digitalization of production, which regulate the construction of automation systems, integration of technical processes or operation of industrial equipment using digital technologies. these standards define two types of twins, namely digital and physical ones. a dt consists of three parts: 1. a data collection and device management facility in which signatures are also combined. the collected data is pre-processed by the data collection facility. 2. the core, which is responsible for its general operation and management as well as consists of computing environments. 3. the user object, with the help of which various human-system interactions take place, can be provided both in the cloud and in the local network. a physical twin consists of an experimental setup, sensors that facilitate data collection and a device control system to regulate executive functions. in the case of extremely complex non-stationary workflows or when it is not possible to install sensors, numerical modelling can provide an alternative source of data acquisition. to ensure the specific heat consumption remains stable during cyclic thermal processing, simultaneous control of the mass of the fuel mixture and the pressure applied on the charge in the combustion chamber is necessary to form the mixture, fill the chamber and make subsequent corrections. in accordance with the specified requirements, a system for forming the fuel mixture in the thermal pulsation system was developed, which is described in detail in [13]. the object of this study is to develop a mixer for mixing gaseous components, which is part of the fuel generator of an automated thermal pulse processing unit, described in detail in [14]. mixing is frequently one of the most important processes in various industries. all starting materials and products, for example, in the chemical industry, must be homogeneous. in a paper where mixing in reservoirs was studied, a relationship was established between the flow structure in a tank and its geometry [15]. the aforementioned study considered a dt of the process of mixture formation in a mixing chamber by determining the composition of components and degree of homogeneity of the gas mixture obtained. the physical twin of our research objective is a twocomponent mixer (figure 1), which partly consists of a steel body (1), lid (2) and technological plugs (corks) (3). the components of the gas mixture enter through special jets (nozzles) (4) which are further mixed by counter currents in the chamber (5). differences in the crosssectional areas of the through hole in the jets through which the fuel and oxidizer enter control the stoichiometric ratio of the components of the mixture being a supercritical flow at a constant pressure [16]. an apriori physical twin consists of an experimental setup, components that collect data (sensors) and a device control system (executive function). the latest approach to the creation of dts suggests the possibility of representing a physical twin by mathematically modelling it, which is necessary due to the complexity and sometimes even the impossibility of installing sensors as well as measuring the control parameters of processes in real time. for example, this applies to hermetic objects of a small or limited volume and fastacting processes that occur in them. the mixer in question required to mix the components of a gas mixture also falls into this category, that is, where the control parameters are the total mass of the components and the degree of homogeneity of the mixture. by studying the simulation of this process, special and extremely expensive equipment is not required to experimentally determine these parameters in the mixer. 3. modelling of gas mixing in a mixer the calculation area is the internal cavity of the gas mixer (figure 2a). the calculation grid (figure 2b), consisting of 152042 polyhedral elements, was built in the ansys fluent meshing module to make further calculations in the ansys fluent system [17]. in order to model the wall flow of gases accurately, 5 prismatic layers with a growth factor of elements equal to 1.2 were built. to solve the defining equations of the model, the finite volume method (fvm) was used, according to which the values of physical variables were calculated only at the center of the elements, while the mass flows, momentum and energy were calculated at the edges of these elements. 3.1. boundary and initial conditions mixing of the methane-oxygen mixture in the expected stoichiometric ratio according to the reaction сн4+2о2 → со2+2н2о figure 1. mixer model 1 – body; 2 – lid; 3 – corks; 4 – nozzles; 5 – chamber; 6 – fittings; 7 – sensors development of a digital twin for gas mixing in a generator 51(1) pp. 35–42 (2023) 37 was investigated. the directions of the supersonic flow of the gaseous components were normal at the inlets. the calculations were made while the system was stationary. at the tip of the jet, the speed of the gas flow was equal to the speed of sound. the computational model consisted of two domains with a common interface. while a force was applied, the average molar concentrations of oxygen and methane at the outlet of the mixer were monitored. the pressures of methane and oxygen gas at the inlet to the mixer were set at 4.340 and 4.104 atm, respectively. the initial temperature of both gases at the inlets was 20 °c. a single-phase multicomponent flow model was used to describe the mixing. the equations used to calculate the composition of the mixture were as follows [18]: 𝜕𝜌 𝜕𝑡 + 𝑑𝑖𝑣(𝜌�⃗� ) = 0 (1) 𝜌 𝑑�⃗⃗� 𝑑𝑡 = 𝑑𝑖𝑣𝑃 + 𝑓 (2) 𝜌 𝑑𝑒 𝑑𝑡 = 𝑑𝑖𝑣(𝜆𝑔𝑟𝑎𝑑𝑇) + 𝑃 · 𝑔𝑟𝑎𝑑�⃗� (3) where ρ denotes the density of the mixture; �⃗� represents the velocity vector; p stands for the stress tensor; t refers to the gas temperature; λ is the thermal conductivity coefficient of the gas; and e denotes the internal energy of the gas. to ensure that the fuel mixture is stratified from components of different densities, the effect of volume forces, namely gravity, was taken into account (𝑓 ). when calculating the density and gas constant of the mixture, standard mixing rules were used: 1 𝜌 = ∑ 𝑐𝑖 𝜌𝑖 𝑁 𝑖=1 , 𝑅 = ∑ 𝑐𝑖 𝑁 𝑖=1 𝑅 (4) where (ρi) denotes the density of the components i of the mixture; r is the universal gas constant, ci, represents the molar concentration of the components i. to determine the degree of homogeneity of the mixture (ϑ), the following expression was used: 𝜗 = 𝜎𝐶𝑓 [𝐶𝑓] (5) where [cf] denotes a given value of the molar concentration of the fuel, which corresponds to the stoichiometric ratio and σcf stands for the best estimate of the root-mean-square deviation of the molar concentration of the fuel as defined as: 𝜎𝐶𝑓 = √∫ (𝐶𝑓−𝑀𝐶𝑓) 2 𝑑𝑠𝑠 𝑆𝑜𝑢𝑡𝑙𝑒𝑡 (6) where soutlet denotes an area of an outlet from the mixer; cf stands for the molar concentration of the fuel, mcf denotes the following mathematical expression of the molar concentration of the fuel: 𝑀𝐶𝑓 = ∫ 𝐶𝑓 𝑑𝑠 𝑠 𝑆𝑜𝑢𝑡𝑙𝑒𝑡 (7) the mixture was considered to meet the requirements in accordance with the conditions below: [𝐶𝑓] − 𝛿 · [𝐶𝑓] ≤ 𝑀𝐶𝑓 − 𝜎𝐶𝑓 ∪ (8) ∪ 𝑀𝐶𝑓 + 𝜎𝐶𝑓 ≤ [𝐶𝑓] + 𝛿 · [𝐶𝑓] where δ denotes the given permissible deviation in the mass concentration of the fuel. an automatic time step was used for the calculation. the pressure-velocity coupling scheme was selected as the pressure-implicit with splitting of operator (piso). for the discretization of parameters, second order upwind scheme was used. a b figure 2. cross-section of the calculated model of the mixer (a) and finite element grid (b) shypul, garin, tkachenko, plankovskyy and tryfonov hungarian journal of industry and chemistry 38 3.2. the obtained results the velocity fields of gas flows, the mass flow of the components of the gas mixture through the mixer as well as the pressure and temperature fields were obtained by applying computational fluid dynamics (cfd) modelling. the temperature and pressure distribution across the cross-section of the mixer and in the nozzles is presented in figures 3 and 4. after travelling through the jet, a significant local decrease in temperature and pressure was observed due to the acceleration of the gas flow and the supercritical flow regime (figure 5). undoubtedly, such heterogeneous flow conditions affect how accurately the components of the fuel mixture are dosed and must be taken into account when performing calculations. the distribution of the molar concentration of methane across the cross-sections of the mixer and at its outlet is shown in figure 6. cfd simulation results show that the mixer ensured that the fuel mixture was highly homogenous. according to the normalized estimate of the root-mean-square deviation of the molar concentration of methane, the deviation of the methane content from the stoichiometric value did not exceed 3 %. 4. development of a dt of the mixer connected to the system generating the fuel mixture the concept of a dt using ansys twin builder numerical modelling technologies was proposed by ansys, inc. [19]. the results of simulations using dts can be calibrated based on the operating parameters of the physical process. the direct connection between the finite element method in its usual sense and the control scheme slows down the calculation speed when predicting the output parameters. therefore, when developing a dt, reduced order models (rom) were used. creating a rom is possible by studying the physics of the process and extracting its global behaviour from the offline simulation. this can be obtained directly on the basis of the preliminary results from finite-element modelling by only taking into account the main features of the system and process. since the calculation of the result in a separate object subjected to digital reduced order modelling requires only simple algebraic operations, e.g. the addition of vectors and evaluation of response surfaces, the calculation process only requires technical resources for a short period of time and the result can be obtained in almost real time. a b figure 4. pressure fields in the central section of the mixer (a) and its nozzles (b) a b figure 3. temperature fields in the central section (a) of the mixer and its nozzles (b) development of a digital twin for gas mixing in a generator 51(1) pp. 35–42 (2023) 39 with parametric rom, the model can be evaluated and variations in the results quickly investigated depending on the values of the input parameters, thereby emphasizing the importance of suitable roms when simulating the operation of a complex multifunctional system. of course, the results of a dt will be as reliable as the input data used to describe the object or process being modelled as comprehensively as possible. typically, an enormous number of data points were recorded from the full-scale model. several of the most likely characteristic modes were selected from the set of all the generated data, from which a simplified numerical calculation was subsequently made. therefore, it is possible to thoroughly understand how the equipment is operated in different modes. to implement this approach in ansys twin builder, a special hierarchy of input data was drawn up. having such a hierarchy of data files is undoubtedly advantageous because from this it is possible to immediately match the data coming from analog sensors with a dt, that is, a calculation program. the dt of the mixer in the current study was created using the ansys fluent and ansys twin builder programs. in the first stage, a complex model of the gasdynamic process of mixture formation of different component compositions was carried out in ansys fluent in order to determine the parameters that were later transferred to the rom block of the model necessary for creating a dt in ansys twin builder. the rom of the model was transferred in functional mock-up unit (fmu) format. a series of calculations was carried out to prepare the personnel unit required for the construction of the dt using the rom model according to the established range of varied parameters. to create a digital counterpart to this process, the pressures of the fuel and oxidizer at the inlets were selected as the initial parameters. as control (output) parameters, the molar concentration of the components of the gas mixture and its quality were selected. the parameter describing the quality of the gas mixture showed the non-compliance rate along with the stoichiometric value of the gas component in the following form: ^2 sqrt(areaave((areaave(ch4idealgas.molarfraction)@outlet h4idealgas.molarfraction) @outlet) / /(areaave(ch4idealgas.molarfraction)@outlet). c − − according to the algorithm of the parametric calculation, the number of variations (the design points that were used to build the so-called learning points or snapshots of the rom) required was determined. in the case under consideration, 16 of them were found. the scatter plot of variations in the initial data lies within 10 % of the deviations and is determined randomly. therefore, in the framework of solving a parametric problem, after a series of gas-dynamic calculations on the a b figure 5. velocity field throughout the volume of the mixer (a) and in the jets (b) a b figure 6. molar concentration of the fuel injected into the mixing chamber (a) and at the outlet from the mixer (b) shypul, garin, tkachenko, plankovskyy and tryfonov hungarian journal of industry and chemistry 40 full fluent model of the mixing process were made, basic data were obtained for the rom of the dt (figure 7), which clearly show the variations in the values of the inlet pressure parameters of the components of the mixture and the corresponding values at the outlet, that is, the parameter defining the quality of the gas mixtures. to view the goodness of fit for the output parameters in a rom, the absolute error (l-infinity norm error) was calculated for each snapshot (figure 8) according to the following expression: 𝑌𝑖 = 𝑚𝑎𝑥𝑗=1…𝑁|𝑌𝑖,𝑗 − 𝑌𝑖,𝑗 ⃗⃗⃗⃗ ⃗| (9) where yi denotes the i-th snapshot; yi,j refers to the j-th entity of the i-th snapshot; and 𝑌𝑖,𝑗 ⃗⃗⃗⃗ ⃗ represents the rom approximation of the j-th entity of the i-th snapshot. a simplified mixer model can be considered to be a complete dt. meanwhile, considering the mixer as a separate structural component of some hydraulic system, the resulting fmu model of the mixer will act as a structural unit of a higher-order circuit, e.g. "cylinder mixer working tank". in terms of all these calculations, the resulting model should be loaded into the ansys twin builder platform as a separate component. when adding a model of an fmu mixer, attention must be paid to the model-carrying input and output parameters created when the rom was built. therefore, when adding a mixer to the scheme of the digital double, all the parameters of the model of interest were noted before it was imported. the initial parameters here were the values of the fluel_in_press and fluel_in_oxi pressures specified in the ansys fluent parametric study at the outlets of the two cylinders of gases that were being mixed. since the mass content of each component of the mixture at the outlet of the mixer was determined as initial and control parameters, the dt was successfully added to the dt project. in ansys twin builder, data can be assigned in many ways to describe how the equipment is operated or its individual link. the input parameters for this rom of the mixer can be loaded from an external medium in tabular format, the data of "frames" pre-saved measurements from analog devices (sensors) at a certain time interval used or a continuous streaming of data recorded from when the equipment was used with the help of additional macros. when using this mixer as part of a dt of a higher order, the input parameters for the mixer were determined by the output parameters of the previously stationary element, e.g. the gas pressure at the outlet of each of the cylinders. in this work, given that the mixer itself was calibrated and verified, it is sufficient to use the standard "2d lookup table" scheme to determine the pressure of the two oxidizers at each inlet of the mixer. with the help of "2d lookup table" schemes, since the pressures at the inlets to the mixer are represented as tabular functions over time, it is important p re ss u re ( p a) , × 1 0 5 points name 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 160 2.7 2.5 3.1 2.9 3.5 3.3 3.9 3.7 99.65 99.7 99.50 99.55 99.40 99.45 99.25 99.35 99.6 99.30 m ix in g q u al it y ( % ) mixing qualitypressure ch4pressure o2 figure 7. design points vs. parameters 1 0 2 3 4 5 6 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 points name l -i n fi n it y n o rm e rr o r , × 1 0 -6 figure 8. l-infinity norm error for the points taken into account in the construction of the response surface development of a digital twin for gas mixing in a generator 51(1) pp. 35–42 (2023) 41 to match the time ranges of the input parameters with the time settings of the entire solution defined for the project (figure 9). the calculation is performed by applying standard solver settings using the adaptive step trapezoid rule method to integrate time. temporary settings cover all the calculation frames. after preparing and adjusting the model of the dt of the two-component mixer, a calculation was made, the result of which was presented in the form of twodimensional dependence graphs (figure 10) showing changes in the mass fractions of the components of the mixture against the number of snapshots (time). the horizontal axis indicates the number of the calculated snapshot and the vertical axis indicates the mass fraction of the component of the gas mixture. given that the mass fraction of the components of the gas mixture controlled at each calculation point was one, the law of conservation of mass was not violated. the graphs obtained from the built dt with regard to the process of generating the fuel mixture provide visual representations of the percent composition of the mass fractions of each gas mixture depending on the pressure at the outlet of each cylinder. furthermore, how the composition of the mixture changes when the pressure of each component of the fuel mixture at the inlet to the mixer deviated from its optimal value was determined. 5. conclusion the construction of a dt of the system generating the fuel mixture based on the results of a numerical simulation was considered. a combined approach was used to build a dt. an element of the generation system with a complex flow pattern was modelled by a numerical experiment, the results of which were used to build its rom. this model was used as the structural unit of the higher-order contour. the graphs obtained from the built dt of the process used to generate the fuel mixture provide a visual representation of the percent composition of mass fractions of each gas mixture depending on the pressure at the outlet of the cylinders. furthermore, how the composition of the mixture changed when the pressure of each component of the fuel mixture at the inlet to the mixer deviated from the optimal value could be determined. acknowledgements the authors would like to express their gratitude to cadfem ua llc, an official partner of ansys, inc. in ukraine, for helping license the software. figure 9. the scheme of the dt of the mixer 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 times [s] – design points m a ss f ra c ti o n c h 4 0.155 0.150 0.160 0.165 0.170 0.175 0.180 0.185 0.190 0.195 a 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 times [s] – design points m a ss f ra c ti o n o 2 0.810 0.805 0.815 0.820 0.825 0.830 0.835 0.840 0.845 0.850 b figure 10. mass fractions in the form of particles of the components of the gas mixture (а – ch4; b – o2) shypul, garin, tkachenko, plankovskyy and tryfonov hungarian journal of industry and chemistry 42 references [1] qi, q.; tao, f.; hu, t; answer, n.; liu, a.; wei, y.; wang, l.; nee, a.y.c.: enabling technologies and tools for digital 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https://doi.org/10.1016/j.jmsy.2019.10.001 https://doi.org/10.1016/j.compind.2019.103130 https://doi.org/10.1016/j.compind.2019.103130 https://doi.org/10.1007/10_2020_149 https://doi.org/10.1007/s00170-021-07141-z https://doi.org/10.1007/s00170-021-07141-z https://doi.org/10.1016/j.ifacol.2018.08.474 https://doi.org/10.1016/j.cirp.2017.04.038 https://doi.org/10.1109/cpeee51686.2021.9383360 https://doi.org/10.1109/cpeee51686.2021.9383360 https://doi.org/10.1088/1742-6596/1700/1/012097 https://doi.org/10.1016/b978-0-12-817452-4.00014-2 https://doi.org/10.1016/b978-0-12-817452-4.00014-2 https://doi.org/10.33927/hjic-2019-21 https://vant.kipt.kharkov.ua/article/vant_2018_5/article_2018_5_121.pdf https://vant.kipt.kharkov.ua/article/vant_2018_5/article_2018_5_121.pdf https://ansyshelp.ansys.com/account/secured?returnurl=/views/secured/prod_page.html?pn=cfx&pid=cfx&lang=en https://ansyshelp.ansys.com/account/secured?returnurl=/views/secured/prod_page.html?pn=cfx&pid=cfx&lang=en https://ansyshelp.ansys.com/account/secured?returnurl=/views/secured/prod_page.html?pn=cfx&pid=cfx&lang=en https://doi.org/10.2514/3.12149 https://doi.org/10.2514/3.12149 https://ansyshelp.ansys.com/account/secured?returnurl=/views/secured/prod_page.html?pn=twin%20builder&pid=twinbuilder&lang=en https://ansyshelp.ansys.com/account/secured?returnurl=/views/secured/prod_page.html?pn=twin%20builder&pid=twinbuilder&lang=en https://ansyshelp.ansys.com/account/secured?returnurl=/views/secured/prod_page.html?pn=twin%20builder&pid=twinbuilder&lang=en hungarian journal of industry and chemistry vol. 51(2) pp. 27–33 (2023) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2023-15 production of a highly concentrated gold solution from aqua regia gold leachate using sugarcane bagasse nanoparticles oluwasanmi samuel teniola1*, abraham a. adeleke2, simeon ademola ibitoye2 and moshood dehinde shittu2 1 department of mineral and chemical resources engineering, first technical university, km 11, lagos-ibadan expressway, ibadan, oyo state, 200261, nigeria 2 department of materials science and engineering, obafemi awolowo university, p.m.b. 13., ileife, osun state, 220282, nigeria this study produced a highly concentrated gold solution using nanoparticles (nps) synthesized from sugarcane bagasse as an adsorbent for gold(iii) recovery from an aqua regia gold leached lean solution. a 100 kg sample of gold ore collected from a mining site in iperindo was concentrated. mineralogical characterization and a fire assay test of the ore were carried out. atmospheric and agitation leaching were conducted using aqua regia. sugarcane bagasse nps were prepared and used to study the gold(iii) adsorption kinetics. gold -loaded sugarcane bagasse nps were desorbed in a 4 m aqua regia solution. the results revealed that the ore has a low water retention capacity which renders it friable. a microscopic examination established the presence of gold particles and pyrite in the ore. ore leaching was eminently favoured by agitation yielding a weight loss of 6.3 % when an acid concentration of 4 m was used, the temperature was 90 ºc and the leaching time was 30 minutes. synthesized nanocellulose was able to adsorb gold(iii) from the leachate optimally with the following process parameters: 14 ml/g of adsorbent, 106.2 minute-long contact time, a temperature of 56 ºc and an agitation rate of 45 rpm when the concentration of leachate was 84 mg/l. the adsorption efficiency of the sugarcane bagasse nps is comparable with that of commercial activated carbon, namely 92 and 95 %, respectively. the study concluded that nps synthesized from sugarcane bagasse could be effectively used when upgrading gold and in purification processes. keywords: adsorbent, aqua regia, leaching, agitation, nanocellulose, bagasse, gold, mineralogical 1. introduction gold is a precious metal barely constituting about 0.005 parts per million (ppm) in the earth's crust and must be upgraded by a value of about 3500 to obtain commercial concentrates [1]. gold ore deposits that are refractory contain pyrrhotite and pyrite, impeding their cyanidation treatment if a roasting pretreatment is not carried out beforehand [2]. cyanidation presents two challenges related to toxicity and its ability to dissolve gold occluded in carbonaceous materials is limited [3]. when refractory gold ore is processed by a cyanidation treatment, both the concentration and quantity of cyanide required are high, resulting in effluents with cyanide concentrations greater than the permissible level of less than 0.1 ppm [4]. aqua regia is capable of creating a powerful oxidizing environment that can vigorously dissolve both free gold and gold pregrobbed by sulfides and carbonaceous materials [5]. received: 06 july 2023; revised: 19 aug 2023; accepted: 21 aug 2023 *correspondence: oluwasanmi_teni@yahoo.com the isolation and concentration of precious metals involve established methods, namely precipitation, ion exchange, solvent extraction and adsorption. solutions with high concentrations are preferably recovered using precipitation and solvent extraction but adsorption and ion exchange are preferred for solutions containing trace concentrations. activated carbon has been extensively applied for gold recovery by adsorption from leached solutions. gold recovery using activated carbon is usually not quantitative and significant concentrations of gold are usually left in the leachate [6]. bioadsorbents have been prepared from materials sourced from plants, e.g. polysaccharides, cotton, paper and biomass wastes. adsorbents generated from these sources have been utilized in gold(iii) recovery and are more highly selective when recovering gold compared to other metals [7]. it is highly likely that a nanoparticle (np) generated from sugarcane (saccharum officinarum) bagasse will selectively adsorb gold(iii) ions more efficiently than the typically used adsorption gels or activated carbon, https://doi.org/10.33927/hjic-2023-15 mailto:oluwasanmi_teni@yahoo.com teniola, adeleke, ibitoye and shittu hungarian journal of industry and chemistry 28 probably because the total surface area to volume ratio of the nps is very high [8]. 2. materials and methods 2.1. sample collection about 100 kg of gold ore was collected from an active mine in the village of imogbara located in the town of iperindo, within the local government area of atakumosa in the vicinity of ilesha in osun state, nigeria. the sample was collected from 2 different pits that were dug over a surface area of 3 x 3 m to a depth of 4 m below the surface. the ore sample collected was pre-concentrated by panning in a flowing stream close to the mining site. the panned ore was mixed to ensure an even distribution following the method carried out by mallo [9]. sugarcane bagasse was collected from a local juice shop in the vicinity of papalanto in ogun state. the bagasse was washed using distilled water to remove dirt and remnants of sugar. 2.2. sample preparation the dried sample was crushed using a pascal engineering crushing mill with machine number 18862 operated at 415 v, 2200 w, 4.9 a and 50 hz [10]. consequently, a working sample of 1 kg was selected using the coning and quartering method once the bulk sample had been adequately mixed before being pulverized using a pulverizer and sieved through a 75 μm mesh sieve. the oversized particles were pulverized again and sieved until 80 % of them passed through. representative samples of the ore were carefully taken within the size range of 300 μm > x > 75 μm and those x < 75 μm were concentrated using a shaking table with model number 148566q while adopting previously applied methods [11]. the obtained bagasse was sun-dried to constant weight before being dried in an oven at 105 ºc. the dried bagasse was pulverized and sieved through a 125 μm mesh sieve. 2.3. functional group determination infrared spectra of the gold ore samples, sugarcane bagasse and sugarcane bagasse nps were recorded on a perkinelmer ls-55 luminescence spectrometer equipped with a standard attenuated total reflectance (atr) crystal detector. spectra of each sample were scanned within the wavelength range of 500-4000 cm-1. about 10 mg of each pulverized sample was used for each test following a previously applied procedure [12]. 2.4. agitation leaching of the ore with aqua regia agitation leaching of the ore sample was carried out in a conical flask at a temperature of 90 ºc using an aqua regia concentration of 4 m on a magnetic stirrer operated at 300 rpm. leachings over a period of 30 minutes were replicated using 5 g of gold ore sample in a conical flask to which 25 ml of freshly prepared 4 m aqua regia solution was added. the prepared sample was covered with aluminium foil and placed on a magnetic stirrer preset at 90 ºc and 300 rpm before the residual solid was separated, dried and reweighed to determine how much mass was lost. the leachate was collected and stored to be used for the adsorption test, while the concentration of gold in it determined using atomic absorption spectrometry (aas). 2.5. preparation of the sugarcane bagasse np adsorbent the sugarcane bagasse np adsorbent was prepared following a previously applied methodology [13]. the bagasse was washed using distilled water to remove dirt and remnants of sugar before being sun-dried to constant weight and dried in an oven at 105 ºc. the dried bagasse was pulverized and sieved through a 125 μm mesh sieve. the dried bagasse was dewaxed in a soxhlet extractor using n-hexane over five runs. the dewaxed bagasse was delignified four times using acidified sodium chlorite at 75 ºc for 1 hr each to achieve a white product. the product was treated with 2 wt.% koh at 90 ºc for 2 hrs and subsequently treated with 5 wt.% koh at 90 ºc for 2 hrs before being filtered and rinsed until the ph of the residue was neutral. the product obtained was chemically purified cellulose (cpc). about 10 g of cpc was stirred in 50 ml of boiling concentrated sulphuric acid in a beaker at 45 ºc for 45 minutes on a magnetic stirrer. the hydrolysed pulp was centrifuged at 10,000 rpm for 15 minutes to remove excess acid and dialyzed against water until a ph similar to that of distilled water was attained before centrifugation was repeated at 10,000 rpm for 15 minutes. the product was then sonicated for 10 minutes in an ice bath to obtain a concentrated aqueous suspension of cellulose nanocrystals (cncs) which were stored in a refrigerator at 4 ºc. 2.6. adsorption of gold cations gold cations were adsorbed according to a previously applied methodology [14] using the prepared sugarcane bagasse nps in an erlenmeyer flask. about 0.5 g of the adsorbent was mixed into a 20 ml sample of gold leachate containing au3+. the flask was placed on a magnetic hotplate stirrer for various time periods and temperatures, namely 30, 60, 90 and 120 minutes as well as 30, 40, 50 and 60 ºc. this procedure was repeated using 0.75, 1.00 and 1.50 g of the adsorbent. next the phases were separated by filtration and the cation concentration remaining in the leachate measured using aas. the percentage of cation uptake was calculated using the following equation: 𝑢𝑝𝑡𝑎𝑘𝑒 % = (𝐶0−𝐶𝑒) 𝐶0 × 10 (1) production of highly concentrated gold solution 51(2) pp. 27–33 (2023) 29 where co and ce denote the initial and equilibrium concentrations of the cations (mg/l), respectively. 2.7. determination of gold content using aas the analysis was carried out in accordance with a previously applied method [15] using an aas model aa320n. the filtrate obtained by using aqua regia to leach a known mass of the ore was transferred to a 250 ml separatory funnel. the beaker was rinsed with 3 m hcl to ensure the leachate was completely transferred into the funnel. about 10 ml of methyl isobutyl ketone (mibk) was added and the mixture shaken for 5 minutes before the phases were allowed to separate and the aqueous phase was drained off. another 10 ml of washing solution was measured into the separatory funnel and the mixture shaken for 2 minutes. once the phases had completely separated, the aqueous phase was drained off. this washing was done repeatedly to ensure the content was completely removed. the organic phase was stored in a glass tube sealed tightly with a lid. the results obtained were used to construct a calibration curve. 2.8. adsorption kinetics the adsorption kinetics were determined according to a previously applied methodology [16]. approximately 200 mg of sugarcane bagasse nps were thoroughly mixed with 200 ml of gold leachate and stirred on a magnetic hotplate stirrer at 30 ºc. samples of approximately 3 ml were taken at regular intervals of 30, 60, 90, 120 and 150 minutes from the start of the experiment which was repeated at 40 and 50 ºc. the amount of au(iii) adsorbed on the adsorbent was plotted against the shaking time at different temperatures on graphs. 2.9. surface morphology of the adsorbent scanning electron microscopy (sem) analyses were conducted using a jeol jsm-7600f model sem with an acceleration voltage of 15 kv. the prepared sugarcane bagasse nps were coated to a depth of only a few nanometres using a sputtering coater to avoid the coating interfering with the morphology of the sample before the sample was mounted with a conductive bridge carbon tape, which connected it to the sample holder. images showing the surface morphology of the nanocellulose were taken at a magnification of 40,000x. 2.10. preparation of a highly concentrated gold solution a sample of au-loaded adsorbent was prepared by stirring 5 g of the prepared nanocellulose with 200 ml of the leachate solution containing a gold concentration of 84 mg/l. after becoming saturated with gold, the adsorbent was separated from the remaining liquid by vacuum filtration, washed and dried at 50 ºc. desorption of the gold-loaded nanocellulose sugarcane bagasse was carried out using a 4 m aqua regia solution as the eluent. the mixture was stirred for 3 hrs after which the solid phase was separated from the liquid one. the concentration of gold in the liquid was measured and the desorbed percentage calculated. 3. results and discussion 3.1. ore upgrading energy dispersive x-ray fluorescence (edxrf) analysis of the ore fed through a shaking table yielded a gold concentration of 2.4 g/ton. however, the gold figure 1: ftir spectra of the gold ore samples teniola, adeleke, ibitoye and shittu hungarian journal of industry and chemistry 30 concentration in the concentrate obtained from the gravity separation was estimated to be 13.6 g/ton. the results obtained showed that the gold ore from iperindo was significantly upgraded to produce a gold ore concentrate with a high gold concentration. 3.2. functional groups present in the gold ore and sugarcane bagasse from the fourier-transform infrared spectroscopy (ftir) analysis, the results of the gold ore are presented in figure 1. various functional groups can be identified in the gold ore. fes, quartz and sic are represented by peaks 650.03, 1082 and 777.34 cm-1, respectively. the presence of these functional groups in the as-received ore suggests the presence of quartz, pyrite, arsenopyrite and silica. the ftir spectra of sugarcane bagasse and sugarcane bagasse nps are shown in figure 2. two absorbance bands could be observed ranging from 7501750 and 2700-3600 cm-1. the ftir spectra of the two samples displayed a wide band from 3200-3500 cm-1 indicative of the free o-h stretching vibration of the oh groups in cellulose molecules as suggested by kumar et al. [13]. the spectra of the two samples reveal the characteristic c-h stretching vibration at approximately 2890 cm-1. 3.3. determination of the size of the synthetized nanoadsorbent figure 3 shows the sem micrograph of the synthesized sugarcane bagasse nps which shows the fibrils of purified cellulose whose diameter and size were significantly reduced due to the entire removal of the amorphous region of semi-crystalline cellulose leaving nanoscale rod-like crystals. 3.4. adsorption kinetics of au(iii) the data regarding the adsorption kinetics of au(iii) is presented in tables 1 and 2 as well as illustrated in figure 4, which shows the variation in the quantity of au(iii) taken up by the nanocellulose synthesized from sugarcane bagasse relative to the shaking time at the figure 2: ftir spectra of sugarcane bagasse and sugarcane bagasse nanocellulose figure 3: sem of sugarcane bagasse nps table 1: concentration of the leachate after various time intervals (mg/l) time (min) temperature (ºc) 30 40 50 60 0 84 84 84 84 30 53 44 36 59 60 45 34 29 35 90 38 27 21 26 120 32 18 15 19 150 31 18 15 19 table 2: percentage of au(iii) uptake after various time intervals time (min) temperature (ºc) 30 40 50 60 0 0 0 0 0 30 37 48 57 50 60 46 60 65 58 90 55 68 75 69 120 62 78 82 77 150 63 79 82 77 production of highly concentrated gold solution 51(2) pp. 27–33 (2023) 31 different temperatures studied. the initial gold(iii) concentration (co) was 84 mg/l. from figure 5, it was observed that the temperature influences the adsorption rate of au(iii). the time required to reach the adsorption equilibrium was reduced by increasing the temperature up to 50 ºc. a sharp increase in the adsorption rate was noted during the earlier stages of adsorption before decreasing to virtually zero during the final stages. this was observed at all the temperatures examined as a result of the abundant surface area of the nanocellulose available for adsorption during the initial stages which diminished as the period of adsorption advanced. 3.5. highly concentrated gold solution the obtained gold solution in a 4 m aqua-regia solution was analysed to measure the gold concentration using aas which was found to be 2200 mg/l the obtained solution can be effectively processed using electrowinning to obtain metallic gold. 3.6. adsorption isotherms data concerning the adsorption equilibrium of au(iii) ions obtained by stirring 10 mg of nanocellulose from sugarcane bagasse with 10 ml of gold leachate of various au(iii) concentrations, namely 10, 20, 30, 40 and 50 mg/l, in an erlenmeyer flask at a temperature of 40 ºc are presented in table 3, which were fitted to the langmuir, freundlich and temkin adsorption isotherms. langmuir adsorption isotherm a quantitative description of the monolayer formation of the adsorbate on the outer surface of the adsorbent is given by this isotherm after which further adsorption did not occur, representing the equilibrium spread of the gold ion between the liquid and solid particles. equation can be transformed into a linear form to obtain langmuir adsorption parameters: 𝐶𝑒 𝑞𝑥 = 𝐶𝑒 𝑞𝑚 + 1 𝑞𝑚𝐾𝐿 (2) where ce, qx, qm, kl represent equilibrium concentration, equilibrium adsorption capacity, maximum theoretical adsorption capacity and langmuir model constant, respectively. (a) (b) (c) figure 5: (a) langmuir, (b) freundlich and (c) temkin isotherms of gold adsorption y = 0,1251x + 0,7031 r² = 0,9979 0 1 2 3 4 5 6 7 0 10 20 30 40 50 c e/ q x ce y = 0,2612x + 0,4371 r² = 0,9857 0,50 0,55 0,60 0,65 0,70 0,75 0,80 0,85 0,90 0,5 0,7 0,9 1,1 1,3 1,5 1,7 lo g q x logce y = 1,4543x + 1,7221 r² = 0,9895 3,0 3,5 4,0 4,5 5,0 5,5 6,0 6,5 7,0 7,5 1,5 2,0 2,5 3,0 3,5 4,0 q x lnce figure 4: adsorption rate of au(iii) by nanocellulose synthesized from sugarcane bagasse at different temperatures 0 10 20 30 40 50 60 70 80 90 0 50 100 150 200 % a u u p ta k e shaking time (min) 30°c 40°c 50°c 60°c teniola, adeleke, ibitoye and shittu hungarian journal of industry and chemistry 32 qm and kl at the respective temperatures were computed from the gradient and intercept of the langmuir isotherm plot of ce/qx against ce (figure 5a). the essential characteristic of the langmuir adsorption isotherm is expressed by a dimensionless separation constant rl defined by: 𝑅𝐿 = 1 (1+ 𝐾𝐿𝐶0) (3) where co (mg/l) denotes the lowest initial concentration of the gold solution. the rl values indicate that adsorption is irreversible (rl = 0), favourable (0 < rl <1), linear (rl = 1) or unfavourable (rl > 1 or rl < 0) [17]. freundlich adsorption isotherm adsorption onto a heterogeneous surface through a multilayer adsorption mechanism is described by the freundlich adsorption isotherm. the adsorption is heterogeneous because of the availability of a number of functional groups and numerous adsorbate-adsorbent interactions [18]. the linear form of the freundlich adsorption isotherm model used for the adsorption is presented in the following equation: 𝑙𝑜𝑔𝑞𝑥 = 𝑙𝑜𝑔 𝑘𝑓 + 1 𝐶𝑖 ⁄ 𝑙𝑜𝑔 𝐶𝑒 (4) kf and ci at the selected temperature were determined using the values of intercept and gradient of the linear plot between logqx and logce, respectively (figure 5b). based on standards, when 1< ci < 10, adsorption is favourable and the higher ci is, the stronger the adsorption intensity [19]. temkin adsorption isotherm here the heat of adsorption is assumed to vary linearly as a function of the coverage as opposed to against the logarithmic variation in the case of the freundlich equation [20]. the equation of the temkin adsorption isotherm is expressed linearly as follows: 𝑞𝑥 = 𝑅𝑇 𝛽 𝑙𝑛 𝑘𝑡 + 𝑅𝑇 𝛽 𝑙𝑛 𝐶𝑒 (5) where t denotes the absolute temperature (k), r is taken as the gas constant (0.0083 kj/mol·k), β represents the temkin constant which is related to the heat of adsorption (kj/mol) and kt stands for the temkin isotherm constant (l/g). the parameters kt and β at the temperature considered were estimated by plotting the variation in qx against ln ce (figure 5c). the parameters derived from the various graphs plotted for the langmuir, freundlich and temkin adsorption isotherms are shown in table 4. comparing the r2 values that correspond to the isotherms evaluated revealed that the adsorption of gold onto sugarcane bagasse nanocellulose obeys the langmuir adsorption isotherm model preferentially at 40 ºc. furthermore, rl calculated for the langmuir adsorption isotherm model at the three different temperatures considered fell between 0 and 1, strongly indicating that the adsorption of gold was favourable. for the freundlich adsorption isotherm model, ci obtained for the adsorption of gold at the three different temperatures considered fell predominantly between 1 and 10, indicating that adsorption is favourable. however, the values measured were below 4, suggesting a moderate adsorption intensity. table 3: parameters for plotting langmuir, freundlich and temkin adsorption isotherms obtained at 40 °c co (mg/l) ce (mg/l) co ce qx = (co ce)*v/m logce lnce logqx ce/qx 10 5.74 4.26 4.26 0.7589 1.7475 0.6294 1.3474 20 14.45 5.55 5.55 1.1599 2.6707 0.7443 2.6036 30 23.64 6.36 6.36 1.3736 3.1629 0.8035 3.7170 40 33.02 6.98 6.98 1.5188 3.4971 0.8439 4.7306 50 42.96 7.04 7.04 1.6331 3.7603 0.8476 6.1023 table 4: parameters evaluated by using various isotherms for gold ion adsorption onto sugarcane bagasse nanocellulose isotherm type parameters 40 ºc langmuir qm 7.9936 kl 0.1779 r2 0.9979 rl 0.1578 freundlich kf 2.736 ci 3.828 r2 0.985 temkin β (kj/mol) 1.786 kt 3.268 r2 0.989 production of highly concentrated gold solution 51(2) pp. 27–33 (2023) 33 4. conclusions synthesized nanocellulose from sugarcane bagasse using acid hydrolysis was used for the adsorption of gold(iii) from the leachate. the effect of the temperature, agitation speed, adsorbent dosage and adsorption time on the rate as well as efficiency of adsorption was studied. at first, the gold uptake increased as a function of the temperature and peaked at 50 ºc. however, at 60 ºc, the gold uptake capacity of the absorbent began to drop. the various composite graphs showed that the uptake efficiency increased as a function of the contact time, typically peaking after a contact time of approximately 90 minutes beyond which the adsorption efficiency began to reduce. the gold recovery rate varied 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https://doi.org/10.4028/www.scientific.net/amr.634-638.3478 https://doi.org/10.4028/www.scientific.net/amr.634-638.3478 https://doi.org/10.3176/oil.2012.4.05 https://doi.org/10.33927/hjic-2020-26 https://doi.org/10.33927/hjic-2020-26 https://doi.org/10.1007/s10570-011-9628-6 https://doi.org/10.1016/j.cej.2012.05.090 https://doi.org/10.1016/j.jhazmat.2008.07.107 https://doi.org/10.1016/j.jhazmat.2008.07.107 https://doi.org/10.1002/app.1982.070270827 https://doi.org/10.1002/app.1982.070270827 https://doi.org/10.1016/j.apt.2011.01.004 https://doi.org/10.1016/j.apt.2011.01.004 hungarian journal of industry and chemistry vol. 52(2) pp. 11–18 (2024) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2024-14 experimental investigation of the separation of 4-hydroxybenzoic acid employing natural and conventional solvents vishnu p yadav 1*, anil kumar chandrakar1 and kailas l wasewar 2 1 department of chemical engineering, guru ghasidas vishwavidyalaya, koni, bilaspur, 495009, india 2 department of chemical engineering, visvesvaraya national institute of technology, south ambazari road, nagpur, 440010, india 4-hydroxybenzoic acid (4-hba) has a wide range of applications in various chemicals, cosmetics, pharmaceuticals, wines and the polymer industries. in the present study, 4-hba was extracted from the aqueous phase utilizing natural and conventional solvents (nacs) at a constant temperature of 298 k. the natural solvents used were corn oil and cottonseed oil, while the conventional solvents used were isoamyl alcohol, ethyl acetate and diethyl carbonate. five different concentrations, 0.005 to 0.035 mol/liter, were prepared and applied in the batch experiment. various extraction parameters were investigated, including the distribution coefficient (kdhba), extraction efficiency (%ehba), partition coefficient (p) and dimerization coefficient (d). the experimental results revealed the attractive association between the solute and solvent based on their various physicochemical properties. the highest extraction efficiency was obtained for isoamyl alcohol (58.98%) and the lowest for corn oil (39.48%). the order of distribution coefficients was experimentally obtained as follows: isoamyl alcohol (1.438) > ethyl acetate (0.986) > diethyl carbonate (0.961) > cottonseed oil (0.677) > corn oil (0.652). natural solvents have the potential to avoid toxicity and could be explored for large-scale applications. keywords: 4-hydroxybenzoic acid, separation, natural solvents, conventional solvents, distribution coefficient, extraction efficiency 1. introduction phenolic acids are valuable chemicals due to their various applications as antibacterial, antifungal and antioxidation compounds in the pharmaceutical industry, preservatives in the food and cosmetic industries, as well as esters in various biorefineries and polymer industries, etc. [1]-[6]. 4-hydroxybenzoic acid (4-hba) is naturally present in coconuts, gooseberries, raspberries, fennel, etc. [1]-[2]. 4-hba is found in very low concentrations (<0.035 mol/liter) in effluent streams of several foodpreparation units from the pulp and paper industry, olive oil mills and wine industry [7]-[11]. the extremely slow biodegradation rate of 4-hba directly affects the soil quality when disposed of on land. with exceptional physiological characteristics and several appealing uses, it is necessary to separate 4-hba from wastewater and fermentation broth to improve the environment and sustainable economy. the standard methods for recovering 4-hba are adsorption, reactive distillation, precipitation and the fenton process with uv light [12]-[18]. these methods have several drawbacks, received: 19 may 2024; revised: 4 june 2024; accepted: 6 june 2024 *correspondence: vyadav27@gmail.com, vp.yadav@ggu.ac.in including low conversion rates, prolonged processing durations, poor efficacy in diluted solutions, high energy requirements, high costs and the production of hazardous chemicals as by-products. extractive separation has overcome these challenges and provides a better level of efficiency than existing methods. the extractive separation of 2-hydroxypropanoic acid, pyridine-2-carboxylic acid, ethanecarboxylic acid, 2-hydroxyethanoic acid, 4-oxopentanoic acid and other carboxylic acids have been reported in the literature [19]-[26]. studies have also reported using different types of eco-friendly solvents in the extractive separation of carboxylic acids such as ionic liquids (ils), supercritical fluids (scf) and non-toxic organic solvents [22,27-35]. the choice of solvents poses a considerable difficulty because of the existence of microorganisms in the fermentation broth. the most valued attributes of solvents include non-toxicity, accessibility, inability to mix with the water phase and strong solvation properties. some of the most important literature data on extraction of hydroxybenzoic acid with natural solvents are summarized in table 1 [13,30,32]. https://doi.org/10.33927/hjic-2024-14 mailto:vyadav27@gmail.com mailto:vp.yadav@ggu.ac.in yadav, chandrakar and wasewar hungarian journal of industry and chemistry 12 the present work focuses on investigating the extraction of 4-hba from an aqueous phase. five different solvents were used to study the extraction efficiency in batch experiments at a constant temperature of 298 k. corn and cottonseed oils were used as two harmless natural solvents, while isoamyl alcohol (iaa), ethyl acetate (ea) and diethyl carbonate (dec) were used as three conventional solvents. according to the literature [16],[32], the extraction of 4-hba in the presence of these solvents has not yet been reported. the complete experimental analysis elaborates on the interaction between the solute and solvents in terms of polarity, dipole moment and other physicochemical properties. the extraction efficiency of conventional and natural solvents was also investigated as well as the effect of the initial solute concentration on the value of the distribution coefficient. 2. experimental 2.1. samples and measurements the chemicals and solvents used in the experiment were as follows: 4-hydroxybenzoic acid (98%) was bought from himedia laboratories pvt. ltd., india. isoamyl alcohol (98%), ethyl acetate (98%) and diethyl carbonate (98%) were purchased from s d fine chem pvt. ltd., india. corn oil was procured from kush proteins pvt. ltd., india and cottonseed oil from eywa seeds & exports pvt ltd., india. 2.2. methods in the extraction experiment, 4-hba as a solute was prepared in distilled water at varying concentrations (0.005-0.035 mol/liter). considering its maximum availability (<5%) in fermentation broths or industrial effluent streams, the highest concentration (0.035 mol/liter) of the aqueous solute (4-hba) was chosen for experimental analysis and an equilibrium time of 4 hours achieved at a constant temperature of 298 k. 10 milliliters of the aqueous solute phase and 10 milliliters of the solvent were mixed in a conical flask. the volume ratio remained constant at 1:1. next, the conical flask was placed in an orbital shaking incubator (se-363 science enterprises, india) at 298 k and 200 rpm for 4 hours. the sample obtained after shaking was kept in a centrifuge for 5 minutes at 4000 rpm to separate the aqueous and organic phases. the aqueous phase was examined in a uv-vis spectrophotometer (shimadzu uv-1800) at a wavelength of 255 nm. the solute concentration in the organic phase was calculated by a mass balance. the experimental process is presented in figure 1. table 1: comparative analysis of the existing literature on the extraction of hydroxybenzoic acid with natural solvents ref. author and year of publication hydroxybenzoic acid natural solvent used maximum extraction efficiency (%e) distribution coefficient (kd) [32] joshi et al. 2022 4-hydroxybenzoic acid canola oil 18.85 0.23 mustard oil 20.45 0.25 sunflower oil 21.00 0.27 soyabean oil 25.06 0.34 [16] joshi et al. 2021 4-hydroxybenzoic acid sesame oil 33.24 0.49 canola oil 18.85 0.23 [12] de et al. 2018 3,4-dihydroxybenzoic acid canola oil 7.41 0.08 soyabean oil 6.56 0.07 groundnut oil 6.18 0.07 sesame oil 6.17 0.07 sunflower oil 4.70 0.05 figure 1: flow diagram of the experimental process for extracting 4-hba extraction of 4-hydroxybenzoic acid 52(2) pp. 11–18 (2024) 13 2.2.1. statistical analysis of uncertainty experimental uncertainties due to instrument errors and various random variations may be present which can be computed as: 𝜃 = √ ∑ (𝑥𝑗−�̅�𝑗) 2𝑛 𝑖=0 𝑛−1 (1) the mean experimental value is denoted by �̅�𝑗 and the values of experimental observations by xj, while n represents the total number of observations. the uncertainties from the experiment fell within the range of x ± 0.002. 2.2.2. extraction of 4-hba 4-hba was extracted in the presence of three conventional solvents, namely iaa, ea, dec, as well as two natural solvents, that is, corn oil and cottonseed oil. since the attraction between the acid and water as a result of hydrogen bonding is stronger than that of 4-hba itself, 4-hba remained as a monomer. 4-hba appears as dimers in the organic phase because the identical solute molecules form hydrogen-hydrogen bonds in the organic phase due to either lowor non-polar solvents [30]. the physical separation of 4-hba from the aqueous phase was accomplished in three steps: acid detachment, partition of the undissociated 4-hba molecule and dimerization of 4-hba. 2.2.3. detachment of the solute detachment of the solute 4-hba in the aqueous phase is represented in the following equations: 𝐻𝐵𝐴𝑋𝑎𝑞 𝐾𝐻𝐵𝐴𝑋 ↔ 𝐻+ + 𝐵𝐴− (2) 𝐾𝐻𝐵𝐴𝑋 = [𝐻+][𝐵𝐴−] [𝐻𝐵𝐴𝑋]𝑎𝑞 (3) khbax represents the dissociation constant and hbax the 4-hba concentration in moles/liter. 2.2.4. partition coefficient of undissociated 4-hba [𝐻𝐵𝐴𝑋]𝑎𝑞 𝑃 ↔ [𝐻𝐵𝐴𝑋]𝑜𝑟𝑔 (4) the partition coefficient of the solute (4-hba) is denoted by p: 𝑃 = [𝐻𝐵𝐴𝑋]𝑜𝑟𝑔 [𝐻𝐵𝐴𝑋]𝑎𝑞 (5) where [hbax]aq and [hbax]org are the solute concentrations in the aqueous and organic phases in moles per liter, respectively. 2.2.5. dimerization constant of 4-hba in the organic phase, the 4-hba molecules are not in their dissociated form. due to the stronger attraction between solute molecules than between the solute and solvent as a result of hydrogen bonding, dimer molecules were formed. the process is described by the following equation: 2[𝐻𝐵𝐴𝑋]𝑜𝑟𝑔 𝐷 ↔ [𝐻𝐵𝐴𝑋]2 𝑜𝑟𝑔 (6) mathematically, the dimerization constant (d) in liters/mol can be determined using equation 6 as follows: 𝐷 = [𝐻𝐵𝐴𝑋]2 𝑜𝑟𝑔 [𝐻𝐵𝐴𝑋]𝑜𝑟𝑔 2 (7) from a physical extraction perspective, one crucial parameter is the overall distribution coefficient (kdhba). 𝐾𝐷𝐻𝐵𝐴 = [𝐻𝐵𝐴𝑋]𝑜𝑟𝑔 𝑡𝑜𝑡 [𝐻𝐵𝐴𝑋]𝑎𝑞 𝑡𝑜𝑡 = [𝐻𝐵𝐴𝑋]𝑜𝑟𝑔+2[𝐻𝐵𝐴𝑋]2𝑜𝑟𝑔 [𝐻𝐵𝐴𝑋]𝑎𝑞+[𝐵𝐴 −] (8) 𝐾𝐷𝐻𝐵𝐴 = 𝑃[𝐻𝐵𝐴𝑋]𝑎𝑞+2𝐷[𝐻𝐵𝐴𝑋]𝑜𝑟𝑔 2 [𝐻𝐵𝐴𝑋]𝑎𝑞+ 𝐾𝐻𝐵𝐴𝑋[𝐻𝐵𝐴𝑋]𝑎𝑞 [𝐻+] (9) 𝐾𝐷𝐻𝐵𝐴 = 𝑃[𝐻𝐵𝐴𝑋]𝑎𝑞+2𝐷𝑃 2[𝐻𝐵𝐴𝑋]𝑎𝑞 2 [𝐻𝐵𝐴𝑋]𝑎𝑞 ∙ [1+ 𝐾𝐻𝐵𝐴𝑋 [𝐻+] ] (10) 𝐾𝐷𝐻𝐵𝐴 = 𝑃+2𝐷𝑃2[𝐻𝐵𝐴𝑋]𝑎𝑞 [1+ 𝐾𝐻𝐵𝐴𝑋 [𝐻+] ] (11) 4-hba is considered to be a weak acid due to its low pka (4.54) [30]. the ph values of dilute solutions were measured (3.3 to 3.8) and it was found that pka was less than 4.54. for dilute solutions with a ph significantly lower than the pka of acid, the denominator of equation 11 may be neglected because the numerical value of the khbax/[h+] ratio is very low. therefore, kdhba is calculated from equation 11 as the ratio of [𝐻𝐵𝐴𝑋]𝑜𝑟𝑔 𝑡𝑜𝑡 to [𝐻𝐵𝐴𝑋]𝑎𝑞 𝑡𝑜𝑡 . the relationship between extraction and the equilibrium is determined by the concentrations of the solute in the organic and aqueous phases. the distribution coefficient kdhba can be calculated based on this connection. in the following equation, the partition coefficient (p) is predicted as the intercept and the dimerization coefficient (d) as the gradient. 𝐾𝐷𝐻𝐵𝐴 = 𝑃 + 2𝑃 2𝐷[𝐻𝐵𝐴𝑋]𝑎𝑞 (12) these two important parameters of physical extraction determine the extraction capacity of the solvent. additionally, the distribution coefficient (kdhba) is used to calculate the percentage of extraction efficiency (%ehba) as follows: %𝐸𝐻𝐵𝐴 = ( 𝐾𝐷𝐻𝐵𝐴 1+𝐾𝐷𝐻𝐵𝐴 ) × 100 (13) 2.2.6. solvent regeneration recovery of the solute from the organic phase and solvent regeneration constitute the second stage of the process. back extraction and solvent regeneration have been reported by numerous researchers [14-15,21]. a variety of techniques have been described, including the use of hcl, trimethylamine (tma), temperature swing, solvent swing and naoh. based on available research, the most effective method for solvent regeneration is to use tma instead of any other method [14]-[15]. yadav, chandrakar and wasewar hungarian journal of industry and chemistry 14 3. results and discussion the separation of 4-hba from its aqueous solution was accomplished using three conventional and two natural solvents. the physicochemical properties of the solvents used are presented in table 2. the impacts of different solvents such as iaa, ea, dec, corn oil and cottonseed oil on the extraction efficiency and distribution coefficient are displayed in tables 3-7, respectively. a comparative analysis regarding the physical extraction of 4-hba was conducted based on various parameters such as the partition coefficient, dimerization constant, extraction efficiency of solvents and distribution coefficient as presented in table 8. table 2: physicochemical properties of the used chemicals [1,2,29,36-39] chemical  (g/m3) µ (cp) s (g/l) mp (k) mw (g/mol) bp (k) ri  dm (debye) et 4-hydroxybenzoic acid 1460 5 487.6 138.12 607.2 1.46 2.76 isoamyl alcohol 810 3.692 28 156.0 88.15 404.2 1.41 15.60 1.70 47.0 ethyl acetate 902 0.426 64 189.6 88.11 350.2 1.37 6.02 1.88 38.1 diethyl carbonate 975 0.969 0.019 230.0 118.13 399.0 1.38 3.10 1.07 36.2 corn oil 918 51.44 insoluble 255.2 511.2 1.47 3.60 1.85 cottonseed oil 926 62 insoluble 268.1 505.2 1.47 2.90 : density, µ: viscosity, s: solubility in water, mp: melting point, mw: molecular weight, bp: boiling point, ri: refractive index, ε: dielectric constant, dm: dipole moment, et: solvent polarity parameter table 3: extraction of 4-hba using the conventional solvent isoamyl alcohol at 2981 k [hbax]0 (mol/l) [hbax]aq (mol/l) [hbax]org (mol/l) kdhba %ehba ph0 phaq 0.005 0.0041 0.0009 0.228 18.59 3.8 3.9 0.010 0.0060 0.0033 0.558 35.81 3.7 3.8 0.020 0.0096 0.0091 0.949 48.68 3.6 3.7 0.030 0.0128 0.0165 1.292 56.37 3.4 3.6 0.035 0.0144 0.0207 1.438 58.98 3.3 3.4 table 4: extraction of 4-hba using the conventional solvent ethyl acetate at 2981 k [hbax]0 (mol/l) [hbax]aq (mol/l) [hbax]org (mol/l) kdhba %ehba ph0 phaq 0.005 0.0045 0.0005 0.110 9.90 3.8 3.9 0.010 0.0070 0.0023 0.332 24.93 3.7 3.8 0.020 0.0111 0.0077 0.691 40.88 3.6 3.7 0.030 0.0156 0.0138 0.885 46.96 3.5 3.6 0.035 0.0176 0.0174 0.986 49.65 3.4 3.5 table 5: extraction of 4-hba using the conventional solvent diethyl carbonate at 2981 k [hbax]0 (mol/l) [hbax]aq (mol/l) [hbax]org (mol/l) kdhba %ehba ph0 phaq 0.005 0.0044 0.0006 0.140 12.31 3.7 3.9 0.010 0.0071 0.0022 0.305 23.40 3.6 3.8 0.020 0.0115 0.0073 0.636 38.89 3.5 3.7 0.030 0.0158 0.0136 0.859 46.21 3.4 3.6 0.035 0.0179 0.0172 0.961 49.00 3.4 3.5 table 6: extraction of 4-hba using the natural solvent corn oil at 2981 k [hbax]0 (mol/l) [hbax]aq (mol/l) [hbax]org (mol/l) kdhba %ehba ph0 phaq 0.005 0.0048 0.0002 0.048 4.56 3.8 3.9 0.010 0.0076 0.0017 0.221 18.09 3.7 3.8 0.020 0.0131 0.0056 0.431 30.12 3.6 3.7 0.030 0.0184 0.0110 0.596 37.33 3.5 3.6 0.035 0.0212 0.0138 0.652 39.48 3.4 3.5 table 7: extraction of 4-hba using the natural solvent cottonseed oil at 2981 k [hbax]0 (mol/l) [hbax]aq (mol/l) [hbax]org (mol/l) kdhba %ehba ph0 phaq 0.005 0.0047 0.0003 0.065 6.11 3.7 3.9 0.010 0.0077 0.0017 0.217 17.81 3.6 3.8 0.020 0.0134 0.0054 0.403 28.70 3.5 3.7 0.030 0.0187 0.0106 0.569 36.28 3.4 3.6 0.035 0.0209 0.0141 0.677 40.38 3.4 3.5 extraction of 4-hydroxybenzoic acid 52(2) pp. 11–18 (2024) 15 the distribution coefficient which shows the affinity of the solute between two phases was measured. the term distribution coefficient refers to the proportion of acid content in the aqueous and organic phases as well as denotes the degree of selectivity of the solvent or organic phase compared to in water or an aqueous phase. kdhba fell within the range of 0.228-1.438 for isoamyl alcohol, 0.110-0.986 for ethyl acetate, 0.140-0.961 for diethyl carbonate, 0.048-0.652 for corn oil and 0.0650.677 for cottonseed oil. the equilibrium curve presenting the extraction of 4-hba is shown in figure 2, revealing that as the solute concentration increases in the aqueous phase, the solute concentration increases in the organic phase. the conventional solvent iaa is highly polarizable in nature, leading to a better extraction efficiency and distribution coefficient, followed by the aprotic polar solvent ea and aprotic solvent dec. a polar solvent has high values for some physicochemical properties (such as dielectric constant, dipole moment, solvent polarity) and low viscosity, as shown in table 2. a high dielectric constant causes a high degree of polarization, moreover, stronger interactions between the solvent and solute tend to result in a higher extraction efficiency. the polar solvent tends to donate hydrogen atoms which attach to o-(o-h) groups [14]-[21]. the highest extraction efficiency, that is, 58.98%, was achieved when ia was used as a conventional solvent as shown in table 3, while the lowest of 39.48% was recorded by corn oil as shown in table 6. the distribution coefficient with an initial concentration of 4-hba is shown in figure 3, which reveals the interaction between the solvent and solute molecules. as the initial solute concentration increased, the distribution coefficient increased for each solvent as shown in figure 3. however, the highest distribution coefficient, that is, 1.43, was achieved for ia due to its better physicochemical properties with regard to the interaction between solute and solvent molecules when compared to other solvents. another conventional solvent, ethyl acetate, was used to extract 4-hba from the aqueous phase. ea is polar and aprotic in nature. an extraction efficiency and distribution coefficient of 49.65% and 0.986, respectively, were achieved by this solvent (table 4). the dielectric constant and dipole moment for ea (table 2) play a crucial role regarding the interaction between the solute and solvent. a low degree of dimerization and high partition coefficient are observed in figure 4, confirming that the solute-solute interaction is less significant than the solute-solvent interaction. 4-hba was also extracted with diethyl carbonate (table 5). dec is aprotic in nature and yielded the lowest extraction efficiency among the conventional solvents used due to its structural properties. this aprotic solvent does not accept the proton and donates it, causing c-h bonds to not be sufficiently polarized, therefore, the interaction between the solvent and solute molecules is weaker so acts as a poor anionic solvator, resulting in a lower distribution coefficient and extraction efficiency as presented in figures 3 and 5, respectively. table 8: parametric comparison of the extraction of 4-hba using different solvents solvent used range of kdhba avg. kdhba range of %ehba avg. %ehba p d (l/mol) isoamyl alcohol 0.228-1.438 0.893 18.59-58.98 43.69 0.186 1664.41 ethyl acetate 0.110-0.986 0.600 9.90-49.65 34.46 0.139 1719.37 diethyl carbonate 0.140-0.961 0.580 12.31-49.00 33.96 0.123 2090.25 corn oil 0.048-0.652 0.389 4.56-39.48 25.92 0.084 2597.38 cottonseed oil 0.065-0.677 0.386 6.11-40.38 25.86 0.085 2489.36 0.004 0.008 0.012 0.016 0.020 0.004 0.008 0.012 0.016 0.020 isoamyl alcohol ethyl acetate diethyl carbonate corn oil cotton oil [hbax]aq (mol/l) [h b a x ] o rg ( m o l/ l ) figure 2: extraction equilibrium of 4-hba in terms of the concentration of the solute in the aqueous [hbax]aq and organic [hbax]org phases using different solvents 0.005 0.010 0.015 0.020 0.025 0.030 0.035 0.040 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 isoamyl alcohol ethyl acetate diethyl carbonate corn oil cotton oil d is tr ib u ti o n c o e ff ic ie n t (k d h b a ) [hbax]aq (mol/l) figure 3: distribution coefficient at different initial concentrations of 4-hba yadav, chandrakar and wasewar hungarian journal of industry and chemistry 16 dec contains an oxygen double bond where two adjacent oxygen atoms bond together, leading to strong steric repulsion. this affects the interaction between the solute and solvent. a high degree of dimerization and low partition coefficient represented in figure 4 also confirm that the solute-solute interaction is stronger than the solute-solvent interaction. the oh functional group present in 4-hba has a tendency to hydrogen bond with oxygen atoms present in ea and dec. however, ea has a stronger tendency to hydrogen bond with 4-hba due to its methyl group being closer to an oxygen double bond compared to dec. therefore, the extraction efficiency is higher in ea compared to dec. 4-hba was successfully physically extracted using non-toxic natural solvents, namely corn oil and cottonseed oil. these oils are non-toxic compared to the conventional solvents [37]-[38]. the extraction efficiencies of corn oil (39.48%) and cottonseed oil (40.38%) are shown in tables 6 and 7, respectively. the distribution coefficients for corn oil and cottonseed oil were 0.652 and 0.677, respectively. the non-polar nature of natural solvents as well as their low dipole moments and minimal dielectric constants led to low extraction efficiencies and distribution coefficients as shown in figures 3 and 5. the large oil molecules cause a rotating rigid structure, the high density and viscosity of oil as well as the immiscibility of oil with the aqueous phase. therefore, oils are expected to yield low extraction efficiencies and distribution coefficients. however, the high percentages of unsaturated fatty acids in corn and cottonseed oil e.g. 27 and 20% of the monounsaturated fatty acid, oleic acid, as well as 52 and 54% of the polyunsaturated fatty acid, linoleic acid, respectively make them important solvents. the unsaturated fatty acid, linoleic acid, contains a hydroxyl group (oh), which interacts with solute molecules and bonds to them. therefore, natural solvents are emerging as competitive alternatives to traditional solvents with moderate extraction efficiencies and their non-toxic nature. the extraction efficiencies using different solvents were obtained in the following order: ia (58.98%) > ea (49.65%) > dec (49.00%) > cottonseed oil (40.38%) > corn oil (39.48%). from equation 12, the intercept and gradient were calculated to determine the partition coefficient and dimerization coefficient, respectively. the partition coefficient and dimerization coefficient of each solvent are shown in figure 4 and table 8. the highest partition coefficient and lowest dimerization coefficient were obtained for ia due to its strong solutesolvent interactions, while the lowest ones were obtained for dec and corn oil due to their weak solute-solvent interactions as presented in figure 4 and table 8. as the distribution coefficient increases, the partition coefficient increases, while the opposite trend is observed with regard to the dimerization coefficient, meaning that the solute-solvent interaction is stronger than the solutesolute equivalent. the dimerization and partition coefficients are presented in table 8. the dimerization coefficients for different solvents range from 1664.41 to 2597.38, while their partition coefficients range from 0.186 to 0.085. 4. conclusion 4-hba was extracted using different natural and conventional solvents. isoamyl alcohol yielded the best extraction efficiency (58.98%) and distribution coefficient (0.186) among all the solvents used. however, a problem posed by conventional solvents is their toxicity, especially when separated from the fermentation broth. nevertheless, conventional solvents exhibit very hazardous and toxic characteristics so cannot be used in many pharmaceutical and food industries due to their adverse effects on the process and product yield. natural oils like corn and cottonseed oil may be used to overcome this problem due to their non-toxic characteristics. cottonseed oil as a natural solvent yielded the highest extraction efficiency of 21.48%, higher than in the literature [16] when compared to other natural solvents. the extraction efficiency and distribution coefficient with regard to the initial concentration of the solute were determined, moreover, 0.3862 0.3896 0.5802 0.6008 0.893 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.20 p d distribution coefficent (kdhba) p a rt it io n c o e ff ic ie n t (p ) cotton corn dec ea iaa 0 500 1000 1500 2000 2500 3000 d im e ri z a ti o n c o e ff ic ie n t (d ) figure 4: comparative analysis of the partition and dimerization coefficients with regard to the distribution coefficient for different solvents such as cottonseed oil, corn oil, diethyl carbonate (dec), ethyl acetate (ea) and isoamyl alcohol (iaa) 0.005 0.010 0.015 0.020 0.025 0.030 0.035 0.040 0 10 20 30 40 50 60 isoamyl alcohol ethyl acetate diethyl carbonate corn oil cotton oil e x tr a c ti o n e ff ic ie n c y ( % e h b a ) [hbax]aq (mol/l) figure 5: extraction efficiency at different initial concentrations of 4-hba extraction of 4-hydroxybenzoic acid 52(2) pp. 11–18 (2024) 17 the solvent-solute interaction was investigated based on the various physicochemical properties of solvents. the results obtained affirm the use of natural oils as alternative solvents instead of conventional ones, where toxicity is a primary concern in the food and pharmaceutical sectors. symbols 4-hba 4-hydroxybenzoic acid iaa 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in dipolar systems based on an earlier article by the author, in which the probability of chaining for adjacent particles in a new formula of magnetic susceptibility was used. the probability of chaining and the magnitude of the energy criterion can be calculated from the monte carlo (mc) simulation values of magnetic susceptibility. the energy criterion also depends on the dipole moment and the density. at high densities, the energy criterion is well below 70−75%. in addition, it was confirmed by simulation results that the chain length distribution follows a geometric distribution. how the probability of chaining depends on the energy criterion was given empirically and two parameters were fitted to it. keywords: dipolar fluids, chain formation, energy criterion 1. introduction according to the literature, the criterion of chaining in dipolar systems is unclear. usually, an energy criterion is used to decide whether two adjacent particles form part of a chain. the energy criterion defines the limit at a certain level of interaction energy between them, which is usually 70 − 75% of the minimum pair interaction energy [1–4]. according to another definition, if the pair interaction energy is negative and the two particles are closer together than 1.3 in diameter unit, then chaining occurs [5, 6]. the problem with this is that the minimum pair interaction energy depends on the magnitude of the dipole moment, so an identical amount of pair interaction energy between two adjacent particles indicates chaining in one case but not in the other. in another article, the author examined [7] the probability density function of pair interaction energies in a dipolar hard sphere (dhs) system and found that no unit jump-like change in the frequency of the pair interaction energy would justify the introduction of a general criterion based on the pair interaction energy. furthermore, such a general definition does not take into account the effect of density, while it can be assumed that chaining occurs at different densities and different energy levels of the same dipole moments. therefore, this study seeks to determine the magnitude of the energy criterion from another source, that is, a real, measurable, physical parameter. the physical parameter *correspondence: sata123.sandor@gmail.com in this case is magnetic susceptibility. in a previous article [8], the author stated that the chain length distribution in dipolar fluids follows a geometric distribution. if the probability that two adjacent particles form a chain is denoted by p, it can be deduced that the chain length distribution is gk = (1− p) pk−1, (1) where k stands for the chain length. the particle size distribution, which yields the proportion of particles in exactly k-long chains is hk = (1− p)2kpk−1. (2) the average chain length is derived from the properties of the geometric distribution: 1/(1− p). assuming that a chain of length k behaves as if its dipole moment is km, its initial magnetic susceptibility can be deduced (in c.g.s. units) as χ0 = 1 + p 1− p χl ( 1 + 4π 3 χl ) , (3) where χl denotes langevin susceptibility [9], χl = ρm2 3kbt , (4) ρ stands for the density, t represents the temperature, and kb refers to the boltzmann constant. in eq. 3, the expression χp = χl ( 1 + 4π 3 χl ) (5) https://doi.org/10.33927/hjic-2020-28 mailto:sata123.sandor@gmail.com 56 nagy calculates the initial magnetic susceptibility from pshenichnikov’s theory [10]. eq. 3 can be used to determine the value of p at a given density and dipole moment, since χ0 can be determined from simulations and χp can be calculated exactly from p = χ0 − χp χ0 + χp . (6) if the occurrence of chaining is linked to an energy criterion, it is clear that the value of p depends on the magnitude of the energy criterion. thus, if the correct value of p is known from eq. 6, the magnitude of the correct energy criterion can be obtained from the relationship p − ulim. the structure of the results is as follows: firstly, through several examples, it is shown that for any energy criterion, the number of chains follows a geometric distribution; secondly, the p values calculated from the magnetic susceptibility values are given; thirdly, from simulations, the ulim values are determined that provide the desired p value at a given density and dipole moment; finally, by fitting, an empirical formula is derived to describe the relationship p− ulim. 2. simulations and results monte carlo simulations of dhs fluids were performed using a canonical nvt ensemble. boltzmann sampling [11], periodic boundary conditions and the minimumimage convention were applied. in order to take into account the long-range character of the dipolar interaction, the reaction field method under periodic boundary conditions of conduction was used. after 100, 000 equilibration periods, 1, 000, 000 production cycles were conducted involving n = 1, 000 particles. the reduced density was calculated by ρ∗ = ρσ3 and the reduced dipole moment by m∗ = m/ √ σ3kbt , where σ denotes the diameter of the particles. the pair interaction energy between two particles in a dhs system is determined only by the dipolar energy: udd ij = −m 2 r3ij [3 (m̂i · r̂ij) (m̂j · r̂ij)− (m̂i · m̂j)] , (7) where the particles have dipole moments of strength m of an orientation given by unit vector m̂, moreover, the distance between the centers of the particles is denoted by rij and r̂ij = rij/rij . the dots symbolize the scalar product. the lowest and most favorable energy value was determined by udd min = −2m2/σ3. the magnitude of the energy criterion (u) was given in the usual way in proportion to this: u = udd/udd min. to determine the chain length distribution (gk), the number of chains of a given length was counted in each cycle. this required a predefined energy criterion. rearranging eq. 1 leads to the chain length distribution: lg (gk) = lg (1− p) + (k − 1) lg (p) . (8) figure 1: the logarithm of the chain length distribution as a function of chain length at six different dipole moments, densities and energy criteria. according to eq. 8, the value of p (probability of chaining) is also derived from the gradient of the fitted lines as well as the intercept of the vertical axis. from this, it can be seen that if the logarithm of the chain length distribution is plotted as a function of k − 1, the gradient of the fitted straight line yields the logarithm p, while the logarithm of the vertical intercept gives 1 − p. since in each case the resulting lines are linear, it follows that the chain length distribution does indeed follow a geometric distribution. fig. 1 shows the simulation results for the chain length distribution obtained for six different combinations of dipole moments, densities and energy criteria. it can be seen that the fitted lines are linear on the logarithmic scale in all cases. it is clear from the inset graphs that the larger its gradient, the closer its intercept is to zero. the p values shown in fig. 1 were derived from the gradient of the fitted lines. further results are summarized in table 1. in the third column of table 1, using the terms mentioned in the introduction (section 1), the values of p are given. the values of χp can be precisely calculated from eq. 5. the values of χ0 are derived from the simulations. (for the simulation results of χ0, reference [12] was used. the missing χ0 data were supplemented with our own simulation results.) this was followed by the determination of ulim, also from our own simulations. according to eq. 2, the number of particles that do not form a chain or, in other words, which form single-element chains is h1 = (1− p)2. thus, in each step of the simulation, it was only nechungarian journal of industry and chemistry new chaining criteria in dipolar fluids based on monte carlo simulations 57 table 1: the probabilities of chaining (3rd column), the values of the energy criterion (4th column) according to the simulations and the values of the fitted curves (5th and 6th columns) according to eq. 9 (m∗)2 ρ∗ p ulim a b 2 0.1 0.0135 0.74 0.203 2.902 2 0.2 0.0209 0.76 0.358 2.864 2 0.3 0.0316 0.75 0.492 2.863 2 0.4 0.0231 0.80 0.623 2.881 2 0.5 0.0254 0.80 0.751 2.893 2 0.6 0.0387 0.78 0.885 2.901 2 0.7 0.0523 0.77 1.022 2.895 2 0.8 0.1674 0.66 1.167 2.874 2 0.9 0.2641 0.62 1.307 2.821 3 0.1 0.0802 0.68 0.426 2.284 3 0.2 0.0951 0.71 0.607 2.291 3 0.3 0.0772 0.75 0.732 2.333 3 0.4 0.0721 0.77 0.839 2.388 3 0.5 0.0762 0.77 0.943 2.442 3 0.6 0.0840 0.76 1.048 2.498 3 0.7 0.1889 0.67 1.154 2.535 3 0.8 0.3788 0.57 1.270 2.560 3 0.9 0.6745 0.45 1.383 2.547 4 0.1 0.2183 0.67 0.761 1.801 4 0.2 0.1777 0.73 0.900 1.842 4 0.3 0.1278 0.77 0.975 1.900 4 0.4 0.1174 0.78 1.044 1.989 4 0.5 0.1169 0.78 1.107 2.069 4 0.6 0.1818 0.72 1.180 2.159 4 0.7 0.4016 0.59 1.258 2.237 4 0.8 0.6814 0.46 1.341 2.295 essary to count how many particles have the minimum pair interaction energy (counted individually for the other particles) greater than the examined energy criterion. this greatly simplified the complexity of the simulations. therefore, the value of p belonging to the given energy criterion was determined, and for each dipole moment and density, a function was generated to create a relationship between p and ulim. of these, four are shown in fig. 2. the dashed lines indicate the ulim values of the already defined p values of these functions. the fourth column of table 1 shows the ulim values for each dipole moment, density and value of p which are also plotted in fig. 3. (the uncertainty of the functions shown in fig. 3 stems from the uncertainty of the magnetic susceptibilities. for dipole moments less than (m∗)2 = 2, this new energy criterion cannot be examined precisely because the uncertainty in the magnetic susceptibility is too great.) it can be seen that the frequently mentioned 70 − 75% criterion is more or less valid, although it differs significantly from it at high densities. interestingly, the energy criterion is higher at medium densities than at low densities. this may be because the figure 2: the probability of chaining as a function of the value of the energy criterion at four different dipole moments and densities. the dashed lines show the true values of p and thus ulim as well. chains are so close to each other at medium densities that they have an effect on each other, but do not at low densities. it is true that at high densities this effect is even stronger, but at the same time, the strength of the forces acting on the chain also increases. in the following, the relationships between the p − ulim functions are specified by fitting. four of these are shown in fig. 2. in fig. 4, for each of the three dipole moments examined, these functions are plotted at two densities. since the functions are close to zero around ulim = 1, the cosine function seems to be a good choice for describing the curves as follows: p = acosb (π 2 ulim ) (9) figure 3: the values of ulim as a function of the reduced density at three different dipole moments. 48(2) pp. 55–58 (2020) 58 nagy figure 4: the probability of chaining as a function of the energy criterion at three different dipole moments. dashed lines refer to low densities (ρ∗ = 0.1), solid lines refer to high densities (ρ∗ = 0.8). the lines of intermediate densities are between these two lines. where a and b are constants and their magnitudes are given in the fifth and sixth columns of table 1. fits were made within the range ulim = 0.5−1. the absolute error in the values of p is not greater than 0.01285 in all the cases examined. 3. conclusion the main result of this article is shown in fig. 3. a well-explained energy-based chaining criterion resulting from magnetic susceptibility was defined. from the simulated values of magnetic susceptibility, the probability of chaining was calculated. from this, the magnitude of the chaining criterion was derived using simulations as well. therefore, a well-explained theory was developed to define the chaining energy criterion, which produced different results for different values of density and dipole moment in dhs systems. the criterion value of 70−75% commonly given in the literature is only approximately true at low densities (ρ∗ ≤ 0.3). at medium densities (0.3 < ρ∗ < 0.6), the values are generally higher, while at high densities (ρ∗ ≥ 0.6), they are much lower. acknowledgement this research was supported by the european union and co-financed by the european social fund under the project efop-3.6.2-16-2017-00002. references [1] ivanov, a. o.; wang, z.; holm, c.: applying the chain formation model to magnetic properties of aggregated ferrofluids, phys. rev. e, 2004, 69(3), 031206 doi: 10.1103/physreve.69.031206 [2] wang, z.; holm, c.; müller, h. w.: molecular dynamics study on the equilibrium magnetization properties and structure of ferrofluids, phys. rev. e, 2002, 66(2), 021405 doi: 10.1103/physreve.66.021405 [3] valiskó, m.; varga, t.; baczoni, a.; boda, d.: the structure of strongly dipolar hard sphere fluids with extended dipoles by monte carlo simulations, mol. phys., 2010, 108(1), 87–96 doi: 10.1080/00268970903514553 [4] tavares, j. m.; weis, j. j.; telo da gama, m. m.: strongly dipolar fluids at low densities compared to living polymers, phys. rev. e, 1999, 59(4), 4388– 4395 doi: 10.1103/physreve.59.4388 [5] kantorovich, s.; ivanov, a. o.; rovigatti, l.; tavares, j. m.; sciortino, f.: nonmonotonic magnetic susceptibility of dipolar hard-spheres at low temperature and density, phys. rev. lett., 2013, 110(14), 148306 doi: 10.1103/physrevlett.110.148306 [6] rovigatti, l.; russo, j.; sciortino, f.: structural properties of the dipolar hard-sphere fluid at low temperatures and densities, soft matt., 2012, 8(23), 6310–6319 doi: 10.1039/c2sm25192b [7] nagy, s.: the frequency of the two lowest energies of interaction in dipolar hard sphere systems, anal. tech. szeged., 2020, 14(2) in press [8] nagy, s.: the initial magnetic susceptibility of dense aggregated dipolar fluids, hung. j. ind. chem., 2018, 46(2), 47–54 doi: 10.1515/hjic-2018-0018 [9] langevin, p.: sur la théorie du magnétisme, j. phys. theor. appl., 1905, 4(1), 678–693 doi: 10.1051/jphystap:019050040067800 [10] pshenichnikov, a. f.; mekhonoshin, v. v.: equilibrium magnetization and microstructure of the system of superparamagnetic interacting particles: numerical simulation, j. magn. magn. mater., 2000, 213(3), 357–369 doi: 10.1016/s0304-8853(99)00829-x [11] allen, m. p.; tildesley, d. j.: computer simulation of liquids (clarendon press, oxford) 1987, isbn: 978-0-198-55645-9 [12] theiss, m.; gross, j.: dipolar hard spheres: comprehensive data from monte carlo simulations, j. chem. eng. data, 2019, 64(2), 827–832 doi: 10.1021/acs.jced.8b01169 hungarian journal of industry and chemistry https://doi.org/10.1103/physreve.69.031206 https://doi.org/10.1103/physreve.66.021405 https://doi.org/10.1080/00268970903514553 https://doi.org/10.1080/00268970903514553 https://doi.org/10.1103/physreve.59.4388 https://doi.org/10.1103/physrevlett.110.148306 https://doi.org/10.1039/c2sm25192b https://doi.org/10.1515/hjic-2018-0018 https://doi.org/10.1051/jphystap:019050040067800 https://doi.org/10.1051/jphystap:019050040067800 https://doi.org/10.1016/s0304-8853(99)00829-x https://doi.org/10.1021/acs.jced.8b01169 https://doi.org/10.1021/acs.jced.8b01169 introduction simulations and results conclusion hungarian journal of industry and chemistry vol. 51(2) pp. 51–56 (2023) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2023-18 immersion corrosion tests to evaluate polyaspartic coatings on steel abdu elhoud1 1 chemsystems, ambachtstraat 15, malle, 2390, belgium in this study, a waterproof polyaspartic coating used for concrete structures was modified into an anti-corrosion coating system to prevent steel assets from corroding. a micaceous iron oxide barrier, a zinc phosphate corrosion inhibitor and a novel resin hardener were added to the polyaspartic coating. its corrosion performance was assessed through immersion corrosion tests in 3.5% nacl solutions at room temperature (rt) and 35 °c for 30 days. the surface finish of the steel samples was milled and blasted (sa 2.5). the coating was applied directly to the metal substrate. the average thickness of the coating was 220 ±10 µm. the experimental results confirmed the successful enhancement of the control coating on steel that was previously applied to concrete by adding a zinc phosphate corrosion inhibitor and micaceous iron oxide barrier. however , defects in the coating and rust on the substrate of the control coating were hindered by applying the developed coating. keywords: polyaspartic coating, immersion corrosion test, steel, zinc phosphate, iron oxide barrier 1. introduction the primary purpose of coatings is to provide a barrier to prevent assets from corroding. however, in many applications, coatings are exposed to various environments such as acidic, salty or harsh atmospheres as well as temperature variations and radiation, leading to potential flaws in the coatings, e.g. blistering, cracks as well as localized detachment between the coating and substrate. over time, these deficiencies will cause the coating to fail and the metal substrate to corrode [1]. although the adhesive and hydrophobic properties of a coating are two important reasons for applying an effective, functional and corrosion-resistant coating, such characteristics are not always found in one coating system. therefore, the functionalization of coatings by adding anticorrosive and hydrophobic boosters as well as pigments takes priority in terms of the development of coatings. in this context, the importance of developing hydrophobic, homogeneous and adherent coating materials has grown, particularly in corrosion protection systems. a hydrophobic coating can reduce the degree of contact between water and metal surfaces, delaying the progression of corrosion [2]. the phenomenon of water absorption reduces the protective nature and durability of the coating. swelling, voids or cracks in the matrix of the coating may occur when the coating is immersed in an aggressive electrolyte solution, affecting its functionality [3]-[4]. received: 24 aug 2023; revised: 4 sept 2023; accepted: 4 sept 2023 *correspondence: abdu.elhoud@chemsystemstechnology.com therefore, to develop corrosion protection by applying polymeric coatings, the sorption of water by the coating materials must be reduced as well as the diffusion of water across the interface between the coating and metal hindered [5]. polyaspartic coatings are still quite novel, originating from polyurethane technology. polyaspartics are aliphatic polyureas that are formed from a reaction between polyaspartic esters and an aliphatic isocyanate. polyaspartic coatings boast several advantages, e.g. fast curing with a reasonable pot life; the application of thin or thick coatings; high mechanical and chemical resistance; hydrophobic properties; high solids; and the absence or minimal use of volatile organic compounds in the system. as a result of these properties, polyaspartic coatings are being increasingly used as corrosion protective coatings. the incorporation of a zinc phosphate corrosion inhibitor into the coating to improve its relative level of environmental protection, moreover, its level of corrosion resistance has been considered [6]. in this study, the effect of a zinc phosphate inhibitor, micaceous iron oxide barrier and a novel resin hardener on the corrosion performance of a polyaspartic coating was evaluated by carrying out an immersion corrosion test. https://doi.org/10.33927/hjic-2023-18 mailto:abdu.elhoud@chemsystems-technology.com mailto:abdu.elhoud@chemsystems-technology.com elhoud hungarian journal of industry and chemistry 52 2. materials and experiments the study was carried out on polyaspartic coatings applied to structural steel plates. the control polyaspartic coating was designed to protect concrete structures, whereas the modified polyaspartic coating is intended to prevent steel from corroding. the surface finish of the steel panels was milled and blasted (sa 2.5) as can be seen in figures 1a and 1b. one layer of the coatings was applied to each steel sample, consisting of a 150 x 80 x 2mm rectangular plate, using the erichsen film applicator model 358 shown in figure 2. the edges of the steel samples were well covered with tape to avoid premature failure of the coating or rusting of the steel plates. the tested samples were placed in a plastic container filled with 3.5% nacl solution at room temperature (rt) for 30 days, as shown in figure 3. another group of experiments were carried out by leaving a plastic container in an oven set at 35°c (figure 4). the coating was examined every 10 days and the resistance of the coating to the corrosive environment evaluated by identifying any degree of damage or defects on the coating as well as rust on the steel using visual and macroscopic inspection techniques. adhesion tests of the control and modified polyaspartic coatings applied to steel were carried out in accordance with astm d3359-17 [7]. a crosshatch tool scratched a grid into the surface of the coating in order to expose the substrate. then adhesive tape was attached over the grid and pressed firmly for a few seconds before being removed. finally, the percentage of coating pulled off by the adhesive tape in relation to the surface area of the grid was evaluated and rated according to the astm specification whereby 0b and 5b denote low and high levels of adhesion of the coating to the steel substrate, respectively. 3. results 3.1. macroscopic analysis of coatings after immersion corrosion tests visual observations of the control and modified (iron oxide barrier + zinc phosphate inhibitor) coatings after 30 days of immersion in a 3.5% nacl solution at rt and 35 °c are presented in figures 5-12. figure 5 shows the surface morphology of the control polyaspartic coating applied to the milled steel surface after the immersion experiment at rt had finished, whereby localized corrosion rust attached to a blister can be seen. figure 6 shows the corrosion rust of the control polyaspartic coating that formed on the blasted steel surface after the immersion experiment at rt. observations of the coatings containing the zinc (a) (b) figure 1: photographs of the a) milled and b) blasted steel finish figure 4: immersion tests at 35 °c figure 2: erichsen film applicator model 358 figure 3: immersion tests at rt immersion corrosion tests 51(2) pp. 51–56 (2023) 53 figure 5: 1x macro photograph of the control coating applied to the surface of the milled steel after the 30day-long immersion test at rt figure 6: 0.67x macro photograph of the control coating applied to the blasted (sa 2.5) steel surface after the 30-day-long immersion test at rt figure 7: 1x macro photograph of the modified coating (iron oxide barrier + zinc phosphate inhibitor) applied to the milled steel surface after the 30-daylong immersion test at rt figure 8: 1x macro photograph of the modified coating (iron oxide barrier + zinc phosphate inhibitor) applied to the blasted (sa 2.5) steel surface after the 30-day-long immersion test at rt phosphate inhibitor and micaceous iron oxide barrier on milled and blasted steel surfaces following the immersion experiments at rt are illustrated in figures 7 and 8. it should be noted that no defects in the coating or rust can be seen on these modified coating systems. flakes of the lamellar iron oxide barrier are clearly visible. the absence of blisters and corrosion rust on the steel is attributed to the protection afforded by these coatings containing zinc phosphate and an iron oxide barrier. photographs of the coatings after the immersion experiments at 35 °c are shown in figures 9-12. a cluster of blisters and localized rust on the milled steel surface to which the control coating was applied can be seen in figure 9. the control coating applied to the blasted steel surface is presented in figure 10 where a large blister of the coating and rust through a crack in the coating can be observed. the modified coatings on the milled and blasted steel surfaces after the immersion tests at 35 °c are illustrated in figures 11 and 12. some rust can be observed in the photograph of the coating applied to the milled steel surface, while the iron oxide barrier of the coating on both steel surfaces and the absence of blisters can be seen in the macroscopic images. 3.2. adhesion test of the coatings to the substrate after the immersion corrosion tests figures 13-16 show the results of the adhesion tests carried out after the immersion corrosion tests for each surface finish. in figure 13, a loss of grid can be seen on the control coating attached to the milled steel surface. on the other hand, no crosscut squares detached when the control coating was applied to the blasted steel surface, however, the coating expanded along the cut lines of each grid as illustrated in figures 14. nevertheless, no grid loss in the case of the modified coating applied to the milled and blasted steel panels were visible in figures 15 and 16. anti-corrosive pigments in the coating formula enhanced adhesion of the coating and reduced the extent to which the grid coating was removed, thereby increasing the degree of adhesion between the coating and the steel substrate. the adhesion classification of the coatings with regard to the astm d3359 classification is described according to the following categories: 5b – 0% adhesion failure, 4b – 5% adhesion failure, 3b – 515% adhesion failure, 2b – 15-35% adhesion failure, 1b – 35-65% adhesion failure. elhoud hungarian journal of industry and chemistry 54 figure 11: 3x macro photograph of the modified coating (iron oxide barrier + zinc phosphate inhibitor) applied to the milled steel surface after the 30-daylong immersion test at 35 °c figure 12: 1x macro photograph of the modified coating (iron oxide barrier + zinc phosphate inhibitor) applied to the blasted (sa 2.5) steel surface after the 30-day-long immersion test at 35 °c figure 13: astm class 1b adhesion of the control coating to the milled steel surface figure 14: astm class 5b adhesion of the control coating to the blasted (sa 2.5) steel surface expanded coating figure 15: astm class 5b adhesion of the modified coating to the milled steel surface figure 16: astm class 5b adhesion of the modified coating to the blasted steel surface figure 9: 1x macro photograph of the control coating applied to the milled steel surface after the 30-daylong immersion test at 35 °c figure 10: 2x macro photograph of the control coating applied to the blasted (sa 2.5) steel surface after the 30-day-long immersion test at 35 °c immersion corrosion tests 51(2) pp. 51–56 (2023) 55 4. discussion protective coatings are usually applied as barriers in various environments where degradation is more likely, for instance, when continuously immersed in water, under marine and atmospheric conditions as well as in the presence of salts and acids, while the coatings of structures buried in soil are subjected to microbial degradation and humid conditions [1]. although other corrosion investigation techniques, e.g. salt sprays and electrochemical corrosion, are well-established to predict the corrosion characteristics of coatings on a metal substrate, the resistance of a coating to the penetration of water as well as the adhesion of a coating to a substrate remain significant challenges, moreover, other techniques could possibly be implemented [8]. in the present study, immersion corrosion tests were conducted and the results confirmed the applicability of this technique to estimate the corrosion performance and adhesion of the control and modified polyaspartic coatings. the corrosion and corrosion protection mechanisms in this new anti-corrosion coating system can briefly be explained according to the scenario below: 4.1. corrosion behavior of the control coating the control coating, in the absence of both zinc phosphate as a corrosion inhibitor and an iron oxide barrier, applied to the milled surface finish of the steel panels exhibited blisters and rust after the immersion corrosion tests had been conducted at rt. the tendency of this coating to blister increased when the coating was immersed at 35 °c, which can be attributed to the reduction in adhesion between the coating system and the steel substrate. this interpretation is in agreement with the adhesion measurements for the same coating after the immersion corrosion tests. even though the surface finish slightly affects the performance of the control coating, the coating applied on the blasted steel panels exhibited rusting after the immersion corrosion tests at rt, while an isolated large blister was observed on the coating after the tests at 35 °c. 4.2. corrosion behavior of the modified coating the modified coating yielded significantly different results in all the corrosion and adhesion tests compared with the control coating. the flaws that had been observed in the control coating were fully resolved after the formula of the coating was modified by adding the zinc phosphate corrosion inhibitor and the micaceous iron oxide barrier, enhancing adhesion and preventing the coating from forming blisters, cracks or rust on the steel. corrosion resistance was achieved by using an effective hardener, an anticorrosion pigment composed from the corrosion inhibitor zinc phosphate and a lamellar micaceous iron oxide barrier, which in turn resulted in strong bonding and inhibitive characteristics. thereafter, coating defects such as blisters of the modified coating could not be observed after immersion corrosion experiments were conducted in a 3.5% nacl solution over a 30-day period. this can be attributed to strong bonds between the coating and the substrate caused by the new hardener as well as enhanced by the zinc phosphate, which resulted in a defensive film on the steel surface, while the iron oxide barrier prevented the penetration of corrosive elements. the zinc phosphate inhibitor in the modified coating formed a thin film on the substrate, preventing corrosion and supporting adhesion between the coating and the steel. the iron oxide barrier provided protection by controlling the penetration of moisture or water and extending the bath of the corrosive elements to saturate the coating and make contact with the substrate. this can be explained by the insignificant amount of moisture or water that could pass through the coating. however, no blisters were observed in the modified coating compared to the one without a micaceous iron oxide barrier. as a consequence, preferable coating characteristics of the new coating formula such as stability as well as corrosion resistance and inhibition were achieved. combining the zinc phosphate with the iron oxide barrier in the evaluated coating is a promising inhibitive technique to reduce the degradation of the coating and provide a good level of corrosion resistance. the corrosion resistance of the pigmented coating as well as its adhesion to milled and blasted steel substrates in a direct-to-metal system and without surface preparation of the milled steel are attributed to functionalization of the coating after adding the iron oxide barrier and zinc phosphate corrosion inhibitor. furthermore, the new hardener applied to the resin enhanced the adhesion of the film, thereby reducing the tendency of the coating to blister, crack, etc. the role of zinc phosphate in developing the investigated coatings is in agreement with results from other studies, namely that the addition of zinc phosphate to the organic coating improved its adhesion to the steel substrate and prevented the diffusion of the corrosive medium through the coating or onto the interface between the metal and coating [6]. on the other hand, the iron barrier and zinc phosphate inhibitor hindered the penetration of water as well as prevented the steel substrate from blistering and corroding. the hypotheses of the coating-degradation and protection mechanisms have been investigated [9] and are presented schematically in figures 17 and 18. it can figure 17: a schematic diagram of the control coatings [9] steel substrate 1 2 3 initial moisture ingress moisture saturate moisture blisters coating matrix elhoud hungarian journal of industry and chemistry 56 be seen that penetration of the corrosive environment through the unmodified polyaspartic coating is quicker as well as leads to the formation of blisters and rust on the steel surface. the ,odified polyaspartic systems exhibited a good degree of protection as a direct-to-metal system on milled and blasted surface finished steel substrates, which is very beneficial in terms of site application by reducing the cost of the cleaning operation before coating that is normally recommended prior to applying a coating protection system. 5. conclusions the addition of a zinc phosphate corrosion inhibitor and a micaceous iron oxide barrier resulted in highly protective coatings for direct-to-metal systems. resistance to corrosion and blistering as well as the loss of adhesion of the coating to the substrate are immensely improved by the modified polyaspartic coating, which did not corrode in artificial seawater containing 3.5% nacl at rt nor at 35 °c throughout the 30-day-long assessment. to date, the upgraded coating can be readily applied to protect steel structures as a direct-to-metal protection system of milled and blasted surfaces without the need for pre-cleaning or surface preparation before coating. acknowledgements the authors would like to thank vlaio for sponsoring this project conducted by chemsystems (grant hbc.2020.3021) to identify and develop a concrete coating produced by adcos nv for the purpose of extending the application of this product to include the protection of steel assets. references [1] ulaeto, s.b.; rajan, r.; pancrecious, j.k.; rajan, t.p.d.; pai, b.c.: developments in smart anticorrosive coatings with multifunctional characteristics, prog. org. coat., 2017, 111, 294– 314, doi: 10.1016/j.porgcoat.2017.06.013 [2] calabrese, l.; bonaccorsi, l.; capri, a.; proverbio, e.: adhesion aspects of hydrophobic silane zeolite coatings for corrosion protection of aluminium substrate, prog. org. coat., 2014, 77(9), 1341– 1350, doi: 10.1016/j.porgcoat.2014.04.025 [3] xie, l.; hong, f.; he, c.; ma, c.; liu, j.; zhang, g.; wu, c.: coatings with a self-generating hydrogel surface for antifouling, polymer, 2011, 52(17), 3738–3744, doi: 10.1016/j.polymer.2011.06.033 [4] gnedenkov, s.v.; sinebryukhov, s.l.; egorkin, v.s.; mashtalyar, d.v.; alpysbaeva, d.a.; boinovich, l.b.: wetting and electrochemical properties of hydrophobic and superhydrophobic coatings on titanium, colloids surf. a physicochem. eng. asp., 2011, 383(1-3), 61–66, doi: 10.1016/j.colsurfa.2011.01.024 [5] zhang, s.-y.; li, s.-j.; luo, x.-w.; zhou, w.-f.: mechanism of the significant improvement in corrosion protection by lowering water sorption of the coating, corros. sci., 2000, 42(12), 2037–2041, doi: 10.1016/s0010-938x(00)00042-1 [6] wan, h.; song, d.; li, x.; zhang, d.; gao, j.; du, c.: effect of zinc phosphate on the corrosion behavior of waterborne acrylic coating/metal interface, materials, 2017, 10(6), 654, doi: 10.3390/ma10060654 [7] american society for testing and materials astm d3359 -17: (2017). standard test methods for rating adhesion by tape test, doi: 10.1520/d335909e02 [8] elhoud, a.; van everbroeck, t.: rotating technique to assess erosion of polyaspartic coating, mater. perform., 2022, 61(12), 34–37 [9] elhoud, a.; van everbroeck, t.: behavior of control and inhibitive polyaspartic coatings using alkylammonium and zinc phosphate corrosion inhibitors in soi, hung. j. ind. chem., 2022, 50(2), 35–41, doi: 10.33927/hjic-2022-16 figure 18: a schematic diagram of the modified coatings [9] steel substrate zinc phosphate iron oxide barrier no blisters https://doi.org/10.1016/j.porgcoat.2017.06.013 https://doi.org/10.1016/j.porgcoat.2014.04.025 https://doi.org/10.1016/j.polymer.2011.06.033 https://doi.org/10.1016/j.colsurfa.2011.01.024 https://doi.org/10.1016/j.colsurfa.2011.01.024 https://doi.org/10.1016/s0010-938x(00)00042-1 https://doi.org/10.3390/ma10060654 https://doi.org/10.3390/ma10060654 http://dx.doi.org/10.1520/d3359-09e02 http://dx.doi.org/10.1520/d3359-09e02 https://doi.org/10.33927/hjic-2022-16 hungarian journal of industry and chemistry vol. 52(1) pp. 1–7 (2024) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2024-01 an innovative approach to various industrial applications: the fingered citron hilal tasbasi1 and meltem asan-ozusaglam1* 1 department of molecular biology and genetics, art and sciences faculty, aksaray university, bahcesaray district, aksaray, 68100, turkey the fingered citron (citrus medica l. var. sarcodactylis), which originates from india, has spread to different parts of the world over time. in opposition to the increasing resistance to traditional antimicrobial agents, the application of alternative treatments developed using herbs has recently gained interest. the aim of th is study is to investigate alternative applications of the fingered citron in the cosmetics and pharmaceutical industries. for this purpose, the antimicrobial activity of fingered citron leaf water extract (fclwe) against test microorganisms was evaluated using a disk diffusion assay. minimum inhibitory concentration (mic) and minimum cidal concentrations (bactericidal mbc or fungicidal mfc) of the extract were also determined. for fclwe, among the pathogenic test microorganisms, listeria monocytogenes strain atcc 7644 and staphylococcus aureus strain atcc 25923 showed the smallest and the largest inhibition zone diameters, with values of 7.06 and 11.57 mm, respectively. mic and mbc or mfc values of fclwe varied from 10 to 40 µg/µl. in addition, the sun protection factors (spf) of fclwe and a mixture of fclwe and commercial sun creams at different concentrations were determined. the spf value of fclwe was found to be 25. the mixture of fclwe and commercial sun cream at an amount of 10 ml yielded an spf value of 12.26. next, the biological activity of the cream formulation obtained with commercial cream, fclwe and limosilactobacillus fermentum ma-7 (cream-leaf water extract-probiotic cwp) was investigated against test microorganisms using the well diffusion method. cwp exhibited inhibitory activity against l. monocytogenes atcc 7644 (2.56 mm), candida glabrata rskk 04019 (2.81 mm), c. albicans atcc 10231 (4.54 mm) and s. aureus atcc 25923 (5.00 mm). it was observed that the cream formulation of cwp increased the diameters of the inhibition zone by creating a synergistic effect against all pathogenic test microorganisms. fclwe may potentially be used as an alternative natural additive to chemical preservatives in the cosmetics and pharmaceutical industries. keywords: antimicrobial activity, citrus, cream formulation, probiotic, sun protection factor 1. introduction although antibiotics are among the most preferred options when combating bacterial infections [1], their inappropriate and widespread use causes microorganisms to develop resistance, posing a threat worldwide [2]. the increasing microbial resistance to synthetic antimicrobial agents poses a global challenge and the demand for alternative medicines targeting resistant strains is on the rise [3]-[4]. medicinal and aromatic antimicrobial agents that may be effective against resistant strains are under investigation [5]. the medicinal properties of plants have been passed down from one society to the next for centuries [6]. antimicrobial agents found in plants have an enormous therapeutic potential [7]. the medicinal properties of plants are often specific to certain genera of plants and arise from secondary metabolites present in their structure. secondary metabolites found in plants consist of coumarins, alkaloids, terpenes, fatty acids, tannins, steroids and flavonoids [7]-[8]. plants are received: 7 nov 2023; revised: 12 nov 2023; accepted: 14 nov 2023 *correspondence: meltemozusaglam@gmail.com alternative natural resources that exhibit antimicrobial effects [9]. fingered citron (fc) is an evergreen species of tree belonging to the rutaceae family [10]. originating from india, over time it has spread to different regions around the world [11]. this species possesses bioactive compounds such as flavonoids, terpenes, neolignans, coumarins and alkaloids [12]-[14]. clinically, it has demonstrated various health effects, including hypoglycemic properties, efficacy in managing type 2 diabetes, hepatoprotective activity, relief from stomach pain, expectorant properties, potential anticancer activity and immunomodulatory effects [12]-[15]. the skin, which is crucial in protecting internal organs from external factors, is the largest sensory organ in our body. being constantly in contact with external factors, it is exposed to possible dangers posed by harmful microorganisms. the first line of defense of the body against harmful microorganisms is the skin. the specific microbial flora on the skin protects against adverse environmental conditions [16]. probiotics, on the https://doi.org/10.33927/hjic-2024-01 mailto:meltemozusaglam@gmail.com tasbasi and asan-ozusaglam hungarian journal of industry and chemistry 2 other hand, contain live microorganisms that alter the skin flora of the host [17]. probiotic microorganisms are used to reduce skin inflammation, regenerate the skin microbiota, delay aging and treat diseases such as dermatitis [18]-[19]. the fermentation broth called "lactic acid bacteria ferment" according to the international nomenclature of cosmetic ingredients (inci) is used in the production of various cosmetic ingredients [20]. for these reasons, both oral and topical probiotics are used to treat skin diseases and improve skin health by regulating microbial flora [16]-[21]. the sun serves as one of our primary energy sources, enabling life to thrive on earth [22]. working environments and outdoor areas are places where the risk of exposure to the sun's ultraviolet radiation is high [23]. when exposed to ultraviolet radiation from the sun, dermatitis, premature aging, cancer, tanning and sunburn can occur in the human body [22]-[24]. ultraviolet light is divided into 3 regions, namely uva (400-320 nm), uvb (320-290 nm) and uvc (290-200 nm) [25]. it is crucial to promote the use of photoprotective agents to mitigate the detrimental effects of ultraviolet radiation [26]. certain components with photoprotective properties reduce the harmful effects of ultraviolet radiation on the skin. for this reason, the protective properties of plant extracts on the skin are being investigated. bioactive molecules such as flavonoids and carotenoids contained in plant-based cosmetic products protect the skin from sunlight [27]. in this study, the antimicrobial activity of fingered citron leaf water extract (fclwe) obtained using water as a solvent against clinical and foodborne pathogens as well as some probiotic candidate strains such as lactic acid bacteria (lab) was tested. sun protection factor (spf) values of fclwe and cream-fclwe mixtures at different concentrations were measured to determine their potential application in the cosmetics industry as a natural alternative to chemical preservatives. in addition, the potential of new cream formulations prepared with fclwe and the probiotic l. fermentum ma-7 in developing natural products by replacing chemical products in both the cosmetics and pharmaceutical industries was investigated. 2. experimental 2.1. plant material fc leaf was obtained from köyceğiz plant world (muğla-türkiye) in october 2022 (figure 1.a). 2.2. preparation of leaf water extract fc leaves (figure 1.b) were dried in dry conditions in the absence of light. the ground leaves were extracted with water in a water bath (80 °c) over 24 hours (figure 1.c). the fclwe was filtered before being evaporated and concentrated to 100 mg/ml using dimethyl sulfoxide (dmso) then refrigerated at +4 °c until used. 2.3. preparation of bacterial strains in this study, four pathogens and five lab were used. all strains tested (staphylococcus aureus atcc 25923 in a nutrient broth, listeria monocytogenes atcc 7644 in tryptic soy broth, limosilactobacillus fermentum ma-7, limosilactobacillus fermentum ma-8, lactobacillus gasseri ma-1, lactobacillus delbrueckii ma-9, limosilactobacillus vaginalis ma-10 in de manrogosa-sharpe agar at 37 °c as well as candida glabrata rskk 04019 and candida albicans atcc 10231 in yeast peptone dextrose at 30 °c) were incubated at the specified temperature and in a particular environment for 24 hours. 2.4. determination of antimicrobial activity the antimicrobial activity of the fclwe was determined by the disk diffusion method [28]. the concentration (0.5 mcfarland) of test microorganisms was prepared and the prepared suspension (100 µl) spread onto the agar medium. 3 replicates of sterile disks (6 mm) were placed on the agar medium. for the pathogens, 20 µl (2 mg/disk) of fclwe was dripped onto each disk. for the lab, 5 µl (0.5 mg/disk), 10 µl (1 mg/disk) and 20 µl (2 mg/disk) of fclwe were dripped onto the disks. the petri dishes were incubated at the specified temperature for 24 hours as mentioned above. figure 1: samples of fingered citron leaves extracted with water https://www.sciencedirect.com/topics/food-science/lactobacillus the fingered citron 52(1) pp. 1–7 (2024) 3 2.5. minimum inhibitory and minimum bactericidal or fungicidal concentrations the minimum inhibitory concentration (mic) and minimum bactericidal (mbc) or fungicidal (mfc) concentration of the fclwe were determined by the microdilution method [28]. the fclwe and medium were added to the tubes and diluted before the test microorganism was added at a concentration of 0.5 mcfarland. the samples extracted from mic tubes were inoculated onto the solid medium. the fclwe concentration at which the growth of microorganisms stopped was recorded as the mic value. the concentration at which growth stopped in the solid medium incubated at the appropriate temperature for 24 hours was determined as the mbc or mfc value. 2.6. determination of the spf values of fclwe and cream-fclwe mixtures the spf values of the fclwe and cream mixtures (cream-fclwe) at different concentrations were determined using a beckman coulter spectrophotometer. the absorption values of fclwe dissolved in ethanol (96%) were obtained in the range of 290 to 320 nm (every 5 nm). to determine the spf values of the creamfclwe mixtures, 0.5 g of the extract and 1 g of the cream were added to a different tube before the volume was increased to 10 ml with distilled water. after diluting the mixture with ethanol (40%), sonication was performed before being filtered through whatman grade 1 filter paper. 3 replicates of each of the cream-fclwe mixtures obtained at different amounts (2.5, 5.0, 10.0 ml) were measured in a spectrophotometer. spf values were determined based on the formula below [29]: 𝑆𝑃𝐹 = 𝐶𝐹 х ∑ 𝐸𝐸(𝜆) x 𝐼(𝜆) х 𝐴𝑏𝑠 (𝜆) 320 290 (1) where cf is a correction factor, ee(λ) is the erythmogenic effect of radiation with wavelength λ, i(λ) is the intensity of solar light at wavelength λ and abs (λ) is the spectophotometric absorbance value at wavelength λ. 2.7. antimicrobial activity of the cream formulation containing fclwe and probiotic the antimicrobial activity of the cream formulation enriched with fclwe and probiotic (l. fermentum ma7) was evaluated using a modified protocol by following the well diffusion method [30]. the cream formulation was prepared using a commercial cream, fclwe and l. fermentum ma-7 [31]. four different test sample groups were created for this experiment, namely one containing only the cream (control – c), another containing the cream and probiotic (cp), one more containing the cream and leaf water extract (cw) as well as a final group with the cream containing both the leaf water extract and probiotic (cwp). 2.8. statistical analysis the statistical analysis of the data concerning the biological activity was carried out using gnu spss software. the data points were confirmed by performing the one-way analysis of variance (anova) with tukey's post-hoc test (p<0.05 was considered to be statistically significant). 3. results and discussion the spread of pathogenic microorganisms and the development of resistance cause serious health problems [32]. the antimicrobial activity of the fclwe against clinical, foodborne and yeast pathogens was determined using the disk diffusion assay and microdilution methods. the diameters of the inhibition zones obtained from the disk diffusion assay are given in table 1. data referring two antibiotics are also in table 1. in case of fclwe, the maximum diameters of the inhibition zones among the test microorganisms was 11.57 mm with regard to s. aureus atcc 25923. the diameter of the inhibition zone appears to be good when c. glabrata rskk 04019 (9.95 mm) and c. albicans atcc 10231 (10.83 mm) were tested, which were used as fungal test microorganisms. l. monocytogenes atcc 7644 exhibited the smallest diameter of the inhibition zone, that is, 7.06 mm (p<0.05). when evaluated statistically, the difference between s. aureus atcc 25923, c. glabrata rskk 04019 and c. albicans atcc 10231, which exhibited visually large inhibition zones, was also found to be insignificant (p>0.05). the fclwe was biologically active on the test microorganisms. in a study, the antimicrobial activity of an essential oil obtained from the leaves of fc was determined by the disk diffusion method. an inhibition zone of 11 mm in diameter was observed when using s. aureus [33]. in our study, the fclwe exhibited a similar level of antimicrobial activity on s. aureus atcc 25923 (11.57 mm). el hawary et al. determined the antimicrobial activity of the essential oil obtained from the leaves of table 1: diameters of the inhibition zone of fclwe using different pathogens pathogens diameter of the inhibition zone (mm±sd) fclwe am fca s. aureus atcc 25923 11.57±0.69a 21.04±0.80 nd l. monocytogenes atcc 7644 7.06±1.23b 29.57±0.10 nd c. glabrata rskk 04019 9.95±0.51a nd 20.35±0.10 c. albicans atcc 10231 10.83±0.19a nd 21.85±1.76 * fclwe: fingered citron leaf water extract, am: ampicillin, fca: fluconazole, nd: not determined. * different superscript letters indicate significant differences (p<0.05) determined by one-way anova followed by tukey's post-hoc test. tasbasi and asan-ozusaglam hungarian journal of industry and chemistry 4 fc using the well diffusion method. fc oil did not produce a zone of inhibition against s. aureus atcc 6538 whereas a 15 mm zone of inhibition was observed c. albicans nrrl y-477 [34]. in our study, the fclwe exhibited a good degree of antibacterial activity against s. aureus atcc 25923 but a lower level of antifungal activity against c. albicans atcc 10231. differences in the growing conditions of the plant, the method of extraction and the technique used to measure the antimicrobial activity may cause variations in the results. the antimicrobial activity of fclwe against lab strains were determined using the disk diffusion assay and microdilution methods. the obtained inhibition zones are given in table 2. the inhibitory activity of the fclwe on l. fermentum ma-7, l. fermentum ma-8 and l. vaginalis ma-10 was immeasurable at a concentration of 0.5 mg/disk. the results of the statistical analysis showed that no significant difference was observed between the averages of l. fermentum ma-8 and l. vaginalis ma-10 with l. fermentum ma-7 (p>0.05), however, visual data indicates that the smallest inhibition zone was obtained in l. fermentum ma-7 at a concentration of 2 mg/disk. according to these results, the probiotic candidate l. fermentum ma-7 is the least inhibited or not inhibited by fclwe. the mic and mbc or mfc results of the clinical, foodborne and yeast pathogens are given in table 3. the mic and mbc or mfc values of the fclwe varied from 10 to 40 µg/µl. the minimum mic and mbc values of the fclwe were 10 µg/μl against s. aureus atcc 25923, while that of the mfc values was 20 µg/μl against c. glabrata rskk 04019. the results of the biological activity assays indicated that the fclwe exhibits bactericidal and fungicidal effects against all the pathogenic microorganisms tested at various concentrations. in a study by akarca and baytal, the mic and mbc values of extracts obtained from fresh and dried leaves of c. lemon were determined. the mic values of the extracts were recorded as 93.75 and 35.16 µg/µl against s. aureus atcc 6538 but 140.63 and 46.88 µg/µl against l. monocytogenes atcc 51774, respectively. the mbc values of the extracts were recorded as 39.06 and 23.44 µg/µl against s. aureus atcc 6538 but 93.72 and 31.25 µg/µl against l. monocytogenes atcc 51774, respectively [35]. in our study, the mic and mbc values of the fclwe on s. aureus atcc 25923 and l. monocytogenes atcc 7644 were found to be lower than in the referred study. the mic and mbc values of the fclwe against the tested lab are given in table 4 which varied from 10 to 40 µg/µl. the mic value of the fclwe was 10 µg/μl against all the tested bacteria, while the mbc value was 20 µg/μl against l. fermentum ma-7. in the current study, the spf value of the fclwe was determined to be 25. due to its high value, the spf of the cream-fclwe mixture at different concentrations was also examined. the spf values of the creamfclwe mixtures are given in figure 2. the highest spf of the cream-fclwe mixture was 12.26 at an amount of 10 ml. the results of this study examining the spf values of the cream-fclwe mixture at different fclwe concentrations show that fclwe significantly increases the spf of the commercial cream, even at the lowest concentration. vella et al. determined the spf values of essential oils obtained from the shells of various citrus species table 2: diameters of the inhibition zones of fclwe against lab diameter of the inhibition zone (mm±sd) lactic acid bacteria fclwe 0.5 mg/disk 1.0 mg/disk 2.0 mg/disk l. fermentum ma-7 nda 6.32±0.20a 9.22±0.31a l. fermentum ma-8 nda 6.28±0.13a 10.34±0.34a l. gasseri ma-1 6.17±0.14b 6.68±0.63a 10.66±0.28b l. delbrueckii ma-9 6.15±0.11b 6.87±0.22a 11.73±0.32b l. vaginalis ma-10 nda 6.66±0.17a 10.01±0.96a *fclwe: fingered citron leaf water extract, nd: not determined. *different superscript letters indicate significant differences (p<0.05) using the one-way anova followed by tukey's post-hoc test. table 3: mic and mbc or mfc of fclwe against pathogens pathogens fclwe mic (µg/µl) mbc or mfc (µg/µl) s. aureus atcc 25923 10 10 l. monocytogenes atcc 7644 20 40 c. glabrata rskk 04019 20 20 c. albicans atcc 10231 40 40 *fclwe: fingered citron leaf water extract, mic and mbc or mfc: minimum inhibitory and minimum bactericidal or fungicidal concentrations table 4: mic and mbc of the fclwe against lab lactic acid bacteria fclwe mic (µg/µl) mbc (µg/µl) l. fermentum ma-7 10 20 l. fermentum ma-8 10 20 l. gasseri ma-1 10 20 l. delbrueckii ma-9 10 20 *fclwe: fingered citron leaf water extract, mic and mbc or mfc: minimum inhibitory and minimum bactericidal concentrations the fingered citron 52(1) pp. 1–7 (2024) 5 using the mansur equation. the obtained spf values were presented as 2.04 for c. limon, 3.75 for c. reticulata, 8.96 for c. aurantium and 9.74 for c. bergamia [36]. the spf of fclwe measured by vella et al. was higher than recorded in this study. a cream formulation was developed by adding l. fermentum ma-7 sonicated in the fclwe. in order to be effective, the cream must be reliable. the use of lysates or inactivated microorganisms reduces safety issues such as shelf life, translocation and infection, thereby increasing their usability in the cosmetics and pharmaceutical industries [37]. additionally, l. fermentum ma-7 lysate used in the cream formulation is associated with antimicrobial activity and exhibited the smallest inhibition zone in the fclwe. the antimicrobial activities of the cream formulation developed with the commercial cream, fclwe and probiotic were determined using the well diffusion method and the inhibition zones are given in table 5. in the c test sample group, the diameter of the inhibition zone against the pathogenic strains (except for c. albicans atcc 10231) could not be determined. the largest diameters of the inhibition zones in the case of the cw and cwp test sample groups were 2.72 and 5.00 mm against s. aureus atcc 25923, respectively. the developed cream formulation may be used as an antimicrobial agent against contaminations of s. aureus atcc 25923. when c, cw and cwp groups were compared statistically, a significant difference was determined for s. aureus atcc 25923 and l. monocytogenes atcc 7644 (p<0.05). in the cp group, the diameters of the inhibition zones were determined against all the tested microorganisms (except for l. monocytogenes atcc 7644). the statistical analysis indicated that the difference between the antimicrobial activity of the c (2.08 mm) and cw (2.47 mm) groups on c. albicans atcc 10231 was insignificant (p>0.05), but a significant difference was observed between the cp (4.01 mm) and cwp (4.54 mm) (p<0.05) groups. common fungal infections such as c. albicans cause systemic infections by affecting the skin and mucosal surfaces [38]. for this reason, the developed cream formulation can provide a natural solution by exhibiting an inhibitory effect against candida spp. most importantly, an increase in the diameter of the inhibition zones was observed when comparing the c and cwp groups against all pathogen strains. determining the biological effect of the cream formulation comprised of natural ingredients against the pathogenic strains may potentially facilitate its application in the cosmetics and pharmaceutical industries. salako et al. determined the effects of extracts derived from the bulb allium sativum (asb) and c. sinensis peel (csp) using ethanol as a solvent on c. albicans. the antifungal properties of the combinations obtained by blending these extracts at concentrations of 50, 100 and 200 mg/ml and ratios of 1:1, 1:2 and 2:1 were determined by the agar well diffusion method. the asb:csp mixture (1:2) exhibited the highest inhibitory activity with a diameter of the inhibition zone of 21.00 mm when tested at a concentration of 50 mg/ml. this specific asb:csp mixture (1:2) at a concentration of 50 mg/ml was subsequently formulated into an ointment [39]. in our study, it is evident that the cream formulation containing fclwe and probiotic provides significant protective effects against pathogens. additionally, the cosmetics and pharmaceutical industries can develop innovative products such as creams and ointments with these formulations containing natural alternative ingredients. 4. conclusions the antimicrobial activity of fclwe against clinical and foodborne pathogens as well as lab was investigated to determine its possible applications in the pharmaceutical and cosmetics industries. it was determined that fclwe exhibits antimicrobial and antifungal activities. fclwe and cream formulations at different concentrations can be figure 2: spf values of the cream-fclwe mixtures table 5: diameters of the inhibition zones of the fclwe and probiotic cream mixture against pathogens pathogens inhibition zone diameter (mm±sd) c cp cw cwp s. aureus atcc 25923 nda 1.25±0.10a 2.72±0.10b 5.00±1.08c l. monocytogenes atcc 7644 nda nda 1.03±0.00b 2.56±0.53c c. glabrata rskk 04019 nda 2.21±0.44b nda 2.81±0.48c c. albicans atcc 10231 2.08±0.10a 4.01±1.16b 2.47±0.09a 4.54±0.70c *c: cream (control), cp: cream-probiotic, cw: cream-water extract, cwp: cream-water extract-probiotic, nd: not determined *different superscript letters indicate significant differences (p<0.05) by applying the one-way anova followed by the tukey's post-hoc test. tasbasi and asan-ozusaglam hungarian journal of industry and chemistry 6 used as alternative additives to chemical preservatives due to their high spf values. fclwe combined with a probiotic and commercial cream exhibited a high level of antimicrobial activity against clinical and foodborne 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national institute of technology (vnit), south ambazari road, nagpur, maharashtra 440010, india nicotinic acid and its derivatives are extensively used in the food, pharmaceutical and cosmetic industries. the technique for separating nicotinic acid from fermentation broth has a significant impact on overall production costs. the extraction of nicotinic acid was investigated using various kinds of natural non-toxic and conventional solvents such as sesame oil, rice bran oil, cyclohexane, 1-octanol and methyl isobutyl ketone (mibk). the results were presented in terms of extraction efficiencies (e%) and distribution coefficients (kd). to determine these two parameters, experiments were conducted at 298 ± 1 k. the maximum extraction efficiencies of nicotinic acid were found to be 19.550, 16.514, 13.719, 17.526 and 6.216% using mibk, 1-octanol, cyclohexane, rice bran oil and sesame oil, respectively. the differences in the extraction efficienc ies of nicotinic acid using these solvents were explained in terms of dipole moment, dielectric constant and refractive index. further attempts were made to correlate the extraction efficiencies with the other physicochemical properties of the solvents such as viscosity, density, molecular weight, etc. keywords: nicotinic acid, extraction, extraction efficiency, natural solvents, conventional solvents 1. introduction nicotinic acid (na) a carboxylic acid, namely niacin (3-pyridine carboxylic acid) (c6h5no2) and referred to as vitamin b3 is a solid with a white crystalline structure, translucent and contains a carboxyl side chain at position 3 as shown in figure 1 [1]-[3]. the market value of na depends on several factors, including supply and demand, production costs and industry dynamics, as of the last update in january 2022. among other sectors, the pharmaceutical and dietary supplement industries are the main users of nicotine, which may have an impact on the market value of this drug. the market for vitamin b3 was projected to reach us$ 837.1 million in 2023. between 2024 and 2030, this is projected to rise at a compound annual growth rate (cagr) of 4.7%, reaching us$ 1162.3 million [4]. the global demand for the following applications has a direct impact on the rise in the market value of niacin [4]. na is found in avocados, peas, lentils, nuts and seeds as well as meals and meat, moreover, is an essential nutrient for humans that plants and animals produce. 34,000 tons of na were produced worldwide in 2014, 63, 22 and 15% of which was intended to be used as an animal feed additive, food component for healthcare applications and received: 17 sept 2024; revised: 5 oct 2024; accepted: 10 oct 2024 *correspondence: klwasewar@che.vnit.ac.in, k_wasewar@rediffmail.com for industrial purposes such as in the pharmaceutical and cosmetic industries, respectively [5],[6]. na is a potential analgesic and anti-inflammatory [7], moreover, has been widely used as a chelating agent in the food, pharmaceutical and beverage industries for over a century [8]. na has anti-inflammatory properties used in various industrial applications, including biological systems, to stabilize metal ions in solutions used in industrial processes as well as to enhance the solubility and bioavailability of metal ions in agricultural applications [5]-[7]. large commercial applications include in the pharmaceutical industry, e.g. chelation therapy and pharmaceutical formulation. it can also be used to produce skincare products, cosmetics and micronutrient fertilizers, which enhance plant growth and the productivity of personal care products and cosmetics. figure 1: structure of nicotinic acid https://doi.org/10.33927/hjic-2025-02 mailto:klwasewar@che.vnit.ac.in mailto:k_wasewar@rediffmail.com kolhatkar, thakre, shende and wasewar hungarian journal of industry and chemistry 10 some of the applications of na are presented in figure 2. a deficiency of niacin causes pellagra, a nutritional disorder [3],[8]. niacin is administered as a dietary supplement to prevent and treat pellagra. the primary method for avoiding niacin deficiency is through the consumption of food or nutritional supplements as the human body is unable to produce niacin [9]. nicotinamide and nicotinic acid can be produced more effectively by converting 3-cyanopyridine enzymatically [8],[10]. 60-70% of the production costs in this fermentation-based process come from downstream purification costs, including product recovery, concentration, acidity and purification expenses [6],[11]. for over a century, organic acids have been produced via fermentation technology, leading to the production of aqueous solutions [9],[12]-[15]. therefore, a costeffective acid recovery process from the fermentation broth is required [3],[14]-[17]. extracting carboxylic acids can be done in several ways from aqueous streams or fermentation broths, including dialysis, ion exchange, membrane technology, adsorption, precipitation, distillation and reactive extraction [1],[12],[18]. the technique of liquid-liquid extraction (lle), frequently referred to as solvent extraction and partitioning, is the process of dividing substances or metal complexes according to how soluble they are in two distinct liquids that are immiscible, commonly polar water and an organic solvent [19]. this study used conventional and natural solvents, namely methyl isobutyl ketone (mibk), 1-octanol, cyclohexane, sesame oil and rice bran oil, to extract na from the aqueous phase. conventional and natural solvents extracted na from the aqueous phase while reducing toxicity and creating an environmentallyfriendly method. several extraction parameters defined this experiment, including extraction efficiency (e%) and distribution coefficient (kd) [20]. separating na from the broth is crucial and challenging because of the high cost of the process. valuable carboxylic acid can be recovered affordably and sustainably using lle [21]. some authors have employed a lle method using nontoxic solvents to separate valuable carboxylic acids [22]. 2. experimental 2.1. samples and reagents na was purchased from s d fine-chem limited, while the solvents rice bran oil, sesame oil, cyclohexane, 1-octanol and mibk were procured from patanjali ayurved ltd., india; loba chemie pvt. ltd., india and merck specialities pvt. ltd, india (table 1). sodium hydroxide was procured from merck specialities pvt. figure 2: applications of nicotinic acid table 1: details of the chemicals used in the experiment chemical mw (mol l-1) structure molecular formula supplier purity (%) nicotinic acid 123.10 c6h5no2 s d fine-chem limited, india 99.5 rice bran oil 368.34 patanjali ayurved ltd., india 99.0 sesame oil 138.12 patanjali ayurved ltd., india 99.0 cyclohexane 84.16 c6h12 loba chemie pvt. ltd., india 99.5 mibk 100.16 ch3coc4h9 merck specialities pvt. ltd., india 99.0 1-octanol 130.23 ch3(ch2)7oh merck specialities pvt. ltd., india 98.0 extraction of nicotinic acid 53(1) pp. 9–15 (2025) 11 ltd., india for the titration, while oxalic acid was purchased from s d fine-chem ltd., india. oxalic acid was utilized to normalize the naoh. all of the chemicals used in the study were not further purified nor pretreated. 2.2. experimental procedure aqueous solutions of varying na concentrations (0.010-0.102 mol l-1) were prepared by dissolving different amounts of na in double distilled water. a stock solution containing 18 g l-1 na was used for the experiments. nicotinic acid in the aqueous phase and solvents in the organic phase were combined in a 1:1 volume ratio of 10 ml each in 100 ml conical flasks. the mixture was shaken at 230 rpm for 5 hours at a constant temperature of 298 ± 1 k in an orbital shaking incubator (model: s-24bl, remi, india). the samples were placed in centrifuge tubes and spun at 3930 rpm for 5 minutes to achieve the desired phase separation of the aqueous and organic phases (remi centrifuge r-4c, india) (table 2). a 0.01 m naoh solution was prepared before each experiment. a titration with 0.01 mol l-1 naoh was used to determine the amount of nicotinic acid in the aqueous phase. the experimental procedure of the present work is summarized in the block diagram in figure 3. 3. results and evaluation an experimental investigation was conducted into the extraction of na from the aqueous phase using different solvents, namely cyclohexane, 1-octanol, mibk, sesame oil and rice bran oil. the methodology is described below. regarding mass balance, the concentrations in the aqueous phase were used to determine those in the organic phase as follows: [𝐻𝑁𝐴]𝑜𝑟𝑔 = [𝐻𝑁𝐴]𝑖𝑛 − [𝐻𝑁𝐴]𝑎𝑞 (1). e% and kd were determined using experimental data for the separation of na. the distribution coefficient was defined as the ratio between the organic phase and the aqueous phase under equilibrium conditions: 𝐾𝐷 = [𝐻𝑁𝐴]𝑜𝑟𝑔 [𝐻𝑁𝐴]𝑎𝑞 (2), where [hna]org and [hna]aq stand for the concentration of nicotinic acid in mol l-1 in the organic and aqueous phases, respectively, at equilibrium. the extraction efficiency is defined as follows in terms of the distribution coefficient: 𝐸% = 𝐾𝐷 1+𝐾𝐷 ∙ 100 (3). experimental uncertainty to obtain accurate results, a few experiments were repeated twice as instrumental errors or any random fluctuations may cause the results to be uncertain. the calculations were performed using the mean values of the experimental parameters. an error of 1% was taken into consideration and repeated with an experimental error of less than 2%. it was determined that the average experimental uncertainty was close to x ± 0.002 using the following equation: 𝐴(𝑥) = √ ∑ (𝑥𝑖−�̅�)2𝑛 𝑖=𝑛 𝑛−1 (4), where n represents the number of experimental observations, xi represents an experimental observation, �̅� represents the mean of experimental values. 4. discussion the data obtained from the experiments performed to extract na are presented in table 3. table 2: list of instruments in the present study instrument parameters model orbital shaking incubator t = 25 °c rpm = 230 s-24bl, remi, india benchtop centrifuge t = 25 °c rpm = 3930 remi centrifuge r-4c, india figure 3: flow chart of the experimental procedure using nicotinic acid kolhatkar, thakre, shende and wasewar hungarian journal of industry and chemistry 12 the trend in the extraction efficiency values of nicotinic acid was as follows: rice bran oil > 1-octanol > cyclohexane > mbik > sesame oil. this pattern can be rationalized by two factors that affect extractability, namely the level of na hydration and the energy required by the molecules to bond with water. as a result, oxygenated solvents like mibk extract more effectively than natural and other conventional solvents but are advantageously non-toxic unlike conventional solvents. under equilibrium conditions, the extraction data show that as the concentration of na in the aqueous phase rises, na molecules remain relatively soluble in the organic phase. the extraction results can be related to different physicochemical properties, e.g. dipole moment (dm), dielectric constant (ε), etc., listed in table 4. natural solvents have low relative permittivities (ɛ) and cannot donate a hydrogen bond. since the relative viscosity (μ) and density (ρ) of natural solvents are also high and immiscible in the aqueous phase, their e% values are low and their kd values are less than one. as the initial concentration of na increases, their kd and e% decrease, accounting for the separation caused by the stronger na association with water as naturally occurring solvents contain fatty acids. conventional solvents such as cyclohexane and 1-octanol are nonpolar. as the initial concentration of na increases, kd and e% decrease. the polar protic solvent mibk table 3: separation of nicotinic acid using natural and conventional solvents at 298 ± 1 k solvents [hna]in (mol.l-1) [hna]aq (mol.l-1) [hna]org (mol.l-1) kd e% sesame oil 0.010 0.025 0.050 0.075 0.102 0.009 0.023 0.047 0.071 0.100 0.001 0.002 0.003 0.004 0.002 0.111 0.086 0.063 0.056 0.020 9.99 7.91 5.92 5.30 1.96 rice bran oil 0.010 0.025 0.050 0.075 0.102 0.006 0.018 0.044 0.070 0.101 0.004 0.007 0.006 0.005 0.001 0.666 0.388 0.136 0.071 0.009 40.01 28.01 12.00 6.63 0.98 cyclohexane 0.010 0.025 0.050 0.075 0.102 0.007 0.021 0.043 0.070 0.100 0.003 0.004 0.007 0.005 0.002 0.428 0.190 0.162 0.071 0.020 29.97 16.00 14.00 6.67 1.96 1-octanol 0.010 0.025 0.050 0.075 0.102 0.006 0.020 0.041 0.072 0.100 0.003 0.005 0.009 0.003 0.002 0.639 0.247 0.219 0.041 0.020 39.01 19.60 18.00 4.00 1.96 mibk 0.010 0.025 0.050 0.075 0.102 0.008 0.021 0.040 0.059 0.075 0.002 0.004 0.010 0.016 0.027 0.162 0.190 0.250 0.271 0.360 14.00 15.96 20.00 21.32 26.47 table 4: list of pretreatment physicochemical properties of various solvents used for the extraction of nicotinic acid solvents mw (mol l-1) swater (g l-1) µ (cp) ρ (kg m-3) bp (k) mp (k) ɛ dm ri ref. sesame oil 848.00 immiscible 52.50 914 483 267 3.00 1.474 [22],[23] rice bran oil 867.90 immiscible 58.70 916 540 253 2.14 1.467 [23],[24] cyclohexane 84.16 55.00 (25ºc) 0.98 (20ºc) 0.7781 (20ºc) 354 280 2.02 1.426 [22],[23],[25] mibk 100.16 19.10 0.58 779 390 188 13.11 4.20 1.396 [22],[26],[27] octanol 130.23 0.46 7.36 824 468 257 10.30 1.68 1.429 [22] extraction of nicotinic acid 53(1) pp. 9–15 (2025) 13 contains a hydrogen atom bonded to the (c-o) electronegative group, which serves as a donor of hydrogen bonds. this behavior intensifies as the chargeto-volume ratio of the anion to be solvated rises. the highest kd and e% values are 0.162–0.360 and 14.00– 26.47% using mibk, respectively. given that as the concentration of mibk increases, kd and e% increase, mibk can facilitate lle more stable in the aqueous phase because of its strong polarity as well as high relative permittivity (table 4) and extraction efficiency. as a result of its capacity to create hydrogen bonds, it is a more effective solvent for anions. the experimental results yielded the highest values of the kd of 0.666, 0.639, 0.428 and 0.111 using rice bran oil, 1-octanol, cyclohexane and sesame oil, respectively, at a concentration of 0.01 mol.l-1, while in mibk, 0.360 was recorded at a concentration of 0.102 mol.l-1 of na (figure 4). the distribution coefficient was influenced by the initial concentration of na. as the initial concentration of na increased, kd decreased in all the solvents, while in the case of mibk, kd increased as the initial concentration of na increased. when mibk was used with 0.102 mol l-1 of na, a higher kd was observed. compared to conventional and natural solvents like 1-octanol, cyclohexane, sesame oil and rice bran oil represented in figure 5, mibk exhibits a higher distribution coefficient. due to their high viscosity and density in the aqueous phase, conventional and natural solvents are immiscible and unable to form free hydrogen bonds, moreover, these solvents have low kd values. since the aqueous phase is unable to dissolve the organic phase, the organic and aqueous phases are separated by these solvents, resulting in oils with lower distribution coefficients. as the molecular weight and solubility influence the distribution coefficient, the distribution coefficient of acids rises as molecular weight increases. when using all conventional and natural solvents (except for mibk), the initial concentration of na increased and the extraction efficiency decreased. for mibk, e% rose as the initial concentration of na increased (figure 6). from an experimental study, it was found that a maximum extraction efficiency of 26.47% was reached using mibk, whereas the lowest was 1.96% using sesame oil. although their extraction efficiencies decreased compared to other solvents, the lowest was 1.96% using sesame oil. their extraction efficiencies decreased more than the other solvents because of their long fatty acids and non-polar nature. the absence of a dipole moment in natural solvents prevented them from forming complexes with the acid in the organic phase thanks to free electrons as well as from acting as hydrogen donors in solvents other than 1-octanol and mibk. since the polar solvent mibk is positively charged, its use increased the extraction efficiency compared to when 1-octanol was applied. as a result, it dissolves more readily in the organic phase of nicotinic acid, thereby increasing the extraction efficiency. on the other hand, because of its large hydrophobic group, figure 4: equilibrium data for the extraction of nicotinic acid at 298 ± 1 k with different solvents figure 5: variation in the distribution coefficient against the initial concentrations of nicotinic acid at 298 ± 1 k figure 6: variation in the extraction efficiency against the initial concentration of nicotinic acid at 298 ± k kolhatkar, thakre, shende and wasewar hungarian journal of industry and chemistry 14 1-octanol is a non-polar solvent unlike mibk, limiting mass transfer from the aqueous to the organic phase. the maximum extraction efficiencies were 40.01, 39.01, 29.97 and 9.99% when rice bran oil, 1-octanol, cyclohexane and sesame oil were used, respectively, with 0.01 mol l-1 of na. in the case of mibk, an extraction efficiency of 26.47% was observed when 0.102 mol l-1 of na was used (table 5). since the extraction efficiencies of mibk increased as the initial concentration of na increased, unlike for the natural conventional solvents, mibk can be used with several kinds of extractants, e.g. trioctylamine, tributyl phosphate, aliquat 336, etc., to enhance the effectiveness of na extraction. 5. conclusions the recovery of nicotinic acid from aqueous streams through extraction using natural and conventional nontoxic solvents was investigated. the extraction process was analyzed in terms of extraction efficiency and distribution coefficient, moreover, correlations with the physicochemical characteristics of the solvents were found. higher values of kd and e% were observed using mibk with a large relative permittivity and dipole moment. additionally, some kind of a relationship between the extraction equilibrium parameters and the relative viscosity and density of the solvents was observed, however, no generalizations were made because additional investigations are required. an extraction efficiency in excess of 29.47% was observed using mibk. although natural solvents yielded lower extraction efficiencies (1.96%), they are preferable compared to the toxicity of conventional chemical solvents. more stages can be employed to achieve complete extraction, moreover, reactive extraction may be another alternative to increase extraction efficiencies. symbols mw molecular weight swater solubility in water μ viscosity ρ density bp boiling point mp melting point ε dielectric constant (relative permittivity) dm dipole moment ri refractive index kd distribution coefficient e% extraction efficiency [hna]in initial concentration of nicotinic acid [hna]aq concentration of nicotinic acid in the 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https://doi.org/10.33927/hjic-2022-10 https://doi.org/10.1016/j.cdc.2018.07.001 https://doi.org/10.1016/j.cdc.2021.100790 https://en.wikipedia.org/wiki/rice_bran_oil https://doi.org/10.1016/j.cdc.2021.100823 https://doi.org/10.1016/j.seppur.2018.06.037 https://doi.org/10.33927/hjic-2023-13 hungarian journal of industry and chemistry vol. 48(2) pp. 45–49 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-26 adsorption of nickel ions from petroleum wastewater onto calcined kaolin clay: isotherm, kinetic and thermodynamic studies alexander asanja jock *1, anietie ndarake okon1, uchechukwu herbert offor1, festus thomas2, and edmond okwudilichukwu agbanaje3 1department of chemical and petroleum engineering, university of uyo, pmb 1017, uyo, nigeria 2department of engineering infrastructure, national agency for science and engineering infrastructure (naseni), idu industrial area, pmb 391, garki-abuja, nigeria 3chemical and petroleum technique, department of science laboratory technology, university of jos, pmb 2084, jos, nigeria the removal of nickel ions onto calcined kaolin clay using a batch adsorption technique was conducted. the effect of the adsorbent mass, contact time and temperature on the removal process was investigated. the calcined kaolin clay was characterized using x-ray fluorescence (xrf) and fourier-transform infrared spectroscopy (ftir). the adsorption data was analyzed by isotherm, kinetic and thermodynamic studies. the major chemical components in the clay are alumina (41.14 wt %) and silica (53.16 wt %). ftir showed that the functional groups of aluminium monoxide (al-o) and silicon monoxide (si-o) are present in the clay. the study yielded a removal efficiency of 89.89% for nickel ions at 25 ◦c. the adsorption process appeared to follow a freundlich isotherm and pseudo-second order kinetics were found to be in good agreement with the experimental data. the thermodynamics of the rate processes showed the adsorption of nickel ions to be endothermic and negative values of gibbs free energy indicated the spontaneity of these processes. this proves that calcined kaolin clay is a good material for the removal of nickel ions from the wastewater produced by petroleum refineries. keywords: adsorption, kaolin, nickel, wastewater 1. introduction environmental pollution is an anthropogenic phenomenon and mainly a result of industrialization. the contamination of bodies of water by the indiscriminate disposal of heavy metals has led to serious threats to humans as well as aquatic and living creatures. nickel compounds are highly toxic contaminants and are emitted into the environment from various industries, e.g. mining, metal coatings, batteries, chemical, tanneries, etc., in quantities that pose risks to human health [1]. many wastewater treatment methods have been introduced to control water pollution such as chemical precipitation, ion exchange, electrodialysis, reverse osmosis as well as membrane filtration and adsorption. adsorption is one of the most efficient techniques due to its simplicity and affordability, moreover, it is more feasible even at low concentrations of heavy metal ions [2]. the adsorbent used for the adsorption process is of organic origin, e.g. activated carbon and biosorbents, or mineral origin, e.g. natural zeolite, calcium silicate powder and natural clay *correspondence: alsanja@gmail.com [3]. activated carbon is the most commonly used adsorbent for wastewater treatment but due to it expense, lowcost alternatives such as clay, coal, fly ash, peat, siderite, agricultural wastes and charcoal are being developed. low-cost adsorbents are those that require little processing and are abundant in nature, by-products or waste materials from industry [4]. clay minerals such as kaolinite, montmorillonite, vermiculite and illite are potential adsorbents of heavy metals. they have several economic advantages and intrinsic characteristics, e.g. are readily available, inexpensive, have excellent textural and surface properties, are physically and chemically stable in harsh environments as well as offer a cost-effective alternative to the conventional treatment of wastewater [5]. the aim of this study is to investigate the removal of nickel ions from wastewater produced by petroleum refineries using calcined kaolin clay from alkaleri in north-east nigeria. 2. materials and methods 2.1 beneficiation and calcination of samples 10 kg of raw kaolin clay was crushed and soaked in water for 24 hours. the clay-water mixture was plunged for 3 https://doi.org/10.33927/hjic-2020-26 mailto:alsanja@gmail.com 46 jock, okon, offor, thomas, and agbanaje hours at room temperature. colloidal kaolin clay was separated from the quartz-rich sediment and sieved through a 230 mesh tyler sieve to remove other coarse impurities. the thickened clay was then put in a filter cloth and pressed under hydraulic pressure to squeeze out the water. the cake was dried in an oven at 110 ◦c to constant weight before being pulverized. 100 g of the beneficiated clay was fired gradually in an electric furnace at 650 ◦c for 3 hours before being soaked. the calcined clay adsorbent was cooled, characterized and used for adsorption experiments. 2.2 batch adsorption the wastewater used of a known initial concentration of nickel ions was obtained from the effluent of a petroleum refinery operated by kaduna refining and petrochemicals company. the batch experiments were conducted by varying the adsorbent mass, contact time and temperature as described. the effect of the adsorbent mass was determined at 25 ◦c and 0.5 g of oven-dried calcined kaolin was mixed with 50 ml of wastewater in a 250 ml erlenmeyer flask. the mixture was stirred with a magnetic stirrer at 200 rpm for between 10 and 50 mins. the process was repeated by varying the adsorbent mass in increments of 0.5 g, namely 1.0, 1.5, 2.0 and 2.5 g. the effect of the contact time was analyzed using 0.5 g of adsorbent after 10, 20, 30, 40 and 50 mins. the effect of the temperature was investigated within the range of 25-65 ◦c following a contact time of 30 mins. with adsorbent masses of 0.5 and 2.5 g. the residual ni(ii) ions obtained from the filtrate and determined by atomic absorption spectroscopy (aas) were analyzed to evaluate the percentage removal, adsorption kinetics and thermodynamics. 3. results and discussion 3.1 characterization of the adsorbent chemical composition the chemical composition of the adsorbent is shown in table 1. the main components of the clay are sio2 (53.158 wt %) and al2o3 (41.143 wt %). metallic oxides such as tio2, mgo and fe2o3 are present in small amounts, while traces of cao, cr2o3, zno and mn2o3 are detected. the large amounts of sio2 and al2o3 present define the sample as an aluminosilicate clay. generally speaking, kaolin clay, the chemical formula of which is al2si2o5(oh)4, is principally composed of sio2, al2o3 and water [6]. figure 1: fourier-transform infrared spectrum of calcined kaolin clay fourier-transform infrared spectroscopy fourier transform infrared spectroscopy (ftir) shows the functional groups present in the sample of clay. the ftir spectra of the kaolin clay shown in fig. 1 are within the wavenumber range of 4000 400 cm−1. the spectra depict three major absorption bands, namely silicon dioxide, alumina and hydroxyl groups. the peaks at 1030, 1045 and 1049 cm−1 are assigned to the stretching vibrations of the si–o bond and the peak observed at 922 cm−1 corresponds to the al–al–oh bonds. peaks at 733, 750 and 752 cm−1 indicate the presence of oh resulting from the expulsion of water and hydroxyl groups in clay minerals during calcination [7]. the differences in the peak intensities can be attributed to the interaction of ni(ii) ions with functional groups on the kaolin adsorbent surface [8]. 3.2 adsorption studies effect of adsorbent mass the adsorbent mass plays a vital role in adsorption processes. it determines the percentage removal of metal ions and is calculated by: %ads = ci − cf ci (1) where %ads denotes the amount of ni(ii) ions removed, and ci and cf stand for the initial and final concentrations (ppm) of the ni(ii) ions, respectively. the percentage removal of ni(ii) ions increased from 76.31 to 89.04% when the adsorbent mass was increased from 0.5 to 2.5 g as shown in fig. 2. as the adsorbent mass increases, more adsorption sites of nickel ions become available. effect of contact time on the uptake of nickel ions the adsorption isotherm describes the adsorption pattern between the ni(ii) ions adsorbed on the kaolin clay and table 1: chemical composition of the calcined kaolin sample components sio2 al2o3 tio2 mgo fe2o3 cao cr2o3 zno mn2o3 amount (wt %) 53.158 41.143 3.017 0.442 0.126 0.044 0.018 0.013 0.008 hungarian journal of industry and chemistry adsorption of nickel ions onto calcined kaolin clay 47 figure 2: effect of adsorbent mass on the removal of nickel ion figure 3: effect of contact time on the uptake of nickel ions the residual ions. the equilibrium uptake was determined using: qe = (ci − ce)v m (2) where ce denotes the equilibrium concentration, v stands for the volume of the solution and m represents the adsorbent mass. fig. 3 shows that the uptake of nickel ions is increased by increasing the contact time and reaches a maximum or saturation point after 30 to 40 mins., and thereafter the rate of adsorption remains almost constant even as the contact time and adsorbent mass are further increased. the extent of the adsorption of nickel ions initially increased rapidly and then gradually until an equilibrium was attained. the high removal rate was due to the large surface area initially available for adsorption of ni(ii) ions but the capacity of the adsorbent was gradually exhausted over time since the occupation of the few vacant surface sites that remained was inhibited due to repulsive forces between the solute molecules in the solid and bulk phases [9]. as the adsorption sites on the surface become exhausted, the uptake rate is controlled by the rate at which the nickel ions are transported from the exterior to the interior sites of the adsorbent particles [10]. it was reported that during the adsorption of metal ions, initially the ni(ii) ions reach the boundary layer; then have to diffuse onto the surface of the adsorbent and finally, must diffuse into its porous structure. therefore, this process requires a relatively longer contact time [11]. figure 4: langmuir isotherm for the adsorption of nickel ions figure 5: freundlich isotherm for the adsorption of nickel ions 3.3 equilibrium isotherms the langmuir and freundlich models describe this isotherm: 1 qe = 1 qm + 1 qmbce (3) and log qe = logkf + 1 n log ce, (4) where qe denotes the uptake of ni(ii) ions adsorbed on the clay (mg/g), qm and b stand for the single-layer adsorption capacity (mg/g) and the langmuir equilibrium constant (l/mg), respectively, and kf, n and b represent freundlich adsorption constants. the langmuir and freundlich constants shown in table 2 were determined from the gradients and intercepts using the equations displayed in figs. 4 and 5. the magnitudes of kf and n are 0.2535 (mg/g)(l/mg)1/n and −5.08 l/mg, respectively. the constant, n, is related to the ionic strength with regard to the adsorption of ni(ii) ions and kf is related to both the ionic strength and amount of ni(ii) ions adsorbed. the significance of n is as follows: n < 1 (chemical process); n = 1 (linear process) and n > 1 (physical process). the negative value of n (−5.08 l/mg) obtained is indicative of chemical adsorption [12]. the langmuir constant, b, shows the affinity of binding sites for nickel ions of the adsorbent. similarly, the 48(2) pp. 45–49 (2020) 48 jock, okon, offor, thomas, and agbanaje table 2: parameters of freundlich and langmuir isotherm models freundlich model n (l/mg) kf (mg/g)(l/mg)1/n r2 (%) -5.08 0.2535 98.40 langmuir model qm (mg/g) b (l/mg) r2 (%) 0.2378 -11.5210 94.00 table 3: pseudo-kinetics constants for the adsorption of nickel onto calcined kaolin pseudo-first order kinetics pseudo-second order kinetics k1 = −0.0230 (l/min) k2 = 0.0073 (mg/(mg/min)) qe = 1.127 (mg/g) qe = 5.291 (mg/g) r2 = 0.87 r2 = 0.98 negative value of b (−11.5210 l/mg) suggests a low degree of adsorption of ni(ii) ions by kaolin clay as is shown by the maximum adsorption capacity, qm (0.2378 mg/g). the experimental data fitted well in the freundlich model (r2 = 98.40%) indicating multilayer adsorption on the heterogeneous surface. 3.4 adsorption kinetics the kinetics data were determined using the linear equations of pseudo-first and second order kinetics: log (qe − qt) = log qe − 1 2.303 k1t (5) and t qt = 1 k2q2e + t qe . (6) the parameters of adsorption kinetics are useful to predict the adsorption rate and provide considerable information to design and model the adsorption process as well as evaluate the adsorbent and operation control [13]. figs. 6 and 7 showed pseudo-first and second order kinetics, respectively with regard to the adsorption of ni(ii) ions. the kinetics constants are summarized in table 3. the pseudo-first order kinetics exhibit a higher rate constant (k1) and lower uptake (qe). according to the values of r2 in table 3, it is clear that pseudo-second order kinetics fitted better to the adsorption data. this suggests the adsorption process is controlled by a chemisorption mechanism and the rate-limiting step is probably the surface adsorption of nickel ions [5]. 3.5 adsorption thermodynamics the effect of temperature on the adsorption of nickel ions was investigated between 25 and 65 ◦c. the thermodynamic parameters determined from equations kc = qe ce (7) figure 6: pseudo-first order kinetics for the adsorption of nickel ions onto calcined kaolin clay figure 7: pseudo-second order kinetics for the adsorption of nickel ions onto calcined kaolin clay ∆g◦ = −rt lnkc (8) lnkc = −∆h◦ rt + ∆s◦ r (9) ∆g◦ = ∆h◦ − t∆s◦ (10) include changes in gibbs free energy (∆g◦), enthalpy (∆h◦) and entropy (∆s◦). fig. 8 depicts the van’t hoff plots used to evaluate the thermodynamic parameters summarized in table 4. the negative values of ∆g◦ confirm that the adsorption process is feasible and spontaneous while the positive values of ∆h◦ show that the adsorption process of ni(ii) ions is endothermic. ∆h◦ can indicate the type of adsorption process involved. if ∆h◦ of the adsorbent exceeds 40 or is less than 20 kj/mol, chemisorption or adsorption that is physical in nature occurs, respectively [8]. the positive values of ∆h◦ and ∆s◦ obtained show that the adsorption process is physical in nature and the solid-aqueous solution interface becomes more irregular and random during the adsorption of ni(ii) ions by the calcined kaolin adsorbent. 4. conclusions thermally activated kaolin clay as an adsorbent was successfully prepared by calcination and used to remove hungarian journal of industry and chemistry adsorption of nickel ions onto calcined kaolin clay 49 figure 8: effect of temperature with regard to the adsorption of nickel (ii) ions on calcined kaolin table 4: thermodynamic parameters for the adsorption of nickel (ii) ions onto calcined kaolin at 25 ◦c adsorbent mass (g) ∆g◦ (j/mol) ∆s◦ (j/mol k) ∆h◦(j/mol) r2 0.5 -875.26 62.27 17600.74 0.979 2.5 -2553.22 111.07 30545.64 0.951 nickel ions from wastewater produced by a petroleum refinery. adsorption isotherms, kinetics and thermodynamics were also studied. it was discovered that the adsorbent mass, contact time and temperature significantly influenced the adsorption of nickel ions onto the calcined kaolin adsorbent. the removal efficiency was increased by increasing the adsorbent mass, contact time and 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https://doi.org/10.1016/j.ijbiomac.2020.07.032 https://doi.org/10.1016/j.ijbiomac.2020.07.032 https://doi.org/10.1155/2013/961671 introduction materials and methods beneficiation and calcination of samples batch adsorption results and discussion characterization of the adsorbent chemical composition fourier-transform infrared spectroscopy adsorption studies effect of adsorbent mass effect of contact time on the uptake of nickel ions equilibrium isotherms adsorption kinetics adsorption thermodynamics conclusions hungarian journal of industry and chemistry vol. 49(1) pp. 47–58 (2021) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2021-07 development of compartment models for diagnostic purposes bálint levente tarcsay*1, ágnes bárkányi1, tibor chován1, and sándor németh1 1research centre for biochemical, environmental and chemical engineering, university of pannonia, egyetem u. 10, veszprém, 8200, hungary the importance of recognizing the presence of process faults and resolving these faults is continuously increasing parallel to the development of industrial processes. fault detection methods which are both robust and sensitive help to recognize the presence of faults in time to avoid malfunctions, financial loss, environmental damage or loss of human life. in the literature, the use of various model-based fault detection methods has gained a considerable degree of popularity. methods usually based on black-box models, data-based techniques or models using symbolic logic, e.g. expert systems, have become widespread. white-box models, on the other hand, have been applied less despite their considerable robustness because of multiple reasons. firstly, their complexity and the relatively vast amount of technological and modelling knowledge needed to construct them for industrial systems. secondly, their large computational demand which makes them less suitable for online fault detection. in this study, the aim was to resolve these problems by developing a method to simplify the complex computational fluid dynamics models employed to describe the equipment used in the chemical industry into less complex model structures. these simpler structures are compartment models, a type of white-box model which breaks down a complex system into smaller units with idealized behaviour. in the case of a small number of compartments, the computational load of such models is not significant, therefore, they can be employed for the purposes of online fault detection while providing an accurate representation of the system. for the purpose of identifying the compartmental structure, fuzzy logic was employed to create a model which approximates the real behaviour of the system as accurately as possible. our future objective is to explore the possibility of combining this model with various diagnostic methods (expert systems, bayesian networks, parity relations, etc.) and derive robust tools for the purpose of fault detection. keywords: compartment model, computational fluid dynamics, expert system, fuzzy logic 1. introduction fault detection and isolation has become a cardinal problem in industrial practices. as the intricacy of technological processes increases, the probability of faults arising also grows. however, due to the stricter demands for environmentally friendly and profitable technologies, the presence of faults which could potentially cause financial loss, environmental hazards or loss of life cannot be tolerated. faults such as those defined by venkatasubramanian et al. [1] describe the consequences when an observed process variable deviates from its expected value. the source of such process faults is known as a root cause. naturally, if left unmanaged, faults can propagate and lead to serious disasters, e.g., the bhopal disaster or the texas city refinery explosion [2, 3]. to circumvent such occurrences, modern knowledge-based fault detection techniques have become commonplace. these methods use the same common principle for fault detection. firstly, some knowledge is used to cre*correspondence: tarcsayb@fmt.uni-pannon.hu ate a model of the system under normal operating conditions. then the actual operation of the system is observed and, if the behaviour of the system does not match the assumptions drawn from the model, then an abnormality is present [4]. after identifying the presence of an abnormality, various approaches using different techniques trace the fault signature back to the root cause depending on the type of knowledge used to create the system model. therefore, it is possible to differentiate between knowledge that originates from quantitative as well as qualitative models and that from relations based on process history [1, 5, 6]. the aforementioned categorization of knowledge used for fault detection methods stems from the early works of venkatasubramanian [1] and is arbitrary. the expectations of fault detection and isolation methods are that they should be robust, sensitive and accurate. robust, in this sense, means that the method should work reliably, even in the presence of noise, disturbances and changes in operating conditions. sensitive and accurate means that the method should even be able to recognize small prohttps://doi.org/10.33927/hjic-2021-07 mailto:tarcsayb@fmt.uni-pannon.hu 48 tarcsay, bárkányi, chován, and németh cess faults and reliably identify their root causes. usually, the bigger issue with most fault detection methods is their robustness. commonly used models for the purposes of fault detection, e.g., a posteriori models, neural networks and statistical methods, all employ arbitrary relationships between system variables which only hold true in a certain operating regime [4]. if the system itself or the operating point changes, these models often become unreliable. therefore, they lack both robustness and flexibility. among quantitative models used for fault detection, another type of model, the a priori or white-box model, is listed. this modelling technique uses the laws of physics, chemistry or any applicable scientific discipline to describe the behaviour of various systems. since the laws of nature cannot be violated, these models are incredibly robust and hold true for a system regardless of its operating point. the problem is that these models are complex and difficult to create for industrial systems since they require a vast amount of technological and modelling knowledge. additionally, they often require a significant computational load to be solved that renders them impractical for the purposes of online fault detection [1]. this is why they have not garnered widespread use in the field of diagnostic procedures. over the course of this work, our goal was to propose a method for simplifying the complex computational fluid dynamics (cfd) of white-box modelling techniques to describe the behaviour of units used in the chemical industry. cfd methods have become widespread over the last few decades for the purpose of solving the material and energy balance equations of complex systems to describe transport phenomena as well as evaluate flow patterns, velocity fields and mixing in fluid systems. these numerical methods involve the discretization of the differential equations that describe the behaviour of the unit as well as solving them through direct or iterative computation methods [7]. an alternative to these methods is the use of compartment models (cm). cms emulate the behaviour of complex systems by identifying individual elements of the system that can be approximated using idealized models [8]. in the case of chemical technologies, the flow and transport phenomena in a system can be approximated by breaking down the system into compartments that exhibit idealized flow behaviour. cms have become widespread in pharmacokinetic experiments to simulate drug transport in biological systems as well as during the evaluation and modelling of bioreactors and chemical systems. savic et al. [9] used a transit cm in pharmacokinetic studies involving the absorption of four different substances. they compared the results to those of a lag time model and concluded that the proposed cm produced a significantly better match to the observed experimental data and can be used as an alternative to the lag time model. pigou and morchain [10] employed a cm combined with a population balance model and metabolic model to estimate the behaviour of a microbial population within industrial bioreactors. their approach was validated by applying it to a bioreactor containing the escherichia coli. species using experimental data. spann et al. [11] created a risk assessment methodology for the cultivation of lactic acid bacteria based on a cm. they combined a cm with a biochemical model to monitor the species streptococcus thermophilus online. using monte carlo methods, they evaluated the risk of the biomass size not achieving its desired extent under the operating conditions of the system with regard to uncertainties in the production process. kaur et al. [12] developed a model for the simulation of a top spray fluidized bed granulator. in their work, they defined two compartments within the system, a “wet” compartment in which aggregation of the particles is dominant and a “dry” compartment in which the breaking up of the particles is mainly observed. by combining the flow model with a population balance model, they managed to observe the effects of operational parameters on the particle size distribution of the granulated product. the examples show that the cm is a contemporary and popular approach to system modelling. the main question, however, when developing a cm is how to select the appropriate number and characteristics of as well as connections between compartments to obtain a model that accurately represents the flow patterns of the real system. the cm usually employs two types of idealized compartments to approximate a velocity field in a system. these are compartments which are assumed to be perfectly stirred and homogeneous (continuous stirred tank reactor (cstr) model) or compartments exhibiting turbulent plug flow (plug flow reactor (pfr) model). these compartments are linked through mixer (m) and distributor (d) models [13]. these latter units are usually only of mathematical significance and their volume is assumed to be zero. the component balance model for the units is showcased in the following equations. for unit cstr: dccstr (t) dt = fin vcstr (cin (t)− ccstr (t)) (1) fcstr = fin (2) for unit pfr: ∂cpfr (t, x) ∂t = −vpfr ∂cpfr (t, x) ∂x (3) fpfr = fin (4) for unit m: cm = ∑nin i=1 cin,ifin,i∑nin i=1 fin,i (5) fm = nin∑ i=1 fin,i (6) hungarian journal of industry and chemistry development of compartment models for diagnostic purposes 49 figure 1: step responses of ideal flow models [14] for unit d: ~cd = ~αcin (7) ~fd = ~αfin (8) the volumetric flow rate (f ) entering and exiting the units is also provided by assuming a constant temperature and dilute solutions. the models establish relationships between the volume of the unit (v ), the inlet velocity (v) and the inlet as well as actual concentrations in each idealized unit (c). the concentration is introduced as a function of time (t) and/or cartesian coordinates (x). in the case of the distributor unit, the outlet concentration and flow rate depend on the division rate (α). the idealized cstr and pfr models exhibit characteristic responses to known input signals such as the heaviside step function (h) or the dirac delta function (δ). the step response (c) of the ideal flow models as well as the serial combination of cstr units in the tanks in series (tis) model are shown in fig.1. the response functions can be used to characterize the residence time distribution (rtd) of a chemical species within the system [14]. therefore, a popular identification method is to obtain the step response of the system and use the rtd function as a basis for identifying the structure of a compartment and the connections between the various compartments. claudel et al. [15] employed the discipline of possibility theory to provide a method for estimating the structure of a compartment in a unit based on the rtd of the unit and the physical description of the system. they introduced “possibility” and “necessity” rules as well as weighing factors for these rules to assess the rtd function. they summarized the results of the rules to propose the structure of a compartment based on the characteristics of the rtd function. egedy et al. [13] used a qualitative approach to identify the structures of compartments in various systems. their developed algorithm utilized qualitative indicators of the rtd function in an identification algorithm to propose and filter out various cm structures based on their fitness. approaches which use the cfd model as a basis for the estimation of the cm structure have also become popular in recent studies. delafosse et al. [16] utilized cfd methods to create a cm structure for approximating the flow characteristics of a bioreactor. fogarasi et al. [17] developed the cm of a copper leaching reactor based on experimental and cfd results. using the cm, they optimized the operational parameters of the leaching reactor. nauha et al. [18] used a hybrid cfd/cm approach to investigate industrial bioreactors and predict the effects of equipment scale-up on mixing properties within the unit. weber et al. [19] investigated the use of a hybrid cfdbased cm model for analysing a multiphase loop-reactor. they used the cm model to estimate the mass transfer and drop size distribution within the liquid-liquid extraction part of the loop reactor. while all of these publications contained significant contributions towards the development of the cfd/cm hybrid model approach, they mostly suffer from the fact that the compartmentalization was conducted manually. algorithms to automatize the identification of cm structures from cfd have been proposed before. bezzo et al. [8, 20] used spatial partitioning in their works to develop an algorithm that is capable of aggregating volumes in a unit into compartments and estimating the cross flow between the compartments based on cfd results. tajsoleiman et al. [21] utilized a similar methodology for the classification of zones within a bioreactor that, based on cfd results, yielded distinctive flow patterns and clustered the results into a cm. nørregaard et al. [22] developed an algorithm to identify cm structures based on cfd results by using hypothesis-driven logic. they evaluated circumferential, axial and radial bulk flows at different locations within a continuous stirred tank reactor. using the obtained flow profile, they developed the cm model which resulted in a structure with 56 compartments. over the course of this work, the goal was to develop an algorithm capable of identifying the cm structure of a system based on results obtained from cfd methods. the algorithm utilizes two steps to first identify the cm structure and then the flow rates between the individual compartments. expectations for the algorithm were • production of compartments that accurately correspond to the investigated volumes of the physical system • a small number of compartments to make the cm practical for online computations • possibility to integrate empirical knowledge about the system into the compartmentalization process in future works, the possibility of using the acquired cm as a basis for a fault diagnostic system will be explored. 2. modelling concept the proposed algorithm uses cfd results concerning the velocity field within a unit as a basis for identifying the structure of cms. after partitioning the unit into numerous smaller cells, the algorithm utilizes fuzzy logic to evaluate the local velocity field within the cells and categorize them into one of the idealized models. adjacent 49(1) pp. 47–58 (2021) 50 tarcsay, bárkányi, chován, and németh figure 2: the proposed algorithm cells that exhibit similar flow behaviour are agglomerated to form compartments showing idealized behaviour. the flow rate between the individual compartments is estimated through optimization. the chart of the proposed algorithm is displayed in fig. 2. to summarize the procedure, the compartmentalization process is conducted over six steps. 1. calculation of a reliable steady state estimate for the velocity field of the system in question using cfd methods. 2. definition of elementary cells (ec) by dividing the investigated volume. 3. evaluating the flow characteristics in the individual ecs through fuzzy logic and identifying them as cstr, pfr or dead volumes. 4. agglomerating adjacent ecs that exhibit similar flow characteristics into compartments. 5. defining possible connections between compartments based on the physical geometry of the system. 6. estimating flow rates between linked compartments through an optimization based on the step response function of the system. the steps of the proposed method and the results derived from it will be presented in a model system derived from the applications library of a commercial cfd simulator (comsol multiphysics version 5.2a). the top and side views of the system are shown in fig. 3 with its characteristic dimensions. to complete the first step of the algorithm, the cfd model of the unit was developed. the system was the model of a wastewater treatment reactor which originally consisted of four baffles, two of which were removed. to model the system, the fluid within the unit was assumed to exhibit the same properties as water. to investigate the behaviour of the system, the steady-state velocity field of the unit as well as the step response function of the system to an inert tracer were necessary. to obtain these characteristics, the mass, impulse and component mass balance equations of the system have been solved numerically. the impulse balance of the system was solved assuming incompressible turbulent flow figure 3: top and side views of the investigated system (remin ≈ 2 · 105 for the flow at the maximum diameter) within the unit using the k− ε turbulence model. the form of the reynolds-averaged navier-stokes equations under these flow conditions is summarized in ρ (~v∇)~v = ∇ [ −p~i + (µ+ µt ) ( ∇ (~v) + (∇~v)t )] +f (9) ρ∇~v = 0 (10) ρ (∇~v) k = ∇ [( µ+ µt σk ) ∇k ] + pk − ρε (11) ρ (∇~v) ε = ∇ [( µ+ µt σε ) ∇ε ] + cε,1 ε k pk − cε,2 ε2 k (12) µt = ρcµ k2 ε (13) pk = µt [ ∇~v ( ∇~v +∇~vt )−1 ] (14) the component mass balance and the step response function were calculated assuming that the velocity field within the unit had reached its steady state. no reactions were considered within the system and the change in the tracer concentration was attributed to convection and diffusion. the tracer was assumed to have the same physical properties as the water within the tank. under these assumptions, the component mass balance within the unit can be expressed using the partial differential equation ∂c ∂t = −~v∇c−∇ (−d∇c) (15) to solve the balance equations within the unit, a computational mesh was refined by taking into account both the computation time and accuracy of calculations, which was checked by calculating the relative mass balance error within the unit using emass = ( ∑nsim i=0 ain~vin,iρin − ∑nsim i=0 aout~vout,iρout) 2 max ( ∑nsim i=0 ain~vin,iρin; ∑nsim i=0 aout~vout,iρout) (16) hungarian journal of industry and chemistry development of compartment models for diagnostic purposes 51 table 1: parameters of the mesh cell type tetrahedral minimal size (mm) 23.1 maximal size (mm) 77.4 emass 5 · 10−4 table 2: operating conditions of the unit t (◦c) 20 component water vin ( ms−1 ) 0.1 pout(bar) 1 cin ( molm−3 ) 2 the mesh was defined with a construction that allows for both an effectively short computation time and adequate degree of accuracy. the parameters of the mesh are shown in table 1. the steady-state velocity field and step response of the unit were calculated under the operating conditions listed in table 2. after testing different numerical methods, it was found that in the case of the steady-state impulse balance calculations, the generalized minimal residuals iterative algorithm was optimal for computations both with regard to computation time and computational accuracy. in the case of the component mass balance, by taking the same aspects into consideration, the conjugate gradient iterative method was utilized. after solving the impulse balance of the unit under the previously displayed conditions, the streamlined steady-state velocity profile could be observed in fig. 4. the streamlines were defined using the internal option of comsol, while their densities were set proportional to the local velocity field within an observed volume. the figure shows that after the fluid enters the unit (on the left-hand side), various zones with different flow characteristics emerge due to the baffles. the flow entering the unit is at first unidirectional with pfr tendencies. the first baffle breaks this flow profile and creates a secluded area within which a well-mixed, circular, vortex-like flow could be observed. on the opposite side of the first baffle, a volume where small-scale mixing occurred could be observed. by following the main path of the flow, the area between the two baffles was a mixed regime with the presence of a significant dead volume. the area obstructed by the second baffle also showed dead volume tendencies. the flow above the second baffle assumed a tendency that was on the verge of being mixed and pfrlike with a clear pfr tendency dominating near the outlet. during the proposed method, the velocity field was converted into a vector field which is shown in fig. 5. the vectors on the chart represent the tangents of the velocity streamlines within the unit. their density, length and direction, as with the streamlines, was set to be proportional to the local magnitude and direction of the velocity figure 4: steady-state streamlines within the unit ( ms−1 ) figure 5: steady-state velocity vector field within the unit field within the reactor. the step function used to test the system and the response function of the unit are shown in fig. 6. during the solution of the component mass balance equation diffusion coefficient d = 10−4 m2 s−1 was used. based on the step response, the unit exhibited behaviour similar to a mixed cstr unit combined with a pfr unit. the time delay between the step and response functions (0.05 h) is indicative of pfr behaviour within the system, while the curvature of the response shows cstr tendencies. irregularities and jumps within the response, as can be seen at approximately 0.08 h, might be due to internal circulation flows and backflow within the unit. figure 6: step and response functions of the unit 49(1) pp. 47–58 (2021) 52 tarcsay, bárkányi, chován, and németh 3. modelling results once the cfd results had been acquired, the results were processed using matlab r2020b. the geometry of the system was partitioned into ec units. over the course of this investigation, the total volume of the tank reactor (4.96 m3) was broken down into 25 rectangular ecs of equal volumes (0.2 m3) and sizes in accordance with step 2 of the proposed algorithm (fig. 2). investigations using different numbers of ecs were conducted and it was concluded that the most accurate results can be achieved by using a number of ecs where the size of the individual cells is approximately the same as that of the cells used in the cfd simulation. after the partitioning, the vectors characterizing the velocity field displayed in fig.5 were observed within the ecs. since the magnitude, direction and density of the vectors are all based on the attributes of the local velocity field within the tank, key observations can be derived from them about the local flow characteristics within the unit. the following general rules were established: 1. in areas where the flow exhibits pfr characteristics, the velocity vectors are mostly unidirectional with little variance in their magnitude. the magnitude of the velocity vectors is relatively large compared to the magnitude of the inlet velocity. 2. in areas where circular flow is present that exhibits cstr characteristics, the variance with regard to the directional components of the velocity vectors is higher. the magnitude of the velocity vectors in these areas vary but are comparable to the magnitude of the inlet velocity. 3. in areas where little to no flow is present, also referred to as dead volumes, the magnitude of the velocity vectors is negligible compared to that of the inlet velocity. based on these rules, the flow characteristics within a certain volume of the system can be approximately categorized. therefore, the velocity vectors within the individual ecs were observed and classified based on their flow characteristics. to achieve this, three measures were introduced. the average velocity within a cell (v1), the variance in the directional components of the velocity vectors within a cell (v2) and the skewness (v3) with regard to the distribution of velocity vectors within a cell. to calculate the mean velocity within the cells, the total of the velocity vectors was calculated and averaged. then the magnitude of the averaged vector was computed from v1 = ∣∣∣∣∑n~v i=1 ~vi (x, y, z) n~v ∣∣∣∣ (17) the variance and skewness were calculated using similar approaches. since the coordinates determine the directions, ecs that exhibit pfr behaviour where vectors are unidirectional will have a high mean velocity, while those that contain circular flow with varying vector directions will generally have lower mean velocities. however, the variance will increase within ecs that exhibit strong circular flow with velocity vectors pointing in various directions. dead volumes have exceptionally low mean velocities. in the case of all three variables, their numerical values were evaluated in the individual ecs. to properly compare these parameters, the numerical value of each variable within an ec was compared to its maximum value within the investigated system from ui = vi max (vi) (18) therefore, for each variable, a quantity was produced that determines its fractional value compared to its maximum value within the unit. the values of the three parameters within the system can be seen in fig. 7. fig. 7 shows that the indicated variables can be used to differentiate between the flow behaviour of the unit based on the preliminary rules. the figure also explains the need for the inclusion of the skewness of the velocity distribution. given that in the area adjacent to the first baffle, the flow velocity was rather high, the variance in the magnitude and direction of the velocity vectors in that area was exceptionally high. compared to this value, most values of variance within the system were minuscule, except near the outlet where the circular flow met the plug-like flow exiting the reactor. the skewness parameter describes the asymmetry of a given distribution function. in areas with strong circular flow patterns, the directions of the velocity vectors are more evenly distributed on both sides of the mean velocity value, resulting in a more symmetric distribution of the velocity vector direction and lower skewness. however, in areas that exhibit plug flow-like behaviour, the distribution is generally more skewed due to the mostly unidirectional velocity vectors. after obtaining the three quantities used to characterize the flow, their values within the individual ecs were evaluated in accordance with the previously defined rules to obtain the idealized ec structure mentioned in step 3 of the algorithm (fig. 2). during this process, the pfr, cstr and dead volume characteristics of all the individual ecs were examined by converting the established rules using traditional fuzzy logic [23]. fuzzy expert systems utilize empirical knowledge from subject-matter experts to characterize and analyze processes [24]. they contain a working memory, inputs, a collection of rules and outputs. the working memory is the culmination of objects oi, where o denotes the set of all objects. objects consist of a fuzzy vector (~vi) where all members of the vector are fuzzy sets or fuzzy numbers( ~vi,1, ~vi,2, ..., ~vi,n ) . these fuzzy sets describe qualitative information about the objects, which in this case were each of the individual ecs. the inputs of the fuzzy expert system were the variables ui, which were used to describe the flow characteristics within an individual ec. hungarian journal of industry and chemistry development of compartment models for diagnostic purposes 53 figure 7: characteristic velocity variables within the system a set of rules (r) was established, which in this case pertains to the flow characteristics within the unit. a fuzzy subset of r denoted as r with the membership function finput provides finput (r), which symbolizes the level of belief in r for each subset [25]. the degree of belief is a number between 0 and 1 with 0 and 1 denoting disbelief and wholehearted belief in the proposed statement, respectively. the rules are obtained in the form of “if-then” rules with logical operators like “or”, “and”, etc. in the case of our system, the real number inputs ui were converted into fuzzy numbers using monotonic sigmoidal membership functions, their general form is presented finput,j (ui) = 1 1 + e − ( ui−b a ) (19) finput,j (ui) = 1− 1 1 + e − ( ui−b a ) (20) for fuzzy numbers with index j generated from input i. the first equation is used for membership functions which are increasing in tendency, while the latter is for membership functions which are decreasing. parameters a and b define the spread of the fuzzy numbers either side of their central value and the central values of the fuzzy numbers, respectively. the fuzzy numbers obtained through the membership functions represent the linguistic variables p belonging to the set of basic linguistic variables p. in our case, these linguistic variables consisted of the set p1 = {high, low} which was used to describe whether the mean value, variance and skewness of velocity vectors within an ec were high or low compared to the maximum value of the respective attribute within the system. the output actions define a fuzzy set of conclusions. the set g represents the set of possible conclusions of the expert system. a subset of this set represents the outtable 3: parameters of the fuzzy membership functions finput a b foutput a b input1,low 0.01 0.05 outputlow 0.02 0.4 input2,low 0.01 0.05 input3,low 0.02 0.1 input1,high 0.03 0.2 outputhigh 0.02 0.6 input2,high 0.02 0.2 input3,high 0.03 0.3 puts of our object, which in our case meant the characteristics of the pfr, cstr and dead volume of individual ecs [25]. given that the linguistic variables p2 = {high, low} are represented by membership function foutput,j for each characteristic, the membership functions are monotonic and sigmoidal like the input membership functions as shown in foutput,j (finput,j (r)) = 1 1 + e − ( finput,j(r)−b a ) (21) foutput,j (finput,j (r)) = 1− 1 1 + e − ( finput,j(r)−b a ) (22) in this equation, finput,j (r) represents the degree of belief in r for each subset. after defuzzification, the expert system returned crisp values that determined the pfr, cstr and dead-volume characteristics within each ec. the input and output membership functions can be observed in fig. 8 and fig. 9, respectively. since the output membership functions in the case of all three outputs were identical, they have only been displayed once. the first index within the legend represents the input which the membership function belongs to, while the second one corresponds to the linguistic subsets (1→ low, 2→ high) [25]. figure 8: input membership functions 49(1) pp. 47–58 (2021) 54 tarcsay, bárkányi, chován, and németh figure 9: output membership functions figure 10: flow characteristics of the different ec units the parameters a and b of the membership functions are displayed in table 3. using the expert system, the flow characteristics of the ecs were characterized. the pfr (y1), cstr (y2) and dead volume (y3) characteristics within the ecs are shown in fig. 10. to achieve a flow map that describes the behaviour of the velocity field within each unit, the three characteristics were unified. the weighted average of the three output characteristics was computed and a function defined by im (l) ∈ [0, 2] where l (y1, y2) = 0 corresponds to the pure dead-volume behaviour, l (y1, y2) = 1 denotes the pure cstr behaviour and l (y1, y2) = 2 stands for the pure pfr behaviour. l (y1, y2) in each individual ec was calculated from l (y1, y2) = 2 · y1 + y2 3 . (23) since the weighting factor of the dead-volume behaviour is 0, it was not included in the equation. the results of the process are shown in fig. 11. the correlation between fig. 4 and fig. 11 is apparent. the model predicts clear pfr behaviour within the flow near the inlet and outlet which can also be observed from fig. 4. the area beyond the inlet and bounded by the first baffle showed cstr tendencies with some pfr behaviour near the walls. a dead volume could be observed at the centre of the stirred volume which was similar to in the middle of the vortex seen in fig. 4. the area opposite the volume bounded by the first baffle exhibited deadvolume tendencies with a low velocity and occasional circular flow patterns, indicative of slight cstr behaviour. the area between the two baffles showed mixed, cstr figure 11: characteristic flow behaviour within the unit tendencies with a noticeable dead volume present in the middle of the vortex, as can be seen in fig. 4. the area bounded by the second baffle mainly exhibited deadvolume tendencies with a medium degree of circulation. the volume opposite it consisted of a mixed flow. the flow near the outlet, as noted before, exhibited pfr tendencies. the figure presents an approximately accurate description of the flow characteristics when compared to the streamlines obtained from the cfd methods. however, due to fuzzification and the weighted average calculations to ascertain the flow tendencies within the unit, individual flow characteristics of the ecs are unclear. to clarify these values, limits were introduced to clearly categorize the flow behaviour of all ecs, which were calculated according to eq. 24. the limits for this clustering process were determined by observing flow patterns obtained using various limits. it was found that these limits facilitated the most efficient clustering and resulted in a cluster which strongly resembled the flow characteristics observed in the cfd results. ldisc(y1, y2) =  2, if l(y1, y2) > 1.25 1, if 1.25 ≥ l(y1, y2) ≥ 0.75 0, otherwise (24) this equation shows that the values of the corrected function are discrete, that is, the ecs are categorized into three idealized classes of flow depending on which pure idealized class their behaviour most resembles. the plot displaying the flowchart with ecs containing the corrected values is shown in fig. 12. the figure also indicates the locations of the inlet, outlet and baffles. since a rectangular mesh was used to divide the system into ecs, the locations that were not part of the geometry and the baffles were also included in the calculations. since no flow was present at these locations, they have been categorized as clear dead volumes, which can be seen by comparing fig. 11 and fig. 12. for the sake of clarity, these areas were removed from the corrected fighungarian journal of industry and chemistry development of compartment models for diagnostic purposes 55 figure 12: recognized flow behaviour within the ecs figure 13: defined compartments within the system ure. fig. 12 shows a clear map indicating the idealized flow behaviour of individual ecs within the unit. once agglomerated, adjacent ecs that exhibited similar characteristics could be grouped to form compartments of idealized behaviour in accordance with step 4 of the proposed algorithm (fig. 2). the agglomeration of the ecs within this paper was conducted manually. the resulting set of compartments is shown in fig. 13. the unit was partitioned into seven compartments, namely two pfr regions, two cstr regions and three dead volumes. the volumes of the compartments were evaluated by totalling the volumes of the individual ecs which were assigned as part of the compartment in question. it can be seen that the resulting structure of the compartment strongly resembles the results obtained through cfd methods seen in fig. 4. based on the defined structure, a cm consisting of the compartments that exhibited idealized behaviour was constructed to complete step 5 of the algorithm (fig. 2). the cm structure is displayed figure 14: estimated cm structure in fig. 14. the constructed cm structure contains the previously identified compartments seen in fig. 13. connections between the different compartments were established through the use of theoretical mixer and divider units. during the evaluation of the possible connections between compartments, the geometry of the system was taken into account as well, e.g., the placement of baffles, positions of adjacent compartments, etc. the models of the individual compartments, mixers and dividers were formulated according to the equations provided in the introduction. after obtaining the cm structure, step 6 of the identification algorithm (fig. 2) involved estimating the flow rates between compartments. in the case of the structure shown in fig.14, the flow rates between compartments were defined through the division rates (αi) of the d units. these values describe the ratio of mass flow entering the ith adjacent compartment compared to the total mass flow leaving the jth reference compartment. for the identification of the αi values optimization was conducted in matlab r2020b through the simulink interface. the constructed cm structure was defined in simulink along with its connections and individual compartments. the system of differential and algebraic equations describing the behaviour of the system were solved numerically using rosenbrock methods for solving stiff differential equations. the step response of the cm was observed as a function of the αi values and an objective function was formulated to estimate the α values displayed in ec(~α) = ∑nsim i=1 (ccfd,i − ccm,i) 2 max ( ∑nsim i=1 ccfd,i; ∑nsim i=1 ccm,i) (25) the objective function estimates the squared difference between the step response function acquired through cfd methods and the cm over the observed discretetime horizon relative to the maxima of the sum of the two functions. to minimize the objective function with regard to the αi values, the interior-point method was utilized. the step response function of the system obtained through cfd methods and the optimized cm can be seen in fig. 15. the resulting figure shows that the step response of the cm after optimization fits the step response of the system obtained through cfd methods well with an aver49(1) pp. 47–58 (2021) 56 tarcsay, bárkányi, chován, and németh figure 15: step response of the system with cfd methods and cm table 4: optimized α parameters α1 0.7 α6 0 α2 0.25 α7 1 α3 0.05 α8 0 α4 0.8 α9 0.95 α5 0.2 α10 0.05 age fit of 92%. the optimized model parameters rounded up to two decimal places are presented in table 4. the estimated parameters in table 4 are also in line with the general cm structure. it should be noted that the optimized α parameters of flows entering dead volumes (α3, α6, α8, α10) were exceptionally low, moreover, sometimes not even detectable when rounded up to two decimal places. this indicates that the step response of the system is most similar to the response obtained through cfd methods if almost no flow enters the listed volumes, indicating that they are truly dead volumes from a flow perspective. 4. conclusions over the course of this study, the process of creating cms from results obtained through cfd simulations has been presented. the proposed algorithm consisted of two phases. in the first phase, the cm structure of the object was defined. for these investigations, the steady-state velocity field of the system was utilized. the system was partitioned into ecs in which the local velocity field was investigated. by analyzing the direction and magnitude of local velocity vectors within the ecs using fuzzy logic, a set of rules was established to categorize the behaviour of individual ecs and correlate these ecs to units exhibiting idealized behaviour. to characterize the flow behaviour, three measures were defined based on the distribution of the magnitude and direction of velocity vectors within individual ecs. three types of ecs were considered, ones in which the flow is well-mixed and circular, similar to a cstr, ones in which the flow is unidirectional and resembles that found in a pfr, and ones in which little to no flow is present, that is, dead-volume behaviour is exhibited. after the qualitative analysis using fuzzy logic, each ec was assigned an idealized trait. adjacent ecs that exhibited similar traits were clustered into compartments showing idealized behaviour. after determining the idealized compartments, the flow rates between these compartments were estimated through optimization by calculating the flow rates for which the sum of the squared difference between the step response of the cfd model and cm was minimal. the estimated parameters and the observed compartments showed a strong correlation with the flow patterns which could be observed within the cfd results. the method is capable of effectively analyzing cfd results and converting them into cms in a structured framework while also allowing the addition of empirical knowledge using fuzzy logic. the proposed method could serve as a basis for the estimation of robust and computationally inexpensive a priori models to describe equipment utilized within the chemical industry. the physical correlation between the model compartments and the actual flow regimes within the unit could provide opportunities to develop a priori model-based diagnostic strategies for online fault detection among many other applications. 5. acknowledgements this work was supported by the tkp2020-ika-07 project financed under the 2020-4.1.1-tkp2020 thematic excellence programme by the national research, development and innovation fund of hungary. nomenclature fuzzy sets ~v set of fuzzy vectors/numbers g set of possible fuzzy conclusions o set of fuzzy objects p set of linguistic fuzzy variables r set of fuzzy rules greek letters α distribution ratio [−] ε turbulent dissipation rate [m2 s−3] µ kinematic viscosity [m2 s−1] µt turbulent viscosity [kgm−1 s−1] ρ density [kgm−3] σε constant for change in ε [−] σk constant for change in k [−] τ residence time [h] latin letters ~f force [n] hungarian journal of industry and chemistry development of compartment models for diagnostic purposes 57 ~i impulse [kgm s−1] ~v velocity [m s−1] a surface [m2] a fuzzy membership function central value [−] b fuzzy membership function variance [−] c step response function [molm−3] c species concentration [molm−3] cε,1 dissipation rate calculation constant 1 [−] cε,2 dissipation rate calculation constant 2 [−] cµ turbulent viscosity calculation constant [−] d diffusion rate [m2 s−1] e error function [−] f flow rate [m3 s−1] f fuzzy membership function h heaviside (step) function [molm−3] i, j numeric indices [−] k turbulent kinetic energy [m2 s−2] l continuous flow characteristic function [−] ldisc discretized flow characteristic function [−] n absolute number [−] p 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*1,2,3 and csengele barta4 1hungarian department of biology and ecology, faculty of biology and geology, babes, -bolyai university, 5-7 clinicilor st., cluj-napoca, 400006 romania 2 institute for research-development-innovation in applied natural sciences, babes, -bolyai university, 30 fântânele st., cluj-napoca, 400294 romania 3centre for systems biology, biodiversity and bioresources (3b), babes, -bolyai university, 5-7 clinicilor st., cluj-napoca, 400006 romania 4department of biology, missouri western state university, 4525 downs drive, agenstein-remington halls, st. joseph, mo 64507, usa ensuring food security for the world’s growing population is a significant challenge for scientists. efforts are constantly being made to solve this problem, including the use of expensive molecular engineering techniques, which are not always successful. a cost-effective and environmentally friendly biotechnological alternative would be the use of plant growthpromoting rhizobacteria, demonstrated by numerous studies to play many beneficial roles in improving plant traits, e.g. enhanced yields. keywords: plant growth-promoting rhizobacteria (pgpr), yield, environmentally friendly, low-cost 1. introduction cereals like bread wheat (triticum aestivum), maize (zea mays) and rice (oryza sativa) are fundamental and essential grain crops for both human and animal consumption. according to the statista statistics site, in 20202021, maize production exceeded 1.12 billion metric tons, wheat 775.8 million metric tons and rice about 505 million metric tons [1]. since the world’s population is constantly growing, the need to increase cereal production is continuous. however, the increasing occurrence of biotic and abiotic stress factors in the environment constitutes a severe global threat to improving cereal yields [2, 3]. to alleviate the detrimental effects of yield loss, expensive genetic engineering techniques for crop improvement have been developed. the use of plant growthpromoting rhizobacteria (pgpr) could represent a lowcost and environmentally friendly alternative biotechnological option. these kinds of soil bacteria, first described by kloepper and schroth in 1978 [4], were isolated from the immediate vicinity of plants, that is, from the rhizosphere. later, several beneficial effects of pgpr in stimulating plant growth were described [5–7]. nowadays, the pgpr biotechnology is more and more frequently used in the management of biotic and abiotic stress factors for a wide range of crop species in *correspondence: gyongyi.szekely@ubbcluj.ro order to reduce their damaging effects, which ultimately can cause important yield losses [6,7]. understanding the mechanisms at the basis of the pgpr technology in alleviating biotic and abiotic stress-induced damage in crops could be essential to reduce subsequent crop yield losses. exploiting the positive effects of plant-microbe interactions might provide multiple multi-pronged solutions to the global food crisis, reduce the amount of irrigation provided by fresh water as well as solve environmental stress concerns and maintain soil health. 2. the most common effects of pgprs on plants over the last decade, versatile positive properties of pgprs have been intensely documented. dozens of articles highlight the importance of these rhizobacteria in the process of alleviating damage brought about by abiotic stress. a large number of different pgpr species, e.g. pseudomonas alcaligenes, p. mendocina, bacillus polymyxa, b. pumilus and mycobacterium phlei, have been described to play a positive role in stimulating growth in various plant species as well as in the process of improving their tolerance of high temperatures and the salinity of many crops [6, 7]. shrivastava and kumar (2015) indicated that certain pgpr species can produce antioxidants, therefore, can be useful for reducing oxidative stress-induced damage to plants [6]. inhttps://doi.org/10.33927/hjic-2022-03 mailto:gyongyi.szekely@ubbcluj.ro 12 székely and barta figure 1: the impact of biotic and abiotic stress on crop resistance in the absence (panel a) and presence (panel b) of pgpr. oculation with pgprs improved seed germination and seedling growth, increased the concentrations of chlorophylls, antioxidant enzymes, proline, malondialdehyde and flavonoids as well as reduced the na+ content in different crops [8, 9]. recently, a couple of authors documented a set of plant growth-promoting traits, namely the ability to solubilize phosphate as well as produce indole-3-acetic acid (iaa) and 1-aminocyclopropane-1carboxylic acid (acc) deaminase of different pgpr species [7, 10, 11]. furthermore, several physiological traits such as leaf chlorophyll content, stomatal conductance, leaf relative water content and membrane leakage adversely affected by cold stress were mitigated by pgpr [12]. in addition, certain pgpr species are important factors in relieving not only abiotic but also biotic stressinduced damage. plants are commonly attacked by aphids and fungi, which cause substantial yield losses in crops and especially affect the production of cereal grains globally [3, 13, 14]. naeem et al. (2018) showed the positive effect of bacillus spp. and pseudomonas spp. in terms of enhancing the productivity of wheat attacked by aphid populations [3]. fungi represented by the genus fusarium infest cereals worldwide, moreover, f. graminearum is responsible for cereal head blight and maize ear rot in north and south america, europe as well as asia [14, 15]. to reduce the considerable amount of destruction caused by f. graminearum, several authors propose the use of an effective, economical and environmentally friendly biotechnological tool. they demonstrate that different pgpr species have antagonistic effects on f. graminearum and possess the ability to promote wheat growth under adverse biotic and abiotic stress conditions as well [16,17]. fig. 1 illustrates the impact of biotic and abiotic stress on crop resistance in the absence and presence of pgpr. finally, pgpr species can also function as important components of biofertilizers and biopesticides since they can improve the nutrient content and quality of soil through the mechanisms of nitrogen fixation and phosph ate solubilization. as biopesticides, these rhizobacteria protect the plants as a result of their ability to synthesize antibiotics [18, 19]. efforts to implement such environmentally friendly technologies are increasing annually and could be part of the solution to the ever-increasing demand for food to feed the growing global population . 3. pgpr mediates increases in cerealcrop yields biotic and abiotic stress factors usually cause a series of negative effects on crop yield, quantity and quality. under adverse environmental conditions and exposed to multifarious pathogen attacks from viruses, bacteria, fungi, insects, etc., plants respond defensively, implying changes in several physiological and nutritional parameters, hormonal imbalances and important yield losses [7, 10, 18]. globally, wheat, maize and rice are essential staple foods for billions of people. annually, these cereals are grown on hundreds of millions of hectares of land and are consumed by several billion people in hundreds of countries. as a result of population growth, production must continuously be enhanced. predictions state that by the year 2050, consumers will need 60% more wheat compared to the present production rate [20]. this must be hungarian journal of industry and chemistry plant growth-promoting rhizobacteria 13 table 1: beneficial effects of some pgpr species on wheat, maize and rice yields pgpr species effect on yield cereal species reference azospirillum sp. bacillus sp. bacillus megaterium paenibacillus polymyxa raoultella terrigena enhanced grain yield; enhanced straw yield; increased uptake of macro nutrients (n, p, k, ca, mg and s); increased uptake of micro nutrients (fe, mn, zn and cu). wheat [12] bacillus sp. pseudomonas spp. enhanced grain yield; enhanced straw yield; enhanced number of grains per spike; enhanced number of productive tillers. wheat [3] alcaligenes faecalis bacillus aryabhattai pseudomonas corrugat a pseudomonas arsenicoxydans pseudomonas brassicacearum pseudomonas azotoformans enhanced grain yield; enhanced plant growth-promoting traits (shoot and root lengths, fresh and dry weights). wheat [21] bacillus pumilus bacillus safensis lysinibacillus sphaericus paenibacillus alvei enhanced grain yield; phosphate solubilization (except for l. sphaericus); nitrogen fixation. maize [22] cupriavidus necator pseudomonas fluorescens enhanced aerial biomass; increase in n and p use efficienc ies. maize [23] azospirillum brasilense azotobacter chroococcum pseudomonas aeruginosa pseudomonas fluorescens pseudomonas putida enhanced grain yield; enhanced iaa production; enhanced phosphate solubilization. rice [24] bacillus sp. bacillus thuringiensis pseudomonas mosselii enhanced grain yield; enhanced root and shoot biomasses; enhanced production of iaa , siderophores and acc deaminase as well as the ability to solubilize phosphate . rice [26] achieved without expanding the area of arable land and by using eco-friendly and low-cost biotechnological strategies. one of these strategies is the use of pgpr to enhance crop productivity. table 1 presents the impact and efficacy of different pgpr species in enhancing wheat, maize and rice yields [3, 12, 21–25]. 4. conclusions the use of plant growth-promoting rhizobacteria to improve cereal yields represents a prosperous, environmentally friendly and economical strategy. pgpr are useful tools to reduce the effects of biotic and abiotic stress on plants, therefore, could contribute towards optimal plant growth and development as well as enhance their yields. finally, pgpr could represent a resource to ease the emerging global food crisis. references [1] worldwide production of grain in 2021/22, by type https://www.statista.com/statistics/263977/world-grain-production-bytype/ retrieved 27 october 2021 [2] afzal, a.; 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iqbal, a.; ahmed, f.; ahmad, m.: phytobeneficial and salt stress mitigating efficacy of iaa producing salt tolerant strains in gossypium hirsutum, saudi j. biol. sci. 2021, 28(9), 5317– 5324 doi: 10.1016/j.sjbs.2021.05.056 [12] turan, m.; gulluce, m.; çakmakçı, r.; oztas, t.; ţahin, f.; gilkes, r.; prakongkep, n.: the effect of pgpr strain on wheat yield and quality parameters. conference paper: proceedings of the 19th world congress of soil science: soil solutions for a changing world, australia, 2010, 15, 140–143 [13] goswami, r. s.; kistler, h. c.: heading for disaster: fusarium graminearum on cereal crops, mol. plant. pathol. 2004, 5(6), 515–525 doi: 10.1111/j.13643703.2004.00252.x [14] mielniczuk, e.; skwaryło-bednarz, b.: fusarium head blight, mycotoxins and strategies for their reduction, agronomy 2020, 10(4), 509 doi: 10.3390/agronomy10040509 [15] hietaniemi, v.; rämö, s.; yli-mattila, t.; jestoi, m.; peltonen, s.; kartio, m.; sieviläinen, e.; koivisto, t.; parikka, p.: updated survey of fusarium species and toxins in finnish cereal grains, food add. contam. part. a. 2016, 33(5), 831–848 doi: 10.1080/19440049.2016.1162112 [16] abdulkareem, m.; 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(eds.) plant growth promoting rhizobacteria for sustainable stress management. microorganisms for sustainability; springer, 2019, 13 doi: 10.1007/978-981-136986-5_5 [19] riaz, u.; murtaza, g.; anum, w.; samreen, t.; sarfraz, m.; nazir, m. z.: plant growth-promoting rhizobacteria (pgpr) as biofertilizers and biopesticides. in: hakeem, k. r.; dar, g. h.; mehmood, m. a.; bhat, r. a. (eds.) microbiota and biofertilizers; springer. 2021, 181–196 doi: 10.1007/978-3-030-487713_11 [20] wheat in the world https://wheat.org retrieved 27 october 2021 [21] sheirdil, r. a.; hayat, r.; zhang, x. x.; abbasi, n. a.; ali, s.; ahmed, m.; khattak, j. z. k.; ahmad, s.: exploring potential soil bacteria for sustainable wheat (triticum aestivum l.) production, sustainability 2019, 11(12), 3361 doi: 10.3390/su11123361 [22] breedt, g.; labuschagne, n.; coutinho, t. a.: seed treatment with selected plant growth-promoting rhizobacteria increases maize yield in the field, ann. appl. biol. 2017, 171(2), 229–236 doi: 10.1111/aab.12366 [23] pereira, s. i. a.; abreu, d.; moreira, h.; vega, a.; castro, p. m. l.: plant growth-promoting rhizobacteria (pgpr) improve the growth and nutrient use efficiency in maize (zea mays l.) under water deficit conditions, heliyon 2020, 6(10), e05106 doi: 10.1016/j.heliyon.2020.e05106 [24] lavakush, l.; yadav, j.; verma, j. p.; jaiswal, d. k.; kumar, a.: evaluation of pgpr and different concentration of phosphorus level on plant growth, yield and nutrient content of rice (oryza sativa), ecol. eng. 2014, 62, 123–128 doi: 10.1016/j.ecoleng.2013.10.013 [25] kóczán-manninger, k. ; badak-kerti, k. : investigations into flour mixes of triticum monococcum and triticum spelta ,hung.j. ind. chem. 2018, 46(2), 63–66 doi: 10.1515/hjic-2018-0020 [26] aw, x.; li, z.; li, w. c.; ye, z. h.: the effect of plant growth-promoting rhizobacteria (pgpr) on arsenic accumulation and the growth of rice plants (oryza sativa l.), chemosphere 2020, 242, 125136 doi: 10.1016/j.chemosphere.2019.125136 hungarian journal of industry and chemistry https://doi.org/10.3389/fmicb.2018.00148 https://doi.org/10.1128/aem.01533-18 https://doi.org/10.1128/aem.01533-18 https://doi.org/10.3389/fpls.2020.00297 https://doi.org/10.3390/app11052233 https://doi.org/10.3390/app11052233 https://doi.org/10.1016/j.sjbs.2021.05.056 https://doi.org/10.1111/j.1364-3703.2004.00252.x https://doi.org/10.1111/j.1364-3703.2004.00252.x https://doi.org/10.3390/agronomy10040509 https://doi.org/10.3390/agronomy10040509 https://doi.org/10.1080/19440049.2016.1162112 https://doi.org/10.33687/phytopath.003.01.0660 https://doi.org/10.33687/phytopath.003.01.0660 https://doi.org/10.3389/fmicb.2017.01945 https://doi.org/10.3389/fmicb.2017.01945 https://doi.org/10.1007/978-981-13-6986-5_5 https://doi.org/10.1007/978-981-13-6986-5_5 https://doi.org/10.1007/978-3-030-48771-3_11 https://doi.org/10.1007/978-3-030-48771-3_11 https://wheat.org https://doi.org/10.3390/su11123361 https://doi.org/10.1111/aab.12366 https://doi.org/10.1111/aab.12366 https://doi.org/10.1016/j.heliyon.2020.e05106 https://doi.org/10.1016/j.heliyon.2020.e05106 https://doi.org/10.1016/j.ecoleng.2013.10.013 https://doi.org/10.1016/j.ecoleng.2013.10.013 https://doi.org/10.1515/hjic-2018-0020 https://doi.org/10.1016/j.chemosphere.2019.125136 introduction the most common effects of pgprs on plants pgpr mediates increases in cereal-crop yields conclusions hungarian journal of industry and chemistry vol. 51(2) pp. 65–75 (2023) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2023-20 a critical review of the photocatalytic degradation of pharmaceutical residues by a tio2-based photocatalyst thamer adnan abdullah1*, qusay al-obaidi2, thaer a. abdulla3, rashed t. rasheed1, khalda al-azawi1 and faiza meharban4 1 chemistry branch, department applied sciences, university of technology, al senaa street, baghdad, 19006, iraq 2 chemical engineering department, university of technology, al senaa street, baghdad, 19006, iraq 3 chemical engineering department, tikrit university, p.o. box 42, tikrit, 34001, iraq 4 faculty of materials science and engineering, donghua university, 2999 north renmin road, shanghai, 201620, china creating photocatalytic materials to generate clean energy and for ecological detoxification has been a challenge as far as meeting the worldwide demand for energy and cutting pollution is concerned. anti -inflammatory medicines and pharmaceutically active chemicals (phacs) are frequently found in wastewater. since conventional wastewater treatment facilities do not completely remove these micropollutants (pharmaceuticals), alternatives are required. it is still difficult to make an inert and efficient nano-photocatalyst like titanium dioxide (tio2). tio2 photocatalysts have been extensively utilized as innovative photocatalysts for treating contamination because of their distinctive physicochemical characteristics, less toxic nature, biological inertness, improved energy efficiency, low-temperature reaction conditions, insolubility in water, easy accessibility, highly stable chemical nature and natural environmentally friendliness. however, their large band gap energy, that can only be generated under uv light and quickly with charge carrier recombination, restricts their photocatalytic applications. its band gap energy was additionally decreased in order to be active in visible light in a variety of methods. recent research developments concerning the tio2-based heterostructure as a photocatalyst as well as its modifications, factors and removal method are summarized in this review which concludes with an overview and viewpoints on the present difficulties as well as fresh lines of inquiry in this developing f ield of study. keywords: photocatalysts, photocatalysis, tio2 nanoparticles, pharmaceutical residue, antibiotics 1. introduction water is universally recognized as the most important factor in the development of civilization as well as for the survival of life on this planet. obtaining clean and affordable water is one of our most fundamental needs which for the past 200 years has been a major global problem. the largest global problem affecting human health is the pollution of water. numerous pharmaceutical medications have been continually made over recent years. antibiotics are ingested in small doses, moreover, the majority of them are excreted in our urine and faeces, where they end up in aquatic environments. antibiotic concentrations in hospitals and urban wastewater are typically between 0.3 and 100 mg/l [1][3], it is crucial to properly remove these chemicals from contaminated water. however, traditional approaches like coagulation, electrocoagulation and adsorption are inefficient with regard to the breakdown of pharmaceutical components. although techniques that received: 12 june 2023; revised: 14 sept 2023; accepted: 14 sept 2023 *correspondence: 100249@uotechnology.edu.iq utilize biomembranes like reverse osmosis and nanofiltration result in the substantial removal of these impurities, they also have certain limitations because of fouling, which significantly lowers their efficiency [3]. active pharmaceutical chemicals that leak into water are currently regarded as new growing contaminants since they have the potential to have detrimental impacts on the environment as well as on human health. there are two possible pathways of these pharmaceuticals into wastewater; (i) small amounts of these active pharmaceutical ingredients (apis) enter the water systems by being excreted through our urine or faeces as unchanged metabolites or compounds, or (ii) disposal as surplus or expired medications into the environment. pharmaceutical medications often fall into one of several major categories, including analgesics, antiseptics, antibiotics, contraceptives, antiepileptics, beta blockers, hormones, etc. using tio2 as a photocatalyst proved to be the most effective treatment https://doi.org/10.33927/hjic-2023-20 mailto:100249@uotechnology.edu.iq abdullah, al-obaidi, abdulla, rasheed, al-azawi and meharban hungarian journal of industry and chemistry 66 approach for removing such complicated contaminants like antibiotics [3]-[7]. 1.1. pharmaceutical residue in water systems the extensive use of pharmaceuticals, which are not biodegradable, in human healthcare results in their heavy consumption. pharmaceuticals continue to be found in the environment, which, despite their relatively low concentrations in drinking water and groundwater, can be detrimental to people and aquatic life. because of their antipyretic, analgesic and anti-inflammatory effects, nsaids (non-steroidal anti-inflammatory drugs) are among the most frequently utilized pharmacological substances in both veterinary and human therapies. ibuprofen, naproxen, paracetamol, acetylsalicylic acid and diclofenac are the only commonly used nsaids that have been found in water samples from both developed and developing countries as micropollutants. the majority of the time, these nsaids have a hazardous effect on ecosystems and aquatic organisms, which indirectly affects individuals through the food chain [8][14]. 1.2. common pharmaceutical compounds found in water pharmaceuticals, primarily antibiotics and cytostatic medications, have a history of environmental pollution, negative consequences on human health and harming aquatic ecosystems. however, given their crucial nature as far as sustaining a healthy society is concerned, they are significantly utilized. antibiotics are commonly used to treat microbiological infections. a 2013 study found that over 248 thousand tons of antibiotics are used annually, with asia accounting for about 70% of global antibiotic use. antibiotic use in livestock is predicted to increase globally by 67% by 2030. the misuse of antibiotics leads to environmental pollution, notably in water bodies, which poses a serious hazard to human health. therefore, it is important to reduce antibiotic usage and maintain a clean atmosphere [15]. antibiotics are used as extremely significant antibacterial substances for the treatment as well as mitigation of transmittable illnesses in both people and animals. they also play a crucial role in livestock farming, fish farming and medical industries. nevertheless, antibiotics pose serious risks to the aquatic ecosystem due to their misuse. toxic levels of antibiotics and their poor biodegradability present major dangers to human life that must be addressed immediately [1]. although tch (taxotere or taxol, carboplatin and herceptin) is a common antibiotic, because of its solid structure and poor ability to biodegrade, it has detrimental effects on both human and animal health. effective ways to remove tch from wastewater are urgently needed. biological and physical adsorption techniques have both been used to remove tch from wastewater, but they haven't been able to entirely get rid of this pollutant. according to reports, the photocatalytic degradation of tch is the best method since it does not produce residual pollution, is highly efficient and simple. feizpoor et al. used a simple hydrothermal process by placing ag3bio3 nanoparticles (nps) on tio2 to create n-n heterojunctions. tio2/ag3bio3 yielded the best tch photodegradation efficiency, 15.4 times better than tio2. tio2/ag3bio3’s better light absorption capacity and decreased coupling of charged particles produced by light due to the creation of n-n heterojunctions are the main reasons for the increase in the photodegradation efficiency of tch. through the use of reactive species quenching studies, the mechanism enhancing the photodegradation efficiency of tch was discovered [1]. cytostatic or anti-cancer medications, another group of contaminants in the developing pharmaceutical industry, have also been detected in small concentrations on the surface of water, moreover, are toxic and carcinogenic to people. the use of cytostatic medication over an extended period could have a negative impact on the environment. due to the rising number of cancer cases over recent years, the use of these medications, also referred to as anti-cancer or antineoplastic treatments, has surged. these medications impede chromosomal replication or damage dna, killing cells. as a result, only a small number of such medications can be hydrolyzed or photolyzed biologically, making it extremely difficult to remove them from wastewater [15]-[17]. additional detrimental effects are to be anticipated given the continued expansion in the manufacture and utilization of medications as well as the lack of effective methods to evaluate and decrease their ability to adversely effect the environment. changes in antibiotics are possible when biotic and abiotic environmental variables are present. numerous substances can modify their activity by producing secondary pollutants (sp) that are considerably more harmful than the original ones, making them resistant to natural degradation as well. antibiotics and biological accumulation have long-term effects on living things that can prevent plants from growing as well as cause cancer in addition to liver and kidney diseases in mammals amongst other detrimental effects. these compounds from the surroundings can also enter our bodies in drinking water and food, leading to antibiotic resistance, allergic reactions, toxic and neurotoxic consequences, etc. [18]. figure 1 represents the major sources of antibiotics that cause water pollution. 2. photocatalysis the method of photocatalysis uses light energy to accelerate chemical reactions by making use of photocatalysts, which are able to absorb light and increase the rate of a chemical reaction. according to the fundamentals of photocatalysis, electron-hole pairs are produced when the photocatalyst is activated by photons with the appropriate amount of energy. these photoexcited charges can then participate in various reactions such as redox reactions or the degradation of organic compounds. the fundamental principles of a review of photocatalytic degradation 51(2) pp. 65–75 (2023) 67 photocatalysis are discussed in several of the referenced studies. according to mandade, the primary distinction between a photocatalyst and a standard catalyst is the process of activation. while standard catalysts are activated by heating, photocatalysts are activated by photons of the right energy [19]. gusain and kumar et al. explain that photocatalysis relies on the increased surface exposure of the photocatalyst, which enhances its organic degradation activity. moreover, photocatalysts are effective in reducing toxic heavy metals like hexavalent chromium from water systems [20]. additionally, photocatalysis is a topic that encompasses diverse forms of implementation and a wide range of materials. when developing photocatalytic materials, factors like efficiency, stability, scalability and cost must be taken into account [21]. due to their advantageous features, semiconductors are frequently used as photocatalysts, and different types of semiconductors have been investigated [22]. 2.1. tio2 as a photocatalyst tio2, a significant element that occurs in the form of its oxide, is used extensively in the commercial manufacture of numerous products and is significant in a number of industries. there are three primary crystal forms of tio2: (i) brookite; (ii) rutile and (iii) anatase. the characteristics of these vary, including the space group, the lattice constants, etc. the commercial demand for nanoscopic tio2 and its derivatives is driven by their large surface area and short diffusion paths. greater comprehension of the functional characteristics of porous tio2 materials would enable the development of a number of desirable features for a variety of applications such as to promote photocatalytic processes like the splitting of water to make hydrogen gas, mineralization of pharmaceuticals, treatment of wastewater and degradation of organic contaminants to list just a few [23]. table 1 represents different tio2 photocatalysts for the removal of pharmaceutical pollutants, dyes and organic compounds. 2.2. mechanisms of tio2 photocatalysis for the degradation of organic compounds the mechanism of photocatalytic activities using tio2 as a photocatalyst has been covered in a number of studies. when light with a wavelength larger than or equal to the band gap strikes the surface of tio2, electrons from the valence band (vb) jump to the conduction band (cb), creating electrons and holes in the former (h+ vb) and latter (ecb), respectively. while the produced hole acts as a powerful oxidant, oxidizing the water molecule and surface hydroxyl ion to form oh•, the electrons act as a strong reductant, reducing the o2 molecules to form figure 1: mechanism of removing pollutants by the tio2 photocatalyst table 1: tio2 nanomaterials for the removal of organic compounds *pd = photodeposition synthesis organic compound material light source catalyst amount % degradation/time reference rhodamine b dyes ag-tio2-pd* uv irradiation -99 % / 2 h [2] reactive red 120 (rr 120) ac-tio2 365 nm uva light/32 w 50 mg / 100 ml 95 % / 50 min [4] ketoconazole (knz) tio2-nps 365 nm high pressure mercury lamp/250 w 120 mg / l 98.4 % / 60 min [6] reactive green-19 dye tio2-nps 630nm/uvlight 0.030 g /100 ml 98.88 % / 60 min [8] ornidazole (odz) tio2-nps hg vapor lamp/400 w 50 mg / l 66.15 % / 3 h [10][10] rhodamine 6g s-doped tio2 526nm/led bulbs of 12 w 50 mg / 50 ml 91.7 % / 4 h [12] lomefloxacin au/tio2 -10 mg / l 71.8 % / 180 min [13] abdullah, al-obaidi, abdulla, rasheed, al-azawi and meharban hungarian journal of industry and chemistry 68 o2 -•. o2 -•interacts with the h+ ion to make ho2•, which is then successively protonated to form h2o2. these processes take place on the tio2 surface of the photocatalyst. photocatalytic degradation is aided by photogenerated ross (o2 -•, oh•, ho2• and h2o2) [24]. equations 1-6 show how electrons can interact with organic molecules to produce reduction products. since oxygen can interact with the photogenerated electrons, its involvement is crucial. figure 2 represents the overall mechanism of removal of organic pollutants by the tio2 photocatalyst. tio2 + hv → ecb − + hvb + (1) hvb + + ohsurface − → oh⦁ (2) hvb + + h2oabsorbed → oh⦁ + h+ (3) ecb − + oabsorbed → o2 −⦁ (4) hvb + + organic → oxidation products (5) oh⦁ + organic → degradation products (6) 2.3. factors influencing the photocatalytic efficiency of tio2 the photocatalytic efficiency of tio2, a commonly used photocatalytic material, is influenced by various factors. some of these factors affecting tio2 photocatalysis include its specific surface area, crystal phase, crystallite size and crystallinity. although these structural characteristics of tio2 can impact its photocatalytic efficiency, there is some controversy over which factor is the most important [25]. functionalization and doping: the functionalization and doping of tio2 with other materials or metal cations can influence its photocatalytic properties. doping can create donor or acceptor energy levels, generate defects in tio2 and affect its crystallinity, thereby influencing the efficiency of charge carrier separation and recombination [26]. structure and morphology: the morphology and structure of tio2 such as nanotubes or nanoparticles can have an impact on its surface area, light absorption capacity and charge carrier transport, thereby affecting its photocatalytic performance [27]. band gap energy: the band gap energy of tio2 determines the wavelength of light it can absorb. the effective rate of light absorption and subsequent photocatalytic processes can be affected by the band gap energies of the various tio2 crystal shapes [28]. co-catalysts and sensitizers: by adding cocatalysts or sensitizers to tio2, e.g. metals or organic dyes, the photocatalytic effectiveness of the material can be increased by increasing light absorption, the separation of charges and reaction kinetics [29]. reaction conditions: the photocatalytic efficiency of tio2 can be influenced by variables like ph, temperature, reactant concentration and the oxygen content or other reactive species in the reaction environment [30]. 3. application of tio2 photocatalysis for the degradation of pharmaceutical residues tio2 has been used effectively to remove pharmaceutical contaminants from water. the photocatalytic efficacy of tio2 during water treatment is hindered by the effective movement of low-charge carriers and its poor level of sensitivity to visible light. numerous techniques such as the design of heterojunctions, alterations to its surface and doping are thought to be very successful in enhancing the photodegradation capacity of tio2. to increase the photodegradation efficiency and speed up the migration of photogenerated charge, p-n or n-n heterojunctions based on tio2 seem to be a great solution [1]. table 2 represents different tio2 photocatalysts for the removal of pharmaceutical pollutants and their photodegradation efficiency. 3.1. experimental methods for evaluating tio2 photocatalysis the evaluation of tio2 photocatalysis can involve various experimental methods. here are some of the experimental methods commonly used to assess tio2 photocatalysis: decolorization of dyes: one commonly employed method is to evaluate the decolorization or degradation of dyes such as methylene blue (mb) under visible or uv light irradiation [31]. by decreasing the dye concentration or color intensity over time, the photocatalytic activity of tio2 can be determined. photocatalytic activity tests: these tests involve assessing the ability of tio2 to induce desired reactions under light irradiation. for instance, the conversion of organic pollutants or the degradation of target compounds can be measured using specific analytical techniques [32]. the reaction products can be analyzed using various spectroscopic or chromatographic techniques to determine the efficiency of tio2 photocatalysis. quantum efficiency measurements: quantum efficiency measurements provide insights into the figure 2: the principal origins of antibiotics found in water systems a review of photocatalytic degradation 51(2) pp. 65–75 (2023) 69 efficiency of tio2 in converting absorbed photons into photocatalytic reactions. this method involves measuring the amount of photons absorbed and the number of reactive species generated [33]. this information helps to evaluate the overall performance of tio2 photocatalysts. chemical probe tests: chemical probes can be used to evaluate specific reactive species generated during photocatalysis. for example, the generation of hydroxyl radicals (oh•) or superoxide radicals (o2 -•) can be measured using appropriate probe compounds. these tests provide insights into the photocatalytic pathways and mechanisms facilitated by tio2 [34]. transient absorption spectroscopy and timecorrelated single photon counting are two examples of time-resolved spectroscopic methods that can be used to study the dynamics and kinetics of charge carriers in tio2 photocatalysts. these techniques offer details concerning the lifetime of photogenerated charge carriers and recombination rates, two important variables affecting photocatalytic effectiveness [26]. approaches for surface characterization: the structural characteristics and morphology of tio2 photocatalysts can be evaluated using surface characterization techniques like xrd, sem, tem and specific surface area measurements. these methods help the relationship between structural characteristics and photocatalytic efficiency to be comprehended [35]. it is crucial to remember that the selection of the experimental approach depends on the precise objectives of the study and the details sought regarding the tio2 photocatalytic performance. for a thorough knowledge of tio2 photocatalysis, researchers frequently combine these techniques. 3.2. comparison with other techniques tio2 photocatalysis can be contrasted with other advanced oxidation processes (aops), in addition to photocatalysis. aops include a variety of processes that use strong oxidants to break down contaminants. through these processes, highly reactive species are produced, including hydroxyl radicals (oh•), which are capable of quickly destroying organic molecules. ozonation, fenton's reagent (h2o2/fe2+) and oxidation procedures utilizing ultraviolet (uv) radiation are a few examples of aops. tio2 photocatalysis can be compared to other aops in terms of efficiency, reaction kinetics, energy requirements and the suitability of particular procedures regarding various types of pollutants [36]. aops can cause photodegradation in a variety of methods, including deterioration brought about by photolysis, photosensitizers and ros. for example, among aops, it is possible to distinguish between photochemical reactions including the breakdown by uv photons, the combined effect of uv / h2o2, uv / o3, table 2: comparison of photodegradation efficiency in the removal of different pharmaceutical residues *pd = photodeposition synthesis; **mw = formaldehyde assisted microwave synthesis sample pollutant irradiation time (min) light source removal efficiency reference tio2/ag3bio3 tch 210 50w lamp 98.50% [1] tio2 ciprofloxacin (cip) 76 15w uv-c lamp 88.30% [3] zno-tio2-mxene carbamazepine (cbz) 180 150w halogenated high pressure light 97.00% [5] ac/tio2 ibuprofen (ibu) diclofenac (dfc) paracetamol (prc) 180 220w uv lamp 95.32% 83.14% 80.40% [7] fe/tio2-zno sumatriptan succinate (sts) 60 250w highpressure mercury vapor lamp 70.00% [9] uv/tio2 paracetamol 150 uv light 72.50% [11] ag-tio2-pd* ag-tio2-mw** naproxen sodium, flurbiprofen 10 60 uv light 80.00% 74.00% [2] ac-tio2 ofloxacin (ofl) 50 8w mercury uv lamps 82.00% [4] abdullah, al-obaidi, abdulla, rasheed, al-azawi and meharban hungarian journal of industry and chemistry 70 uv / h2o2 / o3, the breakdown by photocatalysis in liquid semiconductor solutions, both ultrasonic procedures and fenton photoreactions, as well as radiological procedures involving ionizing radiation either by itself or in conjunction with o3 and/or h2o2 [37],[38]. aops can use semiconductor nanoparticles as catalysts which are stimulated by light of different wavelengths, from uv to near-ir, determined by the band gap energy [39]. 3.3. efficiency and limitations of tio2 photocatalysis for the degradation of pharmaceutical residues the factors that affect the efficiency of the catalyst are: 1) tio2 photocatalytic effectiveness is inhibited by the transfer limitations of pairs of electrons and holes, which primarily occur on the surface of tio2. titania is prone to electrode and hole charge carrier recombination, which inhibits photocatalytic activity. the inadequate adsorption of organic contaminants on the tio2 surface resulted in poor rates of photocatalytic degradation. 2) photocatalysts have a weak affinity for organic contaminants. immobilization of the photocatalyst may facilitate selective affinity for the target pollutants. 3) due to the volatile nature of nanoparticles, the tio2 nanoparticles may aggregate during photocatalytic degradation, thereby blocking the active centers from absorbing light radiation which would hinder the photocatalytic activity of tio2. tio2 aggregates as a result of organic ionizable molecules connected to the particles. 4) tio2 nanoparticles may cause higher scattering conditions that could reduce the photocatalytic activity of the material. to enhance the photocatalytic activity, the right uv wavelengths and tio2 concentration are essential [40]. 5) the efficient and secure recovery of tio2 nps from the water treated is a significant practical problem for the treatment of organic compounds in wastewater. an earlier study found that a tio2 nanopowder solution is better at dispersing the powder than a fixed support. 6) due to the high band energy of the original tio2 photocatalyst and the fact that sunlight is used to facilitate its decomposition processes, it is thought to be less energy-efficient than conventional heterostructured photocatalysts [40]. to enable the creation of tio2-based photocatalysts that can be activated by visible or solar light, more research must be done to improve both the chemical and physical characteristics of the photocatalyst. the size of the tio2 particles, type of dopant and its concentration must be changed to take advantage of the visible light spectrum and increase its affinity to organic compounds in order to overcome these constraints. secondly, the successful recovery and regeneration of suitable substrates that are very capable of separating tio2 nanoparticles is required. the structural design of substrates can also bring about the absorption of different organic contaminants. thirdly, to optimize photocatalysis, its reaction conditions or other parameters like light intensity, calcination temperature, ph and significant amount of additives need to be assessed [39]. figure 3 represents the overall limitations of tio2 photocatalysts with regard to the degradation of organic compounds, that is, factors affecting the tio2 photocatalytic process. 4. factors affecting the tio2 photocatalytic process 4.1. properties and characteristics of the tio2 catalyst tio2 is a versatile compound that is extensively applied as a catalyst in various fields. its properties and characteristics contribute to its effectiveness in catalytic reactions. based on published research, below are some essential traits and features of tio2 catalysts: tio2 is used as a catalyst in thermoand photo-catalytic processes [41]. it demonstrates catalytic activity in reactions like hydrolysis, oxidation and reduction. due to its semiconductive, photocatalytic and catalytic properties, tio2 catalysts are used in a variety of industries, including the chemical industry [42]. the structural and physicochemical characteristics of tio2 have a considerable impact on the efficiency, specificity and sustainability of its catalytic performance. particle size, surface area, surface flaws and crystal structure are all significant factors [41]. the redox dynamics of pt and cu nanoparticles on tio2 have been studied during photocatalytic oxidation, providing insights into the behavior of metal catalysts on tio2 surfaces [43]. tio2 catalysts exhibit strong metal-support interactions (smsis), which enhance their catalytic performance. smsis are characterized by the coverage of tiox over metal nanoparticles, resulting in an enhanced interaction between the metal and the support material figure 3: limitations of tio2 photocatalysts a review of photocatalytic degradation 51(2) pp. 65–75 (2023) 71 [44]. these interactions enhance the stability and performance of the catalyst. the optical absorption properties of tio2 catalysts are important for their photocatalytic activity. although bare tio2 primarily absorbs uv light, when doped with elements such as iron, a red shift can occur in its absorption band edge, expanding the range of light absorption [45]. tio2 is also a catalyst for hydrolysis and it is a superior catalyst-support material [42] due to its chemical stability and acid-base characteristics. 4.2. influence of ph, temperature and dissolved oxygen on photocatalysis a catalyst and light energy are used in the process known as photocatalysis to promote chemical reactions. numerous variables, including ph, temperature and dissolved oxygen, might affect how well photocatalysis works. here is a detailed breakdown of how these parameters affect photocatalysis based on the literature: ph: photocatalytic activity can be considerably impacted by the ph of the reaction environment. for instance, it was discovered that the crystalline structure and fraction of hydroxyl oxygen in tio2-based photocatalysts are ph-dependent [46],[47]. it has been noted that lowering the ph in some systems accelerates the photodegradation of organic molecules [48]. aqueous ph-responsive photocatalysts have also been investigated for controlling polymer synthesis [49]. the specific ph range and its influence may vary depending on the catalyst and reaction system. temperature: temperature has a significant role in photocatalysis as it affects the reaction kinetics and energy transfer processes. because reactants and intermediates move more quickly at higher temperatures, photocatalytic activity is typically improved when heated [37]. each photocatalytic system may have a preferred temperature range, above which the activity may decline due to thermal deactivation or other temperaturedependent effects. dissolved oxygen: dissolved oxygen can affect how photocatalytic reactions proceed. in photocatalysis, oxygen can participate in the oxidation reactions as an electron acceptor. the overall effectiveness and selectivity of the photocatalytic process might be impacted by the presence of oxygen. in other instances, oxygen defects on the catalyst surface have been suggested to increase its photoactivity [38]. it is crucial to keep in mind that the precise effects of ph, temperature and dissolved oxygen on photocatalysis might change based on the catalytic material, reaction conditions and target reaction. the performance of photocatalysis can also be influenced by additional factors such as the kind of reactants, catalyst loading and light intensity. 4.3. impact of organic and inorganic species on tio2 photocatalysis when analyzing the efficiency of tio2-based photocatalysts, it is crucial to take both organic and inorganic species into account. depending on their type and concentration, organic chemicals can have either positive or negative effects on tio2 photocatalysis. by using tio2-based photocatalysts, certain organic pollutants, including formaldehyde, toluene, benzene, phenol and trichloroethene, can be successfully destroyed [46]. however, the physical and structural characteristics of the tio2 photocatalyst during the oxidation process might be impacted by the presence of natural organic matter (nom) [47]. the efficacy of the photocatalyst and the production of byproducts can be influenced by the quantity and type of organic species as well as how they interact with tio2. species that are inorganic can also significantly affect tio2 photocatalysis. for example, soluble substances like chloride ions (cl-), phosphate ions (po4 3-) and sulfate ions (so4 2-) have been found to impact the efficiency of photocatalytic degradation in water matrices [48]. in some cases, inorganic ions present in wastewater such as cl-, no3 -, so4 2and po4 3can serve as scavengers of reactive oxygen species, thereby competing with the target organic pollutants for these species and impeding the photocatalytic process [49]. according to their type and concentration, different inorganic species may have varying effects. it is significant to highlight that both organic and inorganic compounds can have complex, systemdependent effects on tio2 photocatalysis. different results can be obtained depending on the concentration, type and interactions of these species with the photocatalyst. therefore, when evaluating the effect of organic and inorganic species on tio2 photocatalysis, it is imperative to take into account the particular experimental circumstances and the target pollutants. tio2-based photocatalysts can destroy organic pollutants, moreover, the nature of the aqueous matrix and natural organic matter can affect the efficiency and generation of byproducts by the photocatalytic reaction. similar to how organic species can scavenge reactive oxygen species, inorganic species can do likewise, altering the overall effectiveness of the photocatalytic process. tio2 photocatalysis must be optimized in order to create effective methods for water treatment and pollutant degradation. this requires an understanding of the interactions and effects of these species. 4.4. strategies for enhancing the efficiency of tio2 photocatalysis utilizing modifying agents is a favorable strategy for enhancing the photocatalytic performance of tio2. anionic or cationic additives are both acceptable. the long-term viability of the anatase phase, particle size and other characteristics can all be impacted by the addition of modifying agents. this enables the band gap to be reduced and light to be absorbed in the visible spectrum. due to the expensive nature of f-metals, por d-metal cations are typically utilized in cationic doping. metal ions can modify the photoreactivity of the photocatalyst by controlling the recombination process and acting as photoinduced charge traps. amoxicillin is virtually abdullah, al-obaidi, abdulla, rasheed, al-azawi and meharban hungarian journal of industry and chemistry 72 destroyed (94%) by 300 minutes of irradiation under visible light with even a small amount (0.5%) of tio2 doped with cobalt ion. the use of commercially available degussa p25 and undoped materials results in antibiotic removal efficiencies of 21% and 16%, respectively over the same irradiation time [37]. 5. future perspectives and challenges research into tio2 photocatalysis has been a rapidly evolving field and several emerging trends have gained a significant amount of attention. a substantial area of study has been the production and use of nanostructured tio2 photocatalysts. to improve photocatalytic activity, many approaches, including sol-gel, hydrothermal and template-assisted processes, are being used to change the morphology and structure of tio2 on the nanoscale. uv light, which only makes up a minor portion of the solar spectrum, is primarily absorbed by conventional tio2 photocatalysts. therefore, attempts should be made to expand the range of visible light (wavelength > 400 nm) absorbed by tio2 photocatalysts. • strategies include doping tio2 with transition metal ions, coupling it with other semiconductors and surface modifications with organic dyes or carbonbased materials. these approaches can enhance the absorption of visible light and improve overall photocatalytic performance. • the introduction of co-catalysts onto the tio2 surface can enhance charge separation and transfer kinetics. • the development of heterojunctions and composite materials may also be promising to enhance photocatalysis. • energy efficiency and catalyst recovery are critical aspects regarding the practical applications of tio2 photocatalysis. research should focus on methods to enhance energy efficiency by improving catalyst loading, reaction conditions and light sources. • since the efficiency and adaptability of the remedial process are greatly influenced by the design of the photocatalytic reactor, researchers should focus on designing more efficient reactors. • tio2 photocatalysis depends on the photocatalyst being activated by light. the right choice of light source is essential to achieve optimal photocatalytic activity. uv light, particularly within the range of 300-400 nm, is most commonly used as it matches the absorption range of tio2. however, efforts are being made to extend the absorption range of light by incorporating visible light sources or using modified tio2 materials that exhibit photocatalytic activity in visible light. tio2 photocatalysis can be used in conjunction with other treatments to enhance the removal of pollutants. synergistic approaches include coupling tio2 photocatalysis with adsorption, membrane filtration, advanced oxidation processes or biological processes. these combinations can improve the efficiency of the treatment, reduce energy consumption and remove recalcitrant compounds. tio2 photocatalysis in wastewater treatment systems has the ability to remove a range of organic pollutants effectively and sustainably. the process is still being optimized and scaled up for usage in real-world applications, moreover, problems with regard to catalyst stability, cost and energy efficiency are being addressed. by addressing these challenges and optimizing tio2 photocatalysis through continuous research and development, the efficiency, applicability and feasibility of this technology in wastewater treatment can be enhanced, leading to more sustainable and efficient removal of pollutants. 6. conclusion the elimination of organic pollutants from effluent was highlighted by this study. common forms of organic pollutants were identified, the basic principles of tio2based photocatalysts with regard to the removal of organic pollution outlined, and the first limitations of tio2 photocatalysis in this regard explored. a number of variables that are crucial for the photocatalytic degradation of tio2 were considered. for the future commercial usage of tio2-based photocatalysis, several process variables, including the concentration of the catalyst, particle size, ph adjustment and substrate choice, will be significant. the main benefits of photocatalysis were determined as follows: industrial waste can be indiscriminately converted into harmless substances by tio2-based photocatalysts without causing any additional pollution. solar energy is a free, natural resource that supplies most of the energy needed. however, depending on the properties of effluent, further research needs to be carried out to develop 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dang, z.: photocatalytic removal of organic phosphate esters by tio2: effect of inorganic ions and humic acid, chemosphere, 2018, 206, 26–32, doi: 10.1016/j.chemosphere.2018.04.161 https://doi.org/10.1016/j.cej.2018.11.132 https://doi.org/10.1016/j.jclepro.2020.123895 https://doi.org/10.1016/j.jclepro.2020.123895 https://doi.org/10.3390/w13030288 https://doi.org/10.3390/w13030288 https://doi.org/10.1007/s11356-019-06676-9 https://doi.org/10.1016/j.chemosphere.2018.04.161 hungarian journal of industrial chemistry veszprem vol. 29. pp. 149154 (2001) rheology of alumina slips a. p apo * and l. plant* (dipartimento di scienze e tecnologie chimiche, universita degli studi di udine, via cotonificio,108, 33100 udine, italy) received: october 31, 2001 the aim of the present work is to study the rheological behaviour of concentrated aqueous alumina suspensions. aqueous alumina suspensions were prepared at various solid contents (65 to 77.5 wt% ). rheological tests were carried out at 25±0.1°c by using the rate controlled coaxial cylinder viscometer rotovisko-haake 20, system m5-osc., measuring device sv2p with serrated surfaces. the tests were performed under both continuous and oscillatory flow conditions. all the suspensions studied show a rheological behaviour of the shear-thinning type; in addition. the presence of a yield stress is noticed. some rheological equations of both 't=f( y ) and 11rf(<p, y ) type have been taken into consideration for describing the flow behaviour of the alumina slips investigated. a master-curve procedure was applied in order to give a compact representation of the flow curves drawn for the alumina suspensions examined. finally, the effect of the addition of a dispersing agent (sodium polyphosphate) on the rheology of alumina slips was investigated and its optimum dosage was determined as well. introduction for the preparation of ceramic suspensions by means of techniques such as slip casting and tape casting, submicron sized ceramic powders are needed. however, since very fine ceramic particles spontaneously agglomerate owing to attractive van der waals forces, they must be dispersed in liquid phase using suitable dispersing agents. moreover, different polymeric binders as well as processing aids are u~ually added to the suspension in order to obtain final products with the optimum properties. the mixing of dispersants, binders and processing aids greatly complicates the rheology of the system. alumina is a material widely used in a lot of industrial applications which presuppose the presence of concentrated suspensions. in the light of what said above, the knowledge and control of the rheological properties of alumina suspensions is of paramount importance for improving both the production processes and the quality of final products. however, the rheology of concentrated alumina suspensions is very complex, it being dependent on several factors, which include solid content as well as particle morphology, size and size distribution, surface charge, presence of impurities, aggregation conditions; these latter are strongly influenced by the addition of dispersing agents and/or pii. hence, concentrated alumina suspensions clearly show non-newtonian flow characteristics as well as viscoelastic properties. this article is part of a research program which has been undertaken in order to thorougly characterise the rheological behaviour of alumina suspensions under both continuous and oscillatory flow conditions. particular attention will be focused on the employment of deflocculants of different chemical nature and concentration. here, the aim is to contribute deeper understanding of the applicability in continuous flow conditions of some rheological equations to alumina suspensions prepared at different solid content as well as to investigate their oscillawry shear behaviour and the effect of addition of a commercial dispersing agent on the flow characteristics of these materials. in the last years, several papers regarding the rheology of alumina suspensions have been published; here, mention is made of most papers [ 1-7]. experimental settion materials employed suspensions were prepared with a vane stirrer (ultra~ turrax tso. janke & kunkel, ika~labortechnik) from deionized water and an alumina powder. whose contact information: e-mail: *adriano.papo@dstc.uniud.it; **luciano.piani @dstc.uniud.it 150 table 1 description of the alumina powder employed trade name: purity: dso particle size distribution: density: specific surface: chemical composition: h.p. alumina akp-15, sumitomo chemical co. ltd. (japan) 99.99% 0.68 ~m 83 %< 1 ~m 3.97 g/cm3 3.8 m2/g si=22 ppm; na=5 ppm; mg= 6 ppm; cu< 1 ppm; fe= 19 ppm characteristics are reported in table 1. solid volume fractions varied in the range 0.319 to 0.464 (65 wt% to 77.5 wt% of solid content). solid contents higher than 77.5 wt% were not taken into consideration owing to the very high viscosity of samples. a sodium polyphosphate (molecular weight=1733.39) by aldrich-sigma was selected as dispersing agent; different dispersant concentrations were considered, ranging from 0.01 to 1.0 wt% as calculated on the alumina powder, solid dry weight basis. apparatus and experimental procedure rheological measurements were carried out using the rate controlled coaxial cylinder viscometer rotovisko­ haake 20. system m5-0sc., measuring device sv2p with serrated surfaces. temperature was kept strictly constant at 25 ±0.1 °c. the tests were accomplished under both continuous and oscillatory flow conditions. flow curves were achieved under continuous flow conditions by ascending shear rates ramps from 0 to 389 s-1 at the constant shear ~cceleration of 6.49 s-2, after preshearing at a high constant shear rate carried out in order to suppress the previous rheological history of the sample tested; down curves from 389 to 0 s-1 at the constant deceleration of 6.49 s-2 were also determined. a 0.1 to 1 hz frequency sweep with a 0.7 rad of constant strain was applied as oscillatory testing procedure, in the region of linear viscoelasticy, which was previously determined by applying a 0.2 to 1.3 rad strain sweep with a 0.1 hz constant frequency. results, data reduction and discussion cmztinuous flow tests time~dependent effects under continuous shearing conditions were negligible with au the alumina suspensions examined. a rather good superposition of up and down curves is obsen·ed in the whole range of particle concentration. hence. in the present work attention has been essentially focused on the shear­ dependent behaviour of alumina suspensions. the shear stress vs. shear rate flow curves obtained for the alumina slips investigated are drawn in fig./: it can be seen that all the alumina suspensions studied ~00~======~------------------------~ 't [pa] 2000 1000 "' 77.5wt% v 75wt% • 72.5wt% t>. 70wt% • 65wt% o+---~---.--~~--.---~---.--~--~ 0 100 200 300 y [s-1 ] 400 fig. i shear stress ('t) vs. shear rate ( y ) flow curves for the alumina suspensions studied. show a rheological behaviour of the shear-thinning type; in addition, the presence of a yield stress is made evident. a great increase in viscosity is noticed by passing from 75 to 77.5 wt%. in order to obtain the most suitable equation for describing as well as predicting the rheological behaviour of alumina aqueous suspensions some models of the literature of both 't=f( r ) and rtr=f( <i>' r ) type were taken into consideration. models of the 'i=f( y) type among the rheological models which correlate shear stress with shear rate, only the following literature equations which take into consideration the presence of yield stress were tested: the bingham model (1) the casson model 't=='to+tjoo y +2['t'o11oo]112y 112 (2) the generalized casson model 'tn='t'o n+[tjoo y jll (3) the herschel-bulkley model 't='to+ky n the sisko modified model 't='t'o+lloo y +k y n (4) (5) from a deep examination of figs.2-5 the following general considerations can be put on: 1) no satisfactory correlation with solid volume fraction can be noticed for the generalized casson infinite viscosity; on the other hand, a distinct fitting was obtained by correlating with <p the lloo values determined with eqn. {5) and using the sigmoidal boltzman equation : table 2 standard deviations (std) and coefficient of determination values.(cod) for the alumina suspensions studied eqn.(l) eqn.(2) eqn.(3) eqn.(4) eqn.(5) sid cod. std . cod std cod std cod std cod alumina concentration (wt%) 65.0 70.0 72.5 75.0 77.5 5.78 14.9 17.8 31.1 131 0.982 0.955 0.965 0.976 0.807 8.26 8.07 21.5 20.7 98.4 0.963 0.987 0.950 0.989 0.892 5.90 8.15 18.0 20.2 85.4 0.982 0.987 0.966 0.990 0.922 5.91 8.04 18.0 20.0 84.3 0.982 0.988 0.966 0.991 0.924 5.81 7.99 18.3 19.9 85.0 0.983 0.988 0.966 0.991 0.924 0.319 0.370 0.399 <p 0.430 0.464 fig.2 yield stress (,;0 ) variation with solid volume fraction (<i>) for the alumina suspensions studied. ~~ ~ eqn.2 [mpa.s] eqn. 3 eqn.s 0.319 0.370 0.399 <p 0.430 fig.3 infinite viscosity (floc) variation with solid volume fraction (<i>) for the alumina suspensions studied. floo=a+(b-a)/(l+expi (<1>-<p')/d<p t) (6) the following values for the boltzman parameters were determined: a::0.809; b=0.336; <p~=0.399; dt.p=3.05·104 ; std=0.0768; cod:::::0.991. 2) an irregular variation of the herschel-bulkley consistency with <p can be observed. 3) an irregular variation with 4> can also be noticed for the n parameter of eqn. (5). 4) very close 't0 values were obtained with eqns. { 14). 0.370 0.399 cp 0.430 151 0.464 fig.4 consistency values (k) variation with soiid volume fraction (<1>) for the alumina suspensions studied. n 0.1 0.01 0.319 0.370 0.399 <p 0 eqn.3 -eqn.4 eqn.5 0.430 0.464 fig.s n parameter values variation with solid volume fraction (<p) for the alumina suspensions studied. 5) higher values of the casson generalized '1 parameter were obtained with respect to those determined by zupancic et al. in (2). as can be seen from an examination of both standard deviations estimates (std) and determination coefficient values (cod), which are reported in tabh 2. all the models considered gave a distinct fitting for all the slips investigated except for the most concentrated suspension. obviously, a slightly superior fitting was achieved by applying eqn. (5). it being a model with four adjustable parameters. in addition. as regards the choice of the most suitable model for application to alumina suspensions, no indication can be obtained by comparing experimental and calculated shear stress data. hence, a final contribution to screening among the models proposed may be gained by considering another criterion of choice, i.e. that consisting of checking whether the parameters of the selected models can be assigned a physical meaning. accordingly. the physical consistency of the yield value~ determined by fitting was checked by using the following equation; 1:o=k'[{4mf>o)/(4>m·«~>hm {7) where ¢ 0 (percolation threshold) is the n1lume fraction corresponding to transition from the newtonian or shear-thinning behaviour to the plastic one. i.e. the 152 table 3 parameters ofeqn. (7) model k' q,q <pm m std cod eqn.(l) 284 0.170 0.496 0.769 32.1 0.999 eqn.(2) 256 0.183 0.487 0.648 37.7 0.998 eqn.(3) 291 0.116 0.563 1.01 82.2 0.980 eqn.(4) 330 0.144 0.565 1.03 82.3 0.984 eqn.(5) 10.4 0.264 0.602 4.73 4.16 0.989 lower limit of the solid volume fraction at which the disperse phase behaves as a three-dimensional network structure~ and <pm is the maximum volume fraction, i.e. that corresponding to the maximum particle packing in quiet conditions. eqn. (7) has been already applied to alumina slips by kristoffersson et al. in [1] and by zupancic et al. in (2]. as can be seen in table 3, data regression according eqn. (7) gave the best fitting by using the 1:0 values given by eqns. (1) and (2); moreover, both the bingham and the casson 1:0 parameters can be assigned a physical meaning, in that a good agreement has been evaluated between the <pm values calculated by means of eqn. (7) and that experimentally determined by centrifugation (<pm,exp=0.51). very low values of <p0 with respect to the volume fraction of random particle packing <prp, calculated equal to 0.64 in (8] for suspensions of monomodal non­ interactive hard spheres, denote the presence of strong attractive forces among particles, i.e. the formation of floes and/or clusters. the size distribution of the alumina particles used being hot monomodal, the <prp should be slightly higher than 0.64. for the alumina suspensions investigated pecolation limit values lower than those found by zupancic et al. in [2] were determined; this means that the formation of a three­ dimensional network can be expected at solid volume fractions considerably lower than <prp=0.64. models of the 1jr =f(t1>, y) t}'pe as far as the tlr =f(<p~ i ) rheological models are concerned only the quemada equation [9-l i j in its first formulation was considered. this model, which is based on the dissipation energy by viscous friction, can be written as follows: .k=[ko +k00( y i y c}p}/{ l +( y i y c)p] (9} where k is an intrinsic viscosity with the limiting values ito and too for very low and very high shear rates. respectively. y c is a critical shear rate, beyond which the disaggregation process of the disperse phase prevails over the aggregation one. and p is an empirical exponent .. lying in the range 0 to 1. the p quantity was tentath·ely associated by quemada with particle shape table 4 variation of quemada intrinsic viscosities ko and k.x. and critical shear rate y c with solid volume fraction q, ko koo r c (s-1) 0.319 6.27 5.76 1790 0.370 5.41 5.03 1220 0.399 5.01 4.20 14700 0.430 4.65 4.41 1710 0.464 4.31 3.74 36400 (p=o.s: asymmetric particles; p=l: symmetric particles); better, the p parameter should be connected to the shape of the minimum-dimension aggregates, present even at very high shear rates. by a previous linear regression on the four quemada parameters, p values slightly superior to 0.5 were found, in accordance to the asymmetric shape of alumina particles. accordingly, a new fitting was performed keeping p equal to 0.5. the application of the quemada equation with three adjustable parameters provided very satisfactory results. as for the ko-«p dependence, the hyperbolic law k0 =2/<p was found; as for the koo-<p dependence, a satisfactory correlation was also found by using the law of hyperbolic type: k00=1.8/ci>. accordingly, the quemada equation becomes a model with only one adjustable parameters ( r c), which can be rewritten in this very simple form: fri: =10·(1+1/ .jy:) (10) where: (11) accordingly, the quemada model leads to the casson one. the quemada k0 , koo and y c values are listed in table 4: no regular variation of y c with <p has been noticed, even if their evident increase. with solid volume fraction is in fully agreement with its physical meaning. in the light of the above reported considerations, the casson equation seems to be the most suitable model for correlating shear stress and shear rate data for the alumina slips investigated. finally, in order to give a compact representation of the flow behaviour of the individual members for the alumina suspensions family a master-curve was traced. the master-curve of reduced viscosity, 11r• vs. reduced shear stress, 'tr, is shown in fig.6. for the alumina suspensions family considered the flow curve at «p =0.319 was assumed as reference curve; reduced variables are defined as fol1ows: 11r=anrt tr=ar't (12) shift factors a11 and a. were evaluated starting from the 'to and t}~e values determined by fitting the experimental data with the casson equation. so, they are defined as: (13) where: 65.0 1.00 1.00 table 5 shift factors alumina concentration (wt%) 70.0 72.5 75.0 77.5 0.712 0.473 0.350 0.176 0.549 0.471 0.150 0.136 100.,..---------------------. llr [pa-s] 10 "y 77.5 wt"/o v 75 wt% • 72.5wt% a 70wt% • 65wt% 0,1 +------.-----.----...---.--.--.,..-...,-......--j 100 'tr [pa} 1000 fig.6 reduced viscosity (yjr) vs. reduced shear stress master­ curve for the alumina slips investigated. 1~0~--------------------~ g',g" [pa] 1000 • 0 ,. •••••••••••••••••• ooooooooo • oooooo 00 o 0 ¢··················· ¢ ¢ ¢ 0 0 00 ¢ 0 oooo 0 77.5wt% o 72.5wt% 0 65wt% ro [s·1j ¢<> 0 o¢o 10 fig.7 storage (g') and loss (g") moduli variation with angular velocity (m) for some of the alumina suspensions studied.(0.7 rad of constant strain). 1l"",ref and 'to,ref are the casson parameters of the reference curve ( ci> =0.319), whereas r}oo,<p and 't"o,cll are the corresponding parameters of the suspension at ci> solid volume fraction. shift factors al} and ar are reported in table 5. oscillatory tests it can be observed that dynamic viscosity always decreases monotonically with frequency for all the alumina slips investigated. an inspection of the mechanical spectra determined for the alumina slips formulated without deflocculant, i.e. the plots of storage (g') and loss (g") moduli vs. angular velocity, shows that g" is always greater than g'; hence, one can state 153 "" <> 0.03wt% a a "" a 0.05wl"k """ • 0.10wt"k 10000 at:. "" ....... , ., ... 1.00 wt% ., ".,"., "".,.., ".,.., aai:.a a i:.aa a a 1:. a a a a a a a 6 a a a 10 +o---.----1~00--~--200r--.,..---3~00~-y-. ~[-s·-1)~400 fig.8 apparent viscosity (yj) vs. shear rate ( y ) tlow curves for the 77.5 wt% alumina+ sodium polyphosphate suspensions studied. 100 lj,'l]' [pa·s} rt' n --•-o--10 1 0.1 0.01 0.005 0.01 fig.9 apparent (yj) and dynamic (t} ') viscosit;. -. ~ deflocculant concentration ( y =200s-1 ;m =2s · 1 ). that no gel-like to sol-like transition occurred over the all frequency sweep explored. in addition, it results that both g' and g" are nearly independent of ro within the whole frequency range investigated. an example of both g' and g" variation with angular velocity i ~ reported in fig. 7. effect of deflocculant addition figure 8 reports the apparent viscosity vs. ~hear. rate flow curves obtained for the 77.5 wt% alumma shp to which a sodium polyphosphate was added as dispersing agent. from an examination of fig.b a shear"thinning behaviour is registered within an the defloccu~ant concentration range examined: hence. sod1um polyphosphate behaves in a different manner than in kaolin suspensions~ where its presence mv,jives a dilatant behaviour beyond a critical concentrat1''" t 121. in addition. a viscosity collapse is made ev1dcnt by adding a 0.01 wt% of deflocculant and pa~~u1~ from 0.01 to 0.03 wt% as welt final!;. by exam~nmg t~e results shown in figs. 9 and 10 th~ optimum d<)sage_ :~;r sodium polyphosphate was determmed for cd:::::0.05 \\:t •c · 154 1000~------------------------------~ g',g• [pa} 100 10 0.1 -l-.....------.-................. .......---r--..--..-r-t'.........,r---..-~"t"""5 o.oos om 0.1 cd [wt%j fig./0 storage (g•) and loss (g'') moduli vs. deflocculant concentration (<o =2s'1). conclusions as far as the rheological models of the -t=f( i ) type are concerned, the casson model proved to be the most suitable to describe the flow behaviour of alumina concentrated suspensions in the shear rate range explored and for any alumina concentration examined as well. as for the rheological models of the 11r=f( c!>, i ) type~ the quemada model gave satisfactory results, it reducing to the casson equation for the alumina slips investigated; in addition. the quemada p parameter can be associated tb the asymmetric shape of aggregates. the application of oscillatory techniques did not prove the existence of a gel-like to sol-like transition. finally, the optimum dosage for a sodium polyphosphate employed as dispersing agent was determined by means of rheological techniques. symbols a11, ar shift factors a, b, dcp parameters ofeqn. (6) deflocculant concentration, wt% g' a·~ determination coefficient values storage modulus. pa loss modulus, pa k ko parameter of the quemada equation quemada intrinsic viscosity for a very low shear rate . koo quemada intrinsic viscosity for a very high shear rate k consistency in eqns. ( 4*5) k' constant in eqn. (7) m exponent in eqn. (7) n exponent in eqns. (3~5) p exponent in the quemada equation std standard deviations estimates greek letters y shear rate, s -1 y c critical shear rate in the quemada equation." s-1 y r reduced shear rate in eqn. (11) q, solid (nominal) volume fraction cj>' parameter ofeqn. (6) n. effective volume fraction 'l'eff ci> 0 percolation threshold [see eqn. (7)] maximum solid volume fraction volume fraction of random particle packing apparent viscosity, mpa·s dynamic viscosity, pa·s plastic viscosity [see eqn. (1)], pa·s relative viscosity reduced viscosity , pa s viscosity at infinite shear rate, mpa·s shear stress, pa yield value, pa reduced shear stress, pa angular velocity, s-1 references 1. kr.istofferson a., lapasin r. and zupancic a.: ''proprieta reologiche di sospensioni di allumina: dipendenza dalla concentrazione di disperdente e di solido", in: proceedings of the "v convegno nazionale di reologia applicata", 103-107, 1997 2. zupancic a., lapasin r. and kristofferson a.: j. eur. cer. soc., 1998, 18,467-477 3. cesarano iii j. and aksay i. a.: j. am. ceram. soc. 1988, 71 (4), 250-255 4. cesarano ill j. and aksay i. a.: j. ·am. ceram. soc.1988. 71 (12),1062-67 5. briscoe b. j., khan a. u., luckham p. f. and ozkan n.: key engineering materials, 1997, 132/136,281-284 6. lyckfeldt 0. and ferreira j. m. f.: key engineering materials, 1997, 132/136, 313-316 7. incorvati c. m., lee d. h., reed s. j. and condrate r. a.sr.: am. cer. soc. bull.,j997, 76 (9)~ 65-68 8. pugh r. j. and bergstrom l. (eds.): "rheology of concentrated suspensionsn, in "surfaces and conoid chemistry in advanced ceramics processing", surfactant science series, marcel dekker, new york~ 51, 193-244, 1994 9. quemada d.: rheol. acta, 1977, 16, 82-94 10. quemada d.: rheol. acta, 1978., 17,632-642 11. quemada d.: rheol. acta, 1978., 17 't 643-653 12. papo a.~ piani l. and ricceri r.: colloids and surfaces a: physicochemical engineering aspects, in press page 148 page 149 page 150 page 151 page 152 page 153 hungarian journal of industry and chemistry vol. 45(1) pp. 29–36 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0006 formation, photophysics, photochemistry and quantum chemistry of the out-of-plane metalloporphyrins zsolt valicsek, 1* melitta p. kiss, 1 melinda a. fodor, 1 muhammad imran, 2 and ottó horváth 1 1 department of general and inorganic chemistry, institute of chemistry, faculty of engineering, university of pannonia, egyetem u. 10., h-8200 veszprém, hungary 2 department of chemistry, baghdad-ul-jadeed campus, the islamia university of bahawalpur, 63100 bahawalpur, pakistan among the complexes of porphyrins, special attention has been paid to those possessing out-of-plane (oop) structures, for the formation of which the size, as well as the coordinative character of the metal center are responsible. in these coordination compounds, the central atom cannot fit coplanarly into the cavity of the ligand, hence, it is located above the porphyrin plane, distorting it. equilibria and kinetics of the complex formation, spectrophotometric, photophysical and primary photochemical properties of post-transition and lanthanide oop metalloporphyrins were investigated, in addition electronic structural calculations were performed; hence, the general oop characteristics were determined.meanwhile, few doubtful questions have attempted to be answered concerning the categorization of metalloporphyrins, the borderline case complexes and hyperporphyrins. keywords: out-of-plane metalloporphyrins, formation kinetics, uv-vis spectrophotometry, photochemistry, borderline case complexes 1. introduction porphyrins and their derivatives play important roles in several biochemical systems. four pyrroles are connected through methylidine bridges, forming the porphin ring. its planar structure with an extended conjugated π-electron system provides aromatic characteristics and a special coordination cavity for the binding of metal ions of suitable radius [1-2]. metalloporphyrins are the central parts of naturally important compounds, e.g., magnesium(ii) chlorins in bacteriochlorophylls and chlorophylls; iron(ii) protoporphyrin in hemoglobin; and iron(iii) protoporphyrins in myoglobin, cytochromes, oxidase, peroxidase, catalase, and oxoanion reductase enzymes. ringed tetrapyrroles provide strong chelating effect which can promote the hyperaccumulation of rare metal ions in living cells, and also in abiotic environments, e.g. in kerogens. in porphyrins the conjugation favors a planar structure. however, peripheral substituents or the metal center (originating from its size or axial ligand) can cause geometrical distortion. this certainly affects the functions of enzymes, as well as the biosynthesis of metalloporphyrins. in chemical research, due to distortion, redox potentials, basicity, reactivity, catalytic *correspondence: valicsek@almos.uni-pannon.hu activity and coordinative abilities of porphyrins can be modified. also, due to the distortion, the degree of symmetry decreases, resulting in characteristic spectral changes in various ranges of the electromagnetic spectrum. the most frequent types of distortions are dome, saddle, ruffled and wave (chair-like) [3]. overcrowded substitution on the periphery [3-4] or insufficiently short metal-nitrogen bonds due to the shrinkage of the coordination cavity can cause the ruffled or saddled deformation [2, 5-7]. if, however, the m-n bonds are significantly longer than half the length of the diagonal n-n distance in the free-base porphyrin, dome deformation can occur. this happens if the radius of the metal center exceeds the critical value of about 75-90 pm (depending on the type of porphyrin ligand) or square planar coordination is not preferred. such metal ions are too big to fit into the ligand cavity. hence they are located above the plane of the pyrrolic nitrogens; forming sitting-atop (sat) or out-of-plane (oop see fig.1) complexes, displaying thermodynamic instability, kinetic lability, typical photophysical features and photochemical reactivity [89]. in this work, we review our recent results regarding the formation, structure and photoinduced behavior of water-soluble oop metalloporphyrins. these complexes with a diverse range of metal ions can be more simply produced in aqueous systems than in organic solvents. in this regard one of the most suitable free-base ligands is the anionic 5,10,15,20-tetrakis(4sulfonatophenyl)porphyrin (h2tspp4– see fig.1) due valicsek, kiss, fodor, imran, and horváth hungarian journal of industry and chemistry 30 to its negative charge promoting the coordination of positively charged metal ions. besides, this ligand is the most frequently used reagent among the free-base porphyrins [1]. 2. experimental analytical grade tetrasodium 5,10,15,20-tetrakis(4sulfonatophenyl)porphyrin (c44h26n4o12s4na4·12h2o = na4h2tspp·12h2o) (sigma–aldrich) and simple metal salts such as nitrate, sulfate, chloride or perchlorate were used for the experiments. the solvent was double-distilled water purified with a millipore milli-q system. the ph of the majority of the metalloporphyrin solutions was adjusted to 8 by application of a borate buffer, whilst maintaining the ionic strength at a constant value of 0.01 m. in a few cases, the ph was regulated to 6, and the ionic strength to 1 m, by an acetate buffer, to hinder hydrolysis. the absorption spectra were recorded and the spectrophotometric titrations were monitored by using a specord s-100 or a specord s-600 diode array spectrophotometer. for the measurement of fluorescence spectra, a perkin elmer ls-50b or a horiba jobin yvon fluoromax-4 spectrofluorometer was applied. the latter piece of equipment supplemented with a time-correlated single photon counting (tcspc) accessory was utilized to determine fluorescence lifetimes, too. uv-vis spectrophotometric data (molar absorption, fluorescence quantum yields and lifetimes) of the free-base porphyrin were used as references for the determination of those of metalloporphyrin complexes [1]. for the determination of photochemical properties via continuous irradiations, a piece of amko lti photolysis equipment (containing a 200w xe–hg lamp and a monochromator) was applied. for the electronic structural calculations, the b3lyp density functional theory (dft) method and the lanl2dz basis set were used. on the basis of our earlier quantum chemistry experiences, the sulfonatophenyl substituents exhibit negligible effects on the coordination of the metal center in the cavity; thus, the anionic porphyrin (h2tspp4−) can be modeled on the unsubstituted porphin (h2p) [4, 10]. 3. results and discussion 3.1. uv-vis spectrophotometry porphyrins and their derivatives belong to the strongest light-absorbing materials (both natural and artificial), therefore, ultraviolet-visible spectrophotometry is one of the most fundamental, in addition, most informative spectroscopic techniques in porphyrin chemistry. they possess two ππ* electronic transitions in the visible range of the electromagnetic spectrum: bor soret band at about 350-500 nm, usually with a molar absorbance of 105 m-1cm-1 (fig.2), and q bands at 500-750 nm generally with intensities of one order of magnitude less. these latter bands in free-base ligands split due to the presence of protons on two diagonally situated pyrrolic nitrogens, to be more precise, as a result of the reduced symmetry (because of the disappearance of the four-fold rotation axis) compared to the metallated or deprotonated forms. this split is not detectable in the soret range, hence, these two types of bands in the visible region are remarkably different [1]. in the soret region, compared to the corresponding free-base ligands, the typical in-plane metalloporphyrins (e.g. fe3+, au3+, cu2+, pd2+) exhibit blueshifts because the atomic orbitals of their metal centers which are covalently bonded in the plane can overlap more strongly with the highest occupied molecular orbitals (homo) of the ligand, resulting in a stronger reduction in energy; whereas the lowest unoccupied molecular orbitals (lumo) do not change. thus, the energy gaps between the excited and ground states become greater. in the oop complexes, the atomic orbitals of the more weakly bonded metal ions (e.g. cd2+, hg2+, tl3+) may slightly affect the unoccupied mos and to a lesser extent the occupied ones, leading to a reduction of the energy gaps, i.e. an increase in the corresponding wavelengths (scheme 1) [1, 9]. a) b) figure 1. structure of an in-plane metalloporphyrin {mtspp=metallo-5,10,15,20-tetrakis(4sulfonatophenyl)porphyrin} (a); and that of an out-of-plane complex (b) [9]. study of the out-of-plane metalloporphyrins 45(1) pp. 29–36 (2017) 31 beside electronic factors, due to the rigidity of the porphyrins’ ringed structure, steric effects also influence the spectra: the redshift of absorption bands is one of the most common spectroscopic consequences of the non-planarity of porphyrin [3]. octabrominated freebase porphyrin, h2tsppbr8 4–, was applied to investigate the spectrophotometric effects of the macrocycle’s highly saddle-distorted structure (fig.2). in porphyrins with aryl substituents, this distortion can lead to the extension of delocalization by the twisting of aryl substituents from a nearly perpendicular orientation closer to the porphyrin plane (fig.1) [4]. the larger, post-transition metal ions, e.g. thallium(i), lead(ii) and bismuth(iii) ions, can cause a similarly large redshift of the porphyrins’ absorption bands. since their complexes possess the most highly dome-distorted structures, also a ruffled-like deformation of the periphery superposes on this high degree of doming. considering the spectral effects (bathochromic or not quite exactly hyperchromic effects), the complexes possessing such highly redshifted absorption bands used to be referred to as hyperporphyrins; depending on the highest occupied electron subshell of the metal center, por d-type hyperporphyrins. previously in terms of this categorization of metalloporphyrins, only the electronic effects of the metal ion (through its electron configuration) were taken into consideration and not steric (distorting) effects [1]. nevertheless, in the typical d-type hyperporphyrins, e.g. the low-spin chromium(iii), manganese(iii), nickel(ii) and cobalt(iii) porphyrins, the radius of the metal center, and thus, the metal-nitrogen bonds are too short, resulting in the contraction of the coordination cavity, along with the ruffled deformation of the macrocycle [2, 5-7]. 3.2. equilibrium and kinetics of complex formation porphyrins are peculiar ligands in terms of complexation due to their planar, cyclic, rigid, aromatic, tetradentate, as well as protonated structure. the formation of an out-of-plane complex of a large metal ion is usually at least two orders of magnitude faster than that of an in-plane one since a smaller metal ion is not able to coordinate to all four pyrrolic nitrogens of the reaction intermediate, in the cavity of which the two protons also remain {h2-p-m}. therefore, dissociation of the metal ion is more favorable than that of the protons. besides the insertion of a smaller metal ion, its dissociation from the in-plane complex of the endproduct may be kinetically hindered due to the rigidity of the macrocycle [1]. formation of the in-plane complexes used to be enhanced by the addition of a small concentration of a metal ion with larger ionic radius (e.g. cd2+, hg2+, pb2+) to the solution of the smaller one because the insertion of the larger metal ion into the ligand cavity is much faster. however, the oop complex is considerably less stable. in its dome-distorted structure, two diagonal pyrrolic nitrogens are more accessible from the other side of the ligand, owing to the enhancement of their sp3 hybridization, hence, the metal center can be easily exchanged for the smaller one [1-2, 9]. this accessibility makes the realization of dinuclear out-of-plane monoporphyrins (2:1 complexes) possible if the metal ion possesses a low (single) positive charge and is large, i.e. its charge density is small enough, e.g. mercury(i), silver(i) and thallium(i) ions [1, 8-9]. moreover, the out-of-plane position of the metal center, together with the dome-distorted structure (owing to the twisting of aromatic substituents from a nearly perpendicular position closer to the porphyrin plane) may promote the formation of so-called sandwich complexes of various compositions, in which two metal ions can coordinate to one macrocycle, and, reversely, one metal ion can concomitantly coordinate to two ligands, (fig.3) [1-2, 9]. lanthanide(iii) ions form typical examples of metallo-oligoporphyrins because they are inclined to form complexes of higher coordination number (8-12). however, they are hard lewis acids, hence, their insertion into the coordination cavity of the softer n-donor porphyrin ligand is a slow and complicated process in aqueous solutions. this scheme 1. simplified energy level diagram for the change of the porphyrin’s molecular orbitals in different types of complexes [9]. figure 2. absorption spectra of the free base (h2tspp4–); the highly distorted, octabrominated free base (h2tsppbr8 4–); a typical in-plane (pdiitspp4–); and a typical out-of-plane metalloporphyrin (hgiitspp4–) within the soret range [1]. valicsek, kiss, fodor, imran, and horváth hungarian journal of industry and chemistry 32 phenomenon partly originates from the stability of their aqua complexes. due to the consequence of their pearson-type hard character, they coordinate rather to the peripheral substituents of porphyrin (instead of the pyrrolic nitrogens), i.e. to the ionic group ensuring water-solubility if they possess similarly hard o-donor atoms (e.g. carboxy or sulfonatophenyl groups). at lower temperatures, under kinetic control, the early lanthanide(iii) ions are not able to coordinate into the cavity, rather to the periphery; resulting in the formation of the tail-to-tail dimer of free-base ligands (as the tail used to be referred to as the periphery). higher temperatures and thermodynamic control are also necessary for the insertion of metal ions into the cavity produced by four pyrrolic nitrogens; resulting in the formation of typical metalloporphyrin complexes. after the discovery of the possible coordination bonds between lanthanide ions and sulfonato substituents, the formation of lanthanide bisporphyrins may be realized as a tail-to-tail dimerization of two metallomonoporphyrin complexes through a metal bridge; deviating from the head-to-head connection as in the case of typical sandwich complexes (head refers to the cavity; see fig.3). on the basis of our previous experiences, the coordination position of lanthanide ions was influenced by the change in temperature [1-2], [1113]. during the investigation of the formation of “typical p-type hyperporphyrin” complexes (e.g. tl+, pb2+, bi3+), the species possessing highly redshifted absorption bands are the end-products of metalation only in hydrophobic solvents, since they can appear in aqueous solutions as intermediates with shorter or longer lifetimes depending on the metal ion. the absorption spectra of the end-products of these transformation reactions are very similar (less redshifted) to those of the typical, common out-of-plane metallo-monoporphyrins (e.g. hgii-porphyrin in fig.2). this phenomenon may be accounted for to the considerable coordination ability or the polarizing effect of water molecules, which can enable the complex to overcome the kinetic energy barrier towards the formation of the more stable structure, in which the metal center is located closer to the ligand plane, resulting in decreases in distortion, as well as redshift. furthermore, “hyperporphyrins” can appear as intermediates in smaller amounts during the formation of typical, common out-of-plane metallomonoporphyrins as well [1, 14]. in the case of “d-type hyperporphyrin” complexes (e.g. mn3+, co3+, ni2+), the low-spin and ruffled complex with a contracted cavity can exist in a spinisomerization equilibrium with the high-spin and planar forms, which not only exhibits less redshift, but rather blueshifted absorption bands compared to those of the free-base ligand. this reaction can be influenced by the strength of the m-n bonds (owing to the electronic effects of peripheral or axial substituents), due to the size of the coordination cavity (owing to the substitution or saturation of methylidene bridges or pyrrolic carbons) [1-2, 5-7]. 3.3. photophysics porphyrins represent one of the most interesting groups of compounds in terms of photophysical properties and biological significance. due to their rigid structure and aromatic electronic system, they display two types of fluorescence: beside their relatively strong singlet-1 fluorescence in the range of 550–800 nm, weak and rare singlet-2 luminescence is observable between 400 and 550 nm upon excitation of the soret band (scheme 1) [1]. the quantum yields of s2-fluorescence are about 3 orders of magnitude lower than those of s1-fluorescence in the case of free-base porphyrins, especially ~1200fold for h2tspp4(6.3×10-5 vs. 7.5%). however, this ratio decreases with metalation, mainly in the case of the formation of out-of-plane complexes. since the structure of s2-excited porphyrins may be close to that of the dome-distorted oop complexes that are already in the electronic ground state. another consequence of this structural similarity (namely small stokes shift) is that the directions of the shifts of s2-fluorescence bands invert (according to soret absorption) between the inplane (redshifted) and out-of-plane (blueshifted) complexes when compared to the free-base ligand [1]. singlet-1 fluorescence bands exhibit blueshifts in both types (in-plane and out-of-plane) of metalloporphyrins, as a consequence of the aforementioned split in free-base ligands because of the presence of two protons, as well as their reduced symmetry (scheme 1). furthermore, almost all complexes exhibit similarly large stokes shifts, as well as lifetimes and quantum yields. in the case of in-plane a) b) figure 3. potential structures of 3:2 bisporphyrin: (a) head-to-head or (b) tail-to-tail [2]. study of the out-of-plane metalloporphyrins 45(1) pp. 29–36 (2017) 33 metal centers, the spin-orbit coupling, as an electronic quenching effect, may be dominant. whereas for typical out-of-plane metalloporphyrins, the distortion, as a steric effect, can enhance their non-radiative decay. the highly distorted (dand p-type) hyperporphyrins, the paramagnetic in-plane complexes (e.g. feiiitspp3-), as well as the head-to-head-type oop bisporphyrins {e.g. hgii 3(tspp)2 6-} do not exhibit significant levels of luminescence at room temperature. conversely, the paramagnetic out-of-plane complexes (e.g. lniiitspp3-) possess similar fluorescence properties to that of the diamagnetic ones because a paramagnetic metal ion can cause the disappearance of fluorescence by spin-orbit coupling only if it is located in the plane. in the oop position, it is not able to perturb as efficiently the molecule orbitals of the macrocycle that result in the common absorption and emission out-of-plane characteristics [1-2, 9]. lanthanide(iii) bisporphyrins {lniii 3(tspp)2 3-} have many similarities in terms of absorption and emission properties to those of monoporphyrin complexes (lniiitspp3-). these may only originate from the very weak π–π interactions between the macrocycles in the tail-to-tail-type aggregations (fig.3) [1-2, 11-13]. 3.4. photochemistry porphyrin derivatives are the main components of photosynthesis, synthetically as well. since the overall quantum yield of fluorescence and intersystem crossing resulting in the formation of triplet states is in excess of 95%, merely a slight proportion of excitation energy is dissipated as heat from singlet states. this ratio is the major reason why porphyrins are efficient in terms of optical sensations and photosensitizations. free-base and kinetically inert in-plane metalloporphyrins may be appropriate candidates to be applied in photocatalytic systems based on outer-sphere electron transfer. d-type hyperporphyrins can be particularly promising from this viewpoint owing to their distorted structure which may enhance the (photo)redox reactivity of these coordination compounds. in the presence of a suitable electron acceptor (methylviologen, mv2+) and donor (e.g. triethanolamine, teoa), these complexes proved to be efficaciousl photocatalysts that transfer electrons between the ground-state reactants through an outersphere mechanism, generating the mv•+ radical cation. this system can be applied for the production of hydrogen from water [2, 5-7]. contrarily, the inner-sphere photoredox reactions are characteristic of the out-of-plane metalloporphyrins because of this special coordination (scheme 2): an irreversible photoinduced charge-transfer from the ligand to the metal center (ligand-to-metal charge transfer, lmct) improves the efficiency of charge separation, which allows their utilization as catalysts in cyclic processes for the synthesis of chemicals capable of conserving light energy, hopefully in terms of the photochemical cleavage of water. due to photoinduced lmct the charge of the metal center decreases and its size increases, overall its charge density diminishes, hence, the coordinative bonds can easily split. the reduced metal ion can leave the cavity, primarily in polar solvents, and induce further redox reactions. the latter processes strongly depend on the stability of the reduced metalion in the actual medium. the oxidized and metal-free (cat)ionic radical of porphyrin is a very strong base: it is immediately protonated and forms the free-base radical, which is a long-lived and rather strong electron acceptor, especally in deaerated solutions. since it would only oxidize water to oxygen at higher phs, a slightly more efficent reducer (such as alcohols or aldehydes of low molecular weight) is needed, from which useful byproducts can be produced in terms of photocatalytic hydrogen generation. in the absence of any electron donor that promotes the regeneration of the porphyrin, it undergoes the primary photochemical processes; an overall four-electron oxidation involving a ring-cleavage, the end-product of which is a dioxotetrapyrrole derivative (bilindione). this ring-opening process can be followed by spectrophotometry owing to the disappearance of the soret band, as well as the typical change in the region of q bands [2, 4, 8-16]. photochemical quantum yields of this ring-opening reaction (without regeneration) are about 2-3 orders of magnitude higher for the out-of-plane complexes (10-4 – 10-2) than for the free-base and in-plane metalloporphyrins (10-6 – 10-5). in addition, in the case of out-of-plane complexes, photoinduced dissociation in scheme 2. simplified demonstration of the mechanism for the inner-sphere photoredox reaction of an out-ofplane metalloporphyrin [8]. valicsek, kiss, fodor, imran, and horváth hungarian journal of industry and chemistry 34 the absence of a redox reaction can occur, originating from their lability, and structural transformations to another complex form or conformer were observed in some cases as a photoinduced change of the type or measure of distortion (e.g. dand p-type hyperporphyrins) [2, 4, 8-10, 14-16]. besides the typical post-transition metal ions, lanthanide(iii) ions were also applied for out-of-plane coordination because their contraction makes the finetuning of the out-of-plane distance possible, and their high negative redox potentials promote the photoinduced cleavage of water. photochemical activities of their complexes confirm that the redox potentials of the metal centers are not the main determining factor, rather their out-of-plane distances [2, 11-13]. deviating from the oop complexes of posttransition metal ions, another stable photoproduct was observable during the photolysis of lanthanide(iii) porphyrins. it displays a typical absorption band in the q range (at ~600 nm), which may be assigned as a charge transfer between the metal ion and open-chain, dioxo-tetrapyrrole derivative (bilindione, see scheme 2). its oxo-groups, as donor atoms, may coordinate with the lanthanide ions, as a consequence of their similar pearson-type hard characteristics, contrary to the softer post-transition metal ions [2, 11]. during the photolysis experiments, only small differences appeared between lanthanide(iii) monoand bisporphyrin complexes, which might confirm a special type of aggregation through the peripheral sulfonato substituents with weak π-π interactions (tail-to-tail, see fig.3) [2, 11-13]. deviating from these observations, the differences are much more significant in the case of the most typical, post-transition metallo-bisporphyrin compared to the monoporphyrin equivalent; namely between hgii 3(tspp)2 6and hgiitspp4-. the overall quantum yield is ~2 orders of magnitude higher and the photoinduced dissociation of a metal ion became the dominant reaction in the head-to-head sandwich complex as a consequence of the strong π-π interactions [9-10]. 3.5. quantum chemical calculations the main aims of our electronic structural calculations were to determine the primary consequences for the outof-plane position of a metal center, and confirm the experimentally observed correlation between the uvvis spectral shifts and the coordination position of the metal center (in-plane or out-of-plane). in the light of these aspects, the unsubstituted porphin (h2p, c20h14n4) was used as a model for the calculations, instead of the tetrakis(sulfonatophenyl)porphyrin (h2tspp4–, c44h26n4o12s4 4-). on the basis of the few comparative calculations that were conducted, the phenyl-, as well as the sulfonatophenyl substituents have negligible effects on the coordination of the metal center in the cavity. however, they can significantly influence the formation of bisporphyrin complexes, even in the case of head-tohead structures [4, 10]. according to our quantum chemical experience, the value of the critical radius became ~100 pm instead of the experimentally suggested ~75-90 pm as a consequence of the significant expansion of the coordination cavity to coplanarly incorporate the metal ions. the proportion of borderline cases, i.e. complexes with questionable structures (somewhere between inplane and out-of-plane), increased with further posttransition metal ions (e.g. ag2+ [15], cd2+ [4], tl3+ [16]) that possess ionic radii of ~90-95 pm. calculated bond lengths (m-n) and atomic distances (n-n) considerably deviate from the expected ones supposed on the basis of the values of the deprotonated porphyrins (p2-). to describe this phenomenon, an axial ligand was applied to these metal centers to extract them out of the cavity. consequently, expansion stopped, and the out-of-plane distance increased dramatically together with the degree of dome distortion and redshifts of absorption bands. from this point of view, two possible explanations can be supposed for the borderline-case complexes: the experimentally observed common oop characteristics may originate from this expansion, tension; and small perturbations (e.g. the axial coordination in the calculation or photoexcitation in the experiments) may facilitate the metal center to adopt an out-of-plane position, too. another possibility is that the method of calculation strongly prefers planar structures. in our time-dependent density functional theory (td-dft) calculations, the correlation found between the measured and calculated shifts associated with the position of the metal center was not totally linear, but nevertheless acceptable. the main exceptions were the borderline cases (high-spin mn2+, fe2+ and zn2+) and the d-type hyperporphyrins (because their structures were determined to be totally planar), as well as the p-type hyperporphyrins (because a ruffled-like deformation did not superpose on their dome-like structure). the regression of correlation was much worse within the soret band than in the case of the q bands. the soret band was also split in the calculations, which cannot be detected experimentally. on the basis of further experimental observations and doubts in the literature, the validity of the theoretical model in use at present is questionable. hence, the development of a more suitable one is in progress. 4. conclusion in conclusion, it can be declared that the categorization of metalloporphyrins was complemented by the role of their distortion, which is primarily responsible for their spectral features, whereas the electronic structure of their metal centers is a secondary factor, with a considerable level of emphasis on the in-plane complexes. the position of the metal center (in-plane or out-of-plane) in the monoporphyrin complexes, as well as the type (head-to-head or tail-to-tail) of the bisporphyrin complexes can be determined on the basis of their uv-vis absorption and emission properties. study of the out-of-plane metalloporphyrins 45(1) pp. 29–36 (2017) 35 hyperporphyrin spectra can appear, owing to the peripheral substitution (octabromination) of free-base ligands. furthermore, the high degree of redshift may disappear during the spin isomerization of d-type metalloporphyrins or the transformation of p-type ones. consequently, the real origin cannot be an electronic but rather a steric effect, namely the measure of distortion, which can confirm the absence of their fluorescence. in terms of photochemical activity, several dissimilarities were found between the in-plane and outof-plane metalloporphyrins; the most remarkable of them was the mechanism of their photoredox reactions: outer-sphere electron transfer is typical of the previous ones, while the inner-sphere equivalent is most prevalent for the latter ones. as a further consequence of the oop position of the metal center, photoinduced dissociation and transformation reactions can occur within their complexes. in our electronic structural calculations, the number of borderline-case complexes expanded, on the basis of which common oop characteristics that can be experimentally observed may acquire a novel explanation. acknowledgement this research was supported by the széchenyi 2020 fund under the ginop-2.3.2-15-2016-00016 and efop-3.6.1-16-2016-00015 projects. assistance with quantum chemical calculations provided by professor györgy lendvay (research centre for natural sciences, hungarian academy of sciences) is gratefully acknowledged. finally, this manuscript is dedicated to the memory of professor jános liszi, who, as the head of the doctoral school for chemistry at the university of veszprém, praised the corresponding author’s phd dissertation of a similar title in 2007. references [1] valicsek, z.; horváth, o.: application of the electronic spectra of porphyrins for analytical purposes: the effects of metal ions and structural distortions, microchem. j., 2013 107, 47–62 doi: 10.1016/j.microc.2012.07.002 [2] horváth, o.; valicsek, z.; fodor, m.a.; major, m.m.; imran, m.; grampp, g.; wankmüller, a.: visible light-driven photophysics and photochemistry of water-soluble metalloporphyrins, coord. chem. rev., 2016 325, 59–66 doi: 10.1016/j.ccr.2015.12.011 [3] shelnutt, j.a.; song, x.-z.; ma, j.-g.; jia, s.-l.; jentzen, w.; medforth, c.j.: nonplanar porphyrins and their significance in proteins, chem. soc. rev., 1998 27, 31–41 doi: 10.1039/a827031z [4] valicsek, z.; horváth, o.; lendvay, g.; kikaš, i.; škorić, i.: formation, photophysics, and photochemistry of cadmium(ii) complexes with 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin and its octabromo derivative: the effects of bromination and the axial hydroxo ligand, j. photochem. photobiol. a, 2011 218, 143–155 doi: 10.1016/j.jphotochem.2010.12.014 [5] fodor, m.a.; horváth, o.; fodor, l.; grampp, g.; wankmüller, a.: photophysical and photocatalytic behavior of cobalt(iii) 5,10,15,20-tetrakis(1methylpyridinium-4-yl)porphyrin, inorg. chem. commun., 2014 50, 110–112 doi: 10.1016/j.inoche.2014.10.029 [6] fodor, m.a.; horváth, o.; fodor, l.; vazdar, k.; grampp, g.; wankmüller, a.: photophysical and photochemical properties of manganese complexes with cationic porphyrin ligands: effects of alkyl substituents and micellar environment, j. photochem. photobiol. a, 2016 328, 233–239 doi: 10.1016/j.jphotochem.2016.06.011 [7] major, m.m.; horváth, o.; fodor, m.a.; fodor, l.; valicsek, z.; grampp, g.; wankmüller, a.: photophysical and photocatalytic behavior of nickel(ii) 5,10,15,20-tetrakis(1-methylpyridinium-4-yl) porphyrin, inorg. chem. commun., 2016 73, 1–3 doi: 10.1016/j.inoche.2016.09.001 [8] horváth, o.; valicsek, z.; harrach, g.; lendvay, g.; fodor, m.a.: spectroscopic and photochemical properties of water-soluble metalloporphyrins of distorted structure, coord. chem. rev., 2012 256, 1531–1545 doi: 10.1016/j.ccr.2012.02.011 [9] horváth, o.; huszánk, r.; valicsek, z.; lendvay, g.: photophysics and photochemistry of kinetically labile, water-soluble porphyrin complexes, coord. chem. rev., 2006 250, 1792–1803 doi: 10.1016/j.ccr.2006.02.014 [10] valicsek, z.; lendvay, g.; horváth, o.: equilibrium, photophysical, photochemical and quantum chemical examination of anionic mercury(ii) monoand bisporphyrins, j. phys. chem. b, 2008 112(46), 14509–14524 doi: 10.1021/jp804039s [11] imran, m.; szentgyörgyi, c.; eller, g.; valicsek, z.; horváth, o.: peculiar photoinduced properties of water-soluble, early lanthanide(iii) porphyrins, inorg. chem. commun., 2015 52, 60–63 doi: 10.1016/j.inoche.2014.12.016 [12] kiss, m.p.; imran, m.; szentgyörgyi, c.; valicsek, z.; horváth, o.: peculiarities of the reactions between early lanthanide(iii) ions and an anionic porphyrin, inorg. chem. commun., 2014 48, 22–25 doi: 10.1016/j.inoche.2014.08.001 [13] valicsek, z.; eller, g.; horváth, o.: equilibrium, photophysical and photochemical examination of anionic lanthanum(iii) monoand bisporphyrins: the effects of the out-of-plane structure, dalton trans., 2012 41, 13120–13131 doi: 10.1039/c2dt31189e [14] valicsek, z.; horváth, o.; patonay, k.: formation, photophysical and photochemical properties of water-soluble bismuth(iii) porphyrins: the role of the charge and structure, j. photochem. photobiol. a, 2011 226, 23– 35 doi: 10.1016/j.jphotochem.2011.10.011 valicsek, kiss, fodor, imran, and horváth hungarian journal of industry and chemistry 36 [15] harrach, g.; valicsek, z.; horváth, o.: watersoluble silver(ii) and gold(iii) porphyrins: the effect of structural distortion on the photophysical and photochemical behavior, inorg. chem. commun. 2011 14, 1756–1761 doi: 10.1016/j.inoche.2011.08.003 [16] valicsek, z.; horváth, o.: formation, photophysics and photochemistry of thallium(iii) 5,10,15,20tetrakis(4-sulphonatophenyl)porphyrin: new supports of typical sitting-atop features, j. photochem. photobiol. a, 2007 186, 1–7 doi: 10.1016/j.jphotochem.2006.07.003 hungarian journal of industry and chemistry vol. 49(2) pp. 85–89 (2021) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2021-27 complementary manipulator tool development for safe cobot-assisted hydroponics imre paniti*1,2, jános nacsa1,2, dávid szűr1, sándor rácz3, and józsef tóth4 1elkh sztaki, centre of excellence in production informatics and control, kende u. 13–17, budapest, 1111, hungary 2széchenyi istván egyetem, egyetem tér 1, győr, 9026, hungary 3green drops farm kft., hold u. 56, debrecen, 4034, hungary 4hepenix kft., petőfi sándor u. 39, diósd, 2049, hungary human–robot collaboration is gaining ground in manufacturing, healthcare and logistics but also in agriculture. different types of applications in the latter field are becoming more common. however, in all scenarios, safety assessment and verification are crucial to cope with the related standards and specifications. in this paper, the development and safety testing of a complementary manipulator tool (clip) is presented which can by design limit the physical interaction energy in a hazardous collaborative robot (cobot) scenario, namely when loading the plant of a hydroponic system. keywords: hydroponics, human-robot collaboration, safety 1. introduction using robots in agriculture is a rather old field of interest with many difficult automation problems. incorporating automation can help hydroponic systems become more efficient and productive because according to ref. [1] labor is the biggest cost in this domain. in a review [2] about smart hydroponic systems, some robotic applications were mentioned, e.g. harvesting strawberries and cleaning greenhouses. in the real business world, some companies offer completely robot-based hydroponic environments, e.g. a start-up called iron ox has just received a big investment [3] for their complete hydroponic farming solution. the safety aspects in indoor farming environments were also investigated [4]. in this paper, the technical criteria of a cobotised hydroponic system are presented alongside the development of a complementary manipulator tool which is finally tested against a safety protocol. 2. technical criteria in order to create a safe, cobotised hydroponic system, the directive 2006/42/ec of the european parliament and of the council of 17 may 2006 on machinery [5], and amending directive 95/16/ec (recast [6] needs to be applied, together with the low voltage directive 2014/35/eu [7] which is applicable from 20th april 2016, i.e. the council directive 2006/95/ec of *correspondence: imre.paniti@sztaki.hu 12th december 2006 on the electrical equipment designed for use within certain voltage limits, amended by (93/68/eřf) and the emc directive (2014/30eu [8] applicable from 20th april 2016), that is, the council directive 2004/108/ec of 15th december 2004 on the approximation of the laws of the member states relating to electromagnetic compatibility. furthermore, although a large number of initially considered harmonized standards are present, the main relevant ones are the following: • iso 13855:2010 [9] safety of machinery. positioning of safeguards with respect to the approach speeds of parts of the human body. • en 547-3:2009 [10] safety of machinery. human body measurements. • iso 14123-1:2015 [11] safety of machinery reduction of risks to health from hazardous substances emitted by machinery part 1: principles and specifications for machinery manufacturers. • en 1005-1:2001+a1:2008 [12] safety of machinery human physical performance part 1: terms and definitions. • en 1005-3:2002+a1:2008 [13] safety of machinery human physical performance part 3: recommended force limits for machinery operation. • iso 10218-1:2011 [14] robots and robotic devices. safety requirements for industrial robots. https://doi.org/10.33927/hjic-2021-27 mailto:imre.paniti@sztaki.hu 86 paniti, nacsa, szűr, rácz, and tóth figure 1: set-up of the cobotised hydroponic system with 3 zones. figure 2: hydro pot. • iso 3691-4:2020 [15] industrial trucks. safety requirements and verification part 4: driverless industrial trucks and their systems. • iec 61508-3:2010 [16] functional safety of electrical/electronic/programmable electronic safetyrelated systems part 3: software requirements. • sist en 61508-5:2011 [17] functional safety of electrical/electronic/programmable electronic safety-related systems part 5: examples of methods for the determination of safety integrity levels. the technical specification, iso/ts 15066:2016 [18] robots and robotic devices collaborative robots, should also be taken into consideration. these directives and standards were necessary because the cobotised hydroponic system consists of an ur5 cobot arm mounted on an automated ground vehicle (agv) which is docked to the hydroponic growing tower with an electric pump (see fig. 1). based on the set-up, 3 hazard zones were defined: • zone 1: primary process area • zone 2: secondary process area • zone 3: surrounding equipment figure 3: plant roots in the hydro pot. 3. risk assessment the risk analysis was carried out for zone 1 according to a normal methodology, following the steps of the iso 12100:2010 standard [19]. after recognizing the hazards and the injuries, a risk graph had to be categorized based on iso 13849-1:2015 [20]. as a result of the categorization, the risk level of each hazard could be calculated. the risk level of each hazard was calculated using the worst result. as the cobot arm is equipped with a two-finger gripper and is responsible for loading the seedlings, this is one of the crucial elements of the system in terms of safety. special care needs to be taken when manipulating the plants as on the one hand, damage to the crops, leaves and roots should be avoided, but on the other hand an unintended collision with a plant carrier should not exceed the biomechanical threshold values defined in ref. [18]. 4. clip development green drops farm kft. developed its hydroponic system using a commercially available product called a hydro pot (see fig. 2) with a diameter of 50 mm for creating holes to plant plants by following the same practices adopted by similar pieces of equipment. during the development of automation and robotization, a problem occurred, namely that as the crops grow their roots overgrow the hydro pot so the plant becomes stuck where it is (see fig. 3). as a result, the arm of the cobot is unable to handle the pots, which cannot be used again. in order to be sustainable and recycle, several versions of clips have been designed and commercially available rockwool cubes used. hungarian journal of industry and chemistry tool development for safe cobot-assisted hydroponics 87 figure 4: one of the first clip prototypes. figure 5: clip prototypes with vertical spikes. figure 6: clip prototypes with horizontal spikes. as the cobot arm could not handle the clips because the part (a flag-like handle) it would grab (see fig. 4) had become overgrown by the plant, that part had to be redesigned. in the first versions of the design, the spike on the clips was vertical, but during testing it was demonstrated that it could cause serious injuries to people (see fig. 5), despite the fact that the clips had been created using 3d printing. the end of the spike needed to be blunted and placed horizontally in order to avoid causing potential injuries (see fig. 6). even though horizontal rockwool cubes were produced to facilitate its installation, the plants could still fall off. in the final version, nooks were placed on the clips on which semicircular plant holder rings can be placed at different heights. this prevents plants from falling off and it is safer moving them using the cobot arm (see fig. 7). 5. collision tests tests were carried out on the clips according to a testing protocol entitled "test robot arm for collision with movable object (impact)” from the covr toolkit [21], which functions also as a library for protocol testing of cobot applications. these tests are in harmony with the standards within the frame of cobot usage as described in ref. [22]. force measurements were recorded with a gte kmg 500-75 force cell (spring rate: 75 n/mm with the damping material sh70) while pressure values were measured with fuji prescale llw-type films (see fig. 8). the results of 3 experiments at a cobot speed of 0.1 m/s showed that for a human hand only a transient collision can occur with a maximum force of 47 n (see fig. 49(2) pp. 85–89 (2021) 88 paniti, nacsa, szűr, rácz, and tóth figure 7: final clip design with a clip and plant holder. figure 8: clip collision testing set-up with a force cell and pressure-sensitive measurement film. 9) as in all cases the 3d-printed clip breaks at the same position. the maximum pressure was 300 n/cm2 (see fig. 10). as in some cases the pressure can be close to the threshold, the use of gloves while carrying out clipassisted plant loading is highly recommended. 6. conclusion hydroponics is a subset of hydroculture, which is an environmentally friendly technology for growing plants in the absence of soil by using mineral nutrient solutions dissolved in water. many tasks in the hydroponic production process cannot be fully automated and require safe human-robot collaboration, moreover, cobotised tasks like the loading of plants must be tested with a safety protocol similar to the one followed in this paper. the proposed 3d-printed complementary manipulator tool (clip) was tested by following the protocol "test robot arm for collision with movable object (impact)." test results showed that only transient collisions can occur and force as well as pressure values are below the threshold in the case of a collision with a human hand. figure 9: force measurement results. figure 10: pressure measurement results. however, to maximize safety, it is recommended that gloves are worn. acknowledgement this project was funded by the european union’s horizon 2020 research and innovation programme under grant agreement no. 779966. furthermore, this research was supported by the ‘thematic excellence programme – national challenges subprogramme – establishment of the center of excellence for autonomous transport systems at széchenyi istván university (tkp2020-nka14)’ project. references [1] currey, c. j.: automation for hydroponics, produce grower, 2019 https://www.producegrower.com [2] modu, f.; adam, a.; aliyu, f.; mabu, a.; alhaji musa, m.: a survey of smart hydroponic systems. advances in science, technology and engineering systems journal, 2020, 5, 233-248 doi: 10.25046/aj050130 hungarian journal of industry and chemistry https://www.producegrower.com/article/hydroponic-production-primer-automation-for-hydroponics https://doi.org/10.25046/aj050130 https://doi.org/10.25046/aj050130 tool development for safe cobot-assisted hydroponics 89 [3] leading ag-tech start-up iron ox closes $53 million investment round led by breakthrough energy ventures (news); https://ironox.com [4] gnauer, c.; pichler, h.; tauber, m.; schmittner, c.; christl, k.; knapitsch, j.; parapatits, m.: towards a secure and self-adapting smart indoor farming framework. elektrotechnik und informationstechnik 2019, 136(7), 341-344 doi: 10.1007/s00502-019-00745-0 [5] directive 2006/42/ec, https://eur-lex.europa.eu [6] directive 95/16/ec, https://eur-lex.europa.eu [7] directive 2014/35/eu, https://eur-lex.europa.eu [8] directive 2014/30/eu, https://eur-lex.europa.eu [9] iso 13855:2010, https://www.iso.org [10] en 547-3:2009, https://webstore.ansi.org [11] iso 14123-1:2015, https://www.iso.org [12] en 1005-1:2002+a1:2008, https://standards.iteh.ai [13] en 1005-3:2002+a1:2008, https://standards.iteh.ai [14] iso 10218-1:2011, https://www.iso.org [15] iso 3691-4:2020, https://standards.iteh.ai [16] en 61508-3:2010, https://standards.iteh.ai [17] en 61508-5:2011, https://standards.iteh.ai [18] iso/ts 15066:2016, https://www.iso.org [19] iso 12100:2010, https://www.iso.org [20] iso 13849-1:2015, https://www.iso.org [21] covr toolkit. https://www.safearoundrobots.com/home [22] valori, m.; scibilia, a.; fassi, i.; saenz, j.; behrens, r.; herbster, s.; bidard, c.; lucet, e.; magisson, a.; schaake, l.; bessler, j.; prange-lasonder, g.b.; kühnrich, m.; lassen, a.b.; nielsen, k.: validating safety in human–robot collaboration: standards and new perspectives. robotics, 2021, 10, 65. doi: 10.3390/robotics10020065 49(2) pp. 85–89 (2021) https://ironox.com/leading-ag-tech-startup-iron-ox-closes-53-million-investment-round-led-by-breakthrough-energy-ventures https://doi.org/10.1007/s00502-019-00745-0 https://eur-lex.europa.eu/legal-content/en/txt/?uri=celex%3a32006l0042 https://eur-lex.europa.eu/legal-content/en/txt/?uri=celex%3a31995l0016 https://eur-lex.europa.eu/legal-content/en/txt/?uri=celex:32014l0035 https://eur-lex.europa.eu/legal-content/en/txt/?uri=celex%3a32014l0030 https://www.iso.org/standard/42845.html https://webstore.ansi.org/standards/din/dinen5472009-1297988 https://www.iso.org/standard/66983.html https://standards.iteh.ai/catalog/standards/sist/8bc7ea23-5552-4bbb-90cb-d614dbb21d81/sist-en-1005-1-2002a1-2008 https://standards.iteh.ai/catalog/standards/sist/31a7d76e-1129-4c69-bdc8-141dd223947e/sist-en-1005-3-2002a1-2008 https://www.iso.org/standard/51330.html https://standards.iteh.ai/catalog/standards/sist/2fb9d07e-945e-46b9-a1cd-67d06af82aa6/sist-en-iso-3691-4-2020 https://standards.iteh.ai/catalog/standards/clc/05f944e1-2469-4ae7-ada0-f18751039449/en-61508-3-2010 https://standards.iteh.ai/catalog/standards/sist/240f01cf-6ad7-4be6-9226-6944cb0b729f/sist-en-61508-5-2011 https://www.iso.org/standard/62996.html https://www.iso.org/standard/51528.html https://www.iso.org/standard/69883.html https://www.safearoundrobots.com/home https://doi.org/10.3390/robotics10020065 https://doi.org/10.3390/robotics10020065 introduction technical criteria risk assessment clip development collision tests conclusion hungarian journal of industry and chemistry vol. 47(2) pp. 1–4 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-13 investigations into succinic acid fermentation áron németh *1 1department of applied biotechnology and food science, budapest university of technology and economics, műegyetem rkp. 3, budapest, 1111, hungary succinic acid (sa) is an important chemical intermediate from which fine chemicals ( e.g. detergents), additives (for pharmaceuticals, food (taste), plant growth stimulants) as well as other important intermediates (maleic anhydride, succinimide, 2-pyrrolidinone, dimethyl succinate) can be manufactured. since sa is involved in the central metabolism of cells (in the tricarboxylic acid (tca) cycle), it is a key player in the biochemistry of life, which has the potential of biotechnological production. since sa is formed in the “middle” of the tca cycle it can be formed by both co2 production and fixation. the significance of the latter is that the amount of the product can be controlled by the availability of co2, since stoichiometrically one molecule of co2 is fixed by one molecule of sa. in our studies of compositions of actinobacillus succinogenes media, the role and effect of ph regulator compounds as well as the effect of an inert atmosphere were investigated in terms of the yield. furthermore, in fermentation experiments, the application of higher sugar concentrations was also studied. on the basis of different fermentations, a neural network for modelling and describing how factors influence sa production was established. keywords: succinic acid, actinobacillus succinogenes, neural network, modelling 1. introduction succinic acid (sa), as an intermediate of the tricarboxylic acid (tca) cycle, plays an essential role in the metabolism of microorganisms. sa can be produced by many anaerobes or facultative anaerobes as a metabolic product, thus can be used as an important platform chemical, a precursor of many pharmaceuticals, feed additives, green solvents or biodegradable polymers. sa itself is a colourless, odourless and crystal-forming compound. since this metabolite is bifunctional (pka1 = 4.21, pka2 = 5.72 [1]), it is very reactive so has many potential applications, e.g. it plays important roles in the synthesis of γ-butyrolactone, maleic anhydryde, succinimide, 1,4butanediol, dimethyl succinate, succinonitrile and 1,4diaminobutane. it is industrially produced, mainly synthetically, in a complex way from maleic anhydride found in crude oil, which is both economically and environmentally unfavourable [2]. therefore, its biotechnological production is a current research topic to find an alternative method to avoid the above-mentioned side effects [3]. furthermore, a great advantage of the microbial production of sa is that one of the initial biochemical reactions is the carboxylation of phosphoenolpyruvate [4] which is regulated in the case of anaerobic bacteria by the availability of co2 [2], thus the elevation of the co2 concentration can shift product portfolio from formate and ethanol towards sa (fig. 1). *correspondence: naron@f-labor.mkt.bme.hu despite this fact, the process can help to decrease the co2 emissions of the human population [5]. both fungi and bacteria can be found among the saproducing microorganisms, but their ability to produce sa differs significantly: fungi ∼45 g/l (aspergillus niger, rec. yarrowia lipolytica), gram-negative bacteria (wild-type actinobacillus succinogenes 98.7 g/l, mannheimia succiniciproducens 90 g/l) and grampositive bacteria (clostridium thermosuccinogenes 82.5 g/l, rec. corynebacterium glutamicum 145 g/l) [5]. the most frequently applied strains in the industry are aspergillus niger, aspergillus fumigatus, byssochlamys nivea, lentinus degener, paecilomyces variotii, penicillium viniferum, saccharomyces cerevisiae and actinobacillus succinogenes [4]. the latter bacterium is one of the most prominent producer strains that is isolated from bovine rumen and has been identified as a member of the genus pasteurella, which is a facultative anaerobic, non-motile, gram-negative pleomorphic, rod-shaped bacterium [2]. it has great potential in terms of sa production, because of its higher yield and wide range of applicable substrates, e.g. glucose, cellobiose, maltose, lactose, saccharose, fructose and sorbitol. furthermore, it can tolerate high initial concentrations of glucose, therefore, is suitable for simple batch fermentation instead of the more complex and costly fed-batch culture technique [5]. the most widely applied strains are actinobacillus succinohttps://doi.org/10.33927/hjic-2019-13 mailto:naron@f-labor.mkt.bme.hu 2 németh figure 1: sa metabolism with co2 regulation genes 130z and its variants (fz6, 9, 21, 45 and 53) [2], which can tolerate both high glucose and sa concentrations as well as achieve high sa yields [5]. the aim of this paper is to compare fermentations of actinobacillus succinogenes under different experimental conditions, then – due to the many influential factors – to set up a neural network-based model which can be used to predict high sa titres. 2. materials and methods 2.1 cultivation of the bacteria actinobacillus succinogenes 130z (dsm22257) was cultivated in 10 ml of tryptic soy broth (tsb) (sigma) in an impedimetric bactrac 4100 (sy-lab, austria) anaerobic cell. for a 1 l fermentation with a working volume of 0.8 l, an as medium was applied according to liu et al. [5] as follows: 62.5 g/l total sugar including 44.9 g/l saccharose, 9.8 g/l glucose and 7.2 g/l fructose supplemented with 15 g/l yeast extract, 1.5 g/l nahpo4, 1g/l na2hpo4, 1 g/l nacl, 0.2 g/l mgcl2 and 0.2 g/l cacl2. during preliminary tests, a temperature of 37◦c was not successful for sa production, therefore, 34◦c was applied and the ph regulated by 3m na2co3. after each fermentation, 200 ml of broth remained in the reactor and 600 ml was extracted, while 600 ml of fresh as media was introduced. the 5 different fermentations are compared in the results section. an innovative solution was to apply a co2 economical gas supply through the oxygen enrichment system of a biostat q dcu3 fermentor system in the absence of air and oxygen. the gas mix oxygen enrichment regulator was set at 4 %, therefore, periodically a small amount of co2 was introduced into the fermentation broth. 2.2 analysis during fermentations, samples were taken periodically and the optical density (od) determined by a spectrophotometer (ultrospec plus, pharmacia lkb) at a wavelength of 600 nm (od600) against the supernatant of a centrifuged sample by applying the same dilution factor (5×) as in the case of the samples. the cell dry weight (cdw) was obtained by a multiplication factor of 2 from od600. substrate consumption and product as well as by-product formation were detected by the waters breeze hplc system by applying 5 mm h2so4 in deionized water at a flow rate of 0.5 ml/min through a biorad aminex hpx87h column at 65◦c in a refractive index (ri) detector at 40◦c. 2.3 neural networking for model building and evaluation, neural designer v2.9.5 was used by applying the following 4 steps: 1. fermentation data were combined into a single ms excel spreadsheet and exported to a tab-delimited text file, which could be imported into the modelling software. 9 variables, i.e. 7 inputs (time, lactic acid, acetic acid, propionic acid, glycerol, ethanol, total sugar) and 2 outputs (succinic acid, cdw), were applied to 58 fermentation samples from which 36 were used for training the network, 11 were selected and 11 were used for testing the behaviour of the model. 2. from among the many options, a model was defined (fig. 2) by automatic scaling, without any principle component, with 2 layers and 3 neurons/hidden layers that exhibit a logistic activation function in the absence of a bounding layer. in terms of a training strategy, the normalized mean squared error method was selected using a quasi-newton algorithm and a maximum of 1000 iterations. incremental order was chosen as the order selection algorithm together with the growing inputs. 3. model fit, i.e. performance training, was conducted. 4. output of the model: impact figures of factors were determined (the other parameters were fixed), model equations obtained and predictions made by implementing input data into an input data matrix. 3. results and discussion since actinobacillus succinogenes is a facultative anaerobic microorganism, the first fermentation experiment (fig. 3a) was started in the absence of any specific atmosphere. however, it ran very slowly, therefore, around 48 h (denoted by a red arrow) of continuous 5 % co2 enrichment was applied via a zero flow rate gas inlet. the experiment confirmed that the application of co2 is essential to form sa, therefore, finally 6 g/l sa was achieved and the model fitted very well for both cdw and sa measurements. hungarian journal of industry and chemistry investigations into succinic acid fermentation 3 figure 2: the used neural network for describing sa fermentations therefore, the next fermentation (fig. 3b) was conducted under 5 % co2 enrichment of zero flow rate gas inlet and resulted in the highest 16 g/l sa (besides 11 g/l residual sugar) corresponding to a yield of 37 %. to increase the economic feasibility, the amount of co2 was reduced by 50 % to 2.5 % in the following experiment (fig. 3c). to avoid a fall in the sa concentration, detected by-products (such as lactic acid 3.5 g/l, acetic acid 5.7 g/l, propionic acid 1.7 g/l and glycerol 1.3 g/l) should be repelled as a result of the addition of 20 g/l calcium lactate. the model once again fitted well to the measured cdw and sa values. unfortunately, the carbon flux shifted towards propionic acid formation, therefore, the subsequent experiment (fig. 3d) was both supplemented with 20 g/l lactic acid and 11 g/l propionic acid, but this resulted in a low level of sa and a high level of lactic acid (52 g/l). the model yet again fitted well to the measured csw and sa values. independent fermentation results were also checked by the model (fig. 3e) and resulted in very good fits. it can be concluded that the artificial neural network model constructed described well the sa fermentations, which is in line with the results of li et al. [7], namely that artificial neural network models can describe succinic acid fermentation better than response surface methodology. the presented results revealed that for sa fermentation, 5% co2 enrichment is essential and cannot be fully or partially replaced with the addition of lactic acid or propionic acid. after validating the model by conducting 5 different fermentations, it was used to optimize influential factors via impact figures (directional output plots) (fig. 4). these trends show that all the presented factors correlate with sa concentration, i.e. any increment in their amounts resulted in an increment in sa, with the exception of propionic acid which exhibited a negative correlation. these suggest that the addition of propionic acid can decrease the concentration of sa obtained and the addition of lactic acid can increase it. (a) (b) (c) (d) (e) figure 3: actinobacillus succinogenes fermentations with different degrees of co2 enrichment in combination with lactic acid (la) and propionic acid (pa). dots indicate the measured values and lines indicate the model prediction. 47(2) pp. 1–4 (2019) 4 németh figure 4: factors impact plots: proh – propionic acid (g/l), total sugar (g/l), la – lactic acid (g/l) and co2 – carbon dioxide (%) 4. conclusion five actinobacillus succinogenes fermentations were run under different conditions: semi-anaerobic method, controlled introduction of co2, and introduction of co2 combined with either the addition of lactic acid or both lactic acid and propionic acid. all together 58 samples were taken and analysed, the results of which were entered into neural designer modelling software and used for training and testing the model. while the fermentations resulted in very different final sa concentrations, the established model fitted well to all of the fermentations, even to the one which was not used for model building, testing and validation. while economical co2 enrichment was successfully applied and resulted in the highest sa yield (37 %), the addition of lactic acid and propionic acid was not successful in terms of sa concentration. acknowledgement this research was conducted within the framework of and in cooperation with progressio engineering bureau ltd., mél biotech k+f kft. and budapest university of technology and economics. references [1] tonova, k.: state-of-the-art recovery of fermentative organic acids by ionic liquids: an overview hung. j. ind. chem. 2017 45(2), 41–44 doi: 10.1515/hjic-2017-0019 [2] song, h.; lee, s. y.: production of succinic acid by bacterial fermentation enzyme microb. tech. 2006 39(3), 352–361 doi: 10.1016/j.enzmictec.2005.11.043 [3] sauer, m.; porro, d.; mattanovich, d.; branduardi, p.: microbial production of organic acids: expanding the markets trends biotechnol. 2008 26(2), 100–108 doi: 10.1016/j.tibtech.2007.11.006 [4] zeikus, j. g.; jain,·m. k.; elankovan, p.: biotechnology of succinic acid production and markets for derived industrial products appl. microbiol biot. 1999 51(5), 545–552 doi: 10.1007/s002530051431 [5] liu, y.-p.; zheng, p.; sun, z.-h.; ni, y.; dong, j.j.; zhu, l.-l.: economical succinic acid production from cane molasses by actinobacillus succinogenes bioresource technol. 2008 99(6), 1736–1742 doi: 10.1016/j.biortech.2007.03.044 [6] mika, l.t.; cséfalvay, e.; németh, á.: catalytic conversion of carbohydrates to initial chemicals: chemistry and sustainability chem. rev. 2018 118(2), 505–613 doi: 10.1021/acs.chemrev.7b00395 [7] li, x.; jiang, s.; pan, l.; wei, z.: optimization for the bioconversion of succinic acid based on response surface methodology and back-propagation artificial neural network in: wang, h; low, k. s.; wei, k.; sun, j. (eds.): fifth international conference on natural computation 2009 3, 392– 398 (ieee computer society, los alamitos, usa) isbn: 978-0-7695-3736-8 doi: 10.1109/icnc.2009.20 hungarian journal of industry and chemistry https://doi.org/10.1515/hjic-2017-0019 https://doi.org/10.1515/hjic-2017-0019 https://doi.org/10.1016/j.enzmictec.2005.11.043 https://doi.org/10.1016/j.tibtech.2007.11.006 https://doi.org/10.1007/s002530051431 https://doi.org/10.1016/j.biortech.2007.03.044 https://doi.org/10.1016/j.biortech.2007.03.044 https://doi.org/10.1021/acs.chemrev.7b00395 https://doi.org/10.1109/icnc.2009.20 introduction materials and methods cultivation of the bacteria analysis neural networking results and discussion conclusion hungarian journal of industry and chemistry vol. 49(2) pp. 19–22 (2021) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2021-16 weight reduction of a drone using generative design bálint leon seregi*1 and péter ficzere1 1department of vehicle elements and vehicle-structure analysis, budapest university of technology and economics, műegyetem rkp. 3, budapest, 1111, hungary generative design has the potential to be optimized with different parameters using a design method based on artificial intelligence and by defining the design problem. the use of this method on a drone frame is presented with explanations of the various design phases. the goal of the optimisation was to be able to fit a battery with a larger capacity onto the unmanned aerial vehicle and compensate for its increased weight by reducing the weight of the drone frame using a generative algorithm. as the production possibilities were limited, adaptation to the selected manufacturing technology was also taken into account during the optimization. keywords: generative design, additive manufacturing, weight reduction 1. introduction mechanical design is a complex process. engineers not only design a construction to meet functional and safety requirements, but also have to take into consideration the costs, functional expectations, safety, usage needs, lifespan and manufacturability. that is why the most optimal design, which appropriately fulfils every need, must be selected from several versions when designing a product. the spread of rapid prototyping facilitates the rapid creation and testing of these versions. in connection with this, the phenomenon of the design paradox can be observed, which concerns the relationship between product knowledge and design decisions over time as a function of the product from its design to production (fig. 1). [1] this engineering influence has an outstanding effect on costs, mainly during the design phase and the production preparation process. if an error in the product concept is revealed during the testing phase immediately before production, its reworking increases costs significantly. rapid prototyping is suitable for eliminating this paradox. the main reasons for this are that it • makes communication during the design phase with faster iterations more effective; • reduces the development time; • reduces the likelihood of costly errors (hidden design errors) and those following the release of the product from occurring; • extends the product life cycle by adding required and eliminating unnecessary features early on in the design phase; *correspondence: seregibalint@edu.bme.hu figure 1: the design paradox[1] • can avoid design flaws from occurring early on, even in the concept phase. the generative design is a great solution to lower this influence by making many versions. these outcomes all meet the given requirements (if any one of them cannot be achieved, the algorithm stops as a result of a failure). usually the generative design concerns automotive applications where one or more components are merged into one solid component, thereby also reducing the weight. this is obvious from a transportation point of view since it can reduce the environmental impact by reducing fuel consumption and using less raw materials. for instance, general motors (gm) optimized their seat bracket, which is a standard component that fixes the seat and seat belt lock to the car’s floor. while previously this bracket consisted of 8 components, generative software could come up with more than 150 organic-looking outcomes (fig. 2). the chosen outcome by gm was 40% lighter and 20% stiffer than the original design. [2] https://doi.org/10.33927/hjic-2021-16 mailto:seregibalint@edu.bme.hu 20 seregi and ficzere figure 2: the original and the generative concept [2] additive manufacturing is very different from its predecessor, that is, subtractive manufacturing. over the history of machining, as a result of computer numerical control, technology has made great strides in terms of efficiency, productivity and accuracy. 5-axis machines as well as 6-axis robotic arms have also appeared, which in the case of the tool and material to be machined are the limiting factors. there are geometries which cannot be produced even by 6-axis robotic arms as the tool simply does not fit in some concave areas. for harder materials that are difficult to machine, a tool made of a stronger material is required, which must be specially designed with customised machining parameters. furthermore, depending on the amount of material deposited, the chips as loss are displayed. [3] to demonstrate the reduction in weight as a result of generative design, a small-scale drone frame was optimized. the goal was to create a small flying unmanned aerial vehicle (uav) with a generative designed frame that reduces the overall weight of the vehicle as the maximum speed and range of uavs strongly depend on the performance of their motors and their overall weight. the weight of the battery cannot be reduced because decreasing its capacity would also shorten its available range. therefore, the weight of the frame had to be reduced just as a larger battery with a greater capacity would have had to have been, thereby increasing its range. concerning the size of the motors, the acquirement of high-performing and small ones on the commercial market is preferred. its electronics and control consist of the electronic speed controller, pxfmini autopilot card and a raspberry pi zero. the pxfmini autopilot card contains the basic sensors, e.g., a compass, gps and barometer, which are connected to the onboard computer, that is, the raspberry pi. this electronics stack can facilitate basic functions like stabilization and rc communication. 2. methodology as the combined performance of its four motors can lift 2800 grams in total, this equates to the critical weight of the uav during the design phase. its weight without the frame (the electronics, motors and battery) is 404 grams. this is 1/7 of the critical weight which means that the vehicle can achieve higher speeds and accelerations, moreover, the energy consumption can also be table 1: mechanical parameters of abs [4] young’s modulus [gpa] 2.2 tensile strength [mpa] 30 density [g/cm3] 1.1 poisson’s ratio 0.4 more favourable especially with the reduced weight of the frame. the frame is composed of the plastic acrylonitrile butadiene styrene (abs), the parameters of which can be seen in table 1. these mechanical parameters were used during its generation. first, the basic concept must be created. the electronics can be placed in stacks as a block thanks to their dimensions (fig. 3). the battery was placed under the electronics stack 38 millimetres from the plane of the motors to somewhat increase its in-flight stability. during the design phase, a basic model is required to determine the preserve and obstacle geometries, loads and constraints. the preserve geometry means the volume that cannot be modified by the algorithm (fig. 4). the loads and constraints can be determined on the following areas; in this case the mounting discs of the motors and mounting rails of the electronics. the obstacle geometry is the volume within which the algorithm is not allowed to place material (fig. 5), since it is a placeholder for other components like bolts, batteries and motors. the constraints and loads were defined in different load cases which simulate the lift, weight force of the battery and three crash-landings from different angles. specifying design criteria is also mandatory. figure 3: the electronics stack figure 4: preserve geometry hungarian journal of industry and chemistry weight reduction of a drone using generative design 21 figure 5: obstacle geometry although by default the program is set to minimize the mass, it is possible to specify a specific target mass with a safety factor. in addition, the manufacturing technology can be specified to optimize the result and meet needs. the available options are 2.5 − 5 axis cutting, additive fabrication, casting and indefinite. the indefinite option differs in that it does not take into account the limiting factors of the technologies such as the smallest tool diameter or tool overhang for cutting, alternatively, in the case of additive manufacturing, the manufacturing direction, orientation and maximum overhang angle of the workpiece. during one run, several technologies can be selected according to needs. the weight reduction was set with a target mass of 84 grams and safety factor of 1.2. 3. investigation using fusion 360’s generative design algorithm, 6 different results were generated, from which the most optimal frame was chosen (table 2). the reason for the 6 results is the possibility of different build directions (a key parameter in additive manufacturing), which the program also takes into account and the given model is once more iterated based on this. the generative model generated by the preserve geometry can be seen where the algorithm did not remove any volume and the robotic arms were reduced to smaller robotic arm braces. the amount of weight reduction made it possible to use a battery with a larger capacity that lengthens the flight time. the basic concept was fitted with a 2200 mah battery. from this product family, the next largest capacity of the battery is 2650 mah. the smaller and larger batteries weigh 168 grams and 232 grams, respectively. compared to the origtable 2: parameters of the outcomes mass [kg] max. diplacement [mm] volume [mm3] 0.079 3.15 74962.69 0.073 5.11 68565.46 0.136 2.98 128678.19 0.135 2.42 127491.83 0.23 1.76 217371.08 0.135 2.43 127823.45 figure 6: outcomes of the different orientations inal design, its overall weight was reduced by 25 grams, as the difference in weight between the two batteries is smaller than the weight reduction as a result of changing the frame, resulting in the flight time increasing by about 65 seconds (fig. 7). 4. summary the reduction in the weight of a drone as a result of generative design was presented (the full assembly can be seen in fig. 8). by following this method, a more efficient concept could be created. proper use of generative design helps to develop a new or existing concept in many areas. reducing the weight of vehicles has always been an important aspect of the industry, so further reductions in this field are expected. [5] e-mobility can also be greatly beneficial as the biggest problem is always the size and weight of batteries, which has a big impact on fuel consumption and range. although the weight reduction of passenger cars is more complex, the example presented illustrates that this could be a revolutionary solution for the automotive industry in the future. from another point of view, it is also important to recognise that increased computational capacities make it possible to compare many more types of concepts, thereby providing the opportunity to choose the most optimal solution when designing. figure 7: flight times with different battery capacities 49(2) pp. 19–22 (2020) 22 seregi and ficzere figure 8: assembly of the drone 5. additional questions that arise it can be seen that the results are free form surfaces of organic forms that are aesthetically pleasing which also make a positive contribution to the concept. nevertheless, it is noticeable that although the given loads were symmetrical in all directions, the frame did not become completely symmetrical. this can be eliminated by postmirroring the model, however, the question is will the mirrored construct be equally effective? 6. acknowledgements the authors would like to express their gratitude to arkance systems hu kft. for supporting this work by providing pieces of software. references [1] chang, k.h.: product performance evaluation using cad/cae (academic press), 2013. isbn: 0123984696 [2] alderton, m.: driving a lighter, more efficient future of automotive part design, 2021. https://www.autodesk.com/customer-stories/general-motorsgenerative-design [3] siva rama krishna, l.; srikanth, p.: evaluation of environmental impact of additive and subtractive manufacturing processes for sustainable manufacturing. mater. today: proc., 2021, 45(2), 3054–3060, international conference on advances in materials research 2019. doi: 10.1016/j.matpr.2020.12.060 [4] martinetti, a.; margaryan, m.; van dongen, l.: simulating mechanical stress on a micro unmanned aerial vehicle (uav) body frame for selecting maintenance actions. procedia manuf., 2018, 16, 61– 66, proceedings of the 7th international conference on through-life engineering services. doi: 10.1016/j.promfg.2018.10.160 [5] shahrubudin, n.; lee, t.; ramlan, r.: an overview on 3d printing technology: technological, materials, and applications. procedia manuf., 2019, 35, 1286–1296, the 2nd international conference on sustainable materials processing and manufacturing, smpm 2019, 8-10 march 2019, sun city, south africa. doi: 10.1016/j.promfg.2019.06.089 hungarian journal of industry and chemistry https://www.autodesk.com/customer-stories/general-motors-generative-design https://www.autodesk.com/customer-stories/general-motors-generative-design https://doi.org/10.1016/j.matpr.2020.12.060 https://doi.org/10.1016/j.promfg.2018.10.160 https://doi.org/10.1016/j.promfg.2018.10.160 https://doi.org/10.1016/j.promfg.2019.06.089 introduction methodology investigation summary additional questions that arise acknowledgements hungarian journal of industry and chemistry vol. 47(2) pp. 77–83 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-23 biocomponent-based quality improvement opportunities of binders for road construction gréta tálosi1, péter gergó1, and andrás holló *1,2 1department of mol hydrocarbon and coal processing, institute of chemical and process engineering, university of pannonia, egyetem u. 10, veszprém, h-8200, hungary 2downstream r&d, mol plc., olajmunkás u. 2, százhalombatta, h-2440, hungary in our experimental work, stabilised pinewood-based fast pyrolysis bio-oil and the linear block copolymer styrene butadiene styrene (sbs) were used as additives in bitumen used for road construction (penetration grade 50/70) to produce a higher-performance asphalt binder. our aim was to investigate the modifying effect of the biocomponent on bituminous binders and prepare a comparative analysis. in order to characterize our samples, conventional and rheological measurements were performed. it was concluded that the biocomponent by itself cannot provide a favourable bituminous binder with beneficial mechanical properties, however, a favourable solution may be achieved by combining it with the block copolymer sbs. based on our test results, stabilised pinewood-based fast pyrolysis bio-oil could be blended with the examined bituminous binders up to concentrations of 10 w/w% resulting in good bitumen quality. keywords: bitumen 50/70, polymer modified bitumen, biocomponent, quality improvement 1. introduction the stricter demands of road construction has brought about the application of new and high performance, albeit expensive, binders (e.g. polymer modified bitumen). thus, the development of alternative, high-quality but cheaper bitumen for road construction has become an intensively researched area [1–5]. another aspect is that in line with sustainable development, the use of alternative materials derived from nonfossil sources, e.g. biomass or waste, can be a long-term option for the partial replacement of bitumens derived from crude oil. a further issue is that the production of low carbon fuels in the future might reduce the demand for refining crude oil, which could result in a lack of supply in the bitumen market as well. many researchers have found that different biomass-derived oils could be suitable components for blending, substituting for and modifying bituminous binders [6]. the raw materials of the processed biomass that produce bio-oils include microalgae [7], animal waste [8, 9], maize [10], garden waste [11], tea residue [12], coffee residue [13], rapeseed [14], and soybean [15]. the utilisation of these bio-oils can be beneficial following proper treatment, since these materials could increase the rutting performance of bituminous binders. these studies show that the utilisation of renewable materials can be very promising [16]. many researchers have studied the modifying effect *correspondence: ahollo@mol.hu of different wood-based bio-oils. peralta et al. examined the application of red oak residues as direct alternative binders and to reduce the environmental impact of bituminous binders [17–19]. grilli et al. used pinewood biooil [20], jiménez del barco-carrión et al. used pine resin [21, 22] and lei et al. used bio-oil derived from wood as a rejuvenator [23]. raouf and williams investigated the utilisation options of oak wood bio-oil [24]. cooper et al. [25], ball et al. [26], and bearsley and haverkamp blended bio-oil originated pine derived tall oil as a bitumen extender [27, 28]. gondim et al. studied the effect of plant sap from a “petroleum plant” [29]. yang et al. examined bio-oils derived from waste wood resources as bitumen modifiers and extenders [30]. in summary, bio-oils typically have a softening effect, which improves their performance at low and intermediate temperatures but impairs their high-temperature performance. this negative impact can be mitigated, e.g. by the addition of crumb rubber or other polymers. the application of stabilised wood-based pyrolysis bio-oil as an additive for bitumen binders has been intensively researched but remains a field of future bitumen production that is yet to be clarified. the utilisation of polymer modified bitumen is widespread but the modifying effect of stabilised wood-based pyrolysis bio-oil on polymer modified bitumen has yet to be clearly defined. thus, our target was to investigate the effect of stabilised pinewood-based fast pyrolysis bio-oil on the characteristics of different binders, such as road pavement bituhttps://doi.org/10.33927/hjic-2019-23 mailto:ahollo@mol.hu 78 tálosi, gergó, and holló men (penetration grade 50/70) and polymer modified bitumen. 2. experimental the aim of our study was to examine the quality improvement opportunities of bitumen used in road construction (penetration grade 50/70). over the course of our experiments, the modifying effect of a biocomponent derived from pinewood-based fast pyrolysis biooil on the original bitumen 50/70 (b-series) was investigated. furthermore, experiments that applied the biocomponent together with the block copolymer styrene butadiene styrene (sbs) (p-series) were conducted. 2.1 samples the investigated feedstock was a commercially-available bitumen (producer: mol plc.) with penetration grade 50/70 (softening point: 51 ◦c; penetration: 56 0.1mm). the modifying agent for the polymer modified bitumen samples was the linear block copolymer styrene butadiene styrene (dst l 30-01, producer: voronezhsintezkauchuk ojsc) applied at a concentration of 4 w/w%. the styrene concentration of the copolymer was 30 w/w%. the applied biocomponent was derived from a commercial pyrolysis liquid of pinewood (producer: btg-btl, the netherlands [31], elemental analysis of the btg-btl product: c: 46 %, h: 7 %, o: 47 %; water content: 25 w/w%). before blending, the sample was stabilised. the water content was removed and the volatile organic components that are boiling up to 220 ◦c were removed with the water as well, to adjust the flash point of the additive by distillation. samples of the biocomponent were applied in concentrations of 1, 5, and 10 w/w%. table 1 shows the composition of the samples. 2.2 measurements in order to characterise our samples, conventional bitumen tests were conducted before and after aging. the softening point of the samples was determined according to the standard msz en 1427 using an automatic ringand-ball softening point tester (petrotest rka 5). penetration measurements were conducted according to the standard msz en 1426 using an automatic penetrometer (petrotest pnr 12). aging was simulated by the rolling thin-film oven test (rtfot) according to the standard msz en 12607-1. the change in the rheological properties was investigated by using an anton paar mcr 301 type dynamic shear rheometer (dsr). the linear viscoelastic range (lve range) of the samples was investigated by amplitude sweep analysis. during the measurements, the frequency was constant (10 s−1) and the amplitude varied. the amplitude sweep analysis was measured at 10 and 60 ◦c which resulted in the corresponding γ (deformation) values. the sweep frequency response analysis was table 1: composition of the samples name of the sample bitumen 50/70, w/w% sbs, w/w% biocomponent, w/w% bref 100 bbio01 99 1 bbio05 95 5 bbio10 90 10 pref 96 4 pbio01 95 4 1 pbio05 91 4 5 pbio10 86 4 10 also investigated at 10 and 60 ◦c, within the frequency range of 0.01− 100 hz. the multiple stress creep recovery (mscr) test was performed at 60 ◦c over 10 cycles according to the standard astm d7405. during the analysis, the samples were subjected to a loading force of 100 n for 1 sec which was then removed for 9 secs. after the 10th cycle, the loading force was changed to 3200 n and another 10 cycles measured. from the experimental values the percentage of the recovery could be calculated. the temperature-dependence of the rheological properties was investigated within the temperature range of 10− 70 ◦c, with a heating rate of 1 ◦c/min at a constant frequency of 1 hz. during the measurements, the values of the complex modulus, namely the stiffness and complex viscosity, were investigated. 3. results and analysis 3.1 basic properties as for the conventional properties, the softening points of the samples were increased by the biocomponent as well as sbs when compared to the original bitumen 50/70 (table 2). the increasing effect tendentiously escalated as the amount of applied biocomponent increased. in the case of applying two modifiers simultaneously (biocomponent and sbs polymer), synergistic effects were experienced. in accordance with the softening points, the penetration of the samples decreased by using every blending component, that is the samples became harder (table 2). the increased stiffness could be explained by the blending of the rigid biocomponent. from the results measured after rtfot, it can be stated that in the case of the sbs polymer modified bitumen (pmb) samples, the aging effect was less significant when compared to the sample of reference bitumen. moreover, in the case of the pmb samples, the biocomponent enhanced its resistance to hardening. every sample complied with the technical specifications for road construction currently in force in hungary (for bbio samples msz en 12591, for pbio samples msz en 14023). table 2 shows the conventional properties of the samples before and after aging. hungarian journal of industry and chemistry quality improvement of binders for road construction 79 table 2: basic properties of the samples and the requirements of the bitumen standards before and after rtfot. before rtfot after rtfot softening point, ◦c penetration, 0.1 mm change in mass, w/w% increase in softening point, ◦c retained penetration, % bref 51.0 56 −0.02 5.9 67.9 bbio01 51.1 54 0.006 2.1 75.9 bbio05 51.2 53 −0.30 3.9 77.4 bbio10 51.4 52 −0.50 4.7 71.1 msz en 12591 50/70 46− 54 50− 70 ≤ 0.50 ≤ 8.0 ≥ 55.0 pref 72.5 35 0.04 2.6 82.9 pbio01 74.1 32 0.01 3.6 96.9 pbio05 77.0 31 −0.01 3.1 93.5 pbio10 79.7 29 −0.02 3.2 100.0 msz en 14023 10/40-65 ≥ 65.0 10− 40 ≤ 0.30 ≤ 8.0 ≥ 50.0 25/55-65 ≥ 65.0 25− 55 ≤ 0.50 ≤ 8.0 ≥ 50.0 3.2 rheological properties the results of the amplitude sweep analysis are presented in fig. 1. the deformation values increased by applying the sbs polymer component at 10 ◦c, thus the lve ranges were widened. in every case, the blending of the biocomponent narrowed the lve range. the addition of the rigid component resulted in a stiffer structural material with a lower resistance to deformation. the extent of the decrease was significant in the case of the samples that were only modified with biocomponents. in the other cases, the decrease was less notable, the bituminous matrix could positively compensate for the narrowing effect of the biocomponent. as for the measurements conducted at 60 ◦c, the permanent deformation decreased in every case when compared to the reference sample, nevertheless, the value of the permanent deformation increased. in the case of the samples that were only modified with a biocomponent, the narrowing of the lve ranges was minimal when compared to the values measured at 10 ◦c. fig. 2 shows the results of the sweep frequency response analysis. at 10 ◦c and 60 ◦c, the values of the complex modulus were measured, presented and evaluated at frequencies of 25 hz and 30 hz, respectively. these conditions correlate with similar asphalt tests. at 10 ◦c, the complex modulus values, namely the stiffness, were preferably larger in the case of every modified composition when compared to the reference sample (bref). however, in the case of the samples modified with only a biocomponent, by adding the biocomponent, the stiffness decreased tendentiously. in view of the bbio10 sample (10 w/w%), the value of the complex modulus was almost identical to that of the reference sample. as for the pmb samples, similar behaviour was observed. by blending the biocomponent in small amounts (up to 5 w/w%), the complex modulus decreased, but in accordance with this effect the fatigue performance improved. the stiffness of the samples containing 10 w/w% of biocomponent (bbio10 and pbio10) were comparable to those of the corresponding reference samples (bref, pref), thus the stiffness of the asphalt mixture can be suitable as well. the results measured at 60 ◦c showed that the complex modulus positively increased by the blending in of the sbs polymer. in the case of the samples modified with only a biocomponent, the modifying effect of the blending component was negligible. as for the flexible behaviour, the results of the mscr test are presented in figs. 3 and 4. the loaded and relaxation periods are shown in the diagrams on the left-hand side, while the percentage of the elastic recovery at the end of the 1st and 10th cycles can be seen on the right. every diagram shows the results measured when a loading force of 3200 n was applied. in the case of the samples modified with only a biocomponent, the component applied in small concentrations (up to 5 w/w%) influenced the elastic recovery positively when a loading force of 100 n was applied. however, when applied at a concentration of 10 w/w%, the percentage of the elastic recovery decreased when compared to the reference sample, however, the value of the permanent deformation increased. when high loading forces (3200 n) were applied, the permanent deformation was adversely increased by the biocomponent. the elastic recovery of the samples was negligible, the elastic property practically ceased under the test conditions, their viscosity dominated. in the case of the pmb samples, when a loading force of 100 n was applied, the biocomponent influenced the flexible behaviour positively at every concentration. the permanent deformation decreased and, in line with this positive effect, the percentage of the elastic recovery increased. thus, the rutting performance of the samples was favourable. the higher the blending concentration of the biocomponent was, the more flexible the behaviour 47(2) pp. 77–83 (2019) 80 tálosi, gergó, and holló figure 1: lve range of the samples – a) 10◦c, b) 60◦c. figure 2: complex modulus of the samples – a) 10◦c, 25 hz frequency, b) 60◦c, 30 hz frequency. figure 3: the results of the mscr test of the samples modified with only a biocomponent when subjected to a loading force of 3200n. it exhibited. when high loading forces were applied, the tendency was the same. the favourable values of the pmb samples can be explained by a phenomenon in which the biocomponent did not influence the flexible properties of the pmb matrix, while it could mitigate the liability to deform as a result of its rigid structure. by comparing the values of every sample measured by the mscr test, the flexible behaviour of the pmb samples was significantly better than in the case of the reference bitumen sample. nowadays the modification of bitumen is strictly necessary in order to comply with the more rigid requirements enforced by the technical practices of road construction, namely that the binders have a sufficient degree of rutting performance. according to our measurements, the biocomponent by itself cannot provide a good solution to this problem, however, by blending it with sbs polymer the modifying effect of the biocomponent could be beneficial. the results of the temperature sweep analysis are presented in fig. 5. in the case of the samples that were only modified with the biocomponent, the values of the complex modulus decreased at lower concentrations (up to 5 w/w%), but by applying the biocomponent at 10 w/w%, the values of the complex modulus were almost identical to that of the reference sample (bref). as for the pmb samples, the stiffness increased in every case when compared to the bref sample. the value of the complex modulus increased by increasing hungarian journal of industry and chemistry quality improvement of binders for road construction 81 figure 4: the results of the mscr test of the samples modified with sbs polymer when subjected to a loading force of 3200n. the biocomponent concentration. during the temperature sweep analysis, the temperature dependence of the complex viscosity was measured as well. the tendency was very similar to that of the temperature dependence of the complex modulus. in particular, the complex viscosity significantly increased in the case of the pmb samples when compared to the reference sample (bref). by increasing the blending concentration of the biocomponent, the complex viscosity increased further. 4. conclusion the aim of this work was to investigate the quality improvement opportunities of bitumen used in road construction (penetration grade 50/70) and to provide a comfigure 5: temperature dependency of complex viscosity – a) samples modified only with biocomponent, b) pmb samples. parative analysis of the modifying effect of stabilised pinewood-based fast pyrolysis bio-oil on sbs polymer modified bitumen. according to our measurements, the biocomponent can be blended at a concentration of 10 w/w% with the tested bituminous binders. as for its flexible properties, the utilisation of the biocomponent by itself does not result in a good bitumen quality, but together with the sbs polymer the rutting performance improves significantly. based on these results, further measurements are being planned with other modifying agents to identify the exact and credible binder composition from economical and technical points of view. furthermore, it is necessary to examine the methods of blending and treating opportunities of the biocomponent that can produce a binder with better mechanical properties and possibly with a greater concentration of the biocomponent in the blend. acknowledgements this research was supported by the únkp-18-2 new national excellence program of the ministry of human capacities. the authors thank mol plc. providing the bitumen sample. references [1] read, j.; whiteoak, d.: the shell bitumen handbook (thomas telford, london, uk, 2003) isbn:0 7277 3220 x [2] geiger, a.; holló, a.; fehér, p.: mol rubber bitumen–part 1. mol group scientific magazine 2012/2, 54–61 doi: 10.24193/subbchem.2017.2.19 [3] holló, a.; geiger, a.; gergó, p.: (2017). upgrading options of heavy residues, rubber modified bitumen case study. fuels and lubricants, 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(accessed: 11/06/2019) 47(2) pp. 77–83 (2019) https://www.scionresearch.com/__data/assets/pdf_file/0016/17701/nzjfs2321993ball236-242.pdf https://www.scionresearch.com/__data/assets/pdf_file/0016/17701/nzjfs2321993ball236-242.pdf https://www.scionresearch.com/__data/assets/pdf_file/0016/17701/nzjfs2321993ball236-242.pdf https://doi.org/10.1080/14680629.2007.9690084 https://doi.org/10.1080/14680629.2007.9690083 https://doi.org/10.1080/14680629.2007.9690083 https://doi.org/10.1016/j.jclepro.2016.11.100 https://doi.org/10.1016/j.jclepro.2016.11.100 https://www.btg-btl.com/en/applications/oilproperties https://www.btg-btl.com/en/applications/oilproperties introduction experimental samples measurements results and analysis basic properties rheological properties conclusion hungarian journal of industrial chemistry veszprem vol. 29. pp. 95 -104 (2001) design of a pressure swing adsorption module based on carbon nanotubes as adsorbenta molecular modeling approach a. heyden, t. doren, m. kolkowski and f. j. keil (chair of chemical reaction engineering, technical university of ham.burg-harburg, eissendorfer str. 38, d-21073 hamburg, germany) received: march 21,2001 the prese~t paper describes the first sequence of the skarstrom cycle for bed 1 to analyze the breakthrough curves and study the i~rtance of. the mass ~ansfer resistance for the performance of the psa process which separates a feed stre~ ~onsisti.ng of eqmmolar fractions o~ meth~e ~d ethane. the beds are filled with carbon nanotubes (cnt) of a certam_mner diameter (3 nm). the adsorption bed 1s simulated by a one-dimensional, time-dependent dispersion model. a special feature of the present paper are the adsorption isotherms of the chjc2h6 mixtures and the diffusivities which were calculated by molecular simulation methods. introduction all adsorption separation processes involve two essential steps: a) adsorption, during which the preferentially adsorbed species are picked up from the feed gas, and b) desorption, during which these species are removed from the adsorbent, and is thus regenerated for the next cycle. the essential feature of the pressure swing adsorption (psa) process is the removal of the adsorbed species by reducing the total pressure, rather than by raising the temperature or purging with a sweep ~as. the process operates under approximately isothermal conditions. as the pressure can be changed much more rapidly than the temperature, it is possible to operate a psa process on a much faster cycle, and thereby the throughput per unit of adsorbent bed volume is considerably increased. the major limitation is that psa processes are restricted to components that are not too strongly . adso_rbed. air separation. air drying, hydrogen punfication, carbon dioxide recovery and natu~al ~as purification are at present the most important applt~at10ns of the psa process. detailed descriptions of this process and its applications can be found in books by ruthven et al. [1]. yang [2], and thomas and crittenden [3]. an industrially employed psa cycle is the skarstrom cycle which in its basic form utilizes two pack~ adsorbent beds (see fig.j). the skarstrom cycle conststs of four steps: a) pressurization~ b) adsorption, c) countercurrent blowdown. and d) countercurrent purge. contact information: e-mail: keil@tu-harburg.de in step 1, bed 1 is pressurized to the higher operatino pressure with feed from the feed end (open valves: 1,3; closed valves: 2,4-9) while isolated from bed 2. during this step bed 2 is blown down from high pressure to atmospheric pressure in the opposite direction. these steps are relatively fast in most industrial processes and often have no cignificant influence on the performance of the entire process. in step 2 (open valves: 1,3,5,6,8~ closed valves: 2,4,7,9), high pressure feed flows through bed 1. the product stream is separated from the stronger adsorbing species. the concentration front of the stronger adsorbing species reaches the exit of the bed at a far lower concentration compared to the weaker adsorbing component during this step. a fraction of the effluent stream is withdrawn as product, while the remaining gas is used to purge bed 2 at the low operating pressure. the direction of the purge flow is opposite to that of the feed flow. the purge to feed volume ratio must be at least one in order to sweep bed 2. steps 3 and 4 follow the same sequence with the bed interchanged. the present paper describes lhe first sequence of the skarstrom cycle for bed 1 to analyze the breakthrough curves and study the importance of the mass transfer resistance for the performance of the psa process which separates a feed stream consisling of equimolar fractions of methane and ethane. the beds are filled with carbon nanotubes (cnt) of a certain inner diameter (3 nm). the adsorption bed is simulated by a one-dimensional, time~dependent dispersion model. a 96 raffinate product bed 1 bed 2 feed fig. i schematic diagram of the basic two-bed pressure swing adsorption system. special feature of the present paper is the adsorption isotherms of the chjc2~ mixtures and the diffusivities which were calculated by molecular simulation methods. theory 1 grand canonical monte carlo simulations of adsorption isotherms a monte carlo simulation (mc) generates configurations of a molecular system by making random changes to the positions of the species present (together with their orientations and conformations where appropriate). the potential energy of each configuration of the system, together with the values of other properties, can be calculated from the positions of molecules in space. the mc method thus samples from a 3n-dimensional space of the positions of n particles. in adsorption studies one would like to know the amount of material adsorbed as a function of pressure and temperature of the reservoir with which the porous material is in contact. a proper choice for adsorption studies is the grand canonical ensemble (or j.1 vt ensemble). in this ensemble, the chemical potential j.t, the volume v and the temperature t are fixed. this corresponds to an experimental setup where the adsorbed gas is in equilibrium with the gas in the reservoir. the equilibrium conditions are that the temperature and chemical potential of the gas inside and outside the adsorbent must be equal. the gas that is in contact with the adsorbent can be considered as a reservoir that imposes a temperature and chemical potential on the adsorbed gas. one has to know only the temperature and chemical potential of this reservoir to determine the equilibrium concentration inside the adsorbent. this is done with the grand-canonical ensemble. the temperature and chemical {x)tential are set. fixed and the number of particles is allowed to fluctuate during the simulation. one should keep in mind that the pressure is related to the chemical potential via an equation of state. inside microporous materials the pressure is not defined. the partition function for the grand-canonical ensemble is given by ( 4-6]: q(ji.,v,t) = l exp(f3j.1n;q:vn j dsn exp[fju(sn)](l) n=o n. and the corresponding probability density n (sn n) oc exp(fj!.jn)!n q: exp~ fju(sn)] (2) ~~ ' n! with (3) q: · vn =kinetic energy contribution ofn molecules in the system. ( 4) in a grand-canonical simulation, one has to sample the distribution eq. (2) by doing the following trial moves: a) displacement of particles. a particle is selected randomly and given a new configuration. this trial move is accepted with a probability: acc(s -7 s') = min~,exp{fj[u(s'n) -u(sn)n) (5) b) insertion and removal of particles. a particle is inserted at a random position or a randomly selected particle is removed. the creation of a particle is accepted with a probability acc(n -7 n + 1)= =min[l.~·exp{b(jl-u(n +l)+u(n)]}l ( 6 ) (n +1) j and the removal of a particle is accepted with a probability acc(n -7 n -1) = = min[l.~{{3[u+u(n -1)-u(n)]}l (?) vqt j details of the implementation of eqs. (5-7) may be found in [5]. the grand-canonical mc technique can be applied to spherical molecules and simple models of nonspherical molecules. a common model to represent molecules in simulation is the united atom model. methane is represented by a single sphere whereas chain molecules are represented by several joined spheres each denoting a methyl group of the chain molecule (e.g. ethane is represented by two joined ch3-spheres). in more complicated cases biased sampling techniques have to be used [7]. the main feature of this more sophisticated mc method is that the trial moves are no longer completely random, instead the moves are biased in such a way that the molecule to be e.g. inserted has an enhanced probability to 4'fit" into the existing configuration. this approach was used for ethane in the present paper. the method to increase the speed of mc simulations for chain molecules by mc moves is called configuration-bias monte carlo (cbmc) and was developed by siepmann and frenkel [7]. further details may be found in the book by frenkel and smit [5] and in articles by vlugt et al. [8-10]. the main feature of this more sophisticated mc approach is that the trial moves are no longer completely random, instead they are biased in such a way that the molecule to be, for example, inserted has an enhanced probability to "fit" into the existing configuration. no information about the present configuration of the system is used in the generation of unbiased mc trial moves. this information is used only in the acceptance criteria. the cbmc approach considerably improves the conformational sampling for molecules with complicated structures. to satisfy detailed balance, one has to change the acceptance rules. in the cbmc scheme it is common to split the total potential energy of a trial site into two parts. the first part consists of an internal, bonded, intra-molecular potential uint which is used for the generation of trial orientations. the second part of the potential, the external potential uexr, is used to bias the selection of a site from the set of trial sites. it should be noted that the split of the potential into uint and uext is arbitrary and can be optimized for particular applications. for a new configuration n, a randomly chosen molecule of length n is regrown segment by segment. first, f trial sites for the first bead (the first atom or united atom) of the molecule are placed at random positions in the simulation box. in this work/ is equal to one. this value was chosen as in the present paper only small molecules (methane and ethane) are investigated. for larger molecules f can be larger than 1. the so-called rosenbluth weight of this segment is then [5, 8-10]: f w1 (n) = l exp[u:;r [3] (8) j=l the interaction energy u ii includes all interactions of atom i with other atoms in the system. one of these trial sites is now selected with probability p.~ez(b-)= exp[-utd3] (9) h i ( ) w1 n for all other segments l of the molecule, k trial orientation bi are generated according to the boltzmann weight of the internal potential of that segment p.?en (b _)db = exp[u:t [3}ih lz i f r int/3ll expl-u1 po (10) in the present paper k is set equal to six. this value can be optimized [ 11]. the set of k different trial segments is denoted by (ll) out of these k trial orientations one is chosen according to the boltzmann weight of its external potential 97 (12) this procedure is repeated until the entire chain of length n has been grown. the rosenbluth weight w(n) of the new configuration is then defined as the old configuration (a) is retraced in a similar way, except that for each segment only k-1 (f-1 for the first bead) trial orientations are generated with a probability given in eq. (10). the k-th lf-th) trial orientation is the old orientation. the rosenbluth weight of the old configuration w(o) is then defined as w1 ( o) fi[± exp(-uif" fj ]l w(o) = l=z j=l j (14) f·kn-1 where w1(a) is the rosenbluth weight of the first segment of the old configuration. to satisfy detailed balance, the new configuration is accepted with the probability acc(o -7 n) = mm 1,--. ( w(n)) w(a) (15) in the present paper the following acceptance rules for creation and deletion were employed: creation: deletion: . { n (o) 1 i acc(o-7n)=mm 1,-k_. __ jt ftf3v w(o) (16) (17) in a trial move a molecule is displaced, and rotated in case it is not symmetrical in all directions. the distances and the angels of rotation are chosen randomly but are limited by a maximum displacement in x, y and z direction and maximum rotation angle. a good sampling of configuration space is achieved with an acceptance rate for the trial move of approximately 50%. the maximum limits of displacement are adjusted during the simulation according to this value. it should be kept in mind that a trial move in mc simulation is different from physical motion in that respect that no check for collision on the path between old and new position is done. therefore, the maximum displacement of a molecule should always be small enough to prevent molecules from moving through the pore wall. there is no biasing-like algorithm for the trial move. consequently, the acceptance criteria for a trial move is: 98 acc(o --7 n) z min{l,expf{3(um (n) -um (o )) ]} (18) the new coordinates of each bead of the molecule after a translational move can be calculated as (19) in the rotational case an equivalent equation looks like able to change the internal orientation of the beads of one molecule the partial trial regrowth is used. since the first bead is the same in the old and the new configuration the rosenbluth weight of the first segment is in the old and new configuration the same and can be set equal to one: (27) the rotational matrix a is given by: (20) with this change the same acceptance rule as for a total regrowth trial is employed: the matrix a is described by a quaternion of unit norm. such a quaternion may be thought of as a unit vector in a four~dimensional space: qz(qo,ql,q2,q3) with q~+q~+qi+qi=l (22) · if the reference frame in the center of mass of the molecule is placed in such a way that the eulerian angles are all zero for the orientation of the old configuration, then the quaternion is: q = (1,0,0,0). to determine the quaternion of the new orientation and therewith the rotational matrix the following scheme is used: 1. generate two random numbers , 1, ' 2 between -1 and + 1 which satisfy the condition: (23) 2. generate a second set of two random numbers {3, g between -1 and + 1 which satisfy the same condition: s2 ={i +si ~i (24) 3. the quaternion for the new orientation is: (25) 4. to satisfy the condition that 5q% of the rotational trials are accepted, the following constraint applies: (26) whereby "value" must be adjusted such that the 50%~rule is fulfilled [5]. for molecules which consist of more than one united·atom, trials that change the internal orientation of the beads of one molecule are necessary to speed-up the simulation. there are two trials that change this internal orientation, a total regrowth trial in which the coordinates of an beads of the molecules change~ and a partial regrowth trial where au beads except the first one change their coordinates. for a total regrowth the conventional cbmc scheme described above was used. jn dense systems the insertion of the first bead in a total regrowth trial is unlikely. consequently the success of the entire trial becomes improbable. to be nevertheless acc(o~n)=mm 1,--. ( w(n)) w(o) (28) in dense systems the creation and deletion events occur, despite the use of cbmc, only with a very low probability. therefore, so-called swap trials were introduced where the identity of a molecule changes. this trial is equivalent of deleting a molecule of species i and replacing it by a molecule j. the following acceptance rule for the swap trials was employed: acc(o-7n)==min[l, n;(o) -1 --w(n)· 11 j (29) ,h w(o) n 1(o)+l after 150,000 mc trials equilibrium was reached at all pressures. actually, we used 250,000 equilibration steps. by doing 20 simulations of the same system, one observes that 37,500 mc steps for each pressure are enough to sample the configurational space. 2 molecular dynamics in order to calculate the diffusion coefficients molecular dynamics (md) calculations were done. the md approach is a solution of the n-body problem of classical mechanics by integrating newton's equations of motion for each atom k: (30) after the starting configuration is selected, the force on each united atom is calculated and the equations of motion are integrated. the integration is done by means of the verlet-algorithm [5,6]. first, 250,000 equilibration steps are calculated and then the time steps follow to sample equilibrium to get the desired self­ diffusion coefficients by employing the einstein­ relation: (31) with (32) the transition from self-diffusion coefficients, detennined by means of md calculations, to transport diffusion coefficients was done by a darken factor: d (alnfk) dr,k = s,k dlnp k pi (33) to conclude, first mc simulations in the grand­ canonical ensemble were done. hereby, a specific equilibrium concentration of each component in the pore is determined at certain conditions in the bulk phase. then a molecular dynamics calculation at the equilibrium pore concentrations was done to calculate the self-diffusion coefficients. the darken factor can be obtain~d from equilibrium adsorption isotherm data. therefore, it is necessary to calculate the derivative of the component fugacity with respect to the amount adsorbed of one component by leaving constant the amount adsorbed of the other components. in practice this is not possible since the input data of our simulations are total bulk pressure and gas fraction composition and it is hardly possible to obtain enough data at constant amount adsorbed of one component to calculate an accurate derivative. as a result jacobian transformations were used [12]. with the help of jacobian transformations, eq. (34), the derivative at constant amount adsorbed of one component can be replaced by multiple derivatives with respect to the input data. this facilitates greatly the calculation of accurate derivatives. a(lnfk ,in p 1 ) aijnpk ,lnpj= (34) in case of non-polar molecules like methane and ethane, only external interactions have to be considered. in the present paper the lennard-jones (l-j) potential was employed. the interaction between two lennard-jones sites i andj is given by the potential [5,6]: (35) the parameters aii and eii are obtained from the lorentz­ berthelot mixing rules: (36) {37) the l-j potential is an effective pairwise additive potential. the interaction energy between every l-j site with all other l-j sites must be summed up: 99 u(r)= lluij(rii) (38) i<j the following l-j parameters were used: ch4 (a= 3.81 a, elkb = 148.1 k), ch3-group (a= 3.75a, elkb = 98k). with the usage of a cut-off radius for the potential energy the computation time can be considerably shortened. in the present paper the so-called tail­ corrected l-j potential was used for the gcmc calculations [5,6]. for the md calculations the potential was truncated and shifted, such that the potential vanishes at the cut-off radius: trunc {u(r)-u(rc) r'5:r,c} u (r)= 0 r>rc (39) periodic boundary conditions and the minimum image convention [5,6] were employed along the pore axis. 3 model of the adsorber bed for the psa module a one-dimensional adsorber model was used. the mass balance for each component can be written at all operating conditions of the skarstrom cycle as: dck ={ dck du]_l-e . dqk +d d 2 ck (40) u ':\ +ck ':\ ps ':\ ax ':\ 2 , dt az az e at uz assuming that the axial pressure drop is negligible, the sum of the gas concentrations of an components is constant and no function of the axial coordinate: (41) under this condition, the overall mass balance during the high-pressure adsorption and low-pressure purge steps, where the total pressure is approximately constant, looks like: 3u 1-e "'dq1 c·-+-·ps,l.,;-==0 oz e 1 dt (42) augmented by an appropriate mass transfer model, eqs. (40-42) form a set of equations· which describe the time evolution of the concentration front of each component. for the mass transfer two models were used. first, for comparison, the rather unrealistic equilibrium model, which assumes that the average amount adsorbed per unit volume pellet is equal to the equilibrium amount adsorbed at the concentration of the surrounding gas phase: 3if1 aq; aq; ac;; a;=a;= dc 1 ·a; (43) second, a linear driving force model was employed. which gives a quite realistic description of the adsorption kinetics: 100 table 1 operating conditions and design parameters of the psa process simulations. molar ratio of chjc2ilt; in feed feed mole flow adsorption pressure desorption pressure temperature purge to feed volume ratio bed length bed diameter bed porosity duration of high pressure feed duration of low pressure purge representative pore diameter of the pellets pellet density pellet diameter (lqk f* -) a;-=kk\qk -qk where the glueckauf constant kk [13] 15dek kk=--'­ r2 p 50150 4mol!s lobar 1bar 300k 2 2m 0.4m 0.4 140 s 140 s ·3nm 1500kg!m3 0.004m (44) (45) was introduced. the equilibrium adsorption data, q;, were obtained from configurational bias mc calculations and the diffusivities from md and mc calculations (see below). the axial dispersion coefficient, dax• was estimated by a correlation from wen and fan [14]: 1 peax,p 0.3 (46} for 0.008 <rep< 400 and 0.28 < sc < 2.2 where lid ·p peax,p =ii·dpi dax andre=~ (47) the dynamic gas viscosity was estimated by a correlation from lucas [15], and the diffusion coefficient in the schmidt number was approximated by a correlation from dawson et al. [16]. it was assumed that the axial dispersion coefficient is constant during the adsorption and desorption step, respectively. therefore, the axial dispersion coefficient is only calculated for the conditions at the entrance of the adsorption bed. to sum up, the following assumptions were made in the model: 1. the cycle is isothermal. 2. there are no radial velocity or composition gradients. 3. the axial pressure drop is negligible. 4. the whole adsorbent is utilized during the feed and purge steps. 5. the pressure is constant during the feed and purge steps. 6. the dead volume at the adsorber entrance and exit is negligible. 7. the pressurization with feed and blowdown are so fast that there is no adsorption or desorption during this step. this is the so·calted .. frozen solid" assumption. pressurization and blowdown can be modelled as a pressure step. 8. mass transfer resistance: a) equilibrium model (no mass transfer resistance) b) linear driving force model (ldf) 9. the ideal gas law is assumed. 10. the effective pore diffusion coefficient and axial dispersion coefficient are assumed to be constant during the adsorption and desorption step, respectively. assumption number one is common for psa simulations, although it is known that in general the heats of adsorption are not negligible and temperature differences in the adsorption bed of more than 30 k occur in some processes [2]. assumptions two to six provoke no severe simplifications. the most severe assumption is number seven, the "frozen solid" assumption. the pressurization and countercurrent depressurization steps can be of comparable duration as the adsorption and desorption steps. assumption number eight specifies the mass transfer models employed. assumption number nine is fulfilled for the desorption step at 1 bar. during the adsorption step at 10 bar, deviations of up to 5% in calculating the concentration can occur, since the compressibility factor reaches down to 0.95 for ethane. the last assumption results from the fact that the present authors simulated effective pore diffusion coefficients for methane, ethane mixtures at a total pressure of 10 bar and a bulk composition of 90 mol-% methane. the model equations were solved by the method of lines, whereby the length coordinates were discretized and the time evolution was found by a runge-kutta 4th order integration. for the adsorption step the initial condition was an empty bed (unloaded cnt, q k,i (t = u) = 0) with a constant composition in the gas phase inside the tube of cc,h, (t = 0) = cch .. (t = 0) = 200.5 mo1/m3 • the boundary conditions were a constant gas composition at the inlet cc 2 h 6 \z = uj = cch. tz = uj =· .. wu.j mo1/m3 , no concentration and velocity gradients at the outlet and a constant feed velocity at the inlet of u(z = 0) = 4nads tf(rd;sc )= 0.198 rnls were assumed. for the desorption step, the initial load of the bed is identical to the last bed load in the adsorption step. for the gas phase the initial concentration of each component is a tenth of the concentration at the end of the adsorption step (pods = lopdes). the boundary conditions for the inlet, now at z = l, are for the velocity u(z = l) = -q.396 m!s and for the concentration cch. {z = l) = 40.1 moll~, cc h \z = lj = u. pure methane is used for purging. z furthermore, it was required that at the outlet (now z = 0), no concentration or velocity gradients exist. the operating conditions are presented in table 1. 4 the carbon nanotube carbon nanotube (cnt) is the name of ultra thin carbon fibre with nanosize diameter ( 1 to 4 nm). the structure 101 table 2 calculated effective diffusion coefficients of methane and ethane in a cnt of 3 nm diameter. the temperature is 300 k, the total pressure 10 or 1 bar, respectively. the bulk mole fraction of methane is 0.9. 0.9 de,ch 4 1[10-4cm2 is] at 1 bar 2.70 de,c 2 h 6 1[10-4cm2 is] at 1 bar 0.301 fig.2a carbon nanotube model with one layer zig-zag configuration. the pore illustrated has a length of 7.25 nm and a diameter of 3 nm. the hexagonal arrangement of the graphitic sheet can be observed. fig.2b carbon nanotube with three layers in zig-zag configuration. consists of enrolled graphic sheets (see fig.2a). depending on the way the sheets are enrolled one distinguishes between zig-zag, armchair and helical cnt. cnt's are further classified into multi-walled or single-walled cnt's [17]. the graphitic sheets show the hexagonal arrangement of graphite (see fig.2a). nanotubes can be used as adsorbents or molecular sieves. in the present paper the cnt~s consisted of three enrolled graphitic sheets (see fig.2b) which have a distance of 0.353 nm from each other. the carbon nanotubes layers were positioned in zig-zag configuration, and the carbon atoms were kept fixed in space. the l-j potential parameters for each carbon atom were given as follows: de,ch 4 1[10-4cm2 is] at lobar de,c 2 h" 1[10-4cm2 is] at 10 bar 4.36 0.742 ~ 3.5 ~ 3 x 0 x x ~2.5 x x '0 x (!) 2 £ x 0 x ~ 1.5 x <( x "e 1 )( ~ 0.5 . . x <i; 0 0 0.2 0.4 0.6 0.8 bulk mole fraction of ethane fig.3 simulated amount of methane/ethane adsorbed versus bulk mole fraction of ethane in a cnt under operating conditions given in table i. (10 bar). ~1.4 0> ~ 1.2 .g., '0 .8 0.8 l5 ~ 0.6 <i; "e 0.4 x x • ¥ •• x x x x x x x x x jxethane j j• methane 1 j 0.2 a*---~----~----~~·~·~~~ 0.2 0.4 0.6 .:>8 bulk mole fraction of ett1ane _j l------------fig.4 like fig.3 for 1 h<tr. lf,=0.34nmand ( :: )=28k (48) results to solve the equations of the psa module (see eqs. (4047)) one needs to know equilibrium adsorption data q;, effective pore diffusion coefficients d~.~: and an a..xial dispersion coefficient dax. in figs.3 and 4 the necessary equilibrium adsorption data at 1 and 10 bar obtained by molecular simulation are presented. the effective diffusion coefficients, approximated by the transport diffusion coefficients (eq. 33), obtained from self­ diffusion coefficients multiplied by the darken factors are given in table 2. the self-diffusivities were calculated by molecular dynamics. in fig.5 the concentration profiles of ethane and methane in the gas phase of the adsorber during the first high pressure adsorption step are given. in this case the equilibrium model is used for describing the mass transfer resistance that assumes an instantaneous equilibrium between the gas and solid phase. the concentration fronts are very steep, i.e. the dispersion coefficient is relatively small. one can observe that after 102 ( i i i j i i i i i i 1 { i i i i i j mahane j ...... 1 ethane \ 1 11 \ \ \ _\ _\ 0.5 1.5 zl[mj fig.s simulated methane and ethane concentration fronts in the gas phase at various times and locations inside the bed. the concentrations are plotted every 10 s with a total time plotted of 180s. equilibrium conditions are assumed. 0 0,2 0.4 0.6 0.8 1.2 1.4 1.6 t.s zl[m] fig.6 simulated methane and ethane concentration fronts in the gas phase at various times and locations inside the bed. the concentrations are plotted every 10 s, the total time plotted is 180 s. 0 0.5 1.5 2 zj[m} fig.7 simulated ethane concentration profiles adsorbed on the cnr s at various times and locations inside the bed. the concentrations are plotted every 10 s. the total time plotted is 180s. 180 s the ethane concentration profile has moved 1.6 m away from the inlet of the adsorption bed. if one uses the linear driving force model (ldf) to describe the mass transfer kinetics between the gas and solid phase. one obtains fig.6. the mass transfer resistance reduces the performance of the adsorber. figure 6 shows methane/ethane concentration profiles in the gas phase during the ftrst high pressure adsorption step. one observes significant differences between fig.5 and fig.6. first, the concentration fronts in fig.6 are less steep compared to the fronts in fig.5. second. the ethane concentration front bas reached the outlet of the adsorption bed after 180 s in the ldf model. while for the equilibrium model the ethane concentration front 0.25 ';;;' 0.2 ~ ·e'o.15 j 0.1 "' m g o.os 0.5 1.5 zl[m] fig.8 like fig.7 for methane. 0.5 1 z/[m] 1.5 time fig .9 simulated gas velocity in the adsorption column at various times and locations. the velocities are plotted every 10 s, the total time plotted is 180 s. has just passed less than 80% of the bed. the mass transfer resistance reduces the performance of the adsorber. this can also be realized from the concentration profiles in the bed. figures 7 and 8 present the amount of adsorbed ethane and methane on the carbon nanotubes at various times and locations in the adsorber bed. as it can be observed, the amount adsorbed slowly increases with time at each location in the bed. it takes more than 100 s until 90% of the equilibrium amount of ethane has adso~bed at the inlet of the adsorber. the methane concentration in the bed increases relatively fast. the equilibrium amount of methane adsorbed is reached after 30 s. this faster equilibrium process can be explained by the approximately nine times larger pore diffusion coefficient of methane (see table 2) and the smaller equilibrium amount of methane (see fig.3). after 20 s methane is displaced in the bed by the slower but stronger adsorbing ethane and the methane concentration profile moves slowly out of the bed. figure 9 illustrates the devolution of the gas velocity in the adsorber during the high pressure adsorption step. it is shown that the velocity decreases as soon as molecules in the gas phase adsorb in the cnt pellets of our fixed bed. this results from the fact that the pressure in the adsorber is constant. the common simplification in psa simulations, namely setting the gas velocity in the adsorber to a constant value, is not realistic in the present psa module under the given operating conditions. figures 10 and 11 present the ethane and methane concentration profiles on the cnt pellets at various times and locations during the first desorption step. as expected, both the ethane and the methane concentration in the bed decrease, but the zl£m] fig.l 0 simulated ethane concentration profiles adsorbed m: the cnt' s during the desorption step. z = 0 is the inlet for the purge gas. the concentrations are plotted every 10 s, the total time plotted is 180 s. methane concentration in the bed decreases much faster than the ethane concentration since the pore diffusion coefficient of methane is far larger than the ethane pore diffusion coefficient at the pure pressure of 1 bar. after 180 s, the ethane concentration in the bed is sti1120% at the outlet of the purge stream. this results from the approximately 2.5 times smaller pore diffusion coefficients at 1 bar in comparison with 10 bar. the equilibration process is much slower in the desorption step than in the adsorption step. the adsorption characteristics is very realistic compared to published data for psa adsorbers [1]. conclusion the present paper demonstrated that through a conjunction of an adsorber model with molecular simulations it is possible to simulate the behaviour of a psa module without any experimental psa data. the molecular simulations give far deeper and realistic insights into the molecular processes of adsorption and desorption occuring inside the porous materials compared to merely descriptive models. realistic results compared to published experimental psa data could be obtained. symbols a rotational matrix b trial orientation c total gas concentration ct concentration of component k dr,t transport diffusion coefficient of molecule k ds,k self-diffusion coefficient of molecule k dt!,k effective diffusion coefficient of molecule k dp particle diameter f number of trial sites, function (eq. (41)) h: fugacity of component k f force k number of trial orientations k1: glueckauf constant kb boltzmann's constant mt molar mass of component k n number of molecules 0 p pii peax pk q q r r rep rp s sc s t t u u u v v w w x y z z {3 e tf j.l ' pb p fig.ll like fig.jo for methane. old state total gas pressure probability axial peclet number partial pressure of component k coordinate of quaternion 103 grand-canonical partition function, quaternion (eq. (22)) amount adsorbed of component k per unit mass adsorbent equilibrium amount adsorbed per unit mass adsorbent part of the kinetic energy contribution of one molecule vector between two points distance particle reynolds number particle radius auxiliary variable (eqs. (23-25)) schmidt number generalized position temperature time potential energy potential energy exerted on the system superficial velocity relative coordinate volume rosenbluth weight of a molecule segment rosenbluth weight of a configuration cartesian coordinate gas mole fraction axial coordinate of molecule position in pore length coordinate of adsorber bed greek letters f3 = lf(kb • 1) lennard jones parameter~ bed porosity (eqs. (39, 41)) dynamic viscosity chemical potential random number between -1 and+ l bed density gas density 104 pt amount of k adsorbed per unit volume a lennard jones parameter superscripts ext external gen generating int internal trunc truncated sel selecting subscripts c cut-off ij,l index m molecule p pellet s self, center of mass references 1. ruthven d. m., farooq s. and knaebel k. s.: pressure swing adsorption, vcr, new york, 1994 2. yang r. t.: gas separation by adsorption processes, butterworth, stoneham, 1987 3. thomas w. j. and crittenden b.: adsorption technology and design, butterworth-heinemann, oxford, 1998 4. mcquarrie d. a.: statistical mechanics, harper collins publishers, newyork, 51, 1976 5. frenkel d. and smit b.: understanding molecular simulation, academic press, new york, 117-118, 1996 6. allen m. p. and tildesley d. j.: computer simulation of liquids, clarendon press, oxford, 42, 1993 7. siepmann j. i. and frenkel d.: molecular phys., 1992,75,59-70 8. vlugt t. j. h., martin m. g., smit b., siepmann j. i. and krishna, r.: mol. phys., 1998, 94, 727733 9. vlugt t. j. h., krishna r., smit b.: j. phys. chern., 1999, b 103, 1102-1118 10. vlugt t. j. h.: mol. sim., 1999,23,63-78 11. moou g. c. a.m., frenkel d.: mol. sim., 1996, 17,41-55 12. tester j. w. and modell m.: thermodynamics and its applications, prentice hall ptr, new jersey, 1997 13. glueckauf e.: trans. faraday soc., 1955, 51, 1540-1548 14. wen c. y. and fan l. t.: in: albright l. f., maddox r.n., mcketta j. j. (eds): chemical processing and engineering, marcel dekker, new york, 3, 1975 15. lucas k.: chem.-ing.-techn., 1974, 46, 157 16. dawson r. f., khoury f. and kobayashi r.: aichej., 1970, 16,725-731 17. harris p. j. f.: carbon nanotubes and related structures, cambridge university press, cambridge, 1999 page 99 page 100 page 101 page 102 page 103 page 104 page 105 page 106 page 107 page 108 microsoft word 01-06 1401 gyulai.docx hungarian journal of industry and chemistry veszprém vol. 41(1) pp. 1–6 (2013) vehicle routing approach for lean shop-floor logistics david gyulai1,2! and lászló monostori1,2 1 fraunhofer project centre for production management and informatics, computer and automation research institute (sztaki), kende str. 13–17, budapest, h-1111, hungary 2 department of manufacturing science and technology, budapest university of technology and economics, egry j. str. 1, budapest, h-1111 hungary ! e-mail: david.gyulai@sztaki.mta.hu in order to satisfy the material supply needs of large scale shop-floors and production systems, various logistics solutions are applied. in lean manufacturing enterprises, the material supply is pulled by the demands of manufacturing/assembly processes; therefore, a milkrun service is often applied to support the production without glitches. the milkrun logistics planning is a special case for vehicle routing problem (vrp), and requires effective approach to solution in order to satisfy various constraints, and minimize the cost of service. this study gives an overview about lean logistics as well as the most efficient vrp solver algorithms. furthermore, a novel initial solution with generation heuristics is proposed, which is specially focused on flexible milkrun planning. in order to demonstrate the capabilities of the solution, a software environment is developed as a demonstration that focuses on the main industrial requirements of logistics planning like effective layout definition, quick response of the delivery service and effective order handling. keywords: vehicle routing problem, milkrun, local search, factory logistics introduction the material provision of largeand medium-scale production systems requires prudent planning and control, since it influences the performance of the production and affects the order management directly and storage assignment [1]. in order to manage effectively the material provision of the production, practical transport logistics and distribution tasks are usually formulated as vehicle routing problems, whose objective is to obtain a minimum-cost route plan serving a set of customers with known demands [2]. in state-of-the art manufacturing systems, lean processes are successfully applied to eliminate the wastes on all the levels of production, and they raise the overall efficiency of the system by reducing the nonvalue adding activities in the process chain. the shopfloor logistics processes have to be adapted to the production system; therefore the waste reduction in the material provision also has a key role in balancing the workload and ensuring a smooth running of production. a well-operating lean logistics system keeps the inventories and operational costs on the most cost efficient levels, via by providing the materials what that are needed, exactly when they are needed. for satisfying these requirements, concepts of the lean logistics can be applied that are primarily aimed at controlling the transport services duly to the pull strategy. the paper is focused on the ‘milkrun’ service, which is defined as a manually operated, cyclic transport system delivering raw materials (or sub-assemblies) and disposing empties based on consumption using a fixed route and time schedule [3]. according to this characterization, milkrun scheduling is considered as a special vehicle routing problem with time windows, a limited capacity, and number of vehicles. in this paper a novel, multi-level planning approach is proposed, which combines the advantages of existing algorithms as for example local search for vehicle routing. first, an overview of the state-of-the-art factory logistics is given, considering the recent shop-floor characteristics and planning demands. then the main solution approaches and algorithms are introduced, as well as the critical points of milkrun planning. in section 4, the proposed layout representation hierarchy and the novel initial solution generation heuristics method are described. the latter focuses on the real industrial criteria and give a feasible milkrun schedule. in the last section, an industrial case-study and some numerical results present the efficiency of the milkrun planning method developed. shop-floor logistics the shop floor logistics are part of the production logistics in the supply chains of companies. while logistics in general is about supplying a customer with 2 necessary goods in time, with the goal of efficiency, and the lowest possible costs, production logistics is the task of bringing necessary material to workstations and machines and transferring it to the next station. in the realm of logistics planning methodologies the lean approach, originating in the toyota production system, of overall waste reduction has become a major planning paradigm, constituting the lean logistics approach [4]. principles of lean logistics of the seven waste categories, eliminating unnecessary transports, waiting times, superfluous movement and excess inventory are the most relevant in lean logistics. klug identifies the following characteristics of lean logistics [5]: synchronicity and a clocked material flow, flow orientation, standardization, pull principle, stability, integration, as well as perfection. regarding the pull principle, as the most relevant feature, material is only transferred to a workstation if it is about to process the material thus reducing inventory levels by reducing shop floor stock to safety buffers only. beside the above principles of lean logistics, a relatively novel issue in material provision of production is ‘green logistics’ that is generally about establishing an ecologically sustainable transportation system considering factors like energy consumption and airpollution [7]. while in the general external logistics context theses planning principles are reflected in transport concepts such as the just-in-time delivery, there are also corresponding design concepts in production and shop floor logics. for the supplier/source side, establishing zones for decentralized incoming goods and supermarkets in the vicinity of assembly stations is a means of reducing transport lengths. on the receiving side, standardized shelves and reusable containers, replenishment schemes like ‘kanban’ are applied. for the transport system between supply and workstations, ‘tugger trains’ (fig.1) with fixed time intervals, standardized capacity, and transport lot sizes are preferred over forklift transport in the context of lean logistics; the goal of, which is the reduction of inventory and avoiding erratic peaks in production known as the bullwhip effect [8]. this transport concept of scheduled tugger trains in the context of a lean-oriented logistics system is usually combined with the milkrun transport concept that is in the focus of this paper. especially in production environments with a high product complexity, variety amid a complex and changing material flow, planning a system of milkrun transports is a complex planning task. thus, an efficient system of milkruns could significantly in-crease the efficiency of the overall production logistics. milkrun as a vehicle routing problem vehicle routing (vrp) is a challenging combinatorial optimization problem, introduced first by dantzig and ramser in 1959 [9]. the general vrp is known as the capacitated vehicle routing problem (cvrp), were the aim is to satisfy the needs of all the customers at different locations by having a given number of vehicles with capacity constraints [11]. when milkrun is applied as a material providing system, the time constraint of the runs has also to be added to the general problem (vrp with time windows – vrptw). the general objective is to minimize the costs either by minimizing the total distance travelled, or minimizing the number of vehicles applied. a specific type of vrp is the pickup and delivery problem (pdp) where the vehicles not only provide the locations with materials, but also pick up materials at the stations and deliver them to another one. the milkrun problem is also a pdp, with time windows and cyclic service [12]. several approaches from the operations science are used to solve vrps, as for example constraint programming that manages flexibly the various specific constraints of the vrp [14]. local search is one of the fundamental approaches to find solutions for hard computational – including constraint satisfaction – problems. the basic idea behind local search is to start with a randomly or heuristically generated candidate solution, and to iteratively improve that by means of defined functions [15]. generating the initial solution is always a crucial point when applying local search, since it significantly affects the running time of the algorithm. sophisticated heuristics for the vrp are the two-phased ones, which decompose the problem into a clusteringand a routing problem, with possible feedback loops between the two stages. cluster-first route-second (cfrs) algorithms perform a single clustering of the vertex set and then they determine a vehicle route on each cluster. the bestknown cfrs algorithm is the fisher-jaikumar algorithm, which solves the general assignment problem (gap) to form the clusters [17]. the local search starts from the initial solution and subsequently moves from the present solution to a neighbouring solution in the search space where each solution has only a relatively small number of feasible neighbour solutions and each movement is determined by neighbouring operators [20]. when applying local search, the combination of the neighbourhood operators produces the next local optimum solution (fig.1). although the most general forms of the vrp can be solved effectively with the above approaches, the milkrun planning problem is hard to interpret as a simple graph-search problem, and the general initial solution heuristics are difficult to transform for this problem. the mapping process of the factory layout also requires special processing; therefore general solution methods cannot be applied easily for such a special problem. 3 problem formulation hereby, we provide a definition to the milkrun planning problem. consider a layout of the shop-floor, which is defined by a set of routes and stations. the routes can be either oneor two-way ones, and each route endpoint is defined as a “routenode”. along a specific route, there can be more stations (fig.2). the problem also considers demands that belong to the stations and defined by the amount of the transported goods in standard units and the required cycle-times of the transportation. the goods are transported by vehicles (practically by tugger trains), which are defined by their capacity and average speed. in order to plan feasible milkruns, real-world constraints are considered, such as the capacity constraints of the vehicles, which limit the maximum number of the transported goods. another constraint is the time limit of the plan, which means the total time consumption of a milkrun plan cannot exceed the cycletime of the demands. the loading and unloading points can be reached from both sides of the tugger train, and the train can approach the station from both endpoints of the route that the station belongs to. a milkrun plan is built-up by paths, where each path is given as the list of the visited stations and the list of the routes that the vehicle passes along. the plan does not partition the demands, and a visit of a particular station only occurs in a specific path. a milkrun plan is characterized by its total time consumption, which is required by the vehicle(s) to perform the plan. a milkrun plan is considered to be better than the other one only if its total time consumption is smaller, while it satisfies all the demands. the goal of milkrun planning is to minimize the number of the required vehicles via minimizing the time consumption of the plan. the proposed planning process layout representation for vehicle routing as it was mentioned in the previous section, solving the general vrp is not enough to plan feasible milkrun schedule, since most of the routing algorithms does not calculate with the physical constraints determined by the shop-floor. most of the general solution approaches consider the problem as a graph-search, where the stations are represented by vertices and the routes are represented by edges [21]. in many cases, this representation does not support effectively the planning processes with feasible results, unless the application of the following constraints. frequently, when representing a shop-floor by directed graphs, it turns out that the structure of the layout results some direct and indirect routing constraints. a direct case means that the additional equations can be formalized immediately when constructing the graph, such as the asymmetric edge formulas, while the others require further consideration. indirect constraints are usually implied by the narrow and one-way corridors, which limit the abilities of the vehicles from going to a station directly from another, even if a path connects them. these constraints are implied by the moving abilities of the common applied tugger train, since it cannot turn in the middle of an aisle, and in many of the cases it have to take a detour before visiting the next station (fig.2). in order to handle the shop-floor constraints effectively and be able to avoid impossible movements of the vehicle, a novel hierarchical layout representation is proposed. the layout is defined by three main different classes, each having their own specific attributes. this structure can be handled dynamically during the path calculations, and the asymmetric nature of the distance matrix is represented together with the limitations of vehicles movements. fig.3 shows the hierarchy of the layout, defined by “routenodes”, “routes” and “stations”. to calculate the distance matrix of the layout, storing the shortest paths between the stations, dijkstra’s algorithm was applied that solves the single-source shortest path problem in logarithmic running time [22]. in this case, the input of the algorithm is a directed graph where the vertices are the set of the “routenodes” and the edges are the routes. this graph representation is able to handle all the nodes of the layout with their connections, and by applying dijkstra’s algorithm the asymmetric distance matrix can be calculated. figure 2: layout elements and vehicle movement figure 1: interand intra-route relocate operators 4 initial solution generation in order to plan feasible milkrun cycles with the lowest operational costs, the shop-floor constraints have to be taken into consideration. to handle the constraints effectively, the routing algorithm needs to select the stations to be visited dynamically. thus, a so-called triplet solution is applied, which helps to avoid impossible movements of the vehicle. a triplet is consisted of three identical nodes: three current, the previous and the next position of the vehicle. the next position is calculated dynamically when determining a particular path of the vehicle. the milkrun planning method strongly focuses on the industrial requirements of vehicle routing; therefore, a novel initial solution generation heuristics was implemented. the goal is to generate a solution that is as close to the criterion as possible. the proposed heuristics can be classified as a cfrs type rule, and differs from the fisher-jaikumar algorithm by the cluster generation method, since it does not require solving time-consuming gap, but defines the clusters based on practical reasons [18]. to generate a feasible initial solution, the algorithm calculates a path to each station applying dijkstra’s shortest path algorithm. then a greedy search algorithm is applied to calculate the next node, which must be visited by the vehicle before returning to the depot, so as to avoid violating the turnaround constraints of the vehicle. the greedy search iterates forward the nodes applying a best-first search strategy [23], and finds the first node from, which the shortest path to the depot does not contain the previous node. the “roundtrip” planning method is applied for each station, and detects all the feasible tours on the shop floor. in order to determine the set of paths for the initial solution, the paths with most visits are selected one by one while the set of unsatisfied demands is not void. performing the services required by these cycles provides a feasible and acceptable initial solution for the planning algorithm. the pseudo-code of the proposed algorithm is the following: vv∈ set of stations { }vv|v:p ∈= path }p{p set of paths [ ] v)s,r(|dd rs ∈= distance matrix }p{i initial solution iq demands of the ith station }q{q i= set of demands ct cycle time c capacity of the vehicle initialize v, i, q, c{v}, c, tc foreach i in v calculate d0i foreach v in d0i add v to ci calculate di0 foreach v in di0 add v to ci align c [length(ci+1) < length (ci)] while |q| > 0 while time(c1) > tc or load(c1) > c remove rand v from c1 (v≠i) foreach v in c1 delete qv from q add c1 to i delete c1 from c return i local search strategy and neighbourhood functions in order to improve the initially generated solution, neighbourhood functions are applied. to be able to reach all the points of the search space, both intraand inter-route operators are necessary to calculate with, although in this case the effect of the inter-route functions is more significant since the initial solution heuristics could provide paths with stations in a rather good sequence. the algorithm performs the local search to minimize the paths, and the cycle-time of them. then, a simple bin-packing problem is considered, to allocate the paths to a minimal number of vehicles. to solve the problem, first fit heuristics was applied, which is a proven 11/9 opt solution algorithm [24]. case study and test results the milkrun planner software, which includes both the user interface and the solver algorithms were implemented in a .net environment using c++ language. within the performance evaluation of the implemented software, a real production environment was modelled in order to analyse its capabilities. the purpose of the implemented application is to offer userfriendly and efficient milkrun planning environment; therefore a graphical, point-and-click layout definition interface and xml communication have been applied (fig.4). figure 3: hierarchy of the layout representation 5 first the input parameters are processed and stored in the memory, and dijkstra’s algorithm is applied to calculate the shortest path between each station. the distance matrix is built up from vectors, each having two distance elements. this data structure is required by the applied triplet-based path planning method, which selects dynamically the proper distance parameter from the vector, based on the location of the previously visited station. the initial solution generation uses the distance matrix to create the tours, based on the station loops detected on the layout. the initial solution contains only feasible paths that satisfy the time constraints as well as the capacity constraints of the actual vehicle. to avoid overloaded vehicles, a pre-check method is performed: the vehicle is loaded by all the raw materials in the depot, and then all the other loading and unloading processes are calculated station-by-station to simulate the real milkrun process. in order to calculate with time constraints, both the travel-time (with constant average speed) and the loading/unloading time (time/item) are considered. the purpose of the generated initial paths is to satisfy all the demands by the lowest possible number of feasible cycles. the local search algorithm takes the initial paths and reduces their total time consumption by applying neighbourhood functions where it is possible. the algorithm iterates through all the combinations of the stations, and detects the possible insertions from one path to another. as local search iterates through the paths in a random sequence, different test runs can result different milkrun plans. in order to approximate the global optimum solution, the implemented application performs the local search several times and selects the most appropriate schedule from the generated solutions. the capabilities of the algorithm were tested in a real production environment. this was a large-scale automotive production system with 2 factory halls, 67 stations and 96 routenodes. the milkrun plan has to satisfy 193 various demands in 60 minutes cycle-time. the analysed system requires efficient planning process, since the total length of the routes is over 2.5 km that affects critically the total time of the milkrun schedule. the application of inefficient milkrun schedule results low-utilized vehicles and high number of cycles. in this case, the goal of the test was to minimize the number of vehicles required to perform the services via minimizing the time of the cycles. the proposed initial solution heuristically generated eight feasible paths with 20,400 seconds total time. first, the algorithm tries to optimize the plan by applying one vehicle, and increases the number of the vehicles only if the improvement steps cannot decrease the time requirement of the total plan under the cycle-time (3600 seconds). by this way, the test run could optimize the plan for two vehicles in 177 iterations, and generated a schedule, which time requirement is only 57 minutes (fig.5). conclusions after an overview about the state-of-the art shop-floor logistics, and the general formulations of the vehicle routing problem, a solution was proposed that uses a novel layout representation and initial solution generation heuristics to solve the milkrun planning problem. in order to demonstrate the capabilities of the figure 4: the user interface of the milkrun planner application figure 5: test results of the case study 6 solution, a software prototype was developed and tested on real-life industrial data. future work includes the extension of the model with demand partitioning so as to increase capacity utilization of the transportation vehicles. moreover, handling inhomogeneous demand types (physical aspects of material handling) requires further constraints to be included in the model. secondly, future work will be dedicated for making the solution available in practical industrial applications. in an on going research project the milkrun planning algorithm will be implemented in a factoryand a logistics planning application currently under implementation. acknowledgements the research has been partially supported by the national office for research and technology (nkth) grant "digital, real-time enterprises and networks" (omfb-01638/2009). references [1] kovács a.: optimizing the storage assignment in a warehouse served by milkrun logistics, international journal of production economics, 2011, 133, 312–318 [2] lau h., sim m., teo k.: vehicle routing problem with time windows and a limited number of vehicles, european journal of operational research, 2003, 148(3) 559–569 [3] droste m., deuse j.: a planning approach for inplant milk run processes to optimize material provision in assembly systems, proc. 4th cirp international conference on changeable, agile, reconfigurable and virtual production, 2011, 605–610 [4] arnold d.: handbook of logistics, 3rd edition, springer, 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3rd annual symposium on combinatorial search, 2010, 129–136 [23] russell s.j., norvig p.: artificial intelligence: a modern approach, 2nd edition, prentice hall, 2002 [24] yue m.: a simple proof of the inequality ffd (l) ≤ 11/9 opt (l) + 1, ∀l for the ffd bin-packing algorithm, acta mathematicae applicatae sinica, 1991, 7(4), 321–331 hungarian journal of industry and chemistry vol. 51(1) pp. 1–7 (2023) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2023-01 process simulation of hole mandrelling in steel aircraft parts iryna voronko1*, vitalii voronko2, yuri dyachenko1 and serhii shapar1 1 national aerospace university “kharkiv aviation institute”, 17 chkalova street, kharkiv , 61070, ukraine 2 o. m. beketov national university of urban economy in kharkiv, 17 marshala bazhanova street, kharkiv, 61002, ukraine the processing technology of steel structural elements of aircraft parts is especially important since, if improperly processed, this material can be subjected to weathering, causing corrosion. furthermore, special attention is paid to the walls of holes used for bolting. since holes can become stress concentrators, the paper proposes to strengthen them by implementing the spd (surface plastic deformation) method. the article describes the simulation of the mandrelling process, which is more efficient and less traumatic. therefore, changes in the walls of holes as a result of deformation are shown, which occur after the process of hole mandrelling. keywords: surface plastic deformation, hardening, hole mandrelling, bolting, lubrication, mandrel 1. introduction the fields of modern aeronautical and mechanical engineering are always in search of ways to improve the wear resistance, durability as well as reliability of parts and assemblies. the use of high-strength alloys does not always provide the best solution to this problem, since they entail a number of associated disadvantages. the most successful solution to increase wear resistance, durability, reliability and other properties of a part is to strengthen its surface layer [1]-[3]. this layer is the first to perceive loads, resists them and protects the base material. given that the quality of the surface layer ensures reliable operation of the part, more stringent requirements are imposed on this layer than on the base material of the part. to improve the quality of and eliminate various defects in the surface layer, surface plastic deformation (spd) techniques are used [4]. although the application of spd methods effectively increases the life cycle of free unfilled holes and bolted holes, spd methods are not fully implemented in production due to the high cost, low productivity and limited technological capabilities of the process as well as the availability of devices for strengthening. in general, as the quality of the part increases, the standard of modern air transport will rise and economic efficiency be achieved. in aircraft designs from the 20th century, the amount of steel used accounts for about 10% of the received: 25 oct 2022; revised: 9 nov 2022; accepted: 11 nov 2022 *correspondence: i.voronko@khai.edu weight of an airframe. the main advantages of using steels are their high modulus of elasticity, relatively low price, good degree of interchangeability and operational reliability. corrosion-resistant steels in modern aircraft with a long service life are increasingly replacing medium alloy steels, which enhances the reliability of their parts. steels of this class are used to manufacture welded and non-welded parts of aircraft, engines and units operating at temperatures of up to 800°c. for the purpose of modelling, a material from this class was used, namely corrosion-resistant austenitic chromiumnickel steel. 2. features of using bolted joints in the parts of helicopters and aircraft, threaded joints are most widely used. bolted joints are also widespread in the airframes of aircraft and helicopters [5]. fatigue failures are a common cause of airframe failures. up to 75-80% of all fatigue failures begin at the bolted joints between structural elements of airframes. measures are being developed to increase the longevity of these compounds [6]. the applications of structural elements are set during the design phase, implemented in specific technological solutions during their manufacture and maintained throughout their operation. therefore, all factors that determine the applications of bolted joints are https://doi.org/10.33927/hjic-2023-01 mailto:i.voronko@khai.edu voronko, voronko, dyachenko and shapar hungarian journal of industry and chemistry 2 divided into three groups, that is, design, technological and operational, which are presented in figure 1. approximately 70% of the labour intensity in the manufacture of joints is spent on the formation and processing of bolt holes. the holes are formed using drills, countersinks, reamers and broaches. due to the limited amount of space in which work can be done in these holes, it is necessary to reduce the cross-sectional dimensions of the cutting tool, thereby diminishing its rigidity and increasing the likelihood of vibration while cutting. furthermore, retraction of the tool from the geometric axis of the part becomes problematic. holemaking is further complicated by poor conditions with regard to chip evacuation. great difficulties arise when processing deep holes. in practice, the precise machining of cylindrical holes is more complex than machining their outer cylindrical surface. observations of the surface layers of various parts show that they are often weakened by external damage: cuts, microrelief scratches and traces of corrosion. the surface is the boundary of the metal, moreover, it is of reduced strength due to the damaged integrity of the crystalline grains during machining. the smallest microscopic scratches on the surface of the machined part can lead to its premature failure since they spread into the metal section under the action of dynamic loads, even when relatively small external loads are applied. it has been shown that stress concentrators such as transverse holes located in plates, shafts and connecting rods serve as locations for the formation of fatigue cracks. strengthening the zone with such holes increases the fatigue strength and localizes the sites of fatigue crack initiation [7]. the application of complex aggregates is limited to 10-20% of their maximum level of implementation due to the presence of stress concentration in the holes. furthermore, 60-70% of this figure, that is, the main reason why complex aggregates are not implemented, is due to the presence of cylindrical smooth holes of small and medium diameters without coatings. the application of parts and holes can be increased [8] by carrying out the following activities: improving the quality of hole processing; applying advanced processing methods that do not place the surface layer under tensile stress; bimetallizing holes; selecting the optimal ratio of tensions when setting the bolt in the bolt hole and the axial compressive force; chemical-thermal treatment; design optimization; processing by spd methods. experimental methods for choosing rational technological parameters for the hole mandrelling process in steel aircraft parts require significant financing and high material costs, moreover, are time-consuming. the current level of development of computer technology and software facilitates numerical simulation of this process by the finite element method (fem) [9]-[12]. the purpose of this work is to determine the rational technological process parameters of hole mandrelling in steel aircraft parts by a numerical simulation. 2.1. possibility of hardening holes by the spd method considering its problems, the possible methods of strengthening holes by the spd method are analysed. certain types of surfaces are subjected to their own hardening methods. to harden holes, the most commonly used methods are mandrelling, rolling and shot blasting. although shot blasting of metal is one of the most popular mechanical technologies, it cannot be implemented with a slipway assembly of units. the method of hardening the surfaces of holes by rolling is quite effective, however, requires expensive equipment. furthermore, usually only one side of the part can be treated when using slipway assembly, which significantly complicates the use of this hardening method. hole mandrelling is a method of hardening holes carried out by smoothing broaches or rolling tools referred to as mandrels. during hole mandrelling, the tool, that is, a mandrel, is pushed through the hole with a slightly smaller diameter compared to the tool itself. as a result of plastic deformation, the diameter of the hole increases, the processed metal layer in the hole is hardened and any uneven areas of the surface are levelled so the surface of the hole becomes very smooth [13]. the stress the surface of the hole is subjected to during mandrelling is, in most cases, compressive, which has a favourable effect on the structure of the layer of metal on the surface and the operational properties of that surface. since plastic deformation usually occurs near the layer of metal on the surface when holes are mandrelled, any changes to the metal structure do not penetrate particularly deeply. mandrelling is carried out without the use of finishing and polishing materials, so harmful particles of abrasive grains do not penetrate its surface. portable and stationary presses are used for mandrelling. universal equipment is used as stationary presses. to implement the mandrelling process by complying with the co nditions of a slipway assembly, it is necessary to use pneumatic impulse hammers [14]-[15], which are the most profitable as such devices figure 1. classification of factors determining the applications of bolted joints process simulation of hole mandrelling 51(1) pp. 1–7 (2023) 3 improve working conditions for operators by providing ease of use and maintenance. furthermore, they offer a significant reduction in energy consumption being light weight and small, moreover, as a result, are very reliable, stable, economical as well as function in a cyclic operation. lubrication also plays an important role in mandrelling. the wrong choice can lead to a significant deterioration in the quality of the processed surface, an increase in the mandrel force and a decrease in the durability of the mandrel [16]-[18]. mandrelling without lubrication leads to molecular adhesion of the metal being processed and the tool, causes metal to stick to the tool and can lead to mandrel hardening in the hole. when choosing a lubricant for the mandrelling process, it is necessary to ensure that the best surface finish is produced. lubrication during mandrelling can be considered satisfactory if the conditions required for fluid friction are maintained between the rubbing surfaces throughout the entire process to help reduce traction and mandrel wear as well as improve the cleanliness of the processed surface. when steel is mandrelled, vegetable oil (linseed oil), machine oil or oleic acid is chosen as a lubricant. 2.2. the essence of the hardening process according to the design of the mandrel, different types are used. mandrels of all types, within the working area of their profile, have an intake part that performs the main work of metal deformation; a calibrating (cylindrical) part which increases the wear resistance of the mandrel and improves the quality of the processed surface; and a back part which is designed to reduce frictional forces during mandrelling. the design of the mandrel and its elements are shown in figure 2. plastic deformation of the surface of the hole during mandrelling occurs due to the fact that the maximum diameter of the mandrel is greater than that of the hole to be hardened by a value referred to as the tension. the quality of processing and the value of the tension depend on a number of factors, e.g.: the material of the part as well as its physical and mechanical properties; the initial state, namely the accuracy of the shape, its dimensions and the quality of the surface of the hole; the material, shape and geometric dimensions of the working area of the tool as well as any possibilities to make adjustments; the feed pattern of the tool and part holding; heating of the tool and the processed material. as the main parameter, the tension of mandrelling plays an important role, which is the difference between the initial nominal dimensions of the contact surfaces of the tool and those of the hole in the workpiece crosssection deformed by the mandrel. if the tension is less than necessary, then once the mandrel has been pushed, the surface layer of the metal will almost completely return to its original position in which it was before processing and no residual deformation will occur. however, should the tension be excessive, plastic deformation will result. as the tension increases, roughness decreases, but if the tension is too high, then the mandrelling process will be more difficult, since as the tension increases, the pressure applied on the part by the tool and the coefficient of friction increase. this usually leads to mechanical damage to the surface being hardened and excessive heating of the part which causes the structure of the material to change. under the influence of frictional forces and the normal amount of pressure applied by the mandrel, a complex stress state is created in the metal surrounding the hole, thereby moving the plastic metal wave. in the hole ahead of the mandrel during mandrelling. the height and shape of the generated wave depend on the material being processed, the tension of the mandrel, the wall thickness of the workpiece, the lubricant used as well as the shape and cone angle of the mandrel. the greater the pressure applied by the mandrel on the metal within the intake cone (and the frictional forces corresponding to this pressure), the larger the plastic wave formed in front of the mandrel. 3. simulation of the hole mandrelling process 3.1. preparations simulation of the mandrelling process that aircraft parts made of high-strength steels are subjected to was carried out using the simufact forming simulation tool. solidworks and compass 3d software were used as auxiliary programs for simulating the geometry of all the necessary parts for modelling the process. the first stage consisted of development of the geometry of the mandrel, support and mandrellable plate pack. according to the design scheme, a single-tooth mandrel with a shank was used. the mandrel, which weighed between 4.50 and 4.55 g, was composed of the alloy tool steel хвг. the chemical composition of the alloy includes 1.2-1.6% tungsten, which enhances the wear resistance figure 2. construction of the mandrel: α cone angle of the intake; β inverted cone angle; 1 the intake; 2 calibrating (cylindrical) part; 3 outlet part voronko, voronko, dyachenko and shapar hungarian journal of industry and chemistry 4 of the element. to achieve the necessary rigidity, the composition includes 1% of chromium and carbon, while 0.4% silicon increases its resistance to tempering, moreover, 1-2% manganese ensures structural integrity. the mandrel drawings were made in the compass 3d program, while the 3d models were constructed in solidworks (figure 3). 3d models were made in accordance with all the dimensions outlined by the mandrel drawings and correspond to full-scale mandrel models. two round supports, one at both the top and bottom composed of ст3сп carbon steel, are needed to simulate the mandrelling process. the technical parameters of ст3сп allow it to be used to produce the loaded elements of welded structures as well as machine parts and mechanisms that operate at high temperatures. the pack consists of a sheet in which holes with a diameter of ø5.8 mm are made, reamed and hardened by mandrelling. the sheet is made of the high-strength stainless steel 12x18h9t (corrosionand heat-resistant). a good degree of resistance to atmospheric as well as intergranular corrosion combined with its heat resistance, stability, strength as well as ease of processing and use over a wide temperature range render this steel grade one of the most produced and applied in various industries, particularly in the manufacture of machine parts. simufact forming is a full-featured end-to-end solution for simulating a wide range of metal forming technologies since it gives a realistic representation of technological operations with full 3d visualization of all tools and parts. the program created a process called "cold forming" to which the mandrelling is referred. the parameter (option) "setting" was selected and the type of calculation was 3d. the 3d models of all the necessary components created in solidworks were transferred to the simufact forming software. the previously transferred main geometric components of the mandrelling process with which the simulation was performed, namely the mandrel, the pack to be mandrelled as well as the top and bottom supports, are shown in figure 4. the materials of all the transferred parts were also assigned. to facilitate the calculations and reduce the computational complexity of the model, all the elements involved in the process were divided along the plane of symmetry. this method can be applied, since all the components in the mandrelling process are symmetrical. a hydraulic press was used to push the mandrel. transfer of the necessary force to the mandrel occurred with the help of a spring which was added to the top support. the initial state in which the spring for the hydraulic press was located was “compressed”. the direction of the spring action was from top to bottom. 90 j of work was applied to the mandrel. the press moved at a constant speed of 10 mm/s. the frictional parameters between the 3d models were regarded as standards from the simufact forming software, that is, friction was combinational, the coefficient of friction was equal to µ=0.08 and the coefficient for modelling the wear process was equal to 1. the supports and mandrel were considered to be incompressible and elastic bodies, respectively. since the deformation process is assumed to occur at cold temperatures, the room temperature, which was 20°c, was assumed to be the temperature of the plate and stamp. the heat transfer coefficient to the medium was assumed to be constant, namely 50 w/(m2k). the tension the mandrel was subjected to during the modelling of different holes was not equal but rather ranged from 0.25 to 5%. with such a tension, the pulling force was not excessive, moreover, during the mandrelling process, damaging cracks did not occur in the metal. the contact between the surfaces of the hole and mandrel was taken from the contact table in the software. after adding and adjusting the geometrical parameters, two types of mesh were created; the first completely covered the mandrelled pack, while the second was created around the hole. the latter was somewhat larger than the diameter of the mandrelled hole and went slightly inside the hole. the structural resolution of the second mesh was better, which produced more accurate results from the calculation. this second mesh was in the form of a tube covering the figure 3. dimensions of the mandrel diametrical dimensions of the inlet a and outlet b parts of the mandrel: a1=5.57 mm, b1=6.10 mm a2=5.63 mm, b2=6.16 mm a3=5.70 mm, b3=6.18 mm figure 4. transfer of the previously created geometry to the “simufact forming” software and splitting the symmetrical model process simulation of hole mandrelling 51(1) pp. 1–7 (2023) 5 required area around the hole, the vicinity of which was especially important for this study since plastic deformations and hardening of the walls of the holes took place. the dimensions of the mesh are as follows: height of 3.1 mm, inner radius of 3.0 mm and outer radius of 4.0 mm (figure 5). by enhancing mesh refinement, more accurate simulation results can be obtained. 3.2. simulations the simulation results yielded data on the effective stresses along the hole and radial displacements that arise having been impacted by the mandrel. before and after the mandrel was used as well as contact was made with the walls of the holes are presented in figure 6. the distribution pattern of effective stresses in the vicinity of the walls of the holes is also visible. the stress scale on the left-hand side allows their values to be determined. during the simulation, 3 points were selected: at the entrance to and exit from the hole as well as inside it. at these points, the diameters and radial displacements were measured. the same points were marked in all the experimental holes. the first one was marked at a depth of 0.5 cm from the entrance to the hole, the second in the middle of it and the third at a depth of 0.5 cm from the exit from the hole to avoid errors in the vicinity of where the corset was formed. the modelling process was carried out using five variations in the holes in the same sequence and by applying the same settings. changes were only made to the geometry of the mandrel and to the hole pack. the corset formed after the mandrelling process and metal deformation in the vicinity of the hole after hardening is presented in figure 7. radial movements in the vicinity of the hole indicate that its diameter slightly increased after mandrelling. 4. discussion as a result, radial displacements in the holes after mandrelling were accurately measured as well as at the points selected after modelling at three different heights. the radial displacement data for all five variations in holes are recorded in table 1 from which the graphs shown in figure 8 were drawn. the graphs and figures demonstrate the phenomenon of corset formation inside holes, preventing the walls of the holes from being perfectly cylindrical. this cannot be avoided by using a cutting tool since all the results obtained during hardening would be nullified by removing the mandrelled layer of the hole. figure 5. creation of the second grid a b figure 6. starting point (a) and endpoint (b) of contact with the mandrel figure 7. the appearance of sagging after hardening by the mandrel voronko, voronko, dyachenko and shapar hungarian journal of industry and chemistry 6 part of the hardened material that was cut out of the hole creates an influx around its edge. a disadvantage of this phenomenon is surface distortion. considering that several such holes can be located in certain areas and that bolted joints must fasten the “pack” together, difficulties, e.g. the formation of gaps between the plates, arise when they are stacked on top of each other. 5. conclusions using the numerical model developed in the simufact forming program based on the finite element method, rational parameters of the technological process for impulse hole mandrelling in aircraft parts made of steel were determined for the first time. at the end of the study, the following conclusions were made: 1. the developed numerical model of the technological process of impulse hole mandrelling in aircraft parts composed of steel enables rational parameters to be determined with a given degree of accuracy. 2. the rational parameters of the technological process of impulse hole mandrelling in aircraft parts composed of steel are determined as follows: a) energy requirement of mandrelling is 90 j; b) the angle α in the design of the mandrel must be equal to 3°; c) the tension must fall within the range of 1.5-3.0%; d) the coefficient of friction must be equal to μ=0.08, which corresponds to the use of lubricant type i20. (for the purpose of selecting the lubricant, an analysis of the literature and statistical data from studies on the effect of various types of oil when working with steel was carried out. the lubricant chosen ensured the sample was mandrelled under fluid friction, moreover, did not lead to molecular adhesion between the sample and tool.) 3. simulation of the technological process made it possible to avoid the costs of expensive experimental studies. references [1] moravec, j.; blatnický, m.; dižo, j.: an application of a magnetic impulse for the bending of metal sheet specimens, materials, 2022, 15(10), 3558, doi: 10.3390/ma15103558 [2] yucan, f.; ende, g.; honghua, s.; jiuhua, x.; renzheng, l.: cold expansion technology of connection holes in aircraft structures: a review and prospect, chinese j. aeronaut., 2015, 28(4), 961–973, doi: 10.1016/j.cja.2015.05.006 [3] yuan, q.; liu, z.; zheng, k.; ma, c.: chapter 4 – metal in: civil engineering materials (elsevier), 2021, pp. 205–238, doi: 10.1016/b978-0-12-8228654.00004-0 [4] mouritz, a.p.: chapter 4 – strengthening of metal alloys in: introduction to aerospace materials (woodhead publishing), 2012, pp. 57–90, doi: 10.1533/9780857095152.57 [5] krivtsov, v.s.; voronko, v.v.; zaytsev, v.y.e.: advanced prospects for the development of aircraft assembly technology, sci. innov., 2015, 11(3), 11–18, doi: 10.15407/scine11.03.011 [6] skvortsov, v.f.; boznak, a.o.; kim, a.b.; arlyapov, a.y.; dmitriev, a.i.: reduction of the residual stresses in cold expanded thick-walled cylinders by plastic compression, def. technol., 2016, 12(6), 473–479, doi: 10.1016/j.dt.2016.08.002 [7] plankovskyy, s.; breus, v.; voronko, v.; karatanov, o.; chubukina, o.: review of methods for obtaining hardening coatings in: ictm 2020 lnns, nechyporuk, m., pavlikov, v., kritskiy, d. (eds) (springer), 2021, 188, pp. 332–343, doi: 10.1007/978-3-030-66717-7_28 [8] duncheva, g.v.; maximov, j.t.; ganev, n.: a new conception for enhancement of fatigue life of large number of fastener holes in aircraft structures, fatigue fract. eng. mater. struct., 2017, 40(2), 176–189, doi: 10.1111/ffe.12483 table 1. radial movement of the holes no. initial diameter measuring points tension top middle bottom 1 5.92 6.102 6.088 6.102 3.0% 2 5.90 6.111 6.096 6.096 3.4% 3 5.80 6.110 6.089 6.096 5.0% 4 6.05 6.176 6.154 6.154 1.8% 5 6.17 6.184 6.171 6.177 0.25% figure 8. change in radius data https://doi.org/10.3390/ma15103558 https://doi.org/10.3390/ma15103558 https://doi.org/10.1016/j.cja.2015.05.006 https://doi.org/10.1016/b978-0-12-822865-4.00004-0 https://doi.org/10.1016/b978-0-12-822865-4.00004-0 https://doi.org/10.1533/9780857095152.57 https://doi.org/10.1533/9780857095152.57 https://doi.org/10.15407/scine11.03.011 https://doi.org/10.1016/j.dt.2016.08.002 https://doi.org/10.1007/978-3-030-66717-7_28 https://doi.org/10.1007/978-3-030-66717-7_28 https://doi.org/10.1111/ffe.12483 process simulation of hole mandrelling 51(1) pp. 1–7 (2023) 7 [9] voronko, v.v.: designing of the process and tools for high-speed aperture burnishing in aluminum aircraft constructions (phd thesis) (engineering), kharkiv, 2007, p. 133 [10] voronko, i.o.: development of the pneumopulse mandrelling technology of the holes in aircraft structures made of titanium alloys using robotic workcells (phd thesis) (engineering), kharkiv, 2019, p. 153 [11] vorobiov, i.а.: the scientific basis for the creation of a complex of impulse technologies and equipment for the aggregate assembly of airframes (phd thesis) (engineering), kharkiv, 2020, p. 432 [12] vorobyov, y.; pechenizkiy, i.; garin, v.; tsegelnyk, y.: numerical simulation of laminated plastics pulse riveting process, aerosp. tech. technol., 2007, 39(3), 47–51, http://195.88.72.95:57772/csp/nauchportal/arhiv/aktt/2007/ aktt307/vorobyev.pdf [13] studer, p.; taras, a.: influence of strain‐hardening on the load‐carrying behaviour of bearing type bolted connections, ce/papers, 2022, 5(4), 218–225, doi: 10.1002/cepa.1748 [14] krivtsov, v.s.; vorobev, y.a.; voronko, v.v.: advanced devices for mandreling bores, kuznechno-shtampovochnoe proizvodstvo (obrabotka metallov davleniem), 2004, 12, 18–20, 29–30 [15] vorobiov, i.; maiorova, k.; voronko, i., boiko, m., komisarov, o.: creation and improvement principles of the pneumatic manual impulse devices in: ictm 2021 lnns, nechyporuk, m., pavlikov, v., kritskiy, d. (eds) (springer), 2022, 367, pp. 178–191, doi: 10.1007/978-3-030-94259-5_17 [16] vellanki, c.; choudhury, s.; kumar, s.; vimson, g.; paul, g.: influence of lubrication on the friction and wear characteristics of low carbon steel under sliding reciprocation conditions, iop conf. ser.: mater. sci. eng., 2022, 1248, 012033, doi: 10.1088/1757-899x/1248/1/012033 [17] rajeshkannan, a..; narayan, s.; jeevanantham, a.k.: modelling and analysis of strain hardening characteristics of sintered steel preforms under cold forging, aims mater. sci., 2019, 6(1), 63–79, doi: 10.3934/matersci.2019.1.63 [18] şahin, m.; etinarslan, c.; misirili, c.: materials flow for different lubricants during cold forming, ind. lubr. tribol., 2013, 65(5), 287–296, doi: 10.1108/ilt-02-2011-0011 http://195.88.72.95:57772/csp/nauchportal/arhiv/aktt/2007/aktt307/vorobyev.pdf http://195.88.72.95:57772/csp/nauchportal/arhiv/aktt/2007/aktt307/vorobyev.pdf https://doi.org/10.1002/cepa.1748 https://doi.org/10.1007/978-3-030-94259-5_17 https://doi.org/10.1088/1757-899x/1248/1/012033 https://doi.org/10.1088/1757-899x/1248/1/012033 https://doi.org/10.3934/matersci.2019.1.63 https://doi.org/10.3934/matersci.2019.1.63 https://doi.org/10.1108/ilt-02-2011-0011 https://doi.org/10.1108/ilt-02-2011-0011 conference proceedings hungarian journal of industrial chemistry veszprem vol. 2. pp. 3643 (2000) "protection and development of the natural and built environment" scenarios of omfb (national commission for technological development) tep work group ( 1:sudapest technical university, department of environmental law and economics 2head of omfb tep office 3university ofveszprem, department of environmental engineering and technology) tiris paper was presented at the second international conference on environmental engineering, university ofveszprem, veszprem, hungary, may 29 -june 5, 1999 technology foresight a systematic means of assessing that scientific and technological development which could have a strong impact on industrial competitiveness, wealth creation and quality of life provides an essential tool to this end. hungary launched her foresight programme in 1997. as the country is undergoing fundamental economic and social changes ihat is, the transition towards market economy major institutions are currently shaped. foresight has seemed an adequate tool to bring together business, the science base and government in order to identify and respond to emerging opportunities in markets and technologies. the former socio-economic system has been influential concerning the organisation and management oftep, too.lt has been a well-considered, conscious decision from the very beginning not to involve anybody from the omfb to run the programme (:from a professional point of view, i.e. decision on panel topics, issues to be analysed, priority-setting, etc.). the natural and built environment scenarios relating to the expectable state of the hungarian built and natural environment come from the presumption that hungary will become part of the european big-regional world economic centre in the medium run that is it will join the eu. therefore, the future of hungary in the next 30 years (up to 2030) was examined in relation to the eu regarding all the three scenarios. keywords: teclmology; foresight; environment introduction our world is characterised by an increasingly rapid change in which global trends cannot be stopped at national borders, and new technology plays a growing role. the world is also becoming more competitive, with national competitiveness depending on technological, organisational and social innovation. as it is widely realised firms cannot survive the ever more fierce. global, competition without spending on emerging technologies and strategic research. these activities, however, are often too risky or too expensive for industry to take sole responsibility for them. therefore governments must assume at least part of the :financial responsibility. this, in turn, requires setting r&d priorities, based on thorough, comprehensive. strategic analysis. as even the richest countries cannot afford to support ail research programmes. technology foresight ~ a systematic means of assessing that scientific and technological development which could have a strong impact on industrial competitiveness. wealth · creation and quality of life provides an essential tool to this end. another reason why governments have to take part in foresight is that the exploitation of science and technology largely depends on effective networking between business, academia and government. many governments have realised the importance of foresight activities, and thus this relatively new, and innovative, technology policy tool is spreading across continents. the consideration in this respect was that if hungary during this period failed to join the eu for some reason the result would be great uncertainty and living from day to day in which no long-term strategy only short-term crisis management can be interpreted. the differences among the three versions are in the extent and pace of shift towards sustainable development flj. characteristics of the hungarian foresight process hungary launched her foresight programme in 1997. as the country is undergoing fundamental economic and social changes that is, the transition towards market economy major institutions are currently shaped. the first phase of the transition process is over by now most firms and banks have been privatised, the most important new political and economic institutions have been re-established, e.g. a parliamentary democracy based on a multi-party system, stock exchange, and the so-called transition decline have turned into economic growth in the last few years -, therefore it is high time to think about mediumand long-term issues. in other words, now it is possible to devise strategies aimed at improving the quality of life and the long-term international competitiveness. aims and first steps foresight has seemed an adequate tool to bring together business, the science base and government in order to identify and respond to emerging opportunities in markets and technologies. in short, tep should result in a national innovation strategy based on a comprehensive analysis of world market opportunities (new markets and market niches) trends in technological development strengths and weaknesses of the hungarian economy and r&d system. the above, demanding, aim can only be achieved if researchers, business people and government officials join intellectual forces to assess hungary's current competitive position ana impacts of likely global market and technological trends. hence their re-aligned and reinvigorated relationships can be regarded as a means of the principal goal. however, the process in which these experts with different background communicate and share ideas concentrating on longer term issues, generate consensus, and co-operate with increased commitment in devising and realising a national strategy, seems to be so crucial that it is an end in itself. in other words, the programme is also aiming at strengthening the formal and informal relationships among scientists and engineers, managers and civil servants, alike spreading the co-operative and strategic thinking. hungary is among.ihe six countries about to join the european union in the 'first wave'. accession to the eu is a major challenge since it is likely to shape hungary's future to a significant extent. therefore it requires a dearthough soundvision on hungary's role and opportunities in the enlarged european socio­ economic system. thus tep activities and results can contribute. to. the success of the integration process. in short, wntten tep results will be comprehensive analyses. <if' strengths and weaknesses. scenarios based on these inquiries and likely global trends, as well as recommendations for public policies how to realise the most desirable scenario. these analyses and information should also assist hungarian firms in devising and implementing their strategies to improve their competitiveness. 37 tep is a holistic foresight programme, based on both panel activities (scenarios, swot analysis, recommendations, policy proposals, etc.) and a large scale delphi survey. the two-year programme will conclude in 1999. it is being conducted in three stages, namely pre-foresight (october 1997 -· march 1998), main foresight (april 1998 june 1999) and dissemination and implementation (july december 1999) stages. awareness seminars were held across the country in the pre-foresight stage to promote this new concept among experts and professionals. participants and organisers of these seminars (that is, chambers of commerce and scientific associations) were also invited to nominate panel members. a steering group (sg) of 19 leading industrialists, academics and government officials was set up in october 1997 to oversee the programme. following a thorough discussion the sg has defined the following topics for panel discussions: human resources (education, employment) health (life sciences, pharmaceuticals, medical instruments, health care) information technologies, telecommunication, media natural and built environment manufacturing and business processes (new materials and production techniques, supplier networks, globalisation ... ) agrobusiness and food transport having summarised the reasons to launch tep, and the results of the pre-foresight stage, let us highlight some methodological issues in the remaining sections [1]. strong emphasis on scenarios ('macro' and panel level) institutions and regulation given the transition process, major institutions are still being shaped as opposed to, for instance, the uk, where 'the lawn is cut and watered for centuries'. in other words, the fundamental institutions have crystallised in the advanced counties for quite some time, whereas hungary · is still at a cross-roads. moreover, coming back from the soviet political, military and economic bloc in an attempt to join the eu, which, in tum, is also in a middle of a major transition process, the wider, international institutional context (economic environment) where hungary tries to find her roqm., is changing, toq. therefore it is of the utmost importance to analyse this turbulent environment, hence the emphasis on scenario-building, both at macro level (socio-economic framework conditions) and at the level of panels (micro, mezzo). macro scenarios have not been developed in any other country engaged in foresight activities when we designed our programme. for the same reasons, the hungarian panels devote a significant part of their interest to institutional development and regulatory issues. it is also reflected in 38 the hungarian delphi-statements: quite a few of them deal with these issues, rather than technological ones. education and learning as input of competitiveness there was a leisure and learning panel in the first british foresight exercise, where learning was mainly understood as a market opportunity, not as a major factor of competitiveness. tep has opted for the latter approach for obvious reasons. employment as a unique issue tep has put together education, learning and employment into one panel under the heading of human resources. to our knowledge, employment has not been an issue anywhere else. our decision, however, is self­ explanatory in a country in transition. broad issues as panel topics in general, we have brought together various issues treated separately in most other foresight exercises. for example, our health panel encompass life sciences, related fields of biotechnology, health care system, pharmaceuticals and medical instruments. some of these issues are not analysed at all in other foresight exercises, e.g. the health care system, others are treated in separate panels, e.g. life sciences, pharmaceuticals (as part of chemicals). also, agriculture and food processing belong to a single panel in our c:ffie (as opposed to the first british exercise). cross-cutting issues even so, we have also put strong emphasis on the so­ called cross-cutting (cross-panel) issues. we encourage our panels to identify, and adequately deal with these issues (e.g. education and it in all panels, the various factors of our health life style, medical care, environment, diet; all these issues belonging· to the different panels, although we have tried to set up panels around broad issues, accession to the eu, etc.). some panels have already joined forces, i.e. their budget, in the early phase of our programme, and commissioned together a group of experts to analyse issues from different points <?f view (e.g. healthy diet: health agribusiness and food industry panels, reasons of allergy: again the above two panels). given the legacy of the planned economy that is, strong 'departmentalism• ~ and the inherent isolation of various disciplines. it can be regarded as an achievement in itself. organisation the former socio-economic system has been influential concerning the organisation and management of tep, too. it has been a well-considered, conscious decision from the very beginning not to involve anybody from the omfb to run the programme (from a professional point of view, i.e. decision on panel topics, issues to be analysed, priority-setting, etc.). the role of omfb has been restricted to provide finance and methodological support. therefore no omfb-official sits either on the steering group (sg), or is a member of any panel (the chairman of the steering group was the head of the ost during the first british foresight programme). moreover, members of the sg and panels have been appointed as a result of a wide consultation process. all the major decisions are taken by the sg, the panels or more recently at joint meetings of the sg and panel chairs and secretaries. finally let us present a highly subjective observation to highlight certain difficulties of the process. ambiguous ('double') legacy of planning centrally set, mandatory plan targets were abolished in 1968 in hungary, the first time among the centrally planned economies. yet, its legacy is still rather strong among some experts with two, rather different, consequences, as far as foresight is concerned: some engineers and scientists understand foresight as just another form (tool) of (central) planning, and hence they want to devise just one future (vision, scenario, i.e. not different ones), and seeks funding for that target (as a sort of 'central development programme [plan}'); some other professionals also understand foresight at least at the first glance as just another form (tool) of (central) planning, and hence they reject it immediately. to sum up, the on-going hungarian technology foresight programme its goals, methods and organisation is shaped to a large extent by the legacy of the former socio-economic systems, their impacts on the national system(s) of innovation, the size of the country and the level of her economic development. "protection and development ofthe natural and built environment'' scenarios in the course of drafting the possible scenario of the future, the following main principles and criteria are regarded as authoritative from "enviromnental" aspect. global principle of sustainability. in this respect the examination of the long-term technological development is deemed important to see what accord is created between the life possibilities of the current generation and thefuture generations. the basic principle of sustainability is that the short term benefits of the current economic, social activities should not be funded by the costs of the future. a big-regional (eu) and national criterion is to examine how our eu accession can be organised in a way that harmonisation with the eu and expectable economic growth should at the same time promote the improvement of the environmental elements of welfare. the process is related to the environmental protection requirements in the broadest sense since our development should be harmonised with the fifth environmental action program of the eu whose basic idea is sustainability. regional analyses as well as municipality, entrepreneurial and household levels will play important role in accordance with the "subsidiarity" principle of the eu. investigation levels of the technologies regarding the technologies the approach is the following: investigation of the treatment methods (technological, economic, social, political) of pollution and damage caused by former (probably still operating) polluting technologies. moderation of negative impact of current polluting technologies operating now and in the near-future on the natural and built environment ("end of pipe" procedures, probably change of technology). conditions for future development and introduction of environmentally sound technological developments and clean technologies, as well as domestic opportunities of environmental industry. in the case of all the above three investigation levels it is necessary to evaluate how technological changes themselves affect the hungarian settlement structure, whether they modify and if they do in which direction the life opportunities of the population living in regions of different development levels and whether they contribute to the moderation of differences relating to the area and the type of residential place. possible scenarios of the future the scenarios relating to the expectable state of the hungarian built and natural env.ironment come from the presumption that hungary will become part of the european big-regional world economic centre in the medium run that is it will join the eu. therefore the future of hungary in the next 30 years (up to 2030) was 39 examined in relation to the _eu regarding all the three scenarios. the consideration in this respect was that if hungary during this period failed. to join the eu for some reason the result would be great uncertainty and living from day to day in which no long-term strategy only short-term crisis management can be interpreted. the differences among the three versions are in the extent and pace of shift towards sustainable development [2-13]. scenario of "sustainable development" (optimistic version) the eu expanded with several new member states will strengthen its position against the north american and asian centres. the increased internal market, the concentrated research and development expenditure will result in economic growth above the average in the world economy. one of its driving forces is the strengthening environmental industry, which decreases environmental load along with the historically rapid integration of clean technologies into the material basis of the economy. regarding the use of resources there will be a shift towards human resources; the use of natural capital currently representing great proportion will decrease. improving energy efficiency and the decrease of the specific use of material is partly the reason, partly the result of the shift in proportion, which means the products will demand fewer natural resources. environmental goals among the direct objectives of technological developments will have increasingly greater share; developments for environmental purposes are emerging among the most successful technologies. a uniform system of standards covering all countries will spread as the framework condition of economic management and it will regulate 'the emission values of the individual technologies in details. the organisational and operational specifications of environmental management will be built into the organisational system of management units on the same level and consistency as in the current accountancy application. c the slow but continuous consumption growth of the current "developing world" especially tl'ie asian region will revaluate the raw material stock. the significance of reuse and recycling of raw materials and products will increase in the european region which is poorly supplied by these stocks and consequently waste minimisation will be highlighted during the development and application of process technologies (within that water saving due to vulnerable fresh water reserves). regionally the support system of the eu is directed at the equalisation of the development levels of the member states and those of the regions within them, the role of borders among countries is becoming less important. the basic principle of regional supports and developments is the modernisation of the internal 40 resources of the given regions, in this way the individual regions will be related to and complementing each other as a network and will not be uniform regions side by side. this scenario presumes that the european union implements the goals given in the fifth environmental action program ("towards sustainability") and on that basis is able to advance in the first decade of the next millennium. then between 2010 and 2030 the world economy will change accordingly and development in harmony with the environment will go on. hungary will become member of the eu by 2005 the latest. it will implement its national environmental program valid until 2002 which contains the principles of sustainability and on the basis of an improved program will realise harmonisation with the eu until 2010. the country as a member of the eu will have a share of the benefits from the technological developments of the region. company developments will be characterised by gradual spread of environmentally friendly, clean technologies, the economy will not be receptive to second-hand, second­ class and consequently more polluting technologies. the duration of use of the products (life cycle) will increase, this will make repair and maintenance more attractive with positive effects on employment. the decrease of environmental load, the increase of environmental safety, the decrease of mobility resulting from more balanced regional development and the spread of work at home or nearby (consequently the moderation of pollution -from transport) will on the whole result in the decline of health damage traced back to environmental harm. revaluation of human resources will result in a more evenly "spreading" training; the labour force demand of the individual regions will be met by ''"local" training. as a result of the development of informatics and telecommunication the scope of job opportunities at home and telecommunication services is expanding. in the wake of the above facts labour mobility will decrease and the moderation of harmful impact from transport will come as environmental impact. the character of the settlement environment will be shifted towards so-called disperse towns (this tendency in hungary primarily refers to the capital). relatively big settlement structure of medium density providing space for the natural environment within the settlement and along the borders will become typical. instead of traditional towns with one centre, settlements with several centres and playing servicing. supplying. and entertaining roles will strengthen. this settlement structure wm deconcentrate environmental load typical of junctions and coming from transport and in general from the presence of concentrated crowds of people. at the same time the threat of the segregation of social groups relating to the individual settlement centres due to geographical proximity or other (e.g. ethnic) reasons will strengthen. the importance of public transport will strengthen in order to reduce the pollution from urban and settlement transport, to suppress continuous stress and to ensure timesaving mobility. to this end a part of the transport routes on the surface (especially at junctions) will go under the surface which means underground construction technologies will gain ground. the state of the country in general and within that the policy of the natural and built environment will be similar to that of the current eu cohesion countries (ireland, portugal, spain, greece) with the features resulting from the eastern central european situation. with the newly integrated countries an eastern central european cohesion zone will be created (poland, czech republic, hungary, slovenia, probably estonia) which although lagging a little bit behind will follow the principles of subsidiarity characteristic of the eu average which is also in line with the global environmental requirements of the world. the european integration of the country will promote internal regional integration, the role of smallregions and small-communities as solving environmental problems will increase. the "subsidiarity" principle of the eu will exert influence also in reality. in agriculture, production will be shifted towards organic products, organic and environmentally friendly procedures which will decrease the use of pesticides, fertilisers and the resultant soil pollution. biodiversity will not deteriorate further. this can be traced back partly to the spread of environmentally sound solutions of agriculture, the extension of national parks, environmental areas, more efficient nature conservation on those areas partly to improving environmental conscious attitude on social level. there will be possibility to resettle and preserve some traditional species. the shift towards renewable energy sources may become significant, their share in optimum case may reach 10%. the use of solar energy regarded as an alternative today will continuously increase within energy supply (this will modify the construction technologies in addition to the application of collectors and photovoltaic cells in the case of solar traps at the buildings) and the application of earth houses using traditional heating combined with solar energy and the use biomass will spread. construction technologies will be modified. the materials of the buildings will not change basically but the efficiency of insulation technologies will significantly improve. imposing tax on non-renewable resources will gain ground in economic regulation while taxes, contributions which employment entails will decrease. in this way the regulation in addition to the reduction of environmental pollution will also decrease unemployment. the attitude of environmentally conscious management will increase within company management. the concept of "consumption" will have different value, the demand for healthy way of life will increase in the category of life quality. then not only the interests of the individuals will have an important role but the "maintenance" of human resources revaluated within the production resources will become a strong economic interest. with the spread of waste minimisation technologies and the increase of the non­ material consumption elements of life quality (which will reduce the demand for material goods), environmental load will decrease and requirements for some technologies prompted by environmental safety (decrease of the threat of accidents causing environmental and health damage) will simultaneously increase. a decisive criterion of technological developments and installations is the minimisation of the health damage of the affected population. the external costs of health damage of environmental origin will not come from central funds but will be built into costs on company level especially on the basis of the polluter pays principle. immaterial value scale will become dominant in family and school education, life quality will have priority over pursuing material goods. raising environmental awareness will become a cornerstone of the education system from the lowest level (nurseries) to higher education including further training on different levels. the educational system will deal with environmental impacts of given areas as an organic part of certain subject matters, professions and fields, in addition it will regard and apply environmentally sound thinking as the basic element of education relating to the way of life [2-13]. "business as usual" scenario slow economic growth is going on in the european union, the position of the region in the world economy will slightly deteriorate and the union will not implement the program of sustainable development. the traditional growth orientated development of the world economy will significantly delay the environmentally sound transformation of the profit-orientated relations of nature-economy. the union funds will grow slowly due to the resistance of the donor countries and the demand of the formerly integrated cohesion countries will be strong to preserve the support resources. the central eastern european cohesion integration will proceed slowly. hungary will join the european union after 2005 but the practice of "sustainable growth" will devaluate the principles of ''sustainable development" and will significantly delay realisation. the current production-consumption structure will survive. the proportion of technical development will remain low, the economy will be determined by lease work. (the current level of r+d and the role of hungarian research development centres will keep decreasing.) the financially most successful 41 technologies will not be aimed directly at the protection of environmental elements but as an additional benefit of their application environmental load will decrease. eu support will go for road transport within infrastructure development and more environmentally friendly transport solutions will relatively decrease. accelerated motorway constructions will strengthen the transit nature of the country. the above endeavour is in accordance with the hungarian development of motor­ car production. differences between the transdanubian and eastern regions regarding regional development will not decrease. regarding technological development the basically hungarian owned small and medium sectors will lag behind the advanced level of international large companies. in hungary the multinational companies with high capital level use first class technologies of environmentally friendly nature. small and medium companies due to relative capital shortage on the other hand take over second class procedures, which environmentally are more detrimental. the spread of the latter ones however is not typical. environmental regulation will remain relatively soft since the resistance of the majority of both the population and businesses is streng. within environmental solutions subsequent' environmental protection of low efficiency will dominate. primarily large companies and their suppliers use organisational and operational forms according to environmental management system, which is based on the continuous development of iso 14001 standard. the number of certified companies working on the basis of ems will be a few thousand in hungary. the environmental industrial products and services will be imported into the country deteriorating the international balance of payment. the environmental-health situation will stagnate, in some fields will deteriorate especially in big crowded cities. monitoring systems to observe the impacts of technologies resulting in health damage of environmental origin will be established. during company installations and expansions, environmental impact assessment will certify on the basis of standards · tighter than the current environmental-health ones, the contacts between environmental and health authorities will be continuous. at the same time strategic impact assessments will be hardly used for developments. a part of the valuable natural areas will be lost because of infrastructure development and green field industrial investments. energy efficiency will improve slowly, the interest to increase energy production is much greater than to increase energy efficiency (basic power station fueued by !ignite, perhaps new nuclear power station). because of the poor enforcement of the principle of subsidiarity the role of local governments to reduce environmental damage will strengthen only slightly. the local governments of settlements will organisationally expand and staff trained for 42 environmental tasks will be employed. local governments will have greater control over duties and fees contributed for environmental purposes. in the case of the remaining centralised funds not only a distribution system per capita will exist, the nature and extent of the pollution to be cleaned up will also have significant impact. the environmental tasks of the hungarian local governments will be concentrated on two fields that is waste disposal and sewage purification. knowledge relating to environmental protection as a separate subject will have a broadening role in the educational system, especially on secondary level. this profile of higher education is expanding especially in the fieldsof waste treatment technologies and environmental management. public thinking is primarily influenced by environmental information in the media given separately or built in other types of information. environmental awareness of the public, however, changes slowly because of other impacts working against the environment. it is increasingly difficult for the country to meet the requirements stipulated by international environmental conventions [2-13]. "delayed accession" scenario (pessimistic version) the european union among the major world economic centres regarding power will fall into the background.­ traditional market solutions will dominate in the world economy. global and regional conflicts will sharpen and the permanent crisis management will absorb significant resources. subsequent (end of pipe) instruments of both environmentally and economically low efficiency will become typical in environmental protection. only multinational companies primarily to ensure their green image apply the slowly changing standards of environmental management. the standards in the world 'economic regions are different regarding the stringency of the stipulations. because of the sharpening world economic contradictions the development of the eu will relatively slow down and accession will be postponed to 2010 or iater. in hungary the position of environmental protection will deteriorate and will be subordinated to economic growth of low efficiency. the driving force of technological developments will be profit maximisation in the short term, the reduction of the load on environmental elements with its long-term, indirect benefits will be left out of the group of the economically most successful technologies. rapid developments responding to existing state deterioration will have priority. the threat of using environment polluting technologies in industrial production as a result of economic constraints will grow, the enforcement of environmental criteria will be weak. the number of companies certified on the basis of environmental standards will stagnate at sm:~e hundreds. hungary will be on the periphery within the union, it will determine the level of technologies used here which is typically second class with all the environmental disadvantages. the major countries of the european region will see the eastern end as the domain of the relatively most polluting technologies, development funds will be aimed at the take-over of these technologies. agricultural production is going on with environmentally polluting methods on fragmented areas with ownership structure transformed as result of the lack of knowledge and capital. negative effects of former polluting agricultural technologies (primarily soil pollution) will not be eliminated. processes resulting from the transit character of the country will strengthen in transport, the proportion of road development will grow while the role of railway and public transport will decrease. the vehicle fleet will become older and the technical state will further deteriorate. as a result of short term developments with direct benefit, the second class polluting technologies coming to hungary and the limited · budget opportunities, monitoring of health damage of environmental origin and the treatment of damage on social level will not be highlighted issues. prevention will be restricted and limited to spectacular emergencies (e.g. chemical accidents) which are easily perceptible for the public. the share and typical impact of health damage resulting from environmental pollution will not be clarified. the development funds of local governments usable for environmental protection will be restricted. there is no stake to employ experts who can manage environmental issues on the merit, the regional environmental authorities will control the remediation processes. funds for environmental purposes will be centralised, the distribution system per capita will work -or the funds will be used to eliminate emerging damage. the importance of the medium strata in the society will not change, the development of the civil society will be slow, sensitivity to non-material values and environmental awareness will be on low level. the media will only moderately influence environmental thinking that has subordinated role in the social scale of values since it has no value for advertisement. education will primarily concentrate on knowledge necessary for remediation, the scope of training involving secondary and higher education will be relatively narrow. environmentally friendly way of life will be in the periphery in education, the attitude based on the utility of people measurable in money will prepare the new generation for careers which entail the possession of material goods and are deemed successful by the public. the peripheral nature of the joining central eastern european countries will remain durable. the regional differences and conflicts within the country will strengthen. through lack of adequate resources the eastern territories will not close up fast, developments will be concentrated on areas with existing infrastructure and better qualified labour. biodiversity will drastically deteriorate. the reasons are: decrease of the extent of nature conservation areas, moderation of financial means to preserve values there, utilisation of many chemicals in agriculture on extending territory and narrowing natural living space [2-13]. references 1. havas a.: omfb tep office presentation, oecd workshop on · technology foresight and sustainable development held in budapest on 11 december, 1998 2. bartus g.: possible scenarios for the waste management, omfb tep study, 1998/99 (in hungarian) 3. csutora m.: applying cleaner production, omfb tep study, 1998/99 (in hungarian) 4. fodor 1.: environmental aspects of the regional developing projects, omfb tep study, 1998/99 (in hungarian) 43 5. gereben e.: thesis for the built environment, omfb tep study, 1998/99 (in hungarian) 6. horvath gy.: the future of the rural environment, omfb tep study, 1998/99 (in hungarian) 7. l.tjas istvan: water quality trends in the next 20-25 years, omfb tep study, 1998/99 (in hungarian) 8. llosvay gy.: trends of the ngo's in the next 25-30 years, omfb tep study, 1998/99 (in hungarian) 9. locsmandi g.: the resettlement and the environment, omfb tep study, 1998/99 (in hungarian) 10. palvolgyi t.: environmental policy; r+d and innovation in hungary, omfb tep study, 1998/99 (in hungarian) 11. pinter a.: the future trends in environmental sanitation as a ·function of economic development, omfb tep study, 1998/99 (in hungarian) 12. pomazi 1.: the sustainable development as a function of economi<; development, omfb tep study, 1998/99 (in ·hungarian) 13. v alk6 l.: the environmental education as a function of technology foresight, omfb tep study, 1998/99 (in hungarian) page 42 page 43 page 44 page 45 page 46 page 47 page 48 page 49 microsoft word 16.09 tar.docx hungarian journal of industry and chemistry vol. 44(2) pp. 81–83 (2016) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2016-0009 cloud-based application for smart grid simulation szabolcs tar1* and attila fodor2 1 delta-group holding zrt., szentendrei út 39-53, budapest, 1033, hungary 2 department of electrical engineering and information systems, university of pannonia, egyetem út 10, veszprém, 8200, hungary this study provides an overview of the content of an r&d project for increasing the efficiency of smart grids to analyse the energy market, consumption, generation, and renewable energy usage. the new energy participants, for example decentralized generation, dynamic consumption, and weather-dependent power plants, are facing challenges. this project offers solutions to these challenges: modelling of distribution networks, forecasts of renewable energy sources distributed generation (res-dg), micro-grid management and responses to demand in new, complex solutions. a hardware device is being developed for smart grids and security modules to enhance it security. keywords: renewable energy, smart grid, demand response, cyber-security, network assets 1. introduction the main objective of our project is to utilize the opportunities in smart grids based on smart grid data and remote control to improve energy and cost efficiency. the service package is composed in a way that our solutions are put into use either as a whole or for the fulfilment of subtasks. the services and hardware devices are being developed like one intelligent cloud-based service. the rationale of these solutions is supported by several aspects of the energy market. the vastly proliferating renewable energy sources distributed generation producers (res-dg) are affecting every player in the energy market. the number and built-in power of such power stations are expected to exhibit a rising tendency in the near future according to various energy tenders, see tables 1 and 2. 2. experimental data grid operators should find a solution for operating grids with more entry points replacing the ones utilizing one directional power flow, where the direction of power flow changes over time and is influenced mainly by the performance of weather-dependent power plants. fig.1 shows the electricity consumption of hungary, which displays both domestic generation and importation, as well as planned and actual values of power transmissions from or to neighbouring countries. the prime cost of the electricity and the volume of the consumption set the actual, base, and peak prices of *correspondence: szabolcs.tar@delta.hu table 1. number of (pc.) and power generation (kw/mw) of res-dg producers over recent years in hungary [1]. 2008 2014 2015* pc. kw pc. mw pc. mw solar 107 363 8.8k 68 11k 84 wind 1 10 56 0.5 56 0.5 hydro 1 16 3 0.06 3 0.06 * based on estimated data table 2. use of renewable energy in hungary [2]. available capacity in mid. 2014 (mw) electricity consumption plan for 2020 (gwhr) hydroelectric 66 238 under 1mw 6 12 1 – 10mw 22 67 above 10mw 39 158 geothermal 57 410 solar 63 81 wind 750 1545 biomass 600 3324 steady 500 2688 biogas 100 636 total 1537 5597 figure 1. electricity consumption, export, and import of hungary as of september 25, 2016 (at 5 p.m.) [1]. tar and fodor hungarian journal of industry and chemistry 82 electrical energy. fig.2 shows the hourly average price of the electrical energy in 2015 in hungary. as solar and wind renewable energy sources are somewhat uncontrollable, the integration of renewable sources is a big challenge for transmission operators. as a solution, our group implemented a calculation model of the grid that takes into account parameters of the grid elements and details of network measurements. details about grids are provided by smart measurement and points of consumption defined in the remote reading circuit. measurement data are generated over periods of at least 15 minute in length at these measurement points. 3. simulations the spread of decentralised energy producers based on table 1, cause time-dependent power flows in grid sections. figs.3-5 show the load of a radial grid examined at various times. the lines on the left side of the graphs start from the contact bar of a transformer, the specific points show the power of grid lead-downs. positive values indicate a flow of power from a transformer towards an endpoint of the grid, while negative values illustrate a flow of power from an endpoint of the grid towards a transformer. 4. results and discussion it is reasonable according to the graphs that the built-in power is insufficient but the trends of consumption and production should be taken into account and a mathematical model created to know the exact operating states as well as for the integration requirement of the new production unit. in order to be able to model the integration of new res-dg efficiently and safely over a specific section, new forecast services need to be impremented. our service concept is mainly based on mass useage of solar cells in accordance with table 1. external environmental aspects were taken into account that affect the operation of renewable energy source power stations such as clouds, the temperature, humidity, global isolation as well as characteristics of power stations, such as orientation, tilt angle, integrated power, type and efficiency. the sources of data are defined, e.g. online satellite images and analytics, which in a complex fashion, can be used to create forecasts based on factual measurement data. for microgrid operators, e.g. lowand mediumvoltage operators, private grid operators, industrial parks, multiple household buildings, balancing groups, etc., a complex energy service concept was outlined. in which an opportunity for intervention was provided to facilitate a more efficient operation examining the production and consumption habits involved in the given microgrid. if the green energy produced is to be used as widely as possible, it should be identified where and to what extent the available green energy was consumed. by utilizing storage capacities, energy market transactions should be performed that are regarded as new nowadays, e.g. electrical energy is sold and thermal and hydrogen energy sources, vehicle charging, or other services purchased. our group has proposed a support application service for this. furthermore, settlement and cost allocation becomes more efficient and clearer based on details for operators. meters and sensors as well as intervention devices allow microgrid operators to modify the image of a grid proactively based on up-to-date information reducing service outage, which is highly relevant not only for consumers but also producers and trade licence holders too, as an outage location impacting both consumption plan and production plans. an outage location leads to figure 2. hourly average price of electrical energy in hungary (2015). figure 4. consumption of the electricity network of consumers (power versus 15 minute long sample times). figure 5. consumption on the electricity networof consumers (power versus 15 minute long sample times). figure 3. consumption on the electricity network of consumers only (power versus number of 15 minute sample times). cloud-based application for smart grid simulation 44(2) pp. 81–83 (2016) doi: 10.1515/hjic-2016-0009 83 unplanned resource withdrawal due to the spread of res-dg power stations. microgrid providers can initiate interventions to influence the expected production and consumption, providing basic parameters of energy usage. this basic signal can be a plan or request to balance out deviation in the plan. the controller is a decision logics based on the deviation of measurements and basic signals that issues a command within the available limits, which is based on a complex logics by transferring this to the energy use and consumption process in order to achieve the desired result. the consumer and equipment of the consumer are parts of the energy-use and -production processes (hereinafter referred as to process), respectively. this equipment is connected to smart grids among others via smart home devices. to allow the consumer to interact, a service shall be developed that is users demand. when intervention in the process does not take place automatically, the consumer is provided with detailed and aggregated information via various solutions in which the result of his/her intervention is displayed as well as the decrease or rise in energy use or costs. the means of automatic intervention or interaction are dynamic tariffs, which also require smart grids that provide detailed and instantly available data. this allows for the service provider supplying dynamic tariffs to make an offer that reaches the user in a timely manner, which will be either reviewed or accepted by the user or just received as information, as it is possible to intervene remotely and automatically in processes. the goal of our service is to make this information available on a platform based on priorities, irrespective of service providers, ensuring the opportunity to change of energy provider and the access previous data. we provide information to consumers as well as producers by connecting the initiator of an intervention securely via processes about which information, states, and backtesting are also generated by us to providers. to ensure the overall security of smart grids and services included in smart grids, the situation of cyber security and its expectations shall be mapped. smart grids are regarded as an extended electronic information system, whose endpoints can be accessed and managed remotely. however, they are less verified and have partial physically protection. the main requirements considered are • act. cxii of 2011 on the right of information selfdetermination and information liberty; • act. clxvi of 2012 on the identification, designation and protection of essential systems and facilities; • act. l of 2013 on the electronic information security of stateand local government-owned organisations; • directive 95/46/ec of the european parliament and of the council • relevant provisions of energy legislation • information methodologies and recommendations a hardware development has been implemented to enhance information security and a universal communication device has likewise been developed in the framework of hardware development offering a solution that facilitates efficient communication between various devices of smart grids. 5. conclusion these services and hardware devices reduce the costs for the participants in the energy sector from generation to consumption via distribution networks, and provide more secure itc infrastructure. to manage and forecast generation and consumption, new implementations of res-dg can be easily installed in the current distribution network, without the need for extra investment. the service package is flexible. anyone can choose whether to use services in the future or logged date. the system will be extended to include other new services. such services generate data requirements. further complex analytics provide useful results for the value chain actors, e.g. to improve the reliability of the distribution network. a source of irregular consumption is unchecked loads on the network, which leads to the overload of built-in elements of infrastructure, premature aging and damage. the simulation engine analyses the data and generate alerts concerning the status of network elements. before a failure occurs, the system can take various actions to reduce its duration and damage caused in order to expand cloud-based services for industrial consumers to dynamically control consumption for the network balancing. as far as the value chain is concerned, actors provide further bonuses to reduce energy costs. the devices and services in smart grids, like in telecommunications or it infrastructure create an opportunity for the further integration of sensors and surveillance camera networks. this integration into the management systems of cities is currently being tested. acknowledgement we acknowledge the financial support of this work by the hungarian state under the vksz_12-1-2013-0088 project. references [1] hungarian energy and public utility regulatory authority (mekh), 2015 www.mekh.hu/nemengedelykoteles-kiseromuvek-es-haztartasi-meretukiseromuvek-adatai-2008-2015-villamos-energia [2] hungarian independent transmission operator company ltd. (mavir) analysis of the hungarian electricity network, 2015 www.mavir.hu/documents/ 10258/15461/forr%c3%a1selemz%c3%a9s_2015.pdf [3] hungarian power exchange ltd. (hupx): www.hupx.hu hungarian journal of lndustrial chemistry veszprem vol. 29. pp. 67-70 (2001) least squares and the matrix riccati equation c. storey (the institute of mathematics and simulation sciences, faculty of computing sciences and engineering, de montfort university, the gateway, leicester, lei 9bh, uk) received: july 26, 2001 there are a number of methods for least squares and total least squares solution of linear equations. one such method involves solving an appropriate algebraic matrix riccati equation. this approach is investigated here using an algorithm based on newton's method with an infinite series solution of the resulting linear matrix equations. some numerical examples, from the recent literature, are used to illustrate the techniques. keywords: matrix riccati equation; newton's method; infinite series solution; overdetermined linear systems; least squares and total least squares. introduction when a system of linear equations (1) with land m, m x nand m x p matrices respectively, does not have a unique solution x it is usual to seek a solution that is "best" in some sense by imposing appropriate constraints. this paper is concerned with computing the least squares (ls) solution, which imposes the constraint that x should minimize the norm !ilx mjj~, and the total least squares (tls) solution which requires x to minimize illvjj~ + jjm wjj~ subject to the constraint vx=w. (2) the main difference between ls and tls is that the former assumes the matrix l is exact whereas the latter allows for errors in both l and m. perhaps the most important approach in solving these problems is singular value decomposition (svd) the use of which is fully discussed in [1] and [2} for ls and tls respectively. another possible approach is the following. by using lagrange multipliers, in the usual way, it can be shown [3j, [4], that x satisfies the algebraic matrix riccati equation (amre) xm t lx+ lt lxxm t m lt m = 0. (3) when newton's method is applied to the general amre xpx +qx +xf+g::o (4) a linear matrix equation, solutions xi of which converge to x the solution of eqn. ( 4) under appropriate conditions, is obtained. there are many possible ways of solving this linear matrix equation (see, e.g., (5]) and one of these, which involves infmite series, is studied in {6]. methods for offsetting the difficulties involved if a poor starting approximation is made to the solution and for accelerating convergence are also investigated in [6}. the solution techniques are implemented by two algorithms, ai and a2, depending on whether x is unsymmetric or symmetric. a simplified form of al is given in the appendix for convenience. the aim of the present paper is to illustrate the use of ai in solving ls and tls problems by means of a number of numerical examples from the literature. numerical results example 1 the first example is taken from [7] and is concerned with modelling the biological activity of fifteen different compounds with respect to a set of eight variables which describe the various morphological and physiochemical properties of the compounds. the data used is given in table 1 of {7]. setting the initial approximation x0 =0 in al gave the same least squares solution as in 17] (when rounded). 68 xls = [0.636, 0.080, 0.095, -0.308, 0.169, 0.241, 0.278, 0.238f and, of course, the same value, 0.61, for the residual sum of squares ss. x ls also agrees with l+ m where l+ is the pseudo-inverse of l. the smallest singular value of lis 0.337365 and of [l;m] is 0.335713 so that conditions for a unique tls solution, [2], are gust) satisfied. if a1 is now continued from the solution x ls given above it converges to x= [0.716, 0.259, 0.124, -0.336, 0.186, 0.531, -0.435, 0.337f with e = 0.16 before accuracy begins to deteriorate. (using a line search shows a slight improvement in accuracy before deterioration.) when this model is applied to the whole of the data the resulting sum of squares is 41.893 . , the smallest singular value of [l;m], for this example, is as given above and the svd formula x= [l:.l-(0.335713)2 13j1 ltm gives x = [ -4.28,. 1.20,2.21, -1.29, 2.36, 11.oo, -14.60, 2.1ot which has a residual error e = 6( -4) and which is much better than the previous result from al. if now, however, the above x is used as the starting approx.imation in a1 the result is refined to give a better x with a residual error less than 10(-6). algorithm al was also used to compute the sums of squares, denoted by ''press" in [7], for both ls and tls; these measure the predictive properties of the models used. the same groupings of the date were used as in [7] and table 1 shows the results obtained. table 1 predictive sums of squares for example 1 ls tls group 1 1.172 1.319 group 2 group 3 total 1.183 0.804 3.159 1.540 34.832 37.691 the total for ls agrees with that given in [7]. the total for tls is inflated by the very large value from group 3 and presumably accounts for the comment, .. when full rank is approached, it behaved differently," made regarding tls in [7] and for the use of rank 3 tls rather than full rank. (before making the calculations all the nine sets of data were scaled to have zero mean and unit variance.) example2 this example is taken from { l] and involves finding a linear fit to data given in table 26.1 in that reference. in ( 11 five different ucandidaten solutions are obtained and one of them x =f-2.486~-q.529.-0.l94.1.616,3.455t (5) is proposed as the best ls solution according to a number of statistical criteria. now if a1 is used to find a ls and then a tsl solution the result is x = [ -73.3, 98.4, -78.0, 90.7,78.2f ( 6) which is very different from the solution given in eqn. (5) despite the fact that their residual norms are quite close. it is also interesting that the norm of (5) is only about 4.6 compared with 188 for that of (6) and that the smallness of norm is one of the criteria mentioned above for preferring one solution to another. the tsl solution would not have found much favour from this particular viewpoint. example 3 this example, with l=(~~) and m =g) is of a type often used to show that the tsl problem may not have a solution unless extra constraints are imposed [2]. applying a1, using x~ = 0, gives the ls solution [1,.0f, continuing until convergence now gives the tsl solution [l61803,of. another much used method for solving problems of the kind considered in this paper involves some form of direct minimization (see, e.g., [8]) as in the following treatment. let (xl x2), (xs) and (x7) x3 x4 x6 x8 be estimates of l, x and m respectively; form + (1 \2 2 2 2 j 1 = -xi j + x2 + x3 + x4 + (1-x1x5 -.xzx6 } + (1x:3x5 x4x6 }. or alternatively, with more variables involved, fz =(1-xl} +xz2 +x3 2 +x4 2 +(l-x7} +v-xs} +(x7 -x1xs -x2x6y + (xs x3xs x4x6} (8) and minimize ft or f 2 with respect to all of the variables involved in each case. so, for example, using "find minimum" from "mathema tica" on ft the solution (9) is obtained and using / 2 gives the solution notice that the solution given in eqn.(9) is the same as that found by al. the similar, but simpler example with l= [a.bf and m = [uf can be analysed algebraicauy to quantize the difference between using f 1 and !2 • thus, for example, taking l = [l,-g.9sf gives solutions x = 2.37165 and x ""0.0553169 using a andf~ respectively. (again using jj gives the same solution as al and as the svd formula given in example 1.) example4 this is similar to example 3 but rather more sophisticated; it is taken from {21 where it is analysed usingsvd, r ../6 .(6 l l= j214 -/'il4 .• .fin .fin m =[~ ]·· -..fi using x 0 = 0 as the starting approximation in al gives the ls solution xu =[o.zs2633.o.:zsz633r and then proceeding to convergence gives the tls solution x ns = {0.408248, 0.408248f notice that this is the same as the solution p!../6.11 ji;f given in {2j. jn the same manner, as for the previous example, setting up the appropriate jj and using findminimum gives x = (o.408245, 0.408425f and with the appropriate / 2 the solution x =[o.34186,0.34186t. is obtained. example$ the final example ts concerned wltb parameter fitting and 1s raken from l8j. here l fl l i t i =i o o.9 t.s 2.6 3.3 ... l i i i 1 y 4.4 5 .. 2 6.1 65 7.4 j m=b~s~4~4~3~j~2&2liat5f in dus example the first rolumn of l is. fixed and so one merhod of proc¢alins is. as follows.. f2}; ilmi •> muhtphed by a su1tabfe ho\ilioelmlder matnx to &•'•e 1he newmatn:t (i() :..16:!28 t::t.oi•)t) ii '1004 0 ·4.68666 ::!.7174;'\ 0 -~.78666 l7174s 0 ·::!..9smt\ 1.917451 0 .;!,;86n, 0.8j14j6 0 -u866b j.ol745 0 -0.~86656 0 lf74j6 0 0.513344 0.117446 0 0.913~44 .0.2825$4 0 1.81334 ·1.18:!5~ and algorithm a 1 is now apphcd to the ~ubmatm. obtained by deleting the first row and column of the above matrix. to give the :.«ond componenr .t: of the solution vector x. the first component .t1 of x '" then obtained from .3.16228 xi ::: j 1.7004 -12..07q9t:· ; in this way x :::.{5.7840~.-0.sj55o2f is obtained. direct minimizattt~~l ~an oth.o be u.<ied m 1r1 the i'-'u previous eliiamples to give the two '!o{)!utl<lns x :::. (s. 78404.-o.s455<n f x ,.,[s.sl535,-0.55j802f using sums of !icjuares sim1lar tll { 1 and respectively. it has been demonstrated that an aljonthm few ;..th m~ the amr.e can be wil!d 10 '!o{)fvc ov~-ddermmed systems of hnear cquatttm. a numlxf nt t\urnerk'-111 namples m~tratt the t«hl'llq~ ln\·ulved f. fi. l m, p. q. v, w ("or:ffkjt'flt\ mal~'~' matnx r1tatt• cqual!<m i t\mre • x solutmn of amre. x, 1tera~ 10 ylluuon to amrf: (a,b) tonc.atenated matnli f·>rma.l1rnm m&ut'e~ 4 .andb a.b.c.r.s.cc./lu .t. matn..c:1o dchnc.ltn ·\~nj,, ... ' a• ai. a.? s\'0 trai\.'j)i'tk of matn• a ~udn-mvc:tk ,,f m.auu .. -\ algunthrll\ frnrn j()) \lflgul.u v.-luc d<-<:•'fllp'"'tll<>n' .:nttpr•nc:nl~ ut \('d<'f '"' m.jlfl\ \ k.al-f ~u.uc:~ lul,tllc.-. .. t -.qu.ltc:t.o nmmny mje1. 70 e sums of squares defined in eqns. (7) and (8) euclidian norm of a euclidian norm of residual error in solution of amre m, n, p integers used to give order of matrices references 1. lawson l. and hanson j.: solving least squares problems, prentice-hall, inc., englewood cliffs, new jersey, 1974. 2. van huffel s. and vande walle j.: the total least squares problem: computational aspects and analysis, siam philadelphia, 1991. 3. de moor b. and david j.: systems and control letters,l992, 18, 329-337. 4. lancaster p. and rodman l.: algebraic riccati equations, clarendon press oxford, 1995. .5. barnett s. and storey c.: matrix methods in stability theory, thomas nelson and sons limited, 1970. 6. storey c.: modified newton methods for the algebraic matrix riccati equation, part 1: hung.j. ind. chern., i997, 25,305-308, part2: ibid., i998, 26,309-314, part 3: ibid.,j999, 27, 301-305, part 4: ibid., 2000, 28, 277-280. 7. wolds., ruhe a., wold s. and dunn iii w.j.: siamj. sci. stat. comput., 1984,5,735-743. 8. luus r. and hernaez h.: hung.j. ind. chern., 2000,28,201-207. appendix algorithm ai to solve the general amre xpx + qx + xf + g = 0 let x 0 be an approximate solution. let i = 0 compute: a1 =x1p+q b1 =px1 +f c, =x1px1 -g r; =(in -a;)-1 s; =(inb;)-1 a1 =2r1 -in {31 =2s1 -in m 1 =-2r1c1s1 t 1 <1l =m 1 tz (i) = ~(;} + a;~<il /1; ~ (!) = t 2 (i) + a/t 2 (i) f1f t cil = t (i) z"-''y<nf3z''-'' k+l k +a; k ; (i} when converged set x i+l = tk+l , i = i + 1 repeat page 65 page 66 page 67 page 68 hungarian journal of industry and chemistry vol. 51(1) pp. 55–59 (2023) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2023-08 a survey of the readiness and maturity level of industry 4.0 at twenty companies in pakistan uzair khan1, wasim ahmad1 and muhammad imran2* 1 department of industrial engineering, university of engineering and technology taxila, punjab 47050, pakistan 2 department of basic sciences, university of engineering and technology taxila, punjab 47050, pakistan a survey-based analysis is carried out of twenty major industrial sectors in pakistan to inspect and scrutinize how industry 4.0 is developing and being instigated in production units as well as business. existing technical aspects demonstrate that ancient manufacturing processes are not apt to produce components more accurately and precisely but less lucratively. the objective of this study is to assess the present implementation measures, readiness and maturity level with regard to industry 4.0 as well as the elementary knowledge of workers and technical know-how of experts. this survey may provide a helpful guide for new and already existing enterprises seeking to precisely achieve requisite attributes of industry 4.0. a questionnaire consisting of six questions was sent to various industrial businesses and feedback from production managers with a mean age of 34.56±04.20 years and a minimum of 10 years of experience received. this is a qualitative survey examined by a quantitative method. keywords: industry 4.0, cyber-physical systems, readiness, maturity, survey 1. introduction industry 4.0 has two main features; one is integration and the other interoperability [1]. industry 4.0 is a set of nine digital systems that interlink the physical world of production with its numerical equivalent. this set of innovations controls machines which work autonomously by obeying commands within nanoseconds and with extraordinary precision [2]. it offers many business opportunities for small and medium enterprises. in pakistan, due to a lack of knowledge, the majority of people are unaware of the concept of industry 4.0. therefore, industrial sectors are unable to implement this concept as the government has not made any fruitful decisions nor provided facilities for them. this development has drawn the digital and physical worlds close together through cyber-physical systems (cps) [3]. a cps is a new group of systems with integrated computational and physical capabilities that connect humans to new modalities [4]. the ability to connect and spread the abilities of the physical world with the aid of computation and communication is an important enabler for upcoming industrial and technological developments worldwide [5]. industry 4.0 is a tool to improve manufacturing capabilities and enhance efficiency in industrial sectors. to curtail old received: 17 feb 2023; revised: 18 apr 2023; accepted: 23 may 2023 *correspondence: imran_pk94@yahoo.com fashioned technologies and traditional methods, the implementation of industry 4.0 technologies is likely to generate more revenue for the state, increase the quality of products and enhance the effectiveness of operating systems on the international market. real-time data processing, monitoring and fault detection are all controlled through the internet, thereby saving time as well as reducing labour costs and maintenance expenses. according to a report by khan (2010), a huge decline in the textile industry has been witnessed as a result of industry 4.0 [6] due to which the exports of textile in the future may drop, reducing its contribution to the gross domestic product (gdp) in pakistan which was 4.24% in 2015 [7]. as the share of the gdp concerning the industrial sector is 12.4% 0, to increase the gdp up to its optimum level, the industrial sector must embrace industry 4.0 in large(lsm) as well as small-scale manufacturing (ssm) [8]. the industrial sector is struggling to adopt industry 4.0 in pakistan due to a lack of skills and knowledge [9]. maturity models are generally used as a tool to measure the maturity of industry 4.0 [10]. readiness models are designated with the aim of securing a starting point and enabling the initialization of the development process [11]-[12], which have recently been proposed in the fields of energy, utility management and design [13]. https://doi.org/10.33927/hjic-2023-08 mailto:imran_pk94@yahoo.com khan, ahmad and imran hungarian journal of industry and chemistry 56 industry 4.0 readiness is defined as the degree to which any organizations are able to benefit from industry 4.0 technologies [14], i.e. it concerns how digitally equipped corporations are with regard to implementing industry 4.0 technologies [15]. this digital revolution has reformed the software and hardware aspects of organizations [16]. for example, in engineering, threedimensional simulations and printing have previously been implemented concerning raw materials, finished products and production cycles [17], however, softwareas-a-service applications offer an additional window of opportunity in terms of industry 4.0. these prospects can be better addressed under the umbrella of industry 4.0 technologies that can then contribute towards industry 4.0 readiness, which can also be considered from competitive, scientific, technical and organizational points of view [10]. major studies regard industry 4.0 as disruptive for the same reason. numerous surveys have been carried out concerning industry 4.0 and many websites generated for the purpose of implementing it [18]. furthermore, many models have thoroughly assessed industry 4.0 readiness with regard to its implementation and future perspectives of digitalization [19]. they were not only related to their readiness but also focused on digital enterprises, smart industries and small economies [20] by not only focusing on solutions to current problems but on the needs and design of existing setups. this is not the first paper addressing the readiness and maturity level of industry 4.0 but the scope, depth and specifications discussed are different. 2. materials and methods to assess the readiness, the viewpoints of workers obtained from different industrial setups were gathered and maturity levels of manufacturing enterprises in pakistan determined. in doing so, one principle question arose, that is: “how can industry 4.0 readiness and maturity models be measured and the maturity of manufacturing enterprises assessed in pakistan?” to answer this question, the operational views of innovation were gathered in terms of the social exchange and viewpoints of workers to study the maturity level of industry 4.0 until now in the twenty industrial zones of pakistan. based on these aims and objectives, the research strategy was selected. the main goal of this paper is to adapt the factors on which industry 4.0 depends before exploring them in the different local industries of pakistan using the questionnaire. data collection and analysis were accomplished through quantitative methods. to find a maturity model for assessing the readiness and maturity level of industry 4.0 regarding manufacturing enterprises in pakistan, figure 1 was adopted. it contains four steps to analyse the maturity level and readiness of industry 4.0. the first was comprised of list of industries, suitable for survey and data collected. in the second step questionnaire was sent and data were accumulated, while in the third one, data were processed using ms excel to assess readiness and maturity level. the fourth step consisted of results and deductions after receiving responses and feedback from industrial employees as well as factory workers through the questionnaire. their replies, views and answers were processed by relevant software and the results automatically calculated as well as summarized in a compact maturity report. the questionnaire was answered by various actors, i.e. industrial workers as well as factory employees and managers. the entire questionnaire is presented in table 1 which consists of table 1. questionnaire about the readiness and maturity level of industry 4.0 questions categories details rating 1 2 3 4 5 no info. q1. r ea d in es s o f in d u st ry 4 .0 rate your knowledge about industry 4.0. q2. rate the current level of implementation of industry 4.0 in your industry. q3. how many conventional methods of production are appropriate for manufacturing? q4. m at u ri ty l ev el o f in d u st ry 4 .0 do you implement industry 4.0 in large-scale manufacturing? q5. rate the quality of production as a result of industry 4.0. q6. rate the skill level of industry 4.0 in your industrial setup. figure 1. block diagram – readiness and maturity level of industry 4.0 a survey of industry 4.0 in pakistan 51(1) pp. 55–59 (2023) 57 two main parts and various questions regarding how industries have developed smoothly and the latest technologies like industry 4.0 adopted in pakistan and each question explained. below are the twenty main industries/companies evaluated in this research: 1) hattar group of industries, haripur 2) international polymer industries (pvt.) ltd., islamabad 3) elektro control industries (pvt.) ltd., islamabad 4) potohar steel industries re-rolling mills, islamabad 5) dawn electric industries, islamabad 6) faisalabad textile mills, faisalabad 7) heavy industries taxila (hit), taxila 8) j.k. spinning mills limited, faisalabad 9) poly foils pvt ltd, islamabad 10) khalid modern industries, hasilpur 11) macter international limited, karachi 12) heavy mechanical complex (hmc), taxila 13) carriage factory, islamabad 14) the indus basin company, ict islamabad 15) rani & company (private) limited, karachi 16) cherat cement, nowshera 17) bestway cement, hattar, haripur 18) askari fuels, rawalpindi 19) auto industry chaklala 20) fibre craft industries, lahore 3. results all the results addressing the readiness and maturity level of industry 4.0 have been calculated 2.5 using a ms excel worksheet which determined that the majority of industries in pakistan are aware of industry 4.0 and only a few are unaware, namely some cement manufacturing companies that require manual work using ordinary methods and an unskilled labour force with no need for digital manufacturing. this survey examines the readiness and maturity level of industry 4.0 as shown in table 2. 4. discussion in pakistan, the implementation of information technology means work is done more easily and quickly, bringing about amazing changes in the industrial sector. some of the original manufacturers want to adopt worldwide criteria and boost their productivity, while others have not adopted them yet for various reasons. in several fields, pakistan must embrace industry 4.0, e.g. in production, manufacturing, products and services, supply chains, etc. pakistan should take urgent measures to bring about this development in industry, healthcare and agriculture as in other countries an increase in industrial development has resulted in gdp growth. pakistan’s readiness with regard to industry 4.0 lags behind international industrial zones, which tallies well with results gathered by khan et al. [21]. the mean score regarding its maturity level is also 2.5 out of 5 (50%), as shown in figure 2 and table 3, which tallies well with previous results [22]. therefore, it can be stated that this maturity model is vital in terms of assessing industry 4.0 [23] and is known as the novel model to expose the basic knowledge of the citizens and workers in various industrial sectors of pakistan. 5. conclusions our statistical analysis concluded that the awareness of industry 4.0 in pakistan is very low when compared to other neighbouring countries like india, china and indonesia, whereas its readiness is facilitating new industrial paradigms in the country. although the maturity level of industry 4.0 has resulted in innovation, here in pakistan it is only 50% to date, meaning the country is lagging behind in terms of the worldwide trend table 2. questionnaire results q u e st io n company a v e r a g e 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. q1. 2 2 4 3 5 4 3 4 3 2 2 4 3 4 2 3 2 2 4 3 3.05 q2. 1 1 2 1 2 1 1 2 2 1 2 2 1 2 3 2 1 2 3 4 1.80 q3. 2 3 4 2 2 1 3 1 2 2 3 3 2 1 3 4 2 3 5 5 2.65 q4. 3 2 2 2 1 2 1 2 1 3 1 2 2 5 2 3 3 3 2 2 2.20 q5. 3 3 3 3 2 1 2 2 2 4 3 3 3 2 3 2 2 3 3 3 2.60 q6. 4 2 2 4 2 3 2 4 4 2 2 2 4 2 2 2 3 2 2 4 2.70 average 2.50 2.17 2.80 2.50 2.30 2.00 2.00 2.50 2.30 2.30 2.17 2.70 2.50 2.70 2.50 2.67 2.17 2.50 3.17 3.50 2.50 number of questions = 6, number of respondents = 20, maximum score per question (rating) = 5, mean score of 0 = least effective, mean score of 5 = most effective khan, ahmad and imran hungarian journal of industry and chemistry 58 regarding the fourth industrial revolution. a new maturity model must be proposed in the future to ensure the maturity level of new technologies is raised in pakistan. though this research assesses the readiness and maturity level in the industries of pakistan, it can also be used to further assess industry 4.0. it is the best technology to enhance productivity, reduce costs and waste generation, improve accuracy as well as ensure excellent precision, enabling this advancement to be implemented as soon as possible. therefore, a survey like in this research paper should be conducted to assess the energy sector in pakistan. references [1] romero, d.; vernadat, f.: enterprise information systems state of the art: past, present and future trends, comput. ind., 2016, 79, 3–13, doi: 10.1016/j.compind.2016.03.001 [2] schiele, h.; bos-nehles, a.; delke, v.; stegmaier, p.; torn, r.-j.: interpreting the industry 4.0 future: technology, business, society and people, j. bus. strategy, 2022, 43(3), 157–167, doi: 10.1108/jbs-082020-0181 [3] kagermann, h.; wahlster, w.; helbig, j.: recommendations for implementing the strategic initiative industrie 4.0 (forschungunion, acatech, 2013), https://en.acatech.de/wpcontent/uploads/sites/6/2018/03/final_report__industrie_4.0_ac cessible.pdf [4] baheti, r.; gill, h.: cyber-physical systems, in: the impact of control technology – 1st edition, samad, t.; annaswamy, a. 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https://www.imeko.info/publications/tc10-2017/imeko-tc10-2017-031.pdf https://www.imeko.info/publications/tc10-2017/imeko-tc10-2017-031.pdf https://aisel.aisnet.org/amcis2016/entsys/presentations/9 https://doi.org/10.1080/14615517.2019.1684096 https://doi.org/10.1080/14615517.2019.1684096 https://doi.org/10.1016/j.procir.2016.07.040 https://doi.org/10.1016/j.procir.2016.07.040 https://doi.org/10.1016/j.engappai.2018.11.007 https://doi.org/10.1016/j.engappai.2018.11.007 hungarian journal of industry and chemistry vol. 51(1) pp. 9–13 (2023) hjic.mk.uni-pannon.hu preliminary study of cesium immobilization in a geopolymer matrix erika kocsis1, máté fehérvári1, máté novák1, edit tóth-bodrogi1, tibor kovács1* 1 department of radiochemistry and radioecology, university of pannonia, egyetem u. 10, veszprém, 8200, hungary geopolymers are modern synthetic materials that have many beneficial characteristics, e.g. excellent mechanic al properties, fireand heat-resistance, minimal shrinkage and can be molded into shape. given their aforementioned characteristics, geopolymers could be applicable as conditioning materials, e.g. to handle hazardous waste and radioactive materials. however, their long-term applicability needs to be investigated. the aim of this study is to investigate the mobility of cs-137 radionuclides in embedding materials. different geopolymeric matrices namely kaolinite, bentonite, zeolites and red mud were tested. the leach test was performed according to the astm c1308-08(2017) standard and the activity concentration of cs-137 isotopes was measured by gamma spectrometry using a high-purity germanium (hpge) semiconductor detector. according to our preliminary results, the matrices that resulted in the most significant immobilization effect were those in which bentonite, cement, fly ash and 8m naoh were used, releasing approximately 10% of the cesium. keywords: geopolymer, immobilization, radioactive waste, norms 1. introduction in order to prevent any dispersion of radionuclides from liquid radioactive waste into the environment, this type of waste has been incorporated into various embedding materials. the aim of this process is to make these materials leach-resistant, so that the release of radionuclides is significantly reduced should they come into contact with groundwater. the other reason is to transform these materials into a mechanically, chemically and physically stable form for transport and emplacement [1]. nowadays, the most commonly used solidifying materials are cement, bitumen and various types of polymers. of these materials, cement is the most commonly used because it is widely available, cheaper than the other materials and easy to handle. however, it has been shown that cement is not the best material for immobilizing cs-137 radionuclides. several studies have shown that the sorption capacity of cs-137 is low and the diffusion capacity in hydrated cements is high [2]-[3]. the immobilization properties of cement as an embedding material can be enhanced by using different types of additives that have a higher sorption capacity, e.g. bentonite and zeolites [4]-[5]. given the low hydraulic conductivity and high sorption capacity of cations, bentonite is a promising material with regard to disposing of radioactive waste. zeolites, particularly clinoptilolite, are used worldwide in ion exchange processes with a great degree of success in the removal received: 8 feb 2023; revised: 16 feb 2023; accepted: 17 feb 2023 *correspondence: kovacs.tibor@mk.uni-pannon.hu of cs-137 radionuclides from various types of wastewater. both are natural materials, which means that their extraction has a huge impact on the environment [6]-[7]. as previously mentioned, since they are mixed with cement to obtain a mixture that has good radionuclide immobilization properties, the mining of zeolites and bentonites is not the only activity with a huge environmental impact. the cement manufacturing process is also known to have a huge environmental impact. the process releases several gases into the air, e.g. co2, no2, no3, so2, etc., which have major impacts on global warming [8]-[9]. as a result, research is now being conducted to reduce the amount of raw materials used in the industry and identify replacement materials. testing norms (naturally occurring radioactive materials) which are available in large quantities worldwide as well as could be used as potential additives in commonly used cement, zeolites and bentonite could be promising. one of the ways in which radioactive waste solidifies is through geopolymerisation. norms, e.g. red mud and fly ash, can be used as additives [10]-[12] and are usually deposited in huge amounts, which has a significant environmental impact due to the heavy metals they contain, moreover, can of course increase the dose rate to passers-by or workers near these deposits [13]. therefore, a method is needed to reduce the environmental impact of norms. however, the following question may be raised: why are they unsuitable as replacements for geopolymers nor as embedding materials for liquid radioactive waste. these doi: 10.33927/hjic-2023-02 mailto:kovacs.tibor@mk.uni-pannon.hu https://doi.org/10.33927/hjic-2023-02 kocsis, fehérvári, novák, tóth-bodrogi and kovács hungarian journal of industry and chemistry 10 materials are widely used in construction, water treatment and agricultural fertilization, some of which have good adsorption and water-binding capacities. furthermore, using these materials as additives can reduce the environmental impact of mining and reduce the cost of production. the solidification of liquid radioactive waste by geopolymerisation is one of the cheapest methods of radioactive waste management. the structure of the resulting final product is stable as well as exhibits extremely good heatand fire-resistance capabilities, moreover, the concentration of boric acid in liquid radioactive waste does not destroy the structure of geopolymers and the volume of the resulting final product is significantly smaller compared to that of waste conditioned by cementation [14]-[15]. the aim of this study is to investigate the immobilization of cs-137 in different kinds of geopolymeric materials using norm additives. 2. experimental during the laboratory work, different kinds of geopolymers containing zeolites, bentonite, kaolinite and red mud were prepared, which were mixed in different ratios as presented in table 1 below: table 1. mixing ratio of the used materials experiment used materials mixing ratio i. zeolites – cement 1:1 zeolites – bentonite – cement 1:1:1 zeolites – kaolinite – cement 1:1:1 bentonite – cement 1:1 bentonite – kaolinite – cement 1:1:1 kaolinite – cement 1:1 ii. cement 1 zeolites – cement 1:1 zeolites – cement 2:1 bentonite – cement 1:2 iii. red mud – bentonite – cement 1:1:1 red mud – zeolites – cement 1:1:1 red mud – bentonite – cement 2:1:1 red mud – zeolites – cement 2:1:1 cement as a binder as well as an 8m naoh solution as a wetting agent were added to the mixtures and mixed until a homogeneous mass was obtained. a radioactive cs-137 solution was mixed with the already moldable mass before being placed in a sample container. the molded samples were then dried for 27 days at room temperature in accordance with the requirements of the astm c 1308-08 standard [16]. after the 27 days, the already solidified samples were placed in a 1l plastic container in such a way that they were attached to the lid of the container by means of a thread to prevent them from dropping to the bottom of the container. 250 ml of distilled water was poured into the vessel used for the dissolution test. during the leaching tests, the distilled water in the containers was replaced at the time intervals specified by the standard (figure 1) before the amount of leached radionuclides dissolved from the test samples was measured by gamma spectrometry using a high-purity germanium (hpge) semiconductor detector. according to the astm standard, the incremental fraction leached (ifl) was calculated using the results from gamma spectrometry measurements as follows: 𝐼𝐹𝐿 = 𝑎𝑛𝑖 𝐴0𝑖 (1) where: ian denotes the quantity of species i measured in the leachate from the nth test interval, ia0 stands for the quantity of species i in the specimen at the beginning of the test the cumulative fraction of species i leached over the jth time interval, referred to as the cumulative fraction leached (cflj), was also calculated: 𝐶𝐹𝐿𝑗 = ∑ 𝑎𝑛𝑖 𝑖 𝑛=0 𝐴0𝑖 =∑ 𝐼𝐹𝐿𝑗 𝑖 𝑛=0 (2) in the case of radionuclide i, both terms must be corrected in light of radioactive decay at the beginning of the test. 3. results and analysis during the first part of the experiments, zeolites, bentonite, kaolinite and, of course, cement were used, moreover, the leached amount of radionuclides was measured by gamma spectrometry using a hpge semiconductor detector. these values were used to calculate the cfl values of each matrix, which are shown in figure 2. figure 1. time intervals according to which the water was changed in accordance with the astm c 1308-08 standard [17] preliminary study of cesium immobilization in a geopolymer matrix 51(1) pp. 9–13 (2023) 11 based on the results obtained, it can be seen that during the 10-day-long dissolution tests, the amount of dissolved cs-137 was lowest in the case of the geopolymers containing zeolites – cement and zeolites – bentonite – cement in 1:1 and 1:1:1 ratios, respectively. regarding the sample containing zeolites – cement, the dissolution rate was 9.8%, while for the one consisting of zeolites – bentonite – cement, it was 10.1%. the highest dissolution rate, that is, 17.4%, was measured in the sample containing kaolinite – cement in a ratio of 1:1. the high dissolution rate of kaolinite is due to the structure of kaolin which, like illite, is a layered phyllosilicate in which the absorption of cs ions is not as high when compared to its montmorillonite counterparts due to its crystal structure. on the basis of the results obtained, it can also be seen that the cfl values of the zeolites – cement and zeolites – bentonite samples constantly increase, moreover, after 7 days, the dissolution rate already increased much more slowly compared to the other samples, where a continuous increase was observed. during the initial phase of the dissolution tests, i.e. in the first few days, not only were the cs-137 isotopes embedded in the geopolymer dissolved but also those on the surface of the test specimens. as a result, a larger increase in the cfl value was recorded during the initial phase. once the cs-137 on the surface has completely dissolved, only the dissolution of cs-137 inside the geopolymer affects the obtained values. of course, the amount of dissolved cs-137 is also affected by the small microcracks in the samples that may have occurred during their preparation, possibly increasing the amount dissolved. in the second part of our experiments, ratios resulting in the best cfl values from the previous measurements were used. cement matrices consisting of zeolites mixed in different ratios were measured and the cfl values obtained can be seen in figure 3. it can be seen that the leachability of the cs-137 radionuclide can be significantly reduced using zeolite additives. depending on the quality and quantity of such additives, the dissolution rate may be reduced. as a result of ion exchange processes, the cesium ions absorbed by the zeolites are exchanged for the calcium ions in the cement. the cesium ions are then released from the matrix into the environment by diffusion. the rate at which cesium diffuses away from the matrix is determined by the environment, ion exchange process and rate of diffusion. the ion exchange process can be slowed down by increasing the additive content of the matrices so that the ability of the clay minerals to bind to the calcium hydroxide ions is enhanced, preventing displacement of the cesium ions from the structure of the matrix to such an extent that results in significantly less cesium being released from the matrix. in addition to the calcium ions in the cement, this process can also be influenced by the amount of such ions in the solvent, because if the solvent is rich in calcium, the calcium ions it contains can also displace the cesium ions, thereby increasing the rate at which they escape from the matrix. for this reason, distilled water was chosen as the solvent, as it cannot interfere with the ion exchange processes taking place in the test samples [18]. the results obtained during the dissolution tests were developed in accordance with the aforementioned ion exchange processes. in the case of the cement – zeolites samples in the ratios of 1:1 and 1:2, it can be seen that the amount of dissolved cesium was smaller than in the samples where only cement was present or in larger quantities compared to that of zeolites. in contrast with cement and cement – zeolites specimens, the dissolution rate of cs-137 dissolved from samples containing zeolites – cement in a ratio of 1:1 was 9.8%, while those containing zeolites – cement in a ratio of 2:1 was only figure 2. representation of the change in cfl values obtained during the i. experiment as a function of time 0,00 0,02 0,04 0,06 0,08 0,10 0,12 0,14 0,16 0,18 0 2 4 6 8 10 c l f time [days] zeolites zeolites bentonite zeolites kaolinite bentonite bentonite kaolinite kaolinite figure 3. representation of the change in the cfl values obtained with regard to cement – zeolites matrices in different ratios 0,00 0,02 0,04 0,06 0,08 0,10 0,12 0,14 0,16 0,18 0,20 0 2 4 6 8 10 c l f time [days] cement cement zeolites 1:1 cement zeolites 2:1 cement zeolites 1:2 kocsis, fehérvári, novák, tóth-bodrogi and kovács hungarian journal of industry and chemistry 12 8.3%. in the case of samples consisting of a ratio of 2:1, the amount of dissolved cs-137 was 17.5 and 16.2 %. norms containing bentonite and zeolites were also used as additives during leaching tests. based on recommendations from the literature, red mud was selected as the norm for the experiment. the leaching rates of cs-137 from samples containing bentonite and red mud in the ratios of 1:1 and 1:2 were 5.90 and 8.04%, respectively, whereas those of cs-137 from samples containing zeolites and red mud in the ratios of 1:1 and 1:2 were 10.20 and 11.73%, respectively. the cfl values recorded can be seen in figure 4. based on the results obtained during the dissolution tests, the specimens containing bentonite proved to have a better immobilization effect on cs-137. based on the results obtained, it can be seen that ion exchange processes can be influenced by some parameters such as the slightly alkaline chemical effect resulting from the composition of bentonite and the si/al ratio of the red mud which created favorable conditions for the cesium ions to bind much better in the matrix of the specimens containing bentonite than in those containing zeolites. however, it can also be seen that if the si/al ratio of the samples is increased even more by adding additional red mud to the samples, the rate of dissolution increases. this can be explained by the fact that the al rings in the test specimens become smaller due to the lower si/al ratio, so the rate at which cesium ions escape from the structure reduces. these results are supported by the study written by quanzhi tian, shingo nakama and keiko sasaki in which cesium leaching tests were also carried out on specimens with different compositions and si/al ratios [19]. 4. conclusions the aim of this research was to investigate the applicability of norms with regard to the immobilization of radionuclides in liquid radioactive waste. during the experiments, various compositions with different raw materials were investigated in order to determine the basic material whereby the norm, that is, red mud, is used as an additive. based on the results of the laboratory measurements, it can be said that the best cfl value was obtained with a test batch containing a 1:1 mixture of bentonite and red mud. it can also be concluded that the chemical composition of the norm used as an additive, namely red mud, significantly contributes towards the reduction in ion exchange processes. however, this should be treated with caution as the 1:1 mixture of bentonite and red mud exhibited favorable cfl and diffusion rate values compared to the sample containing twice as much red mud. all in all, it can be stated that the reuse of norms can reduce our impact on the environment. it was observed that norms, especially red mud, can be successfully used as additives to manage liquid radioactive waste. this is an opportunity that must be seized and a field in need of much more thorough research in the future. references [1] plecas, i.: immobilization of 137cs and 60co in concrete matrix, ann. nucl. energy, 2003, 30(18), 1899–1903, doi: 10.1016/s03064549(03)00158-0 [2] 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https://doi.org/10.1007/s10967-020-07578-8 https://doi.org/10.1007/s10967-020-07578-8 http://dx.doi.org/10.14382/epitoanyag-jsbcm.2011.14 https://doi.org/10.1016/j.wasman.2018.11.019 https://doi.org/10.1016/j.heliyon.2020.e03455 https://doi.org/10.1016/j.jhazmat.2021.126402 https://doi.org/10.1016/j.jhazmat.2021.126402 https://doi.org/10.1016/s0301-7516(99)00074-5 https://imwa.info/docs/imwa_2017/imwa2017_seipel_830.pdf https://doi.org/10.2172/5557445 https://doi.org/10.1016/j.scitotenv.2019.06.095 hungarian journal of industry and chemistry vol. 49(2) pp. 77–84 (2021) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2021-26 analysis of roughness parameters determining tribological properties in hard turned surfaces viktor molnár*1 and istván sztankovics1 1institute of manufacturing science, university of miskolc, egyetemváros, miskolc, 3515, hungary hard-machined components built into automotive industrial products play an important role because they incorporate working surfaces. the machining of them is crucial; the accuracy, surface quality and lifetime have to be ensured. in this paper the tribological properties of hard-turned surfaces are characterized and analyzed based on 3d and 2d surface roughness parameters. functional parameters that provide quantitative information about the wear resistance and fluid retention of the machined surfaces were studied. the aim of the study was to summarize the relevant roughness parameters in terms of the functionality of the surfaces and to collect experimental results for their application. keywords: wear-resistance, hard turning, surface roughness 1. introduction many machined surfaces incorporate working surfaces, which move relative to other surfaces. the analysis and development of such surfaces is important because the surface quality [1, 2] and, within this parameter, the topographical characteristics [3, 4] by and large determine the lifetime of parts [5–7]. the characterization of surface topography is highlighted in the automotive industry, that is, predicting the values of roughness parameters [8] and the effect of technological data on the topography are determining factors in the design of machined parts [9]. due to the development of superhard materials, the machining of hardened surfaces by single-point tools has become more common in recent decades [10]. in this paper, the topography of internal cylindrical surfaces machined by hard turning is analyzed from a tribological point of view. tribology focuses on the friction, wear and friction-reducing characteristics of surfaces. by analyzing surface topography with the help of several available surface roughness parameters, the wear resistance as well as load-bearing and fluid-retention capacities of surfaces can be characterized [11]. these parameters have been analyzed in numerous studies which only focus on certain parameter groups, e.g. rk or volume parameters [12–15]. the aim of the present study is to summarize and compare most of the roughness parameters that describe tribological characteristics. these are mainly the areal (3d) roughness parameters because of their exactness [16–18]. if a parameter has a corresponding line parameter (2d), it is also analyzed. while less exact than 3d *correspondence: viktor.molnar@uni-miskolc.hu results, 2d studies can provide useful practical information and are less time-consuming. although certain parameters can be considered as more accurate due to their modernity, e.g. volume parameters, most parameters can provide at least directions with regard to the mentioned tribological characteristics. 2. tribology-oriented roughness parameters the simplest information is provided by the maximum peak height (sp) and maximum valley depth (sv) within the group of height parameters. a higher peak maximum height could be indicative of a relatively long wear-in phase and a higher maximum valley depth of a higher fluid-retention capacity. the skewness (ssk) and kurtosis (sku) parameters are also regarded as height parameters. a negative ssk, e.g,. a burnished surface, means a better fluid-retention capacity comparative to the positive values of highly peaky surfaces. in the case of a zero or negative ssk value, the load-bearing area of the surface is greater, therefore, its wear resistance is also greater [3]. this effect is enhanced by an sku of 3 or lower, which is indicative of a relatively filled surface [19]. these characteristics are summarized in fig. 1 based on 2d profile parameters. the abbott-firestone curve and the related sk parameters (fig. 2) typically help to analyze the functional and tribological properties of a surface [21]. the shape of the curve itself draws attention to some remarkable topographic characteristics. the curve of a random (isotropic) surface, e.g. the ground, is entirely analogous to that of a normal distribution. in the case of periodic, e.g. hardhttps://doi.org/10.33927/hjic-2021-26 mailto:viktor.molnar@uni-miskolc.hu 78 molnár and sztankovics figure 1: the ranges of the rsk and rku parameters for different surface topographies [20] table 1: effects of changes in the parameters determining tribological properties change in roughness parameter sp: _; ssk: _ / ≤ 0; sku: _ / < 3; spk: _; sa1: _; vmp: _; sbi: ^ sv: ^; ssk: _ / ≤ 0; svk: ^; sa2: ^; vvc: ^; vvv: ^; sci: ^; svi: ^ change in tribological characteristics wear resistance and/or loadbearing capacity increases fluid-retention capacity increases turned, surfaces, the change in the gradient of the curve is uneven and the curve is asymmetrical. the procedures that reduce or eliminate the surface peaks, e.g. diamond or ball burnishing, result in a plateaued topography and a filled surface [4, 22], yielding a relatively straight middle section with a gradual gradient in the curve. in this case, since the material volume of the surface peaks is relatively low, the wear resistance of the surface is higher [11]. concerning the sk parameters, the value of the reduced peak height (spk) is low. the increase in the reduced valley depth (svk) indicates a higher fluid retention capacity [23]. in the analysis of sk, volume parameters are also applied to the material volume of peaks (sa1) and the void volume of valleys (sa2) [24]. although similar statements are valid for the volume parameters, this parameter group measures the magnitude of the peak and valley zones in a more exact manner. the lower the peak material volume (vmp) is, the better its wear resistance capacity, moreover, the higher the core void volume (vvc) and valley void volume (vvv), figure 2: the abbott-firestone curve and the determination of the sk parameters the better its fluid retention capacity [11]. in the volume analysis the peak zone is defined as the top 10% and the valley zone as the bottom 20% of the topography. the so-called functional indices are less well-known or at least less frequently applied. rather than being derived from the abbott-firestone curve, they are characterized by the load-bearing and fluid-retention capacities of the surfaces. the higher the surface bearing index (sbi), the higher its load-bearing capacity, while the higher the core fluid retention (sci) and the valley fluid retention (svi) indices, the better its fluid retention capacity. these tribological properties are summarized in table 1. 3. experimental conditions internal cylindrical surfaces (s1, s2 and s3) of three parts were machined by hard turning. various feeds resulted in different topographies when the other cutting parameters were fixed. the cutting experiments were carried out by a hard machining tool enter type emag vdc 400. the applied insert was of the type ccgw 09t308 nc2 and the tool holder of the type e25t-sclcr 09-r. the cutting data are summarized in table 2. the surfaces were bores of gearwheels built into transmission systems. the parts were composed of the steel 20mncr5. the physical and mechanical properties as well as the chemical composition of this steel are summarized in table 3. the diameters of the machined bores were d = 88 mm and their lengths were l = 34 mm. the surface roughness measurements were carried out on an altisurf 520 measuring machine using a cl2type optical sensor with a nominal measuring range of 0−300µm. the resolution along the z axis was 0.012µm and 5µm along the x and y axes. the scanned area was 4.8 × 2.8 mm2. gaussian filtering was applied to the evaluation and the cut-off wavelength was λc = 0.8 mm. for the purpose of evaluating the area parameters, a 2×2 mm2 area was taken into account and the evaluation hungarian journal of industry and chemistry analysis of roughness parameters determining tribological properties 79 table 2: cutting data of the machined surfaces cutting machined surfaces data s1 s2 s3 ap [mm] 0.2 n [1/min] 615 f [mm/rev] 0.1 0.2 0.3 table 3: physical and mechanical properties as well as the chemical composition of the machined workpieces yield strength tensile strength hardness thermal conductivity density elastic modulus σs (mpa) σb (mpa) hrc k (w/mk) ρ (g/cm3) e (gpa) 1034 1158 62− 64 11.7 7.7− 8.03 190− 210 c mn cr si cu s p al 0.17− 0.22 1.1− 1.4 1.0−−1.3 ≤ 0.4 ≤ 0.4 ≤ 0.035 ≤ 0.025 0.02− 0.04 figure 3: evaluation area and profiles applied to the surface topography analysis length for the line parameters was ln = 4 mm. the analysis of the line parameters was carried out based on the average surface roughness values calculated from three profiles per surface. the line profile was extracted from the 3d area. the measurement setup, evaluation area and location of the 2d profiles are presented in fig. 3. for the analysis of the 3d parameters, the geometrical product specification (gps) standard iso 25178 was used, while the standards iso 4287 and iso 13565-2 were used for the 2d parameters. the analyzed functional indices are defined by the standard eur 15178n. 4. results and discussion 4.1 surface characteristics surfaces machined by hard turning exhibit periodic topography in contrast to random surfaces such as ground surfaces. in metrology, this characteristic can be expressed by the degree of isotropy as a percentage or by using the spatial parameter, str (ranging from 0 to 1). the analyzed surfaces are definitely anisotropic; their values vary between 1.46 and 4.28%. the degree of isotropy increases as the feed rate increases. the specific direction of measurement (x) is identical to the direction of the feed, which is perpendicular to the cutting speed vector. in this direction, the roughness height of the turned surface is at its maximum. this direction of measurement is important because the direction of the extracted 2d profiles is x . the dominant texture direction (lay) varies between 90◦ and 90.05◦, which demonstrates the accuracy of the measurements. in table 4, the isotropy of the analyzed surfaces and the texture directions are summarized. frequency analysis was performed for additional characterization of the surfaces. in fig. 4, the power spectral densities (psd) of the surfaces are presented. it can be observed that the wavelengths are identical to the feed rate values. additional components appear as periodic noises in the analyses. they might result from fur49(2) pp. 77–84 (2021) 80 molnár and sztankovics table 4: texture direction and isotropy of the analyzed surfaces surface s1 s2 s3 isotropy: 1.4576% isotropy: 1.8917% isotropy: 4.2799% first direction: 89.9956◦ first direction: 89.9973◦ first direction: 90.0461◦ figure 4: power spectral density (psd) analysis of the surfaces ther topographic characteristics of the surfaces or from mechanical circumstances of the machining. in figs. 5 and 6, the simple height parameters of the surfaces are demonstrated for 3d and 2d measurements, respectively. the arithmetical mean height (sa and ra), the maximum height (sz and rz), the maximum peak height (sp and rp) and the maximum valley depth (sv and rv) have similar values for the different surface topographies, that is, s1 (f = 0.1 mm/rev) and s2 (f = 0.2 mm/rev). this phenomenon highlights the necessity of including additional parameters in the topography in order to characterize it in more detail. by analyzing the deviations in the 2d and 3d height parameters, it can be stated that the maximum peak height (sp) is 1.2−2.2 times higher than the mean of the rp values obtained by averaging the three 2d measurements. this multiplier varies between 1.9 and 2.5 in terms of sv and rv for the surfaces machined using three different feed rates. the maximum height (sz) is 1.5 − 2.3 times higher than the average of the three rz values. by comparing the arithmetical mean heights (sa and ra), it was found that the 3d values are higher than the 2d ones. the sa values are 8 − 15% higher than the ra ones and the percentage differences are higher when lower feed rates were applied (fig. 7). 4.2 analysis of tribological parameters the parameters characterizing tribological properties are found in the height, sk and volume parameter groups as well as among the functional indices. in fig. 8, the 3d parameters that provide information about the wear resistance are summarized for the analyzed surfaces. the lower values of sp, spk, sa1 and vmp indicate better wear resistance. for all four parameters, it can be stated that surface s2 machined at f = 0.2 mm/rev is the most wear-resistant and surface s3 machined at f = 0.3 mm/rev is the least. the same is observed according to the ssk parameter. however, based on the sku parameter, the most wear-resistant surface is s3, which is machined at f = 0.3 mm/rev. the values of these two parameters indicate that the surfaces that have more filled peak zones and, therefore, whose peaks wear out faster are more wear-resistant. the surface is characterized by the sbi parameter according to a different method: it is calculated as the ratio of the sq parameter to the material volume in the top 5% of the surface. as a consequence, the surface machined at a high feed rate (0.3 mm/rev) is ranked first in terms of wear resistance. it should be noted that among the analyzed parameters, the dimensions of sp and spk denote length, of sa1 and vmp represent volume, while ssk, sku and sbi are non-dimensional. if the volume parameter vmp is considered to be the base due to its modernity and accuracy, the order of the surfaces in terms of wear resistance is s2, s1 and s3. this is confirmed by the order of the parameters sp, spk, sa1 and ssk. the parameters that provide information about the fluid-retention capacity of the surfaces are summarized in fig. 9. the parameters sv, svk, sa2, vvv and svi characterize the valley zone and the fluid-retention capacity increases as their values increase. the core zone hungarian journal of industry and chemistry analysis of roughness parameters determining tribological properties 81 figure 5: 3d height parameters of the analyzed surfaces figure 6: the profiles extracted from the scanned surface (one profile per surface) and their 2d height parameters (average of the data from three profiles) figure 7: comparison of the 2d and 3d arithmetical mean heights is characterized by the parameters vvc and sci, moreover, higher values indicate greater fluid-retention capacities. this property is better in the case of low or negative ssk values. concerning the order of the surfaces, deviations can be observed, which may be derived from the different dimensions of the parameters. if the parameter vvv is considered to be the base, the order of the surfaces is s3, s2 then s1. this is not confirmed by any other parameters. regarding the valley zone, the parameters ssk, sa2 then svi yield the identical order, that is, s2, s1 then s3. based on the fluid-retention capacity of the core zone, that is, parameter vvc, the order is s3, s2 then s1. this order is confirmed by the other parameter of the core zone, sci. by analyzing the 2d profile parameters (fig. 10), it was found that all of them provide the same order as their 3d counterparts. by considering the 3d values as bases, the following can be stated based on the 2d pa49(2) pp. 77–84 (2021) 82 molnár and sztankovics figure 8: 3d roughness parameters characterizing wear resistance rameters with regard to the three surfaces. the values of the parameters rp are 46 to 83% of those of sp. the rate of the parameter rv varies between 40 and 52%, while those of rsk and rku are 21 − 143% and 71 − 112%, respectively. the differences in terms of tpk and rvk are smaller, namely 90− 112% and 90− 105%, respectively. in table 5, the order of the surfaces is summarized based on the findings detailed above concerning wear resistance and fluid-retention capacity. 5. conclusions from the analysis of the general characteristics of the surfaces, it was found that for the applied cutting data the hard-turned surface is anisotropic and the degree of isotropy varies between 1.5 and 4.3%. the power spectral density analysis clearly determined that the wavelengths are identical to the feed rates. the 3d height parameters (sv, sp, sz, sa) of the surfaces machined by lower feed rates, namely f = 0.1 and 0.2 mm/rev, show absolute differences of between 5 and 17% and this difference in the case of the 2d parameters (rv, rp, rz, ra) varies between 11 and 17%. by comparing the 3d and 2d parameters, it was found that the sa value of the 3d measurement is at most 15% higher than the ra value of the 2d measurement. the sv, sp and sz values can be up to 2.5 times higher than their 2d counterparts. from the analysis of the surface roughness parameters that indicate tribological properties, the following can be stated: figure 9: 3d roughness parameters characterizing fluidretention capacity 1. based on the parameters that evaluate the roughness peaks and indicate the wear resistance (sp, ssk, spk, sa1 and vmp), the most and least wear-resistant are the surfaces hard turned at feed rates of 0.2 and 0.3 mm/rev, respectively. the other parameters yielded different orders, which can be explained by their calculation methods. 2. the order of the surfaces with regard to the parameters of the core zone that indicate the fluid-retention capacity (vvc, sci) is identical: the surfaces machined at feed rates of 0.3 and 0.2 mm/rev exhibit the best and worst fluid-retention capacities, respectively. 3. the order of the surfaces with regard to the parameters of the valley zone that indicate the fluidretention capacity (ssk, sa2 and svi) is identical: the surfaces machined at feed rates of 0.2 and 0.3 mm/rev exhibit the best and worst fluid-retention capacities, respectively. the other parameters yielded different orders, which can be explained by their calculation methods. another useful research direction would be the comparison of different workpiece materials. in addition to this, based on systematic experimental design, carrying out hungarian journal of industry and chemistry analysis of roughness parameters determining tribological properties 83 figure 10: 2d roughness parameters characterizing wear resistance and fluid-retention capacity table 5: order of the surfaces based on the analyzed tribological properties and roughness parameters peak parameter order valley parameter order core parameter order sp s2 > s1 > s3 sv s3 > s1 > s2 vvc s3 > s1 > s2 ssk s2 > s1 > s3 ssk s2 > s1 > s3 sci s3 > s1 > s2 sku s3 > s2 > s1 svk s1 > s2 > s3 spk s2 > s1 > s3 sa2 s2 > s1 > s3 sa1 s2 > s1 > s3 vvv s3 > s2 > s1 vmp s2 > s1 > s3 svi s2 > s1 > s3 sbi s3 > s2 > s1 machining experiments using various cutting parameter setups would lead to generalizable statements. furthermore, why the fluid-retention capacity of the valley zone is characterized by relatively large deviations based on the different roughness parameters could be investigated. references [1] blawucki, s.; zaleski, k.: the effect of the aluminium alloy surface roughness on the restitution coefficient. adv. sci. technol. res. j., 2015, 9, 66– 71 doi: 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results and discussion surface characteristics analysis of tribological parameters conclusions hungarian journal of industry and chemistry vol. 52(1) pp. 15–18 (2024) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2024-03 membrane reactors in photocatalytic processes katalin bélafi-bakó1* and gábor tóth1 1 research group on bioengineering, membrane technology and energetics, university of pannonia, egyetem u. 10, veszprém, h-8200; hungary photocatalytic membrane reactors are integrated systems where the photocatalytic process and separation by a membrane occur simultaneously. this simultaneous arrangement has been found to be more effective than traditional methods. in this mini review, the membrane techniques applied as well as their features, behavior and operation in addition to some of the applications of pmrs are presented. keywords: membrane separation, pollutants, oxidation, membrane techniques 1. introduction membrane reactors are special setups where a chemical reaction step and a separation step take place simultaneously [1]-[3], moreover, the two steps are connected. in general, they are used in equilibrium reactions where catalysts are present and the insertion of a (in-situ or in-line) separator may enhance the effectiveness of the reaction. membrane reactors can be applied in, for example, the petrochemical industry for dehydrogenation and hydrogenation processes [3]-[4]. the reaction takes place in a membrane bioreactor if biocatalysts are used instead of catalysts, where bioprocesses and membrane techniques are coupled [5]. these systems have been studied extensively in our research group and various membrane techniques inserted into enzymatic or fermentation processes [6]-[8]. photocatalysis is a process where special semiconductor materials are used to facilitate redox reactions, i.e. oxidation, when they are irradiated with light of a suitable energy [9]-[11]. photocatalytic oxidation, which is characterized as an “advanced oxidation process” (aop), has recently been comprehensively studied and found to break down some organic pollutants in wastewater. titanium dioxide is widely used as a photocatalyst due to its high chemical stability, relatively low cost, optical and electronic properties as well as its non-toxicity. a semiconductor catalyst – mainly related to tio2 – is mostly applied as a powder suspended in a liquid, hence is referred to as heterogeneous photocatalysis. therefore, it is necessary to insert a separation step into the technology to recover it. this can be realized by membranes, which are able to prevent the catalyst from being washed out, moreover, received: 5 dec 2023; revised: 15 dec 2023; accepted: 20 dec 2023 *correspondence: belafine.bako.katalin@mk.uni-pannon.hu some membrane techniques are capable of controlling the amount of products or by-products in the photooxidation process [12]-[13]. these membrane processes have become more and more attractive due to their beneficial features, namely chemical additives are not necessary and little energy is required. when photocatalytic oxidation is integrated with membrane separation, photocatalytic membrane reactors (pmrs) can be assembled. when the catalyst is in a suspended form in the photoreactor, the system is often called a suspension photocatalytic membrane reactor (spmr). pmrs boast numerous advantages [13]-[14] when compared to conventional photocatalytic processes, e.g.: the photocatalyst remains in the reaction thanks to a membrane; the process can be continuous, moreover, the photocatalysts can be recovered and the products separated simultaneously; the treated water does not contain any biocatalysts; the process can be controlled better, moreover, is more stable and efficient; no additional operations are necessary, e.g. coagulation, flocculation, sedimentation, etc., moreover, their installation occupies less space and consumes less energy. 2. membrane techniques various membrane separation processes can be coupled to a photocatalytic reactor [1, 12-14], which are listed in table 1. among the pressure-driven methods, microfiltration, ultrafiltration and nanofiltration may be https://doi.org/10.33927/hjic-2024-03 mailto:belafine.bako.katalin@mk.uni-pannon.hu bélafi-bakó and tóth hungarian journal of industry and chemistry 16 applied. the driving force in these techniques is the transmembrane pressure and are often called “membrane filtration methods” since the separation is based on the pore size of the membrane. membrane filtration processes were the first membrane techniques applied in photocatalysis in water treatment technologies during the 1960s. pervaporation is a process where the liquid feed flows into the primary side of the non-porous membrane film and the permeate is obtained in vapor phase under a vacuum (which can be condensed to convert the permeate into a liquid). in membrane distillation, the volatile compounds of the feed are evaporated and passed through the pores of the hydrophobic membrane before being condensed into the permeate. the driving force is the difference in vapor pressure on either side of the membrane. in the case of membrane contactors, the membrane not only separates the phases but also functions as a contact site between them, facilitating the transportation of certain components. membrane contactors can be classified as gas–liquid, liquid–liquid and liquid–gas membrane contactors. although the main driving force is the difference in concentration, in some cases, solubility may play a role, e.g. when an organic solvent is applied in the secondary phase, extraction occurs whereby distribution coefficients are the determining factors. this kind of contactors are called pertractors (derived from the words ‘permeation’ and ‘extraction’). dialysis is driven by the difference in concentration on either side of the membrane and the transport mechanism is diffusion. regarding the membrane module, a flat sheet as well as hollow fiber modules are used in spmrs in addition to ceramic tubular modules. 3. photocatalytic membrane reactors membrane filtration techniques have been applied in pmrs to separate and recover the photocatalytic particles [13, 15-16]. in this way, the loss of photocatalysts can be minimized, rendering the operation more reliable and cost-effective. using pmrs, several types of dyes (congo red, methylene blue, rhodamine b, eosin y), pharmaceuticals (ibuprofen, diclofenac, carbamazepine, tetracycline), pesticides (diuron, chlorfenvinphos) and other pollutants (phenol, humic acids) were degraded before being removed. sedimentation of the suspended photocatalysts can be controlled by applying fine bubble aeration and intermittent membrane filtration as reported by huang et al. (2007) [17]. a pervaporation unit was integrated into the photocatalytic process to remove 4-chlorophenol (4‐cp) [18]. in this hybrid system, the solution contained the pollutant which passed through the photocatalytic reactor into the pervaporation module by means of a pump before the permeate was obtained as a vapor. the retentate was recycled in the photoreactor. it was found that the removal of 4‐cp was greatly enhanced by this integrated system, indicating a synergistic effect between photocatalysis and the pervaporation process. photocatalysis was coupled with membrane distillation [19] to remove 3 azo dyes from the water. 0.0014 m2 polypropylene (pp) hollow fiber membranes were used. a 3 dm3 photoreactor containing the dyes and the photocatalyst aeroxide tio2 p25 was positioned in front of the membrane module for the photocatalytic reaction. when the system was operated in batch mode, the photoreactor also acted as the feed tank. when the system was operated in continuous flow mode, an additional feed tank was applied to continuously supply fresh feedwater to the photoreactor. a uva lamp was positioned above the photoreactor as the light source. the fresh feedwater was heated to 333 k by a heater at the start of the experiment. the retentate was reintroduced into the feed tank and the permeate collected in the distillate tank. another type of separation which can be coupled with photocatalysis uses membrane contactors [12]. the main driving force of the separation is the distribution coefficient of the transported species. photocatalytic membrane contactors have several advantages compared to other configurations of reactors, e.g. it is possible to selectively separate the product(s) of interest during the photosynthetic process, preventing undesirable secondary reactions from occurring. dialysis was used in the spmr system where a model pollutant, namely 2,4-dihydroxybenzoic acid (2,4dhba), was mineralized from turbid waters by photocatalysis [20]. the membrane retained the tio2 catalyst in the photoreactor compartment, so filtration was unnecessary. meanwhile, the organic compounds were allowed to pass through the membrane without transmembrane pressure. table 1: membrane processes applied in photocatalytic processes membrane process reference ultrafiltration microfiltration nanofiltration molinari (2002) [13] pervaporation camera-roda (2007) [18] membrane distillation mozia (2008) [19] membrane contactor loddo (2011) [12] dialysis azrague (2007) [20] membrane reactors in photocatalysis 52(1) pp. 15–18 (2024) 17 4. special considerations when applying microfiltration or ultrafiltration, two different spmrs can be described [13] regarding the operation as presented in figures 1 and 2. in one of them, the catalyst is suspended in a recirculation reactor (tank), while the membrane module – as an external unit – is connected to the reactor. the permeate is forced to pass through the membrane by pressurizing the primary side of the membrane surface. this kind of operation often causes severe fouling which should be controlled by, for example, backwash or backflush [21]. to overcome fouling, another type of pmr was developed [22], where the membrane module is immersed in the reactor. the catalyst is suspended in the reactor and the permeate withdrawn by a vacuum pump. it can be referred to as an internal (or depressurized) system. as an example, the decomposition of reactive orange 29 (ro29) was carried out in this kind of submerged pmr. although external (pressurized) and internal (depressurized, submerged) membrane reactors are also well-known when treating wastewater, microorganisms are used during the degradation process, therefore, are considered as membrane bioreactors [23]-[24]. the two systems with the photocatalysts and biocatalysts, however, are analogous configurations of the membrane reactors, moreover, their operations are similar in several ways. 5. immobilized photocatalysts more recently, in addition to suspension photocatalytic membrane reactors (spmr), another configuration of membrane reactor known as an immobilized photocatalytic membrane reactor (ipmr) was studied, where the catalyst is immobilized on the membrane surface [16]. thus, the membrane has two functions namely to support photocatalysts and separate. photocatalysts can be fixed on the membrane by various methods, e.g.: physical deposition dip coating phase inversion hydrothermal synthesis—filtration electrospinning and hydrothermal reactions atomic layer deposition in these systems, the most important factor is the stability of the membrane since severe photodegradation might occur during the process. 6. outlook since pmrs were originally successfully developed for water treatment and environmental processes, their success was a motivation to expand the application areas [16]. recently, several novel usages of pmrs have been reported, e.g.: photocatalytic conversion of co2; photocatalytic water splitting for hydrogen production; other oxidative chemical processes like the conversion of ferulic acid into vanillin or the direct oxidation of benzene into phenol; disinfection of water. these new applications are making pmrs more and more known worldwide in industrial and environmental engineering areas, moreover, novel, innovative applications may arise. acknowledgements this research was partly supported by the national multidisciplinary laboratory for climate change, rrf2.3.1-21-2022-00014 figure 1: scheme of an external photocatalytic membrane reactor figure 2: schematic diagram of an internal photocatalytic membrane reactor bélafi-bakó and tóth hungarian journal of industry and chemistry 18 references [1] baker, r.w.: membrane technology and applications (second edition) (john wiley and sons, chichester, uk), 2004, isbn: 0-470-85445-6 [2] mulder, m.: basic principles of membrane technology (kluwer academic publishers, dordrecht), 1996, doi: 10.1007/978-94-009-1766-8 [3] noble, r.d.; 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(a) recursive definition given a knot sequence of real numbers in r.: t = (xo' xi' xz , ••• , xn, xn+l , ••• , xn+l+l) then we define z=o: { 1 if n0 .(x) = ,i 0 xi::;; x :s;;xi+l , i:::::o, ... ,n otherwise l >0: i=o, ... ,n (b) definition by divided differences we use the well-known divided differences to define with { {rx)1 if t ~ x (t-x)~ := 0 lu: ~ t<x contact information: e~mail: herrmann@ifam.uni-hanoover.de 106 i 11-,---1 !• i 0 t i 1 ~ i i ~ 0 l not(x) 2 1 .. 0.75 0.5 t"' ~ 0.25 l.. 0 l 0.75 l 0.25 ~­ ~ 0 n2s{x) (l5 1 t5 2 2.5 3 .3.5 4 4.5 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 fig.l in each figure we see two b-splines of order 0,1,2 and 3. (c) definition by the +-functions without the help of the divided differences we can use the +-functions alone to define the b-splines: i+l+1 nzj (x) := (xi+l+l -xi) · l k;i (xt -x)~ i+l+l it (xt -xz) r=i,r.=k , i =o, ... ,n (d) definition by construction let [a~b}t; r ~ a:= {xot•••txn+t }, x; e r, a=x0 <x1 <· .. <xn <xn+1 =b. then we define: s1(a):={se c1 1{a,b}:sltx,.x .• de ip1 ~t =o,.. .... n} for this vector space we have a basis built with the +­ functions: s1(a} =span< 1~.t,.x2 , ••• ,x1 ,(x-x1i +~ ••• ,(x-x11 ) 1 + > and we can prove the following theorem: theorem: let q..,. :={.x ... }~z,.a;, <xv+t• for each i e z there exists a unique ~pline function s e s1 (a} with ... s(x)=o in(-«>jlx,)u(x1+1• 1,oo) and js(:c}dx=l. it is not very surprising that we can prove it easily that the four definitions lead exactly to the same functions. theorem: all definitions above are equivalent. dermition: we will call the functions developed in the four definitions b-splines. basic properties we summarize some of the important properties of b­ splines in the following theorem: theorem: 1. we have n1/x) = 0 if x\l (xi'xi+l+l), 2. we have nz,;(x)e el-l if xe [xi'xi+l+d' 3. wehave nl,i(x)>o if xe (xi.xi+l+1), 4. we have the property of partition of unity: n-1 l n1,;(x) = 1 if xe [xi,xi+l+d i=-l remarks: l. this means that the b-splines have a small support. only in an interval with l + 2 knots we have a chance to find values unlike zero. 2. here we are told, that the b-splines have a defect of 1, therefore the b-splines of degree l are l-1times continuously differentiable. 3. the b-splines are positive functions. 4. we can conclude on the bound 1 for ali b~splines . seefig.j. t = (to, tt, t2, t:1, t4) = (0~ 1, 2~ a, 4) f(t) 1 t0.75 r .. 0.5 10.2!) [0 0.5 1 1.5 2 2.5 3 3.5 4 lt0.7~ [ o.i:> ; fig.2a 4 intervals /"~\ / '\ 0.25 i/ \""' ;m,....-/~"'----'-~..j....-...-!.1 -"'.;;;.~.;.,.,~---l--'-----'---· t 0 0.5 1 1.5 2 2.5 3 3.5 4 fig.2b 3 intervals fig.2 support-reduction of a b-spline of order 3 from 4 intervals to 2 intervals, if 1 is a knot of multiplicity 3. multiple knots given a knot sequence xo' x1, xz' .•. 'xn 'xn+l' ... , xn+l+l , we did not demand that ail points should be different. what happens if some neighbor points fall together? theorem: if xi = xi+ i = · · · = xi+l+i, then we have n 1,i (x;) = 0, i = o, ... ,n from this we conclude immediately that n1,i = 0, which is not a very interesting result. so we ask for the case when less than l + 2 knots coincide. theorem: if x; is a knot with multiplicity m ~ l , it follows the smoothness of a b-spline decreases therefore with multiple knots. the decrease of the smoothness comes together with a decrease of the support of the b-spline: theorem: if xi is a knot of multiplicity m ~ l , then the support of nr.i(x) is reduced from l +!intervals to l + 1-(m1) intervals. we show this behaviour in fig.2. 1 0.75 0.5 0.25 107 0 0.5 1 1.5 2 2.5 3 3.5 4 . fig.2c 2 intervals fig.3 example of a b-spline curve with knot sequence t=(o,o,o,o, 1,2,3,4,5,6,6,6,6). b-spline curves of degree 1 now we come to curves built with b-splinet, at first the definition: definition: given l e in and points 2 3 d0 ,d1' ... ,d 11 e ir or ir and a knot sequence then we call the following linear combination 1l b1(x) = ld;n1,;(x), i=o a b~spline curve of degree l for the knot sequence t. d0 ,d1p .. ,d 11 are the de boor puints, they build the de boor polygon. one of the most important properties for such a b­ spline curve is its local behaviour. if one of the points ji is changed, the curve will be changed in a small vicinity of ji only. this is what designers whish. so the front of a car can be changed whereas the back remains unchanged. this is the content of the following theorem: 108 theorem: given a b-spline curve n b1(x) = ld;n1,;(x), i=o with knot sequence t and x* e (xi,xi+l). the point on the curve belonging to x* is only influenced by the de boor points di_1,. •• ,dr hereby ji acts in (xpxj+l+l) only. figure 3 gives an example of a b-spline curve. bezier curves the main tool in constructing bezier curves are the berpstein polynomials. defmition: b," (x)= (; }' (!-x)~1 , i = 0, ... , n, x e [0,1] we summarize some important properties of the bernstein polynomials in the following theorem. theorem: bi11 (x) > 0 for xe (0,1) a ba {b;11 h=0, ... ,n is a basis for the vector space of all polynomials of degree ~ n . if lb~ (x)= 1 for xe (0,1) i=o definition: a bezier curve is defined as follows: if x 11 (x):= l:b.b~(x),xe (oj) i=o the points b; are called the controlpoints of the bezier cun·e. there are some relations between b-splines and beziersplines. the next theorem shows that each spline curve can be expressed in terms of b-splines. theorem: lets be a spline function of degree l in [ atb ]. tltefl we hal'e a unique representation it ~. 3 s(x} = £..id;.nu (x), d; e r ,xe [a,b] ; .. _, in a very special case we have a direct coincidence between b-splines and beziersplines. theorem: the b-splines nij (x) of degree i are exactly the bemsteitz polynomials b:(x). if the knot sequence t contains 2( i+ 1) elements where both 0 and / are of multiplicity l+ i: t=(o, ...• o. ...__,_.._ dt-tlli.iim'l l, ... ,l ) ............... tl+htws the algorithm of de boor and de casteljau the formula for a b-spline curve is not easy to handle. for polynomials we have the formula of horner for a quick evaluation of single values. for b-spline curves this part is played by the algorithm of de boor. algorithm (de boor) forb-splines given n+1 de boor points d0 ,d1, ••• ,dn,n?:.l, and a knot sequence find b(x*): 1. find r with xr ~ x* < xr+l * 2. calculate a~ x -xi . 1 l 1 , z = r + , ... ,r -z 1 zdi =(1-a t) d;_1 +atdt 3. for j=2,3, ... ,l,i=r-l+j, ... ,r * a! x -xi l xi+t-u-n -xi j/ = (1-a!) ji-li-1 +a! j/-t l i i l 4. then we have b(x*) = j; the following table gives an impression how this algorithm works. on the horizontal lines we multiply by a/ and on the diagonal lines by 1-a/. the sum of both values gives the new de boor point on the right: dr-1+1 -1 d r-1+1 dr-1+:!. -1 d r-1+2 -z d r-1+2 dr-1+3 -~ d r-1+3 -z d r-1+3 ji-i r-t ii, jtr -z d r {jl-lr tpr =b(x*) the most important advantage of this algorithm is how fast it works. it is possible to evaluate thousands of points in less than a second. so this algorithm makes it possible to change a curve and in the same way a surface nearly in real time. a similar algorithm for the bezier splines was developed by de casteljau. it is based on the recurrence relation: b;(x) = (1-x)b;-1(x)+b 1 l!-l(x) fig.4 13 given points which build a tunnel are interpolated with b-splines. algorithm (de casteljau) for beziersplines given n + 1 bezier points or control points e0 , ••• , en . find x 11 (x*): 1. 2. 3. 4. · -o -o ... -o .... start wzth b0 := b0 ,b1 := bl' ... ,b 11 := bn .... 1 -1 -1 calculate b0 ,b1 , ... ,h11 _ 1 using the recurrence relation above. continue calculating b~ , ... ,bli, i = 2, ... , n thenwehave x 11 (x*)=b;(x*). this calculation cav be filled in a table quite similar to the table for the de boor algorithm above. we have only to replace the de boor points a by the bezier points b and then to multiply in the horizontal line with x*, in the diagonal line with 1x*, and afterwards to sum up. interpolation using b-splines now we will try to compare both methods in their behaviour regarding interpolation problems. consider the points po, .f1, ... , pq-l in ir2 or ir3 • we want to find an interpolating spline curve. for the use of b-splines we could try to take each point in the knot sequence (1+1)-times. then the curve runs through each of the points, but it is really not a smoot!j curve. in each point there is perhaps a sharp cusp. this is therefore no answer to the problem. in order to combine the given points with the points in the knot sequence we should note, that in the interval [x0 , xz] less than l+ 1 b-splines are :1: 0 . so we try the following combination: this leads to the following linear system: it :lji ni;(xl+l,) = p.t, u =o,l, ... ,q-1 io::o 109 this is a system of q linear equations for the n+1unknown d0 ,dp ... ,jn.for q=n-1+2 thereare n + 1(n -l + 2) equations missing. for cubic splines (l=3) we have to find 2 equations more. a typical choice is to consider spline functions which are linear outside the interval [x0, x11 ] • they are called natural and the following two equations are based on the fact that their second derivative is zero: dn_zn~:n-2 (xn+l) +dn-ln~:n(xn+2) +dnn~:n (xn+3) = 0 altogether we come to the following pentadiagonal system for natural cubic splines: 6 12 6 jr ~o l 11 -11 11 0 1 4 1 0 dl po 0 j2 ~ 6 ~:t 0 0 1 4 h~ j pq-1 6 12 0 11 -11 in fig.4 we have interpolated 13 points, which could be understood to build a tunnel, using b-splines. but the oscilating behaviour of the curve is not acceptable. interpolation using beziersplinescomonotone interpoation after the bad result with our tunnel example using b-splines we are interested to develop a better method for interpolating given data. one reason for the misbehaved shape can be seen in fig.4. from the left hand side up to the midpoint the datas are monotone increasing, whereas the spline curve oscilates through the first four points. at first let us define what we want to understand by a comonotone interpolating procedure: deimition: consider the given data (x0,y0),(xpy1), ... ,(xn,yn) with x0 < x1 < ··· < xn. let se c1[x0 ,xn] be a function which interpolates these data. then we will calls comonotone with the data, iff s'(x)·m1 >0 if m; ¢0,xe (xi_1,xi) s"'(x} =0 if mi =0 this is easy to explain. the slope of the spline functions should always be the same sign as the slope of the straight line between two neighb< 'ur points. then swill be monotone increasing or decrea~ing in the same intervals where the data are monotone mcreasing or decreasing. respectively. 110 !) ''"""-'"'"~"--·,.. ... ·-··--,---., i\ 4 ., i ~r j 1 ~ ·~ " .; (j ·u ·4 ..:l {i fig.5 the same 13 given points as in fig a are now interpolated with the comonotone algorithm using bezier­ splines. the bernstein operator and its shape preserving behaviour i the· main point in developing our new algorithm is to use the bernstein operator. it works with the help of the bernstein polynomials. deimition: let f be a vector valued continuous function on the interval [0,1]. then the bernstein operator is defined as in the following theorem we summarize some of the most important properties regarding the shape preserving of the bernstein operator: theorem: for the bernstein operator we have: 1. f bounded ==> bnf is bounded (with the same bounds) 2. f ;?:: 0 in [0,1] :::::? bnf ~ 0 in [0,1] 3. bn/(0) = /(0), bnf(!) = /(1) 4. /monotone ==> bnf monotone 5. f convex ==> blff convex now we are able to explain the algorithm: comonotone algorithm: 1. construct the subknots t 0 , t 1 , •••• t '1.n + 1 x. -x. 1 witlt r. = ' ~hv t 3 • 2. calculate the difference quotients: y;yi-1 . 1 n nz; = , l = , ... , x; -xi-! 3. determine a piecewise linear comonotone function l by l( x; ) := y i , r( x; ) := d; with d0 :=2m1 -d1,dn :=2mn -dn-j andfor i=l, ... ,n-1 0 if mi ·m;+i =0 d ·m; 3mi+i -mi if o<lmtl~lm;+ji i .2 mi+i mi+l 3m; mi+l if jm; i> lmi+ll m; 2 4. calculate l(t1), l(t2i ), l(t2;+1), l(t2n) 5. apply in each subinterval the bernstein operator. this leads to the desired function: remark: the formula in 3. is the heart of the algorithm. the derivative di at the knots xi is evaluated in a way that the resulting linear spline function is comonotone with the data. because of the shape preserving behaviour of the bernstein operator we get therefore the desired comonotone cubic spline function. in fig.5 we show the tunnel data from above, but now comonotone interpolated. the result looks much better. conclusion in this paper we compared b-splines and beziersplines. after a short introduction for both spline cancidates we explained some of the most important properties. the similar algorithms of de boor and de casteljau lead to very fast evaluation processes. several figures show the different behaviour regarding the interpolation procedure. in contrast to the disadvantage of the monotony preserving of the b-splines we propose a comonotone interpolation algorithm using bezier splines. r symbols real numbers knots inr t = (x0 ~ .... xn+l+i) knot sequence n li b-splines (tx)~ +-function a =(x0 , ••• ,xn+l) given knots c1 1[a.b] (l-1)-times continuously differentiable functions ip 1 vector space of polynomials of degree less or equall s1(a) q"" b1(x) do, ... ,dn bt(x) xn(x) s(x) a/ po, ... ,pq l(x) vector space of spline functions infinite knot sequence b-spline curve de boor points bernstein polynomials bezier curve spline function coefficients in the de boor algorithm interpolation points linear spline function difference quotients references 1. costatini, p., morandi, r.: monotone and convex cubic spline interpolation, calcolo, 1984, 21,281-294 111 2. costatini, p., morat~di, r.: an algrithm for computing shape-preserving cubic spline interpolation to data, calcolo, 1984,21, 295-305 3. deppe, u.: anwendung der bem auf eine integralgleichung 1. art zur bestimmung der porenradienverteilung eines slp-katalysator­ pellets diploma thesis, universitat hannover, 1994 4. farin, g.: curves and surfaces for computer aided geometric design, academic press, boston et al., 1990 5. gronewold, g.: co-monotone splineinterpolation in chemical engineering, hung. j. ind. chern., 1997,25,59-62 6. herrmann, n.: hohere mathematik fur ingenieure i, ii, oldenbourg verlag, mtinchen, 1995 7. herrmann, n.: spline-funktionen und ihre anwendung, preprint institut fiir angewandte mathematik, uni. hannover, 1996 8. herrmann, n.: surface fitting in cagd via finite elements, hung. j. ind. chern., 1997,25,63-69 9. i!oschek, 1., lasser, d.: grundlagen der geometrischen datenverarbeitung, b. g. teubner, stuttgart, 2. ed. 1992 page 109 page 110 page 111 page 112 page 113 page 114 page 115 hungarian journal of industry and chemistry vol. 51(2) pp. 57–63 (2023) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2023-19 case study of continuous itaconic acid fermentation by aspergillus terreus in a bench-scale bioreactor éva hülber-beyer1*, nándor nemestóthy1 and katalin bélafi-bakó1 1 research group on bioengineering, membrane technology and energetics, university of pannonia, egyetem u. 10, veszprém, 8200; hungary itaconic acid (ia) is a highly important bioproduct. the traditional biotechnological production of organic acids generates large quantities of biomass and water streams as waste. bipolar membrane electrodialysis is a suitable technique for directly recovering ia from clarified fermentation broth whereby itaconic acid is separated without chemical loading. as a result, the remaining diluate stream can be reintroduced into the fermentation process. this membrane operation can be integrated into a continuous fermentation process in order to carry out the process using a high glucose concentration in the effluent, opening up new possibilities for the implementation of continuous itaconic acid fermentation. in this study, a possible highly successful implementation of this technique is presented. the applied gentle stirring technique as well as the low dilution rate of 0.007 s-1 is necessary to be complemented by highly efficient oxygenation, thereby promoting itaconic acid generation. with an inlet supplying pure oxygen gas, the acid accumulated and an average of 30.1 g·l-1 titer of ia was achieved in the effluent. the volumetric oxygen uptake rate was monitored during the fermentation which fluctuated from 40-88% so further investigation of this may be worthwhile in the future. keywords: bipolar membrane electrodialysis; clump morphology; integrated system; oxygen uptake rate 1. introduction itaconic acid (ia) – a five-carbon, unsaturated dicarboxylic metabolite of aspergillus terreus (a. terreus) – has important industrial applications, e.g. as a crosslinking agent in synthetic latex production and as a monomer for unsaturated polyester resins [1]. in addition, much research is being conducted into the potential for further applications of ia in food packaging, pharmaceuticals and environmental protection [2]-[3]. ia is an industrial biotechnological product [4]. one disadvantage of most technological solutions implemented in industry for the production of organic acid via fermentation is the generation of significant waste streams, e.g. massive amounts of biomass and waste water. bipolar membrane electrodialysis (edbm) is a promising technique in biotechnology since the separating force is not a chemical reaction based on the addition of a chemical compound but an electric voltage [5]. this separation method results in three valuable material streams: the product in acidic form as well as an alkaline solution generated from alkali metal ions separated from the broth and the diluate – the broth in the absence of small ionic compounds but containing all the residual nutrients. received: 15 oct 2023; revised: 18 oct 2023; accepted: 20 oct 2023 *correspondence: beyer.eva@mk.uni-pannon.hu in the case of ia, the applicability of edbm was proven in our laboratory not only from model solutions [6]-[7] but also on a real, clarified fermentation broth [8]. in the following step, our goal was to implement a continuous fermentation with a relevant titer of ia in the effluent. in the study on model solutions, it was established that the electrodialysis unit operated more efficiently when the concentration of ia was towards the higher end of the investigated range, namely 5-33 g·l-1. the effect of reintroducing the diluate from edbm back into the fermentation process has not yet been studied. a few studies, the last of which was published in 2000, have been reported on continuous ia fermentations with a. terreus as the producing organism [9]. the achieved acid concentrations, the effective volume and the applied dilution rates are listed in table 1. the application of the free mycelia of a. terreus resulted in a maximum ia concentration of 7.8 g·l-1 as reported by rychtera and wase [12]. immobilization [11],[13] by applying a complex reactor design [10] resulted in enhanced titers of ia (see table 1). the morphology of a. terreus is highly important. clumps (loose pellets) 0.4-0.5 mm in diameter are considered to be optimal for acid production [14], moreover, were found to be controllable by manipulating the degree of mechanical stress. https://doi.org/10.33927/hjic-2023-19 mailto:beyer.eva@mk.uni-pannon.hu hülber-beyer, nemestóthy and bélafi-bakó hungarian journal of industry and chemistry 58 in the case of fermentation with free mycelia, it is apparent that by reducing the dilution rate, the achievable titer of ia in the effluent is enhanced. therefore, it can be assumed that by using a wellselected apparatus with a low dilution rate, free-mycelia fermentation with pellet growth can be achieved, producing results similar to when immobilized. oxygen is an important substrate for ia formation [15]. during a batch operation, to achieve maximal biomass growth, 2% saturation of dissolved oxygen was shown to be sufficient but ia generation proved significantly better when above 30% [16]. an important factor influencing the production of ia is the variation of dissolved oxygen levels in the fermentation. the monitoring of oxygen uptake during continuous ia fermentation with a. terreus has not yet been reported in the scientific literature. 2. experimental methods 2.1. microorganism and culture media in this research, a. terreus nrrl 1960, a filamentous fungus, was used as the ia-producing organism maintained on potato glucose agar (honeywell fluka™, usa) into which solutions of 20 g·l-1 sodium chloride and 10 g·l-1 glucose monohydrate were added before sterilization. a conidial suspension served as the inoculum for the fermentation. the suspension was obtained from a solid-state colony in a roux culture flask with an agar surface area of 150 cm2 that was incubated for 7 days at 33 °c. the harvesting solution was 100 ml of a physiological saline solution containing 0.01 w/w % tween 80. the composition of 1 l of the continuous fermentation medium: 165.0 g of glucose monohydrate, 0.10 g of kh2po4, 3.0 g of nh4no3, 1.0 g of mgso4*7h2o, 5.0 g of cacl2*2h2o, 1.67x10-3 g of fecl3*6h2o, 8x10-3 g of znso4*7h2o and 1.5x10-2 g of cuso4*7h2o. the ph was set at 3.0 before sterilization with a 10% (w/w) sulphuric acid solution to prevent the glucose from browning during sterilization. the complete medium was sterilized in the reactor at 121 °c for 45 minutes. the composition of the refilling medium per liter: 206.25 g of glucose monohydrate, 0.10 g of kh2po4, 2.25 g of nh4no3, 1.0 g of mgso4*7h2o, 5.0 g of cacl2*2h2o and 8·10-3 g of znso4*7h2o, while the ph remained constant. during the last period of fermentation that lasted two days, the glucose-rich deacidified stream from electrodialysis was reintroduced. the chemicals applied in this study purchased from merck were of analytical reagent grade, except for glucose which was supplied by hungrana starch and isosugar manufacturing and trading ltd. 2.2. fermentation process the experiment was carried out in a lambda minifor (lambda instruments gmbh, switzerland) bench-top autoclavable laboratory fermenter equipped with a 3 liter nominal volume glass vessel. the effective volume was 1.8 l and the medium was tempered at 33 °c. this instrument was equipped with a special ‘fishtail’ up-and-down agitator (i.e. non-rotational), which facilitated the efficient transfer of energy in the liquid culture medium. according to its description, this kind of mixing is gentle but efficient in both the horizontal and vertical directions as well as provides optimal oxygenation and gas exchange in the absence of air flooding, which are advantageous properties when working with filamentous microorganisms. this technique was used to achieve clump growth of the productive strain during the continuous ia fermentation. table 1: continuous ia fermentations with a. terreus spp. as the producing microorganism veff : effective volume; d: dilution rate; u: flow rate; cia: itaconic acid concentration in the effluent *calculated values based on veff and d; **calculated value at the point of maximum productivity; ***when ph=3.1 ref. strain specification technique veff [ml] d [h-1] u [ml·h-1] (u = d*veff) cia [g·l-1] [10] a. terreus nrrl 1960 mycelia immobilized in a porous disk 3600 0.017 60 18.2 [11] a. terreus g-026 mycelia immobilized in polyacrylamide gels 100 0.04 4* 15** [12] a. terreus nrrl 1960 free mycelia 3000 0.04 120* 7.8*** [9] a. terreus nrrl 1963 free mycelia 1800 0.06 108* 0.3 [9] a. terreus nrrl 1963 free mycelia 1800 0.1 180* 0.15 [13] a. terreus nrrl 1960 mycelia immobilized on celite r-626 14 0.111 1.56* 11 continous itaconic acid fermentation 51(2) pp. 57–63 (2023) 59 this morphology proved to be the most efficient iaproducing form of a. terreus [14], the formation of which can be influenced by the degree of stirring. the applied up-and-down movement occurred at a rate of 3.0 s-1 during the experiment. the ph was not controlled. a low ph reduces the possibility of microbial contamination. according to hevekerl et al. [17], the growth rate is reduced when the ph is not controlled but similar ia concentrations can be achieved. moreover, significantly less biomass may be formed compared to when the ph is controlled. the potential uses of fungal biomass from the production of organic acids are limited and mostly regarded as waste. at the start of the fermentation, air was supplied at a rate of 1.5 volume gas per volume broth per minute (vvm). after one week, the air supply was replaced by pure oxygen gas at a rate of 0.2 vvm. 6 ml samples were taken daily with a sterile needle and syringe through a silicone septum on top of the fermenter. the instantaneous glucose and ia concentrations in the reactor were determined and the microscopic appearance checked. the oxygen uptake rate of the mycelia was determined daily. continuous operation of the fermenter started on day 4. the flow rate was 12 ml·h-1, corresponding to a dilution rate of 0.007 h-1. the refilling medium was introduced from above through a stainless steel pipe. the end of the pipe was 5 cm above the surface of the broth. the effluent was drained through another stainless steel tube that stretched to the bottom of the reactor vessel. a 2-channel precision peristaltic pump (masterflex l/s easy-load ii., masterflex llc, us) was used to simultaneously drain and refill. the direction of flow of the two streamlines countered each other. the effluent container was replaced every 24 hours and the collected effluent volume analyzed for glucose and ia content. collected effluent volumes with ia concentrations in excess of 20 g∙l-1 were combined and clarified by filtration using a glass fibre depth filter disk with a pore size of 1.2 µm (55 g·m-2, 270 µm thick). the ph of the clarified broth was adjusted to 5.0 before electrodialysis with a 10% (w/w) solution of sodium hydroxide. ia was recovered in a commercial edbm unit, resulting in three separate liquid fractions: 1. purified and acidified product stream; 2. alkaline solution; 3. diluate – containing components from the broth which failed to or could not penetrate the ion-exchange membranes in the module, e.g. glucose. the diluate was acidified to ph 3.9 with a 10% (w/w) solution of sulphuric acid. to maintain sterility, it was heat-treated for 30 mins at 90 °c and cooled to room temperature before being used in the continuous fermentation to replace the refilling medium every two days. 2.3. determination of oxygen uptake rate to determine the oxygen uptake rate (our), the air flow via the inlet was shut off and the rate at which the dissolved oxygen level decreased monitored. an in-line o2 probe (lambda instruments gmbh, switzerland) was connected with a precision amperometer (metrix mtx 3281, chauvin arnoux group, france), which recorded data every second for 30 seconds. then the air flow was restarted until an equilibrium was reached again, i.e. when the rate of oxygen consumption was equal to the rate of oxygen dissolution. three parallel data points were obtained when each measurement was made in µg(o2)∙l-1∙s-1 and averaged. since after a time, the biomass concentration could not be monitored in the bulk, it was not possible to record data per unit of biomass dry weight (bdw). 2.4. analytical methods ia concentration was determined by hplc on a yl9100-type device (young lin instrument co., ltd., south korea) containing a hamilton prp-x300 hplc column (150 x 4.1 mm, 7 µm) as well as a uv/vis detector at a detection wavelength of 210 nm. the analytical method employed a gradient elution, where the moving phase was comprised of ‘a’ (1 mm h2so4) and ‘b’ (gradient grade methanol, chem-lab nv, belgium) solutions (0 min – 100% a; 1 min – 70% a, 30% b; 6 mins – 70% a, 30% b; 8 mins – 100% a). before the analysis, the samples were filtered through a 0.2 µm pore-sized nylon syringe filter (nantong filterbio membrane co., ltd) before being diluted a 1000 times using 1 mm sulphuric acid. the injection volume was 100 µl. the glucose concentration was determined by the dnsa method once the sample had been appropriately diluted [18]. bdw was determined from 3 × 1.5 ml samples until only loose mycelia were present from which point on a homogeneous distribution of biomass was assumed until the 120th hour. the samples were centrifuged at 10,000 rpm for 5 minutes in 1.5 ml eppendorf tubes with precisely measured weights. the supernatant was removed and the sedimented cells resuspended in 1 ml of sterile water before the centrifugation process was repeated. the washing of wet mycelia was performed three times before the washed mycelia were dried at 80 °c to constant weight. a zeiss primostar microscope (carl zeiss ag., germany) was used to conduct the microscopic investigation using phase contrast equipment at 1000x magnification. 3. results and analysis the continuous fermentation lasted 547 hours (23 days), the final 460 h of which were operated with volume changes. the ph decreased to 1.9 but no ia was detected for a week despite the obvious growth of the fungus. the bdw achieved a concentration of 4 g·l-1 and its morphology resembled loose mycelia (figure 1). maintaining the sterility of the fermentation was challenging because of the significant amount of foam hülber-beyer, nemestóthy and bélafi-bakó hungarian journal of industry and chemistry 60 that formed. however, no microbial contamination was detected during the experiment. on day 4, the continuous operation was switched on at a dilution rate of 0.007 h-1, by which time large amounts of submerged spores had been produced by the fungus. the formation of spores and simultaneous germination was detectable throughout. low oxygen availability has been identified as the main parameter hindering the formation of ia. to overcome this, from the 167th hour onwards, pure oxygen was introduced into the fermenter instead of air. therefore, the equilibrium concentration of oxygen in the medium increased fivefold according to henry's law compared to that achievable with an air supply, allowing the gas inlet volume to reduce and the formation of foam to be moderated. the abundant oxygen supply enhanced the production of biomass and the mycelia conglomerated into large clumps with a diameter of 5-8 mm. the extracellular fluid was clear and pale yellow in color. to precisely determine the bdw in such an inhomogeneous broth, a very large sample size would have been ideal but the small effective volume of the bioreactor did not allow this. after switching to pure oxygenation, ia began to accumulate. over six days, the ia concentration reached 25 g·l-1 and remained above this value until the end of the experiment. a maximum concentration of 35 g·l-1 ia was measured in the effluent collected on days 15, 16 and 18. the fermentation did not reach a steady state (figure 2). the concentration of glucose in the bioreactor exceeded 120 g·l-1, but varied greatly during ia production. the ia concentration, however, did not follow these variations. the our was determined regularly between the 40th and 160th hour. under these oxygen-limited conditions, the biomass consumed oxygen at an average rate of 10 µg·l-1·s-1. nevertheless, measurements could be made since the apparent dissolved oxygen level was 6-7 mg·l-1. after replacing the air with oxygen and noticing that ia had started to accumulate, measurements were resumed from the 260th h onwards. the our exhibited unexpectedly large variations periodically (figure 2). a maximum time period of 47 h could be calculated from the discrete data. the maximum and minimum our values were between 48-65 and 8-19 µg·l-1·s-1, figure 1: macro-morphological evolution of a. terreus during the continuous ia fermentation figure 2: concentrations of glucose and ia as well as the measured instantaneous values of the oxygen uptake rate (our) in the fermenter continous itaconic acid fermentation 51(2) pp. 57–63 (2023) 61 respectively, resulting in at least a 40% change in this parameter during one period. the effluent collected from day 12 until day 19 with an ia concentration in excess of 20 g·l-1 was subjected to edbm to recover a pure solution of the acid. the glucose and ia concentrations of the effluent collected are presented in figure 3. the refilling medium was replaced in the 495th hour with this diluate without any supplementation. once the ia in the edbm module had been recovered, the glucose and residual ia concentrations in the diluate were 128 and 1.3 g·l-1, respectively. reintroduction of the unsupplemented diluate into the fermentation caused the glucose concentration in the bioreactor to decrease. the ia concentrations were 25.5 and 26.9 g·l-1 on the first and second day of diluate dosing, respectively. replacement of the refilling medium coincided with a sharp decrease in the our. the microscopic morphology shifted to elongated thin filaments from the densely branched thicker form previously present (figure 4). 4. discussion in this study, a continuous ia fermentation was performed using a. terreus as the producing organism. a special stirring technique was applied along with a high glucose centration and low dilution rate. it was observed that the oxygen supply is a key parameter to promote ia generation and growth of the microorganism in the preferred clump form. pure oxygen gas of 0.2 vvm was introduced into the fermenter instead of air. a maximum product titer of 35 g·l-1 was successfully achieved following the 16-day-long iaproducing period, which is higher than those reported in previous continuous fermentations. the average ia concentration in the effluent after 286 hours was 30.1 g·l-1, which approximates to the 33 g·l-1 concentration proposed for ia recovery by the edbm technique. for the first time, the volumetric our was measured in the broth during a continuous ia fermentation. the our was monitored during oxygenlimited and oxygen-enriched periods of the fermentation. during oxygen-limited periods, the our was quite stable at approximately 10 µg·l-1·s-1. it was found that with an unlimited supply of oxygen and under the applied conditions, the our varied periodically with sharply increasing and declining stages, achieving a maximum of 48-65 µg·l-1·s-1. unfortunately, the biomass concentration in the reactor could not be monitored once the clumps had grown, since specific data would be more informative. nevertheless, it can be assumed that the biomass concentration did not change drastically as the our increased or decreased during the 8 hours when it was measured more frequently 469 to 477 hours after the fermentation had begun. therefore, the sharp fluctuation in the our is highly important, which varied from 4088%, and the maximum periodic time was calculated to be 47 hours in duration. it is possible that the anomaly was a consequence of oxygen stress caused by the introduction of pure oxygen into the reactor. however, the formation and germination of spores during fermentation resulted in the presence of different growth kinetics simultaneously, which supposedly had an influence on the our. another uncontrolled parameter during the fermentation was the amount of light the glass fermenter was exposed to. it is known that illumination can influence the metabolic pathways of aspergilli [19][21]. oxygen could also be introduced through special membranes [22], which would possibly further diminish foaming of the broth. figure 3: glucose and ia concentrations in the collected effluent; the portions denoted with (*) were subjected to edbm product recovery while those labelled with (“) were collected when the diluate was recycled figure 4: the change in morphology after replacing the refilling medium with diluate from edbm: a) original morphology; b) morphology 24 h after the replacement; c) filamentous growth after 48 h hülber-beyer, nemestóthy and bélafi-bakó hungarian journal of industry and chemistry 62 to the best of our knowledge, a diluate was recirculated from the edbm product recovery operation for the first time. the reintroduced diluate contained glucose and residual ia concentrations of 128 and 1.3 g·l-1. during electrodialysis, the monovalent metal ions and some of the divalent ones were separated from the alkaline stream. even though these ions were not supplemented by the diluate, which also contained 37.4% less glucose than the original refilling medium, ia continued to be produced in the reactor. the microscopic morphology of fungus changed into its filamentous form, indicating that only a limited amount of nutrients was available. this case study suggests that after appropriate supplementation, it would be suitable for the diluate to be reintroduced into the ia fermentation. further experiments shall be conducted in the future while paying special attention to the composition of the diluate from edbm. more continuous fermentations shall be performed to obtain significant results and collect data on the volume of biomass, possibly using a reactor volume at least one order of magnitude larger. although the special mixing technique in the bioreactor contributed to the formation and maintenance of fungal clumps, under oxygen-limited conditions, biomass growth was slow and loose mycelia formed. oxygen enrichment also seemed to be important to develop the optimal ia-producing morphology. 5. conclusions in this study, a possible application of continuous ia fermentation using a. terreus was presented. an average ia concentration of the effluent of 30.1 g·l-1 was achieved, which to the best of our knowledge is the highest titer obtained by adopting such a process. the availability of oxygen and gentle mixing contributed to the formation of fungal clumps, which are the preferred conditions for ia production. the applied low dilution rate proved to be adequate to achieve a high ia concentration. effluent collected from the fermentation was subjected to edbm in order to recover the ia. the diluate stream of the downstream operation was reintroduced into the same fermentation. ia continued to be produced even though the microscopic morphology of the fungus shifted to thin filaments. supplementation of the diluate will be an important research area in the future. in order to account for the periodic changes in the our during the productive stage of the fermentation, further research must be carried out. the our measurement implemented could be easily automated and by taking frequent measurements, the nature of this periodicity could be determined. references [1] di lorenzo, r.d.; serra, i.; porro, d.; branduardi, p.: state of the art on the microbial production of industrially relevant organic acids, catalysts, 2022, 12(2), 234, doi: 10.3390/catal12020234 [2] teleky, b.-e.; mitrea, l.; plamada, d.; nemes, s.a.; călinoiu, l.-f.; pascuta, m.s.; varvara, r.-a.; szabo, k.; vajda, p.; szekely, c.; martău, g.-a.; elemer, s.; ranga, f.; vodnar, d.-c.: development of pectin and poly(vinyl alcohol)-based active 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https://doi.org/10.33927/hjic-2020-21 hungarian journal of industry and chemistry vol. 53(2) pp. 73–78 (2025) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2025-20 nitrite and nitrate analysis by capillary electrophoresis with direct uv absorbance detection: a mini-review róbert farsang1, kinga hogyor1, gábor járvás1* and andrás guttman1,2 1 translational glycomics research group, research institute of biomolecular and chemical engineering, university of pannonia, egyetem u. 10, veszprém, 8200, hungary 2 horváth csaba memorial laboratory of bioseparation sciences, research centre for molecular medicine, faculty of medicine, university of debrecen, nagyerdei krt. 98, debrecen, 4032, hungary the analysis of nitrite and nitrate ions is of great importance in environmental samples, food and various human samples. in contrast to conventional spectrophotometric methods, nitrite and nitrate ions are relatively easy to analyze by capillary electrophoresis as both are negatively charged over a wide ph range as well as absorb over a broad uv range so that they can be analyzed simultaneously by capillary electrophoresis. in this paper, different separation strategies for the analysis of nitrite and nitrate by capillary electrophoresis with direct uv abso rbance detection are presented. keywords: capillary electrophoresis, nitrite, nitrate, analysis 1. introduction the analysis of nitrite (no2 -) and nitrate (no3 -) ions is of great importance in several aspects, especially in the fields of food safety [1], environmental monitoring [2] and protection [3], drinking water quality management [4] as well as human health [5]. monitoring nitrate levels in ambient water samples is important for environmental protection as high levels contribute to eutrophication, which reduces the oxygen content of natural bodies of fresh water through algal overgrowth [3]. nitrate and nitrite are harmful in high concentrations. in the human body, nitrite converts hemoglobin into methemoglobin, which cannot transport oxygen [6], moreover, is also converted in the body into nitrosamines, which are carcinogenic [7]. nitrite is often used to preserve meat products so monitoring its limit exceedance is a major analytical problem [8]. nitric oxide (no), produced in the body, is a vasodilator signal transduction molecule that is not stored, making its direct diagnostic measurement difficult. however, its degradation products (nitrite and nitrate) can be measured, so that the excessive production of nitric oxide can be monitored by determining nitrite and nitrate concentrations in human serum [9]. since nitrite and nitrate molecules are excreted in urine, their concentrations can also be an indicator of some diseases [10]. received: 18 aug 2025; revised: 22 aug 2025; accepted: 22 aug 2025 *correspondence: jarvas.gabor@mk.uni-pannon.hu the most commonly used methods for nitrate determination can be classified into three types based on their underlying analytical approaches: (1) direct determination (colorimetry, potentiometry, uv absorption and chromatography); (2) reduction of nitrate with ammonium or nitric oxide followed by detection of the concentration of the product (colorimetry, potentiometry, fluorimetry and coulometry); (3) a colorvariable complexation reaction of the nitrate [11]. the most widely used method for the determination of nitrite is the griess test, which is based on the formation of an azo dye in the presence of nitrite in an azo coupling reaction, which allows quantification by spectrophotometric measurement [12]. nitrite and nitrate have direct absorbance in the uv range 190-250 nm and a single negative charge over a wide ph range, so they can be simultaneously analyzed by the capillary electrophoresis (ce) separation method. in this mini-review paper, capillary electrophoresis separation methods using direct uv absorbance detection for the analysis of nitrite and nitrate ions are presented. 2. basics of nitrite and nitrate separation by ce nitrite and nitrate are relatively small ions, so capillary zone electrophoresis (cze) is an effective method for https://doi.org/10.33927/hjic-2025-20 mailto:jarvas.gabor@mk.uni-pannon.hu farsang, hogyor, járvás and guttman hungarian journal of industry and chemistry 74 separating these analytes. the electrophoretic mobility of nitrite and nitrate ions is determined by their hydrodynamic volume to charge ratio. both ions have a negative charge over a wide ph range (~ph > 4), so their separation is due to the difference in their hydrodynamic volume within this ph range. most capillary electrophoresis methods use this concept to facilitate separation, because the high separation power of ce provides an efficient way to separate such compounds over relatively short analysis times [13]-[25]. the difference in mobility can be significantly increased if the ph is reduced below 3.5, since the pka of nitrite is 3.15. therefore, the mobility of nitrite is significantly reduced while that of nitrate remains unchanged (pka = -1.3), resulting in better separation, i.e. higher resolution. given that its decreased mobility also means that the nitrite and nitrate peaks are shifted in the electropherogram, the migration time of the nitrate peak is shorter as reported in [26]-[30]. these methods are highly sensitive to the ph of the background electrolyte (bge), moreover, even a small alteration can significantly affect the electrophoretic mobility of nitrite. on the other hand, nitrate is less affected, so the relative migration times of the sample components can vary significantly. different methods published in the literature based on capillary zone electrophoresis to determine the nitrite and nitrate by absorbance detection are listed in table 1. the sample types, capillary dimensions, separation medium, possible methods for modifying electroosmotic flow (eof), injection methods, detection wavelength, limit of detection (lod) values, separation voltage and analysis time are all compared. 3. electroosmotic flow modification electroosmotic flow is often an effective method to improve ce separation. the phenomenon is based on the fact that the silanol groups on the inner wall of the bare fused-silica (bfs) capillary are deprotonated at higher phs (> 4), so the positively charged buffer components electrostatically attach to the negative surface of the inner capillary wall. the positive layer migrates towards the cathode under the applied electric field, creating a bulk flow across the entire cross-section of the capillary [31]. the negatively charged sample components migrate towards the detector window under reversed polarity, that is, the cathode on the injection side, resulting in upstream eof (flow towards the inlet) in the bfs capillary. this increases the migration time of the sample components and can also cause peak broadening by increasing electromigration dispersion. to reverse the direction of the eof in a bfs capillary, it is possible to coat the inner wall of the capillary with temporarily or permanently positively charged materials. in the reviewed publications, cetrimonium chloride (ctac) [14,18,27]; didodecyldimethylammonium bromide (ddab) [26]; ofm-oh[15,17,19,20,22,23]; tetradecyltrimethylammonium bromide (ttab) [24],[25]; tetradecyltrimethylammonium hydroxide (ttaoh) [29] and spermine [28] were used as dynamic eof modifiers. in one case, a polyethyleneimine (pei) coating as a permanent eof modifier was used [13]. in another publication, the inner wall of the capillary was protonated in a highly acidic medium, reversing the direction of the eof [30]. most publications demonstrate a method that reduces the migration time by reversing the direction of the eof while still achieving the baseline separation of nitrite and nitrate due to the high efficiency of ce [13-15,17-20,22-30]. studies have been published where the direction of the eof remains unchanged so that the upstream eof is able to remove the large sample matrix from the capillary inlet end, making the degree of conductivity during separation more consistent despite the large volume hydrodynamically injected [16],[21]. 4. sample types nitrite and nitrate content were determined on several types of samples such as biological samples (rat brain [20],[27]; human plasma [15,20,21,23-25]; human serum [17]; human urine [17],[19]; human extracellular fluids [25] and food samples [13,22,30]), water samples (drinking water [18]; environmental water [16]) and artificially produced samples [14,26,29]. for liquid samples, with the exception of filtration before separation, sample preparation is by and large unnecessary [16],[18]. nitrite and nitrate are often extracted from solid samples after homogenization and filtration [13,22,30]. 5. quantitative analysis one advantage of cze separation is that given the relatively low concentration of buffer solutions, their viscosity is basically equal to that of water. as a result, they can be efficiently injected hydrodynamically (or hydrostatically) from a sample matrix of similar viscosity, obtaining a high degree of reproducibility. the peak areas of the sample components obtained from the electropherogram are proportional to the volume of the injected sample matrix, so that quantification of the analytes is possible using their areas directly after appropriate calibration curves are recorded. although electrokinetic injection often results in a much better lod (up to nanomolar concentrations [14]), this is not always advantageous in terms of quantification due to conductivity-dependent electrophoretic mobility of analytes. depending on the conductivity of the sample, different amounts of nitrite and nitrate ions enter the capillary during electrokinetic injection because of the differences in mobility between these ions and also due to the different degree of voltage drop at the boundary between the sample plug and the bge capillary. thus, samples containing the same concentration of nitrite and nitrate may have different peak areas, preventing direct concentration determination if electrokinetically injected [32]. nitrite and nitrate analysis by capillary electrophoresis 53(2) pp. 73–78 (2025) 75 table 1: separation strategies of nitrate and nitrite by capillary electrophoresis sample type capillary separation media eof modifier (reverse eof) sample injection detection (nm) limit of detection sep. volt. (kv) sep. time (min) ref. meat products, vegetables 75 cm (60 cm eff.) 75 µm i.d. 20 mm tris-hcl; ph 7.5 pei coating 4 kpa 10 s 210 1.6 µm nitrate; 2.3 µm nitrite 28 2.5 [13] reagent grade solution 50 cm (45.5 cm eff.) 50 µm i.d. 20 mm tetraborate; ph 8.94 1.1 mm ctac (a) 6.9 kpa 7 s; (b) 7.5 kv 5 s 200 (a) 6.45 µm nitrate; 8.7 µm nitrite; (b) 16.1 nm nitrate; 21.7 nm nitrite 10 6 [14] human plasma 72 cm; 75 µm i.d. 25 mm sodium phosphate 5% ofm-oh6 kv 20 s 214 50 µm nitrate; 50 µm nitrite 21.6 n/a [15] environmental water 60 cm (50 cm eff.) 50 µm i.d. 75 mm tris-hcl; ph 7.25 55 kpa 8 s 200 0.21 µm nitrate; 0.43 µm nitrite 30 4.5 [16] human urine, human serum 60 cm; 100 µm i.d. 15 mm sulfate; ph 8.0, 2.5% ofm-oh 10 cm 30 s (hydrostat.) 214 10 mm nitrate 15 4 [17] drinking water 62 cm (53.5 cm eff.) 75 µm i.d. 50 mm tris-hcl; ph 7 0.1 mm ctac (a) 3 kpa 3 s (b) 5 kv 15 s 200 (a) 5.3 µm nitrate 14.4 µm nitrite; (b) 160 nm nitrate 65 nm nitrite 20 2.2 [18] human urine 104 cm eff.; 75 µm i.d. 25 mm sodium sulfate-; ph 4.8 5% ofm-oh 3 kpa 30 s 6 kv 20 s 214 n/a 30 5 [19] human plasma; rat brain 60 cm; 100 µm i.d. 10 mm sodium sulphate 2.5% ofm-oh 10 cm 20 s (hydrostat.) 214 0.4 µm nitrate; 0.54 µm nitrite 15 3.1 [20] plasma and cerebrospinal fluid (csf) 36.5 cm (30 cm eff.) 75 µm i.d. 10 mm borate; ph 10 3.5 kpa 5 s 214 0.43 µm nitrate; 0.57 µm nitrite 15 5.2 [21] farsang, hogyor, járvás and guttman hungarian journal of industry and chemistry 76 table 1 (continued): separation strategies of nitrate and nitrite by capillary electrophoresis sample type capillary separation media eof modifier (reverse eof) sample injection detection (nm) limit of detection sep. volt. (kv) sep. time (min) ref. range of food (cheese, cabbage, puree, fruit juice, water, variety of meat products) 75 cm (50 cm eff.) 75 µm i.d. 1540 ppm nacl (1000 ppm chloride) electrolyte 0.5 mm ofm-oh20 kpa•s 210 n/a 20 2 [22] human plasma 65 cm 75 µm i.d. 750 mm nacl 5% ofm-oh 10 cm 90 s (hydrostat.) 214 1.6 µm nitrate 20 15.5 [23] human plasma 67 cm (60 cm eff.) 50 µm i.d. 200 mm lithium chloride; 5 mm triethylamine 0.7 mm ttab 3.5 kpa 5 s 200 n/a 17 4.5 [24] human extracellular fluids 47 cm (40 cm eff.) 50 µm i.d. 5 mm tris-hcl; 150 mm sodium chloride, ph 7.4 2 mm ttab n/a 214 n/a 10 3.2 [25] reagent grade solution 30 cm (7 cm eff.) 50 µm i.d. 20 mm phosphate; ph 2.5 0.10 mm ddab 5 kv 5 s 214 100 nm nitrate; 1 µm nitrite 30 0.17 [26] rat brain 40 cm (22 cm eff.); 75 µm i.d. 20 mm phosphate; ph 3.5 2 mm ctac 16 kv 2 s 214 2.86 µm nitrate; 0.96 µm nitrite 10 1.5 [27] rat plasma 72 cm (22 cm eff.) 75 µm i.d. 50 mm phosphate; ph 3 0.5 mm spermine 17 kpa 1.5 s 214 6.0 µm nitrate; 10 µm nitrite 25 3.5 [28] rat airway surface liquid (asl) 72 cm (22 cm eff.) 50 µm i.d. 50 mm phosphate; ph 3 0.5 mm spermine 17 kpa 1.5 s 214 10 µm nitrate; 30 µm nitrite 26 6.0 [28] reagent grade solution 85 cm (50 cm eff.) 75 µm i.d. 10 mm imidazolesulfate; 2 mm 18crown-6; ph 3.8 0.05 mm ttaoh 5 kv 5 s 214 n/a 30 2.75 [29] vegetables (spinach, chard, carrots) 32.5 cm (21.5 cm eff.) 75 µm i.d. 50 mm phosphate; ph 2.5 reverse eof due to the acidic buffer n/a 214 4.8 µm nitrate; 7.4 µm nitrite 25 1.9 [30] nitrite and nitrate analysis by capillary electrophoresis 53(2) pp. 73–78 (2025) 77 in most publications reviewed in this paper, linear calibration equations covering several orders of magnitude with r2 fit >0.99 assumed for the two sample components [13,14,18-20,23-27,30]. 6. conclusions the need for the quantification of nitrite and nitrate in the food, environmental protection and diagnostics industries requires the development of sensitive and high-resolution analytical methods. capillary zone electrophoresis with uv absorbance detection may offer a promising alternative to conventional spectrophotometric methods for determining nitrite and nitrate content which rely on color-change reactions. the great advantages of cze are extremely short analysis times, few necessary resources for sample preparation, excellent lod values, the automation capability and the simultaneous determination of the two sample components. in this mini-review, the most popular methods for the cze-based analysis of nitrite and nitrate by uv detection have been presented. abbreviations bfs bare-fused silica bge background electrolyte ce capillary electrophoresis ctac cetrimonium chloride cze capillary zone electrophoresis ddab didodecyldimethylammonium bromide eof electroosmotic flow i.d. inner diameter lod limit of detection pei polyethyleneimine ttab tetradecyltrimethylammonium bromide ttaoh tetradecyltrimethylammonium hydroxide acknowledgement the authors gratefully acknowledge the support of the university of debrecen program for scientific publications and the tudfin grant #1g3dbk0ctuf247 as well as the atbg korea v4 joint project (#20231.2.1-era_net-2023-00015), university research fellowship programme (2024-2.1.1-eköp), and the advanced_150780 grant from the national research development and innovation office of hungary. this is contribution #225 from the horváth csaba memorial laboratory of bioseparation sciences. the research presented in the article was carried out within the framework of the széchenyi plan plus program with the support of the rrf 2.3.1-21-2022-00008 project. references [1] karwowska, m.; 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revised: 28 aug 2025; accepted: 29 aug 2025 *correspondence: skodane.foldes.rita@mk.uni-pannon.hu methods necessitate the application of strong bases like alkali alkoxides [7]. recently, much attention has been paid to the development of synthetic methodologies towards the use of the abundant, low-cost and safe raw material co2 as a c1 building block for the construction of organic molecules [13]-[15]. these methods include several pathways towards 2-oxazolidinones starting from unsaturated (propargylic, allylic, allenic) amines [16], aziridines [17], amino alcohols [18] and propargylic alcohols together with primary amines [19]. a great variety of catalysts were tested for the latter reaction, including metal salts, -complexes or -nanoparticles (ru [20], cu [21]-[25], ag [23,26-28] or zn [29]) and organocatalysts [30]-[33]. these procedures usually require high pressure co2 (often exceeding 5 mpa). to the best of our knowledge, these methodologies have yet to be applied for the synthesis of steroidal oxazolidinones. based on our previous experience concerning the application of ionic liquids as solvents and/or catalysts for the conversion of steroidal substrates [34]-[37] and the fact that cu(i) is known to be a highly suitable catalyst for the activation of the c≡c triple bond [38]-[40], the possibility of using a cu(i)/[bmim][bf4] catalytic system was explored, previously only reported for simple molecules [21], to produce 17-spiro-5’oxazolidin-2’-ones with the estrane skeleton from the https://doi.org/10.33927/hjic-2025-24 mailto:skodane.foldes.rita@mk.uni-pannon.hu ispán, küzdő, gecse, vágvölgyi, ulbert, kovács and skoda-földes hungarian journal of industry and chemistry 102 readily available 17α-ethynylestradiol, a well-known synthetic hormone that exhibits estrogenic activity. 2. experimental 2.1. general analytical methods 1h and 13c{1h} nmr spectra were recorded in cdcl3 by a bruker avance ii spectrometer at 400.13 mhz and 100.62 mhz, respectively. chemical shifts (δ) are reported in ppm relative to chcl3 (7.26 ppm (1h) and 77.00 ppm (13c)). esi-ms spectra were obtained using a sciex 3200 q trap ms/ms mass spectrometer (ab sciex llc, marlborough, usa) in the positive electrospray ionization mode. all reactions were monitored by thin layer chromatography on merck neutral aluminum oxide (tlc, uv254 nm) plates. tlc visualization was accomplished in an iodine chamber. column chromatography was carried out on aluminum oxide (40-300 µm, 60a, neutral, brockmann i, thermo scientific chemicals). the copper leaching was evaluated by icp-oes. 2.2. materials all reagents were purchased from sigma-aldrich. the copper complex with 3-(carboxymethyl)-1-methyl-1himidazol-3-ium ligands (cul2) was synthesized by a known method [41] and its spectroscopic properties corresponded well to data found in the literature. the steroid required for the synthesis was provided by the chemical works of gedeon richter plc. 2.3. general procedures for the synthesis of steroidal oxazolidinones in a typical experiment, the catalyst (0.010 mmol) was placed in a stainless-steel autoclave. the steroid (0.17 mmol), amine (0.17 or 0.34 mmol) and [bmim][bf4] were transferred into it. the autoclave was charged with carbon dioxide (0.5-4.0 mpa) and heated while stirred in an oil bath at 120 °c for 24 hours. after having been cooled to room temperature, the product was extracted with diethyl ether (5x3 ml) from the ionic liquid containing the catalyst that was reused after ether residues had been removed under vacuum. the reaction mixtures were analyzed by 1h nmr measurements. the products were purified by column chromatography (al2o3, toluene/meoh, 10:1). 2.4. characterization of the products (17s)-3’-benzyl-4’-methylene-2’-oxo-spiro[3hydroxyestra-1,3,5(10)-trien-17,5’-oxazolidine] (3a) 1h-nmr (cdcl3, 400.13 mhz) δh: 7.37-7.27 (5h, m, nch2-ar); 7.08 (1h, d, j=8.4 hz, 1-h); 6.61 (1h, dd, j=2.6 hz; 8.4 hz, h-2); 6.55 (1h, d, j=2.6 hz, 4-h); 4.85-4.93 (1h, brs, oh); 4.82 (1h, d, j=15.7 hz, nch2,a-ar); 4.47 (1h, d, j=15.7 hz, n-ch2,b-ar); 4.24 (1h, d, j=2.9 hz, c=ch2,a); 4.08 (1h, d, j=2.9 hz, c=ch2,b); 2.87-2.77 (2h, m, 6-h2); 2.45-2.38 (1h, m, 11-hα); 2.19-1.22 (12h, m, ring protons); 1.02 (3h, s, 18h3). 13c{1h}-nmr (cdcl3, 100.62 mhz) δc: 156.5; 153.7; 149.7; 138.1; 135.5; 132.2; 128.8 (2c); 127.9; 127.6 (2c); 126.6; 115.4; 112.9; 94.9; 84.4; 48.4; 48.2; 45.5; 43.4; 39.0; 35.5; 31.3; 29.7; 27.5; 26.1; 23.1; 15.1. esi-ms: [m+h]+: 431.00 m/z, calculated molecular mass: 429.97 da. rf: 0.51 (al2o3, toluene/meoh, 10:1), white powder. yield: 80%. (17s)-3’-(4-methylbenzyl)-4’-methylene-2’-oxo-spiro[3hydroxyestra1,3,5(10)-trien-17,5’-oxazolidine] (3b) 1h-nmr (cdcl3, 400.13 mhz) δh: 7.24-7.16 (4h, m, nch2-ar); 7.09 (1h, d, j=8.6 hz, 1-h); 6.69 (1h, dd, j=2.7 hz; 8.6 hz, h-2); 6.63 (1h, d, j=2.7 hz, 4-h); 6.42-6.59 (1h, brs, oh); 4.82 (1h, d, j=15.8 hz, nch2,a-ar); 4.47 (1h, d, j=15.8 hz, n-ch2,b-ar); 4.32 (1h, d, j=2.9 hz, c=ch2,a); 4.15 (1h, d, j=2.9 hz, c=ch2,b); 2.78-2.86 (2h, m, 6-h2); 2.37-2.48 (1h, 11hα); 2.39 (3h, s, 4’-me); 2.24-1.29 (12h, m, ring protons); 1.03 (3h, s, 18-h3). 13c{1h}-nmr (cdcl3, 100.62 mhz) δc: 156.8; 154.1; 149.4; 137.8; 137.4; 132.2; 131.5; 129.4 (2c); 127.4 (2c); 126.3; 115.4; 113.0; 95.0; 84.8; 48.3; 48.0; 45.1; 43.3; 38.9; 35.4; 31.2; 29.5; 27.4; 26.0; 23.0; 21.2; 15.0. esi-ms: [m+h]+: 445.40 m/z, calculated molecular mass: 443.85 da. rf: 0.48 (al2o3, toluene/meoh, 10:1), white powder. yield: 79%. (17s)-4’-methylene-2’-oxo-3’-(4-trifluoromethylbenzyl)spiro[3-hydroxyestra-1,3,5(10)-trien-17,5’-oxazolidine] (3c) 1h-nmr (cdcl3, 400.13 mhz) δh: 7.62-7.66 (2h, m, h3’, h5’); 7.39-7.45 (2h, m, h2’, h6’); 7.08 (1h, d, j=8.3 hz, h-1); 6.66 (1h, dd, j=3.0 hz; 8.3 hz, h-2); 6.60 (1h, d, j=3.0 hz, 4-h); 6.08-6.26 (1h, brs, oh); 4.87 (1h, d, j=16.1 hz, n-ch2,a-ar); 4.56 (1h, d, j=16.1 hz, n-ch2,b-ar); 4.24 (1h, d, j=3.2 hz, c=ch2,a); 4.17 (1h, d, j=3.2 hz, c=ch2,b); 2.73-2.91 (2h, m, 6-h2); 2.41-2.51 (1h, m, 11-hα); 1.23-2.26 (12h, m, ring protons); 1.03 (3h, s, 18-ch3). 13c{1h}-nmr (cdcl3, 100.62 mhz) δc: 156.6; 154.0; 149.4; 139.4 (q, j=1.1 hz); 137.8; 131.6; 130.2 (q, j=32.0 hz); 127.7 (2c); 126.4; 125.8 (2c, q, j=3.7 hz); 124.1 (q, j=272.1 hz); 115.4; 113.0; 95.3; 84.8; 48.4; 48.2; 45.0; 43.3; 38.9; 35.5; 31.3; 29.6; 27.5; 26.0; 23.1; 15.0. esi-ms: [m+h]+: 499.00 m/z, calculated molecular mass: 498.00 da. rf: 0.54 (al2o3, toluene/meoh, 10:1), white powder. yield: 67%. 3. results and discussion first, 17α-ethynylestradiol (1) reacted with benzylamine (2a) (figure 1) in the presence of cucl (table 1, entry 1) and cui (table 1, entry 2) in the ionic liquid 1-butyl-3methylimidazolium tetrafluoroborate ([bmim][bf4]) at high pressure (4.0 mpa). the reaction mixture was synthesis of n-benzyl 17-spiro-5’-oxazolidin-2’-ones with the estrane skeleton 53(2) pp. 101–106 (2025) 103 extracted with diethyl ether then analyzed by tlc and, after the solvent had been removed, with 1h nmr. interestingly, in contrast to the reaction of 1-ethynyl-1-cyclohexanol with cyclohexylamine reported [21], cui was found to be a superior catalyst compared to cucl, so further carboxylation reactions were carried out using the former one. the following experiments were performed under lower pressure to determine the mildest conditions appropriate for the synthesis of steroidal oxazolidinones. although the yield of product 3a decreased considerably when the pressure was reduced (table 1, entries 3-6), a 53% yield could be achieved even at 0.5 mpa (table 1, entry 6). in comparison, gu et al. [21] found that the yield of the simple oxazolidinone product dropped from 92 to 9% when the co2 pressure was changed from 2.5 to 1.5 mpa, but these experiments were carried out at 373 k for 10h. a slightly better yield could be achieved when the amount of the amine reaction partner (2a) was doubled (table 1, entry 7). the possible use of cu(ii) catalyst precursors was also tested (table 1, entries 8-12). although cu(oac)2 turned out to be a less effective catalyst than cui (table 1, entry 8), the addition of excess benzylamine (2a) improved the yield considerably (table 1, entries 9-10). as an example, a yield of 80% could be achieved even under 1 mpa (table 1, entry 10). however, the reaction under 0.5 mpa co2 only led to the product in a moderate yield (table 1, entry 11). a cu(ii) complex with imidazolium carboxylate ligands (cul2, figure 2) was also synthesized [41] and tested in the carboxylation of steroid 1 (table 1, entry 12). in this case, however, the yield of 3a was only slightly higher than under the same conditions with cu(oac)2 (table 1, entry 8). in order to determine the optimal conditions for catalyst recycling, the copper content of the ethereal extracts of the reaction mixtures was determined by icpoes (table 2). the lowest leaching of copper to the organic phase could be detected in the cui-catalyzed reaction (table 2, entry 1). although the increase in the amine/steroid ratio had a favorable effect on the yield of the oxazolidinone product (table 1, entries 7 and 9), it led to a noticeable increase in the loss of the metal (table 1, entry 4). the highest copper content was measured in the crude product obtained in the presence of cu(oac)2. based on these findings together with the results of the catalytic experiments, the conditions corresponding to entry 3, table 1 were chosen to test catalyst recycling. after extraction of the product with diethyl ether and removal of the residue of the organic solvent under vacuum, fresh reagents were added to the ionic liquid/catalyst mixture and carboxylation/cyclization was repeated under the same conditions. the results (figure 3) show a slight decrease in the activity of the catalyst in multiple consecutive experiments, but product 3a formed with a yield of 80%, even in the 5th run. it should be mentioned that copper leaching also decreased steadily with a value of 1.9% in the 5th experiment. the optimal conditions were used to convert steroid 1 into oxazolidinones 3b and 3c in 79% and 67% yields, respectively, using benzylic amines 2b and 3b as reaction partners. ho h oh h h co2 cu-catalyst [bmim][bf4] 393 k + arh2n h n o o ar 1 2a ar=ph 2b ar=4-me-c6h4 2c ar=4-cf3-c6h4 3a ar=ph 3b ar=4-me-c6h4 3c ar=4-cf3-c6h4 figure 1: reaction of 17α-ethynylestradiol (1) with benzylic amines and co2 in the presence of cu catalysts in [bmim][bf4] table 1: carboxylative cyclization of steroid 1 and benzylamine (2a) in the presence of different cu catalystsa entry amine (2) catalyst pressure (mpa) yield of 3 (%)b 1 2a cucl 4.0 75 2 2a cui 4.0 >98 3 2a cui 2.0 93 4 2a cui 1.5 80 5 2a cui 1.0 71 6 2a cui 0.5 53 7 2ac cui 2.0 98 8 2a cu(oac)2 2.0 61 9 2ac cu(oac)2 2.0 85 10 2ac cu(oac)2 1.0 80 11 2ac cu(oac)2 0.5 41 12 2a cul2 d 2.0 68 [a]: reaction conditions: 0.17 mmol 1, 0.17 mmol 2a, 0.010 mmol catalyst, 0.017 mmol base, 170 μl [bmim][bf4], 24 h, 393 k [b]: determined by nmr based on the ratio of the integral areas of one of the exomethylene protons and that of aromatic protons h2 and h4 [c]: 0.34 mmol 2a; [d]: l=3-(carboxymethyl)-1methyl-1h-imidazol-3-ium tetrafluoroborate n n o o bf4 n no o bf4 cu cul2 (4) figure 2: structure of the cul2 catalyst (4) ispán, küzdő, gecse, vágvölgyi, ulbert, kovács and skoda-földes hungarian journal of industry and chemistry 104 4. conclusions the mixture of cui and [bmim][bf4] was proven to be an active and recyclable catalytic system in the synthesis of new steroidal oxazolidinone derivatives. cui was found to be superior to cucl, cu(oac)2 and cu carboxylate cul2 catalyst precursors in terms of activity and metal leaching. by the application of this methodology, three novel steroid derivatives were produced. acknowledgements this research was funded by the research fellowship programme (code: 2024-2.1.1-eköp) of the ministry of culture and innovation from the national research, development and innovation fund and by the tkp2021nkta-21 project financed under the 2021 thematic excellence programme funding scheme. the authors are grateful to gedeon richter plc. for providing the starting material 17α-ethynylestradiol. references [1] sharma, k.; 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mainly small and medium-sized enterprises (smes). in spite of these efforts, statistics show that the visegrád group remains underdeveloped in the field of industry 4.0. [1] this article tries to detect the reasons for this lag by summarising the available statistics and findings concerning this topic. first, the organisation for economic co-operation and development (oecd) information and communications technology (ict) usage data and robotisation data are examined before the results of several surveys concerning the introduction of industry 4.0 are analysed. finally, the personal interviews conducted in the visegrád group are evaluated. among the problems and challenges of small domestic companies, it was found that the most important is the human factor, namely the lack of necessary skills and the risk-avoiding managerial mindset. *correspondence: elteto.andrea@krtk.hu 2. data on industry 4.0 in the visegrad group the oecd “ict access and usage by businesses” database contains several such elements that can be bound to a functioning industry 4.0 system. these statistics show to what extent the companies in the given country use certain elements of digitalisation and automation. compared to all the european union (eu) member states, the visegrád group is situated relatively close to the bottom of the ranking. naturally, differences according to the indicators and countries are present. table 1 shows the relevant figures with regard to the use of some basic digital tools (having a website or highspeed broadband) as well as the share of companies applying big data analytics, cloud computing, additive manufacturing, digital company resources and customer relationship management software. as a “reference country”, germany was included in the table because the concept of industry 4.0 stems from this country, moreover, business contacts and production chains between the visegrád group and germany are highly significant. (it must be noted that although the performance of germany is good, its indicators are not always the best among the eu member states.) the table shows three phenomena. firstly, in the selected areas, slovakia and hungary are the weak performers and the czech republic is the best in the visegrád group. secondly, germany performs much better than the visegrád group in all fields. thirdly, although the use of 3d printing and enterprise resource planning (erp) software in every country is more widespread with regard https://doi.org/10.33927/hjic-2021-17 mailto:elteto.andrea@krtk.hu 24 éltető table 1: selected indicators of industry 4.0 for manufacturing sectors compared to all sectors in 2020 as a % of all companies (source: oecd ict access and usage by businesses database) poland czech republic sector all man. all man. website 71.32 77.13 83.32 85.02 broadband 42.77 38.47 34.44 28.99 erp* 28.54 32.48 38 48.36 crm* 30.92 20.91 20.86 20.19 cloud comp. 24.42 23.06 28.89 26.52 big data 8.47 6.51 9.12 7.98 3d printing 3.42 7.56 6.25 12.89 ict training 17.75 16.14 24.74 27.6 slovakia hungary sector all man. all man. website 75.82 75.22 63.23 72.96 broadband 32.12 27.45 35.77 31.11 erp* 31.12 38.11 14.33 20.41 crm* 22.19 20.88 12.10 11.44 cloud comp. 25.57 24.2 25.21 23.17 big data 5.6 3.93 6.99 7.12 3d printing 3.89 7.99 3.4 6.78 ict training 16.18 17.83 15.97 17.25 germany sector all man. website 88.35 92.52 broadband 44.86 40.38 erp* 29.26 50.33 crm* 44.21 47.15 cloud comp. 33.32 30.71 big data 17.83 12.25 3d printing 7.35 18.02 ict training 23.76 26.58 *data for businesses using enterprise resource planning (erp) and customer relationship management (crm) software are from 2019 man.: manufacturing website: businesses with a website or home page broadband: businesses with a broadband download speed of at least 100 mbps cloud computing: businesses purchasing cloud computing services big data: businesses implementing big data analytics 3d printing: businesses using 3d printing technology ict training: businesses that have provided any type of training to develop the ict-related skills of their employees within the last 12 months. to manufacturing than the average, in other areas no significant sectoral difference is found. around 16 − 25% of companies within the visegrád group provided some kind of ict training to their employees in the previous year. in the database, data are also classified according to table 2: selected percentage indicators of industry 4.0 for large and medium-sized enterprises in 2020 (source: oecd ict access and usage by businesses database) poland czech republic company size large medium large medium website 92.49 88.64 93.47 90.52 broadband 69.4 52.17 55.44 38.5 erp/2019 87.27 53.87 87.02 68.05 crm/2019 79.66 52.47 46.33 35.19 cloud comp. 59.55 37.68 55.63 36.88 big data 28.37 12.76 24.75 13.5 3d printing 17.39 6.28 25.83 10.35 ict training 71.02 32.67 77.22 43.96 slovakia hungary company size large medium large medium website 88.84 79.66 86.24 78.05 broadband 41.39 33.62 55.27 40.46 erp/2019 72.24 47.95 62.03 31.97 crm/2019 48.34 33.9 34.44 21.91 cloud comp. 50.62 33.28 58.83 36.75 big data 16.7 7.71 19.28 10.69 3d printing 17.79 5.43 14.67 4.65 ict training 62.19 32.84 65.45 30.64 germany company size large medium website 97.17 93.16 broadband 73.41 54.16 erp/2019 77.35 55.62 crm/2019 68.15 58.28 cloud comp. 62.05 41.18 big data 35.81 22.23 3d printing 23.2 11.55 ict training 73.07 43.22 the size of the company. as is presented in table 2, it is salient that large firms are by far the best, not only compared to small ones but also compared to medium-sized firms. this is true of germany as well, although differences here are smaller than in the case of companies from the visegrád group. as for the countries from the visegrád group that have been integrated into the global supply chains and host affiliates of large multinational enterprises (mnes) [2], these data, which is later underlined by surveys, show that the application of industry 4.0 is most advanced at large foreign companies. therefore, industry 4.0 reinforces duality among local firms and the dependency on foreign capital (foreign direct investment (fdi) led development model) in the visegrád group. [1] with the reduction in the price of robots, automation has gained momentum worldwide. even though the visegrád group has rapidly increased its stock of industrial robots, it is still overshadowed by the level of germany. the robot densities of the given countries are hungarian journal of industry and chemistry challenges of industry 4.0 in the visegrád group 25 figure 1: robot density (no. of multipurpose industrial robots per 10,000 employees) in the manufacturing sector (source: international federation of robotics) shown in fig. 1. it can be seen that this indicator is the lowest in poland and the highest in slovakia. according to the international federation of robotics, the automotive industry is the largest customer of robots, followed by the electrical/electronics sector, which is also true of the economies in the visegrád group. the automotive industry plays the biggest role in the czech republic, slovakia and hungary in the region, moreover, robotisation is more advanced in these economies. 3. experiences according to surveys and interviews with the spread of the industry 4.0 concept, several surveys have been conducted among companies in the visegrád group concerning the introduction of these technologies as well as the opportunities, barriers and challenges they present. the main findings of these surveys were grouped according to certain areas of concern and the literature references are provided at the end. introduction of industry 4.0 the visegrád group is less prepared for industry 4.0 than western european economies. generally, it is an important feature of this region that the main actors of industry 4.0 are foreign companies, mostly multinationals. based on international indices as well as rankings of governance, technology and entrepreneurial competences, the czech republic and hungary performed better than the other two countries. [3, 4] the readiness of domestic firms given that domestic companies usually do not have strategies, a fear of taking risks is present. managerial attitude and capability is often inadequate. the activity and knowledge of domestic firms with regard to industry 4.0 are relatively weak, sometimes even perceiving it as a threat. however, as time passes, the domestic companies have become more confident and started to apply the new technologies of industry 4.0. [5–14] opportunities for domestic firms it is beneficial that industry 4.0 tools detect organisational weaknesses. opportunities stemming from industry 4.0 are different for smes and mnes. companies are rethinking their pricing strategies by making it more sophisticated and room for price setting is growing. [15–18] challenges and problems automation in many cases was induced by labour shortages and the obsolete production technologies that were available. data storage and security is a challenge as companies do not want to share their data with business partners. the shortage of skilled labour is acute. production complexity and customer requirements have increased. the compatibility of new technologies is problematic and information on them is insufficient. there is a lack of financial resources for introducing industry 4.0 technologies at smes. the corporate culture in domestic companies needs to change. [14, 19–22] production control and organisation in the visegrád group, since robotization relies on the localization decisions of mnes and is mainly based on the automotive industry, it is “robotisation-dependent.” competition as well as the lower cost and better quality of robots encourage automation. at some companies, functional upgrading is taking place but the structure of value creation remains, that is, no specialisation occurs in terms of advanced activities and higher value added per unit. [19, 23] in a study from 2020 [24], interviews were completed with experts from the business and academic fields. in poland, hungary, the czech republic and slovakia, 16, 13, 6, and 6 interviews were conducted in person, over the phone or online, respectively. although this sample is relatively small, different institutions, companies and agencies were questioned so the opinions of various groups were gathered. table 3 shows the essence of these opinions concerning the aforementioned topics. 4. discussion the described surveys and interviews show that the perception as well as maturity of industry 4.0 vary among firms in the visegrád group. some companies are just beginning to contemplate such technologies, while others already regard them as necessary. over the past decade, “industry 4.0 awareness” has clearly developed. a lot depends on the managerial mindset. contrary to foreign firms, a constant development culture in domestic firms is often lacking, therefore, risks and novelties are avoided. however, a change in generation is occurring at many firms, the retirement of old owners is bringing about new possibilities. once a plan or strategy to implement industry 4.0 has been drawn up, preparation, piloting and testing are important. adaptation can be time-consuming, moreover, the investment can take as long as two years 49(2) pp. 23–27 (2021) 26 éltető table 3: industry 4.0 in the visegrád group – issues raised during the interviews (source: own compilation from the interviews conducted as part of the study [24]) topic opinions from the interviews introduction of industry 4.0 primarily foreign firms apply for these technologies readiness of domestic firms poor and lagging. the degree of innovation is low, few enterprises have a plan or strategy. opportunities for domestic firms mental adjustment at the executive level is necessary. a change in generation may improve the situation. challenges and problems long-term and expensive investment with delayed benefits. inadequate education system. skills needed; managerial capabilities are mostly weak and brain drain. production control and organisation mne headquarters usually retain the know-how and r&d, industry 4.0 gives more power to mnes, decisions about its usage are made locally by the management of the subsidiaries. to be implemented, leading to results only materialising later. the results of surveys and interviews support the statistics, proving a duality among firms from the visegrád group: large, mostly foreign companies perform much better than smaller domestic firms. the interviews confirmed that business models as well as cooperation between foreign headquarters and local subsidiaries will be changed due to industry 4.0 technologies. although multinational enterprise (mnes) develop r&d on their own, they partly share their results with local subsidiaries. decisions about the usage of industry 4.0-related technologies are mostly made by the management of local subsidiaries. for the successful functioning of a production chain, the absorptive capacity and collaboration of the subsidiaries are essential. several challenges of and barriers to industry 4.0 for domestic smes were presented, which can be grouped into technological, financial and human factors. in my opinion, the problem of the human labour force is the most difficult to surmount. data from eurostat show that the number of graduates per thousand inhabitants in science, technology, engineering, mathematics and computing is only 60% of the eu average in hungary and slovakia, 80% in the czech republic and 96% in poland.† a considerable proportion of these graduates later work abroad, diminishing the skilled workforce in the home countries. industry 4.0 is changing the characteristics of human capital, decreasing the labour intensity of certain produc†eurostat (educ_uoe_grad04). tion phases. those jobs that cannot or can hardly be automated require creativity, social intelligence and high cognitive abilities. the risk of unemployment is less with better education indicators (logic, mathematics, reading comprehension). [25] suitable competencies in an industry 4.0 world are the ability to learn, cooperation, flexibility, problem-solving, creativity and also non-cognitive skills. [26] these competencies – that should have already been developed at primary school – facilitate retainment, which has become critical in this rapidly changing technological environment, not to mention during a pandemic. at present, the education systems in the visegrád group do not strengthen these competencies and any reforms only bring about results in the long run. 5. conclusion regarding several elements of the complex technologies of industry 4.0, the statistics show the slowness of the visegrád group to adopt them compared not only to germany but also to other semi-periphery eu member states. however, the statistics on automation (robot density in manufacturing) demonstrate that rapid development has taken place especially in slovakia, the czech republic and hungary. this contradiction can be explained by the fact that automation is driven mostly by the automotive industry, while in the other statistics the characteristics of all sectors are reflected. the statistics for an entire country also cover the differences between large and small as well as foreign and domestic companies. large and foreign companies are much more advanced in terms of applying industry 4.0 technologies in the visegrád group. despite government incentives and programmes, domestic firms are in general less willing to introduce new technologies, e.g., few of them have a strategy for implementing industry 4.0, however, a learning process is present. traditional corporate culture, obsolete technologies and the lack of financial resources are important challenges for a small or medium-sized firm. the major barrier, however, is that the bulk of the human labour force lacks the proper skills and competencies to meet the demands of industry 4.0. since the present education system is not ready to deal with this problem, huge and rapid changes in this regard cannot be expected. references [1] éltető, a.; sass, m.: a kapitalizmus változatai és az ipar 4.0 a visegrádi országokban. közgazdasági szemle, 2021, 68(5), 490–514 doi: 10.18414/ksz.2021.5.490 [2] sass, m.: fdi-based models in the visegrád countries and what the future may have in store for them, wiiw monthly report 2021/02, vienna, wiiw, pp. 18–26 [3] naudé, w.; surdej, a.; cameron, m.: the past and future of manufacturing in central and eastern europe: ready for industry 4.0? iza discussion paper, 2019, 12141 http://hdl.handle.net/10419/196639 hungarian journal of industry and chemistry https://doi.org/10.18414/ksz.2021.5.490 https://doi.org/10.18414/ksz.2021.5.490 http://hdl.handle.net/10419/196639 challenges of industry 4.0 in the visegrád group 27 [4] szabó, s.: transition to industry 4.0 in the visegrád countries. european economy economic brief 052, brussels, european commission, 2020. 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[25] nedelkoska, l.; quintini, g.: automation, skills use and training, oecd social, employment and migration working papers, 2018, 202 doi: 10.1787/1815199x [26] pató, g.; kovács, k.; abonyi, j.: a negyedik ipari forradalom hatása a kompetenciacserélődésre. vezetéstudomány / budapest management review, 2021, 52(1), 56–70 doi: 10.14267/veztud.2021.1.05 49(2) pp. 23–27 (2021) https://doi.org/10.3390/su10103491 https://doi.org/10.2478/mape-2018-0081 https://doi.org/10.2478/mape-2018-0081 https://doi.org/10.2478/picbe-2018-0003 https://doi.org/10.2478/picbe-2018-0003 https://doi.org/10.36689/uhk/hed/2019-01-025 https://doi.org/10.36689/uhk/hed/2019-01-025 https://doi.org/10.3846/tede.2018.6397 https://doi.org/10.3390/socsci8050130 https://doi.org/10.3390/socsci8040104 https://doi.org/10.3390/socsci8040104 https://doi.org/10.11118/actaun202068030637 https://doi.org/10.14267/veztud.2021.02.06 https://doi.org/10.14267/veztud.2019.09.05 https://doi.org/10.1016/j.techfore.2019.05.021 https://doi.org/10.14267/veztud.2020.04.02 https://doi.org/10.18414/ksz.2019.1.72 https://doi.org/10.14267/veztud.2019.01.02 https://doi.org/10.17512/pjms.2018.17.1.19 https://doi.org/10.1080/09654313.2019.1694647 https://doi.org/10.1080/09654313.2019.1694647 https://doi.org/10.1787/1815199x https://doi.org/10.1787/1815199x https://doi.org/10.14267/veztud.2021.1.05 introduction data on industry 4.0 in the visegrad group experiences according to surveys and interviews discussion conclusion untitled hungarian journal of industry and chemistry vol. 53(1) pp. 73–80 (2025) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2025-09 the industrial specialisation of science and technology parks through the example of zalazone park andrea csordás1, andrás háry2* and csilla tóth2 1 bti management foundation, zalazone út 1, zalaegerszeg, 8900, hungary 2 zalazone science park ltd., dr. michelberger pál út 3, zalaegerszeg, 8900, hungary science and technology parks provide an integrated environment where industrial companies, service sector actors and r&d activities can operate in a coordinated way, fostering the development of innovation ecosystems as well as increasing the competitiveness of the region. the theoretical background of science and technology parks is presented to support this theme, highlighting industry specificities and their impacts. the aim of this thesis is to examine, through the example of zalazone park, the sectoral aspects of science and technology parks that play a crucial role in the development of cooperation between the actors operating in the park. since 2020, zalazone park has been a full member of the international association of science parks and areas of innovation (iasp), which brings together science parks and innovation centers from around the world. in this context, the industry and technology profile of the park is compared with the data published by the iasp global survey 2022. the research is based on two main methodological approaches. firstly, it groups the organizations operating in zalazone park according to their activities. secondly, it classifies the actors according to their technological focus, revealing the correlations between industry and technological orientation. in the final analysis, the mapping of collaboration opportunities between the actors in the park highlights the impact of sector specialization on the diversity of cooperation. the analysis of this theme will help other science and technology parks as well as innovation ecosystems to develop more effective strategies to increase their competitiveness. while research has typically defined industry orientation by focusing on technology, the present study adopts an analytical approach based on activity data and collaboration potential. keywords: cooperation, science and technology parks, sectoral and technological focus 1. introduction the main aim of this article is to analyze the sectoral issues of science and technology parks (stps) through the case study of zalazone park, as sectoral questions might be key factors in establishing cooperation between actors in the park. as a basis for this paper, first, the background of science and technology parks is presented, emphasizing the specificities of the sectoral environment and their influencing effect. following the theoretical overview, the study examines the diversity of the sectoral focus from three different perspectives: nace code (nace rev. 2 is the statistical classification of economic activities in the european union). sectoral focus and technological orientation. based on these perspectives, zalazone park is placed in the activity-based classification system of innovation ecosystems, the analysis of which provides an opportunity for other science parks and areas of innovation (aois) to carry out a self-assessment according to the outlined framework, thereby outlining new strategic directions. the results will also be compared with the network of contacts in the received: 4 apr 2025; revised: 8 apr 2025; accepted: 9 apr 2025 *correspondence: andras.hary@apnb.hu park to reveal possible connections between sectoral focus and the diversity of relationships, encouraging further self-reflection with regard to science parks to support the creation of new development paths. zalazone park provides a platform for numerous research institutes, industrial partners and governmental actors to develop their joint research and scientific activities. the park was established next to the automotive proving ground in zalaegerszeg in 2019, so one of its focus areas is aimed at testing and developing autonomous vehicles as well as intelligent transportation systems. the activities of the park support the realization of the following goals: • increasing the industrial and r+d attractiveness of the region, • exploiting the modern park infrastructure, promoting industrial and economic cooperation between actors and the university sector, • strengthening cooperation between partners through student projects, https://doi.org/10.33927/hjic-2025-09 mailto:andras.hary@apnb.hu csordás, háry and tóth hungarian journal of industry and chemistry 74 • linking dual and apprenticeship programs to meet specific industry as well as research and development needs. since zalazone park and the surrounding region is rapidly developing, the established business strategy integrates continuous innovations, complying with market changes and current trends. the proper management of the sectoral focus provides an opportunity to create future strategic directions. 2. experimental 2.1. samples and measurements much research has shown that innovation ecosystems exist in different forms with different specificities. an analysis [1] divided ecosystems into three groups: business, innovation and knowledge ecosystems. oh et al. [2] mentioned seven types of ecosystems: corporate (open innovation) ecosystems, regional and national innovation ecosystems, digital innovation ecosystems, city-based innovation ecosystems and innovation districts, high-tech sme-centered ecosystems, incubators and accelerators, as well as university-based ecosystems. pereira et al. [3] grouped them as follows: technology incubators, technology innovation centers and technology parks. they detail the characteristics of business, innovation and platform ecosystems related to the professional activities of that ecosystem. the authors pointed out that platform-based innovation ecosystems are, in particular, where actors are organized around a specific technological theme. cobben [4] analyzed four types of ecosystems: business, innovation, entrepreneurship and knowledge ecosystems. according to related research, ecosystems that differ in terms of their nature have different characteristics and it is advisable to also examine them from the point of view of activity characteristics. the activity characteristics can be interpreted regarding the mentality of the sector of actors operating in ecosystems and the technologies used. based on research on innovation ecosystems, it is essentially agreed that these ecosystems do not fit into the classical customer-supplier relationship, represented by the value creation model of the earlier porter model [5]. in innovation ecosystems, the focus is on innovation as well as the set of components and complements. adner [6], the author of the original approach, approaches the ecosystem as "collaborative agreements" through which companies combine their individual offerings into a coherent, customer-centric solution. therefore, it is extremely important to understand how the actors interact with each other and how interconnectivity is possible through their activities or technologies. if interconnectivity within the ecosystem is not sufficiently efficient, the innovation ecosystem cannot achieve its maximum level of performance. this aspect has been analyzed in a number of related studies, namely adner [7]; adner and kapoor [8] and kapoor and lee [9]. the role of technological areas is therefore decisive because it is an important condition for connected value creation. the works of gawer and cusumano [10], ceccagnoli et al. [11], jacobides [12] and cennamo [13] are cited in this regard. the analysis of wareham et al. [14] highlights the role of companies that are decisive in the value chain of the ecosystem, indirectly referring to the issue of concentration. according to winden and carvalho [15], the physical proximity of companies to various industries can provide synergy and innovation through collaboration between otherwise disparate disciplines. this is particularly important in terms of geographical concentration as this synergistic effect can underpin park-like ecosystems and is one of the topics addressed on these sites. in the related literature, research into the sectoral analysis of geographically concentrated innovation ecosystems is very limited. one exception and very thorough analysis is the work of liberati et al. [16] based on the processing of the double-digit nace codes of 548 companies. as a result of a systematic examination of technology parks, the paper identified four types of forms: generally dispersed enterprises from a wide range of sectors; a mixture of sectors where the concentration is neither too high nor too low; a specialized environment where the majority of enterprises are concentrated in a few sectors; and no variant identifiable in terms of concentration. the authors of the current paper addressed this issue in detail in their earlier work [17] which will be referred to later. the present analysis is also related to a previous work presented by the authors at an iced conference [18]. science and technology parks, which are the subject of the present analysis, can be considered as specialized innovation ecosystems. one of the most thorough reviews on this topic is the work of albahari et al. [19]. in the introduction of another paper [20], albahari defines technology parks as a specific subset of agglomerations, which well describes the dual role of these ecosystems. on the one hand, they are geographically defined, park-like systems, while on the other hand, are structures closely related to their regional environment. related research concerns many aspects of science and technology parks, e.g. the satisfaction of residents, success of parks, service characteristics, role of universities, etc., while sectoral and technological specificities have been addressed less. this is precisely what makes the present paper unique, albeit on the example of a park, but with regard to the international science and technology park community. 2.2. theoretical methodologies the research methodology is based on two aspects. firstly, it groups the organizations that have settled in zalazone park according to their field of activity. secondly, it organizes the actors according to their technological focus, assessing the relationship between their sectoral and technological focus. finally, the map of zalazone park 53(1) pp. 73–80 (2025) 75 cooperation opportunities between the actors at zalazone park points out the connection between sectoral focus and diversity of cooperation. the methodology is based on the classification of science and technology parks according to sectoral concentration and sectoral diversification (figure 1). on the vertical axis, in the case of sectoral concentration, either a dominant sector is present or cannot be named. the degree of sectoral diversification can also vary, with many or fewer sectors named. on this basis, the following four fields should be interpreted [11]: 1. diverse, varied 2. few kinds 3. diverse, there is a professional direction 4. few kinds, there is a professional direction. according to this study, the sectoral nature of innovation areas can be characterized by the duality of sectoral diversification and sectoral concentration [11]. by applying this approach, the sectoral character of zalazone park can be determined. although only a few studies in the literature deal in such depth with the sectoral nature of science and technology parks, a strong connection between the activity-based classification method of innovation ecosystems and the current research is found, offering a basis for further research development. the present study analyses in detail the relationships, similarities and differences between sectoral grouping according to nace, the sectoral grouping formed as a result, and the technological classification, thereby determining the classification section. 3. results and analysis in the following section, the relevant data from the summary of the public version of the research compiled in the international association of science parks and areas of innovation (iasp) global survey 2022 were used. the chapter “sectors” of the survey was used to analyze activities and specialization, comparing this with the case study of zalazone park. after comparing the data, specific charts addressing zalazone park are shown to reflect the diverse analytical possibilities of the sectoral focus, revealing similarities and differences. the results obtained will be further evaluated according to the activity-based classification method of the innovation ecosystems already referenced. finally, parallels between the multiplicity of the obtained outputs and the network of relationships will also be explored. based on figure 2, it can be seen that in the case of international examples, 50% of the participants are engaged in manufacturing activities with restrictions, while the main profile of zalazone park does not focus on manufacturing activities. next, the details of the technological focus areas are presented in figures 3a and 3b. the chart on the left depicts the technological focus of parks involved in iasp representing 113 respondents. it can be seen that info-communications and telecommunications, computer technology and hardware, software development, biotechnology and energy are the most widely used technologies in the cases examined as these processes shape the operation of the market globally. in comparison, in the portfolio of zalazone park, the focus of the automotive industry can be observed on the right-hand side by applying artificial intelligence, thereby complying with market processes. in relation to the technological focus of zalazone park, business and industrial services, metrology and services, as well as mechanics and components are the most decisive aspects. business and industrial services, comprising 78%, should be highlighted from the list of other technological focuses, which includes scientific as well as research and development activities, business management, management consulting and real-estate transactions. figure 1: activity-based classification of innovation ecosystems figure 2: manufacturing activity csordás, háry and tóth hungarian journal of industry and chemistry 76 figure 3a: technology sectors found in aois/stps 13,30% 15,00% 18,60% 19,50% 20,40% 22,10% 25,70% 25,70% 27,40% 31,00% 31,90% 31,90% 31,90% 32,70% 35,40% 41,60% 45,10% 47,80% 50,40% 51,30% 54,90% 56,60% 56,60% 62,80% 65,50% 69,90% 70,80% 72,60% 75,20% 77,00% 82,30% 0% 20%40%60%80%100% maritime military and defence metrology and services atmospheric and…physics land transportation optics cultural industry and…sport, tourism,…space technology mechanics,…civil engineering aeronautics &…audiovisual micromachines and…agriculture and…chemistry and…food sciences pharmaceuticals materials services for business…manufacturing and…environment healthcare electronics artificial intelligence energy biotechnology software engineering computer science and…ict figure 3b: technology sectors found in zalazone park zalazone park 53(1) pp. 73–80 (2025) 77 in the following section, the activity-based classification of innovation ecosystems according to the hungarian unified sectoral classification system (teáor) can be seen in figure 4. the teáor is the comparable version of the nace code, it is referred to below as the nace code for simplicity. the sectoral distribution of zalazone park is illustrated in figure 5 based on the main activity of the settled companies of the ecosystem according to the nace code. based on the results, it can be said that the most typical activity of the park is code 72 (scientific and technological research and development), carried out by one third of the settled companies. the leasing and operation of owned and rented real estate as well as code 71 (engineering activities and technical consulting) are also decisive. it can be seen that zalazone park mostly concerns the technical field with its technological focus linked to scientific research and development. this is confirmed by figure 3 since 78% of the technology sectors belong to the business and industrial services group, the main activity of 52% of which is scientific research and development with nace code 72. the sectoral groupings generated on the basis of the nace codes used in europe are shown in figure 6. the essence of the classification is to create categories that take into account the nace codes that show a more realistic picture of the sectoral character of zalazone park. for this reason, 9 classifications were established as shown in this figure. given that in the literature, grouping predominantly occurs according to technology focus, it can be said that the results of the data series are closer to those when grouping according to the technology focus than the breakdown by nace codes. according to this approach, business management and management consulting are the most widespread sectoral foci of the settled organizations at zalazone park, however, the automotive industry as well as research and development activities are also decisive, representing 65% of the focus areas in total. in terms of technological focus, 9 different categories can be distinguished in relation to zalazone park. the most common category is business and industrial services, which can be considered in parallel with business management and management consulting illustrated in the previous diagram. in terms of technological focus, in addition to business and industrial services, metrology and related services are also actively present in the park, which can be traced back to the goals of zalazone park. regarding the activity-based classification of innovation ecosystems, it can be stated that, based on the interpretation according to nace, zalazone park is located in the lower left quadrant as shown in figure 1, which means that the scope of activities is wide but defined professional directions are found. the resulting category and the interpretation according to the figure 4: sectoral distribution of zalazone park according to nace codes figure 5: sectoral distribution of zalazone park according to reasonable alternatives b u si n e ss m a n a g e m e n t … a u to m o ti v e r + d a ct iv it y r e a l e st a te t ra n sa ct io n a d v o ca cy t e ch n ic a l te st in g , … m a n u fa ct u re o f … e d u ca ti o n m a n u fa ct u re o f … 0 1 2 3 4 5 6 7 8 9 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% figure 6: the technological focus of zalazone park b u si n e ss a n d … m e tr o lo g y … p ro d u ct io n … m e ch a n ic s, … s o ft w a re … a rt if ic a l … m a te ri a l c iv il … m il it a ry a n d … 0 5 10 15 20 25 30 csordás, háry and tóth hungarian journal of industry and chemistry 78 technological focus, on the other hand, places the park in the lower right quadrant, which presupposes a less diverse sectoral focus, implying the existence of professional directions. summarizing the previous three figures, it can be stated that the park has a designated technological focus, but its technological diversity is moderately high. the cooperation matrix of zalazone park is shown in figure 7, with singular anonymous numbers representing the organizations between which some kind of cooperation can be named, highlighted with a yellow background color. based on the matrix, it can be concluded that cooperation between the settled organizations is intensive with the goal of the park attracting new actors into the ecosystem in the future. its aim is also to bring together organizations that have not yet started cooperating with each other and encourage the development of mutual cooperation, not just one-way cooperation. the means of this are, among others, strengthening the relationship between the actors by generating various projects, organizing joint events within the park and developing a common value system. in addition to the previous figure, the network of contacts is illustrated by figure 8, which confirms the presence of an active connection between the settled actors. the figure shows that for each organization (e.g. g, q, j, t, u) thickenings can be seen, which indicate the cardinality of the relationships. cooperation between the organizations, denoted by the letter codes aa and af, and other actors is currently less but this may be due to the fact that recently established actors fall into this category. within science and technology parks, cooperation is particularly important as the resulting collaborations create knowledge transfer and exchange of experience which are indispensable factors to raise the collective level of knowledge, greatly contributing to the strengthening of regional development and corporate competitiveness. therefore, the main task of park management is to encourage cooperation between the settled actors in the park. the companies denoted by the letters "g" and "q" have established the most relationships with other organizations in the ecosystem according to figure 9, comprising 27 connections, meaning that the most active organization at zalazone park is in contact with 84% of actors at the park. furthermore, it can be seen that the multitude of contacts of other organizations is also decisive. the moderate gradient of the chart also illustrates that the median values fall above the arithmetic mean line, i.e. the gradient of the chart does not suddenly change. based on this, it can be said that most actors strive to establish as many relationships with each other as possible. this is reinforced by the fact that 62% have more relationships with each other than on average and, these relationships are unidirectional or mutual. the figure 7: the cooperation matrix of zalazone park a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af a 0 0 0 0 1 1 1 1 1 1 1 1 0 1 0 1 0 1 0 0 1 0 1 0 0 0 1 0 0 1 0 b 1 1 1 0 1 0 1 1 0 0 1 1 1 1 1 1 1 1 1 0 1 0 1 1 0 1 1 0 1 1 c 1 1 1 1 0 1 1 0 1 1 1 0 1 1 0 0 1 1 1 1 1 1 1 0 1 0 0 0 0 d 0 0 1 0 1 1 0 0 1 1 0 1 0 1 1 1 1 0 1 0 1 1 0 1 1 0 0 0 e 1 1 0 0 1 1 1 0 0 1 1 1 1 1 1 1 0 1 1 0 1 0 1 1 0 1 0 f 1 1 0 1 1 1 0 0 1 1 1 1 1 1 1 1 1 1 1 0 1 1 0 0 1 0 g 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 1 1 1 1 0 h 0 0 1 1 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0 i 1 1 0 1 1 1 1 1 1 1 1 1 0 0 1 1 1 0 0 0 0 1 0 j 0 1 1 1 1 1 1 1 1 1 1 1 1 1 0 1 0 1 0 1 1 0 k 1 1 0 1 1 1 1 0 1 1 1 1 1 1 1 1 1 1 0 1 1 l 0 0 1 0 1 1 1 1 0 0 0 1 1 0 0 1 0 0 0 0 m 1 1 1 0 1 1 1 1 0 0 1 1 1 0 0 0 0 0 0 n 1 1 1 1 0 1 1 1 1 1 0 1 0 0 0 1 1 0 o 0 1 1 0 1 1 1 1 1 1 0 1 1 1 1 0 0 p 1 1 1 1 1 1 1 1 1 1 0 0 1 1 1 0 q 1 1 1 1 1 1 1 1 1 1 1 1 0 1 0 r 0 1 1 1 1 1 1 0 0 1 1 1 0 0 s 0 1 1 1 1 1 1 0 1 1 1 1 0 t 1 1 1 1 1 1 0 1 0 1 1 0 u 1 1 1 1 1 0 0 1 1 1 0 v 0 1 0 0 0 1 0 0 0 0 w 0 1 0 0 0 0 0 0 0 x 1 1 0 1 0 0 1 0 y 1 0 0 1 0 1 0 z 0 0 0 1 0 0 aa 0 0 0 0 0 ab 1 0 1 1 ac 1 1 1 ad 0 1 ae 0 af figure 8: the network of connections at zalazone park zalazone park 53(1) pp. 73–80 (2025) 79 short-term goal is that a significant proportion of relationships should be bidirectional, thereby creating similarly large benefits for both parties. 4. discussion the main aim of this paper was to analyze the sectoral questions of science and technology parks through the case study of zalazone park. since the literature presents different types of innovation ecosystems with various characteristics, it is worth examining the activity characteristics as well which can be examined according to the sector of actors operating in the ecosystems as well as from the point of view of the technologies used. following the theoretical overview, the research introduced the activity-based classification method of innovation ecosystems, which foresees the definition of the sectoral character of zalazone park, the pillars of which are nace codes, the sectoral focus generated from them and the technological focus. in the first round, the public data from the iasp global survey 2022 and parameters of zalazone park were compared according to the manufacturing activity and technological focus. it was possible to conclude that the service portfolio of zalazone park integrates manufacturing activities similarly to international examples, moreover, its technological focus mainly addresses business and industrial services. this set includes scientific as well as research and development activities, business management, management consulting as well as real-estate transactions and advocacy. according to different points of view, 12 different types of sectors are found according to nace codes, while in the case of the version created on this basis and in terms of the technological focus, 9 categories are found in each. in the literature, grouping according to technological focus is prevalent, so the results of the data series formed more closely resemble grouping by technological focus than the breakdown by nace codes. in light of the above, it can be concluded that the sectoral focus of zalazone park according to nace codes concerns scientific research and development, which is further clarified by the classification generated on the basis of these. the technological direction is focused on business and industrial services, which is closely related to the previous categories since 52% of business and industrial services are mainly engaged in scientific research and development (nace code 72). regarding the activity-based classification of innovation ecosystems, it can be stated that, based on the interpretation according to nace codes, although the scope of activities at zalazone park is wide, defined professional directions exist. however, the interpretation according to the technological focus supposes a less diverse sectoral focus, implying the existence of professional directions. it can be stated that the park has a designated technological focus but its technological diversity is moderately high. in light of the above, the research also touched upon cooperation between the actors settled at zalazone park, based on which it can be stated that the organizations actively cooperate with each other. management at the park encourages the development of such cooperation through various projects and events. future goals include further expanding these relations and making them reciprocal in one-way relationships. the results confirm the main research question, namely that the sectoral nature of science parks can be examined on the basis of various aspects, based on which classification according to technological focus provides a real picture of the nature of the ecosystem. it can also be assumed that parks with a technological orientation are more likely to build relationships between actors. although the research focused on the zalazone park, the methodology can be applied to the analysis of other parks and innovation ecosystems, which could be a subject of further research. 5. conclusions overall, since it can be stated that the nace classification is not always clear, this study confirms the analytical method of other research because classifying according to the technological focus can provide a better picture of the activities of the organization. furthermore, it can also be concluded that similarities are observed between the sectoral classification and technological focus based on international examples. a unit difference can be identified in terms of the cardinality of the categories according to this interpretation, moreover, classifying according to the activity undertaken in this way yields the same result. this classification positions zalazone park as sector-focused but lacking technological diversity. this statement represents its actual status and serves as a signal for the development of technological diversity, thereby increasing the ability to respond to rapidly changing market conditions. by harmonizing the three different approaches, zalazone park is an innovation ecosystem with a figure 9: distribution of relations between the settled actors at zalazone park csordás, háry and tóth hungarian journal of industry and chemistry 80 medium degree of diversity and an outlying sector which can be developed by integrating new sectors. acknowledgements the data in this study was provided by iasp from their global survey 2022 published at: https://www.iasp.ws/our-industry/knowledgeroom/iasp-global-survey-2022--science-and technologyparks-and-areas-of-innovation-throughout-the-world the authors acknowledge the participation of iasp in the current research. 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https://doi.org/10.1002/smj.2904 https://doi.org/10.1177/0149206316658350 https://doi.org/10.1287/orsc.2014.0895 https://doi.org/10.1007/s10961-015-9397-8 https://doi.org/10.1007/s10961-022-09949-7 https://doi.org/10.1007/s10961-018-9661-9 hungarian journal of industry and chemistry vol. 50 pp. 23–28 (2022) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2022-05 production of chiral (s)-2-phenyl-1-propanol by enantioselective biocatalysts piroska lajtai-szabó *1, tímea brigitta bagó1, and nándor nemestóthy1 1research group on bioengineering, membrane technology and energetics, university of pannonia, egyetem u. 10, veszprém, 8200, hungary enantioselective production of (s)-2-phenyl-1-propanol is important as in order to be applied in industry, a high degree of optical purity is required. besides organocatalysts and metal complexes, biocatalysts can be used for its synthesis in their isolated form or as whole-cell biocatalysts, both of which have various advantages and disadvantages. in this research, saccharomyces cerevisiae, as a whole-cell biocatalyst, and recombinant horse-liver alcohol dehydrogenase (adh), as an isolated enzyme, were investigated in terms of their activity, kinetics and enantioselectivity. in the case of yeast, the rate of cofactor regeneration was twice that of substrate conversion, moreover, the biocatalyst saccharomyces cerevisiae can be characterised by substrate-limited kinetics and low enantioselectivity. in contrast, the isolated enzyme recombinant horse-liver adh exhibited biphasic kinetics and cofactor regeneration was the rate-limiting step. the outstanding enantioselectivity of recombinant horse-liver adh renders it a promising catalyst for the purpose of this synthesis. keywords: alcohol dehydrogenase, whole-cell biocatalyst, saccharomyces cerevisiae 1. introduction 2-phenyl-1-propanol is a fragrance ingredient that produces the lila-hyacinth odour commonly used in cosmetics, fine fragrances and household cleaners [1]. besides, it is the basis of some non-steroidal anti-inflammatory drugs and the precursor of other fragrances [2]. these fields of use require a high degree of optical purity since the enantiomers of the compound, by and large, bring about different biological effects [3]. asymmetric syntheses are preferentially obtained using enzymes, given the capability of most to catalyse organic reactions with high enantioselectivity under mild conditions [4, 5]. besides isolated enzymes, whole cells are also being applied more and more often as biocatalysts, given the disparate attributes of both. wholecell biocatalysts ensure the optimal environment for the enzyme, thereby providing a quite stable system. furthermore, they contain cofactors and are able to bring about cofactor regeneration without the necessary addition of any other compounds [6]. however, the presence of a variety of enzymes may lead to side reactions. also, isozymes with different enantiomeric preferences may lower the overall enantiomeric excess into recieved: 11 march 2022; revised: 21 march 2022; accepted: 21 march 2022 *correspondence: lajtai-szabo.piroska@mk.uni-pannon.hu the bargain [7]. unlike whole-cell biocatalysts, isolated enzymes improve the level of control over the process in the absence of side reactions, thereby enhancing its reproducibility. in addition, inhibition is less likely to occur because of the greater degree of tolerance concerning the concentrations of both the substrate and product. on the other hand, the provision of a cofactor and its regenerating system significantly increases costs. in order to choose the optimal catalyst for a given synthesis, a detailed comparison of their advantages and disadvantages, e.g. attainable yield, productivity, product purity, required downstream processes and costs, should be made [8]. in this research, two types of alcohol dehydrogenases (adh) were investigated with regard to the conversion of racemic 2-phenylpropionaldehyde to (s)-2-phenyl-1propanol. for the catalysis, the cofactor nicotinamide adenine dinucleotide (nadh) is required by the enzyme which has to be regenerated in order to ensure continuous product formation. ethanol was applied as an auxiliary substrate for the regeneration which was catalysed by the adh. the reaction schemes are presented in fig. 1. because of the low solubility of the substrate and the product in aqueous media, a two-phase system was applied. saccharomyces cerevisiae was applied in dried form (instant baker’s dry yeast) as a whole-cell biocatalyst. over recent decades, both wild and genetically modified strains of yeast have been gaining more and more attention as biocatalysts in the production of fine chemicals [7]. although (s)-alcohol is generally the predominant https://doi.org/10.33927/hjic-2022-05 mailto:lajtai-szabo.piroska@mk.uni-pannon.hu 24 lajtai-szabó, bagó and nemestóthy figure 1: reaction scheme enantiomer in the reduction of racemic carboxylic acid compounds by applying yeast [6], this is dependent on the given substrate [9]. our second catalyst was recombinant horse-liver adh expressed in e. coli. isolated recombinant horse-liver adh is frequently applied for asymmetric syntheses [10–12], moreover, its variant expressed in bacteria can be a cheaper and more accessible alternative. the aim of this research was to characterise the aforementioned biocatalyst in terms of activity, kinetics and enantioselectivity, thereby enabling their critical comparison. in addition, mass transfer through the organic-water interphase was also investigated in order to characterise the relationship between the rates of each step. 2. experimental methods 2.1 applied chemicals all chemicals were commercially available and used without further purification. diisopropyl ether (puriss), ethyl alcohol (a.r.), dodecane (a.r.), trifluoroacetic anhydride (98%), racemic 2-phenylpropionaldehyde (98%) and s-(2)-phenyl-1-propanol (97%) were purchased from sigma-aldrich. recombinant horse-liver alcohol dehydrogenase (expressed in e. coli) as well as lyophilised powder (1.5 u/mg) and β-nicotinamide adenine dinucleotide (sodium salt, 98%) were obtained from sigmaaldrich and thermo fisher scientific, respectively. k2hpo4, kh2po4 and na2co3 were purchased from vwr, while instant baker’s dry yeast was purchased from a local store. 2.2 activity measurements a spectrophotometric method was used to determine the catalytic activity characteristic of cofactor regeneration. given that the maximum adsorption of nadh is at 340 nm while that of nad+ is negligible at this wavelength, conversion of the cofactor can be followed by the change in the wavelength of adsorption. in the case of isolated adh, 10 µl of enzyme solution (10 mg/ml), 600 µl of nad+ solution (4 mg/ml) and 1240 µl of buffer solution were mixed in a quartz cuvette. the reaction was initiated by the addition of 150 µl cc. of ethyl alcohol and the change in absorbance was measured at 340 nm by a shimadzu uv-1800 ultraviolet-visible spectrophotometer. in the case of the whole-cell biocatalyst, 10 µl of an instant yeast suspension (10 mg/ml) was applied instead of an enzyme solution. the catalytic activity was calculated based on the following equation: va = da dt vcuvette εd venzyme h (1) where va denotes the volume activity [u/cm3], da dt represents the gradient of the line (by plotting absorbance vs. time), vcuvette stands for the volume of the mixture [cm3], ε refers to the molar extinction coefficient of nadh at 340 nm [6.22 cm2/µmol], d is the width of the cuvette [1 cm], venzyme denotes the volume of the enzyme solution [cm3] and h represents dilution. the catalytic activity characteristic of the conversion of 2-phenylpropionaldehyde cannot be measured by a spectrophotometer since the reaction mixture consists of two phases. therefore, the catalytic activity characteristic of the whole process (substrate conversion, cofactor regeneration and mass transfer through the organic-water interface) was calculated from the results gained by measuring the kinetics, as described in sec. 2.4. 2.3 mass-transfer rate since experimental conditions applied by conversion measurements are unsuitable for determining the masstransfer rate through organic-water interface, a simplified system was applied for this purpose [13]. 13.4 mg of 2-phenylpropionaldehyde and 18.5 mg of dodecane, which served as an internal standard for gas chromatography (gc) analysis, were dissolved in 10 ml of diisopropyl ether. a schott glass bottle was filled with 6 l of distilled water and the organic solution carefully poured onto the surface of the water phase. during the following 27 hours, samples were taken from the organic phase and analysed by gc. (the parameters of chromatographic analysis were the same as described in sec. 2.4). the ratio of aldehyde to dodecane was plotted as a function of time and a kinetic model was fitted to the measured data in accordance with the following equation: j = d(c0 − acw) (2) where j denotes mass transfer through the interface [mol/(min cm2)], d represents the mass transfer coefficient [cm/min], c0 stands for the initial substrate concentration in the organic phase [mol/cm3], cw refers to the substrate concentration in the water phase [mol/cm3] and a is the ratio of the activity coefficients. the difference between the measured and calculated data was minimized by the excel solver plug-in. although the water phase was gently mixed by a magnetic stirrer, the water–organic interface was stationary. therefore, its surface can be regarded as a constant. the mass transfer rate can be calculated by dividing the mass transfer (j) by the interfacial area. hungarian journal of industry and chemistry production of chiral (s)-2-phenyl-1-propanol 25 table 1: heating program ramp rate [◦c/min] temperature [◦c] hold time [min] 70 25 1 110 0 20 180 2 2.4 kinetics in all the experiments, 7 cm3 of organic solvent and 7 cm3 of phosphate buffer (75 mm, ph 8.0) were used. the molar ratio of 2-phenylpropionaldehyde to ethyl alcohol was set at 3.7, based on data from the literature [14]. in the case of isolated adh, 60 µl of nadh solution (7.5 mg/ml, freshly made with a buffer solution) was added to the reaction media. (the optimal amount of cofactor was determined during preliminary measurements, however, this data is not shown.) in the case of instant baker’s dry yeast, since the cell contained a sufficient amount of cofactor, no further addition of nadh was necessary. the reactions were initiated by adding the catalyst – 300 mg of instant baker’s dry yeast or 500 µl of enzyme solution (10 mg/ml, freshly made with a buffer solution). the reaction mixtures were shaken in a thermostatic incubator (ika ks 4000 i control) at 200 rpm and 30 ◦c. to investigate the product formation, samples were taken from the organic phase and analysed by an hp 5890 gas chromatograph (140 ◦c isothermal). the gc was equipped with a db-ffap column (1 µm × 30 m × 0.53 mm, agilent technologies) and a flame ionisation detector. 2.5 enantioselectivity while measuring the enantioselectivity, the content of the reaction mixture and operational parameters were the same as described in sec. 2.3. before gc analysis, preliminary derivatization was required. 1 ml of trifluoroacetic anhydride and 1 ml of diisopropyl ether were added to 500 µl of the sample while heating the mixture under reflux at 70 ◦c for 30 mins. once the reaction mixture had been cooled to room temperature, it was neutralized with 4 ml of na2co3 (20%) and a sample from the organic phase analysed by a shimadzu gc-2014 gas chromatograph equipped with a lipodex e capillary column (0.2 µm × 25 m × 0.25 mm, macherey-nagel) and a flame ionisation detector. table 1 contains the parameters of the applied heating program. the peaks were deconvoluted by originpro software to fit the gaussian curves. to identify the peaks of the enantiomers, derivatization and analysis was performed using pure s-(2)-phenyl-1-propanol. the retention time of the derivative of the product was 52.5 mins. 3. results and evaluation 3.1 kinetics by plotting the amount of product as a function of time, a line can be fitted to the initial linear phase of the graph and its gradient is the initial rate of reaction as a result of the given substrate concentration. a kinetic curve results from repeating the method with different initial substrate concentrations, yielding information about the dependence of the reaction rate on it. in the case of whole-cell biocatalysts, the product formation can be described by the single-substrate michaelis-menten model as the amount of cofactor can be considered to be constant due to its fast regeneration (see sec. 2.3). in the region of lower substrate concentrations, firstorder kinetics was observed as expected (fig. 2). however, at 0.267 m, the curve peaked followed by a relatively steady decrease instead of phase saturation. as a result, it can be concluded that higher amounts of substrate limit enzymatic conversion, therefore, 0.267 m is the optimal initial concentration to maximise the reaction rate. in contrast to yeast cells, by applying recombinant adh, the reaction rate of cofactor regeneration may limit product formation (see section 3.2), therefore, cannot be neglected. since two reactions involved multiple substrates catalysed simultaneously by the same enzyme, the kinetics did not follow the michaelis-menten model. alternatively, a biphasic model was applied which divides the curve into two phases: at low substrate concentrations, the enzyme’s affinity is relatively high while the turnover number is low. on the contrary, a low affinity and high turnover number is characteristic of the region of high substrate concentration (fig. 3). biphasic kinetics can be modelled by the following equation [15]: v = vmax1 [s] + clint[s] 2 km1 + [s] (3) where vmax1 as well as km1 describe the first high affinity–low-turnover phase and clint – equal to the ratio vmax2 : km2 – denotes the second low-affinity–highturnover phase. figure 2: kinetics of the whole-cell biocatalyst 50 pp. 23–28 (2022) 26 lajtai-szabó, bagó and nemestóthy figure 3: biphasic enzyme kinetics [15] figure 4: kinetics of the isolated enzyme apart from one exception (at 0.22 m), since model data calculated using eq. 3 fitted well to the measured data (fig. 4), biphasic kinetics is presumably a suitable model to describe the kinetics of an isolated enzyme. having been minimized by the excel solver plug-in, the model parameters were the following: vmax1 = 7.523; clint = 3.458; km1 = 0.464. according to manevski [15], biphasic kinetics may imply the presence of multiple substrate binding sites. however, the applied methods were unsuitable for further investigating the underlying mechanisms of the reactions taking place. 3.2 activity the activity of the catalysts was measured during both cofactor regeneration and the process as a whole (table 2). one unit (u) stands for the amount of catalyst necessary to produce 1 µmol of product in 1 minute under the measurement parameters. (substrate conversion could not be investigated separately as previously mentioned in sec. 2.2). although normally the catalytic activity should be measured in the saturation phase of the kinetics, none of the kinetic curves enabled this. therefore, measurements were made at a substrate concentration of 0.27 m, which is the substrate concentration at which the kinetic table 2: activity of the catalysts yeast cell [u/mg] recombinant adh [u/mg] cofactor regeneration 0.19 0.05 complete reaction (0.27 m) 0.02 0.7 complete reaction (1.08 m) – 1.64 curve of the yeast-cell catalyst is at its maximum. in the case of the isolated enzyme, the activity was measured at the same concentration as that of yeast in order to compare the two catalysts. this was also determined at the highest measured point of the kinetic curve, namely at 1.08 m. based on the results, cofactor regeneration is one scale faster when applying a whole-cell biocatalyst instead of an isolated enzyme. although the same enzyme catalyses both substrate conversion and cofactor regeneration when isolated adh is used, yeast cells contain several enzymes that are capable of participating in regeneration reactions which can occur more rapidly as a result. on the other hand, the overall reaction rate using the same substrate concentration was 35 times higher when recombinant adh was used and further increases in substrate concentration resulted in even higher reaction rates. 3.3 mass transfer through the organic–water interface in order to determine the rate-limiting step of the whole process, the mass transfer rate through an organic–water interface was investigated. owing to simplifications of the measurement and the imprecise nature of model fitting, the calculated mass transfer rate may be somewhat inaccurate. nevertheless, the goal was to estimate its order of magnitude rather than determining its precise value. based on the kinetic model fitted to the measured data (fig. 5), the mass transfer rate was calculated to be 1.33 · 10−5 mol/min. by comparing this value with the figure 5: mass transfer process hungarian journal of industry and chemistry production of chiral (s)-2-phenyl-1-propanol 27 table 3: enantiomeric excess (ee) and degree of conversion from studies on the production of (s)-2-phenyl-1-propanol catalyst solvent substrate conc. product, degree of conversion ee (s) ref. horse-liver adh 0.24 u/ml buffer, 165 mm 41 mm, 25 % (2 h) 91 % [14]isopropyl ether (63 % v/v) 82 mm, 50 % (24 h) 88 % horse-liver adh 0.01 mg/ml buffer ph= 7.5, ch3cn (10 % v/v) 0.5 mm 0.36 mm, 72 % (5 h) 78 % [12] recombinant horse-liver adh, exp. in e. coli 0.5 u/ml buffer ph= 8.0, diisopropyl ether (1:1 v/v) 267 mm 45 mm, 17 % (1 h) 100 % this work ctxr d51a mutant e. coli, 4 gcdw/l buffer ph= 7.5 100 mm 41 mm, 41 % (2 h) 95 % [2] whole-cell 40 gcdw/l 70 mm, 70 % (2 h) 45 % s. cerevisiae, 43 gcdw/l buffer ph= 8.0, 267 mm 74 mm, 28 % (1 h) 24 % this work whole-cell diisopropyl ether (1:1 v/v) 345 mm 55 mm, 16 % (1 h) 36 % reaction rates of both catalysts, it could be established that the mass transfer rate is two or three times faster than those of product formation or cofactor regeneration. therefore, the rate-limiting step of the whole process is cofactor regeneration and substrate conversion when an isolated enzyme and whole-cell biocatalyst is applied, respectively. 3.4 enantioselectivity the enantioselectivity of the whole-cell biocatalyst was measured at three different initial substrate concentrations: at the maximum of the kinetic curve (0.267 m) as well as at two higher values (0.345 m and 0.746 m) to examine whether increasing the substrate concentration is beneficial as far as achieving optical purity is concerned. the enantiomeric ratio was calculated from the ratio of the peak areas at 0.5, 1.0 and 1.5 hours (fig. 6). changes in the enantiomeric ratio as the reaction progressed were insignificant, moreover, the difference in the reaction time between 0.345 m and 0.746 m was negligible. at 0.267 m, the final result was 0.62, while the best result, that is, 0.68, was achieved at 0.746 m. as a result, figure 6: the enantioselectivity of the wholecellbiocatalyst it could be established that to achieve an optimal reaction rate and enantioselectivity, different initial substrate concentrations are required. in the case of the isolated enzyme, the enantioselectivity was measured at the same substrate concentrations as when the whole-cell biocatalyst was applied. however, since only one peak corresponding to the (s)-enantiomer of the derivative was detected, further analysis was unnecessary and the enantioselectivity regarded as 100%. as in terms of consumption optical purity is a key concern, the results of this work were compared with some data from the literature (table 3). in the case of whole-cell biocatalysts, the results of rapp et al. [16] are more favourable than ours. however, since both studies suggest that the maximum degree of conversion and enantiomeric excess cannot be achieved simultaneously, a compromise must be made. in the case of the isolated enzyme, the degree of conversion in this study is promising if the reaction time is also taken into account. as for the enantiomeric excess, our result is clearly outstanding, therefore, recombinant horse-liver adh provides a satisfactory alternative for catalysing the production of (s)-2phenyl-1-propanol. 4. conclusion in this work, the conversion of racemic 2phenylpropionaldehyde into (s)-2-phenyl-1-propanol was investigated by applying a whole-cell biocatalyst (saccharomyces cerevisiae) and an isolated enzyme (recombinant horse-liver adh expressed in e. coli). significant differences were observed between the catalysts in terms of all the considered parameters. firstly, the whole-cell biocatalyst exhibited substrate-limited kinetics, while the isolated enzyme could be described by biphasic kinetics. the yeast cell contained a sufficient amount of cofactor for the reaction, moreover, its regeneration was twice as fast as in the case of the isolated 50 pp. 23–28 (2022) 28 lajtai-szabó, bagó and nemestóthy enzyme. therefore, the whole-cell biocatalyst is more beneficial from this point of view. on the other hand, the enzymatic activity of the whole process was at least 35 times higher when recombinant horse-liver adh was applied and could be further enhanced by increasing the initial substrate concentration. most importantly, the isolated enzyme catalysed the conversion with 100 % enantioselectivity, which is also clearly outstanding compared to data from the literature. in conclusion, although recombinant horse-liver adh is more expensive, it is definitely a more efficient catalyst than yeast as a whole-cell biocatalyst. therefore, recombinant horse-liver adh is a promising biocatalyst with regard to the synthesis of (s)-2-phenyl-1-propanol. acknowledgement this research was supported by the ministry for innovation and technology; the national research, development and innovation office and the new national excellence programme. this study was financed by the national laboratory for climate change (hungary) project number nkfih471-3/2021. references [1] scognamiglio, j.; jones, l.; letizia, c. s.; api, a. m.: fragrance material review on βmethylphenethyl alcohol, food chem. toxicol., 2012, 50(2), 199–203 doi: 10.1016/j.fct.2011.10.023 [2] rapp, c.; pival-marko, s.; tassano, e.; nidetzky, b.; kratzer, r.: reductive enzymatic dynamic kinetic resolution affording 115 g/l (s)-2phenylpropanol, bmc biotechnol., 2021, 21, 1–13, doi: 10.1186/s12896-021-00715-5 [3] klebe, g.: optical activity and biological effect, in: klebe. g (ed.): drug design: methodology, concepts, and mode-of-action, pp. 89–110 (springer berlin heidelberg; berlin, heidelberg, germany) 2013 doi: 10.1007/978-3-642-17907-5_5 [4] lajtai-szabó, p.; nemestóthy, n.; gubicza, l.: the role of water activity in terms of enzyme activity and enantioselectivity during enzymatic esterification in non-conventional media, hung. j. ind. chem., 2020, 48(2), 9–12 doi: 10.33927/hjic-2020-22 [5] reetz, m. t.: controlling the enantioselectivity of enzymes by directed evolution: practical and theoretical ramifications, proc. natl. acad. sci., 2004, 101(16), 5716–5722 doi: 10.1073/pnas. 0306866101 [6] silva, j.; alarcón, j.; aguila, s. a.; alderete, j. b.: bioreduction of some common carbonylic compounds mediated by yeasts, z. naturforsch., c, 2010, 65(1-2), 1–9 doi: 10.1515/znc-2010-1-201 [7] pscheidt, b.; glieder, a.: yeast cell factories for fine chemical and api production, microb. cell fact., 2008, 7(1), 25 doi: 10.1186/1475-2859-7-25 [8] schallmey, a.; domínguez de maría, p.; bracco, p.: biocatalytic asymmetric oxidations in stereoselective synthesis, in: andrushko v.; andrushko, n. (eds.): stereoselective synthesis of drugs and natural products, pp. 1089–1114 (john wiley & sons, inc., hoboken, usa) 2013 doi: 10.1002/9781118596784.ssd036 [9] hu, q.; xu, y.; nie, y.: highly enantioselective reduction of 2-hydroxy-1-phenylethanone to enantiopure (r)-phenyl-1,2-ethanediol using saccharomyces cerevisiae of remarkable reaction stability, bioresour. technol., 2010, 101(22), 8502– 8508 doi: 10.1016/j.biortech.2010.06.044 [10] díaz-rodríguez, a.; iglesias-fernández, j.; rovira, c.; gotor-fernández, v.: enantioselective preparation of δ-valerolactones with horse liver alcohol dehydrogenase, chem. cat. chem., 2014, 6(4), 977– 980 doi: 10.1002/cctc.201300640 [11] kim, k.; plapp, b. v.: inversion of substrate stereoselectivity of horse liver alcohol dehydrogenase by substitutions of ser-48 and phe-93, chem. biol. interact., 2017, 276, 77–87 doi: 10.1016/j.cbi.2016.12.016 [12] giacomini, d.; galletti, p.; quintavalla, a.; gucciardo, g.; paradisi, f.: highly efficient asymmetric reduction of arylpropionic aldehydes by horse liver alcohol dehydrogenase through dynamic kinetic resolution, chem. commun., 2007, 39, 4038– 4040 doi: 10.1039/b712290j [13] hidekazu, d.; yuri, n. toyokichi, k.: mass transfer of acetylacetone, ethylene glycol mono-n-butyl ether and ethylene glycol monophenyl ether across water-carbon tetrachloride and water-chloroform interfaces, anal. chim. acta, 1990, 237, 237–240 doi: 10.1016/s0003-2670(00)83923-9 [14] kelemen-horváth, i.; nemestóthy, n.; bélafi-bakó, k.; gubicza, l.: stereoselective reduction of 2phenylpropionaldehyde by alcohol dehydrogenase with cofactor regeneration, chem. pap., 2002, 56, 52–56 url [15] manevski, n.: activity and enzyme kinetics of human udp-glucuronosyltransferases: studies of psilocin glucuronidation and the effects of albumin on the enzyme kinetic mechanism, academic dissertation, university of helsinki, 2013 url [16] rapp, c.; pival-marko, s.; tassano, e.; nidetzky, b.; kratzer, r.: reductive enzymatic dynamic kinetic resolution affording 115 g/l (s)-2phenylpropanol, bmc biotechnol., 2021, 21, 58 doi: 10.1186/s12896-021-00715-5 hungarian journal of industry and chemistry https://doi.org/10.1016/j.fct.2011.10.023 https://doi.org/10.1186/s12896-021-00715-5 https://doi.org/10.1007/978-3-642-17907-5_5 https://doi.org/10.33927/hjic-2020-22 https://doi.org/10.1073/pnas. 0306866101 https://doi.org/10.1515/znc-2010-1-201 https://doi.org/10.1186/1475-2859-7-25 https://doi.org/10.1002/9781118596784.ssd036 https://doi.org/10.1002/9781118596784.ssd036 https://doi.org/10.1016/j.biortech.2010.06.044 https://doi.org/10.1002/cctc.201300640 https://doi.org/10.1016/j.cbi.2016.12.016 https://doi.org/10.1039/b712290j https://doi.org/10.1016/s0003-2670(00)83923-9 https://www.chemicalpapers.com/file_access.php?file=561a52.pdf https://helda.helsinki.fi/bitstream/handle/10138/38186/activity.pdf?sequence=1&isallowed=y https://doi.org/10.1186/s12896-021-00715-5 introduction experimental methods applied chemicals activity measurements mass-transfer rate kinetics enantioselectivity results and evaluation kinetics activity mass transfer through the organic–water interface enantioselectivity conclusion hungarian journal of industry and chemistry vol. 50(1) pp. 1–65 (2022) hjic.mk.uni-pannon.hu contents antioxidant effect of humic substances from hungarian leonardite attila csicsor and etelka tombácz 1–5 a survey of sars-cov-2 genetic material reduction during a traditional wastewater treatment technology orsolya adamcsik, renáta gerencsér-berta, borbála oláhné horváth, nikoletta kovács, viola somogyi, endre gábor domokos, gábor kemenesi, endre gábor tóth, ferenc jakab and ildikó galambos 7–10 plant growth-promoting rhizobacteria – biotechnological tools to improve cereal yields gyöngyi székely and csengele barta 11–14 membrane unit for integrated gas separation – membrane bioreactor (gs-mbr) system zbyněk pientka, jakub peter and robert válek 15–22 production of chiral (s)-2-phenyl-1-propanol by enantioselective biocatalysts piroska lajtai-szabó, tímea brigitta bagó and nándor nemestóthy 23–28 production and characterization of sand-plastic composite floor tiles alexander asanja jock, messiah luke akpan and francis asokogene oluwadayo 29–32 unraveling the novel bacterial assisted biodegradation pathway of morpholine rupak kumar, suman kapur and srinivasa rao vulichi 33–43 enzyme reaction engineering as a tool to investigate the potential application of enzyme reaction systems nevena milčić, ivana ćevid, mehmet mervan çakar, martina sudar and zvjezdana findrik blažević 45–55 developing plant models of reduced complexity by chemical process engineering way of thinking mónika varga 57–65 https://hjic.mk.uni-pannon.hu/ hungarian journal of industry and chemistry vol. 50 pp. 1–5 (2022) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2022-01 antioxidant effect of humic substances from hungarian leonardite attila csicsor*1,2 and etelka tombácz1,3 1doctoral school of environmental sciences, university of szeged, rerrich béla tér 1, szeged, 6720, hungary 2hymato products kft., kossuth lajos u. 33, szentkirályszabadja, 8225, hungary 3soós ernő water technology research and development center, university of pannonia, zrínyi miklós u. 18, nagykanizsa, 8800, hungary humic substances are natural substances that are continuously formed from the decay of plant residues. these materials have a very diverse range of properties, making them versatile. according to many new studies, these humic substances also exhibit antioxidant propensities. the aim of this paper was to shed light on whether humic substances really have antioxidant properties. keywords: humic substances, humic acid, fulvic acid, himatomelanic acid, antioxidant, leonardite 1. introduction the majority of the population of hungary suffers from one of the diseases associated with free radicals, e.g. diseases of civilization, obesity, cardiovascular disease, malignant neoplasms, etc. although it is well-known that our consumption of vegetables and fruit lags far behind those of the other member states of the european union, it has been scientifically proven that essential fresh vitamins and provitamins as well as minerals are fundamental not only for the smooth functioning of the body but also for their antioxidant components. furthermore, they can play a key role in terms of disease prevention. berries have become a major player in a number of related research papers as they are also essential in the prevention as well as aftercare of cancer and cardiovascular disease. what other options are available and what other substances may still have high antioxidant contents? based on the aforementioned points, it is also important and justified to study the antioxidant properties of new compounds such as humic substances and determine which of their components play a crucial role in the development of their antioxidant effect, both qualitatively and quantitatively. the aim of this research is to compare the antioxidant properties of humic acids with already wellknown natural antioxidants. firstly, different humic acid recieved: 26 august 2021; revised: 16 september 2021; accepted: 20 september 2021 *correspondence: csicsor.attila@gmail.com fractions were prepared. the expected results should help to more accurately interpret the complex behavior of humic acids, thereby helping to expand their range of applications. therefore, if the results are convincing, this could open up new fields with regard to the application of humic acids in the food and cosmetics industries [1]. 2. humic substances humic substances are a group of naturally occurring macromolecules found throughout nature, that is, in soil, air, water, carbon deposits and peat. chemically illdefined humic substances are natural organic colloids comprised of decomposition products of plant-derived biomass as the result of a process called humification. their conversion into stabilized humic material is one of the most complex and least understood biogeochemical processes of the carbon cycle. most natural humic acids (ha) are found in older peat, lignite and juvenile lignite. in hungary, the ha content of the so-called leonardite, a famous source of ha, is close to 70% in its natural form. (a near-surface deposit of leonardite is located in dudar, where this geological formation can be mined). in the humification process, dead plant matter that enters the soil is broken down by enzymes found in soil bacteria and fungi, so simple compounds like sugar and ammonia are formed from carbohydrates, fats, proteins and lignin, which on the one hand serve as a source of food for the soil microbes but on the other hand as a source in the formation of humic substances. as a result of biotic and abiotic (condensation and polymerization) processes, https://doi.org/10.33927/hjic-2022-01 mailto:csicsor.attila@gmail.com 2 csicsor and tombácz the decomposition products form high-molecular-weight humus compounds, the presence of which is characteristic of the soil [2]. on the basis of differences in solubility, humic substances can be divided into several groups such as the main fractions humin, ha, and fulvic acids (fa), as well as the alcohol soluble himatomelanic acids (hy). they are a mixture of similarly behaving, yellow-brown-black, acidic, high-molecular, natural organic substances that are operationally defined. humic substances themselves contain too many kinds of molecules that can be separated by changing the solubility conditions. even though these molecules behave similarly, each fraction has different properties and their molecular structure is not uniform [2]. the nomenclature of fractions that can be separated according to their solubility is suggested in the guidelines of the international humic substances society (ihss): • humin a black fraction of humic substances that is insoluble in water at any ph. • humic acids the fraction of humic substances that is insoluble in water under acidic conditions (ph < 2) but soluble in water at higher ph values. they can be extracted by various alkaline solutions before being precipitated by a strong acid and are dark brown or black in color. • fulvic acids the fraction of humic substances that is soluble in water at all ph values. fulvic acids are light yellow or yellowish brown in color. • himatomelanic acids the fraction of humic substances that is soluble in an alcohol. 3. antioxidants the most important physiological role of antioxidants is to neutralize the free radicals that are continuously formed in the szent-györgyi-krebs cycle and counteract the free radicals with different oxidizing forces that enter the body. an antioxidant is a substance that inhibits oxidation, more broadly speaking, retards or hinders oxidation. they are chemically reducing agents, i.e. electron donors. these materials are usually organic compounds but include metals and organometallic complexes. many different types of antioxidants exist, which usually work together and do not neutralize free radicals on their own. although our body itself is able to produce some antioxidants, sometimes it is necessary for us to ingest these substances from external sources. together, these antioxidants already form a very strong line of defence in our body, e.g. vitamin c, vitamin a, flavonoids, glutathione, resveratrol, unsaturated fatty acids, etc. [3, 4] 4. methods for measuring the antioxidant capacity the antioxidant capacity is the combined free radical scavenging effect of all antioxidant compounds in the system studied. since the need for its accurate numerical determination is growing, a number of analytical procedures and measurement systems have been developed. given that methodologies are constantly being modified and refined, nowadays, the number of applied methods exceeds one hundred. in the literature, the majority of studies use several methods to determine the antioxidant capacity [5]. the most common methods of measuring the antioxidant capacity can be divided into two main groups: electron transition-based ones (ferric iron reducing antioxidant power, total polyphenol content, copper ion reducing antioxidant capacity, trolox equivalent antioxidant capacity, and 2,2-diphenyl-1-picrylhydrazyl (dpph)) as well as those based on hydrogen atom transfer (oxygen radical absorptance capacity, total peroxyl radical-trapping potential, chemiluminescence-based methods, and photochemiluminescence measurements just to mention the most commonly used methods). although these two types of measurements determine the antioxidant capacity, the results obtained do not necessarily have to be correlated with each other, since the reducing power of a sample is not necessarily related to its ability to scavenge for the reaction of test compounds. electron transfer reactions involve colour changes, from which the antioxidant capacity can be deduced. the essence of these methods is to create a free radical as the result of a reaction. to this free radical, the antioxidant is added at various dilutions leading to a colour change, which is monitored by a spectrophotometer and then the antioxidant capacity of the test substance is calculated from the results obtained. methods involving hydrogen atom transfer are based on the kinetics of the reaction. tests measure how effective a sample is against a given free radical, namely its free radical scavenging capacity [5]. 5. antioxidant effect of humic substances the question may arise as to why humic substances would exhibit an antioxidant effect. humic acids are chemically very complex mixtures of composite molecules, that is, natural polymers formed during the varying degrees of polymerization of basic building blocks. according to their chemical structure, they are polyhydroxy carboxylic acids with quinone and semiquinone groups. in some respects, they are similar to flavonoids and phenols, in which the so-called flavone skeleton is polysubstituted by hydroxy groups. however, they also have a quinoid structure that is known to be responsible for antioxidant properties. these properties of ha have already been demonstrated in a number of scientific publications by both classical analytical methods (redox titrations) and instrumental analytical measurements (electron spin resonance) [6]. the general structure of ha and the formulae of some well-known antioxidants are presented in fig. 1 from hungarian journal of industry and chemistry antioxidant effect of humic substances 3 figure 1: model structure of ha and identical moieties of known antioxidants [2] their structure, it is clear that ha are comprised of a number of groups such as already well-known antioxidants, so will exhibit exceptionally high antioxidant capacities [7]. 6. results 6.1 measurement of total phenolic content all measurements of total phenolic content were made according to the method developed by shetty et al. [8]. during these measurements, only high-quality (a.r.) chemicals were used. the fractions of humic substances were extracted by ourselves from samples of leonardite retrieved from dudar. rather than indirectly measuring the antioxidant property of the sample, the method measures its total phenolic content, from which its antioxidant capacity can be deduced. the method consisted of diluting 1 ml of the sample in 5 ml of distilled water and 1 ml of 95% ethanol in a test tube before adding 0.5 ml of 50% folin-ciocalteu (fc) reagent (half of distilled water in half fc reagents) to each sample. after being stirred for 5 minutes, 1 ml of 5% na2co3 was added to the reaction mixture and allowed to stand for 1 hour before the absorbance values of the samples were measured at 725 nm. these absorbance values were then converted into µg gallic acid equivalents in order to compare the measured values with each other and with other data from the literature. whilst measuring the total phenolic content of the samples, a series of dilutions was made from our samples of known mass, for which the total phenolic content was measured. a series of dilutions had to be produced in order to measure an absorbance value of approximately one for each sample. this was necessary to be able to compare the samples because the three different fractions yielded one absorbance value at different concentrations once the reaction was complete. furthermore, since the samples are coloured (brownish dark brown), the measured absorbance values had to be calibrated in light of the background of the samples. therefore, the samples were diluted to the concentration present in the reaction volume. after measuring the series of samples, their total phenolic content was calculated from the calibration curve, which can be seen in fig. 2, and the results obtained are shown in table 1. the results show that different initial concentrations of the various samples are required to achieve a similar absorbance. in the humic acid samples, since the majority of the phenol groups are in this fraction, the lowest initial concentration is required to achieve an absorbance of approximately one. himatomelanic acid has an average number of phenol groups while fa is comprised of the figure 2: calibration curve of gallic acid 50 pp. 1–5 (2022) 4 csicsor and tombácz table 1: the measured and corrected absorbance of the samples and the gallic acid equivalent (gae) values sample corrected concentration [mg/ml] abs measured abs corrected gae [mg/ml] from the calibration curve gae [mg/g] hy 0.59 1.027 0.953 0.103 174.5 fa 1.18 0.999 0.948 0.102 86.8 ha 0.35 1.024 1.024 0.11 310.3 ihss fa 0.684 1 0.107 156.8 ihss ha 0.212 1 0.107 506.1 table 2: the ic50 readings of the different samples name of the sample original concentration ic50 [µg/ml] hy 1.5 mg/ml 200 fa 2 mg/ml 300 ha 3.25 mg/ml 460 fewest. the results suggest that the studied humic fractions are likely to exhibit an antioxidant effect. 6.2 dpph method measurement of the antioxidant capacity based on stable dpph radical scavenging is one of the first methods. the reaction proceeds as follows: the dark purple radical formed in the reaction mixture loses its colour when it reacts with antioxidants. this method is widely used because the radicalforming molecule dpph is commercially available, stable as well as not particularly reactive nor aggressive, which is beneficial in the reactions that take place as taking measurements is simple. on the other hand, a stable radical that is not found in the living organism is used instead of a radical formed during the normal metabolism in the cell. using this method, it is not possible to estimate how effective the sample is as an antioxidant with regard to biological radicals [8]. during the measurements, 6 ml of a dpph working solution (0.1 mg/ml) was added to one ml of the sample, vortexed and stored in the dark for 30 minutes until the colour reaction began. after 30 minutes, the absorbances were measured at 517 nm. from the measured values that had previously been corrected, the percentage of inhibition (inhibition%, inhib.%) and the value corresponding to 50% inhibition (ic50 value) were calculated. while the measurements were taken, in the same way as when the total phenolic content was measured, a series of dilutions was made from a sample of known concentration. from the measured absorbances, after background correction the percentages of inhibition of the samples were calculated and plotted as a function of the concentration in order to determine the ic50 values of the samples (fig. 3). from the data, it can be concluded that the materials prepared and tested exhibit antioxidant properties because they inhibit the decomposition of the dpph radical. figure 3: percentage of inhibition of himatomelanic acid (top), humic acid (middle), and fa (bottom) as functions of the concentration to determine the ic50 values their ic50 values (table 2) are promising and comparable with other data in the literature [9]. 7. conclusions although the results revealed that the samples made from domestic raw materials exhibit antioxidant properties, further studies are needed to gain a complete picture of the antioxidant capacity of these substances. furthermore, in the future, it is our intention to confirm the results collected so far with in-vitro and in-vivo experiments. hungarian journal of industry and chemistry antioxidant effect of humic substances 5 references [1] balogh, e.; hegedus, a.; stefanovits-banyai, e.: application of and correlation among antioxidant and antiradical assays for characterizing antioxidant capacity of berries sci. hortic., 2010, 125(3), 332– 336 doi: 10.1016/j.scienta.2010.04.015 [2] stevenson, f.j.: humus chemistry: genesis, composition, reactions (wiley & sons, new york, usa) 1994, pp. 188–210 isbn: 978-0-471-59474-1 [3] nccih: antioxidants: in depth, retrieved 20 june 2018 https://www.nccih.nih.gov/health/antioxidants-in-depth [4] škvára, p.; kezmanová, j.; mišl’anová, c.; vojs staňová, a.: analysis and identification of polyphenolic compounds in green foods using a combination of hplc-esi-it-tof-ms/ms hung. j. ind. chem., 2018 46(1), 35–38 doi: https://doi.org/10.1515/hjic-2018-0008 [5] huang, d.; ou, b.; prior, r.l.: the chemistry behind antioxidant capacity assays j. agric. food chem., 2015, 53(6), 1841–1856 doi: 10.1021/jf030723c [6] csicsor, j.; gerse, j.; tikos, a.: the biostimulant effect of different humic substance fractions on seed germination, in: humic substances in the global environment and implications on human health, n. senesi and t. m. miano (eds.) pp. 557–562; proc. 6th intern. meeting of the intern. humic substances soc., monopoli, bari, italy, sept. 20–25, 1994 [7] ponomarenko, e.v.; anderson, d.w.: importance of charred organic matter in black chernozem soils of saskatchewan can. j. soil sci., 2001, 81(3), 285– 297 doi: 10.4141/s00-075 [8] vattem, d.a.; shetty, k.: ellagic acid production and phenolic antioxidant activity in cranberry pomace (vaccinium macrocarpon) mediated by lentinus edodes using a solid-state system process biochem., 2003, 39(3), 367–379 doi: 10.1016/s00329592(03)00089-x [9] ruiz-torralba, a.; guerra-hernández, e.j.; garcíavillanova, b.: antioxidant capacity, polyphenol content and contribution to dietary intake of 52 fruits sold in spain. cyta journal of food, 2018, 16(1), 1131-1138 doi: 10.1080/19476337.2018.1517828 50 pp. 1–5 (2022) https://doi.org/10.1016/j.scienta.2010.04.015 https://www.nccih.nih.gov/health/antioxidants-in-depth https://doi.org/https://doi.org/10.1515/hjic-2018-0008 https://doi.org/https://doi.org/10.1515/hjic-2018-0008 https://doi.org/10.1021/jf030723c https://doi.org/10.1021/jf030723c https://doi.org/10.4141/s00-075 https://doi.org/10.1016/s0032-9592(03)00089-x https://doi.org/10.1016/s0032-9592(03)00089-x https://doi.org/10.1080/19476337.2018.1517828 hungarian journal of industry and chemistry vol. 50 pp. 7–10 (2022) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2022-02 a survey of sars-cov-2 genetic material reduction during a traditional wastewater treatment technology orsolya adamcsik*1, renáta gerencsér-berta1, borbála oláhné horváth1, nikoletta kovács1, viola somogyi2, endre gábor domokos2, gábor kemenesi3, endre gábor tóth3, ferenc jakab3, and ildikó galambos1 1soós ernő water technology research and development center, university of pannonia, zrínyi miklós u. 18, nagykanizsa, 8800 hungary 2research centre for biochemical, environmental and chemical engineering, university of pannonia, egyetem u. 10, veszprém, 8200 hungary 3national virology laboratory, szentágothai jános research centre, university of pécs, ifjúság u. 20, pécs, 7624 hungary the transmission of severe acute respiratory syndrome coronavirus-2 in a community can be monitored by a wastewater-based epidemiological approach due to fecal shedding. although sewage surveillance has gained a considerable amount of attention over the last 16 months, an indirect issue within the topic is whether traditional wastewater treatment technologies are sufficiently efficient to eliminate the genetic material of sars-cov-2. samples were taken from the wastewater treatment plant in nagykanizsa before the virus was concentrated, nucleic acid extracted and sars-cov-2 detected by rt-qpcr (quantitative reverse transcription pcr). the influent and primary treated samples tested positive, while after the secondary treatment, all the results were negative. consequently, the activated sludge process proved to be efficient in terms of the removal of sars-cov-2. keywords: warning system, covid-19, wastewater-based epidemiology 1. introduction during the transmission of severe acute respiratory syndrome coronavirus 2 (sars-cov-2) since the start of the covid-19 pandemic, wastewater-based epidemiology (wbe) has gained a considerable amount of attention as a surveillance system. numerous research groups and health authorities are currently engaged in sewage monitoring worldwide. apart from viruses, various compounds can be monitored, e.g. pharmaceuticals or illicit drugs, to indirectly monitor the behavior or habits of a defined population [1]. furthermore, the approach allows anonymous, area-based monitoring in a community that is cost-, laborand time-efficient compared to human nasopharyngeal swab test campaigns [2]. moreover, fecal shedding can occur earlier than the onset of symptoms [3, 4], should any be expressed. while the ratio and role of asymptomatic and mild-symptomatic cases is debatable [5, 6], the wbe approach estimates the sars-cov2 rna concentration of the total community that is inderecieved: 26 august 2021; revised: 20 september 2021; accepted: 20 september 2021 *correspondence: adamcsik.orsolya@sooswrc.hu pendent of patients’ perception of well-being. although wbe has its own limitations, sewage monitoring and human test campaigns can also support national and municipal decision-making. considering the successful detection of sars-cov-2 from wastewater and during the consecutive steps of wastewater treatment, a considerable amount of aerosol formation has been observed. moreover, since droplets are regarded as the most important transmission route of sars-cov-2, the working conditions at wastewater treatment plants (wwtp) should be addressed in terms of safety. according to the who [7], no special care is required other than the usual safety protocols at such plants since sars-cov-2 particles present in untreated and treated wastewater have been proven to be non-infectious. another side interest within this topic is whether the sewage treatment technology is sufficiently effective to eliminate the sars-cov-2 virus particles detected in the influent to ensure the wwtp effluents are sars-cov-2-free, even if their infectivity has already been ruled out. the aim of this work is to assess the presence and concentration of sars-cov-2 rna in untreated and treated wastewater samples. https://doi.org/10.33927/hjic-2022-02 mailto:adamcsik.orsolya@sooswrc.hu 8 adamcsik, gerencsér-berta, oláhné horváth, et al. table 1: sars-cov-2 rna detection from wastewater influent and effluent samples at nagykanizsa wwtp. sample type date cq value (e-gene) influent 30/09/2020 +(35.69) influent 14/10/2020 +(33.88) influent 09/11/2020 +(32.39) influent 10/11/2020 +(33.70) influent 11/11/2020 +(34.27) influent 18/11/2020 +(36.67) influent 25/11/2020 +(37.03±0.11) effluent 25/11/2020 – influent 02/12/2020 +(33.70±0.50) effluent 02/12/2020 – 2. materials and methods sampling was conducted by délzalai víz és csatornamű zrt. at nagykanizsa wwtp during the morning peak time. from may until december 2020, samples of influent and occasionally effluent as well were taken at various sampling frequencies. while in december, on three consecutive days, in addition to influent and effluent sampling points, primary and secondary treated samples were also checked. the pairs of influent and effluent samples were processed in duplicates, while to assess the efficacy of the wwtp, three repetitions were used over three consecutive days. 1 l grab samples were taken and placed in sterile bottles, transported to our laboratory at 4 ◦c and immediately processed. the virus was concentrated and nucleic acid extracted according to meleg et al. [8] with minor modifications. concentrates were stored and transported at −80 ◦c to the national virology laboratory, university of pécs for specific sars-cov-2 detection by the quantitative reverse transcription polymerase chain reaction (rt-qpcr) technique, targeting the e and rdrp genes. modular sars-cov-2 e-gene and modular sars-cov-2 rdrp-gene detection kits (roche, germany) on the mygo pro real-time pcr instrument were employed. quantification cycle values (cq values) were used to compare the sars-cov-2 rna concentration of the above-mentioned samples. 3. results and discussion sewage samples tested negative during the summer months of 2020 (data not shown), which is plausible considering the insignificant number of open cases nationwide [9] and the temperature of the sewage as one of the most important environmental factors [10]. at the end of september, as the second wave progressed, the concentration of sars-cov-2 rna increased above the detection limit of the methods in the influent samples, while all effluent samples tested negative. during the autumn of 2020 although the first positive result was registered, followed by fluctuating quantification cycles all the results from influent samples (table 1) were positive, while table 2: sars-cov-2 rna concentration at different stages of wastewater treatment at the nagykanizsa wwtp (due to the rules of pcr amplification, higher quantification cycle values are linked to lower sars-cov-2 rna concentrations) sample type date cq value (e gene) 08/12/2020 +(28.89) influent 09/12/2020 +(34.06) 10/12/2020 +(31.04) 08/12/2020 +(40.04) primary treated 09/12/2020 +(35.43) 10/12/2020 +(37.13) 08/12/2020 – secondary treated 09/12/2020 – 10/12/2020 – 08/12/2020 – effluent 09/12/2020 – 10/12/2020 – their effluent sample pairs all tested negative without exception. from this information alone, it can be concluded that the commonly used, complex wastewater treatment technology itself is sufficiently efficient to decrease the sars-cov-2 rna load from wastewater without any additional steps, e.g. uv light treatment or surplus chemicals. our results concerning the influent-effluent pairs are in good agreement with earlier findings by haramoto et al. [11] by progressing one step further, samples were tested after primary and secondary treatment at the nagykanizsa wwtp (table 2). over three consecutive days while the influent samples tested positive, although the primary treated wastewater exhibited a slightly lower concentration of sars-cov-2 rna the results were still positive (manifesting in higher quantification cycles). from this reduction, it can be seen that the majority of the sars-cov-2 particles are not attached to the solid particles sedimented in this step. however, the duration of sars-cov-2 particles in wastewater is also an important factor [10] that can be partially responsible for the loss in rna load compared to the raw influent. after the activated sludge process, the estimated duration of sarscov-2 particles was longer than 8 hours and all samples tested negative. this loss of signal is reasonable considering the lengthy nature of the secondary treatment, the microbial activity together with the limited resistance of these viral particles to external agents [12] as well as the extreme sensitivity of the rna. as in the case of the earlier tested influent-effluent pairs, all treated effluent samples yielded negative results. over the last year, numerous other research groups have tested various wwtps with partially different technological setups [11,13–16] to that employed at nagykanizsa wwtp. a general consensus has been reached in all these experiments regarding the negative results of all the effluent material flow (treated hungarian journal of industry and chemistry a survey of sars-cov-2 genetic material reduction 9 effluent water and sludge line). even though some studies yielded positive results for some of the secondary treated effluents [11,13] or secondary sludges [16], in these cases all the treated materials exiting the wwtp produced negative results without exception. 4. conclusion according to our findings, which are in good agreement with other published research on this topic, the common treatment of wastewater is capable of decreasing the sars-cov-2 rna concentration below the complex detection limit of the multi-step measurement process. wwtps are capable of minimizing the presence of coronavirus nucleic acid without having to add further steps to the traditional technology. all in all, the sars-cov-2 viral particles are particularly stable in aquatic environments, so the treated wastewater discharge and risks related to its reuse have not proved to be considerable. 5. acknowledgement financial support was received from the national research, development and innovation office (grant no. 2020-2.2.1-ed-2020-00014). the authors would like to express their gratitude to the mol group for their cooperation. references [1] lorenzo, m.; picó, y.: wastewater-based epidemiology: current status and future prospects, curr. opin. environ. sci. health, 2019, 9, 77–84 doi: 10.1016/j.coesh.2019.05.007 [2] bivins, a. et al.: wastewater-based epidemiology: global 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the fate of sars-cov-2 in wwtps points out the sludge line as a suitable spot for monitoring, sci. total environ., 2020, 772, 145268 doi: 10.1101/2020.05.25.20112706 hungarian journal of industry and chemistry https://doi.org/10.1016/j.scitotenv.2020.140621 https://doi.org/10.1016/j.scitotenv.2020.140621 https://doi.org/10.1101/2020.05.25.20112706 hungarian journal of industry and chemistry vol. 50 pp. 11–14 (2022) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2022-03 plant growth-promoting rhizobacteria – biotechnological tools to improve cereal yields gyöngyi székely *1,2,3 and csengele barta4 1hungarian department of biology and ecology, faculty of biology and geology, babes, -bolyai university, 5-7 clinicilor st., cluj-napoca, 400006 romania 2 institute for research-development-innovation in applied natural sciences, babes, -bolyai university, 30 fântânele st., cluj-napoca, 400294 romania 3centre for systems biology, biodiversity and bioresources (3b), babes, -bolyai university, 5-7 clinicilor st., cluj-napoca, 400006 romania 4department of biology, missouri western state university, 4525 downs drive, agenstein-remington halls, st. joseph, mo 64507, usa ensuring food security for the world’s growing population is a significant challenge for scientists. efforts are constantly being made to solve this problem, including the use of expensive molecular engineering techniques, which are not always successful. a cost-effective and environmentally friendly biotechnological alternative would be the use of plant growthpromoting rhizobacteria, demonstrated by numerous studies to play many beneficial roles in improving plant traits, e.g. enhanced yields. keywords: plant growth-promoting rhizobacteria (pgpr), yield, environmentally friendly, low-cost 1. introduction cereals like bread wheat (triticum aestivum), maize (zea mays) and rice (oryza sativa) are fundamental and essential grain crops for both human and animal consumption. according to the statista statistics site, in 20202021, maize production exceeded 1.12 billion metric tons, wheat 775.8 million metric tons and rice about 505 million metric tons [1]. since the world’s population is constantly growing, the need to increase cereal production is continuous. however, the increasing occurrence of biotic and abiotic stress factors in the environment constitutes a severe global threat to improving cereal yields [2, 3]. to alleviate the detrimental effects of yield loss, expensive genetic engineering techniques for crop improvement have been developed. the use of plant growthpromoting rhizobacteria (pgpr) could represent a lowcost and environmentally friendly alternative biotechnological option. these kinds of soil bacteria, first described by kloepper and schroth in 1978 [4], were isolated from the immediate vicinity of plants, that is, from the rhizosphere. later, several beneficial effects of pgpr in stimulating plant growth were described [5–7]. nowadays, the pgpr biotechnology is more and more frequently used in the management of biotic and abiotic stress factors for a wide range of crop species in *correspondence: gyongyi.szekely@ubbcluj.ro order to reduce their damaging effects, which ultimately can cause important yield losses [6,7]. understanding the mechanisms at the basis of the pgpr technology in alleviating biotic and abiotic stress-induced damage in crops could be essential to reduce subsequent crop yield losses. exploiting the positive effects of plant-microbe interactions might provide multiple multi-pronged solutions to the global food crisis, reduce the amount of irrigation provided by fresh water as well as solve environmental stress concerns and maintain soil health. 2. the most common effects of pgprs on plants over the last decade, versatile positive properties of pgprs have been intensely documented. dozens of articles highlight the importance of these rhizobacteria in the process of alleviating damage brought about by abiotic stress. a large number of different pgpr species, e.g. pseudomonas alcaligenes, p. mendocina, bacillus polymyxa, b. pumilus and mycobacterium phlei, have been described to play a positive role in stimulating growth in various plant species as well as in the process of improving their tolerance of high temperatures and the salinity of many crops [6, 7]. shrivastava and kumar (2015) indicated that certain pgpr species can produce antioxidants, therefore, can be useful for reducing oxidative stress-induced damage to plants [6]. inhttps://doi.org/10.33927/hjic-2022-03 mailto:gyongyi.szekely@ubbcluj.ro 12 székely and barta figure 1: the impact of biotic and abiotic stress on crop resistance in the absence (panel a) and presence (panel b) of pgpr. oculation with pgprs improved seed germination and seedling growth, increased the concentrations of chlorophylls, antioxidant enzymes, proline, malondialdehyde and flavonoids as well as reduced the na+ content in different crops [8, 9]. recently, a couple of authors documented a set of plant growth-promoting traits, namely the ability to solubilize phosphate as well as produce indole-3-acetic acid (iaa) and 1-aminocyclopropane-1carboxylic acid (acc) deaminase of different pgpr species [7, 10, 11]. furthermore, several physiological traits such as leaf chlorophyll content, stomatal conductance, leaf relative water content and membrane leakage adversely affected by cold stress were mitigated by pgpr [12]. in addition, certain pgpr species are important factors in relieving not only abiotic but also biotic stressinduced damage. plants are commonly attacked by aphids and fungi, which cause substantial yield losses in crops and especially affect the production of cereal grains globally [3, 13, 14]. naeem et al. (2018) showed the positive effect of bacillus spp. and pseudomonas spp. in terms of enhancing the productivity of wheat attacked by aphid populations [3]. fungi represented by the genus fusarium infest cereals worldwide, moreover, f. graminearum is responsible for cereal head blight and maize ear rot in north and south america, europe as well as asia [14, 15]. to reduce the considerable amount of destruction caused by f. graminearum, several authors propose the use of an effective, economical and environmentally friendly biotechnological tool. they demonstrate that different pgpr species have antagonistic effects on f. graminearum and possess the ability to promote wheat growth under adverse biotic and abiotic stress conditions as well [16,17]. fig. 1 illustrates the impact of biotic and abiotic stress on crop resistance in the absence and presence of pgpr. finally, pgpr species can also function as important components of biofertilizers and biopesticides since they can improve the nutrient content and quality of soil through the mechanisms of nitrogen fixation and phosph ate solubilization. as biopesticides, these rhizobacteria protect the plants as a result of their ability to synthesize antibiotics [18, 19]. efforts to implement such environmentally friendly technologies are increasing annually and could be part of the solution to the ever-increasing demand for food to feed the growing global population . 3. pgpr mediates increases in cerealcrop yields biotic and abiotic stress factors usually cause a series of negative effects on crop yield, quantity and quality. under adverse environmental conditions and exposed to multifarious pathogen attacks from viruses, bacteria, fungi, insects, etc., plants respond defensively, implying changes in several physiological and nutritional parameters, hormonal imbalances and important yield losses [7, 10, 18]. globally, wheat, maize and rice are essential staple foods for billions of people. annually, these cereals are grown on hundreds of millions of hectares of land and are consumed by several billion people in hundreds of countries. as a result of population growth, production must continuously be enhanced. predictions state that by the year 2050, consumers will need 60% more wheat compared to the present production rate [20]. this must be hungarian journal of industry and chemistry plant growth-promoting rhizobacteria 13 table 1: beneficial effects of some pgpr species on wheat, maize and rice yields pgpr species effect on yield cereal species reference azospirillum sp. bacillus sp. bacillus megaterium paenibacillus polymyxa raoultella terrigena enhanced grain yield; enhanced straw yield; increased uptake of macro nutrients (n, p, k, ca, mg and s); increased uptake of micro nutrients (fe, mn, zn and cu). wheat [12] bacillus sp. pseudomonas spp. enhanced grain yield; enhanced straw yield; enhanced number of grains per spike; enhanced number of productive tillers. wheat [3] alcaligenes faecalis bacillus aryabhattai pseudomonas corrugat a pseudomonas arsenicoxydans pseudomonas brassicacearum pseudomonas azotoformans enhanced grain yield; enhanced plant growth-promoting traits (shoot and root lengths, fresh and dry weights). wheat [21] bacillus pumilus bacillus safensis lysinibacillus sphaericus paenibacillus alvei enhanced grain yield; phosphate solubilization (except for l. sphaericus); nitrogen fixation. maize [22] cupriavidus necator pseudomonas fluorescens enhanced aerial biomass; increase in n and p use efficienc ies. maize [23] azospirillum brasilense azotobacter chroococcum pseudomonas aeruginosa pseudomonas fluorescens pseudomonas putida enhanced grain yield; enhanced iaa production; enhanced phosphate solubilization. rice [24] bacillus sp. bacillus thuringiensis pseudomonas mosselii enhanced grain yield; enhanced root and shoot biomasses; enhanced production of iaa , siderophores and acc deaminase as well as the ability to solubilize phosphate . rice [26] achieved without expanding the area of arable land and by using eco-friendly and low-cost biotechnological strategies. one of these strategies is the use of pgpr to enhance crop productivity. table 1 presents the impact and efficacy of different pgpr species in enhancing wheat, maize and rice yields [3, 12, 21–25]. 4. conclusions the use of plant growth-promoting rhizobacteria to improve cereal yields represents a prosperous, environmentally friendly and economical strategy. pgpr are useful tools to reduce the effects of biotic and abiotic stress on plants, therefore, could contribute towards optimal plant growth and development as well as enhance their yields. finally, pgpr could represent a resource to ease the emerging global food crisis. references [1] worldwide production of grain in 2021/22, by type https://www.statista.com/statistics/263977/world-grain-production-bytype/ retrieved 27 october 2021 [2] afzal, a.; 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hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2022-04 membrane unit for integrated gas separation – membrane bioreactor (gs-mbr) system zbyněk pientka *1, jakub peter1, and robert válek2 1institute of macromolecular chemistry cas, heyrovského nám. 2, 162 06 prague 6, czech republic 2membrain s.r.o., pod vinicí 87, 471 27 stráž pod ralskem, czech republic one of the research directions of renewable energy sources is the production of biohydrogen from the dark fermentation of organic matter. during this fermentation process, since hydrogen is produced along with a complex mixture of other gases and vapors, hydrogen gas requires further purification. one relatively easy solution to this problem might be the utilization of gas separation membrane modules given their low energy consumption, simple operation and ease of upscaling. in this work, hollow fiber (hf) membranes based on polyetherimide (pei) were developed and tested. hf membranes were spun from a polymer solution of pei using the wet phase inversion process into a water bath using a pilot-scale spinning device. gas transport measurements showed that membranes exhibited permeances of between 9.3 and 19.2 gpu with co2/h2 selectivities within the range of 3.3 − 5.6. morphology studies showed regular shapes resembling hollow fibers with outer diameters within the range of 250−320 microns, depending on various parameters of the spinning process. the best performing membranes were selected and a morphological analysis carried out. selected fibers were incorporated into two types of membrane modules. one type was a laboratory-scale membrane mini-module used for preliminary tests, while the other membrane module was designed for the treatment of larger amounts of biohydrogen. two types of laboratory-scale membrane separation units were constructed. for laboratory use, the low-pressure unit proved more accurate regulation to match the fermenters performance with the separation unit in comparison with the high-pressure one. keywords: polymer membranes, gas separation, hollow fibers, membrane module 1. introduction the motivation of this research is the need to reduce the ecological footprint of society by developing green technologies enabling carbon sequestration, sustainable production of valuable chemicals and environmentallyfriendly energy production. this task is to be completed by the development of a novel, circular-loop gas separation membrane bioreactor system. microalgae grown in a photobioreactor capture refused-co2 from the fermentative reactor, which simply ferments these microalgae. during the process, a mixture of hydrogen and co2 is produced. the hydrogen can be separated and utilized for energy production. in addition, some valuable chemicals are produced. the newly developed system is known as a gas separation membrane bioreactor (gs-mbr) [1]. a key component of the gs-mbr is a membrane unit, which forms technological solutions for the separation of recieved: 17 december 2021; revised: 3 january 2022; accepted: 4 january 2022 *correspondence: pientka@imc.cas.cz h2 and co2 from the fermentation product. the basic elements in the membrane unit are membrane modules that utilize hollow fiber (hf) membranes. 2. experimental 2.1 materials pei (ultem™ 1000 resin grade) was purchased from sabic. the chemical structure of a repeated unit of ultem™ 1000 resin and the details regarding its preparation have previously been presented [2]. 2.2 development of hf membranes hollow fiber membranes were prepared with the strategic cooperation of the company membrain s.r.o. located in the czech republic. the procedure was described in our previous paper [2]. the spinline used for fabrication of the membranes is shown in fig. 1. 2.3 development of hf membrane modules the hc1 hf membrane mini-module was prepared by fixing 10 − 20 fibers into the swagelok tube fitting using https://doi.org/10.33927/hjic-2022-04 mailto:pientka@imc.cas.cz 16 pientka, peter and válek figure 1: the spinline used for the fabrication of hf membranes 3m of the epoxy resin dp100. the same resin was used to create the dead end of the fibers. the whole assembly was inserted into the 12-mm-wide tube using the corresponding swagelok tube fittings as presented in fig. 2. the module was equipped with 6-mm-wide connectors. p2-type hf membrane modules were constructed in a similar manner to those reported in [2], that is, from an arranged bundle of 250 a5-7 fibers (membrane area: 844 cm2) inserted into a pvc pipe. a schematic diagram of the p2-type hf membrane module and a photograph of it are presented in fig. 3. figure 2: hc1 hf membrane mini-module 2.4 determining the gas transport properties of the hf membrane laboratory modules containing 10 − 20 fibers of about 20 cm in length were prepared. one end of the fibers was sealed by an epoxy resin. the outer surface of the fibers was exposed to a mixture of gases which permeate into their hollow centers. gas permeation experiments were carried out using a mixture of co2 and h2 (1 : 1 volume ratio) at 2.0 and 4.2 bars (∆p was 1.0 and 3.2 bars, respectively) to determine the separation properties of the asymmetric pei hf membrane. its composition, pressures and flow rates were managed by the poseidon figure 3: schematic diagram of a cross-section of the p2type hf membrane module convergence inspector poseidon gp figure 4: testing of gas tranport properties of prepared hf membranes hungarian journal of industry and chemistry membrane unit for integrated gas separation 17 table 1: process parameters with regard to the production of asymmetric pei membranes sample polymer dope dose bore liquid dose towing speed m/min air gap cm od µm id µm ml/min ml/min a5-1 4.2 2.1 12 2 417 248 a5-2 4.2 2.1 9.7 5 405 234 a5-3 4.2 2.6 12 5 410 265 a5-7 6 2.6 12 2 420 239 b3-1 0.75 0.625 12 2.5 289 186 b3-2 0.75 0.625 15 6 270 190 b3-3 0.75 0.45 12 6 290 185 b3-7 0.9 0.45 12 2.5 320 171 convergence inspector gas permeation (convergence industry b.v.). the permeate flow rate was measured by a bubble flowmeter and the composition of the permeate stream analyzed by a prima bt bench top mass spectrometer (thermo fisher scientific). six laboratory modules were tested in series, where the retentate from the first module was used as a feed for the second module and so on (fig. 4). although this setting minimizes gas consumption and saves time, the correct mass balance on each module should be calculated. more information with regard to this can be found in [3]. the permeance pi for co2 and h2 as well as the co2/h2 mixed gas selectivity α∗ i/j were evaluated from measured data. the permeance pi is defined as the volumetric flow rate per unit driving force per unit area: pi = qp · yi (pp · xi − pp · yi) ·a (1) whereqp denotes the flow rate of the permeate, yi stands for the mole fraction of gas i in the permeate, p represents the absolute pressure in the feed or permeate and a is the membrane area. 2.5 development of the membrane separation unit the membrane apparatus was built using fittings from superlok; tubing 6 mm in diameter and parker 201lg solenoid valves manufactured by parker, 250 kpa bd sensors pressure sensors and a bp300-1-s back pressure regulator by pressure tech; a kk15 a 035/62 compressor by dürr technik: oil-free, max. performance = 25 l/min, 8 bar, max. pressure = 12 bar; a rocker 410 oil-free vacuum pump; a control unit based on an arduino uno microcomputer and software developed by the authors. 3. results and discussion 3.1 preparation of hf membranes the preparation of hf membranes was carried out using 4 spinnerets simultaneously, resulting in a higher towing speed (15 m/min) which corresponds to the production of 3600 m of hf membrane per hour. there were two series (denoted as a5 and b3) of fibers prepared using various spinning process parameters. the significant difference between the a5 and b3 series are the dimensions of the nozzles. for the a5 series, the outer outlet diameter (od) of the larger nozzle was used (0.512 mm), whereas for the b3 series, the outer od of the nozzle was 0.330 mm. the process parameters with regard to the production of the asymmetric pei membranes are listed in table 1. as can be seen, all the membranes with a dosing of polymer dope of 0.75 ml/min apparently had a smaller outer outlet diameter (od) than the fibers with a flow rate of polymer dope of 0.9 ml/min. it can also be observed that at higher towing speeds, the ods of hf membranes were lower (with the exception of membranes b3-6). 3.2 characterization of gas transport across hf membranes each sample of membrane was measured in three membrane modules by simultaneously connecting six modules to a poseidon group system (i.e. two samples of membrane were tested simultaneously). the average values were recorded and presented in table 2. the results showed that all the membranes exhibited permeances within the range of 9.3−19.2 gpu and h2/co2 selectivities within the range of 3.3−5.6. it is well known that gas separation in polymers can be described by a solutiondiffusion model [4] which states that the permeability coefficient is the product of the diffusion and solubility cotable 2: gas transport properties of the prepared hf membranes for the h2/co2 mixture measured at a pressure of 8 bars. sample co2 permeance (gpu) h2/co2 selectivity a5-1 11.5 4.4 a5-2 10.3 4 a5-3 17.5 5.3 a5-7 19.2 5.6 b3-1 9.5 4.4 b3-2 9.3 4 b3-3 10.3 5.3 b3-7 20.3 4.5 50 pp. 15–22 (2022) 18 pientka, peter and válek (a) (b) (c) (d) figure 5: optical microscopy image (a); sem micrographs (b-c) and afm micrograph (d) of the cross-section and surface of the prepared hf membranes. efficients. in our case, h2 permeates faster than co2 and since the diffusion coefficient of h2 is significantly larger than that of co2 [5], it can be concluded that the separation is based on differences in diffusivities. this is typical for glassy polymers, including the pei applied in this paper. the best membrane from the a5 series was used to fabricate the p2 membrane module containing 250 fibers. from the whole b3 series, the two best membranes, namely b3-3 and b3-7, were selected to be incorporated into the membrane mini-modules. 3.3 morphology of hf membranes the resulting hollow fiber membranes (fig. 5) had a regular round shape with a sponge-like structure containing typical relatively small finger-like pores (<30 µm). as determined using an optical microscope, the outer and inner diameters of the hollow fibers were 313 ± 9 µm and 290 ± 5 µm, respectively. the separation layer was on the outer surface for all the fibers. atomic force microscopy (afm) of the surfaces of the fibers revealed a relatively smooth surface consisting of a protective coating of pdms with no defects. 3.4 hollow fiber membrane modules hc1 mini-modules once the best membranes from the b3 series had been chosen (b3-3 and b3-6), the requirements of the project coordinator with regard to modules for membrane bioreactors were established. according to the requirements, three hc1 modules were manufactured with assistance from membrain s.r.o. their single gas transport properties were measured and are summarized in table 3. the first two modules (hc1_1 and hc1_2) contained the same b3-7 hf membrane, the only difference between them was the number of fibers they consisted of and thus their membrane areas. hc1_1 consisted of 10 fibers with a corresponding membrane area of 19.7 cm2, while hc1_2 consisted of 20 fibers with a corresponding membrane area of 39.3 cm2. hydrogen permeation flow rates were 28.2 (for hc1_1) and 53.0 ml/min (for hc1_2) at a feed pressure of 4.2 bars (abs) and achieving ideal h2/co2 selectivities of 4.4 and 3.7, respectively. the permeate was released at atmospheric pressure. the slightly lower selectivity of the second module can be attributed to the variation in the membrane properties, minuscule leakage within the module or a combination of both. the hc2 mini-module consisted of 23 fibers of b33 membrane, corresponding to a membrane area of 41.9 cm2. as can be seen in table 3, the permeate fluxes of the membrane modules were more than two times lower and only yielded negligibly higher selectivities. the modules were handed over to a korean participant in the aforementioned project for further testing on real biogas. the same modules were also tested for the h2/co2 mixture to demonstrate their ability to concentrate the hydrogen. from table 4, it can be seen that the modules were able to concentrate hydrogen from an initial percent concentration of 57 % to 88 % in the case of the hc1_1 module at a membrane stage cut of 96 % and from 57 % to 77 % in the case of the hc2 module at a membrane stage cut of 88 %. the membrane stage cut is defined as the ratio of the permeate flow rate to the feed flow rate. generally, by increasing the membrane stage cut, the concentration of the more permeating penetrant is also higher. on the other hand, the hydrogen recovery is lower because most of the hydrogen from the feed is transferred into the low-concentration permeate. p2-type module thicker hf membranes with an average od of 420 µm were incorporated into a quarter-scale membrane module. from the number of fibers the module consisted of, that is, 250, and their active length, namely 25.6 cm, the total membrane area of the module was calculated to be 844 cm2. the membrane module was tested against the gas transport properties of various single gases. the measured values are presented in table 5. according to the measurements, the permeances more than doubled compared to the same membrane measured in a smallscale laboratory module. furthermore, different values of h2/co2 selectivities were calculated, the selectivity dropped from 5.6 to almost 3.0 to be exact. this perhaps indicates the presence of some microdefect on one of the fibers or a minuscule leakage between the feed and permeate. nevertheless, the separation performance was sufficient to demonstrate the concept of biohydrogen purifihungarian journal of industry and chemistry membrane unit for integrated gas separation 19 table 3: characterization of hc1 and hc2 mini-modules gas transport properties were measured for single gases at pressure differentials of 1.0 and 3.2 bars as well as at a temperature of 25 ◦c gas number fiber fiber ∆p permeate flow membrane permeance h2/co2 of fibers diameter (cm) length (cm) (bar) rate (ml/min) area (cm2) (gpu) selectivity module hc1_1 co2 10 0.0313 20 1 1.96 19.7 22.1 4.41 10 0.0313 20 3.2 6.45 19.7 22.8 4.37 h2 10 0.0313 20 1 8.65 19.7 97.7 10 0.0313 20 3.2 28.2 19.7 99.6 module hc1_2 co2 20 0.0313 20 1 3.92 39.3 22.1 4.46 20 0.0313 20 3.2 14.3 39.3 25.2 3.71 h2 20 0.0313 20 1 17.5 39.3 98.9 20 0.0313 20 3.2 53 39.3 93.6 module hc2 co2 23 0.029 20 1 1.65 41.9 8.7 4.5 23 0.029 20 3.2 5.54 41.9 9.2 4.3 h2 23 0.029 20 1 7.43 41.9 39.4 23 0.029 20 3.2 23.8 41.9 39.4 table 4: gas transport properties of the hc1 and hc2 membrane mini-modules for the co2/h2 mixture measured at a feed pressure of 3.6 bars (abs) module parameter composition [%] feed retentate permeate hc1_1 h2 permeance (gpu) – 57 54 88 co2 permeance (gpu) – 43 46 12 membrane stage cut 0.96 – – – co2/h2 selectivity 4.2 – – – hc1_2 h2 permeance (gpu) – 41 40 63 co2 permeance (gpu) – 59 60 37 membrane stage cut 0.94 – – – co2/h2 selectivity 4.3 – – – hc2 h2 permeance (gpu) – 57 38 77 co2 permeance (gpu) – 43 62 23 membrane stage cut 0.88 – – – co2/h2 selectivity 5.7 – – – cation. 3.5 development of the membrane gas separation unit using the membrane modules, this project included the construction of a membrane gas separation unit, the optimization of the fermentation system and the integration of the gas separation unit into the gs-mbr. 50 pp. 15–22 (2022) 20 pientka, peter and válek table 5: gas separation properties of the p2 membrane module measured for single gases at 25 ◦c (number of fibers = 250, average od = 420 microns, membrane area = 844 cm2) gas ∆p (bar) permeate flow rate (ml/min) permeance (gpu) h2/co2 selectivity co2 2 356 46.2 2.92 5.6 949 44 2.99 h2 1.2 625 135.3 – 2 1012 131.5 – o2 0.65 28 11.2 – 1.1 46 10.9 – high-pressure membrane unit utilizing a laboratory air compressor the model membrane unit consisted of a p2 hf membrane module, a laboratory air compressor, three pressure sensors, a pressure regulator valve, two solenoid valves, a back pressure regulator, fittings and an arduino control unit. a schematic diagram and photograph of the unit are presented in fig. 6. both bioreactors were simulated by pressure vessels with inlets. the control unit senses the pressures in both pressure vessels (bioreactors) and at the feed of the membrane module. to achieve a high degree of efficiency, it is necessary to match the fermentation performance of both bioreactors to the performance of the membrane gas separation unit. an attempt was made to control the compressor using pulses, namely the compressor was switched on when the fermented amount of biogas in the main bioreactor reached the specified limit. since the power of the compressor considerably exceeded the performance of both fermenters and the membrane unit, it was necessary to control the flow of the compressed gas mixture into the membrane module by means of a back pressure regulator, which transferred the excess amount of compressed gas into the bypass. in order to maintain the pressure in the loop at close to atmospheric pressure, an expansion vessel was connected to it. the compressor was controlled by pulses once again – an arduino microcontroller opened the solenoid valves when the amount of biogas in the main bioreactor exceeded the set limit. the regulating valve in the retentate stream of the membrane module regulates its stage cut. when the pressure in the main bioreactor decreased under the set limit, the arduino microcontroller closed the solenoid valves. this type of control guaranteed that the feed pressure in the membrane module was sufficiently high to maintain the required separation efficiency. the pressure was kept by back-pressure regulator. the flow rate of the gas mixture that was simultaneously fed into the membrane module varied from 0 to 3 l/min, which is given by the pulse width or duty cycle. it should be noted that the mixture of hydrogen and carbon dioxide is reactive under certain conditions [6]. it probably cannot be ruled out that the pressures and temperatures in the compressor together with the presence of metal alloys will not trigger any undesired hydrogenation. the compressor must therefore be an internal atex version. the problem can be managed as shown in [7], where the same gas mixture was pressurized up to 380 bars. low-pressure membrane unit utilizing a vacuum pump the second model membrane unit generates the driving force at the membrane by the suction force supplied by a vacuum pump. the unit again consists of the p2 hf membrane module, a laboratory vacuum pump, two pressure sensors, two solenoid valves, a peristaltic pump, fittings and an arduino microcontroller. a schematic diagram and photograph of the unit is presented in fig. 7. when the pressure of the biogas in the main bioreactor exceeded the set limit, the arduino microcontroller opened both solenoid valves and started the peristaltic pump. the flow rate produced by this pump regulated the membrane stage cut. the permeate flux was considerably lower as the pressure differential was smaller than in the first unit. however, regulation in laboratory-scale experiments more accurately matched the performance of the fermenter with that of the gas separation unit. the amount of gas mixture fed into the membrane module can vary from 0 to 0.5 l/min, which is given by the pulse width or duty cycle as presented in the first set-up. 4. conclusion a series of 8 batches of hf membranes was prepared. each batch had different spinning process parameters. the morphology and gas transport properties were characterized to select the 2 best hf membranes which were incorporated into 2 types of membrane modules. the first module was designed for laboratory tests and had a small membrane area and low permeate flow rate. the other module consisting of 250 hollow fibers was constructed for larger flow rates and scale. all membrane modules were tested for singleas well as mixed-gas transport properties and exhibited good levels of performance. the design and development of a membrane separation unit is a very complex task. firstly, membranes in the form of hollow fibers based on pei were prepared. then modules from each batch were built and characterized according to gas transport. the most efficient module achieved a separation factor for h2/co2 in excess of 5. three modules of this type were fabricated as well as tested using a model mixture and may hopefully be appropriate for real-life gas separation [8], which is going to be carried out by our partners. hungarian journal of industry and chemistry membrane unit for integrated gas separation 21 (a) (b) figure 6: schematic diagram (a) and photograph (b) of the high-pressure membrane unit for the integrated gs-mbr system: 1 pressure vessel, 2 pressure sensor, 3 p2 membrane module, 4 laboratory air compressor, 5 expansion vessel, 6-7 two solenoid valves, 8 back pressure regulator, 9 regulating valve with a flow meter, 10 arduino microcontroller. (b) (a) figure 7: schematic diagram (a) and photograph (b) of the low-pressure laboratory-scale membrane unit: 1 pressure vessel, 2 pressure sensor, 3 p2 membrane module, 4 laboratory vacuum pump, 5 expansion vessel, 6-7 two solenoid valves, 8 peristaltic pump, 9 pressure vessel – retentate recipient, 10 arduino control unit. 50 pp. 15–22 (2022) 22 pientka, peter and válek two types of laboratory membrane separation units were constructed using the larger p2 hf membrane module. the high-pressure unit utilizes a compressor to pressurize the gas mixture into the feed of the module, while the low-pressure unit utilizes a vacuum pump to maintain a low pressure in the permeate of the membrane module. to ensure the separation efficiency remains high, pulse regulation was utilized. for laboratory use the lowpressure unit proved more accurate regulation to match the fermenters performance with the separation unit. acknowledgement this part of the international cooperation was supported by project 8f17005 and contract no. msmt-20364/20173/5 provided by the czech ministry of education, youth and sports. thanks to all participants of the common korea – visegrad countries project i-algmemb for cooperation. references [1] bakonyi, p.; kumar, g.; bélafi-bakó, k.; kim, s.h.; koter, s.; kujawski, w.; nemestóthy, n.; peter, j.; pientka, z.: a review of the innovative gas separation membrane bioreactor with mechanisms for integrated production and purification of biohydrogen, bioresour. technol., 2018, 270, 643–655 doi: 10.1016/j.biortech.2018.09.020 [2] bakonyi, p.; peter, j.; nemestóthy, n.; malý, d; kumar, g; koter, s; kim, s.-h.; kujawski, w.; bélafi-bakó, k.; pientka, z.: feasibility study of polyetherimide membrane for enrichment of carbon dioxide from synthetic biohydrogen mixture and subsequent utilization scenario using microalgae, int. j. energy res., 2021, 45, 8327–8334 doi: 10.1002/er.5732 [3] válek, r.; malý, d.; peter, j.; gruart, m.: effect of the preparation conditions on the properties of polyetherimide hollow fibre membranes for gas separation, desalin. water treat., 2017, 75, 300–304 doi: 10.5004/dwt.2017.20747 [4] wijmans, j. g.; baker, r. w.: the solutiondiffusion model: a review, j. membr. sci., 1995, 107(1–2), 1–21 doi: 10.1016/0376-7388(95)00102-i [5] freeman, b.; yampolskii, y.; pinnau, i. (eds.): materials science of membranes for gas and vapor separation (john wiley & sons, ltd, chichester, uk) 2006. doi: 10.1002/047002903x [6] zeng, l.; wang, z.; wang, y.; wang, j.; guo, y.; hu, h.; he, x.; wang, c.; lin, w.: photoactivation of cu centers in metal-organic frameworks for selective co2 conversion to ethanol, j. am. chem. soc. 2020, 142, 75–79 doi: 10.1021/jacs.9b11443 [7] härtel, g.; püschel, t.: permselectivity of a pa6 membrane for the separation of a compressed co2/h2 gas mixture at elevated pressures, j. membr. sci. 1999, 162, 1–8 doi: 10.1016/s03767388(99)00066-6 [8] rózsenberszki, t.; koók, l.; bakonyi, p.; nemestóthy, n.; bélafi-bakó, k.: comparative study on anaerobic degradation processes of pressed liquid fraction of organic solid waste, hung. j. ind.chem., 2021, 49(1), 31–35 doi: 10.33927/hjic-2021-05 hungarian journal of industry and chemistry https://doi.org/10.1016/j.biortech.2018.09.020 https://doi.org/10.1016/j.biortech.2018.09.020 https://doi.org/10.1002/er.5732 https://doi.org/10.1002/er.5732 https://doi.org/10.5004/dwt.2017.20747 https://doi.org/10.1016/0376-7388(95)00102-i https://doi.org/10.1002/047002903x https://doi.org/10.1021/jacs.9b11443 https://doi.org/10.1016/s0376-7388(99)00066-6 https://doi.org/10.1016/s0376-7388(99)00066-6 https://doi.org/10.33927/hjic-2021-05 https://doi.org/10.33927/hjic-2021-05 hungarian journal of industry and chemistry vol. 50 pp. 23–28 (2022) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2022-05 production of chiral (s)-2-phenyl-1-propanol by enantioselective biocatalysts piroska lajtai-szabó *1, tímea brigitta bagó1, and nándor nemestóthy1 1research group on bioengineering, membrane technology and energetics, university of pannonia, egyetem u. 10, veszprém, 8200, hungary enantioselective production of (s)-2-phenyl-1-propanol is important as in order to be applied in industry, a high degree of optical purity is required. besides organocatalysts and metal complexes, biocatalysts can be used for its synthesis in their isolated form or as whole-cell biocatalysts, both of which have various advantages and disadvantages. in this research, saccharomyces cerevisiae, as a whole-cell biocatalyst, and recombinant horse-liver alcohol dehydrogenase (adh), as an isolated enzyme, were investigated in terms of their activity, kinetics and enantioselectivity. in the case of yeast, the rate of cofactor regeneration was twice that of substrate conversion, moreover, the biocatalyst saccharomyces cerevisiae can be characterised by substrate-limited kinetics and low enantioselectivity. in contrast, the isolated enzyme recombinant horse-liver adh exhibited biphasic kinetics and cofactor regeneration was the rate-limiting step. the outstanding enantioselectivity of recombinant horse-liver adh renders it a promising catalyst for the purpose of this synthesis. keywords: alcohol dehydrogenase, whole-cell biocatalyst, saccharomyces cerevisiae 1. introduction 2-phenyl-1-propanol is a fragrance ingredient that produces the lila-hyacinth odour commonly used in cosmetics, fine fragrances and household cleaners [1]. besides, it is the basis of some non-steroidal anti-inflammatory drugs and the precursor of other fragrances [2]. these fields of use require a high degree of optical purity since the enantiomers of the compound, by and large, bring about different biological effects [3]. asymmetric syntheses are preferentially obtained using enzymes, given the capability of most to catalyse organic reactions with high enantioselectivity under mild conditions [4, 5]. besides isolated enzymes, whole cells are also being applied more and more often as biocatalysts, given the disparate attributes of both. wholecell biocatalysts ensure the optimal environment for the enzyme, thereby providing a quite stable system. furthermore, they contain cofactors and are able to bring about cofactor regeneration without the necessary addition of any other compounds [6]. however, the presence of a variety of enzymes may lead to side reactions. also, isozymes with different enantiomeric preferences may lower the overall enantiomeric excess into recieved: 11 march 2022; revised: 21 march 2022; accepted: 21 march 2022 *correspondence: lajtai-szabo.piroska@mk.uni-pannon.hu the bargain [7]. unlike whole-cell biocatalysts, isolated enzymes improve the level of control over the process in the absence of side reactions, thereby enhancing its reproducibility. in addition, inhibition is less likely to occur because of the greater degree of tolerance concerning the concentrations of both the substrate and product. on the other hand, the provision of a cofactor and its regenerating system significantly increases costs. in order to choose the optimal catalyst for a given synthesis, a detailed comparison of their advantages and disadvantages, e.g. attainable yield, productivity, product purity, required downstream processes and costs, should be made [8]. in this research, two types of alcohol dehydrogenases (adh) were investigated with regard to the conversion of racemic 2-phenylpropionaldehyde to (s)-2-phenyl-1propanol. for the catalysis, the cofactor nicotinamide adenine dinucleotide (nadh) is required by the enzyme which has to be regenerated in order to ensure continuous product formation. ethanol was applied as an auxiliary substrate for the regeneration which was catalysed by the adh. the reaction schemes are presented in fig. 1. because of the low solubility of the substrate and the product in aqueous media, a two-phase system was applied. saccharomyces cerevisiae was applied in dried form (instant baker’s dry yeast) as a whole-cell biocatalyst. over recent decades, both wild and genetically modified strains of yeast have been gaining more and more attention as biocatalysts in the production of fine chemicals [7]. although (s)-alcohol is generally the predominant https://doi.org/10.33927/hjic-2022-05 mailto:lajtai-szabo.piroska@mk.uni-pannon.hu 24 lajtai-szabó, bagó and nemestóthy figure 1: reaction scheme enantiomer in the reduction of racemic carboxylic acid compounds by applying yeast [6], this is dependent on the given substrate [9]. our second catalyst was recombinant horse-liver adh expressed in e. coli. isolated recombinant horse-liver adh is frequently applied for asymmetric syntheses [10–12], moreover, its variant expressed in bacteria can be a cheaper and more accessible alternative. the aim of this research was to characterise the aforementioned biocatalyst in terms of activity, kinetics and enantioselectivity, thereby enabling their critical comparison. in addition, mass transfer through the organic-water interphase was also investigated in order to characterise the relationship between the rates of each step. 2. experimental methods 2.1 applied chemicals all chemicals were commercially available and used without further purification. diisopropyl ether (puriss), ethyl alcohol (a.r.), dodecane (a.r.), trifluoroacetic anhydride (98%), racemic 2-phenylpropionaldehyde (98%) and s-(2)-phenyl-1-propanol (97%) were purchased from sigma-aldrich. recombinant horse-liver alcohol dehydrogenase (expressed in e. coli) as well as lyophilised powder (1.5 u/mg) and β-nicotinamide adenine dinucleotide (sodium salt, 98%) were obtained from sigmaaldrich and thermo fisher scientific, respectively. k2hpo4, kh2po4 and na2co3 were purchased from vwr, while instant baker’s dry yeast was purchased from a local store. 2.2 activity measurements a spectrophotometric method was used to determine the catalytic activity characteristic of cofactor regeneration. given that the maximum adsorption of nadh is at 340 nm while that of nad+ is negligible at this wavelength, conversion of the cofactor can be followed by the change in the wavelength of adsorption. in the case of isolated adh, 10 µl of enzyme solution (10 mg/ml), 600 µl of nad+ solution (4 mg/ml) and 1240 µl of buffer solution were mixed in a quartz cuvette. the reaction was initiated by the addition of 150 µl cc. of ethyl alcohol and the change in absorbance was measured at 340 nm by a shimadzu uv-1800 ultraviolet-visible spectrophotometer. in the case of the whole-cell biocatalyst, 10 µl of an instant yeast suspension (10 mg/ml) was applied instead of an enzyme solution. the catalytic activity was calculated based on the following equation: va = da dt vcuvette εd venzyme h (1) where va denotes the volume activity [u/cm3], da dt represents the gradient of the line (by plotting absorbance vs. time), vcuvette stands for the volume of the mixture [cm3], ε refers to the molar extinction coefficient of nadh at 340 nm [6.22 cm2/µmol], d is the width of the cuvette [1 cm], venzyme denotes the volume of the enzyme solution [cm3] and h represents dilution. the catalytic activity characteristic of the conversion of 2-phenylpropionaldehyde cannot be measured by a spectrophotometer since the reaction mixture consists of two phases. therefore, the catalytic activity characteristic of the whole process (substrate conversion, cofactor regeneration and mass transfer through the organic-water interface) was calculated from the results gained by measuring the kinetics, as described in sec. 2.4. 2.3 mass-transfer rate since experimental conditions applied by conversion measurements are unsuitable for determining the masstransfer rate through organic-water interface, a simplified system was applied for this purpose [13]. 13.4 mg of 2-phenylpropionaldehyde and 18.5 mg of dodecane, which served as an internal standard for gas chromatography (gc) analysis, were dissolved in 10 ml of diisopropyl ether. a schott glass bottle was filled with 6 l of distilled water and the organic solution carefully poured onto the surface of the water phase. during the following 27 hours, samples were taken from the organic phase and analysed by gc. (the parameters of chromatographic analysis were the same as described in sec. 2.4). the ratio of aldehyde to dodecane was plotted as a function of time and a kinetic model was fitted to the measured data in accordance with the following equation: j = d(c0 − acw) (2) where j denotes mass transfer through the interface [mol/(min cm2)], d represents the mass transfer coefficient [cm/min], c0 stands for the initial substrate concentration in the organic phase [mol/cm3], cw refers to the substrate concentration in the water phase [mol/cm3] and a is the ratio of the activity coefficients. the difference between the measured and calculated data was minimized by the excel solver plug-in. although the water phase was gently mixed by a magnetic stirrer, the water–organic interface was stationary. therefore, its surface can be regarded as a constant. the mass transfer rate can be calculated by dividing the mass transfer (j) by the interfacial area. hungarian journal of industry and chemistry production of chiral (s)-2-phenyl-1-propanol 25 table 1: heating program ramp rate [◦c/min] temperature [◦c] hold time [min] 70 25 1 110 0 20 180 2 2.4 kinetics in all the experiments, 7 cm3 of organic solvent and 7 cm3 of phosphate buffer (75 mm, ph 8.0) were used. the molar ratio of 2-phenylpropionaldehyde to ethyl alcohol was set at 3.7, based on data from the literature [14]. in the case of isolated adh, 60 µl of nadh solution (7.5 mg/ml, freshly made with a buffer solution) was added to the reaction media. (the optimal amount of cofactor was determined during preliminary measurements, however, this data is not shown.) in the case of instant baker’s dry yeast, since the cell contained a sufficient amount of cofactor, no further addition of nadh was necessary. the reactions were initiated by adding the catalyst – 300 mg of instant baker’s dry yeast or 500 µl of enzyme solution (10 mg/ml, freshly made with a buffer solution). the reaction mixtures were shaken in a thermostatic incubator (ika ks 4000 i control) at 200 rpm and 30 ◦c. to investigate the product formation, samples were taken from the organic phase and analysed by an hp 5890 gas chromatograph (140 ◦c isothermal). the gc was equipped with a db-ffap column (1 µm × 30 m × 0.53 mm, agilent technologies) and a flame ionisation detector. 2.5 enantioselectivity while measuring the enantioselectivity, the content of the reaction mixture and operational parameters were the same as described in sec. 2.3. before gc analysis, preliminary derivatization was required. 1 ml of trifluoroacetic anhydride and 1 ml of diisopropyl ether were added to 500 µl of the sample while heating the mixture under reflux at 70 ◦c for 30 mins. once the reaction mixture had been cooled to room temperature, it was neutralized with 4 ml of na2co3 (20%) and a sample from the organic phase analysed by a shimadzu gc-2014 gas chromatograph equipped with a lipodex e capillary column (0.2 µm × 25 m × 0.25 mm, macherey-nagel) and a flame ionisation detector. table 1 contains the parameters of the applied heating program. the peaks were deconvoluted by originpro software to fit the gaussian curves. to identify the peaks of the enantiomers, derivatization and analysis was performed using pure s-(2)-phenyl-1-propanol. the retention time of the derivative of the product was 52.5 mins. 3. results and evaluation 3.1 kinetics by plotting the amount of product as a function of time, a line can be fitted to the initial linear phase of the graph and its gradient is the initial rate of reaction as a result of the given substrate concentration. a kinetic curve results from repeating the method with different initial substrate concentrations, yielding information about the dependence of the reaction rate on it. in the case of whole-cell biocatalysts, the product formation can be described by the single-substrate michaelis-menten model as the amount of cofactor can be considered to be constant due to its fast regeneration (see sec. 2.3). in the region of lower substrate concentrations, firstorder kinetics was observed as expected (fig. 2). however, at 0.267 m, the curve peaked followed by a relatively steady decrease instead of phase saturation. as a result, it can be concluded that higher amounts of substrate limit enzymatic conversion, therefore, 0.267 m is the optimal initial concentration to maximise the reaction rate. in contrast to yeast cells, by applying recombinant adh, the reaction rate of cofactor regeneration may limit product formation (see section 3.2), therefore, cannot be neglected. since two reactions involved multiple substrates catalysed simultaneously by the same enzyme, the kinetics did not follow the michaelis-menten model. alternatively, a biphasic model was applied which divides the curve into two phases: at low substrate concentrations, the enzyme’s affinity is relatively high while the turnover number is low. on the contrary, a low affinity and high turnover number is characteristic of the region of high substrate concentration (fig. 3). biphasic kinetics can be modelled by the following equation [15]: v = vmax1 [s] + clint[s] 2 km1 + [s] (3) where vmax1 as well as km1 describe the first high affinity–low-turnover phase and clint – equal to the ratio vmax2 : km2 – denotes the second low-affinity–highturnover phase. figure 2: kinetics of the whole-cell biocatalyst 50 pp. 23–28 (2022) 26 lajtai-szabó, bagó and nemestóthy figure 3: biphasic enzyme kinetics [15] figure 4: kinetics of the isolated enzyme apart from one exception (at 0.22 m), since model data calculated using eq. 3 fitted well to the measured data (fig. 4), biphasic kinetics is presumably a suitable model to describe the kinetics of an isolated enzyme. having been minimized by the excel solver plug-in, the model parameters were the following: vmax1 = 7.523; clint = 3.458; km1 = 0.464. according to manevski [15], biphasic kinetics may imply the presence of multiple substrate binding sites. however, the applied methods were unsuitable for further investigating the underlying mechanisms of the reactions taking place. 3.2 activity the activity of the catalysts was measured during both cofactor regeneration and the process as a whole (table 2). one unit (u) stands for the amount of catalyst necessary to produce 1 µmol of product in 1 minute under the measurement parameters. (substrate conversion could not be investigated separately as previously mentioned in sec. 2.2). although normally the catalytic activity should be measured in the saturation phase of the kinetics, none of the kinetic curves enabled this. therefore, measurements were made at a substrate concentration of 0.27 m, which is the substrate concentration at which the kinetic table 2: activity of the catalysts yeast cell [u/mg] recombinant adh [u/mg] cofactor regeneration 0.19 0.05 complete reaction (0.27 m) 0.02 0.7 complete reaction (1.08 m) – 1.64 curve of the yeast-cell catalyst is at its maximum. in the case of the isolated enzyme, the activity was measured at the same concentration as that of yeast in order to compare the two catalysts. this was also determined at the highest measured point of the kinetic curve, namely at 1.08 m. based on the results, cofactor regeneration is one scale faster when applying a whole-cell biocatalyst instead of an isolated enzyme. although the same enzyme catalyses both substrate conversion and cofactor regeneration when isolated adh is used, yeast cells contain several enzymes that are capable of participating in regeneration reactions which can occur more rapidly as a result. on the other hand, the overall reaction rate using the same substrate concentration was 35 times higher when recombinant adh was used and further increases in substrate concentration resulted in even higher reaction rates. 3.3 mass transfer through the organic–water interface in order to determine the rate-limiting step of the whole process, the mass transfer rate through an organic–water interface was investigated. owing to simplifications of the measurement and the imprecise nature of model fitting, the calculated mass transfer rate may be somewhat inaccurate. nevertheless, the goal was to estimate its order of magnitude rather than determining its precise value. based on the kinetic model fitted to the measured data (fig. 5), the mass transfer rate was calculated to be 1.33 · 10−5 mol/min. by comparing this value with the figure 5: mass transfer process hungarian journal of industry and chemistry production of chiral (s)-2-phenyl-1-propanol 27 table 3: enantiomeric excess (ee) and degree of conversion from studies on the production of (s)-2-phenyl-1-propanol catalyst solvent substrate conc. product, degree of conversion ee (s) ref. horse-liver adh 0.24 u/ml buffer, 165 mm 41 mm, 25 % (2 h) 91 % [14]isopropyl ether (63 % v/v) 82 mm, 50 % (24 h) 88 % horse-liver adh 0.01 mg/ml buffer ph= 7.5, ch3cn (10 % v/v) 0.5 mm 0.36 mm, 72 % (5 h) 78 % [12] recombinant horse-liver adh, exp. in e. coli 0.5 u/ml buffer ph= 8.0, diisopropyl ether (1:1 v/v) 267 mm 45 mm, 17 % (1 h) 100 % this work ctxr d51a mutant e. coli, 4 gcdw/l buffer ph= 7.5 100 mm 41 mm, 41 % (2 h) 95 % [2] whole-cell 40 gcdw/l 70 mm, 70 % (2 h) 45 % s. cerevisiae, 43 gcdw/l buffer ph= 8.0, 267 mm 74 mm, 28 % (1 h) 24 % this work whole-cell diisopropyl ether (1:1 v/v) 345 mm 55 mm, 16 % (1 h) 36 % reaction rates of both catalysts, it could be established that the mass transfer rate is two or three times faster than those of product formation or cofactor regeneration. therefore, the rate-limiting step of the whole process is cofactor regeneration and substrate conversion when an isolated enzyme and whole-cell biocatalyst is applied, respectively. 3.4 enantioselectivity the enantioselectivity of the whole-cell biocatalyst was measured at three different initial substrate concentrations: at the maximum of the kinetic curve (0.267 m) as well as at two higher values (0.345 m and 0.746 m) to examine whether increasing the substrate concentration is beneficial as far as achieving optical purity is concerned. the enantiomeric ratio was calculated from the ratio of the peak areas at 0.5, 1.0 and 1.5 hours (fig. 6). changes in the enantiomeric ratio as the reaction progressed were insignificant, moreover, the difference in the reaction time between 0.345 m and 0.746 m was negligible. at 0.267 m, the final result was 0.62, while the best result, that is, 0.68, was achieved at 0.746 m. as a result, figure 6: the enantioselectivity of the wholecellbiocatalyst it could be established that to achieve an optimal reaction rate and enantioselectivity, different initial substrate concentrations are required. in the case of the isolated enzyme, the enantioselectivity was measured at the same substrate concentrations as when the whole-cell biocatalyst was applied. however, since only one peak corresponding to the (s)-enantiomer of the derivative was detected, further analysis was unnecessary and the enantioselectivity regarded as 100%. as in terms of consumption optical purity is a key concern, the results of this work were compared with some data from the literature (table 3). in the case of whole-cell biocatalysts, the results of rapp et al. [16] are more favourable than ours. however, since both studies suggest that the maximum degree of conversion and enantiomeric excess cannot be achieved simultaneously, a compromise must be made. in the case of the isolated enzyme, the degree of conversion in this study is promising if the reaction time is also taken into account. as for the enantiomeric excess, our result is clearly outstanding, therefore, recombinant horse-liver adh provides a satisfactory alternative for catalysing the production of (s)-2phenyl-1-propanol. 4. conclusion in this work, the conversion of racemic 2phenylpropionaldehyde into (s)-2-phenyl-1-propanol was investigated by applying a whole-cell biocatalyst (saccharomyces cerevisiae) and an isolated enzyme (recombinant horse-liver adh expressed in e. coli). significant differences were observed between the catalysts in terms of all the considered parameters. firstly, the whole-cell biocatalyst exhibited substrate-limited kinetics, while the isolated enzyme could be described by biphasic kinetics. the yeast cell contained a sufficient amount of cofactor for the reaction, moreover, its regeneration was twice as fast as in the case of the isolated 50 pp. 23–28 (2022) 28 lajtai-szabó, bagó and nemestóthy enzyme. therefore, the whole-cell biocatalyst is more beneficial from this point of view. on the other hand, the enzymatic activity of the whole process was at least 35 times higher when recombinant horse-liver adh was applied and could be further enhanced by increasing the initial substrate concentration. most importantly, the isolated enzyme catalysed the conversion with 100 % enantioselectivity, which is also clearly outstanding compared to data from the literature. in conclusion, although recombinant horse-liver adh is more expensive, it is definitely a more efficient catalyst than yeast as a whole-cell biocatalyst. therefore, recombinant horse-liver adh is a promising biocatalyst with regard to the synthesis of (s)-2-phenyl-1-propanol. acknowledgement this research was supported by the ministry for innovation and technology; the national research, development and innovation office and the new national excellence programme. this study was financed by the national laboratory for climate change (hungary) project number nkfih471-3/2021. references [1] scognamiglio, j.; jones, l.; letizia, c. s.; api, a. m.: fragrance material review on βmethylphenethyl alcohol, food chem. toxicol., 2012, 50(2), 199–203 doi: 10.1016/j.fct.2011.10.023 [2] rapp, c.; pival-marko, s.; tassano, e.; nidetzky, b.; kratzer, r.: reductive enzymatic dynamic kinetic resolution affording 115 g/l (s)-2phenylpropanol, bmc biotechnol., 2021, 21, 1–13, doi: 10.1186/s12896-021-00715-5 [3] klebe, g.: optical activity and biological effect, in: klebe. g (ed.): drug design: methodology, concepts, and mode-of-action, pp. 89–110 (springer berlin heidelberg; berlin, heidelberg, germany) 2013 doi: 10.1007/978-3-642-17907-5_5 [4] lajtai-szabó, p.; nemestóthy, n.; gubicza, l.: the role of water activity in terms of enzyme activity and enantioselectivity during enzymatic esterification in non-conventional media, hung. j. ind. chem., 2020, 48(2), 9–12 doi: 10.33927/hjic-2020-22 [5] reetz, m. t.: controlling the enantioselectivity of enzymes by directed evolution: practical and theoretical ramifications, proc. natl. acad. sci., 2004, 101(16), 5716–5722 doi: 10.1073/pnas. 0306866101 [6] silva, j.; alarcón, j.; aguila, s. a.; alderete, j. b.: bioreduction of some common carbonylic compounds mediated by yeasts, z. naturforsch., c, 2010, 65(1-2), 1–9 doi: 10.1515/znc-2010-1-201 [7] pscheidt, b.; glieder, a.: yeast cell factories for fine chemical and api production, microb. cell fact., 2008, 7(1), 25 doi: 10.1186/1475-2859-7-25 [8] schallmey, a.; domínguez de maría, p.; bracco, p.: biocatalytic asymmetric oxidations in stereoselective synthesis, in: andrushko v.; andrushko, n. (eds.): stereoselective synthesis of drugs and natural products, pp. 1089–1114 (john wiley & sons, inc., hoboken, usa) 2013 doi: 10.1002/9781118596784.ssd036 [9] hu, q.; xu, y.; nie, y.: highly enantioselective reduction of 2-hydroxy-1-phenylethanone to enantiopure (r)-phenyl-1,2-ethanediol using saccharomyces cerevisiae of remarkable reaction stability, bioresour. technol., 2010, 101(22), 8502– 8508 doi: 10.1016/j.biortech.2010.06.044 [10] díaz-rodríguez, a.; iglesias-fernández, j.; rovira, c.; gotor-fernández, v.: enantioselective preparation of δ-valerolactones with horse liver alcohol dehydrogenase, chem. cat. chem., 2014, 6(4), 977– 980 doi: 10.1002/cctc.201300640 [11] kim, k.; plapp, b. v.: inversion of substrate stereoselectivity of horse liver alcohol dehydrogenase by substitutions of ser-48 and phe-93, chem. biol. interact., 2017, 276, 77–87 doi: 10.1016/j.cbi.2016.12.016 [12] giacomini, d.; galletti, p.; quintavalla, a.; gucciardo, g.; paradisi, f.: highly efficient asymmetric reduction of arylpropionic aldehydes by horse liver alcohol dehydrogenase through dynamic kinetic resolution, chem. commun., 2007, 39, 4038– 4040 doi: 10.1039/b712290j [13] hidekazu, d.; yuri, n. toyokichi, k.: mass transfer of acetylacetone, ethylene glycol mono-n-butyl ether and ethylene glycol monophenyl ether across water-carbon tetrachloride and water-chloroform interfaces, anal. chim. acta, 1990, 237, 237–240 doi: 10.1016/s0003-2670(00)83923-9 [14] kelemen-horváth, i.; nemestóthy, n.; bélafi-bakó, k.; gubicza, l.: stereoselective reduction of 2phenylpropionaldehyde by alcohol dehydrogenase with cofactor regeneration, chem. pap., 2002, 56, 52–56 url [15] manevski, n.: activity and enzyme kinetics of human udp-glucuronosyltransferases: studies of psilocin glucuronidation and the effects of albumin on the enzyme kinetic mechanism, academic dissertation, university of helsinki, 2013 url [16] rapp, c.; pival-marko, s.; tassano, e.; nidetzky, b.; kratzer, r.: reductive enzymatic dynamic kinetic resolution affording 115 g/l (s)-2phenylpropanol, bmc biotechnol., 2021, 21, 58 doi: 10.1186/s12896-021-00715-5 hungarian journal of industry and chemistry https://doi.org/10.1016/j.fct.2011.10.023 https://doi.org/10.1186/s12896-021-00715-5 https://doi.org/10.1007/978-3-642-17907-5_5 https://doi.org/10.33927/hjic-2020-22 https://doi.org/10.1073/pnas. 0306866101 https://doi.org/10.1515/znc-2010-1-201 https://doi.org/10.1186/1475-2859-7-25 https://doi.org/10.1002/9781118596784.ssd036 https://doi.org/10.1002/9781118596784.ssd036 https://doi.org/10.1016/j.biortech.2010.06.044 https://doi.org/10.1002/cctc.201300640 https://doi.org/10.1016/j.cbi.2016.12.016 https://doi.org/10.1039/b712290j https://doi.org/10.1016/s0003-2670(00)83923-9 https://www.chemicalpapers.com/file_access.php?file=561a52.pdf https://helda.helsinki.fi/bitstream/handle/10138/38186/activity.pdf?sequence=1&isallowed=y https://doi.org/10.1186/s12896-021-00715-5 hungarian journal of industry and chemistry vol. 50 pp. 29–32 (2022) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2022-06 production and characterization of sand-plastic composite floor tiles alexander asanja jock*1, messiah luke akpan1, and francis asokogene oluwadayo2 1department of chemical and petroleum engineering, university of uyo, uyo, nigeria 2department of chemical engineering technology, auchi polytechnic, auchi, edo, nigeria the amount of plastic waste generated in developing nations like nigeria is increasing day by day, which is nonbiodegradable and causes environmental pollution. among the plastics used, low-density polyethylene is abundant. these plastics can be removed from the environment and recycled into useful products. in this study, low-density polyethylene plastic waste was utilized in the manufacture of floor tiles to curb its generation. the tiles were produced by mixing fine sand with molten plastic waste in different proportions. the physical and mechanical properties of the floor tiles such as water absorption, density, tensile and compressive tests, modulus of elasticity as well as impact strength and friction tests were investigated. the water absorption ranged from 0.02 − 0.38 %(m/m), while the density varied between 998.5 and 1289 kg/m3. the tensile strength and modulus of elasticity fell within the range of 0.050 to 0.232 mpa and 0.924 to 2.806 mpa, respectively. this result proved the applicability of recycled plastic waste in the formulation of floor tiles. keywords: plastic waste, floor tiles, low-density polyethylene, pollution, properties 1. introduction plastic waste is now a global problem and one that must be addressed in order to solve worldwide problems concerning resources and energy. plastics are a generic group of synthetic or natural materials consisting of highmolecular-weight chains composed predominantly if not entirely of carbon. they are classified into two categories, namely thermoplastics and thermosetting plastics, moreover, are found in different forms, e.g. as bags, furniture, cups, basins, drinking and food containers, etc. [1]. the increasing consumption of plastic products in various fields generates a significant amount of waste products, equating to more than 12% of municipal solid waste. since plastics are non-biodegradable, that is, cannot easily reenter the natural carbon cycle, the life cycle of plastic materials ends at solid waste disposal facilities and in water bodies. however, the full extent of plastic pollution goes far beyond macroplastic litter. microplastics can contain additives, which have the potential to leach into the surrounding environment, resulting in toxicity to organisms, including carcinogenesis and disruption of the endocrine system in humans [2]. there are several methods for disposing of municipal and industrial plastic waste such as landfill, incineration, recieved: 23 january 2022; revised: 7 february 2022; accepted: 9 february 2022 *correspondence: alsanja@gmail.com true material recycling and chemical recovery. treating plastic waste suitably is crucial to waste management and important in terms of energetic, environmental, economic and political viewpoints. some plastics can safely be recycled, while others cannot so litter the environment [3]. a large and increasing amount of household plastic waste is being produced. the composition of waste varies from country to country, since it is affected by socioeconomic characteristics, consumption patterns and waste management programmes. nevertheless, generally speaking, the proportion of plastics concerning the composition of waste is high. the largest component of plastic waste is polyethylene, followed by polypropylene, polyethylene terephthalate and polystyrene [4]. polyethylene is the most common plastic and can be classified into several different categories based mainly on its density and branching. important grades pf polyethylene are high-density polyethylene (hdpe), linear low-density polyethylene (lldpe) and low-density polyethylene (ldpe). plastic is recycled worldwide since it reduces environmental impacts associated with the improper disposal of plastic waste. therefore, this study focused on the production of floor tiles by mixing sand and plastic waste in different proportions. the characterization of the tiles will provide some insight into the suitability of applying sand-plastic composites in building constructions. https://doi.org/10.33927/hjic-2022-06 mailto:alsanja@gmail.com 30 jock, akpan, and oluwadayo (a) shredded ldpe (b) fine sand figure 1: formulation samples 2. materials and methods 2.1 sample collection and preparation the plastic waste was collected from the university of uyo water company landfill site in uyo, south-south nigeria. the ldpe plastic waste was washed with water to remove dust and other impurities. the washed sample was sun dried for 48 h and shredded into smaller pieces (fig. 1a). a clay-free sample of fine sand (fig. 1b) was obtained from ifiayoung stream in uyo, sun dried for 24 h, then oven dried at 105 ◦c for 4 h before being sieved through a 125 µm mesh. 2.2 formulation and production of floor tiles 35 g of plastic waste was continuously introduced into a fabricated melting pot made of stainless steel and heated to a temperature of 160 ◦c , whilst being stirred continuously to ensure homogeneous melting. 105 g of fine sand was then added to the melted plastic waste before being well mixed. the mixture was transferred into a stainlesssteel mould with the dimensions of 10.0 × 10.0 × 1.5 cm coated with a lubricating oil to facilitate demoulding. the mixture in the mould was compressed by applying figure 2: samples of floor tiles a force before being cooled in a water bath for 5 mins. the resulting tile was then removed from the mould. the production process was repeated by varying the proportions of plastic waste and fine sand. the samples of tiles produced using different formulations are shown in fig. 2. 2.3 characterization of floor tiles water absorption water absorption tests were carried out in accordance with the astm-c373 standard test method. each sample was oven dried at 110 ◦c to constant weight (wo) before being immersed in distilled water at room temperature (25 ◦c) for 24 h. the samples were removed from the distilled water, cleaned with a cotton fabric and weighed (wt). the amount of water absorbed (wa) by each sample was calculated using %wa = (wt −wo) wo × 100 (1) density the density of each sample was calculated using density = mass of sample sample volume (2) impact strength impact strength was measured using a jbs-300n model charpy impact testing machine and determined according to the astm d6110-18 standard test method. a standard sample was prepared with the dimensions 1×8 cm while maintaining the original thickness before being placed on the plate of the impact testing machine, wherein the jack handle was carefully released to allow the load to strike the sample of the ceiling board. the energy of the impact was recorded and the impact strength calculated by hungarian journal of industry and chemistry production and characterization of sand-plastic composite floor tiles 31 impact strength = absorbed energy cross-sectional area (3) tensile strength this was determined using the mohan brothers tensile testing machine cap, 500kgf iso9001 model. the samples were prepared for this test according to the astm c1185 standard test method (type ii). each sample was carefully placed in the tensile testing machine and clamped at both ends. the machine was turned on and the load at which each sample fractured recorded. the tensile strength was calculated by tensile strength = maximum load original cross-sectional area (4) young’s modulus of elasticity young’s modulus of elasticity (y ) is a measure of stress per unit strain and was calculated using y = stress strain (5) friction test a friction test was conducted using the cussons friction test device graduated from 0 − 90° and was performed based on the astm d1037-94 standard test method. the sample was placed on an inclined plane of the piece of equipment and the angle at which the specimen slid freely down the surface was recorded. the coefficient of friction was calculated by: coefficient of friction = tan θ (6) where θ denotes the angle of repose. compressive strength a compressive strength test was carried out using a universal testing machine and performed based on the astm d790 standard test method. the specimens with dimensions of 20 by 20 mm were prepared and tested on a support span of 130 mm in length as per the standard test method. the load at which each sample was compressed as a result of the force applied on it by the machine was recorded. the compressive strength was calculated using compressive strength = maximum load cross-sectional area (7) table 1: composition and physical properties of floor tiles sample composition (%(m/m)) water density ldpe fine sand absorption (kg/m3) (%(m/m)) a 25 75 0.38 1289.6 b 35 65 0.04 1269.5 c 50 50 0.02 1168.2 d 65 35 0.24 1015.6 e 75 25 0.3 998.5 3. results and discussion 3.1 physical properties of floor tiles the physical properties of floor tiles are presented in table 1. water absorption is the ability of a bisque tile to absorb water or moisture. the calculated water absorption of the floor tiles was between 0.02 and 0.38%(m/m). the lowest water absorption (0.02%(m/m)) was obtained in batch c with a composition of 50%(m/m) ldpe and 50%(m/m) fine sand. the amount of water absorbed closely resembled that of ceramic tiles of 0.03%(m/m). generally, tiles with a high level of water absorption have a low resistance to chloride and sulphate as well as to water penetration [5]. the density of the tiles ranged from 998.5 kg/m3 to 1289.6 kg/m3 as is shown in table 1. the lowest density, calculated in batch e, was due to the large quantity of ldpe in the formulation. the density decreased as the proportion of ldpe increased. a rise in the density resulted in an increase in the compressive strength and a decrease in water absorption by the tile [6]. 3.2 mechanical properties of the formulated tiles the mechanical properties of the batches are shown in table 2. the tensile strength of the floor tiles was between 0.050 and 0.232 mpa. the tensile strength of a material is a measure of the force required to pull a material to the point where it breaks. batches a and e exhibited the lowest and highest tensile strengths, respectively, possibly due to the amount of ldpe used as a binding agent in their formulations. the young’s modulus of elasticity with regard to the batches of tiles ranged from 0.924 to 2.810 mpa as depicted in table 2. the young’s modulus of elasticity is a measure of the stiffness of an elastic material and it is an important parameter in evaluating the deformation of materials subjected to a working load. the lowest young’s modulus of elasticity that was calculated in batch a may result in a lower stiffness compared to that of batch e that yielded the highest. the compressive strength of the tiles presented in table 2 was between 91.7 and 133.0 mpa. batches d and b 50 pp. 29–32 (2022) 32 jock, akpan, and oluwadayo table 2: mechanical properties of floor tiles sample tensile young’s modulus compressive impact strength coefficient strength (mpa) of elasticity (mpa) strength (mpa) (kj/m2) of friction a 0.05 0.924 116.7 1912 0.6 b 0.067 0.975 91.7 1883 0.53 c 0.083 2.666 118 1955 0.51 d 0.082 2.653 133 2346 0.58 e 0.232 2.806 115 1933 0.58 exhibited the highest and lowest compressive strengths, that is, 133.0 mpa and 91.7 mpa, respectively. this implies that the impact strength of batch d to compressive loading will be greater than that of batch b. impact strength is the resistance of a material to fracture by being hit, expressed in terms of the amount of energy absorbed before the fracture. the impact strength of the batches ranged from 819.05 to 1720 kj/m2. since batches d and b exhibited the highest and lowest impact strengths, respectively, batch b will easily be fractured. table 2 shows that the coefficient of friction of the floor tiles is between 0.51 and 0.60. however, given that these values are similar, all the floor tiles responded similarly to sliding freely over the same surface. the coefficient of friction depends on the surface finish of the floor tiles and the values obtained are in good agreement with the acceptable value of 0.5 outlined by the astm standard test method [7]. 4. conclusion floor tiles were successfully developed from plastic waste and fine sand. although the physical and mechanical properties of batch d yielded the best results, this recycled plastic waste can be used to produce some industrial products like floor tiles which are resistant to highly corrosive environments like offshore platforms. competing interests the authors declare that there are no competing interests. references [1] osarumwense, o.j.; salokun, o.; okundaye, o.a.: utilization of low-density polyethylene (ldpe) plastic wastes in the production of paving tiles, j. mater. environ. sci., 2020, 11(12), 2052–2060 https://www.jmaterenvironsci.com [2] bishop, g.; styles, d.; lens, n.l.p.: recycling of european plastic is a pathway for plastic debris in the ocean environ. int., 2020, 142, 105893 doi: 10.1016/j.envint.2020.105893 [3] puttaraj, m.h.; basavaraj, p.; gagan, m.s.; shivu, s.; manjunath, s.h.: reuse of plastics waste for the production of floor tiles, j. seybold report, 2020, 15(8), 1633–1639 [4] alla, m.m.g.; ahmed, a.i.; abdalla, b.k.: conversion of plastic waste to liquid fuel, int. j. tech. res. appl., 2014, 2(3), 29–31 https://www.ijtra.com [5] namarak, c.; bumrungsri, c.; tangchrirapat, w.; jaturapitakkul, c.: development of concrete paving blocks prepared from waste materials without portland cement, mater. sci., 2018, 24(1), 92–99 doi: 10.5755/j01.ms.24.1.17566 [6] yalley, p.p.; kwan, a.: use of waste and low energy materials in building block construction. int. refereed j. eng. technol., 2013, 2(1), 1–5 https://www.irjes.com [7] american society for testing and materials (astm c1028) (2008) standard test method for coefficient of friction for manufactured tiles. hungarian journal of industry and chemistry https://www.jmaterenvironsci.com/document/vol11/vol11_n12/jmes-2020-11175-osarumwense.pdf https://doi.org/10.1016/j.envint.2020.105893 https://doi.org/10.1016/j.envint.2020.105893 https://www.ijtra.com/download.php?paper=conversion-of-plastic-waste-to-liquid-fuel https://doi.org/10.5755/j01.ms.24.1.17566 https://doi.org/10.5755/j01.ms.24.1.17566 https://www.irjes.com/papers/vol2-issue11/a02110105.pdf hungarian journal of industry and chemistry vol. 50 pp. 33–43 (2022) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2022-07 unraveling the novel bacterial assisted biodegradation pathway of morpholine rupak kumar*1, suman kapur2, and srinivasa rao vulichi2,3 1central drugs standard control organization, new delhi, india 2birla institute of technology and science – pilani, hyderabad campus, hyderabad, india 3svu college of pharmaceutical sciences, sri venkateswara university, tirupati, india most xenobiotics are biodegradable, persistent or recalcitrant in nature. morpholine, a typical xenobiotic, was initially regarded as recalcitrant, however, later proved to be biodegradable by bacterial species like mycobacterium and pseudomonas in particular. however, establishing the metabolic pathways involved for the successful biodegradation of morpholine is challenging because of its extreme level of water solubility that affects various analytical procedures. in addition, to date, no suitable analytical methods have been reported to directly estimate morpholine and its degradable products or intermediates. nevertheless, methods, especially optical density, gas chromatography and mass spectrophotometric analysis, could indirectly estimate the degradation product(s) of morpholine formed as a result of its biotransformation. in the present study, the degradation pathway of morpholine was ascertained by selected bacterial isolates by measuring their capacity to degrade morpholine. based on this analysis of culture filtrates, it was determined that the novel isolate is the genus halobacillus blutaparonensis which follows the diglycolic acid route from the metabolic degradation pathway of morpholine to induce one of two branches of the morpholine biodegradation pathway. in the presence of concentration of morpholine, out of two branches of morpholine degradation one branch is induced, while the other branch is inhibited. whatever the branches with regard to the degradation pathway of morpholine exhibited by bacteria are, ammonia is the final end product of degradation which might be biochemically utilized by the isolate. keywords: morpholine, xenobiotic, recalcitrant, glycolic acid route, ammonia 1. introduction environmental pollution has become a global problem. due to the indiscriminate and frequent release of xenobiotics as a result of different anthropogenic activities, each and every day our environment becomes increasingly devastated by the pollutants. morpholine (1-oxa4-azacyclohexane) is one such heterocyclic xenobiotic organic chemical with different versatile applications in various processes in the rubber, paper, iron, textile, personal care, pharmaceutical and agricultural industries amongst others. as a consequence of its vast operational usage, a significant amount of this chemical is released into the environment through the differential process of discharging at both microand macro-concentrations. therefore, it is necessary to mention that anthropogenic environmental pollutants, even at low concentrations, often produce deleterious effects on organisms, which are recieved: 1 march 2022; revised: 20 april 2022; accepted: 26 april 2022 *correspondence: rupakraman@gmail.com difficult to predict because measurable effects are expressed only after prolonged exposure. in the environment, the majority of exposure to morpholine originates from water and leads to the formation of the carcinogen n-nitrosomorpholine (nmor) by the process of natural nitrosation [1] (fig. 1). furthermore, it is pertinent to mention that this process of nitrosation may occur in biological systems when directly consumed, ingested, inhaled and applied to the skin. in addition, nmor is known as a mediator of various debilitating cancers associated with organs like the digestive tract, respiratory tract, kidneys and liver, which is eventually biomagnified through different trophic levels of biota by its application or the intake of polluted water leading to this carcinogen entering the food chain. in figure 1: formation of nmor https://doi.org/10.33927/hjic-2022-07 mailto:rupakraman@gmail.com 34 kumar, kapur, and vulichi this regard, it would be best to provide a solution for its efficient discharge or effective removal by different physical and chemical processes. recently, photocatalysis using catalysts irradiated by ultraviolet or visible light has been applied for the mineralization of toxic organic dyes in water and carbon dioxide [2, 3]. however, a costeffective, environmentally-friendly biological tool powered by microbes has been widely used as an ancient core concept for the purpose of conserving the natural environment and resources to curb the negative impacts on biotic components. therefore, a sustainable solution driven by microbes must be explored to elucidate the degradation pathway and measure how potent microbes are for the purposes of decontaminating a wide range of pollutants and their mitigation. in general, most pollutants are organic and may be biodegradable (transformed by biological mechanisms which might lead to mineralization), persistent (fail to undergo bioremediation in the environment or under a specific set of experimental conditions) or recalcitrant (inherently resistant to biodegradation) in nature. biogenic or naturally occurring compounds are biodegradable while man-made (anthropogenic) compounds may be biodegradable, persistent or recalcitrant. in terms of xenobiotics that are man-made, the microbial communities present in the environment may not have evolved suitable mechanisms for their degradation. many possible mechanisms exist which differ from one xenobiotic to another. one common mechanism is the binding of enzymes analogous to their natural substrates which contain xenobiotic functional groups, assuming these do not greatly alter or change the active site which catalyzes a reaction with the xenobiotic. the success of this enzymatic reaction (as a biodegradation mechanism) also depends on other factors such as the ability of the xenobiotic as an inducer or inhibitor and the nature of the product/intermediate formed. specific to morpholine, the metabolic degradation pathway has been very difficult to establish because of the aforementioned technical limitation. 1.1 sustainable remediation of morpholine and its degradation pathway although morpholine was previously thought to be recalcitrant, several microbes have proven to metabolically degrade it. the majority of studies showed that the species mycobacterium and pseudomonas are the two potential bacterial isolates that utilize morpholine as their sole source of carbon and nitrogen, thereby undergoing degradation [4–7]. a few studies have been carried out to understand the biodegradation of morpholine and its regulation [8–10]. later a hypothetical pathway was proposed for the complete mineralization of morpholine that could proceed via 2-(2-aminoethoxy)acetate to produce its diglycolate salt and/or ethanolamine [5, 11, 12]. these two different routes of degradation are called the ethanolamine/monoethanolamine pathway (pathway 1) (a) (b) figure 2: (a) hypothetical pathway of morpholine degradation where x = 2-(2-aminoethoxy)acetaldehyde, y = 2(2-aminoethoxy)acetate and a, b, c indicate the position of carbon atoms in the ring. (b) postulation of the morpholine degradation pathway after 1h-nmr and ion spectroscopic analyses where 1 = 2-(2-aminoethoxy)acetate, 2 = diglycolic acid and 3 = glycolic acid. and diglycolic acid/glycolate pathway (pathway 2), respectively (fig. 2a). the illustrated degradation pathway might start with the cleavage of the c-n bond, leading to the formation of an intermediary amino acid which is followed by deamination and oxidation of this amino acid to form a diacid [11, 12]. the degradation of morpholine via the ethanolamine or glycolate pathways has been described in the presence of mycobacterium chelonae and m. aurum mo1 [8, 9] (fig. 2a). the degradation of morpholine is likely to begin with the breakage of a bond between a heteroatom and an adjacent carbon atom by the enzyme morpholine monooxygenase, which is responsible for the ring cleavage. morpholine monooxygenase is an important enzyme in the degradation of morpholine as it catalyzes the biotransformation of morpholine to form 2(2-aminoethoxy)acetic acid and contains a catalytic subunit of cytochrome p450 [1, 10]. morpholine could serve as a substrate for flavin-containing monooxygenases or cytochromes p450 which is associated with oxygen consumption [13]. further inhibitory effects of metyrapone on the degradation of the mycobacterium strain rp1 have been attributed to the involvement of cytochromes p450 hungarian journal of industry and chemistry bacterial assisted biodegradation pathway of morpholine 35 in the biodegradation of morpholine [5]. depending on the concentration of morpholine in the culture medium, one pathway could be expressed while the other might be inhibited [11]. recently, a new approach was applied in which the culture filtrate was analyzed by 1h-nmr spectroscopy and ion spectroscopy to identify the metabolic intermediates of morpholine degradation by m. aurum mo1 [11, 12] (fig. 2). although many different species of mycobacterium have been shown to degrade morpholine via this shared group of degradation reactions, little information is known about the enzymes involved (fig. 2b). furthermore, the byproducts of the microbial processes can be indicative of a successful bioremediation process. consequently, since only hypothetical pathways have been proposed, limited interpretations of various experimental designs can be made to establish the degradation pathway that follows the route of degradation pathway that follows the route of pathway 1 and /or pathway 2 via the shared formation of 2-(2aminoethoxy)acetate. 2. materials and methods 2.1 environmental samples the sample used in the present degradation study was collected from natural sources (soil) in and around durgapur steel plant, west bengal, india. the site is located in durgapur at a latitude of 51◦50’43.8” north and a longitude of 8◦16’35.8” west in the state of west bengal, india. soil samples consisted of blackish fine-to-medium sub-angular gravel in the upper surface, including fine sand and a high content of iron flecks. samples were collected in a clean, sterile plastic container before being transferred to the laboratory and stored at room temperature until used for further analysis. 2.2 chemicals and reagents all chemicals and reagents were of analytical grade and used as received without any further purification. even though milli-q water (elix essential 3 water purification system with a conductance of 0.12 siemens) was used to prepare an aqueous solution of reagents, autoclaved double distilled water was used because of the microbial cultures. 2.3 screening, characterization and sequence accession of the morpholinedegrading isolate for the initial isolation and cultivation of bacteria, tenfold serial diluted samples were spread onto nutrient agar plates, which were prepared according to the manufacturer’s instructions. the specific colonies obtained were subcultured further to isolate the pure bacterial strain. the selected pure bacterial isolate was identified based on morphological, biochemical and molecular characterization. morphological characterization was achieved by visually observing colonies in terms of their appearance, shape, color, arrangement, optical nature, margin, texture and elevation. however, the biochemical tests were performed as per standard methods [14]. furthermore, the pure colony was then identified by 16s rrna gene sequence analysis. in order to verify the phylogenetic affiliation of the selected isolate, a single colony was collected for the purpose of dna isolation (instagenetm matrix genomic dna isolation kit (bio-rad catalog # 7326030) as per the kit instructions and procedures) and subjected to polymeric chain reaction (pcr) analysis using primers targeting two 16s rrna genes [27f (5’-agagtttgatcmtggctcag-3’) and 1492r (5’tacggytaccttgttacgactt-3’-). a pcr reaction (20 µl) was performed containing 8 µl of taq dna polymerase master mix, 1 µl of both 10 µm stock 27f/1492r primers, 9 µl of double distilled water and 1 µl of a dna template. the pcr (mj research ptc200 peltier thermal cycler; bio-rad ptc-200) reaction was conducted using specified conditions from the literature [15]. dna was denatured at 94◦c for 5 mins, followed by 35 cycles of amplification, each consisting of the following components: 94◦c for 45 secs (denaturation), 55◦c for 60 secs (annealing), 72◦c for 60 secs, (extension) followed by 72◦c for 10 mins (final extension). the pcr product was sequenced by yaazh xenomics, chennai, tamil nadu, india. the 16s rrna gene was sequenced using the national center for biotechnology information’s basic local alignment search tool (blast). the phylogenetic analysis of the sequence using the closely related sequence of blast results was performed by multiple sequence alignment. the program muscle 3.7 was used for multiple sequence alignments [16]. the resulting aligned sequences were filtered using the program gblocks 0.91b, which eliminates poorly aligned positions and divergent regions, that is, removes alignment noise [17]. finally, the program phyml 3.0 alrt was used for phylogenetic analysis and hky85 as a substitution model. the nucleotide sequence of the isolated bacterium was included in ncbi’s genbank and assigned an accession number consisting of 2 letters and 6 numbers [18]. 2.4 cultivation and acclimatization of the isolate: microbial adaptation against morpholine bacterial inocula were prepared by aseptically transferring the selected identified pure colonies to 10 ml of an enriched media called knapp buffer. alternatively, a mineral salt solution (mss) comprised of 100 mg of kh2po4, 100 mg of k2hpo4, 4 mg of mgso4.7h2o and 0.2 mg of fecl3 was used as previously described by the author supplemented with 0.1% v/v morpholine as previously described by the author [19]. cultures were incubated at 37oc as well as 150 rpm for 1−2 weeks and 50 pp. 33–43 (2022) 36 kumar, kapur, and vulichi table 1: gc parameters for the estimation of the monoethanolamine concentration parameters specificity column and its configuration rtx-35 30 mm × 0.32 mm × 1 µm oven/column temperature initial temp.: 60 ◦c hold: 1 min ramp rate: 30 ◦c/min final temp.: 240 ◦c maintained for 3 mins linear velocity: 37.6 cm/sec (for nitrogen) injection port temp.: 200 ◦c split ratio: 30:1 injection volume: 1 µl carrier gases (mobile phase) column gas flow rate: 2 ml/min purge gas flow rate: 1 ml/min hydrogen gas flow rate: 40 ml/min zero air flow rate: 400 ml/min nitrogen gas flow rate: 15 ml/min stationary phase 60% dimethylpolysiloxane and 35% diphenyl polysiloxane detector flame ionization detector at 300 ◦c analysis time 10 mins software gc solution workstation windows 8 their absorbance at 600 nm was taken regularly as a measure of growth. based on their growth, when an optical density of 0.5 was reached (data not shown), the culture was diluted to 1 : 100 before being further spread onto mss-agar plates (treated with 2% agar + 0.1% morpholine) to confirm the acclimatization of the isolate against morpholine stress. furthermore, the growing culture was centrifuged at 6500 rpm for 10 mins and the pellet was resuspended in the mss medium while gradually increasing the concentration of morpholine to 0.2% which was referred to as a seeded acclimatized bacterial inoculum. for each increased acclimatization study, the tested bacteria were grown in an mss broth supplemented with an increased concentration of morpholine and a respective mss-agar plate with the same concentration of morpholine to confirm the said acclimatization. the acclimatized inoculum was later grown in the presence of an intermediate degradation product of morpholine to explore whether this particular isolate follows pathway 1 or 2. this was further validated by performing in-vitro chemical and analytical assay(s) with the availability of intermediate product of morpholine degradation in the culture filtrate. lastly, estimation of the ammoniacal nitrogen (measure of the amount of ammonia) in the culture filtrate revealed the complete degradation of morpholine by this isolate following the concerned pathway. 2.5 growth on different hypothetical degradation intermediate compounds the growth of the isolate on various substrates (degradation intermediate compounds) was investigated by adding the corresponding compounds (0.15%) to the mss. the ph of the media was adjusted to 7 and growth carried out at 37◦c as well as 150 rpm for 48 hours. at regular time intervals, the absorbance was measured in terms of optical density to establish whether these degradation products might have been formed to facilitate the growth of the isolated bacteria. 2.6 chemical tests of intermediate(s) in the degradation pathway chemical tests on degradation products, mainly monoethanolamine (primary amine) and morpholine (secondary amine), were carried out by the standard simon test 1 (rimini test) and simon test 2 (modified rimini test) on the culture filtrate to determine the presence of primary and secondary amines [20]. the amine undergoes a nucleophilic addition reaction with nitroprusside ions in the presence of acetaldehyde or a ketone to yield the characteristic color of primary amines (blue) or secondary amines (violet). 2.7 gas chromatography (gc) studies of degradation intermediate(s) a gc system (shimadzu gc-2010) equipped with a standard oven for temperature ramping, split condition, injection ports, a flame ionization detector and a rtx-35 amine column (30 mm × 0.32 mm × 1µm film thickness) in the presence of nitrogen as a carrier gas by the direct injection method was used for the analysis of monoethanolamine (mea). the analytical parameters for the analysis of mea are summarized in table 1, as per the method (by modifying the column and its parameters) reported in the literature [21]. hungarian journal of industry and chemistry bacterial assisted biodegradation pathway of morpholine 37 table 2: ms operating parameters for intermediate(s) parameter specificity ionization electrospray ionization needle voltage = 4.5 kv interface temperature 350 ◦c temperature of heating block 200 ◦c sheath/drying gas flow rate 15 l/min nebulizer gas flow rate 1.5 l/min acquisition time 2 mins acquisition mode positive/negative scan m/z 50− 200 scan speed = 52 units/sec sampling acquisition time = 1.56 hz (640 msec) detector electron multiplier software lab solutions workstation windows 7 a standard solution of 0.125 to 0.5% v/v mea (corresponding to ppm and prepared in methanol) was injected along with the processed culture supernatant (1:10, filtrate volume of 1 and 9 volumes of methanol), as per the method described above. gc of the test samples was run against blank media using positive controls to quantify or estimate the presence of mea in the culture filtrate by analyzing the area under the curve (auc) calculated by the machine. 2.8 mass spectrometry studies of degradation intermediate(s) the mass spectrometry (ms) system of an integrated liquid chromatography-mass spectrometry instrument (shimadzu lcms-2020) equipped with an inlet interface, ion source, mass analyzer and detector was used to analyze the degradation products of morpholine. the analytical parameters for ascertain the morpholine degradation products are summarized in table 2. the sample for injection was prepared without using a solvent, as per the method reported in the literature [12]. the culture sample (5 ml) was centrifuged at 10,000 rpm for 10 mins before the supernatant was filtered through a nylon filter with a pore size of 0.22 µm (axiva sichem biotech, india) to remove any bacterial cells. 1 ml of neat filtrate was injected directly into the ms instrument. 2.9 estimation of the ammonia concentration the presence of ammonia in the culture supernatant was estimated by the standard nessler’s method [22], which involves coupling of ammonium to the nessler’s reagent figure 3: estimation of the ammoniacal nitrogen concentration by nessler’s method to produce a yellow color under strongly alkaline conditions (fig. 3). the resulting yellow color was formed in proportion to the ammonium (nh+ 4 ) concentration and was measured at a wavelength of 405 nm using an elisa reader (elx50/8ms biotek india) against a reagent blank. the ammonia level in terms of ammoniacal nitrogen was expressed in mg/l (ppm). a standard solution of 10 ppm of nh+ 4 −n was prepared by dissolving 4.773 mg of ammonium chloride in 125 ml of doubledistilled water and further diluted to make solutions of 1− 5 ppm nh+ 4 −n. a calibration curve was plotted and is presented in the results section. 3. results and discussion 3.1 morphological, biochemical and molecular identification morphologically, the isolate was found to be white in color with a dull opaque appearance, rod-shaped, have a smooth texture and grow as a convex elevation colony. standard staining reported it to be a gram-negative bacterium with high motility which also showed signs of growth on a selective medium, namely hicrome uti agar m1353. the primary sequence of the 16s rrna from the present bacterial isolate was determined. the program phyml 3.0 alrt for phylogenetic analysis and hky85 as a substitution model on the 16s rrna gene sequences determined the phylogenetic position of said isolate to be a species closely related to the genus halobacillus blutaparonensis with a sequence representative of e. coli (fig. 4). nucleotide sequence accession was assigned by genbank, ncbi and an accession number of kc345029 was figure 4: molecular phylogeny of the 16s rrna gene sequence and sequences from identified bacteria in the database. the sequence of e. coli served as the outgroup for rooting the tree. 50 pp. 33–43 (2022) 38 kumar, kapur, and vulichi figure 5: growth of the isolate in the presence of intermediates of morpholine degradation figure 6: gc (rtx-35)flame ionization detector chromatogram of mea assigned to this bacterial isolate of genus halobacillus blutaparonensis. 3.2 growth on intermediates the isolate grew in the presence of morpholine and the intermediate, namely aminoethoxy ethanol (reduced product of aminoethoxy acetate) by consuming it as a source of carbon and nitrogen. however, no growth was recorded in the presence of ethanolamine in the culture media shown in fig. 5. the count of bacterial cells was adjusted to 1×108 cells/ml (1 unit of absorbance = 5×108 cells) by varying the incubation periods up to 48 hours. 3.3 chemical assay of intermediate(s) based on simon tests 1 and 2 [20], the presence of mea and morpholine in the culture filtrate is shown in table 3. 3.4 gc studies of mea in the culture supernatant gc of the culture supernatant was run at different concentrations (ppm) of a standard mea solution. table 4 and fig. 6 indicate a retention time of mea equal to 2.2 mins which was absent in the diluted culture supernatant. gc analysis revealed that no mea was present in the culture supernatant suggesting that bacteria might prefer the diglycolic route (pathway 2) of morpholine degradation which was later confirmed by ms analysis. 3.5 ms studies of the culture filtrate ms was run directly with a neat culture filtrate. each sample was analyzed separately in both the positive and negative ion modes (table 5 and fig. 7). it was observed that the m/z peak of the neat culture filtrate (fig. 7) indicates the presence of 2-(2aminoethoxy)acetate (c4h9no3, molecular weight = 119.119 and m/z = 120 as [m+h]+) and an anion of diglycolic acid (c4h6o5, molecular weight = 134.09 and m/z = 133 as [m-h]–) which supports the fact that this particular isolate prefers the degradation pathway of diglycolic acid (pathway 2), similar to a strain of mycobacterium reported earlier by conducting electrospray ionization mass spectrometry on the culture filtrate [12]. further ms analysis supports the gc findings that mea is not present in the culture filtrate because it might have an inhibitory effect on the bacteria. therefore, the said bacterial isolate prefers the diglycolic acid route of the metabolic pathway given the fact that in the presence of morpholine, one of the two branches of morpholine biodegradation was induced while the other was inhibited. the illustrated degradation pathway might start with the cleavage of c-n bond, leading to the formation of an intermediary amino acid followed by deamination and oxidation of this amino acid to form a diacid as is shown in fig. 2b. 3.6 ammonia release: as the end product of morpholine degradation morpholine can be degraded by bacteria which releases ammonia. whichever degradation pathway of morpholine is followed, ammonia is produced as an end product. the concentration of ammoniacal nitrogen produced by the isolate was calculated (table 6 and fig. 8) by the regression equation of a standard curve (y = 0.137x with r2 = 0.98) and found to be present at a concentration of 5.2 ppm based on nessler’s quantification. the initial morpholine concentration in the culture supernatant (before degradation) was reported to be 2000 ppm. the molar ratio with regard to the conversion of morpholine into ammonia was found to be 1 : 0.014. furthermore, it was shown that the final ph of the media throughout the experiment did not change, supporting the fact that a low concentration of ammonia was released as an end product of morpholine degradation. hungarian journal of industry and chemistry bacterial assisted biodegradation pathway of morpholine 39 table 3: simon tests for the presence of the primary amine mea and secondary amine morpholine in the culture supernatant sample test feature remark result morpholine simon 1 characteristic blue color of the secondary amine morpholine positive mea simon 2 characteristic violet color of the primary amine mea positive culture media simon 1 no characteristic blue color morpholine negative simon 2 no characteristic violet color mea negative culture supernatant (filtrate) simon 1 no characteristic blue color morpholine negative simon 2 no characteristic violet color mea negative 50 pp. 33–43 (2022) 40 kumar, kapur, and vulichi table 4: gc analysis of the diluted culture filtrate vial retention time (mins) auc interpretation (compound) methanol 1.331 378534920.9 methanol 5000 ppm mea 1.333 2.218 366649701.7 2748948.5 methanol mea 2500 ppm mea 1.331 2.216 374551161.2 2397300.9 methanol mea 1250 ppm mea 1.331 2.211 378803557.4 1149593.1 methanol mea culture supernatant (1:10) 1.334 2.331 310947764.4 92353.6 methanol no/negligible mea table 5: expected intermediate according to the ms analysis of the culture filtrate. sample m/z positive mode m/z negative mode remark neat culture filtrate 120 [m+h] + 2,2 aminoethoxy acetate 133 [m-h] – anion of diglycolic acid figure 7: electrospray ionization ms spectra recorded under positive and negative ionization of the neat culture filtrate. hungarian journal of industry and chemistry bacterial assisted biodegradation pathway of morpholine 41 table 6: estimation of ammoniacal nitrogen concentration by nessler’s reagent well 10 ppm stock nh4-n+ (µl) milli-q water (µl) culture media (µl) 50% na-k tartrate (µl) nessler’s reagent (µl) net absorbance at 405 nm 1 ppm 25 225 — 5 5 0.091 2 ppm 50 200 — 5 5 0.284 3 ppm 75 175 — 5 5 0.353 4 ppm 100 150 — 5 5 0.552 5 ppm 125 125 — 5 5 0.725 culture supernatant 250 — 5 5 0.725 figure 8: standard curve of ammoniacal nitrogen concentration by nessler’s reagent 4. discussion based on the results summarized, it has been reported that the isolate prefers to undergo the diglycolic acid route of degradation instead of the ethanolamine pathway, which might be an inhibitory effect on bacterial growth. the illustrated degradation pathway starts with cleavage of the c-n bond, leading to the formation of an intermediary amino acid which is followed by deamination and oxidation to form the diacid (fig. 9). this diacid, namely diglycolate, later participates in intermediate metabolism and is converted indirectly into tca by the krebs cycle, which is beyond the scope of the present article. moreover, the presence of degradation intermediate compounds in culture filtrate also favors this finding with the conclusion that the diglycolic acid route of biodegradation might be a common degradation mechanism, which is also shown by other strains of bacteria, proceeding via 2-(2-aminoethoxy)acetate. the said investigation to reveal the degradation pathway of morpholine is supported by similar findings published by other authors [5, 10–12]. furthermore, whatever the degradation pathway exhibited by the bacterial isolate, the end product, that is, ammonia, will be biochemically produced and used. our studies confirm the presence of ammonia as an end product in a molar conversion ratio of morpholine to ammonia of 1 : 0.014. due to the low concentration of ammonia produced, the ph of the culture medium did not change throughout the experiment. however, a higher molar ratio of morpholine to ammonia brought about an inhibitory effect on the growth of bacteria by increasing the ph of the medium and making it more alkaline. the molar ratio of morpholine to ammonia was found to be different for different strains of bacteria as viz., namely 1 : 0.5 for mycobacterium sp. he5 [6], 1 : 0.89 for mycobacterium sp. [7] and 1 : 0.82 for mycobacterium sp. mo1 [9]. 5. conclusions the large scale industrial applications of morpholine and its known carcinogenic effect thus have an environmental interest for its biodegradation and exploring the degradative pathway so that unrevertable damage to the natural environment and biota can be minimized. along with the mycobacterium and pseudomonas sp. another potential isolate namely halobacillus blutaparonensis has been investigated for its ability to removal of morpholine by adopting the diglycolate degradation pathway. hence, sustainable remediation practice by utilizing effective microbes should be applied to bring the environmental cleanup or facilitate the existing system of effluent treatment mechanism incorporation with biological approaches to minimize the impact of xenobiotic pollutants in the anthropocentric epoch. conflicts of interest the authors confirm no conflicts of interest with regard to the results derived from this study on the sustainable remediation of morpholine and its micro-scale degradation pathway. references [1] sielaff, b.; 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manga, p.; gupta, s.; kapur, s.: biological approaches for treating industrial effluents containing morpholine. industrial and environmental biotechnology, edited by krishna pramanik and jayant kumar patra, studium press india pvt ltd new delhi, 2014, 255–264 isbn: 9789380012674 [20] united nations office on drugs and crime, scientific and technical notes scitec/20, december 2005 https://www.unodc.org [21] gerster, f. m.; hopf, n. b.; huynh, c. k.; plateel, g.; charrière, n.; vernez, d.: a simple gas chromatography method for the analysis of monoethanolamine in air. j. sep. sci., 2012, 35(17), 2249–2255 doi: 10.1002/jssc.201200196 [22] crosby, n. t.: determination of ammonia by the nessler method in waters containing hydrazine. analyst, 1986, 93(1107), 406–408 doi: 10.1039/an9689300406 50 pp. 33–43 (2022) https://doi.org/10.1111/j.1472-765x.1996.tb00202.x https://doi.org/10.1111/j.1472-765x.1996.tb00202.x https://www.wjpr.net/abstract_show/2951 https://doi.org/10.1093/nar/gkh340 https://doi.org/10.1093/nar/gkh340 https://doi.org/10.1080/10635150701472164 https://doi.org/10.1080/10635150701472164 https://www.ncbi.nlm.nih.gov/genbank https://www.unodc.org/pdf/scientific/scitec20-fin.pdf https://doi.org/10.1002/jssc.201200196 https://doi.org/10.1039/an9689300406 https://doi.org/10.1039/an9689300406 hungarian journal of industry and chemistry vol. 50 pp. 45–55 (2022) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2022-08 enzyme reaction engineering as a tool to investigate the potential application of enzyme reaction systems nevena milčić 1, ivana ćevid1, mehmet mervan çakar1, martina sudar1, and zvjezdana findrik blažević *1 1faculty of chemical engineering and technology, university of zagreb, marulićev trg 19, zagreb, hr-10000, croatia it is widely recognized and accepted that although biocatalysis is an exquisite tool to synthesize natural and unnatural compounds under mild process conditions, much can be done to better understand these processes as well as detect resulting bottlenecks and help to resolve them. this is the precise purpose of enzyme reaction engineering, a scientific discipline that focuses on investigating enzyme reactions with the goal of facilitating their implementation on an industrial scale. even though reaction schemes of enzyme reactions often seem simple, in practice, the interdependence of different variables is unknown, very complex and may prevent further applications. therefore, in this work, important aspects of the implementation of enzyme reactions are discussed using simple and complex examples, along with principles of mathematical modelling that provide explanations for why some reactions do not proceed as planned. keywords: enzyme kinetics, modelling, reaction optimisation 1. setting up the reaction conditions for an enzyme reaction in each reaction system, first a proper buffer must be selected and the ph dependence of the enzyme activity determined in order to identify the optimal working conditions [1]. although the impact of temperature on enzyme activity is also important, it should be remembered that the temperature at which the enzyme exhibits the highest level of activity is not necessarily that at which the enzyme stability is optimal. at higher temperatures, the enzyme activity is often increased but at the cost of progressive and irreversible denaturation due to poor thermal stability [2,3]. when multiple enzymes are present in the reaction system and are supposed to operate in the same reactor, as is the case in cascade reactions, the optimal conditions can seldom be chosen for all of them. usually, a compromise must be reached whereby the selection of the reaction conditions depends on the enzyme activity required to catalyse the reaction [4, 5]. after selecting the buffer, temperature and ph for the studied reaction system, it must be analysed in detail, starting from the reaction scheme. even though the reaction scheme usually clearly depicts the reaction, it should be noted that recieved: 4 april 2022; revised: 10 april 2022; accepted: 11 april 2022 *correspondence: zfindrik@fkit.hr issues beyond the reaction scheme of the enzymatic reaction need to be discussed and analysed. in many cases, unwanted but insignificant side reactions may take place that sometimes also have a detrimental effect on the outcome of the reaction. although this may not be so important on the laboratory scale as far as screening for enzyme activities is concerned, given that the concentrations applied on that scale fall within the range of a few mm, it must be noted that the rate of chemical reactions increases as the concentration of reactants increases, e.g. firstand second-order reactions. therefore, further analyses to determine the effect of increasing the scale of the reaction by hundreds of mm are required. the same applies to the chemical stability of compounds present in the reactor. in this case, engineering methodology is priceless for the purpose of exploring the possibility of slowly feeding the reactive compound into the reactor. alternatively, if an intermediate is reactive, the reaction rate in the reactor may be tuned to ensure its concentration is always minimal. for example, in the case of epoxides that are substrates of halohydrin dehalogenases [6], it is known that their stability is poor [7,8]. as a result, in these reactions, a prochiral substrate is often used to start the reaction [9,10]. the same is true in this case whereby an epoxide intermediate is formed in situ and immediately spent in the subsequent reaction with the same or a different enzyme such as the one presented in scheme 1. additionally, since both epoxides and their correhttps://doi.org/10.33927/hjic-2022-08 mailto:zfindrik@fkit.hr 46 milčić, ćevid, çakar, sudar and findrik blažević scheme 1: synthesis of (r)-γ-chloro-β-hydroxybutyronitrile from an achiral substrate scheme 2: synthesis of l-homoserine in a cascade reaction sponding nucleophiles can inhibit the catalytic activity of an enzyme [11], the selection of their concentrations in the reactor is crucial in facilitating a successful reaction [12]. clearly, these are very complex reaction systems and the suitable set up of a reactor as well as reaction conditions determined by the model-aided approach can be vital [13]. multi-step reactions cannot always be performed simultaneously in one pot due to complex relationships between the process variables [14, 18]. in a study of an innovative reaction scheme for the preparation of the atorvastatin side-chain precursor, it was found that the two reaction steps consisting of aldol addition and the oxidation of the corresponding product amino lactol could not be performed simultaneously [14]. this was mostly due to the fact that acetaldehyde as the substrate in the first reaction step interferes with the oxidoreduction and coenzyme regeneration by acting as a substrate for the oxidoreductase or as an inhibitor as well as deactivator of both oxidoreductase and nadh oxidase. it is important to determine if all the reaction steps are compatible with each other before deciding how to develop the reaction. although this might suggest a significant amount of experimental work, this can be considerably reduced by evaluating the enzyme kinetics [13, 19, 20]. forming the reaction model enables a vast variable space to be explored in silico. apart from that, combining the kinetic model with mass balances in different reactors enables different types of reactors to be explored in each system. this was found to be crucial with regard to improving the process metrics in the synthesis of lhomoserine [21], a system governed by the unfavourable equilibrium of the transaminase-catalysed reaction and aided by the pyruvate recycling system catalysed by aldolase (scheme 2). the application of model-based optimization techniques led to a doubling of the product concentration (up to 80 gl−1) and an 18% increase in the volumetric productivity (up to 3.2 gl−1h−1) in comparison with a previously published work [22]. in this system, it was crucial that both reactions were carried out simultaneously to improve the position of the equilibrium. formaldehyde was gradually added to the system by using a pump due to its reactivity and inhibiting effect on enzyme activity. additionally, pyruvate and l-alanine were added sequentially once the pyruvate had been consumed in several doses, which, according to calculations, was found to work in silico experiments (fig. 1 a-b) and subsequently proved experimentally (fig. 1 c-d). 2. side reactions and their effect on the reaction scheme. when studying a complex reaction system, possible side reactions must be taken into account. these can be caused by the instability of reactants, products or intermediates; by chemical reactions between the compounds present in the reaction mixture; as well as by the side reactions hungarian journal of industry and chemistry enzyme reaction engineering as a tool 47 (a) (b) (c) (d) figure 1: cascade synthesis of l-homoserine [20] in a fed-batch bioreactor by gradually adding formaldehyde via a pump as well as sequentially adding pyruvate and l-alanine incrementally once the pyruvate had been consumed. (a) (black line – l-alanine, dashed line – pyruvate, dotted line – formaldehyde), (b) (grey line – l-homoserine, grey dashed line – aldol intermediate). in silico experiments, (c) experimental validation (black triangles – l-alanine, white squares – pyruvate, blue diamonds – formaldehyde), and (d) experimental validation (red circles – l-homoserine, grey stars – aldol intermediate). scheme 3: synthesis of the aldol product (3s,4r)-6-[(benzyloxycarbonyl)amino]-5,6-dideoxyhex-2-ulose in a cascade reaction 50 pp. 45–55 (2022) 48 milčić, ćevid, çakar, sudar and findrik blažević caused by the catalytic enzymes due to their low purity or ability to catalyse more than one reaction [8, 23, 24]. reactions are often carried out with a crude enzyme extract or whole cells in order to reduce the costs of synthesising the protein by avoiding the necessity for purification. although such systems often offer an additional advantage in terms of enhancing the operational stability of the desired enzyme within the protein mixture or cell compartment, other enzymes in these systems can also catalyse undesirable enzymatic reactions [23]. all of these aforementioned reactions can lower the concentration of the target product as well as decrease the reaction yield, moreover, in some cases, even prevent the formation of the target product. one example of such an event is the oxidation of an alcohol to form an aldehyde catalysed by horse liver alcohol dehydrogenase that reacts further by oxidizing the aldehyde to form the corresponding acid as a side product. in the cascade synthesis of (3s,4r)-6[(benzyloxycarbonyl)amino]-5,6-dideoxyhex-2-ulose (scheme 3), n-cbz-3-aminopropanoic acid was the dominant main product following our first attempt, with only 2% of the target product being formed [25, 26]. considering the complexity of the system, reaction engineering methodology was applied to determine the reason behind this. a statistical model implied the occurrence of this side reaction [25] which was later confirmed by kinetic studies [26]. not only did the aforementioned studies reveal the reasons for the poor yield but also determined how to improve it to between 79 and 92%, respectively. in many cases, although commercial compounds that contain small quantities of certain additives are purchased for research purposes, these additives can also frequently act as enzyme inhibitors, such as in the case of 4methoxyphenol as a stabilizer of acrylonitrile that was used as a substrate in one of the reactions studied by us [27]. in fact, this was one of the crucial reasons why it was not possible to obtain significant amounts of product in any reactor. 3. investigation of the kinetics of the enzyme-catalysed reaction to formally identify the system, the effect of all the compounds present in the reaction mixture on the enzyme activity / reaction rate can be evaluated. during these measurements, the effects of all the compounds on the enzyme activity can be measured and, in many cases, substrate, intermediate and product inhibition can be detected, which subsequently help with regard to decisionmaking and selection of the reactor mode to be used for the reaction. some examples of reactor designs that can be applied, according to the properties of the studied reaction and desired outcome, are given in fig. 2. in theory, it is known that the fed-batch bioreactor is a favourable choice for reactions subjected to substrate inhibition to increase the concentration of the obtained product [31]. (a) (b) (c) figure 2: schemes of different reactors applied in biocatalysis: (a) batch reactor, (b) fed-batch bioreactor, (c) continuous stirred tank reactor for product-inhibited reactions, a continuous stirred tank reactor operating at the maximum concentration of the product is not recommended and, therefore, the resultant enzyme activity is unsatisfactory [32, 33]. in practice, reactions are rarely inhibited by a single compound, moreover, in many cases, several important inhibitions and/or side reactions take place. therefore, the reactor mode cannot be easily set by viewing the results of the effect of substrates on the reaction rate. in these cases, kinetic models help simulate different scenarios and enable the best choice for the studied reaction system to be made [13]. the simulations of a relatively simple doublesubstrate reaction in which the kinetics can be described by double michaelis-menten kinetics with both substrate and product inhibition are presented in fig. 3. the impact of reaction conditions on substrate conversion and volumetric productivity in the batch reactor is presented in figs. 3a and 3b, while 3c and 3d show the same for the continuous stirred tank reactor (cstr). substrate conversion is governed by the enzyme concentration as well as the reaction time and residence time in the batch reactor and cstr, respectively. the main difference that can be hungarian journal of industry and chemistry enzyme reaction engineering as a tool 49 (a) (b) (c) (d) figure 3: model simulations demonstrating the impact of the reaction conditions on the conversion and volumetric productivity in the batch and continuous stirred tank reactors observed is in terms of volumetric productivity, which explains why continuous processes are currently in the spotlight. in this simulation, the maximum volumetric productivity of the cstr is fourfold greater than that of the batch reactor. nevertheless, it must be noted that the operational stability of the enzyme is important and that the enzyme activity was assumed to be constant. in practice, since the enzyme activity inevitably drops over time and, therefore, enzymes must be stabilized by a form of immobilization, ensuring the continuous process functions is not a straightforward task. the first step to investigate enzyme kinetics is to find an appropriate method that will result in the rapid collection of enzyme kinetic data. this can be done by applying a spectrophotometric enzyme assay and microtiter plate reader, however, should these methods be unavailable, this can also be achieved in a traditional manner by determining the initial reaction rates from hplc or gc data with regard to the concentrations of substrates and products [13]. given that data collection must be accurate and reliable, analytics is the foundation of the research. data must be reproducible and trustworthy to be used for modelling. an example of kinetic data is presented in fig. 4 where the grey line denotes the experiment where the enzyme concentration was too high. furthermore, even though the linear dependence of absorbance over time is obvious in the initial part of the curve, the error of such measurements can be high and depends on the individual measuring. on the other hand, the black line clearly figure 4: the impact of enzyme concentration on the quality of the experimental data 50 pp. 45–55 (2022) 50 milčić, ćevid, çakar, sudar and findrik blažević (a) (b) (c) (d) figure 5: estimation of kinetic parameters for a two-substrate reaction by applying linear (a and b) and nonlinear regression (c and d) analyses represents linear data with a relatively small gradient, indicating that the measurements were made properly and the dependence is undoubtedly linear within that range. a series of such experiments performed at different concentrations of substrates, products and intermediates is required to obtain one set of experimental data to be subsequently used for the estimation of kinetic parameters. based on the kinetic data, the kinetic parameters can be estimated by using nonlinear regression analysis, which is far better than the still commonly used linear regression analysis [34]. this can be illustrated by the example presented in fig. 5 whereby a double-substrate reaction was considered and the kinetic data concerning the dependence of the specific enzyme activity on the concentration of the reactants measured. by measuring the initial reaction rate (conversion less than 10%), the effect of product inhibition or enzyme deactivation could be minimized [35]. this example will be used to illustrate the differences between the values of the estimated kinetic parameters when various methods of estimation are applied. in the first case, linear regression analysis was applied by using a lineweaver-burk plot (figs. 5a-5b). the data show discrepancies and, in the case of 5b, two points needed to be removed from the analysis as they were outliers. the estimated kinetic parameters are presented in table 1. in the second case, the kinetic parameters were estimated by using singlesubstrate michaelis-menten kinetics, which in all likelihood is frequently used in practice. the estimated kinetic parameters presented in table 1 are very different from the ones obtained following linear regression analysis. furthermore, since the maximum reaction rates differ for each substrate, the measurements in all probability were not made in the area of substrate saturation. michaelis constants estimated by using double-substrate michaelis-menten kinetics strongly resemble the values estimated by using single-substrate michaelis-menten kinetics. however, when the maximum reaction rates are compared, a significant discrepancy between them can still be observed. estimating the maximum reaction rate by using double-substrate michaelis-menten kinetics is the optimum solution offering a unique value of vm and taking into consideration the case when the non-varying substrate was not saturated. therefore, in the case when both substrates are saturated, single-substrate michaelismenten kinetics and nonlinear regression analysis offer a suitable solution to estimate the kinetic parameters. 4. investigation of the operational stability of the enzyme enzyme activity inevitably decreases in the reactor over time, which means that the operational stability reduces as well [28–30]. this also needs to be quantified from the hungarian journal of industry and chemistry enzyme reaction engineering as a tool 51 parameter linear regression analysis 1 r = 1 vm + km vm 1 c nonlinear regression analysis – single-substrate kinetics r = vmc km + c nonlinear regression analysis – double-substrate kinetics r = vmc1c2 (km1 + c1) (km2 + c2) vm [u/mg] 0.743 (3.539) 1.448 (2.119) 4.177 km1 [mmol/dm3] 2.56 8.2 9.09 km2 [mmol/dm3] 46.366 7.726 9.191 table 1: comparison between different methods to estimate the values of kinetic parameters in an enzymatic reaction experimental data [29] and incorporated into the kinetic model. in many cases, the enzyme activity can be followed by an independent enzyme assay. in other cases, it can be estimated by using the kinetic model and other experiments. the operational stability of enzymes is an important topic not only in terms of research but also with regard to their applications. understanding and describing quantitatively as well as qualitatively how enzyme function and structure change during conversion in a bioreactor is of crucial importance [28, 36]. in their work, börner et al. investigated the mechanistic reasons for the poor operational stability of amine transaminases along with the influence of quaternary structure, cofactors and substrates. through their kinetic and thermodynamic experiments, they were able to identify the structural domain that appears to confer stability. the study revealed that the enzyme is significantly more stable when at rest than in its operational state, moreover, its operational stability was lower and experiments suggested a mechanism that brought about substrate-induced deactivation [28]. in many reports to date, it has been stated that the presence of substrates and their concentrations can have both positive [37] and negative [30] effects on enzyme stability. in a study by česnik et al. [30], formaldehyde as a substrate was found to have a negative effect on enzyme activity during experiments (fig. 6a). subsequently, it was found that this could be correlated with the operational stability of the enzyme (fig. 6b). considering the reactivity of formaldehyde and the size of this molecule, chemical damage to the protein may occur in its presence, as reported in other studies. in a study involving the dehalogenation of 1,3-dichloro2-propanol (1,3-dcp) catalysed by halohydrin dehalogenases (hhdhs), it was found that the substrate 1,3-dcp causes enzyme deactivation during incubation, moreover, as observed in the previously described case, the substrate concentration has a significant effect on enzyme activity (unpublished data, fig. 6c). experiments conducted in batch reactors corroborated that the operational stability decay rate constant can be directly correlated to the substrate concentration (unpublished data, fig. 6d). these are not the only examples of this behaviour. in a study by vasić-rački et al., it was also shown that glycolaldehyde caused operational stability decay in the reactor, the rate of which was dependent on its concentration [38]. in all of these cases, the quantification of the operational stability decay rate constant and the modelling approach improved the outcome of the reaction and increased process metrics values. another example of the effect of a substrate on enzyme activity can be demonstrated by different oxidases. in one study, the operational stability of d-amino acid oxidase was investigated in the presence and absence of aeration [40]. the enzyme operational stability decay rate of d-amino acid oxidase from porcine kidneys was reduced by increasing the oxygen concentration in the reaction solution and the enzyme activity decreased more rapidly. similar conclusions were drawn in a later study on glucose oxidase [40]. this can be related to the oxidation of protein residues in the presence of oxygen and requires some sort of quantification to enable development of the reaction by focusing on resolving bottlenecks. if operational stability is considered in a very simple reaction with only a basic michaelis-menten model, its effect during dynamic simulations can be observed (fig. 7a). when the enzyme activity reduces in the batch reactor, the shape of the curve changes slightly. to the untrained eye, this can also resemble the result of reaching equilibrium or product inhibition. therefore, if the kinetics of the reaction are completely unknown, it is very difficult to draw the right conclusion. the situation is quite different if the continuous stirred tank reactor is used, since this reactor ideally works at a stationary state and, therefore, no changes in enzyme activity nor in stationary concentrations of reactants and products occur. hence, enzyme operational stability decay in cstrs results in the stationary state being lost and the clearly visible shape of the curve caused by the reduction in enzyme activity (fig. 7b). a third type of reactor often applied in biocatalysis due to substrate inhibition are fed-batch bioreactors. although enzyme operational stability decay can be observed from the shape of the curve (fig. 7c), here, like in the case of the batch reactor, it is more difficult to clearly define the reason for this trend. the answer that is suggested here concerns quantification of enzyme activity during the reaction. 5. choosing the best enzyme variant for the reaction techniques for genetically modifying enzymes have advanced greatly over recent years and can be applied to produce industrially suitable catalysts more quickly and 50 pp. 45–55 (2022) 52 milčić, ćevid, çakar, sudar and findrik blažević (a) (b) (c) (d) figure 6: (a)the influence of the initial concentration of formaldehyde on the enzyme activity of fsad6q during incubation; (b) dependence of the operational stability decay rate constants of fsad6q on the initial concentration of formaldehyde; (c) the influence of the initial concentration of 1,3-dcp on the enzyme activity of hhdh during incubation; (d) dependence of the operational stability decay rate constants of hhdh on the initial concentration of 1,3-dcp (a) (b) (c) figure 7: the effect of operational stability decay on model curves in different types of reactors: (a) batch reactor, (b) continuous stirred tank reactor, (c) fed-batch bioreactor parameter unit enzyme 1 enzyme 2 enzyme 3 vm u/mg 3.42± 0.05 1.74± 0.11 0.74± 0.03 km mm 102.24 ± 4.01 67.52 ± 7.22 36.33 ± 8.82 ki mm 679.94 ± 38.81 183.19 ± 29.25 377.28 ± 68.70 table 2: estimated kinetic parameters for the three enzyme variants cost-effectively. however, in order for new biocatalysts to be worthy of industrial large-scale production, reliable and comprehensive methods for the initial kinetic characterization of possible enzyme variants are necessary. in search of an optimal enzyme variant, the enzyme with the highest activity (highest vm value) or highest affinity for the substrate (lowest km value) is often sought [41]. this is only valid when michaelis-menten kinetics are applied, however, in practice, the situation is rarely that simple. for example, this is not so in the case hungarian journal of industry and chemistry enzyme reaction engineering as a tool 53 (a) (b) 5(c) figure 8: comparison between the three enzyme variants which exhibit substrate inhibition at different levels of michaelis-menten kinetics with substrate inhibition, when the substrate concentration used during screening is critical. given that screening seems to only be conducted at one concentration, accurate data of enzyme activity is not provided, considering that the shape of the michaelismenten curve is unknown. since variants of the same enzyme differ with regard to the estimated values of their kinetic constants, combinations of the relevant kinetic parameters (vm, km, ki) were obtained for each variant (table 2). although it may be assumed that the enzyme with the minimum michaelis constant and highest activity is most suitable, in practice, this enzyme may exhibit a higher level of substrate inhibition as a result. three enzyme variants were kinetically characterized and the dependence of their specific enzyme activities on the substrate concentration is presented in fig. 8, while the kinetic parameters are shown in table 2. the best applied variant was found to be enzyme 1, written in bold, in table 2 because the level of substrate inhibition it is subjected to is by far the least pronounced. in practice, this means a broader substrate concentration area in which the highest enzyme activities can be obtained in the reactor (fig. 8a) and enhanced stability of the reactor’s operating conditions. simulations presented in fig. 8 also show that when screening the enzyme variants, it is important to not only evaluate their activities but also estimate all their kinetic parameters. in further stages of process development, the application of reaction engineering to identify process bottlenecks is required to exploit the full potential of novel enzymes. to develop novel green routes in biocatalysis and scale them up, it is crucial to adopt a multidisciplinary approach by combining the fields of chemistry, biology and chemical engineering. 6. conclusions enzyme reaction engineering can provide explanations for and give answers to different phenomena that occur in bioreactors. this is of particular importance when it comes to multienzyme systems which are very important in terms of sustainable development and green synthesis. many obstacles to their development must be overcome, for example, adjusting enzyme activities, choosing suitable enzyme variants, selecting the best reactor and determining the optimal reaction conditions while considering the side reactions that may occur. therefore, a combined effort and multidisciplinary approach are required to prepare complex enzyme reaction systems for industrial applications. acknowledgement authors would like to thank the croatian science foundation for the phd scholarship of n. milčić. this work was partly supported by the project cat pharma (kk.01.1.1.04.0013) co-financed by the croatian government and the european union through the european regional development fund the competitiveness and cohesion operational programme (i. ćevid). we acknowledge the funding from eu h2020-msca-itn2020 project c-c top under the grant agreement no. 956631 (m. m. çakar). references [1] burgess, r.r.; deutscher, m.p.: guide to protein purification (academic press, cambridge, uk), 2nd edition, 2009, isbn: 978-008-092-317-8 [2] robinson, p.k.: enzymes: principles and biotechnological applications, essays biochem, 2015, 59, 1–41. doi: 10.1042/bse0590001 [3] bisswanger, h.: enzyme kinetics: principles and methods (wiley, new york, usa), 3rd edition, 2017 isbn: 978-352-780-646-1 [4] siedentop, r.; claaßen, c.; rother, d.; lütz, s.; rosenthal, k.: getting the most 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from the process net of the underlying state and transition elements. two special-state elements are introduced for the short-term storage of the supplied biomass to be distributed and of the uptake of nutrient-containing water, necessary for evapotranspiration and photosynthesis. the transition-oriented description of functionalities follows the essential causalities and balances of natural self-control. implementation of the model is illustrated by a simple example. keywords: plant model, reduced complexity, stoichiometric processes, process network, supply/demand logistics, natural self-control 1. introduction the bio-based circular economy is crucial to secure the supply of food and materials for mankind given the burden of depleting non-renewable resources and finite reservoirs. the replacement of open process systems with circular ones needs conscious engineering planning and operations while systemically overviewing the underlying processes. multisectoral process networks require the coupling of sub-models from various disciplines on different scales. in the bio-based circular economy, the photosynthetic biosystems (plants) represent biomass production from solar energy, i.e. from the only external, unlimited energy resource for our planet. accordingly, the model-based analysis, planning and operation of cultivated and natural plants plays an important role. recently, motivated also by the increasingly integrated engineering of natural and man-made systems, intensive bidirectional learning has commenced between the computational modeling of natural and man-made processes whereby: • the principles of more sustainable and resilient natural ecosystems can be applied in the design and control of man-made systems on the one hand, while recieved: 26 may 2022; revised: 7 june 2022; accepted: 7 june 2022 correspondence: varga.monika@uni-mate.hu • the experiences of industrial systems designed by engineers can be taken into account with regard to the model-based analysis, planning and operation of agricultural cultivation on the other. although systems of chemical process engineering played a unique role in this knowledge transfer because the underlying multidisciplinary processes were complex enough to represent various features, they were not too complex for the application of formerly applied computational tools. the lessons learnt from chemical process systems are still clearly important in terms of the rapidly developing model-supported problem-solving of complex agri-food and agro-environmental process systems. this paper shows how chemical process engineering can be used to develop plant (crop) models of limited complexity. first, some available plant models will be overviewed in brief. two different approaches are available, namely (i) empirical (statistical) models to calculate various specific sources of biomass production and (ii) the mechanistic (biophysical) models that describe the underlying physical, chemical and biological processes, representing causalities and balances. this overview focuses on the mechanistic crop models. physiological models are important to further our understanding of metabolism, growth and how plants respond to environmental conditions, e.g. climate change [1]. the detailed dynamic modeling of physiological processes is not a novel endeavor, in fact it was https://doi.org/10.33927/hjic-2022-09 mailto:varga.monika@uni-mate.hu 58 varga already applied at the end of the previous century [2–5]. however, because of the increasing complexity of waterenergy-food-ecosystems nexus [6–8], besides detailed biophysical models, the systemic coupling of these biophysical models from various disciplines is also necessary, which also requires flexible models to couple economic considerations [9]. regarding the level of detail, the improved understanding of physiological characteristics and the expected response to environmental changes require mechanistic models at both the cellular and organ level [10]. however, their practical applicability, considering the available data and knowledge, also requires the development of advanced coupling models. various complex crop models are available. in a recent paper, eight kinds of crop models are classified and compared [11], the most important of which are as follows: agricultural production systems simulator (apsim) is an actively evolving tool for the modeling and simulation of a wide range of agricultural systems, including plants, animals and soil, which also takes into consideration management actions and climatic effects [12]. the crop-related parts contain the detailed biophysical description concerning the phenology, biomass accumulation and distribution of newly synthesized biomass as well as the uptake of water and components by taking into account the related limitations and dependencies on environmental conditions. stics is a detailed biophysical modeling tool that considers water, carbon as well as thermal and radiation energy balances for many (ca. 20) different crops ([13, 14]). it also clearly represents the phenological stages and the most important biophysical processes, e.g. light interception, transpiration, uptake of water and nutrients, etc. cropping systems simulation model [15] is also a frequently used simulation model that takes into consideration the soil water budget, soil-plant nitrogen budget, crop-canopy and root growth, dry matter production, yield, residue production and decomposition as well as several management options, e.g. cultivar selection, crop rotation, irrigation, fertilization, tillage operations, residue management, etc. recently, the rediscovery of advantages regarding the coupling of tree and crop systems by combining their models has also come to the fore. both apsim and stics follow this direction. a few validated tree models are available that are integrated in apsim to be used in combination with plants [12]. on the other hand, a stics crop model is embedded in the hi-safe agroforestry tool [16]. 2. challenges and objective plant models for well-defined important crops and trees are available. these detailed, specific models require a considerable set of parameters to be identified, moreover, the increasing design space of the bio-based circular economy needs simplified, approximate, unified, flexible, extensible and connectible plant models. the objective of this paper is to introduce the conceptual framework and experimental implementation of a unified plant model of reduced complexity. to develop the model, the following chemical process engineeringbased principles were applied: • generalized unit operations; • specific stoichiometric composition of pseudocomponents and other entities; • stoichiometric conservation processes based on the model-specific conservation laws, e.g. conservation of atoms in chemistry; and • demand-supply chain-like representation of material flows driven by the underlying push or pull logistics. 3. materials and methods 3.1 data and calculation formulae for a typical example of a plant to be modelled as an illustrative example of a man-made and operational plant ecosystem, a cultivated field of maize was modeled, where 9600 individual plants were cultivated over an area of 1600 m2. the maize-related specific data were derived from the literature [17–19]. within the contours of the outlined system, this cultivated field was associated with the connected layers of soil and the compartment of air. the environmental conditions were taken into consideration in accordance with the data from the respective meteorological database. the initial data of the plants refer to the stage following the sowing of the seeds when the initial biomass of the plants is contained within the seeds and sprouting has not yet occurred. the initial conditions of the seed biomass (based on estimations by experts) and its components [20, 21] are the following: biomass = 0.0003 kg/plant c = 0.03747 kmol/kg h = 0.06999 kmol/kg o = 0.02846 kmol/kg n = 0.00154 kmol/kg p = 0.00011 kmol/kg x = 0 kmol/kg h2o = 0.118 kmol/kg o2 = 0.00066 kmol/kg germination is an event-driven process that occurs after the time-driven sowing. sowing, which is a management process, is modelled by putting the seeds into downflow material storage. afterwards, in the event of the appropriate environmental (meteorological and hydrological) conditions, the seeds germinate resulting in the release of these stored materials in accordance with the following parameters (based on estimations by experts): seed biomass = 0.0001 kg/pc hungarian journal of industry and chemistry developing plant models of reduced complexity 59 seed rate = 6.579 × 10−7 kg/h proportion of leaves = 0.853 proportion of roots = 0.147 surface area ratio of leaves = 6.667 m2/kg surface area ratio of roots = 3.003 m2/kg in our example model, the germination period is from april 20th until may 9th. after the leaves and roots appear, resulting from the event-driven process of germination, the life processes of plants, that is, photosynthesis, growth, respiration, evapotranspiration and uptake, start. the rate of photosynthesis is calculated by the following simplified equations [19]: ∆biomassdry = num rad ft et ρ dt (1) where ∆biomassdry = biomass produced, kg, num = number of plants, pc. rad = radiation, w/mj2 ft = proportion of radiation absorbed by the plants et = radiation-use efficiency, kgdry matter/wabsorbed radiation ρ = density, number of plants/m2, where ft = 1 − e−ktlaiact (2) laiact = leavessurf num aact (3) aact = lairatio landsurf (4) ρ = num aact (5) landsurf = surface area of land, m2 lairatio = 1 m2 area of leaf / m2 area of land kt = 0.8 light extinction coefficient [19] et = 0.01409 kg/mj, radiation-use efficiency [19] the process of evapotranspiration is calculated from the reference evapotranspiration (et0, mm/day), determined from meteorological data according to the wellknown penman-monteith combination equation [22]. based on this equation, the evaporation from the land and plants during a time step are calculated separately based on the following equations: etland = ke etm landsurf dt (6) etplants = kcb etm surf num dt (7) where etm = reference evapotranspiration, recalculated from et0 / kmol/h etland = land-related evapotranspiration, kmol etplant = plant-related evapotranspiration, kmol landsurf = surface area of the land, m2 surf = surface area of the leaves, m2 num = number of plants, pc ke = 1 m−2, soil-related part of the dual crop coefficient [22] kcb = 1 m−2, basal plant-related part of the dual crop coefficient [22] dt = the time step in hours, distinguished for the changing actual daylight or night period growth is calculated after germination and is interpreted as the distribution of the photosynthetic biomass between the parts of the plants. before the timeor eventdriven appearance of the product, the following ratios are applied in line with estimations by experts: proportion of leaves = 0.853, proportion of roots = 0.147. afterwards: proportion of leaves = 0.637, proportion of products = 0.253, proportion of roots = 0.110. respiration is calculated for the individual parts of the plants. for all the parts, two kinds of respiration is simulated: one as a given proportion of the biomass synthesized and the other as a given proportion of the already existing biomass. the applied equations are the following: rleaves = k dmleaves + c mleaves num dt (8) rprod = k dmprod + c mprod num dt (9) rroot = k dmroots + c mroots num dt (10) where rleaves = respired biomass of leaves, kg rprod = respired biomass of product, kg rroot = respired biomass of roots, kg dmleaves = synthesized biomass of leaves, kg dmprod = synthesized biomass of product, kg dmroots = synthesized biomass of roots, kg mleaves = existing biomass of leaves, kg mprod = existing biomass of product, kg mroots = existing biomass of roots, kg k = the constant of 0.1 h−1 [22] c = the constant of 0.0001 h−1 [22] num = number of plants, pc. dt = the time step in hours, distinguished for the changing actual daylight or night period the uptake of water, nitrogen and phosphorus (or of other optional elements) is calculated as the minimum amount: • required for evapotranspiration and photosynthesis together and • available in the soil. 50 pp. 57–65 (2022) 60 varga 3.2 non-conventional methodology of programmable process structures programmable process structures (pps, [23–26]) have developed from its antecedent, that is, direct computer mapping [27]. pps offers automatic generation of easily extensible, connectible and combined dynamic balanceand rule-based models for the analysis, planning and operation of complex process systems, even beyond industries that apply cim (chemical integrated manufacturing). these models consist of unified state and transition elements, transition-oriented representations of structures as well as locally programmable functional prototypes. the main sources of inspiration behind pps are: 1) the general functional definition of process systems in kalman’s state space model [28]; 2) the structural representation of general net theory [29]; 3) the concept of communicating autonomous programs in terms of agentbased modeling [30]. accordingly, pps models are derived from two general (state and transition) "meta-agents," namely the structure of the generated state and transition elements form a net structure, moreover, the locally programmed state and transition prototypes represent the distributed functionalities in terms of kalman’s model. in addition, pps can consciously make a distinction between modelspecific conservation laws based on additive measures and signals. in fact, pps models can be generated from two general meta-prototypes and from the corresponding description of the process net. the local program containing prototype elements (that are responsible for the casespecific calculations), are also derived from the same meta-prototypes. the simulation can be executed according to the connections between the actual state and transition elements, accompanied by the data transfer between the actual elements and their calculated prototypes. this architecture and its ai programming language-based (swi-prolog to be exact) implementation strongly support the integration of various fieldand task-specific models. 4. results and discussion 4.1 chemical process engineering-inspired principles and hypotheses of plant models natural and cultivated plants, including crops, vegetables, herbs, grasses and bushes, trees, etc. in a broader context, cover a wide variety of biological species embedded in a naturally occurring and partly human-controlled process system. since many different species exist, at first glance this resembles the early stages of chemical engineering when individual technologies were interpreted as a system of various case-specific reactors, separators, etc. the essential invariant elements were later generalized according to the concept of unit operations. similarly, the unified, essential features of agricultural models can be formulated as “biological engineering unit operations” within the complex system of the connected agrotechnological, ecological and environmental systems. considering the need for unified and simplified biological, ecological and environmental engineering process units, these systems must be represented by the necessary and sufficient types as well as numbers of state and transition elements calculated by a limited set of generally usable program prototypes. the coherent and connectible set of the underlying ‘first principles’-based mechanistic (physical, chemical and biological) models must be based on causally correct, model-specific conservation laws-based material and energy balances. considering the numerous biochemical compounds and biological objects, that is, organs, etc., synthesized from these compounds, the various typical biological units can be characterized by their specific stoichiometric composition that facilitates the representation of balances in accordance with the conservation of atoms and in line with chemical principles. besides the conservation-based balances, the causally determined (driving force-based) transformations and transportations are the second pillar of process engineering models. in this regard, plant-like biological process units represent a special case because the major driving force is solar radiation originating from beyond the contours of the system. this feature determines the unique position of plants in the bio-based circular carbon economy. in fact, solar radiation-driven photosynthesis produces a stoichiometric composition of biomass that supplies biomass in the various state elements of plants through downflow transporting short-term storage. moreover, the forces of solar radiation-driven evapotranspiration result in the uptake of water and dissolved nutrients through upflow transporting short-term storage that supplies the additional resources required for photosynthesis as well as removes the by-products of the energyproducing respiration. accordingly, the essential self-control of plant life is organized by the solar radiation-driven push logistics of downflow as well as by the solar radiation-driven pull logistics of upflow. the daily and seasonal changes in plant behavior are determined by the temporally changing environmental functionalities, while human intervention can be taken into consideration by the respective managerial events. the hypotheses for the simplified and unified plant model can be summarized as follows: • the state elements are described by the specific biomass (or mass); the stoichiometric amounts of c, h, o, n, p and optional x atoms; as well as those originating from h2o, o2 and co2. • the transition elements, e.g. photosynthesis, growth, respiration, evapotranspiration, uptake, etc., determine the functionalities resulting in stoichiometric changes in the aforementioned sources hungarian journal of industry and chemistry https://www.swi-prolog.org/ developing plant models of reduced complexity 61 of biomass, mass, atoms and components in the respective state elements. • the life processes of plants as self-controlled living systems can be characterized by (i) the supply logistics of the photosynthesis-driven utilization of co2 from air and h2o, n, p, etc. (from top soil) to produce o2 which is emitted into the atmosphere in addition to stoichiometric pools of c, h, o, n and p that is incorporated into downflow material storage, as well as by (ii) the demand logistics of the solar energy-driven evapotranspiration-controlled uptake of h2o, n and p from the soil and the emission of co2 and h2o into the air. 4.2 structure of the investigated process system the process net structure of the simplified plant model, embedded in its natural environment and extended with human managerial interventions, is illustrated in fig. 1. in the net model, the dots and bars represent the state and transition elements, respectively. the state and transition elements of the simplified plant model are the following: plant-related model elements: • state elements: – roots (responsible for the water uptake, transportation of dissolved nutrients and long-term biomass storage that is also capable of generating useful products); – leaves (including stems which are responsible for solar radiation-driven photosynthesis and evapotranspiration); – products (which facilitate the storage of biomass for reproduction that also generates useful products); – downflow of material (short-term storage of photosynthesized biomass to be distributed amongst the roots, leaves and products); – upflow of material (short-term storage of uptaken water and nutrients as well as of respired components to be distributed between evapotranspiration and photosynthesis). • transition elements: – photosynthesis: utilizes solar radiation to synthesize biomass from atmospheric carbon dioxide, uptaken water and dissolved components, e.g. nitrogen, phosphorus, etc.; – growth: distributes the photosynthesized biomass between the parts of the plant according to the phenological phase-specific stoichiometry; – respiration: creates energy to synthesize tissues from already synthesized biomass and in part maintain existing plant biomass; – evapotranspiration: which is determined by the atmospheric conditions, i.e. level of solar energy, generates the driving force for the uptake of water and dissolved nutrients from the soil as well as releases the co2 and h2o produced by respiration; – uptake: supplies the necessary water and dissolved nutrients from the soil. soil-related model elements: • state elements: – residue (only in the topsoil): contains organic residues, e.g. from leaf littering or the ploughing of roots; – humus (only in the topsoil): transformed organic biomass in the soil; – solution containing water and dissolved components; – inorganic solid phase. • transition elements: – transform (only in the topsoil): describes the production of humus and dissolved nutrients from the residues; – air_land (only in the topsoil): calculates the levels of precipitation and nitrogen fixation from the atmosphere into the soil as well as those of evaporation and co2 emission from the soil into the atmosphere; – miner_deminer: determines the degrees of mineralization and demineralization of dissolved components in the soil; – seepage: calculates the vertical downflow of water and dissolved components between the layers of soil. human interventions in terms of cultivation: • typical state elements: manure, seeds, harvested products, etc. • typical timeand/or event-driven transition elements: manuring, sowing, harvesting, ploughing, etc. other environmental state elements: the atmosphere (air), solar radiation-related meteorology, ground layer below the soil that absorbs water and nutrients. 4.3 solar radiation-driven “natural supply logistics” of plant biomass generation the essential functionalities of the investigated process system can be represented as solar energy-driven as well as predominantly self-regulated, natural supply-anddemand logistics. moreover, the respective supply-anddemand processes are causally connected that establish a natural (basically cooperative) feedback between each other. solar radiation facilitates the synthesis of biomass, the latter is calculated according to eqs. 1-5. the related subprocesses of the plant model are denoted in green lines in fig. 1. the synthesis of biomass is driven by solar radiation but limited by the available amounts of water, nitrogen and phosphorus with regard to the upflow material to be 50 pp. 57–65 (2022) 62 varga figure 1: process network of the simplified plant model stored. the rate of photosynthesis also depends on the surface area of the leaves and stem. controlled by these conditions and limitations, the synthesis sequestrates the calculated amount of the practically unlimited supply of atmospheric co2 in the biomass. simultaneously, photosynthesis emits o2 into the atmosphere as a result of the oxidation of uptaken water, while the associated hydrogen is incorporated into the synthesized biomass. the photosynthesized biomass supplies the downflow of material to be stored according to the plant-specific atomic stoichiometry. in the case of the studied maize, the stoichiometry of the synthesized dry matter was as follows [20, 21]: [c, h, o, n, p, x] = [0.037, 0.062, 0.029, 0.00087, 4.8 × 10−5, 0] the dry matter is supplied by an additional amount of h2o, according to the average water content of the plant (in our case 0.682). the synthesized biomass is divided between the leaves, roots and product state elements of the plant, according to the plant-specific ratios that also depend on the phenological condition of the model. furthermore, different stoichiometries can be used by the various parts of the plant. in addition to the increase in the amount of synthesized biomass, a given proportion of that which is stored in the short term is utilized to meet the energy demand supplied by respiration for the synthesis of plant biomass according to eqs. 8-10. 4.4 solar energy-driven “natural demand logistics” of water and nutrient uptake considering the “natural demand logistics,” the solar energy facilitates the uptake of water and dissolved nutrients from the soil as well as of h2o and co2, the byproducts of respiration. the respective evapotranspiration is calculated according to the penman-monteith combination equation [22] as well by eqs. 6-7. the related subprocesses of the plant model are denoted in red lines in fig. 1. depending on the meteorological conditions, the h2o and co2 content of the uptaken material to be stored is emitted into the atmosphere by the process of evapotranspiration. simultaneously, the by-products of respiration, namely h2o and co2, accumulate here, moreover, the necessary amounts of h2o as well as of dissolved nitrogen and phosphorus are utilized for photosynthesis from this store. in the knowledge of the resultant actual conditions with regard to the uptaken material to be stored, the uptake is controlled by demand-determined pull actions according to the concentration bounds and uptake rules as follows: lower and upper bounds for h2o as well as n and p atoms are known. the rule that is applied is the following: if actual ≤ lower, then demand = min((upper-actual), available), otherwise demand = 0, where actual = actual amount of uptaken material to be stored, lower = lower bound, hungarian journal of industry and chemistry developing plant models of reduced complexity 63 upper = upper bound, demand = quantity to be uptaken, available = available amount in the topsoil. 4.5 generation and simulation of the pps model the files describing the respective model are found in the “plant” directory of a mendeley database [31]. the process network of the example model is defined in the text file named plant_n.pl. the initial conditions (mass, biomass, components, etc.) and parameters (coefficients of equations, bounds, etc.) are described in the text file entitled plant_d.pl, which was derived using an appropriately configured ms excel spreadsheet. starting from these case-specific files and the general definition of state and transition meta-prototypes, the general-purpose kernel program generates the editable graphical model plant_g.graphml. in parallel, by utilizing the meta-prototypes-based templates, modeling experts have to prepare the local programs for the respective elements of the prototypes. the locally executable programs of the prototypes are described in the file entitled plant_g_prot.graphml. in the knowledge of the prototype elements, the second generating algorithm of the pps kernel prepares the dynamic databases of the simulation, namely • plant_exp.pl containing the declaration of the prolog clauses describing the local programs; and • plant_use.pl containing the declaration of the prolog facts describing the case-specific elements of the model along with their initial values and parameters. the actually selected simulation results are saved in the file named plant_out.csv, while the data can be visualized using a case-specific ms excel spreadsheet. some examples of the simulated results are illustrated in figs. 2-5. fig. 2 shows the change in the total amount of biomass produced over one hectare during consecutive half days in the simulation. time = 0 indicates when the land was sowed. biomass begins to be produced following germination and stops at the end of the vegetation period. fluctuations in biomass production indicate that its rate is higher during the daytime compared to at nighttime. in fig. 3, water that evaporated from the plant (blue) and from the land (red) are illustrated. evaporation from the land follows the weather conditions much more closely and dominates during the early stages of the growing season, particularly when the leaves develop. similarly to the production of biomass, evaporation rates are also higher in this simulation during the daytime. in fig. 4, the biomass of the parts of one plant (leaves, stem, roots, products) can be seen. the leaves, stem and roots begin to develop at the point of germination, while products appear later on. although the leaves, stem and products are removed at harvest time, the roots are transformed into residues as a result of ploughing. of course, figure 2: total amount of photosynthesized biomass per hectare figure 3: dynamic changes in the evaporation rate of h2o from plants and the surface of the land figure 4: biomass of plant parts throughout the growing season the stepwise increase in biomass is insignificant in this integrated illustration. fig. 5 shows the sequestrated co2 over one hectare during consecutive half days of the simulation. the negative values refer to the reduction in its concentration in the surrounding atmosphere. 5. conclusion although detailed plant models for well-defined important crops are available that require hundreds of parame50 pp. 57–65 (2022) 64 varga figure 5: amount of sequestrated co2 ters to be identified, the increasing complexity of agricultural systems within the broader context of the bio-based circular carbon economy requires simplified and unified plant models, which can describe the primary production of biomass. the suggested conceptual framework and its experimental implementation show how the chemical process engineering principles of process units, stoichiometric conservational processes, process networks, driving force-controlled functionalities and supply/demand processes can result in a reduced, unified plant model. the structure of the model can be generated from the process net of the underlying state and transition elements. the model contains two special state elements for the short-term storage of the synthesized biomass to be distributed amongst the state elements of the plant as well as for the short-term storage of the uptaken aqueous nutrients required for evapotranspiration and photosynthesis. these two forms of logistical storage used represent the roles of phloem and xylem in detailed biophysical models. the transition-related dynamic models follow the essential causalities and balances of natural self-control. solar radiation-driven photosynthesis produces a stoichiometric composition of biomass that, as a result of the downflow of products to be stored in the short term, increases the biomass in the various plant elements. moreover, solar radiation-driven evapotranspiration forces water and dissolved nutrients to be uptaken through the upflow of products to be stored in the short term, which increases the amount of water and the additional resources for photosynthesis required, as well as removes the by-products of energy-producing respiration. the natural self-control of 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https://doi.org/10.1016/j.biosystems.2016.12.005 https://doi.org/10.1016/j.ecolmodel.2017.09.014 https://doi.org/10.1016/j.aquaeng.2020.102073 https://doi.org/10.1016/j.envsoft.2020.104755 https://doi.org/10.1016/j.envsoft.2020.104755 https://doi.org/10.1007/3-540-10001-6_21 https://doi.org/10.1016/j.cosrev.2017.03.001 https://doi.org/10.1016/j.cosrev.2017.03.001 https://doi.org/10.17632/nw3cjv75j5.1 introduction humic substances antioxidants methods for measuring the antioxidant capacity antioxidant effect of humic substances results measurement of total phenolic content dpph method conclusions introduction materials and methods results and discussion conclusion acknowledgement introduction the most common effects of pgprs on plants pgpr mediates increases in cereal-crop yields conclusions introduction experimental materials development of hf membranes development of hf membrane modules determining the gas transport properties of the hf membrane development of the membrane separation unit results and discussion preparation of hf membranes characterization of gas transport across hf membranes morphology of hf membranes hollow fiber membrane modules hc1 mini-modules p2-type module development of the membrane gas separation unit high-pressure membrane unit utilizing a laboratory air compressor low-pressure membrane unit utilizing a vacuum pump conclusion introduction experimental methods applied chemicals activity measurements mass-transfer rate kinetics enantioselectivity results and evaluation kinetics activity mass transfer through the organic–water interface enantioselectivity conclusion introduction materials and methods sample collection and preparation formulation and production of floor tiles characterization of floor tiles water absorption density impact strength tensile strength young's modulus of elasticity friction test compressive strength results and discussion physical properties of floor tiles mechanical properties of the formulated tiles conclusion introduction sustainable remediation of morpholine and its degradation pathway materials and methods environmental samples chemicals and reagents screening, characterization and sequence accession of the morpholine-degrading isolate cultivation and acclimatization of the isolate: microbial adaptation against morpholine growth on different hypothetical degradation intermediate compounds chemical tests of intermediate(s) in the degradation pathway gas chromatography (gc) studies of degradation intermediate(s) mass spectrometry studies of degradation intermediate(s) estimation of the ammonia concentration results and discussion morphological, biochemical and molecular identification growth on intermediates chemical assay of intermediate(s) gc studies of mea in the culture supernatant ms studies of the culture filtrate ammonia release: as the end product of morpholine degradation discussion conclusions setting up the reaction conditions for an enzyme reaction side reactions and their effect on the reaction scheme. investigation of the kinetics of the enzyme-catalysed reaction investigation of the operational stability of the enzyme choosing the best enzyme variant for the reaction conclusions introduction challenges and objective materials and methods data and calculation formulae for a typical example of a plant to be modelled non-conventional methodology of programmable process structures results and discussion chemical process engineering-inspired principles and hypotheses of plant models structure of the investigated process system solar radiation-driven ``natural supply logistics'' of plant biomass generation solar energy-driven ``natural demand logistics'' of water and nutrient uptake generation and simulation of the pps model conclusion hungarian journal of industry and chemistry vol. 53(2) pp. 55–59 (2025) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2025-18 valorization of biomass-derived low-cost adsorbents for sustainable pesticide remediation from aqueous solutions: a comparative study melkamu birlie genet1, nikoletta kovács1, etelka tombácz1 and gábor maász1* 1 soós ernő research and development center, university of pannonia, zrínyi miklós utca 18, nagykanizsa, h-8800, hungary escalating pesticide usage over recent decades has severely compromised global water resources, necessitating cost-effective remediation. adsorption employing affordable sorbents has emerged as a promising solution. this research evaluates two low-cost adsorbents, derived from wheat straw and ground branches, to remove the pesticides atrazine, imidacloprid, metolachlor and tebuconazole from aqueous solutions. surface modification with naoh and citric acid enhances the specific surface area and functionality of adsorbents. a batch adsorption experiment was quantified using a uplc-ms/ms measurement method. citric acid-modified wheat straw demonstrated superior removal efficiencies for atrazine (76.03%), imidacloprid (59.32%) and metolachlor (70.34%) compared to the other sorbents investigated due to enhanced functional groups on its surface (–cooh, –oh). however, untreated wheat straw and ground branches exhibited suboptimal pesticide removal, with a singular exception for ground branches, which showed a notable 75.08% removal efficiency for tebuconazole. generally, these economical adsorbents are suitable for the remediation of low-concentration pesticides from aqueous solutions. keywords: low-cost adsorbent, pesticides, surface modification, wheat straw, ground branches 1. introduction the exponentially growing global population necessitates a substantial increase in food and fiber production, leading to widespread pesticide use in intensive agricultural systems. this practice is crucial for controlling pests, diseases and weeds, thereby boosting the yield per hectare as well as ensuring food security for a population projected to reach nearly 11 billion by 2100 [1]. the use of pesticides significantly improves agricultural output by mitigating pest damage, which accounts for an approximate 45% annual loss in agricultural production, and preventing numerous diseases [2],[3]. the agricultural advantages of pesticides, particularly their role in enhancing crop yields, have led to their application worldwide. consequently, global pesticide use has grown by over 1.5 times over the past three decades [4]. pesticides are chemical compounds utilized in the agricultural sector to kill/repel/control pests, including fungi, rodents, insects and weeds. pesticides generally encompass insecticides, herbicides, fungicides, rodenticides and nematicides [5]. furthermore, pesticides are broadly categorized into several classes including organophosphates, carbamates, pyrethroids, organo received: 16 june 2025; revised: 25 june 2025; accepted: 27 june 2025 *correspondence: maasz.gabor@pen.uni-pannon.hu chlorines and neonicotinoids with insecticides being a major group. globally, over 3.5 million tons of pesticides are applied annually, 47.5, 29.5, 17.5 and 5.5% of which are herbicides, insecticides, fungicides and other types of chemicals, respectively [1]. in addition, the major classes of pesticides include phosphonates, chlorophenoxy herbicides and dipyridyl herbicides, alongside fungicides such as thiocarbamates, triazoles and strobilurins. organophosphates, which are derivatives of phosphoric or phosphoramidic acid, are now the most prevalent in agriculture due to their higher efficacy and lower environmental persistence compared to organochlorines and carbamates, representing over 36% of the global market. the top ten pesticide-consuming nations are china, the usa, argentina, thailand, brazil, italy, france, canada, japan and india [6]. despite their agricultural benefits, the widespread use of pesticides has become a significant environmental and human health problem. pesticides infiltrate the environment through various pathways, predominantly via their agricultural application, where excess and residual amounts come into contact with soil in the form of rainfall, irrigation and diffusion. they contaminate groundwater through leaching and enter bodies of surface water via agricultural runoff, especially flood-like rain, as well as other pathways. these often mobile and https://doi.org/10.33927/hjic-2025-18 mailto:maasz.gabor@pen.uni-pannon.hu genet, kovács, tombácz and maász hungarian journal of industry and chemistry 56 persistent pollutants accumulate in ecosystems, degrading food quality and fostering pest resistance. ultimately, this accumulation in the environment facilitates their entry into the food chain, exposing humans to risks via their consumption and inhalation as well as dermal contact [2]. water contamination by pesticides is particularly pressing, threatening aquatic life, compromising drinking water as well as leading to bioaccumulation and biomagnification [7]. the ubiquitous presence of these chemicals and their metabolites across various environmental compartments, originating from both point and nonpoint sources [8] poses a grave threat to both human well-being and the environment. chronic exposure to pesticide residues has been linked to numerous serious health issues, including various cancers, reproductive impairments, neurological damage and endocrine disruption [8]. these critical issues highlight an urgent need for effective strategies to remove agrochemicals from water systems. consequently, the development of low-cost, efficient and environmentally-friendly innovative methods is crucial to prevent pesticide pollution. various methods exist for pesticide remediation, including photocatalytic decomposition, chemical oxidation, advanced oxidation processes, membrane technologies, electrochemical decomposition, coagulation, flocculation, biological remediation and hybrid approaches [4],[9]. however, many of these techniques are often expensive, complex and produce a substantial amount of sludge. adsorption stands out as a preferred alternative due to its simplicity, economic viability, ease of operation, versatility and high removal efficiency [10]. furthermore, low-cost adsorbents derived from agricultural byproducts such as barley straw, rice straw, wheat straw, sugarcane bagasse, sawdust, banana peel and orange peel offer numerous advantages, including being environmentally sound, easy to use, abundant and sustainable [11]. the utilization of agricultural wastes as adsorbents for pesticide removal presents a viable and advantageous alternative as it adds value to these waste materials while leveraging an abundant, low-cost raw resource. these waste materials are primarily composed of cellulose, hemicelluloses, lignin, lipids, proteins, simple sugars, water and hydrocarbons, containing various functional groups that offer potential sorption capacity for a diverse range of pollutants [12]. agricultural byproducts can be used in their natural form, typically involving washing, grinding and sieving to achieve a desired particle size for adsorption tests. alternatively, they can be used in a modified form, undergoing pre-treatment through established modification techniques to enhance their performance. this study investigates the removal of the pesticides atrazine, imidacloprid, metolachlor and tebuconazole from water using low-cost adsorbents derived from agricultural waste, specifically wheat straw and ground branches. to address the inherent variability of agricultural waste as a raw material for adsorption, chemical modifications were employed to create a functionalized adsorption surface and increase pore volume, which in turn improves their removal capacities. the research specifically assessed the effectiveness of these adsorbents having been modified by naoh and citric acid in order to compare their pesticide removal efficiencies against those of native (unmodified) adsorbents, namely wheat straw and ground branches. 2. experimental 2.1. materials unmodified wheat straw and ground branches are agricultural byproducts that serve as adsorbents. furthermore, the raw wheat straw and ground branches were modified with naoh and citric acid to enhance their surface functionalities [13] as well as improve pesticide removal as shown in figure 1. these unmodified and modified adsorbents were obtained from the geographical institute, hun-ren research centre for astronomy and earth sciences. pesticide standards (atrazine, imidacloprid, tebuconazole and metolachlor), citric acid and naoh were obtained from sigma-aldrich. ultrapure water was used to wash the adsorbents and for other adsorption process activities. 2.2. methods initially, the adsorbents were washed with ultrapure water. subsequently, batch adsorption experiments were conducted using an adsorbent dosage of 0.1 g, an initial concentration (ci) of 10 µg/l, a ph of 7.5 and a contact time of 24 hours at 20 °c in 3 ml of solvent. the adsorbents were separated from the treated water by centrifugation (3000 rpm for 20 mins, ohaus fc5816r) and syringe filtration (gf/pet, 0.45 µm, figure 1: samples of straw washed with ultrapure water (a), modified with naoh (b), modified with citric acid (c), ground branches (d), modified with naoh (e) and modified with citric acid (f) d f e pesticide remediation from aqueous solutions using low-cost adsorbents 53(2) pp. 55–59 (2025) 57 chromafil). pesticide quantification was performed using an acquity uplc h-class system coupled with an xevo tq-s micro mass spectrometer (waters). target analytes were separated in an xbridge premier beh c18 column (2.5 µm, 2.1 i.d., 100 mm, waters) at 60 °c. multiple reaction monitoring (mrm) transitions for quantification were as follows: 216→174 (atrazine), 256→209 (imidacloprid), 284→252 (metolachlor) and 308→70 (tebuconazole). the adsorption removal efficiency was calculated using the following equation: removal efficiency (%) = 𝐶0− 𝐶𝑒 𝐶0 × 100 (1), where c0 denotes the initial concentration of the pollutant in the solution (before adsorption) in mg/l and ce represents the equilibrium concentration of the pollutant in the solution (after adsorption had reached its equilibrium) in mg/l. 3. results and discussion 3.1. removal efficiency of unmodified adsorbents the removal efficiencies of unmodified native adsorbents, namely wheat straw and ground branches, to remove the pesticides atrazine, imidacloprid, metolachlor and tebuconazole from aqueous solutions are presented in figure 2. the results revealed that unmodified wheat straw and ground branches exhibit suboptimal pesticide removal efficiencies with the notable exception of tebuconazole. specifically, the unmodified adsorbent ground branches achieved a 75.08% removal efficiency for tebuconazole, potentially attributable to their elevated lignin content, which appears to exhibit a selective affinity for this particular pesticide. 3.2. removal efficiency of modified adsorbents compared to their unmodified counterparts washed with ultrapure water (upw) and modified by naoh, wheat straw as an adsorbent modified by citric acid exhibited significantly enhanced pesticide removal capacities, as is shown in figure 3. specifically, citric acid-modified wheat straw achieved superior removal efficiencies, reaching 76.03, 59.32 and 70.34% for atrazine, imidacloprid and metolachlor, respectively. this enhanced performance of citric acid-modified wheat straw is attributed to the introduction of carboxyl (–cooh) and hydroxyl (–oh) functional groups onto the adsorbent surface, thereby creating additional adsorption sites and augmenting the removal of specific target pesticide compounds [14]. conversely, naohmodified wheat straw exhibited comparatively lower removal efficiencies, specifically for atrazine, imidacloprid and metolachlor that achieved 53.02, 25.45 and 34.16%, respectively. this is likely because a high activation temperature is required to break hydrogen bonds between cellulose fibers of wheat straw, thereby increasing the surface area of the adsorbent, in conjunction with its modification by naoh to enhance its adsorption efficiency. 4. conclusions the widespread use of pesticides poses a significant threat to both the environment and human health. while various remediation techniques exist, many are hindered by their high costs and complexity. in contrast, low-cost adsorbents derived from abundant and renewable agricultural byproducts offer a promising alternative. the properties and applications of these materials vary based on their source, treatment and functionalization methods. specifically, both unmodified and chemically modified (with citric acid and naoh) adsorbents of wheat straw and ground branches were employed to remove pesticides from aqueous solutions in this study. citric acid-modified wheat straw demonstrated paramount removal efficiencies for atrazine, imidacloprid and metolachlor of 76.03, 59.32 and 70.34%, respectively, compared to others attributed to enhanced surface functionalities (–cooh, –oh). however, untreated and naoh-modified wheat straw and ground branches figure 2: removal efficiency of (a) wheat straw washed with ultrapure water (upw) and (b) ground branches 44,58 30,29 37,91 0 10 20 30 40 50 60 70 80 90 100 atrazine imidacloprid metolachlor r em o v al e ff ic ie n cy , [% ] (a) upw straw 33,04 46,58 44,34 75,08 0 10 20 30 40 50 60 70 80 90 100 atrazine imidacloprid metolachlor tebuconazole r em o v al e ff ic ie n cy [ % ] (b) ground branches genet, kovács, tombácz and maász hungarian journal of industry and chemistry 58 exhibited low pesticide removal efficiencies with the exception of untreated ground branches, which resulted in a notable 75.08% removal efficiency for tebuconazole. generally, although these economical adsorbents demonstrate high removal efficiencies for low concentrations of pesticides from aqueous solutions, further studies are needed to investigate the disposal and regeneration mechanisms of these adsorbents. acknowledgements this research was supported by the national research, development and innovation office (nkfih), hungary within the framework of project identification number 2020-1.1.2-piaci-kfi-2021-00309. references [1] carpio, m.j.; sánchez-martín, m.; rodriguez-cruz, m.s.; marin-benito, j.m.: effect of organic residues on pesticide behavior in soils: a review of laboratory research, environments, 2021, 8(4), 32, doi: 10.3390/environments8040032 [2] chaudhari, y.s.; kumar, p.; soni, s.; gacem, a.; kumar, v.; singh, s.; yadav, k.v.; dawane, v.; piplode, s.; jeon, b.-h.; ibrahium, h.a.; hakami, r.a.; alotaibi, m.t.; abdellattif, m.h.; cabralpinto, m.m.s.; yadav, p.; yadav, k.k.: an inclusive outlook on the fate and persistence of pesticides in the environment and integrated eco-technologies for their degradation, toxicol. appl. pharmacol., 2023, 466, 116449, doi: 10.1016/j.taap.2023.116449 [3] ahmad, a.; shahid, m.; khalid, s.; zaffar, h.; naqvi, t.; pervez, a.; bilal, m.; ali, 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thukral, a.k.: worldwide pesticide usage and its impacts on ecosystem, sn appl. sci., 2019, 1(11), 1446, doi: 10.1007/s42452-0191485-1 [7] de souza, t.f.; dias ferreira, g.m.: biochars as adsorbents of pesticides: laboratory-scale performances and real-world contexts, challenges, and prospects, acs est water, 2024, 4(10), 4264– 4282, doi: 10.1021/acsestwater.4c00399 figure 3: the removal efficiencies of chemically modified adsorbents containing the pesticides (a) atrazine, (b) imidacloprid and (c) metolachlor 44,58 53,02 76,03 0 10 20 30 40 50 60 70 80 90 100 upw naoh citric acid r em o v al e ff ic ie n cy [ % ] (a) atrazine 30,29 25,45 59,32 0 10 20 30 40 50 60 70 80 90 100 upw naoh citric acid r em o v al e ff ic ie n cy [ % ] (b) imidacloprid 37,91 34,16 70,34 0 10 20 30 40 50 60 70 80 90 100 upw naoh citric acid r em o v al e ff ic ie n cy [ % ] (c) metolachlor https://doi.org/10.3390/environments8040032 https://doi.org/10.1016/j.taap.2023.116449 https://doi.org/10.1007/s11356-018-3169-6 https://doi.org/10.1007/s10311-021-01183-1 https://doi.org/10.1016/j.scitotenv.2021.149129 https://doi.org/10.1007/s42452-019-1485-1 https://doi.org/10.1007/s42452-019-1485-1 https://doi.org/10.1021/acsestwater.4c00399 pesticide remediation from aqueous solutions using low-cost adsorbents 53(2) pp. 55–59 (2025) 59 [8] abuquamar, s.f.; el-saadony, m.t.; alkafaas, s.s.; elsalahaty, m.i.; elkafas, s.s.; mathew, b.t.; aljasmi, a.n.; alhammadi, h.s.; salem, h.m.; abd el-mageed, t.a.; zaghloul, r.a.; mosa, w.f.a.; ahmed, a.e.; elrys, a.s.; saad, a.m.; alsaeed, f.a.; el-tarabily, k.a.: ecological impacts and management strategies of pesticide pollution on aquatic life and human beings, mar. pollut. bull., 2024, 206, 116613, doi: 10.1016/j.marpolbul.2024.116613 [9] kamalanathan, s.; amran, f.; zaini, m.a.a.: oxidized mangosteen peel-derived hydrochar for the removal of methylene blue, hung. j. ind. chem., 2025, 53(1), 1–7, doi: 10.33927/hjic-2025-01 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2016, 4(3), 3122–3142, doi: 10.1016/j.jece.2016.06.025 https://doi.org/10.1016/j.marpolbul.2024.116613 https://doi.org/10.33927/hjic-2025-01 https://doi.org/10.1007/s10311-018-0786-8 https://doi.org/10.1016/j.susmat.2016.06.002 https://doi.org/10.1016/j.cej.2015.01.135 https://doi.org/10.1016/j.jece.2016.06.025 conferenceproceedn{gs hungarian journal of n{dustrial chemistry veszprem vol. 2. pp. 25-29 (2000) rf thermal plasma treatment of a flue dust from the siemens-martin process i. mohai, j. szepvolgyi and m. t6th1 (research laboratory of materials and environmental chemistry,chemical research center, hungarian academy of 1 sciences, pusztaszeri ut 59-67, budapest, h-1025, hungary research laboratory for geochemistry, research center for earth sciences, hungarian academy of sciences budai:irsi ut 45, budapest, h-1112, hungary) this paper was p!ese~ted at the se~ond international conference on environmental engineering, umvennty of veszprem, veszprem, hungary, may 29 -june 5, 1999 recovery of iron, zinc and lead from a flue dust of31.1% fe, 17.4% zn and 7.7% pb content has been studied in an rf thermal plasma reactor under reducing conditions. thermodynamic calculations based on the minimisation of gibbs free enthalpy were made ~o estimate the product composition. effects of the plate power of the rf generator and feed rate of powder on the cheuncal, surface, phase compositions and morphology of products have been investigated in details. it has been pro~ed that the rf thermal plasma treatment makes it possible to recover a considerable part of zinc and lead from the parttcular dust on the one hand, and a product of increased iron content can be produced on the other hand. keywords: rt plasma; metallurgical waste; reduction; xrd; xps; sem introduction steel-making dusts tend to be rich in zinc and lead because of the use of galvanised and other zinc~ containing scrap in the charge. processes developed for the processing of particular dusts, however, do not provide economic recycling. these dusts are mostly regarded as hazardous wastes due to the leaching of their toxic constituents on dumping. application of the rf thermal plasma technology in the waste management is based on the ability to deliver high-grade heat independently of the oxygen potential compact units of high output can be constructed, and they are able to handle cheap feed stock with a minimum environmental impact [1]. the commercial plasma processes developed for the recycling of ferrous wastes are mainly based on arc plasmas and they usually require granulated raw materials. among others, plasmadust system by skf (combination of a plasma gas heater with a coke­ ftlled shaft furnace) and trd (tetronics research and development) process (smelting in a transferred-arc furnace) [2j belong to these technologies. in plasmarec process [31 the plant can easily be mobilized and transported to the required site to eliminate e.g. local contamination. the rf thermal plasmas make it possible to ensure any required (oxidative, reducing or neutral) atmosphere for high temperature reactions, independently of the temperature. it is a very attractive feature in terms of waste processing. in this paper the application of a rf thermal plasma system for the treatment of a ferrous dust in reducing conditions is investigated. experimental a dust separated from the flue gas of a siemens-martin furnace (sm-dust} was treated in a laboratory size rf thermal plaslrta reactor with a quartz-glass confinement tube of 2.8 em inner diameter. the rf generator operated at 27 mhz with a continuous adjustment of the plate power in the range of 1 to 7 kw. the reactor was connected to an air cooled, two-stage powder collector. argon was used as the central plasma gas (7 dm3 min"1 ) and as the sheath gas (19 dm3 min"1 ), as welt the powder was injected into the plasma reactor by· an argon carrier gas passed through a fluidised and vibrated powder-bed. hydrogen used as reducing agent was injected into the. plasma tail flame region with a feed rate of 1 dm3 min"1• a more detailed description of the plasma reactor was published previously [4]. 26 run 1 2 3 4 5 6 7 8 9 10 11 12 table 1 conditions of thermal plasma treatment spec. energy (kwhg-1) 0.16 0.3 0.4 0.69 0.75 0.95 0.95 1.0 1.1 1.6 1.6 0.13 plate power (kw) 2.4 2.8 2.5 3.0 2.2 2.4 2.5 3.0 2.7 3.0 2.5 2.1 powder feeding rate (g h-1) 15.0 10.2 6.4 4.3 2.9 2.6 2.6 3.0 2.6 1.9 1.6 15.8 reactor type* a a b a d b b a a a b e *a: powder feeding into the plasma gas, b: powder feeding into the tail flame region through two radial inlets, d: powder feeding into the tail flame region through one tangential inlet, e: hot wall reactor the experimental conditions are listed in table 1. in the second column of table 1, the specific energy calculated as the ratio of plate power to the powder feed rate is presented. hence, this parameter considers two process variables simultaneously. the raw material and the products as well were characterised in terms of particle size, bulk and surface chemical compositions, phase conditions and morphology. in each run products were collected both ·from the reactor (r) and from the dust collector (c). particle size distribution was measured by a particle size analyser (malvern 2600c). bulk chemical compositions were measured on dissolved samples by icp-aes technique (labtest psx7521). surface chemical compositions were characterised by x-ray photoelectron spectroscopy (xps, kratos xsam800). phase conditions were determined by x-ray diffraction analysis (xrd, philips pw 1710). morphology was investigated using scanning electron microscope (jeol jsn50a). results and discussion characterisation of the starting material according to the particle size analysis the original sm­ dust has a broad particle size distribution between 1-200 pm with a mean particle size of 4.6 pm. as particles above 10 pm in diameter can not evaporate completely in the plasma due to the short residence time, prior to the reduction the sm dust was milled in a fritsch mill. the resulted powder had a mean particle size of 1.9 pm with a distribution from 0.5 to 18 pm. chemical composition of the sm-dust was determined by icp-aes after dissolution in diluted hn03 in a microwave digestion system. main components of particular dust are fe: 31.1%, zn: 17.4%, ph: 7.7%. the minor (0.1-l%) elements include si, ai. ca. mg, cr, ni, mn, cu, cd, and sn. the sm dust contains non-metallic components, such as: s: 5.5%, p: 0.4%, c: 0.6%, cl: 1%, f<l%. according to ";'~ 2.0 "' ci l1.5 g ~ 1.0 iii g 2 8 0.5 7 a.a l~d::::i:=::;:===t::c=::::j:!::::;::::____j 0 1 coo 2000 3000 4000 5000 6000 7000 t(k) fig. i equilibrium compositions as the function of the temperature at atmospheric pressure (feeding rate of sm dust: 1 g h-1). assignation: 1: fe(s,l), 2: zns(s,l), 3: pb(s,l), 4: fe, 5: zn, 6: pb, 7: fe+\ 8:zn+\ 9: pb+1 the xps investigations the sample is covered by a surface oxide layer. the main crystalline phases of the sm-dust were franklinite (zno·fe20 3) and magnetite (feo·fc].o:>)­ traces of other zn-containing phases such as zincite (zno) and sphalerite (zns) were also detected. the lead was present in the original powder as plattnerite (pboz). minor amounts of other iron containing phases such as wlistite (feo) and pyrrhotite (pes) were also detected. thermodynamic calculations the thermodynamic calculations are of outstanding importance in the particular case, because in thermal plasma reactors the first condensed phase that appears on cooling will be the dominant phase of the products. the high cooling rate in thermal plasmas does not make possible reactions involving liquid or solid phases. the equilibrium compositions as a function of temperature (in the range of 773-6000 k) during reduction of the sm dust with hydrogen were calculated by the use of a computer program based on the minimisation of the gibbs free entalphy [5]. assuming a feed ·rate of 1 g h-1 sm dust, 60 dm3 h-1 h2 and 1740 dm3 h-1 argon, the equilibrium composition of the elements, ions and compounds can be seen in fig.l. although in the calculations ail analysed components were considered, only the fe, zn and ph containing compounds are represented in fig. i. on cooling of the gaseous species formed in the plasma flame region the first condensed phase th,at appears below 2000k is fe(s,l). minor amount of silicates, mn and ca sulphides and cr20 3 condensate, as well. when zn vapours start to condensate below llook zns and some zno may be formed because of the relatively high concentration of h20 and h2s vapour in this temperature range. when h2s concentration decreases (t <800k) condensation of metallic zinc is also probable. pb content of the starting material condensates in metallic form below 973 k. increasing the feed rate of powder from 1 g n1 to 15 g h-1 results in 100-200k higher condensation temperatures of the metal vapours. in this case in addition to metallic fe, fes appears as well. to table 2 results of the thermal plasma trea~ent of sm dust run e,p sl fe zn pb l(fe+zn+p feizn (kwh f') amp e (wt%) (wt%) (wt %) b)(wt %) (%/%) 0 1 2 3 4 5 6 7 8 9 10 11 12 .e e c !::! q) 1.!.. 0 sm 31.1 17.4 7.7 0.16 r 34.5 20.9 9.3 c 36.5 20.5 7.9 0.3 r 45.1 17.3 6.5 c 36.9 23.9 7.3 0.4 r 45.1 16.0 7.3 c 34.0 25.6 8.7 0.69 r 47.3 13.2 7.2 c 32.0 30.3 8.9 0.75 r 47.2 18.3 8.1 c 30.0 28.8 9.2 0.95 r 46.6 15.9 6.4 c 36.8 24.1 8.0 0.95 r 49.3 12.5 6.9 c '25.5 36.7 9.9 1.0 r 53.1 14.5 6.1 c 32.2 30.2 7.1 1.1 r 46.0 15.4 8.6 c 33.4 25.7 6.1 1.6 r 51.2 13.4 5.3 c 27.2 33.8 9.5 1.6 r 55.1 12.0 5.9 c 35.5 25.6 7.7 0.13 rl 68.1 4.3 3.3 r2 18.8 43.2 12.5 c 15.0 51.5 12.4 •hot wall (r) hotwall (c) \ .. . .. .. •• • • .. .. ...... 0,5 1 esp {kwh.g'1) 56.2 64.7 64.9 69.0 68.1 68.4 68.3 67.7 71.2 73.6 68.0 68.9 68.9 68.3 72.1 73.7 69.5 70.0 65.2 69.8 70.5 73.0 68.8 75.7 74.2 78.9 1.5 : {r) "{c) .. 1.8 1.7 1.8 2.6 1.5 2.8 1.3 3.6 1.1 2.6 1.0 2.9 1.5 3.9 0.7 3.7 1.1 3.0 1.3 3.8 0.8 4.6 1.4 15.8 0.4 0.3 fig.2 the fe/zn ratio as the function of specific energy c: samples from the collector, r: samples from the torch conclude it all: in the given system metallic fe, pb and some zn can be formed as a result of complete reduction. appearance of zns and zno, and at higher feed rates of powder that of fes can be expected, as well. reduction of model compounds as the chemical composition of the sm dust was rather complex studies on the reduction started with simple model compounds, such as fe20 3, zno and a fe203+zno mixture. the latter had an fe/zn ratio similar to the sm dust. according to the changes of the standard molar free entalphy of the model compounds in the function of temperature, reduction of zno with hydrogen needs higher temperatum (> 1500k) than that off~03 (>900k). however, reduction rate for zno was more than 95%, while for fe20 3 it was only 88% on thermal plasma treatment. the contradiction between 27 the thermoqynamic calculations and experimental data can be reasoned by the different mean particle sizes of zno and fez03 (3.7 j..l.m and 11.4 j..l.m, respectively). reduction of the fe20 3+zn0 mixture resulted in a me'.\allization of 86-90%. it is worth mentioning that a complete metallization can not be reached because the ultradisperse particles condensed from the vapour phase tend to oxidise during handling in the ambient air (e.g. fine iron particles collected from the reactor started to ignite spontaneously when contacted with air). results of the plasma treatment in · the plasma reduction tests four different reactor constructions were used (table 1). in reactor a powder was fed into the argon plasma gas. this operation is similar to that of analytical icp torches, and utilizes the heat of the plasma with a good efficiency. however, in our case the plasma flame became unstable during this operation, due to the difficulties in the steady feeding of the particular powders. reactor b had two radial inlets for powder feeding into the plasma tail flame region. however, the bent inlets tended to clog. for this reason reactor d had only a single inlet. it was tangential in order to extend the residence time in the hot zone of the reactor. to reduce the heat loss, and hence to ensure the so-called "hot-wall" conditions, reactor d was covered in a test by a refractory lining (reactor e). unfortunately, the insufficient cooling in reactor e impedes longer reaction periods because the quartz reactor wall can be damaged. the bulk chemical composition of plasma treated samples indicates an increasing reduction rate with specific energy (table 2. runs 1-11). samples collected from the reactor wall (r) have higher fe and lower zn content as compared to samples c collected from the dust collector. it is explained by the gradual decrease in the temperature of the reactor wall and the powder collecting system with the distance from the plasma flame. this phenomenon makes possible the selective condensation of metals with different boiling points. in the case of espec == 1.6 kwh g'1 the feizn ratio of 1.8 of the sm powder (fig.2) increased to 4.6 for the sampler from run 11. however, it decreased to fe/zn = 0.7 in sample c from run 7. the segregation improved further when the heat loss of reactor was reduced by the refractory lining (run 12). in this experiment, when espec was 0.13 kwh g"1 , fe/zn ratio was 15.8 in sample rl and 0.3 in sample c. we would like to emphasize that in run 12 a specific energy amounting less than 10% of espec of run 11 was applied. in run 12 two samples were collected from the reactor: rl from top section, near the plasma flame, and r2 from the bottom of the reactor. such sampling made it possible to investigate the changes in fe and zn concentrations with the distance from the injection point of the dust (fig.3). sample rl from run 12 had high fe (68.1%) and low zn (4.3%) contents. by increasing the distance, a region with no powder deposition could be observed 28 eo 70 ~ 60 60 40 :30 fe 20 0 • 10 60 60 fig .3 changes in the concentration of fe and zn against the distance from the sm dust inlet tube (run 12) in the hot wall (e) reactor. the existence of such powder free region refers to different condensation mechanisms in the upper and lower parts of the reactor, respectively. gjrschick [6] considers that particles deposited on the wall near the plasma flame are formed by an ion-induced nucleation mechanism. however, at lower sections the particles are formed by homogenous nucleation from the vapor phase convecting downwards axially. we suppose that in our system, where the condensation temperatures of components are rather different, even heterogeneous nucleation can not be excluded. · samples r2 and c from run 12 have higher zn and lower fe content than sample r1 (fig.3). however, contrary to our expectations, the fe content can not be lowered to zero in sample c. most probably, the mass transport by convection dep;ressed the segregation of fe and zn in this case. significant pb segregation between samples r and c could only be observed in run 12 (hot-wall reactor) because of the high boiling point ofpb (1620°c). the xps. investigations of original and thermal plasma treated sm dusts indicated that both powders were coyere$1 by an uppermost surface oxide layer. hydrocarbon-type surface carbon contamination was also detected in all samples. surface compositions were calculated by taking into account the carbon contamination [7}. the bulk and surface compositions were referred to l mole fez03 in order to facilitate their comparison (table 3). a considerable surface segregation of zinc and lead was observed both in the original sm-dust and in the reduced powders produced therefrom. however, the thermal plasma treatment increased segregation. an especially high surface enrichment of zno was detected in sample 4c. although calculations on surface composition referred to oxides, occurrence of zns is very probable especially in sample 4r (molar ratios of zno and s03 are very dose to each other). however, zno and zns can not be distinguished in the xp spectra, because they practically have the same chemical shift. both the bulk chemical composition of the treated samples and the xrd results (see below) re~er to the table 3 bulk and surface molar ratios related to f~03 samele fe20j zno pboz sio~ kzo cl so~ r* smbulk 1.0 t.o 0.1 smsurf. 1.0 9.6 1.2 2.3 0.0 2.7 2.1 1.3 4rbulk 1.0 0.5 0.1 4r surf. 1.0 6.2 2.2 2.3 2.0 2.0 6.5 0.9 4cbulk 1.0 1.6 0.1 4c surf. 1.0 37.9 4.1 2.9 0.9 7.1 11.3 0.7 * ratio (omfoc) of the measured and calculated amount of oxygen. 10000 8000 d 6000 { c ~ 4000 b 2000 a 25 30 35 40 45 26(") fig.4 x-ray diffractograms of sm-dust (a) and of plasma treated samples r for specific energies of 0.16 kwh t 1 (b), 0.69 kwh g· (c) and 1.00 kwh g·1 (d). assignation of peaks: f-franklinite, m-magnetite, w-wiistite, py-pyrrhotite, plplattnerite, s-sphalerite, z-zincite, fe-iron, ph-lead reduction of zno·fez03. therefore, the surface enrichment of zno in the plasma-treated sample 4c can be traced back to the condensation and subsequent oxidation of zn vapour on the surface of iron-rich nuclei. changes in the ratio of the measured and calculated amount of oxygen also refer to reduction. x-ray diffraction patterns of plasma-treated samples collected from the reactor indicated a significant decrease in the intensity of the fra:nklinite, magnetite, zincite and plattnerite peaks, even at the lowest specific energy used in these tests. at higher energies further decrease of the fra:nklinite with a simultaneous increase of the metallic fe was observed (fig.4). however, the intensity of the metallic pb peak in r samples decreased in some extent with the specific energy due to a partial segregation of lead. zinc content of franklinite was probably transformed into a· quasi­ amorphous material in terms of xrd analysis: in spite of the considerable amount of zn in the bulk and on the surface, no xrd peaks of metallic zn, zincite or sphalerite could be detected. the zinc containing phase might form a thin surface layer, which is transparent to thex-rays. xrd intensity of the wi.istite peak actually did not change during the thermal plasma treatment. the wi.istite phase is probably located in the core of the grains. samples r and c have quite different morphology (fig.s). sample r, which was deposited on the reactor wall. mainly consists of large, agglomerated particles. fig.5 sem micrographs of plasma reduced samples 4r (a) and4c (b) on the contrary, sample c has rather uniform, fine particles, which form loose agglomerates~ the agglomeration most probably occurred after deposition, not during the flight [6]. therefore the high temperature of the reactor wall in the case of samples r accelerated the agglomeration. conclusions the rf thermal plasma treatment of an oxidic sm-dust in a hydrogen flow makes it possible to reduce its iron, zinc and lead oxide content. the extent of reduction greatly depends on the plate power, and hence the specific energy related to unit feed rate of powder. products collected from the different parts of the experimental set-up have different compositions. the 29 further is collected the powder from the plasma flame, the higher is its zinc content. in the high temperature zones powders of high iron content were separated. a considerable surface segregation of zinc and lead was detected even in the original sm-dust. thermal plasma treatment resulted in products of even less uniform composition: zinc and lead were concentrated near to the surface of grains. the products are susceptible to surface oxidation. the sulphur content of sm dust has a disadvantageous effect on the reduction with hydrogen due to zinc sulphide formation even at low h2s tension. acknowledgement the authors are grateful for the financial support from the otka fund (no. f016178). the authors would also like to thank to mr. ferenc till for the particle size analysis, to mr. mikl6s mohai for the xps measurements and to ms zsuzsa farkas for preparing sem micrographs. references 1. hare a.l.: non-ferrous metals and miscellaneous applications of plasma technology. in plasma technology in metallurgical processing (ed. j. feinman) iss, warrendale, pa, 1987, pp. 175-184 2. eriksson s., johansson b. and santen s.: application of plasma technology to steelplant waste treatment. in plasma technology in metallurgical processing (ed. j. feinman) iss, warrendale, pa, 1987, pp.l25-130 3. bdffelner w., burkhard r., haefeli v. and sun h.: application of thermal plasma for recovery of metals and destruction of waste. proc. 13-th international symposium on plasma chemistry, beijing, china, pp. 1915-1919, 1997 4. szfu>volgyi j. and mmw-t6tii i.: j.mater.chem., 1995, 5 (8), 1227-1232 5. balmaeva l.m., lalner j.a., babievskaya l.z. and krenev v.a.: zh. neorg. khim.l994, 391292-1297. 6. girsffick s.l., cmu c.-p., muno r., wu c. y., yang l., sjngh s.k. and mcmurry p.h.: j. aerosol sci., 1993, 24 (3), 367-382 7. mohai m and bert6u i.: correction for surface contaminations in xps: a practical approach. proc. ecasja 95 (eds. h.j. mathieu, b. reihl, d. briggs), john willey & sons, chichester-new york-brisbane­ toronto-singapore, 1995, pp. 675-678 page 31 page 32 page 33 page 34 page 35 hungarian journal of industry and chemistry vol. 49(1) pp. 77–82 (2021) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2021-10 daphnia magna acute immobilization test: an opportunity to test the ecotoxicity of alternative fuels katalin eszter hubai*1 1center for natural sciences, university of pannonia, egyetem u. 10, 8200 veszprém, hungary the increasing need for environmental protection has led to the development of alternative biofuels. while the use of alternative fuels has significantly increased recently, only a few studies have addressed the problem of their ecotoxicity. the main aim of this work was to provide a short review of the daphnia magna acute immobilization test, which has been the most commonly discussed in the literature. keywords: daphnia magna, immobilization, ecotoxicology, alternative fuels 1. introduction over recent decades, rapid population growth has been accompanied by a growth in the consumption of energy and use of transport fuels, which has caused irreversible environmental degradation and climate change [1]. desires for a green environment have increased the demand for alternative fuels which in turn has necessitated researchers and industries to develop renewable alternative and cleaner energy sources worldwide [2]. biofuels are energy-enriched substances manufactured from vegetable oils, recycled cooking grease and oil as well as animal fats through a chemical process known as transesterification, which is described below, to produce chemical compounds known as fatty acid methyl esters (fame) [3, 4]. biodiesel is the name given to these esters when they meet biodiesel standards such as the american astm d6751 or the european en14214 for use as transport fuels [4]. biodiesel is an eco-friendly form of fuel and may provide a solution to some problems associated with petroleum diesel [5]. alternative fuels are key to improving the eu’s security of energy supply, reducing the impact of transportation on the environment and boosting the eu’s competitiveness. they are also an important building block for the eu’s transition towards a low-carbon economy. in 2007, the production of biofuels in the eu reached 8,500 ktoe (kilotonnes of oil equivalent), while in 1996, this figure was less than 500 ktoe [6]. in 2010, 15.5% of power generation and 1.3% of energy consumption worldwide was attributed to renewable energy, while today, it is estimated that 86,000 kt per year of biofuels are produced, with the usa and brazil being the primary producers [7]. *correspondence: hubai.katalin@mk.uni-pannon.hu more studies have shown that the use of biodiesel would reduce emissions of hydrocarbons, carbon monoxide and volatile organic compounds [8,9]. however, the results of analyzing the biological effects related to the presence of biodiesel in the environment are ambiguous [10]. although the use of alternative fuels has significantly increased recently, relatively few studies have addressed the problem of their ecotoxicity. therefore, the main objective of this study is to provide a short overview of the daphnia magna acute immobilization test which has been the most frequently discussed in the literature. 2. methodology 2.1 test organism in addition to the chemical characterization of a substance, ecotoxicological tests provide an important tool for ecological risk assessments [11], giving a quantitative estimation of the overall toxic effect of the test organisms selected [12]. in general, the daphnia magna acute immobilization test is amongst the most widely used ecotoxicological methods [13]. international standards apply such as oecd 202:2004 [14] or iso 6341:1996. the test organisms are the freshwater crustaceans d. magna and d. pulex. for the tests, neonates (newborn, freshly hatched juveniles) are used. (the main purpose of any standard protocol is to increase quality assurance which in turn might increase the credibility of the data produced [15]. in order to minimize any possible errors caused by improper maintenance of stock cultures, so-called toxkits have been developed and marketed by microbiotests inc. (mariakerke-gent, belgium) [16]. the main benefits of using a toxkit are that they are maintenance-free and user-friendly [17] test organisms https://doi.org/10.33927/hjic-2021-10 mailto:hubai.katalin@mk.uni-pannon.hu 78 hubai figure 1: freshly hatched d. magna neonate whose genetic material is practically uniform and, prior to testing, juveniles of approximately the same age are reproduced (fig. 1). 2.2 implementation of experiments there are several options for conducting alternative fuel toxicology studies. in one part of the research, the fuel was stirred in water before the test organisms were introduced into the test chamber [18–20]. in this method, the layer of oil on the top of the wells can cause some problems. in other experiments, aqueous extracts were used, for example, a stock solution was made by adding seawater (depending on the test organism) to the sample and stirring the mixture for 10− 24 h [21–23]. three different biodiesels, that is, two based on the vegetable oils produced by canola and soybean as well as waste frying oil that originated from animals, were used by hollebone et al. [24]. oil-in-water dispersions (owd) and water-accommodated fractions (waf) were used for the daphnia magna assay. different results were observed during the tests; higher lc50 values were measured in wafs compared to in owds. this suggests that the soluble fraction is of lower toxicity compared to the physical danger of the organisms being smothered by the oily fuel (see table 1). müller et al. [23] assessed the toxicity of the watersoluble fraction (wsf) of biodiesel on d. magna in comparison to the wsf of diesel [24]. the tested sample of biodiesel was a fatty acid methyl ester (fame) mainly produced by soybean oil (95%). this biodiesel did not elucidate a measurable degree of toxicity either following acute or chronic exposure. on the other hand, in a study by eck-varanka et al. [21], the ecotoxicity of a rapeseed biodiesel was profiled using a battery of test organisms and d. magna exhibited an extremely high degree of toxicity, being the most sensitive assay in the battery. khan et al. [18] carried out an extensive study to compare the ecotoxicity of diesel, neat biodiesel (b100) and blends of both (b50, b20 and b5). b100 was produced from recycled cooking oils and fats. the lowest and highest levels of ecotoxicity were exhibited by b100 and diesel, respectively, while the ecotoxicity of the blends, expressed both in terms of mortality rates and ec50 values, were in the intermediate range. however, the differences between the measured responses were quite small: the lc50 values of daphnia magna in neat biodiesel and diesel were 4.65 and 1.78 ppm, respectively. tjarinto et al. (2014) conducted a similar study on biodiesel produced from waste vegetable oil and reported an ec5 value of 3.157 ppm for daphnia magna [25]. heger et al. [26] compared the ecotoxicity of two biofuel candidates (1-octanol and 2-butanone) and found that 1-octanol exhibited a significant level of ecotoxicity on d. magna while 2-butanone did not. however, assays conducted on other test organisms revealed that the metabolites of the tested products could pose a higher risk of toxicity. heger et al. [27] applied the d. magna acute immobilization test to compare the aquatic toxicity of the two biofuel candidates, namely 2-methyltetrahydrofuran (2-mthf) and 2-methylfuran (2-mf), and found that the latter induced a significantly higher mortality rate than 2-mthf (see table 1). ecotoxicity, more precisely the ecotoxicity impact, is also included in the life cycle assessments (lca) of alternative fuels [28]. since lcas follow the whole production line of a product, bunzel et al. [29] used a d. magna assay to evaluate pesticide runoff from agricultural fields used for the cultivation of energy crops. khan et al. [18] stressed that one possible major purpose of ecotoxicity testing is assessing the potential risk of fuel spills in aquatic ecosystems. as such, it should be emphasized that daphnia magna, being a freshwater taxon, cannot represent marine ecosystems, instead marine surrogates are used such as the brine shrimp artemia salina [30]. gateau et al. [31] investigated water-soluble fractions (wsfs) of four different vegetable oil methyl esters. lower ec50 values (> 1000 mg/l) were calculated for vegetable oil methyl esters than for regular diesel (ec50< 100 mg/l) (see table 1)). the toxicity of biodiesel blends and crude oils have been investigated in other studies and biodiesel has been found to be less toxic to d. magna than both the biodiesel blends and crude oil (see table 1). 3. conclusion in conclusion, it should be emphasized that the number of available studies is surprisingly low. furthermore, these studies are extremely difficult to compare due to the following reasons: since the studies have been conducted on alternative fuels of very different origins, more extensive research on their chemical compositions to determine potential toxic effects is required. by taking into considhungarian journal of industry and chemistry daphnia magna acute immobilization test 79 ta bl e 1: r es ul ts of th e d ap hn ia m ag na ac ut e im m ob ili za tio n te st (w a f: w at er -a cc om m od at ed fr ac tio n; o w d :o ilin -w at er di sp er si on ) fu el ty pe m et ho d l c 50 r ef er en ce 1oc ta no l w a f; m et ho ds of ac ut e to xi ci ty te st in g us in g fis h, m ac ro in ve rt eb ra te sa nd am ph ib ia ns (u s e pa ) 52 0 m g/ l l eb la nc ,1 98 0 [3 2] 1oc ta no l o w d ;s ec tio n 5, pa ra .1 “n o. 3 of th e r eg ul at io n on a pp lic atio n d oc um en ts an d e vi de nc e un de r th e c he m ic al s a ct " (f ed er al e nv ir on m en ta la ge nc y) 26 m g/ l k ün h et al ., 19 89 [3 3] r ap es ee d oi lm et hy le st er s (r m e ) w a f; o e c d 20 2 > 10 00 w a f m g/ m l g at ea u et al ., 20 05 [3 1] e ru ci c r ap es ee d oi lm et hy le st er s (e r m e ) > 10 00 w a f m g/ m l su nfl ow er oi lm et hy le st er s (s m e ) > 10 00 w a f m g/ m l h ig h o le ic su nfl ow er oi lm et hy le st er s( h o sm e ) > 10 00 w a f m g/ m l d ie se lf ue l < 10 0 w a f m g/ m l ba se d on ve ge ta bl e oi lp ro du ce d fr om ca no la o w d ;e nv ir on m en tc an ad a te st m et ho d "b io lo gi ca lt es tm et ho d: a cu te l et ha lit y te st u si ng d ap hn ia sp p" 28 0 (2 00 -4 10 )m g/ l h ol le bo ne et al ., 20 08 [2 4] ba se d on ve ge ta bl e oi lp ro du ce d fr om so il cr op s 37 .8 (2 3. 063 .1 )m g/ l ba se d on w as te fr yi ng oi lp ro du ce d fr om an im al s 58 2 (3 16 -1 08 0) m g/ l u ltr al ow su lp hu rd ie se l 15 .2 (8 .2 -2 9. 3) m g/ l l ow su lp hu rd ie se l 17 .9 (1 2. 725 .3 )m g/ l ba se d on ve ge ta bl e oi lp ro du ce d fr om ca no la w a f (2 5 g/ l fu el (1 :4 0, fu el :w at er ); e nv ir on m en tc an ad a te st m et ho d "b iol og ic al te st m et ho d: a cu te l et ha lit y te st u si ng d ap hn ia sp p" 24 65 0 (2 50 014 00 00 )m g/ l ba se d on ve ge ta bl e oi lp ro du ce d fr om so il cr op s 75 00 (5 10 011 00 0) m g/ l ba se d on w as te fr yi ng oi lp ro du ce d fr om an im al s 75 00 (5 10 011 00 0) m g/ l u ltr alo w su lp hu rd ie se l 33 00 (1 80 058 00 )m g/ l l ow su lp hu rd ie se l > 25 00 0 m g/ l bi od ie se l( fa tty ac id m et hy le st er ) w a f; o e c d 20 2 0. 02 26 % (1 00 % w as 1: 1 w ate r: bi od ie se l) e ck -v ar an ka et al ., 20 18 [2 1] 2bu ta no ne (m et hy le th yl ke to ne ) o w d ;o e c d 20 2 21 52 .1 ± 44 .6 m g/ l h eg er et al ., 20 18 [2 6] 2m et hy lte tr ah yd ro fu ra n (2 -m t h f) o w d ;o e c d 20 2 1. 11 6± 0. 10 2 m g/ l h eg er et al ., 20 18 [2 7] 2m et hy lf ur an (2 -m f) 0. 03 2± 0. 00 4 m g/ l 49(1) pp. 77–82 (2021) 80 hubai eration the practical aspects of the tests, different periods of exposure have been employed (chronic exposures of 24, 48 and even 96 h). sample preparation protocols also differ: oil-in-water dispersions (owd) and wateraccommodated fractions (waf) have also been used as alternatives [34]. generally, the daphnia magna acute immobilization tests show an appropriate degree of sensitivity to a wide variety of compounds or complex mixtures [35–37]. however, as different components of an ecosystem will exhibit taxon-specific sensitivity to a chemical, a carefully composed battery of biotests should be used to gain a more comprehensive understanding [38]. it is possible that these tests will represent different functional and/or taxonomic groups as the ecotoxicity of pollutants influences the function and structure of aquatic or terrestrial ecosystems [39], moreover, possible endpoints will differ [40]. the minimum battery should involve the luminescent bacteria test, algae and zooplanktonic crustaceans [41]. acknowledgments this study was funded by the ntp-nftö-19-b-0148 project. references [1] darda, s.; papalas, t.; zabaniotou, a.: biofuels journey in europe: currently the way to low carbon economy sustainability is still a challenge, j. clean. prod., 2019, 208, 575–588 doi: 10.1016/j.jclepro.2018.10.147 [2] shote, a.s.: biofuel: an environmental friendly fuel, in anaerobic digestion, eds.: banu, j.r. 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https://doi.org/10.1186/s12302-019-0192-2 82 hubai of products: a contribution to the decision-making process toward sustainability. j. clean. prod., 2018, 188, 888–899 doi: 10.1016/j.jclepro.2018.03.307 [40] jos, a.; repetto, g.; rios, j.c.; hazen, m.j.; molero, m.l.; peso, a.; salguero, m.; fernándezfreire, p.; pérez-martín, j.m.; cameán, a.: ecotoxicological evaluation of carbamazepine using six different model systems with eighteen endpoints. toxicol. in vitro, 2003, 17, 525–532 doi: 10.1016/s08872333(03)00119-x [41] manusadžianas, l.; sadauskas, k.; vitkus, r.: comparative study of indices used in toxicity evaluation of effluents. desalination, 2010, 250, 383–389 doi: 10.1016/j.desal.2009.09.061 hungarian journal of industry and chemistry https://doi.org/10.1016/j.jclepro.2018.03.307 https://doi.org/10.1016/s0887-2333(03)00119-x https://doi.org/10.1016/s0887-2333(03)00119-x https://doi.org/10.1016/j.desal.2009.09.061 introduction methodology test organism implementation of experiments conclusion hungard\njournal of industrial chemistry veszprem vol. 29. pp. 135138 (2001) : quality management system as a tool of process control for food and agro industries g. kollar, z. syposs, g. vicz1an 1 , l. meszaros and k. kollar-hunek1 (postharvest department, szent istvan university, 1118. budapest, menesi ut 45, hungary 1 dept of chemical information technology, budapest university of technology and economics, hl521 budapest, pf.91. hungary) received: october 10, 2001 this paper was presented at the 7th international workshop on chemical engineering mathematics, bad honnef, germany, august 12-17 2001 the new iso 9001:2000 standards have changed determination and implementation of quality and the systems in connection of quality. one of the most important changes is, that the quality systems focus more and more on the customer requirements i.e. not only those ones that are in every detail described in the corresponding contracts, but the so called ''hidden" requirements are also considered. these "hidden" requirements are living only in the customer's mind. the aim of the new iso standard is to describe and also satisfy these hidden requirements as well as possible. we discuss our experiences, theoretical and practical results in these fields, including quality audit experiences and some internet methods for the investigation of customer requirements in food and agro industries. keywords: quality management, iso 9001:2000, customer requirements and satisfaction, internet forms, food and agro industries introduction a great number of prescription, rules, standards and monitoring practices are ensuring "from farm to fork", that the food we eat becomes and remains safe and healthy, free from harmful substances, such as microbes or chemicals [2-4]. as important as the properties above, is that the foodstuff should satisfy customer's expectations in taste, shape, shelf-life, price, etc. we investigated how to use the new elements of iso 9001:2000 [6] measuring customer confidence, continuous improvement of processes and production, applying the modern tools of information technology. food quality and -safety in agro sector specific quality management systems generally the food/agro specific quality management system (qms) works as it is shown in fig.l. contact information: e-mail: koharg@omega.kre.hu the elements of qms that are shown in fig./ have the given effectiveness as it follows: • gmp/gap (good manufacturing practice j good agricultural practice) are covering the basic requirements • haccp (hazard analysis, critical control points) foresees the special entities of food safety • qa (quality assurance) foresees the general entities of food safety • tqm (total quality management} contains the q­ developing strategy application of the first three elements is necessary to introduce the tqm to food/agro activity. the quality assurance systems <qas) according to the iso 9000:94 standards have been created for industrial activities. some elements of thc:>e :-.ti.mdards are not compatible with food/agro activitie\. they \vere only in the last years transformed and intn xlu~erl there. the new iso 9000:2000 standards are takin!! in fl(l..'ount these specialties of food/agro industry. 136 fig.] basic elements and their effects of qms in food/agro industries haccp system is one of the methods, which helps to ensure food safety by a simple but effective way. it identifies hazardous problems in advance uses briefly the following steps: identifies potential hazards and the corresponding critical control points, establishes control procedures, monitoring procedures, corrective actions, effective record keeping procedures and the procedures of verification [1]. both gmp and haccp programs are building qm toward the new iso 9000:2000 requirements. the new iso 9001:2000 standards and the implementation of quality the new edition of iso 9001 carries a title, which does not include the term qa. this reflects the fact, that the qms requirements not only_ address the qa of product conformity, but also include the need for an organisation to demonstrate its capability to achieve customer satisfaction. the iso 9001:2000 standard encourages the adoption of the process approach for the management of the organisation and its processes, as it is shown in fig.2. any activity or operation receives inputs and converts them to outputs. so it can be considered as a process. in the new process approach of the qm model the most important input elements are the customer requirements~ similarly, the most important output element is customer satisfaction. this approach is true~ right and clear in the food/agro sector of course if we are in another field of the economical life (i.e. education) then it is an important question how to define customer and how to define satisfaction. one of the most important changes of qms: focusing more on the customer requirements and satisfaction to show the real importance of the changes in the new iso 900 l standard we citate the points corresponding to the most important input/output definition of the process approach of qms: fig.2 quality management process model • (5.2) top management shall ensure that customer needs and expectations are determined and converted into requirements with the aim of achieving customer confidence. • (5.6.1) the organisation shall establish a qms ... ensuring that the product and/or service conform to customer requirements. • (7 .2.1) the organisation shall establish a process for identifying customer requirements. • (7 .2.3) the organisation shall implement arrangements for communication with customers, with the aim of meeting customer requirements. • (8.2.1) the organisation shall determine and establish processes for measurement of qms performance. customer satisfaction shall be used as one measure of system output. • (8.2.1.1) the organisation shall monitor information on customer satisfaction and/or dissatisfaction. the methods and measures for obtaining and utilising such information and data shall be defmed. • (8.4) the organisation shall analyse applicable data to provide information on customer satisfaction and/or dissatisfaction conformance to customer requirements as we see among these citations, it is a very important part of an effective working qms, how to determine the measuring method of customer requirement and satisfaction. in the 21st century internet offers a good tool for data collection in these fields and information technology, and computer programs m~e it easy to use the methods of mathematical statistics on the collected data sets. internet methods and experiences in identification and analysis of customer requirements and satisfaction using our quality audit experiences, two internet ~uesti?nnaire forms have been created to identify and to mvesugate customer requirements, satisfaction and preferences. one of them is developed for the "end fig.3 internet form for general food "end customers" thank.yoqjqr yo!ly postharvf..strep}y! · •· . · firiviia·-· --·witatij,a i!f<ng~n areyooh~w1i!seietlim.~ 3:;,~:~%~~irl~ ps) y-~tffi?' i.tfum.~~ (fv)~js<!ect one ij big venture {>5g ~s) the ratio ofyourmshfvf~qll tn~totol:feodtmt511j1ljltioo: ~ . wltl>fistlojos1>11rteo!~~fv~~1jse~cton• •.... fj ;t;,. ·c.tle!1)),4,sj.,.;n..~~~~~~~~~iathti~@hle tkws,~l) >sjlli . · ijpf!lf~~~~~ fig.4 postharvest internet form about fruits and vegetables customers", using shopping centers for the food consumption of their own household, and the second, special one put questions from the postharvest point of view to the small, medium ot big ventures about fruit and vegetable consumption. the internet questionnaire forms are shown in figs.3 and 4, they are available in the following urls: http://knight.kit.bme.hulbea and http://knight.kit.bme.hu/postharvest in the first internet form we investigated general food consumption, as it occurs in a real household. we collected data about the preference of the big sc-s, including the percentages of shopping different food in the most preferred and in other sc-s. it was very important in these questionnaires to take in account the difference in the ages of the internet using group and of the hard copy fulfilling control group. the second questionnaire was made for agricultural and horticultural firms growing or producing fruit and vegetables. the questions covered those properties of ~e most important fruits/vegetables in hungary that are mfluenced by the postharvest activities and procedures. from the point of view of mathematical statistics this second internet form has not enough answers for the 137 nate' st>nt: tue, 19 jun 2111l1 d7:~>8:1t9 '~'02011 fro111: tn: subject; fogyaszt ff=1&no .. s&gy·c~auye,..onll:shopc"'tt> . tlisu=1uike,.1&vasu,.d.5tvake"0.5tcus:u--1t.cuke"11l:susu"qtsuke"u &tesu,.1 (lt.teke,.5&zgsu"'1 fl&zgke•5t.sasu"l)t.sakezljtaij sus 11\lllllkf' .. 11 • t.bfsu•11l&bfke .. 8&sllsu•lt&shkt'•4t\uisu"6atuike~2 ita 1 slt·m~ 1 ke•f ll:coment.,l'lindent*egy+helyen+~.tiszonylag•olcs\f3n•~~~es•lelll!t+uenni ~ ..• 1 1 fig.5 a row answer file of the first internet form j emails to asc . i!ii!j £j ?j!el_ c: []. 12:7 c:\ (2} bhonnef ::3. select -folder ;where mail1xt file are then click collect button .......•.......... ::.::::: .rij.:::::::::: .. ·,........... .. .... ,. • 0 ..... collect to one file! . . ... . . . . . . . . . "' . • .. '·~ .. . . .. ~ .. ' .. ) fig.6 user form of the first evaluation step of the e-re plies of the first internet form correct evaluation, and it is not easy to sw:cessfully suggest farmers to use internet. (although even internet surfing will become more and more general. and nor only in the cities!) both internet forms collect e-repltes that are evaluated by a vba program. an example from the row answer files of the first form is shown in fig.5 and the user form of the first evaluation step is shown in fig.6. as one can see, the e-replies have to be en~odcd. this procedure is made by the vba program, whid~ was built into an excel module. by this way the statistical and graphical tools of excel are availahle for the evaluation of the data set. in our first attempt we dtd not want to put complicated questions on the internet. in the work of one of the co~authors [4], it was proved. that too long or complicated questions on internet do not lead to enough and high quality information. which are necessary to carry out statistical tests precisely. for the evaluation of the first internet form. we have chosen a control group, too. the members of the control group filled in the same questionnaire. but they have got a "hard copy". as long as the internet using gwup handed in forms containing jess than lqf;} (\f theoretically wrong or not usable answer.... among the "hard copf' answers we have found more than 30lk wrong, not correctable ones .. of course. the two gmups are from different ages internet u"lll~ people are mostly young. and the control group co\ ~.·re-d 18-(10 year old customers, mostly above 40 year u:j people. \vc consider as correctable answer for e:x~nnplc. if the customer wtites an ··o" nr a •. _.. character m .... tcad nf .. o·· 138 bestltotal% (e-replles) (car-71% d families, auchan=35%) fig.7 a part of the statistical evaluation of the first internet form character or an unfilled box. these errors can be automatically (by software) corrected in e-replies, or by the time typing the data in the computer in the case of hard copy answers. we have taken in account the possibility in the internet questionnaire to reject and give back wrong replies, but in our first attempt we wanted to compare the percentage of wrong replies, too, and· the hard copy users can not get back their wrong answers in a short way. in both internet or hard copy replying groups the number of customers using car for food shopping is quite high. as best properties for the most preferred shopping centre they mentioned the low prices, the possibility to buy several kinds of food in the same place, and the comfortable parking places for their cars. comparing internet and hard copy replies we found an interesting difference between the two groups in fruit/vegetable and in meat consumption. the members of the internet using group buy only a very small part of their fruit/vegetable needs (:::::5%) in the most preferable shopping centre, this percentage in the other group is considerably higher (:::::25%). the difference between their meat consumption is not as considerable, but in this field the "hard copy" group's consumption in the most preferred sc is lower. see figs.7 and 8. conclusions the new iso 9001:2000 standards focus considerably more on the customer requirements and satisfaction in qms. our goal was to create internet and computer using methods to identify~ investigate and evaluate customer requirements and satisfaction. process approach of qms uses these points as most important input and output of the system. as a first attempt we have developed two internet forms, that are available on the urls: knight.kit.bme.hulbea and knight.kit.bme.hu/postharvest using these forms we could avoid a lot of formal errors in the replies. and of course the statistical evaluation is easier if we have from the very beginning a computer database. in the future we want to extend our evaluation process and program by determining the most suitable statistical methods and building in these methods in our ~omputer program. best/total% (hardcopy ans.) (carsin 7811 offam, auchan=451i i fig.8 a part of the statistical evaluation of the first internet form acknowledgements the authors wish to express their gratitude to the voluntary student researcher, ms beata kapolna and to the co-workers of prenor (szombathely) and det norske veritas (budapest). the work has been supported by the hungarian national research foundation (otka, grant # t025750/98.) gmp gap haccp qa qas qm qms sc tqm vba symbols good manufacturing practice good agricultural practice hazard analysis, control of critical points quality assurance quality assurance system quality management quality management system shopping centre total quality management visual basic for application references 1. evans j. r. and lindsay w. m.: the management and control of quality, west publ. co., new york, 1993 2. kollar g., viczian zs., fdstos zs. and kollar­ hunek k.: quality assurance systems and information technology in bioengineering, hung. j. ind. chern., 1999, 27, 63 3. kollar g., viczian zs., fostos zs. and hunek k.: problems and results of computer aided qas in food industry and bioengineering, computers & chern. eng., 1999,23,687 4. kollar g., viczian zs., syposs z., fdsros zs. and di6spatonyi i.: quality assurance, information technology and bioindustry, hung. j. ind. chern., 2000,28,162 5. vicztan g.: diploma work budapest university of economical sciences, 1998 6. iso/cd2 9001:2000, quality management systems -requirements\ iso!fc 176/sc 2/n 434~ 1999 page 136 page 137 page 138 page 139 hungarian journal of industry and chemistry vol. 48(2) pp. 1–4 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-20 combination of chemical and biological methods for effective plant protection dávid vozik 1 and katalin bélafi-bakó*1 1research institute on bioengineering, membrane technology and energetics, university of pannonia, egyetem u. 10, veszprém, 8200, hungary the application of combined biological and chemical techniques to control undesirable processes in plant cultivation is becoming ever more important to maintain sustainable and environmentally friendly agricultural systems. entomopathogenic nematodes and bacteria can provide an effective and special technology in the field of plant protection. keywords: antimicrobial, entomopathogenic nematodes, bacteria 1. introduction nowadays, one of the most important challenges worldwide is the sufficient cultivation of edible plants and crops due to the rising trend in population growth and food demand. moreover, it is important to solve this problem by implementing sustainable agriculture which prefers natural protection and tries to minimize the intervention of radical chemicals. it was confirmed recently that some synthetic pesticides are environmental hazards. since the biological degradation of certain pesticides is slow, their bioaccumulation might cause significant damage to ecosystems, soil, natural waters, etc. therefore, the idea of protecting crops has been extended and a new concept, “integrated pest management” (ipm), introduced which involves chemical, biological and biotechnological methods together with modern cropping, cultivation and breeding technologies [1] in a way which minimizes any risk of environmental damage. to apply this concept in practice requires comprehensive knowledge of the crops, fitopathogenic microorganisms as well as their enemies, and the behaviour of chemicals (e.g. pesticides) that may be used. a field that has hardly been researched are the so-called entomopathogenic nematodes and bacteria which have been studied in hungary for a significant period of time [2]. 2. entomopathogenic nematodes and bacteria entomopathogenic nematodes are a group of thread worms that kill certain insects. they enter – in the form of infective juveniles – into the insects, live as parasites *correspondence: bako@almos.uni-pannon.hu inside them and cause host mortality within 1-2 days. it has turned out, however, that this is not only caused by the nematodes themselves but certain bacteria play an important role as well. entomopathogenic bacteria live in symbiosis with entomopathogenic nematodes [3,4]. the nematodes provide shelter for the bacteria, an area of the interior part of the intestine of the infective juveniles is transformed into a bacterial chamber where cells of symbiotic bacteria are located. the relationship is highly specific: e.g. the nematodes of steinernema usually carry species of xenorhabdus bacteria, while heterorhabditis carry photorhabdus bacteria. when entering an insect, infective juveniles release the bacteria, which start multiplying rapidly in the haemolymph. it has been proven that although the bacteria are primarily responsible for the mortality of the insect host, the nematodes also produce a toxin which is lethal to the insect. these nematode-bacteria complexes can be applied successfully as biological control agents against insect pests in agriculture [5]. some of these agents are available commercially, as listed in table 1, where the target insects, habitats and places of usage are presented [6–8]. 3. antimicrobial compounds entomopathogenic bacteria contribute not only to the successful activity of entomopathogenic nematodes but can produce special compounds with an antimicrobial effect as well. the main purpose of producing these compounds is to protect the colonized cadaver in the soil [9]. the antimicrobial compounds of entomopathogenic bacteria have been tested and it would seem that these natural agents show a wide range of bioactivities of medical and https://doi.org/10.33927/hjic-2020-20 mailto:bako@almos.uni-pannon.hu 2 vozik and bélafi-bakó table 1: examples of the successful application of nematode-bacteria complexes [6–8] target habitat where japanese beetle popillia japonica subterranean lawn, turf black vine weevil otiorhynchus sulcatus subterranean strawberry plants fungus gnats lycoriella species, bradysia species subterranean mushroom production diaprepes root weevil diaprepes abbreviatus epigeal citrus invasive mole cricket scapteriscus vicinus epigeal lawn, turf codling moth cydia pomonella cryptic apple, pome fruit table 2: plant pathogens tested pathogen effect ref. phytophthora nicotianae root rot disease of tobacco [13] erwinia amylovora fire blight disease of several plants that belong to rosaceae, e.g. apple, pear, etc. [14] ralstonia solanacearum brown rot disease of potato [15] agricultural interest, e.g. antibiotic, antimycotic and insecticidal effects [10,11]. for analytical purposes, fourier transform infrared spectrometry (ftir) was used to identify these compounds [12]. in our laboratories, secondary metabolites of xenorhabdus budapestiensis (isolated in hungary) have been investigated [13]. the bacterium was maintained on a luria agar (la) medium and freshly subcultured. the cells were cultured in 1000 ml flasks and incubated on a gyrorotary shaker at 25 ◦c . then the cells were removed by centrifugation and the supernatant extracted. the cell-free filtrate was further purified by chemical methods (adsorption and filtration) to obtain a peptide-rich fraction. this fraction was applied to test for various plant pathogens, as listed in table 2, including pathogens of tobacco, apple and potato (the latter of which is widespread in hungary, causing serious damage to inland agriculture). the investigations involved in vitro bioassays, where the antibacterial activity of the biofraction was determined on solid media. in an agar diffusion test, the tested bacterium was mixed with soft agar poured onto la plates, then a small hole was made in the centre and the biopreparation of the filtrate added [13]. for the so-called overlay test [13], the antimicrobial preparation was incubated on the solid luria broth agar (la) plate then the pathogenic microorganism in soft agar was spread onto the surface. in both cases, an inhibition zone can be identified and determined, if the biopreparation was effective against the pathogenic strain. an example of the agar diffusion bioassay is given in fig. 1. a picture taken from a successful overlay bioassay test is shown in fig. 2. in our laboratory, in vitro bioassays proved that the biopreparations containing the antimicrobial compounds could be successfully used against these pathogens. moreover, in planta (in field trials), a bioassay was conducted using infected apple blossom (erwinia amylovora) which was treated with the biopreparation. it was concluded to be suitable to reduce the symptoms of the infected plants, thus it can be considered as a promisfigure 1: antibacterial effect of the preparation in the agar diffusion test. figure 2: the antagonistic effect of x. budapestensis against e. amylovora ea1 bacteria in an overlay test. hungarian journal of industry and chemistry effective plant protection 3 figure 3: infected apple blossom treated with the biopreparation. ing biological agent [14,15]. this successful treatment is illustrated in fig. 3. other than plant pathogens, the peptide-rich fraction of xenorhabdus budapestiensis has recently been tested against species of fungi in vitro [16] in clinical samples. candida albicans, candida lusitaniae, candida krusei, candida kefyr, candida tropicalis and candida glabrata were used in the research by applying the agar diffusion method. the results proved that every candida species is sensitive to the preparation, thus it would seem that the fraction has a fungicide impact as well. 4. conclusion in summary, the symbiotic complex of entomopathogenic nematodes and bacteria can be considered as efficient biological agents to control some insect pests, but the secondary metabolites of the bacteria can be effectively used against other pathogenic bacteria and fungi. as a result, their applications can contribute significantly to successful plant protection by providing numerous environmental benefits and can be considered as an important component of “integrated pest management” (ipm). references [1] act xxxv on plant protection (2000, hungary) http://www.kvvm.hu/szakmai/hulladekgazd/jogszabalyok/2000 _xxxv_tv.htm [2] lengyel, k.; lang, e.; fodor, a.; szállás, e.; schumann, p.; stackebrandt, e.: description of four novel species of xenorhabdus, family enterobacteriaceae: xenorhabdus budapestensis sp. nov., xenorhabdus ehlersii sp. nov., xenorhabdus innexi sp. nov., and xenorhabdus szentirmaii sp. nov., syst. appl. microbiol. 2005, 28(2), 115–122 doi: 10.1016/j.syapm.2004.10.004 [3] boemare, n. e.; akhurst, r. j.; mourant, r. g.: dna relatedness between xenorhabdus spp. (enterobacteriaceae), symbiotic bacteria of entomopathogenic nematodes, and a proposal to transfer xenorhabdus luminescens to a new genus, photorhabdus gen. nov., int. j. syst. bacteriol. 1993, 43(2), 249–255 doi: 10.1099/00207713-43-2-249 [4] thomas, g. m.; poinar, g. o.: xenorhabdus gen. nov., a genus of entomrnopathogenic, nematophilic bacteria of the family enterobacteriaceae, int. j. syst. bacteriol. 1979, 29(4), 352–360 doi: 10.1099/00207713-29-4-352 [5] smart, g. c.: entomopathogenic nematodes for the biological control of insects, j. nematology 1995, 27(4s), 529–553 https://www.ncbi.nlm.nih.gov/pmc/articles/pmc2619649/pdf/ 529.pdf [6] koppenhöfer, a. m.: nematodes, in lacey, l.a.; kaya, h.k. (eds.): field manual of techniques in invertebrate pathology. application and evaluation of pathogens for control of insects and other invertebrate pests (springer, dordrecht, the netherlands) 2007, isbn: 978-1-4020-5933-9 [7] georgis, r.; koppenhöfer, a. m.; lacey, l. a.; bélair, g.; duncan, l. w.; grewal, p. s.; samish, m.; tan, l.; torr, p.; van tol, r. w. h. m.: successes and failures in the use of parasitic nematodes for pest control, biol. control 2006, 38(1), 103–123 doi: 10.1016/j.biocontrol.2005.11.005 [8] lacey, l. a.; georgis, r.: entomopathogenic nematodes for control of insect pests above and below ground with comments on commercial production, j. nematology 2012, 44(2), 218–225 https://www.ncbi.nlm.nih.gov/pmc/articles/pmc3578470/pdf/ 218.pdf [9] akhurst, r. j.: antibiotic activity of xenorhabdus ssp., bacteria symbiotically associated with insect pathogenic nematodes of the families heterorhabditidae and steinernematidae, j. gen. microbiol. 1982, 128(12), 3061–3065 doi: 10.1099/00221287-12812-3061 [10] mcinerney, b. v.; gregson, r. p.; lacey, m. j.; akhurst, r. j.; lyons, g. r.; rhodes, s. h.; smith, d. r.; engelhardt, l. m.; white, a. h.: biologically active metabolites from xenorhabdus spp., part 1. dithiolopyrrolone derivatives with antibiotic activity, j. nat. prod. 1991, 54(3), 774–784 doi: 10.1021/np50075a005 [11] webster, j. m.; chen, g.; hun, k.; li, j.: bacterial metabolites, in: gaugler, r. (ed.) entomopathogenic nematology (cabi publishing, new york, usa) 2002, 145–168 isbn: 08-5199-567-5 [12] vozik, d.; madarász, j.; csanádi, zs.; fodor, a.; dublecz, k.; bélafi-bakó, k.: study on analysis of antibiotic compounds from entomopathogenic bacteria by ft-ir, hung. j. ind. chem. 2012, 40(2), 83–86 https://mk.unipannon.hu/hjic/index.php/hjic/article/download/346/316 [13] böszörményi, e.; érsek, t.; fodor, a.; földes, l. sz.; hevesi, m.; hogan, j. s.; katona, z.; klein, m. g.; kormány, a.; pekár, sz.; szentirmai, a.; sztaricskai, f.; taylor, r. a. j.: isolation and activity of 48(2) pp. 1–4 (2020) http://www.kvvm.hu/szakmai/hulladekgazd/jogszabalyok/2000_xxxv_tv.htm http://www.kvvm.hu/szakmai/hulladekgazd/jogszabalyok/2000_xxxv_tv.htm https://doi.org/10.1016/j.syapm.2004.10.004 https://doi.org/10.1016/j.syapm.2004.10.004 https://doi.org/10.1099/00207713-43-2-249 https://doi.org/10.1099/00207713-29-4-352 https://www.ncbi.nlm.nih.gov/pmc/articles/pmc2619649/pdf/529.pdf https://www.ncbi.nlm.nih.gov/pmc/articles/pmc2619649/pdf/529.pdf https://doi.org/10.1016/j.biocontrol.2005.11.005 https://www.ncbi.nlm.nih.gov/pmc/articles/pmc3578470/pdf/218.pdf https://www.ncbi.nlm.nih.gov/pmc/articles/pmc3578470/pdf/218.pdf https://doi.org/10.1099/00221287-128-12-3061 https://doi.org/10.1099/00221287-128-12-3061 https://doi.org/10.1021/np50075a005 https://doi.org/10.1021/np50075a005 https://mk.uni-pannon.hu/hjic/index.php/hjic/article/download/346/316 https://mk.uni-pannon.hu/hjic/index.php/hjic/article/download/346/316 4 vozik and bélafi-bakó xenorhabdus antimicrobial compounds against the plant pathogens erwinia amylovora and phytophtora nicotianae, j. appl. microbiol. 2009, 107(3), 746–759 doi: 10.1111/j.1365-2672.2009.04249.x [14] vozik, d.; bélafi-bakó, k.; hevesi, m.; böszörményi, e.; fodor, a.: effectiveness of a peptiderich fraction from xenorhabdus budapestensis culture against fire blight disease on apple blossoms, not. bot. horti agrobot. cluj-napoca 2015, 43(2), 547–553 doi: 10.15835/nbha4329997 [15] vozik, d.; bélafi-bakó, k.; hevesi, m.; böszörményi, e.; polgár, zs.; fodor, a.: effectiveness of antimicrobial compounds produced by entomopathogenic nematode symbiotic bacteria to control pests and bacterial plant diseases, international organization for biological control west palaearctic regional section bulletin 2016, 113 17–21 isbn: 978-92-9067-296-8 [16] burgetti-böszörményi, e.; németh, s.; bélafibakó, k.; vozik, d.; barcs, i.; csima, z.: the antifungal effect of xenorhabdus budapestiensis bacteria biopreparatum on some candida species in vitro, dev. health sci. 2018, 1(7), 57–62 doi: 10.1556/2066.2.2018.17 hungarian journal of industry and chemistry https://doi.org/10.1111/j.1365-2672.2009.04249.x https://doi.org/10.15835/nbha4329997 https://doi.org/10.1556/2066.2.2018.17 https://doi.org/10.1556/2066.2.2018.17 introduction entomopathogenic nematodes and bacteria antimicrobial compounds conclusion conference proceedings hungarian journal of industrial chemistry veszprem vol. 2. pp. 7175 (2000) applications of membrane technologies in water reuse fields i. zsirai and g.kicsi (z~n_on systems ltd., vigado u., tatabanya, h-2800, hungary, a substdiary of zenon enviroilillental inc., oakville, ontario, canada) this paper was p:ese~ted at the second international conference on enviroilillental engineering, umvers1ty of veszprem, veszprem, hungary, may 29 june 5, 1999 this paper. presen.ts _the application of micro filtration and reverse osmosis membrane technologies in water reuse and recycle projects within the power industry, through one pilot scale and two full-scale case studies. the paper also describes a relatively new micro filtration technology, based on zeeweed® a shell-less outside-in hollow fibre n:embr~e i~ersed into a process tank and operated by applying a small suctlon to the ~embrane's lumen. o~eratmg at differential pressures of -7 to -55 kpa, the immersed membrane is an energy efficient membrane. in addition to 1ts low en~rgy con~umption, offers a nilillber of advantages e.g. chlorine and oxidant resistance, exceptional durability, small footpnnt, low .m~astructure costs and allowance to high suspended solids. these features provide flexibility to a membrane plant, which m turn allows for treatment of a variety of streanis. keywords: prefiltration; pre-treatment; membrane technology; microfiltration; reverse osmosis; hollow fibre; zeeweed® membrane; wafer reuse and recycle introduction the increased public concern over health and the e~vironment, the .increasingly stringent effluent dtscharge criteria, the limited water supplies for meeting prevailing and projected water demand at a specific location along with the increasing fresh water costs strongly affect the large industrial water consumers, such as the power industry. . to extend existing water supplies, to limit the discharge of pollutants as well as to recover useful materials where is possible, industrial frrms are looking for technical solutions which enable them to reuse treated wastewaters (e.g. from sewage treatment plant) or to recycle internally their own technological wastewater. in the context of technology advances, the answer to this obvious challenge is the combination of tv:o membrane separation techniques, namely: nucrofiltration (mf) and reverse osmosis {ro). reverse osmosis is a membrane desalination pr?cess, commercialised during the 1960s especially in and regions of the middle east. since its introduction, due to ever decreasing membrane prices and accumulating process knowledge through experience, the ro technology is successfully implemented on large and diverse scale. for successful application in the treatment train of troublesome waters, which contain some combination of high and variable suspended solids, organics, inorganics (e.g. iron and manganese) and bio-contaminants (microorganisms: bacteria, algae etc.)[l], the pre-treatment of the feed water to the r.o system should be reliably and well established. in the past, the pre-treatment was entirely solved through conventional technologies e.g. clarification and multimedia filtration or multimedia filtration alone. the success of this pre-treatment depended largely on the control and monitoring of the coagulant addition. this control was extremely difficult with variable raw water supply, which rendered an unreliable, unstable and unpredictable property to this conventional pre­ treatment process. an insufficient amount of coagulant could contribute to process fouling due to contamination, whereas an excess of coagulants could lead to ro membrane fouling by the coagulants themselves. therefore the elaboration and further development of the microfiltration membrane process presented a breakthrough in the field of ro pre­ treatment as well. 72 fig. i operational concept ofzeeweed® membrane filtration membrane penreate to top header support material aeration bubbles (for fluid agitation) coarse bobble diffuser penreate to bottom header bulk fluid (concentrate) fig.2 zeeweed® membrane fiber schematic microfiltration membranes microfiltration membranes operate on the principle of particle separation based on pore size and port< size distribution. microfilters have pore sizes that vary from 0.015 micron to 3 microns. depending on the membrane selected, it will allow separation of suspended solids, bacteria. cysts etc., which have a diameter larger than the largest pore size of the membrane. this allows for production of microorganism and suspended solids free water without the need of chemicals. the first microfilters were of the depth filter type, where particles and microorganisms are entrapped within the internal structure of the filter [2]. due to the need for regular replacement, depth microfilters have had limited application in the pre-treatment process. among the membrane module geometries. spiral wound configurations were the first commercially available. due to their fiat-sheet nature, these membranes could not tolerate very wen solids, which prevented their widespread use. therefore, the most commonly employed configurations are the tubular and hollow fibre mf membranes. however. the higher packing density and lower energy consumption of the membrane systems with hollow fibre modules win favour their use over the tubular modules especially in larger plants. based on the flow regimes, two types of hollow fibre membranes are distinguished: inside-out membranes, where the influent is fed inside the membrane's lumen and the clean water travels from the inside of the fibre to the outside. outside-in membranes where the influent is fed from the outside of the membrane and the clean water travels from the outside to the inside of the membrane fibre. the common pressure driven hollow fibre membranes, known to the market, are installed within pressure vessels, necessary to apply the pressure for proper fluid transfer. typical operational pressure for these membranes is 103 to 207 kpa. the introduction of vacuum driven hollow fibre membrane process, the zee weed® membrane process, by zenon environmental inc. further revolutionised the microfiltration market. the zeeweed® membraneprocess description the zee weed® based water filtration is a novel, low energy membrane process that employs outside-in, shell-less hollow fibre microfiltration modules inunersed in raw feed-water. the zeeweed® microfilter has a 0.085 micron nominal and a 0.1 micron absolute pore size, ensuring that particles with diameter exceeding 0.1 microns do not escape to the treated water stream. the membranes operate under a small vacuum created within the hollow fibres by the operation of a centrifugal pump. the treated water passes through the membrane, enters the hollow fibres and is pumped out to distribution by the permeate pumps. fig. i illustrates the operational concept of zee weed® membrane filtration. a low-pressure airflow is introduced at the bottom of the membrane module to create turbclence, which scours and cleans the outside of the membrane fibres allowing them to function at a high flux. this air will also oxidise iron and other organic compounds, generating better quality water than provided by microfiltration alone. fig.2 shows a schematic of a zeeweed® membrane fibre in operation. in order to remove fouling material from the surface of the membrane, in addition to air scouring, at regular intervals, collected permeate is pumped in the reverse direction, forcing flow through the membrane from the inside of the hollow fibre to the outside, cleaning the membrane pores and fibre surface. this in­ situ cleaning process is termed backpulse. due to the high permeability of the zeeweed® membrane, the backpressure during backpulsing is low. the small variations in operating pressure that the membrane is subject to occur smoothly over relatively long periods so that at no time is the membrane stressed. this in turn, results in a microfiltered permeate with the lowest, sustainable particle count on the market, the reject water called concentrate is discharged directly from the process tank intermittently or continuously depending on system operating parameters and design. intermittent discharge (no concentrate removal during backpulse) offers the advantage of decoupling the hydraulic recovery from the backpulsing operation [4]. the hydraulic recovery is simply controlled by setting a bleed rate from the process tank. to prevent pump cavitation and the development of water hammers in the distribution system, the zee weed® process is equipped with air separator columns, which remove the entrained air from the permeate. accumulated membrane foulants are removed when a limiting suction is reached by on-line or off-line chemical cleaning. several procedures and cleaning agents may be employed, depending on the application. off-line chemical cleaning interval is typically one to several months, and takes 2 to 4 hours, depending on the number of steps required. the zee weed® membrane modules consist of many hollow fibres, which are coated on the outside with the membrane and run vertically between top and bottom permeate headers on the membrane module. individual modules are assembled to cassettes, which in turn are attached to frames. therefore, the resulting systems are extremely compact. the system does not need elaborate pre-treatment, even if the feed water contains clays and fine particles, only coarse screening. therefore, in a single process, it replaces the coagulation, flocculation, clarification and sand filtration steps of conventional plants and also eliminates the pre-treatment required by spiral and inside-out membranes. applications of mf & ro in water reuse projects within the power industry driven by unsatisfied user needs due to unreliable operation of the conventional · pre-treatment, technological development in the field of microfiltration and membrane manufacturing cost reductions due to increasing application of microfiltration membranes throughout the water and wastewater industry, microflltration is being increasingly applied to replace conventional boiler feed water pre-treatment processes. moreover, as discussed, due to the application of mf in the pre-treatment step of a ro system, "difficult to treat" waters could also be considered as primary feed source, which represents considerable savings and contributes to environmental protection. case study ibokod power station at the bokod power station (235 mw) in oroszlany, hungary, the 52 m3 h-1 demineralised, boiler feed water stream is produced directly from the coolir.g lake, which contains up to 100 mg dm-3 of suspended solids and 225·106 counts dni3 of algae during bloom periods [7]. prior to the installation of the mf & ro membrane s~stems, due to the cooling system blow-down discharges, the cooling lake has enriched in total 73 01.,4 02.94 03.94 04.94 05.94 06.94 07.94 (}8.94 09.94 10,94 11.94 12.94 01.99 02.9:9 03.99 04.99 fig.3 bokod power plantconductivity, sulphate and chloride content of the cooling lake dissolved solids (tds of 6000 mg dm-3 ). since the start up of the new treatment system (may 1994), the pressurised hollow fibre mf pre-treatment train delivers · constantly a filtrate virtually free of suspended solids and with a silt density index (sdi) of less than three. the effluent of the ro system has a conductivity of 1015 f..ts crri1 . as a result of the combined mf and ro treatment system, the operating cost of the boiler feed water production has been reduced by more than 50% in comparison to the cost occurred during the formerly employed conventional technology. the five year operation has demonstrated the reliable operation of both membrane systems, a constant high quality effluent production and a positive change in the cooling lake quality. fig.3 presents the conductivity, sulphate and chloride concentration of the water from the cooling lake through 1994 and during the fin,l four months of 1999. due to the implementation of the membrane treatment processes, the average total dissolved solids concentration has dropped to 800 mg dm"3 , in the cooling lake water. case study iilagisza power plant the main objectives of the stage·wise modernisation of the water treatment plant (wtp) at the lagisza power station (875 mw) in poland were to use the closed cooling water circuit blow-downs as the boiler feed water source and to improve the quality of the cooling water, facilitating the discharge of unused portion of blow-downs to surface water receivers. the three individual process train, each consisting of a pressurised hollow fibre mf unit, an ro system and mixed bed. ion exchange (mbix) columns, and each having a capacity of 50 m3 h"1, were commissioned at the end of june 1997, at the beginning of january 1998 and at the end of march 1998, respectively. the stage~wise completion was dictated by the fact that the wtp had to produce continuously a quantity of 150 m3 l:i1 demineralised water(8j. since start up, the mf filtrate quality is constant, having an average turbidity content of 0.1 ntu (but always less than l nttj) and a sdi while the source 74 1600 1400 400 200 ill.tmr. 04.l91jt, os.t997r. 06.1997~. 07.1~ot.tmr. 09.j997r. 10.19971'. ll.imr. 1;!.1997r. 01.1991't. 02.1991r, fig.4 lagisza power plantcooling water conductivity ~~--------------------------------, ~~-,~----------------------------~ ~~+ .. :~1:~--------------------------~ e 1t$+ .. ,1~l',h.:'f------------------------~ ~ >m.j,ji.,!-j.''j_ fig.6 lagisza power plantchloride concentration of the cooling water water suspended solid concentration varies between 15 34 mg dm-3 • the :mf membrane pre-treatment step also prevents the bio-fouling of the ro membranes and reduces their cleaning frequency since assures at least 5 bacterial log removal. the ro membrane system performs the pre-treated water demineralisation, which is monitored through the conductivity reduction. on average, at an operating temperature of 30 °c, the ro feed water conductivity is approximately 900 j.1s cm'1 whereas the ro permeate conductivity is within the 2.;5-7 .5 j.1s cm'1 range, which represents a 99.1-99.7% reduction. the treated water after the ion exchange units has an average conductivity of 0,09 ¢s cm4 (but always less than 0.1 j.1s cm"1) and a silica content of <0.005 mg cm·3• in addition to the demineraiised water production with excellent quality, the installed treatment process successfully improved the water quality in the cooling circuit in fairly short time. this quality improvement is well illustrated by figs.3-6. the concentration of the three parameters presented, i.e. conductivity, sulphate and chloride, decreased after the installation of the new process train. moreover, the improved quality of the cooling water circuit was well within the surface water discharge criteria. therefore. the lagisza power plant obtained permission from the local authorities to discharge the unused portion of the cooling water blow's; 350 ,g 300 g "i ::: 8 ~ 150 ~ 100 50 ~l.l!l!i7j", !1uji97r. os.i997r 06.1!19?r. 07.19.971", oiu~. «1.1"7r. 10,1'197r. jl.l997r. iz.l!197r. jll.lh!i<. 02.l!l!illr, months fig.5 lagisza power plantsulphate concentration of the cooling water table 1 zeeweed® pilot study results on stp effluent raw feed zeeweed® #of parameter (stp effluent) mf effluent observations suspended solids 6-32 <2 75 -tss(rng drn-3 ) turbidity (ntu) 10-50 <1 10 silt density index unmeasurable 0.9-2.4 31 -sdibod5 (rng drn-3 ) 2-32 <2 70 fecal coliforrns 3-600 <4 18 ( cfu/1 00crn3 ) downs to the nearby rivers. ultimately, the better cooling water quality reduced the quantity and/or frequency of the blow-down discharges, as well as the operational cost of the boiler feed water production (through reduced chemical consumption 90% less chemical usage -, waste heat utilisation from cooling water condensation, reduced waste generation). case study iiie.c katowice power plant the limited fresh water supplies for meeting projected water demand at the e. c. katowice power plant, forced the management to look for alternative water sources. it was found that the most convenient source would be the secondary clarifier effluent from the local sewage treatment plant, located adjacent to the power plant. after the evaluation of treatment alternatives, 'zi:.eweed® microfiltration was selected to polish the sewage treatment plant effluent and supply water for the cooling circuit of the power plant. the 'zi:.eweed® tertiary treatment system is under construction and will be commissioned during this summer. it is designed to supply a 225 m3 h'1 microfiltered permeate, by employing three separate zeeweed® treatment train, each having a capacity of 75 m3 h-1 . in a pilot study conducted at another location, on biologically treated sewage, the 'zj:.eweed® :mf process demonstrated its ability to supply an effluent suitable for reuse or further ro treatment. the process efficiency is well illustrated by the results of the pilot study included in table 1. conclusions water scarcity at a specific region, regulatory pressure and economical considerations impact the decision making process of industrial water consumers during the evaluation of raw water source alternatives. the inefficiency of conventional filtration plants to treat troublesome waters has forced engineers to look into new technologies. the combination of microfiltration and reverse osmosis membrane technologies enable the power industry and other industrial firms to consider "difficult to treat" waters as their raw water source. furthermore, the application of coupled mf and ro treatment trains allow the reuse of sewage treatment effluents and recycle of technological wastewaters. moreover, these applications also limit the discharge of pollutants, therefore, they contribute to the process of natural environment preservation. due to its predictable, reliable, flexible and stable nature, the mf process is not only effective in pretreating the raw water for the ro technology but also minimises the capital and operating costs of the downstream technologies (i.e. ro, ix) through the reduction of the ro membrane inventory and chemical usage. immersed outside-in membranes are competing against dead-end outside-in microfilters and cross flow inside-out membranes due to their lower energy requirements. microfiltration plants, being modular, can be built to treat volumes as small as 2m3 h-1 but are also currently being sold for treatment of> 3154 m3 h-i. symbols mf microfiltration ro reverse osmosis tds sdi mbix ix wtp stp total dissolved solids silt density index mixed bed ion exchange ion exchange water treatment plant sewage treatment plant references 75 1. tonelli t. and kroll s.: microfiltration technology the next generation, paper presented at the international water conference, pittsburgh, pa, 1997 2. a wwa, lyonnaise des eaux, water research connnission of south africa: water treatment membrane processes, mcgraw-hill, ppll.l-11.7, 1996. 3. mourato d.: applications of immersed membranes in the drinking water field, paper presented at the 1997 a ww a membrane technology conference, new orleans, louisiana, febmary 25, 1997 4. cote p., mourato d., gongerich c., russell j. and haughton e.: immersed membrane filtration for the production of drinking water: case studies,_presented at iwsa, amsterdam, september 21-24, 1998 5. mourato d. and best g.: application of immersed microfiltration membranes for drinking water treatment, presented at the florida state a ww a conference, november 1998 6. mourato d., benson m. and parker e.: applications of immersed membranes in the drinking water and water reuse fields, submitted to the new zealand water & wastes association, september 23-25, 1998, auckland, new zealand 7. durham b., randles n., hideg m. and layson a.: 2640 mw power plant reuses sewage for feetiwater & eutrophic surface water feeds hungarian power plant, presented at powergen conference, budapest, hungmy, 1996 8. krain f., sakol d., zsirai i. and wawrzynczyk j.: from the cooling system to boiler, presented at ziad conference, poland, may 1998 page 77 page 78 page 79 page 80 page 81 hungarian journal of industry and chemistry vol. 53(2) pp. 31–35 (2025) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2025-14 upgrading potential of waste fermentation-based c4-c5c6 carboxylic acid mixtures using electrochemical oxidative decarboxylation tamás rózsenberszki1, katalin kucsera1, boglárka bocska1, gergely farkas2 and lászló koók1* 1 research group on bioengineering, membrane technology and energetics; university of pannonia; egyetem u. 10; veszprém; 8200; hungary 2 research group of organic synthesis and catalysis, university of pannonia, egyetem u. 10, veszprém, 8200, hungary electrochemical upgrading techniques could provide a powerful tool to complement biorefineries processing waste materials, thereby making progress towards the electrification of these platforms. among them, (non) -kolbe electrolysis, that is, electrochemically driven oxidative decarboxylation of carboxylic acids, plays a key role as its product palette consists of alkanes (kolbe products) as well as competing non-kolbe products, including shortchain alkenes, alcohols, esters, ketones and aldehydes. the formation of alkanes takes place via the dimerization of radicals after the decarboxylation of carboxylic acids and requires relatively high acid concentrations (> 0.5 m) and a high current (> 200 ma cm-2). in this work, the upgrading potential of vfa mixtures of c4-c5-c6 acids under conditions representing real waste-based fermentation effluents (lower vfa concentrations) and a suboptimal current density (100 ma cm -2) was investigated. in addition, the effect of the initial vfa concentration ratios and the operation time (faraday equivalents of fe = 0.25 and 1.0) on product selectivity and yields was studied. it was shown that mostly non-kolbe products were formed – namely alcohols, esters and smaller amounts of ketones – in both experiments. an extended operation time favored ester and ketone formation, while alkanes (octane, nonane and decane) were presumably produced at the beginning of the electrolysis, since the process duration did not influence their yields. in addition, since butyric acid – the compound with the highest concentration in both model solutions – participated mostly in alcohol and ester formation, no butyrate radical dimerization (resulting in hexane) was observed. the results indicate that by not concentrating the vfas in the fermentation ef fluents (via e.g. electrodialysis), the oxidative decarboxylation of vfas at low/moderate current densities will likely result in non-kolbe products. keywords: carboxylic acid, electrochemical upgrading, esters, kolbe electrolysis, liquid alkanes 1. introduction the electrification of biorefineries is a strategy with enormous potential to achieve efficient power-to-x for the utilization and (chemical) storage of excess renewable electricity. as a result, x can refer to various industrially interesting compounds such as hydrogen [1][3], methane [4], ammonia [5] as well as even food [6] and fuels [7]. state-of-the-art electro-biorefineries underline the importance of targeting components with high specific value since the main technological limits appear to be scaling up and productivity. therefore, specialty chemicals and fuel components are of particular interest. although examples of studies related to specialty chemicals (e.g. the enantioselective bioelectro-synthesis of chiral alcohols for the pharmaceutical industry) are found in the literature [8]-[9], this approach assumes the received: 13 may 2025; revised: 31 may 2025; accepted: 31 may 2025 *correspondence: kook.laszlo@mk.uni-pannon.hu use of pure (and often genetically engineered) cultures and specific reaction media / high process costs. meanwhile, valuable compounds can be produced by mixed culture systems based on organic waste such as volatile fatty acids (vfas) – referring to carboxylic acids containing 2-8 carbon atoms – via acidogenic dark fermentation (df) [10]. in most cases, ethanol or lactatedriven chain elongation during df facilitates the production of vfas up to caproic acid (c6). after separation, the market value of the obtained vfas is already remarkable, however, in a biorefinery platform, their upgrade to value-added chemicals is often considered via chemical, electrochemical and biological post-treatment processes. among them, electrochemical methods could be considered as drivers to demonstrate electrified biorefineries. the (bio)electrochemical reduction of vfas, for instance, could be used to obtain the respective alcohols [11]. another promising approach is the so-called kolbe https://doi.org/10.33927/hjic-2025-14 mailto:kook.laszlo@mk.uni-pannon.hu rózsenberszki, kucsera, bocska, farkas and koók hungarian journal of industry and chemistry 32 electrolysis, which involves anodic electrochemical decarboxylation. oxidation of the vfas leads to free radicals which, under suitable conditions, can dimerize to form linear alkanes with a carbon chain length of c(2n-2), where n denotes the number of carbon atoms of the vfa (for example, valeric acid, c5, results in octane, c8) [12]. on the one hand, kolbe electrolysis has several major advantages such as the spontaneous separation of the alkane-rich phase from the aqueous vfa solution or the formation of excess h2 at the cathode during electrolysis, thereby contributing to the hydrogen yield in addition to the df. on the other hand, besides the necessity of using a pt catalyst, several challenges limit the applicability of kolbe electrolysis, including selectivity issues (the utilization of free radicals in nonkolbe side reactions, e.g. alcohol, ester and ketone formation) as well as the requirement of usually high initial vfa concentrations (> 0.5 m) and current densities (> 200 ma cm-2) [13]. in this work, the liquid alkane production selectivity and efficiency of kolbe-electrolysis are investigated using model mixtures of c4, c5 and c6 vfas representing acid ratios in real acidogenic fermentations, i.e. under suboptimal conditions. in addition, the effect of the operation time (or supplied charge) on the product composition is addressed. 2. experimental 2.1. model vfa solutions mixtures of butyric (c4), valeric (c5) and caproic (c6) acid (merck, germany) were prepared by diluting with distilled water. the applied ratios of initial concentrations of c4:c5:c6 acids were 0.23:0.11:0.083 m and 0.40:0.04:0.077 m in experiments a and b, respectively, based on the experienced titer range of previous fermentations (data not shown). the ph of the solution was set in both cases at 7 using 5 m naoh. 2.2. kolbe electrolysis tests kolbe electrolysis was carried out in a 100 ml customized schott laboratory glass bottle reactor in experiment a containing 80 ml of a model vfa solution. in experiment b, the reaction took place in an 80 ml heart-shaped borosilicate glass reactor with ground-glass joints, enhancing how efficiently the produced gases were collected. the reaction media volume was 60 ml. the electrolysis was conducted using two pt plate electrodes with a surface area of 2 cm2 each. galvanostatic control was applied by using a keysight e3643a dc power supply (keysight, usa), ensuring a fixed current density of j = 100 ma cm-2. the reactors were connected to a 100 ml gas syringe by tygon tubing to measure gas evolution before the collected gaseous samples were transferred to 500 ml aluminum gas sampling bags. in experiment a, the operation time was limited by the transfer of charge of q = 1000 c, corresponding to t = 83 mins. in experiment b, the transferred charge was q = 4000 c corresponding to t = 333 mins. these values represent faradic equivalents of fe = 0.25 and 1.0, respectively, where fe represents the ratio of the charge required to achieve complete substrate conversion and the actual transferred charge. 2.3. extraction and analysis of the organic phase after electrolysis, the reaction media was transferred to a 250 ml glass separatory funnel before 40 and 30 ml of dichloromethane was added in experiments a and b, respectively. the mixture was then shaken vigorously and left to separate over 30 mins. after the bottom organic layer was removed, the procedure was repeated to ensure complete extraction was achieved. the collected extraction solution was analyzed via gas chromatography – mass spectrometry (gc-ms) using a shimadzu gcms-qp2010 se (shimadzu, japan) spectrometer with an aoc-20i auto-injector. the injector (split) temperature was 250 °c and he (6.0) was used as the carrier gas. an agilent j&w db-5ms column (agilent, usa) was applied. the heating program was set to 35 °c for 5 mins before being increased to 300 °c at a rate of 20 °c/min. 2.4. analysis of aqueous samples the vfa content of the aqueous phase after the electrolysis was determined via gc using a shimadzu gc-2014 gas chromatograph (shimadzu corporation, japan) with a flame ionization detector. injection port and detector temperatures were 240 and 250 °c, respectively. the length and inner diameter of the db-ffap column were 10 m and 0.53 mm, respectively, with a film thickness of 1 m. the column temperature was initially 50 °c over 2 mins before gradually being increased to 200 °c at a rate of 40 °c/min and maintained at 200°c for 2 mins. this device was equipped with an aoc-20i auto-sampler and n2 was used as the carrier gas. 2.5. calculations the transferred charge was calculated according to the following equation, considering the applied current iappl and the reaction time: 𝑄 = 𝐼𝑎𝑝𝑝𝑙 ∙ 𝑡 (1). the acid conversion (vfa) and yield of product i (yi) were determined based on the initial (nvfa,in) and final (nvfa,fin) amount of vfa as well as the amount of dimer produced (ndimer) according to the equations below: 𝜇𝑉𝐹𝐴 = 100 × (𝑛𝑉𝐹𝐴,𝑖𝑛−𝑛𝑉𝐹𝐴,𝑓𝑖𝑛) 𝑛𝑉𝐹𝐴,𝑖𝑛 (2), 𝑌𝑖 = 100 × 𝑧 × 𝑛𝑖 (𝑛𝑉𝐹𝐴,𝑖𝑛−𝑛𝑉𝐹𝐴,𝑓𝑖𝑛) (3). electro-upgrading of carboxylic acids from waste fermentation 53(2) pp. 31–35 (2025) 33 where z denotes the ratio of product to vfa molecules (z = 1 for alcohols, ketones, aldehydes and alkenes but z = 2 for alkanes and esters). 3. results and discussion 3.1. vfa conversion efficiency the relatively short operation time (fe = 0.25) applied in the first experiment (a) is indicative of a limited degree of vfa conversion. from the results presented in figure 1, it can be seen that the degree of conversion was indeed limited. the lowest value was obtained for butyrate (c4 = 19.3%), which was expected being the dominant component of the model solution and corresponds with nc4 = 3.56 mmol. meanwhile, c5 and c6 acids yielded c5 = 24.1% (nc5 = 1.70 mmol) and c6 = 28.5% (nc6 = 1.28 mmol), respectively. experiment b (fe = 1.0) aimed to provide insights into rather suboptimal conditions for kolbe electrolysis in terms of concentrations of vfas – especially c5 and c6 acids – significantly lower than recommended in the literature. nevertheless, such conditions represent potential compositions of real dark fermentation effluent without taking into consideration concentrating the acid content (e.g. by selective extraction or electrodialysis). as for the conversion of vfas during electrolysis when fe = 1.0, high values were expected thanks to the longer operation time and lower concentrations. indeed, conversions of c4, c5 and c6 vfas up to 35.4, 70.1 and 72.4% could be achieved, respectively (figure 1). the corresponding amounts were nc4 = 8.48, nc5 = 1.68 and nc6 = 3.34 mmol. it could be observed from the results that absolute vfa conversion is proportional to the initial vfa concentrations in both cases. this shows that the electrolysis showed no notable degree of selectivity towards particular carboxylic acids. therefore, electrooxidative decarboxylation takes place independently and in parallel for each vfa. accordingly, the product composition can be estimated from the initial vfa content when the product selectivity of a certain vfa is known. this aspect is discussed in the next section. 3.2. product selectivity and yields kolbe electrolysis results in alkanes after the dimerization of decarboxylation-originated c(n-1) radicals. however, the competing processes, namely the synthesis of non-kolbe products, may significantly reduce dimer selectivity. predominantly, alcohols as well as esters (via the reactions between alcohols and present carboxylic acids) form but aldehydes, ketones and shortchained alkenes can also be produced. moreover, o2 evolution on the anode is a known competing reaction. overall, more hydrophobic vfas, higher vfa concentrations and higher current densities promote the formation of the kolbe product. in contrast, the present experimental setups focus on the composition of real waste-based dark fermentation effluents and intentionally investigate the process efficiency at lower current densities compared to in the literature. as for the results for the tests when fe = 0.25 and 1.0, a fairly consistent product composition could be observed. firstly, in the case of experiment a, almost 70% of the electrolysis products were identified as alcohols (figure 2). esters and alkanes accounted for 11.7 and 3.3%, respectively, moreover, a notable amount of ketones (7.0%) was identified in addition to minor components. similarly, when fe = 1.0, alcohols were the dominant products accounting for 52.8%, while esters, alkanes and ketones accounted for 18.0, 3.4 and 17.8%, respectively (figure 2). it could be observed that alcohol production was predominant and, consequently, in the presence of excess carboxylic acids, considerable amounts of esters were formed, which was also observed when fe = 1.0 implying that, over time, the formation of esters exceeds the accumulation of alcohols. similarly, the amount of generated ketones rose significantly as the operation time lengthened. meanwhile, the final ratio of alkanes in the product mixture was nearly equal in both experiments regardless of the electrolysis duration suggesting that under the applied conditions, kolbe-product formation figure 1: conversion values of butyrate, valerate and caproate when fe = 0.25 and 1.0 figure 2: final product composition in terms of main compound groups when fe = 0.25 and 1.0 rózsenberszki, kucsera, bocska, farkas and koók hungarian journal of industry and chemistry 34 presumably occurs in the early phase of electrolysis and probably becomes suppressed as the non-kolbe reactions proceed. this aspect, however, should be confirmed by follow-up experiments with more frequent sampling of the reaction media during the operation time. it is also important to mention that aldehyde formation was observed only in traces, while short-chain alkanes and alkenes were not detected in the samples. to further evaluate product formation, the specific component yields are presented in figure 3. considering the alcohols, the most significant difference is that when fe = 0.25, a high yield of propan-2-ol (or isopropanol) was observed, while when fe = 1.0, this compound was not observed. it can be argued that thanks to the longer reaction time, propan-2-ol is completely consumed as a result of esterification. according to figure 3, such a phenomenon may be supported by the fact that yields for butyric, valeric and caproic acid isopropyl ester were higher when fe = 1.0. in contrast, butan-2-ol (or secbutanol) seems to accumulate over extended operation times. moreover, it could also be observed that 2-butyl esters form only with butyric acid, i.e. butan-2-ol, does not present strong ester-forming reactivity. a similar trend was recorded for butan-2-on, which also accumulates over longer operation times of electrolysis. as for the alkanes, mostly octane, nonane and decane could be obtained with yields of 1.67, 0.64 and 1.06% when fe = 0.25 as well as 1.64, 0.60 and 1.70% when fe = 1.0, respectively. thus, a longer process time was beneficial with regard to dimer formation from caproic acid radicals. octane, the dimer of valeric acid radicals, was not significantly influenced by fe nor nonane. this latter compound, formed by the coupling of a valeric and a caproic acid radical, is the only heterodimer produced observed in detectable amounts. besides, it could also be concluded that c3 radicals from butyric acid decarboxylation presumably do not form homonor heterodimers as no hexane nor heptane could be found in the organic phase. this is also in line with the lower conversion rate of butyric acid as well as the higher amounts of propan-2-ol and isopropyl/n-propyl esters. waste-based acidogenic fermentations with sufficient chain elongation usually result in an effluent particularly rich in c4 and c6 vfas with varying c5 content (in addition to c2 acetic and c3 propionic acids). in the light of the presented results, it can be stated that at a low current density and moderate/low initial vfa concentration, kolbe-product formation is significantly suppressed by mostly alcohol and ester production. 4. conclusions in this work, the upgrading potential of c4-c6 vfas via electrochemical oxidative decarboxylation was investigated with model solutions representing the common concentrations of these compounds in wastebased acidogenic fermentation effluents. it was shown that effective vfa conversion can be achieved as a function of the operation time (and fe). under the applied conditions – low/moderate current density, low vfa concentrations – predominantly non-kolbe products formed, i.e. alcohols and a wide range of esters, as well as ketones. kolbe dimers were formed with yields of only 3.3% and 3.4% for fe = 0.25 and fe = 1.0, respectively, consisting mainly of octane, nonane and decane. it could be assumed that butyric acid-derived radicals never or seldomly formed dimers. an extended operation time favored ester and ketone formation. further research should address the time course of product formation to provide a more detailed picture of the competing processes. acknowledgements this research was funded within the framework of project rrf-2.3.1-21-2022-00014 of the national multidisciplinary laboratory for climate change by the government of hungary and supported by the 20242.1.1-eköp university research fellowship program of the ministry of culture and innovation financed by the national research, development and innovation fund. references [1] robinius, m.; raje, t.; nykamp, s.; rott, t.; müller, m.; grube, t.; katzenbach, b.; küppers, s.; stolten, d.: power-to-gas: electrolyzers as an alternative to network expansion – an example from a distribution system operator, appl. energy, 2018, 210, 182–197, doi: 10.1016/j.apenergy.2017.10.117 figure 3: yields of the identified components in the organic sample phase 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https://doi.org/10.33927/hjic-2024-19 https://doi.org/10.33927/hjic-2024-19 https://doi.org/10.1016/j.rser.2017.08.004 https://doi.org/10.1016/j.ijhydene.2018.06.121 https://doi.org/10.1007/s11367-020-01771-3 https://doi.org/10.1016/j.fuel.2017.05.061 https://doi.org/10.1002/cssc.201900413 https://doi.org/10.1002/cssc.201903428 https://doi.org/10.1016/j.jenvman.2023.119379 https://doi.org/10.1021/acs.energyfuels.8b04215 https://doi.org/10.1039/c9gc03264a https://doi.org/10.1002/cssc.202201426 https://doi.org/10.1002/cssc.202201426 hungarian journal of industry and chemistry vol. 52(2) pp.29–34 (2024) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2024-16 evaluation of experiences over the eight-year-long operation of the ultrafilter setup constructed for the protection of drinking water in miskolc lilla hárs1*, gábor rácz1, gábor lakner1, józsef lakner2 and nándor nemestóthy3 1 hidrofilt ltd., magyar u. 191, nagykanizsa, 8800, hungary 2 óbuda university alba regia technical faculty, budai u. 45, székesfehérvár, 8000, hungary 3 research group on bioengineering, membrane technology and energetics, university of pannonia, egyetem u. 10, veszprém, 8200, hungary as a result of careful, persistent work over several years, since the successful technical handover in september 2015, the new water treatment plant is one of the most powerful ultrafiltration drinking water purifiers in central europe and continuously ensures high-quality drinking water for the population. not only was the construction of the water treatment plant essential for the safe supply of drinking water to the city, it is also capable of solving regional water supply problems in the event of a disaster, as the last eight years of its operation have demonstrated. our present study is intended to summarize the most important operating experiences since the technical handover in september 2015. keywords: ultrafiltration, drinking water, karst water 1. introduction the waterworks on average meets more than half of the water demand required by the city of miskolc and has been continuously operating since 1913. over the second half of the last century, anthropogenic pollution has become significant. in the event of water pollution caused by raw sewage above the acceptable limit (in the absence of water purification technology), the operator often had to stop producing water. the main cause of the emerging problems is the increase in turbidity and microbiological contamination of karst springs on the surface of the land after periods of rainfall. since the technology of ultrafiltration provides a suitable and safe solution to the problems that arise, in 2013, after the conclusion of the construction tender, the winning mi-du-hi consortium (duna aszfalt ltd., hidrofilt ltd.) was able to start constructing a new water purification plant, which was successfully handed over in september 2015. karst aquifers are an important supply of freshwater for about 25% of the world’s population. the preservation of chemically safe karst water should be of paramount importance to protect human health. because of the peculiar geographical and hydrogeological circumstances of karst regions, this water is vulnerable to pollution from human activities and the effects of climate change, e.g. steadily decreasing average annual received: 18 june 2024; revised: 27 june 2024; accepted: 28 june 2024 *correspondence: hars.l@hidrofilt.hu precipitation and global warming [1]-[5]. water infiltrating the aquifer may originate from precipitation (rain and/or snow) in the karst region itself (diffuse infiltration; autogenic recharge) or accumulate in adjacent regions before flowing into the karst as sinking streams (concentrated, point infiltration; allogenic recharge). underground, it flows fast through large openings, for instance, caves or conduits (turbulent flow). alternatively, it can also move slowly through small and narrow openings in low-permeability zones (laminar flow) [6]-[7]. filtration processes through membranes are increasingly used as alternatives for treating freshwater and wastewater in the anticipation of more stringent quality standards [8]-[11]. however, meeting the quality standards of drinking water using conventional water treatment processes has become increasingly challenging because of the discharge of various organic chemicals and heavy metals into water bodies. the problem is induced by rapid industrialization, urbanization and population growth, which gradually deteriorate surface water quality, affect drinking water security and increase the treatment costs of drinking water [12]. in developing countries, drinking water production is potentially a very large market for ultrafiltration (uf) membranes. given that one of the most critical problems is the lack of drinking water, people in these regions are supplied with surface water which contains a significant number of https://doi.org/10.33927/hjic-2024-16 mailto:hars.l@hidrofilt.hu hárs, rácz, g. lakner, j. lakner and nemestóthy hungarian journal of industry and chemistry 30 microorganisms that can cause several diseases. globally, the application of uf technology is increasing with regard to drinking water treatment, with an estimated market value projected to reach $2.14 billion in 2023 [13]. filtration processes in the treatment of surface water are the fastest developing application of membrane technology [14]-[17]. uf uses low-pressure membranes with pore sizes of between 0.001 and 0.1 µm [18] as well as pore diameters from 1,000 to 100,000 da [19]-[20]. uf membranes are physical barriers which are able to efficiently remove suspended particles, bacteria, colloids, algae, parasites and viruses as well as prevent turbidity for purification and disinfection purposes. uf technology has many advantages such as the superior quality of treated water, its compact system, easy operation and maintenance, lack of chemicals as well as the minimal production of sludge [11],[12],[14],[21]. although uf is a promising technology for water and wastewater treatment, it has many significant disadvantages, e.g. membrane fouling and the insufficient removal of soluble contaminants [20]. membrane fouling refers to the accumulation of particulates and colloids, dissolved organic and inorganic matter as well as microorganisms on the membrane surface and within the membrane pores, resulting in the reduction in its permeability. consequently, membranes must be cleaned periodically to reduce membrane fouling [19],[22]-[25]. the objectives of this study were to evaluate uf performance in terms of permeability and the quality of treated water as well as present the most important operating experiences. 2. brief introduction to the water treatment system by modernizing the existing waterworks, an ultrafiltration capacity of 1,500 m3/h was realized with two 500 m3 outdoor filtered water storage tanks. the role of ultrafiltration technology during water treatment is to reduce the content of suspended matter and microbiological pollutants in the water, i.e. to remove colloids, bacteria, viruses and protozoa as well as macromolecules with a molecular weight greater than 100 kda. during the operation, the dissolved salts and water molecules flow over the surface of the uf membrane before the purified water, after being disinfected, is sent to the surface tanks then into the network. the technical parameters of the equipment are shown in table 1. 2.1. feedwater the feedwater for the uf membrane is karst water from caves. the raw water is first sent to the pre-filter unit to ensure its safe. here, impurities larger than 300 µm are filtered out. 2.2. ultrafiltration process during water production by ultrafiltration, the well pumps provide the pressure and flow rate necessary for the treatment process during which the resulting filtrate is sent to the clean water storage tank with a nominal flow rate of 198 m3/h per unit. in order to optimize the degree of stress on the membrane, all processes involving liquid flow (backwashing, rinsing, water production, etc.) are carried out alternately from below and above. the uf modules are cleaned immediately based on a timed program or when the tmp (trans membrane pressure) of the filtrate increases (during backwashing). the backwashed water is supplied per device at a flow rate of 600 m3/h as well as at a pressure of 2.5 bars. the typical operating parameters of the equipment are shown in tables 2 and 3. table 1: the most important technical parameters of the ultrafiltration equipment characteristics of the uf equipment values quantity of modules 8 units; 40 modules/unit, i.e. a total of 320 modules total membrane surface 19 200 m2 module type inge dizzer xl 0.9 mb 60 t-rack pore size 0.02 µm membrane material pesm membrane surface/module 60 m2 table 2: main operating parameters (during normal operation) characteristics of the uf equipment values gross flux, l/m2/h 82.5 net flux, l/m2/h 78.1 yield, % 96.5 filtering time, min 80 backwash duration, s 50 forward flush duration, s 0 acid ceb frequency, h 168 base ced frequency, h 168 naocl ced frequency, h 168 table 3: main forms of chemical cleaning base acid naclo solution backwashing, s 50 50 50 chemical injection, s 60 60 60 soaking, min 15 15 0 chemical leaching, s 60 60 60 evaluation of the eight-year-long operation of the ultrafilter setup 52(2) pp. 29–34 (2024) 31 2.3. data querying/service the variable parameters (temperature, flow rate, pressure, turbidity) were measured in real time by a data transmission device. each variable was queried with millisecond precision. when multiple values were measured within a millisecond, the highest value was recorded. these values were then converted into daily datasets for each variable. only values greater or equal to 10 were considered during this conversion process which were averaged to determine the daily values. the permeability values were determined individually for the 8 uf units on a daily basis. for easier handling, they were converted into average annual permeability values. the operational values over the past 8 years were analyzed. 3. results and analysis 3.1. measurements between 2016 and 2023, the following parameters were determined on a daily basis (i = 1, 2, ..., 365 denotes the day number): turbidity (zi) from which the daily load (wi) was calculated, daily precipitation (qi), average daily permeability (pi) over 8 measurements, average daily water production and total annual water production. the summarized annual results are presented in table 4. it should be noted that between 2016 and 2018, no significant maintenance was performed. in 2019, the system was optimized and has been regularly maintained ever since. linear regression analysis using excel was employed to determine the correlation between the measured values and their corresponding functions: 𝑦 = 𝛼 ∙ 𝑥 + 𝛽 (1). in addition to determining the parameters, the regression coefficient 𝑟2 was calculated. 𝑟2=1 indicates a perfect correlation, while 𝑟2=0 suggests no correlation. the actual values typically fell between 0 and 1 with values closer to 1 indicating a stronger correlation. deciding when data are considered to be correlated is a matter of definition (typically a significant correlation is when 𝑟2>0.8). 3.2. changes in average annual permeability the average annual permeability was calculated using the following relation: �̅� = 𝑝0 + 1 365 ∑ 𝑝𝑖 365 𝑖=1 (2), where i refers to the day number of the year for the nth year �̅� = 𝑝𝑛̅̅ ̅. when the sample sizes are small, the correlation depends not only on 𝑟2 but also on the degrees of freedom (f), which is determined by the sample size (n), e.g. when n=2, 𝑟2=1. this relationship can be expressed as follows: 𝑡𝑓 ≡ √𝑓 𝑟 √1−𝑟2 (3). in the case of linear regression, 𝑓 = 𝑛 − 2, following a student's t-distribution. from this t-table, the critical value t95 corresponding to the given probability level and degrees of freedom was determined. if tf > t95, then the function can be approximated by a straight line when the confidence level is equal to 95%. the change in the average annual permeability between 2016 and 2023 is shown in figure 1. for the correlation line fitted over the entire range, 𝑟2=0.1902, indicating no significant correlation between permeability and time in years. in 2019, the system was optimized, resulting in an increase in permeability. if the operational periods are divided into two intervals, namely 2016–2018 and table 4: annual data regarding the measured parameters between 2016 and 2023 year annual precipitation (q) (mm) average turbidity of raw water (z) (ntu) average permeability (p) (l/m2/h/bar) average load (w) (kg/day) average water production (m3/day) annual water production (m3/year) 2016 874 1.35 304 22.28 16 482 5 557 067 2017 773 1.42 239 26.70 18 795 6 860 189 2018 608 2.52 191 49.24 19 527 7 107 900 2019 687 0.79 267 17.27 21 963 7 533 300 2020 703 1.18 327 22.22 18 898 6 916 680 2021 663 1.35 327 28.03 20 838 7 606 020 2022 588 1.66 304 42.87 25 880 9 446 240 2023 699 2.71 291 54.16 20 023 5 286 010 hárs, rácz, g. lakner, j. lakner and nemestóthy hungarian journal of industry and chemistry 32 2020–2023 representing periods during which maintenance was not (before period) and was carried out (after period), respectively, and separate lines are fitted to the data series for each interval, we obtain the followings: 𝑝𝑏𝑒𝑓𝑜𝑟𝑒̅̅ ̅̅ ̅̅ ̅̅ ̅ ≡ 310 − 57.0 ∙ 𝑡 (4), 𝑝𝑎𝑓𝑡𝑒𝑟̅̅ ̅̅ ̅̅ ̅̅ ≡ 330 − 13.1 ∙ (𝑡 − 4) (5), where p represents the permeability and t denotes the number of years since 2016. in this case, segment-wise correlations show strong results: • before maintenance, 𝑟2=0.9916 and according to equation 3, 𝑡𝑓=10.8 > t95=6.31, • after maintenance, 𝑟2=0.9683 and 𝑡𝑓=7.81> t95=2.92. therefore, both relationships can be considered linear at a confidence level of 95%, as shown in figure 1. in both cases, permeability decreases, however, the rate of decrease before renovation is more than four times that after renovation. due to regular maintenance and backwashing following renovation, permeability increased, resulting in a slower rate of decrease compared to the period during which maintenance was not carried out. the annual decreases are consistent with the similar annual results obtained, although the ratio is slightly higher in the latter but not significantly. from the two periods (poorly maintained and well maintained), one year was selected for each to examine the daily permeability. permeability was measured simultaneously through the 8 units and the averages of these measurements are shown in figures 2 and 3. in 2017, the decrease in average daily permeability was 32%. in 2023, the decrease in average daily permeability was 6%. 3.3. optimization in 2019 up until 2019, the uf units only underwent warranty repairs. in this year, permeability decreased, prompting maintenance to be carried out. the trends in permeability in 2019 are shown in figure 4. maintenance revealed that the system was improperly optimized. changes to the control program, ceb (chemical enhanced backwash) frequency and the chemical settings were required. the cip (cleaning in place) of the 8 uf units was completed. during the integrity test, 20 damaged uf modules were replaced. the period during which the optimization took place is marked in figure 4. figure 1: the change in average annual permeability between 2016 and 2023 figure 2: average daily permeability as a function of time in the year 2017 (the dots represent the measured values and the dashed line denotes the fitted regression line.) figure 3: average daily permeability as a function of time in the year 2023 (the dots represent the measured values and the dashed line denotes the fitted regression line.) figure 4: average daily permeability as a function of time in the year 2019 with the optimization period marked evaluation of the eight-year-long operation of the ultrafilter setup 52(2) pp. 29–34 (2024) 33 4. conclusions it can be concluded that if the system had not been optimized in 2019, the permeability would have dropped to almost zero by 2021, indicating that the maintenance of systems during the warranty period is crucial. every system is different, moreover, their optimization and regular professional supervision are very important to help prevent membranes from failing as well as ensure the long-term operational functioning of the system without clogging and flux reduction. in order to correlate the available data, it was important to separate it. further ongoing analyses of the available data need to be performed to clarify the relationships. acknowledgements the authors are grateful for the experimental support provided by ferenc horváth (chief engineer at local waterworks). references [1] shi, j.; jiang, g.; sun, z.; liu, f.; wang, q.: the migration and transformation processes of dissolved organic matter in rainwaterdrip waterphreatic water of a typical karst 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pollution prevention; rnedicina introduction our life is getting even better with the new improvements industries give us. we use the latest achievements in our ordinary life. but even the latest developments bring up new problems. the technological progr~~s made a new concept that does not existed in the nature; the pollution. pollution has different forms (e.g. gas, solid), and could occur almost anywhere (e.g. as a local emission, or regional toxic fume). these emissions are poisoning our life, so we must find their sources. mostly these sources are connected to a factory from the chemical or oil-industry. it is easy to analyse the financial condition of the factory, only we have to audit its financial balance. and when we want to know about its technology. we check their manufacturing standards. but when we want to know its environmental performance we are faced with the problem that this performance mainly depends on the person who is telling it to us. environment (and its quality) means a bit different to different persons. those who lives in a large city are less sensitive to air pollution, than a villager, because they are used to it the point is that the quality of the environment depends on who is talking about it. there are numerous tools which are trying to describe the environment using some kind of standards [1-6). different environmental tools it could be so simple if it were onlyone assessment method to evaluate the environmental burdens, but as we can see in table i. there are a lot more assessment methods in the wild. we do not want to discuss about these tools except for the last one. life-cycle assessment is an evolving management approach for reducing the impact of a product, package, or activity upon human health and the environment. it examines each stage of the life span through productit)n or construction, distribution, use, support and disposal or recycling. 54 table i the different environmental tools goal name environmental impact assessment identifies the environmental effects of one economic activity, usually at one specific location, and at one point in time only. eia is used as an aid to public decision making on larger projects, both public and private. risk assessment analysis the low probability of highly undesirable effects. this type of analysis is characterised by a probabilistic approach. . physical input-output analysis and materials balance methods form a set of related tools for analysis substance flow analysis in which the flows and accumulations of substances are studied. technology assessment environmental audit the assessment of the impacts of the introduction of new technology. a tool, which can establish that the operations of industrial facilities comply with a standard, or may be used, focused on opportunities for cleaner products and processes. sustainable process index life-cycle assessment analysing the environmental affects with some basic rules, numbers. still in developing stage. identify and analyse the environmental affects of a given product, process. iso 14040 define its rules. i. impact assessment 3. improvement assessment • to protect the humap. health, • to protect the nature, • 2. inventory database • material and non-materials, • production, • using, • waste-management. fig i brief framework of life-cycle assessment the brief framework of lca (fig.l) shows us the main stages of the assessment. when we make an lca, first we need to define the purpose of the analysis. than we should collect the necessary data, data are stored in the inventory database. the impact assessment step uses the inventory database. the environmental effects of the given production, product are calculated this time. the final stage is the report making, in addition to the improvement assessment. lca (and any other technique) is only worth using if it gives not just the facts about the process, but gives advice, guideline to improve the process. at this time lca is not capable for that, but with other pollution prevention tools it could be capable. for example, in the chemical industry there are a lot of dangerous chemicals. when they are handled incorrectly, they poiiute the environment. lca describes this effect with some important environmental component. in europe the eco-lndicator method {made by the dutch pre consultant) is used widely when we talk about environmental components. in the eco­ indicator method there are i i environmental components. those are the following: greenhouse effect {mainly connected to c02, ch4, cfc's, etc.)~ ozone layer depletion (e.g. cfc's); acidification (e.g. sox, nox); eutrophication (e.g. cod, nox, phosphate); heavy metals (e.g. cd, ba, hg); smog (summer and winter smog); pesticides (e.g. fungicides, herbicides); energy; soil. fig.2 shows the method to convert the given data to an indicator value; as pre consultant called ecopoints. most of the life-cycle assessment tools use this eco­ pointing method. the impact analysis can be done manually or by a computer-aided method. so if we change the pointing method, we get different results. in fig.2, we can see how we get the result with the eco-indicator 95 from the impact of the different environmental parameters (such as cfc, heavy metals, dust, etc.). the last step before we get the result from the damage is the valuation. the effects of the elements are well known (for example from laboratory tests), but the valuation is where the science has to develop, because, for example, the importance of a pollutant is changing with the development of science, reveals new aspects. nowadays experts use software to evaluate the different environmental load of a given product, or activity. many lca software (like simapro4, which can be used for industrial analysis) use theeco-indicator 95. as we can see, this method does not care about pollution prevention, it is just identifies, than analyses the given data. 55 impact effect damage valuation fig.2 weighting method for environmental effects [2] mpt ozone w.tmog •·•11109 pesticid enerw sefid •'carbinol .magnesii.rmignots .tetrahf ometiijodid2 l!idmpc -;:-l£1:;=:,"':....d'"""."ib7"enzs_zu_be_ro,n_-:-::--;~·:::;...,be:,..nz:::e:.::ne:.__-::---=·~n:.:.;h:.::4c::;_i ___ ~j11::::.:;el::::h"::;"o:::_f ___ ~·.e_fect_rici!_·y_h_ung_arj ____ _ ana!yse 1 kg processing 'carbinol'; method: simapro 3.0 eco·indicator 95/ europe gievaluation fig.3 the base state of the chemical process pollution prevention tools in the following i will introduce how can we use the idea of a pollution prevention tool came from the ?hemical industry. they wanted to fmd a technique to tmprove the production, because waste can be valuable. if they could reduce the waste, the profit gets higher. here are some pollution prevention tools which can be usable in the chemical processes: cpas (clean process advisory systems) data are stored in database, uses modules to analyse the process, it has module for the separation, the cleaning, the waste-reduction, etc. processes war (waste reduction) algorithm with a simulation tries to find which process has lower pollution index men (mass exchange network) it tries to improve the mass exchange in the process ear (environmentally acceptable reactions) its goal is to find another ways of chemical reactions with simulation, the specialist then will choose from them p arls (program for assisting the replacement of industrial solvents) tries to find other solvent for the chemical process, with the help of chemical and physical-chemical rules both lca and pollution prevention tools to improve the environmental performance. the project first make a process. we will discuss about a chemical reaction, which uses ethanol, dibenzsuberon, methyl­ iodide, tetrahydrofuran, magnesium, dimethyl-amino­ propyl-chloride. from these sources the product will be carbinol. the process uses a vast amount of benzene, as a solvent. first let us see the lca results for this production (fig.3). in fig.3, we show higher and lower bars, and the eleven (previously mentioned) environmental components. in this case, the higher value means higher impact on the environment (more pollution), the lower means smaller impacts. the highest impact is at the acidification, so what lca says at the first look at, is that this process harms the environment with gases, and liquids that cause acidification in the soil. the..<>e chemicals are e.g. sox, nox, ammonia, hcl, hf, etc. (the eco-indicatnr method define them). next we can see that greenhouse 56 mpt 15 carbinol magnesium t etrahf iilnots .gceenh. .ozone .acidif. owtroph. ill h. metals .energy !qcaccin. llll!w.smog ••. smog ]llpesticid ••olid --------------!\~~;;]kg pc;;,:;;,.,ing 'ca;b];;ol'; m;i~d: simapro 3:[) e co-indicator 95le;:,ope g .i indicator fig.4 the indicator figure of the base state mp<. 0 0 greenh. -ozone acidil. eutroph. hmetals carcin. w.smog .,.smog pesocid energy fig.5 result with toluene is the second (with 6.72 millecopoint), summer smog is the third, etc. there is another figure, which gives us the same numbers but in a different view. that is called the indicator figure (fig.4). in fig.4, the chemicals are shown arranged horizontally, processes (as we defined during the analysis). from this picture we can easily pick up the best/worst chemical. in our case this is benzene. what should we do to improve the environmental performance? use a pollution prevention tool. phase!. we have problem with the solvent. the paris algorithm tries to find a better solvent for us. the algorithm calculates the chemical, physical-chemical attributes for benzene, and from its database tries to find an alternative solvent. for benzene in our case, toluene or c-hexane could be this one. we have a new solvent, but will this new one improve the process's environmental performance. paris could not tell this, we should use once again life-cycle assessment. we should run the analysis, we have to change from benzene to toluene. fig.5 shows the new results if toluene was used. the result looks better. acidification had 14.2 mpt at the base state, now he bas 13.7 mpt. this is 3% decrease. greenhouse had 6.72 mpt, now only 6.05. this is almost 10% decrease. every environmental component has lower numbers, than before. the percent of decrease depends on how big the benzene influence on the given component. we should see the indicator figure (fig.6), too. mpt. 12,5 7.5 q,l._~--+ carbin<>! t91uene .greenh, . lllcorcin. .so]d ••cidif. .s.smog 57 nh4ci ethanol electdcity hungary oeutroph. lllh.metals ill pesticid • energy :--.,analyse 1 kg processing 'carbinolto!u~j;i;•; method: simapro<lo ecq-indicolor 95/ etirope g/ indici(ltor fig.6 the indicator figure with toluene 0 0 :greenh.. ozone acidif. eulroph. ltmetals carcin. w.smog s.smog pes\icid energy solid .carbinol toluene !ii.dibenzszuberon ··toluene .ma!;]nesium ignois .!91uene ometiijod"ld2 fllethanol iiidmpc .eiectdcity hungary analyse l ~g jjlocessir)g 'catbinoiloiuene'; .method: simapro 3.0 eco-indic~lor.95/ europe ll i ev.>luation • fig.7 results with reused toluene we changed only the solvent, so changes in any other chemical mean trouble. luckily, only the values of the solvent have changed. from 13.9 mpt to 12 mpt (-13%). this means that paris calculated well, and we reach our goal; to improve the environmental performance. for the total impact this change causes only 5% decrease. phase ii. we changed the solvent, what else can be done? change the process. the easiest way is to reuse some chemicals. with the help of a simulation we got to know that toluene can be separated from the others. if we separate the solvent, we could recycle it in the process. the simulation was made with aspen by j. redei (3]. the simulation says that 90% of toluene can be separated, so only 10% of the total amount should be fresh toluene. let us run an analysis with recycled toluene. this figure is similar to fig.s, but here are some negative numbers. these numbers show us how much can be earned with the recycling. the numb~rs can be added, to get the actual result. in our case winter smog has only 3.61mpt (4.67-1.06). with the help of recycling the greenhouse effect decreased by 54%! acidification decreased by 23%. at the indicator figure (fig.8) we can see that only toluene gets negative number. this is logical, because only toluene was reused. the improvement of the total environmental performance is 30%. with a few tools we were able to achieve a high change in the environmental performance of the process. 58 mpt carbinol 'liagnesiurt t etrahf metiljodid dmpc jellzszubet toluene nh4ci ethanol electric'~y toluene ignots 2 hungary iijgreenh. iij<lzone lllacidif. oeutropb. ill h:mefals. ill energy glcarcin. llw.smog lllumog ll!pesticid ill solid analyse tkq'pr-;;-c-;.ssing 'carbinol toluene'; method: simapio 3.0 eco·iridicator 95/· europe g .i indicator fig.8 indicator figure with reused toluene conclusion life-cycle assessment is an evolving management approach for reducing the impact of a product, package, or activity upon human health and the environment. it examines each stage of the life span through production or construction, distribution, use, support and disposal or recycling. lca (and any other te~hnique) is only worth using if it gives not just the facts about the process, but gives advice, guideline to improve the process. at this time lca is not capable for that, but with other pollution prevention tools it could be capable. in this presentation we did see that the life-cycle assessment shows the results of the given process in an easy way, and with the help of pollution prevention tools the differences show up. in this case we decreased the total environmental burdens by 13% in the first step. but in the second stage, with the help of reusing this value got up to 30%. this means that with just two kinds of technique the values change a lot, so we have to search for other tools, to protect our environment. references 1. iso 14040. environmental management ufe cycle assessment principles and framework, the international organization for standardization, 1997 2. isoifdis 14041. environmental management life cycle assessment goal and scope definition and inventory analysis, the international organization for standardization, geneve, 1998 3. iso/cd 14042.3. environmental management life cycle assessment life cycle impact assessment, the international organization for standardization, geneve, 1998. 4. iso/cd 14043.3. environmental management life cycle assessment life cycle interpretation, the international organization for standardization, geneve, 1998. 5. vjzi sz., tamaska l., herner k.: using life-cycle assessment, 6th roundtable on cleaner production, budapest, hungary, 1999 6. weidema b.; environmental assessment of products, a textbook on life cycle assessment, the finnish association of graduate engineers, helsinki, 1997 7. goedkoop m., demmers m. and collignon m.: the eco-indicator 95, pre consultant, 1996 8. redel j.: lca for the pharmaceutical product, msc thesis, veszprem. 2000 (in hungarian) page 59 page 60 page 61 page 62 page 63 page 64 hungarian journal of industry and chemistry vol. 50(2) pp. 1–6 (2022) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2022-10 separation of fumaric and maleic acid crystals from the industrial wastewater of maleic anhydride production edisa papraćanin1, abdel đozić2, ermin mujkić3, maida hodžić3, irma hodžić1, belmin poljić1 and ajla ramić1 1department of chemical engineering, faculty of technology, university of tuzla, urfeta vejzagića br. 8, 75000 tuzla, bosnia and herzegovina 2department of environmental engineering, faculty of technology, university of tuzla, urfeta vejzagića br. 8, 75000 tuzla, bosnia and herzegovina 3global ispat coke industry, željeznička 1, 75300 lukavac, bosnia and herzegovina in this research, a physicochemical analysis of the industrial wastewater from a factory that produces maleic anhydride was performed. based on the conducted analysis (ph, electrical conductivity, density of the liquid phase, boiling point of the waste suspension, chemical as well as biological oxygen demand, and dry matter), it can be concluded that the waste stream obtained at the outlet pipe from the plant resulting from the production of maleic anhydride requires appropriate treatments. some of the parameters measured, e.g. ph (0.97±0.06), boiling point (106.8±1.3°c) and acidity, indicate the presence of organic acids such as fumaric and maleic acid s, which are formed during the production of maleic anhydride. the possibility of extracting crystals by adding urea and thiourea followed by forced cooling in a heat exchanger was investigated. the most effective method was the addition of thiourea when the most significant amount of crystals was obtained, namely 17.29 wt%. the addition of thiourea in combination with forced cooling greatly facilitates the process of separating the solid and liquid phases of the waste suspension, which could later be adequately treated by physical, chemical or biological methods. keywords: man production, separation, thiourea, cooling, wastewater 1. introduction since the chemical industry and the waste streams generated during chemical production have a harmful effect on the environment, it is necessary to minimize their harmful impact before releasing them into the environment and comply with legal regulations, both locally and globally. moreover, it is important to conduct environmental impact assessments and environmental management with regard to the practical implementation of environmental regulations [1], e.g. determining the informative environment qualifying index. the production process of maleic anhydride (man) is based on two different technological processes in the gas phase, namely the oxidation of benzene and the oxidation of n-butane [2]. in 2015, the global capacity of man production amounted to 2800 million metric tons [3]. scientific and technological developments in the manufacture and use of maleic anhydride as well as maleic and fumaric acids have been reviewed over the past 20 years [4]. during man production, a certain amount of wastewater is generated, which must be received: 30 aug 2022; revised: 12 sept 2022; accepted: 15 sept 2022  correspondence: edisa.papracanin@untz.ba processed and treated in order to minimize environmental pollution. the increasing need to mitigate environmental impacts has led industries to develop more sustainable processes, which may be an arduous task since economic, safety, social and environmental factors must be considered [5]-[6]. the impact assessment of the chemical industry on the environment is becoming more and more important with regard to projecting and designing processes. a special problem is represented by facilities involved in exploitation, which are in the process of complying with eu regulations on environmental protection. given that bosnia and herzegovina, a country in transition, is increasingly adopting the laws of the european union, it is necessary to take measures that will reduce the harmful effects of the chemical industry both locally and globally. furthermore, the federation of bosnia and herzegovina has introduced legislation [7] which is in accordance with eu legislation. due to the fact that man production facilities have a detrimental impact on the environment, various methods have recently been applied for the treatment of wastewater streams. the wastewater flow from the man https://doi.org/10.33927/hjic-2022-10 mailto:edisa.papracanin@untz.ba papraćanin, đozić, mujkić, hodžić, hodžić, poljić, and ramić hungarian journal of industry and chemistry 2 production plant consists of a mixture of organic omponents, containing mainly fumaric and maleic acids, which can be treated by following different physical, chemical and biological methods [8]-[14]. considering the physical characteristics of fumaric and maleic acids [15], especially their solubility in water (fumaric acid is poorly soluble in water), a waste stream consisting of a crystal suspension as well as a mother liquor of fumaric and maleic acids is obtained at the outlet of the plant. before any treatment, such a suspension must be separated into the crystal flow and the mother liquor flow, which, if necessary, could be treated later or possibly reused to obtain products that do not require highly pure fumaric or maleic acid. this research was carried out in order to examine the possibility of separating the wastewater suspension from the industrial man production plant and the crystal stream, which consists of a mixture of fumaric and maleic acids along with other organic impurities, from the mother liquor stream. considering the physical, chemical and biological properties of the waste stream as well as its components, the goals of this research are to choose the most efficient method to separate the crystalline product from the waste stream in addition to making recommendations concerning its processing and further use in the industrial production of unsaturated polyester resins. another aim is to make recommendations for possible biological treatments by analyzing the liquid component of the waste stream. 2. experimental 2.1 treatment of the waste stream the waste stream of the suspension at the outlet of the man production facility owned by the company global ispat koksna industrija lukavac (gikil) (bosnia and herzegovina) was used in this research. the abovementioned waste stream is generated discontinuously by the process of washing the distillation column and cooler with water at a temperature of 100°c. in the aforementioned industrial plant, the distillation system is washed every 4 days when approximately 70 m3 of water is consumed in an hour, resulting in water with a low ph due to the presence of maleic and fumaric acids. the aftercooler is washed twice a month, consuming 10 m3 of water. given that wastewater contains fumaric acid, which is the basic raw material for the production of unsaturated polyester resins, it is necessary to investigate the possibility of using this waste stream in terms of extracting (crystallizing) fumaric acid. the total amount of waste suspension generated under industrial conditions on a monthly basis is approximately 300 m3, which has a significant impact on the environment if it is not processed adequately. experimental research and analyses were carried out in the chemical engineering laboratory of the faculty of technology at the university of tuzla. samples were taken twice a month directly at the outlet of the tank used to collect the waste stream. most samples were taken after the first wash when the concentration of organic matter is the highest. the samples immediately after being taken from the plant and after being delivered to the laboratory are shown in fig.1. they were collected and delivered to the laboratory in plastic containers with a volume of 5l. certain aliquots were extracted to perform physicochemical and other analyses. based on the research objectives, the following tasks were conducted: laboratory modelling of the washing of the distillation column and the discharge of the waste stream was performed; physical and chemical analyses of the waste stream were performed under laboratory conditions; the quantity of the resulting crystalline product was determined in relation to the volume of the waste stream under laboratory conditions; examination of the possibility of extracting crystals from the waste stream was carried out in several ways: a) by cooling the flow under laboratory conditions, b) by adding urea and thiourea, c) by cooling the waste stream with water in a system of tubular heat exchangers. among the physicochemical analyses, the ph, electrical conductivity, boiling point as well as the chemical and biological oxygen demand were measured. all measurements refer to a homogenized sample, moreover, after separating the liquid and solid phases, the dry matter and acidic properties of the liquid phase were determined. (a) (b) figure 1. the samples: (a) immediately after being taken from the plant; (b) after being delivered to the laboratory. separation of fumaric and maleic acid crystals 50(2) pp. 1–6 (2022) 3 the density of the liquid phase was determined using a pycnometer and the bulk density of the dried crystalline product was measured according to the iso 1183-1:2004 standard. 2.2 materials and methods for the purpose of experimental modelling, washing of the distillation column and the discharge of the waste stream, a special system was designed, consisting of a glass container with a volume of 25 liters with openings at the top and bottom. the vessel includes a distillation column and a glass vessel of the same volume was used as a receiving vessel. the amount of sample used was 5 liters and was preheated to 100°c. to obtain a real picture of the industrial plant, the process of crystal formation was tested by cooling down the waste stream to ambient temperature (laboratory conditions). 250 ml samples that were observed were taken from a 5-liter sample after mixing and heating to a temperature of 100°c. the resulting crystals were filtered and air-dried under laboratory conditions. following the addition of urea and thiourea, the 400 ml samples preheated to 100°c, the temperature of the rinsing water, were taken from a 5-liter sample. the test was performed by adding urea and thiourea in different percentages concerning the volume of the sample. after the addition of urea and thiourea, the samples were allowed to settle before the crystals were separated by filtration on filter paper and air-dried. for the purposes of testing whether the waste suspension stream crystallizes, a cooling system consisting of three laboratory-scale tubular heat exchangers was designed. the cooling conditions and crystal formation were investigated for different flow rates of cooling water. the cooling system is shown in fig.2. the total area for heat exchange of the laboratoryscale cooling system was about 0.43 m2. once the waste suspension had passed through the tubular cooling system, the resulting crystals were collected on a metal grid and placed on a glass container before being dried and weighed on an analytical scale. all measurements were performed three times and statistical data processing was conducted in microsoft excel, namely the mean and standard deviation were calculated. electrometric measurements of the ph and electrical conductivity were carried out by direct measurements using a mettler toledo fe 2030/el 20-30 ph meter/conductometer. the ph was measured using the standard method bas en iso 10523, while the electrical conductivity was determined using the standard method bas en 27888. the chemical oxygen demand (cod) is the oxygen equivalent of the amount of potassium dichromate consumed during the complete oxidation of the organic matter in the measured volume of the sample. the cod and biological oxygen demand (bod) are determined by the bas iso 6060 and bas en 1899-1 methods, respectively. after separating the liquid and solid phases, the liquid sample was filtered, evaporated at 100°c and dried overnight in an oven before the mass of the dry matter was measured on an analytical scale. the content of the dry matter was determined according to method 2540solid b [16]. furthermore, the solid phase in the solid sample was analysed gravimetrically by drying it at 105°c for 24 h. 3. results and evaluation 3.1 characterization of the waste stream considering that the waste stream represents a heterogeneous mixture (suspension) under laboratory conditions, for the purpose of the analysis, the samples were homogenized and heated to a temperature of 100°c because the waste stream was obtained by washing the distillation column in the man plant with water at a temperature of 100°c. on the walls of the distillation column, organic substances, predominantly fumaric and maleic acids, are deposited that may occur during the production of man. due to its physical and chemical properties, fumaric acid is insoluble in water, while the solubility of maleic acid in water is 478.8 g/l at 20.0°c, i.e. 3926 g/l at 97.5°c [17]. therefore, by washing the distillation column, a suspension is formed in which crystals of fumaric acid as well as a solution of maleic and fumaric acids are present. considering the aforementioned fact and the boiling points of the pure acids, fumaric acid at 287°c and maleic acid at 135°c [15], the boiling point of the suspension was measured to be 106.81.3°c under laboratory conditions. this data indicate the presence of other substances that have significantly lower boiling points compared to the components that are primarily present. as expected, the measured ph is very low, namely 0.970.06, due to the presence of organic acids, while the measured electrical conductivity is 33.624.03 ms. in view of the ph prescribed in [6], the measured value does figure 2. schematic diagram of the waste-stream cooling system: 1) glass container for rinsing, 2) system consisting of three tubular heat exchangers, 3) cup containing the sample, 4) glass funnel, 5) metal grid for collecting crystals papraćanin, đozić, mujkić, hodžić, hodžić, poljić, and ramić hungarian journal of industry and chemistry 4 not comply with the legal framework, which indicates that this waste stream of industrial wastewater should be treated in an appropriate way. the relatively low electrical conductivity, for which no legally prescribed limits are found, indicates a low concentration of free ions in the waste stream. a pycnometer measured the density of the liquid phase after separation to be 1038.844.31 kg/m3, while the bulk density of the solid phase was 394.01.4 kg/m3. to further examine the characteristics of the waste stream, the cod and bod of the homogenized sample were determined to be 233600 and 87280 mg o2/l, respectively. the permitted limits for the discharge of a waste stream into the environment for cod and bod are 25-250 and 135-700 mg o2/l, respectively, which indicates the need for pretreatment of the waste stream before being discharged into the environment. by separating the solid and liquid phases by filtering and decanting under laboratory conditions, a homogenized 2.5 l sample contains 5.090.05 wt% of dry crystalline products. as a result, the total amount of solid matter discharged every month (300 m3) is about 15.27 kg. therefore, a huge amount of solid waste can be treated or possibly used for other purposes. the amount of dry matter in the liquid phase is 16.30.2 wt%, which also exceeds the permitted limits. by titration of the liquid phase with naoh and phenolphthalein as an indicator, it was determined that 1 g of the liquid solution is titrated with 3.95 mmol of naoh. in simple terms, if the acidity is due to the presence of maleic acid, this would correspond to a maleic acid concentration of 0.247 mg/ml. 3.2 separation efficiency considering the results of the physicochemical analysis of the industrial waste stream resulting from man production, it was observed that this waste stream must be adequately treated before being discharged into the environment. due to the composition and characteristics of the waste stream, it is necessary to separate it into the solid and liquid phases. in this research, several experiments based on different methods were conducted to obtain an efficient method for separation. as described earlier in the experimental section, before testing the aforementioned methods, laboratory modelling of the process by which the distillation column is washed was carried out. the reason for performing the experimental simulation is to experimentally and visually determine how the crystals are formed during the discharge of the waste-stream suspension into the collector. during the simulation, it was observed that immediately after the waste stream comes out of the outlet pipe, a larger amount of crystals were formed, meaning that other organic substances, predominantly maleic acid, also crystallized. simply by highlighting the flow, a sudden drop in the temperature of the flow from 100°c to ambient temperature is observed, during which more intense crystallization occurs. following this observation, a system of three heat exchangers (fig.2) was designed under laboratory conditions to cool down the waste stream more quickly and test such an efficient way of separating the solid and liquid phases. at the outlet from the cooling system, a container collected the waste flow, on top of which a metal grid to separate the crystals was placed. after the cooling and separation processes, the crystalline product obtained was dried and measured. the mass of crystals obtained by forced cooling (sample volume of 5 l) was 638.372.34 g, that is, 12.3 wt% of the dry crystalline product. compared with the amount of crystals obtained by natural cooling to ambient temperature, it can be seen that this method (forced cooling and separation by filtration) is significantly more efficient. this technique of collecting crystals on a metal grid is very simple to perform due to the very structure and size of the resulting crystals. the appearance of the crystals obtained is shown in fig.3. after experiments were performed using forced cooling, the influence of the addition of urea and thiourea on the formation and separation of crystals of organic substances in the industrial waste stream was examined. these components were added to better isolate the crystalline product from the mixture of fumaric and maleic acids, that is, thiourea acts as a catalyst in the isomerization of maleic acid to fumaric acid [18]. the masses of the resulting crystalline product following the addition of urea and thiourea are presented in table 1. analyses were performed using a sample that figure 3. crystals obtained by forced cooling table 1 mass of the crystalline product obtained following the addition of urea and thiourea mass added (g) volume of filtrate collected (ml) mass of crystals (g) thiourea urea thiourea urea 1 100 200 69.0 44.9 3 60 210 71.4 46.7 5 150 200 71.8 46.9 separation of fumaric and maleic acid crystals 50(2) pp. 1–6 (2022) 5 was heated to 100°c and homogenized in a volume of 400 ml. the masses of urea and thiourea added were 1, 3 and 5 g. samples where different amounts of urea and thiourea were added (u1 and t1 1g, u2 and t2 3g, u3 and t3 5g) are shown in fig.4. as can be seen in table 1, the largest amount of crystalline product was obtained following the addition of 5 g of thiourea. as a percentage of the 400 ml sample, this value is 17.29 wt% of dry crystalline product, which is significantly more compared to forced and natural cooling of the waste stream. the addition of urea also enhances separation of the solid phase from the suspension of the waste stream, however, considering the results obtained, the effect of adding thiourea on the separation process is significantly greater. as can be seen in the table, given that the amounts of the crystalline product obtained following the addition of all three amounts of thiourea are very similar, an additional experimental optimization of the mass of thiourea to be added to the waste stream was performed. amounts of less than 1 g were added to see if a larger difference in the amount of crystalline product formed was observed. amounts of thiourea added of less than 1 g are presented in table 2. as can be seen, even small amounts of thiourea significantly enhance the separation of crystals from the waste stream. if 1 g of thiourea is added to a suspension sample of 400 ml as an optimal cost price and to achieve separation of the crystals when treating the waste stream generated from an industrial plant, it would be necessary to add 750 kg to 300 m3 of waste suspensions per month, which is a huge amount. however, if 0.25 g of thiourea is added to a suspension sample of 400 ml, which equates to approximately 0.06%, about 1250 kg of thiourea would need to be added annually at a cost of approximately $98,550 [19]. in this case, this price is reasonable if the separated fumaric acid crystals were to be used for the production of resins. in light of the research conducted, in the future, some other methods for extracting the mixture of fumaric and maleic acid crystals should be examined, which would be economically profitable and technologically feasible in an already existing plant. furthermore, the composition of the crystalline product following the addition of thiourea should be tested using appropriate methods and analyses. 4. conclusions in this research, a physicochemical analysis of the wastewater flow from an industrial plant resulting from the production of maleic anhydride was conducted. based on the obtained results, it is evident that a very low ph as well as electrical conductivity indicate the presence of organic acids left over from distilling man. given that the resulting flow is a suspension flow at the temperature of water used to wash the distillation column as well as the physical and chemical properties of fumaric and maleic acids, it can be stated that both are the two dominant components in the waste flow. this was also confirmed by determining the acidity by titration with naoh. the research determined the density of the liquid phase as well as the bulk density of the separated crystalline product. by carrying out different experimental methods, the crystals were separated from the waste suspension by a combination of cooling and the addition of thiourea, a technique which can be applied in an industrial plant, facilitating the isomerization reaction of maleic to fumaric acid. furthermore, the installation of a metal grid at the inlet to the receiving court is a simple structural solution whereby the resulting crystalline product, with appropriate analyses, could be used in processes that do not require highly pure fumaric acid, e.g. resin production. the liquid component, that is, the mother solution obtained by separating the waste suspension, due to the high cod and bod, following the adjustment of other parameters like ph, could be successfully treated by the process of anaerobic digestion or co-digestion. therefore, the liquid stream could serve as a good co-digestate for adjusting the characteristics of waste sludge that is normally applied in anaerobic digestive processes. following a literature review, since it was observed that very few studies have been conducted in this regard or require significant financial resources, this research opens up new possibilities and perspectives for the implementation of simple as well as inexpensive industrial and implementable solutions. figure 4. separation of crystals by cooling at room temperature following the addition of urea and thiourea: u1, u2, u3 – samples to which urea was added; t1, t2, t3 – samples to which thiourea was added table 2 mass of the obtained crystalline product following the addition of smaller quantities of thiourea mass added (g) volume of filtrate collected (ml) mass of crystals (g) 0.25 180 45.2 0.50 160 52.7 0.75 170 60.3 papraćanin, đozić, mujkić, hodžić, hodžić, poljić, and ramić hungarian journal of industry and chemistry 6 references [1] utasi, a.; sebestyén, v.; rédey, á.: informative environment qualifying index, hung. j. ind. chem., 2000 48(2), 23–36, doi: 10.33927/hjic-2020-24 [2] abbas, s.k.: production of maleic anhydride from oxidation of n-butane, a design project submitted to the faculty of engineering and built environment in partial fulfilment of the requirements for design of chemical processes computer aided class kkkk6014, 2015 p. 4, doi: 10.13140/rg.2.1.4096.8569 [3] mestl, g.; lesser, d.; turek, t.: optimum performance of vanadyl pyrophosphate catalysts, top catal, 2016 59, 1533–1544, doi: 10.1007/s11244016-0673-0 [4] felthouse, t.r.; burnett, j.c.; horrell, b.; mummey, m.j.; kuo, y.j.: maleic anhydride, maleic acid, 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(eds.): standard methods of water and wastewater (amer public health assn, washington, d.c.) 2005 21st ed., pp. 2–61, isbn: 0875530478 [17] verschueren, k.: handbook of environmental data on organic chemicals (john wiley & sons, new york, ny.) 2001 12 4th ed., p. 1396 [18] lobo, v.t.; pacheco ortiz, r.w.; gonçalves, v.o.o.; cajaiba, j.; kartnaller, v.: kinetic modeling of maleic acid isomerization to fumaric acid catalyzed by thiourea determined by attenuated total reflectance fourier-transform infrared spectroscopy, org. process res. dev., 2020 24(6), 988–996, doi: 10.1021/acs.oprd.9b00487 [19] https://www.chemicalbook.com/price/thiocarbamide.htm https://doi.org/10.33927/hjic-2020-24 https://doi.org/10.13140/rg.2.1.4096.8569 https://doi.org/10.1007/s11244-016-0673-0 https://doi.org/10.1007/s11244-016-0673-0 https://doi.org/10.1002/0471238961.1301120506051220.a01.pub2 https://doi.org/10.1002/0471238961.1301120506051220.a01.pub2 https://www.researchgate.net/publication/330422302-environmental_analysis_of_the_maleic_anhydride_production_process https://www.researchgate.net/publication/330422302-environmental_analysis_of_the_maleic_anhydride_production_process https://www.researchgate.net/publication/330422302-environmental_analysis_of_the_maleic_anhydride_production_process https://doi.org/10.1016/j.ces.2019.115313 https://doi.org/10.1016/j.ces.2019.115313 https://fbihvlada.gov.ba/bosanski/zakoni/2012/uredbe/2hrv.html https://doi.org/10.1007/bf01570024 https://doi.org/10.1007/bf01570024 https://doi.org/10.1023/a:1010245903543 https://doi.org/10.1023/a:1010245903543 https://doi.org/10.1080/01496390701446498 https://doi.org/10.1080/01496390701446498 https://doi.org/10.1016/j.desal.2007.09.105 https://doi.org/10.1016/j.memsci.2012.02.053 https://doi.org/10.1016/j.memsci.2012.02.053 https://doi.org/10.1016/j.chroma.2021.462165 https://doi.org/10.1016/j.chroma.2021.462165 https://doi.org/10.1016/j.desal.2017.01.039 https://doi.org/10.1016/j.desal.2017.01.039 https://www.ilo.org/dyn/icsc/showcard.home https://doi.org/10.1021/acs.oprd.9b00487 https://www.chemicalbook.com/price/thiocarbamide.htm hungarian journal of industrial chemistry veszprem vol. 29. pp. 143-147 (2001) explosion areas of flammable substances and their numerical approximation g. viczian, m. molnarne-jobbagy 1 , j. heszberger and k. kollar-hunek (dept. of chemical information technology, bp. univ. of technology and economics. hl521 budapest, pf.91. hungary, 1federal institute of materials research and testing, bam, 12200 berlin, germany) received: october 10,2001 this paper was presented at the 7th international workshop on chemical engineering mathematics, bad honnef, germany, august 12-17 2001 chemsafe® database [1], developed as a joint project between bam, ptb and dechema, contains safety characteristics of flammable liquids, gases, dusts and their mixtures. the bam is responsible for evaluated data on gases and dusts. triangle software, originally developed by the bam for the processing, quality assurance and visualisation of measured data describing the explosion area of ternary systems consisting of flammable, inert and oxidising gases. 2d figures in the program represent isothermal or isobaric level curves of the explosion areas. in order to better describe the limiting curve of the explosion range, by the bute (budapest university of technolcgy and economics) the akima­ spline interpolation has been replaced by special comonoton splines in triangle. for the 3d visualisation of the whole temperatureor pressure-dependent ternary explosion surfaces the trigon program of bute was extended. keywords: ternary flammable systems, inerting, explosion areas, spline curves and surfaces, 2d and 3d visualisation introduction in order to avoid explosion with flammable substances, generally applied solution in industrial processes is purging with inert gases. reliable measured data are required concerning the explosion range of ternary systems. the chemsafe® database, which is available world wide through stn international and internet, contains rated safety characteristics of flammable liquids, gases, dusts and their mixtures, such as explosion limits, flash points, ignition temperatures, etc. the in-house version of chemsafe allows a graphical representation of the measured explosion range in triangular diagrams as a function of the concentration of flammable, oxidising or inert gases. in the data processing phase a flexible software procedure is needed to solve 2d and in certain cases also 3d visualisation for the explosion area of ternary gas mixtures. the triangle program, created by bmf and extended by the common research group of bute and bam, provides the 2d triangular diagrams. when the influence of additional parameters is to be shown, for 3d explosion surfaces the extended trigon software offers a good solution. characteristics of the explosion range explosion areas need to be explicitly defined by unambiguous characteristic parameters. table i and fig. i show the acronyms applied in chemsafe. as an example, let us consider the iar hne in fig. i. this line represents a limit in the ternary flammable system: all mixture compositions existing on the right hand side of this line will not cause an explosion regardless of the added amount of flammable gas. the interception of the iar line and the oxidising gas axis determines the mai point. the minimum required inert gas content of the binary inert·oxidlsing gas system which is necessary to avoid an expjostt.m, similarly, the icr line gives a limiting ratio between 144 table i characteristic values for explosion area of ternary systems containing flammable gas i inert gas i oxidising gas acronym in chemsafe .qescripdon lower explosion limit lel uel icr jar upper explosion limit minimum inert gas i combustible ratio minimum inert gas i air (oxidising gas) ratio' mxc maximum permissible amount of combustible mai minimum required amount of inert gas moc or loc maximum oxygen (oxidising gas) content or limiting oxygen concentration explosion .range :meth.ne!nitroal:llfair • !l mt-alateqi'lillc ropin 511$49 25 'c, t.llo.ospi>o:rit: p..nitrogen fig.! representation of the explosion area inert and flammable gas at which by adding any amount of flammable gas to the system no explosion will occur. the triangle program is used for processing measured values of such systems. the boundary curve around the explosion area is generated by applying numerical interpolation on the measured data. after the .. evaluation of the characteristic values of the system the program returns the results in tables and in ternary diagrams both in cartesian and in triangle co~ordinates. 2d approximation problems solved by comonoton parametric vector splinesadditions and extensions in triangle for the characterisation of the explosion range well determined tangent lines of the explosion areas are neededt such as the iar or icr lines. for these to be accurate we have to apply the best possible numerical approximation of the 2d explosion limit curves. comonoton parametric vector splines possess the best numerical properties for this task. [2~ 5]. the conditions of comonotonity for the set of measured points {:r,; y, }:,, are given as following [4, 6]: (1) table 2 comparison of different interpolation methods butene/nitrogen/air-system (t=297 k; p=o,l mpa) mai moc mxc iar icr traditional spline 51,83 9,94 2,68 1,08 36,35 comonoton spline 51,78 9,96 2,71 1,07 35,93 linear interpolation 51,78 9,98 2,72 1,07 35,71 12~----------------------------~ 10 8 6 4 -evaluated ~ measured 0+----------r----------r---------~ 0 20 40 60 fig.2 butene/nitrogen/air-system (t=297 k; p=o,l mpa) traditional spline interpolation 12~------------------------------~ 10 8 6 4 2 -evaluated ~ measured 0+------.-------r-------t i o 20 40 60 fig.3 butene/nitrogen/air~system (t=297 k; p=o,l mpa) comonoton spline interpolation where s denotes the usual arc length parameter. then it holds for the slope coordinates x'(s) and y'(s): v s e (s; t ;s;): x:(s )· (m;}x > 0 if (mjx * 0 (2.a) y (s )· (m; ) 1 > 0 if (mj 1 :t: 0 [ ] x'(s) = 0 if (mi) = 0 \j se s1_1;si : '() . ( )x (2.b) y s =0 if m. =0 l y using the conditions above, we created subroutines for the comonoton parametric vector splines and built them in the triangle program. similarly, we also created subroutines for the traditional parametric vector splines l9~ 10] and compared the differently evaluated characteristics. 18 16 14 -evaluated 12 fl. measured 10 8 6 4 2 0 0 10 20 30 40 fig.4 methane/coiair-system (t=297 k; p=o,l mpa) traditional spline interpolation 18~------------------------------, 16 14 12 10 8 -evaluated fl. measured 61-~~~~~~~ 4 2 0+-------r-------r-----~-------4 0 10 20 30 40 fig.s methane/c02/air-system (t=297 k; p=o,l mpa) comonoton spline interpolation some representative results are shown in figs.2 and 3 and in table 2. for the butene/nitrogen/air ternary system, and in figs.4, 5, and in table 3 for the methane/coz/ air ternary system. in the case of the butene/nitrogen/ air-system the traditional spline interpolation produces an undesired curvature on the uel curve, near the apex of the explosion area. it has a slight effect on the mal, mxc, and icr values as it is shown in table 2. in the second example, in the case of the methane/co:c'air-system with the traditional spline interpolation, the undesired curvature appears on the lel curve, again, near the apex of the explosion area. in this case the curvature causes a considerable error in the mxc point and in the slope of the icr line. by using comonoton vector splines both above mentioned errors can be avoided. it needs to be mentioned that traditional spline approximation had been found to produce similar errors in five out of the about twenty investigated systems. on the programming side the new parametric vector splines required changes in 3 of the 4 worksheets, 3 of the 7 diagrams, 8 of the 11 modules and 3 of the 5 forms of the original triangle (visual basic for excel) program. 145 table 3 comparison of ditierent interpolation methods methane/c02/ air-system (t=297 k; p=o, i mpaj traditional comonoton linear spline spline inte~lation mal 31,02 31,02 31,02 moc 13,52 13,54 1355 mxc 16,95 17,39 17,39 jar 0,45 0,45 0,45 icr 4,9 4,75 4,75 80~~~--~~~~--~~~~ 70~~~~-r~--,---~ 60+-~~~~--r-----~~ 50+--+--~~~~~~--~ 40+--+--t-~~~~~--~----~-; 30+--+--+-~~~~~--,-~--~-i 20+--+--+-------~j 10+-~--~~--~~ 10 20 30 40 50 60 70 80 90 100 l_ ________________________________ _ fig.6 isothermal level curves ofh2/c02/air j 3d visualisationexamples of the extended trigon application the trigon program was created for visualisation of triangular (ternary) vapour-liquid equilibrium (vlej surfaces [7, 11]. as we recognized the interesting possibility to visualize the temperature or pressure dependence in the explosion areas of ternary systems containing flammable gas, we tried to utilize trigon and its embedded bezier surfaces. although < lur minimal energy bezier surfaces have many useful properties [2, 6-8], we could not directly apply t~em. for the ternary explosion surface (tes) approxtmauon. because their computational algorithm needs the whole triangle as domain for the surfaces. a simila: proble~ occurred with the application of shepard s metnc interpolation [3]. . after investigating the above problems, we dec~ded to use the 2d comonoton spline level curves comb1~ed by bilinear interpolation. the comonoton sphne (isothermal) level curves of hydrogen/carbon dioxide! air-system are shown in fig.6 as an example. the five data sets belonging to the temperatures ~0. i 00~~ 200, 300 and 400 c are from the chl~is.~fe· database. the bilinear interpolation allowed ,1 mmple restriction of the whole triangle domain. using the inner and the outer level rurves 146 extended units of trigon without new routines extension: diagr: 8 new routines helper: 1 new routine development in the future: motion (reading co-ordinates from the figures) t~-i~~~i<;, fig. 7 extensions necessary for trigon visualizing tes (l(20) and l(400) in fig.6) as boundaries in the restricting inequalities. parametric comonoton vector splines were used for the (isothermal or isobaric) level curves and a bilinear interpolation was used for the trapezoid inner part between the level curves. to accomplish this, we had to extend the vle trigon software according to fig. 7. the tes trigon program version contains the menu and hpemu units [11] unchanged, but in the diagr unit we had to develop 8 new routines, and one in the helper unit. the output of the tes-trigon software for two example ternary systems (hydrogen i carbon dioxide i air-system defined by isothermal level curves and ethene i nitrogen i air-system defined by isobaric level curves) are shown in figs.8 and 9. in the approximation of the apex of explosion surfaces we had to solve a "apex accumulation" problem. as it is shown in fig.8, in the first solution we slightly broke the "level curves condition''. even though in the real explosion of surface plots this is unnoticeable, we continue to work on a solution that does not break the condition of the level curve system. the different rotation and view angle changing features of trigon show the properties of the ternary explosion areas very \veil. in the case of the ethene!nitrogeniair~system. given by isobaric level curves, in the fig.9, the lower pressure part between 0.1 and 1 mpa is interesting, because the dangerous part is wider than in higher pressure, between 1 and 10 mpa. conclusions for correct 2d visualisation of isothermal or isobaric explosion areas of ternary gas mixtures containing flammable gas. we extended the triangle software (created by bam. berlin). to reach the desired accuracy for the approximation of explosion characteristics we used parametric comonoton vector splines. the software and the method had already been tested on many systems in chemical safety engineering. ~~~~ ,, ............................................................. . fig.8 3d explosion areas of hydrogen/carbon dioxide/air­ system given by isothermal level curves, plotted by testrigon fig.9 3d explosion areas ofethene/nitrogen/air-system given by isobaric level curves, plotted by tes trigon in some cases, when 3d visualisation is necessary, the extended tes trigon software (created by bute, budapest) gives good results. in this program the base of the numerical surface approximation was comonoton vector spline, the same as in the 2d visualisation. between the isobaric or isothermal explosion level curves we used bilinear interpolation that made the necessary domain restriction also easy to implement. acknowledgements the authors wish to express their gratitude to thomas bendrich and to michael bulin (bam), to dr. prof. norbert herrmann (univ. of hannover) and to dr. marta lang-lazi (bute). the work has been supported by the hungarian national research foundation (otka, grant # t023258/97), by the bam (berlin) and by the varga j6zsef foundation of the chemical engineering faculty, bute. symbols iar minimum inert gas i air (oxidising gas) ratio icr minimum inert gas i combustible ratio lel lower explosion limit l(t) isothermal level curve of tes mal minimum required amount of inert gas moc maximum oxidising gas content mxc maximum permissible amount of combustible gas p pressure, ~a s arc length parameter t temperature, k or c tes ternary explosion surface uel upper explosion limit (x,y) cartesian co-ordinates vle vapour liquid equilibrium references 1. chemsafe®-database for safety characteristics, bam, berlin, ptb, braunschweig, dechema, frankfurt am main, v1.4, 2001 147 2. f~sshauer g. e. and schumaker l. l.: computer aided geometric design, 1996, 13, 45 3. gordon w. j. and wixom j. a.: math. and comput., 1998, 32, 253 4. gronewold g.: hung. j. ind. chern., 1996,25,59 5. herrmann n.: hung. j. ind. chern., 1996, 25, 263 6. kolia.r-hunek k., lang-lazi m., herrmann n., miklos d. and kovacs i.: hung. j. ind. chern., 1998,26,269 7, koliar-hunek k., viczian zs. and lang-lazi m.: hung. j. ind. chern., 1999, 27, 6 8 .. lang-lazi m., diospatonyi i., viczian g. and heszbergerj.: hung. j. ind. chern., 1999,21,317 9. shikin e. v. and pus a. i.: handbook on splines for the user; crc press, boca raton, fl, usa, 1995 10. spath h.: algorithmen zur konstriktion glatter kurven und flachen, oldenburg, mlinchen, wien, 1983 11. viczran g., lang-lazi m., heszberger, j., diospatonyi i. and kollar-hunek k.: hung j. ind. chern., 2000, 28, 311 page 143 page 144 page 145 page 146 page 147 hungarian journal of industry and chemistry vol. 53(2) pp. 45–48 (2025) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2025-16 possibilities of recycling end-of-life ro membrane modules as a low-cost alternative to water treatment girma deme1*, áron bóna1 and ildikó galambos1 1 soós ernő research and development center, university of pannonia, zrínyi m. u. 18., nagykanizsa, 8800, hungary this study explores the possibilities of recycling end-of-life reverse osmosis membranes as a significant low-cost alternative to water treatment, addressing both waste reduction and affordable filtration solutions. although reverse osmosis membranes play a vital role in water treatment, the limited lifespan of membrane modules presents environmental and economic challenges. reverse osmosis membrane modules consist of multiple layers including polymeric membranes, support materials and adhesives often combined with fiberglass or metal housings, which makes the separation of individual materials and recovery difficult. currently, most end -of-life membranes are disposed of in landfills or incinerated, resulting in ecological issues and the loss of valuable resources. therefore, the drive to recycle and reuse end-of-life membranes over recent years stems from a desire to maximize resource efficiency and lower their environmental impact. the ability to reuse end -of-life reverse osmosis membranes as well as downcycle them into membranes with nanofiltration or ultrafiltration properties is the most effective and promising solution, providing such membranes with effective levels of water permeability and pollutant rejection comparable to commercial membranes. keywords: end-of-l ife reverse osmosis membrane, low-cost water treatment, recycling 1. introduction despite its importance in sustaining life and for human usage, water is very susceptible to contamination [1]. one of the most significant challenges facing the world in the 21st century is the rising issue of water availability, both in terms of quantity and quality. this problem has worsened as a result of climate change, population growth and economic development, which have exacerbated the pollution of water resources [2]. in response to water-scarce conditions, seawater and brackish water desalination has emerged as a key solution to facilitate economic development, providing highquality water for various uses, including irrigation, domestic supply and in industry. in line with this, in 2019, there were 21,123 desalination plants operating worldwide, producing approximately 126.57 million m3 of freshwater per day [3]. alongside a forecasted compound annual growth rate (cagr) of approximately 10.3% between 2020 and 2025, reverse osmosis (ro) desalination is poised for continued expansion. the dominance of reverse osmosis in the desalination market is largely attributed to its status as the most energy-efficient industrial technology currently available, proven by the fact that ro systems constituted 84% of operational desalination plants in 2018 and produced 69% of the world's desalinated water that year received: 16 june 2025; revised: 23 june 2025; accepted: 24 june 2025 *correspondence: girmishdeme@gmail.com [4]. furthermore, according to market forecast data, the ro market worldwide was projected to be worth $11 billion by 2021, showing a 10.9% growth rate compared to in 2016 [5]. however, the use of ro technology raises certain environmental concerns. once ro membranes used in seawater desalination reach their relatively short lifespan (5-10 years), they become end-of-life reverse osmosis (eol ro) waste, which is ultimately disposed of through landfilling or incineration [6]. disposing of spent ro membranes via incineration or landfill poses environmental challenges [7]. the volume of this waste is substantial, with more than 840,000 ro membrane modules being generated annually and forecasts predicting over 2 million discarded units by 2025 [8]. the limited options for the disposal of eol ro membrane modules, such as incineration or landfill, have created an environmental issue that necessitates the development of alternative handling solutions. recently, recycling has become the most desirable solution for disposing of eol ro membranes. this includes directly reusing or converting them into different types of membranes such as ultrafiltration (uf) and nanofiltration (nf) ones. various recycling methods can be applied to eol ro membranes, each producing membranes with distinct characteristics. this paper discusses down-cycling methods for converting eol ro https://doi.org/10.33927/hjic-2025-16 mailto:girmishdeme@gmail.com deme, bóna and galambos hungarian journal of industry and chemistry 46 membranes into reconditioned membranes and presents their performance test results. 2. eol ro membrane recycling methods thin-layer composite ro membranes frequently employed in saltwater desalination, brackish water treatment as well as water recycling for residential and commercial uses primarily utilize aromatic polyamides (pas) due to their outstanding ability to separate substances. a layer of non-woven polyester, a microporous polysulfone (psf) support and a dense pa layer are the typical components of these ro membranes [9]. constant fouling by suspended particles, dissolved organic matter and solids as well as bacteria might cause the performance of ro modules to irreparably decline, moreover, ultimately lead to the end of their usable life. recently, eol ro membranes have been reused by cleaning the fouling and removing the pa layer, thereby reducing the filtration power of the membrane. among different methods, downcycling is a common technique employed to treat eol ro membranes and is discussed in the following subsection. eol membranes are chemically treated using downcycling methods to create recycled membranes directly with reduced separation accuracy. specifically, the main method involves partly or completely removing the selective layer of ro membranes by often utilizing chemicals such as kmno4 [10], naocl [11] and h2o2 [12] to eliminate the polyamide coating from the fouled membrane. the most widely utilized chemical agent for downcycling eol ro membranes is naocl, since polyamide material is susceptible to it [13]. downcycling is achieved through careful regulation of the naocl concentration and duration of exposure or by specifying the desired naocl treatment strength, which is quantified in ppm.h [14]. the final properties of the membrane are a direct consequence of the concentration of and duration of exposure to free chlorine in the solution. the degradation of the pa layer caused by hypochlorite solutions leads to increased membrane permeability (l) and a reduction in the salt rejection coefficient (sr). despite these challenges, eol ro membranes can be modified into nf-like membranes by carefully degrading their pa coating [15]. this involves an initial treatment with naocl solution to create uf membranes, followed by a layer-by-layer (lbl) polyelectrolyte deposition technique to achieve nf properties. studies in which eol ro membranes were transformed into microfiltration (mf), uf and nf ones are summarized in table 1. 3. application of recycled eol ro membranes recently, several studies have been conducted to convert eol ro membranes and use them for different purposes. in a 2024 study, moreira et al. investigated the potential of recycled membranes for treating uraniumcontaminated groundwater in order to produce safe drinking water [23]. two eol ro membranes denoted as nf-1 and nf-2 were subjected to various oxidative treatments with 440,000 and 220,000 ppm.h of naocl, respectively. the nf-1 membrane exhibited a permeate flux of 21.4 ± 0.3 l.m-2.h at 0.5 bar and achieved approximately a water recovery of 90%. however, after a recovery of 40%, the uranium concentration in the permeate was 0.03 mg/l. in contrast, the nf-2 membrane effectively removed uranium down to concentrations compliant with drinking water standards, as illustrated in figure 1c. this module performed excellently since its contaminant levels remained below the maximum threshold, even at higher percentages of recovery. with a rejection rate of 71.6%, it closely met the expectations for nanofiltration membranes. in another work, wang et al. converted si-al fouled ro membranes into nf and uf-like ones using naocl treatment methods [19]. the results, depicted in figure 1a, demonstrated that the water permeance of downcycled membranes considerably increased and the rate of na2so4 rejection gradually declined over extended periods of exposure. furthermore, as depicted table 1: summary of studies on the recycling of eol ro membranes protocol membrane obtained permeability (l.m-2.h-1.bar-1) salt rejection (%) ref. exposure to naocl, sonication for 30 mins mf membrane 377.2 0.71 nacl [16] exposure to 300,000 ppm.h of naocl uf membrane 59 < 1 nacl [17] exposure to 13,000-240,500 ppm.h of naocl nf membrane 18 92 nacl, 98 mgso4 [18] exposure to 50 ml of 0.5% naocl for 4h nf membrane 27 62 na2so4 [19] exposure to 300,000 ppm.h of kmno4 uf membrane 68.1 11.1 nacl [20] exposure to 300,000 ppm.h of naocl uf membrane 17.2 < 5 nacl [21] exposure to 150,000 ppm.h of naocl uf membrane 18 < 5 nacl [22] possibilities of recycling ro membrane modules 53(2) pp. 45–48 (2025) 47 in figure 1b, a 24-hour alkaline wash and subsequent naocl treatment yielded a loose, nf-like membrane with a water permeability of 27 l.m-2.h-1.bar-1 and 62% na2so4 rejection. the recycled membrane, exhibiting ultrafiltration-like properties, also demonstrated a significantly higher degree of water permeability, ranging from approximately 60 to 90 l.m-2.h-1.bar-1, but its rejection of na2so4 was less than 5%. in an independent study, moreira et al. examined recycled household eol-ro systems as point-of-use ones for groundwater treatment [24]. the researchers successfully repurposed the eol ro membranes by treating them with 440,000 ppm.h of naocl and confirmed their long-term viability by operating them for an extended period of time. their findings indicated a significant increase in water permeability from 4.5 to 50.4 l.m-2.h-1.bar-1 coupled with a substantial decrease in salt rejection from 99.4 to 11.6%, suggesting the effective transformation of the ro membrane into an uf membrane. furthermore, the modified membrane demonstrated an efficient level of water treatment and minimal fouling over a prolonged period of use at its point of use. monitoring data revealed a consistent permeate flux of 21.2 ± 0.46 l.m-2.h and a filtration resistance of 6.37 ± 0.16 * 1014 m-1, resulting in a total permeate production of 3,000 l, comparable to commercially available filtration systems. a recent study by nieminen et al. examined the process of repurposing eol desalination membranes for nanofiltration applications [25]. the new membrane demonstrated a pure water permeability of 17 l.m-2.h-1.bar-1. additionally, it achieved a retention rate of 88% for mgso4 and 8% for nacl with a molecular weight cut-off of 320 da. remarkably, the membrane achieved over a 95% reduction in the phosphorus concentration while also removing over 80% of various pharmaceutical micropollutants. 4. conclusions different management strategies are necessary, considering the significant environmental concern that end-of-life reverse osmosis membranes pose. the present study surveyed several methods for reusing these membranes such as repurposing them for different applications, employing less severe treatments and thoroughly cleaning them with chemicals to facilitate their rejuvenation. studies have demonstrated that recycled ro membranes can achieve a comparable level of performance to commercial membranes in different application areas, which makes them an affordable option for water desalination and wastewater treatment. it is anticipated that extending the lifespan of eol ro membranes as well as recycling and reusing them will ultimately lower the social and environmental costs associated with their use, promoting a greater degree of sustainability. acknowledgements this research was funded by the tkp2021-nkta-21 program with support provided by the hungarian ministry of culture and innovation from the national research, development and innovation fund financed under the thematic excellence programme 2021 funding scheme. references [1] kamalanathan, s.; amran, f.; zaini, m.a.a.: oxidized mangosteen peel-derived hydrochar for the 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https://doi.org/10.1016/j.jclepro.2022.132495 https://doi.org/10.1016/j.memsci.2025.123690 hungarian journal of industry and chemistry vol. 53(2) pp. 1–6 (2025) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2025-11 enantioselective alkoxylation of β-substituted aromatic nitroalkenes with allyl alcohol gulahmad mirahmad talybov 1* 1 department of chemistry technology, recycling and ecology, azerbaijan technical university, javid avenue 25, baku, az 1073, azerbaijan enantioselective alkoxylation of β-substituted aromatic nitroalkenes with propargyl alcohol in the presence of a chiral ligand – n-ethyl-n-{[(2s)-pyrrolidin-2-yl]methyl}ethanamine – leads to enantioselective synthesis of nitrocontaining ethers in high yields and enantioselectivity. keywords: enantioselectivity; nitro-containing ethers; propargyl alcohol; chiral catalyst 1. introduction chiral nitro-containing ethers are widely distributed in biologically active natural and pharmaceutical preparations [1],[2]. one of the most effective methods for the synthesis of optically active chiral compounds is the catalytic enantioselective addition of nucleophiles to α,βunsaturated compounds leading to a variety of diverse organic compounds [3]-[8]. one of the methods for the synthesis of chiral unsaturated nitro-containing ethers is the catalytic enantioselective alkoxylation of unsaturated nitro compounds with propargyl alcohol (figure 1). the goal of synthesizing chiral unsaturated nitrocontaining ethers with excellent yields and enantioselectivity can be achieved using a organocatalyzed reaction. received: 10 march 2025; revised: 21 march 2025; accepted: 8 apr 2025 *correspondence: gtalibov61@gmail.com 2. experimental the structures and compositions of the obtained target compounds no. 1-9 were confirmed by i̇r, 1h and 13c nmr spectroscopy as well as elemental analysis data. some of the spectra are shown as examples. methylene protons, when magnetically equivalent, associated with the nitro groups in compounds no. 1-9 are diastereotopic ( 0.4 ppm) in the form of two separate singlets at 1.03–1.05 ppm and appear in 1h nmr spectra in the form of two doublets with a geminal coupling constant 2j = 11.8 hz. this shape of the signals in the nmr spectra of these groups of protons is associated with their diastereotopy. diastereotopicity is due to the appearance of asymmetric centers in the structure as a result of alkoxylation with non-unionized c3 alcohols to figure 1: reaction scheme ho ch=ch2 ph no2 ph no2 o ch=ch2 + kat. -40 o c ph= c6h5 (1), 1-mec6h4 (2), 4-mec6h4 (3), 2-clc6h4 (4), 4-clc6h4 (5), 2-brc6h4 (6), 4-brc6h4 (7), 2-meoc6h4 (8),,4-meoc6h4 (9) 1-9 kat.=n-ethyl-n-{[(2s)-pyrrolidin-2-yl]methyl}ethanamine https://doi.org/10.33927/hjic-2025-11 mailto:gtalibov61@gmail.com talybov hungarian journal of industry and chemistry 2 the multiple bond of β-substituted nitroalkenes of the aromatic series. commercially available reagents from sigma– aldrich were used. the melting points were measured with an electrothermal 9100 melting point apparatus (uk). 3. results and analysis as a result of our syntheses, the following compounds were obtained: compound no. 1: {(1s)-2-nitro-1-[(prop-2-en-1-yl)oxy]ethyl}benzene phenylnitrostyrene (0.1 mmol, 1.0 eq.) and catalysts (1 mol%) were dissolved in 0.5 ml thf at 40°c before being stirred for 5 mins. propargyl alcohol (0.12 mmol, 1.2 eq.) was added at 40°c and stirred for 4 hours under tlc control until the nitrostyrenes were completely consumed. the mixture was then purified directly with flash cryogenic column chromatography over silica gel (0.5–2% etoac/pe) to obtain the products with a yield of 75%. compound no.1 is an oily yellow liquid, [α]d20+82.1 (with 0.3, chcl3), rf 0.48 (petroleum ether– etoac, 3:2). 1h nmr (300 mhz, cdcl3, figure 2): δ ppm: 7.29-7.34 (m, 3h), 7.17 (d, j= 7.2 hz, 2h), 5.85 (d.d.d, j=17.22, 9.15 , 5.34 hz, och=, 1h), 5.31 (d.d.d, j= 17.22, 1.57, 1.61 hz, h2c=, 1h), 5.17 (d.d.d, j=9.15, 1.57, 1.23 hz, h2c=, 1h), 4.76 (d.d.d, j= 22.1, 10.9, 7.7 hz, 2h), 4.63 (d.d, j=12.7, 5.9 hz, 1h), 4.61 (d.d, j=12.13, 5.34 hz, och2, 1h), 4.17 (d.d.d, j=12.13, 1.61, 1.23 hz, och2,1h) 13c nmr (100 mhz, cdcl3, figure 3): δ ppm: 136.3, 134.63 (-hc=), 133.7, 131.9, 127.6, 117.67 (h2c=), 78.5, 72.32 (=c-ch2o), 49.9 enantiomeric excess (ee): 92%, which was determined by a chiral phase chiralpak ie column (98/2 hexane/ i-proh, flow rate 0.5 ml/min, λ = 238 nm, tmajor = 22.0 min, tminor = 20.2 min). compound no. 2: 1-methyl-2-{(1s)-2-nitro-1-[(prop-2-en-1yl)oxy]ethyl}benzene yield: 63%. oily yellow liquid, [α]d20+80.1 (with 0.3, chcl3), rf 0.50 (petroleum ether–etoac, 3:2). 1h nmr (300 mhz, cdcl3): δ ppm: 7.08-7.14 (m, 2h), 7.06 (t, j= 7.0 hz, 1h), 6.99 (d, j= 7.7 hz, 1h), 5.85 (d.d.d, j= 17.23, 9.15, 5.34 hz, och=, 1h), 5.31 (d.d.d, j= 17.23, 1.57, 1.61 hz, h2c=, 1h,), 5.16 (d.d.d, j= 9.15, 1.57, 1.23 hz, h2c=, 1h), 4.99 (d.d.d, j= 9.8, 6.0 hz, 1h), 4.87 (d.d, j= 13.2, 9.9 hz, 1h), 4.64 (d.d, j= 13.2, 6.0 hz, 1h), 4.61 (d.d, j = 12.15, 5.34 hz, och2, 1h), 4.16 (d.d.d, j= 12.15, 1.61, 1.23 hz, och2, 1h), 2.40 (s, 3h) 13c nmr (100 mhz, cdcl3): δ ppm: 152.4, 136.5, 134.63 (-hc=), 128.3, 126.41, 126.40, 125.8, 117.67 (h2c=), 77.8, 72.32 (=c-ch2o), 45.6, 34.7, 31.2, 19.2 ee: 91% chiral phase chiralpak ic column (98/2 hexane/iproh, flow rate 0.5 ml/min, λ = 241 nm, tmajor = 25.0 min, tminor = 29.3 min) compound no. 3: 1-methyl-4-{(1s)-2-nitro-1-[(prop-2-en-1yl)oxy]ethyl}benzene yield: 0.44 g (89%). oily yellow liquid, m.p. 87–90°c. [α]d20+12.0 (c 0.51, chcl3), rf 0.50 (petroleum ether– etoac, 3:2). 1h nmr (300 mhz, cdcl3): δ ppm: 7.08 (d, j= 7.9 hz, 2h), 7.04 (d, j= 7.8 hz, 2h), 5.83 (d.d.d, j= 17.20, 9.15, 5.34 hz, och=, 1h), 5.31 (d.d.d, j= 17.20, 1.57, 1.61 hz, h2c=, 1h), 5.17 (d.d.d, j= 9.15, 1.57, 1.23 hz, h2c=, 1h), 4.69-4.77 (m, 2h), 4.60 (d.d, j= 12.14, 5.34 hz, och2, 1h), 4.54-4.64 (m, 1h), 4.16 (d.d.d, j=12.14, 1.61, 1.23 hz, och2, 1h), 2.25 (s, 3h) 13c nmr (100 mhz, cdcl3): δ ppm: 152.2, 134.63 (-hc=), 128.7, 127.5, 126.4, 117.67 (h2c=), 78.8, 72.32 (=c-ch2o), 49.7, 34.7, 31.2, 21.1 ee: 90% chiral phase chiralpak ib column (98/2 hexane/iproh, flow rate 0.5 ml/min, λ = 238 nm, tmajor = 33.3 min, tminor = 23.0 min). compound no. 4: 1-chloro-3-{(1s)-2-nitro-1-[(prop-2-en-1yl)oxy]ethyl}benzene yield: 50%. oily yellow liquid, [α]d20+200.7 (with 0.1 chcl3), rf 0.50 (petroleum ether–etoac, 3:2). 1h nmr (300 mhz, cdcl3, figure 4): δ ppm: 7.18 (d, j= 7.4 hz, 2h), 7.10 (s, 1h), 7.05 (d, j= 7.0 hz, 1h), 5.84 (d.d.d, j= 17.23, 9.14, 5.34 hz, och=, 1h), 5.31 (d.d.d, j= 17.23, 1.57, 1.61 hz, h2c=, 1h), 5.17 (d.d.d, j= 9.14, 1.57, 1.23 hz, h2c=, 1h), 4.68-4.75 (m, 2h), 4.644.67 (m, 1h), 4.61 (d.d, j= 12.16, 5.34 hz, och2, 1h), 4.17 (d.d, j= 12.16, 1.61, 1.23 hz, och2, 1h) 13c nmr (100 mhz, cdcl3, figure 5): δ ppm: 152.7, 134.63 (-hc=), 128.7, 127.9, 127.6, 126.5, 125.8, 117.67 (h2c=), 78.2, 72.32 (=c-ch2o), 49.4, 34.7, 31.2 ee: 93% chiral phase chiralpak ie column (98/2 hexane/i-proh, flow rate 0.5 ml/min, λ = 238 nm, tmajor = 18.3 min, tminor = 22.2 min). compound no. 5: 1-chloro-4-{(1s)-2-nitro-1-[(prop-2-en-1yl)oxy]ethyl}benzene yield: 53%. oily yellow liquid, [α]d20+200.7 (with 0.1 chcl3), rf 0.50 (petroleum ether–etoac, 3:2). 1h nmr (300 mhz, cdcl3): δ ppm: 7.26 (d, j= 8.4 hz, 2h), 7.12 (d, j= 8.3 hz, 2h), 5.85 (d.d.d, j= 17.22, 9.15, 5.34 hz, och=, 1h), 5.31 (d.d.d, j= 17.22, 1.57, 1.61 hz, h2c=, 1h), 5.17 (d.d.d, j= 9.15, 1.57, 1.23 hz, h2c=, 1h), 4.67-4.75 (m, 2h), 4.63 (d.d, j=12.13, 5.34 hz, och2, 1h), 4.59 (k, j= 11.1 hz, 1h), 4.16 (d.d.d, j=12.13, 1.61, 1.23 hz, och2, 1h) enantioselective alkoxylation of β-substituted aromatic nitroalkenes 53(2) pp. 1–6 (2025) 3 figure 2: 1h nmr (300 mhz) spectrum of compound 1 figure 3: 13c nmr (100 mhz) spectrum of compound 1 talybov hungarian journal of industry and chemistry 4 figure 4: 1h nmr (300 mhz) spectrum of compound 4 (acetone-d6) figure 5: 13c nmr (100 mhz) spectrum of compound 4 (acetone-d6) enantioselective alkoxylation of β-substituted aromatic nitroalkenes 53(2) pp. 1–6 (2025) 5 13c nmr (100 mhz, cdcl3): δ ppm: 152.6, 134.63 (-hc=), 129.0, 127.9, 126.5, 117.67 (h2c=), 78.4, 72.32 (=c-ch2o), 49.3, 34.7, 31.2 ee: 96.3% chiral phase chiralpak ie column (98/2 hexane/i-proh, flow rate 0.5 ml/min, λ = 239 nm, tmajor = 24.0 min, tminor = 21.2 min). compound no. 6: 1-bromine-3-{(1s)-2-nitro-1-[(prop-2-en-1yl)oxy]ethyl}benzene yield: 50%. oily yellow liquid, [α]d20+200.7 (with 0.1 chcl3), rf 0.50 (petroleum ether–etoac, 3:2). 1h nmr (300 mhz, cdcl3): δ ppm: 7.33 (d.d, j= 6.1, 2.6 hz, 1h), 7.22 (t, j=6.3 hz, 3h), 5.85 (d.d.d, j=17.21, 9.15, 5.34 hz, och=, 1h), 5.31 (d.d.d, j= 17.21, 1.57, 1.61 hz, h2c=, 1h), 5.16 (d.d.d, j= 9.15, 1.57, 1.23 hz, h2c=, 1h), 4.69 (t.t, j= 15.3, 7.7 hz, 2h), 4.63 (d.d, j= 11.0, 4.1 hz, 1h), 4.61 (d.d, j= 12.14, 5.34 hz, och2, 1h), 4.16 (d.d, j= 12.14 , 1.61, 1.23 hz, och2, 1h) 13c nmr (100 mhz, cdcl3): δ ppm: 152.8, 134.63 (-hc=), 130.4, 126.6, 126.5, 126.3, 122.8, 116.67 (h2c=), 78.11, 72.31 (=c-ch2o), 49.4, 34.7, 31.2 ee: 98.1% chiral phase chiralpak ic column (98/2 hexane/iproh, flow rate 0.5 ml/min, λ = 238 nm, tmajor = 16.9 min, tminor = 19.7 min). compound no. 7: 1-bromine-4-{(1s)-2-nitro-1-[(prop-2-en-1yl)oxy]ethyl}benzene yield: 50%. oily yellow liquid, [α]d20+200.7 (with 0.1 chcl3), rf 0.50 (petroleum ether–etoac, 3:2). 1h nmr (300 mhz, cdcl3): δ ppm: 7.37 (d, j= 8.3 hz, 2h), 7.06 (d, j= 8.3 hz, 2h), 5.85 (d.d.d, j= 17.23, 9.15, 5.34 hz, och=, 1h), 5.31 (d.d.d, j= 17.23, 1.57, 1.61 hz, h2c=, 1h), 5.17 (d.d.d, j= 9.15, 1.57, 1.23 hz, h2c=, 1h), 4.67-4.74 (m, 2h), 4.61 (d.d, j=12.14, 5.34 hz, och2, 1h), 4.58-4.63 (m, 1h), 4.17 (d.d.d, j= 12.14, 1.61, 1.23 hz, och2, 1h) 13c nmr (100 mhz, cdcl3): δ ppm: 152.6, 134.62 (-hc=), 127.8, 126.5, 122.6, 117.66 (h2c=), 72.31 (=c-ch2o) ee: 96.8% chiral phase chiralpak ie column (98/2 hexane/i-proh, flow rate 0.5 ml/min, λ = 238 nm, tmajor = 11.8 min, tminor = 12.8 min). compound no. 8: 1-methoxy-3-{(1s)-2-nitro-1-[(prop-2-en-1yl)oxy]ethyl}benzene yield: 50%. oily yellow liquid, [α]d20+200.7 (with 0.1 chcl3), rf 0.50 (petroleum ether–etoac, 3:2). 1h nmr (300 mhz, cdcl3): δ ppm: 7.14-7.18 (m, 1h), 6.72-6.81 (m, 2h), 6.69 (s, 1h), 5.85 (d.d.d, j= 17.22, 9.15, 5.34 hz, och=, 1h), 5.30 (d.d.d, j= 17.22, 1.57, 1.61 hz, h2c=, 1h), 5.16 (d.d.d, j= 9.15, 1.57, 1.23 hz, h2c=, 1h,), 4.70-4.77 (m, 2h), 4.65 (d.d, j= 12.15, 5.34 hz, och2, 1h), 4.57-4.63 (m,1h), 4.17 (d.d.d, j= 12.15, 1.61, 1.23 hz, och2, 1h), 3.66 (s, ch3o, 3h) 13c nmr (100 mhz, cdcl3): δ ppm: 159.8, 134.63 (-hc=), 128.3, 126.4, 119.8, 117.66 (h2c=), 114.1, 113.4, 78.6, 72.32 (=c-ch2o), 55.2, 50.0, 34.7, 31.2 ee: 95.7% chiral phase chiralpak ie column (98/2 hexane/i-proh, flow rate 0.5 ml/min, λ = 241 nm, tmajor = 24.0 min, tminor = 21.2 min). compound no. 9: 1-methoxy-3-{(1s)-2-nitro-1-[(prop-2-en-1yl)oxy]ethyl}benzene yield: 50%. oily yellow liquid, [α]d20+200.7 (with 0.1 chcl3), rf 0.50 (petroleum ether–etoac, 3:2). 1h nmr (300 mhz ???, cdcl3): δ, ppm: 7.13 (d, j= 8.5 hz, 2h), 6.78 (d, j= 8.6 hz, 2h), 5.85 (d.d.d, j= 17.22, 9.13, 5.34 hz, och=, 1h), 5.31 (d.d.d, j= 17.22, 1.57, 1.61 hz, h2c=, 1h), 5.17 (d.d.d, j= 9.13, 1.57, 1.23 hz, h2c=, 1h), 4.78–4.69 (m, 2h), 4.63–4.55 (m,1h), 4.61 (d.d, 1h, j= 12.14, 5.34 hz, och2, 1h), 4.17 (d.d.d, j= 12.14, 1.61, 1.23 hz, och2, 1h), 3.71 (s, ch3o, 3h) 13c nmr (100 mhz ???, cdcl3): δc, ppm: 159.7, 134.63 (-hc=),128.3, 126.4, 117.66 (h2c=),114.4, 78.9, 72.31 (=c-ch2o), 55.3, 49.4, 34.7, 31.2 ee: 98.1% chiral phase chiralpak ic column (98/2 hexane/iproh, flow rate 0.5 ml/min, λ = 241 nm, tmajor = 18.6 min, tminor = 20.4 min). 4. discussion enantioselective alkoxylation of β-substituted aromatic nitroalkenes with allyl alcohol facilitates the synthesis of individual stereorearrangers of unsaturated nitroesters. the synthesized compounds are of interest as intermediate products in organic synthesis. 5. conclusions enantioselective alkoxylation of β-substituted aromatic nitroalkenes with propargyl alcohol in the presence of a chiral ligand n-ethyl-n-{[(2s)-pyrrolidin2-yl]methyl}ethanamine leads to enantioselective synthesis of nitro-containing ethers with high yields (up to 98%) and enantioselectivity (up to 99% e.h.). the enantioselective three-component reaction of a carbonyl compound, amine and alkyne was studied as a simple method for the synthesis of chiral propargylamides. talybov hungarian journal of industry and chemistry 6 references [1] thompson, a.m.; blaser, a.; anderson, r.f.; shinde, s.j.s.; franzblau, s.g.; ma, z.; denny, w.a.; palmer, b.d.: synthesis, reduction potentials, and antitubercular activity of ring a/b analogues of the bioreductive drug (6s)-2-nitro-6-{[4(trifluoromethoxy)benzyl]oxy}-6,7-dihydro-5himidazo[2,1-b][1,3]oxazine (pa-824), j. med. chem., 2009, 52(3), 637–645, doi: 10.1021/jm801087e [2] milčić, n.; ćevid, i.; çakar, m.m.; sudar, m.; findrik-blažević, z.: enzyme reaction engineering as a tool to investigate the potential application of enzyme reaction systems, hung. j. ind. chem., 2022, 50(1), 45–55, doi: 10.33927/hjic-2022-08 [3] thompson, a.m.; sutherland, h.s.; palmer, b.d.; kmentova, i.; blaser, a.; franzblau, s.g.; wan, b.; wang, y.; ma, z.; denny, w.a.: synthesis and structure-activity relationships of varied ether linker analogues of the antitubercular drug (6s)-2-nitro-6{[4-(trifluoromethoxy)benzyl]oxy}6,7-dihydro5h-imidazo[2,1-b][1,3]oxazine (pa-824), j. med. chem., 2011, 54(19), 6563–6585, doi: 10.1021/jm200377r [4] zhou, l.; stewart, g., rideau, e., westwood, n.j., smith, t.k.: a class of 5-nitro-2furancarboxylamides with potent trypanocidal activity against trypanosoma brucei in vitro, j. med. chem., 2013, 56(3), 796–806, doi: 10.1021/jm301215e [5] thompson, a,m.; o’connor, p.d.; blaser, a.; yardley, v.; maes, l.; gupta, s.; launay, d.; martin, d.; franzblau, s.g.; wan, b.; wang, y.; ma, z.; denny, w.a.: repositioning antitubercular 6-nitro-2,3-dihydroimidazo[2,1-b][1,3]oxazoles for neglected tropical diseases: structure–activity studies on a preclinical candidate for visceral leishmaniasis, j. med. chem., 2016, 59(6), 2530–2550, doi: 10.1021/acs.jmedchem.5b01699 [6] thompson, a.m.; o’connor, p.d.; marshall, a.j.; yardley v.; maes, l.; gupta, s.; launay, d.; braillard, s.; chatelain, e.; franzblau, s.g.; wan, b.; wang, y.; ma, z.; cooper, c.b.; denny, w.a.: 7-substituted 2-nitro-5,6-dihydroimidazo[2,1-b] [1,3]oxazines: novel antitubercular agents lead to a new preclinical candidate for visceral leishmaniasis, j. med. chem., 2017, 60(10), 4212–4233, doi: 10.1021/acs.jmedchem.7b00034 [7] thompson, a.m.; o’connor, p.d.; marshall, a.j.; blaser, a.; yardley v.; maes, l.; gupta, s.; launay, d.; braillard, s.; chatelain, e.; wan, b.; franzblau, s.g.; ma, z.; cooper, c.b.; denny, w.a.: development of (6r)-2-nitro-6-[4-(trifluoromethoxy)phenoxy]-6,7-dihydro-5h-imidazo[2,1-b] [1,3]oxazine (dndi-8219): a new lead for visceral leishmaniasis, j. med. chem., 2018, 61(6), 2329– 2352, doi: 10.1021/acs.jmedchem.7b01581 [8] talybov, g.m.: enantioselective catalytic threecomponent synthesis of optically active propargyl amino ethers, hung. j. ind. chem., 2025, 53(1), 39– 42, doi: 10.33927/hjic-2025-05 https://doi.org/10.1021/jm801087e https://hjic.mk.uni-pannon.hu/index.php/hjic/article/view/1161 https://hjic.mk.uni-pannon.hu/index.php/hjic/article/view/1161 https://hjic.mk.uni-pannon.hu/index.php/hjic/article/view/1161 https://doi.org/10.33927/hjic-2022-08 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30. pp. 215218 (2002) time series and the algebraic matrix riccati equation c. storey (the institute of mathematics and simulation sciences, faculty of computing sciences and engineering, de montfort university, the gateway, leicester, lel 9bh, uk) received: september i 0, 2002 one way of modelling certain kinds of time series is via the yule-walker equations. these are a set of (over-determined) linear equations for estimating the parameters in the models. the coefficients in these equations are estimates, obtained from the data, of the autocorrelations. in this paper two ways of solving the yule-walker equations are considered. the first is the well known method using the pseudo-inverse and the second uses the algebraic matrix riccati equation. a number of numerical examples are used to illustrate and compare the two different approaches. keywords: autoregressive time series, yule-walker equations, algebraic matrix riccati equations, total least squares introduction determination of the autoregressive parameters ai,i = o,l,···,n, (1) in the stochastic process (2) where (3) i=o is investigated. in eq.(2), y(t) denotes noisy data, w(t) is white noise and d(q-1 ) is a polynomial containing the moving average parameters of the process. the expression q-1 in eq.(2) is the unit delay operator defined by q -1 y(t) = y(t 1). more extensive details and background material can be found in ref. [1]. here the yule-walker method is used to estimate the parameters ai by two different techniques. firstly the direct method involving the inverse or pseudo-inverse of the autocorrelation matrix, depending on the invertability or otherwise of the latter, is used. secondly an algorithm is used which is based on the result that a total least squares solution to the yule­ walker equations can be found by solving an appropriate matrix riccati equation. a number of numerical examples from ref. [1] serve to illustrate the two techniques and to compare the results with a more sophisticated stochastic analysis given in ref. [1]. a simil'!r investigation has been carried out in ref. [5] but the tsl solutions to the yule~ walker equation are obtained by singular value decomposition and simulated time series are used. the yule-walker method for a pure (i.e., d(q-1 )= 1) ar process the yule­ walker equations are (ref.[ 1 ], ref. [2]), r rli tn li ... rn-i a i 'i to ···~z-2 a'2 rj = (5) rm rm-1 ••• rm-(n-1) an r., 216 table 1 numerical results for series c nxm lxl lxlo lx50 lxloo tent final ls -.805 -.814 -.847 -.881 -.81 -.82 tls -.805 -.815 -.854 -.892 -.81 -.82 table 2 numerical results for series d nxm lxl lxlo lx50 lxloo tent final ls -.861 -.860 -.908 -.908 -.86 -.87 tls -.861 -.860 -.916 -.912 -.86 -.87 ck is an estimate of the relevant unknown autocovariance given by ck =_!_ ~(yt-y y yt+ky), k=o,l,2,··· n t=! a and n is the number of observations in the time series. in case m > n then the linear equations (eq.(s)) are overdetermined and the pseudo-inverse has to be used. numerical investigation four different autoregressive time series taken from ref. [1] have been used as numerical illustrations. ~ample i series c this is a time series, with n = 226 observations, of temperatures in a chemical process taken at one minute intervals. a model with two possible sets of parameters, one tentative (tent) the other more finalized (final) is given in ref. (1). these are the following: tent: vy(t)0.81vy(ti) = w(t) , final: vy(t)-0.82vy(t-l)=w(t). the results of the numerical investigation are given in table 1. the table entries are solutions (rounded to 3 decimal places) of n x m yule~ walker equations by the least squares method (ls) and by the total least squares method (tls). the former is found using the pseudo­ inverse matrix and the latter using algorithm l of [3]. (a convenient check on the ls solution is also obtained by using al as explained in [4]). for this example a closer analysis shows that m = 22 is about the best number of equations to use and tls is slightly better than ls. example 2 series d the tentative and final models for this example are: tent: y(t)0.86y(tl) = '"1t) table 3 numerical results for series e. model i nxm 2x2 2x10 2x50 2x99 tent final ls -1.318 -1.398 -1.475 -1.515 -1.32 -1.42 .634 .704 .724 .770 .63 .73 tls -1.318 -1.432 -1.549 -1.586 -1.32 -1.42 .634 .733 .790 .834 .63 .73 table 4 numerical results for series e. model2 nxm 3x3 3x10 3x50 3x99 tent final ls -1.369 -1.821 -2.104 -2.155 -1.37 -1.57 0.740 1.378 1.775 1.849 0.74 1.02 -0.0805 -0.367 -0.571 -0.599 -0.08 -0.21 tls -1.369 -1.975 -2.363 -2.412 -1.37 -1.57 0.740 1.609 2.188 2.277 0.74 1.02 -0.0805 -0.485 -0.783 -0.825 -0.08 -0.21 final: y(t)-0.87y(t-l)=w(t). there are n = 310 observations and the data is a set of chemical process viscosity readings taken at hourly intervals. the numerical results are shown in table 2. for this example m = 19 appears to be the best number of equations to take with tls getting nearer to 0.87 than ls with the same number of equations. example 3 series e for this, much studied example, the data shows the number of sunspots that occurred in each year from 1770 to 1869; so there are 100 observations. two different sets of parameter values are given for each of two different suggested models: modell tent: y(t) -1.32y(t -1) + 0.63y(t2) = w(t) , final: y(t) -1.42y(t -1) + 0.73y(t2) = w(t) , model2 y(t) -1.37y(t -1) + tent: , +0.72y(t-2)-0.08y(t-3) = w(t) final: y(t) -1.57 y(t -1) + . + 1.02y(t-2)0.21y(t3) = w(t) t abies 3 and 4 give the numerical results in this case. for the first model m = 9 or 10 give good approximations to the parameter values given in [ 1] and for the second model m = 7 or 8 seem to be reasonable values. table 5 numerical results for series f nxm 2x2 2x10 2x50 2x69 tent final ls 0.32 0.319 0.331 0.365 0.32 0.34 -0.18 -0.170 -0.178 -0.149 -0.18 -0.19 tls 0.32 0.323 0.385 0.451 0.32 0.34 -0.18 -0.168 -0.157 -0.104 -0.18 -0.19 example 4 series f here the time series f consists of 70 readings of the yields from a batch chemical process and the suggested model is: tent y(t) + 0.32y(t-1) -0.18y(t2) = w(t) final: y(t) + 0.34y(t -1)0.19y(t2) = w(t) the results of the calculations are shown in table 5. for this example the second parameter increases with m so the best m for this parameter is 2! for the first parameter, however, m = 25 gives a value of -0.338 with 0.169 for the second parameter. "portmanteau" lack-of-fit test a test for model adequacy, which depends on the first k auto-correlations of the residuals rk ( q) , is proposed in [1]. the statistic k q = n(n+2) l.rk2(t1)/(n-k) (6) k==l is computed and referred to a table of the chi-squared distribution. in eq.(6) n = n -d where d is the degree of differencing required to approximate to stationarity in the time series being analysed. for series d, with k = 25 , there are 24 degrees of freedom and eq.(6) becomes 25 q =310x31il,rk\t1)/(310-k) , k=i which is readily computed by mathematica, for example, as follows: subtract the mean of series d (9.13258) from each of its elements and can the resulting series, augmented by a back-forecasted value as its initial value, s(d). compute the series of residuals. s(d) =table [part [s(d),z1$ part[s(d),i-l],{i,2,310}] with $ the estimate of the model parameter. compute q as follows: s(d)=table[part[s(d),z1-0.0024394l,{i,l,310}] (0.00243941 is the mean of the previous s(d)). ro(a) = sum[part[s(d),i]* part[s(d),i],{i,l,310}] 217 g = table[sum[part[s(d),i] * * part[s(d),i+ j],{i,l,310j}],{j,l,l}]lr,,(a) (this produces a table of l auto-correlations of residuals) q = 310*312sum[part[g,if2/(310-i),{i,l,25}]. taking $ = -0.87 (the final value from [1]) gives q=l1.5 now when m x n = 19xl the parameter <i> obtained by ls is 0.868034 and by tls it is 0.868979. the corresponding values of q are 11.44 and 1 1.47. similarly when m x n =20xl the values for <i> are 0.870544 and 0.87177 with corresponding values of 11.51 and 11.55 for q. thus tls gets closer to the value of q given in [1] with fewer linear equations. conclusion a numerical study has shown that the tls method is slightly superior to the ls method for finding the unknown parameters in models of auto~regressive time series. the techniques used can be extended to estimation of moving average parameters [2]. special purpose methods for solving the yule-walker equation are also discussed in [2]. finally, when algorithm 1 is used on its own, and not in comparison with other methods as it is here. the computations should be stopped as soon as some test of lack of fit (such as the portmanteau test from [1]) is adequately satisfied. ai a,d q·l y{t) w(t) n m y n d symbols autoregressive parameters polynomials in q-1 unit delay operator noisy data white noise number of autoregressive parameters number of yule-walker equations mean ofy(t) number of observations in time series degree of differencing for stationarity q statistic used in portmanteau test i, j, k running incides l number of autocorrelations taken in portmanteau test. references 1. box g. e. p .• jenkins g. m. and reinsel g. c.: time series analysis: forecasting and control. 218 prentice hall inc., englewood cliffs, new jersey, 3rd edition, 1994 2. soderstrom t. and stoica p.: system identification, prentice hall international, 1989. 3. storey c.: hung j. ind. chem.j997, 25,305-308 4. storey c.: ibid, 2001,29,67-70 5. stoian a., stoica p. and van huffel s.: scientific bulletin, electrical eng. series, polytechnic institute of bucharest, 52, no.2, 81-89 page 217 page 218 page 219 page 220 untitled hungarian journal of industry and chemistry vol. 52(1) pp. 79–88 (2024) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2024-10 a review of the determination of diclofenac sodium with electrochemically modified sensors in various biological, pharmaceutical and water sources juan hidalgo1,2*‚ ildikó galambos1, graziella turdean2, luis hidalgo3 1 soós ernő research and development center, university of pannonia, zrínyi miklós street 18 , nagykanizsa, 8800, hungary 2 research center of electrochemistry and non-conventional materials, department of chemical engineering, faculty of chemistry and chemical engineering, babes-bolyai university, arany janos street 11, cluj-napoca, 400028, romania 3 department of mechanical engineering, faculty of mechanics, la escuela superior politécnica de chimborazo, panamericana sur km 1 1/2, riobamba, 060110, ecuador diclofenac sodium (dcf) has attracted must attention because it is one of the most common pharmaceuticals in water matrices and can potentially harm aquatic life. although most techniques used to analyze it are expensive and require highly trained professionally to operate such equipment, it is possible to detect dcf with electrochemical sensors. despite being able to identify this contaminant in different samples (tablets, blood, urine), only a few articles have been reported regarding the testing of dcf in wastewater. therefore, the papers selected in this review were organized according to the type of modifier used in the working electrode. furthermore, recent improvements in the detection of diclofenac by electrochemical techniques in pharmaceutical formulations, biological fluids and environmental materials are discussed along with a brief description of the results and methods employed in research. keywords: diclofenac sodium, wastewater, modifier, electrochemical detection 1. introduction over recent decades, industry and the global population have been growing rapidly, leading to an increase in the anthropogenic emission of contaminants into the environment, especially into water sources, which has greatly increased over the past few years [1]-[2]. as a result, different types of contaminants in water sources are gradually becoming more common. even if only at trace levels, they are harmful to the environment, animals and human health [3]-[4], perhaps causing several toxic side effects such as changes in behavior, the inhibition of cell proliferation and reproductive damage. furthermore, studies have shown that high concentrations of antibiotics cause several changes to the structure of bacteria, bringing about resistance to many strains and greatly affecting the food chain, which may contaminate sources of drinking water [5]-[6]. among these antibiotics, diclofenac sodium (dcf), which is a commonly used human and veterinary pharmaceutical prescribed to reduce inflammation and manage pain, has attracted much interest because it is one of the most common pharmaceuticals in water matrices and has the received: 1 march 2024; revised: 8 march 2024; accepted: 10 march 2024 *correspondence: juansannin2595@gmail.com potential to harm aquatic life [7]-[8]. it enters the water bodies through wastewater treatment plants, whereas most diclofenac residues in animals are released directly into the ecosystem [9]. moreover, unused and expired diclofenac from households is disposed directly into water sources down sinks or toilets [9]. consequently, several analytical methods have been developed to quantify the concentration of dcf in pharmaceutical and biological samples such as chromatographic methods (liquid chromatography (lc), gas chromatography-mass spectrometry (gc-ms)), tandem mass spectrometry, capillary zone electrophoresis (cze), spectrophotometry [11]-[12] and spectrofluorimetry [13]-[14], which are very sensitive with low limits of detection (lod) but require organic solvents, costly apparatus and highly qualified specialists, moreover, sample preparation is mandatory prior to analysis, making them unsuitable for screening [10]. in comparison, potentiometric sensors are environmentally friendly, simply designed, portable for in situ monitoring, require tiny samples as well as yield sensitive and reliable results cheaply [10]. in addition, one of the most important developments to enhance drug detection and increase the https://doi.org/10.33927/hjic-2024-10 mailto:juansannin2595@gmail.com hidalgo, galambos, turdean and hidalgo hungarian journal of industry and chemistry 80 electron transfer rate on the surface of the electrode is electrode modification, which can be achieved by designing a highly electroconductive, stable modifier equipped with a high-degree molecular recognition system, an active area, large surface binding sites and excellent catalytic activity [15]. a good example of this are tio2 nanoparticles which are versatile compounds extensively applied as a catalyst in various fields [56]. their properties and characteristics contribute towards its effectiveness in catalytic reactions, moreover, can be used as a modifier in electrochemical sensing. however, since the novel determination techniques have not been widely studied for analyzing the concentration of dcf in sources of wastewater, they may be developed and applied in this respect to improve the precision of measurements and reduce costs. in this study, the most promising and viable methods for creating electrochemically modified sensors to assess the concentration of dcf in various sources (blood, urine, wastewater, groundwater) are presented based on performance characteristics such as pricing, limit of detection, preparation technology, linear range and selectivity/chemical interference (figure 1). these methods are illustrated in the form of tables and graphs. finally, in the future, the compiled information will be expanded to prepare electrochemically modified sensors to determine the concentration of dcf in groundwater, wastewater and municipal water, providing an easy, fast and cheap way of measuring this contaminant globally, particularly in, for example, south america and africa, where the technology to perform the cited analytical methods is lacking. 2. experimental 2.1. literature review theoretical methodology this analysis included publications from scopus, sciencedirect and the web of science (wos) database as well as searched for using goolge scholar. except for a few additional publications due to their academic value, articles published between 2015 and 2022 were preferred. in terms of the literature review and selection of articles, at least two key phrases in search strings were evaluated. the first word refers to the material the working electrode is composed of (glassy electrodes, glassy carbon electrodes (gces), multiwalled carbon nanotubes (mwcnts), carbon nanotubes (cnts), single-walled carbon nanotubes and metals), while the second refers to surface modification techniques (imprinted, coating and cyclic voltammetric techniques). only literature published in english up until october 10, 2022 was evaluated. a systematic review and metaanalysis using published simulated data [16] were used to assess the manual examination of the published studies selected. 2.2. qualification analysis of the literature the considered publications were downloaded in a separate folder in order of the authors and entitled after the material the working electrode is composed of as well as the method used to make it. the titles and abstracts of these publications were selected based on their primary content. finally, the core idea and key findings of each study were extracted and compared to the other articles published. 2.3. data extraction and analysis the data from the publications were separated into two groups according to the baseline data they contain, as stated in the preceding sections. literature based on characteristics such as the accessible technology in the electrochemistry laboratory at babes-bolyai university, year of publication, place of origin, nature of the study, type of article, study area and study design were prioritized. afterwards, the type of low-cost working electrode and electrochemical surface modification technique(s) used, modification category, in-depth discussions on the surface characterization techniques applied (electrostatic force microscopy (efm), energy dispersive x-ray analysis (edx), fourier-transform infrared spectroscopy (ftir), analysis of cyclic voltammograms (cv), electrochemical impedance spectroscopy (eis)) as well as sample preparation were the most popular criteria for searching and extracting data from the chosen publications. the important data from the analysis were originally organized in a table to examine it clearly and statistically. ibm spss statistical software version 17.0 (ibm corp., tx, usa, 2021) was employed to analyze the collected data. hungarian journal of industry and chemistry provided a limited amount of disk space to distribute electronic supporting information. figure 1: various modified electrodes for the electrochemical determination of dcf in different sources diclofenac sodium determination 52(1) pp. 79–88 (2024) 81 3. results and analysis 3.1. statistical results 100 valuable published studies were retrieved following a thorough statistical analysis, the majority of which were from wos-indexed journals. 40 studies were eliminated because of duplicated downloads, reducing the number to 60. 20 more publications were eliminated from this total of 60 owing to a lack of importance and in-depth analysis. furthermore, 12 records were temporarily omitted because of a lack of information and their years of publication, resulting in just 28 articles being considered. the importance of the research published in these studies was briefly reviewed below and the results classified according to their field of development and year of publication. 3.2. electrochemical sensors to determine the diclofenac concentration electrochemical sensors are by far the most commonly used type of sensor because of their advantages, which include limits of detection as low as picomoles, rapidity and the low-cost equipment used for sensing. the analytical information in electrochemical sensors is derived from the electrical signal produced by the interaction between the target analyte and recognition layer [54]. the following focuses on potentiometric sensors that analyze specific interactions between sensors and analytes. when no current is allowed to flow through the system, a nernstian equilibrium is formed at the sensor interface, providing information about the concentration of the analyte. in this regard, it is critical to account for the chemical reaction that will occur on the surface of the electrode in order to detect diclofenac. previously, the oxidation mechanism of the drug (see figure 2) was studied in which the oxidation peak that occurs between 0.65 and 0.70 v that is sensitive to changes in the ph of the electrochemical system is clearly visible [34]. furthermore, in the presented mechanism, dcf is irreversibly oxidized to 5-hydroxydiclofenac in a process of losing 2eand 2h+ giving rise to an oxidation peak at ~662 mv when the sweep was initiated in the positive direction. 5-hydroxydiclofenac is reduced as a result of the successive cathodic sweeps to diclofenac 2,5-quinone imine. during the second anodic sweep, a new oxidation peak was observed relating to the oxidation of diclofenac 2,5-quinone imine, involving 2e− and 2h+ [45]. therefore, it is necessary to create a surface that allows the reaction mechanism to occur beneath its surface. it is also necessary to determine what surface characteristics are preferable and their level of importance in influencing the peak potential, thereby changing the sensing characteristics. as a result, the information compiled in the following sections is divided according to how the surface electrode was modified and the characteristics of the sensors. 3.3. diclofenac detection using cnts as a modifier several studies were conducted using a gce modified with carbon nanotube composites as a working electrode for determination. furthermore, the working electrode was modified by incorporating f-mwcnts which provide a larger surface area, a high degree of mechanical strength and improved electrical conductivity. diclofenac is found in different sources, namely commercial tablets and human biological fluids [17][28], due to its low cost and easy fabrication as well as techniques available to fabricate the sensors. as a result, these types of electrodes are still the most commonly used. furthermore, the broad range of ph, from acidic to basic environments (4-8), facilitates different applications, thereby ensuring their robustness. the mechanism cited in section 3.1 can occur at the surface of the modified electrochemical sensor using gce/cnt sensors, ensuring accurate identification of the drug present in different samples. for example, the gce was modified using nanocellulose/mwcnts prepared by drop-casting techniques and the contaminant was tested using differential pulse voltammetry (dpv) [49]. the working concentration range reported by this sensor was 0.1 – 0.5 𝜇m with a lod of 0.0012 𝜇m. the applicability of the sensor was tested on samples of human blood and urine obtained from different patients. in contrast, gce sensors that were not modified reported a low limit of detection when the tables were analyzed within a linear range and lod equal to 0.01 – 0.05 𝜇m and 0.0053 – 1.6 𝜇m, respectively [27]. although the concentration of diclofenac was determined using the same technology (dpv) in all tests, the ph varied allowing how the ph affects the extent of the reaction to be observed. furthermore, modified gces have a large electroactive surface area, ensuring that the reactions can occur in the sensor. in addition, working electrodes modified by mwcnts have piqued the interest of researchers due to their unique properties such as increased surface area, sharp electrochemical response, good adsorption capacity, improved chemical stability, significant electrical conductivity and increased mechanical strength. figure 2: oxidation mechanism of dcf proposed by [45] at ph 7.0 under a gce modified with mwcnts hidalgo, galambos, turdean and hidalgo hungarian journal of industry and chemistry 82 the majority of the current trends in the preparation of sensors modified by mwcnts is summarized in table 1 in which the major parameters used to describe the differences between the various manufactured sensors, that is, the modifier, electrochemical technique used for determination, linearity, lod and source of the analysis, are presented. furthermore, since fabrication of these modified sensors is simple, large-scale production, the use of relatively low-cost materials and the potential to be used over a wide concentration range of dcf is possible. in addition, this type of sensor can ensure accurate analyses within seconds as fast scan rates can be used without the need for bulky expensive equipment, solvents and special gases. when the baseline correction (the moving average) is performed in a high potential region, interference with the peak height of the analyte occurs due to the presence of high background currents following the onset of oxygen evolution and possibly carbon oxidation reactions, making the determination of compounds above +0.8 v unreliable. finally, the modified sensors demonstrate remarkable electrocatalytic activity in the electro-oxidation of dcf by dramatically lowering the oxidation overpotential and increasing peak currents. to detect dcf concentrations, the modified electrodes demonstrated a low lod, wide linear concentration range and quick response as well as high degree of stability and repeatability [21]. 3.4. diclofenac detection using go as a modifier researchers have shown much interest in graphene and its derivative graphite because of its remarkable electrical characteristics resulting from the arrangement of carbon atoms in a perfect honeycomb lattice. the backbone is comprised of hybridized sp2 orbitals which are important in sensing applications because they allow graphenebased materials to interact with their environment and convert these interactions into a readable electrical signal [45]. furthermore, within the internal structure of graphene and its derivatives, a phenomenon known as ballistic transport occurs in which electrons travel less than a micrometer without scattering. as a result, graphene-based sensors are extremely electrically robust [46]. nevertheless, under ambient conditions, the mobility of charge carriers is still limited by impurity scattering which decreases the sensing ability in wastewater samples [46]. on the other hand, thanks to a strong ambipolar electric field effect, graphene can be electrically doped by transferring the charge carriers between electrons and holes. this is critical in the field of water quality monitoring since selectivity for the desired analyte is essential and graphene may be readily doped with a wide variety of compounds [47]. for example, the performance of the sensor was improved by adding carboxyl-functionalized graphene oxide to it [23]. under normal conditions, the lod of the sensors was low, that is, equal to 0.09 𝜇m which was 10 times lower than that of the graphene sensors prepared without a modifier, when tested in urine [29]. to summarize, graphene oxide-modified electrodes are resilient because of the electrical properties of graphene and a key feature is the ability of graphene to be doped by pand n-doping, facilitating the inclusion of chemically sensitive diclofenac. the price of the prepared sensors, on the other hand, is the key hurdle in the implementation of this type of sensor in the industry. however, if it is possible to integrate low-cost analyses, the demand for wastewater analysis will skyrocket. finally, the pencil graphite electrode (pge)-modified sensors offered a high degree of sensitivity and low lod, moreover, can be used to determine diclofenac concentrations at trace levels. these characteristics make them an appropriate type of sensor for determining the concentration of dcf in aqueous solutions (table 2). 3.5. diclofenac detection using nanoparticles of metals or metal oxide particles as a modifier metals and alloys have been widely studied in the construction of sensors to identify different contaminants in water. the metals gold and titanium in particular have a huge range of applications due to their high electrocatalytic activity and mechanical properties (see table 3). consequently, a new electrochemical sensor based on au-pt bimetallic nanoparticles supported on mwcnts which have a large specific surface area, exhibit high electrical conductivity and can significantly facilitate the electron transfer process of the redox probe on the electrode surface was produced [41]. furthermore, a linear calibration curve within the concentration range of 0.5 to 1000 μm was obtained. the lod of the prepared sensor was 0.3 μm. finally, the presence of interfering species in the solution had no significant table 1: principal outcomes in the determination of the diclofenac concentration in different sources using cnts as a modifier in working electrode modifier method linearity (𝜇m) lod (𝜇m) ref. ncfmwcnts cun/gce swv 0.05 80 0.00048 [48] mwcnts dpv 0.047 12.95 0.017 [30] ncfmwcntscun swv 0.05 80 0.00014 0.00048 [49] mwcntschitosan swv 0.3 200 0.021 [25] nanocellulose/ f-mwcnts cv 0.05 50.00 0.2 [26] cellulose/ f-mwcnts dpv 0.05 1.00 0.0012 [49] non-modifier dpv 0.01 0.05 0.053 1.6 [27] diclofenac sodium determination 52(1) pp. 79–88 (2024) 83 effect on the dcf current response and the changes in peak current were < 5 %. additionally, iron oxide nanoparticles functionalized with ionophoric polymer β-cd were applied to detect diclofenac in wastewater [42]. the sensor achieves an lod equal to 0.11 μm as well as the highest degree of selectivity towards dcf anions in the presence of organic compounds and some inorganic anions that may exist in pharmaceutical dosage forms which are likely to be present in wastewater. finally, the results of dosage-form and wastewater analysis showed the applicability of the sensors in terms of both quality control and environmental studies without the need for sample treatment beforehand. the application of metal-decorated particles in contaminant sensing is evident as a result of the electrochemical performance of the electrode, which is determined by its electrical conductivity and accessible surface areas. therefore, the electrochemical performance of sensors can be improved by building composites from mixing highly electrocatalytically active materials with outstandingly conductive substances to change the electrode surface. furthermore, the modification of metallic electrodes is one of the most important developments to increase drug detection and the electron transfer rate at the electrode surface [47]. 3.6. diclofenac detection using polymers as a modifier one of the most successful potentiometric sensors in use today, primarily in clinical analysis and quality control, is based on conductive polymeric membranes with ionophores incorporated directly into the polymeric matrix [33]. furthermore, some polymers can modify the internal structure of the working electrodes (table 4). for example, an imprinted electrochemical sensor based on a polyaniline nanocomposite was prepared [32]. the electrochemical studies of the prepared sensor demonstrated a change in the peak-to-peak separation equal to 0.248 v due to a more reversible charge-transfer process on the polyamide-printed electrode than that on the pge electrode which may be attributed to a possible catalytic effect of the added nanocomposite on the carbon paste [46]. in addition, the evaluated surface areas of the pge and polyamide-pge electrodes were found to be 0.013 ± 0.001 and 0.019 ± 0.002 cm2, respectively, an enhancement in the active surface area of the modified electrode of about 46 % when compared to the unmodified pge electrode. furthermore, the calculated average concentration (22.7 ± 2.0 mg l−1 of dcf) demonstrated that the proposed sensor can be appropriately reproduced. finally, the tolerance limit was determined as the concentrations of foreign substances, yielding an error of less than ± 5 %. the variation in the peak height observed for dcf in the presence of the tested species (ascorbic acid, glucose and urea) in the table 2: principal outcomes regarding the determination of the diclofenac concentration in different sources using graphite oxide as a modifier in working electrode modifier method linearity (𝜇m) lod (𝜇m) ref. go/cooh cv, lsv 1.2 400 0.09 [23] non-modifier dpv 0.80 9.5 0.76 [29] go/zno swv 18.01 1 5.06 [31] go/ co (oh)2/ cnf cv, swv 3.7 140 0.05 [27] go/ag/zno dpv 0.025 200 0.02 [27] go/cu cv 20 400 0.08 [52] table 3 principal outcomes in the determination of the diclofenac concentration in different sources using nanoparticles of metals or metal oxides as a modifiedr in working electrode modifier method linearity (𝜇m) lod (𝜇m) ref. ceo2 dpv 0.4 0.4 1.6 [20] aunps/ mwcnts cv 0.03 200 0.02 [21] go/cu/ doped zeolite dpv 3.01 15 0.3 [36] mos2 ca 0.05 600 0.03 [37] ru/tio2 cv 0.291 11.48 [38] au/mwcnts/ go cv 0.4 1000 0.09 [39] hg/go cv 0.002 5 0.32 [40] au-pt/ mwcnts cv 0.5 1000 0.3 [41] fe3o4/ iontophoretic polymer cv 0.001 0.1 0.11 [42] c3n4/cual dpv 0.5 60 0.38 [53] hidalgo, galambos, turdean and hidalgo hungarian journal of industry and chemistry 84 ratios of 1:1–1:1000 (dcf to interfering substances in mol l−1) confirms that the presence of different interfering species did not significantly affect the efficiency of the sensor, even when their concentration was 1000 times greater than that of the analyte [32]. 3.7. diclofenac detection using ionic liquids as a modifier potentiometric methods using ionic liquid electrolytes (ile) are appealing alternatives to drug detection because they require simple procedures and low-cost electrodes in addition to offering a good degree of selectivity and sensitivity [34]. recently, iles have been used as the paste binders for fabricating carbon composite electrodes (table 5), which provide an obvious increase in the electrochemical response of electroactive substrates and reduce the overpotentials of some organic substances [35]. in this sense, a sensor based on the combination of mwcnts and butyl-imidazole, propargyl bromide used as an ionic liquid [34]. the aforementioned sensor achieves a lod equal to 0.018 𝜇m and a linear range equal to 0.05 50 𝜇m. furthermore, the stability of the proposed electrode was evaluated by measuring the decrease in cv current of dcf after having been stored for one month. the cv response decreased by only 5 %, indicating that mwcnts-il is sufficiently stable. the author concluded that the main advantage of using the mwcnts-il is facile and quick surface renewal after each use, moreover, the mwcnts-il composite-modified carbon ceramic electrode exhibits high electrocatalytic activity with regard to the oxidation of dcf. 4. conclusions this review includes the most inexpensive technologies for preparing electrochemically modified sensors to determine the diclofenac concentration in different samples (urine, blood, tablets). the different technologies were differentiated by the type of modifier that the different researchers used to construct the sensors which improve their performance and ensure the oxidation reaction of diclofenac during the analysis of the sample. a significant development was reported when graphene was used as a modifier. as these types of sensors can be doped by p-dopants or n-dopants, in the matrix of the sensor, different types of chemicals can be added to improve the oxidation reaction. in this sense, the most selective sensors were prepared with gce and mwcnts by imprinted technologies, reporting an lod equal to 0.017 𝜇m. the other type of sensors cannot achieve these lod values. on the other hand, not many sensors were prepared with metallic electrodes because the selected electrodes are quite expensive, exceeding the estimated budget for our project. furthermore, continuous monitoring of the dcf concentration in real-time samples will be more useful than batch detection and efforts to build continuous systems are encouraging. most of the sensors were evaluated using real-world samples such as pharmaceuticals, biological fluids and environmental samples. furthermore, the examples discussed are represented over a range of suggested electrochemical methodologies, which are mostly based on voltammetric and, to a lesser extent, on amperometric techniques. finally, the current review provides a comprehensive picture of the scope and complexity of the preparation of various electrochemical sensors. the selectivity and sensitivity of electrochemically modified sensors can also be ensured by adjusting their various characteristics. although not much information on wastewater sensors was found, several technologies should be adapted in the laboratory to develop low-cost and sensitive sensors that can be utilized for continuous monitoring of riverwater or different water sources. table 4: principal outcomes in the determination of the diclofenac concentration in different sources using polymers as a modifier in working electrode modifier method linearity (𝜇m) lod (𝜇m) ref. maa/egdma cv not reported 5 [24] tio2/pedot cv 0.715 1.62 0.02 0.03 [28] go/polyamide cv 1.61 1.2 [32] go/polypyrrole cp 0.011 0.310 19 [33] pdms/pc cv 1.01 5.01 5 [43] pvc cv 0.005 0.5 0.32 [44] mip cv not reported 0.077 [32] table 5: principal outcomes in the determination of the diclofenac concentration in different sources using ils as a modifier in working electrode modifier metho d linearity (𝜇m) lod (𝜇m) ref. mwcnts–il dpv 0.05 50 0.018 [34] go/[bpim][dcf] dpv 3.18 0.318 0.015 [35] mwcnts/ cu(oh)2 nanoparticles/ il nanocomposite dpv 0.18 119 0.04 [52] diclofenac sodium determination 52(1) pp. 79–88 (2024) 85 acknowledgements this research was supported by the ph.d. fellowship offered by the tempus public foundation under the stipendium hungaricum scholarship program financed by hungarian government decree 285/2013 (26.07). nomenclature aunp: gold nanoparticle ca: chronoamperometry cnf: carbon nano-flakes cnt: carbon nanotube cp: chronopotentiometry cun: copper nanoparticles cv: cyclic voltammograms cze: capillary zone electrophoresis dcf: diclofenac sodium dpv: differential pulse voltammetry edx: energy dispersive x-ray efm: electrostatic force microscopy egdma: ethylene glycol dimethacrylate eis: electrochemical impedance spectroscopy ftir: fourier-transform infrared spectroscopy gce: glassy carbon electrode gc-ms: gas chromatography-mass spectrometry go: graphene oxide go-cooh: carboxyl-functionalized graphene oxide il: ionic liquid ile: ionic liquid electrolyte lc: liquid chromatography lod: limit of detection lsv: linear sweep voltammetry mip: molecularly imprinted polymer mwcnt: multi-walled carbon nanotube nc: nanocellulose pc: polycarbonate pdms: poly(dimethylsiloxane) pedot: poly(3,4-ethylene dioxythiophene) pge: pencil graphite electrode pvc: polyvinyl chloride swv: square wave voltammetry technique wos: web of science [bpim][dcf]: associate of diclofenac with an imidazolium moiety references [1] starling, m.c.v.m.; amorim, c.c.; leāo, m.m.d.: occurrence, control and fate of contaminants of emerging concern in environmental compartments in brazil, j. hazard. mater, 2018, 372, 17–36, doi: 10.1016/j.jhazmat.2018.04.043 [2] souza, m.c.o.; rocha, b.a.; adeyemi, j.a.; nadal, m.; domingo, 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chem., 2023, 51(2), 65– 75, doi:: 10.33927/hjic-2023-20 https://doi.org/10.1016/j.matchemphys.2022.127002 https://doi.org/10.1016/j.msec.2012.04.066 https://doi.org/10.1016/j.msec.2012.04.066 https://doi.org/10.3390/chemosensors10090363 https://doi.org/10.33927/hjic-2023-20 hungarian journal of industry and chemistry vol. 49(2) pp. 15–18 (2021) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2021-15 study on the photo-based 3d scanning process álmos kristály*1 and péter ficzere1 1department of railway vehicles and vehicle system analysis, budapest university of technology and economics, műegyetem rkp. 3, budapest, 1111, hungary the experiment aims to determine the practical applicability of photo-based 3d scanning technologies. with the help of computer software, 3d printable, simulation-ready models are created from regular photographs. the accuracy and consistency of such models are evaluated regarding usability engineering. keywords: 3d modelling, 3d scanning, photo-based 3d models 1. introduction with the development of manufacturing and modelling technologies, more and more complex geometries can be created. at the beginning of the 20th century, point-perfect shop drawings were used for production. nowadays, computer numerical control (cnc) is used exclusively for the control of machine tools worldwide. cnc codes can be generated directly from digital 3d geometries (cad models, fig. 1) and immediately sent to the machine tool via online connected systems. cad models are created based on planned or measured dimensions. although this method is faster than handmade shop drawings, a complex cad model can still take months to create from scratch. a more straightforward method is reverse engineering, during which all data necessary for simulation or manufacturing is documented from an already existing part [1]. planning is unnecessary; for the purpose of creating the cad model, it is sufficient to measure the part. difficulties can occur in the case of spherical, parabolic or other irregular surfaces that are hard to measure. 3d scanning technologies substantially simplify this process. since the 1960s, numerous methods have been invented [2]. at first, contact probes were used to measure each point of a surface, which were then saved as coordinates with regard to the machine coordinate system. later on, optical methods were developed. by photographing an object from two different positions, the respective focal lengths can be compared to determine the dimensions of the object. a more advanced method uses laser beams and sensors to calculate these lengths based on the speed of the beam and the duration of the reflection from the surface. the *correspondence: almos99@freemail.hu figure 1: cad model of the shell of a handheld game console. current position of the device is also required [2]. none of these methods requires physical contact with the object. today, 3d scanning devices fit in our pockets: numerous smartphones and pieces of computer software are available that can create 3d models based on photos. entry-level, free software typically offers cloud-based processing that may take days to finish. in order to access higher-end, engineering-level software, a subscription must be taken out, however, instant results are provided. at least 40 photos are required to model the geometry the more photos, the better the result. photos should be taken from roughly equiangular positions on a circle with a 30 − 300 cm radius around the object in a static environment. the software overlaps the photos based on the surroundings of the target object (like pieces of a jigsaw puzzle), ultimately creating a three-dimensional replica of the environment with the https://doi.org/10.33927/hjic-2021-15 mailto:almos99@freemail.hu 16 kristály and ficzere figure 2: rubbish bin and garden chair. object in the middle. this technology is applied in practice to map nature reserves [3], to investigate crime and accident scenes [4], as well as in medical and production technologies [5]. 2. experiment the piece of software “autodesk recap photo” was used with an educational license to generate models during the experiment. the accuracy of their size, shape and ratio was evaluated, along with their potential practical applications. however, this strongly depends on the type of usage and an accuracy within a range of 1− 2 % is generally expected [6]. the photos were taken with a 16-megapixel smartphone camera. the software supports both landscape and portrait image orientations. model generation is cloud-based, meaning powerful hardware is not required, however, a processing time of 20 − 70 hours should be expected. models are generated by the aforementioned overlaying principle. the more photos there are, the more accurate the layering and, therefore, the model itself will be [7]. a total of 4 objects of different sizes and complexities were modelled. the experiments and their results are presented below. the first objects that were attempted to be modelled were a plastic rubbish bin and a garden chair (fig. 2). photos were taken from both sides and above. the photographic parameters used are summarized in table 1. since the photos were taken outdoors, a heightened level of attention was needed to include any moving objects (tree branches, cats, birds, etc.) in the photos as well as achieve consistent lighting and minimal shading or glistening off the surfaces. these distructions had a negative effect on the generated model. the results (cut and positioned) can be seen in fig. 3. table 1: photographic parameters. object distance number from camera of photos rubbish bin 120− 150 cm 49 garden chair 120− 150 cm 40 figure 3: models of the rubbish bin and garden chair. the bottom parts of the models are visibly inaccurate and hollow since no information was present in the photos. the model of the rubbish bin is specifically inaccurate around the wheels and a minimal degree of waviness of the side panels can be observed. the model of the garden chair features one large and several smaller holes on the back, supposedly as a result of its thin structure, inappropriate lighting and shades. nevertheless, the fundamental shapes and details are present, significantly reducing the post-processing time to create a perfect model compared to manual measurements and modelling from scratch. although the models are highly detailed, a high level of accuracy and rational dimensions are also crucial for practical applications. a rectangular box was used to determine the accuracy of the software. the box along with its dimensions can be seen in fig. 4. once the project has been processed, the model can figure 4: rectangular box with dimensions used to validate the level of accuracy. hungarian journal of industry and chemistry study on the photo-based 3d scanning process 17 figure 5: generated dimensions. be edited directly from recap photo. it is possible to move, rotate or remove parts of the object. a dimension can be set manually between two arbitrary points, after which all the dimensions are calculated by the software proportionally. the model can then be exported in various polygon mesh formats and imported into various pieces of cad software for post-processing. dassault systèmes’ catia software was used to measure the generated dimensions. the results can be seen in fig. 5. the comparison between the actual and generated dimensions is presented in table 2. as can be seen in table 2, the most significant deviation is −4.863 %. however, this is the only dimension in connection with the deformed bottom surface, the geometry of which is inaccurate due to the photography. the deviation in the other two directions is under 1 %; this accuracy is acceptable in most branches of engineering. in the case of a significant practical application, a higher-quality camera should be used to achieve better photographs as well as a pedestal to prevent any surfaces from touching the ground, thereby achieving an exponentially higher-quality model. as a final project, an attempt was made to model an automobile and a motorcycle. these objects include extensive, complex geometries and irregular, glistening, transparent surfaces, which pose a challenge for the software. photos of both vehicles and the generated models can be seen in figs. 6 and 7, respectively. several faults can be observed in the models. the roof of the car is inaccurate due to the lack of top view photos. the windows are not smooth and its surface is wavy in certain areas as if it was “molten”. this can also table 2: comparison between the actual and generated dimensions. actual dimensions generated dimensions difference (mm) difference (%) 235 mm 234.94 mm 0.06 mm 0.0256 % 165 mm 163.822 mm 1.178 mm 0.714 % 60 mm 62.918 mm 2.918 mm −4.863 % figure 6: photographs of the automobile and the motorcycle. figure 7: generated models of the automobile and the motorcycle. be seen on the motorcycle, along with the inaccuracy of the tires, especially on areas close to the ground. despite these faults, the main shapes and ratios are maintained. modifying these models by post-processing is more straightforward and quicker than creating one from scratch. 49(2) pp. 15–18 (2021) 18 kristály and ficzere 3. conclusion with the development of 3d printing, an increased emphasis is being placed on reverse-engineering technologies to quickly and efficiently copy existing geometries either for the purpose of recreation or simulations. photo-based 3d scanning software play a crucial role in simplifying and drastically shortening this process, offering an economical, quick and space-saving alternative to traditional 3d scanning devices. the method can be used outside of engineering applications, e.g., in medicine to create custom implants and prostheses or in accident scene investigation by running simulations on the modelled wreckage. the study shows that the accuracy of recap photo is sufficient for these 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& durability, 2013, 1, 241– 247 issn: 1844-640x [6] mankovits, t.; szabó, t.; kocsis, i.; páczelt, i.: optimization of the shape of axi-symmetric rubber bumpers. stroj. vestn.-j. mech. e ., 2014, 60(1), 61– 71 doi: 10.5545/sv-jme.2013.1315 [7] fedorko, g.; stanova, e.; molnar, v.; husakova, n.; kmet, s.: computer modelling and finite element analysis of spiral triangular strands. adv. eng. softw., 2014, 73, 11-21 doi: 10.1016/j.advengsoft.2014.02.004 hungarian journal of industry and chemistry https://doi.org/10.1109/tsmc.1985.6313354 https://doi.org/10.22306/asim.v4i4.54 https://doi.org/10.3390/rs3061104 https://doi.org/10.3390/rs3061104 https://doi.org/10.1117/12.920728 https://doi.org/10.5545/sv-jme.2013.1315 https://doi.org/10.1016/j.advengsoft.2014.02.004 https://doi.org/10.1016/j.advengsoft.2014.02.004 introduction experiment conclusion hungarian journal of industry and chemistry vol. 50 pp. 7–10 (2022) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2022-02 a survey of sars-cov-2 genetic material reduction during a traditional wastewater treatment technology orsolya adamcsik*1, renáta gerencsér-berta1, borbála oláhné horváth1, nikoletta kovács1, viola somogyi2, endre gábor domokos2, gábor kemenesi3, endre gábor tóth3, ferenc jakab3, and ildikó galambos1 1soós ernő water technology research and development center, university of pannonia, zrínyi miklós u. 18, nagykanizsa, 8800 hungary 2research centre for biochemical, environmental and chemical engineering, university of pannonia, egyetem u. 10, veszprém, 8200 hungary 3national virology laboratory, szentágothai jános research centre, university of pécs, ifjúság u. 20, pécs, 7624 hungary the transmission of severe acute respiratory syndrome coronavirus-2 in a community can be monitored by a wastewater-based epidemiological approach due to fecal shedding. although sewage surveillance has gained a considerable amount of attention over the last 16 months, an indirect issue within the topic is whether traditional wastewater treatment technologies are sufficiently efficient to eliminate the genetic material of sars-cov-2. samples were taken from the wastewater treatment plant in nagykanizsa before the virus was concentrated, nucleic acid extracted and sars-cov-2 detected by rt-qpcr (quantitative reverse transcription pcr). the influent and primary treated samples tested positive, while after the secondary treatment, all the results were negative. consequently, the activated sludge process proved to be efficient in terms of the removal of sars-cov-2. keywords: warning system, covid-19, wastewater-based epidemiology 1. introduction during the transmission of severe acute respiratory syndrome coronavirus 2 (sars-cov-2) since the start of the covid-19 pandemic, wastewater-based epidemiology (wbe) has gained a considerable amount of attention as a surveillance system. numerous research groups and health authorities are currently engaged in sewage monitoring worldwide. apart from viruses, various compounds can be monitored, e.g. pharmaceuticals or illicit drugs, to indirectly monitor the behavior or habits of a defined population [1]. furthermore, the approach allows anonymous, area-based monitoring in a community that is cost-, laborand time-efficient compared to human nasopharyngeal swab test campaigns [2]. moreover, fecal shedding can occur earlier than the onset of symptoms [3, 4], should any be expressed. while the ratio and role of asymptomatic and mild-symptomatic cases is debatable [5, 6], the wbe approach estimates the sars-cov2 rna concentration of the total community that is inderecieved: 26 august 2021; revised: 20 september 2021; accepted: 20 september 2021 *correspondence: adamcsik.orsolya@sooswrc.hu pendent of patients’ perception of well-being. although wbe has its own limitations, sewage monitoring and human test campaigns can also support national and municipal decision-making. considering the successful detection of sars-cov-2 from wastewater and during the consecutive steps of wastewater treatment, a considerable amount of aerosol formation has been observed. moreover, since droplets are regarded as the most important transmission route of sars-cov-2, the working conditions at wastewater treatment plants (wwtp) should be addressed in terms of safety. according to the who [7], no special care is required other than the usual safety protocols at such plants since sars-cov-2 particles present in untreated and treated wastewater have been proven to be non-infectious. another side interest within this topic is whether the sewage treatment technology is sufficiently effective to eliminate the sars-cov-2 virus particles detected in the influent to ensure the wwtp effluents are sars-cov-2-free, even if their infectivity has already been ruled out. the aim of this work is to assess the presence and concentration of sars-cov-2 rna in untreated and treated wastewater samples. https://doi.org/10.33927/hjic-2022-02 mailto:adamcsik.orsolya@sooswrc.hu 8 adamcsik, gerencsér-berta, oláhné horváth, et al. table 1: sars-cov-2 rna detection from wastewater influent and effluent samples at nagykanizsa wwtp. sample type date cq value (e-gene) influent 30/09/2020 +(35.69) influent 14/10/2020 +(33.88) influent 09/11/2020 +(32.39) influent 10/11/2020 +(33.70) influent 11/11/2020 +(34.27) influent 18/11/2020 +(36.67) influent 25/11/2020 +(37.03±0.11) effluent 25/11/2020 – influent 02/12/2020 +(33.70±0.50) effluent 02/12/2020 – 2. materials and methods sampling was conducted by délzalai víz és csatornamű zrt. at nagykanizsa wwtp during the morning peak time. from may until december 2020, samples of influent and occasionally effluent as well were taken at various sampling frequencies. while in december, on three consecutive days, in addition to influent and effluent sampling points, primary and secondary treated samples were also checked. the pairs of influent and effluent samples were processed in duplicates, while to assess the efficacy of the wwtp, three repetitions were used over three consecutive days. 1 l grab samples were taken and placed in sterile bottles, transported to our laboratory at 4 ◦c and immediately processed. the virus was concentrated and nucleic acid extracted according to meleg et al. [8] with minor modifications. concentrates were stored and transported at −80 ◦c to the national virology laboratory, university of pécs for specific sars-cov-2 detection by the quantitative reverse transcription polymerase chain reaction (rt-qpcr) technique, targeting the e and rdrp genes. modular sars-cov-2 e-gene and modular sars-cov-2 rdrp-gene detection kits (roche, germany) on the mygo pro real-time pcr instrument were employed. quantification cycle values (cq values) were used to compare the sars-cov-2 rna concentration of the above-mentioned samples. 3. results and discussion sewage samples tested negative during the summer months of 2020 (data not shown), which is plausible considering the insignificant number of open cases nationwide [9] and the temperature of the sewage as one of the most important environmental factors [10]. at the end of september, as the second wave progressed, the concentration of sars-cov-2 rna increased above the detection limit of the methods in the influent samples, while all effluent samples tested negative. during the autumn of 2020 although the first positive result was registered, followed by fluctuating quantification cycles all the results from influent samples (table 1) were positive, while table 2: sars-cov-2 rna concentration at different stages of wastewater treatment at the nagykanizsa wwtp (due to the rules of pcr amplification, higher quantification cycle values are linked to lower sars-cov-2 rna concentrations) sample type date cq value (e gene) 08/12/2020 +(28.89) influent 09/12/2020 +(34.06) 10/12/2020 +(31.04) 08/12/2020 +(40.04) primary treated 09/12/2020 +(35.43) 10/12/2020 +(37.13) 08/12/2020 – secondary treated 09/12/2020 – 10/12/2020 – 08/12/2020 – effluent 09/12/2020 – 10/12/2020 – their effluent sample pairs all tested negative without exception. from this information alone, it can be concluded that the commonly used, complex wastewater treatment technology itself is sufficiently efficient to decrease the sars-cov-2 rna load from wastewater without any additional steps, e.g. uv light treatment or surplus chemicals. our results concerning the influent-effluent pairs are in good agreement with earlier findings by haramoto et al. [11] by progressing one step further, samples were tested after primary and secondary treatment at the nagykanizsa wwtp (table 2). over three consecutive days while the influent samples tested positive, although the primary treated wastewater exhibited a slightly lower concentration of sars-cov-2 rna the results were still positive (manifesting in higher quantification cycles). from this reduction, it can be seen that the majority of the sars-cov-2 particles are not attached to the solid particles sedimented in this step. however, the duration of sars-cov-2 particles in wastewater is also an important factor [10] that can be partially responsible for the loss in rna load compared to the raw influent. after the activated sludge process, the estimated duration of sarscov-2 particles was longer than 8 hours and all samples tested negative. this loss of signal is reasonable considering the lengthy nature of the secondary treatment, the microbial activity together with the limited resistance of these viral particles to external agents [12] as well as the extreme sensitivity of the rna. as in the case of the earlier tested influent-effluent pairs, all treated effluent samples yielded negative results. over the last year, numerous other research groups have tested various wwtps with partially different technological setups [11,13–16] to that employed at nagykanizsa wwtp. a general consensus has been reached in all these experiments regarding the negative results of all the effluent material flow (treated hungarian journal of industry and chemistry a survey of sars-cov-2 genetic material reduction 9 effluent water and sludge line). even though some studies yielded positive results for some of the secondary treated effluents [11,13] or secondary sludges [16], in these cases all the treated materials exiting the wwtp produced negative results without exception. 4. conclusion according to our findings, which are in good agreement with other published research on this topic, the common treatment of wastewater is capable of decreasing the sars-cov-2 rna concentration below the complex detection limit of the multi-step measurement process. wwtps are capable of minimizing the presence of coronavirus nucleic acid without having to add further steps to the traditional technology. all in all, the sars-cov-2 viral particles are particularly stable in aquatic environments, so the treated wastewater discharge and risks related to its reuse have not proved to be considerable. 5. acknowledgement financial support was received from the national research, development and innovation office (grant no. 2020-2.2.1-ed-2020-00014). the authors would like to express their gratitude to the mol group for their cooperation. references [1] lorenzo, m.; picó, y.: wastewater-based epidemiology: current status and future prospects, curr. opin. environ. sci. health, 2019, 9, 77–84 doi: 10.1016/j.coesh.2019.05.007 [2] bivins, a. et al.: wastewater-based epidemiology: global 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the fate of sars-cov-2 in wwtps points out the sludge line as a suitable spot for monitoring, sci. total environ., 2020, 772, 145268 doi: 10.1101/2020.05.25.20112706 hungarian journal of industry and chemistry https://doi.org/10.1016/j.scitotenv.2020.140621 https://doi.org/10.1016/j.scitotenv.2020.140621 https://doi.org/10.1101/2020.05.25.20112706 introduction materials and methods results and discussion conclusion acknowledgement untitled hungarian journal of industry and chemistry vol. 53(1) pp. 43–60 (2025) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2025-06 comprehensive techno-economic assessment and process simulation of bioethanol production from rice straw via subcritical water pretreatment and enzymatic hydrolysis ahmad mustafa1,2*, hussein n. nassar2-4, m. shaaban sadek5, abdallah r. ismail3, ozben kutlu6, konstantza tonova7, cassamo u. mussagy8, basma a. ali9 and yasmin elshamakh1 1 faculty of engineering, october university for modern sciences and arts (msa), 26 july mehwar road intersection with wahat road, 6th october city, giza, 12451, egypt 2 center of excellence, october university for modern sciences and arts (msa), 26 july mehwar road intersection with wahat road, 6th october city, giza, 12451, egypt 3 egyptian petroleum research institute (epri), 1 ahmed el-zomor street, el zohour region, nasr city, cairo, 11727, egypt 4 biochemistry department, faculty of physical therapy, october university for modern sciences and arts (msa), 26 july mehwar road intersection with wahat road, 6th october city, giza, 12451, egypt 5 department of chemical engineering, faculty of engineering, minia university, minya governorate, minia, 61516, egypt 6 ege university solar energy institute, evka-3, 119/1. sk. no:2, bornova/izmir, 35100, turkey 7 institute of chemical engineering, bulgarian academy of sciences, acad. g. bonchev str., bldg. 103, sofia, 1113, bulgaria 8 escuela de agronomía, facultad de ciencias agronómicas y de los alimentos, pontificia universidad católica de valparaíso, av. brasil no. 2950, valparaíso, 2340025, chile 9 general organization for export and import control (goeic), cairo, 11522, egypt rice straw is a plentiful source of lignocellulosic biomass that has significant promise as a raw material for sustainable energy systems. the management of rice straw in egypt presents considerable difficulties due to its indispensability and abundant availability. efficient pretreatment methods are therefore necessary to overcome the resistive composition of lignocellulosic biomass in order to convert it into biofuels. this study suggests combining experimental and computational methodologies to enhance the combined impact of the green subcritical water (scw) pretreatment and enzymatic hydrolysis of rice straw. this strategy aims to reduce the need for chemicals and energy consumption. the findings suggested that the most favorable parameters for the pretreatment process were a temperature of 160.3°c, an extraction time of 63.4 minutes and a water -to-rice straw mass ratio of 5:2. the application of enzymes led to a substantial 370% rise in the concentration of glucose after extracting it using subcritical water. furthermore, the fructose concentration rose almost threefold, while the cellobiose levels increased twofold. after simulating the entire process with an annual plant capacity of 72,600 tons, economic indicators were determined. an investment opportunity that is financially feasible is evidenced by the following: a favorable internal rate of return (irr) of 27%, a favorable net present value (npv) of $152.6 million and a brief repayment period of 5 years. by employing a comprehensive approach, this endeavor aims to promote the development of biofuel manufacturing routes that are more environmentally friendly, sustainable and efficient, thereby mitigating the ecological consequences associated with meeting global energy demands. to the best of the authors' knowledge, this is the first paper that combines both the technical and economic feasibility of bioethanol production from egyptian rice straw using a combination of subcritical water technology followed by enzymatic hydrolysis. keywords: subcritical water, enzymatic hydrolysis, rice straw, simulation 1. introduction the exponential advancement of human societies in the twenty-first century has resulted in a significant surge in received: 29 aug 2024; revised: 3 oct 2024; accepted: 21 oct 2024 *correspondence: ammhamed@msa.edu.eg energy requirements. this has occurred during a period when economically viable and readily accessible fossil fuels as well as nonrenewable resources, including coal, natural gas and oil, are becoming considerably scarcer [1]-[3]. as a result, a growing level of attention has been https://doi.org/10.33927/hjic-2025-06 mailto:ammhamed@msa.edu.eg mustafa, nassar, sadek, ismail, kutlu, tonova, mussagy, ali and elshamakh hungarian journal of industry and chemistry 44 directed towards renewable energy sources. biofuels such as bioethanol and methane are noteworthy alternatives among these [4]. in addition to being renewable and environmentally sustainable, they presently provide between 10 and 14 percent of energy needs worldwide [5]-[6]. lignocellulosic biomass is predominantly composed of cellulose (40–50%), hemicellulose (25–30%) and lignin (15–20%) as its constituent parts. cellulose consists of a linear polymer composed of glucose units joined by β-1,4 glycosidic bonds. on the other hand, hemicellulose is an intricate heteropolymer that is branched and comprised of a multitude of sugars, including d-xylose, l-arabinose, d-mannose, d-glucose, d-galactose and d-glucuronic acid. three phenolic substances are comprised of lignin: syringyl, p-hydroxyphenyl and guaiacyl [7]-[8]. lignin covalently binds to hemicellulose to form the outermost layer of plant cell walls; cellulose, hemicellulose and lignin are interwoven within the structure of lignocellulosic biomass [9]. nonetheless, in order to facilitate the conversion process, particularly into ethanol, cellulose must be broken down into glucose, a basic carbon source that is commonly utilized by microorganisms [10]. in order to deconstruct the intricate structure of lignocellulosic biomass prior to enzymatic hydrolysis and fermentation, a pretreatment phase is required. this procedure increases the accessibility of the enzymes and the exposure of cellulose. a multitude of pretreatment methodologies have been investigated such as steam explosion as well as alkaline and acidic approaches [11]. rice straw, a prominent agricultural byproduct, has garnered considerable interest as a source of biomass owing to its plentiful accessibility and potential as a feedstock for renewable energy. for rice straw to be utilized in a sustainable manner, it is critical to implement pretreatment methods that are effective in breaking down its intricate structure. this process should liberate fermentable carbohydrates in the form of glucose, which can subsequently be converted into biofuels and other products with added value. within this particular framework, the investigation of environmentally-friendly and sustainable pretreatment approaches has become a pivotal field of study with the objective of alleviating the adverse ecological consequences linked to traditional biomass processing methods. subcritical water (scw) technology presents a multitude of benefits in comparison to conventional chemical approaches when it comes to the pretreatment of lignocellulosic biomass [12]. operating at elevated pressures and temperatures ranging from 100 to 374 °c, subcritical water is a multipurpose solvent that can break down complex biomass into fermentable carbohydrates [13]. by reducing the production of noxious byproducts and eliminating the need for harsh chemical solvents, this method is environmentally friendly. furthermore, by expediting hydrolytic reactions, the utilization of water under these conditions increases the efficiency of the biomass conversion process and, consequently, the overall yield of valuable biochemicals [14]. in addition, when compared to alternative thermal processes, scw technology is comparatively energy-efficient since it utilizes the distinctive characteristics of water in the vicinity of its critical point, where it can efficiently solvate substances that are both hydrophobic and hydrophilic. this characteristic renders it highly compatible with the processing of various forms of biomass, providing a method for biofuel production that is scalable, environmentally friendly and sustainable [5]. the enzymatic hydrolysis of hydrolysates produced by scw pretreatment technology offers numerous advantages, particularly with regard to the conversion of biomass into biofuels and bioproducts. an important benefit is the increased efficacy of sugar release. the scw pretreatment process efficiently breaks down the intricate structures present in lignocellulosic biomass, resulting in the partial removal of lignin and hemicellulose as well as a reduction in cellulose crystallinity. the altered configuration is more receptive to enzymatic activity, thereby facilitating the access of enzymes to and conversion of cellulose into glucose more efficiently [11]. furthermore, enzymatic hydrolysis is characterized by its exceptional specificity and operation at low temperatures, both of which contribute to preserving the integrity of liberated sugars and preventing the formation of degradation products that may impede fermentation processes [15]. this particularity additionally diminishes the necessity for severe chemicals and elevated temperatures, thereby conforming to sustainability objectives through the reduction of energy usage and the mitigation of ecological repercussions. moreover, the integration of enzymatic hydrolysis and scw pretreatment enables a more comprehensive as well as regulated conversion process, enabling the customization of both processes in order to optimize efficiency and productivity in accordance with the type of biomass employed. in conclusion, this integrated methodology improves the cost efficiency and practicability of biofuel and biochemical production as a whole, thereby establishing itself as a highly auspicious technology for industrial implementations [16]. the majority of published research on biomass pretreatment is primarily concerned with optimizing the technical aspects of the process with the economic viability of these methods when scaled up for industrial applications frequently being neglected [17]-[18]. in light of this knowledge deficit, our research endeavors to implement a thorough techno-economic analysis that encompasses not only the meticulous simulation of the pretreatment procedure utilizing scw technology but also an elaborate economic evaluation. by adopting this methodology, it is possible to assess the practicability of the suggested approach on a significant magnitude. by incorporating economic sustainability and technological performance into our analysis, a more realistic and balanced perspective on the applicability of this technology is gained. by providing stakeholders with information regarding the potential costs, benefits and scalability challenges, our study aims to enable them to make more informed decisions regarding the implementation of this technology in industrial settings. simulation of bioethanol production from rice straw 53(1) pp. 43–60 (2025) 45 to the best of the authors' knowledge, this is the first paper that combines both the technical and economic feasibility of bioethanol production from rice straw using a combination of scw technology followed by enzymatic hydrolysis. 2. materials and methods 2.1. rice straw the rice straw originated from the egyptian city of fayoum. the gathered biomass was dried for 24 hours at 60 °c in an oven. after that, a knife mill fitted with a 20-mesh screen was used to grind it. prior to being employed in experimental trials, the processed biomass was stored for up to two months. 2.2. analysis of the moisture content and chemical composition of rice straw to determine the moisture content, 5 grams of rice straw was placed in petri dishes and dried in an oven at a temperature of 105 °c for 4 hours. after weighing the samples, they were placed back in the oven for an extra hour and then weighed once more. this procedure was iterated until a consistent mass was attained. in order to conduct a chemical composition analysis, 2 grams of rice straw was subjected to soxhlet extraction by boiling it in a solvent consisting of a mixture of ethanol and toluene in a ratio of 2:1 for 4 hours. the extracted material was then carefully washed and subsequently dried overnight at a temperature of 105 °c in an oven with air circulation. the desiccated biomass was measured and split into two equal parts. fraction a was simply weighed and did not undergo any further treatment. fraction b underwent treatment with 24% potassium hydroxide to remove hemicellulose, after which its dry mass was recorded. the difference between fractions a and b represented the hemicellulose content (a b). fraction b then underwent further treatment with 72% sulfuric acid to remove cellulose, leaving only the lignin behind. the remaining mass, referred to as fraction c, was considered to be the lignin content. the difference between fraction b (after the removal of hemicellulose) and fraction c represented the cellulose content (b c). 2.3. rice straw pretreatment using scw technology the studies were carried out over two stages: i) hydrolysis reaction and ii) separation of hydrolysis products. the rice straw was hydrolyzed using water in a subcritical state under different conditions. the experimental configuration employed in this investigation is depicted in figure 1. the optimization tests involved conducting scw hydrolysis in a stainlesssteel reactor made of aisi 316l. the reactor had an exterior diameter of 0.5 inches, was 6 inches in length and sealed using swagelok caps. in order to begin an experimental run, the reactor tube was filled with water and rice straw with liquid/solid (l/s) mass ratios (g/g) of 5.0, 7.5 and 10.0. the tube was then completely sealed and placed in a prepared thermal oil bath (mobiltherm 605). the hydrolysis process was carried out between 160 and 200 °c. the pressure inside the reactor was determined using steam tables specifically designed for subcritical conditions. following the designated duration of the reaction, the reactor was promptly cooled by submerging it in a bath of cold water. the hydrolysis products were isolated during the second step. the solid and liquid phases were isolated using the process of vacuum filtration followed by centrifugation. the resultant liquid underwent four washes and was further filtered using filter papers to eliminate any remaining particles. the ultimate blend was preserved in a cryogenic freezer at a temperature of -20 °c until examined. the experimental process is illustrated in figure 1. the studies were conducted three figure 1: experimental set-up of rice straw pretreatment using subcritical water technology mustafa, nassar, sadek, ismail, kutlu, tonova, mussagy, ali and elshamakh hungarian journal of industry and chemistry 46 times and the concentrations of reducing sugars reported as the average values. 2.4. analysis of hydrolysate 2.4.1. determination of the total reducing sugar dns assay 1 ml of dns reagent was added to two tubes: one containing 1 ml of a sugar solution and the other containing 1 ml of water as a reference sample. the tubes were immersed in a heated water bath and boiled for 10 minutes, after which they were allowed to cool down to the ambient temperature. subsequently, 5 ml of distilled water was introduced into each tube. a spectrophotometer (model jasco v-570) was used to measure the change in color intensity from yellow to orange at a wavelength of 540 nm. glucose was utilized as the standard. a calibration curve was generated using doses spanning from 25 to 2200 mg/l. the saccharification% was determined using the methodology outlined by uma and muthulakshmi [19], as per the following equation: 𝑠 ℎ % = x 0.9 x x 100 ℎ (1), where rs denotes the total reducing sugars and df the dilution factor. 2.4.2. sugars and bioproducts the analytes were measured on a hplc instrument which consisted of a pump (knauer smartline pump 1000), a ri detector (knauer azura rid 2.1l), a lc control module for hplc/ce control and a software program (clarity extensible cfr21/glp). all the acids, sugars and furans were separated on a sepax carbomix h-np10 column that was thermostated at 35 °c with a mobile phase of 2.5 mm h2so4 at a flow rate of 0.6 ml/min. to achieve a greater degree of precision, the monosaccharides in the samples were secondarily analyzed in a sepax carbomix pb-np10 column at 75 °c with a mobile phase of deionized water at a flow rate of 0.6 ml/min. using both columns, the volume of sample injected was 20 µl. for all measurements, the temperature of the ri detector was kept constant at 35 °c. each sample was analyzed at least twice. in each series, the deviation from the mean concentration was within 4% for all substances, except for furans for which it fell within 6%. the concentration of reducing sugars (rs) in mg/l was obtained for each hydrolysis experiment. in addition, the yield of reducing sugars (yrs), measured in grams of glucose equivalents per 100 grams of raw material, was determined using: = x 100 (2). the efficiency (e), measured in grams of glucose equivalents per 100 grams of carbohydrates (hemicellulose and cellulose) was computed using the following equation: = x 100 (3), where mrs represents the mass (g) of reducing sugars in the hydrolyzed solution, min designates the initial mass (g) of rice straw placed in the reactor at the start of the operation and mca stands for the initial mass (g) of carbohydrates (hemicellulose + cellulose). 2.5. time-dependent behavior of the pretreatment process before optimizing the pretreatment conditions, the appropriate extraction time was first determined. in this set of experiments, the concentration of reducing sugars was measured periodically every 30 mins. the experimental setup was the same as in section 2.3. the kinetics experiments were carried out at a temperature of 200 °c and a l/s mass ratio (g/g) of 7.5. by the end of the kinetics experiments, the lower and upper extraction limits could be defined for the subsequent optimization study as detailed below. 2.6. experimental design in this project, the box-behnken experimental design was employed. the influence of three selected independent variables (l/s mass ratio, temperature and time) on the response (the concentration of reducing sugars) was investigated. a three-factor, three-level boxbehnken design matrix with five replicate experiments at the central point was added, resulting in a total of seventeen experiments. the factor levels in the design matrix are provided in table 1. the influence of the variables on the response variable was assessed by applying analysis of variance (anova). a quadratic polynomial equation was employed to establish a mathematical relationship between the independent factors and the response: = 0 + ∑3 =1 + ∑ 23 =1 + ∑.2 =1 ∑3 = +1 (4), where y represents the reduced sugar concentration, while x denotes the independent variables, namely the l/s mass ratio, temperature and time. the subscripts i and j are used to distinguish between different factors, while the constants 0, i, ii and ij correspond to the regression coefficients for the intercept, linear, quadratic and interaction model terms, respectively. the regression model was constructed with a confidence level of 95%. the experimental design, anova and optimization table 1: the levels of three factors in the design matrix variables factor levels -1 0 1 l/s mass ratio (g/g) a 5 7.5 10 temperature (°c) b 160 180 200 time (min) c 60 105 150 simulation of bioethanol production from rice straw 53(1) pp. 43–60 (2025) 47 were carried out using the stat-ease 360 design of experiments (doe) software tool (stat-ease, usa). 2.7. effect of enzymatic hydrolysis in order to assess the effect of enzymatic hydrolysis on the amount of sugar produced, the biomass solution that had been treated with subcritical water at 200 °c was mixed with a solution containing 10% enzymes. the enzymes, viscozyme l and a cellulase enzyme blend, were obtained from sigma-aldrich (saint louis, mo, united states). the enzyme blend was combined with the hydrolysates in a flask following the procedure outlined by kim and lee [11]. the ratio of enzyme blend to hydrolysates was 1:1 based on the weight of the biomass with the volumes measured in a volume-to-volume (v/v) ratio. the mixture was then placed in a shaking incubator and incubated at a speed of 170 rpm and a temperature of 45 °c for 48 hours. once the enzymatic hydrolysis process had finished, samples of the liquid portion were taken for examination using high performance liquid chromatography (hplc). 2.8. process simulation the software aspen plus was utilized to simulate the rice straw-based production of the proposed secondgeneration bioethanol. inserting chemical components, selecting the thermodynamic property model, determining the necessary operating units as well as configuring the input conditions for the streams and units (e.g. flow rate, temperature, pressure, etc.) comprised the majority of the process simulation steps. the process flowchart, as illustrated in figure 2, is comprised of four stages: i) scw hydrolysis, ii) cellulase-enzymatic hydrolysis, iii) fermentation of the saccharification’s product iv) separation as well as purification. in order to accurately represent the numerous processes involved in this procedure, the components used in the simulation were defined in accordance with the nrel report [20]. the non-random two-liquid (nrtl) method was selected as the property estimation method for analyzing the thermodynamic interactions between the components of the system. this method is renowned for its precision in describing non-ideal liquid mixtures, which allowed the behavior of the system to be accurately modelled. in order to faithfully represent the vapor phase association of acetic acid with dimers, it was crucial to employ a local property method called nrtl-hard sphere overlap contribution (nrtl-hoc) to consider the intricate behavior of acetic acid under the given conditions. the feed composition of rice straw was entered into aspen plus according to the analysis performed as per section 2.2. the other missing elemental components were assumed to be identical to those composing the egyptian rice straw [21]-[22] as shown in tables 2a and 2b. the core of our simulation resided within the rstoic reactor model, strategically employed due to the availability of conversion data for the pretreatment reactions. these reactions, pivotal in the transformation of rice straw, were represented within this model. a summary of the components involved in the hydrolysis, enzymatic hydrolysis and fermentation reactions is shown in table 2c. the specifics of these reactions and their fractional conversions are meticulously shown in table 3a, illustrating how key components such as cellulose, hemicellulose and lignin are progressively converted into various products. the fractional conversion values indicate the proportion of each component transformed in the simulation, reflecting the evolving nature of this hydrolytic process [23]. furthermore, it is imperative to underline that our simulation was conducted under conditions mirroring the experimental setup. this entailed maintaining a constant temperature of 200 °c and a pressure of 15 atm for the hydrolysis with subcritical water stage. this entailed maintaining a constant temperature of 200 °c and a pressure of 15 atm for the hydrolytic stage with subcritical water. enzymatic hydrolysis and fermentation processes were also simulated using the rstoic model since the conversion rates of the reactions are available. the reactions and conversion rates are shown in tables 3b and 3c. cellulose was hydrolyzed by the enzyme cellulase into glucose and then fermented by saccharomyces cerevisiae yeast to obtain ethanol. finally, the fermentation product was separated and purified using dstw and radfrac distillation units established in aspen plus. the ethanol solution from the fermentation was separated in a purifying distillation column to obtain approximately 92 wt% ethanol as the final product. figure 2: process steps of rice straw conversion into bioethanol mustafa, nassar, sadek, ismail, kutlu, tonova, mussagy, ali and elshamakh hungarian journal of industry and chemistry 48 table 2a: rice straw composition (this study) component wt% cellulose 35 hemicellulose 30 lignin 12 ash 13 table 2b: elemental analysis of rice straw available in egypt [22] ultanal element wt%, dry basis proxanal element wt% sulfanal element wt%, dry basis c 39.2 volatile matter 60 organic 100 h 3.8 fixed carbon 20 sulfate 0 cl 0.9 ash 20 pyritic 0 n 0.3 moisture 10 ash 20.0 table 2c: summary of components involved in hydrolysis, enzymatic hydrolysis and fermentation reactions component description component description component description cellulos cellulose arabolig arabinooligosaccharides ethanol ethanol glucolig glucooligosaccharides arabinos arabinose co2 carbon dioxide h2o water arabinan arabinan zymo zymomonas mobilis (biomass) cellob cellobiose lignin lignin glycerol glycerol glucose glucose aacid acetic acid succacid succinic acid hmf hydroxymethylfurfural lgnsol lignin soluble fraction lacid lactic acid hemicell hemicellulose levul-01 levulinic acid csl corn steep liquor (nutrient) furfural furfural formi-01 formic acid dap diammonium phosphate (nutrient) tar tar propi-01 propionic acid d-fru-01 d-fructose derivative gluconic gluconic acid table 3a: list of subcritical water hydrolysis reactions with fractional conversion stoichiometry fractional conversion fractional conversion of component cellulos(cisolid) --> glucolig(mixed) 0.0007 cellulos h2o + 2 cellulos(cisolid) --> cellob(mixed) 0.012798519 cellulos h2o + cellulos(cisolid) --> glucose(mixed) 0.012830795 cellulos cellulos(cisolid) --> hmf(mixed) + 2 h2o(mixed) 0.000264835 cellulos hemicell(cisolid) --> furfural(mixed) + 2 h2o(mixed) 0.000977414 hemicell h2o + hemicell(cisolid) --> tar(cisolid) 0 hemicell h2o + cellulos(cisolid) --> d-fru-01(mixed) 0.019839841 cellulos hemicell(cisolid) --> arabolig(mixed) 0.00025 hemicell h2o + hemicell(cisolid) --> arabinos(mixed) 0.01361932 hemicell h2o + arabinan(cisolid) --> tar(cisolid) 0 arabinan lignin(cisolid) --> 2.57833 aacid(mixed) 0.004242377 lignin 3 h2o + furfural --> tar(cisolid) 1 furfural 3 h2o + hmf --> 1.2 tar(cisolid) 1 hmf lignin(cisolid) --> lgnsol(mixed) 0.0021 lignin cellulos(cisolid) + 2 h2o --> 1.7 levul-01(mixed) 0.000950471 cellulos cellulos(cisolid) + h2o --> 2 propi-01(mixed) + o2(mixed) 0.00102319 cellulos lignin(cisolid) --> 3.36304 formi-01(mixed) 0.003459427 lignin cellulos(cisolid) + h2o --> 0.918367 gluconic(mixed) 0.001274245 cellulos simulation of bioethanol production from rice straw 53(1) pp. 43–60 (2025) 49 table 3b: list of enzymatic hydrolysis reactions with fractional conversion stoichiometry fractional conversion fractional conversion of component cellulos(cisolid) --> glucolig(mixed) 0.0007 cellulos h2o + 2 cellulos(cisolid) --> cellob(mixed) 0.080323131 cellulos h2o + cellulos(cisolid) --> glucose(mixed) 0.33318555 cellulos cellulos(cisolid) --> hmf(mixed) + 2 h2o(mixed) 0.0070934 cellulos hemicell(cisolid) --> furfural(mixed) + 2 h2o(mixed) 0.007373716 hemicell h2o + hemicell(cisolid) --> tar(cisolid) 0 hemicell h2o + cellulos(cisolid) --> d-fru-01(mixed) 0.212763003 cellulos hemicell(cisolid) --> arabolig(mixed) 0 hemicell h2o + hemicell(cisolid) --> arabinos(mixed) 0 hemicell h2o + arabinan(cisolid) --> tar(cisolid) 0 arabinan lignin(cisolid) --> 2.57833 aacid(mixed) 0.004860943 lignin 3 h2o + furfural --> tar(cisolid) 1 furfural 3 h2o + hmf --> 1.2 tar(cisolid) 1 hmf lignin(cisolid) --> lgnsol(mixed) 0 lignin cellulos(cisolid) + 2 h2o --> 1.7 levul-01(mixed) 0.00103824 cellulos cellulos(cisolid) + h2o --> 2 propi-01(mixed) + o2(mixed) 0.000934299 cellulos lignin(cisolid) --> 3.36304 formi-01(mixed) 0.003418227 lignin cellulos(cisolid) + h2o --> 0.918367 gluconic(mixed) 0.00129263 cellulos cellob + h2o --> 2 glucose(mixed) 1 cellob table 3c: list of fermentation reactions with fractional conversion stoichiometry fractional conversion fractional conversion of component glucose --> 2 ethanol(mixed) + 2 co2(mixed) 0.9 glucose glucose + 0.04696 csl + 0.018 dap --> 6 zymo(cisolid) + 2.4 h2o(mixed) 0.04 glucose glucose + 2 h2o --> 2 glycerol(mixed) + o2(mixed) 0.004 glucose glucose + 2 co2 --> 2 succacid(mixed) + o2(mixed) 0.006 glucose glucose --> 3 aacid(mixed) 0.015 glucose glucose --> 2 lacid(mixed) 0.002 glucose d-fru-01 --> 2 ethanol(mixed) + 2 co2(mixed) 0.9 d-fru-01 d-fru-01 + 0.04696 csl + 0.018 dap --> 6 zymo(cisolid) + 2.4 h2o(mixed) 0.04 d-fru-01 d-fru-01 + 2 h2o --> 2 glycerol(mixed) + o2(mixed) 0.004 d-fru-01 d-fru-01 + 2 co2 --> 2 succacid(mixed) + o2(mixed) 0.006 d-fru-01 d-fru-01 --> 3 aacid(mixed) 0.015 d-fru-01 d-fru-01 --> 2 lacid(mixed) 0.002 d-fru-01 3 arabinos --> 5 ethanol(mixed) + 5 co2(mixed) 0.8 arabinos arabinos + 0.03913 csl + 0.015 dap --> 5 zymo(cisolid) + 2 h2o(mixed) 0.04 arabinos 3 arabinos + 5 h2o --> 5 glycerol(mixed) + 2.5 o2(mixed) 0.003 arabinos 3 arabinos + 5 co2 --> 5 succacid(mixed) + 2.5 o2(mixed) 0.015 arabinos 2 arabinos --> 5 aacid(mixed) 0.014 arabinos 3 arabinos --> 5 lacid(mixed) 0.002 arabinos mustafa, nassar, sadek, ismail, kutlu, tonova, mussagy, ali and elshamakh hungarian journal of industry and chemistry 50 3. economic assessment the assessment of the financial feasibility of industrial processes is a crucial function performed by technoeconomic studies. these studies focus on three fundamental goals: preliminary identification of potential sources of revenue, a thorough evaluation of project expenses related to administration as well as execution, and a final prediction of the overall viability of the project [24]-[26]. by conducting an exhaustive analysis, they offer invaluable insights into the anticipated financial flows, thereby exerting a substantial impact on the processes by which decisions are made. the present study, which is presented as a technoeconomic analysis, intends to provide a thorough and intricate examination of the suggested 2g ethanol manufacturing process. its primary objective is to function as an indispensable asset for the ethanol manufacturing community. through providing insights into the economic environment pertaining to this technology, relevant parties can acquire the necessary knowledge to formulate well-informed judgments concerning the viability and strategic trajectory of forthcoming 2g ethanol manufacturing undertakings. 3.1. total capital investment (tci) to launch a project, a crucial factor is understanding the total upfront financial commitment, known as the total capital investment, which represents the combined cost of building the physical plant (fixed capital investment), covering initial operations (working capital) and any onetime startup costs [27]. 3.1.1. fixed capital investment (fci) the fci serves as a cornerstone for initiating projects, encompassing all expenses related to establishing the physical plant (e.g. construction, planning, installation of equipment and modifications to the facility) [24]. accurate fci estimates are crucial for effective project planning and preventing operational setbacks. the fci can be further broken down into four main cost categories: inside battery limits, outside battery limits, engineering costs and contingency costs [28]. inside battery limits (isbl) the accurate estimation of the isbl cost is crucial for evaluating the overall economic viability of a project. bridgewater's method [29] offers a suitable approach for estimating the isbl costs in processes involving liquid and solid streams, particularly when detailed design information is lacking. this method leverages a correlation between the plant costs and the number of processing steps. bridgewater's method requires the following information: plant capacity (metric tons per year), reactor conversion (mass of desired product per mass of feed) and the number of functional units within the process. functional units encompass major unit operations that significantly contribute to the overall plant costs, typically excluding pumps and heat exchangers. based on the proposed flowsheet analysis, this project necessitates 6 functional units. the designed capacity of the plant is 72,600 tons per year with a projected reactor conversion of 46%. for plant capacities in excess of 60,000 tons per year, the following equation from the bridgewater's method is applicable [24]: = 4,320 ( )0.675 (5), where c represents the isbl capital cost (us$), n refers to the number of functional units, q denotes the capacity of the plant (metric tons per year) and s is the reactor conversion rate (desired mass of product in relation to the mass fed into the reactor). the selection and application of this specific equation will be presented in the subsequent section. outside battery limits (osbl) the osbl cost encompasses expenses associated with facilities and utilities located outside the plant boundary but are essential for its operation. this includes storage tanks for raw materials and products, waste treatment facilities, utility lines for water, electricity and steam as well as any off-site modifications to infrastructure [27]. due to the limited information regarding the condition of the existing site and its infrastructure, an estimated proportion of the isbl cost is often used to approximate the osbl cost. this value typically ranges from 10 to 100% of the isbl, depending on the specific requirements of the project [24],[26]. in this study, considering the lack of detailed site information, a conservative estimate of 30% of the isbl cost was assumed for the osbl. this value will be refined as the project progresses and more site-specific data becomes available. estimation of engineering costs (ec) ec encompass the fees associated with the professional services required to bring a project to life. this includes chemical engineers, mechanical engineers and other specialists involved in designing the layout of the plant and process control systems, selecting equipment as well as other technical aspects. estimating the ec can be challenging due to factors like the prevailing economic climate and the complexity of the project. however, for large-scale industrial processes, a rule-of-thumb approach can be employed. in this project, the ec is estimated to be 10% of the combined direct capital cost (dcc = isbl + osbl). this estimation will be further refined as the project progresses and more detailed engineering design information becomes available. estimation of contingency costs (cc) the cc are included in budgets of the project to account for unforeseen circumstances that may arise when executing the project, including unexpected fluctuations in material prices, delays in the delivery of equipment or simulation of bioethanol production from rice straw 53(1) pp. 43–60 (2025) 51 unforeseen technical challenges encountered during its construction. although the minimum recommended cc for projects is typically 10% of the dcc, this value can be adjusted based on the level of technological uncertainty associated with the project. in this study, considering the established nature of the technologies employed (many processes are similar to at existing bioethanol production facilities), a cc of 10% of the dcc was assumed. this value reflects the anticipated level of project risk associated when utilizing proven technologies. as the project progresses and further engineering details are finalized, the estimate of contingency costs may be refined to account for any project-specific risks that are identified [30]. 3.1.2. estimation of the working capital (wc) in order to simplify the estimation of costs in this study, the wc will be calculated as 15% of the total direct capital cost. this method is in line with established practices in the field, as referenced in [24]. as the project progresses, a more refined estimate of the working capital may be developed based on a detailed analysis of anticipated operational costs. 3.1.3. estimation of start-up costs start-up costs encompass one-time costs incurred when initially commissioning the plant and during the ramp-up phase, including training personnel with regard to operational procedures and safety protocols, initial product quality testing and analysis to ensure adherence to specifications, permitting costs associated with waste disposal or environmental regulations as well as consumables and utilities required when starting up the plant and during the initial production period. to predict the initial costs, start-up costs are typically estimated to be a percentage of the direct capital cost. in this study, a conservative estimate of 10% of the dcc was assumed for the start-up costs. this value will be further refined as the project progresses and a more detailed commissioning plan is developed. 3.2. operating expenditure (opex) the opex represents the ongoing costs associated with running a production facility. these expenses are crucial for sustaining day-to-day operations and directly impact the profitability of the project. 3.2.1. fixed cost of production (fcop) the fcop encompasses expenses incurred regardless of the production rate within the operational range of the plant. these costs are independent of the production volume and remain constant during its operation. the fcop significantly impacts the economic viability of the project and necessitates careful consideration when estimating costs. optimizing plant operations to reduce the fcop is generally limited. labor costs represent a major component of the fcop and encompass the salaries as well as wages of personnel, including operators and supervisors, required to maintain a continuous operation. the number of personnel needed per shift position significantly influences labor costs. the variables considered to estimate the fcop are detailed in table 4, along with the assumptions made for each variable during the calculations. a thorough understanding of the fcop is crucial for ensuring the project is economically feasible and developing strategies to manage operational expenses effectively [24]. 3.2.2. variable cost of production (vcop) the vcop directly correlates with the output of the bioethanol plant, encompassing expenses like raw materials, utilities, consumables, waste disposal as well as packaging and shipping the product. as the production process design and operational plan are further refined, estimates of the vcop become more accurate. importantly, the vcop can lead to optimization by improving the design or operation, emphasizing the value of continuous cost reduction efforts. 3.2.3. revenues project revenues will be generated from the sale of products manufactured by the bioethanol production facility, including income from the primary product, namely bioethanol, and any potential revenue streams from by-products generated during the process. while carbon dioxide (co2) is a common by-product of bioethanol production, its economic viability as a source of revenue needs further investigation. the feasibility of capturing and selling co2 will depend on factors like market demand, transportation costs as well as potential applications for the captured co2. 3.2.4. gross margin a key metric in this analysis is the gross margin, which represents the difference between the revenue generated by the project and the cost of raw materials. this can be expressed mathematically as follows: gross margin = revenues raw-material cost (6). the gross margin indicates the proportion of sales revenue that remains after accounting for the direct cost of the primary feedstock. a higher gross margin signifies a more profitable project as it reflects a greater contribution towards covering other operational expenses and generating profit [31]. 3.2.5. profitability analysis a profitability analysis is a critical aspect of project evaluation, assessing its potential to generate financial returns. a key metric in this analysis is net profit, which represents the profit remaining after accounting for all expenses. mustafa, nassar, sadek, ismail, kutlu, tonova, mussagy, ali and elshamakh hungarian journal of industry and chemistry 52 3.2.6. cash cost of production (ccop) the ccop is a crucial parameter for estimating the profitability of the project, reflecting the total cash outflow associated with producing the bioethanol and excluding any return on the invested equity capital. mathematically, the ccop can be expressed as follows: ccop = vcop + fcop – by-product revenue (7), where by-product revenue = revenue generated from the sale of any by-products. 3.2.7. profit calculation the gross profit of the project can be calculated by subtracting the ccop from the total revenue generated from bioethanol sales and represents the profit before deducting taxes. the net profit is the ultimate measure of project profitability, reflecting the profit remaining after accounting for all expenses, including taxes. it can be calculated as per the following equation: net profit = gross profit tax expenses (8), tax expenses = taxable income (gross profit – depreciation) x tax rate (9). the specific tax rate applicable to the project will need to be determined based on the relevant tax regulations and accounting practices. depreciation, a common tax allowance, can be deducted from the gross profit to determine the taxable income used for tax calculations. 3.2.8. corporate tax corporate tax is a levy imposed on the profits generated by corporations. the specific tax rate applicable to a project can vary depending on the geographical location, industrial sector and prevailing tax regulations. in the united states, corporations paid a federal tax rate of 21% on their profits in the year 2018 [32]. 3.2.9. depreciation depreciation is an accounting expense that does not involve actual cash. it refers to the progressive decrease in the value of physical assets over time due to normal wear and tear. this technique reduces the recorded value of the asset on financial statements and provides a tax benefit by reducing taxable income. the modified accelerated cost recovery system (macrs) is a commonly used depreciation technique in the united states for tax purposes. the macrs classifies biorefineries as chemical manufacturing facilities and table 4: breakdown of fixed cost of production (fcop) components parameter assumption explanation operating labor $60,000 usd/year (based on average salary per shift position) this value represents the estimated average annual salary for a single shift position within the plant. the plant will produce liquid products (biodiesel and glycerol) and solid coffee pellets. number of shift positions 4 the minimum estimated number of shift positions required for a continuous operation is 3 with an additional position assigned to the dedicated handling of solids. supervision costs 25% of operating labor this value represents the estimated cost of plant supervision as a percentage of the total operating labor costs. overhead costs 50% of (operating labor + supervision costs) this is a conservative estimate of overhead costs, encompassing indirect labor and other administrative expenses associated with the plant operation. it accounts for 50% of the combined operating labor and supervision costs. maintenance costs 5% of isbl investment this value reflects the anticipated higher maintenance costs due to the presence of significant moving equipment within the plant such as conveyor belts and machinery handling solids. property taxes and insurance 2% of isbl investment this assumption incorporates potential property tax and insurance costs associated with the plant facilities. rent of land 2% of (isbl + osbl) this cost is included as the land is assumed to be rented not purchased. it represents 2% of the combined direct capital costs (isbl + osbl). general plant overheads 65% of (operating labor + supervision costs + direct overhead costs + maintenance costs) this value represents the estimated cost of various miscellaneous expenses associated with the overall plant operation calculated as a percentage of the sum of operating labor, supervision, direct overhead (e.g. office supplies) and maintenance costs. environmental charges 1% of (isbl + osbl) this cost provision accounts for potential charges associated with environmental regulations and superfund payments. simulation of bioethanol production from rice straw 53(1) pp. 43–60 (2025) 53 assigns them a standard class life of 9.5 years. typically, when estimating project costs, a 5-year recovery period is commonly assumed, factoring in the depreciation expenses and analyzing the cash flow. it is important to acknowledge that the most effective technique of reducing the value of an asset over time and the length of time it takes to recover the cost of the asset may vary depending on the specific accounting rules and tax laws in place. hence, it is recommended to seek guidance from a tax expert in order to ascertain the most accurate method for a specific project. 3.2.10. discount rate a discount rate, or interest rate, of 11% is assumed to account for the time value of money in the financial analysis of the project, reflecting the minimum expected return on investment for undertaking this project. 3.3. financial performance metrics this section examines essential financial indicators employed to assess the economic feasibility and future profitability of the project. these measurements take into account the concept of the time value of money, which recognizes that a dollar today is worth more than a dollar in the future. 3.3.1. net present value (npv) the npv is an essential measure that takes into account the concept of the time value of money in order to evaluate the profitability of an investment. the calculation involves determining the current value of all anticipated future cash inflows related to the project before subtracting the current value of all cash outflows [24]. a positive npv signifies a project that is anticipated to have a favorable return on investment. the next equation is utilized to compute the npv in the following manner: = ∑ (1 + )= =1 (10), where cfn = cash flow in year n, i = discount rate (interest rate) and t = project lifespan in years. 3.3.2. return on investment (roi) the roi is a financial measure that indicates the profitability of an investment as a percentage. it quantifies the increase in or profit generated from the initial capital invested in a project. a higher roi percentage is indicative of a more appealing investment prospect, suggesting that its profits are likely to surpass its costs [24]. the roi is determined by applying the following equation: = x 100 (11). 3.3.3. internal rate of return (irr) the irr is the rate at which the npv regarding the cash inflows of a project is equal to the npv of its cash outflows. put simply, it denotes the lowest satisfactory rate of return for the project to reach a break-even point, taking into account the concept of the time value of money [24]. a greater irr typically signifies a more favorable investment prospect. the equation for irr can be solved by an iterative process according to the steps outlined as follows: = ∑ (1 + ′)= =1 = 0 (12). 3.3.4. payback period the payback period is a metric that quantifies the period of time needed for an investment to recoup its initial expenditure. it offers a clear evaluation of its liquidity and risk characteristics. a reduced payback period is indicative of a diminished investment risk, since the initiative swiftly recoups its initial investment. the payback period can be determined by applying the formula below: = ℎ (13). although each statistic provides useful insights, it is advisable to evaluate them collectively when making investment decisions. npv and irr take into account the concept of the time value of money, whereas roi offers a perspective on the return expressed as a percentage. the payback period provides a rapid evaluation of the project's schedule for recovering its initial investment. by combining these measurements, a thorough comprehension of the project's prospective profitability and risk profile can be obtained, which in turn facilitates well-informed financial decisions to be made. 4. results and analysis 4.1. time-dependent approach of rice-straw pretreatment with scw technology time plays a pivotal role in determining how the rs concentration changes. in this proposed study, as shown in figure 3, it was observed that increasing the figure 3: reducing sugars concentration against time using subcritical water technology. extraction temperature = 200 °c, l/s mass ratio = 7.5 0 200 400 600 800 1000 1200 1400 1600 30 60 90 120 150 180 r s ( m g / l ) time (min) mustafa, nassar, sadek, ismail, kutlu, tonova, mussagy, ali and elshamakh hungarian journal of industry and chemistry 54 pretreatment time from 30 to 60 mins increased the concentration of reducing sugars. however, beyond 60 mins, the concentration of the rs unfavorably declined, possibly due to the degradation of some reducing sugars into other bioproducts and inhibitors as a result of the long pretreatment time. 4.2. statistical analysis results 4.2.1. verification of model equations the results obtained in accordance with the designed experimental matrix are presented in table 5. although the higher order polynomial equations model is often suitable, the linear equation model is more suitable for predicting the concentration of reduced sugar based on the factor levels. the linear model equation is formulated as follows, relying on the actual factor values: reduced sugar = +8.46 – 0.31·a – 0.015·b – 0.005·c (14), where a denotes the l/s mass ratio (g/g), b stands for the temperature (°c) and c represents the time (min). this model equation can be employed to estimate the amount of reduced sugar corresponding to any factor level. it is important to note that these levels should be defined in their original units. in the model designed with a second-order polynomial equation, the p-values for some interaction terms did not yield significant results, indicating that the interaction terms of the selected variables hardly influence the model equation. accordingly, the insignificant terms were removed from the quadratic equation to obtain the linear model equation in which the sign of the regression coefficients also indicates the direction effect on the response [33]. at this point, it is understood that all three variables negatively affect the reduced sugar concentration. according to the anova results provided in table 6, the fit of the model is evident from all four different outcomes (r-squared, f-value, pvalue and lack of fit). the p-value for the linear model was calculated to be less than 0.0001 and remained lower than 0.05 [33], indicating that the model and its equation can be considered significant. the f-value is approximately 100, demonstrating that it is not affected by any statistical noise, thereby strengthening its case as a significant model. on the other hand, the lack of fit p-value is greater than 0.05 and the f-value of 0.30 indicates that the lack of fit is not significant relative to the pure error. this result further supports the adequacy of the model, which was previously deemed suitable for the experimental data. moreover, r-squared of the preferred linear model equation was calculated as 95.9%. before removing the terms of the insignificant model, r-squared of the quadratic model was calculated to be 97.3%. however, considering the other results, its reduction by 1.5% is deemed acceptable and r-squared of the linear equation also supports a strong fit. the difference between the predicted and adjusted r-squared is reasonable (<0.2) [34]-[35] and consistent. additionally, the high adequate precision result serves as evidence that this model equation can be used for predictions within its design boundary. in addition to determining that the linear model equation was appropriate, the effects of the variables on the response were also examined based on their f-values. the parameter with the highest f-value was observed to be the l/s mass ratio, indicating that the highest impact on reduced sugar could be achieved by varying the mass ratio. the temperature correlated with table 5: experimental results of the pretreatment of rice straw run factor levels a: l/s mass ratio [g/g] b: temperature [°c] c: time [min] response: reducing sugar [g/l] 1 0 − + 7.5 160 150 2.91 2 + + 0 10.0 200 105 1.84 3 0 0 0 7.5 180 105 2.85 4 0 + + 7.5 200 150 2.32 5 0 + − 7.5 200 60 2.76 6 + 0 − 10.0 180 60 2.35 7 − 0 + 5.0 180 150 3.34 8 − + 0 5.0 200 105 3.30 9 + − 0 10.0 160 105 2.30 10 0 0 0 7.5 180 105 2.85 11 − − 0 5.0 160 105 4.09 12 − 0 − 5.0 180 60 4.00 13 0 0 0 7.5 180 105 2.85 14 0 − − 7.5 160 60 3.30 15 0 0 0 7.5 180 105 2.90 16 0 0 0 7.5 180 105 3.30 17 + 0 + 10.0 180 150 1.99 table 6: anova output of the fitted model (adequate precision: 31.43) ss df ms f-value p-value r-squared (r2) adjusted r2 predicted r2 model 6.01 3 2.00 99.98 <0.0001 0.9585 0.9489 0.9391 residual 0.2604 13 0.02 lack of fit 0.1054 9 0.0117 0.3022 0.9372 pure error 0.1550 4 0.0387 cor total 6.27 16 simulation of bioethanol production from rice straw 53(1) pp. 43–60 (2025) 55 the mass ratio, moreover, the extraction time was identified as the parameter that had the lowest effect among these factors. in similar research, carried out by muharja et al. [36], using coconut husk, it was reported that the mass ratio had the highest impact, even at higher factor levels than the present study. however, it was observed that the ranking of other factor effects varied in similar research due to the use of different raw materials and the selection of other parameters at lower factor levels. 4.2.2. assessment and optimization of parametric interactions the potential effects of factors on the response were evaluated using three-dimensional surface plots. as observed in figure 4, each pairwise interaction generated linear contour plots and it was observed that the maximum reduced sugar concentration was obtained when the factor levels for all parameters were at their minima. this result was observed when evaluating the signs of the model in the optimization study conducted with the adequate model equation. the results observed in the pairwise interaction plots were confirmed. during optimization, the aim was to maximize the reduced sugar concentration without imposing any constraints on the variables within the experimental range. consequently, a total of 100 solutions were obtained, where the reduced sugar concentration ranged from 3.88 to 4.15 g/g. regarding the optimal solution that provided the highest performance, it was calculated that a reduced sugar concentration as high as 4.12 g/g could be produced. the optimal conditions for this amount were determined to be a mass ratio of 5.2, an extraction time of 63.4 minutes and a temperature of 160.3 °c. if a constraint is introduced to minimize the most critical parameter in the model, namely the mass ratio, in this optimization scenario, only the extraction time would increase to 78.5 minutes. in terms of the response, factor a, which exhibits the highest individual effect, also exerts a significant impact as a result of its combined interactions (ab and ac) with other factors. in the ab and ac plots, a decrease in time and temperature, respectfully, both result in a consistent effect yielding the same gradient and an increase in the reduced sugar concentration. when examining the bc plot, it is evident that these factors do not significantly influence the reduced sugar concentration at the selected factor levels. although both the temperature and extraction time influence the model, at the chosen factor levels, neither parameter nor their interactions seem to have a significant positive effect on increasing the reduced sugar concentration. figure 4: pairwise interaction plots (3d surface plots) while one factor was kept constant at its zero-factor level; the interaction between the mass ratio & temperature (a), mass ratio & time (b) and temperature & time (c) mustafa, nassar, sadek, ismail, kutlu, tonova, mussagy, ali and elshamakh hungarian journal of industry and chemistry 56 at this juncture, it is apparent that the mass ratio is the most influential factor in the pretreatment of rice straw. however, caution should be exercised in managing this variable to increase the reduced sugar concentration. 4.3. effect of enzymatic hydrolysis enzymatic hydrolysis of the hydrolysate obtained from the scw extraction of rice straw notably enhanced the yield of fermentable sugars. notably, the concentration of glucose, a pivotal sugar when producing biofuels, exhibited a dramatic increase from 3.827 g/l in the initial extract to 17.988 g/l following enzymatic treatment, representing an approximate 370% increase and underscoring enzymatic efficiency in the saccharification of polysaccharides. likewise, fructose levels nearly tripled, ascending from 3.112 to 10.084 g/l. the concentration of cellobiose, which is a dimer of glucose, also nearly doubled from 2.162 to 4.243 g/l, indicating the effective enzymatic breakdown of β-1,4 glycosidic bonds. xylose, a five-carbon sugar, showed a modest increase from 0.630 to 0.696 g/l, suggesting that the enzymatic treatment was less effective at hydrolyzing hemicellulose into xylose or that the majority of xylose had already been released during the subcritical water extraction process. these findings are in line with those in the literature, for instance, kim & lee [11] observed a similar pattern where enzymatic hydrolysis significantly improved the yield of monosaccharides from lignocellulosic biomass. 4.4. process simulation results 4.4.1. rice-straw pretreatment using scw technology: process simulation the pretreatment of rice straw using subcritical water was simulated using aspen plus software and the corresponding process flow diagram is presented in figure 5. the reactor (scw hydrolyzer) received a main feed stream (biomass) at a flow rate of 80 tons/h at 20 °c and a pressure of 1 atm. to increase the pressure of the water stream (h2o) from 1 to 15 atm, a 27.58 kw pump (pump) was employed before feeding the water into the reactor (scw hydrolyzer). additionally, the heat duty of the reactor was approximately 18.229 mw. in addition, the software supplied all the data regarding mass and energy balances. the material exiting the pretreatment reactor undergoes flash cooling to 1 atm in a blowdown tank (t201). subsequently, the bottom stream is used in subsequent processes such as saccharification, fermentation and ethanol production. 4.4.2. enzymatic hydrolysis and fermentation as shown in the flowsheet simulation, the same reactor was used during both stages. the pretreated stream (hydrlyzt) was cooled to 47 °c (cooler-1), that is, the operating temperature for the enzymatic process. the enzyme cellulase was introduced at a rate of 15 mg cellulase/g dry biomass [20],[37]. following the hydrolysis simulation step, the resulting slurry was cooled in a dedicated cooling unit (b2) to ensure optimal fermentation conditions typically at 35 °c. after cooling, one tenth of the hydrolyzed slurry was diverted via a stream splitter unit (sachspt) into a dedicated seed train tank in which yeast (saccharomyces cerevisiae) is cultivated – the industry standard for fermenting glucose into ethanol. to promote the robust growth of dry yeast, the process utilizes corn steep liquor (csl), a source of nutrients containing water, protein and lactic acid alongside diammonium phosphate (dap) as an additional nutritional supplement. the dap concentration within the broth was assumed to be 0.67 g/l while csl was introduced at a loading rate of 0.5 wt% [37]. the fermentation process itself achieved a conversion rate of 90%, transforming glucose into the desired biofuel – ethanol. notably, a small portion (4%) of the glucose was utilized, along with lactic acid and dap, to cultivate the saccharomyces cerevisiae yeast culture itself. the fermentation stage utilizes a reactor (fermnter) for the purpose of process modeling. the temperature in the reactor was meticulously maintained at 35 °c, ensuring the optimal conditions for yeast activity. within this controlled environment, glucose underwent fermentation and was efficiently converted into ethanol at a conversion rate of 90% [20]. figure 5: simulation of rice straw pretreatment using subcritical water and aspen plus software simulation of bioethanol production from rice straw 53(1) pp. 43–60 (2025) 57 4.4.3. ethanol recovery and purification the subsequent stages focus on recovering and purifying the ethanol produced during fermentation. a twopronged approach was employed to achieve a final ethanol purity of 99.5%. distillation served as the primary separation technique, while adsorption onto a molecular sieve provided final purification. the raw fermentation broth, also known as "beer," was distilled within a designated column (dist-1) to separate the ethanol from the by-products of fermentation. to maximize efficiency and reduce energy requirements, a preheating step utilizing a dedicated heater (heater-2) elevated the temperature of the mixed stream (s15) to near its boiling point before entering the column. the distillation column operated with a reflux ratio of 6 and a distillate to feed ratio of 0.208 utilizing 22 theoretical stages. this configuration achieved a high recovery rate, extracting essentially all the ethanol fed into the system and concentrating it to approximately 92.5 wt%. following distillation, adsorption onto a molecular sieve unit achieved final purification by removing any remaining water from the nearly azeotropic ethanolwater mixture through a vapor phase adsorption process. regeneration of the adsorption columns necessitates the ethanol-water mixture to be recycled back into the distillation process for ethanol recovery. 4.4.4. ethanol vent recovery to minimize ethanol loss, fermentation vent streams, primarily containing co2 but also trace amounts of ethanol, were directed through a water scrubber (scrubber) which efficiently captured nearly all the ethanol with the resulting effluent being reintroduced into the distillation column (dist-1) alongside the fermented beer. overall, this multistage approach ensured the efficient recovery and final purification of 99.5% bioethanol from the fermentation process, suitable for various applications. 4.5. economic analysis 4.5.1. capital expenditure (capex) the initial investment of the project is a critical factor for manufacturers. as expected, the isbl plant cost, representing the expense of constructing the core facility, forms a significant proportion of the total capital expenditure. utilizing bridgewater's method, the process proposed in this study resulted in an isbl cost of $83.6 million. 4.5.2. production costs beyond the initial investment, ongoing production expenses significantly impact project feasibility, which reached $1321 per ton, playing a crucial role in the overall financial assessment. 4.5.3. profitability analysis the npv considers the time value of money and assesses the disparity between the present values of future cash inflows and outflows over a specified period (in this case, 15 years). a positive npv signifies a project that is strongly economically viable. the project timeline commences with the design stage in year 1, marking the initial cash outflow. the construction and installation phases, anticipated in year 2, are factored into the evaluation. by year 3, the facility reaches its maximum production capacity. however, depreciation costs lead to a subsequent decline in gross profit over time. 4.5.4. favorable investment metrics in this work, the proposed enzymatic process exhibited a positive npv of $121.2 million alongside a promising roi of 422, strongly suggesting a successful and highly profitable investment opportunity. 4.5.5. rapid capital recovery the project's irr stands at 25%, further emphasizing its attractiveness. additionally, the projected payback period for this investment is just 7 years, indicating a relatively rapid timeline of capital recovery. these combined outcomes convincingly support the financial feasibility and allure of commencing production of second-generation bioethanol using the proposed enzymatic process. overall, the economic analysis paints a promising picture for this project. the positive npv, high roi, attractive irr and rapid payback period all point towards a financially sound investment opportunity. 5. conclusions in conclusion, this study underscores the significant potential of using subcritical water pretreatment combined with enzymatic hydrolysis for converting rice straw into valuable biofuels, addressing the increasing global demand for sustainable energy. through the optimized application of the response surface methodology (rsm) and simulation techniques, it was successfully demonstrated that green subcritical water pretreatment can efficiently convert rice straw into reducing sugars with high yields, thereby minimizing energy consumption and chemical use. the enzymatic treatment following this pretreatment significantly enhanced glucose concentrations by approximately 370%, proving the effectiveness of the enzymes used and further increasing the yield of crucial biofuel precursors such as fructose and cellobiose. the economic analysis supports the viability of scaling up this process to a plant capacity of 72,600 tons per year, highlighting its financial attractiveness with a positive net present value of $152.6 million, a high return on investment of 665%, an attractive internal rate of return of 27% and a rapid payback period of 5 years. these results not only affirm the economic benefits of the proposed green route but mustafa, nassar, sadek, ismail, kutlu, tonova, mussagy, ali and elshamakh hungarian journal of industry and chemistry 58 also its potential to contribute significantly towards the development of more sustainable and efficient biofuel production pathways. ultimately, this approach marks a promising step forward in meeting the 21st century’s pressing energy requirements while reducing the environmental impact. acknowledgements this work was supported by the bilateral scientific cooperation between the academy of scientific research and technology (asrt) (egypt) and the bulgarian academy of sciences (bulgaria). 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file:///c:/users/bmek/downloads/10.1088/1757-899x/778/1/012095 hungarian journal of industry and chemistry vol. 50(2) pp. 27-33 (2022) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2022-15 investigation of the pyrolysis of animal manure in a laboratory-scale tubular reactor: the effect of the process temperature and residence time maria elena lozano fernandez1, szabina tomasek1*, csaba fáyköd2 and andrea somogyi3 1 research centre for biochemical, environmental and chemical engineering, department of mol hydrocarbon and coal processing, university of pannonia, egyetem u. 10, veszprém, 8200, hungary 2 felső-bacska storage windpark ltd., arany jános út 200, fadd, 7133, hungary 3 solver unio ltd., ábel jenő u. 8, budapest, 1113, hungary this paper focuses on the pyrolysis of animal manure in a laboratory-scale tubular reactor between 300 and 900°c at nitrogen flow rates of 1 and 5 dm3/h. during the experiments, it was found that both the temperature and nitrogen flow rate had significant effects on the product yields and compositions. the highest gas yield and syngas content were observed at 900°c at a nitrogen flow rate of 1 dm3/h. in this case, since the gaseous product was characterized by a h2/co ratio of 0:5, its quality must be improved prior to being used for synthesis. the composition of the solid residue was also affected by the pyrolysis parameters . based on the hydrogen/carbon and oxygen/carbon ratios, it was concluded that both the water-gas shift and boudouard reactions were the most critical. keywords: cattle manure, pyrolysis, tubular reactor, product yield, composition 1. introduction the rapid growth of the world’s population is leading to a significant rise in the demand and consumption of food, including meat and animal-derived products. as a consequence, farms and this sector generate huge amounts of waste such as livestock manure, sewage sludge and poultry litter [1]-[2]. the inadequate management of manure and sewage sludge causes serious health and environmental issues, e.g. water and air pollution as well as the emission of greenhouse gases and heavy metals in addition to the spread of pathogens. the composition of this residue includes a wide variety of chemical and biological compounds which are associated with the specific species of animals and age ranges amongst other factors. the residue consists of a complex mixture of compounds, mainly microbiota, lignocellulose, proteins as well as a significant amount of inorganic matter such as s, n, p, k, ca, mg and cl. additionally, heavy metals such as cu, pb, cd, zn and mn can be found in the residue due to the use of antibiotics and hormones supplied to the animals [3]-[5]. some of the practices concerning the disposal of sewage sludge and manure include landfilling, agricultural utilization, composting, anaerobic digestion and thermochemical conversion [6]. one of the most received: 26 sept 2022; revised: 10 oct 2022; accepted: 11 oct 2022 *correspondence: tomasek.szabina@mk.uni-pannon.hu traditional and practical alternatives is the usage of these residues in agricultural land due to the high content of n and p which are essential elements required in plant fertilization. however, nowadays, this practice has diminished due to the enormous amount of waste generated, exceeding the nutritional requirements of the soil. environmental regulations establish limits on the values allowed for the usage of sewage sludge in agriculture. the excessive use of manure on land causes problems such as contamination of the subsoil and surface, odors as well as the emission of greenhouse gases and ammonia [5,7-10]. therefore, new alternatives for the proper management of this type of waste have been explored as well as studied more comprehensively in an attempt to solve the environmental and social impacts [8]. for example, thermal conversion techniques such as pyrolysis and gasification could be alternatives for transforming the residue into valuable products such as oil, char and gaseous products. additional advantages of these techniques are that the huge volume generated is reduced, microorganisms are degraded and pathogenic organisms destroyed [1,9-10]. it is important to take into consideration that the percentage of humidity in the residues in the material is high and should be reduced while using the thermal techniques. the material could https://doi.org/10.33927/hjic-2022-15 mailto:tomasek.szabina@mk.uni-pannon.hu lozano fernandez, tomasek, fáyköd and somogyi hungarian journal of industry and chemistry 28 be dried through natural, mechanical and thermal drying techniques [11]. depending on the thermal degradation technique applied, the composition of the feedstock; process conditions, e.g. temperature and heating rate; as well as product distribution and its composition will vary [11]. for example, during pyrolysis, degradation in the absence of oxygen occurs at high temperatures. through pyrolysis, the feedstock decomposes to form char, oil and light non-condensable gases [11]. in the case of the raw material containing a large amount of hemicellulose and cellulose, a product consisting of a higher percentage of gases could be expected, while lignin contributes towards the formation of char. regarding the temperature, the formation of char is favored by low temperatures, while that of oil and volatile gaseous components is more likely at high temperatures [12]. the products can be further utilized depending on their characteristics. char has interesting physical properties, for example, a high surface area, microporosity as well as high adsorption and ion exchange capacities. char potentially could be used as an adsorbent, a catalyst, in power plants or as a fertilizer. char obtained from manure is rich in elements such as k, p, ca and mg [10], [12]. in the oil fraction, hydrocarbons are produced but the pyrolysis oil from manure and sewage sludge is not regarded as of high quality since the oil produced contains oxygen, which gives rise to the production of compounds such as alcohols, ketones, aldehydes and esters that decrease the quality of the product [1]. the gas produced contains a mixture of co, co2, ch4, h2 and some light hydrocarbons (c2h2, c2h4, c2h6 and c3h8) [13]. the gas may be valuable because the energy it contains could be used in gas turbines and power plants or its compounds applied as a feedstock to be processed into a more addedvalue chemical product [13]-[14]. despite the wide range of possible uses of the products, relatively few studies have investigated the pyrolysis of cattle manure. consequently, limited information about the product yields and compositions is available. in light of the above, this study focuses on the pyrolysis of cattle manure within the temperature range of 300-900°c using nitrogen flow rates of 1 and 5 dm3/h as well as on the impact of the process parameters. 2. materials and methods 2.1. raw material cattle manure was used as a feedstock for the pyrolysis experiments. before the experiments, the raw material was dried at 110°c to constant mass. to determine the physical and chemical properties, the proximate and ultimate analyses of cattle manure (table 1) were carried out. as data show, the raw material is characterized by 40.6% ash, 53.5% volatile compounds and 0.3% water content. the c, h, n, s and o contents were determined by a carlo erba-type elemental analyzer and in order to identify the inorganic compounds, e.g. ca, p, s, si, na, mg, fe and al, energy dispersive x-ray analysis was performed (shimadzu edx). 2.2. pyrolysis experiments pyrolysis was performed in a laboratory-scale horizontal tubular reactor (fig.1). the cattle manure was placed in the center of a glass wool tube. the experiments were performed at 300, 500, 700 and 900°c. a n2 atmosphere was used and the flow rates established were 1 and 5 dm3/h. the heating rate used for this experiment was 100°c/min. the reaction system was equipped with a scrubber and silica gel-filled tube, where the gaseous products were purified to remove possible impurities and dried. at the end of the reaction, the product yields were estimated by measuring and calculating their difference in mass. 2.3. product analysis the composition of the gaseous products was determined by a dani-type gas chromatograph using a flame ionization and thermal conductivity detectors. the equipment contained two capillary columns (rtx-1 pona (100 m x 0.25 mm x 0.5 µm) and carboxen tm-1006 plot (30 m x 0.53 mm)). regarding the isothermal conditions of the pona capillary column, the injector and detector temperatures were both 230°c. in terms of the carboxen tm-1006 plot capillary column, the applied heating program was as follows: 35°c for 18 mins before being heated to 120°c at a heating rate of 15°c/min and maintained at 120°c for 2 mins. the table 1. proximate and ultimate analyses of cattle manure parameter value (%) p ro x im at e an al y si s fixed carbon 5.59 ash content 40.68 volatile organic compounds 53.43 water content 0.30 u lt im at e an al y si s c 24.80 h 3.00 n 2.90 s 1.30 o 45.30 others (ca, p, s, si, na, mg, fe, al) 22.70 figure 1. experimental setup pyrolysis of animal manure 50(2) pp. 27-33 (2022) 29 retention times of the components were determined using gas mixtures and individual components. 3. results and discussion 3.1. product yields the product yields of the pyrolysis experiments are summarized in fig.2. during the experiments, only gas and char were formed. as expected, the gas yields and amount of solid residue produced increased and decreased, respectively, as a function of the reaction temperature. during the pyrolysis process, a series of complex reactions took place. up to 200°c, to all intents and purposes, only the water was removed from the cattle manure (fig.3). in the torrefaction stage, since cellulose, hemicellulose and lignin were only slightly degraded, the final product was a solid carbonaceous material. this stage was followed by the pyrolysis process, where a significant reduction in mass resulted. in addition, a sharp peak appeared at approximately 300°c in the derivative thermogravimetric diagram (dtg), indicating that the reduction in mass occurred at a high speed. it is well known that cellulose degradation occurs between300 and 350°c, while protein decomposes between 450 and 660°c. in addition, deamination also took place. during the pyrolysis stage, approximately 30% of the initial mass was lost. above 600°c, another significant proportion of mass, ~25%, was lost. this reduction in mass was related to the degradation of chains of lignin, carbon and minerals. it was also observed that the rate at which the mass reduced was low and relatively stable. this effect could be attributed to the minerals and possible carbonated forms. additionally, it is worth mentioning that within this temperature range, co2 was also formed. co2 acts as an oxygen donor, promoting the boudouard reaction and, therefore, the formation of co. another peak is also visible at 800°c in the dtg curve, which can be attributed to the devolatilization of the char and decomposition of the mineral matter. at the end of the test, that is, at a temperature of 900°c, the percentage of mass consisting of ash and fixed carbon remaining in the crucible was the same as that reported during the proximate analysis. it is important to note that the n2 flow rate also had an effect on the product yields. the lower flow rates facilitated the formation of the gaseous products. given the longer residence time, the volatile vapors resuting from the pyrolysis exited the reactor more slowly, so they had sufficient time to degrade more comprehensively. 3.2. composition of the gaseous products although the gaseous products consisted of h2, co, co2 and ch4, c2-c6 hydrocarbons were also formed (fig.4). h2 was formed by dehydrogenation, however, it could have formed as a result of the reforming reactions. co may be related to the reactions that facilitated the cleavage of bonds in the ether groups and decarbonylation from proteins [15]-[16]. as fig.4 shows, the formation of co considerably increased above 700°c and the highest level was obtained at 900°c. this large increase was attributed to the boudouard reaction, which has already been referred to in the thermogravimetric analysis. the boudouard reaction can also be catalyzed by carbonates present in the manure [17]. the increase in co can also be justified by a reaction between co2 and other compounds generated during pyrolysis, the reduction of co2 to co figure 3. thermogravimetric results with regard to the raw material d ry in g to rr e fa ct io n p yr o ly si s p yr o ly si sga si fi ca ti o n d m /d t w e ig h t lo ss , % 0. 0 1. 0 2. 0 3. 0 4. 0 5. 0 6. 0 0 25 50 75 10 0 temperature, °c 200 400 600 800 1000 200 400 600 800 1000 figure 2. product yields of pyrolysis 0 20 40 60 80 100 300 500 700 900 gas yield, % t e m p e r a tu r e , °c 5dm3/h 1dm3/h 0 20 40 60 80 100 300 500 700 900 char yield, % t e m p e r a tu r e , °c 5dm3/h 1dm3/h lozano fernandez, tomasek, fáyköd and somogyi hungarian journal of industry and chemistry 30 and simultaneously the oxidation of the carbon of the pyrolysis product through a homogeneous reaction [18]. the quality of the gaseous product can be defined in terms of its chemical composition and calorific value. fig.5 represents the content of syngas, namely h2 and co, in the product. from the results, it is remarkable that the production of syngas only took place above 500°c and the yield increased in proportion to the temperature. the highest syngas yields (~80%) were observed at 900°c. it is important to emphasize that the n2 flow rate also had an effect on the syngas yield. the yield of syngas was higher at lower n2 flow rates, in the same manner as the overall gas yield. the h2/co ratio of syngas (fig.6) is extremely important. the typical initial ratios for the transformation of methanol into chemicals are >2:1 for light olefins; <2:1 for diesel; 1.5:1 for aldehydes, higher alcohols and dimethyl ether; 1:1 for oxygen-containing alcohols and acetic acid; and 1:2 for polycarbonate [19]-[20]. as data in fig.6 show, although the ratio of h2/co at 500°c was approximately 1, at 700 and 900°c it was below 0.6. the heating values of the gases were also estimated. as is depicted in fig.7, at lower temperatures (300 or 500°c) and an n2 flow rate of 1dm3/h, the calorific value of the gas mixture was higher (~30 mj/m3), meanwhile, at higher n2 flow rates, the heating value of the gaseous product was about 15 mj/m3 at the same temperatures. this can be explained by the fact that a higher percentage of light hydrocarbons is present, the individual components of which provide a higher (n2 flow rate: 1 dm3/h) (n2 flow rate: 5 dm3/h) figure 4. composition of the gas products 0 20 40 60 80 300 500 700 900 composition, % t e m p e r a tu r e , °c c2-c6 ch4 co2 co h2 0 20 40 60 80 300 500 700 900 composition, % t e m p e r a tu r e , °c c2-c6 ch4 co2 co h2 (n2 flow rate: 1 dm3/h) (n2 flow rate: 5 dm3/h) figure 5. syngas yields 0 20 40 60 300 500 700 900 yield, mmol/g raw material t e m p e r a tu r e , °c co, mmol/g h2, mmol/g 0 20 40 60 300 500 700 900 yield, mmol/g raw material t e m p e r a tu r e , °c co, mmol/g h2, mmol/g figure 6. h2/co ratios of syngas 0,0 0,5 1,0 1,5 300 500 700 900 h2/co ratio t e m p e r a tu r e , °c 5dm3/h 1dm3/h figure 7. heating values of the gaseous products 0 10 20 30 40 300 500 700 900 heating value, mj/m3 t e m p e r a tu r e , °c 5dm3/h 1dm3/h pyrolysis of animal manure 50(2) pp. 27-33 (2022) 31 calorific value than the other compounds present in the mixture [21]. another interesting correlation is the difference in the proportions of different elements contained in the gas as well as the resultant study and proposition of possible reaction mechanisms at different temperatures. the trends observed when the ratio of components were estimated are summarized in table 2. from the process, the water-gas shift reaction and boudouard reaction are some of the critical reactions that took place [14]. 3.3. char according to the international biochar initiative (ibi), the char obtained from the pyrolysis experiments can be regarded as biochar [22], in which the c content is greater than 10% except for during the tests carried out at 900°c. to determine the possible applications of char, it is recommended to evaluate the relationship between the proportions of some elements. for example, the c/n ratio could be a positive parameter to determine the microbial activity should this residue be used in soils. another aspect possibly worth evaluating and analyzing is the h/c and o/c ratios of the manure as well as the char obtained in each test (table 3). the ratios are valuable for understanding the reaction mechanisms during pyrolysis under specific conditions [15]. the atomic ratios show that the process of carbonization changed the chemical compositions by removing functional groups. due to the cleavage of the functional groups, the nitrogen contents significantly decreased, moreover, as a result of the formation of co, co2 and ch4, the carbon contents also reduced. table 2. the proportions of different elements component ratio n2 flow rate: 1 dm3/h n2 flow rate: 5 dm3/h relationship proposed reaction h2/co optimum (highest peak at 500°c) optimum (highest peak at 500°c) higher ratio at a flow rate of 5 dm3/h (except for at 500°c) 𝐶𝑛 𝐻𝑚 + 𝐻2 → 𝑛 + 𝑚 2𝐻2 + 𝑛𝐶𝑂 𝐶𝑂 + 𝐻2𝑂 → 𝐶𝑂2 + 𝐻2 co/co2 increasing increasing higher ratio at a flow rate of 5 dm3/h 𝐶 + 𝐶𝑂2 → 2𝐶𝑂 h2/ch4 optimum (highest peak at 500°c) optimum (highest peak at 500°c) higher ratio at a flow rate of 5 dm3/h 𝐶 + 𝐻2 → 𝐶𝐻4 co/ch4 optimum (highest peak at 700°c) increasing higher ratio at a flow rate of 5 dm3/h 𝐶𝑂 + 3𝐻2 → 𝐶𝐻4 + 𝐻2𝑂 co2/ch4 decreasing decreasing higher ratio at a flow rate of 5 dm3/h 𝐶𝑂2 + 4𝐻2 → 𝐶𝐻4 + 2𝐻2𝑂 2𝐶𝑂 + 2𝐻2 → 𝐶𝐻4 + 𝐶𝑂2 table 3. elemental analysis of the char products cattle manure at n2 flow rate of 1 dm3/h at n2 flow rate of 5 dm3/h 300°c 500°c 700°c 900°c 300°c 500°c 700°c 900°c elements content (%) c 24.8 23.40 20.20 20.90 6.30 23.50 20.50 18.90 7.20 h 3.00 1.80 0.70 0.30 0.80 1.60 0.60 0.30 0.80 n 2.90 2.50 1.50 1.00 0.40 2.30 1.60 0.80 0.80 s 1.20 1.50 1.40 1.40 2.50 1.40 1.60 1.40 2.90 o 45.30 48.20 53.50 53.70 67.30 48.50 53.10 55.80 65.60 al 0.60 0.99 0.98 1.55 1.39 0.72 1.06 1.48 1.57 ca 14.12 12.61 12.91 12.83 15.74 12.36 12.40 11.92 14.74 cl 0.71 0.82 0.70 0.84 0.21 0.63 0.67 0.78 0.40 fe 0.60 0.55 0.18 0.39 0.54 0.72 0.53 0.53 0.52 k 1.76 3.39 2.90 3.22 1.18 2.75 2.93 2.58 1.31 mg 1.19 1.11 1.19 1.55 0.96 1.11 1.13 1.23 0.91 mn 0.03 0.03 0.04 <0.001 <0.001 0.05 0.03 0.04 <0.001 p 2.16 1.40 1.99 2.32 0.96 1.93 2.09 2.05 1.17 si 1.48 1.81 1.82 0.00 1.71 2.42 1.86 2.09 2.09 atomic ratios c/n 8.6 9.4 13.5 20.9 15.8 10.2 12.8 23.6 9.0 h/c 0.10 0.08 0.03 0.01 0.13 0.07 0.03 0.02 0.11 o/c 1.8 2.1 2.6 2.6 10.7 2.1 2.6 2.9 9.1 lozano fernandez, tomasek, fáyköd and somogyi hungarian journal of industry and chemistry 32 4. conclusions in this study, cattle manure was pyrolysed in a horizontal tubular reactor between 300 and 900°c at n2 flow rates of 1 and 5 dm3/h. during the experiments, 20-60% gaseous and 40-80% solid carbonaceous residues were formed. the gas yields increased in proportion to the reaction temperature and residence time, while the amount of char decreased. the decomposition process resulted in the formation of h2, co, co2, ch4 and c2-c6 hydrocarbons. syngas was only produced above 500°c. the ratio of h2/co at 500°c was 1, while at 700 and 900°c, the proportion of co was greater than that of h2. at lower temperatures (300 or 500°c) and at an n2 flow rate of 1dm3/h, the calorific value of the gas mixture was higher (~30 mj/m3) than at the higher n2 flow rate and same temperatures (~15 mj/m3). the process of carbonization changed the chemical 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https://doi.org/10.1016/j.energy.2018.04.084 https://doi.org/10.1016/j.jclepro.2021.129109 https://doi.org/10.1016/j.jclepro.2021.129109 https://doi.org/10.1016/j.jpowsour.2022.231453 https://doi.org/10.1016/j.fuel.2022.124124 https://doi.org/10.1016/j.wasman.2006.07.015 https://doi.org/10.1016/j.wasman.2006.07.015 https://doi.org/10.1016/j.jiec.2008.10.004 hungaru\njournal of industrial chemistry veszprem vol. 30. pp. 229-234 (2002) internet based survey as 110 support in process approached qms of food/agro industries b. kapolna, r. szabo, g. viczian1 , g. kollar (postharvest department, szent istvan university, 1118. budapest, menesi ut 45, hungary 1dept of chemical information technology, bp. univ. of technology and economics, h1521 budapest, pf.91. hungary) received: october 17, 2002 this paper was presented at the 8th international workshop on chemical engineering mathematics, bad honnef, germany, september 18-21 2002 the iso 9001:2000 standards encourage the adoption of the process approach for the management of organizations and their processes. using our quality audit experiences, several internet questionnaires have been created to identify and support the most important i/0 elements in a process approached qms in different fields of the foodlagro industries. evaluating the internet answers, we found some interesting properties of meat and fresh fruit/vegetable (ffv) consumption. in our internet based qm research we have focused on these two special fields. keywords: quality management, meat and fresh fruit/vegetable consumption, internet cgi-forms introduction any activity that receives inputs and convert them to outputs can be considered as a process. the goal of a quality management system is to explore and to satisfy customers' requirements at the highest level, developing and using a policy that ensures the goal of real time satisfaction [1,3]. the new iso 900x:2000 standard family uses the term "quality control" instead of the category uquality assurance" and a process approach of qms (quality management system) whose most important input/output element is customer requirements and satisfaction. in one of our earlier papers [4] we discussed internet vs. paper-based replies to questionnaires surveying the rates of food consumption in different areas of food market comparing these types of replies we found an interesting~ but in view of the number of answers insignificant difference between the two groups in ffv consumption and in meat consumption. this fact inspired our workgroup to create newer questionnaires on these topics, and to develop new software that makes it easy to evaluate both internet based and hardcopy answers. contact information: e-mail: kollarg@omega.kee.hu the qm process model and the model of customers' habits the iso 9001:2000 standard helps on one hand the top management to be increasingly successful if they pay attention to their customers' requirements. on the other hand if the organisations use this standard they will come closer to the tqm, which is the last step in the quality control process [2j. in addition to the input/output elements there is another very important part of the process model: the product service. this can help customers in case they have any problems or questions regarding a product or service. and this information could help the consumers in their decisions. in the model on fig.j, one can see the three factors, which influence consumers. the fig.l describes a decision process that consists of the following three factors: • property of food attributes it contains physiological influences. • personal factors biological, psychological and social impressions. 230 personal facto res biological psychological l social property of food atlributes physiological influences evaluating choosing fig.l customer habit's model environmental facto res cultural economical marketmg • environmental factors cultural, economical and marketing impressions. all of these factors have impressions on all customers when they realize their demands. they collect information about the product or service and then by their own opinion they choose the best. that's why organisations should offer as much information as possible e.g. in forms of advertisements. using our quality auditing experiences, we have created several internet based questionnaire forms to identify and to investigate customer requirements, satisfaction and preferences [7]. evaluating the replies to the web-forms and to the control group consisting of hardcopy answers [ 4] we have found an interesting difference between the groups with respect to the meat and ffv consumption. considering this fact we have decided to investigate deeper these fields, and we have created three new internet-forms to be found at the following web sites: http:/ /knight.kit.bme.hulbea, http://knight.kit.bme.hu!rita on the first and second questionnaires we have investigated the ffv producers, market and cqnsumption. the questions covered properties of fruits and vegetables grown in hungary, which are influenced by postharvest activities and procedures. in the last ten years the number of hyperand supermarkets in hungary have been increasing. they offer goods at low prices. which are welcome to the customers, but their quality is not as good as the price. that's why we investigated price, quality and customer service of distribution centres. on the third internet form we attempted to get information about hungarian meat consumption. earlier surveys show that most of the hungarians consume meat everyday. in the last years. however some problems have aroused (e.g. bse~ foot and mouth disease) and healthy nutrition has also become more and more important in our lives. for this we wanted to gather more details of the "new .. hungarian meat consumption habits. web server: knightkit.bme.hu mailing server and client in szt. istvan univ. accepting emails, extracting and processing answers by mailproc (delphi or vba) filling in internet questionnaire anywhere fig.2 internet data collection using email mailproc: separating answer-variable's name and value, rewriting hungarian fonts from hexadecimal characters statistical evaluation, diagram specification and drawing yes opening kmt answer-file extracting sender's name, address and answer-line, closing the file fig3 the main steps of processing email answers the structure of internet data collection and evaluation in our first internet questionnaires we used forms posting the answers in email although the evaluation of emailed answers is more complicated than the evaluation of forms sending answers to a cgi program, at first we decided to use email answers. the plain reason for this being that it is not easy to get farmers and housewives to use the internet (or a pc questionnaire at all). in several cases they do not have full internet connections, at most they are familiar with emailing. they usually have only email connections to the internet. the html files of the web-forms generating email replies can be sent to users via email, then it is possible for the users to fill out the forms offline. the completed questionnaire is then saved in the outbox folder, to be automatically sent back at the next dialup connection to the internet. the process flow of this kind of data collection and email processing is shown on figs.2 and 3: ~;~r ~. client in szt. istvan univ. downloading answer-file, processing by tabproc filling in internet questionnaire anywhere fig.4 internet data collection using cgi program tabproc: {*) qd file includes: • #of questions {qnum) • questions' type and description as it is given in fig 6. comparing k11 question in ica and qd detecting question's type processing each answers (parameter of answer-processing routine is the question's type) fig.5 steps of processing cgi program-collected answers we tried to find the food customers, who could use this type-1 questionnaire, but in several fields the number of answers was not enough for proper statistical evaluation. at this point we decided to create a cgi program on our server. type-2 questionnaires were created to utilise the cgi script. the process flow of this type of data collection and evaluation is shown on fig sa and 5. as one can see on figs.2 and 4 or on figs.3 and 5, there are no big theoretical differences between type-1 and type-2 questionnaires and their processing programs. the difficulty in type-1 is the collection and separation of email messages; in type-2 on the other hand we have to generate a questionnaire description (qd) file before running the processing software. some parts of this qd description file is shown on fig. 6 comparing with the corresponding parts of the iitml file. when the qd file is generated from the html source, we have the possibility not only to collect internet answers, but also to collect the hardcopy answers in a separated~ but very similar file. 231 <select n~orf<> and the q-description file: <option val~~<><" selected> <option valua:"whit<>"> <option value='blue"> <option valup"bolh"> <option value="r<>lired"> <option value="student'> <is elect> "rellsonof·\-,•hite meat". 1, 3 "health', "like', "bse" 'preferred type (besl=1, worsl=3}", 2, 3 "raw", 'buffet', "semiprep" <seloot name="dlly/year"> <option value><"" sl)l<>cled> <option valoo="365"> <option value="52'> <option value="12"> <option value="o"> <lset..ct> r""son of white meat <ld colspan..s> <input type=chackbox nalllq="hea1th"> <input typ~ackbox narne="lika"> <input type=chackbox nama='bse"><iid> preferred type (besl=1, worat=3) <ld><input natne='raw' size=2>)<11d> <ld><input name='buffet" size=2><11d> <id><input name=•s,amiprep• aize=2><11d> fig.6 qd file generated from a web-form fig. 7 source of ffv consumption :adequate: 2% fig.8 qualification of infonnation system in distribution centres evaluation of ffv consumption data from our ffv project we show here the evaluation­ graphs of extreme qualifications, as well as the answers about the most important hungarian ffv areas with respect to produced quantities in hungary or hungarian customers' habits. on figs.7-9 we show some results of our first web­ based questionnaires. 44 % of responders said they had bought ffv in small shops and 36 % of them in hypermarketslsupermarkets. fig.8 gives information about the preferred distribution centres in this question we wanted to know if the participants were satisfied with the information system of the chosen distribution centre or not. unfortunately most responders said that the amount and quality of the information had nor been adet~uate (56%) and only 2% of them said that it had been 232 fig.9 frequency of ffv consumption storage: 11% fig.l 0 most important factor at buying fig.ll qualification of fv freshness and quality at distribution centres adequate. the e participant do their shopping in market pia es \ here they can get references about fv from the farmer. fi .9 how that mo t hungarian people eat ffv daily. thi i a ery good rat a thi mean that\! e try to live healthler but v e ha een many of them do not h e nough inform tion about u age of thes produ t . la k of ge in tru tion i the ftr t problem but as we an e in the fig.jo mo t r ponder an \ ered to th que tion con eming the pur h e influen ing f tor that th pric \ a le important than quality. it' well kn wn that hungarian people demand but as fig.jj how , the qualifi ation of and quality i not enough to ati fy the tom r. fig. 1 ummarize the qualifi ation of apple. apple i one of the mo t popular fruit in hungary. cu tomer can buy it in e er ea on and hungarian apple produ tion i on iderable in europ t o. figs.jj-1hm: the many problems among the pr fl rred and qualifi d pr p rtie of ffv ry well. e -·····35 30 ~ 25 i"'j..£ 20 i ~ r 15 ii'--.._._'-lk10 ~u i~ ~ i}~ lft 5 0 1 point 2polnt 3 point 4 polm 5polnt orljleness 0 0 10 33 15 cwholeness 0 6 23 21 b orreshness 0 1 22 23 12 a selected 0 13 25 12 b •pack ina 7 t9 21 7 4 a information 17 13 18 7 3 fig.l2 qualification of apple ~5/ 30 v ~~ ii 25 i' 1/ ~ t 20 1/ 15 ·j~ • 1 point 2poinl 3 point 4 point 5polnt orloeness 2 3 19 23 10 owholeness 0 0 15 32 10 ofreshnes:s 0 3 19 29 6 osalected 0 6 19 22 10 •~aching 2 10 14 21 10 o information 10 17 16 14 0 fig.l3 qualification of citrus have investigated the same problems with similar results for other fruits and vegetables: stone fruits, citru tomato, paprika, cabbage, onion, root vegetables and mushrooms. from the ffv investigation we will now discuss the results concerning the citrus group (fig.l3). as our climate is not appropriate to grow citrus fruits, the properties of the imported citrus are sati factory quite on every level. the lack of customers' information is the only problem in this field. evaluation of meat consumption data meat con umption patterns vary widely with the economic conditions and cultural or relioious ba kground of different region . in reasing fracti~n of the younger generation cannot cook so they need the emi prepared produ ts. among others, this is the rea on f; r the in rea ing demand for the deep frozen produ t and the 1i ed old meat in hungary. another fa tor i , that cu tomer prefer white meat to red one, be a e of health con ideration [56]. sin e the fir t igns of the bse cri is turkey on umption ha grown especially: experiment in germany ha e hown an increase of 8,6 ~ . in the first part of year _oo 1 it ha reached 16 ~ . this increase is al o alid for the fre h and deep-frozen products. the pri e have a1 o been grm: ing, becau e the upply wa 5% 1% 1% fig.l4 the meat consumption patterns in hungary fig. is form of bought meat not able to keep pace with the demand. even after expanding the livestock the prices seem to stay at this higher level. in july of 2001 turkey costed 17 %higher, than in the previous year. furthermore in the last few years there were some epidemics (bse, foot and mouth disease) in western europe. customers are frightened, because the meat could be infected, so they prefer the product from their own country. the most important aspect for them is the safety. to understand the structure of the meat consumption patterns in hungary, a type-2 internet based survey was applied. the online forms consisted of simple, multiple­ choice questions and text fields. the first part of the questionnaire included questions regarding to the demographic backgrounds of the subject, for example gender, age etc ... in the second part we asked the consumers about their meat consumption habits. in the following section we summarise the statistical evaluation of over 200 replies to this survey. fig.l4 shows, that amongst the people replied, only a small percentage ( 1 %) is vegetarian. 50 percent consumes meat every week, and also a big fraction (43 %) of them has meat daily. the reason for these is that in hungary the healthy way of living is not yet usual. the other reason could be, that meat consumption belongs to the traditional hungarian lifestyle. the next question was, how much money would be spent monthly for meat ( fig.15 ). more than half of the returned answers suggested that over 1500 huf were spent for meat products. it was an interesting experience to see, that mostly the retired have pent below 500 huf. this is in connection with their lower incomes. fig.l6 shows, where the meat products are purchased. 43 ~ get the meat from the butcher, which is possibly the best way, because you can always get meat of highest quality. 233 12% 1% 10% fig.j6 meat production purchase in hungary 2% fig.j7 the meat consumption patterns in hungary in hungary the hypermarkets and supermarkets are also gaining ground. that is why 34 % goes to hypermarkets, when they need these products. the growing needs and the increasing work time require faster shopping. these hypermarkets have the sale strategy to sell as much as possible, so th~y have long opening hours, or they are open 24 hours a day, even days a week (sometimes non-stop). they k ep the largest product variety, and because of the huge amounts, the prices can be lower. they can afford regular sales, which is also preferable for the customer . it is a weekend family program, too, you can find there something interesting, no matter, how old you are. market is also a beloved place to get meat products. especially retired people and hou ewives go there. where they have time to look for the highest qualit. at the lowest price. they are those people who would travel across the city to save some coin on a pound o meat. 12 % belongs to the other group who hop at small shops or they rai e their animals. fig.l7 shows a clear trend in the ratio f red and white meat consumption, in favour of the latter. thi can be the result of both the recent health crisis (foot and mouth bse, etc.), and the growing number of health conscious consumers. the bse, or bovine spongiforme encephalopathie is an infection of the cattle. the whole nervey tern i destroyed, and the animal die . it take about 5 years from the infection to the fir t isible sign. cattle catch this di ease with the feed, which contain flour made from animal meat or bone . the first b · ri i started in year 2000. at that time the price o b f fell. but afterwards the price were rai ed again b ·aus in the etherland there was foot and mouth di a e, o there wa a hortage of beef. 234 fig.l8 form ofbought meat the literature writes about this trend extensively, so we were curious, what people think about this question. we asked them, why they preferred the white meat. they were listed 3 options, with a possibility to mark several of them. most of the customers eat meat because they like it, but an increasing fraction of them are cautious about what they eat, because they are interested in healthy food, as they want to stay healthy. it was interesting to see, that more and more people in hungary are worried about bse, so they prefer the white meat. the next question was, in which form they eat the meat. they had to mark, whether they eat it row, semi prepared or buffet (fig.18). we can see a trend, because earlier the raw meat was very popular, and now it is at third place. the people work a lot, they have less time for cooking, so they prefer the semi prepared meat, because it is much easier to prepare, this way they can save time. the last question was, about the most important aspect of buying meat. this was also a multiple-choice. it was very interesting to see, that the quality is much more important, than price ( fig.19 ). because of the diseases in the last few years, everybody is looking for safe food. conclusions using our audit experiences in foodlagro industries and the literature data, we developed effective internet questionnaires to identify the ffv and meat consumption patterns and customers' requirements in hungary. two types of web forms were created to collect the replies; both types contain several questionnaires each having its special application area. for the statistical analysis of the replies we developed the corresponding software in delphi and in vba. applying our different web forms the number of replies was between 50 and 300. acknowledgements the authors wish to express their gratitude to the members of the postharvest club~ to klara kollar200 154 150 100 50 0 price quality healthy fig.l9 aspects of buying meat hunek (bute, budapest) and to zoltan lakner (sziu, budapest). the work has been supported by the hungarian national research foundation (otka, grant # t030241199). symbols bse bovine spongiforme enzephalopathie cgi common gateway interface ffv fresh fruit and vegetable ica internet collected answers i/0 input/output qm quality management qms quality manag~ment system sc shopping centre qd questionnaire description vba visual basic for application references 1. iso/cd2 9001: 2000, quality management systems requirements, isoffc 176/sc 2/n 434, 1999 2. kollar g., viczian z., fostos z. and hunek k.: computers & chern. eng. 1999, 23, 687 3. kou.ar g., viczian z., syposs z., fosms z. and di6spatonyi i.: hung. j. ind. chern., 2000, 28, 162 4. kollar. g., syposs z., viczian g., meszaros l. and kolla.r-hunek k.: hung. j. ind. chern., 2001, 29, 135 5. lakner z., szab6 e., monspartne senyi j. and baglyas f.: publication of horticulturalfood­ and landscape sciences of sziu, ed. papp j., szlli, budapest 2001, 60, 18 6. syposs z. and lakner z.: 44th european quality congress business excellence in the new millenium quality for society 2000, 2, 419 7. viczian g., kollar g., kapolna b. and kou..ar-hunek k.: mkn 2002 (veszprem), 2002, 1, 162 (in hungarian) page 230 page 231 page 232 page 233 page 234 page 235 hungarian journal of industry and chemistry vol. 51(2) pp. 1–6 (2023) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2023-11 study of composite pipelines damaged by corrosion: control by non-destructive testing samir lecheb1, abdelhakim daoui2, chahira brihmat3, hamza mechakra1, ahmed chellil1, brahim safi2*, hocine kebir4 1 motor dynamics and vibroacoustics laboratory, faculty of technology, m'hamed bougara university of boumerdès, frantz fanon city, boumerdès, 35000, algeria 2 materials, processes and environment research unit, faculty of technology, m’hamed bougara university of boumerdès, frantz fanon city, boumerdès, 35000, algeria 3 mechanical solids and systems laboratory, faculty of technology, m'hamed bougara university of boumerdès, frantz fanon city, boumerdès, 35000, algeria 4 roberval laboratory (umr 7337), university of technology of compiègne, rue du docteur schweitzer cs 60319, compiègne, 60203, france since the degradation of material properties and defects often occur in engineering structures due to fatigue loading, it is necessary to develop non-destructive testing methods to assess the safety of engineering structures. in the aerospace industry in particular, the demand for early crack detection to ensure the safety and durability of engineered structures is growing. the automated inspection of pipelines using non-destructive testing (ndt) is desirable because visual inspections are not always consistent. in addition, automated inspections reduce the cost of the inspection process and improve its quality. since the identification of cracks in engineering materials is very valuable for understanding initial and slight changes in the mechanical properties of materials in complex working environments, numerical simulations of propagating lamb waves in a cracked pipeline were performed to study their non-linear behavior. finally, the shapes of all the signal responses can be used to identify the depth, length, shape and orientation of cracks. the elapsed time before signal responses are received varies as a function of the orientation of a crack. keywords: composite material, pipeline, degradation, damage, non-destructive testing 1. introduction it is necessary to develop non-destructive testing (ndt) methods to assess the safety of engineering structures. in the aerospace industry in particular, the demand for early crack detection to ensure the safety and durability of engineered structures is growing. linear ultrasonic testing has been widely used to detect cracks, holes, corrosion and other defects in materials, but is only sensitive to severe defects [1]-[4] through which ultrasonic waves pass [1]-[2]. therefore, linear ultrasonic testing may well fail to detect closed cracks [2]. compared to linear ultrasonic testing, long-range and highly sensitive lamb waves propagate over relatively long distances (a few meters in composites), enabling each ultrasonic pulse to inspect the entire field between the transmitter and receiver, in contrast to traditional step-by-step inspection techniques. the proposed technique will therefore rely on the integration of sensors capable of generating and detecting such waves within or on the surface of the structures to be tested. such a system received: 6 may 2023; revised: 27 may 2023; accepted: 1 june 2023 *correspondence: safi_b73@univ-boumerdes.dz must be capable of automatically acquiring, storing and processing data. the presence of a fault will be identified by observing changes in the signal response relative to a reference response recorded before the structure was damaged. due to the curvature of a tubular structure, the wave properties are more complex than through a plate. theoretical and numerical analyses of higher-order harmonic generation were conducted on non-linear waveguides of arbitrary cross-sections in weakly nonlinear cylinders and plates with large-radius pipes. the simulation showed that cumulative second-harmonic generation with longitudinal, torsional or flexural mode excitation was also observed in pipes when two conditions, namely phase velocity matching and nonzero power flow, as in plates were satisfied. furthermore, the method of simulating material non-linearity in plates can also be applied to pipes. experiments concerning material non-linearities in pipes also confirmed the phenomenon of cumulative second-harmonic generation with longitudinal or circumferential wave excitation [4][19]. https://doi.org/10.33927/hjic-2023-11 mailto:safi_b73@univ-boumerdes.dz lecheb, daoui, brihmat, mechakra, chellil, safi and kebir hungarian journal of industry and chemistry 2 in this context, the theory and interpretation of the temporal characteristics of lamb wave signals are mainly based on linear elasticity, i.e. signal characteristics are extracted within the frequency band at which they are generated. in this sense, the temporal characteristics, e.g. the tof (timer off) delay, exhibit to some extent a linear correlation as the material or structural parameters are altered due to damage. therefore, they are referred to as the temporal features of linear lamb waves in this study and the associated signal-processing steps are referred to as temporal feature processing. in particular, the tof delay, one of the simplest but informative linear temporal features, has proven to be effective in locating gross damage, i.e. damage with characteristic dimensions comparable to the wavelength of the sound wave such as open cracks, through holes and voids [5]. 2. experimental study 2.1. types of defects in pipelines regarding the different types of defects, the pipeline operators forum (pof) has classified the different existing defects into various categories [20]. it should be noted that since ultrasonic testing cannot detect cracks that occur perpendicular to a section of pipe, these types of defects are have been disregarded. the following four families of defects are predominant and generally detected during inspections: delamination; corrosion; geometric defects (sinking and ovalization); metal loss (arc cutting, scratching, grinding, spalling). in the vast majority of cases, these are natural defects, so their characteristics, that is, size, depth, shape, residual texture, etc., vary significantly. the most common forms of pipeline defects are shown in figures 1a-e. corrosion is the most frequent initial cause of damage in hydrocarbon pipelines [21] in which the condition of the pipeline deteriorates over time via a singular degradation mechanism. corrosion degradation can be evaluated in many ways (phenomenologically [22], by making random adjustments [23], using stochastic mechanisms [24], carrying out numerical simulations [25] or conducting empirical studies). based on these degradation mechanisms, the challenge is to predict how the condition of the pipeline will change between inspections to anticipate any possible internal damage. given the importance of the fluids transported, containment can result in human, environmental or economic losses. several factors that have an impact on the evolution of corrosion must be considered, e.g. the temperature in its current state, the initiation of degradation and the chemical composition of the steel. most publications dealing with ultrasonic scrapers have focused on concrete pipelines [26]. however, the nature of the defects sought in this application is also different as in this type of pipeline only large cracks are dangerous. finally, many publications have focused on the ultrasonic technology [27]. 2.2. principle modeling? leaks and ruptures in pipelines due to ageing and rapid deterioration cost millions of dollars per year, which underlines the necessity of continuous, automatic safety monitoring systems capable of rapidly detecting and warning of defects. before a major catastrophe occurs, this article examines how sensor networks can detect these problems. ultrasonic guided waves (lamb waves) can be employed to transmit energy along the length of the pipeline, making it possible for energy to be transferred wirelessly over a longer distance without being hindered by the electromagnetic shielding of the structure [28]. research has shown that it is possible to detect defects over a large area using active detection devices for simultaneous actuation and detection. sensors can be mounted on the surface of the curved pipeline to generate and measure guided waves propagating along the curve [29]. lamb waves follow the curvature of the structure and detect subsurface defects by measuring the structure on one side and allowing subsurface defects to be detected by measuring the inclination on that side. 2.3. ndt of cracked pipelines since the application of lamb waves in the real world is extremely complex, numerical simulations are one of the best ways to understand their behavior and implementing the abaqus model is invaluable. this simulation can yield the distribution of displacement and the displacement field, where (see figure 2): geometry: rin=0.09mm; rex=0.10mm; carbon/epoxy composite material. 3. results and discussion in this study, two models were used: the first without any figure 1: the studied types of pipeline defects study of composite pipelines 51(2) pp. 1–6 (2023) 3 cracks and the second with. one sensor was created to check the data along the circumference of the model (see figure 3). this figure also presents the form of the investigated crack. figure 4 shows that the crack size increases. in the first part of our experiments, we investigated how response signal changes with crack size propagation. 5 sizes of cracks are considered in each model: a1=0.10 mm, a2=0.08 mm, a3=0.06 mm, a4=0.04 mm and a5=0.02 mm. in order to highlight the response behavior, the crack angle  (orientation of the crack) was fixed and the crack size varied as described above as well as shown in figure 5. the response signals detected during ndt are presented in figure 6. it was noted that when =0°, crack initiation causes the amplitude of the signal response to decrease. the same is true when =30°, figure 6 shows that the amplitude decreases as a function of the increase in crack size. when =45°, significant decreases in amplitude following crack initiation can be observed. in the case of =60, the difference between the signals responses is negligible. logically, when =90°, the signals are identical, which is one of the limitations of the ultrasonic testing of perpendicular cracks. signal of u2 when =0° signal of u2 when =30° signal of u2 when =45° signal of u2 when =60° signal of u2 when =90° figure 6: response signals detected during ndt when measuring the crack orientation figure 2: composite pipeline figure 3: ndt of the pipeline figure 4: crack formation figure 5: crack size propagation lecheb, daoui, brihmat, mechakra, chellil, safi and kebir hungarian journal of industry and chemistry 4 in the second part of our study, with a fixed crack size, crack orientation was changed in each model as follows: =0°, =30°, =45°, =60° and =90° as shown in figure 7. the results obtained are given in figure 8 for each crack size studied. this field data shows the importance of global coordinates. some positive and negative u2 signals at the excitation source can be seen because the global coordinate was located in the y-z plane. it should be noted that the time that elapsed before the signal responses were received varies as a function of the angle of crack orientation. for the purpose of an experimental comparison, the measurements were made in both damaged as well as undamaged areas on flat structures and pipelines. a reference signal was first obtained in the undamaged areas before being received in the damaged ones [28][33] the two time signals were superimposed and when the two signals were compared, the signal from an area where a defect is present was amplified, resulting in a frequency shift between the two areas. the characteristics of the lamb wave time signal were compared using a sensor when different defects were detected in an aluminium tube. two damage indices were applied based on respective characteristics of lamb waves. 4. conclusions it can be concluded that this difference in amplitude is due to the absence of matter (a discontinuity) preventing a part of the waves from propagating through the pipeline walls, resulting in significant attenuation of the signal amplitude of the waves. this phenomenon is referred to as the scattering of lamb waves. when =0°, crack initiation causes the amplitude of the signal response to attenuate. when =30°, the amplitude decreases as the crack size increases. from the graph depicting =45°, a significant reduction in the amplitude is observed during crack initiation. however, when =60°, the difference between the signals responses is negligible. logically, when =90°, the signals are identical. this phenomenon, known as perpendicular cracking, is one of the limitations of ultrasonic testing. the signal responses when no cracks are present and when =0o are identical. the time elapsed before signal responses are received varies as a function of the angle of crack orientation. finally, the shapes of all these signal responses can be used to identify the depth, length, shape and orientation of cracks. figure 7: crack propagation signal of u2 when a=0.10 mm signal of u2 when a=0.08 mm signal of u2 when a=0.06 mm signal of u2 when a=0.04 mm signal of u2 when a=0.02 mm figure 8: response signals detected during ndt when measuring the size of the cracks study of composite pipelines 51(2) pp. 1–6 (2023) 5 references [1] barkanov, e.n.; dumitrescu, a.; parinov, i.a.: non-destructive testing and repair of pipelines (springer international publishing ag), 2018, doi: 10.1007/978-3-319-56579-8 [2] mingxi, d.: cumulative second-harmonic generation accompanying nonlinear shear horizontal mode propagation in a solid plate, j. appl. phys., 1998, 84(7), 3500–3505, doi: 10.1063/1.368525 [3] praetzel, r.; clarke, t.; schmidt, d.; de oliveira, h.; dias da silva, w. c.: monitoring the evolution of localized corrosion damage under composite repairs in pipes with guided waves, ndt e int., 2021, 122, 102477, doi: 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vehicle system analysis, budapest university of technology and economics, műegyetem rkp. 3, budapest, 1111, hungary today, additive manufacturing technologies are becoming increasingly popular. in order to take advantage of the opportunities offered by these new technologies, a different way of thinking at the design stage needs to be adopted. this new design thinking must be introduced into engineering education. in order to achieve this at the right level, practical experience is needed in parallel with a theoretical background on the technologies. this paper provides a brief overview of my research and results in the field of additive manufacturing. keywords: additive manufacturing, 3d printing, generative design, fused deposition modeling, material properties 1. introduction the spread of additive manufacturing technologies continues unabated. more and more applications are becoming commonplace. however, in certain areas, they must be applied cautiously. in many areas, questions are raised about which materials and technology to use from health, mechanical and strength points of view. similarly, whether it is economically worthwhile to use this manufacturing process if other methods can be implemented to produce the part is a matter of debate. since the process is becoming more and more prevalent in industry, its inclusion in higher technical education is necessary. however, practical experience is also needed to ensure an adequate level of education. another benefit of introducing additive manufacturing technologies into education is that it is a novel, interesting and exciting field that attracts the interest of students, which in turn boosts research in this area. my research on additive manufacturing technologies began at the department of railway vehicles and vehicle system analysis formerly known as the department of vehicle elements and vehicle system analysis (drvvsa) at the budapest university of technology and economics (bute) in 2007 through my phd research. at that time, my research was supported by varinex zrt. who produced test specimens for the investigations. in 2015, the department also acquired two fused deposition modeling (fdm) 3d printers, increasing the number of opportunities and expanding the spectrum of *correspondence: ficzere.peter@kjk.bme.hu my research. by this time, my investigations mainly focused on handmade pieces. a significant proportion of the required measurements was carried out at the department of polymer engineering and in the research laboratories at the biomechanical cooperative research centre both at the bute. the results of my research are presented in this paper. 2. method a significant amount of experimentation is necessary to properly understand production technologies. during these experiments, questions often arise as to whether this or that can be achieved with this or that technology. therefore, the fields of application were extended and the printers made available to students, which led to even more interesting and often questionable outcomes. as the printers purchased (prusa i3 and zortrax m200) are open-source, the production parameters could be set as desired and the effects of each setting tested. another important and continuously explored as well as developed area is the investigation into the applicability of the technology. 3. results 3.1 accuracy tests specimens of different shapes and geometries were produced to determine the accuracy of the machine and the surface quality of the printed parts. unfortunately, the studies did not provide precise and clear figures [1] since their accuracy is affected by https://doi.org/10.33927/hjic-2021-23 mailto:ficzere.peter@kjk.bme.hu 60 ficzere • the geometry of the part to be printed (flat or curved surfaces, curvature rate, position of the planes (horizontal, vertical or inclined)); • tolerances of conversion from the original cad geometry to the stl file (input for the printer) • the layer thickness • the printing speed • the printing temperature • heating the table • the orientation • different levels of accuracy in the x-y (layer) plane and perpendicular (z-direction) to it of course, these variables refer to printing using the same machine and different values may be obtained should another machine of an alternative type be applied. it is important to note that some errors due to the manufacturing principle can be eliminated by preliminary modifications of the cad model (toolpath correction), but some more advanced cam software (code generators) are already capable of doing this. the size correction needed to connect parts in operating assemblies was also investigated. 3.2 fields of application due to a lack of space, only some of the completed projects are presented here, but many other smaller objects were printed, e.g., parts for robotic cars for the bosch future mobility challenge, miniature copies of traffic signs for sign-recognition simulations (for the department of automotive technologies at the bute), various sprockets, battery holders, unique pieces of “jewellery”, ornaments, parts, representation and marketing materials, utility items, educational aids, etc. supply of spare parts in many cases, given that it is not possible to obtain spare parts for a component that has failed in an older device, a copy of the component in question must be manufactured, otherwise the device becomes inoperable and therefore worthless. although this technology is particularly important for veteran vehicles, in this case special attention must be paid to the stresses and strains on the components produced by the new method, moreover, should the part produced be non-compliant, it could even damage other irreplaceable parts [2]. several individual parts that seemed to be irreplaceable have also been redesigned and manufactured (fig. 1). nowadays, it is also important to note that more and more people are considering this solution to the lack of spare parts, purely for economic reasons. in the case of a major automotive unit or structure, the supply of spare figure 1: replacement of individual parts [2] parts has to be ensured even decades after its production has stopped. it is of course impossible to determine in advance exactly how many parts will need to be replaced. for this reason, manufacturers often accumulate unreasonably large stocks of specific parts, which are extremely costly to store or the machines and tools that produce them are costly to maintain. prototype development several prototypes have been developed at our department. one of the most interesting of which was the development of a medicine capsule. as is well known, the action of so-called retard capsules (composed of soft gelatine that is dissolved by acidic conditions found in the human stomach) is delayed. this delay and the extent of its effect also depend on the individual, making it difficult for the optimal dose of the active ingredient to be hungarian journal of industry and chemistry research on and practice of additive manufacturing technologies 61 figure 2: prototype development (capsule) [3] figure 3: the manufacture of assistive devices [3] determined correctly. the basic idea was to produce capsules of the same size as the original capsules, with various numbers of holes of different dimensions and shapes. the effect of such modifications on the rate and extent of release was then investigated. for the purposes of the studies, the individually designed capsules were printed and filled with a given quantity of caffeine pellets (figs. 2 and 3) [3, 4]. it can easily be seen that designing a modified mould for a part produced in large quantities by injection moulding before stopping production and changing the mould for a few parts needed for testing is not a cost-effective solution, which can lead to a serious loss of revenue [5]. in the same case, in order to fill the miniscule and lightweight caffeine pellets (it was particularly difficult to fill the capsules with the amount measured out into small sachets to the nearest microgram), a small funnel was designed and printed within a few minutes. making tools and moulds in many cases, high demands for the material the parts are composed of may be infeasible by applying some additive manufacturing technologies. in a case study when individual castings have to be produced, a casting mould for the remanufacture of a cylinder from the engine of a veteran vehicle can be seen in the middle photo of fig. 4. on the left-hand side of the figure, a 3d cad model is shown, which was used to print the mould from acrylonitrile butadiene styrene (abs) using an fdm printer to produce (and later functionally assemble) the casting (right-hand side of fig. 4) [6]. figure 4: cad model, 3d-printed casting mould and casted cylinder [6] figure 5: cad model of a human metacarpal remodeled from ct scans and the printed pieces [8] the manufacture of medical implants and devices one of the areas where additive manufacturing is expected to make the greatest amount of progress is the rapid and customizable production of medical implants and devices. since the geometry of a given implant has to perfectly match the intact body parts of the person, very stringent requirements must be met with regard to the formal design (shape) of the model [7, 8]. however, these pieces also need to match the stiffness of a person’s individual bone in terms of mechanical strength. the department has carried out several research projects along these lines. in the case of the human metacarpal shown in fig. 5 and 6, the geometry had to be modelled from ct scans. the stiffness of the real bone was measured, then the geometry of the 3d cad assigned to the model with the 3d-printed material properties and the internal geometry changed by shape optimization until the stiffness of the printed piece perfectly matched the stiffness of the original bone. optical photostress investigations since it is also possible to print from transparent (translucent) materials, the coating required for optical photostress investigations (which is difficult and timeconsuming for complex geometries) can be easily printed given the right thickness and quality, thereby saving much time and reducing the amount of effort required (fig. 7) [9, 10]. an additional advantage of this method is that it allows us to detect and determine the residual stresses that develop during production (fig. 8) [11]. 49 pp. 59–64 (2021) 62 ficzere figure 6: validation of the material model used by the numerical simulation of a human metacarpal with measurements on a real printed part [7] figure 7: fringe pattern on a 3d printed test specimen as a result of bending [9] 3.3 economic analysis when printing individual parts, how manufacturing costs are affected by the production of the workpiece quickly becomes apparent. • chosen procedure • production time, the 3d printing speed • placement on the workspace • position, orientation • the quantitative requirement for support materials • type of support materials • percentage of filling • type of filling • layer thickness • choice of materials • number of units to be produced several economic calculations have been made to identify areas where the technology offers real advantages over other manufacturing processes [12]. how the aforementioned parameters affect production costs either directly or indirectly has also been investigated [5, 13]. figure 8: residual stresses in specimens subjected to tensile testing [11] figure 9: test specimens produced in different directions and positions [14] 3.4 material investigations additive manufacturing technologies are characterized by the fact that they compose arbitrarily complex parts, even with hollow geometries inside, layer by layer [14]. this implies that the bonding of layers to each other is assumed to be different from the bond strength within the layers [15], which has been proven in several cases. in several manufacturing processes of different materials, how the material properties (of lying and standing specimens) in different directions relate to each other has been investigated (fig. 9). the tensile curves in the highlighted directions were measured: • fullcure 720 produced by the polyjet process [1] • fdm process and polylactic acid (pla) [16] • fdm process and acrylonitrile butadiene styrene (abs) [17] • selective laser sintering (sls) process and polyamide 12 (pa12) [18] • fdm process and soft pla (flexible plastic) [19] • fdm process and high temperature (ht) pla (thermosetting plastic) [20] apart from the sls process, the results show that the behavior of additively manufactured parts can be described by the model of an orthotropic material under all circumstances. therefore, the determination of the corresponding material properties is a more complex task [21], where it is insufficient to only use young’s modulus e and poisson’s ratio ν to describe the behavior of a material. in addition, the shear modulus of elasticity g must be measured [22]. hungarian journal of industry and chemistry research on and practice of additive manufacturing technologies 63 figure 10: validation of a material model by the optical photostress method [25] figure 11: identifying the causes of errors [25] of course, after determining the material models and material properties using a tensile testing machine, the results need to be validated. for this purpose, a method has been developed [23]. the effects of certain manufacturing parameters on strength have also been determined [24] and the reasons for these explored (figs. 10 and 11) [25]. dynamic materials testing as certain components are also subject to dynamic loads, it is necessary to examine the parts manufactured by these processes for dynamic stresses. this test method has also been developed and performed on parts composed of pla manufactured by fdm (fig. 12) [26]. modification options affecting material properties several options have been investigated that influence the mechanical strength parameters, including active cooling [27], the effect of heat treatment (publication in progress) and ironing (publication in progress). 3.5 examination of the impact of infill the possibilities of producing parts subjected to quasiuniform stresses in a way that reduces the cumbersome and lengthy post-processing operations were also investigated. such a method is the modification of the internal filling according to the stresses [28]. figure 12: difficult and easy to manufacture uniform strength supports [28] figure 13: drone to be manufactured by 3d printing using generative design 3.6 generative design in terms of additive manufacturing technologies artificial intelligence-based design methods that can be used to design geometries according to different criteria, which by and large can only be produced by additive manufacturing, are currently being investigated (fig. 13). acknowledgments the author would like to express their gratitude to györgy falk (varinex zrt.) who greatly helped with the research in terms of both printing and giving professional advice. the author is grateful to dr. lászló lovas who, as the head of the department, recognized the research potential of 3d printing and purchased the printers for the department as well as the necessary materials. last but not least, the author would like to thank dr. gábor szebényi who provided the material investigations. references [1] ficzere, p.; borbás, l.; török, á.: theoretical and practical investigation of rapid prototyping, in: borkowski, s.; selejdak, j.; jelacič, d.; hadzima, b. 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https://doi.org/10.47273/ap.2021.22.18-32 https://doi.org/10.7708/ijtte.2021.11(1).05 https://doi.org/10.7708/ijtte.2021.11(1).05 https://doi.org/10.3311/pptr.9144 https://doi.org/10.17489/2018/2/10 https://doi.org/10.30657/pea.2020.26.24 https://doi.org/10.30657/pea.2020.26.24 https://doi.org/10.1016/j.matpr.2018.08.104 http://epa.niif.hu/03300/03334/00044/pdf/epa03334_gep_2018_4_049-053.pdf https://doi.org/10.33894/mtk-2020.13.21 https://doi.org/10.21278/tof.42103 https://doi.org/10.21278/tof.42103 https://doi.org/10.21496/ams.2014.002 https://doi.org/10.1088/1757-899x/903/1/012008 https://doi.org/10.3390/polym13040556 https://doi.org/10.3390/polym13040556 https://doi.org/10.3311/pptr.13947 http://www.mdesign.ftn.uns.ac.rs/download.php?fid=1223 https://www.uni-miskolc.hu/dms/docs/dms_vol10_nr2_2020/04_ficzere.pdf introduction method results accuracy tests fields of application supply of spare parts prototype development making tools and moulds the manufacture of medical implants and devices optical photostress investigations economic analysis material investigations dynamic materials testing modification options affecting material properties examination of the impact of infill generative design in terms of additive manufacturing technologies hungarian journal of industry and chemistry vol. 50(2) pp. 23–26 (2022) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2022-14 separation of dissolved gases from aqueous anaerobic effluents using gas-liquid membrane contactors merve visnyei1*, péter bakonyi1, nándor nemestóthy1 and katalin bélafi-bakó1 1 research group on bioengineering, membrane technology and energetics; university of pannonia; egyetem u. 10; veszprém; h-8200; hungary this study aimed to evaluate a gas-liquid membrane contactor for recovering the dissolved gases of methane (ch4) and carbon dioxide (co2) from model aqueous anaerobic effluents. for this purpose, synthetic effluents were prepared by using the gas mixtures of se-1: 100/0, se-2: 0/100 and se-3: 50/50 ch4/co2 vol.% as well as di water. the units in which the synthetic effluent was prepared were coupled with a dense hollow fiber membrane module by employing argon gas at atmospheric pressure. the desorption of the gases ch4 and co2 dissolved in the effluents was investigated with a countercurrent flow of the liquid on the lumen side. the effect of the sweep gas flow rate on the removal rate was also investigated. the results showed that the recovery rate of ch4 was slightly affected by increasing the sweep gas flow rate, while the recovery rate of co2 was enhanced considerably. by applying a sweep gas flow rate of 20 ml/min, the recovery rate of both gases from se-3 exceeded 50%. keywords: gas separation; membrane contactor; biogas recovery; anaerobic effluent 1. introduction anaerobic wastewater treatment is a widely used technology to convert organic waste into well-stabilized sludge. compared to aerobic systems, the major advantages of anaerobic-based ones are that the process produces higher-quality effluent and has the potential to be a net energy producer by utilizing energy from the biogas produced. raw biogas mainly consists of ch4 and co2, moreover, may contain small quantities of hydrogen sulphide, moisture and siloxanes [1]. the composition of biogas can vary depending on the operating conditions and concentrations of organic compounds in the treated water. typically, although the methane content in biogas is within the range of 50-70%, it can be as high as 90% depending on its interaction with the aqueous phase of the carbon dioxide [2]-[3]. furthermore, important benefits of anaerobic treatment include the requirement of less nutrients as well as lower energy consumption and higher organic loads than most conventional biological treatments. membranes are crucial for the separation of biomass and effluent as they enable higher concentrations of organic compounds to be used in reactors, generation less sludge as well as increase the rate of biogas production [4]. therefore, an anaerobic membrane bioreactor system has emerged as a potential alternative technology for wastewater treatment by coupling anaerobic bioreactors with membrane separation, facilitating easy scaling up and selective received: 19 oct 2022; revised: 24 oct 2022; accepted: 26 oct 2022 *correspondence: merve.visnyei@phd.uni-pannon.hu separation with low energy consumption [5]. biogas as a renewable fuel consisting of 50-70% ch4 and 30-50% co2 can be produced with this method [6]. since the treatment process occurs in a completely closed environment, it is crucial that the dissolved gases in the produced effluent are in equilibrium with the biogas in the headspace, resulting in a significant quantity of dissolved ch4 and dissolved co2 being lost in the effluent solution [7]-[8]. both dissolved gases are desorbed into the environment and contribute towards greenhouse gas emissions. several researchers have reported that a considerable amount of the methane generated is dissolved and wasted in the liquid phase [1][2], [9]-[12]. methane loss as a function of the temperature of bodies of municipal wastewater containing an average soluble cod of 200 mg/l is presented in fig.1. since the figure 1. dissolved methane in the wastewater as a function of temperature 40 45 50 55 60 65 70 75 80 85 90 0 5 10 15 20 25 30 35 d is s o lv e d m e th a n e i n w a s te w a te r, % temperature, c https://doi.org/10.33927/hjic-2022-14 mailto:merve.visnyei@phd.uni-pannon.hu visnyei, bakonyi, nemestóthy and bélafi-bakó hungarian journal of industry and chemistry 24 solubility of methane increases as the temperature decreases, the amount of dissolved methane is higher, even as high as 88% at 0°c, at lower temperatures. methane is a greenhouse gas, its global warming potential is estimated to be 28–36 times higher than that of co2 over 100 years [13], moreover, is flammable with a lower explosive limit of 5 vol.% [2]. consequently, the importance of recovering and utilizing methane entrapped in effluent during biogas production is significant in order for anaerobic treatment systems to be sustainable. the membrane degassing technology using gasliquid membrane contactors (glmcs) has emerged as a potential approach for recovering entrapped methane in fermentation liquor [7]. preferably, glmcs are assembled into hollow fiber membrane modules since they yield a higher gas desorption rate by providing high volumetric mass transfer coefficients [14]. the goal of this research was to determine the recovery rates of ch4 and co2 gas dissolved in synthetic effluents by applying a non-porous hollow fiber membrane. the effect of gas and liquid flow rates on the removal rate was also investigated. 2. experimental pure ch4 (98%)/co2 (99%) and deionized water were used to prepare the synthetic effluents (ses) in glass bottles with a volume of 5 l. a peristaltic pump was used to displace the air from the bottle to create an anaerobic environment, which was confirmed with a dissolved oxygen analyzer. saturation was achieved by bubbling ch4 (se-1), co2 (se-2) or a mixture of ch4 and co2 (50-50%: se-3) into the deionized water for 3 hours. the composition of the headspace was monitored by a hewlett packard hp 5890 series ii gas chromatograph equipped with a thermal conductivity detector (tcd). a capillary carboplot® column was employed (agilent technologies, length: 60 m, id: 0.32 mm, film thickness: 1.5 mm) with ar (99.9 %) as a carrier gas at a flow rate of 15 ml/min. the applied split ratio was 100:1. the temperatures of the injector, column oven and detector were 130, 90 and 115°c, respectively. at the saturation point, the concentration of ch4/co2 in the headspace was in a steady state. once stability had been ensured, deoxygenated and ch4/co2-saturated water was pumped against the membrane by a peristaltic pump. the units in which the synthetic effluent was prepared were coupled with a permselect® silicone, non-porous hollow-fiber membrane module with a surface area of 1.0 m2. the membrane was operated with a countercurrent flow of the liquid on the lumen side to examine the desorption of ch4 and co2 gases dissolved in the effluents. argon (99.9%) was used as a sweep gas in the experiments. the concentration of the outlet gas at the membrane module was measured by the gas chromatograph at regular intervals. henry’s law and the liquid flow rates were used to calculate the mass flow rate of gases entering the membrane module, while based on the ideal gas law, results obtained from gc and gas flow rates were used to calculate the mass flow rate of gases exiting from the membrane module. based on the results obtained, the recovery rates of ch4/co2 were calculated. 3. results and discussion based on the preliminary experiments, in this research, the liquid flow rate used was 15 ml/min, adjusted by a peristaltic pump and monitored with a balance. the sweep gas flow rate varied from 5-60 ml/min and was adjusted by a control valve as well as measured with a soap film flowmeter. recovery rates of ch4/co2 from se-1/se-2 as a function of the sweep gas flow rate at a liquid flow rate of 15 ml/min are shown in tables 1 and 2 as well as summarized in fig.2. table 1. recovery rates of ch4 from se-1 as a function of the sweep gas flow rate liquid flow rate (ml/min) sweep gas flow rate (ml/min) recovery rate of ch4 (%) 15 15 15 15 5 10 20 60 57.1 58.0 58.6 35.9 table 2. recovery rates of co2 from se-2 as a function of the sweep gas flow rate liquid flow rate (ml/min) sweep gas flow rate (ml/min) recovery rate of co2 (%) 15 15 15 15 5 10 20 60 9.2 29.0 47.0 61.6 figure 2. recovery rates of ch4/co2 from se-1 and se-2 as a function of the sweep gas flow rate 0 10 20 30 40 50 60 70 0 10 20 30 40 50 60 70 r e c o v e ry o f g a s e s (% ) sweep gas flow rate (ml/min) ch4 (lf:15) co2 (lf:15) separation of dissolved gases 50(2) pp. 23-26 (2022) 25 the results showed that the recovery rate of ch4 at a sweep gas flow rate of 5-20 ml/min was almost constant (57.1-58.6%) and rapidly decreased to 35.9% by increasing the gas flow rate to 60 ml/min. similar effects of the gas flow rate on the recovery ratios of the gases have been reported by cookney et al. [15], where increasing the gas flow rate had little effect on the mass transfer coefficient of ch4 due to mass transfer controlled by the resistance in the liquid phase. rongwong et al. [7], [16] also reported that the ch4 concentration is diluted in the outlet gas in the case of high gas flow rates, which was also observed in this study. although the recovery rate of co2 was increased by increasing the sweep gas flow rate, these values were much lower than those of ch4 except for at a gas flow rate of 60 ml/min. se-3 was prepared by purging a mixture of ch4 and co2 gases (50:50) into deionized water for 3 hours to investigate the impact of this mixture on the recovery rate of the membrane module. the results were compared with those obtained from synthetic effluents prepared with pure gases. the recovery rates of co2 and ch4 as a function of the sweep gas flow rate are given in table 3 and fig.3. the results from se-3 showed a similar tendency to those obtained in the case of individual gases. the recovery rate of co2 was increased from 36.2 to 62.9% by increasing the sweep gas flow rate, while these values for ch4 at a gas flow rate of 10-20 ml/min were 53.161.3% but dropped drastically to 11.9% by applying a gas flow rate of 60 ml/min. at the latter gas flow rate, the recovery rate of the membrane module with regard to ch4 from se-1 was 35.9%, therefore, the presence of co2 in the synthetic effluent may have a negative effect on the recovery of ch4. nevertheless, by applying a sweep gas flow rate of 20 ml/min, the recovery rate of both gases from se-3 exceeded 50%. 4. conclusions the anaerobic digestion of wastewater is a commonly used technology to produce biogas by converting organic waste into well-stabilized sludge. since the process takes place in a completely closed environment, it is crucial that the dissolved gases in the produced effluent are in equilibrium with the biogas in the headspace, leading to a significant quantity of dissolved ch4 and dissolved co2 being lost in the effluent solution. as a result, the recovery of dissolved ch4 is critical to increase anaerobic energy production while minimizing the environmental impact of greenhouse gases. in this study, synthetic effluents were prepared by purging ch4/co2 into deionized water. a membrane contactor was employed as a mass transfer device for measuring the recovery rates of ch4 and co2 gases dissolved in synthetic effluents by applying a non-porous hollow fiber membrane. the effect of the sweep gas flow rate on the removal rate was also investigated. the results showed that the recovery rate of ch4 was slightly affected by increasing the sweep gas flow rate, while the recovery rate of co2 was enhanced considerably. acknowledgements this research was supported by the otka k 138232 research grant entitled “stabilization of anaerobic effluents in a novel, integrated bioprocess towards controlled demethanization and energy recovery.” references [1] visnyei, m.; bakonyi, p.; bélafi-bakó, k.; nemestóthy, n.: integration of gas–liquid membrane contactors into anaerobic digestion as a promising route to reduce uncontrolled greenhouse gas (ch4/co2) emissions, 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csengele éva barta4 1 hungarian department of biology and ecology, faculty of biology and geology, babeș -bolyai university, 5-7 clinicilor st., cluj-napoca, 400006, romania 2 institute for research, development and innovation in applied natural sciences, babeș-bolyai university, 30 fântânele st., cluj-napoca, 400294, romania 3 centre for systems biology, biodiversity and bioresources (3b), babeș -bolyai university, 5-7 clinicilor st., cluj-napoca, 400006, romania 4 department of biology, missouri western state university, 4525 downs drive, agensteinremington halls, st. joseph, mo 64507, usa the continuous rise in soil salinity and the expansion of saline areas present a worldwide threat to agriculture by reducing the amount of arable land available for crop cultivation. halophytes, naturally inhabitants of saline environments, are the sole group of plants able to populate and thrive in saline soils. with highly efficient adaptive strategies, these plants tolerate extreme saline conditions indefinitely. some of these species are metal hyperaccumulators, particularly those growing under saline conditions frequently rich in heavy metals that are often polluted. one mechanism enabling them to tolerate these extreme conditions is the accumulation of osmoprotectant metabolites. even though these protective compounds are generally produced by plants to help them tolerate extreme environmental conditions, usually halophytes accumulate more osmolytes than glycophytes. although many publications discuss the potential of halophytes in the remediation of areas polluted by heavy metals, relatively little is documented about the role of compatible solutes in alleviating the toxic effects of heavy metals. this review focuses on the role of the most common osmoprotectant, that is, proline, produced by halophytes to mediate cellular damage caused by the hyperaccumulation of metal ions and addresses the biosynthetic pathways of this compound. reclaiming land polluted by heavy metals by populating it with halophytes and enhancing osmoprotective solute production through genetic engineering in halophytes presents viable solutions to restore pollution-ridden areas for potential agricultural use worldwide. keywords: halophytes, proline, heavy metals, toxicity, mitigation 1. introduction natural terrestrial habitats where enhanced levels of soil salinity and heavy metals (hms) greatly diminish crop yield and quality are considerably widespread throughout the world, restricting the productive use of arable land [1]-[3]. owing to the progressively decreasing amount of precipitation, irrigation with saline water and inadequate agricultural practices, the amount of land contaminated by saline soils is continuously increasing. it has been estimated that about 20% of arable land (45 million ha) has already been negatively affected by salinity. by 2050, 50% of agricultural land will become saline and inappropriate for common crop cultivation [1]. on the other hand, human industrial activities and mining have also had detrimental effects on fertile soils in the environment, leading to hm pollution and retention in soils [2],[4]. these activities have contaminated soils with potentially toxic elements and hms, including received: 24 june 2024; revised: 5 july 2024; accepted: 5 july 2024 *correspondence: gyongyi.szekely@ubbcluj.ro arsenic (as), silver (ag), cadmium (cd), cobalt (co), chromium (cr), copper (cu), iron (fe), mercury (hg), manganese (mn), molybdenum (mo), nickel (ni), lead (pb) and zinc (zn) [5]-[6]. salinity generates osmotic stress and a water deficit in the soil, reducing its water potential and altering the water balance in plants. plants have evolved a diverse range of morphological, physiological and biochemical adaptive mechanisms allowing salinity tolerance [7]-[11]. high na+ and clconcentrations in chloroplasts decrease photosynthetic activity, affecting carbon metabolism and photophosphorylation, while photosynthetic electron transport is less sensitive to saline conditions [12]. high levels of salinity also alter the composition of plasma membrane protein and lipids as well as cause an ionic imbalance across membranes, ultimately leading to hyperosmotic stress [13]. salt stress triggers osmotic stress and ion toxicity. na+ is toxic when its concentration exceeds 10 mm in the cytosol, but 100-200 mm of k+ is needed in the cytosol for https://doi.org/10.33927/hjic-2024-20 mailto:gyongyi.szekely@ubbcluj.ro székely and barta hungarian journal of industry and chemistry 64 physiological functions. many enzymes are sensitive to na+/k+ ratios and excessively high cytosolic na+ concentrations could impair their activities. to achieve optimal metabolic conditions, the cytosol should have a low na+ concentration and low na+/k+ ratio [14]. halophytes, accounting for only approximately 1% of terrestrial plants, can survive and thrive in naturally saline soils containing at least 200 mm of nacl [15]-[16]. saline soils are frequently polluted with hms, increasing the likelihood of salt and hm stress. to alleviate the damaging effects of factors causing environmental stress (drought, salinity, extreme temperatures, heavy metals) and as a hm detoxification mechanism, halophytes accumulate osmoprotective solutes [17]-[19]. osmoprotectants, or compatible solutes, are small, highly soluble molecules with low molecular weights and a neutral charge that do not exhibit toxic effects at molar concentrations [20]. osmolytes mitigate cellular injury by stabilizing proteins and membranes as well as maintaining the cellular osmotic potential during periods of stress. while not all plant species respond to stress by producing osmolytes, a range of stress-tolerant species upregulate the biosynthesis of these highly effective protective molecules [18]-[19]. furthermore, osmoprotectants are also key molecules for maintaining turgor pressure and protecting cells from oxidative damage by scavenging detrimental reactive oxygen species (ros). aside from the direct quenching activities of ros, they may also exert their antioxidant defense potential indirectly, triggering the enhanced synthesis of antioxidants and the upregulation of antioxidant enzymatic activities [7, 9, 21]. osmoprotectants are in the form of amino acids (proline, alanine, arginine), ammonium compounds (glycine betaine and polyamines) and soluble carbohydrates (sugars and polyols) as compatible solutes to modulate cellular osmotic potential. here the essential role of proline (pro) in alleviating damage as a result of heavy metals in halophytes is described. 2. proline biosynthesis in plants the synthesis of compatible solutes such as pro is one of the strategies that plants use to cope with hm stress [22]-[23]. pro is synthesized both under adverse and nonstressed physiological conditions. although pro biosynthesis occurs via two pathways, namely the glutamate and ornithine pathways, the glutamate pathway accounts for stress-induced pro accumulation [24]. glutamate-derived pro is synthesized in the cytoplasm in a reaction catalyzed by 1-pyrroline-5carboxylate synthetase (p5cs), which generates pyrroline-5-carboxylate (p5c) from glutamate in a twostep reaction. the intermediate product is glutamate-γsemialdehyde (gsa), synthesized in an atp and nadph-dependent reaction. next, p5c is further reduced to pro. pro is reduced in a nadph-dependent reaction catalyzed by p5c reductase (p5cr) [25]. although the activity of the enzyme p5cs represents the rate-limiting step of pro biosynthesis, it should be mentioned that p5cs consists of two isoforms, p5cs1 and p5cs2. székely et al. demonstrated [7] that the two isoforms appear with non-redundant functions, with chloroplast-localized p5cs1 having an impact on stressinduced pro synthesis, while the activity of cytosolic p5cs2 may cause embryo abortion during the later stages of seed development in arabidopsis. on the other hand, ornithine-derived pro is synthesized in the mitochondria in a reaction catalyzed by ornithine-δ aminotransferase (oat), which converts ornithine into glutamate-semialdehyde (gsa) and p5c, that is finally transformed into pro. the catabolic pathway is mitochondrial; pro is oxidized into glutamate over two steps. in the first rate-limiting step, pro catabolism is catalyzed by flavin-dependent proline dehydrogenase (prodh), which reduces pro to p5c. next, p5c is oxidized to glutamate by nad+-dependent p5c dehydrogenase (p5cdh) [24]. in plants, two isoforms of prodh have been detected with different localizations. similarly to isoforms of p5cs, prodh1 and prodh2 appear with non-redundant functions; prodh1 is expressed at the whole plant level, while prodh2 shows a vasculature-specific expression [26]. the reciprocal regulation of p5cs and prodh genes is critical in order to control pro levels during and after periods of stress [27]. intracellular pro levels are determined by its biosynthesis, catabolism and transport between organelles and cells. proline biosynthetic enzymes (p5cs1, p5cs2 and p5cr) are thought to be localized in the cytosol, whereas the enzymes of pro catabolism (e.g. prodh1, prodh2, p5cdh and oat) are considered to be located in mitochondria [17]. 3. multifaceted roles of proline with regard to the adaptation of halophytes to environmental stresses halophytes accumulate pro in response to salinity stress, and their capacity to accumulate pro reflects their salinity tolerance [28]. free pro accumulation can be as high as 10-20% of the shoot dry weight in various species of halophytes with pro representing the most abundant component of the amino acid pool in salt-tolerant plants [17],[28]. a later work demonstrated that aside from salinity other environmental stress factors (e.g. water deficit, extreme temperatures or heavy metal contamination) may also activate pro synthesis. pro accumulation proved to be one of the most important defense responses of plant cells encountering the aforementioned stress factors [17],[29]. many halophytes such as sesuvium portulacastrum, thellungiella salsuginea, mesembryanthemum crystallinum and lepidium crassifolium accumulate a significant amount of pro to benefit from its protective effects [30]-[32]. the major effects of proline in mitigating the negative impacts of adverse environmental stress factors in plant cells are illustrated in figure 1. halophytes and proline 52(2) pp. 63–67 (2024) 65 a clear correlation between hm accumulation and an increase in pro level has been documented in many species of halophytes [22, 33–34]. while few hmtolerant species such as armeria maritima, deschampsia cespitosa and silene vulgaris contain high pro concentrations under environmental stress conditions unaffected by metal ions, increased levels of pro accumulation have generally been associated with hm tolerance [33]. as an osmolyte, pro alleviates damage induced by hms, can stabilize cell membranes by interacting with phospholipids, protects protein structures [35] and acts as a chelator to bind metals [33]. pro also plays a role in stress protection as an antioxidant, neutralizing ros by quenching singlet oxygen, superoxide, hydrogen peroxide and hydroxyl radicals [7, 9, 32, 36]. pro also enhances the photochemical activities of photosystem ii [37] and maintains a low nadph to nadp+ ratio in photosystem i, lowering the likelihood of singlet oxygen formation. furthermore, pro alleviates the harmful effects of singlet oxygen and hydroxyl radicals on photosystem ii, delays plant senescence [38] and suppresses apoptosis under stress conditions [17],[32]. furthermore, pro stabilizes mitochondrial respiration, protecting complex ii of the mitochondrial electron transport chain. similarly, increased pro levels under cadmium (cd) stress mitigate the adverse effects of stress-induced ros in the halophyte atriplex halimus [39]. nevertheless, it is documented that pro protects key enzymes such as glucose-6-phosphate dehydrogenase and nitrate reductase against the toxic effects of zn and, to a lesser extent, cd through the reduction of free metal ions due to the formation of metal-proline complexes. this data suggests that osmoregulation and enzymatic protection rather than metal sequestration may represent the primary roles of metal-induced pro accumulation [40]. to further underscore the importance of proline, some species of halophytes that accumulate pro as a defense strategy to withstand different types of hm pollution are presented in table 1. the amino acid proline is essential for halophytes to endure hms. according to the studies mentioned in table 1, the accumulation of pro is a common response in halophytes like aeluropus littoralis, mesembryanthemum crystallinum and atriplex halimus when exposed to hms such as cd, co, pb and ag. these results highlight the widespread efficiency of pro in different plant species and hm-polluted environments. moreover, the accumulation of other amino acids such as leucine, isoleucine and valine enhance hm tolerance. suaeda salsa, for example, accumulates several amino acids when exposed to cd and zn, suggesting a well-defined and diverse strategy for osmoprotection. the variety of amino acids involved demonstrates how complex the interaction between metabolic adaptations is to alleviate hm stress. other species of halophytes such as walsura monophylla respond by increasing their level of glutamine when exposed to enhanced levels of ni [1], while deschampsia cespitosa accumulates asparagine when experiencing zn toxicity [46]. similarly, the presence of cd triggers an increase in the levels of amino acids like arginine, leucine, isoleucine, glutamate, glutamine, phenylalanine, valine, tryptophan and tyrosine in suaeda salsa. however, it is unclear whether such accumulation can be directly attributed to metal tolerance or is a consequence of protein degradation [47]. 4. concluding remarks the ability of halophytes to remediate hm stress-induced damage reflects a complex interplay between physiological and biochemical processes. generally, pro accumulation is associated with enhanced tolerance to stress. however, because of the extremely versatile strategies to tolerate stress, the exact mechanisms by which enhanced levels of pro accumulation help plants cope with hm stress still remain unknown. further research into the roles of pro in mitigating hm toxicity may be useful in different areas: elucidating gene expression patterns and signaling pathways could help to determine molecular stress responses; studying the synergistic effect of pro with other stress-protective molecules could identify interactions more effectively with regard to stress tolerance compared to pro alone; developing transgenic plants with a high level of pro figure 1: roles of proline in plant adaptation to environmental stress conditions table 1: selected reports describing the accumulation of proline in halophytes in response to heavy 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https://doi.org/10.1016/s1360-1385(00)01692-7 https://doi.org/10.3389/fpls.2015.00552 https://doi.org/10.1016/j.envexpbot.2008.07.005 https://doi.org/10.1016/s0031-9422(98)00282-9 https://doi.org/10.1023/a:1025652510658 https://doi.org/10.1046/j.1469-8137.1997.00639.x https://doi.org/10.1046/j.1469-8137.1997.00639.x https://doi.org/10.1039/c4mb00567h https://doi.org/10.1111/j.1469-8137.1987.tb00905.x https://doi.org/10.1111/j.1469-8137.1987.tb00905.x https://doi.org/10.1007/s10646-011-0699-9 hungarian journal of industry and chemistry vol. 49 pp. 71–75 (2021) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2021-25 analysis of formed chips in the case of turning different polymer materials ádám sarankó*1, gábor kalácska1, and róbert zsolt keresztes1 1institute of technology, hungarian university of agriculture and life sciences, páter károly u. 1, gödöllő, 2100, hungary in this paper, turning input parameters were defined for 12 different polymer materials that can be used in technical practices. our goal was to determine turning input parameters where chip formation is favourable or continuous chips do not cause any problems. our tests included the examination of detached chips and the values of the average surface roughness of the machined surfaces. keywords: chip formation, polymer materials, turning 1. introduction nowadays, in addition to the 3d printing of polymers, the machining of polymer and polymer composite materials still plays an important role. turning is one of the most productive machining technologies used to make cylindrical products. polymers that exhibit good levels of machinability favour the development of chip formation. however, technical practices often use polymer materials that exhibit favourable properties (hardness, toughness, flexibility) but are difficult to machine. the most common problem is continuously flowing chips. in this case, rather than the chip being moved away from the material, it is pushed in front of the tool. as a result, the heat cannot dissipate from the chips and the detached chips are in constant contact with the tool, which generates additional heat. since polymers tend to withstand high temperatures less than metals, their machined surfaces melt and their surface roughness becomes unacceptable. researchers have already studied the shape of detached chips. the literature is mainly concerned with the study of types of chips generated during the machining of metallic materials such as c45 [1, 2], al/sicp [3] and aisi d2 tool steel [4]. kharlevich and venuvinod analysed the formation of 3d chips in general as a result of metal cutting [5,6], while others have researched methods of chip breaking for machining tools [7, 8]. although chip detachment and formation are very important aspects in machining, in the case of polymers, this area has not yet been investigated. *correspondence: saranko.adam@uni-mate.hu 2. experimental methods 12 different polymer materials were tested, namely pa6 g-h, pa66 gf30, pet tf, pet, pom-c, pom-gf25, pom-h, pp, ptfe, pvc, textile bakelite and uhmwpe. according to a manufacturer of polymer materials, the aforementioned materials are the most commonly used, excluding the so-called high-performance ones. in this research, turning tests were performed to determine input parameters that can be used in practice to avoid such problems, e.g. melted surfaces, caused by continuously flowing chips. the turning tests were run on an e 400 conventional lathe machine and an nct euroturn-12b cnc lathe machine. both devices are located in the workshop of the institute of technology. in all the experiments, a sclcr 20.20 k09 tool shank and a ccgt 09t304-as ic20 polished turning insert were used. after each test, a close-up photo of the surface was taken and the average surface roughness measured. for surface measurements, a mitutoyo surftest sj-201p surface roughness tester was used. furthermore, the formed chips were collected before being analysed. the input parameters of all the tests are shown in table 1. in the case of roughing, the depth of cut was 3 mm, while a depth of cut of 0.25 mm was used for finishing. the air-cooled solution was mainly suitable for blowing off the detached chips. at first, all the experiments were tried without implementing any cooling methods. however, in the case of certain materials, flowing chips were formed in all cases, so chip blowing was used for these materials. https://doi.org/10.33927/hjic-2021-25 mailto:saranko.adam@uni-mate.hu 72 sarankó, kalácska, and keresztes table 1: input parameters of all tests input parameters for roughing on a cnc lathe machine (nct euroturn-12b) pa6 g-h pa66 gf30 pet tf pet pom c pom gf25 vc (m/min) 250 250 250 250 250 250 f (mm/rot.) 0.2 0.2 0.15 0.15 0.2 0.2 cooling pom h pp ptfe pvc textile bakelite uhmw-pe vc (m/min) 250 250 250 250 250 250 f (mm/rot.) 0.2 0.2 0.2 0.1 0.2 0.15 cooling input parameters for finishing on a cnc lathe machine (nct euroturn-12b) pa-6 g-h pa-66 gf-30 pet tf pet pom c pom gf-25 vc (m/min) 300 300 300 300 300 300 f (mm/rot.) 0.1 0.1 0.1 0. 1 0.1 0.1 cooling air air air air air air pom h pp ptfe pvc textile bakelite uhmw-pe vc (m/min) 300 300 300 300 300 300 f (mm/rot.) 0.1 0.1 0.1 0.1 0.08 0.1 cooling air air air air air input parameters for roughing on a conventional lathe machine (e 400) pa-6 g-h pa-66 gf-30 pet tf pet pom c pom gf-25 vc (m/min) 61 52 59 75 58 52 f (mm/rot.) 0.75 0.75 0.4 0.4 0.6 0.6 cooling pom h pp ptfe pvc textile bakelite uhmw-pe vc (m/min) 66 76 58 58 59 58 f (mm/rot.) 0.6 0.75 0.6 0.2 0.75 0.4 cooling input parameters for finishing on a conventional lathe machine (e 400) pa-6 g-h pa-66 gf-30 pet tf pet pom c pom gf-25 vc (m/min) 65 62 63 79 62 62 f (mm/rot.) 0.1 0.1 0.1 0.1 0.1 0.1 cooling air air air air pom h pp ptfe pvc textile bakelite uhmw-pe vc (m/min) 71 80 57 63 63 62 f (mm/rot.) 0.1 0.1 0.1 0.1 0.1 0.1 cooling air air air air 3. results the input parameters shown in table 1 can also be considered as results. these parameters were determined experimentally. in other aspects, however, the main results are the average surface roughness of the machined surfaces and the properties of the detached chips. table 2 shows the results of the average surface roughness measurements. although other setups can be used, by applying the parameters described above, safe and productive machining can be achieved by avoiding problems caused by continuously flowing chips. the detached chips were examined subjectively rather than by making specific measurements. however, the results obtained in this way can be used in practice and provide a suitable point of reference. photos of the detached chips in all cases are presented in fig. 1, while the properties of these chips are shown in table 3. 4. conclusions in general, the turning of tough polymeric materials results in the formation of continuous chips. due to the big hungarian journal of industry and chemistry analysis of formed chips in the case of turning different polymer materials 73 table 2: average surface roughness values material average surface roughness (µm) nct euroturn-12b e 400 roughing finishing roughing finishing pa6 g-h 4.06 1.18 12.95 1.58 pa66 gf30 3.12 1.27 12.32 1.55 pet tf 1.73 0.95 5.24 1.47 pet 1.75 0.9 5.18 1.13 pom-c 3.48 0.66 8.62 1.14 pom-gf25 3.75 1.2 8.56 1.43 pom-h 3.44 0.68 8.72 1.14 pp 3.38 0.89 12.72 1.45 ptfe 5.01 1.77 18.44 1.93 pvc 1.01 0.78 2.35 0.87 textile bakelite 6.81 3.15 10.30 1.59 uhmwpe 2.53 1.81 11.27 1.67 table 3: properties of the detached chips properties of the detached chips nct euroturn-12b e 400 roughing finishing roughing finishing pa6 g-h 5, 6, 7, 8 5, 6, 9 5, 6, 8 3, 4, 7 pa66 gf30 3, 4 4, 5 3, 4 3, 4 pet tf 4, 5 4, 5 3, 10 4, 5 pet 4, 5 4, 5 5, 10 4, 5 pom-c 1, 2 3, 4 1, 2 3, 4 pom-gf25 1, 2 1, 2 1, 2 3, 4 pom-h 1, 2 3, 4 1, 2 3, 4 pp 4, 5, 6 4, 5 3, 8 4, 5 ptfe 3, 4 3, 4 3, 4 3, 4 pvc 4, 5 4, 5 4, 5 3, 4 textile bakelite 4, 11 11 1, 4, 11 11 uhmwpe 3, 6, 7, 10 3, 6, 9 3, 6, 7, 8 3, 6, 7 1: elemental, 2: rigid, 3: curved, continuously flowing, 4: easy to tear, 5: straight, continuously flowing, 6: tough, 7: stretches, 8: does not tear, 9: tears after being stretched, 10: hard to tear, 11: dust-like cross-section of chips during the roughing operation, the mass of individual detached chips influences in which direction they start to flow. this is less of a problem because the ventilation effect of the chuck does not adversely affect the cooling of the chips. in the case of the finishing operation, the cooling of the chips is critical. it is recommended to use air cooling, although not specifically for the purpose of cooling, in order to blow chips away from the workpiece and tool. even though the quality of the machined surfaces can be improved by tools with bigger radius, chips can still cause problems. during the experiments, chip blowing was worthwhile in all cases, especially during smoothing operations. future research can be conducted by precisely defining the air-cooling method, applying other tools and investigating high-performance polymeric materials. in the case of chip blowing, the distance between the workpiece and the chuck, the weight of the detached chips as well as the ventilation effect of the chuck must be taken into account. the direction and velocity of the air is also significant. it was found that a strong airflow is not always the 49 pp. 71–75 (2021) 74 sarankó, kalácska, and keresztes figure 1: photos of the detached chips most desirable. the distance between the nozzle and the tool is limited by the geometries of the machine as well as the workpiece. by precisely defining these parameters, more practical information can be provided. acknowledgement the authors would like to thank quattroplast kft. for providing the engineering polymeric materials. nomenclature vc cutting speed (m/min) f feed rate (mm/rotation) ra average surface roughness (µm) pa6 g-h cast polyamide 6, hungarian version pa66 gf30 polyamide 66 with 30 m/m% glass fiber pet tf polyethylene terephthalate with the addition of ptfe hungarian journal of industry and chemistry analysis of formed chips in the case of turning different polymer materials 75 ptfe polytetrafluoroethylene pet polyethylene terephthalate pom-gf25 polyoxymethylene with 25 m/m% glass fiber pom-c polyoxymethylene copolymer pom-h polyoxymethylene homopolymer pp polypropylene pvc polyvinyl chloride uhmwpe ultra-high molecular weight polyethylene references [1] segreto, t.; simeone, a.; teti, r.: chip form classification in carbon steel turning through cutting force measurement and principal component analysis procedia cirp, 2012, 2, 49–54 doi: 10.1016/j.procir.2012.05.038 [2] segreto, t.; simeone, a.; teti, r.: principal component analysis for feature extraction and nn pattern recognition in sensor monitoring of chip form during turning. cirp j. manuf. sci. technol. 2014, 7(3), 202–209 doi: 10.1016/j.cirpj.2014.04.005 [3] sun, w.; duan, c.; yin, w.: chip formation mechanism in machining of al/sicp composites based on analysis of particle damage. j. manuf. proc.. 2021, 64, 861–877 doi: 10.1016/j.jmapro.2021.02.032 [4] mohan, r.; harshavardhana, n.; chaudhari, m.; jeyanthi, s.; abimannan, g.: analysis on surface finish and chip morphology during dry turning process. mat. today: proc. 2021, 46(2), 999–1002 doi: 10.1016/j.matpr.2021.01.137 [5] kharkevich, a.; venuvinod, p. k.: basic geometric analysis of 3-d chip forms in metal cutting.: part 2: implications. int. j. mach. tools manuf. 1999, 39(6), 965–983 doi: 10.1016/s0890-6955(98)00066-2 [6] kharkevich, a.; venuvinod, p. k.: extension of basic geometric analysis of 3-d chip forms in metal cutting to chips with obstacle-induced deformation. int. j. mach. tools manuf. 2002, 42(2), 201–213 doi: 10.1016/s0890-6955(01)00115-8 [7] wu, m.; yu, a.; chen, q.; wang, y.; yuan, j.; sun, l.; chi, j.: design of adjustable chip breaker for pcd turning tools. int. j. mech. sci.. 2020, (172), 105411 doi: 10.1016/j.ijmecsci.2019.105411 [8] yilmaz, b.; karabulut, s.; güllü, a.: a review of the chip breaking methods for continuous chips in turning. j. manuf. proc. 2020, 49, 50–69 doi: 10.1016/j.jmapro.2019.10.026 49 pp. 71–75 (2021) https://doi.org/10.1016/j.procir.2012.05.038 https://doi.org/10.1016/j.procir.2012.05.038 https://doi.org/10.1016/j.cirpj.2014.04.005 https://doi.org/10.1016/j.jmapro.2021.02.032 https://doi.org/10.1016/j.matpr.2021.01.137 https://doi.org/10.1016/j.matpr.2021.01.137 https://doi.org/10.1016/s0890-6955(98)00066-2 https://doi.org/10.1016/s0890-6955(01)00115-8 https://doi.org/10.1016/j.ijmecsci.2019.105411 https://doi.org/10.1016/j.jmapro.2019.10.026 https://doi.org/10.1016/j.jmapro.2019.10.026 introduction experimental methods results conclusions hungarian journal of industry and chemistry vol. 51(1) pp. 29–34 (2023) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2023-05 manufacturing of large and polished ceramic pistons by cold isostatic pressing viktor gerlei1, tibor kránicz1, tamás korim2, and miklós jakab2* 1 bakony technical ceramics, csererdei út 36, veszprém, 8200, hungary 2 department of materials engineering, university of pannonia, egyetem u. 10, veszprém, 8200, hungary this paper discusses the challenges involved in producing high-quality alumina ceramics, particularly when it comes to achieving a suitable degree of surface roughness and high accuracy. alumina ceramics are widely used in various applications due to their exceptional properties, including high strength, wear resistance and chemical stability. the alumina ceramic pistons with the desired properties and performance were produced from commercially available raw materials. to improve the densification and mechanical properties of the sintered ceramics, an organic binder was used. the use of a diamond abrasive slurry for polishing was also studied, which has proven to be particularly effective in achieving a high degree of surface finish. the study aims to produ ce alumina-based pistons with a low level of surface roughness as well as discusses the techniques and methods used to achieve this goal. the results of this paper include the porosity, mechanical properties and microstructure of the alumina ceramics produced in addition to the effectiveness of the techniques and methods applied . keywords: alumina ceramic pistons, advanced ceramics, reactive alumina 1. introduction alumina ceramics are widely used in various applications due to their excellent properties such as high strength, wear resistance and chemical stability. however, production of alumina ceramic components with the desired properties and performance can be challenging, especially when it comes to achieving a high degree of surface smoothness and accuracy [1]-[2]. in the case of alumina-based advanced ceramics, especially where a particular spare part must fit precisely, the purity of the raw materials and the surface roughness of the finished product are particularly important. the surface finish of alumina ceramics can significantly affect their performance, especially in applications that require a low level of friction, tight tolerances and exceptional aesthetics [3]-[4]. therefore, the development of effective polishing techniques for alumina ceramics has been extensively studied over the years. the aim of this study is to produce pressing granules that are suitably fine and develop an alumina ceramic-based piston with a low degree of surface roughness [5]. the production of alumina granules can be challenging as such materials are typically formed from fine powders that require careful processing to prevent agglomeration. during the production of pistons, it is particularly important to use appropriately homogeneous granules in order to determine the density, porosity and received: 16 march 2023; revised: 27 march 2023; accepted: 27 march 2023 *correspondence: jakab.miklos@mk.uni-pannon.hu strength of the product [6]. one approach to overcome these challenges is the use of organic binders, which can help to form granules from fine powders. organic binders are typically added to the alumina powders to improve the handling and processing characteristics of the materials such as strength, flowability and compressibility [7]-[8]. in addition to granulation techniques, isostatic pressing has been extensively studied to improve the properties and performance of ceramic materials [9], which is a technique that involves applying an equal degree of pressure from all directions on a ceramic powder or green body using a fluid medium to aid pressing and detachment of the mold. these agents optimize the production process by reducing friction between the granules as well as providing a separating effect between the pressing tool and the pressed material. polyvinyl alcohol (pva) is a water-soluble polymer that is used as a binder in isostatic pressing, which has proven to be effective in the production of ceramics [10]. padmaja et al. studied the preparation and characterization of alumina ceramics using isostatic pressing with pva as a binder. their results showed that the addition of pva improved the densification and mechanical properties of the sintered ceramics [11]. to separate the pre-press molds, polyoxyethylene-based organic additives are widely used, which thoroughly moisten the surface so the green body can be easily https://doi.org/10.33927/hjic-2023-05 mailto:jakab.miklos@mk.uni-pannon.hu gerlei, kránicz, korim and jakab hungarian journal of industry and chemistry 30 removed from the surface of the pressing tool. wang et al. used polyoxyethylene in order to produce appropriately shaped yttria-based advanced ceramics that exhibit a suitable degree of surface roughness [12]. the isostatic pressing process can significantly improve the density, homogeneity and mechanical properties of ceramic materials. the desired mechanical strength and porosity can be achieved by heat treating the green bodies. after sintering, the products must be polished to achieve a suitable degree of surface roughness and high accuracy [1-2, 10]. alumina ceramics can be polished using various methods, including mechanical polishing, chemical polishing and electrolytic polishing. among these techniques, mechanical polishing using abrasive slurries is the most commonly used method [13]. the use of diamond abrasives has proven to be particularly effective in achieving a high degree of surface finish. the diamond abrasive slurry polishing process involves the use of a rotating disk covered with a diamond abrasive slurry that grinds and removes material from the surface of the ceramic component. the surface finish achieved by diamond abrasive slurry polishing is significantly better than by other mechanical polishing methods [14]-[15]. hudai et al. reported the polishing of sintered alumina ceramics using diamond abrasive slurries, who investigated the effects of various polishing parameters such as polishing pressure, polishing time and diamond particle size on the surface roughness and material removal rate from alumina ceramics. they concluded that the polishing pressure and diamond particle size both have a significant impact on the surface finish and material removal rate from alumina ceramics, moreover, that the use of diamond abrasive slurries can significantly improve and reduce the surface finish and surface roughness of alumina ceramics, respectively [16]. hooper et al. investigated the polishing of high-purity zirconia ceramics using diamond abrasive slurries by comparing the surface finish achieved by diamond abrasive slurry polishing and mechanical polishing methods. they reported that the former significantly improved and reduced the surface finish and surface roughness, respectively, when compared to other polishing methods [17]. the purpose of this study was to produce alumina ceramic pistons with a purity of 99 % using commercially available alumina powders. the porosity, mechanical properties and microstructure of the products manufactured with the same production parameters were determined. according to previous results and the literature, the sintered products were polished with a diamond abrasive slurry in order to achieve a suitable degree of surface roughness. 2. experimental 2.1. fabrication of alumina ceramic pistons ceramic pistons were produced using high-grade calcined reactive alumina powders. base material “a” was manufactured by almatis gmbh., while type “b” was produced by silkem hungary kft. and type “c” by nabaltec ag. the main parameters of the raw materials are summarized in table 1, which is based on the manufacturer’s datasheet. the microstructures of the alumina powders are illustrated in figure 1. the raw materials were ground in an industrial ball mill using ceramic balls with a diameter of 25 mm, where a grinding additive dolapix pc21 (zschimmer & schwarz chemie gmbh.) was added to the alumina powders. this grinding additive facilitates moistening of the granules and optimizes the grinding process. after 48 hours of grinding, a pva-based organic binder (optapix pa42, zschimmer & schwarz chemie gmbh.) was added to the sludge at a rate of 2.0 wt.% of dry solids content per feedstock. the thermogravimetric curve in figure 2 shows that the optapix pa42 organic binder started to decompose above 300 °c, which ensured that the sludge remained stable during spray drying and the green body did not crack during the heating phase of the sintering process. the mixture was homogenized for 4 hours before the ready-to-press feedstock was spray dried. in an automated atomizer unit (niro atomizer d200), the slurry was fed at 21.4 bars and dried at 280 °c. the density of the sludge was 1.95 g/cm3 during the drying process and the morphology of the granules after spray drying is shown in figure 3. table 1. main properties of the base materials sample al2o3 content particle size specific surface area na2o content (wt.%) (µm) (m2/g) (wt.%) a 99.8 0.3 7.5 0.1 b 99.6 2.0-6.0 0.7 0.1 c 99.8 2.0 0.7 0.1 figure 1. sem micrographs of sample a (a – from the manufacturer’s datasheet), sample b (b) and sample c (c) manufacturing of ceramic pistons by cold isostatic pressing 51(1) pp. 29–34 (2023) 31 after the spray-drying process, a polyoxyethylenebased additive (zusoplast o 59, zschimmer & schwarz chemie gmbh.) was added to the mixture at 0.5 wt.% to make it easier to separate the green bodies from the pressing tool. the coarse fraction of the granules was separated on a vibrating sieve. from the spray-dried granules obtained, the test specimens were pressed by cold isostatic pressing (cip) using a densomatic isostatic press at a pressure of 1000 bars for 3 seconds. regarding the isostatic pressing of large pistons manufactured for high pressure equipment, the decompression time is critical. based on previous research results, the decompression time for all three types of alumina granules was 210 seconds. after cip, the test specimens were ground to the appropriate size and shape before being fired in a muffle furnace at 1550 °c for 4 hours in order to produce a completely solid product. to check the exact firing parameters, the products were re-sintered using the same parameters. if the density of the products is greatly reduced during the subsequent heat treatment, it can be concluded that the parameters set for the first firing were inappropriate. the density values of the pistons after isostatic pressing, sintering and re-sintering are summarized in table 2. the results clearly show that after a single heat treatment the density of the pistons increased significantly and did not change during the resintering, i.e. the product was already sufficiently dense after the first sintering. the linear shrinkage values after the first heat treatment of the test specimens are summarized in table 3. since the changes in the density and linear shrinkage of the products pressed from different raw materials were similar, no significant difference between the various granules was observed. following the sintering process, a penetration test was carried out using pfinder 902 (grimas kft.), a fluorescent penetrant, to determine whether internal cracks were present. after being immersed, the samples were exposed to uva radiation and the result obtained by examining the defective product is illustrated in figure 4. following the heat treatment, a negligible amount of cracking was observed on the products. after sintering, the pistons were ground into their final shape and form before being polished by a stahli flm 500-r polishing machine for 16 minutes table 2. density of the test specimens sample density after cip density after sintering density after re-sintering (g/cm3) (g/cm3) (g/cm3) a 2.40±0.12 3.81±0.04 3.81±0.02 b 2.40±0.09 3.78±0.05 3.77±0.03 c 2.41±0.11 3.78±0.04 3.78±0.01 table 3. linear shrinkage values of the sintered samples sample transverse shrinkage longitudinal shrinkage (%) (%) a 14.30±0.09 13.78±0.12 b 14.67±0.12 13.35±0.13 c 14.44±0.10 13.11±0.08 table 4. surface roughness values after various surface machining processes sample arithmetic mean surface roughness (ra) after grinding after polishing a 0.452±0.032 0.209±0.002 b 0.485±0.022 0.288±0.005 c 0.471±0.027 0.282±0.004 figure 2. thermogravimetric curve of the added optapix pa42 organic binder figure 3. the shape of the particles formed after the spray-drying process figure 4. defective product after penetration test gerlei, kránicz, korim and jakab hungarian journal of industry and chemistry 32 using an abrasive slurry containing diamond particles of 3 µm in diameter. the average surface roughness (ra) values resulting from grinding and polishing are summarized in table 4. the results show that a finer surface roughness can be achieved on the pistons made of material type "a" by applying the same manufacturing and machining parameters. as reported in previous studies, the lower the ra value, the better the tribological properties of the specimens [18]. this phenomenon is attributed to the fact that the average particle size of sample “a” (0.3 µm) was much smaller than for the other base materials (2.0-6.0 µm). according to the literature, polishing with a diamond abrasive slurry can produce a piston with excellent surface roughness properties on an industrial scale. a picture of pistons of different sizes produced with the same technological parameters is shown in figure 5. products 42.0±0.1 mm in length and 18.0±0.02 mm in width were used for the measurements. the products, produced with the same manufacturing and machining parameters as well as verified by penetration testing, were used for further tests. 2.2. characterization the microstructures of the raw materials and the granulates were tested by a fei/thermo fisher scientific apreo lovac scanning electron microscope and a keyence vhx-2000 optical microscope. thermogravimetric measurements were taken by a mom q-1500 d thermogravimetric analyzer. the maximum temperature recorded was 800 °c, while the heating rate was 10 °c/min. the densities of the pressed and sintered samples were determined by the well-known archimedes’ principle using water as the immersion fluid. the surface roughness of the pistons was measured by a taylor hobson surtronic s-128 profilometer with a total stroke length of 20 mm. the compressive and bending strengths of the sintered samples were tested by an instron 5967 dual column tensile testing machine at a feed rate of 144 kn/min. the microhardness of the samples was characterized by a vickers microhardness tester model wolpert 402 mvd with a loading force of 1 kgf. the internal structure of the samples was examined by x-ray computed tomography using a nikon xt h 225. the evaluation was carried out using 2d images to determine their internal porosity and compactness. 3. results and analysis 3.1. mechanical properties the most important parameters of alumina ceramic pistons used in high-pressure equipment are their bending and compressive strengths. the results obtained by measuring the bending strength are summarized in figure 6, where “sa” denotes the sintered product made from material type “a”. the same marking was applied to the patterns on sintered products “sb” and “sc”. the measurements were carried out at room temperature and in each case 5 parallel measurements were taken. the results show that alumina powder type "a" with a smaller particle size and larger specific surface area was able to produce a product with the highest bending strength and lowest standard deviation. this phenomenon can be explained by the fact that these particles are homogeneously distributed throughout the total volume of the product and fit more tightly than in the case of the other two raw alumina powders. regarding alumina powders “b” and “c”, a similar degree of flexural strength can be observed, which is associated with the same particle size distribution of the base material. the measurements of the compressive strength were taken on the cylindrical surface of the piston as the instrument is capable of applying a maximum compressive force of 250 kn and the axial strength of the products is much higher than that. the compressive strength values are illustrated in figure 7. in relation to the measurements made of the flexural strength, the highest compressive strength was achieved on the pistons produced using alumina powder type “a”. the results of the strength tests show that the microhardness of pistons produced with the same technological parameters and machined under the same conditions is favorable when the average grain size and specific surface area of the starting material used is smaller and larger, respectively. figure 5. the sintered and polished alumina ceramic pistons figure 6. bending strength of the sintered samples 300 310 320 330 340 350 360 370 sa sb sc b en d in g s tr en g th ( m p a) sample manufacturing of ceramic pistons by cold isostatic pressing 51(1) pp. 29–34 (2023) 33 the microhardness values measured on the surface of the pistons are illustrated in figure 8. the microhardness of the samples made from different materials is almost identical, however, the standard deviations for samples “sb” and “sc” are higher. this phenomenon can be explained by the fact that the surface roughness of “sa” which was more polished and the particle size of its starting material much smaller is lower. therefore, a denser product can be produced during the sintering processes. 3.2. microstructure the 2-dimensional x-ray computed tomographic images are illustrated in figure 9. the tests were carried out after the sintering process. for the product manufactured from alumina powder type “a”, a compact structure is observed, that is, the sample does not contain large pores or cracks. however, in the case of the sample labelled “sb”, small pores and thin cracks are visible in the part denoted in blue. such small cracks are not detectable by the aforementioned penetration test. in the case of the sample labelled "sc", no cracking was observed, however, a few small pores were visible in this sample which are highlighted in red. the decrease in strength observed in both samples "sb" and "sc" during the compression and bending tests is explained by the pores they contain. 4. conclusions this experimental work demonstrated that a sufficiently dense and polishable ceramic piston can be produced by adding pva and polyoxyethylene as described in the literature. by applying the same manufacturing parameters, alumina from different manufacturers behaved in the same way, namely shrunk to the same extent during heat treatment and sintered to yield the same degree of compactness. however, during the final machining stage, a lower surface roughness was obtained by applying the same polishing parameters for the product produced from particles with a small average grain size and large specific surface area. the mechanical properties test showed that the strength of the product produced from raw material type “a” was best but the microhardness values were the same for all three raw materials. if a reactive alumina powder with a small average particle size and large specific surface area is used, a more polishable product with a low surface roughness is produced, therefore, a better fitting component can be manufactured. the structure of this piston is more compact and its mechanical properties better than those made from larger particles. acknowledgements this research was carried out within the framework of ginop-2.1.7-15-2015-00488 supported by the european structural and investments funds and the hungarian government. figure 7. compressive strength of the sintered pistons 500 510 520 530 540 550 560 sa sb sc c o m p re ss iv e st re n g th ( m p a) sample figure 8. microhardness of the pistons 12,0 12,1 12,2 12,3 12,4 12,5 12,6 12,7 12,8 12,9 sa sb sc m ic ro -h ar d n es s (g p a) 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https://doi.org/10.1111/j.1151-2916.2000.tb01357.x https://doi.org/10.1111/j.1151-2916.2000.tb01357.x https://doi.org/10.1016/0043-1648(89)90188-9 https://doi.org/10.1016/0043-1648(89)90188-9 https://doi.org/10.33927/hjic-2021-26 hungarian journal of industry and chemistry vol. 50(2) pp. 43–49 (2022) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2022-17 study on adsorption of essential oils on polylactic acid microparticles lilla virág1*, róbert bocsi1 and dóra pethő1 1 research centre for biochemical, environmental and chemical engineering, faculty of engineering, university of pannonia, egyetem u. 10, veszprém, 8200, hungary polylactic acid (pla) is a biodegradable polymer that is widely used in medical devices, drug delivery systems, fibers for packaging containers and textiles. however, given that interactions between the polymer and the materials in contact with it affect its applications, it is important to study its adsorption and diffusion properties. the adsorption capacity of different polylactic acid particles regarding different additives, e.g. essential oils (thymus vulgaris, melissa officinalis and foeniculum vulgare), was investigated. pla microparticles of various sizes were prepared by a solvent emulsification evaporation method. in this study, the specific adsorption of essential oils on pla microparticles was also investigated, which is related to the solubility parameters of essential oils. the experiments were performed using three different solutions of essential oils and ethanol as a solvent. two sets of pla microparticles were prepared with different solvents using three different particle sizes. pla microparticles exhibited different adsorption properties depending on the solvent that was used for their production. samples of particles prepared using the solvent dichloromethane had a higher essential oil uptake than those prepared with chloroform. the uptake of essential oil solution did not change significantly (∼60%) by varying either the type of solvent used for pla preparation or pla particle size. the solubility of the essential oils affects the specific adsorption of essential oils on the microparticles. among the components of the hansen solubility parameters (hsps), the polarity of essential oils is strongly related to adsorption. keywords: polylactic acid, microparticles, essential oil adsorption, hansen solubility parameters 1. introduction biodegradable polymers are important feedstocks in industry as they offer an environmentally-friendly alternative to fossil-based polymers in biomedical, agricultural and household applications [1]. pla is an aliphatic polyester as well as one of the most commercially available, bio-based, biodegradable and biocompatible polymers. pla is commonly considered for different applications such as in drug delivery systems, tissue engineering, packaging and textiles. the fields of application of this polymer are limited by certain properties, e.g. its low mechanical strength or hydrophobicity [2]-[3]. different additives, e.g. essential oils, can be incorporated into biodegradable polymers to improve their functional properties [4]. different types of essential oils such as thyme, cinnamon, oregano and basil are incorporated into biodegradable polymer films, e.g. for the development of food packaging films to enhance antimicrobial properties [5]. essential oils also act as plasticizers in polymers. due to their plasticizing properties, the structural and mechanical properties of such polymers can be altered [6], thereby also changing the sorption properties of pla. received: 18 oct 2022; revised: 24 oct 2022; accepted: 24 oct 2022 *correspondence: virag.lilla@mk.uni-pannon.hu interactions between essential oils and pla have been studied by several researchers (dusankova et al., martins et al., dicastillo et al.) using different processing methods [7]-[9] and are mainly determined by the composition of the essential oil and its polarity. dusankova et al. studied pla microspheres containing different components of essential oils. they found that the more polar components adsorb better in the microspheres than the more apolar ones, as pla itself is polar [7]. martins et al. came to a similar conclusion. when the incorporation and release of the components of the essential oils thymol and p-cymene were studied, the diffusion rate of these components through the pla matrix differed significantly (diffusion coefficient was 1.99 × 10−16 m2/s for thymol and 4.34 × 10−16 m2/s for pcymene), which could be explained by their difference in polarity [8]. in our work, the adsorption properties of polylactic acid particles regarding different essential oils like those from lemon balm, fennel and thyme were investigated. the microparticles were prepared by a solvent emulsification evaporation method [10]. the structure of the polymer particles formed is critical, as their particle size distribution and porosity influence their adsorption properties. the properties of the particles that are https://doi.org/10.33927/hjic-2022-17 mailto:virag.lilla@mk.uni-pannon.hu virág, bocsi and pethő hungarian journal of industry and chemistry 44 produced by the solvent emulsification evaporation method are mostly affected by the concentration of the pla solution, type and amount of surfactant as well as the mixing speed. besides the concentration of the pla solution, its composition is also important [11]. the organic solvent in which pla is dissolved will affect the structure of the microparticles produced [10], [12]. shi et al. found that pla particles prepared using chloroform as the solvent were less porous than those prepared in ethyl acetate [12]. consequently, in our work, the adsorption of essential oils on pla microparticles as a function of the pla particle size was investigated. to modify the particle size distribution, the concentration of pla solution was changed during the emulsification method. 2. experimental 2.1. materials natureworks ingeo biopolymer 3d850 pla granules, dichloromethane (>99.8%, fisher), chloroform (technical grade, stabilized with ~0.6% of ethanol, vwr) and polyvinyl alcohol (fully hydrolyzed, mw approx. 60,000; merck) were used to prepare the pla microparticles. to measure the degree of adsorption, ethanol (99.8% g.r., iso reagent, lach-ner, s.r.o.) and three kinds of essential oils: melissa officinalis (from lemon balm, neuston healthcare kft.), foeniculum vulgare (from fennel, neuston healthcare kft.) and thymus vulgaris (from thyme, neuston healthcare kft.) were used. 2.2. methods microparticles were prepared based on a solvent emulsification evaporation method. the particles were prepared as follows: firstly, 200 ml of pla solution of a given concentration (2.5, 5.0 and 7.5 wt. %) using dichloromethane or chloroform as a solvent; secondly, the solution was added to 400 ml of 1 wt. % polyvinyl alcohol (pva) solution. the emulsion was stirred with a magnetic stirrer at 820 rpm for 24 or 48 hours, depending on the solvent used (dichloromethane or chloroform, respectively). after filtering and washing, the solid particles were dried in a binder fd 53 oven at 50 °c for 24 hours. to determine the average diameter and size distribution of the particles, an image was taken using an optical microscope (lacerta, zoom: 40x). the particle size was determined from the images using the program imagej. to measure the degree of adsorption, 1.000 g of pla particles were weighed on an ohaus adventurer ar3130 analytical balance in a pre-weighed dry test tube, then 2.000 g of a 1.00 mg/ml ethanolic solution of essential oil was added to it. the microparticles were soaked for 24 hours before the samples were separated by filtration. the essential oil concentrations of the residual ethanolic solutions were analyzed by uv-vis spectrophotometry. the absorption spectra of the samples were recorded between 200 and 800 nm using an agilent cary 60 uv-vis spectrophotometer. differential scanning calorimetry (dsc) was performed with a netzsch dsc 214 polyma differential scanning calorimeter. the measurements were carried out under a 60 ml/min n2 flow rate according to the following protocol: first the sample was heated from 20 to 200 °c at a heating rate of 10 °c/min before being cooled from 200 to 20 °c at a cooling rate of 10 °c/min then reheated from 20 to 200 °c at the same heating rate. notation was applied to the samples, e.g. pla_k_100_el. the first letter refers to the solvent that was used for pla preparation (dkm for dichloromethane and k for chloroform), the number refers to the size of the microparticles (table 1). at the end of the sample identification, the first letter refers to the type of solvent used for essential oil solution (e for ethanol) and the last letter refers to the essential oil, namely l for lemon balm, t for thyme and f for fennel. 3. results and discussions 3.1. microparticle properties the properties of the microparticles such as their particle size distribution are shown in fig.1. as the concentration of the pla solution increased, the size of the particles produced also increased. the correlation between the concentration of pla solution and the diameter of the particles is linear. the solvent emulsification evaporation method mainly produced spherical particles that did not aggregate (fig.2). 3.2. solution uptake by microparticles regarding the uptake of ethanolic solution of essential oil by the particles prepared from a pla solution prepared in dichloromethane, it was concluded that the solution uptake increases slightly by 10% on average as the particle size increases. however, the presence of essential oils in the solutions did not significantly affect the solution uptake of the particles. for a given particle size, the solution uptake was practically the same for all examined solutions. the average solution uptake by table 1. notation for the microparticles sample name pla-solution – solvent type average size, µm pla_dkm_50 dichloromethane (dkm) 57±12 pla_dkm_100 116±21 pla_dkm_200 207±57 pla_k_50 chloroform (k) 56±14 pla_k_100 121±31 pla_k_200 198±40 essential oils adsorption on polylactic acid 50(2) pp. 43–49 (2022) 45 particles 50, 100 and 200 µm in diameter is 60, 66 and 75%, respectively. 3.3. adsorption of essential oils on microparticles the different types of pla microparticles exhibited different adsorption properties (figs.3 and 4) regarding various essential oils. it was found that in the case of lemon balm, the uptake of essential oils by pla_dkm particles from ethanolic solutions and the specific amount of the essential oil adsorbed increased as the particle size increased, while the degree of uptake and adsorption decreased in the case of ethanolic solutions of thyme and fennel. lemon balm essential oil yielded an outstanding result. in this case, by increasing the particle size from 50 to 100 µm and then to 200 µm, the degree of essential oil uptake increased by 19% and then by a further 16%. it was concluded that the effect of pla_k particle size on the specific adsorption of thyme and fennel essential oils is insignificant, there is no correlation between the amount of essential oil adsorbed and the particle size. however, in the case of the lemon balm essential oil, the degree of specific adsorption increased as the particle size increased. in general, it was concluded that for pla_dkm particles, the essential oil uptake mainly resulted from the differences between the microparticles (degree of crystallinity, size, porosity) and the types of essential oils present in the solutions. nonetheless, in the case of pla_k particles, the specific amount of essential oil adsorbed on the surface or in the pores of the particles did not change significantly as the particle size changed, rather each essential oil was adsorbed differently on the particles. the particles prepared by using dichloromethane as a solvent had a higher specific essential oil adsorption (0.8-3.4 mg eo/g pla) than particles prepared in chloroform (0.6-1.6 mg eo/g pla). variation in the adsorption properties of the particles was probably caused by the differences in their structure. the different solvents used in the production process caused the particles to solidify at different rates, leading to possible differences in their internal structure and porosity. 3.4. the correlation between adsorption properties in light of the hansen solubility parameters (hsps) adsorption properties are affected by the composition and properties of the adsorbate. the connection between figure 1. particle size distribution of the different pla microparticles figure 2. images of the microparticles: a.) pla_k_100 and b.) pla_dkm_100 figure 3. essential oil uptake (%) by the microparticles in the case of a.) particles prepared in dichloromethane and b.) particles prepared in chloroform 0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 pla_dkm_50 pla_dkm_100 pla_dkm_200 e ss en ti a l o il u p ta k e, % el et ef a. 0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 pla_k_50 pla_k_100 pla_k_200 e ss en ti a l o il u p ta k e, % el et ef b. virág, bocsi and pethő hungarian journal of industry and chemistry 46 the solubility of essential oils and the adsorption properties of pla was investigated. solubility can be characterized by the hsps, which describe the affinity of the polymer for different organic substances. hansen total solubility parameter (δt) is composed of three parameters, one indicating the contribution to the dispersion forces (δd), another characterising the polar interactions (δp) and one more demonstrating the formation of h-bonds (δh). these solubility parameters can be determined using different methods such as the group contribution method (hoftyzer-van krevelen method) [13]-[15]. the specific amount of essential oil adsorbed on pla can be related to the total solubility parameter or one of its components. since different essential oils have different solubility parameters depending on their composition (table 2), the specific adsorption on pla is different for different essential oils. a correlation between the adsorbed amount of the essential oil and δδp,eo was observed. (δδp,eo shows how much the δp of an essential oil differs from that of pla.) in the case of pla_dkm particles, the specific adsorption decreased as δδp,eo increased (fig.5). in contrast, it was found that the specific amount of essential oil adsorbed on pla_k particles deviated in the case of δδp,eo less than 5.5 (mpa1/2). 3.5. thermal properties of the pla particles dsc was used to evaluate the thermal properties of the samples. the glass transition (tg), cold crystallization (tcc) and melting temperatures (tm) of the pla particles were determined during the second heating of the dsc measurement. the degree of crystallinity (xc%) was calculated from the enthalpy of melting (δhm) and the enthalpy of cold crystallization (δhcc), taking into account an enthalpy of melting (δhm 0) of 94 kj/kg for 100% crystalline pla [16]-[17]: xc% = [(δhm-δhcc)/δhm] × 100 (1) both types of pla particles exhibited two exothermic, cold crystallization peaks and an endothermic melting peak (fig.6). for both pla_dkm and pla_k particles, the glass transition occurred at ~61°c (61.3±0.6 and 60.9±0.3°c, respectively) and the melting at 177°c (177.3±0.8 and 176.6±0.3°c, respectively). however, a difference is observed in the cold crystallization temperatures between the two types of particles. for the pla_k and pla_dkm particles, the first cold crystallization peaks appeared at 96.7±0.6°c and 104.4±0.2°c, respectively. the probable reason for this is that during the emulsification method, the particles solidified at different rates based on the organic solvent used for the pla solution. as the particles solidified at different rates, their structure and porosity vary. the thermal properties of the granules did not change even when the concentration of the pla solution was changed during their preparation. the degree of crystallinity of the pla_k particles was approximately 25.0±0.7%, while that of pla_dkm was different. the degree of figure 4. specific adsorption of essential oil (eo) on microparticles (mg eo/g pla) in the case of a.) particles prepared in dichloromethane and b.) particles prepared in chloroform 0.00 0.50 1.00 1.50 2.00 2.50 pla_dkm_50 pla_dkm_100 pla_dkm_200 m g e o / g p l a el et ef a. 0.00 0.50 1.00 1.50 2.00 2.50 pla_k_50 pla_k_100 pla_k_200 m g e o / g p l a el et ef b. table 2. hansen solubility parameters (hsps) of the materials material δd (mpa1/2) δp (mpa1/2) δh (mpa1/2) δt (mpa1/2) pla 18.6 9.9 6.0 21.9 ethanol 15.1 8.4 18.3 25.2 lemon balm essential oil 16.4 4.6 5.1 17.8 thyme essential oil 21.5 3.3 9.6 23.8 fennel essential oil 24.3 3.9 28.0 37.3 essential oils adsorption on polylactic acid 50(2) pp. 43–49 (2022) 47 crystallinity of the pla_dkm_50, pla_dkm_100 and pla_dkm_200 particles was 24.3±0.4, 19.6±0.7 and 21.5±0.8, respectively. after the degree of adsorption was measured, the thermal properties of the microparticles did not change due to their interaction with the essential oils (fig.7). however, the adsorption of essential oils had an effect on the degree of crystallinity of the particles, as the degree of crystallinity of the pla_dkm particles increased by 2% and that of pla_k_50 particles increased to 30%. the degree of crystallinity of the pla_k_100 and pla_k_200 particles was not influenced by which essential oil was used. based on the results, it was found that the thermal properties of the pla microparticles are affected by the type of solvent used during their preparation rather than by the concentration of the pla solution used. it was concluded that the thermal properties of the microparticles were not changed by the adsorption of essential oils. therefore, the amount of essential oil adsorbed was insufficient to cause a significant change to the pla structure. 4. conclusion in our work, the adsorption properties of polylactic acid particles for lemon balm, fennel and thyme essential oils were investigated. the adsorption of these essential oils on the pla particles was investigated as a function of particle size (50, 100 and 200 µm). it was concluded that the adsorption of essential oils is affected by both differences between types of microparticles (degree of crystallinity, size, porosity) and the types of essential oils present in the solutions of pla_dkm samples. although the specific amount of essential oil adsorbed on the surface or in the pores of pla_k particles did not change significantly as the figure 5. correlation between the hsps and the specific adsorption of essential oil (eo) on microparticles (mg eo/ g pla) in the case of a.) particles prepared in dichloromethane and b.) particles prepared in chloroform figure 6. the second heating dsc curves of the pla granules and microparticles in the case of a.) their different types and b.) their different sizes 4.0 4.5 5.0 5.5 6.0 6.5 7.0 0.00 1.00 2.00 3.00 pla_d_100_el pla_d_100_ef pla_d_100_et pla_d_200_el pla_d_200_ef pla_d_200_et 0.00 0.50 1.00 1.50 2.00 2.50 5.0 6.0 7.0 m g e o /g p l a δδp,eo (mpa1/2) a. 4.0 4.5 5.0 5.5 6.0 6.5 7.0 0.00 50.00 100.00 pla_k_50_el pla_k_50_ef pla_k_50_et pla_k_100_el pla_k_100_ef pla_k_100_et pla_k_200_el pla_k_200_ef pla_k_200_et 0.00 0.50 1.00 1.50 2.00 2.50 5.0 6.0 7.0 m g e o /g p l a δδp,eo (mpa1/2) b. -1.40 -1.20 -1.00 -0.80 -0.60 -0.40 -0.20 0.00 0.20 20 80 140 200 m w /m g temperature, c pla_dkm_100 pla_k_100 a.a. -1.40 -1.20 -1.00 -0.80 -0.60 -0.40 -0.20 0.00 0.20 20 80 140 200 m w /m g temperature, c pla_dkm_50 pla_dkm_100 pla_dkm_200 b. virág, bocsi and pethő hungarian journal of industry and chemistry 48 particle size varied, the degree of adsorption of the essential oils on the particles varied. the particles that were prepared in dichloromethane as a solvent, exhibited a higher specific adsorption of 0.8-3.4 mg eo/g pla compared to particles prepared in chloroform of 0.6-1.6 mg eo/g pla. the difference in the adsorption properties of the particles is probably caused by variations in their structure. the different solvents used in the production process caused the particles to solidify at various rates, which may lead to differences in their internal structure and porosity. the reason for differences in the degree of adsorption of the essential oils is variation in the composition of the essential oil solutions, which is characterized by the hsps. in ethanolic solutions, a correlation between the adsorbed amount of the essential oil and the δp component of the total hsps was observed. based on the results, it was determined that the thermal properties of the pla microparticles are affected by the type of solvent used during their preparation rather than by the concentration of pla solution applied. it was concluded that the thermal properties of the microparticles were not affected by the degree of adsorption. references [1] ranakoti, l.; gangil, b.; mishra, s.k.; singh, t.; sharma, s.; ilyas, r.a.; el-khatib, s.: critical review on polylactic acid: properties, structure, processing, biocomposites, and nanocomposites, materials, 2022, 15(12), 4312, doi: 10.3390/ma15124312 [2] li, g.; zhao, m.; xu, f.; yang, b.; li, x.; meng, x.; teng, l.; sun, f.; li, y.: synthesis and biological application of polylactic acid, molecules, 2020, 25(21), 5023, doi: 10.3390/molecules25215023 [3] nofar, m.; sacligil, d.; carreau, p.j.; kamal, m.r.; heuzey, m.c.: poly (lactic acid) blends: processing, properties and applications, int. j. biol. macromol., 2019, 125, 307–360, doi: 10.1016/j.ijbiomac.2018.12.002 [4] qin, y.; li, w.; liu, d.; yuan, m.; li, l.: development of active packaging film made from poly (lactic acid) incorporated essential oil, prog. org. coat., 2017, 103, 76–82, doi: 10.1016/j.porgcoat.2016.10.017 [5] ahmed, j.; hiremath, n.; jacob, h.: antimicrobial, rheological, and thermal properties of plasticized polylactide films incorporated with essential oils to inhibit staphylococcus aureus and campylobacter jejuni, j. food sci., 2016, 81(2), 419–429, doi: 10.1111/1750-3841.13193 [6] tarach, i.; olewnik-kruszkowska, e.; richert, a.; gierszewska, m.; rudawska, a.: influence of tea tree essential oil and poly(ethylene glycol) on antibacterial and physicochemical properties of polylactide-based films, materials, 2020, 13(21), 4953, doi: 10.3390/ma13214953 [7] dusankova, m.; pummerova, m.; sedlarik, v.: microspheres of essential oil in polylactic acid and poly(methyl methacrylate) matrices and their blends, j. microencapsul., 2019, 36(3), 305–316, doi: 10.1080/02652048.2019.1623337 [8] martins, i.m.; rodrigues, s.n.; barreiro, m.f.; rodrigues, a.e.: release studies of thymol and pcymene from polylactide microcapsules, ind. eng. chem. res., 2012, 51(35), 11565–11571, doi: 10.1021/ie301406f [9] de dicastillo, c.l.; villegas, c.; garrido, l.; roa, k.; torres, a.; galotto, m.j.; rojas, a.; romero, j.: modifying an active compound’s release kinetic using a supercritical impregnation process to incorporate an active agent into pla electrospun mats, polymers, 2018, 10(5), 479, doi: 10.3390/polym10050479 [10] o'donnell, p.b.; mcginity, j.w.: preparation of microspheres by the solvent evaporation technique, adv. drug deliv. rev., 1997, 28(1), 25–42, doi: 10.1016/s0169-409x(97)00049-5 [11] singh, b.; singh, p.; sutherland, a.j.; pal, k.: control of shape and size of poly (lactic acid) microspheres based on surfactant and polymer concentration, mater. lett., 2017, 195, 48–51, doi: 10.1016/j.matlet.2017.02.068 figure 7. the second heating dsc curves of the pla microparticles after measuring the adsorption of a.) particles prepared in chloroform and b.) particles prepared in dichloromethane. -1.40 -1.20 -1.00 -0.80 -0.60 -0.40 -0.20 0.00 0.20 20 80 140 200 m w /m g temperature, c pla_k_50 pla_k_50_el pla_k_50_et pla_k_50_ef a. -1.40 -1.20 -1.00 -0.80 -0.60 -0.40 -0.20 0.00 0.20 20 80 140 200 m w /m g temperature, c pla_dkm_50 pla_dkm_50_el pla_dkm_50_ef pla_dkm_50_et b. https://doi.org/10.3390/ma15124312 https://doi.org/10.3390/ma15124312 https://doi.org/10.3390/molecules25215023 https://doi.org/10.1016/j.ijbiomac.2018.12.002 https://doi.org/10.1016/j.porgcoat.2016.10.017 https://doi.org/10.1016/j.porgcoat.2016.10.017 https://doi.org/10.1111/1750-3841.13193 https://doi.org/10.3390/ma13214953 https://doi.org/10.1080/02652048.2019.1623337 https://doi.org/10.1021/ie301406f https://doi.org/10.3390/polym10050479 https://doi.org/10.3390/polym10050479 https://doi.org/10.1016/s0169-409x(97)00049-5 https://doi.org/10.1016/j.matlet.2017.02.068 https://doi.org/10.1016/j.matlet.2017.02.068 essential oils adsorption on polylactic acid 50(2) pp. 43–49 (2022) 49 [12] shi, x.-d.; sun, p.-j.; gan, z.-h.: preparation of porous polylactide microspheres and their application in tissue engineering, chinese j. polym. sci., 2018, 36(6), 712–719, doi: 10.1007/s10118-0182079-x [13] hansen, c.m.: hansen solubility parameters: a user’s handbook, second edition, (crc press, boca raton, fl, usa), 2007, doi: 10.1201/9781420006834 [14] van krevelen, d.w.; te nijenhuis, k.: properties of polymers: their correlation with chemical structure; their numerical estimation and prediction from additive group contributions, fourth edition, (elsevier, amsterdam, the netherlands), 2009, pp. 201–225, isbn: 978-008054819-7 [15] sato, s.; gondo, d.; wada, t.; kanehashi, s.; nagai, k.: effects of various liquid organic solvents on solvent-induced crystallization of amorphous poly(lactic acid) film, j. appl. polym. sci., 2013, 129(3), 1607–1617, doi: 10.1002/app.38833 [16] saiter, a.; delpouve, n.; dargent, e.; saiter, j.m.: cooperative rearranging region size determination by temperature modulated dsc in semi-crystalline poly(l-lactide acid), eur. polym. j., 2007, 43(11), 4675–4682, doi: 10.1016/j.eurpolymj.2007.07.039 [17] ahmed, j.; zhang, j.-x.; song, z.; varshney, s.k.: thermal properties of polylactides: effect of molecular mass and nature of lactide isomer, j. therm. anal. calorim., 2009, 95(3), 957–964, doi: 10.1007/s10973-008-9035-x https://doi.org/10.1007/s10118-018-2079-x https://doi.org/10.1007/s10118-018-2079-x https://doi.org/10.1201/9781420006834 https://doi.org/10.1002/app.38833 https://doi.org/10.1016/j.eurpolymj.2007.07.039 https://doi.org/10.1007/s10973-008-9035-x https://doi.org/10.1007/s10973-008-9035-x hung~ journal of lndustrial chemistry veszprem vol. 29. pp. 11 15 (2001) modified scale crystallization and dispersion stability in magnetic water treatment l. c. lipus, j. krope, l. garbai 1 (faculty of chemistry and chemical technology, university of maribor, smetanova 17, 2000 maribor, slovenia 1mechanical engineering faculty, tebnical univesity of budapest, mtiegyetem rkp. 9, budapest h-1521 hungary) received: november 30, 2000 the effects of magnetic water treatment (mwt) devices are discussed with the emphasis on modified dispersion stability and modified cac03 crystallization. mwt mechanism, most probably consisting of several interacting effects, is strongly dependent on water composition, solid phase presence and working conditions. keywords: water treatment, magnetic hydrodynamics, water dispersion systems introduction mwt is an alternative method of water conditioning for scale control. it has also become important for amelioration in other industrial dispersion areas. mwt equipment has had practical application for over half a century. working experience has shown it to be a cheap and non polluting application for hard scale prevention, and the improvement of dispersion separation [ 1-4]. several empiricauy based designs of mwt devices have been produced. however, their mechanism, how a magnetic field precisely acts in a treated water system, still remains uncertain. a precise theoretical understanding is crucial when designing reliably efficient equipment for specific technological systems because of the delicate dependency on water composition and operational conditions. certain theoretical conclusions have been reached from widespread laboratory research. these state that the process of modified scale crystallization and dispersion destabilization most probably consists of three parallel interacting steps: magnetically modified hydration of ions and solid i solution interfaces, ~ lorentz force effect on water dispersion systems and concentration effects in working channels of mwt devices. these three hypotheses are being developed. firstly, there is a theoretical possibility of magnetic resonance of two neighbouring protons in hydration net during magnetic treatment, which could cause spin transition from a ground state (antiparallel orientation of spins) into an agitated state (parallel orientation). this would indirectly lead to weakening of the hydrogen bond [5}. secondly, during the use of the dynamic mwt type, the lorentz force, fl (eq.l), occurs on ions in the solution causing them to shift towards the surfaces of the dispersed particles (eq.2). therefore, the stability of water dispersion could be affected [6j. where parameters are: b =magnetic field density, e = electric charge, eo= electron charge= l,6·io·l9as, r1 = ion radius, {1} (2) v = flow velocity of dispersion through the channel of mwt device, ax; = lorentz shift of ion, z1 = ion valence, 11 = water viscosity, z = retention time of dispersion in channel of mwtdevice. the b'tv product is known as the technical module and is an important criterion for the practical efficiency of mwt devices. thirdly, concentration effects partially explain the aggregation of fine, already destabilized, particles into 12 x 0 /' / i • i 0 \ x fig.l scheme of electric layer and adherent electrical potential bigger ones. whilst modified crystallization and destabilization of dispersed scale forming components are better explained by the first two hypotheses. which mechanism prevails, depends on water composition and treatment conditions. the mwt mechanism's action on dispersed particles will be discussed here. possible explanations for magnetic destabilization of water dispersions it is well known that dispersed particles are essentially electrically charged on their surfaces even at very low solution concentration of electrolytes due to both the dissociation of the solid surface in contact with water molecules, and the selective adsorption of electrolytes from bulk solution. the ions which are adsorbed on stllid surfaces are named co -ions. in the surrounding water layer, so called counter~ions are concentrated for the neutralization of the charged solid surface. the double electrical layer theory (voyutski (1), 1979; hunter {8), 1996) describes the concentration distribution of counter ions and adherent electrical porendals, as is shown in fig. 1. the neutralization layer consists of two layers: the stern layer the first. thin and condensed layer due to the strong electrostatic and adsorption a~ttactions of counter ions to sotid surface. and of the gouv chapman layer the second. '1.\ider and scanered l~yer due to l\uker electrostatic aruactions and the thermal motion of the ions. the distribution of counter ions in the slern layer is quantitatively siml!ar to langmuir adsorption (represented by equation (4). whilst the disttibution in the oouy chapman layer is determined by the boltzmann equation (5). the electrical potential as a function of distance to solid surface (equation (6) is derived from the poisson equation (8) together with equation (5). parameters in these equations are defined in the nomenclature. . (3) c"" +exp((8± ±zf<p8 )/ rt) (4) c+ = c"" exp(± zf<p i rt) (5) tanh(zf<p) = tanb(zf(/js )exp(-k(x-8)) (6) 4rt 4rt . ?~ 2 2f"-'z; ci= k = 11---'~--rtc (7) characteristic parameters of dispersion stability are <p0 electrical potential on the stem border and k debye ruckel parameter. namely, in most stable dispersions, the failure of particle collisions due to electrostatic repulsion in an overlapped electric layer, is responsible for very slow coagulation. the more condensed and thinner the layer is, the more particles are neutralized and able to aggregate. the electrical potential of the stem layer <p0 depends on its composition, which is specific for each solution i dispersion system. a determination of the precise (/1 0 value is difficult. usually, the empirical parameter t;­ electrokinetical potential of slipping plane, is taken as an approximation for <p0 .. the possible mechanism for magnetic destabilization could be predicted by measuring electrical conductivity, ph and cpotential. theoretical possibilities are schematically shown in fig. 2. alternatively, the abundant precipitation of aragonite could be explained by lorentz ion shifts, which have an influence on the value of ko and on the concentration of crystal forming ions at the growing surface. surfaces of cac03 particles in natural waters, which are commonly neutral or slightly acid, are charged positively. therefore, ca.2+ ions could be considered as co ions. table l shows that shifts of ca2+ are by a factor of 3.8 longer than the hc03-, which drastically ~ten the relativ~ concentrations of crystal forming mns on the growing surface and accelerates the caco3 growth according to eq. (9). table i lorentz ion shifts and relaxation times at bv ;: 0,2 vim and -r = 0, i s for some ions at room temperature i na+ mg2+ ca2+ hc03 sol r;(i0-10m) 0.95 0.65 0.99 1.85 2.3 z; +1 +2 +2 -1 -2 l1x;(nm) 1.8 5.3 3.4 0.9 1.5 threshold inhibitors (i.e.mg2+, fe2+, zn2+) of the calcite growth have smaller radii than ca2+. their incorporation into active calcite sites and their more intensive hydration than ca2+ions retards the calcite growth and gives priority to the aragonite growth. this is more favourable from the viewpoint of hard scale prevention due to its lower adhesivety. table 1 shows that shifts of mg2+ are by a factor of 1.5 longer than that of ca2+. this leads to a concentration rise of mg2+ ions on the growing surface, lowers the value of ko in eq.(9) for calcite and gives priority to the aragonite formation. conclusion the key to mwt effectiveness in hard scale prevention is the forming of modified large crystals, which in supersaturation conditions serve as a basis for scale precipitation in a suspended form. the mwt mechanism could be considered as complex, strongly linked with the presence of solid surfaces and consisting of several phenomena. the modified hydration could essentially affect water dispersions and solutions even under static magnetic treatment. however, the most successful mwt devices are of the dynamic type (with the flowing of supplied water through static or pulsated magnetic fields) where the lorentz effect on solid surfaces could become more noticeable and prevail under the effects of hydration. symbols magnetic field density, v stm2 i counter ion concentration in bulk solution, moifm3 electrical charge, as electron charge= 1,6·10-19 as activation energy for dehydration of crystal -forming ions, j/mol factor of ionic strength i, dimensionless faraday constant= 9,6·lo4aslmol lorentz force, n empiric parameter of water impurities, m/smol solubility product of cac03, mot2/m6 r; r s t t z; ion radius , m general gas constant= 8,3j/molk crystal surface, m2 time, s absolute temperature, k radial coordinate, m lorentz shift of ion, m i ion valence, dimensionless greek symbols t: dielectric constant of fluid, as/vm 1] water viscosity, nstm2 (jj electrical potential, v qj 0 (jj on solid surface (x = 0), v (jj 8 (jj on stern border (x :::: 8), v 13 k debyehiickel parameter, defined by (6), lim e adsorption energy, j/mol cj' surface electric charge density, as/m2 -r retention time of dispersion in channel of mwt device, s !; electrokinetical potential at slipping plane {;v; =a), v reference 1. donaldson j.d.: "magnetic treatment of fluids­ preventing scale"; hdl symposia at the universities of york and aston, january 1988, new scientist, p. 117, (1988). 2. klassen v.i.: "magnetic treatment of water in mineral processing"; developments in mineral processing part b, mineral processing, pp. 1077~ 1097, (1981). 3. hibben s.g.:"magnetic treatment of water"; national technical information service, no. 16224, (1973). 4. grutsch j. f.: usa/ussr symposium on physical~mechanical treatment of wastewaters p. 44, epa~ cincinati, (1977}. alternatively, the abundant precipitation of aragonite could be explained by lorentz ion shifts, which have an influence on the value of ko and on the concentration of crystal forming ions at the growing surface. surfaces of cac03 particles in natural waters, which are commonly neutral or slightly acid, are charged positively, therefore, ca2+ ions could be considered as co ions. table 1 shows that shi'fts of ca2+ are by a factor of 3.8 longer than the hco:[. which drastically alters the relative concentrations of crystal forming ions on the growing surface and accelerates the cac03 growth according to eq. (9). 14 table 1 lorentz ion shifts and relaxation times at bv == 0,2 vim and -r = 0,1 s for some ions at room temperature 1 na+ mg2+ ca2+ hc03 sol r; (10-10m) 0.95 0.65 0.99 1.85 2.3 z; +1 +2 +2 -1 -2 ax;(nm) · 1.8 5.3 3.4 0.9 1.5 threshold inhibitors (i.e.mg2+, fe2+, zn2+) of the calcite growth have smaller radii than ca2+. their incorporation into active calcite sites and their more intensive hydration than ca2+ions retards the calcite growth and gives priority to the aragonite growth. this is more favourable from the viewpoint of hard scale prevention due to its lower adhesivety. table 1 shows that shifts of mg2+ are by a factor of 1.5 longer than that of ca2+. this leads to a concentration rise of mg2+ ions on the growing surface, lowers the value of ko in eq.(9) for calcite and gives priority to the aragonite formation. conclusion the key to mwt effectiveness in hard scale prevention is the forming of modified large crystals, which in supersaturation conditions serve as a basis for scale precipitation in a suspended form. the mwt mechanism could be considered as complex, strongly linked with the presence of solid surfaces and consisting of several phenomena. the modified hydration could essentially affect water dispersions and solutions even under static magnetic treatment. however, the most successful mwt devices are of the dynamic type (with the flowing of supplied water through static or pulsated magnetic fields) where the lorentz effect on solid surfaces could become more noticeable and prevail under the effects of hydration. b symbols magnetic field density, vsfm2 i counter ion concentration in bulk solution, mo1jm3 electrical charge, as electron charge = 1 ,6·1 o-19 as activation energy for dehydration of crystal -forming ions, j/mol factor of ionic strength -1, dimensionless faraday constant= 9,6·1o4 as/mol lorentz force, n empiric parameter of water impurities, rnlsmol ks solubility product of cac03, mol2jm6 r; r s t t z; ion radius , m general gas constant== 8,31/molk crystal surface, m2 time, s absolute temperature, k radial coordinate, m lorentz shift of ion, m i ion valence, dimensionless greek symbols s dielectric constant of fluid, asnm 1] water viscosity, nsfm2 qj electrical potential, v ({j 0 qj on solid surface (x == 0), v (/j 0 (/jon stern border (x = 8), v k debye -ruckel parameter, defined by (6), lim e adsorption energy, j/mol a surface electric charge density, asfm2 -r retention time of dispersion in channel of mwt device, s s electrokinetical potential at slipping plane (x = ll), v reference 5. donaldson j.d.: "magnetic treatment of fluids­ preventing scale"; hdl symposia at the universities of york and aston, january 1988, new scientist, p. 117, (1988). 6. klassenv. i.: "magnetic treatment of water in mineral processing"; developments in mineral processing :part b, mineral processing, pp. 10771097, (1981). 7. hmben s.g.:"magnetic treatment of water"; national technical information service, no. 16224, (1973). 8. grutsch j. f.: usa/ussr symposium on physical-mechanical treatment of wastewaters p. 44, epacincinati, (1977). 9. llpus l. and krope j.: ''modified scale crystallization in mag~etic water treatment"; the international congress of sithok, maribor, no.4, pp40-41, (2000). 10. llpus l., krope j. and garbai l.: " magnetic water treatment for scale prevention"; hung. j. ind. chern. 1998, 26, 109 11. voydtski s.: "colloid chemistry"; mir publisher moscow, (1978). 12. hunter r. j.: "introduction to modern colloid science"; oxford science publications, new york, (1996). 13. tombacz e., ma c., busch k.w. and busch m.a.:coll. poly. sci. 1971, 269,278 14. higashitani k., okuhara k. and hatade s.: j. coll. interface sci. 1992, 1, 152 15. higashitanik. and oshitanij.: trans i. chern. e, 1997, 75, 115 16. grimes s.m.: "magnetic field effect on crystals"; tube international, march (1988). 17. 18. 19. 20. 15 higashitani k., kage a., katamura s., lmaik. andhatades.: j. coll. interface sci.1993, 156, 90 nancollas g. h. and reddy m. m.: "crystal growth kinetics of minerals encountered in water treatment processes"; -environmental chemistry of metals, new york, (1974). nielsen a. e.: pureappl. chem.1981, 53,2025 klassen v.i.: "magnetization of water systems"; himija, moscow, (1982). page 14 page 15 page 16 page 17 page 18 hungarian journal of industry and chemistry vol. 50 pp. 1–5 (2022) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2022-01 antioxidant effect of humic substances from hungarian leonardite attila csicsor*1,2 and etelka tombácz1,3 1doctoral school of environmental sciences, university of szeged, rerrich béla tér 1, szeged, 6720, hungary 2hymato products kft., kossuth lajos u. 33, szentkirályszabadja, 8225, hungary 3soós ernő water technology research and development center, university of pannonia, zrínyi miklós u. 18, nagykanizsa, 8800, hungary humic substances are natural substances that are continuously formed from the decay of plant residues. these materials have a very diverse range of properties, making them versatile. according to many new studies, these humic substances also exhibit antioxidant propensities. the aim of this paper was to shed light on whether humic substances really have antioxidant properties. keywords: humic substances, humic acid, fulvic acid, himatomelanic acid, antioxidant, leonardite 1. introduction the majority of the population of hungary suffers from one of the diseases associated with free radicals, e.g. diseases of civilization, obesity, cardiovascular disease, malignant neoplasms, etc. although it is well-known that our consumption of vegetables and fruit lags far behind those of the other member states of the european union, it has been scientifically proven that essential fresh vitamins and provitamins as well as minerals are fundamental not only for the smooth functioning of the body but also for their antioxidant components. furthermore, they can play a key role in terms of disease prevention. berries have become a major player in a number of related research papers as they are also essential in the prevention as well as aftercare of cancer and cardiovascular disease. what other options are available and what other substances may still have high antioxidant contents? based on the aforementioned points, it is also important and justified to study the antioxidant properties of new compounds such as humic substances and determine which of their components play a crucial role in the development of their antioxidant effect, both qualitatively and quantitatively. the aim of this research is to compare the antioxidant properties of humic acids with already wellknown natural antioxidants. firstly, different humic acid recieved: 26 august 2021; revised: 16 september 2021; accepted: 20 september 2021 *correspondence: csicsor.attila@gmail.com fractions were prepared. the expected results should help to more accurately interpret the complex behavior of humic acids, thereby helping to expand their range of applications. therefore, if the results are convincing, this could open up new fields with regard to the application of humic acids in the food and cosmetics industries [1]. 2. humic substances humic substances are a group of naturally occurring macromolecules found throughout nature, that is, in soil, air, water, carbon deposits and peat. chemically illdefined humic substances are natural organic colloids comprised of decomposition products of plant-derived biomass as the result of a process called humification. their conversion into stabilized humic material is one of the most complex and least understood biogeochemical processes of the carbon cycle. most natural humic acids (ha) are found in older peat, lignite and juvenile lignite. in hungary, the ha content of the so-called leonardite, a famous source of ha, is close to 70% in its natural form. (a near-surface deposit of leonardite is located in dudar, where this geological formation can be mined). in the humification process, dead plant matter that enters the soil is broken down by enzymes found in soil bacteria and fungi, so simple compounds like sugar and ammonia are formed from carbohydrates, fats, proteins and lignin, which on the one hand serve as a source of food for the soil microbes but on the other hand as a source in the formation of humic substances. as a result of biotic and abiotic (condensation and polymerization) processes, https://doi.org/10.33927/hjic-2022-01 mailto:csicsor.attila@gmail.com 2 csicsor and tombácz the decomposition products form high-molecular-weight humus compounds, the presence of which is characteristic of the soil [2]. on the basis of differences in solubility, humic substances can be divided into several groups such as the main fractions humin, ha, and fulvic acids (fa), as well as the alcohol soluble himatomelanic acids (hy). they are a mixture of similarly behaving, yellow-brown-black, acidic, high-molecular, natural organic substances that are operationally defined. humic substances themselves contain too many kinds of molecules that can be separated by changing the solubility conditions. even though these molecules behave similarly, each fraction has different properties and their molecular structure is not uniform [2]. the nomenclature of fractions that can be separated according to their solubility is suggested in the guidelines of the international humic substances society (ihss): • humin a black fraction of humic substances that is insoluble in water at any ph. • humic acids the fraction of humic substances that is insoluble in water under acidic conditions (ph < 2) but soluble in water at higher ph values. they can be extracted by various alkaline solutions before being precipitated by a strong acid and are dark brown or black in color. • fulvic acids the fraction of humic substances that is soluble in water at all ph values. fulvic acids are light yellow or yellowish brown in color. • himatomelanic acids the fraction of humic substances that is soluble in an alcohol. 3. antioxidants the most important physiological role of antioxidants is to neutralize the free radicals that are continuously formed in the szent-györgyi-krebs cycle and counteract the free radicals with different oxidizing forces that enter the body. an antioxidant is a substance that inhibits oxidation, more broadly speaking, retards or hinders oxidation. they are chemically reducing agents, i.e. electron donors. these materials are usually organic compounds but include metals and organometallic complexes. many different types of antioxidants exist, which usually work together and do not neutralize free radicals on their own. although our body itself is able to produce some antioxidants, sometimes it is necessary for us to ingest these substances from external sources. together, these antioxidants already form a very strong line of defence in our body, e.g. vitamin c, vitamin a, flavonoids, glutathione, resveratrol, unsaturated fatty acids, etc. [3, 4] 4. methods for measuring the antioxidant capacity the antioxidant capacity is the combined free radical scavenging effect of all antioxidant compounds in the system studied. since the need for its accurate numerical determination is growing, a number of analytical procedures and measurement systems have been developed. given that methodologies are constantly being modified and refined, nowadays, the number of applied methods exceeds one hundred. in the literature, the majority of studies use several methods to determine the antioxidant capacity [5]. the most common methods of measuring the antioxidant capacity can be divided into two main groups: electron transition-based ones (ferric iron reducing antioxidant power, total polyphenol content, copper ion reducing antioxidant capacity, trolox equivalent antioxidant capacity, and 2,2-diphenyl-1-picrylhydrazyl (dpph)) as well as those based on hydrogen atom transfer (oxygen radical absorptance capacity, total peroxyl radical-trapping potential, chemiluminescence-based methods, and photochemiluminescence measurements just to mention the most commonly used methods). although these two types of measurements determine the antioxidant capacity, the results obtained do not necessarily have to be correlated with each other, since the reducing power of a sample is not necessarily related to its ability to scavenge for the reaction of test compounds. electron transfer reactions involve colour changes, from which the antioxidant capacity can be deduced. the essence of these methods is to create a free radical as the result of a reaction. to this free radical, the antioxidant is added at various dilutions leading to a colour change, which is monitored by a spectrophotometer and then the antioxidant capacity of the test substance is calculated from the results obtained. methods involving hydrogen atom transfer are based on the kinetics of the reaction. tests measure how effective a sample is against a given free radical, namely its free radical scavenging capacity [5]. 5. antioxidant effect of humic substances the question may arise as to why humic substances would exhibit an antioxidant effect. humic acids are chemically very complex mixtures of composite molecules, that is, natural polymers formed during the varying degrees of polymerization of basic building blocks. according to their chemical structure, they are polyhydroxy carboxylic acids with quinone and semiquinone groups. in some respects, they are similar to flavonoids and phenols, in which the so-called flavone skeleton is polysubstituted by hydroxy groups. however, they also have a quinoid structure that is known to be responsible for antioxidant properties. these properties of ha have already been demonstrated in a number of scientific publications by both classical analytical methods (redox titrations) and instrumental analytical measurements (electron spin resonance) [6]. the general structure of ha and the formulae of some well-known antioxidants are presented in fig. 1 from hungarian journal of industry and chemistry antioxidant effect of humic substances 3 figure 1: model structure of ha and identical moieties of known antioxidants [2] their structure, it is clear that ha are comprised of a number of groups such as already well-known antioxidants, so will exhibit exceptionally high antioxidant capacities [7]. 6. results 6.1 measurement of total phenolic content all measurements of total phenolic content were made according to the method developed by shetty et al. [8]. during these measurements, only high-quality (a.r.) chemicals were used. the fractions of humic substances were extracted by ourselves from samples of leonardite retrieved from dudar. rather than indirectly measuring the antioxidant property of the sample, the method measures its total phenolic content, from which its antioxidant capacity can be deduced. the method consisted of diluting 1 ml of the sample in 5 ml of distilled water and 1 ml of 95% ethanol in a test tube before adding 0.5 ml of 50% folin-ciocalteu (fc) reagent (half of distilled water in half fc reagents) to each sample. after being stirred for 5 minutes, 1 ml of 5% na2co3 was added to the reaction mixture and allowed to stand for 1 hour before the absorbance values of the samples were measured at 725 nm. these absorbance values were then converted into µg gallic acid equivalents in order to compare the measured values with each other and with other data from the literature. whilst measuring the total phenolic content of the samples, a series of dilutions was made from our samples of known mass, for which the total phenolic content was measured. a series of dilutions had to be produced in order to measure an absorbance value of approximately one for each sample. this was necessary to be able to compare the samples because the three different fractions yielded one absorbance value at different concentrations once the reaction was complete. furthermore, since the samples are coloured (brownish dark brown), the measured absorbance values had to be calibrated in light of the background of the samples. therefore, the samples were diluted to the concentration present in the reaction volume. after measuring the series of samples, their total phenolic content was calculated from the calibration curve, which can be seen in fig. 2, and the results obtained are shown in table 1. the results show that different initial concentrations of the various samples are required to achieve a similar absorbance. in the humic acid samples, since the majority of the phenol groups are in this fraction, the lowest initial concentration is required to achieve an absorbance of approximately one. himatomelanic acid has an average number of phenol groups while fa is comprised of the figure 2: calibration curve of gallic acid 50 pp. 1–5 (2022) 4 csicsor and tombácz table 1: the measured and corrected absorbance of the samples and the gallic acid equivalent (gae) values sample corrected concentration [mg/ml] abs measured abs corrected gae [mg/ml] from the calibration curve gae [mg/g] hy 0.59 1.027 0.953 0.103 174.5 fa 1.18 0.999 0.948 0.102 86.8 ha 0.35 1.024 1.024 0.11 310.3 ihss fa 0.684 1 0.107 156.8 ihss ha 0.212 1 0.107 506.1 table 2: the ic50 readings of the different samples name of the sample original concentration ic50 [µg/ml] hy 1.5 mg/ml 200 fa 2 mg/ml 300 ha 3.25 mg/ml 460 fewest. the results suggest that the studied humic fractions are likely to exhibit an antioxidant effect. 6.2 dpph method measurement of the antioxidant capacity based on stable dpph radical scavenging is one of the first methods. the reaction proceeds as follows: the dark purple radical formed in the reaction mixture loses its colour when it reacts with antioxidants. this method is widely used because the radicalforming molecule dpph is commercially available, stable as well as not particularly reactive nor aggressive, which is beneficial in the reactions that take place as taking measurements is simple. on the other hand, a stable radical that is not found in the living organism is used instead of a radical formed during the normal metabolism in the cell. using this method, it is not possible to estimate how effective the sample is as an antioxidant with regard to biological radicals [8]. during the measurements, 6 ml of a dpph working solution (0.1 mg/ml) was added to one ml of the sample, vortexed and stored in the dark for 30 minutes until the colour reaction began. after 30 minutes, the absorbances were measured at 517 nm. from the measured values that had previously been corrected, the percentage of inhibition (inhibition%, inhib.%) and the value corresponding to 50% inhibition (ic50 value) were calculated. while the measurements were taken, in the same way as when the total phenolic content was measured, a series of dilutions was made from a sample of known concentration. from the measured absorbances, after background correction the percentages of inhibition of the samples were calculated and plotted as a function of the concentration in order to determine the ic50 values of the samples (fig. 3). from the data, it can be concluded that the materials prepared and tested exhibit antioxidant properties because they inhibit the decomposition of the dpph radical. figure 3: percentage of inhibition of himatomelanic acid (top), humic acid (middle), and fa (bottom) as functions of the concentration to determine the ic50 values their ic50 values (table 2) are promising and comparable with other data in the literature [9]. 7. conclusions although the results revealed that the samples made from domestic raw materials exhibit antioxidant properties, further studies are needed to gain a complete picture of the antioxidant capacity of these substances. furthermore, in the future, it is our intention to confirm the results collected so far with in-vitro and in-vivo experiments. hungarian journal of industry and chemistry antioxidant effect of humic substances 5 references [1] balogh, e.; hegedus, a.; stefanovits-banyai, e.: application of and correlation among antioxidant and antiradical assays for characterizing antioxidant capacity of berries sci. hortic., 2010, 125(3), 332– 336 doi: 10.1016/j.scienta.2010.04.015 [2] stevenson, f.j.: humus chemistry: genesis, composition, reactions (wiley & sons, new york, usa) 1994, pp. 188–210 isbn: 978-0-471-59474-1 [3] nccih: antioxidants: in depth, retrieved 20 june 2018 https://www.nccih.nih.gov/health/antioxidants-in-depth [4] škvára, p.; kezmanová, j.; mišl’anová, c.; vojs staňová, a.: analysis and identification of polyphenolic compounds in green foods using a combination of hplc-esi-it-tof-ms/ms hung. j. ind. chem., 2018 46(1), 35–38 doi: https://doi.org/10.1515/hjic-2018-0008 [5] huang, d.; ou, b.; prior, r.l.: the chemistry behind antioxidant capacity assays j. agric. food chem., 2015, 53(6), 1841–1856 doi: 10.1021/jf030723c [6] csicsor, j.; gerse, j.; tikos, a.: the biostimulant effect of different humic substance fractions on seed germination, in: humic substances in the global environment and implications on human health, n. senesi and t. m. miano (eds.) pp. 557–562; proc. 6th intern. meeting of the intern. humic substances soc., monopoli, bari, italy, sept. 20–25, 1994 [7] ponomarenko, e.v.; anderson, d.w.: importance of charred organic matter in black chernozem soils of saskatchewan can. j. soil sci., 2001, 81(3), 285– 297 doi: 10.4141/s00-075 [8] vattem, d.a.; shetty, k.: ellagic acid production and phenolic antioxidant activity in cranberry pomace (vaccinium macrocarpon) mediated by lentinus edodes using a solid-state system process biochem., 2003, 39(3), 367–379 doi: 10.1016/s00329592(03)00089-x [9] ruiz-torralba, a.; guerra-hernández, e.j.; garcíavillanova, b.: antioxidant capacity, polyphenol content and contribution to dietary intake of 52 fruits sold in spain. cyta journal of food, 2018, 16(1), 1131-1138 doi: 10.1080/19476337.2018.1517828 50 pp. 1–5 (2022) https://doi.org/10.1016/j.scienta.2010.04.015 https://www.nccih.nih.gov/health/antioxidants-in-depth https://doi.org/https://doi.org/10.1515/hjic-2018-0008 https://doi.org/https://doi.org/10.1515/hjic-2018-0008 https://doi.org/10.1021/jf030723c https://doi.org/10.1021/jf030723c https://doi.org/10.4141/s00-075 https://doi.org/10.1016/s0032-9592(03)00089-x https://doi.org/10.1016/s0032-9592(03)00089-x https://doi.org/10.1080/19476337.2018.1517828 introduction humic substances antioxidants methods for measuring the antioxidant capacity antioxidant effect of humic substances results measurement of total phenolic content dpph method conclusions conferenceproceed~gs hungarian journal of ~ustrial chemistry veszprem vol. 2. pp. 4447 (2000) advantages and disadvantages of different sampling techniques for sampling volatile organic hydrocarbons in air · . rtolnai\ a. gelencser2 , h. pr0mke3 , d. m6ller 3 , h. becker\ m. dostler 4 , . . j. hlavay 1 and e. meszaros 1 · · (depart~ent of earth and environmental sciences, university ofveszprem, p.o. box 158, veszprem, h-8201, . hungary 2 air chemistry group of the hungarian academy of sciences, p .0. box 158, veszprem, h-8201, hungary 3 chair. for atmospheric chemistry and air quality, brandenburg university of technology, berlin, d-12489, germany 4 central analytical laboratory, brandenburg university of technology, cottbus, d-03044, germany) this paper was presented at the second futemational conference on environmental engineering, university ofveszprem, veszprem, hungary, may 29june 5, 1999 the sampling and analysis of volatile organic compounds (voc) in air are a great challenge. air is a matrix very difficult to handle, the pollutants are usually present at very low concentration, so their detection and quantitation require precise sampling, sample preparation, analysis and data evaluation. voc air samples are almost never sufficiently concentrated to be directly introduced into a capillary gc system via a standard gas-sampling valve. the respective advantages and limitations of these different sampling methods will be reviewed. the observations are based on the results of two sampling campaign, nainely in february-may 1998, in veszprem, where diffusive samplers were used for the determination of btex compounds, and july-august 1998, in berlin (germany), where pumped sorbent tubes, passivated canisters and on-line air stream samplers were used for the determination of 54 voc compounds. voc measurements contribute to improving our current understanding and will help to clarify what if any remedial action is required. keywords: volatile organic compounds; diffusive sampling; gas chromatography introduction environmental air pollution largely remains a series of unanswered questions: what pollutants are present? at what concentration? where are they coming from?. what harm do they do? reliable answers to these questions can only be obtained by improving the quality and quantity of air monitoring data collected. today, a wide range of gc compatible air sampling techniques is available. these include pumped sorbent tubes, passivated canisters, diffusive samplers, semi­ continuous on-line air stream sampling. a vast number of voc concentration measurement and pollution source emission profiles are required before the fate of pollutants in the atmosphere is understood and before the extent and potential hazard of manmade pollution can be correctly assessed. a large variety of volatile organic compounds (voc) have been identified recently in ambient air. many of them have the potential to cause a variety of adverse health effects. these include aliphatic and aromatic hydrocarbons, chlorinated hydrocarbons and various ketones and aldehydes [l]. some of these have been suggested as possible carcinogens, such as benzene and 1,1,1-trichloroethane [2]. vocs in the atmosphere play an important role in the formation and transformation of atmospheric oxidants [3-5]. understanding the role of voc requires sound analytical methods for the quantification of these compounds in air in order to locate the major sources of air contamination. these include sample collection and storage, separation of vocs of interest, and detection and identification. hydrocarbons are generally released from anthropogenic sources, vegetation, soils, and oceans, as shown in table 1. in cities anthropogenic sources predominate. major sources are vehicular exhaust, gasoline evaporation and spillage, leakage of natural gas, emission from petrochemical manufacturing plants and refineries, and chemical solvents f6j. in the industrialized counties, the contribution of biomass burning to the total anthropogenic emissions is table i hydrocarbons emitted from anthropogenic and biogenic sources to the air [6] source combustion and chemical industry natural gas organic solvents biomass burning foliage emission grasslands soil ocean waters oceans emission (tg year·!) type of hydrocarbons anthropogenic sources 36 mainly alkanes, alkenes and aromatic hydrocarbons 5 mainly light alkanes 15 higher alkanes and aromatic compounds 40 mainly light alkanes and alkenes biogenic sources 830 mainly isoprene and monoterpenes, some alkenes and alkanes terpenes 4 7 light alkanes and higher hydrocarbons <3 mainly ethene 6-10 light alkanes and alkenes <26 c9-c28 alkanes comparatively minor. in tropics, however, the practices of slash, burn, and shift agriculture, in addition to deforestation, make biomass burning a major source of hydrocarbons at least during the preferred dry season of the year. went [7] pioneered the idea that plants may release substantial amounts of hydrocarbons to the atmosphere, partly by volatilization of essential oils. it appears that isoprene is the predominant hydrocarbons emitted from forest species such as oak, poplar, sycamore, willow, cottonwood and eucalyptus, whereas many other plants, especially conifers, emit primarily monoterpenes. the emission rate from grasslands is small compared with~ that for hydrocarbons released from foliage, but it is competitive with anthropogenic emissions. finally, one must consider the ocean as a source of non-methane hydrocarbons. lamdntage et al. [8] have reported that ethane, propane, ethene and propene occur dissolved in marine surface waters with concentration exceeding those expected if the gases were in equilibrium with atmospheric concentration. for certain ocean areas the fluxes can be estimated. the atmosphere above the ocean contains c9-c-28 n-alkanes in addition to low-weigh hydrocarbons [9]. different sampling techniques for sampling volatile organic hydrocarbons iu air whole air sampling whole air sampling procedures, using passivated stainless steel canisters, tedlar bags or some other suitable container, have been developed primarily for apolar species ranging in volatility from acetylene to trichlorobenzene. passivated stainless steel canisters, in particular, have been extensively evaluated in the us for "air taxies" and c2-c9 hydrocarbons. during analysis an aliquot of canister air is drawn into the focusing trap using a pump and mass flow controller. canisters and bags offer advantages for sampling very 45 volatile components which cannot be quantitatively retained on conventional sorbents at ambient temperature and also benefit from low artifact interferences provided the contain~rs are well cleaned. however, canisters are expensive to buy and transport, and can be difficult to clean once contaminated. specific conditions in terms of temperature, humidity and pressure are also required for the air inside the canister if the full range of target analytes is to be monitored without joss of high boilers. collecting .grab samples or air using canister is simply achieved by opening a valve on ·an evacuated canister and closing it again once the pressure inside approaches atmospheric. however, the collection of time weighted average sample requires relative complex apparatus, which can be difficult to assemble and operate in the field. most canister methods also specify that only a relatively small air sample volume should be transferred from the canister to the gc analytical system and this limits the sensitivity of the method. air sampling using sorbent tubes sorbent tubes provide a much lower cost, more practical and more versatile alternative to canisters or other containers for most voc air monitoring applications. they are not suitable for collecting ultra volatile components such as c2 hydrocarbons at ambient temperature, but are compatible with both apolar and polar compounds and offer quantitative retention of organics ranging in volatility from c3 hydrocarbons. some inorganic vapors such as n20 and cs2 can also be quantitatively collected at ambient temperature. other advantages include the collection of several liter air sampling if required that the sample tubes are clean and ready for immediate reuse at least 10 times before the sorbent needs replacing. one limitation of sample tubes is that artifacts from the sorbent material may interfere with component analysis unless strict conditioning and storage procedures are applied. active sampling air is usually pumped into one or more sorbent tubes using a personal monitoring pnmp. several replicate samples may be collected in parallel using constant flow type pumps in instances where a repeat analysis capability is essential. the direction of the gas flow ,is always reversed during thermal desorption so that the higher boiling compounds are backflushed easily from the sampling end of the tube. if the target analytes cover a wide volatility range, tubes may be packed with series of sorbents of increasing strength. diffusive sampling diffusive sampling has long been available as an alternative to active sampling in occupational hygiene to 46 determine the concentrations of toxic volatile organic compounds in workplace air. nowadays, this technique is widely used in environmental monitoring. diffusive sampling has many advantages including increased sampling time, simplicity and lower unit sample cost. in this method volatile organic compounds are taken up by an adsorbent from the air at the rate controlled by diffusion. this is most suited to monitoring individual organic compounds or a narrow volatility range of components as only one sorbent can be used at any one time. several different monitors may be worn or placed simultaneously if required. the relatively slow sampling rate restricts detection limits around 1-10 ppb for normal 24 h sampling period. long term (3-28 days) diffusive sampling times are currently under evaluation and may be used for the ppt detection limits. on-line air stream sampling semi-continuous on-line air sampling and gc analysis . is a relatively new technique with applications ranging from urban air quality testing to occupational hygiene. the procedure involves a volume of air being pumped directly into the focusing trap via an inert mass flow controller. after sample collection, the trap heats rapidly, transfers the sample to the gc analytical column and initiates the gc separation. as soon as the trap recools the system is ready to collect the next sample. the chromatographic analysis of the previous sample continues while the next sample is collected. experimental section sampling, instrumentation, operating parameters, procedures between february and may 1998, samples were taken in veszprem by diffusive sampling with standard perkin-elmer sample tubes (a = 0.2 cm2 ; l = 1.5 em) filled with 250 mg of tenax ta adsorbent for the determination of btex (benzene, toluene, ethyl­ benzene, m,p-xylene) compounds. the sampling sites were selected to cover a range of sampling locations from heavily polluted downtown areas to less polluted urban locations. the locations were· as follows (in the order of decreasing level of pollution): site a. in the downtown of veszprem, a medium-sized town in the northwestern part of hungary, near a busy crossroads, 5 m above ground level. sit~ b. in the suburb of veszprem, with moderate urban traffic, 5 m above ground level. site c. in a conurban location near veszprem, 5 m above ground level, low level of pollution is expected. at each sampling site three of each type of adsorbent tube.c; were applied simultaneously. samples were analysed with a gas chromatograph coupled to a perkin elmer atd 400 automatic thermal desorber. gas chromatograph: gc 6000 vega series 2, column spb-1, 15 m, 0.53 mm i.d., film 1.5 ij.m. an ibm compatible pc was used for data acquisition and processing. in july and august 1998, air samples were collected over berlin (germany) on board of an airplane using stainless steel canisters v = 800 cm3 , p = 3 bars. the samples were analysed in two ways: 1. directly introducing the sample into a gc-ms-fid system using cryogenic focusing, and 2. trapping the components on solid adsorbent which was followed by thermal desorption, cryogenic enrichment and gc-ms analysis. both sampling techniques are suitable for detecting very low concentrations of volatile organic compounds. system 1: the collected samples were analysed directly from the canister by a gas chromatograph: fisons instruments gc 8000 series, column db-1, 60 m, 0.25 rum i.d., film 1.50 ij.m, coupled with an md800 mass spectrometer and fid. system 2: three different adsorbents were used in a multilayer-bed tube for trapping the vos's: carbotrap c 20/40 mesh (for relative high molecular weight airborne contaminants), carbotrap 20/40 mesh (for c5c9 compounds) and carbosieve sill 60/80 mesh (for small airborne molecules such as c2 hydrocarbons). samples were analysed with a gas chromatograph coupled to a ama system da816/ka-d4 automatic thermal desorber: focuser temperature: -80 oc (2 min), desorption: 300 °c for 5 inin, injection to gc focuser: 250 oc for 2 min, conditioning: tubes: 350 oc for 20 min, focuser: 250 °c for 20 min. quartz tube: 15 em, 6 mm o.d., 4 mm i.d. were used in the analysis. gas chromatograph: fisons instruments gc 8000 series, column permabond ov-624-df, 50 m, 0.25 mm i.d., film 1.40 !j.m. vg-quattro fisons instruments triple quadrupole mass spectrometer 4000, ei+, electron energy 70 ev, scan range 22-350 amu (atomic mass unit), scan time 1.0 s, tranferline temperature 150 °c, source temperature 150 °c, acquisition time 41 min, tune reference compound is heptacosa (perfluoro­ tributyl-amine). the carrier gas was helium (linde 4.6), flow rate 1 cm3 min-1 • all-pure gas specific purifier module and helium purifier from alltech was used as helium ·purifies. different gas standards were used for making the calibration curves: a: matheson gas products t0-14 enviro-mat ozone precursor cat.#34420 lot#12713 55 compound lppm, b: linde 20 ppb ethane, n-butane, benzene, toluene and c: internal standard 10 ppb dichlormethane-d2, acetone-d6, cyclohexane-d12, benzene-d6, toluene-d8. results and discnssion aromatic hydrocarbons were analysed in veszprem. the samples were collected using diffusive sampling. a few of these results are presented in this paper to illustrate the usefulness of this method (table 2). the concentration of benzene, toluene, ethyl-benzene and table 2 the concentration of btex compounds in different parts of veszprem site a. site b. site c. f;!g:m·3 j;!g:m·3 j;!g:m·3 benzene 5.75±0.15 1.52±0.04 1.09±0.01 toluene 16.72±0.50 5.45±0.15 2.95±0.06 ethyl-benzene 4.01±0.10 1.15±0.03 0.44±0.01 m,p-xylene 13.07±0.41 2.52±0.05 0.97±0.02 table 3 the concentration (c) of volatile organic hydrocarbons found above detection limits over berlin name propene propane i-butane 1-butene 3-methyl-1-butene 2-methylbutane pentane trans-2-pentene isoprene cis-2-pentene 2,2-dimethylbutane 4-methyl-1-pentene cyclopentene 2-methylpentane cyclopentane 3-methylpentane 2-methyl-1-pentene 0.69 hexane 0.04 trans-2-hexene 0.57 cis-2-hexene 1.90 methyl-cyclopentane 0.07 2-methylhexane 0.30 cyclohexane 0.38 3-methyl-hexane 0.12 benzene 0.80 2,2,4trimethylpentane 0.14 heptane 0.45 methylcyclohexane o.q1 2,3,4trimethylpentane 0.16 2-methylheptane 0.16 3-methylheptane 0.14 ethylbenzene 0.28 styrene 0.68 a-pinene ~-pinene 8.30 0.23 0.17 0.37 0.18 1.02 0.24 2.22 0.90 0.74' 0.28 0.13 0.22 0.43 1.37 0.14 3.28 0.57 m,p-xylene was highly variable in the city depending on location. the concentration ranged from 0.44 to 16.72 (lg m3 • the concentration of all the aromatic hydrocarbons was highly correlated with each other (r2 2:: 0.95) which suggests the presence of only one major emission source. this is probably due to the high traffic in veszprem. the benzene: toluene: ethyl-benzene: m,p­ xylene ratios were on average = 1: 3.1: 0.6: 2, respectively. the high toluene/benzene ratio suggests the proximity of traffic emission sources [10]. diffusive sampling is an inexpensive and reliable method for monitoring long term average concentration of hydrocarbons in the environment. the precision of the method has been determined by parallel sampling, and is roughly 3 %. one week sampling period is sufficient to obtain time-weighted average concentrations of aromatic hydrocarbons with a fair degree of accuracy. results are shown in table 2. in july and august 1998, air samples were collected over berlin (germany) on board of an airplane using stainless steel canisters for the determination of 54 vocs. the following advantages of stainless steel canister sampling were established: 1. well-suited for grab sampling of c2-c8 hydrocarbons. the risk for irreversible losses due to wall adsorption increase with increasing boiling point and polarity of the analytes, 2. very low blank levels can be obtained, 47 3. the samples can be stored for several weeks without changes in sample composition. however, the technique has some disadvantages: ~. the bottles are heavy, therefore the transportation is limited, 2. the speciaj inert bottle surface and the clean shut­ off valves makes it rather expensive, 3. the sample may contain significant amount of water, which should be removed before analysis, resulting in evaporative losses of the less volatile (>c8 hydrocarbons) compounds. by trapping the compounds on a solid sorbent, this latter limitation is largely overcome. the concentrations of volatile organic hydrocarbons in a selected sample are given in table 3. different classes of organic compounds were found: alkanes, alkenes, aromatic hydrocarbons and terpenes. the precision of the measurements was ±5 to 20 %. conclusion different sampling techniques are available for the sampling of volatile organic compounds in air. this fact, in itself, indicates that each of them has its field of application. we have shown that each has advantages and limitations but they are not really comparable. the selection of a sampling technique is primarily governed by the objective of the analysis. if long-term time­ weighted average concentrations of vocs are needed for monitoring, diffusive sampling is the only feasible method. sampling aboard an airplane requires instantaneous and more sensitive methods, such as grab sampling. active sampling is probably the most common of all air sampling techniques, 11ow being challenged by diffusive sampling on one side and automated semi-continuous sampling on another. one should remember, however that sampling is only a part of a system on which the quality of the analytical data relies. references 1. johansson i.: atmos. environ., 1978, 12, 1371 2. mm a.l., ghosh t.k., loyalka s.k. and warder r.c. jr.: indoor air quality and control, prentice-hall, englewood cliffs, nj, 1993 · 3. hough a.m and derwent r.g.: atmos. environ., 1987, 21, 2015-2033 4. lopez a., barthomeuf m.o. and huertas m.l.: atmos. environ., 1989,23, 1456-1478 5. mackenzffi a.r., harrison r.m., colbeck i. and hewrrrc.n.: atmos. environ., 1991, 25a, 351-359 6. warneck p.: chemistry of the natural atmosphere, new york, academic press, pp. 223-267, 1988 7. wentf.w.: air pollution, sci. a., 1955, 192,63-72 8. lamontage r.a., swinnerton j. and linnenboom v.j.: tehus, 1974, 26, 7h7 9. eicbmanr., ke'rseridis g., schebeskeg., jaenickbr., hahn j., warneck p. and junge c.: atmos. environ., 1980, 14, 695-703 10. gelencser a., siszler k. and hlavay j.: . environmental science & technology, 1997, 31,2869 page 50 page 51 page 52 page 53 hungarian journal of industry and chemistry vol. 52(2) pp. 47–56 (2024) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2024-18 how to avoid acid corrosion of laminated solar panels by replacing the encapsulant gergely balázs patthy1, márton szigeti2, zsófia závodi-fodor3, mátyás vasáros3 and miklós jakab1* 1 department of materials engineering, research centre for engineering sciences, university of pannonia, egyetem u. 10, veszprém, 8200, hungary 2 research group of corrosion, university of pannonia, egyetem u. 10, veszprém, 8200, hungary 3 corecomm si ltd., lőpor körút 9, veszprém, 8200, hungary solar power is gaining more and more importance in terms of electricity generation worldwide. as the solar industry today is still linear (the majority of the panel waste is not recycled), ensuring a long lifetime of the panels is important. today, the most commonly used encapsulant is ethylene-vinyl acetate (eva), a copolymer prominent since the 1980’s. however, as this material ages, it releases acetic acid, which is highly corrosive. as a result, alternatives to eva are required. in this paper, a prospective alternative, a polyethylene-based elastomer-type foil, namely a polyolefin elastomer (poe), is investigated and compared to eva from a corrosion point of view. firstly, the two raw materials are compared on the basis of their chemical composition and thermal stability. both foils are used to manufacture a batch of standard solar panels, which are then subjected to a standardized climate chamber test. during and after these tests, the power generated by the solar panels is monitored and the state of the wafers examined by an electroluminescence test. furthermore, the effect of the free acetic acid is examined in a corrosion model test, where the subjected wafers are compared in a before-and-after microscopic examination. keywords: solar panels, eva, eva alternatives, solar poe, acetic acid corrosion 1. introduction over recent years, solar power has gained significant importance. according to the international energy agency (iea), the total amount of electricity generated by this means was 825 700 gwh globally in 2020, a 25.8 times increase compared to 2010, where this value was just 32 004 gwh, moreover, further growth is anticipated [1]. because of its growing significance, the reliability and longevity of solar panels must be ensured. the actual lifetime of solar panels, however, is difficult to predict as their ageing and failure modes are not only dependent on the materials used and manufacturing technique but also on the climate as well as where and how they were installed (the latter is not only important from a corrosion and degradation point of view but also in terms of energetics) [2]-[3]. during their lifetime, solar cells must endure the degrading effects of weather such as temperature fluctuations, moisture originating from rain and humidity, uv radiation as well as different mechanical forces such as the wind or snow. these forces degrade the solar panels and eventually lead to their total failure. in a survey conducted by the iea, it received: 6 june 2024; revised: 9 aug 2024; accepted: 9 aug 2024 *correspondence: jakab.miklos@mk.uni-pannon.hu was revealed that the most common failure modes in the climate category ‘moderate’ were potential induced corrosion/degradation (pid for short) and delamination [3]. according to multiple works, pid is a special corrosion phenomenon caused mostly by the polarizing effect of sunlight (but other electrochemical routes are also known). it is a localized corrosion method where conducting ions and the polarizing light induce a current between the wafers and the ground as the cell matrix will have a more negative potential when compared to the ground. the rate of corrosion is dependent on numerous factors, e.g. the potential of the cell measured regarding the ground as well as the structure and materials of the cell [4]-[5]. according to hasan et al., the local negative potential is mainly caused by the free sodium ions, which leave the glass in an ion exchange/glass corrosion mechanism. this local buildup of ions is conductive and because of the severe corrosion it causes the pid irreversibly damages the affected area. this effect is almost always accompanied by delamination, which could originate from the degradation and decomposition of the encapsulant [6]. as an encapsulant, one material stands out in the industry, namely ethylene-vinyl acetate (eva). this https://doi.org/10.33927/hjic-2024-18 mailto:jakab.miklos@mk.uni-pannon.hu patthy, szigeti, závodi-fodor, vasáros and jakab hungarian journal of industry and chemistry 48 copolymer has outstanding qualities: if it is baked correctly in a vacuum furnace, the final product becomes entirely transparent and creates a strong bonding force both with the other base materials and with itself, making it suitable for lamination techniques. as a result, it is suitable as a mechanical coupler as well as an electrical and thermal insulator, while letting light into the wafers [3, 6-7]. these qualities have rendered eva the dominant encapsulating-binding agent in the solar power industry since the 1980’s. however, later studies found mechanisms and qualities that made the use of this material questionable [6, 8-9]. the degradation of the polymer has been described by marín et al., who even described the kinetic model of decomposition. however, only the high-temperature thermal degradation of eva was taken into account, which was observed by thermogravimetric analysis between 530 and 560 k. this revealed a really detrimental mechanism: the main decomposition product of which was found to be acetic acid [10]. later works also investigated the degradation of eva at lower temperatures. under normal operating conditions, the effects of decomposition and corrosion still occur [11]-[13]. decomposition of the eva foil is the result of a thermal and photo-induced series of reactions which can be categorized into two parts: the formation of an organic oxo compound, which is typically an aldehyde or acid, resulting from norrish reactions. the other subcategory consists of the further oxidation of the remaining polymer chain as a result of environmental oxygen, typically the oxidation of polyene. the norrish reactions can be further divided into three subcategories. these reactions are in the form of the uv-induced decomposition of radicals and can be seen in figure 1. in the first norrish reaction, an acetocarbonyl radical leaves the main chain before reacting with another molecule with free hydrogen atoms, leaving behind acetaldehyde, methane, carbon dioxide or carbon monoxide, depending on the other molecule. the second norrish reaction is the most significant one whereby a whole acetic acid molecule leaves the polymer chain resulting in a polyene molecule and acetic acid. this reaction causes the discoloration of eva and a free corrosive to form in the solar panel. the third norrish reaction is very similar to the first, however, the resulting products are acetaldehyde and a ketone [14]-[15]. further oxidation of the polymer chain usually produces α,β-unsaturated carbonyl compounds. after the formation of acetic acid as a result of a second norrish reaction, an oxygen molecule binds to the remaining polymer chain, essentially creating a hydroperoxide. next a water molecule leaves the chain to produce a carbonyl (ketone)-type molecule, resulting in a diluted aqueous solution of acetic acid [15]. the yield of this second norrish reaction can be high. in one experiment, miller et al. found that at higher operating temperatures, more acid is produced, e.g. a 50 mg sample held at 80 °c for 526 days yielded 176 ng of acetic acid [16]. for this reason, other additives, mainly uv absorbers and antioxidants, were introduced in the polymer to enhance its degradation resistance [14]-[15]. despite these efforts, these materials only delayed the degradation of the encapsulant and could not stop the production of acetic acid. as this chemical causes severe corrosion in the solar panel (both direct acidic corrosion and while reacting with the glass as the result of an ion exchange mechanism, pid), other materials are also used in the industry [12-13, 17-18]. most alternative materials for encapsulants, e.g. polyurethanes or epoxy resins, are not used extensively. however, other groups are promising, that is, the so-called thermoplastic polyolefins (tpo) and polyolefin elastomers (poe). these materials can be crosslinking or non-crosslinking, the latter can even eliminate the problems associated with peroxideinduced crosslinking mechanisms. the main goal of this development is to achieve properties as close as possible to those of eva without the negative mechanisms associated with it. moreover, future solar panels should be easier to recycle than those currently produced, as the economic structure of solar panels is currently linear and the aim would be to make them circular [7, 14, 17, 19-20]. one such elastomer is the subject of this paper, which is examined from a corrosion and degradation standpoint. the goal of this article is to compare the degradation and aging effects of the two types of plastic encapsulants. first, the exact composition of the foils is determined. artificial aging of the factory-assembled panels is achieved by treating the cells in a climate chamber which has a standardized temperature curve [21]-[22]. the solar panels were subjected to a handful of measurements to precisely determine the outcome of the treatment. during the research, the effects of acetic acid on the wafers was also investigated to understand the severity and mechanisms of degradation of these components. 2. experimental 2.1. manufacturing process of the examined solar panels the solar panels are made with a laminated object manufacturing technology by our industrial partner. in accordance with the secrecy agreements, the names of the figure 1: the decomposition routes of eva [14] avoiding acid corrosion of laminated solar panels 52(2) pp. 47–56 (2024) 49 products and parameters of lamination are considered insider know-how data and have been omitted from this paper. the main components of the cells are the wafers. these are standard anti-glare monocrystalline silicon solar wafers. with dimensions of 156 mm x 156 mm, they are manufactured in china, one-way doped with phosphorus (n-type) at an illumination level of 1000 w/m2 yielding a power of 5 w at 0.5 v and 10 a. using a laser cutting machine, the wafer is cut into smaller pieces to prevent loss in electrical power as the magnitude of the current is proportional to the surface area of the wafer. to prevent having a negative effect on the depleted zone if cut through, the laser cutter only scratches the surface, the cutting is finished manually. these pieces are then ordered according to polarity and sent to an automatic soldering line, where they are soldered in series, creating the basic unit of electricity generation, the strings. the connecting material is called ribbon, which is sourced from china and is made of a copper wire coated with a lead-based solder consisting of ~60 wt.% tin and ~40 wt.% lead fluxed externally. after this step, the assembly of the solar panel begins by hand on a multi-station production line. these stations are connected by a bosch transfer system. firstly, a glass pane is put into the jig which acts as the main carrier material. it is construction-grade, thermally tempered soda-lime glass manufactured in china. the glass pane is cleaned with isopropyl alcohol manufactured in hungary before the first layer of binding-insulating foil is laid onto it. the foil is often an eva foil sourced from china, that is, a copolymer consisting of 72 wt.% ethylene and 28 wt.% vinyl acetate. poe can also be used here, which is composed of polyethylene and a small amount of polyamide according to the chinese manufacturer’s datasheet. after the layering step, the operators inserted two strips of polytetrafluoroethylene (ptfe) to protect the glass and the foil during the soldering step. the strings are then arranged in accordance with their polarity by a special jig. the strings are fixed in place by applying a small amount of heat to the back of the wafers, making the binding foil adhere to them. the strings are then soldered together with ribbons on one side which contains schottky diodes that isolate the string from the cell matrix while not under a sufficient level of illumination. next a layer of glass foil to ensure that the strings remain still while the lamination process is ongoing, a layer of binding foil and the backsheet are inserted. the backsheet is made of black and whitecolored isotactic polypropylene manufactured in india. after a quick inspection and voltage test, the cell is placed on the conveyor belt of the oil vacuum laminator where it is heated under vacuum for about 600 seconds at ~160 °c. after the treatment, the panel is left to cool down and the excess plastic cut off. the layers and their thicknesses are summarized in table 1. 2.2. testing methods as corrosion resistance is directly related to the materials used in the manufacturing process, examination of both the materials and final solar panel was deemed necessary to obtain both chemical and physical information from the samples and base materials. in order to obtain these data, fourier-transform infrared spectroscopy (ftir), differential scanning calorimetry (dsc), gel content test and energy dispersive x-ray spectroscopy (eds) methods were used. the stability of the binding foil in its final state can be predicted by the gel content test. the product was subjected to a climate chamber test to simulate the effects of weather on the solar panels. these effects were examined by a power measurement and electroluminescence (el) test. the materials were subjected to a corrosion model test to simulate decomposition of the eva foil, the effects of which were observable by microscopic methods. fourier-transform infrared spectroscopy (ftir) ftir was used to determine the exact composition of the used plastic materials by irradiating the sample with infrared light and detecting the level of absorbance at that particular wavelength. the method used a narrow spectrum (non-monochromatic) light source to collect data in relation to the wavenumber. after this, the data was subjected to a fourier-transform and the result obtained. the type of plastic was then identified with the help of a software library. a perkinelmer spectrum two spectrometer was operated in attenuated total reflectance (atr) mode and the results given in percent transmittance. differential scanning calorimetry (dsc) the dsc analysis of poe and eva samples was carried out using a setaram c80 d reaction calorimeter. the samples were weighed on a mettler toledo analytical scale before being placed into an aluminium foil sample holder and a standard stainless-steel measurement cell. only the aluminium foil was used as a reference. prior to taking measurements, the system was pre-heated to 30 °c (room temperature + 10 °c) at a rate of 0.1°c/min and maintained at that temperature for an additional 2.0 hours to establish a thermal equilibrium. the dsc measurements were performed at a low heating rate of 0.6 °c/min from 30 to 280 °c which is justified because of the need to examine within the polymerising range. the results were analysed using calisto software version 1.076. peak integration was conducted using a sigmoidaltangent peak baseline. the degree of crystallinity (xc%) table 1: the layers of the solar panels layer thickness (mm) 1 glass (tempered, soda lime) 3.2 2 eva/poe foil 0.2 3 cell matrix assembly (wafers and ribbons) 0.5 4 eva/poe foil 0.2 5 isotactic pp backsheet 0.2 patthy, szigeti, závodi-fodor, vasáros and jakab hungarian journal of industry and chemistry 50 of samples of granulated pet waste was determined according to the following equation: 𝜒𝑐(%) = 𝛥𝐻𝑚𝑝 𝛥𝐻100 × 100% (1), where δhmp denotes the specific enthalpy of the melting transition and δh100 the specific enthalpy of the melting transition of completely crystalline polyethylene (288 j/g). gel content test the goal of this test was to determine the degree of polymerization of the binding foil. the sample was prepared by placing the raw foil between two layers of ptfe before laminating them as complete solar panels. the eva and poe samples must be examined in different ways in accordance with the manufacturer’s recommendations. in the case of the eva sample, it is placed into a soxhlet-extractor device and extracted over 24 hours with toluene (sigma-aldrich, 99.5%). the poe sample is extracted with xylene (sigma-aldrich, 99.5%) and simply submerged in the solvent at 100 °c for 12 hours. in both cases, the degree of polymerization or the crosslinking ratio was calculated according to the difference in mass, where the foil is measured in its raw form before the test and in its dried out form after. the degree of polymerization is obtained by dividing the mass of the final product by the mass of the raw material. climate chamber test the goal of this test was to simulate the effects of the environment on the solar panels and predict how they might respond to these impacts by conducting a standardized climate chamber test in accordance with the standard iec 61215-2:2021 (msz en iec 612152:2021). during the test, the solar panels were subjected to a temperature cycle which consisted of a cold (-40 °c) and a warm-humid (85 °c) phase. these phases were maintained for 10 minutes before being cooled or heated at a maximum temperature gradient of 100 °c/hour. one cycle lasted 6 hours. the panels were subjected to 5, 10, 16 and 20 cycles. a visual representation of the cycle is shown in figure 2. for the test, a climats excal 5423 ha climate chamber was used [23]. the original goal was to gain data on the degradation of the cell with regard to the overall effects of the environment, which were simulated by the chamber. when the root cause was sought, it was found that even this test was sufficient to initiate the desired changes, rendering the design of a new measuring method such as a damp heat test unnecessary. electroluminescence (el) test the test visualized the degradation of the panels and loss of the actual active surface of the wafers. the test took into account the fact that all solar cells emit light when a voltage is applied across their terminals in the forward direction (electroluminescence) in the infrared domain of the electromagnetic spectrum which is easily recordable with a camera. the obtained image then showed the active surface of the wafer as brighter areas, while the inactive, non-conducting parts remained dark. flash test multiple methods are available to test the power produced by solar panels. one of the quicker methods is the flash test where a predetermined, sudden flux of light was applied to the surface of the panel while the electrical output was connected to a changing artificial load and power meter. the maximum power output of the solar panel was then calculated from the measured electrical parameters. the measuring station was custom built and the light source an ecoprogetti ecosun plus led paneltype flashing lamp that was separated from the panel by a glass surface onto which the tested sample had to be placed wafer down. the outputs were connected to an itech it8813-type load. corrosion model test to simulate the effects of acetic acid on the strings of the solar panel, a corrosion model test was utilized. in this test, 1 and 10 vol.% solutions of the acid (diluted from a sigma-aldrich 20 vol.% solution) acted as corrosives. the test samples were pieces of ready-to-integrate strings sourced directly from the manufacturing line which were submerged in the solutions and left in closed containers at room temperature for a week. after this, the samples were washed with distilled water before being dried and visually evaluated by light and electron microscopy methods to simulate the results of long periods of operation in the field. while it would have been better to examine whole panels, the panels cannot be disassembled without directly damaging the components, leading to false results. microstructural examination using scanning electron microscopy (sem) observations using a fei/thermo fisher apreo s sem were conducted under high-vacuum conditions with an accelerating voltage of 20.0 kv. the samples were washed in an ultrasonic bath using ethanol and acetone before the backscattered images were taken and the chemical composition determined by an edax/ametek octane elect plus. figure 2: thermal cycle diagram according to iec 61215-2 [23] avoiding acid corrosion of laminated solar panels 52(2) pp. 47–56 (2024) 51 3. results and discussion during the work, two different material systems were used as the encapsulation foil. the first was a solar-grade eva foil, while the other was a ‘thermoplastic solar grade polyolefin’ system, both are available commercially. during their manufacture, the parameters and methods recommended by the manufacturers were followed. first, the exact chemical composition was determined using ftir spectroscopy. in these tests, samples from the raw foil taken before the laminating process were examined. a comparison of the spectra can be found in figure 3, where the spectrum of the eva is colored pink and that of the poe blue. for the pink spectrum, the major transmittance valleys appeared at wavenumbers of 2917 (c-h), 2850 (c-h), 1737 (c=o), 1466 (c-h, methylene group), 1370 (c-h, methyl group), 1220 (c-o, vinyl ether), 1019 (c-o, vinyl ether) and 718 (c=c, cis-type alkene) cm-1. these peaks and intensity ratios correspond to a copolymer which consists of 28 wt.% polyvinyl acetate and 72 wt.% polyethylene [18]. the blue spectrum consisted of less major transmittance valleys which appeared at wavenumbers of 2917 (c-h), 2850 (c-h), 1462 (c-h, methylene group) as well as 719 (c=c, cis-type alkene) cm-1 and can be attributed to the thermoplastic polyethylene [24]. however, other minor peaks were also present, suggesting the presence of additives or impurities in the foil. these peaks appeared at wavenumbers of 2932 (c-h, alkane), 1634 (n=o, secondary amine), 1536 and 679 (c=c, alkene) cm-1. according to the database of atr-ft-ir spectra of various materials [25], these wavenumbers correspond to polyamide nylon 6 which are significantly smaller than those of polyethylene, meaning that it is mostly composed of polyethylene with a small amount of nylon 6. these results are in accordance with information provided by the supplier about them. the dsc data analysis of both poe and eva samples shows distinct differences. poe resulted in secondary and primary melting transitions occurring at lower temperatures along with reduced levels of thermal absorption compared to the eva sample. in addition, poe exhibits lower onset and offset temperatures. the calculated degree of crystallinity for the secondary melting transition was 5.60% for poe and 5.35% for eva, while for the primary melting transition it was 8.21% for poe and 4.58% for eva. the measured dsc curves of the poe and eva samples are shown in figure 4 with the obtained data presented in table 2. these values fall within the range of degree of crystallinity reported in the literature for uncured polymers. both samples exhibited wide and segmented exothermic crosslinking transitions. in the case of poe, the peak took on a fronting shape with lower onset and offset temperatures but a higher peak maximum during the second reaction phase. conversely, eva displayed a tailing shape peak with higher onset and offset temperatures but a lower peak maximum during the first phase of the reaction. the exothermic oxidation peak of poe began at a significantly lower temperature compared to that of eva where more heat was released [26]-[28]. figure 3: ftir spectra of eva (pink) and poe (blue) figure 4: dsc curves of poe and eva samples over a heating range from 30 to 280 °c (heating rate: 0.6 °c/min) 1 = secondary melting transition (smt) 2 = primary melting transition (pmt) 3 = crosslinking transition (ct) 4 = exothermic oxidation / degradation (eod) table 2: the obtained data from the dsc measurements of the eva and poe samples eva peak onset (°c) peak max (°c) offset (°c) heat (j/g) 1 smt 38.5 48.4 16.1 2 pmt 73.7 86.1 23.7 3 ct 123.3 127.3 157.5 -9.2 4 eod 202.7 214.4 228.1 -29.0 poe peak onset (°c) peak max (°c) offset (°c) heat (j/g) 1 smt 36.7 45.9 15.4 2 pmt 68.5 78.5 13.2 3 ct 117.9 137.1 151.4 -12.9 4 eod 171.3 208.7 260.6 -65.2 patthy, szigeti, závodi-fodor, vasáros and jakab hungarian journal of industry and chemistry 52 the degree of polymerization is an important quality of solar panels which shows how much of the plastic has polymerized as well as what proportion remained in oligomeric and monomeric forms. it must closely resemble the percentage given by the manufacturer of the foil at which the encapsulation foil exhibits optimal properties. during the experiments, the laminator was always set up according to the foil’s manufacturer’s recommendations to ensure that the mechanical properties of and imperfections in the foils did not distort the results of the climate chamber tests. measurements were also taken according to the preferred and official methods stated by the manufacturer. for the eva foil, soxhlet-extraction with toluene for 24 hours was performed. the poe foil was immersed in xylene and kept at 100 °c for 12 hours. samples were taken by cutting off a piece of the raw foil, measuring its weight, layering it between two strips of ptfe and feeding it into the laminator as if it were to become a solar panel. having cooled down, the extraction processes were performed and the samples dried before measuring their weights. the determined crosslinking ratio or gel content of these samples can be found in table 3, where av denotes the average of these measurements and sd their standard deviation. it was found that all the foils closely resembled the optimal degree of polymerization based on the manufacturer’s recommendations, that is, 85 wt.% for the eva foil and 66 wt.% for the poe foil. as a result, these foils are not likely to suffer mechanical failures and provide a good basis for comparisons. while it would have been better to have the plastics examined directly from the manufactured solar panels, the plastic encapsulant cannot be removed from the laminate without damaging the materials in question, falsifying the results. as a result, the ptfe foils were used instead. in addition, the initial mass was not measurable directly. while the weight of the individual raw foil could be measured, a considerable amount of plastic was lost in the lamination process, which was removed as excess foil. this waste product also yielded false results as the backsheet and the eva/poe foil were mixed in it, falsifying any measurements. during the research, all the solar panel specimens were subjected to a climate chamber test. the thermal cycle and other test conditions were established according to the iec 61215-2 standard. after a given number of cycles, the panels were taken out of the chamber before measurements were taken on them. to examine the degrading effects of the weather on the panels, a flash test was conducted from which the main parameters for determining the operating conditions of the solar panels were obtainable, namely the short circuit current (isc), the open circuit voltage (voc) as well as the current (ipm) and voltage (vpm) at the maximum power point. from these values, the maximum power of the panels could be calculated. these measured parameters can be found in table 4. the measurements were taken before the test as well as after 5, 10, 16 and 20 cycles. the maximum output power of the measurements as a function of the number of thermal cycles the panels were subjected to is shown in figure 5. although it is clearly observable that both types degrade over time, the rate of this degradation varies. the samples made with eva foil denoted in red exhibited accelerated power loss between the 10th and 20th cycles amounting to a reduction in the maximum power of around 30%. the solar panels made with poe denoted in black were much more resistant as their power loss fell within the margin of the measurement error. table 3: degree of polymerization of the different encapsulating agents gel content (%) av sd eva_1 86.50 eva_2 83.40 84.70 1.61 eva_3 84.20 poe_1 66.27 poe_2 65.16 66.25 1.08 poe_3 67.32 av: average of the measured values, sd: standard deviation of the measured values figure 5: the performance of solar panels manufactured with eva (red) and poe (black) as a function of the number of cycles in climate chamber tests table 4: the electrical parameters of panels manufactured with different foils after a certain number of thermal cycles. isc (a) voc (v) ipm (a) vpm (v) pm (w) eva_0 0.263 51.401 0.224 43.022 9.637 eva_5 0.264 51.259 0.225 42.888 9.652 eva_10 0.263 51.620 0.224 42.038 9.408 eva_16 0.262 51.375 0.200 39.515 7.902 eva_20 0.263 50.875 0.197 34.845 6.865 poe_0 0.260 51.077 0.233 43.647 10.152 poe_5 0.261 50.942 0.232 43.623 10.133 poe_10 0.262 51.146 0.237 43.239 10.238 poe_16 0.260 50.956 0.235 42.983 10.117 poe_20 0.261 50.599 0.235 42.626 10.015 isc: short circuit current, voc: the open circuit voltage, ipm: the current, vpm: voltage at the maximum power point, pm: maximum power avoiding acid corrosion of laminated solar panels 52(2) pp. 47–56 (2024) 53 after every power measurement, the panels were subjected to an el test to visually observe the degradation of the conductive parts. the images of the panels made with eva are presented in figure 6 in which only the most prominent series are shown. these images clearly show an advanced degree of degradation since the wafers got progressively darker as the number of cycles increased. however, a more concerning sign of degradation was the uneven level of luminescence of the wafers. even in figure 6b after 5 thermal cycles, some wafers only emitted light from areas near to the external conducting material. this effect becomes more prominent as the number of cycles increases. the darkening pattern suggests increased series resistance, perhaps originating from microstructural changes in the ribbons, caused by corrosion. on the other hand, according to figure 7, the alternative material is promising from corrosion and degradation points of view as the darkening effect is not visible, only a slight change in brightness. this suggests that the corrosion is induced by the acetic acid originating from the decomposition of eva. the el test results are further supported by the flash test. here, the series resistance of the modules made with eva in some cases even tripled after 20 cycles, whereas only a minor change was observable in the other group. this lead to the tendency shown in figure 8 where the two types of panels initially responded equally, however, as the test progressed, the rate of degradation of the eva cells increased and their maximum power deteriorated drastically. in one case after 20 cycles, the output power of the cell dropped by 40% compared to at the beginning of the test. in the case of the poe-based material, this change was not prominent since the largest reduction was around 10%. to simulate the effects of the decomposing eva foil, a corrosion model test was performed where solutions of acetic acid were prepared at concentrations of 1 and 10 vol.%. the samples, which were ready-tointegrate pieces of string, were immersed in these solutions for one week before being washed and dried samples examined then compared visually to their initial state and with sem methods. during the instrumental analysis, an attempt was made to reproduce all the initial images. while the measurements are over-representative with regard to the stresses the material is actually subjected to over 20 thermal cycles, the goal here was to create a test where the effects of the acid could be examined relatively quickly. degradation was confirmed visually. the backside of the wafers was shiny, compared to its initial matte finish. the thin busbars, which run along the surface of the wafers, were damaged. in both cases, one of the ribbons detached from the wafers. the reason for the reduction in power shown in figure 6 can be explained by the sem images shown in figure 9. the pairs of images taken at low levels of magnification (figures 9a, 9c, 9e and 9g) show roughening of the surface of the ribbons proving that they had started to decay. in the higher magnification images (figures 9b, 9d, 9f and 9h), it can be seen that the acetic acid did not react equally with the materials the ribbon is a) 0th thermal cycle b) 5th thermal cycle c) 10th thermal cycle d) 16th thermal cycle e) 20th thermal cycle figure 6: electroluminescence images of the evabased panels after a certain number of thermal cycles a) 0th thermal cycle b) 5th thermal cycle c) 10th thermal cycle d) 16th thermal cycle e) 20th thermal cycle figure 7: electroluminescence images of the poebased panels after a certain number of thermal cycles figure 8: the normalized power of the cells in relation to the number of thermal cycles 0,6 0,7 0,8 0,9 1 1,1 0 5 10 15 20 n o rm al iz ed p o w er ( p m 0 = 1 ) thermal cycles patthy, szigeti, závodi-fodor, vasáros and jakab hungarian journal of industry and chemistry 54 composed of and consumed the darker-colored areas. as the imaging method is based on the detection of backscattered electrons (bse), the lighter areas and/or pixels represent elements with lower atomic numbers, e.g. tin (sn), detrimentally affecting the mechanical stability of the ribbons as the reduction in tin content may cause these parts to break. in addition, the series resistance increased, increasing power loss from the solar panel. darkening of almost the whole of the affected wafers can be explained by the breaking of the busbars. after the corrosion model test, the remaining acetic acid solution was evaporated and the remaining powder sample analyzed by sem using the eds detector. the spectra recorded suggest the composition shown in table 5. the high carbon content and the almost twice as large oxygen content suggested that the powder was some kind of acetate salt. the high aluminum content explains why the backside of the wafers became shiny, namely they were completely corroded by the acetic acid. the aluminum may have also originated from the ribbon as a component of a combined metal. the selective consumption of the ribbon was also observable here since the tin content of the recovered crystals was much higher than their lead content. in fact, the lead content of the sample was just barely higher than the background noise of the detector, rendering it hardly detectable. 4. conclusions in this article, the causes and effects of the decomposition of eva foil in solar panels were examined as well as discussed. the effects of the corrosion agent were simulated and the results compared before and after. an alternative material based on polyethylene was also examined and a series of solar panels containing it was subjected to the same standardized accelerated aging tests as the ones equipped with eva. the experimental results clearly show that acetic acid corrosion causes severe irreversible damage to the electrical components of solar cells preventing much of each wafer from producing electricity. as this detrimental effect did not occur when the other polyethylene-based foil was used, it can be stated that this foil is a promising alternative to the classical eva foil. while the manufacturer’s datasheet states that the properties of the final product should be identical to one made with eva, an intensive life-cycle test amongst other tests (mechanical, chemical resistance tests, etc.) would be required to verify this claim. acknowledgements the research was supported by the únkp-23-1 new national excellence programme of the ministry for innovation and technology financed by the national research, development and innovation fund. the ginop_plusz-2.1.1-21-2022-00225 project was implemented with the support of the ministry for innovation and technology through the national research, development and innovation fund. before 1% v/v acetic acid treatment a) low magnification b) higher magnification after 1% v/v acetic acid treatment c) low magnification d) higher magnification before 10% v/v acetic acid treatment e) low magnification f) higher magnification after 10% v/v acetic acid treatment g) low magnification h) higher magnification figure 9: sem images of the wafers before and after the corrosion model tests (the images were captured by a bse detector.) table 5: composition of the remaining crystals from the corrosion model test determined by eds analysis element atomic % c 26.59 ± 2.70 o 56.83 ± 4.76 na 0.85 ± 0.18 al 12.09 ± 0.71 si 0.57 ± 0.09 pb 0.05 ± 0.01 cl 0.20 ± 0.04 sn 2.87 ± 0.13 avoiding acid corrosion of laminated solar panels 52(2) pp. 47–56 (2024) 55 references [1] energy statistics data browser – data tools – iea https://www.iea.org/data-and-statistics/data-tools/energystatistics-databrowser?country=world&fuel=energy%20supply&indicator =elecgenbyfuel (accessed 2023.10.22.) 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https://doi.org/10.1109/pvsc40753.2019.8981151 https://doi.org/10.1016/j.renene.2013.10.013 de gruyter open hung. j. ind. chem. 2017 45(1), 1–84 table of contents dynamical temperature from the phase space trajectory andrás baranyai ............................................................................................................................................ 1-3 separation of gases by membranes: the effects of pollutants on the stability of membranes nándor nemestóthy ...................................................................................................................................... 5-8 selective removal of hydrogen sulphide from industrial gas mixtures using zeolite naa tamás kristóf .............................................................................................................................................. 9-15 dynamic simulator-based apc design for a naphtha redistillation column lászló szabó, klára kubovicsné stocz, laura szabó, sándor németh, and ferenc szeifert .......... 17-22 replacement of biased estimators with unbiased ones in the case of student's t-distribution and geary’s kurtosis gergely tóth and pál szepesváry ........................................................................................................... 23-27 formation, photophysics, photochemistry and quantum chemistry of the out-of-plane metalloporphyrins zsolt valicsek, melitta p. kiss, melinda a. fodor, muhammad imran, and ottó horváth .................. 29-36 improvement possibilities of heterogeneous photocatalysis with the aim of in-field use orsolya fónagy, péter hegedűs, erzsébet szabó-bárdos, annamária dobrádi, and ottó horváth ...................................................................................................................................................... 37-48 adapting the sdewes index to two hungarian cities viktor sebestyén, viola somogyi, szandra szőke, and anett utasi ..................................................... 49-59 surface energy heterogeneity profiles of carbon nanotubes with a copolymer-modified surface using surface energy mapping by inverse gas chromatography fruzsina gerencsér, norbert rieder, csilla varga, jenő hancsók, and andrás dallos .................. 61-66 initial electrical parameter validation in lead-acid battery model used for state estimation bence csomós, dénes fodor, and gábor kohlrusz ............................................................................... 67-71 simulating ion transport with the np+lemc method. applications to ion channels and nanopores. dávid fertig, eszter mádai, mónika valiskó, and dezső boda ............................................................... 73-84 . lászló rácz hungarian journal of industry and chemistry vol. 45(1) editorial preface hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0021 in memoriam jános liszi this issue is dedicated to professor jános liszi who was the rector of the university of veszprém in 1989-1995. the university acquired this name during his term in an era of severe political and economic challenges (today: university of pannonia). under his leadership the university took on these challenges and has been modernized to become an institution with a wider scope. he was the head of the department of physical chemistry for many years. the department was also reshaped during this period. his early death was unexpected and mourned. he influenced the life of many and left his mark on his alma mater in veszprém, but he also had an impact on other institutions as the commemoration of lászló rácz below indicates. lászló rácz was the head of the chemistry department in eger when professor liszi joined to teach physical chemistry there. it was an honor to organize and edit this issue to salute my respected supervisor. veszprém, 10 october 2017. dezső boda issue editor the eger-connection of professor liszi he was a tough and righteous man towards himself just as towards his colleagues in veszprém. i can say that the same was true regarding his relationship with the colleagues and students of the chemistry department at the eszterházy károly college in eger. that is why we got to like him so much. when a position for teaching physical chemistry became available in our department, it was not easy to find the right person to fill the boots left by an excellent colleague who had held this position for 30 years. according to the urgent need to yield the proper knowledge to our students, our director indicated to professor liszi that there was a problem to be solved in eger. he did not hesitate and drove 230 km to eger right away. he assisted with our teaching work for many years. a fruitful professional relationship had been established between veszprém and eger. we gladly accepted the support offered by professor liszi. beyond his physical chemistry courses in the curriculum, he regularly gave seminars about various topics not only to our students but also to colleagues and students from other departments. an example that i witnessed characterizes his professional work. after a class, a student from the physics programme approached him and said, “i will enter the chemistry programme because this was so beautiful and logical”. and he did. he became a physics-chemistry teacher and now works in the physics department. since 2015, our college has functioned as a university. i am sure that the support of professor liszi has contributed to the development of our institution considerably. he has also contributed to my personal development because he encouraged me to defend my habilitation thesis. he also contributed to the education of our team beyond the field of physical chemistry. during excursions to tihany and at the benedictine order he acted as a guide and demonstrated his vast knowledge of history and classical culture. the expertise of our department, making wine, also belongs to classical culture. it was a pleasure to host him and his wife for wine tastings on several occasions. at such times, we discussed the science of wine-making. time flew and we got onto the subject of the thermodynamics of multicomponent homogeneous systems after a few glasses of wine. sadly the blessing of st. john had to come early because he had an early start the following morning. the minimum 1000 m session in the swimming pool could not be left unperformed. together with him we profess that technical details can only come after the firm scientific basics have been laid down. he achieved a lot for higher education and research in eger. we are grateful for his efforts we respected and loved him not only for his knowledge, but also for his humanity. eger, 12 october 2017 hungarian journal
of industry and chemistry vol. pp.45(1) pp. 1–3 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0001 dynamical temperature from the phase space trajectory andrás baranyai * department of theoretical chemistry, eötvös loránd university, p. o. box 32, budapest, 1518, hungary in classical statistical mechanics the trajectory in phase space represents the propagation of a classical hamiltonian system. while trajectories play a key role in chaotic system theory, exploitation of a single trajectory has yet to be considered. this work shows that for ergodic dynamical systems the dynamical temperature can be derived using phase space trajectories. keywords: temperature, statistical mechanics a hamiltonian system of n mass points is related to the microcanonical ensemble of statistical mechanics when the volume, v, and the energy, e, of the system are fixed. a microscopic state of the system is a point in phase space represented by a 6n-dimensional vector, ),...,,,...,( 2121 nn pppqqqγ  . the time evolution of this point is described as a trajectory in phase space. in microcanonical ensembles, since the energy is fixed, the evolution of the system is restricted to a 6n-1 dimensional hypersurface. the logarithm of the area of this hypersurface yields the entropy, s, of the system. since the entropy of a stable thermodynamic system is a monotonically increasing function of the internal energy, the accessible phase space increases with energy. this provides the opportunity to determine the thermodynamic derivative, tes nv /1)/( ,  , where t is the absolute temperature. the trajectories within the limit of infinite time perfectly cover the 6n-1 dimensional hypersurface according to the ergodic hypothesis. this means that the length of the trajectory for a period of time,  , is proportional to the microcanonical entropy: .limln 0 2             γdtks (1) eq.(1) is a line integral measuring the length of the path of the moving system in phase space. this equation can be rewritten as: .limlnlimln 00 2                                   γγ h dtk h dtks (2) *correspondence: baranyai@chem.elte.hu let us consider two hamiltonian systems, h and h’, with only a minor difference between their energy parameters, e and e’. the distance covered in phase space by these systems is different because the two energies belong to different areas of the hypersurface to be covered by the trajectories. if the difference in entropies between the two systems is calculated, the quotient in the argument of the logarithm makes it possible to use equality instead of a mere proportionality. . ' ln ' ln lim lim ln)()( 0 0                                                                             τ γ τ γ γ γ h h k h h k h dt h dt keses       (3) in eq.(3) the time integral was replaced with the product of time and the time-average of the integrands. the hamiltonian, h’, can be approximated as .γ γ d h hh    (4) then . 2 2 γ γγγ d hhh         (5) baranyai hungarian journal of industry and chemistry 2 using eq.(5), eq.(3) can be rewritten as . ln)()( 2 2 2 2 γ γ γ γ γ γγ                             h d h k h d hh keses (6) in the second equality of eq.(6), the xx  )1ln( approximation was exploited. to obtain the temperature, division with the energy difference should be included: . 1 )()( 2 2 2 2 2 th h k d h h d h k ee eses                 γ γ γ γ γ γ γ (7) the dynamical temperature was derived first by rugh as a time average of )/( 2 hh  on the energy surface [1]. . 1 2 h h kt    (8) later, butler et al. applied a similar approach and derived eq.(8) only for the configuration part of the phase space and also checked the performance of the method numerically [2]. the essence of both derivations was to transform the phase-space vector, γ , from system e into γ of system e’ by a vector containing the hamiltonian gradient. in this way arelationship was established between the phase-space points of the two systems. our result uses the average speed of evolution of trajectories in phase space, therefore, a hamiltonian gradient is not required to connect the two sets of phasespace points. expansion of the energy in eq.(4) is sufficient to relate the two trajectories. certainly, the results are identical which proves the validity of this alternative approach while, at the same time, it is a nice example of ergodicity: the method which uses the difference in area of hypersurfaces in an ensembleaverage fashion leading to results that are identical to the method that uses relative trajectory propagation in time. the explicit form of eq.(7) can be written as , / /3 1 1 22 2 1        n i i n i m m kt q q p (9) where  is the position-dependent potential in the hamiltonian and m is the mass of a particle. eq.(9) contains two terms that feature both in the numerator and denominator. the quotient of the first terms is the well-known kinetic temperature and the quotient of the second terms is the configurational temperature. in actual calculations these two temperatures can be calculated contrary to the full form of eq.(9) which contains dimensional discrepancies in both the numerator and denominator. the configurational temperature calculation was suggested as an algorithmic check for monte carlo computer simulations where the boltzmann temperature is an input parameter [2]. for completeness, the third, very simple method of deriving the configurational temperature is mentioned [3].the previous derivations did not state whether the two temperatures, the kinetic and configurational, are equal. using a trivial derivation it is shown that the two quotients are equal [3]. a further advantage of this method is that there is no need for the condition of n to accept the validity of a microcanonical result in terms of the canonical ensemble. the temperature from the momenta of the particles is . 3 1 1 2   n i i nkm t p (10) if this temperature remains constant over time: ,0 11    n i ii n i ii cct fppp  (11) where, for the sake of simplicity, the constant factor is denoted in front of the sum as c and  ii qf  / is the newtonian force, it is also possible to write that .0 )( 1 ,, 2 2 1                    n i zyx ii i n i iiii m p fc ct     f fpfp  (12) at equilibrium in isotropic systems the different cartesian directions are equivalent and there is no correlation between velocities and position-dependent quantities. thus, dynamical temperature from the phase space trajectory 45(1) pp. 1–3 (2017) 3 . 3 2 2 2    q q kt p m (13) eq.(13) can be written in this form when t is manipulated. the results would be the same. therefore, if the expectation value of the temperature is constant, the kinetic and configurational temperatures are equivalent. as for the temperature derivation from the phasespace trajectory it is important to note that the  condition is essential. finite segments of trajectories do not cover the hypersurface completely and only contain minimal information about the temperature and force distributions of the system. references [1] rugh, h.h.: dynamical approach to temperature, phys. rev. lett., 1997 78(5), 772-774 doi:10.1103/physrevlett.78.772 [2] butler, b.d.;ayton, g.a.;jepps, o.g.;evans, d.j.: configurational temperature: verification of monte carlo simulations, j. chem. phys., 1998 109, 65196522 doi:10.1063/1.477301 [3] baranyai, a.: on the configurational temperature of simple fluids, j. chem. phys., 2000 112, 39643966 doi:10.1063/1.480995 hungarian journal
of industry and chemistry vol. pp.45(1) pp. 5–8 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0002 separation of gases by membranes: the effects of pollutants on the stability of membranes nándor nemestóthy* research institute of bioengineering, membrane technology and energetics, university of pannonia, egyetem u. 10, veszprém, h-8200, hungary the long-term stability of membranes is determined mainly by their sensitivity to pollutants. their stability was tested using a novel, multichannel measuring system, which is based on pressure differences. this measuring system is suitable to determine the changes in permeability of polymer membranes. the damaging effects of h2s, btx and n-dodecane were investigated in terms of polyimide gas separation membranes using nitrogen gas. keywords: multichannel test equipment, pressure difference, hydrogen sulphide, btx 1. introduction previously, it was thought that the stability of membranes is determined by the mechanical stress (shear) and the natural aging of polymers. recently, however, it has been confirmed that their stability is limited mainly by the sensitivity of membranes to certain pollutants. these aggressive compounds, pollutants, e.g. chlorine, hydrogen sulphide, hydrocarbons, etc., may damage the structure of the polymer, thus its physical and chemical properties change, and consequently the permselectivity of the membrane changes, as well. it is known that polymeric reverse osmosis membranes are sensitive to strong oxidising agents, especially chlorine compounds [1], therefore, intensive research has been conducted to avoid or at least reduce any damage [2-3]. similar levels of membrane degradation are observed in proton-exchange membrane (pem) fuel cells and batteries containing membranes, where oxidising compounds are in contact with the membranes, as well [4-5]. the stability of polymeric gas separation membranes has hardly been investigated. the long-term effects of h2s on inorganic membranes has been studied by australian researchers at low concentrations (50 ppm) [6]. however, h2s may not only cause long-term, but immediate damage, mainly in the form of swelling, which strongly influences the gas transport properties of membranes. koros and co-workers presented the effects of extremely high h2s concentrations on a polymer membrane (50,000 100,000 ppm) [7]. in the field of membrane technology, sensitivity can be measured by a sort of effectiveness unit. the *correspondence: nemesn@almos.uni-pannon.hu product of the concentration and time period yields a value where the effectiveness of the membrane decreases from 95 to 90 and then to 70% of its original value (e.g. 1000 ppm*hour means that the membrane was exposed to 1000 ppm of pollutant for 1 hour, or 0.1 ppm of pollutant for 10,000 hours during the tests). according to the literature these types of measurements have yet to be published for gas separation membranes, thus the aim of this work was to design, construct and operate a piece of test equipment that conducts reliable laboratory tests. for the determination of stability, direct and indirect methods can be used to measure the gas volumes passing through the membranes. direct methods are usually preferred, and – if the composition of the gas is known – are more exact than indirect ones. however, when the gas composition varies and small amounts of gases need to be measured, indirect methods are often more suitable. in this work an indirect method based on a pressure differential technique was chosen, where the pressure of a closed vessel is measured and the varying pressure yields information about the volume of the gas passing through the membrane. during the investigation the effects of pollutants on the permeability of nitrogen was to be studied. the following pollutants were used:  compounds containing sulphur at associated gas  btx mixture (benzene, toluene, xylene)  heavy hydrocarbons in this research the aim was to determine quantitatively the effects of pollutants on the membranes to define the tolerance range of particular membranes. nemestóthy hungarian journal of industry and chemistry 6 figure 1. the small modules constructed for the tests 2. experimental for this series of measurements, polyimide gas separation membranes (synthesised by ube) were used. they were taken from a hollow fibre module and can accurately model the properties of industrial gas separation membranes. from the hollow fibres small modules containing 6 capillaries were constructed (fig.1) and their ends were closed, thus their tests were carried out in a “sack” configuration. in the design of the test system it was important that several parallel measurements should be conducted and the measuring channels combined with each other. the scheme of a measuring channel can be seen in fig.2 the gas was introduced into the measuring system through valve v1 (which can be adjusted by valve v2 if necessary). before measurements were taken the pressure of the vessel was checked by pressure transducer pt1. to start the test the pressure was adjusted by regulating valve pv1, which was checked by pressure transducer pt2. then the membrane was installed into the thermostatic system in a way that ensured its mobility was not restricted, thus the permeation of gas could not influence the flux. a photograph of the measuring system is shown in fig.3. for the permeability measurements nitrogen gas from a cylinder was used (99.5%; messer hungarogáz kft., hungary). the permeability of the membrane was determined from the pressure of the vessel and the transmembrane pressure measured on-line during the experiments. in the experiments, h2s, methyl mercaptan and ammonia (compounds containing s or n), oleic acid, ethyl figure 2. the scheme of the test system figure 3. the test system alcohol, moreover, a benzene-toluene-xylene mixture (btx) and n-dodecane (as a heavier hydrocarbon) were used as pollutants. for the stability experiments the small membrane modules were put in a closed vessel (fig.4) where the headspace was saturated with the given pollutant. the vessels were placed in a thermostatic incubator at 27 °c usually for between 1 and 7 days. certain materials (e.g. btx) damaged the epoxy resin glue used to adhere the fibres of the membranes, therefore, these experiments were repeated using polyether-sulfone glue instead. 3. results the nitrogen permeability of the membranes was determined before and after the incubations. in the preliminary experiments, the ammonia solution and methyl mercaptan severely damaged the surface of the membranes, thus no flux could be measured. oleic acid and ethyl alcohol hardly influenced the flux, while btx, h2s and n-dodecane changed the permeability of nitrogen considerably. for further investigation of the pollutants an experimental design was constructed, using appropriate figure 4: the membranes in the closed vessel the effects of pollutants on the stability of membranes 45(1) pp. 5–8 (2017) 7 table 1. the parameters of the experimental design pollutant cmin ppm cav ppm cmax ppm tmin d tav d tmax d h2s 100,000 300,000 500,000 1 3.5 7 btx mixt. 1,000 750 500 1 3.5 7 dodecane 1,000 5,500 10,000 1 3.5 7 statistical methods. the parameters selected were the concentrations of the pollutants (minimum, maximum and average) and the incubation time (minimum, maximum and average). the statistica 8 computer program was applied to the design presented in table 1. firstly the effect of h2s on the nitrogen permeability of the membranes was measured. the experimental results are presented in fig.5. it can be seen that the permeability of nitrogen increased even when the concentrations of pollutants were low and rose by using higher concentrations and longer periods of exposure. from the h2s concentration and the incubation time it was possible to calculate a special parameter of exposure with the unit of ppm*h. permeability was presented as a function of this parameter (fig.6), where an almost linear relationship was observed. the results suggest that the process can be described as a first-order reaction, which means that no safe limit can be determined where h2s is regarded as harmless, on the contrary, it should be considered at all times. the effect of the btx mixture was studied using a similar methodology. the results are summarized in fig.7. this figure shows that the permeability of nitrogen increased at low concentrations of the btx mixture. at higher concentrations and over longer periods of time, no further significant changes were observed. the exposure parameter was also calculated in the unit of ppm*h and permeability was presented as its function (fig.8). the diagram can be described as a saturation-type curve. 2**(2-0) design; ms residual=49886.27 > 2000 < 2000 < 1500 < 1000 < 500 < 0 figure 5. the effect of h2s on the nitrogen permeability exposure [m ppm * h] 0 20 40 60 80 100 p e rm e a b ili ty c h a n g e [ % ] 0 500 1000 1500 2000 2500 figure 6. permeability changes against exposure to h2s 2**(2-0) design; ms residual=2675.592 > 400 < 360 < 310 < 260 < 210 < 160 < 110 < 60 figure 7: the effect of the btx mixture in the last series of experiments, the effect of exposure to n-dodecane was investigated experimentally. the results are presented in fig.9. n-dodecane caused – unlike h2s and btx – a reduction in the permeability of nitrogen even at low concentrations. the flux fell to zero at higher concentrations and over longer incubation periods. permeability was investigated as a function of exposure (fig.10). the process can be described as a first-order reaction, thus the effect of heavier hydrocarbons, e.g. n-dodecane, should always be considered. exposure [k ppm * h] 0 20 40 60 80 100 120 140 160 180 p e rm e a b ili ty c h a n g e [ % ] 0 100 200 300 400 figure 8: permeability changes against btx exposure nemestóthy hungarian journal of industry and chemistry 8 2**(2-0) design; ms residual=40.32141 > 100 < 96 < 76 < 56 < 36 figure 9: the effect of n-dodecane 4. conclusion the long-term stability of polyimide gas separation membranes was tested against various pollutants: h2s, a btx mixture and n-dodecane. these compounds significantly affected the nitrogen permeability of the membranes which were described by using a special parameter of exposure. it was found that h2s and the btx mixture increased the permeability, while ndodecane reduced the permeability of the membranes. further investigations are planned to investigate the effect of other pollutants, moreover, to determine the permeability of additional gases, e.g. carbon dioxide, methane, etc. acknowledgement we acknowledge the financial support of széchenyi 2020 under the efop-3.6.1-16-2016-00015 project. this research was supported by the jános bolyai research scholarship of the hungarian academy of sciences. references [1] glater, j.; hong, s.k.; elimelech, m.: the search for a chlorine-resistant reverse osmosis membrane, desalination, 1994 95(3), 325-345 doi: 10.1016/0011-9164(94)00068-9 exposure [ k ppm * h] 0 50 100 150 200 p e rm e a b ili ty c h a n g e [ % ] 0 10 20 30 40 50 60 70 figure 10. change in permeability against exposure to n-dodecane [2] zhang, y.; zhao, c.; yan, h.; pan, g.; guo, m.; na, h.; liu, y.: highly chlorine-resistant multilayer reverse osmosis membranes based on sulfonated poly(arylene ether sulfone) and poly(vinyl alcohol), desalination, 2014 336, 58-63 doi: 10.1016/j.desal.2013.12.034 [3] gohil, j.m.; suresh, a.k.: chlorine attack on reverse osmosis membranes: mechanisms and mitigation strategies, j. membr. sci., 2017 541, 108-126 doi: 10.1016/j.memsci.2017.06.092 [4] huang, x.; pu, y.; zhou, y.; zhang, y.; zhang, h.: in-situ and ex-situ degradation of sulfonated polyimide membrane for vanadium redox flow battery application, j. membr. sci., 2017 526, 281292 doi: 10.1016/j.memsci.2016.09.053 [5] lapicque, f.; belhadj, m.; bonnet, c.; pauchet, j.; thomas, y.: a critical review on gas diffusion micro and macroporous layers degradations for improved membrane fuel cell durability, j. power sources, 2016 336, 40-53 doi: 10.1016/j.jpowsour.2016.10.037 [6] uhlmann, d.; smart, s.; diniz da costa, j.c.: h2s stability and separation performance of cobalt oxide silica membranes, j. membr. sci., 2011 380(1), 48-54 doi: 1016/j.memsci.2011.06.025 [7] kraftschik, b.; koros, w.j.; johnson, j.r.; karvan, o.: dense film polyimide membranes for aggressive sour gas feed separations, j. membr. sci., 2013 428, 608-619 doi: 10.1016/j.memsci.2012.10.025 hungarian journal of industry and chemistry vol. 45(1) pp. 9–15 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0003 selective removal of hydrogen sulphide from industrial gas mixtures using zeolite naa tamás kristóf* department of physical chemistry, institute of chemistry, university of pannonia, egyetem u. 10., veszprém, h-8200, hungary hydrogen sulphide removal from simple gas mixtures using a highly polar zeolite was studied by molecular simulation. the equilibrium adsorption properties of hydrogen sulphide, hydrogen, methane and their mixtures on dehydrated zeolite naa were computed by grand canonical monte carlo simulations. existing all-atom intermolecular potential models were optimized to reproduce the adsorption isotherms of the pure substances. the adsorption results of the mixture, also confirmed by iast calculations, showed very high selectivities of hydrogen sulphide to the investigated non-polar gases, predicting an outstanding performance of zeolite naa in technological applications that target hydrogen sulphide capture. keywords: hydrogen sulphide, zeolite, selectivity, gas mixture, molecular simulation 1. introduction hydrogen sulphide is a highly toxic, acidic and corrosive substance. it is present naturally in landfills, natural and biogases, as well as in several synthesis gases. one of its main anthropogenic sources is the processing of crude oil in industrial refineries, where hydrodesulfurization (hds) of a variety of streams (e.g. engine fuels) produces hydrogen sulphide-containing gas mixtures, which need to be purified. the economic removal of hydrogen sulphide is a long-standing task of the oil and gas industry. adsorptive separation involves the use of solid substrates with a specific affinity with particular compounds of the mixture. zeolites have been applied as catalysts in the petrochemical industry for a relatively long time and these materials can also be used for purification/separation purposes. zeolites are crystalline aluminosilicates consisting of a threedimensional framework of sio4 and alo4 tetrahedra of a highly regular porous structure [1]. the typical size of zeolitic micropores is similar to that of many small molecules. in contrast to various other adsorbents, zeolites generally endure high temperatures and pressures well, and can tolerate harsh chemical environments. the si/al ratio is a key factor in the application of zeolites. zeolites with lower si/al ratios are more hydrophilic, whereas high-silica zeolites often possess fewer structural defects. these latter adsorbents are preferred in the separation of non-polar gases. zeolite naa is a synthetic microporous zeolite which accommodates extraframework na+ ions. it exhibits an especially high affinity with small polar *correspondence: kristoft@almos.uni-pannon.hu molecules such as water. the adsorption and separation properties of zeolite naa have already been examined in several experimental [2-6] and theoretical/simulation [7-16] works. in our laboratories, the adsorption characteristics of zeolite naa and its performance as a drying agent by classical atomistic simulations [10, 1214] were studied, and new intermolecular potential models for this zeolite [12-14] proposed. our models were optimized for the study of the selective adsorption of water from its mixtures with less polar or non-polar molecules like simple alcohols, carbon monoxide, hydrogen and methane. in this paper, the selective removal of hydrogen sulphide by zeolite naa is investigated. molecular simulation predictions for mixture adsorption from two and three-component gas mixtures containing hydrogen sulphide (h2s), hydrogen (h2) and methane (ch4) are presented. 2. models and simulation details zeolite naa [17-18] is of lta framework type, the structure of which belongs to the fm-3c space group with a lattice parameter of 2.4555 nm. the threedimensional cubic arrangement of its framework atoms is comprised of three kinds of rings with four (4r), six (6r) or eight (8r) oxygen atoms. the interconnection of 4r and 6r rings forms nearly spherical cages (sodalite cages) and these cages are linked by oxygen bridges, shaping straight channels of supercages with a maximum diameter of about 1.2 nm. the standard type of zeolite naa has a si/al ratio of 1. in the present study, the unit-cell composition of the standard type of zeolite naa was chosen: it consists kristóf hungarian journal of industry and chemistry 10 of 576 framework atoms, namely 96 silicon, 96 aluminium and 384 oxygen atoms. the framework atoms were fixed at the atomic positions measured in xray diffraction experiments [17] and the 96 nonframework na+ ions were allowed to move. according to the löwenstein rule that prohibits aloal linkages, each alo4 tetrahedron of this framework is connected to a sio4 tetrahedron. realistic and rigid all-atom intermolecular potential models, consisting of lennard-jones and coulombic interaction sites, were used in the simulations. in these models, the interaction sites were fixed at their experimental atomic positions and assigned their lennard-jones energy (ε) and size (σ) parameters, as well as point charges (q). for zeolite naa, the model that was developed earlier was modified slightly [14] by adding weak lennard-jones interaction sites with realistic size parameters [16, 19] to the (originally) pure coulombic silicon and aluminium atoms, thus preserving the dominant role of oxygen atoms in the dispersion interactions of the framework. for hydrogen sulphide, a rigid four-site model proposed recently by shah et al. [20] was adopted, in which the location of the charge parameter of the sulphur atom is offset on the hsh angle bisector towards the hydrogen atoms. an opls-aa model [21] was used for the methane molecules, and its lennard-jones h parameters were also applied to the h2 molecules, with partial charges on the atomic sites and on the molecular centre of mass [22]. table 1 lists the potential parameters of the above models. instead of the generally accepted lorentz-berthelot combining rule, the unlike lennard-jones interactions were computed by the combining rule proposed by waldman and hagler [23]. this combining rule links the behaviour of the unlike energy parameter εij to the relative sizes of atoms i and j and yields somewhat smaller values for the parameters εij and ij when ii≠jj. song et al. [24] found that the experimental thermodynamic properties of pure methane can be reproduced more accurately using the waldman-hagler combining rule. gas adsorption simulations were carried out by the standard grand canonical monte carlo methodology [25]. total pressure p and partial pressures in the gas phase were specified by the chemical potentials of the components; in a diluted gas, these can be calculated from the ideal gas law [12]. the long-range coulomb interactions were treated with the wolf method [26-27] using a convergence parameter of  = 2/rc and cutoff radius of rc = l/2 (l is the length of the simulation box). the simulations involved an equilibration period of 5×107 monte carlo moves and an averaging period of 2×108 moves, consisting of 70% molecular insertion/deletion and 30% molecular translation steps. since the random insertion of molecules is unable to take into account the inaccessibility of the sodalite cages by multiatomic molecules (the physical diffusion pathways to them), creation of h2s and ch4 molecules inside these cages was blocked artificially by placing repulsive dummy atoms at the centres of the cages. as h2 molecules are sufficiently small to pass through the windows of the sodalite cages, the insertion of h2 molecules into these cages was permitted. in either case, the transition of molecules into sodalite cages via translational trial moves was not artificially prevented. in addition to the adsorption loading, the isosteric heat of adsorption was calculated using the equation: tv a a tp b b n u n h q ,,                       , (1) where hb and ua stand for the residual enthalpy and residual internal energy, respectively, n is the number of moles of the substance in the adsorbed (a) or bulk (b) phases. in the grand canonical ensemble, the second part of the equation can be determined from the particle number fluctuations of the simulation and the crosscorrelation of potential energy and particle number fluctuations [28-29]. assuming the ideal gas adsorbates, the first part of the equation is equal to rt, where r is the gas constant and t is the temperature. predictions for mixture adsorption were also made using the ideal adsorbed solution theory (iast) [30-31], which is an analogue of the ideal raoult’s law. using iast, mixture adsorption loadings at a given t can be obtained from single-component adsorption loadings by determining the bulk pressure of each component po at the same spreading pressure  of the adsorbed phase: )(/ o i b i a i ppyy  . (2) table 1. lennard-jones energy (ε), size parameters (σ) and partial charges (q) for the models used in this work (d is the bond length, k is the boltzmann constant). interaction site σ / nm (ε/k ) / k q / electron charge position in the structure/molecule na+ (naa) 0.250 100 0.60 random positions in supercages si (naa) 0.230 22.0 2.40 experimental atomic positions [17] al (naa) 0.240 16.5 1.80 experimental atomic positions [17] o (naa) 0.330 190 -1.20 experimental atomic positions [17] s (h2s) 0.360 122 ds-h = 0.134 nm h (h2s) 0.250 50.0 0.21 hsh angle: 92° xs (h2s)* -0.42 ds-x = 0.03 nm c (ch4) 0.350 33.21 -0.24 dc-h = 0.109 nm h (ch4) 0.250 15.1 0.06 hch angle: 109.47° h (h2) 0.250 15.1 0.4829 dh-h = 0.0741 nm centre of mass (h2) -0.9658 geometric centre of the linear h2 molecule *off-atom site on the h–s–h angle bisector towards the hydrogen atoms selective removal of hydrogen sulphide using zeolite 45(1) pp. 9–15 (2017) 11 here, y i is the mole fraction of component i, and )(o ip is given implicitly by:  o 0 o ln)()( ip a ii pdpn a rt p , (3) where a is the surface area of the adsorbent. 3. results and discussion the intermolecular potential models were tested by determining equilibrium adsorption isotherms for pure h2s, h2 and ch4 on zeolite naa. experimental data at 298 k are available for h2s [32] and h2 [8] and nearly room-temperature (t = 283 k) data for ch4 were taken from [33]. fig.1 shows that the models are largely able to reproduce the experimental adsorption data for these substances. the reproduction of the experimental isotherm is quite good for h2s and h2. in the case of ch4, the extent of overestimation of the experimental results at 283 k is considered acceptable, given that the availability of transferable zeolite models that are appropriate as far as adsorption predictions are concerned for both polar and non-polar compounds is rather limited [16]. furthermore, it is expected that the observed discrepancies between simulation and experimental results for this non-polar component are unable to cause significant errors in terms of mixture adsorption data, where the ch4 content of the gas phase is low and the adsorption of h2s is dominant. the calculated isosteric heat of adsorption data together with available experimental results for h2 and ch4 [5] are also plotted in fig.1. the pressuredependence of these data is weak. the general order of qh2s > qch4 > qh2 is in line with expectations, bearing in mind that the isosteric heat of adsorption at low loadings proves the strength of interaction between the zeolite framework and the adsorbate molecules. q values are considerably higher for polar h2s than for non-polar substances and the order of magnitude of the former indicates the significance of electrostatic interactions. the relation of qch4 > qh2 can be attributed to the greater polarizability of ch4 molecules (this is implicitly included in the attracting lennard-jones terms of the potential model), and to that the explicitly modelled real quadrupole moment of h2 molecules is very weak. considering the greater uncertainties of these simulation results and that the experimental data for h2 and ch4 were obtained for zero coverage within a given temperature range, these simulation results also confirm the suitability of the models used in this study. equilibrium adsorption selectivities were predicted for typical hydrodesulfurization stream outlets of petroleum refinery units separated by zeolite naa at near-atmospheric pressures. the studied gas streams were comprised of between 1 and 2% h2s and ~95% h2; the remaining hydrocarbon content (low alkanes) was represented by the presence of ch4 in the model mixtures. for comparison, other compositions including very low and reasonably high h2s contents, as well as low pressure ranges were also investigated. the raw simulation results for the h2s-h2 mixtures in comparison with iast predictions shown in fig.2 illustrate well the dissimilar levels of adsorption of the two substances, with the exception of the nearly zero h2s contents of the bulk mixture. the iast calculations underestimate the simulation results for h2 at higher pressures and on the whole overestimate the simulation results for h2s at lower pressures (for visual reasons, data obtained within the very low pressure range are not presented in this figure). the most accurate estimations were achieved at 10 kpa, which is an impractical parameter for the present applications. strictly speaking, the hypothesis of iast which states that the different adsorbate molecules have access to the same adsorbent surface cannot be applied to microporous adsorbents such as zeolite naa, where the accessible surface area depends on the size of the adsorbate. in light of this, the iast predictions can be considered to be remarkably accurate. a b c figure 1. equilibrium adsorption loading (n) and isosteric heat of adsorption (q) as a function of the bulk-gas pressure for pure hydrogen sulphide (a), hydrogen (b) and methane (c) on zeolite naa at the temperatures indicated. the statistical uncertainties of the simulations results do not exceed the size of the symbols. the lines connecting simulation data at 298 k are only drawn to guide the eyes. sim.: simulation data; exp.: experimental data. kristóf hungarian journal of industry and chemistry 12 the calculated equilibrium selectivities are defined as: b j b a j a nn nn s / / sh sh 2 2 , (4) where nj stands for the equilibrium number of moles of h2 in the investigated two-component mixtures or the sum of the equilibrium numbers of moles of h2 and ch4 in the three-component mixtures, as plotted in fig.3. on the whole, this zeolite exhibits an exceptional level of selectivity of h2s to the other substances; this is not surprising given the significant differences between the equilibrium adsorption loadings of the pure components (cf. fig.1). in the case of the two-component gas mixtures, the tendency of the data satisfies the criterion that at the low-pressure limit the selectivity as defined here should be independent of the composition of the bulk-gas mixture (it is the quotient of the ratio of the single-particle partition function of the two substances in the adsorbed phase and the ratio of their free-particle partition functions [34-35]). because of technical reasons, at lower pressures the uncertainties of the selectivity data are relatively large as these data are calculated from simulation results at very low zeolite loadings. at higher pressures the separation efficiency of this zeolite is somewhat weaker. this and the fact that the change with pressure is less intense at lower h2s contents suggest the existence of a ‘crowding’ effect, which inhibits more strongly the sorption of the larger molecule, h2s. in the case of the investigated three-component mixtures, the overall picture is similar, but the selectivity values are smaller. this makes sense since the competitive effect of the additional component, ch4, for the adsorption sites is stronger. yet, the values far in excess of 1000 obtained for the typical hydrodesulfurization streams (1-2% h2s and ~95% h2) are compelling. from the mixture adsorption data, once again it was verified that electrostatic effects control the adsorbent-adsorbate interactions with this zeolite, which implies that the amount of adsorption of pure h2 and ch4 should always be small. adsorbed mole number data showed that the presence of the non-polar components does not affect the sorption of h2s in the adsorbed phase. this conclusion is also supported by the heat of adsorption data (not presented) calculated by assuming one-component mixtures (i.e. using eq.(1)). these data turned out to be simply the amount-weighted average of the q values of pure components and are very close to qh2s at the given pressure. on the other hand, the degree of adsorption of the non-polar substances is reduced by the presence of h2s. selectivities under real conditions (at 50, 100 and 200 kpa and with realistic h2s contents; 1, 2 and 5%) shown in fig.4 make this fact obvious. here, s values obtained from mixture adsorption simulations significantly exceed their counterparts calculated for an ideal case of independent adsorption (i.e. by substituting into eq.(4) the purecomponent adsorption loadings determined at pressures that are equal to the partial pressures of the mixture components). extensive non-ideality in the adsorbed phase can also be seen from the comparative failure of iast (which utilizes the assumption that the adsorbed mixture is an ideal solution) to predict the simulation results accurately at near-atmospheric pressures. it is remarkable that the selectivity of h2s to the two non-polar substances decreases as the temperature and partial pressure of h2s in the bulk gas increase. as the adsorption loading of the zeolite rises, steric hindrance plays an increasingly important role, and sorption of the larger h2s molecules reduces to a greater extent. the impact of an increase in temperature is as expected, e.g. from the higher qh2s values, but the magnitude of decrease in selectivity with temperature changes significantly as a function of the partial pressure of h2s. data lines at the two investigated temperatures seem to converge to similar values at higher partial pressures, because the drop in the sorption of h2s as the temperature increases already becomes figure 2. comparison of the iast predictions with simulation data for hydrogen sulphide (black) and hydrogen (blue). equilibrium adsorption loading (n) as a function of the mole fraction of hydrogen sulphide (yh2s) in the binary gas phase mixture on zeolite naa at 298 k and at the pressures indicated. the statistical uncertainties of the simulation results do not exceed the size of the symbols. (for interpretation of the references to colour in this figure, the reader is advised to refer to the online version of this article.) a b figure 3. equilibrium adsorption selectivity (s) on zeolite naa at 298 k as a function of the bulk-gas pressure for binary (a) and ternary (b) gas mixtures with the compositions indicated. selective removal of hydrogen sulphide using zeolite 45(1) pp. 9–15 (2017) 13 less significant at higher loadings. the two panels of fig.4 also illustrate the above-mentioned difference between the data of the binary (a) and ternary (b) mixtures, i.e. the numerical values are smaller for the ternary mixtures. besides this, the scatter of the points is larger in panel b, because the ratio of nh2 to nch4 in the bulk gas unavoidably changes as the partial pressure of h2s increases (for compositions, see fig.3). finally, panel c in fig.4 illustrates the influence of adsorbateadsorbate attraction on the adsorption characteristics. it was simulated by eliminating the coulomb potential and the attractive part of the lennard-jones potential, but retaining its soft-sphere repulsion potential component, when calculating the instantaneous adsorbate-adsorbate pair interactions in the adsorbed phase. the observed reduction in nh2s and selectivity is sizable enough to establish that like-like attraction is an important factor in the adsorption of h2s. 4. conclusion in this work, molecular simulation predictions for the adsorption of h2s from simple non-polar gas mixtures of technological interest (hydrodesulfurization stream outlets in petroleum refinery units) on zeolite naa were presented. the realistic all-atom intermolecular potential models adopted for the computations were validated by comparing the calculated isotherms of the pure substances with available experimental adsorption data. what is especially noticeable here is the matching of the experimental and simulated adsorption loadings for h2s that was achieved. the investigated zeolite exhibited a remarkable ability to capture h2s, from either binary or ternary mixtures with non-polar gases, namely h2 and ch4. the interactions between the polar h2s molecules and the hydrophilic zeolite framework were found to be particularly favourable, and the mixture-adsorption loadings for h2s essentially agreed with the corresponding pure component loadings (with the exception of the very low h2s contents of the bulkgas mixture). the reverse is true when considering the adsorption of the non-polar gaseous components under technological conditions (at near-atmospheric pressures and with a small proportion of h2s in the bulk); their bindings to the inner surface sites of the zeolite were suppressed by h2s. these results can be of practical importance in terms of selectivity. selectivities of h2s to the non-polar substances were generally higher at lower h2s partial pressures in the bulk gas, and well over 1000 for the range of h2s contents of the typical hydrodesulfurization streams. the obtained order of magnitude of the isosteric heat of adsorption data and the large decrease in selectivity with increasing temperature suggest that electrostatic interactions play a more pronounced role in the selective removal of h2s by zeolite naa and the effect of size has only a limited impact. in association with this, it was also revealed that h2s-h2s attraction contributes to the preferred adsorption of this substance. acknowledgement present article was published in the frame of the project ginop-2.3.2-15-2016-00053 (“development of engine fuels with high hydrogen content in their molecular structures (contribution to sustainable mobility)”). we gratefully acknowledge the financial support of the hungarian national research fund (otka k124353). the author would like to thank tamás kovács and zoltán ható (department of physical chemistry, institute of chemistry, university of pannonia) for their assistance in terms of data analysis. references [1] auerbach, s.m.; carrado, k.a.; dutta, p.k. (eds.): handbook of zeolite science and technology (marcel dekker, new york) 2003 isbn: 0-8247-40203 a b c figure 4. equilibrium adsorption selectivity (s) as a function of the partial pressure of hydrogen sulphide in the bulk gas for selected binary (a) and ternary (b) gas mixtures on zeolite naa at 298 k and 323 k, and at bulk gas pressures of 50 kpa, 100 kpa, and 200 kpa. comparison of the mixture selectivity data with the selectivity data for independent adsorption (indep. ads.; panels a, b) and with mixture selectivity data calculated without adsorbate-adsorbate attractions (no attr., panel c). 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10.1021/j100181a059 [35] battisti, a.; taioli, s.; garberoglio, g.: zeolitic imidazolate frameworks for separation of binary mixtures of co2, ch4, n2 and h2: a computer simulation investigation, microporous and mesoporous mat. 2011 143, 46-53 doi: 10.1016/j.micromeso.2011.01.029 hungarian journal of industry and chemistry vol. 45(1) pp. 17–22 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0004 dynamic simulator-based apc design for a naphtha redistillation column lászló szabó, 1 * klára kubovicsné stocz, 1 laura szabó, 1 sándor németh, 2 and ferenc szeifert 2 1 department of technology and development, mol plc., olajmunkás u 2., százhalombatta, h-2443, hungary 2 department of process engineering, university of pannonia, egyetem u 10., veszprém, h-8200, hungary in this simulation study the operation of a naphtha redistillation column (a column with two feeds and three products) was analyzed with the application of aspen hysys ® software. the simulator, structure of local controllers and the product-quality estimators were based on the data of an industrial column in the danube refinery. the aim of the analysis was to identify the dynamic and steady-state effects of heating and cooling as well as the sidestream of product qualities. the relationship between the tray temperatures and the quality of the products was also identified and inferential calculations were made. based on the identified relationships, a twolevel hierarchical control structure was developed. on the lowest level of the hierarchy are the local controllers of flowrates, liquid levels, pressure and duty. the inferential calculations are important components of the controller which serve as the controlled variables at the coordination level. the inputs of the estimators are the process data of the column, e.g. temperature, pressure and flowrate. on the top level of the control hierarchical structure the quality of the products are controlled by manipulating the setpoint of the local controllers. based on the analysis of the controlled variable – manipulated variable relationship, closed-loop quality control was achieved with pid controllers. the result of the analysis may form the basis of advanced process controller implementation. keywords: distillation, multilevel control, mimo, inferential, naphtha distillation, plant data 1. introduction distillation is the most widely used separation technique in the chemical and petrochemical industries. around 95 % of the separation tasks of components are performed using distillation in the chemical industry, and the distillation units use approximately 3% of the total energy consumption of the world [1]. therefore, the improvement of distillation controllers and processes is important because of their widespread use and huge levels of energy consumption. distillation is a complex task because all of the equipment are multiple input, multiple output (mimo) objects from a control point of view with strong interactions [2]. the performance of distillation controllers directly affects the productivity rates, utility usage and product quality. during the operation, attaining a sufficient level of product quality is the final goal. hence, the precise calculation of the qualities is very important from an economic point of view. in this work, the multilevel control structure of the naphtha redistillation column has been analyzed (fig.1). furthermore, a simulator with the same local control *correspondence: lszaboszhb@mol.hu structure as the existing distillation column in the danube refinery was created. the model was adapted according to the data of the sensors and laboratory measurements. the controlled quality values were provided by inferential calculations based on archived data of the unit. during the analyses a control structure was created which could be suitable for the quality control of the column, and also the resulting models can be used in the implementation of advanced process controllers (apc). figure 1. structure of the control system szabó, kubovicsné stocz, szabó, németh, and szeifert hungarian journal of industry and chemistry 18 2. experimental for the analyses of dynamic responses a piece of commerical simulation software was used. data evaluation and parameter identification of the inferential calculations were performed with r programming language. 2.1. separation task the column has two feeds, the light naphtha feedstock possesses an initial boiling point of 12 °c and a final boiling point of 150 °c, while the boiling range of the heavy naphtha feedstock stretches from 57 to 197 °c. the task of the column is to separate the two feeds into three different naphtha products. the specification of the product streams are the following: distillate final boiling point should be between 58 and 65 °c, the final boiling point of the side product should be between 87 and 147 °c, and the initial boiling point of the bottom product should be between 99 and 103 °c. the simulator was implemented using aspen hysys ® software. the structure of the simulator is shown in fig.2. 2.2. simulator the implementation of the column was achieved over two main steps. in the first step, a steady-state simulator of the column was developed. the structure of the simulator follows the process flow diagram in fig.2. the column is divided into two parts, the light feedstock is loaded into the upper section (column 107), and the heavy feedstock is fed into the lower section (column 102). the towers, air coolers and heat exchangers were simulated with rigorous blocks and the model was adapted to data of the sensors and laboratory measurements. in the second step, the dynamic simulator was created based on the steady-state model. during the implementation of the dynamic simulator the calculation blocks were defined from the sizes of the actual equipment, e.g. the parameters of the trays in the tower. in some cases, pseudo pieces of equipment had to be defined to achieve a more realistic simulator, e.g. the bottom of the columns were modelled with a vertical drum to create a more detailed model. 2.3. measurement disturbances before determining the parameters of the controller, noise and time delays were applied to the calculated values. the disturbaces were determined based on our previous experience. transfer function blocks were used to simualte measuring instruments. their parameters can be seen in table 1. these signals were used later as controlled values. 2.4. control structure of column fig.1 represents the overall structure of controllers. on the lower level of the hierarchy the local controllers can be found. on this level, the controllers maintain the operating conditions (pressure and liquid level controllers) of the column and eliminate the disturbances (mass flowrate controllers) of the environment. the controller output variables are the valve positions and the process variables are the mass flowrates, liquid levels and pressure. the structure of the local controllers can be seen in fig.2, which is the same as the structure of the controller in the real column. the fc1 and fc2 controllers eliminate the fluctuation of the feed mass flowrate. the pc and the tc controllers compensate for weather changes and the fluctuation of fuel gas. the liquid level controllers (lc1, lc2 and lc3) were necessary to ensure normal operation because the refluxes and the boil-up flowrate would be zero if there is no liquid phase in the reflux drum and at the bottom of the columns [3]. pi controllers were applied at the local level. the degree of separation is based on the sustenance of the temperature difference between table 1. disturbances value type noise delay lag mass flowrate 1.0 % 15 s 0 s pressure 0.2 % 0 s 0 s temperature 0.3 % 30 s 60 s level 1.0 % 60 s 0 s figure 2. structure of the simulator dynamic simulator-based apc design 45(1) pp. 17–22 (2017) 19 products. the main target of the operation is to achieve specified product qualities. the provision of online quality values for the control is an important task in the industry. one of the feasible solutions is to apply inferential calculations. generally the inputs of these calculations are temperatures, because the quality of products is strongly correlated with the tray temperatures of the columns. consequently, the temperature and quality controls serve the same purpose. therefore, in this paper the quality of the products was controlled at the top level of the control hierarchy. the controller outputs on this level were the setpoints of the local controllers (fc3, fc5 and tc) and the controlled values were the outputs of the inferential calculations. 3. results and analysis 3.1. validation of the simulator in the first analysis, the dynamic behavior of the simulator was validated. (the steady-state accuracy was validated during the construction of the model.) the model was compared to the historical data of the real column. as fig.3 shows, the coil outlet temperature (cot) of the furnace was changed over two steps. during this process the top temperature of column 107 was controlled. the head and bottom temperatures of column 102 were analyzed, because the effect of the cot was significant on these parameters. the operating point of the real column was different from the simulated one, however, in this analysis only its dynamic behavior was evaluated. therefore, in the simulator the setpoint of the cot was changed in the same direction and by the same amount as the measured data. the signals were normalized in order to compare the trends easily. it can be seen that the curves possess the same correlation in both the simulated and real columns. the dynamics of the responses were also identical in both cases, thus the simulator was found reliable for further analyses. 3.2. analysis of local controllers for the tuning of the local controllers previous experiences were drawn on [4]. it was assumed that the controllers exhibit no significant interactions so they can be tuned independently. before determining the parameters of the controllers, filters were applied, hence, the dynamics of the loops were approximated to the real control loops. the control loops were tuned in the following order: flowrate (fc1-7), the liquid level (lc1-3) and pressure (pc) controllers. in the last step the parameters of the coil outlet temperature controller (tc) were determined. for the loops, honeywell equation b [5-6] was used, and the proportional and integrating parameters were determined using the built-in autotuner tool. after automatic tuning, the loops were tested and fine tuning was carried out to avoid fluctuation of the loops. the behavior of the fc1 is presented in fig.4. as the figure shows, the controllers follow the setpoint without exceeding it, which ensures a robust local controller system. the raw calculated signal, the signal loaded with noise and the filtered (controlled) signals are also presented in fig.4. as the results show, the control of the raw values is stable and is the first signal to reach a setpoint. 3.3. inferential calculations the quality estimators were created for the final boiling points of the distillate and the side product and for the initial boiling point of the bottom product. for the inferential fitting the laboratory and process data was used; the data was collected over a period of one year. in the case of the process data, all relevant measurement points of the column were considered (flowmeters, figure 4. fc1 controller figure 3. validation of the simulator szabó, kubovicsné stocz, szabó, németh, and szeifert hungarian journal of industry and chemistry 20 temperature and pressure measurements). one hourlong periods were aggregated from the online data before each laboratory sample time. from these values pressure compensated temperatures (pct) and ratios of the mass flowrates were also calculated. the inputs of the equations (see table 2) were determined using correlation analysis, thus the qualities were calculated from the most relevant values. the parameters of the equations were calculated using linear regression. the results of the fittings are presented in fig.5. 3.4. structure of quality controllers according to the separation task the controlled variables (cv) are: distillate final boiling point (cv1), sideproduct final boiling point (cv2) and bottom product initial boiling point (cv3). the manipulated variables are the following: setpoints of fc3 (mv1), fc5 (mv2) and tc (mv3). the structure of the quality controllers was determined with the help of the relative gain array (rga) [7]. to create the array, a step test was performed for each manipulated variable (mv) in the simulator. the rga is presented in table 3. the elements of the matrix evaluate a possible loop with the given mv – cv pair. if the element of the array is negative, closing other loops will reverse pairing gain. this configuration will become unstable if the other loops operate. if the element of the rga exceeds one, interaction with other loops has an inhibiting effect. closing other loops decreases pairing gain. if the value is between 0 and 1 then pairing gain will increase by closing the other loops; the interaction is the greatest at 0.5. in the case of this pairing the loop should be tuned when the other loops are automated. if the rga value is 1 then the other loops have no effect on the pairing gain. in the case of the cv1 the evident manipulated variable is mv1. the other two can be paired in two ways. according to the rga, the obvious pairing should be cv2 – mv2 / cv3 – mv3. however, there is a primary effect between mv2 and cv2, and it possesses a negative gain. this behavior could make the control loop instable, or the settling time of the controlled object would be large. the dynamic responses are presented in fig.6. in this analysis the mvs were stepped during the first minute. only the local controllers were in closed loops during the analyzed period. table 2. input parameters of inferential calculations inferential input 1 input 2 final boiling point of distillate pct of 107 head temperature final boiling point of side product pct of 107 bottom temperature ���ℎ� ���ℎ�ℎ� ���ℎ� ���� initial boiling point of bottom product pct of 102 bottom temperature figure 6. open loop test cv2 – mv2 table 3. relative gain array mv1 mv2 mv3 cv1 7.7 -1.2 -5.5 cv2 -6.9 1.9 6.0 cv3 0.2 0.3 0.5 figure 5. performance of inferential calculations dynamic simulator-based apc design 45(1) pp. 17–22 (2017) 21 the following final control pairings were applied: cv1 – mv1, cv2 – mv3 and cv3 – mv2. according to this analysis quality control can be achieved using simple pid control loops. therefore, the analysis of the closed-loop quality control in the following chapter was performed using only pid loops. this analysis was also the basis of an apc implementation. the initial apc models can be seen in fig.7. 3.5. operation of quality controllers in this analysis the operation of the quality controllers was analyzed in the case of a disturbance. the mass flowrate of the light naphtha feed was changed at 5 o’clock. during the analyzed period all of the local and quality controllers were in closed loops. according to the results in fig.8, the controller system can compensate for this change. in the figure the values of the mvs were normalized between their minimum and maximum limits. in the case of cv1 this quality did not violate the specification limit, and the controlled variable was close to the setpoint after 2.5 hours. this parameter possessed the smallest peak of the three cvs at approximately 1.3 °c. cv2 exhibited a peak at approximately 2 °c, nevertheless, this was well within the specification limit so it did not violate it. the settling time was about 7.5 hours. cv3 exhibited a peak at approximately 3 °c which violated the specification limit. after 2.5 hours the cv once again exceeded the limit. the settling time was ~15 hours. as can be seen the outputs (op) were moved after the settling of the cvs, but because of the long settling time the whole time period was not presented. figure 8. operation of quality controllers figure 7. apc models szabó, kubovicsné stocz, szabó, németh, and szeifert hungarian journal of industry and chemistry 22 4. conclusion for the analysis of the naphtha redistillation column at mol plc. the dynamic simulator of the unit was adapted to the data of the real equipment. the steadystate accuracy and the dynamic behavior of the model were evaluated. the simulator is reliable for the analysis of the column. for the operation of the distillation column a twolevel control structure was implemented in the simulator. on the lower level of the control hierarchy controllers were created which facilitated normal operating conditions of the column (pressure and liquidlevel controllers) and eliminated the disturbances of the environment (mass flowrate controllers). to ensure quality signals, inferential calculations were created based on the historical data of the real column. the inputs of the calculations were mainly the temperature measurements of the columns. hence, the controlled temperatures were chosen during the correlation analysis of the inferential calculations; on the top level of the control hierarchy the controlled variables were the outputs of the quality estimators. the manipulated variables were the setpoints of the local controllers. the pairing of the manipulated and controlled variables should be defined carefully. the first aspect of the pairing was the gain between the variables, however, the dynamic responses were also considered. to eliminate the interaction and to improve the performance of the quality controller, decoupling [8] or a model predictive controller [9] was recommended. the simulator-based column analysis can be a good foundation for an advanced process controller. the cv-mv pairing and resulting single input-single output models can be used as initial models in advanced process controllers. furthermore, the simulator can be used for the analysis of column operation issues in the plant. the resulting inferential calculations have already been implemented and are available for the operators to facilitate quality control. acknowledgements we acknowledge the financial support of széchenyi 2020 under the project efop-3.6.1-16-2016-00015. references [1] mansour, k.; mansour, e.: rigorous optimization of heat-integrated and petlyuk column distillation configurations based on feed conditions, clean techn. environ. policy, 2009 11(1), 107–113 doi: 10.1007/s10098-008-0171-6 [2] skogestad, s.; morari, m.: the dominate time constant for distillation columns, computers and chemical engineering, 1987 11(6), 607–617 doi: 10.1016/0098-1354(87)87006-0 [3] buckley, p.s.: techniques of process control, (wiley, london, united kingdom) 1964 isbn10:0882757776 [4] szabó, l.; németh, s.; szeifert, f.: three-level control of a distillation column, engineering, 2012 4(10), 675–681 doi: 10.4236/eng.2012.410086 [5] honeywell: application module algorithm engineering data, 1-800 343-0228 [6] aspentech: aspen hysys unit operations reference guide, version number: v10 [7] skogestad, s.: dynamics and control of distillation columns: a tutorial introduction, chemical engineering research and design, 1997 75(6), 539–562 doi: 10.1205/026387697524092 [8] benz, s.j.; scennal, n.j.: an extensive analysis on the start-up of a simple distillation column with multiple steady states, the canadian journal of chemical engineering, 2002 80(5), 865–881 doi: 10.1002/cjce.5450800510 [9] luyben, w.l.: process modeling, simulation, and control for chemical engineers (mcgraw-hill, new york, usa) 1990 isbn-10:0070391599 hungarian journal of industry and chemistry vol. 45(1) pp. 23–27 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0005 replacement of biased estimators with unbiased ones in the case of student's t-distribution and geary’s kurtosis gergely tóth* and pál szepesváry institute of chemistry, faculty of science, eötvös loránd university, 1/a pázmány péter sétány, budapest, h-1117, hungary the use of biased estimators can be found in some historically and up to now important tools in statistical data analysis. in this paper their replacement with unbiased estimators at least in the case of the estimator of the population standard deviation for normal distributions is proposed. by removing the incoherence from the student’s t-distribution caused by the biased estimator, a corrected t-distribution may be defined. although the quantitative results in most data analysis applications are identical for both the original and corrected tdistributions, the use of this last t-distribution is suggested because of its theoretical consistency. moreover, the frequent qualitative discussion of the t-distribution has come under much criticism, because it concerns artefacts of the biased estimator. in the case of geary’s kurtosis the same correction results (2/π)1/2 unbiased estimation of kurtosis for normally distributed data that is independent of the size of the sample. it is believed that by removing the sample-size-dependent biased feature, the applicability domain can be expanded to include small sample sizes for some normality tests. keywords: unbiased estimator, normal distribution, anscombe-glynn test, jarque-bera test, bonett-seier test 1. introduction the student's t-distribution [1] is one of the most widely used statistical functions in experimental practice. it is well documented that experts active in analytical, physical and clinical chemistry, biology, agriculture, ecology, economy as well as forensic science or even legal representatives apply this tool to formulate solid statements, e.g. population means, to differentiate between two sample means, etc., which are in most cases necessarily based on a limited number of observations. fortunately, scientists are in this respect soundly supported by a lot of textbooks, standards, software, software systems, and last but not least trained in elements of statistics. however, it should be a moral obligation to be aware of the evolution of this routinely used method, its principles and often tacitly supposed assumptions. although not crucial in daily use, it is worthwhile to know that besides student’s t-distribution there are different functions which may be suitable for the determination of percentiles in the same way as the t-distribution. they may differ mainly in terms of alternate estimators for the population mean and population standard deviation. an attractive variant is presented in this work emphasizing its theoretically fully consistent feature on the contrary to the student's t-distribution. *correspondence: toth@chem.elte.hu the student’s t-distribution corresponds to a ratio of normally distributed random variables to chidistributed random variables (see the references in the historical review of zabell [2]). chi-distributed variables postulate normally distributed data as well. gosset [1] used in his definition an estimate of the standard deviation which is biased relating the population standard deviation and even the variance in the case of normally distributed random variables as was shown earlier by helmert [3-4]. amazingly, when fischer proposed a transformation of gosset’s original z variable to 1 nzt [5-6], he chose an estimate for the standard deviation which is also biased relating σ. a corrected tcdistribution is proposed that fulfils all theoretical requirements and yields a more normal distribution-like shape. it is consequently based on normal sample data and uses an unbiased estimator. a similar correction can be applied to geary’s kurtosis that is the ratio of the mean deviation to the standard deviation [7]. in this work the use of the correction is proposed in order to eliminate the sample-size dependency of the mean geary’s kurtosis on normally distributed data. finally, some remarks are made on statistical tests based on sample-size dependent values in order to extend their applicability to small sample sizes. tóth and szepesváry hungarian journal of industry and chemistry 24 2. theoretical background the square root of the mean of the square of the centred observations of the random variable, y,   n yy s n i i n     1 2 (1) may be an estimator of the population standard deviation, σ, of a sample. n is the sample size and y denotes the sample mean. bessel pointed long before to the bias of sn and proposed:   1 1 2      n yy s n i i . (2) although �� is already an unbiased estimator of the variance, ��, irrespective of the distribution of y, the statistics �� and � are both biased in terms of the standard deviation, �. however, there is a correction [5-6, 89]: , 2 1 2 1 2 )(4                  n n n nc (3) which applies to � by transforming it, in the case of normally distributed variables, into an unbiased statistic:  nc s s 4 c  . (4)  nc4 follows from helmert’s papers or cochran's theorem [10]. for normally distributed y, )(1 sn  exhibits a chi distribution with n-1 degrees of freedom.  nc4 is the expected value of s/σ. there is a  nc2 value as well, that is equal to the expected value of �� �⁄ . the correcting effect of  nc4 may be considerable for low values of n (table 1). table 1. selected c4(n) corrections n c4(n) 2 0.7979 3 0.8862 4 0.9213 5 0.9400 10 0.9727 20 0.9869 30 0.9914 figure 1. student’s t-distribution compared with the standard normal distribution the correction term is frequently used in statistical process control (spc) to define ±3σ intervals and process standard deviations that are determined for samples of different sizes. 3. results and discussion 3.1. discussion of the density functions of the student’s t-distribution let y be an independent n(μ,σ2) variable. the ns y t /   (5) statistic exhibits the usual student t-distribution with n1 degrees of freedom. the density function (eq.(6)) can be derived as the quotient of normal and chi-distributed random variables. the independency of the nominator and denominator can be shown and it is also proved by a series of theorems that t defined in eq.(5) follows a student’s t-distribution with n-1 degrees of freedom (see the references in [2]):   22 1 1 2 1 2 1 1 )( n n t n n n tf                              (6) the distribution sketched in fig.1 is widely known and needs no comments except for its flaw: it is based on the biased statistic (eq.(2)) for σ. by replacing the standard deviation of the sample, s, in eq.(5) with the unbiased equivalent one, sc, corrected by c4(n), results in a new value: ns y t /c c   , (7) and in the density function: note on student’s t-distribution 45(1) pp. 23–27 (2017) 25       2 2 4 2 c 2 2 4 2 c 4 c 1 1 2 1 1 1 2 1 1 2 )( 1 )( n n nc t nc t n n n nc tf                                         . )( )( )1,2/(crit 4 )1,2/(crit 4 )1,2/(crit cc     n nn st nct nc s ts   table 2. sample-size dependence of geary’s and pearson’s kurtosis. the c4(n)-corrected geary’s and the size-corrected pearson’s kurtosis [11] provided the ∞ limit values for all sample sizes within the statistical uncertainty of the 105 random samples. n geary’s kurtosis pearson’s kurtosis 3 0.9004 1.5000 4 0.8659 1.8005 5 0.8489 1.9996 6 0.8385 2.1437 7 0.8319 2.2501 8 0.8267 2.3340 9 0.8233 2.4006 10 0.8200 2.4557 20 0.8085 2.7141 50 0.8021 2.8820 100 0.7999 2.9408 ∞ 0.7979 3.0000 (8) which is shown in fig.2. as expected, the corrected student’s t-distribution (student’s tc-distribution) consists of more distinct peaks, it exhibits fatter tails than the standard normal distribution, but rather oddly at its maximum, i.e. when tc = 0, the value f(tc) does not depend on n and is represented by the value 2/1 , the same as for those of normal distribution. the function f(tc) and the student’s t-distribution without a doubt differ in this respect. the obvious differences between the student and modified student distributions do not complicate their daily usage. the confidence intervals calculated using s and t or sc and tc estimators and distributions, respectively, n ts y n )1(,2/ cc    and n st y n )1(,2/    (9) do not differ, because (10) evidently, corresponding estimators and functions should be used. 3.2. the effect of the correction to geary’s kurtosis geary’s kurtosis [7], wn, is the ratio of the mean absolute deviation (mad) to the standard deviation (eq.(11)). it is an alternative to pearson’s kurtosis based on the fourth moment. the expected value of geary’s kurtosis depends on the sample size even for normally distributed data [7]. the mean values of 105 random samples from standard normal distributions are shown in table 2. n n i i n s yy n w     1 1 (11) if the c4(n) corrections (table 1) are applied during the calculation of the nominator of the ratio as wn,corr=wn c4(n), the expected value of the kurtosis is (2/π)1/2 for all sample sizes. this means that the platykurtic and the leptokurtic features of a sample can be found without searching for the size-dependent dividing value in tables. 3.3. sample-size bias in statistical tests geary’s kurtosis and its transformed values are used in normality tests due to their enhanced sensitivity to some leptokurtic deviations from normality [12]. contrary to the case of the student’s t-distribution, where the correction has no effect on the t-test, here the effect of the correction is not cancelled. generally, the size dependence decreases the performance of the tests for small sample sizes. this feature is interpreted by users as a recommendation that the tests are unsuitable for small sample sizes. in the same way, neglect of sample-size dependence is applicable in tests where pearson’s kurtosis is used. the calculated mean value of pearson’s kurtosis is shown in table 2 but its convergence is rather weak to the theoretical value of 3. it should be noted here that the sample-size unbiased estimator of kurtosis can be easily calculated [11]. figure 2. corrected student’s t-distribution compared with the standard normal distribution tóth and szepesváry hungarian journal of industry and chemistry 26 table 3. sample-size dependence of five normality tests based on unbiased or sample-size-dependent biased estimators. the numbers show the ratio of the rejected null hypotheses to all trials at a significance level of 0.05 from 105 random samples. n shapirowilk d’ agostino anscombeglynn bonettseier jarque -bera 4 0.0502 5 0.0521 0.0373 6 0.0477 0.0189 0.0087 7 0.0492 0.0343 0.0282 8 0.0505 0.0365 0.0348 9 0.0507 0.0538 0.0369 0.0390 0.0024 10 0.0498 0.0528 0.0394 0.0417 0.0058 20 0.0497 0.0525 0.0406 0.0421 0.0089 50 0.0498 0.0500 0.0466 0.0470 0.0241 100 0.0499 0.0493 0.0533 0.0490 0.0368 in table 3 the type-i error of some normality tests calculated on 105 standard normal samples is shown. in the calculation the ‘moments’ package in r was used [13]. table 3 contains the ratio of the samples to all samples where the h0 hypothesis of normality was rejected at the significance level of 0.05. the shapirowilk method [14] uses the ratio of two unbiased estimators of the variance, and is suitable for all data sizes. the skewness test of d’agostino [15] slightly overestimates the number of rejected cases. it is based on the normalized third-order central moment definition of skewness, where the expected value is estimated without bias. the anscombe-glynn [16] test applies pearson’s kurtosis without size correction using a biased estimation of normally distributed data. the bonettseier [12] test shown here uses geary’s kurtosis and the jarque-bera test [17] combines skewness and pearson’s kurtosis. the performance of the last three tests was rather weak for small sample sizes, whereof one cause might be the lack of correction for small sample sizes even for normally distributed data. these tests are usually only recommended for medium and large sample sizes. the correction should extend the applicability domain to small sample sizes. of course, the type-i error of normally distributed data is only one narrow aspect of a test, detailed analysis should be performed to investigate the effect of correction on many distributions, like, e.g. in ref. [12]. 4. conclusion nowadays, data are evaluated by computers and biased estimators can be replaced by unbiased ones, even if their calculation schemes are complex. it has been shown that, in terms of student’s tdistributions, to decide upon the confidences of statistics one has two functions which are completely equivalent as far as practical applicability is concerned. they can, however, be distinguished theoretically. the assertion that only the unbiased estimator should be recognized as the correct one implies the use of the corrected student’s t-distribution, f(tc). in that case the known shape of the student’s t-distribution may be labelled as an artefact and the usual application of the student’s tdistribution as a production of “correct numbers by an incoherent theory”. in the case of geary’s kurtosis, the correction removes the sample-size dependence from the expected value. this change of distinguishing platykurtic or leptokurtic features of the sample is simpler than using the original version of geary’s kurtosis. furthermore, subtracting (2/π)1/2 results in a number to be interpreted in a similar way to the excess kurtosis obtained by subtracting 3 from the pearson’s kurtosis. as a further study, the use of unbiased/samplesize-dependent corrections to extend the applicability domain to small sample sizes in the case of normality tests is recommended. it is believed that the use of biased estimators was acceptable before the age of computers and a systematic change to unbiased ones might be necessary in terms of statistics and standards with regard to industrial processes. acknowledgement the authors are sincerely grateful for the valuable comments of prof. s. kemény and other participants during the scientific discussion after the presentation concerning student’s t-distribution at the scac 2010 conference in budapest in september 2010. references [1] student (gosset, w.s.): the probable error of a mean, biometrika 1908 6(1), 1–25 doi: 10.2307/2331554 [2] zabell, s.l.: on student’s 1908 article “the probable error of a mean”, j. am. stat. assoc. 2008 103(481), 1–7 doi: 10.1198/016214508000000049 [3] helmert, f.r.: über die wahrscheinlichkeit der potenzsummen der beobachtungsfehler und über einige damit in zusammenhang stehende fragen, z. math. phys. 1876 21, 192–218 [4] helmert, f.r.: die genauigkeit der formel von peters zur berechnung des wahrscheinlichen beobachtungsfehles directer beobachtungen gleicher genauigkeit, astronomische nachrichten 1876 88(8-9), 113–131 doi: 10.1002/asna.18760880802 [5] fischer, r.a.: applications of “student’s” distribution, metron 1925 5, 90–104 [6] fischer, r.a.: statistical methods for research workers, (oliver & boyd, edinburgh and london) 1925. [7] geary, r.c.: moments of the ratio of the mean deviation to the standard deviation for normal samples, biometrika 1936 28(3/4), 295–307 doi: 10.2307/2333953 [8] grubbs, f.e.; weaver, c.l.: the best unbiased estimate of population standard deviation based on group ranges, j. am. stat. assoc. 1947 42(238), 224–241 doi: 10.1080/01621459.1947.10501922 note on student’s t-distribution 45(1) pp. 23–27 (2017) 27 [9] vincze, i.: matematikai statisztika ipari alkalmazásokkal, (műszaki kiadó, budapest), 1975 pp. 58, 89, 165–168 isbn 963-10-0472-4 [10] cochran, w.g.: the distribution of quadratic forms in a normal system, with applications to the analysis of covariance, math. proc. cambridge 1934 30(2), 178–191 doi: 10.1017/s0305004100016595 [11] joanes, d.n.; gill, c.a.: comparing measures of sample skewness and kurtosis, j. roy. stat. soc. dsta. 1998 47(1), 183–189 doi:10.1111/1467-9884.00122 [12] bonett, d.g.; seier, e.: a test of normality with high uniform power, comput. stat. data an. 2002 40(3), 435–445 doi: 10.1016/s0167-9473(02)00074-9 [13] komsta, l.; novomestky, f.: moments r package, version 0.14, 2015 at http://cran.r-project.org, accessed in october 2017 [14] shapiro, s.s.; wilk, m.b.: an analysis of variance test for normality (complete samples), biometrika 1965 52(3/4), 591–611 doi: 10.1093/biomet/52.3-4.591 [15] d’agostino, r.b.: transformation to normality of the null distribution of g1, biometrika 1970 57(3), 679–681 doi: 10.1093/biomet/57.3.679 [16] anscombe, f.j.; glynn, w.j.: distribution of the kurtosis statistic b2 for normal samples, biometrika 1983 70(1), 227–234 doi: 10.1093/biomet/70.1.227 [17] jarque, c.m.; bera, a.k.: efficient tests for normality, homoscedasticity and serial independence of regression residuals, economic letters 1980 6(3), 255–259 doi: 10.1016/0165-1765(80)90024-5 hungarian journal of industry and chemistry vol. 45(1) pp. 29–36 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0006 formation, photophysics, photochemistry and quantum chemistry of the out-of-plane metalloporphyrins zsolt valicsek, 1* melitta p. kiss, 1 melinda a. fodor, 1 muhammad imran, 2 and ottó horváth 1 1 department of general and inorganic chemistry, institute of chemistry, faculty of engineering, university of pannonia, egyetem u. 10., h-8200 veszprém, hungary 2 department of chemistry, baghdad-ul-jadeed campus, the islamia university of bahawalpur, 63100 bahawalpur, pakistan among the complexes of porphyrins, special attention has been paid to those possessing out-of-plane (oop) structures, for the formation of which the size, as well as the coordinative character of the metal center are responsible. in these coordination compounds, the central atom cannot fit coplanarly into the cavity of the ligand, hence, it is located above the porphyrin plane, distorting it. equilibria and kinetics of the complex formation, spectrophotometric, photophysical and primary photochemical properties of post-transition and lanthanide oop metalloporphyrins were investigated, in addition electronic structural calculations were performed; hence, the general oop characteristics were determined.meanwhile, few doubtful questions have attempted to be answered concerning the categorization of metalloporphyrins, the borderline case complexes and hyperporphyrins. keywords: out-of-plane metalloporphyrins, formation kinetics, uv-vis spectrophotometry, photochemistry, borderline case complexes 1. introduction porphyrins and their derivatives play important roles in several biochemical systems. four pyrroles are connected through methylidine bridges, forming the porphin ring. its planar structure with an extended conjugated π-electron system provides aromatic characteristics and a special coordination cavity for the binding of metal ions of suitable radius [1-2]. metalloporphyrins are the central parts of naturally important compounds, e.g., magnesium(ii) chlorins in bacteriochlorophylls and chlorophylls; iron(ii) protoporphyrin in hemoglobin; and iron(iii) protoporphyrins in myoglobin, cytochromes, oxidase, peroxidase, catalase, and oxoanion reductase enzymes. ringed tetrapyrroles provide strong chelating effect which can promote the hyperaccumulation of rare metal ions in living cells, and also in abiotic environments, e.g. in kerogens. in porphyrins the conjugation favors a planar structure. however, peripheral substituents or the metal center (originating from its size or axial ligand) can cause geometrical distortion. this certainly affects the functions of enzymes, as well as the biosynthesis of metalloporphyrins. in chemical research, due to distortion, redox potentials, basicity, reactivity, catalytic *correspondence: valicsek@almos.uni-pannon.hu activity and coordinative abilities of porphyrins can be modified. also, due to the distortion, the degree of symmetry decreases, resulting in characteristic spectral changes in various ranges of the electromagnetic spectrum. the most frequent types of distortions are dome, saddle, ruffled and wave (chair-like) [3]. overcrowded substitution on the periphery [3-4] or insufficiently short metal-nitrogen bonds due to the shrinkage of the coordination cavity can cause the ruffled or saddled deformation [2, 5-7]. if, however, the m-n bonds are significantly longer than half the length of the diagonal n-n distance in the free-base porphyrin, dome deformation can occur. this happens if the radius of the metal center exceeds the critical value of about 75-90 pm (depending on the type of porphyrin ligand) or square planar coordination is not preferred. such metal ions are too big to fit into the ligand cavity. hence they are located above the plane of the pyrrolic nitrogens; forming sitting-atop (sat) or out-of-plane (oop see fig.1) complexes, displaying thermodynamic instability, kinetic lability, typical photophysical features and photochemical reactivity [89]. in this work, we review our recent results regarding the formation, structure and photoinduced behavior of water-soluble oop metalloporphyrins. these complexes with a diverse range of metal ions can be more simply produced in aqueous systems than in organic solvents. in this regard one of the most suitable free-base ligands is the anionic 5,10,15,20-tetrakis(4sulfonatophenyl)porphyrin (h2tspp4– see fig.1) due valicsek, kiss, fodor, imran, and horváth hungarian journal of industry and chemistry 30 to its negative charge promoting the coordination of positively charged metal ions. besides, this ligand is the most frequently used reagent among the free-base porphyrins [1]. 2. experimental analytical grade tetrasodium 5,10,15,20-tetrakis(4sulfonatophenyl)porphyrin (c44h26n4o12s4na4·12h2o = na4h2tspp·12h2o) (sigma–aldrich) and simple metal salts such as nitrate, sulfate, chloride or perchlorate were used for the experiments. the solvent was double-distilled water purified with a millipore milli-q system. the ph of the majority of the metalloporphyrin solutions was adjusted to 8 by application of a borate buffer, whilst maintaining the ionic strength at a constant value of 0.01 m. in a few cases, the ph was regulated to 6, and the ionic strength to 1 m, by an acetate buffer, to hinder hydrolysis. the absorption spectra were recorded and the spectrophotometric titrations were monitored by using a specord s-100 or a specord s-600 diode array spectrophotometer. for the measurement of fluorescence spectra, a perkin elmer ls-50b or a horiba jobin yvon fluoromax-4 spectrofluorometer was applied. the latter piece of equipment supplemented with a time-correlated single photon counting (tcspc) accessory was utilized to determine fluorescence lifetimes, too. uv-vis spectrophotometric data (molar absorption, fluorescence quantum yields and lifetimes) of the free-base porphyrin were used as references for the determination of those of metalloporphyrin complexes [1]. for the determination of photochemical properties via continuous irradiations, a piece of amko lti photolysis equipment (containing a 200w xe–hg lamp and a monochromator) was applied. for the electronic structural calculations, the b3lyp density functional theory (dft) method and the lanl2dz basis set were used. on the basis of our earlier quantum chemistry experiences, the sulfonatophenyl substituents exhibit negligible effects on the coordination of the metal center in the cavity; thus, the anionic porphyrin (h2tspp4−) can be modeled on the unsubstituted porphin (h2p) [4, 10]. 3. results and discussion 3.1. uv-vis spectrophotometry porphyrins and their derivatives belong to the strongest light-absorbing materials (both natural and artificial), therefore, ultraviolet-visible spectrophotometry is one of the most fundamental, in addition, most informative spectroscopic techniques in porphyrin chemistry. they possess two ππ* electronic transitions in the visible range of the electromagnetic spectrum: bor soret band at about 350-500 nm, usually with a molar absorbance of 105 m-1cm-1 (fig.2), and q bands at 500-750 nm generally with intensities of one order of magnitude less. these latter bands in free-base ligands split due to the presence of protons on two diagonally situated pyrrolic nitrogens, to be more precise, as a result of the reduced symmetry (because of the disappearance of the four-fold rotation axis) compared to the metallated or deprotonated forms. this split is not detectable in the soret range, hence, these two types of bands in the visible region are remarkably different [1]. in the soret region, compared to the corresponding free-base ligands, the typical in-plane metalloporphyrins (e.g. fe3+, au3+, cu2+, pd2+) exhibit blueshifts because the atomic orbitals of their metal centers which are covalently bonded in the plane can overlap more strongly with the highest occupied molecular orbitals (homo) of the ligand, resulting in a stronger reduction in energy; whereas the lowest unoccupied molecular orbitals (lumo) do not change. thus, the energy gaps between the excited and ground states become greater. in the oop complexes, the atomic orbitals of the more weakly bonded metal ions (e.g. cd2+, hg2+, tl3+) may slightly affect the unoccupied mos and to a lesser extent the occupied ones, leading to a reduction of the energy gaps, i.e. an increase in the corresponding wavelengths (scheme 1) [1, 9]. a) b) figure 1. structure of an in-plane metalloporphyrin {mtspp=metallo-5,10,15,20-tetrakis(4sulfonatophenyl)porphyrin} (a); and that of an out-of-plane complex (b) [9]. study of the out-of-plane metalloporphyrins 45(1) pp. 29–36 (2017) 31 beside electronic factors, due to the rigidity of the porphyrins’ ringed structure, steric effects also influence the spectra: the redshift of absorption bands is one of the most common spectroscopic consequences of the non-planarity of porphyrin [3]. octabrominated freebase porphyrin, h2tsppbr8 4–, was applied to investigate the spectrophotometric effects of the macrocycle’s highly saddle-distorted structure (fig.2). in porphyrins with aryl substituents, this distortion can lead to the extension of delocalization by the twisting of aryl substituents from a nearly perpendicular orientation closer to the porphyrin plane (fig.1) [4]. the larger, post-transition metal ions, e.g. thallium(i), lead(ii) and bismuth(iii) ions, can cause a similarly large redshift of the porphyrins’ absorption bands. since their complexes possess the most highly dome-distorted structures, also a ruffled-like deformation of the periphery superposes on this high degree of doming. considering the spectral effects (bathochromic or not quite exactly hyperchromic effects), the complexes possessing such highly redshifted absorption bands used to be referred to as hyperporphyrins; depending on the highest occupied electron subshell of the metal center, por d-type hyperporphyrins. previously in terms of this categorization of metalloporphyrins, only the electronic effects of the metal ion (through its electron configuration) were taken into consideration and not steric (distorting) effects [1]. nevertheless, in the typical d-type hyperporphyrins, e.g. the low-spin chromium(iii), manganese(iii), nickel(ii) and cobalt(iii) porphyrins, the radius of the metal center, and thus, the metal-nitrogen bonds are too short, resulting in the contraction of the coordination cavity, along with the ruffled deformation of the macrocycle [2, 5-7]. 3.2. equilibrium and kinetics of complex formation porphyrins are peculiar ligands in terms of complexation due to their planar, cyclic, rigid, aromatic, tetradentate, as well as protonated structure. the formation of an out-of-plane complex of a large metal ion is usually at least two orders of magnitude faster than that of an in-plane one since a smaller metal ion is not able to coordinate to all four pyrrolic nitrogens of the reaction intermediate, in the cavity of which the two protons also remain {h2-p-m}. therefore, dissociation of the metal ion is more favorable than that of the protons. besides the insertion of a smaller metal ion, its dissociation from the in-plane complex of the endproduct may be kinetically hindered due to the rigidity of the macrocycle [1]. formation of the in-plane complexes used to be enhanced by the addition of a small concentration of a metal ion with larger ionic radius (e.g. cd2+, hg2+, pb2+) to the solution of the smaller one because the insertion of the larger metal ion into the ligand cavity is much faster. however, the oop complex is considerably less stable. in its dome-distorted structure, two diagonal pyrrolic nitrogens are more accessible from the other side of the ligand, owing to the enhancement of their sp3 hybridization, hence, the metal center can be easily exchanged for the smaller one [1-2, 9]. this accessibility makes the realization of dinuclear out-of-plane monoporphyrins (2:1 complexes) possible if the metal ion possesses a low (single) positive charge and is large, i.e. its charge density is small enough, e.g. mercury(i), silver(i) and thallium(i) ions [1, 8-9]. moreover, the out-of-plane position of the metal center, together with the dome-distorted structure (owing to the twisting of aromatic substituents from a nearly perpendicular position closer to the porphyrin plane) may promote the formation of so-called sandwich complexes of various compositions, in which two metal ions can coordinate to one macrocycle, and, reversely, one metal ion can concomitantly coordinate to two ligands, (fig.3) [1-2, 9]. lanthanide(iii) ions form typical examples of metallo-oligoporphyrins because they are inclined to form complexes of higher coordination number (8-12). however, they are hard lewis acids, hence, their insertion into the coordination cavity of the softer n-donor porphyrin ligand is a slow and complicated process in aqueous solutions. this scheme 1. simplified energy level diagram for the change of the porphyrin’s molecular orbitals in different types of complexes [9]. figure 2. absorption spectra of the free base (h2tspp4–); the highly distorted, octabrominated free base (h2tsppbr8 4–); a typical in-plane (pdiitspp4–); and a typical out-of-plane metalloporphyrin (hgiitspp4–) within the soret range [1]. valicsek, kiss, fodor, imran, and horváth hungarian journal of industry and chemistry 32 phenomenon partly originates from the stability of their aqua complexes. due to the consequence of their pearson-type hard character, they coordinate rather to the peripheral substituents of porphyrin (instead of the pyrrolic nitrogens), i.e. to the ionic group ensuring water-solubility if they possess similarly hard o-donor atoms (e.g. carboxy or sulfonatophenyl groups). at lower temperatures, under kinetic control, the early lanthanide(iii) ions are not able to coordinate into the cavity, rather to the periphery; resulting in the formation of the tail-to-tail dimer of free-base ligands (as the tail used to be referred to as the periphery). higher temperatures and thermodynamic control are also necessary for the insertion of metal ions into the cavity produced by four pyrrolic nitrogens; resulting in the formation of typical metalloporphyrin complexes. after the discovery of the possible coordination bonds between lanthanide ions and sulfonato substituents, the formation of lanthanide bisporphyrins may be realized as a tail-to-tail dimerization of two metallomonoporphyrin complexes through a metal bridge; deviating from the head-to-head connection as in the case of typical sandwich complexes (head refers to the cavity; see fig.3). on the basis of our previous experiences, the coordination position of lanthanide ions was influenced by the change in temperature [1-2], [1113]. during the investigation of the formation of “typical p-type hyperporphyrin” complexes (e.g. tl+, pb2+, bi3+), the species possessing highly redshifted absorption bands are the end-products of metalation only in hydrophobic solvents, since they can appear in aqueous solutions as intermediates with shorter or longer lifetimes depending on the metal ion. the absorption spectra of the end-products of these transformation reactions are very similar (less redshifted) to those of the typical, common out-of-plane metallo-monoporphyrins (e.g. hgii-porphyrin in fig.2). this phenomenon may be accounted for to the considerable coordination ability or the polarizing effect of water molecules, which can enable the complex to overcome the kinetic energy barrier towards the formation of the more stable structure, in which the metal center is located closer to the ligand plane, resulting in decreases in distortion, as well as redshift. furthermore, “hyperporphyrins” can appear as intermediates in smaller amounts during the formation of typical, common out-of-plane metallomonoporphyrins as well [1, 14]. in the case of “d-type hyperporphyrin” complexes (e.g. mn3+, co3+, ni2+), the low-spin and ruffled complex with a contracted cavity can exist in a spinisomerization equilibrium with the high-spin and planar forms, which not only exhibits less redshift, but rather blueshifted absorption bands compared to those of the free-base ligand. this reaction can be influenced by the strength of the m-n bonds (owing to the electronic effects of peripheral or axial substituents), due to the size of the coordination cavity (owing to the substitution or saturation of methylidene bridges or pyrrolic carbons) [1-2, 5-7]. 3.3. photophysics porphyrins represent one of the most interesting groups of compounds in terms of photophysical properties and biological significance. due to their rigid structure and aromatic electronic system, they display two types of fluorescence: beside their relatively strong singlet-1 fluorescence in the range of 550–800 nm, weak and rare singlet-2 luminescence is observable between 400 and 550 nm upon excitation of the soret band (scheme 1) [1]. the quantum yields of s2-fluorescence are about 3 orders of magnitude lower than those of s1-fluorescence in the case of free-base porphyrins, especially ~1200fold for h2tspp4(6.3×10-5 vs. 7.5%). however, this ratio decreases with metalation, mainly in the case of the formation of out-of-plane complexes. since the structure of s2-excited porphyrins may be close to that of the dome-distorted oop complexes that are already in the electronic ground state. another consequence of this structural similarity (namely small stokes shift) is that the directions of the shifts of s2-fluorescence bands invert (according to soret absorption) between the inplane (redshifted) and out-of-plane (blueshifted) complexes when compared to the free-base ligand [1]. singlet-1 fluorescence bands exhibit blueshifts in both types (in-plane and out-of-plane) of metalloporphyrins, as a consequence of the aforementioned split in free-base ligands because of the presence of two protons, as well as their reduced symmetry (scheme 1). furthermore, almost all complexes exhibit similarly large stokes shifts, as well as lifetimes and quantum yields. in the case of in-plane a) b) figure 3. potential structures of 3:2 bisporphyrin: (a) head-to-head or (b) tail-to-tail [2]. study of the out-of-plane metalloporphyrins 45(1) pp. 29–36 (2017) 33 metal centers, the spin-orbit coupling, as an electronic quenching effect, may be dominant. whereas for typical out-of-plane metalloporphyrins, the distortion, as a steric effect, can enhance their non-radiative decay. the highly distorted (dand p-type) hyperporphyrins, the paramagnetic in-plane complexes (e.g. feiiitspp3-), as well as the head-to-head-type oop bisporphyrins {e.g. hgii 3(tspp)2 6-} do not exhibit significant levels of luminescence at room temperature. conversely, the paramagnetic out-of-plane complexes (e.g. lniiitspp3-) possess similar fluorescence properties to that of the diamagnetic ones because a paramagnetic metal ion can cause the disappearance of fluorescence by spin-orbit coupling only if it is located in the plane. in the oop position, it is not able to perturb as efficiently the molecule orbitals of the macrocycle that result in the common absorption and emission out-of-plane characteristics [1-2, 9]. lanthanide(iii) bisporphyrins {lniii 3(tspp)2 3-} have many similarities in terms of absorption and emission properties to those of monoporphyrin complexes (lniiitspp3-). these may only originate from the very weak π–π interactions between the macrocycles in the tail-to-tail-type aggregations (fig.3) [1-2, 11-13]. 3.4. photochemistry porphyrin derivatives are the main components of photosynthesis, synthetically as well. since the overall quantum yield of fluorescence and intersystem crossing resulting in the formation of triplet states is in excess of 95%, merely a slight proportion of excitation energy is dissipated as heat from singlet states. this ratio is the major reason why porphyrins are efficient in terms of optical sensations and photosensitizations. free-base and kinetically inert in-plane metalloporphyrins may be appropriate candidates to be applied in photocatalytic systems based on outer-sphere electron transfer. d-type hyperporphyrins can be particularly promising from this viewpoint owing to their distorted structure which may enhance the (photo)redox reactivity of these coordination compounds. in the presence of a suitable electron acceptor (methylviologen, mv2+) and donor (e.g. triethanolamine, teoa), these complexes proved to be efficaciousl photocatalysts that transfer electrons between the ground-state reactants through an outersphere mechanism, generating the mv•+ radical cation. this system can be applied for the production of hydrogen from water [2, 5-7]. contrarily, the inner-sphere photoredox reactions are characteristic of the out-of-plane metalloporphyrins because of this special coordination (scheme 2): an irreversible photoinduced charge-transfer from the ligand to the metal center (ligand-to-metal charge transfer, lmct) improves the efficiency of charge separation, which allows their utilization as catalysts in cyclic processes for the synthesis of chemicals capable of conserving light energy, hopefully in terms of the photochemical cleavage of water. due to photoinduced lmct the charge of the metal center decreases and its size increases, overall its charge density diminishes, hence, the coordinative bonds can easily split. the reduced metal ion can leave the cavity, primarily in polar solvents, and induce further redox reactions. the latter processes strongly depend on the stability of the reduced metalion in the actual medium. the oxidized and metal-free (cat)ionic radical of porphyrin is a very strong base: it is immediately protonated and forms the free-base radical, which is a long-lived and rather strong electron acceptor, especally in deaerated solutions. since it would only oxidize water to oxygen at higher phs, a slightly more efficent reducer (such as alcohols or aldehydes of low molecular weight) is needed, from which useful byproducts can be produced in terms of photocatalytic hydrogen generation. in the absence of any electron donor that promotes the regeneration of the porphyrin, it undergoes the primary photochemical processes; an overall four-electron oxidation involving a ring-cleavage, the end-product of which is a dioxotetrapyrrole derivative (bilindione). this ring-opening process can be followed by spectrophotometry owing to the disappearance of the soret band, as well as the typical change in the region of q bands [2, 4, 8-16]. photochemical quantum yields of this ring-opening reaction (without regeneration) are about 2-3 orders of magnitude higher for the out-of-plane complexes (10-4 – 10-2) than for the free-base and in-plane metalloporphyrins (10-6 – 10-5). in addition, in the case of out-of-plane complexes, photoinduced dissociation in scheme 2. simplified demonstration of the mechanism for the inner-sphere photoredox reaction of an out-ofplane metalloporphyrin [8]. valicsek, kiss, fodor, imran, and horváth hungarian journal of industry and chemistry 34 the absence of a redox reaction can occur, originating from their lability, and structural transformations to another complex form or conformer were observed in some cases as a photoinduced change of the type or measure of distortion (e.g. dand p-type hyperporphyrins) [2, 4, 8-10, 14-16]. besides the typical post-transition metal ions, lanthanide(iii) ions were also applied for out-of-plane coordination because their contraction makes the finetuning of the out-of-plane distance possible, and their high negative redox potentials promote the photoinduced cleavage of water. photochemical activities of their complexes confirm that the redox potentials of the metal centers are not the main determining factor, rather their out-of-plane distances [2, 11-13]. deviating from the oop complexes of posttransition metal ions, another stable photoproduct was observable during the photolysis of lanthanide(iii) porphyrins. it displays a typical absorption band in the q range (at ~600 nm), which may be assigned as a charge transfer between the metal ion and open-chain, dioxo-tetrapyrrole derivative (bilindione, see scheme 2). its oxo-groups, as donor atoms, may coordinate with the lanthanide ions, as a consequence of their similar pearson-type hard characteristics, contrary to the softer post-transition metal ions [2, 11]. during the photolysis experiments, only small differences appeared between lanthanide(iii) monoand bisporphyrin complexes, which might confirm a special type of aggregation through the peripheral sulfonato substituents with weak π-π interactions (tail-to-tail, see fig.3) [2, 11-13]. deviating from these observations, the differences are much more significant in the case of the most typical, post-transition metallo-bisporphyrin compared to the monoporphyrin equivalent; namely between hgii 3(tspp)2 6and hgiitspp4-. the overall quantum yield is ~2 orders of magnitude higher and the photoinduced dissociation of a metal ion became the dominant reaction in the head-to-head sandwich complex as a consequence of the strong π-π interactions [9-10]. 3.5. quantum chemical calculations the main aims of our electronic structural calculations were to determine the primary consequences for the outof-plane position of a metal center, and confirm the experimentally observed correlation between the uvvis spectral shifts and the coordination position of the metal center (in-plane or out-of-plane). in the light of these aspects, the unsubstituted porphin (h2p, c20h14n4) was used as a model for the calculations, instead of the tetrakis(sulfonatophenyl)porphyrin (h2tspp4–, c44h26n4o12s4 4-). on the basis of the few comparative calculations that were conducted, the phenyl-, as well as the sulfonatophenyl substituents have negligible effects on the coordination of the metal center in the cavity. however, they can significantly influence the formation of bisporphyrin complexes, even in the case of head-tohead structures [4, 10]. according to our quantum chemical experience, the value of the critical radius became ~100 pm instead of the experimentally suggested ~75-90 pm as a consequence of the significant expansion of the coordination cavity to coplanarly incorporate the metal ions. the proportion of borderline cases, i.e. complexes with questionable structures (somewhere between inplane and out-of-plane), increased with further posttransition metal ions (e.g. ag2+ [15], cd2+ [4], tl3+ [16]) that possess ionic radii of ~90-95 pm. calculated bond lengths (m-n) and atomic distances (n-n) considerably deviate from the expected ones supposed on the basis of the values of the deprotonated porphyrins (p2-). to describe this phenomenon, an axial ligand was applied to these metal centers to extract them out of the cavity. consequently, expansion stopped, and the out-of-plane distance increased dramatically together with the degree of dome distortion and redshifts of absorption bands. from this point of view, two possible explanations can be supposed for the borderline-case complexes: the experimentally observed common oop characteristics may originate from this expansion, tension; and small perturbations (e.g. the axial coordination in the calculation or photoexcitation in the experiments) may facilitate the metal center to adopt an out-of-plane position, too. another possibility is that the method of calculation strongly prefers planar structures. in our time-dependent density functional theory (td-dft) calculations, the correlation found between the measured and calculated shifts associated with the position of the metal center was not totally linear, but nevertheless acceptable. the main exceptions were the borderline cases (high-spin mn2+, fe2+ and zn2+) and the d-type hyperporphyrins (because their structures were determined to be totally planar), as well as the p-type hyperporphyrins (because a ruffled-like deformation did not superpose on their dome-like structure). the regression of correlation was much worse within the soret band than in the case of the q bands. the soret band was also split in the calculations, which cannot be detected experimentally. on the basis of further experimental observations and doubts in the literature, the validity of the theoretical model in use at present is questionable. hence, the development of a more suitable one is in progress. 4. conclusion in conclusion, it can be declared that the categorization of metalloporphyrins was complemented by the role of their distortion, which is primarily responsible for their spectral features, whereas the electronic structure of their metal centers is a secondary factor, with a considerable level of emphasis on the in-plane complexes. the position of the metal center (in-plane or out-of-plane) in the monoporphyrin complexes, as well as the type (head-to-head or tail-to-tail) of the bisporphyrin complexes can be determined on the basis of their uv-vis absorption and emission properties. study of the out-of-plane metalloporphyrins 45(1) pp. 29–36 (2017) 35 hyperporphyrin spectra can appear, owing to the peripheral substitution (octabromination) of free-base ligands. furthermore, the high degree of redshift may disappear during the spin isomerization of d-type metalloporphyrins or the transformation of p-type ones. consequently, the real origin cannot be an electronic but rather a steric effect, namely the measure of distortion, which can confirm the absence of their fluorescence. in terms of photochemical activity, several dissimilarities were found between the in-plane and outof-plane metalloporphyrins; the most remarkable of them was the mechanism of their photoredox reactions: outer-sphere electron transfer is typical of the previous ones, while the inner-sphere equivalent is most prevalent for the latter ones. as a further consequence of the oop position of the metal center, photoinduced dissociation and transformation reactions can occur within their complexes. in our electronic structural calculations, the number of borderline-case complexes expanded, on the basis of which common oop characteristics that can be experimentally observed may acquire a novel explanation. acknowledgement this research was supported by the széchenyi 2020 fund under the ginop-2.3.2-15-2016-00016 and efop-3.6.1-16-2016-00015 projects. assistance with quantum chemical calculations provided by professor györgy lendvay (research centre for natural sciences, hungarian academy of sciences) is gratefully acknowledged. finally, this manuscript is dedicated to the memory of professor jános liszi, who, as the head of the doctoral school for chemistry at the university of veszprém, praised the corresponding author’s phd dissertation of a similar title in 2007. references [1] valicsek, z.; horváth, o.: application of the electronic spectra of porphyrins for analytical purposes: the effects of metal ions and structural distortions, 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10.1016/j.jphotochem.2006.07.003 hungarian journal of industry and chemistry vol. 45(1) pp. 37–48 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0007 improvement possibilities of heterogeneous photocatalysis with the aim of in-field use orsolya fónagy, 1 péter hegedűs, 1 erzsébet szabó-bárdos, 1 annamária dobrádi, 2 and ottó horváth 1* 1 department of general and inorganic chemistry, university of pannonia, egyetem u. 10., h-8200 veszprém, hungary 2 institute of materials engineering, university of pannonia, egyetem u. 10., h-8200 veszprém, hungary heterogeneous photocatalysis can be successfully applied for the degradation of organic pollutants, although the efficiency of this method is insufficient. it can be increased by modification of the catalyst with precious metals (e.g. silver) or heterogeneous catalysis can be combined with other oxidative procedures such as ozonation. another obstacle to the infield use of the method is that separating the catalyst from the liquid phase is difficult. this problem can be eliminated by the immobilization of the catalyst. the poly(vinyl alcohol)-tio2 immobilized catalyst has been prepared for this purpose. during tio2-based photocatalysis, active oxygen species such as the hydroxyl radical, superoxide radical and hydrogen peroxide are produced. the formation rate of the oxidative •oh radicals was also determined in the case of the previously mentioned techniques. as a scavenger of this radical, coumarin was added. keywords: tio2-based photocatalysis; triton x-100; benzenesulfonic acid; silver-deposited tio2; immobilization; thermal decomposition of pva 1. introduction nowadays, a great proportion of anthropogenic pollutants cannot be mineralized by traditional biological and physicochemical wastewater treatment procedures. therefore, important developments in chemical wastewater treatment technologies and in their utilizations are required. for economic, technological and healthcare reasons, in terms of both type and quantity, it is important to use as few chemical additives as possible. their applicability against remarkably different pollutants using minimal levels of energy consumption is even more important. advanced oxidation processes satisfy these challenges [1]. a common characteristic of these processes is the generation of oxidative radicals, predominantly hydroxyl radicals, using solar radiation or other kinds of energy. hydroxyl radicals are able to oxidize a great variety of organic compounds, therefore, heterogeneous photocatalysis has become an intensively studied field of research. in the pharmaceutical industry, benzenesulfonic acid is mostly used for producing other speciality chemicals. a variety of pharmaceutical drugs are prepared as salts of benzenesulfonic acid, known as besilates. triton x-100 *correspondence: horvath.otto@mk.uni-pannon.hu with an average n ≈ 9.5 is one of the most widely applied man-made non-ionic surfactants. non-ionic surfactants are more stable than ionic tensides and not sensitive to ph and electrolytes. besides the hydrophilic polyethoxy chain, it also contains a hydrophobic octylphenyl group. both compounds can hardly be degraded by biological treatments [2–4]. hence, a more efficient degradation method like heterogeneous photocatalysis is indispensable for the total mineralization of these pollutants. 1.1. photodegradation of model compounds the titanium dioxide-mediated photocatalyzed degradation of benzenesulfonic acid (later abbreviated as bs) was investigated by monitoring the absorption and emission spectral changes, sulfate concentration, ph, as well as the total organic carbon (later abbreviated as toc) content in both argon-saturated and aerated systems. during the degradation of benzenesulfonic acid, a characteristic change in the π→π* transition (typical of aromatic systems) in the absorption spectrum of bs (λmax=262 nm, ε=439 m–1 cm–1) can be observed. at first, there is a slight increase in the 260-270 nm range, while two new shoulders appear at around 280 and 300 nm and as the period of irradiation progresses the level of absorbance decreases. the reason for the increase in absorbance observed in the spectrum of this aromatic surfactant is that the absorbances of the intermediates fónagy,hegedűs,szabó-bárdos,dobrádi, and horváth hungarian journal of industry and chemistry 38 formed in the initial period of the process are higher than that of the starting compound. on the basis of the characteristic molar absorbances of 4hydroxybenzenesulfonic acid (4-hbs) (λmax=277 nm, ε=868 m–1 cm–1) and 2,5-dihydroxybenzenesulfonic acid (λmax=302 nm, ε=3300 m–1 cm–1) as commercially available standards, the appearance of a shoulder at 280300 nm suggests the formation of hydroxylated intermediates. the results indicate that the initial step of the degradation is hydroxylation of the starting surfactant, resulting in the production of hydroxyand dihydroxybenzenesulfonates [5–7]. therefore, liquid chromatography-mass spectrometry analysis was utilized for the detection of intermediates. the sulfonate group of the substrate to be degraded can easily be oxidized by oxygen-containing reactants generated in these systems. sulfate ions were detected in the irradiated reaction mixtures, which means that the hydroxylation reactions were accompanied by desulfonation. the initial rate of this process was lower in each case than that for the transformation (i.e. hydroxylation) of the starting compound (bs). these results indicate that the first step of mineralization is hydroxylation; desulfonation takes place afterwards. during the photocatalytic oxidation of bs, especially in the first 180 min, a continuous decrease of ph was observed in both the argon-saturated and the aerated systems, i.e. strong acidification occurred. probably, there is a direct correlation between the formations of hydrogen and sulfate ions, due to the following reaction (eq.(1)), which can take place between the sulfonate group and hydroxyl radical, the main oxidizing agent in these systems: •rsohr•hsooh•rso 2 443   (1) the hydroxy species did not decay during the irradiation in the absence of dissolved oxygen. in the aerated system desulfonation and hydroxylation was much more efficient, moreover, a significant decrease in toc took place during the initial stage. further hydroxylation resulted in the cleavage of the aromatic system, through the formation of polyhydroxy derivatives, followed by ring-opening, which led to the production of aldehydes and carboxylic acids. total mineralization was realized by the end of the photocatalysis. it has been proved that in this photocatalytic procedure the presence of dissolved oxygen is indispensable for the cleavage of the aromatic ring because hydroxyl radicals photochemically formed in the deaerated system alone are not able to break the c-c bond [5]. the degradation mechanism of triton x-100 was also investigated [8]. in the case of this surfactant, hydroxyl radicals can attack in three ways; on the ethoxy chain, on the aromatic ring or on the alkyl chain. according to the absorption spectrum (no shift in the longer wavelength (275 nm) band and no new shoulders), no hydroxylation of the aromatic ring took place during the photocatalytic degradation. after the total disappearance of the starting surfactant (after approx. 60 min), an appreciable degree of absorbance arose at 275 nm, which indicates that aromatic intermediates were formed during the first hour. in liquid chromatographic experiments, triton x-100 produced a multiple-peaked chromatogram. the retention time of these non-ionic surfactant components is in strong correlation with the length of the ethoxy chain. intermediates formed from various lengths of ethoxy chains and others with aromatic rings were detected in the reaction mixture after irradiation started. the concentration of the shorter-chain molecules increased during the initial stage (in the first 10 min) of the irradiation, indicating that the fragmentation of the longer polyethoxy chains of the starting components initially increased the concentration of those with shorter ones, which was followed by a gradual decay. the component with a relative molecular weight of 206 dalton could be clearly identified. based on its structure, it was identified as the alkyl phenol part of the original triton x-100. its concentration peaked at around the 50th minute of irradiation. this is the result of the total cleavage of the polyethoxy chains without any oxidation of the rest of the original tenside molecules. based on the results so far, it can be stated that hydroxyl radicals attack the ethoxy side-chain and subsequently the alkyl group, afterwards, the ring opens. 1.2. challenges of heterogeneous photocatalysis the obstacle to the practical application of heterogeneous photocatalysis is that its efficiency is relatively low. fortunately there are several ways to improve its mineralization effect: by the combination of heterogeneous catalysis with other oxidative procedures such as ozonation [6, 9-10] or by the modification of the catalyst with precious metals. the latter solution helps promote charge separation by accumulating the electrons on the surface of the silver particles [11-12]. the other obstacle is that the catalyst is in a suspended form, therefore, its separation from the liquid phase is difficult and makes the technology more expensive. this problem can be eliminated if the catalyst is immobilized. there are several methods for immobilization, for example, the catalyst particles can be fixed directly into polymers. between a polymer and the catalyst usually a physical contact is formed, but in some cases, such as with poly(vinyl alcohol), a chemical bond can be formed. unfortunately, this method is not free of disadvantages. the fact that immobilization decreases the active surface area of the catalyst has to be taken into consideration, thus, it will become less efficient [13–16]. irradiation in the near uv range generates electron-hole pairs in the tio2 nanoparticles. under aerobic conditions the electrons in the conduction band are scavenged by adsorbed oxygen molecules with a relatively high quantum yield, producing o2• – ions, which are readily protonated in acidic media. beides, improvement possibilities of heterogeneous photocatalysis 45(1) pp. 37–48 (2017) 39 the holes, in the absence of reducing species, oxidize the surface-adsorbed water or hydroxide ions to hydroxyl radicals. the •oh radical can also be formed by thermal reactions following the primary electron transfer processes that occur at the surface of semiconductor particles or in the liquid phase [13,17]. the hydroxyl radical is often assumed to be the major reactant responsible for the photooxidation of various organic molecules. the first step of the mineralization of benzenesulfonic acid is hydroxylation of the aromatic ring, while the degradation of triton x100 is initialized by hydroxyl radicals, which attack the ethoxyl side chain (fig.1). due to the high reactivity and short lifetime of •oh, the direct detection of this species is difficult. appropriate methods such as steady-state fluorescence were applied to measure the quantity of scavenged hydroxyl radicals. recent studies have proved that several nonor weakly luminescent test molecules, such as coumarin, produce strongly luminescent compounds (7-hydroxycoumarin) with hydroxyl radicals. thus, these molecules can be utilized for detecting and measuring •oh radicals produced by uv excitation of tio2 particles in heterogeneous systems [18-19]. the main goal of our work was to investigate the effect of silver doping and immobilization of the catalyst applied for photocatalytic degradations. in this work, coumarin was used as a scavenger to determine the formation rate of hydroxyl radicals under various circumstances. 2. experimental section 2.1. materials for the experiments, the following materials were used: benzenesulfonic acid (c6h5o3s alfa aesar), 4hydroxybenzenesulfonic acid (c6h4(oh)o3s alfa aesar), silver nitrate (agno3 aldrich), degussa p25 tio2: 25±5% rutile, 75±5% anatase with a specific surface area of 50 m2 g–1 (now called evonik aeroxide® tio2 p25), coumarin (c9h6o2 vwr), triton x-100 (c14h22o(c2h4o)9.5 alfa aesar), and poly(vinyl alcohol) ((later abbreviated as pva) m=146000-186000 g mol–1, hydrolysis: 99+% aldrich). the materials used for the hplc and ic measurements were the following: methanol (ch3oh sigma-aldrich), tetra-n-butylammonium bromide ((ch3ch2ch2ch2)4nbr sigma-aldrich), sodium sulfate (na2so4 vwr), 37% cc. hydrochloric acid (hcl vwr) and sodium hydroxide (naoh vwr). high purity water, used in this study as a solvent, was double distilled and then purified using a milli-q system. 2.2. analytics for the analysis, 4 cm3 samples were taken, the solid phase was removed by filtration using millipore millexlcr ptfe 0.45 m filters. the absorption spectral changes of the reaction mixtures irradiated were followed using a perkinelmer lambda 25 uv-vis spectrophotometer, while the emission spectra were recorded using a perkinelmer ls 50b spectrofluorometer. both measurements were carried out in 1 cm quartz cuvettes. mineralization was followed by measuring the total organic carbon (toc) concentration, utilizing a thermo electron corporation toc tn 1200 apparatus. the ph of the aqueous phase of the reaction mixture was determined by a sp10t electrode connected to a consort c561 instrument. hplc analyses of the benzenesulfonic acid samples were carried out using an agilent 1100 instrument. a water:methanol (in a volume ratio of 95:5) solvent mixture containing 0.1 % (v/v) formic acid was the mobile phase with a flow rate of 1 cm3 min–1. during the experiments a 100×2 mm synergi hydro-rp c18 (phenomenex, torrance, ca, usa) column packed with 2.5 m particles was used. the column was thermostated at 30°c. the sample volume injected was 1 μl, photometric detection was applied at wavelengths of 262, 277 and 302 nm. degradation of triton x-100 was followed by the 1290 infinity uhplc system (agilent technologies inc., santa clara, ca, usa). the mobile phase was 65:35 methanol:water for five minutes of analysis, then it was gradually increased to 75:25 over the following five minutes. the signal was detected with a dad detector. the column used during the experiments was a 100×2 mm synergi hydro-rp c18 (phenomenex, torrance, ca, usa) column packed with 2.5 μm particles. the column was thermostated at 50 °c. the flow rate of the eluent was 1 cm3 min−1. during the study of the degradation mechanism an agilent 6890n gas chromatograph with an agilent db5ms ultra inert column (30 m×0.25 mm×250 μm) was used for the separation. as a detector, an agilent 5973 n-type mass spectrometer was used. the surface of immobilized catalysts was tested using a philips/fei xl30 scanning electron microscope at an accelerating voltage of 20 kv, using backscattered electron imaging. the composition was measured by an edax genesis energy dispersive x-ray analyzer. prior to testing, the samples were sputter coated by a 10 nm figure 1. the role of •oh radicals in the degradation of the model compounds. fónagy,hegedűs,szabó-bárdos,dobrádi, and horváth hungarian journal of industry and chemistry 40 thick layer of gold. elements of the qualitative composition do not overlap with the gold, therefore, the gold coating did not disturb the analysis. 2.3. experimental circumstances the concentration of benzenesulfonic acid to be degraded was 10–3 m in each experiment, while that of the catalyst was 1 g dm–3 in all cases. for homogenization, the suspension was stirred for 20 minutes in the reactor before irradiation. the silverdeposited tio2 was prepared by photoreduction from a mixture initially containing 10−4 m agno3 and 1 g dm–3 tio2 as a photocatalyst. after 1 hour of photoreduction the catalyst, brown in color, was separated by vacuum filtration then dried at room temperature. to re-suspend the catalyst powder before each experiment an ultrasonic bath was applied in order to achieve a dispersion of particles sufficiently small in size. during subsequent ultrasonic treatment, the substrate to be degraded was added to the system only after a period of time, so that the •oh radicals generated during the sonication could recombine and not tamper with the experimental results. a detailed description of the production of immobilized catalyst can be found in our previous article [20]. the pva-tio2 catalyst was prepared by using a pva with a molecular weight of 146 000-186 000 and a 99+% degree of hydrolysis and degussa p-25 tio2. immobilization was carried out using a solutioncasting method [21]. the pva-tio2 mixture was stirred at 90 then 60°c, subsequently a viscous solution was obtained, which was then poured into a petri dish and dried. the average weight of the immobilized catalyst was 0.47 g with a pva content of 40%. before its use, it was subjected to a 2 hour-long thermal treatment in an argon atmosphere to increase its stability. the triton x100 concentration was 2∙10–4 m with 1.5 g dm−3 tio2. it is important to note that when comparing the efficiencies of the catalyst in various forms, the amount of tio2 immobilized in pva (0.3 g) and used as a suspension in 200 cm3 of reaction mixture were both 1.5 g dm−3. photochemical experiments were carried out using two different reactors and light-source setups. one was a laboratory-scale reactor with an effective volume of 2.5 dm3, equipped with a 40 w light tube located in the middle of the reactor. it emitted most of its energy at wavelengths exceeding 300 nm (λmax=350 nm, i.e. within the uva range) [5]. the photon flux of the light source was i0 = 4.3∙10-6 mol photon dm–3 s–1, which was measured by the actinometry of trisoxalatoferrate(iii). the heterogeneous reaction mixture was circulated by using a peristaltic pump through the reactor and a buffer vessel. compressed air was bubbled through the reaction mixtures from gas bottles, to facilitate stirring and (with its o2 content) as an electron acceptor. o3 was produced by a lab2b ozone generator, and introduced into the same airstream. the ozone concentration was determined by iodometry, using sodium iodide as a reagent and sodium thiosulfate for the titration of the iodine formed. the ozone dosage was estimated to be 0.35 mm min–1. the other setup consisted of one small reactor made of borosilicate glass (its volume was 250 cm3) [20]. the catalyst film was placed on a perforated glass platform (foil holder) standing on a glass frit, through which compressed air was bubbled from a gas bottle at a flow rate of 10 dm3 h−1, ensuring a constant oxygen concentration. the 200 cm3 reaction mixture (triton x100 solution or distilled water in the case of pretreatment) was circulated by a magnetic stirrer. it was irradiated from above using an oriel lcs-100 solar simulator resulting in a light intensity of 72 mw cm–2 on the surface of the reaction mixture. fig.2 shows the change in toc during the photodegradation of benzenesulfonic acid under various experimental conditions. the band-gap energy of tio2 is 3.2 ev, indicating that the catalyst can be excited by light of 360 nm in wavelength. the difference between the two light sources used is clearly visible. the radiation intensity of the solar simulator in the uv range is very low, so the total organic carbon content of the initial solution decreased by only 10 mg over 360 minutes, while total mineralization was achieved using the uv lamp within this period. 3. results 3.1. increase in photocatalytic efficiency using various methods as mentioned previously, the efficiency of heterogeneous photocatalysis can be increased in multiple ways: by combination with other oxidative procedures such as ozonation and by modification of the catalyst surface using noble metals. since the first reaction in the mechanism of photocatalytic oxidative degradation of benzenesulfonic figure 2. change in the toc concentration in the case of two different light sources used for irradiation. c(bs)0=10-3 m, air: 40 dm3 h-1, c(tio2)=1 g dm-3 – air+tio2+solar simulator  – air+tio2+uv lamp improvement possibilities of heterogeneous photocatalysis 45(1) pp. 37–48 (2017) 41 acid is hydroxylation of the aromatic ring, the determination of the rates of formation of hydroxyl radicals as the main oxidant in these systems was indispensable as far as the elucidation of the mechanism under various circumstances was concerned. coumarin was used as an •oh scavenger. an intensive band at 278 nm and a shoulder at around 300 nm is visible in the absorption spectrum of coumarin. the level of absorbance quickly decreased under irradiation (fig.s1), while the concentration of the fluorescent 7-hydroxycoumarin rapidly increased during the initial period, and subsequently decreased gradually, i.e. degraded (fig.s2). by depicting the intensity of the emission line at 453 nm as functions of the irradiation time, the initial rate of formation of 7hydroxycoumarin, which is proportional to that of the hydroxyl radicals formed, can be determined from the initial gradients of the increasing sections, so it is easy to compare the ability of each process to generate hydroxyl radicals [18]. before measuring the formation of 7hydroxycoumarin in the photocatalytic oxidative systems that apply ozone, blind probes were used (fig.3). the reaction between coumarin and ozone in the dark (at 10–4 m coumarin and 0.35 mm min-1 ozone concentrations) yielded a negligible spectral change after 2 hours. although ozone itself is a strong oxidant, a very low rate of formation of 7-hydroxycoumarin (0.32 int min–1) was observed under these experimental conditions. upon uv irradiation of this probe, the rate of formation slightly increased (to 1.84 int min–1). ozone can be absorbed over a wide range, from infrared to vacuum uv, but is optimal at 254 nm. the light source applied in this work emits most of its radiation in the 300-380 nm range, where the molar absorbances of o3 are rather low. thus, it can poorly promote the dissociation of ozone via the homolytic cleavage of a bond. contrary to the blind probe with ozone, significant spectral changes were observed in irradiated reaction mixtures containing catalysts. the surface of the catalyst was also modified with silver and combined with ozonation, then the difference between the effects of the two methods of improvement was investigated by determining the rate of formation of oxidative •oh radicals (fig.4). the combination of heterogeneous photocatalysis with ozonation resulted in a 2.5 fold increase in the rate of formation (from 7.42 int min–1 to 19.4 int min–1). a further increase was achieved by the application of surface-modified (silver-deposited) titanium dioxide (to 21.9 int min–1). these results are in accordance with the fact that silver deposited on the surface of the catalyst diminishes the probability of the recombination of the photogenerated electron-hole pair, i.e. promotes charge separation [11]. 3.1.1. degradation of benzenesulfonic acid our research group has been studying the combination figure 3. change in the luminescence intensity of 7-hydroxycoumarin formed (λexc=332 nm). c(coumarin)0=10-4 mol dm-3, air: 40 dm3 h-1, c(o3)=0.35 mm, ℓ=1 cm  – o3  – o3+uv figure 4. change in the luminescence intensity of 7-hydroxycoumarin produced (λexc=332 nm) (a) and rates of formation of •oh radicals under various circumstances (b). c(coumarin)0=10–4 mol dm–3, air: 40 dm3 h–1, c(o3)=0.35 mm, c(catalyst)=1 g dm–3, ℓ=1 cm ♦ – air+tio2+uv ● – o3+tio2+uv ▲ – air+ag-tio2+uv a b fónagy,hegedűs,szabó-bárdos,dobrádi, and horváth hungarian journal of industry and chemistry 42 of heterogeneous photocatalysis and ozonation in detail. it has been established that a joint application of these procedures results in synergic effects [6]. another possibility of enhancing the efficiency of photocatalysis is the modification of the catalyst surface by the deposition of silver. our results in this work are compared with previous observations [17]. the spectral changes during the irradiations of suspensions containing ag-tio2 agree with earlier results. the degree of light absorption increases during the initial period (until the 50th minute), then it decreases (fig.s3). the fine-band structure gradually disappears, while new bands arise at longer wavelengths (277 and 302 nm), suggesting the formation of isomers of hydroxyand dihydroxybenzenesulfonic acid [6]. characteristic changes can also be observed in the emission spectra of the samples in these experiments: an increase in the intensity of luminescence for 60 minutes, then a decrease accompanied by a red-shift of the 290 nm band (characteristic of the starting compound) and the appearance of a new emission band at about 330 nm (fig.s4). the band-shift becomes considerable (46.5 nm) after the first hour of irradiation: from 286 nm to 333 nm. this finding also confirms the formation of hydroxy and dihydroxy intermediates with em.max.=305 nm and 352 nm, respectively. the changes in the concentrations of benzenesulfonic acid and the hydroxylated intermediates were followed by hplc analyses (fig.5). of the three possible hydroxy isomers, the absolute concentration could only be determined for the commercially available 4-hydroxybenzenesulfonic acid (4-hbs, rt=0.86 min). although the concentration of the substrate gradually decreases, the content of the benzenesulfonic acid in the reaction mixture is practically zero by the 180th minute of irradiation. on the basis of the concentration vs. time plot, the rate of decay of the model compound was determined by polynomial fit: 2.1∙10–2 mm min–1. regarding the heterogeneous catalytic experiments (untreated tio2 catalyst), 8∙10–3 mm min–1 was the degradation rate of the starting surfactant, while 1.4∙10–2 mm min–1 was measured in the case of combination with ozonation (table 1) [6]. mineralization of the model compound was followed by toc (total organic carbon content) measurements. taking the difference between the toc value of the reaction mixture (toc of the solution) and that of the benzenesulfonic acid (toc of bs, calculated from its actual concentration), the toc value regarding the intermediates in the solution can be obtained (fig.6).this figure also displays the toc values belonging to 4-hbs (calculated from its actual concentrations, see fig.5) the concentration of the starting material and its toc value rapidly decrease in the heterogeneous photocatalytic experiments involving silver-modified tio2, while the amount of intermediates (predominantly hydroxy and dihydroxy derivatives) gradually increases. the initial rate of decrease in toc for the reaction mixture was 1.58∙10–1 mg dm–3 min–1. the first step of the degradation of the model compound is hydroxylation. the highest initial rate of decay of bs was observed in the case of the system containing the silver-modified catalyst (fig.7, table 1). these results are in good agreement with those obtained for the experiments using coumarin, an efficient scavenger of •oh. the highest initial rate of formation of hydroxyl radicals was obtained on the ag-tio2 catalyst. table 1. comparison of the initial rates*. toc benzenesulfonic acid [mg dm-3 min-1] [mm min-1] air+ ag-tio2+uv 1.58∙10-1 2.3∙10-2 air+tio2+uv 2.24∙10-1 6.5∙10-3 o3+tio2+uv 5.92∙10-1 1.3∙10-2 *the error of the rate determinations is ±10%. figure 5. transformation of the initial compound and change in concentration of the 4-hbs intermediate. c(bs)0=10-3 m, air: 40 dm3 h-1, c(ag-tio2)=1 g dm-3 figure 6. change in toc contents during the treatment. c(bs)0=10-3 m, air: 40 dm3 h-1, c(ag-tio2)=1 g dm-3  – toc of the solution (measured)  – toc of bs (calculated)  – toc of intermediates (calculated)  – toc of 4-hbs (calculated) improvement possibilities of heterogeneous photocatalysis 45(1) pp. 37–48 (2017) 43 the cleavage of the aromatic ring is indispensable in terms of the mineralization of the model compound, besides the fragmentation of the hydrocarbon chain. szabó-bárdos et al. rendered it probable that ringopening takes place in the reaction of hydroxylated intermediates with reactive oxygen-containing species (o2• –/ho2•, o2( 1g)) [5]. deviating from the decrease in the bs concentration, the lowest rate of the decrease in toc, an indicator of mineralization, was observed in the case of the silver-modified catalyst, while the highest value (3.7 times higher than the previous one) was obtained for the combined procedure (fig.7, table 1). based on our results, the application of heterogeneous photocatalysis with silver-modified tio2 only accelerates the formation of hydroxyl radicals, while its combination with ozonation also increases the amount of other oxidative radicals (o2• –/ho2•, o2( 1g)). 3.2. immobilization of the catalyst with poly(vinyl alcohol) the thermal treatment of the immobilized catalysts, the preparation of which was thoroughly described in section 2.3, resulted in significant physical and chemical changes; on the one hand, their thickness varied (fig.8), on the other hand, their color turned from their original white to brown (fig.9). song et al. described similar results [22]. the thickness of the foils prepared was tested by scanning electron microscopy prior to and after the thermal treatment. following the treatment, the average thickness decreased from about 75.6 µm to about 69.6 µm (fig.8). the shrinkage of about 6 µm can be attributed to the evaporation of water content. it has been established in our earlier studies that during the thermal treatment the polymer underwent dehydroxylation and cracking processes; compounds containing double and triple bonds as well as aromatic rings appeared on the surface of the foil, increasing its degree of light absorption [20]. irradiation of the immobilized catalysts in the absence of the model compound led to the dissolution of the side-products of the cracking processes, and they also underwent heterogeneous photocatalytic degradation due to the presence of tio2. accordingly, stearic acid and its derivatives containing double bonds such as linoleic acid (9,12-octadecadienoic acid (z,z)and oleic acid (9octadecanoic acid) were detected by gc-ms analysis of figure 7. change in concentrations of bs (a) and toc (b) under various circumstances. c(bs)0=10-3 m, air: 40 dm3 h-1, c(o3)=0.35 mm, c(catalyst)= 1 g dm-3 ♦ – air+tio2+uv ● – o3+tio2+uv ▲ – air+ag-tio2+uv a figure 8. cross sections of scanning electron micrographs of pva-tio2 foils before (a) and after (b) thermal treatment. a b b fónagy,hegedűs,szabó-bárdos,dobrádi, and horváth hungarian journal of industry and chemistry 44 the liquid phase. during the photocatalytic degradation, organic acids with shorter hydrocarbon chains were also produced, e.g. tetradecanoic acid (c14), caprylic acid (c8) and malic acid (c4) [20]. although thermal treatment improves the stability of the foil, it restricts its efficiency because a considerable proportion of the oxidative radicals formed during photocatalysis are consumed in the reactions with the pollutants produced during the thermal treatment. taking all these factors into consideration, how the temperature of the thermal treatment affects the stability of the immobilized catalyst was also studied. the foils heated at different temperatures were submersed in 200 cm3 of distilled water, then irradiated for 8 hours. the change in toc of the liquid phase is shown in fig.10/a, while the reductions in the foil masses are displayed in fig.10/b. for the interpretation of the results, the increase in the temperature of the solution due to irradiation also has to be taken into account, because it enhances the solubility of poly(vinyl alcohol), i.e. the amount of the dissolved pva, which increases the actual toc value. the organic materials (pva and the products of the thermal treatment) dissolved off the foil which also underwent photocatalytic degradation in the presence of tio2. both processes determine the change in toc in the liquid phase, along with the mass reduction of the foil. the stability of the foils treated at lower temperatures (e.g. at 60oc) is rather modest, the pva is dissolved in water, the toc value of the liquid phase increased to 130 mg dm–3 by the end of the experiment, and the mass of the foil decreases considerably. the stability of the foils treated at higher temperatures (e.g. at 140oc or 200oc) significantly increased, while the toc value of the liquid phase only grew slightly (to 34 mg dm–3 at 140°c, to 18 mg dm–3 at 200oc), in a similar fashion to the weight loss of the foils (140°c m=93 mg, 200oc m=24 mg). the results clearly indicate that by increasing the temperature of the thermal treatment, the stability of the foil is gradually improved, due to efficient crosslinking [21]. the thermally treated immobilized catalysts cannot be applied for photocatalytic purposes, because they undergo degradation themselves during the irradiation, increasing the toc value of the solution phase. besides, the brownish organic compounds formed in the cracking processes diminish the catalytic efficiency because they occupy the active sites on the catalyst surface. hence, a compromise has to be made between stability and efficiency. efforts were made to mineralize the products of cracking during a pretreatment. before the photocatalytic experiments, the thermally treated foils were cleaned by three sequential 8-hour-long pre-treatments, to remove the pollutants formed during the cracking processes. since the pollutants formed whilst heated at the higher temperature (200oc) were rather difficult to remove, 140°c was applied for the thermal treatment of the foils in further experiments of ours [20]. 3.2.1. efficiency of •oh production during pretreatments of immobilized catalysts to detect the hydroxyl radicals formed during the irradiation of tio2 particles embedded in the polymer, 10-4 m of coumarin as a scavenger was applied. following the thermal treatment to enhance the stability of the foils, the undesirable products of this procedure have to be removed. in the first cycle of this process, when the foil is yet brown, the immobilized photocatalyst starts to work upon irradiation, but oxidative radicals formed in this process are mostly involved in the degradation of the products of cracking. the initial rate for the formation of 7-hydroxycoumarin just slightly exceeds the value observed in blind experiments (in the absence of a catalyst); 3∙10–2 int min–1 (blind), 4∙10–2 int min–1 (1st cycle) (fig.11). figure 9. immobilized catalysts before and after heat treatment. figure 10. change in the toc content of the liquid phase after various heat treatments (a) and the weight loss of foils after 8 hours of irradiation (b) 200 cm3 distilled water, air: 10 dm3 h-1,-c(tio2)=1.5 g dm-3 improvement possibilities of heterogeneous photocatalysis 45(1) pp. 37–48 (2017) 45 the rate of formation of the hydroxyl radicals significantly increases during the 2nd cycle; the emission intensity at the end of this cycle (v0=10–1 int min–1) is more than twice as high as in the previous one. the results obtained during the 3rd cycle are similar to those during the 2nd one. practically, during the three sequential 8-hour-long periods of irradiation, the polluting compounds that originate from the thermal treatment are totally degraded, hence, the active sites on the surface of the catalyst become more accessible, resulting in a much higher rate for the formation of oxidative radicals (in the 4th cycle v0=2.5-2.8∙10–1 int min–1, see fig.11). in other applications, the radical producing efficiency of the catalyst does not change significantly, i.e. the foil can be applied at constant efficacy. the lower value determined during the 7th cycle suggests a slow rate of degradation of the immobilized catalyst, which has to be taken into consideration during its application. 3.2.2. degradation of the model compound the photocatalytic degradation of the model compound was investigated following the cleaning procedure. the average degree of degradation of triton x-100 in three sequential cycles was 62%; the deviations might originate from measurement errors (fig.12). this value is significantly lower than that observed in the case of the suspended catalyst (90%). although the catalyst concentrations with regard to the volume of solution were equal (1.5 g dm–3), immobilization considerably diminished the specific surface of the catalyst, leading to a substantial decrease in its efficiency. mineralization of triton x-100 takes place via cleavage-producing intermediates. the cleavage of the alkyl-phenyl part of the starting components of triton x-100 took place from the beginning of the irradiation period. as completive intermediates originated from such a cleavage, ethylene glycol and dioxolane derivatives were detected by gc-ms. at the beginning of the irradiation the edge of the starting molecules or the initially generated intermediates mineralize to co2. therefore, the decrease in toc is much less than expected from the concentration change. the concentration changes of triton x-100 components and the typical intermediates are in accordance with our previous results using a similar system that applied a suspended catalyst (see section 1.1). remarkably, gcms analyses did not detect any intermediates which might derive from the pva support. this suggested that three pre-treatment cycles of irradiation and rinsing were sufficient for a satisfactory level of removal of the derivatives formed during the thermal treatment. 3.2.3. surface morphology of foils sem analysis the behavior of the active surface of immobilized photocatalysts after repeated use raises an important issue. the surfaces of titanium dioxide containing pva before and after thermal treatment are shown in figs.13/a and 13/b, respectively. some tio2-rich islands (fig.14) are not fully covered by the pva film, these are visible on the surface. otherwise, no significant changes are observed after the thermal treatment. however, simulated solar radiation (repeated usage) induces visible changes in the morphology of the b figure 11. change in the intensity of luminescence of 7-hydroxycoumarin formed. c(coumarin)0=10-4 m, air: 10 dm3 h-1, λexc=332 nm figure 12. change in concentration change of triton x-100 during the irradiation. c(tx-100)0=2∙10-4 m, air: 10 dm3 h-1, c(tio2)=1.5 g dm-3 fónagy,hegedűs,szabó-bárdos,dobrádi, and horváth hungarian journal of industry and chemistry 46 surface. such a period of radiation partially or totally removes the pva layer covering the tio2 agglomerates. this process is enhanced after prolonged use: after four cycles the homogeneously distributed particles are already visible (fig.13/c). extended use seven cycles will enhance grain boundaries by removing more of the pva matrix, indeed some of the particles become loosely bounded to the rest of the agglomerate (fig.13/d). the observed changes in thickness strongly correlate with the degradation of films (fig.15). after four cycles, a significant decrease in thickness can be observed: the foil thickness decreases to about 58.5 µm (from 69.6 µm). this corresponds to a decrease of about 2.7 µm / cycle. as for the thickness measured after seven cycles, the last three cycles only represent a decrease of about 0.9 µm/cycle. these observations imply a more intense degree of degradation during the initial stage. 4. conclusion heterogeneous photocatalytic procedures are widely applied for the degradation of organic pollutants. the degradation of benzenesulfonic acid and triton x-100 by heterogeneous photocatalysis was investigated under various circumstances. the formation of hydroxyl radicals as one of the major reactants responsible for the photooxidation of these molecules was also measured in the case of both setups of the catalyst. silver deposition on the surface of the tio2 catalyst significantly increased the initial degradation (hydroxylation) rate of bs, due to the hindered recombination of the photogenerated electron-hole pairs, increasing the rate of •oh production. however, mineralization of the intermediates was not accelerated by this method, deviating from the combination of the tio2-based photocatalysis with ozonation. the degradation efficiency in the latter procedure indicated a synergic effect on the mineralization rate as a consequence of the enhanced production of oxidative agents other than •oh radicals [6]. these reactive oxidants play key roles in the ring-opening processes needed for the mineralization of aromatic intermediates. quantitative determinations of such reactants (e.g. o2• – and o2( 1g)) to gain a deeper understanding of the mineralization mechanism are in progress. our results indicate that the methods applied for the enhancement of the degradation efficiency in heterogeneous photocatalysis affect the generation of the oxidizing agents in different ways, which ought to be taken into consideration in further studies. in general, suspensions of the photocatalyst are used in these procedures. thus, at the end of these processes the semiconductor particles have to be separated from the cleaned solution. this operation can be taken out by immobilization of the catalyst, which was achieved by using poly(vinyl alcohol) in this work. figure 13. scanning electron micrographs of foil surfaces. a) before and b) after thermal treatment c) after 4 irradiation cycles d) after 7 cycles of irradiation a b c d figure 14. energy dispersive x-ray spectra of the tio2 island. in te ns it y / au improvement possibilities of heterogeneous photocatalysis 45(1) pp. 37–48 (2017) 47 the stability of the pva support proved to be too low for practical use. the stability of the pva-based foils could be considerably improved by thermal treatment. however, before photocatalytic application the watersoluble products of the heating process had to be removed from the surface of the pva-tio2 foil. according to the efficiency of •oh formation, three cycles of irradiation and rinsing proved to be sufficient for this purpose. the foil pre-treated by this method could be applied for the photocatalytic degradation of a frequently used non-ionic detergent, triton x-100. when using the immobilized catalyst, it should be noted that the foil catalyst is degraded, its thickness decreases and the catalyst particles become more and more accessible on the surface. acknowledgements this work was supported by széchenyi 2020 under the projects ginop-2.3.2-15-2016-00016 and efop-3.6.116-2016-00015. references [1] dewil, r.; mantzavinos, d.; poulios, i.; rodrigo, m. a.: new perspectives for advanced oxidation processes, j. environ. manage., 2017 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change and provide a liveable environment in the context of sustainable development. in order to measure these efforts, benchmarking performance would be a good solution. methods for environmental analysis have their limitations when it comes to evaluating a city and other aggregated indicators focus on certain aspects of a sustainable or liveable settlement. the sdewes index was used for benchmarking several cities of different sizes in terms of metrics related to energy, water and environmental systems successfully thus it was chosen to compare the performance of veszprém and zalaegerszeg, two environmentally conscious hungarian county seats of roughly the same size and population. the sdewes index consists of 7 dimensions, namely energy consumption, industrial profile with co2 emissions, co2-saving measures, r&d, renewable energy potential and utilization, water and environmental quality, and social environment and sustainability policy. each dimension is composed of 5 indicators that provide information on sustainable development of energy, water and environmental systems in cities. using the sdewes index the strengths and weaknesses of the two cities are highlighted, locating those key parameters where improvement can be achieved. both for veszprém and zalaegerszeg progress could be realized concerning energy-saving measures and the proportion of green areas could be increased. to improve the method and facilitate a more comprehensive comparison of cities of differing sizes, data should be provided concerning the territory or population. also, the definition and inclusion of a worst and best case scenario that takes into account the parameters would be advantageous in terms of a comparison. these were named ‘horror’ and sdewes cities by the authors, respectively. keywords: sdewes index, sustainability, city development, sustainable energy action plan, city sample 1. introduction sustainability is a key issue when it comes to the development of cities. in 2014, 54% of the world’s population lived in urban areas and according to the prognosis, the proportion will be as high as 66% by 2050 [1]. while the number and population of megacities is on the rise, 43% of urban dwellers lived in settlements consisting of less than 300,000 inhabitants in 2014 (in europe the corresponding data was 58%) and only a modest decrease is estimated by 2030 [2]. looking at these numbers, it is easy to notice that urbanised areas have a huge impact on achieving sustainable development. various cities have started to address this issue and several indicators and comparisons were created to measure specific aspects of sustainable development. a few of these numerous examples are listed in this paper. the city development index [3] studies the municipalities from social and governance aspects. the global power city index (gpci) has ranked 40 metropolises since 2008 [4] considering 70 individual indicators regarding the environment, liveability and *correspondence: somogyiv@uni-pannon.hu r&d among others. the green city index is focused on the environmental sustainability of large cities [5]. carbon footprints of twelve metropolitan areas [6] and the san francisco bay area [7] were determined. several others are listed by lópez-ruiz et al. [8] but usually smaller towns do not fall within the scope of these benchmarks. environmental analysis, on the other hand, facilitates the evaluation of the impacts of human activities (different actions, projects or investments) with regard to the local environment, economy and society. in this way it provides information on the status quo and helps the practical implementation of sustainable development by focusing attention on the points to be improved [9]. several methods have been developed to carry out the procedure: checklists [10], the matrix technique [11], the network approach [12], gis-based methods [13] and quantitative methods [14] may be used to evaluate environmental impacts. aggregating methods such as the global pollution index (ipg) [15] may be suitable up to a point in providing a comprehensive sustainability analysis as they are only based on immission values. several multiple-criteria decision-making (mcdm) techniques designed to assist with decision-making, e.g. the analytic hierarchy process (ahp) [16] or the technique for order preference by similarity to ideal solution systems (topsis) [17] combined with simple sebestyén, somogyi, szőke, and utasi hungarian journal of industry and chemistry 50 additive weighting (saw) [18], can be used as well [19]. these hierarchical methods (topsis, saw and ahp) rank the examined parameters which may be useful when deciding between options of individual investments but are problematic in terms of adapting them to the decision-making process with regard to development strategies of the settlements. the sustainable development of energy, water and environment systems (sdewes) city sustainability index was developed to overcome the disadvantages and limitations of other measures with regard to benchmarking the performance of cities in terms of energy, water and environment systems. so far a list of 58 cities assessed by the sdewes index can be accessed online on the sdewes centre homepage [20]. also, articles concerning the benchmarking of 12 south east european cities (such as athens and belgrade) [21], 22 mediterranean port cities (e.g. barcelona and venice) [22], and a further 18 south east european cities (including budapest and pécs) [23] were published, and the inventory will no doubt be expanded upon in the near future. in this paper two cities were evaluated by using the composite sdewes index and to test the method itself. veszprém and zalaegerszeg are two hungarian county seats of roughly the same size and population, both are environmentally conscious, and are aiming to become environmentally friendly, liveable and sustainable cities. veszprém is near lake balaton with a population of around sixty-two thousand people and and a surface area of 126.9 km2. the city has won the climate star award † [24] and aims to become an eco-city. in its energy strategy [25] the following objectives were set by 2026:  20% of the energy demand should be satisfied by renewable energy resources while the energy renovation of public and residential buildings should be 70% complete resulting in a reduction in greenhouse gas (ghg) emissions of 25%;  35% of transportation has to be conducted by means of public transport with environmentally friendly vehicles that are less than 10 years old and 10% of the vehicle-kilometres should be undertaken by bicycles;  increasing the proportion of green areas to 25 m2/capita and 60% of rainwater should be reused in some way. zalaegerszeg is situated in the west of the country and consists of sixty-two thousand inhabitants and a surface area of 100 km2. since the millennium its urban development strategies have focused on becoming a “sustainable city”. in the strategy formulated in 2014 † the climate star award was founded by the climate alliance with the aim of demonstrating how climate protection initiatives can be implemented from the grass roots up [24]. cities with initiatives in the fields of sustainable energy, mobility, consumption, urban and regional development, and citizen involvement may apply for the call in four categories. [26] a major goal was to improve energy efficiency by 20% while producing more than 20% of its energy using local renewable resources by 2030. this would result in a reduction of 36% in terms of energy-related costs. taking 2005 as a base the ghg emissions should be reduced by 20% by 2030 while the particle pollution pm10 is planned to be mitigated by 10% by 2023. besides achieving these indicators, the city council aims to create and strengthen its image of being an environmentally conscious, modern and sustainable green city. 2. experimental the sdewes index consists of 7 dimensions and 35 main indicators (table 1). the indicators of each dimension are explained in detail in ref. [21]; only those that need further clarification or some sort of adjustment due to problems concerning the access of data are highlighted in this paper. the data for each indicator were normalised according to the min-max method [27]. depending on whether the lower or higher values are more desirable, either eq. (1) or (2) is used [21-22]. an example of the first case, i.e. when lower values are favourable, would be co2 emissions, while the normalised data for the number of local universities would be calculated by eq. (2). since the leader (��,����� = max���,��) equals 1 and the laggard (��,����� = min���,��) 0, if only two cities are compared and the values are identical, the denominator would become 0. to avoid this ��,����� should be set to 0 for such cases. another solution would be to include further cities in the benchmark. ��,����� = ���,������max���,��� �min���,���max���,��� (1) ��,����� = ���,������min���,��� �max���,���min���,��� (2) where: i – normalised value of the indicator, x – dimension number, y – indicator number within a dimension, cj – jth city, i – data input before normalization. value aggregation is done according to sdewes���� = ∑ ∑ �� � ��� ��,����� � ��� , (3) where ∑ �� = 1� ��� and αx is the weight of the xth dimension. the sdewes index of the jth city is calculated by a double summation, where α1 and α5 are 0.22 since these dimensions include energy and co2 emissions data. other dimensions are weighed less (αx=0.11) as they are not directly related to the sustainable energy action plan [21-22]. adapting the sdewes index 45(1) pp. 49–59 (2017) 51 table 1. the dimensions and indicators [21-23]. dimensions d1: energy consumption and climate d2: penetration of energy and co2-saving measures d3: renewable energy potential and utilization d4: water and environmental quality d5: co2 emissions and industrial profile d6: city planning and social welfare d7: r&d, innovation and sustainability policy in di ca to rs energy consumption of buildings [mwh] sustainable energy action plan (seap) solar energy potential [wh/m2/day] domestic water consumption [m3/capita] co2 emission of buildings [t co2] price of a public transport ticket [eur] r&d and innovation policy orientation energy consumption of transport [mwh] combined heat and power-based district (h/c) wind energy potential [m/s] water quality index [/100] co2 emissions of transport [t co2] urban form and protected sites national patents in clean technologies total energy consumption per capita [mwh/capita] energy savings in end-usage (buildings) geothermal energy potential [mw/m2] annual mean pm10 concentration [µg/m3] average co2 intensity [t co2/mwh] gdp per capita [ppp$ national] local public/private universities heating degree days (hdd) [day °c] density of the public transport network renewable energy usage for electricity [%] ecological footprint [gha/capita] number of co2-intense industries inequality adjusted wellbeing (hpi) national hindex of scientific publications cooling degree days (cdd) [day °c] efficient publiclighting armatures biofuel share in transport [%] biocapacity [gha/capita] airport carbon accreditation (levels) tertiary education rate (national) reduction target for co2 emission reduction (2020) 2.1. data of veszprém and zalaegerszeg as of october 2017, neither of the cities are signatories of the covenant of mayors movement, therefore, alternative sources of data had to be found. besides the sources suggested by the developer of the index, the energy and integrated city development strategies were used to retrieve data. necessary changes and the simplification of the original method is explained in detail below. 2.1.1. energy consumption and climate (d1): the energy consumption of buildings (municipal, residential and commercial) and transportation (public, private and the municipal vehicle fleet) are indicators on their own (table 2) but also included in terms of the total energy use per capita [21]: � �(��) = �∑ �b � ��� �∑ �� � ��� ��g��d� ����� (4) where  e – total energy consumption (mwh),  p(cj) – population of the jth city (capita),  eb – energy consumption of buildings (1: municipal, 2: residential and 3: commercial) (mwh),  et – energy consumption of transport (1: public, 2: private and 3: municipal vehicle fleet) (mwh),  eg – energy consumption of public lighting (mwh),  ed – energy consumption of industry (mwh). the energy consumption of transport was calculated based on the number of vehicles registered according to the energy strategies of the cities [25-26] by presuming an average mileage of 15,000 km/year and average consumption of 7.5 l/100 km [25]. the energy content of diesel and gasoline was assumed to be 10.83 kwh/l and 8.89 kwh/l, respectively. data for commercial buildings are only included in the total energy consumption indicator as the consumption of the service sector and industries was not collected separately by the cities. as for the municipal vehicle fleet, due to a lack of data for veszprém, this had to be neglected for both towns. it has to be noted that the data for veszprém were from between 2007 and 2009 as stated in the strategy while for zalaegerszeg information sebestyén, somogyi, szőke, and utasi hungarian journal of industry and chemistry 52 could only be obtained from between 2012 and 2013. in later documents, only improvements are mentioned, newly obtained data on overall consumption is not stated. monitoring the energy consumption of public buildings and lighting is an issue for both cities that needs to be solved. 2.1.2. penetration of energy and co2-saving measures (d2): neither of the cities have a sustainable energy action plan (seap) as of 2017 [31], therefore, both received zero for the first indicator (table 3) though veszprém is currently in the process of creating its sustainable energy and climate action plan (secap). in the case of veszprém, a cogeneration plant was recently installed [29] while there are only plans for such a system in zalaegerszeg (though one district heating system operates using geothermal energy) [30]. energy savings have been accomplished and are continuously implemented in both cities by renovating public buildings and installing photovoltaic systems, e.g. on the flat roofs of a grammar and primary school in veszprém and on the mayor’s office in zalaegerszeg (the performance of which can be accessed online from the webpage of the city). nonetheless, there is no building with net zero co2 emissions, that is why both cities received 1 point for the ‘energy savings in endusage’ indicator. the difference in size of the cities does not necessitate different types of public transport; both zalaegerszeg and veszprém have local bus routes that are operated by the same regional bus company. further points could have been allocated for tram and subway lines (2 for existing, 1 for planned) and an extra point would have been given to the city with the longest tram/subway network [20]. led technology is considered an efficient public lighting solution (1 point) and an additional point can be gained if solar energy is used to power armatures. recent investments were made in both cities to improve the energy efficiency of public lighting after the introduction of the cited strategies. 2.1.3. renewable energy potential and utilization (d3): the renewable energy potential is highly dependent on the location, topology and geology of the area but the local government can have a strong influence on the utilisation of these resources. while regional data could be gathered for the potentials, national data [32] had to be used for the share of renewable sources in terms of electricity production and biofuel use in transport indicators because there was no reliable local information for veszprém (table 4). for zalaegerszeg biogas from the regional municipal wastewater treatment plant is converted to provide the local buses with liquid fuel. based on a presentation [33] the tanked volume is known for 2015, therefore, the biofuel utilization in terms of transportation was modified accordingly. to attain an accurate comparison the national value for 2015 was considered in the case of veszprém. table 4. the data of the renewable energy potential and utilization (d3) indicator veszprém zalaegerszeg solar energy potential [wh/m2/day] 3,425 [25] 3,014 [26] wind energy potential [m/s] 4.921 [34] 3.505 [34] geothermal energy potential [mw/m2] 60 [35] 90 [35] renewable energy usage for electricity [%] 8.76 [32] 8.76 [32] biofuel utilization in terms of transport [%] 4.15 [32] 5.46 [32-33] table 2. the data of energy consumption and climate (d1) indicator veszprém zalaegerszeg energy consumption of buildings [mwh] 309,393 [25] 313,434 [26] energy consumption of transport (mwh] 225,479 [25] 217,228 [26] total energy consumption [mwh/capita] (in brackets: population) 19.50 (61,721) [25] 11.65 (59,499) [26] number of heating degree days (hdd) 2,890 [28] 2,850 [28] number of cooling degree days (cdd) 1,619 [28] 1,607 [28] table 3. the data of penetration of energy and co2saving measures (d2) indicator veszprém zalaegerszeg sustainable energy action plan (seap) 0 [31] 0 [31] combined heat and power-based district heating/cooling system 2 [25] 1 [26] energy savings in endusage (buildings) 1 [25] 1 [26] density of public transport network 1 [29] 1 [30] efficient public lighting armatures 2 1 adapting the sdewes index 45(1) pp. 49–59 (2017) doi: 10.1515/hjic-2017-0049 53 2.1.4. water and environmental quality (d4): there were no available local data for the domestic blue water footprint, ecological footprint and biocapacity, therefore, national values were applied in the calculation. air quality is only described in terms of the pm10 concentration [20]. the water quality index was ambiguous as the articles [21-22] referred to the indicator as drinking water quality but the water quality index (watqi) refers to natural water quality [36]. the index relies on the global database of the united nations gems/water programme and includes five indicative parameters: dissolved oxygen, ph, conductivity, total nitrogen and total phosphorous. unfortunately the watqi of countries are only available for 2008 [37], from 2012 the water quality index was replaced with access to sanitation and drinking water in terms of the aggregated environmental performance. it has to be noted that in the case of hungary the drinking water is supplied from underground reservoirs that are only linked indirectly to surface waterbodies while in other countries these serve as direct sources of drinking water. thus using water quality indices for inland water bodies may be good indicators of safe access to water. 2.1.5. emissions and industrial profile (d5): as in the case of the first dimension the emission values of the commercial buildings and municipal vehicle fleet were unavailable, therefore, these could not be included in the calculation. information on co2-intense industries was gathered by going through an online company database [41]. the indicator carbon accreditation of airports became zero for both cities for different reasons: veszprém has no airport and the one near zalaegerszeg has no accreditation. since the first case means no emissions while in the second case the existing emissions are not measured, the purpose of the indicator is not fully achieved. the original aim was to include the emissions of the airports in some way in the sdewes index as the seaps do not take them into consideration [21]. table 6. the data of co2 emissions and industrial profile (d5) indicator veszprém zalaegerszeg co2 emissions of buildings [t co2] 87,882 [25] 82,579 [26] co2 emissions of transport [t co2] 71,711 [25] 70,282 [26] average co2 emissions [t co2/mwh] 0.393 0.292 number of co2 intense industries 4 [41] 4 [41] carbon accreditation of airport [levels] 0 0 [42] 2.1.6. city planning and social welfare (d6): two indicators need further explanation (table 7). the prices of public transport were introduced in ref. [21] instead of the share of public transport in terms of total passenger kilometres [22], the latter not being accessible in all cases. the more a single ticket costs, the less likely people will choose public transport. on the other hand, easy access to public transport should result in positive externalities such as cleaner air and less traffic jams, by and large a more liveable city. the urban form and protected sites indicator is an aggregation of several factors (table 8): compact city form (whether it is mono or polycentric), urban green areas and surrounding green corridors are evaluated. to determine the compactness of the cities, the energy consumption of transport compared against population density was chosen, as a compact city can be described as of high population density [47] and because of the short distances cars are less likely to be used. thus the smallest value received 3 points while the highest received 1. urban green spaces were examined in table 5. the data of water and environmental quality (d4). indicator veszprém zalaegerszeg domestic water consumption [m3/capita] 7 [38] 7 [38] water quality index [/100] 92 [37] 92 [37] average air quality pm10 [µg/m3] 23.59 [39] 29.60 [39] ecological footprint [gha] 2.9 [40] 2.9 [40] biocapacity [gha] 2 [40] 2 [40] table 7. the data of city planning and social welfare (d6) indicator veszprém zalaegerszeg price of public transport ticket [eur] (1 eur = 310 huf) 1.07 [43] 1.10 [43] urban form and protected sites 1 2 gdp per capita [ppp$ national] 25,068.9 [44] 25,068.9 [44] inequality adjusted well-being (hpi) 4.3 [45] 4.3 [45] tertiary education rate (national) [%] 21 [46] 21 [46] sebestyén, somogyi, szőke, and utasi hungarian journal of industry and chemistry 54 comparison with the hungarian county seats [48]: 0-30 m2/capita: 1 point, 30-50 m2/capita: 2 points and over 50 m2/capita: 3 points. green corridors were also assessed on a county basis [49] instead of using the suggested gisbased method [20]. the categories were determined from 1-3 by only taking the green corridor areas of hungarian counties into consideration. 2.1.7. r&d, innovation and sustainability policy (d7): results for the seventh dimension are listed in table 9. the number of public and private universities yielded an unexpected result for the two cities in question. universities seated in the town and those where only a faculty is based there were equally counted. if only those universities that are seated in the said city were taken into consideration, veszprém would have 2 versus 0 in zalaegerszeg. additional points were given if the university was listed in the scimago institutions rankings [53]. the energy strategy of veszprém envisions a 25% co2 emissions reduction by 2026, the basis being 2007 [25], while zalaegerszeg aims to achieve a 36% reduction by 2030, compared to 2012 [26]. to facilitate a comparison, goals for 2020 were calculated by linear interpolation. 3. results after processing the necessary calculations, the sdewes indices of both veszprém and zalaegerszeg were 1.54. as is clear in fig.1, the values are integers and, except for one case (d5), veszprém achieved better or equal results. it also has to be noted that on several occasions the difference between the data was very small. still, the better city was awarded with 1 and the worse value with zero in the normalisation process. in order to eliminate this problem, a third city was included in the benchmark. ohrid was chosen as the size of this historical macedonian town is similar to the other two and all data were available from kilkis [21]. also, this was the only city in this comparison that had no seap. as an alternative solution the ‘average south east european (see) city’ from the same article was included to put the two hungarian cities to the test to see where they would be in the ranking of the see cities of that sample. the inclusion of these two examples changed the order of the cities (table 10). while the results of both veszprém and zalaegerszeg improved, zalaegerszeg gained more from the inclusion of another city from a different country in the benchmark. the reason for the improvement of the indices is that in several cases the national data had to be included in the calculation and hence, the indicator became 0. while both veszprém and zalaegerszeg gained points from increasing the sample size, the accumulated increase was larger for zalaegerszeg (10.03 compared to 8.12). the arrows show in which direction the indicators changed. in the case of veszprém, data for d3 and d6 decreased but not significantly, for zalaegerszeg there was no change in d3 and only a slight decline in d5. the sdewes index results are similar, the difference between the highest and lowest values is 0.37. nonetheless, heterogeneity exists with regard to the individual indicators. results for each dimension are visualised in fig.2. both hungarian towns performed well concerning d1 (energy consumption and climate), d4 (water and environmental quality) and d7 (r&d, innovation and sustainability policy), while there is room for improvement in the fields of co2-saving measures and city planning. the average see city, on the other hand, possesses lower values regarding energy consumption and environmental and water quality. table 8. data for grading urban form and municipal management veszprém zalaegerszeg urban form and protected sites 1 2 compact city form 1 3 monocentric x x polycentric population density [capita/km2] 486.38 580.99 urban green spaces 1 2 urban park intensity [m2/capita] 21 [29] 34.6 [30] green corridors 1 1 protected sites x x national park/ramsar x x table 9. the data of the r&d, innovation and sustainability policy (d7) indicator veszprém zalaegerszeg r&d and innovation policy orientation 3 [50] 2 [50] national patents in clean technologies 2.5 [51] 2.5 [51] number of public/private universities (city) 3 [52-53] 5 [52-53] h-index of scientific publications 301 [54] 301 [54] reduction target for co2 emissions (2020) [%] 18 [25] 16 [26] adapting the sdewes index 45(1) pp. 49–59 (2017) 55 figure 1. results of the first comparison on radar charts. 4. conclusion the process of gathering data revealed that both veszprém and zalaegerszeg need to collect and measure data related to energy efficiency and other indicators of sustainable development more precisely. creating a database of detailed information on energy use, co2 emissions and use of renewable sources which is regularly updated would help to achieve the ambitious goal of becoming a sustainable city within a relatively short timespan. also, the development of a seap or secap and becoming a member of the covenant of mayors would be advantageous and for which veszprém has started taking steps. based on the dimensions of the sdewes index, veszprém needs to improve in terms of d3 and d6. the individual indicators highlight that the energy consumption of public transport could be reduced, based on the example of zalaegerszeg, and also utilization of renewable energy should be improved. in terms of city planning and social welfare the number and area of urban parks can be increased more easily than that of protected sites. establishing green areas is included within the urban development strategy of the city [29], so improvements may be expected in terms of this indicator. also, progress in developing a compact city form is anticipated based on the plans to reform the public transport system and relocate the central bus station to next to the railway station [29]. in the case of zalaegerszeg, dimensions d2, d3 and d6 are lower. energy-saving measures could be improved by constructing a cogeneration plant to improve the penetration of district heating, using solar panels in public lighting, and also using the wastewater heat to facilitate the full utilization of biogas as a liquid biofuel [55]. in the case of d3, the potential of solar and wind energy cannot be increased and no information concerning the local use of renewable energy resources in terms of electricity was found. as for d6 the same suggestions as in the case of veszprém can be made to increase the values of the individual indicators. it has to table 10. results of calculating the sdewes index veszprém zalaegerszeg ohrid average see city d1 3.53 ↑ 3.93 ↑ 3.78 1.43 d2 2.45 ↑ 0.95 ↑ 2.00 3.50 d3 1.99 ↓ 2.00 1.60 3.12 d4 4.17 ↑ 3.43 ↑ 2.45 1.16 d5 2.28 ↑ 2.79↓ 3.00 2.45 d6 0.98 ↓ 1.95 ↑ 4.00 3.65 d7 3.72 ↑ 3.97 ↑ 1.08 1.75 sdewes 2.74 ↑ 2.83 ↑ 2.71 2.47 sebestyén, somogyi, szőke, and utasi hungarian journal of industry and chemistry 56 figure 2. results of the second comparison on radar charts. be pointed out though that the use of the ticket price for public transport resulted in an unjust outcome: since in ohrid there is no means of local public transport, this indicator became zero, which could also mean that transportation is free. therefore, ohrid will always receive the highest value in terms of the process of normalisation as long as there are no local buses in the city. in terms of the process of evaluating the two hungarian county seats, the benchmarking method was assessed as well. without a doubt, the sdewes index has its benefits. it uses environmental, economic and social indicators, gives credit to co2 reduction goals and also considers the possible use of renewable resources. also, human resources are included presuming that higher education and research and development seek to achieve sustainability. on the other hand, the authors identified some drawbacks, too. the first and the fifth dimensions both focus on energy consumption and co2 emissions. since these data strongly correlate with each other, the inclusion of both measures leads to redundancy. also, these two dimensions are weighed more than the others, therefore, energy-related information outweighs other aspects of sustainability. furthermore, some of the parameters favour smaller cities over larger ones and vice versa. for example if the absolute values of energy consumption of a small city and a capital are compared, the small city will undoubtedly achieve a better result. figure 3. the evaluation intervals of sdewes index indicators adapting the sdewes index 45(1) pp. 49–59 (2017) 57 an example of the opposite would be a city with an accredited airport (aca 3) as opposed to a town with no airport (small towns do not always have airports). similarly in a capital, where subway and tram lines are at one’s disposal, the density of the public transport network would be high while it would be uneconomical to have trams in a smaller town where the bus lines are sufficient. to overcome the problem of favouring results of cities of different sizes, using data which is proportional to area or population is suggested wherever possible. another problem was that the scoring of the qualitative indicators such as the urban form and protected sites was not always clear. if the sdewes index is to be used widely then these calculations have to be made transparently and be well documented. due to the nature of the min-max method, small differences may be magnified and large differences may diminish. also, as the index requires certain data that can only be obtained on a national level, the comparison between cities in the same country is somewhat limited. a solution to this problem may be to include towns from different countries and to choose a range (by including more than two cities) in such a way that provides balanced scales in terms of the indicators. while normalisation facilitates the inclusion of values on different scales, the min-max method makes it difficult to compare the results of two sets of cities. at present, the extremes are defined by the individual parameters of the cities chosen to be included in the benchmark (fig.3). in terms of another comparison with a different batch of cities (that can have a common set as with the previous version) the two evaluation intervals may not be equal (��1 ≠ ��2 since �� ∈ ��2 and �� ∉ ��1). as the two extremities are different in the two benchmarks, the results cannot be compared to each other. in the case of extremities a change in the order might appear as was the case in this paper. including the average of a different batch of cities (given that the average of any parameter is not equal to that of either city) may resolve the limitations of the min-max method but only momentarily. since the ranking is dynamic and changes as the cities develop, the average sdewes index of a previous time period will not provide relevant information with regard to the current situation concerning the sample from which the average city was created and neither on the sample of two cities one wanted to expand. besides the obvious solution of having a sample size of at least three cities, the authors suggest the following: two artificial sets of parameters should be created to serve as absolute extremes of the sdewes index. the worst case scenario is referred to as the ‘horror city’ and the best case scenario is named ‘sdewes city’ after the index itself. the legend for fig.3 is as follows:  ai, bi, ci – the measured/real indicator values of the analysed cities in the first calculation.  si – the measured/real indicator value of the city to be included in the second calculation.  ii1 – the evaluation interval, when the new city’s value is between the other indicator values.  ii2 – the evaluation interval, when the new city’s value falls outside of the other indicator values.  zi – the theoretical minimum value of indicator i, the ‘horror city’.  wi – the theoretical maximum value of indicator i, the ‘sdewes city’. to resolve this problem with regard to the evaluation intervals changing from time to time, the minimum and maximum values of each indicator must be determined in a way that the examined cities could be included in the evaluation intervals: ��1 = ��2 = ��� (5) �� ∈ ��2 , �� ∈ ��1 ... �� ∈ 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[5]. chen et al. [6] demonstrated that fe nanoparticles encapsulated in cnts are promising catalyst in ftp to synthesize light olefins. the catalytic consequence of hydrothermal liquefaction of microalgae to produce bio-oil over cnt *correspondence: dallos@almos.vein.hu supported transition metal (co, ni, pt) catalysts was reported by chen et al. [7]. to change the wettability and chemical character of the cnts or to avoid agglomeration in nanocomposites, the cnt surfaces are often exposed to surface functionalization [2] and modification processes using polyfunctional anchoring, capping, and coupling agents [8]. research has shown that metal–support bindings can be strengthened by functional groups that are covalently bonded (grafted) to the support. functionalized carbon nanotube-supported pt nanoparticles were applied with favourable results in terms of selective olefin hydrogenation [9]. because cnts adsorb molecules well, functionalized cnts are attractive chromatographic stationary phases for separation of normal and isoalkanes and aromatic compounds in the development of alternative fuels with high hydrogen/carbon ratios [10]. however, non-covalent functionalization using coupling agents or compatibilizers does not perturb the structure of the carbon nanotubes, establishes proper interactions between carbon nanotubes and the polymer matrix, and prevents the formation of nanotube agglomerates [11]. in terms of the properties of the reinforced composites of cnts, the couplings between the nanotubes and the matrix are important beside the mechanical properties of the building parts [12]. these interactions depend on the surface properties and energies of the two materials. the surfaces of chemically derivatizated cnts were investigated by means of various ana gerencsér, rieder, varga, hancsók and dallos hungarian journal of industry and chemistry 62 lytical methods, e.g. thermal analysis [9-10,13-14], infrared spectroscopy (ir) [10,13], transmission electron microscopy (tem) [13,16], raman [16] and atomic force microscopy [10], and inverse gas chromatography (igc). igc is a precise analytical method which is suitable for determining the surface energetic characteristics of the cnts [13,15-17]. igc was used for the characterization of the chemical character of the surface and was utilized to measure dispersive and specific surface energies, of numerous cnt substances [18]. the quantitative characterization of surface functionalization by surface energy mapping is of great importance. however, previous papers have presented surface energy values for functionalized cnts over unclear surface coverages without energetic profiles and surface energy distribution functions, which, therefore, could not give correct information on the surface of the cnts. in this study, the dispersive, specific (acid-base) components of the surface energy with their heterogeneity charts and energy probability density functions of untreated and compatibilized mwcnts are presented. a comparative quantitative characterization of the effectiveness and quantitative control of surface treatment is given. the exclusive energy scaling of the surfaces of the mwcnts by energy heterogeneity charts with surface energy probability density functions over wide surface coverages is the new approach and main novelty of this paper. 2. experimental and methods 2.1. samples and measurements multi-walled carbon nanotubes (mwcnts) were manufactured at 973 k by the chemical vapour deposition (cvd) process over a fe/co bimetallic catalyst at the department of chemical engineering science (university of pannonia, veszprém, hungary) [19]. their diameter was between 10 and 20 nm and their average length was above 30 μm. an olefin-maleic-anhydride-ester-amide (fig.1) copolymer (omaea) was used as a compatibilizer. the coupling agent was synthesized at the department of mol hydrocarbon and coal processing (university of pannonia, veszprém, hungary). the surface of mwcnts was covered by the compatibilizer from a hydrocarbon solution of the coupling agent while the mixture was stirred for 1 hour at 333 k. the solvent was subsequently evaporated and the treated mwcnts were dried at 383 k for 2 hours in air [11]. the surface energies of as-received and compatibilized samples of mwcnts were measured by a surface energy analyzer (igc-sea, surface measurement systems ltd., alperton, uk) over a series of surface coverages from (n/nm) = 0.005 to (n/nm) = 0.030. igc samples were produced by filling 20-25 mg of cnts into silanized pyrex glass tubes of i.d. = 3 mm under a vacuum and moderate vibration. the samples of mwcnts were stabilized in the column with plugs of silanized glass wool. the samples were preconditioned in the column at the actually measured temperature for 60 minutes before each measurement. the igc experiments were carried out at a column temperature of 353 k, with a helium carrier gas flow of 10 cm3/min. methane gas was used as a dead-time marker using a flame ionization detector; and n-hexane, n-heptane, n-octane, n-nonane, chloroform and toluene as test compounds. the surface energy values were estimated using the specific retention volumes of the test compounds [20]. the specific retention volumes were obtained from the adjusted retention times: spw mvtv /c ' r  (1) the mean flow rate of the carrier gas in the column, cv , was evaluated as given in ref. [20]. 2.2. theoretical methodologies the dispersive component of the surface energy ( d s ) and its heterogeneity profile of samples of mwcnts were calculated using the dorris-gray method [21] over different surface coverages:   2 ch c,1c, ch d s 22 /ln 4 1             an vvrt nwnw   (2) when plotting rtln(vw,nc) against carbon number, nc, for the n-alkane probes, a straight line is generated from the gradient from which the dispersive free energy of the sample surfaces of the mwcnts, d s , can be calculated. the specific (lewis acid-base) surface energy ab s of samples of mwcnts was calculated from the basic component (  s ) and the acidic component (  s ) of the surface energy:  ss ab s 2  (3) the basic and acidic components of the surface energy were obtained from the specific parts of free enthalpy changes of adsorption ab ,ads ig of polar probes i: figure 1. structure of the olefin-maleic-anhydrideester-amide copolymer (omaea) coupling agent, where r1: alkyl chain with length of the olefinic monomer; r2: alkyl chain with r1–2 carbon number; a, b: 2–21; k: 0.2–2; l: 1–7; m: 1–7 and n: 0.3–2 [11] surface energy heterogeneity profiles of carbon nanotubes 45(1) pp. 61–66 (2017) 63        ss ab ,ads 2  iiii ang (4) applying the van oss-chaudhury-good theory [22] with the della volpe scale [23]. the specific free energy changes of adsorption of the polar probes were obtained as suggested by donnet et al. [24]. 3. results and analysis 3.1. experiments the dispersive surface energy profiles of the untreated samples of mwcnts and those treated with the olefinmaleic-anhydride-ester-amide copolymer (omaea) coupling agent compatibilized at 353 k and over low surface coverages (n/nm) are presented in fig.2. the energy profiles show reasonable devaluation of dispersive surface energy for mwcnts after surface modification detected by n-alkane molecular probes: the dispersive surface energy ( d s ) of the mwcnts decreased to half of its initial value. the untreated samples of mwcnts exhibited dispersive surface energies of ~110 mj/m2 at 353 k, which is comparable to the values reported by other researchers studying carbon nanotubes [13-15] and graphitic carbon materials [25]. the relatively high values of the dispersive surface energy of untreated mwcnts can be attributed to a strong nonpolar interaction potential to build physical long-range keesom, debye, and london attractions, which explains their high tendency to agglomerate [14]. however, the anchoring of olefinmaleic-anhydride-ester-amide (omaea) up on the mwcnts surface caused a marked decrement in dispersive part of surface energy from ~110 mj/m2 to ~48 mj/m2 at 353 k. the large drop in the value of d s of surface-treated mwcnts shows that the dispersive surface energy of mwcnts has been obviously altered by the coupling agent. the surface treatment also affected the dispersive surface energy heterogeneity profile of the mwcnts. the surface energy mapping of the samples of mwcnts indicated that the dispersive components of surface energies of untreated samples of mwcnts are almost constant within the region of low surface coverage. consequently, the surface of the untreated mwcnts can be considered quasi-homogeneous. however, the dispersive surface energy heterogeneity profiles of the treated mwcnts prove that the copolymer-modified mwcnt surface is energetically slightly heterogeneous, because the dependence of d s on surface coverage is relatively strong within the region of low surface coverage. in addition, the distributions of the dispersive surface energies (fig.3) obtained by point-by-point integration of dispersive surface energy profiles over the investigated range of the surface coverage support in a more illustrative manner also results in an increase in the dispersive surface energy heterogeneity. the dispersive surface energy probability function of the mwcnts became more spread out after modification of the surface indicated a greater degree of energetic surface inhomogeneity. the specific surface energy ( ab s ) profiles of the untreated samples of mwcnts and those treated with omaea compatibilized at 353 k and over various surface coverages (n/nm) are presented in fig. 4. the untreated samples of mwcnts possess specific surface energy of ~10 mj/m2 at 353 k, which value is near to that given by lou et al. (8.84 mj/m2) for pristine carbon nanotubes at 373 k and over undefined degrees of surface coverage [14]. the quantitative surface energy analysis obtained by igc-sea methodology demonstrated that surface treatment of mwcnts resulted in figure 3. dispersive surface energy probability functions of untreated samples of mwcnts and those treated with an olefin-maleic-anhydride-ester-amide copolymer (omaea) coupling agent compatibilized at 353 k (the solid correlation lines are only to improve visualization). figure 2. dispersive surface energy profiles of untreated samples of mwcnts and those treated with an olefin-maleic-anhydride-ester-amide copolymer (omaea) coupling agent compatibilized at 353 k and over various surface coverages (the dotted correlation lines are only to improve visualization). gerencsér, rieder, varga, hancsók and dallos hungarian journal of industry and chemistry 64 significant changes in surface energies: the specific surface energy of cnt surfaces increased more than fourfold, from ~10 mj/m2 to ~41 mj/m2. furthermore, the dependence of ab s on surface coverage is pronounced for the compatibilized samples of mwcnts which indicates that energetic heterogeneity attributed to chemical heterogeneity and the existence of electron donor-acceptor atomic groups on the surface. however, the quasi-constant specific component of surface energy for untreated mwcnts suggests an energetically homogeneous surface and the absence of high specific energy surface sites. the specific surface energy values of compatibilized mwcnts are much higher than those of the untreated surfaces, declared the enhanced connection between compatibilized mwcnts and polar analytes. the observed diversity in specific surface energies is accomplished from the adsorbed polar atomic clusters: namely the moderately electron-withdrawing maleic anhydride groups; and the electron-donating ester and amide groups with different nucleophilic or electrophilic characteristics. the specific surface energy distributions in fig. 5 represent the heterogeneity of the samples of mwcnts and reveal that the untreated mwcnts exhibited ab s values which varied from 9.9 to 10.3 mj/m2. this small variation in the specific surface energy demonstrated a fairly energetically homogeneous surface for untreated mwcnts. however, as surface treatment increased the concentrations of polar clusters on the surface of mwcnts, the modified surface exhibited great variations in ab s (from 37.3 to 42.9 mj/m2), implying that the compatibilized mwcnts are surface energetic heterogeneous. the surface treatment also modified the chemical characteristics of the mwcnts. the acid-base surface energy mapping of the samples of mwcnts (figs.6 and 7) indicate that both the electron-accepting and donating abilities of the mwcnts were raised appreciably after compatibilization of untreated mwcnts consistent with the adsorption of electron-withdrawing and electron-donating atomic groups on the surface. the untreated samples of mwcnts possess base surface energy of ~16 mj/m2 at 353 k, which value is near to that given by lou et al. (12.97 mj/m2) for pristine carbon nanotubes at 373 k and over undefined surface coverage [14]. the surface energy mapping using the igc-sea methodology confirms that the surface treatment of mwcnts raised the basic component (  s ) of surface energy of mwcnts: it resulted in a sevenfold increase from ~16 mj/m2 to ~112 mj/m2. the acidic component of surface energy  s of untreated samples of mwcnts was measured as ~1.7 mj/m2 at 353 k, which is in good agreement with that reported by lou et al. (1.51 mj/m2) for pristine carbon nanotubes at 373 k and over undefined surface coverages [14]. the surface modification of mwcnts resulted in a more than twofold increase in the value of the acidic component (  s ) of the surface energy of mwcnts from ~1.7 mj/m2 to ~3.7 mj/m2. however, the profiles of acid-base surface energy heterogeneity of the treated mwcnts also prove that the copolymer-modified mwcnt surface became energetically more heterogeneous, because the dependencies of  s and  s on surface coverage are relatively stronger than those of the untreated mwcnts. the presence of non equi-energetic active surface centers exposes that the surfaces of the compatibilized mwcnts are not energetically uniform for specific acid-base interactions and the surface treatment considerably altered the ability of mwcnts to connect with molecular species by specific interactions. figure 5. specific surface energy probability functions of untreated samples of mwcnts and those treated with an olefin-maleic-anhydride-ester-amide copolymer (omaea) coupling agent compatibilized at 353 k (the solid correlation lines only improve visualization). figure 4. specific surface energy profiles of untreated samples of mwcnts and those treated with an olefinmaleic-anhydride-ester-amide copolymer (omaea) coupling agent compatibilized at 353 k and over various surface coverages (the dotted correlation lines only improve visualization). surface energy heterogeneity profiles of carbon nanotubes 45(1) pp. 61–66 (2017) 65 the larger change in the base component of the surface energy (  s ) after compatibilization with a polyalkenyl-poly-maleic-anhydride-ester-amide additive indicates a higher concentration of electron-donating ester and amide groups on the surface. the large value of  s (relative to  s ) implies a more basic characteristic and donor properties of the surface of the treated mwcnts. 4. conclusion the experimental data demonstrated that igc is a useful methodology of characterizing the variation in the surface characteristics of mwcnts after non-covalent functionalization. the exclusive energy scaling of the sea methodology using energy heterogeneity charts with surface energy probability density functions over wide surface coverages presents profitable additional information on the differences in terms of the nature, homogeneity and heterogeneity of surface energies resulting from surface transformations. the multilateral surface energy analysis of sea presents a quantitative control of the effectiveness of surface treatment and demonstrates the importance of the dependence of surface energy analysis on coverage. acknowledgement the present work was published within the framework of the project ginop-2.3.2-15-2016-00053. symbols 2cha , ai cross sectional area of an adsorbed methylene group and of probe i ab ,ads ig specific free enthalpy of adsorption msp mass of the adsorbent in the column n avogadro’s number r gas constant t temperature ' rt adjusted retention time cv mean flow rate of the carrier gas vw specific retention volume ab s , d s specific and dispersive parts of the surface energy of solid sample material 2ch surface energy of a methylene group  s ,  s acid-base components of the surface energy of solid sample material  i ,  i acid-base components of the surface tension of polar liquid probe i θ=n/nm surface coverage references [1] dresselhaus, m.s.; 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good, r.; chaudhury, m.k.: additive and nonadditive surface tension components and the interpretation of contact angles, langmuir, 1988 4(4), 884-891 doi: 10.1021/la00082a018 [23] della volpe, c.; sibioni, s.: some reflection on acid-base solid surface free energy theories, j. colloid interf. sci., 1997 195(1), 121-136 doi: 10.1006/jcis.1997.5124 [24] donnet, j.b.; park, s.j.; balard, h.: evaluation of specific interactions of solid surfaces by inverse gas chromatography. a new approach based on polarizability of the probes, chromatographia, 1991 31, 435-440 doi: 10.1007/bf02262385 [25] donnet, j.b.; park, s.j.: surface characteristics of pitch-based carbon fibers by inverse gas chromatography method, carbon, 1991 29(7), 955-961 doi: 10.1016/0008-6223(91)90174-h hungarian journal of industry and chemistry vol. 45(1) pp. 67–71 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0010 initial electrical parameter validation in lead-acid battery model used for state estimation bence csomós, dénes fodor, * and gábor kohlrusz department of automotive mechatronics, institute of mechanical engineering, university of pannonia, egyetem u. 10., veszprém, h-8200, hungary the paper presents a current impulse-based excitation method for lead-acid batteries in order to define the initial electrical parameters for model-based online estimators. the presented technique has the capability to track the soc (state of charge) of a battery, however, it is not intended to be used for online soc estimations. the method is based on the battery’s electrical equivalent randles’ model [1]. load current impulse excitation was applied to the battery clamps during discharge while the voltage and current was logged. based on the randles’ model, a model function and a fit function were implemented and used by exponential regression based on the measured data. the diffusion-related non-linear characteristic of the battery was approximated by a capacitorlike linear voltage function for speed and simplicity. the initial capacitance of this bulk capacitor was estimated by linear regression on measurements recorded in the laboratory. then, the rc parameters of the equivalent battery model were derived from exponential regression on transients during each current impulse cycle. the battery model with initial rc parameters is suitable for model-based online observers. keywords: battery, soc, exponential regression, randles’ model, load current impulse 1. introduction in our daily lives, the number of mobile devices and utilities that can operate without grid connections is increasing. even though lithium batteries possess better performance properties and energy indicators, lead-acid batteries are still cheaper, significantly present in commercial applications and almost fully recyclable. therefore, any developments in lead-acid battery systems are still of interest. according to ref. [1], several methods exist to estimate a battery’s state of charge (soc) and state of health (soh) but model-based prediction is the most widespread because of its reliablity and robustness. model-based methods, as the name suggests, need a valid, properly detailed electric battery model. the randles’ model as a standard battery model is very popular in the contexts of lead-acid and lithium-ion batteries because of its cost-effectiveness and the similarities of both types. by similarity it is meant that the same model can be reasonably used for the parameter estimation of both battery types [2-3]. some additions to the standard randles’ model can be made if more details in electrochemistry are required such as diffusion in the bulk and porosity amongst others. the model requires values of initial resistance (r) and capacitance (c). the more accurate the initial *correspondence: fodor@almos.vein.hu parameters of the model, the faster and more reliable the convergence of a model-based predictor to the actual state, that is, the actual soc. the scope of the present work is to identify the initial values of rc components (parameters) by evaluating the voltage impulse responses excited by load currents in the time domain. 2. battery model for impulse excitation in this paper, a standard randles’ model [7-12] was analyzed that consists of charge-transfer resistance, rct, battery serial resistance, rs, double-layer capacitance, cdl, and bulk capacitance, cb (fig.1). the voltage references of the capacitors and currents in fig.1 were set for discharge. figure 1. randles’ battery model applied to a discharging battery pack rct cdl cb udl ub ibi(t) uocv(t) rs ict idl csomós, fodor, and kohlrusz hungarian journal of industry and chemistry 68 2.1. state-space model and model function by neglecting the intermediate mathematical steps and rearranging the state-space model, the system can be written in the following form: i c c u u rc u u dt d                                   b dl b dl ctdl b dl 1 1 00 0 1 (1) ir u u u s10 01 ocv b dl              . (2) by solving the output in eq.(2) in terms of the time domain using a current impulse as the system input, the output function in eq.(2) can be expressed by eq.(3) that can be considered as the model function of the system. this form of the output equation serves as a basis for creating a fit function on measured voltage data and then, derive r and c values from the fit parameters. for clarity, each of the terms of the output equation are grouped by alphabetical letters: dbtaetu t   )(ocv (3) where tags a, b and c can be written according to )(ctdl0 tirua  (4) t u c ti b 0b b )(  (5) )()( cts tirrd  (6) where uocv is the battery’s open-circuit voltage,  is the system’s time constant, t is the measurement time, and i(t) is the impulse load current. since the proposed method is based on load and relaxation cycles that follow each other during the analysis, ub0 represents the initial voltage of the bulk capacitor while udl0 is the initial voltage of the double-layer capacitor at the beginning of each impulse cycle. it should be noted that changes in current during each impulse cycle can be neglected as a result of working in the short time-constant region of the discharge curve, thus the current can be considered as a constant. the battery model shown in fig.1 is prepared for short-time transient analysis. even though the model can be used and remains valid for modelling discharge processes that last for several hours, that is, for longtime transients, the accuracy of the model becomes poor under such circumstances. the reason for this is that the battery model presented excludes the diffusion effect that can even be observed by the initial valley-like voltage drop and later as a circle-like voltage response on the long-time discharge voltage curve (fig.2). such an exclusion was made because the scope of the current work is to focus on short-time voltage responses to avoid excessive measurement time intervals and computational resources. consequently, the battery model was optimized for fast soc detection by shorttime battery checks. 2.2. determining the initial capacity of cb in eq.(1), the ub voltage represents the equilibrium voltage of the battery, therefore, it is related to the battery’s main charge and as a result its soc. if the battery is excited by small c/10 c/30 currents, ub and uocv can be considered equal. instead of ub, uocv can be measured at the battery terminals. therefore, the relationship between uocv and soc is important and can be determined from laboratory ocv measurements. a small discharge current was applied to the battery terminals under controlled conditions until the battery’s ocv reached the factory’s minimum voltage threshold from a fully charged state. the voltage, current and temperature were logged while the soc could be calculated by the simple coulomb-counting method during the process and saved in a lookup table. then, the lookup table could be used to determine a discrete relationship betwen uocv and soc in itself. the uocv soc characterisation method can be extended by the regression on lookup data in order to create a continous uocv soc relationship. a linear function, such as a capacitor-like regression of uocv soc characteristics can be legitimate if the battery’s excitation current is small, i.e. between c/10 and c/15 and is not discharged under 20-25% of soc. this could be the case when low-power devices are considered as loads. in the case of plain discharge, the soc changes can be basically tracked by the basis of the b term like in eq.(5) as conducted in the coulomb-counting method [1]. in the presented battery model, the b term provides information on the long-term state of the battery and requires initial parameters such as cb and ub0. the former represents the battery’s initial capacity, the latter is related to the battery’s initial voltage at the beginning of each impulse cycle. right before the first current impulse, ub0 is equal to the battery’s equilibrium voltage since a relaxation time of between 30 minutes and one hour is sufficient for chemical processes to decay. figure 2. discharge characteristics of a 15ah agm battery excited by different load currents initial electrical parameter validation in lead-acid battery model 45(1) pp. 67–71 (2017) 69 the initial value of cb is crucial because it has a strong influence on both the initial voltage drop and the gradient of the long-time discharge voltage curve. in the proposed model, a simplified, that is, capacitor-like formula was used for initial battery capacity estimation so it approximates the battery non-linear discharge characteristic linearly. the introduction of a regression error of a few percent, however, can lead to an easier and faster determination of the initial capacity cb. the calculation of the battery’s initial capacity was realized according to [4]. the fully charged battery at room temperature needed to be slowly discharged by a c/15 current until its ocv voltage reached the factory recommended minimum voltage threshold. once the discharge had finished, 2 hours of relaxation had to be observed in order to return the battery back to its almost equilibrium state. then, a c/15 slow charge had to proceed until the battery’s ocv voltage reached the factory recommended maximum voltage threshold. in both cases, the battery’s ocv voltage, current and temperature were recorded (fig.3/a). after averaging the discharge and charge-voltage measurements, linear regression was conducted on it according to 0bb b 15/c| )( 1 )( utq c tuocv  (7) where qb(t) can be estimated by qb(t) = i0 t. eq.(7) can be identified by the standard form of the linear curve y=mx+b. in eq.(7), cb is the battery’s initial capacity, qb(t) is the actual charge of the battery and ub0 is the actual voltage of cb at the beginning of the impulses. by rearranging eq.(7), cb can be determined. even though charge/discharge currents and soc levels are constrained, the ambient temperature should be controlled as well to provide a constant temperature during the test periods. the value of cb was calculated as 37766 f at 22°c using c/15 load currents. 3. exponential regression to derive rc model parameters the evaluation of measurement data and the comparision of measurements and simulations were realized using matlab. the rc parameters in the model shown in fig.1 and later in an orcad circuit were derived by an exponential regression using an appropriate fit function on the measured voltage data. the regression error between the measured and modelled characteristics can be minimized if the fit function follows the form of the model function, that is, both of them implement similar dynamics and the physical background of the inspected system. therefore, the fit function can be written as beatu t ˆˆ)( ˆ ocv     (8) in a form that is similar to eq.(3). the hat sign means that the form of eq.(8) is similar to eq.(3), but uses a different reference system. when using eq.(8) attention must be paid to the determination of rc parameters. eq.(8) gives voltage references with respect to the ground, that is the x-axis, while eq.(3) yields the references udl and us which correspond to ub. references used by eqs.(3) and (8) must be matched to derive correct rc parameters (fig.3/b). it can be seen that eq.(8) neglects the linear term from eq.(3). since the effect of continuous slow discharge of the battery, which is linked to the cb bulk capacitance in the battery model, possesses a timeconstant several orders of magnitude higher than the cdl-rct subsystem, it cannot be observed during the short impulse cycles. however, it should be considered during the whole discharge process so eqs.(3) and (8) need to be used together to estimate the soc during long-term discharge processes. according to refs. [5-6], it is practical to evaluate only the discharge component of the voltage responses during every load cycle. this method is also supported by the fact that the dynamic behaviour of the battery for both load and relaxation states can be described by the same battery model since both responses originate from the same battery structure. because load curves are only needed, the measured voltage should be separated from global data and then, concatenated right after each other. since voltage data has been prepared in this way, a b figure 3. (a) linear regression on the average of c/15 discharge and charge voltage data to derive initial value of cb. initial cut-off has been filtered. (b) references of model function and fit function csomós, fodor, and kohlrusz hungarian journal of industry and chemistry 70 regression can be made during every discharge impulse cycle simultaneously. the relaxation time during each impulse was set to provide enough time for the battery’s double-layer capacitance to almost fully discharge. it is practical because it simplifies eq.(8) by reducing the effect of the udl0 term in eq.(4). the load time was set taking into consideration the time constant of the cdl rct subsystem. according to experiments, it is within the range of 1 4s. the calculation method of the term b̂ in (8) is based on the calculation of the limit of the exponential term in eq.(8). practical experiments have proven that maintaining a load cycle of 4 in length can speed up and correct the regression. the rc values change during discharge. due to offline voltage response evaluation, it is not possible to optimise these parameters according to load conditions. therefore, the average rc values can be used for the whole period of discharge though this introduces a slight misalignment between the measured and modelled voltage characteristics. by applying eq.(8) on the prepared measurement data, the average rc parameters shown in table 1 were derived. 4. model implementation and validation of the impulse excitation method in orcad the aim of the orcad implementation was to validate the proposed battery model and the applicability of the impulse excitation method for rc parameter determination. the equivalent circuit model shown in fig.1 was transformed into an electric circuit. the duration of the simulation was set to 1 hour and the time step was equal to the sample time of the real measurement, namely 100 ms. 4.1. initialization of the orcad simulator and rc elements the initial voltages of the capacitors and the proper directions of orcad elements should be set carefully. orcad uses a reference system of its own that influences the current references of each component. this should be considered while placing an element in the circuit editor and when comparing the electric circuit references to the randles’ model. the initial voltages of the capacitors, udl and ub, were set to describe the battery’s discharge process and thus also follow the voltage references of the randles’ model, shown in fig.1. the values of initial capacitor voltages were derived from the chemical background and assumptions. cdl can be considered fully discharged through rct after the battery had relaxed (no load) for 2 hours so its initial voltage, udl, was set to 0. the bulk capacitance of the battery, cb, reflects the lengthy time constant as well as diffusion-related processes and is related to the main charge storage capability of the battery. if the relaxation time is sufficiently long, the battery reaches an equilibrium state and its ocv becomes equal to ub. an optimal relaxation time that is sufficiently long was derived from preceding measurements of discharge/charge cycles by applying different load currents and relaxation times. based on experiments, a relaxation time of 2 hours was applied and as a result the ocv could be considered equal to ub. using these assumptions, the initial voltage, ub, was set to 12.7 v and udl to 0 v. the introduction of the load current as an impulse excitation can be achieved through a switched power resistor element which is setup in a similar way to the real arrangement (fig.3/b). the switching routine of the orcad element was tuned in accordance with real load-relaxation cycles that were applied to the real testbench. the resistor sets the load current that discharges the battery. during this work, a load current of 3a was used with a load of 5s and relaxation cycles that lasted 10s. all of the initial values are summarized in table 2. 4.2. comparing the simulation with the battery model in fig.4/a, the results of measured and simulated voltage responses are shown. the validity of the model was analyzed by the comparison of measured and simulated voltages. according to the setup, the comparison is performed within a time frame of 5,600 s. the blue curve that represents the simulated data has a longer tail than the red one because filtering needed to be performed on the measured data to cut the initialization process at the beginning of the testbench. the zoomed-in segment shows the fitness of the simulated voltage response. the difference between the curves is relatively small, around 0.05 v to be precise. this error occurred because average rc values were used in the model instead of online tuned ones. table 2. initial values of simulation parameters that need to be set before a run simulation parameter initial value simulation step time 100 ms simulation duration 1 hour udl0 0 v ub0 12.7 v relaxation time / cycles 10 s load time / cycles 5 s load current 3 a (with a 4 ohm load) table 1. derived rc values of the battery model from regression derived parameter name average value rct 0.032 ohm cdl 92 f rs 0.056 ohm soc after discharge 87.9 % initial electrical parameter validation in lead-acid battery model 45(1) pp. 67–71 (2017) 71 5. conclusions this work shows a current impulse-based excitation method that can be used to either track soc changes during moderate discharge or find proper rc model values for model-based algorithms. the method is founded on an equivalent model-based approach that can implement the dynamic behaviour of a battery without using excessive chemical equations. the technique uses offline analysis of a battery, therefore, it is not able to reasonably track soc changes in real-time. this technique is not intended to estimate the soc of batteries by itself, indeed, it estimates good set points for online estimators such as kalman filters or other model-based observers. the advantages of the presented approach are its rapid nature and simplicity while minimising the error of soc estimation. the disadvantages of this method are its offline nature and related consequences. this technique could potentially be applied to embedded systems and commercially. 6. acknowledgement this research was supported by the efop-3.6.1-162016-00015 project. the project was supported by the hungarian government and co-financed by the european social fund. the project was supported by the european union and co-financed by the european social fund (efop3.6.2-16-2017-00002). references [1] piller, s.; perrin, m.; jossen, a.: methods for stateof-charge determination and their application, journal of power sources, 2001 96(1), 113–120 doi: 10.1016/s0378-7753(01)00560-2 [2] spagnol, p.; rossi, s.; savaresi, s.m.: kalman filter soc estimation for li-ion batteries, ieee international conference on control applications, 2830 sept. 2011, denver, usa, issn 1085-1992 [3] devarakonda, l.; wang, h.; hu, t.: parameter identification of circuit models for lead-acid batteries under non-zero initial conditions, american control conference, 4-6 june 2014, portland, usa [4] platt, g.l.: battery modeling, vol. i., 2015 isbn-13: 978-1-63081-023-8 [5] banaei a.; fahimi b.: real time condition monitoring in li-ion batteries via battery impulse response, ieee vehicle power and propulsion conference (vppc), 1-3 sept. 2010, lille, france issn 1938-8756 [6] banaei a.; khoobroo a.; fahimi b.: online detection of terminal voltage in li-ion batteries via impulse response, ieee vehicle power and propulsion conference, 2009. vppc '09, 7-10 sept. 2009, dearborn, usa issn 1938-8756 [7] kularatna, n.: dynamics and modeling of rechargeable batteries, ieee power electronics magazine, 2014 1(4), 23–33 doi: 10.1109/mpel.2014.2361264 [8] lee, y.-d.; park, s.-y.; han, s.-b.: online embedded impedance measurement using high-power battery charger, ieee transactions on industry applications, 2015 51(1), 498-508 doi: 10.1109/tia.2014.2336979 [9] kiani, m.: high resolution state of charge estimation in electrochemical batteries, applied power electronics conference and exposition (apec), twenty-eighth annual ieee, 17-21 march 2013, long beach, usa [10] kujundzic, g.; ileš, š.; matuško, j.; vašak, m.: optimal charging of valve-regulated lead-acid batteries based on model predictive control, applied energy, 2017 187 189–202 doi: 10.1016/j.apenergy.2016.10.139 [11] bhangu b.s.; bentley, p.; stone, d.a.; bingham c.m.: observer techniques for estimating the stateof-charge and state-of-health of vrlabs for hybrid electric vehicles, vehicle power and propulsion 2005 ieee conference, 2005 doi: 10.1109/vppc.2005.1554646 [12] wang, y.; fang, h.; zhou, l.; wada, t.: revisiting the state-of-charge estimation for lithium-ion batteries, ieee control systems magazine, 2017 37(4), 73–96 doi: 10.1109/mcs.2017.2696761 a b figure 4. (a) validation of modelled (orcad) and measured voltage data in matlab environment (b) battery testbench used during the analyzis hungarian journal of industry and chemistry vol. 45(1) pp. 73-84 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0011 simulating ion transport with the np+lemc method. applications to ion channels and nanopores. dávid fertig ∗1, eszter mádai1, mónika valiskó1, and dezső boda1,2 1department of physical chemistry, university of pannonia, egyetem u. 10., veszprém, h-8200, hungary 2institute of advanced studies kőszeg (iask), chernel u. 14., kőszeg, h-9730, hungary we describe a hybrid simulation technique that uses the nernst-planck (np) transport equation to compute steady-state ionic flux in a non-equilibrium system and uses the local equilibrium monte carlo (lemc) simulation technique to establish the statistical mechanical relation between the two crucial functions present in the np equation: the concentration and the electrochemical potential profiles (boda, d., gillespie, d., j. chem. theor. comput., 2012 8(3), 824–829). the lemc method is an adaptation of the grand canonical monte carlo method to a non-equilibrium situation. we apply the resulting np+lemc method to ionic systems, where two reservoirs of electrolytes are separated by a membrane that allows the diffusion of ions through a nanopore. the nanopore can be natural (as the calcium selective ryanodine receptor ion channel) or synthetic (as a rectifying bipolar nanopore). we show results for these two systems and demonstrate the effectiveness of the np+lemc technique. keywords: ion transport, nernst-planck, monte carlo simulation, nanopore, ion channel 1. introduction we dedicate this paper to honoring professor jános liszi, who was the supervisor of one of the authors (db) and respected senior to another (mv), supporting to the careers of both. we (db and vm) publish this paper together with our students (df and em) to demonstrate that the lesson of professor liszi — one of the most important goals of senior scientists is to pave the way to the junior ones — has not been left unconsidered. the goal of this work is to present a computer simulation technique for computing steady-state ion transport that was developed and applied in our research group with the essential help of dirk gillespie [1]. the method is based on the nernst-planck (np) transport equation coupled to the local equilibrium monte carlo (lemc) simulation technique and is described in sec.(2) in detail. the method, called np+lemc, was applied for various problems in the last couple of years. these problems include particle transport through model membranes [1, 2], ion channels [3–5], and nanopores [6–8]. the basic goal is to have a computationally efficient simulation technique using reduced models of steady-state systems, where particles (ions being the focus) diffuse as a result of a maintained driving force that is a concentration gradient and/or an electrical potential gradient (that is, an electrochemical potential gradient). we tend to regard these kind of systems as nanode∗correspondence: fertig.david92@gmail.com vices that yield a macroscopic output signal (electrical current, for example) as a response to an input signal (voltage, for example). reduced models have the advantage of including those degrees of freedom of the manyparticle system that are essential in reproducing device behavior, namely, the relationship of the output and input signals [6]. we present two case studies here to demonstrate both the effectiveness (and also possible source of errors) of the method and the power of reduced models. in the ryanodine receptor (ryr) calcium release ion channel, we needed to model only those amino acids of the channel protein that are inside or near the selectivity filter and hang into the ionic pathway. in the bipolar nanopore, we needed to reproduce the variation of the electric field along the pore axis properly. the most important reduction in the degrees of freedom, however, is that we model water as a dielectric continuum. the effect of using implicit solvent instead of an explicit solvent model was discussed in our previous work [6] through comparisons to molecular dynamics (md) simulations. our computational method is not the only one that is able to determine ionic current through biological and synthetic nanopores using reduced models. while the brownian dynamics (bd) simulation method [9–14] is the obvious candidate to simulate this problem, it has disadvantages from the point of view of sampling the flux of ions. the poisson-nernst-planck (pnp) theory [11, 15–18] also uses the np equation to compute flux, but uses a mean-field approach, the poisson-boltzmann 74 fertig, mádai, valiskó, and boda (pb) theory, to describe the statistical mechanical relationship between the concentration and electrochemical potential profiles. to use something more state-of-the-art to provide this relationship beyond the pb level is the essence of our approach. we suggest the lemc technique, which is a particle simulation method based on a three-dimensional model producing all the ionic correlations missing from pb. gillespie et al. proposed a different technique, in which a density functional theory (dft) was coupled to the np equation [19, 20] and used to method (np+dft) to describe the behavior of the same ion channel that we study here, the ryr ion channel [21–23]. dft is a continuum theory, but a very sophisticated one, where ionic correlations are included through a series expansion of the free energy functional and the finite size of ions is taken into account through the fundamental measure theory [24]. its accuracy was demonstrated by computing electrical double layers in extreme conditions and comparing to monte carlo (mc) simulations [25, 26]. the disadvantage of this method is that it can be used efficiently only in one dimension. this reduction in dimensionality, however, is often feasible provided that we reduce the model in an intelligent way. 2. modeling and methodology a good model should be able to explain complex phenomena in a simplified way while it stays in agreement with experimental data. the nanopore systems (both natural and synthetic) studied in this work have some common features. the primitive model of electrolytes, that represents ions as charged hard spheres, is used. the interaction potential between two ions is defined by coulomb’s law in a dielectric material: uij(r) =    ∞ if r < ri +rj 1 4πε0ε qiqj r if r ≥ ri +rj (1) where ri and rj are the radii, qi and qj are the charges of the different ionic species, ε0 is the permittivity of vacuum, ε = 78.5 is the relative permittivity of the solvent, and r is the distance between two ions. solvent (water, in this work) is not modeled explicitly; it is rather represented by two response functions. energetically, solvent acts as a dielectric background that screens the electric field of ions by just dividing by ε in the coulombpotential (eq.(1)). dynamically, solvent molecules collide with ions and impede their diffusion; we take that effect into account by a diffusion coefficient function, di(r). the ions of the electrolyte diffuse through a pore between two bulk containers (see fig.1). the pore penetrates a membrane that separates the two containers. the pore and the membrane are also modeled in a reduced way; they are confined by hard walls with which the hard sphere ion cannot overlap. other details of the figure 1: simulation cell used in the application of the np+lemc method. the model is rotationally symmetric: the three-dimensional model is obtained by rotating the figure about the z-axis. the domain confined by the blue line is the non-equilibrium transport region (the solution domain of the np+lemc system) that includes the pore and the two access regions. the electrochemical potential in this region is not constant, but changes from one constant value to another (the values in the two bulk regions) in a monotonic manner to provide the driving force of ionic transport. parameters r and h characterize system size. pores (amino acid side chains and surface charges) will be presented in sec.(3) for the respective ion channel and nanopore systems. ion transport is steady-state; concentrations and electrical potentials, therefore, are kept fixed at the boundaries of the two baths on the two sides of the membrane (blue line in fig.1). we assume that ion transport is described by driftdiffusion. our procedure is a hybrid method that separates the configuration degrees of freedom of ions (ion positions) from the kinetic degrees of freedom (ion velocities). in bd simulations they are treated together and ionic current is measured by counting ions that pass through the pore. the bd method has the disadvantage of weak sampling of flux especially at low concentrations (as in our ion channel example) and in cases, when current is limited by ionic depletion zones (as in our bipolar nanopore example). separation of the two parts of the phase space is a usual practice in equilibrium statistical mechanics, where the kinetic part is described by the ideal gas equations, while the excess quantities that produce all the peculiarities beyond ideal-gas behavior are from the potential energy, that, in turn, depends only on the configuration coordinates [27–30]. out of equilibrium, however, this separation is not so obvious. classical mechanics is still valid, so particles’ motion can be described by newton’s equations of motion (md simulations can be used). in the conhungarian journal of industry and chemistry simulating ion transport with np+lemc 75 tinuum solvent framework, langevin’s equation is used in bd simulations. the meaning of various thermodynamic quantities, however, loses the solid ground that it has in equilibrium. there is no well-established non-equilibrium statistical mechanics finding its way into textbooks despite the fact that many authors made considerable advances in this field [31–36]. the most problematic quantities are those containing entropic effects, such as the chemical potential, µi. in the case of charged particles, we use the term electrochemical potential, but we talk about the same thing. this is a crucial quantity, because its homogeneity defines thermodynamic equilibrium (let us assume that the other two intensive parameters, temperature and pressure, are constant). if µi is not constant, species i will diffuse until it becomes constant according to the second law of thermodynamics. the gradient of µi(r), therefore, is the driving force of particle diffusion. the empirical transport equation that is most widely used to describe transport of charged particles (electrodiffusion) is the np equation, ji(r) = − 1 kt di(r)ci(r)∇µi(r), (2) where di(r) is the diffusion coefficient profile of ionic species i, ci(r) is the concentration profile, µi(r) is the electrochemical potential profile, ji(r) is the particle flux density, k is boltzmann’s constant and t = 298.15k is the temperature. the resulting ji(r) must satisfy the continuity equation: ∇ · ji(r) = 0. (3) the np equation separates the configuration and kinetic parts of the phase space in a way that it provides flux as a function of three profiles that, in turn, depend only on configuration coordinates. thus, we reduced our statistical mechanical task to averaging over states in the configuration space just as we did in the case of equilibrium statistical mechanics. if we treat di(r) as a parameter, the task is reduced to finding the proper relation between ci(r) and µi(r). defining local concentration in a nonequilibrium situation is the same as in equilibrium: we compute the average number of particles in a small volume element and divide it with the volume of that element (though we will also compute concentration in a different way on the basis of the potential distribution theorem [37], see later). eletrochemical potential, on the other hand, is more problematic. the trick in this case is that we assume local equilibrium (le). if we divide the simulation cell into subvolumes bα, we can characterize this subvolume with the electrochemical potential, µα i , and assume that this value is constant in bα. we designate the µα i and cαi values to the mass centers of the bα volume elements. the assumption of le is also present in other methods (though not necessarily stated explicitly), where the ci(r) vs. µi(r) relationship is considered, such as in the pnp theory or in the np+dft method of gillespie et al. [19, 20]. the main proposal of our technique was to use an mc method for this purpose. we assumed that the subvolumes are open systems and they are in le with a constant volume (v α), temperature (t ), and electrochemical potential (µα i ). thus, we suggested to use grand canonical monte carlo (gcmc) simulations, where particle insertion/deletions are attempted in the simulation cell. the acceptance probability depends on which subvolume we try to insert to (or where is the particle that we try to delete): min(1; pαi,χ(r)), where pαi,χ(r) = nα i !(v α)χ (nα i + χ)! exp ( − ∆u(r)− χµα i kt ) . (4) here, nα i is the number of ions of type i in subvolume bα before insertion/deletion, ∆u(r) is the change of the system’s potential energy during particle insertion to position r (or deletion from there), χ = 1 for insertion, and χ = −1 for deletion. the difference between this method and equilibrium gcmc is that µi is space-dependent and the acceptance criterion is referred to a given subvolume instead of the whole simulation cell. the effect of the surrounding of subvolume bα, however, is taken into account in the simulation through the energy change that includes all the interactions from other subvolumes, not only interactions between ions in bα. although it is tempting to view the subvolume bα as a distinct thermodynamic system with its own ensemble of states and to include the effect of other subvolumes as an external constraint, this is not the case. the ensemble of states belongs to the whole system, because ion configurations in subvolume bα should be collected for every possible ion configurations of all the other subvolumes. therefore, the independent variables of this ensemble are t and {v α, µα i }, where α and i run over the volume elements and particle species, respectively. for comparison, the variables in global equilibrium are t , v , and µi, where v is the total volume and µi does not depend on space. we solve the np+lemc system in an iterative way. the electrochemical potential is adjusted until conservation of mass (∇ · ji(r) = 0) is satisfied. the procedure can be summarized as µα i [n] lemc −−−−→ cαi [n] np −−→ jαi [n] ∇·j=0 −−−−→ µα i [n+ 1]. (5) the electrochemical potentials for the next iteration, µα i [n+ 1], are computed from the results of the previous iteration, cαi [n], on the basis of the divergence-theorem (also known as gauss-ostrogradsky’s theorem). the continuity equation is converted to a surface integral: 0 = ∫ bα ∇ · ji(r) dv = ∮ sα ji(r) · n(r) da, (6) where volume bα is bounded by surface sα and n(r) denotes the normal vector pointing outward at position 45(1) pp. 73-84 (2017) 76 fertig, mádai, valiskó, and boda r of the surface. every sα surface is divided into sαβ elements. along these elements, bα and bβ are adjacent cells. it is assumed that the concentration, the gradient of the electrochemical potential, the flux density and the diffusion coefficient are constant on a surface sαβ . they are denoted by hat: ĉαβi , ∇µ̂αβ i , ĵαβi , and d̂αβ i . the ĉαβi values are obtained from the values cαi and cβi via linear interpolation. the ∇µ̂αβ i values are also obtained from µα i and µβ i assuming linearity. thus the integral in eq.(6) for a given surface sα is replaced by a sum over the surface elements that constitute sα: 0 = ∑ β,sαβ∈sα ĵ αβ i · nαβaαβ , (7) where aαβ is the area of surface element sαβ and nαβ is the outward normal vector in the center of sαβ . the iteration procedure is described by the following steps: 1. an appropriately chosen initial set of electrochemical potentials is chosen (µα i [1]; in general: µα i [n], where [n] denotes the nth iteration). 2. using these µα i [n] parameters as inputs, lemc simulations are performed. the resulting concentrations are denoted by cαi [n]. 3. the flux computed from the {µα i [n], c α i [n]} pair usually does not satisfy eq.(7). the next set of electrochemical potential is calculated by assuming that the {µα i [n + 1], cαi [n]} pair does satisfy eq.(7). if we write the value of ĵαβi as given by the np equation into eq.(7), we obtain 0 = ∑ β d̂αβ i ĉαβi [n]∇µ̂αβ i [n+ 1] · nαβ aαβ , (8) where β runs over all the surface elements sαβ that constitute sα. eq.(8) is a system of linear equations; the unknown variables are denoted by µα,cal i [n + 1], where cal refers to the fact that these values come from calculations by solving eq.(8). 4. to achive faster and more robust convergence in the case of large driving forces, the electrochemical potential used in the (n+ 1)th iteration is mixed from the values calculated in the (n+ 1)th iteration from eq.(8) and the values mixed in the nth iteration: µα,mix i [n+ 1] = biµ α,cal i [n+ 1] + (1− bi)µ α,mix i [n], (9) where bi is a mixing parameter that determines the ratio of mixing. if the parameter is close to 1, faster iteration can be achieved, however, it may result in the system fluctuating between local minima. smaller bi values prevent this fluctuation at the price of making the convergence slower. 5. the input of the (n + 1)th lemc simulation is µα,mix i [n+ 1]. the system of linear equations contains the boundary conditions for the electrochemical potential and concentration via the boundary elements that are at the system’s boundaries (blue line in fig.1). if the sαβ face is on the system’s boundary, the values of ĉαβi and µ̂αβ i are those prescribed on that face. the electrochemical potentials on the left (l) and right (r) boundaries are computed from µl i = kt ln cli + µex,l i + qiφ l (10) and µr i = kt ln cri + µex,r i + qiφ r, (11) where µex,l i and µex,r i are the excess chemical potentials in the absence of an external field (determined by the adaptive gcmc method of malasics et al. [38]), while qiφ l and qiφ r are the interactions with the applied electrical potentials. prescribing φl and φr on the system’s boundary means that we use an electrostatic dirichlet boundary condition. voltage is defined as u = φl−φr. ultimately, we have boundary conditions for ion concentrations on the two sides of the membrane and for the voltage (ground is on the right in this study). the energy change ∆u contains not only the interactions between particles (and interactions of particles with the pore), but also the interaction with an external electrical potential, φappl(r). this applied potential is calculated by solving laplace’s equation ∇2φappl(r) = 0 (12) for the system (inside the blue line) with the prescribed dirichlet boundary condition on the system’s boundaries (φl and φr on the left and right blue line, respectively). in the portion of the blue line inside the membrane, we interpolate between φl and φr. we solve this equation with the induced charge computation method [39, 40]. in the present geometry, the elementary cells are ∆z× ∆r rectangles in the (z, r) plane. in three-dimensional space, these correspond to concentric rings with the zaxis in their centers. the concentration in an elementary cell bα can be computed from dividing the average number of ions in the cell with the volume of the cell. this route is disadvantageous if ion concentrations are small. an alternative method is based on the potential distribution theorem [37] that practically corresponds to the widom particle insertion method [41, 42]. the total excess chemical potential (containing also the interaction with the applied field) is µα i − kt ln cαi and can be computed as exp [− (µα i /kt − ln cαi )] = 〈exp [−∆uα i /kt ]〉 , (13) where ∆uα i is the energy change associated with the insertion of a test particle of species i into a randomly chosen position in the elementary cell α. this is the same energy computed in the particle insertion step of the lemc technique, therefore, it does not require additional computational cost. the concentration can be calculated from hungarian journal of industry and chemistry simulating ion transport with np+lemc 77 eq.(13) because µα i is known (that is the input of the simulation) and the ensemble average on the right hand side can be obtained from the lemc insertions. this route provides a more accurate value for cαi , because this sampling is not discrete as just counting particles, but rather continuous, because we always gain information from the simulation at every ion insertion via the energy ∆uα i . the route of counting particles, however, might be better, when concentrations are very large in the volume element. in the case of long enough simulations, the two methods give identical results (within a statistical error). because of this statistical error, the iteration does not converge to an exact value of the ionic flux density, but it fluctuates around a limiting value. the final solution is obtained from a running average over iterations. longer lemc simulations and more iterations result in a more reliable outcome. the net flux of the diffusing ions through the cross section of the pore is calculated via averaging: ji(z) = 2π ∫ r(z) 0 rji(z, r) · nz dr (14) where r(z) denotes the radius of the pore at coordinate z (|z| < hmemb/2, where hmemb is the thickness of the membrane) and nz is the unit vector along the z-axis. the electrical current of an ion is then ii = qiji, (15) and the total current is i = ∑ i qiji. (16) 3. results and discussion 3.1 calcium release channel there are two important classes of calcium channels that have been our focus. the l-type calcium channel is found in excitable cell membranes [43] such as those of nerve cells and muscle cells (both cardiac and skeletal). these are strongly ca2+ selective channels, meaning that the presence of only a µm ca2+ in the bulk decreases the na+ current to half of its value compared to its value in the absence of ca2+. this is called micromolar ca2+ affinity (or ca2+ block) because a very small amount of ca2+ is enough to block the channel [44]. the price of high ca2+ selectivity is low ca2+ current through this channel. the ca2+ ions flow into the muscle cell when the l-type calcium channels open in response to an electrical signal (action potential) in a small quantity that is not sufficient to initiate muscle contraction. the solution of nature for this problem is an amplification mechanism. a large amount of ca2+ ions are stored in organelles, the sarcoplasmic reticulum (sr), that are situated inside the muscle cells. there are calcium release channels (also known as ryr calcium channels) embedded in the membrane of the sr that are opened by the ca2+ ions provided by the l-type channel (in cardiac muscle) or via a direct link between the two types of calcium channels (in skeletal muscle). the ryr channels provide the large ca2+ flux that is necessary for muscle contraction by binding to tropomyosins on the actin filaments and allowing myosin to climb up the filament. these channels are wider (also, less ca2+ selective) than the l-type channels. a large amount of experimental data is available for this channel [45–47]. on the basis of this database, gillespie et al. developed a model for the ryr channel [21,22]. although the model was a onedimensional reduction, studied with a one-dimensional np+dft, they were able to reproduce hundreds of experimental current-voltage curves. later, when the np+lemc method became available, we developed [4] a three-dimensional version of the model of gillespie et al. the model is similar to that used by boda et al. [3, 4, 40, 48–54] for the l-type calcium channel inspired by the “space-charge competition mechanism” proposed by nonner et al. [55]. from the point of view of ion selectivity and permeation, the important part of the channel is the selectivity filter, the bottleneck of the pore. this region is lined by four p-loops that are parts of the four membrane-spanning subunits. these loops contribute four glutamic acids (in the l-type calcium channel) to the filter-lining region (the eeee locus). the coo− groups of the carboxyl side chains are thought to reach into the pore lumen and interact with the passing ions [44]. in the case of the ryr channel, they are four aspartates (d4899, see fig.2). gillespie et al. [21–23, 46, 47] identified additional e and d amino acids in the two vestibules on the cytosolic and luminal sides (fig.2). it has been shown [3, 4, 40, 48–55] that the strong ca2+ selectivity can be reproduced by a reduced model where eight half-charged oxygen atoms (o1/2−) of the four coo− groups force a strict competition between ca2+ and na+ ions for space in the crowded filter. the exact positions of the o1/2− ions are not known and even irrelevant from the point of view of the selectivity of the model. what matters is that they attract the cations into the filter with their charge, and, at the same time, they exert a hard sphere exclusion and make it difficult for the cations to find space in the filter. therefore, it proved to be sufficient to model the structural groups of the filter as mobile o1/2− ions that are confined to the filter region. the profiles shown in fig.2 are results of the simulations and show how the eight o1/2− ions distribute in a given segment of the channel. there are 32 such o1/2− ions, plus point charges placed on a ring on the luminal side. the geometrical features (filter radius is 5.5 å, filter length is 15 å, and radii of left and right vestibules are 22 and 9 å, respectively) are also designed on the basis of gillespie’s model that, in turn, are based on fitting to experimental data. this model was designed and used unchanged in ev45(1) pp. 73-84 (2017) 78 fertig, mádai, valiskó, and boda figure 2: the three-dimensional model [4] of the ryr calcium channel based on the model of gillespie et al. [21,22]. each curve shows the distribution of eight o1/2− ions that are confined to the given region but otherwise free to move there. the charges of the e4902 amino acids are represented as point charges (−1/2e) at fixed positions on a ring. the thickness of the membrane is hmemb = 46 å. the dielectric constant is ε = 78.5. ery calculation. what remains to be specified are the diffusion coefficient profiles of the various ionic species. these profiles depend only on z, di(z); we assume no variation in the radial dimension. the values outside the channel and in the selectivity filter, db i and df i , respectively, are constant. in the vestibules at the two entrances of the channel, the diffusion constant profiles are interpolated between the db i and df i values in a way that their value changes in proportion with the cross section of the channel. the bulk vales, db i , are taken from experiments; they are 1.334 ·10−9, 7.92 ·10−10, and 2.032 ·10−9 m2s−1 for na+, ca2+, and cl−, respectively. the values inside the cylindrical selectivity filter are fitted to two experimental data points: 250 mm symmetric nacl at 100 mv for na+, while added 10 mm luminal cacl2 at -100 mv for ca2+. the resulting values (1.27·10−10 and 1.27·10−11 for na+ and ca2+, respectively) are fixed and never changed. the cl− value is irrelevant, because cl− ions do not carry significant current. these values have been obtained for a moderate system size (h = 54 å, r = 48 å). currents, and, therefore, diffusion coefficients fitted to currents can depend on system size (see later). here, we show results for a nacl-cacl2 mixture, where there is 250 mm na+ on both sides of the membrane, while there is 4 µm ca2+ on the cytosolic (left) and 50 mm ca2+ on the luminal (right) side. the voltage is changed from -150 mv to 150 mv with the ground on the right. the current vs. voltage curves are shown figure 3: currents vs. voltage curves as obtained from experiment [21], the model of gillespie et al. [21, 22] obtained from dft coupled to the np equation, and from the np+lemc method. in the case of the np+lemc method, the currents carried by na+ and ca2+ are also shown. in fig.3. total currents are shown in black as obtained from experiments (× symbols), gillespie’s np+dft calculations (dashed line), and our np+lemc calculations (solid line with filled triangles). agreement with experiment is very good using both models. the slope of the i − u curve is larger for positive voltages than for negative voltages. more details and understanding can be gained from the current curves for the separate ions, na+ and ca2+ (blue and red curves, respectively). at positive voltages, the ca2+ current is practically zero, so the total current is carried by na+ ions. at negative voltages, on the other hand, both na+ and ca2+ ions contribute to the current. the explanation of this behavior can be drawn from concentration and electrochemical potential profiles shown in fig.4. let us discuss the na+-profiles first (blue curves). the driving force for the na+ ions is the voltage because na+ concentration is the same on the two sides. the difference between na+ currents at -100 and 100 mv voltages, therefore, is the result of the different competition between na+ and ca2+ ions at the two voltages. to understand the difference in this competition, we need to understand the behavior of ca2+ ions. at 100 mv, the driving force for ca2+ ions is small because the concentration difference balances the electrical potential difference (see the ca2+ electrochemical potential profile in the right panel of fig.4b). this results in a small ca2+ current. ca2+ concentration is small in the left bulk, therefore, a ca2+ depletion zone is formed in the left vestibule and in the selectivity filter of the channel (beware the logarithmic scale of the concentration axis). that depletion zone results in a decreased concentration of ca2+ ions compared to na+ ions inside the channel. in the case of -100 mv, on the other hand, the ca2+ depletion zone in the left vestibule is absent because ca2+ ions arrive from the right and “fill up” the left hungarian journal of industry and chemistry simulating ion transport with np+lemc 79 (a) (b) figure 4: (a) concentration and (b) electrochemical potential profiles of na+ and ca2+ for two opposing voltages: -100 mv (left panels) and 100 mv (right panels). the striped parts indicate the cytosolic and luminal vestibules, while the gray area is the selectivity filter. vestibule. there is a more balanced competition between ca2+ and na+ ions in the channel and ca2+ ions can use the free-energetic advantage that they have over na+ [22, 53]. this means that ca+ ions are favored by the crowded selectivity filter, because they provide twice the charge (compared to na+ ions) to balance the charge of o1/2− ions while occupying about the same space (their diameters are similar: 1.98 and 1.9 å for ca2+ and na+, respectively). the finite size of the ions plays a crucial role in the selectivity mechanism. this kind of selectivity could not be produced with the pnp theory. because ca2+ concentration is large in the left vestibule of the channel, it drops quickly to the 4 µm value at the left boundary of the solution domain. this introduces a severe system-size dependence into the calculations in this case that is analyzed in fig.5. small ca2+ concentration on the left hand side corresponds to a large debye-length in the double layer at left hand side of the membrane (in the left access region). that double layer should fit into the simulation cell (as it does in the case of a larger cell, see black curves in fig.5). if the cell is too small (see red curves in fig.5), there is not enough space for the ca2+ concentration to reach the 4 µm limiting value at the left boundary of the cell. the electrochemical potential cannot reach its limiting value either (see the bottom panel). the np+lemc calculation, however, provides a solution in this case too, because the layer near the left outer boundary of the cell takes care of the missing access region in an averaged manner. the concentration has a small value in the layer, figure 5: concentration (top panel) and electrochemical potential (bottom panel) profiles of ca2+ for -100 mv. the results of simulations for two system sizes are shown: h = 54 å (red) and h = 180 å (black). while the electrochemical potential profile drops abruptly (large driving force). an appropriate value of the ci∇µi product, therefore, is provided by the self-consistent solution so that the continuity equation is satisfied. this solution, however, is approximate. a large portion of the access region with considerable resistance is taken into account in an averaged way by the layer near the system edge. this introduces an error into the value of the ca2+ current that is indicated in fig.5 for both cases. the good behavior of the current-voltage curves compared to experiments and dft calculations is due to the fit of the ca2+ diffusion coefficient, df ca2+ , inside the filter. that value was fitted for negative voltage at the given system size balancing the system-size error. this result points out the importance of system size in the case of small ionic concentrations, but it also shows the role of the diffusion coefficient profile in np+lemc calculations. in confined geometries, the di(r) profile, although it has a strong relation to the mobility of ions, is primarily an adjustable parameter that is fitted to experiments (as in the present case) or to md results [6]. the value of df i takes into account interactions that are absent in the reduced model or accounts for resistances of regions that are absent in the model. in the case of the ryr channel, for example, the diffusion coefficient profile includes effects of the parts of the ion channel not included in the model: the real ryr channel is much larger than the 46 å portion modeled here. that region also tunes the total current, but it is not selective. the selectivity filter and its close neigh45(1) pp. 73-84 (2017) 80 fertig, mádai, valiskó, and boda figure 6: bipolar nanopore geometries: cyl: cylindrical; sc: single conical; dc: double conical. the pore is positively charged on the left hand side (−30 < z < 0 å), while negatively charged on the right hand side (0 < z < 30 å) keeping the surface charge fixed (σ = ±0.1 c/m2). minimal and maximal pore radii are 10 and 20 å, respectively. borhood modeled here determines ion selectivity and is able to reproduce complex behavior such as anomalous mole fraction experiments discussed previously by gillespie [21–23] and boda [4]. 3.2 rectifying bipolar nanopores ion channels are natural nanopores with stable welldefined structures that are very narrow at their selectivity filters (often below 1 nm in radius) to make them suitably selective. the disadvantages, however, are considerable. the structures are often unknown. they are difficult to handle experimentally. their manipulation is cumbersome with point mutations. synthetic nanopores, therefore, quickly gained attention due to the fact that they have special properties compared to those of micropores. these special properties arise because the screening length of the electrolyte is comparable to the radius of the nanopore. this fact gives nanopores properties that resemble those of ion channels. one advantage of synthetic nanopores is that are relatively easy to fabricate [56–63]. they are either solid state nanopores using ion-beam or electron-beam sculpting in, for example, silicon compound membranes, or they are track etched into polymer membranes. two basic properties of such nanopores are their geometry (shape) and the pattern of surface charge on the pore wall. figure 7: current-voltage relations for the three nanopore geometries (cyl, sc, and dc from bottom to top). currents carried by na+ (solid blue), cl− (dashed red), and their sum (dot-dashed black) are shown as a function of voltage. the insets magnify the results for negative voltages. in our previous works, we studied the bipolar nanopore, where the surface charge is positive on the left hand side of the pore, while it is negative on the right hand side [6, 7]. these nanopores rectify ionic current, meaning that they let a much larger amount of ions through at a given sign of voltage than at the opposite sign. in those papers, we used a cylindrical geometry for the nanopore and focused on the effect of the charge pattern, pore radius, and concentration. here, we discuss the effect of pore geometry on the rectification properties of a bipolar nanopore. we performed np+lemc calculations for three different geometries, the cylindrical (cyl), single conical (sc), and double conical (dc) shown in fig.6. simulations for different voltages have been performed from -150 mv to 150 mv. the concentration of the electrolyte was 0.1 m on both sides. the electrolyte is a 1:1 system (let us call it nacl), but the diameters of the cations and anions are the same in order to avoid effects from ion size asymmetry. for the same reason, the same diffusion coefficients were used for the two ions. this makes it possible to focus on the balance of charge and geometrical asymmetries. if the nanopore’s shape is symmetric, for example, the cations and anions carry the same amount of current (cyl and dc). figure 7 shows the current-voltage relations. rectification is observed in all three geometries: current is much larger at positive than at negative voltages. the rectifihungarian journal of industry and chemistry simulating ion transport with np+lemc 81 figure 8: rectification (defined as the absolute value of the current ratio in the on and off states) as a function of the absolute value of the voltage for the three nanopore geometries. cation is defined as the ratio of currents at positive (on state) and negative voltages (off state). the results are shown in fig.8. the basic explanation of rectification can be depicted from the concentration profiles (fig.9). there are depletion zones for cations in the positively charged half region (left), while there are depletion zones for anions in the negatively charged half region (right). in the off state (negative voltage) these depletion zones are deeper than in the on state (positive voltage). more detailed explanation have been given in our previous works [6,7]. here we focus our discussion to the effect of pore shape. total currents are larger in the sc and dc geometries due to their wider entrances. interestingly, total currents are the same in the sc and dc geometries despite the quite different pore shapes. whether this is a coincidence or it has a deeper explanation requires further investigation. what is different in the sc and dc geometries is the partitioning of the total current between na+ and cl−. while na+ and cl− currents are the same in the dc geometry due to the symmetric shape, they are different in the sc geometry. the current carried by na+ ions is smaller than the current carried by cl− ions (middle panel of fig.7). this is reflected in concentration profiles (see middle panel of fig.9). the explanation is that the tip of the sc nanopore (left entrance) is positively charged so the depletion zones of na+ ions there is deeper than the depletion zone of cl− ions on the other side where the pore is wider. deeper depletion zones result in smaller currents. therefore, na+ current is smaller in the whole voltage range, but more so in the off state at negative voltages. rectification is largest in the cyl geometry because the depletion zones are the deepest in that geometry for both ions. the deepest points of the depletion zones are formed around |z| = 10 å. there are different effects that form the concentration profiles inside the pore. in the left region, for example, (1) the positive surface charge on the pore wall repels na+ ions, (2) the negative surface charge figure 9: concentration profiles of na+ (blue) and cl− (red) in the on (solid lines) and off (dashed lines) states for the three nanopore geometries (cyl, sc, and dc from bottom to top). on the right hand side attracts them, (3) the 0.1 m bulk region acts as a source for the ions, (4) applied potential in the off state drives na+ ion to the right, where they have a peak, and (5) cl− ions (that have a peak on the left) attract them. the balance of all these effects forms the deep depletion zone of na+ at z ≈ −10 å in the off state. because the cyl geometry has the smallest radius at the |z| ≈ 10 å positions, this geometry provides the deepest depletion zone as a result of the dominant effect from the above list, the effect of repelling surface charge. 4. summary we presented the np+lemc method that is a hybrid technique, harvesting the advantageous properties of both the np transport equation (fast calculation of flux) and lemc particle simulation method (correct calculation of ionic correlations). we applied the method to compute ionic currents through reduced models of an ionic channel and a bipolar nanopore. reduced models have the advantage of fast calculation (lemc would not be feasible for an explicit-water model) and intellectual focus. with these models, we can concentrate on those properties of the system that are important to reproduce its behavior as a device. for the ryr calcium channel, for example, the reduced model is able to reproduce complex selectivity behavior in agreement with experiments by modeling only the “important” amino acids in a reduced way 45(1) pp. 73-84 (2017) 82 fertig, mádai, valiskó, and boda [21,22]. for the bipolar nanopore, the reduced model using implicit water is able to reproduce md results for an explicit-water model [6]. with further methodological and model development, we intend to simulate nanodevices as close to their real size as possible. acknowledgement the financial support of the national research, development and innovation office (nkfih k124353) is gratefully acknowledged. the present article was published in the frame of the project no. ginop-2.3.2-15-201600053 and supported by the unkp-17-4 (to m.v.) and unkp-17-1 (to e.m.), the new national excellence program of the ministry of human capacities. we thank dirk gillespie for helpful discussions. references [1] boda, d., gillespie, d.: steady state electrodiffusion from the nernst-planck equation coupled to local equilibrium monte carlo simulations, j. chem. theor. comput., 2012 8(3), 824–829, doi: 10.1021/ct2007988 [2] ható, z., boda, d., kristóf, t.: simulation of steady-state diffusion: driving force ensured by dual control volumes or local equilibrium monte carlo, j. chem. phys., 2012 137(5), 054109, doi: 10.1063/1.4739255 [3] boda, d., kovács, r., gillespie, d., kristóf, t.: selective transport through a model calcium channel studied by local equilibrium monte carlo simulations coupled to the nernst-planck equation, j. mol. liq., 2014 189, 100, doi: 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fundamental studies and practical applications of bioinspired smart solid-state nanopores and nanochannels, nano today, 2016 8(3), 1470–1478, doi: 10.1016/j.nantod.2015.11.001 hungarian journal of industry and chemistry hungarian journal of industry and chemistry vol. 49(2) pp. 35–38 (2021) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2021-19 investigation of the resistance a sailboat is subjected to in the case of draft changes caused by modifying the powertrain emese lévai*1 and péter ficzere1 1department of railway vehicles and vehicle system analysis, budapest university of technology and economics, műegyetem rkp. 3, budapest, 1111, hungary in our research, calculations were performed using the example of a specific ship when a modification was made to the powertrain of a vehicle. these results were used to observe whether the ship is expected to decelerate or the change in the draft is likely to cause stability problems. in recent years, the rules concerning the use of inland waterways by recreational crafts have been tightened for environmental reasons. in many cases, these restrictions affect the drive chain, making the workflow of the conversion involved frequent. in this case, it is extremely important for shipowners to know how the draft will change and at what speed the ship will operate after the conversion. this study on a numerical flow simulation provides an excellent opportunity to find out. keywords: sailing, computational fluid dynamics, simulation, modifying the powertrain 1. introduction with the boom in lake navigation, the technical equipment of small watercraft has also expanded to include important details. since the number of sailing vessels, which were originally only wind-powered, has increased in ports, in order to prevent subsequent disruptions and facilitate emergency maneuvering, these vessels carry an engine as a secondary source of propulsion. in addition, small boats that are purely motor-powered have also entered the market for private individuals. generally speaking, this size of engine has had a detrimental effect on life in shallow lakes, such as lake balaton, in several ways and emissions have noticeably increased. as a result, a regulation [1] came into force whereby recreational (i.e., not emergency, port maneuvering, etc.) trips can only be powered by electric motors on lake balaton. for this reason, shipowners have had to convert their propulsion systems from internal combustion engines to electric versions. although the effect of this on the draft and speed varies from boat to boat, this data is important for shipowners. our article presents a method for calculating such data for a specific ship. *correspondence: levai.emese@edu.bme.hu 2. methods 2.1 weight and dive calculation the examined vessel is a 50 m2 cruising, capitalweighted sailboat designed for tours that is 13.2 m long and weighs 6.8 t (figs. 1 and 2). the differences between the results of the weight calculations on the blueprints and the actual ship, as well as the knowledge of the mass of the elements of the electric and diesel powertrain, were sufficient to determine the change in the draft [2]. the draft varies from 1.68 m to 1.7 m (fig. 3). the calculation was performed using the maxsurf hydromax program. 2.2 fluid dynamics simulation the purpose of the calculation in this case is twofold: to determine the drag (resistance) force acting on the hull while in motion (‘x’ component) and the buoyancy (‘z’ component). the practical goal of the tests is to calculate the resistance force acting on the boat during two different dives using the same engine power, as this has a major impact on the speed of travel (because if the boat moves in the ‘x’ direction, the resistance force will always be in the ‘x’ direction). the tests were performed using the floefd extension of the siemens solid edge program. the initial values were the dive (1.68 m and 1.7 m according to the weight calculation) (fig. 3), flow characteristics test, free surface, and the boundary between https://doi.org/10.33927/hjic-2021-19 mailto:levai.emese@edu.bme.hu 36 lévai and ficzere figure 1: a piece of the original item and weight chart (1950) different media, as well as their required properties (e.g., density, method, etc.). as an external force, the magnitude and direction of gravity had to be taken into account. the flow rate of the tested medium was also adjusted to the medium in the appropriate direction, that is, opposite to the direction of travel. the mesh was compressed locally by 3-stage compression around the surfaces delimiting the body (figs. 4 and 5). this is partly due to the fact that unnecessarily accurate calculations of values at points unrelated to the hull would lengthen the duration of the test and partly the result of the calculation being as accurate as possible at critical locations (where plating and water intersect). the load cases were chosen according to the dives and the selected speed points at a froude number of up to 0.45 can be assigned to the characteristic operating conditions of the ship (while displacing water) [3]. the values at the selected speed points were recorded within this range. 3. results after running the analysis, the series of measurements was tested separately for each load case at each of the six speed points. convergence was observed under all circumstances. the results, which are shown in figs. 6 and 7, were plotted on graphs and presented in tables. it can be seen that in both the ‘x’ and ‘z’ direction, the higher the speed at which the vessel travels, the greater both the force acting on the hull and the greater the vertical distances measured between the points of the curve on the graphs are. as can be seen in fig. 4, the resistance (vertical axis) resulting from lighter load cases (denoted by the orange line) was less than for heavier load cases when the electric drive chain was in use (denoted by the gray line). the expected results were also recorded in the evaluation of the buoyancy forces. regarding the load case belonging to the original drive chain (denoted by the gray line), the buoyancy forces are lower than in terms of the load figure 2: a portion of the new batch and weight chart (2020, field survey) case belonging to the new drive chain (denoted by the blue line). the parabolic nature of the curves was also in line with the preliminary expectations as the resistance and velocity are square proportional. on the curve depicting the resistance, the wavy nature (at a froude number of approximately 0.5) is due to the effect of the wave resistance on the total resistance. this also means that even as a result of small changes in dive, the increase in resistance becomes more significant as the vessel accelerates. therefore, even on a larger ship, it might be beneficial to select lighter components for the powertrain. not only does dive cropping change the size of the wetted surface and thus the resistance force, the shape of the wetted surface and the waterline section is also modified. in the present case, it geometrically cuts a wider shape out of the water surface as a result of the hull, so figure 3: characteristic curves calculated from vessel data hungarian journal of industry and chemistry investigation of the resistance a sailboat 37 figure 4: locally compressed mesh around the stern of the hull figure 5: locally compressed mesh around the stern of the hull (side view) the current image must also be examined (fig. 7). if the immersion shape changes leading to the flow rate generating early-breaking vortices around the hull or accelerating too quickly around the maximum width, a drastic reduction in speed results. 4. analysis by examining the results, several findings are made. at higher speeds, as was expected, the resistance force on the ship differs greatly between the two dives, increasing the draft from 1.68 m to 1.7 m by 4606 n. therefore, the effect of changing the draft in the order of a few centimeters is also significant. by plotting the velocity distribution around the vessel from the current image, it was found that behind the point where the width of the vessel is greatest (towards the stern) next to the side plate, the flow rate accelerates locally and then decelerates again back to the velocity observed around the front of the vessel. around the ship, in addition to the surface that is in the shadow of the overflow (i.e., the accelerated flowlines next to the ship do not–or only partially–affect), the velocity of the medium decreases significantly. the velocity of the medium at and around the intersection of the waterline area and the axis of the steering bearing is close to 0 m/s. it can be seen that neither the magnitude (13.7 m/s) nor the location of the maximum flow velocity (the narrowing arc behind the main rib) causes a large decrease in velocity (fig. 8). 5. conclusion it can be said that by replacing the internal combustion engine and its associated drive chain, this ship will be subjected to an excessive resistance force which will reduce its forward speed. the test vessel is mass-produced figure 6: comparison of the magnitude of the resistance a ship is subjected to under two load cases figure 7: comparison of the magnitude of the buoyancy acting on a ship under two load cases figure 8: flow velocity around the ship (higher: red, lower: orange) and, in the case of vessels operating with possible minor modifications to its class, the calculation is expected to yield the same result with similar engines. for other types of vessels, by following the testing methodology, accurate answers to the questions raised in section 2.2 are provided, which are vital, for example, before a sailing race (in which case, the engine is merely excess ballast). since the calculations were performed on a horizontally floating sailboat, the subject of a further study could be the examination of a tilted vessel or of a hull protruding whilst accelerating using the same methodology. questions may also be raised about an excessive number of additional batteries that may be inserted to increase the range of the electric motor and their possible placement in the light of swimmers as this presupposes additional dive options. references [1] xlii/2000,water transport act [2] lévai, e.: elektromos segédhajtás beépítése egy acél építési anyagú, 50 m2-es tengeri cirkáló típusú, 49(2) pp. 35–38 (2021) 38 lévai and ficzere kedvtelési célú vitorlás kishajóba, 2021, 2–21, 30– 35 [3] simongáti, gy.; hargitai, l.: kishajók. budapest, 2012, 14–15 isbn: 978-963-279-643-7 hungarian journal of industry and chemistry introduction methods weight and dive calculation fluid dynamics simulation results analysis conclusion hungarian journal of industry and chemistry vol. 50(2) pp. 35–41 (2022) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2022-16 behavior of control and inhibitive polyaspartic coatings using alkylammonium and zinc phosphate corrosion inhibitors in soil abdu elhoud1* and tim van everbroeck1 1 chemsystems, ambachtsstraat 15, malle, 2390, belgium this study is part of an anti-corrosion coating development project at chemsystems. the corrosion performance was assessed through erosion, immersion and soil corrosion experiments. the erosion results have previously been published. this article discusses the impact of soil on control polyaspartic coatings used to protect concrete and the modified polyaspartic coating intended to protect underground steel substrates. the modified polyaspartic coating was boosted with a micaceous iron oxide barrier, a liquid alkylammonium corrosion inhibitor, a powdered zinc phosphate corrosion inhibitor and a novel hardener. the surface finish of the steel samples was of a milled and blasted nature (sa 2.5). the coating was applied directly to the metal without the application of a primer or second layer of coating. the average thickness of the coating was 220±10 µm as a direct-to-metal protection system. the experiments were conducted in soil at room temperature (rt) and 35°c over 30 days. the experimental results of the control polyaspartic coating loaded on steel substrates exhibited severe blistering. the polyaspartic coating dispersed with a liquid alkylammonium inhibitor also exhibited blistering, whereas the modified polyaspartic coating with a zinc phosphate corrosion inhibitor showed an adequate degree of resistance to the impact of soil under the evaluated conditions. the results confirmed that the presence of a zinc phosphate corrosion inhibitor in combination with a micaceous iron oxide barrier improved the resistance of the coating to the evaluated soils in which it was positioned and at the investigated temperatures. keywords: soil, polyaspartic coating, corrosion inhibitor, iron oxide barrier 1. introduction carbon steels with desirable mechanical properties are widely used in infrastructure, including in underground assets such as pillars, foundations, storage tanks and pipelines. in the field, these structures are more likely to degrade and rust due to direct contact with the soil, especially if no protection system is provided to hinder the effect of the corrosive elements. corrosion due to soil is influenced by the temperature, moisture content, oxygen content, environmental ph, microbial activity and soluble salts. soil moisture contains a wide range of chemicals which have penetrated through the soil surface. some examples of these chemicals are salts, e.g. chlorides, nitrates, nitrites, sulfates, etc., and heavy metals, e.g. cadmium, chromium, copper, iron, manganese, nickel, lead, zinc, etc. along with the influence of microbial activity and environmental factors such as temperature, ph, conductivity and dissolved oxygen concentration, salts and heavy metals make the study of soil moisture an interesting topic as they are related to the corrosion of underground metal structures [1]. jiao chen et al. 2015 [2] studied the soil corrosion of steel as a function of anions in the soil, namely total received: 7 oct 2022; revised: 19 oct 2022; accepted: 25 oct 2022 *correspondence: abdu.elhoud@chemsystems-technology.com soluble salts, cl−, so4 2− and hco3 −, and soil nutrition, that is, moisture content, organic matter, total nitrogen, alkaline hydrolysable nitrogen, available phosphorus and available potassium. many attempts have been made in this regard to reduce the risk of soil corrosion on submerged steel and concrete structures. organic, inorganic and metal coatings such as zn, al and ni are considered to be very effective means to protect submerged assets from premature corrosion and degradation [3]-[4]. corrosion inhibitors in powdered and liquid forms have been incorporated into coatings to enhance their antirust and adhesive characteristics when applied to substrates. zinc phosphate is commonly dispersed into coating formulae during manufacturing and effectively reduced the tendency of a coating to fail and substrates to rust. nevertheless, although further investigations are still favorable to evaluate the efficiency of corrosion inhibitors in coatings exposed to soil, in this study, an attempt was made to compare the efficiency of two types of corrosion inhibitors in combination with iron oxide coatings for the purpose of developing control and inhibited polyaspartic coatings in soils at room temperature (rt) and 35°c applied to milled-surfacefinished and sandblasted steels (sa 2.5). https://doi.org/10.33927/hjic-2022-16 mailto:abdu.elhoud@chemsystems-technology.com elhoud and van everbroeck hungarian journal of industry and chemistry 36 2. materials and experiments the study was carried out on polyaspartic coatings applied to structural steel plates. the tested plates composed of hot-rolled steel grade s235, which was chosen due to its wide range of applications in infrastructure projects in belgium and throughout europe, were manufactured by ask romein malle nv, a steel company based in malle, belgium. the control polyaspartic coating was designed to protect concrete structures, whereas the modified polyaspartic coating containing inhibitors and a barrier was planned to prevent steel from corroding. the surface finish of the steel panels, as received from the supplier, was milled and blasted (sa 2.5). before blasting, the mill scale was removed by immersing the steel plates in 10% h2so4 for 30 minutes at 60°c before being cleaned and dried by acetone to ensure a suitable steel surface before blasting. sand blasting was carried out using a blasting cabinet, while blast cleaning was performed using granular aluminum oxide abrasive media. the steel samples were 150 x 80 x 2 mm rectangular plates. an example of the surface morphology of both the milled and blasted steel surface finishes are displayed in figs.1a and 1b, respectively. polyaspartic coatings consist of two components. component (a), which also contains a corrosion inhibitor and an oxide barrier, is the active material, while component (b) is the hardener. the required amount of component (a) was added to component (b) and mixed for 120 seconds before being applied to the steel. one layer of each coating was applied to each steel sample using an erichsen 358 spiral film applicator and left for one day before being buried in the soil. the edges of the steel samples were well covered with tape to avoid premature failure of the coating or rusting of the steel plates. the edges of the steel plates were carefully smoothened and curved. during the coating, extra layers were applied to the edges, moreover, a strong tape was placed over them to prevent them from rusting and the coating from failing. an example of a coated steel panel is displayed in fig.2. the soil used in this study was loamy sandy soil according to the belgian soil analysis report [5] collected from arable, residential and light industrial flattened land located in malle in the vlaanderen region of belgium. the average climate of the soil in the region of vlaanderen is temperate maritime with an average 800 mm of precipitation falling annually. in many locations, the concentration of heavy metals in the soil and groundwater still exceeds environmental quality standards due to the use of ash material for road stabilization, which has also resulted in the spread of heavy metals. the actual carbon content of arable land parcels in flanders is considered to be fairly good. salinization is a minor concern in the region of the tested soil because it is regarded as being situated far from the coastline [5]. the soil was collected at a depth of 0.5 m and filtered using sieves of two different mesh sizes to remove dirt and purify the soil (fig.3). (a) (b) figure 1. photographs of a) milled steel finish, b) blasted steel finish figure 2: materials used in the soil experiment: an example of a coated steel panel figure 3: soil experiment materials: soil collection and coated steel samples buried in soil behavior of control and inhibitive polyaspartic coatings 50(2) pp. 35–41 (2022) 37 the рη of the soil was controlled before each experiment and measured to be between 6.5 and 7.0. the tested samples were placed in soil in a plastic container (fig.3) for 30 days at both room temperature and 35°c using an oven. the resistance of the coating to soil attack was evaluated by identifying any forms of coating damage and defects as well as signs of rust on the steel using visual and macroscopic inspection techniques. 3. results and discussion optical observations of the control and inhibited polyaspartic coatings loaded onto milled and blasted steel panels after having been buried in soil for 30 days at rt and 35°c are displayed in figs.4-15. the coatings exhibited varying degrees of blistering and, in some cases, some rusting was also present following the test. the experimental results are presented and discussed according to the type of coating applied and the experimental conditions. 3.1. control polyaspartic coating in soil at rt and 35°c the macroscopic observations after soil experiments had been conducted on the control polyaspartic coating applied to the milled and blasted surface finished steel panels are depicted in figs.4-7. a cluster of blisters on the control polyaspartic coating applied to the milled surface finished steel after a soil experiment had been conducted at rt can be seen in fig.4. furthermore, cracking of the blisters is also clearly visible as indicated by the arrows, where rust can be observed under the peeled off blisters. additional clustered and isolated open blisters on the control polyaspartic coating tested in soil at 35°c are presented in fig.5. blisters in isolated spherical shapes of the control polyaspartic coating applied to the blasted, surface finished steel panels are documented in figs.6-7. however, in fig.6, the surface morphology contains a collection of smaller blisters on the control polyaspartic coating applied to the blasted, surface finished steel after the soil experiments had been conducted at rt. on the other hand, in fig.7, bigger blisters on the control polyaspartic coating are visible following the soil experiments at 35°c. figure 4. control polyaspartic coating, milled steel panel, rt figure 6. control polyaspartic coating, blasted steel panel, rt figure 7. control polyaspartic coating, blasted steel panel, 35°c figure 5. control polyaspartic coating, milled steel panel, 35°c elhoud and van everbroeck hungarian journal of industry and chemistry 38 3.2. polyaspartic coating loaded with an alkylammonium corrosion inhibitor tested in soil at rt and 35°c corrosion inhibitors are used to reduce the risk of corrosion on metal substrates in aqueous media by forming a barrier film or controlling the corrosion reactions of the corrosion cell. alkylammonium salt inhibitors exhibit excellent biocidal and anticorrosive properties [6]. corrosion inhibitors have been added to coating systems as one of the direct additives or in capsular form in the smart coating. although the addition of a corrosion inhibitor to a coating system is primarily intended to improve its degradation resistance, adhesion between the film coating and metal substrate may also be improved to some extent. nevertheless, some corrosion inhibitors have a tendency to degrade in microbial cultures such as soils. in this regard, the performance of the alkylammonium inhibitor in the examined polyaspartic coating submerged in soil is presented in this section. surface morphological observations of the polyaspartic coating incorporated with the alkylammonium inhibitor and micaceous iron oxide barrier following soil corrosion experiments at rt and 35°c are displayed in figs.8-11. in fig.8, it can be seen that the liquid alkylammonium inhibitor reduced but did not prevent the formation of blisters on the polyaspartic coating applied to the milled surface finished steel panels tested in soil at rt. perforations through the coatings of the alkylammonium corrosion inhibitor and iron oxide barrier were visible after having been immersed in soil for 30 days at rt. for clear verification, the images of the perforations were inverted horizontally and vertically as documented in figs.8a and 8b, respectively. since these perforations were not observed when the coating was applied and before it was immersed in the soil, they may have resulted from the corrosion reactions occurring underneath the coating or the coating substances reacting with the soil causing leaching of coating contents such as the corrosion inhibitors. groups of blisters and the iron oxide barriers on black spots distributed over the surface of the coating layer can be seen in fig.8c. as for the samples tested in soil at 35°c presented in fig.9, damage to the coating was in the form of wider bulging blisters, moreover, iron oxide barriers were visible. the effect of the surface finish of the steel panels on the organic inhibitor polyaspartic coating was not noticeable. however, the degree of blistering still visible on the coating applied to the blasted panels as well as tested in soil at rt and 35°c is illustrated in figs.10 and 11, respectively. the experiments in this study simulated to a certain extent the performance of both steel structures immersed in soil and coatings as one of the most commonly used protection systems for underground assets. in this regard, the examined soils at rt and 35°c were found to threaten the control polyaspartic coating and polyaspartic coating dispersed with the alkylammonium corrosion inhibitor. this outcome is proven by the penetration and accumulation of the figure 8. polyaspartic coating (alkylammonium corrosion inhibitor + iron oxide barrier), milled steel panel, rt figure 9. polyaspartic coating (alkylammonium corrosion inhibitor + iron oxide barrier), milled steel panel, 35°c behavior of control and inhibitive polyaspartic coatings 50(2) pp. 35–41 (2022) 39 aggressive elements in moisture through the coating matrix, whereas the visual and macroscopic interpretations confirmed the existence of a mass of blisters and cracks in the control coating. the identified blisters in the coating are most likely caused by a combination of factors such as saline conditions as well as the presence of sulfate, bacteria and sulfide. the role of such parameters, in addition to chemical, mechanical and biological activities, in the corrosion of buried steel on top of the degradation of other materials are discussed elsewhere [2,7-8]. furthermore, the microbial culture of the soil has a tendency to cause the biodegradation of the alkylammonium salt that exists in the chains of some corrosion inhibitors in the main structure. this type of biodegradation has been studied by several previous researchers, who summarized that a closely packed nitrogen atom yields biodegradable alkylammonium salts. however, its degree of resistance improves significantly in correlation with the number of long alkyl chains associated with the nitrogen atom [9]. 3.3. polyaspartic coating loaded with a zinc phosphate corrosion inhibitor tested in soil at rt and 35°c figs.12-15 depict the macroscopic observations of a polyaspartic coating containing a zinc phosphate inhibitor and a micaceous iron oxide barrier applied to milled and blasted steel panels. it was clearly observed that the combination of zinc phosphate and the iron oxide barrier in the polyaspartic coating significantly inhibited the formation of blisters. the optical photographs of the polyaspartic coating tested in soil at rt and 35°c on the milled surface finished and blasted surface finished steel panels are strongly in line with the presence of the zinc phosphate corrosion inhibitor and iron oxide barrier, since neither blisters nor rust were recorded. only flakes of the iron oxide barrier dispersed in the matrix of the polyaspartic coating are visible. the experimental results show that the dispersion of the zinc phosphate corrosion inhibitor and iron oxide barrier in the polyaspartic coating led to the development of its resistance to soil attack without exhibiting any considerable indications of deterioration. the resistance of this type of coating to the soil is attributed to the effectiveness of the zinc phosphate corrosion inhibitor, which reacted with and bonded to the steel substrate, forming a zinc phosphate protective layer and an iron oxide barrier composed of the phosphating figure 10. polyaspartic coating (alkylammonium corrosion inhibitor + iron oxide barrier), blasted steel panel, rt figure 11. polyaspartic coating (alkylammonium corrosion inhibitor + iron oxide barrier), blasted steel panel, 35°c figure 12. polyaspartic coating (zinc phosphate corrosion inhibitor + iron oxide barrier), milled steel panel, rt figure 13. polyaspartic coating (zinc phosphate corrosion inhibitor + iron oxide barrier), milled steel panel, 35°c elhoud and van everbroeck hungarian journal of industry and chemistry 40 film containing fepo4, fe2o3 and feo. the effectiveness of both the zinc phosphate and barrier are in agreement with the findings of several studies that investigated epoxy and waterborne acrylic coatings [10]. 3.4. mechanism of blister formation blistering phenomena are associated with the absorption of water into the coating. two of the most common types of coating blisters are: 1) osmotic blisters associated with the diffusion of water through the coating due to the presence of soluble salts on substrates or interlayers; 2) non-osmotic blisters due to swelling and buckling of the coating associated with the absorption of water in the coating [11]. in figs.4 and 5, rust is observed under blisters in the control coating on the milled surface finished steel panels. the blisters on the milled surface finished steel panels can be classified as osmotic blisters because the milled layer might contain impurities resulting in a weak degree of adhesion of the coating to the substrate, thereby leading to the possible formation of blisters given the presence of the penetrated moisture. however, since the same coating on blasted steel yielded isolated blisters, as can be seen in figs.6 and 7 after soil experiments were conducted at rt and 35°c, it seems that the steel finish controlled the formation of blisters on the control polyaspartic coating. horizontal and vertical flip images of perforations in the alkylammonium coating on milled steel plates following soil tests at rt are depicted in figs.8a and 8b, respectively. these can be explained by either corrosion reactions beneath the coating leading to osmotic blisters and subsequently perforations or reactions between the soil and the contents of the coating yielding perforations in the coating due to leaching of some of its contents such as the corrosion inhibitor. nevertheless, examination of the coating before being buried in the soil did not exhibit perforations, which were only seen after the soil tests. the same sample in fig.8c shows a group of unperforated blisters. the hypothesis for the formation of blisters recorded in the experimental results is schematically described in fig.16. how moisture from the soil penetrated through the coating is outlined in fig.16a; with regard to the control coating, which does not contain inhibitive pigments or a coating loaded with the alkylammonium corrosion inhibitor, the moisture can easily pass through the coating into the substrate causing blistering. however, the presence of the zinc phosphate corrosion inhibitor and the iron oxide barrier protected the coating against soil attack (fig.16b). anyway, hightech investigative techniques such as sem could be applied in future studies to better understand the behavior of polyaspartic coatings in soils. 4. conclusions since the content of the coating and temperature are important factors controlling the impact of soil on the performance of coatings and its reliability, the following conclusions have been drawn: figure 14. polyaspartic coating (zinc phosphate corrosion inhibitor + iron oxide barrier), blasted steel panel, rt figure 15. polyaspartic coating (zinc phosphate corrosion inhibitor + iron oxide barrier), blasted steel panel, 35°c a) b) figure 16. a schematic diagram representing the formation of blisters in the control and inhibitive coatings: a) control coating and b) zinc phosphate + iron oxide barrier inhibitive coating behavior of control and inhibitive polyaspartic coatings 50(2) pp. 35–41 (2022) 41 • increasing the soil temperature from rt to 35°c increased the severity of blistering in the control polyaspartic coating and polyaspartic coating loaded with the alkylammonium corrosion inhibitor after 30day-long soil experiments due to the high degree of moisture absorption. • the advantages of applying the zinc phosphate corrosion inhibitor and the micaceous iron oxide barrier are significant in eliminating the soil risk to buried steel. • this coating efficiently protects milled surface finished steel as well as blasted steel in soil experiments conducted over 30 days at rt and 35°c. • the newly invented coating formula may well be applied as a protection system for steel assets submerged in soil in industry and the infrastructure sectors. • the soil experimental results of the polyaspartic coating containing the zinc phosphate corrosion inhibitor supported the final remarks that this type of coating exhibits a good degree of resistance to erosion when immersed, as determined in earlier stages of this project. future studies should include experimentally measuring and examining the soil parameters as well as physical testing, which could not be examined at this stage of the project: 1. soil parameters such as soil type, ph variation, bacterial activity, water content and soil resistivity. 2. physical and mechanical testing of coatings, e.g. with regard to their compatibility with protective coatings and cathodic protection, cathodic disbondment, flexibility, cracking resistance, electrical and insulation resistance as well as compressive and tensile strength. 3. thermal resistance and permeability of the coating in the simulation of anticipated working environments. acknowledgements the authors would like to thank vlaio for sponsoring this project conducted by chemsystems (grant hbc.2020.3021) to identify and develop a concrete coating produced by adcos nv in order to extend the application of this product to include the protection of steel assets. references [1] emori, w.; okafor, p.c.; bassey, v.m.: physicochemical characteristics of soil moisture and their effects on the corrosion behavior of buried mild steel in calabar metropolis, nigeria, j. environ. prot. 2018, 9, 801–814, doi: 10.4236/jep.2018.97050 [2] chen, j.; chen, z.; ai, y.; xiao, j.; pan, d.; li, w.; huang, z.; wang, y.: impact of soil composition and electrochemistry on corrosion of rock-cut slope nets along railway lines in china, sci. rep., 2015, 5, 14939, doi: 10.1038/srep14939 [3] putra, r.; muhammad; huzni, s.; ali, n.; fonna, s.: effect soil resistivity in mapping potential corrosion in underground pipelines area, aip conf. proc., 2018, 1977, 040011, doi: 10.1063/1.5042981 [4] jiang, c.; cheng, x.: anti-corrosion zinc phosphate coating on building steel via a facile one-step brushing method, electrochem. commun., 2019, 109, 106596, doi: 10.1016/j.elecom.2019.106596 [5] van liedekerke, m., gentile, a., barceló-cordón, s., soil country analyses: belgium (joint research centre report 2009), doi 10.2788/27334 [6] brycki, b.; szulc, a.: gemini surfactants as corrosion inhibitors. a review, j. mol. liq., 2021, 344, 117686, doi: 10.1016/j.molliq.2021.117686 [7] yahaya, n.; lim, k.s.; noor, n.m.; othman, s.r.; abdullah, a.: effects of clay and moisture content on soil-corrosion dynamic, malays. j. civ. eng., 2011, 23(1), 24–32, doi: 10.11113/mjce.v23.15809 [8] abdulameer, e.a.; al-uqaily, r.a.h.; al-bayaty, s.a.h.: the effect of both moisture and clay content on the soil corrosion process for different periods of time as a geomorphological study in al-kut city, iop conf. ser.: earth environ. sci., 2022, 961(1), 012083, doi: 10.1088/1755-1315/961/1/012083 [9] van ginkel, c.g.; kolvenbach, m.: relations between the structure of quaternary alkyl ammonium salts and their biodegradability, chemosphere, 1991, 23(3), 281–289, doi: 10.1016/0045-6535(91)90184-f [10] hao, y.; liu, f.; han, e.-h.; anjum, s.; xu, g.: the mechanism of inhibition by zinc phosphate in an epoxy coating, corros. sci., 2013, 69, 77–86, doi: 10.1016/j.corsci.2012.11.025 [11] li, j.c.m.; him, l.k.; chang, b.t.a.: blister initiation mechanism of fbe coatings, nace international corrosion conference series, 2019, 13508, issn: 03614409 https://doi.org/10.4236/jep.2018.97050 https://doi.org/10.4236/jep.2018.97050 https://doi.org/10.1038/srep14939 https://doi.org/10.1063/1.5042981 https://doi.org/10.1016/j.elecom.2019.106596 https://doi.org/10.2788/27334 https://doi.org/10.1016/j.molliq.2021.117686 https://doi.org/10.1088/1755-1315/961/1/012083 https://doi.org/10.1016/0045-6535(91)90184-f https://doi.org/10.1016/0045-6535(91)90184-f https://doi.org/10.1016/j.corsci.2012.11.025 https://doi.org/10.1016/j.corsci.2012.11.025 untitled hungarian journal of industry and chemistry vol. 53(1) pp. 61–66 (2025) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2025-07 the concept and practical challenges of membrane gradostat reactors piroska lajtai-szabó1* and éva hülber-beyer1 1 research group on bioengineering, membrane technology and energetics, university of pannonia, egyetem u. 10, veszprém, 8200, hungary developing a new technology from a theoretical concept to its industrial application is generally a long and burdensome procedure. the membrane gradostat reactor (mgr) – which was invented for the continuous production of secondary metabolites – is now at the initial stage of this process. therefore, even though it was patented a quarter of a century ago, relatively few studies have been published concerning this device. in this opinion article, the structure of the mgr, transport mechanisms through the bio film and membrane, methods and challenges of inoculation as well as the aspects determining the structure of a suitable membrane and species will be overviewed. the findings are based on the observations from other publications as well as the own experiences of the authors. keywords: membrane bioreactor, secondary metabolites, biofilm structure, streptomyces 1. introduction microbial secondary metabolites are extremely important in the life of microorganisms as well as in the human economy. besides antibiotics and other pharmaceutical compounds, their lesser-known representatives include biosurfactants, food additives, environmentally-safe herbicides and insecticides [1]. among the microorganisms that produce them, streptomyces species are of great significance as they are the basis of around 100,000 antibiotics and a wide range of additional bioactive compounds such as pesticides, neurogicals, enzyme inhibitors and siderophores [2]. in compliance with their biological roles – e.g. protection against other species or toxic conditions, decomposition of complex nutrients, etc. – secondary metabolites are produced in the late or stationary growth phase when unfavorable conditions evolve such as the exhaustion of nutrients [1]. this environmental signal triggers a global alteration in gene expression resulting in morphological differentiation as well as a shift towards secondary metabolism. while stress factors are necessary for production, they hinder bacterial growth and cannot be maintained in the long term [3]. therefore, batch operations have proliferated in the industry in spite of the advantages of a continuous operation, e.g. higher throughput, advanced quality control and economic benefits [4]. this issue could be handled by a unique device called a membrane gradostat reactor (mgr), a biofilm received: 7 march 2025; revised: 14 march 2025; accepted: 17 march 2025 *correspondence: lajtai-szabo.piroska@mk.uni-pannon.hu reactor which enables the continuous renewal of biofilms and the production of secondary metabolites simultaneously. due to the construction of the reactor, downstream processes have become simpler than in the case of conventional submerged fermentations, therefore, the effluent does not contain large amounts of biomass. moreover, the extracellular polymeric substances (eps) fraction of the biofilm – a valuable source of biomaterials applied in the pharmaceutical, food and cosmetics industries [5] – can be harvested after fermentation cutoff. while these advantages make mgrs a promising technology, only a limited number of publications have been written concerning these devices since they were patented in 1999 [6]. therefore, several questions remain unanswered regarding both their theoretical foundation and practical implementation. from among these issues, this study focuses mainly on the inoculation process as well as the requisite properties of the membranes and microorganisms which make them applicable in mgrs. regarding species, the streptomyces genus is focused on because of its industrial importance. besides the main findings of other publications, this article presents the own experiences of the authors, which did not lead to a quantified result but can help to understand and develop the system. due to limited space, details of these experiments – all of them carried out with streptomyces coelicolor – are not presented, however, they are provided as supplementary data. the aim is to https://doi.org/10.33927/hjic-2025-07 mailto:lajtai-szabo.piroska@mk.uni-pannon.hu lajtai-szabó and hülber-beyer hungarian journal of industry and chemistry 62 draw attention to this system and its untapped potential while revealing a part of the long and winding road that hopefully will lead to the successful implementation of this technology. 2. the structure of an mgr an mgr is a bioreactor in which capillary membranes serve as a solid support for the biofilm and maintain a nutrient gradient inside it. when operating, the medium solution is fed into the lumen of the hollow fibres from which the nutrients diffuse through the membrane onto its surface where microorganisms form a biofilm. since the hollow fibres are surrounded by air, the oxygen diffuses through the biofilm in the opposite direction to the components of the medium [7]. as the biofilm – along with growth of the biomass – thickens, different zones evolve inside of it according to substrate availability (figure 1). the layer of the biofilm closest to the membrane gains enough nutrients to grow and reproduce [7], while further away from the membrane, i.e. from the nutrient source, the cells are in the stationary or declining phase and nutrient limitation leads to the production of secondary metabolites. in conclusion, the special structure of an mgr makes the system suitable for the production of secondary metabolites in the long term due to continuous biofilm renewal. moreover, culture conditions in the mgr are similar to in the natural environment of soil bacteria like streptomyces and several other microorganisms [8]. this feature might be favorable in the industry, especially in the case of those species that are sensitive to shear stress [9] or cannot produce secondary metabolites during submerged fermentation [10]. however, certain aspects of this system have not yet been comprehensively researched. will the mentioned zones really evolve or the effective nutrient transport inside the colonies hinder the development of a gradient? what happens to dead cells in the outermost layer? will they be removed (as in the case of submerged cultures) or remain attached resulting in an “infinitely” growing biofilm? what are the limitations of this process? in the following sections, some of these issues will be addressed. 3. gradients and transport in the biofilm 3.1. limitations of biofilm thickness based on the theoretical concept of mgrs, biofilm thickness presumably has a lower boundary which has to be reached in order to achieve nutrient limitation in the outer layer. our assumption is that the value of this boundary might depend on the species and fermentation parameters such as the temperature, ph and composition of the culture medium. this is based on the observation that the listed parameters have a great impact on the properties of eps that strongly influence biofilm formation and the transport process through the biofilm [11],[12]. however, to the best of our knowledge, no studies have been published focusing on this issue, and thus these hypotheses cannot be confirmed. on the other hand, since air is supplied in the extracapillary space, the direction of the oxygen gradient is the opposite to that of the nutrient gradient. as a result, the outer layer of the biofilm gains the most oxygen while the inner regenerating layer gains less. as oxygen penetration is limited, an upper boundary thickness, presumably depending on the species and other parameters, similar to that of the lower boundary might result. above this value, oxygen deficiency might occur in certain zones which might cause severe problems in the case of aerobic microorganisms. these regions become inactive and separate from the membrane resulting in the leakage of culture medium and the absence of a nutrient gradient [9]. in order to prevent an oxygen shortage, different strategies have been applied during the cultivation of aspergillus terreus in a single capillary mgr [9],[13]. one of them is controlling the biofilm thickness by a socalled two-stage feeding strategy [9]. after inoculation, a culture medium optimal for cell growth is provided until the desired biofilm thickness is achieved. at that point, further growth might be hindered by the changing composition of the medium since cells enter the stationary phase and start to produce secondary metabolites. this effect might come about by altering either the nitrogen source [13] or c/n ratio of the culture medium [9]. another possible approach concerns the influence of the structure of the biofilm. it has been observed during microparticle-enhanced cultivations (mpec) that cell morphology might be affected by the addition of microparticles [14]. based on this, mohseny et al. [13] supplied talc particles (hydrous magnesium silicate) to the spore suspension which led to a looser structure and improved oxygen penetration even though the biofilm thickness was approximately the same as in the case of the control. figure 1: structure and concept of a single capillary mgr (the phases consist of primary growth (i.), stationary growth (ii.) and decline (iii.)) (this figure was created using figure 2 of [7]) membrane gradostat reactors 53(1) pp. 61–66 (2025) 63 3.2. effect of biofilm growth on the hydrodynamics of mgr biofilm growth affects not only oxygen uptake but also the transmembrane flux of a culture medium. a study by godongwana et al. [15] on the hydrodynamics of mgr is summarized as follows: a single ceramic capillary membrane was inoculated with streptomyces coelicolor and introduced into the mgr in the dead-end mode. the differential pressure across the membrane was constantly maintained at 3 kpa, moreover, the biofilm thickness and volume of the permeate were measured in order to calculate the flux and hydraulic permeability (neglecting fouling). over the first 72 hours, as the biofilm was growing, the transmembrane flux and consequently the hydraulic permeability decreased as expected. however, after this period, the permeability remained approximately constant and fluctuated only slightly while the biofilm continued to thicken by about 2.5 times. these results are explained by the special structure of the biofilm. starting from the surface of the membrane, three different regions could be detected in the biofilm, namely the primary growth zone, transition zone and aerial mycelium zone. based on the previous findings by the authors, the primary and aerial mycelium layers grow only in the first period – in this case, during the first 72 hours – therefore, further increase of the biofilm thickness depends on the development of the transition zone. hence the primary zone mainly determines the density of the biofilm, while the hydraulic permeability remains unchanged after the thickness of the primary layer becomes constant. 4. inoculation of the mgr the generally applied method of inoculating the mgr is reverse filtration. the name denotes that the inoculum is filtrated through the membrane from the ecs to the lumen so the flow direction is opposite to that of the nutrients. the inoculum is pumped into the shell side and the ecs is pressurized in order to channel the inoculum towards the hollow fibers. the liquid phase passes through the membrane but spores are retained which attach to the membrane surface or the walls of the pores [16]. during the initial period of reactor operation (approximately the first 24 hours), it is advisable to fill the lumen with the nutrient medium and close all inlets and outlets of the system. in this way, spores can germinate and strengthen their affinity with the membrane, thereby avoiding the washing out of spores in the nutrient flow [17]. govender et al. [16] assumed – based on observations by previous researchers – that using vegetative mycelium instead of spores as an inoculum might lead to inconsistencies in the biofilm. however, according to a recently published study investigating the effect of the harvesting time and ph on the filtration characteristics of the fermentation broth [18], the features of broths can be significantly influenced by the aforementioned parameters, therefore, it is possible that optimal conditions for inoculation might be reached so this is worthy of further investigation. 5. microorganisms during an optimal inoculation method, spores or cells are evenly distributed on the membrane surface. even if they do not cover the whole surface, motile microorganisms can colonize the membrane during cell growth resulting in a homogeneous biofilm. the genus streptomyces, however, has evolved to maximize nutrient uptake within a certain region and protect themselves by inhibiting neighboring microorganisms [19], rendering them one of the greatest producers of secondary metabolites, although their ability to colonize further areas is strongly limited. in this way, they do not tend to spread on the membrane surface in mgrs. this is neatly illustrated by the experiment with a pentair x-flow ultrafiltration membrane module conducted by the authors, which was inoculated with a spore suspension of streptomyces coelicolor by reverse filtration. during the inoculation, spores only attached to the membrane in certain regions probably due to unfavorable flow conditions. as the experiment proceeded, cells did not colonize the membrane surface but remained at their starting point and passed into the secondary metabolite-producing phase. the results can be easily visualized because the microorganisms produce pigmented antibiotics so their colonies are deep purple in color (figure 2). two recently discovered phenomena might enable this problem to be resolved. it is already known in nature that insects and nematodes spread streptomyces spores, however, is has only recently come to light that motile microbes are capable of transporting their immotile counterparts over figure 2: incontiguous colonies on the surface of the pentair x-flow hollow fibre module lajtai-szabó and hülber-beyer hungarian journal of industry and chemistry 64 short distances [20]. mouk et al. [21] observed that streptomyces coelicolor spores can attach to the flagellum of bacillus subtilis, thereby taking advantage of its motility. they use the apt ‘hitchhiking’ term to describe this type of movement and suggest that it is conserved across the genus streptomyces. another novel discovery is the special exploratory behavior of streptomyces species, which occurs in response to certain environmental conditions. the exact underlying mechanism of such behavior is not fully known but is presumably triggered by the glucose consumption of neighbouring yeast. in addition, a rise in ph and the presence of certain volatile organic compounds (e.g. trimethylamine) may also play a crucial role in this process. although explorer cells are hydrophilic just as ‘normal’ vegetative hyphae, they are nonbranching, which may enable these colonies to spread, even though abiotic surfaces. moreover, some species produce surfactants to further facilitate exploration [19]. the aforementioned phenomena might be exploited to facilitate membrane colonization in mgrs by cocultivation. for this purpose, such an ‘auxiliary’ species has to be found that supports the development of a suitable biofilm but that does not impair the growth nor secondary metabolite production of the producer species. since exploratory growth might be triggered by applying vocs as info-chemicals, the presence of another microorganism might be unnecessary. on the other hand, another aspect other than the colonizing ability has to be taken into consideration when choosing a species that is suitable for inoculation, namely intracellular transport and its effect on substrate distribution in the biofilm. regarding fermentations in mgrs, filamentous organisms are predominantly used as producing strains, e.g. filamentous fungi [9],[22] or actinomycetes [8],[15]. there are a number of reasons for this choice: the wide range of important extracellular secondary metabolites [1], the proven ability of forming a biofilm on their own [23],[24] as well as the fact that the filaments penetrate the pores before becoming interwoven, therefore, adhesion between the membrane and biofilm mat is expected to be stable. however, filamentous microorganisms exhibit apical growth supported by intracellular transport, a phenomenon which is barely taken into consideration when it comes to the development of radial gradients in mgrs. the fungal hyphae elongate apically. the filamentous growth of fungi is facilitated by effective intracellular vesicle transport to the hyphal tips by mechanisms that require microtubules and an f-actin cytoskeleton [25]. the apical growth of streptomycetes by elongation resembles that of filamentous fungi which implies the existence of inner transport mechanisms. however, these transport mechanisms are less sophisticated compared to fungi as they are prokaryotes. in the absence of a complex cytoskeleton, they rely primarily on diffusion [26], which might be limited by the cross-walls [27], therefore, the chance of a gradient forming might be higher than in the case of fungi. based on these findings, investigating the application of unicellular microorganisms would be worthwhile as in their case the development of a radial gradient is more likely than by filamentous microbes. 6. membrane as it was previously mentioned, the membrane plays a pivotal role in an mgr by providing a solid surface for the cells to grow on and enabling the maintenance of a nutrient gradient inside the biofilm. accordingly, the membrane is expected to fulfil several criteria, most importantly: • surface properties (e.g. hydrophobicity, rugosity, surface area, etc.) favorable for cell adhesion [16]; • high porosity, preferably with increasing pore size towards the outer surface; • sterilization capability (either chemically or with steam); • mechanical stability (especially important during the long-term operation of large-scale mgrs). in most research, polysulfone or ceramic membranes were applied, which exhibit certain different qualities that should be taken into consideration when choosing a suitable membrane [7]. it is worth mentioning that commercially available membranes are generally designed to avoid biofouling, which is important for most applications (like in microbial fuel cells [28]), however, antifouling is a hindrance in the case of mgrs. these membranes have a relatively small surface area with blunt-ended macrovoids that hinder cell attachment, moreover, an external skin is also often applied to further enhance this feature [29]. in contrast, the hollow fibers applied in mgrs are microfiltration membranes with a sponge-like structure and cavities on the outer surface provide a large surface area for cell attachment. on the lumen side, an ultrafiltration skin layer is formed in order figure 3: biofouling inside the hollow fibre membrane gradostat reactors 53(1) pp. 61–66 (2025) 65 to prevent cells getting into the lumen [7]. although this precaution might seem excessive, it might be essential in some cases as exemplified by the following observation by the authors. during experiments with a single capillary mgr, it was experienced in some cases that on the upper region of the membrane – close to the feed – the biofilm developed as a clump, while below this cluster, colonies were only sparsely present. after cutting open the membrane, it was ascertained that the microorganisms passed through the wall of the membrane, colonized its inner surface and clogged the lumen, therefore, the lower region had no access to a nutrient medium and cell growth was hindered (figure 3). there are two possible explanations for this phenomenon. while hollow fiber membranes can be characterized by a mean pore size, a few pores with much larger diameters might develop during the production process. when applied in non-biological systems, large pores might slightly reduce selectivity but not significantly. however, in bioreactors, even if only a few cells get across the membrane, they can grow and clog the capillary, thereby hindering the flow of the culture medium. assuming the absence of such large pores, streptomyces species have a surprising ability, that is, they can pass through membrane pores much smaller than the diameter of hyphae. observations by wolf et al. [30] indicate that these microbes are flexible to a certain extent – the diameter of their hyphae can shrink from 0.7 to 0.2 µm – allowing them to grow through conventional microfiltration membranes. based on these experiences, an inner ultrafiltration layer is a requisite for membranes in mgrs in order to prevent cell infiltration into the lumen – at least in the case of streptomyces species. 7. conclusions and perspectives theoretically, membrane gradostat reactors might be suitable for the production of any microbial secondary metabolites during continuous operation. however, as was pointed out in this article, some practical issues may limit the scope of potential producing microorganisms. among other factors, transport mechanisms inside the biofilm and the colonizing ability of the microorganism should be scrutinized when choosing the species. furthermore, since commercially available membranes are mostly designed to exhibit antifouling properties, the modification of existing membranes or the creation of new ones might be necessary. developing alternative inoculation methods is also worth considering as they strongly affect the efficiency of mgrs. should the gradostat concept not be feasible – due to the structure of the biofilm or the transport mechanisms inside it – the system still exhibits several beneficial properties such as: • culture conditions mimic the natural habitat of many microorganisms which might have a positive impact on secondary metabolite production; • product recovery and downstream processes are relatively simple; • the eps fraction of the biofilm can be easily harvested after fermentation cut-off. in order to make this technology available on an industrial scale, several theoretical and practical issues should be addressed. future lines of research should focus on the feasibility of the gradostat concept; the development, structure and ageing of the biofilm; the practical limitations of the system; as well as the methods of inoculation and process control. acknowledgements this research was supported by otka project no. k 138232 of the national research, development and innovation office of hungary entitled “study of anaerobic effluent demethanization by membrane contactors in a novel, integrated bioprocess”. references [1] barrios-gonzalez, j.; fernandez, f.j.; tomasini, a.: microbial secondary metabolites production and strain improvement, indian j. biotechnol., 2003, 2(3), 322–333 [2] alam, k.; mazumder, a.; sikdar, s.; zhao, y.-m.; hao, j.; song, c.; wang, y.; sarkar, r.; islam, s.; zhang, y.; li, a.: streptomyces: the biofactory of secondary metabolites, front. microbiol., 2022, 13, 968053, doi: 10.3389/fmicb.2022.968053 [3] liu, g.; chater, k.f.; chandra, g.; niu, g.; tan, h.: molecular regulation of antibiotic biosynthesis in streptomyces, microbiol. mol. biol. rev., 2013, 77(1), 112–143, doi: 10.1128/mmbr.00054-12 [4] cole, k.p.; johnson, m.d.: continuous flow technology vs. the batch-by-batch approach to produce pharmaceutical compounds, expert rev. clin. pharmacol. 2018, 11(1), 5–13, doi: 10.1080/17512433.2018.1413936 [5] wu, s.; huo, h.; shi, y.; zhang, f.; gu, t.; li, z.: chapter three extraction and application of extracellular polymeric substances from fungi, in: advances in applied microbiology, gadd, g.m.; sariaslani, s. 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https://doi.org/10.33927/hjic-2020-27 https://doi.org/10.1111/j.1574-6968.1989.tb03345.x hungarian journal of industry and chemistry vol. 53(2) pp. 17–30 (2025) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2025-13 life cycle assessment of technological shifts in municipal wastewater treatment plants réka harasztiné hargitai1*, viktor sebestyén1, balázs volf2 and viola somogyi1 1 sustainability solutions research laboratory, university of pannonia, egyetem u. 10, veszprém, 8200, hugary 2 bakonykarszt zrt., pápai u. 41, veszprém, 8200, hungary the challenges faced by municipal wastewater treatment plants (wwtps) to improve effluent quality while reducing environmental impacts are increasing. this study employs a life cycle assessment to evaluate the development of effluent water quality and overall environmental impacts through seven years of technological advancements at a wwtp using real world data. scenarios include biogas optimization, transition ing to biological phosphorus removal, solar energy integration, optimized effluent control and hypothetical quaternary wastewater treatments (ozonation and sequential h2o2 treatment). transitioning to biological phosphorus removal reduced chemical use by 26.2% and achieved the highest nutrient removal efficiency but increased energy consumption, slightly raising fossil depletion (fd). solar energy reduced fd by 18.4% and contributed 7.75% of energy needs, albeit with seasonal limitations. optimized effluent control achieved the highest level of nutrient removal, improving freshwater eutrophication by 41.4% but increased sludge production by 10.4%, leading to a 23.9% rise in metal depletion. ozonation significantly increased environmental burdens, while sequential h 2o2 treatment had less of an impact, offering future potential for wastewater reuse. the findings underscore the importance of balancing energy, chemical use and effluent quality with biogas optimization playing a key role in reducing flaring. this study highlights the trade-offs inherent in wwtp upgrades and provides actionable insights into optimizing environmental performance. keywords: life cycle assessment, wastewater treatment, technology improvement, water circularity 1. introduction in light of the new urban wastewater treatment directive [1], the pressure on municipal wastewater treatment plants (wwtps) to enhance treatment efficiency while striving for energy neutrality is increasing once again. biological wastewater treatment systems as mature technologies, effectively remove macronutrients to meet water quality requirements under various conditions [2]. when coupled with anaerobic digestion, organic matter can be converted into energy [3], potentially enabling the system to achieve energy neutrality or even a net-positive energy balance [4]. the utilization of agro-wastes in biohydrogen fermentation not only enhances waste management efficiency but also contributes to the integration of renewable energy sources in wastewater treatment plants, supporting the achievement of energy neutrality [5]. however, insufficient methane storage may lead to unintended greenhouse gas emissions [6]. on the other hand, zeroemission technologies in wastewater treatment have the potential to reduce the carbon footprint by 69.7% [7]. received: 25 april 2025; revised: 6 may 2025; accepted: 6 may 2025 *correspondence: hargitai.reka@mk.uni-pannon.hu wastewater treatment plants must also prepare treated water for reuse. for example, treated effluent can alleviate water stress [8] by substituting freshwater resources for irrigation purposes [9]. many disinfection methods, such as ozonation, can simultaneously inactivate bacteria and oxidize micropollutants [10], addressing the challenges in facilitating wastewater reuse. addressing the aforementioned objectives requires an integrated evaluation of sustainability targets and operational modifications to ensure that new technologies are both sustainable and efficient. life cycle assessment (lca) provides a comprehensive framework for analyzing the environmental impacts of such technological shifts and comparing development alternatives [11]. while new technologies require additional resources, leading to greater environmental impacts [12], these can be balanced out by the subsequent benefits of improved effluent quality [13]. benchmarking different wastewater treatment plants or technologies requires careful deliberation either as a result of local characteristics [14] or differences between applied technologies [15]. inventory data are https://doi.org/10.33927/hjic-2025-13 mailto:hargitai.reka@mk.uni-pannon.hu harasztiné hargitai, sebestyén, volf and somogyi hungarian journal of industry and chemistry 18 created from monthly or yearly averages [11] and while the temporal variations beyond one year might not be substantial [16], they might add to the deviation caused by technological interventions. in the planning phase it could be sufficient to use the yearly averages of the key performance indicators to identify the impacts potential technological interventions would cause [17]. however, when analyzing the previous environmental performance of a facility that had continuously been upgraded over the years, fluctuations in the quality and quantity of influent may overshadow the impacts on technological changes. recent studies have highlighted the importance of integrating advanced monitoring systems to better record these variations and improve the accuracy of environmental impact assessments in wastewater treatment processes [18]. this study aims to fill a critical gap in the literature by evaluating the environmental impacts of real-world technological advancements in wwtps over a sevenyear-long period. using time-series operational data, the authors assess how modifications such as transitioning to biological phosphorus removal, reducing reliance on chemical additives and integrating renewable energy sources affect the overall sustainability of the plant. furthermore, the study extends its scope to model future quaternary treatment scenarios, such as ozonation and sequential hydrogen peroxide treatment, in order to assess their feasibility of facilitating wastewater reuse. 2. materials and methods the impacts of technological changes made in a real wastewater treatment plant were examined in terms of life cycle assessment. the criteria for selecting the facility was a robust operation ensuring satisfactory effluent water quality, distinct technological interventions that do not overlap with each other as well as the availability of and access to all data necessary for carrying out a lca. long-term data of operation along with detailed descriptions of developments within the chosen wwtp were collected and analyzed. the structure of the plant together with the flow rates of influent and effluent wastewater are shown in figure 1. details of the operation are provided in section 2.1. after processing the data, six periods were selected where the effect of technology change was measurable and all the data necessary for model (scenario) identification were available. based on that, six different simulations were carried out with the corresponding measurement data as their inputs to assess the overall impacts of the scenarios. two quaternary treatment solutions were added alternatively to the last configuration to evaluate the lifecycle impacts of potential future investments that will be necessary should the wastewater be further used for agricultural or other purposes. the study was carried out following the principles of the international standards iso 14040:2006 [19] and iso 14044:2006 [20]. following the established standards, the initial step was to define the goal and scope of the analysis. this was followed by the collection and analysis of data. the third phase was the impact assessment which was then followed by an evaluation of the results. the sphera modelling environment (software version 10.6.1.35) [21] was employed as it offers a comprehensive database on wastewater treatment plants and the materials used. the data utilized in the research figure 1: structure of the analyzed wastewater treatment plant, highlighting the water and sludge treatment line in the lower right quadrant, the quality of the effluent wastewater is shown, the former divided between the two biological processes. lca of a wastewater treatment plant 53(2) pp. 17–30 (2025) 19 were collected during the operational period. the authors did not consider the periods of construction and downtime. 2.1. technological details of the evaluated municipal wastewater treatment plant this section provides information on the chosen municipal wastewater treatment plant based on the technological data between the years of 2015 and 2022. the data were sourced from certified meter readings and plc data recordings. on-site laboratory measurements were employed to derive quality parameters for raw wastewater, treated water and compost. an overview of the technological data is shown in table 1. at the time of writing, the plant was capable of biological nutrient removal equipped with anaerobic digesters and solar panels to generate energy. the flow rates during the examined period ranged between 12,331 and 13,788 m3/d. municipal wastewater from a number of towns and other settlements was treated as well as wastewater from industrial sources. as can be seen in figure 1, two similar parallel lines utilizing activated sludge technology consisting of anaerobic, anoxic and oxic treatment tanks were used. on average, the influent was divided between the first and second line in a 52.24:47.62 ratio but varied over time to meet operational needs. the operating hours of the blowers were split in the proportions of 54.27% and 50.40% between the aeration system of the two trains with four nozzles on the first line and five on the second. due to the different structures and years of construction, the energy consumption was distributed differently, that is, 69.47% of it was consumed by the first line compared to just 30.53% by the second. the quality of the wastewater fluctuated notably over the examined time period in line with the monthly and seasonal changes that are usually present in a municipal wwtp (figure 1). on average, the effluent contained 1,016 mg/l cod, 142 mg/l tn and 12.37 mg/l tp with maximum values of 3,156 mg/l, 142 mg/l and 34 mg/l, respectively. the effluent contained 30.49 mg/l cod, 8.59 mg/l tn and 0.67 mg/l tp on average with peak concentrations of 64 mg/l, 19.9 mg/l and 3.9 mg/l occurring only seldomly, respectively. however, even the maximum values were below the permissible amount, namely 75 mg/l for cod, 20 mg/l for tn and 4 mg/l for tp [22], resulting in high removal percentages of the macronutrients. as a reference, the limit values are highlighted, moreover, the effluent concentrations and respective nutrient ratios can be seen in figure 1. the figures include the identified scenarios of technological additions which will be discussed in section 2.2. following the sludge line, the primary and secondary sludge was sent to the anaerobic digesters after being homogenized. the digesters accepted a variety of sludge, including primary and excess sludge, as well as mixed wastes, e.g. sludge from other plants, fat and oil from industries. the quantity and quality of the biogas was contingent upon the type of sludge. between 2015 and 2022, 0.20 to 0.69 m3 of biogas was produced per m3 of treated water, equating to an average of 1.32 kwh of table 1. primary data on the technology change per 1 m3 of treated water. different periods were named after the dominant new technology case influent [m³] c:n:p flared biogas [m³] electricity consumed [kwh] electricity generated by gas engines [kwh] electricity generated by solar panels [kwh] chemicals for p removal [l] chemicals for sludge dewatering [l] transported dried sludge [kg] conventional operation 1.16 100:8.29:1.21 0.35 0.29 0.02 45.48 2.06 intensive flaring 1.14 100:7.31:1.26 0.54 0.29 0.43 0.01 38.39 1.91 chemical p removal 1.19 100:7.77:1.20 0.06 0.36 0.48 0.01 60.84 2.66 biological p removal 1.20 100:7.77:1.20 0.04 0.31 0.41 44.90 2.29 solar energy 1.17 100:7.80:1.18 0.01 0.31 0.42 0.06 54.28 2.10 optimized effluent control 1.15 100:10.07:1.08 0.03 0.25 0.49 0.06 67.38 2.32 ozonation quaternary treatment 1.15 100:10.07:1.08 0.03 0.25 0.49 0.06 67.38 2.32 sequential h₂o₂ quaternary treatment 1.15 100:10.07:1.08 0.03 0.25 0.49 0.06 67.38 2.32 harasztiné hargitai, sebestyén, volf and somogyi hungarian journal of industry and chemistry 20 electricity recovery per m3 of biogas. furthermore, the heat generated by the biogas production process is utilized for heating buildings. the residual sludge from the digesters was transferred to a degasser before the anaerobically stabilized sludge was dewatered. although the quality parameters of the dried sludge met the quality requirements of the compost [23], it was not utilized for composting purposes, only for reclamation. to assist the different processes both in the biological tanks and in the solids line, chemicals can be added at three points in the facility. the first is to the biological tanks where an aluminum salt solution containing polymerized iron was used to reduce the phosphorous content before the plant turned to full biological removal. a total of 0.01-0.02 l of chemicals were utilized to treat 1 m3 of wastewater prior to that. the second is to the thickener to remove h2s. polyelectrolyte, and before the end of 2020, ferric(iii) chloride, was added to the sludge line. for foam control, an antifoaming agent and polyelectrolyte were added to the centrifuge. during the overall treatment process, 2.22 kg of dried sludge (15.3-18.3% d.m.) was generated while applying an average of 51.88 l of chemicals. over the years, improvements have been made to reduce the operating costs and further increase the removal efficiency while striving to achieve energy neutrality. in addition to utilizing biogas, a solar farm was developed. further additions to the aforementioned detailed technology are discussed in section 2.2 with a timeline and key points. 2.2. identification of technological shifts using the lca model based on the collected data, the operating periods were identified and considered for lca models to better understand the impacts of municipal wastewater treatment using different configurations within the same technological set-up which is the reality of a facility serving the population. the overlap between maintenance, upgrades and testing periods led to fluctuating data, e.g. in terms of the energy consumption and operating hours of devices, which were omitted from the analysis. the scenarios have been delineated following the technological shifts as follows: conventional operation: this configuration is described in detail in the previous section. the classical a2/o system serves as the baseline for comparing scenarios with a pre-treatment stage, two parallel biological treatment reactors and an anaerobic digestion phase. the impacts per 1 m3 of treated water in terms of the conventional operation are shown in appendix a. intensive flaring: in the context of this study, intensive flaring refers to introducing biogas flaring without implementing measures to minimize its quantity which happened in 2016. even though subsequent technological developments led to a more controlled approach to biogas flaring in order to achieve the maximum level of efficiency in terms of energy recovery, they were not considered in this study. chemical p removal: chemical p removal means that the biological processes were assisted with chemical means. the first two thirds of 2020 (january-august) was the last period when phosphorous removal was not achieved solely by microorganisms and thus serves as a comparison to the next stage. additionally, this scenario is linked to the optimal performance of the gas engine. biological p removal: starting from september 2020, the utilization of chemicals on the biological line was entirely discontinued. this scenario was named biological p removal which took place between july and december 2020. similarly to the previous scenario, the gas engine performance was optimal. solar energy: the solar energy scenario corresponds to the year 2021 when solar panels were installed to reduce the amount of electricity drawn from the grid, meanwhile, the rate of energy consumption increased. optimized effluent control: the final real-life scenario is characterized by the best effluent quality. regarding the timeline, this scenario is based on the year 2022, by which time operation of the previous modifications had already become established. furthermore, the proportion of green energy (biogas and solar) was augmented. ozonation quaternary treatment: as a hypothetical scenario, ozonation, a quaternary treatment solution, was added to the plant to facilitate further use of the treated water in alignment with prevailing development trends. sequential h2o2 quaternary treatment: as an alternative to ozonation treatment, a sequential h2o2 quaternary treatment was investigated. the method utilizes sunlight and h2o2 together with the solar photofenton process with ethylenediamine-n,n’-disuccinic acid (edds) at a neutral ph in a raceway pond reactor. according to [24], this method has reduced the environmental impact more than ozonation. data on the hungarian energy mix [25] were taken from the literature and other information was obtained from the sphera database [21] such as data regarding electricity from solar thermal energy, the components of the chemicals and the quality of the material flows. the recipe method [26] was chosen as a comparative analysis. the study by karolinczak et al. [27] was referred to in order to determine the impact data of biogas and the impacts of quaternary treatment were calculated based on the results published by maniakova et al. [24]. the system boundaries of all the scenarios are presented together in figure 1. although the functional unit was chosen to be 1 m3 of treated water to align with the prevailing literature, in certain instances the results are also presented in other forms, e.g. /kwh of biogas. lca of a wastewater treatment plant 53(2) pp. 17–30 (2025) 21 3. results 3.1. performance evaluation in terms of effluent the mean efficiency values of the wwtp over the whole examined period were 97.2%, 88.8% and 93.7% for cod, tn and tp, respectively, suggesting that the plant performed excellently even in the baseline "conventional operation" scenario (cod: 98.0%, tn: 87.6%, tp: 92.3%). the best performance was achieved in 2022 (96.6%, 90.5%, 95.7%). even though the cod removal rates gradually decreased from 98.0% to 96.6%, both tn and tp removal slightly improved during the examined time period. the changes in performance can be attributed partly to the interventions and partly to the influent nutrient ratios. the best removal efficiencies were achieved at cod:tn:tp ratios of approximately 100:10:1 which coincided with those at the end of the study period. although the literature suggests that the ratio of 100:5:1 is appropriate for municipal wastewater treatment [27], others have found that 100:11:2 is also suitable [28]. 3.2. performance evaluation in terms of life cycle aspect the scenarios are discussed in the same order listed in section 2.2. to illustrate changes in environmental impacts, a heat map chart was used. it should be noted that to interpret the data, a dual representation was applied in instances where the data series yielded negative values (figure 2). the upper triangle of the cells indicates the method employed for the other impacts. the negative gradient is denoted by red, while the positive one is indicated by green. the scattering of values above 100% and below -100% yielded a darker shade visible when the gradient was both positive and negative. in the cells, coloring is reversed for the lower triangle as a change from negative to positive represents a negative impact on the environment. 3.2.1. conventional operation the main material flows associated with the impacts per m3 of treated water are shown in appendix a together with the results from other scenarios. each indicator is highlighted in a specific color indicating the main drive within that impact category. since the majority of the impact categories (ten out of eighteen) are influenced by energy consumption, the substantial amount used by the biological reactors (first line 49.30% and second line 26.32%) was notable in the results from the conventional operation scenario (appendix b). the impacts related to the sludge line made up 3.92%, the receiving station 0.54% and the other energy-consuming activities of the plant accounted for the remaining 19.92%. biological treatment dominated the freshwater and marine eutrophication (feu, meu) indicators accounting for 46.92% of the first line and 53.09% of the second, figure 2: comparison of the scenarios against the conventional operation scenario in the upper triangle of the cells, a negative change is denoted in red while a positive one is indicated in green. the coloring is reversed for the lower triangle, as a change from negative to positive represents a negative impact on the environment (feu, meu). the scatter of values above 100% and below -100% are shown in a darker shade for both negative and positive changes. harasztiné hargitai, sebestyén, volf and somogyi hungarian journal of industry and chemistry 22 moreover, only 0.01% was related to other activities. in terms of indicator values, this equated to -2.46⋅10−3 kg p eq. and -1.45⋅10−2 kg n eq. per m3 in the conventional operation. in terms of the remaining six out of eighteen impact categories, the sludge line dictated the results with values between 98.74% and 100.00%: human toxicity potential cancer (htp𝑐) and non-cancer (htp𝑛𝑐), freshwater consumption (fc) and ecotoxicity (fec), marine ecotoxicity (mec) and metal depletion (md). the remaining less than 1.5 % was associated with the biological reactors. considering md and fc, the chemicals in the sludge (for p removal, foam control and sulfide removal) contributed 99.97% and 98.69%, while the activity of microorganisms was responsible for only 0.02% and 0.99% of the total values of the parameters, respectively. furthermore, the addition of chemicals did not have an effect on the other parameters. it should be noted that even though the amount of chemicals can be reduced, they are necessary to counteract the impacts of potential disturbances in terms of biology and essential with regard to sludge dewatering. the htp𝑛𝑐 indicator stands out among the indicators determined by the sludge characteristics with a value of 156.93 kg 1,4-db eq. per fu, due to the manner in which the dried sludge is disposed of. the elements in the sludge contributing to the indicator are 98% metallic with the remaining 2% comprising semi-metallic and non-metallic elements. 3.2.2. intensive flaring the main change in the second scenario compared to the first one was that 71.54% of the biogas was flared in an intensive manner due to uneven production and subsequent safety concerns. regarding the timeline, this scenario covers the year 2016 in its entirety. as a comparison, 0.54 m3 of biogas per 1 m3 of treated water was flared while in other years this value was between 0.01 and 0.06 m3 of gas/m3 of water. the energy consumption was 0.72 kwh per m3 of treated water, 59.32% of which was produced from the biogas and the remaining amount purchased from the electrical network. the impact of flaring can be observed across all impact types (figure 2). additionally, the annual wastewater flowrate increased by 1.85%, while the influent load between the two lines became more balanced with the first line receiving 50.86% and the second 48.28%. the influent c:n:p ratio changed from 100:8.29:1.21 to 100:7.31:1.26 which led to an increase in energy consumption, however, a reduction of 15.58% in chemical usage was observed. although the energy consumption of the receiving station reduced to 51.42% (from 0.0035 kwh to 0.0018 kwh per m3 of treated water), this was only associated with a reduction in the influence of the station on the impact categories from an average of 0.30% to 0.08%. six of the impact indicators that are determined by energy consumption (climate change (cc), fine particulate matter formation (fpmf), photochemical ozone formation on ecosystems (phof𝑒) and human health (phofℎℎ), stratospheric ozone formation (od), terrestrial ecotoxicity (tec)) resembled those from the conventional operation scenario. the waterline accounted for 65.40% while the sludge line accounted for 3.73%, moreover, 30.62% was due to other activities. despite the loss of biogas due to flaring, an average reduction of 17.04% per 1 m3 of treated water in the values of the aforementioned parameters was consistent with the change in energy sources. while the energy consumption increased by 11.54%, the proportion of utilized biogas also increased from 45.30% (0.29 kwh/m3 of treated water) to 59.32% (0.43 kwh/m3 of treated water). in the intensive flaring scenario, the two indicators concerning eutrophication reflected the change in the biological load. even though the meu value decreased by 5.14%, it remained within the favorable range. the feu value shifted from within the negative range (favorable condition) to the positive range (unfavorable condition) compared to the previous range of -2.46⋅10−3 kg p eq. to 2.18⋅10−3 kg p eq. per 1 m3 of treated water. a shift in both the manner by and extent to which technological categories dominated certain impact indicators was observed. the heavy impact of sludge management on htp𝑛𝑐, mec and md remained the same while flaring gained a substantial level of influence in htp𝑐, fc and fec accounting for 94.44 to 99.47%. regarding fc, intensive flaring even masked the positive effect of reduced chemical usage which defined 98.69% of the fc category in the conventional treatment scenario, whereas in the intensive flaring scenario, the share of the chemical dosing effects reduced to 0.52%. as a result, fc increased from 0.05 to 7.36 m3 per fu. the introduction of biogas flaring led to a change in the composition of four additional impact categories: fossil depletion (fd), ionizing radiation (ir), land use (lu) and terrestrial acidification (ta). the share of flaring ranged from 97.0% (ir) to 109.0% (lu) compared to their overall values. percentages over 100 were associated with the offset effect of the biological line: -2.72% for fd and -5.91% for lu. the most prominent change was experienced in the case of ta from 1.25⋅10−4 kg so2 eq. to 37.33 kg so2 eq. per fu. 3.2.3. minimizing the amount of chemicals used for biological treatment phosphorus was removed by both biological and chemical means during the earlier periods. however, in 2020, the management decided to eliminate chemicals from the process. this process can be divided into two phases. during the initial period, which spanned the first eight months of the year, a gradual reduction in chemical phosphorous removal was observed and was named the chemical p removal scenario for the sake of simplicity. in contrast, the second half was characterized by the full implementation of biological phosphorous removal and named as the biological p removal scenario. the performance of both scenarios was primarily determined by a reduction in the value of flared biogas from 0.54 to 0.06 m3 per 1 m3 of treated water, which represented a decline of nearly 90%. energy consumption increased from 0.72 to 0.85 kwh during the lca of a wastewater treatment plant 53(2) pp. 17–30 (2025) 23 chemical p removal scenario and returned to 0.72 kwh in the biological p removal scenario. the self-produced energy ratios were 57.28 and 56.37%, respectively. furthermore, a change in aeration was observed, namely an increase to 122.45 m3 during the chemical p removal scenario from 98.58 m3 in the intensive flaring scenario before declining to 70.68 m3 during the biological p removal scenario. the relationship between aeration and energy consumption was evident with the waterline accounting for approximately 92.65 to 98.74% of the total volume. a gradual reduction in the chemicals used led to a continuous and simultaneous increase in energy consumption and biological respiration. this transition can be considered gradual with biological adaptation occurring in a similar manner. both p removal scenarios were distinguished by sludge swelling, the dominance of filamentous organisms and poor settling. in mid-february, the nutrient composition of the wastewater was 100:3.9:1, caused by a cod concentration of 2,042 mg/l. in mid-june, the ratio shifted to 100:4.3:0.8 with a cod concentration of 1,548 mg/l. by mid-july, it had decreased to 100:3.5:1.4, with a cod concentration of 1,179 mg/l. in light of the imbalance between cod and nitrogen, it is understandable that organisms reacted to the situation in terms of filamentation along with increased energy consumption as the proportional increase in oxygen concentration, in conjunction with an increase in organic matter, serves to prevent the proliferation of filamentous organisms [29]. the quantity of chemicals utilized for the sludge treatment increased by approximately 50% compared to the conventional operation scenario, which is closely related to sludge swelling due to the extracellular polymeric substances (eps) produced by filamentous microorganisms [30]. despite the aforementioned operational challenges, both the chemical p removal and biological p removal scenarios performed better when compared to the intensive flaring scenario as can be seen in figure 2. moreover, the indicators that exhibited a significant increase due to flaring (fc, fec, htp𝑐, ir and ta) decreased by 82-89%. however, the increase in electricity consumption at the beginning of the year resulted in a 23% increase in the energy-related impacts (cc, fpmf, phof𝑒, phofℎℎ, od, tec) which translated to 2.21% higher values compared to the conventional operation scenario. the indicators related to eutrophication improved due to the higher removal efficiency during this period (90% n and 94% p), which was approximately 2% better than in the conventional operation scenario. a slight difference between the two p removal scenarios was observed due to the change in flow rates with feu and meu decreasing by 2.19 and 1.26% in the biological p removal scenario, respectively. nevertheless, it is also worthwhile contrasting between the two scenarios in terms of technological advancements. the blowers operated for 43.31% fewer hours per day during the biological p removal scenario, resulting in a 42.47% reduction in energy consumption. consequently, this led to a 12.91% decrease in the effects influenced by energy (cc, fpmf, fec, phof𝑒, phofℎℎ, od, tec). additionally, a 26.20% reduction in the amount of chemicals used in the sludge line was observed during the biological p removal scenario. moreover, the 32.14% reduction in biogas flaring contributed to mitigation of the effects. furthermore, the reduction in the amount of chemicals used for phosphorous removal resulted in a 26.15% decrease in the value of md. for the impacts affected by biogas flaring, a reduction in the impact value was observed, ranging from 28.41 to 51.24%. in the case of mec and htp𝑛𝑐, the impacts are still determined by the sludge treatment. between the two scenarios, a decrease of 14.03 and 14.11%, respectively, was observed, although the former showed a 30% increase compared to the intensive flaring scenario. this can be attributed to the quantity of treated sludge initially increasing from 1.91 to 2.66 kg before subsequently decreasing to 2.29 kg per 1 m3 of treated water. 3.2.4. solar energy as a supplementary energy source, solar panels were installed producing 0.06 kwh energy per m3 of treated water. while the amount of energy generated was lower than the 0.42 kwh generated by gas engines from biogas per fu, it accounted for 7.75% of the total energy consumption during the sunny periods as opposed to 4.13% over the entire year. in the conventional operation scenario, 54.70% of the energy consumed was purchased from the electrical network, which was gradually reduced. during the solar energy scenario (15th june to 31st december 2021), the percentage remained at 39.09% compared to as high as 46.62% over the entire year due to gas engine failures. the failures were offset for by the purchase of electricity. the compositions of the energy consumption in the different scenarios (appendix c, left) as an indication of the fraction of purchased electricity during 2020 and 2021 (when the different scenarios did not cover the whole year) are indicated in red in appendix c. on the right-hand side, the amount of energy generated and purchased daily is shown with the flared biogas given as negative values. although the energy output of gas engines gradually increased over time, the total energy consumption at the plant fluctuated according to technological shifts. the highest energy consumption in total and per m3 of treated water was the highest registered in the chemical p removal scenario while the lowest values were observed in the conventional operational stage. although introducing solar energy did not result in a massive reduction in the amount of energy consumed (0.8 kwh/m3), 129 mwh was saved during this period. on the other hand, solar energy exhibits seasonal variations which must be considered a factor in the operation. it is possible to mitigate the impact of reduced solar irradiation by increasing the amount of energy generated from biogas during critical periods. additionally, the quantity of flared biogas was reduced to 0.02 kwh per m3 of treated water. despite the occurrence of malfunctions in the gas engine, the amount of biogas energy utilized increased by 3.91%. harasztiné hargitai, sebestyén, volf and somogyi hungarian journal of industry and chemistry 24 in the solar energy scenario, the use of chemicals for sludge thickening increased by 20.88% compared to during the previous year, resulting in a deterioration of 21.31% in md, corresponding to an increase of 0.54 to 0.65 kg cu eq. per 1 fu. although the added dewatering agent contributes to a higher environmental impact associated with chemical usage, the reduced moisture content of the sludge leads to lower transportation costs and emissions. on the other hand, the environmental impact was mitigated in most of the indicator categories, achieving the best results among the scenarios with investments, attributing to the combined effects of reduced flaring, the adoption of solar energy and the increased proportion of biogas energy utilized. the degree of aeration increased by 52.65% per cubic meter of treated water, whereas the energy consumption increased by only 10.19%. the first biological line accounts for 69.77% of electricity consumption, while the second for 28.96%. the use of solar energy contributes, on average, 1.17% of energy consumed by all impacts but 7.75% of the total energy used. among the effects closely related to energy, od is influenced the least by the new energy source, that is, by up to 0.73%. the results indicate that tec increased by 4.75%, fpmf by 1.71%, phof𝑒 by 0.95% and phofℎℎ by 0.94%. the influence of the technological units within the individual categories of impacts is comparable to that presented in the intensive flaring scenario with two exceptions: the value of lu increased 2.6-fold due to solar panels, while ir reduced by half because of the lower flaring rate. the values were 0.01 annual crop eq.·y and 0.01 kbq co-60 eq. to air per 1 fu, respectively. opposing trends could be perceived with regard to the two indicators influenced by the biological processes. due to the changes in the hydraulic and nutrient load, feu increased from -4.00⋅10−3 to 4.02⋅10−4 kg p eq./fu while meu improved by 1.86% (from -1.76⋅10−2 to 1.80⋅10−2 kg n eq./fu). in comparison to the biological p removal scenario, the daily volume of influent decreased by 1,071 m3/day resulting in a 2.31% drop in the influent-effluent ratio (from 1.20 to 1.17 m3 of wastewater / m3 of treated water). altogether the pollution mass flow rate was reduced by 7% and due to optimization, the effluent mass flow rate decreased by 12%. 3.2.5. optimized effluent control at the beginning of 2022, the optimization efforts were twofold. the share of purchased energy was reduced from 39.09 to 31.16%, corresponding to a decrease from 0.31 kwh/m3 of treated water to 0.25 kwh/m3 of treated water compared to in the previous scenario. this improvement could be achieved although the amount of electricity consumed increased compared to other scenarios. solar panels supplied 7.14% of the total annual energy consumption (6.78% on average over the year) and energy generated from biogas increased by 15.30% even though the amount of the flared biogas tripled during this time period, reaching 0.03 kwh/m3 of treated water. simultaneously, the nutrient composition of the wastewater was nearly ideal (100:10.07:1.08), enhancing the nutrient removal efficiency in the biological train. this manifested in the highest phosphorous removal rate without added chemicals: between the conventional operation scenario and the optimized control phase, the total phosphorous content of the treated water decreased from 0.93 to 0.46 mg/l, achieving a 96.33% removal rate as opposed to the initial 93.38%. the nitrogen removal efficiency also improved, rising from 87.66 to 90.53% and reducing the total nitrogen content of the effluent from 10.28 to 7.87 mg/l. these efficiency gains were outstanding, particularly when compared to the discharge limit values of 4 mg/l for total phosphorus and 20 mg/l for total nitrogen as shown in figure 1. however, since the increased efficiency was due to the optimal ratio of food to biomass, the sludge yield was also higher, which led to some drawbacks. despite replacing the membranes in the aeration system, which were supposed to reduce the energy consumption, the higher sludge yield resulted in a 2.35% increase in energy consumed for aeration contrary to the fact that the number of daily operating hours of the blowers was reduced by 4.66%. additionally, 24.13% more chemicals were used for sludge thickening compared to in the solar energy scenario and 10.38% more dried sludge produced from the sludge treatment line per fu. the impacts related to energy savings (cc, fpmf, phof𝑒, phofℎℎ, od, tec) yielded an average saving of 20.50%. however, the increase in flaring resulted in between 60.21 and 182.78% higher values for fc, htp𝑐, ir and ta. nonetheless, the fd value decreased by 182.76%, indicating a positive effect of purchasing less energy from the grid. considering the indicators related to the quality of the effluent water, a 2.66% rise in the value of meu was observed compared to the solar energy scenario due to the opposing effect of a slightly improved nitrogen removal efficiency and an increase in the amount of dissolved solids by 4.87%. however, the value of feu decreased by a factor of 2.7, indicating that 0.011 kg p eq. was saved for every m3 of treated water due to the reduction in the emitted phosphorous content by 41.44%. the impacts related to the sludge treatment line increased in value when compared to the solar energy scenario. the md value rose by 23.96% due to increased chemical usage. in the case of fec, which grew by 49.20%, biogas flaring accounted for 42.69% of the impact. however, the values of htp𝑛𝑐 and mec were determined solely by the dried sludge, so the 10.43% increase in the impacts equates to 1 m3 of treated water, resulting in a 10.38% rise in quantity. 3.3. impact of the introduction of quaternary treatment while the examined wastewater treatment plant was not required to disinfect its effluent before being discharged, this might change in the future when different usage options will have to be considered. the potential introduction of quaternary treatment to meet legislative lca of a wastewater treatment plant 53(2) pp. 17–30 (2025) 25 requirements was examined [1] using information published by maniakova et al. [24] on the processes: ozonation (o3) and sequential h2o2 treatment (st). the chosen solutions were shown to remove organic micropollutants besides disinfecting the effluent. utilization, which would require the consideration of further infrastructure, was beyond the scope of the current study. however, quaternary treatment of some sort would be a prerequisite for further usage of treated water. two main aspects of the proposed processes were considered: energy consumption and chemical dosage. for the treatment plant under consideration, the impact of 1 kwh of local energy used, the chemical impact of the disinfection experiment referenced and the energy demand of the equipment were used to calculate the impact of quaternary treatment. the energy consumption of ozonation was taken to be 0.42 kwh/m3 and because the st was solar driven, the energy increment was three degrees of magnitude less (3⋅10−4 kwh/m3). to ensure continuity over time, the technological properties of the last scenario (optimized effluent control) were used as an input in the quaternary treatment scenarios. the resulting impacts were also plotted in the form of a heat map chart to compare the two options for disinfection with the current level of technological development (figure 2). 3.3.1. ozonation quaternary treatment the introduction of the disinfection step increased the environmental burden of the wastewater treatment plant across multiple indicators, consistent with the findings of maniakova et al. [24] (see appendix a), with twelve of the eighteen indicators showing the highest values. exceptions included fc, fec, htpnc, ir, mec and ta; however, even in these cases, the values for ozonation exceeded the optimized effluent control scenario. the largest increment was observed in ozone depletion (od), which rose by five orders of magnitude compared to the preceding scenario (3.82·10−3 kg cfc-11 eq. per fu). small increases of less than 1% compared to the optimized effluent control scenario were noted for htpnc, ta and mec in ascending order. the higher energy consumption associated with the new processes naturally had a detrimental effect on energy-related indicators, albeit to varying extents. although tec nearly doubled (91.22%), it remained low (0.04 kg 1,4 db eq./m3 of treated water). however, many indicators previously heavily influenced by energy usage became more strongly influenced by chemical consumption during quaternary treatment. these indicators were cc, fpmf, lu, phofe, phofhh and od. the most particular concern was the increased impact caused by chemical usage in the ozonation process compared to the optimized effluent control scenario. in terms of ozonation, the increases were 21 times higher for cc, 107 times higher for htpc, 124 times higher for fpmf and 9,323 times higher for phofℎℎ. additionally, land usage increased to 0.13 annual crop eq.·y per m3 of treated water. another consequence of ozonation was the loss of the benefits of freshwater eutrophication achieved by the earlier technical interventions with values reaching 0.48 kg p eq. per fu. this number is in line with the value in the biological p removal scenario. a few of the indicators remained in the same category in terms of their primary influencing factors. freshwater and marine ecotoxicity were both governed by sludge treatment and exhibited only modest increases. freshwater consumption, ionizing radiation and terrestrial acidification were all primarily determined by the amount of flared biogas. ir increased by 15.92% compared to the optimized effluent control scenario but accounted for only 8.55% of the value observed during the introduction of flaring. metal depletion changed only by 13.84% and was mainly influenced by the chemicals used for sludge dewatering. 3.3.2. sequential h2o2 quaternary treatment the sequential h2o2 treatment exhibited only moderate increases in environmental burdens as opposed to ozonation. notably, none of the indicators yielded maximum values relative to the other scenarios. regarding governing processes, the primary influences across most categories remained similar to those observed in the other quaternary treatment. an exception was mec where the effects were governed by the biological processes, as in other scenarios, whereby an environmental benefit continued to be evident. while od was still substantially higher than in the optimized effluent control scenario, the impact was only 16% of that observed with regard to ozonation. fd decreased due to the use of renewable energy but remained within the positive range, indicative of environmental costs along with feu. human health impacts were 1.8 times higher for cc, 23 times higher for htp𝑐 and 1.8 times higher for phofℎℎ compared to the optimized effluent control scenario. the sequential treatment also retained some benefits present when implementing previous technical interventions. tec increased by only 2.85% while the impact of ionizing radiation rose marginally, namely by just 0.01%, compared to the optimized effluent control scenario. this figure represented 7.37% of the ir values observed when flaring was introduced, indicating minimal environmental concerns. regarding other indicators, negligible increases were observed for fec, htpnc, mec and ta. given these results, the sequential h2o2 treatment appears to be a more viable option due to its less significant environmental impacts overall. this method may also have long-term impacts, particularly if wastewater reuse, e.g. for irrigation, becomes feasible. 4. discussion biogas optimization played a pivotal role in mitigating the environmental impacts of the wastewater treatment plant. in the conventional operation scenario, 1.35 kwh/m3 of biogas was produced, which increased to 1.98 kwh/m3 in the intensive flaring scenario. however, 71.54% of the biogas was flared due to uneven harasztiné hargitai, sebestyén, volf and somogyi hungarian journal of industry and chemistry 26 production, suggesting a potential for additional energy recovery. other wwtps have achieved biogas yields of 6.0 [31] or even 6.5 kwh/m3 [32], demonstrating the feasibility of increased energy production. achieving this would require expanding biogas storage capacity and incentives to feed excess electricity into the mains electricity network. in the long term, the digester efficiency can be improved by the co-digestion of industrial and agricultural waste [33]. incorporating food waste, manure and grease trap sludge into biogas production enhances methane extraction [34], facilitating the goal of energy neutrality and reducing its environmental footprint [35]. in terms of energy efficiency, the total energy consumption of the plant was 0.72 kwh per m3 of treated water on average with 59.32% of this energy being selfgenerated. for the sake of comparison, secondary treatment consumes between 0.272 to 1.27 kwh/m3 of treated water [36] depending on factors such as the size, age and location of the facility as well as the climate. these findings, combined with the fact that 13 impact categories were affected by flaring due to imbalanced biogas production and utilization, underscore the potential for environmental savings and energy neutrality simultaneously. however, variations in biogas production highlighted the need for improved storage solutions and the proactive maintenance of biogas engines. regulating the quality of the feedwater is also critical to ensure a more consistent output and improved energy portfolio. despite advancements in biogas production, energy-related trade-offs have persisted. the introduction of solar energy while reducing grid dependency highlighted the importance of taking into account seasonal variations. nevertheless, increasing solar energy production may assist in achieving energy neutrality [37], though decarbonizing energy production on a national level would yield the greatest life-cycle benefits [38]. until that happens, the importance of balancing renewable and biogas-based energy sources during critical operational periods is crucial to achieve an optimal operation. environmental trade-offs were also expected. technological advancements in terms of nutrient removal improved effluent quality but at the cost of increased sludge production and higher chemical consumption during dewatering. improved effluent quality can also ramp up energy consumption as noted in [39]. similar issues arose when phasing out chemicals for phosphorous removal along with suboptimal nutrient ratios, resulting in increased aeration demand due to the appearance of filamentous microorganisms. these bacteria tend to reduce the oxygen transfer efficiency by up to 50% [40]. future quaternary treatment requirements will introduce further compromises in terms of effluent quality, energy requirements and overall environmental impacts. in the near future, wastewater treatment plants above 100,000 pe will have to monitor antimicrobial resistance and by the year 2045, wwtps above 10,000 pe in areas at risk will have to implement quaternary treatment solutions [1]. ozonation has proven to remove 90% of micropollutants [41] and further mitigate chemical oxygen demand by 16–71% [42]. however, its environmental feasibility is limited due to the impacts of high chemical usage and ozone depletion. the level of removal efficiency can be modified by the level of ozone production at the expense of energy consumption [43]. great degrees of pollutant removal and thus reduced toxicity could be achieved at the cost of greenhouse gas emissions. on the other hand, sequential h2o2 treatment exhibited relatively lower environmental costs, comparable to some of the other real-world scenarios. its application still resulted in trade-offs such as increased terrestrial ecotoxicity. it has to be stated that the current model did not consider micropollutants in the life cycle inventory, therefore, ecotoxicity values might differ from current calculations. future implementations must carefully weigh up the aforementioned trade-offs to achieve long-term sustainability. water-saving measures could significantly shift priorities [44]. with increasing water scarcity even in europe, benefits arising from the utilization of treated water for non-potable purposes may outweigh other environmental impacts [45]. an earlier study [46] found that reclaiming 1 m3 of treated water can save 0.8 m3 of freshwater. although quaternary treatments may increase environmental impacts, carefully selected methods remain viable for addressing antibiotic-resistant microorganisms and micropollutants. with regard to the reuse of treated water for irrigation purposes, which is currently supported, it is important that crops intended for human consumption are free of these types of contaminants. 5. conclusions this study delivered a comprehensive lca of technological advancements implemented at a hungarian municipal wwtp over a seven-year-long period. the management of the wwtp sought to improve effluent water quality in a cost-effective manner, including a reduction in chemical consumption and an increase of renewable energy generation at the plant. by incorporating real operational data, the authors evaluated the environmental impacts of transitions to renewable energy, improved nutrient removal processes and hypothetical quaternary treatments. the novelty of this work lies in its integration of real-time operational scenarios with standardized lca methodologies to address trade-offs between energy consumption, effluent quality and environmental burdens. the key findings indicate that transitioning to biological phosphorus removal and optimizing biogas utilization can significantly reduce chemical dependency as well as greenhouse gas emissions, however, these benefits are offset by increased energy demands. similarly, while solar energy integration showed promise, seasonal limitations underscore the need for complementary energy solutions. the study lca of a wastewater treatment plant 53(2) pp. 17–30 (2025) 27 demonstrated that achieving low environmental impacts requires balancing technological upgrades with operational efficiency. quaternary treatments, though necessary for future wastewater reuse, present notable environmental trade-offs requiring the careful selection of technologies such as sequential h2o2 treatment to mitigate impacts. future technological advancements will necessitate assessing the long-term impacts of effluent reuse, particularly in relation to emerging pollutants such as microplastics and pharmaceuticals. the insights from the analysis highlight the importance of using lca to guide decision-making in wwtp operations, ensuring that technological upgrades align with both environmental and regulatory goals. this work provides a framework for wwtp operators and policymakers to evaluate sustainable solutions that balance operational efficiency with long-term environmental performance. symbols bod5 biological oxygen demand cc climate change cod chemical oxygen demand edds ethylenediamine-n,n′-disuccinic acid eps extracellular polymeric substances fc freshwater consumption fd fossil depletion fec freshwater ecotoxicity feu freshwater eutrophication fpmf fine particulate matter formation htpc human toxicity potential, cancer htpnc human toxicity potential, non-cancer ir ionising radiation lca life cycle assessment lu land use mec marine ecotoxicity meu marine eutrophication md metal depletion od stratospheric ozone formation phofe photochemical ozone formation, ecosystems phofhh photochemical ozone formation, human health ta terrestrial acidification tec terrestrial ecotoxicity tkn total kjeldahl nitrogen tn total nitrogen tp total phosphorous tss total suspended solids wwtp wastewater treatment plant acknowledgements the research presented in this article was carried out within the framework of the széchenyi plan plus program with the support of the rrf 2.3.1-21-202200008 project. references [1] european parliament. directive (eu) 2024/3019 of the european parliament and of the council of 27 november 2024 concerning urban wastewater treatment (recast), 2024 https://eur-lex.europa.eu/eli/dir/2024/3019/oj/eng (retrieved 22 january 2025) [2] meng, x; huang, z.; ge, g.: upgrade and reconstruction of biological processes in municipal wastewater treatment plants, desalin. water treat., 2024, 317, 100299, doi: 10.1016/j.dwt.2024.100299 [3] 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https://doi.org/10.1016/j.scitotenv.2012.07.084 https://doi.org/10.1016/j.jenvman.2013.08.018 https://doi.org/10.1016/j.jclepro.2016.07.209 harasztiné hargitai, sebestyén, volf and somogyi hungarian journal of industry and chemistry 30 appendix a: the results of the scenarios for the discharge of 1 m3 of treated water each result is highlighted by the color assigned to technological elements with the highest influence appendix b: the composition of the plant units for each impact category for the conventional operation case of the analysed wastewater treatment plant. the impact categories with a similar composition are summarised in the figure on the left-hand side. in the corresponding table on the right-hand side, the percentage differences are indicated by minimum and maximum values. the indicators are categorised by energy (cc, fpmf, fd, ir, lu, phof𝑒, phofℎℎ, od, ta, tec), sludge (htp𝑐, htp𝑛𝑐, fec, mec), chemicals for sludge (fc, md) and microorganisms (feu, meu) appendix c: the composition of energy use in each case is illustrated on the left-hand side (a), while the composition of energy use after the implementation of the solar panels is illustrated on the right-hand side (b). it should be noted that the amount of flared biogas, which is represented by the negative value in the diagram, could have reduced the amount of electricity purchased if it had been used hungarian journal of industry and chemistry vol. 47(2) pp. 1–83 (2019) hjic.mk.uni-pannon.hu contents investigations into succinic acid fermentation áron németh 1–4 production of the enzyme cyclodextrin glycosyltransferase using different fermentation techniques réka czinkóczky and áron németh 5–10 analysis of crude oil in terms of fouling and corrosion richárd katona, roland lócskai, gergő bátor, antal krójer, and tibor kovács 11–15 immobilization of laccase in alginate beads béla varga, mónika meiczinger, and viola somogyi 17–23 multistage gravity beneficiation of rutile in a tar-free sand residue rukayat akande and abraham adeleke 25–30 gpu-accelerated simulation of a rotary valve by the discrete element method balázs füvesi and zsolt ulbert 31–42 residence time distribution-based analysis of an industrial-scale biogas fermenter andrás tankovics, dávid takács, judit szendefy, béla csukás, and mónika varga 43–51 programmable process structure based analysis of hydrogen supply chains mónika varga, catherine azzaro-pantel, josé manuel flores-perez, and béla csukás 53–61 investigation of mixing in tanks of a special geometry bálint levente tarcsay, attila egedy, janka bobek, and dóra rippel-pethő 63–70 assessment of the ecotoxicity of nanoplastics nóra kováts, bettina eck-varanka, zsófia békéssy, dorina diósi, katalin hubai, and jános korponai 71–75 biocomponent-based quality improvement opportunities of binders for road construction gréta tálosi, péter gergó, and andrás holló 77–83 hungarian journal of industry and chemistry vol. 47(2) pp. 1–4 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-13 investigations into succinic acid fermentation áron németh *1 1department of applied biotechnology and food science, budapest university of technology and economics, műegyetem rkp. 3, budapest, 1111, hungary succinic acid (sa) is an important chemical intermediate from which fine chemicals ( e.g. detergents), additives (for pharmaceuticals, food (taste), plant growth stimulants) as well as other important intermediates (maleic anhydride, succinimide, 2-pyrrolidinone, dimethyl succinate) can be manufactured. since sa is involved in the central metabolism of cells (in the tricarboxylic acid (tca) cycle), it is a key player in the biochemistry of life, which has the potential of biotechnological production. since sa is formed in the “middle” of the tca cycle it can be formed by both co2 production and fixation. the significance of the latter is that the amount of the product can be controlled by the availability of co2, since stoichiometrically one molecule of co2 is fixed by one molecule of sa. in our studies of compositions of actinobacillus succinogenes media, the role and effect of ph regulator compounds as well as the effect of an inert atmosphere were investigated in terms of the yield. furthermore, in fermentation experiments, the application of higher sugar concentrations was also studied. on the basis of different fermentations, a neural network for modelling and describing how factors influence sa production was established. keywords: succinic acid, actinobacillus succinogenes, neural network, modelling 1. introduction succinic acid (sa), as an intermediate of the tricarboxylic acid (tca) cycle, plays an essential role in the metabolism of microorganisms. sa can be produced by many anaerobes or facultative anaerobes as a metabolic product, thus can be used as an important platform chemical, a precursor of many pharmaceuticals, feed additives, green solvents or biodegradable polymers. sa itself is a colourless, odourless and crystal-forming compound. since this metabolite is bifunctional (pka1 = 4.21, pka2 = 5.72 [1]), it is very reactive so has many potential applications, e.g. it plays important roles in the synthesis of γ-butyrolactone, maleic anhydryde, succinimide, 1,4butanediol, dimethyl succinate, succinonitrile and 1,4diaminobutane. it is industrially produced, mainly synthetically, in a complex way from maleic anhydride found in crude oil, which is both economically and environmentally unfavourable [2]. therefore, its biotechnological production is a current research topic to find an alternative method to avoid the above-mentioned side effects [3]. furthermore, a great advantage of the microbial production of sa is that one of the initial biochemical reactions is the carboxylation of phosphoenolpyruvate [4] which is regulated in the case of anaerobic bacteria by the availability of co2 [2], thus the elevation of the co2 concentration can shift product portfolio from formate and ethanol towards sa (fig. 1). *correspondence: naron@f-labor.mkt.bme.hu despite this fact, the process can help to decrease the co2 emissions of the human population [5]. both fungi and bacteria can be found among the saproducing microorganisms, but their ability to produce sa differs significantly: fungi ∼45 g/l (aspergillus niger, rec. yarrowia lipolytica), gram-negative bacteria (wild-type actinobacillus succinogenes 98.7 g/l, mannheimia succiniciproducens 90 g/l) and grampositive bacteria (clostridium thermosuccinogenes 82.5 g/l, rec. corynebacterium glutamicum 145 g/l) [5]. the most frequently applied strains in the industry are aspergillus niger, aspergillus fumigatus, byssochlamys nivea, lentinus degener, paecilomyces variotii, penicillium viniferum, saccharomyces cerevisiae and actinobacillus succinogenes [4]. the latter bacterium is one of the most prominent producer strains that is isolated from bovine rumen and has been identified as a member of the genus pasteurella, which is a facultative anaerobic, non-motile, gram-negative pleomorphic, rod-shaped bacterium [2]. it has great potential in terms of sa production, because of its higher yield and wide range of applicable substrates, e.g. glucose, cellobiose, maltose, lactose, saccharose, fructose and sorbitol. furthermore, it can tolerate high initial concentrations of glucose, therefore, is suitable for simple batch fermentation instead of the more complex and costly fed-batch culture technique [5]. the most widely applied strains are actinobacillus succinohttps://doi.org/10.33927/hjic-2019-13 mailto:naron@f-labor.mkt.bme.hu 2 németh figure 1: sa metabolism with co2 regulation genes 130z and its variants (fz6, 9, 21, 45 and 53) [2], which can tolerate both high glucose and sa concentrations as well as achieve high sa yields [5]. the aim of this paper is to compare fermentations of actinobacillus succinogenes under different experimental conditions, then – due to the many influential factors – to set up a neural network-based model which can be used to predict high sa titres. 2. materials and methods 2.1 cultivation of the bacteria actinobacillus succinogenes 130z (dsm22257) was cultivated in 10 ml of tryptic soy broth (tsb) (sigma) in an impedimetric bactrac 4100 (sy-lab, austria) anaerobic cell. for a 1 l fermentation with a working volume of 0.8 l, an as medium was applied according to liu et al. [5] as follows: 62.5 g/l total sugar including 44.9 g/l saccharose, 9.8 g/l glucose and 7.2 g/l fructose supplemented with 15 g/l yeast extract, 1.5 g/l nahpo4, 1g/l na2hpo4, 1 g/l nacl, 0.2 g/l mgcl2 and 0.2 g/l cacl2. during preliminary tests, a temperature of 37◦c was not successful for sa production, therefore, 34◦c was applied and the ph regulated by 3m na2co3. after each fermentation, 200 ml of broth remained in the reactor and 600 ml was extracted, while 600 ml of fresh as media was introduced. the 5 different fermentations are compared in the results section. an innovative solution was to apply a co2 economical gas supply through the oxygen enrichment system of a biostat q dcu3 fermentor system in the absence of air and oxygen. the gas mix oxygen enrichment regulator was set at 4 %, therefore, periodically a small amount of co2 was introduced into the fermentation broth. 2.2 analysis during fermentations, samples were taken periodically and the optical density (od) determined by a spectrophotometer (ultrospec plus, pharmacia lkb) at a wavelength of 600 nm (od600) against the supernatant of a centrifuged sample by applying the same dilution factor (5×) as in the case of the samples. the cell dry weight (cdw) was obtained by a multiplication factor of 2 from od600. substrate consumption and product as well as by-product formation were detected by the waters breeze hplc system by applying 5 mm h2so4 in deionized water at a flow rate of 0.5 ml/min through a biorad aminex hpx87h column at 65◦c in a refractive index (ri) detector at 40◦c. 2.3 neural networking for model building and evaluation, neural designer v2.9.5 was used by applying the following 4 steps: 1. fermentation data were combined into a single ms excel spreadsheet and exported to a tab-delimited text file, which could be imported into the modelling software. 9 variables, i.e. 7 inputs (time, lactic acid, acetic acid, propionic acid, glycerol, ethanol, total sugar) and 2 outputs (succinic acid, cdw), were applied to 58 fermentation samples from which 36 were used for training the network, 11 were selected and 11 were used for testing the behaviour of the model. 2. from among the many options, a model was defined (fig. 2) by automatic scaling, without any principle component, with 2 layers and 3 neurons/hidden layers that exhibit a logistic activation function in the absence of a bounding layer. in terms of a training strategy, the normalized mean squared error method was selected using a quasi-newton algorithm and a maximum of 1000 iterations. incremental order was chosen as the order selection algorithm together with the growing inputs. 3. model fit, i.e. performance training, was conducted. 4. output of the model: impact figures of factors were determined (the other parameters were fixed), model equations obtained and predictions made by implementing input data into an input data matrix. 3. results and discussion since actinobacillus succinogenes is a facultative anaerobic microorganism, the first fermentation experiment (fig. 3a) was started in the absence of any specific atmosphere. however, it ran very slowly, therefore, around 48 h (denoted by a red arrow) of continuous 5 % co2 enrichment was applied via a zero flow rate gas inlet. the experiment confirmed that the application of co2 is essential to form sa, therefore, finally 6 g/l sa was achieved and the model fitted very well for both cdw and sa measurements. hungarian journal of industry and chemistry investigations into succinic acid fermentation 3 figure 2: the used neural network for describing sa fermentations therefore, the next fermentation (fig. 3b) was conducted under 5 % co2 enrichment of zero flow rate gas inlet and resulted in the highest 16 g/l sa (besides 11 g/l residual sugar) corresponding to a yield of 37 %. to increase the economic feasibility, the amount of co2 was reduced by 50 % to 2.5 % in the following experiment (fig. 3c). to avoid a fall in the sa concentration, detected by-products (such as lactic acid 3.5 g/l, acetic acid 5.7 g/l, propionic acid 1.7 g/l and glycerol 1.3 g/l) should be repelled as a result of the addition of 20 g/l calcium lactate. the model once again fitted well to the measured cdw and sa values. unfortunately, the carbon flux shifted towards propionic acid formation, therefore, the subsequent experiment (fig. 3d) was both supplemented with 20 g/l lactic acid and 11 g/l propionic acid, but this resulted in a low level of sa and a high level of lactic acid (52 g/l). the model yet again fitted well to the measured csw and sa values. independent fermentation results were also checked by the model (fig. 3e) and resulted in very good fits. it can be concluded that the artificial neural network model constructed described well the sa fermentations, which is in line with the results of li et al. [7], namely that artificial neural network models can describe succinic acid fermentation better than response surface methodology. the presented results revealed that for sa fermentation, 5% co2 enrichment is essential and cannot be fully or partially replaced with the addition of lactic acid or propionic acid. after validating the model by conducting 5 different fermentations, it was used to optimize influential factors via impact figures (directional output plots) (fig. 4). these trends show that all the presented factors correlate with sa concentration, i.e. any increment in their amounts resulted in an increment in sa, with the exception of propionic acid which exhibited a negative correlation. these suggest that the addition of propionic acid can decrease the concentration of sa obtained and the addition of lactic acid can increase it. (a) (b) (c) (d) (e) figure 3: actinobacillus succinogenes fermentations with different degrees of co2 enrichment in combination with lactic acid (la) and propionic acid (pa). dots indicate the measured values and lines indicate the model prediction. 47(2) pp. 1–4 (2019) 4 németh figure 4: factors impact plots: proh – propionic acid (g/l), total sugar (g/l), la – lactic acid (g/l) and co2 – carbon dioxide (%) 4. conclusion five actinobacillus succinogenes fermentations were run under different conditions: semi-anaerobic method, controlled introduction of co2, and introduction of co2 combined with either the addition of lactic acid or both lactic acid and propionic acid. all together 58 samples were taken and analysed, the results of which were entered into neural designer modelling software and used for training and testing the model. while the fermentations resulted in very different final sa concentrations, the established model fitted well to all of the fermentations, even to the one which was not used for model building, testing and validation. while economical co2 enrichment was successfully applied and resulted in the highest sa yield (37 %), the addition of lactic acid and propionic acid was not successful in terms of sa concentration. acknowledgement this research was conducted within the framework of and in cooperation with progressio engineering bureau ltd., mél biotech k+f kft. and budapest university of technology and economics. references [1] tonova, k.: state-of-the-art recovery of fermentative organic acids by ionic liquids: an overview hung. j. ind. chem. 2017 45(2), 41–44 doi: 10.1515/hjic-2017-0019 [2] song, h.; lee, s. y.: production of succinic acid by bacterial fermentation enzyme microb. tech. 2006 39(3), 352–361 doi: 10.1016/j.enzmictec.2005.11.043 [3] sauer, m.; porro, d.; mattanovich, d.; branduardi, p.: microbial production of organic acids: expanding the markets trends biotechnol. 2008 26(2), 100–108 doi: 10.1016/j.tibtech.2007.11.006 [4] zeikus, j. g.; jain,·m. k.; elankovan, p.: biotechnology of succinic acid production and markets for derived industrial products appl. microbiol biot. 1999 51(5), 545–552 doi: 10.1007/s002530051431 [5] liu, y.-p.; zheng, p.; sun, z.-h.; ni, y.; dong, j.j.; zhu, l.-l.: economical succinic acid production from cane molasses by actinobacillus succinogenes bioresource technol. 2008 99(6), 1736–1742 doi: 10.1016/j.biortech.2007.03.044 [6] mika, l.t.; cséfalvay, e.; németh, á.: catalytic conversion of carbohydrates to initial chemicals: chemistry and sustainability chem. rev. 2018 118(2), 505–613 doi: 10.1021/acs.chemrev.7b00395 [7] li, x.; jiang, s.; pan, l.; wei, z.: optimization for the bioconversion of succinic acid based on response surface methodology and back-propagation artificial neural network in: wang, h; low, k. s.; wei, k.; sun, j. (eds.): fifth international conference on natural computation 2009 3, 392– 398 (ieee computer society, los alamitos, usa) isbn: 978-0-7695-3736-8 doi: 10.1109/icnc.2009.20 hungarian journal of industry and chemistry https://doi.org/10.1515/hjic-2017-0019 https://doi.org/10.1515/hjic-2017-0019 https://doi.org/10.1016/j.enzmictec.2005.11.043 https://doi.org/10.1016/j.tibtech.2007.11.006 https://doi.org/10.1007/s002530051431 https://doi.org/10.1016/j.biortech.2007.03.044 https://doi.org/10.1016/j.biortech.2007.03.044 https://doi.org/10.1021/acs.chemrev.7b00395 https://doi.org/10.1109/icnc.2009.20 hungarian journal of industry and chemistry vol. 47(2) pp. 5–10 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-14 production of the enzyme cyclodextrin glycosyltransferase using different fermentation techniques réka czinkóczky1 and áron németh *1 1department of applied biotechnology and food science, budapest university of technology and economics, műegyetem rkp. 3, budapest, 1111, hungary cyclodextrins produced by cyclodextrin glycosyltransferase (cgtase) are widely used in the pharmaceutical industry to improve the solubility of drug substances as well as protect them against oxidation. the use of this enzyme in the cosmetics industry is also significant. cgtase is an enzyme that belongs to the α-amylase family, which is part of the group of non-leloir glycosyltransferases. enzyme-catalysed transglycosylation reactions may involve cyclization, coupling and disproportionation processes. the enzyme cgtase is mostly used to produce cyclodextrins (cds). cgtase can produce α-, βand γ-cds during transglycosylation reactions, depending on the number of glucopyranose units involved (6, 7 or 8). the enzyme cgtase can also be used for enzymatic bioconversion, e.g., in the development of alternative sweeteners, where the bitter aftertaste of the product is reduced during the enzymatic bioconversion of steviol glycosides, thereby obtaining an even sweeter and more advantageous material. in our research, the enzyme cgtase was produced using different fermentation techniques to compare the activity and amount of cgtase produced by each process and optimize the subsequently planned scale-up. in our studies, the strain dsm 13 of bacillus licheniformis was used, which produced cgtase extracellularly. during the experiments the batch, fed-batch and semi-continuous fermentation techniques were compared in terms of enzymatic production. all cultivation processes were carried out in a desktop lab scale fermenter. keywords: cyclodextrin glycosyltransferase, fermentation, cyclodextrins, bacillus licheniformis 1. introduction cyclodextrin glycosyltransferase (cgtase, ec 2.4.1.19) is a starch-degrading enzyme, which is a member of the α-amylase family. the formal name of cgtase is [1,4-αd-glucan 4-α-d-(1,4-α-glucano)-transferase(cyclizing). kuriki et al. [1] reported that cgtase has the same four highly conserved regions as the α-amylases. cgtase catalyses four kinds of transglycosylation reactions (fig. 1): cyclization, coupling, disproportionation and hydrolysis. these reactions are all transglycosylations, in which cyclization is intramolecular, coupling and disproportionation are intermolecular, and hydrolysis is the conversion of sugar to h2o [2]. the formation of cyclodextrin (cd) by the enzyme cgtase is an intermolecular transglycosylation reaction [3]. many microorganisms are capable of producing cgtase, e.g., bacillus macerans [4, 5], bacillus amyloliquefaciens [6], bacillus clarkii [7], bacillus megaterium [8], bacillus subtilis [9], bacillus licheniformis [10, 11], bacillus firmus [12,13], bacillus circulans [14,15], bacillus ohbensis [16, 17], geobacillus stearothermophilus [18], thermoanaerobacter sp. [19], klebsiella pneumoniae, and klebsiella oxytoca [20]. *correspondence: naron@f-labor.mkt.bme.hu figure 1: cgtase-catalysed reactions: a: cyclization, b: coupling, c: disproportionation, d: hydrolysis https://doi.org/10.33927/hjic-2019-14 mailto:naron@f-labor.mkt.bme.hu 6 czinkóczky and németh figure 2: general structure of cyclodextrins (n: number of glucopyranose units, n = 6 α-cd, n = 7 β-cd, n = 8 γ-cd) (figure adapted from: https://commons.wikimedia.org/wiki/file:cyclodextrin.svg cc by-sa 3.0) (08.07.2019) ) the molecular weight of cgtases may vary from 60 to 110 kda, typically its proteins have a mass of 75 kda [21]. the most important demand of metal ions for them is ca2+, which protects the protein against heat denaturation. most cgtases are strongly inhibited by zn2+, cu2+ and fe2+ [22]. cyclodextrins, produced from starch or its derivatives via enzymatic conversion, proceed through an intramolecular transglycosylation reaction using cgtases and to a lesser extent α-amylases [3]. they are cyclic oligosaccharides composed of α-1,4-glycosidic-linked glucosyl residues [23]. three different types of cyclodextrins exist and are characterised according to the number of glucosyl residues in the molecule: α-, βand γcyclodextrins consist of 6, 7 and 8 glucose units, respectively (fig. 2). cyclodextrins are cyclic molecules with a hydrophilic exterior and a hydrophobic cavity that enables them to form specific inclusion complexes with small hydrophobic molecules [24]. cyclodextrins are chiral non-reducing oligosaccharides. glucose is the decomposition product of all cyclodextrins in acidic solutions. the rate of hydrolysis follows the order of γ > β > α. under acidic conditions, cyclodextrins are more slowly hydrolyzed than maltooligosaccharides. the glycosidic bonds in the cyclodextrins can be hydrolyzed by α-amylase, but β-amylase is unable to perform this hydrolysis. the rate of enzymatic hydrolysis is the fastest for γ-cd, followed by βthen α-cd. all cds are very stable and soluble in alkaline solutions at high ph. cds are more resistant to acid or alkaline degradation than starch. cds do not even degradate at temperatures as high as that of caramelization (> 200 ◦c, sterilization) under both dry or aqueous conditions of between ph 2 and 12. they are also stable up to 250 ◦c under an inert atmosphere of, for example, nitrogen [20, 25, 26]. the widespread use of cyclodextrins is due to their specific structure. since each guest molecule is uniquely surrounded by the cd (or one of its derivatives), it is microencapsulated from a molecular microscopic point of view. this can result in beneficial changes to the chemical and physical properties of guest molecules, e.g., lightor oxygen-sensitive materials can be stabilized; very volatile substances fixed; the chemical reactivity of molecules modified; the solubility of materials improved; changes between phases achieved from liquid substances into powders; degradation of microorganisms avoided; bad smells and tastes masked; and pigments or colors of materials coated. as a result of these characteristics, cds (and their derivatives) can be used in analytical chemistry, agriculture, the pharmaceutical as well as food industries and other masking areas. cgtase can be used for the transglycosylation of stevioside to rebaudioside through which the edulcorant quality can also be improved by increasing the substitution of steviol glycoside with the help of cornstarch hydrolyzate and cgtase [27–30]. 2. materials and methods 2.1 cultivation of the bacteria the applied bacterial strain was bacillus licheniformis b.01470 (dsm 13) purchased from the national collection of agricultural and industrial microorganisms in hungary. bacillus licheniformis is a gram-positive, rodshaped, endospore forming, facultatively anaerobic bacteria. nutrient agar was used to maintain the bacterium in petri dishes [31]. in our research, three types of fermentation techniques for the production of cgtase were compared: batch, fed-batch, and semi-continuous fermentation techniques. all cultivation processes were carried out in a benchtop lab scale fermenter (fig. 3) (biostat q, b. braun biotech international, germany). in the fed-batch fermentation, after 24 hours 15 v/v % of the medium was fed into the bioreactor. during the semi-continuous fermentation at the end of each cycle, 80 % of the broth was replaced by fresh media. for the experiments in the bioreactor, horikoshi ii medium was used for the cultivation of bacteria containing 1.0 % soluble starch, 0.5 % peptone, 0.5 % yeast extract, 0.1 % k2hpo4, 0.02 % mgso4 •7 h2o, and 1.0 % na2co3 (all concentrations are given in w/v in distilled water) [32]. hungarian journal of industry and chemistry https://creativecommons.org/licenses/by-sa/3.0/deed.en production of the enzyme cyclodextrin glycosyltransferase 7 figure 3: the bioreactor used in the experiments 2.2 the modelling of microbial growth in order to monitor the growth of bacterial cells, samples were taken during fermentations and the optical density (od) measured at 600 nm. microbial growth is described by µx = 1 x dx dt , (1) where µx is the specific growth rate of the microbe. it was evaluated through fitting the generalized logistic function z = zmax 1 + exp(a+ bt+ ct2 + dt3) (2) to the measured cell dry weight (cdw) values (calculated from at od600). to fit the curve, sigmaplot version 12.0 software was applied. if the coefficient of determination (r2) was not high enough, the last two members of the generalized logistic function were omitted resulting in z = zmax 1 + exp(a+ bt) , (3) figure 4: colorimetric analysis of cgtase activity which also corresponds to the modified monod model. the derivative of the fitted function is dz dt = −z ( 1− z zmax ) dh dt (4) where dh dt = b+ 2ct+ 3dt2 (5) is the derivative of the internal function. the auxiliary variable z in eq. 2, 3, and 4 was x (biomass in g/l), s (substrate in g/l), and pi (product in g/l), respectively, while zmax was xmax, s0 and pi,max, respectively. if the fit was successful, then, by using determined constants of the model, the velocities and specific growth rates could be calculated by derivation from eq. 4. 2.3 measurement of cgtase activity during the fermentations, samples were regularly extracted into eppendorf tubes, which were centrifuged at 12,000 rpm for 6 minutes, then the cell-free supernatants were used to determine the enzyme activity. the measurement of extracellular cgtase activity was adapted from the method of kaneko et al. [33] with slight modifications (with a reduced concentration of phenolphtalein). the colorimetric reaction (fig. 4) was measured by a spectrophotometer at 550 nm. the experiments were conducted in 15 ml centrifuge tubes in a water bath at 40 ◦c. first, 4.5 ml 50 mm trishcl buffer (ph = 9) was added containing a 1 % (w/v) water-soluble starch suspension, then 0.5 ml of cell-free supernatant containing the extracellular cgtase enzyme was introduced and homogenized thoroughly with a vortex mixer. then four 0.5 ml samples were taken from each tube which were boiled for 5 minutes to inactivate the enzyme. the boiled samples were transferred into 2 ml cuvettes that contained a staining solution (1.2 ml 0.06 mm phenolphthalein in 0.5 m na2co3 solution). four absorbances at 550 nm of a given assay were plotted against time and the gradient (mmol/min) converted into enzyme activity with the help of a molar extinction coefficient (32, 263 m−1cm−1) resulting in the cgtase activity in unit/ml supernatant. 47(2) pp. 5–10 (2019) 8 czinkóczky and németh figure 5: microbial growth during the batch fermentation figure 6: microbial growth during the fed-batch fermentation 3. results and discussion 3.1 batch fermentation fig. 5 shows the microbial growth during the batch fermentation and also represents the changes in the specific growth rate. the maximum value of the specific growth rate was 0.53 1/h. at the end of the fermentation, the final activity of cgtase was 0.3 u/ml and the productivity was 11.8 mu/(ml h). 3.2 fed-batch fermentation fig. 6 represents microbial growth during the fed-batch fermentation. unfortunately, due to poorly scheduled sampling, it was not possible to adjust the generalized logistic equation, therefore, it was impossible to calculate the specific growth rate. a fresh medium of 15 % was injected after 24 hours. the final enzyme activity was 0.5 u/ml and the enzyme productivity was 12.3 mu/(ml h). 3.3 semi-continuous fermentation the semi-continuous fermentation is shown in fig. 7, which consisted of 3 cycles. the highest value of the maximum growth rate was during the first cycle (0.5 1/h). as the fermentation progressed, the maximum specific growth rate decreased. figure 7: optical density and specific growth rate changes during the semi-continuous fermentation figure 8: cgtase activities at the end of each cycle fig. 8 shows that the enzyme activity of cgtase increased as the fermentation progressed. 3.4 comparison of the different fermentation techniques table 1 summarizes the enzyme activities and productivities achieved by each fermentation technique. the maximum specific growth rates reached in the batch and semicontinuous fermentations were approximately the same, which is characteristic of when the microorganism can multiply. the enzyme activities at the end of the fermentations table 1: comparison between the results of the different fermentation techniques type µmax [1/h] final enzyme activity [u/ml] productivity [mu/(ml h)] batch 0.53 0.3 11.8 fed-batch n.d. 0.5 12.3 semicontinuous 0.50 2.4 29.95± 0.3 hungarian journal of industry and chemistry production of the enzyme cyclodextrin glycosyltransferase 9 rose as the complexity of the fermentation technique increased. while the fed-batch fermentation elongated the declining phase of the microbial growth cycle, in the semi-continuous fermentation technique an attempt was made to operate in the exponential growth phase. it is assumed that this difference caused the higher activity and productivity in the case of the semi-continuous fermentation. 4. conclusion in our experiments, the effect of the fermentation technique on the activity of the produced enzyme cgtase was investigated. there was no significant difference between the activities of the produced cgtase and productivities of the systems when the batch and fed-batch fermentations were compared. in contrast, bacteria produced a much more active enzyme during the semi-continuous fermentation, moreover, the productivity of this system was also significantly higher than that of the other two fermentation techniques. from the results, it can be assumed that the microbes produce the enzyme during the exponential growth phase, since no significant difference was observed between the batch and fed-batch fermentations. meanwhile, a repeated exponential growth phase resulted in a much higher activity and productivity. this suggests that cgtase production follows growth associated-type product formation. acknowledgement the research was supported by the gedeon richter’s talentum foundation, founded by gedeon richter plc. 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https://doi.org/10.1016/s0734-9750(02)00020-4 https://doi.org/10.1016/j.foodchem.2012.10.124 https://doi.org/10.1134/s0003683806010030 https://doi.org/10.1134/s0003683806010030 https://www.dsmz.de/microorganisms/medium/pdf/dsmz_medium1.pdf https://www.dsmz.de/microorganisms/medium/pdf/dsmz_medium1.pdf https://doi.org/10.1080/00021369.1989.10869443 https://doi.org/10.5458/jag1972.34.45 hungarian journal of industry and chemistry vol. 47(2) pp. 11–15 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-15 analysis of crude oil in terms of fouling and corrosion richárd katona1, roland lócskai1,2, gergő bátor1,2, antal krójer1, and tibor kovács*1 1institute of radiochemistry and radioecology, university of pannonia, egyetem u. 10, veszprém, 8200, hungary 2social organisation for radioecological cleanliness, józsef attila u. 7/a, veszprém, 8200, hungary the present-day oil refining market has the potential to process opportunity crudes. the degree of corrosion and fouling issues has increased in terms of processing opportunity crudes. in the case of changing crude slates, predicting the impacts of crude oil on production is necessary to ensure safe and profitable processing. crude oil can be characterized by the quantitative and qualitative analyses of saturates, aromatics, resins, asphaltenes and contaminants as well as the determination of its physical and chemical properties. the complementary nature of these analyses is necessary to identify the root causes of fouling and corrosion problems and quantify the impact of them. in this study, analytical methods were developed to investigate the effect of crude oils on production in terms of fouling and corrosion, which can be used to characterize crude oil from different sources. the compatibility, emulsification tendency and fouling potential of crude oil were analyzed by the developed analytical methods. the measurement method to assess the compatibility of crude oils is based on the determination of the flocculation tendency of asphaltenes in oils. a porla glx step analyzer was used for the compatibility tests. emulsification and fouling tendencies were measured by our in-house designed laboratory equipment. these measurements were conducted under typical operating conditions. the developed analytical methods were validated by crude oils from five different sources. keywords: crude oil, fouling, corrosion, emulsion, desalter, compatibility, asphaltenes 1. introduction refineries have had to handle problems associated with fouling and corrosion for a prolonged period of time. the degree of corrosion and fouling issues has increased since the processing of opportunity crudes and co-processing of renewable feeds were introduced [1, 2]. it is well known that crude oils contain water, chloride salts and organochlorine compounds [3]. when crude oils are preheated in the heat exchangers of crude units, the hydrolysis of chloride salts and organochlorine compounds occurs. in these chemical reactions, gaseous hydrochloric acid is released. the gaseous hydrochloric acid present in the steam phase can easily dissolve in condensed water, resulting in very low ph values. the concentrated caustic solution can cause general corrosion of equipment in crude units composed of carbon steel [4, 5]. desalting is the first line of defense against corrosion induced by the hydrochloric acid [6]. earlier studies showed that the efficiency of desalter apparatus is influenced by the stability of the emulsion generated. the stability of the emulsion increases and the efficiency of the desalter decreases when the asphaltene content of the crude oil is high [7]. besides the desalting process, *correspondence: kt@almos.uni-pannon.hu neutralizers and corrosion inhibitors are also used against corrosion in crude units [8]. fouling deposits can be categorized into inorganic and organic types. organic fouling results from asphaltenes and high molecular weight hydrocarbons which become insoluble in the system [9]. the asphaltene molecules can become unstable due to the effect of blending and heating incompatible crude oils. the precipitated molecules can be deposited on the surface of heat exchangers [10]. corrosion products of iron (fes, fe2o3) and inorganic contaminants in crude oils can cause inorganic fouling. in the crude oil preheat train, the viscosity of the oil is lowered because of heating and the deposition of inorganic contaminants increases. regardless of the cause, high fouling rates can lead to excessive equipment cleaning requirements and costs. chemicals–such as dispersants and inhibitors–are used to effectively reduce fouling in several critical areas throughout a refinery [11]. in the case of changing crude slates, predicting the impacts of crude oil on production is necessary for safe and profitable processing [12]. in this study, analytical methods were developed to investigate the effect of crude oils on production with regard to fouling and corrosion, which can be used for characterizing crude oil from difhttps://doi.org/10.33927/hjic-2019-15 mailto: kt@almos.uni-pannon.hu 12 katona, lócskai, bátor, krójer, and kovács figure 1: schematic drawing of laboratory desalter model equipment. ferent sources. the key causes of crude oil processing issues are incompatibility, the emulsification tendency and the fouling potential [3]. 2. experimental five crude oils from different sources were used in this study to validate the developed procedure. api gravity, total acid number (tan), water content, asphaltene content, inorganic contaminants and the distillation curve of crude oils were measured in accordance with astm d4052, astm d664, astm d4807, msz en 459, msz en iso 9029 and astm d7096. in addition, the total chlorine content of one desalted crude oil was measured by neutron activation analysis. 2.1 emulsification tendency in the first section of the determination of the emulsification tendency, 950 ml of crude oil and 50 ml of water were agitated using an ultra-turrax stirrer at 75 °c and 13, 500 rpm for 5 minutes. then 80 ml of emulsion was poured out into a tube that was made according to the standard test method astm d96. after that the emulsification tendencies of crude oils were analyzed by our in-house-designed laboratory desalter simulator. the schematic drawing of the equipment used is shown in fig. 1. the desalter simulator apparatus consists of a thermoblock, 8 transformers and toroidal transformers. the emulsion separation tubes are located in the aluminium thermoblock. the electric field in the tubes is controlled by the installed transformers. the connection between tubes and toroidal transformers is provided by special caps with two isolated electrodes. the temperature of the thermoblock can be adjusted by the control unit of the apparatus. during the measurement, the temperature was 110 °c and the electrical voltage was 2, 500 v. the emulsion was resolved in the separation tubes in accordance with the known method of providing an electric field to polarize water droplets. the volume of water that dropped into each tube was recorded after 10, 20, 30, and 60 minutes. the more water that dropped and the clearer the water phase, the more effective the desalting process [13]. 2.2 fouling tendency the fouling tendency was measured in the highperformance thermoblock. the equipment is an aluminium thermoblock in which 8 places for special tubes and an electric heater coil are located. the heating can be regulated by a control unit. the special tubes are pressure vessels 100 ml in volume. into the tubes, 25 g of crude oil samples were measured. the samples were heated at 250 °c for 48 hours then cooled to 80 °c and filtered under a vacuum through a 0.7 µm membrane filter. the filter along with the residue was washed with petrol, dried and weighed to yield the final result. in order to measure the amount of generated deposits on the wall of the tubes, they were washed with petrol and then the petrol wash was filtered under a vacuum through a 0.7 µm membrane filter too. the deposit was calculated from s = 10000 (m2 −m1)100 25 , (1) where the mass of the filter is denoted by m1, the mass of the filter with the deposit by m2 and the amount of deposits in ppm by s [14]. 2.3 neutron activation analysis neutron activation analysis determines the total chlorine content in the sample regardless of its oxidation, inorganic or organic states. the measurement is capable of handling inhomogeneous samples of greater masses, thus mitigating the uncertainties of sampling. the measuring range spans several times the magnitude of the range of alternative techniques, and has a small measurement error [15]. samples were prepared in 1 ml vials and sealed in polyethylene bags. the samples were then placed in larger 5 cm plastic vials that were irradiated. to provide redundancy in the case of a leakage, the outer vial was heat sealed using a hot iron. the masses of the samples were approximately 1 g and were irradiated by a 1.1 mw mark ii triga reactor at the university of texas in austin. in order to examine the total chlorine content, samples were irradiated using a reactor power of 500 kw for 5 minutes. thermal neutrons were used due to favorable cross-sections for radiative capture within this range. the following reaction was used to determine the total chlorine content: 37cl(n, γ)38cl with its half-life of 37 minutes. samples were allowed to decay for 15 minutes prior to being counted by a gamma-ray spectrometer. the samples themselves were counted for between 600 and 2, 700 seconds, depending on the net count rate under the 1, 642 kev photopeak for chlorine. hungarian journal of industry and chemistry analysis of crude oil in terms of fouling and corrosion 13 table 1: summary of the properties of the crude oils crude oil a b c api 29 46 42 tan (mg koh/g) 0.19 0.0448 0.0459 water content (%) 0.1 0 0 asphaltene content (%) 2.42 0.017 0.25 inorganic contamination (ppm) 260 110 82 total chlorine content after desalting (ppm) 8.08± 0.18 yield of fractions (%) c1-c10 18 40 32 c11-c14 9 12 12 c15-c25 23 27 26 c26-c50 25 16 19 c51+ 25 5 11 emulsification tendency fig. 2 s (ppm) 1286 472 248 sbn (-) 77.6 43.3 64 in (-) 44.6 lower lower crude oil d e api 29 31 tan (mg koh/g) 0.17 0.0726 water content (%) 0 0 asphaltene content (%) 2.05 1.6 inorganic contamination (ppm) 149 198 yield of fractions (%) c1-c10 18 20 c11-c14 8 5 c15-c25 22 25 c26-c50 25 27 c51+ 27 23 emulsification tendency fig. 2 s (ppm) 1187 772 sbn (-) 79.5 68.4 in (-) 30.8 25.1 2.4 compatibility the compatibility test of crude oils is based on the oil compatibility model. this model enables the insolubility number (in) and solubility blending number (sbn) of crude oils to be calculated. two tests were carried out to measure the solubility parameter. the first test involved determining the maximum volume of n-heptane that can be added to a given volume of oil without the precipitation of asphaltenes. then the minimum percent of toluene in the mixture with n-heptane to dissolve asphaltenes was determined. the volume percentage of toluene in the toluene–n-heptane mixture was plotted against the volume ratio of oil to the toluene–n-heptane mixture. the insolubility number is where a line drawn through the two points intercepts the y-axis. the solubility blending number can be calculated by sbn = in [ 1 + ml heptane ml oil ] . (2) the criterion for the compatibility of the oil mixture is that the volume average sbn is greater than the in of all types of oil in the mixture. it follows that the higher the sbn, the more compatible the crude oil is [16, 17]. a porla glx step analyzer was used to analyze the compatibility of crude oils. the laboratory analyzer performs the dilution in an aromatic solvent and the titration with paraffin hydrocarbon automatically. the analyzer was used in accordance with the factory-preset program. insoluble asphaltenes were detected by an optical detector according to the intensity of scattered visible light. the wavelength of the light was selected to be sensitive enough to detect even minute concentrations of asphaltene particles in the measuring solution. 3. results and discussion the results of analytical measurements are summarized in table 1. samples b and c are light crude oils, while a, d and 47(2) pp. 11–15 (2019) 14 katona, lócskai, bátor, krójer, and kovács figure 2: the emulsification tendencies and the pictures of emulsions after the measurements. the order of the crude oils in the pictures from left to right is the following: crude oil a, b, c, d and e. e are medium crude oils according to api gravity. the crude oils in order of asphaltene content from lowest to highest are: b, c, e, d and a. it is recognized that the highest emulsification of water occurs when the asphaltene content is high [6]. in bluefig. 2, it can be seen that the crude oil with the highest content of asphaltenes (a) formed the most stable emulsions. on the other hand, the emulsification tendencies of crude oils b and c showed that the emulsion of light crude oil can be easily resolved. the quantities of water phases following the measurements are presented in fig. 2. the water phases of stable emulsions are oily, while those of emulsions with lower asphaltene contents are clear. the total chlorine content of desalted crude oil was measured by neutron activation analysis. the total chlorine content in the desalted crude oil may be the result of the remaining dissolved salts and organic chlorides. organic chlorides present a more significant problem in crude oil refineries when compared to inorganic chlorides, since they are not removed by the desalting process [18]. the fouling tendency can also be correlated with the asphaltene content. the lowest amount of deposit was measured for the crude oil of the lowest content of asphaltenes (crude oil b). from table 1, it can be seen that the higher the asphaltene content of crude oil, the greater the amount of the deposit. however, the asphaltene content of crude oil c is higher than that of b, but the amount of the deposit of crude oil c is lower than figure 3: compatibility test results of a mixture of crudes b-d. figure 4: compatibility test results of a mixture of crudes a-c. figure 5: compatibility test results of a mixture of crudes c-e. that of b. this is explained by the amount of inorganic contaminants which is higher for crude oil b than c. furthermore, as the results of the compatibility test show, lower sbns belong to the light crude oils with low asphaltene contents. in figs. 3-5, the evaluation of three crude oil blends is shown. inmax denotes the greater in of the two respective crude oils that were blended. in all three cases, the volume average sbn is always greater than the inmax, so the mixtures of crude oils b-d, c-a and c-e are compatible with any blending ratios. the ins of crude oils b and c were not determined because the software of the analyzer just shows the highest in among the blended crude oils. 4. conclusion fouling and corrosion exact significant economic and operational penalties. the risk of prosecution has increased with the processing of opportunity crudes and coprocessing of renewable feeds [19]. in this paper, some laboratory methods were developed to investigate the effect of crude oils on production in terms of fouling and hungarian journal of industry and chemistry analysis of crude oil in terms of fouling and corrosion 15 corrosion. the emulsification tendency as well as the effect of blending and heating on crude oils were measured by the developed laboratory methods. these methods can be used for characterizing crude oil from different sources. the results of developed laboratory methods were compared with the composition of crude oils. as is confirmed by the results, asphaltenes and high molecular weight hydrocarbons have a significant impact on the production of crude oils in terms of fouling and corrosion. the cost and complexity of the determination of total chlorine content by neutron activation analysis make it unfit for routine analytical purposes, but the precision of the results makes it a perfect choice as a reference method [20]. our plan is to propose methods to quantify lower amounts of total chlorine content in crude oils using neutron activation analysis as a reference method. references [1] ropital, 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hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-16 immobilization of laccase in alginate beads béla varga*1, mónika meiczinger2, and viola somogyi1 1institute of environmental engineering, university of pannonia, egyetem u. 10, veszprém, 8200, hungary 2research institute of biomolecular and chemical engineering, university of pannonia, egyetem u. 10, veszprém, 8200, hungary the elimination or degradation of micropollutants from wastewater is becoming ever more important nowadays. using oxidoreductase enzymes to treat different micropollutants seems a promising solution. however, the viability of the process is highly dependent on the availability and stability of the applied enzymes. in order to improve the stability and provide faster reaction rates, enzymes can be immobilized in various carriers. properties such as simple production, easy retention and biodegradable carrier material are advantageous, e.g. entrapping laccase in alginate beads. this paper shows the results of the preparation and characterization of immobilized laccase entrapped in calcium alginate beads. the technique of adding a mixture of sodium alginate and laccase dropwise into calcium chloride has been applied, improved and standardized to produce laccase-containing beads of uniform size and activity. for the purpose of characterization, a widely used substrate, 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt, was used to evaluate the performance of the laccase-containing alginate beads. in addition to the characterization of the laccase-containing alginate beads, the enzyme kinetic constants (km = 26.43 µm, vmax = 0.23 µm/min) were determined. the reduction in the activity during storage has been described by a decay constant (0.26 d−1) that provides information concerning the design constraints of the process. results will be used to test the method in terms of the removal of organic micropollutants in continuous systems. keywords: laccase, immobilization, alginate, abts, micropollutants 1. introduction awareness concerning the spread of micropollutants in water bodies has been raised in many countries [1] due to their toxic effects on ecological systems [2]. additionally, these pollutants can infiltrate into reservoirs of drinking water in several ways resulting in public health concerns [3]. since conventional treatment systems were designed to easily remove biodegradable compounds [4], the efficiency of micropollutant degradation is insufficient [5]. the partial elimination of these substances is driven by physical adsorption by the sludge [6] and cometabolism during microbial growth [7]. therefore, the development of advanced technologies to improve the efficiency of removal and mitigate ecological effects is needed [8]. organic micropollutants could be converted by oxidoreductase enzymes such as tyrosinase, peroxidase and laccase. laccase has received attention since it does not require additional cofactors. it promotes the production of an organic radical which combines with different transformation products [9]. the toxicity of these compounds is a subject of ongoing research [10], although a reduction in toxicity has been shown in many cases [11]. *correspondence: vargabela@almos.uni-pannon.hu immobilization can be advantageous compared to the free form of the enzyme [12]. it can enhance the stability of the enzymes under more extreme conditions, namely higher ph and temperature [13], and makes the separation of the catalyst from the effluent easier. for example, separation by applying an external magnetic force is possible when laccase is immobilized on magnetic particles [14]. by using macro-sized supports, e.g. alginate beads [15] – unlike nanoparticles – the carriers can be retained by an outlet sieve, thus using them in continuous packedbed reactors is possible [16]. alginates extracted from brown algae [17] are good candidates for water treatment because of their advantageous properties [18], low-cost production and low health risks [19]. calcium alginate microspheres, successfully used to immobilize polygalacturonase for the purpose of cleaning edible products, have shown improved operational stability as the optimum temperature increases and even modifies the ph dependence of the enzyme [20]. calcium alginate beads are formed by reversible crosslinking bonds with bivalent calcium ions between chains of α-l-guluronic acid and β-d-mannuronic acid [19]. their unique properties allow them to be used as an adsorbent for dye removal [21]. transformation of the phehttps://doi.org/10.33927/hjic-2019-16 mailto: vargabela@almos.uni-pannon.hu 18 varga, meiczinger, and somogyi nolic compound with laccase entrapped in alginate was successfully tested for bisphenol a [22] and the decolourization of textile dyes [23]. the aim of this study was to investigate the immobilization of laccase in calcium alginate beads and determine its kinetic behaviour by measuring the conversion of 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (abts). since this substrate is widely used, the results may be easily compared with other laccase immobilization methods. 2. materials and methods 2.1 materials laccase from trametes versicolor (catechol oxidase activity ≥ 0.5 u/mg) and abts were purchased from sigma-aldrich. food grade sodium alginate was purchased from dragonspice naturwaren. citric acid and sodium phosphate used for making mcilvaine buffer solution [24] were supplied by vwr international. calcium chloride was purchased from reanal. reagents were of analytical reagent grade except for sodium alginate. 2.2 measurement of enzyme activity laccase activity was determined by measuring the change in concentration of the abts radical formed in the catalysed oxidation. measurements were performed in a macherey-nagel nanocolor uv/vis spectrophotometer at 420 nm in a citrate-phosphate buffer solution at ph = 5 and within the range of laboratory temperatures (20± 3 °c). the formation of the product was registered by using the extinction coefficient of the abts radical (ε = 36, 000 m−1cm−1 [25]) and calculated using an equation a = evsample lεvtotal (1) based on the beer-lambert law [26], wherea denotes the activity (u/l),e is a measure of the change in absorbance at 420 nm over 1 minute (min−1), vsample represents the amount of enzyme contained in the sample used (ml), l is the pathlength of the beam of light (cm), ε stands for the extinction coefficient of the abts radical (m−1cm−1), and vtotal expresses the total volume used (ml). in the case of immobilized laccase, beads were placed into the tubes instead of the liquid samples. the specific activity was calculated by measuring the weight and number of beads before the activity in a closed tube was measured. between measurements, the beads were stored in distilled water in order to minimize the loss of water. 2.3 immobilization of laccase inside an alginate matrix the immobilization protocol was based on entrapment of the enzyme before the formation of insoluble alginate beads according to daâssi et al. [23]. the sodiumalginate crystals were dissolved in 5 ml of 1 mg/ml laccase stock solution to produce a gel with 2 w/v% alginate content. this was added dropwise from a height of 25 cm into a 2 m/m% solution of calcium chloride where beads formed, then the beads were left for 30 mins to solidify. after this procedure, the beads were extracted from the solution by filtration and washed with distilled water in order to eliminate the unbonded laccase. the beads were stored in distilled water until used for further investigations. the efficiency of the immobilization was determined by measuring the activities of the laccase stock solution (ainitial), the solution of calcium chloride after immobilization (acacl2 ) and the washing liquid (awashing) used. immobilization efficiency (η) was calculated using the following formula η(%) = 100 ainitial −acacl2 −awashing ainitial . (2) 2.4 characterization of the immobilized laccase the weight was measured frequently in a closed vessel by using an analytical balance (kern abj 220-4nm). the size of the drops was determined by measuring the diameter of the freshly prepared beads after filtration on a square membrane filter. in order to determine the water content, twenty pieces of freshly prepared beads were put into an oven at a temperature of 105 °c and dried until their weight became constant. 2.5 effect of temperature on alginate beads in order to gather information regarding the effect of temperature on enzyme activity within the optimal temperature range of wastewater treatment plants [27], the reaction rate of the abts transformation was determined inside a thermostatic cabinet (20− 35 °c). 2.6 storage stability of the beads the storage stability of the immobilized laccase was determined by storing the laccase-containing beads in ultrapure water at 20 °c without mixing. beads were removed every 24 hours from the vessel in order to determine the change in their activity. the exponential decay constant was calculated by fitting the following equation at = ainitiale −kdt (3) to the measured activities, where ainitial and at indicate the specific activities [u/bead] at the initial and given time, respectively, kd denotes the decay constant [d−1] and t stands for the time of sampling [h]. 2.7 reuse of the alginate beads the laccase-containing beads were mixed with a 0.05 mg/ml abts solution in a phosphate-citrate buffer solution (ph = 5) and the change in the abts radical concentration was determined spectrophotometrically. after hungarian journal of industry and chemistry immobilization of laccase in alginate beads 19 figure 1: change of size during drying of the beads (a) beads freshly prepared, (b) beads after drying, grid size: 3 mm measuring the activity of the beads (after 5 mins), they were filtered and washed with 5 ml of distilled water which was considered to be one cycle. during the filtration, a picture was taken to document the change in the size and shape of the beads. after washing, the beads were put into a fresh volume of buffer solution that contained abts and the same cycle repeated six more times. 2.8 determination of kinetic parameters with abts ten beads were put into a ph = 5 citrate-phosphate buffer solution, then different amounts of abts stock solution were pipetted in order to obtain different initial substrate concentrations ([s] = 23, 46, 91, 228, 456, and 911 µm). the change in absorbance was recorded at 420 nm to calculate the concentration of abts radicals (p). the michaelis-menten constant (km) and maximum rate of reaction (vmax) were determined by fitting the michaelis-menten equation. d[p] dt = vmax[s] km + [s] (4) with non-linear regression. 3. results and analysis 3.1 characterization of the alginate beads using the technique described, it was possible to produce a uniform bead weight: 0.0152 g (sd = 0.0016 g) of high immobilization efficiency (98.2 %). the diameters of the beads were between 2 and 3 mm. the weight and density of the beads constantly changed during their handling due to the rapid rate of evaporation of water. therefore, the number of beads was used to calculate the specific activity instead of weight, in a similar way to daâssi et al. [23]. a specific activity of 0.005 u/bead was achieved, which equates to 0.005 µm production of abts radicals in one minute. the water content of the beads was determined to be 98± 1 %. the size of the beads shrank twofold whilst being dried as is shown in fig. 1. 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 0 200 400 600 800 1000 a b t s ra di ca l co nc en tr at io n (µ m ) time (s) figure 2: change of abts radical concentration 3.2 determination of kinetic parameters the change in the concentration of abts radicals as a function of time is presented in fig. 2. a linear curve could be fitted with the results during the initial 2 minutes indicating a first-order reaction. the rate of the reaction can be determined from the gradient of the curves. by plotting the initial rates of reaction against the concentration of the substrate, a lower initial substrate concentration shows a better fit (r2 = 0.96 − 0.99) when compared to the higher range (r2 = 0.95). as a result, common michaelis-menten kinetics were shown (fig. 3). by fitting an equation to the data gathered from three independent experiments with nonlinear least squares regression, the kinetic constants can be determined, namely km = 26.43 µm, vmax = 0.23 µm/min. 3.3 effect of temperature on alginate beads in the range of 20 − 35 °c, the rate of reaction, thus the enzyme activity, increased rapidly as can be seen in fig. 4. as expected, the highest activity was measured at 35 °c since, in the case of the free laccase from trametes versicolor, the optimal temperature for maximum activity was approximately 40 °c [26]. figure 3: fitting of michaelis-menten curve to the measure. initial concentrations used for calculation: 5 µm, 9 µm, 23 µm, 46 µm, 91 µm. 47(2) pp. 17–23 (2019) 20 varga, meiczinger, and somogyi 0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 20 25 30 35 a ct iv ity ( u /b ea d) temperature (�c) figure 4: effect of temperature on the activity of the immobilized enzyme. 3.4 storage stability of the beads during storage, a slow decreasing trend can be observed in the activity of the beads, namely a reduction of 33 % over 5 days. by fitting equation to the measured values, the decay coefficient can be determined as 0.26 d−1. the change in activity and the decay curve produced by the equation are presented in fig. 5. 3.5 reuse of the beads the activity of the beads also decreased when repeatedly used. as an example, the results of an experiment were presented in fig. 6. while the activity of the beads decreased, their weight increased gradually. the change in the size of the beads and accumulation of the green reaction products can be seen in fig. 7. this figure also shows the deformation of the beads in between the experiments. 4. discussion using the method described in this study, uniform beads can be produced with regard to their size and weight by controlling the size of their droplets and the height from which they are dropped. since the alginate powder was dissolved directly in the stock solution of laccase and the thick layer solidified instantly when it came 0.000 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0 1 2 3 4 5 6 7 a ct iv ity ( u /b ea d) storage time (d) measured calculated figure 5: change of the activity during storage of the immobilized laccase. figure 6: change of activity and weight of the beads during reuse into contact with the cacl2 solution, the entrapment was instant and effective. as a result, a high immobilization efficiency was achieved (98.2 %). otherwise, the weight of the beads changed quickly whilst being handled after their formation as the beads dried out easily. however, the change in their water content did not influence their activities. therefore, in order to achieve reliable results for specific activities, the number of beads was calculated rather than their weight. evaluation of the reaction kinetics resulted in a michaelis-menten curve in the case of immobilized laccase, in a similar manner to its free form [28]. this indicates that the mechanism of the reaction was not influenced by the entrapment. nonetheless, the activity of the beads is different from that of free laccase due to steric effects and limitations with regard to the diffusion of reactants. in order to achieve higher degrees of activity, the temperature could be increased. this would have advantageous effects on the rate of reaction and diffusion. additionally, by increasing the number of beads used, the rate of reaction could be fine-tuned to suit the requirements of their application in a similar way to the use of free enzymes. in order to determine the product yield or space-time yield, further investigations are recommended. due to the nature of abts, from visual inspection of radicals in itself, it was evident that the reaction products accumulate inside the beads (see fig. 7). this could result in the deactivation of the enzyme by product inhibition. on the other hand, this phenomenon could be used to remove the transformation products after enzymatic conversion by means of adsorption. as tanaka et al. [29] concluded, the diffusion properties depend on the molecular size of the substrate. since laccase-catalysed reactions tend to result in coupled products of higher molecular weight [9], its release from the beads could be limited by diffusion. in the case of low-molecular-weight compounds, e.g. abts, free diffusion can be assumed in the alginate matrix [30]. as the experiments concerning repeated usage have shown, the beads suffer from major structural changes hungarian journal of industry and chemistry immobilization of laccase in alginate beads 21 cycle 1 cycle 2 cycle 3 cycle 4 cycle 5 cycle 6 cycle 7 figure 7: photos of the laccase containing alginate beads during the repeated use in buffer solutions that contain high concentrations of monovalent cations. this is due to the fact that crosslinking with calcium ions is reversible. these structural changes may result in the enzyme leaking and the specific activity decreasing following repeated usage. the reduction in enzyme activity during storage could also be a result of leakage. however, experiments performed in distilled water fitted well with the decay equation, therefore, this can be taken into consideration during the design of the process. moreover, in the case of a complex solution, e.g. treated wastewater or even tap water, the presence of bivalent cations may limit the deformation of the beads. 5. conclusions uniformly sized alginate beads were produced in the laboratory using a widely available biodegradable polymer. the mechanism of immobilized laccase was similar to that of its free form with regard to the conversion of abts, although the effects of diffusion and adsorption should be taken into consideration. due to the structure of the alginate beads, the use of monovalent ions that contain buffers for measurements results in major structural changes. the beads produced were reused successfully over 7 cycles, while a rapid reduction in activity and structural changes were observed. however, the beads can be stored in distilled water and the reduction in activity estimated by an exponential decay equation which facilitates the design of the process. although further investigations regarding the efficiency of enzymatic transformation are needed, immobilization of laccase in alginate beads is a promising technique for the enzymatic treatment of micropollutants in continuous systems. symbols a activity [u/l] acacl2 activity of calcium chloride solution after immobilization [u/l] ainitial activity of the laccase stock solution used [u/l] at specific activity at a given time [u/bead] awashing activity of the washing liquid [u/l] e change in absorbance at 420 nm over 1 minute [min−1] kd decay constant [d−1] km michaelis-menten constant [µm] l path length of light beam [cm] p reaction product, abts radical concentration [µm] s initial substrate concentration [µm] t time [min.; d] vmax maximum reaction rate [µm/min] vsample amount of enzyme-containing sample used [ml] vtotal total volume used [ml] ε extinction coefficient of abts radicals[m−1cm−1] η immobilization efficiency [%] acknowledgement the financial support of széchenyi 2020 under the projects ginop-2.3.2-15-2016-00016 and tét_15_in1-2016-0094 is greatly appreciated. references [1] ebele, a.j.; abou-elwafa abdallah, m.; harrad, s.: pharmaceuticals and personal care products (ppcps) in the freshwater aquatic environment. emerg. contam., 2017 3(1), 1–16 doi: 10.1016/j.emcon.2016.12.004 [2] shao, y.; chen, z.; hollert, h.; zhou, s.; deutschmann, b.; seiler, t.-b.: toxicity of 10 organic micropollutants and their mixture: implications for aquatic risk assessment. sci. total environ., 2019 666, 1273–1282 doi: 10.1016/j.scitotenv.2019.02.047 [3] ahmad, j.; naeem, s.; ahmad, m.; usman, a.r.a.; al-wabel, m.i.: a critical review on organic micropollutants contamination in wastewater and removal through carbon nanotubes. j. environ. manage., 2019 246, 214–228 doi: 10.1016/j.jenvman.2019.05.152 [4] monteiro, s.c.; boxall, a.b.a.: occurrence and fate of human pharmaceuticals in the environment. in: reviews of environmental contamination 47(2) pp. 17–23 (2019) https://doi.org/10.1016/j.emcon.2016.12.004 https://doi.org/10.1016/j.emcon.2016.12.004 https://doi.org/10.1016/j.scitotenv.2019.02.047 https://doi.org/10.1016/j.scitotenv.2019.02.047 https://doi.org/10.1016/j.jenvman.2019.05.152 https://doi.org/10.1016/j.jenvman.2019.05.152 22 varga, meiczinger, and somogyi and toxicology. 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matsumura, m.; veliky, i.a.: diffusion characteristics of substrates in ca-alginate gel beads. biotechnol. bioeng., 1984 26(1), 53–58 doi: 10.1002/bit.260260111 [30] puguan, j.m.c.; yu, x.; kim, h.: diffusion characteristics of different molecular weight solutes in ca–alginate gel beads. colloids surfaces a physicochem. eng. asp., 2015 469, 158–165 doi: 10.1016/j.colsurfa.2015.01.027 47(2) pp. 17–23 (2019) https://doi.org/10.1002/bit.260260111 https://doi.org/10.1002/bit.260260111 https://doi.org/10.1016/j.colsurfa.2015.01.027 https://doi.org/10.1016/j.colsurfa.2015.01.027 hungarian journal of industry and chemistry vol. 47(2) pp. 25–30 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-17 multistage gravity beneficiation of rutile in a tar-free sand residue rukayat akande*1 and abraham adeleke1 1department of materials science and engineering, obafemi awolowo university, ile-ife, nigeria this study reports on the concentration of rutile in the sand recovered from tar sand in ondo state in nigeria. the tar-free sand residue, approximately 90 % of which passes through a sieve with a pore size of 355 µm, was subjected to sieve analysis as well as sequences of panning gravity pre-concentration and shaking-table concentration at a slurry density of 25 % solids to improve the rutile content. the sand residue recovered in addition to the panned pre-concentrate and shaking table concentrates were also subjected to reflected light microscopy as well as transmitted light microscopy, counting using imagej software and x-ray fluorescence spectroscopy. the micrographs obtained showed that the samples contain rutile, dark-brown in color, interlocked with the major silica content and the content of rutile estimated by imagej software increased in the pre-concentrate from 7.90 % to 19.23 % in the final concentrate. x-ray fluorescence spectroscopy also showed that the rutile content increased in the pre-concentrate from 1.43 % to 31.02 % in the final concentrate. therefore, the rutile content was successfully increased by the cheap gravity techniques of panning and shaking tables. keywords: tar sand, rutile, panning, shaking table, pre-concentrate, concentrate 1. introduction tar sands, also known as oil sands, are a combination of clay, sand and water saturated in a dense and extremely viscous form of petroleum technically referred to as bitumen. tar sands are impregnated sands that yield mixtures of liquid hydrocarbons, which require further processing other than mechanical blending before becoming finished petroleum products. tar sand deposits are found in various parts of the world including canada, madagascar, venezuela, russia, the united states and nigeria [1]. tar sand is exceedingly rich in oil as well as other valuable minerals and metals in varying proportions [2]. tar sand deposits are composed primarily of quartz sand, silt, clay, water and bitumen along with trace amounts of metallic minerals such as rutile, pyrite, zircon and gemstones like tourmaline. rutile is a major source of the element titanium and it is industrially used as a white pigment for paint, a ceramic glaze and in optical equipment [3, 4]. it is also used in sunscreen products due to its ability to reflect ultraviolet light [5]. nigeria has a large deposit of natural bituminous tar sand, which is estimated to be the fourth largest in the world after canada, russia and venezuela [6]. it is estimated that about 34 to 45 billion barrels of heavy oil is trapped in tar sand deposits in ondo state in southwestern nigeria alone, with more reserves in edo and ogun states. the reserve of tar sand in ondo state alone is es*correspondence: akanderukayat2@gmail.com timated to be 31 billion metric tons [7]. the tar sand here is located in the eastern part of the dahomey basin, a coastal sedimentary basin that extends from the ghanaivory coast border through togo and the republic of benin to western nigeria [8]. adeleke et al. [9] leached tar sand from ondo state using sodium hydroxide and sodium carbonate to strip off bitumen from the admixture of sand and also conducted a solubility test on the tar sand using toluene. sodium hydroxide was found to yield a higher percent recovery of bitumen than sodium carbonate over the same leach contact time. adebiyi et al.[10] determined the elemental composition of oil sand from southwestern nigeria by total reflection x-ray fluorescence and detected twelve elements, namely k, ca, ti, v, cr, mn, fe, ni, cu, zn, as and pb. ignasiak [11] reported that a nigerian deposit of bitumen-free sand residue contains only 0.06 wt% tio2. gravity beneficiation techniques make use of the difference in the specific gravity of minerals to separate them. therefore, heavy minerals such as rutile can be separated from the associated lighter minerals like silica. in the gravity method of shaking tables, a flowing film of water effectively separates coarse light particles from small dense particles [12]. mixed rutile and ilmenite ores were subjected to coarse concentration using a mineral jig [13]. in this research, the lean content of the mineral rutile in a residue of tar sand from ondo was increased over a sequence of gravity beneficiation by panning and shaking https://doi.org/10.33927/hjic-2019-17 mailto:akanderukayat2@gmail.com 26 akande and adeleke tables. 2. materials and methods 2.1 the collection of samples the basic raw materials used in this work were lumps of bituminous tar sand obtained from ondo state, nigeria. lumps of the semi-solid black tar sand of about 50 kg in weight were collected from the villages of agbabu and loda in the local government area of irele in ondo state. the local government area of irele is situated to the east of the local government area of okitipupa which lies at 40° 3” in longitude east of the greenwich meridian and at 50° 45” and 80° 15” in latitude north of the equator. the samples were collected from two open pits at a depth of about 3 feet. after field sampling, the lumps of tar sand extracted were stored in large plastic bags. 2.2 sample preparation the black lumps of tar sand were crushed and ground thoroughly with a steel rod. the ground tar sand was then homogenized in a mortar by pounding it with a pestle. the resultant mass of tar sand was composed of a finer mixture of particles and bitumen. 2.3 stripping of bitumen by leaching whilst being stirred the tar sand was leached on a magnetic hotplate stirrer using a 32 factorial design, that is, at three different temperatures and by applying variables concerning the concentration process. the 250 ml beaker reactor containing the slurry of tar sand and 25 ml of 0.5 m sodium hydroxide at a pulp density of approximately 40 g/l was initially homogenized for 5 minutes. the beaker was placed on a stuart magnetic hotplate stirrer, model number r000101019, which was set to 50 °c and 90 rpm to yield the t1c1 test combination. the magnetic stirrer was switched on and the pulp of tar sand allowed to react with the leachant, sodium hydroxide, for 30 minutes. after 30 minutes, the concentrate of bitumen was skimmed off and the leachant filtered to remove the remaining bitumen. the procedure was repeated for combinations t1c2, t1c3, t2c1, t2c2, t2c3, t3c1, t3c2, and t3c3. 2.4 stripping of bitumen by leaching in the absence of stirring a slurry of tar sand with a pulp density of approximately 40 g/litre was prepared by mixing 25 ml of 1.5 m sodium hydroxide and 1 g of tar sand in a 500 ml beaker. the beaker containing the slurry of tar sand was then placed on a hp-11electric hot plate. the slurry was stirred continuously for 30 minutes with a glass rod to agitate it to facilitate the recovery of bitumen from the tar sand. subsequently, the bitumen was decanted off and the residue washed with water to remove the bitumen. the residue was washed again with toluene to dissolve traces of bitumen in the tailings. the residue was then dried at 70 °c in an oven and the procedure repeated using 20, 3, 4, 5, 6, 7, 8, 9, and 10 g of tar sand which resulted in pulp densities of approximately 80, 120, 160, 200, 240, 280, 320, 360, and 400 g/l, respectively. the same procedure was repeated using 30 g of tar sand and the slurry prepared by mixing 300 ml of 1.5 m sodium hydroxide and 30 g of tar sand in a 500 ml beaker. the procedure was repeated several times until 7 kg of tar-free sand was recovered. a blank test was conducted using 25 ml of distilled water and 1 g of tar sand in a 500 ml beaker reactor. the beaker containing the slurry of tar sand was then placed on the hp-11 electric hot plate. the slurry was stirred continuously with a glass rod to agitate it to facilitate the recovery of bitumen from the tar sand. 2.5 panning of the tar-free sand about 50 g of the sample was thoroughly mixed and agitated with 50 ml of water in a 500 ml plastic bowl. the panning process caused the lighter mineral particles to float while the denser particles sank. the floating light particles were decanted off while the denser residue was dried and weighed. the procedure was repeated but with 100, 150, 200, 250, 300, and 350 ml of water. following preliminary panning, the remaining sample that weighed 36.25 g was subjected to further panning using the same 350 ml of water. the procedure was repeated ten more times by weighing the wet residue together with a content of 4.02 g after each panning. the same procedure was employed for the shaking tabling of approximately 138 g of the sample. 966 ml of water was used for panning the 138 g of tar-free sand ten times and the final product weighed and dried before proceeding to the shaking table. 2.6 determination of the specific gravity of tar-free sand a density bottle was washed, dried and its weight, m1, measured. subsequently, 5 g of tar-free sand residue was placed inside the dried bottle and its weight, m2, determined. then, 50 ml of distilled water was poured into a measuring cylinder and weighed to give m4. lastly, distilled water was added to the tar-free sand in a covered bottle and shaken very well for thorough mixing, moreover, additional distilled water was added to increase the volume to 50 ml and then weighed to give m3. to determine the specific gravity, thsese values were inserted into equation [12] g = m2 −m1 (m4 −m1)− (m3 −m2) (1) where m1 is the mass of empty bottle, m2 is the mass of bottle + dry soil, m3 is the mass of bottle + dry soil + hungarian journal of industry and chemistry multistage gravity beneficiation of rutile 27 figure 1: weight percentage of tar sand recovered following stripping on an electric hot plate. water, and m4 is the mass of bottle filled with water only. after deriving the specific gravity, the ratio of solids to water required to make the slurry was also determined as the feed should be composed of about 25 % solids by weight. 2.7 shaking tabling a slurry composed of 25 % solids by weight was produced by mixing 108 g of the panned sample in 324 ml of water which was introduced via the feed box of a shaking table, model number ed808148566q. the slurry was distributed evenly over the table, wash water was dispersed along the balance length of the feed launder. the table was then vibrated longitudinally using a slow forward stroke and a rapid return strike which caused the mineral particles to ‘crawl’ along the deck parallel to the direction of motion. as a result, the minerals were subjected to two forces, one due to the motion of the table and the other at right angles to it due to the flowing film of water. consequently, the particles moved diagonally across the deck from the feed end and fanned out on the table – the smaller, denser particles rode on top towards the concentrate launder at the far end. the larger lighter particles were washed into the tailings launder, which runs along the length of the table. an adjustable splitter at the concentrate launder was used to separate the product into three fractions, namely a high-grade concentrate and two medium-grade fractions. the concentrate continued to be shaken nine more times and the products weighed wet after every shaking. the final products were dried separately and then weighed [12]. 2.8 particle size analysis using a sieving method the eight sieves with pore sizes of between 850 and 63 µm were chosen based on the square root of two rule. the weights of the empty sieves were recorded and stacked on top of each other with the coarsest sieve with a pore size of 850 µm on the top and the finest of 63 µm at the bottom. a fitting receiver was placed below the bottom sieve to collect any undersized particles and a lid placed on top of the coarsest sieve to prevent the sample from escaping. fig. 1 shows the sieving machine and the setup of the sieves. a 300 g sample of the recovered tar-free sand was poured onto the uppermost, coarsest sieve, and the nest of sieves placed in an endecotts test sieve shaker, model number 9205. the nest of sieves was vibrated in a vertical plane. the period of shaking was set to 30 mins using an automatic timer. during the shaking, the undersized material dropped through successive sieves until it was retained on a sieve with a pore size slightly smaller than the diameter of the particles. in this way, the sample was separated into size fractions. after the required time, the nest of sieves was dismantled and the amount of material retained on each sieve weighed [12]. 2.9 reflected light microscopy the sample was deposited on a slide which was placed on the stage of an accu-scope microscope, serial number 0524011. the diaphragm was then used to vary the intensity and size of the cone of light that was projected upwards through the slide. the microscope was connected to a laptop to capture the plane section of the image which was captured using image capture software on a laptop as soon as a clear image was obtained. reflected light microscopy was used to view the raw sample, panned sample, samples obtained from the particle size analysis and those from the shaking table. imagej was used to analyze the images obtained from reflected light microscopy. 2.10 thin section microscopy the sample was impregnated since it was a loose sample by mixing equal amounts of araldite (resin and hardener) and sample together which was placed on a glass slide. the glass slide was placed on a hot plate for 5 mins and left to cool overnight. the cooled glass slide was ground by a lapping machine, transferred to a lapping plate for further grinding and viewed intermittently several times under the microscope till it became thin enough for light to penetrate through. the glass slide was dried on the hot plate, covered in araldite and viewed under a brunel petrographic microscope, model no. 1287599. 2.11 x-ray fluorescence spectroscopy a 3 g sample was pulverized into a fine homogenous mass and pelletized. an x-ray fluorescence spectrometer, model no. edx3600b, was used to analyze the sample. the desired method was selected on the measuring instrument and the sample carefully placed onto the instrument according to the set-up of its benchtop measurement position. the compartment containing the sample was covered to prevent x-ray radiation from being scattered. the measurement conditions were set, the details of the sample entered and the complete spectrum recorded which 47(2) pp. 25–30 (2019) 28 akande and adeleke table 1: screened distribution of sand recovered from tar sand. pore-size range of sieve (µm) weight of sieve fraction (g) weight of sieve fraction (%) nominal aperture size (µm) cumulative undersize distribution (%) cumulative oversize distribution (%) +850 1.02 0.37 850 99.63 0.37 850 to +500 0.92 0.33 500 99.26 0.74 500 to +355 5.05 1.84 355 97.45 2.55 355 to +212 20.44 7.45 212 89.97 10.03 212 to +150 178.7 65.14 150 24.86 75.14 150 to +125 50.51 18.41 125 6.45 93.55 125 to +90 16.62 6.06 90 0.39 99.61 90 to +63 0.96 0.35 63 0.04 99.96 < 63 0.11 0.04 lasted 60 to 120 seconds per sample, moreover, all detectable elements were measured simultaneously. raw quantitative spectra and quantified results were acquired and saved. 3. results and discussion it can be seen from fig. 1 that the weight percent of recovered tar-free sand reduces as the mass of the tar sand increases which indicates that the percent recovery decreases as the pulp density increases. therefore, pulp density is one of the factors that affects leaching, hence the laboratory-scale leaching of about 40 g/l was conducted. the decrease in the leaching rate as the pulp density increases is due to increased particle crowding and a lower concentration of leachant available per unit volume of the slurry [14]. it was observed that the smallest bitumen recovery of 55 % obtained from stirred leaching on the magnetic stirrer hotplate was greater than the highest recovery of 45 % for the unstirred leaching on the ordinary hotplate. this confirms that slurry stirring is an important process variable in the hydrometallurgical approach to leaching [14]. the sieve analysis showed that the majority of the sample was found within the 212 to 150 µm pore-size range, namely 65.14 % of the sample. the results obtained suggest that the residue of the tar sand is fairly coarse as the fraction smaller than 63 µm is insignificant. coarse-sized ores are preferred for gravity concentration as they are more efficiently treated than finer ones [12]. the results are presented in table 1. the lighter minerals from the 350 ml volume of water were further reduced following nine sequential pannings. the residue obtained after ten sequential pannings was found to contain many of the denser minerals given that the majority of the lighter minerals had been previously removed as shown in table 2. this table shows that the mass of the denser sand residue obtained after panning generally decreased as the volume of water used for panning increased. the results obtained suggest that panning efficiency increases as the volume of water increases. this may be due to the fact that by increasing table 2: the recovery of denser materials as a function of the volume of water used during panning. volume (ml) residue (g) mass recovered (%) 50 47.43 94.86 100 45.42 90.84 150 45.38 90.76 200 44.01 88.02 250 40.18 80.36 300 38.63 77.26 350 36.25 72.5 the water content, a more dilute slurry subject to less particle crowding, a better degree of free flow and settling of mineral particles is produced, thus enhancing the separation of lighter particles from denser ones. fig. 2 indicates that generally the mass of denser residues decreased as the sequence of panning stages progressed. the results suggest that as the sequence of panning advances, the minerals composed of denser particles are progressively concentrated into the concentrates of denser residues [12]. it was observed from fig. 3 that the more the shaking table charge was subjected to a sequence of shaking tabling, the greater the proportion of denser rutile that was separated from the lighter silica mineral. the weight of the dry concentrates and tailings obtained after the sefigure 2: residue obtained after panning the sand residue with various volumes of water. hungarian journal of industry and chemistry multistage gravity beneficiation of rutile 29 table 3: summary of the numbers of total and rutile counts as well as the estimated percentage of the raw and panned samples in addition to the concentrates and tailings from the shaking table obtained from the xrf spectroscopy of each sample. type of sample total count rutile count imagej estimated % of rutile the % of rutile by xrf spectroscopy raw sand residue 1265 192 7.9 1.43 panned sand residue 913 192 10.04 17.5 shaking table concentrate of sand residue 1061 204 19.23 31.02 shaking table tailings of sand residue 2041 99 4.85 5.01 quence of ten shaking tablings of the charge were 10.55 and 48.29 g, respectively. this figure shows that the mass of the concentrates of denser particles recovered generally decreased while that of the tailings increased with some minor exceptions. the results obtained confirm the concentration of rutile in the concentrate increased as the sequence advanced. the sequential stages of shaking progressively improved the grade of the concentrates in terms of denser minerals. the plane-polarized and cross-polarized images obtained from reflected light microscopy and thin section microscopy of the raw and panned samples, in addition to the concentrate and tailings from the shaking table were analyzed. according to francis [15], rutile was translucent and dark red-brown in color, while silica was transparent and whitish in color under a thin section microscope. further observations showed that pure crystalline rutile was not abundant in the sample as most of the rutile under cross-polarized light was observed to be interlocked with silica. the plates further indicated that the rutile content of the concentrate on the shaking table exceeded that of the panned concentrate. a summary of the number of total and rutile counts as well as the percent distribution estimated for the raw and panned samples in addition to the concentrates and tailings of the shaking table is shown in table 3. imagej counting estimated the rutile content in the recovered sand residue as well as in the concentrates of the shaking table and following panfigure 3: recovered masses of concentrates and tailings from ten sequential shaking tables. ning as 7.9, 19.23 and 10.04 %, respectively. fig. 4 shows the results from the x-ray fluorescence spectroscopy of the recovered and panned sand residues in addition to the concentrates from the shaking table. the percentage of silica in the recovered sand residue was reduced from 49.9 % to 47.6 % in the panned preconcentrate and further to 41.4 % in the concentrate of the shaking table. moreover, the titanium content of the recovered sand residue was enhanced from 0.86 % to 10.6 % in the panned pre-concentrate, while that of the concentrate from the shaking table in the panned preconcentrate was further improved to 18.3 %. therefore, the results obtained showed that the rutile content of the recovered sand residue was enhanced from 1.43 % to 17.50 % in the panned concentrate and finally to 31.02 % in the concentrate from the shaking table. the decrease in the silica content and increase in the titanium content strongly suggest that the panning and shaking table were efficient methods to improve the rutile content of the residue of tar sand. the results obtained from imagej counting also compare favorably with that of xrf spectroscopy except for the sample as received where both appeared to be significantly different. the flow diagram of the beneficiation process is shown in fig. 5. figure 4: percent recoveries of the elements ti, si, fe, sn and al in the concentrates. 47(2) pp. 25–30 (2019) 30 akande and adeleke figure 5: flow diagram of the bench-scale beneficiation of tar sand from ondo. 4. conclusions the rutile content of the tar-free residue obtained from tar sand extracted from ondo was successfully improved by gravity beneficiation of the sand residue. the results obtained show that a sequence of panning preconcentrations followed by a sequence of shaking tabling improved the rutile content from 1.43 % to 31.02 %. references [1] falebita, o. a.; koul, s.: sustainable development of oil sands and host communities: preliminary system dynamics assessment. (managing intellectual capital and innovation for sustainable and inclusive society: proceedings of the makelearn and tiim joint international conference 2, toknowpress, 2015), pp. 2095–2109 [2] allen, c.: mineralogy of tar sand in the upper part of the green river formation in the eastern utah basin, utah. u.s. geological survey open-file report 76-381, pp. 27. [3] erdogan, l. dielectric properties of oil sands at 2.45 ghz determined with rectangular cavity resonator. m.sc. thesis, université de montréal, montréal, qc, canada. https://publications.polymtl.ca/732/1/2011_leventerdogan.pdf retrieved on 12 november 2019 [4] lavat, a. e.; gayo, g. x.: new environmental friendly yellow ceramic pigments of the type (fe111mv)-ti02. j. chem. chem. eng. 2014 8: 1026–1035 doi: 10.17265/1934-7375/2014.11.003 [5] reddy, k. m.; manorama, s. v.; reddy, a. r.: bandgap studies on anatase titanium dioxide nanoparticles. mat. chem. phys. 2003 78(1): 239– 245 doi: 10.1016/s0254-0584(02)00343-7 [6] adegoke, o. s.; ako, b. d.; enu, e. i.: geotechnical investigations of the ondo state bituminous sands, geology and reserves estimate. unpublished manuscript. department of geology, obafemi awolowo university, ile-ife, nigeria. [7] emmanuel, e.; ajibade, o. m.: elemental composition and geochemistry of heavy oil in parts of eastern dahomey basin, southwestern nigeria. j. env. earth sci. 2014 4(12): 18–25 [8] enu, e. i.: textual characteristics of the nigeria tar sands. sedimentary geology, 44: 65–81. doi: 10.1016/0037-0738(85)90032-6 [9] adeleke, a. a.; ibitoye, s. a.; oladokun, c. b.; oluwasegun, k. m.: an evaluation of the hot aqueous caustic leaching of nigerian ondo tar sand. petroleum and coal, 2011 53(4): 320–323 [10] adebiyi, f. m.; asubiojo, o. i.; ajayi, t. r.; obiajunwa, e. i.: trace element and physico-chemical characteristics of the sand and water fractions of nigerian bituminous sands. chemistry and ecology, 2005 21(5): 369–380 doi: 10.1080/02757540500291725 [11] ignasiak, a. k.: microscopic structure of athabasca oil sand. can. j. chem. eng., 0982 60(4): 538–545 doi: 10.1002/cjce.5450600416 [12] wills, b. a., napier-munn, t.: mineral processing technology (elsevier, 2015) isbn: 978-0-08-097053-0 [13] 911 metallurgist. metallurgists & mineral processing engineers. https://www.911metallurgist.com retrieved on 25 august 2018 [14] ghosh, a.; ray, h. s.: principles of extractive metallurgy. (new age international, 1991) isbn: 9788122403220 [15] francis, c.: characterization and upgrading of a rutile concentrate produced from the oil sands tailings. m.sc. thesis, university of alberta, edmonton, ab, canada, pp. 95-96. https://era.library.ualberta.ca/items/79044641-a67d410f-b072-4bf5b4cadb0d/view/f051e5bd-3406-4262-abc8dd479e66f11a/mq81377.pdf retrieved on 12 november 2019 hungarian journal of industry and chemistry https://publications.polymtl.ca/732/1/2011_leventerdogan.pdf https://doi.org/10.17265/1934-7375/2014.11.003 https://doi.org/10.1016{/}s0254-0584(02)00343-7 https://doi.org/10.1016/0037-0738(85)90032-6 https://doi.org/10.1016/0037-0738(85)90032-6 https://doi.org/10.1080/02757540500291725 https://doi.org/10.1002/cjce.5450600416 https://www.911metallurgist.com https://era.library.ualberta.ca/items/79044641-a67d-410f-b072-4bf5b4cadb0d/view/f051e5bd-3406-4262-abc8-dd479e66f11a/mq81377.pdf https://era.library.ualberta.ca/items/79044641-a67d-410f-b072-4bf5b4cadb0d/view/f051e5bd-3406-4262-abc8-dd479e66f11a/mq81377.pdf https://era.library.ualberta.ca/items/79044641-a67d-410f-b072-4bf5b4cadb0d/view/f051e5bd-3406-4262-abc8-dd479e66f11a/mq81377.pdf hungarian journal of industry and chemistry vol. 47(2) pp. 31–42 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-18 gpu-accelerated simulation of a rotary valve by the discrete element method balázs füvesi1 and zsolt ulbert*1 1department of process engineering, university of pannonia, egyetem u. 10, veszprém, 8200, hungary the rotary valve is the most frequently used piece of equipment that is suitable for the controlled feeding or discharging of products in powdered or granular form. it is usually connected to silos, hoppers, pneumatic conveying systems, bag filters or cyclones. in this paper, a simulation study is presented on the discharge of solid particles from a silo through a rotary valve. the discrete element method (dem), which accounts for collisions between particles and particle-wall collisions, was used to model and simulate the motion of individual particles. the diameter of the simulated silo was 0.2 m and a total of 245, 000 particles were calculated. in the simulations, the effect of the geometric and operational parameters of the rotary valve on the mass outflow rate was investigated. the diameter of the rotary valve varied between 0.06 and 0.12 m and the rotational speed of the rotor was changed between 0.5 and 5 s−1. the simulations showed that the mass outflow rate of the particles from the rotary valve changes periodically due to its rotary cell structure. within the lower range of rotational speeds of the rotor, the mass outflow rate of particles changes linearly in correlation with the rotational speed. the identification of this linear section is important in terms of control as this would facilitate the implementation of control devices by applying well-established linear control algorithms. adjacent to the linear section, the dependence of the average mass outflow rate on the rotational speed was found to be nonlinear. within the upper range of examined rotational speeds for each diameter of the rotary valve, the mass outflow rate reaches a maximum then decreases. the simulations were performed using gpu hardware. the application of parallel programming was an essential aspect of the simulations and significantly decreased the calculation time of simulations. in the treatment of particle-wall contacts, a novel flat triangular-based geometric representation technique was used which allows the particle-wall contacts to be calculated more effectively and their treatment implemented more easily into the parallel programming code. using the calculated particle positions, the particles were visualized to view the effect of the interactions between the particles and rotor blades on particle motion. the simulation results showed that the discrete element method is capable of determining the detailed flow patterns of particles through the rotary valve at various rotational speeds. keywords: silo, rotary valve, simulation, discrete element method, gpu 1. introduction the handling of solids is part of many industrial technologies in the chemical, pharmaceutical and food industries amongst others. from simple storage (e.g. storage silo) and transport operations (e.g. pneumatic transport) to gas-solid or liquid-solid two-phase flows (e.g. gassolid fluidization, gas-solid catalytic reactions), a number of technological operations involve solid and particulate materials. a common feature of gas-solid two-phase flow is that the interaction between the solid and gas phases can facilitate effective phase mixing in addition to intensive mass and heat transfer for a variety of operational purposes (e.g. gas-solid chemical reactions). the movement of the solid phase may result in different flow mechanisms and flow patterns, depending on the frequency of collisions between the particles and effects as a result of the gas stream. the experimental investigation of the unit *correspondence: ulbert@fmt.uni-pannon.hu operations of particulate solids is time-consuming and costly. measurements in this type of systems are often inaccurate due to the limitations of the measuring devices and difficulty of taking measurements in a solid flow without changing its flow properties. although a number of advanced measurement techniques for measuring the flow properties of solids, e.g. phase doppler particle analyzer, high-speed video processing, magnetic resonance tomography, positron emission particle tracking, etc., exist which provide useful information on the movement of particles, many factors that significantly influence the flow structure such as the forces between the colliding particles are not yet available. however, experiments can be performed more easily using computer simulation if a sufficiently detailed model is available to investigate the system. the modeling and simulation of the flow of particulate solids are becoming increasingly popular and intensive research has been undertaken in this field. the flow of particulate solids is https://doi.org/10.33927/hjic-2019-18 mailto:ulbert@fmt.uni-pannon.hu 32 füvesi and ulbert always coupled with the flow of the interacting gas phase and in this sense the entire particulate flow can be considered to be a gas-solid two-phase flow. however, the construction of the model depends on the degree of interaction between the solid and gas phases. the effect of the gas phase on the solid particles may vary from one unit operation to another. for example, in terms of the gravity discharge of solids from a silo, the effect of the gas phase is negligible on the motion of the particles and the calculation of any interaction between the solid particles and gas phase and the calculation of the gas phase flow are unnecessary. on the other hand, when pneumatic transportation is used to transport solids, the interaction between the two phases is significant, therefore, the modelling and calculation of flow characteristics of both the solid particles and gas phase as well as their interactions is necessary. two main methods for the treatment of solid particles with regard to gas-solid two-phase flows are proposed by the authors. the euler method considers both the solid and fluid phases as a continuous phase and these methods are referred to as two-fluid models (tfm) in the literature. in these models, both phases are calculated by volume-averaged flow equations that are supplemented by terms which describe the interaction between the two phases. the disadvantage of these methods is that the solid particles are treated as a continuous phase and no information is provided about the motion of individual particles. in another method, the gas phase is treated as a continuous phase and described by volume-averaged flow equations, however, the solid particles are treated as discrete systems with their own mass, independent motion and velocity. the flow equations for the gas phase also include terms that describe the interaction between the solid particles and the gas phase. to model and calculate the forces that result from particle-particle and particle-wall collisions, the discrete element method (dem) based on the softor hard-collision model is used. these calculation methods are referred to as the euler-lagrange, eulerdiscrete element method (euler-dem) or the computational fluid dynamics discrete element method (cfddem). if the effect of the gas phase on the particles is negligible, the motion of the particles can be calculated by applying the discrete element method alone without taking into account any interactions with the gas phase. the discrete element methods have the advantage of providing detailed information about the flow characteristics of solid particles. however, since all the particles are handled independently, they require significant computing capabilities in the case of a large number of particles. in the application of “two-fluid” theory, anderson and jackson [1] first introduced interaction terms in the volume-averaged navier-stokes equation that is used to describe the particle-fluid and particle-particle interactions. in the 1990s, a significant amount of research using tfms in the modeling and simulation of two-phase flow in fluidized beds was conducted by bouillard et al. [2], ding and gidaspow [3], kuipers et al. [4–6] and nieuwland et al. [7]. mckeen et al. [8] simulated the movement of catalyst particles in a fluidized-bed catalytic cracking reactor. wang et al. [9] developed a tfm including chemical reaction source terms that are capable of describing homogeneous and heterogeneous reactions. pougatch et al. [10] simulated particle attrition in a fluidized bed introducing an attrition term into the model. however, given the complexity of two-fluid models, they are unable to describe the discrete particle dynamics and flow properties of individual particles. the rapid development of computers and parallel computing over recent decades has led to the popularization of discrete element methods in terms of the simulations of solid particulate flows and gas-solid two-phase flows. in the application of discrete element methods, the movement of each individual particle in the particulate flow is calculated. the motion of particles is calculated in accordance with newton’s three laws of motion by taking into account the forces acting on the particles as a result of collisions with other particles or from their interactions with the gas phase. over the last two decades, numerous papers have been published regarding the application of the discrete element method. tsuji et al. [11] and kawaguchi et al. [12,13] presented simulations of gas-solid fluidization by applying a soft collision model developed by cundall and strack [14]. in these simulations, the mixing of particles inside the fluidized bed was examined. hoomans et al. [15, 16] used a hard-sphere collision model in their simulations and studied the effect of gas velocity on the flow of particles in a fluidized bed. kaneko et al. [17] also used the cfd-dem simulation method in the simulation of a polymer reactor. using the temperature and velocity field of the gas phase, they calculated the kinetics of the polymerization reaction and the reaction heat for each individual particle. ulbert et al. [18] presented a cfd-dem simulation study on the simulation of a reactive gas-solid two-phase flow in a circulating mediator recirculation integrating technology (merit) fluidized bed combustor. the model proposed by the authors contains the balance equations for the components of the reaction and the shrinking core model was used to describe the gassolid chemical reaction for each particle. tsuji et al. [19] presented a simulation study that calculated the motion of 4.5 million particles in a fluidized bed using parallel computation. yang et al. [20] examined the effect of the surface energy of particles on the transitions between different flow types in a fluidized bed. fan et al. [21] presented a simulation study on the simulation of cohesive particles. accordingly, the cohesive surface interaction between the particles was taken into account when the interacting forces were calculated. hou et al. [22] simulated a fluid bed equipped with heat transfer tubes using the cfd-dem simulation method. the authors examined the heat transfer between the tubes and the fluidized bed. hou et al. [23] studied the effect of the particle-gas interaction, particle-particle collisions, gravity and friction on the transfer of energy between particles in particulate hungarian journal of industry and chemistry gpu-accelerated simulation of a rotary valve 33 figure 1: cross-sectional view of a silo equipped with a rotary valve. solid flows and gas-solid two-phase flows. as can be seen from the aforementioned examples, in addition to the calculation of the motion of discrete particles, the discrete element method is suitable to treat the discrete nature of the solid particle phase by taking into account further characteristics of discrete particles, e.g. temperature, concentration, etc. the subject of this paper is the simulation of the operational characteristics of a rotary valve that is often connected to a silo that stores solids (fig. 1). during the discharge of solids from silos, the effect of the gas phase on the movement of particles is negligible, i.e. it is unnecessary to consider the interaction between solid particles and the gas phase. many examples are documented in the relevant literature related to the simulation of discharging solids from silos using the discrete element method. masson and martinez [24] simulated silo feeding and discharge using the discrete element method. in their simulation studies, the effect of the mechanical parameters of the particles on particle flow was studied. it has been shown that the friction and elasticity of the particles have a significant effect on the properties of particle flows. yang and hsiau [25] simulated silo feeding and discharge. in their research, different types of inserted elements were used and tested to improve the quality of the outflow of solid material from a silo. goda and ebert [26] presented a simulation study that investigated the effect of particles on a wall using the discrete element method. gonzalez-montellano et al. [27] examined a laboratorysized silo experimentally and by simulation to identify the coefficient of friction of the particles. zeng et al. [28] examined the fluctuation in the velocity of the particles being discharged from a silo. they showed that the velocity of particles fluctuates above a critical value of the coefficient of friction. few reports in the literature are related to experimental and simulation studies on rotary valves used to discharge or feed solids. a rotary valve connected to a silo was experimentally studied by al-din and gunn [29]. the authors investigated the dependence of particulate mass flows delivered by the rotary valve on the rotational speed of the rotor and a linear relationship was found between the rotational speed and mass flow only within a certain range of rotational speed. kirkwood et al. [30] used a rotary valve to discharge solids from a silo and examined the mixing and segregation of solids inside the silo by analyzing the residence times. it was found that at low rotational speeds the particles segregated inside the silo and dead spaces developed in which the particles moved down significantly more slowly. however, at higher rotational speeds the entire particle bed of the silo moved evenly downwards, thereby ensuring that the solid layers that were fed into the silo did not mix. the application of rotary valves occurs in all industrial areas where solids are stored in silos. the controlled discharge of the content of silos is important from both technological and control aspects. a deeper understanding of operational characteristics can significantly contribute to their geometric and operational design parameters. the simulation method used in our simulation study is the discrete element method, which provides a detailed insight into the flow of the solid phase inside a rotary valve. the purpose of the simulations is to determine how the geometric and operational design parameters of the rotary valve influence the mass outflow rate of solid material through the rotary valve. the following chapters of this paper describe the discrete element method used in the modeling and simulation of particle flow, the triangular geometric representation technique used in the analysis of particle-wall collisions, the main features of the gpu hardware and parallel programming used in calculations, and the simulation results of the investigation of the effect of geometric and operational parameters of rotary valves on the mass outflow rate of solid particles. 2. discrete element method the discrete element method has become a popular method in the modeling and simulation of particulate flows. it is capable of calculating the motion of individual particles. the interactions between the particles and the boundary of the system are the collisions between particles and the particle-wall collisions which result in contact forces. the total contact force that acts on a single particle is the sum of the contact forces with regard to the forces that proceed from all the neighboring contacts. the individual particles exhibit two types of motion: translational and rotational. translational motion is 47(2) pp. 31–42 (2019) 34 füvesi and ulbert caused by the contact forces and gravity. rotational motion is generated only by the contact forces. in the case of when the effect of the gas phase is negligible, the threedimensional translational and rotational motion of particles is expressed by newton’s three laws of motion as follows: miai = j=qi∑ j=1 (fcn,ij + fct,ij) +mig, (1) iω̇i = j=qi∑ j=1 (tij +mij) , (2) where qi denotes the number of particles simultaneously in contact with particle i. mi, ai, and ω̇i are the mass, translational acceleration, and angular acceleration of particle i, respectively. fcn,ij and fct,ij stand for the normal and tangential components of the contact force between particles i and j, tij is the torque at the point of contact between particles i and j due to the tangential contact force, mij denotes the rolling resistance acting on particle i with regard to particle j, i represents the moment of inertia of particle i, g stands for the gravitational force vector, and ri is a vector from the center of particle i to the point of contact. the torque tij is calculated using the tangential contact force by the vector cross product tij = ri × fct,ij . (3) the rolling resistance mij is expressed by the following equation (wensrich and katterfeld [31]): mij = −µr rirj ri + rj |fcn,ij | (ωiri − ωjrj) , (4) where µris the rolling resistance coefficient and ri and rj denote the radii of particles i and j, respectively. when the particle collides with a wall, eq. 4 is simplified as mij = −µrri |fcn,ij | (ωiri) . (5) after the contact forces and torque have been calculated, the translational and angular accelerations can be expressed from eqs. 1 and 2 and the translational and angular velocities as well as position of particles can be calculated by numerical integration. the calculation of contact forces can be divided into two groups, namely the calculation of normal and tangential contact forces. in our simulation, the contact forces were calculated in accordance with the soft-sphere contact model developed by cundall and strack [14]. in this model, the contact forces are calculated on the bases of simple mechanical models such as spring, dashpot and friction elements (fig. 2 ). these mechanical elements influence particle motion through the parameters of the spring constant k, damping coefficient η and coefficient of friction µ. the sum of the normal forces is yielded by the normal forces generated by the spring and dashpot element: fcn,ij = (−knδn,ij − ηnvr,ij · nij)nij . (6) figure 2: soft-sphere contact model: (a) normal direction, (b) tangential direction. similarly, in the tangential direction, the sum of tangential forces acting on particle i is fct,ij = −ktδt,ij − ηtvrs,ij , (7) where vector nij denotes a unit vector from the center of particle i to the center of particle j, vr,ij represents the relative translational velocity of the colliding particles, δn,ijstands for the normal particle displacement, δt,ij is the tangential particle displacement vector and vrs,ij denotes the relative slip velocity of the particles. 2.1 calculation of the normal and tangential displacement of particles during elastic collisions between particles, at first particles are deformed and compressed, then expand and start to move in the opposite direction. this mechanism is modeled in the soft-sphere contact model by assuming the shape of particles is unchangeable. when two particles collide, they overlap with each other and the distance between their centers becomes smaller than the sum of their radii. based on this overlapping, a normal displacement δn,ij , as shown in fig. 3, can be defined as δn,ij = (di + dj)/2− |pi − pj | , (8) where di and pi in addition to dj and pj are the diameters and position vectors of particles i and j, respectively. the calculation of contact forces in the tangential direction is also based on a displacement defined in the tangential direction. as the particles first make contact, the points of impact a and b are the same points of the space (fig. 3). the location of two points is continuously changing due to the translational and rotational motion of particles and a distance (c) between the two points evolves which is equal to the absolute value of the tangential displacement vector δt,ij . the direction of δt,ij is perpendicular to the unit vector nij and extends from the actual point of contact. as the collision proceeds, the absolute value and direction of the displacement vector hungarian journal of industry and chemistry gpu-accelerated simulation of a rotary valve 35 figure 3: illustration of normal and tangential particle displacement. change according to the instantaneous relative slip velocity at the point of contact. moreover, the directions of the unit vector nij and tangential displacement vector δt,ij also change in accordance with the translational movement of particles during the collision (fig. 4). for this reason, the value of the tangential displacement vector is corrected by two steps. at first, the original value of the tangential displacement vector is transformed into the new position of particles defined by the unit vector nij . in the second step, the transformed tangential displacement vector is corrected by the time integration of the relative slip velocity. 2.2 calculation of the slip velocity the tangential component of the relative translational velocity vrt,ij can be determined as vrt,ij = vr,ij − (vr,ij · nij)nij , (9) where vr,ij = vp,i − vp,j is the relative translational velocity. the circumferential velocity vc at the point of contact is calculated by the angular velocity ω of the particles. for particle i, it is given as vc,i = (|ri|ωi)× nij . (10) by using the circumferential velocities, the relative slip velocity can be determined from vrs,ij = (vc,i − vc,j) + vrt,ij . (11) 2.3 calculation of the slide of particles when two particles come into contact, the normal force fcn,ij presses them together. the sliding motion of surfaces introduces a tangential force of friction that acts on the surface in the direction which opposes the motion. in our simulations, the coulomb’s law of friction is applied to calculate the slide of particles. the magnitude of the tangential contact force vector is verified against the value of µ |fcn,ji|, where µ represents the coefficient of friction between particles i and j. if the absolute value of figure 4: change in particle orientation during the collision. fct,ij exceeds that of µ |fcn,ji|, the particles slide and the value of the tangential contact force is changed in accordance with fct,ij = µ |fcn,ij | tij , (12) where tij = fct,ij/|fct,ij | defines a unit vector. when the particles slide, the tangential contact force fct,ij is considered to be exerted only by the spring. therefore, a new value of tangential displacement vector δt,ij , which is identical to the new value of the tangential contact force, must be calculated: δt,ij = µ |fcn,ij | k δij |δij | . (13) 2.4 calculation of the damping coefficient the damping coefficient η of a dashpot can be related to the coefficient of restitution e according to η = −2 √ mk ln e√ π2 + (ln e) 2 (14) developed by analytically solving the equation that describes a damped oscillatory system containing a mass, spring and dashpot (tsuji et al. [11]). 2.5 treatment of particle-wall collisions particle-wall contacts can be deduced from particleparticle contacts. on the external side of the wall the particle comes into contact with, a mirror particle is placed with an angular velocity of zero (fig. 5). the unit vector nij , from the center of particle i to the center of mirror particle j, is always perpendicular to the wall plane. in the case of a motionless wall, the translational velocity of a mirror particle is zero. consequently, the relative velocity between the contacting and mirror particles is the same as the velocity of the contacting particle. when the particle comes into contact with a moving wall, the translational velocity of the mirror particle is identical to the velocity of the point of impact. under these conditions, the contact forces for particle i can be calculated in a similar way to in the case of particle-particle contacts. 47(2) pp. 31–42 (2019) 36 füvesi and ulbert figure 5: the placement of a mirror particle during a particle-wall collision. 3. conditions of simulation simulation of the three-dimensional motion of particles was conducted in a silo equipped with a rotary valve as shown in fig. 1. the dimensions of the silo and rotary valve are given in table 1. the number of spherical particles of uniform size used in the simulation study was 245, 000. the particle properties used in the simulation are summarized in table 2. the initial particle bed completely filled the silo above the rotary valve as shown in fig. 1. in the simulation study, the effect of the geometric design and operational parameters of the rotary valve on the mass outflow rate was examined. in total 48 simulation runs were accomplished. the diameter of the rotary valve varied between 0.06 and 0.12 m. the rotational speed of the rotor was adjusted between 0.5 and 5 s−1. the parameters of the simulation runs are summarized in table 3. the specifications of the computer and gpu used in the simulation study are shown in table 4. 4. geometric representation of the silo and rotary valve during the discharge of the silo through the rotary valve, particles come into contact with each other and the walls. the walls of the silo are stationary, on the other hand, in the case of the rotary valve, the walls of the body are stationary and the walls of the rotating rotor move. the detection and treatment of particle-wall collisions require the calculation of the distance between the particle and wall which is based on the normal vector of the table 1: geometric and operational parameters. height of silo, m 0.49 diameter of silo, m 0.2 half-angle of cone 45◦ height of rotary valve, m 0.14 diameter of rotary valve, m 0.06, 0.072, 0.084, 0.096, 0.108, 0.12 rotational speed, s−1 0.5, 1, 1.5, 2, 2.5, 3, 4, 5 table 2: particle properties used in the simulations. diameter, m 0.004 density, kg/m3 1190 spring constant, normal direction, n/m 800 spring constant, tangential direction, n/m 800 coefficient of restitution, e 0.6 friction coefficient, µ 0.43 rolling resistance coefficient, µr 10−4 table 3: parameters of simulation runs. number of particles 245, 000 simulation time, s 4 timestep, s 5× 10−5 interval for data saving, s 0.002 number of standing wall elements 500− 600 number of moving wall elements 24 wall surface. in the case of flat walls, the normal vector can be determined easily. however, in the case of curved surfaces, the calculation of the normal vector of the surface and contact point is much more computationally complex. the number of calculations can also be increased significantly when collisions with moving walls are taken into consideration. therefore, in our simulation technique, the equipment walls are approached in accordance with a set of flat triangles which allows wall collisions to be detected and contact forces to be easily calculated. this has two advantages over the conventional treatment of particle-wall collisions using the mathematical definition of curved surfaces. on the one hand, any curvature wall can be easily defined by a set of flat triangles using methods developed in the field of computer graphics. the surfaces and geometries created using computer graphics software can be saved and imported into the simulation program along with the other simulation parameters. as a result, the geometry of the equipment can be altered in the program without changing the programming code. in the case of the application of moving walls, the description of the movement of the triangles is also produced by computer graphics software and imported into the simulation program. another advantage is that the gpu can work more table 4: details of the computer hardware. cpu intel core i5-3570 3.4ghz memory size 16gb motherboard gigabyte ga-z77-d3h gpu nvidia geforce gtx 1080 ti number of cuda cores 3, 584 gpu memory size 11gb gpu gigaflops (single precision) 10, 609 hungarian journal of industry and chemistry gpu-accelerated simulation of a rotary valve 37 figure 6: the flat triangular approximation of the silo geometry. efficiently if the threads need to conduct similar calculations simultaneously. thus, it is advantageous for the gpu to process the treatment of many triangles of the same structure as opposed to just a few but different structures of equations for the surface. a further advantage of the flat triangular approximation is that its accuracy can be increased where required by using more triangles, e.g. the approximation of the silo geometry by a set of flat triangles is shown in fig. 6. in the treatment of particle-wall collisions, it is necessary to determine the position of mirror particles. when using the flat triangular approximation, firstly it is necessary to check whether the given particle can collide with the given triangle. if the particle collides, the point of the triangle closest to the particle is determined using the method developed by mark w. jones [32]. then the position of the particle is mirrored on the opposite side of the triangle in the direction given by the normal vector. 5. application of the gpu to apply the discrete element method effectively, the computer hardware used for the calculations has to be capable of parallel computing the motion of individual particles. in our simulation study, gpu cores and parallel programming were used to calculate the particles in parallel. a gpu core was assigned to each particle. a core can only write data in the memory associated with the particle but can read all the data from the memory associated with the other particles to analyze collisions between particles. as a consequence, all the data that results from the calculation of a collision between two particles is stored in two memory places. this solution had to be applied to avoid problems related to the writing of duplicates. additionally, because of the way data is read, associated problems may arise when new data is calculated from the data in both the previous and current iterations. to overcome these problems, two data units were used, one always contained the data of the previous iteration and the other stored that of the current iteration. the number of particles simulated may exceed the number of cores in the gpu, therefore, particles are calculated in consecutive batches. after calculating a batch of particles assigned to the gpu cores, a new group of particles is added to the gpu cores and they are calculated. this process is repeated until each particle has been calculated, then the next iteration is executed. it is also important to note that during the parallel execution all the calculation data is stored in the memory of the gpu and that the cpu only gives instructions to the gpu about which calculations to perform. therefore, at the beginning of the simulation, all the initial data concerning particles and walls are copied into the memory of the gpu and the cpu is used to instruct the gpu to perform the calculations. since the copying of data between the memories of the gpu and computer (host) is slow, this would increase the run time of the program, so it is important that the copying of data between the two memories is limited. for this reason, two computational cycles were defined. during the internal cycle, only the gpu is working, it executes a defined number of iterations. at the end of the internal cycle, control is passed on to the external cycle and the data is copied to the host memory and saved as a file. it is also important to note that executing the code on the gpu is effective if all the gpu cores conduct the same calculation. attention should be paid to the use of branch instructions as they can significantly impair performance. 6. simulation results and discussion in the aforementioned simulations, the startup process of silo discharge and the effects of the diameter of the rotary valve and rotational speed of the rotor on the mass outflow rate of particles leaving the rotary valve were investigated. 6.1 the startup process of silo discharge the startup process of silo discharge through the rotary valve is shown in a cross-sectional view in figs. 7 and 8 at different rotational speeds. fig. 7 shows the startup process at a rotational speed of 0.5 s−1. the positions of the particles were visualized six times per revolution. at this rotational speed, the particles have sufficient time to fill the entire volume of the cell. particles entering the cell are forced to pass by the blades of the rotor. when a cell reaches the outlet, all the particles fall out of the cell. fig. 8 shows the startup process of discharge at a rotational speed of 5 s−1. in this case, the blades of the rotor rotate so fast that the particles do not have sufficient time to fill the entire volume of the cell. approximately only one third of the volume of the cell is filled with particles. the 47(2) pp. 31–42 (2019) 38 füvesi and ulbert figure 7: the startup process of silo discharge at a rotational speed of 0.5 s−1. blades push the particles so strongly that they collide with the wall of the outlet channel and accumulate. as a result, not all the particles are capable of falling out of the cell and some remain in the rotary valve. 6.2 analysis of the mass outflow rate through the rotary valve during silo discharge through a rotary valve, the mass outflow rate exhibits a pulsating, periodic change over time as a consequence of the rotating cellular structure of the rotary valve. following a finite period of time after the rotary valve starts to operate, a periodic change in the outflow of particles develops of constant amplitude and frequency. depending on the geometric and operational parameters, the amplitude and frequency of this periodic change may vary. to compare the effect of the various geometric and operational parameters on the mass outflow rate, it is necessary to calculate the time-averaged pulsating mass outflow rate. therefore, the simulation time was sufficient to obtain at least ten cycles of change of constant amplitude and frequency. the time-averaged mass outflow rate was calculated from the simulation data saved after certain intervals of time. first, the number of particles discharged from the silo during the time interval between data saves was determined. next, the resulting data was multiplied by the volume and density of the particles and divided by the time interval between data saves to obtain the periodic time variation of the mass outflow rate. finally, the timeaveraged mass outflow rate was obtained by averaging the values throughout the simulation. for example, figs. 9 and 10 show the dynamic change in the mass outflow rate of particles at rotational speeds of 0.5 and 5 s−1 when the diameter of the rotary valve was 0.12 m. when the rotational speed was 5 s−1, only the initial part of the entire simulation observed a highfrequency periodic change in the mass outflow rate more clearly. by comparing the two figures, it can be seen that figure 8: the startup process of silo discharge at a rotational speed of 5 s−1. hungarian journal of industry and chemistry gpu-accelerated simulation of a rotary valve 39 figure 9: the dynamic change in the mass outflow rate at a rotational speed of 0.5 s−1. as the rotational speed increases, a periodic change of higher frequency and smaller amplitude was observed. fig. 11 shows the dependence of the time-averaged mass outflow rate on the rotational speed of the rotor when the diameter of the rotary valve was varied. the curves represent different diameters of the rotary valve. it can be observed that as the diameter increases, the average mass outflow rate rises. in the first section of the curves, the mass outflow rate increases linearly as the rotational speed of the rotor rises. this section is significant in terms of its control. linear industrial controllers are well established and suitable for the application of control theory for linear systems. the linear control theory applies to systems whose output is proportional to their input. these types of systems are governed by simple linear differential equations, while nonlinear systems are often governed by nonlinear differential equations and mathematical techniques developed to handle them are much more complex and far less general. due to the linear dependence of these sections, the mass outflow rate can be easily controlled by common industrial control systems figure 10: the dynamic change in the mass outflow rate at a rotational speed of 5 s−1. figure 11: the dependence of the rotational speed on the time-averaged mass outflow rate using different rotary valve diameters. based on linear control algorithms. in fig. 11, it can also be observed that the length of linear sections depends on the diameter of the rotary valve. the linear section in the case of the smallest diameter of 0.06 m occurs between rotational speeds of 0.5 − 3 s−1, while in the case of the largest diameter of 0.12 m it occurs between rotational speeds of 0.5− 1.5 s−1. since a desired mass outflow rate can be more easily controlled in a linear section with a smaller gradient, it is advisable to keep the diameter as small as possible. following the initial linear section, the mass outflow rate reaches a maximum value, the larger the diameter, the greater the maximum value of the mass outflow rate. if a mass outflow rate in excess of the maximum value is required, this can only be achieved by increasing the diameter and not by raising the rotational speed. as the diameter of the rotary valve decreases, the rotational speed at which the maximum is observed increases, as shown in fig. 11. after the maximum is achieved, a decreasing section follows where the time-averaged mass outflow rate begins to decrease. since the location of the maximum shifts towards higher rotational speeds as the diameter of the rotary valve increases, the decreasing section also shifts. between the rotational speeds of 4 and 5 s−1, the mass outflow rates for each diameter converge. the optimal value of the diameter of the rotary valve can be determined based on the length of the linear section. a given mass outflow rate can only be achieved with a sufficiently large diameter. however, the use of a larger diameter is not recommended as the gradient of the linear range increases as the diameter increases and control of the system becomes less precise. by considering the range beyond the maximum, it is clearly unnecessary to operate a rotary valve of a given diameter at higher rota47(2) pp. 31–42 (2019) 40 füvesi and ulbert figure 12: the flow patterns of particulate flows at different rotational speeds of the rotor. tional speeds to increase the level of performance, since the maximum mass outflow rate cannot be exceeded, in fact it may even decrease. 6.3 flow patterns of the particles at different rotational speeds of the rotor as was shown in figs. 9 and 10, the mass outflow rate exhibits a constant periodic change after the startup process of discharge. in order to understand the phenomena that occur inside the rotary valve with a greater degree of accuracy, the positions of the particles were visualized to obtain the instantaneous particle flow patterns visible at various rotational speeds of the rotor (fig. 12). in all cases, a cross-sectional view of the rotary valve is presented when the rotor blades were in the same position and the operation was already within the range of the constant periodic change. fig. 12 shows the gradual decrease in the charge of cells as the rotational speed increases. at a rotational speed of 0.5 s−1, the cells still have sufficient time to fully recharge. between rotational speeds of 1.0 to 1.5 s−1, an empty volume fraction remains in the cells after being charged. at these rotational speeds, this empty volume fraction is still small and the accelerated feed and discharge periods can compensate for the decreasing mass outflow rate. at a rotational speed of 2 s−1, the time-averaged mass outflow rate reaches its maximum. when the rotational speed was 2.5 s−1, the resulting empty volume fraction of the cells becomes even bigger but the particles rest on the lower blade. at a rotational speed of 3 s−1 a significant change can be observed in the operation. at this rotational speed, the particles seem to float between the blades of the cell, i.e. the speed of the blades is equal to the rate at which the particles drop. at a rotational speed of 4 s−1, the particles are already pushed forward by the top blades. by further increasing the rotational speed (5 s−1), the time the cells have to be recharged is so small that the mass outflow rate begins to decrease even more. 7. conclusions generally speaking, it can be said that by using the discrete element method in particulate flow simulations, it is possible to observe particle flows in detail and to better understand related phenomena. the simulation study presented in this paper focused on the simulation of the discharge of solid particles from a silo controlled by a rotary valve using the discrete element method. in the simulations, the mass outflow rate of particles was analyzed along with different geometric and operational parameters of the rotary valve. by applying the discrete element method, it was possible to dynamically simulate the movement of individual solid particles through the rotary valve and examine the mass outflow rate of particles. by visualizing the individual particles at their positions, the effect of the interaction between the particles and the blades of the rotary valve on the flow patterns of particles at different rotational speeds was observed. the simulations showed that the mass outflow rate of the particles leaving the silo changes periodically due to the rotating cell structure of the rotary valve. the dependence of the time-averaged mass outflow rate on the rotational speed of the rotary valve was found to be nonlinear within the upper range of examined rotational speeds. however, for each diameter of the rotary valve, a range of rotational speeds in which the mass outflow rate changes hungarian journal of industry and chemistry gpu-accelerated simulation of a rotary valve 41 linearly with the rotational speed was observed. within these ranges of linear speed, the rotary valve can be used more advantageously to perform different control tasks. following the linear range, for each diameter of the rotary valve, the mass outflow rate reaches a maximum then decreases. the simulations were performed using gpu hardware. the application of parallel programming is an essential part of the simulations and can significantly decrease the calculation time of simulations from a few days to just a few hours. by considering the treatment of particle-wall contacts, a novel flat triangular-based geometric representation technique was proposed which also made it possible to calculate the particle-wall contacts in parallel by gpu. symbols p position vector of a particle, m v velocity vector of a particle, m/s a acceleration vector of a particle, m/s2 g gravitational acceleration vector, m/s2 f force vector, n t torque vector, nm i moment of inertia of a particle, kgm2 d diameter of a particle, m r radius of a particle, m e coefficient of restitution, dimensionless k spring constant, n/m m mass of a particle, kg n unit vector, dimensionless t unit vector, dimensionless greek letters δ normal displacement, m δ tangential displacement vector, m η damping coefficient, kg/s µ coefficient of friction, dimensionless µr coefficient of rolling resistance, dimensionless ρ density of a particle, kg/m3 ω angular velocity vector, s−1 subscripts c circumferential cn normal contact ct tangential contact n normal direction, normal component r relative rt relative tangential rs relative slip t tangential direction, tangential component acknowledgement this research was supported by the state of hungary within the framework of the project 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publications/1995_3d_distance.html hungarian journal of industry and chemistry https://doi.org/10.1680/geot.1979.29.1.47 https://doi.org/10.1016/0009-2509(95)00271-5 https://doi.org/10.1016/0009-2509(95)00271-5 https://doi.org/10.1016/s0032-5910(99)00225-9 https://doi.org/10.1016/s0032-5910(99)00225-9 https://doi.org/10.1016/s0009-2509(99)00153-0 https://doi.org/10.1016/s0009-2509(99)00153-0 https://doi.org/10.1016/j.powtec.2007.11.042 https://doi.org/10.1016/j.ces.2012.12.034 https://doi.org/10.1016/j.powtec.2015.11.023 https://doi.org/10.1016/j.powtec.2015.03.028 https://doi.org/10.1016/j.powtec.2015.03.028 https://doi.org/10.1016/j.ces.2016.12.017 https://doi.org/10.1016/s0032-5910(99)00234-x https://doi.org/10.1016/s0032-5910(01)00277-7 https://doi.org/10.1016/s0032-5910(01)00277-7 https://doi.org/10.1016/j.powtec.2005.04.019 https://doi.org/10.1016/j.powtec.2005.04.019 https://doi.org/10.1016/j.ces.2011.07.009 https://doi.org/10.1016/j.powtec.2017.03.022 https://doi.org/10.1016/0032-5910(83)80005-9 https://doi.org/10.1016/j.powtec.2011.10.057 https://doi.org/10.1016/j.powtec.2011.10.057 http://cs.swan.ac.uk/~csmark/publications/1995_3d_distance.html http://cs.swan.ac.uk/~csmark/publications/1995_3d_distance.html hungarian journal of industry and chemistry vol. 47(2) pp. 43–51 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-19 residence time distribution-based analysis of an industrial-scale biogas fermenter andrás tankovics1, dávid takács1, judit szendefy2, béla csukás1, and mónika varga*1 1institute of methodology, university of kaposvár, guba sándor u. 40, kaposvár, 7400, hungary 2biogas plant, magyar cukor zrt., pécsi u. 10, kaposvár, 7400, hungary residence time distribution (rtd) measurement-based analysis of mixing conditions on an industrial-scale (13, 000 m3) anaerobic digester of pressed sugar-beet slices at kaposvár sugar factory of magyar cukor zrt. was studied. the lithium salt tracing technique was applied, while the quantity of the lithium chloride tracer and the sampling of the effluent were designed by a preliminarily studied simulation model of mixing. the lithium concentration at the outlet was analysed by inductively coupled plasma–optical emission spectroscopy (icp-oes). taking into account the geometrical arrangement, the biogas flow produced and the cyclically changing recycle flow, various mixing models were generated with different compartmentalization and flow structures by applying the method of programmable process structures. the simulation-based approximate identification of the mixing model was accomplished by a heuristic approach that took into consideration multiple structures with changing mixing flows. a model with an advantageously small number of compartments and parameters was sought which satisfies the measured rtd. the results suggest the intensive mixing of upper levels with a poorly mixed lower level, which contributes to the long tail in the rtd. the actual set-up supports a good horizontal distribution of the sugar-beet slices and the microbial biomass, while the limited degree of vertical mixing helps to avoid the elutriation of the useful microbiome. the suggested mixing model will be combined with the formerly elaborated model involving 9 bacterial groups. keywords: anaerobic digestion, mixing of digester, residence time distribution, lithium tracing, programmable process structures 1. introduction the mixing of anaerobic digesters is a critical issue because it should support the uniform distribution of raw materials to be digested and the bacterial biomass along the cross-section of the unit. moreover, the excessive sedimentation of the solid (bacterial) phase at the bottom of the digester should be avoided. however, an unnecessarily high degree of mixing may elutriate the bacterial biomass that decreases the effectiveness of transformations and may cause surplus environmental load. the computational modelling of anaerobic digesters was developed from the modelling of wastewater treatment and degradation [1, 2] and from the adm models designed by iwa [3, 4]. a comprehensive review from 2013 is available [5]. knowledge about mixing in large biogas digesters is still in its infancy, so the objective of this study is to broaden this by determining the minimum retention time of substrates fed into anaerobic digesters and estimate the distribution time of substrates before being extracted from the investigated digester. *correspondence: varga.monika@ke.hu over the last century, compartmentalized models were successfully used given the lack of computational fluid dynamics (cfd) models available, e.g. for studying an interesting scale-up problem, where the partially mixed pilot performed better than the perfectly mixed laboratory unit [6]. moreover, at that time, a review comparing compartmentalization with cfd was published [7] which concluded that cfd is the most scale–independent method for mixing and scale-up studies, however, it is hampered by limitations such as high computational demands and the inadequacy of submodel consideration, e.g. biokinetics. in a recently published detailed review [8], the authors concluded that “compartmental models allow multi-scale modelling with low computational time compared to a full coupled model (e.g. reactive numerical simulations). thanks to these main characteristics, compartmental models are able to model complex full-size industrial systems. an effective compartment model could handle multiple, multiphysics phenomenological models (detailed kinetic reaction scheme, complex heat and mass transfer model, population balance, etc.) that could not be included in cfd analysis. observed deviation between https://doi.org/10.33927/hjic-2019-19 mailto:varga.monika@ke.hu 44 tankovics, takács, szendefy, csukás, and varga fully detailed cfd model and compartment model show very small results deviation despite of very significant reduction in calculation time (3 orders of magnitude).” an interesting new example of a hypothesis-driven compartmental model is given in [9]. two full-scale digesters from a biogas plant (2, 000 m3 and 1, 500 m3) equipped with different mixing systems and filled with different substrates were investigated by kamarad et al. [10]. to characterize the substrate distribution, solutions of lithium hydroxide monohydrate were used in tracer tests at concentrations of 45− 50 mg li+/kg ts in digesters. the tracer concentration in the effluent of the digester was measured. although the data calculated by cfd methods were in very good agreement with the results, a full comparison was not made kaposvár sugar factory of magyar cukor zrt. developed an internationally straightforward anaerobic fermentation technology to generate onsite used and surplus energy with a reduced amount of waste emitted by producing fuel gas of high methane content from the pressed sugar beet slices. in a former phd thesis [11], a detailed simulation model was developed and validated for an approximately perfectly mixed pilot unit that took into consideration 9 pseudogroups of bacteria by applying the available earlier version of direct computer mappingbased modelling methodology. the scaling up of the model to an industrial scale [12] requires more detailed knowledge about the hydrodynamic conditions of the appropriately compartmentalized volume. the objective of this work was to measure and analyse the residence time distribution of a large industrial unit by a lithium tracer technique. the final goal of this analysis was to embed the formerly developed detailed digestion model into the compartmentalized mixing model to enhance the investigated fermenter. 2. experimental work the industrial digester (see fig. 1) was a cylindrical unit with a diameter of 25 m and height of 28 m. the effluent was removed from a volume of approximately 13, 000 m3 at a level of 20 m. spatially uniform feeding and appropriate mixing was ensured by the recycle flow from a level 20 m in height from the base of the unit and fed into the annularly placed 6 subsequent bottom segments with a prescribed cyclic change of the flow. the pressed sugar beet slices were also fed into this recycle flow via a screw feeder. mixing was enhanced significantly by the increasing upward flow of the generated biogas. moreover, three small mechanical mixers ensured the raw materials and bacteria were uniformly distributed in the lower third of the unit. the slowly accumulating inorganic residue could be removed from the middle of the bottom of the digester by means of a slowly rotating agitator. figure 1: schematic diagram of the industrial-scale fermenter of 13, 000 m3 in volume 2.1 tracing and measurement technique for the tracing of the flow, 40 kg of lithium chloride p.a. was dissolved in 150 litres of tap water. considering the contamination of sugar beet slices with many ions, lithium was chosen given the sensitivity of its measurements. a blank sample was tested and a calibration prepared by adding known amounts of lithium chloride to the blank solution of realistic composition. this amount was added to the sludge flow of fresh sugar beet slices at a rate of 43 m3/h on average. the duration of tracing was 150 seconds, while the main recycle flow was switched off during this time. before and after the tracer inlet, the recycle flow was maintained at 200 m3/h. differing from the geometrically arranged order of annular segments 1-2-3-4-5-6, the actually applied order of feeding was 1-2-(3)-6-4-5, while during the experiments the inlet to segment #3 was closed (because of a malfunctioning valve). accordingly, the cyclic feeding sequence was changed to 1-2-6-4-5 over 360 seconds. the tracer was fed into segment 4, while the samples were taken from the effluent and discharged from segment 5 at a height of 20 m. the draft samples of 1-2 litres in volume were filtered before being analysed. the concentration of li+ was measured by the icpoes spectrometer at kaposvár university. 2.2 modelling and simulation methodology for the modelling and simulation of the flow structure of the fermenter, the methodology of programmable process structures (pps) was applied [9, 10]. in pps (see fig. 2), the locally programmable structure of process models could be generated from two general meta-prototypes and from the standardized description of the actual process network automatically, resulting in the dynamic structure of unified state and transition hungarian journal of industry and chemistry residence time distribution-based analysis 45 figure 2: schematic diagram of the generation of the process model by the method of programmable process structures elements. the prototype elements, which describe the functionalities of the model, could also be derived from the general meta-prototypes. the freely editable, actual prototype programs contain symbolic input, parameter and output variables as well as a locally executable program code. in various applications, many state and transition elements can be modelled with the same or similar, reusable local programs (referred to as actual prototypes). the state and transition elements of the actual model can be parameterized and initialized concerning their casespecific prototypes. its execution, namely connectionbased communication between the state and transition elements of the programmed structure, is solved by the general-purpose kernel program of the method. during the simulation, the actual elements are initialized by initial conditions and parameters, moreover, the output values are recalculated stepwise by taking into consideration input and parameter data according to the associated local program prototype. the identified input and output connections of the extensive/intensive properties and signals make the combined execution of the balance-based and signal-based functionalities possible. 3. results and analysis 3.1 experiments the quantity of the lithium chloride tracer (40 kg) and the sampling of the effluent during the measurement of the rtd were designed by some preliminarily studied, approximate mixing models. the concentration of lithium chloride in the effluent was measured every 0.5−2 hours during the first period and daily or even less frequently over the following 23 days (when production slowed down by ending campaign). the data are summarized in table 1 and in fig. 3. 3.2 possible flow structures and parameters by taking into consideration the geometrical layout, the produced biogas flow and cyclically changing recycle flow, various mixing models with different compartmentalization and flow structures were generated by applying the method of programmable process structures. table 1: measured concentrations of lithium chloride in the effluent sample id date time, hours li+, mg/l 0 blind 0 <0.100 1 2018.12.18 0.5 <0.100 2 2018.12.18 1 0.226 3 2018.12.18 2 0.347 4 2018.12.18 4 0.311 5 2018.12.18 6 0.237 7 2018.12.18 8 0.811 8 2018.12.19 26 0.627 9 2018.12.19 38 0.538 10 2018.12.20 48 0.625 11 2018.12.22 96 0.536 12 2018.12.24 144 0.401 12b 2018.12.26 192 0.516 13 2018.12.28 240 0.423 14 2019.01.02 360 0.325 15 2019.01.04 408 0.361 16 2019.01.07 480 0.384 17 2019.01.10 552 0.323 the most detailed compartmentalization (d1) is shown in fig. 4. here the sludge zone of the process unit was divided into three vertical layers which were divided further into an inner cylinder, surrounded by an annulus that was divided into six parts. the mixing flows between the 21 (approximately perfectly mixed) compartments are as follows: circflowmix: cyclically changing recycle flow, superposed by a bidirectional mixing flow between the annular slices above each other; gasflowmix: bidirectional mixing flow, induced by the upward biogas flow between the compartments above 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0 5000 10000 15000 20000 25000 30000 35000 40000 c o n ce n tr a ti o n , m g /l time, hour measured tracer concentration in effluent figure 3: measured tracer concentration of li+ in the effluent of the industrial-scale fermenter (40 kg of lithium chloride dissolved in 150 litres of tap water was added to a sludge of sugar beet slices that entered segment #4 at a flow rate of 43 m3/h for 150 seconds). 47(2) pp. 43–51 (2019) 46 tankovics, takács, szendefy, csukás, and varga figure 4: the most detailed schematic diagram of the fermenter (scheme d1). each other (for practical considerations, circflowmix and gasflowmix can be integrated into a single flowmix); permix: peripheral bidirectional mixing flow between the subsequent annular slices of the same layer , horizontally; radmix: radial bidirectional mixing flow between the annular slices and the inner cylinder of the same layer, horizontally. the flow rate of the biogas increased as the height of the unit increased. accordingly, gasflowmix was higher between layers 2 and 3 than between 1 and 2. it is worth mentioning that the outflow rate of the effluent was considerably less than the inflow rate of the sludge composed of pressed sugar beet slices because a significant proportion of the raw material was converted into biogas that escaped through the upper gas dome. in scheme d2 (fig. 5 which was finally proven to be the best solution), the inner cylinder and the related vertical and horizontal mixing flows were removed because they slowed down the mixing in scheme d1 by an unfeasible degree. as a further simplification, the upper layer was not decomposed at all. it should be noted that an interaction between the changes in the structures and their parameters exists. as an example, scheme d3 (fig. 6) behaved in a similar way to d2 with the highest horizontal mixing flows in the upper layer. planned future research will focus on using less compartments which might also be advantageous in terms of embedding the detailed dynamic model of anaerobic digestion into the flow structure. accordingly, scheme d4 (fig. 7) was also tested, where only the lower layer was decomposed. as a marginal solution, the case of scheme d5 (fig. 8) was also studied with only vertical decomposition of the process unit. figure 5: schematic diagram of the best performing fermenter (scheme d2). 3.3 generation of the simulation models the process network of the various schemes can be defined by a general declarative program. a characteristic part of the definitions of scheme d2 is as follows: states([c11],[sludge]). states([c12,[sludge]). ... states([c36,[sludge]). states([env,[sludge,feed]). transitions([c11],[flowmix,permix]). transitions([c12],[flowmix,permix]). ... transitions([c26],[flowmix,permix]). transitions([c31],[permix]). transitions([c32],[permix]). figure 6: simplified schematic diagram of the fermenter without decomposition of the upper layer (scheme d3). hungarian journal of industry and chemistry residence time distribution-based analysis 47 figure 7: a more simplified schematic diagram of the fermenter (scheme d4). figure 8: trial in the absence of horizontal compartmentalization (scheme d5). ... transitions([c35],[permix, feeding\_recirc]). transitions([c36],[permix]). dcode(sludge,[li]). dcode(feed,[li]). where states and transitions are declared by the state and transition elements in the given compartments, respectively. meanwhile, the lowest level components of the state elements are described by the dcode() predicates. the transition-based representation of the flow structure is defined by the facts of predicate: trans(transitionname,compartment, inputcomponents,inputsigns, outputcomponents,outputsigns). for example, trans(flowmix,[c13], [n([c13],[sludge]), n([c23],[sludge])], [n([c13],[sludge]), n([c23],[sludge])],[],[]). generates bidirectional connections for mixing flows between compartments [c13] and [c23] of the first and second layers, respectively. similarly, trans(permix,[c32], [n([c32],[sludge]), n([c33],[sludge])], [n([c32],[sludge]), n([c33],[sludge])],[],[]). generates peripheral flows between compartments [c32] and [c33] in the third layer. the initial concentrations and parameters of the various state and transition elements were recorded in an ms excel file from where they were transformed into a textual form of declarative predicates. according to fig. 2, the automatic generation of the programmable process structures was conducted: • from the two general prototypes [9, 10], • from the textual description of the actual process network, and • from the textual declaration of initial values and parameters. the automatically generated structural model of scheme d2 is illustrated in fig. 9. 3.4 local programming of the generated process structure the functionalities of the flow-structure models can be represented by locally executable programs embedded in the prototype elements. the prototype elements can be prepared from the copies of the meta-prototypes, e.g. the local program for the calculation of flowmix is presented below: figure 9: programmable process structure of scheme d2. 47(2) pp. 43–51 (2019) 48 tankovics, takács, szendefy, csukás, and varga { program ( ’ p e r m u t a t i o n ( inpconcs , [ d ( [ coord1 , s ludge , l i ] , [ c1 ] , g_m3 ) , d ( [ coord2 , s ludge , l i ] , [ c2 ] , g_m3 ) ] ) , p e r m u t a t i o n ( p a r a m e t e r s , [ d ( vgas , [ vgas ] , m3_h ) , d ( v c i r c , [ v c i r c ] , m3_h ) ] ) , g ( dt , dt) , p l u s f l o w ( coord1 , vci rc , vplus ) , dm1 i s ( vgas+vplus ) / 6 0 * ( c2−c1 )*dt, dm2 i s ( vgas+vplus ) / 6 0 * ( c1−c2 )*dt, outcomps = [ d ( [ coord1 , s ludge , l i ] , [dm1] , g ) , d ( [ coord2 , s ludge , l i ] , [dm2] , g ) ] , ou ts igns = [ ] , re po r t = [ ] . p l u s f l o w ( [ coord1 ] , vci rc , vplus ) :− sub_atom ( coord1 , 2 , 1 , 0 , column ) , g ( s e l e c t e d , column ) , ! . p l u s f l o w ( _ , _ , 0 ) . ’ ) } this program illustrates how the input, parameter and output data are represented by the unified d(identifier,list_of_values,dimension) triplets. the input data for calculations originated from the respective compartments coord1 and coord2. the parameters define the vgas mixing flow associated with the gas flow and the vplus mixing flow generated by the recycle upflow between the given vertical segments. the actually active segment was determined by the integer value of column in the g(selected,column) global predicate (which was actualized by another local program, responsible for the cyclic switching of the recycle flow). the auxiliary clause plusflow() considers mixing flow vcirc only if the recirculation is actually associated with the given compartments, otherwise the surplus mixing is equal to zero. the outcomps output of the program forwarded the changes in the amount of tracing component dm1 and dm2 in the compartments coord1 and coord2, respectively. 3.5 evaluation of the rtd measurements the mass flow of the produced biogas was calculated from the measured total volumetric flow rate of the three parallel operating digesters, divided according to the individually measured loads of sugar beet slices of the parallel lines whilst taking into consideration the measured composition of the biogas. the slightly changing output 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0 1000 2000 3000 4000 5000 6000 c o n ce n tr a ti o n , p p m time, min characteristic part of shemes d1 and d5 measured values d1 scheme d5 scheme figure 10: initial period of scheme d1 that was insufficiently mixed and scheme d5 that was overmixed. flow of the effluent was calculated from the changing load and biogas mass flows. regarding the identification and validation of the multiple structure, it must be emphasized that this task was underdetermined. considering the multiple interactions between the structures and parameters, instead of a rigorous optimization procedure, a heuristic trial and error approach was applied, controlled by the main features first and then the values of the normalized root mean square error (nrmse) in the refinement. the evaluation was effectively aided by monitoring the change in concentrations in each compartment. first, d1 (being insufficiently mixed) and d5 (being overmixed) were excluded as can be seen in fig. 10. afterwards, d2-4 were studied and based on the calculated nrmse values, d3 and d4 were stepwise rejected. finally, the parameters of d2 were refined. the simulated and measured data are illustrated in figs. figs. 11–14 in addition to the calculated nrmse values. fig. 10 (and many trials using other parameters) showed that even schemes d3-5 were unable to model the evident initial peaks of the measurements. 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0 5000 10000 15000 20000 25000 30000 35000 c o n ce n tr a ti o n , p p m time, min simulated effluent concentration for scheme d3 simulated measured figure 11: trial using horizontal compartmentalization in two lower layers only (scheme d3, nrmse = 12.10 %). hungarian journal of industry and chemistry residence time distribution-based analysis 49 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0 5000 10000 15000 20000 25000 30000 35000 c o n ce n tr a ti o n , p p m time, min simulated effluent concentration for scheme d2 simulated measured figure 12: trial using horizontal compartmentalization in three layers (scheme d2, nrmse = 12.08 %). the horizontal decomposition in all layers (without an inner tube) is able to express the main features using many parameters (an example is shown in fig. 11). decomposition scheme d2 (compartment volume is 685.3 m3) with improved parameterization describes the measured data better (see fig. 12). the change in the concentration in the various compartments (except for the traced bottom and output top ones) is shown in fig. 13. this shows that because of the changing input bottom compartment of the recycle flow, the initial peak in concentration does not appear in each compartment. the long tail is partly a consequence of the great difference between the input feed and output effluent flows as well as of the limited degree of mixing between the layers and annular zones (especially in the bottom layer). it is also worth noticing the constant difference in concentration in the compartments. unfortunately, the continuation of measurements was limited by the closing end of the campaign. moreover, were they to continue, the sensitivity of the concentration measurements would decrease far below 0.3 ppm. the computation time, depending on the number of 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0 5000 10000 15000 20000 25000 30000 35000 c o n ce n tr a ti o n , p p m time, min effluent concentration for scheme d2 (modified parameters) calculated measured figure 13: scheme d2 with a feasible parameter set (nrmse = 21 %). 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 0 5000 10000 15000 20000 25000 30000 35000 c o n ce n tr a ti o n , p p m time, min calculated concentrations in the compartments of scheme d2 sludge [c22] li sludge [c23] li sludge [c24] li sludge [c25] li sludge [c26] li sludge [c21] li sludge [c32] li sludge [c33] li sludge [c35] li sludge [c34] li sludge [c11] li sludge [c12] li sludge [c13] li sludge [c15] li sludge [c16] li sludge [c36] li sludge [c31] li figure 14: change in concentration in the various compartments of the experiment shown in fig. 12. compartments and the flow structure, was between 2 and 90 minutes but was typically less than 10 minutes. a large difference in the volume of the compartments leads to an increase in computational efforts, while an equidistant volume distribution accelerates computation. 4. discussion the results prove that the fermenter is thoroughly mixed but by no means perfectly mixed. accordingly, detailed modelling needs to take into consideration hydrodynamics, e.g. by using mixing flows between the compartments of the volume. it should be emphasized that an interaction between the fermentation model and mixing exists because mixing is considerably enhanced by the produced biogas. in due course, this coupling has to be taken into consideration in the final implementation of the model. it is a specific feature of the residence time distribution of anaerobic digesters that the output liquid effluent flow is much less than the input load of the fresh sugar beet sludge (because of the production of biogas). this contributes to the slowly decreasing long tail of the rtd. by considering the approximately identified parameters, the mixing conditions can be characterized by the following features: • in the bottom layer, no bidirectional, horizontal mixing flow occurs between the annular segments. the horizontal mixing flow between the annular segments can also be neglected in the middle layer. however, in the intensively bubbling upper layer, significant mixing occurs characterized by a flow rate of 200 m3/h between the adjacent segments. • regardless of the very limited horizontal mixing in the bottom and middle layers, the appropriate distribution of the fluid and solid phases is achieved by the frequent change in location of the recycle flow (and feed) between the bottom segments. 47(2) pp. 43–51 (2019) 50 tankovics, takács, szendefy, csukás, and varga • the estimated mixing flow rate of the vertical sludge, generated by the upward biogas flow, was 150 m3/h and 300 m3/h between the bottom & middle and middle & upper layers, respectively. • the estimated vertical mixing flow rate in the changing active sites, generated by the recycle flow, was 200 m3/h between the vertically connected segments (i.e. the mixing ratio was 0.5). 5. conclusions the kaposvár sugar factory of magyar cukor zrt. has developed an internationally straightforward anaerobic fermentation technology to generate onsite used and surplus energy with decreased emissions of waste by producing fuel gas of high methane content from pressed sugar beet slices. the development of an improved computer model as well as the analysis-based development of the technology required more detailed knowledge of the hydrodynamic conditions found within the process unit. the objective of this work was to measure and analyse the rtd of the appropriately compartmentalized industrial unit of 13, 000 m3 in volume. spatially uniform feeding and appropriate mixing was ensured by the recycle flow, fed into the annularly placed six subsequent bottom segments with cyclic changes in location. the pressed sugar beet slices were also fed into this recycle flow via a screw feeder. mixing was enhanced significantly by the upward increasing upstream flow of generated biogas and three mechanical agitators. by considering the geometrical arrangement, produced biogas flow and cyclically changing recycle flow, various mixing models were generated with different compartmentalization and flow structures via the method of programmable process structures. a lithium salt-based tracer technique was applied, while the quantity of the lithium chloride tracer and the sampling of the effluent during the measurement of the residence time distribution were designed by some preliminarily studied simulation models of mixing. the lithium chloride concentration at the outlet was initially measured every 2 hours and daily or less frequently during longer periods. the lithium chloride concentration was analyzed by icp-oes. for the simulation-based approximate identification of the mixing model, a heuristic approach was used that took into consideration multiple structures with changing mixing flows. a model of an advantageously smaller number of compartments and parameters was sought which satisfies the measured residence time distribution. the results suggest the intensive mixing of upper levels with a limitedly mixed lower part that contributes to the long tail of the rtd. the applied arrangement supports the horizontal distribution of the sugar beet slices to be digested and the multiple groups of bacteria. moreover, limited vertical mixing helps to avoid the elutriation of the bacteria and undigested organic materials into the environment. the suggested mixing model will be combined with the formerly elaborated model of the anaerobic fermentation process that consists of 9 groups of bacteria in our future work. abbreviations adm anaerobic digestion model cfd computational fluid dynamics icp-oes inductively coupled plasma optical emission spectroscopy iwa international water association nrmse normalized root mean square error pps programmable process structures rtd residence time distribution ts total solid content acknowledgement the authors are grateful for the financial support from the project efop-3.6.1-16-2016-00007. references [1] batstone, d.j.; keller, j.; newell, r.b.; newland, m.: modelling anaerobic degradation of complex wastewater. i: model development. bioresour. technol., 2000, 75, 67–74, doi: 10.1016/s09608524(00)00018-3 [2] batstone, d.j.; keller, j.; newell, r.b.; newland, m.: modelling anaerobic degradation of complex wastewater. ii: parameter estimation and validation using slaughterhouse effluent. bioresour. technol., 2000, 75, 75–85, doi: 10.1016/s0960-8524(00)00019-5 [3] blumensaat, f.; keller, j.: modelling of two-stage anaerobic digestion using the iwa anaerobic digestion model no. 1 (adm1). water res., 2005, 39, 171–183, doi: 10.1016/j.watres.2004.07.024 [4] fezzani, b.; cheikh, r.b.: modelling of the mesophilic anaerobic co-digestion of olive mill wastewater with olive mill solid waste using anaerobic digestion model no. 1 (adm1). bioresour. technol., 2008, 99, 6565–6577, doi: 10.1016/j.biortech.2007.11.035 [5] lauwers, j.; appels, l.; thompson, i.p.; degrčve, j.; impe, j.f.v.; dewil, r.: mathematical modelling of anaerobic digestion of biomass and waste: power and limitations. prog. energ. combust., 2013, 39, 383–402, doi: 10.1016/j.pecs.2013.03.003 [6] csukás, b.; balogh, s.: combining genetic programming with generic simulation models in evolutionary synthesis. computers in industry, 1998, 36, 181–197, doi: 10.1016/s0166-3615(98)00071-2 hungarian journal of industry and chemistry https://doi.org/10.1016/s0960-8524(00)00018-3 https://doi.org/10.1016/s0960-8524(00)00018-3 https://doi.org/10.1016/s0960-8524(00)00019-5 https://doi.org/10.1016/j.watres.2004.07.024 https://doi.org/10.1016/j.biortech.2007.11.035 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https://doi.org/10.11118/actaun201361051269 hungarian journal of industry and chemistry vol. 47(2) pp. 53–61 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-20 programmable process structure based analysis of hydrogen supply chains mónika varga *1, catherine azzaro-pantel2, josé manuel flores-perez2, and béla csukás1 1institute of methodology, university of kaposvár, guba sándor u. 40, kaposvár, 7400, hungary 2laboratoire de génie chimique, université de toulouse, 4 allée emile monso, toulouse, 31030, france the planning and operation of hydrogen supply chains (hsc) often require easily extensible, generic dynamic simulation tools. in this paper, the non-conventional modeling and simulation methodology of programmable process structures is applied for the description of these process systems. programmable process structures of hsc models are generated from the two general functional meta-prototypes of the method and from the description of the studied hsc network. the actual program prototypes of production, transformation, transportation, utilization and intermediate storage are copied from the meta-prototypes and filled with the locally executable declarative program code for the various classes of elements. the actual state and transition elements are parameterized and initialized according to their case-specific prototypes. the execution of the programmed hsc structures is solved by the general purpose kernel program. the application of methodology, developed in other fields, is illustrated by a fictitious, simplified hsc example. analysis of this example model illustrates that the coordination of the hectically changing energy production of renewable resources with its seasonally and tendentiously changing demands is in need of dynamic simulation-based planning. keywords: hydrogen supply chains, dynamic simulation, model generation, simulation-based planning, programmable process structures 1. introduction according to the recently published special section of the aiche journal about “hydrogen deployment” [1], the importance of hydrogen energy is expected to grow in the future because stakeholders have just started to discover the potential advantages of it worldwide [2]. hydrogen supply chains (hscs) contain geographically distributed, heterogeneous elements, while many of them are time-specifically constrained by meteorological or seasonal characteristics. having analyzed some comprehensive case studies [3–5], it is obvious that the zero emissions of hydrogen burning and the relatively easy storage of hydrogen is perspectivic. at present, a deadlock exists because a lack of infrastructure inhibits production, while a lack of production impedes the development of infrastructure. dynamic modeling and simulation-based design tools may play an important role in accelerating developments. primary renewable resources of hydrogen production are solar radiation, wind power and hydroelectric power produced by environmental systems. the utilization of solar energy requires natural or cultivated land, which is a special finite resource that is also generated for use in other industries, e.g. food-producing agriculture. *correspondence: varga.monika@ke.hu the direct utilization of solar energy is achieved by various photovoltaic processes with a limited degree of efficiency and capacity. intensive research and developments are in progress that make use of many new resources involving special organisms (e.g. microalgae [6]) or artificial biomimetic systems (e.g. artificial leaves [7]). the indirect utilization of solar energy is realized by the construction of power plants, which also compete for land suitable for food production. wind farms and some smaller hydroelectric power stations produce electrical energy periodically (often randomly), so on-site conversion to electrical energy is necessary for their effective utilization. however, electrical grids do not tolerate such erratic changes and no good solutions for temporary electricity buffering and storage exist. primary non-renewable resources are nuclear raw materials, natural gas and coal. nuclear raw materials need to be transported to specifically located nuclear power stations. natural gas is available from widespread pipelines. on the contrary, coal-based processing requires stations to be constructed in the vicinity of mining sites. large hydroelectric and nuclear power plants produce easily transportable electrical energy that can contribute to buffered hydrogen production by on-site electrolysis. https://doi.org/10.33927/hjic-2019-20 mailto:varga.monika@ke.hu 54 varga, azzaro-pantel, flores-perez, and csukás the most frequently applied process, steam methane reforming (smr), competes with other applications of natural gas but can produce hydrogen-containing gas anywhere in the vicinity of pipelines. on the contrary, coal gasification has to be conducted near to the resource, even though it produces more expensive hydrogen-containing gas from a resource, which is less convenient for traditional applications and petrochemical production, than natural gas. in addition, everything depends on short-term prices, however, thorough preparation for the future requires longer-term decisions. intermediate energy-containing products and byproducts exist in hsc networks, which originate from many distributed districts. biomass energy plants as well as some agricultural byproducts and waste appear seasonally, however, municipal biological wastes are constantly emitted. biomass is processed by gasification, while biological wastes produce biogas by anaerobic fermentation. the enrichment of the hydrogen content in the fermentation process is supported by some experimental results [8, 9]. energy-consuming, direct hydrogen-producing resources are electrical energy resulting from various chains, and hydrogen-containing gases that originate from smr and gasification processes. the two corresponding kinds of hydrogen production processes are electrolysis and the different methods of gas separation for hydrogen enrichment, e.g. membrane separation, pressure swing adsorption, etc. the produced raw hydrogen has to be conditioned in production sites by liquefaction or compression. the resultant liquidized or compressed hydrogen product needs a production or storage site for liquid or gaseous hydrogen, respectively. hydrogen can be transported from production to consumption sites by tanker trucks, tube trailers, railway tankers, railway tube cars or pipelines. pure liquid or gaseous hydrogen needs to be stored at the site of consumption. the utilization of hydrogen is connected to these storage sites. in addition to fueling cars and other vehicles, especially aircraft, hydrogen can be used to generate thermal energy as well as in various industrial processes, e.g. ammonia production, synthesis of organic products, metal processing, etc. in the long-term development of energy supply, hydrogen can serve as a clean and safe energy carrier that contributes to the adoption of a low-carbon economy. considering the slow but definite development towards a hydrogen economy, the optimal design, planning and operation of a hydrogen supply chain have come to the fore of research over the last decade. supply chain network design is a dynamic field of research, not only in the context of hsc but in general. a comprehensive set of various fields of applications was reviewed by govindan [10]. regarding the generally applied modeling methods for the planning and design of hsc, a review from 2012 lists the main approaches [11] such as mathematical optimization as well as geographic information system (gis) based models and frameworks. in conclusion, mainly mathematical programming-based optimization methods are used to design and plan hscs worldwide. in 2017, another paper [12] provided an overview once more about the actual situation on the basis of almost 100 references. various mathematical optimization methods such as mixed-integer linear programming (milp), mixed-integer nonlinear programming (minlp), mathematical programming problem (mpp), mathematical optimization (mop) as well as gis-based approaches and transition models illustrate progress over the last five years. regardless of some alternatively applied system dynamics (sd) and agent-based modeling (abm) solutions, mathematical programming-based optimization methods are still the most widely used tools in planning and design. this preferred approach is based on mixed-integer linear programming (milp) in which binary variables denote the selection of technologies and establishment of transportation links, while continuous ones denote mass and energy flows, capacities of the supply chain nodes, as well as the cost and environmental performance metrics. these decision variables are optimized subject to mass balance constraints, capacity limitations and calculations of objective functions [13, 14]. life cycle analysis (lca) is an appropriate methodology to evaluate the environmental performance and potential impacts associated with a product system across its entire life cycle. among various lca studies that evaluated the environmental benefits of using hydrogen over conventional energy sources, the so-called well-towheels (wtw) studies an lca approach to evaluate the environmental advantages of alternative fuel vehicles (afvs) over conventional engine vehicles across the entire automotive fuel pathway are studied including hydrogen supply chains [15]. multiple spatial and temporal scales imply a big challenge. samsatli et al. [16] highlights the need for the combined consideration of various temporal scales. a simple example of this is that the representation of energy storage requires a short (e.g. hourly) timescale, so taking into consideration years-long planning may result in computationally intensive models. dynamic simulation-based approaches (including the actually studied programmable process structures) may contribute towards solutions to these problems. another big challenge is the question of managing uncertainty throughout the design optimization procedure. accounting for multiple criteria, e.g. costs, environmental impacts, safety, etc., is an obvious expectation of green supply chain design, while the incorporation of these issues generates another interesting task to be solved [17]. many aspects of these challenges in design, deployment and operation in the field of hsc have been summarized in a recently published book [18]. hungarian journal of industry and chemistry analysis of hydrogen supply chains 55 dynamic simulation automatic generation meteo data, changing demands evaluated results of hsc two general meta-prototypes local program of specific classes description of hsc structure initial values and parameters actual hsc to be studied figure 1: scheme of hsc model generation by the method of programmable process structures. 2. applied modeling method: programmable process structures by considering the aforementioned overview of challenges that computational model-supported hsc planning and operation face, a simple trial with our nonconventional approach was conducted. accordingly, the methodology of programmable process structures (pps) [19, 20] was applied for the simulation-based analysis of a fictitious but typical hydrogen supply chain. in pps (see fig. 1), the locally programmable structure of process models can be generated from the graphml-based graphical implementation of one state and one transition defining meta-prototypes, as well as from the unified textual description of the studied hsc network automatically resulting in a dynamic structure of the standardized state and transition elements. the programmable prototype elements that describe production, transformation, transportation, utilization and intermediate storage in the model can also be derived from the two general meta-prototypes. the freely editable, actual program of the prototypes contain symbolic input, parameter and output variables, as well as a locally executable gnu prolog [21] code. in the various cases, the actual state and transition elements can be modeled with the same or a similar reusable local program, while the number of program prototypes is considerably less than the number of actual elements. the state and transition elements of the programmable hsc structures can be parameterized and initialized concerning their case-specific prototypes. during the simulation, the actual elements are executed by the prototypes associated with them. this execution results in cyclically stepwise, connection-based communication of the state and transition elements of the programmed structure with the general-purpose kernel that works like an operational system. when the simulation is run, the actual elements start with the initial conditions and parameters, while the output values are recalculated stepwise by taking into consideration the knowledge of input and parameter data in accordance with the associated local program prototypes. distinguished input and output connectors as well as connections exist for the conservation measures (extensive/intensive properties) and signals, respectively. this solution supports the combined execution of the balancebased and signal-based functionalities, i.e. the hybrid models of hybrid processes. 3. modelling and analysis of hydrogen supply chains by programmable process structures 3.1 description of the example hsc process network in the following sections, the following notations of prolog syntax shall be used: anything* = list of anything; [h|t] = list of any elements or functors with a head h and a list of tail t; [] = empty list; full stop = end of logical sentence; if (or :-) implication in the sense of horn clauses; comma in the program body of clauses = and. the general declarations of multi-compartment (multilevel, multi-scale) state and transition elements are as follows: states(coordlist,statelist). transitions(coordlist,transitionlist). coordlist = coord* statelist = state* transitionlist = transition* the transition-based declaration of the structures is described by the individual transitions as follows: trans(transition,inpconcs,outcomps,inpsigns, outsigns). inpconcs; inpsigns; outcomps; outsigns= specified_state* specified_state = n(coordlist,state) where the n() functors of inpconcs, inpsigns, outcomps and outsigns contain the coordinate and name of the state connected with the given input measure, input signal, output measure or output signal, respectively. this solution allows the same state names in the various compartments, levels or scales to be used because they are identified by the spatial coordinate and name together. our simplified example process network contains 38 state and 39 transition elements altogether in four regions, i.e. coordinates. the interpretation and abbreviation of the elements is explained in table 1. the declaration of the process network is illustrated by a characteristic part of the definitions as follows: states([0], [raw_renew,raw_gas,raw_nucl,h2heating,co2,o2]). states([1], [h2cons,demand,h2carfuel,eleng,hydrogen,h2prod ]), etc ... transitions([0],[]). transitions([1], [t_h2refuel1,t_photovolt1,t_nucl1, t_electrolysis1,t_compression1, t_tankertruck11,t_h2heat1]), 47(2) pp. 53–61 (2019) 56 varga, azzaro-pantel, flores-perez, and csukás table 1: list of involved state and transition elements. type of element name of element short symbol renewable resources raw_renew cultivated land raw_land natural gas raw_gas raw materials for nuclear energy raw_nucl energy-producing biomass biomass biological waste biowaste electrical energy eleng state hydrogen-containing gas h2contgas element raw hydrogen produced hydrogen compressed h2 produced h2prod compressed h2 available for consumers as a fuel h2cons fuel demand of cars demand h2 utilized as a motor fuel h2carfuel heat energy h2heating carbon dioxide co2 oxygen o2 cultivation of land t_cultivation photovoltaic process t_photovolt wind power station t_wind hydroelectric power station t_hydro nuclear power station t_nucl steam methane reforming t_smr transition biomass gasification t_gasify element anaerobic fermentation t_ferment electrolysis t_electrolysis gas separation t_gassep compression t_compression transportation (tanker truck) t\tankertruck refueling cars (vehicles) t_h2refuel heat production t_h2heat etc ... trans(t_h2refuel1,[n([1],h2cons)],[n([1],h2cons ), n([1],h2carfuel)],[n([1],demand)],[]). trans(t_h2refuel2,[n([2],h2cons)],[n([2],h2cons ),n([2],h2carfuel)],[n([2],demand)],[]). trans(t_h2refuel3,[n([3],h2cons)],[n([3],h2cons ),n([3],h2carfuel)],[n([3],demand)],[]). trans(t_h2refuel4,[n([4],h2cons)],[n([4],h2cons ),n([4],h2carfuel)],[n([4],demand)],[]). trans(t_tankertruck11,[n([1],h2prod)],[n([1], h2prod),n([1],h2cons)],[n([1],h2cons)],[]). trans(t_tankertruck22,[n([2],h2prod)],[n([2], h2prod),n([2],h2cons)],[n([2],h2cons)],[]). trans(t_tankertruck33,[n([3],h2prod)],[n([3], h2prod),n([3],h2cons)],[n([3],h2cons)],[]). trans(t_tankertruck31,[n([3],h2prod)],[n([3], h2prod),n([1],h2cons)],[n([1],h2cons)],[]). trans(t_tankertruck32,[n([3],h2prod)],[n([3], h2prod),n([2],h2cons)],[n([2],h2cons)],[]). trans(t_tankertruck44,[n([4],h2prod)],[n([4], h2prod),n([4],h2cons)],[n([4],h2cons)],[]). trans(t_tankertruck41,[n([4],h2prod)],[n([4], h2prod),n([1],h2cons)],[n([1],h2cons)],[]). trans(t_tankertruck42,[n([4],h2prod)],[n([4], h2prod),n([2],h2cons)],[n([2],h2cons)],[]). trans(t_compression1,[n([1],hydrogen)],[n([1], hydrogen),n([1],h2prod)],[],[]). trans(t_compression2,[n([2],hydrogen)],[n([2], hydrogen),n([2],h2prod)],[],[]). trans(t_compression3,[n([3],hydrogen)],[n([3], hydrogen),n([3],h2prod)],[],[]). trans(t_compression4,[n([4],hydrogen)],[n([4], hydrogen),n([4],h2prod)],[],[]). etc ... 3.2 meta-prototypes-based generation and analysis of the example model generation of the programmable process structure originates from the graphml description of general metaprototypes that belong to the methodology (see their illustration in the upper part of fig. 2) and from the aforementioned description of the actual process network. the initial values and parameters of state elements as well as the parameters of transition elements can be added automatically from an excel based text file. the generated general-purpose algorithm results in a graphml file that contains the two meta-prototypes and structure of the whole hsc model in addition to the initial values and parameters. the example structure is illustrated in fig. 2. the graphml model can be further edited by various graph editors (yed graph editor to be precise). the structure also contains the two empty meta-prototypes. the generated programmable process structure describes all of the state (storage of resources, intermediates and products) and transition elements that represent the transformation and transportation in the various compartments (spatial scales) individually, because they may have different parameters and connections. by default, the transportations belong to the sending compartment. this representation does not result in the multiplication of the program code because many elements are executed by the same meta-prototypes that contain the local programs (see the next section). the connections from the state to transition elements represent the causally right transfer of quantitative and qualitative amounts and signals necessary for the calculation of the transitions. the connections from the transition to state elements represent the increases and decreases in the corresponding additive measures as well as the calculated signals. accordingly, the model is prepared for the common but distinguished representation of the extensive/intensive properties as well as of the signals and rules. consequently, the programmable process structures make both the elements and structure visible during the simulation process. this supports the easy (optionally multiscale) temporal consideration of external data, e.g. related to meteorology, the climate and supply & demand. moreover, the flux routes and influence routes can be seen and evaluated explicitly. furthermore, this (apparently too abundant) knowledge representation makes the unified execution of quite hungarian journal of industry and chemistry analysis of hydrogen supply chains 57 figure 2: programmable process structure of the investigated hsc. different hybrid dynamical models possible by applying the same kernel program. figure 3: some meta-prototypes-based case-specific prototypes of hsc networks. 3.3 meta-prototypes-based functional prototypes of the example model first, the programmable prototypes have to be prepared by making copies from the application-independent meta-prototypes. afterwards, the declaration of the actual local program follows. the implementation of state and transition prototype elements of the hsc model needs creative collaboration between the modeller and field experts. the preparation of the case-specific local programs is supported by the meta-knowledge embedded in the meta-prototypes, in accordance with the generated programmable process structure. the basic meta-prototypes and some actual programmed prototypes are illustrated in fig. 3. the example prototypes in fig. 3 are as follows: transition prototypes: prot_compr: compression of hydrogen; prot_electrol: electrolysis; prot_nucl: nuclear reactor-based electrical energy supply; prot_photovolt: photovoltaic system-based electrical energy supply; prot_refueling: hydrogen utilization by the refueling of cars (planes); prot_truck: transportation of hydrogen by truck ; prot_wind: wind power system-based electrical energy supply; state prototypes: prot_demand: scheduled hydrogen demand; 47(2) pp. 53–61 (2019) 58 varga, azzaro-pantel, flores-perez, and csukás prot_storage: hydrogen storage; prot_condstorage: hydrogen storage, associated with condition signaling capabilities. as an example, see the simplified local program of prot_photovolt that calculates the produced electrical energy as a function of the actual meteorological conditions. this textual code is to be embedded into the respective prototype element as follows: program\prot\photovolt = ’permutation(parameters, [d(area,[area],m2),d(coeff,[coeff],nd)\textbar \], time(\,t,\), abs\time(t,y,m,d), meteo(y,m,d,radiation,\,\,\,\,\), g(dt,dt), energy is coeff*area*radiation*dt, report = [d(energy,[energy],kwh)], outcomps = [d(eleng,[energy],kwh)], outsigns = [],!.’ 3.4 generation and simulation of the example hsc system programming of the process structure is followed by its automatic interpretation into the executable dynamic databases of the given model. now the general model generator of the kernel reads the graphml file and generates: • the facts that describe the actual state & transition elements and those that determine state → transition and transition → state connections in the “user” file; • the clauses that declare the program prototypes in the “expert” file. the resultant user and expert files contain a detailed description of the process model, including the locally executable program prototypes as well as the actual elements and connections that contain the initial data and parameters. having generated the model, the executable code has to be supplemented by the (optionally scale-specific) global data, e.g. g(dt,dt ), that also declares the main time step in the previous example code. dynamic simulation is executed by the general kernel program that comprises the cyclically repeated processing of state elements, state → transition connections, transition elements and transition → state connections. for example, the execution of all transitions associated with the prototype of prot_photovolt are executed by the the unification of them, e.g. a(y,t_photovolt2,[2],prot_photovolt,[c( antecedent,dl,[]),c(consequence,dl,[]),c( cond,dl,[]),c(param,dl,[d(area,[1000],m2),d (coeff,[0.20000000000000001],nd)])],[i(inp, dl,[]),i(conc,dl,[])],[o(comp,dl,[]),o(out, dl,[]),o(report,dl,[])],[],[],[]). is unified with the prototype v(y,spatial,prot_photovolt,[c(antecedent,dl, antecedent),c(consequence,dl,consequence),c (cond,dl,conditions),c(param,dl,parameters) ],[i(inp,dl,inpsigns),i(conc,dl,inpconcs) ],[o(comp,dl,outcomps),o(out,dl,outsigns),o (report,dl,report)],temporal,possibilities, evaluations) :program_prot_photovolt. where program_prot_photovolt refers to the example code above. the variables in prototypes are described by alphanumeric symbols that start with a capital letter. the variables and constants in the functors i(), c() and o() are described by lists of the triplets d(identifier, variable_list, instructions). 3.5 analysis of the simulated results some characteristic parameters in these illustrative examples were the following: coefficient of photovoltaic model: 0.2 photovoltaic areas: 1000, 2000, 3000, 800 m2 coefficient of wind-power units: 20 kw h3/km3/ unit number of units: 100, 200 power consumption of electrolysis: 52.5 kwh/kg power consumption of compression: 3.0 kwh/kg some of the simulated results are illustrated with a specific part of a simplified hsc model. in this case, a seasonally and randomly changing continuous increase in the demand of cars for hydrogen fueling over the next decade was assumed, as can be seen in fig. 4. in terms of production, the available capacity of photovoltaic power stations and wind farms in the studied region was investigated. these renewable resources produce electrical energy depending on the actual meteorological conditions (solar radiation and wind speed). however, the available climate scenarios did not contain data concerning radiation and wind speed, so meteorological data from the past ten years was used to imitate realistic changes in radiation and wind speed. the calculated electrical energy production of the investigated system is illustrated in fig. 5. 0 2000 4000 6000 8000 10000 12000 14000 16000 k g/ d a y time, day daily hydrogen fuel consumption figure 4: hypothetical data for the seasonally changing and increasing demand for hydrogen. hungarian journal of industry and chemistry analysis of hydrogen supply chains 59 0 500000 1000000 1500000 2000000 2500000 3000000 3500000 0 5000 10000 15000 20000 25000 30000 35000 40000 p h o to vo lt a ic , k w h /d time, day photovoltaic and wind based electric energy pv production, kwh/d wind w in d , k w h /d figure 5: electrical energy production of the involved wind power and photovoltaic systems (to be converted into hydrogen by electrolysis). in the studied area, wind power can produce more electrical energy than photovoltaic systems, however, it fluctuates very erratically. the contribution of photovoltaic systems is smoother with characteristic seasonal changes. increasing demands for hydrogen production can be met by more renewable energy production or additional hydrogen production from the available electrical energy (e.g. originating from nuclear power stations) and additional hydrogen production (e.g. from steam-methane reforming, biomass gasification, etc.). in the case of lower fuel demands for cars (over a short initial period), the solar energy-based renewable resources can produce the necessary energy for hydrogen production. furthermore, some extraordinary surplus amounts can be produced over randomly appearing short periods by wind farms, as can be seen in figs. 5 and 6. the results underline that dynamic simulation models need to be applied to solve planning problems in the case of rapidly changing supply and demand. 4. discussion as has been summarized in the introduction, mainstream hsc planning and operation applies mathematical programming, where a simplified model is usually embedded in a superstructure-based optionally multi-objective optimization program. the suggested non-conventional approach might have some potential advantages. having analyzed the characteristics of hydrogen supply chains and their typical elements, programmable process structures may offer some useful options: • the methodology tolerates case-specific multiscale extensions (e.g. when a proportion of the elements is in need of a more detailed model and/or refined spatial or temporal resolution). • by taking into consideration the intensive development of new hydrogen-producing methods, pro-20000 -10000 0 10000 20000 30000 40000 50000 60000 k g h 2/ d a y time, day uncovered daily h2 demand figure 6: the change in hydrogen demand produced by the available direct renewable resources. grammable process structures are capable of embedding any detailed prototypes of nonlinear dynamic models into existing structures. • the extensibility of programmable process structures favours stepwise structural and functional changes in supply and demand without reformulation of the model. • optional multiscale compartmentalization helps to represent multiple districts and sites via the optional connection between spatial coordinates of the elements with an external gis tool. • individual elements and connections can be associated with a time-driven execution at given points in time and/or over prescribed time intervals. • material and energy balances can be combined with signal and rule-based, event-driven processes. • a programmable process structure has built-in capabilities for robust communication with external (e.g. meteorological) databases and collaborating (e.g. metaheuristic optimization) programs. • the method supports the handling of the extraordinary uncertainty of coefficients of cost and some other parameters over a longer time horizon. the embedded elementary evaluations and elements of evaluation may be prepared for a multi-objective case involving a set of time-invariant natural objective functions. 5. conclusion regardless of the well-established mathematical programming-based methods of the planning and operation of hydrogen supply chains, problem-solving in terms of these systems might also require an easily modifiable, generic dynamic simulation-based approach. as was also shown by the studied illustrative example, the representation of energy storage corresponding to renewable resources requires a short (e.g. hourly, daily) 47(2) pp. 53–61 (2019) 60 varga, azzaro-pantel, flores-perez, and csukás timescale as opposed to a years-long planning time horizon. the reason for this is that these large-scale, long-term supply chains are not only affected by uncertainly changing demands, but by erratically changing supply, partly originating from natural resources, determined by erratically changing extreme weather conditions and a slowly changing climate. by considering these challenges with regard to the planning and operation of a hydrogen supply chain, the non-conventional modeling and simulation methodology of programmable process structures was implemented as developed in other multidisciplinary fields. the suggested programmable process structures may contribute to the solution to these problems. programmable process structures of hsc models can be generated from the description of a (optionally geographically determined and multiscale) process network and two general functional meta-prototypes, automatically. the case-specific, functional program prototypes can be derived from the two meta-prototypes. simultaneously, the actual elements of the process network can be parameterized and initialized according to the case-specific prototypes. the simulation of the model can be solved by a general-purpose kernel program. the method also allows different time steps for the various classes of elements to be used. the application of programmable process structures was illustrated by a fictitious example of a simple hydrogen supply chain. planned future work, in collaboration with hsc experts, will focus on the application of a repeated forward/backward simulation-based iterative methodology to reach a reasonable compromise between changing demands and supplies. furthermore, programmable process structures will be combined with metaheuristic optimizers for the multi-objective optimization of hsc planning. notations gis geographic information system graphml a comprehensive and easy-to-use file format for graphs hsc hydrogen supply chain milp mixed integer linear programming minlp mixed-integer nonlinear programming mpp multi-period problems mop multi-objective problems pps programmable process structure acknowledgement this research was supported by the tét_16-1-20160116 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programmable process structures, generated from a network and from functional meta-prototypes. in: 2017 aiche annual meeting proceedings, computing and systems technology division, software tools and implementations for process systems engineering. minneapolis (mn), usa, 2017. paper 448e https://www.aiche.org [20] varga, m.; prokop, a.; csukás, b.: biosystem models, generated from a complex rule/reaction/influence network and from two functionality prototypes, biosystems, 2017, 152, 24–43 doi: 10.1016/j.biosystems.2016.12.005 [21] http://www.gprolog.org/ 47(2) pp. 53–61 (2019) https://doi.org/10.1016/j.compchemeng.2009.11.012 https://doi.org/10.1002/aic.12024 https://doi.org/10.1002/aic.12024 https://doi.org/10.1016/b978-0-12-811197-0.09988-7 https://doi.org/10.1016/j.ijhydene.2015.10.032 https://doi.org/10.1016/j.ijhydene.2015.10.032 https://doi.org/10.1016/j.ijpe.2016.08.028 https://doi.org/10.1016/j.ijpe.2016.08.028 https://doi.org/10.1016/b978-0-12-811197-0.09988-7 https://doi.org/10.1016/b978-0-12-811197-0.09988-7 https://www.aiche.org/conferences/aiche-annual-meeting/2017/proceeding/paper/448e-programmable-process-structures-generated-network-and-functional-meta-prototypes https://doi.org/10.1016/j.biosystems.2016.12.005 https://doi.org/10.1016/j.biosystems.2016.12.005 http://www.gprolog.org/ hungarian journal of industry and chemistry vol. 47(2) pp. 63–70 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-21 investigation of mixing in tanks of a special geometry bálint levente tarcsay*1, attila egedy1, janka bobek2, and dóra rippel-pethő2 1department of process engineering, university of pannonia, egyetem u. 10, veszprém, 8200, hungary 2department of chem. eng. sci.s, university of pannonia, egyetem u. 10, veszprém, 8200, hungary mixing is one of the most crucial processes in the chemical industry. homogeneity is a requirement for all feedstocks and industrial products. the degree of mixing depends on the hydrodynamic properties of the fluid in the units. the residence time distribution (rtd) was investigated in a tank of a special geometry. mixing was investigated using various geometries of the tank by applying the heaviside function in step-response experiments. after obtaining experimental results, the rtd function was calculated. the flow structure in the tank was approximated by fitting black-box transfer function models onto the rtd function of the system. two general model structures were defined and their fitness compared. by evaluating the fitted models, a relationship was established between the flow structure in the tank and its geometry. keywords: tanks with of special geometry, mixing, flow pattern, transfer function model 1. introduction in industrial processes, the thorough homogeneity of materials is a necessity to ensure the quality of the finished products and the safety of the production process. therefore, various industrial-scale techniques for the homogenisation of materials of various densities and phases have been developed over the years. in the case of fluids, homogenization can be achieved through the application of mixers in a device. the optimal type and geometry of these stirred tanks can be approximated by specific models which take the properties of the materials to be mixed and the desired degree of homogeneity into consideration [1]. in the case of the homogenisation of large volumes of liquids (petrochemical and radiochemical industries), external recirculation can be more advantageous since it is considerably more inexpensive in terms of both installation and operation. the operation of stirred tanks has been thoroughly investigated by using mathematical and experimental methods, however, research on mixing achieved by external recirculation is lacking [2]. optimization of the mixing process to achieve the most homogenous product possible in an external recirculation tank can only be achieved after the flow structure of the unit is known. the aim of this research was to analyze the flow structure in a tank of special geometry, moreover, to determine the connection between the flow structure and geometry of the tank. this research forms the basis for future investigations where the flow structure and homogenization in a tank will be tested through an external recirculation mixing *correspondence: tarcsaybalint95@gmail.com process. mixing in stirred tanks can traditionally be analyzed by step-response experiments. step-response experiments are a widely accepted and simple way of determining the flow structure of process units [3]. during these experiments, the input of the system is a tracer fed according to the heaviside function. the time evolution of the tracer concentration in the output of the tank holds information regarding the flow and mixing properties of the system. the heaviside function is the integral of the dirac delta function δ(t): s(t) = ∫ ∞ −∞ δ(t)dt = { 0 if t < t∗ 1 if t ≥ t∗ (1) used as an input in pulse-response experiments [4]. the heaviside function, s(t), as a function of time takes on a value of 0 if the investigated time t is less than the time of the tracer feed t∗ and a value of 1 during and after being fed. after experimental data was collected on the response function of the system, the residence time distribution function (rtd) could be calculated. the rtd function approximates the probability that the residence time of the fed tracer agent is less than a specified residence time [4]. the rtd function, f , was calculated from f (t) = rt −rt−1 rsteady −r0 , (2) wherersteady andr0 are the values of the response function in the steady state and at the beginning of the experiment, respectively. by analyzing the rtd curve in the studied unit, mixing and flow can be characterised and compared to the https://doi.org/10.33927/hjic-2019-21 mailto:tarcsaybalint95@gmail.com 64 tarcsay, bobek, egedy, and rippel-pethő figure 1: response functions of various ideal flow models [3]. flow structure of ideal hydrodynamic models [5, 6]. in this study, the ideal hydrodynamic models, which were used to describe the response, include the plug flow reactor (pfr) and tanks-in-series (tis) model. the pfr model is useful for modelling systems with a continuous flow of cylindrical geometry. it works under the assumption that the flow through a pfr is perfectly mixed in the radial direction but not in the axial direction. it is also assumed that the residence time of each fluid unit within the system is equal to the mean residence time, τ . because of these conditions, the step response function of a system with pfr tendencies is identical to the step function which was used as an input but with a time delay equal to the mean residence time in the unit. an altered version of the pfr model is the laminar flow reactor (lfr) model. the lfr model assumes a laminar flow structure within the system. therefore, the residence time of the fluid phase within the system has a distribution. this causes the shape of the response function to become slightly altered compared to the step function. the tis model is an extension of the continuous stirred tank reactor model (cstr) which defines a system that is perfectly mixed and, therefore, homogeneous. upon entering the unit, the tracer is dispersed throughout the whole tank, therefore, it immediately appears in the output without a time delay. the tis model examines a series of cstr units. the rtd function in this model is dependent on the number of tanks that have been linked. the rtd function of the tis model converges towards the pfr model as the number of units increases and towards the cstr distribution as the number of units decreases. one tank returns the rtd function of a cstr and as the number of tanks in series approaches infinity, the rtd function converges towards the pfr model. the characteristic rtd curves of the aforementioned ideal flow models are shown in fig. 1 [3]. in this figure, t∗ denotes the duration of tracer injection and dt represents the time delay when the tracer appears in the outlet. in this investigation, black-box models were used to approximate the behavior of the tank. blackand whitebox modelling are two distinct modelling techniques to describe the traits of various systems. white-box models utilize well-known physical and chemical laws to characterize a system. these laws come in the form of differential equations, algebraic equations, etc. the model defines the internal functioning of the system and calculates the specific output from the input by taking these into consideration. generally in the case of complex mixing problems, computational fluid dynamics (cfd) simulators are utilized to solve the white-box model of the system [7,8]. cfd simulations can determine the flow field in various units [9]. these simulators can be used to solve scientific problems from a diverse spectrum of disciplines, e.g. aerodynamics, hydrodynamics, ocean engineering, chemical engineering, etc. [10]. to solve these problems, various numerical methods have been invented over the years among which the finite element method (fem) is one of the more frequently applied approaches [11]. however, in cases where the fem is insufficiently advanced, alternative numerical methods can also be implemented, e.g. the spectral element method (sem) [12]. their disadvantage is, however, that since they model the systems so thoroughly, they require considerable computational power and computation time. through these methods, it is possible to analyze processes which are more complex or require long experimentation times to be dissected. despite this, these methods also require experimental data for validation. black-box models, on the other hand, provide generalized means for the modelling of various problems [13]. they often employ empirical methods to calculate the output of a system from the input without thoroughly describing the internal properties of the system [14]. the relationship between the input and output can be modelled using various techniques with the most popular being neural networks as well as state-space and transfer function models [15]. in this study, the transfer function model was utilized to approximate the behavior of a tank of special geometry. 2. experimental and the modelling process the geometry of the investigated tank is shown in fig. 2. the tank consists of 5 cylindrical units integrated with each other. a removable wall was implemented which makes it possible to create the desired number of cylinders from the main tank. therefore, the number of cylindrical units can be varied between 1 and 5. during the investigation, geometries consisting of 1, 3 and 5 cylindrical units were investigated. the residence time, calculated from the inlet volume flow rate and volume of the liquid, was 3 h for all geometries. therefore, the inlet volume flow rate changed as the volume of liquid and number of cylindrical units varied. to obtain the response function of the system, a heaviside function was used. the utilized tracer was a borax solution of low concentration (6.24 gl−1). the tracer was fed into the tank which hungarian journal of industry and chemistry mixing in tanks of a special geometry 65 figure 2: the investigated tank. was filled with a high concentration of borax solution (29.16 gl−1). conductivity measurements were used to monitor the change in concentration and obtain the response function. the experimental equipment is shown in fig. 3. the experimental conditions for the feed and residence time are shown in table 1. the positions of the inlet and outlet during the experiments are shown in table 2. the (0, 0, 0) coordinates of the system were defined as the bottom of the tank at the position of the outlet. the coordinates x, y and z correspond to the longitudinal, vertical and horizontal distances, respectively. the rtd curves of the three different geometries of the tank were investigated. after experimentally obtaining the data from the rtd curves, transfer function models were fitted to the experimental results. two types of fitted functions were investigated. both were black-box convolution models of the pfr and tis. however, one contained only serial links between the perfectly mixed units, the other assumed parallel connections as well. differential equations describe the change in concentration of the output of the tank as a function of the input. in various ideal flow models, these equations were converted into algebraic equations by using the laplace transform. after this the transfer function of the ideal flow modfigure 3: setup of the experimental equipment (1– experimental tank, 2–tracer containment tank, 3– peristaltic pump, 4–buffer unit, 5–rotameter, 6–output containment tank). table 1: experimental parameters. number of cylinders τ (h) b (lh−1) 1 0.4 3 3 1.1 5 1.7 table 2: inlet and outlet positions. number of cylinders inlet position outlet position x (mm) y (mm) z (mm) x (mm) y (mm) z (mm) 1 75 100 0 0 2 0 3 225 100 0 0 2 0 5 375 100 0 0 2 0 els was defined as the ratio of the output (the laplace transformed response function) to the input of the system (the step function of the tracer injection). if the product of multiple elementary transfer functions is computed, a tis model can be generated. a general model structure for this network can be seen in fig. 4. on the other hand, by combining the elementary transfer functions of ideal flow models, a network of flow models with parallel links can be created. a general model for this structure is shown in fig. 5. in both cases, a pfr unit has been included in the structure, in general this is useful for modelling systems with a time delay. the time delay in the rtd function could point to either pfr tendencies in the flow structure or the presence of dead volumes within the tank. to distinguish which is present, further investigations with a cfd simulator are required. the general form of the transfer function that only uses serial connections is gfitted = a bnsn + bn−1sn−1 + · · ·+ b0s0 e−tds, (3) where n denotes the order of the denominator and bn, a, and td are parameters of the transfer function. in the case of the model containing both parallel and serial links, the general transfer function is gfitted= an−1s n−1 + · · ·+ a0s 0 bnsn + bn−1sn−1 + · · ·+ b0s0 e−tds, (4) where n is the order of the denominator and bn, an, and td are parameters of the transfer function. however, due to the parallel connections, the elementary transfer functions are not just multiplied but totalled. therefore, the figure 4: general model structure involving only serial links [5, 6]. 47(2) pp. 63–70 (2019) 66 tarcsay, bobek, egedy, and rippel-pethő figure 5: general model structure involving both serial and parallel links [5, 6]. nominator also contains a higher order polynomial. the order of this polynomial can be one at most below the order of the denominator for the system to be suitable. in both cases, the fitted rtd curve ffitted was calculated from the step response of the system which was characterized by the transfer function, gfitted. the overall parameters of the transfer function were determined by numerically solving a minimization problem. the minimization problem is expressed in min [e (n, a, b, d)] = ∑ [fexp − ffitted (n, a, b, d)] 2∑ (fexp) 2 (5) where e is a function denoting the sum of the squared difference of the experimental and fitted rtd functions divided by the sum of the square of the experimental rtd curve. as such,e is a function similar to the relative error of the fitting which is dependent on the parameters of the transfer function, gfitted. inversely, the goodness of the fit, i , can be defined as the complementer of the fitting error: i (n, a, b, d) = 1− e (n, a, b, d) . (6) for the minimization of the function, the interior-point method was applied in matlab r2011. constraints were defined for the lower and upper boundaries of the parameters, namely 0 and 100 for all parameters, respectively. the fitting algorithm was modified to favor transfer functions with the smallest possible order and smallest relative error. the algorithm can be seen in fig. 6. the algorithm follows a general route for fitting both parallel and serial models. during the first step, a loworder (first-order) transfer function is created. after that the parameters of this transfer function are identified using the interior point method. after obtaining the parameters, the e function is calculated to evaluate the error of the fitting. if the error is less than a predefined threshold (erropt), then the fitting will stop and the current transfer function be defined as the best possible fit. if the error of the fit exceeds the defined threshold, then the fitting continues. in this case, the order of the denominator is increased and the error of the higher order transfer function evaluated as well. if the error of fitting is less than the lower order transfer function, then the fitting continues until either a transfer function which satisfies the error boundary is identified or the error of the fitting does not decrease significantly even though the order of the denominator increases. in the case of models which include parallel links, this algorithm contains an additional iteration step. during this step, the algorithm investigates the fit of an nth order transfer function (if n ≥ 2) with varying orders of the nominator. to achieve this, the fitting is evaluated by applying increasing orders of the nominator. during this process, either the maximum order of the nominator (n − 1) is reached or a point where the increase in the order of the nominator is identified that does not significantly impact the fitting error. in either case, fitting is stopped and the solution accepted as the best possible fit for a transfer function with order of the denominator, n. to evaluate the proposed fitting algorithm for both models, a custom-defined transfer function was analyzed. this reference transfer function (gref is defined by gref = 1 1.6s2 + 2.6s+ 1 e−5s (7) in the case of the model contains only serial links. the step response function for this transfer function was used as reference data. the extrema of function e were numerically determined by using the devised algorithm. the fitted transfer function is gref = 1 1.58s2 + 2.59s+ 1 e−5s. (8) fig. 7 shows the fitting of the rtd of the identified transfer function to the reference rtd function. the goodness of the fit was 98.2 %. the testing was also conducted in cases where parallel links are present besides serial links. in this case, the reference system is characterized by the transfer function: gref = 8.6s+ 1 s4 + 2.5s3 + 11s2 + 10s+ 1 e−2s. (9) the fitting algorithm was augmented to identify both the optimal orders of the nominator and denominator. the fitted transfer function is gfitted = 8.95s+ 1 s4 + 2.37s3 + 11.14s2 + 10.33s+ 1 e−2s. (10) the results of the fitting are displayed in fig. 8. in this case, the goodness of the fit exceeded 99 %. both fig. 8 and the measurements of the parameters show that the algorithm is capable of precisely fitting both models, therefore, it is suitable for identifying the transfer functions of the system. after validating the fitting hungarian journal of industry and chemistry mixing in tanks of a special geometry 67 figure 6: the general applied fitted algorithm for a model containing both serial and parallel links. figure 7: the results of the algorithm validation for fitting the model containing only serial connections. figure 8: the results of the algorithm validation for fitting the model containing parallel and serial links. method, transfer functions were identified for the tank by using the experimental rtd curves. 3. results and analysis the results of the fittings in the case of the model with only serial connections can be seen in figs. 9–11 for all three geometries of the tank that were investigated. the geometry consisting of 5 cylinders was originally modeled using a second order transfer function that yielded the best fit for the experimental rtd curve (92 %). however, to compare the parameters of the fitting figure 9: results of the fitting of the serial model for 1 cylindrical unit. figure 10: results of the fitting of the serial model for 3 cylindrical units. and characterise the system, it was more favorable to fit a third order transfer function here as well since it describes the other two rtd curves best. in this case, the average goodness of the fit was 91 % with the goodness of the fit in the case of the geometry consisting of 5 cylindrical units (86 %) being the lowest. the numerical parameters of the fit are shown in table 3. the results are as follows: to describe the system in the cases of 1 and 3 cylindrical units, a third order transfer function was used. in the case of 5 cylindrical units, a second order transfer function was optimal. in the case of the model containing both parallel and 47(2) pp. 63–70 (2019) 68 tarcsay, bobek, egedy, and rippel-pethő figure 11: results of the fitting of the serial model for 5 cylindrical units. table 3: fitted parameters for the model containing only serial links. parameters n n a0 b3 b2 b1 b0 td (h) i (%) 1 3 1 0.1 0.3 1.0 1 0.9 93.43 3 3 1 0.2 0.6 1.5 1 0.6 94.00 5 3 1 0.3 0.7 2.0 1 0.7 85.76 5 2 1 0.9 2.3 1 0.7 92.00 serial links, the fitted curves are displayed in figs. 12–14. in the case of the model containing both parallel and serial connections, the tendencies are similar to the results of the fitting conducted using the model consisting of only serial links. however, the goodness of the fit was enhanced compared to the simpler models (over 99 % for all investigated geometries). in this case, the behavior of the tank consisting of 1 cylindrical unit was described by a transfer function where the orders of the nominator and denominator were 4 and 2, respectively. in the case of 3 and 5 cylindrical units, the orders of the denominator and nominator were 3 and 1, respectively. the order of the transfer function (the number of cstr units in the tis model) increases as the number of cylinders decreases. this is evident of an increase in the pfr/lfr tendencies of the functions which can also be seen in the figfigure 12: results of the fitting of the parallel model for 1 cylindrical unit. figure 13: results of the fitting of the parallel model for 3 cylindrical units. figure 14: results of the fitting of the parallel model for 5 cylindrical units. ures. it should also be noted, however, that the fitting in all models was exceedingly high (over 95 % on average). this might suggest that the model algorithm is too precise and the model was also fitted according to the experimental noise remaining in the data. in the absence of the noise, such tendencies might be clearer and the decrease in the order of the nominator between the different geometries more prominent. further investigations carried out by cfd simulations may clarify these concerns. the parameters of the fit are displayed in table 4. 4. conclusion in this paper, the velocity field of a tank of special geometry was investigated. in order to determine the relationship between the flow profile and geometry of the tank, step-response experiments were conducted. the rtd curves of the system were measured by applying various geometries of the tank. by analyzing the experimental rtd curves, a model was proposed to be fitted onto the results. the transfer function of the system was optimized by minimalizing the squared difference of the experimental and fitted rtd curves. the interior-point method was applied to minimalize the difference. the following conclusions were drawn from the fitted rtd curves: hungarian journal of industry and chemistry mixing in tanks of a special geometry 69 table 4: fitted parameters of the model containing both parallel and serial links. parameters n n m a2 a1 a0 b4 b3 b2 b1 b0 td (h) i (%) 1 4 2 6 2.4 1 1 4.3 8 3.12 1 1.2 98.28 3 4 1 − 5.5 1 1 3.4 8.5 7.1 1 0.6 99.77 5 3 1 − 12 1 1 3.5 18 14.4 1 0.5 99.43 in the case of models containing only serial links, 1 and 3 cylindrical units could be optimally described using a third order transfer function. the geometry consisting of 5 cylindrical unitscan be described by a second order transfer function. the average goodness of the fit in this case was 91 %. in the case of the model utilizing parallel links, the rtd function of the tank consisting of 1 cylindrical unit was approximated by a transfer function where the orders of the denominator and nominator were 4 and 2, respectively. in the cases of 3 and 5 cylindrical units, the orders of the denominator and nominator were 3 and 1, respectively. the goodness of fit on average in the case of this model was over 99 %. it can be concluded that all geometries of the tank can be described using fourth order or lower transfer functions with increasing model parameters according to the number of cylinders. further investigations to characterise the reasons for such behavior will be carried out by using cfd methods. simultaneously, different step-response experiments will be conducted to observe the behavior of the system. during these experiments, instead of feeding the solution of lower concentration into that of higher concentration within the tank, a positive step function will be used. as a result, the orders will be reversed with the solution of low concentration being in the tank and that of high concentration in the feed. notations latin letters a nominator parameter of transfer function b denominator parameter of transfer function dt time delay [h] h order of the nominator of transfer function (1,n-1) n order of the denominator of transfer function [-] t time [h] td time delay of transfer function [h] x longitudinal coordinate [mm] y vertical coordinate [mm] z horizontal coordinate [mm] capital letters b volume flow rate [lh−1] e error of fitting [%] f residence time distribution function g transfer function i goodness of fit [%] n number of cylinders r response function [gl−1] s step function [gl−1] greek letters δ dirac delta function τ mean residence time [h] indices ∗ time of tracer injection d delay exp experimental fitted fitted ref reference steady steady 0 initial acknowledgement this research was supported by the project efop-3.6.116-2016-00015 “smart specialisation strategy (s3) comprehensive institutional development program at the university of pannonia to promote sensible individual education and career choices”. references [1] nienow, a. w., edwards, m. f., harnby, n. mixing in the process industries. (elsevier, oxford, united kingdom 1997) isbn: 07506-3760-9 [2] blais, b., lassaigne, m., goniva, c., fradette, l., bertrand, f. development of an unresolved cfd–dem model for the flow of viscous suspensions and its application to solid–liquid mixing. j. comp. phys., 2016, 318, 201-221 doi: 10.1016/j.jcp.2016.05.008 [3] levenspiel, o. chemical reaction engineering. ind. eng. chem. res., 1999, 38(11), 4140–4143 doi: 10.1021/ie990488g [4] danckwerts, p. v. continuous flow systems: distribution of residence times. chem. eng. sci., 1995, 50(24), 3857–3866 doi: 10.1016/0009-2509(96)81811-2 [5] fazli-abukheyli, r., darvishi, p. combination of axial dispersion and velocity profile in parallel tanks-in-series compartment model for prediction of residence time distribution in a wide range of non-ideal laminar flow regimes. chem. eng. sci., 2019, 195, 531–540 doi: 10.1016/j.ces.2018.09.052 [6] haag, j., gentric, c., lemaitre, c., leclerc, j. p. modelling of chemical reactors: from systemic approach to compartmental modelling. int. j. chem. reactor eng., 2018, 16(8), 1–22 doi: 10.1515/ijcre-2017-0172 [7] blazek, j. computational fluid dynamics: principles and applications. 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(springer, heidelberg, germany 1999) isbn: 978-3-662-03492-7 [9] pawlowski, s., nayak, n., meireles, m., portugal, c. a. m., velizarov, s., crespo, j. g. cfd modelling of flow patterns, tortuosity and residence time distribution in monolithic porous columns reconstructed from x-ray tomography data. chem. eng. j., 2018, 350, 757–766 doi: 10.1016/j.cej.2018.06.017 [10] delafosse, a., collignon, m. l., calvo, s., delvigne, f., crine, m., thonart, p., toye, d.: cfd-based compartment model for description of mixing in bioreactors. chem. eng. sci., 2014, 106, 76–85 doi: 10.1016/j.ces.2013.11.033 [11] zienkiewicz, o. c., taylor, r. l., zhu, j. z. the finite element method: its basis and fundamentals. (elsevier, oxford, united kingdom, 2005) isbn: 07506-6320-0 [12] solin, p., segeth, k., dolezel, i. higher-order finite element methods. (chapman and hall/crc, new york, 2003) isbn: 978-0-42-920527-9 [13] witt, c., bux, m., gusew, w., leser, u. predictive performance modeling for distributed batch processing using black box monitoring and machine learning. information systems 2019, 82, 33–52 doi: 10.1016/j.is.2019.01.006 [14] suykens, johan a. k.; vandewalle, joos p. l. (ed.) nonlinear modelling: advanced black-box techniques. (springer science and business media, leuven, 2012) isbn: 978-1-4613-7611-8 [15] bunge, m. a general black box theory. philosophy of science, 1963, 30(4), 346–358 doi: 10.1086/287954 hungarian journal of industry and chemistry https://doi.org/10.1016/j.cej.2018.06.017 https://doi.org/10.1016/j.ces.2013.11.033 https://doi.org/10.1016/j.ces.2013.11.033 https://doi.org/10.1016/j.is.2019.01.006 https://doi.org/10.1016/j.is.2019.01.006 https://doi.org/10.1086/287954 hungarian journal of industry and chemistry vol. 47(2) pp. 71–75 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-22 assessment of the ecotoxicity of nanoplastics nóra kováts*1, bettina eck-varanka1, zsófia békéssy1, dorina diósi1, katalin hubai1, and jános korponai2 1institute of environmental sciences, university of pannonia, 8200 veszprém, egyetem u. 10, hungary 2department of environmental science, sapientia hungarian university of transylvania, 400193 cluj-napoca, calea turzii 4, romania the presence of microand nanoplastics in aquatic environments (including freshwater and marine ecosystems as well as their sediments) is becoming an increasingly serious problem worldwide. a wide range of studies have addressed the ecological effects these particles pose on biota. the main exposure pathway are food chains, e.g. under laboratory conditions these particles accumulate in the brain tissues of fish that feed on zooplankton causing brain damage. these studies, however, report mainly on the physical effects. in order to establish actual ecotoxicological effects, nanoplastics (50 nm in diameter) were assessed using the vibrio fischeri bioluminescence inhibition bioassay (vfbia). our results showed that even environmentally relevant concentrations might trigger ecotoxicological effects. this study can be considered to be a first screening, however, results indicate the need for more complex testing on a battery of aquatic test organisms. keywords: nanoplastic; ecotoxicity; vibrio fischeri ; kinetic assay 1. introduction aquatic environments contaminated by plastic litter are an emerging problem. remote, pristine mountainous areas are even contaminated by atmospheric microplastic deposition [1]. polymer particles < 5 mm in diameter are defined as microplastics (mp) and may be derived directly from the use of industrial pellets or indirectly from the degradation and fragmentation of plastic particles [2]. polystyrene was proven to degrade into microand nanoplastics under laboratory conditions [3]. high levels of contamination have been reported in both marine and freshwater habitats [4, 5]. microand nanoplastics (np) can float freely in bodies of water or be deposited as sediments. the highest risk associated with these particles is their ingestion, which occurs at different levels in the aquatic food chain. jabeen et al. [6], for example, listed approximately 150 different fish species where ingestion and accumulation have been reported. particles can also progress upwards in the trophic levels of the food chain, i.e. fish can be exposed to the ingestion of zooplankton which is not able to discriminate between different food sources and consumes microand nanoplastics [7]. an experimental study showed that in fish exposed to nps via the food chain, these particles caused brain damage and behavioural disorders as a result of accumulation in *correspondence: kovats@almos.uni-pannon.hu brain tissues [8]. biomagnification may also affect food safety and human health, though certain knowledge gaps exist in this field [9]. ingestion may actually lead to starvation and eventually the impairment of their physical condition. under laboratory conditions, daphnia magna exposed to polystyrene nanoparticles (ps-np) exhibited reduced body size and severe alterations in terms of reproduction [10]. d. magna is a widely studied species due to its key role in the aquatic food chain. it was shown to ingest nanoand microplastics (20 nm to 70 µm in diameter) from water [11]. in a laboratory study by mattsson et al. [8], particles 52 nm in diameter elucidated the most severe effects. cui et al. [12] exposed d. galeata to psnps (5 mg/l, 52 nm in diameter) and detected a significant mortality rate after 2 days of exposure until the end of the study which lasted 5 days. although a standard ecotoxicological test was conducted in this case, the mechanisms of mortality are still unclear: physical contact might have led to a reduction in the survival rate. in general, most ecotoxicological studies have used relatively high concentrations. manfra et al. [13] investigated the impact of green fluorescently labeled carboxylated polystyrene nanoparticles of 40 nm in diameter with various surface charges on the marine rotifer brachionus plicatilis. it was found that anionic ps-nps did not elucidate mortality within the range of concentrations tested (0−50 µg/ml), while cationic ps-nps caused mortality at https://doi.org/10.33927/hjic-2019-22 mailto:kovats@almos.uni-pannon.hu 72 kováts, eck-varanka, békéssy, diósi, hubai, and korponai concentrations ≥ 2.5 µg/ml. changes in oxidative stress enzymes were detected within the concentration range of 10−20 µg/ml in different organisms, e.g. the rotifer brachionus koreanus and the marine copepod paracyclopina nana [14]. the same concentration, 10 µg/ml, was reported to cause 40 % growth inhibition in the green microalga dunaliella tertiolecta [15]. in order to distinguish real (eco)toxicological effects from physical damage, a test based on the bioluminescence inhibition of the marine bacterium vibrio fischeri was selected. the species has been reclassified as aliivibrio fischeri [16], however, as most standards and even recent papers from the literature still use the name v. fischeri, it will be used hereinafter. bioluminescence is regulated by the enzyme system nad(p)h:fmn oxidoreductase-luciferase. in toxic environments, enzyme inhibition is reflected by a rapid decrease in the luminous emittance of the bacterium. the reduction in light intensity is easy to measure as it is proportional to the strength of the toxicant, therefore, provides a quantifiable endpoint. this test has been used in various environmental matrices [17–19]. lappalainen et al. [20,21] developed a special version of the test which was later standardised (iso 21338:2010: water quality kinetic determination of the inhibitory effects of sediment, other solids and coloured samples on the light emission of vibrio fischeri (kinetic luminescent bacteria test)) in which bacteria are kept in suspension in direct contact with potentially toxic solid particles. luminescence readings were taken when the test commenced and the light intensity continuously monitored over the first 30 secs after the sample had been mixed with the bacteria. the light output pattern, therefore, might already provide some indication of the expected toxicity of the sample [22]. the light intensity was measured once more after the pre-set exposure time (5, 15 or 30 mins as per standard). toxicity values are normally expressed as ec50 and ec20, i.e. concentrations causing luminescence inhibitions of 50 and 20 % in this assay, respectively. 2. materials and methods in our experiments, the ascent luminometer (flash system, marketed by aboatox, finland) was used. a suspension of the test bacteria (nrrl b-11177) was prepared in accordance with manufacturer instructions (hach lange gmbh). polystyrene particles with a nominal diameter of 50 nm were used as a sample (supplier thermo fisher scientific). as no comparative data were available on the potentially toxic concentration, a range-finding concentration series was set [23]. three initial sample concentrations were selected (1 g/l, 1 µg/l and 1 ng/l), which were further diluted, the number of dilutions was 11 (the number of concentrations the 96-multiwell plate permits) and the dilution ratio 1 : 2. table 1: the measured ec20 values of the polystyrene nanoparticles. concentration 1 g/l 1 µg/l 1 ng/l ec20 5.2 17.31 30.51 the vibrio fischeri strain nrrl b-11177 was reconstituted by adding the contents of one vial of +4 ◦c 1243551 reagent diluent. the reconstituted reagent was equilibrated at +4 ◦c for 30 min. then the reagent was stabilised at +15 ◦c for 30 mins before being pipetted into the wells. luminescence readings were taken when the test commenced, time0, and after the pre-set exposure time of 30 mins, time30. the luminescence inhibition of each sample was calculated as follows: cf = ic30/ic0 inh \% = 100 $-$ 100 x (it30 / cf x it0) where cf = correction factor ic30 = luminescence intensity of the control sample after the contact time (30 mins) in the rlu ic0 = initial luminescence intensity of the control sample in the rlu it30 = luminescence intensity of the test sample after the contact time (30 mins) in the rlu it0 = initial luminescence intensity of the test sample in the rlu ec20 values were calculated using the ascent software, also developed by aboatox oy. 3. results and discussion table 1 shows the ecotoxicity expressed in ec20, i.e. the calculated concentration of the sample that caused 20 % bioluminescence inhibition. fig. 1 illustrates the bioluminescence inhibition during the first 30 secs for the samples of 1 g/l and 1 ng/l in concentration. ec20 (or in some cases, ec10) are considered thresholds for the estimation of the lowest observed effective concentration [24], i.e. the sample is normally considered (eco)toxic if the elucidated effect exceeds 20 %. these results show that the v. fischeri bioassay detected a measurable degree of toxicity even at a concentration of 1 ng/l. booth et al. [25] used the non-kinetic version of this bioassay (microtox®), however, in their study, the calculated toxic concentration exceeded the range of concentrations studied (0.001−1000 mg/l). the same negative effect was reported by casado et al. [26]. the higher degree of (detectable) toxicity in our study might be explained by the differences in the test system used. while microtox® is a non-kinetic test, the flash system (ascent luminometer) was especially developed to test the toxicity of different suspensions or samples containing solid particles. the ascent luminometer uses a 96-multiwell microplate. a specific feature of it is that hungarian journal of industry and chemistry assessment of the ecotoxicity of nanoplastics 73 (a) (b) figure 1: kinetic diagram of the 1 g/l (a) and 1 ng/l (b) samples. the light output is recorded over the first 30 seconds. after the peak, toxicity causes a rapid reduction in the light output, on the other hand, it remains constant during the control. the two columns show the two replicates. e1-f1/g1-h1 (left): control. e2-f2/g2-h2 (right): sample, maximum concentration. during luminescence readings, the microplate is continuously shaken by the instrument, resulting in the resuspension of particles. according to our results, environmentally relevant concentrations might already pose ecotoxic effects. actual environmental concentrations are relatively difficult to compare and assess, mostly due to difficulties in sampling and the lack of standardized sampling methodologies [27,28]. indicative data are available: e.g. microplastic concentrations of 0.4 − 34 ng/l in bodies of freshwater in the usa [29] or 0.51 mg/l in marine environments [10]. however, in real-world environments, even higher levels of toxicity can be expected as particles might absorb organic pollutants from the surrounding water [30], including highly toxic pesticides or polychlorinated biphenyls (pcbs) [31]. though their bioavailability is still questionable [32], batel et al. [33] conducted a laboratory study on microplastics and one polycyclic aromatic hydrocarbon (pah), benzo[a]pyrene (bap). it was demonstrated that bap adsorbed on microplastics and was transferred via an artificial food chain. these particles might also possess inherent toxicity due to the use of additives during manufacturing processes [34]. 4. conclusions it is a well-known paradigm in ecotoxicology that the sensitivity of different test organisms to a particular chemical varies, therefore, the v. fischeri test can be regarded as a first screening. the bioluminescence inhibition assay is an acute test that uses a maximum exposure of only 30 minutes. naturally, chronic effects cannot be extrapolated from these results. however, the fact that the tested nanoplastics have already elucidated ecotoxicological effects in environmentally relevant concentrations emphasises the need for more complex ecotoxicological testing involving a properly selected battery of test organisms. in addition to widely used aquatic test organisms such as the aforementioned daphnia magna, an ideal candidate could be the caenorhabditis elegans test. it is a standardised bioassay using a sediment-dwelling, widely distributed nematode. however, in order to distinguish physical damage from toxic effects, the measurement of changes in oxidative stress enzymes can be useful no matter which test organism is applied. acknowledgement this work was funded by the bionano_ginop-2.3.215-2016-00017 project. references [1] allen, s.; 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[25], ball et al. [26], and bearsley and haverkamp blended bio-oil originated pine derived tall oil as a bitumen extender [27, 28]. gondim et al. studied the effect of plant sap from a “petroleum plant” [29]. yang et al. examined bio-oils derived from waste wood resources as bitumen modifiers and extenders [30]. in summary, bio-oils typically have a softening effect, which improves their performance at low and intermediate temperatures but impairs their high-temperature performance. this negative impact can be mitigated, e.g. by the addition of crumb rubber or other polymers. the application of stabilised wood-based pyrolysis bio-oil as an additive for bitumen binders has been intensively researched but remains a field of future bitumen production that is yet to be clarified. the utilisation of polymer modified bitumen is widespread but the modifying effect of stabilised wood-based pyrolysis bio-oil on polymer modified bitumen has yet to be clearly defined. thus, our target was to investigate the effect of stabilised pinewood-based fast pyrolysis bio-oil on the characteristics of different binders, such as road pavement bituhttps://doi.org/10.33927/hjic-2019-23 mailto:ahollo@mol.hu 78 tálosi, gergó, and holló men (penetration grade 50/70) and polymer modified bitumen. 2. experimental the aim of our study was to examine the quality improvement opportunities of bitumen used in road construction (penetration grade 50/70). over the course of our experiments, the modifying effect of a biocomponent derived from pinewood-based fast pyrolysis biooil on the original bitumen 50/70 (b-series) was investigated. furthermore, experiments that applied the biocomponent together with the block copolymer styrene butadiene styrene (sbs) (p-series) were conducted. 2.1 samples the investigated feedstock was a commercially-available bitumen (producer: mol plc.) with penetration grade 50/70 (softening point: 51 ◦c; penetration: 56 0.1mm). the modifying agent for the polymer modified bitumen samples was the linear block copolymer styrene butadiene styrene (dst l 30-01, producer: voronezhsintezkauchuk ojsc) applied at a concentration of 4 w/w%. the styrene concentration of the copolymer was 30 w/w%. the applied biocomponent was derived from a commercial pyrolysis liquid of pinewood (producer: btg-btl, the netherlands [31], elemental analysis of the btg-btl product: c: 46 %, h: 7 %, o: 47 %; water content: 25 w/w%). before blending, the sample was stabilised. the water content was removed and the volatile organic components that are boiling up to 220 ◦c were removed with the water as well, to adjust the flash point of the additive by distillation. samples of the biocomponent were applied in concentrations of 1, 5, and 10 w/w%. table 1 shows the composition of the samples. 2.2 measurements in order to characterise our samples, conventional bitumen tests were conducted before and after aging. the softening point of the samples was determined according to the standard msz en 1427 using an automatic ringand-ball softening point tester (petrotest rka 5). penetration measurements were conducted according to the standard msz en 1426 using an automatic penetrometer (petrotest pnr 12). aging was simulated by the rolling thin-film oven test (rtfot) according to the standard msz en 12607-1. the change in the rheological properties was investigated by using an anton paar mcr 301 type dynamic shear rheometer (dsr). the linear viscoelastic range (lve range) of the samples was investigated by amplitude sweep analysis. during the measurements, the frequency was constant (10 s−1) and the amplitude varied. the amplitude sweep analysis was measured at 10 and 60 ◦c which resulted in the corresponding γ (deformation) values. the sweep frequency response analysis was table 1: composition of the samples name of the sample bitumen 50/70, w/w% sbs, w/w% biocomponent, w/w% bref 100 bbio01 99 1 bbio05 95 5 bbio10 90 10 pref 96 4 pbio01 95 4 1 pbio05 91 4 5 pbio10 86 4 10 also investigated at 10 and 60 ◦c, within the frequency range of 0.01− 100 hz. the multiple stress creep recovery (mscr) test was performed at 60 ◦c over 10 cycles according to the standard astm d7405. during the analysis, the samples were subjected to a loading force of 100 n for 1 sec which was then removed for 9 secs. after the 10th cycle, the loading force was changed to 3200 n and another 10 cycles measured. from the experimental values the percentage of the recovery could be calculated. the temperature-dependence of the rheological properties was investigated within the temperature range of 10− 70 ◦c, with a heating rate of 1 ◦c/min at a constant frequency of 1 hz. during the measurements, the values of the complex modulus, namely the stiffness and complex viscosity, were investigated. 3. results and analysis 3.1 basic properties as for the conventional properties, the softening points of the samples were increased by the biocomponent as well as sbs when compared to the original bitumen 50/70 (table 2). the increasing effect tendentiously escalated as the amount of applied biocomponent increased. in the case of applying two modifiers simultaneously (biocomponent and sbs polymer), synergistic effects were experienced. in accordance with the softening points, the penetration of the samples decreased by using every blending component, that is the samples became harder (table 2). the increased stiffness could be explained by the blending of the rigid biocomponent. from the results measured after rtfot, it can be stated that in the case of the sbs polymer modified bitumen (pmb) samples, the aging effect was less significant when compared to the sample of reference bitumen. moreover, in the case of the pmb samples, the biocomponent enhanced its resistance to hardening. every sample complied with the technical specifications for road construction currently in force in hungary (for bbio samples msz en 12591, for pbio samples msz en 14023). table 2 shows the conventional properties of the samples before and after aging. hungarian journal of industry and chemistry quality improvement of binders for road construction 79 table 2: basic properties of the samples and the requirements of the bitumen standards before and after rtfot. before rtfot after rtfot softening point, ◦c penetration, 0.1 mm change in mass, w/w% increase in softening point, ◦c retained penetration, % bref 51.0 56 −0.02 5.9 67.9 bbio01 51.1 54 0.006 2.1 75.9 bbio05 51.2 53 −0.30 3.9 77.4 bbio10 51.4 52 −0.50 4.7 71.1 msz en 12591 50/70 46− 54 50− 70 ≤ 0.50 ≤ 8.0 ≥ 55.0 pref 72.5 35 0.04 2.6 82.9 pbio01 74.1 32 0.01 3.6 96.9 pbio05 77.0 31 −0.01 3.1 93.5 pbio10 79.7 29 −0.02 3.2 100.0 msz en 14023 10/40-65 ≥ 65.0 10− 40 ≤ 0.30 ≤ 8.0 ≥ 50.0 25/55-65 ≥ 65.0 25− 55 ≤ 0.50 ≤ 8.0 ≥ 50.0 3.2 rheological properties the results of the amplitude sweep analysis are presented in fig. 1. the deformation values increased by applying the sbs polymer component at 10 ◦c, thus the lve ranges were widened. in every case, the blending of the biocomponent narrowed the lve range. the addition of the rigid component resulted in a stiffer structural material with a lower resistance to deformation. the extent of the decrease was significant in the case of the samples that were only modified with biocomponents. in the other cases, the decrease was less notable, the bituminous matrix could positively compensate for the narrowing effect of the biocomponent. as for the measurements conducted at 60 ◦c, the permanent deformation decreased in every case when compared to the reference sample, nevertheless, the value of the permanent deformation increased. in the case of the samples that were only modified with a biocomponent, the narrowing of the lve ranges was minimal when compared to the values measured at 10 ◦c. fig. 2 shows the results of the sweep frequency response analysis. at 10 ◦c and 60 ◦c, the values of the complex modulus were measured, presented and evaluated at frequencies of 25 hz and 30 hz, respectively. these conditions correlate with similar asphalt tests. at 10 ◦c, the complex modulus values, namely the stiffness, were preferably larger in the case of every modified composition when compared to the reference sample (bref). however, in the case of the samples modified with only a biocomponent, by adding the biocomponent, the stiffness decreased tendentiously. in view of the bbio10 sample (10 w/w%), the value of the complex modulus was almost identical to that of the reference sample. as for the pmb samples, similar behaviour was observed. by blending the biocomponent in small amounts (up to 5 w/w%), the complex modulus decreased, but in accordance with this effect the fatigue performance improved. the stiffness of the samples containing 10 w/w% of biocomponent (bbio10 and pbio10) were comparable to those of the corresponding reference samples (bref, pref), thus the stiffness of the asphalt mixture can be suitable as well. the results measured at 60 ◦c showed that the complex modulus positively increased by the blending in of the sbs polymer. in the case of the samples modified with only a biocomponent, the modifying effect of the blending component was negligible. as for the flexible behaviour, the results of the mscr test are presented in figs. 3 and 4. the loaded and relaxation periods are shown in the diagrams on the left-hand side, while the percentage of the elastic recovery at the end of the 1st and 10th cycles can be seen on the right. every diagram shows the results measured when a loading force of 3200 n was applied. in the case of the samples modified with only a biocomponent, the component applied in small concentrations (up to 5 w/w%) influenced the elastic recovery positively when a loading force of 100 n was applied. however, when applied at a concentration of 10 w/w%, the percentage of the elastic recovery decreased when compared to the reference sample, however, the value of the permanent deformation increased. when high loading forces (3200 n) were applied, the permanent deformation was adversely increased by the biocomponent. the elastic recovery of the samples was negligible, the elastic property practically ceased under the test conditions, their viscosity dominated. in the case of the pmb samples, when a loading force of 100 n was applied, the biocomponent influenced the flexible behaviour positively at every concentration. the permanent deformation decreased and, in line with this positive effect, the percentage of the elastic recovery increased. thus, the rutting performance of the samples was favourable. the higher the blending concentration of the biocomponent was, the more flexible the behaviour 47(2) pp. 77–83 (2019) 80 tálosi, gergó, and holló figure 1: lve range of the samples – a) 10◦c, b) 60◦c. figure 2: complex modulus of the samples – a) 10◦c, 25 hz frequency, b) 60◦c, 30 hz frequency. figure 3: the results of the mscr test of the samples modified with only a biocomponent when subjected to a loading force of 3200n. it exhibited. when high loading forces were applied, the tendency was the same. the favourable values of the pmb samples can be explained by a phenomenon in which the biocomponent did not influence the flexible properties of the pmb matrix, while it could mitigate the liability to deform as a result of its rigid structure. by comparing the values of every sample measured by the mscr test, the flexible behaviour of the pmb samples was significantly better than in the case of the reference bitumen sample. nowadays the modification of bitumen is strictly necessary in order to comply with the more rigid requirements enforced by the technical practices of road construction, namely that the binders have a sufficient degree of rutting performance. according to our measurements, the biocomponent by itself cannot provide a good solution to this problem, however, by blending it with sbs polymer the modifying effect of the biocomponent could be beneficial. the results of the temperature sweep analysis are presented in fig. 5. in the case of the samples that were only modified with the biocomponent, the values of the complex modulus decreased at lower concentrations (up to 5 w/w%), but by applying the biocomponent at 10 w/w%, the values of the complex modulus were almost identical to that of the reference sample (bref). as for the pmb samples, the stiffness increased in every case when compared to the bref sample. the value of the complex modulus increased by increasing hungarian journal of industry and chemistry quality improvement of binders for road construction 81 figure 4: the results of the mscr test of the samples modified with sbs polymer when subjected to a loading force of 3200n. the biocomponent concentration. during the temperature sweep analysis, the temperature dependence of the complex viscosity was measured as well. the tendency was very similar to that of the temperature dependence of the complex modulus. in particular, the complex viscosity significantly increased in the case of the pmb samples when compared to the reference sample (bref). by increasing the blending concentration of the biocomponent, the complex viscosity increased further. 4. conclusion the aim of this work was to investigate the quality improvement opportunities of bitumen used in road construction (penetration grade 50/70) and to provide a comfigure 5: temperature dependency of complex viscosity – a) samples modified only with biocomponent, b) pmb samples. parative analysis of the modifying effect of stabilised pinewood-based fast pyrolysis bio-oil on sbs polymer modified bitumen. according to our measurements, the biocomponent can be blended at a concentration of 10 w/w% with the tested bituminous binders. as for its flexible properties, the utilisation of the biocomponent by itself does not result in a good bitumen quality, but together with the sbs polymer the rutting performance improves significantly. based on these results, further 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(accessed: 11/06/2019) 47(2) pp. 77–83 (2019) https://www.scionresearch.com/__data/assets/pdf_file/0016/17701/nzjfs2321993ball236-242.pdf https://www.scionresearch.com/__data/assets/pdf_file/0016/17701/nzjfs2321993ball236-242.pdf https://www.scionresearch.com/__data/assets/pdf_file/0016/17701/nzjfs2321993ball236-242.pdf https://doi.org/10.1080/14680629.2007.9690084 https://doi.org/10.1080/14680629.2007.9690083 https://doi.org/10.1080/14680629.2007.9690083 https://doi.org/10.1016/j.jclepro.2016.11.100 https://doi.org/10.1016/j.jclepro.2016.11.100 https://www.btg-btl.com/en/applications/oilproperties https://www.btg-btl.com/en/applications/oilproperties introduction materials and methods cultivation of the bacteria analysis neural networking results and discussion conclusion introduction materials and methods cultivation of the bacteria the modelling of microbial growth measurement of cgtase activity results and discussion batch fermentation fed-batch fermentation semi-continuous fermentation comparison of the different fermentation techniques conclusion introduction experimental emulsification tendency fouling tendency neutron activation analysis compatibility results and discussion conclusion introduction materials and methods materials measurement of enzyme activity immobilization of laccase inside an alginate matrix characterization of the immobilized laccase effect of temperature on alginate beads storage stability of the beads reuse of the alginate beads determination of kinetic parameters with abts results and analysis characterization of the alginate beads determination of kinetic parameters effect of temperature on alginate beads storage stability of the beads reuse of the beads discussion conclusions introduction materials and methods the collection of samples sample preparation stripping of bitumen by leaching whilst being stirred stripping of bitumen by leaching in the absence of stirring panning of the tar-free sand determination of the specific gravity of tar-free sand shaking tabling particle size analysis using a sieving method reflected light microscopy thin section microscopy x-ray fluorescence spectroscopy results and discussion conclusions introduction discrete element method calculation of the normal and tangential displacement of particles calculation of the slip velocity calculation of the slide of particles calculation of the damping coefficient treatment of particle-wall collisions conditions of simulation geometric representation of the silo and rotary valve application of the gpu simulation results and discussion the startup process of silo discharge analysis of the mass outflow rate through the rotary valve flow patterns of the particles at different rotational speeds of the rotor conclusions introduction experimental work tracing and measurement technique modelling and simulation methodology results and analysis experiments possible flow structures and parameters generation of the simulation models local programming of the generated process structure evaluation of the rtd measurements discussion conclusions introduction applied modeling method: programmable process structures modelling and analysis of hydrogen supply chains by programmable process structures description of the example hsc process network meta-prototypes-based generation and analysis of the example model meta-prototypes-based functional prototypes of the example model generation and simulation of the example hsc system analysis of the simulated results discussion conclusion introduction experimental and the modelling process results and analysis conclusion introduction materials and methods results and discussion conclusions introduction experimental samples measurements results and analysis basic properties rheological properties conclusion hungarian journal of industrial chemistry veszprem vol. 29. pp. 155-160 (2001) application of life .. cycle assessment for a pharmaceutical product k. herner, j. redel, l. tamaska, sz. vizi and a. redby (department of environment engineering and chemical technology, university ofveszpn!m, egyetem st. 10., veszprem, h-8200, hungary) received: november 22, 2001 in this paper the object is a life-cycle assessment (lca) of a pharmaceutical product. the target of the analysis is to compare different packaging alternatives from environmental aspect. the product is an antidepressive produced by one of the leading hungarian pharmaceutical factories. in the market the product appears as injection and as a pill packaged in two different ways, in glass bottle and in blister (aluminium and plastic foils laminated together). these three systems: injection, glass and blister are compared in this paper using lca. keywords: pharmaceutical product, life-cycle assessment (lca), packaging alternatives introduction pharmaceutical products as well as other products have certain affects on the environment during their entire life-cycle. the life-cycle of a product means the steps from the excursion of the raw materials, the production, the usage of the product to the waste management. the affect depends on the raw material of the product, the technology, and the waste management as well as the function of the product. lca [6] is a method used for analysing the environmental effects connected to a given product and it gives an overview of the contribution to the environmental problems during the life-cycle stages of the product. it deals with data of the material and energy usage, the emissions and waste output, connecting them to the following environmental effects: • greenhouse effect • ozone depletion • acidification • eutrophizaton • heavy metal • carcinogenic • winter smog • summer smog • pesticide in this way the environmental performance of the ?roduct can be clarified so the priority for the improvements can be done. by using the method the differentiation between products, raw materials or energy sources is becoming possible by environmental aspect. thus lca is a tool of the cvntmuing environmental development and a tool for the environmental performance improvement of the product or firm [5]. environmental analysis method lca is an internationally accepted and applic:d environmental management tool for improving the environmental performance of a product or for comparing alternative products. the iso 1404049 (.t] · international standards contain the basic principles of the analysis but the method can differ as they are under development in several parts of the world. the method used for this analysis is the eco­ indicator 95 method, developed by preconsultants b.v. in the netherlands and an lca software called simapro 4.0 developed by the same firm. the principles of the method are explained by goedkoep et al. t 1996} {2}. the software uses the same method. eco-indicator 95, but it simplifies the calculations. the results are histograms and tables. the hist{lgrams "an give the following information: the relative contrihuti,m to the environmental effects of the materials and processes during the product life-cycle (characterint~t'n). which environmental effects are bigger (normah7.ationj. the relative importance of the effects tvaluj!f\lnl. beside~ 156 these~ the life-cycle stages of the product become comparable (indicator) [2]. the reliability of data is important for the analysis. a part of data is based on the software database while other data originate from the pharmaceutical firm ·[1]. data missing from both sources was developed by our own publications and handbooks mentioned in the references [7-10]. life-cycle stages of the product the first step is the production of the elementary substance and the production of the effective substance of it. then a part of the effective substance is granulated and pearled, the result is dragee, while injection is made from the other part of the effective substance. the next step of the technological process is packaging: injections in 2 ml glass ampoules, dragees in 15 g glass bottles with pe bottle caps and cotton-wool damper or pvc and aluminium blisters. life-cycle stages of the product continue through the distribution to the waste management. all the stages of the process involve material and energy input, emissions to water and air and waste output. waste treatment in this case means landfill or incineration. packaging processes dragee packaging a part of the pharmaceutical products are packed in 15 g glass bottles with written tickets and collected in loose cards. the following materials are used for dragee packaging: • pill • glass material • cotton~wool • paper products (tickets~ loose-cards, consignment note) • others (pe bottle-cap, adhesive tape) blistering the other part of the pius packed in blister~ which is a cut and signed pvc-aluminium packaging form. materials used for the packaging: • pm • primary packaging materials: pvc, pvcipvdc foil~ aluminium fod • secondary packaging materials: tickets. boxes, loose-cards. • packaging with complement information: consignment note. tickets. • auxiliary materials: paints, reducer, pe tape for bundle (60 mm wide, 40-50 j.un thick pe foil), sticking tickets (50 mm in diameter), plastic adhesive tape. blister is made of pvc and pvc/pvdc foil and printed aluminium foil closed with welding. packaging of injection: the 5 pieces of 2 ml injections are placed in one hard, covered, white pvc foil. two of these pvc foils are placed in one loose-card provided with a consignment note. this means there are 10 injections of 2 ml in one package. distribution pharmaceutical end-products are going to the next step of the distribution chain: from the factory to the wholesalers and from these through the pharmacies and hospitals to the consumers. waste management it was assumed that the packaging of the pharmaceutical product becomes waste at the consumer and treated as household waste. as household waste most of it is deposited in landfills. waste generated through the processing is incinerated as industrial waste. life-cycle assessment for the pharmaceutical product analysis is made for the following steps of the products life-cycle: • elementary substance • effective substance • production and packaging of the injection • production and packaging in glass bottles of the dragee • production and packaging of the dragee in blisters since the object of this analysis does not extend to the effects of the elementary and effective substances and to the changes of these effects, and since these effects are included in the analysis of packaging forms, this paper only deals with the analysis of the three packaging forms. for the analysis, simapro 4.0 software was used, the results are presented in histograms below [2]. there are four types of histograms. showing the different aspects of the environmental loads connected to the materials and processes of the life-cycle steps [3]. characterization: the histogram shows the contribution of the technological steps to each environmental problem in percentages. energy oolid bjisiorchkompotatoeo bjgiooo"' tzllaclo>o m>~oorin []tole (sig<>i<gl 181drogoepockogi1g bjdrogeec""'< fliamitr~hydochlakie ijieieclrir:ifyhllllg"jj ·~-,p~·;o;~~·id;u;;;rs~j:ot~.;;"re·'i·e;,;;;g:r;~~;··-~· · fig. i evaluation histogram for dragee production normalisation: the absolute volume of the environmental problems connected to the product. evaluation: it shows the relative importance of the environmental problems caused by the life-cycle steps of the product expressed in ecoindicator points (pt), which show the contribution of the process or material to the environmental problems. the higher point means bigger environmental load. the most significant environmental loads and technological steps are signed by this histogram. indicator: it summarizes the environmental loads of each technological process stages to make them comparable. in this way it assigns the life-cycle step of the product with the most significant environmental load. results dragee form packaged in glass bottles environmental effects of the dragee production are connected to the production of the effective substance and the packaging. the effects of the production are significant for all the environmental problems except the ozone and heavy metals, in which case the effects of the packaging (the glass production) are more significant. other life-cycle steps as effective substance production, dragee cover and electricity generation hungary (electricity hungary) have significantly lower effects. by the evaluation, the highest value can be found at the environmental problem of heavy metals with 2.01 ecopoint. this is partly caused by the glass production connected to the dragee packaging. glass production can cause pb, ba, cr, ni, as, cd, hg, cu emission to air and water. a heavy metal, mercury also originates from the production of hydrochloride acid used for the effective substance. besides these, the electricity generation, the production of the effective substance, the transportation and the usage of tioz for the covering involve heavy metal emission. acidification is the next environmental problem occurring through the life-cycle of the product with 1.76 ecopoints. acidification is the result of the elementary substance production, the packaging in 30% and the covering in 8%. it is caused by the s02 emission from pt <!..,it go(.m orpoc<ago!g bl<><one 0ocidrf. cjeutrqlll 181w."""'j blu/1109 flipoohcd 157 d~ ~ l~.~ []ln-. !jlonorll' fig2 indicator histogram for dragee production gr...;,. ozono ilcd "'*"ph h."'""" ..,.;., wtm09 •-.1 ar.o~q~ bjistorr.hfn>nbjgilcooo 0ltc!];t'*' !s!g<>i<gl ~drogocbklol bjot-cc.« fli~~::ce~t~"9i'' ·~·t~~n7~[i;biot~f;i.4~s·~~ioe~·$; e_.;~91ov......., fig.3 evaluation histogram for dragee blister the covering and the effective substance. the no,. emission from the dragee packaging, the nhj emission of the elementary emission, and the hci emtssh •il from the effective substance. other problems have smaller ecopoints but the elementary production is the main cause in these, roo. besides these, the c02 and the methane emission from the dragee packaging play a role in the greenhouse effect and the dust by the covering have an influence on the winter smog. by comparing the environmental problems connected to the life-cycle stages of the dragee production the result is that the packaging has . the greatest environmental contribution with 2.74 ecopomts. this is mostly due to the heavy metal emission of the glass production mentioned . befor:. the . next is .the effective substance productmn w1th 2.61 ecopomts caused by acidification. environmental effects caused by the dragee covering are the acidification and dust from the transportation and have 0.267 ecopoints. elementary sustances do not have significant effects because the analysis only counted data of transportation. data on production of elementary substances is missing. dragee form packaged in blis:~·~. the histogram fig.3 differs from the gla!oi~ fprm~ r·ig.l in the following aspects: the results of the pa.:.,.agmg are 158 sto<eh .... g~ -" ~ kl~ g,_., tz]acidil, lsi""""11llwtmo~~ cum:'ll cd"** ..w;;;1j;~'i),~'ti;boiio.r:m..in<i¢si.'i.a~iiif~!ilf..w;g:;~ fig.4 indicator histogram for dragee blister more significant in all environmental problems, but mostly the ozone, carcinogenic effect and the summer smog. the histogram shows that the biggest environmental problem is the carcinogenic with 2.42 ecopoint, caused by the packaging in blisters. ·poliaromatic-hidrocarbons occur in the aluminium foil production and cause carcinogenic problems. the next more important environmental effect is acidification with 2.1 ecopoint, caused by nox and s02 emissions occur in plastics production. besides the effect of the packaging, the production of elementary substance also generates acidification. at the covering the s02 emission occurs at the transportation causing acidification. greenhouse effect has 0.726 ecopoint. the contribution of the effective substance production is 60% while 30% proceeds from packaging. in both cases the greenhouse gases cause the problem emitted by the energy generation. summer and winter smog are caused by the production of effective substance. heavy metals such as pb. ni~ cr, ba, as are emitted by the aluminium foil production used for blister packaging. as the histogram shows, among the life-cycle stages the packaging, the blister production has the most significant contribution to the environmental problems. it has 4.07 ecopoints, 30% of it is carcinogenic effect caused by the poliaromatic-hydrocarbons and ni emission of the aluminium production. acidification and ozone depletion are also important effects, caused by the poliaromatic-hydrocarbons and the sol. after the packaging~ the production of the eftective substance has important effects, mainly in the acidification. dragee covering has lower influence~ but it contributes to the acidification and winter smog caused by the transportation and production. elementary substance has very jow effects on the histogram because only the effects of the transportation were counted as mentioned before. life-cycle assessmem for the injection form: the other form of the pharmaceutical product is injection packed in 2 ml colourless ampoules. this form is mostly used in hospitals and surgeries. assessed !lllgeeon !:lozano lsi""""~w.jrno!i ,j]j"'"'!,. ,,,, .. ,, _____ ,_, ..... ,~---, ...... , ......... , .. --·· ---··----·,, .. ,,,, , __ , _______ ,_,,, .... ,., ..... , ... , ...... ,.,,,, ... , ... . anoiy<ol p~lriooboo': m-simaf'lo:ioe-95/ eu"opeg/in<icalo< fig.5 indicator histogram for injection production injection form contains the same amount, 50 mg effective substance, as the dragee form to make them comparable. summarising the environmental effects connected to the injection form, in the following the indicator histogram shows that packaging has bigger influence on environmental effects. injection packaging has 6.36 ecopoints, the heavy metal contribution to it is 80%, caused by the heavy metal emission of the glass production. environmental load connected to the generation and usage of energy is equal to 2.58 ecopoints, two thirds of it is caused by acidification and carcinogenic effects. carcinogenic are benzene, benzpyrene, poliaromatic-hydrocarbons, chrome and nickel. these occur from the energy generation. gas burning causes the third part of the emitted benzpyren and poliaromatic-hydrocarbons. effective substance production also has an influence (2.61 pt) on the acidification, greenhouse effect, summer and winter smog. heat diesel used for disinfecting has low influence on environmental effects. elementary substance2 also has very low influence because the program only counted the data of the transportation. there are no data on the production of these substances. the contribution of the generation and usage of energy and heat energy are significant. electricity has a contribution to winter smog and carcinogenic effect in 50%. comparison of the three packaging forms by their indicator histograms with the same effective substance containment (lp) the potential environmental load of the different forms become comparable. the histogram fig.6 shows the scale of the packaging forms from environmental aspect. the most significant environmental load is connected to the injection form. it should be noticed that the function of the injection form is not the same as the dragee form, so they can not be compared as alternatives. injection form is needed in hospitals and surgeries and can not be discharged with the dragee form. b<!_...n. g_,. 0<ridil. g;jeurop~t []nrn«o~o is!cdfcin li!ilw.>n>~jg g~~pm!icid !jl'"""w []ooi:i -~~-,;;;p:c~~s~aiie~·iirfu;;p;ii/~----·--·--··-·--·-·--·····-··--·-··--·---··-· ·· fig.6 indicator histograms of dragee in glass, dragee blister and injection forms. between the two packaging alternatives for the dragee form the glass packaging seems to be better from environmental aspect, the differences is almost 20%. this alternative is better in the following environmental problems: carcinogenic, ozone depletion, acidification, while it is worth in heavy metals as the blister packaging. summarising the dragee form packed in glass is the best solution from environmental aspect. the injection form of the pharmaceutical product has the biggest effect on the environment, but its function is differs so it cannot be changed. conclusions by the assessment of the product life-cycle we got a view on the potential environmental load. the most important environmental problems, which occur through the entire life-cycle of the pharmaceutical product are acidification, carcinogenic and heavy metals. the acidification is mainly caused by the elementary substance production, and extracting solvents in it. through the effective substance production the contribution of the organic acids is important. besides these, the s02 and nox emissions from the pvc plastic production also generate acidification. this occurs at the dragee blister form of the pharmaceutical product. in addition, at dragee covering s02, at dragee packaging nox and at the elementary substance! ammonium is emitted. carcinogenic effect is mainly caused by the poliaromatic-hydrocarbons and nickel emitted by aluminium foil production used for the dragee blister. besides these the contribution of the emissions occurred at the energy generation and the diesel oil used for transportation at the elementary substance production is significant. by the dragee production the acid extraction and the diesel oil usage is responsible for the carcinogenic effect. carcinogen effects by the injection form are caused by the benzene, benzpyrene, poliaromatic-hidrocarbons, chrome and nickel occurred at the energy generation and the poliaromatic~ hidrocarbons and benzpyrene generated at the gas burning. 159 heavy metal emissions of the pharmaceutical products are caused by the glas<) production, needed at the injection and dragee glass packaging forms. during the glass production the next heavy metals can occur and are emitted to air or water: pb, ba, cr, ni, as cd, hg, cu. besides these the antimonies, arsenic, cadmium and barium emission also cause heavy metal effect, which occurs in the fly ash originated from the energy generation. some of the elementary substances also have a contribution to the heavy metal problem because of the energy generation. mercury emission occurs at mercury-pool cathode acid production used in the elementary and effective substance production. pb, ni, cr, ba, as emission can occur during the aluminium production for dragee blister packaging form. dragee covering also has a contribution to these effects. the previous shows that the main part of the potential environmental effects are originated from the packaging, so the conclusion is that it is worth paying attention to the alternative solutions and choose the right and most environmentally friendly one. this harmonizes the interests of the pharmaceutical factory, the interests of the environment and the interests of the environmentally conscious customers in order to satisfy the environmental demands which are an important part of the competitive position. figure 6, which compares the packaging alternatives with the same effective containment, shows that the dragee form packed in glass bottle is the best from environmental aspect. the next is the dragee blister form and the injection form seemed w have the mnq environmental loads. inspite of these fa~ts the injectw1~ form is needed in hospitals and surgerie~. finally, the result of the analysis is that besides the effects of the packaging, the production of the pharmaceutical product causes the most potential environmental effects. the reduction of the environmental load connected to the product <:<m h~ probable and effective in these two stages of the lite~ cycle. by choosing the right packaging alternative some of the environmental effects connected to the product can be reduced or avoided. the analysis also reflects the ••weak" points of the production, in which cleaner production changes can be used to improve the environmental performance of the analysed product. references 1. redel l: lca for the pharmaceutical product mst.~ thesis. veszprem. 2000 2. goedkoop m., demmers m. and cou.jgno!'i m.: the eco~indicator 95, preconsultam. 1996 3. herner k.: usage of life~cydc asses~mern in hungary through a case shl~i ~ ms<.' thcsi:-~. veszprem, 1999 4. iso 14040. environmental manjgement ·ufe~ cycle assessment principles and lrame\\'otk, !he international organization fnr standardilatton. 1997 160 5. vizi sz.~ tamaska l. and herner k.: using life­ cycle assessment~ 6th roundtable on cleaner production, budapest, hungary, 1999 6. jensen~ elkington, chrustiansen, hoffmann, moller, schmidt and dijk: final report, life cycle assessment, report to the european environmental agency, copenhagen, denmark, 1997 7. hommel g.: dangerous materials, budapest, 1977 8. medicine codex '92 9. dr. kedvessy gy.: medicine technology, budapest, 1981 10. gerhar'iz, elvers, ravenscraft, rounsaville and schul'iz: ullman's encyclopedia of industrial chemistry page 154 page 155 page 156 page 157 page 158 page 159 hungarian journal of industry and chemistry vol. 49(1) pp. 1–8 (2021) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2021-01 the experimental verification of a generalized model of equivalent circuits zoltán lukács*1, dávid baccilieri1, and tamás kristóf1 1center for natural sciences, university of pannonia, egyetem u. 10, 8200 veszprém, hungary the determination of typical parameters of electrochemical systems, e.g. the polarization or charge transfer resistances, can be critical with regard to the application of electrochemical impedance spectroscopy (eis) if the lower frequency range is biased as a result of transport and/or adsorption/desorption processes. in such cases, the charge transfer resistance should be assessed from the higher frequency range which is typically inadequate in itself as an input for nonlinear parameter fitting. in earlier publications, an alternative mathematical treatment of both the equivalent circuit (ec) and of the parameter dispersion was provided using a generalized model of ecs and also a dispersion-invariant model of the electrochemical interface. in the present work, the previously presented experimental eis results were crosschecked to verify the performance of the generalized model against a series of redox and corrosion systems. the results proved that the applied method is consistent and provides a fairly good correlation between the principal resistance data assessed by different methods. keywords: electrochemical impedance spectroscopy, parameter dispersion, linearized model, equivalent circuit, polarization resistance 1. introduction electrochemical impedance spectroscopy (eis) is used to study systems in many electrochemical fields, e.g., electrode kinetics, the testing of bilayer systems, batteries, galvanic cells, corrosion, solid-state electrochemical processes, bioelectrochemistry, photovoltaic systems etc. in eis, the studied system is perturbed from its equilibrium (or stationary) state by a small-amplitude sinusoidal potential signal. for this ac potential signal, it is assumed that the transfer function of the electrochemical kinetic system can be represented by a so-called equivalent circuit (ec). the simplest circuit of this kind is the voigt circuit, a parallel rc circuit, complete with a resistor representing the pure ohmic† solution resistance, which approximates the transfer function of the electrochemical system well in many cases‡ (see fig. 1a). the transfer function of model a in figure 1 is given by z (ω) = rs + rct 1 + iωτ , (1) where i denotes the imaginary unit, ω stands for the angular frequency and τ = rctcdl represents the time constant of the rc circuit. eq. 1 describes an ideal theoretical *correspondence: lukacs.zoltan@mk.uni-pannon.hu †pure ohmic in the electrochemically relevant frequency range. ‡in this section, the effects of the transport and adsorption/desorption steps are not considered. they are mentioned in sufficient detail in the section where the experimental results are discussed. model and the eis curves plotted from it yield a perfect semicircle on the so-called nyquist diagram. the value of the ohmic solution resistance (rs) is determined from the high-frequency data (∼ 10 khz −1 khz). if diffusion, adsorption or other processes do not influence the curve, then the sum of the solution and charge transfer resistances can be determined from the low-frequency data. in contrast with the theoretical expectations, in practice, the impedance spectroscopy diagrams measured have always been slightly flattened (‘depressed semicircles’). this depression can be modelled phenomenologically by using a power of less than 1 in the frequency-dependent term of eq. 1: z (ω) = rs + rct 1 + (iωτ) 1−β , (2) where 0 < β � 1 denotes the constant phase coefficient and the resulting element with the fractional power in eq. 2 is referred to in the literature as a constant phase element. as the fractional power expression results in a constant phase impedance at high frequencies, this phenomenon is commonly referred to as the constant phase element (cpe). research into the cpe and related phenomena dates back many decades. cole and cole [1, 2] investigated the capacitance of solid and liquid dielectrics as well as interpreted the appearance of the cpe as dependent on the frequency of the dielectric constant. the application of ac methods and eis in particular to a wide range of electrohttps://doi.org/10.33927/hjic-2021-01 mailto:lukacs.zoltan@mk.uni-pannon.hu 2 lukács, baccilieri, and kristóf figure 1: equivalent circuits corresponding to models ad and frequently applied in the relevant literature (see further comments in the text). chemical systems has become quite common in electrochemical kinetics [3–8], electrode surface structure investigations [9–14], corrosion studies [15–21], battery and fuel cell development [22–26], membrane studies [27,28] and many other fields in electrochemistry. the cpe appears in all the cited works and can be regarded with a high degree of certainty as an inherent characteristic of electrochemical systems. however, the origin and evaluation of the cpe has remained a controversial issue. most works on the topics agree that the cpe can be interpreted as a consequence of the distribution of the time constant of rc circuits representing the characteristics with regard to the capacitance and conductivity of the electrochemical interface. cole [1] assumes a lognormal distribution of the relaxation time constants. a similar distribution function is proposed by brug [3]. in subsequent works, the appearance of the cpe is frequently interpreted by means of equivalent circuits that include many rc elements in parallel or series. (implicitly, the distribution functions can also be recurred to such equivalent circuits.) the applicable equivalent circuits can be roughly divided into two categories. some fall into the category of the so-called ‘3d’ (three-dimensional) dispersion models which correspond to the structures perpendicular to the surface, contributing to the conventional equivalent circuit with a series of additional parallel rc circuits [14, 15], as shown in model b in fig. 1. the 3d model (or its derivatives, see below) has been successfully applied in the description of passive films and coatings [29–31]. the so-called 2d dispersion models [3, 14] are intended to describe the distribution of the eis parameters in two dimensions on the electrode surface. this dispersion can be attributed to the heterogeneity of the surface and the resulting deviations of the (intensive) kinetic parameters, i.e., the time constants. discussions concerning the 2d dispersion can lead, however, to an unexpected conclusion if this is consequently carried out. the 2d dispersion model, i.e., the dispersion of the time constants of the rc circuits, representing the kinetic parameters of the individual active reaction sites connected in parallel to each other, as shown in model c in fig. 1, will degenerate to model a. in order to avoid this, the effect of the solution resistance is taken into account to re-establish the ability of conventional ec patterns to interpret cpe behaviour (‘while an ohmic resistance in physical systems cannot be avoided, the example illustrated in fig. 1b illustrates the crucial role played by the ohmic resistance in cpe behavior associated with surface distributions.’ [14]). however, there are at least three very important reasons to have serious reservations with regard to this concept. firstly, pajkossy has shown [10] that ‘capacitance dispersion due to irregular geometry appears at much higher frequencies than is usual in electrochemical methodologies’ which means that the irregular geometry, which acts on the eis impedance function through the variation in the (local) solution resistance, cannot be the reason for the dispersion in the generally applied and electrochemically relevant frequency range. secondly, in highly conductive solutions and/or with high-resistance (i.e., slow) electrochemical reactions, the contribution of the solution resistance to the overall impedance can be negligible compared to that of the charge transfer resistance, especially at lower frequencies. thirdly, strictly speaking, the solution resistance is not an inherent part of the impedance of the electrochemical impedance system. by moving the tip of the luggin capillary closer or farther away, the value of the measured solution resistance can be varied significantly, therefore, any calculations using it in the modelling or evaluation of the kinetic process are debatable. in conclusion, models c and d in fig. 1 are not applicable in the interpretation of the cpe phenomenon. consequently, by proceeding forwards on this path, it follows that model a in fig. 1 is not and cannot be the ultimate model (transfer function) of the electrochemical interface. the ultimate model is something more complex, which can, in certain cases, be simplified to model a as far as the accuracy of measured data is concerned. in an earlier paper [32], this issue was already discussed in brief (see fig. 3 and the relevant text in the cited paper). this contradiction was realized in the relevant literature decades ago. in a noteworthy work, agarwal et al. [33] approximated a number of ecs to model b which obviously does not match the physical content of the approximated ecs, however, the fitted curves match the experimental ones very well. these results are also confirmed from another point of view. it has been proven [34, 35] that some ecs, exhibiting quite different elements and connection patterns, have the same transfer function. these findings also show that the concept of the ‘equivalent circuit’ is by no means as solid nor unambiguous as it would seem to be at first sight. after all, the question what is the minimum statement that can be both relevant and unambiguous concerning the eis equivalent circuit and parameter determination in general is raised. a possible answer to this question was presented in two recent publications [36, 37]. it was assumed that model a in fig. 1 is approximately correct and deviahungarian journal of industry and chemistry the experimental verification of a generalized model of equivalent circuits 3 figure 2: model e by applying the general scheme and model f with the series of maxwell circuits connected in parallel. tions from it are due to the parameter dispersions and/or mechanistic effects, moreover, all these effects can be fitted using a properly chosen series of ec elements. after due consideration, the model of a voigt circuit (equivalent to model a) and a series of maxwell circuits connected in parallel was chosen (see fig. 2, model f). model f has some important features which have practical advantages; the part of the ec corresponding to model a, representing the ‘ideal’ behaviour of the interface, is separated parallel from the rest of the ec. this arrangement results in a linear separation in the compensated admittance: yc = ypr + iωcpr + k∑ k=1 iωcd,k 1 + iωτd,k (3) where ypr = 1/rpr and cpr denote the principal admittance and capacitance, respectively, cd,k represents the capacitance and τd,k stands for the time constant of the kth maxwell circuit connected in parallel. the physical interpretation, performance and limitations of the principal parameters as well as the linearization in general are discussed in detail in previous papers [36, 37]. in ref. [36], an equation to determine the principal admittance was published by our group (x = ω2): ∂ lnx ∂ lny ′c = ypr ∂ lnx ∂y ′c + 1 (4) the principal admittance which is, under certain conditions, equivalent to the reciprocal of the charge transfer or polarisation resistance, can be determined from a relatively narrow frequency range approximate to or higher than the critical frequency§. this is a serious advantage to any nonlinear model fitting which requires impedance data from a wider and, in particular, a lower frequency range (i.e., lower than the critical frequency) where the adsorption/desorption or transport (diffusion) processes may have a stronger impact on the measured impedance data. in a previous paper [36], eq. 4 was tested in an §critical frequency is understood as the frequency value where the imaginary part of the impedance has a (local) extremum at the ‘top’ of the ‘depressed semicircle.’ the accurate value of the critical frequency can be calculated via a quadratic fitting of the nearest points. in some eis spectra, such an extremum cannot be established. experimental system (quinhydrone redox system in 10% hcl) and, in a more recent paper [37], other methods developed to determine the principal admittance were tested in the quinhydrone as well as three other systems, namely fe, cu and cor (see their descriptions in the experimental section below). in this paper, the testing of eq. 4 against the latter three systems is presented and discussed. 2. experimental in order to gain a comprehensive overview concerning the performance of the proposed new parameter evaluation method based on eq. 4, three test systems were created (the short names, used for identification in the paper, are in brackets): fe3+/fe2+ redox system (fe): metallic iron was dissolved in 10% m/v hcl at a concentration of 8 · 10−4 mol/dm3 and fecl3 • 6h2o was added to set the same concentration of 8× 10−4 mol/dm3 for fecl3. solutions were diluted using 10% hcl to the concentrations indicated in table 1. the working, reference and counter electrodes were all composed of platinum for this system. the working electrode was a platinum plate with a surface area of 2 cm2, the reference electrode was a larger platinum sheet with a surface area of 5 cm2 and the counter electrode was a platinum net with an approximate surface area of 20 cm2. the potential of the platinum reference electrode was measured before and after the eis measurements against a saturated ag/agcl electrode to check if the redox potential of the system was reasonably close to the expected, calculated values. cu2+/cu non-corrosive copper/copper ion system (cu): the cuso4 concentrations and the supporting electrolyte are included in table 1. the working electrode was a cylindrical copper electrode 30 mm in length and with a diameter of 6 mm in a teflon holder, while the geometric surface area of the electrode was 5.94 cm2. the reference electrode was composed of copper with the same dimensions and the counter electrode was a copper sheet with a surface area of approximately 20 cm2. in the corrosive systems (cor), the working electrode was a din st 52-type cylindrical steel electrode 30 mm in length and with a diameter of 6 mm in a teflon holder, while the geometric surface area of the electrode was 5.94 cm2. the saturated ag/agcl electrode was used as the reference electrode and a platinum net with an approximate surface area of 20 cm2 as a counter electrode. the electrolyte compositions are shown in table 1. all the working electrodes were degreased in acetone. the platinum electrodes were kept in a 10% hcl solution for at least 3 hours before the experiment. the copper and steel electrodes were polished with #400, #600 and finally #1000 emery paper, while the copper electrodes were etched in a solution of 20% hno3 for 5 minutes. the steel electrodes used for the corrosion experiments 49(1) pp. 1–8 (2021) 4 lukács, baccilieri, and kristóf table 1: summary of the parameters and identifiers of the systems and series. system series electrode electrolyte abbreviation short description id definition fe fe(ii)/fe(iii) redox 1e-4 fe(ii), fe(iii) concentration, m platinum 10% hcl 2e-4 4e-4 8e-4 cu cu/cu(ii) reversible metal 1e-4 cu(ii) concentration, m cu 1m h2so4 2e-4 4e-4 8e-4 cor corrosion system cor1 n/a st-52 steel 5% nacl + 0.5% hac* cor2 5% nacl + 0.1% hcl cor3 1% hcl cor4 10% hcl *acetic acid (system cor) were pre-treated in a 10% hcl solution for 5 minutes before being placed in the cell. all the experiments were carried out in a conventional three-electrode electrochemical cell with a volume of approximately 700 cm3. the experiments were conducted at room temperature and the solutions were not deaerated. all eis spectra were measured twice and both runs were evaluated. in all three systems (fe, cu and cor), the electrodes were prepared before the first run and only the electrolytes were replaced for the purpose of measuring the subsequent runs. the parameters and identifiers (used to denote the measurement systems and runs in the discussion of the results) are shown in table 1. consecutive runs using the same solution composition are denoted with a -1 or -2 suffix at the end of the ids, e.g., 1e-4-1 and 1e-4-2 for the fe3+ and fe2+ concentrations in the fe system, respectively, namely 10−4 mol/dm3 (m). the eis spectra were measured with a metrohm autolab pgstat 302n-type potentiostat using nova 1.11 software. the amplitude of the applied potential signal was 10 mv (i.e., 20 mv p-p). all spectra were taken within the 10 khz −100 mhz range and 20 frequency points were measured per decade over a logarithmically equidistant distribution. in all the experiments, two spectra were measured in order to assess the rate of impedance drifts over time. the linear fittings were generally very good which involved a high count of 9s in the correlation coefficient. in order to avoid the cumbersome counting of the digits, the precision factor pr was introduced according to pr = − lg ( 1−r2 ) , (5) wherer2 denotes the square of the correlation coefficient (e.g., if r2 = 0.999, then pr = 3). 3. results and discussion the nyquist diagrams of the fe, cu and cor systems are shown in figs. 3-5, respectively. the corresponding bode plots are available in ref. [37]. the three systems exhibit quite different characteristics with regard to how well they fit to the conventional ec parameters and nonlinear least squares methods. the fe system could be fitted with a randles circuit including a cpe instead of a double layer capacitance if the diffusion-controlled lowfrequency range was longer and consequently better separated. this fitting procedure was tried but yielded uncertain results with high parameter errors and strong correlations in the hessian matrix. in general, the analytic methods do not yield good results if the measurement data do not have ranges where they are mainly sensitive to one parameter only. the measurements below 100 mhz last for quite a lengthy period of time and during this time range, the nonstationarity (‘time drift’) can produce a significant degree of bias with regard to the measurement data which should be avoided. the cu system is a bit worse because the low-frequency range data cannot be interpreted in terms of the conventional ec parameters at all. the cor system is, however, quite different since it can be fitted with a conventional cpe and charge transfer resistance. the common feature in all three systems is a relatively regular and similar arc in the frequency range higher than the critical frequency (i.e., the frequency where the imaginary part of the impedance has a maximum – this is somewhat unclear in the case of the cu system but the regular behaviour exhibited in the highfrequency range is clearly visible). the similarities in and regularities of the higher-frequency range impedance data would suggest that only this range should be used to determine both the double layer capacitance, which is inherhungarian journal of industry and chemistry the experimental verification of a generalized model of equivalent circuits 5 figure 3: nyquist plots of the fe system. figure 4: nyquist plots of the cu system. ently related to the high frequency range, and the charge transfer resistance, which is, in contrast, related to the lower frequency data range. this circumstance requires a more sophisticated approach, which has been outlined in ref. [36] and is applied in this paper, for the three systems discussed. based upon the aforementioned considerations, the importance of developing methods that can determine the charge transfer resistance from the higher frequency data alone is indisputable. the testing of eq. 4 with the discussed experimental systems is shown in figs. 6 to 8. the data points are obtained by calculating the gradient ypr according to eq. 4 using the two adjacent points (method (i)) and by fitting the gradients of the lines to 5 points of both greater and smaller frequencies at each frequency (method (ii) in ref. [36]). therefore, the lines are formed figure 5: nyquist plots of the cor system. by effectively averaging out the points. the curves are strongly dependent on the frequency and, in this case, selecting the most appropriate value to characterize the charge transfer resistance of the system is always an issue. the optimal value of the principal admittance was selected on the basis of the linear-fitting correlation data, moreover, the data set providing the highest correlation coefficient was accepted as the ‘real’ value. the pr maxima at very high frequencies were not taken into account (see fig. 6). by comparing figs. 3-5 with figs. 6-8, it can be concluded that the more regular (depressed) semicircles are formed in the nyquist diagram, the more established principal admittance data can be obtained from eq. 4. however, if regular semicircles are formed by a system, then the practical usefulness of the proposed evaluation is strongly limited because in such cases, conventional evaluation methods can generally be applied. this is the case with the cor system. the application of the method is necessitated in systems like that of fe and cu where conventional nonlinear fitting methods or any other simple methods (e.g. the graphical determination of rct [36,37]) cannot be used at all or with only a very limited degree of precision. in order to also test the versatility of the method in such systems, the principal admittance values determined via method (ii) were compared to those calculated by eq. 13 in ref. [37]¶ for the three systems investigated in this paper and also for the quinhydrone (qh) system published in the previous paper [36] on the subject, the results of which are presented in fig. 9. according to the results, a fairly good correlation coefficient is obtained which indicates that both methods, namely method (ii) and eq. 13, calculate the same phys¶the derivation leading to eq. 13 (in ref. [37]) is also based on eq. 3 (in this paper) but includes specific mathematical transformations based on the elimination of the dispersion parameters from the respective equations. 49(1) pp. 1–8 (2021) 6 lukács, baccilieri, and kristóf figure 6: principal admittance of the fe system calculated by eq. 4 using method (i) (points) and method (ii) (dotted lines). solid lines indicate the pr values obtained using method (ii). figure 7: principal admittance of the cu system calculated by eq. 4 using method (i) (points) and method (ii) (dotted lines). solid lines indicate the pr values obtained using method(ii). figure 8: principal admittance of the cor system calculated by eq. 4 using method (i) (points) and method (ii) (dotted lines). solid lines indicate the pr values obtained using method(ii). figure 9: correlation between the logarithms of the principal admittance obtained by method(ii) using eqs. 4 and 13 in ref. [37]. the linear fit was calculated from the logarithms of the principal admittance data. the qh (quinhydrone) data were taken from ref. [36]. ical quantity. the data in fig. 9 prove that both methods are applicable for the determination of the principal admittance. the question that is typically raised in similar situations is which method is better. in our opinion, it is still too early to make such a judgement given that in ref. [37] several additional equations were also published to calculate the principal admittance. some of these equations differ in terms of their initial physical considerations (compare eq. 4 in this paper and eq. 13) in ref. [37]], while others differ only as far as the weighting of data points is concerned (compare eq. 8 with 8a or eq. 13 with eq. 14 in ref. [37]). it is recommended that these methods should be applied especially in those cases when the impedance data in the low-frequency range (typically below the critical frequency) are not interpretable or cannot be fitted for some reason (e.g., the applicable ec cannot be assessed unambiguously). in such cases, by applying two or more of the proposed equations, the uncertainty in this determination can be decreased by only utilizing parameters, which are sufficiently close to one another. 4. conclusions a recent method developed to determine the principal admittance was tested on electrochemical redox and corrosion systems in order to check and compare the performances of the methods. the characteristics of the impedance with regard to such electrochemical systems exhibited features which often make conventional nonlinear fitting methods unusable or at least inaccurate. the new method was applied to determine the principal admittance from the impedance data obtained in the higher frequency range which exhibit a more regular shape but hungarian journal of industry and chemistry the experimental verification of a generalized model of equivalent circuits 7 are not applicable to conventional fitting methods alone. by comparing this new method with another also newly developed method (eq. 13 in ref. 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hancsók, j.; kristóf, t.: a dispersion-invariant model of the electrochemical impedance, electrochim. acta, 2021, 390, 138828 doi: 10.1016/j.electacta.2021.138828 hungarian journal of industry and chemistry https://doi.org/10.1149/1.1391759 https://doi.org/10.1149/1.1391759 https://doi.org/10.1016/s0378-7753(00)00576-0 https://doi.org/10.1016/s0378-7753(00)00576-0 https://doi.org/10.1021/jp1088788 https://doi.org/10.1016/j.electacta.2011.02.119 https://doi.org/10.1016/j.jpowsour.2013.04.011 https://doi.org/10.1016/j.jpowsour.2013.04.011 https://doi.org/10.1016/j.ssi.2013.07.010 https://doi.org/10.1016/j.energy.2015.12.058 https://doi.org/10.1016/j.energy.2015.12.058 https://doi.org/10.1016/j.porgcoat.2021.106387 https://doi.org/10.1016/j.porgcoat.2021.106387 https://doi.org/10.1016/j.porgcoat.2021.106155 https://doi.org/10.1016/j.porgcoat.2021.106155 https://doi.org/10.1016/j.electacta.2005.12.047 https://doi.org/10.1016/j.electacta.2005.12.047 https://doi.org/10.1016/s0022-0728(98)00471-9 https://doi.org/10.1016/s0022-0728(98)00471-9 https://doi.org/10.1149/1.2069522 https://doi.org/10.1149/1.2055011 https://doi.org/10.1016/j.electacta.2011.01.067 https://doi.org/10.1016/j.electacta.2020.137199 https://doi.org/10.1016/j.electacta.2021.138828 introduction experimental results and discussion conclusions hungarian journal of industry and chemistry vol. 49(1) pp. 59–69 (2021) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2021-08 polyvinylpyrrolidone as a corrosion inhibitor for carbon steel in a perchloric acid solution: effect of structural size abbes benchadli1, tarik attar*1,2, boulanouar messaoudi1,2, and esma choukchou-braham1 1laboratory of toxicomed, university abou beker belkaid tlemcen, bp 119, 13000 tlemcen, algeria 2higher school of applied sciences tlemcen, bp 165 rp bel horizon, 13000 tlemcen, algeria polymers are materials composed of macromolecules characterized by duplicates of smaller molecules that are covalently bonded together to provide a set of properties. corrosion inhibition by such compounds is usually attributed to their adsorption on the metal-solution interface. the inhibition effect of different sizes of polyvinylpyrrolidone (pvp) on the corrosion of carbon steel (c-steel) in solutions of perchloric acid was investigated. the inhibition efficiency increases as the size of the inhibitor and its concentration increases, but decreases as the temperature increases and can reach a value of 81.53 % and 5.0×10−3 mol l−1 (pvp: 58,000 g mol−1) at 30 ◦c. the most remarkable inhibition efficiency was confirmed by the presence of the film formed on the metal surface by scanning electron microscopy. the kinetic and thermodynamic parameters for the corrosion of c-steel and adsorption of the inhibitor were determined and discussed. the combination of pvp with potassium iodide produced a strong synergistic effect on the inhibition of c-steel corrosion leading to a significant improvement in the inhibition efficiency. quantum chemical parameters were studied using density functional theory to determine the possible relationship between the inhibitor and its electronic properties. keywords: polyvinylpyrrolidone, weight loss, synergistic effect, sem, dft 1. introduction despite its relatively limited corrosion resistance, carbon steel (c-steel) is widely used in chemical processing, nuclear and fossil fuel power plants, the oil and gas industries, construction and metal-processing equipment, mining, pipelines, transportation and marine applications. the corrosion of c-steel in acidic media is important because of its high mechanical properties and low cost [1]. levels of corrosion increase rapidly after the failure of the preventive barrier and are followed by a number of reactions that change the properties as well as composition of the metal surface [2]. generally speaking, a corrosion inhibitor is a compound that reduces or stops the rate of metal dissolution whenever introduced or added in small quantities to a corrosive environment by producing a preventive barrier film [3]. moreover, a good corrosion inhibitor presents many characteristics such as high solubility, non-toxicity, biodegradability, stability, shortand long-term durability and low cost. the inhibition efficiency is often related to different variables like the structural chemistry and amount of the inhibitor in the medium, the nature of the metal and aggressive electrolyte as well as its ph, *correspondence: att_tarik@yahoo.fr temperature, and immersion time [4, 5]. organic inhibitors mostly contain triple bonds, aromatic rings, and heteroatoms such as o, n, and s which are active centers for the adsorption process on the metal surface [6]. these atoms are characterized by higher basicity and electron density, thus act as corrosion inhibitors. organic compounds behave as effective inhibitors due to their ability to be adsorbed onto the metal surface. green corrosion inhibitors are drawing much attention in the field of corrosion because of their biodegradability, safety, renewability and ecological acceptability [7]. the mechanism of adsorption can be either physical or chemical as a result of the protective layer or adsorbed blanketing on the metal surface [8]. chemical adsorption implies charge transfer or charge sharing from the adsorbate to the atoms of the metal surface in order to form a coordinate bond. the free energy of chemisorption is higher than that of physisorption. the latter type is due to electrostatic attraction between the inhibiting organic ions or dipoles and the electrically charged surface of the metal. the use of polymers as corrosion inhibitors has attracted considerable attention recently because of their ability to form complexes with metal ions on the electrode surface. these complexes occupy a large surface, https://doi.org/10.33927/hjic-2021-08 mailto:att_tarik@yahoo.fr 60 benchadli, attar, messaoudi, and choukchou-braham thus blanketing the metal surface and protecting it from corrosive agents present in the solution [9, 10]. the applications of polyvinylpyrrolidone (pvp) are extensive in pharmaceutical, medicinal, cosmetics and industrial products [11]. it is used in food additives, adhesives, membranes, ceramics, paper, coatings and personal care products, e.g., toothpastes and shampoos, as well as in batteries, paints, environmental applications, etc. [12]. the pvp added to iodine (i2) forms a complex called povidone-iodine (pvp-i) that is widely used in various products like liquid soaps, ointments, surgical scrubs and pessaries due to its antiseptic properties or as an antimicrobial and antibacterial agent in medical devices [13]. this complex is commonly known under the trade names of wokadine, pyodine, or even betadine. quantum chemistry calculations have been extensively used to explain experimental phenomena. they have proven to be very effective in evaluating the corrosion inhibition efficiency [14]. the conceptual density functional theory (cdft) has been used to analyze the molecular activity of inhibitors [15]. the aim of the present work is to determine the effect of the size of polyvinylpyrrolidone compounds and their protection efficiencies on the corrosion of carbon steel in a solution of 1 m perchloric acid by weight loss methods. the synergistic corrosion inhibition effect between pvp and potassium iodide (ki) was also investigated and the steel surface examined by scanning electron microscopy (sem). afterwards, quantum chemical calculations using dft were performed to elucidate the interaction between the main constituents of pvp and the carbon-steel surface. 2. experimental 2.1 material preparation four forms of pvp polymers with molecular weights of 8,000, 29,000, 40,000 and 58,000 g mol−1 and the vinylpyrrolidone monomer were purchased from sigmaaldrich. the blank solution was 1 m perchloric acid prepared by diluting a concentrated solution of hclo4 (sigma-aldrich). the tested samples employed in this work and the chemical composition of c-steel are shown in table 1. 2.2 preparation of the test sample before conducting any tests, the samples of c-steel were mechanically abraded using different grades of emery paper, namely 100, 400, 600, 800, 1000, and 1200, before being washed with distilled water, degreased with acetone, air-dried then dipped into the corrosive or/and anticorrosive medium. these samples were used to study the loss in weight. 2.3 weight loss technique weight loss techniques provide more realistic results with regard to uniform corrosion than electrochemical techniques because the experimental conditions simulate reallife conditions. weight loss measurements of the c-steel samples were calculated in the solution of perchloric acid with and without the addition of different concentrations and molecular weights of polyvinylpyrrolidone. loss in the weight of the specimen was resolved by measuring the difference in weight between the carbon-steel substrates before and after being placed in the acidic medium. each sample was weighed by an electronic balance (±0.0001 g) before being placed in the acid solution (50 ml). the immersion time was 2 h within the temperature range of 293 − 333 k. the experiments were each performed three times and the average weight loss noted [16]. the corrosion rate (cr) (mg cm−2 h−1) was determined by [17] cr = (mb −ma)/ts, (1) where mb and ma denote the weight losses (mg) before and after being immersed in the acidic solution, respectively, s stands for the total surface area of the specimen (cm2), and t represents the immersion time (h). the inhibition efficiency (ie) (%) was calculated using [17] ie = 100 (cr′ − cr)/cr′ (2) the degree of surface coverage (θ) which represents the part of the metal surface covered in inhibitor molecules was calculated using [17] θ = 1 − cr/cr′, (3) where cr′ and cr denote the corrosion rates of c-steel samples in the absence and presence of polyvinylpyrrolidone, respectively. 2.4 synergism between inhibitors and iodide ions one potential method to cost-effectively increase the corrosion inhibition efficiency is to use the concept of synergism and employ a combination of inhibitors [18]. the synergism phenomenon in terms of corrosion inhibition results in an improvement in the capacity of the inhibitor table 1: chemical composition of c-steel (wt. %). c mn cu cr ni si s ti co fe 0.370 0.680 0.160 0.077 0.059 0.023 0.016 0.011 0.009 bal hungarian journal of industry and chemistry polyvinylpyrrolidone as a corrosion inhibitor for carbon steel 61 to resist corrosion in the presence of secondary compounds in the corrosive medium [19]. the presence of halide ions in acid media containing organic inhibitors has been found to stabilize the adsorption of organic cations, which leads to an increase in inhibition efficiency [20]. it has been shown that the synergistic effect of halide ions increases in the following order: chloride (cl−) < bromide (br−) < iodide (i) [21]. iodide exhibited a higher synergistic effect compared to the other halide ions because of its large size and ease of polarization [22]. therefore, the purpose of this study is to increase the inhibition efficiency by using iodide ions in a similar way to the synergistic effect with inhibitors tested with regard to the corrosion of c-steel in a solution of 1 m perchloric acid. in order to determine the synergistic effect between inhibitors and iodide ions, the synergistic parameter (sθ) was calculated from [23] sθ = (1 − θpvp+ki)/(1 − θ′pvp+ki) (4) and θpvp+ki = (θpvp + θki) − (θpvp × θki), (5) where θpvp denotes the surface coverage of the pvp inhibitor, θki stands for the surface coverage of ki, and θ′pvp+ki represents the combined surface coverage of pvp and ki. if sθ is less than unity, this indicates an antagonistic effect which may lead to competitive adsorption and when sθ approaches unity, the inhibitor compounds stop interacting with each other, whereas when sθ is greater than unity, a synergistic effect exists between the selected inhibitors [24]. 2.5 scanning electron microscopy (sem) the surface morphology of the specimens of carbon steel was studied by sem using a hitachi tm1000 tabletop scanning electron microscope at a scale of 100 µm and magnification of ×1.0k. the samples were immersed in a solution of 1 m hclo4 and the effect of the inhibitors investigated. after 24 h of immersion under optimum conditions, the sem images of both the polished specimens of carbon steel and those immersed in perchloric acid in the presence and absence of inhibitors were captured. 2.6 theoretical calculations the dft method using the b3lyp/6-31g* approach was employed to test the quantum chemical calculations of the inhibitor using the gaussian 09 program package. the values of the highest molecular orbitals (ehomo) and the lowest occupied ones (elumo) were calculated. other parameters such as electronegativity (χ), softness (σ), global hardness (η), electron affinity (a) and the ionization potential (i) were determined by koopmans’ theorem [25]. the homo energy is related to the ionization potential (i), whereas the lumo energy is dependent on the electron affinity (a), as is shown in [26] a = −elumo , i = −ehomo. (6) the energy gap (∆e) and global electronic chemical potential (µ) are determined from ∆e = elumo − ehomo (7) and µ = 1 2 (elumo + ehomo), (8) respectively [27, 28]. using the electron affinity (a) and ionization potential (i), the electronegativity (χ) and global hardness (η) can be calculated from χ = 1 2 (i +a) (9) and η = 1 2 (i −a) (10) respectively [29]. global softness (σ) demonstrates the capacity of an atom or group of atoms to receive electrons and is estimated from [30] σ = 1/η. (11) the electrophilicity index (ω) is calculated from [31, 32] ω = µ2/2η. (12) the number of electrons transferred (∆n ) was calculated from [33] ∆n = (χfe − χinh)/2(ηfe + ηinh), (13) where χfe and χinh denote the absolute electronegativities of iron and the inhibitor, while ηfe and ηinh stand for the absolute hardness of iron and the inhibitor, respectively. the theoretical values (χ = 7 ev mol−1 and η = 0 ev mol−1) for iron were taken from the literature [34]. 3. results and discussion 3.1 effect of the acid medium acidic solutions have been widely applied in industry, e.g., in the removal of mill scale from metal surfaces, acid pickling, acid descaling, acidizing oil wells and industrial acid cleaning. in the oil industry, the acidization of petroleum oil wells, an important stimulation technique, is used to enhance production [35]. hcl, hclo4 and h2so4 are the most applied acidic solutions because of their highly corrosive nature with regard to many metals and alloys even at low concentrations [36], whereas hno3 and h3po4 are used occasionally. in this study, the inhibition efficiencies of polyvinylpyrrolidone are mainly applied in different acid media such as perchloric acid, 49(1) pp. 59–69 (2021) 62 benchadli, attar, messaoudi, and choukchou-braham figure 1: variation in inhibition efficiency of carbon steel in different acid media (pvp: 58, 000 g mol−1 with 1.0×10−3 mol l−1 of acid medium for 2 h at 303 k). hydrochloric acid, sulfuric acid, phosphoric acid and nitric acid. according to fig. 1, the best inhibition efficiency (80.55 %) is obtained in perchloric acid compared to hydrochloric acid (67.74 %), sulfuric acid (61.71 %), phosphoric acid (34.68 %) and nitric acid (18.01 %). this could be due to the beneficial adsorption of perchlorate ions on the c-steel surface. the inhibitor molecules strongly interact with the metal surface in the presence of perchlorate ions due to the low coordination capacity of perchlorate ions. however, the coordination of chloride, sulfate, phosphate and nitrate ions with the metal surface render it less able to adsorb the inhibitor molecules. in this work, the study was conducted exclusively in perchloric acid because of the better adsorption of pvp in this acid compared to other acids that were tested. 3.2 effect of concentration and molecular weight the inhibition effect of pvp on the corrosion of carbon steel at 303 k in 1 m hclo4 as the corrosive medium was evaluated by a weight loss method. the effect of different molecular weights, namely the monomer and polymers of 8,000, 29,000, 40,000, and 58,000 g mol−1, on the inhibition efficiency (ie) was studied. the dependence of the inhibition efficiency on the concentration as well as on the different molecular weights of pvps is presented in fig. 2. the improvement in the inhibition efficiency compared to the polymer concentration and molecular weight of pvps suggests that more molecules are required to cover the metal surface when the concentration of the inhibitor is low. no further increase in ie beyond 10−3 mol l−1 of different molecular weights of pvp is attributed to the saturation of the adsorption process. the experimental results prove that the pvp with a molecular weight of 58,000 g mol−1 is more effective figure 2: variation in the inhibition efficiency against concentration in a 1 m hclo4 solution, using various molecular weights of the inhibitor. in inhibiting the corrosion of c-steel in the aggressive medium than any other molecular weight of pvp at all concentrations. the monomer presents the least corrosion inhibition at all the concentrations studied and reaches a maximum efficiency of 21.81 % at 5×10−3 mol l−1. 3.3 effect of immersion time the study of this parameter was conducted in order to avoid any confusion between the phenomenon of passivation which could occur if the dive time is very long and the inhibition rate of the inhibitors. the effect of the immersion time for all the inhibitors tested with regard to ie is shown in the results presented in fig. 3. the inhibition efficiency is calculated from 1 to 24 hours in uninhibited hclo4 and in the presence of the optimum concentration of the monomer (10−3 mol l−1) and different molecular weights of pvp at 303 k. it can be concluded that the inhibition efficiency increases as the immersion time lengthens due to the stability of the adsorbed layer on the surface of c-steel up until 2 hours of immersion at different concentrations and molecular weights of the inhibitors. the inhibition efficiency decreases from 80.55 % to 68.25 % after immersion times of pvp58000 of 2 hours and 24 hours, respectively. this may be explained by the desorption of inhibitor molecules from the c-steel surface and the instability of the inhibitor film on the metal surface [37]. 3.4 effect of temperature and activation energy the effect of the temperature introduces many changes on the metal surface such as adsorption, desorption, rearrangement or decomposition of the inhibitor. the effect of the temperature and different molecular weights of pvp on the corrosion inhibition of c-steel in 1 m hclo4 hungarian journal of industry and chemistry polyvinylpyrrolidone as a corrosion inhibitor for carbon steel 63 figure 3: variation in the inhibition efficiency against immersion time for carbon steel at various molecular weights of inhibition in a 1 m hclo4 solution. was studied between 293 and 333 k to determine the dependence of the inhibition efficiency on the temperature and corrosion behavior of c-steel in perchloric acid in the presence of inhibitors. according to the results presented in table 2, at higher temperatures there is an appreciable decrease in the adsorption of the inhibitors on the metal surface leading to a rise in the corrosion rate. at a temperature of 60◦c, the polyvinylpyrrolidone with a molecular weight of 58,000 g mol−1 showed a maximum inhibition efficiency of 69.41 %, while that of the monomer was only 6.35 %. those for the other molecular weights of pvp, namely 8000, 29000, and 40000 g mol−1, were equal to 56.55, 59.43 and 63.81 %, respectively, at the maximum tested concentration of 5×10−3mol l−1. an increase in the temperature of the solution reduces the inhibition effect by facilitating the counter-process of desorption [38]. the high rate of dissolution of c-steel in a 1 m hclo4 solution observed at elevated temperatures could be attributed to an increase in the dissolution energy effect acquired by the corrosive agent within the aggressive medium. moreover, the desorption of the adsorbed inhibitor caused by enhanced agitation of the solution as a result of higher rates at which hydrogen gas evolves as the temperature rises is possible and can cause the capacity of the inhibitor to be adsorbed on the c-steel surface to be reduced [39]. for chemical adsorption, the inhibition efficiency is expected to increase as the temperature rises, but for physical adsorption, the inhibition efficiency is expected to decrease as the temperature increases [40]. the arrhenius equation can be used to show the effect of the temperature on the inhibition performance of the studied compounds [41]: cr = a exp (−eact/rt ) , (14) where cr denotes the corrosion rate of carbon steel, a stands for the pre-exponential factor of the arrhenius equation, eact (kj mol−1) representsth e activation energy, r refers to the gas constant (8.314 j mol−1 k−1) and t is the temperature (k). the activation enthalpy ∆hact and entropy of activation ∆sact can be calculated by the following transition state equation [42]: log ( cr t ) = log ( r nah ) + ∆sact 2.3r − ∆hact 2.3rt , (15) where r denotes the gas constant, na stands for avogadro’s number, and h represents planck’s constant. a plot of log(cr/t ) against 1/t yields a straight line with a gradient of −∆hact/2.3r and an intercept of (log(r/nah) + ∆sact/2.3r) from which the values of ∆hact and ∆sact can be calculated as is presented in table 3. ∆gact > 0, which means a non-spontaneous corrosion reaction, the rate of which increases as the concentration of the inhibitor increases [42]. the entropies of activation were negative in the absence and presence of inhibitors implying that a decrease in disorder occurred as the reaction proceeded. the higher activation energy of the process in the presence of an inhibitor compared to in its absence is attributed to its physisorption, whereas the opposite is a result of its chemisorption [43]. the positive values of the activation enthalpy in the presence and absence of different concentrations of the inhibitors reflect the endothermic nature of c-steel dissolution. this simply means that the dissolution process of steel is difficult [44]. 3.5 adsorption isotherm the adsorption isotherms provide information about the interaction between the inhibitor and c-steel surface [45]. the type of interaction is related to the adsorption of inhibitor compounds as a result of chemisorption and physisorption [46]. it depends on many factors, e.g., the number of adsorption centers, mode of interactions with the metal surface, molecular weight and structure of the inhibitor. the data were used graphically using different isotherms such as frumkin, temkin and langmuir. the langmuir adsorption isotherm was found to best describe the adsorption. it can be seen that the results of the surface coverage in the presence of inhibitors are in good agreement with the weight loss technique (eq. 3). the langmuir adsorption isotherm model was employed using [47] c θ = 1 kads + c, (16) where θ denotes the surface coverage by the inhibitor molecules, c stands for the concentration, and kads represents the equilibrium constant for the adsorptiondesorption process. the value of the equilibrium constant obtained can be used to calculate the standard free energy by from [48] ∆gads = −rt log(55.5kads), (17) 49(1) pp. 59–69 (2021) 64 benchadli, attar, messaoudi, and choukchou-braham table 2: the percentage inhibition efficiency of c-steel in 1 m hclo4 using five inhibitors tested between 293 and 333 k. c (mol l−1) 293 k 303 k 313 k 323 k 333 k 5×10−5 6.25 4.22 3.1 2.25 1.50 7.5×10−5 8.33 8.05 5.63 4.55 3.42 monomer 10−4 15.5 11.25 8.1 6.6 4.2 1×10−3 20.65 19.81 10.43 8.7 6.15 5×10−3 21.97 21.34 10.5 8.78 6.35 5×10−5 43.37 35.01 24.17 16.85 10.19 7.5×10−5 50.19 43.67 35.82 23.42 16.29 8,000 10−4 60.53 45.07 43.98 33.75 30.7 10−3 78.2 65.9 62.2 58.85 56.42 5×10−3 78.46 67.59 62.35 58.95 56.55 5×10−5 45.5 37.55 29.24 19.31 12.23 7.5×10−5 62.51 45.81 41.21 25.93 21.54 29,000 10−4 65.17 49.02 45.03 41.97 36.91 10−3 82.17 67.44 64.61 61.35 59.39 5×10−3 82.12 68.95 64.68 61.42 59.43 5×10−5 50.18 44.22 36.86 22.16 15.95 7.5×10−5 66.57 48.21 45.13 28.18 23.73 40,000 10−4 70.41 59.47 50.32 45.73 43.33 10−3 84.09 75.53 70.88 68.41 63.6 5×10−3 84.27 76.86 70.9 68.54 63.81 5×10−5 55.19 46.89 38.91 26.17 19.07 7.5×10−5 70.07 52.77 46.50 31.04 25.66 58,000 10−4 75.23 69.33 58.53 52.72 48.71 10−3 85.1 80.55 77.21 75.13 69.34 5×10−3 85.34 81.53 77.29 75.2 69.41 table 3: thermodynamic activation parameters of the dissolution of carbon steel in 1 m hclo4 in the absence and presence of different concentrations and molecular weights of the inhibitors by applying arrhenius and transition state plots. cinh eact ∆hact ∆sact ∆gact 303k (mol l−1) (kj mol−1) (kj mol−1) (j mol−1 k−1) (kj mol−1) hclo4 1 58.79 56.2 −105.43 88.21 5×10−5 59.8 57.21 −102.48 88.26 7.5×10−5 59.81 57.22 −102.66 88.31 monomer 10−4 61.08 58.48 −98.88 88.44 10−3 61.99 59.39 −96.27 88.55 5×10−3 62.05 59.46 −96.08 88.57 5×10−5 68.35 65.75 −77.44 89.21 7.5×10−5 69.69 67.1 −74.13 89.56 8,000 10−4 69.53 66.94 −75.84 89.91 10−3 71.74 69.14 −72.78 91.19 5×10−3 72.28 69.69 −72.16 91.55 5×10−5 68.61 66.01 −76.95 89.32 7.5×10−5 73.42 70.82 −63.04 89.92 29,000 10−4 69.61 67.02 −76.33 90.14 10−3 73.83 71.23 −66.83 91.48 5×10−3 74.07 71.47 −67.14 91.81 5×10−5 69.96 67.37 −73.26 89.57 7.5×10−5 74.95 72.38 −58.54 90.11 40,000 10−4 71.86 69.27 −70.24 90.55 10−3 74.45 71.86 −66.34 91.96 5×10−3 74.95 72.36 −64.86 92.01 5.0×10−5 71.07 68.47 −70.18 89.73 7.5×10−5 76.77 74.18 −53.27 90.32 58,000 10−4 74.21 71.61 −64.18 91.05 10−3 72.53 69.94 −74.07 92.38 5×10−3 73.15 70.55 −72.22 92.43 hungarian journal of industry and chemistry polyvinylpyrrolidone as a corrosion inhibitor for carbon steel 65 table 4: thermodynamic parameters for the adsorption of five inhibitors on c-steel tested in a 1 m hclo4 solution at different temperatures. t r2 ∆hads ∆sads ∆gads (k) (kj mol−1) (j mol−1 k−1) (kj mol−1) monomer 293 0.999 28.76 −28.64 303 0.999 28 −28.7 313 0.999 −20.21 30.68 −29.82 323 0.999 29.93 −29.88 333 0.999 27.7 −29.44 293 0.999 −9.42 -34.39 303 0.999 −7.72 −34.81 8,000 313 0.999 −37.15 −8.79 −34.4 323 0.999 −8.42 −34.43 333 0.998 −9.13 −34.11 293 0.999 −4.44 −35.12 303 0.999 −3.99 −35.21 29,000 313 0.999 −36.42 −2.68 −35.58 323 0.999 −4.18 −35.07 333 0.998 −4.44 −34.95 293 0.999 1.09 −35.59 303 0.999 0.13 −35.31 40,000 313 0.999 −35.27 2.81 −36.15 323 0.999 0.15 −35.32 333 0.999 1.05 −35.62 293 0.999 −7.06 −36.2 303 0.999 −6.91 −36.18 58,000 313 0.999 −38.29 −6.17 −36.34 323 0.999 −7.74 −35.77 333 0.999 −6.67 −36.05 where r denotes the gas constant (8.314 j mol−1 k−1) and t stands for the absolute temperature (k). the constant value of 55.5 mol l−1 is the concentration of water in dilute aqueous solutions. the calculated changes in the enthalpy, entropy and free energy of adsorption are presented in table 4. in this study, the negative values of the enthalpy of adsorption, which vary between −20.21 and −38.29 kj mol−1, indicate that the adsorption of the inhibitors on the c-steel is an exothermic process. high values of ∆gads show that the inhibitor is strongly adsorbed on the metal surface in the corrosive media. the negative values of the free energy of adsorption indicate that the adsorption of the inhibitors on the steel surface is spontaneous. the variation in ∆gads between −29.06 and −36.34kj mol−1 indicates that the adsorption of inhibitors on the carbon steel surface in a solution of 1 m perchloric acid at between 293 and 333 k is a mixture of chemical and physical adsorption. the determination of the free energy of adsorption provides information about the strength of adsorption of the molecules. generally speaking, values of ∆gads between −40 and −20 kj mol−1 are consistent with physical adsorption, while those below −40 kj mol−1 are indicative of chemical adsorption [49]. 3.6 synergistic effect synergistic inhibition is brought about by the combination of pvp58000 and iodide ions for the corrosion of c-steel in 1m hclo4 as halide ions have a greater tendency to be adsorbed on the surface as a result of their attraction to organic cations. the relationship between the efficiency and concentration of each inhibitor added by potassium iodide at different temperatures is shown in table 5. the obtained results in the present study clearly show that the inhibition efficiency was substantially enhanced following the addition of ki and could occur because of the existence of synergism between different concentrations of the tested inhibitor and iodide ions. the values of sθ are higher than those for all concentrations indicating that the interaction between pvp and ki is a synergistic effect. it is well known that the maximum efficiency reaches 97.18 % as a result of the synergistic effect, while for pvp in the absence of ki it is 85.34 %. the inhibition efficiency increased following the addition of potassium iodide ions due to the synergistic effect but decreased as the temperature rose. it has been concluded that more effective barrier films of inhibitor molecules are produced on the surface of the sample due to synergy, thus blocking the active sites on the steel surface to protect carbon steel from corrosion [50]. 49(1) pp. 59–69 (2021) 66 benchadli, attar, messaoudi, and choukchou-braham table 5: synergism parameter (sθ) for different concentrations of pvp58000 and in the presence of a solution of 5×10−6 m ki from weight loss measurements at 293, 313, and 333 k. c (mol/l) 293 k 313 k 333 k ie(pvp) ie(pvp+ki) sθ ie(pvp) ie(pvp+ki) sθ ie(pvp) ie(pvp+ki) sθ 5×10−5 55.19 91.29 1.25 38.91 55.53 1.12 19.07 32.89 1.05 10−4 75.23 94.57 1.11 58.53 73.32 1.27 48.71 62.62 1.2 5×10−3 85.34 97.18 1.26 77.29 83.68 1.14 69.41 74.92 1.07 figure 4: sem images of carbon steel (a) before immersion, (b) after immersion in the acidic solution (1 m hclo4) in the absence of inhibitors, (c) after immersion in the acidic solution containing 5×10−3 m pvp58000, and (d): (c) + ki. figure 5: (a) optimized molecular structure, (b) homo and (c) lumo of the protonated polyvinylpyrrolidone molecule. 3.7 scanning electron microscopy to confirm adsorption of the polyvinylpyrrolidone on the carbon-steel surface in the presence and absence of the inhibitor in 1 m hclo4, scanning electron microscopy experiments were carried out. fig. 4a shows the surface morphology before corrosion testing. it is obvious that specimens immersed in the solution in the absence of pvp58000 and ki additives show significant degradation of the surface and pitting corrosion is evident from the surface morphology as is shown in fig. 4b. however, in the presence of pvp, an obvious reduction in the degradation of the surface is shown. this amelioration can be attributed to the adsorption of pvp on the metal surface and the formation of a protective film, thereby isolating the carbon-steel surface (fig. 4c). the addition of ki improves the degree of inhibition and the stability of the corrosion product on the steel surface as is shown in fig. 4d. this indicates that the adsorption of iodide ions on carbon steel leads to the formation of more stable films. the scanning electron microscopy (sem) study confirmed that the corrosion inhibition of carbon steel and synergistic effect occur following the adsorption of inhibitor molecules on the metal surface. 3.8 quantum chemical calculations the experimental study was completed by a theoretical study at the b3lyp/6-31g* level in order to correlate the results obtained experimentally with the molecular structure and electrical properties of polyvinylpyrrolidone as is presented in fig. 5. the energies of the homo and lumo, total energy (e), number of transferred electrons (∆n), softness (σ), electrophilicity index (ω) and global hardness (η) were calculated and are listed in table 6: the energy gap between the homo and lumo is another important descriptor that must be considered. in table 6, it is shown that the pvp inhibitor has a higher ehomo (−6.29 ev) energy and lower elumo (1.01 ev) energy as well as a small energy gap ggap ∼ −7.3 ev between ehomo and elumo. this strengthens its inhibitory action on the c-steel surface. the electrophilicity index is another important parameter which shows the tendency of the molecule to accept electron(s). the charge transfer of 0.6 ev indicates that the pvp inhibitor hungarian journal of industry and chemistry polyvinylpyrrolidone as a corrosion inhibitor for carbon steel 67 table 6: homo and lumo energies as well as the global reactivity indices µ, σ, ω, ∆n , and gap for polyvinylpyrrolidone compound at the b3lyp/6-31g* level of theory. ehomo (ev) elumo(ev) µ (ev) η (ev) σ (ev−1) ω (ev) ∆n (ev) gap (ev) −6.29 1.01 −2.65 3.65 0.27 0.96 0.6 7.3 is a strong electron donor [3]. generally, if the fractions of electrons transferred are less than 3.6 ev, the inhibition efficiency increases by increasing the electron donating capacity on the metal surface [51]. softness (σ) and chemical hardness (η) are important chemical properties to measure molecular reactivity and stability. therefore, the chemical reactivity increases as the inhibition efficiency of adsorption rises. actually, the molecule with the smallest chemical hardness should exhibit the greatest inhibition efficiency [52]. the pvp inhibitor exhibits a good degree of chemical reactivity on the metal surface due to the decrease in the chemical hardness (η = 3.65 ev) and increase in the softness (σ = 0.27 ev−1). 3.9 inhibition mechanism different techniques (weight loss, sem, and dft) were used to determine the inhibitory effect of different molecular weights of polyvinylpyrrolidone on the corrosion of c-steel in a solution of perchloric acid. pvp58000 yielded the highest corrosion inhibition, while the monomer exhibited the lowest. the results showed that inhibition efficiencies on carbon steel increase as the concentration of the inhibitors (pvps) rises and were enhanced following the addition of potassium iodide (ki) due to synergism. it is well known that iron exhibits coordinate affinity towards nitrogen-, sulfurand oxygenbearing ligands [53]. in this study, the electron pairs of oxygen and nitrogen atoms are responsible for chemical bonding to the c-steel surface. 4. conclusion the obtained results showed that polyvinylpyrrolidone is effective in the presence of perchloric acid. the studied compounds exhibited good corrosion inhibition performances of pvp (58,000 g mol−1) on c-steel in perchloric acid and its activity increased as the concentration of the inhibitor rose, while the efficacy decreased as the temperature increased. the thermodynamic adsorption parameters show that the studied inhibitors are adsorbed on the c-steel surface following an exothermic, spontaneous process. inhibition is achieved by the adsorption of the molecules on the c-steel surface and follows the langmuir isotherm. the inhibition efficiency increased following the addition of iodide ions due to the synergistic effect and decreased by increasing the temperature. the sem images illustrated the formation of a protective layer on the carbon-steel surface as well as supported the corrosion inhibition activity and synergistic effect. the inhibition efficiencies of the inhibitors obtained from the weight loss method and density functional theory are in good agreement. acknowledgements the authors would like to express 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https://doi.org/10.1007/s40090-014-0019-3 https://doi.org/10.22036/pcr.2019.198787.1665 https://doi.org/10.22036/pcr.2019.198787.1665 https://doi.org/10.1155/2008/138407 https://doi.org/10.1155/2008/138407 https://doi.org/10.1016/j.corsci.2014.12.005 https://doi.org/10.1016/j.corsci.2014.12.005 https://doi.org/10.1016/j.molliq.2018.05.140 http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.533.1438 https://www.derpharmachemica.com/pharma-chemica/corrosion-inhibition-of-cold-rolled-steel-in-05m-h2so4-by-potassium-iodide.pdf https://www.asjp.cerist.dz/en/article/59641 https://doi.org/10.1016/j.corsci.2011.05.027 https://doi.org/10.1016/j.corsci.2013.12.006 https://doi.org/10.5006/1.3290328 https://doi.org/10.5006/1.3290328 https://doi.org/10.1016/j.jtice.2014.08.033 https://doi.org/10.1016/j.jtice.2014.08.033 https://doi.org/10.1016/j.corsci.2009.04.009 https://doi.org/10.1016/j.corsci.2009.04.009 introduction experimental material preparation preparation of the test sample weight loss technique synergism between inhibitors and iodide ions scanning electron microscopy (sem) theoretical calculations results and discussion effect of the acid medium effect of concentration and molecular weight effect of immersion time effect of temperature and activation energy adsorption isotherm synergistic effect scanning electron microscopy quantum chemical calculations inhibition mechanism conclusion hungarian journal of industry and chemistry vol. 47(2) pp. 71–75 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-22 assessment of the ecotoxicity of nanoplastics nóra kováts*1, bettina eck-varanka1, zsófia békéssy1, dorina diósi1, katalin hubai1, and jános korponai2 1institute of environmental sciences, university of pannonia, 8200 veszprém, egyetem u. 10, hungary 2department of environmental science, sapientia hungarian university of transylvania, 400193 cluj-napoca, calea turzii 4, romania the presence of microand nanoplastics in aquatic environments (including freshwater and marine ecosystems as well as their sediments) is becoming an increasingly serious problem worldwide. a wide range of studies have addressed the ecological effects these particles pose on biota. the main exposure pathway are food chains, e.g. under laboratory conditions these particles accumulate in the brain tissues of fish that feed on zooplankton causing brain damage. these studies, however, report mainly on the physical effects. in order to establish actual ecotoxicological effects, nanoplastics (50 nm in diameter) were assessed using the vibrio fischeri bioluminescence inhibition bioassay (vfbia). our results showed that even environmentally relevant concentrations might trigger ecotoxicological effects. this study can be considered to be a first screening, however, results indicate the need for more complex testing on a battery of aquatic test organisms. keywords: nanoplastic; ecotoxicity; vibrio fischeri ; kinetic assay 1. introduction aquatic environments contaminated by plastic litter are an emerging problem. remote, pristine mountainous areas are even contaminated by atmospheric microplastic deposition [1]. polymer particles < 5 mm in diameter are defined as microplastics (mp) and may be derived directly from the use of industrial pellets or indirectly from the degradation and fragmentation of plastic particles [2]. polystyrene was proven to degrade into microand nanoplastics under laboratory conditions [3]. high levels of contamination have been reported in both marine and freshwater habitats [4, 5]. microand nanoplastics (np) can float freely in bodies of water or be deposited as sediments. the highest risk associated with these particles is their ingestion, which occurs at different levels in the aquatic food chain. jabeen et al. [6], for example, listed approximately 150 different fish species where ingestion and accumulation have been reported. particles can also progress upwards in the trophic levels of the food chain, i.e. fish can be exposed to the ingestion of zooplankton which is not able to discriminate between different food sources and consumes microand nanoplastics [7]. an experimental study showed that in fish exposed to nps via the food chain, these particles caused brain damage and behavioural disorders as a result of accumulation in *correspondence: kovats@almos.uni-pannon.hu brain tissues [8]. biomagnification may also affect food safety and human health, though certain knowledge gaps exist in this field [9]. ingestion may actually lead to starvation and eventually the impairment of their physical condition. under laboratory conditions, daphnia magna exposed to polystyrene nanoparticles (ps-np) exhibited reduced body size and severe alterations in terms of reproduction [10]. d. magna is a widely studied species due to its key role in the aquatic food chain. it was shown to ingest nanoand microplastics (20 nm to 70 µm in diameter) from water [11]. in a laboratory study by mattsson et al. [8], particles 52 nm in diameter elucidated the most severe effects. cui et al. [12] exposed d. galeata to psnps (5 mg/l, 52 nm in diameter) and detected a significant mortality rate after 2 days of exposure until the end of the study which lasted 5 days. although a standard ecotoxicological test was conducted in this case, the mechanisms of mortality are still unclear: physical contact might have led to a reduction in the survival rate. in general, most ecotoxicological studies have used relatively high concentrations. manfra et al. [13] investigated the impact of green fluorescently labeled carboxylated polystyrene nanoparticles of 40 nm in diameter with various surface charges on the marine rotifer brachionus plicatilis. it was found that anionic ps-nps did not elucidate mortality within the range of concentrations tested (0−50 µg/ml), while cationic ps-nps caused mortality at https://doi.org/10.33927/hjic-2019-22 mailto:kovats@almos.uni-pannon.hu 72 kováts, eck-varanka, békéssy, diósi, hubai, and korponai concentrations ≥ 2.5 µg/ml. changes in oxidative stress enzymes were detected within the concentration range of 10−20 µg/ml in different organisms, e.g. the rotifer brachionus koreanus and the marine copepod paracyclopina nana [14]. the same concentration, 10 µg/ml, was reported to cause 40 % growth inhibition in the green microalga dunaliella tertiolecta [15]. in order to distinguish real (eco)toxicological effects from physical damage, a test based on the bioluminescence inhibition of the marine bacterium vibrio fischeri was selected. the species has been reclassified as aliivibrio fischeri [16], however, as most standards and even recent papers from the literature still use the name v. fischeri, it will be used hereinafter. bioluminescence is regulated by the enzyme system nad(p)h:fmn oxidoreductase-luciferase. in toxic environments, enzyme inhibition is reflected by a rapid decrease in the luminous emittance of the bacterium. the reduction in light intensity is easy to measure as it is proportional to the strength of the toxicant, therefore, provides a quantifiable endpoint. this test has been used in various environmental matrices [17–19]. lappalainen et al. [20,21] developed a special version of the test which was later standardised (iso 21338:2010: water quality kinetic determination of the inhibitory effects of sediment, other solids and coloured samples on the light emission of vibrio fischeri (kinetic luminescent bacteria test)) in which bacteria are kept in suspension in direct contact with potentially toxic solid particles. luminescence readings were taken when the test commenced and the light intensity continuously monitored over the first 30 secs after the sample had been mixed with the bacteria. the light output pattern, therefore, might already provide some indication of the expected toxicity of the sample [22]. the light intensity was measured once more after the pre-set exposure time (5, 15 or 30 mins as per standard). toxicity values are normally expressed as ec50 and ec20, i.e. concentrations causing luminescence inhibitions of 50 and 20 % in this assay, respectively. 2. materials and methods in our experiments, the ascent luminometer (flash system, marketed by aboatox, finland) was used. a suspension of the test bacteria (nrrl b-11177) was prepared in accordance with manufacturer instructions (hach lange gmbh). polystyrene particles with a nominal diameter of 50 nm were used as a sample (supplier thermo fisher scientific). as no comparative data were available on the potentially toxic concentration, a range-finding concentration series was set [23]. three initial sample concentrations were selected (1 g/l, 1 µg/l and 1 ng/l), which were further diluted, the number of dilutions was 11 (the number of concentrations the 96-multiwell plate permits) and the dilution ratio 1 : 2. table 1: the measured ec20 values of the polystyrene nanoparticles. concentration 1 g/l 1 µg/l 1 ng/l ec20 5.2 17.31 30.51 the vibrio fischeri strain nrrl b-11177 was reconstituted by adding the contents of one vial of +4 ◦c 1243551 reagent diluent. the reconstituted reagent was equilibrated at +4 ◦c for 30 min. then the reagent was stabilised at +15 ◦c for 30 mins before being pipetted into the wells. luminescence readings were taken when the test commenced, time0, and after the pre-set exposure time of 30 mins, time30. the luminescence inhibition of each sample was calculated as follows: cf = ic30/ic0 inh \% = 100 $-$ 100 x (it30 / cf x it0) where cf = correction factor ic30 = luminescence intensity of the control sample after the contact time (30 mins) in the rlu ic0 = initial luminescence intensity of the control sample in the rlu it30 = luminescence intensity of the test sample after the contact time (30 mins) in the rlu it0 = initial luminescence intensity of the test sample in the rlu ec20 values were calculated using the ascent software, also developed by aboatox oy. 3. results and discussion table 1 shows the ecotoxicity expressed in ec20, i.e. the calculated concentration of the sample that caused 20 % bioluminescence inhibition. fig. 1 illustrates the bioluminescence inhibition during the first 30 secs for the samples of 1 g/l and 1 ng/l in concentration. ec20 (or in some cases, ec10) are considered thresholds for the estimation of the lowest observed effective concentration [24], i.e. the sample is normally considered (eco)toxic if the elucidated effect exceeds 20 %. these results show that the v. fischeri bioassay detected a measurable degree of toxicity even at a concentration of 1 ng/l. booth et al. [25] used the non-kinetic version of this bioassay (microtox®), however, in their study, the calculated toxic concentration exceeded the range of concentrations studied (0.001−1000 mg/l). the same negative effect was reported by casado et al. [26]. the higher degree of (detectable) toxicity in our study might be explained by the differences in the test system used. while microtox® is a non-kinetic test, the flash system (ascent luminometer) was especially developed to test the toxicity of different suspensions or samples containing solid particles. the ascent luminometer uses a 96-multiwell microplate. a specific feature of it is that hungarian journal of industry and chemistry assessment of the ecotoxicity of nanoplastics 73 (a) (b) figure 1: kinetic diagram of the 1 g/l (a) and 1 ng/l (b) samples. the light output is recorded over the first 30 seconds. after the peak, toxicity causes a rapid reduction in the light output, on the other hand, it remains constant during the control. the two columns show the two replicates. e1-f1/g1-h1 (left): control. e2-f2/g2-h2 (right): sample, maximum concentration. during luminescence readings, the microplate is continuously shaken by the instrument, resulting in the resuspension of particles. according to our results, environmentally relevant concentrations might already pose ecotoxic effects. actual environmental concentrations are relatively difficult to compare and assess, mostly due to difficulties in sampling and the lack of standardized sampling methodologies [27,28]. indicative data are available: e.g. microplastic concentrations of 0.4 − 34 ng/l in bodies of freshwater in the usa [29] or 0.51 mg/l in marine environments [10]. however, in real-world environments, even higher levels of toxicity can be expected as particles might absorb organic pollutants from the surrounding water [30], including highly toxic pesticides or polychlorinated biphenyls (pcbs) [31]. though their bioavailability is still questionable [32], batel et al. [33] conducted a laboratory study on microplastics and one polycyclic aromatic hydrocarbon (pah), benzo[a]pyrene (bap). it was demonstrated that bap adsorbed on microplastics and was transferred via an artificial food chain. these particles might also possess inherent toxicity due to the use of additives during manufacturing processes [34]. 4. conclusions it is a well-known paradigm in ecotoxicology that the sensitivity of different test organisms to a particular chemical varies, therefore, the v. fischeri test can be regarded as a first screening. the bioluminescence inhibition assay is an acute test that uses a maximum exposure of only 30 minutes. naturally, chronic effects cannot be extrapolated from these results. however, the fact that the tested nanoplastics have already elucidated ecotoxicological effects in environmentally relevant concentrations emphasises the need for more complex ecotoxicological testing involving a properly selected battery of test organisms. in addition to widely used aquatic test organisms such as the aforementioned daphnia magna, an ideal candidate could be the caenorhabditis elegans test. it is a standardised bioassay using a sediment-dwelling, widely distributed nematode. however, in order to distinguish physical damage from toxic effects, the measurement of changes in oxidative stress enzymes can be useful no matter which test organism is applied. acknowledgement this work was funded by the bionano_ginop-2.3.215-2016-00017 project. references [1] allen, s.; 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ghosh, u.: differential bioavailability of polychlorinated biphenyls associated with environmental particles: microplastic in comparison to wood, coal and biochar, environ. poll. 2017, 220, 150–158 doi: 10.1016/j.envpol.2016.09.033 [33] batel, a.; linti, f.; scherer, m.; erdinger, l.; braunbeck, t.: the transfer of benzo[a]pyrene from microplastics to artemia nauplii and further to zebrafish via a trophic food web experiment–cyp1a induction and visual tracking of persistent organic pollutants, environ. toxicol. chem. 2016, 35(7), 1656–1666 doi: 10.1002/etc.3361 [34] avio, c.g.; gorbi, s.; regoli, f.: plastics and microplastics in the oceans: from emerging pollutants to emerged threat, mar. environ. res. 2017, 128, 2– 11 doi: 10.1016/j.marenvres.2016.05.012 47(2) pp. 71–75 (2019) https://doi.org/10.1016/j.envpol.2016.09.033 https://doi.org/10.1002/etc.3361 https://doi.org/10.1016/j.marenvres.2016.05.012 introduction materials and methods results and discussion conclusions hungarian journal of industry and chemistry vol. 49(2) pp. 29–34 (2021) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2021-18 design and quality assured manufacturing of free form metal prostheses by selective laser melting technology artúr benjámin acél1, györgy falk2, ferenc dömötör3, and jános takács*3 1econ engineering kft., kondorosi út 3, budapest, 1116, hungary 2varinex informatics inc., fehér út 10, budapest, 1106, hungary 3department of automotive technologies, budapest university of technology and economics, stoczek u. 4, budapest, 1111, hungary this paper concerns the key steps in the design, manufacturing and certification of customized acetabular cups. the process is based on the compilation of computed tomography scans to create a surface that is generated from the point cloud of the surface model. as a result, the surface model is obtained. the final step is the manufacturing itself. the features of selective laser melting, also referred to as direct metal laser sintering in the literature, the placement of workpieces in the construction space and peculiarities of the support design are described. important technological preparations of the eos m 100 3d camera for the manufacturing of implants will be described. implants were made of the 316l and ti6al4v metal powders. the finished test pieces were subjected to non-destructive as well as destructive mechanical and material structural testing to qualify implants by using the appropriate quality assurance system. keywords: 3d printing, computed tomography, metal prostheses 1. introduction recently, the level of development of additive manufacturing has advanced. during the first level, the basics of the technology were elaborated on before the various fields of application were discovered during the following stage. barriers have been removed and the application has become more and more effective. in the clinical and medical sciences, several companies have been trying to replace traditional implants with those produced by additive manufacturing. although the imagination of designers in the field of engineering technology has no limits, limitations are imposed by medical doctors. nowadays, individual implants can be applied in many individual cases without any complications [4]. our paper describes the full sequence of preparing a real, customized acetabular cup. 2. tailor-made human implant 2.1 accessing the necessary input data unfortunately, the scapula of a woman was attacked by bone cancer. since important muscles join to its surface, it is vital that this bone be replaced. using computed tomography (ct) and magnetic resonance imaging (mri) *correspondence: janos.takacs@gjt.bme.hu figure 1: tailor-made implant to replace the scapula [1] images, engineers and medical doctors were able to reconstruct the bone to be replaced. the implant before and after implantation can be seen in fig. 1. [1] the left-hand side of fig. 1 shows that the implant can be lightened or the solid (dense) material replaced by a barred structure. to properly attach the muscles at the edge of the implants, suitable connections can be created. even in this case, the implant was fixed properly; it sat properly and the patient did not exhibit any symptoms after the operation. this case study can form the basis for proving that implants are useful and important. [1] 2.2 dicom to stl conversion tailor-made requirements were formulated during a meeting between a doctor and engineer. as a first step, https://doi.org/10.33927/hjic-2021-18 mailto:janos.takacs@gjt.bme.hu 30 acél, falk, dömötör, and takács figure 2: the object model compiled from ct scans figure 3: the “cleaned” surface model and the surface the socket must be adjusted to the doctor has to submit proper records stored on cds to the engineer. these records are usually stored on cds or dvds that can be read by any cd/dvd drive. the invesalius software carries out the conversion, which is very user-friendly. the surface model for the socket to be manufactured, prepared by invesalius software, can be seen in fig. 2. given that the model generated by the invesalius software can be imported and the surfaces that are unnecessary for designing implants removed from the surface model, the surface model is simpler and the storage of big files is not required. the autodesk meshmixer software can carry out this type of cleaning. in fig. 3, the part of the surface where the implant has to be inserted can be seen. the background produced by the ct scanner on this surface model was removed from the femur and one half of the hip bone. during the next step, the file of the model had to be saved as an “stl” file to create the surface from triangles before proceeding with the design. 2.3 creation of the socket model if the corners of the triangles can be determined and substituted by points, a point cloud is produced. this point cloud has to be cleaned further, moreover, for the remaining points, a surface can be adjusted. by highlighting the adjusted surface, the shape and volume model of the socket is obtained. the rhino 6 program can do this task. the point cloud generated from the saved surface model can be seen in fig. 4. it is also possible to simply delete any unnecessary points. during this step, how to fix the implant and what figure 4: the point cloud generated from the “stl” file figure 5: generated surface with an insufficient number of control points its role will be must be taken into account. it is important to mention that the fixed points cannot be determined from the ct images. the location of the screws in the bones is based on the experience of medical professionals. the general purpose of the socket is to compensate for the missing bone that disintegrated on the surface of the femur. it is important that it can be fixed in several ways, e.g. the volume of the implant is cavernous so the bone can grow into the holes of the bones. bolts are used to fix traditional implants. this implant is designed to be fixed to the highly strong hip bone. at least three fastening points are required to safely fasten the socket while ensuring that a sufficient amount of space remains for the bolts. by taking into account all of the aforementioned points, the point cloud can be approximated by a surface. the program must follow set conditions to determine how many control points the surface should be generated from. in this case, 20× 20 was determined as suitable. if the number of control points is any less, the point cloud cannot be simulated properly. this case is shown in fig. 5. hungarian journal of industry and chemistry design and quality assured manufacturing of free form metal prostheses 31 figure 6: the superfluous points of the point cloud are shown in detail on the generated surface figure 7: after determining the limitations of the socket, the directions of the normal vectors of the surface are designated by red circles. as can be seen in fig. 6, should too many control points be present, the program shows the undesirable defects of the surface that result. when the surface is ready, then the point cloud can be removed. the boundaries of the surface are not determined. the control points cannot be given in such a way that they reach the boundary of the point cloud. the limitations of the implant have to be determined. in this piece of software, it is possible to reshape the surface that results. predetermined sections can be projected onto the surface. using these projected sections, the individual parts of the surface can be detached, as can be seen in fig. 7. after forming the required shape, it is possible to stretch the surface in the direction of its normal vector to create the required thickness of the wall. it should be noted that this surface will make contact with the bone, so must be stretched in the opposite direction. the stretched surfaces can be seen in fig. 8. it is important that the surface model forms a closed surface to imitate the body. this closed surface model can be transferred into a body using the rhino 6 program. this model of a body can be stored in an “stp” file format. any traditional cad program is capable of opening this format. as the next step, the holes for fixing the bolts have to be created in the cad system before the model of the body can be prepared for manufacturing and its verificafigure 8: the final closed surface model after being stretched in the direction of the normal vector tion. 2.4 powder bed fusion for the additive manufacturing of metal parts using laser beams selective laser melting, similarly to other additive manufacturing technologies like direct metal laser sintering, constructs the workpiece layers by layer. at the department of automotive technologies at bme, a special method has been developed for the eos m 100 3d camera with the following operating principles: • the first step is to build a layer (on a heated base plate) that sinks proportionally to the thickness of the powder. • the second step is to provide a dose of powder from the automated supply equipment. • the third step is to spread the dose of powder over the work surface and push the superfluous amount into the container located on the other side of the work surface. • the fourth step is to scan the laser beam over the work surface before melting and fastening the particles of powder. the melting will result in the thickness of the layer of powder decreasing. • the fifth step is that the recoter returns to its original position (end position on the left-hand side) before being prepared for the portioning. four doses (denoted as 1-2-3-4) can be set on the working set and spread by the working blade to a thickness of 20 µm. positioning of the workpiece in the building space should several workpieces be present, their positions are important. the working blade must spread the powder smoothly and any fluctuations of forces acting on the blade must be avoided since these might cause vibrations leading to variations in the thickness of the powder. another problem can occur if the workpieces are arranged in a row because the separated small workpieces 49(2) pp. 29–34 (2021) 32 acél, falk, dömötör, and takács figure 9: an optional advantageous arrangement of the workpieces [2] figure 10: generation of a support (denoted in blue) depending on the angle of incidence [3] might jam the blade. an optional advantageous arrangement can be seen in fig. 9. according to our experience, small workpieces should not be placed on an edge because the temperature distribution here is not uniform which can cause problems. design of a workpiece support on the heated base plate proper binding of the initial layer of the workpiece is essential, otherwise the support will be subjected to thermal stress due to differences in temperature. if the support is not fastened properly to the base plate, then the workpiece might be torn and, consequently, production might have to be stopped. another important factor is heat transfer and cooling because the workpiece can burn due to a prolonged period at high temperatures resulting in failure of the surface and structural features. the materialise magics program can design a support for the workpieces. the following recommendations should be followed. it is undesirable to leave the surface unsupported if the angle of incidence is more than 45 degrees (fig. 10). bulging, overhanging parts also have to be supported. they might become superfluous as well because the workpiece can be placed in different orientations in the workspace. preparation for the manufacturing of a tailor-made socket as a first step, the workpiece has to be imported into the materialise magics program before being placed in the figure 11: bottom view of the surfaces with a maximum angle of declination of 45 degrees. proper position. it is advisable to minimize the number of supports. once the model has been placed in the building space, it can be adjusted into its final position. for this purpose, the module “supported area preview” is an excellent tool providing coloured data about the steepness of the surfaces. the location of the socket can be seen in fig. 11. the next step is to partition common supports by following the command “fragmentation,” resulting in a reduction in the total manufacturing time because no additional supports are required and consequently less powder is needed. lightening of load-bearing walls means the holes should be diamond-shaped or rectangular. this enables powder which is not molten to be cleared from the load-bearing walls. after clearing, the superfluous material can easily be removed and the construction time reduced because the laser no longer needs to scan the vector section. "fragmentation" and lightening of the diamond shape can be seen in fig. 12. the so-called "teeth" connect the workpiece to the supports. since the program separates the workpiece and the supports, it is no longer necessary to scan the teeth supporting the workpiece. ingrowing can be prevented by following the “z offset” command as shown in fig. 13. 2.5 checking the manufacturing of the prepared socket model due to thermal deformation during the manufacturing process, the blade may get jammed in the workpiece. furthermore, it is possible that the workpiece will crack due to the tension. the production process will stop in both cases due to overloading of the blade. to avoid this, the manufacturing plan has to be checked. naturally, the signals have to be verified and taken into account or manually neglected by the supervisor. hungarian journal of industry and chemistry design and quality assured manufacturing of free form metal prostheses 33 figure 12: “fragmentation” and lightening of the diamond shape highlighted by a red circle figure 13: prevention of the ingrowing of the teeth on the workpiece figure 14: sockets made of the alloy 316l the building platform is fastened in place by a vacuum system. the zero positions in the vertical direction must be fixed and the whole building surface levelled to achieve the required degree of flatness. the powder container must be filled and pushed into place. the protective cover must be cleaned with alcoholic tissue paper before manufacturing. the next step is to cover the door of the workspace. the entire manufacturing process takes place in an atmosphere of inert argon gas. two sockets were designed. the workspace was filled with 99.99% argon gas, which is heavier than air so fills figure 15: sockets made of the alloy ti6a14v figure 16: measurement arrangement of the 3d systems capture scanner the space from the bottom up. if less than 0.1% of oxygen is present, then the manufacturing process can commence. during the first manufacturing process, the designed sockets were made of the alloy 316l. one of the sockets was designed by using the simufact program to facilitate geometrical measurements. in the manufacturing workspace, more trial workpieces were placed. the sockets were manufactured successfully, as can be seen in fig. 14. during the second manufacturing process, the sockets were made of the alloy ti6a14v supplied by eos and can be seen in fig. 15. 49(2) pp. 29–34 (2021) 34 acél, falk, dömötör, and takács figure 17: surface with the reference net after being scanned by the 3d camera figure 18: surface model after smoothing 3. evaluation and quality control by the geometrical measurements varinex informatics inc. carried out the geometrical measurements using the scanner presented in fig. 16. before the measurements were taken, the workpieces were sprayed in a “processing powder" to avoid glittering. the workpieces to be measured are placed at the centre of the reference net. the exposition time has to be adjusted according to the light conditions. during the scanning, two images of the workpiece are made before the program generates a powder cloud of the surface as can be seen in fig. 17. surfaces scanned from several directions have to be compiled manually because the forms are unusual and the program is unable to smoothen these surfaces, which can be seen in fig. 18. unfortunately, due to the support, one part of the surface could not be scanned. this surface model can be compared with the original cad model using the geomagic design x program. the socket models were scanned in raw, heat-treated and cut statuses. these surfaces were compared with the original cad geometry and the results can be seen in fig. 19. the limits of measurements during the comparison were between 1 mm and −1 mm. differences in size are denoted by colours. the maximum values and distributions are also presented in this image. figure 19: results of the comparison of the scanned surface with the original cad model in conclusion, based on the results of the comparison, it can be seen that the calibration of the simufact program was successful. the geometry of the preformed model approximates better to the original cad model after being subjected to heat treatment and cut than to the model without preformation. the accuracy of the measured data always fall within the acceptable range of ±0.5 mm. acknowledgement the authors are grateful that this project was carried out with the full support of the national research, development and innovation office. the title of the project was “the design and quality assured manufacturing of freeform metal prostheses by selective laser melting.” the identification number of the project is nvkp_16-1-20160022. references [1] willemsen, k.; nizak, r.; noordmans, h. j.; castelein, r. m.; weinans, h.; kruyt, m. c.: challenges in the design and regulatory approval of 3dprinted surgical implants: a two-case series. the lancet digital health, 2019, 1(4): e163-e171; doi: 10.1016/s2589-7500(19)30067-6 [2] summary for the eos m290 system advanced user training – level 1 https://www.eos.info [3] d. magyar: testing features of models manufactured by laser additive manufacturing, scientific work of students, 2018, faculty of transportation engineering and vehicle engineering, bme budapest university of technology and economics https://tdk.bme.hu [4] hoang, d.; perrault, d.; stevanovic, m.; ghiassi, a.: surgical applications of three-dimensional printing: a review of the current literature & how to get started. ann. transl. med., 2016, 4(23):456 doi: 10.21037/atm.2016.12.18 hungarian journal of industry and chemistry https://doi.org/10.1016/s2589-7500(19)30067-6 https://doi.org/10.1016/s2589-7500(19)30067-6 https://www.eos.info/04_consulting_service_software/additive-minds/additive-minds-academy/additive_minds_academy_training_catalogue_03-20_en.pdf https://tdk.bme.hu/ksk/at7/lezeres-additiv-gyartassal-keszult-modellek https://doi.org/10.21037/atm.2016.12.18 https://doi.org/10.21037/atm.2016.12.18 introduction tailor-made human implant accessing the necessary input data dicom to stl conversion creation of the socket model powder bed fusion for the additive manufacturing of metal parts using laser beams positioning of the workpiece in the building space design of a workpiece support on the heated base plate preparation for the manufacturing of a tailor-made socket checking the manufacturing of the prepared socket model evaluation and quality control by the geometrical measurements hungarian journal of industry and chemistry vol. 49(1) pp. 23–30 (2021) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2021-04 optimisation of the physical properties of rice husk ash in ceramic materials using the response surface methodology asotah wisdom*1, udochukwu mark1, elakhame zeberu2, and abraham adeleke3 1department of metallurgical and materials engineering, federal university of technology, owerri, imo state, nigeria 2federal institute of industrial research oshodi, lagos state, nigeria 3department of materials science & engineering, obafemi awolowo university, ile-ife, nigeria optimisation of the physical properties of rice husk ash (rha) in ceramic materials was carried out using response surface methodology. the independent variables, namely the firing temperature and residue content, were statistically combined in a central composite design with the effects on water absorption, linear shrinkage, bulk density, apparent porosity and apparent specific gravity determined. physical and microstructural analyses were carried out to obtain information on the processes that occurred within the ceramic materials. the results obtained were analysed to determine the optimum physical properties of the ceramic materials within the range investigated. the residue content had a significant influence (at 95% confidence level) on the bulk density, water absorption, apparent porosity and apparent specific gravity but not on the linear shrinkage. the firing temperature had a more significant effect on the linear shrinkage than on the residue content, so that when elevated it contributed to an increase in linear shrinkage. the optimum residue content and firing temperature to enhance physical properties within the range investigated were 5.85% rha and 1029.64 ◦c, respectively. these optimal conditions are expected to produce a ceramic material with a bulk density, linear shrinkage, apparent porosity, water absorption and apparent specific gravity of 1.64 g/cm3, 0.29%, 0.29 g/cm3, 18.26% and 2.11, respectively with a composite desirability of 100%. keywords: ceramics, rice husk ash, central composite design, linear shrinkage, water absorption 1. introduction global concerns remain with regard to how best to manage the ballooning quantity of waste materials generated on an annual basis. waste is made up of different materials and could be classified more specifically based on its physical state (solid, liquid, gas), source (agricultural, industrial, mining) or environmental impact (hazardous and non-hazardous waste) [1]. agricultural (food) waste is common and has been on the rise globally, with an average annual increase of between 5 and 10% [2]. rice husk ash (rha) is a residue generated when rice husk is burnt to ashes. rice husk itself is a form of agricultural waste and a by-product of rice cultivation. rice is a staple food that is widely cultivated and consumed globally. therefore, waste generated from its production is abundant. the estimated global production from rice paddies is 600 million tonnes with 21 million tonnes of ash generated per year [3]. open burning of the husk has a deleterious effect on the environment, polluting our air by the release of harmful gases, smoke and dust particles, *correspondence: wisdomasotah@gmail.com which, when inhaled, can cause respiratory diseases [2]. this has led researchers to focus on managing this waste stream to reduce potential environmental concerns. rice husk ash has been found to contain a very significant percentage of silica, namely about 85 − 90% [3, 4]. given its high silica content, rha is an excellent potential surrogate to replace quartz in triaxial ceramic bodies [5]. research has shown that clay-based ceramics can tolerate the incorporation of waste materials in terms of their product formulation. this natural inclination has encouraged researchers to incorporate various industrial and agricultural by-products into ceramic bodies, potentially reducing environmental pollution [5–8]. the introduction of rha as a substitute for quartz in triaxial ceramic bodies has been found to reduce the thermal expansion and maturing temperature as well as increase the glassy phase while marginally improving their strength. this reduction in the maturing temperature will lead to cost savings in terms of energy consumption, lowering overall production costs [9]. however, the introduction of this type of residue in compositions used to produce ceramic tiles needs to be further analysed. one way https://doi.org/10.33927/hjic-2021-04 mailto:wisdomasotah@gmail.com 24 wisdom, mark, zeberu, and adeleke table 1: analysed parameters: firing temperature (ft), residue content (rc) – their levels and coded values. factor coded levels −α low medium high +α −1.414 −1 0 1 1.414 ft (◦c) 1030 1040 1065 1090 1100 rc (%rha) 5.85 10 20 30 34.12 of analysing the effects of replacing rice husk ash in triaxial ceramic bodies is through the statistical design of experiments, which has many advantages over the onefactor-at-a-time method. the factorial design of the experiment allows for the simultaneous investigation of the effects (direct and interactive) of two or more independent variables on the dependent variable [10]. response surface methodology is a powerful statistical tool that allows researchers to develop a second-order polynomial model to determine the optimum condition for an improved response [11]. this study has dual objectives. he first is to create a mathematical model that describes the physical properties (dependent variables) as a function of the firing temperature (ft) and the residue content (rc, in unit %rha), the independent variables. this modelling is based on the central composite design of experiments and regression analysis, an efficient statistical technique, to determine the regression coefficients that ensure the best fit of the predictive polynomial. data analysis would involve evaluating the experimental design using various estimates of the regression matrix and model analysis. the second objective was to determine the optimum conditions (ft, rc) that improve its physical properties. 2. experimental the following raw materials were used in this study: rice husk collected within epe, a town in lagos state; as well as feldspar and kaolin sourced in the vicinity of ogijo and shagamu in ogun state. to evaluate the effect of the ft and rc on the physical properties of the material, response surface methodology combined with central composite design were used. the central composite design method consisted of two factors at two levels, namely 22, which yielded 4 cube points with 4 axial (star) points and 5 center points. minitab 19 statistical software (minitab inc., usa) was used to design the experiment and analyse the results. table 1 presents the factors as well as their levels and coded values. initially, the kaolin was beneficiated by being soaked in water for 24 hours and then sieved through the mesh of a 150 µm sieve (particles with diameters of less than 150µm down to submicron and nanoparticles passed through). particles larger than 150µm (predominantly sand, silt and debris) were extracted. the slurry was left to stand and the excess water decanted. the wet clay was air-dried and milled using a ball mill (model 87002 figure 1: fired ceramic samples. limongs – france a50 – 43). feldspar rock was also milled to particle sizes of less than 150µm. the rice husk ash was dried and sieved to particle sizes of less than 150µm. all the sieving was conducted using a bs 410 sieve to eliminate ions and other debris. the dry powders were measured in the right proportions according to the experimental design using the coded and uncoded values presented in table 2 as well as a metro weighing scale with a sensitivity of 0.001 mg. water was added and the mixture homogenized to make it workable. a quantity of the ceramic composite was put into a metal mould and placed on a press die’s mantelpiece. a minimum pressure of 300 kn/m2 was applied uniaxially upon the sample in the press die. the mould was constantly lubricated to facilitate the easy removal of the composite. the pressed specimens were stored overnight before being dried at 90 ± 100 ◦c for 48 hrs in an oven (memmert gmbh, germany). the dried specimens were fired in a laboratory electric furnace (thermolyne 46200) at a rate of 5◦c/min between 1000 ◦c and 1100 ◦c according to the phase change corresponding to the composition of the mixture. the chosen parameters for the firing cycle on a laboratory scale were adapted from the parameters used in industry. the following physical properties were evaluated: water absorption (wa), bulk density (bd), apparent porosity (ap), apparent specific gravity (ap-sg), and linear shrinkage (ls). the ls was determined from the variation in the linear dimension of the specimen. according to archimedes’ method, wa and bd were determined using water at room temperature as the immersion fluid. the volume of open pores was determined by the ap, while the ap-sg evaluated how impervious the ceramic is to water. the crystalline phases of the fired samples were analysed by the x-ray diffraction (xrd) technique using a rigaku miniflex benchtop x-ray diffractometer. the fracture surfaces of the samples were morphologically characterised by scanning electron microscopy (sem) using a phenom prox sem and energy dispersive x-ray (edx) analysis determined the elemental composition of the samples. the fired samples are presented in fig. 1. hungarian journal of industry and chemistry optimisation of the physical properties of rice husk ash in ceramic materials 25 3. results and discussion table 3 describes the elemental composition of the ceramic samples. by analysing the morphology and elemental composition of the various structures, information on the processes that occurred within the ceramic body when subjected to independent variables and on the nature of the minerals was obtained. edx measurements showed that the ceramic samples were mainly composed of primary metals such as na, k, ca, mg, fe, ag and ti as well as non-metals like p and s – the contents of which vary between samples and even within individual samples depending on the composition of the investigated area. the high concentrations of si and al are related to the raw materials, that is, rice husk ash and kaolin. silica, an oxide of si, is commonly found in several mineralogical clay-rich and clay-deficient phases such as kaolin, mica, feldspar and quartz. alumina, an oxide of al, is usually associated with some of these mineralogical phases. potassium (k2o) and sodium (na2o) oxides generally originate from feldspars, hence the presence of p and na in the edx data. the low content of fe is essential to produce white ceramics since it can lead to the development of a reddish colour during sintering [6, 12]. values of the dependent variables (observed and predicted), namely ls, wa, ap, ap-sg, and bd, from the ceramic samples are listed in table 4. all values were calculated using the experimental planning matrix produced by minitab 19 software. the results of the regression analysis, namely the values of the polynomial equation for the dependent variables, are shown in eqs. 1–5 and the corresponding coefficients of the regression analysis, that is,r-squared (r2) and adjustedr-squared (r2(adj.)), are presented in table 5. bd(g/cm 3 ) = −28.92 + 0.015rc + 0.0572ft− 0.000337rc2 − 0.000027ft2 (1) wa(%) = −25.44 + 0.0188rc + 0.04789ft− 0.000295rc2 − 0.000022ft2 − 0.000006rc×ft (2) apsg = −388.1 + 0.233rc + 0.730ft− 0.003957rc2 − 0.000341ft2 − 0.000062rc×ft (3) ap(g/cm 3 ) = −52.50 + 0.0348rc + 0.0987ft −0.000596rc2−0.000046ft2−0.000009rc×ft (4) ls = −32.7 + 0.0420rc + 0.0600ft+ 0.000104rc2 − 0.000027ft2 − 0.000042rc×ft (5) table 6 shows the regression coefficients obtained when the observed values of ls in table 4 were fitted to the quadratic model. the statistical significance of each independent variable on this fitting was determined using the p value, f statistic on its linear and quadratic terms as well as the interaction between regression coefficients. the smaller the p value, the more significant the corresponding regression coefficient; p value < 0.05 indicated that the regression coefficient was statistically significant at 95% confidence interval. as can be seen in table 6, only the ft exhibited statistical significance over the range investigated. the main regression coefficients (linear and quadratic) for the rc did not show any significance. therefore, the ft had a more significant effect on changing the ls than the rc. the ls determines the degree of compaction and densification by analysing the linear variation with regard to the length of the sample after firing, which is essential for table 2: parameters with coded and uncoded values. run/sample coded form of independent variables uncoded form of independent variables x1 x2 x1 x2 1 0 0 1065 20 2 0 −1.414 1065 5.8579 3 1 −1 1090 10 4 −1.414 0 1030 20 5 0 0 1065 20 6 1 1 1090 30 7 0 0 1065 20 8 1.414 0 1100 20 9 0 1.414 1065 34.1421 10 0 0 1065 20 11 −1 −1 1040 10 12 0 0 1065 20 13 −1 1 1040 30 x1 = firing temperature (celsius); x2 = residue content (%rha) 49(1) pp. 23–30 (2021) 26 wisdom, mark, zeberu, and adeleke table 3: edx data of ceramic samples. element (atomic concentration %) sample 9 11 4 2 13 3 6 8 7 si 62.15 57.98 62.44 59.97 58.85 56.15 68.07 58.03 54.70 al 21.66 27.71 17.12 26.02 24.19 29.44 18.62 28.46 29.07 fe 3.20 2.78 3.15 2.9 4.51 3.43 1.99 3.32 3.52 k 2.48 1.65 2.72 1.57 2.33 1.75 2.15 1.48 2.19 na 0.53 0.58 1.43 0.67 0.55 0.54 0.31 0.79 0.39 table 4: observed and predicted values of the linear shrinkage (ls), water absorption (wa), bulk density (bd), ap-sg (ap-sg) and apparent porosity (ap). ls bd (g/cm3) ap ap-sg wa observed predicted observed predicted observed predicted observed predicted observed predicted 0.086 0.086 0.086 0.086 0.499 0.499 3.525 3.525 0.283 0.283 0.054 0.087 1.687 1.675 0.371 0.361 2.684 2.605 0.22 0.216 0.135 0.962 1.683 1.701 0.384 1.403 2.732 2.868 0.228 0.236 0.026 0.023 1.72 1.726 0.421 0.436 2.968 3.059 0.245 0.253 0.086 0.086 0.086 0.086 0.499 0.499 3.525 3.525 0.283 0.283 0.114 0.103 1.722 1.731 0.421 0.425 2.972 3.018 0.244 0.245 0.086 0.086 0.086 0.086 0.499 0.499 3.525 3.525 0.283 0.283 0.051 0.081 1.752 1.735 0.462 0.446 3.259 3.137 0.264 0.257 0.133 0.127 1.717 1.718 0.389 0.399 2.814 2.862 0.227 0.232 0.086 0.086 0.086 0.086 0.499 0.499 3.525 3.525 0.283 0.283 0.05 0.034 1.694 1.696 0.395 0.391 2.798 2.782 0.233 0.231 0.086 0.086 0.086 0.086 0.499 0.499 3.525 3.525 0.283 0.283 0.071 0.083 1.733 1.726 0.441 0.423 3.1 2.995 0.255 0.246 table 5: relevant statistics for the analysis of variance of the mathematical models that describe the variables bd, ap, ap-sg, wa and ls. variable model f statistic p value r2 r2(adj.) bd quadratic 15.78 0.001 0.92 0.86 ap quadratic 29.38 0 0.95 0.92 ap-sg quadratic 29.58 0 0.95 0.92 wa quadratic 30.06 0 0.96 0.92 ls quadratic 2.95 0.096 0.68 0.45 controlling the dimensions of the finished ceramic product [6]. the model yielded a positive value (0.06) for the regression coefficient of the ft (eq. 5), suggesting that the ft is directly dependent on the ls. it is expected that as the temperature rises, the degree of ls increases. as the temperature rises during firing, a more significant amount of the liquid phase is produced and its viscosity decreases. this facilitates the elimination of pores, thereby increasing the extent of ls. the adequacy of the model was determined by the correlation coefficient r, which was calculated as 0.68, moreover, the high p value and low coefficient of determination are indicative of the model’s considerable degree of variability (table 5). the data points in the normal percentage distribution curves shown in fig. 2 lie close to the line indicating no significant deviation from normality nor any need for response table 6: statistics for the analysis of the variance of the model that describes linear shrinkage (ls). model term regression coeff. p value f statistic intercept −32.7 rc 0.042 0.144 2.7 ft 0.06 0.047 5.78 rc2 0.000104 0.292 1.3 ft2 −0.000027 0.102 3.54 rc×ft −0.000042 0.411 0.76 transformation. the residual versus fitted plot should resemble a scatter plot as shown in fig. 3. if the plots do not present a random scattering of data as represented in fig. 2, then any trends will indicate flaws in the assumptions [6, 11]. regression coefficients obtained when the observed values of bd, wa, ap and ap-sg were fitted in the quadratic model are shown in tables 7–10, respectively. the main independent variable, namely the ft, did not exhibit any significance over the range investigated. among the interacting regression coefficients shown in tables 7–10, interactions between the rc and ft were not found to be statistically significant. the wa capacity is directly related to the type of microstructure that developed while the samples were sinhungarian journal of industry and chemistry optimisation of the physical properties of rice husk ash in ceramic materials 27 figure 2: normal probability plot of the residual plot for linear shrinkage (ls). figure 3: residual plot against the fitted plot for linear shrinkage (ls). figure 4: normal probability plot of the standardized residual of the bulk density (bd). tering and its level of porosity. this is regarded as a simple way to predict the technological properties of the final products [6, 13]. within the range investigated, the rc was shown to be more dependent on the wa, bd, ap and ap-sg, which is in good agreement with the model prediction. the adequacy of this prediction is confirmed by the coefficient of determination, r2, values of bd, ap, apsg and wa which were calculated to be 0.92, 0.95, 0.95 and 0.96, respectively (table 5). the high values of r2 given as 0.86, 0.92, 0.92 and 0.92 (table 5) indicate that the adjusted models do not present a considerable degree of variability. this is also evident on the normal percenttable 7: statistics for analysis of variance of the model that describes the bulk density (bd). model term regression coeff. p value f statistic intercept −28.92 rc 0.015 0.008 13.14 ft 0.0572 0.506 0.49 rc2 −0.000337 0 57.44 ft2 −0.000027 0.007 14.15 rc×ft 0 1 0 table 8: statistics for analysis of variance of the model that describes water absorption (wa). model term regression coeff. p value f statistic intercept −25.44 rc 0.0188 0.043 6.08 ft 0.04789 0.593 0.31 rc2 −0.000295 0 128.25 ft2 −0.000022 0.001 28.88 rc×ft −0.000006 0.676 0.19 table 9: statistics for analysis of variance of the model that describes apparent specific gravity (ap-sg). model term regression coeff. p value f statistic intercept −388.1 rc 0.233 0.031 7.23 ft 0.73 0.447 0.65 rc2 −0.003957 0 119.58 ft2 −0.000341 0.001 34.79 rc×ft 0.000062 0.755 0.11 table 10: statistics for analysis of variance of the model that describes apparent porosity (ap). model term regression coeff. p value f statistic intercept −52.5 rc 0.0348 0.03 7.33 ft 0.0987 0.522 0.45 rc2 −0.000596 0 123.29 ft2 −0.000046 0.001 28.91 rc×ft −0.000009 0.76 0.1 age distribution curve and the residuals versus fits plot (figs. 4 and 5, respectively), which show that the data set is normally distributed and falls within (−2, 2) for bd. furthermore, similar plots are produced for wa, ap and ap-sg with a statistical significance of 95% and less than 5% as outliers observed. fig. 6 shows the xrd patterns of the ceramic samples with rcs of 5.85% and 34.14%, that is, the lowest and highest rcs studied in the present work. according to the xrd patterns, all the ceramic samples consisted of similar minerals, namely kaolinite [al2si2o5(oh)4], montmorillonite [namgalsio2(oh)h2o], suessite [fe3si], and illite [kal2si3alo10(oh)2]. with rcs of 34.14%, 49(1) pp. 23–30 (2021) 28 wisdom, mark, zeberu, and adeleke figure 5: plot of the standardized residual against the fitted values of the bulk density (bd). (a) 5.86% rha (b) 34.14% rha figure 6: xrd patterns of samples against their rcs (%rha). orthoclase and synthesised quartz were present. quartz exhibited the highest peak, which confirms the high concentration of si according to the edx data. little or no difference was detected between the intensities of the peaks. all ceramic samples contained clay minerals; quartz, kaolinite, illite and albite are the mineral phases of the raw materials used. the micrograph (fig. 7) shows that the ceramic matrix of samples sintered at higher temperatures (1090 ◦c (a) 1030 ◦c (b) 1040 ◦c (c) 1065 ◦c (d) 1090 ◦c (e) 1100 ◦c figure 7: sem micrograph of fracture surfaces of ceramic samples against rc. and 1100 ◦c) was more finely dispersed and densely packed. a reduction in porosity was observed compared to samples sintered at lower temperatures (1030 ◦c, 1040 ◦c and 1065 ◦c) which were more porous and irregular as at higher sintering temperatures. as observed, increase in ft led to an increase in vitreous phase, facilitating the elimination of pores and an increase in densification. this hypothesis is in good agreement with other research [6, 12, 13]. 3.1 response optimisation the optimised responses with regard to the physical properties of ceramics in which rice husk ash is used as a silica precursor and their criteria are presented in table 11, moreover, the desired quality is shown in fig. 8. from the optimisation results and plot presented in fig. 8, the optimum rc and ft to achieve the desirable physical properties are 5.85% and 1029.64 ◦c, respectively. these optimal conditions are expected to produce a ceramic product with a bd of 1.64 g/cm3, ls of 0.29, ap of 0.29 g/cm3, wa of 18.26%, and ap-sg of 2.11. the optimal combination of the factors shown in fig. 8 effectively maximises the ls as well as minimises the hungarian journal of industry and chemistry optimisation of the physical properties of rice husk ash in ceramic materials 29 figure 8: optimisation plot of the variables. bd, wa, ap-sg, and ap. the composite desirability of 100% showed how the settings optimise all five quality responses when they are considered as objective response functions simultaneously [11]. 4. conclusions the physical properties of the ceramic samples using the response surface methodology were optimised. the modelling was based on central composite design and it was table 11: criteria and results of the optimisation of the process conditions. response goal response desirability linear shrinkage (%) minimum 0.29 100% bulk density (g/cm3) minimum 1.64 100% apparent porosity (g/cm3) minimum 0.29 100% apparent specific gravity minimum 2.11 100% water absorption (%) minimum 18.26 100% composite desirability – 100% possible to obtain significant mathematical models which correlate the factors ft and rc with the dependent variables ls, wa, ap, ap-sg, and bd. the ft had a statistically significant effect on the ls so that raising the temperature enhanced the degree of shrinkage. however, the rc had a more significant effect on the bd, ap, ap-sg, and wa. it can be concluded that the optimum physical properties within the range investigated are a bd of 1.64 g/cm3, ls of 0.29, ap of 0.29 g/cm3, wa of 18.26%, and ap-sg of 2.11 with a rc of 5.85% and a ft of 1029.64 ◦c. the composite desirability to achieve the optimal settings is 100% and yielded favourable results for all responses when the objective functions were considered simultaneously. references [1] amasuomo, e.; baird, j.: the concept of waste and waste management, j. manage. sust., 2016, 6(4), 88–96 doi: 10.5539/jms.v6n4p88 [2] wang, b.; dong, f.; chen, m.; zhu, j.; tan, j.; fu, x.; wang, y.; chen, s.: advances in recycling and utilisation of agricultural wastes in china: based on environmental risk, crucial pathways, influencing factors, policy mechanism. procedia env. sci., 2016, 31, 12–17 doi: 10.1016/j.proenv.2016.02.002 [3] jamo, u.; maharaz, m. n.; pahat, b.: influence of addition of 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https://doi.org/10.1155/2015/695061 https://doi.org/10.17577/ijertv7is070117 https://doi.org/10.1016/j.jeurceramsoc.2017.07.018 https://doi.org/10.1016/j.jeurceramsoc.2007.02.217 introduction experimental results and discussion response optimisation conclusions hungarian journal of industry and chemistry vol. 48(2) pp. 5–8 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-21 enhancement of oxygen transfer through membranes in bioprocesses péter komáromy *1, katalin bélafi-bakó1, éva hülber-beyer1, and nándor nemestóthy1 1research institute on bioengineering, membrane technology and energetics, university of pannonia, egyetem u. 10, veszprém, 8200, hungary in several aerobic bioprocesses, it is extremely important to provide a sufficient amount of oxygen, which is a difficult task since the solubility of oxygen in aqueous systems, namely in water, is low. thus oxygen transfer techniques should be designed, built, studied and operated very carefully in biosystems. moreover, in certain cases, special techniques, e.g. involving membranes, must be applied. in this paper, three different bioprocesses are presented where oxygen was supplied by membrane aeration: wastewater treatment by microbial consortia (i), itaconic acid fermentation by a single microorganism (ii) and an oxidative enzyme catalytic process for the elimination of glucose (iii). keywords: biotechnology, aerobic microbes, silicone membrane, enzyme 1. introduction at the dawn of applied and industrial biotechnology, the use of engineering tools to establish reliable bioprocesses for manufacturing certain bioproducts was inevitable [1– 4]. for the effective production of acetic acid, ethanol and later citric acid, etc. by biological processes, the technical skills and experience of chemical engineering were used together with microbiological knowledge and practices to establish bioengineering and bioprocess engineering. several bioprocesses require oxygen for various purposes, e.g., respiration, certain energy-producing metabolic pathways, direct oxidation, the oxidative degradation of some substrates, etc. [1–3]. oxygen is usually supplied by surface aeration, bubble aeration (sparging), by entering oxygen or air directly, aeration combined with agitation or in airlift bioreactors. regardless, oxygen is always transported from a gas stream to an unsaturated liquid [5]. the steps of this pathway are as follows and are outlined in fig. 1: • from the inside of the bubble to the surface (gas side) (1); • through the boundary layer of the bubble (liquid side) (2); • from the surface to the bulk liquid (broth) (3); • from the bulk liquid to the liquid film layer of the cell (4); *correspondence: komaromy.peter@mk.uni-pannon.hu • into the microbial cells (through the liquid film layer) (5). moreover, it is important to take into consideration that the oxygen demand changes as a function of time and according to the characteristics of the particular form of cell. in the liquid film layers, the transfer occurs by diffusion, while in the bulk phase, it always takes place via convective transport (which can be enhanced by mixing). the rate-limiting step is diffusion through the boundary film layer of the bubble on the liquid side, which is highly influenced by its surface area. on the other hand, membranes have been used in bioprocesses for an extensive period of time [6–9]. however, firstly they were exclusively applied for separations [6–8]. membranes that are distinctly selective towards certain gases were used to develop gas separation techniques. some of these membranes are permeable to oxygen molecules in the gaseous phase, therefore, it was a breakthrough to apply them for oxygen transfer into the aqueous (liquid) phase [9]. one of the most important benefits of this kind of aeration is the amplified surface area between the gaseous (air or pure oxygen) and liquid phases. in this work, three different bioprocesses are presented where oxygen was supplied by membrane aeration: • wastewater treatment by microbial consortia; • fermentation by a single microorganism (under sterile conditions) for the manufacture of an organic https://doi.org/10.33927/hjic-2020-21 mailto:komaromy.peter@mk.uni-pannon.hu 6 komáromy, bélafi-bakó, hülber-beyer, and nemestóthy figure 1: the pathway of oxygen transfer. acid; • an enzymatic oxidation for the elimination of glucose. 2. membrane-aerated bioreactors for the treatment of wastewater the combination of membrane technology with the biological treatment of municipal and industrial wastewater has been investigated and applied for an extensive period of time. coupling the two systems resulted in a special, new type of reactor called a membrane bioreactor (mbr). the roles of membranes in these biological systems include: • separation of solids; • aeration; • extraction of special pollutants. the supply of oxygen to microbes through a membrane is carried out by a membrane-aerated bioreactor (mabr). this type of bioreactor was developed in 1978 and has been studied ever since. the membrane itself has to exhibit a high degree of oxygen permeability. among gas-separation membranes, silicone (polydimethylsiloxane) was used for oxygen enrichment (from air), thus seemed suitable for this purpose. oxygen mass transfer through a silicone membrane was closely examined [9] and it was determined that the membrane aeration system was approximately 7 times more effective in terms of oxygen supply than the standard activated sludge process, hence it was experimentally proven to have strong potential. in different wastewater treatment processes, various gas-permeable membranes were tested with regard to oxygen supply systems [11–14]: • polyethylene; • ethyl cellulose; • polystyrene; • polytetrafluorethylene; • polypropylene; ho c o ch2 c ch2 c o oh figure 2: chemical structure of itaconic acid. • polyetherimide; • silicone. in terms of configuration, mainly hollow fibre modules were successfully applied (though plate-and-frame modules can also be used). the membrane was placed into the liquid waste (submerged system) and oxygen from the air was pumped inside the lumen. oxygen was transferred by diffusion through the membrane directly into the biomass that formed on the shell side of the membrane. the main benefits of the system are that no bubbles are formed and bubble-to-liquid transfer (diffusion limitation) could be avoided. the membrane aerated bioreactor system is continuously being developed and finally a truly reliable, robust and viable system was established [15], namely the zeelung system. it consists of a silicone, non-porous polymer membrane with an extremely small outer diameter (50-70 µm) and wall thickness (5-20 µm). thus the module has a very high surface area, low packing density and an efficient rate of oxygen transfer can be maintained under low pressure. the new system (technology) resulted in an energy efficiency four times greater than that of conventional bubble aeration. by comparing membrane aeration with traditional bubble aeration, another benefit can be recognized. a homogeneous oxygen concentration can be achieved throughout the reactor by pumping through air or oxygen bubbles. when membrane aeration is applied, it is possible to establish different oxygen levels within the reactor: several zones with various oxygen levels (as required for certain biological processes) can be created. 3. fermentation of itaconic acid itaconic acid is an unsaturated five-carbon dicarboxylic acid that is considered to be an important platform molecule of high potential (bio-based building block) (fig. 2). it was specified by the united states department of energy as one of the 12 most promising chemicals obtained from biomass. itaconic acid is mainly produced biologically by filamentous fungi, e.g. aspergillus terreus [16–20]. the fermentation of itaconic acid is a quite sensitive process that requires a high initial substrate concentration of glucose, precise control of operational parameters (e.g. ph, temperature, presence/deficiency of certain ions, etc.) and a high oxygen level since a high level of oxygen tension in the fermenter enhances the formation of itaconic hungarian journal of industry and chemistry enhancement of oxygen transfer through membranes 7 acid. a sufficient oxygen supply can be ensured by increasing the mixing rate, however, filamentous fungi are generally very sensitive to high shear rates. moreover, intensive foaming may result which must be avoided. as the fermentation progresses, ever more biomass and protein is produced in the broth, hence these phenomena may occur more acutely. in addition, the oxygen demand continuously increases. oxygen can be supplied by conventional techniques, e.g. airlift bioreactors, air bubbling equipped with propeller agitators, etc. for example, an airlift bioreactor was combined with a modified draft tube to achieve a high (2,430 1/h) volumetric oxygen transfer coefficient [21]. in our laboratory, membrane aeration was applied by pumping 600 l/h of air at a pressure of 1.1 bar into the broth by using a special permselect hydrofluoric acid (hf) silicone membrane which was immersed into the fermenter. this membrane was originally an oxygenselective gas separation membrane, consisting of 10 thousand fibres (od = 150 µm) with a surface area of 1 m2. since oxygen permeated faster than other compounds, it resulted in a high oxygen supply. our successful experiments have proven that by applying membrane aeration, enhanced oxygen transport and a higher yield of itaconic acid are achieved. 4. enzymatic removal of glucose in the food industry, some processes require the removal of glucose [22]. for example, in the manufacture of powdered egg white, the reaction between glucose and protein results in the maillard browning reaction during the spray-drying step, leading to an undesirable brown discolouration and poor quality [23]. another example is the manufacture of low-calorie, low-alcohol beverages from fruit juices [24]. the content of fermentable sugar can be reduced significantly by converting it into other compounds which cannot be metabolised into ethanol (less alcohol forms). glucose (or dextrose, its chemical name is dglucopyranose) is the most abundant monosaccharide, a six-carbon sugar (hexose) with five hydroxyl groups. its name is derived from the greek word “glukos” which means “sweet”. the extraction of glucose from a mixture containing compounds of similar molecular size is generally difficult as well-known separation techniques are unsuitable [6–8]. therefore, a special enzymatic method has been developed where glucose is oxidised. the enzyme catalysing the reaction is called glucose oxidase (god), e.c. 1.1.3.4 [25,26]. during the reaction, glucose is converted into d-glucono-1,5-lactone, which spontaneously hydrolyses non-enzymatically into gluconic acid: β-d – glucose + o2 −−→ d – gluconic acid + h2o2 the reaction uses oxygen and releases hydrogen peroxide as a by-product, which has a strong inactivation effect on god itself, therefore, it must be eliminated from the mixture. h2o2 can be converted into water and molecular oxygen by another enzyme called catalase, e.c. 1.11.1.6.: h2o2 −−→ h2o + 1 2 o2 the two enzymes can be applied together, such an enzyme mixture can be manufactured by various moulds, e.g., species of aspergillus. for the successful operation of the enzyme, a sufficient amount of oxygen should be supplied. in the case of the production of powdered egg white, traditional aeration methods (e.g. bubble aeration) cause a high degree of foaming, thus another technique should be implemented. in our laboratory, membrane aeration was studied and applied [27]. the enzyme complex was immobilized on a resin and a packed column reactor set up for the reaction. then a perforated silicone tube membrane was placed inside the bioreactor in a spiral configuration to provide oxygen directly to the site of the enzymatic oxidation reaction. 5. conclusion in summary, three different bioprocesses were presented in this paper where oxygen was supplied using a special method, namely membrane aeration. firstly, the treatment of wastewater by microbial consortia (i), secondly, the fermentation of itaconic acid by a single microorganism (ii) and finally, an oxidative enzymatic process (iii) for the elimination of glucose were examined in detail. acknowledgement the research work was supported by the national research, development and innovation fund project k 119940 entitled “study on electrochemical effects on bioproduct separation by electrodialysis” and project efop3.6.1-16-2016-00016. references [1] doran, p. m.: bioprocess engineering principles (academic press, waltham, massachusetts, usa) 2013, isbn: 978-00-8091-770-2 [2] ratledge, c.; kristiansen, b. 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(nova science publishers, new york, usa) 2010, pp. 289–299 isbn: 978-161209599-8 hungarian journal of industry and chemistry https://doi.org/10.1016/s0958-1669(00)00201-9 https://doi.org/10.1016/0922-338x(91)90113-u https://doi.org/10.1016/0922-338x(91)90113-u https://doi.org/10.1002/(sici)1097-0290(19960320)49:6<601::aid-bit1>3.0.co;2-s https://doi.org/10.1002/(sici)1097-0290(19960320)49:6<601::aid-bit1>3.0.co;2-s https://doi.org/10.2175/106143009x12487095236991 https://doi.org/10.2175/106143009x12487095236991 https://doi.org/10.1002/bit.24599 https://doi.org/10.1002/bit.24599 https://doi.org/10.1016/b978-0-12-811520-6.00010-6 https://doi.org/10.1515/hjic-2018-0017 https://doi.org/10.1515/hjic-2018-0017 https://doi.org/10.1007/s00253-015-6735-6 https://doi.org/10.1007/s00253-015-6735-6 https://doi.org/10.3390/fermentation5020031 https://doi.org/10.1016/0922-338x(93)90067-i https://doi.org/10.4315/0022-2747-36.10.509 https://doi.org/10.1016/j.enzmictec.2006.02.010 https://doi.org/10.1016/j.enzmictec.2006.02.010 https://doi.org/10.15255/cabeq.2018.1391 https://doi.org/10.15255/cabeq.2018.1391 introduction membrane-aerated bioreactors for the treatment of wastewater fermentation of itaconic acid enzymatic removal of glucose conclusion hungarian journal of industry and chemistry vol. 53(2) pp. 85–92 (2025) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2025-22 assessment of ufmsw as a soil amendment: effects on plant development eliza molnár1*, renáta rauch1, janka bobek-nagy1, róbert kurdi1 1 faculty of engineering, university of pannonia, egyetem u.10, veszprém, 8200, hungary municipal solid waste management faces challenges in handling the undersized fine fraction, which is typically landfilled due to its heterogeneous composition. unlike source-separated organic waste, undersized fraction of municipal solid waste (ufmsw) from mixed household waste streams contains both organic and inorganic material, limiting its suitability for conventional composting. increasing restrictions on landfilling demand alternative valorization routes. owing to its high organic content, the incorporation of ufmsw into soil or planting media is promising, yet its complex composition necessitates the evaluation of its effects on plant growth and contaminant uptake. this study assessed soil properties, plant performance and heavy metal accumulation using ufmsw-treated (20–100% w/w) potting soil. ufmsw was pre-stabilized over 4 weeks beforehand and consisted of particle sizes <4.5 mm in diameter. garden cress (lepidium sativum) was used for germination tests and marigold (tagetes erecta) for growth as well as uptake studies. higher ufmsw contents (b60–b100) caused sharp increases in cod, bod, conductivity and tds, indicating high organic loads and salinity stress. l. sativum germination declined as the concentration increased, showing complete inhibition at ≥b60. in contrast, t. erecta at b20 exhibited enhanced growth in terms of its leaves, branches, reproductive structures and the diameter of its stem without notable metal accumulation. no plants survived when treated with b40–b100 due to severe dehydration. these findings highlight that while high ufmsw levels are phytotoxic, low-level amendments (20%) can enhance growth without increasing metal uptake, supporting targeted waste valorization strategies. keywords: ufmsw, tagetes erecta, waste valorization, plant test, climatic chamber 1. introduction municipal solid waste (msw) management faces the significant global challenge of effectively handling the undersized fine fraction, which is often disposed of in landfills [1]. despite its widespread use, landfilling remains the least preferred waste management option due to severe environmental implications, including groundwater, river and lake contamination from leachate [2]; air pollution from gaseous emissions mostly consisting of methane and carbon dioxide [3]; as well as broader ecological impacts [1], health hazards [4] in addition to fire and explosion risks [5]. consequently, increasing regulatory pressure is being applied by, for example, the eu landfill directive [6] to reduce the reliance on landfilling and explore alternative valorization pathways for these complex waste streams. undersized fraction of municipal solid waste (ufmsw) is derived from mixed household waste streams subjected to the mechanical-biological treatment (mbt) technology [7] and is defined as the particle fraction less than 80 mm in diameter. other studies indicate that these fractions constitute a massive proportion (50-70%) [8] of municipal solid waste received: 21 aug 2025; revised: 28 aug 2025; accepted: 29 aug 2025 *correspondence: molnar.eliza@mk.uni-pannon.hu (msw), depending on different factors such as consumption habits and socio-economic background [9]-[11]. unlike source-segregated organic waste, its heterogeneous composition, including organic and inorganic components such as paper, plastic, wood chips as well as sanitary products [12] generally renders it unsuitable for conventional composting [13]. after preliminary stabilisation, this material is commonly used for landfill coverings or is directly landfilled. in the literature, studies often focus on composts from source-segregated organic materials, examining their varied effects on plant growth and soil properties, which can range from enhancing the yield [14], soil nutrient content [15]-[16] and water-holding capacity [17] to impeding growth due to salinity or heavy metal stress [18]. besides, the aerobic route for organic fractions can be subjected to anaerobic digestion and recover energy from the process [19]. some studies have investigated pulverized refuse fines, a material somewhat analogous to ufmsw [20], and provided general insights into the characteristics of fine msw [21]-[23]. however, detailed investigations specifically focusing on the physical and chemical properties of stabilized ufmsw below 4.5 mm or 5.0 mm derived from mixed https://doi.org/10.33927/hjic-2025-22 mailto:molnar.eliza@mk.uni-pannon.hu molnár, rauch, bobek-nagy and kurdi hungarian journal of industry and chemistry 86 municipal solid waste streams in the context of its use as an agricultural soil treatment remain limited. this study aims to fill this critical gap by directly addressing the application of stabilized ufmsw obtained from mixed waste streams, rather than focusing predominantly on fully composted, source-segregated or broadly defined msw-derived materials. through a unique and integrated methodology, this research provides novel insights into the agricultural viability and potential phytotoxicity of stabilized ufmsw, thereby bridging the current gap between waste valorization and environmental safety. 2. experimental 2.1. ufmsw sample collection and preparation the undersized fraction of municipal solid waste with particle sizes of less than 60 mm in diameter was obtained from the kökény waste management centre operated by dél-kom nonprofit kft. this facility manages approximately 150,000 tons of waste annually from 319 settlements, employing selective waste separation, mechanical-biological treatment of msw, garden waste composting and landfilling. the ufmsw is generated during the mbt process, where incoming msw is shredded to <350 mm while pvc and ferromagnetic metals are removed before being trommelscreened to separate the fraction <60 mm. after collecting the sample, this sample less than 60 mm was stabilized for up to four weeks under natural temperature conditions, mixed on a weekly basis and protected from the rain in a container. having been stabilized, the sample was sieved through a 4.5 mm hand sieve. the experimental planting media were formulated by thoroughly mixing pretreated ufmsw with commercial potting soil (garri, obi gmbh, veszprém, hungary) using a paddle mixer drill attachment. five mixtures with ufmsw concentrations of 20, 40, 60, 80 and 100% (w/w) were prepared. 2.2. germination assay seed germination assays were conducted using garden cress (lepidium sativum) (rédei kertimag zrt., réde, hungary) in germination pots containing the prepared ufmsw-potting soil mixtures. 0.2 g of seeds, ~100 pieces in total, were uniformly distributed on the surface of each soil mixture in a 50x50 mm pot. the seeds were incubated in a climatic chamber at 20-22 °c with a 16/8-hour light/dark cycle and 70% relative humidity for 7 days. 2.3. plant growth experiment the plant growth experiment involving marigold (tagetes erecta) (rédei kertimag zrt., réde, hungary) was conducted in two distinct phases. initially, tagetes erecta seeds were sown in a general, non-polluted potting soil (garri, obi gmbh, veszprém, hungary), then allowed to germinate and grow for a period of four weeks. following this germination period, the most vigorous and uniformly developed seedlings were selected and transplanted into the experimental planting media. the control plants were also transplanted into a fresh control soil. the plants were maintained in a controlled climatic chamber at 20-22 °c with a relative humidity of 70% and a 16/8-hour light/dark cycle. the plants were watered twice a week with 100 ml of tap water per pot by adjusting the water quantity as required. the growing period lasted approximately 12 weeks until the control group bloomed. 2.4. analytical methods 2.4.1. physicochemical characterization of the soil samples the physicochemical properties of the growing media were determined using standardized methods. the ph was measured according to iso 10390:2021 (soil quality — determination of ph). the electrical conductivity was determined using iso 11265:1994 (soil quality — determination of the specific electrical conductivity). the dry matter and water content were measured on a mass basis by a gravimetric method following iso 11465:1993 (soil quality — determination of dry matter and water content on a mass basis — gravimetric method). total dissolved solids were quantified using epa method 160.1 (total dissolved solids). biochemical oxygen demand for 5 days (bod₅) was determined according to en 1899-2:2000 (water quality — determination of biochemical oxygen demand after n days — part 2: method for undiluted samples). the chemical oxygen demand was determined using epa 410.4:1993. 2.4.2. metal accumulation test sample preparation the soil samples were oven-dried at 105 °c to a constant weight. the plant samples (flowers, leaves, stems and roots) from 12-week-old plants were separated, cut and subsequently dried at 105 °c before being gently grinded. for metal determination, the dried plant samples were incinerated at 550 °c for 2.5 hours to produce ash, which was then cooled to room temperature. digestion and measurements all the samples were digested using an anton paar 600 w multiwave 3000 device. digestion took place in 6 ml of aqua regia (4.5 ml hcl + 1.5 ml hno₃, vwr chemicals, analytical grade) in sealed hf100 vessels heated to 175 °c for 30 minutes followed by a 30-minute contact time. having been cooled, the digested samples were diluted to 25 ml. the metal content was then determined using a perkinelmer’s icp-oes instrument. assessment of ufmsw as a soil amendment 53(2) pp. 85–92 (2025) 87 3. results and discussion 3.1. physicochemical tests on the soil the soil quality parameters exhibited pronounced changes (table 1) as the ufmsw content increased. ph values shifted from neutral in the control (7.07) to slightly alkaline in all the samples treated with ufmsw (7.74–8.17). research by soobhany confirmed that during the composting of organic constituents of msw, ph values were observed to increase to 7.4–7.5, which is slightly more acidic than in our findings [24]. vandergheynst et al. investigated different green waste composts with a similar alkaline ph from 7.9 to 8.6, depending on the input materials [25]. the conductivity and total dissolved solids (tds) increased progressively as the amount of ufmsw added increased, reaching an extremely high electrical conductivity (ec) in b100 (23,500 μs/cm), indicative of substantial ionic loading. in line with the study by vandergheynst et al. on green waste [25] as well as the literature review by agnew and leonard on compost [26], our ec results of ufmsw-treated soil fall within the same order of magnitude. high electrical conductivity values, indicative of highly soluble salts, are known to be detrimental to plants, particularly during their sensitive early growth stages when metabolic processes and the nutrient balance are disrupted [27]. organic matter-related parameters also rose sharply: the cod and bod values were highest in b80–b100 (cod: 2467–2770 mg/l; bod: 428–473 mg/l), reflecting elevated concentrations of biodegradable organic compounds. the bod and cod results of ufmsw-treated soils are comparable to the cod and bod values reported for compost leachates in the study by christensen and nielsen [28]. the at4 index, representing the biological degradation potential, increased from 2.06 mg o₂/g dry matter (dm) in the control to 41.36 mg o₂/g dm in b100, pointing to more intense microbial activity and biological instability. overall, higher ufmsw proportions in the soil substantially increased salinity, organic load and biodegradability. 3.2. soil macronutrient test the chemical characterization of compost generally depends on its agronomic value and pollutant content (e.g. heavy metals) [29]. the analysis of major nutrient concentrations in the ufmsw-treated soil revealed distinct patterns, reflecting the significant contribution of the waste material (figure 1). potassium (k) levels consistently increased as the ufmsw content rose, ranging from approximately 9100 mg/kg in b20 to 12,554 mg/kg in b100. these k concentrations are slightly higher than those reported for municipal solid waste composts, which can vary, for example, from 1851 to 6615 mg/kg according to dimambro et al. [30]. however, it should be noted that the concentration of k in the initial potting soil was also higher (9211 mg/kg dm). similarly, the phosphorus (p) content exhibited a considerable increase from 1575 mg/kg in the control to 4819 mg/kg in b100. reported p concentrations in msw composts ranged from 23 to 247 mg/kg and 680 to 1820 mg/kg according to dimambro et al. [30] and soumaré et al. [29], respectively, indicating that ufmsw is a rich source of this macronutrient with our observed values being at the higher end or exceeding these ranges. calcium was already present in substantial quantities in the control soil, moreover, its concentration rose across all treatments, ranging from approximately 56,678 to 74,435 mg/kg in ufmsw-treated samples. this is consistent with the fact that mineral nutrients, including calcium, are generally present in msw composts but mainly in smaller quantities [29],[31]. magnesium concentrations ranged from 6117 to 8809 mg/kg in the figure 1: macronutrient content in ufmsw-treated soil table 1: physicochemical parameters (ph, conductivity, tds, cod, bod, at4) of the leachates from soil treated with different proportions of ufmsw (b20–b100) compared to the control parameter ph conductivity (µs/cm) tds (mg/l) control 7.07 344 912 b20 7.85 1119 2690 b40 7.86 1367 2833 b60 7.74 1720 3342 b80 8.17 1720 3865 b100 7.79 23,500 4420 parameter cod (mg/l) bod (mg/l) at4 (mg o₂/g dm) control 187 187 2.06 b20 275 42.2 11.99 b40 365 67.5 23.96 b60 1126 160 27.79 b80 2467 428 28.85 b100 2770 473 41.36 molnár, rauch, bobek-nagy and kurdi hungarian journal of industry and chemistry 88 ufmsw-treated samples, which supports the presence of magnesium as a key mineral nutrient in compost derived from municipal solid waste [29]. critically, sodium levels exhibited a sharp increase as samples were treated with more ufmsw, rising from 1127 mg/kg in the control to 6527 mg/kg in b100. this marked elevation in na aligns with observations that mixed waste composts can contain higher levels of total salts, predominantly due to high concentrations of various elements, including na. this also correlates with previously observed increases in electrical conductivity, highlighting the potential for heightened salinity, a key consideration regarding the agricultural application and environmental impact of ufmsw [29],[30]. in the literature, studies consistently report that elevated concentrations of soluble salts in composts or amended soils can critically limit plant growth, interfering with water uptake by roots as well as leading to physiological dehydration and reduced nutrient absorption [32],[33]. collectively, these findings demonstrate that ufmsw serves as a valuable source of essential plant macronutrients while simultaneously emphasizing the necessity of managing potential salinity concerns associated with its high sodium content. 3.3. soil essential and heavy metal test the analysis of the heavy metal content reveals distinct differences between the control soil and the ufmswtreated media, generally indicating an increase in various metal concentrations with the incorporation of the waste material (figure 2). specifically, essential metals like copper and zinc, alongside lead and barium, consistently show elevated levels in all ufmsw-treated samples compared to the control with concentrations generally rising as the proportion of ufmsw increases. for instance, the concentration of pb soars from 15.86 mg/kg in the control to a high of 77.61 mg/kg in b80, while zn rises from 86.32 to 442.63 mg/kg in b80, highlighting ufmsw as a significant source of these elements. other metals such as cadmium, cobalt and tin, which were absent in the control, were found in the ufmsw-treated soils, however, their levels did not always correlate directly with the increasing ufmsw content. conversely, chromium and nickel generally showed lower concentrations in the ufmsw-treated samples compared to the control before slightly increasing as the ufmsw content rose. the concentrations of these elements are approximately equal to or below the values as stated in previous studies by koledzi et al. [34] as well as sharifi and renella [35]. arsenic and molybdenum exhibited more complex trends, initially increasing at lower ufmsw concentrations but then decreasing at higher levels with that of arsenic even falling below the control values in b80 and b100. this differential accumulation pattern underscores the heterogeneous nature of ufmsw derived from mixed household waste streams and its varied impact on metal profiles in soil, necessitating the careful consideration of application rates to manage potential environmental risks associated with elevated heavy metal concentrations. 3.4. germination experiments a clear negative trend was observed in both germination rate and early seedling development with increasing ufmsw content (figures 3 and 4a). the number of sprouts decreased sharply from 72 in the control to only 1 in b60, indicating a strong inhibitory effect of high ufmsw content on germination. the moderate reduction observed in b20 and b40 (44 and 45 sprouts, respectively) still suggests some level of phytotoxic stress or suboptimal conditions compared to in the control. in terms of seedling growth, the total length of the plants was highest in the control (98.3 mm) and decreased progressively as the ufmsw content increased. using b60, seedling growth was severely stunted (35.0 mm in total), suggesting that this level of ufmsw is not suitable for seedling development. when analyzing separately the shoot and root growth, similar trends were found. while the growth of parts above ground decreased from 47.2 mm in the control to 25.0 mm in b60, root development was even more drastically inhibited with a drop from 51.2 mm in the control to just 10.0 mm in b60. the significant negative trend observed in both germination rate and seedling development with increasing ufmsw content is likely attributable to multiple interacting factors. the strong inhibitory effect on germination and severely stunted seedling growth, particularly of roots, is strongly consistent with the figure 2: heavy metal content in ufmsw-treated soils figure 3: the effect of undersized fine municipal solid waste on the germination and early seedling development of lepidium sativum 0.00 20.00 40.00 60.00 80.00 100.00 control b20 b40 b60 number of sprouts [pcs] total lenght [mm] above ground lenght [mm] root lenght [mm] assessment of ufmsw as a soil amendment 53(2) pp. 85–92 (2025) 89 effects of immature composts, which often contain phytotoxic compounds [36] as proven by the high cod, bod and at4 values. this suggests that ufmsw may still contain substantial amounts of readily degradable organic matter or specific toxic metabolites that inhibit plant development as well as hinder seed germination and root elongation [37]. 3.5. plant test in a climatic chamber 3.5.1. morphological analyses b20 significantly enhanced both the vegetative and reproductive growth of tagetes erecta compared to in the control shown in figure 4b and 5. plants cultivated in soil treated with 20% ufmsw yielded approximately 73% more leaves (mean of 67 vs. 39 for the control) as well as 33% more stems and branches (mean of 4 vs. 3 for the control). furthermore, the mean number of reproductive organs doubled in b20 (4 vs. 2 for the control), indicating a pronounced stimulation of the flowering potential. the mean stem diameter was also greater for plants in b20 (5.5 vs. 4.7 mm), suggesting enhanced structural development. these collective results indicate that the moderate incorporation of ufmsw facilitated increased biomass allocation to vegetative structures and augmented the reproductive output without inducing visible morphological damage, a response consistent with a nutrient-enrichment effect. figure 5: morphological parameters of tagetes erecta grown in the control soil (control) and soil containing 20% ufmsw (b20): (a) number of leaves, (b) number of stems and branches, (c) number of reproductive organs and (d) stem diameter figure 4: seed germination inhibition at high ufmsw contents (a) and the healthy development of tagetes erecta using 20% ufmsw (b) molnár, rauch, bobek-nagy and kurdi hungarian journal of industry and chemistry 90 3.5.2. metal accumulation the distribution of different metals in tagetes erecta was strongly organ-specific with roots acting as the primary sink across all treatments (table 2). the treatment with 20% ufmsw (b20) markedly enhanced the accumulation of as, ba, co, mo and pb in the roots with as and pb increasing by ~43% and ~86%, respectively, relative to the control. levels of pb accumulation aligned with previous research conducted by madanan et al. [38]. in the leaves of b20-treated plants, an increase in cu (+49%) and ni (+139%) was observed, while as and pb concentrations decreased. in the stems, the concentrations of ba, cu, and pb moderately increased while those of as, mo and ni declined. in contrast, flowers generally exhibited reduced metal concentrations in b20, except for pronounced increases in ni and mo. the allocation of nickel to flowers had previously been observed in the same test plant [39]. overall, b20 shifted the metal accumulation profile toward the greater root sequestration of toxic elements and enhanced foliar enrichment of micronutrients such as cu and ni, indicating altered plant translocation and partitioning patterns. 4. conclusions collectively, this study identified the complex role of ufmsw as a soil amendment, contingent on its application rate. while high concentrations of ufmsw (b40-b100) exhibited severe phytotoxicity, leading to significantly reduced germination rates and stunted seedling development in lepidium sativum as well as complete plant mortality in tagetes erecta, moderate concentrations (b20) yielded substantial benefits. the observed phytotoxicity at elevated ufmsw levels is attributable to a combination of factors, including the presence of immature organic matter and toxic compounds, as evidenced by the high cod, bod and at4 values as well as critically pronounced osmotic stress due to elevated sodium concentrations in addition to the associated high electrical conductivity and total dissolved solids. conversely, b20 significantly enhanced both the vegetative and reproductive growth of tagetes erecta, underscoring the nutrient-enrichment potential of ufmsw at optimized application rates. furthermore, while metal accumulation within tagetes erecta was organ-specific, with roots primarily acting as a sink, b20 did not lead to its increase in edible or transferable parts that would compromise plant safety. this indicates that a carefully controlled incorporation rate can mitigate concerns regarding contaminant uptake, supporting its potential as a safe and effective amendment. in conclusion, despite the inherent phytotoxic risks associated with high ufmsw concentrations, this research highlights that targeted low-level amendments can substantially improve plant growth and yield, effectively transforming a challenging waste stream into a valuable resource. these findings are crucial for the development of sustainable waste valorization strategies, bridging the current gap between effective waste management and environmentally sound agricultural practices. acknowledgement this study was funded by the research fellowship program (code: 2024-2.1.1-eköp) of the ministry of culture and innovation of hungary from the national research, development and innovation fund. references [1] vaverková, m.d.: landfill impacts on the environment—review, geosciences, 2019, 9(10), 431, doi: 10.3390/geosciences9100431 [2] brennan, r.b.; healy, m.g.; 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fb ing. wiss., d-06099, halle, germany) received; february 27, 2002 crystals of dimenhydrinate were coated with a gastric-soluble polymer (hydroxypropyl-methylcellulose) in a fluidized bed apparatus in order to increase the poor flowabilty of crystals. the amount of coating polymer can influence the wetting, the dissolution rate of the active ingredient and the sensitivity to heat. there was an increase in particle size due to the coating, but the increase is less than that during conventional granulation. the flow properties was increased by the film coating. the different wetting behaviour of the crystals is explained in terms of the contact angle of distilled water on the surface of tablets. here different quantities of film forming polymer were exanjined. the characteristic water uptake reflects the wetting of the crystals. the thermal sensitivity, determined by a differential scanning calorimetry, was improved by the coating. the quantity of the polymer in the film plays an important part in the thermal sensitivity. keywords: dimenhydrinate, dissolution, flow properties, hpmc, melting point, wetting introduction solid dosage forms (tablets or capsules) are the forms most widely used in therapy. the main problem which arises during the preparation of the solid dosage form is when the particles exhibit an insufficient flow. decomposition of the materials in the solid dosage form is another serious problem; it can be caused by heat, oxygen, moisture and light, and can happen during the preparation or storage of the product. such problems can be avoided if the preparation is coated with a thin film. the aim of preformulation is to eliminate these problems. numerous factors affect the flow properties of powders, e.g. particle shape, size, size distribution, the roughness of surface of the particles, packing properties, etc. [1}. various methods are applied to increase the flow properties of drugs, e.g. spherical crystallization [2-4], granulation [5}, film coating [6], etc. film coating is a very widespread method for protection, retardation and identification. gastric-soluble polymers are used to protect ingredients from light, moisture and oxygen, and for identification. intestine-soluble polymers or permeable polymers which provide drug diffusion .are utilized for retardation [7]. a film coating can be used to increase the flowability of particles. in this study., film coating with a gastric-soluble polymer was applied to increase the flowabuty of crystals with low-flow properties and to provide them with a protection by harmful factors. the thickness of such a polymer film is very important. the film smoothness and thickness determine the protective effect of the coating. these parameters are well measurable on the surface of tablets or pellets by means of image analysis [8]. the film coating of fine particles can be a useful procedure in tablet making but the sticking of these particles disturbs the determinat~on of film thickness. therefore, the amount or quantity of polymer is used instead. . . three samples with different quantity of gastnc­ soluble polymer were prepared. the wettability of the preparations, the characteristic time of water ~~take, the dissolution of the active agent. the flowabxhty (flow time, mass by volume, and angle of repose) and the behaviour of the material on exposure to heat were examined. the effects of different amount of the polymer were studied. . . the wetting of a solid dosage form 1s the first step m the dissolution of the active ingredient, and it can influence the bioavailability of the drug [9]. there is a relationship between the wetting of the particles and the bioavailability [10]. the aims of this study were to compare the above properties of untreated and treated crystals and to study how the amount of polymer influences these parameters. 144 experimental materials the model drug was dimenhydrinate (usp 23), which is an ethanolamine derivative antihistamine used for the treatment of motion sickness, nausea and vomiting [ 11 j. the drug is well absorbed by the gastrointestinal tract. in the event of oral administration, the onset of the effect occurs after about 15 min [12]. this material is sensitive to heat: it decomposes at the melting point, as indicated by industrial experience and a previous study [13]. the film-forming agent was hydroxypropyl­ methylcellulose (hpmc) (sepifilm lp 010®) (seppic, paris, france). sepifilm lp 010® was applied in an aqueous dispersion, containing binder, pigment and plasticizer. coating a strea-1 apparatus (niro-aeromatic ag., switzerland) was applied with the top spray method. the coating material was a 10% aqueous dispersion of sepifilm lpoio®. parameters: nozzle diameter: 0.8 mm inlet temperature: 45 °c outlet temperature: 30 oc blow-out pressure: 5.6 bar atomizing pressure: 2 bar · peripmnp: 2 m1/min sample i (dim 1) a 40 g aqueous dispersion was used for 100 g dimenhydrinate. sample 2 (dim 2) a 55 g aqueous dispersion was used for 100 g dimenhydrinate. sample 3 (dim 3) a 70 g aqueous dispersion was used , for 100 g dimenhydrinate. morphological study microscopy. and especially scanning electron microscopy (sem), has been widely used to test the shape and surface of particles. a hitachi s2400 (hitachi scientific instruments ltd, tokyo, japan} scanning electron microscope was utilised. a sputter coat,ug apparatus (bicrrad sc 502®, vg microtech, uk) was applied to induce electric conductivity on the surface of the samples. the air pressure was 1.3-13 mpa. · particle size distribution a laborlux s light microscope and a quantimet 500 (qsoomc) image processing and analysis system (leica cambridge ltd.. cambridge, uk} were used. 500 were measured. before the tests, the dimenhydrinate crystals were dispersed in paraffin because of their tendency to aggregate. the coated crystals were measured without this treatment. flow properties a powder testing system ptg-1 (pharma test apparatebau gmbh, germany) was applied for the determination of mass of heap, flow time of 100 ml of sample and angle of repose. thermal analysis a dsc 82le (mettler-toledo gmbh, switzerland) apparatus was used to check the features of the material on exposure to heat. 7.3-7.6 mg sample were measured into the pans (40 j.ll, aluminium). the heating method involved an isothermal segment (25 °c, 3 min) and a dynamic segment (from 25 oc to 130 oc at a heating rate of 5 °c/min). three parallel experiments were performed. water uptake an enslin apparatus with a glass filter and a pipette with 0.01 ml accuracy were used for these experiments. a monolayer of particles took up the maximum quantity of water possible through a filter paper under these conditions. the characteristic water uptake time (1{;3.2%) is the time which is necessary for the uptake of 63.2% of the maximum quantity of water. the rrsbw equation was used. this equation can be used for the determination of characteristic dissolution time of active ingredient from solid dosage forms [14]. since the mechanism of water uptake is similar to dissolution this equation can be used in this case. where: m == amount of water taken up after time t mo= maximum amount of water taken up t =delay time ~=shape parameter a = time parameter linearized regression from parameters ~ and a without t gives mo lnln = pint -ina mo-m (2) where f3 is the slope and the in a is the intercept. this equation was lineart.t.ed by langenbucher [15): in a= ~*in 1{;3.2 '*' (3) table 1 particle sizes of samples sample length breadth ( m) ( m) dimenhydrinate 83.84 49.40 (sd=54.50) (sd=29.28) diml 201.95 133.68 (sd=114.47) (sd=73.63) dim2 239.49 155.09 (sd=129.69) (sd=80.75) dim3 229.90 149.93 (sd=159.57) (sd=102.24) linear regression (p<0.05) was carried out for the determination of 4;3_2%. three parallel experiments were performed. wettability measurements on wetting of fine particles are very difficult, and therefore several methods are used for its determination [16]. comprimates were made from materials under high pressure in this study. high pressure causes the deformation and breaking of crystals, which can alter the wetting. on the other hand, high pressure causes a lower porosity, which can cause disturbances during the measurements. the disintegration of comprimates did not influence the measurements, as indicated by the use of an erweka usp disintegration tester (erweka gmbh, frankfurt am main, germany). the tablets were not disintegrated in distilled water at 37 oc within 15 min. this test procedure was used because dimenhydrinate is commercially available in tablet form. the same parameters of the tablet machine were applied in every case. each sample contained only treated or untreated dimenhydrinate. parameters: tablet machine: korsch eko instrumented eccenteric tablet machine (emil korsch maschinenfabrik, berlin, germany) tablet diameter: 10 mm flat bevelled edge pressure force: 18±1.5 kn volume of die cavity: 100 mm3 a sessile drop analysis system (tropfenkonturanalyse-system g 10/dsa 10, kross gmbh, hamburg, gemany) was used to determine the contact angle of distilled water on the tablet surface. the measurements were made at room temperature. the same parameters were applied in every case. five parallel experiments were performed. the results were compared to the characteristic water uptake times. dissolution test the dissolution of dimenhydrinate was studied with a paddle method. test parameters: apparatus: pharma test ptwii (equipped with a rotating paddle) (pharma test gmbh, germany) 145 fig. i dimenhydrinate crystals (sem) paddle speed: 100 rpm dissolution medium: 900 m1 artificial gastric juice (ph==1.2±0.1) temperature: 37.0 ± 1 oc samples taken at: 1, 3, 5, 10, 20, 30, 45 and 60 min number of samples: 6 mass of sample: 0.50 g measurement: with a uv spectrophotometer (spectromom 195d, mom, hungary) at 275 nm. preliminary examinations demonstrated that the coating material did not disturb the measurements. results aud discussion the habit of the crystals is shown in the sem photo. the dimenhydrinate consisted of crystals with mainly columnar form and a wide size distribution (fig.l) (table 1). many particles were broken. an increase in the size of the crystals was detected during coating, but this was different from that in general during granulation or pelletization (figs.2-4, table 1). the 2.53.0 times increase in dimensions correspond to aggregation of 15-27 (2.53-3.03 ) crystals in a coated particle. the shape of the coated crystals were not similar to that of granules or pellets. an increase in particle size occurs during the coating of the fine particles and this is difficult to avoid [17j. this method therefore does not involve a conventional granulation, but a few particles can stick together and fluid bridges can be formed, which will become solid bridges during drying [18, 19). there was obviously no relationship between the solid content of the coating film and the particle size. this can be explained by the a simultaneous breaking of the crystals and of the breaking film during the coating. flowability tests revealed, that the flow properties of the original crystals were inappropriate (table 2). these crystals were unsuitable for the tabletting process {20]. it can be seen from the data, however, that the coated crystals displayed excellent flow properties. an increase of the amount of polymer decreases the flowability of the treated crystals. this can be explained by the deterioration of the shape. which can be seen in the sem photos {figs.2-4). the disadvantageous change in the shape of the particles decreased the 146 table 2 flow properties of samples sample dimenhydrinate diml dim2 flow time (s) no measurable 6.4 (sd=0.05) (rsd=0.8) 7.1 (sd=0.09) (rsd=1.3) angle of repose (") 52.53 (sd=l.i3) (rsd=2.2) 32.4 (sd=0.63) (rsd=l.9) 33.4 (sd=0.64) (rsd=l.9) fig.2 dim 1 sample (sbm) fig3 dim 2 sample (sbm) mass of heap (g) 41.73 (sd=0.31) (rsd=7.3) 43.9 (sd=0.29) (rsd=0.7) 41.5 (sd=0.83) (rsd=2.0) fluwability because the possibility of adhesion of the particles increased. the behaviour of the material on exposure to heat is very important. dsc experiments were therefore performed and the melting of the samples was observed. the coated crystals displayed a significantly (p<0.05) higher virtual melting point than that of the uncoated crystals. which could be caused by the reduction of the thermal conductivity of the crystals by the macromolecular film (table 3). this was supported by . another experiment. a thin (55±10.2 !aid) sepifilm lp 010 film was laid on the bottom of the pan and he powder was then measured into the pan. the detected virtual melting point, calculated by the software, significantly increased, from 103.35±0.57 °c to 106.62±0.39 °c. these experiments demonstrated that this sepifilm lp 010 even film decreases the heat conductivity to the crystals, the heating program continues and therefore the software detects a higher virtual melting point. the bulk crystals and the treated crysta1s exhibited very similar dsc curves, but two differences can be seen in the dsc curve for the coated (dim 2) crystals table 3 detected virtual melting points of samples sample dimenhydrinate dim] dim2 dim3 melting point (°c) 103.35 (sd=0.57) 105.53 (sd=0.34) 105.98 (sd=0.25) 104.97 (sd=0.09) fig.4 dim 3 sample (sbm) melting peakfig.s dsc curve of uncoated crystals r­ ~l----g~r------~ melting peakfig.6 dsc curve of coated crystals (dim 2) (figs.5 and 6). the slight change at about 50 oc can be explained by the glass transition (gt) of coating polymer for coated crystals. both the other coated samples gave similar curves. dsc methods are widely used for the determination of glass transition [21-23]. the second difference is the wider peak, which indicates that the coating film disturbs the thermal conductivity. this was verified by in a previous study [13]. we a1so examined the water uptake and the wetting of the samples. the characteristic water uptake time (163.2%} of the bulk crystals was the shortest (table 4). a table 4 characteristic time of water uptake of the samples sample characteristic water r value ina uetake time(s) [3 dimenhydrinate 9.83 0.9910 -2.0340 0.8796 dim i 18.90 0.9977 -2.8617 1.0122 dim2 38.65 0.9690 -3.5414 0.9716 dim3 45.80 0.9970 -3.9039 1.0217 t,,,. (s) so,------------, 40 30 20 10 • observed fitted line film thickness (!f dry materiayloo g dimenhydrinate) fig.7relationship between film thickness and characteristic water uptake time contactlll'lgle (") 40,.------------. 30 20 • observed 1~~2---.----2----~---n----4 fitted line fllmtbickness (gdlymoterial/100 g<fimejjilyilrinate) fig.8 relationship between film thickness and contact angle hig~er_ amount of polymer causes a longer wetting time, as indicated by a linear regression (p<o.l), where the r value was 0.9374, the slope was 5.22 and the intercept was 6.76 (fig.7). the untreated crystals were the most difficult to compress because the filling of the die and therefore the pressure force were uneven. hence, the mass of the tablets was also uneven. the filling with the coated crystals was very good, and the mass of the tablets was u~~orm. the tablets of the coated crystals were very snmlar. the uniformity of filling can be characterized by the relative standard deviation (rsd) of pressing force measured on the upper punch. the rsd of the upper punch force was 18.03% for dimenhydrinate, 1.97% for dim i. 3.23% for dim 2 and 5.76% for dim 3. the untreated crystals displayed the smallest contact angle and the largest standard deviation in the wettabiiity test (table 5). the polymer film decreased the wetting of the crystals. the contact angle of distilled water increased with increase of the polymer content, as demonstrated by linear regression (p<0.05), where the r value was 0.9899, the slope was 3.43 and the intercept was 12.57 (fig.8). 147 table 5 contact angle of distilled water on different tablets dimenhydrinate contact angle(0 ) 11.68 sd 4.22 dim i 28.40 0.63 dim2 31.42 1.20 dim3 35.43 0.43 table 6 rate constant of drug release from preparation sample dimenhydrinate dim] dim2 dim3 k 0.0325 0.2832 0.5000 0.0926 •or------------, 20 10!---:::cto--:-:20,....--30--..,~---lso contact angle(") r value 0.9801 0.9918 0.9652 0.9849 fig.9 relationship between characteristic water uptake time and contact angle 120 10 20 30 40 so "' time(min) fig. i 0 dissolution of dimenhydrinate from samples regression analysis revealed a relationship between the characteristic water uptake time and the contact angle (fig.9). more results are required for the determination of an exact relation, but the tendency is observed to a logarithmic regression curve (p<o.l) where the r value is 0.9438, the slope is 13.94 and the constant is -17.55. since the onset of the effect of dimenhydrinate after oral administration is quick, the dissolution of the active ingredient from the preparation must be very rapid. this phenomenon can be seen in fig.jo. there was no significant difference in the shapes of the curves of dissolution from the coated crystals with different amounts of polymer. each sample displayed first-order kinetics (table 6). a plot of the logarithm of thequantity of undissolved material against time yielded a straight line, which was supported by the linear regression (p<(j.05) [241. the uncoated crystals exhibited the slowest dissolution, which was confirmed by the drug release rate constant (k). this is explained by the sticking of the wet crystals. which could then disintegrate only after a few minutes. the coated crystals underwent rapid dissolution. there was a well~ 148 soluble polymer film on the surface of the treated crystals which influences the eroding of the crystals. a slight sticking of the wet crystals was observed for dim 1, but the disintegration of these agglomerates was rapid. the dissolution was slower for dim 3 than for the other two samples, which was explained by the polymer content of the film and possibly by slow wetting. the dim 2 sample underwent the most rapid dissolution, because the particles did not display sticking and did not contain too high amount of polymer. the stirring effect of the paddle and the sticking of particles in the gastric fluid influences the wetting of the samples. therefore, there was no way to perform a mathematical comparison of the results of water uptake and contact angle measurements and the dissolution of dimenhydrinate. finally, it can be stated that the coating increases the dissolution of dimenhydrinate from these samples. conclusion the coating of dimenhydrinate crystals improved the low-flow properties of the original particles. there was an increase in particle size, but this was not as large as that after the granulation. the increase of the polymer content of the film did not alter the size significantly. there are relationships between the characteristic water uptake time, the contact angle of distilled water on the surface of tablets made from different samples, and the amount of polymer. the use of this gastric-soluble film for coating does not significantly influence the dissolution. the detected virtual melting point of the coated crystals was higher, which is very useful if a drug decomposes at its melting point the quantity of the polymer did not significantly influence this alteration. finally, it can be concluded that the presence of a gastric-soluble polymer film disturbs the wetting of the material. it is therefore important to determine the ideal amount of polymer, because tablet wetting can be decreased and thus delays the disintegration of the tablet and finally the bioavailiability. crystal coating with a suitably quantity of polymer can be more useful for crystal preparation for tabletting than crystal agglomeration because the polymer coating provides additional possibilities to influence positively the disadvantageous properties of the materials (light, moisture and oxygen sensitivity, or a very unpleasant odour and taste). aknowledgement this work was prepared in a cooperation mob and daad (no. 58). this work was supported by hungarian scientific research fund (otka) grants t~006351 and t~026579. references 1. wrayp. e.: drug dev. ind. pharm., 1992, 18,627658 2. szab6-revesz p., goczo h., pintye-h6di k., 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run· chu: j. control. ret, 2000,68, 343-350 23. dred.an j., antal i. and ra.cz i.: int. j. pharm., 1996, 145, 61~64 24. wagnerj. g.: j. pharm sci., 1969,58, 1253-1257 page 141 page 142 page 143 page 144 page 145 page 146 hungarian journal of industry and chemistry vol. 53(2) pp. 93–99 (2025) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2025-23 green synthesis of carbon quantum dots derived from orange peel for high-sensitivity ph biosensing ayush tawade1, ashwini thakre2*, c. ravikumar3, diwakar shende2 and kailas wasewar2* 1 mit school of bioengineering sciences and research, mit adt university, loni kalbhor, pune, maharashtra 412201, india 2 department of chemical engineering, visvesvaraya national institute of technology (vnit), south ambazari road, nagpur, maharashtra 440010, india 3 department of chemical engineering, indian institute of technology (iit) dharwad, chikkamalligawad, dharwad, karnataka 580011, india carbon quantum dots (cqds) are nanoscale, fluorescent carbon-based substances known for their outstanding biocompatibility, solubility in water and flexible optical characteristics . the environmentally-friendly creation of such nanoparticles through the use of non-toxic, renewable resources and energy-efficient techniques is known as green synthesis. utilizing orange peel as an affordable, sustainable precursor, the ecologically -friendly synthesis of cqds and nitrogen-doped cqds (ncqds) using both hydrothermal and microwave-assisted methods are presented. small, homogeneous cqds (2–3 nm) with a modest quantum yield (~11%) were created by the hydrothermal method, but the microwave-assisted method instantly produced larger cqds (4–8 nm) with improved fluorescence intensity and enhanced quantum yield (~54%). the optical properties of both cqds and ncqds at different ph levels (4, 7 and 10) were studied using uv-vis spectroscopy. with a significant redshift in absorbance peak wavelengths from 429 nm at ph 4 to 445 nm at ph 10, cqds exhibited robust ph-responsive activity and high ph sensitivity. the slightly blue-shifted but more stable optical response with ncqds, on the other hand, makes them suitable for applications requiring signal reliability. a ph biosensor is an analytical tool used in biomedical, industrial and environmental monitoring to analyze changes in hydrogen ion concentration, providing a rapid, visual or digital input about the acidity or alkalinity of a given environment. these findings demonstrate that cqds and ncqds generated from orange peel are viable, non-toxic and promising nanomaterials for colorimetric ph biosensing. each has unique advantages tailored to particular sensing conditions that can be applied to intracellular ph imaging, water and soil quality evaluation, smart packaging, food freshness detection, biological diagnostics (such as wound and saliva monitoring) as well as medicine stability tracking. keywords: carbon quantum dots, orange peel, green synthesis, ph biosensor, microwaveassisted synthesis 1. introduction due to their remarkable characteristics, carbon quantum dots (cqds) are considered to be one of the most recognized and interesting varieties of nanomaterials composed of carbon. these features include outstanding physicochemical capabilities, minimal toxicity, vivid multicolor visual properties, exceptional chemical stability, high water solubility and remarkable biocompatibility [1],[2]. carbon dots, often referred to as cds, are semi-spherical nanoscale materials smaller than 10 nm in diameter composed of hydrogen, oxygen and carbon [3]. the optical properties of cqds, most specifically their characteristic fluorescence emissions, are vital for potential applications among their countless other attributes. in spite of the benefits of large-scale received: 29 july 2025; revised: 5 sept 2025; accepted: 12 sept 2025 *correspondence: klwasewar@che.vnit.ac.in, k_wasewar@rediffmail.com production and straightforward surface modification, cqds are still notable due to their bright fluorescence, enhanced fluid solubility, chemical stability and resistance to photobleaching. photoluminescent carbonbased quantum dots are fascinating with regard to their technological applications because they contain more stable, controlled fluorescence emission levels, are inert to chemical reactions and dissolve better in aqueous solutions than conventional semiconductor quantum dots [4]. a variety of natural materials, including orange juice and peels as well as amino acids, have been used to create fluorescent cqds. investigating novel and ecofriendly precursors is essential to produce fluorescent cqds at a reasonable cost [5]. among some of their unique physicochemical characteristics are stable https://doi.org/10.33927/hjic-2025-23 mailto:klwasewar@che.vnit.ac.in mailto:k_wasewar@rediffmail.com tawade, thakre, ravikumar, shende and wasewar hungarian journal of industry and chemistry 94 photoluminescence (pl), remarkable hydrophilicity, compatibility with biological systems, low toxicity, emission that changes according to the excitation wavelength and environmental friendliness. numerous fields, including sensing, solar cells, bio-imaging, bioelectrochemistry, nanomedicine and photocatalysis, may benefit from the use of cqds [6]. the most widespread species of orange, citrus sinensis, produces a large quantity of peel that is thrown away once its juice is extracted. this peel could be an outstanding source of carbon for the synthesis of cqds due to its abundance in proteins and fibers but lack of oils and antioxidants [7]. hydrothermal processes, microwave techniques, electrochemical oxidation, chemical oxidation, ultrasonic techniques and laser ablation treatments are some of the methods used to synthesize and develop cqds that can be classified into either the top-down or bottom-up groups [8]. furthermore, their unique sizes, shapes and surface chemistry facilitate effective dispersion in polar solvents like water or ethylene glycol and polymer matrices, which are vital for membrane applications. in order to improve membrane features and overall performance, cqd-modified membranes have been designed [9]. heteroatom doping of cqds represents an intriguing and efficient strategy to enhance their quantum yield (qy). among the various elements available, nitrogen is similar in size to carbon, thereby facilitating effective doping, which could result in significant modifications to the intrinsic properties of cqds. these changes might affect their optical qualities, electrical features and surface chemical reactivity, which could ultimately enhance the qy [10]. one fascinating method to improve the fluorescence performance of quantum dots composed of carbon and increase their use in sensing systems is to incorporate nitrogen into them. the recently reported rise in fluorescence is probably due to the protonation caused by these nitrogen atoms on quantum dots along with the creation of various additional polyaromatic compounds brought about by the integration of nitrogen atoms into them. research indicates that nitrogen-doped carbon quantum dots (ncqds) can function as a multifunctional platform for fluorescence-based sensing, facilitating the measurement of ph values as well as the detection of ag(i) and fe(iii) in aqueous solutions [11]. as the ph rose from acidic to basic values (ph 3–12), the fluorescence intensity decreased, suggesting that the cqds are sensitive to variations in ph [12]. the concentration of free hydrogen ions in food products can be directly determined through its ph value. bacteria, mold and yeast are just some of the microorganisms that are dependent on the ph levels of food products. extreme ph values, whether low or high, inhibit the growth of these microorganisms [13]. maintaining a ph balance in the body is essential for enzymatic function, nutrient absorption, cellular processes and immune response. ph measurements are typically conducted using synthetic chemical sensors which have drawbacks, including toxicity, that can pose risks to human health. this highlights the need for quick, simple, inexpensive, user-friendly and non-toxic ph sensors. biosensors have emerged as innovative devices that are selective, affordable, portable and easy to use, making them valuable across various industries for detecting contaminants such as heavy metals, harmful microorganisms and pesticides (figure 1). to efficiently detect chemical pollutants, certain biosensors use advanced colorimetric approaches. these sensors use color-sensitive receptors that react with target analytes to cause visibly distinct changes in color, resulting in rapid, cost-effective and instrument-free detection. additionally, natural plant resources serve as an excellent source of colorants and bioactive compounds that enhance the specificity and sensitivity of these biosensors [14]. the distinct changes in color of each cqd in response to different ph levels driven by changes in surface functional groups highlight their strong potential for accurate and real-time ph detection in biosensor applications. the two types of synthetic methodologies for cqds are top-down and bottom-up. the bottom-up method produces cqds from small molecules using techniques like microwave irradiation, hydrothermal treatment or pyrolysis [10]. in order to create cqd-based nanoprobes that are especially designed for use in ph biosensors, a novel microwave-assisted technique that employs orange peel as a sustainable and natural source of carbon has been devised. because of its amazing simplicity and time efficiency, this method is attracting a lot of interest from the scientific community. it facilitates the quick manufacture of cqds without requiring intricate chemical reactions [15]. orange peel, a by-product of processing oranges in one serving, is a great carbon precursor since it is rich in carbohydrates as well as contains a variety of useful components. these properties enhance the fluorescence, water solubility and biocompatibility of cqds [16]. the present study investigates two green synthesis techniques, namely hydrothermal and microwave-assisted, for creating cqds and ncqds from orange peel. the absorbance peak shifts at ph 4, 7 and 10 are then compared using uv-vis spectroscopy, revealing remarkable phresponsive behaviors that underscore their potential as non-toxic, environmental-friendly ph biosensors. figure 1: applications of ph biosensor-derived cqds from orange peel green synthesis of cqds from orange peel for ph sensing 53(2) pp. 93–99 (2025) 95 2. experimental 2.1. materials in the second week of june 2025, fresh oranges were purchased from a small local market in nagpur, india. two kinds of peel from citrus sinensis were used in the study: one with and one without the white pith layer. in nagpur, the average diameter of oranges was 7 cm. double distilled water, combined with either urea or ethylenediamine, was employed for the purpose of nitrogen doping. a standard laboratory ph buffer kit (alpha 01, india) typically consists of solutions calibrated at ph levels of 4, 7 and 10. all the required solutions were prepared fresh and each experiment conducted utilized distilled water. 2.2. methods 2.2.1. preparation of orange pericarp to remove surface contaminants, the orange pericarp was thoroughly washed with distilled water. it was then sliced into small pieces and sun-dried for 24 hours to ensure complete dehydration. the dried material was subsequently oven-dried in a hot air oven (bio technics india) at 60 °c for 5 hours until a firm, crisp texture was achieved. two types of pericarp samples were prepared: one containing the white fibrous pith layer and one without. the dried orange peel samples were then ground into a fine powder using a mechanical grinder to obtain a uniform consistency suitable for the subsequent synthesis of cqds. 2.2.2. hydrothermal methods 200 ml of deionized water was mixed with 5 grams of crushed orange peel that had been dried for five hours at 60 °c and ground to a fine consistency. to promote carbonization and the creation of cqds, the suspension was moved to a stainless steel autoclave lined with teflon and heated to 200 °c for 8 to 12 hours. large particles were extracted from the mixture by filtering it through whatman filter paper after it had naturally cooled down to room temperature. a remi r-4c centrifuge was used to centrifuge the resultant filtrate for 10 minutes at 4000 rpm before the supernatant was finally collected. the solution was dialyzed against deionized water for 24 hours after passing through a 0.22 µm pvdf syringe filter to ensure subsequent purification [8]. a schematic diagram of this procedure is depicted in figure 2. 2.2.3. microwave irradiation technique to prepare the solution, 5 grams of orange peel powder was mixed with 200 ml of double distilled water. in a separate mixture, 2.5 grams of orange peel powder (including the pith) were combined with 100 ml of double distilled water and 1 ml of urea to facilitate nitrogen doping. the latter mixture was stirred continuously at between 50 and 60 °c for 2 hours to ensure uniform dispersion as well as the partial prereaction of the dopant. subsequently, the mixture was subjected to sonication (labman, india) for 20 minutes at a frequency of 40 khz to break down agglomerates and enhance homogeneity at the molecular level. an ifb 25sc4 convection microwave oven was then used to heat both samples at 700–900 w until the mixtures began to boil. after initially boiling, the samples were allowed to cool for 30 seconds and then reheated repeatedly until a visible color change to brown or dark brown was observed, typically within 10 mins, indicating the formation of carbonized nanostructures. following cooling, the mixtures were centrifuged at 4,000 rpm for 15 mins and the clear supernatant carefully collected. to ensure the removal of large particles and residual impurities, the solutions were filtered using a 0.22-micrometer syringe filter, yielding purified cqd and ncqd suspensions suitable for further characterization [16]. this experimental approach is presented in figure 3. 2.2.4. microwave-assisted synthesis 5 grams of orange peel powder, which had been previously dried in a hot air oven at 60 °c for 5 hours and subsequently ground into a fine powder, was mixed with 200 ml of deionized water. the resulting mixture was figure 2: schematic diagram of the hydrothermal production of cqds from orange peel figure 3: microwave irradiation synthesis route for orange peel-derived cqds tawade, thakre, ravikumar, shende and wasewar hungarian journal of industry and chemistry 96 then heated using a microwave synthesis apparatus (nuwav-pro, nutechanalytical, india) initially at 800 w for 2 mins followed by 700 w for an additional 30 mins. upon completion of the heating process, the solution was allowed to cool and then filtered to obtain the carbon quantum dot suspension (figure 4). it is important to note that due to the rapid boiling point of water when used as a solvent, appropriate precautions were taken throughout the procedure to avoid overheating [17]. 2.2.5. interaction of ph buffers with cqds the ncqds and filtered cqds, synthesized using the previously described methods, were utilized for phresponsive analysis. at each ph level (4, 7 and 10), 2 ml of the cqds solution was mixed with 2 ml of the corresponding ph buffer. the resulting mixtures were then analyzed using a uv-vis spectrophotometer to evaluate the optical responses of both the undoped and nitrogen-doped carbon quantum dots (figure 5). all prepared samples were stored in a dark environment at 4 °c to maintain their stability prior to analysis. 3. results and discussion the synthesis of cqds based on precursor materials is conducted using both "top-down" and "bottom-up" approaches. however, "bottom-up" approaches using small molecules, polymers and biocompatible materials are more cost-effective and environmentally friendly as they do not require carbon-rich precursors like carbon nanotubes and graphene oxide. generally, harsh conditions such as during hydrothermal procedures, combustion and acidic pyrolysis are used to synthesize bottom-up cqds from tiny molecules [18]. during the hydrothermal process, precursor molecules are dissolved in water, put in an autoclave made of stainless steel lined with a teflon coating and then heated to extremes of pressure as well as temperature over many hours inside a hydrothermal chamber. various waste materials, organic compounds, proteins, polymers, amino acids, glucose and polyols are examples of the precursor molecules used for synthesis. the hydrothermal method has attracted a lot of interest lately worldwide because of its one-step approach, simplicity, non-toxic qualities, affordability and environmental friendliness. cqds produced via the hydrothermal treatment exhibit a wide array of advantageous properties such as high homogeneity, water solubility, monodispersity, photostability, salt tolerance, controlled particle size and an elevated quantum yield without the necessity for surface passivation [19]. these methods often involve dissolving tiny organic raw materials or macromolecules in either a naturally occurring solvent (solvothermal) or water (hydrothermal). next, the resultant solution is put in an autoclave for heating. the creation of carbon-based cores, which constitute the fundamental components to develop cqds, is then initiated by subjecting the mixture to high temperatures. various chemical compounds can be utilized during their preparation to change the functional groups on the surface of the cqds, enabling further customization and the integration of specific properties as needed [20]. one well-known bottom-up technique for creating cqds is microwave irradiation, which is distinguished by its straightforward, efficient approach and viability for commercial use. by activating the polar compounds in the solvent with microwave energy, this method allows for atomic-level heating despite the need for a material to be heated. the intrinsic flexibility and rapid ability to generate the high-yielding response of this method make it a time-efficient and environmentally-friendly method for producing cqds. by using a customized version of a normal microwave device, microwave radiation creates strong interactions between polar molecules which lead to instantaneous temperature changes at the atomic level. by directly applying high-frequency electromagnetic radiation, this process significantly increases the reaction rate compared to conventional heating methods while promoting a quick and selective yield. the process is well regarded for its quick synthesis time, environmental friendliness, energy and time efficiency, low impurity incorporation as well as exact control over temperature and size parameters. all of these benefits together produce high-quality synthetic cqds with a good level of reproducibility [21]. microwave-assisted synthesis with the nuwav-pro creates carbon quantum dots (cqds) through microwave-induced dielectric heating, where polar substances (such as water, citric acid and urea) absorb microwave energy, generating heat quickly that breaks chemical bonds and initiates carbonization into nanometer-sized graphitic cores with fluorescent surface characteristics. meanwhile, infrared (ir) sensing offers real-time, non-contact monitoring of temperature figure 4: stepwise green synthesis of cqds from orange peel using microwave and sonication techniques figure 5: workflow showing the ph-dependent uvvis spectroscopic optical examination of cqds and ncqds green synthesis of cqds from orange peel for ph sensing 53(2) pp. 93–99 (2025) 97 (usually with ir sensors and pt100 probes), allowing precise regulation of the reaction to prevent overheating as well as guarantee a consistent particle size and optical features. additionally, modalities like ultrasound for enhanced mixing or uv for surface modifications after synthesis can be integrated, while the fundamental concept is rapid employing uniform volumetric heating for the quick (within minutes) and environmentallyfriendly production of cqds which is most effective for lab-scale synthesis utilizing simple, eco-friendly precursors [22]. these green approaches have been used for various applications such as the recovery of carboxylic acids, use of natural solvents, enzymatic/catalytic reactions, etc. [23]-[26]. hydrothermal synthesis utilizing an autoclave and microwave-assisted methods both convert orange peel into carbon quantum dots (cqds) through bottom-up, environmentally-friendly processes; however, their mechanisms and applications are significantly different. hydrothermal autoclaving involves the heating of biomass in sealed, pressurized vessels at temperatures typically ranging from 150 to 200 °c over several hours. this approach facilitates a slow, controlled carbonization process that yields cqds with uniform sizes of approximately 2 to 3 nanometers in diameter, a good degree of crystallinity and moderate quantum yields of around 11%. these characteristics render them particularly suitable for applications that require precise optical properties, although this method is timeconsuming and energy-intensive. in contrast, microwave-assisted synthesis, whether performed on the domestic or laboratory scale with power settings between 500 and 1000 w for durations of 2 to 10 mins, employs rapid volumetric dielectric heating to instantaneously carbonize the orange peel extract. this technique results in slightly larger cqds, ranging from 4 to 8 nm, with a higher quantum yield of up to approximately 54%, excellent fluorescence as well as a process that is both environmentally friendly and cost-effective. however, this method is associated with less precise size control and necessitates post-process purification. consequently, hydrothermal autoclaving is most suitable when uniform, well-defined cqds of controlled morphology are essential as well as when the processing time and cost are less critical, particularly in contexts such as material characterization, device fabrication or academic studies. conversely, microwave-assisted methods are preferable when speed, simplicity, high yield and adherence to the principles of green chemistry are sought, making them suitable for applications involving rapid prototyping, sensing, bioimaging or scalable production from orange peel waste. the optical characteristics of cqds were investigated through the use of fluorescence and uv absorbance spectroscopy. the ph was found to be roughly 4.3 in the absence of a buffer, moreover, both cqds and ncqds exhibited an absorbance peak at 412 nm. because of the interaction with orange peel, the ph was modestly acidic when the buffer was added. the uv absorbance and fluorescence spectra (shimadzu uv-1800) of cqds are shown in figure 6. the absorbance spectra are represented on the y-axis, while the wavelength is shown on the x-axis. the changes in uv-vis absorption seen in this graph demonstrate a clear ph-responsive behavior of cqds made from orange peel showing a progressive redshift and increasing absorbance as the ph rises from 4 to 10. at acidic ph, the absorption peak is approximately 429 nm and of lower intensity, whereas at alkaline ph, it shifts to around 445 nm with a significantly higher level of absorbance. this pattern is associated with the deprotonation and protonation that occur on surface functional groups, namely -oh, -nh₂ and -cooh, which modifies the optical transitions of the cqds by altering the π‑conjugation and electron distribution inside them. such consistent and tunable changes in absorption suggest that orange peel-derived cqds are well suited for use as colorimetric ph biosensors. by calibrating the peak wavelength or absorbance intensity against specific ph values, the ph of unknown samples can be accurately assessed. potential applications include environmental monitoring (e.g. soil or water quality), wound-care sensors and foodfreshness indicators, wherein visible spectral shifts provide simple, non-invasive readouts. therefore, this experiment validates the viability of orange wastederived cqds as eco-friendly, cost-effective and sensitive ph probes with a broad range of applications in the biomedical, environmental and smart-packaging industries. both undoped cqds and ncqds made from orange peel exhibit distinct ph-dependent wavelength alterations as shown in table 1. cqds exhibit a clear monotonic redshift as the ph rises from 4 to 10; the absorbance peak wavelength shifts from 429 nm at ph 4 to 435 nm at ph 7 and then 445 nm around ph 10. ncqds, on the other hand, exhibit a subtler trend with peak wavelengths shifting from 414 nm at ph 4 to 412 nm at ph 7 and then slightly decreasing to 409 nm at ph 10. these results indicate that the protonation-deprotonation of surface amine and carboxyl groups influences their electronic structure in various ways. figure 6: absorbance spectra of cqds at various phs, illustrating their sensitivity to ph changes tawade, thakre, ravikumar, shende and wasewar hungarian journal of industry and chemistry 98 the larger δλ observed with regard to cqds suggests a more responsive optical reaction to ph changes, making them particularly effective as ph biosensors. calibration graphs relating wavelength to ph could thus facilitate quick, non-invasive measurements. meanwhile, ncqds exhibit a lower level of sensitivity but greater signal stability and enhanced quantum yield as a result of nitrogen-induced auxochromes that improve fluorescence brightness and suppress non-radiative losses. importantly, both types of dots are synthesized via eco-friendly, water-based methods from orange peel waste, avoiding the use of heavy metals and in accordance with the principles of green chemistry. in practical applications, cqds are well suited for tasks requiring high ph sensitivity and a wide dynamic range such as in water quality monitoring or ph-responsive indicator strips, whereas ncqds are better suited for environments demanding consistent signal performance such as in prolonged bioassays or intracellular ph imaging. 4. conclusions in this study, both hydrothermal and microwave-assisted (microwave / solvothermal) methods were employed to successfully create cqds and ncqds from orange peel using environmentally acceptable, waste-derived resources. characterization through uv-vis spectroscopy at ph levels of 4, 7 and 10 showed that both cqds and ncqds display ph-responsive optical properties, making them suitable low-cost, non-toxic, environmentally-friendly ph biosensors. importantly, cqds exhibited a significant and consistent redshift in absorbance peak wavelength as the ph increased, providing a substantial and clear δλ between ph levels that enhances sensitivity. in contrast, ncqds displayed minimal or decreasing wavelength shifts, likely due to amine-functional surface groups balancing out their response. both types benefit from the eco-sustainability of using orange peel as a precursor, employment of water-based production methods and the absence of hazardous chemicals. however, cqds are particularly advantageous for applications that require a wide range of dynamics and clear spectral differences across a range of ph levels. ncqds, with their enhanced stability and fluorescence efficiency, might be more suitable in applications where signal durability is prioritized over sensitivity. in summary, both cqds and ncqds show significant promise as biosensors: cqds are superior when sensitivity and clear signal are essential, while ncqds are preferable in scenarios that require photostability and durability. references [1] zhang, z.; wu, l.; wang, p.; zhang, y.; wan, s.; guo, x.; jin w.; zhang, j.: carbon quantum dots modified la2ti2o7 nanosheets for visible light photocatalysis, mater. 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revised: 15 oct 2022; accepted: 15 oct 2022 *correspondence: naron@f-labor.mkt.bme.hu one of the most effective methods for combating environmental degradation mainly as a result of petroleum hydrocarbons, which pose a significant danger to ecosystems. this includes bacteria that use toxic materials as carbon sources, resulting in the breakdown of polluted components into low-molecular-weight or less harmful chemicals with no adverse effects [9]. biosurfactants can decrease the surface tension of water to between 35 and 27 mn/m, which has been recorded by biosurfactant-producing bacteria [10]-[11], as well as increase the emulsifying activity from 20 to 30% for different hydrocarbon compounds during experiments on the emulsification index. a ccd was used to create appropriate testing levels for our response surface methodology (rsm). this analysis will create relevant parameters by making observations or taking measurements to determine the best combination of media that produces the desired response as well as characterizing the reaction so the conventional medium optimization strategy of modifying one independent variable while keeping the rest constant can be applied [12]. the main aim of our research is to produce biosurfactants to study their antifungal effects on crops in agriculture. therefore, the first step is to produce biosurfactants efficiently. for this purpose, media optimization is commenced by using statistical optimization for cell growth in the fermentation broth to https://doi.org/10.33927/hjic-2022-18 mailto:naron@f-labor.mkt.bme.hu sakiyo and németh hungarian journal of industry and chemistry 52 increase the biosurfactant yield, i.e. decrease the surface tension and increase the emulsification index of the biosurfactant produced by bacillus licheniformis dsm13. 2. materials and methods 2.1. microorganism and cultivation of strain the bacillus licheniformis dsm13 strain was purchased from hungary's national collection of agricultural and industrial microorganisms. the biosurfactant fermentations were conducted in 500 ml shake flasks (erlenmeyer flasks with cotton plugs covered with aluminum foil). the inoculum was incubated for two days at 150 rpm and 37°c in a rotary shaker (new brunswick excella e24) by applying an inoculation ratio of 10 %. during the biosurfactant fermentation, the starting total volume, including the inoculum, was 150 ml, with an aeration greater than the working volume. for the biosurfactant fermentation, a minimal medium was used; 1 liter of minimal media (ph=6) contained 1.0 g nh4no3, 34.0 g glucose (hungrana kft., szabadegyháza, hungary), 6.0 g kh2po4, 2.7 g na2hpo4, 0.1 g mgso4*7h2o, 1.2x10-3 g cacl2, 1.65x10-3 g feso4*7h2o, 1.5x10-3 g mnso4*4h2o and 2.2x10-3 g na-edta (reanal laborvegyszer kft., hungary) joshi et al. [13]-[14]. 2.2. unoptimized (reference) fermentation scale-up tests were conducted in a 1 l benchtop fermenter biostat q bioreactor (b braun co) filled up to 700 ml. during batch fermentation, the temperature was maintained at 37°c, the agitation rate at 300 rpm and the aeration rate at 0.5 vvm without ph control. a collection vessel was added to the exhaust air of the fermenter to collect the foam produced during the fermentation. 2.3. statistical analysis of ccd (rsm) for optimization using a ccd for two variables, the power of the response surface approach to maximize biosurfactant production by bacillus licheniformis was investigated in this study, which has served as the foundation for the simulated experimental plan and subsequent analysis. the randomized empirical findings were statistically analyzed using the statistical program tibco statistica (version 13 for windows) to detect the significant differences between the independent variables, namely (a) glucose concentration between 10 and 36 g/l and (b) ph between 4 and 9, to achieve maximum biosurfactant production by b. licheniformis dsm13 (table 1). 2.4. biomass analysis a camspec m501 spectrophotometer was used to determine the biomass content via optical density measurements at a wavelength of 600 nm (od600). 2.5. surface tension analysis surface tension is the force per unit length measured in millinewtons per meter (mn/m). the surface tension was measured using a stalagmometer (wilmad-labglass lg-5050-100) according to the method of czinkóczky et al. [11]. 2.6. ph analysis initially, the ph of the media was set by adjusting it to several ph values ranging from 4 to 9 with 5m hcl or 6m naoh. the ph was measured by a mettler toledo fiveeasy™ ph meter. 2.7. emulsification index (e24) the emulsification index measurement applied was established by plaza et al. [15]. the emulsification index was determined from the supernatant of the fermented broth at intervals corresponding to the sampling frequency during the fermentation. in a test tube, 2 ml of crude oil and 2 ml of cell-free media (supernatant) were introduced and homogenized for 2 minutes by vortexing at 4000 rpm. the emulsifying activity was once more determined after 24 hours as follows: the relative height of the two liquid layers was documented by photos and the pixel size divided to obtain the values of the emulsification index [16]. e24 (%) is defined as [(total height of the emulsified layer) / (total height of the liquid layer) x 100] after 24h of vortexing. table 1. ccd runs showing factors and their levels standard run 2**(2) central composite, nc=4 ns=4 n0=2 runs=10 glucose [g/l] ph 3 34.00 5.00 8 20.00 9.83 1 10.00 5.00 6 36.97 7.00 7 20.00 4.17 2 10.00 9.00 5 3.03 7.00 4 34.00 9.00 10 (c) 20.00 7.00 9 (c) 20.00 7.00 bacillus licheniformis for biosurfactant production 50(2) pp. 51–55 (2022) 53 2.8. isolation and purification of the biosurfactant acid precipitation was used to isolate the biosurfactants. the bacterial cells were first removed by centrifugation and the remaining supernatant containing the biosurfactant was acidified with 2m hcl solution until the ph reduced to 2. the mixture was then incubated at 4 °c for 24 hours. the precipitate was collected by centrifugation at 10,000 rpm and 4°c for 30 minutes. the residue was then resolved in distilled water and the ph reset to neutral before being freeze-dried by a martin christ alpha 1-4 lscbasic lyophilizer [13]. 3. results 3.1. unoptimized (reference) fermentation an unoptimized fermentation according to section 2.2. was carried out and the parameters that were measured during the process are shown in fig.1. the highest reduction in the surface tension (st) was observed 4 30 hours after the fermentation commenced. st ranged from 75.5 to 68.3 mn/m. after 8 hours, the foam began to overflow and was collected in a vessel for further processing. the collected foam had a st of 60 mn/m, indicating that the biosurfactants produced are mainly collected in the foam phase. 3.2. rsm the effects of the glucose concentration and ph is shown in fig.2. the highest biomass growth (od) was recorded at a glucose concentration of 40 g/l and a rather higher ph value of approximately 9 resulting in an optical density of 4.5. the mixed effect of the ph and glucose concentration regarding the surface tension is shown in fig.3. the minimum surface tension was achieved while fermenting at ph 7. according to fig.4, the smallest product amount was achieved when the ph was extremely high at 11 and the glucose concentration was the lowest, while at a higher glucose concentration, the highest product yield was still achieved. this indicates that the gradient of the surface is minimal and very high at low and high glucose concentrations, respectively; moreover, depends on the ph. therefore, the ph was the most important factor leading to an increase in the amount of biosurfactant produced. figure 1. growth, surface activity and emulsification index (e24) of bacillus licheniformis in a 1 l fermenter during growth on a mineral salt medium 0 1 2 3 4 5 6 40 45 50 55 60 65 70 75 80 0 5 10 15 20 25 30 35 o d 6 0 0 [ -] st [ m n /m ], e 2 4 [% ] time (h) surface tension emulsification index od600 figure 2. 3d rsm plot of the interactive effects of glucose concentration (g/l) and ph on biomass production sakiyo and németh hungarian journal of industry and chemistry 54 the model predicted the following ideal conditions to maximize the biosurfactant productivity using bacillus licheniformis dsm13: ph=8 and glucose concentration=40g/l. the anticipated optimum point was confirmed experimentally, moreover, the observed and isolated product was 2.7 g/l. these findings show a strong connection between the predicted and actual experimental values, moreover, this model accurately represents biosurfactant production in the presence of bacillus licheniformis dsm13. since the highest product yield (i.e. lowest surface tension, fig.3) was observed at different conditions, it is recommended to examine product purity in the future as the presence of contaminants can depend on the ph because of phdependent precipitation during product isolation. 4. conclusions biosurfactants are emerging as suitable alternatives to their predominant, less sustainable, petroleum-derived counterparts. in this study, the ccd, in conjunction with the response surface approach, is used to predict the optimization of bacillus licheniformis dsm13 effectively. an increase in the glucose concentration yielded a high biosurfactant concentration while also increasing the fermentation time. at a lower ph level, the strain achieved a low biomass yield and lower biosurfactant yield but no change in the surface tension was observed. it was observed that the best operating conditions for biosurfactant 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https://doi.org/10.1002/abio.200390043 hungarian journal of industry and chemistry vol. 52(1) pp. 9–14 (2024) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2024-02 synthesis of sugar esters using maize seed lipase as a biocatalyst salim ferdjani1* and ouassila selaimia1 1 department of chemistry, faculty of science and technology, chadli bendjedid university el tarf, el tarf, pb 73, algeria this work is devoted to the extraction of a lipase from maize seeds obtained at low cost without extensive purification technology and used as a biocatalyst in the synthesis of various sugar esters as potential biosurfactants in the detergent industry. indeed, several reactions have been carried out between different sugars namely glucose, galactose, saccharose, lyxose, fructose and sorbitol and stearic acid in a ratio of 2.5:1 in hexane at 50 °c. kinetic monitoring of the target reactions was carried out by volumetric analysis in order to determine the conversions (c). the best results obtained were c = 76, 71 and 67% in the presence of glucose, lyxose and galactose, respectively. in addition, hplc and tlc analyses revealed that for every sugar used two types of esters formed. keywords: biocatalysis, plant extract, maize seeds, sugar ester, biosurfactant 1. introduction chemicals are essential for healthy living and modern comforts, moreover, are at the heart of many industrial processes for the manufacture of important products [1]. among these products, surfactants play an important role in several fields such as in the food, cosmetics and detergent industries [2]. these applications depend on the structure of such compounds which can be anionic, cationic, amphoteric or nonionic [1]. sugar esters are non-toxic, biodegradable and nonionic surfactants [2]. their synthesis is carried out chemically, resulting in particular in the production of a significant amount of byproducts that must be eliminated, necessitating relatively high purification costs and extreme conditions amongst other drawbacks. these problems can be avoided by opting for a much more specific synthetic route based on the use of enzymes, mainly lipases [3]. these biocatalysts are widespread in animals, microbes and plants [4]. the high cost of commercial lipases, mainly of microbial origin, limits the possibility for this process to be scaled up to an industrial level [1]. as an example, for the synthesis of glucose fatty acid esters, commercial immobilized lipases (novozym 435, lipozyme rm im and lipozyme tl im) have been used as biocatalysts [5]-[6] but the purification process required as well as their immobilization, loss of activity and the high cost of these lipases are the main drawbacks for the production of such sugar esters on an industrial scale. plant biomass represents an alternative as a received: 11 nov 2023; revised: 6 dec 2023; accepted: 7 dec 2023 *correspondence: s.ferdjani@univ-eltarf.dz potential source of inexpensive lipases that are very abundant and easily exploitable [7]-[8]. indeed, seed lipases have already been used successfully in the synthesis of sugar esters [9]. this enzymatic reaction in non-conventional media continuously produces water which strongly affects enzyme activity. to maintain the reaction parameters, the water activity (aw) should remain constant [10]. in lipase-catalyzed esterification reactions, water activity is a major factor because a sufficient amount of water must be present to retain the active structure of the enzyme, however, if in excess in the reaction medium, the lipase will catalyze a competing hydrolysis reaction [11]. in addition, aw can influence the rate and equilibrium yield as well as the stability of enzymes [12]. the objective of this work is to use a plant extract from maize seeds (msl) to catalyze the synthesis of sugar esters for the first time, without using a desiccant. to date, msl has only been used in the synthesis of low molecular weight flavor esters [13]. 2. experimental 2.1. material maize (zea mays) was purchased from the local market. substrates (glucose, saccharose, lyxose, sorbitol, galactose, fructose and stearic acid) as well as solvents were purchased from sigma-aldrich, while all other chemicals and reagents were of analytical grade. https://doi.org/10.33927/hjic-2024-02 mailto:%20s.ferdjani@univ-eltarf.dz ferdjani and selaimia hungarian journal of industry and chemistry 10 2.2. general procedures the course of the reactions was followed by thin-layer chromatography (tlc) (pre-coated silica gel 60 f254 sheets manufactured by e. merck) and hexane:chloroform (1:1, v/v) was used for elution. the different spots were identified using a solution of basic potassium permanganate (10 g of potassium carbonate, 1.5 g of potassium permanganate in 150 ml of water and 1.25 ml of a 10% aqueous sodium hydroxide solution). ft-ir analysis was performed using a infralum ft-08 spectrometer and the obtained spectra were compared to those of stearic acid and different sugars. an agilent 1260 instrument as well as an agilent zorbax carbohydrate analysis column were used for the hplc analysis of all reaction mixtures and products. 2.3. lipase extraction 10 g of seeds were soaked in water for 12 h at room temperature before being collected and placed on moist absorbent paper to facilitate germination. the seeds were then spread out and covered with a second layer of cotton and watered on a daily basis. after five days, the germinated seeds were dried at room temperature then grounded with a domestic blender. the obtained seed powder was incubated and continuously stirred in 30 ml of cold acetone for 12 h. after incubation, the mixture was filtered through filter paper with a diameter of 150 μm before being washed 5 to 7 times with 20 ml of cold acetone until the solution became clear. finally, the residue was dried and the powder (crude msl) stored at 4 °c. 2.4. hydrolytic activity the assay of the lipase activity was carried out using a previously described titrimetric method [14]. in a flask, 5 g of olive oil and 2.5 ml of hexane were stirred at 50 °c for 15 mins. 1 g of the crude msl was added to the mixture and left to react for 1 h while continuously stirred. having been incubated, 25 ml of acetone:ethanol (1:1 v/v) was added to stop the reaction. a 0.1m solution of naoh was used to quantify the amount of released free fatty acids (ffas) using phenolphthalein as an indicator before the specific activity (sa) of the enzyme was calculated according to the following formula: 𝑆𝐴 = 𝑛𝐹𝐹𝐴 (𝜇𝑚𝑜𝑙) 𝑥(𝑚𝑔)×𝑡(𝑚𝑛) (1) where nffa denotes the number of moles of free fatty acids, x stands for the mass of the lipase extract and t represents the reaction time. the lipase extraction experiments and the corresponding lipase activity measurements were carried out in triplicate and the average standard deviation of which was approximately 3%. 2.5. general procedure for the esterification of sugars the sugar (glucose, galactose, saccharose, sorbitol, lyxose or fructose) and the fatty acid (stearic acid) were dissolved in 5 ml of hexane at 50 °c. having been stirred for 30 minutes, 0.375g of msl was added to the mixture. 0.2 g samples were taken from the reaction medium before adding the enzyme and every 24 h after its addition for the following 72 h. the reaction was then stopped, and the mixture filtrated using filter paper with a diameter of 60 mm to eliminate the msl before the hexane was eliminated using a rotary evaporator. the amount of unreacted fatty acids was determined by titration according to the following procedure: 0.2 g of the reaction mixture was diluted in 5 ml of a 0.1% solution of phenolphthalein in ethanol. a 0.1 m solution of naoh was then added until a pale pink color was observed. the conversion (c%) was calculated according to the following formula: c% = (vi−v)×[naoh] nsa × 100% (2) where vi denotes the volume of naoh consumed during the reaction before the enzyme (control) was added, v stands for the volume of naoh consumed during the different reactions at different intervals after adding the enzyme, [naoh] represents the concentration of naoh and nsa refers to the molar quantity of stearic acid. all esterification reactions and the corresponding conversion measurements were repeated twice. 3. results and discussion 3.1. lipase extraction although lipases are widely distributed within plants, they are found mainly in seeds, which are generally rich in triacylglycerol that serves as an energy source for the newly emerging plant. during germination, the lipid reserves in the albumen or cotyledons of these seeds begin to disappear since the lipase facilitates the hydrolysis of these nutrient reserves. indeed, during germination, lipase activity is high [15]. in this work, maize seeds were used as a source of lipase and the enzyme extract was obtained after five successive steps, namely soaking in water, germination, drying, crushing and then defatting [14]. the filtration residue of the defatted maize seeds was dried at room temperature before being stored at 4 °c. this msl was used for the synthesis of sugar esters. 3.2. hydrolytic activity the hydrolysis test was carried out in the presence of the prepared msl using olive oil as a substrate according to the protocol described in the experimental section. the msl had a specific activity of 0.0015 ui/mg under the synthesis of sugar esters using maize seed lipase 52(1) pp. 9–14 (2024) 11 used operating conditions. it should be noted that a reaction was carried out under the same conditions in the absence of the enzyme but no hydrolytic activity was observed. 3.3. choice of operating conditions many studies have been carried out to determine the ideal conditions for the synthesis of sugar esters by primarily focusing on the sugar:acid molar ratio, type of the solvent, nature and amount of the enzyme as well as temperature [16]. many articles on the synthesis of enzymes have focused on glucose fatty acid esters and especially glucose stearate using stearic acid as a natural fatty acid [17]. it has also been reported that the best solvents used in this biocatalysis are tetrahydrofuran, acetone, tert-butanol and n-hexane [16],[18]. the optimum temperature of the msl is 50 ℃ according to [19]. the quantity of msl used in this work (figure 1) was 0.375 g in accordance with the optimized amount used in a previous work (data not shown). according to the literature, esterification reactions are carried out using different sugar:acid molar ratios [16]. therefore, in order to determine the best molar ratio, three reactions were performed as a starting study. the first one was performed with equimolar quantity of the two reactants (1:1), the second with a small excess of sugar (1.25:1) and the third with a small excess of acid (1:1.25) all at 50 ℃ in hexane in the presence of 0.375 g of msl. the obtained results (table 1: entries 1-3) indicate that the conversion progresses from 17% after 24 h to 64% after 72 h when the 1.25:1 molar ratio was applied. on the other hand, for the other reaction with an excess of acid, a maximum conversion rate of 54% was reached after 48 h. the results with an equimolar quantity of the two reactants, namely 1:1, were no better than in the case of the 1.25:1 reaction. 3.4. effect of temperature to determine the ideal temperature for this synthesis, three reactions were carried out with the molar ratio of 1.25:1 at 30, 40 and 60 °c (table 1: entries 4-6). the conversions obtained were compared to those at 50 ℃ (table 1: entry 2). the results show that the conversion of stearic acid in the reaction carried out at 50 ℃ was better than in the other reactions, so the ideal temperature expected for this synthesis is 50 ℃ [19]. 3.5. effect of the sugar:stearic acid ratio according to the results obtained previously concerning the effect of the molar ratio, a slight excess of sugar yielded better conversion rates. therefore, a reaction with a greater excess of sugar was studied. for this purpose, the synthesis of glucose stearate was carried out with molar ratios of sugar:stearic acid of 2:1, 2.5:1 and 3:1 at 50 ℃ in hexane (table 1: entries 7-9). the best results were obtained when using a ratio of 2.5:1, when the conversion increased from 50% after 24 h to 76% after 72 h. a larger excess of sugar seems to affect the enzyme activity. these results suggest that the ideal conditions for the synthesis of sugar esters are 2.5 eq. of sugar, 1 eq. of stearic acid and 0.375 g of msl in hexane at 50 ℃. 3.6. synthesis of sugar esters and kinetic study this reaction occurs between stearic acid and various sugars namely glucose, galactose, saccharose, lyxose, fructose and sorbitol catalyzed by msl whilst being stirred by a magnetic stirrer in hexane at 50 °c (figure 2). the reactions were monitored by a volumetric analysis (see the experimental section). during the different reactions, samples of the reaction mixture were taken every 24 h in order to follow the esterification by a volumetric analysis with a basic 0.1m naoh solution to determine the amount of unreacted acid and, therefore, calculate the conversion. the kinetic monitoring of these esterification reactions catalyzed by msl in hexane and the conversion obtained for the different reactions are shown in figure 3. the time dependence of esterification reactions over 72 h is shown in figure 3. the conversions of stearic acid gradually increase over time. during the first 24 hours, the initial rate is faster for the esterification table 1: effect of different reaction conditions on the conversion entry molar ratio (glucose:stearic acid) t (°c) conversion (%) 24h 48h 72h 1 1:1 50 18 54 59 2 1.25:1 50 17 58 64 3 1:1.25 50 32 54 54 4 1.25:1 30 15 30 35 5 1.25:1 40 17 40 41 6 1.25:1 60 20 49 51 7 2:1 50 33 61 70 8 2.5:1 50 50 74 76 9 3:1 50 43 62 68 figure 1: synthesis of glucose stearate reaction conditions: d-glucose:stearic acid (different molar ratio), 0.375g of msl in 5 ml of hexane at different temperatures figure 2: esterification of sugars with stearic acid in the presence of msl reaction conditions: 2.5 eq. of sugar, 1 eq. of stearic acid, 0.375g of msl and 5 ml of hexane at 50 °c ferdjani and selaimia hungarian journal of industry and chemistry 12 with glucose compared to with the other sugars. after 24 h, the reaction rate gradually increases to reach a maximum conversion. except for lyxose, the reactions reach equilibrium after approximately 48 h. even though these are multiphase reactions with difficult mass transfers, organic solvents reduce the activity and stability of lipases. after 72 hours, the best conversions of 76, 71 and 67% were obtained with glucose, lyxose and galactose compared to 51, 38 and 37% with saccharose, sorbitol and fructose, respectively. furthermore, no correlation was observed between the sugar structure and the obtained conversions. it should be noted that for each synthesis carried out previously with the different sugars, the reaction was performed in the absence of an enzyme and no conversion was observed. 3.7. tlc analysis according to the literature, mono-esters of sugars have been identified by this method with a frontal ratio of approximately 0.50 using a mixture of hexane and chloroform in a ratio of 1:1 as an eluent [20]. for all the reactions, the tlc plate analyses indicate the formation of two new products which are the expected mono-esters with an rf of 0.50-0.59 [20] and probably sugar di-esters. since the latter are less polar, their rf are between 0.84 and 0.90 (table 2). the general profile of the different chromatograms is illustrated in figure 4. according to a study by cao et al. [21], selectivity is often considered to be the main advantage of the lipasecatalyzed syntheses of sugar esters. it has been observed that selectivity is influenced by the type of lipase, sugar structure, organic solvent, fatty acid chain and solubility of the products in the liquid phase. the probable positions of esterification of the used sugars [2, 21-24] are shown in figure 5. the ir spectra of the different products display an absorption band at 1740 cm-1 attributed to the carbonyl group of the ester, indicating the formation of sugar stearates [25]. interestingly, by monitoring the different esterification reactions by hplc, the production of two new compounds for all the reactions is clearly indicated (data not shown). the identification of these esters, especially the di-esters, that is, the position of the ester bond, is under investigation. 4. conclusions the facile extraction of lipase from maize seeds was used to catalyze the esterification of stearic acid in the presence of different sugars, namely glucose, galactose, figure 3: kinetic monitoring of the different esterification reactions in the presence of msl (c% = f (t)) figure 4: thin-layer chromatography for the reaction between galactose and stearic acid lanes (s), (a) and (r) correspond to the sugar used, stearic acid and the reaction mixture, respectively table 2: frontal ratios rf of the formed monoand di-esters (1 and 2) sugar rf glucose 𝑅𝑓1 = 0.57 𝑅𝑓2 = 0.92 galactose 𝑅𝑓1 = 0.58 𝑅𝑓2 = 0.90 saccharose 𝑅𝑓1 = 0.52 𝑅𝑓2 = 0.88 lyxose 𝑅𝑓1 = 0.59 𝑅𝑓2 = 0.87 fructose 𝑅𝑓1 = 0.51 𝑅𝑓2 = 0.84 sorbitol 𝑅𝑓1 = 0.54 𝑅𝑓2 = 0.85 glucose galactose saccharose lyxose fructose sorbitol figure 5: preferred positions of esterification for the different sugars synthesis of sugar esters using maize seed lipase 52(1) pp. 9–14 (2024) 13 saccharose, lyxose, fructose and sorbitol. a preliminary study was carried out in order to determine the right reaction conditions for the synthesis of sugar esters, that is, a molar ratio of sugar:acid of 2.5:1 at 50 ℃ using hexane as an organic solvent. the kinetic monitoring of target reactions by volumetric analysis facilitated the determination of the conversions for the various prepared sugar esters. indeed, the best conversions of 76 and 71% were obtained for glucose and lyxose, respectively, after a reaction time of 72 h. in addition, tlc and hplc analyses suggested the formation of monoand di-esters for all sugars used. the results showed that the extract of maize seeds contains one or more lipases, the catalytic activity of which can be exploited without prior purification for the synthesis of sugar esters. despite the advantages of the enzymatic route, it remains a challenge to convince manufacturers of these interesting biotechnological properties in order to substitute the chemical route with the enzymatic one. references [1] le guenic, s.; 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zhang, j.; zhao, a.; ma, x.: study of glucose ester synthesis by immobilized lipase from candida sp., catal. commun., 2008, 9(6), 1369–1374, doi: 10.1016/j.catcom.2007.11.036 https://doi.org/10.3109/10242429809003620 https://doi.org/10.1080/10408398.2020.1798346 https://doi.org/10.1016/j.molcatb.2009.02.014 https://doi.org/10.3109/21691401.2012.743899 https://doi.org/10.1016/j.catcom.2007.11.036 hungaru\njournal of industrial chemistry veszprem vol. 30. pp. 137142 (2002) study on the turbulence in pulsed stagewise extraction columns: turbulent macroscale g. angelov and c. gourdon1 (institute of chemical engineering, bulgarian academy of sciences, acad. bonchev st., bl. 103, 1113 sofia, bulgaria 1ecole nationale superieure d'ingenieurs en arts chimiques et technologiques, toulouse, france) received: february 06, 2002 the authors studied a particular turbulent parameter turbulent macroscale, which characterizes the size of large energy containing eddies, and it is one of the basic parameters with essential role in the concept of turbulent motion. pulsed turbulent liquid flow in stagewise column type apparatuses with internals of disks and rings is considered. the distribution of turbulent macroscale l over the stage is determined as depending on stage geometry and re number. · insignificant changes of l are registered in the course of pulsation cycle. similarly, the dynamic flow parameters, expressed by the value of re number, pulse amplitude and frequency, demonstrate slight and not pronounced influence on the size of turbulent macroscale. most important effect on l has the stage geometry with pronounced influence of interplate distance and lesser dependence on plate free area. it was found that the zones of large l-values correspond to zones of intensive drop breakage, located experimentally. a correlation is proposed for determination of the mean value of turbulent macroscale as a function of stage geometry parameters. comparison with other correlations is made along with discussion on their advantages and inconveniences. keywords: plate extraction colunms,-flow hydrodynamics, pulsed flow, turbulen~l!lacroscale introduction as known from practical experience, the turbulence increases the efficiency of transfer processes. many chemical apparatuses operate under turbulent flow regimes, although in most cases they are empirically tuned. studies on turbulent flows are helpful for understanding and quantification of the influence of turbulence on process intensification. this paper focuses on a particular turbulent parameter turbulent macroscale. it characterizes the size of energy containing eddies and is one of the basic parameters with essential role in the concept of turbulent motion. as far as the energy containing eddies produce larger interphase contact surface by dispersing greater drops to smaller droplets, it is worthy to study them through the behavior of their characteristic parameter. turbulence model the expression for turbulent macroscale is derived applying dimensional analysis with assumption that the amount of dissipated turbulent energy is determined by the energy containing large-scale motion at high re numbers [1,2] l=cjs2!3:... £ (1) where l is turbulent macroscale characterizing the size of the large energy containing eddies, k is the kinetic energy of turbulent motion per unit mass, e is the dissipation rate of kinetic energy, cl is an empirical constant of order of unity [1]. regarding eq.( 1 ), larger l-value means higher kinetic energy with respect to its dissipation rate. consequently, larger turbulent macroscale means larger level of non-dissipated energy that can provoke drop breakage, respectively, increase of the interphase surface. thus, the zones of higher values of l should be expected to be places of drop breakage and interface surface production. it is seen from eq.( 1) that l depends on the ratio of two other terms kinetic energy and its dissipation rate (k and e). their distribution over the flow field can be derived from their transport equations, included in the standard ke model of turbulence {2}. 138 ::. 1_<:: p:•' r "?:: ,d h 'f' i..,j~ n: n. a) b) c) fig.] apparatus scheme: a) internals axonometry; b) general column scheme; c) limits of simulation domain where u; is the mean velocity vector, v kinematic viscosity, vtturbulent viscosity, x space coordinate, c,., c~<> c8, c,r, c82 are constants of the model taking standard values, recommended in the relevant literature [3]. in previous papers [ 4,5] we have reported in details the full set of model equations ~or the considered case along with the method of resolution and boundary conditions for the particular apparatus geometry described below. so, adapted ke model equations are resolved in order to determine the distribution of l. apparatus description the turbulent macroscale l is studied in case of stagewise pulsed columns (fig.l) with .internals of discs and rings (called also discs and doughnuts column [6j). this apparatus design has shown great performance in various solvent extraction applications [7-10] and is produced in large scale for industrial applications [11]. immobile discs and rings are alternately placed at equal distance in cylindrical column body forming a · series of identical stages. the turbulence is enhanced by a piston like mechanical device inducing osciuati 1g motion to the fluids. as should be expected, the geometrical periodicity creates flow periodicity along the column. previous experimental hydrodynamic studies have shown that in n~ality the flow picture is repeatedly reproduced on the adjacent stages. and flow symmetry with respect to column axis exists [12}. so, a typical flow pattern is observed in the vertical cross~section of a stage limited by the column wail. and two rings {fig.jc). the stage geometry is defined by two dimensionless parameters: the ratio of interplate distance h and column diameter de bounds the stage height to column size h=hfdc (4) the ratio of plate cross-section open to flow sp and column cross section sc defines the plate free area e e= spl sc =d/ i d/ = (d/-di) i d/ (5) the free area of both plate configurations disc and ring, is taken equal as practiced in the real drc design. results and discussion the results for turbulent macroscale l are obtained by simulation of incompressible newtonian liquid flowing in a typical stage at various flow regimes and variable stage geometry. their effect on turbulent macroscale l is registered and discussed below. evolution of turbulent macroscale during a pulsation cycle the pulsation created by a piston device corresponds to periodic sinusoidal pulsation described by the expression u(t) = napf cos(2nft) (6) where u(t) is the superficial velocity of pulsed flow at the instant t, ap is pulsation amplitude, f = 1/t is pulsation frequency, t is the period of pulsation. the results show that turbulent macroscale l is slightly changed during the pulse period t. for example, the maximal values of l at two moments of the pulsation corresponding to rather different instant flow velocities (tff = 0 maximal velocity and tff = 0,2 flow velocity approaches zero) are changed from 3,8.10-2 m to 4,1.10"2 m. it can be conclude'd that the value of the turbulent macroscale l does not depend significantly on the instant flow velocity during the pulsation cycle. influence of flow regime the above result implies that the flow regime in the apparatus should not affect pronouncedly the turbulent macroscale. this suggestion is verified below. the mean flow regime is defined by renumber ud re=~ v (7) where um is the mean superficial flow ·velocity; v is kinematic viscosity. integrating eq.(7) over a period of pulsation, the mean flow velocity is obtainr.d 0.05 .--------------~ 0.04 e. --' <ll ~ 0.03 § ro e -5i 0.02 :; .0 :; f0.01 0.00 -t-----.-----,------1 4000 8000 12000 16000 . renumber fig.2 influence of re number on turbulent macroscale l: • lmax (h=0,155; f=0,43); 0 lm (h=0,155, f=0,43); e lmax (h=0,086; f=0,23); 0 lm (h=0,086; f=0,23) and eq.(7) becomes re= 2a fd p c v (8) (9) in this study, re number of a water flow has been var~ed from 5 000 to 15 000. it corresponds to pulse regimes with different intensity of the turbulence from unstable transition regimes at lower re to established turbulent regimes at higher re xalues [13]. fig.2 represents maximal (lmax) and mean (l,j values of turbulent macroscale on the stage as depending on re number. the results illustrate two e~treme s~ge configurations . smaller interplate distance with small plate free area and larger interplate distance with large plate free area. it is seen that in all ~ases the flow regime has slight and not pronounced mfluence on the size of turbulent macroscale. similar weak influence was observed by aoun et al. [6] that have reported a correlation for l with small power tenns for the quantities a, and f. on the contrary, the curves on .pig.2 indicate qualitatively for stronger influence of the stage geometry on both mean and maximal l-values. influence of stage geometry the range of variation of geometry parameters in this study is plate free area e = 0,2 0,5 interplate distance to column diameter ratio h = 0,08 -0,4 the above values have been selected by practical considerations [14]. for example, a direct vertical flow through the colunm will reduce apparatus efficiency due to axial mixing phenomena. to avoid it, the disc 139 ; : : ; : : : : ~ ~ :: ~ .! ! ; ~ ; ; t !: ! ~ ~ 1 ~ '""' "'~: '<~ ~ .-~ .. .., " fig.3a size and distribution of turbulent macroscale lon stages at same interplate distance and different plate free area e: e=0,23; linax= 3,8.10-2 m; l!llli!l'li!ili2,5.10-2 <l<3,5.10-2 m; 3,5.10.2 < l < 3,8.10-2 m ..• ·~.., .. • ~~. ~ "' \'j ·• " 1) ", r ,, ' ' ' . .. fig.3b size and distribution of turbulent macroscale lon stages at same interplate distance and different plate free area e: e = 0,43; lmax = 4,1.10-2 m; -2,5.10-2 < l < 3,5.10-2 m; -3,5.10'2 < l< 4,1.10-2 m diameter dr should not be smaller than ring aperture dr­ the above requirement limits the possible upper value of e to 0,5, at which dr= dd. influence of plate free area the distribution of l on the stage is shown for a lower and a higher value of the free area at fixed interplate distance h (fig.3). it is seen that in case of small free area, the zones of high l-values are smaller in volume and are fou1ld in both parts of the stage over and under the disk. in case of large free area, the zones of high l­ values become larger. however, the zone under the disk bas disappeared. the maximal values of l in these two cases are rather similar, i.e. there are no significant changes in the turbulent macroscale due to plate free area, only the volume and location of the zones are affected. · influence of interplate distance fig.4 illustrates the case of different interplate distance h at fixed plate free area. lt is seen that the interplate distance affects strongly the volume and the maximal values of the turbulent macroscale. when doubling the interplate distance, l increase significantly, the maximal 140 figaa size and distribution of turbulent macroscale l on stages at same plate free area and different interplate distance h: h:=;0,086; lmax = 1,9.10"2 m; -1,5.10-2 <l< 1,9.10-2 m l-value is increased as much as twice, and the zones of high l-values become much larger in volume. the conclusion is that the interplate distance is the most important parameter controlling the size of turbulent macroscale. the results of figs. 3 and 4 refer to ascending (down to up) flow. the picture for the descending phase of the pulsation is symmetrical with respect to disk the marked zones take mirror positions on the other side of the disk. in all cases, larger values of turbulent macroscale are located in the median zones between the disk and respective ring. the experimental observations [15] in a column of same geometry have shown that namely these median zones in the stage are places of intensive drop breakage. this fairly good correspondence of modeling and experience attributes more reliability to the simulation results obtained here. correlation development summarizing the influence of geometry and dynamic parameters. the following general tendencies have been put in evidence: the dynamic parameters ap and f (re) have negligible influence on l; the turbulent macroscale rises when increasing the interplate distance or/and plate free area; the influence of interplate distance on l is stronger than that of plate free area. additional considerations are taken into account in the development of corresponding correlation: ~ when plate free area e approaches 1 case of hollow column. no matter the value of h. l should tend to a value lo corresponding to hollow column; the interpiate distance parameter h =hide shm·ld control l when h s 1 • i.e. until the interplate distance is smaller than the column diameter. at interplate distance larger than column diameter. the latter becomes the limiting geometry dimension and the influence of h should diminish. an expression translating these tendencies has been developed fig.4b size and distribution of turbulent macroscale lon stages at same plate free area and different interplate distance h: h = 0,155; lmax = 3,8.10-2 m; -1,5.10-2 < l < 2,5.10-2 m; llllllllliii2,5.10-2 <l<3,5.10.2 m; -3,5.10-2 <l<3,8.10:2 m the unknown empirical terms have been identified by a procedure based on gauss-newton algorithm, using the mean space and time values (lm) of computed discrete values of turbulent macroscale at various geometry parameters: djlo=22,38; a= 1,49; 13 = 0,48 comparison with existing correlations for a hollow column, brodkey [16] has proposed the expression (subscript o designates the terms in a hollow column) (11) from eqs.(l) and ( 11) it is derived k 312 d lo~-0-=_c sa 8,8 (12) this result shows also, that the turbulent macroscale in a hollow column depends only on column diameter and is independent on flow regime (re). our correlation (10) can provide the value of lin a hollow column. in this limit case, the free area e becomes equal to 1 and eq.( 1 0) is reduced to djl., = djlo = 22,38 from where (13) the results (12) and (13) are of the same order. their similarity could be considered as relatively good, accounting that the empirical coefficient cl in (1) has been taken approximately equal to 1. more fine coincidence is found applying another approach. the friction velocity in the wall zone ur is bound to the kinetic energy and its dissipation rate by the equations [1,2] (14) e=u/!ckl from (14) and (15) it is obtained (15) (16) in the above relation ck = 0,41 is von karman constant [2], c'" = 0,09 is standard constant of k-£ turbulence model [3]. applying eq.( 16) for hollow column with use of our result for lo (13), it follows eo= 8,9 k 312 d o c (17) comparing eq.(l7) to the relation of brodkey (11), encouraging similarity is seen. aoun et al. [6] have proposed the correlation (18) with the following values of the empirical coefficients: a=8,4.10-2 ; b=0,27; c=0,31; d=-0,05; g=-0,05 the above values show relatively weak dependence of lm on the pulsation parameters ap and f. this is close to our observations that allowed us to develop a simpler correlation excluding the participation of dynamic terms. regarding the free area term e in (18), its influence is even more important than that of interplate distance. in our opinion, the main parameter defining the space where the vortices can develop and extend to the available geometry limits, is the interplate distance and not the plate free area. for this reason, it seems more logical to expect stronger influence of the interplate distance as we have registered, studying the stage distribution of l. this dependence is clearly reflected by the correlation (10). unfortunately, correlation (18) cannot be unconditionally applied for parameter values outside the particular studied range, which is approximately the same as our parameter range. for example, the increase of h will produce unlimited rise of lu,. it is known, however, that the size of eddies is limited by the column diameter when interplate distance is too large. in the considered case of hollow column, the influence of dynamic parameters still remains, which is in conflict with relation (11) and its result {12). nevertheless, if assume for hollow column case h=l and e=l, eq.(ib) produces for lo values around 0,04dc, which is close to our result (13). in case of various stage geometry parameters, correlations (10) and (18) give rather similar results although their different structure. conclusions the turbulent macroscale l of a pulsed liquid flow in stagewise column apparatuses with internals of discs and rings was studied by use of k~e model of turbulence. 141 the local distribution of l on the stage is thoroughly studied as a function of flow regime and stage geometry parameters. small variation of l during the pulsation cycle is registered, i.e. the size of large eddies does not depend on the instant superficial flow velocity changes during the pulsation. similarly, low dependence ofl on renumber, pulse amplitude and frequency is observed. strong influence of the geometry parameters on l was found, not too pronounced for the plate free area, but rather significant as regarding the interplate distance. the zones of high values of turbulent macroscale are located. they correspond in position to the zones where intensive break-down of drops has been experimentally observed. , this fact attributes reliability to the results obtained. a correlation for determination of mean value of turbulent macroscale is proposed that reflects adequately the influence of main process parameters. acknowledgements the study is carried out with partial financial support from cnrs france and bulgarian academy of sciences. symbols ap pulsation amplitude, m ell, cb c,, ceh c,2 standard constants of k£ turbulence model, ck von karman constant, de column diameter, m dd disc diameter, m dr ring diameter, m e plate free area,£ dissipation rate of turbulent kinetic energy, m2s-3 f pulsation frequency, s·1 h interplate distance, m h ratio of interplate distance and column diameter, ~ k turbulent kinetic energy, m2s-2 l turbulent macroscale, m lm mean value of turbulent macroscale, m lmax maximal value of turbulent macroscale, m lo turbulent macroscale for hollow column, m v kinematic viscosity, m2s·1 v1 turbulent viscosity, m2s-1 re reynolds number, sp plate cross-section open to flow, rrt sc column cross section, m 2 t time, s t period of pulsation, s ur friction velocity, ms1 ui mean velocity vector, ms-1 u mean superficial flow velocity, ms"1 m ~ u(t} flow superficial velocity at the moment t, ms x space coordinate, m 142 references l rodi w.: introduction to modeling of turbulence, von karman institute, karlsruhe, 1985 2. schiestel r.: modelisation et simulation des ecoulements turbulents, hermes, 1993 3. launder b. e. and spalding d. b.: comp. meth. in appl. mech. eng., 1974, 3, 269-289 4. angelov g. and gourdon c.: hung. j. ind. chern., 1997,25, 223-228 5. angelov g. and gourdon c.: hung. j. ind. chern., 1999,27,281-286 6. aoun nabli m. s., guiraud p. and gourdon c.: trans. icheme, 1998,76,951-960 7. milot l f., duhamet j., gourdon c. and casamatta g.: chern. eng. sci., 1990, 45 111116 , 8. haunold c.: extraction of pyrethrines modeling and development of a continuous process, ph.d. thesis, inp-toulouse, 1991 9. hanssens a.: scale-up in diameter of pulse columns, summer school on liquid extraction, toulouse, 1991 10. ngamprasertsith s.: solvent extraction of vegetable materials in a discs and rings column, ph.d. thesis, inp-toulouse, 1993 11. bateman: pulsed columns making solvent extraction work better, www.bateman.co.za presented at technical exhibition, int. solvent extraction conf., barcelona, 1999 12. angelov g., journe e., line a. and gourdon c., chem. eng. j., 1990, 45, 87-97 13. oh w. z.: hydrodynamics of a pulsed column with discs and rings study of velocity field ph.d. thesis, inp-toulouse, 1984 14. angelov g., gourdon c. and line a.: chem. eng. j., 1998,71, 1-9 · 15. laulan a.: hydrodynamics and drop breakage in a pulsed column with disks and rings, ph.d. thesis, inp-toulouse, 1980 16. brodkey r.: turbulence in mixing operations, academic press inc., 1975 page 135 page 136 page 137 page 138 page 139 page 140 untitled hungarian journal of industry and chemistry vol. 52(1) pp. 55–70 (2024) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2024-08 application of experimental design-based predictive models and optimization in additive manufacturing – a review ágota drégelyi-kiss1* 1 bánki donát faculty of mechanical and safety engineering, óbuda university, bécsi út 96/b, budapest, 1034, hungary experiments play a crucial role in additive manufacturing to help researchers develop new materials with enhanced properties or in several types of process optimization tasks. design of experiments (doe) is a valuable tool that is efficient, statistically rigorous and offers a systematic approach to experimentation. in this article, several types of doe methods such as one-factor-at-a-time (ofat), full and fractional factorial designs, taguchi, response surface methodology (rsm) and descriptive screening designs (dsd) are briefly described in addition to some singleand multi-objective optimization methods. the optimization methods apply utility theory (ut), taguchi and desirability optimization as well as some non-conventional, artificial intelligence-based multiobjective optimization methods illustrated by examples from the field of additive manufacturing. in the second part, the potential factors and response variables are reviewed during the investigation of the seven main categories of additive manufacturing, namely binder jetting (bjt), directed energy deposition (ded), material extrusion (mex), material jetting (mjt), powder bed fusion (pbf), sheet lamination (shl) and vat photopolymerization (vpp). keywords: response surface method, experimental design, additive manufacturing technologies, optimization method, doe, taguchi method, definitive screening design 1. introduction in manufacturing technology, several methods are applied to prepare prototypes, whether for low-volume or mass production. one of the leading modern technologies for machining parts and products is additive manufacturing (am) whereby objects are built layer by layer, while in conventional manufacturing (cm), the process typically involves subtractive methods where a material is removed from a bulk structure. there are some advantages of am as opposed to cm such as design flexibility, complex geometries, the generation of less waste during the manufacturing process and its environmentally-friendly nature. on the other hand, cm is more cost-effective regarding mass production. the production speed is significantly faster, a wider range of materials are used, often a better surface finish is achieved and tighter tolerances. by combining am and cm processes, industrial manufacturing processes are optimized. according to a standard [1], am is defined as a process that builds parts by joining materials layer by layer using 3d model data. the standard defined seven process categories for am are as follows: binder jetting (bjt), directed energy deposition (ded), material received: 8 dec 2023; revised: 30 jan 2024; accepted: 2 febr 2024 *correspondence: dregelyi.agota@bgk.uni-obuda.hu extrusion (mex), material jetting (mjt), powder bed fusion (pbf), sheet lamination (shl) and vat photopolymerization (vpp). the qualification of technological processes and components is crucial when describing the behaviour of examined procedures. the performed experiments and their subsequent evaluation play crucial roles in scientific methods, research and decision-making in the manufacturing industry. several types of design of experiments (doe) exist, starting from the simplest onefactor-at-a-time (ofat) method up to the i-optimized response surface methods (rsm). the evaluation of the measured data could be followed by visual interpretation, statistical tests, regression and optimization. in this article, the experimental design methods as well as their evaluation and optimization are reviewed before being explained within the field of am processes (chapter 2). the purpose of this work is to clarify the steps of evaluation of different procedures as well as explain the differences between the used doe methods and optimization approximations. choosing appropriate input or control parameters and response variable(s) for the investigation of a certain quality is particularly difficult when experimenting. in chapter 3, the possible factors concerning the seven different am processes are https://doi.org/10.33927/hjic-2024-08 mailto:dregelyi.agota@bgk.uni-obuda.hu drégelyi-kiss hungarian journal of industry and chemistry 56 collected separately and the frequently used response variables illustrated by examples from recent am research. the abbreviations used in this article are presented in table 1. 2. experiments, modelling and optimization investigations in the field of am consist of several important parts such as experimentation, designing an appropriate part and mathematical evaluation of the data. the purpose of am research could be to improve the quality of a process by carrying out experimental work. numerous parameters can affect the quality of an am process. by applying a doe approach, the expense and duration of experimental work could be decreased significantly. initially, the main goal of parameter screening, that is, describing the process mathematically, optimizing factors or process robustness, must be defined [2]. the flowchart whereby the am process is examined is shown in figure 1. the design of experiments experimentation evaluation of data optimization (doe-exp-eval-opt) process can reveal the main elements of the work and provide an opportunity to clarify the main purpose of the investigations or research. the first main step of the research is to design the experimental work. it can be stated that "all experiments are designed experiments, it is just that some are poorly designed, and some are well-designed" [2],[3]. to investigate the behaviour of a certain process, the effects of the so-called input parameters as well as the controllable and uncontrollable factors influencing the output of the process must be examined. it is important to define all the response variables and factors as well as their levels carefully before performing experiments. the different experimental designs are described in chapter 2.1. the second main step when examining am is experimentation itself. the selection and creation of the design [4]-[6] is followed by the am of the specimen. response parameters should be measured properly. the quality and validity of the data play important roles during am. some examples from the metrology of am parts are presented [7]-[11]. the next step is the evaluation of data (figure 1). data visualization helps scientists understand and interpret information more effectively [12],[13]. statistical analysis of the data allows the effects of the factors on the experimental results to be investigated and characterized. methods are available from the simplest two-sample hypothesis tests up to the more advanced and complex hypothesis tests. in chapter 2.2, some frequently used tests to evaluate statistical data are shown. if the am process must be described by mathematical methods, linear or nonlinear regression analysis might be most suitable. optimization is the last optional step of the doeexp-eval-opt process when examining am. several methods are found in the literature for single or multiresponse optimization of manufacturing processes, a few of which are detailed in chapter 2.3. within the following subchapters, the citations from a particular doe method concern the practice of am. the doe methods according to am technologies are presented in chapter 3. table 1: abbreviations figure 1: main steps during am examinations the doe-exp-eval-opt process design of experiments and optimization in additive manufacturing 52(1) pp. 55–70 (2024) 57 2.1. experimental designs in this chapter, the most commonly used methods for the experimental design of am technologies are described. researchers often use this selection of methods to tailor their experimental settings, even if further mathematical equations and the optimization of a process are unnecessary. five main categories of the doe are briefly defined. the mathematical modelling of these designs is found in chapter 2.2. one-factor-at-a-time (ofat) one experimental strategy that is extensively applied is the ofat approach [2]. the ofat method consists of selecting a starting point, or baseline set of levels, for each factor before successively varying each factor over a particular range while keeping the other factors constant at their baseline levels [14],[15]. once all the tests have been performed, a series of graphs are usually constructed showing how the response variable is affected by varying each factor separately while all the other factors are kept constant. the purpose of this approach is to investigate the impact of individual factors on a process without having to consider potential interactions between factors. the ofat method is suggested to be used during pre-experiments. pre-experiments can play an important role in making sure that the experimental design is correct and effective before carrying out the actual research or experiment. these can help reduce the risk of errors and increase the success of the research project or experiment. since the main experiment usually involves several control parameters for examinations, the correct experimental strategy is to conduct a factorial experiment. factorial design during factorial designs, several factors are varied simultaneously instead of one at a time, that is, 3 control parameters, namely 3 layer thicknesses, 2 drying times and 4 baseline temperatures. if all possible combinations are examined, then the factorial design consists of 3 x 2 x 4 = 24 experimental runs. this type of factorial design is referred to as the full factorial design [16]-[20] whereby all combinations of each factor at all levels are tested, thereby including the examination of all possible interactions as well as main effects and higher-order interactions. if all the factors have 2 levels, the usual notation for the n-factor full factorial design is 2n, which is equal to the number of experimental runs. if each factor has 3 levels, then 3n experimental runs are performed. by increasing the number of levels of the control parameters, the number of experimental runs required will rise exponentially. one type of factorial design which allows researchers to study the main effects and some desired interaction effects over a minimum number of trials or experimental runs is called a fractional factorial design. in the case of fractional factorial designs, which are orthogonal arrays where the settings for the independent variables are orthogonal to one another so it is possible to estimate them independently, a fraction (e.g. 1/2, 1/4, 1/8) of the experimental runs can be conducted. twolevel fractional factorial designs are expressed using the notation 2(k−p) where k denotes the number of variables (factors) investigated and p describes the size of the fraction of the full factorial search space used [2]. the main purpose of fractional factorial designs is to decide which control parameters or factors have the most influence on the response variable(s) when a relatively small number of experiments are conducted. therefore, experimental screening designs are used when the number of factors is larger than 6 [21]-[23]. a sequential experimentation strategy could be applied when fractional factorial designs are used correctly [2,14,24]. screening designs consist of several types such as plackett-burman [25],[26] and latin square designs [27] or taguchi methods. taguchi methods taguchi has developed experimental designs using orthogonal arrays (oa) [28] where the factors can have 2, 3, 4 or more levels and the main effects can be evaluated. this form of experimental designs is common and popular among researchers who suppose that the effect of parameters on the response variable is approximately linear. one main advantage of taguchi methods is that several levels, that is, more than 2, of a certain parameter can be investigated, moreover, a smaller number of experiments have to be performed compared to in full factorial experiments (table 2). a huge number of taguchi oas are found in the field of am from various areas [29]-[35]. response surface methodology (rsm) rsm is a collection of mathematical and statistical techniques to model and analyse problems in which a response of interest is influenced by several variables and the objective is to optimize this response. the response surface is usually represented by graphs on a surface or contour plot. rsm consists of two different types, namely central composite designs (ccd) and boxbehnken designs (bbd). as an example, three factorial experimental designs along with their factor levels are presented in table 3. rsm ccds involve a combination of factorial designs and axial points. the number of table 2: comparison of the number of experiments conducted in full factorial designs and taguchi methods number of factors levels of factors taguchi oa no. of exp. taguchi no. of exp. full factorial 3 2 l4 (23) 4 8 7 2 l8 (27) 8 128 4 3 l9 (34) 9 81 11 2 l12 (211) 11 2048 1;7 2;3 l18 (21·37) 18 4374 drégelyi-kiss hungarian journal of industry and chemistry 58 levels for each factor can vary depending on the specific experimental design. ccds are flexible and enable the number of levels and the ranges for each factor to be chosen based on specific requirements and knowledge of the process under investigation. levels should be chosen carefully to accurately model and optimize the response variable according to the available data points. ccd is an extension of the factorial design, and includes both factorial points and axial points. the axial points are placed at a distance α from the centre. a special type of ccd is face-centred central composite design (fc ccd), which is particularly useful when the centre point, that is, the point at the centre of the design space, is either unnecessary or infeasible for experimentation. in the case of fc ccd α = 1, only 3 levels are found for each factor compared to 5 in ccd [36]. rsm bbd is an independent quadratic design since an embedded factorial or fractional factorial design is not included. three levels of each factor are found, while the design consists of a combination of low, high and centre levels for each factor [2]. bbds typically require fewer experiments compared to ccds, making the former more efficient when the budget or resources are limited. ccd is often considered more efficient in terms of modelling complex response surfaces when the purpose of the experiments is to develop a regression model for the data (see the examples in tables 4–7 presented later in this article). despite the importance of ccds and bbds, researchers sometimes cannot afford the required number of experimental runs. therefore, optimal designs have been developed that follow the so-called alphabetic optimality criteria [36], some of which focus on accurately estimating model parameters while others on predicting the design region well. one type of optimal design known as i-optimal design is found from the field of additive manufacturing [37],[38], which seeks to optimise prediction variance. definitive screening designs (dsd) response surface methods can describe the relationship between the factors and the response variable if more than two levels for each factor must be chosen. when 2-3 factors are considered, approximately 20 experimental runs are conducted. in the case of 6 factors, a full rsm ccd consists of 90 experimental runs, while when 10 factors are examined, a rsm bbd contains 170 runs. in order to reduce the number of experimental runs but continue to benefit from the advantages of rsm, a new three-level screening design known as definitive screening design (dsd) was developed whereby the number of experimental runs is one more than twice the number of factors [39]. in the case of 6 factors, the number of experimental runs is 13, while when 10 factors are selected, 21 runs are performed, which is far less than in rsm designs. rsm and dsd for 8 factors and one response variable for mex-printed pla parts were compared [38]. dsd was found to be more economical than rsm due to the reduced number of experimental runs. 17 experimental runs were planned based on a dsd compared to 55 on a rsm design. several dsd experimental designs are found in the literature [40]-[43]. 2.2. data evaluation after conducting the designed experiments, data must be statistically evaluated. firstly, the results must be visualized by groups in graphs such as individual value, box and violin plots or histograms. visualizing data in groups or categories is a common approach to gain insights into how data is distributed as well as identify patterns and differences between these groups. the graphs produced enable accurate hypotheses to be suggested during the following statistical tests. during the statistical tests following a doe, the following null hypothesis is frequently used, that is, there is no significant difference between the means of the groups compared. if two groups exist, then the twosample t-test is the most appropriate method. if more than two groups are found for one factor and more than two factors are involved, then the common test is analysis of variance (anova), which helps determine whether the variation between the means of groups is statistically significant or can be attributed to random sampling variation. if the doe consists of more factors and the types of variables are different from numerical ones, e.g. they are categorical variables, the general linear model (glm) is table 3: the factor levels in coded form of a ccd, face-centred ccd and box-behnken design for three factors design of experiments and optimization in additive manufacturing 52(1) pp. 55–70 (2024) 59 a more general framework that can handle various types of dependent variables by taking into account a broader range of data types and statistical models in addition to the comparison of means [2]. regression previously mentioned tests of significance comparing means could be sufficient for researchers. sometimes the purpose of research is not only to define the significance of a certain factor or parameter but to describe the process mathematically and accurately by regression equations. although several types of regression equations or models exist, in this paper, statistical regression approximations are addressed [2]. the simplest regression model which can be fitted to three-factor experimental designs is a multiple linear regression model with only main effects: 𝑦 = 𝛽0 + 𝛽1 ∙ 𝑥1 + 𝛽2 ∙ 𝑥2 + 𝛽3 ∙ 𝑥3 + 𝜀 (1) where 𝑦 denotes the response variable, βi represents the regression coefficients, xi are the values of th ith variable and ε stands for the random error term. while statistically evaluating the screening of two-level designs and taguchi methods, this type of equation with only main effects could be developed [32],[44]. the minimum number of experimental runs is the number of factors plus one. if the doe contains more experimental runs than the minimum number required, the interaction between the factors can be estimated. in the case of a full factorial 23 doe, the following multiple linear regression can be estimated: 𝑦 = 𝛽0 + 𝛽1 ∙ 𝑥1 + 𝛽2 ∙ 𝑥2 + 𝛽3 ∙ 𝑥3 +𝛽12 ∙ 𝑥1 ∙ 𝑥2 + 𝛽13 ∙ 𝑥1 ∙ 𝑥3 + 𝛽23 ∙ 𝑥2 ∙ 𝑥3 +𝛽123 ∙ 𝑥1 ∙ 𝑥2 ∙ 𝑥3 + 𝜀 (2) where 8 βi should be estimated so a minimum of 8 experimental runs must be conducted. within this form of multiple linear regression, there are 3 main effects (x1, x2, x3), 3 interactions between two factors (x1·x2, x2·x3, x1·x3) and 1 interaction between three factors. (x1·x2·x3). this type of regression was applied in a wire-based electron beam additive manufacturing process [45]. if the doe contains a factor with more than two levels, then quadratic effects of that factor could be estimated besides the main effects and interactions. the following equation is an example of a factorial design consisting of at least 3 levels and at least 10 experimental runs: 𝑦 = 𝛽0 + 𝛽1 ⋅ 𝑥1 + 𝛽2 ⋅ 𝑥2 + 𝛽3 ⋅ 𝑥3 + 𝛽12 ⋅ 𝑥1 ⋅ 𝑥2 + 𝛽13 ⋅ 𝑥1 ⋅ 𝑥3 + 𝛽23 ⋅ 𝑥2 ⋅ 𝑥3 + 𝛽11 ⋅ 𝑥12 + 𝛽22 ⋅ 𝑥22 + 𝛽33 ⋅ 𝑥32 + 𝜀 (3) this latest type of regression models has been addressed in the literature [46],[47]. these are the most common types of statistical regression model used when studying am technologies. besides these models, some are emerging in artificial neural network (ann) models to determine the relationship between the input and output parameters of am processes. research articles have been published where the modelling capability of rsm and ann methods is compared or combined to describe am processes [29,48,49]. 2.3. optimization the regression model parameters can be estimated and equations visualized graphically as a response surface. having determined the equation, the minimum, maximum or target value of a certain response variable can be calculated as an optimization goal. this type of optimization is referred to as numerical and denoted in tables 4–7. based on the purpose of the research, typically two or more response variables are investigated in a designed experiment. two types of optimizations related to the handling of response variables are found, namely singleobjective and multi-objective optimizations. if the singleobjective optimization is chosen, the calculation is easier, while the multi-objective optimization can use even neural network for problem-solving. the use of utility theory (ut) simplifies multiobjective optimization into single-objective optimization. in this theory, a utility, that is, a value of individual response factors (y1, y2, ..., yn), is calculated and finally a combined value calculated by using the relations. if xi measures the effectiveness of an attribute (characteristic) i and n attributes evaluate the outcome space, the overall utility function is a linear sum of individual utilities which can be adjusted by providing a weight, transforming the overall utility function into: 𝑈(𝑋1, 𝑋2, … , 𝑋𝑛) = ∑ 𝑊𝑖𝑈𝑖(𝑋𝑖)𝑛𝑖=1 (4) where ui(xi) denotes the utility of the ith attribute, wi stands for the weight assigned to the attribute i and the sum of the weights for all attributes is equal to 1 [50]. if the composite measure is maximized, the evaluation of utility will automatically be optimized. ut assumes that the response variables are independent which might not be the case in practice. ut was used to analyse the response parameters of surface roughness, dimensional accuracy and flatness together by maurya et al. [32]. the taguchi method for optimization single-objective optimization could be performed by the taguchi signal-to-noise (s/n) method, which is a robust design and optimization whereby the larger the s/n ratio calculated, the better the certain level of a factor. based on the objective function, several types of optimization problem can arise: (i) smaller-the-better [51], (ii) largerthe-better [31],[52] and (iii) nominal-the-best [28,53,54]. multi-objective optimization with taguchi orthogonal arrays could be conducted by grey relational analysis (gra), which is based on the grey system theory to convert multi-response problems into single-response ones [55]. first, gra normalises experimental data between 0 and 1 before a grey relational coefficient is calculated that determines the ratio between the desired (ideal) values and the actual (experimental) response data. a grey relational grade is then calculated as a drégelyi-kiss hungarian journal of industry and chemistry 60 weighted sum that considers the grey relational coefficient corresponding to each process response and their corresponding weights [56]. in the literature, the compressive strength, measured porosity and dimensional accuracy of fabricated porous scaffolds were optimized simultaneously with this method [57]. desirability optimization method (dom) one of the first approaches to multi-response optimisation based on a desirability function was proposed using process targets and response deviations to represent a single-objective function [58]. the desirability function is used to determine the desirability of the process parameters set compared to all potential solutions and with respect to the required nominal response values. individual desirability (di) evaluates how the process parameters settings optimize the ith single response, while composite desirability (d) evaluates how the settings optimize a set of responses overall. the individual desirability functions for each response variable should be defined. the desirability function has a lower and an upper limit, goal (maximize, minimize or target) and importance [59]. composite desirability is defined as the weighted geometric mean of the individual desirabilities for the responses: 𝐷 = √𝑑1 ∙ 𝑑2 ∙ … ∙ 𝑑𝑛𝑛 (5) desirability has a range of 0 to 1 whereby 1 represents the ideal case and 0 indicates that at least 1 response falls outside the acceptable limits. non-conventional, artificial intelligence (ai)-based multi-objective optimization methods metaheuristic search techniques belong to artificial intelligence and have drawn significant attention over the last two decades for solving multi-response optimisation problems. in the case of 10 different ai optimizations (namely genetic algorithm optimization, simulated annealing algorithm optimization, particle swarm optimization, grey-wolf optimization algorithm, moth flame optimization algorithm, whale optimization algorithm, jaya optimization algorithm, sunflower optimization algorithm, lichtenberg optimization algorithm and forensic-based investigation optimization algorithm) for the mex manufacturing process, response variables [60] have been utilized to predict the optimal settings of experiments. genetic algorithm optimization (ga) a stochastic search technique inspired by the principles of natural evolution has been proven as a potent multi-directional heuristic search method for optimising highly nonlinear, nonconvex and complex functions since it is less likely to get trapped at a local optimum than traditional gradientbased search methods. the individuals in a population are then evaluated based on their fitness value whereby the individuals with the highest fitness values are taken as bases (‘parents’) for the next generation. the procedure is iterative, that is, continues till the termination criterion is reached. some examples of gabased multi-response optimization are found in the literature [18,29,31,61,62]. another evolutionary metaheuristic technique is particle swarm optimization (pso) inspired by the social behaviour of flocks of birds and schools of fish. similarly to ga, pso is also a population-based heuristic computational method whereby the population of the potential solutions is referred to as a swarm and each individual solution within the swarm is called a particle. the algorithm is initialised with a population of random solutions (a flock of birds where a bird is called a particle) and searches for the optimum by updating generations. unlike ga, pso has no evolution operators such as crossover and mutation. two research articles presented one example each of this type of optimization [63],[64]. a new metaheuristic algorithm, namely grey wolf optimization, inspired by the social hierarchy and hunting behaviour of grey wolves (canis lupus) was developed [65]. this modern population-based algorithm was used to optimize the process whereby the functional relationship between five important fdm process parameters concerning polyethylene terephthalate glycol (petg) was studied regarding their effect on the flexural strength of this material [66]. the maximum flexural strength obtained by the algorithm was approximately 14% higher than the best result obtained by the series of experiments. 3. modelling in different types of additive manufacturing 3.1. binder jetting (bjt) binder jetting (bjt) is an am process in which a liquid bonding agent is selectively deposited to join powder materials together [1]. bjt can work with various types of materials, including metals, ceramics, polymers and composites. metal powders such as stainless steel, aluminium and titanium are used in aerospace, automotive and medical device manufacturing as well as in ceramic powders in dental implants and electronics, sand powders in moulds in addition to polymer powders to create prototypes. the binding agent is used to selectively bond and solidify the powdered material in specific areas layer by layer to create a three-dimensional object. the binding agent chosen depends on the material being printed and the desired properties of the final object. several parameters or factors influence the quality of the bjt process (appendix figure 2). in the case of doe, the main goal is to study the effects of the various parameters on the response variable and quality characteristic of a certain manufacturing process. since most of the factor levels are controllable, they are potential factors for doe investigations. the input and/or controllable parameters in the case of bjt can be divided into five main categories, namely material, manufacturing process, temperature, time and equipment. two types of material, that is, powders and design of experiments and optimization in additive manufacturing 52(1) pp. 55–70 (2024) 61 fluids, as well as their characteristics are important in bjt. the temperature and the different time conditions can affect the output of the process. the parameters set for the equipment such as the build, number of layers, binder drop and roller properties play a crucial role in the manufactured specimen. the parameters set in the manufacturing process, that is, feed-to-powder ratio, layer thickness and binder saturation, also affect the am process. one critical quality characteristic when examining the binder jetting am process other than compressive strength and porosity is transverse rupture strength (trs) that measures the maximum stress a material can withstand just before it breaks when subjected to a bending load [57],[67]. since the dimensional accuracy can also influence the quality of the bjt process, the shrinkage percentage ((actual dimension of a sample — designed dimension of a sample)/(designed dimension of a sample) x 100 %) can be determined [51]. besides the dimensional accuracy, the surface roughness of the produced specimen can be a response variable [29]. in the case of the bjt process, 3-5 factors are varied by doe methods and mainly the linear effects of the parameters investigated (table 4). the main purpose of the studies is to describe the process mathematically and optimize the bjt process for the selected response variable(s). 3.2. directed energy deposition (ded) directed energy deposition (ded) is an additive manufacturing process in which the focused thermal energy is used to fuse materials by melting them as they are being deposited [1]. the energy source in ded can be a high-powered laser, electron beam or plasma arc. ded is used mainly in the aerospace, automotive, rapid tooling and biomedical industries to produce functional metal parts, add material to existing parts and for repairs [73]. the material selected depends on the specific application. titanium, aluminium and nickel alloys are used in the aerospace industry, while titanium and cobaltchromium ones are applied in medical equipment [74]. the typical workflow of the metal additive manufacturing process is design, conversion, file transfer, configuration, print, removal, machining (optional), heat treatment (optional), inspection (optional) and handover (optional) [75]. the quality of the ded additive manufactured specimen depends on several factors such as the material, feeding, equipment and energy source (appendix figure 3). two types of materials have to be chosen, one for the wire/powder and another for the substrate. while the feeding parameters in addition to the feed rates of the carrier gas and wire/powder can be set, the geometric position, angle and direction are other optional factors when investigating a ded process. regarding the equipment itself, temperature settings and manufacturing strategies as well as the energy source could also affect the quality of the part produced. the response variables of doe during the investigation of ded processes are usually related to the geometry and characteristics of the bead deposited. the geometries of these beads are width, height, angles and dilution [30,61,69], however, the hardness [59], roughness [72], porosity [53] or coefficient of friction [45] could be measured as outputs. according to table 4, mainly 3-5 factors are chosen to describe the ded process, but a screening design, that is, taguchi l18, varies 9 factors simultaneously. 3.3. material extrusion (mex) material extrusion is an am process in which material is selectively dispensed through a nozzle or orifice [1]. a wide variety of materials can be extruded using mex: thermoplastics such as acrylonitrile styrene acrylate (asa), acrylonitrile butadiene styrene (abs), polycarbonate, polyetherimide, polylactic acid (pla), high impact polystyrene (hips), thermoplastic polyurethane (tpu) and aliphatic polyamides (pa, nylon) as well as high-performance plastics such as polyether ether ketone (peek) and polyetherimide (pei) [76]. mex additive manufacturing technologies have gained widespread popularity and applications due to their simplicity, reliability and affordability. the possible factors for doe during mex experimentation can be divided into four categories, namely temperature, equipment, material and the manufacturing process (appendix figure 4). the temperature conditions e.g. that of the build platform, nozzle as well as the printing and cooling conditions play a significant role as far as the quality of a mexproduced specimen is concerned. regarding the equipment, the fan speed and diameter of the nozzle are optional factors, moreover, the characteristics of the material can affect the output parameters. the manufacturing process consists of such parameters as the infill and its properties, flow rate, support, wall and layer thickness as well as build orientation. the quality of the mex process could be described by dimensional parameters and mechanical properties. the dimensional accuracy of the produced specimen is characterized by its length, width, thickness or dimensional error [60,77-81]. the surface quality of the part is measured by its surface roughness [38],[82] as well as by geometrical dimensioning and tolerancing (gd&t) parameters [83]. its mechanical properties such as strength refer to the capacity of a material to cope with external loads and stresses. during mex processes, the table 4: doe in the fields of bjt and ded (abbreviations are based on [1]) drégelyi-kiss hungarian journal of industry and chemistry 62 following mechanical properties can be used as response variables of doe: flexural strength [31,62,66,84], tensile strength [85],[86] and the young’s modulus [77],[87]. the energy factor and consumption as response variables in a mex experimental design were optimized by barbose et al. [88]. doe methods are widely used for the description and optimization of the mex additive manufacturing process. applications of all types of doe methods from the simplest to more advanced designs are found in the literature (table 5). more screening designs such as taguchi l27 for linear effects and definitive screening design for quadratic effects are available. 3.4. material jetting (mjt) material jetting (mjt) is an am process in which droplets of feedstock material are selectively deposited [1]. it is possible to apply thin layer thicknesses that enable high-quality parts to be printed as well as diminish staircase effects and thin walls [91]. mjt can be applied in rapid prototyping, the aerospace industry, dental and orthodontic applications, jewellery, architecture and construction. the materials used in mjt are usually thermoset photopolymers. the possible input or controllable parameters during the experimentation of mjt manufacturing processes are shown in appendix figure 5. the quality of the process can be affected by 4 categories, namely material, temperature, equipment and manufacturing process. like the mex technology, the temperature of parts of the equipment, that is, the nozzle, platform and printer, can cause deviations in the response variables of mjt. the chemical and mechanical characteristics of the material are important factors as far as the parameters of the equipment, i.e. build position, orientation and layer thickness, are concerned. four factors influence manufacturing processes, namely the curing process, drop properties, inkjet printhead parameters and type of support. the dimensional accuracy, surface roughness and mechanical properties of mjt-printed parts are crucial to obtain correct and reliable results after measurements are taken and ensure they function properly following final assembly. the length, width and height of the specimen [17,18,92]; the roundness and cylindricity [20]; as well as the surface roughness were analysed as response variables [16,32,93]. mechanical properties such as tensile strength were examined [14],[94] and the colour of the mjt-produced part can be output parameters referring to its quality [95]. doe methods are used to characterize the mjt process and each type of experimental design can be found in the literature as presented in table 6. 3.5. powder bed fusion (pbf) powder bed fusion (pbf) is an am process in which thermal energy selectively fuses regions of a powder bed [1]. as one of the most applied processes, pbf is increasingly being used to manufacture products in, for example, the aerospace, medical, automotive, tooling and consumer goods industries. one of the significant advantages of pbf is its ability to produce highly customized and personalized products, supporting a wide range of materials including metals, polymers and ceramics. the input and controllable parameters of the pbf additive manufacturing process can be divided into four categories, namely equipment, material, energy source and manufacturing process (appendix figure 6). within the equipment category, the layer thickness, working distance and gas flow can affect the output of the pbf process. the material composition and characteristics of the powder such as its distribution, particle shape and density are other examinable factors. different energy sources and their settings affect the quality. the most investigated parameters by doe are hatch space, temperature and scanning within the manufacturing process category. the response variables for characterizing the pbf process could be dimensional such as the length, width and depth of the melt pool [96] as well as the surface roughness [99],[103] and dilution rate [33]. the porosity of the manufactured specimen [44,49,98] is particularly critical as it can significantly affect the mechanical properties of components, cause structural failures as well as decrease their strength and young’s modulus. some researchers have measured the mechanical table 5: doe in the field of mex (abbreviations are based on [1]) table 6: doe in the fields of mjt pbf (abbreviations are based on [1]) design of experiments and optimization in additive manufacturing 52(1) pp. 55–70 (2024) 63 properties of the specimen [48],[100] and hardness of the produced part [101]. details about the doe and optimization in the case of pbf processes are contained in table 6. typically 3-5 input parameters are varied during the experimental designs and every type of doe can be an example of this technology. 3.6. sheet lamination (shl) sheet lamination (shl) is an am process in which sheets of material are bonded together to form a part [1]. the raw materials (worksheets) are cut by lasers or cutters depending on their geometry before the lamination process. the sheets are stacked layer by layer and bonded by diffusion instead of melting. laminated object manufacturing (lom) and ultrasonic additive manufacturing (uam) are the main techniques in this process. the processing speed is relatively high with low operating costs and easy material handling. various materials such as polymers, ceramics, paper and metals can be used in this shl process, the main advantages of which are its ability to be integrated into a hybrid manufacturing system by working with ceramic and composite fibre materials without the need for support structures. the main limitation of this process is the limited availability of materials and the removal of excess materials after lamination. the possible factors of doe are presented in appendix figure 7 in the case of the shl process that can be divided into three categories, that is, equipment, material and manufacturing process, based on a literature review. the temperature, force and pressure can be varied to investigate the performance of the shl process. the material characteristics such as thermal properties, flexibility, strength or type can affect the quality of the process. moreover, the speed, sheet thickness and type of heat source or binding method are possible factors when examining quality in the case of the shl additive manufacturing process. the response variables of the shl process can be measured from bending and tensile tests [34,47,104] or linear weld density [105]. some applications of sheet lamination in the field of doe can be seen in table 7. 3.7. vat photopolymerization (vpp) vat photopolymerization (vpp) is an am process in which a liquid photopolymer in a vat is selectively cured by light-activated polymerization [1]. vpp is widely utilized in the fields of engineering, manufacturing, dentistry, healthcare, education, entertainment, jewellery and audiology. dental applications of vpp are emerging, e.g. the mechanical properties of 3d-printed resin-based dental parts like their biocompatibility, accuracy as well as antimicrobial and surface properties [109]. the possible factors of experiments concerning the vpp process are detailed in appendix figure 8. the quality performance of the vpp process can be influenced by the parts of the equipment such as the tank, light source or platform. the chemical, mechanical and physical characteristics of the resin can affect the vpp process. the environmental conditions such as temperature and humidity as well as the design of the specimen are possible factors worth investigating within this field. the manufacturing process parameters such as print speed, post-processing and duration can be varied. response variables of the vpp process include tensile strength, hardness and energy consumption [19],[106] as well as printing time [107]. among the dimensional parameters of the specimen, its length, width, gd&t parameters, shrinkage and surface roughness can be investigated [35],[108]. during vpp, mainly taguchi and rsm methods with multi-objective optimization are addressed in the literature (table 7). 4. discussion this review describing the critical-to-quality characteristics of a certain additive manufacturing process contains several important steps and decisions. it is important to precisely declare the purpose of carrying out research before designing experiments. although several types of doe are available in the mathematical literature, in the field of am, taguchi and rsm methods are the most common. nowadays, definitive screening designs are emerging. augmenting a dsd will greatly assist practitioners to avoid the problems of underfitting and overfitting [110]. the rsm approach is based on a philosophy of sequential experimentation, whereby the objective is to approximate the response with a low-order polynomial in a relatively small region of interest that contains the optimum solution. some computer experimenters advocate a somewhat different philosophy by seeking to create a model that approximates the true response surface over a much wider range of design variables, sometimes extending over the entire region of operability [36]. even though only a few applications of sequential experimentation have been studied in the literature, it may still be useful in the future. the role of the doe-exp-eval-opt process (figure 1) is not only important in research into am processes but perhaps during mass-production am processes to decrease costs and increase the quality of a certain type of additive manufactured part. table 7: doe in the fields of shl and vpp (abbreviations are based on [1]) drégelyi-kiss hungarian journal of industry and chemistry 64 references [1] iso/astm 52900:2021 international standard: additive manufacturing general principles fundamentals and vocabulary [2] montgomery, d.c.: design and analysis of experiments (9th edition) (john wiley & sons), 2017, isbn: 9781119113478 [3] fisher, r.a.: the design of experiments (7th edition) (hafner publishing company, new york), 1960 [4] klahn, c.; leutenecker, b.; meboldt, m.: design strategies for the process of additive manufacturing, procedia cirp, 2015, 36, 230–235, doi: 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factors for the critical-to-quality (ctq) characteristics of mjt additive manufacturing figure 6: possible factors for the critical-to-quality (ctq) characteristics of pbf additive manufacturing figure 7: possible factors for the critical-to-quality (ctq) characteristics of shl additive manufacturing figure 8: possible factors for the critical-to-quality (ctq) characteristics of vpp additive manufacturing hungarian journal of industry and chemistry vol. 50(2) pp. 57–60 (2022) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2022-19 utilization of agro-wastes in biohydrogen fermentation by various microorganisms katalin bélafi-bakó1*, gábor tóth1, péter bakonyi1 and nándor nemestóthy1 1 research group on bioengineering, membrane technology and energetics, university of pannonia, egyetem u. 10, veszprém, 8200, hungary biohydrogen production based on agro-industrial wastes might be an attractive and effective technology for providing an energy source in the future. dark fermentation is considered to be one of the most suitable biohydrogen formation processes. in this paper, various agro-industrial wastes as well as microorganisms applied for biohydrogen formation are reviewed. keywords: anaerobic process, dark fermentation, bioreactor 1. introduction hydrogen produced biologically (biohydrogen) can be considered as a renewable source of energy [1]-[4]. moreover, it is regarded as one of the most promising, environmentally-friendly “fuels” of the future due to its favourable characteristics, e.g., only water is formed by the combustion of h2, no environmental pollution is produced, highest energy density of 143 kj/g. agroindustrial residues seem to be suitable feedstocks for the production of biohydrogen [5]. large amounts of solid and liquid waste are formed in agriculture every year, moreover, the majority of it is unutilized. however, promising technologies are available whereby agro-industrial residues are applied to produce value-added products and green energy by biological methods [6]. liquid wastes are usually found in the form of wastewater. solid agro-wastes can be classified into four groups [7]: (i) field residues (ii) waste of processing (iii) livestock waste (iv) chemical waste field residues generally originate from crop production and consist of the remains of crops, e.g., leaves, stalks, stems, seeds, straw, husks, shells, pulp, roots, woodland waste, etc. industrial food processing results in solid wastes which are mainly by-products of and leftovers from various plants, e.g., bagasse, sugarcane molasses, wheat bran, rice bran, groundnut shells, apple pomace, fruit peels, de oiled rice bran cake and oil cakes. recieved: 19 sept 2022; revised: 28 sept 2022; accepted: 28 sept 2022 *correspondence: belafine.bako.katalin@mk.uni-pannon.hu livestock waste consists of by-products of slaughterhouses or originates from processing, e.g., bones, feathers, shells of crustaceans, as well as bedding/litter, carcasses and damaged feeders. chemical waste includes plant protection compounds, e.g., pesticides, insecticides and herbicides, as well as their containers and bottles. however, since these materials cannot be utilized in biological methods, this study focuses on the first three groups of solid wastes. biological hydrogen production from agroindustrial wastes includes dark fermentation, photofermentation and microbial electrolysis cells (mec) [5]. photofermentation is a process whereby organic substrates are converted into hydrogen by photosynthetic organisms under anoxic conditions. h2 production in mecs is a bioelectrochemical process, where electrochemical and biological techniques are combined [8]. given that dark fermentation is one of the most common methods used for hydrogen production from agro-wastes due to its higher hydrogen production rate, it is the focus of this mini-review. 2. biohydrogen production by dark fermentation the composition and certain characteristics of agrowastes are determining factors of biohydrogen production. generally speaking, although these materials are rich in carbon sources, the majority of them require some sort of pretreatment. the lignin content in particular should be treated to increase the efficiency of https://doi.org/10.33927/hjic-2022-19 mailto:mailto:belafine.bako.katalin@mk.uni-pannon.hu bélafi-bakó, tóth, bakonyi and nemestóthy hungarian journal of industry and chemistry 58 biodegradation and conversion processes [5]-[7]. pretreatments of agro-industrial residues include: (i) physical, (ii) chemical, (iii) physicochemical and (iv) biological methods. physical methods involve ultrasonication, ozonization, thermaland microwave-assisted techniques as well as size-reduction processes, e.g., milling, grinding, etc. chemical methods include acid or alkali treatments, moreover, more recently organic solvents have been applied. in physicochemical methods, a combination of physical and chemical techniques is used, e.g., steam explosion, hydrothermal treatment and chemical treatment complemented with microwave irradiation. biological methods include enzymatic and microbial (whole cell) treatments, where mainly the degradation of biopolymers occurs. using these pretreatment methods, higher yields and more efficient hydrogen formation can be achieved. dark fermentative biohydrogen production can be carried out by facultative anaerobes and obligate microbes [1], [4]-[5]. in many cases, the suitable types of microorganisms are determined by the substrate applied and mixed microbial consortia are frequently used. nevertheless, numerous microbes have still been used in dark fermentative biohydrogen production based on agro-wastes, examples of which are listed in table 1: table 1: examples of the utilization of various agro-wastes to produce biohydrogen agro-waste microorganism h2 production rate or yield ref. sugar and rice mill wastewater acinetobacter junii rate 5.23 mlh2l-1h-1 [9] rice mill wastewater clostridium beijerinckii yield 214.9 mlh2l-1 [10] cheese whey powder enterobacter asburiae yield 1.19 ± 0.01 molh2mol-1 [11] sugarcane molasses eisenia fetida yield 1571.81 mlh2l-1 [12] cashew apple bagasse clostridium roseum yield 15 mmolh2 l-1 hydrolysate [13] fruit and vegetable wastes + seawater thermotoga maritima rate 12.4 mmolh-1l -1 [14] fruit wastes (apple, banana, grape, melon, orange) consortia from biogas sludge yield 523 ml/g vs (volatile solid) [15] sweet sorghum bagasse caldicellulosiruptor saccharolyticus yield 73.6 mlh2mmol-1 c6 sugars [16] cornstalk thermoanaerobacterium thermosaccharolyticum yield 89.3 mlh2g-1 db (dry biomass) [16] distillers grains caldicellulosiruptor thermocellum yield 29.2 mlh2g-1 db [16] fruit and vegetable wastes as well as corn stover anaerobic sludge yield 1.91 molh2mol-1 glucose [17] beer lees consortia from cow dung compost yield 68.6 mlh2/g tvs [18] corn straw ethanoligenens harbinense yield 9 mlh2g-1 [19] wheat straw consortia from cow dung compost yield 68 mlh2g-1 [20] grass silage manure yield 16 mlh2g-1 [19] extracts of sweet lime peel anaerobic mixed consortia yield 76.4 ml/g cod [21] palm oil mill effluent thermoanaerobacteriumrich sludge yield 84.4 mlh2g-1 [22] beet pulp mixed culture from anaerobic sludge yield 115.6 mlh2g-1 cod [24] sunflower stalks clostridium sp. yield 2.04 molh2mol−1 eq. hexose [25] miscanthus sinensis thermotoga elfii rate 23.99 mlh2h-1 [16] cassava pulp hydrolysate mixed culture yield 342 mlh2g-1 codreduced [26] tequila vinasse eisenia fetida yield 1246.36 mlh2l-1 [12] sugarcane bagasse eisenia fetida yield 232.72 mlh2l-1 [12] https://www.sciencedirect.com/topics/engineering/hexose agro-wastes in biohydrogen fermentation 50(2) pp. 57–60 (2022) 59 as can be seen, although several types of agrowastes and microbes have been used for biohydrogen fermentation, the results regarding the yield or production rate of the processes are difficult to compare since their units vary and the data on hydrogen formation is diverse. moreover, in this study, no information was collected about the treatment of the substrate (if any) nor which kind of bioreactor, set-up or mode of operation was used, making their comparison even more difficult. therefore, only some special considerations can be discussed in this work. 3. special considerations in addition to single microorganisms, mixed consortia are often applied in these processes, which originate from various sources [19], e.g., sludge from biogas production; anaerobic sludges from municipal wastewater treatment plants and cow-dung composts; cattle or dairy residue composts; sludge from palm oil mill effluent; soil, rice and straw composts; fermented soybean meal, etc. even though these sources usually contain the microbes which are able to form biohydrogen, they need to be acclimated which includes some sort of pretreatment, e.g., heat shock, starving for a couple days, etc., to enrich the suitable microorganisms [3], [28] or sometimes bioaugmentation [10]. in hydrogen-producing consortia, a wide range of species have been isolated [19], e.g., under mesophilic conditions, clostridium (c. pasteurianum, c. saccharobutylicum, c. butyricum), enterobacter (e. aerogenes) and bacillus, while under thermophilic conditions, the genera thermoanaerobacterium (t. thermosaccharolyticum), caldicellulosiruptor (c. saccharolyticus, c. thermocellum) and bacillus thermozeamaize. regarding the utilization of certain fruit wastes, some flavor compounds were found to exhibit an antimicrobial effect [15], e.g., a citrus flavor, since d-limonene is able to weaken the fermentation even at very low concentrations (0.01% w/v). therefore, the undesired effect of these substrates can be diminished by special treatments, e.g., encapsulation of the microbes in a membrane or pretreatment of the feedstock. 4. conclusions in biohydrogen production, the application of agroindustrial residues has a great potential since they are renewable, huge amounts of them are formed year 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[2] studied the effect of various cutting parameters, including cutting speed, feed rate and depth of cut on the surface roughness. their findings show that the cutting speed and feed rate have significant effects on the surface roughness. wojciechowski et al. [3] analyzed the forces and process efficiency whilst machining hardened 55nicrmov6 steel using ball-end milling. their results indicate that the surface inclination has a significant effect on the cutting forces. mersni et al. [4] used the taguchi method to optimize the milling parameters to obtain a better surface finish using ball-end milling of a titanium alloy ti-6al-4v. they point out that the radial depth of cut (ap) is the most *correspondence: mgherony.abdulwhab@uni-obuda.hu important factor followed by the cutting speed (νc) and then the feed per tooth (fz). yao et al. [5] studied the influence of the tool orientation on the surface of the tc17 titanium alloy. their findings emphasize the importance of tool orientation on surface roughness during ball-end milling. similarly, gao et al. [6] investigated the effect of the tool inclination angle on the surface roughness while machining the titanium alloy ti-6al-4v using a ball-end mill. they point out that tilting the tool has a significant effect on the quality of the grooves and using the appropriate inclination angle can reduce the roughness of the surface and improve its form. vyboishchik [7] presented a geometric model of the surface topology in the case of flat, concave (cv) and convex (cx) surfaces. according to this model, the surface inclination has a significant effect. matras and zębala [8] optimized the cutting data and tool path pattern for machining the freeform surface of steel in a hardened state using a ball-end mill. the results show that the surface roughness and cutting-force components can be controlled by modifying the feed rate based on the locally machined cross-sectional area. magalhães and ferreira [9] used different tool path strategies to machine parts with complex geometries from hardened h13 steel. their findings show that the tool path has a significant effect on the roughness of the complex surface. daymi et al. [10] highlighted the importance of the inclination angle in ball-end milling when machining the titanium alloy ti-6al-4v. this research investigates the effect of changing the surface inclination on the cutting speed and the https://doi.org/10.33927/hjic-2021-14 mailto:mgherony.abdulwhab@uni-obuda.hu 10 mgherony and mikó figure 1: the cv and cx workpieces consequences of a variable cutting speed on the surface roughness as well as provides an insight into the importance of the feed rate and width of cut on the machining process when using a 3d ball-end mill. 2. materials and methods the machining tests were performed on cv and cx surfaces of the same material, namely the low-alloy steel 42crmo4. 42crmo4 is used to manufacture parts with high-tensile strengths of compressors, turbines and working elements of heavy equipment used aboveground and underground as well as components of agricultural machinery. the chemical composition of 42crmo4 is given in table 1. the cv and cx parts consist of a cylindrical surface with a 45 mm radius connected to a horizontal plane with a 10 mm radius. fig. 1 shows both workpieces and table 2 shows the angles of the normal vector of the surface. the machining was performed by a mazak vertical center nexus 410a-ii cnc vertical machining centre. the surface roughness was measured by a mahr’s marsurf gd120 instrument. the ra and rz parameters were measured in the x-direction perpendicular to the milling direction at 11 different positions. the milling was done using a fraisa x7450.450 ball-end milling cutter with a diameter of 10 mm (dc = 10 mm) and 4 teeth (z = 4). five test surfaces were created by ball-end milling with different feed rates and widths of cut. table 3 shows the applied cutting parameters in machining these surfaces. since the surface inclination changes, the effective diameter also changes. a geometrical model is presented by mikó and zentay [11] to calculate the effective diameter. fig. 2 shows the calculated effective diameter at each measured point in the case of the cv and cx workpieces. the actual cutting speed can be calculated depending on the effective diameter at each measured point using the following formula: νc = deff n π 1000 (1) figure 2: the effective diameters at each measured point figure 3: the actual cutting speed at each measured point figs. 2 and 3 show the effective diameter and actual cutting speed. even though the diameter of the tool is 10 mm, the actual cutting diameter is smaller. in the case of the cv surfaces, it changes between (3.4 and 6.8 mm), while in the case of the cx surfaces, it changes between (3.4 and 5.8 mm). on the other hand, the effective diameter and, as a result, the cutting speed are the smallest in the middle of the workpieces, where the value of the normal vector is 0°. in addition, although it can be seen from fig. 3 that the value of the cutting speed is higher in the case of the cv surfaces compared to the cx equivalents, the cutting speed curve is similar for both cv and cx test parts. 3. results and discussion fig. 4 shows the average surface roughness of the test pieces. the diagram shows that the surface of the cv test parts is better than that of the cx test parts under the same cutting parameters, as the actual cutting speed in the case of cv surfaces is higher than that of the cx equivalents. on the other hand, when the feed rate is 0.08 mm and the width of cut is 0.35 mm, the surface roughness is the worst for both cv and cx surfaces. the surface roughness of the workpieces was measured at several points. the results show that the surface inclination has a significant effect on the surface roughness, as can be seen in figs. 5–9, since the quality of the surface is less at the middle of the test pieces where the cutting speed is at its minimum. hungarian journal of industry and chemistry the effect of the cutting speed on the surface roughness 11 table 1: chemical composition of the low-alloy steel 42crmo4: (analysis in %) c si mn p s cr mo cu 0.38− 0.45 0.1− 0.4 0.6− 0.9 ≤ 0.025 ≤ 0.035 0.9− 1.2 0.15− 0.3 ≤ 0.4 table 2: angles of the normal vector of the surface measuring points (y) 25 20 15 10 5 0 5 10 15 20 25 cx angles (°) 30 23.58 17.46 11.54 5.74 0 −5.74 −11.54 −17.46 −23.58 −30° cv angles (°) −38.7 −30 −22 −14.5 −7.2 0 7.2 14.5 22 30 38.7 table 3: cutting parameters used in the test test part id. cv-01 cv-02 cv-05 cv-03 cv-04 cx-01 cx-02 cx-05 cx-03 cx-04 cutting speed vc [m/min] 160 spindle speed n [rpm] 5100 feed per tooth fz [mm] 0.08 0.08 0.08 0.12 0.16 feed speed vf [mm/min] 1630 1630 1630 2450 3260 depth of cut ap [mm] 0.3 width of cut ae [mm] 0.35 0.25 0.15 0.15 0.15 in the case of cx-01 and cx-02, the surface roughness is worse than on the other three pieces. on these two pieces, rz is approximately 16 µm at the middle compared to 10 µm at the middle of the other pieces. in the case of the cv pieces, cv-05 exhibits the best figure 4: average rz of each test parts figure 5: rz surface roughness in the case of cx-01 and cv-01 surface roughness and the value of rz is less than 6 µm at the middle, while it is approximately 12 µm on the other pieces. this variation in the surface roughness from piece to piece is due to changes in the feed rate and width of cut. the feed rate is at its minimum when machining cx-01 figure 6: rz surface roughness in the case of cx-02 and cv-02 figure 7: rz surface roughness in the case of cx-03 and cv-03 49(2) pp. 9–13 (2021) 12 mgherony and mikó figure 8: rz surface roughness in the case of cx-04 and cv-04 figure 9: rz surface roughness in the case of cx-05 and cv-05 and cv-01 but increases to its maximum when machining cx-04 and cv-04. however, the width of cut decreases gradually to its minimum when machining cx-04 and cv-04. figs. 10 and 11 show the main effect of changing the width of cut and feed rate on the surface roughness in the case of cv and cx surfaces. as is shown, the width of cut has a significant effect on the surface roughness. by increasing the width of cut, the rz value of surface roughness increases. on the other hand, the feed rate has a minor effect on the surface roughness, especially in the case of cv surfaces. the actual cutting speed and the effective diameter have exactly the same effect on the surface roughness, as can be seen in figs. 12 and 13. the rz value of surface roughness decreases by increasing the effective diameter and the cutting speed. however, in the case of cx surfaces, the roughness of the surface increases again by about 1 µm at a cutting speed of 70 m/min. 4. conclusion in this article, the effect of the cutting speed on surface roughness has been studied. based on the obtained data, under the same cutting parameters, the surface roughness of the cv test parts is better than that of the cx equivalents. however, changes in the surface inclination cause the actual cutting speed to vary, which affects the surface quality. the cutting speed reduces to a very low value when the normal axis of the ball-end mill is applied on the workpiece surface. given that the figure 10: the effect of the width of cut and feed rate in the case of cv surfaces figure 11: the effect of the width of cut and feed rate in the case of cx surfaces figure 12: the effect of the effective diameter and actual cutting speed in the case of cv surfaces figure 13: the effect of the effective diameter and actual cutting speed in the case of cx surfaces hungarian journal of industry and chemistry the effect of the cutting speed on the surface roughness 13 variation in cutting speed is a major problem in the case of 3-axis milling machines, modifying the cutting speed during the milling process can solve this problem and ensure a higher surface quality. on the other hand, the surface roughness depends on other cutting parameters as well such as feed rate and width of cut. it has been determined that by increasing the width of cut, the surface roughness is increased, while changing the feed rate only has a minor effect. acknowledgment this publication was financed by the national research, development and innovation fund under project 20181.3.1-vke-2018-00041. references [1] chang, l.: a parametric design of ball end mill and simulating process (concordia university), 2016 [2] radhwan, h.; sharif, s.; shayfull, z.; suhaimi, m.; khushairi, m.m.; najmi, m.: optimization of cutting parameters for surface roughness in ball end milling of aluminium epoxy using taguchi method. aip conference proceedings, 2129(1), 020156 doi: 10.1063/1.5118164 [3] wojciechowski, s.; maruda, r.; barrans, s.; nieslony, p.; krolczyk, g.: optimisation of machining parameters during ball end milling of hardened steel with various surface inclinations. measurement, 2017, 111, 18–28 doi: 10.1016/j.measurement.2017.07.020 [4] mersni, w.; boujelbene, m.; salem, s.b.; alghamdi, a.s.: optimization of the surface roughness in ball end milling of titanium alloy ti-6al-4v using the taguchi 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https://doi.org/10.1016/j.measurement.2017.07.020 https://doi.org/10.1016/j.promfg.2018.02.040 https://doi.org/10.1007/s00170-017-0523-7 https://doi.org/10.1007/s00170-017-0523-7 https://doi.org/10.1007/s00170-017-0305-2 https://doi.org/10.1007/s00170-017-0305-2 https://doi.org/10.1016/j.proeng.2016.07.103 https://doi.org/10.1016/j.proeng.2016.07.103 https://doi.org/10.3390/ma13051109 https://doi.org/10.1177/0954405418755824 http://jamme.acmsse.h2.pl/papers_vol35_1/35110.pdf https://doi.org/10.1007/s00170-019-03968-9 introduction materials and methods results and discussion conclusion untitled hungarian journal of industry and chemistry vol. 52(1) pp. 29–35 (2024) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2024-05 the role of tool pin imprints on the mechanical behavior of structures repaired using the friction stir welding (fsw)technique hadj boulenouar hasna1, mazari mohamed1, belaziz azzeddine2*, hadj boulenouar rachid3 1 laboratory of materials and reactive systems (lmsr), university of sidi bel abbes, 22000, algeria 2 center of research in mechanics, university campus of chaab erssas, 73b freres ferrad, constantine, 25017, algeria 3 laboratory of mechanics and physics of materials (lmpm), djillali liabes university, sidi bel abbes, 22000, algeria among the various techniques employed to repair structures comprised of materials containing cracks, one of the most prominent is the utilization of friction stir welding (fsw). this method involves a solid-state assembly process. the adoption of fsw as a structural repair technique offers a swift response to meet contemporary industrial demands. when applied to the 5083 h111 aluminum alloy, this technique extended the operational lifespan of components following their repair. keywords: friction stir welding (fsw), service life, cracks, repair, tool 1. introduction since the 1990s, friction stir welding (fsw) has been a patented technique applied to aluminum alloys developed by the welding institute (twi) [1]-[2]. this innovative method (figure 1) is highly efficient and particularly useful for welding non-ferrous materials such as copper and aluminum alloys [3]-[4]. classified among the most frequently used assembly processes, the fsw technique is considered a novel method in the world of assembly [5]-[6]. although this particular process causes microstructural changes, residual tensions at joints and distortions that are difficult to regulate, it remains a promising technique due to its unique ability to weld parts in the solid state, eliminating defects related to solidification and creating low internal stresses compared to traditional welding methods [7]-[8]. as a result, fsw can be used to join alloys that were previously considered difficult to weld [9]. the principle of fsw is based on the concept of kneading and plasticizing the material using the heat generated by the friction between the tool and the parts to be welded, which are held rigidly to prevent any movement during this process [10]. a multitude of process parameters including the rotational speed, velocity and angle of inclination of the tool as well as the depth to which the received: 16 nov 2023; revised: 11 jan 2024; accepted: 24 jan 2024 *correspondence: belaziz2013@gmail.com tool is immersed have a direct impact on the quality of the final product obtained thanks to fsw [11]. in addition, other parameters can influence the final properties of fsw seals [12]-[13]. many unique properties of aluminum alloys, in particular their lightness and good structural strength, allow them to be used in structural components [14]. aluminum alloys meet the needs of the aerospace and automotive industries for lightweight materials [15]. the aluminum alloys aa6xxx and aa5xxx are commonly used in the manufacture of aircraft structures and in other structural applications [15]. several studies of fsw with regard to various aa5xxx and aa6xxx joints have been reported in the literature [16]. shigematsu et al. [17] attempted an fsw assembly of alloys aa5083 and aa6061 with different thicknesses, moreover, studied the microstructure and mechanical properties of the joints. peel et al. [18] studied the processing window of 3 mm-thick aa5083 and aa6082 joints and found that the rotational speed of the tool affected heat generation during welding more than the feed rate. peel et al. [18] studied the effects of the rotation and velocity of the tool on the microstructure, hardness and distribution of the precipitates of 3-mm thick aa5083 and aa6082 joints. steuwer et al. [19] quantified the effects of tool rotation and velocities on the residual stress in 3 mm-thick aa5083 and aa6082 joints. he concluded that the https://doi.org/10.33927/hjic-2024-05 mailto:belaziz2013@gmail.com hadj boulenouar, mazari, belaziz and hadj boulenouar hungarian journal of industry and chemistry 30 rotational speed of the tool is a useful process variable to minimize residual stresses. in this work, an attempt was made to produce an aa5083 h111 aluminum alloy using fsw and study the influence of the tool pin imprint on delaying crack propagation in an aluminum alloy welded by fsw. 2. experimental study the analysis was carried out experimentally in the laboratory of materials and reactive systems using an instron machine driven by a servo hydraulic actuator with a capacity of 50 kn and 100 kn in static and dynamic modes, respectively (figure 2). the fsw process was carried out on a modified conventional milling machine in the workshop of the mechanical engineering department at djillali liabes university of sidi bel abbes. 2.1. material studied the material studied was an aluminum alloy of the 5000 series, type 5083 in the h111 condition (25% deformed by rolling). the alloy 5083 h111 was chosen because the proportions of magnesium and manganese quite closely resemble those of the 2024 alloy used in aeronautical structures of fuselages. its chemical composition and characteristics are given in table 1 [21] where e – elastic modulus, ys -yield strength, uts – ultimate tensile strength, a elongation, hv – vickers hardness, ki – stress intensity factor. 2.2. tensile test the mechanical characteristics of the alloy studied were determined by a tensile test carried out on a dumbbell specimen (figure 3) [22]. a tensile test was performed using extensometers. the machine was controlled in accordance with a standard at a velocity of 20 mm/min and an initial load of 1 kn. the traction curve of this test is represented in figure 4. figure 1: schematic diagram of the fsw process [20] figure 2: instro machine used for traction figure 3: geometry of the dumbbell specimen [22] table 1: plant material characteristics: aluminum alloy 5083 h111 [21] al si fe cr mn mg cr zn ti (%) 0.1 0.4 0.4 0.1 0.1 4.9 0.2 0.2 0.1 5 0 0 0 0 0 5 5 5 e ys uts a hv ki (mpa) (mpa) (mpa) (%) (j/cm2) 71008 155 236 16.5 88 45 figure 4: tensile curve of aluminium alloy 5083 h111 in the longitudinal l direction 0 50 100 150 200 250 300 0,00% 1,00% 2,00% 3,00% 4,00% 5,00% 6,00% 7,00% 8,00% 9,00%  σ the role of tool pin imprints 52(1) pp. 29–35 (2024) 31 dumbbell-shaped specimens of the relevant material were extracted (figure 5) by following the astm e8-04 standard [23], which includes a calibrated central section with a cross sectional area of s=400 mm2 and a length of l=200 mm. the tensile tests were conducted at room temperature. table 2 illustrates the main mechanical characteristics obtained. 2.3. fatigue test in this study, ct75 specimens in the aluminum alloy 5 mm thick (b) and 75 mm wide (w) (figure 6) were used according to the astm e647-00 standard [24]. 2.4. description and analysis of the tests all the tests were performed under constant amplitude loading with the stress applied ranging from 26 to 42 mpa. some trials were stopped before the specimens broke. test no. 1: during this test, initiation took place at 36270 cycles. the maximum load (max) applied was 2500 n with a load ratio (r) of 0.1. the crack extended to 26.7 mm in length before rupturing, which corresponds to 229270 cycles (figure 7). test no. 2: initiation took place at 40000 cycles. the applied max was 2500 n, r = 0.1. the crack extended to 26.7 mm in length before rupturing, which corresponds to 217000 cycles (figure 8). figure 9 represents the results obtained for the two specimens regarding the length of the crack as a function of the number of cycles (n). it can be seen that the two results exhibit the same trend and are similar. propagation rates: to compare the change in cracking rate in the case of the two specimens (figure 10), the seven-point method was applied from the experimental data points to obtain a linear regression. for both specimens, the propagation speed (da/dn) changed as a function of the amplitude of the stress intensity factor (δk) following the same trend and obeying the paris’ law: 𝑑𝑎𝑑𝑁 = 𝐴(∆𝐾)𝑚 (1) [25] figure 5: set-up of the tensile test figure 6: dimensions of the ct75 specimens figure 7: change in crack length (a) as a function of the number of cycles (n) when δp was constant (test no.1) 10 15 20 25 30 35 40 45 50 0 50000 100000 150000 200000 250000 figure 8: change in the crack length (a) as a function of the number of cycles (n) when δp was constant (test no.2) 10 15 20 25 30 35 40 45 50 0 50000 100000 150000 200000 250000 300000 table 2: mechanical characteristics of alloy 5083 h111 e ys uts a hv (mpa) (mpa) (mpa) (%) 49891 175 250 8 138 hadj boulenouar, mazari, belaziz and hadj boulenouar hungarian journal of industry and chemistry 32 where a and m refer to two characteristic constants of the material. table 3 represents the results obtained for the two specimens. it is noteworthy that the da/dn values for the two specimens are almost identical. 2.5. welding operation to carry out a friction stir welding operation, the mechanical action of the tool on the part is important. the welding energy is purely mechanical and essentially corresponds to the work of the torque. the significant forces applied by the tool on the parts to be welded require the use of positioning and holding systems [26]. the heat generated by the friction between the shoulder and the pin transforms the material into a pasty state in the vicinity of the tool, moreover, facilitates the penetration and movement of the tool along the joint to be welded to form the weld after cooling [26]. 2.6. welding tool generally speaking, the welding tool is cylindrical, consisting of a profiled pin and a shoulder. the welding cycle begins with a sequence of penetrations of the rotating pin into the plates to be welded. the shoulder resting against the parts allows the material it will contain to flow [27]-[28]. the tool used was made in the mechanical manufacturing workshop of the mechanical engineering department at djillali liabes university of sidi bel abbes from the alloy tool steel z200c12 (figure 11): nowadays, z200c12 steel, along with its derivatives, constitutes one of the first families of tool steel, both in terms of the importance of the tonnages used each year and the extraordinarily diverse range of its applications. however, despite the long-established and widespread use of its steels, users still sometimes encounter serious difficulties with its implementation, particularly regarding its heat treatment [29]. figure 12 depicts the fsw processing and the fsw tool. 2.7. machine used for fsw the fsw welding process was carried out on a modified conventional milling machine in the workshop of the mechanical engineering department. before the fsw process, a good clamping system had to be made. by clamping it down with a stepped test piece, this technique positioned the test piece on an anvil fixed to the table to avoid the part from separating when table 3: coefficients and exponents of the paris’ law specimen da/dn (mm/cycle) δk (mpa·m1/2) 1 3x10-7δk2.60 7 to 17 2 2x10-7k2.87 7 to 15 figure 9: results of the fatigue tests regarding the crack length of the aluminum alloy 5083 h111 as a function of the number of cycles (n) 10 15 20 25 30 35 40 45 0 50000 100000 150000 200000 250000 300000 1 2 figure 10: change in the cracking rate as a function of δ δδ 1,00e-05 1,00e-04 1,00e-03 1,00e-02 7,00 1 2 figure 11: manufacturing of the tool figure 12: fsw welding tool the role of tool pin imprints 52(1) pp. 29–35 (2024) 33 the tool penetrates it. figure 13 represents the clamping mode used. 2.8. the welding parameters in this process, a non-standardized tool geometry relative to the thickness of the specimen was used to obtain an imprint with a small diameter. several tests were carried out to obtain the right parameters that result in a good weld seam, which are as follows: feed speed (va) = 160 m/min rotational speed (v) = 2000 rpm angle of inclination (θ) = 1.5º the indentation tests were conducted in the lmsr laboratory (figure 14). two methods were used for welding: firstly, welding took place outwards to avoid traces of the imprint on the zone to be welded; and secondly, inwards to leave the imprint. 2.9. welded specimen without an imprint after the welding step, the fatigue tests on the two specimens were replicated. during this test, initiation took place at 70000 cycles. the applied max was 2500 n with r = 0.1. the crack extended to 29.6 mm in length before rupturing, which corresponds to 279500 cycles (figure 15). 2.10. welded specimen with an imprint during this test, initiation took place at 85000 cycles. the applied max applied was 2500 n with r = 0.1. the crack extended to 29.6 mm in length before rupturing, which corresponds to 641600 cycles (figure 16). figure 17 represents the results obtained for the two specimens after welding regarding the length of the crack as a function of the number of cycles after welding. it can be seen that in the specimen with the imprint, the delay in the propagation of the cracks (nd) is equal to figure 13: clamping mode figure 14: the ct75 specimens after welding figure 16: change in crack length (a) as a function of the number of cycles (n) when δp was constant 10 15 20 25 30 35 40 45 50 55 0 100000 200000 300000 400000 500000 600000 700000 figure 15: change in crack length as a function of the number of cycles (n) when δp was constant figure 17: esults of the fatigue tests on the aluminum alloy 5083 h111 regarding the crack length (a) as a function of the number of cycles (n) 10 15 20 25 30 35 40 45 50 55 0 100000 200000 300000 400000 500000 600000 700000 specimen with imprint specimen without imprint hadj boulenouar, mazari, belaziz and hadj boulenouar hungarian journal of industry and chemistry 34 approximately 2.2x105, which is significant since it clearly shows the influence of the imprint of the tool pin on the propagation of the crack. 2.11. propagation rates the tests concerning the propagation rate of the fatigue cracks were carried out on both specimens after welding (figure 18, table 4). 3 zones were identified: zone a corresponds to the area where the crack initiated; zone b represents the domain of paris (the quasilinear curve illustrating continuous propagation of the cracks). zone c refers to the imprint of the pin of the tool. this phenomenon is characterized by a fairly significant delay (nd) of 220,000 cycles before the crack continued to lengthen. 2.12. validation our results, presented in figure 16, are consistent with those recorded in a study by h. wu (figure 19) [30], which digitally simulated the propagation of fatigue cracks after the cracked 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candidate mechanisms in deriving the rate law of a catalytic reaction l. t. fan,r bert6k\f. friedler1,ands. shafie (department of chemical engineering, kansas state university, ks-66506 manhattan, u.s.a. 1 department of computer science, university of veszprem, veszprem, egyetem u. 10., p.o. box 158, veszprem h-8201 hungary) received: august 20,2001 stoichiometrically exact, candidate pathways, i.e., mechanisms, for deriving the rate law of the catalytic synthesis of ammonia have been determined through the synthesis of networks of known elementary reactions constituting such pathways. this has been undertaken to reassess the validity of available mechanisms and to explore the possible existence of additional ones for the catalytic synthesis of ammonia. synthesizing the networks of elementary reactions is exceedingly convoluted due to the combinatorial complexity arising from the fact the number of elementary reactions involved usually far exceeds that of available elementary balances, which is only 2 for the ammonia synthesis. such a complexity can be circumvented by the rigorous and highly efficient, graph-theoretic method adopted in the present contribution. this method follows the general framework of a mathematically exact, combinatorial method eslablished for process-network synthesis. it is based on a unique graph-representation in terms of process graphs (p-graphs), a set of axioms, and a group of combinatorial algorithms. the method renders it possible to generate with dispatch all feasible independent reaction networks, i.e., pathways, only once. the pathways violating any first principle of either stoichiometry or thermodynamics are eliminated. moreover, the method is capable of directly generating rapidly the acyclic combinations of independent pathways. keywords:ammonia synthesis, reaction pathways, mechanism, networks, identification, synthesis, algorithms, p. graph. introduction the mechanisms or pathways of the catalytic synthesis of ammonia from nitrogen and hydrogen, n2 + 3h2 ~ 2nh3, have been investigated intensively as well as extensively because of its long history, theoretical importance, and enormous economic implication. nevertheless, the number of stoichiometrically exact mechanisms proposed as the candidates for deriving the rate law for this reaction increases continuauy as new computing methods are devised and additional elementary reactions are proposed [1-9]. the latter is probably attributable to the ever-enhancing sensitivity and accuracy of analytical instrumentation, in general, and spectroscopic instrumentation, in particular, for detecting active species; to the ever-enlarging variety of catalysts for increasing the yield {10]; and to the ever-expanding ranges of operating conditions for improving plant efficiency. the determination of candidate mechanisms for deriving the rate law plays a key role in the study of the kinetics of catalytic reactions. such mechanisms must be stoichiometrically exact [7, 11-14]. a reaction pathway, comprising the steps of elementary reactio.ns, routes the precursors (starting reactants) of t!:te react1on to the targets (final products) and vice versa; in other words, a reaction pathway signifies the mechanism of the reaction. the reaction pathway per se yields no information on the rate, reversibility, equilibrium, and extent of the reaction. any reaction pathway is in the form of a network of the steps of elementary reactions containing a .loop or loops. ln constituting a pathway, or network, each elementary reaction among plausible elementary reactions contributes the forward, reverse or no step to the network. as such, the possible combinations 41f these 3 possibilities that must be taken into account .are 72 (3 11-1) or 177,146 even if the network comprises only 11 elementary reactions. this can readily give rise to more than 100 plausible networks from which the feasible candidate pathways are to be identified; by any measure, this is a daunting task. difficulties involved in constructing networks of chemical reactions that can be the elementary reactions leading to the mechanism of a catalytic reaction are "the combinatorial explosion of the number of resultant networks, and the complexity involved in rendering a computer program to implement the algorithm for network construction effective both synthetically (from precursors towards targets) and retrosynthetically (fr~m targets towards precursors)" [15, 16]. substantial progress has been made to circumvent such difficulties mainly by resorting to various paradigms of linear algebra (1, 8, 11, 16-32]; nevertheless, much remains to be done. the current contribution aims at reassessing the validity of available pathways or mechanisms of the catalytic synthesis of nh3 and exploring if additional candidate pathways exist from the stoichiometric point of view. this is accomplished by resorting to a method of synthesizing a network of elementary reactions, corresponding to the pathway, i.e., mechanism, of a catalytic reaction [33]. this method, totally algorithmic in nature, has been developed by judiciously adapting the three available algorithms of the mathematically exact, graph-theoretic method for process-network synthesis. these algorithms are msg for generating the maximal structure of the network, ssg for generating all the combinatorially feasible network structures, and abb for determining · optimal and near optimal networks. the method is firmly rooted in a set of axioms and expressed in the parlance of process graph or p-graph, in brief [34-39]. in reality, researchers in the field of catalysis have been remarkably successful in deriving the satisfactory rate laws for reactions of interest without having a complete set of stoichiometrically exact candidate mechanisms. this is mainly achieved through the judicious identification of plausible elementary reactions on the basis of spectroscopic measurements, which is frequently aided by energetic analysis of such elementary reactions. an expression for the rate law is usually derived by postulating, for simplification, the existence of the rate-controlling and equilibrium steps among the elementary reactions proposed. the final determination of the rate law is accomplished by fitting the resultant expression to the experimentally measured rate data [40-51]. more often than not, however, a multitude of stoichiometrically exact mechanisms emerges from a single set of plausible elementary reactions, some of which clearly resemble each other. frequently, it is nearly impossible to discriminate statistically the rate laws derived from such mechanisms in the light of the experimental data. hence, it would be highly advantageous to obtain a complete set of stiochiometricauy exact candidate mechanisms prior to launching an effort for the rate-law determination. in fact, to do so would greatly facilitate the execution of such an effort because it exactly defines the boundary and limits its scope. methodology the current methodology for identifying the stoichiometrically complete mechanisms for a given overall reaction is based on the two sets of axioms, one being the set of 6 axioms of feasible reaction pathways and the other being the set of 7 axioms of combinatorially feasible networks, as well as on the graph representation of reaction steps irt terms of p­ graphs. in view of formal graph-theoretic description of the reaction-pathway identification problem (see appendix 1), these axioms and p-graph representation give rise to the 3 combinatorial algorithms, including algorithm rpimsg for the generation of the complete reaction network; algorithm rpissg for the generation of the combinatorially feasible pathways; and algorithm pbt for the final determination of the feasible pathways. inputs: rpi problem(}!:, m, 0); output: maximal structure (m, o ); begin comment: reduction part of the algorithm; repeat m:='¥(0); exc:=0; for allxem begin comment: case 1 if xe m(e) and v-(x)=0 then exc:=excuv\x); comment: case 2 if x~ m(e) and v+(x)=0 then exc:=excuv-(x); comment: case 3 ifxem(e) and i v-(x) i =1 and v+(x)=x(v-(x)) then exc:=excuv(x); comment: case 4 if x~ m-(e) and ltnx) i =1 then exc:=excux( v-(x)); comment: case 5 if xll: m\e) and j v+(x) j =1 then exc:=excux(v+(x)); end; 0:=0\exc; until exc=0; comment: composition part of the algorithm; m:::=al(e); ();::::0; repeat add:=qr(m)\o; o:=ouadd; m:=mu'¥-(o); until add=0; if m-(e)\m~0 or o.t(e)\m~0 then stop; comment: there is no maximal structure. write (m, o ); end. fig. 1. algorithm rpimsg. monochloroacetic acid, ammonia solution and ca(oh)z were purchased from aldrich (germany) and were used as received. axioms according to the classical chemical thermodynamics, the overall reaction and all elementary reactions in any mechanism are reversible, and each reaction step, either forward or reverse, is stoichiometrically exact [7, 1114]. when a pathway leading from the starting reactants (precursors) to the final products (targets) is formed by selecting one or none of the steps of each elementary reaction, the complete mechanism is naturally recovered by supplementing the opposite step to each step of the pathway. moreover, the principle of microscopic reversibility prohibits the inclusion of any cycle in a pathway. the following set of 6 axioms of feasible reaction pathways can be formed from these first principles and conditions for any given overall reaction. (rl) every final product (target) is totally produced by the reaction steps represented in the pathway input: reaction pathway identification problem (e, o, m) output: all conbinatorially feasible structure (m, o) begin prissg(w\e), 0, 0, 0); end. procedure prissg(p, dp, inc, exc) begin exc:=rpirsg(exc); if (incnexc;t0) then return; if w-(e)\'r(o\exc)¢0 or m+(e)\y(o\exc)-#;0 then return; inc:=nx(inc, exc); for allxep if ( v-(x)\exc\in=0) then begin dp:=dpu{x}; p:=(pu'r(v-(x)ninc)) \dp; end; ifp=0then begin o:=inc; m:=':p(o); print (m, o); return; end; letxep; ox:= v-(x)\exc; oxb:= v-(x)ninc; c:=g<j(o,.\oxb); if oxb=0 andx~w-(e) then c:;:::c\{0}; for all cec end; rpissg( (pu'¥-(euoxb)) \ (dpu{x }), dpu{x }, incuc, excu(ox\oxb\c)ux(c) ); fig. 2. algorithm rpissg and subsidiary algorithms. 73 (r2) every starting reactant· (precursor) is totally consumed by the reaction steps represented in the pathway. ~3) every active intermediate produced by any reactwn step represented in the pathway is totally consumed by .one or more reaction steps in the pathway, and every active intermediate consumed by any reaction step represented in the pathway is totally produced by one or more reaction steps in the pathway. (r~) all reaction steps represented in the pathway are defmed a priori. (r5) the network representing the pathway is acyclic. (r6) at least one elementary-reaction step represented in the pathway activates a starting reactant (precursor). to focus on the combinatorial properties of the network comprising the feasible reaction pathways, the condition imposed by axiom (r5) is relaxed except for the cycles formed by the forward and reverse steps of individual elementary reactions, and the condition imposed by axiom (r6) is totally relaxed. then, axioms (rl) through (r5) can be recast as the seven axioms of the combinatorially feasible reaction networks, leading from the starting reactants (precursors) to the final products (targets) of any given overall reaction; this set of axioms is given in the following. (tl) every final product (target) is represented in the network. (t2) every starting reactant (precursor) is represented in the network. function rpirsg(exc) begin repeat m:= '¥(0\exc); ex:=0; for allxem begin comment: case 1 if x~ w(e) and v(x)\exc=0 then ex:=exuv+(x); comment: case 2 if x~ w(e) and v+(x)\exc=0 then ex:=exu!f(x}; comment: case 3 if xil w(e) and i v-(x)\exc i :::1 and v+{x)\exc=x(v-(x)\exc) then ex:=exuv(x); comment: case 4 if x~ ar(e) and i v-(x)\exc i ==1 then ex:=exux( v-(x)\exc); comment: case 5 if x~ w+(e) and i v+(x)\exc i ==1 then ex:=exux(v+(x)\exc); end; ex:;:::ex\exc; exc:=excuex; untilex=0; returnexc; end; fig. 2. (cont'd.). 74 function nx(inc, exc) begin repeat m:= 'p(inc)uw(e); in:=0; forallxem begin if x<£ of(e) and [ v-(x)\exc ! =1 then in:=inuv-(x)\exc; ifx~al(e) and i v+(x)\exc i =1 then in:=inuv+(x)\exc; end; in:=in\inc; inc:=incuin; until in=0; return inc; end; fig. 2. (cont'd.). (t3) each reaction step represented in the network is defined a priori. (t4) every active species represented in the network has at least one path leading to a final product (target) of the overall reaction. (ts) every chemical or active species represented in the network must be a reactant for or a product from at least one reaction step represented in the network. (t6) a reactant of any elementary reaction represented in the reaction network is a starting reactant (precursor), if it is not produced by any reaction step represented in the network. (t7) the network includes at most either the forward or reverse step of each elementary reaction represented in the network. it is indeed worth noting that axioms (tl) through (t7) straightforwardly reduce to axioms (sl) through (85) established for process-network synthesis [34-36}. the phrase, "every active species," at the outset of axiom (t4) can be replaced with the phrase, "any reaction step," since every active species generated by 8uy reaction step is totally consumed by one or more of , other reaction steps represented in the network. p-graphs the elementary-reaction steps are directed; thus, every network constituting a reaction pathway containing these steps can be represented by directed graphs, whereas such networks can not be uniquely represented by conventional graphs. the p-graphs, which are bipartite graphs, serve this purpose. in the p-graphs, the elementary-reaction steps are represented by horizontal bars; and the chemicals and active species. by circles. p­ graph (m, 0) representing a reaction network leading ftom the starting reactants (precursors) to the final products (targets) of the overall reaction of interest is comhinatorially feasible, if it satisfies axioms (tl) through {t7). furthermore. p-grapb (m, 0) representing a reaction pathway is feasible if it also satisfies axioms (rl) through (r6). algorithms the axioms naturally give rise to efficient algorithms necessary for carrying out the synthesis of a feasible network of elementary reactions; these algorithms are rpimsg given in fig. 1 for generating the maximal networks; rpissg given in fig. 2 for generating all the combinatorially feasible solution networks; and pbt given in fig. 3 for generating not only independent pathways but also the linear combination of such pathways, all of which are acyclic. input: reaction pathway identification problem (e, 0, m) output: all feasible pathway (m, o) begin pbt(ut(e), m(e), 0, 0, 0, 0); end. procedure pbt(p, c, dp, de, inc, exc) begin exc:=rsg(exc); if (incnexc;t:0) then return; if m-(e)\'p-(o\exc);t:0 or m+(e)\'p+(o\exc);t:0 then return; inc:;:;nx(inc, exc); for allxep if (v-(x)\exc\inc=0) then begin dp:=dpu{x};p:=(pu'p-(v(x)ninc)) \dp; end; for all yep if (v+(y)\exc\inc=0) then begin dc:=dcu{y}; c:=( cu'p+(v+(y)ninc)) \de; end; if3(m, o) ((m, o)eavoid, oc;inc) then return; if p=0 and c=0 then begin o:=inc; m:='p(o); if dp=dc and solution( (m, o)) then print (m, o); return; end; if (inc\sol#c-0) or (exc\ ( 0\sol) ;t: 0 ) or (sol=0) then sol=candidatesolution( inc, exc); if (sol=0) then return; ifp0 then let xe p, where pfreedom(x, inc, exc) is :mininal; ifc#c-0 then letyec, where cfreedom(y, inc, exc) is :mininal; ifc=0 or (poft-0 and pfreedom(x, inc, exc)<cfreedom(y, inc, exc)) then begin ox.:= v-(x)\exc; dxb:= v-(x)ninc; c:=p(o:x\oxb); if oxb=0andx<£ur(e) then c::c\{0}; forallqec pbt( (puy(qvoxb)) \ (dpu{x}), c, dpu{x}, de, incuq, excu(ox\oxb\q)ux(q) ); end; else begin oy :== v+(y)\exc; oyb:"" u+(y)ninc; c:=p(oy\oyb); if oy0=0 and y!l: m+(e) then c:=c\{ 0}; forallcec pbt(p, (cuy(quoy0)) \ (dcu{y}), dp, dcu{y}, incuq, excu(oy\oyb\q)ux(q) ); end; end; fig. 3. algorithm pbt and subsidiary algorithms. function candidatesolution( inc, exc) begin · lp: '\/ v;::::l e;einc l va=e e;eo\exc if lp is not feasible then return 0; else begin solvelp; sol := {e;: e;e 0\exc, v;> 0}; return sol; end; end; fig. 3. (cont'd.). function solution( (m, o)) begin end; lp: l.vi~max e;eo if lp is not feasible then return false; else begin end; solvelp; if v(vi :::;; !) e;eo c then begin avoid:= avoid u {(m, x(o))}; return true; end; else begin o := { ei: vi > ! } ; m := 'p(o ); avoid:= avoid u {(m, o), (m, x(o))}; return false; end; fig. 3. (cont'd.). the methodology presented above has been applied to two sets of available elementary reactions, one comprising elementary reactions (1) through (10) together with elementary reaction {14) in table 1, function pfreedom(x, inc, exc) begin if xeof(e) or v-(x)ninc=0 end; then return i v-(x)\inc\exc i else return i v-(x)\inc\exc l-1; function cfreedom(y, inc, exc) begin ifyeot(e) or v\y)ninc=0 then return j v+(y)\inc\exc) else return i v+(y)\inc\exc l-1; end; fig. 3. (cont'd.). table 1 list of plausible elementary reactions (1) hz+£~h2£ (2) h2£+ .e ~h.e + h.e (3) nz+f~nz£ (4) n2£+£~n£+n (5) nz£ + hz£ ~ nzhz£ + £ (6) nzhz£ + £ ~ nh£ + nh£ (7) n.e + h.e ~ nh£ + £ (8) nh£+ h£~nh2£+ £ (9) nh£ +hz£~ nh3£+ £ ( 10) nh2£+ h£ ~ nh3£ + £ (11) nh£+n£~n2h£ + .e (12) nhz£ + n.e ~ nzhz£ + £ (13) nzhz£ + h2f ~ n2h2£+ n£ (14) nh3£~nh3+ £ 75 fig. 4. p-graph representation of the network comprising the forward steps of elementary reactions (1) and (2). and the other comprising elemenetary reactions (1) through (14) in the same table. for illustration, the p~ graph of a network consisting of elementary reactions (1) and (2) is depicted in fig. 4. 76 table 2 independent mechanisms resulting from the first set of eleven elementary reactions mechanism 1 mechanism2 ill m (1) hz+l~hzl (1) hz+l~hz£ (2) hz£+£~ h£ + h£ (3) nz+i~nz£ (3) nz+i~nz£ (4) nz£ + £ ~ni! + n (5) n2£ + hz£~ nzhal + 1! (6) nzhz£ + £ ~ nh£ + nh£ (7) n£ +hi!~ nh£ + 1! (8) nh£ +hi!~ nhzi! + £ (9) nh£ + ha£ ~ nh3i!+ 1! (10) nh2£ + h£ ~ nh3£ + 1! (14) nh3£ ~ nh3 + ££ (14) nh3£ ~ nh3 + £ mechanism3 mechanism4 i1j1 [8. 251 (1) ha+f.~hz£ (1) hz+i~hz£ (2) h2£ + £ ~hr. + h£ (3) nz+i~nz£ (3) na+i~nz£ (4) n2£ + f. ~nl + n (4) n2£ + 1! ~n£ + n (5) nzi! + hzl ~ nahz£ + £ (7) nl + hr.~ nh£ + f. (7) nf. +hr.~ nh£ + £ (8) nh£ +hi~ nhzf. + i (8) nh£ +hr.~ nhz£ +f. (9) nh£ + h2£ ~ nh3£+ 1! (10) nha£ +hi~ nh3i + 1! (10) nh2i + hr.~ nh3£ + f. (14) nh3£ ~ nh3 + l {14) nh3i ~ nh3 + i mechanisms mechanism6 [8, 251 [8. 25j (1) ha+l~hzl (1) hz+i~h21! (2) h2£+ £~hr. +hi (3) na+i.~na£ (3) na+i~nz£ (4) nzl+i~nl+n (5) n:at + hzl ~ nahz£ + i (5) naf. + hz£~ nahz£ + l (6} nahal+ l ~ nh£ + nh£ (6) ·nahal+ l ~ nhi + nh£ (7) nl+hl*nhl+ t (s) nht + ht ~ nh2£ + l (8) nh£ + hi~ nhal + l (10) nh2t +hi* nh3l + l (10} nhal + hl * nh3£ + i table 3 summary of computational results and the corresponding computational requirements 1. independent pathways number of elementary reactions number of lps computation time* number of combinatorially independent pathways problem#1 11 13 0.06 s 6 problem#2 14 581 l.ls 35 2. a-cyclic pathways (independent and combined) problem #1 problem #2 number of elementary 11 14 reactions number of lps computation time* number of combinatorially independent pathways 35 0.06 s 17 *pentium ii celeron 450 mhz pc, 128 mb ram result and discussion 984 1.7 s 367 when applied to the set of 11 elementary reactions in table 1 [1-9, 25], the current method has recovered 6 independent mechanisms in 0.06 s on a pc (pentium ii celeron 450 mhz and 128 mb ram). all 6 mechanisms are identical with those available in the literature [1, 2, 7, 8,25], which are listed as mechanisms 1 through 6 in table 2. moreover, the method has generated 17 acyclic combined mechanisms in 0.6 seconds on the same pc, 11 of which have resulted from linearly combining the 6 independent mechanisms. one of the combined mechanisms corresponds to the mechanism consisting of the 11 candidate elementary reactions [8]. it is worth noting that the number of elementary reactions reported in the literature is 9 instead of 11. this increase is a result of splitting the initiation step into 2 and adding the desorption step for nii3 signifying termination. it is logical to postulate that the initiation proceeds in two steps, each involving a single active site and that the termination occurs through the desorption of nh3 formed on the active site: any elementary reaction would be far more likely to be bi­ molecular than tri-molecular £7, 9, 13, 52, 53]. an extensive review of the available literature [4-6, 9} indicates that elementary reactions (11), (12), and (13), also listed in table 1, are highly plausible to be in the pathway of ammonia-synthesis reaction. with the addition of these 3 elementary reactions, the current method has yielded 35 independent mechanisms in 1.1 seconds and 367 acyclic mechanisms in l 7 seconds on the same pc, 332 of which have resulted from linearly combining the independent mechanisms. table 3 summarizes the results described above. note that there is no direct correspondence between the computational effort required for the identification of independent feasible pathways and that required for the identification 77 of acyclic feasible pathways. when the number of candidate elementary reactions is appreciable, the former tends to be greater than the latter: the two efforts resort to different sets of algorithms. with the number of elementary balances remaining invariant at 2, one for nitrogen and the other for hydrogen, each increment in the number of elementary reactions automatically translates into an exponential magnification of combinatorial complexity, thereby adding substantially to the computational time for mechanism determination. it has been amply demonstrated that the current method is capable of coping with this added burden. nevertheless, caution should be exercised so that an excessively large number of candidate elementary reactions is not proposed in implementing the current method; otherwise, we would be confronted with a bewildering number of feasible mechanisms, thus rendering inordinately difficult the final selection of the valid mechanism through experimental reaction-rate and spectroscopic measurements in conjunction with theoretical and computational studies. in fact, it is highly desirable that the final selection be conducted sequentially and iteratively starting with a relatively modest set of candidate elementary reactions which are plausible on the basis of empirical and theoretical evidence. concluding remarks the current work has yielded a substantial number of stoichiometrically exact independent as wei! as acyclic combined candidiate mechanisms for deriving the rate law of the catalytic synthesis of ammonia. these mechanisms include those published hitherto, thereby validating them. moreover, the current work has unequivocally demonstrated that the mathematically exact, graph-theoretic method presented herein for identifying such mechanisms is inordinately effective. references 1. happel j.: catalysis reviews, 1972,6, 221~260 2. horiutij.: ann. n.y. acad. sci.,/973, 213,5-30 3. temkin m.i.: the kinetics of transfer of labeled atoms by reaction, ann. n.y. acad. sci., 213, pp. 79-89, 1973 4. ertl g. and huber m.: j. catal., 1980, 61, 537539 5. njelson a.: catal. rev.-sci.eng., 1981,23, 17-51 6. grunze m.: chern. phys. solid surf. 1982, 4, 143194 7. boudart m. and djega-mariapassou g.: kinetics of heterogeneous catalytic 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j. of phys. chern. b, 1997, 101, 3000-3004 50. neurockm.: stud. in surf. sci. and catal., 1997, 109,3-34 51. dumesic j.a., rudd d.f., aparicio l.m., rekoske j.e., and trevino a.a.: the microkinetics of heterogeneous catalysis, acs publications, washington, dc, 1993 52. temkin o.n., zeigarnik a.v. and bonchev d.: chemical reaction networks: a graph-theoretical approach, crc press, 1996 53. chang w.: physical chemistry for chemical and biological sciences, university science and books, sausalito, ca, p. 463, 2000 54. masel richard i.: chemical kinetics and catalysis, wiley, 2001 appendix 1. formal graph-theoretic description of the reaction-pathway­ identification problem here, a formal description is given of the problem of reaction·pathway identification. it is couched in the parlance of graph theory in general and that of p-graph in particular [34, 35, 39]. problem definition let a reaction-pathway-identification problem be defined by triplet (e, 0, m), where e is the overall reaction; 0 = { eh ez, ... , en}, the finite ordered set of elementary reactions; m == {ah a2, ••• , a1}, the finite ordered set of chemical and active species; e = [et. e2, .•. , ez]te z1, where ej is the difference between the number of moles of the j-th chemical produced and that consumed by the overall reaction; and e,· = [e1 · e2 · · t l ·,t, ,l, ••• , e!,i] e z , where ej,i is the difference between the number of moles the j-th chemical or active specie produced and that consumed by the i-th elementary-reaction step. since every elementary reaction is reversible, both its forward and reverse steps are included in set 0, i.e., 'v'e; (e; e 0 => -e; e 0) in other words, for any elementary-reaction step e1 defined, its opposite step, denoted by -e1, is also defined in the problem. it is assumed that mn0=0ande~ oum. representation elementary reactions, chemicals, and active species are represented by p-graphs as follows: 79 if oi..e;) denotes the set of chemical and active species consumed or produced by the elementary-reaction step ei> we have for any chemical or active species aj-e m, let v-(aj) and v-(aj) denote the set of elementary-reaction steps consuming and producing aj, respectively; it follows that and if v(ai) denotes the set of elementary-reaction steps consuming or producing ai, we have obviously for any set of the elementary-reaction steps, o ~ 0, let 'i'(o) and t(o) denote the set of chemical and active species consumed and produced by any element of o, respectively; it follows that 'i'(o) = u of(e1) e;eo for the overall reaction, e, let of(e) and ol(e) denote the set of starting reactants (precursors) and final products (targets), respectively; it follows that and and if oi..e) is the set of chemical species consumed or produced by the overall reaction, e, we have naturally a£.. e) = of(e) u ol(e). for any elementary-reaction step e1 e 0, let ot(e1) and al(e1) denote the set of reactants and products of e;, respectively; it follows that and t(o) = u al(e;). e;eo if l¥(o) is the set of chemical and active species consumed or produced by any element of o, we have for any set of chemical or active species m ~ m, let qf(m) and ql(m) denote the set of elementary­ reaction steps producing and consuming any element of m, respectively; it follows that and qf(m} ::::: u v-(aj) oj'?.m ql'{m) = u v""(ai). aiem 80 if (/j(m) is the set of elementary-reaction steps producing or consuming any element of m, we have for any set of elementary-reaction steps o ~ 0, let x(o) where any vertex corresponding to set m is termed m­ type, and any vertex corresponding to set o is termed 0type. the set of arcs is denote the set of opposite steps of the elementarywhere reaction steps included in set o; then, x(o) ~ {e;:-eie o}. any p-graph representing a set of chemical or active species and elementary-reaction steps is given by pair (m, o ), where o ~ 0 is the set of the elementary­ reaction steps, and m ~ m is the set of chemical and active species, where 'p(o) k;m. the set of vertices of the graph is v=oum, and in graphical representation, vertices of the 0-type are denoted by horizontal bars, and vertices of them-type are denoted by solid circles. page 69 page 70 page 71 page 72 page 73 page 74 page 75 page 76 page 77 page 78 conferenceproceed]ngs hungar~journal of industrial chemistry veszprem vol. 2. pp. 1 6 (2000) assessing impacts of a hydropower plant: ebro river, spain f.m. capel, f.h. rodriguez1 , d.g. de jal6n lastra and m.s. de los terreros (lab oratorio de zoologia, escuela tecnica superior de ingenieros de montes, universidad politecnica de madrid, ciudad universitaria, madrid, 28040, espana 1centro de investigaciones forestales de louriziin, aptdo. de correos 127, pontevedra, 36.080, espana) this paper was presented at the second international conference on environmental engineering, university ofveszprem, veszprem, hungary, may 29june 5, 1999 ebro river is one of the largest river in the iberian peninsula. a small hydropower plant, viana iii, was built in navarra province (north spain), so a small dam was constructed to divert flow from the mainstream to the plant channel. in the reach (''by-pass") affected by the flow reduction (around 263.550 :d of aquatic habitat) we studied the impact on the benthic and fish assemblages. before (autumn 1995) and after (autumn 1996) the plant started to operate, different habitat types (fast and slow waters) were sampled by electrofishing and trammel nets to estimate fish populations. invertebrates were sampled by neil cylinder in lotic habitats. densities and biomasses were estimated for invertebrates and fish populations. besides, growth, condition coefficients and mortalities were estimated for fish. having compared the flow regime before and after the station began to work, we estimated there was a considerable loss of aquatic habitat (40%). in consequence, in fast and shallow waters we noticed a dramatic decrease for the biomass (61 %) of the fish assemblage, although we observed an important increase for density (28%). in different types of habitat (fast and slow waters) where we sampled by nets, we also detected notable decreases in the catch ratio (40%) and average weight (59%). we also estimated a remarkable reduction in the density (56%) and biomass (35%) of the benthic fauna. results suggest the need of developing latest methods for the impact assessment, studying the natural regime of flow by a set of parameters based on historical data [1] and estimating habitat loss for fish and benthonic assemblages by the instreamflow incremental methodology [2]. introduction ebro river has the highest mean annual flow among the rivers flowing in the iberian peninsula. in the mainstream a small dam was constructed in order to divert flow to a channel from the mainstream to the new hydropower plant "viana lit'. this channel connects to the ebro river downstream the study reach again. we studied the by-pass reach of the river affected by the flow reduction. the study site (around 3360 m long) is located 10 km downstream logroiio city. we surveyed benthos and fish fauna before the plant started to operate, and after 1 year of work. the questions we were wondering were: what changes occurred in the flow regime? how could they affect the available habitat for benthic and fish fauna? how were the benthic and fish populations going to change in terms of biomass, density and structure? study reach the by-pass reach affected is part of the mainstream of the ebro river, 10 km downstream logrofio city. it represents the boundaries between navarra and la rioja provinces, entering the last one in the lowest part of the reach. since the reach is 3360 m long and the mean width is 78.4 m, we estimated the aquatic habitat to be 263,550 m2 after the dam, 1.2 m height, was constructed and before the plant started to operate. the thalweg gradient is estimated to be 0.126% and the mean altitude 341 m asl. we found the main part of the reach was slow waters (56.2%) but not much more than the fast water areas (43.8%), the ratio fast/slow lengths was 0.93. the flow regime was studied in mendavia gauge station, based on the data from october 1966 to september 1995. the results are included in fig.!. the mean annual flow is 123.4 m3 s·1 and the river has a pluvial discharge regime. we found a low flow period 2 400.00 ~ 350.00 ~ 300.00 g 250.00 ~ 200.00 tq 150.00 .<:: u .!! 100.00 0 50.00 0.00 ~ 1\ i \ i \ i \ _. ........._ i ~ ~ .-/" ...... ....,_ .-........... ~ 4 0 ~ ~ ~ ~ ~ ~ ~ ~ ~ d>.?cj((f~'<'<i~'r./f~"o/ 's ~tft /--natural regime -----1996 regime / fig.] historical data: mendavia (navarra) ! j j i i ! i ! fig.2 map of the study between july and october, the minimum flow occurs in september and the maximum in february. the riparian habitat was strongly affected by human activities (mainly agriculture). however, we ' found little areas wher~ the shrubs and trees provided a well structured riparian habitat: basically populus, salix, tamarix, ulmus and alnus. a map of the study reach and the sampling sites can be seen in fig.2. method based on the gaugings controlled by the confederaci6n hidrografica del ebro the flow regime was studied. mendavia was the gauge station selected because only leza creek {with very little flow compared with the mainstream) joins ebro river between the study reach and the gauge station. we calculated the mean annual flow for every month using the historical data from 1966 to 1995. after the plant started to operate, a new study was done. based on the turbinated flow by the plant {data given by the company in charge}. the new gauge in the ebro river was estimated, obtaining the mean flow for every month in the period january-september 1996. both methods, electrofishing and nets, were used to survey the fish assemblage in different sites of the reach. every fish was weighed (1-2 gr. error) and its fork length measured. hydroacoustic techniques were not suitab~e in the study reach, where the depths (less than 2-3m) do not get to the necessary values to apply this technique successfully. thanks to the low flow in september-october, a wadeable unit (1491 m2 in 1995 and 1161 ~in 1996) was found. we netted off the unit and applied electrofishing in order to obtain quantitative results. the unit was a glide in a side channel with an estimated mean depth of 50 em. electrofishing technique was applied with removal method (we did 3 passes). the rectificator device was custom-made in our laboratory and the power was supplied by a 1200 w generator. with 220 v, we obtained 2.5 a, avoiding danger for the fish [3] and the sampling team. the first step to study the fish populations was the calculation of length frequency [4], assimilating normal distribution to every age class. mean length and weight was calculated for every age class with a 95% confidence interval. weight/length relationship was calculated according to ricker {5,6] and condition coefficients were calculated for every age class. 3 table 1 historical data (q natural regime avg.: 129.9; q 1996 regime avg.: 44.1) hxctrolo!;iical xear oct nov dec jan 1966 44.0 76.8 251.2 167.3 66-67 105.2 357.2 210.2 122.7 67-68 38.1 120.2 257.7 327.7 68-69 48.3 25.8 38.6 66.4 69-70 33.3 28.1 272.0 319.7 70-71 39.7 37.7 43.7 47.1 71-72 33.8 150.3 191.4 180.8 72-73 78.2 57.4 7524.0 110.8 73-74 62.4 54.1 96.9 103.1 74-76 116.4 187.7 101.0 100.3 76-76 55.0 148.0 145.1 74.3 76-77 51.7 74.9 78.3 105.5 77-78 58.3 58.3 103.9 287.8 78-79 77.2 69.9 122.1 307.7 79-80 103.5 276.7 114.1 225.1 80-81 72.8 67.2 255.3 345.7 81-82 49.0 33.2 95.5 115.2 82-83 51.8 101.3 328.9 108.5 83-84 50.8 41.4 75.6 137.5 84-85 70.9 145.4 88.8 166.3 85-86 28.4 41.4 36.2 101.8 86-87 33.2 31.8 61.4 116.1 87-88 41.9 83.8 116.2 122.3 88-89 34.8 26.3 38.3 32.6 89-90 19.9 28.8 43.2 45.0 90-91 12.5 22.3 82.3 66.2 91-92 29.8 119.1 57.1 32.3 92-93 185.7 159.3 188.3 54.9 93-94 60.1 41.6 170.8 209.4 94-95 20.6 37.8 35.4 252.1 natural regime (m3 s'1) --t i 56.9 90.1 374.1 148.4 1996regime 69.2 length/age relationship was calculated adjusting a von­ bertalanffy curve [7]. using the same asymptotic value pennitted the comparison between 95 and 96 population growth. in the unit surveyed, the mathematical method to estimate the total number of fish was the maximum weighted likelihood [8], the most robust method recommended by cowx [9]. in order to minimize the error due to the different catch probability in every species and age class, we calculated the 95% confidence interval independently for every species and, when necessary, for every age class. biomass was calculated by assigning a mean weight to the fish in every species and age class. finally, relative density (number of fish per m2 ) and biomass (g m·2) was calculated for the unit surveyed. we studied the changes in the fish assemblage comparing the total number of fish, total biomass and composition between 1995 and 1996. indexes of diversity and evenness were also calculated. besides, we made electrofishing from a raft in deeper sites. as we could not net off a piece of water, no quantitative results could been obtained. these data completed our data base to study the fish assemblage composition and the age, length and weight relationships for every species. we got more data about the :fish assemblage by sampling different habitats with trammel nets. these nets consist of three parallel panels of netting, the two outer panels are of large-mesh netting and the inner panel is of a small mesh. the three panels are suspended from a float line and attached to a lead line. our feb mar apr may jun jul aug sep 241.7 232.4 133.0 105.3 158.3 77.4 62.8 64.1 95.2 98.1 101.0 104.0 57.0 43.4 50.7 43.2 220.0 200.3 217.9 112.6 68.6 44.2 48.1 83.9 75.7 128.4 154.7 119.1 76.7 41.8 42.1 74.9 231.6 251.2 88.7 84.8 43.1 21.1 23.6 26.9 54.7 116.0 128.7 248.8 164.0 63.8 42.9 40.4 380.1 217.0 169.0 258.6 126.6 70.8 58.2 71.9 312.9 125.0 147.0 76.0 183.2 61.9 58.2 53.1 199.9 282.7 184.3 74.8 58.6 63.6 55.6 54.6 90.7 145.8 350.1 152.7 110.3 64.0 59.6 60.9 235.4 99.6 201.9 92.9 57.3 57.3 52.3 54.2 132.1 78.4 134.8 199.8 277.9 104.4 85.1 61.2 515.4 283.3 322.5 307.0 131.2 94.3 85.3 77.2 430.9 222.6 347.0 157.8 92.1 85.9 78.2 84.3 92.4 199.9 210.5 230.4 126.5 78.4 67.6 63.6 132.4 114.7 183.7 130.1 62.9 50.7 51.8 54.7 103.5 137.5 57.3 39.7 52.6 65.4 58.3 43.9 185.0 161.4 25o.4 116.3 56.6 64.2 139.0 75.6 182.6 197.3 157.4 202.5 132.6 61.4 64.4 66.3 128.7 126.5 124.9 142.9 65.9 65.4 51.0 47.4 201.1 119.4 116.2 91.5 52.8 58.9 58.6 42.2 174.8 109.2 160.0 52.9 52.0 60.2 58.9 53.2 156.7 208.4 396.9 156.2 107.4 86.6 57.5 44.9 26.0 45.8 120.6 53.4 48.0 56.6 45.0 32.6 43.6 26.4 148.4 35.7 22.7 13.3 51.0 143.1 215.6 229.5 49.2 42.3 40.0 26.9 26.4 67.3 275.7 77.7 116.6 74.3 52.7 33.0 33.0 154.4 93.6 112.5 65.2 65.2 50.9 25.8 102.0 84.4 103.5 56.9 50.8 55.7 45.9 27.1 102.4 218.8 55.1 44.4 46.1 62.4 52.0 28.5 165.3 153.2 178.3 128.9 90.4 63.5 58.5 51.~ 116.1 84.7 36.3 21.5 23.2 17.6 14.9 13.7 trammel nets were 1.5 m tall and 12 m long. they were sited in different habitats and stayed floating one night. based on all the data obtained by trammel nets, we calculated catch per unit effort (cpue) and the mean weight for every species. we grouped the results obtained from nets sited in fast water and slow water habitats. then we compared the situation in every group before and after the plant was in operation. this way of sampling gave us more data about the assemblage composition and its variation in different types of habitats in the study reach. the benthonic fauna plays a crucial role as a bio­ indicator for the quality of the aquatic habitat. to study the benthos assemblage we used the neil cylinder, taking 4 replicates of 0.1 m2 each. the sample was done in lotic habitats, close to the same glide where we did electrofishing. in every replicate, we removed the cobbles to sample the complete assemblage living upon the river bed. we estimated the density and biomass for every population and the assemblage in 1995 and 1996. diversity and water quality indexes were calculated as well. results the natural flow regime based on the monthly data from 1966 to 1995 was compared with the flow regime registered after the plant started to operate. the natural flow had a winter peak in december (374,12 m3 s·1) and a low period between july and october, with the minimum in september (51 m3 s"1 }. 4 table 2 data obtained by sampling with trammel nets in 1995 and 1996 trammel nets year 1995 year 1996 fastwater slowwater fastwater slowwater habitats habitats habitats habitats cpue mean weight cpue mean weight cpue mean weight cpue mean weight 5.75 307.9 7.00 559.2 4.25 31.7 5.25 64.7 barbus graellsii carassius auratus cyprinus carpio chondrostoma toxostoma gobiogobio total (mean) 0.75 278.3 3.00 746.7 2.75 283.8 1.00 410.0 2.25 2.25 340.1 42.33 3.25 4.50 312.3 29.8 9.50 34.5 6.25 33.3 0.25 10.0 19.00 (162.6) 17.25 the flow regime based on the data from 1996 showed strong changes in the drought period. from april to september we observed a mean flow of 21,18 m3 s·1 (17% of the natural mean annual flow -maf-) and a reduction of 27% in the minimum (13,66 m3/s) that still occurs in september. using the month averages, the maximum/maf ratio was studied. it reveals strong changes in the torrential regime: the ratio was 3 for the natural regime and 0.94 for the available data of 1996. as we expected, the flow regime line started to become flatter in 1996. the mean reduction in flow was calculated and a 66% of the maf was obtained. the available series of data is considered time enough to evaluate the changes in the habitat available for benthos and fish fauna. the lfim, iqstream flow incremental methodology (2), permitted us to estimate the potential usable habitat (m2 m-1 of available habitat) for fish based on a very simple survey. at least ten cross-sections (measuring mean velocity, depth, substrate and cover for fish) enable us to run a hydraulic model and predict changes in the habitat caused by changes in flow. therefore, a 66% reduction in the maf can be evaluated in terms of suitable habitat for fish, based on the suitability curves that were calculated for cyprinids in spain [10]. processing data by the rhyhabsim program [11], the weighted usable area (wua) was related to the discharge and a 40% of potential loss of habitat was obtained for the cyprinids. the structure of the fish assemblage suffered patent changes after the plant started io operate. the data obtained by electrofishing and trammel nets are showed in tables 2 and 3. in the unit where we made electro fishing, a notable increase of relative density was detected (+28%), mainly due to the increase of the young of the year. relative density was 1.14 ind. m·2 in 1995 and 1.46 ind. m·2 in 1996. dominant species in number were barbus graellsii and chondrostoma. toxostoma. the frrst increased its importance from 5% to 17%. whereas the second decreased from 89% to 17% in the assemblage. the changes in the importance for the rest ofspecies were not representative, except for rutilus arcasii and phoxinus pho;-.;inus that were not found in 1996. in terms of biomass. the relative values of the unit surveyed feil a 61% related to 1995, due to the reduction in the number of fish belonging to the older classes. biomass changed from 41.4 g m"2 (1995) to 15.9 g m·2 (1996). relative importance of th"e principal (392.6) 8.75 (113.75) 13 (114.54) table 3 results obtained for the benthic assemblage year 1995 year 1996 benthic assemblage average standard average standard deviation deviation mean density of samples (ind m·2) mean biomass of samples (g m"2 ) 1856 1.15 765.9 0.50 808 452 0.74 0.62 species stayed the same in 1995 and 1996. barbus graellsii (70%), cyprinus carpio (20%) and chondrostoma toxostoma (9%) were the most important, and the rest of species maintained each one under 1% of the assemblage biomass. the results obtained by trammel nets also reveal great differences between the 1995 and 1996 situation. in the slow water areas, the mean decrease of the capture per unit effort (cpue) for all the species was 25% related to 1995 and the decrease of the mean weight was 71%. in fast water areas, the results were a 54% of reduction in the average of cpue and a 30% of the mean weight. carassius auratus was captured only in the first survey, in 1995. based on the two methods, every fish population was studied. in the electrofishing area. barbus graellsii increased its stock of youngest classes (0-2+), which number were multiplied by 10. oldest classes (5-7+) suffered an important reduction: 50% for relative density and a 65% in terms of relative biomass. results by trammel nets were in concordance with the results obtained by electrofishing. no data could be obtained for the young classes by nets, because the smallest fish captured was 115 mm long (age 1+) for this species. both types of results showed that the population was getting younger; results represent a change in the mean weight from the typical barbel 6-8 years old to a 2 years old barbel. chondrostoma. toxostoma. suffered an increase in the stock of young of the year -yoy(10%) but a decrease in the rest of the classes. in general, it supposed a 62% reduction in the total biomass in the electrofishing area. the results obtained by nets also revealed big reductions in the stocks and a movement of the adults to the faster waters from the lentic areas. the minimum size of the fish captured was 120 mm {age l+}. ln the area shocked, cyprinus carpio suffered a general reduction in the stocks (47%), which supposed a 6.3% reduction in the biomass. by trammel nets we captured 3 times more carps in the slow water habitats and the number decreased in the nets sited in the fast water habitats. the minimum size of the fish captured was 78 mm (age 0+). gobio gobio was the only species that clearly increased its stocks. in the electrofishing area, its number was multiplied by 4.5 and the biomass by 2.5. we only captured a fish in 1995 by nets, due to their small size. noemacheilus barbatulus stayed in the same patterns in both surveys. we only fished 2 individuals of rutilus arcasii and none of phoxinus phoxinus by electrofishing in 1996. carassius auratus was only fished in 1995 by nets and none was observed in the 1996 survey. length/weight and length/age relationships were calculated only for barbus g., cyprinus c. and chondrostoma t. lengtblweight relationship didn't show relevant changes between 1995 and 1996. the von-bertalanffy curves showed the same pattern as well. condition coefficients k (100 g cm.3) did not reveal clear changes in any species. mortalities could not be calculated due to the lack of fish in different age classes of the principal species. the benthic fauna is crucial to study how the physical changes affect the aquatic habitat. most of the fish species living in the study reach feed on the benthic fauna, therefore its density and biomass are considered fundamental elements to explain the changes that we. observe in the fish assemblage. the index of tuffery-verneaux [12], extended biotic index [13] and bmwp' [14] were calculated in 1995 and 96, showing no representative changes in the water quality. in both_years, the water was polluted and diversity was very low. the survey team found that silt particles were abundant in the site where the samples were taken. the flow was between 20 and 25 d s·1 in both surveys. strong reduction in terms of density and biomass was observed. density fell 56% and biomass 36% related to the 1995 survey, so we noticed an important loss in the available quantity of food for cyprinids in the lotic areas. discussion the instream flow·regime after the plant started to operate was characterized by a notable reduction in the minimum month average. besides, the drought period became longer and more intense (the flow was lower than before in the summer). based on the available data from 1996, we calculated an important decrease in the mean annual flow. applying the instream flow incremental methodology to the cyprinid populations, we calculated that a reduction of 66% in the mean annual flow potentially represented a 40% of loss for the aquatic habitat. the changes in the aquatic habitat affected the fish assemblage in different manners: the assemblage composition, the populations' structure and the relative density and biomass of each species. 5 the percentages of relative importance for the principal species mantained the same in the assemblage, in terms of biomass. however, in terms of density, we observed higher importance of barbels and lower of chondrostoma toxostoma related to 1995. we think that these changes are due to the physiological conditions of each species, as barbel is considered a genus that tolerates a very wide range of conditions while chondrostoma is a genus very adapted to the fast water habitats that decreased in the study reach. the population structure also changed for the , principal species. in the area where we could sample the young classes, a general increment of the recruitment was noticed for chondrostoma toxostoma and specially for barb us graellsii. we think that the reason was the reduction in the mean velocity and depth in the area, because this reduction created better conditions for the survival ofthe young of the year. the relative biomass obtained by electrofishing survey for barbus graellsii, chondrostoma toxostoma and cyprinus carpio suffered great reductions (the average loss was about 60%). in general, the results obtained by tranunel nets were in accordance with these results, showing great reductions in the cpue and the mean weights of the fishes captured. only the carp was a different case, because it multiplied its number by 3 in the slow water'habitats; the explanation is that the carp is considered as a species completely adapted to the slow waters. gobio gobio, species that was introduced in spain, was the only one that increased its stocks greatly in the area of electrofishing. the wide range of conditions that it tolerates in terms of velocity and depth permits it to spread widely in the spanish rivers today. the same as the carp, carassius auratus prefers slow water habitats, and it was captured by nets only in 1995. we think that they have not disappeared of the study reach. the rest of species: rutilus arcasii, phoxinus phoxinus and noemacheilus barbatulus, are benthic and ephibenthic species. they vary in their capture efficiency because they are very small, mobile and cryptic, and they hide on the river bed. the population density and structure of the environment strongly modify the size of error, so it is difficult to get reliable results by electro fishing [ 15]. we did not notice changes in the water quality based on the study of macroinvertebrates. however, their relative density suffered a 56% reduction and a 36% in their relative biomass after 1995. another study in austrian rivers also found important reductions in the benthic biomass with no changes in the diversity {hi]. the declination of the benthos assemblage was due to the fine particles deposition because of the flow reduction that caused the increasing filling of the interstitial habitat. the great reduction of fish biomass is explained by the loss of the basic food for the principal species. chondrostoma toxostoma and barbus graellsii feed on the benthos fauna in different stages of growth. however, the carp feeds on the abundant silt of the river bed and does not depend on the benthos populations. 6 therefore, the increase of lentic habitats largely benefits the carp populations. conclusion the impacts of viana iii hydropower plant in river ebro ecosystems can be synthesised as follows. an increasing bed-filling in the study reach was due to the abundance of fine particles and a notable decrease of the mean flow. this loss of suitable habitat for macroinvertebrates caused a great reduction of their biomass. in different manners, every fish population was affected by the changes in the available habitat and by the food reduction in the reach. while a slow waters species (the carp) found greater areas of available habitat, the rest of the species suffered important decrement in the stock of adults. we remark that a better comprehension of the habitat selection by fish, and the application of new methods to study the aquatic habit~t [1,2,10,11,17] are hot points to take into account for this kind of studies. acknowledgments we thank for the help of alicia lizarraga (hidroelectrica de navarra) and the friends of the lab. of hydrobiology who participated in the surveys. special thanks to ester, she was crucial for the final redaction of this text. references 1. baeza sanz d. and garcia de jalon lastra d.: limnetica, 2000, in press 2. bovee k.d.: a guide to stream habitat analysis using the instream flow incremental methodology. u.s. fish and wildlife service, fws/obs-82/26. 248 pp. fort collins, colorado, 1982 3. sharber n.g. and carothers s.w.; influence of electric fishing pulse shape on spinal injuries in adult rainbow trout. in: developments in electric fishing. oxford, fishing new books, pp. 19-26, 1990 4. petersen c.g.j.: rep.dan.biol.stn., 1896, 6, 1-48 5. ricker w.e.: j.fish.res.board can., 1973, 30, 409-434 6. ricker w.e.: bull.fish.res.bd.canada, 1975, 191, 1383 7. von bertalanffy l.: hum.biol., 1938, 10(2), 181-213 8. carle f.l. and strub m.r.: biometrics, 1978, 34, 621830 9. cowx i. g.: fish.mgmt., 1983, 14 (2), 67-82 10. garcia de jal6n d.: technical report for cedex, madrid, 1997 (in spanish) 11. joweti i.g.: river hydraulic and habitat simulation, rhyhabsim computer manual. new zealand fisheries miscellaneous report 49. ministry of agriculture and fisheries, christchurch, 1989 12. tuffery g. and verneaux j.: trav. sect. tech. p. et p. paris, 1967 (in french) 13. armitage p.d., moss d., wright j.p. and furse m.t.: wat.res., 1983, 17,333-347 14. alba tercedor j. and sanchez ortega a.: limnetica, 1988,4, 51-56 (in spanish) 15. zai.ewskim.: fish.mgmt., 1983,14 (4), 177-186 16. moooo.: regulated rivers: res. andmgmt., 1993,8,5-14 17. parasiewicz p., schmu1z s. and moog 0.: fish. mgmt. andecol., 1998,5,403-417 page 7 page 8 page 9 page 10 page 11 page 12 hungarian journal of industry and chemistry vol. 48(1) pp. 109–115 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-16 localization accuracy improvement of autonomous vehicles using sensor fusion and extended kalman filter istván szalay∗1, krisztián enisz1, hunor medve1, and dénes fodor1 1research institute of automotive mechatronics and automation, university of pannonia, egyetem u. 10, veszprém, 8200, hungary advanced driver assistance systems and autonomous vehicles rely heavily on position information, therefore, enhancing localization algorithms is an actively researched field. novel algorithms fuse the signals of common vehicle sensors, the inertial measurement unit and global positioning system. this paper presents a localization algorithm for vehicle position estimation that integrates vehicle sensors (steering angle encoder, wheel speed sensors and a yaw-rate sensor) and gps signals. the estimation algorithm uses an extended kalman filter designed for a simplified version of the single track model. the vehicle dynamics-based model only includes calculation of the lateral force and planar motion of the vehicle resulting in the minimal state-space model and filter algorithm. a tesis vedyna vehicle dynamics and mathworks simulink-based simulation environment was used in the development and validation process. the presented results include different lowand high-speed maneuvers as well as filter estimates of the position and heading of the vehicle. keywords: vehicle localization, extended kalman filter, sensor fusion, dead reckoning 1. introduction vehicle navigation systems are important components of autonomous driving solutions. these systems acquire the position, velocity and heading of the vehicle by using onboard or externally installed sensors such as wheel speed sensors, gyroscopes, accelerometers, inertial navigation systems (ins), compasses, radio frequency receivers, etc. [1]. the two most common vehicle localization techniques are dead reckoning and the use of a global navigation satellite system (gnss), like the global positioning system (gps). in dead reckoning, distance and heading sensors are used to measure the vehicle displacement vector which is then integrated recursively to determine the current position of the vehicle. measurement errors are accumulated by this integration, therefore, the accuracy of the position estimation is constantly decreasing. on the other hand, gps provides absolute vehicle positions without the accumulation of errors associated with dead reckoning through the use of satellites as the reference points. localization methods typically integrate gps with other sensors since gps suffers from outages and errors. many papers have integrated gps with ins [2–5]. others have integrated gps with the inertial measurement unit (imu) [6,7]. this paper integrates gps with vehicle sensors, similarly to refs. [8–10]. the continuous avail∗correspondence: szalay.istvan@mk.uni-pannon.hu ability of signals from vehicle sensors required by dead reckoning as well as the absolute positioning accuracy of gps render them combinable to achieve better performance [8, 9]. in this paper, a vehicle localization algorithm is presented that uses an extended kalman filter (ekf) to integrate dead reckoning with gps. dead reckoning is based on a simplified version of the single track model (stm) and uses a steering angle encoder, wheel speed sensors and yaw rate measurements. 2. modeling strategy the aim of the localization algorithm is to estimate the current position (x and y coordinates) and heading (yaw angle ψ) of the vehicle by fusing gps measurements with dead reckoning based on vehicle sensor signals. gps measurements provide the noisy xgps and ygps coordinates. vehicle sensors provide the steering angle δ, the four wheel speed signals ωi and the yaw rate ψ̇. these measurements are available in most commercial vehicles. the lateral acceleration sensors were not used because the acceleration signal is usually less reliable and noisier than the other vehicle signals. the localization algorithm fuses these signals using an extended kalman filter which requires an appropriate system model. the system model connects the available and estimated signals with inputs, states and outputs of the system. the simplest and most practical solution is to https://doi.org/10.33927/hjic-2020-16 mailto:szalay.istvan@mk.uni-pannon.hu 110 szalay, enisz, medve, and fodor xe ye ~r0 ∆~r1 ∆~r2 t0ts x0 u0 noise f ( x0, u0, p0 ) = y1 = h ( x1, u1,m1 ) 1ts x1 u1 noise f ( x1, u1, p1 ) = y2 = h ( x2, u2,m2 ) 2ts x2 u2 noise figure 1: dead reckoning steps and propagation of the system state formulate the system model in a way that produces the true-position and heading state variables, the input variables of vehicle sensor signals and the outputs of gps signals. 3. dead reckoning algorithm dead reckoning or path integration is the process of estimating the current position of a vehicle by using a previously determined position, and projecting that position based upon known or estimated speeds over a time period and course that has elapsed. dead reckoning is subject to cumulative errors. in continuous time, dead reckoning results in the integration of the velocity vector or double integration of the acceleration vector with respect to time. in discrete time of sample time ts, the equivalent of integration can be written as the following in vector-sum form: ~rk = ~rk−1 + ∆~rk = ~r0 + k∑ i=1 ∆~ri (1) the equivalent coordinate form of eq. 1 for a vehicle in planar motion is[ xk yk ] = [ xk−1 yk−1 ] + [ ∆xk ∆yk ] = [ x0 y0 ] + k∑ i=1 [ ∆xi ∆yi ] (2) in the vector form, ~rk denotes the position of the vehicle’s center of gravity (cog) at tk = kts and ∆~rk stands for the displacement between tk−1 = (k − 1)ts and tk = kts. the initial position in vector form is ~r0 and in coordinate form is [x0, y0] t (see fig. 1). dead reckoning is performed in the earth-fixed coordinate system xe − ye. using the vehicle sensors, displacements in the vehicle axis system xv − yv can be calculated. to rotate the displacement into the earthfixed coordinate system, changes in the heading or yaw angle ψ of the vehicle have to be tracked. the yaw angle can be estimated by integrating the yaw-rate signal ψ̇ as ψk = ψk−1 + ψ̇kts = ψ0 + k−1∑ i=1 ψ̇its (3) the displacements ∆xv,k and ∆yv,k have to be calculated in the vehicle axis system xv − yv. the displacements from the vehicle axis system to the earth-fixed coordinate system are transformed using a two-dimensional rotation matrix r(ψk−1) that rotates around the vertical axis ze by ψk−1.[ ∆xk ∆yk ] = [ cosψk−1 − sinψk−1 sinψk−1 cosψk−1 ] ︸ ︷︷ ︸ r(ψk−1) [ ∆xv,k ∆yv,k ] (4) the simplest estimation of the longitudinal displacement ∆xv,k involves the estimation of the longitudinal speed vk as the average of the wheel speed signals divided by the effective radius of the tires r: ∆xv,k = vk−1ts, where vk−1 = r 4 4∑ i=1 ωk−1,i (5) the lateral displacement ∆yv is estimated by the second integral of the lateral acceleration, assuming an initial lateral velocity of zero: ∆yv,k = 1 2 ay,k−1t 2 s . (6) the lateral acceleration ay can be in the form of a sensor signal from an accelerometer or calculated based hungarian journal of industry and chemistry localization accuracy improvement of autonomous vehicles 111 s ~r = [ x y ] xe ye xv + ψ xw xv yv l1 l2 ~v1 ~v ~v2 ~ay o ~fy1 ~fy2 + ψ̇ − α2 − β − α1 + δ ze color coding: velocities: ~v, ~v1, ~v2 forces: ~fy1, ~fy2 lateral acceleration: ~ay yaw rate: ψ̇ figure 2: the physical quantities of the single track vehicle model following [11] on the vehicle dynamics model and other vehicle sensor signals. usually, the accelerometer signals are less reliable and noisier than those of the steering angle, velocity and yaw-rate sensors, therefore, ay was calculated based on a vehicle model and signals from vehicle sensors, in a similar way to ref. [9]. 4. lateral vehicle dynamics as a basis for modeling the lateral vehicle dynamics, the well-known single track vehicle model defined by riekert and schunck [12] was used. fig. 2 shows the physical quantities related to the single track vehicle model. this paper uses the sign conventions defined in ref. [11]. the classical single track vehicle model includes several important simplifications. it only describes lateral motion and rotation around the vertical axis, while neglects vertical dynamics as well as rolling and pitching. furthermore, the equations of motion of the single track vehicle model are linearized. to define the lateral acceleration as a function of the steering angle δ, longitudinal velocity v and yaw rate ψ̇, the lateral force equation of the model can be used: may = fy1(α1) + fy2(α1) (7) the linearized tire forces as the products of the cornering stiffnesses (c1 and c2) and tire slip angles (α1 and α2) are calculated as follows: fy1(α1) = −c1α1 and fy2(α2) = −c2α2. (8) tire slip angles (α1 and α2) are defined by the velocity triangles of the two axles in the following nonlinear forms (see fig. 3): tan (α1 + δ) = v sinβ + ψ̇l1 v cosβ (9) tanα2 = v sinβ − ψ̇l2 v cosβ (10) eq. 9 corresponds to the yellow part of the velocity triangle corresponding to the front axle and eq. 10 to the rear axle. the tire slip angle equations are linearized and the sideslip angle β omitted: α1 ≈ β + ψ̇l1 v − δ ≈ ψ̇l1 v − δ (11) α2 ≈ β − ψ̇l2 v ≈ − ψ̇l2 v (12) the lateral acceleration ay depends on the values of the vehicle sensors according to ay ≈ − c1 m ( ψ̇l1 v − δ ) + c2 m ψ̇l2 v (13) front axle xw xv ~v1 ~v ~̇ψ×~l1 + δ − β − α1 + δ + α1 rear axle xv ~v ~v2 ~̇ψ×~l2 − β − α2 figure 3: velocity triangles in the single track vehicle model 48(1) pp. 109–115 (2020) 112 szalay, enisz, medve, and fodor in this way, the lateral acceleration depends on the usually available cornering stiffnesses (c1 and c2), the mass and length of the vehicle (m, l1 and l2), and the signals of the vehicle sensors. if available, the lateral acceleration signal from an accelerometer can be incorporated into the sensor fusion algorithm. 5. extended kalman filter design the application of an extended kalman filter requires a stochastic mathematical model of the system in a statespace representation including the statistical properties of the process and measurement noises [13, 14]. 5.1 state-space model the state-space representation includes both the state and measurement equations in vector form by introducing the functions f and h, the known input vector u, processnoise vector p and measurement-noise vector m: xk = f ( xk−1, uk−1, pk−1 ) (14) yk = h ( xk,mk ) (15) the system is time invariant, therefore, f and h are not indexed. the discrete-time indexing of the difference equations is illustrated in fig. 1. to estimate the vehicle’s position, the dead reckoning eqs. 2–6 are used augmented to include the lateral acceleration (eq. 13) as a computed value. the resulting state equation of the discrete-time state-space model is eq. 18. by examining eq. 18, it can be concluded that the system is nonlinear and, therefore, a linear kalman filter is unsuitable. in this paper, an extended kalman filter is used. the output vector y of the system includes the gps measurements that consist of the true position and measurement noise m defined by the output function h: yk= [ xgps,k ygps,k ] = [ xk +mx,k yk +my,k ] = h ( xk,mk ) (16) 5.2 jacobians the extended kalman filter requires the jacobians of both the state and measurement functions with respect to the state vector: f k = ∂f ∂x ∣∣∣∣∣ x̂+ k−1 and h = ∂h ∂x ∣∣∣∣∣ x̂+ k−1 = [ 1 0 0 0 1 0 ] (17) the elements of h are constant, while the elements of f k depend on the discrete time k, as defined by eq. 19. the sample time ts was 100 ms, which was sufficiently small to capture the vehicle’s movement but not too small for gps sampling. xk =  xk yk ψk  =  xk−1 + vk−1ts cos (ψk−1)− 1 2 ay,k−1t 2 s sin (ψk−1) + px,k−1 yk−1 + vk−1ts sin (ψk−1) + 1 2 ay,k−1t 2 s cos (ψk−1) + py,k−1 ψk−1 + ψ̇k−1ts + pψ,k−1  = f ( xk−1, uk−1, pk−1 ) (18) f k =  1 0 − sin (ψk−1) vk−1ts − 1 2 cos (ψk−1) ay,k−1t 2 s 0 1 cos (ψk−1) vk−1ts − 1 2 sin (ψk−1) ay,k−1t 2 s 0 0 1  , uk = ay,kvk ψ̇k  (19) 5.3 noise model during the design of the extended kalman filter, a timeinvariant and normally distributed process as well as measurement noise were assumed: p ∼ n ( 0, q ) , m ∼ n ( 0, r ) (20) for the development and testing of our extended kalman filter algorithm, a tesis vedyna vehicle dynamics-based simulation environment was used with configurable noise models (see section 6). although it was possible to match the noise and covariances of the filter perfectly, the filter and noise models were tuned in a slightly different way. the measurementand processnoise covariances for both the filter and noise models have been estimated based on the characteristics of the sensor and gps range error statistics [15]: q = diag ( 0.2 m2, 0.2 m2, 0.01 rad2 ) (21) r = diag ( 1.5 m2, 1.5 m2 ) (22) hungarian journal of industry and chemistry localization accuracy improvement of autonomous vehicles 113 our algorithm performs the dead reckoning in the earthfixed coordinate system and, therefore, no predetermined difference between the direction covariances xe and ye is present, so q11 = q22 and r11 = r22. the displacement variance of 0.2 m2 corresponds to an error of 4.5 m s−1 in the wheel speed-based velocity calculation. in the presence of non-normally distributed noise, the filter is not optimal. 5.4 the extended kalman filter algorithm the extended kalman filter algorithm follows wellknown steps [14]. the prediction equations are x̂−k = f ( x̂+k−1, uk−1, 0 ) (23) p− k = f kp + k−1f t k +q (24) calculation of the kalman gain is kk = p− k h t k ( hkp − k h t k +r )−1 (25) the correction equations are x̂+k = x̂−k +kk ( yk − hk ( x̂−k , uk, 0 )) (26) p+ k = ( i −kkhk ) p− k (27) the initial state is determined based on the first several gps observations whilst in motion. 6. simulation environment the development of the localization algorithm was conducted in a mathworks matlab/simulink-based vehicle dynamics simulation environment. the tesis vedyna model library was used to model the vehicle, road system and maneuvers (fig. 4). the advantage of our simulation platform lies in its integrated structure. algorithms developed in matlab and simulink can be integrated into the tesis vedyna vehicle dynamics simulation which enables softwarein-the-loop testing and real-time hardware-in-the-loop analysis to be implemented by the national instruments pxi hardware system. in our platform, real streets using gps coordinates or map databases can be modeled. this enables the direct comparison of simulations and real-world measurements. 7. simulation results the extended kalman filter was tuned and studied in simulated test maneuvers during which data were collected. the test maneuvers were performed on a virtual test track that included lowand high-speed driving, accelerating, braking and cornering. the size of the test track was around 2 by 2 km and the simulated test maneuvers lasted for 528 s. our extended kalman filter was compared to simple dead reckoning and gps observations. the true path, the result of dead reckoning and the position, estimated by the implementation of our extended kalman filter, are shown in fig. 5. figure 4: tesis dynaanimation user interface 7.1 comparison with dead reckoning dead reckoning without the aid of the extended kalman filter accumulated a large position error during the test maneuvers. the error of the dead reckoning reached 100 m, as can be seen in fig. 5. the position estimated by our extended kalman filter did not include error accumulation and performed better than dead reckoning alone. 7.2 comparison with gps due to the large difference between the size of the path and the position errors, the difference between gps observations and the extended kalman filter estimates were not as clearly visible as the error of dead reckoning (fig. 5). zooming in on certain parts of the path enables visual evaluation of a particular part of the path 0 500 1000 1500 2000 0 500 1000 1500 2000 position, x, [m] po si tio n, y ,[ m ] true path dead reckoning ekf estimation figure 5: the real path, dead reckoning only and ekf estimation 48(1) pp. 109–115 (2020) 114 szalay, enisz, medve, and fodor 0 2 4 6 8 10 12 14 16 18 20 22 24 26 −2 0 2 4 displacement, x, [m] d is pl ac em en t, y ,[ m ] real path gps position ekf estimation figure 6: the initial section of the true, estimated and gps-observed paths (fig. 6). to evaluate the extended kalman filter estimate and make it numerically comparable to the gps observations, the instantaneous and average distance errors were calculated. the distance error dk of the estimation is calculated as the distance between the estimated and true positions: dk = √ (x̂k − xk) 2 + (ŷk − yk) 2 (28) the distance error dgps,k of gps observations is dgps,k = √( xgps − x )2 + ( ygps − y )2 (29) the average distance errors are d̄ = 1 n n∑ k=1 dk and d̄gps = 1 n n∑ k=1 dgps,k (30) the distance errors of the gps observations and the extended kalman filter position estimates are shown in fig. 7. the timespan of the test maneuvers was 528 s, moreover, at a sample time of 100 ms, it produced 5280 points. the average distance error of the gps observations was d̄gps = 751 mm. our extended kalman filter reduced the average distance error significantly, d̄ = 457 mm. besides the average values, the distributions of the distance errors are also of interest. the distance errors are discrete values whose distributions can be approximated by their histograms. such histograms are shown in (fig. 8) with a bin width of 10 cm. 8. conclusions in this paper, a real-time vehicle localization algorithm developed and implemented in a tesis vedyna vehicle dynamics simulation environment was presented. the localization algorithm used an extended kalman filter to fuse gps observations with vehicle sensor measurements of only the steering angle, yaw rate and wheel speeds. the underlying state-space model is based on planar dead reckoning that calculates the longitudinal displacement using wheel speed and lateral displacement in a simplified version of the single track model. the state-space model only includes the x and y coordinates and the yaw angle ψ to minimize the model and filter algorithm. the performance of the position estimator was analyzed during different highand low-speed maneuvers. compared to the dead reckoning and gps observations that were not integrated, the integrated system performed significantly better. the average distance error was reduced by 39 %. further improvement of localization accuracy would be possible by using a more sophisticated vehicle model resulting in a more complex implementation of an extended kalman filter with a much higher computational burden. 0 100 200 300 400 500 0 1 2 3 4 time, t, [s] d is ta nc e er ro rs ,d an d d g p s ,[ m ] gps distance error dgps ekf distance error d gps average d̄gps = 751 mm ekf average d̄ = 457 mm figure 7: distance error comparison hungarian journal of industry and chemistry localization accuracy improvement of autonomous vehicles 115 0 1 2 3 4 0 200 400 600 800 1000 distance error, d, [m] c ou nt histogram of dgps histogram of d d̄gps = 751 mm d̄ = 457 mm figure 8: distance error histograms acknowledgement this research was supported by the project efop-3.6.216-2017-00002 entitled "research of autonomous vehicle systems related to the autonomous vehicle proving ground of zalaegerszeg". references [1] karlsson, r.; gustafsson, f.: the future of automotive localization algorithms: available, reliable, and scalable localization: anywhere and anytime, ieee signal processing magazine, 2017, 34(2), 60–69 doi: 10.1109/msp.2016.2637418 [2] farrell, j.a.; givargis, t.d.; barth, 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international organization for standardization, geneva, ch, 2011 [12] riekert, p.; schunck, t.e.: zur fahrmechanik des gummibereiften kraftfahrzeugs, ingenieur-archiv, 1940, 11(3), 210–224 doi: 10.1007/bf02086921 [13] bucy, r.s.: linear and nonlinear filtering, proceedings of the ieee, 1970, 58(6), 854–864 doi: 10.1109/proc.1970.7792 [14] simon, d.: optimal state estimation: kalman, h infinity, and nonlinear approaches (wileyinterscience, new york, ny, usa), 2006 isbn: 0471708585 [15] faa william j. hughes technical center: global positioning system (gps) standard positioning service (sps) performance analysis report, 2019 https://www.nstb.tc.faa.gov/reports/ 48(1) pp. 109–115 (2020) https://doi.org/10.1109/msp.2016.2637418 https://doi.org/10.1109/87.852915 https://doi.org/10.1109/taes.2002.1008998 https://doi.org/10.1109/taes.2012.6178100 https://doi.org/10.1109/taes.2012.6178100 https://doi.org/10.1109/tvt.2010.2070850 https://doi.org/10.1109/tvt.2010.2070850 https://doi.org/10.1109/syscon.2019.8836794 https://doi.org/10.1109/fcst.2006.27 https://doi.org/10.1109/fcst.2006.27 https://doi.org/10.1109/vnis.1991.205808 https://doi.org/10.1109/tcst.2006.886439 https://doi.org/10.1109/tcst.2006.886439 https://doi.org/10.1109/plans.2000.838306 https://doi.org/10.1109/plans.2000.838306 https://doi.org/10.1007/bf02086921 https://doi.org/10.1109/proc.1970.7792 https://doi.org/10.1109/proc.1970.7792 https://www.nstb.tc.faa.gov/reports/ introduction modeling strategy dead reckoning algorithm lateral vehicle dynamics extended kalman filter design state-space model jacobians noise model the extended kalman filter algorithm simulation environment simulation results comparison with dead reckoning comparison with gps conclusions hungarian journal of industrial chemistry veszprem vol. 29. pp. 91 94 (2001) approximate models application for modelling of fixed bed reactors m. szukiewicz and r. petrus (department of chemical engineering and process control, rzesz6w university of technology, al. powstafic6w warszawy 6, 35-959 rzesz6w, poland) received: july 7, 2000; revised: january 17,2001 the approximate linear driving-force model which is typical and commonly used for diffusion processes, fails in the case of diffusion with reaction processes (e.g. heterogeneous catalysis). this results from the rapidity of the mass transfer for processes with chemical reaction. a method based on a solution for a single catalyst pellet has been used to evaluate coefficients of the mentioned approximate formula. the application of this formula for modeling of an isothermal fixed­ bed reactor with non-linear kinetic rate is presented. accuracy of the proposed model is very good. the error does not exceed 0.02 for the steady state. introduction fixed bed reactors are commonly used in industrial practice for heterogeneous catalysis processes. there are two groups of models applied in modeling of such type of apparatus. (i) pseudohomogeneous models, which assume the same temperature and component concentrations in the fluid bulk and catalyst particles. due to this assumption the model is described by partial differential equations (pde) only for fluid phase. pseudohomogeneous models, despite of their low accuracy in most cases, are relatively easy to solve and they are willingly used for description of reactors. (ii) heterogeneous models, in contrast to pseudo­ homogeneous ones, give results with quite good accuracy. they are described by pde both for fluid and for catalyst pellet but their solution is difficult to obtain. the widely reported way to avoid this drawback is to use an effectiveness factor concept. it reduces the equations set of the heterogeneous model and makes the solution much easier to obtain. unfortunately, for most cases, finding the proper value of the mentioned factor is difficult and/or lengthy that limits its application. there is another way for simplification of mathematical modeling, which is widely reported for diffusion and adsorption processes. in this approach pde for mass balance in a pellet is replaced by a proper ordinary differential equation (ode) ~ so-called .,approximate model" that simplifies greatly the model solution at the same or only slightly worse accura(:y. for description of diffusion and reaction processes a small number of equations that approximate a mass balance in the porous particle has been found in literature. kim [1] has proposed linear driving force approximation model that characterises good accuracy but also complexity of derived formula. moreover the individual terms of the model accumulation, rate of mass transfer and reaction rate have no longer their physical meaning. goto and hirose [2], have presented a number of approximate models, but their accuracy for diffusion and reaction processes are unsatisfactory for a wide range of thiele modulus and time. szukiewicz [3] has presented the approximate formula free of the mentioned drawbacks. reported models concern only first -order reactions. the application of an approximate linear driving­ force model of the catalyst pellet for modeling of a fixed bed reactor is presented. a method based on a solution for a single catalyst pellet has been used to evaluate coefficients in the approximate formula. the method can be used for any type of kinetic equations. accuracy of the proposed model is very good. the error does not exceed 0.02 for the steady state. models it is assumed that a single, isothermal and irreversible reaction is to be carried out on catalyst pellets in a contact information: e-mail:ichms@prz.rzeszow.pl; tel (0-48) 178651216 92 heterogeneous fixed-bed reactor. both models are presented in dimensionless form. heterogeneous (exact) model mass balance for fluid and for a pellet with initial and boundary conditions are described by eqs. (1)(5) ic: bc: e deb +deb + (l-se)st(cb -cj= 0 (1) e d'l: dz c(o,x)=o cb(o,z)=o, cb(7:,0)=1 e£1 -0 ~x=o' (2) (3) (4) (5) in the above equations a pellet surface concentration is denoted by c8, i.e. cs = c(1:,x = 1). approximate model this model is based on the concept of approximate model for the pellet. using it in heterogeneous model of the reactor leads to replacing all terms described mass transfer between a pellet and its surrounding by a single term describing overall mass transfer flux with an assumption that concentration profile inside the pellet is replaced by an average concentration cav· see also derivation of the approximate model for the catalyst pellet [3] and presented there references concerned diffusion and adsorption processes. mass balance for fluid and for a pellet with initial and boundary conditions are described by eqs. ( 6) (9) e ocb+ocb+(l-ee)s't·k(cb-cav)=o (6) t' a-r (}z (7) 13 12 11 10 --n=1.0 ·········· n=1.5 ·················n=2.0 --n=2.5 --n=3.0 0 10 fig.l coefficient fvs. thiele modulus. 1 (11) k 1+ bi 111 / f in the approximate model of the catalyst pellet an unknown coefficient f occurs, which is a reflection of the rapidity in the mass transfer rate resulting from chemical reaction. passing over this coefficient leads to significant errors for larger values of thiele modulus (cf. cited above goto and hirose [2]). the f value can be calculated as follows. firstly a model of a single catalyst pellet (eq. (2) with accompanied ic and bc} for inlet reactor conditions should be solved that gives a concentration profile inside the pellet. generally, it can be done numerically. finding this solution is the basic difficulty of the presented method, however this task is relatively simple, well reported in literature (e.g. finlayson [4], davis [5]). next, the found concentration profile enables calculation of both steady-state mass flux of a reactant (using e.g. the second of the boundary condition (5)) and steady-state average concentration in the pellet (using eq. (10)). comparison of mentioned mass flux and overall mass flux gives a value of coefficient f. although this coefficient is time­ dependent the steady-state value· of it is accepted for calculations [3]. for both models partial differential equations have been reduced to a set of ordinary differential equations by applying orthogonal collocation method. the set of odes has been solved using procedure lsoda. results and discussion ic: c11 (0.z)=o, c11 (r,o)=l (8) calculations have been carried out for power-law type of kinetic rate: bc: where (9) (12) where n=[l.o, l.5, 2.0, 2.5, 3.0] (10) firstly, for all values of n the coefficient f was computed assuming for the pellet the inlet reactor conditions. results are presented in fig.l. value off rises with thiele modulus. it is, as mentioned above, a 1.0 0.9 0.8 0 c::: .q 0.7 "§ ~ 0.6 0 s::: 8 0.5 -a; '5 0.4 0 0.3 --eqs {1 )-(2) -·-······· eqs (6)-(7) bim=500 0.2 l----l---l---'--...1---'---'------.j.---l----'---' 0 2 4 thiele modulus, q, fig.2 steady state reactor outlet concentration vs. thiele modulus for small external mass transfer resistance. 1.0 0.8 0 c::: ~ 0.6 ~ "e (]) 0 § 0.4 0 ]! "5 0 0.2 --eqs (1 )-(2) --········ eqs (6)-(7) bim=50 2 4 thiele modulus, .p fig.3 steady state reactor outlet concentration vs. thiele modulus for large external mass transfer resistance. 10 10 reflection of the rapidity in the mass transfer rate resulting from chemical reaction. it is significant that values of coefficient f for linear type kinetic are exactly the same as calculated analytically (see [3]). secondly both presented models have been compared in wide range of thiele modulus ( 4>e [0 .. 1 oj) and biot number (bime[lo .. oo]). furthermore, it was assumed st=loo, ee=0.3 and £p=0.5. all tests have shown good compatibility of the results obtained for heterogeneous and approximate models at steady state. the maximum absolute error has not exceeded 0.02. for linear type of kinetic rate the outlet concentrations were the same for entire range of thiele modulus, for non­ linear one the error grew with the value of mentioned parameter. it should be emphasized that for small and intermediate values of thiele modulus (that is for most cases in practice) the error is very small. examples of these observations are presented in fig.2 and in fig.3. it could be expected that the dynamic behaviors of the considered models are not the same. taking into account the time dependence of a concentration a slightly worse compatibility for approximate and exact models was observedsee fig.4. it is qualitative only but not bad. the models start from the same initial conditions so that differences grow firstly for 1:<0.3 (near this time the maximal deviation between results is 1.0 0.8 0 s::: ._g 0.6 ~ c ~ 0.4 c 0 0 0.2 -eqs (1)-(2) ......... eqs (6)-(7) <!>>=5, bi>=500, n=2 93 0.2 0.4 0.6 0.8 1.0 reactor length, z fig.4 time-dependence of concentration profiles for approximate and exact models. observed), next drop and for a sufficiently long time vanish (here for 't~0.6 appropriate curves for both models are the same). some problems cause the defining of the time after which both considered models give the same results. this time depends on the model parameters values and it is difficult to find a simple relationship to define it. for practical purposes the inequality derived for the model of single catalyst pellet with linear reaction rate (given by szukiewicz [3]) can be used (in modified form). for tested values of the model parameters considered time was shorter than 'ta (eq. 13). 25 "( = , a 3j +$" (13) summarizing, the approximate model evaluates the exact solution well for sufficiently long times, which results from the way of calculating the coefficient f. the presented method of the heterogeneous fixed­ bed reactor simulation can be recommended because the approximate model is much more tractable for solution than the exact one. we can get great simplificjtion of the analysis of the heterogeneous fixed-bed rea~.:tor operation condition at the expense of solving a catalyst pellet model. the method is especially convenient with regard to steady-state conditions which task is of great importance in practice. conclusions the approximation of the catalyst pellet by the lumped parameter model yields an essential simplification of analysis and computation for fixed-bed reactors. the accuracy of calculations is very good with respect to steady state and good with respect to time-dependence of concentration profiles. for short times compatibility of results is qualitative only but error quickly vanish as time passes. the presented method has a shortcoming. it is needed to sqlve the model of single catalyst pellet (to determine the coefficient f \'alue). however this problem is relatively simple, well reported in literature. 94 symbols bim mass biot number c concentration of a reagent cav average concentration of a reagent in a pellet cb bulk concentration of a reagent cs surface concentration of a reagent f coefficient ra dimensionless reaction rate st stanton number x spatial variable in a pellet z spatial variable in a reactor ee bed porosity ep pellet porosity <p thiele modulus t time 'ta time after which both considered models give the same results references 1. kim d.h.: linear driving force formulas for diffusion and reaction in porous catalysts, aiche j., 1989, 35, 343 2. goto m. and hirose t.: approximate rate equation for intraparticle diffusion with or without reaction, chern. eng. sci., 1993,48, 1912 3. szukiewicz m. k.: new approximate model for diffusion and reaction in a porous catalyst, aiche j., 2000, 46, 661 4. finlayson b. a.: nonlinear analysis in chemical engineering, mcgraw-hill inc., new york, 1980 5. davis m.: numerical methods and modeling for chemical engineers, wiley, new york, 1984 page 95 page 96 page 97 page 98 hungarian journal of industry and chemistry vol. 51(1) pp. 61–66 (2023) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2023-09 investigation of regional differences in the organic fraction of municipal solid waste in hungary eliza tóth1*, janka bobek-nagy1 and róbert kurdi1 1 sustainability solutions research lab; research centre for biochemical, environmental and chemical engineering; faculty of engineering; university of pannonia; egyetem u. 10, veszprém, 8200, hungary municipal solid waste management is crucial in terms of the environment, sustainability and the circular economy. the directly landfilled organic fraction of municipal solid waste (ofmsw) offers a lot of potential with regard to energy recovery or as a soil substrate. in this study, the regional differences in hungary according to various living structures and conditions (villages and urban areas) were demonstrated to provide a foundation for further usage or treatment. the fact that the biological fraction (leaves, kitchen waste and fine soil-like material) of ofmsw from typically urban areas like the examined city of pécs is larger than in a rural area, e.g. marcali district, was highlighted. on the other hand, the ofmsw from rural areas contains more hazardous materials such as medicinal ampoules due to the lack of possibilities to dispose of them suitably. after evaluating the composition of the ofmsw, the directly landfilled quantity of msw could be further reduced. in conclusion, according to the high proportions of plastic and paper as well as its promising heating value, the largest particle size fraction (>4 cm) could be utilized as refuse-derived fuel (rdf) and the finer, organic material-rich fraction as a soil substitute following further purification. keywords: ofmsw, regional differences, rdf, mbt 1. introduction despite being well-engineered, landfilling is one of the least favorable waste management methods because of the significant environmental risk presented by it (leaching, methane formation) [1]. the eu landfill directive to accelerate the transition to a circular economy has introduced restrictions on landfilling to decrease the total amount of municipal waste deposited to under 10% by 2035 without exception [2]. in hungary, the ofmsw is less than 60-80 mm in diameter and separated by a trommel screen during mechanical biological treatment (mbt). the ofmsw has a big share of the total quantity according to studies, 40-85% of the total msw in fact [3] depending on the country concerned, the majority of which is found at least 100 mm below the surface [4]. accordingly, the reduction in the organic fraction as a result of energy recovery or other utilizations will effectively fulfill the directive. regional differences were mainly observed in the composition of the ofmsw. differences between nations and regions are observed, moreover, the causal factors are the various infrastructure developments, the current situation of the inhabitants and the classification of the categories [5]-[8]. the utilization of waste remains an unresolved issue worldwide. due to its high level of received: 31 march 2023; revised: 11 april 2023; accepted: 14 april 2023 *correspondence: toth.eliza@mk.uni-pannon.hu plastic content, the ofmsw could be used in energy recovery as refuse-derived fuel (rdf) or as a raw material for pyrolysis/gasification. besides, anaerobic digestion is also a promising solution to utilize the ofmsw [9]-[12]. on the other hand, fine fractions could be used in construction materials such as in bricks [13] as well as a substitute for planting soil throughout their analysis and purification [14]. consequently, the importance of investigating the ofmsw can be recognized because its usage largely depends on its material composition and physico-chemical properties. in addition, the quality of waste streams could be improved by raising public awareness as well as educating people about the importance of waste separation and using the available services to not only separate the usual recyclable materials but also compost, kitchen waste, garden waste, etc. 2. materials and methods 2.1. raw materials in this study, samples from two different hungarian waste collection regions were examined, which were collected from the marcali és térsége közszolgáltató https://doi.org/10.33927/hjic-2023-09 mailto:toth.eliza@mk.uni-pannon.hu tóth, bobek-nagy and kurdi hungarian journal of industry and chemistry 62 nonprofit kft. (mtksz) and dél-kom nonprofit kft. (kökény). mbt technologies and the day of sampling were identical in both cases to ensure the ofmsw data could be evaluated by only considering the regional differences. stabilization periods also apply in both technologies. mbt is carried out on the non-hazardous waste inside the plants; the technological scheme of mbt is shown in figure 1. the first step of mechanical processing is the weighing and shredding of the waste into particle sizes of <350 mm in diameter before the magnetic metals are separated. the next step is trommel sorting where the biological waste stream of particle size <60 mm in diameter (ofmsw) is removed for further treatment. the residue of ofmsw (>60 mm in diameter) passes through an eddy current separator (ecs) where the non-ferrous metals are recovered before the air separation unit divides the waste stream into two parts. the heavy fraction containing mostly stones and bricks is dumped directly in a landfill site. the light and middle fractions are driven through a post-treatment shredder (<50mm) and a second magnetic separation where the excess ferrous metals are extracted from the waste stream. the residue for refuse-derived fuel (rdf) is baled. the input of the kökény plant is 116,979,583 kg/year, moreover, the rdf and organic fraction produced are 39,528,620 kg/year (34%) and 46,899,164 kg/year (40%), respectively, based on data from 20182021 [15]. the capacity of the mtksz plant is smaller, the input of which was 25,185,980 kg according to data recorded in 2021 from which 10,444,850 kg (35%) was rdf and 11,746,624 kg (40%) the organic fraction [16]. 2.2. stabilization process before the stabilization process was conducted over 28 days, size separation was carried out by a cz screen ms micro mobil-type vibrating screener using screening nets 1, 2 and 4 cm in diameter. the masses of the different particle size fractions were recorded and the fractions larger than 1 cm in diameter transferred to an open container for stabilization. the sample was homogenized and left in a prism shape to cure. on the 7th day of every week, the screening process was repeated and its mass remeasured before the fractions bigger than 1 cm in diameter were stabilized in the container according to the same method. this procedure lasted 28 days (4 weeks). the fraction smaller than 1 cm in diameter was extracted from the stabilization process after every screening. to determine the moisture content (mc), after every screening process, 3 parallel samples were collected from the fraction <1 cm in diameter before being dried at 105 °c to constant weight in a drying oven and the mc calculated from the data. 2.3. measurements using stabilized samples the material composition of the different fractions was determined by hand sorting and the mass of each recorded. the fraction with a diameter of <1 cm was separated into two size ranges, namely 0-0.5 and 0.5-1 cm, the compositions of which were only defined as foreign and organic fractions because the fraction of <0.5 cm in diameter resembles a fine, soil-like material, while the one 0.5-1 cm in diameter contains more foreign material. furthermore, while investigating the utilization of ofmsw fractions for energy-recovery purposes, a lower heating value was detected from shredded samples dried to constant weight by a parr 6200 isoperibol calorimeter. 3. results and analysis 3.1. mass loss figure 2 shows the mass reduction during the examined period. the mass loss over the first 7 days was the highest, that is, 29% (from 23.5 to 16.6 kg) and 34% (34.4 to 19.9 kg) in the cases of the marcali and pécs samples, respectively. after the second week, their masses stabilized, so the main mass loss occurred during the first 14 days. accordingly, regarding the reduction in transportation costs, a two-week-long stabilization process is sufficient. 3.2. moisture content figure 3 demonstrates the continuous decrease in moisture content throughout the stabilization process. the moisture content of the marcali sample was higher at the beginning (54.43%) than in the pécs sample (46.51%) but dropped rapidly. after 28 days, the mc of figure 1. technological scheme of the mbt plants in marcali and pécs garbage trucks scaling pretreatment shredder < 350 mm magnet sort trommel sort ferrous metals ofmsw < 60 mm air separatorheavy fraction stones, bricks landfill i. stabilization biological treatment hall municipal solid wastes manual presorting ii. stabilization open-air trommel sort 60-350 mm eddy current sort nonferrous metals post treatment shredder < 50 mm magnet sort ferrous metals srf/rdf combustable material > 20 mm investigation of regional differences 51(1) pp. 61–66 (2023) 63 the marcali and pécs samples were 31.10 and 24.78%, respectively. 3.3. particle-size distribution during the 28-day-long stabilization process, the weights of each particle size fraction (<1, 1-2, 2-4 and >4cm in diameter) were recorded after every screening as presented in figure 4. although the fraction 2-4 cm in diameter was largest each week, the >4 cm one was also significant. in the case of the <1 cm fraction, the amount increased constantly as the stabilization process progressed. in the case of the pécs sample, <1 cm-sized particles were produced in larger amounts because of their higher organic content and the fine particles derived from it. 3.4. composition once the 28-day-long stabilization process had finished, the material composition of the different fractions of >1 cm in diameter was analyzed by hand sorting. the samples were categorized into 8 fractions: hazardous (batteries, medicinal ampoules, hygiene products), glass, stone (porcelain, bricks, gravel, rocks), textile, metal, organic (garden waste: leaves, pine cones, bark, twigs, seeds; kitchen waste: bones, food waste, etc.), paper and plastic (all types of plastics combined). the composition of the fraction 1-2 cm in diameter was as follows: plastic (pécs: 15%, marcali: 10%), paper (pécs: 15%, marcali: 22%), organic (pécs: 24%, marcali: 13%), hazardous (pécs: 3%, marcali: 4%), glass (pécs: 32%, marcali: 33%), stone (pécs: 8%, marcali: 16%), figure 2. the mass loss of the marcali and pécs samples during the 28-day-long stabilization process compared to on day 0 figure 3. moisture content of the <1cm particle size fractions from the marcali and pécs samples during the stabilization period 0% 5% 10% 15% 20% 25% 30% 35% 7. day 14. day 21. day 28. day m a s s l o s s [ % ] marcali pécs 0% 10% 20% 30% 40% 50% 60% 0. day 7. day 14. day 21. day 28. day m o is tu r e c o n te n t [% ] marcali pécs figure 4. composition of particle size fractions in samples from marcali and pécs during the stabilization process tóth, bobek-nagy and kurdi hungarian journal of industry and chemistry 64 textile (pécs: 1%, marcali: 0%) and metal (pécs: 2%, marcali: 2%). the composition of the fraction between 2-4 cm in diameter was the following: plastic (pécs: 24%, marcali: 15%), paper (pécs: 18%, marcali: 17%), organic (pécs: 15%, marcali: 14%), hazardous (pécs: 0%, marcali: 3%), glass (pécs: 19%, marcali: 25%), stone (pécs: 24%, marcali: 23%), textile (pécs: 1%, marcali: 2%) and metal (pécs: 0%, marcali: 2%). compared to studies from other nations, even though it can be seen in poland that the organic ofmsw fraction is almost twice as large as in hungary, the plastic fraction >4 cm in diameter is approximately 10-40% depending on the season similar to in hungary [17]-[18]. another similar study in the vicinity of taipei in taiwan shows that food waste is responsible for 34% of ofmsw in total like in the areas investigated by us, while only 17% of it consists of plastic which is lower than the average in hungary (~25-30%). in the vicinity of taipei, paper has the biggest share of 43%, significantly higher than that recorded in hungary (~15-30%) according to the samples from pécs and marcali [19]. based on the results of hand sorting, the organic fraction that originated predominantly from kitchen waste is the largest with a diameter <4 cm. >4 cm in diameter, the organic fraction accounts for only 8% and 6% of the samples from marcali and pécs, respectively, which presumably originated mostly from garden waste. although the proportion of the organic fractions 1-2 and 2-4 cm (12-15%) in diameter accumulated in equal measure in the marcali sample, this total accounted for 38% in the pécs sample from which 24% was found between 1 and 2 cm in diameter. the higher organic content could be a result of the different living conditions, which could be backed up by regional living and structural conditions. the area served by mtksz consists of 28 settlements, including 27 villages and 1 town (marcali). 59% of the inhabitants, that is, 16,692 in total, live in village-like conditions in the 27 settlements of the region, 49% of which (11,541 habitants) live in the small town of marcali. the kökény plant collects waste from 319 settlements, of which 301 are villages and 18 are towns/cities (including pécs). two thirds (67%, 287,427) of the inhabitants live in urban areas and the county seat, pécs, accounts for nearly half of them (145,985). 33% of the inhabitants live in rural areas (139,465). this data shows that in the case of the area served by kökény, the majority of inhabitants come from urban areas, where the main residential form are blocks of flats instead of detached houses with gardens and their own yards, so most do not have the opportunity to compost or keep livestock, moreover, separating garden waste is neither compulsory nor widespread as a result so more organic matter ends up in the communal waste stream than is treated by mtksz. the differences are presented in figure 5. this observation also applies to the quantity of the fine fraction of <1 cm in diameter which is more abundant in the urban area (pécs) than in the countryside. the share of the plastic fraction increases as the particle size of ofmsw increases, therefore, for the fraction >4 cm in diameter, the proportion of plastics is about a third of the total mass in both samples (pécs: 39%, marcali: 33%). regarding the fraction >4 cm in diameter, paper has the second biggest share with 29% (pécs) and 27% (marcali). it can be concluded that in the case of the plastic and paper fractions, the region does not influence their quantities too significantly. figure 5. material composition of the particle size fractions in samples from marcali and pécs after a 28-day-long stabilization process investigation of regional differences 51(1) pp. 61–66 (2023) 65 the final third is divided among the rest of the fractions (organic (pécs: 6%, marcali: 8%), hazardous (pécs: 6%, marcali: 10%), glass (pécs: 2%, marcali: 1%), stone (pécs: 3%, marcali: 14%), textile (pécs: 8%, marcali: 3%) and metal (pécs: 7%, marcali: 5%)). it should also be mentioned that since the density of inert fractions such as glass, stone and ceramics is higher than their paper and plastic counterparts, their mass is significant even though they occur in small proportions. in the marcali sample, the most hazardous material comprising 10% is found in the fraction >4 cm in diameter because it is more difficult to dispose of such waste correctly in rural areas. the glass fraction is mainly 1-2 cm in diameter as a result of fragmentation during waste processing. 3.5. lower heating value in the fractions between 2 and 4 cm in diameter, the lower heating values of samples from marcali (12.28 mj/kg) and pécs (13.05 mj/kg) are nearly as high as the average value of dry firewood (17-20 mj/kg) [20]. in fractions with diameters >4 cm, the lower heating values are even higher (marcali: 24.57 mj/kg, pécs: 22.68 mj/kg) and comparable with brown coal (21-25 mj/kg) [21]. the minimum heating value required according to who is 6500 mj/kg for incineration plants [22]. the results regarding the heating values of the plastic fractions are shown in figures 6 and 7. due to the high lower heating value and plastic content as well as the low quantity of the organic fraction with a diameter of >4 cm, the average diameter following trommel sorting could be downsized to 4 cm instead of 6-8 cm. 4. conclusion the following observations can be made: 1. since the size of the directly landfilled fraction of msw can be reduced due to the separation of kitchen and food waste, the organic fraction of ofmsw is as high as 60% in the sample from pécs. 2. the reduction in the average diameter following trommel sorting will improve the amount of plastic recovered. as was demonstrated in the fraction >4 cm in diameter, plastic and paper have a big share of this fraction, which could be utilized as rdf because of its high lower heating value of 24.57 mj/kg. 3. the fraction with a diameter of <1 cm could be used as a substitute for planting soil after further purification. 4. given that regional differences in the composition of msw are observed caused by the various living structures and conditions, no one-size-fits-all solution can be suggested with regard to technologies and the order of sorting. acknowledgements this work was implemented by the project tkp2021nkta-21 with support provided by the ministry of culture and innovation of hungary as well as the national research, development and innovation fund financed under the 2021 thematic excellence programme. the authors are grateful to dél-kom nonprofit kft. and marcali és térsége közszolgáltató nonprofit kft. for providing information. references [1] vaverková, m.d.: landfill impacts on the environment review, geosci., 2019, 9(10), 431, doi: 10.3390/geosciences9100431 [2] directive (eu) 2018/850 of the european parliament and of the council of 30 may 2018, https://eur-lex.europa.eu/legalcontent/en/txt/html/?uri=celex:32018l0850&from=hu (accessed march 24, 2023) [3] nanda, s.; berruti, f.: municipal solid waste management and landfilling technologies: a review, environ. chem. lett., 2021, 19(2), 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https://doi.org/10.3390/su13105432 https://doi.org/10.1016/j.wasman.2018.04.017 https://ojs.uni-miskolc.hu/index.php/multi/article/view/124/120 http://www.matud.iif.hu/2007-11.pdf https://apps.who.int/iris/handle/10665/108620 microsoft word 16.07 zaini.docx hungarian journal of industry and chemistry vol. 44(2) pp. 129–133 (2016) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2016-0016 metal-chloride-activated empty fruit-bunch carbons for rhodamine b removal muhammad abbas ahmad zaini1,2* and mohd shafiq mohd shaid1 1 faculty of chemical & energy engineering, universiti teknologi malaysia, johor bahru, johor, 81310, malaysia 2 centre of lipids engineering & applied research, ibnu sina institute for scientific & industrial research, universiti teknologi malaysia, johor bahru, johor, 81310, malaysia this study aimed to investigate the adsorptive ability of activated carbons derived from empty boil palm fruitbunch carbons through metal-chloride activation. the derived activated carbons were characterized in terms of yield, ph, surface functional groups, and specific surface area. rhodamine b dye was used as a pollutant probe to evaluate the performance of activated carbons. results show that empty, zncl2-activated fruit-bunch carbon exhibits a higher surface area of 866 m2 g-1 and a rhodamine b removal yield of 105 mg g-1. activation at the same temperature of 600 ºc using the recovered fecl2 yields an activated carbon with nearly twice the surface area compared to the fresh one. a direct correlation was obtained between the roles of the specific surface area and removal of rhodamine b. empty fruit-bunch carbon is a promising adsorbent precursor for colour removal from water. keywords: activated carbon, chemical activation, empty fruit-bunch, metal-chloride, rhodamine b 1. introduction malaysia and indonesia are the leading producers worldwide of palm oil. due to the growth in palm oil production and despite the high economic returns, this industry also generates a huge amount of was that has negative implications on the environment. as one of the largest oil palm producers in the world, malaysia generates abundant empty fruit-bunch (efb) residues amounting to 12.4 million tonnes annually [1]. at present, only a small quantity of efb is used as fuel for boilers in the oil palm mills while the remaining large quantity is left to decay in fields or disposed of in landfills. due to the limited area of landfill sites and other associated environmental implications, the quest for the effective utilization of efb has become a subject of significant interest. because efb is rich in carbon and lignin, it has a great potential to be converted into adsorbent or activated carbon for a variety of purification and environmental purposes [2]. nasir et alia [3] reported the selectivity of methylene blue removal over copper(ii) ions by empty fruit-bunch. yet, the uptake capacity was too small (32.3 mg methylene blue per g of efb) to warrant large-scale adsorption operation. in a recent related work, wirasnita et alia [4] reported the preparation of zncl2-activated empty fruit-bunch carbon with a specific surface area of 86.6 m2 g-1. however, the *correspondence: abbas@cheme.utm.my surface area obtained is somewhat small to be regarded as that of activated carbon [5]. there are also reports on the use of co2 and steam to physically activate the efb into activated carbons. however, the surface area is often not controllable and the yield is very low because of high activation temperatures (800 to 900 ºc) [6,7]. our present work aimed to evaluate the adsorptive characteristics of metal-chloride-activated empty fruitbunch carbons. zinc(ii) chloride and iron(ii) chloride were used for the chemical activation of efb. attempts were also made to recover the activator for the second activation. rhodamine b was used as a model pollutant to establish the adsorption data. the activated carbons were characterized and the adsorptive results compared and discussed. 2. experimental oil palm empty fruit-bunch (efb) was obtained from sungei kahang palm oil factory in johore state, malaysia. the material was oven-dried at 110oc overnight to remove moisture. all chemicals used in the preparation of activated carbons and adsorption were of analytical reagent grade. 2.1. preparation of activated carbon empty fruit-bunch was loosened and separately modified with zinc chloride and iron(ii) chloride in the mass ratio (activator : efb) of 3:2. firstly, the activator was dissolved in water, sufficient for the efb to be immersed. next, the efb-activator mixtures were zaini and shaid hungarian journal of industry and chemistry 130 stirred at 90 ºc for 40 minutes. after that, the sample was placed in the oven overnight at 110 ºc for impregnation. the impregnated sample was put in a crucible wrapped in aluminium foil, and heated in a furnace for 1.5 h at 300 ºc and 550 ºc for zinc chloride activation and iron(ii) chloride activation, respectively. the selected activation temperatures are half of the boiling points of the activators. the resultant activated carbon was washed with distilled water, and the washed water was used for the second activation using the same impregnation ratio of 3:2 at 550 ºc for both activators. activated carbons were designated as z1 and f1 for activation using fresh zinc(ii) chloride and iron(ii) chloride, respectively, and z2 and f2 when using recovered activators, respectively. 2.2. characterization of activated carbon the yield of activated carbon was calculated from the mass of the resultant product over that of the dried efb used. the adsorbent ph was determined by soaking 1 g of adsorbent in 100 cm3 of distilled water. the ph was measured using a ph meter (hi 8424, hanna instruments). the specific surface area of activated carbon was measured using a surface area analyser (pulse chemisorb 2705, micromeritics) at the temperature of liquid n2, 77 k. fourier transform infrared spectroscopy (ftir) (ir tracer-100, shimadzu) was used to obtain the peaks of functional groups at specific wave numbers ranging from 400 to 4000 cm-1. 2.3. adsorption of rhodamine b rhodamine b of commercial purity was utilized without further purification. 500 mg of rhodamine b powder was weighed using an analytical balance and then dissolved in 1 dm3 of distilled water in a volumetric flask to make up a stock solution. the dilution of stock solution was needed for preparing the working concentrations for adsorption. adsorption was performed according to the bottlepoint technique. briefly, about 0.5 g of activated carbon was added to 50 cm3 of rhodamine b solution at varying concentrations. the mixture was allowed to equilibrate on an orbital shaker at 120 rpm and room temperature for 72 h. the residual concentration was measured using a spectrophotometer (halo vis-10, dynamica scientific ltd.) at a wavelength of 555 nm (absorption unit = 0.014 × concentration, r2 = 0.99). the adsorption capacity (mg g-1) was calculated by a simple material balance (eq.(1)), and the adsorption data were analysed by general isotherm models, namely langmuir (eq.(2)) and freundlich (eq.(3)). the respective constants were solved by non-linear regression using solver as implemented in ms excel for the smallest sum-of-squared error (sse) and optimum coefficient of determination (r2). 𝑞! = (!!!!!) ! 𝑉 (1) 𝑞! = !"!! !!!!! (2) 𝑞! = 𝐾!𝐶! ! ! (3) where, qe (mg g-1) is the adsorption capacity of rhodamine b, co and ce (mg dm-3) are the initial and equilibrium concentrations, respectively, m (g) is the mass of activated carbon, and v (dm3) is the volume of rhodamine b solution. constant q (mg g-1) is the maximum monolayer capacity, b (dm3 g-1) is the adsorption intensity, and kf ((mg g-1)(dm3 mg-1)1/n) and 1/n are the freundlich constants related to the adsorption capacity and intensity, respectively. 3. results and analysis 3.1. characteristics of activated carbons chemical activation using freshly prepared metalchlorides was performed at a temperature of about half of the boiling point of each activator. the boiling point of zncl2 and fecl2 are 723 and 1023 ºc, respectively. this is to allow a sufficient amount of activator to be recovered upon activation as it is commonly understood that chemical activators, e.g. zncl2, koh, etc., are prone to intercalate with the matrix material and/or lost when the activation is done close to the boiling point of the activators. in addition, it enables one to evaluate the effectiveness of activated carbon preparation at the selected temperatures. table 1 displays the yield, ph, and specific surface area of metal-chloride-activated empty fruit-bunch carbons. in general, the yield of activated carbons ranges between 38 and 47%. this indicates the underlying role of metal-chlorides as dehydrating agents to enhance the burning off the carbonaceous material. this is also true for zncl2 activation at a temperature of 300 ºc. in addition, it signifies that a significant portion of metalchlorides could be recovered for the subsequent activation. the ph values of activated carbons are in the range of 3.8 to 5.3. the activated carbons are slightly acidic because both metal-chloride activators are lewis acids. the ph values were found to increase when the recovered activators were used in the activation. this could be attributed to the decreased amount of metalchlorides that probably could not be fully recovered after the first activation. from table 1, the developed surface area of z1 upon activation is undeniably small, even smaller than for raw efb (28.4 m2 g-1) [3]. this could be due to the table 1. properties of activated carbons. activator type temp. (°c) yield (%) ph surface area (m2 g-1) zncl2 fresh (z1) 300 44.0 3.8 2.64 recovered (z2) 550 41.2 4.9 866 fecl2 fresh (f1) 550 46.8 4.6 98.4 recovered (f2) 550 37.9 5.3 226 metal-chloride-activated empty fruit-bunch carbons 44(2) pp. 129–133 (2016) doi: 10.1515/hjic-2016-0016 131 blockade of existing pore channels because of the intercalation of zinc cations within the material matrix. intercalation of a chemical activator normally creates new pathways for the porous structure when adequate heat is supplied to the impregnated material. this often results in an increase in pore volume, thus increasing the specific surface area. yet, the activation temperature for z1 (300 ºc) may not be sufficient to initiate the job, consequently the activator becomes lodged inside the rudimentary pores even though burning off decreases the activated carbon yield. therefore, z1 could not be regarded as activated carbon because of its inferior development of surface area. activation using the recovered activators was performed at 550 ºc. there is a tremendous increase in the surface area of z2 using the recovered zncl2 from z1. although the amount of zncl2 in the recovered solution is presumably less than for the fresh one (ratio 3:2), the elevated activation temperature shows a positive effect in increasing the surface area by more than 300 times. this could be related to the fact that more volatiles (nearly 65% weight loss) are liberated from the empty fruit-bunch at 550 ºc [8]. it is suggested that the liberation of volatiles from the material also contributes to creating the pore pathways. these combined effects bring about the development of activated carbon with a high surface area. from table 1, f2 shows a higher surface area than for f1 at the same activation temperature. this could be associated with the optimum impregnation ratio in the preparation of activated carbon. the specific surface area of activated carbon normally increases as the impregnation ratio increases, but decreases when an excessive amount of activator is used. too much activator may result in the collapse of pore textures, thus decreasing the surface area [9]. in other words, fecl2 used in the activation of f1 could have already exceeded the optimum impregnation ratio. however, further experimental works of varying impregnation ratios of fecl2 are needed to establish the optimum surface area of fecl2-activated empty fruit-bunch carbons. nevertheless, f2 demonstrates a 3.8 times lower surface area than z2. this shows that zncl2 is an effective activator for empty oil palm fruit-bunch-based activated carbon. fig.1 shows the ftir spectra of efb and its derived activated carbons. the designated possible functional groups are summarized in table 2. the spectroscopy technique measures the absorption of various wavelengths of infrared light by materials of interest to identify specific organic functional groups on the surface of activated carbon. from fig.1, the efb displays various peaks that correspond to the presence of functional groups. the broad and strong band at 3300 cm-1 is assigned to the stretching vibration of the (–oh) hydroxyl group. the intensity of the peak decreased by the order of efb > z1 > f1 ≈ f2 > z2. the peak completely disappeared in z2 probably due to the stronger dehydrating effect of zncl2 compared to fecl2 in activating the efb at 550 ºc. it also signifies that the activation of z1 remains incomplete because most of the attributes of efb spectra remained unchanged. as the efb is converted into activated carbon, the complicated peaks become simplified indicating the liberation of functional groups in the activated carbons. the absorption peaks at 2930– 2850 cm-1 are attributed to the (c–h) stretching vibration of the (–ch3) group. the peaks between 1400 and 1000 cm-1 are ascribed to (c–o) stretching or (si– o) of silica containing minerals (ash). the peak at 1026 cm-1 in z1 is assigned to the out of plane (c–h) bending. 3.2. adsorption of rhodamine b water polluted with dyes especially from the textile industries has become a subject of great concern because of the disruption to biodiversity and food chains [10]. basic or cationic dyes are very bright dyes that are water-soluble. in this work, rhodamine b (c28h31c1n2o3, mw = 479 g mol-1, solubility in water = 15 g dm3) was chosen as the model dye to evaluate the performance of empty fruit-bunch-based activated carbons. the ph of the rhodamine b solution was not adjusted, and the values were measured as 5.1±0.2 for all concentrations. at equilibrium, the ph values slightly changed as they are measured to be 5.3±0.1. fig.2 illustrates the molecular structure of rhodamine b. figure 1. ftir spectra of efb and activated carbons. table 2. functional groups used in characterizing samples. wave number (cm-1) functional group type sample 3100–3550 a o—h alcohol efb, f1, f2, z1 1000 c—o 2900, 2810 c—h aldehyde efb, z1 1600, 1470 c=c aromatic efb, z1 1600 c=c alkene efb, z1, f1, f2 3300 n—h amine efb 1300 c—n a broad feature zaini and shaid hungarian journal of industry and chemistry 132 fig.3 shows the removal of rhodamine b by efbderived materials. from fig.3, the removal of rhodamine b was found to increase with concentration by the order of z2 > f2 > f1 > z1. activated carbon z2 demonstrates the highest rhodamine b removal of 105 mg g-1. this trend is in agreement with the increase in specific surface area of adsorbents. in general, the concentration of dye in the solution provides a driving force for adsorption if the adsorbent or activated carbon possesses abundant active sites. in this case, the active sites are directly associated with the surface area. fig.4 displays the correlation between the removal of rhodamine b and the surface area. a linear relationship for rhodamine b removal (mg g-1) = 0.124 × specific surface area (m2 g-1), r2 = 0.993 was obtained. a bigger surface area normally provides better interaction probabilities for the rhodamine b molecules to lodge onto the pore channels. in addition, it is presumed that all types of pore play a dominating role in the adsorption especially mesopores [5,11]. the adsorption data were analysed using the langmuir and freundlich models, and the constants are tabulated in table 3. the adsorption data reasonably fitted to both adsorption models with r2 ranging between 0.71 and 0.97, except for z2 according to the langmuir model. the values of langmuir model capacity (q) are in close proximity to the experimental data (qexp). in addition, z2 shows a higher adsorption affinity (b) for rhodamine b when compared with the other counterparts. this signifies a higher removal efficiency (~99%) at concentrations below 80 mg dm-3. similar explanations apply for the freundlich model. the deviation of the lines of the model from the experimental data is shown in fig.3, which indicates that the removal of rhodamine b by efb-based materials is neither a strict monolayer adsorption nor heterogeneous coverage, but could be a blend of the two – monolayer adsorption onto a heterogeneous surface [11]. in a related work, santhi et alia [12] reported a removal capacity of 22.3 mg g-1 of rhodamine b using h2so4-treated a. nilotica leaves. generally, z2 shows a higher dye removal capacity compared to this chemically treated natural adsorbent. this is likely due to the well-developed graphitic structure and surface area of z2 for the effective removal of rhodamine b. figure 2. chemical structure of cationic rhodamine b dye. figure 3. removal of rhodamine b by (a) z1, f1 and f2, and (b) z2. lines were predicted by the langmuir (solid) and freundlich (dashed) models. figure 4. correlation between rhodamine b removal and specific surface area. table 3. parameters of isotherm models. z1 z2 f1 f2 qexp (mg g-1) 2.33 105 14.8 33.4 langmuir model q (mg g-1) 2.85 97.9 18.5 42.2 b (dm3 g-1) 0.166 2.92 0.248 0.187 r2 0.907 0.434 0.857 0.967 sse 0.233 403 23.7 26.3 freundlich model kf (mg g-1)(l mg-1)1/n 0.560 72.5 4.73 8.86 n 2.10 13.4 2.61 2.33 r2 0.882 0.707 0.718 0.869 sse 0.435 209 44.7 94.3 metal-chloride-activated empty fruit-bunch carbons 44(2) pp. 129–133 (2016) doi: 10.1515/hjic-2016-0016 133 4. conclusion oil palm empty fruit-bunch was used in the preparation of activated carbons via metal-chloride activation. zinc chloride is a more effective activating agent for activated carbon than iron(ii) chloride. activation at 500 ºc yields empty fruit-bunch-based activated carbon with a surface area of 866 m2 g-1. a bigger surface area offers greater removal of rhodamine b dye and a higher adsorption affinity at lower dye concentrations. the maximum removal efficiency was recorded as 105 mg g-1. the mechanism could be described as monolayer rhodamine b adsorption onto heterogeneous activated carbon. empty fruit-bunch is a promising alternative to activated carbon precursors for wastewater treatment. acknowledgement the research was supported by universiti teknologi malaysia through tier one research grant #10h42. references [1] tanaka, r.; rosli, w.; magara, k.; ikeda, t.; hosoya, s.: chlorine-free bleaching of kraft pulp from oil palm empty fruit-bunches, jpn. agric. res. 2004 38(4), 275–279 doi: 10.6090/jarq.38.275 [2] duan, x.; peng, j.; srinivasakannan, c.; zhang, l.; xia, h.; yang, k.; zhang, z.: process optimization for the preparation of activated carbon from jatropha hull using response surface methodology, energy sources, part a: recovery util. environ. effect, 2011 33(21), 2005–2017 doi: 10.1080/ 15567030903515047 [3] nasir, n.h.m.; zaini, m.a.a.; setapar, s.h.m.; hassan, h.: removal of methylene blue and copper(ii) by oil palm empty fruit-bunch sorbents, j. teknologi 2015 74(7), 107–110 doi: 10.11113/ jt.v74.4707 [4] wirasnita, r.; hadibarata, t.; yusoff, a.r.m.; lazim, z.m.: preparation and characterization of activated carbon from oil palm empty fruit-bunch wastes using zinc chloride, j. teknologi 2015 74(11), 77–81 doi: 10.11113/jt.v74.4876 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(nova science publishers, inc., new york, usa) pp. 217–234, 2015 [6] hidayu, a.r.; mohamad, n.f.; matali, s.; sharifah, a.s.a.k.: characterization of activated carbon prepared from oil palm empty fruit-bunch using bet and ft-ir techniques, proc. engng. 2013 68, 379–384 doi: 10.1016/j.proeng.2013.12.195 [7] alam, m.z.; ameem, e.s.; muyibi, s.a.; kabbashi, n.a.: the factors affecting the performance of activated carbon prepared from oil palm empty fruit-bunches for adsorption of phenol, chem. engng. j. 2009 155(1–2), 191–198 doi: 10.1016/j.cej.2009.07.033 [8] nyakuma, b.b.; johari, a.; ahmad, a.; abdullah, t.a.t.: thermogravimetric analysis of the fuel properties of empty fruit-bunch briquettes, j. teknologi 2014 67(3), 79–82 doi: 10.11113/jt.v67.2768 [9] zaini, m.a.a.; okayama, r.; machida, m.: adsorption of aqueous metal ions on cattlemanure-compost based activated carbons, j. hazard mater. 2009 170(2–3), 1119–1124 doi: 10.1016/j.jhazmat.2009.05.090 [10] ming-twang, s.; zhi-yong, q.; lin-zhi, l.; peiyee, a.y.; zaini, m.a.a.: dyes in water: characteristics, impacts to the environment and human health, and the removal strategies. in: advances in chemistry research, ed.: taylor, j.c. (nova science publishers, inc., new york, usa) vol. 23, pp. 143–156, 2015 [11] zaini, m.a.a.; zakaria, m.; setapar, s.h.m.; yunus, m.a.c.: sludge-adsorbents from palm oil mill effluent for methylene blue removal, j. environ. chem. engng. 2013 1(4), 1091–1098 doi: 10.1016/j.jece.2013.08.026 [12] santhi, t.; prasad, a.l.; manonmani, s.: a comparative study of microwave and chemically treated acacia nilotica leaf as an eco-friendly adsorbent for the removal of rhodamine b dye from aqueous solution, arabian j. chem. 2014 7(4), 494–503 doi: 10.1016/j.arabjc.2010.11.008 hungarian journal of industry and chemistry vol. 53(2) pp. 7–16 (2025) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2025-12 potassium hydroxide-activated palm kernel shell carbon for methylene blue adsorption: reagent recovery and regeneration strategies teow zi xian1, fadina amran2, agus arsad1 and muhammad abbas ahmad zaini1-2* 1 faculty of chemical & energy engineering, universiti teknologi malaysia, 81310 utm johor bahru, johor, malaysia 2 centre of lipids engineering and applied research (clear), ibnu sina institute for scientific and industrial research, universiti teknologi malaysia, 81310 utm johor bahru, johor, malaysia this study investigates the preparation and characterization of activated carbon derived from palm kernel shell, utilizing recovered potassium hydroxide (koh) as the activating agent. the research seeks to address dye water pollution and the release of toxic chemicals from washing activated carbon upon its activation that are detrimental to aquatic ecosystems. fresh activation was performed in a furnace at a temperature of 550 °c for one hour. the resultant activated carbon was washed and the recovered koh solution was used for subsequent activation. the activated carbons were characterized to determine their surface area, morphology, functional groups and batch adsorption capacity. the fresh activated carbon exhibited a yield of 14.2% and a surface area of 7.24 m²/g. notably, the surface area of 55.1 m²/g of the activated carbon produced using recycled koh solution was greater with an enhanced level of methylene blue removal. the adsorption data could be described by the redlichpeterson isotherm and pseudo-second-order kinetic models, suggesting a hybrid of physicochemical interactions. the adsorption process is endothermic and spontaneous when the temperature of the solution is high. this work also showcases the regeneration of activated carbon by using 0.1 m hcl and distilled water as solvents, underscoring the sustainability and cost-effectiveness of manufacturing activated carbon. keywords: adsorption, activated carbon, methylene blue, palm kernel shell, potassium hydroxide, reagent recovery 1. introduction the rapid increase in the global population has led to a significant rise in pollution levels across various environments. among the most considerable problems the world is experiencing currently is water pollution, moreover, one of the major contributing factors is the industrial discharge of dyes. reports state that roughly 10 to 20% of dye molecules are released into the environment along with industrial wastewater, triggering detrimental effects to aquatic life and human health [1]. according to the environmental quality report for malaysia, dye waste produced in the textile industry in malaysia has escalated to nearly 800 tons and accounts for 22% of wastewater produced in the country [2]. several treatments have been introduced to address the issue of wastewater pollution, moreover, one of the preferred and effective methods is activated carbon adsorption. activated carbon is a porous carbon-based adsorbent with a large surface area, allowing it to adsorb a wide range of pollutants from water. received: 1 apr 2025; revised: 20 apr 2025; accepted: 30 apr 2025 *correspondence: abbas@cheme.utm.my commercially available activated carbon derived from coal and petroleum pitch is renowned for its outstanding adsorption performance, making it an excellent choice for environmental protection. however, its high cost somewhat inhibits broad applications across various industries [3]. malaysia is well known for its abundance of palm oil. nearly 4.3 million tons of palm kernel shell (pks) are generated yearly [4], making it an abundant and underutilized biomass resource in the palm oil industry. pks is a potent carbon feedstock for manufacturing activated carbon as well as provides a sustainable and eco-friendly approach to wastewater treatment. activated carbon is produced through a process known as activation. potassium hydroxide (koh) is among the most common used activators to develop a porous network within a carbon matrix. nonetheless, the reagent is toxic and could result in secondary pollution due to its release during the washing of activated carbon. therefore, the washed water from the aforementioned step must be cautiously handled to minimize undesirable impacts to human health and the environment [5]. https://doi.org/10.33927/hjic-2025-12 mailto:abbas@cheme.utm.my xian, amran, arsad and zaini hungarian journal of industry and chemistry 8 conventional washing can be employed as a reagent recovery method to minimize the release of spent koh. distilled water was used to dissolve, extract and recover spent koh from the activated carbon. the washing liquid was collected and reused for subsequent activation [4] in order to manufacture another batch of activated carbon, while minimizing the chemical discharge. this supports the circular economy initiative within the activated carbon industry. in this work, methylene blue adsorption was performed to evaluate the performance of pks activated carbons. the equilibrium, kinetics and thermodynamics of dye adsorption were analyzed as well as discussed to provide an insight into the governing mechanisms. since dealing with dye-loaded activated carbon remains challenging, identifying suitable solvents for regeneration is also crucial for resource recovery [6]. 2. experimental palm kernel shell was collected from felda taib andak palm oil mill. the model dye, methylene blue (mb, c16h18cln3s, 319.85 g/mol) was purchased from r&m marketing, uk. all chemicals used are analytical-grade reagents. 2.1. preparation and characterization of activated carbon potassium hydroxide (koh) was dissolved and mixed with 20 g pks in a koh:pks weight ratio of 2:1. the mixture was impregnated in an oven at 110 °c overnight. the dried sample was activated in a furnace at 550 °c for 1 h and the resultant activated carbon denoted as ac1. next, it was washed using distilled water to recover the excess koh and the wash water was used for another activation with 20 g of pks. the previous steps were repeated and the resultant activated carbons were designated as ac2 and ac3. for the purpose of a comparison, pks char was produced without koh at 550 °c for 1 h. the textural properties of the activated carbon samples were determined using a surface area analyzer by following the brunauer-emmett-teller (bet) method. the surface morphology of the sample of activated carbon was obtained by a tm3000 tabletop scanning electron microscope (hitachi, japan). the surface functional groups were qualitatively identified from peak assignments using a spectrum one fourier transform infrared spectrometer [4]. 2.2. adsorption studies mb solutions of various concentrations ranging from 25 to 200 mg/l were prepared by diluting the stock solution. the flasks containing 20 ml of solution were loaded with 20 mg of activated carbon and the mixtures allowed to equilibrate at room temperature for 72 h. next, the residual concentrations were measured using a spectrumlab 752 pro uv-vis spectrophotometer at a wavelength of 620 nm. the dye capacity at equilibrium, qe, was calculated according to the method applied in previous studies [7],[8]: 𝑞𝑒 = (𝐶𝑜−𝐶𝑒) 𝑊 𝑉 (1), where co and ce (mg/l) denote the initial and equilibrium concentrations, respectively, v (l) stands for the volume of the solution while w (g) represents the mass of activated carbon. the effect of the contact time was analyzed by measuring the residual concentrations of dye solution at preset intervals from the 5 mins after the activated carbon was loaded into the solution until equilibrium was attained. multiple dye concentrations were prepared to demonstrate the change in capacity over time until equilibrium was reached. adsorption at time t, qt, was calculated as [8]: 𝑞𝑡 = (𝐶𝑜−𝐶𝑡) 𝑊 𝑉 (2), where ct (mg/l) denotes the dye concentration at a specified time. the effect of temperature on dye adsorption was investigated for ac1 at solution temperatures of 30, 45 and 55 °c. the temperature was adjusted using a temperature-controlled water bath. the dye concentration was fixed at 50 mg/l and the mixtures were left for 72 h. 2.3. regeneration studies distilled water and 0.1 m hcl were prepared as solvents to regenerate spent activated carbon ac1. 20 mg mbloaded ac1 was mixed with 20 ml of solvent at room temperature for 72 h [6]. the desorption capacity, qd, was calculated as: 𝑞𝑑 = 𝐶𝑓𝑉 𝑊 (3), where cf (mg/l) denotes the dye concentration in the desorbing solution. the desorption efficiency, d%, was calculated as: 𝐷% = 𝑞𝑑 𝑞𝑒 × 100 (4). the regeneration efficiency, r%, was calculated as: 𝑅% = 𝑞𝑓 𝑞𝑖 × 100 (5), where qf denotes the mb adsorption capacity after regeneration and qi represents the adsorption capacity using fresh ac1. the adsorption and desorption experiments were repeated over 4 cycles. 3. results and discussion 3.1. characteristics of activated carbon the textural properties of ac1, ac2 and ac3 are summarized in table 1. the ph of all acs was basic from 8.9-9.6 due to chemical reactions during activation. palm kernel shell activated carbon for methylene blue adsorption 53(2) pp. 7–16 (2025) 9 the koh activator interacts with the carbon matrix, thereby producing several potassium species. potassium ions (k+) in particular are known for their basic nature in activated carbon [9]. the yield of activated carbon ranked as ac2 ≈ ac3 > ac1. ac1 recorded the lowest yield of 14.2 %, while ac2 and ac3 yielded 30 %. the lower yield of ac1 was due to aggressive carbon burning-off and the dehydrating effect of koh during carbonization. the heating process is anticipated to encourage bond cleavage of weakly connected bridges in the impregnated material, releasing volatiles and causing subsequent weight loss caused by oxidation reactions [3]. in contrast, the greater yield observed for ac2 and ac3 may have resulted from the less significant dehydrating effect of koh. the amount of koh recovered upon activation is presumably less as some has been consumed and evaporated during the initial activation. the bet surface area of the acs ranked as follows: ac3 (55.1 m²/g) > ac2 (30.3 m²/g) > ac1 (7.24 m²/g). generally, the higher koh ratio leads to an increase in the surface area of activated carbon. the koh enhances the development of pores during the carbonization process. nevertheless, an optimal ratio is found beyond which a further increase in the amount of koh decreases the surface area. an excessive amount of koh used in activation significantly damages the carbon structure, collapsing the pore walls and producing larger pores at the expense of smaller ones [10]. this relationship is illustrated by the average pore size of acs as presented in table 1 in the order of ac1 > ac2 > ac3. the n2 adsorption-desorption isotherms of ac1, ac2 and ac3 are depicted in figure 1. all acs exhibit characteristics of type iv isotherms typically associated with mesoporous materials (pore sizes ranging from 2 to 50 nm). a key feature of this isotherm is the presence of hysteresis loops, which arise from capillary condensation within the pores, indicating that the adsorption and desorption processes do not follow the same mechanism. the observed hysteresis loop for ac1 suggests significant capillary condensation within its pores. in contrast, the shape of the hysteresis loops for ac2 and ac3 implies a unique pore texture, resembling that of ink-bottle or slit-like pores. the pore size distribution of the acs is displayed in figure 2. the curves typically exhibit distinct peaks corresponding to specific pore widths, highlighting where most of the surface area is concentrated. for ac1, a sharp peak at 2 nm suggests the predominance of micropores (pore width < 2 nm) and small mesopores (~2 3 nm), while a small but consistent increase in pore volume thereafter for pore widths ranging from 5 to 15 nm indicates the contribution of mesopores. conversely, ac2 and ac3 only demonstrate a peak centered at 2 nm, suggesting that they are highly microporous with a minimal amount of mesopores. the presence of functional groups such as o–h, c=c, c–o, c–h, c–h and c≡c plays a considerable role in mb adsorption. the hydroxyl (o–h) groups form hydrogen bonds with dye molecules and act as acidic sites to facilitate ion exchange [7],[11]. the carbonyl (c=o) groups are electrostatically attracted to positively charged dye molecules, moreover, can form complexes with mb, thereby increasing the removal performance [12]. the ether and ester (c–o) linkages enhance the reactivity of the carbon surface, increasing the likelihood of interactions with dye molecules [12]. furthermore, the presence of c–h bonds promotes hydrophobic interactions with non-polar moieties of mb [12]. additionally, alkynes (c≡c) and a graphitic surface facilitate non-covalent interactions via π-π stacking between the aromatic rings of methylene blue [7],[13]. as shown in figure 3, all the activated carbons exhibit identical spectral patterns. notably, the intensity of some peaks for ac1 is greater than for ac3. the abundance of acidic oxygen functional groups like hydroxyl (o–h) in ac1 suggests a stronger affinity to interact with mb. furthermore, ac1 contains more aromatic c=c groups than ac3. this observation is in line with the adsorption performance, wherein ac1 outperforms ac3 although the surface area of the former is smaller. table 1: textural properties of ac1, ac2 and ac3 sample ac1 ac2 ac3 ph 9.6 8.9 9.4 yield (%) 14.2 30.3 29.9 bet surface area (m2/g) 7.24 30.3 55.1 total pore volume (cm3/g) 0.0211 0.0196 0.0298 micropore volume (cm3/g) 0.00131 0.00811 0.0174 mesopore volume (cm3/g) 0.0198 0.0115 0.0124 average pore size (nm) 11.7 2.59 2.16 figure 1: n2 adsorption-desorption isotherms of ac1, ac2 and ac3 0 5 10 15 20 0 0,2 0,4 0,6 0,8 1 q u an ti ty a d so rb ed ( cm ³/ g) relative pressure (p/p°) adsorption ac1 desorption ac1 adsorption ac2 desorption ac2 adsorption ac3 desorption ac3 xian, amran, arsad and zaini hungarian journal of industry and chemistry 10 the surface morphology of the acs is shown in figure 4. ac2 and ac3 exhibit a well-developed porous texture characterized by a honeycomb-like structure. in contrast, ac1 displays a surface with rudimentary pores that correlates well with its lower surface area and possible pore collapse during activation. 3.2. equilibrium adsorption an adsorption isotherm describes the equilibrium between the amount of dye adsorbed and its concentration in the solution [14]. the equilibrium of mb adsorption onto koh-activated carbons is shown in figure 5. generally, the dye capacity increases as the concentration increases. the concentration gradient acts as a driving force to enhance the transport of dye molecules to overcome the mass transfer resistance between the aqueous (bulk) and solid phases [3]. dye molecules can be lodged into surfaces with vacant sites prior to reaching its saturation limit that determines its maximum capacity. the level of adsorption (qe) increases as the concentration (ce) increases in all curves but levels off as different removal capacities are reached. the concave upward shape implies preferable dye removal onto ac samples [15]. the adsorption capacity is proportional to the concentration until the sites become mostly occupied at higher concentrations. at this point, the level of affinity subsides and qe increases at a diminishing rate [16]. the adsorption of mb follows the order given: ac1 > ac3 > ac2 > char. this infers the importance of koh activation in developing the surface chemistry and texture of ac samples for mb adsorption. ac1 exhibits a higher dye capacity of 35 mg/g. the superior performance of acs is partly attributed to its higher ph that encourages the deprotonation of oxygenated groups such as carboxyl, phenolic and hydroxyl. the hydroxide ions (oh⁻) in the solution facilitate the removal of protons from these acidic groups, thereby creating the negatively charged sites on the carbon surface which are electrostatically attracted to the cationic dye molecules. the optimal ph for mb adsorption typically falls between ph 7 and 11, combining the effects of increased negative charge on the carbon surface and reduced competition with protons (h+) [17]. a greater removal rate by ac3 when compared to ac2 also signifies the roles of basic solutions and deprotonation on mb adsorption. in conclusion, the oxygen-containing functional groups release protons, rendering the carbon surface negatively charged [18]. methylene blue is a basic dye that carries a positive charge [19] and will adhere onto the surface via electrostatic attraction, coordination mechanisms and the formation of complexes. the driving force for adsorption is essentially powered by the concentration difference between the bulk solution figure 3: ftir spectra of char, ac1 and ac3 40 60 80 100 600110016002100260031003600 % t wavenumber (cm¯¹) char ac1 ac3 (a) (b) (c) figure 2: incremental pore volume vs. pore width of (a) ac1, (b) ac2 and (c) ac3 0,0 0,1 0,2 0,3 0 5 10 15 20 in cr em en ta l p o re v o lu m e (c m ³/ g) pore width (nm) 0,0 0,5 1,0 1,5 2,0 2,5 0 5 10 15 20 in cr em en ta l p o re v o lu m e (c m ³/ g) pore width (nm) 0,0 0,5 1,0 1,5 2,0 2,5 0 5 10 15 in cr em en ta l p o re v o lu m e (c m ³/ g) pore width (nm) palm kernel shell activated carbon for methylene blue adsorption 53(2) pp. 7–16 (2025) 11 (a) (b) (c) figure 4: sem images of (a) ac1, (b) ac2 and (c) ac3 at a magnification of 3000× figure 5: equilibrium of mb removal onto kohactivated carbons 0 10 20 30 40 0 50 100 150 200 e q u il ib ri u m a d so rp ti o n , q e (m g/ g) equilibrium concentration, ce (mg/l) ac1 char ac2 ac3 (a) (b) (c) (d) figure 6: rate of methylene blue adsorption by activated carbons at concentrations of (a) 5.0, (b) 8.5, (c) 14.5 and (d) 25.0 mg/l 0 1 2 3 4 5 6 7 8 0 500 1000 1500 2000 a d so rp ti o n c ap ac it y, q t (m g/ g) time, t (min) ac1 ac2 ac3 0 2 4 6 8 10 0 500 1000 1500 2000 2500 a d so rp ti o n c ap ac it y, q t (m g/ g) time, t (min) ac1 ac2 ac3 0 2 4 6 8 10 12 14 16 0 500 1000 1500 2000 a d so rp ti o n c ap ac it y, q t (m g/ g) time, t (min) ac1 ac2 ac3 0 5 10 15 20 25 0 500 1000 1500 2000 a d so rp ti o n c ap ac it y, q t (m g/ g) time, t (min) ac1 ac2 ac3 xian, amran, arsad and zaini hungarian journal of industry and chemistry 12 and carbon surface [20]. however, the driving force diminishes over time as an equilibrium is reached. ac1 exhibits a greater affinity that indicates a strong tendency to bind with dye molecules at low dye concentrations [14]. typically, this is due to high-energy adsorption sites that are composed of carboxyl, phenolic and hydroxyl groups [21]. three isotherm models, namely langmuir, freundlich and redlich-peterson, were used to analyze as well as describe the equilibrium data of dye adsorption. the constants of isotherm models are presented in table 2, calculated using solver add-in in microsoft excel by minimizing the sum of squared errors (sse) to achieve the best correlation coefficient (r²). all carbon samples fell in line with the redlich-peterson isotherm with r² > 0.88. the applicability of this model suggests a monolayer coverage on homogeneous and heterogeneous surfaces, thereby giving rise to a hybrid of physicochemical adsorption mechanisms [22]. 3.3. adsorption kinetics the contact time between the dye molecules and activated carbon determines the degree of adsorption and provides insights into the adsorption kinetics [14]. the rate of mb adsorption onto ac samples at different concentrations is shown in figure 6. the dye capacity increases with the holding time, confirming a timedependent process [14]. rapid adsorption during the first 300 mins is ascribed to the plentiful availability of active sites for mb removal. the adsorption rate started to reduce because of repulsion between dye molecules once sites became occupied. it was observed that longer contact times would be required at higher dye concentrations. the contact time for adsorption to reach equilibrium at low concentrations of 5.0-8.5 mg/l is approximately 200-600 mins, while 800-1400 mins is needed at concentrations of 14.5-25.0 mg/l. initially, dye molecules have to overcome the boundary layer effect before diffusing into the surface of activated carbon then further diffusing into the porous network of activated carbon and finally interacting with the carbon surface, often referred to as adsorption [23]. likewise, a higher initial concentration usually results in a greater amount of dye adsorbed [7]. the pseudo-first-order, pseudo-second-order and intraparticle diffusion models were used to analyze the rate of mb adsorption and the results are summarized in table 3. the rate of mb removal corresponds well to the pseudo-second-order model with r² → 1. therefore, the rate of adsorption is likely controlled by chemisorption, involving the sharing and exchange of electrons between the dye molecules and the functional groups [24],[25]. further analysis was performed by plotting qt vs. t0.5 that yielded a linear plot passing through the origin, implying that intraparticle diffusion is the only limiting step [26]. in this work, all the plots are linear with an intercept of c > 0, confirming the involvement of intraparticle diffusion, but not as a sole limiting step controlling the adsorption process, except for ac2 at co = 5.0 mg/l. from table 3, ac3 exhibits a higher rate constant, k2, compared to ac1, indicating a steeper gradient before equilibrium is reached over a short period of time. the swift initial adsorption phase can be attributed to its greater specific area that facilitates the rapid diffusion of methylene blue molecules onto its surface. moreover, the large pore volume allows more accessible pathways to interact with the carbon surface [7],[23]. when an adsorbent has a high affinity for a specific adsorbate, the interactions between them are strong enough to facilitate rapid adsorption. as a result, ac3 could effectively capture mb molecules, making it particularly suitable for applications that require the immediate removal of contaminants. 3.4. adsorption thermodynamics at higher temperatures, the reduction in viscosity allows the dye molecules to move more freely in the solution [27], thereby facilitating rapid diffusion across the external boundary layer and into the internal pores of the activated carbon, increasing the overall adsorption capacity of the system [28]. the increase in the temperature of the solution also causes thermal vibration that helps to overcome weak intermolecular forces that hold the aggregates (clustered dye molecules) together [29],[30]. the concept of gibbs free energy (δg° = δh° tδs°) is crucial to understand the thermodynamics of the adsorption process. to determine the enthalpy, δh°, and entropy, δs°, the graph of ln k vs. 1/t was plotted as table 2: the constants of isotherm models for methylene blue adsorption by koh-activated carbons sample char ac1 ac2 ac3 langmuir qm (mg/g) 7.90 37.5 13.2 20.7 b (l/mg) 0.399 0.696 1.22 0.450 sse 1.32 5.83 10.7 65.3 r² 0.795 0.995 0.809 0.787 freundlich kf 3.20 15.3 7.10 8.04 n 3.60 4.96 5.97 4.72 sse 2.16 133 8.26 39.7 r² 0.654 0.886 0.853 0.867 redlich-peterson a 1.36 27.5 37.3 40.8 b 0.00120 0.785 4.25 4.23 g 2.77 0.984 0.887 0.827 sse 0.00 5.14 7.21 37.3 r² 1.00 0.996 0.872 0.875 palm kernel shell activated carbon for methylene blue adsorption 53(2) pp. 7–16 (2025) 13 shown in figure 7. the thermodynamic parameters for mb adsorption by ac1 are summarized in table 4. a positive δh° indicates that the adsorption process is endothermic, with increasing mb removal as the temperature of the solution rises, suggesting that more energy is required to increase the level of adsorption. a high δh° (> 80 kj/mol) typically indicates that adsorption involves the formation of strong chemical bonds such as covalent or ionic bonds. accordingly, breaking these bonds requires a substantial amount of energy [31]. the positive δs° suggests an increase in the disorder or randomness of the adsorption system. as dye molecules approach the carbon surface, they lose some of their translational and rotational freedom but might gain additional degrees of freedom due to interactions at the interface, leading to an overall increase in entropy. the formation of new bonds during chemisorption can create more complex structures, which may facilitate an increase in molecular motion or rearrangement, contributing to a positive entropy change. on the other hand, δg° describes the spontaneity and feasibility of adsorption [14]. the negative δg° proves that the process is thermodynamically favorable. 3.5. regeneration of activated carbon the regeneration of activated carbon, which is essential to restore its effectiveness, involves several cycles of adsorption and desorption. in this work, spent ac1 was regenerated using 0.1 m hc1 and distilled water. the efficiency of adsorption and desorption after four cycles is shown in figure 8. clearly, adsorption and desorption decreased as the number of cycles increased. both solvents become less effective at restoring the adsorptive characteristics of ac1 over the successive cycles. the desorption capacity remains small throughout all cycles. notably, the desorption capacity falls closely in line with the subsequent adsorption capacity, a feature of chemisorption [24],[25]. once adsorbed, it may not be easy for these molecules to desorb without a substantial energy input or chemical alteration. the desorption efficiency of hcl peaks in cycle 3 (83.0 %) but declines to 63.3 % in cycle 4, suggesting that the solvent becomes less efficient over time. likewise, the desorption efficiency of water is 166 % in cycle 3 but sharply declines to 36.8 % in cycle 4. overall, the use of hcl appears to be more consistent over several cycles, even though its efficiency and adsorption capacity gradually decline. analyzing the global trend table 3: the constants of kinetic models for methylene blue adsorption by koh-activated carbons co (mg/l) 5.0 8.5 14.5 25.0 sample ac1 ac2 ac3 ac1 ac2 ac3 ac1 ac2 ac3 ac1 ac2 ac3 pseudo-first-order qe (mg/g) 6.59 4.85 4.90 7.77 6.59 6.50 13.1 8.68 7.16 19.3 8.11 9.71 k1 (min-¹) 0.0039 0.0026 0.0089 0.0062 0.0100 0.0063 0.0042 0.0051 0.0057 0.0035 0.0048 0.0063 sse 3.96 1.79 6.68 1.25 16.6 4.19 7.16 5.46 3.16 8.59 2.94 7.28 r² 0.956 0.965 0.877 0.993 0.935 0.970 0.986 0.975 0.977 0.991 0.982 0.969 pseudo-second-order qe (mg/g) 7.75 6.11 5.51 8.55 6.94 7.08 14.7 9.52 7.84 22.4 9.01 10.5 k2 (g/mg min) 0.0006 0.0004 0.0022 0.0010 0.0011 0.0013 0.0004 0.0008 0.0010 0.0002 0.0007 0.0009 sse 2.32 1.55 3.03 0.370 0.810 0.786 1.75 1.28 0.816 3.29 1.18 2.08 r² 0.974 0.973 0.935 0.998 0.993 0.993 0.996 0.993 0.993 0.997 0.993 0.990 intraparticle diffusion kp (mg/g min½) 0.196 0.135 0.135 0.168 0.142 0.137 0.309 0.196 0.160 0.485 0.194 0.219 c 0.246 0.00 1.18 1.71 1.09 1.58 1.48 1.47 1.32 0.823 0.921 1.79 sse 7.40 3.29 4.20 28.4 15.1 12.7 34.5 18.3 17.1 45.7 16.0 28.6 r² 0.916 0.944 0.901 0.805 0.848 0.860 0.917 0.893 0.859 0.952 0.900 0.865 figure 7: the van’t hoff plot for methylene blue adsorption by ac1 0 0,2 0,4 0,6 0,8 1 1,2 0,00305 0,0031 0,00315 0,0032 0,00325 0,0033 ln k d 1/t (k¯¹) xian, amran, arsad and zaini hungarian journal of industry and chemistry 14 for both solvents, hcl would be a better option to stabilize carbon regeneration. the performance of hcl could be attributed to the dissolution and displacement of mb molecules on the active sites due to electrostatic repulsion [33],[34]. 4. conclusions samples of activated carbon were prepared from palm kernel shell using fresh koh activator and recycled koh. the activated carbon produced using the second recycled koh solution (ac3) exhibits a higher specific surface area of 55.1 m²/g when compared to one prepared using fresh koh solution (ac1, 7.24 m²/g). accordingly, the former removes more methylene blue, highlighting the feasibility of using recycled activator solution for the subsequent preparation of activated carbon. nonetheless, ac1 still demonstrates a strong affinity for methylene blue due to its plentiful supply of surface functional groups. the fitting of adsorption models suggests that adsorption is driven by physicochemical interactions. the thermodynamic parameters conclude that the process is endothermic and spontaneous at high solution temperatures, thereby supporting the viability of using activated carbon for wastewater treatment applications. the regeneration by 0.1 m hcl is more consistent and effective over multiple adsorption-desorption runs and long-term use. acknowledgement this work was funded by utm fundamental research grant no. 23h09. references [1] xu, r.; chi, t.; tian, j.; chen, l.: a new sustainable wastewater management: simultaneous mineralization and dehalogenation treatment of high salinity dye wastewater, j. clean. prod., 2024, 445, 141046, doi: 10.1016/j.jclepro.2024.141046 [2] prasetyo, h.; norrdin, m.n.a.m.; othman, m.h.d.; jaafar, j.; yoshioka, t.; li, z.; rahman, m.a.: technologies for treating wastewater from textile industry: a review, mater. today proc., 2022, 65, 3066–3072, doi: 10.1016/j.matpr.2022.04.214 [3] 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10.33927/hjic-2024-19 study of green hydrogen-air mixture formation in a closed chamber with a given composition olga shypul1*, vadym garin1, oleh tryfonov1, vitalii myntiuk1 and attila egedy2 1 national aerospace university “kharkiv aviation institute”, 17 chkalova str., kharkiv, 61070, ukraine 2 department of process engineering, university of pannonia, egyetem u. 10, veszprém, 8200, hungary the subject of this study is the formation of a hydrogen-air fuel mixture with a given composition and the required degree of homogeneity in a closed chamber while taking into consideration conditions for generating hydrogen by an electrolytic method. this study includes an industrial technology fueled by combustible gases to process thermoplastic parts. the motivation behind this research is the transition to carbon-free processing technology, which would not only reduce emissions and is in line with the concept of a climate-neutral industry but also raises the level of safety with regard to these technologies to a high level. one of the main conditions of high -quality thermal processing fueled by combustible gases is still the precise quality control of the composition of the mixture and its operating pressure. based on the specific requirements of the researched technology, a mathematical model for generating fuel mixtures was developed, which determines the characteristics of a multi -component gas mixture while the working chamber is filling and during the holding period after the gas supply has stopped. the developed mathematical model is supplemented with criteria for evaluating the quality of the fuel mixture. a numerical study using computational fluid dynamics (cfd) was conducted to assess the specified criteria required to achieve a quality fuel mixture. keywords: green hydrogen, fuel mixture, evaluation criteria of fuel mixture, numerical simulation, mixture generation 1. introduction the research area is inspired by the european green deal under the new industrial strategy and climate and energy policy framework, as well as the srri roadmap (2021), aiming to improve energy efficiency and reduce greenhouse gas emissions from industrial processes. this research covers industrial technologies fueled by combustible gases to process thermoplastic parts and possibly replace energy sources based on fossil fuels (coal and methane) with hydrogen produced using electricity. such a transition to carbon-free processing technologies would not only reduce emissions and help to facilitate a climate-neutral industry but ensure the level of production safety of these technologies is high. the goal behind the researched technology, based on the thermal energy method (tem), is the final processing of various materials, including plastics [1]. at present, engineering plastics and high-performance plastics (ep and hpp) due to their low weight, high strength and corrosion resistance are widely used in the automotive and aerospace industries, in medicine, in numerous electronic gadgets and devices as well as in received: 31 july 2024; revised: 8 aug 2024; accepted: 9 aug 2024 *correspondence: o.shipul@khai.edu power electronics. the production of plastic parts requires thermal polishing, curing the pores of thermoplastic structures and removing surface defects. currently, tem is applied to hydrogen-air mixtures with an excess of hydrogen for removing burrs, fogging and the partial surface polishing of parts made of some thermoplastic materials, e.g. acrylic, polyurethane, polyethylene, etc. [2]. stoichiometric mixtures or mixtures containing an excess of fuel are best suited for the tem processing of thermoplastic parts. according to [3], the ratio of oxygen to hydrogen in the fuel mixture should be 1:3 (with a stoichiometric ratio of 1:2). however, these statements relate to oxygen-hydrogen mixtures rather than the air-hydrogen mixtures under study, neglect the effect of the composition of the mixture on the energy capacity as well as do not take into account the presence of the treated object in the combustion chamber nor its properties. as a result, they must be refined to ensure the predicted quality of treatment. in light of this, this research investigates the formation of a green hydrogen-air mixture in a closed chamber in order to establish the best way to form a fuel mixture with a given composition and the required degree of homogeneity while taking into account the conditions https://doi.org/10.33927/hjic-2024-19 mailto:o.shipul@khai.edu shypul, garin, tryfonov, myntiuk and egedy hungarian journal of industry and chemistry 58 necessary to generate green hydrogen. an additional task in this regard is to select an effective way of obtaining green hydrogen. the issue of generating green hydrogen is quite well studied. in works [4] and [5], hydrogen production technologies, storage technologies as well as the end-use applications of hydrogen based on the source of the input energy, operating conditions, conversion efficiency, energy density and unit investment costs were comprehensively reviewed, moreover, the advantages and disadvantages, technological readiness of hydrogen production technologies in addition to storage methods highlighted. the analysis of the indicated data proves the possibility and rationality of obtaining green hydrogen for the technology studied in an electrolytic way by directly using an electrolyzer with a known level of productivity [6]. the main factors affecting the quality of plastics processed by tem include the composition of the mixture, initial pressure, ignition method, combustion modes and time during which parts are in contact with combustion products [7]. due to the large number of parameters that affect the development of the specified patterns, it is advisable to set them consistently and in a connected manner in an analytical way. therefore, within the framework of this work, a mathematical model of the generation of a hydrogen-air mixture is developed to determine the characteristics of a multi-component gas mixture. moreover, numerical studies of the filling process are carried out by taking into account the conditions required to accurately determine the mixture of the composition and its degree of homogeneity. 2. problem statement tem uses a type of pulse machines for thermal pressure treatment utilizing energy generated by the combustion of gas-fuel mixtures. regarding how the mixture is formed, most studies devoted to the design of systems to generate fuel mixtures for machines of this type have focused on such indicators as drive efficiency, specific effective work and full drive efficiency. meanwhile, our preliminary research on tem processing has proven the high significance of and influence on the processing quality of parameters of the fuel mixture such as the mass of the charge, its composition and degree of homogeneity [8]. in turn, the degree of homogeneity depends on a number of filling parameters, including the geometry of the tank being filled [9]. in terms of thermal pulse processing, it is essential that the total amount of heat absorbed per unit surface area of the part during the processing time peaks precisely when the stoichiometric composition of the fuel mixture is achieved. when changing, for example, the mass concentration of the fuel by ±5%, its value increases from 30% (with an excess of oxidizer) to 40% (with an excess of fuel). therefore, the subject of this study is the process of mixture formation in a closed combustion chamber using tem equipment. an experimental setup of a temequipped combustion chamber with a volume of 3.9 liters (figure 1a) and its cad model (figure 1b) consists of two specified inlets through which fuel and oxidizer enter. the outlet is used to achieve a vacuum in the chamber before the fuel mixture enters and remove combusted gases afterwards. the inlets through which the fuel and oxidizer enter were separated to accurately measure the amount of fuel gas produced by the electrolyzer. the calculation domain is the internal cavity of the combustion chamber (figure 2a). the computational mesh (figure 2b) was built in the ansys cfx mesh module to make further calculations in the ansys cfx system [10]. the computational mesh, consisting of 182735 finite volumes, combines tetrahedra and hexahedra. to correctly model the near-wall flow of gases, 5 prismatic layers with a growth factor of elements equal to 1.2 were built. the computational mesh was chosen ensuring that the courant number fell within the range from 2 to 10 to maintain a balance between the accuracy of the obtained results and the performance of the calculations. the courant number determines the relationship between the timestep and the resolution of the mesh at a given flow rate (figure 2c). during the filling stage, the accuracy of the composition of the mixture is ensured by using appropriate conditions of needed mass. during the calculations, the courant number during the holding stage did not exceed 7.8, particularly in the near wall zones which are not critical with regard to the investigated mixing process in the chamber. mixing of the hydrogen-air mixture in the expected stoichiometric ratio according to the reaction 2н2+о2+3.71n2 = 2h2о+3.71n2 a) b) figure 1: experimental setup of tem-equipped combustion chamber (a) and its cad model (b) a) b) c) figure 2: the internal cavity of the combustion chamber (a), the computational mesh (b) and the courant number (c) study of green hydrogen-air mixture formation 52(2) pp. 57–62 (2024) 59 was investigated. the direction of the subsonic gas flow through the inlets was normal. the calculation was carried out in a transient setting. during the simulation, the value of the molar fraction of h2 was monitored along the height of the chamber. the stages over which the mixture formed are shown in figure 3. in the study, the following initial conditions were set: initial pressure after achieving a vacuum was 0.01 mpa, initial temperature of the chamber wall and gas was 20 c. the mass flow rates of h2 and air were 8·10-8 and 3.137·10-5 kg/s, respectively. 3. mathematical model the gas mixing in the chamber and the gas path elements are described by a system of three-dimensional equations of single-phase multicomponent flow, including the laws of the conservation of mass, momentum and energy in their differential forms. the component balance equation is used to determine the distribution regarding the composition of the mixture. in general, the equations used to describe the generation of a fuel mixture are presented in table 1. the stress tensor can be represented as the sum of 𝑷 = – 𝑝𝑰 + 𝝉 , where 𝑰 denotes the unit tensor and 𝝉 represents the deviatoric stress tensor. the last terms in equations 2 and 3 take the forms  ∇ ⋅ 𝑷 =– ∇𝑝 + ∇ ⋅ 𝝉 and  𝑷: ∇𝐮 =– 𝑝∇ ⋅ 𝒖 + 𝝉: ∇𝒖, respectively. the system of equations 1-5 is somewhat different with regard to supplying the components of the mixture and storing the fuel mixture in the working chamber due to the features of mixture formation described above. when mixing gases that are fed into the chamber or elements of the gas path, the main factor is the velocity of the jets of gas. therefore, in equations 2 and 3, the mass forces given by the terms ∑ 𝜌𝑖𝒈𝑁 𝑖=1 and ∑ 𝒋𝑖𝒈 𝑁 𝑖=1 can be neglected. the rate of thermal and barodiffusion while mixing gases to form the fuel mixture is much lower than that of molecular and turbulent diffusion, allowing these processes to be neglected when writing equations 5. since the rate of molecular diffusion is negligible compared to that of mechanical gas mixing, molecular diffusion can be ignored when modeling the filling of the working chamber with the gas mixture components and only taken into account while the fuel mixture is being stored in the working chamber. figure 3: schematic diagram of the stages over which the mixture was formed: flow velocity contours (a – c) and h2 volume fraction contour (d) table 1: the equations used to describe the generation of a fuel mixture during the gas supply stage: the mixture in the chamber during the holding stage: 𝜕𝜌 𝜕𝑡 + ∇ ⋅ (𝜌𝒖) = 0 (1) 𝜌 𝐷𝒖 𝐷𝑡 = ∇ ⋅ 𝑷 𝜌 𝐷𝒖 𝐷𝑡 = ∑ 𝜌𝑖𝒈 𝑁 𝑖=1 +  ∇ ⋅ 𝑷 (2) 𝜌 𝑑𝑒 𝑑𝑡 = ∇ ⋅ (𝜆∇𝑇) + 𝑷: ∇𝒖 𝜌 𝑑𝑒 𝑑𝑡 = ∇ ⋅ (𝜆∇𝑇) + ∑ 𝒋𝑖 ⋅ 𝒈 + 𝑁 𝑖=1 𝑷: ∇𝒖 (3) 𝜌 𝜕𝑐𝑖 𝜕𝑡 = −∇ ⋅ 𝒋𝑖 , 𝑖 = 1, . . . , 𝑁 − 1 (4) 𝒘𝑖 = −(𝐷𝑖 + 𝐷𝑖𝑇)∇𝑐𝑖 (5) 𝐷 𝐷𝑡 : material derivative defined as 𝜕 𝜕𝑡 + 𝒖 ⋅ ∇; 𝜌(𝜌𝑖),  𝑝(𝑝𝑖) : density and pressure of the mixture and its components; 𝑷 : stress tensor; 𝑐𝑖 : mass concentration of the i-th component of the mixture; 𝑒 : internal energy of a gas; 𝑁 : number of components in the mixture; 𝒋𝑖 = 𝜌𝑖𝒘𝑖 : diffusion flux vector; 𝐷𝑖 , 𝐷𝑖𝑇 : coefficients of molecular and turbulent diffusion of the i-th component in the mixture. shypul, garin, tryfonov, myntiuk and egedy hungarian journal of industry and chemistry 60 when calculating the density, pressure, enthalpy and gas constant of the mixture, the mixing rules for ideal gases are used: 1/𝜌  = ∑ 𝑐𝑖/𝜌𝑖 𝑁 𝑖=1 , 𝑝  = ∑ 𝑝𝑖 𝑁 𝑖=1 , ℜ = ∑ 𝑐𝑖 𝑁 𝑖=1 ℜ𝑖, 𝐻 = ∑ 𝑐𝑖 𝑁 𝑖=1 𝐻𝑖 (6). the equations of state and experimental data are used to determine the thermophysical properties of a fluid, i.e. dependence of the density, viscosity, thermal conductivity, specific heat capacity and diffusion coefficients of fluids on the pressure and temperature. taking into account the fact that the flow in fuel-mixture generation systems of thermo-impulse equipment is significantly turbulent, in order to close the system of equations 1-6 it is necessary to also use one of the turbulence models integrated into standard computational gas dynamics packages. when choosing a turbulence model and formulating the system of governing equations, the features inherent when generating the fuel mixture in a thermo-impulse equipment were taken into account. considering the requirements to achieve computational efficiency, semiempirical turbulence models based on the reynoldsaveraged navier-stokes (rans) equations were considered to construct the computational model. fourier's law for turbulent heat flow was used to estimate the temperature of the gas: 𝒒т =– 𝜆𝑡∇т (7), where the turbulent heat transfer coefficient was defined by: 𝜆𝑡 = 𝐶𝑝𝜇𝑡 𝑃𝑟т (8), and 𝑃𝑟тdenotes the turbulent form of the prandtl number. the equations obtained from reynolds averaging describe the behavior of the averaged characteristics of the turbulent flow, where the viscosity and thermal conductivity coefficients are taken as effective values equal to the sum of the laminar as well as turbulent viscosity and thermal conductivity, respectively, i.e.: 𝜇 = 𝜇𝑙 + 𝜇𝑡 , 𝜆 = 𝜆𝑙 + 𝜆𝑡 (9). to simulate turbulence, the shear stress transport (sst) model was used being the most suitable in such cases [11]. the system of equations 1-9 fully determines the characteristics of a multi-component gas mixture when mixing while feeding components into the working chamber or elements into the gas flow as well as during aging after the gas has been supplied. as noted in the previous section, based on the specific requirements associated with the peculiarities of thermal energy treatment, the model should be supplemented with criteria for assessing the quality of the fuel mixture. such criteria may include: – the accuracy of its composition 𝑀(𝑐𝑛)=∫ 𝑐𝑛𝑑𝑉𝑉 ∫ 𝑑𝑉𝑉 ∈ [𝑐𝑛] ± 𝛿(𝑐𝑛) (10); – homogeneity of the fuel mixture 𝜎(𝑐𝑛) = √ ∫ (𝑐𝑛− ∫ 𝑐𝑛𝑑𝑉𝑉 ∫ 𝑑𝑉𝑉 ) 2 𝑑𝑉𝑉 ∫ 𝑑𝑉𝑉 ≤ [𝜎(𝑐𝑛)] (11); – dosing accuracy of the charge 𝐺𝑛с = ∫ 𝜌𝑑𝑉 𝑉 ∈ [𝐺𝑛с] ± 𝛿(𝐺𝑛с) (12). the first criterion (equation 10) determines how accurate the composition of the mixture is which is especially important when mixing during thermoplastic pulse processing. an excess of oxidizer in such processes can lead to the ignition of the processed parts and an excess of fuel (if hydrocarbon compounds are used as the fuel) can lead to soot deposits on the processed parts. the second criterion (equation 11) is the standard deviation of the mass concentration of the fuel in the mixture within a certain volume compared to a set value and is the main parameter when designing mixing devices as well as determining the holding time of the mixture in the working chamber from the moment the gas supply stops until the mixture is ignited. finally, the third criterion (equation 12) determines the accuracy with regard to the mass dosing of the charge and is crucial to stabilize the processing quality. 4. the obtained simulation results as a result of cfd modeling, the velocity fields of gas flows, components of gas mixtures and volume fractions inside the chamber were determined. the velocity profiles and vector patterns over a cross-section of the chamber at corresponding stages of mixing while the chamber was being filled are shown in figures 4-6. while establishing a vacuum, the air was pumped out from the chamber until the pressure fell to 0.01 mpa. after that, h2 and air were sequentially injected inside the chamber until a stoichiometric mixture was achieved. injecting components of the mixture this way provided both a high concentration of its components and dosing accuracy of its charge. accuracy criteria (equation 10 and 12) were used to define the exact mass of h2 and air corresponding to the stoichiometric mixture, moreover, were used as termination criteria for calculations. although the accuracy of its composition and dosing accuracy of the charge did not exceed 2%, such heterogeneous flow conditions affected the accuracy of the mixing processes inside the chamber because of the different densities of h2 and air. the distributions of the molar concentration of h2 over the characteristic cross-sections of the chamber after injecting air are presented in figure 7. the results show that the normalized standard deviation of the h2 molar fraction (10) was equal to 20%. the mixture was poorly homogeneous and needed to be held. therefore, after injecting the components, the mixture was held. several monitoring points were used to control the h2 volume fraction in the chamber at different heights (figure 8a). study of green hydrogen-air mixture formation 52(2) pp. 57–62 (2024) 61 a) b) figure 4: gas flow field in the central section of the chamber while establishing a vacuum (t=0.73 s after the process was started) (a) velocity profile; (b) vector patterns a) b) figure 5: gas flow field in the central section of the chamber while injecting h2 (t=433.23 s after the process was started) (a) velocity profile; (b) vector patterns a) b) figure 6: gas flow field in the central section of the chamber while injecting air (t=600 s after the process was started) (a) velocity profile; (b) vector patterns figure 7: h2 molar fraction in the central section of the chamber after injecting air (t=600 s after the process was started a) b) figure 8: h2 volume fraction at different heights in the chamber (a) location of the monitoring points; (b) h2 volume fraction vs. holding time figure 9: homogeneity of the mixture vs. holding time figure 10: h2 molar fraction in the central section of the chamber after being held (t=766 s after the process was started shypul, garin, tryfonov, myntiuk and egedy hungarian journal of industry and chemistry 62 after holding the mixture for 1 minute, the gas stopped moving and turbulence decay was observed. during approximately the following 2 minutes, the fuel mixture slowly became more homogeneous as a result of diffusion (figure 8b) until the accuracy of homogeneity reached 2% (figure 9): the final distribution of the h2 volume fraction after being held for approximately 3 minutes is shown in figure 10. 5. conclusions cfd simulation results showed that the mixer provides a high degree of homogeneity of the fuel mixture. according to the normalized estimate of the root mean square deviation of the h2 molar concentration, the deviation of the methane content from the stoichiometric value did not exceed 2%. according to calculations, the mixture needed to be held for approximately 3 minutes to achieve the required homogeneity of the gas mixture in the combustion chamber, which was longer than expected. this problem can be solved by modernizing the main inlets of the components as well as introducing additional mixing mechanisms. however, changes in the configuration of tem equipment will be required while implementing the pilot technology during cyclic production. for research purposes, the holding time does not affect the essence of the process but must be determined and taken into account. in addition, the influence of heating the walls of the combustion chamber during its cyclic operation on the quality indicators of the fuel mixture needs to be further studied. acknowledgements this research was funded by the eurizon project under grant agreement no.871072 of the european union. the authors would like to express their gratitude to cadfem ua llc and the ansys channel partners in ukraine for their help with regard to software licensing. 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https://doi.org/10.4018/978-1-7998-7864-3.ch003 https://doi.org/10.1007/978-3-031-18487-1_11 https://doi.org/10.33927/hjic-2019-21 https://ansyshelp.ansys.com/account/secured?returnurl=/views/secured/prod_page.html?pn=cfx&pid=cfx&lang=en https://ansyshelp.ansys.com/account/secured?returnurl=/views/secured/prod_page.html?pn=cfx&pid=cfx&lang=en https://doi.org/10.1080/10407782.2020.1746155 hungarian journal of industry and chemistry vol. 53(2) pp. 37–43 (2025) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2025-15 online learning for surrogate model maintenance balázs palotai1,2*, gábor kis1, tibor chován2 and ágnes bárkányi2 1 mol group plc., dombóvári út 28, budapest, 1117, hungary 2 department of process engineering, university of pannonia, egyetem utca 10, veszprém, 8200, hungary in the process industry, flowsheet models are commonly used to create digital representations of real processes. while these models provide detailed simulations, they often struggle with computational demands in dynamic operating environments. surrogate models offer a more efficient alternative, but their level of accuracy must be continuously aligned with actual system behavior. this paper presents an mlops-aligned online surrogate calibration method that maintains and improves surrogate model accuracy by dynamically incorporating localized operational data. unlike traditional global surrogates trained on static datasets, the proposed approach adapts to changing conditions while preserving previously learned knowledge, effectively addressing the challenge of catastrophic forgetting. demonstrated on a heat exchanger network, the method significantly improves prediction accuracy in previously unmodeled operating regimes, enhancing the robustness and reliability of digital twins in industrial applications. keywords: surrogate model, online learning, digital twin, model maintenance 1. introduction simulation and optimization are essential in the process industry to achieve operational efficiency and ensure system safety [1]. traditionally, detailed process simulations are carried out using high-fidelity flowsheet models, which support in-depth analysis, scenario evaluation, performance enhancement and equipment condition monitoring [2]. these models, grounded in physical laws and thermodynamic relationships, serve as reliable tools for data-driven decision-making. however, maintaining their accuracy over time can be challenging, especially when integrated into real-time applications where the underlying physical systems evolve continuously [3]. to overcome the computational complexity of flowsheet simulations, surrogate models—also referred to as reduced-order or metamodels—have emerged as a practical alternative [4]. these models emulate the behavior of complex simulations using simplified mathematical frameworks, thereby enabling faster analysis and optimization. constructing an effective surrogate model typically requires sampling data from the original high-fidelity flowsheet model. two common approaches are one-shot sampling and adaptive sampling [5]. one-shot techniques, such as latin hypercube sampling (lhs), generate statistically distributed samples across the design space in a single step [6]. in contrast, adaptive sampling strategies iteratively select received: 16 june 2025; revised: 19 june 2025; accepted: 23 june 2025 *correspondence: bpalotai@phd.uni-pannon.hu new data points to enhance the precision of a model with fewer evaluations [7]. while both sampling strategies are efficient with regard to initial surrogate development [4], they may not ensure a sufficient level of accuracy during its actual operation. the real system may operate in regions that were underrepresented or completely absent in the initial sampling, especially when the operating range of a derived parameter is unknown beforehand. as a result, surrogates trained offline may underperform in dynamic or previously unseen regimes. to address this gap, online learning offers a way to refine surrogate models during their implementation by incorporating real-time data. this continuous adaptation enables the model to respond to new operational scenarios and maintain predictive accuracy. this study proposes and evaluates an online surrogate learning framework that iteratively updates the model based on observed process data. the goal is to maintain a high level of accuracy across both well-known and emerging operating conditions, enhancing the robustness and reliability of the surrogate in practical industrial settings. 2. methodology in practical applications, surrogate models are used to replace high-fidelity simulations for the purpose of https://doi.org/10.33927/hjic-2025-15 mailto:bpalotai@phd.uni-pannon.hu palotai, kis, chován and bárkányi hungarian journal of industry and chemistry 38 reducing computational load. in this research context, the role of a surrogate model is to support the calibration of the flowsheet model by estimating calibration factors that align the simulation with the real process [8]. to demonstrate the effectiveness of online learning approaches, this study focuses on retraining the surrogate model. in simple terms, the flowsheet model is treated as a stand-in for the real system, generating data that the surrogate is expected to replicate. it is assumed that the flowsheet model accurately represents the real process at all operating points and the surrogate model learns from this data accordingly. 2.1. problem statement lhs is a widely used one-shot technique for surrogatemodel training due to its ability to maintain generality as dimensionality increases, while ensuring well-distributed sampling across the input space [9]. this method requires predefined minimum and maximum ranges for each input parameter, typically based on the normal operating window of the real process. however, defining appropriate ranges becomes challenging for derived parameters—such as fouling factors in heat exchangers—when prior knowledge is lacking. as illustrated in figure 1, if the surrogate model is trained on hypothetical parameter ranges that differ significantly from the actual distribution observed while in operation, its predictive accuracy can reduce. ideally, surrogate-model training would be based on the true parameter ranges relevant to the system, but this information is often unavailable during offline model development, moreover, only becomes accessible once the model is deployed and real operational data are collected. 2.2. introduction to online learning most conventional machine learning approaches operate under the classical paradigm, where the complete dataset is available prior to training. these models are built on the assumption that the data distribution remains static and the underlying structure does not change over time [10]. when new data become available, the typical solution is to retrain the entire model from scratch, which can be computationally intensive and inefficient. in contrast, online learning offers a framework for continuous model adaptation in response to a stream of incoming data [11]. this approach processes data incrementally, updating the model one sample at a time, facilitating model training to occur sequentially as new data become available: 𝑠1, 𝑠2, … , 𝑠𝑖 ⇒ ℎ1, ℎ2, … , ℎ𝑖 (1), where 𝑠𝑖 represents the training sample at time step 𝑖 and ℎ𝑖 denotes the state of the model after learning from that sample. each training sample is composed of an input– output pair: 𝑠𝑖 = (𝑥𝑖 , 𝑦𝑖), 𝑥𝑖 ∈ 𝑅𝑛 , 𝑦𝑖 ∈ 𝑅𝑚 (2), where 𝑥𝑖 stands for the input feature vector with 𝑛 dimensions and 𝑦𝑖 denotes the corresponding labeled output vector with 𝑚 dimensions. the model at time step 𝑖, denoted by ℎ𝑖, is updated based on the previous model state ℎ𝑖−1 and the most recent 𝑝 samples: ℎ𝑖 = 𝑓(ℎ𝑖−1, 𝑠𝑖 , 𝑠𝑖−1, … , 𝑠𝑖−𝑝) (3). this formulation reflects the online learning paradigm where the model incrementally evolves with each new data point, arbitrarily incorporating a small window of past samples. online learning is particularly useful in dynamic environments where data evolve over time and an immediate response is required. this method is commonly employed in systems that operate autonomously, such as in robotics or self-driving vehicles [12], as well as in applications where training signals are provided progressively through human interaction or feedback [13]. unlike traditional training, which assumes a static environment, online learning enables systems to remain adaptable and responsive to new information as it becomes available. online learning offers a range of advantages, particularly in dynamic environments where timely adaptation and efficient data handling are essential. one of its primary strengths lies in efficient resource utilization. unlike traditional methods that require access to the entire dataset, online learning processes incoming data incrementally, reducing memory and computational demands by only storing and updating a limited subset at any given time [14]. another key advantage is real-time adaptation. models can adjust their predictions and internal parameters continuously, allowing them to respond immediately to changes in the environment or system behavior. this feature is especially useful in scenarios where system conditions evolve rapidly, such as in financial forecasting, industrial automation or non figure 1: (a) comparison between the sampling range of the fouling factor (left) and the range of the actual process fouling factor (right); (b) prediction of the offline-trained base model (red) versus actual process data (blue) from the use case online learning for surrogate model maintenance 53(2) pp. 37–43 (2025) 39 stationary domains like weather prediction, where patterns shift over time and data relevance quickly reduces [15]. however, online learning also presents several challenges. a notable limitation is catastrophic forgetting, a phenomenon where the model gradually loses previously acquired knowledge while adapting to new data [16]. this can compromise long-term model stability and degrade performance in tasks learned earlier. furthermore, handling concept drift—sudden or gradual shifts in the underlying data distribution— remains a significant challenge, often requiring advanced strategies to detect and adapt to such changes effectively. finally, an inherent risk of overfitting in online settings must be addressed. since updates are made frequently and often based on small or recent data segments, the model may become overly sensitive to recent fluctuations, leading to poor generalization. balancing adaptability with robustness is therefore a critical aspect in the design of effective online learning systems [17]. 2.3. compared methodologies in real-world applications, online learning provides an effective framework for continuously adapting surrogate models to reflect the behavior of the actual process. however, ensuring long-term reliability requires careful design to prevent overfitting to recent data and mitigate catastrophic forgetting, where the model loses its ability to generalize from past knowledge. to evaluate the effectiveness of different online learning strategies, this study compares several update mechanisms, each with distinct learning dynamics and memory usage: • incremental: the model is updated as each new data point arrives (figure 2a), allowing for immediate adaptation but with an increased risk of forgetting prior knowledge. • mini-batch: the model accumulates a small number of new data points, namely 5, before performing an update (figure 2b). this buffering approach smooths out fluctuations and reduces overfitting to individual samples. • incremental replay: this is similar to the incremental approach, but a small proportion (1%) of the original offline training data is blended into each new data point (figure 2c) in order to preserve past knowledge while adapting to new patterns. • cumulative: with each update, the model is trained using the complete offline dataset combined with all new incoming data (figure 2d). this strategy provides strong memory retention but increases computational cost over time. • hybrid: the model updates incrementally with each new data point. however, when prediction accuracy drops below a practical threshold, the corresponding data points are stored and later used in a cumulative update after a defined number of samples, in this case 5, is collected (figure 2e). the aim of this approach is to balance adaptability against long-term stability by selectively reinforcing learning as the level of performance declines. the practical threshold reflects the practical requirements of implementing the surrogate model. it is important to recognize that pursuing the highest possible degree of accuracy does not always translate into improved practical outcomes and may, in fact, increase the risk of overfitting. 2.4. metrics the primary objective of continuously retraining surrogate models is to maintain or improve predictive accuracy as new operational data become available. ideally, each successive version of a model should outperform its predecessor at the next working point. to evaluate this progression in real time, a modified version of the mean absolute scaled error (mase) is introduced. unlike the traditional mase metric—which evaluates forecast accuracy by comparing the performance of a model to that of a naïve baseline [18]— the modified mase proposed here compares the error of the newly updated model to that of the previously deployed model on the same data point. this adaptation provides a direct measure of improvement in performance between sequential updates to a model. 𝑀𝑜𝑑𝑖𝑓𝑖𝑒𝑑 𝑀𝐴𝑆𝐸𝑡 = 𝑀𝐴𝐸𝑡 (𝑝) 𝑀𝐴𝐸𝑡 (𝑐) (4), 𝑀𝐴𝐸𝑡 (𝑐) = 1 𝑛 ∑|𝑦𝑡 (𝑖) − �̂�𝑡 (𝑐,𝑖) | 𝑛 𝑖=1 (5), 𝑀𝐴𝐸𝑡 (𝑝) = 1 𝑛 ∑|𝑦𝑡 (𝑖) − �̂�𝑡 (𝑝,𝑖) | 𝑛 𝑖=1 (6), where: • 𝑡: the current time step or working point, • 𝑛: the number of output variables, figure 2: illustration of compared online learning methodologies. palotai, kis, chován and bárkányi hungarian journal of industry and chemistry 40 • 𝑦𝑡 (𝑖) : the true value of output 𝑖 at time 𝑡 • �̂�𝑡 (𝑐,𝑖) : the prediction of the current model after online retraining, • �̂�𝑡 (𝑝,𝑖) : the prediction of the previously deployed model before an update. however, this metric only reflects the relative level fo improvement between versions of a model in terms of the latest sample and does not account for potential degradation in the overall accuracy of the model, particularly in terms of the original training distribution. to address this, each updated model is also evaluated with regard to both the original offline and online datasets. this dual evaluation ensures that gains in local adaptability do not come about at the expense of broader model robustness. 3. experimental 3.1. introduction to the use case the proposed online learning strategies were evaluated using a simplified heat exchanger network model. the flowsheet model was developed using aspen hysys v14 (figure 3), moreover, the corresponding input and output parameters used for surrogate modeling are summarized in table 1. to implement the surrogate model, the neural network architecture was chosen due to its flexibility in terms of capturing complex nonlinear relationships. specifically, the mlpregressor from scikit-learn was used as it provides native support for incremental learning via the partial_fit() method that allows the model to be updated progressively with new data without reinitializing the learned weights, which is essential in online learning scenarios. the initial surrogate model was constructed using lhs, generating 200 samples from the flowsheet model. a feedforward neural network with one hidden layer, containing 50 neurons, was trained on this dataset. the input sampling range was predefined based on expected operational bounds for the system, serving as the baseline for both surrogate training and subsequent online updates. the baseline model achieved an average r² of 0.9701 and a mean absolute percentage error (mape) of 0.0218 across the output parameters (figure 4). 3.2. test “online” data to evaluate the performance of the online learning strategies, a test dataset consisting of 730 data points was table 1: use case model input output parameters type description uom input feed1 mass flow rate kg/h input feed1 temperature °c input prod1 mass flow rate kg/h input prod1 temperature °c input e1 fouling factor h°cm2/kj input e2 fouling factor h°cm2/kj output prod1e1in temperature °c output feed1e1out temperature °c output feed1out temperature °c output prod1out temperature °c figure 5: visualization of the generated test “online” dataset, showing offline data points on the left and sequentially introduced online data on the right. figure 4: scatter plot illustrating the predictive accuracy of the base surrogate model in terms of the monitored output parameters. figure 3: flowsheet representation of the heat exchanger network modelled in aspen hysys v14 in the use-case scenario. online learning for surrogate model maintenance 53(2) pp. 37–43 (2025) 41 generated. this dataset simulates realistic process variability by introducing gradual changes to input parameters, added noise and the effects of heat exchanger fouling (figure 5). in contrast, an ideal scenario—where the test data is available during offline training and combined with the lhs dataset—would allow the model to achieve an enhanced level of performance with an average r² of 0.988 and a mape of 0.0069 (as shown in figure 6). this comparison highlights the potential performance gap that online learning aims to bridge by progressively incorporating new data into the model. 3.3. online learning workflow the performance of the base surrogate model was evaluated using the test dataset in a sequential manner, simulating a real-time operation. new data points were introduced one by one, allowing the model to be assessed under conditions that reflect actual operational dynamics. at each working point, the predictive accuracy of the model was recorded both in terms of the new and original dataset to evaluate its ability to adapt to changing conditions and robustness with regard to retaining previously learned knowledge. based on the selected online learning strategy, the model was retrained continuously using the incoming data, following the specific update procedures described in section 2.3. 4. results and discussion the results are evaluated from two perspectives: adaptability, which reflects how effectively the model adjusts to new operating conditions, and robustness, which measures the model's ability to maintain its level of performance in terms of the original offline lhs dataset. 4.1. adaptability the adaptability performance of all the evaluated online learning strategies assessed using the modified mase metric is presented in figure 7. in this context, a mase value greater than 1 indicates that the updated model performed better than its previous version at a given working point with higher values denoting an improved level of adaptability to new data. all the evaluated strategies demonstrated adaptability, consistently achieving mase values above 1. this confirms that each method was able to effectively learn from incoming data points and improve model predictions over time. among the tested approaches, the hybrid and incremental learning strategies exhibited the strongest level of adaptability, consistently outperforming the other methods throughout the dataset. this outcome is in line with expectations as mini-batch learning delays updates to models until multiple data points, e.g. 5, are collected, which slows the level of responsiveness to sudden changes. cumulative learning, while comprehensive, tends to underrepresent the newest data during retraining due to the overwhelming influence of the older, larger offline dataset. 4.2. robustness figure 8 compares the performance of the various online learning strategies against both the original surrogate model (baseline) and an ideal offline-trained model. this figure 7: adaptability performance of online learning solutions, measured using the modified mase metric figure 8: robustness performance of online learning solutions with regard to the original lhs data (orange) and the level of adaptability to the test "online" data (blue) figure 6: comparison between the base surrogate model and ideal model prediction accuracy of the test dataset palotai, kis, chován and bárkányi hungarian journal of industry and chemistry 42 comparison is conducted across two datasets: the test dataset—representing evolving operational conditions— and the original lhs dataset used for initial model training. the goal is to approach the performance of the ideal model with regard to the test data while preserving the accuracy of the baseline model in terms of the original data, thereby achieving a balance between adaptability and robustness. the hybrid learning approach emerged as one of the most effective strategies. it achieved a high degree of accuracy in terms of the test data, comparable to the ideal offline model, while also preserving the original performance of the surrogate model concerning the lhs dataset. this confirms its ability to maintain previously acquired knowledge while adapting effectively to new conditions. the incremental learning strategy also performed strongly with regard to the test dataset, reflecting a high level of adaptability. however, it suffered a noticeable drop in accuracy in terms of the original lhs dataset, suggesting signs of catastrophic forgetting. this issue was partially mitigated by incorporating a 1% replay of the original training data during each update cycle. while this replay strategy helped preserve the level of performance in terms of the original dataset, it introduced a slight reduction in predictive accuracy with regard to the test data—highlighting the trade-off between retaining old knowledge and adapting to new trends. on the other hand, the cumulative learning strategy prioritized retention of the original training data and achieved similar levels of accuracy in terms of the lhs dataset. however, this came at the cost of a lower level of performance regarding the test dataset as the large volume of historical data overshadowed the influence of the newly acquired samples, thereby reducing its ability to adapt swiftly to evolving process conditions. the mini-batch learning method, while showing a modest degree of improvement compared to the baseline on the test dataset, yielded the lowest level of accuracy during the test among the tested approaches. additionally, infrequent updates to this model were insufficient to maintain robustness in terms of the original dataset, resulting in a suboptimal level of performance with regard to both adaptability and robustness. in summary, the hybrid learning method demonstrated the most effective trade-off between adaptability and robustness, achieving a strong level of accuracy in terms of the test dataset as shown in figure 9 and still a good degree of accuracy with regard to the original dataset shown in figure 8. incremental learning offered a strong level of adaptability but required mitigation strategies to preserve older knowledge. cumulative learning ensured robustness but limited adaptability, while mini-batch learning lagged behind due to its delayed response to new data. 5. conclusions the proposed online learning approaches demonstrate significant potential in terms of enhancing the adaptability of surrogate models under evolving operating conditions. all the investigated methods contributed to refining the base surrogate model by enabling effective adaptation to new data. a critical challenge in online learning is the preservation of previously acquired knowledge, which was successfully addressed by the hybrid approach, combining the strengths of both incremental and cumulative learning strategies. additionally, in terms of incremental learning, a small replay, 1% in this use case, of the original training data is incorporated during each update cycle, ensuring that essential past information is retained while allowing the model to adapt to new data. achieving an optimal trade-off between adaptability and robustness requires careful calibration of the online learning process. in particular, setting a realistic accuracy threshold is essential, namely one that reflects the practical requirements necessary to implement the surrogate model. it is important to recognize that pursuing the highest possible level of accuracy does not always translate into improved practical outcomes and may, in fact, increase the risk of overfitting. therefore, the design of online learning strategies should consider both the enhancement of performance and long-term stability of the model in order to be reliably deployed in real-world industrial systems. additionally, ongoing monitoring of model performance is essential to maintain its credibility and ensure it continues to meet operational requirements. figure 9: comparison of the accuracy of the base model and hybrid learning model with regard to the online test data online learning for surrogate model maintenance 53(2) pp. 37–43 (2025) 43 acknowledgements this work was supported by the cooperative doctoral programme of the university research scholarship programme headed up by the ministry of culture and innovation and financed by the national research, development and innovation fund (2024-2.1.2-eköpkdp-2024-00017/1). references [1] tarcsay, b.l.; bárkányi, á.; chován, t.; németh, s.: development of compartment models for diagnostic 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https://doi.org/10.1109/iros58592.2024.10801619 https://doi.org/10.1088/1742-6596/1168/2/022022 https://doi.org/10.1016/j.ijforecast.2006.03.001 hungarian journal of industry and chemistry vol. 51(1) pp. 67-73 (2023) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2023-10 self-diffusion coefficient of water in the presence of alkali halide ions andrás baranyai 1* 1 institute of chemistry, eötvös loránd university, po box 32, budapest 112, h-1518, hungary the self-diffusion coefficient of water in aqueous solutions of alkali halides at different concentrations was studied using the polarizable bk3 model of water [1]. as ion potentials, initially the alkali halide force field fitted to this water potential by the solvation free energy, ion-water clusters as well as, for the purpose of crosschecking, to the ambient crystal energy and density was investigated. it was found that the strength of attraction between the central ion and the water molecules in the hydration shell is stronger than in reality , which manifests itself in the reduced mobility of water. for small ions, this discrepancy is small. by omitting the dipolar polarization of larger ions, the estimates could be improved. similarly, increasing the size of the anions within reasonable limits also enhances the results but the structural breaking effect is insufficient. if the relative permittivity of water is smaller than that measured experimentally, typically ionic charges in non-polarizable water models can be decreased to recover the correct semi-macroscopic coulomb energy. since our polarizable water model reasonably estimates the relative permittivity, smaller ionic charges were used to quantify the differences in the strengths of ion-water attraction. our estimates of self-diffusion in aqueous solutions by varying the concentration of ions are presented and discussed for licl, nacl, nabr, nai, rbf and rbi. keywords: aqueous solution, polarizable bk3 model, simulation 1. introduction the strict tetrahedral structure of hexagonal ice breaks down in liquid water. in ambient water, depending on the calculation method, the average number of hydrogen bonds in a molecule is 3.2-3.6. the bonds break and reform but maintain this imperfect network. since a relatively dilute liquid is maintained by this arrangement, external pressure destroys the network to some extent, leading to extreme conditions during transport processes. at low temperatures, an external pressure of several hundred kilobars breaks the bonds resulting in faster transport, while under even larger pressures, the compressive force decreases the rate of transport again as is the case with normal liquids. this behavior is reproduced qualitatively by the bk3 and tip4p/2005 models of water [1]-[3]. charged solutes in water also formally increase the pressure because the energy density in the dielectric dimensionally is pressure. therefore, it should be straightforward to determine the degree of self-diffusion of water by calculating the pressure caused by the ions and connecting this to the appropriate value in a diagram by plotting the pressure against the degree of selfdiffusion. an essential part of this procedure is the relative permittivity of water. in a strong electric field, the dielectric constant exhibits nonlinear behavior which received: 23 march 2023; revised: 15 april 2023; accepted: 15 april 2023 *correspondence: baranyai.andras@ttk.elte.hu in the case of an electrolyte equates to a function dependent on the distance from the ion. near to the ion, the dielectric constant decreases as a result of two phenomena, namely the break-down of the structure of the liquid and dielectric saturation. the initial value is the internal index of refraction, which originates from the atomic and electronic polarization of the particle as well as corresponds to the high frequency limit of this parameter. the experimental optical dielectric constant of water under ambient conditions is n2 = ε∞ = 1.78, which increases with distance until the frequency, ε0, falls to zero and the static dielectric constant is reached. for water under ambient conditions, ε0 = 78.4. the nonlinear dielectric behavior was studied in detail by ruff, liszi and mészáros for several solvents and solutes, who even drew up a function of the distance-dependent dielectric constant which, beyond 0.4-0.8 nm, depending on the solvent, asymptotically approached the corresponding ε0 [4]-[7]. they also tested it in terms of the solvation free energy which yielded good results. the size of the ion, that is, the radius of the ionosphere, determined the values of the function that should be used. for small ions, this interaction was stronger. since small ions strongly attract water molecules, the energy density corresponds to a high-pressure state where the self-diffusion and viscosity exhibit the behavior of a normal compressed liquid with a lower degree of transport. for large ions, given that the https://doi.org/10.33927/hjic-2023-10 mailto:baranyai.andras@ttk.elte.hu baranyai hungarian journal of industry and chemistry 68 attraction is weaker, the resulting energy density in the first hydration shell corresponds to a moderate pressure as the transport of momentum or particles increases [8]. although this semi-macroscopic and semi-empirical idea qualitatively describes the phenomena, it does not reveal any information about the microscopic nature of a granulated liquid. obviously, the dielectric behavior of the liquid in an ionic solution is a crucial factor. the dielectric constant is a difficult property to determine by computer simulation because it is time-consuming to calculate. the dielectric constant is a function of the dipole moment as well as the dipole moment distribution and structure in polarizable models. regarding the bk3 model [1], the average dipole moment in ambient water is ≈ 2.65d which is much larger than in non-polarizable models which severely underestimate this parameter because their fixed dipole moment is most commonly fitted to the ambient internal energy, density and the pair correlation function or even self-diffusion. the moderate dipole moments prevent these models from reproducing the experimental ε0. kann and skinner wanted to reproduce the self-diffusion of water in the presence of alkali halide ions using computer simulations by considering possibilities and surveying the literature on interaction models [9]. as a result, kann and skinner introduced a scale based on the following equality [9]: 𝑞2 / 𝜀0𝑟 = 𝑞𝑒𝑓𝑓 2 / 𝜀𝑠𝑖𝑚𝑟 (1) they used the new qeff in their calculations, carried out a comprehensive number of simulations of different models and managed to improve the self-diffusion of water in the presence of alkali halides. our aim is to study polarizable water and ion models. the bk3 model with its gaussian charges, charge-on-spring polarization and exponential repulsion covers the entire phase diagram from high-pressure solids to vapors with an acceptable degree of accuracy [1]. for ambient liquids, the estimates are correct even numerically. most importantly, the temperaturedependent dielectric constant within the margin of error is accurate [1]. a further advantage is that the model qualitatively reproduces the pressure-dependent extremes of self-diffusion and viscosity [2]. as models of ions, polarizable force fields parametrized to the bk3 model were used and the fitted properties were the hydration free energy, energy and geometry of the ionwater cluster as well as the ambient crystal energy and structure [10]. granulated water is quite different from a semimacroscopic model. there are two effects which sometimes compete with each other that need to be taken into account: the strength of attachment of the water molecule to the ion and the breakage of the hydrogenbond network by the ion. a water molecule, depending on the ion attached to it, spends approximately 10 picoseconds [11] before leaving the hydration shell, allowing other molecules to hydrate. during this time, the ion joins the attached water molecules and creates a larger but less mobile entity. even though the strength of this attachment is obviously large for smaller ions like li+ and na+, because of their size they can only be surrounded by 4 or 5 molecules, respectively [10]. the degrees of coordination of the oxygen in water to k+, rb+ and cs+ using this model are 6.99, 8.18 and 9.55, respectively. for anions, the hydration shell is less definite, mainly as a result of the smaller degree of attraction and the imperfect structural fit of the ion [10], thereby increasing the presence of large anions close to the free surface of water [12]. the degrees of coordination of water molecules to f-, cl-, brand iare 5.40, 5.85, 6.18 and 6.37, respectively [10]. these values were obtained from evaluating the partial pair correlation functions. it was concluded that no water molecule is bonded by both of its hydrogen atoms [10]. interestingly, although the repulsive parameters of chloride closely resemble those of water (see tables 1 and 2), its coordination number is 5.85. in this paper, the impact of three parameters on the self-diffusion of water is studied. in certain cases, the polarization is omitted and, within reasonable limits, the size of anions is increased. a relatively free approach is adopted and the charges of ions varied to quantify the “apparent” connection strength between the ion and its solvation shell. this approach creates a slightly unrealistic system because the smaller charge not only interacts with its adjacent neighbors. however, other charges in the system, including the relatively large partial charges of water, screen these interactions. while an error is introduced with regard to the energy of the system, it will only have a moderate impact on the longdistance structure. experimental results for several typical ion pairings reported by müller and hertz are taken into consideration [13]. 2. details of the simulations the gaussian charges of a molecule or ion in general are represented by a spherical charge distribution as follows: 𝜌𝑖𝑎(r) = 𝑞𝑖𝑎 (2𝜋𝜎𝑖𝑎 2 )3/2 𝑒𝑥𝑝 ( −|r − r𝑖𝑎| 2 2𝜎𝑖𝑎 2 ) (2) where ρia denotes the charge density of site a on molecule i centered at ria, whose charge is represented by qia and its distribution width by σia. the corresponding coulomb interaction energy, uqq, between gaussian charges then becomes: 𝑈𝑞𝑞 = 1 2 ∑∑ 𝑞𝑖𝑎𝑞𝑗𝑏 4𝜋𝜀0|r𝑖𝑎 − r𝑗𝑏| 𝑒𝑟𝑓 𝑎,𝑏 𝑁 𝑖,𝑗≠𝑖 ( |r𝑖𝑎 − r𝑗𝑏| √2(𝜎𝑖𝑎 2 + 𝜎𝑗𝑏 2 ) ) (3) where erf denotes the error function. it can be seen from eq. (3) that as the distribution width approaches zero, i.e. σ → 0, the usual formula for the coulomb interaction energy between point charges is recovered. this energy is a function of the σ -s, namely the wider the distribution is, the higher the energy will be between two opposite self-diffusion coefficient of water 51(1) pp. 67-73 (2023) 69 point charges positioned the same distance from each other. eq. (3) can be estimated by using the ewald method previously described in detail [14]. a nonelectrostatic form is added to the charge-charge interactions: 𝑈(𝑟) = 𝐴 exp(−𝐵𝑟) − 𝐶/𝑟6 (4) kong suggested a combined rule [15] based on the following approximation: 𝑈𝑖𝑗(𝑅) = 1 2 [𝑈𝑖𝑖(2𝑟1) + 𝑈𝑗𝑗(2𝑟2)] (5) where 𝑟1 + 𝑟2 = 𝑅 and 𝑑𝑈𝑖𝑖(𝑟) 𝑑𝑟 | 𝑟=2𝑟1 = 𝑑𝑈𝑗𝑗(𝑟) 𝑑𝑟 | 𝑟=2𝑟2 by applying it in terms of exponential repulsion leads to: 𝐴𝑖𝑗 = 1 2 [𝐴𝑖𝑖 ( 𝐴𝑖𝑖𝐵𝑖𝑖 𝐴𝑗𝑗𝐵𝑗𝑗 ) 𝐵𝑖𝑖 𝐵𝑖𝑖+𝐵𝑗𝑗 + 𝐴𝑗𝑗 ( 𝐴𝑗𝑗𝐵𝑗𝑗 𝐴𝑖𝑖𝐵𝑖𝑖 ) 𝐵𝑗𝑗 𝐵𝑖𝑖+𝐵𝑗𝑗 ] (6a) 𝐵𝑖𝑗 = 2𝐵𝑖𝑖𝐵𝑗𝑗 𝐵𝑖𝑖 + 𝐵𝑗𝑗 (6b) it is used not just for ion-ion but for ion-water interactions as well. the advantage of this formula if the sizes are additive was presented earlier [10]. the c parameters are combined according to the typical formula below: 𝐶𝑖𝑗 = √𝐶𝑖𝑖𝐶𝑗𝑗 in table 1, the parameters of repulsion are presented [10]. the simulations were conducted using our own code in a cubic simulation box and under periodic boundary conditions. the integrator was an isothermal-isobaric implementation of the velocity verlet algorithm [16], while the rotational degrees of freedom for water were handled by quaternions along with an algorithm [17]. the iteration of the three chargeon-spring (cos) charges for water and the ion have previously been described [1,10,14,18]. typically, a predictor-corrector scheme was used to decrease the number of iterations before the minimum energy of the actual atomic configuration was reached. the pressure and temperature were fixed at 1 bar and 298 k, respectively. the parameters of the bk3 model are presented in table 2. point m denotes the base of the negative charge on the bisector of the hoh angle. 250 water molecules were examined and the ions implanted by replacing water molecules with 4, 10, 14, 18, 22, 30 and 50 ions corresponding to 0.45, 1.57, 1.65, 2.16, 2.68, 3.79 and 6.94 mol/kg of solvent, respectively. these solutions were equilibrated with a general ion pair. the time step was 2fs and for each ion pair studied, the system was equilibrated further for 200-600 thousand time steps and diffusion data collected according to the expression: 𝐷 = lim 𝑡→∞ 1 6𝑡 〈 1 𝑁 ∑[r𝑖(𝑡) − r𝑖(0)] 2 𝑁 𝑖=1 〉 (7) for 800 thousand time steps. the results were tested over longer time ranges as well. the results remained practically identical and any irregularities originated from the small size of the system which sometimes can stabilize special local configurations. the lines were fitted to the last 2,500 time steps of the 4,000-time-steplong dataset of eq. (7). since the self-diffusion coefficients calculated under periodic boundary conditions depend strongly on the size of the system, the following correction factor to eliminate the finite-size effect was applied [19]: 𝐷0 = 𝐷𝑃𝐵𝐶 + 2.837297 𝑘𝐵𝑇 6𝜋𝜂𝐿 (8) where d0 denotes the self-diffusion coefficients of the infinite system, dpbc stands for the value calculated under periodic boundary conditions, η represents the viscosity and l refers to the length of the cubic simulation box. the viscosity of the bk3 model under ambient table 2. interaction parameters for the water model as taken from [1] geometry electrostatics polarization nonelectrostatic 𝑑𝑂𝐻 = 0.975 å 𝑞𝐻 = 0.584 𝑒𝑠𝑢 ∝= 1.44 å3 𝐴 = 322000 𝑘𝐽/𝑚𝑜𝑙 𝜃𝐻𝑂𝐻 = 104.52° 𝑞𝑀 = −1.168 𝑒𝑠𝑢 ∝𝐻= 0.25 ∝ = = 0.36 å3 𝐵 = 3.56/å 𝑑𝑂𝑀 = 2.661 å 𝜎𝐻 = 0.4 å−1 ∝𝑀= 0.5 ∝= = 0.72 å3 𝐶 = 3320 𝑘𝐽å6/𝑚𝑜𝑙 𝜎𝑀 = 0.71 å −1 table 1. interaction parameters of ions taken from [10] (polarizability (α), gaussian distribution width (σ) as well as the parameters of repulsion (a, b and c)) α (å3) σ (å) a (kj/mol) b (å-1) c (kjå6/mol) li+ 0.032 0.37 1.8x1012 20 150 na+ 0.157 0.65 8.5x1012 15 550 k+ 0.830 0.70 1.7x1015 13 1900 rb+ 1.37 0.75 1.95x1013 10 4500 cs+ 2.36 0.85 1.22x1012 8 9000 f1.30 0.78 1.2x104 2.4 1000 cl3.50 0.96 9.4x105 3.1 8000 br4.60 1.01 4.4x108 4.5 11000 i7.50 1.14 1.25x1013 6.5 20000 baranyai hungarian journal of industry and chemistry 70 conditions is η = 951.0 ± 007.0 mps, slightly larger than the experimental value of 0.896. the self-diffusion coefficient, dw (10-9m2s-1) = 2.28 ± 0.04, closely resembles the experimental value of 2.30 [1]. these quantities were not used to fit the parameters for the bk3 model. 3. results and discussion measurements of water self-diffusion [13] can be separated into two groups of aqueous solutions of alkali halides. although the list is not comprehensive for the 20 possible combinations, the trends are quite clear. small cations like li+ and na+ decrease the self-diffusion of water as the ion concentration increases monotonically (licl, libr, nacl, nabr, nai) as do fluorides (kf, rbf, csf) because the anion is very small. this trend can be observed less rapidly for kcl as both ions are of medium size. for larger combinations of cations and anions, local maxima were observed for kbr, rbcl, rbbr, rbi, cscl, csbr and csi in this order of the size of the maxima, however, the data for the last two ion pairs is not so comprehensive. following some pilot calculations, it became clear that the attraction between the ions and water molecules in the hydration shell is stronger than that implied by the experimental data. since previous calculations only dealt with static properties, the dynamics of the electrolyte system were not examined [10]. to quantify the discrepancies, the charges of the ions were varied, in some cases the polarization of ions was ignored, and repulsion increased to change the steric effects. although such a drastic change in the charges seems unphysical, this introduces a more tangible factor about overestimating the strength of forces in the original model [10] than polarization or increased repulsion. nevertheless, even though the latter two are the most significant, they should be more realistic, that is, more complex than dipolar polarization and repulsion with more appropriate functional forms and parameters not necessarily fixed in different surroundings. since the change in charge for the hydration shell alone cannot be limited, the system will be somewhat artificial. as examples, licl, nacl, nabr, nai, rbf and rbi were dealt with. the figures for these systems are presented. a previous model is referred to as the original to simplify the explanation [10]. the symbols are the same for all the figures (see explanation under the figures). the results for licl are shown in figure 1. although the original model underestimates the experimental results, the difference is not that significant. by decreasing the charges, the results are improved since the simulation overestimates the experimental values when 0.50 esu is applied. it is true of all systems that for smaller charges the absence of polarization is less important simply according to the charge-on-spring technique of the method. the underestimation of the experimental data by the original model of nacl is larger than that of licl. even though the repulsion of the chloride ion is similar to that of water as has previously been alluded to before, it cannot be involved in hydrogen bonding. by removing the polarization, the calculated results are significantly improved (figure 2). the results of nabr are similar to those of nacl but their difference compared to the experimental ones is larger (figure 3). for nai (figure 4), again the non-polarizable form of the original is significantly improved, even though the data points are scattered. the scattered values were checked with a long equilibration and data collection but the results remained practically the same. the scattered nature is assumed to be an artifact of the limited size of the system. while the difference between the polarized and non-polarized values with 0.65 esu for the chloride ions was negligible, for iodide this cannot be neglected because it is highly polarizable. the results for rbf are shown in figure 5. since the degree of polarization of both ions is moderate, the improvement by removing polarization is also moderate. the charge of 0.50 esu for rbf provides a good estimate of the experimental results. on this figure, the results calculated by the original potential when parameter a for the repulsion of fluoride (green dots) is ten times larger are shown. the impacts of this enhanced repulsion and the removal of polarization are similar. from our chosen samples, the real challenge is the aqueous solution of rbi (figure 6). the experimental self-diffusion coefficient values of water show a rapid increase and after a moderate maximum remain high even at large concentrations, indicating that these ions destroy the hydrogen-bonded network of the system by only weakly attracting their neighbors. it is shown in figure 6 that by removing the dipolar polarization, the results are significantly improved but far worse than the experimental ones. (the data points for the original were so low at the highest concentrations that a linear trend from eq.(6). was not obtained). decreasing the charges in itself did not help. the dark blue diamonds denote the results when repulsion of the iodide ions was increased by a factor of 10 for the non-polarizable model with a charge of 0.50 esu. the brown diamonds represent the results when parameter a of the repulsive wing was multiplied by 10 for both ions. although the plot of these results is scattered, such interactions are necessary to reproduce the experimental results. the factor of 10 with regard to parameter a of the iodide ions is not as unrealistic as it seems. ambient crystals of alkali halides provide lattice constants which approximately give the size of the ions. however, the size of one ion should be chosen arbitrarily, otherwise the problem is underestimated, thereby distributing the relative sizes of cations vs. anions. its size is manifested by a repulsion wing which is a continuous function according to a chosen mathematical form. the height and gradient characterize the function which in classical simulations is constant. clearly, this is not the case in reality. while the polarizability of anions is large, especially of iodide, it is reasonable to presume that it is manifested by the rapid redistribution of local charge densities in response to the self-diffusion coefficient of water 51(1) pp. 67-73 (2023) 71 ● (black dots) experimental ■ (red squares) original ▲ (red triangles) original without polarization ♦ (yellow diamonds) original with a charge of 0.75 esu ■ (blue squares) original with a charge of 0.65 esu ▲ (blue triangles) original with a charge of 0.65 esu without polarization ■ (purple squares) original with a charge of 0.50 esu ▲ (purple triangles) original with a charge of 0.50 esu without polarization ● (green dots) original with a(i)used = 10xa(i)orig ♦ (dark blue diamonds) original with a charge of 0.50 esu without polarization and a(i)used = 10xa(i)orig ♦ (brown diamonds) original with a charge of 0.50 esu without polarization and a(i)used = 10xa(i)orig and a(rb)used = 10xa(rb)orig figure 2. self-diffusion coefficient of water in terms of nacl concentration, c, in mol/kg of solvent. the selfdiffusion coefficient, d, is given in 10-9m2s-1. figure 3. self-diffusion coefficient of water is shown in terms of nabr concentration, c, in mol/kg of solvent. the self-diffusion coefficient, d, is given in 10-9m2s-1. figure 4. self-diffusion coefficient of water in terms of nai concentration, c, in mol/kg of solvent. the selfdiffusion coefficient, d, is given in 10-9m2s-1. figure 5. self-diffusion coefficient of water in terms of rbf concentration, c, in mol/kg of solvent. the selfdiffusion coefficient, d, is given in 10-9m2s-1. figure 6. self-diffusion coefficient of water in terms of rbi concentration, c, in mol/kg of solvent. the selfdiffusion coefficient, d, is given in 10-9m2s-1. figure 1. self-diffusion coefficient of water is shown in terms of licl concentration, c, in mol/kg of solvent. the self-diffusion coefficient, d, is given in 10-9m2s-1. baranyai hungarian journal of industry and chemistry 72 liberation of neighboring water molecules. nevertheless, the ion predominantly remains a spherical entity in contrast to the result of dipolar polarization. therefore, while alkali halides seem to be simple and strongly ionic particles exhibiting spherical symmetry, good results to determine particular properties either in their pure form or in solution are not guaranteed. a good example is the lithium ion with bromide or iodide anions in crystalline form. the lithium ion gets much closer to these anions than any reasonable set of additive ion sizes would predict [10]. it is futile to vary the parameters of water since the performance of the model for pure water is excellent. regarding ions, other parameters, e.g. parameter b which represents the steepness of repulsion, could obviously have been changed. furthermore, the energy of the neighboring ion could have been changed by varying σ, but this would have been complicated to examine as a result of varying too many parameters. 4. conclusions the self-diffusion coefficient of water in alkali halide solutions by molecular dynamics simulations was examined. licl, nacl, nabr, nai, rbf and rbi were selected as examples. our system contained 250 water molecules and the ions were implanted by replacing water molecules with 4, 10, 14, 18, 22, 30 and 50 ions corresponding to 0.45, 1.57, 1.65, 2.16, 2.68, 3.79 and 6.94 mol/kg of solvent, respectively. our water model was bk3 [1] and our ionic model was taken from the literature [10]. these models were developed consistently by measuring the gaussian charges, chargeon-spring polarizability and exponential repulsion [1],[10]. the static results for the 20 combinations of ions were given with regard to solvation free energy, ionwater clusters and the structure of the solutions in terms of pair correlation functions. the energy and density of ambient crystals were determined as a crosscheck, the results of which were satisfactory [10]. in this paper, the self-diffusion coefficient of water in solutions was calculated and our results compared to experimental values. the results, which were underestimated in all cases, were small for licl but gradually increased as the ions became larger (figure 1). the attraction between the ion and water in the solvation shell was stronger than in reality. to measure the apparent behavior, the charges of the ions were decreased. gradually smaller charges yielded good estimates as the size and polarizability of the ions increased, namely 0.65 for licl and nacl (figure 2) as well as 0.50 for nabr (figure 3) and nai (figure 4). the removal of polarizability from the original model per unit of charge improved the results by enhancing the mobility of the ions, which is shown for nacl and nai. by removing the polarization of the chloride, the results very closely resembled the experimental ones, while for nai, the data points were quite scattered but nevertheless the estimation was obviously substantially improved. for rbf (figure 5), the charge of 0.50 esu yielded a good estimate. it can be seen from the figures that the ions without polarization improve the estimates at mainly small or moderate concentrations. by increasing the repulsion of fluoride by a factor of 10, the results also improve by approximately as much as they improved by removing polarization, indicating that a somewhat better formulation of ionic polarization using the polarized bk3 model can provide accurate results for these systems. the presence of rbi strongly enhances the water mobility yielding a moderate maximum throughout the concentration range measured (figure 6). although the results are substantially improved by removing dipolar polarization, to closely resemble the experimental results, the repulsion had to be increased by multiplying factor a in the potential by 10 and the apparent charge of the ions decreased to 0.50 esu. a tenfold enhancement of repulsion can be obtained by defining smaller cations and larger anions. changing the typical size ratio of cations to anions to a much greater degree can give good results with identical charges, however, this would destroy other properties of the pure alkali halides. the structural breaking effect of iodide is not simply a size-related phenomenon. the response of water to the spherical polarization of iodide can destroy the hydrogen-bond network which enhances the free motion of water molecules. this study examined whether polarizable models can estimate the experimental values for the selfdiffusion coefficient of water in the presence of alkali halides. since the bk3 potential of water performs excellently in general, especially under ambient conditions, it is unnecessary to change the parameters of water. previously, the melting properties of alkali halides were studied [20]-0. first, only the original potential without dipolar polarization was varied, assuming that the symmetric character of the crystals remains approximately valid when melted. although the results improved [20], they remained unsatisfactory, so an attempt was made to create individual ion potentials by combining the non size-additive rule to predict the correct melting temperature while maintaining the correct internal energy and density of the crystal. while this is straightforward to obtain good results for pairs [21], the possibility to combine individual potentials is limited 0. melting results in temperature instability which gradually disintegrates the crystal. in this respect, the bottom of the potential well where the ion is positioned and the internal energy is determined as well as the pressure are not the determining factors. given that the higher parts of the potential well are the barriers that need to be overcome by the ion, the requirements of a potential model are more complex. the present results also indicate that integrated properties like solvation free energy can be obtained with a reasonable degree of accuracy even for semi-macroscopic models, however, the prediction of more subtle properties, either in pure form or in solutions, is far from trivial. self-diffusion coefficient of water 51(1) pp. 67-73 (2023) 73 acknowledgements this study was financed by otka fund no. k128136. references [1] kiss, p.t.; baranyai, a.: a systematic development of a polarizable potential of water, j. chem. phys., 2013, 138(20), 204507, doi: 10.1063/1.4807600 [2] kiss, p.t.; baranyai, a.: anomalous properties of water predicted by the bk3 model, j. chem. phys., 2014, 140(15), 154505, doi: 10.1063/1.4871390 [3] abascal, j.l.f.; vega, c.: a general purpose model for the condensed phases of water: tip4p/2005, j. chem. phys., 2005, 123(23), 234505, doi: 10.1063/1.2121687 [4] ruff, i.; liszi, j.; mészáros, l.: calculation of the average relative permittivity of electrolyte solutions from the non-linear dielectric behaviour of the solvent, acta chim. acad. sci. hung., 1980, 104(1), 69–77, http://real-j.mtak.hu/3752/1/actachimica_104.pdf [5] liszi, j.; mészáros, l.; ruff, i.: the field dependence of the kirkwood factor and the nonlinear dielectric behavior of some liquids, j. chem. phys., 1981, 74(12), 6896–6901, doi: 10.1063/1.441100 [6] liszi, j.; mészáros, l.; ruff, i.: non-linear dielectric behaviour in normal alcohols and water, acta chim. acad. sci. hung., 1980, 104(1), 273– 278, http://real-j.mtak.hu/3752/1/actachimica_104.pdf [7] ruff, i.: recent developments in the theory of the non-linear dielectric behaviour of liquids, acta chim. hung., 1986, 121(1-2), 203–213, http://realj.mtak.hu/3787/1/actachimica_121.pdf [8] baranyai, a.; ruff, i.: unpublished data [9] kann, z.r.; skinner, j.l.: a scaled-ionic-charge simulation model that reproduces enhanced and suppressed water diffusion in aqueous salt solutions, j. chem. phys., 2014, 141(10), 104507, doi: 10.1063/1.4894500 [10] kiss, p.t.; baranyai, a.: a new polarizable force field for alkali and halide ions, j. chem. phys., 2014, 141(11), 114501, doi: 10.1063/1.4895129 [11] baranyai, a.: unpublished data [12] jungwirth, p.; tobias, d.j.: molecular structure of salt solutions:  a new view of the interface with implications for heterogeneous atmospheric chemistry, j. phys. chem. b, 2001, 105(43), 10468– 10472, doi: 10.1021/jp012750g [13] müller, k.j.; hertz, h.g.: a parameter as an indicator for water-water association in solutions of strong electrolytes, j. phys. chem., 1996, 100(4), 1256 – 1265, doi: 10.1021/jp951303w [14] baranyai, a.; kiss, p.t.: a transferable classical potential for the water molecule, j. chem. phys., 2010, 133(14), 144109, doi: 10.1063/1.3490660 [15] kong, c.l.: combining rules for intermolecular potential parameters. ii. rules for the lennard‐ jones (12–6) potential and the morse potential, j. chem. phys., 1973, 59(5), 2464–2467, doi: 10.1063/1.1680358 [16] martyna, g.j.; tuckerman, m.e.; tobias, d.j.; klein, m.l.: explicit reversible integrators for extended systems dynamics, mol. phys., 1996, 87(5), 1117–1157, doi: 10.1080/00268979600100761 [17] rozmanov, d.; kusalik, p.g.: robust rotationalvelocity-verlet integration methods, phys. rev. e, 2010, 81(5), 056706, doi: 10.1103/physreve.81.056706 [18] kiss, p.t.; sega, m.; baranyai, a.: efficient handling of gaussian charge distributions: an application to polarizable molecular models, j. chem. theory comput., 2014, 10(12), 5513–5519, doi: 10.1021/ct5009069 [19] yeh, i.-c.; hummer, g.: system-size dependence of diffusion coefficients and viscosities from molecular dynamics simulations with periodic boundary conditions, j. phys. chem. b, 2004, 108(40), 15873–15879, doi: 10.1021/jp0477147 [20] baranyai, a.: alkali halide force fields: a search for an acceptable compromise, j. mol. liq., 2020, 297, 111762, doi: 10.1016/j.molliq.2019.111762 [21] baranyai, a.: alkali halide force fields: utilizing the melting temperature, j. mol. liq., 2021, 343, 117575, doi: 10.1016/j.molliq.2021.117575 baranyai, a.: alkali halide force fields: search for versatility, j. mol. liq., 2022, 362, 119788, doi: 10.1016/j.molliq.2022.119788 https://doi.org/10.1063/1.4807600 https://doi.org/10.1063/1.4871390 https://doi.org/10.1063/1.2121687 https://doi.org/10.1063/1.2121687 http://real-j.mtak.hu/3752/1/actachimica_104.pdf https://doi.org/10.1063/1.441100 https://doi.org/10.1063/1.441100 http://real-j.mtak.hu/3752/1/actachimica_104.pdf http://real-j.mtak.hu/3787/1/actachimica_121.pdf http://real-j.mtak.hu/3787/1/actachimica_121.pdf https://doi.org/10.1063/1.4894500 https://doi.org/10.1063/1.4894500 https://doi.org/10.1063/1.4895129 https://doi.org/10.1021/jp012750g https://doi.org/10.1021/jp951303w https://doi.org/10.1063/1.3490660 https://doi.org/10.1063/1.1680358 https://doi.org/10.1063/1.1680358 http://doi.org/10.1080/00268979600100761 http://doi.org/10.1103/physreve.81.056706 http://doi.org/10.1021/ct5009069 https://doi.org/10.1021/jp0477147 http://doi.org/10.1016/j.molliq.2019.111762 http://doi.org/10.1016/j.molliq.2021.117575 http://doi.org/10.1016/j.molliq.2022.119788 http://doi.org/10.1016/j.molliq.2022.119788 microsoft word 15.15 tóth.docx hungarian journal of industry and chemistry vol. 44(1) pp. 29–32 (2016) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2016-0003 separation of process wastewater with extractive heterogeneous-azeotropic distillation andrás józsef tóth,* ágnes szanyi, enikő haaz, and péter mizsey department of chemical and environmental process engineering, budapest university of technology and economics, műegyetem rkp. 3., budapest, 1111, hungary the application of vapour-liquid equilibria-based separation alternatives can be extraordinarily complicated for the treatment of process wastewaters containing heterogeneous-azeotropic. despite dissimilar successfully tested methods for separation, there is possibility to get better distillation method by enabling the separation of more and more specific process wastewater. extractive heterogeneous-azeotropic distillation (ehad) is a new advance in treatment of fine chemical wastewater showing special features to cope with the treatment of highly non-ideal mixtures. this method combines the worth of heterogeneous-azeotropic and extractive distillations in one apparatus without addition of any extra materials. the study of the separations of ternary component process wastewater from the fine chemical industry shows both in the modelled and experimental results that ehad can be successfully applied. the measured and modelled compositions at extreme purities, that is, close to 0% or 100%, can be different because of the inaccuracies of the modelling. this highlights the paramount importance of the experiments if special extra-fine chemicals with almost no impurities, e.g. of pharmacopoeial quality are to be produced by special distillation technique. this study expands the application of ehad technique, this new field is the separation of process wastewaters. keywords: process wastewater, non-ideal mixtures, extractive heterogeneous-azeotropic distillation 1. introduction the words of dr. james r. fair are still true: “distillation, king in separation, will remain as the workhorse separation device of the process industries. even though it is old in the art, with a relatively mature technology support base, it attracts research and professional interest. without question, distillation will sail into the future with clear skies and a strong wind. it will remain the key separation method against which alternate methods must be judged” from ref. [1]. the above quote clearly explains why distillation should be investigated continuously [2–4]. in our work, the separation of process wastewater is studied. such mixtures are quite common in pharmaceutical industry, where the treatment of generally azeotropic mixtures and then fine chemical quality should be achieved; while simultaneous, it is challenging to balance the energetic and environmental consequences. corresponding non-ideal process wastewaters commonly include different varieties of aldehydes, alcohols, ethers and esters in aqueous media. these compounds already foretoken these problems may resurrect during vapuor-liquid equilibria-based treatment. the separation of a water, isopropyl acetate, ethyl acetate and ethanol process wastewater from the *correspondence: andras86@kkft.bme.hu pharmaceutical industry [5] has drawn attention to the need for the improvement of the vapour-liquid equilibria-based separation techniques that includes the worth of using different treatment solutions. a new hybrid treatment alternative, the so-called extractive heterogeneous-azeotropic distillation (ehad), has been introduced [6–9] that associates the advantages of heterogeneous-azeotropic and extractive distillations (fig.1). the heterogeneous-azeotropic opportunity presumes that water component is current in the process wastewater and moreover limited immiscibility may exist. heteroazeotropic distillation utilizes deviations in volatility and liquid-liquid phase figure 1. scheme of the ehad technique [9]. tóth, szanyi, haaz, and mizsey hungarian journal of industry and chemistry 30 split by connecting a column and phase separator/decanter [10–12]. ehad differs from heterogeneous-extractive distillation [13] because no new azeotropic mixture is created, videlicet the entrainer is water in the case and it is already current in the process wastewaters to be treated. furthermore, relative volatility changing and extractive effect of entrainer agent is absolutely utilised and there is no rectifying section in the column [9]. the capability of the extractive heterogeneous-azeotropic distillation can be demonstrated with a case study. this was carried out for a separation method of 9 devices, extractors and distillation columns [14]. if fine purity is required, e.g. in biofuel or pharmacopoeial applications further unit operations might be needed, e.g. rectification again. however, it can be observed that within the range of extreme purities (close to 0% or 100%) the modelling is not reliable enough and the experiments cannot be omitted. the applicability and effectiveness of extractive heterogeneous distillation has been already tested on many different highly non-ideal mixtures with simulations and experiments verifying the accuracy of modelling [8–9]. the strategy clearly shows that ehad is a forceful method for separation of heterogeneous azeotropic mixtures containing water. 2. experimental in spite of the clear guidelines for the applicability of ehad [8], further application areas are going to be investigated. on the other hand, the separation of actual process wastewater should be interpreted explaining the unit operation and identifying new possible application areas. 2.1. simulations for the sake of our aims, a process wastewater was selected: ethyl acetate (etac), methyl alcohol (meoh) and water (h2o). flowsheet simulations were achieved with chemcad in advance on experiments in order to reduce the necessary number of measurements and to look up promising separation alternatives. moreover, cooling and heating demands, massand waste-flow rates and ideal reflux ratio were also determined. the uniquac equilibrium method is applied [15–18] for the computation of vapour-liquid equilibria of non-ideal mixtures. if binary pairs exist without the availability of uniquac data, the unifac method was applied [19]. liquid-liquid equilibria were also considered in the form of a vapour-liquid-liquid equilibria (vlle) model [20]. unifac and uniquac equilibrium models have vll equilibria options. the flowsheet of ehad and intricacies of process wastewater are demonstrated in fig.2 computed with chemcad. there are one heterogeneous and one homogeneous azeotropes, all in all two binary type [20– 23]. 2.2. experiments to save material (amount of sample) and experimental time, first of all, comprehensive flowsheet simulations should be implemented. the results of computer simulations foretoken and prepare the measurements. the measurements are achieved on the distillation column of laboratorial size demonstrated in fig.3. the major specifications of the distillation apparatus are succeeding: internal width of 2 cm structured packing. the theoretical plates of the column are measured with methyl-alcohol – water mixture, that is 10. the feed (f) is not forewarmed, it is injected on the fifth plate of the apparatus and flow value is kept at 0.06 kg h-1. the entrainer is injected on the tenth plate of the tower and flow value is kept at 0.31 kg h-1. the apparatus warming is directed with a 0.300 kw heating crater. the overhead product, after condensation goes to the decanter, or phase separator. the upper phase is measured and the lower phase is pumped as reflux into the apparatus. the concentration of feed, distillate (d), and waste output (w) were measured using a gc-14b type shimadzu gas chromatographer with cp-sil-5cb capillary column. figure 2. separation of the process wastewater in flowsheet simulator environment. figure 3. scheme of ehad laboratory column. separation of process wastewater 44(1) pp. 29–32 (2016) doi: 10.1515/hjic-2016-0003 31 3. results and analysis we summarise the measured and calculated results in table 1. the comparison also shows the accuracy of ehad in the ternary case selected for the given study. the water addition (xf,water) and the feed content of ternary mixture (xf,solvent) are presented in fig.4, along with the theoretical waste output (xw) and distillate (xd) content as well. the two-phase region is found under the dashed curve. operation of this column is shown by the operating lines. 3.1. modelling of high purity separation the concentrations 0% and 100% are two extreme numbers, since these do not exist in practical separation technology. we can approach these numbers with ever more advanced and expensive technologies, but we can never arrive at them. moreover, the problem of extreme concentrations poses two questions: (i) do we have sophisticated enough analytical techniques to do measurements in such regions, and (ii) can we calculate/model these regions accurately/reliably? positive answers are crucial in the case of high purity distillation. modelling is important since it is used for the reduction of solution space and to find promising alternatives. modelling can therefore be applied to the preparation and selection of the experiment(s). this philosophy is also applied to high purity rectification problems. in our ternary example we arrive at such an extreme concentration range where our analytics is not capable of following the separation. but the modelling shows some promise here. another case studies [6–8] from the fine chemical industry highlights that modelling is not reliable in those regions that are close to the extreme numbers of 0% and/or 100%. a demonstrative example for such a crucial situation is the production of ethanol of pharmacopoeial purity. the ethanol produced of this purity may contain contaminants only in concentrations of a few ppm. there are alternative processes for the production of such extremely pure ethanol involving rectification. however, modelling alone can be misleading and it might show such solution alternatives that prove to be unacceptable if they are experimentally tested. on the other hand, the modelling results are definitely uncertain within such extreme purity ranges. the modelled results in all likelihood cannot be supported by experiments. these examples show that if rectification-based process alternatives are investigated the experiments yield reliable results, since modelling is unreliable at purities close to the extreme concentration ranges. 4. conclusion ehad separation technique improves in the separation of heterogeneous azeotropic mixtures. it opens an alternative solution for distillation specialists. treatment of difficult process wastewaters can be solved costeffective and easily with application of ehad. comparison of modelling techniques and experiments shows good agreement; however, there might be contradictions among measured and modelled data if high purity products are required. our results obtained as a solution to fine chemical industrial and other, e.g. pharmacopoeial purity distillation problems show that close to 0% and/or 100% concentrations the experiments and modelling can provide unreliable results underlining the paramount importance of experiments and proper analytics. symbols b.d.l. below detection limit d distillate ehad extractive heterogeneous-azeotropic distillation etac ethyl acetate f feed meoh methyl-alcohol vle vapour-liquid equilibrium vlle vapour-liquid-liquid equilibria w waste output xf,solvent feed concentration xf,water entrainer concentration xd distillate concentration xw waste output concentration table 1. results of ehad technique: simulated and measured data (in mass percent) f simulation experiment d w d w h2o 4 3.6 94.7 5.3 94.6 meoh 26 0.1 5.2 0.2 5.4 etac 70 96.3 0.1 94.5 b.d.l. figure 4. calculated equilibria and operating lines of ehad. residue curve map, ethyl acetate / methanol /water by uniquac tóth, szanyi, haaz, and mizsey hungarian journal of industry and chemistry 32 acknowledgement the research was supported by the otka 112699 grant. references [1] kister, h.: distillation design (mcgraw-hill education, new york) 1992 [2] szabó, l.; németh, s.; szeifert, f.: separation of multicomponent mixtures, hung. j. ind. chem., 2011 39(2), 295–300 [3] toth, a.j.; gergely, f.; mizsey, p.: physicochemical treatment of pharmaceutical wastewater: distillation and membrane processes, per. pol. chem. eng., 2011 55(2), 59–67 doi 10.3311/pp.ch.2011-2.03 [4] mizsey, p.; toth, a.j.: application of the principles of industrial ecology for the treatment of process waste-waters with physicochemical tools, indust. ecol., 2012 1(1), 101–125 [5] mizsey, p.; szanyi, a.; raab, a.; manczinger, j.; fonyo, z.: intensification of a solvent recovery technology through the use of hybrid equipment, comp. aided chem. eng., 2002 10(1), 121–126 10.1016/s1570-7946(02)80048-7 [6] szanyi, a.; mizsey, p.; fonyo, z.: novel hybrid separation processes for solvent recovery based on positioning the extractive heterogeneousazeotropic distillation, chem. eng. proc., 2004 43(3), 327–338 doi 10.1016/s0255-2701(03)00132-6 [7] szanyi, a.; mizsey, p.; fonyo, z.: optimisation of nonideal separation structures based on extractive heterogeneous azeotropic distillation, ind. eng. chem. res., 2004 43(26), 8269–8274 doi 10.1021/ie049575l [8] szanyi, a.; mizsey, p.; fonyo, z.: separation of highly non-ideal quaternary mixtures with extractive heterogeneous-azeotropic distillation, chem. biochem. eng. q., 2005 19(2), 111–121 [9] szanyi, a.: separation of non-ideal quaternary mixtures with novel hybrid processes based on extractive heterogeneous-azeotropic distillation (phd dissertation, bme, budapest) 2005 [10] franke, m.; gorak, a.; strube, j.: design and optimisation of hybrid separation processes, chem. eng. tech., 2004 76(3), 199–210 doi 10.1002/cite.200406150 [11] skiborowski, m.; harwardt, a.; marquardt, w.: conceptual design of distillation-based hybrid separation processes, annu. rev. chem. biomol. eng., 2013 4(1), 45–68 doi 10.1146/annurevchembioeng-061010-114129 [12] skiborowski, m.; harwardt, a.; marquardt, w.: conceptual design of azeotropic distillation processes (in eds.: gorak, a.; sorensenm, e.; distillation: fundamentals and principles, academic press, aachen, germany) 2014, chapter 8, p. 321 [13] wijesinghe, a.m.j.c.: development of industrial complexes of special rectification techniques for solvent recovery (phd dissertation, lomonosov institute of fine chemical engineering, moscow) 1985 [14] raab, a.: separation of highly non-ideal mixtures for solvent recovery (msc thesis, bme, budapest) 2001 [15] abrams, d.s.; prausnitz, j.m.: statistical thermodynamics of liquid mixtures: a new expression for the excess gibbs energy of partly or completely miscible systems, aiche j., 1975 21(1), 116–128 doi 10.1002/aic.690210115 [16] egner, k.; gaube, j.; pfennig, a.: gequac, an excess gibbs energy model describing associating and non-associating liquid mixtures by a new model concept for functional groups, fluid phase equilib., 1999 158–160, 381–389 doi 10.1016/s03783812(99)00137-5 [17] klamt, a.; krooshof, g.j.p.; taylor, r.: cosmospace: alternative to conventional activity-coefficient models, aiche j., 2002 48(10), 2332–2349 doi 10.1002/aic.690481023 [18] wiśniewska-goclowska, b.; malanowski, s.x.k.: a new modification of the uniquac equation including temperature dependent parameters, fluid phase equilib., 2001 180(1–2), 103–113 doi 10.1016/s0378-3812(00)00514-8 [19] fredenslund, a.; jones, r.l.; prausnitz, j.m.: group-contribution estimation of activity coefficients in non-ideal liquid mixtures, aiche j., 1975 21(6), 1086–1099 doi 10.1002/aic.690210607 [20] akita, k.; yoshida, y.: phase-equilibria in methanol-ethyl acetate-water system, j. chem. eng. data, 1963 8(1), 484–490 doi 10.1021/je60019a003 [21] gmehling, j.; menke, j.; krafczyk, j.; fischer, k.: azeotropic data (wiley-vch verlag gmbh & co. kgaa, weinheim, germany) 1994 [22] gmehling, j.; onken, u.; rarey-nies, j. r.: vaporliquid equilibrium data collection (dechema, virginia, usa) 1978 [23] marsden, c.: solvents and allied substances manual with solubility chart (cleaver-hume and elsevier, london) 1954 hungarian journal of industry and chemistry vol. 52(2) pp. 19–27 (2024) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2024-15 reuse of fine concrete demolition wastes as a supplementary cementitious material in concrete lynda kheddache1, djamila aboutaleb1, brahim safi1*, samir lecheb2, ahmed chellil2 and hamza mechakra2 1 research unit materials, processes and environment (urmpe), faculty of technology, m’hamed bougara university of boumerdes, frantz fanon city, boumerdes, 35000, algeria 2 laboratory of motor dynamics and vibroacoustics (ldmv), faculty of technology, m’hamed bougara university of boumerdes, frantz fanon city, boumerdes, 35000, algeria materials from demolition are only recycled if they are economically competitive on the one hand and technically acceptable on the other, meaning they can be implemented without risking disruption to the performance of the construction material. among these materials are demolished concretes. this type of material (waste) is currently reused as recycled aggregate, commonly referred to as gravel. indeed, the latter contains grains of anhydrous clinker, which may play a significant role in determining the properties of concrete. in the context of waste valorization, this study focuses solely on the influence of incorporating finely crushed concrete demolition waste (cdw) as an active additive or as a supplementary cementitious material in the cement matrix used to make concrete. the results showed that the addition of up to 10% of concrete demolition waste significantly improved physical properties such as the air void content and workability of fresh concrete. furthermore, the compactness of hardened concrete also improved based on adding 10% of cdw as a result of increasing the speed of sound. therefore, the compressive strength of concrete was also improved by 20% when 10% waste was added compared to the control concrete. this indicates that concrete demolition waste (finely crushed) can replace cement and therefore contribute to reducing binder consumption. keywords: recycling wastes, concrete demolition wastes, cement paste, workability, mechanical strength analysis 1. introduction materials for building construction are continuously being produced, which must either be disposed of or reused. a significant volume of waste materials such as demolished concrete and by-products is generated from various manufacturing processes, service industries and municipal solid waste management systems worldwide [1]-[6]. consequently, solid waste management has emerged as a critical environmental issue globally. with growing environmental awareness, dwindling landfill space and rising disposal costs, the utilization of waste materials and by-products has emerged as an appealing alternative to traditional disposal methods. the high consumption of natural resources, substantial production of industrial waste and environmental pollution necessitate innovative solutions for sustainable development. in recent years, the emphasis on incorporating waste materials and by-products into construction materials has been increasing [5]-[10]. this utilization offers a partial solution to environmental and ecological challenges. integrating these materials into received: 25 may 2024; revised: 21 june 2024; accepted: 5 july 2024 *correspondence: safi_b73@univ-boumerdes.dz cement, concrete and other construction materials not only reduces the cost of manufacturing but also yields several indirect benefits, including decreased landfill expenses, energy savings and the mitigation of potential environmental pollution. moreover, their utilization can enhance the microstructure, mechanical strength as well as durability of mortar and concrete, aspects that are often challenging to achieve with conventional portland cement alone [9]-[15]. concrete production as well as the creation of construction and demolition waste are significant sources of ongoing carbon dioxide emissions. numerous studies have examined the potential use of demolition waste as aggregates or mineral additives in concrete manufacturing. recent studies have concentrated on improving the characteristics of recycled aggregate concrete by incorporating various supplementary materials. some research suggests that incorporating recycled aggregates ranging from 30 to 50% can achieve strength levels comparable to those of natural aggregate concrete, particularly when combined with supplementary cementitious materials [10]-[16]. nevertheless, further initiatives are required to establish https://doi.org/10.33927/hjic-2024-15 mailto:safi_b73@univ-boumerdes.dz kheddache, aboutaleb, safi, lecheb, chellil and mechakra hungarian journal of industry and chemistry 20 standards and effectively manage the challenges posed by hydrated cement paste adhering to the surface of crushed coarse aggregate in a cost-effective manner. despite the potential of recycled aggregates (ra), their usage is constrained by the lack of structural standards for ra, limiting their application as substitutes for naturally sourced materials. the adoption of construction and demolition waste (cdw) materials as substitutes for natural aggregates has become a priority within the circular economy framework. globally, the production of fresh concrete consumes about 20 billion tons of natural resources annually, a figure expected to triple over the next 20 to 30 years. however, the demolition of existing buildings generates a significant amount of solid waste, comprising 20 to 40% of total waste and posing a major environmental hazard. ra offers a sustainable solution to resource exploitation, land-space restoration and landfill waste reduction. by replacing 5 to 30% of the mass of cement in mortar samples, researchers found that an optimal amount of recycled brick powder (rbp) could actually improve the mechanical properties of the mortar without significantly impacting its durability. similarly, li et al. explored the use of recycled concrete powder (rcp) as a substitute for 10 to 30% of the cement, yielding results comparable to those achieved with rbp. nevertheless, some studies have suggested that using rcp/rbp as a partial substitute for cement could negatively impact the workability or compressive strength of the mortar/concrete mixtures. this decrease in workability or compressive strength becomes more pronounced, especially when rcp/rbp replaces more than 30% of the cement. past studies have shown that the effectiveness of mortar/concrete may drastically reduce when the quantity of construction and demolition waste (cdw) powder surpasses a specific limit [17]-[18]. hence, when assessing the cost and carbon emissions associated with mortar/concrete when utilizing recycled concrete powder (rcp) or recycled brick powder (rbp), it is crucial to consider alterations in strength and additional properties like durability simultaneously. several researchers have acknowledged this necessity and undertaken initial explorations in this regard. in terms of environmental sustainability, incorporating demolition waste into concrete reduces the need for landfill space, alleviates the burden on natural resources by reducing the demand for virgin materials and mitigates carbon emissions associated with traditional concrete production. on the other hand, in order to preserve resources, an alternative must be sought. fine concrete demolition wastes, when processed and utilized effectively, offer a sustainable alternative to traditional supplementary cementitious materials like fly ash and slag. this helps conserve natural resources and reduces the environmental impact of concrete production. furthermore, to improve performance, properly processed demolition wastes can improve certain properties of concrete such as durability, workability and long-term strength. however, the effects may vary depending on factors like the composition and characteristics of the waste material as well as the concrete mix design. the use of demolition wastes as supplementary cementitious materials (scm) in concrete shows promise but presents several challenges. these include variability in material quality and composition, potential contaminants as well as the need for effective processing methods to ensure consistency and compatibility with concrete. compliance with construction material regulations and standards through rigorous testing is crucial to ensure performance and safety. while incorporating demolition wastes as scm can reduce costs compared to traditional materials, economic viability depends on waste availability, processing, logistics and the market demand for sustainable materials. further research is necessary to optimize the use of fine concrete demolition wastes, address technical hurdles and establish guidelines for their integration into construction projects. overall, utilizing these wastes could potentially enhance sustainability, performance and cost-effectiveness in construction assuming the careful management of processing, quality control, regulations and economic factors. our study aims to evaluate the influence of adding finely crushed concrete demolition waste on the physicomechanical properties of concrete. the study investigates both the physical properties of the matrix and the concrete because it is too laborious to determine physical properties by only focusing on specific attributes (such as density, setting time, workability and air void content) as well as on the main mechanical properties (compressive strength). for this purpose, concrete mixtures have been studied by using concrete demolition wastes (cdw) as supplementary cementitious materials as a partial substitute for cement (0, 2.5, 5, 7.5, 10, 12.5, 15 and 20% by the weight of the cement) and as a mineral additive without substituting for cement (0, 2.5, 5, 7.5, 10, 12.5, 15 and 20% by the weight of the cement). 2. experimental study 2.1. materials used our study focuses on an ordinary concrete containing the components (cement, aggregates, mixing water and additives) used for construction with an envisaged compressive strength of 30 mpa using locally sourced materials (figures 1 and 2). cem ii 42,5 portland cement was used in this study in conformity with the european standards (en). the chemical, physical, mineralogical and mechanical properties of this cement are given in table 1. the fine aggregate used was a river sand. the coarse aggregates used are gravels of class 8/15, the characteristics of which are given in table 2. the grain distribution of all the aggregates used is given in figure 3. reuse of fine concrete demolition wastes 52(2) pp. 19–27 (2024) 21 2.2. mix proportions of the studied concretes the formulation of the concrete was determined using the dreux-gorisse method which offers a simple and rapid approach to obtain a composition with minimal variations to the studied concrete by taking into account the compressive strength and workability required for each type of construction. for our study, the compressive strength was fixed at 30 mpa using a plastic concrete. the mix details of the control concrete are shown in table 3. other variants were obtained using concrete demolition waste (cdw) as a supplementary cementitious material by partially substituting for cement (0, 2.5, 5, 7.5, 10, 12.5, 15 and 20% by the weight of the cement) and by adding cdw as a mineral additive without substituting for cement (0, 2.5, 5, 7.5, 10, 12.5, 15 and 20% by the weight of the cement). all the concrete mixtures of the studied cases are presented in tables 4 and 5. the mixing method was kept constant for all mixtures of mortar. all the mixtures were prepared in a concrete mixer. the waste was first mixed and homogenized with the cement. the aggregates (gravel and sand) were then introduced into the mixer, followed by the mixture of cement and waste. the entire mixture was mixed until it had become completely homogenized and dry. subsequently, water was gradually added to the mixture and mixed until completely homogenized to obtain the concrete. for all formulations, tests on fresh concrete were conducted before being placed in the molds using a vibrator. cylindrical specimens with the dimensions of 32 diameters and 16 heights (3216) were prepared and placed in the curing tank according to the env standard. demolding was performed after 24 hours of mixing. mechanical tests were conducted after 3, 7 and 28 days of laboratory curing at 23°c. table 1: characteristics of the portland cement used portland cement (pc) chemical composition [%] sio2 22.97 al2o3 5.76 fe2o3 4.36 cao 58.43 mgo 2.03 k2o + na2o 1.11 so3 2.64 mineralogical composition [%] c3s 53 c2s 27 c3a 05 c4af 13 caofree 02 physical properties specific surface area (cm2/g) 3510 density (specific gravity) 3.12 setting times (initial final) (min) 155-212 mechanical properties [mpa] compressive strength after 2 days 17.20 compressive strength after 28 days 40.60 table 2: physical properties of the aggregates natural sand coarse aggregates g8/15 apparent density (kg/m3) 1450 1400 absolute density (kg/m3) 2760 2560 fineness modulus 3.20 2.47 sand equivalent (%) 85 table 3: control concrete composition component [kg/m3] portland cement natural sand gravel 8/15 water control concrete 400 761 1006 190 figure 1: materials used: (a) cement, (b) natural sand, (c) gravels figure 2: concrete demolition wastes (cdw): (a) preparation zone, (b) cdw crushed finely figure 3: particle size distribution of aggregates (sand and gravel) kheddache, aboutaleb, safi, lecheb, chellil and mechakra hungarian journal of industry and chemistry 22 2.3. preparation, curing of samples and test methods workability the concrete slump test evaluates the viscosity of freshly mixed concrete prior to its hardening to assess the workability of newly prepared concrete, thereby determining its flowability. this workability test was carried out using a metal mold in the shape of a conical frustum known as a slump cone or abrams cone (figure 4) that is open at both ends and has attached handles (see figure 4a). the workability of concrete can be measured using the following steps (figures 4b and 4c) by filling the cone in three layers packed with a pointed steel rod 16 mm in diameter at a rate of 25 strokes per layer before carefully lifting the mold and measuring the sag in cm. bulk density the density of the hardened concrete was determined either by simple dimensional checks followed by weighing and calculating or by weight in air/water buoyancy methods. in this work, the density of hardened concrete specimens (cylindrical specimens 3216) was measured by calculating the ratio of weight to volume of each specimen (figure 5). air content the air content measurement evaluates the amount of occluded air in the fresh concrete. the test is based on the compressibility of air bubbles contained in the fresh concrete. the standard device presented in figure 4 was made out of a 1 liter container in which mortar was placed in two layers and compacted by simply tamping it (the air content in the concrete is shown in figure 6). the device directly measures the air content as a percentage. ultrasonic pulse velocity test the ultrasonic pulse velocity (upv) test employs a non table 4: mixture details of the studied concretes by substituting cement with concrete demolition waste (cdw) mix cdw pc ns g8/15 w 0 % 00 400 761 1006 190 2.5 % 10 390 761 1006 190 5 % 20 380 761 1006 190 7.5 % 30 370 761 1006 190 10 % 40 360 761 1006 190 12.5 50 350 761 1006 190 15 % 60 340 761 1006 190 20 % 80 320 761 1006 190 table 5: mixture details of the studied concretes by adding cdw (without substituting for cement) mix cdw pc ns g8/15 w 0 % 00 400 761 1006 190 2.5 % 10 400 761 1006 190 5 % 20 400 761 1006 190 7.5 % 30 400 761 1006 190 10 % 40 400 761 1006 190 12.5 50 400 761 1006 190 15 % 60 400 761 1006 190 20 % 80 400 761 1006 190 figure 4: concrete workability: (a) abrams cone and slump test, (b) workability testing, (c) measuring concrete slump figure 5: concrete samples: (a) bulk density measurement, (b) cylindrical samples prepared for mechanical testing figure 6: air content measurement of the concrete (occluded air) reuse of fine concrete demolition wastes 52(2) pp. 19–27 (2024) 23 destructive approach, enabling the assessment of concrete structures without inducing any harm or disturbance. this method is invaluable for identifying defects as well as evaluating the general quality and uniformity of concrete materials. the method involves measuring the travel time of acoustic waves in a medium and correlating it with the elastic properties and density of the material. the travel time of ultrasonic waves reflects the internal state of the test zone. the test is commonly performed using transducers positioned at opposing ends of the concrete element under scrutiny, a setup referred to as through-transmission or direct configuration (figure 7). the concrete compactness was estimated by measuring the speed of sound through concrete 28 days after curing. compressive strength compressive strength tests were carried out in accordance with astm c192/c192m [24]. cylindrical specimens (3216) for each mixture were stored one day after casting in water at 21±1°c (figure 8). all uniaxial compressive strength tests were carried out 3, 7 and 28 days after hardening began. 3. results and discussion the main objective of our study was economic and technical by recycling as well as using concrete demolition waste (cdw). in order to determine the influence of the incorporation of cdw on the characteristics of concrete, the aim was to study the effect of using concrete demolition wastes (cdw) as a mineral additive on the fresh and hardened properties of concrete. the various results of the physico-mechanical tests on cdw-based concretes are presented in tables 6 and 7. 3.1. use of cdw by partially substituting for cement a) fresh properties: workability and content of occluded air the fresh characteristics of the concretes studied based on concrete demolition wastes (cdw) are given in figures 9 and 10. according to the obtained results, the following finding is observed. a slight increase in the workability of the concrete was recorded when between 5 and 10% of the concrete was replaced (figure 9). from a waste content of 12% upwards, an increase in the slump flow was recorded according to the abrams cone test, which could be attributed to the fineness of the waste, thereby increasing the slump flow, and the presence of small hydrated grains. when up to 7.5% of the cement was substituted by waste, no effect on the air void content of fresh concrete was noted. beyond 10%, a slight decrease in this property was observed (figure 10). this suggests that the cdw can fill voids. b) hardened properties: bulk density and compressive strength the obtained results of the hardened characteristics, that is, bulk density and compressive strength, are given in table 7 and presented in figures 11 and 12. it should be noted that: a slight increase of approximately 2.5% was table 6: fresh characteristics of the studied concretes mix occluded air (%) workability (cm) vibration time (s) c o n cr et es b y s u b st it u ti n g ce m en t w it h c d w 0 % 2.1 0.5 40 2.5 % 2.2 0.5 45 5 % 2.2 1.0 39 7.5 % 2.1 1.0 37 10 % 1.2 1.0 35 12.5 1.5 0.5 45 15 % 1.5 0.5 48 20 % 1.5 0.5 42 c o n cr et es b y a d d in g c d w 0 % 2.1 0.5 40 2.5 % 2.1 0.5 45 5 % 2.0 1.0 36 7.5 % 1.5 1.2 34 10 % 1.2 1.5 33 12.5 1.2 0.5 40 15 % 1.0 0.5 42 20 % 1,0 0,5 45 figure 7: ultrasonic pulse velocity test: (a) upv device, (b) upv testing of concrete sample figure 8: mechanical testing: (a) cylindrical specimens (3216), (b) uniaxial compressive strength tests kheddache, aboutaleb, safi, lecheb, chellil and mechakra hungarian journal of industry and chemistry 24 table 7: hardened characteristics of the studied concretes mix bulk density (kg/m3) upv (m/s) compressive strength (mpa) 3d 7d 28d c o n cr et es w it h ce m en t su b st it u ti o n b y c d w 0 % 2348 4413 13.44 27.25 32.00 2.5 % 2364 4429 13.27 27.18 31.60 5 % 2364 4442 12.13 25.82 30.03 7.5 % 2379 4452 11.69 23.94 27.84 10 % 2380 4456 11.04 22.52 26.19 12.5 2379 4461 7.37 15.08 17.54 15 % 2368 4461 7.31 14.96 17.40 20 % 2365 4457 6.72 13.75 16.00 c o n cr et es b y c d w a d d in g 0 % 2348 4413 13.44 27.25 32.00 2.5 % 2400 4455 13.65 27.95 32.50 5 % 2400 4450 14.58 29.80 34.60 7.5 % 2400 4492 14.30 29.33 34.10 10 % 2350 4468 15.18 31.00 36.20 12.5 2400 4470 13.90 28.55 33.20 15 % 2400 4487 12.60 25.80 30.00 20 % 2400 4466 12.00 24.60 28.00 figure 9: workability of the studied concretes when cement was substituted by cdw figure 10: content of occluded air of the studied concretes when cement was substituted by cdw figure 11: bulk density of the studied concretes when cement was substituted by cdw figure 12: change in the compressive strength of the studied concretes when cement was substituted by cdw reuse of fine concrete demolition wastes 52(2) pp. 19–27 (2024) 25 observed in the density of concrete made with recycled waste (crushed concrete waste) compared to the control concrete as the proportion of waste increased. however, this increase was not significant because the fineness and specific mass of the waste closely resembles that of cement (figure 11). the change in the compressive strength of concrete over time is highlighted. indeed, the strength of concrete is determined by the strength of cement (the product of mineral hydration from clinker). it is clear from the curve in figure 12 that the compressive strength of concrete increased over 28 days of curing. however, a very slight reduction in compressive strength was noted, followed by a considerable and remarkable reduction when more than 10% of the cement was substituted by waste (figure 12). this is explained by the substitution of some cement with waste, resulting in a decrease in the production of csh (calcium silicate hydrate), which determines its strength. however, the variations in strength are significant when the waste content exceeds 10%, [20], maybe because the waste contains grains of csh. these grains act as nuclei during cement hydration and trigger direct crystallization of csh from cement. 3.2. adding cdw as a mineral additive a) fresh properties: workability and the content of occluded air regarding the use of cdw as a mineral additive without substitution for cement in concrete, the results of tests on samples of fresh concrete are given in figures 13 and 14. it was noted that: the addition of waste without substituting for cement improves the workability of these concrete mixes compared to the control concrete. an increase in slump as the rate at which waste is added increases is shown in figure 13. the filling of voids by the waste is also reflected in the reduction in the occluded air content (figure 14), which is evident in the mixes prepared by adding waste [19-20,26]. b) hardened properties: bulk density and compressive strength the obtained results of the hardened characteristics, that is, bulk density and compressive strength, are given in figures 15 and 16. it should be noted that: figure 13: workability of the occluded air of the studied concretes when cdw was added without substituting for cement figure 14: content of occluded air of the studied concretes when cdw was added without substituting for cement figure 15: bulk density of the studied concretes when cdw was added without substituting for cement figure 16: compressive strength of the studied concretes when cdw was added without substituting for cement kheddache, aboutaleb, safi, lecheb, chellil and mechakra hungarian journal of industry and chemistry 26 a significant increase in the bulk density of concrete prepared by adding waste was observed. it is evident that the waste occupied and filled voids, thereby increasing the degree of matrix filling in the concrete (figure 15). regarding the concretes prepared with a waste content of 10% without substituting for cement, a significant improvement in compressive strength of approximately 20% up to a waste content of 20% was observed as shown in figure 16. it is noteworthy that the latter increased the compactness of the concrete in addition to the presence of unhydrated clinker grains. these grains contribute to the formation of csh, thereby increasing the strength of the concrete [20,26-27]. 3.3. ultrasonic pulse velocity test the curve depicted in figure 17 illustrates the change in the speed of sound through the concrete as a function of the rate at which waste was added. it is evident that the velocity of sound increases as the waste content increases. however, it is noteworthy that the velocity of sound of the hardened concrete made with waste was higher than that made by substituting cement with waste. it is clear here that the addition of waste increases the compactness of the concrete by filling voids, resulting in a reduced travel time. it is worth noting that the velocity is higher when the concrete is denser [19-20,26]. 4. conclusions our study focused firstly on the possibility of recycling and reusing concrete demolition waste as an active additive in concrete. currently, this waste is used as aggregates for concrete in france but concrete made with rubble has shown inferior properties compared to regular concrete. secondly, our aim was to improve the physicomechanical properties of concrete by incorporating finely crushed waste concrete. through this work and the results obtained, the following conclusions were drawn: adding up to 10% of waste as a partial substitute for cement significantly improved physical properties such as the occluded air content and workability of fresh concrete, indicating that waste can partially replace cement, thereby reducing binder consumption. however, this waste degraded the mechanical properties of hardened concrete to some extent. nonetheless, the compressive strength of concrete obtained with a waste content of 10% and even up to approximately 13% is satisfactory for building applications, surpassing the required standards. adding 10% of waste to the concrete mix as an active additive noticeably enhanced both the fresh and hardened properties of concrete. because the waste is very fine and possesses physical properties like specific mass and surface area similar to those of cement, it fills the voids previously occupied by air, reducing the occluded air content and consequently increasing the density and compactness of fresh concrete. this increase in compactness is also observed in hardened concrete, as indicated by the increased speed of sound as the rate at which waste is added rises. additionally, the compressive strength of concrete is improved by 20% by adding 10% of waste compared to the control concrete. this improvement is attributed to the interaction between concrete demolition waste and cement. since the waste is very fine and 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osamah ihsan ali1,2, istván gábor gyurika2, tamás korim1 and miklós jakab1* 1 department of materials engineering, research centre for engineering sciences, university of pannonia, egyetem u. 10, veszprém, 8200, hungary 2 department of mechanics, research centre for engineering sciences, university of pannonia, egyetem u. 10, veszprém, 8200, hungary this paper describes the wear and friction behavior of titanium nitride (tin)-based coatings produced via chemical vapor deposition (cvd) in detail. coatings composed of tin, titanium carbide (tic) and aluminum oxide (al 2o3) layers were applied to a tungsten carbide-cobalt composite and steel substrates. the elemental and phase compositions of these coatings, manufactured with varying deposition parameters and layer thicknesses, were determined using scanning electron microscopy (sem) and x-ray diffraction (xrd) analyses. the mechanical properties of the coatings were evaluated through vickers microhardness testing, lubricant -free tribological model tests and scratch testing. for the linearly alternating tribological tests, a static counterpart made of yttri a-stabilized zirconium oxide was utilized. the wear, friction and adhesive properties of the coatings were studied, revealing significant differences in tribological behavior based on their hardness, crystal structure and surface roughness. the tribological tests highlighted that coatings with sharp, spherical crystal structures on their surfaces exhibited the greatest resistance to abrasive and frictional stresses. the durability of the surface coatings was found to be primarily dependent on their adhesion and surface roughness. keywords: cvd, tin, wear resistance, coating adhesion 1. introduction surface treatments and coatings have become increasingly essential in addressing critical tribological challenges encountered in product design and when manufacturing machinery. desired attributes include enhanced abrasion and wear resistance, favorable frictional behavior as well as reduced adhesion propensity coupled with substrate qualities such as toughness, machinability, cost-effectiveness and physical properties. however, the expanding array of commercially available treatments complicates the selection of optimal surface coatings. in order to effectively select them, comprehensive knowledge not only of the physical and mechanical properties as well as process characteristics of available coatings is required but also of their tribological performances under application-specific conditions [1]-[2]. wear and friction behaviors are heavily influenced by the unique tribological system of each application, incorporating factors such as loading conditions, velocity, relative surface movements, lubrication, temperature and the atmosphere. while the specifics vary, laboratory tribological tests conducted under controlled conditions offer valuable insights into received: 6 june 2024; revised: 20 june 2024; accepted: 20 june 2024 *correspondence: jakab.miklos@mk.uni-pannon.hu anticipated real-world performance. nonetheless, discrepancies in experimental procedures and conditions from published data hinder a reliable comparison of the tribological behaviors of coatings [3]-[5]. to address this challenge, a series of unlubricatedsliding pin-on-disk tests were conducted at a constant sliding speed as well as loading and atmospheric conditions. the primary aim was to collect data facilitating the selection of surface coatings for unlubricated sliding bearing-surface applications. coatings produced via physical vapor deposition (pvd), chemical vapor deposition (cvd) and plasma spray (ps) techniques were tested individually and in combination with each other as well as with an uncoated hardened steel tool to examine the impact of the coating on the wear of the steel [6]. in the realm of metal forming, cutting tools composed of cemented carbide (tungsten carbide (wc) with co binder phase) have long been favored. however, concerns over the toxicity of cobalt have prompted the search for alternative materials in the binder phase like fe and ni. meanwhile, escalating demands for quality and productivity underscore the imperative for highperformance tools [3],[7]. to augment the wear resistance of cutting tools, hard protective coatings, typically applied via cvd or https://doi.org/10.33927/hjic-2024-17 mailto:jakab.miklos@mk.uni-pannon.hu ali, gyurika, korim and jakab hungarian journal of industry and chemistry 36 pvd, are employed. cvd-coated wc-co cutting tools often feature a multilayer system comprised of titanium nitride titanium carbonitride aluminum oxide (tin-ticn-al2o3) with titanium nitride (tin) serving as the innermost layer [8]. however, changes in the wc-co binder phase necessitate an investigation into the interactions between the gas phase and the new binder to maintain coating-substrate performance. cvd of tin onto various potential binder phases such as ni and stainless steel has been studied, revealing variations in growth rate, texture and coating morphology. the adhesion of tin coatings may also be affected by diffusion of the binder-phase material into the coating. studies have shown that substrates containing co exhibit superior tool-coating adhesion compared to fe and nibased substrates. while porous coatings typically exhibit inferior mechanical properties unsuitable for metal cutting applications, the growth of cvd of tin on ni surfaces has demonstrated porous characteristics, potentially due to the interaction between ticl4 and ni forming ni chlorides in the gas phase. understanding such interface chemistry during cvd of tin can help suppress the formation of intermetallic phases, thereby enhancing mechanical properties conducive to cutting tool applications [9]. titanium nitride (tin) coatings are commonly applied to cemented tungsten carbide cutting tools using a hot-wall cvd reactor, employing mixtures of ticl4, n2, h2 and ar. the deposition reaction yields solid tin and gaseous hcl, thermodynamically favored above approximately 750 °c at atmospheric pressure. while ticl4 and n2 provide coating components, h2 facilitates the reduction of ticl4 while ar enhances gas mixing and serves as a carrier gas to achieve reasonable deposition rates. although the process typically operates at atmospheric pressure, low-pressure cvd of tin has been demonstrated. the gases, introduced at room temperature, are rapidly heated within the reactor which is maintained at 900-1200 °c. deposition rates of 0.030.20 µm min-1 are achieved under these conditions [10]. the cvd process, conducted at temperatures ranging from 950 to 1050 °c, known as high-temperature cvd (ht-cvd), synthesizes ticn coatings with small equiaxed crystals. the composition of ti(cx,ny) grains can be adjusted to achieve various c/n ratios, crucial for optimizing coating properties while increasing cutting speeds. the morphology, orientation and size of grains as well as the presence of defects significantly influence coating properties. controlling crystallite size and morphology is achievable by adjusting cvd parameters and doping with species like h2s, co, co2 or zrcl4 [11]-[12]. zheng et al. [13] demonstrated control over the grain morphology and hardness of tin wear-resistant coating layers by manipulating the (h2+n2)/ticl4 ratio at a specified cvd temperature. fieandt et al. [14] proposed improving the chipping resistance of coatings by precisely controlling the distribution of c and n atoms in the crystal lattice of ticn coatings. reducing grain size is desirable as nanocrystalline coatings exhibit superior wear resistance attributed not only to the hallpetch relationship but also to grain boundary effects like dislocation and strain hardening. a vacuum-tight chamber heated by resistance or radiation from high-temperature materials like graphite or kanthal super® is typically used. cutting tools are densely packed onto trays and stacked to form a load that nearly fills the chamber. the temperature is precisely controlled using a multizone heater, facilitating temperature ramping in the direction of the gas flow to achieve faster reaction rates. commercial cvd reactors for coating cutting tools incorporate subsystems to facilitate a vacuum, gas handling and scrubbing as well as process control, often operated by software, which minimizes the need for human intervention [15]. various modifications to the process have been introduced, e.g. interrupting film deposition to promote the nucleation of finer-grained layers in addition to using dopants like alcl3 to reduce grain size as well as enhance the strength and lifespan of the coating [16]. plasma-enhanced cvd processes have also been explored, depositing coatings at lower temperatures and consuming less gas, in spite of complexities. additionally, low-temperature cvd of tin has been demonstrated, yielding coatings at temperatures as low as 40 °c, albeit with low densities and high impurity content, hindering adhesion and performance. studies on the kinetics of cvd of tin have identified temperature-dependent rate-controlling steps, typically assumed by modeling due to difficulties in making direct measurements. these studies have provided insights into the influence of precursor concentrations and reaction mechanisms on deposition rates, aiding the optimization of process parameters for specific reactor configurations. however, the transferability of findings between reactors remains a challenge due to reactor-specific conditions [17]-[18]. nevertheless, research continues to refine cvd processes to enhance the properties and performance of tin coatings. investigating these coatings in terms of mechanical properties, chemical composition and structure helps to select optimal coatings for specific industrial applications. tribological tests are crucial to evaluate changes in the coefficient of friction, the adhesion of coatings to substrates and abrasion resistance. understanding the wear process by carrying out detailed investigations of worn surfaces is vital to enhance the wear resistance of machine elements and tools. the "pin-on-disk" test is a commonly used method to assess tribological properties, simulating wear through contact and relative rotation. this study aimed to analyze the tribological properties of hard, wear-resistant coatings produced by cvd on tungsten carbide and steel substrates. 2. materials testing methods a morphological analysis was performed utilizing an apreo s by thermofisher scientific (formerly fei) scanning electron microscope (sem) in a high vacuum, employing an accelerating voltage of 20.0 kv. prior to observations, the samples were cleaned in an ultrasonic comparison of the properties of titanium nitride-based coatings 52(2) pp. 35–46 (2024) 37 bath containing ethanol and acetone to optimize resolution for back-scattered electron imaging. the images were taken by a keyence vhx-2000 digital light microscope. cross-sections were prepared by embedding samples in epoxy resin (nx met xf40) before being polished. the elemental compositions were determined using an edax ametek octane elect plus energy dispersive x-ray analyzer with an accelerating voltage of 20 kv and a data collection time of 180 s. a microhardness assessment was conducted on both the coated and uncoated (reference) samples using the vickers microhardness method (4.903 n, wolpert 402 mvd) with a loading force of 0.05 kgf. the hardness values were determined as the average of five readings per specimen. the indentation diameter measured during hardness testing can be used to calculate the penetration depth of the diamond pyramid. the geometry of the diamond pyramid is known based on the manufacturer's datasheet. by determining the penetration depth, it is clear whether the measured hardness pertains solely to the coating and if the hardness of the substrate also influences it. the x-ray diffraction (xrd) analyses were conducted using a philips pw 3710 diffractometer with cu-k α radiation (50 kv, 40 ma), employing a scan rate of 0.02 2θ/s over a range of 10 to 70 degrees 2θ and incorporating a curved graphite monochromator. xrd pattern data were collected using x’pert data collector software, while phase identification and quantitative phase analysis were performed utilizing highscore plus 5.0 software using the rietveld method. the crystalline phases were identified by comparing xrd patterns with the 2021 powder diffraction files (pdf-2 2021) from the international centre for diffraction data (icdd). the tribological performance was evaluated through dry-sliding experiments utilizing an anton paar trb3 tribometer in a ball-on-disc configuration, following standards astm g99-05 [19] and astm g133-05 [20]. coatings were subjected to tests against steel balls 6 mm in diameter (anton paar, 100cr6 steel ball) and zirconia balls 5 mm in diameter (max fritsch, zirconium oxide grinding ball) at 25 °c in ambient air with a relative humidity of 46±3%. the maximum sliding speed and normal load were maintained at 15.71 cm/s and 20 n, respectively. the coefficient of friction (µ) was continuously monitored in relation to the sliding distance. following tests, the wear track was cleaned with alcohol to remove loose wear debris and subsequently measured using a profilometer. the wear volume (vp, mm3) values were then calculated in accordance with the aforementioned standards to compare the wear resistance of the coatings. 𝑉𝑝 = (𝜋ℎ/6)[3𝐷2/4 + ℎ2] (1), where h denotes the height of the removed material from the ball (mm) and d represents the diameter of the wear scar on the ball. the height of the material removed can be calculated as follows: ℎ = 𝑅 − [𝑅2 − (𝐷2/4)]1/2 (2), where r denotes the original radius of the ball (mm). a customized scratch test methodology was employed to assess the adhesion of the coating. the examination utilized an anton paar trb3 tribometer with a fixed total stroke length of 10 mm and a consistent normal force of 5 n. diamond indentation marks left on the surface were scrutinized via sem. furthermore, the surface roughness was analyzed using a taylor hobson/ametek surtronic s-128 surface roughness tester. a c-therm tci™ thermal conductivity analyzer was used to determine the thermal conductivity of the test samples. the heating element was heated to 150 °c, the heat pulse lasted for 3 seconds and the total measurement time was 7 seconds. five parallel measurements were conducted. in each case, distilled water was used as a contact agent. 3. results and discussion the samples examined during the experimental work and their abbreviations are summarized in table 1. the titanium nitride-based coatings were produced with varying manufacturing parameters, including the volumetric flow rate of precursors, temperature and table 1: abbreviations and the type of cvd coatings investigated sample layer type substrate thickness (µm) layer 1 layer 2 layer 3 tin1 single layer wc 0.3-0.6 tin2 single layer wc 0.7-0.9 tin3 single layer wc 1.8-2.8 tin4 single layer wc 2.9-3.8 tin5 single layer wc 5.8-7.2 tin6 single layer wc 6.3-7.8 tic/tin two-layer wc 1.2-1.4 1.5-3.1 ticn/al/tin multi-layer wc 8.1-8.6 2.2-3.1 0.9-1.1 ticn single layer st 0.5-0.7 ali, gyurika, korim and jakab hungarian journal of industry and chemistry 38 pressure. the test specimens presented in the study were produced by büttner kft. (nagyatád, hungary) in a newly developed reactor located at their site. tungsten carbide-cobalt cermet and steel were used as substrates for the coatings. one of the most important parameters in this experiment is the thickness of the deposited layers. to determine the layered structure, the samples were embedded in epoxy resin and polished with various grades of abrasive papers. the final polishing step was performed with a suspension containing diamond particles 3 µm in diameter. after polishing, the layer thicknesses were measured using sem. six different samples of titanium nitride-based coatings were examined during the work with thicknesses ranging from 0.3 to 7.8 µm. for the wc-co substrate coated with layers of titanium carbide and titanium nitride, the main goal was to study the effect of the titanium carbide layer on the tool life in a similar manner to the sample containing the layer of aluminum oxide support. the purpose of examining the steel sample was to study the tribological properties of the coating less than 1 micrometer thick. 3.1. microstructure and composition the atomic percentage composition of the surfaces is summarized in table 2. before being examined by energy-dispersive x-ray analysis, the samples were cleaned in an ultrasonic bath with acetone for 5 minutes and then wiped with a lint free cloth. the elemental composition on the surfaces of the samples was determined over areas of approximately 1 mm2. for each specimen, three parallel measurements were taken. the elemental composition of the wc-labeled substrate shows that, in addition to the wc-based crystalline phases, it contains chromium and cobalt binders. the steel-based substrate (st) primarily consists of iron with small amounts of alloying elements such as carbon, manganese and chromium, indicating that the substrate is a wear-resistant steel alloy. the elemental composition of the titanium nitridebased coatings reveals that they mainly contain titanium and nitrogen with varying atomic percentage ratios depending on the manufacturing parameters. however, for samples tin1-tin4, characteristic x-ray peaks indicative of the substrate were also observed in the energy-dispersive spectra, suggesting that the excitation (information) volume depth caused by the electron beam is greater than the thickness of the coating. samples tin1 and tin3 contain relatively high cobalt concentrations, implying that cobalt diffused to the surface due to the high temperatures used during coating deposition [21], potentially affecting the structure of the coating as well as its wear and friction properties. when the coating thickness exceeded 5 µm, elements indicative of the substrate were no longer detectable in the composition. the results from the x-ray diffraction analysis of the coatings are summarized in table 3. similar to the findings from the elemental composition analysis, reflections characteristic of the different types of substrate were observed alongside the reflections from the crystalline phases of the coating. for the titanium nitride-based coatings, the primary crystalline phase is tin in all cases. however, depending on the manufacturing parameters, samples tin1, tin2 and tin4 also exhibit reflections characteristic of the tio crystalline phase. this indicates that the vacuum or the flow rate of the precursors during production was not perfect, causing partial oxidation of the coating at high temperatures, thereby adversely affecting the desired coating quality. for the two-layer coating, it is evident that one of the main components of one layer is the tin crystalline phase, while the other layer is comprised of a ticn crystalline phase. in the case of the coating reinforced with an aluminum oxide phase, reflections characteristic of al2o3 are present. for the steel-based sample, reflections corresponding to the crystalline phases typical of steel are observed. the microstructure of various types of coatings is illustrated in figure 1. it is evident that the tin crystalline phases in samples tin1 (figure 1a), tin2 (figure 1b), tin3 (figure 1c) and tin4 exhibit a table 2: the atomic percentage composition of substrates and the different types of coatings wc st tin1 tin2 tin3 tin4 tin5 tin6 tic/tin ticn/al/ tin ticn w 30.5±1.1 0.2±0.1 0.5±0.1 3.7±0.2 0.8±0.2 0.8±0.2 co 8.6±0.5 0.3±0.1 10.4±0.3 1.9±0.1 0.7±0.2 c 55.6±5.9 0.8±0.2 33.1±1.2 21.6±2.1 o 4.7±0.7 2.1±0.2 0.8±0.1 1.2±0.1 6.3±0.6 ti 62.1±0.7 50.6±0.7 31.6±0.6 53.7±0.2 59.1±0.8 54.5±0.8 30.9±0.4 34.8±0.6 8.9±0.2 n 33.5±2.1 48.1±3.7 54.3±4.1 42.5±0.8 40.9±2.5 45.5±2.6 36.4±1.3 49.8±3.5 24.1±2.2 fe 98.6±1.9 45.1±0.9 mn 0.3±0.1 0.2±0.1 cr 0.6±0.2 0.3±0.2 0.9±0.2 0.2±0.1 al 9.2±0.6 comparison of the properties of titanium nitride-based coatings 52(2) pp. 35–46 (2024) 39 predominantly spherical morphology. in these cases, the layer thickness is less than 4 µm. although samples tin1, tin3 and tin4 are composed of spherical crystals of similar size, these crystals are much more densely packed on the surface of sample tin4. the crystals in sample tin2 are smaller compared to the others. previous studies indicate that these spherical crystals form when the coating temperature is below 990 °c. in sample tin3, the spherical crystals appear slightly elongated, likely due to cobalt diffusion. samples tin5 and tin6 display star-shaped and lenticular-like crystals, which form at reaction temperatures above 1050 °c. the tin/tic sample exhibits star-shaped and rounded particles on its surface, which typically form around 990 °c [4],[12]. the multi-layered sample also exhibits spherical and lenticular-like crystals, whereas the coating on the steel substrate does not show distinctive crystal shapes, only a few spherical crystals on the surface. the hardness of the coatings (values 1, 2 and 3) and the penetration depth (pd) of the diamond pyramid are summarized in table 4. the results show that the coatings on the wc substrate generally increased the hardness of the test specimens. however, a decrease in hardness is observed in samples tin5 and tin6. as seen in the sem images (figure 1), these coatings consist of plate-like crystals that fill the available area less effectively, resulting in higher porosity and lower hardness values. for samples tin1-tin4 and ticn, since the penetration depth exceeds the coating thickness, this phenomenon must be considered when interpreting the data. nonetheless, the sem images clearly show that the spherical and star-shaped crystals cover the surface more uniformly compared to the lenticular-like ones. the effect of the cvd coating on the hardness of the steel substrate could not be measured as the coating thickness is less than 1 µm and the penetration depth on the relatively soft steel greater than 10 µm. consequently, the measured hardness essentially reflects the hardness of the steel itself. table 3: the phase composition of the substrates and coatings jcpds card number phase wc st tin1 tin2 tin3 tin4 tin5 tin6 tic/ tin ticn/ al/tin ticn 01-085-4359 wc x x x x x x x x x 01-089-7373 co x x x x x x x x 01-089-2005 fe3c x x 00-006-0696 fe x x 00-051-0997 fe5c2 x x 01-074-8388 tin x x x x x x x x 03-065-9875 tic0.496n0.502 x x 00-008-0117 tio x x x x 00-023-1455 ti2n x 03-065-4761 w5n4 x x 00-026-0031 al2o3 x table 4: vickers-hardness (in hv) of the samples wc st tin1 tin2 tin3 tin4 tin5 tin6 tic/ tin ticn/al/ tin ticn value 1 (hv) 1801 226 2027 1850 2119 2250 1709 1810 1875 3093 238 value 2 (hv) 1900 238 2246 2189 2181 2119 1668 1790 1983 3203 162 value 3 (hv) 2122 130 1874 1983 1889 2092 1862 1785 2249 2889 170 av. (hv) 1941.1 198.0 2049.0 2007.3 2063.0 2153.7 1746.3 1795.0 2035.7 3061.7 190.0 sd. (hv) 164.4 59.2 187.0 170.8 153.8 84.5 102.2 13.2 192.5 159.3 41.8 hardness (gpa) 19.0 1.9 20.1 19.7 20.2 21.1 17.1 17.6 20.0 30.0 1.9 pd (µm) 2.1 2.4 2.7 5.1 2.9 4.0 2.4 2.0 10.4 av.: average of the vickers-hardness values 1-3, sd.: standard deviation of vickers-hardness values 1-3, pd: penetration depth penetration depth ali, gyurika, korim and jakab hungarian journal of industry and chemistry 40 a) tin1 b) tin2 c) tin3 d) tin4 e) tin5 f) tin6 g) tin/tic h) ticn/al/tin i) ticn figure 1: microstructure of the coatings comparison of the properties of titanium nitride-based coatings 52(2) pp. 35–46 (2024) 41 the thermal conductivity of various types of coatings is summarized in figure 2. the wc-co samples exhibit fundamentally lower thermal conductivities compared to those measured for steel. for the test specimens coated with tin and tic/tin, the coating thickness was nearly identical, but a slight increase in thermal conductivity was observed compared to the reference values. the coating that included a corundum layer exhibited the highest thermal conductivity among the wc-co samples. for the steel-based test specimen, the highest measured value was 51.2 w/mk. when interpreting the results, the measurement error due to irregularities in the surface of the test specimens must be considered. as observed in the sem images, air gaps between the spherical surface particles can affect the measured thermal conductivity of the coated products. based on the thermal conductivity values, it can be concluded that using wc-co composites as machining tools is advisable as these typically have lower thermal conductivities, thereby heating up less during machining. 3.2. tribological behavior to determine the experimental parameters for the tribological model tests, a test specimen with a ticn/al/tin composite coating was used. the layer structure is illustrated in the elemental map in figure 3, which clearly shows that the layer closest to the substrate contains both nitrogen and carbon, indicative of the ticn layer. this is followed by an aluminum-containing support layer and then an upper titanium nitride layer. according to the results presented in table 1, the thickness of the upper titanium nitride layer is approximately 1 µm. in the first step of the tribological investigations, a steel ball 6mm in diameter was used as the static counterpart. during the measurements, the degree of displacement was 10 mm, the maximum speed of the coated sample 15.71 cm/s and the total distance covered 500 m. throughout the experimental series, the normal compressive forces applied were 10, 20 and 60 n. in the measurement conducted with a loading force of 10 n, it was observed that the steel used as the static counterpart smeared onto the surface and, after a certain time, the wear and friction mechanism became uninterpretable. this phenomenon indicates that over time, wear surfaces of steel-on-steel were formed rather than measuring the wear of the coating. even though the experiment was repeated with higher normal compressive forces (20 and 60 n), similarly to the previous attempts, the wear surface was not evaluable (figure 4a). subsequently, the surface was washed with an 18 vol.% hydrochloric acid solution to remove the smeared steel layer as shown in figure 4b from which it is evident that the wear surfaces are virtually identical. furthermore, despite increasing the normal compressive force, the approximately 1 µmthick tin coating was not removed, even after the 500 m long test. figure 2: thermal conductivity of the samples 32,69 33,08 33,46 33,70 50,36 20,0 25,0 30,0 35,0 40,0 45,0 50,0 55,0 wc ref. tin4 tic/tin ticn/al/tin ticn t h er m al c o n d u ct iv it y [w /m k ] a) b) c) figure 3: elemental map of the cross-section of the ticn/al/tin sample where yellow indicates nitrogen (a), purple indicates carbon (b) and red indicates aluminum (c) ali, gyurika, korim and jakab hungarian journal of industry and chemistry 42 the experiments conducted with the steel static counterpart confirmed that using a material system with a hardness comparable to that of the coating under investigation is advantageous regarding the tribological analysis of titanium nitride and titanium carbide-based coatings [22]-[24]. in this regard, yttrium-stabilized zirconium dioxide balls were subsequently employed with a hardness of 13-14 gpa [25]. in this case, the hardness of the static counterpart is slightly lower than that of the coatings. however, this setup allows for the examination of the wear track formed due to wear and friction effects as well as of the volume removed from the contact surface of the ball. accordingly, further investigations were conducted with zro2-based static counterparts using the previously described measurement parameters. the normal compressive force applied in each case was 20 n. to interpret the wear and friction conditions, the diameter of the circular wear track formed on the bottom of the contact surface of the zro2 ball due to wear (d) was measured using a light microscope. with d and the radius of the ball (r=2.5 mm) known, the wear height of the static counterpart (h) could be calculated using equation 2 before calculating the wear volume (vp) using equation 1. the results obtained are summarized in table 5 in which the last column shows the average surface roughness (ra) specific to each sample. the surface roughness and crystalline structure formed on the surface also have a significant impact on tribological properties. the coefficient of friction was periodically recorded using anton paar trb3 version 9.0.16. software. should this coefficient increase, it can be inferred that abrasive particles have moved between the contact surfaces, causing abrasion to both the zirconium oxide ball used and the sample surface. first signs of the abrasive wear effect were noticed when the coefficient of friction reached 0.5. from the known measurement time and speed, the distance traveled could be calculated, after which it was presumed that the coating probably had detached from the sample surface. to confirm the detachment of the surface layer from the wear track, energy-dispersive x-ray analysis was performed. according to the results, sample tin2 exhibited the smallest surface roughness and wear volume with a layer thickness of 0.7-0.9 µm. a) b) figure 4: lm images after the experiments conducted with the steel test specimen where (a) denotes the smeared steel and (b) denotes the surface of the sample after hydrochloric acid cleaning table 5: reduction in wear volume and average surface roughness sample d (mm) h (mm) vp (mm3) vp (µm3) ra (µm) tin1 0.440 4.84e-03 3.68e-04 3.68e+05 0.61 tin2 0.268 1.80e-03 5.07e-05 5.07e+04 0.16 tin3 0.567 8.04e-03 1.02e-03 1.02e+06 0.25 tin4 0.470 5.53e-03 4.79e-04 4.79e+05 0.56 tin5 0.505 6.38e-03 6.39e-04 6.39e+05 0.36 tin6 0.498 6.20e-03 6.04e-04 6.04e+05 0.34 tic/tin 0.389 3.78e-03 2.25e-04 2.25e+05 0.39 ticn/al/tin 0.609 9.28e-03 1.35e-03 1.35e+06 0.33 ticn 0.541 7.32e-03 8.42e-04 8.42e+05 0.74 d: diameter of the wear scar on the ball, h: height of the removed material from the ball, vp: wear volume, ra: average surface roughness comparison of the properties of titanium nitride-based coatings 52(2) pp. 35–46 (2024) 43 in this case, based on the energy-dispersive x-ray spectroscopy (eds) results, the coating did not wear off during the test. although the coefficient of friction exceeded µ=0.5 after 30 m, the abrasive particles did not abrade the surface. similar results were observed for the tic/tin, two-layered sample as well. the average surface roughness in this case was more than double that measured for sample tin2 and the wear volume nearly an order of magnitude higher. as seen in figure 1, the surface of this sample consists of sharp crystals in the tin layer, which have a particularly good abrasive effect. however, while measuring the elemental composition, it was observed that the coating did not detach from the surface. in this case, signs of abrasion appeared on the time-coefficient of friction diagram after 4.7 m. although the coefficient of friction continued to increase steadily throughout the remaining measurement time, no further layer detachment was observed. for sample tin4, the coefficient of friction exceeded 0.5 after 204.9 m. based on the eds results, in this case, the 2.9-3.8 µm-thick coating did not wear off during the tests. samples tin5 and tin6 behaved similarly during the tribological tests. detachment of abrasive particles was first noticed after traveling 7.2 and 7.8 m, respectively. the coefficient of friction remained constant throughout the experiment (µmax=0.95). for the ticn/al/tin sample, signs of detachment of the top layer were visible after 7.1 m. based on the eds results, only the upper ~1 µm-thick tin layer partially detached, while the underlying aluminum oxide layer remained intact. however, the wear volume was the highest in this case, indicating that although the tin layer partially wore off the surface, the abrasive effect of the coating continued during the test. in the case of samples tin1 and tin3, the coating completely wore off. for sample tin1, with a coating thickness below 1 µm, it fully detached from the surface after 1.3 m. for sample tin3, the coating likely detached after 150 m according to the tribological test. the steel substrate coated with a ticn layer exhibited the highest surface roughness but the coating wore off the surface after 15.4 m. subsequently, the coefficient of friction remained constant throughout the test, indicating that the zirconium oxide ball only abraded the steel substrate. the effect of surface roughness and microhardness on wear volume is illustrated in figures 5 and 6 from which it is evident that in the case of stable coatings, that is, those that did not wear off, the coefficient of friction figure 5: the effect of average surface roughness on wear volume 0 200000 400000 600000 800000 1000000 1200000 1400000 1600000 0,00 0,10 0,20 0,30 0,40 0,50 0,60 0,70 0,80 tin1 tin2 tin3 tin4 tin5 tin6 tic/tin ticn/al/tin ticn v o lu m e lo ss [ µ m 3 ] r a [ µ m ] surface roughness volume loss figure 6: the effect of microhardness on wear volume 0 200000 400000 600000 800000 1000000 1200000 1400000 1600000 0 500 1000 1500 2000 2500 3000 3500 v o lu m e lo ss [ µ m 3 ] v ic k er sh a rd n es s vickers-hardness volume loss ali, gyurika, korim and jakab hungarian journal of industry and chemistry 44 a) tin1 b) tin2 c) tin3 d) tin4 e) tin5 f) tin6 g) tin/tic h) ticn/al/tin i) ticn figure 7: scratch test-induced scratch tracks on the surfaces of the test samples comparison of the properties of titanium nitride-based coatings 52(2) pp. 35–46 (2024) 45 and wear volume changed analogously. however, no similar observation was made regarding hardness. a good example of this is seen in the tin2 and ticn/al/tin samples, where the surface roughness is the lowest among the samples examined, however, their wear volume differs significantly. therefore, from a tribological perspective, in tin-based systems, it is advantageous for the coating to be fairly dense, exhibit a low degree of porosity as well as have surface roughness and hardness values significantly greater than those of the applied counterpart or the tools in the case of the test specimen being machined. in terms of tribology, apart from the wear and friction conditions, adhesion of the coating to the surface is crucial. for this purpose, a custom-developed scratch test was employed during which a diamond stylus with a geometry similar to that used for vickers hardness testing was drawn along the surface of the test samples over a length of 10 mm while applying a normal load of 2 n. as depicted in figure 7, the coating flaked off along the scratch line of the tin1 and tic/tin samples, indicating poor adhesion of the coating to the surface, which is significant in the case of the bilayer coating that exhibited favorable properties during tribological tests, however, adhesion of the layer is weak. the least amount of deformation was observed in the tin2 and ticn/al/tin coatings. in these cases, as evident from the diameter of the scratch, the stylus did not penetrate deeply into the surface and no signs of detachment nor cracking were observed along the scratch line. similarly, for samples tin4-tin6, although the width of the scratch was quite large, no signs of detachment were observed. however, in the case of sample tin3, as seen in the backscattered electron image, traces of wc substrate particles were visible along the scratch line, indicating that the coating detached from the surface due to scratching. an image of the steel-based coated product after the scratch test at a lower magnification compared to the other images is shown in figure 7i. in this case, the penetration depth was too high and the stylus progressed practically without resistance along the surface, easily detaching the coating. 4. conclusions in evaluating the research results, the main goal was to qualify the coatings primarily for practical usage purposes. the more resistant a coating applied on a tool is, the longer its expected lifespan, in all likelihood leading to a significant reduction in costs. drawing conclusions from the qualification of coatings formed using various structures and thicknesses through the cvd process, the following can be inferred: • for tribological model testing of tin-based coatings, it is necessary to select a static counterpart with a hardness resembling that of the test specimen as if insufficient, the coating may not be detached at all, even when normal loading is increased. • in terms of tribology, the average surface roughness of the test specimens has a greater impact on the wear volume than their hardness. • the stability of coatings is not dependent on their thickness but rather on their surface roughness and hardness. • from a tribological and micromachining perspective, it is much more advantageous to use tools coated by a cvd process that results in sharp, lenticular-like crystals on the surface. • in the event of long-term usage, it is advisable to develop a coating that includes a support layer between the titanium-based layers. • since tribological model tests do not always adequately reflect adhesion of the respective coatings to the surface, it is advisable to conduct supplementary scratch tests. symbols cvd chemical vapour deposition eds energy-dispersive x-ray spectroscopy ht-cvd high-temperature cvd ps plasma spray pvd physical vapor deposition sem scanning electron microscopy tic titanium carbide ticn titanium carbonitride tin titanium nitride wc tungsten carbide wc-co tungsten carbid cobalt xrd x-ray diffraction vp wear volume d the diameter of the wear scar on the ball h the height of the removed material from the ball pd penetration depth r the original radius of the ball ra average surface roughness µ coefficient of friction acknowledgements this work was supported by the tkp2020-nka-10 project financed under the 2020-4.1.1-tkp2020 thematic excellence programme by the national research, development and innovation fund of hungary. the project 2019-1.1.1-piaci-kfi-2019-00506 was implemented with financial support provided by the ministry of innovation and technology through the national research, development and innovation fund. the project was funded under the market-driven research and innovation projects support programme. ali, gyurika, korim and jakab hungarian journal of industry and chemistry 46 references [1] franklin, s.e; beuger, j.: a comparison of the tribological behaviour of several wear-resistant coatings, surf. coat. technol., 1992, 54-55, 459–465, doi: 10.1016/s0257-8972(07)80066-1 [2] rebenne, h.e.; bhat, d.g.: review of cvd tin coatings for wear-resistant applications: deposition processes, properties and performance, surf. coat. technol., 1994, 63(1-2), 1–13, doi: 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rev. odontol. unesp, 2014, 43(6), 379–383, doi: 10.1590/1807-2577.1049 https://doi.org/10.1016/s0257-8972(07)80066-1 https://doi.org/10.1016/s0257-8972(05)80002-7 https://doi.org/10.1016/s0257-8972(05)80002-7 https://doi.org/10.1016/0257-8972(95)02527-8 https://doi.org/10.1016/j.surfcoat.2010.09.013 https://doi.org/10.1016/j.ijrmhm.2021.105495 https://doi.org/10.1361/105994998770347440 https://doi.org/10.1016/j.jmatprotec.2005.04.032 https://doi.org/10.1016/j.surfcoat.2004.07.098 https://doi.org/10.1016/j.ceramint.2017.03.096 https://doi.org/10.1007/s11249-010-9664-7 https://doi.org/10.1007/s11249-010-9664-7 https://doi.org/10.1007/s00170-020-05000-x https://doi.org/10.1007/s00170-020-05000-x https://doi.org/10.1016/j.ceramint.2023.02.255 https://doi.org/10.1016/j.vacuum.2018.07.012 https://doi.org/10.1016/j.surfcoat.2017.11.063 https://doi.org/10.1016/j.ijrmhm.2016.07.005 https://doi.org/10.3390/cryst13010112 https://doi.org/10.1016/j.ijrmhm.2015.06.006 https://doi.org/10.1016/j.ijrmhm.2012.07.001 https://doi.org/10.1007/s11669-005-0027-2 https://doi.org/10.33927/hjic-2021-26 https://doi.org/10.1016/s0043-1648(03)00391-0 https://doi.org/10.1515/313 http://dx.doi.org/10.1590/1807-2577.1049 conferenceproceed]ngs hungar~journal of ]ndustrial chemistry veszprem vol. 2. pp. 16-20 (2000) production of environmentally friendly gasoline blending components a. hollo, j. hancsok, j. gergely1 andj. perger1 (department of hydrocarbon and coal processing, university of veszprem, p.o. box 158, veszprem, h-8201, hungary 1division of production and trade, molhungarian oil and gas co., p. 0. box 1, szazhalombatta, h-2440, hungary) this paper was presented at the second international conference on environmental engineering, university ofveszprem, veszprem, hungary, may 29june 5, 1999 our paper describes and evaluates the environmentally friendly possibilities to satisfy some new regulations for motor gasolines. during the research work the hydroisomerization of n-heptane containing n-hexane fractions was investigated on platinum/h-mordenite catalyst. the effect of temperature and liquid hourly space velocity on the yield of liquid and gas products, as well as their composition and properties were examined. the gained and our previous results indicated that the used catalyst with suitably chosen process conditions is applicable to upgrade a hexane fraction containing a few percents of n-heptane. with gasoline blending and emission predicting calculations we proved the advantageous properties of isoparaffin rich fractions. thus we pointed out that the production of a gasoline containing more isoparaffins, less aromatics, olefins and mtbe decreases its potential harmful effects. keywords: environmentally friendly gasoline; hydroisomerization; reduction of emission introduction as a by-product of the fast industrial development and motorization, our earth suffers from serious environmental harms and damages. among others one of the roost significant is air pollution, the major part of which originates form the use of motor vehicles, as well as from the production, transportation and storage of their fuels. besides the carbon dioxide causing greenhouse effect, the emissions of nitrogen-oxides, carbon monoxide and ·various hydrocarbons are significant because of human biological aspects, the aromatic compounds getting to the atmosphere and within these the light aromatics as benzene and toluene are especially dangerous. the carcinogen benzene causes reversible depression of bone marrow activity and acute myeloid monolytic leukaemia, while toluene can generate nerve system damage [ 1j. the disadvantageous property of heavy aromatics is that they have the largest photochemical activity besides olefins in motor gasoline. thus they greatly contribute to the formation of ozone and photochemical smog [24]. in turn ozone, even in low concentration, can cause lung damage. nevertheless according to the car manufacturers aromatic hydrocarbons are not oruy dangerous for biological organisms, but they also have a harmful effect on the catalysts of motor v:ehicles. these compounds are blamed for the deposits forming on the surface on the catalysts, and thus for their reduced activity. however, gasoline blending components containing significant amount of aromatic compounds (e.g. reformate, pyrolisys gasoline, etc.) largely contribute to the gasoline pool even nowadays, since their high research octane number greatly helps in the production of unleaded motor gasoline having excellent anti-knock property. because of the preceding the benzene content, and later on possibly the total aromatic content of motor gasoline will be limited in the developed world [5]. the elimination of aromatic compounds like benzene decreases the octane number, especiruly the front octane number. the originating quantitative and qualitative demands have to be satisfied with the use of other gasoline blending components. one possible, widely used solution is the application of oxygenates (mtbe, etbe, tame, ethanol. methanol, etc.) having hlgh octane nnmber and volatility. due to their oxygen content these compounds table 1 main feed properti~s feed type pro_eerties a b c d e composition, % 2,3-dimethylbutane 0.1 2-methylpentane 0.4 0.5 0.3 0.3 0.3 3-methylpentane 0.4 1.0 0.6 0.3 0.5 n-hexane 98.7 96.5 95.8 93.2 89.5 methylcyclopentane 0.4 0.9 0.3 0.4 0.5 n-heptane 1.1 3.0 5.8 9.2 sulphur content, ppm 24-28 water content, ppm 37-48 research octane number 31.7 31.8 30.7 29.7 27.9 motor octane number 30.6 30.8 29.7 28.8 27.9 promote the perfect burning, although their thermal values are lower than those of the commonly used gasoline blending components containing hydrocarbons. on the other hand oxygenates are soluble in water, therefore in case of leakage they can go further into water like other blending components, endangering seriously the animal world and flora [6]. it implies further dangers that their atmospheric reactivity (tame, etbe) and ozone producing activity are high, too [2-4]. furthermore, animal evidence suggests that mtbe may be a weak carcinogen. the u.s. petrochemical industry and u.s. epa reviewed the results of a 3.5 million usd study on mice and rats exposed by inhalation . to mtbe. at high concentrations, rats exhibited kidney lesions and tumours, and mice developed liver tumours [6,7]. on the basis of these results, mtbe-free gasoline was put into market in california. instead of mtbe the less harmful ethanol was used [8]. in addition to oxygenates numerous, environmentally more friendly motor gasoline blending components (e.g. alkylate, isomerate) are at the refineries disposal to satisfy quality and quantity demands originating from the reduction of benzene and total aromatic content of motor gasolines. however, their production in larger quantity is not possible, because the availability of their raw materials is limited, or their production is too expensive. thus the economic and combined way to produce motor gasoline with reduced benzene and total aromatic content is the reduction of concentration of aromatic hydrocarbons in blending components having large aromatic content, and their use in lower quantity. since one of the most significant benzene and aromatic sources is reformate, a possible way to produce gasolines with less aromatics is the use of reformate with reduced aromatic content. one possible solution is the increase of the initial boiling point of feeds of reforming units. in this way benzene, its precursors and partly the precursors of toluene (the heptanes) are removed from the feed. thus these compounds go to the light gasoline [9,10}. this light fraction has low octane number, thus it cannot be used as gasoline blending component without any conversion. this could be the catalytic isomerisation. however, there is little information on 17 the isomerisation of heptanes containing hexane fractions (especially n-heptane having ron of 0) [11]. thus during our research work the isomerisation of n­ heptane containing hexane fractions was studied on an isomerisation catalyst active at middle-temperature. with gasoline blending calculations we proved the advantageous properties of isoparaffin rich fractions. furthermore we pointed out that the .connection of isomerisation and reforming units will become more important in the refineries. experimental materials experiments were carried out with different n-heptane containing hexane fractions. table 1 shows the main properties of feeds. hydrogen was purified by passing thtough an oxygen converter containing pd/alumina catalyst, followed by a molecular sieve linde 4a trap at room temperature. a 0. 4 % pt!h-mordenite/alumina was applied as catalyst. apparatus experiments were performed in a continuous tubular reactor free of back mixing which made possible pre­ treatments (drying, reduction) of the catalyst and the study of its activity. the description of the apparatus is given elsewhere [12]. method the catalyst was packed in the isothermal zone of the reactor between two layers of raschig rings and activated in situ, in flowing hydrogen as described according to the following. the temperature of catalyst bed was increased from room temperat!}ie to 300±2°c with a rate of 25-30°c h"1 in 40±1 dm3 h-1 dry hydrogen flow at atmospheric pressure. the catalyst was kept at this temperature for 5 h in hydrogen flow, then it was heated to 450±2°c as before kept at· this temperature for 2 h, and cooled to the reaction temperature with a rate of 25-30°c h"1 in hydrogen flow. the composition of feeds and products was determined according to the astm-d 5134-90 standard. the research and motor octane numbers (ron and mon) were calculated on the basis of the blending octane numbers of the components and their volume percent. the applicability of the high quality products as favourable gasoline blending components was proven by a product blend optimisation program run under hpi gasoline blending optimizer (model-mg) software package for the case of achieving maximum profitability and limiting benzene, aromatics and mtbe. 18 table 2 process parameters temperature, oc pressure, bar parameters liquid hourly space velocity (lhsv), h-1 hydrogen/hydrocarbon molar ratio 210-270 20-40 1.0-3.0 1:1-3:1 (1) (2) (3) (4) 85+-------~------~------~----~ 200 220 240 260 280 temperature, °c fig.l the yield of liquid products as a function of temperature, n-heftane in feed: 3.0%: 1) lhsv: 3.0 h"1 , 2) lhsv: 2.0 h. , 3) lhsv: 1.5 h·l, 4) lhsv: 1.0 h-1 results and discussion during our research work the effect of process conditions and n-heptane content on the yield of liquid (c5+) and gas products (c4-), their quality and octane number were examined. process parameters applied in the reactor system are shown in table 2. in the following, the favourable results in respect of isomerisation of n-hexane are discussed. the yield of liquid products decreased with increasing temperature in all cases, as fig.l shows for 3.0% n-heptane containing feed. of course the yield of gas products changed inversely containing mainly isobutane and propane. on the other hand the amount of liquid products almost linearly decreased with n-heptane content of feeds, and as fig.2 indicates these lines become more precipitous as temperature increased. the isomerisation reactions of n-hexane were characterised by the approach of equilibrium concentration of 2,2-dimethylbutane at the given temperature, since the reaction rate of 2,2dimethylbutane formation is the lowest during the isomerisation of n-hexane. therefore, all the other components in the product approach their equilibrium concentrations to greater degrees than 2,2dimethylbutane. this is well proven as an example by . the data reported for 2and 3-methypentane in table 3. the datec values for 2,2-dimethylbutane decreased on increasing n-heptane content in the feed (table 3). n-heptane inhibited the isomerisation of n­ hexane and this inhibition was most pronounced for the slowest isomerisation conversion, i.e. for the formation of 2,2-dimethylbutane. the yield of the mixture of isoparaffins also decreased with increasing n-heptane content in the feed because of reasons discussed before. the ron of isoparaffin mixtures is nearly the same for all feeds (82.6-83.2, table 3). n-heptane slows down to some so+-----~-----r----~------~--~ 4 10 n-heptane content,% fig.2 the yield of liquid products as a function of n-heptane in feeds, lhsv: 1.5 h. : 1) 210°c, 2) 220°c, 3) 230°c, 4) 240°c, 5) 250°c, 6) 260°c, 7) 270°c 100~------------------------------. § ~ 80 60 40 20 50 o-­ =-o--o---o----.:,__-tl-_-c (1) __ ,___,___,___,___~ (2) iso 250 350 450 temperature, oc fig.3 the equilibrium octane number of 1) hexanes and 2) heptanes extent the isomerisation of n-hexane, but simultaneously it isomerises to isoheptanes. however, as fig.3 shows, the ron of hexanes is higher than that of heptanes at equilibrium composition. the advantageous properties of isomerate were proved by blend optimisation runs (hpi gasoline blending optimizer, model-mg) performed with the use of other gasoline blending components (mtbe, n­ butane, light straight run gasoline, alkylate, fcc gasoline, reformate, hydrocrackate, raffinate, aromatics). the addition of isomerate helps to satisfy the new regulations by decreasing the· total aromatic, olefin, benzene and mtbe content (table 4). the sulphur content of the blended gasoline also decreased from 0.0199 % to 0.0175 % applying isomerate. but gasoline with less than 1 vol. % benzene can only be produced, if the reformate has less benzene content, i.e. its precursors are eliminated before the reforming unit [10]. the light gasoline can be upgraded in the isomerisation unit together with its original feed rich in csfc6 n-paraffins . in table 4 we also summarised the predicted emissions gained by the use of calculated gasoline properties. to predict the emissions the following equations, developed by auto/oil programme and conca we, were used [13,14]. emission of carbon monoxide, g km"1: eco= l2.459-q05513ei00+u000534§.~00+ +q009226ca -q000310!(97-cg)]. ·[i-q37·(~ -175)].[1-uoo& c-&.50-902)] 19 table 3 summary of the most important isomerisation results feed type a b c d e n-he12tane in feed, % 0.0 1.1 3.0 5.8 9.2 temperature, oc 260-270 260-270 260-270 260 260 hydrogen/hydrocarbon molar ratio 2:1 lhsv,h'1 1.0-1.5 1.0-1.5 1.0-1.5 1.0 1.5 liquid (c5+ )product characteristics yield,% 96.5-94.9 93.5-3.6 90.2-89.9 86.4 84.5 datec of2,2-dmb,% 77.4-68.2 73.3-63.2 64.0-63.2 60.8 43.0 datec of2-mp and 3-mp, % 99.8-99.9 99.8-99.7 99.8-99.6 98.5 89.2 isoand cycloparaffins yield,% 76.4-72.9 72.9-70.7 68.4-67.7 64.3 55.0 ron 82.4-82.2 82.4-82.0 82.1-82.0 82.1 81.6 mon 82.9-82.7 82.9-82.4 82.6-82.5 82.6 82.1 emission of hydrocarbons, g km-1 : ech= ~1347-0.000548!ca + 257 ca e -{o.264~oo) -0.000040$7-g;,)] [1-0.004 (col. -4.97)] [1-0.02~cbz -175)] [1-0.ol (e150-902)] emission of nitrogen oxides, g km'1: enox =[0.1884-0.001438ca +0.00001959e100 ·ca -0.00005302(97 -cs )]. . . [1 +o.oo(cm -4,97)]. [1 +0.001-(cez -175)]. · ~ +0.00~ei50 -90.2 )) emission of benzene; g km-1 : the emission predicting results confirm that the use of isomerate highly decreased the emission of co and benzene. the emission of hydrocarbons did not decreased significantly, though that of nox slightly increased. conclusions hexane fractions containing few percents (1-2 %) n­ heptane can be upgraded resulting in high octane number increase on pt/h-mordenite!alumina catalyst, under suitably chosen process parameters and recycling of components having low octane number. naturally the application of isomerisation of light gasoline fractions containing n-heptane strongly depends on the availability of technologies of a given refmery, needs of petrochemicals and the environmental protection regulations. however, based on our gasoline blending calculation data we proved the advantageous properties of isoparaffin rich fractions. furthermore, we pointed out that the connection of isomerisation and reforming units will become more important in the future. table 4 summary of the gasoline blending and emission predicting calculations number of blending calculation 1 2 3 4 some specifications of gasoline ron at least 95 limit of ea max., vol. % 40 limit of eb max., vol. % 2.0 2.0 1.0 1.0 benzene content of reformate, vol. % 4.0 4.0 4.0 2.0 blended gasoline at maximum profit use ofisomerate no yes yes yes aromatic content, vol. % 34.9 32.8 32.6 31.5 benzene content, vol. % 2.0 1.8 1.7' 1.0~ olefin content, vol. % 9.3 9.3 8.6 7.9 mtbe content, vol. % 0.9 0.5 0.9 0.5 sulphur content, % 0.0199 0.0204 0.0188 0.0175 calculated emissions, g km-1 co 1.25 1.18 1.18 1.16 hc 0.18 0.17 0.17 0.17 nox 0.15 0.16 0.16 0.16 benzene 0.063 0.059 0.058 0.050 moreover, emission-predicting results confirm that the use of isomerate decreases the emission of carbon monoxide, hydrocarbons, benzene, though that of nox slightly increases. symbols mtbe methyl tertiary butyl ether etbe ethyl tertiary butyl ether tame tertiary amyl methyl ether u.s.epa united states environmental protection agency ron research octane number mon motor octane number lhsv liquid hourly space velocity 2-:mp 2-methylpentane 3-:mp 3-methylpentane 2,2-dmb 2,2-dimethylbutane datec degree of approach of thermodynamical equilibrium concentration fcc fluid catalytic cracking concawe conservation of clean air and water europe 20 eco ech enox eb ewo e1so ca cm. coz cb cs emission of carbon monoxide, g krn-1 emission of hydrocarbons, g kni1 emission of nitrogen oxides, g krn-1 emission of benzene, g krn-1 volume percent distilled at 100°c, % volume percent distilled at 150°c, % total aromatics content, vol. % total olefin content vol. % oxygen content, % benzene content,vol. % sulphur content, % references 1. bur.ke n.j., claydon m. and cooper j.r.b.: development of a health surveillance programme for workers in the downstream petroleum industry, conca we report no. 96/54, 1-56, 1996 2. 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papraćanin, abdel đozić, ermin mujkić, maida hodžić, irma hodžić, belmin poljić and ajla ramić 1–6 optimization of erythritol fermentation by high-throughput screening assays edina eszterbauer and áron németh 7–10 the rhizosphere of petrosimonia triandra may possess growth-inducing and salinity-tolerance potential gyöngyi székely, norbert zsolt szígyártó, andrás tóth and csengele barta 11–15 investigations into the usage of the mineral alginite fermented with lactobacillus paracasei for cosmetic purposes pál tóth and áron németh 17–21 separation of dissolved gases from aqueous anaerobic effluents using gas-liquid membrane contactors merve visnyei, péter bakonyi, nándor nemestóthy and katalin bélafi-bakó 23–26 investigation of the pyrolysis of animal manure in a laboratory-scale tubular reactor: the effect of the process temperature and residence time maria elena lozano fernandez, szabina tomasek, csaba fáyköd and andrea somogyi 27–33 behavior of control and inhibitive polyaspartic coatings using alkylammonium and zinc phosphate corrosion inhibitors in soil abdu elhoud and tim van everbroeck 35–41 study on adsorption of essential oils on polylactic acid microparticles lilla virág, róbert bocsi and dóra pethő 43–49 optimization of bacillus licheniformis dsm13 for biosurfactant production using response surface methodology jesse john sakiyo and áron németh 51–55 utilization of agro-wastes in biohydrogen fermentation by various microorganisms katalin bélafi-bakó, gábor tóth, péter bakonyi and nándor nemestóthy 57–60 evaluation of pc-fmea using network analysis edina ungvári and istván gábor gyurika 61–64 https://hjic.mk.uni-pannon.hu/ hungarian journal of industry and chemistry vol. 50(2) pp. 1–6 (2022) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2022-10 separation of fumaric and maleic acid crystals from the industrial wastewater of maleic anhydride production edisa papraćanin1, abdel đozić2, ermin mujkić3, maida hodžić3, irma hodžić1, belmin poljić1 and ajla ramić1 1department of chemical engineering, faculty of technology, university of tuzla, urfeta vejzagića br. 8, 75000 tuzla, bosnia and herzegovina 2department of environmental engineering, faculty of technology, university of tuzla, urfeta vejzagića br. 8, 75000 tuzla, bosnia and herzegovina 3global ispat coke industry, željeznička 1, 75300 lukavac, bosnia and herzegovina in this research, a physicochemical analysis of the industrial wastewater from a factory that produces maleic anhydride was performed. based on the conducted analysis (ph, electrical conductivity, density of the liquid phase, boiling point of the waste suspension, chemical as well as biological oxygen demand, and dry matter), it can be concluded that the waste stream obtained at the outlet pipe from the plant resulting from the production of maleic anhydride requires appropriate treatments. some of the parameters measured, e.g. ph (0.97±0.06), boiling point (106.8±1.3°c) and acidity, indicate the presence of organic acids such as fumaric and maleic acid s, which are formed during the production of maleic anhydride. the possibility of extracting crystals by adding urea and thiourea followed by forced cooling in a heat exchanger was investigated. the most effective method was the addition of thiourea when the most significant amount of crystals was obtained, namely 17.29 wt%. the addition of thiourea in combination with forced cooling greatly facilitates the process of separating the solid and liquid phases of the waste suspension, which could later be adequately treated by physical, chemical or biological methods. keywords: man production, separation, thiourea, cooling, wastewater 1. introduction since the chemical industry and the waste streams generated during chemical production have a harmful effect on the environment, it is necessary to minimize their harmful impact before releasing them into the environment and comply with legal regulations, both locally and globally. moreover, it is important to conduct environmental impact assessments and environmental management with regard to the practical implementation of environmental regulations [1], e.g. determining the informative environment qualifying index. the production process of maleic anhydride (man) is based on two different technological processes in the gas phase, namely the oxidation of benzene and the oxidation of n-butane [2]. in 2015, the global capacity of man production amounted to 2800 million metric tons [3]. scientific and technological developments in the manufacture and use of maleic anhydride as well as maleic and fumaric acids have been reviewed over the past 20 years [4]. during man production, a certain amount of wastewater is generated, which must be received: 30 aug 2022; revised: 12 sept 2022; accepted: 15 sept 2022  correspondence: edisa.papracanin@untz.ba processed and treated in order to minimize environmental pollution. the increasing need to mitigate environmental impacts has led industries to develop more sustainable processes, which may be an arduous task since economic, safety, social and environmental factors must be considered [5]-[6]. the impact assessment of the chemical industry on the environment is becoming more and more important with regard to projecting and designing processes. a special problem is represented by facilities involved in exploitation, which are in the process of complying with eu regulations on environmental protection. given that bosnia and herzegovina, a country in transition, is increasingly adopting the laws of the european union, it is necessary to take measures that will reduce the harmful effects of the chemical industry both locally and globally. furthermore, the federation of bosnia and herzegovina has introduced legislation [7] which is in accordance with eu legislation. due to the fact that man production facilities have a detrimental impact on the environment, various methods have recently been applied for the treatment of wastewater streams. the wastewater flow from the man https://doi.org/10.33927/hjic-2022-10 mailto:edisa.papracanin@untz.ba papraćanin, đozić, mujkić, hodžić, hodžić, poljić, and ramić hungarian journal of industry and chemistry 2 production plant consists of a mixture of organic omponents, containing mainly fumaric and maleic acids, which can be treated by following different physical, chemical and biological methods [8]-[14]. considering the physical characteristics of fumaric and maleic acids [15], especially their solubility in water (fumaric acid is poorly soluble in water), a waste stream consisting of a crystal suspension as well as a mother liquor of fumaric and maleic acids is obtained at the outlet of the plant. before any treatment, such a suspension must be separated into the crystal flow and the mother liquor flow, which, if necessary, could be treated later or possibly reused to obtain products that do not require highly pure fumaric or maleic acid. this research was carried out in order to examine the possibility of separating the wastewater suspension from the industrial man production plant and the crystal stream, which consists of a mixture of fumaric and maleic acids along with other organic impurities, from the mother liquor stream. considering the physical, chemical and biological properties of the waste stream as well as its components, the goals of this research are to choose the most efficient method to separate the crystalline product from the waste stream in addition to making recommendations concerning its processing and further use in the industrial production of unsaturated polyester resins. another aim is to make recommendations for possible biological treatments by analyzing the liquid component of the waste stream. 2. experimental 2.1 treatment of the waste stream the waste stream of the suspension at the outlet of the man production facility owned by the company global ispat koksna industrija lukavac (gikil) (bosnia and herzegovina) was used in this research. the abovementioned waste stream is generated discontinuously by the process of washing the distillation column and cooler with water at a temperature of 100°c. in the aforementioned industrial plant, the distillation system is washed every 4 days when approximately 70 m3 of water is consumed in an hour, resulting in water with a low ph due to the presence of maleic and fumaric acids. the aftercooler is washed twice a month, consuming 10 m3 of water. given that wastewater contains fumaric acid, which is the basic raw material for the production of unsaturated polyester resins, it is necessary to investigate the possibility of using this waste stream in terms of extracting (crystallizing) fumaric acid. the total amount of waste suspension generated under industrial conditions on a monthly basis is approximately 300 m3, which has a significant impact on the environment if it is not processed adequately. experimental research and analyses were carried out in the chemical engineering laboratory of the faculty of technology at the university of tuzla. samples were taken twice a month directly at the outlet of the tank used to collect the waste stream. most samples were taken after the first wash when the concentration of organic matter is the highest. the samples immediately after being taken from the plant and after being delivered to the laboratory are shown in fig.1. they were collected and delivered to the laboratory in plastic containers with a volume of 5l. certain aliquots were extracted to perform physicochemical and other analyses. based on the research objectives, the following tasks were conducted: laboratory modelling of the washing of the distillation column and the discharge of the waste stream was performed; physical and chemical analyses of the waste stream were performed under laboratory conditions; the quantity of the resulting crystalline product was determined in relation to the volume of the waste stream under laboratory conditions; examination of the possibility of extracting crystals from the waste stream was carried out in several ways: a) by cooling the flow under laboratory conditions, b) by adding urea and thiourea, c) by cooling the waste stream with water in a system of tubular heat exchangers. among the physicochemical analyses, the ph, electrical conductivity, boiling point as well as the chemical and biological oxygen demand were measured. all measurements refer to a homogenized sample, moreover, after separating the liquid and solid phases, the dry matter and acidic properties of the liquid phase were determined. (a) (b) figure 1. the samples: (a) immediately after being taken from the plant; (b) after being delivered to the laboratory. separation of fumaric and maleic acid crystals 50(2) pp. 1–6 (2022) 3 the density of the liquid phase was determined using a pycnometer and the bulk density of the dried crystalline product was measured according to the iso 1183-1:2004 standard. 2.2 materials and methods for the purpose of experimental modelling, washing of the distillation column and the discharge of the waste stream, a special system was designed, consisting of a glass container with a volume of 25 liters with openings at the top and bottom. the vessel includes a distillation column and a glass vessel of the same volume was used as a receiving vessel. the amount of sample used was 5 liters and was preheated to 100°c. to obtain a real picture of the industrial plant, the process of crystal formation was tested by cooling down the waste stream to ambient temperature (laboratory conditions). 250 ml samples that were observed were taken from a 5-liter sample after mixing and heating to a temperature of 100°c. the resulting crystals were filtered and air-dried under laboratory conditions. following the addition of urea and thiourea, the 400 ml samples preheated to 100°c, the temperature of the rinsing water, were taken from a 5-liter sample. the test was performed by adding urea and thiourea in different percentages concerning the volume of the sample. after the addition of urea and thiourea, the samples were allowed to settle before the crystals were separated by filtration on filter paper and air-dried. for the purposes of testing whether the waste suspension stream crystallizes, a cooling system consisting of three laboratory-scale tubular heat exchangers was designed. the cooling conditions and crystal formation were investigated for different flow rates of cooling water. the cooling system is shown in fig.2. the total area for heat exchange of the laboratoryscale cooling system was about 0.43 m2. once the waste suspension had passed through the tubular cooling system, the resulting crystals were collected on a metal grid and placed on a glass container before being dried and weighed on an analytical scale. all measurements were performed three times and statistical data processing was conducted in microsoft excel, namely the mean and standard deviation were calculated. electrometric measurements of the ph and electrical conductivity were carried out by direct measurements using a mettler toledo fe 2030/el 20-30 ph meter/conductometer. the ph was measured using the standard method bas en iso 10523, while the electrical conductivity was determined using the standard method bas en 27888. the chemical oxygen demand (cod) is the oxygen equivalent of the amount of potassium dichromate consumed during the complete oxidation of the organic matter in the measured volume of the sample. the cod and biological oxygen demand (bod) are determined by the bas iso 6060 and bas en 1899-1 methods, respectively. after separating the liquid and solid phases, the liquid sample was filtered, evaporated at 100°c and dried overnight in an oven before the mass of the dry matter was measured on an analytical scale. the content of the dry matter was determined according to method 2540solid b [16]. furthermore, the solid phase in the solid sample was analysed gravimetrically by drying it at 105°c for 24 h. 3. results and evaluation 3.1 characterization of the waste stream considering that the waste stream represents a heterogeneous mixture (suspension) under laboratory conditions, for the purpose of the analysis, the samples were homogenized and heated to a temperature of 100°c because the waste stream was obtained by washing the distillation column in the man plant with water at a temperature of 100°c. on the walls of the distillation column, organic substances, predominantly fumaric and maleic acids, are deposited that may occur during the production of man. due to its physical and chemical properties, fumaric acid is insoluble in water, while the solubility of maleic acid in water is 478.8 g/l at 20.0°c, i.e. 3926 g/l at 97.5°c [17]. therefore, by washing the distillation column, a suspension is formed in which crystals of fumaric acid as well as a solution of maleic and fumaric acids are present. considering the aforementioned fact and the boiling points of the pure acids, fumaric acid at 287°c and maleic acid at 135°c [15], the boiling point of the suspension was measured to be 106.81.3°c under laboratory conditions. this data indicate the presence of other substances that have significantly lower boiling points compared to the components that are primarily present. as expected, the measured ph is very low, namely 0.970.06, due to the presence of organic acids, while the measured electrical conductivity is 33.624.03 ms. in view of the ph prescribed in [6], the measured value does figure 2. schematic diagram of the waste-stream cooling system: 1) glass container for rinsing, 2) system consisting of three tubular heat exchangers, 3) cup containing the sample, 4) glass funnel, 5) metal grid for collecting crystals papraćanin, đozić, mujkić, hodžić, hodžić, poljić, and ramić hungarian journal of industry and chemistry 4 not comply with the legal framework, which indicates that this waste stream of industrial wastewater should be treated in an appropriate way. the relatively low electrical conductivity, for which no legally prescribed limits are found, indicates a low concentration of free ions in the waste stream. a pycnometer measured the density of the liquid phase after separation to be 1038.844.31 kg/m3, while the bulk density of the solid phase was 394.01.4 kg/m3. to further examine the characteristics of the waste stream, the cod and bod of the homogenized sample were determined to be 233600 and 87280 mg o2/l, respectively. the permitted limits for the discharge of a waste stream into the environment for cod and bod are 25-250 and 135-700 mg o2/l, respectively, which indicates the need for pretreatment of the waste stream before being discharged into the environment. by separating the solid and liquid phases by filtering and decanting under laboratory conditions, a homogenized 2.5 l sample contains 5.090.05 wt% of dry crystalline products. as a result, the total amount of solid matter discharged every month (300 m3) is about 15.27 kg. therefore, a huge amount of solid waste can be treated or possibly used for other purposes. the amount of dry matter in the liquid phase is 16.30.2 wt%, which also exceeds the permitted limits. by titration of the liquid phase with naoh and phenolphthalein as an indicator, it was determined that 1 g of the liquid solution is titrated with 3.95 mmol of naoh. in simple terms, if the acidity is due to the presence of maleic acid, this would correspond to a maleic acid concentration of 0.247 mg/ml. 3.2 separation efficiency considering the results of the physicochemical analysis of the industrial waste stream resulting from man production, it was observed that this waste stream must be adequately treated before being discharged into the environment. due to the composition and characteristics of the waste stream, it is necessary to separate it into the solid and liquid phases. in this research, several experiments based on different methods were conducted to obtain an efficient method for separation. as described earlier in the experimental section, before testing the aforementioned methods, laboratory modelling of the process by which the distillation column is washed was carried out. the reason for performing the experimental simulation is to experimentally and visually determine how the crystals are formed during the discharge of the waste-stream suspension into the collector. during the simulation, it was observed that immediately after the waste stream comes out of the outlet pipe, a larger amount of crystals were formed, meaning that other organic substances, predominantly maleic acid, also crystallized. simply by highlighting the flow, a sudden drop in the temperature of the flow from 100°c to ambient temperature is observed, during which more intense crystallization occurs. following this observation, a system of three heat exchangers (fig.2) was designed under laboratory conditions to cool down the waste stream more quickly and test such an efficient way of separating the solid and liquid phases. at the outlet from the cooling system, a container collected the waste flow, on top of which a metal grid to separate the crystals was placed. after the cooling and separation processes, the crystalline product obtained was dried and measured. the mass of crystals obtained by forced cooling (sample volume of 5 l) was 638.372.34 g, that is, 12.3 wt% of the dry crystalline product. compared with the amount of crystals obtained by natural cooling to ambient temperature, it can be seen that this method (forced cooling and separation by filtration) is significantly more efficient. this technique of collecting crystals on a metal grid is very simple to perform due to the very structure and size of the resulting crystals. the appearance of the crystals obtained is shown in fig.3. after experiments were performed using forced cooling, the influence of the addition of urea and thiourea on the formation and separation of crystals of organic substances in the industrial waste stream was examined. these components were added to better isolate the crystalline product from the mixture of fumaric and maleic acids, that is, thiourea acts as a catalyst in the isomerization of maleic acid to fumaric acid [18]. the masses of the resulting crystalline product following the addition of urea and thiourea are presented in table 1. analyses were performed using a sample that figure 3. crystals obtained by forced cooling table 1 mass of the crystalline product obtained following the addition of urea and thiourea mass added (g) volume of filtrate collected (ml) mass of crystals (g) thiourea urea thiourea urea 1 100 200 69.0 44.9 3 60 210 71.4 46.7 5 150 200 71.8 46.9 separation of fumaric and maleic acid crystals 50(2) pp. 1–6 (2022) 5 was heated to 100°c and homogenized in a volume of 400 ml. the masses of urea and thiourea added were 1, 3 and 5 g. samples where different amounts of urea and thiourea were added (u1 and t1 1g, u2 and t2 3g, u3 and t3 5g) are shown in fig.4. as can be seen in table 1, the largest amount of crystalline product was obtained following the addition of 5 g of thiourea. as a percentage of the 400 ml sample, this value is 17.29 wt% of dry crystalline product, which is significantly more compared to forced and natural cooling of the waste stream. the addition of urea also enhances separation of the solid phase from the suspension of the waste stream, however, considering the results obtained, the effect of adding thiourea on the separation process is significantly greater. as can be seen in the table, given that the amounts of the crystalline product obtained following the addition of all three amounts of thiourea are very similar, an additional experimental optimization of the mass of thiourea to be added to the waste stream was performed. amounts of less than 1 g were added to see if a larger difference in the amount of crystalline product formed was observed. amounts of thiourea added of less than 1 g are presented in table 2. as can be seen, even small amounts of thiourea significantly enhance the separation of crystals from the waste stream. if 1 g of thiourea is added to a suspension sample of 400 ml as an optimal cost price and to achieve separation of the crystals when treating the waste stream generated from an industrial plant, it would be necessary to add 750 kg to 300 m3 of waste suspensions per month, which is a huge amount. however, if 0.25 g of thiourea is added to a suspension sample of 400 ml, which equates to approximately 0.06%, about 1250 kg of thiourea would need to be added annually at a cost of approximately $98,550 [19]. in this case, this price is reasonable if the separated fumaric acid crystals were to be used for the production of resins. in light of the research conducted, in the future, some other methods for extracting the mixture of fumaric and maleic acid crystals should be examined, which would be economically profitable and technologically feasible in an already existing plant. furthermore, the composition of the crystalline product following the addition of thiourea should be tested using appropriate methods and analyses. 4. conclusions in this research, a physicochemical analysis of the wastewater flow from an industrial plant resulting from the production of maleic anhydride was conducted. based on the obtained results, it is evident that a very low ph as well as electrical conductivity indicate the presence of organic acids left over from distilling man. given that the resulting flow is a suspension flow at the temperature of water used to wash the distillation column as well as the physical and chemical properties of fumaric and maleic acids, it can be stated that both are the two dominant components in the waste flow. this was also confirmed by determining the acidity by titration with naoh. the research determined the density of the liquid phase as well as the bulk density of the separated crystalline product. by carrying out different experimental methods, the crystals were separated from the waste suspension by a combination of cooling and the addition of thiourea, a technique which can be applied in an industrial plant, facilitating the isomerization reaction of maleic to fumaric acid. furthermore, the installation of a metal grid at the inlet to the receiving court is a simple structural solution whereby the resulting crystalline product, with appropriate analyses, could be used in processes that do not require highly pure fumaric acid, e.g. resin production. the liquid component, that is, the mother solution obtained by separating the waste suspension, due to the high cod and bod, following the adjustment of other parameters like ph, could be successfully treated by the process of anaerobic digestion or co-digestion. therefore, the liquid stream could serve as a good co-digestate for adjusting the characteristics of waste sludge that is normally applied in anaerobic digestive processes. following a literature review, since it was observed that very few studies have been conducted in this regard or require significant financial resources, this research opens up new possibilities and perspectives for the implementation of simple as well as inexpensive industrial and implementable solutions. figure 4. separation of crystals by cooling at room temperature following the addition of urea and thiourea: u1, u2, u3 – samples to which urea was added; t1, t2, t3 – samples to which thiourea was added table 2 mass of the obtained crystalline product 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https://doi.org/10.1016/j.desal.2017.01.039 https://www.ilo.org/dyn/icsc/showcard.home https://doi.org/10.1021/acs.oprd.9b00487 https://www.chemicalbook.com/price/thiocarbamide.htm hungarian journal of industry and chemistry vol. 50(2) pp. 7–10 (2022) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2022-11 optimization of erythritol fermentation by high-throughput screening assays edina eszterbauer1 and áron németh1* 1 department of applied biotechnology and food science, budapest university of technology and economics, műegyetem rkp. 3, budapest, 1111, hungary in this research, the erythritol-producing ability of three yarrowia lipolytica strains was investigated. the focus of our research was to achieve the highest possible erythritol concentration by examining and optimizing the cultivation conditions of erythritol fermentation. the complex utilization of the produced fermentation broth was also sought, e.g. the ergosterol extraction of yeast cells and isolation of a biodetergent from the foam formed during erythritol fermentation. erythritol is a naturally occurring, widespread sugar alcohol that is gaining popularity, moreover, due to increases in usage, its demand among consumers is rising, which is why the importance of its biological production is becoming all the more critical in the food industry. erythritol is 60 -70% as sweet as sucrose and a low-calorie sweetener. some microorganisms are capable of producing erythritol from glucose, meanwhile yarrowia lipolytica strains have been reported as glycerol-consuming erythritol producers. these two sources of carbon were compared despite being subjected to further conditions like the initial ph, nitrogen sources and some additives. the largest production of erythritol was achieved by y. divulgata resulting in 44g/l on glycerol compared to only 2g/l on glucose. the best supplementation was found to include ammonium nitrate and sodium citrate resulting in a product yield of 33%. keywords: erythritol, fermentation, yarrowia, glycerol, glucose 1. introduction due to the current lifestyle of society, the number of people suffering from diabetes mellitus and obesity is increasing. the desire of consumers to become healthier has created a whole market for sugar-free and zerocalorie foods, an important part of which is the production of sugar alcohols called polyols. erythritol (c4h10o4) is a naturally occurring sugar alcohol. since the synthesis of erythritol is more difficult than those of other polyols, intensive research has been conducted to optimize its production in terms of the erythritol concentration, production rate (productivity) and/or yield [1]. although erythritol is 60-70% as sweet as table sucrose, it is almost calorie-free (0.2 kcal/g), does not affect the blood sugar level nor cause tooth decay [2], has antioxidant effects, binds free radicals, possesses a glycemic index of 0 and increases the ability to absorb fructose [3]. many methods are available to produce erythritol, both chemically and biotechnologically. even though one of the most well-known chemical methods is high-temperature chemical synthesis from dialdehyde starch in the presence of a metal catalyst, namely nickel, which yields equimolar amounts of erythritol and ethylene glycol, this chemical process involves several received: 2 sept 2022; revised: 16 sept 2022; accepted: 20 sept 2022 *correspondence: naron@f-labor.mkt.bme.hu steps [2,4-5]. however, it is not used in industry due to its very low yield and relatively high costs. currently, biotechnological methods are far superior to chemical methods. the large-scale production of erythritol uses microbial fermentation processes with pure glucose, sucrose and glucose syrup from chemically and enzymatically hydrolyzed wheat and corn starches [2]. the main microbiological strains in the synthesis of erythritol are osmophilic yeasts, e.g. moniliella pollinis, trichosporonoides megachiliensis and y. lipolytica, as well as many strains of lactic acid bacteria, e.g. oenococcus oeni, leuconostoc mesenteroides and lactobacillus sanfranciscensis [5]. within the food industry, erythritol is mainly used as a sweetener in finished goods. sugar-free, reduced sugar and calorieor sugar-free alternative foodstuffs can be produced. as a sugar substitute, erythritol can be found as a tabletop sweetener as well as a sweetener in drinks, chewing gum, chocolate, candy and baked goods. polyols are also commonly used in products from the personal care industry such as cosmetics or toiletries. as an additive, it is increasingly included in care products such as toothpastes, mouthwashes, creams, make-up, perfumes or deodorants. due to its properties, erythritol offers good fluidity and stability as an excipient, making it an ideal candidate for active ingredients in sachets and capsules [6]. yarrowia lipolytica is one of the most https://doi.org/10.33927/hjic-2022-11 mailto:naron@f-labor.mkt.bme.hu eszterbauer and németh hungarian journal of industry and chemistry 8 widely studied species of yeast [7]. y. lipolytica exhibits strong proteolytic and lipolytic activity [8-9]. one of its most important products is lipase, an enzyme widely used in various areas of industry. y. lipolytica can produce succinic acid [15] as well as erythritol and mannitol using glycerol as a substrate both in the presence and absence of sodium chloride [10]. erythritol (170 g/l) was produced at ph 3.0 with the acetate-negative strain y. lipolytica wratislavia k1 by fed-batch fermentation [11]. in terms of its industrial use, it is most widespread in the food industry, moreover, is known for both its positive and negative effects [8]. to increase erythritol production, the effects of various additives, including sodium citrate and mannitol, were investigated in order to down-regulate the formation of by-products during erythritol fermentation. furthermore, the supplementation of metal ions provides cofactors for key enyzmes [10], various nitrates [13] and polyethylene glycol (peg) as an osmoticum [12]. 2. experimental the planned experiment in terms of erythritol production was performed by three yarrowia lipolytica strains from the national collection of agricultural and industrial microorganisms (ncaim, hungary), namely ncaim yarrowia lipolytica 00597, ncaim yarrowia lipolytica 00594 and ncaim yarrowia divulgata 1485. during the fermentations, a 24-well deep-well microtiter plate (fig.1) was applied with a sandwich cover by enzyscreen.com (the netherlands) for each strain separately since many small-scale experiments can be conducted at the same time. due to the high osmotic pressure and low ph during erythritol production, cells grow slowly, so a thorough study of many parallel fermentations needs to be performed. using the microtiter plate, 24 experiments in different or even the same media in parallel fermentations were performed simultaneously to provide a comparison. the ability of the strains to produce erythritol and the conditions required for erythritol fermentation were examined in order to increase the efficiency of production and achieve the highest possible erythritol concentration. the effects of the initial ph and c:n ratio were investigated during the fermentation. given that previous studies [12,14] have shown that proper osmolarity has a significant effect on erythritol production, the effect of changing it was also investigated to determine the most appropriate range of osmolarity for erythritol production with these strains. the main consideration was the comparison of two substrates, that is, glycerol and glucose, in terms of erythritol production. after determining the most efficient fermentation conditions, our intention was to scale up the process. in the case of significant erythritol production, extraction of the product from the fermentation medium was sought. our aim was to use the residual cells, e.g. yarrowia lipolytica lysates, to further investigate cosmetic purposes after ultrasonic treatment. all the inoculum medium was contained, that is, glycerol (50 g/l), yeast extract (3 g/l), malt extract (3 g/l) and peptone (5 g/l). the erythritol fermentation medium was also contained, namely glycerol (150 g/l), nh4cl (3 g/l), mgso4*7h2o (1 g/l), kh2po4 (0.2 g/l) and yeast extract (1 g/l) [11]. in order to increase erythritol production, the effects of the following additives was also tested. 20 g/l of both mannitol and sodium citrate were added during the fermentation. metal ion supplementation resulted in the following concentrations of salts in the medium: cuso4*5h2o (2.5 mg/l), feso4*7h2o (10 mg/l), mnso4*7h2o (25 mg/l) and znso4*7h2o (20 mg/l). 100 g/l of the supplement peg (polyethylene glycol) was added, moreover, 4.6 g/l of nitrate supplementation was applied. furthermore, cofermentation was investigated in combination with the two carbon sources, namely glucose and glycerol. the strains were inoculated in 100 ml of inoculum medium in 250 ml flasks and incubated on a rotary shaker (new brunswick innova 40) at 250 rpm for 3 days at 25°c. all wells of the microplate contained 5 ml of fermentation medium and were incubated on a rotary shaker at 250 rpm for at least 20 days at 25°c. the ph was measured by a mettler toledo fiveeasy ph meter and controlled at 3.0 with naoh (6n). the cell density was measured optically at 600 nm by a camspec m501 single beam uv/vis spectrophotometer every other day. fermentation products were determined by a waters breeze isocratic hplc system equipped with a bio-rad aminex hpx87h column at 65°c. an ri detector was applied at 40°c and the eluent was 5mm h2so4 in ultrapure water (simplicity, millipore). to determine the osmotic pressure of the fermentation, 60 µl of fermentation medium was analyzed by measuring the freezing-point depression using an osmometer (gonotec osmomat 3000). figure 1. deep-well microplate erythritol fermentation 50(2) pp. 7–10 (2022) 9 3. results and discussion 3.1. yarrowia lipolytica strain 594 y. lipolytica strain 594 was produced using the least amount of erythritol compared to the other two tested strains. the highest concentration (10.95 g/l) was achieved on the 14th day of the fermentation in the basic fermentation media containing 100 g/l glycerol with 50 g/l glucose supplementation, i.e. co-fermentation. the highest product yield of 14.81% was also recorded using the same experimental setup, where glycerol in the media was completely consumed but not the glucose. in the case of y. lipolytica strain 594, it can be stated that erythritol was not produced when only glucose was used as a substrate together with any of the other supplements. the highest erythritol concentration of 8.65 g/l was achieved when glycerol was used as the substrate supplemented with peg, which is also rather low in comparison to other reports. glucose as a substrate was not useful with regard to erythritol production using y. lipolytica strain 594. 3.2. yarrowia lipolytica strain 597 y. lipolytica strain 597 was able to produce more erythritol than y. lipolytica strain 594. the highest concentration (14.04 g/l) was produced in glycerol containing a medium supplemented with nano3, which was achieved on the 20th day of fermentation and corresponded to a yield of 30.31%. the average osmolarity with a slight decrement was 2243 mosmol/kg, which is twice that of glucose. the maximum osmolarity of the medium containing glucose was approximately 1200 mosmol/kg, which decreased in correlation with the reduction in glucose concentration. this may explain why erythritol was produced in larger quantities in the medium containing glycerol. glycerol was only completely consumed by the end of the fermentation when the media were combined, containing 100 g/l of glucose and 50 g/l of glycerol. on the 14th day, erythritol production had reached its maximum (11.13 g/l), after which its amount began to decrease. although the osmolarity was 1043 mosmol/kg on the 14th day, it was initially 1346 mosmol/kg. in the case of glucose, the highest concentration of erythritol was 2.04 g/l, which was achieved in a medium supplemented with ammonium sulfate and corresponded to a yield of 4.54%. using this setup, even though the average osmolarity was 1165 mosmol/kg, which is very low for erythritol production, 4.24 g/l of mannitol was produced. therefore, when glucose was used as the substrate supplemented with ammonium sulfate, mannitol was produced by y. lipolytica strain 597 instead of erythritol. 3.3 yarrowia divulgata strain 1485 once again, two different substrates, namely glycerol and glucose, were compared. among the tested additives (fig.2a), the largest increase in erythritol concentration was experienced in the case of sodium citrate compared to the control samples. the highest concentration of erythritol (44.38 g/l) was produced by y. divulgata on the 18th day of the fermentation using glycerol as a substrate supplemented with sodium citrate (fig.2b). the glycerol was completely used up in the medium. the highest productivity of 0.1 (g/l)/h and highest yield of 37.86% were achieved with this supplementation. the osmolarity of the medium decreased in correlation with the exhaustion of glycerol from 2371 mosmol/kg initially to 1099 mosmol/kg by the end of the fermentation. in the case of peg and metal supplementation, 32.44 and 8.31g/l of erythritol had been produced by the end of the fermentation, respectively. among the tested nitrogen sources (fig.2c), ammonium nitrate yielded the highest erythritol concentration of 30.75 g/l, corresponding to a yield of 31.11% based on glycerol. compared to the control media, neither of the nitrogen figure 2. results of y. divulgata strain 1485 a) effect of supplements, b) time course of best run, c) effect of n-sources a b c eszterbauer and németh hungarian journal of industry and chemistry 10 sources could significantly increase the erythritol production. by the end of the fermentation supplemented with ammonium nitrate, 5.13 g/l of mannitol had been produced. regarding the fermentations supplemented with ammonium sulfate and sodium nitrate, 27.60 and 23.87 g/l of erythritol had been produced by the end of the fermentation, respectively. in the case of the substrate glucose, the highest production of erythritol (12.95 g/l) was achieved in the medium supplemented with sodium citrate. 4. discussion in the present work, 3 strains of yarrowia species were examined on two carbon sources, namely glycerol and glucose, in terms of erythritol fermentation. glycerol proved to be more usable. among the 3 yarrowia strains tested, y. divulgata was the most productive, achieving 44.38 g/l of erythritol in the media supplemented with sodium citrate during the microplate fermentation. in the case of y. lipolytica strain 594, the highest erythritol concentration of 10.95 g/l was achieved without supplementation but in a medium containing 100 g/l of glycerol supplemented with 50 g/l of glucose on the 14th day of the fermentation. finally, in the case of y. lipolytica strain 597, the highest concentration of erythritol was 14.04 g/l in the medium supplemented with sodium nitrate. the tested supplementations could increase the erythritol concentration from 24.70 to 44.38 g/l, yield from 33.15 to 37.86% and productivity from 0.049 to 0.102. among the reported yarrowia results, although the aforementioned erythritol concentrations achieved are not particularly high, y. divulgata may reach the recently used strains after optimization. in addition to the use of erythritol alone, the complex utilization of the broth for the application of ergosterol and cosmetics may be of greater interest and feasibility. in the future, given the high number of variables influencing erythritol productivity, a neural network will be used to optimize erythritol fermentation for y. divulgata strain 1485, which proved to be the best. additionally, isolation and determination of the ergosterol content of 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https://doi.org/10.33927/hjic-2019-13 hungarian journal of industry and chemistry vol. 50(2) pp. 11–15 (2022) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2022-12 the rhizosphere of petrosimonia triandra may possess growthinducing and salinity-tolerance potential gyöngyi székely1,2,3*, norbert zsolt szígyártó1,2, andrás tóth1,2 and csengele barta4 1 hungarian department of biology and ecology, faculty of biology and geology, babeș -bolyai university, 5-7 clinicilor st., cluj-napoca, 400006, romania 2 institute for research-development-innovation in applied natural sciences, babeș-bolyai university, 30 fântânele st., cluj-napoca, 400294, romania 3 centre for systems biology, biodiversity and bioresources (3b), babeș -bolyai university, 5-7 clinicilor st., cluj-napoca, 400006, romania 4 department of biology, missouri western state university, 4525 downs drive, agensteinremington halls, st. joseph, mo 64507, usa the root microbiome of halotolerant plants can represent a great source of salt-tolerant plant growth-promoting rhizobacteria (st-pgpr) with a wide range of beneficial effects on plants growth, development and productivity. the better understanding of the variety of complex salt tolerance and adaptive mechanisms of haloph ytes can contribute to improve salt tolerance in crops, and as a result, a better and increased use of saline areas worldwide. in addition, reclaiming saline areas for agricultural use may be able to alleviate the global threat of progressive soil salinization. keywords: st-pgpr, molecular analysis, saline soil 1. introduction although the threat of the continuous expansion of areas of saline soil exhibiting enhanced levels of salinity has a negative effect on soil structure, fertility and plant health, by progressively constraining plants in narrower habitats, they can grow and develop optimally without experiencing the negative, stressful impacts of saline conditions. habitat narrowing is expected to decrease biodiversity and have negative impacts on the usability of land for agricultural practices. one of the most damaging abiotic stress factors for plants is the excessive accumulation of salt in their natural habitats caused by soil salinization. soil salinity is most often defined by its electrical conductivity (ec) with values above 4 dsm−1 indicative of saline soils [1]. soil salinity can be determined by the occurrence of a variety of salts such as nacl, na2so4, na2co3, mgso4, mgcl2, kcl and caso4. all of these salts have the potential to induce salinity stress in plants. from among the aforementioned salts, the accumulation of nacl is the most frequent in soils. the adverse effects of nacl stress on plants has been extensively documented [2-4]. saline soils represent a substantial limiting factor for the development and propagation of the majority of plant species belonging to the group of non-halophytes (also referred to as glycophytes). only halophytes, that is, received: 20 sept 2022; revised: 27 sept 2022; accepted: 27 sept 2022 *correspondence: gyongyi.szekely@ubbcluj.ro plants adapted to and capable of achieving optimal development in saline environments, can persist in saline soils. to counteract salinity stress, salt-tolerant species have developed a wide range of tolerance traits such as osmotic adjustment, ion sequestration, ion exclusion, adaptations of the membrane transport system and protection enhanced by the synthesis of a variety of macromolecules with osmolytic properties, e.g. glycine betaine, proline, etc. [5]. petrosimonia triandra is a halophyte able to complete its life cycle under moderate saline conditions (ec: 4.45 dsm−1) native to the saline area of cojocna in cluj county, romania (fig.1) [6]. while the salt tolerance mechanisms of p. triandra are currently poorly understood, podar et al. (2019) documented several adaptive mechanisms in this species that can withstand soil salinity such as morphological, physiological and biochemical adaptations, e.g. the development of efficient photosynthetic and antioxidative systems as well as the accumulation of the protective osmolyte proline. similar salt tolerance mechanisms have also been documented in other halophyte species [7-8]. another strategy of halophyte plant species to improve their range of salt tolerance is co-habitation with groups of rhizosphere-specific bacteria called plant growth-promoting rhizobacteria (pgpr), which live in the immediate vicinity of plants’ root systems (also referred to as the rhizosphere) as well as exert a positive https://doi.org/10.33927/hjic-2022-12 mailto:gyongyi.szekely@ubbcluj.ro székely, szígyártó, tóth and barta hungarian journal of industry and chemistry 12 effect on plant growth and development. these effects are underpinned by diverse mechanisms such as the addition of essential nutrients (n, k, zn, fe, po4); production of 1-aminocyclopropane-1-carboxylate (acc) deaminase, volatile organic compounds and phytohormones; as well as the facilitation of favorable plant-microbe interactions, antifungal effects, etc. [9-10]. some pgpr species have been found to be salt tolerant, namely st-pgpr, and successfully used over recent decades to enhance crop yield and improve soil fertility. most recently, ayub et al. (2020) clearly emphasized the role of pgprs in the salt tolerance of halophytes. in addition, nowadays, st-pgprs are also used as bioinoculants to improve crop productivity and provide protection from phytopathogens [11-12]. therefore, stpgprs are promising tools to enhance the salinity tolerance of plants. the goal of the current study was to identify stpgpr species from the rhizosphere of p. triandra. a better understanding of the rhizobial community contributing to the enhancement of salt tolerance in species adapted to and native to saline areas is expected to lead to valuable applications, thereby enhancing the tolerance of high-value crops and other species of horticultural use as well as provide technologies to expand land-use practices for agricultural purposes to underutilized, highly saline areas [13]. 2. experimental 2.1. soil sampling site soil samples were collected from the rhizosphere of the halophyte p. triandra, native to the saline zone of cojocna in cluj county, romania (gps coordinates n46.74328 e23.84295, fig.1). the salinity of this site is characterized by ec = 4.45 dsm-1, which corresponds to moderate saline soil [1]. the specific physicochemical characteristics of the soil at the sampling site have been described in our former study [6]. 2.2. isolation of bacterial species from the rhizosphere of p. triandra p. triandra plants were carefully dug up and removed from the soil before gently shaking their roots to remove the excess soil. the soil that was directly adhered to the roots was collected and transported back to the laboratory for analysis where it was transferred into a flask containing 99 ml of sterilized distilled water. after shaking the flask for 15 minutes, the soil samples were subjected to a 10-fold serial dilution and 100 µl of the solution was spread on plates containing nutrient agar (na) media (merck, germany) supplemented with 2, 4, 6, 8, 10, 11, 11.5, 12, 12.5 and 13% nacl, respectively. the plate containing na without external nacl was used as the control sample. the plates were incubated at room figure 1. a: location of the study zone in cojocna, romania; b: the habitat of p. triandra in cojocna; c: young p. triandra plants temperature with colonies appearing 3-4 days after inoculation. 2.3. identification of salt-tolerant rhizobacteria using a 16s rrna gene sequence to identify the rhizosphere of bacterial species, strains exhibiting the highest salt tolerance were selected, namely 11.5, 12 and 12.5% nacl. thirty colonies were selected for dna isolation, pcr and gene sequencing of their 16s rrna gene. having extracted the total genomic dna (qiagen, germany), a fragment of the 16s rrna gene was amplified by pcr using the 16s rrna universal primers (27f: 5′agagtttgatcctggctcag-3′ and 1492r: 5′ggttaccttgttacgactt-3′). the pcrs were mixed using a bioline pcr kit with the polymerase mytaq red mix (bioline, meridian bioscience, memphis, tn) in a final volume of 50 µl. the pcrs were performed using a multigene optimax thermal cycler (labnet, cary, nc) under the following cycling conditions: 5 mins. at 95°c, followed by 30 cycles lasting rhizosphere of petrosimonia triandra 50(2) pp. 11–15 (2022) 13 table 1. identified rhizosphere bacteria and the salt concentration facilitating their optimum growth no. pgpr name nacl tolerance (%) 1. bacillus hwajinpoensis fjat-46935 12.5 2. bacillus sp. ls-x7 12.5 3. bacillus sp. ebw4 12.0 4. bacillus sp. ytm5 11.5 30s each at 94°c, 30s each at 55°c and 1.5 mins. each at 72°c followed by a final extension step at 72°c for 7 mins. 5 μl aliquots of each reaction were analyzed on 1% (w/v) agarose gel in tbe buffer, stained with midori green advance nucleic acid staining solution (nippon genetics europe, düren, germany). the resulting ~1500 bp pcr product was purified using an agarose gel extraction kit (jena bioscience, jena, germany) according to the manufacturer’s protocol and sent for sequencing at the genomic sequencing service provider macrogen (south korea, http://dna.macrogen.com/eng). blast analysis and gene sequencing were also performed by macrogen. 3. results and discussion 3.1. determination of the nacl tolerance of the rhizobacteria p. triandra rhizobacteria isolated in close proximity to the roots of p. triandra could survive in a media supplemented with up to 12.5% nacl (fig.2). 46 bacterial colonies were able to grow in the presence of salinities as high as 11.5, 12 and 12.5% nacl. the number of bacterial colonies grown in saline media decreased as the nacl concentration increased. a total number of 26, 12 and 8 bacterial isolates survived in salinities of 11.5, 12 and 12.5% nacl, respectively. the 8 most salt-tolerant bacterial isolates survived in the presence of 12.5% nacl. based on their highest level of salt tolerance and diverse morphology, 30 isolates were selected for molecular identification. 3.2. identification of salt-tolerant rhizobacteria the bacterial 16s rrna gene sequence analysis determined that of the 30 selected isolates, 26 belonged to the bacillus genus (bacillus sp. strains ebw4, ls-x7, ytm5) with one of them identified as the b. hwajinpoensis strain fjat-46935. the other four isolates could not be identified. the names of the isolates and their highest salinity tolerance are presented in table 1. the important role of some of the identified p. triandra rhizobacteria in enhancing plant growth, yield and salt tolerance has been described previously [14]. a plant growth-promoting effect of the rhizosphere bacterial strain bacillus sp. ebw4 was reported by utkhede and smith in 1992 [15], who highlighted an figure 2. bacterial isolates growing on na media supplemented with 12.5% nacl increase in the growth of apple trees and fruit yield after applying bacillus sp. ebw4. another pgpr identified is b. hwajinpoensis, which was also characterized as a halotolerant rhizobacterial species with plant growthpromoting traits by ferreira et al. (2021) [16]. furthermore, many other bacillus sp. strains were also described as st-pgprs. experiments with several plant species proved that a diverse range of bacillus strains such as b. pumilus, b. paramycoides and b. amyloliquefaciens exhibit elevated salinity tolerance following the induction of a series of salt-tolerance mechanisms in plants, e.g. enhance antioxidant enzyme activity and reduce lipid peroxidation [16-19]. ferreira et al. (2021) described the plant growth-promoting characteristics of salt-tolerant bacillus sp., e.g. production of indole-3-acetic acid (iaa) and siderophores, enhanced 1-aminocyclopropane-1carboxylic acid (acc) deaminase activity as well as phosphate solubilization [16]. moreover, nawaz et al. (2020) studied the individual or synergistic effects of stpgprs on wheat growth as well as yield under saline conditions and found that these bacteria may be used as bioinoculants to enhance crop yield in saline environments [20]. our findings regarding the bacillus sp. strains lsx7 and ytm5 in the rhizosphere of the salt-tolerant p. triandra populated by numerous st-pgpr species are novel, moreover, it is hypothesized that these strains are also potential candidates for st-pgpr activity along with the other described species and bacillus strains. the potential st-pgpr function of the aforementioned strains requires further investigation, namely analysis of their acc deaminase activity, phytohormone production and plant-microbe interactions, which are the goals of our future studies. in summary, based on our results and prior findings, the root microbiome of the halophyte p. triandra is likely to be a useful source for the isolation, discovery and characterization of yet unknown st-pgprs providing tools with further applications with regard to inducing halotolerance in plants of high economic value. therefore, understanding the salt tolerance mechanisms of halotolerant plants in general, e.g. that of p. triandra in our study, may ultimately facilitate the exploitation of székely, szígyártó, tóth and barta hungarian journal of industry and chemistry 14 saline areas for agricultural purposes, especially in the carpathian basin. 4. conclusions p. triandra, similarly to a series of other halophyte species, has evolved various morphological, physiological and biochemical salt adaptation mechanisms to counteract the harmful effects of elevated salinity [6]. the isolation of halotolerant bacteria from the rhizosphere of this species indicates that plantmicrobe cohabitation may influence the adaptive strategy of the plant. although further investigations are necessary to characterize the novel identified bacterial strains and demonstrate their pgpr ability, our 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plant growth-promoting mechanisms of bacillus strains in elevating rice growth and its interaction with salt stress, front. plant sci., 2022 13, 994902, doi: 10.3389/fpls.2022.994902 [20] nawaz, a.; shahbaz, m.; asadullah; imran, a.; marghoob, m.u.; imtiaz, m.; mubeen, f.: potential of salt tolerant pgpr in growth and yield augmentation of wheat (triticum aestivum l.) under saline conditions, front. microbiol., 2020 11, 2019, doi: 10.3389/fmicb.2020.02019 https://doi.org/10.1186/s43141-021-00186-3 https://doi.org/10.1186/s43141-021-00186-3 https://doi.org/10.3389/fpls.2022.994902 https://doi.org/10.3389/fpls.2022.994902 https://doi.org/10.3389/fmicb.2020.02019 hungarian journal of industry and chemistry vol. 50(2) pp. 17-21 (2022) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2022-13 investigations into the usage of the mineral alginite fermented with lactobacillus paracasei for cosmetic purposes pál tóth1 and áron németh1* 1 department of applied biotechnology and food science, budapest university of technology and economics, műegyetem rkp. 3, budapest, 1111, hungary a remarkable interplay between the skin and the fermentation of lactic acid bacteria (lab) occurs. the lactate and amino acids in the supernatant of this bacteria help to hydrate the skin. the fermentation broth of lactic acid bacteria, generally referred as "lactic acid bacteria ferment" according to international nomenclature of cosmetic ingredients (inci), has been used to make a variety of cosmetic components. the goal of this study was to evaluate new approaches to assess ferment filtrates (also known as cell-free fermentation broths) that could be used in cosmeceuticals. despite years of research on the production of lactic acid, aesthetic evaluations have not yet been performed. first, the lactobacillus paracasei strain ncaim b.01525 was employed in our research. furthermore, a fermentation broth was produced containing the hungaricum mineral alginite and the impact of hydration on human skin tested. the influence of alginite on the fermentation of lab was also examined. according to the results of the trials, although alginite might double and triple biomass and specific growth rates, respectively, it cannot facilitate hydration of the skin. these results might contribute to the development of more widely accessible, environmentally-friendly cosmetic components in the future. keywords: human skin, dermatoscope, moisturizing effect 1. introduction the use of cosmetics dates back 7,000 years to ancient egypt and were later used in the roman empire, for example, according to some legends, cleopatra bathed in goats' milk to preserve the youthfulness of her skin. later, milk baths became popular in the english royal court, for instance, catherine parr, the last queen of the house of tudor, and later elizabeth i, queen of england, regularly used a milk bath to preserve their beauty. in today's modern world, using natural ingredients in cosmetics has come to the fore again. although our laboratory has been dealing with lactic acid producers for many years, to date, no measurements have been made in terms of cosmetics. the structure of the skin and the composition of the stratum corneum (sc) are shown in fig. 1, including the natural moisturizing factor (nmf). the skin consists of two main layers, namely the dermis and epidermis. the epidermis is further divided into two main layers, that is, the viable epidermis and the stratum corneum (sc), which is the outermost layer mainly consisting of dead cells. the essential function of the sc is to act as a barrier, preventing dehydration caused by water loss from the body. the sc contains 30% nmf, which received: 2 sept 2022; revised: 15 oct 2022; accepted: 15 oct 2022 *correspondence: naron@f-labor.mkt.bme.hu consists of 40% amino acids such as serine, glycine and alanine as well as 12% lactate, which is capable of retaining water in the stratum corneum [2]. on the other hand, lactic acid bacteria (lab) are generally defined as gram-positive, non-spore-forming, catalase-negative, aerotolerant, acid-tolerant, nutrientdemanding and strictly fermentative organisms that lack cytochromes as well as produce lactic acid as the main end product of carbohydrate metabolism [3]. lab contains cell wall-bound proteinase that initiates the transformation of extracellular proteins into oligopeptides [4]. the protease activity as well as figure 1. composition of the skin and its natural moisturizing factor (nmf), where pca is pyrrolidone carboxylic acid [1] https://doi.org/10.33927/hjic-2022-13 mailto:naron@f-labor.mkt.bme.hu tóth and németh hungarian journal of industry and chemistry 18 catabolic production of proteins and peptides enable lab to produce amino acids in the fermentation broth [5]. since many amino acids are contained in various lab-fermented foods such as cheese [6], sausage [7] and even japanese sake [8], a lab-fermented ingredient contains large amounts of lactic acid and amino acids, which together form the nmf. therefore, these ingredients exert a hydration effect when they are applied on the skin. furthermore, a particular combination of a substrate and a strain of lab could provide another beneficial functional impact on the skin. our goal was to investigate how the mineral alginite affects fermentation and moisturization of the skin. another aim of this study was to screen for new methods to evaluate the ferment filtrate, i.e. cell-free broth, in terms of usage in cosmeceuticals. 2. experimental 2.1. fermentation the planned experiment concerning the production of lactobacillus ferment filtrate was performed using a strain of lactobacillus paracasei from the national collection of agricultural and industrial microorganisms (ncaim, hungary), namely ncaim lactobacillus paracasei b.01525. the fermentations were conducted in 250 ml shake flasks and 10 ml bactrac impedance tubes (sy-lab, austria fig. 2) at 37°c. only the shake flasks were shaken at 150 rpm. the fermentations could be monitored online using a sy-lab bactrac 4100 microbiological analyzer due to changes in the impedance of the medium (m%) and on the surface (e%) of the electrodes by following the same method previously reported by áron németh [9]. the measurements were performed using the bactrac analyzer and the results displayed by bacmonitor y 1.39er software. since the bactrac program only shows curves and does not give the corresponding points, these points had to be extracted in a different way. the curves were saved as qrp files, which were converted into jpeg format using smartqrp software. the jpeg files had already been recognised by digitizeit, which made it easy to determine the points associated with the curves. the points were copied into a microsoft excel spreadsheet and curves were fitted to the points using sigmaplot 2001 software for windows version 7.0. the generalized logistic equation by verhulst-pearl was used [10]. the nutrient solution was the following marierogosa-sharpe medium: peptone (10.0 g/l), yeast extract (5.0 g/l), beef extract (10.0 g/l), glucose (20.0 g/l), kh2po4 (2.0 g/l), sodium acetate (5.0 g/l), magnesium sulfate (0.2 g/l), manganese sulfate (0.05 g/l), tween 80 (1.08 g/l) and ammonium citrate (2.0 g/l). the fermentations with alginite were supplemented with 10g/l of alginite. during the fermentation, the changes in glucose and lactic acid concentrations were monitored by a waters breeze hplc system consisting of a bio-rad aminex hpx-87h column, waters 717 plus autosampler and waters 2414 ri detector. after appropriate dilution steps, the samples were mixed with a 0.2 µm-pore-size mixed ester syringe filter (vialab magyarország kft.). the dry matter was measured as follows: the contents of the bactrac tubes, that is, 10 ml of fermentation broth, were loaded into falcon conical centrifuge tubes and centrifuged at 6000 rpm for 10 mins. using a hermle z200a centrifuge. the supernatant was then decanted before the cells were suspended in distilled water and centrifuged once more. the supernatant was decanted again and the biomass poured into the crystallization cup with 2-3 ml of distilled water before being dried relatively quickly using our sartorius ma35 moisture analyzer. 2.2. determination of moisture content the short-term/immediate hydration effect of the ferment filtrates was determined by taking triplicate measurements using a dermatoscope (fig. 3). on the forearm of the subject, three 1 cm2 areas were marked out onto which 20 µl of fermented juice was pipetted. after 5 mins., these areas were wiped with a dry hand towel and then the hydration on that part of the subject’s skin was measured at given intervals with the installed corneometer (capacitance) sensor. in order to establish a basis for comparison, the hydration of the subject’s skin figure 2. bactrac and its vials with electrodes figure 3. measuring with a dermatoscope mineral alginite fermented with lactobacillus paracasei 50(2) pp. 17-21 (2022) 19 was recorded before measurements were taken and the values displayed here corrected according to this value. 3. results and discussion 3.1. bactrac results the effect of alginite on the kinetics of lab fermentation was also investigated. the fermentations were monitored by bactrac online by replicating both setups three times, that is, in the presence and and absence of alginite, supplemented with a noninoculated (blank) reference. the reference bactrac tube contained the medium mrs and 10 g/l of noninoculated alginite. the replicates were compared by excluding outliers from further processing and their curves are presented in fig. 4. the resulting curves clearly show the impedance of lactobacillus paracasei fermentations in the presence of alginite during the declining growth phase is twice as high as that of nonalginite fermentations. furthermore, the specific growth rate was also determined to quantitatively compare the effect of alginite on fermentation kinetics as is presented in fig. 5. the specific growth rates also differ significantly between the normal and alginite fermentations, namely 0.6 and 1.9 l/h, respectively (fig. 5). therefore, the specific growth rate of fermentation with alginite is three times higher than without. the data obtained from dry matter measurements also indicate that alginite fermentations achieved higher yields (fig. 6). 3.2. skin hydration since a lactic acid-producing strain was investigated, firstly the moisturizing effect of solutions of different lactic acid concentrations, namely 5, 10, 15 and 20 g/l of lactic acid in distilled water, was determined by a dermatoscope. how skin hydration changes over time once the given concentration of the lactic acid solution had been reduced is represented in fig. 7. it is clearly visible that the level of hydration rapidly decreases over time but eventually stabilizes after ca. 35 mins. since the initial phase is difficult to quantify, the steady-state values after 30, 35, 40 and 45 minutes were used before being plotted against concentration as presented in fig. 8. the trend is clear, that is, as the concentration of lactic acid increases, so does the moisturizing effect. the effect of the 5g/l lactic acid solution is so minimal that it has a relatively mild dehydration effect on the skin. a trendline was fitted to the points (r^2>0.99) and from the resulting equation, the hydration effect of the fermentation broth was predicted based on its lactic acid content. while our technique for measuring the moisturizing effect is first described and applied here, the lactic acid sting test (last), which also measures capacitance figure 4. lactobacillus paracasei fermentations in bactrac tubes figure 5. specific growth rates of l. paracasei fermentations figure 6. concentration of dry matter in the l. paracasei fermentations figure 7. the moisturizing effect of the lactic acid (la) solutions tóth and németh hungarian journal of industry and chemistry 20 using a corneometer (similarly to our dermatoscope’s corneometer) is highly comparable to it [11]-[13]. the only two differences are that the cited authors applied the ferment filtrates to the facial skin, to nasolabial folds to be exact, where the hydration effect was 6 times higher in contrast to on the forearm in our study, and that they only reported the measured level of hydration after 10 mins., which according to our time profile varies rapidly over time suggesting it may be more reliable. overall, a correlation with regard to the lactic acid solutions is observed between our results and those from the cited studies. the effect on skin hydration of the lactobacillus paracasei fermented broths was also measured and plotted against time (fig. 9). a comparison concerning the steady-state values of the fermentation samples in the presence and absence of alginite is presented in fig. 10. according to the results, the samples containing alginite were less hydrating than the cell-free fermentation broth. this may be due to the higher concentrations of lactic acid produced in the alginite-free fermentation broth, namely 23.8 g/l and 28.8 g/l, respectively. by applying the equation in fig. 5, hydration values of 15.2 and 11.7% were predicted for the alginite-free and alginitecontaining fermentation broths, respectively, based on these lactic acid concentrations. although the measured results in both cases are slightly lower, the difference is insignificant. 4. conclusion the current study investigated the effects of the mineral alginite on the fermentation of lactobacillus paracasei and its moisturizing effects on the skin. this study also aimed to test novel approaches for evaluating ferment filtrates (also known as cell-free fermentation broths) for use in cosmeceuticals. according to studies on the process, alginite increases the specific growth rate and dry matter content during fermentation. while the latter doubled, from 1.6 to 3.3 g/l to be exact, the former tripled from 0.60 to 1.91 l/h. based on these encouraging findings, it was predicted that the hydration effect of the filtrate in the presence of alginite would outweigh that without. however, dermatoscopic measurements provided evidence to the contrary. the measured hydration levels of the alginite-free and alginitecontaining fermentation broths were 13.9 and 8.1%, respectively. our future studies will focus on the effects of fermented broths containing alginite on additional aesthetic aspects such as antioxidants, skin whitening or the inhibition of the enzyme hyaluronidase. references [1] izawa, n.; sone, t.: cosmetic ingredients fermented by lactic acid bacteria, in: microbial production: from genome design to cell engineering, (springer, tokyo) 2014, pp. 233–242, doi: 10.1007/978-4-431-54607-8_20 [2] spier, h.w.; pascher, g.: zur analytischen und funktionellen physiologie der hautoberfl äche (analytical and functional physiology of the skin surface), hautarzt, 1956, 7(2), 55–60, 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questionnaire and lactic acid sting test play different role on the assessment of sensitive skin: a cross-sectional study, clin. cosmet. investig. dermatology, 2021, 14, 1215–1225, doi: 10.2147/ccid.s325166 [12] an, s.; lee, e.; kim, s.; nam, g.; lee, h.; moon, s.; chang, i.: comparison and correlation between stinging responses to lactic acid and bioengineering parameters, contact derm., 2007, 57(3), 158–162, doi: 10.1111/j.1600-0536.2007.01182.x [13] wu, y.; wang, x.; zhou, y.; tan, y.; chen, d.; chen, y.; ye, m.: correlation between stinging, tewl and capacitance, skin res. technol., 2003, 9(2), 90–93, doi: 10.1034/j.1600-0846.2003.00026.x https://doi.org/10.1007/s002840010324 https://doi.org/10.3168/jds.s0022-0302(93)77354-3 https://doi.org/10.3168/jds.s0022-0302(93)77354-3 https://doi.org/10.1021/jf980834p https://doi.org/10.6013/jbrewsocjapan1988.99.659 https://doi.org/10.33927/hjic-2019-13 https://doi.org/10.1002/bit.260100208 https://doi.org/10.2147/ccid.s325166 https://doi.org/10.2147/ccid.s325166 https://doi.org/10.1111/j.1600-0536.2007.01182.x https://doi.org/10.1034/j.1600-0846.2003.00026.x hungarian journal of industry and chemistry vol. 50(2) pp. 23–26 (2022) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2022-14 separation of dissolved gases from aqueous anaerobic effluents using gas-liquid membrane contactors merve visnyei1*, péter bakonyi1, nándor nemestóthy1 and katalin bélafi-bakó1 1 research group on bioengineering, membrane technology and energetics; university of pannonia; egyetem u. 10; veszprém; h-8200; hungary this study aimed to evaluate a gas-liquid membrane contactor for recovering the dissolved gases of methane (ch4) and carbon dioxide (co2) from model aqueous anaerobic effluents. for this purpose, synthetic effluents were prepared by using the gas mixtures of se-1: 100/0, se-2: 0/100 and se-3: 50/50 ch4/co2 vol.% as well as di water. the units in which the synthetic effluent was prepared were coupled with a dense hollow fiber membrane module by employing argon gas at atmospheric pressure. the desorption of the gases ch4 and co2 dissolved in the effluents was investigated with a countercurrent flow of the liquid on the lumen side. the effect of the sweep gas flow rate on the removal rate was also investigated. the results showed that the recovery rate of ch4 was slightly affected by increasing the sweep gas flow rate, while the recovery rate of co2 was enhanced considerably. by applying a sweep gas flow rate of 20 ml/min, the recovery rate of both gases from se-3 exceeded 50%. keywords: gas separation; membrane contactor; biogas recovery; anaerobic effluent 1. introduction anaerobic wastewater treatment is a widely used technology to convert organic waste into well-stabilized sludge. compared to aerobic systems, the major advantages of anaerobic-based ones are that the process produces higher-quality effluent and has the potential to be a net energy producer by utilizing energy from the biogas produced. raw biogas mainly consists of ch4 and co2, moreover, may contain small quantities of hydrogen sulphide, moisture and siloxanes [1]. the composition of biogas can vary depending on the operating conditions and concentrations of organic compounds in the treated water. typically, although the methane content in biogas is within the range of 50-70%, it can be as high as 90% depending on its interaction with the aqueous phase of the carbon dioxide [2]-[3]. furthermore, important benefits of anaerobic treatment include the requirement of less nutrients as well as lower energy consumption and higher organic loads than most conventional biological treatments. membranes are crucial for the separation of biomass and effluent as they enable higher concentrations of organic compounds to be used in reactors, generation less sludge as well as increase the rate of biogas production [4]. therefore, an anaerobic membrane bioreactor system has emerged as a potential alternative technology for wastewater treatment by coupling anaerobic bioreactors with membrane separation, facilitating easy scaling up and selective received: 19 oct 2022; revised: 24 oct 2022; accepted: 26 oct 2022 *correspondence: merve.visnyei@phd.uni-pannon.hu separation with low energy consumption [5]. biogas as a renewable fuel consisting of 50-70% ch4 and 30-50% co2 can be produced with this method [6]. since the treatment process occurs in a completely closed environment, it is crucial that the dissolved gases in the produced effluent are in equilibrium with the biogas in the headspace, resulting in a significant quantity of dissolved ch4 and dissolved co2 being lost in the effluent solution [7]-[8]. both dissolved gases are desorbed into the environment and contribute towards greenhouse gas emissions. several researchers have reported that a considerable amount of the methane generated is dissolved and wasted in the liquid phase [1][2], [9]-[12]. methane loss as a function of the temperature of bodies of municipal wastewater containing an average soluble cod of 200 mg/l is presented in fig.1. since the figure 1. dissolved methane in the wastewater as a function of temperature 40 45 50 55 60 65 70 75 80 85 90 0 5 10 15 20 25 30 35 d is s o lv e d m e th a n e i n w a s te w a te r, % temperature, c https://doi.org/10.33927/hjic-2022-14 mailto:merve.visnyei@phd.uni-pannon.hu visnyei, bakonyi, nemestóthy and bélafi-bakó hungarian journal of industry and chemistry 24 solubility of methane increases as the temperature decreases, the amount of dissolved methane is higher, even as high as 88% at 0°c, at lower temperatures. methane is a greenhouse gas, its global warming potential is estimated to be 28–36 times higher than that of co2 over 100 years [13], moreover, is flammable with a lower explosive limit of 5 vol.% [2]. consequently, the importance of recovering and utilizing methane entrapped in effluent during biogas production is significant in order for anaerobic treatment systems to be sustainable. the membrane degassing technology using gasliquid membrane contactors (glmcs) has emerged as a potential approach for recovering entrapped methane in fermentation liquor [7]. preferably, glmcs are assembled into hollow fiber membrane modules since they yield a higher gas desorption rate by providing high volumetric mass transfer coefficients [14]. the goal of this research was to determine the recovery rates of ch4 and co2 gas dissolved in synthetic effluents by applying a non-porous hollow fiber membrane. the effect of gas and liquid flow rates on the removal rate was also investigated. 2. experimental pure ch4 (98%)/co2 (99%) and deionized water were used to prepare the synthetic effluents (ses) in glass bottles with a volume of 5 l. a peristaltic pump was used to displace the air from the bottle to create an anaerobic environment, which was confirmed with a dissolved oxygen analyzer. saturation was achieved by bubbling ch4 (se-1), co2 (se-2) or a mixture of ch4 and co2 (50-50%: se-3) into the deionized water for 3 hours. the composition of the headspace was monitored by a hewlett packard hp 5890 series ii gas chromatograph equipped with a thermal conductivity detector (tcd). a capillary carboplot® column was employed (agilent technologies, length: 60 m, id: 0.32 mm, film thickness: 1.5 mm) with ar (99.9 %) as a carrier gas at a flow rate of 15 ml/min. the applied split ratio was 100:1. the temperatures of the injector, column oven and detector were 130, 90 and 115°c, respectively. at the saturation point, the concentration of ch4/co2 in the headspace was in a steady state. once stability had been ensured, deoxygenated and ch4/co2-saturated water was pumped against the membrane by a peristaltic pump. the units in which the synthetic effluent was prepared were coupled with a permselect® silicone, non-porous hollow-fiber membrane module with a surface area of 1.0 m2. the membrane was operated with a countercurrent flow of the liquid on the lumen side to examine the desorption of ch4 and co2 gases dissolved in the effluents. argon (99.9%) was used as a sweep gas in the experiments. the concentration of the outlet gas at the membrane module was measured by the gas chromatograph at regular intervals. henry’s law and the liquid flow rates were used to calculate the mass flow rate of gases entering the membrane module, while based on the ideal gas law, results obtained from gc and gas flow rates were used to calculate the mass flow rate of gases exiting from the membrane module. based on the results obtained, the recovery rates of ch4/co2 were calculated. 3. results and discussion based on the preliminary experiments, in this research, the liquid flow rate used was 15 ml/min, adjusted by a peristaltic pump and monitored with a balance. the sweep gas flow rate varied from 5-60 ml/min and was adjusted by a control valve as well as measured with a soap film flowmeter. recovery rates of ch4/co2 from se-1/se-2 as a function of the sweep gas flow rate at a liquid flow rate of 15 ml/min are shown in tables 1 and 2 as well as summarized in fig.2. table 1. recovery rates of ch4 from se-1 as a function of the sweep gas flow rate liquid flow rate (ml/min) sweep gas flow rate (ml/min) recovery rate of ch4 (%) 15 15 15 15 5 10 20 60 57.1 58.0 58.6 35.9 table 2. recovery rates of co2 from se-2 as a function of the sweep gas flow rate liquid flow rate (ml/min) sweep gas flow rate (ml/min) recovery rate of co2 (%) 15 15 15 15 5 10 20 60 9.2 29.0 47.0 61.6 figure 2. recovery rates of ch4/co2 from se-1 and se-2 as a function of the sweep gas flow rate 0 10 20 30 40 50 60 70 0 10 20 30 40 50 60 70 r e c o v e ry o f g a s e s (% ) sweep gas flow rate (ml/min) ch4 (lf:15) co2 (lf:15) separation of dissolved gases 50(2) pp. 23-26 (2022) 25 the results showed that the recovery rate of ch4 at a sweep gas flow rate of 5-20 ml/min was almost constant (57.1-58.6%) and rapidly decreased to 35.9% by increasing the gas flow rate to 60 ml/min. similar effects of the gas flow rate on the recovery ratios of the gases have been reported by cookney et al. [15], where increasing the gas flow rate had little effect on the mass transfer coefficient of ch4 due to mass transfer controlled by the resistance in the liquid phase. rongwong et al. [7], [16] also reported that the ch4 concentration is diluted in the outlet gas in the case of high gas flow rates, which was also observed in this study. although the recovery rate of co2 was increased by increasing the sweep gas flow rate, these values were much lower than those of ch4 except for at a gas flow rate of 60 ml/min. se-3 was prepared by purging a mixture of ch4 and co2 gases (50:50) into deionized water for 3 hours to investigate the impact of this mixture on the recovery rate of the membrane module. the results were compared with those obtained from synthetic effluents prepared with pure gases. the recovery rates of co2 and ch4 as a function of the sweep gas flow rate are given in table 3 and fig.3. the results from se-3 showed a similar tendency to those obtained in the case of individual gases. the recovery rate of co2 was increased from 36.2 to 62.9% by increasing the sweep gas flow rate, while these values for ch4 at a gas flow rate of 10-20 ml/min were 53.161.3% but dropped drastically to 11.9% by applying a gas flow rate of 60 ml/min. at the latter gas flow rate, the recovery rate of the membrane module with regard to ch4 from se-1 was 35.9%, therefore, the presence of co2 in the synthetic effluent may have a negative effect on the recovery of ch4. nevertheless, by applying a sweep gas flow rate of 20 ml/min, the recovery rate of both gases from se-3 exceeded 50%. 4. conclusions the anaerobic digestion of wastewater is a commonly used technology to produce biogas by converting organic waste into well-stabilized sludge. since the process takes place in a completely closed environment, it is crucial that the dissolved gases in the produced effluent are in equilibrium with the biogas in the headspace, leading to a significant quantity of dissolved ch4 and dissolved co2 being lost in the effluent solution. as a result, the recovery of dissolved ch4 is critical to increase anaerobic energy production while minimizing the environmental impact of greenhouse gases. in this study, synthetic effluents were prepared by purging ch4/co2 into deionized water. a membrane contactor was employed as a mass transfer device for measuring the recovery rates of ch4 and co2 gases dissolved in synthetic effluents by applying a non-porous hollow fiber membrane. the effect of the sweep gas flow rate on the removal rate was also investigated. the results showed that the recovery rate of ch4 was slightly affected by increasing the sweep gas flow rate, while the recovery rate of co2 was enhanced considerably. acknowledgements this research was supported by the otka k 138232 research grant entitled “stabilization of anaerobic effluents in a novel, integrated bioprocess towards controlled demethanization and energy recovery.” references [1] visnyei, m.; bakonyi, p.; bélafi-bakó, k.; nemestóthy, n.: integration of gas–liquid membrane contactors into anaerobic digestion as a promising route to reduce uncontrolled greenhouse gas (ch4/co2) emissions, 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time maria elena lozano fernandez1, szabina tomasek1*, csaba fáyköd2 and andrea somogyi3 1 research centre for biochemical, environmental and chemical engineering, department of mol hydrocarbon and coal processing, university of pannonia, egyetem u. 10, veszprém, 8200, hungary 2 felső-bacska storage windpark ltd., arany jános út 200, fadd, 7133, hungary 3 solver unio ltd., ábel jenő u. 8, budapest, 1113, hungary this paper focuses on the pyrolysis of animal manure in a laboratory-scale tubular reactor between 300 and 900°c at nitrogen flow rates of 1 and 5 dm3/h. during the experiments, it was found that both the temperature and nitrogen flow rate had significant effects on the product yields and compositions. the highest gas yield and syngas content were observed at 900°c at a nitrogen flow rate of 1 dm3/h. in this case, since the gaseous product was characterized by a h2/co ratio of 0:5, its quality must be improved prior to being used for synthesis. the composition of the solid residue was also affected by the pyrolysis parameters . based on the hydrogen/carbon and oxygen/carbon ratios, it was concluded that both the water-gas shift and boudouard reactions were the most critical. keywords: cattle manure, pyrolysis, tubular reactor, product yield, composition 1. introduction the rapid growth of the world’s population is leading to a significant rise in the demand and consumption of food, including meat and animal-derived products. as a consequence, farms and this sector generate huge amounts of waste such as livestock manure, sewage sludge and poultry litter [1]-[2]. the inadequate management of manure and sewage sludge causes serious health and environmental issues, e.g. water and air pollution as well as the emission of greenhouse gases and heavy metals in addition to the spread of pathogens. the composition of this residue includes a wide variety of chemical and biological compounds which are associated with the specific species of animals and age ranges amongst other factors. the residue consists of a complex mixture of compounds, mainly microbiota, lignocellulose, proteins as well as a significant amount of inorganic matter such as s, n, p, k, ca, mg and cl. additionally, heavy metals such as cu, pb, cd, zn and mn can be found in the residue due to the use of antibiotics and hormones supplied to the animals [3]-[5]. some of the practices concerning the disposal of sewage sludge and manure include landfilling, agricultural utilization, composting, anaerobic digestion and thermochemical conversion [6]. one of the most received: 26 sept 2022; revised: 10 oct 2022; accepted: 11 oct 2022 *correspondence: tomasek.szabina@mk.uni-pannon.hu traditional and practical alternatives is the usage of these residues in agricultural land due to the high content of n and p which are essential elements required in plant fertilization. however, nowadays, this practice has diminished due to the enormous amount of waste generated, exceeding the nutritional requirements of the soil. environmental regulations establish limits on the values allowed for the usage of sewage sludge in agriculture. the excessive use of manure on land causes problems such as contamination of the subsoil and surface, odors as well as the emission of greenhouse gases and ammonia [5,7-10]. therefore, new alternatives for the proper management of this type of waste have been explored as well as studied more comprehensively in an attempt to solve the environmental and social impacts [8]. for example, thermal conversion techniques such as pyrolysis and gasification could be alternatives for transforming the residue into valuable products such as oil, char and gaseous products. additional advantages of these techniques are that the huge volume generated is reduced, microorganisms are degraded and pathogenic organisms destroyed [1,9-10]. it is important to take into consideration that the percentage of humidity in the residues in the material is high and should be reduced while using the thermal techniques. the material could mailto:tomasek.szabina@mk.uni-pannon.hu lozano fernandez, tomasek, fáyköd and somogyi hungarian journal of industry and chemistry 28 be dried through natural, mechanical and thermal drying techniques [11]. depending on the thermal degradation technique applied, the composition of the feedstock; process conditions, e.g. temperature and heating rate; as well as product distribution and its composition will vary [11]. for example, during pyrolysis, degradation in the absence of oxygen occurs at high temperatures. through pyrolysis, the feedstock decomposes to form char, oil and light non-condensable gases [11]. in the case of the raw material containing a large amount of hemicellulose and cellulose, a product consisting of a higher percentage of gases could be expected, while lignin contributes towards the formation of char. regarding the temperature, the formation of char is favored by low temperatures, while that of oil and volatile gaseous components is more likely at high temperatures [12]. the products can be further utilized depending on their characteristics. char has interesting physical properties, for example, a high surface area, microporosity as well as high adsorption and ion exchange capacities. char potentially could be used as an adsorbent, a catalyst, in power plants or as a fertilizer. char obtained from manure is rich in elements such as k, p, ca and mg [10], [12]. in the oil fraction, hydrocarbons are produced but the pyrolysis oil from manure and sewage sludge is not regarded as of high quality since the oil produced contains oxygen, which gives rise to the production of compounds such as alcohols, ketones, aldehydes and esters that decrease the quality of the product [1]. the gas produced contains a mixture of co, co2, ch4, h2 and some light hydrocarbons (c2h2, c2h4, c2h6 and c3h8) [13]. the gas may be valuable because the energy it contains could be used in gas turbines and power plants or its compounds applied as a feedstock to be processed into a more addedvalue chemical product [13]-[14]. despite the wide range of possible uses of the products, relatively few studies have investigated the pyrolysis of cattle manure. consequently, limited information about the product yields and compositions is available. in light of the above, this study focuses on the pyrolysis of cattle manure within the temperature range of 300-900°c using nitrogen flow rates of 1 and 5 dm3/h as well as on the impact of the process parameters. 2. materials and methods 2.1. raw material cattle manure was used as a feedstock for the pyrolysis experiments. before the experiments, the raw material was dried at 110°c to constant mass. to determine the physical and chemical properties, the proximate and ultimate analyses of cattle manure (table 1) were carried out. as data show, the raw material is characterized by 40.6% ash, 53.5% volatile compounds and 0.3% water content. the c, h, n, s and o contents were determined by a carlo erba-type elemental analyzer and in order to identify the inorganic compounds, e.g. ca, p, s, si, na, mg, fe and al, energy dispersive x-ray analysis was performed (shimadzu edx). 2.2. pyrolysis experiments pyrolysis was performed in a laboratory-scale horizontal tubular reactor (fig.1). the cattle manure was placed in the center of a glass wool tube. the experiments were performed at 300, 500, 700 and 900°c. a n2 atmosphere was used and the flow rates established were 1 and 5 dm3/h. the heating rate used for this experiment was 100°c/min. the reaction system was equipped with a scrubber and silica gel-filled tube, where the gaseous products were purified to remove possible impurities and dried. at the end of the reaction, the product yields were estimated by measuring and calculating their difference in mass. 2.3. product analysis the composition of the gaseous products was determined by a dani-type gas chromatograph using a flame ionization and thermal conductivity detectors. the equipment contained two capillary columns (rtx-1 pona (100 m x 0.25 mm x 0.5 µm) and carboxen tm-1006 plot (30 m x 0.53 mm)). regarding the isothermal conditions of the pona capillary column, the injector and detector temperatures were both 230°c. in terms of the carboxen tm-1006 plot capillary column, the applied heating program was as follows: 35°c for 18 mins before being heated to 120°c at a heating rate of 15°c/min and maintained at 120°c for 2 mins. the table 1. proximate and ultimate analyses of cattle manure parameter value (%) p ro x im at e an al y si s fixed carbon 5.59 ash content 40.68 volatile organic compounds 53.43 water content 0.30 u lt im at e an al y si s c 24.80 h 3.00 n 2.90 s 1.30 o 45.30 others (ca, p, s, si, na, mg, fe, al) 22.70 figure 1. experimental setup pyrolysis of animal manure 50(2) pp. 27-33 (2022) 29 retention times of the components were determined using gas mixtures and individual components. 3. results and discussion 3.1. product yields the product yields of the pyrolysis experiments are summarized in fig.2. during the experiments, only gas and char were formed. as expected, the gas yields and amount of solid residue produced increased and decreased, respectively, as a function of the reaction temperature. during the pyrolysis process, a series of complex reactions took place. up to 200°c, to all intents and purposes, only the water was removed from the cattle manure (fig.3). in the torrefaction stage, since cellulose, hemicellulose and lignin were only slightly degraded, the final product was a solid carbonaceous material. this stage was followed by the pyrolysis process, where a significant reduction in mass resulted. in addition, a sharp peak appeared at approximately 300°c in the derivative thermogravimetric diagram (dtg), indicating that the reduction in mass occurred at a high speed. it is well known that cellulose degradation occurs between300 and 350°c, while protein decomposes between 450 and 660°c. in addition, deamination also took place. during the pyrolysis stage, approximately 30% of the initial mass was lost. above 600°c, another significant proportion of mass, ~25%, was lost. this reduction in mass was related to the degradation of chains of lignin, carbon and minerals. it was also observed that the rate at which the mass reduced was low and relatively stable. this effect could be attributed to the minerals and possible carbonated forms. additionally, it is worth mentioning that within this temperature range, co2 was also formed. co2 acts as an oxygen donor, promoting the boudouard reaction and, therefore, the formation of co. another peak is also visible at 800°c in the dtg curve, which can be attributed to the devolatilization of the char and decomposition of the mineral matter. at the end of the test, that is, at a temperature of 900°c, the percentage of mass consisting of ash and fixed carbon remaining in the crucible was the same as that reported during the proximate analysis. it is important to note that the n2 flow rate also had an effect on the product yields. the lower flow rates facilitated the formation of the gaseous products. given the longer residence time, the volatile vapors resuting from the pyrolysis exited the reactor more slowly, so they had sufficient time to degrade more comprehensively. 3.2. composition of the gaseous products although the gaseous products consisted of h2, co, co2 and ch4, c2-c6 hydrocarbons were also formed (fig.4). h2 was formed by dehydrogenation, however, it could have formed as a result of the reforming reactions. co may be related to the reactions that facilitated the cleavage of bonds in the ether groups and decarbonylation from proteins [15]-[16]. as fig.4 shows, the formation of co considerably increased above 700°c and the highest level was obtained at 900°c. this large increase was attributed to the boudouard reaction, which has already been referred to in the thermogravimetric analysis. the boudouard reaction can also be catalyzed by carbonates present in the manure [17]. the increase in co can also be justified by a reaction between co2 and other compounds generated during pyrolysis, the reduction of co2 to co figure 3. thermogravimetric results with regard to the raw material d ry in g to rr e fa ct io n p yr o ly si s p yr o ly si sga si fi ca ti o n d m /d t w e ig h t lo ss , % 0. 0 1. 0 2. 0 3. 0 4. 0 5. 0 6. 0 0 25 50 75 10 0 temperature, °c 200 400 600 800 1000 200 400 600 800 1000 figure 2. product yields of pyrolysis 0 20 40 60 80 100 300 500 700 900 gas yield, % t e m p e r a tu r e , °c 5dm3/h 1dm3/h 0 20 40 60 80 100 300 500 700 900 char yield, % t e m p e r a tu r e , °c 5dm3/h 1dm3/h lozano fernandez, tomasek, fáyköd and somogyi hungarian journal of industry and chemistry 30 and simultaneously the oxidation of the carbon of the pyrolysis product through a homogeneous reaction [18]. the quality of the gaseous product can be defined in terms of its chemical composition and calorific value. fig.5 represents the content of syngas, namely h2 and co, in the product. from the results, it is remarkable that the production of syngas only took place above 500°c and the yield increased in proportion to the temperature. the highest syngas yields (~80%) were observed at 900°c. it is important to emphasize that the n2 flow rate also had an effect on the syngas yield. the yield of syngas was higher at lower n2 flow rates, in the same manner as the overall gas yield. the h2/co ratio of syngas (fig.6) is extremely important. the typical initial ratios for the transformation of methanol into chemicals are >2:1 for light olefins; <2:1 for diesel; 1.5:1 for aldehydes, higher alcohols and dimethyl ether; 1:1 for oxygen-containing alcohols and acetic acid; and 1:2 for polycarbonate [19]-[20]. as data in fig.6 show, although the ratio of h2/co at 500°c was approximately 1, at 700 and 900°c it was below 0.6. the heating values of the gases were also estimated. as is depicted in fig.7, at lower temperatures (300 or 500°c) and an n2 flow rate of 1dm3/h, the calorific value of the gas mixture was higher (~30 mj/m3), meanwhile, at higher n2 flow rates, the heating value of the gaseous product was about 15 mj/m3 at the same temperatures. this can be explained by the fact that a higher percentage of light hydrocarbons is present, the individual components of which provide a higher (n2 flow rate: 1 dm3/h) (n2 flow rate: 5 dm3/h) figure 4. composition of the gas products 0 20 40 60 80 300 500 700 900 composition, % t e m p e r a tu r e , °c c2-c6 ch4 co2 co h2 0 20 40 60 80 300 500 700 900 composition, % t e m p e r a tu r e , °c c2-c6 ch4 co2 co h2 (n2 flow rate: 1 dm3/h) (n2 flow rate: 5 dm3/h) figure 5. syngas yields 0 20 40 60 300 500 700 900 yield, mmol/g raw material t e m p e r a tu r e , °c co, mmol/g h2, mmol/g 0 20 40 60 300 500 700 900 yield, mmol/g raw material t e m p e r a tu r e , °c co, mmol/g h2, mmol/g figure 6. h2/co ratios of syngas 0,0 0,5 1,0 1,5 300 500 700 900 h2/co ratio t e m p e r a tu r e , °c 5dm3/h 1dm3/h figure 7. heating values of the gaseous products 0 10 20 30 40 300 500 700 900 heating value, mj/m3 t e m p e r a tu r e , °c 5dm3/h 1dm3/h pyrolysis of animal manure 50(2) pp. 27-33 (2022) 31 calorific value than the other compounds present in the mixture [21]. another interesting correlation is the difference in the proportions of different elements contained in the gas as well as the resultant study and proposition of possible reaction mechanisms at different temperatures. the trends observed when the ratio of components were estimated are summarized in table 2. from the process, the water-gas shift reaction and boudouard reaction are some of the critical reactions that took place [14]. 3.3. char according to the international biochar initiative (ibi), the char obtained from the pyrolysis experiments can be regarded as biochar [22], in which the c content is greater than 10% except for during the tests carried out at 900°c. to determine the possible applications of char, it is recommended to evaluate the relationship between the proportions of some elements. for example, the c/n ratio could be a positive parameter to determine the microbial activity should this residue be used in soils. another aspect possibly worth evaluating and analyzing is the h/c and o/c ratios of the manure as well as the char obtained in each test (table 3). the ratios are valuable for understanding the reaction mechanisms during pyrolysis under specific conditions [15]. the atomic ratios show that the process of carbonization changed the chemical compositions by removing functional groups. due to the cleavage of the functional groups, the nitrogen contents significantly decreased, moreover, as a result of the formation of co, co2 and ch4, the carbon contents also reduced. table 2. the proportions of different elements component ratio n2 flow rate: 1 dm3/h n2 flow rate: 5 dm3/h relationship proposed reaction h2/co optimum (highest peak at 500°c) optimum (highest peak at 500°c) higher ratio at a flow rate of 5 dm3/h (except for at 500°c) 𝐶𝑛 𝐻𝑚 + 𝐻2 → 𝑛 + 𝑚 2𝐻2 + 𝑛𝐶𝑂 𝐶𝑂 + 𝐻2𝑂 → 𝐶𝑂2 + 𝐻2 co/co2 increasing increasing higher ratio at a flow rate of 5 dm3/h 𝐶 + 𝐶𝑂2 → 2𝐶𝑂 h2/ch4 optimum (highest peak at 500°c) optimum (highest peak at 500°c) higher ratio at a flow rate of 5 dm3/h 𝐶 + 𝐻2 → 𝐶𝐻4 co/ch4 optimum (highest peak at 700°c) increasing higher ratio at a flow rate of 5 dm3/h 𝐶𝑂 + 3𝐻2 → 𝐶𝐻4 + 𝐻2𝑂 co2/ch4 decreasing decreasing higher ratio at a flow rate of 5 dm3/h 𝐶𝑂2 + 4𝐻2 → 𝐶𝐻4 + 2𝐻2𝑂 2𝐶𝑂 + 2𝐻2 → 𝐶𝐻4 + 𝐶𝑂2 table 3. elemental analysis of the char products cattle manure at n2 flow rate of 1 dm3/h at n2 flow rate of 5 dm3/h 300°c 500°c 700°c 900°c 300°c 500°c 700°c 900°c elements content (%) c 24.8 23.40 20.20 20.90 6.30 23.50 20.50 18.90 7.20 h 3.00 1.80 0.70 0.30 0.80 1.60 0.60 0.30 0.80 n 2.90 2.50 1.50 1.00 0.40 2.30 1.60 0.80 0.80 s 1.20 1.50 1.40 1.40 2.50 1.40 1.60 1.40 2.90 o 45.30 48.20 53.50 53.70 67.30 48.50 53.10 55.80 65.60 al 0.60 0.99 0.98 1.55 1.39 0.72 1.06 1.48 1.57 ca 14.12 12.61 12.91 12.83 15.74 12.36 12.40 11.92 14.74 cl 0.71 0.82 0.70 0.84 0.21 0.63 0.67 0.78 0.40 fe 0.60 0.55 0.18 0.39 0.54 0.72 0.53 0.53 0.52 k 1.76 3.39 2.90 3.22 1.18 2.75 2.93 2.58 1.31 mg 1.19 1.11 1.19 1.55 0.96 1.11 1.13 1.23 0.91 mn 0.03 0.03 0.04 <0.001 <0.001 0.05 0.03 0.04 <0.001 p 2.16 1.40 1.99 2.32 0.96 1.93 2.09 2.05 1.17 si 1.48 1.81 1.82 0.00 1.71 2.42 1.86 2.09 2.09 atomic ratios c/n 8.6 9.4 13.5 20.9 15.8 10.2 12.8 23.6 9.0 h/c 0.10 0.08 0.03 0.01 0.13 0.07 0.03 0.02 0.11 o/c 1.8 2.1 2.6 2.6 10.7 2.1 2.6 2.9 9.1 lozano fernandez, tomasek, fáyköd and somogyi hungarian journal of industry and chemistry 32 4. conclusions in this study, cattle manure was pyrolysed in a horizontal tubular reactor between 300 and 900°c at n2 flow rates of 1 and 5 dm3/h. during the experiments, 20-60% gaseous and 40-80% solid carbonaceous residues were formed. the gas yields increased in proportion to the reaction temperature and residence time, while the amount of char decreased. the decomposition process resulted in the formation of h2, co, co2, ch4 and c2-c6 hydrocarbons. syngas was only produced above 500°c. the ratio of h2/co at 500°c was 1, while at 700 and 900°c, the proportion of co was greater than that of h2. at lower temperatures (300 or 500°c) and at an n2 flow rate of 1dm3/h, the calorific value of the gas mixture was higher (~30 mj/m3) than at the higher n2 flow rate and same temperatures (~15 mj/m3). the process of carbonization changed the chemical composition of the raw material by removing functional groups, which also indicates the occurrence of the water-gas shift and boudouard reactions. acknowledgement this project (2019-2.1.13-tét_in-2020-00071) was financed by the ministry for innovation and technology from the national research, development and innovation fund within the 2019-2.1.13-tét_in program. references 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chemistry vol. 50(2) pp. 35–41 (2022) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2022-16 behavior of control and inhibitive polyaspartic coatings using alkylammonium and zinc phosphate corrosion inhibitors in soil abdu elhoud1* and tim van everbroeck1 1 chemsystems, ambachtsstraat 15, malle, 2390, belgium this study is part of an anti-corrosion coating development project at chemsystems. the corrosion performance was assessed through erosion, immersion and soil corrosion experiments. the erosion results have previously been published. this article discusses the impact of soil on control polyaspartic coatings used to protect concrete and the modified polyaspartic coating intended to protect underground steel substrates. the modified polyaspartic coating was boosted with a micaceous iron oxide barrier, a liquid alkylammonium corrosion inhibitor, a powdered zinc phosphate corrosion inhibitor and a novel hardener. the surface finish of the steel samples was of a milled and blasted nature (sa 2.5). the coating was applied directly to the metal without the application of a primer or second layer of coating. the average thickness of the coating was 220±10 µm as a direct-to-metal protection system. the experiments were conducted in soil at room temperature (rt) and 35°c over 30 days. the experimental results of the control polyaspartic coating loaded on steel substrates exhibited severe blistering. the polyaspartic coating dispersed with a liquid alkylammonium inhibitor also exhibited blistering, whereas the modified polyaspartic coating with a zinc phosphate corrosion inhibitor showed an adequate degree of resistance to the impact of soil under the evaluated conditions. the results confirmed that the presence of a zinc phosphate corrosion inhibitor in combination with a micaceous iron oxide barrier improved the resistance of the coating to the evaluated soils in which it was positioned and at the investigated temperatures. keywords: soil, polyaspartic coating, corrosion inhibitor, iron oxide barrier 1. introduction carbon steels with desirable mechanical properties are widely used in infrastructure, including in underground assets such as pillars, foundations, storage tanks and pipelines. in the field, these structures are more likely to degrade and rust due to direct contact with the soil, especially if no protection system is provided to hinder the effect of the corrosive elements. corrosion due to soil is influenced by the temperature, moisture content, oxygen content, environmental ph, microbial activity and soluble salts. soil moisture contains a wide range of chemicals which have penetrated through the soil surface. some examples of these chemicals are salts, e.g. chlorides, nitrates, nitrites, sulfates, etc., and heavy metals, e.g. cadmium, chromium, copper, iron, manganese, nickel, lead, zinc, etc. along with the influence of microbial activity and environmental factors such as temperature, ph, conductivity and dissolved oxygen concentration, salts and heavy metals make the study of soil moisture an interesting topic as they are related to the corrosion of underground metal structures [1]. jiao chen et al. 2015 [2] studied the soil corrosion of steel as a function of anions in the soil, namely total received: 7 oct 2022; revised: 19 oct 2022; accepted: 25 oct 2022 *correspondence: abdu.elhoud@chemsystems-technology.com soluble salts, cl−, so4 2− and hco3 −, and soil nutrition, that is, moisture content, organic matter, total nitrogen, alkaline hydrolysable nitrogen, available phosphorus and available potassium. many attempts have been made in this regard to reduce the risk of soil corrosion on submerged steel and concrete structures. organic, inorganic and metal coatings such as zn, al and ni are considered to be very effective means to protect submerged assets from premature corrosion and degradation [3]-[4]. corrosion inhibitors in powdered and liquid forms have been incorporated into coatings to enhance their antirust and adhesive characteristics when applied to substrates. zinc phosphate is commonly dispersed into coating formulae during manufacturing and effectively reduced the tendency of a coating to fail and substrates to rust. nevertheless, although further investigations are still favorable to evaluate the efficiency of corrosion inhibitors in coatings exposed to soil, in this study, an attempt was made to compare the efficiency of two types of corrosion inhibitors in combination with iron oxide coatings for the purpose of developing control and inhibited polyaspartic coatings in soils at room temperature (rt) and 35°c applied to milled-surfacefinished and sandblasted steels (sa 2.5). https://doi.org/10.33927/hjic-2022-16 mailto:abdu.elhoud@chemsystems-technology.com elhoud and van everbroeck hungarian journal of industry and chemistry 36 2. materials and experiments the study was carried out on polyaspartic coatings applied to structural steel plates. the tested plates composed of hot-rolled steel grade s235, which was chosen due to its wide range of applications in infrastructure projects in belgium and throughout europe, were manufactured by ask romein malle nv, a steel company based in malle, belgium. the control polyaspartic coating was designed to protect concrete structures, whereas the modified polyaspartic coating containing inhibitors and a barrier was planned to prevent steel from corroding. the surface finish of the steel panels, as received from the supplier, was milled and blasted (sa 2.5). before blasting, the mill scale was removed by immersing the steel plates in 10% h2so4 for 30 minutes at 60°c before being cleaned and dried by acetone to ensure a suitable steel surface before blasting. sand blasting was carried out using a blasting cabinet, while blast cleaning was performed using granular aluminum oxide abrasive media. the steel samples were 150 x 80 x 2 mm rectangular plates. an example of the surface morphology of both the milled and blasted steel surface finishes are displayed in figs.1a and 1b, respectively. polyaspartic coatings consist of two components. component (a), which also contains a corrosion inhibitor and an oxide barrier, is the active material, while component (b) is the hardener. the required amount of component (a) was added to component (b) and mixed for 120 seconds before being applied to the steel. one layer of each coating was applied to each steel sample using an erichsen 358 spiral film applicator and left for one day before being buried in the soil. the edges of the steel samples were well covered with tape to avoid premature failure of the coating or rusting of the steel plates. the edges of the steel plates were carefully smoothened and curved. during the coating, extra layers were applied to the edges, moreover, a strong tape was placed over them to prevent them from rusting and the coating from failing. an example of a coated steel panel is displayed in fig.2. the soil used in this study was loamy sandy soil according to the belgian soil analysis report [5] collected from arable, residential and light industrial flattened land located in malle in the vlaanderen region of belgium. the average climate of the soil in the region of vlaanderen is temperate maritime with an average 800 mm of precipitation falling annually. in many locations, the concentration of heavy metals in the soil and groundwater still exceeds environmental quality standards due to the use of ash material for road stabilization, which has also resulted in the spread of heavy metals. the actual carbon content of arable land parcels in flanders is considered to be fairly good. salinization is a minor concern in the region of the tested soil because it is regarded as being situated far from the coastline [5]. the soil was collected at a depth of 0.5 m and filtered using sieves of two different mesh sizes to remove dirt and purify the soil (fig.3). (a) (b) figure 1. photographs of a) milled steel finish, b) blasted steel finish figure 2: materials used in the soil experiment: an example of a coated steel panel figure 3: soil experiment materials: soil collection and coated steel samples buried in soil behavior of control and inhibitive polyaspartic coatings 50(2) pp. 35–41 (2022) 37 the рη of the soil was controlled before each experiment and measured to be between 6.5 and 7.0. the tested samples were placed in soil in a plastic container (fig.3) for 30 days at both room temperature and 35°c using an oven. the resistance of the coating to soil attack was evaluated by identifying any forms of coating damage and defects as well as signs of rust on the steel using visual and macroscopic inspection techniques. 3. results and discussion optical observations of the control and inhibited polyaspartic coatings loaded onto milled and blasted steel panels after having been buried in soil for 30 days at rt and 35°c are displayed in figs.4-15. the coatings exhibited varying degrees of blistering and, in some cases, some rusting was also present following the test. the experimental results are presented and discussed according to the type of coating applied and the experimental conditions. 3.1. control polyaspartic coating in soil at rt and 35°c the macroscopic observations after soil experiments had been conducted on the control polyaspartic coating applied to the milled and blasted surface finished steel panels are depicted in figs.4-7. a cluster of blisters on the control polyaspartic coating applied to the milled surface finished steel after a soil experiment had been conducted at rt can be seen in fig.4. furthermore, cracking of the blisters is also clearly visible as indicated by the arrows, where rust can be observed under the peeled off blisters. additional clustered and isolated open blisters on the control polyaspartic coating tested in soil at 35°c are presented in fig.5. blisters in isolated spherical shapes of the control polyaspartic coating applied to the blasted, surface finished steel panels are documented in figs.6-7. however, in fig.6, the surface morphology contains a collection of smaller blisters on the control polyaspartic coating applied to the blasted, surface finished steel after the soil experiments had been conducted at rt. on the other hand, in fig.7, bigger blisters on the control polyaspartic coating are visible following the soil experiments at 35°c. figure 4. control polyaspartic coating, milled steel panel, rt figure 6. control polyaspartic coating, blasted steel panel, rt figure 7. control polyaspartic coating, blasted steel panel, 35°c figure 5. control polyaspartic coating, milled steel panel, 35°c elhoud and van everbroeck hungarian journal of industry and chemistry 38 3.2. polyaspartic coating loaded with an alkylammonium corrosion inhibitor tested in soil at rt and 35°c corrosion inhibitors are used to reduce the risk of corrosion on metal substrates in aqueous media by forming a barrier film or controlling the corrosion reactions of the corrosion cell. alkylammonium salt inhibitors exhibit excellent biocidal and anticorrosive properties [6]. corrosion inhibitors have been added to coating systems as one of the direct additives or in capsular form in the smart coating. although the addition of a corrosion inhibitor to a coating system is primarily intended to improve its degradation resistance, adhesion between the film coating and metal substrate may also be improved to some extent. nevertheless, some corrosion inhibitors have a tendency to degrade in microbial cultures such as soils. in this regard, the performance of the alkylammonium inhibitor in the examined polyaspartic coating submerged in soil is presented in this section. surface morphological observations of the polyaspartic coating incorporated with the alkylammonium inhibitor and micaceous iron oxide barrier following soil corrosion experiments at rt and 35°c are displayed in figs.8-11. in fig.8, it can be seen that the liquid alkylammonium inhibitor reduced but did not prevent the formation of blisters on the polyaspartic coating applied to the milled surface finished steel panels tested in soil at rt. perforations through the coatings of the alkylammonium corrosion inhibitor and iron oxide barrier were visible after having been immersed in soil for 30 days at rt. for clear verification, the images of the perforations were inverted horizontally and vertically as documented in figs.8a and 8b, respectively. since these perforations were not observed when the coating was applied and before it was immersed in the soil, they may have resulted from the corrosion reactions occurring underneath the coating or the coating substances reacting with the soil causing leaching of coating contents such as the corrosion inhibitors. groups of blisters and the iron oxide barriers on black spots distributed over the surface of the coating layer can be seen in fig.8c. as for the samples tested in soil at 35°c presented in fig.9, damage to the coating was in the form of wider bulging blisters, moreover, iron oxide barriers were visible. the effect of the surface finish of the steel panels on the organic inhibitor polyaspartic coating was not noticeable. however, the degree of blistering still visible on the coating applied to the blasted panels as well as tested in soil at rt and 35°c is illustrated in figs.10 and 11, respectively. the experiments in this study simulated to a certain extent the performance of both steel structures immersed in soil and coatings as one of the most commonly used protection systems for underground assets. in this regard, the examined soils at rt and 35°c were found to threaten the control polyaspartic coating and polyaspartic coating dispersed with the alkylammonium corrosion inhibitor. this outcome is proven by the penetration and accumulation of the figure 8. polyaspartic coating (alkylammonium corrosion inhibitor + iron oxide barrier), milled steel panel, rt figure 9. polyaspartic coating (alkylammonium corrosion inhibitor + iron oxide barrier), milled steel panel, 35°c behavior of control and inhibitive polyaspartic coatings 50(2) pp. 35–41 (2022) 39 aggressive elements in moisture through the coating matrix, whereas the visual and macroscopic interpretations confirmed the existence of a mass of blisters and cracks in the control coating. the identified blisters in the coating are most likely caused by a combination of factors such as saline conditions as well as the presence of sulfate, bacteria and sulfide. the role of such parameters, in addition to chemical, mechanical and biological activities, in the corrosion of buried steel on top of the degradation of other materials are discussed elsewhere [2,7-8]. furthermore, the microbial culture of the soil has a tendency to cause the biodegradation of the alkylammonium salt that exists in the chains of some corrosion inhibitors in the main structure. this type of biodegradation has been studied by several previous researchers, who summarized that a closely packed nitrogen atom yields biodegradable alkylammonium salts. however, its degree of resistance improves significantly in correlation with the number of long alkyl chains associated with the nitrogen atom [9]. 3.3. polyaspartic coating loaded with a zinc phosphate corrosion inhibitor tested in soil at rt and 35°c figs.12-15 depict the macroscopic observations of a polyaspartic coating containing a zinc phosphate inhibitor and a micaceous iron oxide barrier applied to milled and blasted steel panels. it was clearly observed that the combination of zinc phosphate and the iron oxide barrier in the polyaspartic coating significantly inhibited the formation of blisters. the optical photographs of the polyaspartic coating tested in soil at rt and 35°c on the milled surface finished and blasted surface finished steel panels are strongly in line with the presence of the zinc phosphate corrosion inhibitor and iron oxide barrier, since neither blisters nor rust were recorded. only flakes of the iron oxide barrier dispersed in the matrix of the polyaspartic coating are visible. the experimental results show that the dispersion of the zinc phosphate corrosion inhibitor and iron oxide barrier in the polyaspartic coating led to the development of its resistance to soil attack without exhibiting any considerable indications of deterioration. the resistance of this type of coating to the soil is attributed to the effectiveness of the zinc phosphate corrosion inhibitor, which reacted with and bonded to the steel substrate, forming a zinc phosphate protective layer and an iron oxide barrier composed of the phosphating figure 10. polyaspartic coating (alkylammonium corrosion inhibitor + iron oxide barrier), blasted steel panel, rt figure 11. polyaspartic coating (alkylammonium corrosion inhibitor + iron oxide barrier), blasted steel panel, 35°c figure 12. polyaspartic coating (zinc phosphate corrosion inhibitor + iron oxide barrier), milled steel panel, rt figure 13. polyaspartic coating (zinc phosphate corrosion inhibitor + iron oxide barrier), milled steel panel, 35°c elhoud and van everbroeck hungarian journal of industry and chemistry 40 film containing fepo4, fe2o3 and feo. the effectiveness of both the zinc phosphate and barrier are in agreement with the findings of several studies that investigated epoxy and waterborne acrylic coatings [10]. 3.4. mechanism of blister formation blistering phenomena are associated with the absorption of water into the coating. two of the most common types of coating blisters are: 1) osmotic blisters associated with the diffusion of water through the coating due to the presence of soluble salts on substrates or interlayers; 2) non-osmotic blisters due to swelling and buckling of the coating associated with the absorption of water in the coating [11]. in figs.4 and 5, rust is observed under blisters in the control coating on the milled surface finished steel panels. the blisters on the milled surface finished steel panels can be classified as osmotic blisters because the milled layer might contain impurities resulting in a weak degree of adhesion of the coating to the substrate, thereby leading to the possible formation of blisters given the presence of the penetrated moisture. however, since the same coating on blasted steel yielded isolated blisters, as can be seen in figs.6 and 7 after soil experiments were conducted at rt and 35°c, it seems that the steel finish controlled the formation of blisters on the control polyaspartic coating. horizontal and vertical flip images of perforations in the alkylammonium coating on milled steel plates following soil tests at rt are depicted in figs.8a and 8b, respectively. these can be explained by either corrosion reactions beneath the coating leading to osmotic blisters and subsequently perforations or reactions between the soil and the contents of the coating yielding perforations in the coating due to leaching of some of its contents such as the corrosion inhibitor. nevertheless, examination of the coating before being buried in the soil did not exhibit perforations, which were only seen after the soil tests. the same sample in fig.8c shows a group of unperforated blisters. the hypothesis for the formation of blisters recorded in the experimental results is schematically described in fig.16. how moisture from the soil penetrated through the coating is outlined in fig.16a; with regard to the control coating, which does not contain inhibitive pigments or a coating loaded with the alkylammonium corrosion inhibitor, the moisture can easily pass through the coating into the substrate causing blistering. however, the presence of the zinc phosphate corrosion inhibitor and the iron oxide barrier protected the coating against soil attack (fig.16b). anyway, hightech investigative techniques such as sem could be applied in future studies to better understand the behavior of polyaspartic coatings in soils. 4. conclusions since the content of the coating and temperature are important factors controlling the impact of soil on the performance of coatings and its reliability, the following conclusions have been drawn: figure 14. polyaspartic coating (zinc phosphate corrosion inhibitor + iron oxide barrier), blasted steel panel, rt figure 15. polyaspartic coating (zinc phosphate corrosion inhibitor + iron oxide barrier), blasted steel panel, 35°c a) b) figure 16. a schematic diagram representing the formation of blisters in the control and inhibitive coatings: a) control coating and b) zinc phosphate + iron oxide barrier inhibitive coating behavior of control and inhibitive polyaspartic coatings 50(2) pp. 35–41 (2022) 41 • increasing the soil temperature from rt to 35°c increased the severity of blistering in the control polyaspartic coating and polyaspartic coating loaded with the alkylammonium corrosion inhibitor after 30day-long soil experiments due to the high degree of moisture absorption. • the advantages of applying the zinc phosphate corrosion inhibitor and the micaceous iron oxide barrier are significant in eliminating the soil risk to buried steel. • this coating efficiently protects milled surface finished steel as well as blasted steel in soil experiments conducted over 30 days at rt and 35°c. • the newly invented coating formula may well be applied as a protection system for steel assets submerged in soil in industry and the infrastructure sectors. • the soil experimental results of the polyaspartic coating containing the zinc phosphate corrosion inhibitor supported the final remarks that this type of coating exhibits a good degree of resistance to erosion when immersed, as determined in earlier stages of this project. future studies should include experimentally measuring and examining the soil parameters as well as physical testing, which could not be examined at this stage of the project: 1. soil parameters such as soil type, ph variation, bacterial activity, water content and soil resistivity. 2. physical and mechanical testing of coatings, e.g. with regard to their compatibility with protective coatings and cathodic protection, cathodic disbondment, flexibility, cracking resistance, electrical and insulation resistance as well as compressive and tensile strength. 3. thermal resistance and permeability of the coating in the simulation of anticipated working environments. acknowledgements the authors would like to thank vlaio for sponsoring this project conducted by chemsystems (grant hbc.2020.3021) to identify and develop a concrete coating produced by adcos nv in order to extend the application of this product to include the protection of steel assets. references [1] emori, w.; okafor, p.c.; bassey, v.m.: physicochemical characteristics of soil moisture and their effects on the corrosion behavior of buried mild steel in calabar metropolis, nigeria, j. environ. prot. 2018, 9, 801–814, doi: 10.4236/jep.2018.97050 [2] chen, j.; chen, z.; ai, y.; xiao, j.; pan, d.; li, w.; huang, z.; wang, y.: impact of soil composition and electrochemistry on corrosion of rock-cut slope nets along railway lines in china, sci. rep., 2015, 5, 14939, doi: 10.1038/srep14939 [3] putra, r.; muhammad; huzni, s.; ali, n.; fonna, s.: effect soil resistivity in mapping potential corrosion in underground pipelines area, aip conf. proc., 2018, 1977, 040011, doi: 10.1063/1.5042981 [4] jiang, c.; cheng, x.: anti-corrosion zinc phosphate coating on building steel via a facile one-step brushing method, electrochem. commun., 2019, 109, 106596, doi: 10.1016/j.elecom.2019.106596 [5] van liedekerke, m., gentile, a., barceló-cordón, s., soil country analyses: belgium (joint research centre report 2009), doi 10.2788/27334 [6] brycki, b.; szulc, a.: gemini surfactants as corrosion inhibitors. a review, j. mol. liq., 2021, 344, 117686, doi: 10.1016/j.molliq.2021.117686 [7] yahaya, n.; lim, k.s.; noor, n.m.; othman, s.r.; abdullah, a.: effects of clay and moisture content on soil-corrosion dynamic, malays. j. civ. eng., 2011, 23(1), 24–32, doi: 10.11113/mjce.v23.15809 [8] abdulameer, e.a.; al-uqaily, r.a.h.; al-bayaty, s.a.h.: the effect of both moisture and clay content on the soil corrosion process for different periods of time as a geomorphological study in al-kut city, iop conf. ser.: earth environ. sci., 2022, 961(1), 012083, doi: 10.1088/1755-1315/961/1/012083 [9] van ginkel, c.g.; kolvenbach, m.: relations between the structure of quaternary alkyl ammonium salts and their biodegradability, chemosphere, 1991, 23(3), 281–289, doi: 10.1016/0045-6535(91)90184-f [10] hao, y.; liu, f.; han, e.-h.; anjum, s.; xu, g.: the mechanism of inhibition by zinc phosphate in an epoxy coating, corros. sci., 2013, 69, 77–86, doi: 10.1016/j.corsci.2012.11.025 [11] li, j.c.m.; him, l.k.; chang, b.t.a.: blister initiation mechanism of fbe coatings, nace international corrosion conference series, 2019, 13508, issn: 03614409 https://doi.org/10.4236/jep.2018.97050 https://doi.org/10.4236/jep.2018.97050 https://doi.org/10.1038/srep14939 https://doi.org/10.1063/1.5042981 https://doi.org/10.1016/j.elecom.2019.106596 https://doi.org/10.2788/27334 https://doi.org/10.1016/j.molliq.2021.117686 https://doi.org/10.1088/1755-1315/961/1/012083 https://doi.org/10.1016/0045-6535(91)90184-f https://doi.org/10.1016/0045-6535(91)90184-f https://doi.org/10.1016/j.corsci.2012.11.025 https://doi.org/10.1016/j.corsci.2012.11.025 hungarian journal of industry and chemistry vol. 50(2) pp. 43–49 (2022) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2022-17 study on adsorption of essential oils on polylactic acid microparticles lilla virág1*, róbert bocsi1 and dóra pethő1 1 research centre for biochemical, environmental and chemical engineering, faculty of engineering, university of pannonia, egyetem u. 10, veszprém, 8200, hungary polylactic acid (pla) is a biodegradable polymer that is widely used in medical devices, drug delivery systems, fibers for packaging containers and textiles. however, given that interactions between the polymer and the materials in contact with it affect its applications, it is important to study its adsorption and diffusion properties. the adsorption capacity of different polylactic acid particles regarding different additives, e.g. essential oils (thymus vulgaris, melissa officinalis and foeniculum vulgare), was investigated. pla microparticles of various sizes were prepared by a solvent emulsification evaporation method. in this study, the specific adsorption of essential oils on pla microparticles was also investigated, which is related to the solubility parameters of essential oils. the experiments were performed using three different solutions of essential oils and ethanol as a solvent. two sets of pla microparticles were prepared with different solvents using three different particle sizes. pla microparticles exhibited different adsorption properties depending on the solvent that was used for their production. samples of particles prepared using the solvent dichloromethane had a higher essential oil uptake than those prepared with chloroform. the uptake of essential oil solution did not change significantly (∼60%) by varying either the type of solvent used for pla preparation or pla particle size. the solubility of the essential oils affects the specific adsorption of essential oils on the microparticles. among the components of the hansen solubility parameters (hsps), the polarity of essential oils is strongly related to adsorption. keywords: polylactic acid, microparticles, essential oil adsorption, hansen solubility parameters 1. introduction biodegradable polymers are important feedstocks in industry as they offer an environmentally-friendly alternative to fossil-based polymers in biomedical, agricultural and household applications [1]. pla is an aliphatic polyester as well as one of the most commercially available, bio-based, biodegradable and biocompatible polymers. pla is commonly considered for different applications such as in drug delivery systems, tissue engineering, packaging and textiles. the fields of application of this polymer are limited by certain properties, e.g. its low mechanical strength or hydrophobicity [2]-[3]. different additives, e.g. essential oils, can be incorporated into biodegradable polymers to improve their functional properties [4]. different types of essential oils such as thyme, cinnamon, oregano and basil are incorporated into biodegradable polymer films, e.g. for the development of food packaging films to enhance antimicrobial properties [5]. essential oils also act as plasticizers in polymers. due to their plasticizing properties, the structural and mechanical properties of such polymers can be altered [6], thereby also changing the sorption properties of pla. received: 18 oct 2022; revised: 24 oct 2022; accepted: 24 oct 2022 *correspondence: virag.lilla@mk.uni-pannon.hu interactions between essential oils and pla have been studied by several researchers (dusankova et al., martins et al., dicastillo et al.) using different processing methods [7]-[9] and are mainly determined by the composition of the essential oil and its polarity. dusankova et al. studied pla microspheres containing different components of essential oils. they found that the more polar components adsorb better in the microspheres than the more apolar ones, as pla itself is polar [7]. martins et al. came to a similar conclusion. when the incorporation and release of the components of the essential oils thymol and p-cymene were studied, the diffusion rate of these components through the pla matrix differed significantly (diffusion coefficient was 1.99 × 10−16 m2/s for thymol and 4.34 × 10−16 m2/s for pcymene), which could be explained by their difference in polarity [8]. in our work, the adsorption properties of polylactic acid particles regarding different essential oils like those from lemon balm, fennel and thyme were investigated. the microparticles were prepared by a solvent emulsification evaporation method [10]. the structure of the polymer particles formed is critical, as their particle size distribution and porosity influence their adsorption properties. the properties of the particles that are https://doi.org/10.33927/hjic-2022-17 mailto:virag.lilla@mk.uni-pannon.hu virág, bocsi and pethő hungarian journal of industry and chemistry 44 produced by the solvent emulsification evaporation method are mostly affected by the concentration of the pla solution, type and amount of surfactant as well as the mixing speed. besides the concentration of the pla solution, its composition is also important [11]. the organic solvent in which pla is dissolved will affect the structure of the microparticles produced [10], [12]. shi et al. found that pla particles prepared using chloroform as the solvent were less porous than those prepared in ethyl acetate [12]. consequently, in our work, the adsorption of essential oils on pla microparticles as a function of the pla particle size was investigated. to modify the particle size distribution, the concentration of pla solution was changed during the emulsification method. 2. experimental 2.1. materials natureworks ingeo biopolymer 3d850 pla granules, dichloromethane (>99.8%, fisher), chloroform (technical grade, stabilized with ~0.6% of ethanol, vwr) and polyvinyl alcohol (fully hydrolyzed, mw approx. 60,000; merck) were used to prepare the pla microparticles. to measure the degree of adsorption, ethanol (99.8% g.r., iso reagent, lach-ner, s.r.o.) and three kinds of essential oils: melissa officinalis (from lemon balm, neuston healthcare kft.), foeniculum vulgare (from fennel, neuston healthcare kft.) and thymus vulgaris (from thyme, neuston healthcare kft.) were used. 2.2. methods microparticles were prepared based on a solvent emulsification evaporation method. the particles were prepared as follows: firstly, 200 ml of pla solution of a given concentration (2.5, 5.0 and 7.5 wt. %) using dichloromethane or chloroform as a solvent; secondly, the solution was added to 400 ml of 1 wt. % polyvinyl alcohol (pva) solution. the emulsion was stirred with a magnetic stirrer at 820 rpm for 24 or 48 hours, depending on the solvent used (dichloromethane or chloroform, respectively). after filtering and washing, the solid particles were dried in a binder fd 53 oven at 50 °c for 24 hours. to determine the average diameter and size distribution of the particles, an image was taken using an optical microscope (lacerta, zoom: 40x). the particle size was determined from the images using the program imagej. to measure the degree of adsorption, 1.000 g of pla particles were weighed on an ohaus adventurer ar3130 analytical balance in a pre-weighed dry test tube, then 2.000 g of a 1.00 mg/ml ethanolic solution of essential oil was added to it. the microparticles were soaked for 24 hours before the samples were separated by filtration. the essential oil concentrations of the residual ethanolic solutions were analyzed by uv-vis spectrophotometry. the absorption spectra of the samples were recorded between 200 and 800 nm using an agilent cary 60 uv-vis spectrophotometer. differential scanning calorimetry (dsc) was performed with a netzsch dsc 214 polyma differential scanning calorimeter. the measurements were carried out under a 60 ml/min n2 flow rate according to the following protocol: first the sample was heated from 20 to 200 °c at a heating rate of 10 °c/min before being cooled from 200 to 20 °c at a cooling rate of 10 °c/min then reheated from 20 to 200 °c at the same heating rate. notation was applied to the samples, e.g. pla_k_100_el. the first letter refers to the solvent that was used for pla preparation (dkm for dichloromethane and k for chloroform), the number refers to the size of the microparticles (table 1). at the end of the sample identification, the first letter refers to the type of solvent used for essential oil solution (e for ethanol) and the last letter refers to the essential oil, namely l for lemon balm, t for thyme and f for fennel. 3. results and discussions 3.1. microparticle properties the properties of the microparticles such as their particle size distribution are shown in fig.1. as the concentration of the pla solution increased, the size of the particles produced also increased. the correlation between the concentration of pla solution and the diameter of the particles is linear. the solvent emulsification evaporation method mainly produced spherical particles that did not aggregate (fig.2). 3.2. solution uptake by microparticles regarding the uptake of ethanolic solution of essential oil by the particles prepared from a pla solution prepared in dichloromethane, it was concluded that the solution uptake increases slightly by 10% on average as the particle size increases. however, the presence of essential oils in the solutions did not significantly affect the solution uptake of the particles. for a given particle size, the solution uptake was practically the same for all examined solutions. the average solution uptake by table 1. notation for the microparticles sample name pla-solution – solvent type average size, µm pla_dkm_50 dichloromethane (dkm) 57±12 pla_dkm_100 116±21 pla_dkm_200 207±57 pla_k_50 chloroform (k) 56±14 pla_k_100 121±31 pla_k_200 198±40 essential oils adsorption on polylactic acid 50(2) pp. 43–49 (2022) 45 particles 50, 100 and 200 µm in diameter is 60, 66 and 75%, respectively. 3.3. adsorption of essential oils on microparticles the different types of pla microparticles exhibited different adsorption properties (figs.3 and 4) regarding various essential oils. it was found that in the case of lemon balm, the uptake of essential oils by pla_dkm particles from ethanolic solutions and the specific amount of the essential oil adsorbed increased as the particle size increased, while the degree of uptake and adsorption decreased in the case of ethanolic solutions of thyme and fennel. lemon balm essential oil yielded an outstanding result. in this case, by increasing the particle size from 50 to 100 µm and then to 200 µm, the degree of essential oil uptake increased by 19% and then by a further 16%. it was concluded that the effect of pla_k particle size on the specific adsorption of thyme and fennel essential oils is insignificant, there is no correlation between the amount of essential oil adsorbed and the particle size. however, in the case of the lemon balm essential oil, the degree of specific adsorption increased as the particle size increased. in general, it was concluded that for pla_dkm particles, the essential oil uptake mainly resulted from the differences between the microparticles (degree of crystallinity, size, porosity) and the types of essential oils present in the solutions. nonetheless, in the case of pla_k particles, the specific amount of essential oil adsorbed on the surface or in the pores of the particles did not change significantly as the particle size changed, rather each essential oil was adsorbed differently on the particles. the particles prepared by using dichloromethane as a solvent had a higher specific essential oil adsorption (0.8-3.4 mg eo/g pla) than particles prepared in chloroform (0.6-1.6 mg eo/g pla). variation in the adsorption properties of the particles was probably caused by the differences in their structure. the different solvents used in the production process caused the particles to solidify at different rates, leading to possible differences in their internal structure and porosity. 3.4. the correlation between adsorption properties in light of the hansen solubility parameters (hsps) adsorption properties are affected by the composition and properties of the adsorbate. the connection between figure 1. particle size distribution of the different pla microparticles figure 2. images of the microparticles: a.) pla_k_100 and b.) pla_dkm_100 figure 3. essential oil uptake (%) by the microparticles in the case of a.) particles prepared in dichloromethane and b.) particles prepared in chloroform 0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 pla_dkm_50 pla_dkm_100 pla_dkm_200 e ss en ti a l o il u p ta k e, % el et ef a. 0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 pla_k_50 pla_k_100 pla_k_200 e ss en ti a l o il u p ta k e, % el et ef b. virág, bocsi and pethő hungarian journal of industry and chemistry 46 the solubility of essential oils and the adsorption properties of pla was investigated. solubility can be characterized by the hsps, which describe the affinity of the polymer for different organic substances. hansen total solubility parameter (δt) is composed of three parameters, one indicating the contribution to the dispersion forces (δd), another characterising the polar interactions (δp) and one more demonstrating the formation of h-bonds (δh). these solubility parameters can be determined using different methods such as the group contribution method (hoftyzer-van krevelen method) [13]-[15]. the specific amount of essential oil adsorbed on pla can be related to the total solubility parameter or one of its components. since different essential oils have different solubility parameters depending on their composition (table 2), the specific adsorption on pla is different for different essential oils. a correlation between the adsorbed amount of the essential oil and δδp,eo was observed. (δδp,eo shows how much the δp of an essential oil differs from that of pla.) in the case of pla_dkm particles, the specific adsorption decreased as δδp,eo increased (fig.5). in contrast, it was found that the specific amount of essential oil adsorbed on pla_k particles deviated in the case of δδp,eo less than 5.5 (mpa1/2). 3.5. thermal properties of the pla particles dsc was used to evaluate the thermal properties of the samples. the glass transition (tg), cold crystallization (tcc) and melting temperatures (tm) of the pla particles were determined during the second heating of the dsc measurement. the degree of crystallinity (xc%) was calculated from the enthalpy of melting (δhm) and the enthalpy of cold crystallization (δhcc), taking into account an enthalpy of melting (δhm 0) of 94 kj/kg for 100% crystalline pla [16]-[17]: xc% = [(δhm-δhcc)/δhm] × 100 (1) both types of pla particles exhibited two exothermic, cold crystallization peaks and an endothermic melting peak (fig.6). for both pla_dkm and pla_k particles, the glass transition occurred at ~61°c (61.3±0.6 and 60.9±0.3°c, respectively) and the melting at 177°c (177.3±0.8 and 176.6±0.3°c, respectively). however, a difference is observed in the cold crystallization temperatures between the two types of particles. for the pla_k and pla_dkm particles, the first cold crystallization peaks appeared at 96.7±0.6°c and 104.4±0.2°c, respectively. the probable reason for this is that during the emulsification method, the particles solidified at different rates based on the organic solvent used for the pla solution. as the particles solidified at different rates, their structure and porosity vary. the thermal properties of the granules did not change even when the concentration of the pla solution was changed during their preparation. the degree of crystallinity of the pla_k particles was approximately 25.0±0.7%, while that of pla_dkm was different. the degree of figure 4. specific adsorption of essential oil (eo) on microparticles (mg eo/g pla) in the case of a.) particles prepared in dichloromethane and b.) particles prepared in chloroform 0.00 0.50 1.00 1.50 2.00 2.50 pla_dkm_50 pla_dkm_100 pla_dkm_200 m g e o / g p l a el et ef a. 0.00 0.50 1.00 1.50 2.00 2.50 pla_k_50 pla_k_100 pla_k_200 m g e o / g p l a el et ef b. table 2. hansen solubility parameters (hsps) of the materials material δd (mpa1/2) δp (mpa1/2) δh (mpa1/2) δt (mpa1/2) pla 18.6 9.9 6.0 21.9 ethanol 15.1 8.4 18.3 25.2 lemon balm essential oil 16.4 4.6 5.1 17.8 thyme essential oil 21.5 3.3 9.6 23.8 fennel essential oil 24.3 3.9 28.0 37.3 essential oils adsorption on polylactic acid 50(2) pp. 43–49 (2022) 47 crystallinity of the pla_dkm_50, pla_dkm_100 and pla_dkm_200 particles was 24.3±0.4, 19.6±0.7 and 21.5±0.8, respectively. after the degree of adsorption was measured, the thermal properties of the microparticles did not change due to their interaction with the essential oils (fig.7). however, the adsorption of essential oils had an effect on the degree of crystallinity of the particles, as the degree of crystallinity of the pla_dkm particles increased by 2% and that of pla_k_50 particles increased to 30%. the degree of crystallinity of the pla_k_100 and pla_k_200 particles was not influenced by which essential oil was used. based on the results, it was found that the thermal properties of the pla microparticles are affected by the type of solvent used during their preparation rather than by the concentration of the pla solution used. it was concluded that the thermal properties of the microparticles were not changed by the adsorption of essential oils. therefore, the amount of essential oil adsorbed was insufficient to cause a significant change to the pla structure. 4. conclusion in our work, the adsorption properties of polylactic acid particles for lemon balm, fennel and thyme essential oils were investigated. the adsorption of these essential oils on the pla particles was investigated as a function of particle size (50, 100 and 200 µm). it was concluded that the adsorption of essential oils is affected by both differences between types of microparticles (degree of crystallinity, size, porosity) and the types of essential oils present in the solutions of pla_dkm samples. although the specific amount of essential oil adsorbed on the surface or in the pores of pla_k particles did not change significantly as the figure 5. correlation between the hsps and the specific adsorption of essential oil (eo) on microparticles (mg eo/ g pla) in the case of a.) particles prepared in dichloromethane and b.) particles prepared in chloroform figure 6. the second heating dsc curves of the pla granules and microparticles in the case of a.) their different types and b.) their different sizes 4.0 4.5 5.0 5.5 6.0 6.5 7.0 0.00 1.00 2.00 3.00 pla_d_100_el pla_d_100_ef pla_d_100_et pla_d_200_el pla_d_200_ef pla_d_200_et 0.00 0.50 1.00 1.50 2.00 2.50 5.0 6.0 7.0 m g e o /g p l a δδp,eo (mpa1/2) a. 4.0 4.5 5.0 5.5 6.0 6.5 7.0 0.00 50.00 100.00 pla_k_50_el pla_k_50_ef pla_k_50_et pla_k_100_el pla_k_100_ef pla_k_100_et pla_k_200_el pla_k_200_ef pla_k_200_et 0.00 0.50 1.00 1.50 2.00 2.50 5.0 6.0 7.0 m g e o /g p l a δδp,eo (mpa1/2) b. -1.40 -1.20 -1.00 -0.80 -0.60 -0.40 -0.20 0.00 0.20 20 80 140 200 m w /m g temperature, c pla_dkm_100 pla_k_100 a.a. -1.40 -1.20 -1.00 -0.80 -0.60 -0.40 -0.20 0.00 0.20 20 80 140 200 m w /m g temperature, c pla_dkm_50 pla_dkm_100 pla_dkm_200 b. virág, bocsi and pethő hungarian journal of industry and chemistry 48 particle size varied, the degree of adsorption of the essential oils on the particles varied. the particles that were prepared in dichloromethane as a solvent, exhibited a higher specific adsorption of 0.8-3.4 mg eo/g pla compared to particles prepared in chloroform of 0.6-1.6 mg eo/g pla. the difference in the adsorption properties of the particles is probably caused by variations in their structure. the different solvents used in the production process caused the particles to solidify at various rates, which may lead to differences in their internal structure and porosity. the reason for differences in the degree of adsorption of the essential oils is variation in the composition of the essential oil solutions, which is characterized by the hsps. in ethanolic solutions, a correlation between the adsorbed amount of the essential oil and the δp component of the total hsps was observed. based on the results, it was determined that the thermal properties of the pla microparticles are affected by the type of solvent used during their preparation rather than by the concentration of pla solution applied. it was concluded that the thermal properties of the microparticles were not affected by the degree of adsorption. references [1] ranakoti, l.; gangil, b.; mishra, s.k.; singh, t.; sharma, s.; ilyas, r.a.; el-khatib, s.: critical review on polylactic acid: properties, structure, processing, biocomposites, and nanocomposites, materials, 2022, 15(12), 4312, doi: 10.3390/ma15124312 [2] li, g.; zhao, m.; xu, f.; yang, b.; li, x.; meng, x.; teng, l.; sun, f.; li, y.: synthesis and biological application of polylactic acid, molecules, 2020, 25(21), 5023, doi: 10.3390/molecules25215023 [3] nofar, m.; sacligil, d.; carreau, p.j.; kamal, m.r.; heuzey, m.c.: poly (lactic acid) blends: processing, properties and applications, int. j. biol. macromol., 2019, 125, 307–360, doi: 10.1016/j.ijbiomac.2018.12.002 [4] qin, y.; li, w.; liu, d.; yuan, m.; li, l.: development of active packaging film made from poly (lactic acid) incorporated essential oil, prog. org. coat., 2017, 103, 76–82, doi: 10.1016/j.porgcoat.2016.10.017 [5] ahmed, j.; hiremath, n.; jacob, h.: antimicrobial, rheological, and thermal properties of plasticized polylactide films incorporated with essential oils to inhibit staphylococcus aureus and campylobacter jejuni, j. food sci., 2016, 81(2), 419–429, doi: 10.1111/1750-3841.13193 [6] tarach, i.; olewnik-kruszkowska, e.; richert, a.; gierszewska, m.; rudawska, a.: influence of tea tree essential oil and poly(ethylene glycol) on antibacterial and physicochemical properties of polylactide-based films, materials, 2020, 13(21), 4953, doi: 10.3390/ma13214953 [7] dusankova, m.; pummerova, m.; sedlarik, v.: microspheres of essential oil in polylactic acid and poly(methyl methacrylate) matrices and their blends, j. microencapsul., 2019, 36(3), 305–316, doi: 10.1080/02652048.2019.1623337 [8] martins, i.m.; rodrigues, s.n.; barreiro, m.f.; rodrigues, a.e.: release studies of thymol and pcymene from polylactide microcapsules, ind. eng. chem. res., 2012, 51(35), 11565–11571, doi: 10.1021/ie301406f [9] de dicastillo, c.l.; villegas, c.; garrido, l.; roa, k.; torres, a.; galotto, m.j.; rojas, a.; romero, j.: modifying an active compound’s release kinetic using a supercritical impregnation process to incorporate an active agent into pla electrospun mats, polymers, 2018, 10(5), 479, doi: 10.3390/polym10050479 [10] o'donnell, p.b.; mcginity, j.w.: preparation of microspheres by the solvent evaporation technique, adv. drug deliv. rev., 1997, 28(1), 25–42, doi: 10.1016/s0169-409x(97)00049-5 [11] singh, b.; singh, p.; sutherland, a.j.; pal, k.: control of shape and size of poly (lactic acid) microspheres based on surfactant and polymer concentration, mater. lett., 2017, 195, 48–51, doi: 10.1016/j.matlet.2017.02.068 figure 7. the second heating dsc curves of the pla microparticles after measuring the adsorption of a.) particles prepared in chloroform and b.) particles prepared in dichloromethane. -1.40 -1.20 -1.00 -0.80 -0.60 -0.40 -0.20 0.00 0.20 20 80 140 200 m w /m g temperature, c pla_k_50 pla_k_50_el pla_k_50_et pla_k_50_ef a. -1.40 -1.20 -1.00 -0.80 -0.60 -0.40 -0.20 0.00 0.20 20 80 140 200 m w /m g temperature, c pla_dkm_50 pla_dkm_50_el pla_dkm_50_ef pla_dkm_50_et b. https://doi.org/10.3390/ma15124312 https://doi.org/10.3390/ma15124312 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d.w.; te nijenhuis, k.: properties of polymers: their correlation with chemical structure; their numerical estimation and prediction from additive group contributions, fourth edition, (elsevier, amsterdam, the netherlands), 2009, pp. 201–225, isbn: 978-008054819-7 [15] sato, s.; gondo, d.; wada, t.; kanehashi, s.; nagai, k.: effects of various liquid organic solvents on solvent-induced crystallization of amorphous poly(lactic acid) film, j. appl. polym. sci., 2013, 129(3), 1607–1617, doi: 10.1002/app.38833 [16] saiter, a.; delpouve, n.; dargent, e.; saiter, j.m.: cooperative rearranging region size determination by temperature modulated dsc in semi-crystalline poly(l-lactide acid), eur. polym. j., 2007, 43(11), 4675–4682, doi: 10.1016/j.eurpolymj.2007.07.039 [17] ahmed, j.; zhang, j.-x.; song, z.; varshney, s.k.: thermal properties of polylactides: effect of molecular mass and nature of lactide isomer, j. therm. anal. calorim., 2009, 95(3), 957–964, doi: 10.1007/s10973-008-9035-x https://doi.org/10.1007/s10118-018-2079-x https://doi.org/10.1007/s10118-018-2079-x https://doi.org/10.1201/9781420006834 https://doi.org/10.1002/app.38833 https://doi.org/10.1016/j.eurpolymj.2007.07.039 https://doi.org/10.1007/s10973-008-9035-x https://doi.org/10.1007/s10973-008-9035-x hungarian journal of industry and chemistry vol. 50(2) pp. 51–55 (2022) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2022-18 optimization of bacillus licheniformis dsm13 for biosurfactant production using response surface methodology jesse john sakiyo1 and áron németh1* 1 department of applied biotechnology and food science, budapest university of technology and economics, műegyetem rkp. 3, budapest, 1111, hungary biosurfactants are surface-active compounds that can reduce surface tension in both aqueous solutions and hydrocarbon mixtures, which in recent times have become more valuable due to their lower toxicity and are generally referred to as green or organic surfactants. such products are much better than chemical surfactants in terms of their enhanced biodegradation rates and the bioavailability of organic contaminants. fungi, yeast and bacteria are mainly capable of producing microbial biosurfactants. bacteria, especially bacillus, are one of the most frequently applied and studied biosurfactant producers. this study investigated the kinetics of cell growth, the production of biosurfactants as well as the effect of and interactions between the (a) ph within the range of 4.1 to 9.8, (b) glucose concentration between 3.0 and 36.9 g/l, (c) surface tension and (d) emulsification index to maximize biosurfactant production. the analysis was carried out using a central composite design (ccd) model with four factors and five levels. the optimized medium (ph=8 and glucose concentration = 38 g/l) decreased the surface tension to 60 mn/m and increased the product yield up to 2.7 g/l. keywords: cell growth, effect of ph, glucose concentration 1. introduction surfactants are surface-active compounds that reduce the surface tension between two liquids. surfactant molecules are comprised of hydrophobic and hydrophilic, that is, water-hating and water-loving components, respectively. they are also regarded as detergents because of their wetting potential and emulsifying as well as foaming agents. biosurfactants are also surfactants but from a microbial source. they have proven to be more sustainable due to their ability to leave less of or even no chemical residues after their use. biosurfactants have been commonly used in industries such as the petroleum, cosmetics, antimicrobial, pharmaceutical and bioremediation industries [1]-[4]. biosurfactants, also known as biological surfactants, are structurally varied molecules with high surface and emulsifying activities [5]-[6]. glycolipids, lipopeptides and polymeric biosurfactants are the three major groups of biosurfactants. biosurfactants have many advantages over conventional surfactants, including their ease of renewability, large-scale production, economic viability, cheaper substrates, more significant degree of foaming, good selectivity, turbidity, good biocompatibility, effectiveness at high temperatures or ph levels, chemical diversity and environmentally-friendliness [7]-[8]. biodegradation is received: 28 sept 2022; revised: 15 oct 2022; accepted: 15 oct 2022 *correspondence: naron@f-labor.mkt.bme.hu one of the most effective methods for combating environmental degradation mainly as a result of petroleum hydrocarbons, which pose a significant danger to ecosystems. this includes bacteria that use toxic materials as carbon sources, resulting in the breakdown of polluted components into low-molecular-weight or less harmful chemicals with no adverse effects [9]. biosurfactants can decrease the surface tension of water to between 35 and 27 mn/m, which has been recorded by biosurfactant-producing bacteria [10]-[11], as well as increase the emulsifying activity from 20 to 30% for different hydrocarbon compounds during experiments on the emulsification index. a ccd was used to create appropriate testing levels for our response surface methodology (rsm). this analysis will create relevant parameters by making observations or taking measurements to determine the best combination of media that produces the desired response as well as characterizing the reaction so the conventional medium optimization strategy of modifying one independent variable while keeping the rest constant can be applied [12]. the main aim of our research is to produce biosurfactants to study their antifungal effects on crops in agriculture. therefore, the first step is to produce biosurfactants efficiently. for this purpose, media optimization is commenced by using statistical optimization for cell growth in the fermentation broth to https://doi.org/10.33927/hjic-2022-18 mailto:naron@f-labor.mkt.bme.hu sakiyo and németh hungarian journal of industry and chemistry 52 increase the biosurfactant yield, i.e. decrease the surface tension and increase the emulsification index of the biosurfactant produced by bacillus licheniformis dsm13. 2. materials and methods 2.1. microorganism and cultivation of strain the bacillus licheniformis dsm13 strain was purchased from hungary's national collection of agricultural and industrial microorganisms. the biosurfactant fermentations were conducted in 500 ml shake flasks (erlenmeyer flasks with cotton plugs covered with aluminum foil). the inoculum was incubated for two days at 150 rpm and 37°c in a rotary shaker (new brunswick excella e24) by applying an inoculation ratio of 10 %. during the biosurfactant fermentation, the starting total volume, including the inoculum, was 150 ml, with an aeration greater than the working volume. for the biosurfactant fermentation, a minimal medium was used; 1 liter of minimal media (ph=6) contained 1.0 g nh4no3, 34.0 g glucose (hungrana kft., szabadegyháza, hungary), 6.0 g kh2po4, 2.7 g na2hpo4, 0.1 g mgso4*7h2o, 1.2x10-3 g cacl2, 1.65x10-3 g feso4*7h2o, 1.5x10-3 g mnso4*4h2o and 2.2x10-3 g na-edta (reanal laborvegyszer kft., hungary) joshi et al. [13]-[14]. 2.2. unoptimized (reference) fermentation scale-up tests were conducted in a 1 l benchtop fermenter biostat q bioreactor (b braun co) filled up to 700 ml. during batch fermentation, the temperature was maintained at 37°c, the agitation rate at 300 rpm and the aeration rate at 0.5 vvm without ph control. a collection vessel was added to the exhaust air of the fermenter to collect the foam produced during the fermentation. 2.3. statistical analysis of ccd (rsm) for optimization using a ccd for two variables, the power of the response surface approach to maximize biosurfactant production by bacillus licheniformis was investigated in this study, which has served as the foundation for the simulated experimental plan and subsequent analysis. the randomized empirical findings were statistically analyzed using the statistical program tibco statistica (version 13 for windows) to detect the significant differences between the independent variables, namely (a) glucose concentration between 10 and 36 g/l and (b) ph between 4 and 9, to achieve maximum biosurfactant production by b. licheniformis dsm13 (table 1). 2.4. biomass analysis a camspec m501 spectrophotometer was used to determine the biomass content via optical density measurements at a wavelength of 600 nm (od600). 2.5. surface tension analysis surface tension is the force per unit length measured in millinewtons per meter (mn/m). the surface tension was measured using a stalagmometer (wilmad-labglass lg-5050-100) according to the method of czinkóczky et al. [11]. 2.6. ph analysis initially, the ph of the media was set by adjusting it to several ph values ranging from 4 to 9 with 5m hcl or 6m naoh. the ph was measured by a mettler toledo fiveeasy™ ph meter. 2.7. emulsification index (e24) the emulsification index measurement applied was established by plaza et al. [15]. the emulsification index was determined from the supernatant of the fermented broth at intervals corresponding to the sampling frequency during the fermentation. in a test tube, 2 ml of crude oil and 2 ml of cell-free media (supernatant) were introduced and homogenized for 2 minutes by vortexing at 4000 rpm. the emulsifying activity was once more determined after 24 hours as follows: the relative height of the two liquid layers was documented by photos and the pixel size divided to obtain the values of the emulsification index [16]. e24 (%) is defined as [(total height of the emulsified layer) / (total height of the liquid layer) x 100] after 24h of vortexing. table 1. ccd runs showing factors and their levels standard run 2**(2) central composite, nc=4 ns=4 n0=2 runs=10 glucose [g/l] ph 3 34.00 5.00 8 20.00 9.83 1 10.00 5.00 6 36.97 7.00 7 20.00 4.17 2 10.00 9.00 5 3.03 7.00 4 34.00 9.00 10 (c) 20.00 7.00 9 (c) 20.00 7.00 bacillus licheniformis for biosurfactant production 50(2) pp. 51–55 (2022) 53 2.8. isolation and purification of the biosurfactant acid precipitation was used to isolate the biosurfactants. the bacterial cells were first removed by centrifugation and the remaining supernatant containing the biosurfactant was acidified with 2m hcl solution until the ph reduced to 2. the mixture was then incubated at 4 °c for 24 hours. the precipitate was collected by centrifugation at 10,000 rpm and 4°c for 30 minutes. the residue was then resolved in distilled water and the ph reset to neutral before being freeze-dried by a martin christ alpha 1-4 lscbasic lyophilizer [13]. 3. results 3.1. unoptimized (reference) fermentation an unoptimized fermentation according to section 2.2. was carried out and the parameters that were measured during the process are shown in fig.1. the highest reduction in the surface tension (st) was observed 4 30 hours after the fermentation commenced. st ranged from 75.5 to 68.3 mn/m. after 8 hours, the foam began to overflow and was collected in a vessel for further processing. the collected foam had a st of 60 mn/m, indicating that the biosurfactants produced are mainly collected in the foam phase. 3.2. rsm the effects of the glucose concentration and ph is shown in fig.2. the highest biomass growth (od) was recorded at a glucose concentration of 40 g/l and a rather higher ph value of approximately 9 resulting in an optical density of 4.5. the mixed effect of the ph and glucose concentration regarding the surface tension is shown in fig.3. the minimum surface tension was achieved while fermenting at ph 7. according to fig.4, the smallest product amount was achieved when the ph was extremely high at 11 and the glucose concentration was the lowest, while at a higher glucose concentration, the highest product yield was still achieved. this indicates that the gradient of the surface is minimal and very high at low and high glucose concentrations, respectively; moreover, depends on the ph. therefore, the ph was the most important factor leading to an increase in the amount of biosurfactant produced. figure 1. growth, surface activity and emulsification index (e24) of bacillus licheniformis in a 1 l fermenter during growth on a mineral salt medium 0 1 2 3 4 5 6 40 45 50 55 60 65 70 75 80 0 5 10 15 20 25 30 35 o d 6 0 0 [ -] st [ m n /m ], e 2 4 [% ] time (h) surface tension emulsification index od600 figure 2. 3d rsm plot of the interactive effects of glucose concentration (g/l) and ph on biomass production sakiyo and németh hungarian journal of industry and chemistry 54 the model predicted the following ideal conditions to maximize the biosurfactant productivity using bacillus licheniformis dsm13: ph=8 and glucose concentration=40g/l. the anticipated optimum point was confirmed experimentally, moreover, the observed and isolated product was 2.7 g/l. these findings show a strong connection between the predicted and actual experimental values, moreover, this model accurately represents biosurfactant production in the presence of bacillus licheniformis dsm13. since the highest product yield (i.e. lowest surface tension, fig.3) was observed at different conditions, it is recommended to examine product purity in the future as the presence of contaminants can depend on the ph because of phdependent precipitation during product isolation. 4. conclusions biosurfactants are emerging as suitable alternatives to their predominant, less sustainable, petroleum-derived counterparts. in this study, the ccd, in conjunction with the response surface approach, is used to predict the optimization of bacillus licheniformis dsm13 effectively. an increase in the glucose concentration yielded a high biosurfactant concentration while also increasing the fermentation time. at a lower ph level, the strain achieved a low biomass yield and lower biosurfactant yield but no change in the surface tension was observed. it was observed that the best operating conditions for biosurfactant 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https://doi.org/10.1002/abio.200390043 hungarian journal of industry and chemistry vol. 50(2) pp. 57–60 (2022) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2022-19 utilization of agro-wastes in biohydrogen fermentation by various microorganisms katalin bélafi-bakó1*, gábor tóth1, péter bakonyi1 and nándor nemestóthy1 1 research group on bioengineering, membrane technology and energetics, university of pannonia, egyetem u. 10, veszprém, 8200, hungary biohydrogen production based on agro-industrial wastes might be an attractive and effective technology for providing an energy source in the future. dark fermentation is considered to be one of the most suitable biohydrogen formation processes. in this paper, various agro-industrial wastes as well as microorganisms applied for biohydrogen formation are reviewed. keywords: anaerobic process, dark fermentation, bioreactor 1. introduction hydrogen produced biologically (biohydrogen) can be considered as a renewable source of energy [1]-[4]. moreover, it is regarded as one of the most promising, environmentally-friendly “fuels” of the future due to its favourable characteristics, e.g., only water is formed by the combustion of h2, no environmental pollution is produced, highest energy density of 143 kj/g. agroindustrial residues seem to be suitable feedstocks for the production of biohydrogen [5]. large amounts of solid and liquid waste are formed in agriculture every year, moreover, the majority of it is unutilized. however, promising technologies are available whereby agro-industrial residues are applied to produce value-added products and green energy by biological methods [6]. liquid wastes are usually found in the form of wastewater. solid agro-wastes can be classified into four groups [7]: (i) field residues (ii) waste of processing (iii) livestock waste (iv) chemical waste field residues generally originate from crop production and consist of the remains of crops, e.g., leaves, stalks, stems, seeds, straw, husks, shells, pulp, roots, woodland waste, etc. industrial food processing results in solid wastes which are mainly by-products of and leftovers from various plants, e.g., bagasse, sugarcane molasses, wheat bran, rice bran, groundnut shells, apple pomace, fruit peels, de oiled rice bran cake and oil cakes. recieved: 19 sept 2022; revised: 28 sept 2022; accepted: 28 sept 2022 *correspondence: belafine.bako.katalin@mk.uni-pannon.hu livestock waste consists of by-products of slaughterhouses or originates from processing, e.g., bones, feathers, shells of crustaceans, as well as bedding/litter, carcasses and damaged feeders. chemical waste includes plant protection compounds, e.g., pesticides, insecticides and herbicides, as well as their containers and bottles. however, since these materials cannot be utilized in biological methods, this study focuses on the first three groups of solid wastes. biological hydrogen production from agroindustrial wastes includes dark fermentation, photofermentation and microbial electrolysis cells (mec) [5]. photofermentation is a process whereby organic substrates are converted into hydrogen by photosynthetic organisms under anoxic conditions. h2 production in mecs is a bioelectrochemical process, where electrochemical and biological techniques are combined [8]. given that dark fermentation is one of the most common methods used for hydrogen production from agro-wastes due to its higher hydrogen production rate, it is the focus of this mini-review. 2. biohydrogen production by dark fermentation the composition and certain characteristics of agrowastes are determining factors of biohydrogen production. generally speaking, although these materials are rich in carbon sources, the majority of them require some sort of pretreatment. the lignin content in particular should be treated to increase the efficiency of https://doi.org/10.33927/hjic-2022-19 mailto:mailto:belafine.bako.katalin@mk.uni-pannon.hu bélafi-bakó, tóth, bakonyi and nemestóthy hungarian journal of industry and chemistry 58 biodegradation and conversion processes [5]-[7]. pretreatments of agro-industrial residues include: (i) physical, (ii) chemical, (iii) physicochemical and (iv) biological methods. physical methods involve ultrasonication, ozonization, thermaland microwave-assisted techniques as well as size-reduction processes, e.g., milling, grinding, etc. chemical methods include acid or alkali treatments, moreover, more recently organic solvents have been applied. in physicochemical methods, a combination of physical and chemical techniques is used, e.g., steam explosion, hydrothermal treatment and chemical treatment complemented with microwave irradiation. biological methods include enzymatic and microbial (whole cell) treatments, where mainly the degradation of biopolymers occurs. using these pretreatment methods, higher yields and more efficient hydrogen formation can be achieved. dark fermentative biohydrogen production can be carried out by facultative anaerobes and obligate microbes [1], [4]-[5]. in many cases, the suitable types of microorganisms are determined by the substrate applied and mixed microbial consortia are frequently used. nevertheless, numerous microbes have still been used in dark fermentative biohydrogen production based on agro-wastes, examples of which are listed in table 1: table 1: examples of the utilization of various agro-wastes to produce biohydrogen agro-waste microorganism h2 production rate or yield ref. sugar and rice mill wastewater acinetobacter junii rate 5.23 mlh2l-1h-1 [9] rice mill wastewater clostridium beijerinckii yield 214.9 mlh2l-1 [10] cheese whey powder enterobacter asburiae yield 1.19 ± 0.01 molh2mol-1 [11] sugarcane molasses eisenia fetida yield 1571.81 mlh2l-1 [12] cashew apple bagasse clostridium roseum yield 15 mmolh2 l-1 hydrolysate [13] fruit and vegetable wastes + seawater thermotoga maritima rate 12.4 mmolh-1l -1 [14] fruit wastes (apple, banana, grape, melon, orange) consortia from biogas sludge yield 523 ml/g vs (volatile solid) [15] sweet sorghum bagasse caldicellulosiruptor saccharolyticus yield 73.6 mlh2mmol-1 c6 sugars [16] cornstalk thermoanaerobacterium thermosaccharolyticum yield 89.3 mlh2g-1 db (dry biomass) [16] distillers grains caldicellulosiruptor thermocellum yield 29.2 mlh2g-1 db [16] fruit and vegetable wastes as well as corn stover anaerobic sludge yield 1.91 molh2mol-1 glucose [17] beer lees consortia from cow dung compost yield 68.6 mlh2/g tvs [18] corn straw ethanoligenens harbinense yield 9 mlh2g-1 [19] wheat straw consortia from cow dung compost yield 68 mlh2g-1 [20] grass silage manure yield 16 mlh2g-1 [19] extracts of sweet lime peel anaerobic mixed consortia yield 76.4 ml/g cod [21] palm oil mill effluent thermoanaerobacteriumrich sludge yield 84.4 mlh2g-1 [22] beet pulp mixed culture from anaerobic sludge yield 115.6 mlh2g-1 cod [24] sunflower stalks clostridium sp. yield 2.04 molh2mol−1 eq. hexose [25] miscanthus sinensis thermotoga elfii rate 23.99 mlh2h-1 [16] cassava pulp hydrolysate mixed culture yield 342 mlh2g-1 codreduced [26] tequila vinasse eisenia fetida yield 1246.36 mlh2l-1 [12] sugarcane bagasse eisenia fetida yield 232.72 mlh2l-1 [12] https://www.sciencedirect.com/topics/engineering/hexose agro-wastes in biohydrogen fermentation 50(2) pp. 57–60 (2022) 59 as can be seen, although several types of agrowastes and microbes have been used for biohydrogen fermentation, the results regarding the yield or production rate of the processes are difficult to compare since their units vary and the data on hydrogen formation is diverse. moreover, in this study, no information was collected about the treatment of the substrate (if any) nor which kind of bioreactor, set-up or mode of operation was used, making their comparison even more difficult. therefore, only some special considerations can be discussed in this work. 3. special considerations in addition to single microorganisms, mixed consortia are often applied in these processes, which originate from various sources [19], e.g., sludge from biogas production; anaerobic sludges from municipal wastewater treatment plants and cow-dung composts; cattle or dairy residue composts; sludge from palm oil mill effluent; soil, rice and straw composts; fermented soybean meal, etc. even though these sources usually contain the microbes which are able to form biohydrogen, they need to be acclimated which includes some sort of pretreatment, e.g., heat shock, starving for a couple days, etc., to enrich the suitable microorganisms [3], [28] or sometimes bioaugmentation [10]. in hydrogen-producing consortia, a wide range of species have been isolated [19], e.g., under mesophilic conditions, clostridium (c. pasteurianum, c. saccharobutylicum, c. butyricum), enterobacter (e. aerogenes) and bacillus, while under thermophilic conditions, the genera thermoanaerobacterium (t. thermosaccharolyticum), caldicellulosiruptor (c. saccharolyticus, c. thermocellum) and bacillus thermozeamaize. regarding the utilization of certain fruit wastes, some flavor compounds were found to exhibit an antimicrobial effect [15], e.g., a citrus flavor, since d-limonene is able to weaken the fermentation even at very low concentrations (0.01% w/v). therefore, the undesired effect of these substrates can be diminished by special treatments, e.g., encapsulation of the microbes in a membrane or pretreatment of the feedstock. 4. conclusions in biohydrogen production, the application of agroindustrial residues has a great potential since they are renewable, huge amounts of them are formed year by year and have not been utilized. various types of agrowastes have been investigated with regard to biohydrogen production using a wide variety of microbes, namely single microorganisms or consortia. although it seems that both can be effective in terms of fermentation, higher yields and/or production rates could be achieved when carbohydrates – which can be 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research tools. the resulting method also provides two types of evaluations to rank the risks and also facilitates visualization. this study aimed to develop the application of pc-fmea in network research. keywords: network science, pc-fmea, risk assessment, pairwise comparison 1. introduction failure modes and effects analysis (fmea) is a method of identifying and fully understanding the potential causes as well as effects of failures on systems or end users with regard to a given product, process or project [1]. fmea is a risk assessment method that is widely used in several fields [2], particularly in the automotive industry, to formalize a complete set of actions, thereby reducing the risk associated with a system or manufacturing and assembly process [3]. in fmea, each failure is ranked in order of its risk priority number (rpn), which is calculated by multiplying the values of the three risk factors for failure, namely severity, probability of occurrence and probability of detection before the effects of the failure are realized, moreover, is represented by numbers, generally between 1 (in the case of no or a negligible risk) and 10 (in the worst-case scenario) [4]. the new method is based on a reference table, which gives the most critical risk. the fmea team takes into account previous fmeas, test results of similar items, experience with comparable systems and sources of information. a subjective element of this ranking will over time arise as the fmea always includes new parts and all sources of risk must be reexamined. however, the fmea team should be as objective as possible by using the criteria from the scales to help determine the appropriate ranking. therefore, the fmea team defines the classification of the failure modes based on their experience and knowledge [5]. to eliminate subjectivity, an improved method has been developed in which the evaluation is carried out by received: 2 dec 2022; revised: 9 dec 2022; accepted: 23 dec 2022 *correspondence: kulcsar.edina@mk.uni-pannon.hu a pairwise comparison. according to the three criteria, the risks are assessed by the pairwise comparison. the essence of the pairwise comparison can be grasped in the form of a prepared table, the output of which is the ranking of risks [6]. the results evaluated by the pairwise comparison can be further examined using the tools of network research. from the results of the pairwise comparison, a criticality network can be created in which the directed edges represent the direction of the preference and the weight of such edges can also be specified as the weight of the preference. based on the criticality network, pagerank and weighted in-degree values can be used to determine which vertices have the most input edges that are also important or the most high-weight input edges [7]. using the pairwise comparison-based fmea (pc-fmea) along with network research, a risk assessment method can be created where risks are evaluated by pairwise comparisons and the most severe risks extracted from the results of networks. the following section introduces this method. 2. experimental pc-fmea is a method based on a pairwise comparison to improve the precision of a risk evaluation. the members of the fmea team evaluate the risks in pairs based on a defined scale from 0-9, where 0 means equally critical and 9 means extremely critical. the scale was created from the fundamental scale of ahp (analytic hierarchy process), which is a decision-making method https://doi.org/10.33927/hjic-2022-20 mailto:kulcsar.edina@mk.uni-pannon.hu ungvári and gyurika hungarian journal of industry and chemistry 62 [6]. this scale is based on the three evaluation factors, namely severity, occurrence and detection. the second step of the method is to calculate the importance weights based on a comparison matrix [8]. the presented method offers a new method for enhancing the visual evaluation of the importance weights. 2.1. modelling risk assessments with networks since the network compiled from the results of the pairwise comparison is directed, the direction of criticality is shown. the degree of this criticality can also be specified. the edges are merged with the sum of the weights. a weighted network is c = {v, e, w}, where v denotes the set of vertices, e represents the set of edges and w refers to the weights of the edges. in the network, αij denotes the connection of node i to node j and each link (i, j) has a weight wij. the weighted in-degree w1dj is calculated as follows [9]: 𝑤1𝐷𝑗 = ∑ 𝑤𝑖𝑗 (𝑣𝑖,𝑣𝑗)∈𝐸 (1) the other indicator from a network that can be easily used for the evaluation of the weights of the risks is the pagerank value. pagerank is an algorithm that defines the importance of a node in a network. the algorithm is calculated from the data to determine how many connections the vertex has and how important they are. 3. results the methodology combines the techniques of pc-fmea and network research. the evaluation is carried out by a pairwise comparison, which is evaluated by network modeling. the following subsections show how the method can be applied to individual and aggregate risk assessments. in both cases, the weighted in-degree and pagerank values are used for ranking. the weighted indegree shows how many input edges a given node has and their weights [10]. the pagerank indicator also takes into account the role of these nodes in the network [11]. to demonstrate the method, data were generated randomly. 3.1. individual criticality network risk assessments using the fmea methodology are in most cases carried out by a team from different professions. evaluation within the group can be modeled individually and in aggregate with networks. the modeling of an individual evaluation is shown in fig.1, where the vertices indicate the risks and the directed edges between them indicate the preferential relationship. the sizes of the nodes show the weighted in-degree results. the larger the node, the more critical the risk is in that regard. the colors of the nodes illustrate the evaluation according to the pagerank indicator. the darker the node, the more critical the risk. at the edges, weights are visible on a scale of 1 to 7. the sizes of the edges show the extent of the preference. an example scale for the pairwise comparison of the risk according to the occurrence is shown in table 1. the results of the network model are presented in table 2 by the weighted in-degree and pagerank indexes, moreover, are ranked according to the criticality of the risks. it can be seen that the rankings are different based on the two ratings because pagerank also takes into account the role of neighboring nodes in the network. each node in the network is visualized in fig.2 to show the connected edges with their weights. 3.2. aggregate criticality network aggregate criticality networks can be used to evaluate the risk assessment results produced by an fmea team. if the evaluation is conducted by everyone individually, the aggregate result can be modeled with networks. preferences in this case are summarized along with their weights. the results of the aggregate criticality network are shown in fig.3. the visualization of the results is the same as in the individual network. the results of the network model are presented in table 3 in terms of the weighted in-degree and pagerank indexes as well as ranked according to the criticality of the risks. the results of the evaluation are not completely the same in this case either. figure 1. individual criticality network. the sizes of the nodes show the results based on the weighted in-degree values and the colors of the nodes represent the results of the risk assessment based on the pagerank value table 1. scale for the occurrence evaluation value occurrence 0 equally frequent 1 slightly more frequent 2 moderately more frequent 3 more frequent 4 strongly more frequent 5 very strongly more frequent 6 extremely more frequent 7 extremely more ( + ) frequent evaluation of pc-fmea 50(2) pp. 61–64 (2022) 63 each node in the network can be visualized to show the connected edges along with their weights as presented in fig.4. the results of the modeling show that the transformation of the result concerning the pairwise comparison of a risk assessment could yield a new method of evaluation. severity, occurrence and detection values can be evaluated with the weighted indegree and pagerank values. in a traditional fmea, the members of the team assess the risks together and try to come to a common understanding. however, the members could have different opinions and comprehend the criticality of the risks in various ways based on their fields of expertise. to eliminate subjectivity within the team, individual criticality networks can be used. an aggregated criticality network can evaluate the overall opinion of the team. 4. conclusions in this study, how the risks assessed by pairwise comparisons can be modeled by networks was demonstrated. the combination of pc-fmea and the network research toolkit based on pairwise comparisons provides a new method for implementing risk assessment. risks can be assessed individually and in aggregate based on two indicators. this modeling can be table 2. results of the individual criticality network model based on the weighted in-degree and pagerank values id weighted indegree id pagerank e 38 b 0.124224 j 27 e 0.113282 i 24 j 0.092585 d 23 d 0.073775 a 19 i 0.072988 l 18 l 0.070678 m 16 k 0.065196 f 15 f 0.063325 h 14 c 0.058084 c 13 h 0.053769 k 13 m 0.044907 o 10 g 0.044183 g 9 a 0.040232 b 8 n 0.029640 n 7 o 0.023272 p 7 p 0.021036 q 0 q 0.008824 figure 2. visualization of the connection between a vertex in the network and the weights of the preference figure 3. aggregate criticality network. the sizes of the nodes represent the results based on the weighted in-degree value and the colors of the nodes show the results of the risk assessment based on the pagerank value table 3. results of the aggregated criticality network model based on the weighted in-degree and pagerank values id weighted in-degree id pagerank i 227 a 0.111017 q 221 i 0.111016 m 205 q 0.106530 a 176 m 0.096950 j 141 j 0.070793 h 134 c 0.067337 c 98 h 0.058812 e 97 e 0.055613 b 90 b 0.049083 l 74 l 0.043342 n 69 k 0.040657 p 69 n 0.038440 k 65 d 0.036829 o 48 f 0.032958 f 47 p 0.030556 d 40 g 0.026501 g 36 o 0.023568 ungvári and gyurika hungarian journal of industry and chemistry 62 applied to all three bases and additional risk factors. of the two indicators, the fmea team can choose which one they prefer. evaluation is not time-consuming and the use of a pairwise comparison and network research reduces the level of subjectivity. the results are less liable to manipulation by participants than in the traditional fmea, where assessment is added individually to the risks. the results do not match the scales used by the fmea. deriving results from scales could be another research direction. another advantage of this method is that it visualizes the relationship between the risks, which can greatly support their presentation. references [1] stamatis, d.h.: failure mode and effect analysis: fmea from theory to execution (asq quality press), 2003, isbn: 9780873893008 [2] sharma, k.d.; srivastava, s.k.: failure mode and effect analysis (fmea) implementation: a literature review, j. adv. res. aeronaut. space sci., 2018, 5(1-2), 1–17, issn: 2454-8669 [3] ambekar, s.b.; edlabadkar, a.; shrouty, v.: a review: implementation of failure mode and effect analysis, int. j. eng. innov. technol., 2013, 2(8), 37–41, issn: 2277-3754 [4] spreafico, c.; russo, d.; rizzi, c.: a state-of-theart review of fmea/fmeca including patents, comput., sci. rev., 2017, 25, 19–28, doi: 10.1016/j.cosrev.2017.05.002 [5] banghart, m.; babski-reeves, k.; bian, l.; strawderman, l.: subjectivity in failure mode effects analysis (fmea) severity classification within a reliability centered maintenance (rcm) context, int. j. aviat. aeronaut. aerosp., 2018, 5(1), 2, doi: 10.15394/ijaaa.2018.1191 [6] kulcsár, e.; csiszér, t.; abonyi, j.: pairwise comparison based failure mode and effects analysis (fmea), methodsx, 2020, 7, 101007, doi: 10.1016/j.mex.2020.101007 [7] kulcsár, e; gyurika, i.g.; csiszér, t.: application of network science to extend the ahp and qfd methods, proc. 6th world congress mech. chem. mat. eng., 2020, doi: 10.11159/icmie20.137 [8] sebestyén, v.; somogyi, v.; szőke, s.; utasi, a.: adapting the sdewes index to two hungarian cities, hung. j. ind. chem., 2017, 45(1), 49–59, doi: 10.1515/hjic-2017-0008 [9] kulcsár, e.; gyurika, i.g.; csiszér, t.: networkbased – quality function deployment (nb-qfd): the combination of traditional qfd with network science approach and techniques, comput. ind., 2022, 136, 103592, doi: 10.1016/j.compind.2021.103592 [10] barabási, a.l.: network science, (cambridge university press), 2016, isbn: 9781107076266 [11] abbas, m.; inayat, i.; jan, n.; saadatmand, m.; enoiu, e.p.; sundmark, d.: mbrp: model-based requirements prioritization using pagerank algorithm, 26th asia-pacific software engineering conference, putrajaya, malaysia, (ieee), 2019, pp. 31–38, doi: 10.1109/apsec48747.2019.00014 figure 4. visualization of the connection between a vertex in the network and the aggregated weights of the preference https://doi.org/10.1016/j.cosrev.2017.05.002 https://doi.org/10.1016/j.cosrev.2017.05.002 https://doi.org/10.15394/ijaaa.2018.1191 https://doi.org/10.1016/j.mex.2020.101007 https://doi.org/10.1016/j.mex.2020.101007 https://doi.org/10.11159/icmie20.137 https://doi.org/10.1515/hjic-2017-0008 https://doi.org/10.1515/hjic-2017-0008 https://doi.org/10.1016/j.compind.2021.103592 https://doi.org/10.1109/apsec48747.2019.00014 hungarian journal of industry and chemistry vol. 50 pp. 15–22 (2022) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2022-04 membrane unit for integrated gas separation – membrane bioreactor (gs-mbr) system zbyněk pientka *1, jakub peter1, and robert válek2 1institute of macromolecular chemistry cas, heyrovského nám. 2, 162 06 prague 6, czech republic 2membrain s.r.o., pod vinicí 87, 471 27 stráž pod ralskem, czech republic one of the research directions of renewable energy sources is the production of biohydrogen from the dark fermentation of organic matter. during this fermentation process, since hydrogen is produced along with a complex mixture of other gases and vapors, hydrogen gas requires further purification. one relatively easy solution to this problem might be the utilization of gas separation membrane modules given their low energy consumption, simple operation and ease of upscaling. in this work, hollow fiber (hf) membranes based on polyetherimide (pei) were developed and tested. hf membranes were spun from a polymer solution of pei using the wet phase inversion process into a water bath using a pilot-scale spinning device. gas transport measurements showed that membranes exhibited permeances of between 9.3 and 19.2 gpu with co2/h2 selectivities within the range of 3.3 − 5.6. morphology studies showed regular shapes resembling hollow fibers with outer diameters within the range of 250−320 microns, depending on various parameters of the spinning process. the best performing membranes were selected and a morphological analysis carried out. selected fibers were incorporated into two types of membrane modules. one type was a laboratory-scale membrane mini-module used for preliminary tests, while the other membrane module was designed for the treatment of larger amounts of biohydrogen. two types of laboratory-scale membrane separation units were constructed. for laboratory use, the low-pressure unit proved more accurate regulation to match the fermenters performance with the separation unit in comparison with the high-pressure one. keywords: polymer membranes, gas separation, hollow fibers, membrane module 1. introduction the motivation of this research is the need to reduce the ecological footprint of society by developing green technologies enabling carbon sequestration, sustainable production of valuable chemicals and environmentallyfriendly energy production. this task is to be completed by the development of a novel, circular-loop gas separation membrane bioreactor system. microalgae grown in a photobioreactor capture refused-co2 from the fermentative reactor, which simply ferments these microalgae. during the process, a mixture of hydrogen and co2 is produced. the hydrogen can be separated and utilized for energy production. in addition, some valuable chemicals are produced. the newly developed system is known as a gas separation membrane bioreactor (gs-mbr) [1]. a key component of the gs-mbr is a membrane unit, which forms technological solutions for the separation of recieved: 17 december 2021; revised: 3 january 2022; accepted: 4 january 2022 *correspondence: pientka@imc.cas.cz h2 and co2 from the fermentation product. the basic elements in the membrane unit are membrane modules that utilize hollow fiber (hf) membranes. 2. experimental 2.1 materials pei (ultem™ 1000 resin grade) was purchased from sabic. the chemical structure of a repeated unit of ultem™ 1000 resin and the details regarding its preparation have previously been presented [2]. 2.2 development of hf membranes hollow fiber membranes were prepared with the strategic cooperation of the company membrain s.r.o. located in the czech republic. the procedure was described in our previous paper [2]. the spinline used for fabrication of the membranes is shown in fig. 1. 2.3 development of hf membrane modules the hc1 hf membrane mini-module was prepared by fixing 10 − 20 fibers into the swagelok tube fitting using https://doi.org/10.33927/hjic-2022-04 mailto:pientka@imc.cas.cz 16 pientka, peter and válek figure 1: the spinline used for the fabrication of hf membranes 3m of the epoxy resin dp100. the same resin was used to create the dead end of the fibers. the whole assembly was inserted into the 12-mm-wide tube using the corresponding swagelok tube fittings as presented in fig. 2. the module was equipped with 6-mm-wide connectors. p2-type hf membrane modules were constructed in a similar manner to those reported in [2], that is, from an arranged bundle of 250 a5-7 fibers (membrane area: 844 cm2) inserted into a pvc pipe. a schematic diagram of the p2-type hf membrane module and a photograph of it are presented in fig. 3. figure 2: hc1 hf membrane mini-module 2.4 determining the gas transport properties of the hf membrane laboratory modules containing 10 − 20 fibers of about 20 cm in length were prepared. one end of the fibers was sealed by an epoxy resin. the outer surface of the fibers was exposed to a mixture of gases which permeate into their hollow centers. gas permeation experiments were carried out using a mixture of co2 and h2 (1 : 1 volume ratio) at 2.0 and 4.2 bars (∆p was 1.0 and 3.2 bars, respectively) to determine the separation properties of the asymmetric pei hf membrane. its composition, pressures and flow rates were managed by the poseidon figure 3: schematic diagram of a cross-section of the p2type hf membrane module convergence inspector poseidon gp figure 4: testing of gas tranport properties of prepared hf membranes hungarian journal of industry and chemistry membrane unit for integrated gas separation 17 table 1: process parameters with regard to the production of asymmetric pei membranes sample polymer dope dose bore liquid dose towing speed m/min air gap cm od µm id µm ml/min ml/min a5-1 4.2 2.1 12 2 417 248 a5-2 4.2 2.1 9.7 5 405 234 a5-3 4.2 2.6 12 5 410 265 a5-7 6 2.6 12 2 420 239 b3-1 0.75 0.625 12 2.5 289 186 b3-2 0.75 0.625 15 6 270 190 b3-3 0.75 0.45 12 6 290 185 b3-7 0.9 0.45 12 2.5 320 171 convergence inspector gas permeation (convergence industry b.v.). the permeate flow rate was measured by a bubble flowmeter and the composition of the permeate stream analyzed by a prima bt bench top mass spectrometer (thermo fisher scientific). six laboratory modules were tested in series, where the retentate from the first module was used as a feed for the second module and so on (fig. 4). although this setting minimizes gas consumption and saves time, the correct mass balance on each module should be calculated. more information with regard to this can be found in [3]. the permeance pi for co2 and h2 as well as the co2/h2 mixed gas selectivity α∗ i/j were evaluated from measured data. the permeance pi is defined as the volumetric flow rate per unit driving force per unit area: pi = qp · yi (pp · xi − pp · yi) ·a (1) whereqp denotes the flow rate of the permeate, yi stands for the mole fraction of gas i in the permeate, p represents the absolute pressure in the feed or permeate and a is the membrane area. 2.5 development of the membrane separation unit the membrane apparatus was built using fittings from superlok; tubing 6 mm in diameter and parker 201lg solenoid valves manufactured by parker, 250 kpa bd sensors pressure sensors and a bp300-1-s back pressure regulator by pressure tech; a kk15 a 035/62 compressor by dürr technik: oil-free, max. performance = 25 l/min, 8 bar, max. pressure = 12 bar; a rocker 410 oil-free vacuum pump; a control unit based on an arduino uno microcomputer and software developed by the authors. 3. results and discussion 3.1 preparation of hf membranes the preparation of hf membranes was carried out using 4 spinnerets simultaneously, resulting in a higher towing speed (15 m/min) which corresponds to the production of 3600 m of hf membrane per hour. there were two series (denoted as a5 and b3) of fibers prepared using various spinning process parameters. the significant difference between the a5 and b3 series are the dimensions of the nozzles. for the a5 series, the outer outlet diameter (od) of the larger nozzle was used (0.512 mm), whereas for the b3 series, the outer od of the nozzle was 0.330 mm. the process parameters with regard to the production of the asymmetric pei membranes are listed in table 1. as can be seen, all the membranes with a dosing of polymer dope of 0.75 ml/min apparently had a smaller outer outlet diameter (od) than the fibers with a flow rate of polymer dope of 0.9 ml/min. it can also be observed that at higher towing speeds, the ods of hf membranes were lower (with the exception of membranes b3-6). 3.2 characterization of gas transport across hf membranes each sample of membrane was measured in three membrane modules by simultaneously connecting six modules to a poseidon group system (i.e. two samples of membrane were tested simultaneously). the average values were recorded and presented in table 2. the results showed that all the membranes exhibited permeances within the range of 9.3−19.2 gpu and h2/co2 selectivities within the range of 3.3−5.6. it is well known that gas separation in polymers can be described by a solutiondiffusion model [4] which states that the permeability coefficient is the product of the diffusion and solubility cotable 2: gas transport properties of the prepared hf membranes for the h2/co2 mixture measured at a pressure of 8 bars. sample co2 permeance (gpu) h2/co2 selectivity a5-1 11.5 4.4 a5-2 10.3 4 a5-3 17.5 5.3 a5-7 19.2 5.6 b3-1 9.5 4.4 b3-2 9.3 4 b3-3 10.3 5.3 b3-7 20.3 4.5 50 pp. 15–22 (2022) 18 pientka, peter and válek (a) (b) (c) (d) figure 5: optical microscopy image (a); sem micrographs (b-c) and afm micrograph (d) of the cross-section and surface of the prepared hf membranes. efficients. in our case, h2 permeates faster than co2 and since the diffusion coefficient of h2 is significantly larger than that of co2 [5], it can be concluded that the separation is based on differences in diffusivities. this is typical for glassy polymers, including the pei applied in this paper. the best membrane from the a5 series was used to fabricate the p2 membrane module containing 250 fibers. from the whole b3 series, the two best membranes, namely b3-3 and b3-7, were selected to be incorporated into the membrane mini-modules. 3.3 morphology of hf membranes the resulting hollow fiber membranes (fig. 5) had a regular round shape with a sponge-like structure containing typical relatively small finger-like pores (<30 µm). as determined using an optical microscope, the outer and inner diameters of the hollow fibers were 313 ± 9 µm and 290 ± 5 µm, respectively. the separation layer was on the outer surface for all the fibers. atomic force microscopy (afm) of the surfaces of the fibers revealed a relatively smooth surface consisting of a protective coating of pdms with no defects. 3.4 hollow fiber membrane modules hc1 mini-modules once the best membranes from the b3 series had been chosen (b3-3 and b3-6), the requirements of the project coordinator with regard to modules for membrane bioreactors were established. according to the requirements, three hc1 modules were manufactured with assistance from membrain s.r.o. their single gas transport properties were measured and are summarized in table 3. the first two modules (hc1_1 and hc1_2) contained the same b3-7 hf membrane, the only difference between them was the number of fibers they consisted of and thus their membrane areas. hc1_1 consisted of 10 fibers with a corresponding membrane area of 19.7 cm2, while hc1_2 consisted of 20 fibers with a corresponding membrane area of 39.3 cm2. hydrogen permeation flow rates were 28.2 (for hc1_1) and 53.0 ml/min (for hc1_2) at a feed pressure of 4.2 bars (abs) and achieving ideal h2/co2 selectivities of 4.4 and 3.7, respectively. the permeate was released at atmospheric pressure. the slightly lower selectivity of the second module can be attributed to the variation in the membrane properties, minuscule leakage within the module or a combination of both. the hc2 mini-module consisted of 23 fibers of b33 membrane, corresponding to a membrane area of 41.9 cm2. as can be seen in table 3, the permeate fluxes of the membrane modules were more than two times lower and only yielded negligibly higher selectivities. the modules were handed over to a korean participant in the aforementioned project for further testing on real biogas. the same modules were also tested for the h2/co2 mixture to demonstrate their ability to concentrate the hydrogen. from table 4, it can be seen that the modules were able to concentrate hydrogen from an initial percent concentration of 57 % to 88 % in the case of the hc1_1 module at a membrane stage cut of 96 % and from 57 % to 77 % in the case of the hc2 module at a membrane stage cut of 88 %. the membrane stage cut is defined as the ratio of the permeate flow rate to the feed flow rate. generally, by increasing the membrane stage cut, the concentration of the more permeating penetrant is also higher. on the other hand, the hydrogen recovery is lower because most of the hydrogen from the feed is transferred into the low-concentration permeate. p2-type module thicker hf membranes with an average od of 420 µm were incorporated into a quarter-scale membrane module. from the number of fibers the module consisted of, that is, 250, and their active length, namely 25.6 cm, the total membrane area of the module was calculated to be 844 cm2. the membrane module was tested against the gas transport properties of various single gases. the measured values are presented in table 5. according to the measurements, the permeances more than doubled compared to the same membrane measured in a smallscale laboratory module. furthermore, different values of h2/co2 selectivities were calculated, the selectivity dropped from 5.6 to almost 3.0 to be exact. this perhaps indicates the presence of some microdefect on one of the fibers or a minuscule leakage between the feed and permeate. nevertheless, the separation performance was sufficient to demonstrate the concept of biohydrogen purifihungarian journal of industry and chemistry membrane unit for integrated gas separation 19 table 3: characterization of hc1 and hc2 mini-modules gas transport properties were measured for single gases at pressure differentials of 1.0 and 3.2 bars as well as at a temperature of 25 ◦c gas number fiber fiber ∆p permeate flow membrane permeance h2/co2 of fibers diameter (cm) length (cm) (bar) rate (ml/min) area (cm2) (gpu) selectivity module hc1_1 co2 10 0.0313 20 1 1.96 19.7 22.1 4.41 10 0.0313 20 3.2 6.45 19.7 22.8 4.37 h2 10 0.0313 20 1 8.65 19.7 97.7 10 0.0313 20 3.2 28.2 19.7 99.6 module hc1_2 co2 20 0.0313 20 1 3.92 39.3 22.1 4.46 20 0.0313 20 3.2 14.3 39.3 25.2 3.71 h2 20 0.0313 20 1 17.5 39.3 98.9 20 0.0313 20 3.2 53 39.3 93.6 module hc2 co2 23 0.029 20 1 1.65 41.9 8.7 4.5 23 0.029 20 3.2 5.54 41.9 9.2 4.3 h2 23 0.029 20 1 7.43 41.9 39.4 23 0.029 20 3.2 23.8 41.9 39.4 table 4: gas transport properties of the hc1 and hc2 membrane mini-modules for the co2/h2 mixture measured at a feed pressure of 3.6 bars (abs) module parameter composition [%] feed retentate permeate hc1_1 h2 permeance (gpu) – 57 54 88 co2 permeance (gpu) – 43 46 12 membrane stage cut 0.96 – – – co2/h2 selectivity 4.2 – – – hc1_2 h2 permeance (gpu) – 41 40 63 co2 permeance (gpu) – 59 60 37 membrane stage cut 0.94 – – – co2/h2 selectivity 4.3 – – – hc2 h2 permeance (gpu) – 57 38 77 co2 permeance (gpu) – 43 62 23 membrane stage cut 0.88 – – – co2/h2 selectivity 5.7 – – – cation. 3.5 development of the membrane gas separation unit using the membrane modules, this project included the construction of a membrane gas separation unit, the optimization of the fermentation system and the integration of the gas separation unit into the gs-mbr. 50 pp. 15–22 (2022) 20 pientka, peter and válek table 5: gas separation properties of the p2 membrane module measured for single gases at 25 ◦c (number of fibers = 250, average od = 420 microns, membrane area = 844 cm2) gas ∆p (bar) permeate flow rate (ml/min) permeance (gpu) h2/co2 selectivity co2 2 356 46.2 2.92 5.6 949 44 2.99 h2 1.2 625 135.3 – 2 1012 131.5 – o2 0.65 28 11.2 – 1.1 46 10.9 – high-pressure membrane unit utilizing a laboratory air compressor the model membrane unit consisted of a p2 hf membrane module, a laboratory air compressor, three pressure sensors, a pressure regulator valve, two solenoid valves, a back pressure regulator, fittings and an arduino control unit. a schematic diagram and photograph of the unit are presented in fig. 6. both bioreactors were simulated by pressure vessels with inlets. the control unit senses the pressures in both pressure vessels (bioreactors) and at the feed of the membrane module. to achieve a high degree of efficiency, it is necessary to match the fermentation performance of both bioreactors to the performance of the membrane gas separation unit. an attempt was made to control the compressor using pulses, namely the compressor was switched on when the fermented amount of biogas in the main bioreactor reached the specified limit. since the power of the compressor considerably exceeded the performance of both fermenters and the membrane unit, it was necessary to control the flow of the compressed gas mixture into the membrane module by means of a back pressure regulator, which transferred the excess amount of compressed gas into the bypass. in order to maintain the pressure in the loop at close to atmospheric pressure, an expansion vessel was connected to it. the compressor was controlled by pulses once again – an arduino microcontroller opened the solenoid valves when the amount of biogas in the main bioreactor exceeded the set limit. the regulating valve in the retentate stream of the membrane module regulates its stage cut. when the pressure in the main bioreactor decreased under the set limit, the arduino microcontroller closed the solenoid valves. this type of control guaranteed that the feed pressure in the membrane module was sufficiently high to maintain the required separation efficiency. the pressure was kept by back-pressure regulator. the flow rate of the gas mixture that was simultaneously fed into the membrane module varied from 0 to 3 l/min, which is given by the pulse width or duty cycle. it should be noted that the mixture of hydrogen and carbon dioxide is reactive under certain conditions [6]. it probably cannot be ruled out that the pressures and temperatures in the compressor together with the presence of metal alloys will not trigger any undesired hydrogenation. the compressor must therefore be an internal atex version. the problem can be managed as shown in [7], where the same gas mixture was pressurized up to 380 bars. low-pressure membrane unit utilizing a vacuum pump the second model membrane unit generates the driving force at the membrane by the suction force supplied by a vacuum pump. the unit again consists of the p2 hf membrane module, a laboratory vacuum pump, two pressure sensors, two solenoid valves, a peristaltic pump, fittings and an arduino microcontroller. a schematic diagram and photograph of the unit is presented in fig. 7. when the pressure of the biogas in the main bioreactor exceeded the set limit, the arduino microcontroller opened both solenoid valves and started the peristaltic pump. the flow rate produced by this pump regulated the membrane stage cut. the permeate flux was considerably lower as the pressure differential was smaller than in the first unit. however, regulation in laboratory-scale experiments more accurately matched the performance of the fermenter with that of the gas separation unit. the amount of gas mixture fed into the membrane module can vary from 0 to 0.5 l/min, which is given by the pulse width or duty cycle as presented in the first set-up. 4. conclusion a series of 8 batches of hf membranes was prepared. each batch had different spinning process parameters. the morphology and gas transport properties were characterized to select the 2 best hf membranes which were incorporated into 2 types of membrane modules. the first module was designed for laboratory tests and had a small membrane area and low permeate flow rate. the other module consisting of 250 hollow fibers was constructed for larger flow rates and scale. all membrane modules were tested for singleas well as mixed-gas transport properties and exhibited good levels of performance. the design and development of a membrane separation unit is a very complex task. firstly, membranes in the form of hollow fibers based on pei were prepared. then modules from each batch were built and characterized according to gas transport. the most efficient module achieved a separation factor for h2/co2 in excess of 5. three modules of this type were fabricated as well as tested using a model mixture and may hopefully be appropriate for real-life gas separation [8], which is going to be carried out by our partners. hungarian journal of industry and chemistry membrane unit for integrated gas separation 21 (a) (b) figure 6: schematic diagram (a) and photograph (b) of the high-pressure membrane unit for the integrated gs-mbr system: 1 pressure vessel, 2 pressure sensor, 3 p2 membrane module, 4 laboratory air compressor, 5 expansion vessel, 6-7 two solenoid valves, 8 back pressure regulator, 9 regulating valve with a flow meter, 10 arduino microcontroller. (b) (a) figure 7: schematic diagram (a) and photograph (b) of the low-pressure laboratory-scale membrane unit: 1 pressure vessel, 2 pressure sensor, 3 p2 membrane module, 4 laboratory vacuum pump, 5 expansion vessel, 6-7 two solenoid valves, 8 peristaltic pump, 9 pressure vessel – retentate recipient, 10 arduino control unit. 50 pp. 15–22 (2022) 22 pientka, peter and válek two types of laboratory membrane separation units were constructed using the larger p2 hf membrane module. the high-pressure unit utilizes a compressor to pressurize the gas mixture into the feed of the module, while the low-pressure unit utilizes a vacuum pump to maintain a low pressure in the permeate of the membrane module. to ensure the separation efficiency remains high, pulse regulation was utilized. for laboratory use the lowpressure unit proved more accurate regulation to match the fermenters performance with the separation unit. acknowledgement this part of the international cooperation was supported by project 8f17005 and contract no. msmt-20364/20173/5 provided by the czech ministry of education, youth and sports. thanks to all participants of the common korea – visegrad countries project i-algmemb for cooperation. references [1] bakonyi, p.; kumar, g.; bélafi-bakó, k.; kim, s.h.; koter, s.; kujawski, w.; nemestóthy, n.; peter, j.; pientka, z.: a review of the innovative gas separation membrane bioreactor with mechanisms for integrated production and purification of biohydrogen, bioresour. technol., 2018, 270, 643–655 doi: 10.1016/j.biortech.2018.09.020 [2] bakonyi, p.; peter, j.; nemestóthy, n.; malý, d; kumar, g; koter, s; kim, s.-h.; kujawski, w.; bélafi-bakó, k.; pientka, z.: feasibility study of polyetherimide membrane for enrichment of carbon dioxide from synthetic biohydrogen mixture and subsequent utilization scenario using microalgae, int. j. energy res., 2021, 45, 8327–8334 doi: 10.1002/er.5732 [3] válek, r.; malý, d.; peter, j.; gruart, m.: effect of the preparation conditions on the properties of polyetherimide hollow fibre membranes for gas separation, desalin. water treat., 2017, 75, 300–304 doi: 10.5004/dwt.2017.20747 [4] wijmans, j. g.; baker, r. w.: the solutiondiffusion model: a review, j. membr. sci., 1995, 107(1–2), 1–21 doi: 10.1016/0376-7388(95)00102-i [5] freeman, b.; yampolskii, y.; pinnau, i. (eds.): materials science of membranes for gas and vapor separation (john wiley & sons, ltd, chichester, uk) 2006. doi: 10.1002/047002903x [6] zeng, l.; wang, z.; wang, y.; wang, j.; guo, y.; hu, h.; he, x.; wang, c.; lin, w.: photoactivation of cu centers in metal-organic frameworks for selective co2 conversion to ethanol, j. am. chem. soc. 2020, 142, 75–79 doi: 10.1021/jacs.9b11443 [7] härtel, g.; püschel, t.: permselectivity of a pa6 membrane for the separation of a compressed co2/h2 gas mixture at elevated pressures, j. membr. sci. 1999, 162, 1–8 doi: 10.1016/s03767388(99)00066-6 [8] rózsenberszki, t.; koók, l.; bakonyi, p.; nemestóthy, n.; bélafi-bakó, k.: comparative study on anaerobic degradation processes of pressed liquid fraction of organic solid waste, hung. j. ind.chem., 2021, 49(1), 31–35 doi: 10.33927/hjic-2021-05 hungarian journal of industry and chemistry https://doi.org/10.1016/j.biortech.2018.09.020 https://doi.org/10.1016/j.biortech.2018.09.020 https://doi.org/10.1002/er.5732 https://doi.org/10.1002/er.5732 https://doi.org/10.5004/dwt.2017.20747 https://doi.org/10.1016/0376-7388(95)00102-i https://doi.org/10.1002/047002903x https://doi.org/10.1021/jacs.9b11443 https://doi.org/10.1016/s0376-7388(99)00066-6 https://doi.org/10.1016/s0376-7388(99)00066-6 https://doi.org/10.33927/hjic-2021-05 https://doi.org/10.33927/hjic-2021-05 introduction experimental materials development of hf membranes development of hf membrane modules determining the gas transport properties of the hf membrane development of the membrane separation unit results and discussion preparation of hf membranes characterization of gas transport across hf membranes morphology of hf membranes hollow fiber membrane modules hc1 mini-modules p2-type module development of the membrane gas separation unit high-pressure membrane unit utilizing a laboratory air compressor low-pressure membrane unit utilizing a vacuum pump conclusion hungarian journal of industry and chemistry vol. 50(2) pp. 61–64 (2022) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2022-20 evaluation of pc-fmea using network analysis edina ungvári1*, istván gábor gyurika1 1 department of mechanics, university of pannonia, h-8200 veszprém, hungary abstract – pc-fmea is a method that combines the pairwise comparison and basic fmea (failure modes and effects analysis) methods. using the pairwise comparison, which of the risks is more severe, common or noticeable can be determined. the results evaluated by the pairwise comparison can be modeled with networks, where the risks can be ranked according to the criteria using the pagerank and weighted in-degree values. applying these two solutions together, a form of risk assessment can be created where risks are assessed by pairwise comparisons and the results analyzed using network research tools. the resulting method also provides two types of evaluations to rank the risks and also facilitates visualization. this study aimed to develop the application of pc-fmea in network research. keywords: network science, pc-fmea, risk assessment, pairwise comparison 1. introduction failure modes and effects analysis (fmea) is a method of identifying and fully understanding the potential causes as well as effects of failures on systems or end users with regard to a given product, process or project [1]. fmea is a risk assessment method that is widely used in several fields [2], particularly in the automotive industry, to formalize a complete set of actions, thereby reducing the risk associated with a system or manufacturing and assembly process [3]. in fmea, each failure is ranked in order of its risk priority number (rpn), which is calculated by multiplying the values of the three risk factors for failure, namely severity, probability of occurrence and probability of detection before the effects of the failure are realized, moreover, is represented by numbers, generally between 1 (in the case of no or a negligible risk) and 10 (in the worst-case scenario) [4]. the new method is based on a reference table, which gives the most critical risk. the fmea team takes into account previous fmeas, test results of similar items, experience with comparable systems and sources of information. a subjective element of this ranking will over time arise as the fmea always includes new parts and all sources of risk must be reexamined. however, the fmea team should be as objective as possible by using the criteria from the scales to help determine the appropriate ranking. therefore, the fmea team defines the classification of the failure modes based on their experience and knowledge [5]. to eliminate subjectivity, an improved method has been developed in which the evaluation is carried out by received: 2 dec 2022; revised: 9 dec 2022; accepted: 23 dec 2022 *correspondence: kulcsar.edina@mk.uni-pannon.hu a pairwise comparison. according to the three criteria, the risks are assessed by the pairwise comparison. the essence of the pairwise comparison can be grasped in the form of a prepared table, the output of which is the ranking of risks [6]. the results evaluated by the pairwise comparison can be further examined using the tools of network research. from the results of the pairwise comparison, a criticality network can be created in which the directed edges represent the direction of the preference and the weight of such edges can also be specified as the weight of the preference. based on the criticality network, pagerank and weighted in-degree values can be used to determine which vertices have the most input edges that are also important or the most high-weight input edges [7]. using the pairwise comparison-based fmea (pc-fmea) along with network research, a risk assessment method can be created where risks are evaluated by pairwise comparisons and the most severe risks extracted from the results of networks. the following section introduces this method. 2. experimental pc-fmea is a method based on a pairwise comparison to improve the precision of a risk evaluation. the members of the fmea team evaluate the risks in pairs based on a defined scale from 0-9, where 0 means equally critical and 9 means extremely critical. the scale was created from the fundamental scale of ahp (analytic hierarchy process), which is a decision-making method https://doi.org/10.33927/hjic-2022-20 mailto:kulcsar.edina@mk.uni-pannon.hu ungvári and gyurika hungarian journal of industry and chemistry 62 [6]. this scale is based on the three evaluation factors, namely severity, occurrence and detection. the second step of the method is to calculate the importance weights based on a comparison matrix [8]. the presented method offers a new method for enhancing the visual evaluation of the importance weights. 2.1. modelling risk assessments with networks since the network compiled from the results of the pairwise comparison is directed, the direction of criticality is shown. the degree of this criticality can also be specified. the edges are merged with the sum of the weights. a weighted network is c = {v, e, w}, where v denotes the set of vertices, e represents the set of edges and w refers to the weights of the edges. in the network, αij denotes the connection of node i to node j and each link (i, j) has a weight wij. the weighted in-degree w1dj is calculated as follows [9]: 𝑤1𝐷𝑗 = ∑ 𝑤𝑖𝑗 (𝑣𝑖,𝑣𝑗)∈𝐸 (1) the other indicator from a network that can be easily used for the evaluation of the weights of the risks is the pagerank value. pagerank is an algorithm that defines the importance of a node in a network. the algorithm is calculated from the data to determine how many connections the vertex has and how important they are. 3. results the methodology combines the techniques of pc-fmea and network research. the evaluation is carried out by a pairwise comparison, which is evaluated by network modeling. the following subsections show how the method can be applied to individual and aggregate risk assessments. in both cases, the weighted in-degree and pagerank values are used for ranking. the weighted indegree shows how many input edges a given node has and their weights [10]. the pagerank indicator also takes into account the role of these nodes in the network [11]. to demonstrate the method, data were generated randomly. 3.1. individual criticality network risk assessments using the fmea methodology are in most cases carried out by a team from different professions. evaluation within the group can be modeled individually and in aggregate with networks. the modeling of an individual evaluation is shown in fig.1, where the vertices indicate the risks and the directed edges between them indicate the preferential relationship. the sizes of the nodes show the weighted in-degree results. the larger the node, the more critical the risk is in that regard. the colors of the nodes illustrate the evaluation according to the pagerank indicator. the darker the node, the more critical the risk. at the edges, weights are visible on a scale of 1 to 7. the sizes of the edges show the extent of the preference. an example scale for the pairwise comparison of the risk according to the occurrence is shown in table 1. the results of the network model are presented in table 2 by the weighted in-degree and pagerank indexes, moreover, are ranked according to the criticality of the risks. it can be seen that the rankings are different based on the two ratings because pagerank also takes into account the role of neighboring nodes in the network. each node in the network is visualized in fig.2 to show the connected edges with their weights. 3.2. aggregate criticality network aggregate criticality networks can be used to evaluate the risk assessment results produced by an fmea team. if the evaluation is conducted by everyone individually, the aggregate result can be modeled with networks. preferences in this case are summarized along with their weights. the results of the aggregate criticality network are shown in fig.3. the visualization of the results is the same as in the individual network. the results of the network model are presented in table 3 in terms of the weighted in-degree and pagerank indexes as well as ranked according to the criticality of the risks. the results of the evaluation are not completely the same in this case either. figure 1. individual criticality network. the sizes of the nodes show the results based on the weighted in-degree values and the colors of the nodes represent the results of the risk assessment based on the pagerank value table 1. scale for the occurrence evaluation value occurrence 0 equally frequent 1 slightly more frequent 2 moderately more frequent 3 more frequent 4 strongly more frequent 5 very strongly more frequent 6 extremely more frequent 7 extremely more ( + ) frequent evaluation of pc-fmea 50(2) pp. 61–64 (2022) 63 each node in the network can be visualized to show the connected edges along with their weights as presented in fig.4. the results of the modeling show that the transformation of the result concerning the pairwise comparison of a risk assessment could yield a new method of evaluation. severity, occurrence and detection values can be evaluated with the weighted indegree and pagerank values. in a traditional fmea, the members of the team assess the risks together and try to come to a common understanding. however, the members could have different opinions and comprehend the criticality of the risks in various ways based on their fields of expertise. to eliminate subjectivity within the team, individual criticality networks can be used. an aggregated criticality network can evaluate the overall opinion of the team. 4. conclusions in this study, how the risks assessed by pairwise comparisons can be modeled by networks was demonstrated. the combination of pc-fmea and the network research toolkit based on pairwise comparisons provides a new method for implementing risk assessment. risks can be assessed individually and in aggregate based on two indicators. this modeling can be table 2. results of the individual criticality network model based on the weighted in-degree and pagerank values id weighted indegree id pagerank e 38 b 0.124224 j 27 e 0.113282 i 24 j 0.092585 d 23 d 0.073775 a 19 i 0.072988 l 18 l 0.070678 m 16 k 0.065196 f 15 f 0.063325 h 14 c 0.058084 c 13 h 0.053769 k 13 m 0.044907 o 10 g 0.044183 g 9 a 0.040232 b 8 n 0.029640 n 7 o 0.023272 p 7 p 0.021036 q 0 q 0.008824 figure 2. visualization of the connection between a vertex in the network and the weights of the preference figure 3. aggregate criticality network. the sizes of the nodes represent the results based on the weighted in-degree value and the colors of the nodes show the results of the risk assessment based on the pagerank value table 3. results of the aggregated criticality network model based on the weighted in-degree and pagerank values id weighted in-degree id pagerank i 227 a 0.111017 q 221 i 0.111016 m 205 q 0.106530 a 176 m 0.096950 j 141 j 0.070793 h 134 c 0.067337 c 98 h 0.058812 e 97 e 0.055613 b 90 b 0.049083 l 74 l 0.043342 n 69 k 0.040657 p 69 n 0.038440 k 65 d 0.036829 o 48 f 0.032958 f 47 p 0.030556 d 40 g 0.026501 g 36 o 0.023568 ungvári and gyurika hungarian journal of industry and chemistry 62 applied to all three bases and additional risk factors. of the two indicators, the fmea team can choose which one they prefer. evaluation is not time-consuming and the use of a pairwise comparison and network research reduces the level of subjectivity. the results are less liable to manipulation by participants than in the traditional fmea, where assessment is added individually to the risks. the results do not match the scales used by the fmea. deriving results from scales could be another research direction. another advantage of this method is that it visualizes the relationship between the risks, which can greatly support their presentation. references [1] stamatis, d.h.: failure mode and effect analysis: fmea from theory to execution (asq quality press), 2003, isbn: 9780873893008 [2] sharma, k.d.; srivastava, s.k.: failure mode and effect analysis (fmea) implementation: a literature review, j. adv. res. aeronaut. space sci., 2018, 5(1-2), 1–17, issn: 2454-8669 [3] ambekar, s.b.; edlabadkar, a.; shrouty, v.: a review: implementation of failure mode and effect analysis, int. j. eng. innov. technol., 2013, 2(8), 37–41, issn: 2277-3754 [4] spreafico, c.; russo, d.; rizzi, c.: a state-of-theart review of fmea/fmeca including patents, comput., sci. rev., 2017, 25, 19–28, doi: 10.1016/j.cosrev.2017.05.002 [5] banghart, m.; babski-reeves, k.; bian, l.; strawderman, l.: subjectivity in failure mode effects analysis (fmea) severity classification within a reliability centered maintenance (rcm) context, int. j. aviat. aeronaut. aerosp., 2018, 5(1), 2, doi: 10.15394/ijaaa.2018.1191 [6] kulcsár, e.; csiszér, t.; abonyi, j.: pairwise comparison based failure mode and effects analysis (fmea), methodsx, 2020, 7, 101007, doi: 10.1016/j.mex.2020.101007 [7] kulcsár, e; gyurika, i.g.; csiszér, t.: application of network science to extend the ahp and qfd methods, proc. 6th world congress mech. chem. mat. eng., 2020, doi: 10.11159/icmie20.137 [8] sebestyén, v.; somogyi, v.; szőke, s.; utasi, a.: adapting the sdewes index to two hungarian cities, hung. j. ind. chem., 2017, 45(1), 49–59, doi: 10.1515/hjic-2017-0008 [9] kulcsár, e.; gyurika, i.g.; csiszér, t.: networkbased – quality function deployment (nb-qfd): the combination of traditional qfd with network science approach and techniques, comput. ind., 2022, 136, 103592, doi: 10.1016/j.compind.2021.103592 [10] barabási, a.l.: network science, (cambridge university press), 2016, isbn: 9781107076266 [11] abbas, m.; inayat, i.; jan, n.; saadatmand, m.; enoiu, e.p.; sundmark, d.: mbrp: model-based requirements prioritization using pagerank algorithm, 26th asia-pacific software engineering conference, putrajaya, malaysia, (ieee), 2019, pp. 31–38, doi: 10.1109/apsec48747.2019.00014 figure 4. visualization of the connection between a vertex in the network and the aggregated weights of the preference https://doi.org/10.1016/j.cosrev.2017.05.002 https://doi.org/10.1016/j.cosrev.2017.05.002 https://doi.org/10.15394/ijaaa.2018.1191 https://doi.org/10.1016/j.mex.2020.101007 https://doi.org/10.1016/j.mex.2020.101007 https://doi.org/10.11159/icmie20.137 https://doi.org/10.1515/hjic-2017-0008 https://doi.org/10.1515/hjic-2017-0008 https://doi.org/10.1016/j.compind.2021.103592 https://doi.org/10.1109/apsec48747.2019.00014 microsoft word inner cover.docx hungarian journal of industry and chemistry (hjic) formerly (until 2012) hungarian journal of industrial chemistry the hjic is an international periodicals that focuses on results of fundamental and applied research in the field of • biotechnology • chemical engineering science • chemical processes • energetics • environmental chemistry • environmental engineering & technology • industrial management • material science • mechanical engineering • mechatronics • process & system engineering • recycling in the form of original papers, reviews, short communications, and conference proceedings written in english. editorial board editor-in chief: róbert k. szilágyi department of chemistry and biochemistry, montana state university, bozeman, mt, u.s.a. honorary senior editor: géza horváth department of chemical engineering science, university of pannonia, veszprém, hungary associate editors: jános abonyi department of process engineering, university of pannonia, veszprém, hungary dezső boda department of physical chemistry, university of pannonia, veszprém, hungary norbert miskolczi mol department of hydrocarbon and coal processing, university of pannonia, veszprém, hungary dóra rippel pethő department of chemical engineering science university of pannonia, veszprém, hungary editors: lászló bartha mol department of hydrocarbon and coal processing, university of pannonia, veszprém, hungary katalin bélafi-bakó research institute of bioengineering, membrane technology and energetics, university of pannonia, veszprém, hungary peter czermak institute of bioprocess engineering and pharmaceutical technology, mittelhessen university of applied sciences, giessen, germany dénes fodor institute of mechanical engineering, university of pannonia, veszprém, hungary maria gavrilescu department of environmental engineering and management, gheorghe asachi technical university of iasi, romania lászló gubicza research institute of bioengineering, membrane technology and energetics, university of pannonia, veszprém, hungary jenő hancsók mol department of hydrocarbon and coal processing, university of pannonia, veszprém, hungary jiří klemeš centre for process integration and intensification, university of pannonia, veszprém, hungary zoltán kovács department of management, university of pannonia, veszprém, hungary jános kristóf department of analytical chemistry, university of pannonia, veszprém, hungary ákos rédey department of environmental engineering and chemical technology, university of pannonia, veszprém, hungary istván szalai institute of physics and mechatronics, university of pannonia, veszprém, hungary ferenc szeifert department of process engineering, university of pannonia, veszprém, hungary jános szépvölgyi research centre for natural sciences, university of pannonia, veszprém, hungary imre tímár institute of mechanical engineering, university of pannonia, veszprém, hungary gyula vatai department of food engineering, corvinus university of budapest, hungary gábor veress federation of technical and scientific societies – mtesz budapest, hungary ibolya zsoldos department of material science and technology, széchenyi istván university, győr, hungary editorial office: university of pannonia, p.o. box 158, veszprém h-8201 (hungary) tel.: +36 (88) 624-298, e-mail: hjic@almos.uni-pannon.hu; web: hjic.mk.uni-pannon.hu felelős szerkesztő: szilágyi róbert károly phd kiadja: pannon egyetem, 8200 veszprém, egyetem u. 10. levélcím: h-8201 veszprém, postafiók 158, tel.: (88) 624-000 felelős kiadó: a pannon egyetem, mérnöki kar dékánja hung. j. ind. & chem. 2013, vol. 41, pp. 1–136 table of contents vehicle routing approach for lean shop-floor logistics david gyulai, lászló monostori ............................................................................................... 1–6 design of a new chemical injection pump system for gas hydrate inhibition csaba vörös, viktor füvesi, ákos pintér ............................................................................... 7–10 ionic liquids in advanced energy storage cells attila göllei, attila magyar ................................................................................................ 11–15 monitoring and diagnosis of manufacturing systems using timed coloured petri nets adrien leitold, brigitta márczi, anna ibolya pózna, miklós gerzson ......................... 17–26 immediate event-aware model and algorithm of a general scheduler tibor dulai, ágnes werner-stark, katalin m. hangos .................................................... 27–34 estimation of parameters of an extremely low fuel consumption internal combustion engine-based megameter-iii vehicle istván pintér, mihály bagány ................................................................................................ 35–40 influence of can flatness on heat dissipation of aluminium electrolytic capacitor lászló kovács, lászló gál, dénes fodor ............................................................................ 41–46 fine tuning of automated assembly machines using video analysis alíz katona, viktor kovács, dóra tasner, zoltán kovács ............................................ 47–50 quasi-polynomial control of a synchronous generator attila magyar, attila fodor ................................................................................................ 51–57 a structured model based diagnosis method for discrete dynamic processes using event sequences attila tóth, katalin m. hangos, ágnes werner-stark .................................................... 59–64 role of steady state data reconciliation in process model development barbara farsang, sándor németh, jános abonyi .............................................................. 65–75 statistical quality control based performance evaluation of online analyzers tibor kulcsár, jános abonyi .................................................................................................. 77–82 corrosion protection with ultrathin graphene coatings andrás gergely, tamás kristóf ......................................................................................... 83–108 investigations of bio-gasoil production péter solymosi, zoltán varga, jenő hancsók ................................................................ 109–114 hung. j. ind. & chem. 2013, vol. 41, pp. 1–136 table of contents the energy balance of separation opportunities in microalgae technologies zoltán hodai, dóra rippel-pethő, géza horváth, lászló hanák, róbert bocsi ..... 115–118 solid-liquid extraction of chlorophyll from microalgae from photoautotroph open-air cultivation éva molnár, dóra rippel-pethő, róbert bocsi ............................................................... 119–122 calculating the electrostatic potential profiles of double layers from simulation ion density profiles dezső boda, dirk gillespie .................................................................................................. 123–130 degradation of reinforced and unreinforced waste polyamides during mechanical recycling jános sója, nórbert miskolczi ........................................................................................... 131–136 hungarian journal of industry and chemistry veszprém vol. 41(1) pp. 1–6 (2013) vehicle routing approach for lean shop-floor logistics david gyulai1,2! and lászló monostori1,2 1 fraunhofer project centre for production management and informatics, computer and automation research institute (sztaki), kende str. 13–17, budapest, h-1111, hungary 2 department of manufacturing science and technology, budapest university of technology and economics, egry j. str. 1, budapest, h-1111 hungary ! e-mail: david.gyulai@sztaki.mta.hu in order to satisfy the material supply needs of large scale shop-floors and production systems, various logistics solutions are applied. in lean manufacturing enterprises, the material supply is pulled by the demands of manufacturing/assembly processes; therefore, a milkrun service is often applied to support the production without glitches. the milkrun logistics planning is a special case for vehicle routing problem (vrp), and requires effective approach to solution in order to satisfy various constraints, and minimize the cost of service. this study gives an overview about lean logistics as well as the most efficient vrp solver algorithms. furthermore, a novel initial solution with generation heuristics is proposed, which is specially focused on flexible milkrun planning. in order to demonstrate the capabilities of the solution, a software environment is developed as a demonstration that focuses on the main industrial requirements of logistics planning like effective layout definition, quick response of the delivery service and effective order handling. keywords: vehicle routing problem, milkrun, local search, factory logistics introduction the material provision of largeand medium-scale production systems requires prudent planning and control, since it influences the performance of the production and affects the order management directly and storage assignment [1]. in order to manage effectively the material provision of the production, practical transport logistics and distribution tasks are usually formulated as vehicle routing problems, whose objective is to obtain a minimum-cost route plan serving a set of customers with known demands [2]. in state-of-the art manufacturing systems, lean processes are successfully applied to eliminate the wastes on all the levels of production, and they raise the overall efficiency of the system by reducing the nonvalue adding activities in the process chain. the shopfloor logistics processes have to be adapted to the production system; therefore the waste reduction in the material provision also has a key role in balancing the workload and ensuring a smooth running of production. a well-operating lean logistics system keeps the inventories and operational costs on the most cost efficient levels, via by providing the materials what that are needed, exactly when they are needed. for satisfying these requirements, concepts of the lean logistics can be applied that are primarily aimed at controlling the transport services duly to the pull strategy. the paper is focused on the ‘milkrun’ service, which is defined as a manually operated, cyclic transport system delivering raw materials (or sub-assemblies) and disposing empties based on consumption using a fixed route and time schedule [3]. according to this characterization, milkrun scheduling is considered as a special vehicle routing problem with time windows, a limited capacity, and number of vehicles. in this paper a novel, multi-level planning approach is proposed, which combines the advantages of existing algorithms as for example local search for vehicle routing. first, an overview of the state-of-the-art factory logistics is given, considering the recent shop-floor characteristics and planning demands. then the main solution approaches and algorithms are introduced, as well as the critical points of milkrun planning. in section 4, the proposed layout representation hierarchy and the novel initial solution generation heuristics method are described. the latter focuses on the real industrial criteria and give a feasible milkrun schedule. in the last section, an industrial case-study and some numerical results present the efficiency of the milkrun planning method developed. shop-floor logistics the shop floor logistics are part of the production logistics in the supply chains of companies. while logistics in general is about supplying a customer with 2 necessary goods in time, with the goal of efficiency, and the lowest possible costs, production logistics is the task of bringing necessary material to workstations and machines and transferring it to the next station. in the realm of logistics planning methodologies the lean approach, originating in the toyota production system, of overall waste reduction has become a major planning paradigm, constituting the lean logistics approach [4]. principles of lean logistics of the seven waste categories, eliminating unnecessary transports, waiting times, superfluous movement and excess inventory are the most relevant in lean logistics. klug identifies the following characteristics of lean logistics [5]: synchronicity and a clocked material flow, flow orientation, standardization, pull principle, stability, integration, as well as perfection. regarding the pull principle, as the most relevant feature, material is only transferred to a workstation if it is about to process the material thus reducing inventory levels by reducing shop floor stock to safety buffers only. beside the above principles of lean logistics, a relatively novel issue in material provision of production is ‘green logistics’ that is generally about establishing an ecologically sustainable transportation system considering factors like energy consumption and airpollution [7]. while in the general external logistics context theses planning principles are reflected in transport concepts such as the just-in-time delivery, there are also corresponding design concepts in production and shop floor logics. for the supplier/source side, establishing zones for decentralized incoming goods and supermarkets in the vicinity of assembly stations is a means of reducing transport lengths. on the receiving side, standardized shelves and reusable containers, replenishment schemes like ‘kanban’ are applied. for the transport system between supply and workstations, ‘tugger trains’ (fig.1) with fixed time intervals, standardized capacity, and transport lot sizes are preferred over forklift transport in the context of lean logistics; the goal of, which is the reduction of inventory and avoiding erratic peaks in production known as the bullwhip effect [8]. this transport concept of scheduled tugger trains in the context of a lean-oriented logistics system is usually combined with the milkrun transport concept that is in the focus of this paper. especially in production environments with a high product complexity, variety amid a complex and changing material flow, planning a system of milkrun transports is a complex planning task. thus, an efficient system of milkruns could significantly in-crease the efficiency of the overall production logistics. milkrun as a vehicle routing problem vehicle routing (vrp) is a challenging combinatorial optimization problem, introduced first by dantzig and ramser in 1959 [9]. the general vrp is known as the capacitated vehicle routing problem (cvrp), were the aim is to satisfy the needs of all the customers at different locations by having a given number of vehicles with capacity constraints [11]. when milkrun is applied as a material providing system, the time constraint of the runs has also to be added to the general problem (vrp with time windows – vrptw). the general objective is to minimize the costs either by minimizing the total distance travelled, or minimizing the number of vehicles applied. a specific type of vrp is the pickup and delivery problem (pdp) where the vehicles not only provide the locations with materials, but also pick up materials at the stations and deliver them to another one. the milkrun problem is also a pdp, with time windows and cyclic service [12]. several approaches from the operations science are used to solve vrps, as for example constraint programming that manages flexibly the various specific constraints of the vrp [14]. local search is one of the fundamental approaches to find solutions for hard computational – including constraint satisfaction – problems. the basic idea behind local search is to start with a randomly or heuristically generated candidate solution, and to iteratively improve that by means of defined functions [15]. generating the initial solution is always a crucial point when applying local search, since it significantly affects the running time of the algorithm. sophisticated heuristics for the vrp are the two-phased ones, which decompose the problem into a clusteringand a routing problem, with possible feedback loops between the two stages. cluster-first route-second (cfrs) algorithms perform a single clustering of the vertex set and then they determine a vehicle route on each cluster. the bestknown cfrs algorithm is the fisher-jaikumar algorithm, which solves the general assignment problem (gap) to form the clusters [17]. the local search starts from the initial solution and subsequently moves from the present solution to a neighbouring solution in the search space where each solution has only a relatively small number of feasible neighbour solutions and each movement is determined by neighbouring operators [20]. when applying local search, the combination of the neighbourhood operators produces the next local optimum solution (fig.1). although the most general forms of the vrp can be solved effectively with the above approaches, the milkrun planning problem is hard to interpret as a simple graph-search problem, and the general initial solution heuristics are difficult to transform for this problem. the mapping process of the factory layout also requires special processing; therefore general solution methods cannot be applied easily for such a special problem. 3 problem formulation hereby, we provide a definition to the milkrun planning problem. consider a layout of the shop-floor, which is defined by a set of routes and stations. the routes can be either oneor two-way ones, and each route endpoint is defined as a “routenode”. along a specific route, there can be more stations (fig.2). the problem also considers demands that belong to the stations and defined by the amount of the transported goods in standard units and the required cycle-times of the transportation. the goods are transported by vehicles (practically by tugger trains), which are defined by their capacity and average speed. in order to plan feasible milkruns, real-world constraints are considered, such as the capacity constraints of the vehicles, which limit the maximum number of the transported goods. another constraint is the time limit of the plan, which means the total time consumption of a milkrun plan cannot exceed the cycletime of the demands. the loading and unloading points can be reached from both sides of the tugger train, and the train can approach the station from both endpoints of the route that the station belongs to. a milkrun plan is built-up by paths, where each path is given as the list of the visited stations and the list of the routes that the vehicle passes along. the plan does not partition the demands, and a visit of a particular station only occurs in a specific path. a milkrun plan is characterized by its total time consumption, which is required by the vehicle(s) to perform the plan. a milkrun plan is considered to be better than the other one only if its total time consumption is smaller, while it satisfies all the demands. the goal of milkrun planning is to minimize the number of the required vehicles via minimizing the time consumption of the plan. the proposed planning process layout representation for vehicle routing as it was mentioned in the previous section, solving the general vrp is not enough to plan feasible milkrun schedule, since most of the routing algorithms does not calculate with the physical constraints determined by the shop-floor. most of the general solution approaches consider the problem as a graph-search, where the stations are represented by vertices and the routes are represented by edges [21]. in many cases, this representation does not support effectively the planning processes with feasible results, unless the application of the following constraints. frequently, when representing a shop-floor by directed graphs, it turns out that the structure of the layout results some direct and indirect routing constraints. a direct case means that the additional equations can be formalized immediately when constructing the graph, such as the asymmetric edge formulas, while the others require further consideration. indirect constraints are usually implied by the narrow and one-way corridors, which limit the abilities of the vehicles from going to a station directly from another, even if a path connects them. these constraints are implied by the moving abilities of the common applied tugger train, since it cannot turn in the middle of an aisle, and in many of the cases it have to take a detour before visiting the next station (fig.2). in order to handle the shop-floor constraints effectively and be able to avoid impossible movements of the vehicle, a novel hierarchical layout representation is proposed. the layout is defined by three main different classes, each having their own specific attributes. this structure can be handled dynamically during the path calculations, and the asymmetric nature of the distance matrix is represented together with the limitations of vehicles movements. fig.3 shows the hierarchy of the layout, defined by “routenodes”, “routes” and “stations”. to calculate the distance matrix of the layout, storing the shortest paths between the stations, dijkstra’s algorithm was applied that solves the single-source shortest path problem in logarithmic running time [22]. in this case, the input of the algorithm is a directed graph where the vertices are the set of the “routenodes” and the edges are the routes. this graph representation is able to handle all the nodes of the layout with their connections, and by applying dijkstra’s algorithm the asymmetric distance matrix can be calculated. figure 2: layout elements and vehicle movement figure 1: interand intra-route relocate operators 4 initial solution generation in order to plan feasible milkrun cycles with the lowest operational costs, the shop-floor constraints have to be taken into consideration. to handle the constraints effectively, the routing algorithm needs to select the stations to be visited dynamically. thus, a so-called triplet solution is applied, which helps to avoid impossible movements of the vehicle. a triplet is consisted of three identical nodes: three current, the previous and the next position of the vehicle. the next position is calculated dynamically when determining a particular path of the vehicle. the milkrun planning method strongly focuses on the industrial requirements of vehicle routing; therefore, a novel initial solution generation heuristics was implemented. the goal is to generate a solution that is as close to the criterion as possible. the proposed heuristics can be classified as a cfrs type rule, and differs from the fisher-jaikumar algorithm by the cluster generation method, since it does not require solving time-consuming gap, but defines the clusters based on practical reasons [18]. to generate a feasible initial solution, the algorithm calculates a path to each station applying dijkstra’s shortest path algorithm. then a greedy search algorithm is applied to calculate the next node, which must be visited by the vehicle before returning to the depot, so as to avoid violating the turnaround constraints of the vehicle. the greedy search iterates forward the nodes applying a best-first search strategy [23], and finds the first node from, which the shortest path to the depot does not contain the previous node. the “roundtrip” planning method is applied for each station, and detects all the feasible tours on the shop floor. in order to determine the set of paths for the initial solution, the paths with most visits are selected one by one while the set of unsatisfied demands is not void. performing the services required by these cycles provides a feasible and acceptable initial solution for the planning algorithm. the pseudo-code of the proposed algorithm is the following: vv∈ set of stations { }vv|v:p ∈= path }p{p set of paths [ ] v)s,r(|dd rs ∈= distance matrix }p{i initial solution iq demands of the ith station }q{q i= set of demands ct cycle time c capacity of the vehicle initialize v, i, q, c{v}, c, tc foreach i in v calculate d0i foreach v in d0i add v to ci calculate di0 foreach v in di0 add v to ci align c [length(ci+1) < length (ci)] while |q| > 0 while time(c1) > tc or load(c1) > c remove rand v from c1 (v≠i) foreach v in c1 delete qv from q add c1 to i delete c1 from c return i local search strategy and neighbourhood functions in order to improve the initially generated solution, neighbourhood functions are applied. to be able to reach all the points of the search space, both intraand inter-route operators are necessary to calculate with, although in this case the effect of the inter-route functions is more significant since the initial solution heuristics could provide paths with stations in a rather good sequence. the algorithm performs the local search to minimize the paths, and the cycle-time of them. then, a simple bin-packing problem is considered, to allocate the paths to a minimal number of vehicles. to solve the problem, first fit heuristics was applied, which is a proven 11/9 opt solution algorithm [24]. case study and test results the milkrun planner software, which includes both the user interface and the solver algorithms were implemented in a .net environment using c++ language. within the performance evaluation of the implemented software, a real production environment was modelled in order to analyse its capabilities. the purpose of the implemented application is to offer userfriendly and efficient milkrun planning environment; therefore a graphical, point-and-click layout definition interface and xml communication have been applied (fig.4). figure 3: hierarchy of the layout representation 5 first the input parameters are processed and stored in the memory, and dijkstra’s algorithm is applied to calculate the shortest path between each station. the distance matrix is built up from vectors, each having two distance elements. this data structure is required by the applied triplet-based path planning method, which selects dynamically the proper distance parameter from the vector, based on the location of the previously visited station. the initial solution generation uses the distance matrix to create the tours, based on the station loops detected on the layout. the initial solution contains only feasible paths that satisfy the time constraints as well as the capacity constraints of the actual vehicle. to avoid overloaded vehicles, a pre-check method is performed: the vehicle is loaded by all the raw materials in the depot, and then all the other loading and unloading processes are calculated station-by-station to simulate the real milkrun process. in order to calculate with time constraints, both the travel-time (with constant average speed) and the loading/unloading time (time/item) are considered. the purpose of the generated initial paths is to satisfy all the demands by the lowest possible number of feasible cycles. the local search algorithm takes the initial paths and reduces their total time consumption by applying neighbourhood functions where it is possible. the algorithm iterates through all the combinations of the stations, and detects the possible insertions from one path to another. as local search iterates through the paths in a random sequence, different test runs can result different milkrun plans. in order to approximate the global optimum solution, the implemented application performs the local search several times and selects the most appropriate schedule from the generated solutions. the capabilities of the algorithm were tested in a real production environment. this was a large-scale automotive production system with 2 factory halls, 67 stations and 96 routenodes. the milkrun plan has to satisfy 193 various demands in 60 minutes cycle-time. the analysed system requires efficient planning process, since the total length of the routes is over 2.5 km that affects critically the total time of the milkrun schedule. the application of inefficient milkrun schedule results low-utilized vehicles and high number of cycles. in this case, the goal of the test was to minimize the number of vehicles required to perform the services via minimizing the time of the cycles. the proposed initial solution heuristically generated eight feasible paths with 20,400 seconds total time. first, the algorithm tries to optimize the plan by applying one vehicle, and increases the number of the vehicles only if the improvement steps cannot decrease the time requirement of the total plan under the cycle-time (3600 seconds). by this way, the test run could optimize the plan for two vehicles in 177 iterations, and generated a schedule, which time requirement is only 57 minutes (fig.5). conclusions after an overview about the state-of-the art shop-floor logistics, and the general formulations of the vehicle routing problem, a solution was proposed that uses a novel layout representation and initial solution generation heuristics to solve the milkrun planning problem. in order to demonstrate the capabilities of the figure 4: the user interface of the milkrun planner application figure 5: test results of the case study 6 solution, a software prototype was developed and tested on real-life industrial data. future work includes the extension of the model with demand partitioning so as to increase capacity utilization of the transportation vehicles. moreover, handling inhomogeneous demand types (physical aspects of material handling) requires further constraints to be included in the model. secondly, future work will be dedicated for making the solution available in practical industrial applications. in an on going research project the milkrun planning algorithm will be implemented in a factoryand a logistics planning application currently under implementation. acknowledgements the research has been partially supported by the national office for research and technology (nkth) grant "digital, real-time enterprises and networks" (omfb-01638/2009). references [1] kovács a.: optimizing the storage assignment in a warehouse served by milkrun logistics, international journal of production economics, 2011, 133, 312–318 [2] lau h., sim m., teo k.: vehicle routing problem with time windows and a limited number of vehicles, european journal of operational research, 2003, 148(3) 559–569 [3] droste m., deuse j.: a planning approach for inplant milk run processes to optimize material provision in assembly systems, proc. 4th cirp international conference on changeable, agile, reconfigurable and virtual production, 2011, 605–610 [4] arnold d.: handbook of logistics, 3rd edition, springer, heidelberg, germany, 2008 (in german) [5] womack j.p., jones d.t.: lean thinking, free press, 2003 [6] klug f.: logistics management in automotive industry, springer, 2010 (in german) [7] lin c.: survey of green vehicle routing problem: past and future trends, expert systems with applications, 2014, 41, 1118–1138. [8] bichler k., krohn r.: gabler kompaktlexikon logistik, 2nd edition, springer, wiesbaden, germany, 2011 (in german) [9] savelsbergh m.w.p., sol m.: the general pickup and delivery problem, transportation science, 1995, 29(1), 17–29 [10] dantzig g.b., ramser j.h.: the truck dispatching problem, management science, 1959, 6(1), 80–91 [11] pillac v.: a review of dynamic vehicle routing problems, european journal of operational research, 2013, 255(1), 1–11 [12] lu q., dessouky m.: an exact algorithm for the multiple vehicle pickup and delivery problem, transportation science, 2012, 38, 503–514 [13] berbeglia g.: feasibility of the pickup and delivery problem with fixed partial routes: a complexity analysis, transportation science, 2012, 46, 359–373 [14] russel r.: a constraint programming approach to designing a newspaper distribution system, international journal of production economics, 2013, 145, 32–138 [15] rossi f., beek van p., walsh t.: handbook of constraint programming, elsevier, 2006 [16] cacchiani v., hemmelamayr v.c., tricoire f.: a set-covering based heuristic algorithm for the periodic vehicle routing problem, discrete applied mathematics, 2014, 163, 53–64 [17] vidal t., crainic t.g., gendreau m., prins c.: heuristics for multi-attribute vehicle routing problems: a survey and synthesis, european journal of operational research, 2013, 231, 1–21 [18] the vrp web: http://neo.lcc.uma.es/vrp, (last accessed: may 25, 2014) [19] hashimoto h.: studies on local search-based approaches for vehicle routing problems, phd thesis, kyoto university, 2008 [20] carić t.: a modelling and optimization framework for real-world vehicle routing problems, vehicle routing problem, hrvoje gold, 2008 [21] matai r., singh s., mittal m.l.: traveling salesman problem: an overview of applications, formulations, and solution approaches, traveling salesman problem, theory and applications, intech, 2010 [22] wilt c.m., thayer j.t., ruml w.: a comparison of greedy search algorithms, proc. 3rd annual symposium on combinatorial search, 2010, 129–136 [23] russell s.j., norvig p.: artificial intelligence: a modern approach, 2nd edition, prentice hall, 2002 [24] yue m.: a simple proof of the inequality ffd (l) ≤ 11/9 opt (l) + 1, ∀l for the ffd bin-packing algorithm, acta mathematicae applicatae sinica, 1991, 7(4), 321–331 hungarian journal of industry and chemistry veszprém vol. 41(1) pp. 7–10 (2013) design of a new chemical injection pump system for gas hydrate inhibition csaba vörös1!, viktor füvesi1, and ákos pintér2 1,2research institute of applied earth sciences, university of miskolc, miskolc-egyetemváros, pob 2, h-3515 hungary 1department of research instrumentation and informatics, miskolc-egyetemváros pob 2, h-3515, hungary 2department of reservoir and mining chemical engineering, miskolc-egyetemváros pob 2, h-3515, hungary !e-mail: voros@afki.hu in this study the main feature of chemical injection systems used in gas industry are detailed. the two main energy sources of these systems are air and electric power source. the general structure and main properties of these injection systems are discussed. examples for a pneumatic commercial and a newly developed, electric system are compared. keywords: chemical injection system, hydrate inhibition, solar energy, pneumatic system introduction during the production of gas, a major problem is the formation of hydrate crystals in the pipeline. a considerable amount of hydrate crystal can cause hydrate plugs in the pipeline. the hydrate plug effect lengthens production outages and results in loss of money for the maintainer [1], because elimination of the plug is a time consuming procedure. one of the most widely used traditional solutions to prevent hydrate formation is addition of methanol to the steaming gas. the methanol helps to dehydrate the gas, thus, the growth of hydrate crystal is limited [2]. the methanol can be transported from the gas separator station or gas collection station to the gas wells via a dedicated pipeline. this traditional solution was the most popular practice for a long time in gas industry. this technology is safe, but has several drawbacks, such as the cost of additional pipe to the gas wells, the cost of the methanol regeneration [3], and methanol contamination of the environment. regardless the methanol technologies are still major solutions for hydrate inhibition for the currently operating gas wells. the modern installations use methanol in low concentrations for newly installed gas wells. these bring the need for injecting methanol locally at the site of the gas wells. thus, an injection unit is needed for this purpose. the production-related aspects such as the consumers expecting increased flexibility from gas provider cannot be neglected, because of the habits of the consumers and the appearance of competitive energy-saving technologies. therefore the different injection systems spread noticeably dynamically in recent years. in the first part of the paper, the main features of the commercial injection systems are detailed followed by the introduction of a newly developed injection system. chemical injection systems in gas industry there are two applications, where chemical injection is required. the first one is the above described gas hydrate inhibition technology. the second one is where usage of corrosion prevention chemicals is needed. new chemical injection technology appeared in sophisticated form using a wide service range as a result of a change in gas production and distribution in the last decade. structure of pneumatic chemical injection pump systems the most commonly used chemical injection units in gas industry employ the energy of gas for dosing. these systems are called “operating without auxiliary power systems”. in details, the energy of gas steam in the pipeline is used as a power source in the dosing of hydrate inhibiting chemical pump systems. this method has the major advantage that the gas is always available, or it is not necessary to provide a separate power source for the equipment to operate. big disadvantage of the technique is that gas is required for operation and this gas is emitted to environment, which is a harmful effect, moreover, the cost of it is also not negligible. there are some solutions to utilize the emitted gases, but these methods raise the price of the pump. 8 fig.1 shows a common structure of chemical injection pump systems, which illustrates how the actuated gas gets into the injection system through a gas preparation unit. this unit is typically a special tank, which is filled with methanol. by using this type of conditioning one can be sure that the gas is sufficiently dry, thus, the water does not disturb the operation of the pump. it is needed to avoid the risk of freezing out various components. the gas bubbles through the methanol, so it loses a significant part its water content. the replacement of the methanol is needed at appropriate intervals of time as a technology management. after the gas leaves the conditioning unit, the gas steams through a two-stage pressure regulator. this unit provides the required pressure to the system for operation. the timer unit is responsible for providing appropriate technological demands of the schedule, i.e. sufficient number of strokes is needed to operate the pump. the chemical is injected with the piston of the injection pump. the injection system includes other components, which are essential for the operation, such as check valves, ball valves and other fittings. the hydrate inhibitor compound can be found in the tank. the main task of the control system is the monitoring of the injection system, so several parameters are required to be measured, e.g. the level of chemical in the tank, the pressure of the after the regulator and the ambient temperature. one of the most substantial information about the injection pump is the entry of the inhibitor to the pipeline. to measure these parameters, transducers are needed, which require some solar energy for the operation. fig.2 shows a wellorganized, modern gas well in hungary. the injection system used employs the gas of the well for its operation. injection system from haskel milton roy the haskel milton roy company develops and manufactures various injection systems for special oil and gas applications for many years. chemical injection pump (cip) series is one of the most widely used equipment for gas wells. a pneumatic version of the device is shown in fig.3, as a typical system. the driving gas or air is fed from the regulator to the gasdrying unit. the air is let into the injection pump, which includes the timer unit. the chemical enters the pump through the appropriate valves and filters. the dosage of chemicals can be adjusted through the rate setting gauge unit (typically it is a burette) at, which the quantity of chemical of one injection is displayed. the strokes can be counted by using the flow meter on the system. the check valve prevents the injection pump from the backpressure of the process fluid. the company can deliver the complete unit in different versions according to the quantity of injection, e.g. the given series can be adjusted from 0.27–25.8 dm3 min-1. the range of operation pressure is also wide, typically 120–600 bar. structure of electric injection systems this category includes systems, where the electricity is the only energy source. in general, the site of the gas figure 1: block scheme of chemical injection system figure 2: chemical injection system on a gas well figure 3: pneumatic injection system from haskel milton roy [4] 9 well is not equipped with electric power because of the relatively large distance from the processor (separator station, collector, etc.). thus, these systems are not commonly employed in the gas well applications. most of the electric chemical injection pump systems are based on the principle of displacement pumps. these high-pressure pumps provide the chemical injection by using speed adjustment in a wide range, or with different piston volumes. as shown in fig.4, the electrical injection pump system contains relatively few units. it cannot be ignored that the electric pump does not only include a motor-driven piston with frequency inverter, the controller electronics is also an important part of the system. solar energy can be applied as energy source of this type of system. this source can feed the control electronic besides the main actuator of the system. in-house designed injection system the development of the injection system was a part of a bigger project with the scada ltd, a company from automation industry. the aim of development was to create an injection system, which can be used mainly at hungarian gas wells. thus, the temperature requirement of the system was in the -40 °c to 60 °c range. the system must be capable of working in ‘ex’ environment with high efficiency. the power source of the actuator is solar energy to reach close to zero emission of the system. in the system, corrosive chemical has to be injected, thus, a corrosive resistant is required at critical parts of the equipment e.g. piston, piston space, etc. the maximal working pressure was 160 bars. a wide range of injection volume was also a fundamental requirement. these requirements were the main parameters at the design phase of the equipment. the block scheme of the developed system can be seen in fig.5. the base of the system is an ex class asynchronous motor (table 1), which is assembled with a helical gear unit from nord manufacturer. the base of injection system is a crank mechanism, which transforms the rotary motion to alternating motion. the pump has two pistons to reach higher injection volume and a wellbalanced load of the motor. the main parameters of the mechanics can be found in table 1. the sealing of the mechanism is a critical design point. the relatively high pressure, corrosive fluids, and high stroke number require special solution for sealing. a single acting, spring energized-seal was selected. the application conditions demanded the tight guiding of neck of piston, to avoid the damage of seals during the operation of pump (fig.6). the electromechanical actuator gives the opportunity to smoothly alter the injected volume in continuous or in periodic operation. table 2 shows the injected volume of the pump at different frequency of the inverter in continuous mode. the power source of the system is an array of solar cells. the power of solar energy system was 2 kw to get extended service and short recharge time. the capacity of the accumulators was 800 ah. the developed equipment has a plc-based control system to monitor the main parameters of the technology and to change the behaviour of the injection system. figure 4: block scheme of electric power injection system figure 5: block scheme of new injection system table 1: main parameters of the injection pump designed asynchronous motor nominal voltage 230 v(y) /400 v (d), 50 hz nominal power 0,12 kw ex class ptb 07 atex 1058 x ii2g ex de iic t4 type dex 63k/4k vendor hew helical gear unit gear ratio 41,58 ex class ex ii 2g c iic t4 x type sk02f-iec63 /26-63 s/4 tf/2g vendor nord crank mechanism length of stroke 20 mm ratio of mechanics 7 injection unit diameter of piston 5 mm vendor of seals trelleborg type of seals turcon® variseal® 10 the measured parameters are the pressure of siphon of well, drill pipe, injection pipe; the temperature of pipe of well, soil, chemicals, controller, temperature of inverter; the level of the chemical in the tank; the current and the voltage of the inverter. the frequency of the inverter can be changed in function of the conditions of the well. the injection system is able to communicate wirelessly with a server. by using modern computer technology, the main parameters of the system can be monitored and changed. fig.7 shows the website of the system, which shows, on one hand, the main actual online parameters of the system, on other hand, the trends and history of the parameters on diagrams. the structure of the website is user friendly, simple. a model technology for an actual gas well was set up at the site of the scada ltd. near to hajdúszoboszló (fig.8). at the test site, main parameters like level of the chemical in the tank, process gas pressure, frequency of the inverter, etc. were monitored and measured. after the successful test of the model technology, the equipment was moved to a real gas well at békásmegyer in october 2012. conclusion a new solar energy-based chemical injection pump system was developed with a modern control and computerized support system at university of miskolc, research institute of applied earth sciences. the equipment meets the modern requirements. it is an efficient injection system; it has wide operation range and has user-friendly high-level computer support. in the process automation field of gas industry, the adaptation of new approaches appear slower in consumer or in industrial environments than in other fields of industry. the new, energy efficient, solar supplied, standalone chemical injection systems hopefully can enter in the field and will be utilized more wells in hungary. acknowledgement this work was partially supported by the framework of the centre of excellence of mechatronics and logistics at the university of miskolc. references [1] berecz e., balla-achs m.: gázhidrátok, akadémiai kiadó, budapest, hungary, 1980 (in hungarian) [2] hammerschmidt e.g.: formation of gas hydrates in natural gas transmission lines, ind. eng. chem. 1934, 26(8), 851 [3] lederhos j.p., long j.p., sum a., christiansen r.l., sloan, e.d. jr.: effective kinetic inhibitors for natural gas hydrates, chemical engineering science, 1996, 51(8), 1221–1229 [4] williams chemical metering pumps: www.willamspump.com (last accessed: may 25, 2014) figure 7: website of pump system figure 6: section of injection unit table 2: injected volume of pump at 150 bars frequency of inverter, hz injected volume, dm3 h-1 30 21.71 50 36.19 70 50.67 90 65.14 figure 8: block scheme of chemical injection system hungarian journal of industry and chemistry veszprém vol. 41(1) pp. 11–15 (2013) ionic liquids in advanced energy storage cells attila göllei ! and attila magyar department of electrical engineering and information technology, university of pannonia, egyetem str. 10, veszprém, h-8200, hungary !e-mail:gollei.attila@virt.uni-pannon.hu the interest in the research and application of ionic liquids has been increased worldwide, especially in petrochemical industry, nuclear industry, oil and gas industry, chemical, and electro-chemical industry. in the field of chemical operations in microwave field with ionic liquids (organic chemical synthesis, catalytic operations, etc.) new horizons opened that were supported by the dramatically increasing number of studies dealing with this question and their impact. due to the high durability of ionic liquids as a function of temperature, a wider temperature range of operations can be accessed. in addition, it offers environmental friendly solution in the replacement of the toxic solvents with generally low volatility. the area of application extends to electrolytes of novel battery cells. the important prerequisite for application of ionic liquids is the knowledge of their physical and chemical properties. our aim was to test the dielectric properties, viscosity, and temperature dependence of the electrical conductivity. considering our measurements, it can be declared that the aforementioned properties show significant temperature dependence in the case of ionic liquids. this knowledge is important for the usability, design and execution of production and related optimization processes. it is particularly important that energy storage cells can be exposed to large temperature fluctuations. this study discusses the sample materials, the usage possibilities of the sample materials and the obtained results. keywords: ionic liquids, energy storage cells, conductivity, temperature dependence, viscosity introduction the key parameters in the modelling of microwave behaviour of ionic liquids are the dielectric constant, dielectric dissipation factors, in addition the parameters characterizing the polarizability and the microwave energy absorption. traditional measurement methods of the static dielectric constant of ionic liquids fail, because they cause intense shortcut due to their high electrical conductivity. according to literature, these contexts have not been studied systematically because of the novelty of this subject. the significance of these results is critically important in the planning and controlling chemical reactions. ionic liquids (il) opened new technological possibilities at the end of the 1990s providing a wide range of applications, especially for areas of chemistry and particularly in green chemistry. ils are beneficial due to their special chemical and physical characteristics. nowadays, the use of energy storage units, particularly mobile phones, electric vehicles, and uninterruptible power supply systems has more and more importance. recently, room temperature ionic liquids (rtils) have been extensively studied as electrolytes of lithium ion batteries from cellular phones to electric vehicles. the unique properties make rtils attractive candidates for the electrolyte base of safe lithium battery [1, 2]. generally, rtils are well known to be thermally stable and non-flammable and their nature can hopefully improve the safety of electrochemical devices with aprotic solvents, such as li batteries and supercapacitors. 1-ethyl-3-methyl-imidazolium tetrafluoroborate (emim-bf4) has a high ionic conductivity, which is comparable to those of organic solvent electrolytes. in addition, the viscosity of emim-bf4 is low. therefore, emim-bf4 is expected to be a good electrolyte candidate for li batteries. we have found that a li/licoo2 cell with rtils as an electrolyte base works reversibly, indicating that qaimide rtils are quite stable even at the li reduction potential. clearly, rtils improve the safety of li-ion batteries with carbon anodes. to date, rtils are the most promising electrolytes for improving the safety of li-metal batteries, which could be important for higher energy densities [3]. a set of four imidazolium ionic liquids (solid at room temperature) and one imidazolium ionic solid were screened for their potentials as electrolytes in manganese dioxide free leclanché batteries, equipped with a zinc anode and graphite cathode [4]. it should be noted that the ionic liquid 1-ethyl-3methylimidazolium hydrogensulphate (emim-hso4) similar to many other ionic liquids, such as those based on nitrate and dihydrogenphosphate anions, have also been found they work well in this battery design. novel 12 batteries are designed using standard cathode materials such as mno2, pbo2, nio and ago, and anode materials such as zn, sn and pb. additionally, by using a solid polymer electrolyte composed of polyvinyl alcohol and anionic liquid, new types of solid state batteries were demonstrated with discharge voltages ranging up to 1.8 v, depending upon the type of cathode and anode used [5]. ionic liquids like 1-butyl-3-methylimidazolium tetrafluoroborate (imim-bf4) or hexafluorophosphate (imim-pf6) and 1-butyl-4-methylpyridinium tetrafluoroborate (pybf4) were mixed with organic solvents such as butyrolactone (bl) and acetonitrile (acn). the specific ionic liquid used in the given study is shown in fig.1. a lithium salt (libf4 or lipf6) was added to these mixtures for possible application in the field of energy storage (batteries or super-capacitors). viscosities, conductivities and electrochemical windows at a pt electrode of these electrolytes were investigated. all the studied electrolytes are stable toward oxidation and exhibit a vitreous phase transition, which has been determined by application of the conductivity measurements. mixtures containing the bf4 anion exhibit the lowest viscosity and highest conductivity [6]. methods the essential precondition for the application of ionic liquids in batteries is a preliminary examination of its properties. therefore, every measurement method available to us was used on a number of ionic liquids examined. we have carried out microwave measurements, such as temperature change, dielectric properties at 2.45 ghz frequency, electrical conductivity according to temperature and viscosity changes depending on the temperature. the velocity of temperature change of ionic liquids was measured in the cem discover unit. this is a wellknown and commercially available apparatus in microwave chemistry. the device has a cylindrical operating space and on the cylindrical peripheral surface there are many slots where microwave energy can enter. this solution provides a special high homogeneity of the microwave field. the temperature was measured at the bottom of the compartment with an infrared thermometer. the amount of the samples used was 0.5 g, which was placed in an inner diameter of 12.5 mm of borosilicate cylindrical glass flask. it is important to know that during microwave treatment the microwave energy interacts with the treated material, and the material converts the electric energy into thermal energy according to its characteristic of dielectric properties. during this conversion process, the macroscopically observable result is the measurable increase of the temperature in the treated material. the rate of the temperature increase depends on the microwave field and the treated material properties, which is described in the following equation: δt /δt = pv / ρcp = ie 2 fε"/ ρcp (1) where, the ∆t/∆t is the velocity of temperature change in kelvin per second, pv is the absorbed power in the sample, ρ is the density of the sample, cp is the specific heat of the sample, e2 is the strength of the electromagnetic field in the sample, f is the frequency of the field and ε” is the dielectric loss, i means this is a complex value [4]. eq.(1) shows that the temperature of the treated material is influenced by a number of factors. the separate testing of their effects is not an easy task, since ρ, ε, cp features themselves are temperature dependent, and this value is difficult to accurately measure inside a material. in case of strictly homogeneous series of examined compounds the situation is more simplified, because some simplifications are allowed. assuming ρ and cp does not change significantly in the function of temperature, the multiplication ρ cp was almost considered to be constant, so that the rate of temperature change is determined by e and ε" only. further simplifications can be made if the device is single-mode with the same volume and shape, and the microwave energy is constant during the investigation. the value of e is determined by ε' and ε' and ε" and the rate of temperature change is essentially determined by ε" value. figure 1: the structure of investigated ionic liquids table 1: the formulas of investigated ionic liquids compound r y 1 ch3 bf4 2 c2h5 bf4 3 c3h7 bf4 4 c4h9 bf4 5 ch3 pf6 6 c2h5 pf6 7 c3h7 pf6 8 c4h9 pf6 9 c2h5 ci 10 c2h5 br 11 c2h5 scn 12 c2h5 n(cn)2 13 c2h5 n(so2cf3)2 13 measurement setup the schematic representation of the in-house designed experimental set-up for automated online measurement of dielectric properties of ionic liquids in a definite temperature range is shown in fig.2. it is composed of the following devices and instruments; cylindrical sample holder unit, thermostat, peristaltic pump, waveguide, temperature sensor, displaceable piston, stepper motor, magnetron, detectors, control unit, and a pc. the il sample, which is placed in the thermostat to be kept at the desired temperature, is passed across the waveguide having a length of about 3λ through the sample holder tube with the help of a peristaltic pump. the electric energy is transformed into microwave energy by the magnetron. the stepper motor is controlled by a microprocessor control unit equipped with an intel 8-bit microcontroller, a 12 bit a/d converters for receiving the four diode-detector signals, a stepping motor driver, and a rs-232 serial interface to connect it to a pc. the control unit collects the detector signals and the temperature data from the temperature sensor and sends them to the pc. furthermore, it controls the position of the short circuit displaceable piston on the basis of algorithm software elaborated for this purpose. the measurement method is based on the compensation of phase change due to the microwave energy absorption of the liquid sample. the short circuit piston situated behind the sample must be actuated for compensation. the energy conditions created by the wave front in the waveguide are measured by four diode-detectors. dielectric constants, dielectric loss factors and the temperature dependence of the dielectric properties of ionic liquids intended to be used in batteries were determined by the above described self-designed microwave dielectrometric apparatus (fig.3) at the frequency of 2.45 ghz and at different temperatures (30°c, 40°c, 50°c, 60°c, 70°c, 80°c, 90°c, 100°c, 110°c and 120°c). the speed of the change in temperature depends on the electrical field strength in the material (e), the absorbed microwave power, (pv) density (ρ), the specific heat capacity (cp) and the dielectric loss factor ε” and can be given by eq.(1) [7]. results and discussions the effects of r groups (table 1) were examined in case of two anions bf4 (1–4) and pf6 (5–8) at 3 to 5 w of microwave energy. the results indicate that the decrease of the number of c atoms in r increases the rate of temperature change. by increasing the microwave power significantly the temperature rapidly converge and sometimes crossing over, but this is not typical in fig.3. overall, the rate of temperature rising follows the order of ε' and ε" suggesting that in a strictly homologous series the temperature change of ionic liquids is determined by ε" [5]. after evaluating the rate of temperature change, we investigated two additional properties of the ionic liquids used in the advanced batteries. these parameters were the viscosity and the electrical conductivity. both of these parameters are the functions of temperature. they were examined between 20 °c and 100–120 °c temperature range. the viscosity was measured up to 95 °c due to the sample material being heated by a waterfilled heat exchanger. the measurements were performed in a sv-10 type of vibration viscometer (a&d ltd. japan). fig.4 shows that the viscosity at room temperature is high, typically several hundred pa·s. it decreases rapidly with the temperature increase similar to a reciprocal curve. at 100 °c, the value of viscosity can be ten times lower then at the initial value as can shown in fig.4. the investigation of the viscosity is important, since it basically correlates with the mobility of ions in the electrolyte, which can affect the conductivity, and thus the internal resistance of the battery cell. by cooling ionic liquids, the viscosity is increasing rapidly. around freezing temperature the ionic liquids were already similar to a “honey density” mass. since the energy storage cells are used in a wide temperature range, it is important to know that the figure 2: scheme of the experimental setup figure 3: temperature profile for 1-butyl-3methylimidazolium tetrafluoroborate at 3w 14 electrical conductivity of the electrolytes is a function of temperature. fig.5 contains five different electrical conductivity plots of ionic liquids in the function of temperature. it can be seen that the above mentioned bmim-bf4 does not have the highest conductivity value, but the depending on the temperature the conductivity value of this material increases with the greatest intensity [6]. a new and surprising result can be seen in fig.6. the dielectric constant value of bmim-bf4 reaches a value of 1 at close to 100 °c, similarly to the value of the vacuum and with the further raising of the temperature this value decreases into the negative range. this fact suggests that by increasing the temperature the electrical conductivity is rising greatly and this compound is no longer an insulating material, but a conductor. therefore it is important to keep the temperature in an adequate range when batteries are used and especially in the charging period. the dielectric constant (e1), dielectric loss factor values of ils built up of the same bf4 anion and six previously described cations containing alkyl chains with different lengths (dietmeim+, dietetim+, dietprim+, and dietbuim+) at different temperatures between 30°c and 120°c are shown in fig.7. at the initial measuring temperature of 30 °c all four of the studied ils have similar dielectric constants around 7. with the increase in temperature the e1 values for dietmeim(bf4), dietetim(bf4) and dietprim(bf4) slightly increase up to 13, while the dielectric constant for dietbuim(bf4) shows a sudden break at 90°c and at 120°c it reaches the value as high as 27. this could be explained with some sudden changes in the structure of the ils or in the physico-chemical interactions between the anion and the cation. excluding the results for dietbuim(bf4) the values at elevated temperature show that the highest e1 value belongs to dietmeim(bf4), followed by dietetim(bf4) and then by the dietprim(bf4), hence the dielectric constant increases with the decrease in the alkyl chain length of the cation. taking into account the dielectric constant, dielectric loss and electrical conductivity results of all the investigated ils it can be concluded that the alkyl chain length of the cation and the structure of the anion strongly influence the dielectric properties of the ils and that the highest g value is exhibited by the dietmeim(bf4) il at 30°c temperature, hence it is the most suitable candidate for battery applications. furthermore it can be stated that implementing the knowledge about the connection between the il structure and the dielectric properties another ils should be studied in order to select the ones most adequate for electrolyte application. figure 4: viscosity of bmim-bf4 as a function of the temperature figure 5: conductivity of five compounds as a function of temperature figure 6: dielectric constant of bmim-bf4 as a function of the temperature figure 7: dielectric constant of ils containing common bf4 anion and different cations 15 conclusion due to the special characteristics of ils, such as wide electrochemical windows, high inherent conductivities, high thermal and electrochemical stability, tuneable physicochemical properties, etc., they are potentially excellent candidates for environmentally sound, green electrolytes in batteries. in order to predict their success in a specific application, it is essential to gain information about their dielectric properties. however, several techniques have already been published about determination of the dielectric properties of ils, so far no experimental methods were introduced due to the fact that such measurements cannot be realized by classical methods because of the high conductivity of ils. summarizing our results, we can conclude that when ionic liquids in the energy storage cells were used, their physical, chemical and electrical parameters are significantly temperature dependent. in any case, when they are applied, we should specify the range of application temperature. stepping out of this range of the energy storage cell may not meet the expected specification values, or in the worst case it may be permanently damaged. acknowledgements we acknowledge the financial support of the hungarian state and the european union under the tamop4.2.2.a-11/1/ konv-2012-0072. references [1] alarco p.j., yaser a.l., ravet n., armand m.: lithium conducting pyrazoliumimides plastic crystals: a new solid state electrolyte matrix. solid state ionics, 2004, 172(1–4), 53–56 [2] schiffmann r.f.: microwave and dielectric drying, in: 2nd handbook of industrial drying, (ed. mujamder a.s.), vol 1, marcel dekker, new york, usa, 1995, pp. 345–372. [3] hikari s., hajime m., kuniaki t.: application of room temperature ionic liquids to li batteries electrochimica acta, 2007, 53, 1048–1054 [4] zhang z., gao x., yang l.: electrochemical properties of room temperature ionic liquids incorporating bf4 and tfsi anions as green electrolytes, chinese science bulletin 2005, 50(18), 2009 [5] gao x.h., zhu m.j., zhang z.x.: research on room temperature molten salts with alkylated imidazolium salt as electrolytes, chemical world (supplement, i), 2004, 45, 156–157 (in chinese) [6] nishida t., tashiro y., yamamoto m.: physical and electrochemical properties of 1-alkyl-3methylimidazolium tetrafluoroborate for electrolyte, j. fluor. chem., 2003, 120, 135–141 [7] göllei a., vass a., pallai e., gerzson m., ludányi l., mink j.: apparatus and method to measure dielectric properties (ε’ and ε”) of ionic liquids. review of scientific instruments, 2009, 80(4), 6734–6748 advertise upcoming meetings, conferences, and workshops; make public announcements; introduce your research laboratory; a new product or a service in the hungarian journal of industry and chemistry please contact us if interested! editorial office: university of pannonia p.o. box 158, veszprém h-8201 (hungary) tel.: +36 (88) 624-298, e-mail: hjic@almos.uni-pannon.hu; web: hjic.mk.uni-pannon.hu felelős szerkesztő: szilágyi róbert, phd kiadja: pannon egyetem, 8200 veszprém, egyetem u. 10. levélcím: h-8201 veszprém, postafiók 158, tel.: (88) 624-000 hungarian journal of industry and chemistry veszprém vol. 41(1) pp. 17–26 (2013) monitoring and diagnosis of manufacturing systems using timed coloured petri nets adrien leitold1, brigitta márczi2, anna ibolya pózna2, and miklós gerzson2! 1 department of mathematics, university of pannonia, egyetem str. 10, hungary 2 department of electrical engineering and information systems, university of pannonia, egyetem str. 10, hungary !e-mail: gerzson@almos.uni-pannon.hu novel fault modelling and integration method were applied in the case when the faultless operation of the system was modelled by a high-level, coloured petri net. in order to achieve realistic investigations, a timed coloured petri net model of the system was constructed, where faults can occur in the manufacturing lines. the faultless and fault containing models were implemented in cpntools both for non-timed and timed cases. the resulted model was investigated both via simulation and using the occurrence graph. for efficient analysis of the occurrence graph a software module called oganalyser was developed. keywords: monitoring and diagnostics of manufacturing processes, coloured timed petri nets, probabilistic models, occurrence graph introduction models are often used for the description and investigation of complex systems even if they cannot perfectly describe the investigated system. the course of a manufacturing system can be split up to distinct steps of serial or parallel technological sub-processes. this enables the description of the system by a discrete event systems model [1] in the form of petri nets. during the design process of a manufacturing system, often only a model of the faultless operation is created. the integration of possible faults into the model could give important information for more complex investigation of the system. in our previous work [2] we have integrated fault events with different occurring possibilities into low-level petri net models of manufacturing systems in such a way that the size of the model remained almost the same. in our recent work, we applied the above fault integration method for the case when the faultless operation of the system was modelled by a high-level, coloured petri net (abbreviated as cp-nets) [3]. in lowlevel petri nets the transitions fire instantaneously, but the events of a real system take place for a certain amount of time influencing the operation of the system. therefore, a timed coloured petri net model of the system is constructed in order to achieve realistic investigations. cpntools [4] offer tools for modelling and analysing of cp-nets. there are two possibilities for the investigation of a manufacturing system in cpntools: the simulation and the analysis of the occurrence graph. in case of fault modelling using different occurring possibilities; however, the standard occurrence graph does not give information about the probability of the different occurring states of the system. therefore, a special software module, called the oganalyzer has been developed for solving this problem. weights can be assigned to the arcs of the occurrence graph and the software calculates the probability of each node in the occurrence graph, i.e. of each operational state of the system. petri net model of a manufacturing process petri nets enable both the mathematical and the graph representation of a discrete event system to be modelled, where the signals of the system have discrete range space and time is also discrete [5]. petri nets can be used for describing a controlled or open loop system for modelling the events occurring in it, and for analysing the resulted model. for the different application purposes, various modifications of the original petri net were developed with the aim of improving the modelling capabilities. one of the approaches is the coloured petri nets (cp-nets). we use here the cp-nets for modelling technological systems and their diagnosis, i.e. for the determination of faulty operational modes of the investigated system. coloured petri nets the cp-nets combine the modelling advantages of petri nets and the compactness of the functional 18 programming language standard ml [6]. a petri net is bipartite graph having circles and rectangles as nodes. circles refer to the ‘places’ in the net and rectangles to the ‘transitions’. places represent the state of the elements in the modelled system, while transitions correspond to the actions taken place in it. there are ‘arcs’ between places and transitions referring to logical relations of the system. if an arc directs from a place to a transition then the place acts as a precondition of the given transition while the arcs in the opposite direction represent consequences of transitions. each place can be marked with one or more coloured tokens representing the state of the modelled element. here we emphasize two important novelties of cpnets only. the tokens describing the state of the system have data value, the so-called token colour attached to them. in this paper these colours are used to identify workpieces and to describe the operation to be performed on them. places, transitions and arcs can have ‘inscriptions’. an inscription of a place determines the set of colours that a token on the place can have. another place inscription gives the actual number of the tokens on the place, i.e. the current marking of that place. the inscriptions of transitions can contain different types of functions. these functions determine the type of the colour set of the incoming and outgoing tokens and the operation performed on them. the arc inscriptions can be used for evaluating the result of the performed action at the previous transition. these conditional expressions define the colour of the token on the following place. the original petri net concept did not contain the time; however, the firing of transition takes place instantaneously. in case of real technological systems the time has a great role during the occurring of events. cp-nets also offer the possibility of adding time to the operation of transitions. the firing rule of a transition in timed petri nets is as follows: a transition is enabled if all of its input places contain sufficient number coloured tokens defined by the arc functions and the allotted time has elapsed. one of the main advantages of modelling with petri nets is the ability of describing sequences of discrete events that occur both in a serial and in a parallel way. in case of parallelism, we can distinguish two different situations. in the first case the two or more series of events can take place independently of each other. this situation occurs when workpieces can be elaborated in different manufacturing lines in parallel way. in the other case only one of the event sequences can take place because these events exclude mutually each other. these events have the same precondition, and the occurrence of any of them makes this precondition invalid. this kind of parallelism is called ‘conflict situation’. in a petri net the conflict can be recognized when a place is the precondition of two or more transitions. in this case it is randomly selected, which transition takes place. the conflict can have two different sources in technological systems. a conflict occurs in a technological sense when two or more processes want to use the same tool or resource e.g. a robot. usually it is worth to assign priority to each conflicting transition in order to define their sequence. when a fault occurs during the operation of the system, it also causes a conflict situation. this can be avoided by adding a special probability function to arc expression functions. by evaluating this function, the occurrence of the fault can be unambiguously determined during execution. analysis of petri nets there are two basic directions for the analysis of a petri net: (i) the structural method, which is independent of the initial state of the net and (ii) the investigations based on a given initial state (the behavioural analysis). in this paper the latter is used for the investigation of technological system behaviour. simulation is our primary tool for the checking the correctness of a model. starting from a given initial state the user can check whether the operation of the system terminates in the appropriate state. it can also be investigated, which transitions become enabled in certain steps, whether there is a conflict among then. simulation investigations do not give unambiguous answers to questions of formal analysis formulating in petri net literature [7] but they complement them well. another petri net analysis method uses the ‘occurrence graph’. the basic idea of the occurrence graph is to construct a graph, which contains all of the reachable markings from a given initial state. these marking are the nodes of the occurrence graph and the arcs connecting the nodes refer to the logical relations realized by the firing transition between two markings. unfortunately, the occurrence graph even of a small petri net may become very large. therefore, several reduction methods were proposed in order to get a relatively small occurrence graph [7]. most of the simulation tools, as the cpntools [4] used by us, are able to construct the occurrence graph. modelling and analysis of technological systems in the following, we wish to demonstrate the use of cpnets and their occurrence graphs for modelling and analysis of technological processes. both for normal faultless and faulty mode operation of the technological system are considered in the non-timed and timed cases. the analysis is performed via simulation and with different investigations of the occurrence graph. the manufacturing system and its operating procedure a simple case study is presented here for a manufacturing system containing two manufacturing lines and a robot. the arrangement of the system can be seen in fig.1. 19 the workpieces to be processed appear on the input place in. the task of the robot is to put them to the appropriate input place of a manufacturing line m1_in or m2_in according to operational instructions. assume that the two manufacturing lines perform different actions on the workpiece of interest. when the manufacturing process is over, the finished workpiece appears at the output end of the line either on m1_out or m2_out depending on the performed action. if the workpiece has to be modified on the other manufacturing line then the robot puts it onto the other input place. if the manufacturing process is over then the robot puts it into the product container out. assume that one workpiece at a time can be on the input and output places of manufacturing lines. it follows that the robot can only transfer a workpiece from place in to the input place of a manufacturing line if this place is empty and the precondition of the start of a manufacturing process is that the output place of this line should be empty. as a general precondition of all transfer processes the robot has to be free. the cp-net model of the normal (faultless) operation of the manufacturing system in the form of a screenshot from cpntools can be seen in fig.2. the process starts with a token at place start. the transition generator generates the prescribed number of tokens representing workpieces at place in. the colour assigned to a token contains an identifier of the workpiece and a code referring to the manufacturing process or processes to be carried out. four kinds of manufacturing mode are possible in this manufacturing system: the workpiece has to be processed on line 1 (denoted by m1) or on line 2 (m2) only, or it has to go through the line 1 and then through line 2 (m12) or in reverse order (m21). as an example, the token (1,m12) refers to the workpiece having identifier '1' and this piece has to be processed first on line 1 then on line 2. the state of input and output of manufacturing lines is modelled with two places. the places tin_empty, tin_full refer to state of inputs and they are mutually exclusive. the colour of tokens referring to the state of these places consists of the identifier of the line only. if the input place of the line 1 is empty then there is a token having colour m1 on the place tin_empty, and there has not to be a token having colour m1 on the place tin_full. the same applies for the places (tout_empty and tout_full) describing the state of the output places of manufacturing lines. figure 2: the cp-net model of the faultless operation of the manufacturing system figure 1: the manufacturing system 20 the transfer processes are disintegrated into three steps: to transitions referring to the (i) start and (ii) end of the transfer and to a place representing the (ii) transfer itself. transitions transfer#_start correspond to the start of transfer processes from in, if # = 1, from tout_full if # = 2 or 3. the places transfer# represent the transfer process 1, 2 or 3. the transitions transfer#_end refer to completing of transfer process to the input place of a line (# = 1), to product container (# = 2) or to the input place to another manufacturing line (# = 3). the place manuf_line refers to two manufacturing lines and the colour of token shows the line being processed. assume that only a single fault can occur in the system during manufacturing: the identification label of the piece can get damaged therefore it cannot be identified. workpieces with damaged label get into a separate container represented by place out_fault. the repairing of the label is not handled in this example. the modified part of the petri net model can be seen in fig.3, where the occurring of fault is taken into account. the occurrence of the fault is forced by a check function built into arc inscriptions in the petri net model randomly. this check function returns with a fault in predefined probability. this probability of the can be set in the definition part of the net and different fault probability values can be assigned to the two manufacturing lines. by comparing figs.2 and 3, it can be stated that a new place out_fault appears as a consequence of fault modelling and integration and the arc expression functions of arcs starting from transition manuf_line are extended with the fault checking. for realistic investigation of a technological system the timed version of the cp-net model is used as a case study. a time point is assigned to the transitions. the transition generator does not belong to the technological system closely, so it fires under zero time, i.e. instantaneously. different time units are assigned to the other transitions. these time values appear as transition inscriptions ‘@+i’$ (where$ i is an integer number defining the amount of time in seconds) on the net as it can be seen in the fig. 3. during the simulation investigations different time values have been applied in order to check the possibility of a deadlock. preliminary analysis by simulation as a first step, simulation is applied for the investigation of the developed petri net model of the manufacturing system. these were carried out assuming both faultless system operation and when fault can occur during the manufacturing. both non-timed and timed operational modes were considered. the short description of the simulation is as follows. the simulation starts with the generation of tokens representing workpieces. the number of these tokens i.e. the number of workpieces to be processed can be modified in the arc expression function belonging to the transition generator. the type of processes to be performed i.e. the label referring to the manufacturing line(s) of the tokens can be set in the definition part of the cp-net. as a result, the colour of generated tokens refers to the identifier and to the process(es) to be carried out. because of the highest priority of transition generator the transition transfer1_start can only fire after the prescribed number of token appears at the place in. as mentioned above, the transition transfer1_end refers to the completion of the transfer of the workpiece to the input place of a manufacturing line. as a next step, the firing of transition manuf_line corresponds to the completion of manufacturing process. the only fault in the system can occur during this process. if it happens then the token gets into the place out_fault, which represents the fault container. if the fault does not occur then the system checks whether the manufacturing process is over or the workpiece has to be also processed on the other line. in the first case the robot puts it to the place out representing the product container, while in other case it transfers the token representing the piece into the input place of another line. the modelling of the other two transfer processes (transfer of a workpiece from the output place of a manufacturing line either to the product container or to the input place of the other line) is similar to the transfer from place in to place tin_full. if the appropriate input place and the robot are free, another transfer process can start. the primary goal of the simulation is to check the correct operation of the model. another aim is the investigation of possible deadlock situations. in case of deadlock, the process stops without completing all the prescribed technological actions. it can happen in case of timed simulation of our investigated system and it refers to the wrong determination of the timing of actions. figure 3: the petri net model after integration of fault 21 simulation cannot ensure the thorough investigation of the modelled system, but it complements well the further analysis. for the detailed investigations we applied the analysis of occurrence graph. analysis based on the occurrence graph the thorough analysis of the behavioural properties of a cp-net can be performed using its occurrence graph. the concept of the occurrence graph was introduced above. the cpntools generates automatically the occurrence graph, but the check functions used for the fault generation have to be removed from the arc expressions otherwise the occurrence graph is generated only for the normal mode or for the faulty mode. for the illustration of generation and analysis of the occurrence graph let us assume that there are two workpieces to be processed, one of them has to go through manufacturing line 2, while the other has to go first through manufacturing line 1 then through line 2. let the operation of the system be faultless and let the firing of all transition be instantaneous, i.e. the net is non-timed. the resulted occurrence graph can be seen in fig.4. the explanation of numbers in the occurrence graph can be seen in fig.5. the frames in the upper part of boxes are the identifiers of system states. the expression x:y in lower part shows the number of preceding and succeeding states. the token distribution belonging to a node can be obtained by selecting the triangle in left low corner. the opening window contains the name of places and the number and colour of tokens. all the branches on the graph are explained by technological reasons, as there is no built in rule for the robot to start the transfer with any particular workpiece. the graph has only one terminal node (highlighted by green) and it refers to the normal termination of the process i.e. all the prescribed manufacturing processes terminated properly. now we can repeat the simulation with the same initial condition relating to workpieces but assuming that faults can occur during manufacturing process. the resulted occurrence graph can be seen in fig.6. figure 4: the occurrence graph no fault, no timing figure 6: the occurrence graph with fault, no timing figure 5: key for the occurrence graph 22 it can be stated that the occurrence graph has become larger and the number of terminal nodes has increased due the effect of the possible faults. the reason of branches on the graph can be either technological (at the nodes 3, 9, 28, 51 and 54) or due to the fault. only one of the terminal nodes refers to the normal termination of the process (highlighted by green, node 62), the others belong to the faulty cases (highlighted by red, nodes 22, 37, 43, 56 and 57). in case of faulty operation the identification tag of at least one workpiece get damaged during the manufacturing process. next we repeat the simulation again but adding the timing information to the net and assuming faultless operation. let the time duration of transfer processes be equal to unit time, and the time of manufacturing processes is equal to 5 time units. the resulted occurrence graph can be seen in fig.7. the resulted occurrence graph is a tree and its two terminal nodes (nodes 28 and 29) differ only in time stamp of the tokens (the time stamp can be seen only in cpntools with a detailed label for each node). comparing this graph with the occurrence graph in fig.4, it can be stated that the number of parallel branches is less and they have different terminal states. adding timing information to the model reduces the number of the possible different technological variants. as the fourth case, let the simulation be performed with both timing and faults. the resulted occurrence graph (see fig.8) is a tree again, the number of nodes is almost the same but the number of terminal nodes has doubled comparing to the occurrence graph in fig.6. it can be stated based on figs.4 and 6–8 that the occurrence graph is relatively simple in case of small number of workpieces and the analysis of nodes can be done manually. thus, it is easily to find the terminal node or nodes referring to normal, faultless termination of the process, and those terminal nodes where the manufacturing of one piece or of both pieces ends with fault. however, the size of the occurrence graph grows figure 8: the occurrence graph with fault and timing figure 9: the node numbers in occurrence graph figure 7: the occurrence graph no fault, with timing 23 exponentially if the number of pieces becomes larger, as it can be seen in the left part of fig.9 assuming faultless or faulty operational mode, and non-timed or timed net. in case of large number of simpler workpieces when the identification is not necessary for each item, the identification tag can be omitted from the colour of the token. assuming this situation all the simulation investigations (with and without fault, with and without timing) is repeated. the size of the resulted occurrence graphs is less than an order of magnitude simpler compared to the equivalent case with identifier as it can be seen in the right part of fig.9. since the workpieces have to be processed on the same manufacturing line, they have the same colour, thus they are indistinguishable. since the robot selects among workpieces having the same colour, there will be no technological branches on the occurrence graph. this results in a much simpler occurrence graph especially when there are large number of workpieces and the processes to be performed is one or two kind of sorts. as an example, let us investigate the structure of occurrence graphs in case when there is no timing in the system, the token colour contains the identification tag and both faultless and faulty operational mode is assumed. according to data in table 1, the size of the occurrence graph depends on the number of workpieces, the number of manufacturing procedures to be processed, and the presence of fault. if fault can occur during the manufacturing process both the number of nodes and the arcs increases dramatically. there are several terminal nodes, too, but only one refers to normal termination of manufacturing processes the others belong to different faulty situations. the labelling of workpieces has also a significant effect on the complexity of the occurrence graph. if there are one or more workpieces, which should be processed on both manufacturing lines then the number of nodes and arcs is doubled as it can be seen in the corresponding rows in table 1. the results of an investigation with timing information can be seen in table 2. if the number of workpieces is less than four or the workpieces have to be processed on only one manufacturing line, then the size of the occurrence graph depends on the number of workpieces and the presence of fault. on the other hand if there are at least four workpieces and at least two of them have to be processed on both manufacturing lines, but in reverse order then a deadlock situation can occur. a further condition of a deadlock that the manufacturing time should be longer than the transfer time but it is true in general. in case of a deadlock, the process stops because the precondition of transfer processes cannot be fulfilled. there are workpieces on input and output places of both manufacturing lines and therefore no further steps are enabled. if all the workpieces have to be processed on both manufacturing lines and there is no fault then all of terminal nodes refer to a deadlock as it can be seen in the rows marked by a footnote in the table 2. the identification tag can be omitted from the colour of token in certain cases. if the number of workpieces is small and they have to be processed in different ways then there is a significant change in the occurrence graph. on the other hand in case of large number of workpieces, the structure of occurrence graph becomes much simpler if the identification tag is removed from the colour. analysis of the occurrence graph using the oganalyzer as mentioned above, cpntools cannot use the information about the probability of faults at the generation of occurrence graph. however, assigning this value to the appropriate edges, the probability of each node of the occurrence graph, i.e. of each system state can be determined. for this purpose, software called table 1: comparing the structure of occurrence graphs – no timing no. of workpieces label (identifier, manufacturing information) faultless operational mode faulty operational mode nodes arcs tna nodes arcs tna 1 (1,m1) 7 6 1 8 7 2 1 (1,m12) 10 9 1 12 11 3 2 (1,m1)++(2,m2) 29 32 1 42 50 4 2 (1,m1)++(2,m12) 37 40 1 60 70 6 2 (1,m2)++(2,m12) 39 41 1 62 72 6 2 (1,m12)++(2,m21) 42 44 1 82 95 9 3 (1,m1)++(2,m2)++(3,m12) 145 173 1 306 409 12 3 (1,m2)++(2,m12)++(3,m21) 165 189 1 414 536 18 3 (1,m1)++(2,m1)++(3,m1) 107 123 1 210 273 8 4 (1,m1)++(2,m2)++(3,m12)++(4,m21) 631 772 1 2063 2900 36 4 (1,m1)++(2,m1)++(3,m1)++(4,m1) 340 404 1 949 1300 16 5 (1,m2)++(2,m12)++(3,m21)++(4,m1)++(5,m2) 2208 2797 1 9813 14420 72 5 (1,m21)++(2,m12)++(3,m21)++(4,m12)++(5,m21) 3259 3839 1 23709 32939 243 5 (1,m2)++(2,m1)++(3,m2)++(4,m1)++(5,m2) 1621 2165 1 5252 8051 32 6 (1,m2)++(2,m12)++(3,m21)++(4,m1)++(5,m2)++(6,m12) 8698 10980 1 62751 93323 216 6 (1,m21)++(2,m12)++(3,m21)++(4,m12)++(5,m21)++(6,m12) 12184 14562 1 146992 208602 729 6 (1,m2)++(2,m1)++(3,m2)++(4,m1)++(5,m2)++(6,m1) 5638 7686 1 21630 38886 64 a terminal nodes 24 oganalyzer has been developed. we assumed that the occurrence graph belonging to a given initial state of a cp-net model is finite and acyclic. the occurrence graphs of petri nets modelling manufacturing systems fulfil this assumption in general. let the probability of faults be known from technological consideration and let the first step of the analysis be the assignment of the arc weights to the edges of occurrence graph as follows. 1. if a node on the occurrence graph has only one outgoing arc, then the next state follows unambiguously, thus the arc weight is equal to 1. 2. if there is more than one outgoing arcs from a given node then it means that different states can follow from it. these states come into existence with different probabilities depending on whether this branch has technological or fault related reason. a. if there is no fault in the system then every branch has a technological reason, because there is no built-in priority rule for the robot to the selection among the workpieces. it means that every selection that is every arc has the same probability so all of the arcs starting form this node have to get the same arc weight, which is equal to the reciprocal value of the number of outgoing arcs. b. the introduction of the fault into the model causes the appearance of another type of branching in the occurrence graph. let us assume that only one type of fault can occur in a given system state. it results in 2 new system states: one for the normal operation and one for the faulty mode. let the probability of fault be equal to pf. then the weight of arc leading to faulty mode is equal to the probability of the fault while the arc leading to the normal operational mode gets the value 1-pf. assigning these arc weights to the edges of the occurrence graph the probability of a given state on the graph can be determined in the following way if the faults occurring one after the other in the system are independent: 1. if the graph is a tree or only one route leads to the given node then the probability of the state representing by this node is equal to the product of arc weights along the route leading from the node representing the initial state to the given node. 2. if there are more than one route leading to the given node from the initial node then the probability value of each route has to be determined with the production of arc weights along the route as in the first step, then to sum these resulted values. 3. if the faults are not independent from each other, then the probability of nodes can be calculated in a similar way but using conditional probability values. as described above, this determination method and the operation of oganalyzer has been illustrated using the example of two workpieces to be processed and one of them has to go through manufacturing line 2, while the other has to go first through line 1 then trough line 2. faults can occur during the manufacturing process and let the fault probability be equal to 0.3 in case of line 1 and 0.1 in case of line 2. as before, we consider the timed case, when the transfer transitions have the same transition time of 1 time unit, while the manufacturing time is equal to 5 for both lines. after the simulation cpntools generates the occurrence graph, the structure of, which is the input of oganalyzer. as a first step oganalyzer reads the structure of the generated occurrence graph from the data file generated by cpntools and visualizes it in its own window as it is shown in fig.10. the user can get the token distribution belonging to nodes as it is shown at node 1 in fig.10. the next step is the identification of branches. the software can distinguish between the two different types of branches on the occurrence graph (that are technological and fault caused branches). for this the user has to define the fault colour for the appropriate branches in a separate window. table 2: comparing the structure of occurrence graphs – with timing no. of workpieces label (identifier, manufacturing information) faultless operational mode faulty operational mode nodes arcs tn/da nodes arcs tn/da 1 (1,m1) 7 6 1/0 8 7 2/0 1 (1,m12) 10 9 1/0 12 11 3/0 2 (1,m1)++(2,m2) 23 22 2/0 41 40 8/0 2 (1,m1)++(2,m12) 29 28 2/0 59 58 12/0 2 (1,m2)++(2,m12) 29 28 2/0 58 57 12/0 2 (1,m12)++(2,m21) 35 34 2/0 87 86 18/0 3 (1,m1)++(2,m2)++(3,m12) 73 74 4/0 264 263 48/0 3 (1,m2)++(2,m12)++(3,m21) 86 85 4/0 392 391 72/0 3 (1,m1)++(2,m1)++(3,m1) 85 84 6/0 262 261 48/0 4 (1,m1)++(2,m2)++(3,m12)++(4,m21) 173 172 8/2 1473 1472 258/2 4 (1,m1)++(2,m1)++(3,m1)++(4,m1) 365 364 24/0 2121 2120 384/0 5 (1,m2)++(2,m12)++(3,m21)++(4,m1)++(5,m2) 574 573 24/4 9320 9375 1582/8 5b (1,m21)++(2,m12)++(3,m21)++(4,m12)++(5,m21) 154 153 24/24 12076 12075 2196/60 5 (1,m2)++(2,m1)++(3,m2)++(4,m1)++(5,m2) 514 513 24/0 5152 5247 780/0 6 (1,m2)++(2,m12)++(3,m21)++(4,m1)++(5,m2)++(6,m12) 1725 1732 80/40 71817 72336 12300/116 6b (1,m21)++(2,m12)++(3,m21)++(4,m12)++(5,m21)++(6,m12) 325 324 72/72 45541 45540 8280/432 6 (1,m2)++(2,m1)++(3,m2)++(4,m1)++(5,m2)++(6,m1) 2341 2412 72/0 39349 41076 5760/0 a terminal nodes/deadlocks, b labels where all terminal nodes refer to deadlocks 25 it is assumed that the technological branches have the same probability, so oganalyzer assigns the reciprocal of the number of branches to these edges. the fault caused branches are collected into a table and the user has to define the probability of faulty and normal modes as it can be seen in fig.11. the occurrence graph with arc weights depicted in oganalyzer can be seen in fig.12. the black numbers attached to the arcs are the arc weights. values equal to 1 were not depicted. using these probability values the oganalyzer calculates automatically the probability of a node by multiplying arc weights along the path leading from the node representing the initial state to that node. if two or more paths lead to the node then the probability values belonging to these paths are summed. the calculated probability values can be also seen in fig.12 as red numbers assigned to nodes. in this manner the probability of all system states in the investigated system can be calculated. for example, the probability of faultless completing of both workpieces is 0.28 + 0.28 = 0.56, which is equal to the sum of the probabilities belonging to the nodes 55 and 57. the probability of that case when the first workpiece is manufactured without fault, but the label of the other piece gets damaged during the second manufacturing process is 0.03 + 0.03 = 0.06 (sum of the probabilities belonging to the nodes 46 and 48). in case of timed nets the occurrence graph is often a tree and the same token distribution belongs to different nodes because of the different time stamp. for the determination of probability of a given system state, the probability values belonging to different nodes have to be summed up. figure 11: defining the probabilities values of faults figure 12: the occurrence graph with arc weights and probability values figure 10: the occurrence graph of the example in the window of oganalyzer 26 conclusion a novel occurrence graph investigation procedure for discrete event systems described by petri nets was proposed in this paper for model-based diagnostic purposes that utilize the knowledge of the occurrence probability of faults. the model of the investigated system was defined in timed coloured petri net form. the colours of tokens representing the workpieces were used to distinguish them and to assign a label of the processes to be carried out. the arc inscriptions and built-in probability functions were used for the fault modelling and integration. the operation of the system was investigated via simulation both in timed and non-timed cases and in faultless and possible fault operational modes with given number pieces and prescribed manufacturing lines. for the behavioural analysis of the model the occurrence graph method was used. a special software module, called oganalyzer has been developed for the handling of the probabilities on the occurrence graph and for calculating the occurrence probability of system states. acknowledgements this research is partially supported by the hungarian research fund through grant no. k-83440. we also acknowledge the financial support of the hungarian state and the european union under the tamop4.2.2.a11/1/ konv-2012-0072. references [1] cassandras c.g., lafortune s.: introduction to discrete event systems, kluwer academic publishers, 1999 [2] gerzson m., márczi b., leitold a.: diagnosis of technological systems based on their coloured petri net model, argesim report no. s38 (eds. troch i., breitenecker f.) 2012, p. 358/1–6 [3] jensen k.: coloured petri nets: basic concepts, analysis methods and practical use, springerverlag, 1997 [4] cpn group, university of aarhus, denmark: cpntools 2.2.0 http://wiki.daimi.au.dk/cpntools/ (last accessed: may 25, 2014) [5] fanti m.p., seatzu c.: fault diagnosis and identification of discrete event systems using petri nets, proc. 9th international workshop on discrete event systems, wodes, 2008, 432–435 [6] jensen k., kristensen l.m., wells l.: coloured petri nets and cpn tools for modelling and validation of concurrent systems, int. j. of software tools for technology transfer, 2007, 9(3–4), 213–254 [7] murata t.: petri nets: properties, analysis and applications, proceedings of the ieee, 1989, 77(4), 541–580 hungarian journal of industry and chemistry veszprém vol. 41(1) pp. 27–34 (2013) immediate event-aware model and algorithm of a general scheduler tibor dulai1!, ágnes werner-stark1, and katalin m. hangos1,2 1 department of electrical engineering and information systems, university of pannonia, egyetem str. 10, veszprém, h-8200, hungary 2 process control research group, computer and automation research institute, kende u. 13-17, budapest, h-1111 hungary !e-mail: dulai.tibor@virt.uni-pannon.hu a stochastic scheduling problem is investigated in this work that considers workpieces to be manufactured according to individual recipes containing manufacturing steps performed by workstations as resources. unexpected stochastic breakdown of a workstation or the faulty termination of a recipe, when a manufacturing failure renders the workpiece out of specifications, forms the set of immediate events. a model and an algorithm are proposed as the basis of a scheduler, which takes into account the possible immediate events, estimates their probability and suggests resource allocations which provide the best overall work-flow even when an immediate event happens. this model includes the possibility of handling alternative resources that can substitute each other in case of an immediate event, like sudden technical failure of a resource. immediate events are not exactly predictable; however, based on previous experiences, their probabilities can be estimated. our model uses the properties of the resources (including how they can substitute other types of resources) and the required sequence of them during the workflow (i.e. the recipes). the proposed scheduling algorithm constructs a solution workflow that reacts in the best way (in average) even for an unexpected event. the proposed model and scheduling algorithm is illustrated on two industrial case studies. keywords: scheduling, resource allocation, alternative resources, immediate event-awareness introduction scheduling is an important and widely used topic of operations research. besides of its theoretical importance, industries can also benefit from optimal schedules and resource allocation. several different algorithms were established for organizing process elements on the time scale [1, 2], related to for example computer networks [3], business processes [4, 5] or industrial processes [6]. the results are usually represented on a gantt chart. there are also differences between these algorithms related to their application times. some of them are applied offline before the scheduled processes starts, others are applied real-time. real time scheduling techniques, and a special adaptive real-time scheduler is introduced in ref. [10]. for improving their results, there are cases when the methods use historical data during the creation of the schedule [11]. the common scheduling methods usually handle the resources individually and do not take into account the relationships, e.g. the similar functionality between them. only few publications investigate the cooperation possibilities that are enabled by the similar functionality of resources in scheduling [7]. in this paper a scheduling method is proposed, where resources may substitute each other and immediate failures of resources may happen. after we introduce the problem and its main building blocks, we present our model and the algorithm developed. its operation and properties are demonstrated on a simple and a more complex problem as case studies. problem specification a general scheduler intends to determine the placement of activities of resources on the time scale. in an advanced case one might consider additional features given in the problem’s model – like substitution possibility of the resources – which help to redefine the classic scheduling problem to be usable in different reallife applications. this substitution may help in achieving a certain fault tolerance property in such a way that a technical failure causes the least possible negative effect. the basic aspects and sub-tasks related to this extended scheduling problem are collected in this section. 28 cooperation in some cases more than one resource is able to carry out a particular activity (usually with different productivity). it means that when the appropriate resource is busy, there can be another resource that is able to take over a particular task if required. we shall term this case a cooperative situation when substitution is possible, in other words, the resources can cooperate with each other. taking the cooperation aspect into account during scheduling the performance may increase [8]. we introduced the so called substitution vector as an element of our model to handle substitution related sub-problems. any scheduler [1, 2] can be applied as a basis of the cooperative extension, which inputs the sequence of resources as input processes and has to arrange them on the time scale taking into account the availability and temporal constraints. all the improvements are done on this basic schedule. improving fault tolerance when a schedule is ready and the workflow starts, an immediate event (e.g. a technical failure of a resource) in a process may influence other processes, too, in a negative way [9]. if the effects of that event are calculated in the schedule, then the solution with the best answer to immediate events can be selected from the set of solutions with the same performance, and the faults’ negative impact on the schedule decreases. our model deals also with this aspect. the model for the above mentioned problem set, we created an universal model and an algorithm to carry out the scheduling. the work intends to be the basis of several different tasks with the goal that the operation time should be minimal. in this section we introduce our model and the scheduler that works on this model. main parameters, notations and functions the model and its parameters are designed in such a way that it can be applied for different kinds of scheduling problems (e.g. scheduling of industrial production processes, test processes, scheduling and managing the resources of electrical networks, etc.). for this reason we collected the necessary parameters that make possible the development of a general framework, which uses different kinds of resources in different processes. it is able to handle different needs. in this sub-section we introduce the main parameters and functions we use in our work. these are as follows: process = {proc1, …, procj}, (1) stands for the set of processes; p = {p1, …, pl}, (2) stands for the set of product types; r = {r1, …, rm}, (3) stands for the set of resources; o(ri) = {oi1, …, oik}, (4) stands for the set of the operation modes of resource i; a = {a1, …, an, pause(t)}, (5) stands for the set of basic activities, where pause(t) is an empty activity with length of t hour; ra : r × a → {0, 1}, (6) defines a function for determining whether a resource is able to perform an activity; rap: r × a × p → {0, 1}, (7) defines a function for determining whether a special activity of a resource can be applied for a product type; t: r × a × p × o → n, (8) provides the suggested operation time of a resource in a given operation mode performing a given activity on a given product type; q: r × a × p × o → [0,100], (9) provides capacity information: how many percent of a resource capacity is occupied by one piece of a given product type in a given operation mode of a resource while performing a given activity; e: r × a × p × o → [0,100], (10) provides the probability of resource failure during performing a given activity on a given product type in a given operation mode; s: r × a × p × o → {0, 1}, (11) results in a binary decision: whether a resource activity in a given operation mode on a given product type can be suspended without restarting it from its beginning; rreq: r × a × p × o × datetime → p(r, n) (12) (power set on pairs of a resource and a natural number), provides the additional resource need of a resource’s given activity on a given product type in a given operation mode in a given hour subst(ri,aj, pk,oil ) = [ hi1 ... him ] , (13) 29 is the substitution vector, where m is the number of resources, hin is a natural numbers for all 1 ≤ n ≤ m, ri is the ith resource, aj is a basic activity, pk is a product type, oil is an operation mode of resource i, hin denotes how many percent of the productivity of resource i is needed in a given activity in a given operation mode on a given product type to substitute totally resource n supposing unchained operation time. the substitution vector is calculated based on the function ra and other functions (e.g. function t in case of time-based optimization). map: r x datetime → n, (14) provides the information on accessibility of resources: how many resource of a given type is accessible in a given hour; f: r → n, (15) provides the expected number of hours how long a given resource is unavailable in case of its failure; tstart: process → datetime, (16) shows the start time of a process; tmaxend: process → datetime, (17) shows the maximum finish time of a process; prev: process × a × n+ → {a, ø}, (18) provides the prior basic activity of the nth occurrence of a given basic activity in a given process; next: process × a × n+ → {a, ø}, (19) provides the following basic activity of the nth occurrence of a given basic activity in a given process; maxdelay: process × a × n+ → n, (20) provides the maximal duration of time out, which is tolerated by the nth occurrence of a given basic activity in a given process; dur: process × a × n+ → q, (21) provides the time scale, which number the default operation time of the of the nth occurrence of a given basic activity in a given process has to be multiplied with, for getting the real operation time of the activity. the proposed algorithm our algorithm was created to take into account the cooperation possibilities of the resources and to have failure-aware behaviour during scheduling. the algorithm can be separated into three main blocks, as it is shown in fig.1. in the first phase, we associate resources for each basic activity of the processes. at the start, processes are described only as a sequence of basic activities. we have to turn it into the “language” of resources. in this task, we use the function ra for determining, which resources are able to carry out the desired basic activity. furthermore, we deal with the minimization of the operation time; we select the resource, which has the operation mode with the minimal operation time, i.e. ri with min(t(ri, a, p, oil )), ∀oil ∈o(ri ), ra(ri,a) =1 (22) is selected. the first step of our algorithm results in a sequence of resources for each process. the second phase of the algorithm is performed by the main scheduler task, taking into account the alternative resources. the first task in this phase is to select the “basic” process, which has the least robustness. we do it by selecting proci with min(tmaxend (proci )− tstart (proci )−tdur) , (23) where tdur is the sum of the durations of all of the basic activities of proci. after the determination of the basic process, the algorithm enters a loop, in which it selects a process from the set of the remaining processes and attempts to place all the basic activities of the selected process element-by-element on the time scale. during this operation the algorithm handles the substitutability of the resources. the insertion of a basic activity starts at the initial activity of the process and each activity is inserted into the earliest possible time point. this assumption is a fundamental point in the method. the insertion of an activity at its earliest time may have two possible outcomes: • successful insertion • unsuccessful insertion, which means that there is not enough amount of the resource to serve the activity which starts at its earliest time point. we call this case a collision. in case of a collision, the algorithm attempts to find an alternative resource using the substitution vector, figure 1: the basic parts of our algorithm 30 which has enough leftover capacity to carry out the activity at the desired earliest time point. if this is not possible, because there is not enough resource at the desired time, the algorithm tries to shift one of the collided activities to solve the problem. the detailed mechanism of the activity-insertion task is illustrated in fig.2. when the activity-shift resulted in no success, the algorithm attempts to repeat the same process with other alternative resources. if there is no success, the whole process will be left from the final solution; otherwise the initial scheduling is ready. in the final, third phase of our algorithm the schedule is tried to be modified in such a way that it should have a higher fault tolerance than the original one. this phase assumes that fault happens at the processing of special activities of the processes and calculates its effect into the schedule. we do not want to hurt the time constraints of the original problem that’s why one of the main parameters of this phase are the maximum finish time values (tmaxend) of the processes. we process the processes starting from their end in the following way: let wp be the process list we work on. at the start wp = process. for each element of wp, we create a pointer, which points at the penultimate activity of the process. the activities pointed by the pointers (let their set be wa) are candidates for assuming them to have fault. starting from this initial state, this phase of the algorithm works as follows: 1. select the aj activity from wa with the highest error probability: max(e(ri, a j, pk, oil )), a j ∈wa (24) 2. if the start of the basic activity which follows ai can be shifted by ai’s duration plus by f(r(ai)), where r(ai) is the resource which carries out ai without causing collision and without exceeding tmaxend(prock), where prock is the process which belongs ai to, then (i) the shift will be done, and (ii) the basic activity, which precedes ai in the process will be added to wa and ai will be taken out from there. it means that the pointer of the process will be set one step backward. else, ai is taken out from wa and its process is taken out from wp, too. it means that the activities of the process are not modified any more. this phase of the algorithm modifies the placement of the basic activities of the processes on the time scale in such a way that there is no need to change the scheduled activities in case of failures with high probability. it means that these failures will not cause delay and exceed of the maximum finish time. case studies in this section, the previously presented algorithm is applied to two hypothetical manufacturing examples: we show how it takes into account the substitutability of the resources and how to make the schedule ready for possible technical failures. a simple problem and its solution let there be four processes with the same start and maximum finish time (tstart = 0 and tmaxend = 65 are identical in each cases). the sequences of the process activities can be seen in fig.3. in this example, we work only with one product type (p), and we intend to minimize the maximum operation time. let’s suppose that in this example there are two pieces of resource r1, while only 1 piece of the others, and ra(ri, aj) = 1 only if i=j, (25) excepting two cases: ra(r2, a3) = 1 (26) and ra(r3, a2) = 1, (27) as well. moreover, the substitution vector of r2 is: subst(r2,a3,p,o) = [ 0 100 125 0 ] , (28a) while the substitution vector of r3 is: subst(r3,a2,p,o) = [ 0 200 100 0 ] , (28b) figure 3: activity sequence of the example processes figure 2: activity insertion onto the time scale 31 which means that r2 can substitute r3, and r3 can substitute r2. however, the substitution results in 125 percent or 200 percent more time, respectively. another assumption is when only r1 has two operation modes: in one of its operation mode its operation time at a1 activity on product p can be reduced with 10%. as our goal is to minimize the necessary time, we will use this operation mode of r1 in each case. moreover, assume that all the resources are unavailable for 2 time units in case of failure. based on this information, the first step of our algorithm creates the sequence of the resources for each process. this sequence completed with the durations of each activity after user-based modification of the default operation times is illustrated in fig. 4. the second phase of the algorithm determines the basic process; in our case it is proc3 with its 63 unit length. its representation on the time scale is shown in fig.5. after this selection a loop is started, choosing the less robust process from the remaining set. the next process is proc1. its first activity can be placed onto the time scale without collision. the placement of the second activity collides with the basic process’s first activity. the first reaction of the algorithm is to search for alternative resource. resource r2 can substitute r3 without collision; however in this case the operation time will increase from 4 to 5 units. the third activity of proc1 can be inserted, since there are two pieces of resource r1. the fourth activity collides again; however substitution solves this problem, and the problem-free placement of the final activity of the process can be seen in fig.6. the third process to handle is proc4. its first activity can be placed easily; however, the second activity has collision and there is no possibility to substitute it without collision either. this case requires the shift of the activity as illustrated by fig.2. the activity that shifts the later start is reason for a pause was defined in proc4. the third and fourth activities have to be also shifted. the difference between the two cases is the resource that is able to substitute gets free earlier. this is why the fourth activity will be carried out by r2 instead of r1, started after a short pause. after the placement of the process’s final activity and all the activities of proc2,, this provided the schedule with some activities of the previously placed processes shifted necessarily twice, as illustrated in fig.7. the final phase of the algorithm is to make the schedule to be fault-aware. as tmaxend = 65 and the length of proc3 is 64, we will not modify this process. similarly, we will not modify proc1 and proc4 either. only proc2 lets the algorithm to prepare it to be faultaware, and the modification can be applied to all of its figure 5: placement of the basic process onto the time scale figure 6: the schedule after handling proc1 figure 7: the schedule after the second phase of the algorithm figure 8: the final schedule figure 4: sequence of the initial resource allocation 32 activities. the result can be seen in fig.8. a more complex problem and its solution in this example we deal with six processes. in contrast with the previous example, they differ in their start and maximum finish time as shown in table 1, where the values are represented in time units. the activitysequences of the processes are illustrated in fig.9. in the example form fig.9, eight different activities are applied. the next question is which resources are able to carry out these activities. in this example, there are six kinds of resources, six resource types (r1 r6). suppose that two pieces of resource type 2, 3 and 5 exist, while all the other resource types have only one representative. the substitution vectors of the resources are as follows: subst(r1,a2,p,o) = [ 100 150 0 0 0 0 ] , (29a) subst(r2,a1,p,o) = 150 100 0 0 0 0! " # $ , (29b) subst(r3,a5,p,o) = 0 0 100 0 300 0! " # $ , (29c) subst(r5,a3,p,o) = 0 0 120 0 100 0! " # $ , (29d) subst(r4,a1,p,o) = 166 0 0 100 0 0! " # $ . (29e) it means that r1 and r2 resources may substitute each other, r3 and r5 resources are able to substitute each other and r4 resource is capable to substitute r1 resource. other substitutions are not possible. these vectors show that ra(r2, a1) = 1, (30) ra(r1, a2) = 1, (31) ra(r3, a5) = 1, (32) ra(r5, a3) = 1 and (33) ra(r4, a1) = 1. (34) moreover, we suppose that ra(ri, aj) = 1, if i = j; (35) ra(r2, a7) = 1 and (36) ra(r5, a8) = 1. (37) this means that a7 activity can be carried out by r2 resource, and a8 activity can be carried out only by r5 resource. in case of failure, the resources are unavailable as much as shown in table 2. we suppose that each resource works only in one operation mode and all of the resources have the same error probability. in the example we work only with one product type (p), and we intend to minimize the maximum operation time. applying the first step of our algorithm, we create the sequence of the resources for each process. this sequence completed with the durations of each activity after user-based modification of the default operation times as illustrated in fig.10. at this phase we apply the second step of our algorithm and determine the robustness of each processes. in the calculation, we use the following computation method, as we mentioned earlier: tmaxend (proci )− tstart (proci )−tdur (38) the values obtained are summarized in table 3. table 1: some properties of the processes of the second case study process start time, tstart max. finish time, tmaxend p1 0 30 p2 15 30 p3 7 30 p4 3 25 p5 0 23 p6 6 29 figure 9: the activities of the second example’s processes figure 10: resource-sequence of the example’s processes table 2: the effect of failure on the second example’s resources resource r1 r2 r3 r4 r5 r6 time of unavailability (f) [time unit] 2 1 3 2 2 1 33 table 3 indicates that the basic process is proc4, which is the least robust process. we place its activities onto the time scale as a chart illustrates this in fig.11. the black line represents the 0 time point and the red one signs the maximal finish time of the process. the second least robust process is proc3. the placement of its activities onto the time scale can be done easily, without any collision as shown in fig.12. the third least robust process is proc2. during its placement there is one collision: its second activity collides with proc4’s fifth activity. however, it doesn’t cause any problem, because there are two pieces of resource r2. the second resource of r2 resource type can carry out the activity in the originally planned time. the result is shown in fig.13. looking for the next least robust process, proc6 is the next. its fourth activity collides, thus the second piece of r3 resource type has to be used for carrying it out. moreover, its final activity also collides. unfortunately, there is only one piece of r1 resource type. however, r2 resource type can substitute an r1 resource. the problem is that both r2 resources are occupied at the desired time. there is another resource type, r4, which is able to substitute an r1 resource with a bit more necessary time than r2. as r4 is free at the desired time, it will take over the task. the time it requires for its task is 1.66 times more than an original r1-type resource would need for that. fig.14 illustrates the results. the second most robust process is proc5. during the placement of its activities onto the time scale, we find that the second activity collides with proc4’s second activity. fortunately, there is a second piece of r3 resource type which can be used freely for the desired time interval. it solves the problem and results a chart as seen in fig.15. at last, three problematic cases happen during process 1: the collision of the third and fourth activities can be solved by the second piece of the desired resource types; however, in case of the final activity only time shift can solve the collision, because there is only one piece of r4 resource type and it can not be substituted by any other resource. the result is shown in fig.16. after placing all activities onto the time scale and solving all collisions, only the fault-tolerance-related improvement need to be done, as the final step of our algorithm. this phase intends to shift the activities of the processes in time, starting from their end by the duration of their preceding activity plus its f value. because of the maximal finish time constraint, proc4 and proc3 (the first two processes on fig.16) cannot be modified. if we look at fig.16’s third process, its last activity requires f(r1) = 2 time units plus its normal operation time in case of failure. if we take into account the maximal finish time of the process, its place cannot be modified. this is the case for the fourth process, as well. the fifth process in in fig.16 ends with r3 resource. in case of a failure, it requires 8 time units until it reaches the maximal finish time of the process. taking this into account, only 3 time units remain, figure 11: placement of the second example’s basic process onto the time scale (proc4) figure 12: placement of the second example’s second process onto the time scale (proc3) figure 13: placement of the 2nd example’s third process onto the time scale (proc2) figure 14: placement of the second example’s fourth process figure 15: placement of the second example’s fifth process onto the time scale (proc5) figure 16: placement of all processes of the second example onto the time scale (proc1) table 3: the robustness values of the example’s processes process proc1 proc2 proc3 proc4 proc5 proc6 robustness 16 4 2 0 11 8 34 which is not enough for the previous activity. that’s why we do not modify this process, either. the final activity of the last process, proc1 is carried out by an r4 resource. in case of a failure, it requires 4 extra time units. in order to avoid collision we shift this activity a bit more forward as shown in fig.17. as f(r2) = 1, and a2 activity requires 3 time units to be carried out by r2 resource, proc1’s fourth activity can also be shifted in time. its previous activity would require 6 time units after itself. its shift would result 1 extra time unit for previous activity, which is not enough for making it ready for tolerating fault. this hinders building in more fault tolerance. the final result of the algorithm is shown in fig.18, in which we have a schedule, which took into account the possible substitutions, the capabilities of the resources; moreover in some places, it tolerates faults of resources without the need of rescheduling. conclusion we presented a model and algorithm for creating schedules, which tolerate some resource-failures and utilize the substitutability possibilities of the resources. our goal was to establish a model, which can be the basis of applications in different segments of scheduling problems and makes it possible to generate schedules with the optimization criteria related to the operation time. we introduced an algorithm, which creates an initial schedule on the basis of the input processes and the substitutability of the resources. this can be improved with preparation for likely failures of resources. the operation of the algorithm was presented on two hypothetical case studies. acknowledgements this research was supported by the european union and hungary and co-financed by the european social fund through the project támop-4.2.2.c-11/1/konv-20120004 and tamop-4.2.2.a-11/1/konv-2012-0072, and in part by the hungarian research fund (otka) grant number k83440. support from the national research centre for development and market introduction of advanced information and communication technologies is also acknowledged. references [1] pinedo m.l.: scheduling: theory, algorithms, and systems, 4th ed., springer, new york, usa, 2012 [2] brucker p.: scheduling algorithms, 5th ed., springer, osnabrück, germany, 2007 [3] brahimi b., aubrun c., rondeau e.: modelling and simulation of scheduling policies implemented in ethernet switch by using coloured petri nets, proc. 11th ieee int. conf. emerging technologies and factory automation, prague, czech republic, 2006, 667–674 [4] barba i., valle c. del: a job-shop scheduling model of software development planning for constraint-based local search, int. journal of software engineering and its applications, 2010, 4(4), 1–16 [5] xu j., liu c., zhao x., yongcareon s.: business process scheduling with resource availability constraints, proc. otm’10, hersonissos, crete, greece, 2010, 1, 419–427 [6] sule d.r.: production planning and industrial scheduling: examples, case studies and applications, 2nd ed., crc press, ruston, la, usa, 2007 [7] murthy s., akkiraju r., rachlin j., wu f.: agent-based cooperative scheduling, proc. aaai workshop on constraints and agents, providence, ri, usa, 1997, 112–117 [8] dulai t., werner-stark á.: immediate eventaware routing based on cooperative agents, proc. factory automation, veszprém, hungary, 2012, 144–148 [9] palombarini j., martinez e.: smartgantt – an intelligent system for real time rescheduling based on relational reinforcement learning, expert systems with applications: an international journal, 2012, 38(11), 10251–10268 [10] nandanwar j., shrawankar u.: an adaptive real time task scheduler, ijcsi international journal of computer science issues, 2012, 9(6/1), 335–340 [11] gregg c., boyer m., hazelwood k., skadron k.: dynamic heterogeneous scheduling decisions using historical runtime data, proc. 2nd workshop on applications for multiand many-core processors, san jose, ca, 2011 figure 17: building fault tolerance into the last process of the second example figure 18: building fault tolerance into the last process of the second example hungarian journal of industry and chemistry veszprém vol. 41(1) pp. 35–40 (2013) estimation of parameters for an extremely low fuel consumption internal combustion engine-based megameter-iii vehicle istván pintér1! and mihály bagány2 1 department of informatics, kecskemét college, izsáki str 10, kecskemét, h-6000, hungary 2 department of natural sciences and engineering, kecskemét college, izsáki str 10, kecskemét, h-6000, hungary !e-mail: pinter.istvan@gamf.kefo.hu megameter-iii is a special vehicle designed and constructed for international competitions by our team. a crucial part of the vehicle is the internal combustion engine, which ought to have extremely low fuel consumption. the experiences of previous competitions confirmed that it is necessary to develop a professional telemetry system, which allows tracking and logging online important parameters of the engine and the vehicle. in this paper, we discuss results for estimating of several parameters of the engine (angular velocity, angular acceleration, the coulomb-morin external friction torque and the damping constant). in our work, injector-pulses and inductive sensor’s signals were monitored. keywords: internal combustion engine, extremely low fuel consumption, angular velocity, angular acceleration, external friction torque, damping constant introduction since 2010, the racing team at kecskemét college participates in international competitions of fuelefficient vehicles. the vehicles were named after 1 megameter being 1000 km. the first result with megameter-i in gasoline category was 1588 km l-1 (2010, lausitz, germany), and the best result of megameter-ii was 2661 km l-1 (2011, nokia, finland). megameter-iii achieved 2696 km l-1 (2012, rotterdam, nederland. the team-photo can be seen in fig.1). the latest model, the megameter-iv has exceeded the 3000 km/litre dream-limit (3082 km l-1; 2013, nokia, finland) [1]. during the development of the megameter series, it became clear that in order to improve the technical parameters of the vehicle it is necessary to establish a telemetry system suitable for measuring, displaying and logging the engine’s and vehicle’s parameters during the race. this paper presents our recent results in this work, which have already been utilized in developing and construction of the megameter-iv. the measurements were taken using the megameteriii engine, which has the following characteristics: • one cylinder, four-stroke, air-cooled • overhead controlled, overhead valve, intake manifold injection • bore/stroke: 31.5/45 mm • displacement volume: 45 cm3 • compression ratio: 14 • power: 700 w • torque: 2.2 n·m • specific fuel consumption 235 g kwh-1 there are different application areas and methods for estimation of engines’ angular velocity. these estimation procedures are based mainly on crankshaft’s rotation angle [2, 3, 4]. in the problem of model-based estimation of mechanical losses, the dependence of instantaneous angular velocity on angular position plays an important role [4]. a second-order splineinterpolation-based method was proposed in [2] for realtime measurement of angular velocity and angular acceleration. our telemetry system is related to this latter work, and our results proved to be useful in further developing our special vehicle. figure 1: student team photo with the megameter-iii vehicle (rotterdam, 2010, second place) 36 the physical model with its approximations and the parameter estimation in order to achieve ever decreasing fuel consumption it is necessary to uncover the sources of energy losses. for this purpose a suitable physical model of internal combustion engine (ice) is needed [5]. moreover, with an appropriate physical model in hand, one can design the measurement for estimating the parameters of the physical model. physical model for estimating the external friction torque and damping constant the instantaneous angular velocity of the crankshaft is changing even during only one crankshaft revolution. it is smaller on the compression stroke and greater in the midst of power stroke. the friction torque affecting the engine, averaged for two crankshaft revolutions depends on the instantaneous angular velocity. by expanding this function up to the second order we get eq.(1): −m ≈ m 0 + m1 ω1 ω + m 2 ω2 2 ω 2 (1) where the indexed quantities are constant and positive, and they have physical meanings as follows: m0 is the coulomb-morin external friction torque, which is independent of the relative speed of frictional surfaces (in this case the relative speed is the angular velocity); m1/ω1⋅ω defines the damping constant (the second term corresponds to torque resulting from newton’s internal friction’s force, it is proportional to the first power of angular velocity); m2/ω2 2⋅ω2 stands for the drag torque characterizing the turbulent flows in pipes; it is in proportion to the square of angular velocity and it is resulting from the flow resistance in the intake and exhausting channels, in the valve-cage and in the airpipe of the crankcase. our task is the estimation of the external torque from the measured data; therefore it is necessary to estimate the angular velocity. the basic equation of rotational motion is shown in eq.(2): −m = −θ dω dt (2) where after substitution of eq.(2) into eq.(1) we get m 0 + m1 ω1 ω + m 2 ω2 2 ω 2 = −θ dω dt (3) let’s assume that the initial value of the angular velocity is ω0. by separating the variables and integrating we get eq.(4): dω m 0 + m1 ω1 ω + m 2 ω2 2 ω 2ω0 ω ∫ = − dt θ0 t ∫ . (4) the result of the integration is shown in eq.(5). t = − 2θ 4ac− b2 atan 2cω + b 4ac− b2 # $ % & ' (+ + 2θ 4ac− b2 atan 2cω0 + b 4ac− b2 # $ % & ' ( , (5) where three new variables were introduced for more readability as shown in eq.(6). a =m 0 , b = m1 ω1 , c = m 2 ω2 2 2 . (6) by solving eq.(5) for ω one can get the final solution. however, instead of doing so, we analysed two approximate solutions of eq.(4). as we will see below, these approximate solutions fit real measurements well. in order to estimate the engine’s friction torque and damping constant long measurement duration (e.g. 20 s) is necessary. the relevant physical quantities can be estimated from the measured injector pulses. approximation 1: the friction torque is independent from angular velocity by assuming that the other two terms are negligible compared to external friction m0 the differential eq.(4) simplifies to: dω m 0ω0 ω ∫ ≈ − dt θ0 t ∫ , (7) and its solution is: ω =ω0 − m 0 θ t , (8) where ω0 is the value of angular velocity at the beginning of deceleration. the angular velocity of the engine’s crankshaft has to be measured as the function of time for parameter estimation. namely, after line-fitting to measured data the intercept and slope can be computed from relationship ω̂ = a− bt , so both the estimation of coulomb-morin external friction torque and the estimation of initial value of angular velocity can be determined: ω0 = a , m 0 = bθ . 37 approximation 2: the friction torque is independent from the squared value of angular velocity when the engine is running with wide open throttle, and the friction torque of pipe-flow losses is negligible comparing to external and internal losses, the differential equation to be solved is the following: dω m 0 + m1 ω1 ωω0 ω ∫ ≈ − dt θ0 t ∫ . (9) the solution of eq.(9) is: ω = ω1 m 0 m1 +ω0 ! " # $ % &e − t τ −ω1 m 0 m1 , (10) where τ = ω1θ/m1 is the time constant characterising the angular deceleration. by measuring the engine’s crankshaft’s angular velocity as the function of time, and after fitting a biased exponential-type curve we get the estimation cae bt −= −ω̂ , from which the estimates of physical quantities are the following: the external friction torque is: m0 = bcθ, the damping constant is: m1/ω1 = bθ, the initial value of angular velocity resulted from curve-fitting is: ω0 = a-c. estimation of the instantaneous torque and the running irregularity the instantaneous angular acceleration as the derivative of the instantaneous angular velocity is needed for estimation of the instantaneous torque. moreover, knowing the instantaneous angular velocity, another important parameter of the engine, the running irregularity can be determined. from the point of view of measurement, the estimation of instantaneous angular velocity requires the duration of two crankshaft revolutions (e.g. 100 ms). for measuring this, an inductive sensor was used. when determining the running irregularity, the engine and the dynamometer were disconnected and the flywheel ring gear teeth together with an inductive sensor served as signal source. the induced voltage from the sensor can be approximated as: u u0 = ω +β t( ) ω0 cos zω t + z β 2 t 2 ! " # $ % & , (11) where u is the output signal of the sensor, u0 is the amplitude of the sensor corresponding to the constant angular velocity of ω0, ω is the angular velocity of the crankshaft, β is the angular acceleration of the latter, z is the number of teeth of ring gear. in case of zero or small values of angular velocity the relationship eq.(11) simplifies to u u0 = ω ω0 cos zω t( ) . (12) by assuming that during the pass-time of one tooth (tooth-time) the angular velocity is not changing significantly, the signal amplitude during the tooth-time can be well approximated by a constant. that is, the approximated sensor signal when passing the zth tooth is given as u/u0k = cos (z ωk t). the running irregularity is defined as a ratio in eq.(13): δ = ωmax −ωmin ωaverage (13) measurements, estimations and evaluations the measurements were accomplished in the student’s workshop of gamf faculty using an agilent dso-x 2002a digital storage oscilloscope. the oscilloscope is two-channel type with upper input cut-off frequency of 70 mhz, maximum sampling frequency of 2 gs/s and with sample storage of 50000 samples. the algorithms used for evaluation of measured data were intentionally different. in one case the data series were not re-sampled and the differentiation was approximated by finite differences, and in the other case both re-sampling and smoothing derivative algorithm were applied. moreover, the computation method of the trend of angular acceleration was also different. estimation of the external friction torque and damping constant in this setup, an extra flywheel was driven by the engine fixed on the test stand. the measurement setup can be seen on fig.2. the reduced resultant moment of inertia of synchronously rotating components with the crankshaft was θ ≈ 0.0534 kg m2. the dynamometer’s friction torque was approximately constant with a value of mdynamometer ≈ 0.2 n m. figure 2: arrangement for measuring the friction torque 38 the engine’s injector was triggered by a signal from the crankshaft, one injection occurred in every two crankshaft revolutions. the oscilloscope was connected to the injector’s solenoid, and the solenoid’s signal was sampled with a sampling frequency of 2.5 khz, that is the sampling interval was ts = 400 µs. the part of measured injector pulse-signal can be seen on fig.3. the crankshaft’s angular velocity ω = ω (t) as a function of time was determined from the stored samples, with duration of 20 seconds. at the beginning of the measurement, the engine was accelerated to 4000–4200 rpm, then the injector was disconnected from the intake manifold, and the engine was allowed to decelerate freely. by defining a suitable trigger level, the elapsed time t between two consecutive rising edges of the impulse can be determined. the instantaneous frequency is two times the reciprocal value of t (finstantaneous = 2 / t), because every two revolution results in one impulse. the instantaneous angular velocity can be computed from this instantaneous frequency value. as the resulting angular velocity value sequence is nonequidistant, it has been re-sampled using cubic spline interpolation. first, a linear model was fitted (fig.4). the results are summarised in table 1. the two methods gave similar parameters, but the resampling resulted in somewhat better goodness-of-fit. the estimation of the physical quantities from parameters shown in table 1 can be seen in table 2. the estimations resulted by the two methods are similar in case of model of eq.(7). in case of model of eq.(9), the fitting has been fulfilled on the resampled data series. the results are demonstrated on fig.5. from the above results the external friction torque is m0 = b⋅c⋅θ ≈ 0.419 n·m; the average braking torque of the engine is mengine = m0 mdynamometer ≈ 0.219 n·m; the damping constant is m1/ω1 = bθ = 6.94⋅10-4 n·m·s. the initial angular velocity and revolution are ω0 = a – c ≈ 352 rad s-1, n0 = 3358 rpm. we can conclude that the two types of models gave similar results, but the biased exponential model fitted somewhat better the measured data than the linear model, thus the former are preferred. furthermore, the presented data indicate that both the average breaking torque of the engine and the damping constant are acceptable small, therefore the engine is acceptable from this point of view. estimation of the instantaneous torque and the running irregularity from measurements when the running irregularity was measured, the engine and the dynamometer were disconnected. the moment of inertia of the parts running synchronously with the crankshaft was θ = 4000 kg·mm2. a ring gear fixed to the crankshaft was used as signal source (number of teeth is z = 66) together with an inductive sensor fitted from the teeth in a distance of 4 mm. an oscilloscope was connected to the sensor and the voltage signal was sampled with 500 khz sampling frequency (fig.6). it is necessary to use such a great sampling rate because of the following. in order to acceptably estimate the instantaneous angular velocity, it is necessary to measure n samples during the tooth-time. in case of nominal revolution of n0, the sampling frequency is fs = figure 3: measured injector pulses using a power mosfet table 1: results of the fitting of data shown in fig.4 resampling a, rad s-1 b, rad s-2 r2 no 353.78 12.103 0.9954 yes 346.75 10.952 0.9981 table 2: estimation of physical quantities resampling n0, rpm m0, n·m mice, n·m no 3378 0.650 0.450 yes 3311 0.585 0.385 figure 4: linear model: the brake torque is independent of angular velocity figure 5: biased exponential model: the braking torque is independent of the square of angular velocity 39 n0⋅n⋅z / 60, that is in case of n0 = 4000 rpm and n = 100 samples, fs = 440000 hz. the nearest possible setting of the dso is 500 khz. the capacity of the sample storage is 50000 samples, so the duration of the measurable signal is 0.1 s. as it is greater than the duration t2 of two crankshaft revolution, the measurement of at least one full engine cycle is feasible using this dso (t2 = 2⋅(60/n0) = 0.03 s). the instantaneous angular velocity is the reciprocal of the time between two falling edge of the sensor’s signal, so the raw signal had to be smoothed before the zero-crossing detection. two different smoothing methods were implemented in this case as well: a 10-point moving average smoothing and savitzky-golay smoothing with tenth order polynomial and 31-point length window (for the latter see fig.7). because the number of teeth is known, the exact value of the crankshaft angle also with the tooth number can be tracked (see fig.8). as the angular velocity values are nonequidistant, cubic spline interpolation-based resampling was applied as in the previous section. due to the fast sampling rate, we can track very short-time changes in angular velocity values during 100 ms. however, our task is to estimate the crankshaft’s instantaneous angular velocity. for this purpose the trend of the angular velocity curve estimated at teeth is necessary. the trend was determined on the one hand by using a 10-point moving average filter, on the other with fft-based filtering (for the latter see fig.9). in the first case the time of averaging was around 2 ms. using this value for the time-constant τ of a low-pass filter for the fft-based computation, for the cut-off frequency of the low-pass filter we get fh = 1 / (2⋅π⋅t) ≈ 80 hz. following its definition, the running irregularity was computed using the maximum, minimum and average values of the angular velocity trend shown in eq.(14). δ = ωmax −ωmin ωaverage = 389.3−379.7 384.7 ≈ 0.02 . (14) the estimation of instantaneous acceleration was computed with differences in case of moving averagebased trend. in case of fft-based trend, the savitzkygolay smoothing derivative algorithm was applied (tenth order polynomial, 31-point length window). fig.10 illustrates the instantaneous acceleration as a function of time. in this measurement the maximum figure 6: setup for measuring the instantaneous torque figure 8: inductive sensor’s signal labelled with the crankshaft’s angle and tooth number (angles are in degrees) figure 7: the raw and smoothed signal of inductive sensor in case of savitzky-golay smoothing figure 9: instantaneous angular velocity values and the fftbased trend figure 10: estimation of instantaneous acceleration as smoothing derivative of the trend of instantaneous angular velocity 40 value of angular acceleration was 1113 rad s-2, so for the corresponding instantaneous torque we get: mmax =θβmax ≈ 0.004 kg ⋅m2 ⋅1113 rad s2 ≈ 4.5n ⋅m. (15) nearby the power stroke instant higher value of angular acceleration can be estimated. in that measurement the corresponding instantaneous torque was of 16 n·m (for details see ref. [6]). the crankshaft’s torque gets to wheel by a drive train with a reduction ratio of 7, so the maximal torque at the wheel is 112 n·m. the wheel’s maximal slipless torque transmission is 40–50 n·m that is during the maximal instantaneous acceleration the wheel will slip on the road, which results in energy loss. this effect ought to be concerned in designing the drive chain of megameter-iv, e.g. torque-damping torsion clutch should be built in. conclusions two methods were elaborated for instantaneous speed and acceleration of an internal combustion engine via on-line measurement. both the injector-pulse-based and the inductive sensor-based methods gave useful data for developing the next engine, namely the megameter-iv. the results presented in this paper are the numerical estimation of the engine’s internal friction, the damping constant, the instantaneous angular velocity, the instantaneous angular acceleration and the estimation of the instantaneous torque of the engine during the power stroke. these results provided the foundation for the design and construction of the on-board electronic control unit, which can be seen on fig.11. acknowledgement this research is supported by támop-4.2.2.c11/1/konv-2012-0012: "smarter transport" it for co-operative transport system and támop-4.2.2.a11/1/konv-2012-0012: basic research for the development of hybrid and electric vehicles, the project is supported by the hungarian government and cofinanced by the european social fund. references [1] www.eco-marathon.eu (last accessed: may 20, 2014) [2] bélanger p.r.: estimation of angular velocity and acceleration from shaft encoder measurements, proc. ieee international conference on robotics and automation, nice, france, 1992, 585–589 [3] stotsky a., forgo a.: recursive spline interpolation method for real time engine control applications, control engineering practice, 2004, 12, 409–416 [4] cruz-peragón f., palomar j.m., díaz f.a., jiménez-espadafor f.j.: fast on-line identification of instantaneous mechanical losses in internal combustion engines, mechanical systems and signal processing, 2010, 24, 267–280 [5] bagány m.: internal combustion engines, kecskemét college, gamf faculty, 2011, 192 (in hungarian) [6] pintér i., bagány m.: algorithm development for the megameter-iii telemetry system to estimate the parameters of extremely low fuel consumption internal combustion engine, proc. factory automation, veszprém, hungary, 2013, 21–22, 94–99 figure 11: ecu is under development for motor control and telemetry hungarian journal of industry and chemistry veszprém vol. 41(1) pp. 41–46 (2013) influence of can flatness on heat dissipation of aluminium electrolytic capacitor lászló kovács1!, lászló gál1, and dénes fodor2 1 department of aluminium electrolytic capacitor development (sz alu pd), epcos llc, szt. lászló str. 6, szombathely, h-9700 hungary 2 automotive mechatronics department, institute of mechanical engineering, faculty of engineering, university of pannonia, egyetem str. 10, veszprem, h-8200 hungary !e-mail: laszlo.kovacs@epcos.com the lifetime of aluminium electrolytic capacitors highly depends on their core temperature. heat dissipation in general applications happens by the extended cathode, which is in contact with the inner side of the can. in the case of heat sink applications, the most important heat transfer phenomenon is the heat conduction through the bottom of the aluminium can. the quantity of the dissipated heat is in direct proportion to the size of the heat transfer surface. the more dissipated heat may increase the lifetime of the capacitor. therefore, the flatness value of the can bottom is critical. this paper presents a flatness measurement method, which can successfully replace the equipment for a more complex and more expensive 3d measurement. it discusses an implementation of a measurement environment, where data acquisition and visualization are automated by a labview-based software. in addition, this study deals briefly with the influence of production processes on the flatness value of the capacitor produced by leading manufacturers. keywords: aluminium electrolytic capacitor, measurement automation, heat dissipation, graphical programming environment, flatness measurement introduction the aluminium electrolytic capacitor is the most commonly applied capacitor type, due to the fact that the capacitance and voltage range of the components is wide. the rated voltages change from 5 v to 550 v, while the capacitance 1 µf to 3 f. these are applied in many fields of industry, such as energetics, power electronics, automotive application, etc. and used for energy storage, smoothing and filtering function. the lifetime of the capacitor highly depends on its core temperature. each decrease of 10 ºc doubles the lifetime [1]. operating temperature is determined by the ambient temperature, by the applied ripple current, by the used voltage, and by the equivalent serial resistance (esr). there are two ways for the reduction of core temperature. the first one is the extended cathode foil and the second one is the cooling of the capacitor can. cooling in general applications is realized by applying a heat sink at the bottom of a capacitor can. this paper presents the basic construction of capacitors and the most important production steps, introduces the heat conduction between the can and the environment and describes the effect of the flatness of the can to heat conductivity. it also presents the entire measurement environment (measurement station, data acquisition and evaluation software), the database behind the measurement system that stores the results. at last, it discusses the effect of production processes to the measured flatness, and presents the flatness of capacitors produced by leading capacitor manufacturer companies. structure and construction of aluminium electrolytic capacitor the winding of an aluminium electrolytic capacitor contains two foils and papers [1]. these are rolled together tightly into a winding. the material of the anode, positive foil is aluminium with purity higher than 99.9%. the foil has been etched [2] to increase the effective surface area (and thus the capacitance of the capacitor). as a result, the effective surface area becomes typically 20–40 times larger than the plain area of the foil. on the etched surface of the foil an aluminiumoxide layer [3] has been generated electrochemically. the forming voltage of the anodized aluminium foil [4] is 30–60% higher than the rated voltage of the capacitor. the material of the cathode foil is also aluminium and itself has a thin oxide film (the forming voltage is only a few volts regardless of the rated voltage). it is typically etched to slightly increase the surface area. the anode and cathode foils are connected to aluminium tabs, which are coming out from the winding and are riveted to the aluminium terminals of the cover disk. the tab foils are not etched but are provided with an oxide layer made by 42 electrochemical oxidization. before being housed in a suitable container, the complete winding is impregnated with electrolyte. after housing the edges of the can are curled down. before being sleeved and packed, capacitors are first aged. the purpose of this stage is to repair any damage in the oxide layer and thus to reduce the leakage current to very low levels. during manufacturing there are two processes (curling and aging processes), which apply mechanical stress to the casing of capacitors. the effect of flatness of aluminium cans on heat conductivity in common applications with usage of extended cathode (the cathode is wider than the anode and exposed to the bottom of the winding) or different kinds of capacitor cooling (for example air or water cooling) are applied to reduce the core temperature that effects its lifetime. earlier investigations showed that there are three types of heat transfer phenomenon between capacitor and the environment [5]: (i) heat conductivity (mostly at the bottom), (ii) radiation (mostly at the side), and (iii) convection. this paper only deals with heat transfer from the bottom of the capacitor to the environment. from the general theory of thermodynamics the heat conduction can be described by eq.(1). p = ka dt dx , (1) where p represents power of the heat flow (w); a is the size of the tangential surface (m2); dt/dx is the temperature gradient (k m-1); and k stands for heat conductivity of the material (w km-1). in our case the linear approximation is acceptable. as already described, the rate of the heat flow depends on the size of the tangential plane. definition of the flatness was adapted from ref. [6]. it is given as the distance between the two closest tangential planes of the bottom of the aluminium electrolytic capacitor can. in the case of capacitors with higher flatness the tangential surface of the aluminium can is lower. the distance between the bottom of the capacitor and the heat sink is filled by air. it is well known that the heat conduction coefficient of the air is much lower than the aluminium. the aspect ratio between the two constants is in the order of magnitude ~104. therefore the flatness of the bottom in the case of regular heat sink applications is an important value. theoretical background of used measurement method there are several different methods for measuring the flatness of a surface [4]: 1. the entire surface is compared with a known reference surface (holistic methods); 2. points on the surface are compared to a reference plane; 3. straightness of the lines in the surface is measured. the holistic methods (e.g. holographic and interferometric methods) are not suitable for large surfaces with more than 90 mm diameter of screw terminal capacitor [7]. the third method is too complex and time-consuming for applying in serial production. therefore, a point-to-point method (second type) was chosen for this investigation. of course, the expensive optical methods may be more precise (in the order of 100 nm deviations) [8], but in our case this high precision is unnecessary. on the other hand, the pointto-point method is very fast, can be used easier and cost-efficient. for point-by-point methods, the grid size is a critical issue, which determines the lowest limit for observable surface irregularities. in our case, approximately 60 cm2 surface area needs to be characterized. the height difference was measured between n points within the bottom. trials were made to find the applicable grid. finally, a 9-point-grid was chosen with circular symmetry, because the measurement time is short enough and the accuracy of the measurement is acceptable. least mean squares (lms) method was used for plane fitting, because the randomly distributed measurement errors have the smallest influence to the results [9]. eq.(2) was used for the lms: xi 2 i=1 n ∑ xiyi i=1 n ∑ xi i=1 n ∑ xiyi i=1 n ∑ yi 2 i=1 n ∑ yi i=1 n ∑ xi i=1 n ∑ yi i=1 n ∑ 1 i=1 n ∑ " # $ $ $ $ $ $ $ $ % & ' ' ' ' ' ' ' ' × a b c " # $ $ $ % & ' ' ' = zixi i=1 n ∑ ziyi i=1 n ∑ zi i=1 n ∑ " # $ $ $ $ $ $ $ $ % & ' ' ' ' ' ' ' ' , (2) where n is the number of the grid points; xi, yi are coordinates within the measured surface [mm]; zi corresponds to the measured height compared to z1 of the ith point (mm), a, b, c are constants for the fitting. the fitted plane is described by eq.(3). z(x, y) = ax+by+c (3) by solving the system of linear equations, for example with gauss-elimination the fitted plane is given. the gauss-elimination is not necessary if the grid points are centrally symmetric. in this case, the input matrix is diagonal, so the solution of the equation system is simple. the distance between the individual points and the fitted plane was calculated. the sign of this distance describes the location of the point respect to the fitted plane. the flatness is the distance between the farthest points above and under the fitted plane. the fig.1 shows an example of measured points and the fitted plane. 43 implemented measurement environment the base of the hardware was a measuring pad made from stainless steel, which has an extremely smooth surface. by the lms method, the error that comes from the tilt of the steel pad was avoided. to stay clear of the effect of the temperature gradient, the measuring equipment was kept under controlled environmental conditions. the data acquisition programme for the flatness measurement was written in labview with contains two major parts. the first one collects the data from the controlled hardware (height meter) and stores them into a local database in ms excel format. this software communicates through an rs-232 port with the measuring equipment. the user sets the actual position, pushes a button and the module registers the results. the graphical user interface developed is shown in fig.2 with hungarian annotations. the software displays the number of actual measurement points and controls the entire process. for example, if the flatness value exceeds a predetermined limit, the software sends a warning to the operator. the second module can extract the results from the database of an examined capacitor(s) or the user can import the measured values from excel. if the results are in the input table, the evaluation module can calculate the flatness of the capacitor can. the graphical user interface of the second module can be seen in fig.3. the implemented automation environment fits into the measurement automation system (mas) [10] being used at the aluminium electrolytic capacitor development department of epcos llc. the system uses two frameworks: a labview based framework for data acquisition and an asp.net based framework for data management. the measurement part contains automated data acquisition measurements, which are connected to the electrolyte (conductivity, ph, viscosity, etc.) and different kind of capacitor tests. (lifetime, surge voltage and storage test, etc.). the experiments on the electrolyte are controlled by an ni-pxi, which is connected to the database (fig.4). pxi stand for pci extensions for instrumentation. these platforms are used as a basis for building of electronic test equipment, automation system, etc. pxi chassis can handle many modules for example plug-in data acquisition (daq) cards, communication cards like rs-232, and different analogue and digital i/o boards. the capacitor measurements are controlled by computers and not by the ni-pxi, because the current implementation measures the low and high voltages separately. the asp.net part of the system was developed for data management and evaluation. this is a software module that contains useful tools that facilitate data handling. data management module simplifies the registration of the constructive properties of the capacitor (like anode foil, cathode foil, type of can, cover disk, etc.) and helps the data storage of applied figure 1: example of the measured points and the fitted plane figure 3: graphical user interface of the evaluation software figure 2: graphical user interface of the data acquisition software figure 4: architecture of the electrolyte measurements 44 voltage and current, ambient temperature, etc. the evaluation part supports the evaluation process by generating a standardized report. the user can tailor the reports according to its needs by the report generation tool. the desired data appear in a representative way and even the trends of the parameters can be shown. the goal of the mas is to automate the previously manual measurements and eliminate paper-based registration. there are many advantages like making the measurements more precise, more reliable and fault tolerant, running multiple measurements in parallel, which all contribute to speed up the research and development of new component and devices. change of flatness value during the manufacturing the flatness of the capacitor can is measured at the incoming inspection and at the final measurement of the production. the initial value of the flatness of the capacitor is determined by the incoming aluminium cans. these parts are produced by cold extrusion of aluminium slugs, so the irregularities of the cans is in the order of magnitude ~10 µm, which is negligible for our purposes. the fig.5 shows the flatness values measured at the incoming inspection of the capacitors. it can be seen that the mean of the measured flatness values is 0.09 mm. as mentioned above, the flatness is mainly affected by two procedures: curling and aging. during curling the can is closed hermetically by curling back the edges of the aluminium can. this curled edge sinks into the rubber ring of the cover disk. as a consequence, the cover disk presses down the winding. it can affect the flatness value, since for example concave shaped aluminium can turn into a convex shape. during aging, the flaws of the anode foil are repaired by applying voltage to the capacitor and placing it in an oven. as a side effect gas is generated. the pressure of the generated gas can change the geometry of the can. from the distribution of the flatness values the effect of epcos production steps (coloured curves in fig.6) can be estimated. the results show that the different production steps do not influence significantly the bottom flatness of the capacitor at the epcos. experimental results regarding to core temperature measurements two experiments were completed for investigating the importance of the flatness value of the capacitor can. sample capacitors were produced with different bottom flatness values. the aluminium cans were made to be convex. these were ordered directly from the supplier and the used parts were sorted out. regular heat sinks were assembled to the bottom of the parts. the tangential planes of the heat sinks were flat (~2 µm) due to their grinded surface. the heat sinks were fixed to the bottom of the samples with the bottom screw of the capacitors. the mechanical stability of the fixation was made with torque wrench. also guaranteed the same fixation level in each case. during the tests, forced aircooling was not used. heat conductive wires were applied to the core of the samples, which allowed us to measure the core temperature of the capacitors directly. the core temperature measurement system is shown in fig.7. in case of the first measurement, sample capacitors with very similar equivalent serial resistance (esr) and leakage current were selected. these parts were taken to 85 °c oven and rated voltage (450 v) was applied to them for 100 h. this preparation is necessary to avoid the different behaviour of the leakage current of the capacitors (isolated from each other to avoid the heat transfer). during the experiment a sinusoidal current figure 5: the measurement results from incoming inspection department figure 6: the effect of the production processes to the flatness of capacitor table 1: results of the ripple current measurement average flatness (mm) average of temperature at equilibrium state (°c) 0.102 90.6 0.259 90.9 0.509 91.5 45 was applied at 50 hz. the current and the temperature (the upper category temperature) of the test are specified by the data sheet of the capacitor. in this case the examined capacitor was b43586a5278q (c = 2700 µf, ur = 450 v, i (85 °c, 100 hz) = 12 a), the applied current (multiplying with the frequency factor) was 10.8 a. the selected samples were placed into an oven at 85 °c and a rated voltage of 450 v was applied. the core temperature was measured during the test. the equilibrium temperature was measured and compared. test was started with the remaining three prepared samples. in case of the second measurement the behaviour of the capacitors was tested against transient heat. the parts were heated up to 85 °c and removed from the oven after 10 hours. the core temperature of the capacitors was measured during cool down time. the recorded core temperature curves (fig.8) show exponential decay. the time-constant of the decay depends on the flatness value of the bottom. as a comparison, the flatness values for screw terminals capacitors from leading manufacturers were inspected. table 2 summarizes the flatness results by leading manufacturers. conclusion it is possible to measure the flatness of a capacitor can with the presented and implemented measurement environment. the expensive 3d measurement equipment can be replaced with this cost-effective method. the measurement and evaluation software was implemented in labview programming environment, which perfectly fits into the previously presented measurement automation system, which is currently being used at the aluminium electrolytic capacitor product development department of epcos. the faults of previously manual measurements have been lowered with the help of automation and data acquisition software. this study discussed the basic construction of a capacitor and highlighted the critical construction steps from the aspect of flatness. in addition, it reveals the flatness values of other capacitor manufacturers’ products. acknowledgments the authors gratefully acknowledge the support of the hungarian state and european union under the "green energy – cooperation of the higher education sector for the development of green economy in the area of energetics” project (támop-4.1.1.c-12/1/konv2012-0017), and the support of the támop-4.2.2.a11/1/konv-2012-0071. references [1] tdk corporation, aluminium electrolytic capacitors, 2013 [2] park d., kim h.: electrochemical etching of aluminium through porous alumina, analytical sciences, 2001, 17(supplement), a73–a76 [3] church h.f.: the dielectric properties of anodic aluminium oxide films, proc. iee – part b: electronic and communication engineering, 1962, 109, 399–403 figure 8: the behaviour of core temperature in case of different bottom flatness values figure 7: core temperature measurement of a capacitor table 2: flatness results for products from leading manufacturers company capacitor series flatness (mm) epcos b43586 0.095±??? hitachi fxr 0.158±??? kemet als 0.225±??? nichicon nt 0.330 46 [4] chen c., mass w., hutchins g.: anodization of aluminium electrolyte capacitor foil, u.s. patent 4,481,084, 1984 [5] parler s.g. jr.: thermal modelling of aluminium electrolytic capacitor, ieee industry applications society conference, 1999 [6] iso/ts 12781–1: geometrical product specifications (gps) – flatness – part 1: vocabulary and parameters of flatness, 2003 [7] de groot p.j.: grating interferometer for flatness testing, optics letters, 1996, 21(3), 228–230 [8] meijer j.: accuracy of surface plate measurements – general purpose software for flatness measurement, annals of the cirp, 1990, 39, 545–548 [9] haitjema h., meijer j.: evaluation of surface plate flatness measurements, european journal of mechanical engineering, 1993, 38(4), 165–172 [10] kovács l., fodor d., klug o., enisz k.: measurement automation system for aluminium electrolyte capacitor development, ieee instrumentation & measurement magazine, 2013, 16(3), 38–43 hungarian journal of industry and chemistry veszprém vol. 41(1) pp. 47–50 (2013) fine tuning of automated assembly machines using video analysis alíz katona1!, viktor kovács2, dóra tasner3, and zoltán kovács3 1 transmoduls , józsef a. u. 9., veszprém, hungary 2 department of automation and applied informatics, budapest university of technology and economics, magyar tudósok krt. 2., budapest, 1117, hungary 3 department of supply chain management, university of pannonia, egyetem u. 10, veszprém, 8200, hungary !e-mail: katona.aliz@transmoduls.hu human/machine interaction is of still importance in the age of automation. automated assembling devices are customizable products that need basic settings before installation. capabilities of operators have to be taken into consideration in this process. this paper presents a procedure based on video recording to determine time data for machine settings. it allows the engineers to forecast the expected capacity of individual workstation and the entire production line. a case study from industry is used to illustrate the application of the system. keywords: automated assembly machine, human/machine interaction, method time measurement, maynard operation sequence technique, video based process analysis introduction stopwatch, photo and film technologies were used commonly in factories to study how humans work. analogue video technology had some disadvantages compared to traditional film, which contributed to opening a gap in their applications. the advent of digital age in video technology eliminated most drawbacks. today videos have numerous benefits over the film and old videos including framing feature, easy to access and wide spread, affordable equipment, no additional personnel or lab needed, and software supported processing is possible. due to the convergence of the technology, recordings became files that can be acquired by a wide variety of equipment including handheld devices. we carried out analyses in production factories, observing human work where the machine time (process time: pt) was supposed to be unalterable. there were no reason to observe automates, since they did their job in the pace prescribed by the programmer. this is not the case during the development and production of the automated workstations. machine times have to be in sync with human capabilities. fig.1 shows the layout of analysis in the production project of the customised automated assembly station. we have carried out analyses at transmoduls ltd. in order to help programmers to tune the machines before delivering to the customer. as the first such application of our methodology it consisted of video recordings and software components. the outcome of these analyses are measuring times (time study) or improvement of process (method study). we focused on the former in the given study. literature overview the interference of operators and their workstations is critical in manufacturing systems [1]. there are many ways to ground process improvement starting from simple observation until the precise measure of data. motion pictures can be used for time and motion study. the widely accessible digital video technology allows repetitive observations, measuring time and analysing information using software applications. nowadays, several companies focus on digital time analysis. elnekave and gilad verified the method’s abilities for rapid generation of time standards through five case studies. they compared the performance of work analysts for making a maynard operation sequence technique (most) study using the digital video-based approach versus using videotape analysis. the result showed that the use of a digital approach may save ~40% of the time devoted to work measurement [2]. figure 1: the role of analysis in the project 48 as an example, the usage of video-based time and motion study is common in health care. a study was conducted to identify ambulanceand operator factors affecting cardiopulmonary resuscitation device in such environment. the aim was to improve the quality of resuscitation in ambulance [3]. furthermore, a new technique demonstrates the feasibility of tracking workers from statistically placed and dynamically moving cameras [4]. this study reviewed existing techniques to monitor workforce and describe areas, where a work may be improved in engineering application. typical construction site video is processed and analysed to determine the most appropriate tracking method for the video. ma et al. proposed a new framework on the basis of motion-tracking and digital human simulation technique for motion-time analysis of manual operations. they track the worker’s operation during completion of a task. then the motion data are transferred to computer for real-time digital human simulation. the data are used for motion type recognition and analysis [5]. furthermore, video technique is used for observing business life in japan with great efficiency. it gives help in developing ergonomic methods, statistical methods and technology. using this approach, the individual user's everyday behaviour is observed as well as employees' collective work, for example during fixing of gas pipelines [6]. as possible outcomes, the satisfaction of consumers and the creation of safe work environment can be increased at the same time. video recordings were made during the picking processes in car industry, when several hours of work were recorded [7]. the aim of the recording was to allow employees to mark specific motions in the evaluating program called vidar that caused them pain or made them feel uncomfortable. the results showed that after the company received the data they were able to change processes successfully from the ergonomic analysis of complex work. the video-based method can be applied in all cases, where the goal is to better understand the workflow related processes. the camera-based method has advantages and disadvantages, thus its use needs to be evaluated whether it provides the best solution. the measurement framework goal setting and planning we designed a process for addressing the questions, such as when we the measured to be done, how and where the measurement can be done for these intervals, what the benefits of the collected information are, and what information we want from the recordings during our research, we based our measurements on a technique utilizing video recordings. video was recorded of the examined processes and offline analysis was carried out afterwards to extract the required information. the planning phase included decisions on the aforementioned questions, most importantly what to record, how to perform the recording without interfering with the processes and how much captured information is needed to extract certain data. implementation videos were recorded using commercial hdv camcorders. hdv/avchd (1080i50) provides benefit over dv (576i50) due to the higher resolution. higher image resolution offers more details for analysis. both systems are capable of interlaced video recording, which offers doubled number of samples at the expense of resolution (row count is halved). this is a practical feature that balances high resolution and larger frame rates. in order to extract accurate time information in both fields of the video may be used. the recorded videos were transferred to the pc. tape based camcorders require an ieee 1394 port to capture the video stream, while recent flash drive based camcorders offer simple file copying mechanism to download video clips. these video files may be transformed and compressed further for archiving purposes or simply fit them to the capacity of the pc used for analysis. we compressed all source videos to a common mpeg4 format to ease software dependencies for decoding. a custom software application was developed for the evaluation of video recordings. the software enables the user to import a video clip and set up basic parameters of the recording. all these settings may be saved to or load from a project file. several grid views are provided for the user to define the stages of the analysed process. each row of the grid defines a process step, each column defines a cycle of the periodic process. the user is able to control freely the video playback (slow down, speed up, rewind, jump to other positions etc.) and at any time simply insert the frame number into the grid or go back to these positions. so as time advances, the user fills up the table from the starting to the finishing stages. after the process is completed all the timing information are available for the process for each cycle and stage. several tables are available right away to collect information for different (parallel, additional or interrupting) processes. optional comments or the number of processed products for each cycle can be recorded as annotations. data from the grid is transferred to a spreadsheet to analyse the raw data for timing. the pre-defined spreadsheet calculates simple statistical descriptors for the data. in the case redundant observations are available from several cycles, outlier data can be removed and the descriptors can be recalculated. fig.2 shows the screenshot of the software. the spreadsheet calculates a suggested normal cycle time involving extra allowances. the number of cycles and, in case of batch production, the number of product per cycles was also determined. the expected number of products processed in unit time (e.g. hour or shift) is also apparent. this information is essential for production scheduling (see fig.3). the analysing software is available in english and in german. 49 implementation of analysis transmoduls ltd., an engineering and construction company began to fulfil the order of a customer from the automotive industry since april 2012. mechanical and electrical designs were the first steps of the project. fig.4 illustrates the design stage of machines before production. while the mechanical and electrical design tasks were completed, we have gained information about machines. the three individual rotary configuration machines were organized in a production line, thus their operation is not independent from each other. the planned lead-time of the project was 47 weeks that included the mechanical and electrical design, high-value raw materials and components procurement, mechanical and electrical assembly, and installation. mechanical assembly was followed by programing and the machines were tested during this phase. some machine movements were already programmed while the operator dependent ones, such as product forwarding were initialized manually. this allowed for adopting to the operator’s pace. later we took the learning curve into account as well. we used three techniques to obtain time data: (i) method time measurement, mtm, (ii) maynard operation sequence technique, most, (iii) video recordings. the two kinds of products to be produced on the production line are heavy duty (hd) and standard (st). we analysed two areas of the production line: cycle times and capacity. we compared the preliminary traditional calculations (mtm, most) and analysis of video recording. we obtained different results (table 1). one can observe that cycle times determined by video were much longer than those resulted from mtm and most analyses. this can be explained by several reasons, such as the technology is not setup and trained yet, operators are not skilled for the task, supply processes are not ideal, and/or the workplace is not optimized ergonomically. figure 2: screenshot of the software figure 3: example for the result of calculation figure 4: dial-type assembly machines at transmoduls ltd. (graphics were generated by autodesk inventor software) table 1: summary of data obtained for stations method cycle time (hd), s output, pc/shift station 1 mtm 26.316 830 most 24.48 830 video 97.284 290 station 2 mtm 9.2628 910 most 9.72 910 video 16.42 539 station 3 mtm 29.226 620 most 27.72 620 video 67.98 415 50 results from most and mtm can be seen as target values during operation in ideal case, while video recording shows what production planning and control can expect at start-up operation. using the results of time analysis for capacity planning, we are able to forecast the expected value of capacity and capacity utilization independently the source of time data. table 2 presents examples for mtm and most based analyses of planning capacities and effective capacities. additional times were taken into consideration resulting in 10% increase in total capacity. with respect of capacity utilization, the video-based analysis shows that the actual output at least for the first period of operation is lower than the expected output by movement time standard. using this information, we can calculate expected efficiency, which we extended with 10% rest period time. later learning for the operator and process improvement will allow for reducing time to complete a workpiece. recordings allowed us also to analyse ergonomics of work place (fig.4). it became obvious at the start of recording that the planned position of the rack is not optimal. also the upper frame did not allow the operator to use economical movement. these observations suggested constructional changes. conclusions analysis of workstations in final production phase helps developer, operators, and customers to evaluate a given machine in advance before finalizing its design. it allows them to forecast the capacity, capacity utilization, operators’ load, and potential ergonomics problems. tests with operators during the early phase revealed ergonomics problems, such as height, structure and position of hardware elements. implications of their changes were easily observed repetitively. irregular activities such as jam cleaning can be analysed also. references [1] kamath m.: modelling operator/workstation interference in asynchronous automatic assembly systems, discrete event dynamic systems, 1991, 5(1), 93–124 [2] elnekave m., gilad i.: rapid video-based analysis system for advanced work measurement, int. j. prod. res., 2006, 44(2), 271–290 [3] wang h.c., chiang w.c., chen s.y., ke y.l., chi c.l., yang c.w., lin p.c., ko p.c., wang y.c., tsai t.c., huang c.h., hsiung k.h., ma m.h., chen s.c., chen w.j., lin f.y.: video-recording and timemotion analyses of manual versus mechanical cardiopulmonary resuscitation during ambulance transport, resuscitation, 2007, 74, 453–460 [4] teizer j., vela p.a.: personnel tracking on construction sites using video cameras, adv. engng. inform., 2009, 23(4), 452–462 [5] ma l., zhang w., fu h., guo y., chablat d., bennis f., sawanoi a., fugiwara n.: a framework for interactive work design based on motion tracking, simulation, and analysis, human factors and ergonomics in manufacturing & service industries, 2012, 20, 339–352 [6] matsunami h.: service science: applications of observation to real world business, proc. 4th int. conf. universal access in human-computer interaction uahci'07: applications and services, 2007, pp. 951–960 [7] kadefors r., rorsman m.: ergonomic evaluation of complex work: a participative approach employing video-computer interaction, exemplified in a study of order picking, int. j. ind. ergon., 2000, 25, 435–445 table 2: summary of planning and effective capacity considered (qplanning in piece/hour) planning capacity qplanning total a station 1 metal-based 106 4240 station 1 plastic-based 113 4520 station 2 metaland plastic-based 116 4640 station 3 metal-based 79 3160 station 3 plastic-based 86 3440 effective capacity b station 1 metal-based 106 3816 station 1 plastic-based 113 4068 station 2 metaland plastic-based 116 4176 station 3 metal-based 79 2844 station 3 plastic-based 86 3096 a calculated for 8 hours/day and 5 days/week; b 90% efficiency is considered in total table 3: summary of capacity utilization and efficiency considered capacity utilization expected outputa planning capacitya ratio st. 1 metal-based 1475 4240 35% st. 1 plastic-based 1475 4520 33% st. 2 metal-/plastic-based 8580 4640 184% st. 3 metal-based 2075 3160 66% st. 3 plastic-based 2075 3440 60% efficiency st. 1 metal-based 1475 3816 39% st. 1 plastic-based 1475 4068 36% st. 2 metal-/plastic-based 8580 4176 206% st. 3 metal-based 2075 2844 73% st. 3 plastic-based 2075 3096 67% a output and capacity are given in pieces/hour figure 4: a frame from recording for the original layout hungarian journal of industry and chemistry veszprém vol. 41(1) pp. 51-57 (2013) quasi-polynomial control of a synchronous generator attila magyarb1 and attila fodor1 1department of electrical engineering and information systems, university of pannonia, egyetem u. 10., h8200 veszprém, hungary be-mail: magyar.attila@virt.uni-pannon.hu a simple dynamic model of permanent magnet synchronous generator, that is used for electrical energy generation is investigated in this work using a nonlinear technique based on the quasi-polynomial representation of the dynamical model. it is well known that dynamical systems with smooth nonlinearities can be embedded in a quasi-polynomial model. quasipolynomial systems are good candidates for a general nonlinear system representation since their global stability analysis is equivalent to the feasibility of a lmi. moreover, the stabilizing quasi-polynomial state feedback controller design problem is equivalent to the feasibility of a bilinear matrix inequality. the classical stabilizing state feedback problem for quasipolynomial systems has been extended in this work with the ability of tracking time-dependent reference signals. it is shown, that the stabilizing quasi-polynomial servo controller design is equivalent to a bilinear matrix inequality. the results are applied to the model of a synchronous generator. keywords: quasi-polynomial systems, lotka-volterra systems, stability analysis, state feedback control, synchronous generator, wind turbine introduction electrical power systems should operate in an economic way with minimum possible operating cost under normal operating conditions. to ensure this, a preventive controller for power systems has been presented in [1]. it encompasses many types of control actions, including generation rescheduling, load curtailment and network switching reactive compensation. from the viewpoint of the power grid, the electric power generation can be characterized by the operation of the electrical generators, the subject of our study. these power plants should not only be able to follow the timevarying active power demand of the consumers and the central dispatch center, but also keep the quality indicators (frequency, waveform, total harmonic distortion) of the grid on the expected level. this can be achieved by applying proper control methods based on dynamic models of plant (see e.g. [2, 3]) and the involved generators. because of the specialties and great practical importance of the synchronous generators in power plants, their modeling for control purposes is also well investigated in the literature. besides of the basic textbooks (see e.g. [4]) that describe the modeling, specialized papers are also available that use the developed models for the design of various controllers [5]. a wind turbine driving permanent magnet synchronous generator is proposed in [6] with current controlled voltage source inverter, which is the best choice when the output power is small. the current control of the voltage source inverter has bidirectional active and reactive power control ability, avoiding the intricacy of the controller designing. the class of quasi-polynomial (qp) systems plays an important role in the theory of nonlinear dynamical systems because nonlinear systems with smooth nonlinearities can be transformed into a qp form [7]. this means, that any applicable method for qp systems can be regarded as a general technique for nonlinear systems. previous work in the field of qp systems include [8], which proves that the global stability analysis of qp systems is equivalent to the feasibility of a linear matrix inequality (lmi). it has been shown in [9] that the globally stabilizing state feedback design for qp systems is equivalent to a bilinear matrix inequality (bmi). although the solution of a bmi is an np-hard problem, an iterative lmi algorithm could be used. a summary of linear and bilinear matrix inequalities and the available software tools for solving them can be found in [10]. another control synthesis algorithm for polynomial systems is presented in [11]. the goal of this paper is to formulate the servo controller design problem for qp systems based on the results presented in [9] and to design a servo controller for a synchronous generator model using the qp controller synthesis methodology that keeps the active power at the desired level. 52 basic notions in what follows, the basic modeling assumptions and definitions to be used in the sequel are summarized briefly. nonlinear model of a synchronous generator the modeling procedure of the synchronous generator is mainly based on [12] and [13], therefore, only the resulting model is presented here. the model is based on the following simplification assumptions: • a symmetrical tri-phase stator winding system is assumed, • one field winding is considered to be in the machine, • all of the windings are magnetically coupled, • the flux linkage of the winding is a function of rotor position, • the copper loss and the slots in the machine can be neglected, • the spatial distribution of the stator fluxes and apertures wave are considered to be sinusoidal, and • stator and rotor permeability are assumed to be infinite. it is also assumed that all the losses due to wiring, saturation, and slots can be neglected. the four windings (three stators and one rotor) are magnetically coupled. since the magnetic coupling between the windings is a function of the rotor position, the flux linkage of the windings is also a function of the rotor position. the actual terminal voltage v of the windings can be written in the form v = ± jx j=1 (r j i j )± jx j=1 ✓ d' j dt ◆ , (1) where i j are the currents, r j are the winding resistances, and ' j are the flux linkages. the positive directions of the stator currents point out of the synchronous generator terminals. thereafter, the two stator electromagnetic fields, both traveling at rotor speed, can be identified by decomposing each stator phase current under steady state into two components, one in phase with the electromagnetic field and another phase shifted by 90�. with the above, one can construct an air-gap field with its maximal aligned to the rotor poles (d axis), while the other is aligned to the q axis (between poles). this method is called the park’s transformation. as a result of the derivation in [12] the vector voltage equation is as follows v dfq = �ri dfq �l d dt i dfq , (2) with v dfq = ⇥ v d �v f v q ⇤ t i dfq = ⇥ i d i f i q ⇤ t , (3) figure 1: the equivalent circuit of the synchronous generator. where v d , v q and i d , i q are the direct and the quadrature components of the stator voltage and current of the synchronous generator, while v f and i f are the exciter voltage and current of the synchronous generator. furthermore, r and l are the following matrices (see fig.1) rrs! = 2 4 r 0 !l q 0 r f 0 �!l d �! km f r 3 5 l = 2 4 l d km f 0 km f l f 0 0 0 l q 3 5 , (4) where r is the stator resistance, r f is the exciter resistance of the synchronous generator, l d , and l q are the direct and the quadrature part of the stator and rotor inductance, ! is the angular velocity, and m f is linkage inductances. the state-space model for the currents is obtained by expressing d dtidfq from eq. (2), i.e. d dt i dfq = �l�1 r rs! i dfq �l�1 v dfq . (5) the purely electrical model eq. (5) has to be extended with the equation of rotational motion (eq. (6)) that gives the mechanical sub-dynamics, that is d! dt = �l d i q 3⌧ j i d + �km f i q 3⌧ j i f + + l q i d 3⌧ j i q + �d ⌧ j ! + tmech ⌧ j . (6) 2 664 i̇d ˙ if i̇q !̇ 3 775 = 2 6666666664 �lf h kmf h 0 0 kmf h �ld h 0 0 0 0 1 lq 0 0 0 0 1 ⌧j 3 7777777775 2 64 �vd vf �vq tmech 3 75+ 53 2 66666666664 � rlf h kmf rf h �!lf lq h 0 rkmf h � rf ld h !kmf lq h 0 �!ld lq !kmf lq r lq 0 �ld iq 3⌧j �k mf iq 3⌧j lq id 3⌧j �d ⌧j 3 77777777775 2 64 id if iq ! 3 75 (7) where h = k2m2 f � l d l f 2 664 i̇d ˙ if i̇q !̇ 3 775 = 2 64 �1.7100 0.5893 0 0 0.5893 �6.6918 0 0 0 0 �1.7090 0 0 0 0 0.0006 3 75 2 64 �vd vf �vq tmech 3 75+ 2 64 �0.0019 0.0004 �3.4883! 0 0.0006 �0.0042 1.2022! 0 3.5888! 2.6489! �0.0019 0 �0.0004 iq �0.0003 iq 0.0004 id �0.0011 3 75 2 64 id if iq ! 3 75 (8) altogether, the state equations eqs. (5) and (6) have four state variables: i d , i f , i q , and !. the manipulated input vector of the generator is u = ⇥ v f t mech ⇤ t , while the disturbance input vector is d = ⇥ v d d q ⇤ t . realize that the state equations eqs. (5) and (6) are bilinear in the state variables because matrix rrs! depends linearly on !. the obtained model is nonlinear and it has four state variables: i d , i f , i q and ! [14]. output equations of the model: the output active power equation can be written in the following form: p out = v d i d + v q i q (9) and the reactive power is q out = v d i q � v q i d . (10) eqs. (9) and (10) are the output equations of the generator’s state space model. it is important to note, that these equations are bi-linear in the state and input variables. note, that although only the active power is to be controlled in this case, as a possible future extension of the work, reactive power can also be controlled in order to follow an external reference signal. quasi-polynomial representation of nonlinear systems let us denote the element of an arbitrary matrix w with row index i and column index j by w ij . quasipolynomial models are systems of ordinary differential equations (ode) of the following form ẏ i = y i 0 @l i + mx j=1 a ij ny k=1 y bjk k 1 a , i = 1, . . . , n. (11) where y 2 int(rn +), a 2 rn⇥m, b 2 rm⇥n, l i 2 r, i = 1, . . . , n. furthermore, l = [l1 . . . l n ]t . let us denote the equilibrium point of interest of eq. (11) as y⇤ = [y⇤1 y⇤2 . . . y⇤ n ]t . without the loss of generality we can assume that rank(b) = n and m � n (see [15]). lotka-volterra models the above family of models is split into classes of equivalence [16] according to the values of the products m = ba and n = bl. the lotka-volterra form gives the representative elements of these classes of equivalence. if rank(b) = n, then the set of odes in eq. (11) can be embedded into the following mdimensional set of equations, the so called lotkavolterra model: ż j = z j n j + mx i=1 m ji z i ! , j = 1, . . . ,m (12) where m = ba, n = bl, and each z j represents a so called quasi-monomial: z j = ny k=1 y bjk k , j = 1, . . . ,m. (13) stability analysis using linear matrix inequalities henceforth it is assumed that y⇤ is a positive equilibrium point, i.e. y⇤ 2 int(rn +) in the qp case and similarly z⇤ 2 int(rm + ) is a positive equilibrium point in the lotka-volterra case. for lv systems there is a well known candidate lyapunov function family ([8, 17]), which is in the form: v (z) = mx i=1 c i ✓ z i � z⇤ i � z⇤ i ln z i z⇤ i ◆ , (14) c i > 0, i = 1 . . .m, where z⇤ = ⇥ z⇤1 . . . z⇤ m ⇤ t is the equilibrium point corresponding to the equilibrium y⇤ of the original qp system (eq. (11)). the time derivative of the lyapunov function eq. (14) is: v̇ (z) = 1 2 (z � z⇤)(c m +mtc)(z � z⇤), (15) where c = diag(c1, . . . , cm) and m is the invariant characterizing the lotka-volterra form (eq. (12)). therefore, the non-increasing nature of the lyapunov function is equivalent to a feasibility problem over the following set of lmi constraints (see [18] or [19]): c m +mtc  0 c > 0 (16) where the unknown matrix is c, which is diagonal and contains the coefficients of eq. (14). 54 the derivation of global stability analysis for nonautonomous qp systems from the autonomous case is straightforward. the lyapunov function (eq. (15)) also depends on the equilibrium value of the input (u⇤) and has the form ˙̃v (z) = 1 2 (z � z⇤)(c m̃ + m̃ t c)(z � z⇤), (17) where m̃ depends on the coefficient matrices of the input-affine lotka-volterra model (eq. (21)): m̃ = m0 + px l=1 ml u ⇤ l . the corresponding lmi feasibility problem to be solved in order to check global asymptotic stability is c m̃ + m̃ t c  0 c > 0. (18) input-affine qp system models an input-affine nonlinear system model with state vector y, input vector u and output vector ⌘ ẏ = f(y)+ p p i=1 gi(y)ui ⌘ = h(y) (19) is in qp-form if all of the functions f , gi and h are in qp-form. then the general form of the state equation of an input-affine qp system model with p-inputs is: ẏ i = y i 0 @l0i + mx j=1 a0ij ny k=1 y bjk k 1 a+ (20) + px l=1 y i 0 @l li + mx j=1 a lij ny k=1 y bjk k 1 au l where i = 1, . . . , n, a0,al 2 rn⇥m, b 2 rm⇥n, l0,ll 2 rn, l = 1, . . . , p. the corresponding input-affine lotka-volterra model is in the form ż j = z j n0j + mx k=1 m0jkzk ! + (21) + px l=1 z j n lj + mx k=1 m ljk z k ! u l where j = 1, . . . ,m, m0,ml 2 rm⇥m, n0,nl 2 rm, l = 1, . . . , p, and the parameters can be obtained from the input-affine qp system’s ones in the following way m0 = ba0 n0 = bl0 ml = bal nl = bll l = 1, . . . , p. (22) the controller design problem for qp systems globally stabilizing qp state feedback design problem for qp systems can be formulated as follows (for a more detailed desription, see [9]). consider arbitrary qp inputs in the form: u l = rx i=1 k il q̂ i , l = 1 . . . , p, (23) where q̂ i = q̂ i (y1, . . . , yn), i = 1, ..., r are arbitrary quasi-monomial functions of the state variables of eq. (20) and k il is the constant gain of the quasimonomial function q̂ i in the l-th input u l . the closed loop system will also be a qp system with matrices â = a0 + px l=1 rx i=1 k il ail, b̂, l̂ = l0 + px l=1 rx i=1 k il lil. (24) note that the number of quasi-monomials in the closedloop system (i.e. the dimension of the matrices) together with the matrix b̂ may significantly change depending on the choice of the feedback structure, i.e. on the quasimonomial functions q̂ i . furthermore, the closed loop lv coefficient matrix m̂ can also be expressed in the form m̂ = b̂ â = m0 + px l=1 rx i=1 k il mil. (25) then the global stability analysis of the closed loop system with unknown feedback gains k il leads to the following bmi m̂ t c +cm̂ = m0 tc +cm0+ (26) px l=1 rx i=1 k il ⇣ mil tc +cmil ⌘  0. the variables of the bmi are the p⇥ r k il feedback gain parameters and the c j , j = 1, ..,m parameters of the lyapunov function. if the bmi above is feasible, there exists a globally stabilizing feedback with the selected structure. note that (marginal) infeasibility of the bmi (eq. (26)) means only that the closed loop system is not proven to be globally asymptotically stable. however, the solution k il may still guarantee local stability, which is enough in several cases. controller design using bilinear matrix inequalities a bmi is a diagonal block composed of q matrix inequalities of the following form gi 0 + px k=1 x k gi k + px k=1 px j=1 x k x j ki kj  0, i = 1, . . . , q (27) 55 where x 2 rp is the decision variable to be determined and gi k , k = 0, . . . , p, i = 1, . . . , q and ki kj , k, j = 1, . . . , p, i = 1, . . . , q are symmetric, quadratic matrices. the main properties of bmis are that they are nonconvex in x (which makes their solution numerically much more complicated than that of linear matrix inequalities), and their solution is np-hard [10], so the size of the tractable problems is limited. however, there exist practically applicable and effective algorithms for bmi solution [20], [21], or [22]. in matlab environment the tomlab/penbmi solver [23] can be used effectively to solve bmis. quasi-polynomial servo control as in the linear case, the problem statement of the servo, or reference tracking control is as follows. consider a nonlinear system in the form of eq. (20) and an external reference signal r which is to be followed by the system output ⌘. it is possible to define the tracking error signal (eq. (28)) whose time derivative gives the tracking error dynamics which should be stabilized together with the system (eq. (20)). z(t) = z t t0 r(⌧)� ⌘(⌧)d⌧. (28) it is easy to see that the differential equation of the tracking error has the form (eq. (29)). ż(t) = r(t)� ⌘(t), (29) u(t) = �k r z t 0 r(⌧)� ⌘(⌧)d⌧ �k y(t). if the output equation is also in qp form, then the extended closed loop qp system can be written up in lotka-volterra form similar to (eq. (25)) and the bmi for the globally stabilizing controller design can be formulated. quasi-polynomial control of the synchronous generator quasi-polynomial form of the synchronous generator the bilinear nature of the state equations (eq. (8)) enables us to directly apply the qp mechanism without qp embedding [16]. the system has the following set of quasimonomials: ⇢ 1 i d , i f i d , i q ! i d , 1 i f , i d i f , i q ! i f , 1 i q , i d ! i q , i f ! i q , 1 ! , i f i q ! � the qp coefficient matrices of the input-affine system (eq. (20)) are a0 = 2 66666666666666664 �2.323 0 0 0 0.0004 0 0 0 0.5893 0 0 0 �3.4883 0 0 0 0 0.8 0 0 0 0.0006 0 0 0 �6.6918 0 0 0 1.2022 0 0 0 0 �0.7861 0 0 0 3.5888 0 0 0 2.6489 0 3 77777777777777775 t a1 = 2 66666666666666664 0.5893 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 �6.6918 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 3 77777777777777775 t a2 = 2 66666666666666664 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.0006 3 77777777777777775 t feedback structure there is a degree of freedom in the selection of the stabilizing feedback structure. a wise choice of the feedback structure does not increase the number of monomials of the closed loop system. this way the size of the bmi to be solved remains tractable. in our case, a linear full state feedback is applied, i.e. the feedback law is in the form v f = k r1 r t 0 r(⌧)� p out (⌧)d⌧+ +k1 id + k2 if + k3 iq + k4 ! t mech = k r2 r t 0 r(⌧)� p out (⌧)d⌧+ +k5 id + k6 if + k7 iq + k8 !. (30) controller design and verification via simulation using the feedback law (eq. (30)), the closed loop system is also in qp form with 18 quasi-monomials: ⇢ 1 i d , i f i d , i q i d , ! i d , i q ! i d , 1 i f , i d i f , i q i f , ! i f , i q ! i f , 1 i q , i d ! i q , 56 0 10 20 30 40 50 60 70 80 90 100 0 0.5 1 1.5 time pout(t) r(t) figure 2: the controlled output p out of the system (solid line) together with the reference input r (dashed line). i f ! i q , i d ! , i f ! , i q ! , i d i q ! , i f i q ! � . due to the lack of space, the 19⇥19 (the extra dimension comes from the tracking error dynamics) matrices of the bmi and the closed loop lotka-volterra system are not listed here. the bmi (eq. (26)) for the globally stabilizing feedback design case suffers from rank deficiency and the available bmi solvers stop with marginal infeasibility, which means that global stability cannot be proven using the feedback law (eq. (30)). however, simulation results indicate, that the system is locally stable with the controller gain parameters yielded by the globally stabilizing bmi (eq. (26)) formulated for the closed loop generator model extended with the tracking error dynamics. k r1 = 1.0000 k r2 = �0.0002 k1 = �0.2932 k2 = �1.6880 k3 = �1.9609 k4 = 0.2259 k5 = 0.0001 k6 = 0.0000 k7 = �0.0001 k8 = 0.1450 the simulated behavior of the controlled generator can be seen in fig. 2 where the controlled output of the system (i.e. p out ) is shown together with the reference input (r). both of them are dimensionless. the tracking properties of the system are acceptable, moreover, its disturbance rejection is also good (at time 40, a step-like change has been applied to the disturbance input v d ). the simulation has been performed in matlab/simulink environment [24]. conclusions a novel servo control design technique based on the qp representation has been formulated in this work. as an example, an active power tracking controller has been designed for a synchronous generator model. the tracking properties of the closed loop system are satisfactory. further work includes the extension of the method for vector reference signals and use the degree of freedom lying in the bmi problem for formulating a robust/optimal controller design problem. another direction of future research is to apply graph theoretical techniques for controller structure selection that applies the underlying connections between qp systems and chemical reaction networks [25]. acknowledgments this research was supported by the european union and the state of hungary, co-financed by the european social fund in the framework of támop 4.2.4. a/2-11-1-20120001 ’national excellence program’. references [1] verma, k., niazi, k. a coherency based generator rescheduling for preventive control of transient stability in power systems, international journal of electrical power & energy systems, 2013, 45, 10– 18 [2] banavar, r., deshpande, u. robust controller design for a nuclear power plant using h-infinity optimization, in proc. of the 35th conference on decision and control, kobe, japan [3] na, m., jung, d., shin, s., jang, j., lee, k., lee, y.: a model predictive controller for loadfollowing operation of pwr reactors, ieee transactions on nuclear science, 2005, 52,1009–1020 [4] anderson, p., fouad, a. power-systemscontrol and stability (the iowa state university press, ames iowa, usa), 1977 [5] de mello, f., concordia, c. concepts of synchronous machine stability as affected by excitation control, ieee transactions on power apparatus and systems, 1969, pas-88(4), 316–329 [6] muyeen, s., al-durra, a., tamura, j. variable speed wind turbine generator system with current controlled voltage source inverter, energy convers manage, 2011, 52 [7] hernández-bermejo, b., fairén, v. nonpolynomial vector fields under the lotka-volterra normal form, physics letters a, 1995, 206, 31–37 [8] figueiredo, a., gleria, i. m., rocha, t. m. boundedness of solutions and lyapunov functions in quasi-polynomial systems, physics letters a, 2000, 268, 335–341 [9] magyar, a., szederkényi, g., hangos, k. m. globally stabilizing feedback control of process systems in generalized lotka-volterra form, journal of process control, 2008, 18(1), 80–91 [10] vanantwerp, j., braatz, r. a tutorial on linear and bilinear matrix inequalities, journal of process control, 2000, 10, 363–385 [11] tong, c.-f. , zhang, h., sun, y.-x. controller design for polynomial nonlinear systems 57 with affine uncertain parameters, acta automatica sinica, 2007, 33(12), 1321–1325 [12] fodor, a., magyar, a., hangos, k. m. control-oriented modeling of the energyproduction of a synchronous generator in a nuclear power plant, energy, 2012, 39, 135–145 [13] fodor, a., magyar, a., hangos, k. m. parameter sensitivity analysis of a synchronous generator, hungarian journal of industrial chemistry, 2010, 38(1), 21–26 [14] fodor, a., magyar, a., hangos, k. dynamic modeling and model analysis of a large industrial synchronous generator, in applied electronics, pilsen, czech republic, 91–96 [15] hernández-bermejo, b., fairén, v., brenig, l. algebraic recasting of nonlinear odes into universal formats, j. phys. a, math. gen., 1998, 31, 2415– 2430 [16] hernández-bermejo, b., fairén, v. lotkavolterra representation of general nonlinear systems, math. biosci., 1997, 140, 1–32 [17] hernández-bermejo, b. stability conditions and lyapunov functions for quasi-polynomial systems, applied mathematics letters, 2002, 15, 25– 28 [18] boyd, s., ghaoui, l. e. , feron, e., balakrishnan, v. linear matrix inequalities in system and control theory (siam, philadelphia) 1994 [19] scherer, c., weiland, c. linear matrix inequalities in control (disc, http://www.er.ele.tue.nl/sweiland/lmi.pdf), 2000 [20] kocvara, m., stingl, m. a code for convex nonlinear and semidefinite programming, optimization methods and software, 2003, 8, 317–333 [21] tuan, h., apkarian, p., nakashima, y. a new lagrangian dual global optimization algorithm for solving bilinear matrix inequalities, international journal of robust and nonlinear control, 2000, 10, 561–578 [22] cao, y.-y., lam, j., sun, y.-x. static output feedback stabilization: an ilmi approach, automatica, 1998, 12, 1641–1645 [23] kocvara, m., stingl, m. tomlab/penbmi solver (matlab toolbox) 2005, penopt gbr. [24] i. the mathworks: matlab environment 2007) copyright 1984-2007 the mathworks, inc. http://www.mathworks.com [25] hangos, k. m., szederkényi, g. the underlying linear dynamics of some positive polynomial systems, physics letters a, 2012, 376(45), 3129– 3134 advertise upcoming meetings, conferences, and workshops; make public announcements; introduce your research laboratory; a new product or a service in the hungarian journal of industry and chemistry please contact us if interested! editorial office: university of pannonia p.o. box 158, veszprém h-8201 (hungary) tel.: +36 (88) 624-298, e-mail: hjic@almos.uni-pannon.hu; web: hjic.mk.uni-pannon.hu felelős szerkesztő: szilágyi róbert, phd kiadja: pannon egyetem, 8200 veszprém, egyetem u. 10. levélcím: h-8201 veszprém, postafiók 158, tel.: (88) 624-000 hungarian journal of industry and chemistry veszprém vol. 41(1) pp. 59-64 (2013) a structured model-based diagnosis method for discrete dynamic processes using event sequences attila tóth b1, katalin m. hangos1,2, and ágnes werner-stark1 1department of electrical engineering and information systems, university of pannonia, veszprém h-8200, hungary 2computer and automation research institute, budapest, hungary b e-mail: atezs82@gmail.com a novel model-based fault detection and diagnosis method is proposed that is based on following event sequences measured in a discrete dynamic process. the model of the nominal and faulty operation modes is given in the form of event sequences, that are decomposed according to the components and sub-components present in the process system. the faulty event sequences are defined using extended procedure hazid tables. a diagnostic algorithm is also presented that uses a component-wise decomposed form of the event sequences. the operation of the algorithm is illustrated on a simple example of a process system consisting of three similar tanks. keywords: process monitoring, diagnosis, discrete event systems, qualitative models introduction fault prevention and mitigation in the field of process system management is a task of crucial importance in avoiding serious accidents. thus, numerous hazard identification (hazid) techniques have been developed in the past decades to ensure the safe operation of process systems and to relieve effects of faults (see [1] for a broad presentation of the field). among these techniques, the most important methodologies involve the functiondriven hazop (hazard and operability, see [2]) analysis and the component-driven fmea (fault mode and effects analysis). there have been results in the past decade for automating the creation of hazop analysis ([3] with a concrete application described in [4]). blending the component-driven and function-driven analyses also resulted in a novel hazard identification approach described in [5]. although the information collected in the hazop and fmea studies serve the purpose of hazard identification, these studies can be the basis of diagnostic procedures, too. a model-based diagnostic method based on hazop and fmea information is reported in [6]. it is important to note that the above techniques concentrate on the static case when the deviation from a normal steady-state behaviour is of importance. therefore, the transient case when the plant is controlled by an operational procedure is not addressed in these results. a recent study [7] tries to deal with the diagnostic task by using a specially constructed p-hazid analysis and a diagnostic algorithm. in this paper, this diagnostic idea is extended to be able to handle more complex diagnostic tasks by taking advantage of a possible decomposition of typical process systems along their similar components. basic notions in a complex system the full dynamic model that describes its behaviour under normal and faulty operation models is rarely available, therefore one should base the diagnosis on qualitative information both in terms of the dynamic models and in the measured data. here we briefly summarize the basic notions for qualitative model based diagnosis. qualitative range spaces current values of continuous measurable outputs in process systems can be described using a properly selected qualitative range space. for example, to describe the value of a level sensor in a tank, the following range space can be used: qe = {e�, 0, l,n,h, e+}. (1) here, 0 means an empty tank, l, n and h means low, normal and high fluid level, respectively, while e� and e+ refer to unmeasurably low and high fluid levels (this might mean a failure in the level sensor itself). this range space will be used to describe system outputs during operation. input-output event sequences operational procedures in process systems are detailed list of instructions for the plant operator personnel to 60 perform certain operations on the plant. procedures can be formally described using finite input-output event sequences where a single event describes a change in either the inputs or the outputs of the system at a specific time instant. therefore the syntax of a single input-output event (at time instant t) is the following eventt = (t; input values; output values). the input in an event always refers to a state of an actuator component in the process system (e.g., in the case of a valve it can be open (op) or closed (cl)). on the other hand, the output in an event refers to a value of an output of the process system in the qualitative range space using the qualitative set defined in eq. (1). sequences formed from these events are called traces and defined as t (t1, tn) = eventt1 , ..., eventtn . separate events in a trace contain the same inputs and outputs. note that the discrete event time instances ti are abbreviated by their indexes i in the description, i.e. 2 stands for t2. examples of single events for a two-input single output case include (1; cl, op;n) , (2; cl, op; l) where at time instances t1 and t2 the two valve inputs are held closed and open, respectively, while the level decreases form its normal value to the low level. the trace formed form the above two consecutive events is written as t (1, 2) = ((1; cl, op;n), (2; cl, op; l)) . for every operational procedure there exists a trace (called the nominal trace) which describes its behaviour under fault-free conditions. the diagnostic method compares this trace to other traces which may have been executed under faulty conditions (called characteristic traces), and the differences (called deviations) are later used to find possible malfunctions of components in the system. deviations nominal and characteristic traces can be compared by comparing their corresponding event fragments. the difference between two corresponding event fragments is described by a deviation. deviations are formed from a deviation guideword and the nominal event from which the corresponding characteristic trace event is deviating from. the following deviation types are used during diagnosis: • never-happened: when the particular event never happened in the characteristic trace. • later: when the event happened in the characteristic trace, but at a later time instant. • earlier: when the event happened in the characteristic trace, but at an earlier time instant. • greater: when a particular output’s qualitative value was higher in the characteristic event than that of the nominal trace. • smaller: when a particular output’s qualitative value was lower in the characteristic event than that of the nominal trace. for the detailed description of the greater and smaller qualitative relations, please refer to [7]. procedure hazid as a combination and extension of the widely used fmea and hazop analyses (for details, refer to [7] or [1], and in particular to [5]), the procedure hazid (abbreviated as p-hazid) analysis can be used for fault diagnosis during operational procedures in a given process system. the result of this p-hazid analysis is given in the form of a spreadsheet and it consists of deviations together with their implications and possible (root) causes. a cause is considered to be a root cause if it is a nonmeasurable failure mode of a system component (which is an elementary part of the system). for example, a leak on a tank is considered as a root cause. a simple example of a p-hazid table can be found in table 1. using the initial set of differences (deviations) between the characteristic trace and the nominal trace, the set of possible root causes can be found using simple reasoning. for details, refer to ref. [7]. the diagnostic algorithm uses this technique first to find possible p-hazid row(s) to start from (using the set of initial deviations). then, following the deviation chains defined by these rows, the algorithm proceeds towards a possible root cause by traversing new rows based on the initial set of deviations. using this procedure, it may end up at a root cause or at a row with deviations from which it cannot proceed forward, because they are not contained in the initial set of deviations. the algorithm assumes that the root causes are static and they happened before the execution of the procedure began. component based diagnosis it is widely known that complex systems can often be decomposed in a hierarchical way using simple nondividable elements that are called components. the connection of these components is usually specified in terms of a graph called flowsheet. such a decomposition can be used effectively for the operation of a reasoning-based diagnostic algorithm. component based structural decomposition the above mentioned fault diagnosis based on the phazid analysis is only developed for process systems 61 table 1: a simple example of a p-hazid table. inputs: op=open, cl=closed. outputs: 0=no, l=low, n=normal. deviations: nh=never-happened, lat=later, ear=eariler, sml=smaller and gre=greater. faults: tank-leak is the leak of the tank and pos-bias is the positive bias failure of the tank level sensor. cause deviation implication tank-leak nh(2;op,cl;l) nh(3;op,cl;n) nh(2;op,cl;l) nh(3;op,cl;n) nh(4;op,op;n) tank-leak sml(2;op,cl;l) sml(3;op,cl;n) sml(2;op,cl;l) sml(3;op,cl;n) sml(4;op,op;n) pos-bias gre(1;op,cl;0) gre(2;op,cl;l) gre(1;op,cl;0) gre(2;op,cl;l) gre(3;op,cl;n) gre(2;op,cl;l) gre(3;op,cl;n) nh(4;op,op;n) pos-bias nh(1;op,cl;0) ear(2;op,cl;l) nh(1;op,cl;0) ear(2;op,cl;l) ear(3;op,cl;n) consisting of different individual components in [7]; the possible redundancy of such systems (e.g. multiple components of the same characteristics) were not taken into account. however, complex process systems in practice can be decomposed into a connected network of more simple components. for example, the process system in fig. 1 can be decomposed into three smaller similar components each formed by an input and an output valve and a tank. when developing the decomposed form of a process system it can happen that some elements are part of multiple subsystems as in the case of valves vb and vc in fig. 1. these elements are called boundary components, and are assumed to be error-free during the diagnosis. traces affecting different components can also be decomposed into a chain of trace fragments each referring to a single component of the trace. events in such a trace fragment have only a subset of inputs and outputs of the united trace (only the inputs and outputs of the particular component that is present in them). fragments also have information about the next trace fragment (called the next trace), and there is a starting condition (an event) that is associated with them to help the diagnosis. along with the trace fragment, each component has its own associated p-hazid spreadsheet. the component based diagnostic algorithm applying the diagnostic approach described in [7] on a decomposed process system, the components can be diagnosed separately against faults, treating them as a whole system during diagnosis. after the separate diagnosis, the root causes can be collected and the resulting set of root causes yields to the set of root causes in the united system. using the component decomposition, the size of the hazid information required can be made lower in cases when similar connected subsystems form the process system to be diagnosed. on the other hand, va vb vc vd tc tb ta ta level tb level tc level figure 1: process system consisting of 3 similar tanks system-level deviations need to be converted into component deviations by aligning their time and reducing the inputs and outputs in their associated events to componentlevel inputs and outputs. the diagnosis is then performed by comparing the whole nominal trace with the characteristic trace, and then distributing the deviations (differences) among the components. before distributing, time alignment and reduction of input and output states to component level are performed (including the component’s boundary elements). after the distribution, component-level diagnosis may begin to explore possible (root) causes on the component-level. the diagnosis proceeds along the flow direction by starting from the first component, takes the deviations, generates the set of possible root causes from them, and then tries to proceed to the next component by checking the starting condition of the next trace fragment if there is any. if the start condition is fulfilled, the diagnosis continues, otherwise it halts. for example, in the case of fig. 1 the second fragment might have a start condition containing a statement about the minimum level of fluid in tank ta, and in the case of the congestion of valve va no fluid is coming into a system, therefore, tank ta is not even filling up to the specified minimum level. in this case the diagnosis stops. the result of the diagnostic algorithm is always the union of identified and non-identified root causes created by the consecutive diagnostic algorithm that runs on the components of the consequent nominal trace fragments. for reference, the whole diagnostic algorithm is presented as a pseudo-code in algorithm 1. the algorithm collects all root causes (sets inc and irc) given a component decomposition, a starting component, and a possibly faulty characteristic trace. case study in the case study the diagnosis procedure for the simple process system in fig. 1 containing three sequentially connected tanks is used. the measured output of the tanks 62 algorithm 1 component-based reasoning procedure 1: inc {;} 2: irc {;} 3: actualcomponent startcomponent 4: continue true 5: shift 0 6: while continue do 7: dev generatedeviations(actualcomponent, chrtrace, shift) 8: fdp collectfinaldeviationpairs(dev) 9: for all pair 2 fdp do 10: startdeviation proj1(pair) 11: startimplication proj2(pair) 12: reason(startdeviation, startimplication, actualcomponent.phazid) 13: end for 14: if actualcomponent has successive component and its start condition evaluates to true then 15: shift length(actualcomponent.trace)� 1 + shift 16: actualcomponent getcomponent(actualcomponent.successivecomponent) 17: else 18: continue false 19: end if 20: end while 21: function generatedeviations(component, chrtrace, shift) 22: dev {;} 23: nomtrace component.trace 24: reducedtrace trimtrace(chrtrace, shift, shift+ component.trace.length) 25: locchrtrace converttocomponentlevel(reducedtrace) 26: for t := 1 to length(nomtrace) do 27: for all deviation d of locchrtrace from nomtrace at time t do 28: dev dev s (d) 29: end for 30: end for 31: return dev 32: end function 33: procedure reason(deviation, implication, phazid) 34: if 9r 2 rows(phazid), deviation = devphazid(r), implication = impphazid(r) then 35: for all {r, devphazid(r) = deviation and impphazid(r) = implication} do 36: if causephazid(r) 2 rc then 37: irc irc s causephazid(r) 38: return 39: else if causephazid(r) 2 dev and causephazid(r) � devphazid(r) in dev then 40: reason(causephazid(r), devphazid(r), phazid) 41: else 42: inc inc s causephazid(r) 43: return 44: end if 45: end for 46: else 47: inc inc s causephazid(r) 48: return 49: end if 50: end procedure 63 table 2: tank fill operational procedure. time input values output values va vb vc vd ta tb tc 1 op cl cl cl 0 0 0 2 op cl cl cl l 0 0 3 op op cl cl n 0 0 4 op op cl cl n l 0 5 op op op cl n n 0 6 op op op cl n n l 7 op op op op n n n table 3: normal fill in a single tank with no faults. input valve output valve tank level op cl 0 op cl l op op n is the tank level that takes its values from qe in eq. (1), and the input variables are the valve positions (open (op) or closed (cl)). components, operational procedure, and nominal trace every tank may contain no fluid (the tank level is equal to no (0)), may be low on fluid (level value is low (l)), or might have normal fluid level (level value is normal (n)). in every time instant the level increases by one qualitative magnitude (i.e. from no to low or from low to normal) if fluid is coming through the input valve but the output valve is closed. due to the same size of the valves the effect of fluid flow out of the system is similar, but in the opposite direction (from normal to low or from low to no). the valve positions (open (op) or closed (cl)) can be changed by the operator; they are considered as inputs of the system. leak in the tank is assumed to be equal to the size of an open valve (i.e. a quite substantial leak). the considered operational procedure is the initial filling of all the three tanks with fluid (the fill operational procedure in short), and is described in detail in table 2. the process system can be decomposed into three components, therefore the fill operational procedure can also be partitioned into three identical procedure fragments along the component boundaries (the vb and vc valves). the fragment abstracted from the three identical trace fragments associated to the three tanks can be observed in table 3. it has only the subset of inputs and outputs which are directly related to the particular tank component the input and output valve and the tank level. the corresponding component p-hazid table can be found in table 4 with some of the component faults and deviations associated to them. instances of this p-hazid table are used in the case of all three tanks during diagnosis. table 4: p-hazid table of a single tank component with two valves for a reference trace of table 3. faults: tank-leak is leak of the tank, pos-bias is the positive bias fault of the level sensor and neg-bias is the negative bias failure of the level sensor. cause deviation implication tank-leak nh(2;op,cl;l) nh(3;op,op;n) tank-leak sml(2;op,cl,l) sml(3;op,op;n) neg-bias lat(1;op,cl;0) nh(2;op,cl;l) lat(1;op,cl;0) nh(2;op,cl;l) nh(3;op,op;n) neg-bias sml(1;op,cl;0) sml(2;op,cl;l) sml(1;op,cl;0) sml(2;op,cl;l) sml(3;op,op;n) pos-bias nh(1;op,cl;0) ear(2;op,cl;l) nh(1;op,cl;0) ear(2;op,cl;l) nh(3;op,op;n) pos-bias gre(1;op,cl;0) gre(2;op,cl;l) gre(1;op,cl;0) gre(2;op,cl;l) gre(3;op,op;n) table 5: tank fill operational procedure with a leak in the second tank tb. the leak caused two different events in the operational procedure related to tb (in bold), these differences resulted in the four deviations the diagnosis could start from. time input values output values va vb vc vd ta tb tc 1 op cl cl cl 0 0 0 2 op cl cl cl l 0 0 3 op op cl cl n 0 0 4 op op cl cl n 0 0 5 op op op cl n 0 0 6 op op op cl n 0 0 7 op op op op n 0 0 the operation of the diagnostic algorithm the operation of the diagnostic algorithm is illustrated with the case when a rupture of the second tank is present as a root case (fault). a characteristic trace with the leak of the second tank can be seen in table 5. the size of the leak is assumed to be larger or equal to the size of an outbound pipe, therefore, the tank cannot fill up and no fluid can flow to the third tank tc. the starting condition of the tb and tc tank components is the appropriate “normal” level in the preceding tank. in that way it is ensured that diagnosis is done on the operational components only. the diagnosis of this faulty scenario begins by starting with the first tank component ta. there are no differences (and therefore no deviations) regarding this component. the start condition of the second component is fulfilled, therefore, the diagnosis moves towards the next component tb. however, in the case of tb the following deviations are found after comparing the nominal and characteristic traces (due to that two consequent events did not hap64 pened, instead, two events happened with lower output values at time instant 4 and 5 in the operational procedure): • never-happened(4;open,closed;low) • never-happened(5;open,open;normal) • smaller(4;open,closed;low) • smaller(5;open,open;normal) the time instant of the deviations are shifted back by 2 units because the second component’s first event happens at the third system-level time instant. after that, the diagnosis is initiated on the hazid table. searching for the already found deviations and connecting them to possible root causes (as in the case of the original diagnostic idea in [7]) the leak of the second tank can be found. because of the lack of fluid in the second tank, the start condition of the third component is not fulfilled, therefore, the diagnostic process halts at this step resulting in a single possible root cause being the tankleak. conclusions a novel component based extension of the single component diagnostic algorithm presented in [7] is described in this paper. using the extension, the domain of application can be extended to more complex composite process systems. driven by the decomposition of the overall system into components, the p-hazid tables used for diagnosis are processed at component level by the diagnostic algorithm. the extended method is efficient in the cases when the overall process system consists of similar small components. the component-based diagnostic procedure was described on a formal level, along with its proposed pseudocode. a case study for a process system of multiple components and a simple failure was also provided. the following improvements are planned to extend the component-based diagnostic approach: • the procedure is based on the assumption that the boundary elements between different components are free of failures. as a future work, this limitation might be removed by using a higher level reasoning above the components (as in the form of a systemlevel hazid table, for example). • at the moment, the algorithm is only working for already coded static event information in order to find faults in the system. diagnosis would be more valuable if events could be processed dynamically, thus the diagnostic procedure could be executed realtime along with the operational procedures. • diagnosis would be more accurate if the derivatives of internal states (e.g. the derivative of the tank level) were present in the events. acknowledgements the research was supported by the hungarian research fund through grant k83440. we acknowledge the financial support of the hungarian state and the european union under the tamop-4.2.2.a-11/1/konv2012-0072. references [1] cameron, i. t., raman, r. process systems risk management. vol. 6 of process systems engineering (elsevier academic press, san diego, ca) 2005 [2] as iec 61882-2003: hazard and operability studies (hazop studies) application guide [3] venkatasubramanian, v., rengaswamy, r., yin, k., kavuri, s. n. a review of process fault detection and diagnosis part i: qualitative modelbased methods, computers and chemical engineering, 2003, 27(3), 293–311 [4] venkatasubramanian, v., zhao, j. s., viswanathan, s. intelligent systems for hazop analysis of complex process plants, computers and chemical engineering, 2000, 24(9-10), 2291–2302 [5] seligmann, b. j., németh, e., hangos, k. m., cameron, i. t. a blended hazard identification methodology to support process diagnosis, journal of loss prevention in the process industries, 2012, 25 , 746–759 [6] németh, e., lakner, r., cameron, i., hangos, k. m. fault diagnosis based on hazard identification results, in preprints of the 7th ifac symposium on fault detection, supervision and safety of technical processes, barcelona, spain, june 30 july 3, pp. 1515–1520 [7] tóth, a., hangos, k. m. , werner-stark, a. hazid information based operational procedure diagnosis method, in 12th international phd workshop on systems and control, veszprém, 2012. aug. 27 (a. magyar, ed.), isbn 978-615-5044-71-7 (university of pannonia, veszprem), pp. 1–6 (on cd) hungarian journal of industry and chemistry veszprém vol. 41(1) pp. 65-75 (2013) role of steady state data reconciliation in process model development barbara farsangb1, sándor németh1, and jános abonyi1 1university of pannonia, department of process engineering, h-8200 veszprém, egyetem street 10., hungary be-mail: farsangb@fmt.uni-pannon.hu in chemical and hydrocarbon industry operational efficiency is improved by model-based solutions. historical process data plays an important role in the identification and verification of models utilized by these tools. since most of the used information are measured values, they are affected by errors influencing the quality of these models. data reconciliaton aims the reduction of random errors to enhance the quality of data used for model development resulting in more reliable process simulators. this concept is applied to the development and validation of the complex process model and simulator of an industrial hydrogenation system. the results show the applicability of the proposed scheme in industrial environment. keywords: data reconciliation; flowsheeting simulator; validation; balance equation; industrial hydrogenation system introduction in recent years, development of industrial technologies has been determined by the proliferation of computing and information technology. today’s technologies are characterized by widespread application of process engineering tools. the success of these tasks depends on the accuracy of data and applied models [1]. thanks to the evolution of information technology, on-line and historical process data — coming from chemical process systems — are available. the collected data provide the opportunity for engineers to better understand the processes, anomalies, and malfunctions [2]. monitoring of process variables allows us to ensure the consistent product quality. collected data can also be used for the development and validation of process simulators. however, measurements are always affected by errors during the measurement, processing and transmission of the measured signal. errors (gross, random, bias) in measured data affect the quality of process models and can lead to significant decrease in plant performance. estimation of true conditions of process states is important to achieve optimal process monitoring, control and optimization. therefore, several methods have been developed to minimize measurement errors thereby enhancing the reliability, accuracy and precision of data. first, analogue and digital filters were used to reduce the effect of high frequency noise [3]. gross errors were detected with various data validation methods, which include checking whether the measured data and the rate at which it is changing is within predefined operational limits. nowadays, smart sensors are used for determine whether there is any hardware problem or the measured data are appropriate. new methods were statistical quality control tests that are applied to each measured variable separately. although these methods improve the reliability and accuracy of the measured data, they do not ensure consistency of the data with respect to the inter-relationships between different process variables. therefore new methods – data reconciliation and gross error detection – are developed in chemical engineering [4]. the main difference between data reconciliation and other filtering methods is that data reconciliation uses process model constraints and that the results satisfy constraints and balance equations. data reconciliation techniques can be applied to reduce random errors of measurements, while the other techniques mentioned above do not. gross error detection can be used for eliminate systematic errors so simultaneous data reconciliation and gross error detection have emerged as a key of online optimization [5] (see fig. 1). data reconciliation techniques take minimal corrections of the measured variables to satisfy a set of model constraints. based on the difference between the measured and reconciled data, the following questions can be answered. can we consider a related set of measurements acceptable based on our previous knowledge of the system? are the measurements consistent? if not, what can be the source of the error? based on the available measurements and a prior knowledge, what is the most likely state of the system? answers to these questions are important in development of technology (e.g., monitoring, optimization, simulation, control, instrument maintenance). using this technique, we can verify the acceptability of measurements, improve the accuracy of measurements, estimate model parameters and unmeasured variables, and it can be used 66 applications s ys te m s ta tu s id en tif ic at io n r e a l ti m e d a ta b a se reconciliation gross error detection variable classification steady state identification data filtration detection of abnormalities figure 1: general methodology for on-line data correction [6] for fault detection. in order to ensure the consistency of measured process variables, models are used in data reconciliation. during data reconciliation, information is obtained from both measurements and process models. depending on the types of the models, data reconciliation techniques can be separated into two different problems: steady state and dynamic (see fig. 2). in the case of steady state data reconciliation, model constraints are algebraic equations. if we are dealing with dynamic processes, differential equations are used as model constraints. in the case of linear data reconciliation, model constraints are defined by linear equations. the simplest data reconciliation technique is the steady state linear method that can describe, e.g., the mass balance of technology. moreover, most chemical processes have nonlinear characteristics and constraints are nonlinear equations; this problem can be called as nonlinear data reconciliation. the goal of the presented research is to propose a methodology to support the development and validation of complex process models and simulators based on increasing the quality of measurement data used for (kinetic) parameter identification and validation. in section literature survey, a historical background of steady data data reconciliation is briefly reviewed. the basic method of linear and nonlinear steady state data reconciliation is described in section theoretical background of steady state data reconciliation. data reconciliation cannot be used in process development only, but it is a useful tool in model improvement too. the principle of this application is introduced in section combined application of data reconciliation and flowsheeting simulator. our approach aims the reduction of random errors to enhance the quality of data using data reconciliation and flowsheeting simulator simultaneously. the method is described in subsection the developed model based data reconciliation technique. the proposed approach is illustrated based on an industrial hydrogenation system. figure 2: types of data reconciliation [7] in section case study, the analyzed technology is introduced and the applicability of the method is illustrated on the basis of the mass balance of the hydrogenation system. then, some consequences are drawn in section conclusion. literature survey kuhan and davidson presented the first study about minimizing measurement errors in chemical process industry using a data reconciliation technique in 1961 [4]. they described the steady state linear data reconciliation technique and demonstrated a general solution for mass balance of technology. this seminal paper has started a new research area in process engineering. nogita [8] and mah [9] improved a new method capable of detection of gross errors. later, mah [10] found that the base method requires a process system in steady state conditions and that the process constraints must be linear. cao and rhinehart confirmed that the methodology will be successful if process data come from steady state conditions [11]. in these cases, data reconciliation problems can be solved with standard numerical methods like sequential quadratic procedures [12] and quasi-newton algorithms [13]. a multiple gauss-jordan elimination algorithm was published by madron and veverka [14]. the classification method is based on matrix decomposition and permutation. the linear method was improved by crowe (1986) who published a new technique to solve nonlinear data reconciliation using matrix projection [15]. furthermore, bagajewicz and jiang [16] presented an improved method that is applicable for dynamics system. the developed method from prata [17] is suitable for examination of dynamic nonlinear process systems. despite of the numerous good reviews of data reconciliation techniques, industrial application of this method started only in the 1980s. there are several complex software packages supporting data 67 table 1: industrial application of data reconciliation (newer industrial scenario and publications are added to prata’s summary [18]) industrial scenario author (year) absorption refrigeration systems maradiaga et al. (2013) [19] beverage alcohol distillation plant meyer et al. (1993), nounou and bakshi (1999), schladt and hu (2007) chemical extraction plant holly et al. (1989) ethylene and ammonia plant sanchez et al. (1992), sanchez and romagnoli (1996), plácido and loureiro (1998) exxon chemical process mcbrayer et al. (1998) , soderstrom et al. (2000) gas pipeline systems bagajewicz and cabrera (2003) gases network in an iron and steel making plant yi and han (2004) hydrogen plant bussani et al. (1995), chiari (1997), sarabia et al. (2012) [20] industrial coke-oven-gas purification process faber et al. (2006) hu and shao (2006) industrial distillation column islam (1994), weiss et al. (1996), sanchez et al. (1996), bourouis et al. (1998), li et al. (2001), bhat and saraf (2004), chatterjee and saraf (2004), chen et al. (2013) [21], keller et al. (2012) [22] industrial etbe reactor domingues et al. (2012) [23] industrial furnace pierucci et al. (1996), eksteen et al. (2002) industrial hydrometallurgical plants for a gold extraction de andradelima (2006) industrial polymerization reactor vieira et al. (2003), prata et al. (2006, 2008, 2009, 2010 [24]) industrial synthesis gas for production of ammonia christiansen et al. (1997) industrial utility plant lee et al. (1998) methyl-terc-butyl-ether plant al-arfaj (2006) mineral and metallurgical plants vasebi et al(2012) [25] nuclear power reactor valdetaro (2011) [26] refinery piccolo and douglas (1996), zhang et al. (2001) sulfuric acid plant chen et al. (1998), ozyurt and pike (2004) turbine cycle of a boiling water reactor sunde and berg (2003) vinyl acetate and ketene plants dempf and list (1998) water processes martins et al. (2010) [27] 68 reconciliation (for instance sigmaïňąne, datacon, vali, inlibra). these tools have interfaces to information systems used to manage process data and have special model building functionalities that allow almost automatic building of plant-wide balance equations. nowadays, data reconciliation is widely applied in various processing industries (e.g. refining, chemical industry, metals, mining, and power industry). despite of this fact, relatively few articles deal with industrial applications (prata et al. prepared a summary in 2009 [18]; newer applications and papers are collected in table 1). stanley et al. classified variables as observable and unobservable [28]. crowe categorized the variables from another point of view: the basis of classification is the given measured variable can be calculated from other measured variables using process models or not. the names of the two classes are redundant and nonredundant measurements [29]. ali and narasimhan applied graph theory to analyse the sensor network, classify the variables, and compute the redundancy degree of each variable. they claim that not only measured variables can be redundant. those unmeasured variables that can be estimated in multiple ways are also termed as redundant [30]. theoretical background of steady state data reconciliation in this section, the basis of linear and nonlinear data reconciliation techniques are described. different values are distinguished. real values (without error) of variables are designated by diacritic caron (̌ ), measured values by tilde (̃ ), while estimated values by circumflex (̂ ). in general, optimal estimates for process variables by data reconciliation are solutions to a constrained least-squares or maximum likelihood objective function, where measurement errors are minimized with process model constraints. the steady state data reconciliation problem can be formulated as an optimization problem by minimizing j(y̌, ž) = (ỹ � y̌)t v�1 d̃ (ỹ � y̌) (1) subject to f(y̌, ž) = 0 (2) and g(y̌, ž) � 0. (3) the solution of the optimization problem is performed with the following simplifying assumptions • the measurement error is independent from the balance variables. • the expected value of measurement error is zero. • the measurement error is in a normal (gauss) distribution. • errors of measurements are independent from each other (diagonal covariance matrix). • the covariance matrix is positive definite, so its inverse matrix exists. in the following two subsections, solution methods are presented in the cases of linear and nonlinear models. linear data reconciliation in the linear case, when all variables are measured, eq. (1) means minimizing j(y̌, ž) = (ỹ � y̌)t v�1 d̃ (ỹ � y̌) subject to ay̌ = 0. (4) gauss distribution (d̃ ⇠ n � 0,vd̃ � ) is assumed, so the density function of measurement error is f ⇣ d̃ ⌘ = c · exp h �0.5 · d̃tv�1 d̃ d̃ i (5) from which it follows that f (ỹ) = c · exp h �0.5 · (ỹ � y̌)t v�1 d̃ (ỹ � y̌) i (6) and that the f̌ = ay̌ � b = 0 (7) criterion is satisfied in accordance with the balance equation. the essence of the most likely estimation: if ỹ is given and its density function is known, which ỹ ! ŷ parameter of density function will be f (function vector of equality model constraints). since the logarithm function is strictly monotonously increasing, the maximum of the logarithm of the f(y) function recording only positive values is at the same place where the maximum of the argument is. exploiting it on the above function and using the lagrange multipliers method, the result is a vector equation system with two unknowns: v�1 d̃ ŷ �at �̂ = v�1 d̃ ỹ (8) aŷ = b (9) the solution of the vector equation system is ŷ = ⇣ i�vd̃a t � avd̃a t ��1 a ⌘ ỹ + vd̃a t � avd̃a t ��1 b (10) thus, the estimation requires a matrix-vector multiplication and a vector addition. because ỹ is only the variable, in the other operations there are only constants [31]. in practice, not all streams and properties are measured in plant due to physical and economical reasons. the data reconciliation technique is suitable for estimating unmeasured variables. in this case, the optimization problem can be solved by the method of 69 projection matrix. in the first step, the incidence matrix is separated into two parts: ayy̌ + az ž = 0. (11) unmeasured flows (ž) should be eliminated by premultiplying both sides by a projection matrix, such as paz ž = 0. eq. (4) then can be rewritten as min j(y̌, ž) = (ỹ � y̌)t v�1 d̃ (ỹ � y̌) (12) subject to payy̌ = 0. (13) the projection matrix is from q-r factorization of matrix az: az = qr = [q1 q2] [r1 0] t (14) the projection matrix is the transformation of q2 matrix (p = qt 2 ). if a matrix is replaced by matrix pay in eq. (10), then ŷ = ⇣ i�vd̃(pa)t � (pa)vd̃(pa)t ��1 (pa) ⌘ ỹ + vd̃(pa)t � (pa)vd̃(pa)t ��1 b. (15) after reconciled values of measured variables are obtained, the next step is to estimate the unmeasured variables using the information from process models (eq. (11)) as ayy̌ = �az ž (16) this linear equation can be solved to get estimated values of the unmeasured variables. usually, the number of equations is greater than the number of unmeasured variables. the least-squares technique can be applied and the solution is ẑ = �(at z az) �1at z (ayŷ). (17) nonlinear data reconciliation the data reconciliation problem can be extended to nonlinear steady state models. it is necessary because processes in chemical industry cannot be described only by linear models; behaviour of chemical processes are often nonlinear. if we wish to simultaneously reconcile mass flow, composition, or temperature measurements, mass, component, or energy balances have to be included as constraints. sometimes, inequality constraints have to be defined (e.g. mass/mole fraction of components have to be in the [0:1] interval). moreover, if we take thermodynamic equilibrium relationships and complex correlations for thermodynamic and physical properties as constraints, nonlinear data reconciliation techniques have to be used. if all variables are measured, the bilinear data reconciliation problem can be reduced to a linear problem by introducing the “measured” compound flows (‘component flows’ or ‘energy flows’). therefore, solution of the nonlinear data reconciliation problem is figure 3: integrated application of statistical and white box models [32] presented on the basis of the situation when measured and unmeasured variables occur. the objective function is the same as in the previous case (eq. (1)). the difference is that constraints are nonlinear equations. this problem can be reduced to the linear case. this method is referred to as successive linearisation: nonlinear constraints can be linearised around working points using first-order taylor series. the solution of the linearisation can be written as h = byy̌ +bz ž� f(y̌i, ži). (18) the initial values are usually the raw values. after linearisation the procedures of data reconciliation is described in subsection linear data reconciliation (qr factorization, reconciliation of measured values, then estimation of unmeasured variables). if the reconciled and initial values are far from each other, new iteration begins. the initial value will be the result of the previous iteration. different criteria can be defined: number of iteration or ||ŷn � ŷn�1|| is smaller than the specified tolerance values. successive linearisation is a relatively simple and fast solution, but variable bounds cannot be handled with this method. another option to solve nonlinear data reconciliation problem is using nonlinear programming (nlp) techniques that can estimate measured and unmeasured variables simultaneously. sequential quadratic programming (sqp) and generalized reduced gradient (grg) are usual techniques in handling nonlinear problems. these methods are more computationally demanding, but they are numerically more robust [33]. 70 figure 4: iterative model development combined application of data reconciliation and flowsheeting simulator mathematical models describe the connection between the relevant properties of the analyzed phenomena, process, or activities. in the case of complex chemical processes, mathematical models usually contain differential equations whose solution is not always possible analytically. the process simulator (it is often applied to improve complex industrial processes) contains models of the equipments so their mathematical description is unnecessary for the users. in addition, it includes different thermodynamic models and component databases. the flowsheeting simulator can be defined as “use of a computer program to quantitatively model characteristic equations of a chemical process” [34]. the simulator is used in batch processing, integrated process engineering (for example, economic analysis and supply chain forecast, supervisory process control, on-line modeling and optimization, safety and reliability analysis), and process synthesis and design (for instance, heat integration, conceptual design). however, lots of information are needed from technology for the simulator to describe the real process exactly. many of the needed data are measured (e.g., flow, composition, temperature, pressure). if the input of the simulator is faulty, the simulator cannot give reliable results. a new direction is the combination of simulators and data based statistical models that can handle random and gross errors [23, 35]. the structure of these hybrid models are shown in fig. 3. • in the first case, the statistical model is the input of the physical model in the form of differential or algebraic equations or a complex flowsheeting simulator. in this case, the statistical model is used to estimate parameters and phenomena that are figure 5: options of data processing in flowsheeting simulator difficult to model. • combination 2 shows the case when outputs of the physical model are transformed by a statistical model. • in the third option, the difference between measured and calculated variables are the inputs of the statistical model used for correction. model-based data reconciliation techniques are similar to the third approach. using data reconciliation technique random errors can be filtered. when accurate data are available, the flowsheeting simulator gives more reliable results that make further development of models possible. this means that data reconciliation allows us to check the reliability of these measurements [36] and reconsolidated data can be used to build accurate models. the developed model based data reconciliation technique our goal is to design an expert system that can be used to check the acceptability of measurements and improve the flowsheeting simulator of technology. the proposed method is based on model-based data reconciliation techniques. using data reconciliation, faulty measurements can be found. random errors can be filtered using discrete fourier transform. the frequency of the noise is much higher than the frequency of basic process so the discrete fourier transform gives a graphical view about the differences between the basic process and the noise. thus, the filtration of the frequency can be determined so the noise can be separated from the basic process. if the amplitude of the noise is known, the standard deviation can be estimated. thereby, input of simulator is error-free, so systematic model mismatch can be recognized and the tuning of the model can be initiated. data reconciliation requires an accurate model whose parameters require reconciled process data. in th case of an efficient iterative procedure, a properly working simulator can be developed (see fig. 4). since the simulator is able to process historical measured data, the difference between the theoretically achievable values and the measured outputs can give useful information (see fig. 5). four different output 71 figure 6: flowsheet diagram of the c3 hydrogenation system values can be compared in the case of the same variable. measured output values are known. if all necessary information is available for data reconciliation, we get the reconciled output value. in addition, if process model is prepared in the flowsheeting simulator, we have two options for analysis: the input of the simulator can be the measured or the reconciled value. the difference between outputs can be used for two purposes. if the difference is insignificant, the measured data is acceptable and measuring instruments operate properly; calibration is not necessary. moreover, it helps in the development of the flowsheeting simulator. if the calculated results with reconciled input are far from the reconciled output, the simulator do not describe the real process properly; maybe a parameter is not accurate or it needs structural change. the proposed method is illustrated on the basis of an industrial hydrogenation system. the case study shows examples for both cases; when the difference indicates the conformity of measurements and when it warns that some model parameters are incorrect. case study the tisza chemical group plc. (tvk) is the largest petrochemical company of hungary where polymer raw materials (ethylene, propylene, butylenes, etc.) are produced by steam cracking of naphtha or gasoline. at high temperature, numerous free radical reactions occur. cracked gas includes light components that are produced in larger amounts, for example, methane, ethane, ethylene, acetylene, propane, propylene, methyl-acetylene, propadiene, n-butane, isobutane, 1,3-butadiene, etc. some of them are undesirable, because they poison the catalysts for polymerization reactions (e.g. acetylene, methyl-acetylene, propadiene). another problem is that separation of these components is difficult from the main products by distillation. due to these problems, undesirable hydrocarbons are hydrogenated. hydrogenation process of methylacetylene and propadiene is presented in this case study (see fig. 6). the c3-selective hydrogenation process transforms methyl-acetylene and propadiene to propylene by catalytic reaction avoiding the transformation of propylene to propane. the methyl-acetylene and propadiene content of hydrogenated c3 fraction should be less than 1000 ppm. the concentration of the main components (methyl-acetylene, propane) is measured by online analysers (a1, a2 and a3) and there are two places where sample is taken twice a day for laboratory analysis (l1 and l3). hydrogen and liquid olefin stream are fed to the reactor where chemical reactions take place. outlet stream of the reactor is cooled by water so the gaseous c3 component condenses and the hydrogen and the liquid olefin phases are separated. the recirculated stream has two important functions: cools the reactor and dilutes the inlet c3 stream. blowdown is required due to the accumulation of inert components. the most frequent type of hydrogenation reactors is the trickle-bed reactor in the olefin plant. liquid olefin feed and gaseous hydrogen pass through the catalyst bed in the same direction: from top to bottom. cooling of reactor is provided by vaporization liquid flow. the reactions occur in the top region of the reactor. the 72 figure 7: measured and filtered values of product c3 fraction reactions release a large amount of heat. the heat generation is influenced by the methyl-acetylene and propadiene (mapd) content of the inlet c3 and by the partial pressure of the hydrogen. the mapd content of the inlet flow of system is high, so the inlet flow of the reactor is diluted. in the range of 10 � 80 �c temperature, the average reaction heat of main reactions are the following: ma+h2 = c3h6 �hr = �164.8 kj/mole (19) pd+h2 = c3h6 �hr = �172.2 kj/mole (20) c3h6 +h2 = c3h8 �hr = �124.6 kj/mole (21) in the following sections, released heat vaporizes a part of the liquid phase. this phenomenon also ensures the cooling of the product flow. the simulator has been developed in aspen plus software as part of an expert system used for the monitoring and qualification of the operation of the technology. calculations provide useful information about unmeasured variables, validity of on-line analyzers, and efficiency of catalysts. the residence time is small (less than one minute). the sample time was five minutes, so the steady state simulation gives the same result as the dynamic simulation. historical process data entered the simulator by aspen simulation workbook. the developed excel and visual basic macro based framework allows the comparison of the measured data and the calculated results. results and discussion the process has two inlet streams (c3 fraction and hydrogen) and two outlet streams (hydrogenated liquid c3 fraction and blowdown). mass flows of every stream are measured. based on the law of conservation of mass (there is no accumulation): inlet c3 + h2 = blowdown + product c3 (22) figure 8: measured and reconciled values of product c3 fraction if we check whether the measured data satisfy the balance equation, we find that eq. (22) is not fulfilled, so data reconciliation is necessary. steps of the procedure are introduced based on mass flow of c3 product fraction. first time random error is separated from basic process using discrete fourier transformation. fig. 7 shows the measured and the filtered values of product c3 fraction. we defined the random noise as the difference between the measured and filtered values so the standard deviation and covariance matrix of random error (vd̃) can be calculated. since there is no accumulation (i.e., b = 0) eq. (10) is simplified to ŷ = ⇣ i�vd̃a t � avd̃a t ��1 a ⌘ ỹ. (23) since two input and two output streams are in the system, the incidence matrix is a = [1 1 � 1 � 1]. every needed information are known so the matrix operation can be performed. real industrial data are analyzed, so dimensionless units are included in the figures. the result of reconciliation is visible in fig. 8. the result shows that the proposed method gives a minor improvement of the process values. thanks to the validated accuracy of the mass measurements, these process values can be directly used for the validation of the simulator. in the next step, we compare the reconciled output with the values calculated by the simulator in two different ways. first, the input of the simulator is the measured data, then, the reconciled input data. the result of the comparison is shown in fig. 9. first, we thought that the three curves coincide. however, as a portion is zoomed, the difference became apparent (see fig. 10). if the input of simulator is the reconciled data, the calculated and the reconciled output are nearly the same. although the difference between the two calculated curves may seem small in dimensionless space, do not forget that the small percentage difference can mean significant mass flow values in a real industrial process. 73 figure 9: calculated and reconciled data of product c3 fraction if the input of the simulator is the measured and reconciled data figure 10: reconciled and calculated outputs of simulator in case of product c3 fraction we calculated the square error in both cases (deviation from the reconciled output) and found that the difference decreased by 87% if the reconciled values are the input of the simulator. this shows that the simulator gives more accurate results if previously data are reconciled. the simulator supported by data reconciliation can be applied in fault diagnosis. fig. 11 shows how the hydrogen flow changes over time. the continuous line represents the simulator results without data reconciliation, while the dashed line shows the reconciled values. fig. 11 shows the similarity of the calculated and the measured values. after 300 hours of operation the calculated values exceed the measured data. there are several possible reasons. less hydrogen goes to this system if • the mapd content of the inlet stream is lower, because the mass flow of hydrogen is controlled in proportion of the mapd mole flow of the input c3 figure 11: calculated and reconciled dimensionless mass flow of h2 if the input of the simulator is the measured data fraction. • after the regeneration when catalyst is active. • other reactor is regenerated or reactivated. in this case, another reactor in the olefin 2 plant was reactivated (after 300 hours). the reactivation process needed a lot of hydrogen so the hydrogen for the studied reactor was reduced. the received data did not include the rate of reduction. the result of the simulation showed that something was changed in the technology. this shows the technique can be used for monitoring and diagnostics of complex processes because it can be discovered if the operating condition has changed. conclusion data reconciliation is an effective method to obtain accurate process data that satisfy balance equations using process constraints. the application of steady-state data reconciliation is widespread in the process industry. simulators are often applied to improve industrial processes, optimize operation, and identify bottlenecks of technology. historical process data can be used for the identification and verification of models utilized by these tools. usually, measured data do not satisfy balance equations, because all measurements are incorrect to some extent. thus, it is necessary to develop a method which can simultaneously and iteratively improve data and model performance. a method based on data reconciliation technique has been developed for this purpose. an industrial c3 selective hydrogenation process has been analysed as a case study. the steady state simulator of the process has been developed in aspen plus flowsheeting software. calculated and historical process data were compared using aspen simulation workbook. 74 the proposed technique can be used for monitoring complex processes. results showed that the proposed technique slightly improves the quality of flow data. thanks to the accuracy of flow measurements, these process values are directly applicable for the validation of simulator and suitable for further studies, e.g., for the determination of kinetic parameters. acknowledgements this research of barbara farsang and janos abonyi was supported by the european union and the state of hungary, co-financed by the european social fund in the framework of támop 4.2.4. a/2-11-1-2012-0001 ‘national excellence program’. the infrastructure of the research has been supported by the european union and the hungarian republic through the támop 4.2.2/a11/1/konv-2012-0071 project. symbols a incidence matrix ay incidence 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make public announcements; introduce your research laboratory; a new product or a service in the hungarian journal of industry and chemistry please contact us if interested! editorial office: university of pannonia p.o. box 158, veszprém h-8201 (hungary) tel.: +36 (88) 624-298, e-mail: hjic@almos.uni-pannon.hu; web: hjic.mk.uni-pannon.hu felelős szerkesztő: szilágyi róbert, phd kiadja: pannon egyetem, 8200 veszprém, egyetem u. 10. levélcím: h-8201 veszprém, postafiók 158, tel.: (88) 624-000 hungarian journal of industry and chemistry veszprém vol. 41(1) pp. 77-82 (2013) statistical process control based performance evaluation of on-line analysers tibor kulcsár1 and jános abonyib1 1 department of process engineering, university of pannonia, egyetem street 10., h-8200 veszprém, hungary be-mail: janos@abonyilab.com on-line analyzers can provide accurate and timely information for process control and monitoring. statistical process control (spc) techniques can be effectively utilized to support the development and maintenance of these tools. the d629910 astm standard details how on-line analyzers should be validated. the applicability of this standard is demonstrated through the analysis of industrial data collected from an on-line gas chromatograph. the results confirm that automatized spc can effectively improve the reliability of advanced process control systems. keywords: on-line analyzer, software sensor, statistical process control, spc, process monitoring introduction process variables characterizing and influencing product quality have a significant role in process control and optimization. off-line laboratory tests mostly take more than two hours. this time delay can cause control problems resulting in economic loss. in such situations, an improved on-line monitoring system is required. on-line analyzers eliminate the dependence on laboratory data. analysers are valuable instruments for real time control because of their fast response time (1-4 minutes) (see fig. 1) [1]. quality control techniques can be effectively used to support the development of on-line analyzers [2] and advanced process control systems [3]. the d 6299 astm standard (applying statistical quality assurance techniques to evaluate analytical measurement system performance) provides information for the design and operation statistical quality control (qc) tools to monitor and control of analytical measurement systems using a collection of statistical quality control (sqc) tools [4]. the goal of the performance monitoring is the perifigure 1: soft sensors and on-line analyzers enable feedback control odic comparison of the on-line analyzer’s results to the reference value of the same sample measured by laboratory test methods. precision and bias (see fig. 2) are calculated to provide information for updating test methods as well as for indicating areas of potential improvements. control charts and other statistical techniques can be used for performance monitoring. statistical estimates of the measurement system precision and bias can be calculated on the basis of periodically updated data. plotting and interpreting these test results can ascertain the instatistical-control status of the measurement system [5]. on-line statistical process control (spc) based real-time validation of measurement systems has been already refigure 2: type of faults. the dashed line shows when the fault occurs. �: data free of fault; • corrupted data for the following cases: (a) bias, (b) complete failure, (c) drifting, and (d) precision degradation [4] 78 figure 3: illustrative example: mol aromatic block gas chromatograph ip benzene content (m/m %), lab, analyser and apc soft sensor ported in 1997 [6]. the spc based approach can also be applied for off-line performance evaluation [7]. this approach has a wide range of application areas like steel industry [8], electronic device assembling [9], and buildings’ energy demand monitoring [10]. the goal of this paper is to present the theoretical background and application details of spc based performance evaluation of on-line analyzers. the applicability of the concepts is illustrated by a case study based on data collected from an on-line gas chromatograph of the mol plc (see fig. 3) . typical patters that show out of control status of the system are also presented. to check the normality of the residuals, an easily applicable and interpretable tool is proposed. the developed demonstration tools are available at the website of the authors (www.abonyilab.com). control chart based evaluation of system performance the studied d6299 practice is devoted to a special testing of analyzers [4]. quality control (qc) test specimen samples from a specific lot are introduced and tested in the analytical measurement system on a regular basis to establish system performance history in terms of both stability and precision. the control chart is one of the seven basic tools of qc. control charts also known as shewhart charts are used to determine if process is in a state of statistical control. the analysis of the control chart indicates whether the process is currently under control. this means that these charts are used to check the stability of the production. in stable operation, the variations of the process and quality variables are only random, normally distributed variables. in these cases, no corrections of the control parameters are needed. when the chart indicates that the monitored process is out-of-control, the analysis of the chart can help to determine the sources of the variation. typically, control charts are used for time-series data, though they can be used for data that have logical comparability [11]. in this section, we present these charts and detail how these should be applied for the performance assessment of on-line analyzers. control charts run chart the run chart is a plot of sample values in chronological order (fig. 4). the run chart can be used to screen data for unusual patterns such as continuous trending in either direction, unusual clustering, and cycles. the run chart of the data used in our case study is shown in fig. 3. the plotted time series shows the signal of the on-line analyzer and the related laboratory measurements. i chart the i (individual) chart is a run chart to which control limits and center line have been added (see top panel of fig. 5). the center line is based on the mean of the samples, ī = pn i=1 ii n (1) figure 4: example for a run chart 79 figure 5: i and mr charts show out of control samples of the gas chromatograph ip benzene content (m/m) % while the upper and lower control limits are based on the estimated variance (range of the data) mr [12] mr = pn�1 i=1 |ii+1 � ii| n� 1 , (2) ucli = ī + 2.66mr, (3) lcli = ī � 2.66mr. (4) individual values that are outside the upper or lower control limits are indications of an unstable system, and efforts should be made to determine the cause [5]. optionally, any one of the following occurrences should be considered as potential signs of instability: 1. two out of three consecutive results on the i chart that are more than 1.77mr distant from the center line in the same direction; 2. five consecutive results on the i chart that are more than 0.89mr distant from the center line in the same direction; 3. eight or more consecutive points in the i chart that fall on the same side of the center line. mr chart mr (moving range) charts are also used to detect unusual patterns by plotting the sequential range of two values given by �i = mri = |ii � ii�1| , (5) and connecting each point (see fig. 6 for an example). there is no lower control limit for an mr chart [5]. the upper control limit for the mr chart is given by uclmr = 3.27mr. (6) figure 6: example for a mr chart figure 7: example for an ewma chart ewma chart an ewma (exponentially weighted moving average) chart is used to enhance the sensitivity in detecting mean shifts that are small relative to the measurement system precision (see fig. 7 for an example). each ewma value is a weighted average of the current result and previous results with the weights decreasing exponentially with the age of the reading [5]: ewma1 = i1, (7) ewmai = (1� �)ewmai�1 + �ii, (8) where � is the exponential weighting factor. for application of this practice, a � value of 0.4 is recommended. the control limits for the ewma chart are calculated using a weight (�) as follows: ucl� = ī + 2.66mr r � 2� � , (9) lcl� = ī � 2.66mr r � 2� � . (10) the complexity of multivariate and autocorrelated processes makes it difficult to use standard control charts. to construct simple and interpretable charts, dimensional reduction could also be used as simoglu and martin have done [13], but in case of autocorrelated data, modelbased control charts should be applied as kim and jitpitakler have done in their research [14]. pretreatment of test results assessment, control charting, and evaluation are applied only to appropriately pretreated test results. the purpose 80 of pretreatment is to standardize the control chart scales so as to allow for data from multiple check standards to be compared on the same chart. for qc sample test results, no data pretreatment is typically used since results for different qc samples are generally not plotted on the same chart. in our case, the difference between the measurements and their accepted reference values (arvs) are monitored. arv serves as an agreed-upon reference for comparison and that is derived based on (1) a theoretical value, based on scientific principles, (2) an assigned value, based on experimental work, or (3) a consensus value, based on collaborative experimental work under the auspices of a scientific or engineering group. i = test result�arv. (11) assessment of initial results in the initial phase of the application assessment techniques are applied to test results collected during the startup phase of or after significant modifications to a measurement system. it is required to perform the following assessment after at least 15 pretreated results have become available. the purpose of this assessment is to ensure that these results are suitable for deployment of control charts. pretreated results should first be visually screened for values that are inconsistent with the remainder of the data set, such as those that could have been caused by transcription errors. those flagged as suspicious should be investigated. discarding data at this stage must be supported by evidence gathered from the investigation. if after discarding suspicious pretreated results there are less than 15 values remaining, collect additional data and start over. the next step is to examine the pretreated results for non-random patterns such as continuous trending in either direction, unusual clustering, and cycles. one way to do this is to plot the results on a run chart and examine the plot. if any non-random pattern is detected, investigate for and eliminate the root cause(s). typical control chart patterns in the previous sessions, the main charts used for performance measurement were presented. in spc, the western electric rules are the decision rules for detecting “outof-control” or non-random conditions on control charts. locations of the observations relative to the control chart control limits (typically at ±3 standard deviations) and centerline indicate whether the process in question should be investigated for assignable causes. the western electric rules were codified by a specially-appointed committee of the manufacturing division of the western electric company and appeared in the first edition of its statistical quality control handbook in 1956 [15]. their figure 8: this process is out of control because a point is either above the ucl or below the lcl. for example, in fig. 5-b at sequence number 28 there is a unique point below the lcl figure 9: in this case the system produce 2 out of 3 consecutive points either in or beyond zone a. the process on fig. 5-b shows this behaviour at sequence number 45 where the values are close to the upper control limit. purpose was to ensure that line workers and engineers interpret control charts in a uniform way [5, 12]. the eight standard western electric rules are: 1. the most recent point plots outside one of the 3sigma control limits (see fig. 8). if a point lies outside either of these limits, there is only a 0.3% chance that this was caused by the normal process. 2. two of the three most recent points plot outside and on the same side as one of the 2-sigma control limits (see fig. 9). the probability that any point will fall outside the warning limit is only 5%. the chances that two out of three points in a row fall outside the warning limit is only about 1%. 3. four of the five most recent points plot outside and on the same side as one of the 1-sigma control limits. in normal processing, 68% of points fall within one sigma of the mean, and 32% fall outside it. the probability that 4 of 5 points fall outside of one sigma is only about 3%. 4. eight out of the last eight points plot on the same side of the center line, or target value. sometimes you see this as 9 out of 9, or 7 out of 7. there is an equal chance that any given point will fall above or below the mean. the chances that a point falls on the same side of the mean as the one before it is one in 81 two. the odds that the next point will also fall on the same side of the mean is one in four. the probability of getting eight points on the same side of the mean is only around 1%. 5. six points in a row increasing or decreasing. the same logic is used here as for rule 4 above. sometimes this rule is changed to seven points rising or falling. 6. fifteen points in a row within one sigma. in normal operation, 68% of points will fall within one sigma of the mean. the probability that 15 points in a row will do so, is less than 1%. 7. fourteen points in a row alternating direction. the chances that the second point is always higher than (or always lower than) the preceding point, for all seven pairs is only about 1%. 8. eight points in a row outside one sigma. since 68% of points lie within one sigma of the mean, the probability that eight points in a row fall outside of the one-sigma line is less than 1% (see fig. 10). normality checks since the control chart and limits prescribed in this practice are based on the assumption that the data behavior is adequately modeled by the normal distribution, it is recommended that a test of this normality assumption be conducted. one way to do this is to use a normal probability plot and the anderson-darling statistic [16]. if the results show obvious deviation from normality, the statistical control charting techniques described are not directly applicable to the measurement system [5]. quantile-quantile plot (q-q plot) is a graphical tool for comparing two probability distributions by plotting their quantiles against each other. the normality plot of the process can be obtained by comparing the empirical distribution of the data against a standard normal distribution figure 10: long runs (8 or more consecutive points) either above or below the centerline. (see fig. 5-a in range 28-40) figure 11: normality check of the studied gas chromatograph. (see fig. 11). when the results are normally distributed, the plot should be approximately linear. major deviations from linearity are an indication of non-normal distributions of the differences [17, 16]. conclusions we showed that statistical process control can be effectively used to support the development and maintenance of on-line process analyzers. a case study is presented based on the analysis of data taken from the chemical process industry. the proposed concept has been implemented in matlab. the results illustrate the applicability the developed tools in improving the reliability of advanced process control systems. acknowledgements this research of janos abonyi was supported by the european union and the state of hungary, co-financed by the european social fund in the framework of tamop 4.2.4. a/2-11-1-2012-0001 national excellence program. the infrastructure of the research has been supported by the european union and the hungarian republic through the tamop 4.2.2/a11/1/konv-2012-0071. the work of tibor kulcsar was supported by the hungarian scientific research fund under grant k77955. references [1] gidwani, k. k. , beckman, r. f. evaluation of refinery control systems, isa transactions, 1994, 33(3), 217–225 82 [2] roberto, m. f., dearing, t. i. , martin, s., marquardt, b. j. integration of continuous flow reactors and online raman spectroscopy for process optimization, journal of pharmaceutical innovation, 2012, 7(2), 69–75 [3] smith, c. advanced process control: beyond single loop control (john wiley & sons), 2011 [4] a. international: applying statistical quality assurance techniques to evaluate analytical measurement system performance (astm international), 2010 [5] montgomery, d. introduction to statistical quality control (john wiley & sons, inc.), 2009 [6] converse, j. real time validation of on-line measurements utilizing internal standard introduction, isa transactions, 1997, 36(2), 151–158 [7] colledani, m., tolio, t. performance evaluation of production systems monitored by statistical process control and off-line inspections, international journal of production economics, 2009, 120(2), 348–367 [8] kano, m., nakagawa, y. data-based process monitoring, process control, and quality improvement: recent developments and applications in steel industry, computers & chemical engineering, 2008, 32(1-2), 12–24 [9] reis, m. s., delgado, p. a large-scale statistical process control approach for the monitoring of electronic devices assemblage, computers & chemical engineering, 2012, 39, 163–169 [10] braga, l., braga, a. r., braga, c. on the characterization and monitoring of building energy demand using statistical process control methodologies, energy and buildings, 2013, 65, 205–219 [11] poots, a. j. , woodcock, t. statistical process control for data without inherent order, bmc medical informatics & decision making, 12, 2012 [12] chandra, m. statistical quality control (crc press llc), 2001 [13] simoglou, a., martin, e., morris, a. multivariate statistical process control of an industrial fluidised-bed reactor, control engineering practice, 2000, 8, 893–909 [14] kim, s. b. , jitpitaklert, w., park, s.-k. , hwang, s.-j. data mining model-based control charts for multivariate and autocorrelated processes, expert systems with applications, 2012, 39(2), 2073–2081 [15] thomas, d., et al. statistical quality control handbook (western electric co., inc), 2011 [16] thode, h. c. testing for normality (crc press llc), 2002 [17] harris, t., seppala, c., desborough, l. a review of performance monitoring and assessment techniques for univariate and multivariate control systems, journal of process control, 1999, 9(1), 1– 17 hungarian journal of industry and chemistry veszprém vol. 41(2) pp. 83–108 (2013) corrosion protection with ultrathin graphene coatings: a review andrás gergely ! and tamás kristóf department of physical chemistry, institute of chemistry, university of pannonia, egyetem u. 10., veszprém 8200, hungary !email: gergelyandras@almos.uni-pannon.hu developments in surface treatment or finishing, and modification of structural metals have probably never been so dynamic than in recent years due to the need for new approaches to efficient corrosion protection. the application of coatings is a strategy to be followed to physically separate corrosive environments from metal surfaces. the overall protection efficiency depends on the coating’s barrier properties. traditional alternatives to coating suffer from inefficient physical protection in cases of low film thicknesses and at elevated temperatures. one of the most advanced options is to apply ultrathin atomic films to ensure complete separation of the metallic surface from the fluid media. among the numerous materials and methods, exceptional chemical resistance and high domain size make graphene a promising candidate for constituting ultrathin coatings with interfacial atomic layers adherent and homogeneous coverage to feature firm barrier behaviour. this review focuses on the major efforts with notable results and points out some short comings that must be resolved to serve as a basis for further progress in this field. keywords: ultrathin coatings, graphene, metals, corrosion protection introduction nowadays graphene (gr) is undoubtedly of great interest in many fields of science and engineering. the attention is due to its unique structure, electrical properties [1, 2], efficient heat spreading [3], wetting transparency [4], surface wetting tenability [5], and high reflectivity (mirrors for the beams of he and h2) [6]. the gr’s practical impermeability to gases [7-9] is a result of the combination of its strong structure (carbon bond energy and intrinsic strength are 4.9 ev and 43 n m-1, respectively) and its morphology that makes gr to be the thinnest and most impermeable membrane [10]. in addition, because of its chemical inertness [11], especially against oxidation [12, 13], it is highly resistant to corrosion [14] under conditions where other substances would undergo chemical reactions [15, 16]. as a lightweight mono-atomic coating, gr can function as one of the most advanced electronand ion-transfer barriers at the metal-electrolyte interface, without notably altering optical properties and thermal conductivity of the substrates. gr on metal surfaces is expected to afford oxidation resistance [11] based on its airtight balloon behaviour associated with its excellent barrier nature against oxygen diffusion [7]. nevertheless, coherence, and uniformity of gr coatings are apparently vital to achieve good corrosion protection. in accordance with general expectations, electrochemical properties of gr [17, 18] and its coated derivatives were extensively investigated. the main results achieved recently are described in the following sections that are organised from the viewpoint of synthesis techniques and application purposes. pure graphene coatings direct chemical vapour deposition (cvd) on metal surfaces early studies were inspired to synthesise full surface covering gr films of the highest domain (single sheet) size and integrity to exert impermeability over macroscopically large surfaces. later findings proved the viability of this concept as interfacial construction of thin layers is a promising way to provide durable corrosion protection for metallic substrates [19]. generally, coatings play a vital role in improving surface quality and protection of substrates, since much effort has been made to produce films featuring excellent properties. graphene is certainly one of the most prominent representatives of this kind and subsequently has been studied in almost all scientific and engineering fields. this new generation material has been a novel subject to incorporate into the latest corrosion protecting coatings. achievements in utilising gr as a pure and composite coating were first reviewed by tong et al. [20]. the synthesis and functionalisation of gr were briefly discussed and future perspectives suggested. 84 the simplest way is to grow gr directly on metal surfaces, even though this strategy does not provide the most protective coatings due to low adherence of the inorganic layers as consequence of weak interaction. by direct cvd, metals like nickel [21], cobalt [22], iridium [23], ruthenium [24] and copper [21, 25-27] were coated with gr (on large areas in certain cases) [25] using methane or acetylene as a carbon source [28, 29]. deposition kinetics of carbon and the formation of gr layers on copper were thoroughly explored; surface mediation theory was proved when poly-crystalline films were characterised with the domain size of 10 µm2 [30]. except for assessing the influence of grain orientation, the effect of other growth parameters was estimated. the most relevant findings are as follows: 1. the density of gr nuclei decreased, conversely flake domain size increased as temperature increased and partial pressure of the carbon source decreased. 2. when the pressure dropped below a critical threshold then no gr nucleation was observed and film formations terminated before reaching full surface coverage. 3. to achieve complete surface coverage, the partial pressure of methane must have been increased above 500 mtorr then full coverage was reached within 2 to 3 min. only a supersaturated surface relaying on a critical threshold of partial pressure ~285 mtorr was suggested to drive the formation of fully coated copper substrates with a continuous layer of gr flakes. thus, carbon nuclei formed in the first step under a lower pressure followed by a second step of nuclei growth at a higher pressure, promoting full surface coverage. the effects of these parameters coupled with the investigation of the orientation of metal crystals on gr domain size were quantitatively evaluated at low temperatures [31]. the activation energy for gr nucleation under atmospheric pressure was noticeably higher (9 ev) than under low-pressure cvd procedures (4 ev). such a difference was attributed to copper sublimation at low pressure, because copper evaporation probably has a decisive impact on the desorption rate of carbon from the surface. copper evaporation is restricted under atmospheric pressure, so the activation energy is assigned to the desorption of carbon clusters. close to the melting point of copper, large single-crystal gr synthesis was proposed at the highest possible temperature (probably to maintain the highest rate of interfacial mass-transfer, diffusion coefficient of the decomposed and fragmented precursor agents). by following these principles, single gr crystals with a domain size of ~1 mm could be synthesised. the nucleation density was higher on (111) than on (100) and (101) surfaces without any identifiable preference at higher temperatures [32]. under carefully optimised conditions, continuous films of some layers were obtained on polycrystalline nickel without void areas at the flake boundaries [21]. in that case, ambient pressure cvd was to grow gr films of 1-12 layers, with flake sizes of up to 20 µm for singleand bilayers (bls). an ultra high vacuum (uhv) chamber was not needed [33, 34] to finely balance nucleation and growth processes, instead, thermal annealing was employed leading to the emergence of single-crystalline nickel with grain sizes of 1-20 µm. grain surfaces became atomically flat with some terraces and steps similar to single-crystals usually used for epitaxial uhv experiments and gr growth took place probably via the precipitation of carbon in the metal. because metallic grains may independently affect film thickness as a result of the high density of atomic steps at grain boundaries, multi-layer (ml) nucleation occurred mainly at those areas. by using atmospheric pressure cvd, high quality gr was grown on copper, eliminating all the major difficulties associated with the low-pressure method. parameter optimisation involved evaluating the influence of the thickness, purity, morphology and crystallographic orientation of the metal foils on growth rates and the number of gr layers. scanning electron microscopy (sem) images illustrating gr flakes on polished foils besides xrd patterns of annealed foils are presented in fig.1 showing large copper domains on nr foils. the effects of copper impurities on the density of bilayers are signified; complete surface coverage on aa2 (the purest foil (99.999%) without double layers), aa1 and nr. in fig.2, gr quality is presented at various distances along the tube reactor. the methane concentration was higher at the inlet leading to a greater abundance of mls (darker islands in the images). gradual increase of concentration resulted in the formation of single-layer (sl) gr growth over the entire length. a constant methane concentration yielded a high percentage of mls at the inlet, incomplete coverage in the middle and separated single domains (seen as darker islands) at the outlet. as a method of surface pre-treatment, electropolishing [36, 37] in phosphoric acid seemed to be a good choice to achieve an appropriate degree of surface cleaning and minimised roughness. acetic acid was highly efficient at cleaning the copper surface, but only capable of removing oxidised species without any further etching. etching with ferric chloride solution generally gave similar results to electropolishing despite the greater roughness of the fecl3 treated copper foils. this was probably due to the considerable scale of copper recrystallisation during annealing at temperatures close to the melting point of copper before the cvd process, leading to the evolution of a smoother surface with a low density of defects serving as nucleation sites. additionally, the growth rate was estimated depending on the purity and crystallographic orientation of copper but by far not as much as the partial pressure of hydrogen, because the amount of dissolved hydrogen depends less on the thickness of the copper substrate. crystallographic orientation was found to be an important factor, since the growth rate on the surface of substrates characterised by miller indexes (100) was faster than on (111) surface under ambient pressure. in contrast, at low pressure and temperature the (111) surface facilitates the fastest growth rate [38]. furthermore, optimal conditions to achieve full surface covering films with the minimum proportion of mls might greatly vary with purity of the metal specimens. high purity substrates contribute to the formation of sl 85 films, and low purity metals support the evolution of multi-layer (ml) gr coatings. due to the multiple aspects of the reaction mechanism, optimal conditions for long foils are related to low and varied concentrations of carbon sources along the tube reactors, similarly to the application of temperature gradients (furnace dimensions and its relation to foil size) as well. figure 1: sem images illustrate (a) gr growth rate on polished aa1 and polished nr foils. xrd of annealed aa1 shows (100) orientation, the nr foil with the majority of (111) with smaller contributions from (110) and (311); (b) the effect of copper impurities on the density of bilayers [35] (republished by courtesy of the publisher, elsevier) figure 2: gr films at various distances along the cvd reactor used at atmospheric pressure. (a) gradual methane concentration, single-layer gr growth over the tube reactor; (b) multilayers at the inlet, incomplete surface coverage in the middle and separated single domains at the outlet [35] (republished by courtesy of the publisher, elsevier) 86 the gradual increase of methane concentration from 30 to 100 ppm in the mobile phase helps resolve the changing rate of activated carbon production [39]. because methane concentration near the outlet increases slowly as a result of thermal decomposition and deposition, the main purpose of the gradually increasing methane concentration was to minimise bilayer growth at the inlet over the synthesis duration and to ensure full surface coverage near the outlet with the highest concentration of the carbon source. in fact, optimisation in the case of the atmospheric pressure cvd is more complicated than vacuum ones, which process in long tube chambers with small foils. a steady methane concentration at the inlet surely results in an increasing proportion of mls at the inlet and incomplete coverage at the outlet, with visibly separated flake boundaries. the initial methane concentration of less than 30 ppm exclusively led to sl gr at the inlet. high quality gr grows with >99% monolayer coverage and in some cases films consisted of flake sizes of around 100 µm. high temperature etching with oxygen led to the visualisation of inter-domain boundaries as etching started at these boundaries and expanded into domains in a dendritic pattern, leaving diagonal stripes etch-free. efficient corrosion resistive film properties were reported when experiments were made with samples exposed to air at 300 ºc, showing no sign of oxidation (oxygen enrichment in the metallic phase) over gr coated areas in comparison to bare substrates. according to a similar preference, growing gr layers on copper is favourable, because copper does not dissolve carbon as much as nickel at high temperatures. however, it is also possible to grow mls with highly ordered crystalline structures suing atmospheric cvd with controlled film thickness [40]. both pure nickel and copper were covered with cvd grown gr films detected as covering the majority of the metals in a sl form besides some areas of double and fragmented mls (less than 5% of the coating) [41]. an optical micrograph and raman map with the respective raman spectra obtained from the ni–gr and cu–gr surfaces are presented in figs.3 and 4, respectively. electrochemical tests indicated that such coatings substantially reduced the corrosion rate of the substrates. by raman spectroscopy investigation, sl gr showed sharp g (1580 cm-1) and 2d (2650–2700 cm-1) bands with a small g/2d ratio, whereas ml gr with a high g/2d ratio and an altered, less sharp 2d band were detected. hence, 80 and 60% of the copper/nickel surface was covered with gr as a singleor few-layers coating without uniformity on nickel. scanning electron micrographs of the samples showed different thicknesses of the films with various scales of folding, full of wrinkles and edges. thus, the overall conclusion was reached that coherent sl gr is hard to obtain by direct deposition processes. immersion type corrosion tests indicated open circuit potentials (ocps) or free corrosion potentials of copper and nickel shifted towards the positive potential region. the electrochemical test conditions are summarised in table 1. a potential ennoblement of about 0.3 v was measured for the corroding system of nickel/gr and a cathodic shift of ~0.2 v observed with coated copper samples. the cathodic reduction processes were affected, inhibited by the gr layer on copper and the rate of anodic half-reactions was apparently reduced near the steady free corrosion potential. however, during extended linear potential scanning gr/nickel showed higher anodic currents than uncoated substrates opposed to the modified copper that exhibited no changes in the anodic branch after gr deposition. as an oxidation barrier for liquid and liquid–vapour phase-change cooling systems almost the same heat transfer efficiency was reported using bare and gr/copper surfaces in liquid-phase and two-phase thermal performance tests [42]. after thermal treatment, figure 3: optical micrograph, raman map of ~2700 cm–1 peaks and respective raman spectra of the areas on the ni–gr surface [41] (republished by courtesy of the publisher, elsevier) 87 analysis revealed oxide formation on the entire surface of bare copper and limited oxidation at grain boundaries on the coated substrate. in conclusion, few gr layers acted as a protective layer even under vigorous flow conditions near the boiling point of the fluid phase. graphene prepared by microwave (mw) assisted cvd protected substrates from chemical oxidation when samples were heated under atmospheric conditions in a sequential multi-step procedure with dwelling times from 15, or 30 min to 1 h [43]. a very low degree of chemical oxidation of gr over copper was indicated by xps and the presence of cuprous oxide was found on the entire surface of bare specimens. there are special applications such as steering and focusing elements for neutral atomic and molecular beams in de broglie microscopes [44]. these mirrors utilise the quantum reflection of an atomic beam on metal surfaces since interaction volume is strictly limited to an extremely thin atomic layer of the metals. oxidation and any other form of corrosion or adsorption of atmospheric gases might well lead to far lower reflectivity of the metallic surfaces, and the coatings of more than a few atomic layers are unacceptable. thus, there are exceptional requirements of protective coatings and gr films were expected to provide the solution in this matter too. complete and uniform monolayers could be grown on polycrystalline ruthenium of a columnar structure on fused silica, exposing flat surface facets [45]. single-layer gr protects underlying metals with special structures like concave focusing mirrors and non-planar microelectrode arrays from oxidation under ambient gases. ruthenium was recovered by heating the samples under ambient conditions at 250 ºc for half an hour in an ultra-high vacuum, which was indicated by missing peaks in the oxygen (1s) region of the xps spectra. gr on copper provided mediocre protection against electrochemical degradation in chloride environments [46]. impedance measurements showed increased resistance at the metal/solution interface as anodic and cathodic current densities decreased with about hundred times higher charge-transfer resistance besides about thousand times lower double-layer capacitance in comparison to uncoated copper. ennoblement of the free corrosion potential was also observed and related to the good barrier nature of the film. the protection of copper against corrosion by the growing number of gr layers was in part demonstrated [47]. to enable reliable and complete mechanical blockage by the coating exploiting its impermeability and chemical inertness, preparation parameters were balanced to obtain an appropriate film structure. in fig.5, cyclic voltammograms (cvs) of the bare and passivated copper (the latter with 1-3 gr layers) are shown along with the intensity of oxidative currents besides the atomic force microscope image of the cu/gr after etching. fig.6 depicts cvs of gr-coated copper and grcopper post-treated with aluminium oxide (alox) of different thicknesses, along with the comparison of their peak currents. nonetheless, nanometre size structural defects at flake boundaries were the main source of deficiency, decisive in the often-observed limited protection efficacy. to circumvent this problem, a general strategy is to grow ml island-free gr films. selective coverage of defect areas was achieved by atomic layer deposition, resulting in enhanced protection of ~99%. bare copper in an aerated sulphate solution indicated a pitting corrosion rate of ~9 nm s-1 with a density of ~1 µm-2. the estimated diffusion rate of the reactants was above 1 m s-1 limiting the rate of corrosion processes. figure 4: an optical micrograph, raman map of ~2700 cm–1 peaks and respective raman spectra of the areas on the cu–gr surface [41] (republished by courtesy of the publisher, elsevier) 88 interestingly, in the case of the ml gr films, mass transport remained fast across the sheets and parallel along their planes, which was anticipated by the outcome of a water permeation experiment [8]. this may explain the unchanged chemical inertness of the gr coating, owing to the fast mass transport along and across the layers as etchant species permeate through unburied areas in outer layers and diffuse laterally while finding open areas in layers underneath. inertness to electrochemical reactions could only be attained by thin layer deposition of aluminium oxide (within ~5 nm) by the means of an atomic layer deposition technique on gr/copper. only by this way could unburied regions on the copper surface be made void-free. after 160 atomic layer deposition cycles with a ~16 nm thick passivating film inhibition efficiency was ~99%. this was partly confirmed by tafel analysis giving instantaneous general corrosion rates of ~99% to the copper-single layer gr with 16 nm aluminium oxide and 87% to sl gr/cu, in comparison with bare copper. the approach of the direct loading of a precursor, i.e., acetone on copper then annealing it to convert its vapours into gr was investigated [47]. monolayers formed with nearly 100% coverage after rapid thermal annealing. under optimal conditions, acetone derived films with good crystallinity compared to common cvd grown counterparts. the passivity of the metal coated/masked with sl gr was attributed to remarkably inhibited cathodic reduction reactions and barrier action against the diffusion of anions accessing the underlying substrate. so, sl gr/copper exhibited ca. forty times lower corrosion rates compared to the mechanically polished copper, which means an inhibition efficacy of up to 97%. nevertheless, optimal protection performance was proposed to be achieved by the application of four gr layers with their short-term inhibitions of up to 99%. the corrosion current of the gr/copper reduced by ca. sixty times compared to mechanically polished substrates and the ocp shifted towards the negative potential region. electrochemical impedance spectroscopy (eis) indicated ten thousand times lower electrolyte-metal interfacial capacitance (cdl) of the gr/copper samples than those of the mechanically polished specimens. such a notable drop suggests a significant shrinkage of the exposed surface to the electrolyte. cdl of the gr/copper was ca. three times higher in nacl solution (0.6 m) than in its diluted media (0.1 m), but 6.4 times lower than that obtained in 0.1 m na2so4. cdl and constant phase element (cpe) of the gr/copper samples suggest an electrochemically smaller active surface to interfacial charging (discharging) and adsorption (like a non-faradaic helmholtz capacitor) as the density of conductive pathways decreases besides the lower effective surface roughness than that of the mechanically polished substrate. the cpe was 2.7 times higher than that table 1: metallic substrate, type and growth parameters to obtain gr films by direct cvd deposition substrate preparation type & parameters corrosion test parameters surface of the working electrode (cm2) types of electrochemical test ref. cu & ni cvd grown on metal surfaces flat-cell, 0.1 m nacl 0.07 potentiodyn. pol., scan rate: 1 mv s-1, after min at ocp [41] cu cvd grown flow-cell, mass velocity: 38 kg m-2 s-1 for 9 h, t = 59.5±0.5oc 3.06 none [42] cu mw assisted cvd heating at 150oc, in air at 1 atm for 1 h unknown none [43] ru cvd ambient exposure unknown none [45] cu cvd 0.1 m nacl 0.785 potentiodyn. pol., scan rate: 0.5 mv s-1 from ocp, eis after 1 h [46] cu cvd aerated 0.1 m na2so4 0.24 cyclic voltammetry, scan rate: 10 mv s-1 [47] ni cvd treated at 600 ºc in air, then 31 wt.% h2o2 for up to 2 h unknown none [49] cu & ni cvd & mech. transferred by spin-coating with pmma at 4000 rpm for 45 s 0.1 m naso4 0.4 potentiodyn. pol. & cv, scan rate: 0.005 mv s-1, eis [50] cu & si cvd then transfer of layers with pmma cured at 165 ºc ox. at 225 ºc for 60 min and red. of cu at 450 ºc for 90 min under o2 and h2 flow unknown none [60] cu cvd, thiol func.: slg-cu treated with hcl & h2o then 7.5 mm thiol-ethanol treatment for 2 h lymphocyte transformation test & in vivo experiment 1.4 tests: cu conc. by icpoes, cell viability & stimulation index for lymphocyte [80] ni template directed cvd anode in glucose based electrolyte, ni in ferricyanide catholyte 8 cv and eis [116] 89 measured in nacl solution (0.1 m) and over ten times lower than in na2so4 solution (0.1 m). the resistance of coated copper to corrosion (rcorr) was ca. thirty five times higher than those of mechanically polished ones 6×104 and 1.6×103 ω cm2, respectively. rcorr was appreciably lower than that of nacl and higher than with na2so4 solutions. thus, inhibition efficacy was found as follows; >97% in 0.6 m and >71% in 0.1 m nacl. thus, performance was sensitive to the integrity of the gr film as mechanically polished samples indicated rapid protection efficiency losses with increasing chloride concentrations in the test solutions. rigorous corrosion testing of nickel/cvd grown gr films revealed low intensity oxidation of the substrate by heat treatment. oxidation resistance was effective up to 500 ºc for 3 h, and with durable exposure (2 h) to essential hydrogen peroxide (31 wt.%) solution [49]. both nickel and copper were coated with ml gr films [14] by mechanical transfer. cv measurements indicated a remarkable restriction of the evolution of anodic and cathodic current transients, resulting in the effectively decreased electrochemical activity of the metal substrates. fig.7 depicts cvs of bare and grcoated copper samples, and xps spectra of copper under ambient conditions, at 100 mv and sputter cleaning. region (i) and (ii) contains a shoulder and a peak due to cuo and cu2o/cu, respectively. the third part of the figure shows sem images of cu and gr/cu before and after voltammetry scans. based on tafel analysis, corrosion rate assessment (quantification prediction) for bare substrates gave the following results: ca. 6×10-13 and ca. 3×10-14 m s-1 for copper and nickel respectively. graphene/copper indicated lower corrosion rate of ca. 8×10-14 m s-1 up to ca. seven times less than the bare substrate. the gr/nickel showed a reduced rate of ca. twenty times to 2×10-15 m s-1. with two or four folds of gr layers, the corrosion rate of nickel decreased to 2×10-14 and 8×10-15 m s-1 respectively, which is considered as a notable performance improvement. eis measurements suggested an undamaged state of gr, but the metal surface might corrode at high rates around void areas in the film. the most probable electrical network included resistive elements of the solution; rs ≈ 40 (6.5 ω cm2) and charge-transfer at the interface; initial rct ≈ 3±0.5 kω cm2 due to faradaic processes. the mass transport process was modelled with a warburg element (w ≈ 1.0±10-3 ω-1 s0.5 cm-2) as a semi-infinite diffusion component. the inhomogeneity of the surface was handled by incorporating a cpe as a non-ideal capacitance in the circuit due to the impedance dispersity of the electrical double layer component at the metal-liquid interface. double layer capacitance was best achieved with 2.2 µf cm-2 and the cpe was yo ≈ 7.6±10-5 ω-1 s cm-2. increased resistance coupled in series was caused by the electrical surface resistance of gr (≈1 kω) with a double layer capacitance of ~3.8 cm-2. average fitting parameters were changed figure 6: cvs of (a) cu/gr/al samples, (b) peak currents of cu(0) for cu/gr/al with different aluminium thicknesses and in comparison to cu/gr with 1-3 gr layers (adapted with permission from ref. [47] copyright (2014) american chemical society) figure 5: cvs of (a) bare cu and cu passivated by 1-3 layers of gr, (b) intensity of oxidation currents under various passivation conditions, (c) atomic force microscope image of cu/gr after etching (adapted with permission from ref. [47] copyright (2014) american chemical society) 90 accordingly as follows: cdl ≈ 9±5.0 µf cm-2, cpe: yo ≈ 2±10-5 ω-1 s cm-2, w ≈ 3±0.5 ω-1 s0.5 cm-2, and rct ≈ 10±1.2 kω cm-2. the cdl was ca. ten times lower than measured with bare copper, which seemed to be unrealistic. such a difference is thought to originate from the quantum capacitance of the gr film as a contribution in series with the cdl. this is partly due to the small density of states in the gr, which is in good agreement with the reported quantum capacitance of 7– 10 µf cm-2 [50]. the increased rct of the copper samples in comparison with the one measured at the beginning of corrosion test suggested that the minor proportion of the metal substrate was uncoated with gr, participated in corrosion processes. the proportion of this unburied area was estimated to be unexpectedly high (a ≈ 0.3), exceeding the scale impressed by microscopy images (a < 0.05). such a difference was attributed to the access to larger substrate areas by the diffusing depolarisator species and a subsequent greater proportion of helmholtz capacitance then pseudocapacitance based on electrochemical activation of metallic substrates for anodic reactions. nevertheless, the ability of gr to catalyse, and depolarise cathodic reactions such as oxygen reduction [51] by well-coupling micro-galvanic cells in contact with the poly-aromatic sheets [52] either in planar or concentric forms (according to the function of the surface quinone group on carbon electrodes, i.e. garten and weiss’s mechanism) is almost always a concern. thus, protection efficiency depends largely on the deposition technique, quality, and epitaxial pile structure of the gr sheets, affecting ionic and electrical transport through the films. due to low adherence as a result of the lack of direct grafting or anchoring type chemisorption, direct cvd-grown films are classified as fragile coatings liable for potential polarisation and charging of the surface due to their structural alterations [53]. to increase the small domain size of the flakes, high temperature annealing at ~1035 ºc on the metal surface offers a resolution promoting further development of coherency of the films composed of large domains [54]. however, there are many problems with direct cvd deposition on metals like nickel because of the film formation mechanism of polyaromatic carbon materials. the mechanisms of surface catalysis and adsorption during gr growth on copper were determined [13, 55] to be different from film growth on nickel, which is governed by the combination of catalysis and adsorption as well as solubility and rejection. as the cvd technique enables the synthesis of gr on larger metal surfaces [22, 56], carbon sources are thermally decomposed and fragmented into smaller segments, then atoms arrange into 2d honeycomb lattices. the preparation of cvd grown gr films takes place readily on surfaces with face-centred cubic and hexagonal close-packed crystal structures. methane and ethylene, which decompose at a temperature of ~1000 ºc are used as main precursors [24, 25] even though such a high temperature might significantly affect the metallographic state of the substrate, nucleation and deposition kinetics. metals with close to zero solubility of carbon at the reaction temperature, e.g., copper, deposit via a catalytic mechanism and they are more likely to assist the formation of sl gr instead of ml ones owing to the lack of catalytic effect after the first layer is deposited. thus, the metal surface acts as a catalyst facilitating gr growth in the form of a finishing coating, as deposition is restricted to sl [57]. film growth on metals with mediocre carbon solubility at reaction temperatures undergoes via a complicated mechanism in which carbon diffuses into the bulk metal, e.g., nickel, and is rejected during the cooling process because of the decreasing solubility at lower temperatures. the rate of carbon rejection is critical to the development of ml gr coatings. hence, these films form preferentially instead of sls on copper. further complications may arise by the use of thicker metal specimens because thicker substrates dissolve larger amounts of carbon during the cooling phase since they release more carbon to produce larger amounts of carbon soot. although any process that needs to be scaled-up must be optimised for engineering alloys, there are many results of theoretical interests as well. figure 7: cvs of (a) bare cu and gr/cu samples with the blue line corresponds to the measurement with n2 bubbled through the solution; (b) xps spectra of copper under ambient conditions at 100 mv and sputter cleaning with regions (i) and (ii) are due to cuo and cu2o/cu(0), respectively; (c) sem images of cu and gr/cu before and after cv scan (adapted with permission from ref. [14] copyright (2014) american chemical society) 91 a thesis [58] thoroughly investigated the protection efficacy of direct cvd grown gr on copper, depending on flake size and uniformity, duration and temperature of the heat treatment. key factors leading to firm protection performance both in terms of instantaneous and long-term functions are identified as to eliminate defects in the gr sheets, flakes must build up a flawlessly continuous, coherent, and uniform film. low nucleation and high growth rates must be maintained under low pressure to gain a low density of carbon spots (as probability of deposition decreases) and coherent films with the absence of unburied areas at flake boundaries. the films with large flake sizes were tested in a number of experiments to optimise growth parameters in order to reduce the amount of disorders, defects and void areas. a series of chemical oxidation experiments were performed by heating bare and coated copper foils at various temperatures and for various time frames. ellipsometry helped characterise the thickness of oxide layers on the highly reflective copper. heat treatment was carried out at 120 ºc under air for up to 76.5 hours. the growth rate of copper oxide layers, as an inherent indicator of the oxidation rate, almost linearly increased with time and the difference was only ca. a factor of six between the bare and coated copper foils. corrosion deterioration was located at two spots where air leaked through defects in the gr film and around its flake boundaries. following growth time in low pressure cvd experiments, films were grown in a way that their flakes were not connected. therefore, flake growth stopped before expanding sufficiently to connect with one another. then oxidation was performed at 190 ºc for up to 37 h and 26 min. optical microscopy images revealed a remarkable difference between the bare and coated copper samples. then oxidation was repeated with closely spaced gr flakes investigated by optical and sem. the samples with closely spaced flakes gave very good results after a 30 min treatment at 190 ºc. a 13.5 h treatment led to minor deterioration in the substrate exhibiting black oxide patches on the surface but a 23 h and 35 min annealing resulted in corrosion of nearly the entire surface. in a series of experiments, copper substrates coated with continuous gr flakes were treated at 190 ºc for various periods of time. after a 30 min heating, samples exhibited a fine condition with some proportion of the surface composed of dark copper oxide. after a 10 h and 45 min treatment, migration of the corrosion front on the copper surface (cuo formation) proved to be far advancing and the heavily corroded areas showed a homogeneous distribution in the form of tree roots. optical microscope images after 35 hours of heating indicated heavy corrosion, but the surface was not fully covered with oxides. raman spectroscopy quantitatively characterised copper oxidation, which could proceed at flake boundaries as they feature the least hindrance to mass transport of depolarisators and the large sheets did not damage or etch oxidatively inside. apart from growth related issues, electrochemical aspects of the shortfalls may also be relevant. gr films, acting as physical separators, might take part in electron transport, helping interfacial charge-transfer perpendicular to the surface based on good coupling and ballistic electron transport parallel to the basal plane of the sheets. oxygen adsorption and reduction reactions with low activation energies may further complicate the application of this material, which has been recently underlined in a shortand long-term performance test of gr/cu and si substrates [59]. results clarified that the samples heated at 250 ºc for 6 min showed heavy oxidised spots on bare copper, but little oxidation on the gr coated one. therefore, gr served as a sufficient oxidation barrier helping to preserve the metallic state from chemical oxidation over a short time period at high temperatures. nonetheless, long-term annealing of coated copper led to severe oxidation probably because oxygen diffusion proceeded through discontinuities and defects around gr sheets. after 17 h at 250 ºc, coated copper became heavily oxidised in a way indistinguishable from the bare specimens subjected to the same conditions. similarly, a 15 min treatment at 185 ºc resulted in partial oxidisation of bare copper but coated samples remained almost entirely in a pristine state. nevertheless, after 17 h annealing in air at 185 ºc, both bare and monolayer coated substrates became severely corroded and the products were identified as cupric oxide (cuo) in a stoichiometric ratio. the timescale of protection against thermal oxidation by gr on copper was estimated to be ~1 h at 185 oc and ca. ten times faster at 250 ºc. to explore the long-term protection ability under less severe conditions, bare and coated copper specimens were stored under ambient conditions (at 25 ºc) at low but variable humidity levels for up to two years. bare copper showed relatively slow oxidation at room temperature. gr/cu tested after up to eighteen months exhibited oxide-free condition over the first two weeks but within a month the surface started to tarnish non-uniformly (in several hundreds of micrometres in size). within a few months, most of the regions became heavily oxidised with an estimated oxide layer thickness of tens or hundreds of nanometres. alignment between the substrate grains and gr flakes was concluded to have an influence on oxygen and water diffusion along the surface. after eighteen months, the entire surface had become oxidised as edax analysis revealed a predominant percentage of cuprous oxide (cu2o) in the oxide phase. gr/silicon gave similar results as bare and coated samples were compared to each other after one week under atmospheric conditions, indicating an increased oxygen content of silicon as time of exposure increased. according to the outcome of the series of experiments, short-term oxidation testing reflected some degree of protection but long-term propagation unveiled extensive wet corrosion, similar to that seen in the case of bare copper specimens. the high rate of the wet corrosion of copper is due to promoted galvanic cell formation on a micrometre scale at ambient temperature, especially over long-term exposure. as a special field, the majority of medical applications require metals even today, in bone and joint replacements [60, 61], stents [62, 63] dental materials [64, 65], pacemakers and generators [66, 67]. stainless 92 steel, titanium and cobalt alloys are the most common orthopaedic materials for joint prostheses articulated with a plastic bearing surface for many body parts [68, 69]. there are areas that require the use of alloys of mercury, silver, tin, copper along with limited amounts of zinc, palladium, indium, selenium and titanium in dental surgery [70, 71]. despite the numerous successes, the main disadvantage of most of the alloys in medicine is their corrosion and the resulting physical deterioration (disintegration), quantity loss and contingent toxic side effects. the increased concentration of the aforementioned elements as soluble metals surely leads to chemical reactions of altered enzyme functions. it has been proven that soluble metals released because of corrosion processes can induce an innate monocytesmacrophage response and trigger immune responses, causing toxic, inflammatory, allergic or mutagenic reactions to patients [72]. in addition, corrosion leads to the adverse formation of metallic debris; solid particles and inorganic or organometallic compounds, in the periprosthetic soft tissues causing metallosis [73]. furthermore, the corrosion degraded structural integrity leads to the premature failure and loosening of the metal devices [74]. therefore, corrosion protection of metals used in physiological environments is of paramount importance and needs to be properly addressed for the sake of durable successful biomedical applications. currently ceramic coatings are the most widely used to isolate metals from body fluids, e.g., zirconia transited from a zirconium alloy minimises corrosion in knee implants but the implants roughen with time. nano-size diamond coatings and apatite-nano-diamond composites are promising candidates for the protection of metallic implants [75, 76], but they are highly permeable and greater surface roughness notably decreases their performance. nowadays, atomic thin gr films enhance the bioand hemo-compatibility of implants to some extent [77, 78]. interestingly, the outcome of almost all cell viability tests showed the biocompatibility of gr on the nickel-titanium surface with some protection. after considering these facts, studies focused on clarifying the possibility of application of gr as a corrosion protective film on structural metals used for biomedical devices. the most important future application would be the efficient corrosion protection of metallic prosthetics to avoid serious health problems to patients. in an effort to offer an alternative to protect metallic implants, gr was proposed as a biocompatible and protective film as well [79]. copper was the substrate for cell viability tests to reveal any change in immune response (lymphocyte transformation test) and the metal sensitivity test because of its high toxicity [80] making the experiment sensitive to reflect any significant protection. in vivo experiments served to study the protection of copper in live animals to evaluate gr as a biocompatible film in physiological conditions. corrosion inhibition of copper with gr films was studied by the way of release and accumulation of copper ions in biological aqueous environments of phosphate buffered saline, fatal bovine serum and hank’s balanced salt solution. cell culture figure 8: concentration of cu(ii) ions from different biological solutions: in (a) pbs, (b) fbs, (c) hbss solutions, and (d) cell culture media in the presence of sl (black) and bl gr/cu (red), cu (blue) and blank solutions as controls (pink) measured by inductively coupled plasma-mass spectrometry (icp-ms). all results are presented in a mass ratio (ppm) [79] (republished by courtesy of the publisher, nature publishing group) 93 media were monitored with inductively coupled plasma optical emission spectroscopy (icp-oes) for five days. single-layer gr/copper indicated slightly varied but very good conditions on average. the copper ion release rate was found to be at least an order of magnitude lower compared to bare copper that correlates almost linearly with time. the copper concentration in the solutions was higher when bilayer gr/specimens propagated as compared to those of the tests with sl gr obtained in all solutions. this was attributed to the stronger adhesion of sl films to metallic surfaces than bilayer ones, probably because of the better adaption to surface topography with high flexibility [81]. fig.8 shows the concentration of copper ions detected in different biological solutions such as phosphate buffered saline (pbs), fetal bovine serum (fbs), hank's balanced salt solution (hbss) and cell culture media with sl and bl gr films and blank solutions as controls. cell viability tests indicated almost the same results with singleand bilayer gr/copper samples showing ±2.2 and 2.6% differences respectively compared to the control samples after the first day. nonetheless, the results produced by low concentrations of dissolved copper in test solutions do not mean good results overall because the ion concentration could be much higher in a micro-milieu between the cells and coated substrate. the point of such a difference can explain why the cell viability dropped remarkably by more than 90% over the second, third, and fourth days of the test compared to the gr contained samples although the copper concentration in the solutions remained very low (less than 70 ppm). probably interfacial accumulation of metal ions must play a pivotal role in exceeding the toxicity limit, inevitably triggering lower cell viability. to resolve this problem, a further modification of the metal surface was necessary [82, 83]. by self-assembly monolayer treatment with decanethiol, bare and gr/copper was modified with decanethiol, which was obviously assembled on the bare surface around the boundaries of gr flakes. this is because the seemingly proper protection of copper was accompanied by much improved cell viability over three days (fig.9). the thiol modified sl gr/cu indicated that cell viability was ca. 55.8% after an incubation period of three days compared to sl gr/cu (fig.10). thiol modified copper showed an improvement of up to 2% in comparison to the less than 1% viability observed for bare copper. these results suggest that gr on copper is the major factor for protection, which can be appropriately enhanced by thiol modification. the film was also found to reduce immune response to copper in a clinical setting by a lymphocyte transformation test. animal experiments indicated a positive outcome to coated copper samples tested under in vivo conditions. the copper concentration was less than 3 and ~4.5 ppm in blood samples extracted from living rats implanted with sl coated and bare foils, reflecting the potential of thin gr films in biomedical applications. cvd-grown graphene loading on metal surfaces by mechanical and electrical techniques spin-coating there are a number of techniques to obtain high quality thin films. static and dynamic dispense techniques such as dip [84-86], angle-dependent dip [87, 88], and hot dip spin, spin [89-92], spray [93], flow [94, 95], capillary [96, 97], roll [98], and reverse roll coating [99, 100] have developed thin layers on solid surfaces. by careful design, it is also possible to complement one another, offering a way to be tailored to application demands. optimisation of these techniques is mostly dependent on actual parameters of the fluid phases and molecular or colloid solutions such as concentration, temperature, pressure, partial pressure or volatility of substances and solvents, dynamic or kinetic viscosity, and surface tension of fluid phases. the texture (roughness) of the substrate surface has much less influence (except for the surface energy) on the quality and quantity of casting. drying and curing might later take place. from them, the ones featuring well controllable gr growth are detailed in the following. both spin-coating (sc) and kinetic spray (ks) are relatively novel techniques enabling us to form coatings of good quality on any sort of surface texture regardless of the substrates. sc is figure 9: relative cell viability and concentration of cu(ii) ions as a function of time. (a) relative cell viability vs. time for slg/cu, blg/cu and cu; (b) concentration of cu(ii) ions in the cell culture medium after incubation with slg/cu. blg/cu and cu (calculated from icp-ms). a medium taken from a regular cell culture without cu foils was used as the control [79] (republished by courtesy of the publisher, nature publishing group) 94 suitable to work out and implement practical deposition methods for atom-thick films on various metals, although a different approach must be applied for newtonian [101] and non-newtonian fluids [102]. uniform coatings can be obtained over large areas with reproducible thicknesses in a good controllable manner, but only on planar substrates, which is a major limitation of this technique. sc starts by applying a small puddle onto the centre of the substrate, then spinning commences at initially a lower then, within a matter of seconds, at a higher rotational speed (two stages of centrifugation up to ~3000 rpm). the centrifugal force and centripetal acceleration result in excessive spreading of the fluids on the surface (wetting and covering depend on multiple physical-chemical parameters) and an inevitable loss (can be recycled) around the edges of the substrate until the spin-off time is completed. then, a thin film forms releasing solvents and curing takes place, because of chemical reactions. kinetic spray kinetic spray (ks) utilises a laval nozzle to spray gr colloid solutions at a very high speed and the supersonic acceleration leads to the production of very small droplets that evenly disperse then evaporate reducing the tendency of flake aggregation. besides the uniform and smooth layers, defects in the gr flakes were not observed. hence, high quality film production by ks depends on the energy of the impact stretches gr sheets then carbon atoms arrange into flawless hexagons based on plasticity probing of the gr flakes [103]. transmittance of graphene oxide (gro) film spray deposited on soda-lime glass (from a 10 wt.% colloid solution of gro in ethanol) was 73% and sheet resistance was 19 kω sq-1 using incident light at the wavelength of 550 nm. the electrical conductivity of the coatings increased by up to a thousand times after hydrazine reduction and annealing at 400 ºc. additional thermal annealing at 1100 ºc further enhanced conductivity by ca. 10 times. soda-lime glass with a transparency of 80% and electrical conductivity of 209 s cm-1 (or sheet resistance; rs = 2 kx sq-1) as applied to a 14 nm thick gr film [104]. ks is a reliable technique of wide commercial availability and offers a flexible solution to large-scale using according to recently reported corrosion tests [105-107]. electrospinning electrospinning (es) creates polymer fibres with a diameter range of between 40 and 2000 nm. the fibres can be made from solutions or from fused materials, controlling diameter size through the adjustment of figure 10: relative cell viability of (a) bone cells incubated with sl gr and sl gr/cu-sh, cu-sh and bare cu foil for 3 days. control is a regular cell culture without cu foils; (b) relative cell viability of bone cells incubated with tr-sl gr/cu, bare cu, tr-sl gr/cu-sh, and cu-sh for 1 day; (c) concentrations of cu(ii) ions in blood samples extracted from live rats with concentrations of cu(ii) from normal rats before implantation as control (black square), rats with implanted slg/cu foils (blue triangles) and rats with implanted cu foils (red dots) as a function of time [79] (republished by courtesy of the publisher, nature publishing group) 95 surface tension, solution concentration, conductivity and so forth [108-110]. es occurs when the electric force of the surface overcomes the surface tension of the fluid phase triggering an electric spark, results in the solution being expelled from a syringe forming jet flow impacts and deposits. when the expelled material dries out or solidifies, it forms an electrically charged fibre that can be directed or speeded up by electric forces. so, a polymer solution stored in a syringe is charged to a high electrical potential. as the jet stretches and dries, radial electrical forces cause it to splash repeatedly. dried, solidified fibres are collected on an electrically conductive (metal) screen. by es, the composition of nylon 6-6 and gr was prepared and deposited on porous silica then tested under various conditions [111]. oxidation and reduction potentials in acidic, alkaline, and peroxide solutions were assessed by dynamic polarisation. sem observations determined that treatment with acidic and basic solutions led to the formation of solid aggregates and slightly folded gro flakes. thermal treatment at 700 ºc gave samples with a porous structure. after annealing, a subsequent chemical derivatisation with acidic, basic and peroxide solutions assisted with ultrasonication facilitated the separation of gro sheets, leading to a solid composed of lower dimensional flakes, especially in the case of oxidation. oxidation was carried out in koh and the reduction in h2so4 solution. eis data obtained in the immersion test with a na2so4 solution indicated decreasing interfacial capacitance of the es produced samples with the ny-gro coatings. the eis data calculated at 0.8 hz changed between 1.4–4.5×10-5 and 7.5–8.9×10-7 f cm-2 (depending on the concentration of the electrolyte) with the gro content increasing from 0.4 wt.% to 2 wt.%. electrophoresis electrophoretic deposition (epd) is a promising technique to fabricate functionally graded [112-114] and hybrid composites [115, 116], laminated nano-ceramics [117, 118], and functional, nanostructured films and coatings [119-121]. in the last couple of years, numerous epd applications have emerged as industries count on commercial advantages over other fabrication routes. it is a versatile and cost effective technique with acceptable levels of control over microstructure, stoichiometry, and macroscopic-microscopic dimensions and properties [122, 123]. epd is a two-step colloid process in which electrostatically charged particles, suspended in a liquid medium, migrate according to the electric field towards the oppositely charged electrode. then particles deposit, and flocculate on the electrode surface forming a relatively dense, homogeneously packed, bonded layer. increasing the volume fraction of the nanoparticles and their deposition on the surface of any electrically conductive material is relatively easy. usually, a post-treatment is required to increase the density of deposits and eliminate porosity [122]. sometimes special modifications are required to render surfaces with notable properties such as increasing hydrophobicity by silylation. epd is performed in stable colloid solutions in which there are plenty of electrostatically charged particles migrating in response to an impressed dc electric field and deposit either as a loose homogeneous or compact film onto the oppositely charged electrodes. to make deposits denser and eliminate porosity, additional epd or heat treatment is required. oxide particles, conductive polymers [124] and highly dispersed activated carbon [125] of nearly any size in colloidal suspensions [122] were deposited by this method, reflecting its high versatility. furthermore, by electrophoresis uniform thin layers can be made on highly ragged, complex surfaces. moderate electrical conductivity of the resulting substrates is the only requirement. the sample surface is treated as a whole in a uniform manner, whereas dimensions, deposition rate, uniformity and scale up features are also favourable. epd is a preferable alternative to many other methods like slurry dipping, thermal and plasma spraying, sputtering, and physical/chemical vapour deposition. in the course of thick gr layer deposition on copper by epd [126], deoxygenation of carbon was hinted at by bathochromic shifts in the uv spectra because of the electrochemical configuration and reaction mechanism. potentiodynamic scanning showed positively shifted corrosion potentials and lower corrosion currents (icorr), which suggested only mediocre protection by the thick gr films in the initial phase of immersion propagation. the composite coating of reduced gro was prepared by cathodic epd in an aqueous solution in a symmetrical cell-electrode arrangement [127]. optimum conditions for cathodic deposition were found to produce a thickness of ~40 nm by applying 10 v for 30 s. sem observations revealed the size of the gro sheets being 1–2 µm, covering the surface uniformly. the composite coating was shown to protect copper firmly from electrochemical corrosion. potentiodynamic measurements indicated an ennobled free corrosion potential with slightly reduced anodic and cathodic current branches, suggesting a lower corrosion rate of the composite coated copper compared to its bare form during the early phase of propagation. experimental conditions are summarised in table 2. by electrophoresis, gro was uniformly deposited on a permanent magnet, e.g., ndfeb and the coating was subsequently reduced to partially remove functional groups containing oxygen [128]. the epd gro coating showed substantially better adhesion to the substrate compared to the spin-coated ones. the surface of the bare ndfeb was rough and porous but site-dependent topography of the epd-gro modified samples depended on the amount loaded. the relationship between the increasing thickness and decreasing adhesion of the coating with an extension of deposition time was determined. raman, infrared, and x-ray photoelectron spectroscopy (xps) results reflected the strong adhesion of epd films and that was connected to the koble-type decarboxylation mechanism [129, 130] of the surface yielding gro flakes. an unexpected outcome was that several deterioration reactions were observed in gro. the signal of epoxy groups decreased 96 after deposition, which might be explained by the high anodic electrode potential applied to the working electrode and the large potential drop at the interface. the decrease in current density during potentiodynamic scanning and the positive shift in the free corrosion potential of the system reflected efficient initial protection but lower cohesion and adhesion of the thicker coatings, leading to a poorer protection potential. the gro-acrylic polymer composite fully covered the copper substrates, but the sheets were separated far from one another in an island like manner consequently a large percentage of the surface remained unburied [131]. as for the reagents, solution and cell arrangement, epd conditions e.g. voltage (10 v) and deposition time (30 s) proved to be optimal to obtain crack-free films of an average thickness of 45 nm. an electrochemical investigation indicated insignificant protection performance of the composite coating under immersion propagation. a steady corrosion current extrapolated to the ocp region showed slight changes over the anodic and cathodic regions. a current density drop of 38.3–3.5 µa cm-2 was observed in comparison to the bare copper. a polarisation resistance of the composite covered specimen was assessed by eis, assigning an increased charge-transfer resistance of ~25 ω cm-2 (bare copper: ~8 ω cm-2). stainless steel specimens with an exposed geometrical surface of 100 cm2 were almost uniformly deposited with gro in h2so4 solution by coupling the substrate cathodically [132]. for transferring purposes, chemical and electrochemical etching was developed to delaminate the reduced gro film, giving coherent freestanding membranes or deposit them onto other substrates. by optimising electrophoretic parameters, a low voltage of 3 v was found to consolidate reduced gro layers preferentially aligned in an in-plane direction through a cohesive electrophoretic squeezing force in near volume range of the electrode (cathode). the free-standing gr membrane was reduced, annealed at 1000 ºc then a graphite-like architecture evolved with a d-spacing of 3.42 å and c/o ratio of 16.7. electrical conductivity was of high as 5.5×105 s m-1. graphene coated metals in electrochemical cells and batteries because corrosion is a serious problem in energy storage devices like batteries and fuel-cells [133], the application of gro as a barrier coating to inhibit the corrosion of aluminium electrodes in lithium ion batteries is considered to be an innovative solution. spin-coating was employed to coat aluminium with gro and decrease the corrosion rate when the electrode was subjected to the electrolyte of lipf6 (1.0 m) dissolved in ethylene carbonate and dimethylcarbonate (50:50 vol.%) [134]. sem observations with energy dispersive x-ray spectroscopy analysis and atomic force microscopy (afm) scanning suggested increasing surface roughness of aluminium with lower gro quantity, but its greater amount helped reduce the roughness remarkably. the average roughness of the bare substrate was around 350 nm, which changed to 199-154 nm for the gro loaded one. the thickness of the film showed great epitaxial variety even though the coating was relatively thick. cyclic voltammetry showed a decreasing electrochemical current response of the gro coated electrodes with increasing surface loading. this indicated hindered and impeded chargetransfer through the electrode interface without any direct implication of capacitive and adsorption charge loss in the current transients. accordingly, chronoamperometry curves exhibited moderately changing characteristics (as a consequence of altered electrode kinetics) in the early phase of the transients and table 2: metallic substrate, type and growth parameters to obtain gr film by epd and chronoamperometry substrate preparation types and their parameters corrosion test parameters work-electrode surface (cm2) types of potentiodynamic tests ref. cu gro, epd in sol. c = 1.0 mg cm-3, e=1 v / 10 mm-1, 10 min air ox. at 200 ºc for 4 h, in 30 wt.% h2o2 for 2 min, then 0.1 m nacl solution unknown after 1 h at ocp, scan rate: 1 mv s-1 [131] cu red. gro with polyiso-cyanate cured with haa (hydroxyl acrylic acid), epd for 30 s, at e = 10 v 10 mm-1, 0.1 m nabh4 red. for 5 min 3.5 wt.% nacl, at 25 ºc 1 after 2 h at ocp, scan rate: 1 mv s-1 [132] ndfeb gro red., epd in sol. of 1 mg cm−3 gro, ndfeb anode & pt cathodic dep., e=10 v / 10 mm-1, 3.5 wt.% nacl solution at room temperature unknown eis [133] cu gro isocyanate cured with hydroxy acrylic, then silylation, epd on cu at 10-30 v 10 mm-1 3.5 wt.% nacl, at 25 ºc 1 eis [136] cu chronoamperometry of gro at −1.5 v for 10 min in sol. c = 2 g dm-3, in 0.1 m kcl, at −1.5 v for 10 min, then gro red. nabh4 (0.1m) for 5 min ocp 3.5 wt.% nacl sol. after 1 h 1 eis [138] mild steel epd in ni sol. at ph = 3, iρ = 1 a dm-2, at t = 40oc, gr c=100 mg dm-3 3.5 wt.% nacl, at 27 ºc 1 scan rate: 0.01 v s-1, eis [169] 97 decreasing base currents over the complete timescale because of the smaller electroactive surface. eis spectra suggested a somewhat higher resistance against pitting, the lower susceptibility to localised corrosion. thus, gro restricted aluminium oxidation, behaving as a charge-transfer barrier. otherwise, the lower capacity and potential of the cells should have been measured by the set-ups with the gro loaded electrodes during charge–discharge testing. instead, surprisingly the opposite was reported. nevertheless, enhanced cyclelife stability (lower rate of capacity loss) of the modified electrode compared to the cell configuration with bare aluminium is of course self-explanatory. self-discharge was lower as a decreasing rate of open circuit voltage decline was observed to the modified aluminium samples. gro films did not show any corrosion and the underlying native oxide layer remained intact under test conditions. microbiologically induced corrosion (mic) severely limits the structural integrity and lifetime of metallic structures in technological processes and applications because of frequently evolving mechanisms, i.e., crevice and pitting local corrosion phenomena. a microbial fuel cell (mfc) is a galvanic cell producing an electric current that causes bioelectro-chemical oxidation of organic substances on anodes and abiotic reduction on cathodes [135]. mfcs have been used as a galvanic tool to simulate extracellular electron transfer mechanisms of microbes and the bio-electrochemical oxidation of organic substances. in addition, metals are not used as anodes in mfcs due to their fast galvanic corrosion. owing to this, gr films are employed as barrier coatings and the corrosion rate of the working nickel electrode was evaluated by galvanic coupling in the mfc set-up [136]. regarding the experiment, it was determined that the geometrical ratio of the working and counter electrodes was the guarantee to maximise, and concentrate current densities on the working electrode. nevertheless, the cell design did not allow the assessment of adequate kinetic parameters (general corrosion rate) because of the large uncompensated ohmic drop and unfavourable cell geometry. these are all relevant in dc techniques, although inadequate voltammetric data could provide a rough estimation, even though 5 mv s-1 was higher than recommended and might have resulted in the considerable rate of adsorption and pseudo-capacitive current during the measurement. in relation to the impedance measurement and its evaluation, these data are even more sensitive to inappropriate cell design. the protection efficacy of the gr film was assessed under realistic operating conditions, the bare and coated nickel electrodes represented a 3d microporous structure. the overall outcome confirmed a retardation of corrosion processes by the gr film for extended periods. cv scanning showed decreased current transients of coated nickel, which was ca. ten thousand times lower than measured for the bare nickel electrode based mfc after a propagation for 2800 h. nickel dissolution rates of the gr coated anodes were at least ten times lower than the baseline (uncoated) electrode. eis characterisation confirmed impeded mic on the gr/nickel for ca. 40 folds in comparison with uncoated electrodes. the effective masking of nickel from the mixture of microorganisms and their metabolic products was concluded. composite graphene coatings physically mixed and in situ polymerised mixtures chronoamperometry was successfully employed to prepare gr coated copper, starting from an aqueous colloid solution of gro [137]. as a result of the epd process, a seemingly compact and void of area without coating; and polymer film with gr inclusion was obtained. nevertheless, the distribution of gr flakes was highly uneven and inhomogeneous (random), whereas the sheets showed various degrees of folding and overlapping in the polymer matrix. in addition, the fast reduction of gro in the polymer proves the high permeability of the matrix, although it reached a thickness of several micrometres. on the other hand, the coatings with reduced gro provided moderate protection for copper with an initial inhibition rate of 94% drawn from the potentiodynamic polarisation measurement data (at nil impressed potential). the corrosion rate reduced to 0.2 mm yr-1 from the rate for pure copper of ca. 3.65 mm yr-1. this assessment was only made at the beginning of the immersion test (after an hour), whilst waiting for stabilisation of the freshly installed cell set-up. in comparison with the eis investigation, the composite coating provided electrical insulation and ionic diffusion hindrance to the copper surface. so, the protection was related to the increased polarisation resistance of gr loaded coatings of ca. 26 ω cm2 compared to bare copper of 9 ω cm2. intrinsically conducting polymers (icps) like electroactive polyaniline (pani) have been widely used materials for some time providing corrosion protection regardless of the long-standing disagreement over the anodic protection mechanism and the generally less effective barrier nature. pani is a preferable electronconducting polymer with favourable properties over other alternatives. under optimal conditions, the protection mechanism leads to the formation of a passive (dense) metal oxide layer [138-140]. to increase protection performance, many substances such as well dispersed clay [141] with an aspect ratio of ca. 200 was aimed at lengthening mass transport pathways through the composite films for all redox active species. these polymer-clay mixtures exhibited notable protection improvements over neat polymers. besides the several attempts to combine of carbon nanotubes (cnts) with organic [142-156], inorganic, and metal [157-160] matrixes for corrosion protection and resistance, respectively, there are examples from the literature about testing gr-polymer composites for various purposes [160-162]. the main focus of these works was the exploitation of high relative aspect ratio of gr (ca. 500) [163] in comparison to exfoliated clay minerals. hence, gr is a key filler in advanced gas barrier materials, motivating studies to 98 achieve very low oxygen permeability using low filler contents (compared to neat polystyrene and the best polymer-clay mixture known at that time) [164] and underscore the possible obliteration of traditional claypolymer composites [165-169]. thus, a carefully designed and well-prepared pani-gr mixture exhibited outstanding impermeability characteristics against the diffusion of molecular oxygen and water vapour versus neat pani and pani-montmorillonite using a filler content of 0.5 wt.% and the excellent protection performance of steel substrates. potential ennoblement of steel electrodes with coatings of increasing gr content was considerable and an approximately fifteen times lower steady corrosion current was reported. the main reason for the success is mostly related to the high dispersity of gr in the composite of microscopically isolated and macroscopically non-percolating distribution [170]. experimental conditions are summarised in table 3. lower electrical and ionic conductivities always provide better corrosion protection. therefore, metals coated with gr filled composites of electrically less or non-conducting (practically insulating) matrices like epoxy (in the case of high dispersity) can behave as a super-hydrophobic interface [171-176]. these composites are characterised by a water contact angle of at least 150º making them repellent, resistant to water absorption [177] and their exceptionally good antiwetting properties results in good corrosion prevention potentials. the nano-casting prepared epoxy-gr composite featured high hydrophobicity and provided excellent protection for cold-rolled steel (crs) panels [178]. fig.11 shows tafel plots of bare, epoxy, hydrophobic epoxy (he) and hydrophobic epoxy-gr composite (hegc) coated crs panels. the open circuit potential of the immersion tested steel panels coated with epoxygr showed appreciable ennoblement of ca. 0.3 v and ca. ten times lower corrosion currents compared to neat epoxy coated steel. the much higher polarisation resistance was partly attributed to the more hindered mass transport through the gr loaded coating (with less than half the oxygen permeability) and access to its interface on the fluid side as a result of the finely patterned structure of the outer surface. the reproducibility of the data is questionable because parameters were not representative to properly describe the kinetic processes of the system, proceeding at the metal-solution interface. as in other cases, electrochemical techniques gave instantaneous rate assessments (in the first 30 min of the tests). thus, the reported data are not suitable for forecasting long-term corrosion rates. table 3: metallic substrate, type and growth parameters to obtain gr films by spin coating and solution casting. types and settings of corrosion tests and electrodes with the reference number of the article substrate preparation type and parameters corrosion test parameters work-electrode surface (cm2) types of electrochemical tests ref. porous silica electrospin gr-nylon 6-6 in formic acid agitated for 12 h then add. of gro, es at 12 kv, flow rate: 0.2 ml h-1 for hours, electrode: polymer solution 90 wt.% of formic acid with 0.36-2 wt.% gro and ny potentiostatic oxidation in koh (0.5 m) for 3.5 h, reduction in h2so4 at ph = 2 for 8 h, eis in na2so4 in (110-1-10-2-10-3 m) for hours unknown potentiostatic treatment, potentiodynamic polarisation, scan rate: 100 mv min-1, eis [112] alox gro sonication in ethanol then spincoating lipf6 in ethylene carbonate and dimethyl-carbonate (50:50 vol.%); at 1.0 m 100 cyclic voltammetry, chronoamperometry, potentiodynamic polarisation and eis [114] cu spin-coating of gr with acetone (20 cm3 cm-2) then rapid annealing 8001000 ºc for 3 min seawater 3.0–3.5% nacl 0.25 potentiodynamic polarisation, scan rate: 2 mv s-1, eis [136] steel pani-gr comp. (nmp complex and casting) 3.5 wt.% nacl solution unknown potentiodynamic polarisation [153] coldrolled steel gro red. with n2h2, pressing powders then curing (thickness: ~120 µm) 3.5 wt.% nacl, at 25oc 1 potentiodynamic scanning at 10 mv min-1, after 30 min eis [161] low alloy steel 2 wt.% gr/mwcnt/pei & 20 wt.% gr/pei comp.-s, dispersion in paa cured at 150 ºc for 5 min, then 250 ºc for 5 min for imidisation 3.5 wt.% nacl solution 9.62 potentiodynamic polarisation (scan rate: 1.67 mv s-1) [7] figure 11: tafel plots of the (a) bare, (b) epoxy-coated, (c) he coated, and (d) hegc-coated crs electrodes [178] (by courtesy of the publisher, elsevier) 99 a more exotic approach is to develop metal-gr composites for corrosion protection, although this strategy may have more disadvantages than advantages like with the metal-cnts [179-182] because of the cnt activity towards catalytic oxygen reduction reactions [183-185]. electrodeposited thin films of nickel matrix with gr inclusion indicated a slight improvement in general protection performance; ennobled ocps by ~0.1 v and steady corrosion currents reduced by over 50% were observed in comparison with pure nickel coated mild steel [186]. as a result of greatly affected nucleation and growth rate, measurement results are much more related to the highly altered crystalline structure of the nickel host matrix (lower electrical conductivity was unfortunately not characterised) as a consequence of the inclusion of gr sheets, but differences in the texture and hardness of pure nickel and the gr-nickel coatings were reported. similarly to many other works, protection efficacy was not evaluated and reported over long-term immersion testing. on the one hand, the tafel analysis of ni and ni–gr performed in 3.5 wt.% nacl solution (in fig.12) was carried out using high voltage rate scanning without ohmic drop compensation, leading to distorted current legs over both potential regions (from the open-circuit or free corrosion potential of the electrode). a less representative transient is due to the low proportion of faradaic charge-transfer current primarily assigned to the credible corrosion rate assessment. probably due to these reasons, there is not much difference between the given corrosion currents of ni and ni-gr samples. the gr incorporation, cathodic and anodic tafel regions exhibited almost ideal symmetry. this should mean the same scale of activation (expressed as a transfer function) in the cathodic (reduction and deposition) and anodic (oxidation and dissolution and/or deposition) processes. this feature is a kind of ineffectively blocked electrode behaviour, a quite reversible characteristic with less viable hindrance either in the anodic or cathodic processes. this suggestion seems to be confirmed by the reported similar corrosion currents. on the other hand, the adequacy of eis data may also be doubtful as basic requirements of system stability (in the time domain), linearity (immediate response), and causality (the unquestionable relationship between perturbation and type-degree of response) might not be met. the time frame of 5 min to wait for a stationary or a steady-state condition then making measurements is in itself questionable. the large variation in the solution resistance (between the pure and composite ni coating) is surely inadequate. in addition, the highly varied interfacial and coating resistance (swop between them) along with a hundred times difference in the coating capacitance are also unbelievable and can lead only to false interpretation. the depressed semicircle is a result of the complexity of the ni/gr electrode interface. the electrode was a porous electron and ion conductor and such systems need to be carefully handled (modelled with at least two transmission lines) when evaluation of impedance spectra in relation to structure and mechanistic behaviour of a complicated interface comes into the picture. therefore, presented data and the corresponding evaluation are not appropriate and even misleading. an innovative approach is the composite of multiwalled cnts (mwcnts) and exfoliated gr embedded in polyether-imide (pei) serving as a coherent and porefree matrix [187]. this endeavour was made in an attempt to achieve a uniform dispersion of the nano-size additives in the host matrix (without functionalisation of the filler phase) and good adhesion of tailored pei to the substrate, facilitating the maximum attainable corrosion protection performance. the protection mechanism was delineated according to the following: the composite protects steel alloys by a complex, active–passive way, serving as a physical barrier to water permeation against the evolution of ion channels to the metal surface and passivating metal surface by electron depletion at the interface based on the schottky barrier effect [188-190]. figure 12: tafel curves of ni and ni–gr materials [186] (by courtesy of the publisher, elsevier) figure 13: cryo-fractured sem images of (a) and (b), pei, (c) and (d) 2 wt.% nfg/mwcnt/pei, (e) and (f) 20 wt.% unfg/pei [187] (published with permission from the! american ceramic society bulletin) 100 exfoliated but non-functionalised gr was derived from ultrasonication in a solution of n-methyl-pyrrolidone (nmp). pei as a host matrix was selected for its flexibility under a high glass transition temperature (155 ºc), thermal stability, firm resistance against radiation and appropriate interaction with carbon fillers via π–π stacking [191-193]. in situ synthesis and the imidisation protocol yielded coatings with appropriate adhesion properties to the steel surface of a thickness of 15– 20 µm, whereas agglomeration and phase segregation of the fillers were low with the mwcnts. the sem investigation revealed a fairly smooth surface finish without cracks or visible pinholes in the coatings. no phase segregation of the gr and mwcnt fillers was observed in the mixtures around the interface as its clearly seen in fig.13 of the cryo-fractured samples of non-functionalised gr (nfg), carbon nanotubes and pei in 2 wt.% (c and d) and nfg/pei of 20 wt.% (e, f) in comparison with pure pei (a and b). ocps were positively shifted by ~0.6 v, meaning a remarkable ennoblement. this was inferred, although substrates with high resistance coatings showing notable positive potentials must be at least partially attributed to the potential drop through the coatings [194] as a result of masking the real corrosion potential of the metalcoating interface to various extents. a potentiodynamic test indicated current densities of several orders of magnitudes lower (~10-9 a cm-2) for composite coated specimens compared to bare low-alloy and galvanised steel samples with current densities of ~10-5 a cm-2. immersion tested samples were characterised quantitatively with regards to the perspective of corrosion rate or protection of steel substrates by weight-loss measurement (according to the astm-g1 protocol) after 3,144 hours. the substrate coated with 20 wt% gr-pei performed best with ca. thousand times lower corrosion rates (ca. 8.5×10-4 mm year-1) than bare low-alloy steel samples (ca. 1.2×10-1 mm year-1). however, the pei film containing gr and mwcnt (ca. 9.2×10-3 mm year-1) manifested a moderate average corrosion rate of ca. 5.5×10-4 mm year-1 compared to the neat pei film. concluding remarks overall, it is evident that atomic pure graphene films lack uniformity and partly this leads to insufficient instantaneous protection performance. therefore, some sort of physical and/or chemical post-treatment is needed to facilitate long-term protection performance from direct deposition techniques, the broadly and thoroughly investigated cvd technique is undoubtedly a viable alternative when large-scale continuous surface finishing is highly demanded. however, it is far from the best choice when corrosion protection efficiency and durability are the priorities, due to the complexity of growing cohesive films on the surface of metal substrates with preferable orientation of the grains, and weak adherence of gr films sensitive to mechanical and surface charging effects. when performance is an essential preference then spin-coating, kinetic spray, electro-spinning, and electrophoretic deposition should be employed depending on the complexity of the surface, conductivity of the substrate and additional technological aspects in relation to further processes. among them, spin-coating and kinetic spray techniques develop good quality and homogeneous coatings of greatly varied thicknesses. thin and ultra-thin films feature high a dispersity, and an even distribution and sometimes even improved quality of the nanoparticles. when thicker coatings are obtained on electrically conducting substrates with strong adhesion to complex surface geometries without the matter of a certain degree of alteration of the nanoparticles, then electrophoretic deposition must be used. with respect to the utilisation of pure ultra-thin gr films and thicker coatings as gr-filled composites, there are ways to achieve further progress in relation to the ultimate aim of improved corrosion protection. for example, thin gr films can still be used as a primary metal surface finishing. alternatively, strongly adhering matrices with gr filler might obviously mean a far more robust solution with protection efficacy targeting high performance demands for real situations. parameters like the combination and concentration of the fillers, and compatibility with the host matrices besides matching complementary technological requirements need to be carefully optimised to gain appropriate barrier and/or inhibition functions. acknowledgement the publication of this review was supported by associate professor olivér bánhidi, university of miskolc. his contribution is greatly appreciated. references [1] novoselov k.s., geim a.k., morozov s.v., jiang d., zhang y., dubonos s.v., grigorieva i.v., firsov a.a.: 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(eds.): handbook of corrosion protection, theory and practice of electrochemical protection processes, third edition, golf publishing company, houston tx, usa, 1997 hungarian journal of industry and chemistry veszprém vol. 41(2) pp. 109–114 (2013) investigations of bio-gasoil production péter solymosi, ! zoltán varga, and jenő hancsók mol department of hydrocarbonand coal processing, university of pannonia, egyetem u. 10., veszprém, 8200, hungary !email: solymosip@almos.uni-pannon.hu liquid engine fuels are the main source of power for transportation in the passenger sector. it is the projection of the european union (eu) to reach 10% utilisation of renewable fuels by 2020. to achieve this goal the eu created the 2003/30/ec and furthermore the 2009/28/ec directives. for example, the feedstocks of these renewable engine fuels can be non-edible oil plant hybrids, such as rapeseed oils with high euric acid content obtained from special hybrids of rape (e.g. brassica napus) waste lards (used cooking oil and slaughterhouse lards). if the preconditions of utilisation are given with respect to the sustainability and technical compatibility of motor engines and vehicle construction, these bio components can be blended with motor fuels in large quantities. considering the properties of currently used first generation biofuels, the maximum amount of bio-component in engine fuels is approximately 7 (v/v)% fatty acidmethylester in diesel fuels. a reliable production technology of second generation biofuels, which can be blended into diesel fuels is the heterogenic catalytic hydrogenation of triglycerides and waste lards. furthermore, isomerisation can improve the quality of a bio-paraffin mixture. in this context, we studied the isomerisation of bio-paraffin mixtures, which were obtained from the hydrodeoxygenation of vegetable oil. the characteristics of these products were favourable, such as their cetane number being higher than 75, for example. the actual en590:2013 standard does not limit the blending ratio of the paraffinic bio-component in diesel fuels. consequently, these products obtained by the catalytic hydrogenation of vegetable oils can be blended into gasoil by up to 10 % or even more to meet the above eu requirements with respect to the utilisation of renewable fuels. keywords: bio gasoil, hydrodeoxygenation, catalytic conversion, biofuels, blending diesel fuels introduction interest in alternative fuels is on the rise due to the unequal presence of the fossil energy carriers, the periodic rise in the price of fossil fuels, the need for decreasing dependence on crude oil, and the regulations of the european union. they can play a significant role in achieving the eu plan to reach a 10% energy ratio of total fuel consumption using alternative fuels by 2020. thus, the application of the biofuels can be increased to a large degree in the longand medium-terms. for example, in some countries the domestic demand on biofuels could increase to 20% by 2030, along with the decrease in the demand for engine fuels that could be up to 70%. the world’s energy production from biomass could reach 5% by 2050 [4, 5]. accordingly, to ensure the availability of this feedstock the production costs could decrease. to achieve these goals, the eu created several directives (1998/70/ec, 2001/77/ec, 2003/17/ec, 2003/30/ec, 2003/87/ec, 2009/28/ce, and 2009/30/ce). natural triglycerides like vegetable oils (edible or non-edible/waste) can be feedstock for biofuels as alternative energy sources [6, 7], such as special breeding non-edible oil plants [8, 9], animal fats or waste cooking oil [10, 11]. during the conversion of natural triglyceride molecules to bio-gasoil the following reactions take place [1, 2, 3]: • full saturation of double bonds (hydrogenation), • heteroatom removal o oxygen removal " hydrodeoxygenation (hdo reaction, and reduction) " decarboxylation, " decarbonylation o removing of other heteroatoms (sulphur, nitrogen, phosphorous, and metals), • isomerisation of n-paraffins that are formed during the removal of oxygen • different side reactions o hydrocracking of the fatty acid chain of triglyceride molecules, o water-gas shift reaction o methanisation, o cyclisation, aromatisation, etc. during the hdo reduction reaction normal paraffins are formed with carbon numbers that are equal to the fatty acids in triglycerides. in the case of decarboxylation and decarbonylation reactions (hdc) normal alkanes are produced, where the carbon number is one less than that of fatty acids of the original vegetable (fig.1). bio-gasoil is a mixture of gasoil with the boiling range of isoand normal-paraffins. it can be obtained by the hydrogenation of vegetable oils and natural triglycerides 110 from other sources. these constitute the second generation biofuel components of diesel engines. they have good quality characteristics, such as high cetane number, good flow properties, unlimited mixability with engine fuels, and the a production line compatible with existing refinery structures [18, 19]. the actual en 590:2013 standard does not limit the blending ratio of second generation bio-components, while the blending of biodiesel is limited to 7 v/v%. all the above mentioned aspects of alternative fuels can rationalise the investigation of the hydrogenation of non-traditional feedstock sources. these are the vegetable oils that can be obtained from non-edible hybrid oil-plants, rapeseed oil from brassica napus with high euric acid content to produce diesel fuel blending components with good flow properties in colder conditions (below +5 °c). the freezing point of iso-paraffins from bio-sources is lower than for equal chain length normal-paraffins (fig.1) [12-15, 17]. thus, products with high iso-paraffin contents have more favourable cold flow properties (cfpp) with cloud points at lower temperatures (fig.2). the aim of our work was the production of diesel gasoil blending components via the isomerisation of paraffin mixtures obtained from the hydrodeoxygenation of rapeseed oil with high euric acid content. experimental in this work, a diesel gasoil bio-blending component production technique was investigated that meets the requirements of the en:590 standard with the possibility of blending it with engine fuels in unlimited quantities. thus, the hydrodeoxygenation of natural triglycerides and further the isomerisation of the obtained bio-paraffin mixture were investigated over the pt-sapo-11 catalyst [16] developed in-house. the effect of the operation parameters, such as temperature, pressure, and liquid hourly space velocity (lhsv) was studied on the yield, composition, and utilisation properties of the products. experimental apparatus and product separation the experimental tests were carried out in one of the measured sections of a high-pressure reactor system containing two tubular reactors with a isothermal catalyst volume of 100 cm3. the reactor system contained all the equipment and devices applied in the reactor system of a hydrotreating plant. the apparatus is suitable for maintaining if not succeeding the industrial precision of main process parameters. analytical methods the main properties of the feedstock materials and products were determined by standard methods. the hydrocarbon composition of the bio-paraffin mixture was determined by high temperature gas chromatography (shimadzu 2010 gc [column: phonomenex zebron mxt]). process parameters the ranges of the applied process parameters in the isomerisation test on the basis of our earlier experimental results [13, 14, 17, 20-23] were as follows: temperature 300–360 °c, total pressure 20–80 bar, liquid hourly space velocity (lhsv) 1.0 h-1, and h2/feed volume ratio of 400 nm3 m-3. feedstock materials the feedstock of the catalytic tests was a bio-paraffin mixture, which was obtained from the hydrodeoxygenation of rapeseed with euric acid produced in hungary. it was properly filtered as a pre-treatment. the main properties of the feedstock material are shown in table 1. the catalyst was pt-sapo-11 (0.5 % pt), the main properties of this can be found in table 2. figure 1: pathways for the removal of oxygen from vegetable oils figure 2: the freezing point of iso-paraffins as a function of the branch position 111 results and analysis the first step was to produce a bio-paraffin mixture with a boiling range of gasoil from rapeseed with a high euric acid content. the properties of the bio-paraffin are summarised in table 1. the commercially available nimo/al2o3 catalyst was utilised for the production of the bio-paraffin mixture. during the catalytic test the employed operation parameters were as follows: 320– 380 °c, 20–80 bar, lhsv = 1.0 h-1, and h2/ch ratio of 600 nm3 m-3 [8]. it was found that the favourable operation parameters are 340 °c, 40 bar, lhsv=1.0 h-1, and h2/ch ratio of 600 nm3 m-3. the tested catalyst is suitable for the production of bio-paraffin mixtures with high yields from natural triglycerides. due to the moderate acidity of this catalyst, the formation of isoparaffins was lower (5 wt%, fig.3). accordingly, the cfpp of the products was found to be high (27 °c). the product fraction produced in this way, in practice, cannot be blended into diesel fuels in low temperate zone countries. it is necessary then for the improvement of cfpp via the catalytic isomerisation of this mixture with high normal-paraffin content [10, 11]. a large amount of bio-paraffin mixture was produced in a thousand hour, long-term catalytic test. the target fraction of the isomerisation tests was the 180–360 °c boiling range, which is the boiling range of gasoil. the yield of the target products was higher than 94 % in all operation parameter combinations (fig.4). the lighter fraction with a boiling range of up to 180 ºc contains mainly iso-paraffins, which can be outstanding gasoline blending components due to their high octane numbers (>85). we found that by adjusting the operation parameters, such as increasing the temperature, and decreasing the lhsv, the yield of the target fraction was decreased due to the higher yield of the cracking reaction. the target fraction obtained between 70% and 80% table 1: selected properties of the feedstock materials properties rapeseed oil bio-paraffin mixture kinematic viscosity at 40 °c, mm2 s-1 46.56 3.493 density at 15 °c, g cm-3 0.9804 0.7923 cloud point, °c 16 32 cetane number 42 104 compositions, % fatty acid paraffin c16:0 2.3 c140.2 c16:1 0.1 c14 0.1 c18:0 1.2 c15 0 c18:1 28.8 c16 2.3 c18:2 12.4 c17 29.5 c18:3 8.3 c18 28.8 c20:0 0 c19 6.1 c20:1 4.8 c20 5.6 c22:0 0.1 c21 14.8 c22:1 41.8 c22 12.5 other 0.2 c22+ 0.1 figure 3: hydrogenation of rapeseed oil with high euric acid content (diamond: residual triglyceride, square: iso-paraffin content, cross c21/c22 ratio) table 2: selected properties of the isomerisation catalyst used properties pt/sapo-11 pt content, w% 0.5 pt dispersity, % 69 bet surface area, m2 g-1 105 average pore size, nm 0.61 micropore volume, cm3 g-1 0.06 macropore volume, cm3 g-1 0.20 total pore volume, cm3 g-1 0.26 acidity, mmol nh3 g-1 0.13 acidity (rel.), mmol nh3 m-2 cat. 0.0012 112 contained c17–c22 hydrocarbons, as well as other (c13– c16) hydrocarbons from the boiling range of gasoil. the iso-paraffin content of the target fraction increased significantly with the operating temperature (fig.5). the increase of the iso-paraffin concentration occurred at 360 °c then at higher temperatures it started to decrease, due to the thermodynamic hindrance of the exothermic reactions, and the higher rate of cracking reactions. up to ca. 320 °c, mainly mono-branched isoparaffins were formed and were by in large mono-ethylparaffins (fig.6). the freezing points of these products are much lower than normal-paraffins and the cetane number is high enough for a fuel additive. the greater formation of mono-methyl-paraffins over the sapo-11 catalyst can be explained by the reduced formation of iso-paraffins due to steric hindrance. at 340 °c or higher, the formation of multi-branched isomers was significant (fig.6). these compounds have better cold flow properties (below -20 °c), but their cetane numbers are high enough (30–45) as shown in fig.2. the favourable operation parameters in terms of biogasoil yield and iso-paraffin concentration were as follows: t = 360 °c; p = 40 bar; and h2/feedstock ratio = 400 nm3 m-3. the cfpp values of the products as a function of temperature and operation pressures are shown in fig.7. these components have low enough cfpp values to blend into diesel gasoil in moderate amounts. on the basis of the experimental results, it was concluded that the production of bio-gasoil meets the standard’s requirements with a cfpp value of max. +5 °c and 70% iso-paraffin content (fig.8) in the case when the raw material contains 8% c17–c22 isoparaffins. conclusions based on our experimental results, it was concluded that the nimo/al2o3 catalyst is suitable for the long-term production of bio-paraffin mixtures from natural triglycerides via catalytic hydrodeoxygenation. furthermore, the investigated pt-sapo-11 catalyst is suitable for improving the quality of a bio-paraffin mixture that was obtained from the hydrodeoxygenation of rapeseed oil with high euric acid content. during the isomerisation with optimised operation parameters, the yield of the target fraction was higher than 94%. at 340 °c or higher the iso-paraffin content is close to 70%. consequently, the cold flow property of the cloud point is lower than +5 °c. therefore, this approach can produce gasoil bio-blending components with good utilisation properties, such as high cetane number, and low temperature values for cold flow properties. overall, the products described here are suitable for blending components of diesel fuels with concentrations of 10% or higher. figure 6: the composition of the products as a function of operation parameters (pressure: 40 bar, liquid hourly space velocity: 1.0 h-1) figure 7: cffp of the products as a function of operation parameters (liquid hourly space velocity: 1.0 h-1, h2/feed ratio: 400 nm3 m-3) figure 4: the yield of the target fraction as a function of operation parameters (pressure: 40 bar, liquid hourly space velocity square: 1.0 h-1, diamond 2.0 h-1, triangle 3.0 h-1) figure 5: the iso-paraffin concentration of the target fraction as a function of operation parameters (pressure: 40 bar, liquid hourly space velocity: square 1.0 h-1, diamond 2.0 h-1, triangle 3.0 h-1) 113 acknowledgements we acknowledge the financial support of the hungarian state and european union under támop-4.2.2.a-11/1/ konv-2012-0071 and támop-4.1.1.c-12/1/konv2012-0017. references [1] huber g.w., o’connor p., corma a.: processing biomass in conventional oil refineries: production of high quality diesel by hydrotreating vegetable oils in heavy vacuum oil mixtures, appl. catal. a:general, 2007, 329,120-129 [2] da rocha filho g.n., brodzki d., djegamariadassou g.: formation of alkanes, alkylcycloalkanes and alkylbenzenes during the catalytic hydrocracking of vegetable oils, fuel, 1993, 72(4), 543-549 [3] simacek p., kubicka d., sebor g., pospisil m.: fuel properties of hydroprocessed rapeseed oil, fuel, 2010, 89(3), 611-615 [4] schollnberger w.e.: between 2020 and 2030 to be re-joined the course for the global energy mix, erdöl erdgas kohle, 2013, 129(12), 2-7 (in german) [5] shell deutschland oil gmbh: shell study sees great potential for biofuels, erdöl erdgas kohle, 2012, 128(11), 407-411 (in german) [6] krár m., kovács s., kalló d., hancsók j: fuel purpose hydrotreating of sunflower oil on como/al2o3 catalyst, bioresources technology, 2010, 101(23), 9287-9293 [7] krár m., kasza t., kovács s., kalló d., hancsók j.: bio-gasoils with improved low temperature properties, fuel proc. techn., 2011, 92(5), 886-892 [8] solymosi p., baladincz p., hancsók j.: production of motor fuels by the hydrogenation of rapeseed oil with high euric acid content, proc. 19th eu biomass conference and exhibition, berlin, germany, 2011, 2077-2081 [9] solymosi p., kasza t., hancsók j.: investigation of conventional and high oleic acid content rapeseed or sunflower oils, hung. j. ind. chem., 2011, 39(1), 85-90 [10] baladincz p., tóth cs. hancsók, j.: expanding feedstock supplies of the second generation biofuels of diesel engines, hung. j. ind. chem., 2010, 38(1), 1-7 [11] solymosi p., eller z., hancsók j.: motor fuel purpose hydrogenation of used cooking oils, chem. engng. trans., 2013, 35(2), 1351-1356 [12] hancsók j., kasza t., kovács s., solymosi p., holló a.: production of bioparaffins from natural triglycerides, chem. engng. trans., 2011, 25, 821826 [13] kasza t., hancsók j.: isomerisation of bioparaffins over pt-based sapo-11 and almcm-41 catalysts, műszaki kémiai napok, 2011, 29, 220225 (in hungarian). [14] kasza t., holló a., thernesz a., hancsók j.: production of bio-gasoil from bioparaffins over pt/sapo-11, chem. engng. trans., 2010, 21, 1225-1230 [15] hancsók j., kasza t., kovács s., solymosi p., holló a.: production of bio-gasoil from bioparaffins over pt/sapo-11, j. cleaner prod., 2012, 34, 76-81 figure 8: cold flow properties as a function of iso-paraffin concentration (solid squares: cold filtering clugging point, hollow diamonds: cloud point) 114 [16] gergely j., forstner j., balai m., szirmai l., petro j., kovács i., resofszki g., smid l., auer j., baladincz j., szalmásné pécsvári g., tóth l., kubovicsné stotz k., kun j., kántor l., czágler i., lővei j., tóth e., lefkánics gy., tátrai e., pálné borbély g., rosenbergné mihályi m., beyer h., hancsók j.: a selective hydroisomerisation catalyst preparation and application for hydrocarbons hu 225 912, 2001 (in hungarian) [17] kasza t., kalló d., hancsók j.: quality improvement of bio-paraffin mixtures, fuel, 2014, 120, 1-7 [18] hancsók j., krár m., magyar sz., boda l., holló a., kalló d.: investigation of the production of high cetane number biogasoil from pre-hydrogenated vegetable oils over pt/hzsm22/al2o3, micropor. mesopor. mat., 2007, 101(12), 148-152 [19] srivastava s.p., hancsok j.: fuels and fuel additives, wiley and sons, hoboken, nj, usa, 2014, pp. 121-177 [20] kasza t., baladincz p., hancsók j.: production of bio-isoparaffins by the hydroisomerisation of bioparaffins. hung. j. ind. chem., 2009, 37(2), 95–99 [21] kasza t., hancsók j.: production of depressed freezing point bio-gasoil from slaughterhouse waste lard. hung. j. ind. chem., 2010, 38(1), 41– 45. [22] kasza t., hancsók j.: isomerisation of paraffin mixtures produced from sunflower oil. hung. j. ind. chem., 2011, 39(3), 363–368 [23] kasza t.; tóth cs.; hancsók j.: application of improved bio-paraffins in diesel fuels, hung. j. ind. chem., 2012, 40(1), 25–31 hungarian journal of industry and chemistry veszprém vol. 41(2) pp. 115–118 (2013) the energy balance of separation opportunities in microalgae technologies zoltán hodai, ! dóra rippel-pethő, géza horváth, lászló hanák, and róbert bocsi department of chemical engineering science, university of pannonia, veszprém, egyetem u. 10., 8200, hungary !email: hodaiz@almos.uni-pannon.hu algae technology is at the focus of international research and development, since it is a green technology that reduces emissions of harmful chemicals and can be considered as a renewable energy source. carbon dioxide from stack gases and the nitrogen content of wastewater can be considered as food sources for plants and algae. the utilisation of carbon dioxide by algae technologies depends on the technical environment and logistics of teamwork. this technology is a new opportunity in hungary for decreasing emissions. we grew algae populations to utilise the carbon dioxide from a refinery’s stack gas in the continental climate of hungary. critical parameters of the technology are the concentration of the algae suspension and extract, because of high investment and operating costs as well as the long operation time, which determines the feasibility of the algae technology. our specific aim was to separate the algae mass faster and more efficiently from the starting solution. the optimisation of separation operations and technologies took into consideration environmental and economic aspects. keywords: microalgae technology, separation, filtration, renewable energy source introduction the utilisation of microalgae carbon dioxide fixation is an important area of international research and development. the absorption of certain technological exhaust gases is possible on the basis of the photosynthesis of microalgae. the absorption of carbon dioxide can reach a magnitude of hundred ton per hectare. c16-c22 esters are formed in certain algae cells that can be used for the production of biodiesels. this method is thus capable of producing fuels from renewable sources [1-4]. algae production is a promising solution amongst the alternative fuel production processes, because it requires of low specific area for growth and high reproduction rate [5-8]. algae are considered to be one of the most efficient organisms on earth due to their outstanding reproduction rate, and generally high lipid content. for example, they can double their biomass in 24 hours [9-12]. their lipid content on average is 20%, but it can be up to 60-80% for certain species [7, 9, 13, 14]. research into oil production from algae is primarily based on microalgae. these are photosynthesising organisms with a cell size of no greater than 0.5 mm. they can be utilised for carbon dioxide and nitrogen oxide fixation, because they convert these compounds in a photosynthetic energy conversion [15]. the end product of these processes contains a significant amount of solar energy stored as chemical energy. furthermore, considerable amounts of biodiesel can be obtained [16-19]. the composition of a microalgae cell depends on cultivation parameters. we tested the available and applicable species under local climatic conditions. afterwards microalgae that passed the local environmental tests can be considered useable for production. research is being carried out into carbon dioxide fixation from technological flows at our institute [15]. the absorption of carbon dioxide and reduction of the release of other pollutants in wastewater using microalgae are being studied. algae technology utilises waste gases and some environmentally harmful components from wastewaters as nutrients, and thus purifies the growth media. these specific pollutants provide excessive amount of nutrients for the algae, which results in the algae’s exponential growth. in addition to the above-mentioned method of energy extraction, a number of research efforts [4, 5, 8, 10-12, 18, 19 25] are currently dealing with the alternative use of biomass produced in this way, and biomass residue that remains after processing. in addition to the abovementioned advantages, the operating costs can be a limiting factor. the most critical steps in the production of algaebased biofuels are the harvesting of algae (harvesting, dewatering, and drying), and lipid extraction, because of the high level of investment and operating costs. the main challenge of the technology is to reduce costs, which by in large originate from the separation steps that need to be minimised. 116 results and discussions our research focuses on carbon dioxide fixation from technological flows. we designed and built various grower systems at the department of chemical engineering of the university of pannonia (fig.1), as well as at a refinery (figs.2 and 3). by utilising these technological solutions we conducted research into the production of biomass and algae-based products as possible renewable fuels. the propagation and environmental tolerance parameters were examined along with the possibilities of developing the technology. during the experiments, the whole technological chain was examined providing the possibility to optimise the entire chain of operational steps. the utilisation of algae cultures in experimental photobioreactors is examined, together with the optimisation of the operational conditions both for both artificial and natural light with different substrate solutions. the various parameters for algae processing are also determined. the foci of our work were the processing and separation operations. critical points of the technology are the processing steps, such as concentrating the algae suspension and extracting valuable components (lipids). the extraction technologies are of importance because of the high costs of investment and long operation periods. from the literature [5, 10, 12, 15, 17, 22, 23], biodiesel is not yet comparable to fuel produced from petroleum, however the cost of algae technology is dropping. furthermore, algae technology could become viable if we consider the cost of wastewater purification and flue gas adsorption, and the price of products obtained from microalgae. we need to consider separating possibilities and beyond by analysing gains and losses simultaneously. our specific aim was to devise densification and separation processes, which have low energy requirements and advantageous operation times. furthermore, we defined useful components from algae and their optimised extraction, based on the optimisation of extraction techniques and other economical and environmental aspects. separation opportunities harvesting can be carried out by microfiltration, ultra filtration, centrifugation, flocculation, sonochemical techniques, or some new techniques that are under development [21, 22]. in addition to chemical flocculation, clarification, and membrane separation procedures, special attention was paid to auto flocculation phenomena. forms of technology pay more and more attention to convert disposed waste into useful materials. the photosynthesising microorganisms, such as microalgae, utilise solar energy, rapidly reproduce, and do not require any soil to grow in. the biomass product contains solar energy stored in chemical bonds. to process the final product, the suspension, concentration, and extraction of the biomass are the most problematic parts of the methods of algae-based energy production. the main techniques for separation are mechanical operations (filtration, centrifugation, and settling), mechanical operations with admixture (flocculation and defecation), membrane operations (microfiltration and ultrafiltration), and other notable operations (sonochemical techniques, electroflocculation, and flotation). according to examples from the literature [9, 11, 15, 18], there are still only limited generally applicable and proven methods that can be used for biomass production with specific energetic goals. energetic considerations increasingly diluted suspensions were examined during separation operations (fig.4). data from the literature [23-37] need to be brought to a common denominator for carrying out comparisons. for example, our results show that if we want to gradually treat more dilute suspensions using flotation, the energetic considerations can change by orders of magnitude. figure 1: closed grower systems at the university of pannonia figure 2: closed grower systems at a refinery figure 3: open grower systems at a refinery 117 according to fig.4, cross-flow membrane separation, electroflocculation, centrifugation known as “spiral plate”, immersion membrane separation, the flocculation, foam flotation and operation of the flotation by dispersed air are positioned favourably with respect to energetic rating (smaller demand of energy as the energy amount from the separated biomass). the energy balances of chemical flocculation and electroflocculation do not include the costs of the procurement of chemicals and post-treatment, which would complicate the determination of its energy status. the amounts of chemicals used according to the quality of the suspension were between such wide intervals that they could not be considered using simple factors. by energetic rating, we should note the concentration of the kind of algae suspension in the chosen operation. the increase in volume and decrease in concentration of the suspension may require a review of the cost, materials and energy needs of the separation, and thus change its energetic status. for example, we can conduct a thought-experiment for flotation to see whether the treatment of a dilute suspension needs a device with a different energetic rating. because of the fixed size of the flotation’s device, we cannot decrease the amount of gas flow and the dilute suspension could start to foam, which may make it more difficult to handle than the stability and volume of the foam from a more concentrated suspension. due to foaming, it will be more difficult for the algae layer to become thicker in the foam unless we use more chemicals and surfaceactive agents, which result in more parameters to consider. apart from the above, an important question is how we consider the time domain of the technology (periodic, half-continuous, or continuous). the kind of growing system determines how to connect the separation operation. half-continuous or continuous (or almost that) operation is beneficial for industrial biomass production to maximise the capacity of biomass. by running the reactor at the maximum rate of reproduction, we can maximise its capacity. according to the latter, the immersion membrane separation operation would be preferable. conclusions according to our investigations, the usable operations for extraction and concentration in algae cultivation with regards to energetic causes vary greatly with respect to energy demands. for dilute suspensions, flotation and foam flotation are the most useful separation processes. we can use flocculation as well, but we have to consider the costs of and environmental damage caused by waste chemicals. acknowledgements this research was supported by the european union and the state of hungary, and co-financed by the european social fund in the framework of támop 4.2.4. a/211-1-2012-0001 ‘national excellence programme’. references [1] straka f., doucha j., lívansky k.: utilisation of flue gas for cultivation of microalgae (chlorella sp.) in an outdoor open thin-layer photobioreactor, j. appl. phycology, 2005, 17(5), 403-412 [2] olaizola m.: microalgal removal of co2 from flue gases: changes in medium ph and flue gas composition do not appear to affect the photochemical yield of microalgal 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byung-gon r., kyochan k., bokyong k., jong-in h., ji-won y.: continuous microalgae recovery using electrolysis: effect of different electrode pairs and timing of polarity exchange, bioresource technol., 2012, 123(2), 164-170 [31] mascia m., vacca a., palmas s.: electrochemical treatment as a pre-oxidative step for algae removal using chlorella vulgaris as a model organism and bdd anodes, chem. enging. j., 2013, 219(5), 512-519 [32] lee a.k., lewis d.m., ashman p.j.: harvesting of marine microalgae by electroflocculation: the energetics, plant design, and economics, appl. energy, 2013, 108(3), 45-53 [33] amer l., adhikari b., pellegrino j.: technoeconomic analysis of five microalgae-to-biofuels processes of varying complexity, bioresource technol., 2011, 102(20), 9350–9359 [34] edzwald j.k.: algae, bubbles, coagulants, and dissolved air flotation, water sci. technol., 1993, 27(10), 67–81 [35] nurdogan y., oswald w.j.: tube settling of high-rate pond algae, water sci. technol., 1996, 33(7), 229–241 [36] collet p., hélias a., lardon l., ras m., goy r.a., steyer j.p.: life-cycle assessment of a microalgae culture coupled to biogas production, bioresoure technol., 2011, 102(1), 207–214 [37] cowarda t., leea j.g., caldwellb g.s.: development of a foam flotation system for harvesting microalgae biomass, algal research 2013, 2(2), 135-144 hungarian journal of industry and chemistry veszprém vol. 41(2) pp. 119–122 (2013) solid-liquid extraction of chlorophyll from microalgae from photoautotroph open-air cultivation éva molnár, ! dóra rippel-pethő, and róbert bocsi department of chemical engineering, institute of chemical and process engineering, university of pannonia, egyetem u. 10., veszprém, 8200, hungary !email: molnare@almos.uni-pannon.hu among industrial pollutants, strict quotas limit the emission of carbon dioxide in the european union. the capturing and deposition of carbon dioxide requires significant expenditures. one of the newer solutions for the reduction of the carbon dioxide emissions is provided by algae technology. in this technology, the absorption of carbon dioxide is achieved by photosynthesis. besides the reduction of pollutants, algae technology has another advantage by supplying valuable products, such as natural pigments, proteins, vitamins and oils from algae biomass. since it has a high reproduction rate, algae cultivation can be a feasible substitute for plants traditionally used in the production of chlorophyll. the viability of the technology is dependent on whether or not the processing can be done economically. an investigation was carried out in order to compare and contrast two extraction methods (soxhlet extraction and leaching) and four solvents (acetone, diethyl ether, ethanol and methanol) to determine the most effective method for the extraction of chlorophylls from dried microalgae (chlorella vulgaris sp.). it was concluded that methanol is the most effective solvent for the extraction of both chlorophylls a and b using both soxhlet extraction and leaching. keywords: microalgae, extraction solvent, extraction, chlorophyll, spectrophotometry introduction energy demand has been rapidly increasing throughout the world, which is mainly met by the combustion of fossil fuels that results in an increase in the concentration of greenhouse gases in the atmosphere. however as a possible remediation strategy, carbon dioxide levels can be reduced with the use of algae technology [1]. algae technology is of significant interest in research and development since it is a ‘green’ technology that is capable of both decreasing the emission of pollutants and serving as a renewable energy source. the algae absorb carbon dioxide for photosynthesis while producing a number of valuable components [2]. microalgae are a collection of various microscopic species capable of photosynthesis and are typically found in water with an exceptionally high reproduction rate. for propagation, they mainly need light, water and co2. some species can even survive in waste water. algae are good alternatives for plants that are traditionally used for the production of chlorophyll. appropriate conditions are required for the successful cultivation of algae (solar energy, temperature, ph, and mixing) [3, 4]. however, the critical point of algae technology is neither cultivation nor processing. the biggest complication concerns the concentration of the microalgae suspension and the subsequent extraction of the valuable components due to the high investment costs and long operational times [5]. there is, however, an increasing demand for microalgae. the reason for this is that their oil content can be as much as 50% of their body mass, making them important in the production of biodiesel. the natural pigments, proteins and vitamins extracted from microalgae are primarily used by the pharmaceutical, cosmetic and food industries [3, 6]. chlorophyll has been used for centuries as a traditional remedy for unpleasant body odours, for the neutralisation of the odours of stool and urine, and detoxification or sterilisation of wounds. nowadays, its use is even more widespread. it is used as a food additive, food colouring, and nutritional supplement, especially because of its detoxifying and excellent basifying effects. it is also a strong antioxidant, which inhibits the harmful oxidative processes in the body and enhances the protection of cells and tissues [7, 8]. however, the processing of algae still needs to be improved with respect to determining the optimal methods, pieces of equipment, solvents, and parameters for the efficient and economic extraction of chlorophyll. extraction is a process that can be carried out in a number of ways. there are also a number of solvents and preparation methods available. also, variables such as pressure, temperature, the efficiency of contact and time all play an important role [9, 10]. chlorophyll is sensitive to extreme light exposure, ph values and temperatures [7-9]. when choosing the solvent, one has to consider the sensitivity of the extracted component. a number of considerations are important, too: density, viscosity, heat of evaporation, price, effect on the environment and health. it is also essential that the 120 solvent does not react with or cause damage to the extracted component and is not corrosive. different methods can be used for different microalgae species [9-10]. experimental in advance of the extraction experiments the algae suspension (chlorella vulgaris sp.) was concentrated, dried at 60 ºc until it reached a constant mass, then ground in a ball mill. chlorophylls a and b products were obtained by the methods detailed in the following sections from this ground algae powder, which contains approximately 4 wt% water. the soxhlet extraction method one of the most well known pieces of equipment for laboratory scale solid-liquid extraction is the soxhlet extractor. in a soxhlet extractor multiple fractional distillations are carried out, the extraction is always done with the pure condensate [10]. the first step of the extraction was to fill a cellulose casing with 1-3 g of algae powder. the filled casing was placed in the middle part of the piece of equipment (fig.1). the lower round-bottom flask was filled with 400 cm3 of solvent. the soxhlet extraction was carried out with methanol, ethanol, and acetone. pumice and a magnetic stirring rod were placed into the lower flask to ensure proper boiling. the cooling water was set to a continuous flow and then the heating was turned on. after the extracting solvents had reached their boiling points and started to evaporate, they condensed in the reflux condenser and dripped back down onto the algae powder at which point the extraction of the chlorophylls started. the liquid level continuously rose in the middle section until it reached the overflow pipe letting the chlorophyll extract pour back into the lower flask. a sample of 4–6 cm3 was taken at the end of every cycle. the extraction continued as long as the absorption spectra measured by the spectrophotometer did not show a significant change. the method of leaching leaching was carried out with so-called ‘cold solvents’ at room temperature. samples of 0.1 g; 0.5 g; and 0.75 g of algae powder were measured into a test tube, then 5– 5 cm3 of solvent was added. the list of solvents was the same as for the soxhlet extraction method with the inclusion of diethyl ether. the weight of the solvent was also measured and recorded in order to have reference data in the later phases of the experiment. the samples were mixed with vortex and centrifuged for 2 minutes at 4000 rpm. a sample was taken from the top layer after centrifuge and its absorbance measured with a spectrophotometer [11, 12]. calculations the chlorophyll contents of the given samples were calculated with empirical formulae according to eqs.(1)-(8). cchlorophyll-a(90% methanol) = 15.65·a666 7.34·a653 (1) cchlorophyll-b(90% methanol) = 27.05·a653 11.21·a665 (2) cchlorophyll-a(96% ethanol) = 13.95·a665 6.88·a649 (3) cchlorophyll-b(96% ethanol) = 24.96·a649 7.32·a665 (4) cchlorophyll-a(100% acetone) = 11.75·a662 2.35·a645 (5) cchlorophyll-b(100% acetone) = 18.61·a645 3.96·a662 (6) cchlorophyll-a(95% diethyl ether) = 10.05·a662 0.76·a644 (7) cchlorophyll-b(95% diethyl ether) = 16.37·a644 3.14·a662 (8) where aλ is the absorbance at λ (in nm) wavelength, and cchlorophyll-a and cchlorophyll-b denote concentrations of chlorophyll a and chlorophyll b in µg cm-3 [12] as a function of solvents. in soxhlet extraction, the mass of the chlorophyll in the extract was calculated by the multiplication of the measured chlorophyll concentration values by the volume of the liquid in the round bottom flask. this also enabled the calculation of efficiency in mg of chlorophyll per g of dry algae units (relative to 100% dry algae powder). in the leaching experiments, the chlorophyll concentration results calculated with the empirical formulae were multiplied by the volume of the solvent that resulted in the relative chlorophyll mass values in the given samples. knowing the mass and water content of the algae, the efficiency of chlorophyll extraction relative to the mass of the dry algae can be calculated. these results were normalised to match the measurements and average values were calculated. figure 1: soxhlet extractor [12] 121 results and discussion soxhlet extraction the chlorophyll concentration measured changed according to a saturation curve as shown in fig.2. it can be concluded that under the given circumstances the solvents reached their maximum efficiency and there was no need for longer extraction times. the ability of the solvents to extract chlorophyll relative to dried algae mass during the soxhlet extraction is given in fig.3. the experiments were carried out using acetone, ethanol and methanol. it can be concluded that under the conditions of soxhlet extraction, methanol is the most potent extracting solvent of chlorophyll a and b from the algae powder, followed by ethanol and acetone respectively. it can also be pointed out that acetone and methanol are more effective for the extraction of chlorophyll b while ethanol is more effective for the extraction of chlorophyll a. the latter experiment was not carried out with diethyl ether due to health and safety considerations. extraction by leaching figs.4 and 5 illustrate the results of leaching. fig.4 depicts the concentration of chlorophyll for different masses of algae powder introduced into the system. the curves approach a saturation point in concentration, but do not reach the maximum. when we added progressively more and more algae powder to the same volume of solvent we observed increasing saturation behaviour. fig.5 presents the chlorophyll extracting ability of the various solvents when mixing 0.1 g of algae powder and 5 cm3 of solvent. as expected, the best result was obtained by utilising at least 0.1 g of algae powder of. the efficiency ranking was similar to that of the soxhlet extraction. methanol proved to be the most efficient solvent, followed by ethanol, acetone and diethyl ether respectively. the results are summarised in table 1, which contains mg of chlorophyll per g of dry algae yields. this comparison enables the different solvents to be ranked and extraction methods, which is as follows according to their efficiency: methanol, ethanol, acetone, and diethyl ether. additionally, significantly more chlorophyll can be extracted from ground algae with soxhlet extraction than with leaching. in the figure 2: changes in chlorophyll concentration during the soxhlet measurements figure 3: the efficiency of chlorophyll extraction of the various solvents during soxhlet extraction figure 4: change in chlorophyll concentration as a function of mass during leaching figure 5: efficiency of leaching using the various solvents 122 experiments conducted with acetone, it was observed that the extraction efficiency of chlorophyll a or chlorophyll b is greatly dependent on the conditions. methanol, the solvent that proved to be the most efficient, could be removed later from the chlorophyll by low temperature evaporation. conclusions from a systematic investigation of solid-phase extraction of chlorophyll a and chlorophyll b using soxhlet extraction and leaching as a function of the employed solvent, it was found that the most efficient solvent is methanol. in both extraction techniques, the extracted amount of chlorophyll using methanol as a solvent is approximately an order of magnitude higher than in acetone and close to three to four times greater than the results of ethanol. references [1] borowitzka m.a.: energy from microalgae: a short history, develop. appl. phycology (springer, the netherlands), 2013, 5, 1-15 [2] najafi g., ghobadian b., yusaf t.f.: algae as a sustainable energy source for biofuel production in iran: a case study, renewable and sustainable energy reviews, 2011, 15 (8), 3870–3876 [3] mata t.m., martins a.a., caetano n.s.: microalgae for biodiesel production and other applications: a review, renewable and sustainable energy reviews, 2010, 14(1), 217– 232 [4] bocsi r., horvath g., hanak l., hodai z.: extraction examinations of microalgae propagated for biodiesel additives, hung. j. ind. chem., 2011, 39(1), 45-49 [5] faizal b.: biotechnological applications of microalgae: biodiesel and value-added products, crc press, bosa roca, fl, united states, 2013, pp. 80 [6] demirbas a., demirbas m.f.: the importance of algae oil as a source of biodiesel, energy conversion and management, 2011, 52(1), 163170 [7] lanfer-marquez u.m., barros r.m.c., sinnecker p.: antioxidant activity of chlorophylls and their derivatives, food res. int., 2005, 38(89), 885–891 [8] hosikian a., lim s., halim r., danquah m.k.: chlorophyll extraction from microalgae: a review of the process engineering aspects, int. j. chem. engng., 2010, article id 391632 [9] simpson n.j.k., wells m.j.m.: introduction to solid-phase extraction, marcel dekker inc, new york, ny, usa, 2000, pp. 1-18 [10] meireles m.a.a.: extracting bioactive compounds for food products, theory and applications contemporary food engineering series, crc press, dublin, ireland 2009, pp. 140159 [11] lan s., wu l., zhang d., hu c., liu y.: ethanol outperforms multiple solvents in the extraction of chlorophyll-a from biological soil crusts, soil biology and biochemistry, 2011, 43(4), 857–861 [12] wellburn a.r., lichtenthaler h.: formulae and program to determine total carotenoids and chlorophylls-a and b of leaf extracts in different solvents, adv. agricul. biotechn., 1984, 2(1), 9-12 table 1: comparison of the chlorophyll (chl.) extraction results soxhlet extraction leaching chl. a chl. b chl. a & b chl. a chl. b chl. a & b acetone 0.164 0.270 0.435 0.183 0.059 0.242 ethanol 1.329 1.290 2.619 0.395 0.259 0.654 methanol 3.206 3.657 6.862 1.109 1.199 2.307 diethyl ether n/a n/a n/a 0.044 0.017 0.062 hungarian journal of industry and chemistry veszprém vol. 41(2) pp. 123–130 (2013) calculating the electrostatic potential profiles of double layers from simulation ion density profiles dezső boda,b1 and dirk gillespie2 1department of physical chemistry, university of pannonia, egyetem u. 10., veszprém, 8200, hungary 2department of molecular biophysics and physiology, rush university medical center, 1750 w. harrison st., chicago, usa be-mail: boda@almos.vein.hu computer simulations of the planar double layer geometry provide the charge profile with statistical noise. to compute the mean electrostatic potential profile from the charge profile, one must solve poisson’s equation with appropriate boundary conditions (bc). in this work, we show that it is advantageous to use the neumann or dirichlet bcs at the boundaries of the simulation domain with an integrated version of poisson’s equation. this minimises errors from the simulation’s noisy density profiles, in contrast to traditional convolution integrals that amplify the noise. the neumann bc, where the electric field is prescribed, can be used in both the constant surface charge and constant electrode voltage ensembles. in the constant voltage ensemble, where the potential difference between the confining electrodes is prescribed, one can also use the dirichlet bc, where the potentials at the boundaries are set. we show that the new methods provide converged results for the potential profile faster than the convolution integral does. keywords: electrical double layer, poisson equation, boundary conditions, computer simulation introduction the electrical double layer (dl) is formed by a charged surface and a phase (usually, a liquid) containing mobile charge carriers near the surface. depending on the material carrying the mobile charges, dls appear in electrolytes, molten salts, ionic liquids, plasmas, and even fast ion conductors (solid electrolytes). dls in solutions of dissolved ions are particularly important in electrochemistry, biology, and colloid chemistry. dls near electrodes differ from dls near charged objects carrying a fixed surface charge (such as colloids, macromolecules, and porous bodies), because the surface charge on the electrode can be controlled by an external voltage. theoretical studies of dls began with the poissonboltzmann (pb) theory known as the gouy-chapman (gc) theory [1,2] in electrochemistry, the debye-hückel (dh) theory [3] in solution chemistry, and the derjaguinlandau-verwey-overbeek (dlvo) theory [4, 5] in colloid chemistry. the pb theory is still very popular in applications because of its simplicity in spite of the fact that it neglects ionic correlations and effects due to the finite size of ions (e.g., excluded volume). more powerful statistical mechanical theories that are able to take these correlations into account have been developed [6–16]. computer simulations are a versatile method of studying dls in various geometries for various models of the constituents (ions, water, and electrode) [17–35]. this paper focuses on computing the electrical field and potential from a charge distribution obtained from computer simulations. computer simulations of systems containing charged particles must be performed in accordance with the laws of both electrostatics and statistical mechanics [36, 37]. this means that the electrical potential must be computed accurately for every configuration sampled in a monte carlo (mc) simulation. alternatively, the electrical field must be computed accurately in every time step of a molecular dynamics (md) simulation. every configuration of the system (positions of ions) corresponds to a microscopic state. in this case, we consider the system at the microscopic level. a simulation that samples the possible microscopic states must be performed properly according to the probability distribution of a given statistical mechanical ensemble. one typical simulation method to handle various ensembles is mc. the density distribution of ionic species i, h⇢ i (r)i, is obtained as an ensemble average from the simulation. from these, the average charge distribution can be obtained as q(r) = hq(r)i = x i z i e h⇢ i (r)i , (1) where q(r) is the charge distribution in a microscopic state, e is the electronic unit charge and z i is the valence of ionic species i. the average (mean) electrostatic potential can be obtained “on the fly” by computing the potential in the simulation cell for every configuration (denoted by (r)) and then taking the ensemble average, (r) = h (r)i. in this work, we use upper-case symbols for the microscopic quantities ( (r) and q(r)), while we use lowercase symbols for their macroscopic counterparts, namely, 124 their ensemble averages ( (r) and q(r)). the electrical potential in a configuration of the mc simulation, (r), can be computed analytically from coulomb’s law or numerically using a poisson solver. in both cases, we apply electrostatic bcs at the microscopic level. the reverse order, when we compute the ensemble average of the charge distribution (eq.(1)) and then solve poisson’s equation for the mean potential r2 (r) = � 1 ✏ 0 q(r) (2) is more usual (✏ 0 is the permittivity of vacuum). this equation applies to either explicit or implicit solvent models. in the explicit solvent framework, q(r) also contains the charge distribution of the water molecules (in addition to their ionic charges). in the implicit solvent framework, where water is represented by a dielectric background characterised by a dielectric constant, ✏, q(r) also contains polarisation charges induced in the dielectric (in the simplest case, q(r) is the ionic charges divided by ✏). because we are solving a differential equation, we must use appropriate boundary conditions (bcs) when solving eq.(2). because we want an ensemble averaged result, we apply the bcs at the macroscopic level. this paper describes how to numerically integrate the poisson equation with appropriate bcs to efficiently compute the mean electrostatic potential profile from the mean charge profile obtained from simulations. the statistical ensemble applied in the simulation determines which bc to use. in this paper, we consider the two basic ensembles, one where the electrode charges are fixed (constant charge ensemble) and one where the difference between the electrode potentials is fixed (constant voltage ensemble). in the constant charge ensemble, the traditional method of computing the potential profile is via a convolution integral. here, we show that this method is errorprone and numerically inefficient and instead, it is more advantageous to use a different integration scheme with neumann bcs, where the normal electric fields at the boundaries of the system are fixed [38]. in the constant voltage ensemble developed by kiyohara and asaka [39], the electrode potentials are known in advance. therefore, we can also use dirichlet bcs, where the potentials at the boundaries of the system are prescribed. in the following, we describe our model in detail. then, we consider all three issues discussed above (bcs at the microscopic level, statistical mechanical ensembles, and bcs at the macroscopic level) and present various possibilities for the macroscopic bc depending on the statistical mechanical ensemble used. we present results of model calculations to show the self-consistency of these calculations. model and boundary condition at the microscopic level at the microscopic level, we have a system that contains localised discrete and/or continuous distributions of charges q(r). in practice, there are two traditional schools to compute the electrostatic energy (in mc) or forces (in md) for a configuration sampled by a computer simulation. in one school, the potential is computed on a grid from poisson’s equation (eq.(2)) using a partial differential equation (pde) solver with appropriate boundary conditions. this method is generally used in md simulations of explicit solvent systems. in the other school, coulomb’s law is used to calculate the potential: (r) = 1 4⇡✏ 0 ✏ z q(r0)g(r, r0)dr0, (3) where g(r, r0) is the appropriate green’s function. this method is generally used for simulations with implicit solvents. the planar dl geometry means that we have a rectangular simulation cell of length l 2 �l 1 and with a base h ⇥h confined by two planar electrodes at the two ends (x = l 1 and x = l 2 ) carrying surface charges � 1 and � 2 . periodic boundary conditions (pbc) are used in the y, and z dimensions, which means that the green’s function is g(r, r0) = 1x j=�1 1x k=�1 1 |r� r0 + jhn y + khn z | (4) where the sum over j and k represents the interaction with the periodic image charges in the replicas of the central simulation cell in the y and z dimensions set by the unit vectors n y and n z . the term j = k = 0 corresponds to the interaction with the charge in the central simulation cell computed explicitly. in this paper, the interaction with periodic replicas is taken into account using the charged sheet method by smearing these charges into a sheet carrying q/h2 surface charges with a h2 square hole in the middle. the interaction with the holed sheet can be integrated. for further details, see ref. [18, 29]. the statistical mechanical ensemble determines which thermodynamic variables are fixed in the simulation. the attempts in the mc simulations are designed to ensure sampling according to the probability distribution of the given ensemble. moreover, the simulation must be self-consistent in the sense that a prescribed thermodynamic variable must agree with its value computed as an output of the simulation. for example, in an npt simulation (where the pressure is fixed), the pressure can also be computed from the virial sum as an ensemble average in both nv t and npt simulations. this value must be equal to the one prescribed in the npt ensemble. in practice, however, the accuracy of the pressure computed from the virial sum depends on the size of the system, and one obtains the same relationship between pressure 125 and density from nv t and npt simulations only in the limit of very large simulation cells. from the point of view of the dl problem, the question is whether we perform the simulation in the constant charge or constant voltage ensemble. in the constant charge ensemble the surface charges on the confining walls of the simulation cell are fixed. this is the traditional simulation setup used in dl simulations since torrie and valleau [17, 18]. the output of the simulation is the density profiles of the various ionic species h⇢ i (x)i (the pbc applied in the y and z dimensions ensures that the profiles depend on x only), from which the x-dependent charge profile, q(x), is obtained (see eq.(1)). the corresponding form of poisson’s equation is d2 (x) dx2 = � 1 ✏ 0 ✏ q(x), (5) where ✏ is now included so q(x) constrains only ionic and electrode charges. recently, kiyohara and asaka [39] introduced the constant voltage ensemble, where the potential difference between the two confining walls (the electrodes) is prescribed. a special mc step, where a small amount of charge, ��, is transferred from one electrode to the other, has been introduced. the charge exchange is accepted on the basis of the boltzmann factor min  1, exp ✓ ��u kt + h2 � ⇤ �� kt ◆� (6) where �u is the energy change associated with the charge movement and � ⇤ = (l 2 ) � (l 2 ) is the prescribed voltage. here, the surface charges on the electrodes fluctuate, while the potential difference between the electrodes (� ⇤) is an independent, prescribed variable of the ensemble. the mean potential profile can be computed from eq.(5). the computed voltage, namely, the potential difference between the electrodes, � = (l 2 )� (l 2 ), must be equal to the prescribed voltage, � ⇤. in the following, we describe various ways to apply bcs at the macroscopic level using a case study of a 1:1 electrolyte, where the ions are modeled as charged hard spheres with diameters d + = d� = 3 å and the dielectric constant of water is 78.46. the concentration is 1 m and the temperature is 298.2 k. we show results for the special case of � 1 = �� 2 = � = 0.1 cm�2 and l 1 = �l 2 = l, but the equations are presented for the general case. we used 200/200 ions in the mc simulations performed in the canonical (nv t ) ensemble. the dimensions of the cell are l = 50 å and h = 57.2 å. boundary conditions at the macroscopic level boundary conditions set in the bath: the convolution integral let us distinguish between the charge of the ions obtained from the simulation, q ion (x), and the surface charges, p k � k �(x� x k ), at x 1 = l 1 and x 2 = l 2 (in this work, we assume only two charged surfaces at l 1 and l 2 , but there can be more as in the simulations of kiyohara et al. [40–50] for porous electrodes). the total charge is the sum of these: q(x) = q ion (x) + x k � k �(x� x k ). (7) the ionic charge profile is obtained as an ensemble average. the electrode charges are prescribed in the constant charge ensemble, while they are obtained as ensemble averages in the constant voltage ensemble. at the macroscopic level, the issue of electrostatic self-consistency appears when we ask the question: what kind of bc should be applied when we solve poisson’s equation (eq.(5)). the traditional answer to this question is that the bc is set in the bulk electrolyte, where the average electrical field and electrical potential are zero. the corresponding solution of poisson’s equation can then be obtained in the form of a convolution integral (x) = � 1 ✏ 0 ✏ z 1 x (x0 � x)q ion (x0 )dx0. (8) this solution was probably inspired by theories that usually consider an isolated dl where the bcs are set in infinity. because theories (unlike simulations) provide smooth charge profiles (with the property lim x!1 q(x) = 0) without any noise, this integral works well for theories. to the best of our knowledge, the majority of researchers (among others, the authors of this paper) have used this equation in the past [6–35]. in this work, we show that this equation, from a numerical point of view, is a poor choice to compute the potential in simulation studies. the reason is that the upper integration limit is not well defined and that q(x) is subject to a large statistical noise. in practice, the upper integration limit is set somewhere in the middle of the cell where a bulk electrolyte is. here we will use exactly the middle of the cell (x = 0) as the upper integration limit. because of x�x0 in the integrand, this integral is very sensitive to the noise in q(x), because the noise is amplified as one moves further away from the electrode. the results of a very short (200 mc cycles; 1000 attempts to move ions were made in an mc cycle) simulation are shown in fig.1. the density and charge profiles are very noisy. when we compute the potential from eq.(8), the result is subject to a large error and is far from what we are supposed to get (fig.2, top panel). the slope is not necessarily zero in the bath (which means that the electrical field is not zero). if the simulation was run for longer, we would get a completely different result. in general, long simulations are needed to produce a smooth charge profile and a well established potential profile. the problem is even more serious when we try to reproduce small effects, such as the value of the electrode potential at zero electrode charge (pzc) for asymmetric electrolytes. the value of the pzc potential is very small 126 0 1 2 3 4 5 d en si ty p ro fi le s / m -60 -40 -20 0 20 40 60 x / å -4 -2 0 2 4 c ha rg e pr of ile / m figure 1: density profiles (top panel) and a charge profile (bottom panel) obtained from a short (200 mc cycles) constant charge simulation using � 1 = �� 2 = �0.1 cm�2. the charge profile is obtained from p i z i ⇢ i (x), so its unit is m (mol dm�3) and the effect of the noise is dramatic. extremely long simulations are needed to obtain convergent results for the potential [51]. to illustrate this weak convergence, we have plotted the left electrode potential ( (l 1 )� (0), top panel) and the voltage ( (l 2 )� (l 1 ), bottom panel) as computed from eq.(8) as functions of the performed mc cycles in fig.3 (red dashed curves). these potential values fluctuate strongly. the calculated values depend not only on the simulation time, but on the upper integration limit. if we shift that point a bit, we get a different result (data not shown). neumann boundary conditions and the constant charge ensemble here we propose, instead, to use neumann or dirichlet bcs at the boundaries of the simulation cell (at l 1 and l 2 , or, equivalently, at �1 and 1). in the case of the neumann bc, the normal electrical field is prescribed, while in the case of the dirichlet bc, the electrical potential is prescribed at the confining walls. our simulation setup ensures that the simulation cell is always charge neutral. then, gauss law states that the average electrical field is zero outside the cell for the regions z < l 1 and z > l 2 . this information makes the neumann bc applicable both in the constant charge and constant voltage 0 1 2 3 4 ψ (x ) neumann convolution (left) convolution (right) -60 -40 -20 0 20 40 60 x / å 0 0.1 0.2 0.3 0.4 0.5 0.6 q to t(x ) figure 2: potential profiles (top panel) as computed from the neumann bc (eq.(11)) and the convolution integral (eq.(8)). the upper limit of the convolution integral is x = 0 and it is computed for the leftand right-hand sides separately. the bottom panel shows the integral of the charge profile (q tot (x), see eq.(7)). it is closely related to the electric field through eq.(13). the profiles have been obtained from the curves of fig.1. the electrostatic potential is shown in units of kt/e throughout this paper ensembles. in the constant charge ensemble, the potential difference between the electrodes is an output of the calculation. therefore, we cannot use it as a bc, so we cannot apply the dirichlet bc in this case. in the constant voltage ensemble, on the other hand, the potential difference is known in advance (see the next section). in the constant voltage ensemble, therefore, both neumann and dirichlet bcs can be used and they should give the same answer (apart from errors related to the size of the system, see later). the neumann bc for eq.(8) is that the electrical field is zero outside the system: e(x ! �1) = � d (x) dx ���� x!�1 = 0 (9) and the same for x ! 1. by integrating poisson’s equation once, we obtain d (x) dx = � 1 ✏ 0 ✏ z x �1 q(x0 )dx0 + c 1 (10) where c 1 is an integration constant. taking eq.(10) at 127 -4 -3.5 -3 -2.5 -2 -1.5 -1 ψ (l 1 )ψ (0 ) neumann convolution 0 200 400 600 800 1000 mc cycle 2 3 4 5 6 ψ (l 2 )ψ (l 1 ) figure 3: convergence of the left electrode potential (top panel) and the voltage (bottom panel) as computed from the neumann bc (eq.(11)) and the convolution integral (eq.(8)) in the constant charge ensemble. any location x < l 1 (where q(x) = 0) and using the bc (eq.(9)), we get c 1 = 0 for the integration constant. if we use eq.(7) for q(x), we obtain d (x) dx = � 1 ✏ 0 ✏ z x l1 q ion (x0 )dx0 � 1 ✏ 0 ✏ � 1 (11) for l 1 < x < l 2 . the change in the lower integration limit was possible because ions exist only between the two electrodes (q ion 6= 0 only for l 1 < x < l 2 ). introducing q tot (x) = z x l1 q ion (x0 )dx0 (12) for the integral of the ionic charge profile (the total charge density per area in the [l 1 , x] interval), the electrical field can be given as e(x) = 1 ✏ 0 ✏ q tot (x) + 1 ✏ 0 ✏ � 1 (13) for l 1 < x < l 2 . the q tot (x) profile is shown in the bottom panel of fig.2. for the special case of � 1 = �� 2 , the total ionic charge is zero in the system, so q tot (l 2 ) = 0. the nearly constant but noisy profile in the middle of the cell represents the bulk region. integrating once more, we obtain (x) = � 1 ✏ 0 ✏ z x l1 q tot (x0 )dx0 � 1 ✏ 0 ✏ � 1 (x� l 1 ) + c 2 , (14) -3.5 -3 -2.5 -2 ψ (l 1 )ψ (0 ) dirichlet neumann convolution 0 200 400 600 800 1000 mc cycle 4 5 6 7 ψ (l 2 )ψ (l 1 ) figure 4: convergence of the left electrode potential (top panel) and the voltage (bottom panel) as computed from the neumann bc (eq.(11)), the dirichlet bc (eq.(17)), and the convolution integral (eq.(8)) in the constant voltage ensemble where c 2 is another integration constant. its value is inconsequential because we can set the zero level of the potential arbitrarily. fig.2 shows the (x) profile where c 2 = 0. it is usual, however, to set the ground in the bulk, so c 2 = � (0), where (0) is the average of the potential profile over the bulk. kiyohara and asaka [39, 52] used an equation of a convolution form that can be shown to be equivalent to eq.(14), but they seemed to leave out the linear term containing � 1 . eq.(14) is different from the convolution integral (eq.(8)) because it does not suffer from the uncertainty in the upper integration limit and from errors originating from the noise of the q ion (x) profile. the integration is performed for a well defined finite domain from the left electrode to x. fig.3 shows that this equation provides a much better convergence as a function of simulation time for the same simulation (same q ion (x)). this procedure was used in our papers for inhomogeneous electrolyte systems to compute the mean electrostatic potential [53–56]. it was especially useful for electrolytes adsorbed in narrow slits [55,56]. in this case, the dls formed at the walls of the slit overlap so a bulk electrolyte does not form in the middle of the slit and the slit is not charge neutral. the neumann bc is then the natural bc so the electric field is zero behind the walls. in another example, the neumann bc is used to compute the potential for a dl model, where the electrode, the 128 inner layer, and the electrolyte have different dielectric constants [54]. in this case, the polarisation charge induced at the dielectric boundaries must also be included in eq.(14). dirichlet boundary conditions and the constant voltage ensemble an alternative method is the constant voltage ensemble of kiyohara and asaka [39]. here, the electrode charges fluctuate and the potential between the electrodes is prescribed. therefore, we can also apply dirichlet bcs, where (l 1 ) = 0 (15) and (l 2 ) = � ⇤. (16) the general solution for the potential profile in the l 1 < x < l 2 range is (x) = � 1 ✏ 0 ✏ z x l1 q tot (x0 )dx0 +c 1 (x�l 1 )+c 2 , (17) where we integrate from the right-hand side of the electrode at x = l 1 , so the surface charge � 1 is now excluded from the integration. the bc at x = l 1 (eq.(15)) provides the integration constant c 2 = 0, while the bc at x = l 2 (eq.(16)) provides the integration constant c 1 = 1 l 2 � l 1 " � ⇤ + 1 ✏ 0 ✏ z l2 l1 q tot (x)dx # . (18) of course, we can calculate the potential profile using the neumann bcs too. in that case, we must use h� 1 i in eq.(14) instead of � 1 because the electrode charge is now fluctuating so its value is not known in advance. therefore, its ensemble average should be used in eqs.(7-14). in the constant voltage ensemble we need the value of the voltage that corresponds to � 1 = �0.1 cm�2 as used in the previous constant charge simulation. this value we estimated with a very long (50,000 mc cycles) constant charge simulation and was obtained as � ⇤ = 4.398 kt/e. this value was used in the constant voltage simulation as an input parameter. fig.4 is the analogous version of fig.3. the black solid curves are the results obtained from the dirichlet bcs (eqs.(17) and (18)). the red short-dashed curves show the results of the neumann bc using h� 1 i in eq.(14). the convolution integral results (blue longdashed curves) are inaccurate and poorly converged for such a short simulation. in the constant voltage ensemble the electrode charge is a fluctuating quantity. fig.5 shows its convergence. its limiting value is not equal to that used in the constant charge simulation that provided the input voltage value � ⇤ = 4.398 kt/e. the deviation is due to finite size of the system. using a larger simulation box (larger h), a smaller deviation is observed (data not shown). this deviation is also observed in fig.4. the limiting value of the 0 200 400 600 800 1000 mc cycle -0.1 -0.095 -0.09 e le ct ro d e ch ar g e / c m -2 figure 5: convergence of the electrode charge in the constant voltage ensemble potential difference � = (l 2 )� (l 1 ) obtained from the calculation using the neumann bc (bottom panel) is different from the prescribed value (the value used in the dirichlet bc, see also bottom panel). this behaviour is analogous to that discussed earlier regarding the example of the pressure computed in the nv t and npt ensembles. the constant charge ensemble corresponds to the nv t , while the constant voltage ensemble corresponds to the npt ensemble. in the constant charge ensemble, the voltage is computed using the neumann bc, just as the pressure is computed in the nv t ensemble from the virial sum. in the constant voltage ensemble, the voltage is prescribed, just as the pressure is prescribed in the npt ensemble. the voltage can also be computed from the neumann bc, just as the pressure can also be computed from the virial sum in the npt ensemble. conclusion we propose that the neumann or dirichlet bcs should be used in computing the mean electrostatic potential for the planar dl geometry studied by computer simulations. the commonly used convolution integral of eq.(8) requires a vaguely defined upper integration limit and also suffers from numerical problems because it magnifies the effect of the noise in the charge profile that is always present in computer simulations. the problem of noise in the density profiles is unique to simulations and therefore more care must be taken in computing the electrostatic potential. on the other hand, theories [6–16], which produce smooth, noise-free density profiles, can use the convolution integral. we have shown here that the numerical method we proposed is much more efficient than the convolution integral, because we use unambiguous parameters in the bc, specifically, the electrode charge in the case of the neumann bc and the voltage in the case of the dirichlet bc. also, the simulation cell is necessarily finite, therefore, the boundaries of the system are always well de129 fined. overall, our method leads to converged results with very short simulations. acknowledgement the present publication was realised with the support of the projects támop-4.2.2/a-11/1/konv-2012-0071 and támop-4.1.1/c-12/1/konv-2012-0017. references [1] gouy g.: sur la constitution de la charge electrique a la surface d’un electrolyte (english title please), j. phys. 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mol department of hydrocarbon and coal processing, institute of chemical engineering and process engineering, university of pannonia, egyetem u. 10, 8200, hungary !email: mnorbert@almos.uni-pannon.hu the paper discusses the degradation of waste polyamides during mechanical recycling from the automotive sector. two different polyamides were investigated: glass fibre reinforced and unreinforced. raw materials were reprocessed twenty times and the changes in their properties were investigated as a function of reprocessing number. considerable differences were found in relation to the specimen properties between reinforced and unreinforced waste materials. for example, the tensile strengths of reinforced and unreinforced polyamide 6.6 wastes were 84.2 and 165.2 mpa, respectively, which dropped to 38.0 and 97.0 mpa after the twentieth reprocessing cycle. specimens from the reprocessing procedure have been investigated by fourier transformed infrared spectroscopy in the spectral range of 400–4000 cm-1. due to mechanical stress between the rotating screw and plasticising cylinder, the reinforcements broke. the average length of the glass fibre was decreased as a function of the reusing cycle number from 1890 to 580 µm. keywords: polyamide, mechanical recycling, degradation, ftir introduction as a result of the continuously increasing trend in the demand for polymer worldwide, ever increasing amounts of waste polymers are generated. polyamides (pa) are expensive engineering plastics, especially if they are reinforced. in particular, glass fibre composites are widespread among fibre-reinforced materials, as a results of their favourable mechanical and economical properties. the application of glass fibre results in improved tensile and flexural properties. thermoplastic polyamides contain typically 10-30% glass fibres as reinforcements and are applied in many industries such as the automotive sector, civil engineering, packaging, and biomedical applications [1-9,11,16]. a grand challenge is the utilisation of plastic wastes. polymer materials have a high resistance to different environmental and mechanical effects, which yields their favourable characteristics. such advantageous properties can easily become disadvantage owing to waste polymers inability to decompose within a reasonable time frame. unfortunately, a vast amount of polymer waste ends up to landfills, where nondegradable plastics together with other materials accumulate and pollute the environment [10,12-15]. the most studied recycling technologies are mechanical or chemical. chemical recycling is a thermal process for cracking the long carbon chains of polymers into gases and liquid hydrocarbons in the absence of oxygen within in temperature range of 400-1000 °c. the other technology is mechanical recycling, when waste polymers are mixed with original granulates and newly shaped by injection moulding or extrusion. mechanical recycling is a good option for reusing waste plastic, only when selectively collected polymers of high purity are available. similarly to the chemical process, the polymer chains can degrade due to mechanical and thermal stresses during the pre-treating and shaping steps. therefore, it is important to know the behaviour of polymer chains when exposed to thermal and mechanical stresses [9,11-16]. the goal of our work was to investigate the mechanical recycling of reinforced and unreinforced waste polyamides. waste polymers have been reprocessed twenty times and the changes of mechanical amongst other properties were investigated. the effects of reinforcements on the loss of properties during the reshaping procedures were followed. experimental plastics glass fibre reinforced and unreinforced waste polyamides were used as raw materials. the main properties of the raw materials are shown in table 1. table 1: the main properties of raw materials reinforced unreinforced mfi,* g (10 min)-1 15.1 11.8 ash content, % 30.6 0.03 tensile strength, mpa 165.2 84.2 charpy strength, kj m-2 13.4 12.1 * 275 ºc, 5 kg 132 sample preparation due to pa samples being sensitive to humidity, raw materials before processing and samples before testing were dried. drying was carried out in an air circulated drying box at 90 ºc for 2 h. the injection moulding of the specimens was carried out by a microprocessorcontrolled injection moulding machine. the dimensions of dog-boned injection moulded specimens were 3 mm × 10 mm in cross-section and 50 mm in length. fig.1 illustrates the main experimental steps. methods the tensile and three point flexural properties (mainly stress and extension) (msz en iso 527-1-4:1999, msz en iso 14125:1999) were determined using an instron 3345 universal tensile testing machine. the temperature and relative humidity in the laboratory were 23 ºc and 60% respectively, during the mechanical tests. tensile tests were carried out at a crosshead speed of 80 mm min-1. during the investigation of flexural properties, the crosshead testing speed was 20 mm min-1. samples were also investigated by infrared spectroscopy with a tensor 27 type ftir spectrometer (resolution: 3 cm-1, illumination: sic globar light, detector: rt-dlatgs type) within the 400-4000 cm-1 wave number range. a ceast resil impactor was applied to measure the charpy impact strength of the produced samples according to the msz en iso 179-2:2000 standard. results and analysis tensile properties the tensile properties of reshaped specimens are summarised in figs.2a-2c. the tensile strength of reinforced and unreinforced polyamide 6.6 wastes were 84.2 mpa and 165.2 mpa, respectively, which were reduced to 38.0 mpa and 97.0 mpa after the twentieth reprocessing cycle (fig.2a). it is important to note that the decreasing trends were considerably different in the two cases: a fourth order trend line in the case of reinforced samples and a second order one in the case of unreinforced samples were found as shown in fig.2a. a short section with a barely decreasing slope can be found both at the beginning (before the third cycle) and at the end (after the fifteenth cycle) of the trend line for figure 1: the main experimental steps figure 2: tensile properties of reinforced and unreinforced polyamide 6.6 wastes: a) tensile strength, b) elongation and c) tensile modulus c b a number of cycles number of cycles number of cycles number of cycles 133 the reinforced specimens. in the case of unreinforced specimens a similar phenomenon was found only up to the ninth cycle. the elongations of specimens are shown in fig.2b. owing to the rigid property of polyamides the relative elongations are rather small (below 3.8%). as results demonstrate the change in elongations was rather linear, but the gradient was different when the reinforced (tan α = 0.033) and unreinforced (tan α = 0.054) raw materials were investigated; because a slower ratio in change was found in the presence of glass fibres in polyamide wastes. as demonstrated by the tensile strength, tensile moduli show a decreasing trend as well. furthermore, the trend line is highly similar to the measured data for tensile strength. the e-modulus of reinforced and unreinforced wastes was 8219 mpa and 3226 mpa, respectively. those were decreased to 3606 mpa and 1022 mpa according to the mathematical equations in fig.2c. flexural properties the flexural properties of reshaped specimens are summarised in figs.3a-3c. the change in both flexural strength and e-modulus followed a decreasing trend, while the trend in terms of elongation was rather increasing. the results were similar to the tensile properties discussed above. it is important to note that the shapes of trend lines were also similar to results demonstrated before. when reinforced polyamide 6.6 waste material was reprocessed the flexural strength, elongation and e-modulus changed from 248.5 mpa, 4.42% and 5622 mpa to 166.0 mpa, 4.86% and 3416 mpa, respectively. by taking into consideration the results of both tensile and flexural tests it can be concluded that the glass fibre reinforcement helps to keep the high values of strengths and e-moduli in the case of reinforced polymers at the start of property curves as a function of processing cycle number. approximately after the third-to-fifth reprocessing cycles, the dropping ratio was increased step by step. presumably this was the consequence of the glass fibres degrading into pieces. on the contrarily, a relatively constant dropping ratio was found in the unreinforced case. charpy impact strength the charpy impact strength test is one of the most widely specified mechanical tests of polymeric materials to provide information about impact properties. results of charpy tests were summarised in fig.4. the change in charpy impact strength followed a decreasing trend in both cases. moreover, a similar trend in the changes could be found, because the gradients were 13.38 and 12.18 for reinforced samples and unreinforced specimens, respectively. the charpy impact strengths were 12.1 kj m-2 and 13.4 kj m-2 without any reprocessing, and decreased to 8.4 kj m-2 and 9.4 kj m-2 respectively by the end of the procedure. naturally the reinforced samples gave higher values of impact strength. figure 3: flexural properties of reprocessed reinforced and unreinforced polyamide 6.6 wastes a) flexural strength, b) elongation and c) flexural modulus a b c figure 4: charpy impact strength of reprocessed reinforced and unreinforced polyamide 6.6 wastes number of cycles number of cycles number of cycles number of cycles c 134 linear extension coefficient the coefficient of thermal expansion describes the change in dimensions of samples against changing temperature at a constant pressure. regarding polymers the linear extension coefficient is used to classify the materials. as it is known, thermal expansion decreases with increasing bond energy and the thermal extension of the amorphous phase is higher than that of the crystalline phase, because rearrangements in the structure can be achieved at the glass transition temperature. a change in ratio of amorphous and crystalline phases occurs. the coefficients of linear extension are demonstrated in fig.5. results demonstrate well that the coefficient changes randomly in both cases between 2.05 and 2.27 with approximately the same average value of 2.18 ºc-1 for the reinforced and unreinforced specimens within 0.01 ºc-1. presumably no rearrangements in the structures of the tested materials occurred during the reprocessing and the ratio of the amorphous to crystalline phases remained similar. in other words, the specimens a have relatively permanent stability of shape. fourier transformed infrared spectroscopy samples from the reprocessing procedure were also investigated by fourier transformed infrared spectroscopy (ftir), which provides a measure of changes in molecular structures through molecular vibrational excitations. the ftir spectra of reinforced and unreinforced waste polymers as a function of the reprocessing cycles are shown in figs.6a and 6b. by this method, modifications in the molecular structures of polymers could be observed as a result of changes in their chemical bonds. a typical spectrum of polyamide can be described as follows: " stretching vibration of -ch2and -ch3 groups between 2800–3000 cm-1 " symmetric and asymmetric deformation stretching of -ch3 groups between 1430 and 1470 cm-1 and 1365 and 1395 cm-1 " βasymmetricch2 of -ch2groups at 720 cm-1 " bands at 3350, 1730 cm-1, and 630 cm-1 as well referring to the n–h and c=o bonds from –nh– and –co functional groups. the methyl/methylene group (–ch3/–ch2–) ratio in an average molecule was calculated based on the ftir peak intensities in the range of 2800–3000 cm-1. results are summarised in fig.7. as shown, the ratio of methyl and methylene groups slowly decreased in both cases as a function of reprocessing cycles. this suggests that the numbers of methyl groups increased, while the methylene groups decreased in an average molecule. this is a consequence of polymer degradation, when the c-c bonds of main polymer chains are cleaved, which resulted in shorter chains containing less methylene groups. figure 5: coefficient of linear heat extension of reprocessed reinforced and unreinforced polyamide 6.6 wastes figure 6: ftir spectra of reinforced (a), and unreinforced polyamide (b) b a figure 7: the change in the –ch3/–ch2– ratio of an average molecule and the value of log(i/i0) from ftir spectra at 720 cm-1 as a function of the reprocessing cycles in the cases of reinforced and unreinforced polyamides number of cycles number of reprocessing cycles number of reprocessing cycles 135 scanning electron microscope graphs as the polyamide matrix covered the fibres, it was difficult to determine their average length. therefore to investigate the average length of the reinforcements and thus gain insights into their degree of degradation, the samples were burned and the remaining glass fibres were investigated by sem techniques. the results are shown in fig.8. as shown, the average length of the glass fibre reinforcements decreased as a function of the reusing cycle number. the length of glass fibres suddenly decreased from 1890 µm to 660 µm during the first four cycles of reprocessing. then the average length exhibited a relatively constant value between 550 and 640 µm. the mean and standard deviation were 581 µm and 28 µm between the fifth and twentieth cycles, respectively. the cause for the degradation of the reinforcement fibres was the mechanical stress caused by the rotating screw and plasticising cylinder. conclusions we investigated the reprocessing of waste glass fibre reinforced and unreinforced polyamide 6.6 materials. it was found that the mechanical properties of both wastes deteriorated as a function of reprocessing. for example, the tensile strengths of reinforced and unreinforced polyamide 6.6 wastes were 84.2 mpa and 165.2 mpa, respectively, which decreased to 38.0 mpa and 97.0 mpa after the twentieth reprocessing cycle. on the other hand, the trend lines of the changes were significantly different in the case of reinforced and unreinforced wastes. more gradually decreasing ratios could be measured regarding unreinforced plastics until the tenth cycle. based on infrared spectra, it was concluded that the deterioration in mechanical properties presumably was the consequence of polymer degradation. the c-c bonds of the main polymer chains were broken and resulted in the formation of shorter polymer chains. the lengths of glass fibres suddenly decreased from 660 µm to 1890 µm during the first four cycles of reprocessing. then, the average length exhibited a relatively constant value between 550 and 640 µm. the coefficients of linear heat extension changed randomly in both cases between 2.05 and 2.27 ºc-1. the average value was 2.18 ºc-1 for both reinforced and unreinforced samples within 0.01 ºc-1. references 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subodhan kamalanathan1, fadina amran1 and muhammad abbas ahmad zaini1,2* 1 faculty of chemical and energy engineering, universiti teknologi malaysia, 81310 utm johor bahru, johor, malaysia 2 centre of lipids engineering and applied research (clear), ibnu sina institute for scientific and industrial research, universiti teknologi malaysia, 81310 utm johor bahru, johor, malaysia this work aimed to evaluate the performance of hydrochar and oxidized hydrochars for the removal of methylene blue. hydrochar was prepared from mangosteen peel, while ammonium persulfate ((nh4)2s2o8), sulfuric acid (h2so4) and nitric acid (hno3) were used to oxidize the surface of hydrochars. the performance of pristine hydrochar is better compared to its oxidized counterparts, with a maximum adsorption capacity of 110 mg/g. the adsorption data are well described by langmuir and pseudo-kinetic models, while the thermodynamic parameters indicate that the process is endothermic and spontaneous. in conclusion, mangosteen peel is a promising feedstock of hydrochar and oxidation treatment may induce a cationic shield that is unfavorable when extracting methylene blue from water. keywords: adsorption, hydrochar, mangosteen peel, methylene blue, oxidation treatment 1. introduction although water is essential to sustain all living creatures and for human activities, it is also highly susceptible to pollution [1]. the presence of dyes, heavy metals, microplastics, pesticides, etc. in water jeopardizes the aquatic ecosystem, public health and food chain [2]. the effect of dyes in water has attracted attention because of their complex chemical composition, toxicity and lasting implications for water resources [3]. even though dyes are usually used to impart color to fabric, paper, etc., the discharge of effluent that is inadequately treated causes water pollution [1]. the methods to treat dye wastewater can be categorized as physical (coagulation and flocculation, adsorption, membrane filtration, etc.), chemical (ozonation, advanced oxidation processes, photocatalysis, etc.) or biological (biosorption, biodegradation, anaerobic digestion, etc.) [4]. the characteristics of contaminants in water and the intended use of the treated water are key factors in determining the most effective treatment strategies. among others, adsorption is undeniably an effective technique to treat dye wastewater [5]-[6] and is defined as a process whereby the solute is drawn to the solid surface of the adsorbent. the adsorbent material can be manufactured from various carbonaceous resources such as coconut shells, received: 17 june 2024; revised: 14 aug 2024; accepted: 21 aug 2024 *correspondence: abbas@cheme.utm.my wood chips, rice husks, fruit peel, etc. this biomass is sustainable, abundant and low-cost [7]. mangosteen (garcinia mangostana) is a tropical fruit native to southeast asia, with a thick outer peel that accounts for approximately 60% of its total mass [8]. the renewable supply of mangosteen peel has sparked interest given its potential as a promising source of biomass for the production of adsorbents. adsorbents from biomass can be produced through pyrolysis, surface modification, hydrothermal carbonization, etc. in a related work, hydrothermal carbonization was applied to produce carbon-rich hydrochar from mangosteen peel with a maximum methylene blue capacity of 132 mg/g [9]. in this work, the effect of the surface oxidation of mangosteen peelderived hydrochar on the removal of methylene blue was studied. ammonium persulfate ((nh4)2s2o8), sulfuric acid (h2so4) and nitric acid (hno3) were used to modify the surface properties of hydrochars. adsorption took place at different concentrations and temperatures as well as over various contact times in order to investigate the governing removal mechanisms. 2. experimental mangosteen peel was collected from a fruit stall in johor state, malaysia before being oven-dried and crushed https://doi.org/10.33927/hjic-2025-01 mailto:abbas@cheme.utm.my kamalanathan, amran and zaini hungarian journal of industry and chemistry 2 prior to hydrothermal carbonization. (nh4)2s2o8, hno3 (65%), h2so4 (98%) and methylene blue (c.i. 52015) of analytical grade were used as received without further purification. 2.1. preparation and characterization of adsorbents 15 g of dried mangosteen peel was added to 70 ml of distilled water in a teflon reactor. hydrothermal carbonization was carried out at 180 °c for 24 h. the resultant hydrochar was oven-dried and the yield calculated to be 75%. for oxidation treatment, the hydrochar was separately mixed with 50 ml of 0.2 m (nh4)2s2o8, h2so4 and hno3 in beatson clark bottles before being left in a water bath at 65 °c for 24 h. next, the resultant oxidized hydrochars were washed with distilled water to remove residual chemicals. all the samples were ovendried prior to their use. the hydrochar and its oxidized forms (hereinafter referred to as hydrochar adsorbents) were designated as hc (pristine mangosteen peelderived hydrochar), aps (hydrochar oxidized with (nh4)2s2o8), sa (hydrochar oxidized with (h2so4) and na (hydrochar oxidized with (hno3), respectively. the thermal degradation profiles of the pristine hydrochar and its oxidized forms were determined using a thermogravimetric analyzer (perkinelmer, tga 4000) under a n2 flow at a heating rate of 10 ºc/min from room temperature to 900 ºc. the surface functional groups were qualitatively identified using a fourier transform infrared spectrometer (spectrum one). the surface morphology of the hydrochar adsorbents was obtained by a tm3000 (hitachi, japan). 2.2. adsorption studies 30 mg of hydrochar was added to 30 ml of methylene blue solution of varying concentrations (5-200 mg/l) before being left for 6 days to reach equilibrium. the residual methylene blue (dye) concentration was measured using a visible spectrophotometer and the adsorption capacity at equilibrium, qe, calculated as follows: 𝑄𝑒 = (𝐶𝑜−𝐶𝑒) 𝑚 𝑉 (1), where co (mg/l) and ce (mg/l) denote the initial and equilibrium dye concentrations, respectively, v (l) represents the volume of the solution and m (g) refers to the mass of the adsorbent. the adsorption data were analyzed using the langmuir and freundlich isotherm models in the following equations, respectively: 𝑄𝑒 = 𝑄𝑚𝑏𝐶𝑒 1+(𝑏𝐶𝑒) (2), 𝑄𝑒 = 𝐾𝐹𝐶𝑒 1/𝑛 (3), where b (l/mg) denotes the affinity of binding sites, qm (mg/g) refers to the maximum adsorption capacity, kf [(mg/g)(l/mg)1/n] represents the relative capacity and 1/n stands for the adsorption intensity [10]. the rate of adsorption of the selected hydrochar adsorbents was determined. 30 mg of adsorbent was mixed with 30 ml of dye solution at concentrations of 5, 10 and 20 mg/l. the residual dye concentration was measured at pre-set time intervals until an equilibrium was reached and the capacity at time t, qt (mg/g), was calculated as follows: 𝑄𝑡 = (𝐶𝑜−𝐶𝑡) 𝑚 𝑉 (4), where ct (mg/l) denotes the dye concentration at time t. the kinetic data were analyzed using pseudo-first order and pseudo-second order models as expressed in the following equations, respectively: 𝑄𝑡 = 𝑄𝑒(1 − 𝑒−𝑘1𝑡) (5), 𝑄𝑡 = 𝑄𝑒 2𝑘2𝑡 1+𝑄𝑒𝑘2𝑡 (6), where k1 (min−1) denotes the pseudo-first order rate constant, k2 (g mg-1 min-1) represents the pseudo-second order rate constant and t (min) refers to the contact time. the thermodynamic parameters were determined from the effect of the temperature on the adsorption of methylene blue. the selected hydrochar adsorbents were mixed with a dye solution at a concentration of 100 mg/l. adsorption took place at different temperatures, namely 40, 50 and 60 ºc, in a water bath. the parameters of gibbs energy (∆g°), enthalpy (∆h°) and entropy (∆s°) were calculated using the following equations: ln(𝐾𝑑) = − ∆𝐻 𝑅𝑇 + ∆𝑆 𝑅 (7), ∆𝐺 = −𝑅𝑇 ln (𝐾𝑑) (8), 𝐾𝑑 = 𝑄𝑒 𝐶𝑒 (9), where kd denotes the equilibrium constant, while ∆h° and ∆s° were calculated from the gradient and intercept, respectively, when ln(kd) was plotted against 1/t. 3. results and discussion 3.1. characteristics of the adsorbents thermogravimetric analysis (tga) is an analytical technique that examines variations in the mass of a sample as the temperature increases. the thermal degradation profiles of hydrochar adsorbents are shown in figure 1. the common peaks at 70 °c are ascribed to the release of moisture and light volatiles. the degradation rate increased between 200 and 400 °c, corresponding to the peaks of varying intensities at approximately 300 °c as well as signifying the liberation of thermally sensitive surface functional groups. their weight gradually decreased at varying rates between 400 and 700 °c, which can be attributed to the fact that hc contains less functional groups as well as indicative of a successful oxidation treatment to produce aps, na and sa. furthermore, the presence of thermally-stable oxidized mangosteen peel-derived hydrochar 53(1) pp. 1–7 (2025) 3 functional groups is implied that act as a protective layer on the hydrochar surface [11]. the weight loss profiles can be characterized by three distinct stages. the initial stage between 5 and 200 ºc coincides with the vaporization of moisture. the second stage between 200 and 600 °c indicates the liberation of volatiles and organic molecules. sa possesses more thermally-stable functional groups than the other hydrochar forms given the steep gradient with some fluctuations during the second stage. finally, the third stage between 600 and 880 °c is caused by the breakdown of the remaining organic substances [11]. fourier-transform infrared spectroscopy (ftir) is a method to determine the chemical makeup of a material. the ftir spectra of hydrochar adsorbents are shown in figure 2. functional groups such as hydroxyl (oh), alkane (ch), ether (c=o), nitro (no), aromatic ester (c–o) and amine (c=n) were identified from the spectra. all hydrochar adsorbents display an abundance of hydroxyl (oh) functional groups, probably due to the inherent/natural moieties in hc and the ones that evolved during the oxidation treatment. hc and na contain lower concentrations of hydroxyl groups as can be interpreted from the intensity of the peaks. the sem images to visualize the surface texture and morphology of the hc and aps are shown in figure 3. the hc surface is more porous compared to that of aps. during hydrothermal carbonization, some functional groups are subjected to thermal decomposition and interact with organic material to produce gases, i.e. carbon monoxide and carbon dioxide, in addition to water vapor [12]. this process alters the morphology and structure of the hc, typically resulting in the specific area expanding. nevertheless, the porous structure could deteriorate as a result of the substantial loss of material and it collapsing [13]. on the other hand, the oxidation treatment may reduce the number of accessible adsorption sites on hydrochar. the pore opening of hc is larger (8.5 µm) than that of aps (4.3 µm). notably, oxidation treatment resulted in the pore tunnels of hydrochar shrinking. (a) (b) figure 1: (a) tga and (b) dtg profiles of the adsorbents 20 40 60 80 100 0 200 400 600 800 1000 w ei g h t (% ) temperature (°c) hc sa na aps 0 2 4 6 0 200 400 600 800 1000 d er iv at iv e w ei g h t (% ) temperature (°c) hc aps sa na figure 2: ftir spectra of the adsorbents (a) (b) figure 3: sem images of (a) hc and (b) aps kamalanathan, amran and zaini hungarian journal of industry and chemistry 4 3.2. equilibrium adsorption the adsorption isotherm is essential to determine the surface characteristics and affinity of hydrochar adsorbents towards methylene blue. the equilibrium curves of methylene blue adsorption onto hydrochar adsorbents are displayed in figure 4. generally, the adsorption of all hydrochar adsorbents increased as the dye concentration increased until their maximum capacities were reached. the high dye concentration is the driving force to encourage the mass transfer of dye molecules to surpass the resistance of the film [14]. the active sites are mostly occupied at high concentrations, ensuring the adsorption capacity remains constant [15]. the constants of isotherm models for the removal of methylene blue by hydrochar adsorbents are shown in table 1. based on the regression coefficient (r²) and sum-of-squared errors (sse), the equilibrium data for hc, aps and na correspond well with the langmuir isotherm, while those for sa are better described by the freundlich isotherm. hc exhibits a greater qm of 110 mg/g, followed by aps with 90.3 mg/g, perhaps because of the inherent surface functionalities in the former, while the newly evolved oxygen-containing functional groups in the oxidized forms of hydrochar may enhance steric hindrance (cationic shield), inhibiting the diffusion of dye molecules onto the surface of the adsorbent. 3.3. adsorption kinetics kinetics play a crucial role in the design of a treatment system that relies upon the rate at which pollutants are removed. the rate of dye adsorption onto hc and aps is shown in figure 5. obviously, their adsorption capacities increased as the contact time increased at all concentrations studied with the adsorption rate of hc being greater than aps. the rate of dye removal varies with contact time due to the transport of dye molecules in order to overcome the boundary layer effect before diffusing into the active sites [16]. higher concentrations typically require longer contact times to reach table 1: the constants of isotherm models adsorbent hc aps na sa langmuir qm (mg/g) 110.0 90.3 74.5 80.8 b (l/mg) 0.39 0.46 0.42 0.32 r2 0.99 0.96 0.96 0.95 sse 59 297 219 318 freundlich kf ((mg/g)(l/mg)1/n) 31.0 27.4 22.7 22.9 1/n 0.29 0.28 0.27 0.29 r2 0.91 0.95 0.95 0.97 sse 819 350 215 163 (a) (b) (c) figure 5: the rate of methylene blue adsorption by hc and aps at dye concentrations of (a) 5, (b) 10 and (c) 20 mg/l 0 1 2 3 4 0 400 800 1200 1600 a d so rp ti o n c ap ac it y, q t (m g/ g) time, t (min) exp hc exp aps 0 2 4 6 8 0 400 800 1200 1600 a d so rp ti o n c ap ac it y, q t (m g/ g) time, t (min) exp hc exp aps 0 4 8 12 16 0 400 800 1200 1600 a d so rp ti o n c ap ac it y, q t (m g/ g) time, t (min) exp hc exp aps figure 4: equilibrium curves of methylene blue adsorption onto hydrochars oxidized mangosteen peel-derived hydrochar 53(1) pp. 1–7 (2025) 5 equilibrium due to several dye molecules competing to attach to the same active site [17]-[20]. from table 2, the kinetic behavior of hc and aps could be described by both pseudo-first order and pseudo-second order models. the pseudo-first order model describes the rate of adsorption that is directly proportional to the dye concentration, especially when dilute. as the concentration increases, the removal mechanism shifts from physical adsorption to complex interactions between dye molecules and the surface of the adsorbent. the pseudo-second order rate constant, k2, decreases as dye concentration increases. as more sites become occupied at higher concentrations, the availability of free sites decreases, thereby decreasing the driving force and adsorption rate. furthermore, k2 for aps is slower than that of hc, perhaps due to the evolution of a cationic shield that impedes dye molecules from adsorbing onto the sites. 3.4. adsorption thermodynamics the van ’t hoff plot that depicts the adsorption of methylene blue by hc and aps at different temperatures is shown in figure 6 and the thermodynamic parameters are summarized in table 3. it is evident that aps consumes more energy (adsorption enthalpy) compared to hc, probably due to the presence of new oxygen functionalities in aps. since adsorption is endothermic, the dye adsorption capacity increased as the temperature of the solution rose. raising the temperature of the solution accelerates the movement of dye molecules towards active sites. the negative ∆g° suggests that the process is spontaneous and favorable, while the positive ∆s° implies the disorder or randomness of the system during the adsorption process [21]. 3.5. adsorption mechanisms the oxidation treatment modifies the surface chemistry of the adsorbent, resulting in the formation of new functional groups, consequently affecting how the different hydrochar adsorbents interact with dye molecules as illustrated in figure 7a. the presence of oxygen-containing groups in the adsorbent usually facilitates the removal of positively charged pollutants through hydrogen bonding, electrostatic attraction and dispersive interaction [12]. in water, the oxygen-containing functional groups are dissociated, producing a negatively charged surface onto which methylene blue molecules are attracted. however, the excess oxygen functionalities in the oxidized hydrochar inevitably create a h+ layer covering the surface of the adsorbent as visualized in figure 7b. this protective layer functions as a cationic shield, repelling the cationic dye molecules and hindering their table 2: the constants of kinetic models adsorbent hc aps co (mg l-1) 5 10 20 5 10 20 pseudo-first order qe (mg g-1) 3.02 7.22 13.10 3.61 7.10 14.00 k1 (h-1) 1.47×10-2 6.77×10-3 6.69×10-3 3.55×10-3 4.59×10-3 4.77×10-3 r2 0.93 0.99 1.00 0.99 0.99 1.00 sse 1.31 1.41 0.84 0.12 0.65 1.58 pseudo-second order qe (mg g-1) 3.37 8.09 14.80 4.37 8.11 16.00 k2 (g mg-1 h-1) 6.25×10-3 1.10×10-3 5.83×10-4 8.24×10-4 6.71×10-4 3.55×10-4 r2 0.97 0.99 1.00 0.99 1.00 1.00 sse 0.43 0.84 1.09 0.15 0.18 0.40 figure 6: the van ’t hoff plot for methylene blue adsorption onto hc and aps table 3: the thermodynamic parameters adsorbent t (k) δg° (kj mol-1) δh° (kj mol-1) δs° (j mol-1 k-1) hc 40 -2.86 50 -4.68 54.0 182 60 -6.49 aps 40 -3.89 50 -6.10 65.4 221 60 -8.32 kamalanathan, amran and zaini hungarian journal of industry and chemistry 6 diffusion to the active sites on its surface. access to active sites may also be obstructed by water molecules (dipoles) covering the surface. the added oxygencontaining functional groups impede the movement of cations and mass transfer [12]. this combined effect decreases the rate of methylene blue adsorption onto oxidized forms of hydrochar rather than onto the pristine one. in the case of the pristine hydrochar, the dye molecules easily diffuse because of less steric hindrance to occupy its natural functional groups, achieving a greater adsorption capacity. 4. conclusions the hydrochar was prepared from mangosteen peel and the oxidation treatment performed using ammonium persulfate, nitric acid and sulfuric acid. the adsorbents were used to remove methylene blue dye in from water. the adsorption behavior, which is endothermic and spontaneous, is well-described by langmuir isotherm and pseudo-kinetic models with ammonium persulfateoxidized hydrochar consuming more energy (enthalpy) than its pristine counterpart. the hydrochar prepared from mangosteen peel exhibits a better dye adsorption capacity of 110 mg/g compared to its oxidized counterparts. the oxidation treatment unavoidably induces a cationic shield that impedes the diffusion 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https://doi.org/10.1016/j.psep.2018.04.015 https://doi.org/10.1016/j.micromeso.2021.110904 hungarian journal of industry and chemistry vol. 49(1) pp. 9–16 (2021) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2021-02 photocatalytic degradation of rhodamine b in heterogeneous and homogeneous systems asfandyar khan1,2, zsolt valicsek1, and ottó horváth*1 1department of general and inorganic chemistry, center for natural sciences, faculty of engineering, university of pannonia, veszprém, hungary 2department of textile engineering, national textile university faisalabad, pakistan this study focuses on the photocatalytic degradation of rhodamine b (rhb) in heterogeneous and homogeneous photofenton reactions. in the heterogeneous system, iron(ii) doped copper ferrite cuii (x) feii (1−x) feiii 2 o4 nanoparticles (nps) prepared in our previous work were employed as potential catalysts. the photodegradation of rhb was carried out in a quartz cuvette located in a diode array spectrometer. the experimental conditions such as ph, nps dosage and h2o2 dosage with regard to the photocatalytic degradation of rhb were optimized to be 7.5, 500 mg/l and 8.9 × 10−2 mol/l, respectively. in addition, visible light-induced photodegradation of rhb was also carried out by using h2o2 over a wide ph range in the absence of heterogeneous photocatalysts. it was observed that the reaction rate significantly increased above ph 10, resulting in a faster rate of degradation of rhb, which may be attributed to the deprotonation of hydrogen peroxide. furthermore, the potential antibacterial property of such catalysts against the gram-negative bacterium vibrio fischeri in a bioluminescence assay yielded inhibition activities of more than 60% in all cases. keywords: heterogeneous photo-fenton system, iron(ii) doped copper ferrites, deprotonation effect, photodegradation 1. introduction synthetic dyes have numerous applications in several industries, e.g., paper, textile, leather and paint. besides these applications, some dyes are toxic organic compounds and their discharge into the environment causes eutrophication, aesthetic pollution and distress for marine organisms [1, 2]. some synthetic dyes are recalcitrant, that is, resistant to biological degradation and direct photolysis. in addition, many dyes contain nitrogen which produces carcinogenic as well as mutagenic aromatic amines as a result of natural anaerobic reductive degradation [3, 4]. these toxic organic dyes can be mineralized into water and carbon dioxide via photocatalytic reactions using catalysts under ultraviolet or visible light irradiation [5, 6]. only a handful of research groups have developed and applied ferrite nanoparticles (nps) as catalysts which can utilize larger bandwidths of the visible light spectrum. manganese ferrite [7], zinc ferrite [8–10], aluminium doped zinc ferrite [11], manganese doped cobalt ferrite [12], barium ferrite [13], copper ferrite [14], and nickel ferrites [15,16] have been investigated with regard to the degradation of certain dyes and other toxic compounds. *correspondence: horvath.otto@mk.uni-pannon.hu our research group prepared and applied iron(ii) doped copper ferrites cuii(x)feii(1−x)feiii2 o4 (where x = 0, 0.2, 0.4, 0.6, 0.8, 1) for the photo-induced degradation of methylene blue (mb) [17]. here, a detailed photocatalytic study on the degradation of rhodamine b is presented by using heterogeneous photo-fenton systems and compared to homogeneous photocatalytic procedures. in addition, the antibacterial property of iron(ii) doped copper ferrites in the vibrio scheri bioluminescence inhibition assay was investigated. 2. experimental 2.1 materials rhodamine b (molecular formula: c28h31cln2o3) was used as a model dye for visible light-induced photocatalytic degradation. anhydrous copper(ii) sulfate, ferric chloride hexahydrate, ammonium iron(ii) sulfate hexahydrate and sodium hydroxide were used to prepare the catalysts. sodium hydroxide or hydrochloric acid was added to adjust the ph during photocatalysis. hydrogen peroxide (30%w/w) was employed as fenton’s reagent and double distilled water used as a solvent throughout the study. all the laboratory-grade chemicals were obtained from sigma-aldrich (budapest, hungary) and used without further purification. https://doi.org/10.33927/hjic-2021-02 mailto:horvath.otto@mk.uni-pannon.hu 10 khan, valicsek, horváth 2.2 applied catalysts the catalysts applied in this study were iron(ii) doped copper ferrite cuii(x)feii(1−x)feiii2 o4 nps (where x = 0 (np-1), 0.2 (np-2), 0.4 (np-3), 0.6 (np-4), 0.8 (np5), 1.0 (np-6)), which were prepared by a simple coprecipitation-calcination technique. the detailed methods for the synthesis of these catalysts and their structural elucidation have been reported in our earlier studies [17, 18]. 2.3 rhb photocatalytic reactions for photocatalysis, a stock solution of 0.5 g/l rhb was prepared. in order to perform the photocatalysis, a small cuvette used as a reactor was adjusted to a s600 uv/vis diode array spectrophotometer. the concentration of rhb (approximately 1.8×10−5 mol/l) in the cuvette was calculated by using the beer-lambert law [17]. control experiments for the self-degradation of rhb were carried out without ferrite nanoparticles in the absence and presence of both light and hydrogen peroxide (for the oxidant effect). then the np catalyst of a given concentration was added to the rhb solution and stirred for 30 mins to ensure a good degree of dispersion and reach an adsorption equilibrium before photodegradation. the temperature of the photoreactor (25±2 ◦c), concentration of rhb (1.8 × 10−5 mol/l) and duration (140 mins.) of photocatalytic experiments were kept constant. the process variables investigated were the catalyst dosage (80 to 800 mg/l), hydrogen peroxide concentration (2.2× 10−2 to 3.0× 10−1 mol/l) and ph (2 to 12). meanwhile, the original ph of the total aqueous solution was approximately 7.5. the ph was adjusted by adding hcl or naoh before starting the photocatalytic experiment. 2.4 determination of reaction rate the beer-lambert law was used to determine the reaction rate of each experiment. the spectral changes observed in the visible range of the absorption spectrum (fig. 1) indicate that the intermediates and end products formed during the photocatalytic degradation of rhb did not produce any remarkable peaks. therefore, the reaction rate of rhb photodegradation can be determined from the reduction in absorbance at the maximum wavelength (λmax = 554 nm). the addition of heterogeneous photocatalysts caused the baseline in the recorded spectra to change as a consequence of scattering. this problem was resolved during the evaluation of the reaction rate by applying baseline corrections. 2.5 assessment of antibacterial property a luminoskan ascent microplate luminometer (thermo scientific) was used to measure the antibacterial property of the ferrite nps in a vibrio scheri bioluminescence figure 1: spectral changes during rhodamine b photodegradation in the presence of np-3. the inset shows the absorbance vs. time plot at 554 nm. experimental conditions: concentration of rhb is 1.8 × 10−5 mol/l, concentration of h2o2 is 1.8× 10−1 mol/l, concentration of np-3 is 400 mg/l, initial ph is = 7.5, and irradiation time is 140 mins. inhibition assay. according to the manufacturer’s (hach lange gmbh, germany) recommendations, a test specimen of a gram-negative vibrio fischeri (nrrl-b-11177) suspension was prepared with a lifespan of 4 hours after being reconstituted. the same test protocol was followed as reported in the literature [19]. during the evaluation, the results obtained from 2 parallel measurements were averaged before the relative inhibition (%) was calculated using relative inhibition (t) = ic(t)− is(t) ic(t) × 100% (1) where ic(t) denotes the emission intensity of the control sample at time t and is(t) represents the emission intensity of the test specimen at the same time. 3. results and discussion a detailed explanation regarding the control experiments concerning the photodegradation of rhb was reported in one of our previous studies [18]. the experiment used as a basis for comparisons (rhb + h2o2 + light) is shown in fig. 2. after the control experiments, the photocatalytic efficiency of six doped ferrite nanoparticles was investigated. fig. 1 shows the spectral changes obtained during the photocatalytic experiment using np-3 and the decrease in the absorbance of rhb at λmax = 554 nm (inset of fig. 1). the degradation reaction of rhb follows apparent rstorder kinetics (fig. 3), which is also consistent with earlier observations regarding other catalysts [20, 21]. the slight deviation from the straight line is due to the complex nature of this heterogeneous system. fig. 4 reveals that all doped ferrite nps in the series of cuii(x)feii(1−x)feiii2 o4 (x = 0 − 1) delivered higher apparent rate constants for the degradation of rhb compared to the control experiment. doped copper ferrites hungarian journal of industry and chemistry photocatalytic degradation of rhodamine b 11 figure 2: spectral changes during the photodegradation of rhodamine b in the absence of nps. the inset shows the absorbance vs. time plot at λmax = 554 nm. experimental conditions: concentration of h2o2 is 1.8 × 10−1 mol/l, concentration of rhb is 1.8×10−5 mol/l, and irradiation time is 140 mins. figure 3: a plot of the logarithm of the absorbance at 554 nm vs. time for the photodegradation of rhb (see the inset of fig. 1) np-2 and np-3 exhibited outstanding photocatalytic performances in the series studied. nickel doped cobalt ferrite nps revealed a very similar trend with regard to the photo-oxidative degradation of rhb [22]. the higher apparent rate constants for the degradation of rhb using np-2 and np-3 may be attributed to their special needlelike crystalline structure [17]. on the basis of the first experimental series, np-3 was chosen to further investigate three important determinants, namely the catalyst dosage, hydrogen peroxide concentration and ph of the heterogeneous photo-fenton system. 3.1 the effect of catalyst dosage fig. 5 shows the effect of the np-3 dosage (0−800 mg/l) on the apparent rate constant. the increase in dosage from 0−500 mg/l yielded a significant increase in the apparent rate constant. this phenomenon can be attributed to the higher number of available active sites in heterogeneous photo-fenton processes [23]. however, increasing the dosage of nps above 500 mg/l caused a moderate figure 4: photocatalytic efficiency in terms of apparent rate constants (compared to the control experiment) for np-1 to 6. experimental conditions: concentration of nps is 400 mg/l, concentration of rhb is 1.8 × 10−5 mol/l, concentration of h2o2 is 1.8 × 10−1 mol/l, initial ph is 7.5, and irradiation time is 140 mins. figure 5: effect of the concentration of np-3 on the apparent rate constant of rhb photodegradation. experimental conditions: concentration of rhb is 1.8 × 10−5 mol/l, concentration of h2o2 is 1.8 × 10−1 mol/l, initial ph is 7.5, and irradiation time is 140 mins. decrease in the apparent rate constant, which may be attributed to the fact that higher concentrations of nps can increase the turbidity of the reaction system, thereby hindering the absorption of light [4]. therefore, for the photocatalytic experiments that followed, an optimum np-3 dosage of 500 mg/l was used. 3.2 the effect of the hydrogen peroxide concentration at first, the effect of h2o2 on the photodegradation of rhb in the absence of nps was investigated (fig. 6). the concentration of h2o2 was increased from 4.5 × 10−2 to 6.7× 10−1 mol/l. the reaction rate was enhanced by increasing the concentration of h2o2 up to 3.5 × 10−1 mol/l. however, beyond this value, a slight decrease in the apparent rate constant was observed. the second experimental series focused on checking the effect of increasing the concentration of h2o2 from 2.2 × 10−2 to 3 × 10−1 mol/l in the presence of nps 49(1) pp. 9–16 (2021) 12 khan, valicsek, horváth figure 6: effect of the concentration of h2o2 on the apparent rate constant of rhb photodegradation in the absence of nps. experimental conditions: concentration of rhb is 1.8 × 10−5 mol/l, initial ph is 7.5, and irradiation time is 140 mins. figure 7: effect of the concentration of h2o2 on the apparent rate constant of rhb photodegradation in the presence of np-3 in a heterogeneous photo-fenton system. experimental conditions: concentration of rhb is 1.8 × 10−5 mol/l, concentration of np-3 is 500 mg/l, initial ph is 7.5, and irradiation time is 140 mins. in a heterogeneous photo-fenton system (fig. 7). the reaction rate was remarkably improved by increasing the concentration of h2o2 up to 8.9× 10−2 mol/l. a further increase in the concentration of h2o2 did not enhance the reaction rate significantly, moreover, similar results have been published in the literature [24,25]. the excess h2o2 could act as a •oh scavenger, producing the less reactive ho• 2 species instead of the highly potent •oh [4,23,25]. hence 8.9 × 10−2 mol/l as an optimum concentration of h2o2 was used in experiments on the photocatalytic degradation of rhb that followed. 3.3 the effect of ph the surface charge properties of the photocatalyst and the ionic species present in the photocatalytic reactor are greatly influenced by the ph. furthermore, the photodegradation efficiency of the dye is affected by the ionic figure 8: effect of the initial ph on the apparent rate constant of rhb photodegradation in the absence of nps. experimental conditions: concentration of rhb is 1.8×10−5 mol/l, concentration of h2o2 is 8.9×10−2 mol/l, and irradiation time is 140 mins. species and surface charge of the photocatalyst in the reaction mixture. two experimental series were designed to study the effect of ph on the visible light-induced degradation of rhb. in the first series, the ph was varied from 3.8 to 12.1 while the concentrations of rhb and h2o2 were kept constant in the absence of nps. remarkably, neutral and alkaline phs were found to be more effective in this system concerning rhb photodegradation (fig. 8). in addition, the presence and absence of h2o2 were also investigated at higher ph values (approximately ph 12), which can be seen from the last two data points in fig. 8. it was observed that significantly enhancing the fraction of the more reactive deprotonated form of hydrogen peroxide (ho – 2 ) at higher ph values ( pka = 11.75 [26]) noticeably accelerated the rate of rhb degradation. on the basis of fig. 8, it was possible to determine the individual (apparent) rate constants (under these conditions) for the differently protonated forms of peroxide, namely 1.9 × 10−5 s−1 for h2o2 and 6.2 × 10−4 s−1 for ho – 2 . deprotonation resulted in increasing the degradation effect by 32 times. moreover, the effect of the ph in the presence of nps (fig. 9) revealed that a neutral or near alkaline ph could be optimal during this type of reaction. although the best apparent rate constant was observed at ph ≈ 8, further increasing the ph resulted in a slight decrease in the reaction rate. by comparing figs. 8 and 9, it can be observed that the partly hydroxylated forms of the metal ions ([feiii(oh)2] +, [cuii(oh)]+) could also be identified at the local maximum of approximately ph = 8 presented in fig. 9. therefore, the partly hydroxylated metal ions can react with h2o2, resulting in a ≈ 14times increase in the individual (apparent) rate constant (2.7×10−4 s−1 compared to 1.9×10−5 s−1 for h2o2 in the absence of nps). the ph can also alter the charge state of rhb in the reaction mixture. furthermore, at high ph values, rhb aggregates are produced as a result of the excessive concenhungarian journal of industry and chemistry photocatalytic degradation of rhodamine b 13 figure 9: effect of the ph on the apparent rate constant of rhb photodegradation in the presence of np-3 in a heterogeneous system. experimental conditions: concentration of np-3 is 500 mg/l, concentration of rhb is 1.8× 10−5 mol/l, concentration of h2o2 is 8.9 × 10−2 mol/l, and irradiation time is 140 mins. tration of oh– ions, which compete with coo– to bind with n+. in addition, since the surface of the solid catalyst is negatively charged, it repels the rhb due to the presence of ionic coo– groups under basic conditions. therefore, the degradation efficiency on the surface of the photocatalyst is decreased. the same phenomenon in the case of bismuth ferrite nanoparticles has been reported in the literature [4, 27]. however, an increase in the ph above 11 significantly enhanced the reaction rate (fig. 9) in a very similar manner to the reaction in the absence of nps. as a result, the presence of nps does not further increase the reactivity of ho – 2 . in addition, the effect of light, hydrogen peroxide and nps at an approximately constant ph is illustrated in table 1. the light-induced degradation of rhb at ph 12 in the absence of both hydrogen peroxide and np-3 yielded a very low reaction rate (step 1). in step 2, the addition of hydrogen peroxide in the absence of both light and np-3 at ph 11.9 yielded a faster reaction rate. step 3, which represents a heterogeneous fenton system, yielded a much faster reaction rate. the heterogeneous photofenton system shown in step 4 yielded the best reaction rate as far as the degradation of rhb is concerned. the catalyst np-3 (cuii (0.4)feii(0.6)feiii2 o4) was able to overcome the disadvantage of the narrow ph range of conventional photo-fenton processes. based on this experimental series, the catalyst cuii(0.4)feii(0.6)feiii2 o4 is a promising candidate for the degradation of various recalcitrant dyes. 3.4 generalized rhb degradation mechanism a very simple schematic mechanism is proposed for the purpose of rhb degradation since the reactive species produced during irradiation, namely •oh, h+ and •o− 2 , oxidize rhb molecules to intermediates of lower molecular weights. generally speaking, the active species react figure 10: visual and spectrometric comparison of rhb before and after its degradation; experimental conditions: concentration of nps is 500 mg/l, concentration of rhb is 1.8×10−5 mol/l, concentration of h2o2 is 8.9×10−2 mol/l, and irradiation time is 140 mins. with the central carbon atom in the chemical structure of rhb. then the oxidizing agents attack the intermediates produced in the previous step, yielding smaller open-ring compounds. subsequently, the latter compounds are mineralized to water and carbon dioxide [28]. as is displayed in fig. 10, the uv/visible absorption spectrum of rhb degradation yields prominent peaks at 262, 358 and 554 nm. however, no significant peaks were observed following photodegradation (fig. 10) in neither the visible nor uv region, which confirmed the complete mineralization of rhb. the images obtained from the photoreactor (cuvette) before and after photocatalysis also confirmed the complete degradation of rhb, namely a clear, colorless solution was obtained after the removal of solid catalysts (fig. 10) by centrifugal filtration. 3.5 photocatalytic efficiencies under optimized conditions finally, the photocatalytic efficiencies of all six nps (np1 to 6) were determined under optimized conditions for the degradation of rhb (fig. 11). it was observed that all of the nps were active photocatalysts, the application of np-3 yielded the highest reaction rate. these results are quite comparable to those presented in fig. 4 obtained from the first series of experiments. however, the concentration of hydrogen peroxide under the optimized conditions (8.9 × 10−2 mol/l) is considerably lower than in the first series (1.8×10−1 mol/l) and is, therefore, much more economical. although the concentration of the photocatalyst is higher under the optimized conditions (500 vs. 400 mg/l), the nps can be reused over several cycles. according to our results, all nps in the series can potentially be applied for the purpose of environmental remediation. 49(1) pp. 9–16 (2021) 14 khan, valicsek, horváth table 1: comparison of the reaction rate and apparent rate constant at ph ≈ 12 in homogeneous (steps 1 & 2) and heterogeneous (steps 3 & 4) systems. step no. light hydrogen peroxide np-3 (mg/l) initial ph final ph apparent comparison (mol/l) by adding 15 rate constant (1/s) with basic µ l 1m naoh) reaction (%) 1 visible 0 0 12.1 11.7 2.6× 10−6 12 2 no 8.9× 10−2 0 11.9 11 1.6× 10−4 749 3 no 8.9× 10−2 500 11.9 11.3 2.7× 10−4 1256 4 visible 8.9× 10−2 500 11.9 11.2 3.6× 10−4 1642 figure 11: photocatalytic efficiency in terms of apparent rate constants (compared to the control experiment) for np-1 to 6. experimental conditions: concentration of nps is 500 mg/l, concentration of rhb is 1.8 × 10−5 mol/l, concentration of h2o2 is 8.9 × 10−2 mol/l, initial ph is 7.5, and irradiation time is 140 mins. 3.6 assessment of the antibacterial activity of doped copper ferrites the inhibition effect (%) of doped copper ferrites against gram-negative vibrio scheri in bioluminescence assays is illustrated in fig. 12. the inhibition (%) of bacteria in the presence of doped nanoparticles containing varying ratios of copper (cuii) and iron (feii) revealed that all doped copper ferrites yielded sufficient antibacterial activities. in our research, higher ratios of cuii proved to be useful in improving antibacterial activity. the same trend in terms of bacterial inhibition against gram-negative escherichia coli was observed using cobalt ferrite nanoparticles synthesized by co-precipitation [29]. generally speaking, cuii can disrupt the functions of cells in several ways, hence the ability of microorganisms to develop resistance to cuii is remarkably reduced. the attachment of cuii ions to the surface of microorganisms plays a key role in their antibacterial activity [30]. the ions from the surface of doped copper ferrites, especially cuii, are adsorbed onto bacterial cell walls, damaging the cell membrane in two possible ways, namely by altering the functions of enzymes or solidifying the structures of proteins. therefore, the presence of copper ferrites in the bacterial growth medium immobilizes and inactivates bacteria, inhibiting their ability to replicate and ultimately leading to cell death [31]. figure 12: comparison of the degree of bacterial inhibition using doped copper ferrites against gram-negative vibrio scheri. in our study, a mechanism is proposed (fig. 13) in which doped copper ferrites are attached to the cell wall of the bacterium vibrio fischeri, reducing its ability to replicate. the degree of bacterial inhibition in all cases is approximately 60%, which confirms the potential application of doped copper ferrites in terms of antibacterial developments. 4. conclusion iron(ii) doped copper ferrites cuii (x)feii(1−x)feiii2 o4 have been proven to be efficient catalysts for the degradation of organic pollutants under visible-light irradiation in the presence of hydrogen peroxide. the performances of nps with copper(ii) ratios of x = 0.2 and 0.4 were especially promising under optimized conditions. contrary to conventional homogeneous photo-fenton systems, our catalysts exhibit higher efficiencies under neutral and near alkaline conditions. besides their advantageous photocatalytic ability, these nps also show a sufficient degree of antibacterial activity, due to their copper(ii) constituents. by taking both properties into consideration, cuii(0.4)feii(0.6)feiii2 o4 yields the optimum combination of these features. therefore, from the series of nps studied in this work, np-3 is the most promising candidate for the combined photocatalytic purification and disinfection of water. hungarian journal of industry and chemistry photocatalytic degradation of rhodamine b 15 figure 13: proposed mechanism for the attachment of nanoparticles to vibrio 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https://doi.org/10.1046/j.1365-2672.2000.00800.x https://doi.org/10.1016/j.clay.2005.10.010 introduction experimental materials applied catalysts rhb photocatalytic reactions determination of reaction rate assessment of antibacterial property results and discussion the effect of catalyst dosage the effect of the hydrogen peroxide concentration the effect of ph generalized rhb degradation mechanism photocatalytic efficiencies under optimized conditions assessment of the antibacterial activity of doped copper ferrites conclusion hungarian journal of industrial chemistry veszprem vol. 29. pp. 17-20 (2001) the influence of water concentration on the corrosion of low alloy steels in the system methanolethylene glycol­ formic acid d. sutiman, a. cailean (technical university "gh.asachi", faculty oflndustrial chemistry, department oflnorganic chemistry, b-dul d.mangeron 71a, iasi-6600, romania) received: december 8, 2000 the behaviour of three types of steel with a variable carbon content (from 0.2 to 0.4%) is studied in medium of methanol 10% ethylene glycol8% formic acid with water concentration between 2% to 10%. the weight losses are measured; also the polarisation anodic and catodic curves are plotted and the corrosion parameters are established. the corrosion compounds are analysed by ir spectra, x-ray diffraction and chemical analysis. with the obtained data, a corrosion mechanism is assigned and an optimum ratio between water and acid is established in order to obtain the passive oxyhydroxylic layer. introduction in the aqueous electrolytes solutions, water molecules are active participants both in the oxidation process of metals and in the passive layer formation. a lot of authors that had studied this process as lorentz [1-4], sato and cohen [5], okamoto [6-7] had shown that water molecules participate in a polinuclear structure achievement with bonds depending on the value of the anodic potential. at the value noted as the passivation potential, a partial water elimination of the film, together with a decomposition of the groups ho' in oxygen, takes place. in nonaqueous medium, the nature and the concentration of the presented impurities play an important role [8]. these impurities determine a change of some organic medium properties such as conductivity or the dissociation constant. the main impurity in organic solvents is represented by water that has a strong influence on the equilibrium of the solution, determining changes both in the process of ions solving and in the values of the dissociation constants in the electrolyte dissociation. this paper represents a continuation of a study which deals with water influence on corrosion of three types of low alloy steels in organic medium of ethylene glycol and/or methanol at variable water concentration, corrosion reagents being mono and dicarboxylic saturated acids [9-11]. these organic mediums represent important corrosion reagents for the ethylene glycol recuperation in installations for obtaining synthetic fibbers. experimental the steel samples that are used for corrosion ol 37, ol 50 and ol 60 have the chemical composition presented in table 1. the steel samples of 5 cm2 active metallic surface were cut up from a cylindrical bar. they were polished, and dyeing protected the surface that should not be corroded. the corrosion system contained methanol, 10% ethylene glycol and 8% formic acid, the water concentration varied between 2% and 10%. karl-fisher method was used to determine the water content. we used merck reagents and the water was bidistilled, having electrical conductivity of 12 j.!s cm·1 • also the ph-variation of the corrosion medium was measured with a hach ph-meter. before introducing the sample in the corrosive system, they were submitted to a degreasing process in boiling benzene for 30 minutes and then degreased in a solution of hydrochloric acid 3% for 3 minutes. the corrosive system was open, allowing the permanent access of oxygen from the atmosphere. for every value of the water concentration, six metallic samples were used and were placed in the same 18 table i the composition of steels used for corrosion steel %c ol37 0.20 ol50 0.30 ol60 0.40 a %mn 0.80 0.80 0.80 %s 0.06 0.05 0.05 %si 0.40 0.40 0.40 %p 0.06 0.05 0.05 b table 2 the values of indices k and p for the studies steels 2 4 6 8 10 ol37 kip 1.103/0.99 1.235/1.11 0.503/0.45 0.41110.37 0.312/0.28 ol50 kip 0.932/0.84 1.115/1.00 0.480/0.43 0.343/0.31 0.302/0.27 c ol60 kip 0.854/0.77 0.965/0.67 0.464/0.42 0.332/0.30 0.295//0.27 fig.i aspect of the metallic surface of the steels in the system methanol10% ethylene glycol8% formic acid4% water (x 1200) : a-ol 37, b-ol 50, c-ol 60 lgi a/cm2 , fig.2 the polarization curves in the system methanol10% ethyleneglycols% formic acid4% water: • ol 37, x ol 50, o ol60 time in the corrosive system, being subsequently taken off from 10 to 10 days, degreased with hydrochloric acid {3'lt>) for 15 seconds and then were weighed by an analytical balance. from the values of weight losses, the gravimetric fi~re k (g m"2 h'1) and the penetration p (mm m2 year· ) were calculated. the metallic surfaces were visualised by electron microscopy on a tesla b300 microscope. for the values 4%, 6% and 8% of water concentration, the catodic and anodic polarisation curves were plotted on a t acussel s8r potentiometer with input impedance of 1012 0. from the shape of the polarisation curves the kinetic parameters (fist> scor and icor) of the corrosion process were calculated. the corrosion final compounds, for every value of water concentration, were insoluble in the system. they were analysed by x-ray diffraction on a hzg 4c karl zeis yena diffractometer using co (kj radiation, by lr spectroscopy on a specord m82. the chemical composition {c, h, 0 and fe) of the final compounds was also determined. results and discussion the ph-value of the corrosion solution, at the concentration of 8% add formic is 1.42 in an anhydrous medium. when hzo is added to the solution, the ph­ value decreases to 1.37 for s% h20, fact indicating that the acid dissociation takes place in the presence of the two organic solvents, and water has no major contribution to this process. the values of the weight losses, converted into gravimetric figure k and penetration figure p, are presented in table 2. 19 table 3 the values of the corrosion parameters in the system methanol10% ethyleneglycol8% formic acidwater parameters of corrosion 4 ol37 %h20 6 8 4 ol50 ol60 %hz0 %hz0 6 8 4 6 8 e,.,mv ~>con mv icrm f!a/cm 2 -520 -493 -590 -475 -467 -542 -490 -448 -527 -535 -510 -600 -490 -495 -555 -510 -480 -550 25.36 20.36 18.87 23.86 18.12 16.35 20.12 17.25 12.78 ·1 em fig.3 the ir spectrum of the corrosion compounds resulted from ol 37 in the system methanol10% ethyleneglycol8% formic acid 4% water from these values, we can conclude that the corrosion rate is high for water concentration, higher than 4%, a fact indicating that this is the minimal percent of water necessary in passive layer formation. the metallic surface, analysed by electron microscopy (xl200), presented a pitting corrosion for ol 37 and ol 50, and for ol 60, a generalised corrosive process with a ~discontinuous compound layer (figure 1). the polarisation curves were plotted for the values of 4%, 6% and 8% water concentration. the curves have the same variation aspect for all concentrations, not presenting passive domains in the studied potential field. the polarisation curves for 4% water concentration are presented in figure 2. the values of the corrosion parameters calculated from these curves are presented in table 3. the density of the corrosion current decreases with the values of water concentration of 4% and the most stable steel in all water concentrations is ol 60. the corrosion products are insoluble in the system at au water concentrations and do not present x-ray diffraction spectra. the ir-spectra are the same for all the systems, meaning that all the compounds presented the same absorption wave numbers. the ir absorption spectra of the corrosion compounds resulted from ol 37 in the medium containing 4% h20 is presented in figure3. the existence of two peaks, one at 276 cm-1 and the other at 300 cm·i, characteristic of the fe-0 covalent and coordinative bonds are observed. also the displacement of the absorption band, characteristic of the carboxyl group from the formic acid, from the value 1724 cm·1 to the value 1656 cm·l, makes us to resume a stronger bonding of the acid [12-13]. also, the presence of the absorption band of 1080 cm1 , characteristic of table 4 the chemical composition of the corrosion compounds in the system methanol 10% ethyleneglycol 8% formic acid4% water % ol37 ol50 ol60 c 17.87 18.05 18.04 h 3.56 4.07 3.78 0 45.06 44.76 44.83 fe 33.51 33.12 33.35 fig.4 the structure of the corrosion compounds fe(iii) polyformiate the group ho"from the alcohols and the peak characteristic of water are displaced at 3340 cm·1 respectively 2900 cm-1 • the rest of the peaks correspond to the vibration and rotation movements of the bonds c-c, c-h, a.s.o. [12-13]. chemical analysis of corrosion the compounds indicates that all the products present the same composition. in table 4, the chemical composition of the compounds obtained in the system with 4% h20 is presented. this chemical composition is very much alike with that of a compound in which the ratio fe/formiat radical is 1/2. from these data, for the corrosion of iron in the system methanol-ethylene glycol-formic acid-water, the following mechanism is proposed: *02 + h20 + 2e· --+ 2ho­ fe2+ + 2ho. --+ fe(oh)2 nfe(ohh + 2nhcooh --+ [fe(hcoo)i!n + nh20 the structure of the polymeric compound of fe(il) with formic acid is presented in figure 4. the hexacoordination of iron is accomplished by water molecules and .-hogroups as bridge linkage. this structure is justified also by the tittle excess in the percent of oxygen and hydrogen from the elemental analysis of the corrosion compound. 20 • • • conclusion all three types of steel present a value for water concentration for which the corrosion rate has a maximum, and that is 4% h20. at the value 4% h20, the molar ratio water/formic acid is 1.28/1, smaller than the ratio 4/1 that is specified in literature [14-15] as being the minimum ratio in which water can participate in oxyhydroxylic layer formation. this fact can be justified by the dissociation of the formic acid and through the organic solvent molecules, the molecules of water are ''free" to participate in the passive layer formation. the steel with the highest stability is ol 60, which has the highest carbon content. this high value of the stability may be connected to the existence in the steel's structure of a solid solution of iron­ carbon, formed where the carbon concentration is over 0.3% [16]. the corrosion mechanism is a complex one, involving dissolved oxygen. the corrosion compounds being insoluble in the organic system are submitted to a polymerisation process. these products do not form crystalline compounds. references 1. lorentz w. j. and geona d.: electrochim. acta, 1975, 20, 273-278. 2. lorentz w. j. and helman h.: corrosion, 1979, 27, 101-108. 3. larbeer p. and lorentz w. j.: corrosion science, 1980, 20, 405-410. 4. larbeer p. and lorentz w. j.: electrochim. acta, 1980, 25, 375-401. 5. sato n. and cohen m.: j. electrochim. soc. 1964, 111,512-518. 6. heusler k. e.: z. electrochem, 1958, 62, 582-587. 7. kama to 0, saito h, shibata t : corrosion science, 1984, 24, 807-814. 8. lorentz w. j. and heusler k. e.: anodic dissolution of iron group metals in corrosion mechanism, ed. f. mansfeld, dekker, new york, 1987. 9. sutiman d.: bul. i.p.i., 1999, xlv 3-4, 19-23. 10. sutiman d. and cretescu i.: rev. de chim. 1999, 10, 50, 766-770. 11. sutiman d., georgescu 0. and cioroianu t.: hung. j. ind. chern., 1999,27,107-110. 12. avram m.: infrared spectroscopy, ed. tehnica, bucuresti, 1960 (in romanian). 13. the sadler of handbook of infrared spectra, sadler hayden, london, 1978. 14. stypula b.: corr. resit. alloy, 1965, l, 252-257. 15. banas j. and stypula b: metalurgy and foundry engineering, 1995, 6, 2, 112-119. 16. cartis g.: thermal trataments, ed. facia, timisoara, 1982 (in romanian). page 19 page 20 page 21 page 22 hungarian journal of industry and chemistry vol. 48(2) pp. 1–64 (2020) hjic.mk.uni-pannon.hu contents combination of chemical and biological methods for effective plant protection dávid vozik and katalin bélafi-bakó 1–4 enhancement of oxygen transfer through membranes in bioprocesses péter komáromy, katalin bélafi-bakó, éva hülber-beyer, and nándor nemestóthy 5–8 the role of water activity in terms of enzyme activity and enantioselectivity during enzymatic esterification in non-conventional media piroska lajtai-szabó, nándor nemestóthy, and lászló gubicza 9–12 follow-up control of a second order system in sliding mode márk domonkos and nándor fink 13–21 informative environment qualifying index anett utasi, viktor sebestyén, and ákos rédey 23–36 the effect of ph on biosurfactant production by bacillus subtilis dsm10 réka czinkóczky and áron németh 37–43 adsorption of nickel ions from petroleum wastewater onto calcined kaolin clay: isotherm, kinetic and thermodynamic studies alexander asanja jock, anietie ndarake okon, uchechukwu herbert offor, festus thomas, and edmond okwudilichukwu agbanaje 45–49 considerations to approach membrane biofouling in microbial fuel cells szabolcs szakács and péter bakonyi 51–53 new chaining criteria in dipolar fluids based on monte carlo simulations sándor nagy 55–58 temperature and electric field dependence of the viscosity of electrorheological (er) fluids: warming up of an electrorheological clutch sándor mester and istván szalai 59–64 hungarian journal of industry and chemistry vol. 48(2) pp. 1–4 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-20 combination of chemical and biological methods for effective plant protection dávid vozik 1 and katalin bélafi-bakó*1 1research institute on bioengineering, membrane technology and energetics, university of pannonia, egyetem u. 10, veszprém, 8200, hungary the application of combined biological and chemical techniques to control undesirable processes in plant cultivation is becoming ever more important to maintain sustainable and environmentally friendly agricultural systems. entomopathogenic nematodes and bacteria can provide an effective and special technology in the field of plant protection. keywords: antimicrobial, entomopathogenic nematodes, bacteria 1. introduction nowadays, one of the most important challenges worldwide is the sufficient cultivation of edible plants and crops due to the rising trend in population growth and food demand. moreover, it is important to solve this problem by implementing sustainable agriculture which prefers natural protection and tries to minimize the intervention of radical chemicals. it was confirmed recently that some synthetic pesticides are environmental hazards. since the biological degradation of certain pesticides is slow, their bioaccumulation might cause significant damage to ecosystems, soil, natural waters, etc. therefore, the idea of protecting crops has been extended and a new concept, “integrated pest management” (ipm), introduced which involves chemical, biological and biotechnological methods together with modern cropping, cultivation and breeding technologies [1] in a way which minimizes any risk of environmental damage. to apply this concept in practice requires comprehensive knowledge of the crops, fitopathogenic microorganisms as well as their enemies, and the behaviour of chemicals (e.g. pesticides) that may be used. a field that has hardly been researched are the so-called entomopathogenic nematodes and bacteria which have been studied in hungary for a significant period of time [2]. 2. entomopathogenic nematodes and bacteria entomopathogenic nematodes are a group of thread worms that kill certain insects. they enter – in the form of infective juveniles – into the insects, live as parasites *correspondence: bako@almos.uni-pannon.hu inside them and cause host mortality within 1-2 days. it has turned out, however, that this is not only caused by the nematodes themselves but certain bacteria play an important role as well. entomopathogenic bacteria live in symbiosis with entomopathogenic nematodes [3,4]. the nematodes provide shelter for the bacteria, an area of the interior part of the intestine of the infective juveniles is transformed into a bacterial chamber where cells of symbiotic bacteria are located. the relationship is highly specific: e.g. the nematodes of steinernema usually carry species of xenorhabdus bacteria, while heterorhabditis carry photorhabdus bacteria. when entering an insect, infective juveniles release the bacteria, which start multiplying rapidly in the haemolymph. it has been proven that although the bacteria are primarily responsible for the mortality of the insect host, the nematodes also produce a toxin which is lethal to the insect. these nematode-bacteria complexes can be applied successfully as biological control agents against insect pests in agriculture [5]. some of these agents are available commercially, as listed in table 1, where the target insects, habitats and places of usage are presented [6–8]. 3. antimicrobial compounds entomopathogenic bacteria contribute not only to the successful activity of entomopathogenic nematodes but can produce special compounds with an antimicrobial effect as well. the main purpose of producing these compounds is to protect the colonized cadaver in the soil [9]. the antimicrobial compounds of entomopathogenic bacteria have been tested and it would seem that these natural agents show a wide range of bioactivities of medical and https://doi.org/10.33927/hjic-2020-20 mailto:bako@almos.uni-pannon.hu 2 vozik and bélafi-bakó table 1: examples of the successful application of nematode-bacteria complexes [6–8] target habitat where japanese beetle popillia japonica subterranean lawn, turf black vine weevil otiorhynchus sulcatus subterranean strawberry plants fungus gnats lycoriella species, bradysia species subterranean mushroom production diaprepes root weevil diaprepes abbreviatus epigeal citrus invasive mole cricket scapteriscus vicinus epigeal lawn, turf codling moth cydia pomonella cryptic apple, pome fruit table 2: plant pathogens tested pathogen effect ref. phytophthora nicotianae root rot disease of tobacco [13] erwinia amylovora fire blight disease of several plants that belong to rosaceae, e.g. apple, pear, etc. [14] ralstonia solanacearum brown rot disease of potato [15] agricultural interest, e.g. antibiotic, antimycotic and insecticidal effects [10,11]. for analytical purposes, fourier transform infrared spectrometry (ftir) was used to identify these compounds [12]. in our laboratories, secondary metabolites of xenorhabdus budapestiensis (isolated in hungary) have been investigated [13]. the bacterium was maintained on a luria agar (la) medium and freshly subcultured. the cells were cultured in 1000 ml flasks and incubated on a gyrorotary shaker at 25 ◦c . then the cells were removed by centrifugation and the supernatant extracted. the cell-free filtrate was further purified by chemical methods (adsorption and filtration) to obtain a peptide-rich fraction. this fraction was applied to test for various plant pathogens, as listed in table 2, including pathogens of tobacco, apple and potato (the latter of which is widespread in hungary, causing serious damage to inland agriculture). the investigations involved in vitro bioassays, where the antibacterial activity of the biofraction was determined on solid media. in an agar diffusion test, the tested bacterium was mixed with soft agar poured onto la plates, then a small hole was made in the centre and the biopreparation of the filtrate added [13]. for the so-called overlay test [13], the antimicrobial preparation was incubated on the solid luria broth agar (la) plate then the pathogenic microorganism in soft agar was spread onto the surface. in both cases, an inhibition zone can be identified and determined, if the biopreparation was effective against the pathogenic strain. an example of the agar diffusion bioassay is given in fig. 1. a picture taken from a successful overlay bioassay test is shown in fig. 2. in our laboratory, in vitro bioassays proved that the biopreparations containing the antimicrobial compounds could be successfully used against these pathogens. moreover, in planta (in field trials), a bioassay was conducted using infected apple blossom (erwinia amylovora) which was treated with the biopreparation. it was concluded to be suitable to reduce the symptoms of the infected plants, thus it can be considered as a promisfigure 1: antibacterial effect of the preparation in the agar diffusion test. figure 2: the antagonistic effect of x. budapestensis against e. amylovora ea1 bacteria in an overlay test. hungarian journal of industry and chemistry effective plant protection 3 figure 3: infected apple blossom treated with the biopreparation. ing biological agent [14,15]. this successful treatment is illustrated in fig. 3. other than plant pathogens, the peptide-rich fraction of xenorhabdus budapestiensis has recently been tested against species of fungi in vitro [16] in clinical samples. candida albicans, candida lusitaniae, candida krusei, candida kefyr, candida tropicalis and candida glabrata were used in the research by applying the agar diffusion method. the results proved that every candida species is sensitive to the preparation, thus it would seem that the fraction has a fungicide impact as well. 4. conclusion in summary, the symbiotic complex of entomopathogenic nematodes and bacteria can be considered as efficient biological agents to control some insect pests, but the secondary metabolites of the bacteria can be effectively used against other pathogenic bacteria and fungi. as a result, their applications can contribute significantly to successful plant protection by providing numerous environmental benefits and can be considered as an important component of “integrated pest management” (ipm). references [1] act xxxv on plant protection (2000, hungary) http://www.kvvm.hu/szakmai/hulladekgazd/jogszabalyok/2000 _xxxv_tv.htm [2] lengyel, k.; lang, e.; fodor, a.; szállás, e.; schumann, p.; stackebrandt, e.: description of four novel species of xenorhabdus, family enterobacteriaceae: xenorhabdus budapestensis sp. nov., xenorhabdus ehlersii sp. nov., xenorhabdus innexi sp. nov., and xenorhabdus szentirmaii sp. nov., syst. appl. microbiol. 2005, 28(2), 115–122 doi: 10.1016/j.syapm.2004.10.004 [3] boemare, n. e.; akhurst, r. j.; mourant, r. g.: dna relatedness between xenorhabdus spp. (enterobacteriaceae), symbiotic bacteria of entomopathogenic nematodes, and a proposal to transfer xenorhabdus luminescens to a new genus, photorhabdus gen. nov., int. j. syst. bacteriol. 1993, 43(2), 249–255 doi: 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10.33927/hjic-2020-21 enhancement of oxygen transfer through membranes in bioprocesses péter komáromy *1, katalin bélafi-bakó1, éva hülber-beyer1, and nándor nemestóthy1 1research institute on bioengineering, membrane technology and energetics, university of pannonia, egyetem u. 10, veszprém, 8200, hungary in several aerobic bioprocesses, it is extremely important to provide a sufficient amount of oxygen, which is a difficult task since the solubility of oxygen in aqueous systems, namely in water, is low. thus oxygen transfer techniques should be designed, built, studied and operated very carefully in biosystems. moreover, in certain cases, special techniques, e.g. involving membranes, must be applied. in this paper, three different bioprocesses are presented where oxygen was supplied by membrane aeration: wastewater treatment by microbial consortia (i), itaconic acid fermentation by a single microorganism (ii) and an oxidative enzyme catalytic process for the elimination of glucose (iii). keywords: biotechnology, aerobic microbes, silicone membrane, enzyme 1. introduction at the dawn of applied and industrial biotechnology, the use of engineering tools to establish reliable bioprocesses for manufacturing certain bioproducts was inevitable [1– 4]. for the effective production of acetic acid, ethanol and later citric acid, etc. by biological processes, the technical skills and experience of chemical engineering were used together with microbiological knowledge and practices to establish bioengineering and bioprocess engineering. several bioprocesses require oxygen for various purposes, e.g., respiration, certain energy-producing metabolic pathways, direct oxidation, the oxidative degradation of some substrates, etc. [1–3]. oxygen is usually supplied by surface aeration, bubble aeration (sparging), by entering oxygen or air directly, aeration combined with agitation or in airlift bioreactors. regardless, oxygen is always transported from a gas stream to an unsaturated liquid [5]. the steps of this pathway are as follows and are outlined in fig. 1: • from the inside of the bubble to the surface (gas side) (1); • through the boundary layer of the bubble (liquid side) (2); • from the surface to the bulk liquid (broth) (3); • from the bulk liquid to the liquid film layer of the cell (4); *correspondence: komaromy.peter@mk.uni-pannon.hu • into the microbial cells (through the liquid film layer) (5). moreover, it is important to take into consideration that the oxygen demand changes as a function of time and according to the characteristics of the particular form of cell. in the liquid film layers, the transfer occurs by diffusion, while in the bulk phase, it always takes place via convective transport (which can be enhanced by mixing). the rate-limiting step is diffusion through the boundary film layer of the bubble on the liquid side, which is highly influenced by its surface area. on the other hand, membranes have been used in bioprocesses for an extensive period of time [6–9]. however, firstly they were exclusively applied for separations [6–8]. membranes that are distinctly selective towards certain gases were used to develop gas separation techniques. some of these membranes are permeable to oxygen molecules in the gaseous phase, therefore, it was a breakthrough to apply them for oxygen transfer into the aqueous (liquid) phase [9]. one of the most important benefits of this kind of aeration is the amplified surface area between the gaseous (air or pure oxygen) and liquid phases. in this work, three different bioprocesses are presented where oxygen was supplied by membrane aeration: • wastewater treatment by microbial consortia; • fermentation by a single microorganism (under sterile conditions) for the manufacture of an organic https://doi.org/10.33927/hjic-2020-21 mailto:komaromy.peter@mk.uni-pannon.hu 6 komáromy, bélafi-bakó, hülber-beyer, and nemestóthy figure 1: the pathway of oxygen transfer. acid; • an enzymatic oxidation for the elimination of glucose. 2. membrane-aerated bioreactors for the treatment of wastewater the combination of membrane technology with the biological treatment of municipal and industrial wastewater has been investigated and applied for an extensive period of time. coupling the two systems resulted in a special, new type of reactor called a membrane bioreactor (mbr). the roles of membranes in these biological systems include: • separation of solids; • aeration; • extraction of special pollutants. the supply of oxygen to microbes through a membrane is carried out by a membrane-aerated bioreactor (mabr). this type of bioreactor was developed in 1978 and has been studied ever since. the membrane itself has to exhibit a high degree of oxygen permeability. among gas-separation membranes, silicone (polydimethylsiloxane) was used for oxygen enrichment (from air), thus seemed suitable for this purpose. oxygen mass transfer through a silicone membrane was closely examined [9] and it was determined that the membrane aeration system was approximately 7 times more effective in terms of oxygen supply than the standard activated sludge process, hence it was experimentally proven to have strong potential. in different wastewater treatment processes, various gas-permeable membranes were tested with regard to oxygen supply systems [11–14]: • polyethylene; • ethyl cellulose; • polystyrene; • polytetrafluorethylene; • polypropylene; ho c o ch2 c ch2 c o oh figure 2: chemical structure of itaconic acid. • polyetherimide; • silicone. in terms of configuration, mainly hollow fibre modules were successfully applied (though plate-and-frame modules can also be used). the membrane was placed into the liquid waste (submerged system) and oxygen from the air was pumped inside the lumen. oxygen was transferred by diffusion through the membrane directly into the biomass that formed on the shell side of the membrane. the main benefits of the system are that no bubbles are formed and bubble-to-liquid transfer (diffusion limitation) could be avoided. the membrane aerated bioreactor system is continuously being developed and finally a truly reliable, robust and viable system was established [15], namely the zeelung system. it consists of a silicone, non-porous polymer membrane with an extremely small outer diameter (50-70 µm) and wall thickness (5-20 µm). thus the module has a very high surface area, low packing density and an efficient rate of oxygen transfer can be maintained under low pressure. the new system (technology) resulted in an energy efficiency four times greater than that of conventional bubble aeration. by comparing membrane aeration with traditional bubble aeration, another benefit can be recognized. a homogeneous oxygen concentration can be achieved throughout the reactor by pumping through air or oxygen bubbles. when membrane aeration is applied, it is possible to establish different oxygen levels within the reactor: several zones with various oxygen levels (as required for certain biological processes) can be created. 3. fermentation of itaconic acid itaconic acid is an unsaturated five-carbon dicarboxylic acid that is considered to be an important platform molecule of high potential (bio-based building block) (fig. 2). it was specified by the united states department of energy as one of the 12 most promising chemicals obtained from biomass. itaconic acid is mainly produced biologically by filamentous fungi, e.g. aspergillus terreus [16–20]. the fermentation of itaconic acid is a quite sensitive process that requires a high initial substrate concentration of glucose, precise control of operational parameters (e.g. ph, temperature, presence/deficiency of certain ions, etc.) and a high oxygen level since a high level of oxygen tension in the fermenter enhances the formation of itaconic hungarian journal of industry and chemistry enhancement of oxygen transfer through membranes 7 acid. a sufficient oxygen supply can be ensured by increasing the mixing rate, however, filamentous fungi are generally very sensitive to high shear rates. moreover, intensive foaming may result which must be avoided. as the fermentation progresses, ever more biomass and protein is produced in the broth, hence these phenomena may occur more acutely. in addition, the oxygen demand continuously increases. oxygen can be supplied by conventional techniques, e.g. airlift bioreactors, air bubbling equipped with propeller agitators, etc. for example, an airlift bioreactor was combined with a modified draft tube to achieve a high (2,430 1/h) volumetric oxygen transfer coefficient [21]. in our laboratory, membrane aeration was applied by pumping 600 l/h of air at a pressure of 1.1 bar into the broth by using a special permselect hydrofluoric acid (hf) silicone membrane which was immersed into the fermenter. this membrane was originally an oxygenselective gas separation membrane, consisting of 10 thousand fibres (od = 150 µm) with a surface area of 1 m2. since oxygen permeated faster than other compounds, it resulted in a high oxygen supply. our successful experiments have proven that by applying membrane aeration, enhanced oxygen transport and a higher yield of itaconic acid are achieved. 4. enzymatic removal of glucose in the food industry, some processes require the removal of glucose [22]. for example, in the manufacture of powdered egg white, the reaction between glucose and protein results in the maillard browning reaction during the spray-drying step, leading to an undesirable brown discolouration and poor quality [23]. another example is the manufacture of low-calorie, low-alcohol beverages from fruit juices [24]. the content of fermentable sugar can be reduced significantly by converting it into other compounds which cannot be metabolised into ethanol (less alcohol forms). glucose (or dextrose, its chemical name is dglucopyranose) is the most abundant monosaccharide, a six-carbon sugar (hexose) with five hydroxyl groups. its name is derived from the greek word “glukos” which means “sweet”. the extraction of glucose from a mixture containing compounds of similar molecular size is generally difficult as well-known separation techniques are unsuitable [6–8]. therefore, a special enzymatic method has been developed where glucose is oxidised. the enzyme catalysing the reaction is called glucose oxidase (god), e.c. 1.1.3.4 [25,26]. during the reaction, glucose is converted into d-glucono-1,5-lactone, which spontaneously hydrolyses non-enzymatically into gluconic acid: β-d – glucose + o2 −−→ d – gluconic acid + h2o2 the reaction uses oxygen and releases hydrogen peroxide as a by-product, which has a strong inactivation effect on god itself, therefore, it must be eliminated from the mixture. h2o2 can be converted into water and molecular oxygen by another enzyme called catalase, e.c. 1.11.1.6.: h2o2 −−→ h2o + 1 2 o2 the two enzymes can be applied together, such an enzyme mixture can be manufactured by various moulds, e.g., species of aspergillus. for the successful operation of the enzyme, a sufficient amount of oxygen should be supplied. in the case of the production of powdered egg white, traditional aeration methods (e.g. bubble aeration) cause a high degree of foaming, thus another technique should be implemented. in our laboratory, membrane aeration was studied and applied [27]. the enzyme complex was immobilized on a resin and a packed column reactor set up for the reaction. then a perforated silicone tube membrane was placed inside the bioreactor in a spiral configuration to provide oxygen directly to the site of the enzymatic oxidation reaction. 5. conclusion in summary, three different bioprocesses were presented in this paper where oxygen was supplied using a special method, namely membrane aeration. firstly, the treatment of wastewater by microbial consortia (i), secondly, the fermentation of itaconic acid by a single microorganism (ii) and finally, an oxidative enzymatic process (iii) for the elimination of glucose were examined in detail. acknowledgement the research work was supported by the national research, development and innovation fund project k 119940 entitled “study on electrochemical effects on bioproduct separation by electrodialysis” and project efop3.6.1-16-2016-00016. references [1] doran, p. m.: bioprocess engineering principles (academic press, waltham, massachusetts, usa) 2013, isbn: 978-00-8091-770-2 [2] ratledge, c.; kristiansen, b. 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https://doi.org/10.1016/j.enzmictec.2006.02.010 https://doi.org/10.15255/cabeq.2018.1391 https://doi.org/10.15255/cabeq.2018.1391 hungarian journal of industry and chemistry vol. 48(2) pp. 9–12 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-22 the role of water activity in terms of enzyme activity and enantioselectivity during enzymatic esterification in nonconventional media piroska lajtai-szabó1, nándor nemestóthy1, and lászló gubicza *1 1research institute on bioengineering, membrane technology and energetics, university of pannonia, egyetem u. 10, veszprém, 8200, hungary during enzymatic esterification in non-conventional media, the activity and enantioselectivity of the enzyme is significantly influenced by the water content of the reaction medium, which continuously changes as water is produced during the esterification. to provide constant reaction parameters, water activity should be kept constant. the commonly used salt hydrate pairs may be difficult to apply and often hinder enzyme activity. during the enantioselective esterification of racemic 2-bromopropanoic acid in various solvents (organic solvents, ionic liquids), it was proven that the conditions related to the optimal water content required for kinetic examinations can be provided without using any salt or salt hydrate pairs. this conclusion is based on the realization that the optimal water activity can be set by first determining the initial water content that is necessary to achieve the maximum reaction rate in the given solvent. keywords: enzymatic enantioselective esterification, non-conventional media, ionic liquid, racemic acid, effect of water content 1. introduction the history of the intentional use of enzymes as biocatalysts stretches back several decades. in recent years, intensified interest has been shown in applying enzymes in chemical reactions. enzyme technology as an important discipline of biotechnology has begun to develop rapidly. nowadays, it is of great importance in the pharmaceutical and pesticide industries where, in many cases, it has produced intermediates and active substances with enzymes or microorganisms more easily than by chemical synthesis and usually with a high degree of (enantio)selectivity [1–3]. the known advantages of these reactions are the mild reaction conditions, pure products, high yield and, in many cases, environmentally friendly by-products. at first, enzymes were only applied in aqueous media as they exert their catalytic activity under such conditions in various organisms. later, the recognition that enzymes can exert their catalytic activity in organic solvents promoted intensive investigation among organic chemists who tested more and more enzymes from various classes as catalysts of organic chemical reactions [1, 4–7]. contradictory results concerning how the activity and enantioselectivity of a lipase depend on the physical and chemical properties of the solvents can be found in the literature. in some cases, the different enzyme activities and *correspondence: gubiczal@almos.uni-pannon.hu enantioselectivities observed in various organic solvents are not only affected by the solvents, e.g., when solvents with very different polarities are compared without fixing the water activity. in these experiments, the variation in the water activity probably contributes to the change in enzyme activity [6, 8–10]. in terms of the reaction, the water content of the reaction medium is twice as significant. to keep the enzyme activity and enantioselectivity of the lipase constant, a constant amount of water should be provided. as the content of the reaction medium changes as the conversion proceeds, the water adsorption capacity of the reaction medium does not remain constant during the reaction either. water activity is an index which indicates how much water is accessible to the enzyme. polar solvents can adsorb more water, while in non-polar solvents less water is required to achieve saturation and form a new aqueous phase where the water activity of the organic solvent is equal to one (aw = 1). therefore, two solvents of different polarities but equal water activities may contain significantly different amounts of water [11–13]. based on the aforementioned considerations, in the literature a constant water activity is sought instead of a constant concentration of water during enzymatic reactions, e.g. by pervaporation of salt hydrates [14–16]. in reactions where water is not produced, the initial water activity of the reaction medium is fixed and the change in water activity, which is caused by changes in the polarity https://doi.org/10.33927/hjic-2020-22 mailto:gubiczal@almos.uni-pannon.hu 10 lajtai-szabó, nemestóthy and gubicza of the reaction medium, is neglected. in the case of esterifications, where the water activity of the reaction medium significantly increases as the reaction proceeds, the water activity must be constantly controlled [16–19]. in this study, the resolution of (r,s)-2bromopropanoic acid was analyzed. changes in the activity and enantioselectivity of the enzyme candida rugosa lipase, which is suitable when the water content of the reaction medium is changed during the aforementioned reaction, were investigated. identification of the simplest method to sustain a constant water activity required for kinetic examinations was also sought. 2. experimental 2.1 samples and measurements all chemicals were commercially available and used without further purification. candida rugosa lipase (ec 3.1.1.3) (nominal activity: 920 umg−1 enzyme) was obtained from sigma-aldrich (st. louis, usa). racemic 2-bromopropanoic acid and the ionic liquids used, namely [bmim]pf6 (1-butyl-3methylimidazolium hexafluorophosphate), [nmim]pf6 (1-methyl-3-nonylimidazolium hexafluorophosphate) and [bmim]bf4 (1-butyl-3-methylimidazolium tetrafluoroborate), were obtained from merck kgaa (darmstadt, germany). butan-1-ol as well as all the other organic solvents and salts used were manufactured by reanal laboratory chemicals ltd. (budapest, hungary). in a typical experiment, 2 mmol of racemic 2bromopropanoic acid and 12 mmol of butan-1-ol were added to 5 ml of solvent. the water concentration of the reaction mixture was measured using a mettler dl35 karl fischer titrator. the water activity was adjusted using salts of different aw values (licl (aw = 0.11), mgcl2 (aw = 0.33), nabr (aw = 0.57), ki (aw = 0.69), kcl (aw = 0.84) and k2so4 (aw = 0.97)). the reaction was started by adding 0.1 g of enzyme and the closed flasks were shaken in a new brunswick g-24 horizontal shaker incubator. 2.2 analysis the (r)and (s)-esters produced were analyzed by an hp 5890a gc (gas chromatograph) using a 25 m fs-lipodex e chiral capillary gc column from macherey-nagel (aachen, germany). the samples from organic solvents were directly injected into the gc after being extracted from ionic liquids using nhexane. the activity of the lipase was characterised by the amounts of (r)and (s)-esters produced. 3. results and analysis 3.1 experiments to investigate the actual effect of solvents on the enzyme’s activity, the same water activity should be provided in the reaction media to avoid differences in enzyme activity originating from variations in water activity. by choosing the most suitable method, the application of [bmim]bf4 must be considered, which is a polar solvent and miscible with water. the setting of the water activity with salt hydrate pairs and saturated salt solutions can be hindered as salts dissolve in ionic liquids [19]. as an alternative, the fact that the maximum enzyme activity of candida rugosa lipase is achieved at the same water activity in any solvent was exploited [16]. according to the polarity of the solvents, the same water activity results in different water contents in various solvents, namely the reaction rate or conversion that indicate enzyme activity will be at their maxima with different water contents. an opportunity arises from the inversion of these considerations: the optimal initial water activity, required for kinetic examinations, can be set by determining the initial water content that provides the maximum reaction rate for each solvent. naturally, to precisely set a given water activity, the reaction rate should be measured by monitoring the water content infinite times. instead of this, at least five different initial concentrations of water were set for each solvent. to calculate the reaction rates, the amounts of (r)and (s)-2-bromopropanoic acid butyl esters produced until 10% conversion was achieved or over two hours were considered. to determine the equilibrium constant necessary for calculating the enantiomeric ratio, quick reactions with (r)-2-bromopropanoic acid butyl ester were studied in organic solvents until the equilibrium concentration was reached. in contrast, with ionic liquids numerous reaction media had to be prepared as many samples were taken because for gas chromatography (r)and (s)2-bromopropanoic acid butyl esters had to be extracted from the ionic liquids using n-hexane and the subsequent extracts analysed. as a result, 15 reaction media were prepared simultaneously and the products extracted from them when samples were taken. 3.2 effect of water content the reaction rate altered as a function of water content according to optimum curves (fig. 1). the highest reaction rate was obtained in n-hexane and the ionic liquid [bmim]pf6 when the concentrations of water were 0.15 mol dm−3 (8.9× 10−3 mol h−1 g−1) and 0.38 mol dm−3, respectively. the esterification reaction rate was very similar in toluene and [bmim]pf6 (3.2× 10−3 mol h−1 g −1 and 3.0 × 10−3 mol h−1 g−1, respectively), while in the more polar tetrahydrofuran, [bmim]bf4 esters were produced at a very low reaction rate (10−3 mol h−1 g−1) which was observed to be only slightly dependent on the concentration of water. the enantioselectivity of candida rugosa lipase also varied as a function of water content according to optimum curves, however, was shown to be less dependent on the concentration of water than the reaction rate (fig. 2). hungarian journal of industry and chemistry enzyme activity in non-conventional media 11 figure 1: dependence of the reaction rate on the initial concentration of water the enantioselectivities in [nmim]pf6 and [bmim]pf6 were modest (25 and 19, respectively), while were significantly lower in the other solvents. the highest enantioselectivity (e = 10) was obtained in n-hexane among other classic organic solvents. 3.3 discussion in table 1, the concentrations of water are summarized. it is shown that the maximum reaction rate (cw(conv)) or enantioselectivity (e) (cw(e)) can be achieved at 30 ◦c after 2 hours. the enzyme activity and enantioselectivity of candida rugosa lipase varied according to optimum curves that plots water activity, moreover, the maximum reaction rate and enantioselectivity can be obtained at the same water activity regardless of the solvent used. based on these observations, it is probable that the water activity will be the same in reaction media if a suitable cw(conv) concentration of water is set in every solvent. similarly, the water activity of reaction media will be approximately the same by setting the suitable cw(e) concentration of water. it is possible to set approximately the same water activity in reaction media indirectly, even in the absence of salt pairs or salt hydrates. however, it should be mentioned that the cw values required to reach the maximum conversion or enantioselectivity are not necessarily the same. as can be observed in the case of the ionic liquid [bmim]pf6, a maximum conversion of 29.0% was achieved when cw(conv)= 0.38 mol dm−3, while only a conversion of 26.2% was obfigure 2: dependence of the enantioselectivity on the initial concentration of water tained when cw(e)= 0.31 mol dm−3 required for the maximum enantioselectivity of just 20.0. similar observations may be seen in the case of organic solvents, e.g. n-hexane in which a maximum conversion (36.1%) was achieved when e = 8, while maximum enantioselectivity (e = 10) resulted when the conversion was only 31.7%. therefore, it must be decided whether reaching the maximum conversion or maximum enantioselectivity is the aim. the determination of the maximum conversion as a function of the required enantioselectivity will be the subject of future research. 4. conclusion in this study, it has been proven by the esterification of 2-bromopropanoic acid in the presence of candida rugosa lipase that during reactions conducted in such nonconventional media, the determination of the optimal water content can be significantly simplified by setting the optimal concentration of water instead of the water activity, which is difficult to accomplish. for this purpose, the initial water content required to achieve the maximum reaction rate must be determined. as the water contents needed to achieve the maximum conversion or maximum enantioselectivity are usually different, further optimization tasks are necessary. acknowledgement the financial support of széchenyi 2020 under the project efop-3.6.1-16-2016-00015 is acknowledged. table 1: conversion and enantioselectivity during the enantioselective esterification reaction at the optimum cw(conv) and cw(e) values in different solvents (t =30 ◦c, t = 2 h). solvent logp cw (conv) conversion e cw(e) conversion e mol dm−3 % mol dm−3 % [bmim]bf4 -2.44 0.54 4.6 5 0.46 4.0 6 [bmim]pf6 -2.38 0.38 29.0 18 0.31 26.2 20 [nmim]pf6 -2.19 0.31 13.4 24 0.23 8.9 25 tetrahydrofuran 0.50 0.38 4.3 4 0.31 3.2 5 toluene 2.50 0.23 13.9 3 0.15 10.1 5 n-hexane 3.50 0.15 36.1 8 0.08 31.7 10 48(2) pp. 9–12 (2020) 12 lajtai-szabó, nemestóthy and gubicza references [1] carrea, g.; riva, s.: organic synthesis with enzymes in non-aqueous media (wiley-vch verlag gmbh & co. kgaa, weinheim, germany) 2008, pp. 169-190 isbn: 978-3-527-31846-9 [2] bommarius, a. s.; riebel, b. r.: biocatalysis (wiley-vch verlag gmbh & co. kgaa, 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1-butyl-3methylimidazolium bis[(trifluoromethyl)sulfonyl]amide, biotechnol. lett., 2002, 24(10), 763–767 doi: 10.1023/a:1015563801977 hungarian journal of industry and chemistry https://doi.org/10.1002/3527602364.ch12 https://doi.org/10.1002/3527602364.ch12 https://doi.org/10.1186/s13065-017-0276-2 https://doi.org/10.14440/jbm.2015.60 https://doi.org/10.1021/cr0683820 https://doi.org/10.1016/j.ijbiomac.2012.06.020 https://doi.org/10.1016/j.ijbiomac.2012.06.020 https://doi.org/10.1016/j.molcatb.2004.07.003 https://doi.org/10.1016/j.molcatb.2014.01.001 https://doi.org/10.1016/j.molcatb.2014.01.001 https://doi.org/10.3923/jas.2010.337.342 https://doi.org/10.3923/jas.2010.337.342 https://doi.org/10.1021/jf026071u https://doi.org/10.1002/bit.260440502 https://doi.org/10.1016/s0141-0229(03)00219-9 https://doi.org/10.1016/s0141-0229(03)00219-9 https://doi.org/10.4014/jmb.0905.05051 https://doi.org/10.4014/jmb.0905.05051 https://doi.org/10.1039/b810009h https://doi.org/10.1016/j.memsci.2006.04.012 https://doi.org/10.1016/j.memsci.2006.04.012 https://doi.org/10.1002/bit.10627 https://doi.org/10.1002/bit.10627 https://doi.org/10.1515/hjic-2017-0018 https://doi.org/10.1515/hjic-2017-0018 https://doi.org/10.3109/10242429408992127 https://doi.org/10.1023/a:1015563801977 hungarian journal of industry and chemistry vol. 48(2) pp. 13–21 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-23 follow-up control of a second order system in sliding mode márk domonkos *1 and nándor fink1 1department of mechatronics, optics and mechanical engineering informatics, budapest university of technology and economics, bertalan lajos u. 4-6, budapest, 1111, hungary this paper deals with an instantaneous feedback controlled inverter using sliding mode control. the theoretical contribution of this paper is that a common state-space-based sliding surface design method is extended for follow-up control. starting from the basic theory of sliding mode control, the trajectory of the error signal is modelled. the practical contribution of this paper is the relationship between the trajectory of the error signal and the total harmonic distortion (thd) of the output voltage signal. the conditions of the sliding mode control using an uninterruptible power supply (ups) are discussed. a rectifier as a non-linear load is simulated. experimentally validated simulation results are presented. keywords: sliding mode control, hysteresis control, second order system, ups 1. introduction power electronics equipment that produces alternating voltage and current impulses is typical of variable structure systems (vsss). a vss usually consists of a state when it is insensitive to variations in parameters and load disturbances. this state is referred to as the sliding mode. the cost of insensitivity is an infinitely high switching frequency. due to the limits with regard to switching delays and frequencies of controlled switches, an ideal sliding mode does not exist. however, the ideal sliding mode can be approximated with an acceptable degree of accuracy. the theory of variable structure systems and sliding mode control was developed decades ago in the soviet union, mainly by vadim i. utkin [1] and david k. young [2]. according to the theory, sliding mode control should be robust but experiments have shown that it is subject to serious limitations. the main problem with applying the sliding mode is the high frequency of oscillation around the sliding surface, referred to as chattering, which strongly reduces the performance of the control. very few have managed to put the robust behavior predicted by the theory into practice. many have concluded that the presence of chattering makes the sliding mode control a good game theory, which is not applicable in practice. over the following period, researchers invested most of their energy in chattering-free applications, leading to the development of numerous solutions like the discrete-time sliding mode [3], sector sliding mode [4], adaptive sliding mode [5] and terminal sliding mode [6]. *author for correspondence: domonkos@mogi.bme.hu sliding modes can also be used for feedback compensation [7]. the design of a sliding mode controller consists of three main steps. the first is the design of the sliding surface, the second step is the design of the control law which holds the system trajectory on the sliding surface, and the third and key step is implementation of the chattering-free sliding mode control. the systematic sliding manifold design for linear systems was proposed by utkin [1]. this method was extended in several ways and optimal sliding manifold designs proposed, e.g. frequency-shaped sliding mode control (fssmc) [8] surface design based on h∞ control theory [9, 10] and tensor product model transformation-based sliding surface design [11]. the reference signal was constant in all the aforementioned papers. recently, the application of predictive control has become popular [12]. the new element in this paper is that the original method was extended for follow-up control. according to refs. [13] and [14], uninterruptible power supplies (upss) are being broadly adopted for the protection of sensitive loads, e.g. pcs, air traffic control systems, life care medical equipment, etc., against line failures or other perturbations in ac mains. ideally, an ups should be able to deliver: 1) a sinusoidal output voltage with low total harmonic distortion during normal operation, even when feeding nonlinear loads (particularly rectified loads); 2) the voltage dip and recovery time due to a change in load step must be kept as small as possible, that is, provide a fast dynamic response; 3) the steadystate error between the sinusoidal reference and load regulation must be zero. to achieve these, a proportional inhttps://doi.org/10.33927/hjic-2020-23 mailto:domonkos@mogi.bme.hu 14 domonkos and fink tegral (pi) controller is usually used [15], moreover, issues concerning robust stability and controller robustness are discussed in [16]. however, the system using the pi controller subject to a variable load rather than the nominal ones cannot produce a fast and stable output voltage response. in the literature, some hybrid solutions to overcome this problem can be found [17,18]. the principle of pulse width modulation (pwm) plays a very important role in power electronics [19]. in the field of inverter technology, which produces a sinusoidal voltage, a great number of "optimized pwm" techniques have been proposed in the literature. these types of pwm inverters have very good steady-state characteristics, but for the voltage regulator to respond to a sudden change in the load takes a few cycles and nonlinear loads can cause high "load harmonics". this is unacceptable in ups applications for which instantaneous feedback is preferred [20, 21]. the sliding mode control of power electronic inverters is suggested in refs. [22] and [23]. on the one hand the main advantage of the sliding mode-based method proposed in this paper is the direct control of the transistor switches, but on the other hand uncontrolled thd results. that is why the thd is the focus of this paper. the structure of this paper is as follows. after the introduction, section 2 presents the problem statement, describes the system configuration and summarizes the design of the sliding mode control. section 3 describes the equations of the system and shows how the mathematical foundations are applied to a practical example. following the main steps of sliding mode design, namely the surface design, a control law is selected by taking into consideration the reduced chattering. section 4 presents the simulation results, which are validated by experimental measurements of a 10 kva ups. finally, in section 5, the presented results are analyzed. 2. problem statement 2.1 system configuration a simplified diagram of the inverter and filter is shown in fig. 1 vb denotes the battery voltage and vi stands for the input voltage of the system, which is a filter with a load. the input signal consists of three different values (vb, −vb and 0) depending on the switching states of the transistors. the goal is that the transistors must be switched in such a way that vo, the output voltage of the system, follows the sinusoidal reference signal. ls in fig.1 denotes the leakage inductance of the transformer, which has a special structure to increase and set the value of ls. the main field inductance lp cannot be ignored from the point of view of the resonance circuit. the loss of the transformer is modelled by an increased load. vo(t) = √ 2 · 230 cos (2π50t) (1) figure 1: simplified figure of the inverter and filter 2.2 sliding mode control a single-input single-output (siso) system is given in state-space controllable canonical form. ẋ(t) = ax(t) + bu(t) (2) y(t) = cx(t) (3) where x(t) ∈ rn, a ∈ rn×n, b ∈ rn×1, c ∈ r1×n and u(t), y(t) ∈ r. y(t), the output variable of the controlled plant, can be described by a n-th order differential equation supposing that the reference signal yr(t) can be differentiated at least n times. the goal is given in yr(t) = y(t) if t > tc (4) where tc denotes the control period. the system error, ey(t), is given by ey(t) = yr(t)− y(t) (5) thus the error signal, ey(t), can also be differentiated at least n times, so the n − 1-th derivative must exist and is continuous. due to the latter property, when trying to eliminate the error, it is also useful to control its derivatives (including the n − 1-th derivative). otherwise, because of the system inertia, an oscillation with a large amplitude could arise. the essence of sliding mode control could be summarized as follows: in order to eliminate the error in the n-th dimensional phase space, a continuous error trajectory running into the origin has been designed. whilst planning, the physical limits should be taken into account. by implementing our very own transient, the ideal system follows the reference signal without any errors. the control signal is designed so that the hungarian journal of industry and chemistry follow-up control of a second order system in sliding mode 15 trajectory realized does not deviate from the prescribed one or once the origin has been reached, it remains at rest. usually σ, a scalar variable, can be defined as a positive or negative distance between the desired and actual trajectories, or each trajectory sector can be prescribed by a single scalar variable. the task of the controller is to ensure this scalar variable remains zero. in the classical method of sliding mode control, this scalar variable is calculated as a linear combination of the error and its derivatives [1]. when n = 2, the scalar variable can be defined by the following equation: σ(t) = ey(t) + τ ėy(t) (6) where τ denotes a time constant-type control parameter chosen by us. in sliding mode control: σ = 0 (7) and the trajectory is described by the following equation: ey(t) = −τ ėy(t) (8) that corresponds to a −1/τ gradient in the phase plane. this is usually referred to as the sliding line or sliding surface in multidimensional phase space. the solution of eq. 8 is an exponential function with a negative exponent: ey(t) = e0e − t τ t ≥ 0 (9) where e0 = ey(0). consequently, the error will decrease according to the chosen time constant, τ , independently from the system parameters, e.g. load. after an exponential transient process, yr(t) = y(t). to ensure that the system moves in all cases towards the sliding mode (i.e. towards σ(t) = 0), the following condition is necessary: σ(t)σ̇(t) ≤ 0 (10) the design of a sliding mode controller does not require accurate modelling, it is sufficient to only know the boundaries of the model parameters and the disturbance. during sliding mode control, the only task is to switch the control signal so that eq. 10 is valid in every instance. no other information concerning the controlled plant and the disturbances is needed. it is sufficient to determine whether eq. 10 holds or not. in simple cases (or within a range of errors and its derivatives), the signs of the control signal and σ̇(t) are opposite. thus it is often satisfactory to use a relay controller, which switches the control signal according to the sign of the parameter σ(t). 2.3 follow-up control since yr(t) is not constant, wyr,u(s), the transfer function from u(t) (vi(t)) to yr(t) (vo(t)), must be calculated. according to eq. 4, it is the inverse of the transfer function with regard to the inverted system: y(s) = wu,y(s)u(s) (11) wyr,u(s) = w−1u,y(s) (12) usually, the inverse of wu, y(s) cannot be realized. in our case, yr(t) is sinusoidal: yr(t) = √ 2vr cos (ωrt) (13) only two parameters must be calculated, namely the gain (gr) and phase shift (ϕr) of the transfer function of the system at the reference angular frequency (ωr). the definition of the error (eq. 5) must be modified: ey(t) = √ 2 gr vr cos (ωrt− ϕr)− y(t) (14) 3. equations of the system 3.1 filter and load using the notation of fig. 1, the equation for the currents is: ii(t) = io(t) + ip(t) + ic(t) (15) by assuming resistive load rl: io(t) = 1 rl vo(t) (16) the equation of the input voltage is vi(t) = ls dii(t) dt + vo(t) (17) by substituting eqs. 15 and 16 into eq. 17, the filter circuit with a resistive load can be described by the following differential equation: vi(t) = lscpv̈o(t) + ls rl v̇o(t) + 1 g vo(t) (18) where g = lp ls + lp (19) the transfer function from u(t) (vi(t)) to yr(t) (vo(t)) (including the effect of the resistive load) can be calculated from the laplace transformed form of eq. 18: vo(s) = g glscps2 + gls rl s+ 1 vi(s) = w (s)vi(s) (20) 3.2 the states of the state-space equation since the inverter and load are handled separately, the system has two inputs, namely ui and io. since the input current must be calculated, three state variables are selected for the three storage elements, even if they are not independent and the rank of the system matrix is only 2. using the notation of fig. 1, the three state variables are ii(t), ip(t) and vc(t): x(t) =  ii(t)ip(t) vo(t)  (21) 48(2) pp. 13–21 (2020) 16 domonkos and fink the load is connected in parallel to the inverter capacitor cp. the load current includes the effect of transformer losses. the system has three outputs since vo(t) = vc(t) as well as its derivative are necessary to calculate the scalar variable and ii(t) is visualised. in the real system, the current of the capacitor is measured instead of v̇o(t). according to eqs. 15, 16, and 17, the matrices of the system are: a =  0 0 − 1 ls 0 0 1 lp 1 cp − 1 cp 0  b =  0 − 1 ls 0 0 − 1 cp 0  c = 1 0 0 0 1 0 0 0 1  d = 0 0 0 0 0 0  (22) 3.3 error trajectory to calculate the error defined by eq. 14, gr and ϕr must first be calculated. according to eq. 20: w (jωr) = g glscp(jωr)2 + gls rl jωr + 1 (23) gr and ϕr can be calculated from eq. 23, where w (jωr) denotes a simple complex number: gr = |w (jωr)| (24) ϕr = angle(w (jωr)) (25) since the filter must be inductive, ϕr must be negative. therefore, the reference signal must lead to vo(t), which is the controlled signal in eq. 14: y(t) = vo(t) (26) the derivative of the error is: ėy(t) = −ωr √ 2 gr vr sin (ωrt− ϕr)− v̇o(t) (27) the scalar variable of the sliding mode control is calculated by eq. 6. 3.4 control law three different control laws were examined. all of them can directly control the switching of the transistors. this is the main advantage of sliding mode control in the field of power electronics. more advanced controllers can be found in ref. [24]. simple relay the input voltage on the filter is switched according to the sign of σ(t): vi(t) = vbsign(σ(t)) (28) from a practical point of view, the main problems of eq. 28 are • the inverter has a zero state, which is not applied; • the switching frequency is uncontrolled. figure 2: double relay with dead zone and hysteresis double relay the solution to the first problem is the usage of two relays: vi(t) = vb 2 sign(σ(t)) + vb 2 sign(cos (ωrt− ϕr)) (29) vb and 0 are switched in the positive half period, while −vb and 0 are switched in the negative half period. however, eq. 29 does not solve the second problem. double relay with dead zone and hysteresis both problems can be solved by a double relay with dead zone and hysteresis. this control law is shown in fig. 2. 3.5 stability analysis using a simple relay controller, whether or not eq. 10 holds can be verified. first, σ̇(t) must be expressed: σ̇(t) = ėy(t) + τ ëy(t) (30) according to eq. 27: ëy(t) = −ω2 r √ 2 gr vr cos (ωrt− ϕr)− v̈o(t) (31) v̈o(t) can be expressed from eq. 18: v̈o(t) = 1 lscp vi(t)− 1 rlcp v̇o(t)− 1 glscp vo(t) (32) by substituting eq. 28 into eq. 32: v̈o(t) = vbsign(σ(t)) lscp − v̇o(t) rlcp − vo(t) glscp (33) according to eqs. 30 and 31, if the value of v̈o(t) is sufficiently large and the system operates in an area which is close enough to the sliding mode, then the sign of v̈o(t) is the opposite to that of σ̇(t). from eq. 33, it is clear that if the value of vb is sufficiently large and the system operates in an area which is close enough to the sliding mode, then the sign of v̈o(t) is the same as that of σ(t). in conclusion, if the value of vb is sufficiently large and the hungarian journal of industry and chemistry follow-up control of a second order system in sliding mode 17 system operates in an area which is close enough to the sliding mode, then the sign of σ(t) is the opposite to that of σ̇(t). similar analyses can be conducted for all control laws. in practice, the simulations proved that by substituting the actual parameters of the system, all the control laws examined fulfil the condition (eq. 10) during normal operations. 4. simulation matlab-simulink simulations were carried out. 4.1 matlab-simulink model the main elements of the matlab-simulink model are shown in figs. 3–6. even if the structure of the controller shown in fig. 6 is quite simple, its performance is quite robust. 4.2 model validation the simulation results were compared to previous results measured by [25] as shown in fig. 7. the nominal power of the inverter is 10 va. all parameters of (14) and (22) in addition to the values of dead zone and hysteresis shown in fig. 2 are known from ref. [25]. like in real systems, where σ is tuned manually to set the number of switches per period, σ is changed to achieve a similar result in the simulation as in real systems. the simulation result is shown in fig. 8 after the value of σ was set. the first problem faced in the simulation was the steady state. when the real system was measured, the screen of the oscilloscope seemed to be frozen for most settings of σ. therefore, the error trajectory was a closed curve during a period in a steady state. using the default settings of simulink, a quasi-steadystate period of the error trajectory of the simulation resulted as is shown in fig. 9. the consequent periods are slightly different, which causes subharmonics that are crucial from a practical point of view. the main question is whether these subharmonics are an immanent property of the applied switching method or a result of an insufficiently precise simulation. several simulations were carried out using different model configuration parameters in simulink. it is concluded that the precise calculation of the switching instant is key to simulating proper steady states. the ode113(adam) method is the most suitable integral method for switched systems. (the equation solvers for ups are compared in ref. [26]). 4.3 analysis of the simulation results the main advantage of the pwm technique is that the filter can be smaller resulting in a smaller no-load current. the parameters of the filter are given in ls = 3.5mh, lp = 32mh, cp = 320µf (34) figure 3: the whole system. figure 4: subsystem for calculating scalar variables. figure 5: subsystem for the load. figure 6: subsystem for the relay controller of the dead zone and hysteresis τ , the gradient of the switching line in the sliding mode, has been changed. the value of the nominal load is rl = 5.3ω. the relationship between the gradient of the switching line and the number of switches is shown in fig. 10. the larger the value of τ , the smaller the gradient of the switching line and the greater the number of switches per period. on the other hand, the bigger the value of τ , the longer the transient according to eq. 9. the optimum must be calculated. the number of switches per period and the total harmonic distortion (thd) are shown in fig. 11 as a function of τ . the first one is staggered. the larger the num48(2) pp. 13–21 (2020) 18 domonkos and fink figure 7: reference measurement result figure 8: reference simulation result figure 9: error trajectory during a quasi-steady-state period ber of switches is, the greater the switching loss and the smaller the thd are. the optimum is approximately 52 switches, therefore, 13 pulses per period, as is shown in fig.7 and fig. 8. the step concerning the optimal number of switches is magnified in fig. 12. a local minimum of thd is located at the middle of a staircase (in fig. 12) when the transient between the positive and negative half periods is smooth as is shown in fig. 13. by increasing τ , the transients change slightly. first, a v shape appears (see fig. 14). by further increasing τ , the v shape transforms into a loop (see fig. 15) and the last pulses in all half periods have the opposite signs when compared to the reference signal (see fig. 16) which increases the thd. finally, the number of switches per period is increased by 4 and the figure 10: the effect of τ on the number of switches figure 11: number of switches and thd as a function of the gradient of the switching line figure 12: the optimal number of switches and its thd transients are in the form of vs and loops once more (see fig. 17), which disappear at the middle of the staircase. 4.4 non-linear load the most challenging load is the rectifier [27], since its current is not sinusoidal and the value of its peak is relatively large. a rectifier resembling a load is simulated, which has approximately the same root mean square (rms) value of the current as that of the nominal current. the time functions of the output voltage and current in addition to the input current are shown in fig. 18. the rms value of the input no-load current is zero at the beginning of the period, when the output current is zero. since the load current is continuous and the reaction of the sliding mode controller is practically instantaneous as a result, this type of non-linear load has no significant efhungarian journal of industry and chemistry follow-up control of a second order system in sliding mode 19 figure 13: smooth transient of error trajectory figure 14: v-shaped transient of error trajectory figure 15: loop-shaped transient of error trajectory fect on the output voltage the thd depends on the shape of the error trajectory, which is shown in fig. 19: 4.5 switching on the load a nominal resistive load is assumed and the load is switched on at the peak value of the output voltage. the time functions of the voltage and current are shown in fig. 20. since the current is discontinuous, a transient is figure 16: control signal figure 17: transient of error trajectory after the number of switches is increased present, which is recognizable in terms of the shape of the error trajectory in fig. 21. the length of the transient depends on the value of τ , that is, 0.22 ms. the transient caused by any step change in the load occurs extremely quickly and only lasts approximately 1 ms. 5. conclusions this paper introduced a follow-up control method with a sinusoidal reference signal for the design of a sliding surface and the performance of a double relay controller with a dead zone and hysteresis operating in a sliding mode was analysed. the simulation of variable structure systems is very sensitive to the integral method of simulation. the zero-crossing must be detected. even a relatively simple controller, which can be implemented by an analogue operational amplifier, also performs very well with a non-linear load. the positive and negative half periods can be separated by a dead zone and the switching frequency limited by hysteresis. the actual number of switches can be set by the gradient of the sliding line. the value of the thd depends on the shape of the error phase trajectory. a non-linear load with a continuous output current has no significant effect on the output voltage because of the instantaneous behavior of the sliding mode controller. 48(2) pp. 13–21 (2020) 20 domonkos and fink figure 18: output voltage as well as input and output currents with a rectifier-like load figure 19: error trajectory of the non-linear rectifier-like load acknowledgement the research reported in this paper and carried out at the budapest university of technology and economics has been supported by the national research development and innovation fund (tkp2020 institution excellence subprogram, grant no. bme-ie-mifm) based on the charter of bolster issued by the national research development and innovation office under the auspices of the ministry for innovation and technology. references [1] utkin, v. i.: variable structure control optimization (springer-verlag), 1992 doi: 10.1007/978-3-642-84379-2 [2] young, k.: controller design for manipulator using theory of variable structure systems, ieee trans. syst. man cybern. syst., 1978, 8(2), 101–109 doi: 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https://doi.org/10.1109/tia.1984.4504486 https://doi.org/10.1109/tia.1984.4504486 https://doi.org/10.1016/j.rser.2015.12.335 https://doi.org/10.1016/j.rser.2015.12.335 https://doi.org/10.1007/bfb0109978 https://doi.org/10.1142/s0218126695000424 https://doi.org/10.3390/en11102544 https://doi.org/10.12700/aph.11.03.2014.03.6 https://doi.org/10.12700/aph.11.03.2014.03.6 https://doi.org/10.1016/j.ifacol.2017.08.1169 https://doi.org/10.1016/j.ifacol.2017.08.1169 https://doi.org/10.3390/en12040581 hungarian journal of industry and chemistry vol. 48(2) pp. 23–36 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-24 informative environment qualifying index anett utasi *1, viktor sebestyén1, and ákos rédey1 1sustainability solutions research lab, university of pannonia, egyetem u. 10, veszprém, 8200, hungary improvement in the quality of the environment and, as a result, in the quality of life, including environmental impact assessments and environmental management, play an important role in the practical implementation of environmental regulations. the goal of this paper is to develop a new type of quantitative environmental impact assessment method to describe changes in environmental elements as well as the environment in an objective and reliable manner for various projects, investments, plans and proposals. an easily adaptable method was sought which provides a clear and well-interpretable result on the condition of and foreseeable changes in the environment. the algorithm operates using the limit values of environmental elements set forth by national regulations. the evaluation is independent of the number of environmental parameters chosen as it was included in the informativity rates of the method. the process results in an aggregated index for qualifying the total environment but, nonetheless, the affected environmental elements and measured environmental parameters can be analysed independently. the informative environment qualifying index evaluates the environmental parameters in proportion to the strictness of the limit values. the final assessment of the total environment is performed by using varying intervals, therefore, the different cases can be compared to each other. experts interpret the results as well as explain the changes in the state of the environment and, therefore, identify the cause-effect relationships. keywords: environmental impact assessment, quantitative methods, informative environment qualifying index, environmental pollution 1. introduction the state of the environment has been changing drastically in an unfavourable direction due to economic development, rapid population growth, as well as increases in the rates of production and consumption resulting in extremely severe levels of environmental pollution amongst several other consequences. the european union itself is committed to introduce actions and measures in order to take preventive steps to protect the environment. regarding immediate actions to be implemented, environmental protection is an essential objective. the environmental impact assessment (eia) and sustainability planning are intertwined. both approaches aim to optimize future activities in an environmentally sound way and support decision-makers with appropriate, scientifically based evidence. analyses must provide quantified information as well as easily understandable and comparable results, therefore, the aggregation of quantitative methods is widespread. the aim of this work is to develop an informative environment qualifying index. in addition to indexing based on immission limits, it is important to evaluate the sustainability of cities, for *correspondence: utasi.anett@uni-pannon.hu which the sdewes index is an excellent approach [1]. this method has been implemented in southeast european cities [2] and adapted for hungarian cities [3]. toro et al. developed a qualitative methodology for environmental impact assessment (eia) processes, which uses a double matrix to identify the impacts and assign quantitative values to the categories of quality [4]. pavlickova and vyskupova elaborated on a cumulative method for the evaluation of landscape vulnerability by taking this as well as ecological stability and the ratio of different measures of stability into account [5]. herva and roca reviewed the combined approaches and multicriteria analysis for the purposes of evaluating corporate environmental performance. it was suggested to use the multi-criteria decision-making (mcdm) techniques in the industrial sector, decision-making in energy projects, waste management and wastewater treatment [6]. a possible method is the environmental impact assessment, which comprises 25 different eia methods as well as uses a quantitative framework and standard classification method as an optimal technique for the actual evaluation [7]. an integrated weight of evidence approach for environmental risk assessment proposed by caeiro et al. https://doi.org/10.33927/hjic-2020-24 mailto:utasi.anett@uni-pannon.hu 24 utasi, sebestyén and rédey where anthropogenic pollution, the impacts on human health, the exposition of polluted wells and agricultural soils as well as pollutants in sediments are combined with 14 categories of absolute conditions [8]. phillips used an enhanced rapid impact assessment matrix (riam) method to evaluate quantitatively the potential impacts of an onshore wind farm during its construction and operation [9], as well as for the sustainability evaluation of municipal solid waste management [10]. the riam approach was successfully used by brindusa et al. to evaluate the environmental impacts resulting from heavy metal pollution on the southern coast of the romanian black sea [11]. sun and wang developed a comprehensive eia system for shale-gas exploration, which includes the evaluation systems of influence with regard to the natural and macro environments. the algorithm includes social, policy and economic impacts, therefore, it can be adapted to other fields of environmental analysis [12]. robu et al. analysed the impacts and risks of heavy metal pollutants in bodies of surface water. the basis of such evaluations was the measured concentrations of the environmental parameters, therefore, the method is more objective [13]. the reliability of the different quantitative and qualitative methods may be increased by integrating the technical background of environmental risk assessment [14]. an environmental evaluation system (ees) that incorporates relationships between environmental parameters and environmental quality was developed by battelle columbus laboratories [15] and implemented for water resources planning by ferreira et al. [16]. a review of aquatic environmental assessment methods was published by foden et al. in which a new classification system is suggested that differentiates between static and dynamic links [17]. yu et al. developed a universal calibrated model for the evaluation of bodies of surfaceand groundwater. the main advantage of this algorithm is that it works with any combination of water quality indicators. it was developed in accordance with chinese legislation, therefore, must be adapted for international applications [18]. on the basis of the literature review on eia, it can be concluded that the aforementioned methods have several benefits, however, their limits should be taken into consideration. the main advantage of such methods is their suitability to compare different project alternatives. however, in light of its practical applications, two main issues need to be addressed. namely, the assessment is based on the limit values of environmental parameters, measured/calculated values as well as the ranking/weighting/scaling of the environmental parameters and elements. in addition to these, it can also be concluded that the methods in the literature are less sensitive to extreme values, namely to discharges above the limit values. in addition to environmental impacts, risk assessment is important for decision-makers. wu et al. proposed a quantitative environmental risk assessment for the iron and steel industrial symbiosis network, which provides an aggregate index value and is able to identify the most important driving forces [19]. risks were identified in a chemical plant in zhejiang province in china, where an index-based approach with the analytic hierarchy process (ahp) and fuzzy operators was used for the evaluation [20]. the objective of this paper is to develop a new, easily adaptable, objective and reliable quantitative eia method which provides an unambiguous outcome in the case of projects, investments, plants and proposals in comparison with the methods given in the literature. environmental impacts should be identified during the early design phases [21] in order to avoid unlawful and polluting activities. a widely usable, target-oriented, objective and comprehensive new type of quantitative eia technique was sought and its applicability verified. the environmental impacts were linked to human activities in order to explore the cause-and-effect relationships, therefore, systems thinking is crucial in the case of an eia. rocha et al. developed a multiple indicatorbased approach for environmental quality assessment in urban areas [22]. the proposed iieq method is suitable for tracking environmental changes which can be linked to different human activities. 2. results: methodology the informative environment qualifying index (iieq) method was developed in accordance with legal and other relevant stipulations. the iieq characterizing the total environment can be determined as depicted in fig. 1. the environmental assessment of alternatives to the project begins with screening the projects according to the applicable laws and regulations. the preparation of a reference databased bepends on the scope of the analysis. firstly, the relevant environmental elements must be selected and their limit values determined. following the preparation of the database, the algorithm is expanded by defining the environmental parameters studied for the selected environmental elements and the weighting of these parameters determined. the workflow of the method has been developed in such a way that it can be used to study an individual environmental element or complex cases, e.g. where several environmental elements are considered simultaneously. by analysing the environmental parameters (the second block in fig. 1 which qualify the given environmental element, it is possible to plan the optimal mitigation strategy for that element. therefore, the driving forces/drivers in the quality of the element are identified. the analysis with regard to the level of the environmental element provides a comprehensive picture of the state of the studied elements and important information in the evaluation of the environmental impacts of the projects. the environmental analysis (the last block in fig. 1) ensures a basis for the comparison of the different cases investigated. the iieq value helps decision-makers to determine the optimal measure or project alternative. hungarian journal of industry and chemistry informative environment qualifying index 25 figure 1: methodology of the informative environment qualifying index the method is suitable for multilevel analysis. the levels are represented by different colours in fig. 1. the final outcome of the method is the determination of the iieq. these steps are discussed in the following section. 2.1 reference database laws and regulations pertaining to the investigation the basis for the method is the set-up of the environmental reference database according to hungarian stipulations. when used in other countries, the reference database should be adjusted to pertain to the legal regulations of the country in question. the environmental elements are studied in the present paper in light of the hungarian law on the environment. the following environmental elements were taken into consideration: 1. surface water: water flows (w) 2. surface water: lakes (l) 3. groundwater (g) 4. soil (s) 5. air (a) some eia techniques, which were developed for the analyses of specific environmental elements, e.g. németh et al. provided a quantitative tool for bodies of surface water [23] to show changes in water quality of lake balaton, the largest natural shallow lake in central europe [24, 25]. in the case of air pollution, the air quality index (aqi) is a useful tool to improve public understanding and participation [26]. calculations of aqi can be supported by the two-phase decomposition technique and machine learning [27]. indoor environmental quality (ieq) can also be taken into consideration as this was analysed in a university building [28]. the eia techniques can be sector-specific as well, e.g. sanz et al. developed a new well-being index to describe the environmental quality of renewable energy sources and nuclear power [29]. one of the most important goals during the development of the iieq was to provide a tool that facilitates the public understanding of environmental impacts in a simple, clear way, which includes more graphical representations of the impacts and is capable of describing changes in the state of the environment across an aggregated index value. determination of the environmental parameters for the environmental elements studied lists of environmental parameters are collected for every environmental element which is to be evaluated according to the pertaining stipulations. the database includes the names of the environmental parameters as well as their limit values and validity. the list for surface water is based on gd 2010 [31], the water framework directive. the lists for soil as well as groundwater are based on gd 2006 [32], and the one for the environmental parameters of air can be defined on the basis of gd 2011 [33]. environmental parameters for which no limit values are specified can be studied as well, since the numerical target for the environmental parameters should be determined by specialists and such values are to be included in the list of environmental parameters. weight of environmental parameters generally speaking, the objectivity of the eia is compromised or questionable when a specialist defines the weighted preferences for the environmental parameters. in order to solve this problem, the authors have developed a weighting procedure based solely on environmental regulations and specifications. the hypothesis assumes that legislators took the risks and impacts of the environmental parameters into account whilst defining the limit values. the iieq weighting procedure defines different categories of importance with regard to the environmental elements on the basis of the order of magnitude of the limit values. to determine the confined values of the intervals, the lowest (most severe) and highest (mildest) limit values should be sought in the specifications and classified in the appropriate categories of magnitude. the other limit values should be ranked between those two 48(2) pp. 23–36 (2020) 26 utasi, sebestyén and rédey figure 2: weights of the various environmental elements predefined confined values. the environmental parameters are classified by fitting a natural logarithmic curve as can be seen in fig. 2, where the x and y axes indicate the magnitude and weight of the environmental parameters, respectively. weights of 1 and 0.01 represent the most severe and mildest situations, respectively. the equations of the aligned curves are given in fig. 2 by taking into consideration environmental elements (according to hungarian regulations, the same magnitudes are assigned to certain environmental elements). fig. 2 presents the relationship between the air, bodies of surface water, soil and groundwater. using the equations given in fig. 2, weights, presented in table 1, can be generated for the given environmental parameters. in the case of surface water, the limit value of po4-p is 200µg/l, which belongs to the order of magnitude of 102, therefore, its value is 0.122. in the case of mercury, the limit value is 0.05µg/l, which can be assigned to the order of magnitude of 10−2, therefore, its value is 0.505. table 1: weights according to orders of magnitude orders of magnitude of the environmental parameters studied exponent of 10 wa ww&s wg&l 0.000001 -6 1 *o.r. *o.r. 0.00001 -5 0.714 *o.r. *o.r. 0.0001 -4 0.546 1 1 0.001 -3 0.427 0.687 0.714 0.01 -2 0.335 0.505 0.546 0.1 -1 0.26 0.375 0.427 1 0 0.196 0.274 0.335 10 1 0.141 0.192 0.26 100 2 0.093 0.122 0.196 1,000 3 0.049 0.062 0.141 10,000 4 0.010 0.010 0.093 100,000 5 *o.r. *o.r. 0.01 *o.r.: outside the range of interpretation figure 3: the qualifying diagram of an environmental element on the basis of the quality factor (fpi), quality index (ipi) and quality indicator (∆pi) of the environmental parameter 2.2 analysis of parameters in order to better understand the status of environmental elements, a visualization technique has been developed where the pollution/environmental load of an environmental element is represented by circles of defined radii and areas (fig. 3). as a result, the parameters describing the environmental elements can be represented by segments of a circle (hereinafter referred to as “segment”). the following basic considerations were taken into consideration: the radii of the different segments are the ratios of the measured parameters to limit values expressed as percentages, referred to as the so-called environmental parameter quality index. environmental parameter quality index (ipi) the environmental parameter quality index (ipi) specifies the relationship between the immission concentration and limit values defined by the environmental specifications. ipi is determined by ipi = mvi lvi 100 (1) where ipi is the environmental parameter quality index for parameter i, mvi is the measured value of environmental parameter i, and lvi is the limit value of environmental parameter i. if the value of ipi changes between 0 and 100%, the environmental parameter meets the legal specifications. however, if it exceeds 100%, the limit value is exceeded and mitigation measures must be considered. environmental parameter quality factor (fpi) the environmental parameter quality factor (pi) is determined on the basis of the weight. the central angles (fp1, fp2, fp3) of the circle as depicted in fig. 3 are calculated by fpi = wi 360∑npj l=1 wl (2) hungarian journal of industry and chemistry informative environment qualifying index 27 figure 4: immission analysis as a function of the environmental parameter quality index and factor where fpi is the environmental parameter quality factor for environmental parameter i,wl is the weight of the examined environmental parameter, and npj is the number of environmental parameters in the case of environmental element i. environmental parameter quality indicator (∆pi) the environmental parameter quality indicator (∆pi) is given by ∆pi = (ipi) 2 π fpi 360 (3) where ∆pi is the environmental parameter quality indicator for environmental parameter i, ipi is the environmental parameter quality index for environmental parameter i (according to eq. 1), and fpi is the environmental parameter quality factor for environmental parameter i (according to eq. 2). the environmental parameter quality index for environmental parameter i is of square/quadratic form to emphasize the importance of the measured concentration of the parameter. according to this interpretation, the different parameters with different units can be compared to each other so the environmental parameters can be easily qualified whether they exceed the limit values or fall within them. the central angles of the segments (fp1, fp2, fp3) represent the importance of the environmental parameter in question which is expressed as the environmental parameter quality factor as defined by eq. 2 . regarding fig. 3, the expression of the environmental parameter quality indicator is introduced based on the area of the segment (eq. 3), which represents the extent to which the environmental parameter has an impact on the environmental element. immission analysis the environmental parameters defined above can be illustrated in a three-dimensional system, therefore, the key parameters of the studied impact area identified. fig. 4 illustrates the environmental parameter quality indicators (∆pi) as a function of the environmental parameter quality factor (fpi) and the environmental parameter quality index (ipi). fig. 4 shows the environmental parameters, their risks and the environmental damage caused should their values be extreme. according to the informative environment qualifying index method, the risk is a function of the specified limit value or target. the following conclusions can be drawn on the basis of fig. 4. the area (xmin; ymin; zmin) represents the group of environmental parameters for which the limit values are mildest and present in low concentrations, therefore, their negative impact on the environment is minimal. the point (xmax; ymax; zmax) represents the group of environmental parameters for which the limit values are most severe and present in high concentrations, therefore, their negative impact on the environment is maximal. according to the protocol defined here, the key factors can be identified on the basis of a system-oriented method and the outcome of the analysis used for plan48(2) pp. 23–36 (2020) 28 utasi, sebestyén and rédey figure 5: the relationship between the load of the environmental element and the reference areas ning the environmental mitigation measures. 2.3 analysis of the environmental element level the analysis of the environmental element level provides information to specialists about the cumulative impact of the environmental parameters on the environmental element in question. load of environmental elements (elj) the cumulative environmental impacts of the environmental elements can be determined by totalling the environmental parameter quality indicators (∆pi), which are equal to the sum of the areas of the segments. the environmental element can be interpreted as a circle and the total levels of pollution stemming from the environmental parameters are represented by circles with different radii (fig. 5). in fig. 4, the circle with r = 100 represents the case when the load of the environmental element is equal to the total limit load of the environmental parameters. qualification of environmental elements for the numerical evaluation of an environmental element, the relationships required are defined in table 2. on the basis of the outcome of case studies and professional experience, 10 categories were defined for the environmental evaluation: 10-30-50-70-90-100-110-150200-300. in fig. 5, blue-coloured zones mark the acceptable categories (categories in table 2: 10, 30 and 50), the green-coloured zones represent maximum environmental quality with regard to immission limit values (categories 70, 80 and 100), and the orangeas well as yellowcoloured zones represent situations when the level of pollution exceeds the limit value (categories 110, 150, 200 and 300). given these defined categories, the relative radius can be calculated from which, after working out the area of the circle (as = r2π), the corresponding area can be determined (as). this corresponding area can be interrelated to the load of the environmental parameters studied, that is to the total area of the segments (elj) representing the environmental parameters. from the load of the environmental parameters, the total area can be calculated by a numerical evaluation. the qualification/level of pollution of the environmental element can be determined from table 2. the interval when the load of the environmental element (elj) is less than the reference area (as) needs to be determined. table 2 can be used generally to evaluate all environmental elements and is independent from the number of environmental parameters with regard to the environmental elements since the environmental parameter quality factors (flip) are normalized for 360◦. the values of the environmental parameter quality factors depend on the number of environmental parameters and their weights. theoretical number of environmental parameters (ntj) the theoretical numbers of environmental parameters define the number of environmental parameters to be measured as well as monitored according to the stipulations and are based on the reference database. they are summarized in table 3: practical number of environmental parameters (npj) during the environmental impact assessment, specialists define the environmental elements to be studied and the scope of the environmental parameters. the set of environmental parameters can be different in the case of a natural environment, post-disaster situation or artificial environment. the method puts a special emphasis on the determination of the uncertainties. element quality index (iej) the element quality index determines how the immission concentrations are related to the pollutants to be theoretically released into the environment: iej = √ elj π (4) where iej is the element quality index for environmental element j and elj is the environmental load of environmental element j. element quality factor (fej) the element quality factor (fej) specifies the weight of the environmental element during the evaluation process. the goal of this factor is to take the number of environmental parameters into consideration (eq. 7): fej = npj360∑m k=1 ntk (5) hungarian journal of industry and chemistry informative environment qualifying index 29 table 2: the qualification system for evaluating the different environmental elements reference radius (r) reference area (as) evaluation 300 282743 the environmental element is seriously damaged which the ecosystem cannot tolerate. 200 125664 natural regeneration is impossible because the environmental element is seriously damaged. 150 70686 natural regeneration is inhibited because the environmental element is damaged. 110 38013 the concentrations of the environmental parameters defining the environmental element exceed the limit value. 100 31416 the concentrations of the environmental parameters defining the environmental element are equal to the limit values. 90 25447 the concentrations of the environmental parameters defining the environmental element are close to the limit value. 70 15394 the environmental element with environmental parameters below the limit value or influenced by anthropogenic impacts. 50 7854 the environmental element with minimal disturbances. 30 2827 the natural environmental element with indirect or direct anthropogenic impacts. 10 314 the natural environmental element free of anthropogenic impacts. where fej is the element quality factor for environmental element j, npj is the practical number of environmental parameters in the case of environmental element j, ntk is the theoretical number of environmental parameters in the case of environmental element j (table 3), and m is the number of environmental elements. environmental element informativity rate (fij) the environmental element informativity rate (fij) represents the ratio of the number of theoretical environmental parameters (ntk) for which legal requirements are in effect to the number of investigated environmental parameters. the ideal value of the environmental element informativity rate is equal to when all parameters set forth by the legal stipulations are involved in the investigation: fij = npj ntk (6) where fij is the environmental element informativity rate for environmental element j, npj is the practical number of environmental parameters in the case of environmental element j, and ntk is the theoretical number of environmental parameters in the case of environmental element k (table 3). 2.4 environmental analysis the next step to be undertaken, following the investigation of the environmental parameters and elements, is the comprehensive analysis of the whole environment. the whole environmental system should be evaluated by taking the human, health, social, economic and cultural astable 3: the theoretical numbers of environmental parameters (ntk) for different environmental elements environmental element theoretical number of environmental parameters (pcs) surface water: water flow 59 surface water: lake 59 groundwater 58 soil 52 air 33 pects into consideration in an integrated way. it is insufficient to solely focus on the natural or artificial environment. the usability of a given project area depends on several factors, not only on the excellence of one environmental element. therefore, a holistic approach is adopted during the evaluation. element quality indicator (∆ej) the element quality indicator (∆ej) enables the environmental element to be taken into consideration in light of the weights of the environmental parameters that describe the environmental element. those environmental elements which are monitored less contribute to a lesser extent with regard to the characterization of the environment. during the analysis, the cumulative load of the environmental elements is taken into account: ∆ej = i2ejπ fej 360 (7) where ∆ej is the element quality indicator for environmental element j, iej is the element quality index for environmental element j (according to eq. 4), and fej is the element quality factor for environmental element j (according to eq. 5). total environmental load (tl) the total environmental load (tl) represents the proportional pollution of the whole environment, which can be generated by the summation of the element quality indicators (∆eqj). the environmental load is regarded as the most important issue during the calculation of the informative environment qualifying index (iieq) as defined by tl = m∑ j=1 ∆ej (8) where tl is the total environmental load, ∆ej is the element quality indicator for environmental element j (according to eq. 7), and m is the number of environmental elements. 48(2) pp. 23–36 (2020) 30 utasi, sebestyén and rédey table 4: evaluation table of the whole environment reference radius (r) dynamical reference area (ad) evaluation 300 3002πfenv.i degraded area which the ecosystems cannot accommodate. 200 2002πfenv.i the natural regeneration of the environment is impossible because the area is severely damaged. 150 1502πfenv.i natural regeneration is inhibited because of the damaged area. 110 1102πfenv.i the concentration of the environmental parameters exceeds the limit value. 100 1002πfenv.i the concentration of the environmental parameters is equal to the limit value. 90 902πfenv.i the concentration of the environmental parameters is similar to the limit value. 70 702πfenv.i the environment is influenced by levels of pollution under the limit value and directly influenced by anthropogenic impacts. 50 502πfenv.i the environment closely resembles the natural conditions or with minimal disturbances. 30 302πfenv.i the natural environment with direct or indirect anthropogenic impacts. 10 102πfenv.i the natural environment free of anthropogenic impacts. qualification of the total environment table 4 is used to evaluate the total environment, which is based on dynamical reference areas as calculated from ad = r2πfenv.i (9) where ad is the dynamical reference area (the level of the whole environment), r is the reference radius (table 4), and fenv.i is the environment informativity rate (eq. 10). the basis of the dynamical reference area is the reference radius (fig. 5 and table 2) by which 10 different categories of quality were defined. the dynamical reference area depends on the ratio of the studied environmental parameters to the theoretical number of environmental parameters (informativity defined in the method). the numerical assessment of the whole environment results in the element quality indices from the environmental load stemming from the total environmental parameters for the environmental elements. the evaluation of table 4 concerns the results in terms of quality/pollution during the interval, in which case the value of the total environmental load (tl) is less than the dynamical reference area (ad). environment informativity rate (fenv.i) the environment informativity rate (fenv.i) shows the depth of monitoring with regard to the environmental elements during the environmental evaluation: fenv.i = ∑m j=1 npj∑m k=1 ntk (10) where fenv.i is the environment informativity rate, npj is the practical number of environmental parameters in the case of environmental element j, ntk is the theoretical number of environmental parameters in the case of environmental element k, (table 3), and m is the number of environmental elements. the environment informativity rate (fenv.i) indicates the coverage of the environmental parameters used in the investigation compared to the specified environmental parameters. the environmental impact assessment is more informative if the scope of the environmental parameters is larger. lim npj→ntk (fenv.i) = 1 (11) according to eq. 11, the value of fenv.i approaches 1 if the practical number of environmental parameters (npj) closely resembles the theoretical number of parameters (ntk). informative environment qualifying index (iieq) the final outcome of the method that is elaborated on is the informative environment qualifying index, which is a complex indicator (eq. 12). the status of the environment is determined on the basis of the load of the different environmental elements and the informativity. its value depends on the actual load of the environmental elements as well as the practical and theoretical numbers of environmental parameters. from the reference radius of table 4 during the evaluation, iieq determines the accurate radius of the area derived from the actual load of the environmental elements: iieq = √ tl πfenv.i (12) where iieq is the informative environment qualifying index, tl is the total environmental load (eq. 8), and fenv.i is the environment informativity rate (eq. 10). the application of the informative environment qualifying index provides a solid basis to compare the outcomes of different environmental evaluations since certain cases can differ from each other regarding the parameter sets. iieq includes all these variables. the method can be expediently used to evaluate the environment before and after a disaster (e.g. the red mud disaster of devecser), and the outcomes of the studies can be evaluated as a function of time. the method provides an opportunity to compare different cases (industrial parks, settlements, the natural environment) as well as provides a systemized and comprehensive approach to the evaluation. 2.5 a case study zirc is a small city in the heart of the bakony mountains in western hungary. the city and its surroundings is a distinguished touristic area in hungary with several natural attractions. an arboretum and national parks are situated in the direct vicinity of the city. the water quality of the cuha stream which flows through the city is influenced hungarian journal of industry and chemistry informative environment qualifying index 31 table 5: the measured parameters of zirc on june 13, 2016 the basic data of surface water environmental parameters measured value limit value electrical conductivity (µs/cm) 985 1,000 codcr (µg/l) 3,300 30,000 no3-n (µg/l) 1,497.24 2,000 nh4-n (µg/l) 50 400 po4-p (µg/l) 169 200 the basic data of air environmental parameters measured value limit value no (µg/m3) 3.708 100 nox (µg/m3) 8.406 200 co (µg/m3) 278.77 10,000 o3 (µg/m3) 80.77 120 benzene (µg/m3) 0.331 10 pm10 (µg/m3) 16 50 by the wastewater treatment plant located here. the population of zirc is 7, 106 and the main economic activity in the region is agriculture. during the field studies in the summer of 2016, two environmental elements were measured, namely surface water and air. the location of the measurement points is shown in fig. 6. in the case of surface water and air, the environmental parameters as defined in table 5 were measured. the weights as well as quality indices, quality factors and quality indicators of parameters were determined and are summarized in tables 6 and 7. fpi in the last rows of tables 6 and 7 are used as a control since their total value must be equal to 360. values of elj , as defined in table 2, constitute the basis of the numerical evaluation. the value of the parameter quality index for the environmental parameter po4-p calculated on the basis of eq. 1 is illustrated below. the measured value of the parameter po4-p was 169 mg/l and the limit value pertained to it was 200 mg/l [30]. ippo4−p = 169(mg l ) 200(mg l ) 100 = 84.5 the parameter quality factor for the environmental parameter po4-p is determined on the basis of eq. 2. the weight of po4-p is 0.12 and the five numbers in the denominator include the weight of the five environmental parameters of water. fppo4−p = 0.12 · 360 0.06+0.01+0.06+0.12+0.12 = 116.22 the values of ipi and fpi calculated for the environmental parameters listed in tables 6 and 7 constitute the basis of the calculation. parts a and b of fig. 7 refer to the surface water and air, respectively. on the basis of the parametric analysis of surface water, it can be concluded that the maximum limit value is defined for po4-p. therefore, in the following steps, the maximum weight (fpi = max) is assigned to po4-p. the electrical conductivity is close to the limit value and the parameter quality index of no3-n is ∼ 75%. these parameters are key to improve the water quality in zirc and are represented by circles in fig. 7. a similar analysis of air was also carried out. for the environmental parameter po4-p, the parameter quality indicator is based on eq. 2 using the parameter quality index (84.50) and parameter quality factor (116.22): ∆ppo4−p = 84.52 · 3.14 · 116.22 360 = 7, 241.59 the quantitative analysis of the environmental elements of surface water and air is depicted in fig. 8. parts a and b of fig. 8 refer to the surface water and air, respectively. the weights of the environmental parameters can be seen in fig. 8 during the evaluation procedure (the total of the interior angles of the segments is equal to fpi). the radii of the sectors are identical to the values of ipi which provide information on the quality. the load of the environmental element (elw) of the surface water is equal to 15, 296. the qualification system for evaluation of the different environmental elements (table 2) functions by substitution. an assignment in the category of r = 50 (environmental element with minimal disturbances, table 2 is obtained. it can be concluded that the water quality of the cuha stream was disturbed to a minimal extent. nevertheless, the ecosystem can tolerate this level of pollution. by applying eq. 4, the values of the environmental quality index express the actual loads of the environmental elements. on the basis of measurements in zirc, the five parameters for surface water represent an area, iew, equal to r = 69.78, while the six environmental parameters for air represent an area, iea, of r = 31.58: iew = √ 15, 295.6 3.14 = 69.78 iea = √ 3, 132.57 3.14 = 31.58 following these steps, the aforementioned algorithm was followed. the element quality factors for water and air, few and fea, were calculated according to the theoretical number of environmental parameters, altogether 92 parameters are to be monitored according to the specifications of gd 2010 [30] and gd 2011 [32]. in the case studies for surface water and air, five and six environmental parameters were investigated, respectively. few = 5 · 360 92 = 19.57 fea = 6 · 360 92 = 23.48 next, the environmental element informativity rate was determined. the environmental element informativity rates for surface water and air are 0.08 and 48(2) pp. 23–36 (2020) 32 utasi, sebestyén and rédey figure 6: the measuring points and location of zirc in hungary table 6: the results of the calculations (eqs. 1-3) for all measured parameters in the case of surface water from cuha stream, zirc parameter (unit) measured value limit value wi ipi fpi ∆pi electrical conductivity (µs/cm) 985 1,000 0.06 98.5 59.03 4,998.33 cod (mg/l) 3,300 30,000 0.01 11 9.5 10.03 no3-n (mg/l) 1,497.24 2,000 0.06 74.86 59.03 2,887.19 nh4-n (mg/l) 50 400 0.12 12.5 116.22 158.47 po4-p (mg/l) 169 200 0.12 84.5 116.22 7,241.59 total *n/a *n/a *n/a *n/a 360 elw = 15, 296.6 *n/a: not applicable table 7: the results of the calculations (eqs. 1-3) for all measured environmental parameters in the case of air in the vicinity of the mayor’s office, zirc parameter (unit) measured value limit value wi ipi fpi ∆pi no2 (µg/nm3) 3.71 100 0.09 3.71 58.45 7.01 nox (µg/nm3) 8.41 200 0.09 4.2 58.45 9.01 co (µg/nm3) 278.77 10,000 0.01 2.79 6.32 0.43 o3 (µg/nm3) 80.77 120 0.09 67.31 58.45 2,310.77 benzene (µg/nm3) 0.33 10 0.14 3.31 89.17 8.53 pm10 (µg/nm3) 16 50 0.14 32 89.17 796.83 total *n/a *n/a *n/a *n/a 360 ela = 3, 132.57 *n/a: not applicable hungarian journal of industry and chemistry informative environment qualifying index 33 figure 7: immission analysis of the surface water (left-hand side, part a) and air (right-hand side, part b) figure 8: the quantitative analysis of the environmental elements (left-hand side: water, part a; right-hand side: air, part b) 0.18, respectively. it should be noted that the total of feqw/feiw = 19.57/0.08 = 230.87) and feqa/feia = 23.48/0.18 = 129.13) is equal to 360. fiw = 5 59 = 0.08 fia = 6 33 = 0.18 on the basis of eq. 7, the load of the whole environment (∆ej) can be calculated using the actual load of the environmental elements. the actual load is substituted into the equation in the square/quadratic form, while npj/ntj for the informativity is linear. ∆ew = 69.782 · 3.14 · 19.57 360 = 831.28 ∆ea = 31.582 · 3.14 · 23.48 360 = 204.3 the total load of the environment is equal to the total of the summarized loads of the environmental elements (eq. 8). in the case of zirc, the larger proportion of environmental load stems from the surface-water pollution and the load of the air pollution represents roughly 20%. tl = 831.28 + 204.3 = 1, 035.58 the whole environment can be evaluated by the dynamical reference areas as given by eq. 9 and table 4. by substituting tl into table 4, it can be stated that the parameters describing the status of the environment are close to the concentrations of limit values. the radius assigned to the environmental quality of the city is equal to r = 50. a50 = 502 · 3.14 · 0.12 = 939 in the aforementioned formula, the radius is equal to 50, representing the worst category of quality. the environmental element informativity rate is 0.12 (eq. 10) which provides information on the number of environmental parameters in the study. fenv.i = 5 + 6 59 + 33 = 0.12 the informative environment qualifying index (iieq) is calculated on the basis of eq. 12: iieq = √ 1, 035.58 3.14 · 0.12 =52.51 iieq of zirc is 52.51. by substituting this value into table 4, it can be seen that the environmental parameters 48(2) pp. 23–36 (2020) 34 utasi, sebestyén and rédey describing the status of the environment closely resemble the natural conditions with minimal disturbances. specialists agree with the results, which are supported by the outcome of the field study. 3. conclusion the novelty of the informative environment qualifying index method is that the maximum environmental loads of the environmental parameters as stipulated in the legal specifications and the actually measured/calculated levels of pollution are taken into consideration when compared to the methods published in the literature. during the evaluation, the algorithm is applied at different levels, namely at the levels of environmental parameters, environmental elements and the total environment, to expediently elaborate on the planning of environmental mitigation measures. the quantitative methods used in the environmental impact assessment procedure include several subjective components during the weighting/ranking/scaling which could result in different interpretations with regard to the outcome of the evaluation. the informative environment qualifying index method is based on the specifications of national regulations, while the weight of the environmental elements depends on their status and the number of environmental parameters included in the study. the informative environment qualifying index method is suitable for following up and monitoring the status of the environment in the cases of protected areas, national parks, urban areas, disasters, etc. the applicability of the method was demonstrated in the case of zirc, a small city in the heart of the bakony mountains in western hungary. the scope of the evaluation ranges from the category “environment close to the natural conditions or with minimal disturbances” to “natural environmental elements with indirect or direct anthropogenic impacts”. the method casts light on the significant environmental impacts without concealing extreme situations nor distorting the final conclusions. acknowledgement the financial support of széchenyi 2020 under project ginop-2.3.2-15-2016-00016 is acknowledged. the financial support of széchenyi 2020 under the project efop-3.6.1-16-2016-00015 is acknowledged. nomenclature ∆ej quality indicator for environmental element j ∆pi quality indicator for environmental parameter i a subscript, air ad dynamical reference area (level of the total environment) as reference 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(i. 14.) of ministry of rural development (vm) from the ambient air quality limit values and the emission limit values of stationary point sources of air pollutants (in hungarian) hungarian journal of industry and chemistry https://doi.org/10.1016/j.scitotenv.2016.12.018 https://doi.org/10.1016/j.scitotenv.2016.12.018 https://doi.org/10.1016/j.buildenv.2018.05.001 https://doi.org/10.1504/ijgw.2016.075448 https://doi.org/10.1504/ijgw.2016.075448 https://doi.org/10.1515/hjic-2017-0008 https://doi.org/10.1515/hjic-2017-0008 hungarian journal of industry and chemistry vol. 48(2) pp. 37–43 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-25 the effect of ph on biosurfactant production by bacillus subtilis dsm10 réka czinkóczky1 and áron németh *1 1department of applied biotechnology and food science, budapest university of technology and economics, műegyetem rkp. 3, budapest, 1111, hungary the genus bacillus has long been known for its ability to produce many industrially useful products. these bacteria mostly produce extracellular products like organic acids, enzymes and biosurfactants. in this paper, the production of surfactin using the bacillus subtilis strain dsm10 is investigated. biosurfactant was produced in a lab-scale 1-liter fermenter. ph control using different bases (nh4oh and naoh) was compared to observe whether the amount of produced biosurfactant or the quality of the product was influenced. the formation of the product was followed by measuring the surface tension, and the product formed was analyzed by reversed-phase chromatography. the investigation of the effect of ph control showed that it can be omitted during the fermentation of the biosurfactant. the highest concentration of surfactin (5 g/l) was achieved without ph control in contrast with when the ph was kept constant (ph = 7). keywords: biosurfactant, surfactin, fermentation, purification, bacillus subtilis 1. introduction in recent years, the microbial production of tensio-active molecules with various properties, e.g. emulsifying, wetting, foaming, detergency, solubilizing and dispersing, has been gaining interest [1]. biosurfactants are amphiphilic compounds produced by a variety of microbial communities. natural surfactants are of great importance in the pharmaceutical, cosmetic, agricultural and food industries due to their beneficial properties including low toxicity, biodegradability, high selectivity and activity under extreme environmental conditions [2, 3]. the market of bio-based surfactants is predicted to be worth $5.52 billion by 2022 [4]. this is unsurprising given our high degree of dependency on kinds of hygiene products, the majority of which include surfactants or emulsifiers. biosurfactants are classified based on their chemical structure into the following groups: glycolipids, lipopeptides, fatty acids and lipids, as well as polymeric and particulate biosurfactants [3, 5]. one of the most effective biosurfactants is surfactin. this lipopeptide-type surfactant contains a cyclic peptide linked to a fatty acid chain (fig. 1) [6]. bóka et al. reported that the molecular weights of surfactins range from 993 da to 1049 da [7]. several gram-positive bacillus species naturally produce surfactins, which help the bacteria to stabilize their cell membranes and adhere to a surface [8, 9]. the biosynthesis of surfactin occurs through different mechanisms: the conversion of glucose or glycerol as a substrate *correspondence: naron@f-labor.mkt.bme.hu to glucose 6-phosphate through the glycolytic pathway, providing the main precursor of carbohydrates located in the hydrophilic part and the oxidation of glucose to pyruvate then to acetyl-coa, which serves as a precursor for the synthesis of lipids and amino acids (asp, glu, leu, val). however, if the substrate is a hydrocarbon, the metabolism is shifted towards the lipolytic pathway (βoxidation into acetyl-coa) and gluconeogenesis (acetylcoa involved in the synthesis of the precursor glucose 6-phosphate) [1]. the effectiveness of surfactants is defined by their ability to reduce the surface tension (st), defined as the cohesive force between molecules which is proportional to the concentration of surfactant in the solution [2]. their efficiency is measured by the critical micelle concentration (cmc) [1,11]. above the cmc, surfactants form micellar structures, but below it, the aggregates dissociate into monomers. lipopeptides from b. subtilis are particularly compelling because their surface activity has been reported to be strong [6,12,13]. powerful surfactants can decrease the surface tension of water (72 mn/m at 20 ◦c) to less than 30 mn/m [14]. the emulsifying capacity can be monitored by calculating the emulsification index (ei, %) and emulsion stability. as the ph decreases, surfactin becomes less soluble in water because the carboxyl group is protonated [12]. under neutral or basic conditions, the carboxyl group is in the ionic form, thus its solubility and emulsification capability increases [15]. moro et al. evaluated the influence of the ph on the stability of the surfactants produced by species of b. subtilis, b. gibsonii and b. https://doi.org/10.33927/hjic-2020-25 mailto:naron@f-labor.mkt.bme.hu 38 czinkóczky and németh figure 1: chemical structure of surfactin: peptide loop of amino acids: five l-amino acids (val, asp, leu, glu and leu) two d-amino acids (leu and leu), and a α, βhydroxy c13-c15 fatty acid chain [10] amyloliquefaciens [9]. all isolates exhibited surface tensions below 30 mn/m. in strongly acidic conditions, the emulsifying activity significantly decreased for both b. subtilis odw02 and b. subtilis odw15. as the ph was increased from 7 to 12, the stability of the surfactant produced by b. subtilis odw02 decreased even further, but the one by b. subtilis odw15 remained stable. in the case of b. amyloliquefaciens mo13, a significant increase was observed both under acidic and basic conditions. this different ph-responsive behavior makes surfactin applicable in a variety of industrial fields. the choice of fermentation cultivation media (i.e. of average composition, carbon source, nitrogen source and trace elements) as well as fermentation strategies (i.e. temperature, ph, aeration and agitation) also need to be considered in relation to the type of applications. based on a literature review, the best combination among the fermentation conditions was 1.5 vvm at 300 rpm, resulting in a maximum yield of surfactin of 6.45 g/l [16]. b. subtilis atcc 21332 was grown on an iron-enriched minimal salt (msi) medium including glucose (40 g/l). in a recent study, yang et al. used nanoparticles (nps) to improve the total yield of surfactin. 5 g/l of fe nps were added to the fermentation medium of b. amyloliquefaciens mt45, which increased the titer of surfactin from 5.94 to 9.18 g/l. modifying the biosynthesis of surfactin with metabolic engineering tools can further increase production and titers of surfactin in b. subtilis, as demonstrated by wu et al. (12.8 g/l) [17]. few studies have focused on individual characteristics and relative amounts of surfactin variants in the extracts of lipopeptides. many surfactin variants exist with various lengths of fatty acid chains and different amino acid sequences [5]. akpa et al. analyzed the replacement of l-glutamic acid with four other amino acids, namely l-leucine, l-valine, lisoleucine and l-threonine, in the culture medium. the presence of thr was found to be favorable for the synthesis of longer (c15-c16) fatty acid chains in b. subtilis s499 [18]. supplementation with mn2+, cu2+ and ni2+ ions can also promote the production of novel variants of surfactin with different components of fatty acids (c16c18) and amino acids (central aspartic acid methyl ester residue instead of aspartate) [19]. this approach can be useful for studying specific biological activities. the objectives of our study were to explore the effect of ph control on the production of biosurfactants (i.e. on titers and productivity) by the b. subtilis strain dsm10 and evaluate the properties of biosurfactants, i.e. type, surface tension reduction and emulsifying activity. 2. materials and methods 2.1 cultivation conditions bacillus subtilis dsm10 (ncaim b.02624t) was used for biosurfactant fermentation in this study. cultivation was performed at 37 ◦c in 250 ml erlenmeyer flasks containing 100 ml of an inorganic medium based on the composition used by joshi et al. (2013): 34 g glucose, 1.0 g nh4no3, 6.0 g kh2po4, 2.7 g na2hpo4, 0.1 g mgso4•7 h2o, 1.2·10−3 g cacl2•2 h2o, 1.65·10−3 g feso4•7 h2o, 1.5·10−3 g mnso4•4 h2o and 2.2·10−3 g na-edta [20]. the experiments were carried out in a 1 l benchtop bioreactor, with a working volume of 0.8 l (biostat q fermenter, b. braun biotech international, germany) and a 10% v/v inoculum. for biosurfactant production, the temperature was adjusted to 37 ◦c with an agitation speed of 300 rpm and an aeration rate of 0.25 vvm. the ph was controlled by 25% h2so4 and two different bases, namely 25% nh4oh and 25% naoh. biosurfactant fermentation without external ph control served as a controlled experiment. a cyclone separator for reducing foam was connected to the outlet airstream of the fermenter (fig. 2). the foam could overflow from the fermenter via the air outlet, through the cyclone separator to the collector flask. 2.2 analysis of biomass bacterial growth was monitored by measuring the optical density of the fermentation broth at 600 nm using a pharmacia lkb ultrospec plus spectrophotometer in comparison with that of the centrifuged supernatant of the sample. the biomass concentration (g cell dry weight/l) was determined by using a calibration curve (r2 = 1): biomass [g/l] = 0.4283 · od600 + 1.4568 (1) the sampled broth was centrifuged at 6, 000 rpm for 15 mins. the cell pellets were collected and dried at 105 ◦c to constant weight by a sartorius ma35 moisture analyzer to measure the cell dry weight. hungarian journal of industry and chemistry the effect of ph on biosurfactant production by bacillus subtilis dsm10 39 figure 2: fermentation setup with foam-separating glass cyclone 2.3 analysis of glucose consumption glucose consumption was determined using the waters breeze 2 hplc system. the mobile phase was 5 mm h2so4 and the rate of elution was 0.5 ml/min. a biorad aminex hpx-87h (300 × 7.8 mm, 9 µm) column (65 ◦c) was applied with a refractive index detector (40 ◦c). the glucose concentration was calculated from the peak area by the following calibration curve equation (r2 = 1): glucose [g/l] = 4 · 10−6 · peakarea + 0.0147 (2) 2.4 analysis of biosurfactants surface tension measurement the surface activities of biosurfactants produced by the bacterial strains were determined by measuring the surface tension of the samples of cell-free broth using the stalagmometric method with a traube stalagmometer (2.5 ml, wilmad-labglass lg-5050-102 stalagmometer tube for samples of low viscosity) at room temperature (25 ◦c). to increase the accuracy of the surface tension measurements, the averages of triplicates were used in this report. the surface tension can be determined based on the number of drops that fall per unit volume, the density of the sample and the surface tension of a liquid reference, e.g. deionized water. the actual number of drops was calculated using n = n0 + x− y c (3) where n denotes the number of drops of the sample calculated to the nearest tenth of a drop;n0 represents an integer of drops counted between capillary-scale readings x and y; x and y stand for capillary-scale readings based on the maximum data point as 0 and the minimum data point as 40; x and y refer to the distances in millimeters from the beginning of each scale; and c is the capillary-scale calibration in millimeters per drop. the surface tension (st in mn/m) was calculated according to st = stw ·nw ·d n ·dw (4) where stw denotes the surface tension of water at 25 ◦c (72 mn/m);nw represents the number of water drops (20 drops); d stands for the density of the sample in g/ml; n refers to the number of drops of sample, and dw is the density of water at 25 ◦c. emulsifying activity the emulsifying activity was determined by the addition of 2 ml of sunflower oil to the same volume of cellfree sample or surfactin solution in a test tube, which was vortex-mixed vigorously for 2 mins. [21]. the tubes were incubated at 25 ◦c and the emulsification index (ei) determined after 24 hours according to: eit = ( he ht ) 100 (5) where he and ht are the height of emulsion and total height of the liquid in the tube, respectively. to study the emulsion stability, the same protocol was used. the emulsification index (ei, %) was determined after 1 h and the ei measured after 24 h (ei24, %), the tubes were incubated at 25 ◦c. the emulsion stability was expressed as a function of the changes in ei over the 24 h. high-performance liquid chromatography (hplc) the surfactin concentration was measured by hplc using a waters alliance 2695 separations module, which is a high-performance liquid chromatographic system equipped with a waters 2996 photodiode array detector, at 205 nm and a symmetry c18 column (4.6 × 150 mm, 5 µm waters, ireland). the mobile phase consisted of 20% v/v trifluoroacetic acid (tfa) (3.8 mm) and 80% v/v acetonitrile. the elution rate was 1 ml/min at 25 ◦c and the sample volume was 10 µl. the purified surfactin was identified by using commercially available surfactin (wako chemicals) as the authentic compound [22]. 2.5 isolation of the biosurfactant the method for purifying the biosurfactant was adapted from the one outlined by joshi et al. (2008) [23]. the cell-free broth was obtained by centrifuging the fermentation broth at 4, 000 rpm for 20 mins. at 4 ◦c using a janetzki mlw k23d centrifuge. the cell-free broth was used for further purification steps. the biosurfactant was recovered from the supernatant by acid precipitation: the 48(2) pp. 37–43 (2020) 40 czinkóczky and németh table 1: summary of the results of the fermentations without ph control 25% nh4oh 25% naoh biomass yield [g/g] 0.06±0.02 0.06±0.02 0.08 biosurfactant yield [g/g] 0.120±0.04 0.073±0.07 0.123 glucose conversion [%] 78.90±22 71.40±4 58.35 final biosurfactant concentration [g/l] 3.36±2.3 2.00±1.5 2.34 minimum surface tension [mn/m] 51.1±1 54.3±17 68.4 biomass productivity [g/l·h] 0.060±0.03 0.089±0.05 0.064 biosurfactant productivity [g/l·h] 0.100±0.05 0.034±0.02 0.064 ph was adjusted to 2.0 using 6 n hcl and kept at 4 ◦c overnight. the precipitate was collected by centrifugation at 4, 000 rpm for 20 mins. at 4 ◦c, then resuspended in distilled water. the ph was adjusted to 7.0 using 6 n naoh and the solution lyophilized by a christ alpha 2-4 lsc freeze dryer. the concentration of biosurfactant was determined gravimetrically from the resulting yellowish white powder. the concentration of biosurfactant was determined gravimetrically from the lyophilized powder. the identity of the purified biosurfactant was checked by hplc. 2.6 calculation of fermentation parameters to compare the results of the fermentation, the following parameters were determined. substrate (glucose) conversion was calculated according to: ∆s % = s0 − sf s0 (6) where s0 and sf denote the initial substrate and final glucose concentrations, respectively. the biomass yield on glucose (y x s , g/g) was defined by: y x s = xf − x0 s0 − sf (7) where xf and x0 are the final and initial biomass concentrations, respectively. the biosurfactant yield on glucose (yp s , g/g) was defined by: yp s = pf − p0 sf − s0 (8) where pf and p0 are the final and initial biosurfactant concentrations, respectively. the volumetric productivities jx = xmax txmax (9) and jp = pmax tpmax (10) (g/l · h) were calculated as the quotients of the maximum biomass concentration (xmax, g/l) or the maximum biosurfactant concentration (pmax, g/l) and the fermentation time (txmax or tpmax , h) when the maximum concentration was achieved, respectively. 3. results and discussion to evaluate the effect of ph on surfactin production, a series of batch fermentations were performed either with or without ph control. the biosurfactant solution was analysed quantitatively and qualitatively using the hplc method reported by mubarak et al. [24]. an overview of the calculated parameters of the batch runs can be seen in table 1. in the absence of ph control, the maximum biomass concentration achieved was 4.00 g/l after 35 h (fig. 3). without ph control, the increased acidity of the medium inhibited further growth at ph 4.4. the maximum biosurfactant concentration was 4.99 g/l, which resulted in the surface tension decreasing to 50.1 mn/m. in ph-controlled fermentations, the biomass yields (0.06 and 0.08 g/g ph adjusted with 25% nh4oh and 25% naoh to 7.0, respectively) were similar to that in the absence of ph control (0.06 g/g) (table 1), while the production of biosurfactants was unable, with a few exceptions, to reduce the surface tension significantly (66.5 mn/m with 25% nh4oh, table 1; figs. 4 and 5). this may account for the presence of residual glucose concentrations of 8 to 12 g/l (figs. 4 and 5). the maximum surfactant concentrations were 3.50 and 2.34 g/l by adjusting the ph using nh4oh and naoh, respectively. although these results are similar to the average yield of surfactants (3.36 g/l) in the absence of ph control, a significant drop in productivity of approxifigure 3: fermentation of surfactin without external ph control hungarian journal of industry and chemistry the effect of ph on biosurfactant production by bacillus subtilis dsm10 41 figure 4: a) hpl chromatogram of a 1.25 g/l surfactin standard, b) hplc chromatogram of the isolated biosurfactant fraction from the foam out sample figure 5: fermentation of surfactin ph controlled by 25% nh4oh. mately 50% was observed (table 1). the highest value of the emulsifying activity (ei24) was in excess of 70% at the end of the exponential phase of the growth curve (at 35 h, fig. 3). the ei24 values obtained from samples extracted from ph-controlled experiments increased from 45 to 55% (figs. 5 and 6, respectively). these inconsistencies can be explained in part by the fact that different bacillus species and strains are capable of producing numerous surfactin variants with distinct properties. it is highly likely that the production of surfactants is independent of cell growth as ei24 decreased and st increased during the stationary phase perhaps as a result of degradation by enzymatic hydrolysis or uptake under substrate-limiting conditions [25, 26]. since the spectrum of lipopeptide-type biosurfactants is broad, the profiles of the extracts obtained after the purification process were compared to the surfactin standard. fig. 4 presents two representative chromatograms: figure 6: fermentation of surfactin ph controlled by 25% naoh (a) surfactin standard and (b) purified culture broth of b. subtilis dsm10. comparatively speaking, the samples from our study exhibited similar peaks (number of peaks, retention time). the intense peak at the beginning of the chromatogram indicates the presence of some nonretained impurities, namely contaminants and inorganic salts such as nh4no3, which are often co-extracted with the targeted biosurfactant, that may need to be separated. overall, based on the separation of peaks and retention time, the isolated biosurfactant was identified as surfactin. the surfactin titer of b. subtilis dsm10 was compared with the results from relevant studies (table 2). even though the fermentation strategies differ to some extent, the surfactin concentration from our work compares well with the values previously reported in the literature. 4. conclusion the aim of this study was to assess the biosurfactantproducing capability of bacillus subtilis dsm10 and establish an economically feasible fermentative process. this paper investigated the effect of ph control on the amount of biosurfactant production. the maximum amount of biosurfactant (approximately 5 g/l) was recovered from fermentation experiments in the absence of ph control at 37 ◦c. furthermore, a preliminary characterization of the surface-active compounds produced during fermentation was conducted. hplc analysis confirmed the presence of surfactin in the purified product. table 2: surfactin production by bacillus species strain surfactin titer [g/l] ref. b. subtilis atcc 21332 6.45 [16] b. subtilis 2.00 [27] b. subtilis spb1 4.92 [28] b. subtilis dsm10t 3.99 [29] b. subtilis #573 4.80 [6] b. subtilis cn2 7.15 [30] b. subtilis dsm10 4.99 this work 48(2) pp. 37–43 (2020) 42 czinkóczky and németh the minimum surface tension was 50 mn/m. the emulsifying activity achieved using sunflower oil was approximately 70%. these results represent an initial step towards large-scale production of this biosurfactant. from a technical and economic standpoint, the fermentative process of surfactin carried out in the absence of ph control in a mineral salt medium using glucose as the sole carbon source seems to be an effective strategy for pilotand industrial-scale production. acknowledgment the research was supported by the gedeon richter’s talentum foundation, founded by gedeon richter plc. 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alexander asanja jock *1, anietie ndarake okon1, uchechukwu herbert offor1, festus thomas2, and edmond okwudilichukwu agbanaje3 1department of chemical and petroleum engineering, university of uyo, pmb 1017, uyo, nigeria 2department of engineering infrastructure, national agency for science and engineering infrastructure (naseni), idu industrial area, pmb 391, garki-abuja, nigeria 3chemical and petroleum technique, department of science laboratory technology, university of jos, pmb 2084, jos, nigeria the removal of nickel ions onto calcined kaolin clay using a batch adsorption technique was conducted. the effect of the adsorbent mass, contact time and temperature on the removal process was investigated. the calcined kaolin clay was characterized using x-ray fluorescence (xrf) and fourier-transform infrared spectroscopy (ftir). the adsorption data was analyzed by isotherm, kinetic and thermodynamic studies. the major chemical components in the clay are alumina (41.14 wt %) and silica (53.16 wt %). ftir showed that the functional groups of aluminium monoxide (al-o) and silicon monoxide (si-o) are present in the clay. the study yielded a removal efficiency of 89.89% for nickel ions at 25 ◦c. the adsorption process appeared to follow a freundlich isotherm and pseudo-second order kinetics were found to be in good agreement with the experimental data. the thermodynamics of the rate processes showed the adsorption of nickel ions to be endothermic and negative values of gibbs free energy indicated the spontaneity of these processes. this proves that calcined kaolin clay is a good material for the removal of nickel ions from the wastewater produced by petroleum refineries. keywords: adsorption, kaolin, nickel, wastewater 1. introduction environmental pollution is an anthropogenic phenomenon and mainly a result of industrialization. the contamination of bodies of water by the indiscriminate disposal of heavy metals has led to serious threats to humans as well as aquatic and living creatures. nickel compounds are highly toxic contaminants and are emitted into the environment from various industries, e.g. mining, metal coatings, batteries, chemical, tanneries, etc., in quantities that pose risks to human health [1]. many wastewater treatment methods have been introduced to control water pollution such as chemical precipitation, ion exchange, electrodialysis, reverse osmosis as well as membrane filtration and adsorption. adsorption is one of the most efficient techniques due to its simplicity and affordability, moreover, it is more feasible even at low concentrations of heavy metal ions [2]. the adsorbent used for the adsorption process is of organic origin, e.g. activated carbon and biosorbents, or mineral origin, e.g. natural zeolite, calcium silicate powder and natural clay *correspondence: alsanja@gmail.com [3]. activated carbon is the most commonly used adsorbent for wastewater treatment but due to it expense, lowcost alternatives such as clay, coal, fly ash, peat, siderite, agricultural wastes and charcoal are being developed. low-cost adsorbents are those that require little processing and are abundant in nature, by-products or waste materials from industry [4]. clay minerals such as kaolinite, montmorillonite, vermiculite and illite are potential adsorbents of heavy metals. they have several economic advantages and intrinsic characteristics, e.g. are readily available, inexpensive, have excellent textural and surface properties, are physically and chemically stable in harsh environments as well as offer a cost-effective alternative to the conventional treatment of wastewater [5]. the aim of this study is to investigate the removal of nickel ions from wastewater produced by petroleum refineries using calcined kaolin clay from alkaleri in north-east nigeria. 2. materials and methods 2.1 beneficiation and calcination of samples 10 kg of raw kaolin clay was crushed and soaked in water for 24 hours. the clay-water mixture was plunged for 3 https://doi.org/10.33927/hjic-2020-26 mailto:alsanja@gmail.com 46 jock, okon, offor, thomas, and agbanaje hours at room temperature. colloidal kaolin clay was separated from the quartz-rich sediment and sieved through a 230 mesh tyler sieve to remove other coarse impurities. the thickened clay was then put in a filter cloth and pressed under hydraulic pressure to squeeze out the water. the cake was dried in an oven at 110 ◦c to constant weight before being pulverized. 100 g of the beneficiated clay was fired gradually in an electric furnace at 650 ◦c for 3 hours before being soaked. the calcined clay adsorbent was cooled, characterized and used for adsorption experiments. 2.2 batch adsorption the wastewater used of a known initial concentration of nickel ions was obtained from the effluent of a petroleum refinery operated by kaduna refining and petrochemicals company. the batch experiments were conducted by varying the adsorbent mass, contact time and temperature as described. the effect of the adsorbent mass was determined at 25 ◦c and 0.5 g of oven-dried calcined kaolin was mixed with 50 ml of wastewater in a 250 ml erlenmeyer flask. the mixture was stirred with a magnetic stirrer at 200 rpm for between 10 and 50 mins. the process was repeated by varying the adsorbent mass in increments of 0.5 g, namely 1.0, 1.5, 2.0 and 2.5 g. the effect of the contact time was analyzed using 0.5 g of adsorbent after 10, 20, 30, 40 and 50 mins. the effect of the temperature was investigated within the range of 25-65 ◦c following a contact time of 30 mins. with adsorbent masses of 0.5 and 2.5 g. the residual ni(ii) ions obtained from the filtrate and determined by atomic absorption spectroscopy (aas) were analyzed to evaluate the percentage removal, adsorption kinetics and thermodynamics. 3. results and discussion 3.1 characterization of the adsorbent chemical composition the chemical composition of the adsorbent is shown in table 1. the main components of the clay are sio2 (53.158 wt %) and al2o3 (41.143 wt %). metallic oxides such as tio2, mgo and fe2o3 are present in small amounts, while traces of cao, cr2o3, zno and mn2o3 are detected. the large amounts of sio2 and al2o3 present define the sample as an aluminosilicate clay. generally speaking, kaolin clay, the chemical formula of which is al2si2o5(oh)4, is principally composed of sio2, al2o3 and water [6]. figure 1: fourier-transform infrared spectrum of calcined kaolin clay fourier-transform infrared spectroscopy fourier transform infrared spectroscopy (ftir) shows the functional groups present in the sample of clay. the ftir spectra of the kaolin clay shown in fig. 1 are within the wavenumber range of 4000 400 cm−1. the spectra depict three major absorption bands, namely silicon dioxide, alumina and hydroxyl groups. the peaks at 1030, 1045 and 1049 cm−1 are assigned to the stretching vibrations of the si–o bond and the peak observed at 922 cm−1 corresponds to the al–al–oh bonds. peaks at 733, 750 and 752 cm−1 indicate the presence of oh resulting from the expulsion of water and hydroxyl groups in clay minerals during calcination [7]. the differences in the peak intensities can be attributed to the interaction of ni(ii) ions with functional groups on the kaolin adsorbent surface [8]. 3.2 adsorption studies effect of adsorbent mass the adsorbent mass plays a vital role in adsorption processes. it determines the percentage removal of metal ions and is calculated by: %ads = ci − cf ci (1) where %ads denotes the amount of ni(ii) ions removed, and ci and cf stand for the initial and final concentrations (ppm) of the ni(ii) ions, respectively. the percentage removal of ni(ii) ions increased from 76.31 to 89.04% when the adsorbent mass was increased from 0.5 to 2.5 g as shown in fig. 2. as the adsorbent mass increases, more adsorption sites of nickel ions become available. effect of contact time on the uptake of nickel ions the adsorption isotherm describes the adsorption pattern between the ni(ii) ions adsorbed on the kaolin clay and table 1: chemical composition of the calcined kaolin sample components sio2 al2o3 tio2 mgo fe2o3 cao cr2o3 zno mn2o3 amount (wt %) 53.158 41.143 3.017 0.442 0.126 0.044 0.018 0.013 0.008 hungarian journal of industry and chemistry adsorption of nickel ions onto calcined kaolin clay 47 figure 2: effect of adsorbent mass on the removal of nickel ion figure 3: effect of contact time on the uptake of nickel ions the residual ions. the equilibrium uptake was determined using: qe = (ci − ce)v m (2) where ce denotes the equilibrium concentration, v stands for the volume of the solution and m represents the adsorbent mass. fig. 3 shows that the uptake of nickel ions is increased by increasing the contact time and reaches a maximum or saturation point after 30 to 40 mins., and thereafter the rate of adsorption remains almost constant even as the contact time and adsorbent mass are further increased. the extent of the adsorption of nickel ions initially increased rapidly and then gradually until an equilibrium was attained. the high removal rate was due to the large surface area initially available for adsorption of ni(ii) ions but the capacity of the adsorbent was gradually exhausted over time since the occupation of the few vacant surface sites that remained was inhibited due to repulsive forces between the solute molecules in the solid and bulk phases [9]. as the adsorption sites on the surface become exhausted, the uptake rate is controlled by the rate at which the nickel ions are transported from the exterior to the interior sites of the adsorbent particles [10]. it was reported that during the adsorption of metal ions, initially the ni(ii) ions reach the boundary layer; then have to diffuse onto the surface of the adsorbent and finally, must diffuse into its porous structure. therefore, this process requires a relatively longer contact time [11]. figure 4: langmuir isotherm for the adsorption of nickel ions figure 5: freundlich isotherm for the adsorption of nickel ions 3.3 equilibrium isotherms the langmuir and freundlich models describe this isotherm: 1 qe = 1 qm + 1 qmbce (3) and log qe = logkf + 1 n log ce, (4) where qe denotes the uptake of ni(ii) ions adsorbed on the clay (mg/g), qm and b stand for the single-layer adsorption capacity (mg/g) and the langmuir equilibrium constant (l/mg), respectively, and kf, n and b represent freundlich adsorption constants. the langmuir and freundlich constants shown in table 2 were determined from the gradients and intercepts using the equations displayed in figs. 4 and 5. the magnitudes of kf and n are 0.2535 (mg/g)(l/mg)1/n and −5.08 l/mg, respectively. the constant, n, is related to the ionic strength with regard to the adsorption of ni(ii) ions and kf is related to both the ionic strength and amount of ni(ii) ions adsorbed. the significance of n is as follows: n < 1 (chemical process); n = 1 (linear process) and n > 1 (physical process). the negative value of n (−5.08 l/mg) obtained is indicative of chemical adsorption [12]. the langmuir constant, b, shows the affinity of binding sites for nickel ions of the adsorbent. similarly, the 48(2) pp. 45–49 (2020) 48 jock, okon, offor, thomas, and agbanaje table 2: parameters of freundlich and langmuir isotherm models freundlich model n (l/mg) kf (mg/g)(l/mg)1/n r2 (%) -5.08 0.2535 98.40 langmuir model qm (mg/g) b (l/mg) r2 (%) 0.2378 -11.5210 94.00 table 3: pseudo-kinetics constants for the adsorption of nickel onto calcined kaolin pseudo-first order kinetics pseudo-second order kinetics k1 = −0.0230 (l/min) k2 = 0.0073 (mg/(mg/min)) qe = 1.127 (mg/g) qe = 5.291 (mg/g) r2 = 0.87 r2 = 0.98 negative value of b (−11.5210 l/mg) suggests a low degree of adsorption of ni(ii) ions by kaolin clay as is shown by the maximum adsorption capacity, qm (0.2378 mg/g). the experimental data fitted well in the freundlich model (r2 = 98.40%) indicating multilayer adsorption on the heterogeneous surface. 3.4 adsorption kinetics the kinetics data were determined using the linear equations of pseudo-first and second order kinetics: log (qe − qt) = log qe − 1 2.303 k1t (5) and t qt = 1 k2q2e + t qe . (6) the parameters of adsorption kinetics are useful to predict the adsorption rate and provide considerable information to design and model the adsorption process as well as evaluate the adsorbent and operation control [13]. figs. 6 and 7 showed pseudo-first and second order kinetics, respectively with regard to the adsorption of ni(ii) ions. the kinetics constants are summarized in table 3. the pseudo-first order kinetics exhibit a higher rate constant (k1) and lower uptake (qe). according to the values of r2 in table 3, it is clear that pseudo-second order kinetics fitted better to the adsorption data. this suggests the adsorption process is controlled by a chemisorption mechanism and the rate-limiting step is probably the surface adsorption of nickel ions [5]. 3.5 adsorption thermodynamics the effect of temperature on the adsorption of nickel ions was investigated between 25 and 65 ◦c. the thermodynamic parameters determined from equations kc = qe ce (7) figure 6: pseudo-first order kinetics for the adsorption of nickel ions onto calcined kaolin clay figure 7: pseudo-second order kinetics for the adsorption of nickel ions onto calcined kaolin clay ∆g◦ = −rt lnkc (8) lnkc = −∆h◦ rt + ∆s◦ r (9) ∆g◦ = ∆h◦ − t∆s◦ (10) include changes in gibbs free energy (∆g◦), enthalpy (∆h◦) and entropy (∆s◦). fig. 8 depicts the van’t hoff plots used to evaluate the thermodynamic parameters summarized in table 4. the negative values of ∆g◦ confirm that the adsorption process is feasible and spontaneous while the positive values of ∆h◦ show that the adsorption process of ni(ii) ions is endothermic. ∆h◦ can indicate the type of adsorption process involved. if ∆h◦ of the adsorbent exceeds 40 or is less than 20 kj/mol, chemisorption or adsorption that is physical in nature occurs, respectively [8]. the positive values of ∆h◦ and ∆s◦ obtained show that the adsorption process is physical in nature and the solid-aqueous solution interface becomes more irregular and random during the adsorption of ni(ii) ions by the calcined kaolin adsorbent. 4. conclusions thermally activated kaolin clay as an adsorbent was successfully prepared by calcination and used to remove hungarian journal of industry and chemistry adsorption of nickel ions onto calcined kaolin clay 49 figure 8: effect of temperature with regard to the adsorption of nickel (ii) ions on calcined kaolin table 4: thermodynamic parameters for the adsorption of nickel (ii) ions onto calcined kaolin at 25 ◦c adsorbent mass (g) ∆g◦ (j/mol) ∆s◦ (j/mol k) ∆h◦(j/mol) r2 0.5 -875.26 62.27 17600.74 0.979 2.5 -2553.22 111.07 30545.64 0.951 nickel ions from wastewater produced by a petroleum refinery. adsorption isotherms, kinetics and thermodynamics were also studied. it was discovered that the adsorbent mass, contact time and temperature significantly influenced the adsorption of nickel ions onto the calcined kaolin adsorbent. the removal efficiency was increased by increasing the adsorbent mass, contact time and temperature. the adsorption data were described well by a freundlich isotherm and pseudo-second order kinetics fitted well to the adsorption process. the negative values of ∆g◦ indicated that the adsorption of nickel ions was feasible and spontaneous. the positive values of ∆h◦ showed that the process was endothermic and irreversible. generally speaking, the results revealed that calcined kaolin is a potential adsorbent for the treatment of wastewater laden with nickel ions produced by petroleum refineries. references [1] padmavathy, k. s.; madhu, g.; haseena, p. v.: a study on effects of ph, adsorbent dosage, time, initial concentration and adsorption isotherm study for the removal of hexavalent chromium (cr(vi)) from wastewater by magnetite nanoparticles. procedia technol., 2016, 24, 585–594 doi: 10.1016/j.protcy.2016.05.127 [2] zubir, m. h. m.; zaini, a. a. m.: twigsderived activated carbons via h3po4/zncl2 composite activation for methylene blue and congo red dyes removal. sci. 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https://doi.org/10.1016/j.ijbiomac.2020.07.032 https://doi.org/10.1016/j.ijbiomac.2020.07.032 https://doi.org/10.1155/2013/961671 hungarian journal of industry and chemistry vol. 48(2) pp. 51–53 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-27 considerations to approach membrane biofouling in microbial fuel cells szabolcs szakács *1 and péter bakonyi1 1research institute on bioengineering, membrane technology and energetics, university of pannonia, egyetem u. 10, 8200 veszprém, hungary among bioelectrochemical systems, those referred to as microbial fuel cells (mfcs) are widely implemented for wastewater management and simultaneous recovery of electrical energy. mfcs are fundamentally assisted by bacterial populations, mostly mixed cultures to be more exact that, after oxidizing the substrate, are capable of facilitating the passage of electrons to an electron acceptor, usually the anode. however, certain undesired bacterial strains often colonize not only the electrode but the membrane separator over time and cause severe biofouling. the membrane is an architectural element of many mfcs and determines the efficiency of the system. in this paper, this issue is overviewed briefly and some considerations concerning how to approach the problem are presented. keywords: microbial fuel cell, membrane, oxygen mass transfer, biofouling 1. introduction bioelectrochemical systems, including microbial fuel cells (mfcs), are often installed with a physical separator such as a membrane as illustrated in fig. 1 [1]. the membrane, which separates the anode from the cathode, should enable the adequate migration of ions (in this case, cations such as protons) between the electrodes to ensure the mfc continues to produce electricity [2]. furthermore, the membrane should function as a barrier against the crossover effect of substances to avoid the loss of the substrate (which normally is injected into the anode chamber in order to feed the species of electroactive bacteria shown in table 1 living on a biofilm on the electrically-conductive anode surface) and penetration of dissolved oxygen from the aerated cathode chamber to the anaerobic anode chamber [3]. in addition to these requirements which are associated with the physical and chemical properties of the material, the membranes should be relatively affordable. another point that needs to be addressed is the stability of the membrane, which can be influenced by the complex chemical environment of the bulk phases (anolyte in the anode chamber, catholyte in the cathode chamber) in an mfc and microbiological phenomena [5]. altogether, these effects may cause fouling of the membrane during its operation, moreover, when the underlying mechanism is associated with the metabolism and/or growth of microorganisms, the term “biofouling” is more appropriate [6]. in summary, various membranes can be evaluated *correspondence: szakacs.szabolcs@mk.uni-pannon.hu figure 1: scheme of an mfc and ranked based on the characteristics of the membrane materials (typically but not exclusively fabricated from polymers) and their observed behavior during mfc operation which can be monitored by various electrochemical measurements, e.g., recording the cell voltage, as presented in fig. 2. 2. membranes and biofouling in mfcs – the potential role of oxygen mass transfer in accordance with the previous section, the membrane separator divides the anaerobic anode chamber from the aerobic cathode chamber [7]. therefore, it is reasonable to assume that the actual microbial communities developing on the anode and the membrane have completely different structures and relationships with gaseous oxygen. from the literature, it can be concluded with a good degree of certainty that the electrochemically active bacteria https://doi.org/10.33927/hjic-2020-27 mailto:szakacs.szabolcs@mk.uni-pannon.hu 52 szakács, and bakonyi table 1: electroactive species of bacteria and their oxygen tolerance [4] species oxygen tolerance e. coli facultatively anaerobic https://bacdive.dsmz.de/strain/4907 shewanella oneidensis facultatively anaerobic https://img.jgi.doe.gov/cgi-bin/m/main.cgi?section= taxondetail&page=taxondetail&taxon_oid=637000258 geobacter sulfurreducens strict anaerobe https://bacdive.dsmz.de/strain/5792 geobacter metallireducens strict anaerobe https://bacdive.dsmz.de/strain/5791 desulfobulbus propionicus strict anaerobe https://bacdive.dsmz.de/strain/4004 geothrix fermentans strict anaerobe https://bacdive.dsmz.de/strain/17672 paracoccus pantotrophus facultatively anaerobic https://bacdive.dsmz.de/strain/13703 rhodopseudomonas palustris dx-1 strict anaerobe https://bacdive.dsmz.de/strain/1819 on the anode are either strict or facultative anaerobes as shown in table 1 [4]. however, a considerable knowledge gap seems to exist concerning the populations attached to the surface of the membrane and the occurrence of biofouling. in contrast, it is reasonable to suppose that these membrane-bound colonies and biofilms are more tolerant of dissolved oxygen due to the technically direct and long-lasting contact with this substance. in general, the oxygen flux across a membrane in mfcs is described by the oxygen transfer coefficient which can be calculated by [8, 9] ko = − v at ln [ (c0 − c) c0 ] (1) where ko denotes the oxygen transfer coefficient (cm3/cm2s), v stands for the volume of liquid (cm3), a represents the surface area of the membrane (cm2), c0 refers to the saturation oxygen concentration (mol/dm3), c is the actual oxygen concentration measured (mol/dm3) and t denotes the time of the measurement (s); and ko = do l (2) where do stands for the oxygen diffusion coefficient (cm2/s) and l represents the thickness of the membrane (cm). figure 2: schematic diagram of the mfc therefore, it is worth examining which strains colonize the membrane and how these mixed communities vary depending on ko. even though some previous papers have demonstrated the use of various microscopic imaging techniques based on visual observations to study these biofouling layers on the surface of membranes [10–12], qualitative and quantitative feedback to highlight “what type of” and “how many” microbes can coexist is scarce. as a result, experimental methodology involving the apparatus of modern molecular biology, e.g. dna-based identification, should be encouraged and implemented to answer such questions [13]. 3. conclusions the capability of membranes to permeate dissolved oxygen in microbial fuel cells is key. on the one hand, reduced oxygen transport membranes (otms) are likely to maintain the typically less oxygen tolerant, electroactive bacteria located on the surface of the anode in a good condition. on the other hand, oxygen mass transfer through the membrane is expected to affect the biofouling of the separator and thus, how microbial communities respond to changes in material properties, in particular ko, needs to be understood. the assessment of membranes with different values of ko should be carried out relative to nafion, which is by far the most broadly employed polymer for benchmarking studies [14]. acknowledgement this work was supported by the national research, development and innovation office (nkfih, hungary) under grant number fk 131409 and ginop-2.3.2-15-201600016 excellence of strategic r+d workshops, entitled “development of modular, mobile water treatment systems and waste water treatment technologies based on university of pannonia to enhance growing dynamic export of hungary” (2016-2020) hungarian journal of industry and chemistry https://bacdive.dsmz.de/strain/4907 https://img.jgi.doe.gov/cgi-bin/m/main.cgi?section=taxondetail&page=taxondetail&taxon_oid=637000258 https://img.jgi.doe.gov/cgi-bin/m/main.cgi?section=taxondetail&page=taxondetail&taxon_oid=637000258 https://bacdive.dsmz.de/strain/5792 https://bacdive.dsmz.de/strain/5791 https://bacdive.dsmz.de/strain/4004 https://bacdive.dsmz.de/strain/17672 https://bacdive.dsmz.de/strain/13703 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and research, university of pannonia, gasparich márk u. 18/a, 8900 zalaegerszeg, hungary a new energy-based chaining criterion was introduced in dipolar systems based on an earlier article by the author, in which the probability of chaining for adjacent particles in a new formula of magnetic susceptibility was used. the probability of chaining and the magnitude of the energy criterion can be calculated from the monte carlo (mc) simulation values of magnetic susceptibility. the energy criterion also depends on the dipole moment and the density. at high densities, the energy criterion is well below 70−75%. in addition, it was confirmed by simulation results that the chain length distribution follows a geometric distribution. how the probability of chaining depends on the energy criterion was given empirically and two parameters were fitted to it. keywords: dipolar fluids, chain formation, energy criterion 1. introduction according to the literature, the criterion of chaining in dipolar systems is unclear. usually, an energy criterion is used to decide whether two adjacent particles form part of a chain. the energy criterion defines the limit at a certain level of interaction energy between them, which is usually 70 − 75% of the minimum pair interaction energy [1–4]. according to another definition, if the pair interaction energy is negative and the two particles are closer together than 1.3 in diameter unit, then chaining occurs [5, 6]. the problem with this is that the minimum pair interaction energy depends on the magnitude of the dipole moment, so an identical amount of pair interaction energy between two adjacent particles indicates chaining in one case but not in the other. in another article, the author examined [7] the probability density function of pair interaction energies in a dipolar hard sphere (dhs) system and found that no unit jump-like change in the frequency of the pair interaction energy would justify the introduction of a general criterion based on the pair interaction energy. furthermore, such a general definition does not take into account the effect of density, while it can be assumed that chaining occurs at different densities and different energy levels of the same dipole moments. therefore, this study seeks to determine the magnitude of the energy criterion from another source, that is, a real, measurable, physical parameter. the physical parameter *correspondence: sata123.sandor@gmail.com in this case is magnetic susceptibility. in a previous article [8], the author stated that the chain length distribution in dipolar fluids follows a geometric distribution. if the probability that two adjacent particles form a chain is denoted by p, it can be deduced that the chain length distribution is gk = (1− p) pk−1, (1) where k stands for the chain length. the particle size distribution, which yields the proportion of particles in exactly k-long chains is hk = (1− p)2kpk−1. (2) the average chain length is derived from the properties of the geometric distribution: 1/(1− p). assuming that a chain of length k behaves as if its dipole moment is km, its initial magnetic susceptibility can be deduced (in c.g.s. units) as χ0 = 1 + p 1− p χl ( 1 + 4π 3 χl ) , (3) where χl denotes langevin susceptibility [9], χl = ρm2 3kbt , (4) ρ stands for the density, t represents the temperature, and kb refers to the boltzmann constant. in eq. 3, the expression χp = χl ( 1 + 4π 3 χl ) (5) https://doi.org/10.33927/hjic-2020-28 mailto:sata123.sandor@gmail.com 56 nagy calculates the initial magnetic susceptibility from pshenichnikov’s theory [10]. eq. 3 can be used to determine the value of p at a given density and dipole moment, since χ0 can be determined from simulations and χp can be calculated exactly from p = χ0 − χp χ0 + χp . (6) if the occurrence of chaining is linked to an energy criterion, it is clear that the value of p depends on the magnitude of the energy criterion. thus, if the correct value of p is known from eq. 6, the magnitude of the correct energy criterion can be obtained from the relationship p − ulim. the structure of the results is as follows: firstly, through several examples, it is shown that for any energy criterion, the number of chains follows a geometric distribution; secondly, the p values calculated from the magnetic susceptibility values are given; thirdly, from simulations, the ulim values are determined that provide the desired p value at a given density and dipole moment; finally, by fitting, an empirical formula is derived to describe the relationship p− ulim. 2. simulations and results monte carlo simulations of dhs fluids were performed using a canonical nvt ensemble. boltzmann sampling [11], periodic boundary conditions and the minimumimage convention were applied. in order to take into account the long-range character of the dipolar interaction, the reaction field method under periodic boundary conditions of conduction was used. after 100, 000 equilibration periods, 1, 000, 000 production cycles were conducted involving n = 1, 000 particles. the reduced density was calculated by ρ∗ = ρσ3 and the reduced dipole moment by m∗ = m/ √ σ3kbt , where σ denotes the diameter of the particles. the pair interaction energy between two particles in a dhs system is determined only by the dipolar energy: udd ij = −m 2 r3ij [3 (m̂i · r̂ij) (m̂j · r̂ij)− (m̂i · m̂j)] , (7) where the particles have dipole moments of strength m of an orientation given by unit vector m̂, moreover, the distance between the centers of the particles is denoted by rij and r̂ij = rij/rij . the dots symbolize the scalar product. the lowest and most favorable energy value was determined by udd min = −2m2/σ3. the magnitude of the energy criterion (u) was given in the usual way in proportion to this: u = udd/udd min. to determine the chain length distribution (gk), the number of chains of a given length was counted in each cycle. this required a predefined energy criterion. rearranging eq. 1 leads to the chain length distribution: lg (gk) = lg (1− p) + (k − 1) lg (p) . (8) figure 1: the logarithm of the chain length distribution as a function of chain length at six different dipole moments, densities and energy criteria. according to eq. 8, the value of p (probability of chaining) is also derived from the gradient of the fitted lines as well as the intercept of the vertical axis. from this, it can be seen that if the logarithm of the chain length distribution is plotted as a function of k − 1, the gradient of the fitted straight line yields the logarithm p, while the logarithm of the vertical intercept gives 1 − p. since in each case the resulting lines are linear, it follows that the chain length distribution does indeed follow a geometric distribution. fig. 1 shows the simulation results for the chain length distribution obtained for six different combinations of dipole moments, densities and energy criteria. it can be seen that the fitted lines are linear on the logarithmic scale in all cases. it is clear from the inset graphs that the larger its gradient, the closer its intercept is to zero. the p values shown in fig. 1 were derived from the gradient of the fitted lines. further results are summarized in table 1. in the third column of table 1, using the terms mentioned in the introduction (section 1), the values of p are given. the values of χp can be precisely calculated from eq. 5. the values of χ0 are derived from the simulations. (for the simulation results of χ0, reference [12] was used. the missing χ0 data were supplemented with our own simulation results.) this was followed by the determination of ulim, also from our own simulations. according to eq. 2, the number of particles that do not form a chain or, in other words, which form single-element chains is h1 = (1− p)2. thus, in each step of the simulation, it was only nechungarian journal of industry and chemistry new chaining criteria in dipolar fluids based on monte carlo simulations 57 table 1: the probabilities of chaining (3rd column), the values of the energy criterion (4th column) according to the simulations and the values of the fitted curves (5th and 6th columns) according to eq. 9 (m∗)2 ρ∗ p ulim a b 2 0.1 0.0135 0.74 0.203 2.902 2 0.2 0.0209 0.76 0.358 2.864 2 0.3 0.0316 0.75 0.492 2.863 2 0.4 0.0231 0.80 0.623 2.881 2 0.5 0.0254 0.80 0.751 2.893 2 0.6 0.0387 0.78 0.885 2.901 2 0.7 0.0523 0.77 1.022 2.895 2 0.8 0.1674 0.66 1.167 2.874 2 0.9 0.2641 0.62 1.307 2.821 3 0.1 0.0802 0.68 0.426 2.284 3 0.2 0.0951 0.71 0.607 2.291 3 0.3 0.0772 0.75 0.732 2.333 3 0.4 0.0721 0.77 0.839 2.388 3 0.5 0.0762 0.77 0.943 2.442 3 0.6 0.0840 0.76 1.048 2.498 3 0.7 0.1889 0.67 1.154 2.535 3 0.8 0.3788 0.57 1.270 2.560 3 0.9 0.6745 0.45 1.383 2.547 4 0.1 0.2183 0.67 0.761 1.801 4 0.2 0.1777 0.73 0.900 1.842 4 0.3 0.1278 0.77 0.975 1.900 4 0.4 0.1174 0.78 1.044 1.989 4 0.5 0.1169 0.78 1.107 2.069 4 0.6 0.1818 0.72 1.180 2.159 4 0.7 0.4016 0.59 1.258 2.237 4 0.8 0.6814 0.46 1.341 2.295 essary to count how many particles have the minimum pair interaction energy (counted individually for the other particles) greater than the examined energy criterion. this greatly simplified the complexity of the simulations. therefore, the value of p belonging to the given energy criterion was determined, and for each dipole moment and density, a function was generated to create a relationship between p and ulim. of these, four are shown in fig. 2. the dashed lines indicate the ulim values of the already defined p values of these functions. the fourth column of table 1 shows the ulim values for each dipole moment, density and value of p which are also plotted in fig. 3. (the uncertainty of the functions shown in fig. 3 stems from the uncertainty of the magnetic susceptibilities. for dipole moments less than (m∗)2 = 2, this new energy criterion cannot be examined precisely because the uncertainty in the magnetic susceptibility is too great.) it can be seen that the frequently mentioned 70 − 75% criterion is more or less valid, although it differs significantly from it at high densities. interestingly, the energy criterion is higher at medium densities than at low densities. this may be because the figure 2: the probability of chaining as a function of the value of the energy criterion at four different dipole moments and densities. the dashed lines show the true values of p and thus ulim as well. chains are so close to each other at medium densities that they have an effect on each other, but do not at low densities. it is true that at high densities this effect is even stronger, but at the same time, the strength of the forces acting on the chain also increases. in the following, the relationships between the p − ulim functions are specified by fitting. four of these are shown in fig. 2. in fig. 4, for each of the three dipole moments examined, these functions are plotted at two densities. since the functions are close to zero around ulim = 1, the cosine function seems to be a good choice for describing the curves as follows: p = acosb (π 2 ulim ) (9) figure 3: the values of ulim as a function of the reduced density at three different dipole moments. 48(2) pp. 55–58 (2020) 58 nagy figure 4: the probability of chaining as a function of the energy criterion at three different dipole moments. dashed lines refer to low densities (ρ∗ = 0.1), solid lines refer to high densities (ρ∗ = 0.8). the lines of intermediate densities are between these two lines. where a and b are constants and their magnitudes are given in the fifth and sixth columns of table 1. fits were made within the range ulim = 0.5−1. the absolute error in the values of p is not greater than 0.01285 in all the cases examined. 3. conclusion the main result of this article is shown in fig. 3. a well-explained energy-based chaining criterion resulting from magnetic susceptibility was defined. from the simulated values of magnetic susceptibility, the probability of chaining was calculated. from this, the magnitude of the chaining criterion was derived using simulations as well. therefore, a well-explained theory was developed to define the chaining energy criterion, which produced different results for different values of density and dipole moment in dhs systems. the criterion value of 70−75% commonly given in the literature is only approximately true at low densities (ρ∗ ≤ 0.3). at medium densities (0.3 < ρ∗ < 0.6), the values are generally higher, while at high densities (ρ∗ ≥ 0.6), they are much lower. acknowledgement this research was supported by the european union and co-financed by the european social fund under the project efop-3.6.2-16-2017-00002. references [1] ivanov, a. o.; wang, z.; holm, c.: applying the chain formation model to magnetic properties of aggregated ferrofluids, phys. rev. e, 2004, 69(3), 031206 doi: 10.1103/physreve.69.031206 [2] wang, z.; holm, c.; müller, h. w.: molecular dynamics study on the equilibrium magnetization properties and structure of ferrofluids, phys. rev. e, 2002, 66(2), 021405 doi: 10.1103/physreve.66.021405 [3] valiskó, m.; varga, t.; baczoni, a.; boda, d.: the structure of strongly dipolar hard sphere fluids with extended dipoles by monte carlo simulations, mol. phys., 2010, 108(1), 87–96 doi: 10.1080/00268970903514553 [4] tavares, j. m.; weis, j. j.; telo da gama, m. m.: strongly dipolar fluids at low densities compared to living polymers, phys. rev. e, 1999, 59(4), 4388– 4395 doi: 10.1103/physreve.59.4388 [5] kantorovich, s.; ivanov, a. o.; rovigatti, l.; tavares, j. m.; sciortino, f.: nonmonotonic magnetic susceptibility of dipolar hard-spheres at low temperature and density, phys. rev. lett., 2013, 110(14), 148306 doi: 10.1103/physrevlett.110.148306 [6] rovigatti, l.; russo, j.; sciortino, f.: structural properties of the dipolar hard-sphere fluid at low temperatures and densities, soft matt., 2012, 8(23), 6310–6319 doi: 10.1039/c2sm25192b [7] nagy, s.: the frequency of the two lowest energies of interaction in dipolar hard sphere systems, anal. tech. szeged., 2020, 14(2) in press [8] nagy, s.: the initial magnetic susceptibility of dense aggregated dipolar fluids, hung. j. ind. chem., 2018, 46(2), 47–54 doi: 10.1515/hjic-2018-0018 [9] langevin, p.: sur la théorie du magnétisme, j. phys. theor. appl., 1905, 4(1), 678–693 doi: 10.1051/jphystap:019050040067800 [10] pshenichnikov, a. f.; mekhonoshin, v. v.: equilibrium magnetization and microstructure of the system of superparamagnetic interacting particles: numerical simulation, j. magn. magn. mater., 2000, 213(3), 357–369 doi: 10.1016/s0304-8853(99)00829-x [11] allen, m. p.; tildesley, d. j.: computer simulation of liquids (clarendon press, oxford) 1987, isbn: 978-0-198-55645-9 [12] theiss, m.; gross, j.: dipolar hard spheres: comprehensive data from monte carlo simulations, j. chem. eng. data, 2019, 64(2), 827–832 doi: 10.1021/acs.jced.8b01169 hungarian journal of industry and chemistry https://doi.org/10.1103/physreve.69.031206 https://doi.org/10.1103/physreve.66.021405 https://doi.org/10.1080/00268970903514553 https://doi.org/10.1080/00268970903514553 https://doi.org/10.1103/physreve.59.4388 https://doi.org/10.1103/physrevlett.110.148306 https://doi.org/10.1039/c2sm25192b https://doi.org/10.1515/hjic-2018-0018 https://doi.org/10.1051/jphystap:019050040067800 https://doi.org/10.1051/jphystap:019050040067800 https://doi.org/10.1016/s0304-8853(99)00829-x https://doi.org/10.1021/acs.jced.8b01169 https://doi.org/10.1021/acs.jced.8b01169 hungarian journal of industry and chemistry vol. 48(2) pp. 59–64 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-29 temperature and electric field dependence of the viscosity of electrorheological (er) fluids: warming up of an electrorheological clutch sándor mester1 and istván szalai *1 1institute of mechatronics engineering and research, university of pannonia, gasparich márk u. 18/a, zalaegerszeg, 8900, hungary cognition of the temperature-dependence of intelligent fluids, e.g. electrorheological (er) and magnetorheological (mr) fluids, is critical for their application. in this paper, the dependence of the viscosity of er fluids on temperature and electric field strength is examined. a new correlation equation is presented to describe the dependence of the viscosity on temperature by extending the andrade equation. considering the dependence of viscosity on the electric field strength and temperature, that equation is used to model the warming up of an er clutch. keywords: electrorheological fluid, viscosity, heat effect in er fluids, er clutch 1. introduction electrorheological (er) fluids are suspensions made by dispersing micron-sized solid particles with a relative permittivity of εp into a carrier fluid with a smaller relative permittivity of εf [1–3]. normally, small concentrations of stabilizers are also used to avoid sedimentation. the structure and, therefore, the rheological properties are altered by applying an external electric field. the dispersed particles, guided by the electric field, form chain-like structures [4]. these structures impair the motion of the suspended particles resulting in an increase in the apparent viscosity. using silicone oil as the carrier fluid is common, although other oils such as transformer oil have also been examined. the dispersed phase can consist of oxides, carbides, etc. er and magnetorheological (mr) fluids are used in various applications, e.g. couplings, shock dampers, [5, 6] ultra-smooth polishing materials, etc. [7]. most of the applications require the viscosity to be precisely adjusted, however, the viscosity alters as the temperature changes. [8,9] this disadvantage greatly limits its industrial use, as a change can impair fine-tuned systems by creating stern operating conditions. apart from the need to measure the temperature, the dependence of the parameters of the er fluids on temperature ought to be considered as well. in addition to the er effect, an er fluid is also affected by the thermal motion of particles. this motion works against the er effect, as it disrupts the chain-like structure [10, 11]. *correspondence: szalai@almos.uni-pannon.hu 2. experimental the dependence of the viscosity of fluids on the temperature is characterized by a law proposed by andrade: η = a e b t , (1) where η denotes the dynamic viscosity of the fluid, t stands for the temperature, whilea andb represent characteristic constants of the fluid. the constants are experimentally defined for each fluid. for er fluids, this equation is inadequate because their dependency on the electric field strength is not addressed. in the following chapters, the dependence on the electric field in eq. 1 is introduced. 2.1 samples and viscosity measurements to study the thermal and field effects, an anton paar physica mcr 301 rotational rheometer was used to measure the viscosity. different measuring equipment can be used for mr and er fluids, moreover, the samples can also be thermostated. the usage of a cylindrical probe is shown schematically in fig. 1. the length of the probe was l = 40.046 mm, the radius of the probe was ri = 13.33 mm and the inner radius of the chamber was re = 14.46 mm. for the measurements, a self-prepared er fluid was used. the carrier fluid was silicone oil with a viscosity of 1000 mpas at 298 k. the dispersed phase was silica powder of 0.5 − 10 µm in diameter (as the manufacturer https://doi.org/10.33927/hjic-2020-29 mailto:szalai@almos.uni-pannon.hu 60 mester and szalai figure 1: schematic representation of the probe claims that 80% of the particles have diameters of between 1 and 5 µm). as a result, three different concentrations of particles were investigated, namely 10, 20 and 30 wt%. the samples were prepared through a multi-step procedure: after stirring by hand, the fluid was placed in an ultrasonic bath for 15 minutes to mix further. to ensure an air bubble-free er fluid, the sample was exposed to a vacuum for 10 minutes before being placed in the rheometer. the samples were measured at six different temperatures at increments of 10 k ranging from 293 k to 343 k. considering the 1.13 mm gap at the measuring probe, the used voltages resulted in the following electrical field strengths: 0, 0.442, 0.885, 1.327 and 1.769 mv/m. the samples were constantly stirred in the rheometer. a two-minute-long stirring cycle in the absence of an electric field came after setting the temperature. a tenminute-long measuring cycle with an electric field was applied and another one-minute-long stirring cycle followed in the absence of an external electric field. the two mixing cycles at the beginning and end ensured that no residual particle arrangements from the previous measurements were present. the viscosity was measured per second. 3. measurement results and analysis 3.1 temperature dependence of the viscosity as an example, the measurement results of an 30 wt% er fluid at a temperature of 293 k are shown in fig. 2: after an initial rise (while the chain-like structure was forming), the viscosity became roughly constant. the anomalies in the figure were caused by external interferences. for the analysis, the results of a specific mixing ratio, electric field strength and temperature were averaged into figure 2: viscosity measurements under various electric field strengths, c = 30%, t = 295 k figure 3: experimental results and fitted curves (eq. 2) of viscosity at c = 10% under various electric field strengths a single value. the expected tendencies are as follows: as the electric field strength increases, so does the viscosity, while a rise in temperature is inversely proportional to the viscosity. it was found that eq. 1 is inappropriate for the exact representation of the dependence of er viscosity data on temperature, therefore, in terms of the pre-exponential factor, a further temperature dependence was proposed: η = (a0 +a1t ) e b t , (2) where a0, a1 and b denote constants derived by fitting eq. 2 to measurement data. figs. 3–5 demonstrate the fitted curves of the different concentrations of er fluid. the extended formula (eq. 2) correlates well with the measurements: the worst coefficient of determination for the fittings is r2 = 97.3 %. eq. 2 can be used to describe the viscosity of electrorheological fluids as a function of the temperature. hungarian journal of industry and chemistry temperature and electric field dependence of the viscosity of er fluids 61 figure 4: experimental results and fitted curves (eq. 2) of viscosity at c = 20% under various electric field strengths figure 5: experimental results and fitted curves (eq. 2) of viscosity at c = 30% under various electric field strengths 3.2 electric field strength dependence of viscosity the introduced formula does not concern how the viscosity depends on the electric field strength. in the case of many practical applications, the electric field changes, therefore, the temperature-dependent description of viscosity alone is insufficient. eq. 2 can be extended by making the pre-exponential factor dependent on the electric field strength as well. this expansion is carried out via the square of the electric field, indicating that the direction of the field is reversible: η = [ a0 +a1e 2 + ( a2 +a3e 2 ) t ] e b t (3) where a0, a1, a2, a3 and b denote constants, while e stands for the electric field strength. eq. 3 fitted to the measurement data can be seen in figs. 6–8. here the viscosity is represented as a function of the electric field strength and temperature. the coefficients of determination for the fittings are r2 10% = 99.62%, r2 20% = 98.62% and r2 30% = 99.06%. fitting parameters are summarized in table 1. figure 6: viscosity measurement data (•) and the fitted surface (eq. 3) at c = 10% figure 7: viscosity measurement data (•) and the fitted surface (eq. 3) at c = 20% figure 8: viscosity measurement data (•) and the fitted surface (eq. 3) at c = 30% 48(2) pp. 59–64 (2020) 62 mester and szalai table 1: fitted coefficients of eq. 3 at different er fluid concentrations concentration [m/m] 10% 20% 30% a0 -2.17623e-4 0.12252 3.82564 a1 2.47298e-16 2.2336e-14 5.10306e-13 a2 9.7734e-6 -2.32975e-4 -9.89e-3 a3 -6.84985e-19 -5.8753e-17 -1.2747e-15 b 1831.25188 1017.00608 3.82564 figure 9: cylindrical er clutch model for the dissipation of viscous energy 4. temperature rise in an er clutch 4.1 er clutch model a schematic diagram of a simple cylindrical electrorheological clutch is shown in fig. 9. nakamura et al. [12] described the temperature rise of similar clutches: their model consisted of several cylinders with gaps between them with radii from r(i) to r(i+1), where i = 1, 2 . . . n denotes the number of gaps which are filled with er fluid with a viscosity of η. according to the model, assuming the clutch is insulated, the dissipation of the viscous energy per second in the gap i is dei = ∂(τarω) ∂r dr, (4) where a denotes the surface of the cylinder, τ stands for the shear stress and ω represents the rotational speed. by utilizing the attributes of the cylinders and integrating the formula, the following equation can be derived: t (t+ ∆t) = 1 c { n∑ i=1 2πhη(t )ω2r(i) 3 s ∆t } + t (t) , (5) where t denotes the temperature, s stands for the gap, c represents the heat capacity of the fluid, ω refers to the relative rotational speed and h is the height of the cylinder. in our system, only one gap is examined so eq. 5 can be simplified to a differential equation: dt dt = 2πhω2r3 sc η(t ). (6) 4.2 viscous energy dissipation in the clutch using the model of the er clutch (eq. 6), the viscous energy dissipation was calculated by inserting the formula of the viscosity (eq.3): 1 [a0 +a1e2 + (a2 +a3e2)t ] e b t dt = 2πhω2r3 sc dt. (7) the integration of the left-hand side of the equation can be solved numerically using mathematical software. analytical integration requires the expansion of the exponential term into a taylor series:∫ e − b t [a0 +a1e2 + (a2 +a3e2)t ] dt = = ∫ 1 − b t + 1 2! b2 t 2 − 1 3! b3 t 3 + [a0 +a1 · e2 + (a2 +a3e2)t ] dt (8) eq. 7 can be integrated following the expansion into a taylor series resulting in the following expression: t2∫ t1 1 [a0 +a1e2 + (a2 +a3e2)t ] e b t dt = (−1) 0 b0 0! 1 a0 [ 1 c ln (1 + ct ) ]t2 t1 + + (−1) 1 b1 1! 1 a0 [ c1−1(−1) 1 ln 1 + ct t ]t2 t1 + + ∞∑ i=2 (−1) i bi i! 1 a0 ci−1(−1) i ln 1 + ct t + i∑ j=2 (−1) i−j+1 ci−j (j − 1)t j−1 t2 t1 , (9) hungarian journal of industry and chemistry temperature and electric field dependence of the viscosity of er fluids 63 figure 10: heating of an er clutch model as a function of the number of addends, c = 30%, e = 1.327 mv/m and t = 295 k figure 11: heating of an er clutch model over time, c = 10% where a0 = a0 +a1e 2 and c = a2 +a3e 2 a0 . the expression in eq. 9 can be used to calculate the time needed for the clutch to be heated to a given temperature. the closed formula, a double infinite sum, yields varying results depending on how many terms are used. in the present calculation, the following parameters are used: h = 0.04 m, r = 0.0133 m, s = 0.0113 m, ω = 4.057 rad/s and c = 0.05 j/k. the temperature as a function of the number of addends n is shown in fig. 10. after the 5th addend, the numerical and analytical solutions are almost identical. to calculate the amount of heating, the physical properties of the anton paar probe and the calculated parameters (a0, a1, etc.) of the examined er fluids were used. figs. 11–13 show the heating results using three different concentrations of er fluids. as can be observed, as the electric field strength and concentration increase, the temperature also rises faster due to the internal friction. figure 12: heating of an er clutch model over time, c = 20% figure 13: heating of an er clutch model over time, c = 30% 5. conclusion in our paper, a new correlation equation was proposed to describe the dependence of the viscosity of er fluids on temperature and electric field strength. the proposed equation describes the measurement results with a correspondingly small deviation. the temperature rise of the model system examined by using the aforementioned equations can also form the basis for the description of real systems. the applied model can be further refined, e.g. by taking into account the dependence of heat capacities on temperature. acknowledgement this research was supported by the european union and co-financed by the european social fund under project efop-3.6.2-16-2017-00002. references [1] shin, k.; kim, d.; cho, j.-c.; lim, h. s.; kim, j. w.; suh, k. d.: monodisperse conducting colloidal dipoles with symmetric dimer structure for enhancing electrorheology properties, j. coll. interf. sci., 2012, 374(1), 18–24 doi: 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https://doi.org/10.1016/j.ijleo.2017.11.055 https://doi.org/10.1088/1742-6596/412/1/012008 https://doi.org/10.1088/1742-6596/412/1/012008 https://doi.org/10.3221/igf-esis.23.06 https://doi.org/10.4028/www.scientific.net/amr.594-597.2836 https://doi.org/10.4028/www.scientific.net/amr.594-597.2836 https://doi.org/10.1177/1045389x03014002003 https://doi.org/10.1177/1045389x03014002003 introduction entomopathogenic nematodes and bacteria antimicrobial compounds conclusion introduction membrane-aerated bioreactors for the treatment of wastewater fermentation of itaconic acid enzymatic removal of glucose conclusion introduction experimental samples and measurements analysis results and analysis experiments effect of water content discussion conclusion introduction problem statement system configuration sliding mode control follow-up control equations of the system filter and load the states of the state-space equation error trajectory control law simple relay double relay double relay with dead zone and hysteresis stability analysis simulation matlab-simulink model model validation analysis of the simulation results non-linear load switching on the load conclusions introduction results: methodology reference database laws and regulations pertaining to the investigation determination of the environmental parameters for the environmental elements studied weight of environmental parameters analysis of parameters environmental parameter quality indicator (pi) immission analysis analysis of the environmental element level load of environmental elements (elj) qualification of environmental elements theoretical number of environmental parameters (ntj) practical number of environmental parameters (npj) element quality index (iej) element quality factor (fej) environmental element informativity rate (fij) environmental analysis element quality indicator (ej) total environmental load (tl) qualification of the total environment environment informativity rate (fenv.i) informative environment qualifying index (iieq) a case study conclusion introduction materials and methods cultivation conditions analysis of biomass analysis of glucose consumption analysis of biosurfactants surface tension measurement emulsifying activity high-performance liquid chromatography (hplc) isolation of the biosurfactant calculation of fermentation parameters results and discussion conclusion introduction materials and methods beneficiation and calcination of samples batch adsorption results and discussion characterization of the adsorbent chemical composition fourier-transform infrared spectroscopy adsorption studies effect of adsorbent mass effect of contact time on the uptake of nickel ions equilibrium isotherms adsorption kinetics adsorption thermodynamics conclusions introduction membranes and biofouling in mfcs – the potential role of oxygen mass transfer conclusions introduction simulations and results conclusion introduction experimental samples and viscosity measurements measurement results and analysis temperature dependence of the viscosity electric field strength dependence of viscosity temperature rise in an er clutch er clutch model viscous energy dissipation in the clutch conclusion untitled hungarian journal of industry and chemistry vol. 52(1) pp. 37–43 (2024) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2024-06 experimental investigation of hardness and surface roughness in the friction stir welding of the 6061-t6 aluminum alloy mohamed bouamama1*, azzeddine belaziz1, abbes elmeiche2, imane elmeguenni1 and abdelhak elhannani3 1 center of research in mechanics (crm), bp n73b, freres ferrad, ain el bey, constantine, 25021, algeria 2 laboratory of structures mechanics and solids (lmss), faculty of technology, university of sidi bel abbes, sidi bel abbes, 22000, algeria 3 ahmed ben yahia el wancharissi university centre of tissemsilt, tissemsilt, 38000, algeria the interesting process of friction stir welding (fsw) has become popular for connecting a variety of materials. it is crucial for the industry to have an effective assembly process that uses little energy and has a lot of potential regarding mechanical strength. however, the complexity and unpredictability of fsw joints means that their behavior has a significant impact on the dynamic properties of such structures. therefore, the primary goal of this research project is to experimentally investigate the impact of rotational speed and feed rate on the surface condition of joints. the study takes into account the variance in surface roughness (rz), which is crucial when determining the quality of joints. these experiments will help researchers to better understand how these two characteristics affect the surface quality of joints. such knowledge is crucial for the industry because it may help to develop effective fsw joints with increased mechanical strength. keywords: friction stir welding (fsw), assembly, aluminum 6061-t6, hardness, surface roughness (rz) 1. introduction welding is a process which consists of creating a permanent connection between two or more parts whose compositions are identical or different by simultaneously applying heat, pressure or a combination of heat and pressure. although metals and thermoplastics are typically welded, wood can also be. friction stir welding (fsw) is an innovative welding process with numerous applications across various industrial sectors, including the naval, aeronautical, aerospace, railway and automotive industries [1]-[2]. during the early 1990s, fsw emerged as an innovative solid-state joining process, originally developed by the welding institute in the uk. this method produces high-quality, defectfree joints with enhanced mechanical properties in comparison to fusion welding [3]. fsw involves blending the base material through the utilization of a tool comprised of a pin and a shoulder that interact with the upper surface of the sheet to be joined [4]. the generation of heat in the fsw process is the result of friction between the metal tool and the workpiece material given its rotational speed and feed rate. received: 14 nov 2023; revised: 29 jan 2024; accepted: 2 feb 2024 *correspondence: bouamamamohameddoc@gmail.com the tool also provides high mechanical and thermal resistance in order to guarantee a high-quality weld between the two parts to be welded, therefore, loss of plasticity in the materials to be welded is essential for this technique to be executed smoothly [5]-[7]. several researchers have conducted studies on experimental and numerical simulation methods of fsw, including thermal and mechanical responses [8]-[10]; residual stresses [11]-[12]; vibrational characteristics [13]-[15]; as well as fatigue and damage behavior [16][18]. fsw has demonstrated superior microstructural and mechanical attributes, overcoming the shortcomings associated with other welding techniques. the majority of research into fsw has been directed toward investigating its physical, mechanical, microstructural and metallurgical characteristics [19]-[24]. in the literature, numerous researchers have examined the effect of surface roughness on the condition of welded joints. belaziz et al. [25] explored the influence of welding parameters, specifically the rotational and welding speeds, on the surface roughness of fsw joints. https://doi.org/10.33927/hjic-2024-06 mailto:bouamamamohameddoc@gmail.com bouamama, belaziz, elmeiche, elmeguenni and elhannani hungarian journal of industry and chemistry 38 the surface roughness of a 120 mm-long welded joint was assessed at five distinct locations, placing particular emphasis on both the initial and terminal sections of the welding tool. satyanarayana et al. [26] examined how the surface roughness of austenitic stainless steel impacted heterogeneous friction stir welded joints. boulahem et al. [27] introduced a surface roughness model and undertook parametric optimization of the fsw of aa2017 using the taguchi method and response surface methodology. the objective of this research is to investigate the correlation between welding parameters, specifically rotational speed and feed rate, and the surface roughness (rz) of welded joints in the case of 6061-t6 aluminum (al 6061-t6) plates. 2. experimental study experimenting with the fsw process and understanding the intricate interplay between welding variables, particularly the rotational speed and feed rate, as well as their influence on the surface quality of welded joints between al 6061-t6 plates entails the execution of several technical stages. figure 1 illustrates the key steps of the study. 2.1. materials plates of the al 6061-t6 wrought aluminum alloy that were 5 mm thick, 250 mm long and 100 mm wide were joined using fsw. table 1 shows the chemical composition and mechanical properties of the al 6061 t6 aluminum alloy and xc 48 steel. 2.2. fsw process the experimental process of fsw welding was conducted using a 301258 universal milling machine represented in figure 2. fsw was conducted using a tool 16 mm in diameter and a threaded shoulder with a thread pitch of 1 mm. the plunge depth and tilt angle were fixed at 0.1 mm and 2.5º, respectively. fsw was carried out at a traverse speed of 71 mm/min and a rotational speed of 1250 rpm. this profile of the tool was established after several tests in order to determine its optimum diameter, which makes it possible to produce a weld without defects at the root of the joint and on its surface. the configuration of the tool used in this study is shown in figure 3. the two plates used were fixed and tightened by a clamping system (figure 4) to prevent them from moving and slipping. the welding tool rotated at a given rotational speed and moved at a determined speed known according to the transverse length of the plates. although the shoulder of the tool exerts an axial force to keep the joint in contact with the support, it is the clamping system which must perform this function. table 1: chemical composition and mechanical properties of the al 6061-t6 aluminum alloy [25] and xc 48 steel [28] element/ si fe cu mg c rm re a property % % % % % mpa mpa % 6061-t6 0.70 0.25 0.29 0.90 / 304 276 13.6 xc 48 0.38 / / / 0.48 535 468 11.2 rm: maximum stress (mpa); re: elastic stress (mpa); a: elongation (%) figure 1: the various experimental stages of the fsw welding process figure 2: milling machine used for fsw welding investigation of hardness and surface roughness in fsw 52(1) pp. 37–43 (2024) 39 the friction produced by the welding tool heats up the atoms of the solid metal causing them to disperse or migrate. in the absence of fusion, the metal deforms and the atoms of the two plates are joined. heat is produced as a result of friction between the tool and the workpieces, allowing the material to soften and become more pliable. the plasticized substance moves as a result. the present study consists of welding two al 6061t6 plates. during the tests, a single tool configuration was considered. 6 tests were carried out to compare the results with those welded by fsw. the different steps of the fsw process adopted during welding are: positioning of the welding tool above the plates at the beginning of the joint; tool tilt angle of 2.5°; rotational speed of the machine head of 1250 rpm; penetration of the tool pin until the shoulder as a result of a vertical force to ensure it is in contact with the plates to be welded; wait 4.5 seconds (pre-sealing time) until a thermal equilibrium is reached; start moving the tool at a feed rate of 71 mm/min; remove the tool from the two plates to be welded and stop the machine. 2.3. joint characterization the mechanical characteristics of both the base material (bm) and the friction stir welded material were evaluated by conducting tensile and impact tests. for the tensile tests, specimens were extracted from the plates both parallel and perpendicular to the fsw welding path with and without a weld. the specimens, conforming to the dimensions specified in astm e8-04 [29] and the specifications of specimen 1 illustrated in figure 5, were cut from straightened plates. the tensile strength of the specimens was measured by a universal testing machine model using ibertest software controlled at a crosshead speed of 1 mm/min. the tensile tests were conducted with a loading rate of 1 mm/min. the dimensions of the specimens subjected to tensile tests are given in table 2. the machine increasingly elongates the specimens while recording the applied force f and elongation δl. the test continued until the specimens ruptured to determine the ultimate elongation. the geometry and a photo of the machined specimens are shown in figures 5. (a) (b) figure 4: bridle system for fsw welding table 2: the dimensions (in mm) of the specimens subjected to tensile tests nominal width specimen 1 12.5 g (gauge length) 50.0 ± 0.1 w (width) 12.5 ± 0.2 t (thickness, mm) measured thickness of specimen r (fillet radius, mm) 12.5 a (length of reduced section, mm) 60 b (length of gripped section, mm) 75 c (approximate width of gripped section) 20 figure 3: fsw tool bouamama, belaziz, elmeiche, elmeguenni and elhannani hungarian journal of industry and chemistry 40 following tensile shearing tests, the hardness of fsw joints on the sheared surfaces was assessed at the weld center. the brinell hardness tester (figure 6) was then used to evaluate the hardness (hb). at the interface with the plate, the metal of the welded plates was churned up. variations in hardness at the interface with the joint were induced by the stirring of two distinct metal alloys. the difference in stirring between the advancing and retreating sides during welding might explain the hardness differential. several studies revealed that both the rotational and traverse speeds of the tool have a great influence on the quality of the surface. the surface roughness of the fsw specimens was most significantly influenced by the interaction between the tool's rotational and traverse speeds. in this work, the surface roughness of the specimens was also measured using a surface roughness tester. the full factorial design of the experimental approach was employed to examine the effects of the aforementioned fsw process parameters on the surface roughness. figure 7 shows a typical surface texture of a friction stir welded specimen at 1250 rpm and 71mm/min. 3. results and discussion 3.1. tensile test the typical stress-strain curves which characterize the behavior law of base and welded materials in terms of fsw welding parameters proposed by us are presented in figure 8, while the mechanical characteristics are illustrated in table 3. figure 5: tensile specimens [26] figure 6: hb microhardness test equipment (a) (b) figure 7: surface texture of a friction stir welded specimen: (a) general view and (b) area a highly magnified figure 8: curves of the tensile test conducted on the base and fsw welded materials table 3: tensile test results re rmax al ce kn kn mm % base material (bm) 5.49 6.21 5.49 welded plates (fsw) 3.55 4.05 5.02 65.21 investigation of hardness and surface roughness in fsw 52(1) pp. 37–43 (2024) 41 the results obtained show that the curve of the welded material with the parameters n=1250 rpm and va=71 mm/min exhibits better mechanical characteristics when re=3.55 kn and rm=4.05 kn, while the elastic limit of the base material was re=5.49 kn and rmax=6.21 kn (n: rotation speed (rpm); va: feed rate (mm/min)). from these results, a significant reduction in the mechanical properties of the fsw welded joint compared to the bm was observed. the coefficient of efficiency (ce) was calculated to get a clear picture of the behaviour of the welded joint and its approximation to the behaviour of the base material. this coefficient is the ratio between the tensile limit of the bm and that of the welded joint, in our case it is 65.21%. 3.2. hardness of fsw the hardness of the fsw joints with the welding parameters of 1250 rpm and 71 mm/min is shown in figure 9. the hardness test was carried out in the transverse plane using a device on cross sections of the welded joints to evaluate, from a qualitative point of view, the mechanical resistance of the different zones of these welded joints. the hardness profile shown in figure 9 is relatively symmetrical with respect to the joint surface. minimum levels of hardness are achieved in the zatm zone at approximately hb=61. in the welded core, a slight increase in the level of hardness is observed, in particular on the advancing side where the value reached hb=65. the plastic metal could flow and recrystallize sufficiently due to the higher level of frictional heat and the precipitates were also more plentiful. however, the increased frictional heat at 1250 rpm caused grains to form and its hardness to be reduced since the lower exhibits the longest friction duration as can be seen in figure 9. 3.3. surface roughness measurements the intrinsic abnormalities of the welded plates produce semicircular streaks that are influenced by the tool coming into contact with the workpiece, which is how the surface roughness of the welded joint is described in figure 10 that shows a typical surface texture of a friction stir welded specimen at 1250 rpm and 71 mm/min. in the present investigation, the surface quality of the fsw specimen was evaluated by the average rz value using a pce-rt 1200 roughness tester instrument. average rz is one of the profile roughness parameters, it is the average value of the absolute values of the heights of five highestprofile peaks and the depths of five deepest alleys within the evaluation length. the surface roughness (rz) increased along the entire weld length as illustrated in figure 11 which varied between 15.83 and 25.56 μm for the advancing to retreating tools, respectively. it was observed that the retreating tool yielded higher surface roughness values compared to the advancing tool due to the heterogeneity of the fsw weld joint. figure 9: hardness profile through a welded joint figure 10: micrograph showing the surface condition figure 11: roughness data points bouamama, belaziz, elmeiche, elmeguenni and elhannani hungarian journal of industry and chemistry 42 the values of the surface roughness (rz) are displayed in table 4. 4. conclusions although the fsw welding process has been applied since 1991 for assembling different metal structures, its development has intensified over recent years due to the need to better understand the physical and mechanical behaviour of welded joints. in this study, fsw joints were characterized from the results of tensile tests. specimens subjected to tensile tests were prepared from plates in a perpendicular direction to the fsw travelling path including and excluding the weld. the hardness measurements first allowed the different welding zones (core, zatm, zat and base metal) to be delimited and the variation in hardness through these zones to be determined. the main conclusions are as follows: the quality of the fsw solder joint significantly depends on the feed rate and rotational speed; 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comparative study on anaerobic degradation processes of pressed liquid fraction of organic solid waste tamás rózsenberszki*1, lászló koók1, péter bakonyi1, nándor nemestóthy1, and katalin bélafi-bakó1 1research centre for biochemical, environmental and chemical engineering, university of pannonia, egyetem u. 10, veszprém, 8200, hungary anaerobic degradation processes: anaerobic digestion (biogasification), biohydrogen fermentation (dark) and microbial fuel cells were applied to treat the organic fraction of a municipal solid waste. the processes were compared based on their ability of energy recovery and chemical oxygen demand reduction. keywords: organic waste, anaerobic biodegradation, microbial fuel cell, energy recovery, process comparison 1. introduction, background 1.1 waste challenges the world population has more than doubled over the last 60 years. due to this growing tendency and urbanization the world’s energy consumption and value of waste generation present us with major challenges with sustainable development in mind. furthermore, it is obvious that waste treatment is one of the most critical global issue, because it has significant impacts for the health, local and global environment and economy [1]. according to the world bank group, 2.01 billion tonnes of municipal solid waste (msw) around the world are generated annually, and at least one third of that is not managed environmentally acceptable manner [2]. the average waste generated per person per day is 0.74 kilogram, but there are significant differences between data by countries, from 0.11 to 4.54 kilograms. actually, high-income countries only cover for 16 percent of world’s community, although generate around 34 percent of the world’s waste. based on their estimation global waste will grow to 2.2 billion tonnes by 2025 and to 3.40 billion tonnes by 2050 [1, 2]. these facts make solid waste management (swm) is a challenging task for decision-makers, who are required to provide essential waste collection and disposal services, generally under increasingly stringent budgetary pressures and regulatory requirements [3]. 1.2 biowaste msw typically consists of food waste, paper, glass, metals, plastics, textiles, etc. in developed countries the *correspondence: rozsenberszki.tamas@uni-pannon.hu amount of paper and plastics are relatively higher than the case of developing countries, where the main part of msw is organic waste [4]. there are variations in the characteristics of msw across the world, but remarkable part of the municipal solid waste is containing biodegradable organic components (world average: 46%) [1, 5]. there is a variety of treatment alternatives that provide not only disposal of this organic part but also energy recovery options. this section is going to present some anaerobic biodegradation processes so the following part of this section will focus on the organic waste. based on the data of the food and agriculture organization roughly one-third of food produced for human consumption is lost or wasted globally, which amounts more than 1.2 billion tons per year [6, 7]. in the european union, more than 85 million tonnes of food waste are generated per year with associated costs estimated at around 143 billion euros [7, 8]. according to san martin et al. vegetable waste deposited as landfill could be reduced to 30% [9]. some studies in this topic have indicated that vegetable waste has a remarkable potential for use as a raw material for animal feed. for example, garcia at al. concluded that some part of various organic wastes (meat, fish, restaurant and household waste, fruit and vegetable) was possible to use in animal feed formulations [10]. 1.3 treatment processes for the municipal solid waste it is important to notice the reduction of the waste problem should be started at the prevention and reduce the level of the overconsumption. however, in our consumer https://doi.org/10.33927/hjic-2021-05 mailto:rozsenberszki.tamas@uni-pannon.hu 32 rózsenberszki, koók, bakonyi, nemestóthy, and bélafi-bakó figure 1: schematic illustration of an example how to integrate bioprocesses in the mbt for the efficient msw treatment society today the market sphere is not interested in the reduction of the consumption, because the drop of consumption means less profit. it is still common to dump the treated or not treated waste, instead of produce valuable products to sell commercially or for own use, possibly recover energy from them [11]. waste dumping seems convenient and cheap solution but in the long term it is unprofitable and unsustainable technique. as long as this practice is followed, efforts should be made to continue the development such research that can minimize the negative effects of excess use. in the case of society it is an important task to focus on how can expand the environmental friendly thinking already from the basic education. fig. 1 presents the main treating processes of the msw. in most cases the aim is to reduce the toxicity of the waste in addition energy generation and in the case of composting soil conditioners could be recovered. the most unpreferable technique of them is the waste dumping without gas collection or recovery [12]. somewhat better choice is the landfilling which is currently the main technological facility applied to treat and dispose msw worldwide. but this represents still low level based on the waste treatment hierarchy [13, 14]. although landfill seems a cheap alternative, it can pollute the surrounding area (air, soil and also the water). over the years the collected landfill gas has limited use (no more than 60% methane content) [15]. landfill gas with low ch4 content (low calorific gas) is difficult to directly burn so it does not seem to be the best solution [15]. the thermal processes can reduce significantly the volume of the waste but the cost of the plant installation and operation is relatively high. moreover the flue gas and ash resulted need further treatments from environmental point of view [12]. 1.4 biodegradation processes for waste treatment in the case of aerobic biological methods composting can stabilize the organic waste and could produce soil conditioners but the bound energy of the waste cannot be utilized. on the other hand it needs relatively large area and longer time to get valuable products [4]. nevertheless, due to the comparatively simple operation it is still a widely used technique for the treatment of organic rich fraction. staying on the biological line the anaerobic digestion (ad) or biogasification is operating under anaerobic conditions. consequently, organic matter is degraded by a microbial community consisting of bacteria in the absence of oxygen and generating methane, carbon dioxide, and useable residue without any exothermic heat. it seems advantageous to choose ad because the biogas (around 60− 70% methane content) and biomethane are economically more valuable products than compost or the landfill gas. in addition the residue resulted by an anaerobic process integrated with an aerobic stage has the same quality parameters like compost [16]. before the installation of an ad system it is necessary to focus on the typical waste composition for the area because it can show significant diversity. it is not a simple process but there are modelling possibilities. according to cermiato et al. these combined bioprocesses including ad and digestate composting resulted higher performance than those applied pure composting [16]. in addition ad usually causes lower environmental impact than composting because it can fulfill two levels of the waste hierarchy at the same time. actually, the biodegradable waste (e.g., food loss, green waste) can be considered as a type of sustainable resources. in this view through ad process the energy is generated by a renewable source (biowaste) thus avoiding the energy which produced from conventional or fossil sources. generally around 120 m3 of biogas can be produced with a total electricity yield of about 250 kwh and a net electricity yield of 204 kwh from one ton of biowaste [16]. fei et al. carried out life cycle assessment on msw treatment technologies. results showed that the mechanical-biological treatment (mbt) had higher efficiency than landfill and incineration [17]. according to the life cycle assessment the worst option was the raw land filling. the incineration had a higher energy efficiency (20.5% energy recovery) but in this case the large amount of fly ash and exhaust treatment caused more environmental impacts. it seemed the mbt had the highest energy efficiency (38.5%) when it combined with biogas purification method. montejo et al. found similar results about connection mbt and ad [18]. in addition, mbt had less environmental impacts and relatively good stability for the changing composition of msw. on the other hand, mbt had weak economy performance and required economy support policy. hungarian journal of industry and chemistry comparative study on anaerobic degradation processes 33 table 1: main types of the municipal solid waste treatment [12] treatment process thermal treatment biological treatment landfilling method incineration pyrolysis gasification refuse derived fuel anaerobic digestion composting landfill with gas recovery landfill without gas recovery product heat, power gas, oil, charcoal syngas heat, power biogas compost landfill gas energy recovery yes yes yes yes yes no yes no table 2: summary of the results coming from the sample utilization by various anaerobic degradation methods process ad hdf mfc amount of sample (cm3) 25 25 25 volume of inoculum (cm3) 25 25 25 valuable product methane∗(299 cm3) hydrogen∗(91 cm3) electricity theoretical energy recovery∗∗ 11.7 kj 1.14 kj 0.031 kj particular energy recovery∗∗∗ 4.1 kj 0.8 kj 0.031 kj operation time (day) 40 2 30 reduction of cod medium low high * reffering to standard temperature and pressure ** reffering to maximal utilization rate with no losses *** reffering to utilization with losses: ad: biogas motor, hdf: fuel cell, mfc: direct use 2. mbt with other anaerobic processes in this subsection a particular example for an integrated anaerobic treatment is presented. a special sample coming from the organic fraction of a municipal solid waste was studied [19–21]. actually it was concentrated organic rich wastewater produced from mixed collected solid waste by pressing in a mbt plant (királyszentistván). during the mbt separation technology a biodegradable fraction generated called biofraction utilized by the plant’s biological stabilizing hall (compostation) to treat it before the dumping (fig. 1). the aim was to utilize the sample (before the composting process) with different anaerobic biodegradation methods to reduce the organic content and produce energy or valuable products (hydrogen, methane). thus the volume of waste will decrease (from the aspect of environmental protection) whilst the energy content of the waste can be exploited. in the first stage of experimental work the sample was characterized by analytical methods. it has high chemical oxygen demand (cod) and biochemical oxygen demand (bod) content 111 g l−1 and 61 g l−1 respectively, which parameters are promising for the biological treatment used. the various methods were the anaerobic digestion (ad), biohydrogen dark fermentation (hdf) and a kind of bioelectrochemical system (bes): the microbial fuel cell (mfc). as an inoculum mesophilic sludge from a biogas plant was used in each cases. the details about the materials and methods used were described in our previous studies [19–21]. based on the experiments presented in table 2, ad seems to be the most preferable method to integrate in the mbt process. it resulted high cumulative energy recovery (11.7 kj) and medium cod removal, but it needs long time for the degradation mechanism (methanogenic pathways). hdf lasted a few days and during the process 1.14 kj cumulative energy was generated however the cod removal was in low level, thus the effluent needed further treatment. there were successful experiments where ad and mfc were combined to treat the cod of the effluent from hdf. on the other hand hdf is a promising method if the desired final product is the hydrogen which is otherwise an encouraging energy sources for the future [22]. during the two chambered mfc process direct electrical energy was generated, but it had lot of limitation factors including type and structure of the system, electrode materials used, type of membrane, external and internal resistant, operation and adaptation period, biofouling, etc. our results showed that if mfc system was integrated to hdf or ad the system’s energy recovery (coulombic efficiency) and cod removal could be higher. 3. conclusion in many countries the waste management still does not get enough attention. the technologies of the biowaste treatment are already known just need to optimize for the characteristics of the waste streams in that area. decision makers should choose the sustainable and low risk ways for the environment. the results of our and other experimental works showed that mbt combined with anaerobic degradation processes could be an acceptable way to the clean and economical treatment in the case of significant amount of mixed collected msw. however, selectively collected biowaste has even more potential to maximize the recovery of their energy content. depending on the composition of the waste it may be advantageous to 49(1) pp. 31–35 (2021) 34 rózsenberszki, koók, bakonyi, nemestóthy, and bélafi-bakó integrate the different treatment methods to improve for an appropriate level of the effectiveness. acknowledgements the authors thank for the financial support provided by the széchenyi 2020 programme under the project efop3.6.1-16-2016-00015, and by the excellence of strategic r+d workshops under the project ginop-2.3.215-2016-00016 entitled “development of modular, mobile water treatment systems and wastewater treatment technologies based at the university of pannonia to enhance growing dynamic exportation from hungary between 2016 and 2020”. references [1] hoornweg, d.; bhada-tata, p.: what a waste: a global review of solid waste management. urban development series. knowledge papers no. 15, world bank, 2012, 1. https://openknowledge.worldbank.org [2] kaza, s.; yao, l.c.; bhada-tata, p.; van woerden, f.: what a waste 2.0: a global snapshot of solid waste management to 2050. world bank publications, 2018. doi: 10.1596/978-1-4648-1329-0 [3] roberts, k.p.; turner, d.a.; coello, j.; stringfellow, a.m.; bello, i.a.; powrie, w.; watson, g.v.r.: swims: a dynamic life cycle-based optimisation and decision support tool for solid waste management. j. clean. prod., 2018, 196, 547–63 doi: 10.1016/j.jclepro.2018.05.265 [4] logan, m.; visvanathan, c.: management strategies for anaerobic digestate of 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10.1016/j.renene.2017.06.033 [17] fei, f.; wen, z.; huang, s.; de clercq, d.: mechanical biological treatment of municipal solid waste: energy efficiency, environmental impact and economic feasibility analysis. j. clean. prod., 2018, 178, 731–739 doi: 10.1016/j.jclepro.2018.01.060 [18] montejo, c.; tonini, d.; márquez, m. del c.; fruergaard astrup, t.: mechanical-biological treatment: performance and potentials. an lca of 8 mbt plants including waste characterization. j. environ. manage., 2013, 128, 661–673 doi: 10.1016/j.jenvman.2013.05.063 [19] rózsenberszki, t.; koók, l.; hutvágner, d.; nemestóthy, n.; bélafi-bakó, k.; bakonyi, p.; kurdi, r.; sarkady, a.: comparison of anaerobic degradation processes for bioenergy generation from liquid fraction of pressed solid waste. hungarian journal of industry and chemistry https://openknowledge.worldbank.org/handle/10986/17388 https://elibrary.worldbank.org/doi/book/10.1596/978-1-4648-1329-0?chaptertab=true& 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10.1016/j.jclepro.2015.06.116 [22] hosseini, s.e.; wahid, m.a.: hydrogen production from renewable and sustainable energy resources: promising green energy carrier for clean development. renew. sustain. energy rev., 2016, 57, 850– 866 doi: 10.1016/j.rser.2015.12.112 49(1) pp. 31–35 (2021) https://doi.org/10.1007/s12649-015-9379-y https://doi.org/10.1007/s12649-015-9379-y https://doi.org/10.1016/j.chemosphere.2016.12.114 https://doi.org/10.1016/j.chemosphere.2016.12.114 https://doi.org/10.1016/j.jclepro.2015.06.116 https://doi.org/10.1016/j.jclepro.2015.06.116 https://doi.org/10.1016/j.rser.2015.12.112 introduction, background waste challenges biowaste treatment processes for the municipal solid waste biodegradation processes for waste treatment mbt with other anaerobic processes conclusion hungarian journal of industry and chemistry vol. 46(2) pp. 19-25 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0013 strong reachability of reactions with reversible steps eszter virágh ∗1 and bálint kiss1 1department of control engineering and information technology, budapest university of technology and economics, magyar tudósok krt. 2, budapest, 1117, hungary the controllability of reactions is an important issue in the chemical industry. the control of reactions is of great practical interest in order to ensure the energyand time-efficient production of compounds. this paper studies the dynamical models of some chemical reactions in order to verify their controllability with regard to a candidate input signal, namely the change in the ambient temperature of a reaction. keywords: reversible reaction, strong reachability, controllability, lie algebra 1. introduction chemical reactions are widely applied during the synthesis and transformation processes of organic compounds. the reaction mechanism and resulting products depend mainly on the concentrations of the species, the catalyst used, the ambient temperature, and the ambient pressure. if the values of these parameters are changed, one can obtain different products from the original ones but it is also possible to increase the productivity and energyefficiency of the reaction. hence the application of a proper feedback law to ensure the latter scenario may be envisaged. a study of the local controllability by considering the reaction rate coefficient as an input has been presented in ref. [1]. the authors of ref. [2] have also considered the reaction rate coefficient as an input and extended the results by claiming that global controllability holds. the controllability of another control input, namely the dilution ratio, is studied in ref. [3]. general conditions for strong reachability in the case of a temperature input were reported earlier in ref. [4]. moreover, the conditions of strong reachability for polymer electrolyte membrane fuel cells (pemfc), controlled by concentrations, have also been analysed. the motivation to consider the concentrations and temperature (or their rate of change) as input signals is due to the fact that these quantities can be easily modified efficiently by industrial equipment that is currently in use, thus these results can be used as a basis to establish control laws to stabilize a desired reaction performance without major changes being made to the equipment used in production. the oxidation of acetone with hydroxylamine (the oximation reaction) was investigated by raman spectroscopy [5]. knowing the mecha∗correspondence: viragh.eszter@gmail.hu nism, the controllability is important for this reaction. throughout this paper, the candidate variable for control is the rate of change in the temperature ṫ , i.e. the first time derivative of the ambient temperature. from a practical point of view, this is a simplification since the variable which can be changed externally, denoted by u, is not ṫ but an algebraic expression involving u and other variables of the system as well. for the dynamics considered in this paper it is always possible, however, to obtain the values of u as a function of ṫ and other state variables. the remaining part of this paper is organized as follows. sec. 2 briefly revisits the concepts related to the strong reachability of nonlinear dynamical systems and conditions of strong reachability. the differential equations describing the dynamics of reactions are presented so that the rate of change in temperature is considered as the controlled input in sec. 3. in sec. 4 the strong reachability of the oximation reaction is studied. the systems in the case of acidic medium in subsection 4.1 and in weakly basic medium in subsection 4.2 are analyzed. in ref. [4] a sufficient condition for strong reachability was given for reactions with general dynamics. in sec. 5, the conditions for strong reachability are given, if the reaction also contains reversible steps. in the last section the conclusions of the paper are drawn. 2. study of strong reachability consider the following nonlinear dynamical system, given by the differential equation: ξ̇ = f(ξ) + g(ξ)u, ξ(0) = ξ∗ ∈ rn, (1) where f, g ∈ c∞(rn,rn) are smooth vector fields and u ∈ r is the control-input variable. the vector fields mailto:viragh.eszter@gmail.hu 20 virágh and kiss f and g are often referred to as drift and control vector fields, respectively. for the sake of completeness, let us revisit some definitions used in refs. [4, 6]. definition 1 (reachability set). consider the system given by eq. 1. the set r(ξ∗, t) ⊂ rn is referred to as the reachability set from the point ξ∗ at time t and it is the union of values at t of the solutions to eq. 1 for some admissible input function u with the initial condition ξ(0) = ξ∗. definition 2 (strong reachability). the system eq. 1 is referred to as strongly reachable from the point ξ∗, if the setr(ξ∗, t) has an interior point for all t > 0. definition 3 (lie bracket). suppose that f ∈ c∞(rn,rn) and g ∈ c∞(rn,rn), then the lie bracket of the vector fields f and g is [f, g] = dg f −df g. (2) the operator adng f : c∞(rn,rn) × c∞(rn,rn) → c∞(rn,rn) is defined as: ad0 gf = f, adng f = [g, adn−1g f ]. (3) definition 4 (lie algebra). consider the vector fields f, g ∈ c∞(rn,rn). the lie algebra generated by f and g is denoted by λ = lie(f, g) and is the smallest linear subspace of c∞(rn,rn) that satisfies the following conditions: 1. f , g ∈ λ , 2. for any a, b ∈ λ, [a, b] ∈ λ. it should be noted that λ also defines a distribution. definition 5 (distribution). the distribution ∆ is the operator which assigns a linear subspace of rn to ∀x ∈ rn . definition 6 (controllability distribution). the controllability distribution ∆c of eq. 1 is the smallest distribution which satisfies the following conditions: 1. g ∈ ∆c, 2. ∆c is invariant to the vector field f (∀η ∈ ∆c, [η, f ] ∈ ∆c), 3. ∆c is involutive (∀η1, η2 ∈ ∆c, [η1, η2] ∈ ∆c). the controllability distribution has a subspace spanned by vector fields g and [f, g]. the following theorem is a fundamental result used in ref. [6]. theorem 1 (reachability rank condition). consider the controllability distribution ∆c of eq. 1. the system eq. 1 is strongly reachable at point ξ∗ ∈ rn if dim{∆}c (ξ∗) = n. 3. strong reachability of kinetic equations the active control of chemical processes may be necessary to maximize the amount of target products and minimize the amount of by-products. to achieve such a control objective, a suitable input variable must be selected so that the resulting dynamical system is controllable from that input. to check if this requirement is satisfied, the tools introduced in the previous section will be applied to the equations describing the reaction dynamics. consider a system of r reaction steps and with m species (r,m > 0). by borrowing notational conventions from chemistry, each reaction step can be generally defined by m∑ m=1 α(m, r)x(m) kr−−→ m∑ m=1 β(m, r)x(m), r = 1, 2, . . . , r, (4) where α(·, r) = (α(1, r), α(2, r), . . . , α(m, r))t denotes the reactant complex vector, β(·, r) = (β(1, r), β(2, r), . . . , β(m, r))t represents the product complex vector, x(m) is themth species and kr is the reaction rate coefficient of the rth reaction step. the species on the left-hand side of eq. 4 are referred to as reactant species and reactant complexes refer to their formal linear combinations. similarly, one may find the products and their linear combinations (product complexes) on the right-hand side of the reaction described in eq. 4. let us also define the stoichiometric matrix, denoted by γ. the matrix γ consists of r columns and m rows, such that each column is obtained by γ(·, r) = β(·, r)− α(·, r). (5) eq. 4 defines the reaction but it does not specify its mass action kinetics. however, in order to study the controllability, the differential equations of the reaction dynamics need to be obtained in the form of differential equation eq. 1. these equations are obtained from the heat balance [7–9] of reaction eq. 4 as ẋm = r∑ r=1 γ(m, r)krx α(·, r) m = 1, 2, . . . ,m, (6) ṫ = r∑ r=1 1 βr,0 krx α(·, r) + u, (7) where xm denotes the concentration of species m, t is the temperature, and xα(·, r) = ∏m p=1 x α(p, r) p . recall that the single input u appears in the expression of ṫ . the state vector ξ for the dynamics eqs. 6–7 reads ξ = (x1, x2, . . . , xm, t )t . the reaction rate coefficient kr can be given as kr = kr,0e − er r0t (8) hungarian journal of industry and chemistry strong reachability of reactions with reversible steps 21 where kr,0, er, r0 ∈ r+. to study reachability, one has to determine the number of linearly independent lie brackets spanning the lie algebra generated by the vector fields g and adgf . thanks to the special structure of the reaction dynamics, the linear independence can be examined by factorizing the matrix of lie brackets and checking the rank of the factors. first, let us define the reaction dynamics matrix: definition 7 (reaction dynamics matrix dr). introduce the notation k (i) j := ∂i ∂t i kj i, j ∈ {1, 2, . . . , r} (9) the matrix of sizer×r of the derivatives of the reaction rate coefficient defined as dr =  k (1) 1 k (2) 1 . . . k (r) 1 k (1) 2 k (2) 2 . . . k (r) 2 ... ... . . . ... k (1) r k (2) r . . . k (r) r  (10) is referred to as the reaction dynamics matrix. the following lemma and theorem have been shown in ref. [4]. they are also provided here for completeness. lemma 1. consider a reaction with r steps. suppose that the activation energies e1, e2, . . . , er of the reaction steps are all different and strictly positive, then the reaction dynamics matrix dr is of full rank for every t > 0. theorem 1 cannot be applied directly to the reaction dynamics eq. 6–7, because the right-hand sides (rhs) of some equations in eq. 6 may be linearly dependent. let δ denote the number of linearly dependent rhss in eq. 6. the system of chemical reactions is considered to be strongly reachable from a point ξ∗ ∈ rm+1 if and only if the dimension of the controllability distribution is m − δ+ 1. the additional dimension is due to eq. 7 with the temperature t as an additional variable. using theorem 1, the controllability subspace for particular reactions can be deduced, so the conditions for strong reachability of the reactions can be determined. theorem 2. consider a reaction with m species and r reaction steps. suppose that the activation energies e1, e2, . . . , er of the reaction steps are all different and strictly positive. then the reaction dynamics with the temperature change (ṫ ) as an input variable are strongly reachable if the concentrations of all reactant species are positive. theorem 2 provides a condition for the strong reachability of reactions in a general form. however, for some reactions where the reaction dynamics have additional properties, weaker conditions may be sufficient to ensure strong reachability. in sec. 4, the strong reachability conditions in the case of oximation reactions were investigated. 4. controllability study of the oximation reaction the oxidation of acetone with hydroxylamine was investigated by raman spectroscopy in ref. [5]. the reaction is strongly exothermic and the concentration of the intermediate highly depends on the ph and temperature. the process can be hazardous, however, it is not dangerous to run in a laboratory with low concentrations and in a controlled manner. strong reachability is a necessary condition to be able to control the reaction. 4.1 oximation reaction in acidic medium in oximation reactions, the sequence (number and nature) of reaction steps depends on the ph. the equations of the reaction steps are different in acidic and weakly basic media. in the case of acidic media the reaction takes place over two reaction steps as given by for the sake of notational simplicity, the symbols a, b, c, d, e, and f will denote the species such that the two reaction steps above read: a + b k1−−→ c (11) c + d k2−−→ e + f. (12) let us denote the concentrations of the species by a, b, c, d, e, f ≥ 0. it is assumed that the reaction rate coefficients k1, k2 > 0. theorem 2 implies that the reaction is strongly reachable, provided that the conditions are met. it follows from strong reachability that it is possible to arrive at any concentrations of m − δ species and at any temperatures by suitable manipulation of the input. recall that there is no guarantee that such concentrations and temperatures also define a steady-state for the system. note that theorem 2 only provides a sufficient condition for strong reachability. for chemical reactions, the positivity condition of activation energies is almost always satisfied. considering the reaction steps of the oximation reaction in acidic media the two remaining conditions of strong reachability will be studied: (1) the positivity of the concentration of all reactant species; (2) the distinctness of activation energies. let us now suppose that the system in eqs. 11–12 is strongly reachable. the stoichiometric matrix for the re46(2) pp. 19-25 (2018) 22 virágh and kiss action steps reads: γ =  −1 0 −1 0 1 −1 0 −1 0 1 0 1  (13) and it is easy to verify that δ = 2 in this case. the differential equation of the reaction: ȧ ḃ ċ ḋ ė ḟ ṫ  =  −k1ab −k1ab k1ab− k2cd −k2cd k2cd k2cd k1 β ab+ k2 β cd  +  0 0 0 0 0 0 1  u = = f(ξ) + g(ξ)u (14) is in a form similar to eq. 1, where ξ = (a, b, c, d, e, f, t )t and the vector field g(ξ) is constant. since the rank of the stoichiometric matrix γ is 2 and the temperature is a scalar quantity, theorem 1 implies that the system is strongly reachable if dim{∆}c = 2 + 1 = 3. hence, to study strong reachability, the number of linearly independent vector fields spanning the lie algebra generated by the vector fields adgf and g must be determined. the lie brackets adgf and ad2 gf read: ad(i) g f =  −k(i)1 ab −k(i)1 ab k (i) 1 ab− k(i)2 cd −k(i)2 cd k (i) 2 cd k (i) 2 cd k (i) 1 β ab+ k (i) 2 β cd  , (15) where i ∈ {1, 2}. to study the dimension of the controllability distribution ∆c one has to determine the rank of the matrix whose columns are g, adgf and ad2 gf which reads: ( adgf ad2 gf g ) = =  −k(1)1 ab −k(2)1 ab 0 −k(1)1 ab −k(2)1 ab 0 k (1) 1 ab− k(1)2 cd k (2) 1 ab− k(2)2 cd 0 −k(1)2 cd −k(2)2 cd 0 k (1) 2 cd k (2) 2 cd 0 k (1) 2 cd k (2) 2 cd 0 k (1) 1 β ab+ k (1) 2 β cd k (2) 1 β ab+ k (2) 2 β cd 1  . (16) the last row is linearly independent of all other rows in the matrix of eq. 16, hence, by deleting the last row and column from the matix, the rank will be decreased by 1. the remaining matrix is denoted by θ and defined as θ =  −k(1)1 ab −k(2)1 ab −k(1)1 ab −k(2)1 ab k (1) 1 ab− k(1)2 cd k (2) 1 ab− k(2)2 cd −k(1)2 cd −k(2)2 cd k (1) 2 cd k (2) 2 cd k (1) 2 cd k (2) 2 cd  . (17) it is clear that the condition dim{∆c} = 3 holds true if and only if rank(θ) = 2. it is easy to see that the matrix θ can be factorized as θ =  −ab 0 −ab 0 ab −cd 0 −cd 0 cd 0 cd  ( k (1) 1 k (2) 1 k (1) 2 k (2) 2 ) = a ·d2. (18) the condition of rank(θ) = 2 can hold true if and only if the matrices a and d2 are of full rank according to the multiplication theorem of determinants. matrix a is of full rank (rank(a) = 2) if and only if a 6= 0, b 6= 0, c 6= 0 and d 6= 0. the reaction dynamics matrix d2 is of full rank if and only if there is no constant c ∈ r \ {0} such that k(2)1 = ck (1) 1 and k(2)2 = ck (1) 2 , hence k (2) 1 k (1) 1 = k (2) 2 k (1) 2 (= c) (19) cannot be true. recalling that the reaction rate coefficients are kr = kr,0e − er r0t (kr,0, er, and r0 are positive constants), it is easy to determine the time derivatives: k(1)r = ( er r0t 2 ) kr,0e −er r0t , (20) k(2)r = kr,0 ( e2 r r2 0 t 4 − 2er r0 t 3 ) e −er r0t . (21) the ratios of the firstand second-order time derivatives are obtained as k (2) r k (1) r = kr,0 ( e2 r r2 0 t 4 − 2er r0 t 3 ) e −er r0t( er r0t 2 ) kr,0e −er r0t = er − 2r0t r0t 2 . (22) based on eq. 22, the equality in eq. 19 holds true if and only if e1 = e2. as a result it has been proven that if the reaction dynamics are strongly reachable then the concentrations a, b, c and d are positive and e1 6= e2. thus the conditions of theorem 2 are also necessary for strong reachability in the case of oximation reactions in acidic media. 4.2 oximation reaction in weakly basic medium in the case of weakly basic media the reaction occurs according to the reaction steps given by: hungarian journal of industry and chemistry strong reachability of reactions with reversible steps 23 since the specific chemical compositions of the species are irrelevant to the controllability analysis, the symbols a, b, c, d, e, f, and g will denote the species such that the above reaction steps read: a + b k1−−→ c, (23) c k2−−→ d + e, (24) d + f k3−−⇀↽−−− k−3 g + e. (25) let us denote the concentration of the species by a, b, c, d, e, f , g ≥ 0. it is assumed that the reaction rate coefficients are strictly positive: k1, k2, k3, k−3 > 0. recall that theorem 2 only provides a sufficient condition for strong reachability. by considering oximation reactions in weakly basic media the remaining conditions of strong reachability will be studied. let us suppose now that the system of eqs. 23–25 is strongly reachable. the stoichiometric matrix for the reaction steps reads: γ =  −1 0 0 0 −1 0 0 0 1 −1 0 0 0 1 −1 1 0 1 1 −1 0 0 −1 1 0 0 1 −1  . (26) the differential equation of the reaction ȧ ḃ ċ ḋ ė ḟ ġ ṫ  =  −k1ab −k1ab k1ab− k2c k2c− k3df + k−3ge k2c+ k3df − k−3ge −k3df + k−3ge k3df − k−3ge k1 β ab+ k2 β c+ k3 β df + k−3 β ge  + +  0 0 0 0 0 0 0 1  u = f(ξ) + g(ξ)u (27) is in a form similar to eq. 1, where the vector field g(ξ) is constant and ξ = (a, b, c, d, e, f, g, t )t . since the rank of the stoichiometric matrix γ is 3 and the temperature is a scalar quantity, theorem 1 implies that the system is strongly reachable if dim{∆}c = 3 + 1 = 4. hence, the number of linearly independent vector fields spanning the lie algebra generated by the vector fields adgf and g must be determined. the lie–brackets adgf , ad2 gf and ad3 gf read: adigf =  −k(i)1 ab −k(i)1 ab k (i) 1 ab− k(i)2 c k (i) 2 c− k(i)3 df + k (i) −3ge k (i) 2 c+ k (i) 3 df − k(i)−3ge −k(i)3 df + k (i) −3ge k (i) 3 df − k(i)−3ge k (i) 1 β ab+ k (i) 2 β c+ k (i) 3 β df + k (i) −3 β ge  , (28) where i ∈ {1, 2, 3}. to study the dimensions of the controllability distribution ∆c one has to give the rank of the matrix whose columns are adgf , ad2 gf , ad3 gf , and g:( adgf ad2 gf ad3 gf g ) . (29) the last row is linearly independent of all other rows in matrix eq. 30, hence, by deleting the last row and column from the matrix, the rank will be decreased by 1. the remaining matrix is denoted by θ and defined as θ =   −k(i)1 ab −k(i)1 ab k (i) 1 ab− k(i)2 c k (i) 2 c− k(i)3 df + k (i) −3ge k (i) 2 c+ k (i) 3 df − k(i)−3ge −k(i)3 df + k (i) −3ge k (i) 3 df − k(i)−3ge  i=1,2,3  (30) the condition dim{∆}c = 4 holds true if and only if rank(θ) = 3. it is easy to see that the matrix θ can be factorized as θ = a ·d = −ab 0 0 0 −ab 0 0 0 ab −c 0 0 0 c −df ge 0 c df −ge 0 0 −df ge 0 0 df −ge   k (1) 1 k (2) 1 k (3) 1 k (1) 2 k (2) 2 k (3) 2 k (1) 3 k (2) 3 k (3) 3 k (1) −3 k (2) −3 k (3) −3  (31) the condition rank(θ) = 3 can hold true only if rank(a) ≥ 3 and rank(d) ≥ 3. t he 3rd and 4th columns in matrix a are linearly dependent, thus rank(a) ≤ 3. the condition rank(a) = 3 can hold true only if the concentrations a, b, and c as well as the 46(2) pp. 19-25 (2018) 24 virágh and kiss concentrations d and f , or the concentrations g and e are strictly positive. matrix d is of full rank only if d consists of a 3 × 3 times full-rank matrix. lemma 1 implies that the reaction dynamics matrix d3 is of full rank if the activation energies are different. hence, matrix d is of full rank, if 3 different activation energies exist. the system was proven to be strongly reachable if 3 of the activation energies are all different and concentrations a, b, c and d, f , or g, e are positive. thus a condition for strong reachability coule be given more precisely in the case of oximation reaction in weakly basic media. 5. reversible reaction step for reactions of general types, theorem 2 provides a condition for strong reachability. however, it will be shown that if the reaction contains one or more reversible steps, weaker conditions are sufficient for strong reachability. the concentrations are defined by x1, x2, . . . , xm , as in the previous sections. the notationa is introduced for the matrix describing the effect of concentrations: a := γ diag(xα(· ,1), xα(·, 2), . . . , xα(·, r)), (32) where xα(·,r) = ∏m m=1 x α(m, r) m and γ is the stoichiometric matrix as introduced by eq. 5. the vector k = (k1, k2, . . . , kr)t is composed of the reaction rate coefficients. the notation d is introduced for the following matrix composed of the derivatives of reaction rate coefficients: d := ( k(1) k(2) ... k(rank(γ)) ) . (33) lemma 2. the reaction dynamics in eqs. 6–7 with the input variable ṫ are strongly reachable, if rankγ = rank(ad), where γ is the stoichiometric matrix and a and d are defined as above. proof the differential equation of the reaction reads: ( ẋ ṫ ) =  v r∑ r=1 kr βr,0 xα(·, r) + ( 0 1 ) u, (34) where ẋ = (ẋ1, ẋ2, . . . , ẋm )t , u is the control input and the vector field v stands for the vector composed of the right-hand sides of eq. 6. as in the previous sections, the study of strong reachability means verification of the dimension of the controllability distribution ∆c. the dimension of the controlled input (the dimension of the change in temperature) is 1, thus, theorem 1 implies that the system is strongly reachable if and only if dim{∆}c = rank(γ) + 1. the vector fields spanning the controllability distribution are g and adigf for i > 0. the lie bracket adigf reads: adigf=  v(i) r∑ r=1 k (i) r βr,0 xα(·, r) =  a · k(i) r∑ r=1 k (i) r βr,0 xα(·, r)  (35) for i ∈ {1, 2, . . . , rankγ}. the rank of the controllability distribution is hence the rank of the matrix( adgf ad2 gf . . . adrankγ g f g ) = a · k(1) . . . a · k(rankγ) 0 r∑ r=1 k (1) r βr,0 xα(·, r) . . . r∑ r=1 k(rankγ) βr,0 xα(·, r) 1  (36) the last row in eq. 36 is linearly independent of the others, hence, the same reasoning as earlier is followed and the last row and columns are eliminated, thus, decreasing the rank by one. the resulting matrix is denoted by θ and reads: θ = ( a · k(1) a · k(2) . . . a · k(rankγ) ) = = ad. (37) since the dimension of the controllability distribution is rank(θ) + 1, the reaction dynamics are strongly reachable if rankγ = rankθ or if rankγ = rank(ad). theorem 3. consider the reaction dynamics eqs. 6–7 such that the activation energies e1, e2, . . . , er are positive and different in pairs. suppose that the concentrations of reactant species are positive in the case of oneway reaction steps and at least one of the ways is positive in the case of reversible reaction steps. then, the reaction dynamics controlled by ṫ are strongly reachable. proof if the system does not contain reversible reaction steps, theorem 2 is obtained. without loss of generality, it can be supposed that the system contains one reversible reaction step. this step can be replaced by pairs of irreversible reaction steps, with reaction rate coefficients denoted by ke and k−e. the changes in the concentrations are equal in the reaction step with rate coefficient ke and in the reaction step with rate coefficient k−e, only the direction is different. thus, the two columns in matrix γ for the reversible reaction steps are always linearly dependent. lemma 2 implies that the system is strongly reachable if and only if rankγ = rank(ad). if the activation energies are positive and all different, lemma 1 implies that matrix d is of full rank. the matrix a is defined by eq. 32, thus, the columns for ke and k−e are linearly dependent. the column for ke contains the factor of the concentrations of the reactant species in the transformation step and k−e contains the factor of the concentrations of the reactant species in the transformation step in the opposite direction with the arbitrary sign in the place of non-zero elements. by substituting one of the two vector fields with a zero vector field, the rank of matrix a remains unchanged. thus, in the case of reversible reactions for strong reachability, it is sufficient if the reactant species have positive concentrations only in one of the directions, and the activation energies are positive and all different. hungarian journal of industry and chemistry strong reachability of reactions with reversible steps 25 6. conclusion the reaction dynamics of strong reachability where the control variable is selected as the rate of change in the ambient temperature (ṫ ) have been studied. first, the strong reachability was analyzed in the case of the oximation reaction. since the processes depend on the ph, conditions that facilitate strong reachability in acidic as well as weakly basic media were studied. for our analysis, theorem 2 was used. it provides sufficient conditions to facilitate strong reachability, however, these conditions are not always necessary. it was proven that the conditions in theorem 2 are necessary to facilitate strong reachability of the oximation reaction in the case of acidic media. in weakly basic media, the system contained a reversible reaction step, thus, the conditions of theorem 2 could be determined. strong reachability has also been studied for reaction dynamics of a general type that contain at least one reversible reaction step where the conditions of theorem 2 could also be further refined. for reversible reaction steps it has been shown that positive reactant concentrations are unnecessary to facilitate strong reachability in both directions of the reversible steps, in one direction is sufficient. acknowledgement the chemistry-related comments from zsombor kristóf nagy and györgy marosi at the bme department of organic chemistry and technology are gratefully acknowledged. references [1] farkas, g.: local controllability of reactions, j. math. chem., 1998 24, 1–14 doi: 10.1023/a:1019150014783 [2] drexler, d.a., tóth, j.: global controllability of chemical reactions, j. math. chem., 2016 54, 1327– 1350 doi: 10.1007/s10910-016-0626-7 [3] dochain, d., chen, l.: local observability and controllability of stirred tank reactors, j. math. chem., 1992 2, 139–144 doi: 10.1016/0959-1524(92)85003-f [4] drexler, d.a., virágh, e., tóth, j.: controllability and reachability of reactions with temperature and inflow control, fuel, 2017 211, 906–911 doi: 10.1016/j.fuel.2017.09.095 [5] csontos, i., pataki, h., farkas, a., bata, h., vajna, b., nagy, z.k., keglevich, g., marosi, g.j.: feedback control of oximation reaction by inline raman spectroscopy, organic process research & development, 2014 19, 189–195 doi: 10.1021/op500015d [6] isidori, a.: nonlinear control system (springer verlag, london), 1995 doi: 10.1007/978-1-84628-615-5 [7] érdi, p., tóth, j.: mathematical models of chemical reactions. theory and applications of deterministic and stochastic models (princeton university press, princeton, new jersey), 1989 isbn: 9780719022081 [8] turányi, t., tomlin, a.s.: analysis of kinetic reaction mechanisms (springer berlin heidelberg), 2014 isbn: 9783662445624 [9] atkins, p.w.: physical chemistry (oxford university press), 2010 isbn: 9780199543373 46(2) pp. 19-25 (2018) https://doi.org/10.1023/a:1019150014783 https://doi.org/10.1023/a:1019150014783 https://doi.org/10.1007/s10910-016-0626-7 https://doi.org/10.1016/0959-1524(92)85003-f https://doi.org/10.1016/j.fuel.2017.09.095 https://doi.org/10.1016/j.fuel.2017.09.095 https://doi.org/10.1021/op500015d https://doi.org/10.1007/978-1-84628-615-5 introduction study of strong reachability strong reachability of kinetic equations controllability study of the oximation reaction oximation reaction in acidic medium oximation reaction in weakly basic medium reversible reaction step conclusion hungarian journal of industry and chemistry vol. 49(1) pp. 17–21 (2021) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2021-03 a framework for demonstration devices used in distancelearning environments péter decsi*1, ádám bors1, péter kocsor2, bálint vörös2, barnabás horváth2, sándor guba2, zoltán gugolya2, sándor mester1, and istván szalai1,2 1institute of mechatronics engineering and research, university of pannonia, gasparich márk u. 18/a, zalaegerszeg, 8900, hungary 2research centre for engineering sciences, university of pannonia, egyetem u. 10, veszprém, 8200, hungary distance-learning has become widespread around the world. many training areas such as engineering require the acquisition of practical rather than theoretical knowledge. in this paper, a framework is presented in the form of four pilot projects which is used for practical laboratory measurements in a distance-learning environment. four demonstration devices consisting of an induction motor drivetrain, a magnetorheological clutch as well as a rolling resistance and an ultrasonic sensor were built and several examples of measurements presented. the system, based on accessible and user-friendly hardware, is cost-effective, simple to program and can be adapted to suit any application. keywords: distance learning, practice-based learning, demonstration device 1. introduction remote learning provides an effective method for educators and students to remain connected and engage with learning content while working from home. several tools are available to teach theoretical knowledge, e.g., learning management systems and video conferencing solutions. since learning can be synchronous or asynchronous, both approaches require different tools. the efficiency of their usage depends on how prepared the parties involved are. during the covid-19 pandemic, educational institutions had to start using virtual environments as well as stop on-site education and were unable to provide appropriate practical training for their students. even though remote learning can be effective, a transition from traditional methods must be made [1]. although numerous demonstration devices have already been presented [2], few of them are capable of distance learning and many of them are only simulations [3]. since practical training is based on self-experience, available distance learning tools are insufficient. in this paper, a universal tool is presented for distance practical training in the form of four example projects. the demonstration devices are suitable for distance learning. the user is connected to a microcomputer through the internet, after an operator grants access to it. it provides attended and unattended access to multiple *correspondence: decsi.peter@mk.uni-pannon.hu users simultaneously, offline and cloud connectivity, file transfer as well as instant messaging (chat). the educator is able to monitor the learning path and provide instant feedback to students, which is necessary for its effective use [4]. 2. framework access to the front end of the framework is provided by a remote desktop client based on virtual network computing (vnc) technology. the software can be run on multiple platforms; it has versions for windows, macos, linux, ios, android, solaris, hp-ux, and ibm aix operating systems. the back end of the system runs on a raspberry pi microcomputer called the vnc server. the graphical user interface (gui) of the operating system is modified on the server that enables it to be controlled using a touchscreen and remotely simultaneously. the control software of the demonstration device is written in python which is the most common programming language nowadays. the base of the program is a gui that uses the tkinter python module, moreover, the widgets are designed to be simple and readable [5]. the program is tabbed, the first tabs contain lessons and tutorials about its content. it is possible to embed videos from video sharing sites. the teaching materials are image files, which can be created from a premade powerpoint template. the appropriate image size, appearance, font size, etc. is set to look identical and be easily readable on multiple platforms. https://doi.org/10.33927/hjic-2021-03 mailto:decsi.peter@mk.uni-pannon.hu 18 decsi et al. figure 1: graphical user interface of the presented framework. the measurements, control algorithms and displays are unique to the type of demonstration device used. only the gui elements, e.g. buttons, sliders or labels, are provided for the programmers using the framework. in fig. 1, the gui of the induction motor drivetrain is presented. the control algorithms are written in the python language and the integrated development environment (ide) used can be chosen arbitrarily by the programmer, only the necessary python modules need to be installed. students can access live videos from the device to see the effects of their actions. 3. induction motor drivetrain induction motors are widely used in industry due to their simple and rugged construction, cost-effectiveness as well as maintenance-free and efficient operation. their simple and robust construction, reliability and power efficiency also fulfil the challenging requirements of the automotive industry. the key to the application of these motors is the control system. an inverter or variable frequency drive (vfd) controls the frequency and ac voltage to set the rotational speed of the motor. it provides a high starting torque as well as high level of efficiency and offers several options to work as a whole system. engineering students in the industry are expected to have an understanding of the working principles of an induction motor. in this demonstration device, two induction motors are mounted on a plate (fig. 2). one of them is a three-phase two-pole squirrel cage induction motor rated at 200 w, the other is a three-phase four-pole squirrel cage induction motor rated at 120 w. the motors are driven by suitable omron vs mini j7 vfds. they are compact general-purpose inverters, which are simple to use as well as have several digital and analogue channels. the larger motor has a double-sided shaft to which a dc motor is mounted and functions as a tachogenerator that measures the shaft speed, which enables the demonstration of the slip of the motor. the digital inputs of the inverter are used in this project to enable the rotational direction selectors. the analogue input is a speed reference and the output is a current monitor related to the connected motor. the vfd is set to the v/f (voltage, frequency control) mode, so the figure 2: demonstration device of an induction motor drivetrain. one two-pole (2) and one four-pole (3) induction motor were connected with flexible couplings. the motors were driven by frequency converters (8). a small dc motor was used as a tachogenerator (1). the power distribution network and control circuit were placed in a plastic box (4). the raspberry pi microcomputer (7) had a separate power supply (6) and was connected to a 7-inch display (5). voltage and frequency is set according to the set speed by the analogue input. an external mcp3008 analog-to-digital (a/d) converter and a mcp41010 8-bit digital potentiometer are connected to the raspberry pi. the a/d converter is used for the current monitoring and the potentiometer is used to set the reference speed in the vfd. both integrated circuits communicate through serial peripheral interface (spi) communication with the microcomputer. the first three tabs on the program consist of lessons concerning induction motors and vfds as well as a tutorial for configuring the inverters. videos are embedded in the fourth tab about induction motors and vfds. at the time of writing, three measurement tasks are available on this device. one of them is manual control, where tasks written in the provided worksheet can be carried out. automatic measurement tasks are located in the following two tabs, including a demonstration outlining how an induction motor can be started (fig. 3) and example measurements of acceleration due to the centre of gravity of the eccentric mass at multiple rotational speeds. figure 3: measurement example of the induction motor drivetrain. the example presents the starting current of the motor as a function of time using frequency converters. hungarian journal of industry and chemistry framework for demonstration devices 19 figure 4: demonstration device of a magnetorheological clutch. our magnetorheological device uses an induction motor (1) as a torque source driven by a vfd, moreover, both the driver and driven parts are connected by a flexible coupling (2, 5) to the actual clutch (3). the clutch is held in place by slotted placeholders (4). figure 5: schematic diagram of the magnetorheological clutch. the magnetorheological fluid was located between the input (1) and output (2) disks. the input disk was connected to the shaft by a ball bearing. the clutch was sealed by an o-ring at the output disk and an oil seal at the ball bearing. a coil (4) consisting of approximately 1200 turns of copper wire was located around the disks. the magnetic field lines were directed through the fluid with the help of magnetic flux guiders (4). 4. magnetorheological clutch magnetorheological (mr) fluids are intelligent materials that exhibit the remarkable property of being able to change their rheological properties in the presence of an external magnetic field [6]. they are composed of small (10 µm) particles with permeability µp suspended in a carrier fluid with permeability µf (µf < µp). when a magnetic field is applied to the fluid, the particles acquire a magnetic dipole moment and become arranged in pairs before forming chain-like structures, which act against the shear force producing a change in the apparent viscosity. this phenomenon is used in various applications, namely in brakes [7], clutches [8], superfinishing [9], and dampers [10]. it can be used in clutches to precisely control the transmitted torque by varying the magnetic field. magnetorheological clutches can be disk-type or cylindrical. for our demonstration, the disk-type mr clutch depicted in fig. 4 was developed and built. the transmitted static torque was measured indirectly by a strain gauge connected to a hx711 adc (analoguefigure 6: measurement example of the mr clutch. the transmitted torque of the clutch at a constant speed as a function of the magnetic induction. to-digital converter). using the known force, the acting distance torque could be calculated. the induction motor was driven by a frequency converter and the coil excited by pulse-width modulation (pwm). a cross-section of the clutch can be seen in fig. 5. the clutch can transmit approximately 0.6nm of torque at its maximum magnetic induction of 80mt. students can measure the torque in the form of a graph as both a function of the magnetic field fig. 6 and rotational speed using the provided sliders and displays. 5. equipment used to measure the rolling resistance coefficient the rolling resistance force and rolling resistance coefficient (rrc) play important roles in the automotive industry, because they are physical constants that describe the interaction between the road surface and tyres. the rolling friction is a driving resistance force that motor vehicles are subjected to which influences several parameters, including fuel consumption. the goal was to design and implement a piece of experimental equipment for demonstration purposes to measure the coefficient of rolling friction on different modelled road surfaces. the drum arrangement for measuring was chosen, which is widespread in the industry and occupies little space [11]. the measuring equipment consisted of a drum with a large diameter, which represented the modelled road surface, that was rotated by an ac induction motor; a test wheel, which was moved by linear stages; and a frame, which held the parts of the equipment together. although the road surfaces, composed of rubber, textile and a foamlike material, were adhered to the surface of the drum, it was possible to change them. a cad model of the measuring equipment is shown in fig. 7. the rrc was measured based on the measurement of the rolling resistance force. since the rolling resistance is a force, this is the most direct method of measuring it. the rolling resistance acts on the connection point between the wheel and drum. even though the line of action is vertical, its direction depends on the direction of rotation. the apparatus measured the force using load cells rotated in both clockwise and anticlockwise directions be49(1) pp. 17–21 (2021) 20 decsi et al. figure 7: the cad model of the apparatus: 1. drum using different modelled road surfaces, 2. test wheel, 3. test wheel mounted on load cells, 4. linear stage for moving the test wheel towards the drum, 5. frame, 6. linear stage for lowering the test wheel onto different surfaces, 7. ac motor driving the drum. figure 8: the rolling resistance coefficient measured on the three modelled road surfaces. fore calculating the coefficient according to the difference between the two results. on a graphical user interface, the user can select the road surface to be modelled as well as the compressive force between the test wheel and drum. each measurement is also presented on this graphical user interface. several test measurements were made using different settings and the repeatability of each measurement investigated. the rrcs on the different road surfaces are easily distinguishable and the relative standard deviations acceptable (smaller than 20%) for demonstration purposes. although no values for these modelled road surfaces are found in the literature, the measured coefficients correspond to values measured of tyres on asphalt and dirt roads. the dependence of the rrc on the circumferential speed, which varied between 3 km/h and 12 km/h, was investigated. measurements on all three modelled road surfaces were made using the same parameters (20n compressive force and 0.8 bar(g) tyre pressure). the results with descriptive statistics are shown in fig. 8. the rrc increases proportionally to the circumferential speed as expected and is in agreement with the literature [12]. 6. ultrasonic distance measurements made by a sensor ultrasound are high-frequency sound waves ranging from 20 khz to a few mhz that cannot be detected by the hufigure 9: measuring the ultrasonic distance. the device consisted of a fixed ultrasonic transmitter (2) and a receiver (3) moved by a linear stage driven by a stepper motor (5). the control system and circuit (1) as well as the power distribution and power supply system (4) were located in separate boxes. a 7-inch display was installed on the device (6). figure 10: example measurement made by the ultrasonic sensor demonstration device. the example shows the resonance curves of both the transmitter and receiver. man ear. ultrasound can be produced by piezoelectric crystals since when an ac voltage is applied across the crystals, mechanical displacement occurs. by choosing the appropriate degree of excitation, piezoelectric crystals may even exhibit ultrasonic emission. piezoelectric crystals are polarized by mechanical deformation and the voltage can be measured between opposite plates of a crystal. as a result of vibrations (e.g., ultrasound), an alternating voltage can be measured between the opposite plates of a crystal at the same frequency as the vibrational frequency, i.e., these crystals can also act as an ultrasound receiver. the measuring arrangement consisted of an ultrasonic transmitter and an ultrasonic receiver (fig. 9). the distance between the transmitter and receiver could be set using a linear stage. since the ultrasonic transmitter was driven by a pwm (pulse-width modulation) signal, the fill factor and frequency of which could be changed, the device was suitable for two measurement tasks. one of the measurement tasks was measuring the resonance curve (fig. 10). the algorithm set the distance between the transmitter and receiver at 60mm. by changing the frequency of the ultrasound emitted by the transmitter using a slider on the user interface, the resonance curve of the receiver could be determined. the amplitude of the receiver signal could be read on a pop-up window. by plotting the amplitudes as a function of frequency, both hungarian journal of industry and chemistry framework for demonstration devices 21 the resonance curve and resonance frequency could be measured. the frequency could be set between 38 khz and 42 khz. the other measurement task measured the amplitude of the voltage at the receiver as a function of the distance between the transmitter and receiver at the resonance frequency determined by the previous task. the distance could be set between 10mm and 300mm. 7. summary a framework for a demonstration device has been presented by four pilot projects which is capable of providing practical knowledge in distance learning environments. since the device can connect to the internet, students are able to complete tasks set by the educator remotely. the framework is user-friendly for both programmers and users. only authorized persons are allowed to access the device, which also provides real-time monitoring and feedback for the educators. the framework is easily adaptable to many applications. acknowledgement this study was supported by the european union and cofinanced by the european social fund. efop-3.6.2-162017-00002 references [1] unesco ieasalc: covid-19 and higher education: today and tomorrow, tech. rep., unesco, 2020, http://www.guninetwork.org [2] perea martins, j.e.: an educational software for measurements demonstrations and data logging with arduino boards, phys. educ., 2020, 55(6), 063004 doi: 10.1088/1361-6552/abae25 [3] la rocca, p., riggi, f., pinto, c.: remotely teaching arduino by means of an online simulator, phys. educ., 2020, 55(6), 063003 doi: 10.1088/13616552/abaa21 [4] wilson, g., stacey, e.: online interaction impacts on learning: teaching the teachers to teach online, australas. j. educ. technol., 2004, 20(1), 106675 doi: 10.14742/ajet.1366 [5] richardson, r.t., drexler, t.l., delparte, d.m.: color and contrast in e-learning design: a review of the literature and recommendations for instructional designers and web developers, tech. rep.,10(4), 2014 https://jolt.merlot.org/vol10no4/richardson_1214.pdf [6] rankin, p.j., ginder, j.m., klingenberg, d.j.: electroand magneto-rheology, curr. opin. colloid interface sci., 1998, 3(4), 373–381 doi: 10.1016/s1359-0294(98)80052-6 [7] li, w.h., du, h.: design and experimental evaluation of a magnetorheological brake, int. j. adv. manuf. technol., 2003, 21(7), 508–515 doi: 10.1007/s001700300060 [8] latha, k.h., usha sri, p., seetharamaiah, n., assistant, s.: design and manufacturing aspects of magneto-rheological fluid (mrf) clutch, mater. today: proc., 2017, 4(4), 1525–1534 doi: 10.1016/j.matpr.2017.01.175 [9] jang, k.i., seok, j., min, b.k., jo lee, s.: an electrochemomechanical polishing process using magnetorheological fluid, int. j. mach. tool. manu., 2010, 50(10), 869–881 doi: 10.1016/j.ijmachtools.2010.06.004 [10] guan, x.c., guo, p.f., ou, j.p.: modeling and analyzing of hysteresis behavior of magneto rheological dampers, procedia eng., 2011, 14, 2756–2764 doi: 10.1016/j.proeng.2011.07.347 [11] andersen, l.g., larsen, j.k., fraser, e.s., schmidt, b., dyre, j.c.: rolling resistance measurement and model development, j. transp. eng., 2015, 141(2), 04014075 doi: 10.1061/(asce)te.1943-5436.0000673 [12] ehsani, m., gao, y., gay, s.e., emadi, a.: modern electric, hybrid electric, and fuel cell vehicles (crc press), 2004 doi: 10.1201/9781420037739 49(1) pp. 17–21 (2021) http://www.guninetwork.org/files/covid-19_en_090420.pdf https://doi.org/10.1088/1361-6552/abae25 https://doi.org/10.1088/1361-6552/abaa21 https://doi.org/10.1088/1361-6552/abaa21 https://doi.org/10.14742/ajet.1366 https://jolt.merlot.org/vol10no4/richardson_1214.pdf https://doi.org/10.1016/s1359-0294(98)80052-6 https://doi.org/10.1016/s1359-0294(98)80052-6 https://doi.org/10.1007/s001700300060 https://doi.org/10.1007/s001700300060 https://doi.org/10.1016/j.matpr.2017.01.175 https://doi.org/10.1016/j.matpr.2017.01.175 https://doi.org/10.1016/j.ijmachtools.2010.06.004 https://doi.org/10.1016/j.ijmachtools.2010.06.004 https://doi.org/10.1016/j.proeng.2011.07.347 https://doi.org/10.1061/(asce)te.1943-5436.0000673 https://doi.org/10.1201/9781420037739 introduction framework induction motor drivetrain magnetorheological clutch equipment used to measure the rolling resistance coefficient ultrasonic distance measurements made by a sensor summary hungar~journal of indus1rial chemis1ry veszprem vol. 29. pp. 45-51 (2001) investigation of the industrially applicable synthesis of iminodiacetic acid l. gulyas, g. deak\ s. k:eki\ r. horvatiianj?m. zsuga1 (department of chemical engineering, faculty of technical engineering, university of debrecen p.o. box 40, debrecen h-4028 hungary 1department of applied chemistry, university ofdebrecen p.o. box 1, debrecen h-4010 hungary) received: december 28, 2000; revised: april9,2001 the present paper deals with the synthesis of iminodiacetic acid, which is the basic material of the production of the plant-protecting agent n-phosphonomethyl glycine. the most economical procedure for the industrial preparation of iminodiacetic acid involves aminolysis of monochloroacetic acid, where the starting materials are monochloroacetic acid, ammonia and ca(oh)2. we improved the conversion of monochloroacetic acid into the target compound to 91 % from the present 67 % yield. our results show that the rate-determining step is the formation of iminodiacetic acid, while a considerable amount of glycine is present. our important recognition is that glycine, produced together with the desired iminodiacetic acid, can be converted with monochloroacetic acid to iminodiacetic acid after removal of the excess of ammonia from the reaction mixture. keywords: synthesis of iminodiacetic acid, concurrent consecutive, competitive reactions introduction the industrial production of n-phosphonomethyl glycine, an important plant-protecting agent · in agriculture, is based on either iminodiacetic acid, or glycine. starting with iminodiacetic acid, n­ phosphonomethyl glycine can be prepared in two steps. in the first step mannich condensation of iminodiacetic acid, paraformaldehyde, and orthophosphorous acid gives n-phosphonomethyliminodiacetic acid [1-10]. in the second step, catalytic oxidation of n­ phosphonomethyliminodiacetic acid leads to n­ phosphonomethyl glycine. n-phosphonomethyl glycine can also be synthesized directly from glycine. this procedure is based on treatment of a solution of glycine in methanol with paraformaldehyde and dimethylphosphite to obtain the sodium salt of n-dimethylphosphitmethyl glycine. addition of hydrochloric acid results in the precipitation of sodium chloride, and hydrolysis of n­ dimethylphosphit methylglycine sodium salt into n­ phosphonomethyl glycine. because of the higher yield, the procedure starting from iminodiacetic acid appears to be more economical than that based on glycine. the synthesis of iminodiacetic acid has been extensively studied, and most of the literature reports are patents. iminodiacetic acid can be manufactured from the following starting materials: a. hydroxyacetonitrile b. hydrogen cyanide and urotropine c. diethanolamine d. monochloroacetic acid table 1 preparation of iminodiacetic acid starting material reagent added yield,% hydroxyacetonitrile naoh, h3n 74 hcn,hmta diethanolarnine cich2-cooh h~ 90 glycine, naoh 45 glycine, naoh > 45 hcn,hmta cdo,naoh h3n(nacn) h3n, ca(oh)z 85 20-40 85 ref. [1j [2} [3j [41 [5, 6] [6, 7] [8] {9] {10] it is well known that the reaction of monochloroacetic acid with ammonia in an aqueous 46 medium produces a mixture of primary, secondary and tertiary amines and glycolic acid. the iminodiacetic acid-content of the reaction mixture is ca. 20-40 %, depending on the reaction conditions. glycine, as the primary product, may react with excess additional molecules of monochloracetic acid to give iminodiacetic acid and then nitrilotriacetic acid [11-13]. manufacturing of the product is presently based on a modified version of the protocol described in ref. [10]. thus, a 3.5 mol/dm3 aqueous solution of monochloroacetic acid is neutralized with concentrated ammonium hydroxide at 18 °c. to this aqueous solution of the ammonium salt powdered caustic lime is added to liberate ammonia, which takes part in the nucleophilic substitution at elevated temperature. the resulting solution is filtered, concentrated to remove the excess of ammonia, and iminodiacetic acid is liberated from the salt by the addition hydrochloric acid. the product crystallizes from the solution in the form of its hydrochloride salt. the above procedure is useful up to a ca. 67 % conversion of monochloroacetic acid into iminodiacetic .acid. the technological process is uncontinuous, and a further disadvantage is the long reaction time (10 hours). experimental materials monochloroacetic acid. ammonia solution and ca(oh)z were purchased from aldrich (germany) and were used as received. investigation of the reaction rates a solution of monochloroacetic acid (mca) of 8 mo1/dm3 was neutralized with a solution of ammonia of 8 molldm3 • the reaction was started by mixing 50 ml mca ammonia salt solution with 50 ml of a suspension of ca(oh):z of 4 mo1/dm3 • the reaction mixture was thermostated at 40 ac, 50 °c, 60 °c and 70 °c. after a predetermined time interval samples were taken from the reaction mixture and the concentration of cr, glicine and imda was determined. analytical methods for monitoring the reactions for the determination of the rate-equations of formation of iminodiacetic acid in a hatch-type reactor, analytical methods suitable for the determination of the concentration of the components in time are required. for this, key components/intermediates should be selected, and methods for their determination should be elaborated. quantitative determination of iminodiacetic acid for the quantitative determination of iminodiacetic acid various methods are known in the literature. for simplicity, a spectrophotometric method was employed. this methodology is based on the nitrosation reaction of iminodiacetic acid carried out with two-fold molar excess of sodium nitrite under acidic conditions at room temperature. nitrosoiminodiacetic acid possesses an absorption maximum at 350 nm, which follows the lamber-beer law in the concentration interval of 5 10·4-10·2 mol/dm3 • another components present in the system do not disturb the determination. simultaneous determination of glycine and iminodiacetic acid on a layer of strongly acidic cation exchange resin based on the results of devenyi et al. [14], one­ dimensional layer chromatography on a strongly acidic cation exchange resin was applied. the spots were developed by ninhydrin. quantitative evaluation of the chromatograms is accomplished with a videodensitometer. monitoring of the change of the concentration of monochloroacetic acid with a chloride ion-sensitive membrane electrode the chloride ion concentration in the system was measured with a chloride ion-selective electrode, which can be applied in a wide range of cr concentration. results and discussions investigation of the reaction rates in a batch-type reactor no data were found in the literature concerning the kinetics, and equations describing the rate of formation of iminodiacetic acid. the complex chemical reaction (involving monochloroacetic acid, ammonium hydroxide, calcium hydroxide and water), wich serves as the basis of manufacturing the target substance is given by the following series of equations: " kb ;::hz-c~ 2 cl-ch:r--cooh + nh3 + 2 ca(oh}l -..::::....;•:... nh"ca + cac}z + 4 h 2 o (1) c~-c~ ~ 47 km cl-chzcooh + nh3 nh2-ch2coo· + hcl (2) (3) cl-ch2cooh + nh2ch2coo· kzb,.. nh-(ch2coo)f· + hcl 2 k3 cl-chzcooh + nh(ch2coo)z . __ ,.. n -(ch2coo)? + hcl (4) (5) cl-chzcooh + h20 k3b,.. ho-ch2coo+ hcl the stoichiometry of the reaction is determined by a joint contribution of each of these processes. the equation does not represent all of the reactions proceeding in the complex system, and therefore, does not illustrate the contributing reactions which could be modified to obtain a desired better outcome. however, it is still possible to select a few processes which might be rate-determining because of their relatively low rate. such an approach of discussing the reaction rate would permit description of the details of the complex reaction as a whole. we supposed that the chemical process can be described with the following, simplified concurrent consecutive, competitive equations: by investigating the elemental steps and conditions of the reaction of monochloroacetic acid with ammonia we can learn that the reaction system is concurrent, consecutive and competitive. the outcome is clearly a function of the ratio of the two nucleophiles, and also of the preponderance of the intermediary glycine. as no relevant data have been reported, we can thus suppose that apart from the molar ratio of the above components, the ratio of the rate of the two reactions may also be decisive on the formation of iminodiacetic acid. this latter is, naturally, a function of the molar ratio of monochloroacetic acid and ammonia. the reaction of monochloroacetic acid with ammonia results in the formation of glycine as the primary product, which represents a second nucleophile in the system. thus, glycine can react with monochloroacetic acid in a concurrent reaction to produce iminodiacetic acid. this concurrent consecutive reaction is accompanied by the hydrolysis of monochloroacetic acid as a parallel process. under the initial conditions of the reaction the mixture contains calcium hydroxide in an equimolar quantity with that of monochloroacetic acid, thus hydrolysis must be taken into account more pointedly in this stage of the process. to have an overall look on the reaction system we had to determine the rate constants of the individual partial reactions. we have shown that the change of the concentration of monochloroacetic acid can be followed by measuring the chloride ion concentration, and that the effective conversion of this substance can be monitored by the determination of the concentration of iminodiacetic acid. therefore, the progress of the reaction in time was followed by analyzing the quantities of the chloride ion, iminodiacetic acid and glycine at various periods. figure] shows the change of the concentration of iminodiacetic acid, glycine and monochloroacetic acid in the brutto chemical reaction, and one can see that the complete conversion of monochloroacetic acid is associated with a 65 % effective and utilizable transformation into iminodiacetic acid. the chromatographic investigation on cation­ exchange resin layer, followed by videodensitometric evaluation demonstarted that (depending on the reaction temperature) a considerable volume (20-27 %) of glycine is present in the reaction mixture. therefore, further conversion of glycine (produced from monochloroacetic acid) into iminodiacetic acid does not proceed in the lack of monochloroacetic acid, as-for kinetic reasons-the concentration of ammonia has been selected higher than that of monochloroacetic acid. 0.9 0.8 mi 0.7 "" ~ 0.6 ';;;' 0.5 ! 0.4 § 0.3 u 0.2 0.1 50 100 150 200 250 300 350 time{min) fig. i change of the concentration of reactants and products versus time ( • monochloroacetic acid, • iminodiacetic acid, + glycine, at 60 °c) according to the data of figure 1, the apparent rate constants of the conversion of monochloroacetic acid (kb) and the formation of iminodiacetic acid (k2s) can be determined. by plotting the logarithm of the relative concentration of monochloroacetic acid against the time a linear connection is obtained. figure 2 shows this relation, i.e., the rate constants of the conversion of monochloroacetic acid in the brutto reaction. 48 0 -1 -2 .s -3 -4 -5 -6 0 100 200 300 400 500 time (min) fig. 2 logarithm of the relative concentration of monochloroacetic acid versus time ( +40, • 50, a 60, • 70 °c) the observed linear relationship demonstrates the pseudo-first order of the reaction, and the dependence of the· apparent rate constants on the temperature is expressed by eq. 6.: as the complete transformation of monochloroacetic acid in the brutto chemical reaction is of pseudo-first order;and due to the finding that glycine is in an excess compared to the concentration of monochloroacetic acid at the end of the reaction, formation of iminodiacetic acid can also be described by a pseudo-first order equation. for the determination of the k2b rate constant, the logarithm of the concentration of iminodiacetic acid produced in the brutto process is plotted as a function of the reaction time. figure 3 shows this relation, i.e. the rate constants of the formation of iminodiacetic acid in the brutto reaction. 0 -0.05 -0.1 -o.is -0.2 .s -0.25 -0.3 -0.3s -0.4 -0.45 -0.5 +--.---'--r-.-.._,.>~.---.-......,.---.---; a 2& 40 oo 80 100 tro 140 1ro i80 200 t'nne(min) fig. 3 logarithm of the relative concentration of iminodiacetic acid versus time ( +40, • 50, a 60, • 70 °c) the observed linear relationship demonstrates the pseudo-first order of the reaction, and the dependence of the apparent rate constants on the temperature is expressed by eq. 7. determination of the formation of nitrilotriacetic acid the formation of nitrilotriacetic acid in the reaction of iminodiacetic acid with monochloracetic acid is not significant under the applied experimental conditions. "' determination of the rate constant of the hydrolysis of monochloroacetic acid under isolated conditions the rate constant k3b of the hydrolysis was determined as follows: monochloroacetic acid was treated with an excess of calcium hydroxide, and the chloride ion-content of the reaction mixture was measured in given intervals. thus the concentration of monochloroacetic acid can be readily determined in a given state of the reaction. the change of the concentration of monochloroacetic acid as a function of the reaction time is shown in figure 4. me ;g 0.8 ! 0.7 ~ 0.6 ~ 0.5 s 8 0.4 0.3 0.2 +---....----,----,----,-----, 0 100 200 300 400 500 time (min) fig.4 change of the relative concentration of mca versus time ( +40, • 50, a 60, x 70 °c) by plotting the logarithm of the relative concentration of monochloroacetic acid as a function of time a linear relation is obtained, indicating the pseudo­ first order of the reaction (see figure 5). the dependence of the apparent rate constants on the temperature is expressed by eq. 8. (8) 0.2 0 -0.2 -0.4 ... -0.6 ..!l -0.8 -1 -1.2 -1.4 0 ~ ~ ~ d m ~ m ~ ~ time (min) fig.5 logarithm of the relative concentration of mca versus time ( +40,. 50, ... 60, • 70 °c) determination of the rate constant of the formation of glycine the quantity of glycine, produced in the reaction mixture consisting of monochloroacetic acid, calcium hydroxide, ammonia and water cannot be measured directly, as a part of glycine is converted into iminodiacetic acid in a consecutive reaction. therefore, the rate constant of the formation of glycine is determined by calculation. according to the law of conservation of mass, the current composition of the reaction mixture can be described by the following equation: [mca]o=[mca]+[gly]+2[imda]+[ga] where [mca], [gly], [imda] and [ga] represent the ~oncentration of monochloroacetic acid, glycine, i~nodiacetic acid and glycolic acid, respectively, at a glven t time, and the (0) subscript means the initial concentration of these materials. the conversion of glycine from monochloroacetic acid can be calculated from the experimental data with the following equation: where [glyfs=[gly]*+[imda]*= = 1-[mca]*-[imda]*-[ga]* [?lyjsis the total concentration of glycine produced (t.~. the sum of the quantity present in the reaction mixture and that converted into iminodiacetic acid), and the* subscripts_are for the relative concentrations of the components divided by [mca j0. the calculations reveal the pseudo-first order of the formation of glycine, and the dependence of the apparent rate constants on the temperature is expressed byeq. 9.: 49 the apparent rate constant values of the brutto chemical reaction are summarized in table 2. table 2 apparent rate constants of the brutto chemical reaction . 40 50 60 70 3.469'10-~ 8.9so-10·3 18.490'10'3 50.24•10'3 1.346"10"3 4.296•10'3 11.o3·10·3 20.85'10"3 1.25"10"3 3.22"10'3 6.65·10-3 18.09'10"3 0.530"10'4 2.550"10'4 6.740"104 24.80•10"4 as the virtual rate constants are characteristic only of a given system, no suppositions concerning the kinetics can be drawn by their comparison. under the given conditions (i.e. at a given ammonia c~mcentration) km > kza, which means that the reacti~n _js shifted towards the formation of glycine. investigation of the reaction ofmonochloroacetic acid with glycine without ammonia it has been already mentioned that iminodiacetic acid is produced in a consecutive reaction: glycine, formed from monochloroacetic acid and ammonia reacts with monochloroacetic acid as the second nucleophilic reagent present in the reaction mixture according to equation (2). as the value of the rate constant of the formation of glycine (km) is higher than that of the formation of iminodiacetic acid (kz8), a considerable amount (27-30 %) of glycine is left unreacted in the system at the end of the reaction. the rest of glycine can be utilized by the removal of the other nucleophilic partner, ammonia, from the system and by introducing an equimolar amount o~monochloroacetic acid to ensure to react with glycine. th--e~rate constant of the formation of iminodiacetic acid1k2r) under isolated conditions can be then determined by reacting monochloroacetic acid with glycine in the absence of ammonia, in a solution neutralized with calcium hydroxide. the conversion of monochloroacetic acid and glycine is monitored by the determination of the concentration of the chloride ion and iminodiacetic acid. the data of these measurements are shown in figure 6, by plotting the relative concentration values against the reaction time. as figure 6. represents, upon the action of calcium hydroxide, formation of glycolic acid also proceeds in a parallel reaction, and this is demonstrated by the difference in the actual concentration of the chloride ion and iminodiacetic acid. by comparison of the data of figures 1 and 6 one can recognize that the useful {effective) conversion of monochloroacetic acid (which may be as high as 8090% depending on the temperature) is more favourable when irninodiacetic acid is produced with the reaction of glycine and monochloroacetic acid. however, the effective conversion is decreased by the formation of 50 glycolic acid, which can be restrained with ammonia. but such an alternative would lead to the decrease of the production of iminodiacetic acid, as well, due to a concurrent reaction of monochloroacetic acid with ammonia, to result in the increase of the glycine-content of the reaction system. 0 50 100 150 200 250 300 350 400 time (min) fig.6 reaction of monochloroacetic acid with glycine · under isolated conditions at 60 °c ( • monochloroacetic acid, • iminodiacetic acid, + glycolic acid, at 60 °c) the total conversion of monochloroacetic acid, including the effective conversion and hydrolysis of monochloroacetic acid, can be described with a pseudo­ frrst order equation. due to the hydration of glycine, the hydroxide ion concentration of the mixture is also increasing, which results in the ·increase of the rate of the hydrolysis of monochloroacetic acid, as well. in figure 7 the iogaiithm of the relative coneentration values of monochloroacetic acid versus time is depicted. the roughly linear relation suggests that the transformation of monochioroacetic acid is of pseudo-first order, and that the dependence of the virtual rate constants on the temperature can be given by eq.lo. so 100 tso zoo :!so 300 :jso 400 450 'lltiloe(~ f(,. 1 logarithm of the relative concentration of monocbloroacetic acid versus time f• 40, • so, • 60, • 70 °c) 1 6921) k1 = 2.924·107 ·ex1_ -t (10) the reciprocal of the concentration of glycine (which is equal, with the opposite sign, with the change of the iminodiacetic acid concentration) as a function of the reaction time is shown in figure 8. """ q .!! ~e :;:, .!< .... 12 10 8 6 4 2 0 0 50 100 150 200 250 300 350 400 450 time (min) fig.8 reciprocal of the concentration of iminodiacetic acid versus time. (• 40, .. 50, • 60, +70 °c) the obtained linear relation indicates a second order reaction, so that iminodiacetic acid is produced in a second order process. the dependence of the rate constant on the temperature can be approached by the k,n arrhenius equation eq. 11. ku =3.523·10 6 ·ex{6~1) (11) the difference between the total and effective (useful) conversion of monochloroacetic acid comes from the production of glycolic acid, and thus the relative concentration of glycolic acid can be directly calculated. the rate constant values k3s, measured for the formation of glycolic acid, were in good agreement with the calculated rate constant values k31 on the basis of the reaction of glycine with monochloroacetic acid. in table 3 the apparent rate constants of the reactions carried out in the isolated chemical process are summarized. table 3 apparent rate constants of the isolated reaction t kr k21 k31 [ 0cj [min"1j [dm3 min·l mor1] (min"1] 40 7.302·to·3 1.285·10·2 50 14.48"10"3 2.846"10"2 60 27.55"10"3 4.243•10"2 10 5o.so-uf3 7.369·m·2 2.54"104 7.65"104 27.70'104 conclusion during our work, inspection of the reaction system was carried out. in our working hypothesis we supposed that in the manufacturing system, consisting of monochloroacetic acid, ammonia, calcium hydroxide and water, concurrent consecutive, competitive reactions proceeded. we proved that the rate of the formation of nitriloacetic acid is immeasurably low. for monitoring the other three basic reactions, three key­ components were selected, and analytical methods were elaborated for their determinations. the apparent rate constants of the processes were calculated from the concentrations of the key-components. comparison of the rate constants shows that the rate­ determining step of the brutto conversion is the formation of iminodiacetic acid, and in agreement with the data of the measurements, a considerable amount of glycine is present. our important recognition is that glycine, produced together with the desired iminodiacetic acid, can be converted with monochloroacetic acid to iminodiacetic acid after removal of the excess of ammonia from the reaction mixture. during this latter process, the previously produced crop of iminodiacetic acid did not decompose. 51 acknowledgement this work was financially supported by grants nos. t 019508, t 025379, t 025269, t 030519, m 28369, f 019376 given by otka (national found for scientific research development, hungary), and by grant no. fkfp 0444111997. references 1. u.s. pat. 3,153,668 (1959) 2. u.s. pat. 3,812,434 (1974) 3. japan pat. 71 40,611 (1971) 4. japan pat 76 19,718 (1976) 5. u.s. pat. 3,904,668 (1978) 6. german pat. 2,613,994 (1960) 7. german pat. 2,527,120 (1966) 8. u.s. pat. 3,842,081(1977) 9. sai:lorot.: bull. chern. research. inst., tohoku univ.j951, 1, 97-100 10. french pat. 1,554,236 (1967) 11. perkin a. g. and duppar.m.: ann., 1853, 108 12. ortenj.m. andhillm.: j. am. chern. soc., 1931, 53,2797 13. tobie w.c. and ayres g.b.: j. am. chern. soc., 1942,64,725 14. devenyit.: hung. sci. inst., 30, 1974 page 45 page 46 page 47 page 48 page 49 page 50 page 51 hungarian journal of industry and chemistry vol. 52(1) pp. 19–27 (2024) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2024-04 molecular interaction studies of binary mixtures of diethyl oxalate with butyl vinyl ether, diisopropyl ether, anisole and dibutyl ether in terms of thermodynamic, transport and acoustic properties ajit bhumkar1* and pralhad wagh1 1 department of chemistry, vpm’s b.n. bandodkar college of science (autonomous), thane, 400601, india viscosity, the speeds of sound and density were measured in the binary mixtures of diethyl oxalate with butyl vinyl ether, diisopropyl ether, anisole and dibutyl ether at t = 303.15, 308.15 and 313.15 k. the experimental data were used to calculate the excess molar volume 𝑉𝑚 𝐸 ,deviation in viscosity δη and the acoustical parameters, namely isentropic compressibility (ks), free volume (vf ), free length (lf ) and internal pressure (πi). the excess or deviation properties were fitted to the redlich-kister polynomials and the results interpreted in terms of the molecular interactions present in mixtures. theoretical viscosities were calculated using the grunberg-nissan, lobe and krishnan-laddha models before their merits were studied in terms of interaction parameters. keywords: diethyl oxalate, density, viscosity, speeds of sound, isentropic compressibility 1. introduction thermodynamic, transport and ultrasonic properties of liquid-liquid mixtures are essential theoretically and in terms of process design. density, viscosity and speeds of sound as well as their excess or deviation properties are mostly useful in engineering design processes in addition to the chemical and biological industries [1]. the analysis of these properties provides detailed information on the intermolecular interactions present in the liquid mixtures. further excess properties provide key values for calculating the properties of multicomponent mixtures from the data of pure components. they can also provide data to evaluate parameters characterizing interactions between unlike molecules. diethyl oxalate (deo) is a colorless organic compound and the diethyl ester of oxalic acid. deo is used in active pharmaceutical ingredients, polymers and intermediates for dyestuffs as well as a solvent to make esters, resins, fragrances and electronic lacquers. tremendous growth has been seen in the pharmaceutical industry attributed to the high consumption of deo. demand for drugs such as steroids and barbiturates has led to an increase in the usage of deo. while ethers are a class of organic compounds that contain an oxygen between two alkyl groups, they are relatively unreactive so are useful as solvents for fats, oils, waxes, perfumes, resins, dyes, gums and hydrocarbons. vapors of certain received: 14 nov 2023; revised: 18 dec 2023; accepted: 5 jan 2024 *correspondence: ajitnanabhumkar@gmail.com ethers are used as insecticides, mildewcides and fumigants for soil. these numerous applications of ethers have sparked the present study to know more about their possible molecular interactions when mixed with deo. a literature review uncovered several studies on the thermodynamic, transport and volumetric properties of binary mixtures of esters with different organic liquids [2]-[6]. likewise, few studies have been undertaken on the density, viscosity and speeds of sound [7]-[11] of binary mixtures containing deo with ethers as well as polar and non-polar solvents. however, it has been observed that to the best of our knowledge, except for the system of deo with anisole (as), no studies have been found in the literature concerning any of the other binary systems undertaken in our present study. the study of the thermodynamic and transport properties of binary mixtures containing esters with ethers contributes to the understanding of the theory of the liquid state [12]-[17]. in this paper, the densities, viscosities and speeds of sound of the binary mixtures of deo with butyl vinyl ether (bve), diisopropyl ether (dipe), as and dibutyl ether (dbe) at t = 303.15, 308.15 and 313.15 k were reported. from the above experimental data, several excess or deviation parameters were evaluated at the respective temperatures which are important in industrial processes. these excess or deviation properties were fitted to the redlich-kister polynomial equation [18] to derive the binary coefficients and estimate the standard https://doi.org/10.33927/hjic-2024-04 mailto:ajitnanabhumkar@gmail.com bhumkar and wagh hungarian journal of industry and chemistry 20 errors. the experimental viscosity data were used to test correlations between viscosity models proposed by grunberg-nissan [22], lobe [23] and krishnan-laddha [24]. 2. experimental 2.1. materials deo, bve, dipe, as and dbe all with a mass fraction purity of >0.990 were supplied by sigma-aldrich and purified by vacuum distillation. the filtrates of these chemicals were collected in dark bottles over molecular sieve 0.4 nm beads to remove any water then degassed just before their use. gas chromatography (gc) detected no traceable amounts of impurities in the filtrates. the stated purities of these filtered chemicals and their final purities as estimated by gc (hp 8610) analysis are shown in table 1. 2.2. methods the binary liquid mixtures were arranged by mixing known masses of pure liquids in airtight stoppered bottles. all mass measurements were made using a mettler single-pan digital balance with an accuracy of +0.01mg (ae240, switzerland). the resulting mole fraction uncertainty was calculated to be less than 1×10-4. the densities of the pure chemicals and their binary mixtures were fixed by using a density meter (rudolph research analytical ddm 2910). the instrument contains a high-precision platinum thermometer in the density sensor to accurately measure the temperature. the instrument was calibrated frequently before each experiment was started using deionized double distilled water and dry air. the uncertainty in the densities was within 0.0004 g·cm-3. the viscosities of the pure liquids and their mixtures were measured by using a ubbelohde viscometer [17]. the viscometer was calibrated using double distilled water. the uncertainty in the viscosities was estimated to be within 0.10 mpa·s. the speeds of sound of the pure liquids and liquid mixtures were calculated by using a mittal enterprises model f-81 single-crystal variable path interferometer (new delhi, india) operating at a frequency of 2 mhz and with an accuracy of + 0.01ms-1. the instrument was calibrated by measuring the velocity in standard liquids, i.e. ar grade benzene and carbon tetrachloride. the estimated uncertainty in the speeds of sound was found to be within 1%. all measurements were taken at a constant temperature in an insref model iri-016c constant low temperature bath (india) by circulating water from a thermostat around the cell containing the liquid. 3. results and discussion the experimental values of the density (ρ), viscosity (η), speeds of sound (u) and isentropic compressibility (ks) were determined for the studied binary mixtures over the entire composition range expressed as a function x1 of deo at 303.15, 308.15 and 313.15 k. a large number of data are not reported in this paper but are available from the editorial office of this journal. from the density data, excess molar volumes (𝑉𝑚 𝐸) and deviations in viscosity (∆η) were calculated using the following relations: 𝑉𝑚 𝐸 = (𝑥1𝑀1 + 𝑥2𝑀2)/𝜌12 − (𝑥1𝑀1/𝜌1 + 𝑥2𝑀2/𝜌2) (1) ∆𝜂 = 𝜂12 − (𝑥1𝜂1 + 𝑥2𝜂2) (2) where x, m, η and ρ are the mole fraction, molar mass, viscosity and density, respectively, of the pure components 1 and 2. ρ12 denotes the density and η12 the viscosity of the binary mixture. isentropic compressibility (ks), deviation in isentropic compressibility (∆ks), intermolecular free length (lf), internal pressure (πi) and free volume (vf) are calculated using the following equations: 𝐾𝑆 = [1/(𝑈2𝜌)] (3) ∆𝐾𝑆 = (𝐾𝑆)12 − [𝑥1(𝐾𝑆)1 + 𝑥2(𝐾𝑆)2] (4) 𝐿𝑓 = 𝐾 ∙ (𝐾𝑆)1/2 (5) 𝜋𝑖 = 𝑏𝑅𝑇(𝐾𝜂/𝑈)1/2 (𝜌2/3 / 𝑀𝑒𝑓𝑓 7/6 ) (6) 𝑉𝑓 = (𝑀𝑒𝑓𝑓𝑈/𝜂𝐾) 3/2 (7) in equations 5-7, k denotes the temperaturedependent jacobson’s constant and b stands for the cubic packing fraction taken as 2 for all the liquids, while r represents the universal gas constant and t refers to the experimental temperature. meff = ∑ximi. where xi denotes the mole fraction and mi stands for the molecular weight of the ith component. these calculated properties are also available at the editorial office. furthermore, the excess or deviation properties (y) recorded were fitted to the following redlich-kister polynomial equation by the method of least squares to derive the binary coefficients: ∆𝑌 = 𝑥1𝑥2[𝐴0 + 𝐴1(𝑥1 − 𝑥2) + 𝐴2(𝑥1 − 𝑥2)2] (8) table 1: chemical specifications and purity estimation chemical source initial mole fraction purity purification method analysis method final mole fraction purity deo sigmaaldrich 0.990 none gc-8610 > 0.996 bve sigmaaldrich 0.980 distillation gc-8610 > 0.984 dipe sigmaaldrich 0.980 none gc-8610 > 0.984 as sigmaaldrich 0.997 none gc-8610 > 0.997 dbe sigmaaldrich 0.993 distillation gc-8610 > 0.995 gc* gas-liquid chromatography molecular interaction studies of binary mixtures 52(1) pp. 19–27 (2024) 21 where δy represents the relevant excess or deviation property. the standard deviations of 𝑉𝑚 𝐸, ∆η, ∆ks, excess free volume (𝑉𝑓 𝐸), excess intermolecular free length (𝐿𝑓 𝐸) and excess internal pressure (𝜋𝑖 𝐸) were calculated using the following equation: 𝜎(𝑌) = [∑(𝑌𝑒𝑥𝑝 − 𝑌𝑐𝑎𝑙) 2 /(𝑁 − 𝑛)] 1/2 (9) where n denotes the number of data points, n represents the number of coefficients, while yexp and ycal denote experimentally obtained and theoretically calculated excess or deviation properties, respectively. the calculated values of the polynomial coefficients a0, a1 and a2 along with their standard deviations σ are given in table 2, moreover, the results of the excess or deviation properties calculated by equation 8 are graphically represented in figures 1-6. as shown in figure 1, the 𝑉𝑚 𝐸 values for the binary mixtures of deo with bve, deo with dipe and deo with as are negative, whereas for deo with dbe it is positive over the entire range of composition at all the studied temperatures. furthermore, the 𝑉𝑚 𝐸 values decrease as the temperature increases for the mixtures of deo with bve, dipe and dbe, while for deo with as, these 𝑉𝑚 𝐸 values increase as the temperature increases, indicative of the effect of the temperature. the 𝑉𝑚 𝐸 values are found to be more negative for dipe with minima in the isotherm at x1 = 0.5018, while for dbe, the 𝑉𝑚 𝐸 values are positive and the maximum for the excess volume observed at x1 = 0.5018. these 𝑉𝑚 𝐸 values can be ordered as follows: dbe > as > bve > dipe the negative 𝑉𝑚 𝐸 may be due to the interstitial accommodation of the ester molecules with an associated structure, the formation of weak molecular complexes through hydrogen bonds, π-π interactions and dipoledipole interactions. while positive 𝑉𝑚 𝐸 values may be attributed to the breaking of the molecular association of the components. in our present study, the molar masses of deo, bve, dipe, as and dbe are 146.14, 100.16, 102.18, 108.14 and 130.23 g·mol-1, respectively. the molar volumes of deo at t = 303.15, 308.15 and 313.15 k are 137.04, 137.79 and 138.52 cm3·mol-1, respectively. furthermore, the molar volumes for the studied ethers namely bve, dipe, as and dbe are (130.25, 131.12, 132.00), (143.28, 144.34, 145.45), (109.85, 110.37, 110.91) and (170.45, 172.44, 173.45) cm3·mol-1, respectively. these molar volumes of deo differ slightly to those of bve, dipe and as, indicating that the molecules of deo are interstitially accommodated into clusters of bve, dipe and as leading to negative 𝑉𝑚 𝐸 values. the increase in 𝑉𝑚 𝐸 values for as as the temperature increases may confirm the presence of stronger dispersion forces or dipole–dipole interactions between the component molecules leading to greater contraction in volumes as the temperature rises. the positive 𝑉𝑚 𝐸 values observed for deo and dbe may indicate weak molecular interactions. the variation in the deviation in viscosity (∆η) as a function of the mole fraction (x1) of deo at the studied temperatures is shown in figure 2. it was observed that for all the systems of deo, ∆η was found to be negative throughout and at the studied temperatures. these negative ∆η values suggest the presence of weak dipolar forces in mixtures of liquids. it is found that ∆η is large and negative for the mixtures of deo with dipe but less negative for the deo with as ones. as suggested by hasan et al. [19], the destruction of the short-range orientation structural order in pure liquids as a result of hydrogen bonds and dipolar interactions causes dispersive interactions between unlike molecules giving rise to negative deviations in viscosity of liquid mixtures. a graphical comparison of the values of the density, viscosity and excess volume at t = 303.15 and 308.15 k of the deo with as system recorded by baragi et al. [8] figure 1: 𝑉𝑚 𝐸 vs. x 1 for the binary mixtures of: deo with bve at □ 303.15, ◊ 308.15 and δ 313.15 k; deo with dipe at × 303.15, җ 308.15 and ▬ 313.15 k; deo with as at ● 303.15, + 308.15 and ■ 313.15 k; deo with dbe at ◊ 303.15, ▲ 308.15 and o 313.15 k -1,2 -0,8 -0,4 0 0,4 0 0,2 0,4 0,6 0,8 1 v m e /( cm 3 m o l-1 ) x1 figure 2: δη vs. x1 for the binary mixtures of: deo with bve at □ 303.15, ◊ 308.15 and δ 313.15 k; deo with dipe at × 303.15, җ 308.15 and ▬ 313.15 k; deo with as at ● 303.15, + 308.15 and ■ 313.15 k; deo with dbe at ◊ 303.15, ▲ 308.15 and o 313.15 k -0,32 -0,24 -0,16 -0,08 0 0 0,2 0,4 0,6 0,8 1 δ η /( m p a .s ) x1 bhumkar and wagh hungarian journal of industry and chemistry 22 is presented in figures 7-9, respectively. figure 3: δks vs. x1 for the binary mixtures of: deo with bve at × 303.15, җ 308.15 and ▬ 313.15 k; deo with dipe at □ 303.15, 308.15 and δ 313.15 k; deo with as at ● 303.15, + 308.15 and ■ 313.15 k; deo with dbe at 303.15, ▲ 308.15, o 313.15 k figure 4: 𝑉𝑓 𝐸 vs. x1 for the binary mixtures of: deo with bve at ♦ 303.15, ■ 308.15 and δ 313.15 k; deo with dipe at җ 303.15, o 308.15 and + 313.15 k; deo with as at ▬ 303.15, ◊ 308.15 and □ 313.15 k; deo with dbe at × 303.15, җ 308.15 and ● 313.15 k -0,105 -0,085 -0,065 -0,045 -0,025 -0,005 0 0,2 0,4 0,6 0,8 1 v fe /m 3 .m o l -1 x1 figure 5: 𝐿𝑓 𝐸 vs. x1 for the binary mixtures of: deo with bve at □ 303.15, ◊ 308.15 and δ 313.15 k; deo with dipe at × 303.15, җ 308.15 and ▬ 313.15 k; deo with as at o 303.15, + 308.15 and ■ 313.15 k; deo with dbe at ♦ 303.15, ▲ 308.15, ● 313.15 k figure 6: π𝑖 𝐸 vs. x1 for the binary mixtures of: deo with bve at ♦ 303.15, ■ 308.15 and δ 313.15 k; deo with dipe at җ 303.15, o 308.15 and + 313.15 k; deo with as at ▬ 303.15, ◊ 308.15 and □ 313.15 k; deo with dbe at × 303.15, җ 308.15 and ● 313.15 k -0,28 -0,19 -0,1 -0,01 0 0,2 0,4 0,6 0,8 1 π i e /c m 3 .m o l -1 x1 molecular interaction studies of binary mixtures 52(1) pp. 19–27 (2024) 23 table 2: parameters of equation 8 for various functions and the corresponding standard deviations (σ) of the binary mixtures at 303.15, 308.15 and 313.15 k binary mixture t (k) excess property ao a1 a2 𝜎 deo + bve 303.15 𝑉𝑚 𝐸 (cm3·mol-1) -1.6578 -0.2804 1.0443 0.008 𝛥𝜂 (mpa·s) -0.9331 -0.2035 0.0142 0.001 δks (tpa-1) 1.7257 0.0902 0.6977 0.002 vf e × 10-6 (m3·mol-1) -0.2483 0.01275 0.0028 0.000 𝐿𝑓 𝐸 × 10-8 (cm) 0.0335 0.0056 0.0029 0.000 𝜋i e × 10-6 (nm-2) -0.3006 0.1191 0.0761 0.001 308.15 𝑉𝑚 𝐸 (cm3·mol-1) -1.7406 -0.2060 0.7103 0.013 𝛥𝜂 (mpa·s) -0.8227 -0.2035 -0.0003 0.001 δks (tpa-1) 1.6081 0.1759 0.4717 0.005 vf e × 10-6 (m3·mol-1) -0.2268 0.0014 0.0173 0.001 𝐿𝑓 𝐸 × 10-8 (cm) 0.0322 0.0053 0.0090 0.000 𝜋i e × 10-6 (nm-2) -0.2768 0.0957 0.1158 0.002 313.15 𝑉𝑚 𝐸 (cm3·mol-1) -1.8354 -0.1895 0.4415 0.012 𝛥𝜂 (mpa·s) -0.7656 -0.1767 -0.0294 0.001 δks (tpa-1) 1.4733 0.2236 0.3123 0.006 vf e × 10-6 (m3·mol-1) -0.2223 -0.0150 0.0275 0.000 𝐿𝑓 𝐸 × 10-8 (cm) 0.0321 0.0050 -0.0004 0.000 𝜋i e × 10-6 (nm-2) -0.3246 0.0949 0.0019 0.001 deo + dipe 303.15 𝑉𝑚 𝐸 (cm3·mol-1) -3.8814 -0.1995 0.1160 0.016 𝛥𝜂 (mpa.s) -1.1946 -0.3873 -0.0850 0.000 δks (tpa-1) -6.4274 0.9665 0.1169 0.013 vf e × 10-6 (m3·mol-1) -0.3899 0.03931 0.0134 0.001 𝐿𝑓 𝐸 × 10-8 (cm) 0.04034 0.0121 0.0028 0.000 𝜋i e × 10-6 (nm-2) -0.5095 0.0779 0.0665 0.001 308.15 𝑉𝑚 𝐸 (cm3·mol-1) -4.0847 -0.0394 -0.2515 0.014 𝛥𝜂 (mpa·s) -1.0418 -0.3387 -0.0976 0.000 δks (tpa-1) -7.0499 1.2347 -0.2205 0.012 vf e × 10-6 (m3·mol-1) -0.3978 0.0481 0.0185 0.001 𝐿𝑓 𝐸 × 10-8 (cm) 0.04374 0.0117 0.0003 0.000 𝜋i e × 10-6 (nm-2) -0.3914 0.0831 0.0838 0.001 313.15 𝑉𝑚 𝐸 (cm3·mol-1) -4.2667 0.0259 -0.5911 0.018 𝛥𝜂 (mpa·s) -0.9175 -0.2913 -0.0746 0.001 δks (tpa-1) -7.7585 1.4416 -0.5426 0.017 vf e × 10-6 (m3·mol-1) -0.4054 0.0682 0.0011 0.000 𝐿𝑓 𝐸 × 10-8 (cm) 0.04370 0.0136 0.0039 0.000 𝜋i e × 10-6 (nm-2) -0.3220 0.0624 0.0375 0.001 deo + as 303.15 𝑉𝑚 𝐸 (cm3·mol-1) -0.8468 0.0252 -0.2574 0.004 𝛥𝜂 (mpa·s) -0.1699 -0.0186 -0.0318 0.000 δks (tpa-1) 0.7685 0.0434 -0.0821 0.003 vf e × 10-6 (m3·mol-1) -0.0244 0.0016 0.0064 0.000 𝐿𝑓 𝐸 ×10-8 (cm) 0.0042 -0.0002 -0.0007 0.000 𝜋i e × 10-6 (nm-2) -0.0244 0.0016 0.0064 0.000 308.15 𝑉𝑚 𝐸 (cm3·mol-1) -0.7708 0.1124 -0.0633 0.002 𝛥𝜂 (mpa·s) -0.1491 -0.0181 -0.0306 0.000 δks (tpa-1) 0.3415 -0.2199 0.0768 0.005 vf e × 10-6 (m3·mol-1) -0.0277 0.0026 0.0082 0.000 𝐿𝑓 𝐸 × 10-8 (cm) 0.0041 -0.0037 -0.0052 0.000 𝜋i e × 10-6 (nm-2) -0.0277 0.0026 0.0082 0.000 313.15 𝑉𝑚 𝐸 (cm3·mol-1) -0.7053 0.1648 0.1500 0.004 𝛥𝜂 (mpa·s) -0.1336 -0.0183 -0.0041 0.000 δks (tpa-1) 0.1518 -0.1619 -0.1085 0.002 vf e ×10-6 (m3·mol-1) -0.0304 0.0049 0.0016 0.000 𝐿𝑓 𝐸 × 10-8 (cm) 0.0018 -0.0006 -0.0003 0.000 𝜋i e × 10-6 (nm-2) -0.0489 -0.0134 -0.0172 0.001 bhumkar and wagh hungarian journal of industry and chemistry 24 table 2 (continued): parameters of equation 8 for various functions and the corresponding standard deviations (σ) of the binary mixtures at 303.15, 308.15 and 313.15 k binary mixture t (k) excess property ao a1 a2 𝜎 deo + dbe 303.15 𝑉𝑚 𝐸 (cm3·mol-1) 1.2523 -0.4768 -0.1035 0.005 𝛥𝜂 (mpa·s) -0.8823 -0.3128 -0.1872 0.002 δks (tpa-1) -4.5150 -0.0774 0.1275 0.005 vf e × 10-6 (m3·mol-1) -0.0167 -0.0595 0.0480 0.001 𝐿𝑓 𝐸 × 10-8 (cm) 0.0027 0.0001 0.0003 0.000 𝜋i e ×10-6 (nm-2) -1.0201 -0.2342 -0.1808 0.001 308.15 𝑉𝑚 𝐸 (cm3·mol-1) 1.1863 -0.4387 -0.3837 0.005 𝛥𝜂 (mpa·s) -0.7694 -0.2750 -0.1056 0.001 δks (tpa-1) -4.7739 -0.0111 -0.2990 0.002 vf e ×10-6 (m3·mol-1) -0.0196 -0.0437 0.0106 0.001 𝐿𝑓 𝐸×10-8 (cm) 0.0035 -0.0001 -0.0095 0.000 𝜋i e ×10-6 (nm-2) -0.9246 -0.2237 -0.0097 0.001 313.15 𝑉𝑚 𝐸 (cm3·mol-1) 1.0757 -0.4354 -0.4843 0.002 𝛥𝜂 (mpa·s) -0.6759 -0.2224 -0.0089 0.000 δks (tpa-1) -4.9529 0.0234 -0.2893 0.003 vf e ×10-6 (m3·mol-1) -0.0324 -0.0315 -0.0314 0.001 𝐿𝑓 𝐸 × 10-8 (cm) 0.0017 0.0004 -0.0005 0.000 𝜋i e × 10-6 (nm-2) -0.8775 -0.2027 0.0535 0.001 figure 7: comparison between the densities (ρ) for the binary mixtures of: as with deo at ■ 303.15 and ▲ 308.15 k (values measured by baragi et al. [8]) deo with as at ● 303.15 and ▼ 308.15 k (present study) figure 8: comparison between the viscosities (η) for the binary mixtures of: as with deo at ■ 303.15 and ▲ 308.15 k (values measured by baragi et al. [8]) deo with as at ● 303.15 and ▼ 308.15 k (present study) figure 9: comparison between the excess molar volumes (𝑉𝑚 𝐸) for the binary mixtures of: as with deo at ■ 303.15 and ▲ 308.15 k (values measured by baragi et al. [8]) deo with as at ● 303.15 and ▼ 308.15 k (present study) molecular interaction studies of binary mixtures 52(1) pp. 19–27 (2024) 25 close observation of these figures reveals that these values agree with each other quite satisfactorily. the variation in δks with regard to the composition of the mixtures (x1 of deo) at 303.15, 308.15 and 313.15 k is presented in figure 3. it was observed that δks is positive for the mixtures of deo with bve and as, while negative throughout for the mixtures of deo with dipe and dbe at all studied temperatures. strong intermolecular interactions due to dipole-dipole interactions and interstitial accommodation result in the reduction in the deviations in the isentropic compressibility leading to negative deviations, while positive deviations indicate weak intermolecular interactions. the variation in 𝑉𝑓 𝐸 for the studied deo mixtures is plotted in figure 4. it is observed that the values of 𝑉𝑓 𝐸 exhibit negative deviations for the mixtures of deo with bve, dipe and as, while for the mixtures of deo with dbe, 𝑉𝑓 𝐸 showed both positive and negative deviations throughout. the change from positive to negative deviations occurs at x1 = 0.3965. this deviation in 𝑉𝑓 𝐸 depends on the relative strength between the contractive and expansive forces. the factors responsible for volume contraction are specific interactions between the component molecules, namely weak physical forces such as dipole-dipole or van der waals forces. the negative values of 𝑉𝑓 𝐸 suggest the existence of strong dipoledipole interactions. furthermore, the absolute values of 𝑉𝑓 𝐸 increase in the mixture of deo with bve as the temperature increases, suggesting the strengthening of intermolecular interactions between unlike molecules due to thermal energy. however, for the mixtures of deo with dipe, as and dbe, 𝑉𝑓 𝐸 decreases as the temperature increases. figure 5 shows that 𝐿𝑓 𝐸 is positive for all the systems. for the mixture of deo with dipe, 𝐿𝑓 𝐸 increases as the temperature increases, while for those of deo with bve, as and dbe, it decreases throughout at all studied temperatures. the negative values of 𝐿𝑓 𝐸 show that sound waves cover long distances due to a decrease in the intermolecular free length given the strength of interactions between hydrogen bonds of unlike molecules [20]. positive 𝐿𝑓 𝐸 values may be attributed to the dispersion forces [21]. the plots of the 𝜋𝑖 𝐸 against the mole fraction of deo (x1) are shown in figure 6. it was observed from the plots that the values of 𝜋𝑖 𝐸 for all the systems are negative throughout, while for the mixture of deo with dbe, 𝜋𝑖 𝐸 is more negative. the internal pressure values are a reflection of the net cohesive or adhesive forces available in the medium. 3.1. estimation of the theoretical viscosity of mixtures the theoretical viscosity of binary mixtures was calculated using the following semi-empirical relations. grunberg-nissan [22] proposed the following relation: ln 𝜂𝑚𝑖𝑥 = 𝑥1 ln 𝜂1 + 𝑥2 ln 𝜂2 + 𝑥1𝑥2𝑑12 (10) where d12 denotes an interaction parameter. lobe [23] represented a two-parameter relation as follows: 𝑉 = 1𝑣1 ∙ 𝑒𝑥𝑝(2𝛼𝐴) + 2𝑣2 ∙ 𝑒𝑥𝑝(1𝛼𝐵) (11) where v, v1 and v2 denote the kinematic viscosities of the mixtures as well as of pure liquids 1 and 2, respectively. 1 and 2 stand for the volume fractions of the pure components. a, and b represent the interaction parameters a = ab ln(v2/v1) and b = ba ln(v2/v1) where ab and ba denote parameters to fit the experimental data. a three-parameter relation proposed by krishnanladdha [24] is represented as follows: ln 𝜐 = ln 𝜐1 + 𝑥2 ln 𝜐2 + 𝑥1 ln 𝑀1 + 𝑥2 ln 𝑀2 − ln[𝑥1𝑀1 + 𝑥2𝑀2] − 2.303𝑥1𝑥2[𝐵12 + 𝐶12(𝑥1 − 𝑥2) + 𝐷12(𝑥1 − 𝑥2)2] (12) where υ, υ1 and υ2 refer to kinematic viscosities, while b12, c12 and d12 are binary coefficients. the predictive ability of equations 10-12 was tested by estimating the percentage standard deviation σ(%) between the experimental and determined viscosities as follows: 𝜎(%) = [1/(𝑛 − 𝑘) ∑{100(𝑛𝑒𝑥𝑝 − 𝑛𝑐𝑎𝑙)/𝑛𝑒𝑥𝑝} 2 ] 1/2 (13) where n represents the number of data points in each set and k denotes the number of numerical coefficients in the equation, while nexp and ncal denote experimentally obtained and theoretically calculated mixtures viscosities, respectively. the values of the interaction parameters measured from the above relations together with the percentage standard deviations σ(%) are reported in table 3. a close examination of the values of σ(%) reveals that the σ(%) values for one parameter of the grunberg-nissan equation fall between 0.01 and 0.05, for two of the lobe equation between 0.00 and 0.04, while for 3 of the krishnan–laddha equation between 0.00 and 0.01. from these σ(%) values, it can be concluded that the three parameters of the krishnan-laddha relation calculate the theoretical viscosity more satisfactorily than the other two models. 4. conclusions the density, viscosity and speed of sound data have been described for binary mixtures of diethyl oxalate with butyl vinyl ether, diisopropyl ether, anisole and dibutyl ether at 303.15, 308.15 and 313.15 k over the whole range of the composition. using the experimental data, the various excess or deviation properties namely 𝑉𝑚 𝐸, ∆η, δks, 𝑉𝑓 𝐸 , 𝐿𝑓 𝐸 and 𝜋𝑖 𝐸 were assessed. all the calculated excess or deviation properties exhibited either positive or negative deviations as a result of the effect of the temperature. these excess parameters are indicative of the weak interactions (dispersion forces) between bhumkar and wagh hungarian journal of industry and chemistry 26 deo and dbe, while for the other mixtures the strong interactions of charge transfer and dipole-induced dipole forces are implied. it may be suggested that molecular interactions between esters and ethers through hydrogen bonding and dipole-dipole interactions may be present. in comparison with our earlier work [25], the present reported system of deo with ethers was found to yield stronger molecular interactions perhaps due to the molecular weight of vinyl acetate being less than that of deo, resulting in a reduction in the flow time observed for vinyl acetate because smaller molecules are not resistant to flow. therefore, in the case of vinyl acetate, thinner and less viscous substances are produced. additionally, it can be concluded that the carbonyl oxygen of deo may interact with the hydrogen of ethers, resulting in stronger hydrogen bonding. nomenclature ρ density (g·cm-3) ∆η deviation in viscosity (mpa·s) ∆ks deviation in isentropic compressibility (tpa-1) 𝑉𝑚 𝐸 excess molar volumes (cm3·mol-1) 𝑉𝑓 𝐸 excess free volume (m3·mol-1) 𝐿𝑓 𝐸 excess intermolecular free length (cm) 𝜋𝑖 𝐸 excess internal pressure (nm-2) vf free volume (m3·mol-1) ks isentropic compressibility (tpa-1) lf intermolecular free length (cm) πi internal pressure (nm-2) x1 mole fraction of component η viscosity (mpa·s) u speeds of sound (ms-1) references [1] koohyar, f.; rostami, a.a.; chaichi, m.j.; kiani, f.: refractive 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-0.0268 0.0020 0.01 deo + dipe 303.15 -0.2144 0.03 0.7878 -0.5180 0.01 0.1055 -0.0168 -0.0049 0.01 308.15 -0.1851 0.02 0.8573 -0.6411 0.01 0.0912 -0.0096 0.0096 0.01 313.15 -0.1477 0.01 0.9464 -0.7820 0.01 0.0762 -0.0001 0.0060 0.01 deo + as 303.15 0.0131 0.01 1.6888 -1.3706 0.01 -0.0148 0.0017 0.0112 0.00 308.15 0.0178 0.01 1.6912 -1.3825 0.01 -0.0175 0.0020 0.0123 0.00 313.15 0.0242 0.01 1.7449 -1.4375 0.00 -0.0190 0.0036 0.0017 0.00 deo + dbe 303.15 -0.4299 0.04 0.7705 -0.3050 0.04 0.1662 0.0080 0.0431 0.01 308.15 -0.3902 0.03 0.8762 -0.4831 0.02 0.1540 0.0173 0.0099 0.01 313.15 -0.3412 0.04 0.6955 -0.3286 0.02 0.1384 0.0163 -0.0287 0.01 https://doi.org/10.1007/s10953-011-9714-2 https://doi.org/10.1016/j.jct.2004.11.012 https://doi.org/10.1039/b208086a https://doi.org/10.1016/j.jiec.2010.05.016 https://doi.org/10.1016/j.molliq.2018.08.003 https://doi.org/10.1039/b207281p molecular interaction studies of binary mixtures 52(1) pp. 19–27 (2024) 27 [7] pan, i.-c.; tang, m.; chen, y.-p.: 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hungarian journal of industrial chemistry veszprem vol. 30. pp. 167170 (2002) a fuzzy logic approach to the control of the drying process m. baldea, v. m. cristea andp. s. agachi (department of chemistry and chemical engineering, "babes-bolyai" university, 11, arany janos st., 3400 cluj­ napoca, romania) received: march 8, 2002 the paper presents the simulation results of an advanced control algorithm used for the control of the drying process of electric insulators. the industrial batch drier is modelled and three different approaches are taken for its control. in order to investigate its capabilities, fuzzy logic control (flc) is used for controlling the air temperature in the drying chamber. the results describing the controlled variables behaviour under the influence of some typical disturbances are compared with data obtained using model predictive control (mpc) and traditional pid control. the requested drying program consists of a ramp-constant profile, obtained by manipulating the air and natural gas flow rate. moisture content control is actually achieved by controlling the air temperature inside the drying chamber. simulation results reveal clear benefits of the flc approach over the other control methods subjected to our investigation, and prove real incentives for industrial implementation. keywords: batch drying, fuzzy logic, model predictive control, non linear control introduction the high-voltage electric insulator production implies a two-stage batch drying process. during the first step, the moisture content of the drying product is reduced from 18-20% to 0.4% in special gas heated chambers. the second step is carried out in high temperature ovens, in order to achieve an even lower moisture content. gas and air flow rates are controlled according to a special program, during a period of about 100 hours, in order to obtain the desired moisture content and avoiding the risk of unsafe tensions in the drying products. an analytical dynamic model of the process is derived for model predictive control purposes. model description mass and energy balance equations are used to describe the dynamic behaviour of the system. the main studied outputs of the model are: moisture content of the drying product x, outlet air temperature t0 and air humidity x0 ; the input variables: natural gas flow rate if and mass . flow rate of fresh air m,1 • the chamber is divided into three sections as shown in fig.l. section 1 represents contact information: e~mail: mbaldea@chem.ubbcluj.ro the air volume within the drying chamber, section 2 the direct surroundings of the drying product. section 3 represents the drying product itself. the mass balance of steam within section 1 is described by . . ( . . ) v dxo (1) mal ·xf +ma ·xma +mai ·xoacfl. pa ·dt with vach being the volume of the air in section 1. in section 2, the steam fluxes around the drying product are modelled by m ·(x -x)-m · dx ==.e_fy ·p ·x) (2) a o s dt dt \ 42 a with v a2 being the infinitesimal small volume of air in section 2. due to this fact, the last term of the equation can be neglected, which results in the differential equation dx = (x -x)· ma. dt " ms (3) as a result of differentiation of eq.(3) and assuming that, d!x!dr""' 0 the eq.( 1) becomes: ! = 1 ·(m"; ·x1 +m, ·x-(m .. +m"}x,}(4) v.,ch ·pa 168 fig. i description of the drying chamber in section 3, the behaviour of the drying good itself is described with a normalised diagram by means of the following equation [1, 2]: dx __ m., ·a dt m 5 s · (5) the drying velocity for the three periods of the drying process of a hygroscopic material are characterised by the diagrams of fig.2 [2]. this diagram a), only available by experiments and valid for the certain conditions can be normalized to b) according to: (6) it is assumed that x c is constant, not depending on the drying conditions, and that x equ only depends on relative air humidity, but no other factors. it is also assumed that all diagrams of the drying velocity for different drying conditions are geometrically similar. the equilibrium humidity x equ in dependence of the relative air humidity <p , for clay, was considered by a correlation equation. the saturation humidity of the air, x,"u • is dependent of temperature tq • for low partial pressures of steam a simple equation for mstl was considered: (7} with the mass transfer coefficient k determined by experiment data. two energy balance equations, for the chamber: mal·(cpa ·(7; -t,)+xr·(h, +cpst ·1;)-x., ·{h,. +cpst·t,))+ (8) and for the burner: a) b) m:;tll x fig.2 drying rate in dependence of moisture content of drying product: a) absolute b) normalized (9) are used to describe the outlet temperature change. a dynamic sensitivity analysis was carried out on this model, indicating the most important parameters and manipulated variables. according to this analysis, they are: mass transfer coefficient k, heat transfer coefficient of chamber walls ca, heating power of natural gas hf, mass of the drying product ms (clay without humidity), environment temperature of the inlet air t., environment humidity of the inlet air x., volume of the drying chamber vch, surface of the drying chamber ach. surface of the drying product as, critical humidity of clay xc and specific heat of natural gas cpf [3]. the scaled dynamic sensitivity analysis of the output variables with respect to the studied inputs pointed out the natural gas flow rate as the most important manipulated variable (about 10 times more important than the mass flow rate of fresh air). the control system was designed accordingly. results and discussion any process controller's mission is to receive a number of inputs and compute the appropriate outputs in order to annihilate a possible error. the fuzzy controller is no exception: it receives a measured value from the system, if fuzzyfies it (assigns it a membership value), applies the system's rules, computes an overall result of all the rules and then defuzzyfies the result, converting it into a number which is an appropriate command for the system it controls. [4, 5]. the mission of the model predictive controller [6] is accomplished by anticipating the outputs of the system with the aid of the mathematical model. the controller output is generated, based on the anticipated behavior of the system. all control methods investigated in this paper obey the current control practice [7], i.e. driving the evolution of the moisture content of the drying product in the desired way by means of controlling the air temperature inside the chamber. usually, the desired decreasing profile of the drying product moisture content is obtained by imposing an increasing ramp-constant ... -.-.·.·.····.·.·.·-·fig.3 structure of the control system temperature [~c] 90 80 70 60 50 40 30 20 10 0 0.5 a 1.5 time[s) 2.5 3.5 x 10' fig.4 comparative behaviour of fl, mpc and pid control in the presence of the heating power disturbance 45.2 ~44.8 ~ ~44.6 .li >-44.4 44.2 44 1 setpoint : 1 -~-· fuzzy logic -· mpc -pid 1.155 1.16 1.165 1.17 1.175 1.18 1.165 1.19 1.195 1.2 1.205 time [s) x 10' fig.s detailed presentation of the comparative behaviour of fl, mpc and pid control in the presence of the heating power disturbance profile on the air temperature. the setup of the simulated system is shown in fig3. performance testing was carried out for three significant disturbances typically occurring in the industrial practice: a 10 °c inlet air temperature t" drop (from 16 °c to 6 °c), a 10 %heating power capacity hf drop of natural gas and a 10% rise in the moisture content of the inlet air. the disturbances were 169 45.5 l se!point j ··-· fuzz.ylog[c -· mpc -pid 44 • 1.155 1.16 1.185 1.17 1.175 1.18 1.185 1.19 1.195 1.2 1.205 1irre [s] x to' fig.6 detailed presentation of the comparative behaviour of fl, mpc and pid control in the presence of the air inlet temperature drop disturbance 45.6 45.4 44.8 i setpoint l -··· fuzzy !ogle -· mpc -pid 44.6 1.14 1.15 1.16 1.17 1.18 1.19 1.2 1.21 1irne [s] xto' fig. 7 detailed presentation of the comparative behaviour of fl, mpc and pid control in the presence of the air inlet humidity increase disturbance introduced as steps at time t=l16000 s. the simulation results for case of the heating power disturbance are presented in figs.4 and 5. the figures show the response of the controlled variable over the entire time interval and a detailed representation of the period when the disturbance acts and is eliminated. the behaviour of three investigated control methods (fuzzy logic controlflc, model predictive control-mpc and pid control) is presented comparatively. figs.s-7 are magnifications of the area marked as detail a on fig.4. fig.6 presents a detail of the controlled output temperature for the air inlet temperature drop disturbance and fig. 7 represents in the same manner the case of the disturbance consisting in a humidity increase of the inlet air. with respect to setpoint tracking performance, the . results reveal a good behaviour in case of pid and mpc, fl control featuring superior abilities. as it can be seen, flc is very accurate, following with precision both the constant and the ramp sections of the temperature setpoint scheduling· function. 170 63 2.755 2.76 2.755 2.77 2.775 2.78 2.785 2.79 2.795 time [s[ x 10s fig.8 detailed presentation of the ramp setpoint following performance of flc, mpc and pid control all control methods exhibit a low offset behaviour f?r the constant parts of the setpoint function. for the ramp sections, as in fig.8 (detail b on fig.4), the mpc and pid control proved to be less accurate than fl showing a larger offset. this accuracy of the fl control is largely due to the asymmetrical membership function definition. the definition takes into account the need for an asymmetric amplitude of the manipulated variable change (i.e. a controller response of higher amplitude to a negative error compared to a lower amplitude response for a positive error) in the ramp section of the setpoint function. . with respect to disturbance rejection performance, fl control showed a considerably shorter (more than 10 times) response time and smaller (more than five times) overshoot than the other control strategies. conclusions a comparative study of three control methods for the process of drying high voltage ceramic insulators (flc, mpc and pid) was carried out. setpoint tracking and disturbance rejection were investigated for disturbances typically occurring in the industrial practice. fuzzy logic clearly stands out as the preferable control method for the considered process, due to the good setpoint tracking performance, low overshoot and short settling time. flc is easy to implement and adapt in case of process modification due to its similarity with natural language. also, the controller's simple structure is another argument in favour of the industrial implementation of this control method. further research is envisioned for the control of the inferred moisture content of the drying product, with the implementation of an artificial intelligence based method for tuning the fl controller. references 1. van meel d. a.: chern. engng. sci., 1958, 9, 3644 2. krischer 0. and kast w.: die wissenschaftlichen grundlagen der trocknungstechnik, springer­ verlag, 1992 3. perry r. and chilton c.: chemical engineers' handbook, 5. edition, me graw hill,l973 4. fuzzy logic toolbox, for use with matlab®, user's guide v. 2.0, the mathworks, inc. natick, ma, 1999 5. russom.: ieee trans. fuzzy systems, 1998, 6(3), 372-388 6. garcia c. e., preit m. p. and morari m.: automatica, 1989, 25(3), 335-348 7. cristea v. m., baldea m. and agaciit s. p.: model predictive control of an industrial dryer, european symposium on computer aided process engineering-10, florence 2000 page 170 page 171 page 172 page 173 hungarian journal of industry and chemistry vol. 51(1) pp. 43-53 (2023) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2023-07 the effect of different accelerators on the corrosion protection of a surface coating on spheroidal graphite cast iron (ductile iron) beáta herbáth1*, kristóf kovács1, miklós jakab1 1 department of materials engineering, faculty of engineering, university of pannonia, p.o. box 1158, veszprém, h-8201, hungary this study investigates the structure and composition of the zinc phosphate coating formed on the surface of nodular cast iron as well as the corrosion resistance of the electrophoretic paint applied to the conversion layers when nitrite-based and nitroguanidine accelerators are used. in the case of different accelerators, the structure of the zinc phosphate layer that forms when exposed to low, normal and high dosages was examined. this type of casting, in addition to steel casting, is commonly used in the production of agricultural vehicles due to its favorable mechanical properties. although the majority of studies have summarized its application in the automotive industry by focusing on the phosphating of steel, galvanized steel and aluminum-based alloys, on complex vehicle assembly lines, cast iron is also used in phosphating processes that occur simultaneously. during our investigation into the use of different accelerators, a different crystal structure formed on the surface of the cast iron but did not affect the corrosion resistance of the electrophoretic painted samples. keywords: zinc phosphate, accelerator, spheroidal graphite cast iron, cathodic electrodeposition, corrosion resistance 1. introduction zinc phosphate coatings on metal surfaces are very often the first layers of multilayer corrosion protection coatings, which are expected to form a hard, uniform, non-conductive surface coating on the surface of a base metal. these layers adhere tightly to the metal surface, thereby protecting the base metal from the effects of corrosion in the event of damage to the corrosion protection coating and ensuring the applied paint layer adheres properly, because the specific size of the surfaces covered with phosphate crystals is five to six times larger compared to that of the untreated metal surfaces. phosphate treatments are usually applied to carbon steel, cast iron, low-alloy steel, galvanized and hot-dip galvanized steel, as well as aluminum and magnesium alloys, moreover, the zinc phosphate crystals are formed during a chemical conversion process. an important development of zinc phosphate baths was the modern tricationic conversion coating bath containing zn2+, mn2+ and ni 2+, which is suitable for depositing an excellent, highly resistant phosphate coating on multi-metal structures used in vehicle manufacturing, especially for outdoor use in corrosive environments. these coatings are highly suitable in cathodic electrophoretic paints due to their excellent surface properties [1]-[5]. received: 23 march 2023; revised: 11 april 2023; accepted: 14 april 2023 *correspondence: herbathbea@gmail.com influence of the nature of the substrate on coating properties. the difference between the zinc phosphate coating created on the surface of steel and nodular cast iron depends on the alloying elements and surface roughness. phosphatibility is promoted by small amounts of elements such as nickel, chromium and vanadium in the alloy, however, if the concentration of these elements exceeds a certain limit, the formation of the coating will be somewhat inhibited. the amount of carbon, phosphor, sulfur, manganese and silicon can greatly influence the phosphatability of steel. low carbon steels can be easily phosphated, resulting in high-quality surface coatings. nevertheless, by increasing the carbon content, the rate of phosphating decreases and the crystals become larger. a higher surface roughness increases the weight of the coating as well as its fineness and shortens the phosphating reaction time, thereby improving its structure and texture, whereas polished surfaces react poorly to phosphating. the explanation for this is that if a larger number of peaks and grooves are found on the metal surface, the effectiveness of the pickling reaction during phosphating increases due to the larger specific surface area, which also results in a good degree of adhesion of the coating. although the phosphatibility can be improved by increasing the surface roughness [6]-[7], in the case of electrophoretic painting, the weight of the https://doi.org/10.33927/hjic-2023-07 mailto:herbathbea@gmail.com herbáth, kovács and jakab hungarian journal of industry and chemistry 44 coating must be kept within strict tolerance limits since the phosphate layer insulates the base metal and a conductive surface is necessary for electrophoretic painting. this study investigates zinc phosphating of nodular cast iron surfaces on the same technological line using the same parameters as well as nitrite-based (n) and nitroguanidine (ng) accelerators. even though nitritebased accelerators are the most commonly used and most effective for steel surfaces, the disadvantage of these systems is that the nitrite concentration usually must remain high, especially for spraying processes, thereby polluting the effluent and producing toxic nitrous gases. organic nitrogen compounds, e.g. nitroguanidine, are used to reduce or eliminate the effects of the nitrous gases generated when using nitrite-based accelerators, especially in low-zinc baths, resulting in a softer and easily removable sludge. the disadvantage of nitroguanidine accelerators is that they have to be used at relatively high concentrations, moreover, can only be controlled to a sufficient level of accuracy by conducting a complex analysis in the phosphate solution and be dosed as precisely as possible in the ratio of the phosphating agent. one advantage of them is that they do not decompose spontaneously and can be used over a very wide dosage range, allowing robust processes to be developed [2,6-7]. the phosphating bath can be modified, e.g. by adding na2moo4 in the case of cast iron, since the presence of molybdenum in the coating can improve the adhesion of paint to the surface of the casting [8]. the main materials used for making car or vehicle parts and components are steel, aluminum, magnesium, copper, plastics and carbon fiber. lightweight materials such as aluminum or magnesium are increasingly being used in the automotive industry in order to replace steel and iron components. steel has been the dominant material since the 1920s and still remains the primary construction material for automotive bodies. however, the trend of reducing the weight of car bodies to minimize carbon emissions has gradually decreased the use of steel and cast iron. the lightweight nature of vehicles composed of aluminum would reduce fuel consumption but increase pollution resulting from the production of materials relative to those required for a conventional vehicle. iron and steel are the critical elements in the structure of the vast majority of vehicles because they are low-cost [9]-[11]. in recent years, pretreatment processes have been modified not only to accommodate a wide variety of substrates but also to comply with environmental regulations and economic considerations [10]. material substitution is often used to reduce the mass of vehicles. low-carbon steel and iron have been replaced by lighter materials such as aluminum, highstrength steel and plastics. however, the impacts associated with the production of aluminum are more significant than those concerning heavier metals such as iron and steel, a common trade-off for lightweight materials. in comparison to iron, it has poorer mechanical properties (e.g. strength, stiffness, high temperature performance and damping capacity) and higher production costs [12]. the wall thickness of thin wall ductile iron (twdi) with a ferritic-pearlitic matrix or thin wall austempered ductile iron (twadi) with an ausferritic matrix is 3 mm or less, both of which can be significant ferrous alloys to replace the current aluminum alloy parts that have traditionally been cast in ferrous alloys over a diverse range of applications, particularly those with high mechanical requirements, bringing about substantial savings. lightweight nodular iron castings can be loaded to similar twdi or higher twadi working conditions as those the forged aluminum alloy was exposed to without suffering any potential failures [13]-[14]. the decision to substitute cast iron with aluminum alloys, and vice versa, is not always rational and must be preceded by a thorough analysis of all the factors involved such as mechanical properties at room and elevated temperatures, wear and material compatibility with parts made of different materials (galvanic corrosion), damping and noise, total energy consumption, as well as production costs [13]. although cast iron inherently hardens surfaces, this is not the case with al or mg alloys that are not subjected to additional expensive processing. the relatively low damping capacity of al alloys compared to cast iron generally results in significant engine or gearbox noise. in order to reduce such noise, various methods are implementable, however, all of them increase costs and engine weight. the manufacture of cast iron is related to energy savings when compared to aluminum alloys due to the high energy requirement of electrolysis during aluminum production. the cast iron can be remelted as many times as is necessary without its quality deteriorating and its production costs are lower when compared with aluminum alloys. in addition to car production, transportation and agricultural vehicle production has developed significantly with material substitution being used to achieve mass reduction in vehicles such as trucks, tractors and harvesters. however, due to high demand in these sectors, in addition to steel and aluminum castings, iron castings, especially spheroidal iron castings, still play a major role. reducing the thickness of cast iron, referred to as thin-walling, has the potential to enable cast iron to compete with cast aluminum in terms of weight while retaining its superior mechanical properties [15]. lightweight truck-trailers contain wheel hubs and suspensions of austempered ductile iron (adi) due to the following advantages: strength-to-weight ratio, stiffness, noise, cost and recyclability [16]. in addition to the mechanical tests conducted on nodular cast irons, the characteristics that by and large determine the properties of the raw material (yield strength, tensile strength, elongation, brinell hardness, wear resistance) are examined after appropriate surface preparation (grinding, polishing, sample embedding, etching). the size, form and morphology of carbon-based particles as well as the ferrite and pearlite content are usually investigated by light microscopy [17]-[20]. since adhesion of the conversion layer during the zinc the effect of different accelerators on the corrosion protection 51(1) pp. 43-53 (2023) 45 phosphating process carried out on ductile iron may be weaker in the case of larger graphite nodules on the surface than on the adjacent surfaces, it is also important to examine its microstructure [21]. although sufficient dispersion of fine carbon particles in the phosphating bath can improve the degree of corrosion protection [22], this effect cannot be achieved by including graphite particles in the matrix. surface cleaning before chemical surface pretreatment abrasive blast cleaning of cast iron can completely remove rust and mill scale, resulting in a uniform surface light grey in color in the absence of shadows or spots of rust. however, varying degrees of surface cleanliness can be achieved by this method. metallic abrasives such as steel or iron shot and grit as well as wire are widely used. given that surface blasting using steel grit yielded a good level of surface cleanliness, the coating that was subsequently applied resulted in a satisfactory degree of adhesion due to the creation of highly irregular surfaces. this is important for optimal anchoring of the coating and its adhesion. phosphate crystals are electrical insulators but contain pores on approximately 1 % of their surface. this is a very important prerequisite for the deposition of an electrocoating. the typical compositions of the conversion layers on steel, zinc, iron and aluminum substrates are varied in nature. the microstructures of the zinc phosphate coatings on steel, cast iron, zinc and aluminum surfaces are different. although their morphology depends on the type of substrate used, the results in terms of adhesion of the electrocoat primer are similar [23]. electrocoat electrocoat paints are aqueous dispersions consisting of typical paint ingredients such as film-forming agents (resins), pigments, extenders, additives and some solvents. these positively charged paints are suitable for use in coatings applied by cathodic electrodeposition (ced). for components in the automotive industry and now also in vehicle manufacturing, nowadays ced coatings predominantly achieve the best degree of corrosion protection [24]. corrosion testing methods corrosion testing methods can simulate the degradation of coatings and paints in a corrosive cabinet by continuously and strictly controlling the humidity, temperature and concentration of salts. the natural salt spray test (nss) according to iso 9227 is used to test the corrosion resistance of corrosion protection coatings applied to steel surfaces [25]. the effectiveness of phosphate coatings is evaluated by determining the spread of rust from scratches or other forms of surface damage to the paint film from the results of the natural salt spray tests. this test is particularly important because vehicles are often exposed to moisture as well as the salt used to de-ice and remove frost from road surfaces as described by benchaldi et al., who examined the corrosion susceptibility of steels in a perchloric acid environment [26]-[27]. the aim of this study was to examine whether special attention should be paid to the surface pretreatment of cast-iron components during the design of corrosion protection coatings or if they can be pretreated in the same way as steel as is the case with complex workpieces from the automotive industry that contain different base metals. 2. experimental 2.1. samples and measurements 2.1.1. materials ductile iron (spheroidal or nodular) materials are very strong, flexible, durable and elastic in nature due to their unique microstructure. ductile cast iron normally consists of at least 3 percent carbon and its free graphite particles are present as tiny spheres (nodules). its mechanical properties are similar to those of steel and far superior to those of standard forms of cast iron. the tensile strength of ductile iron is excellent and is more resistant to tension than other forms of cast iron, so ductile cast iron does not break easily on impact [28]. casting process of the sample plates the samples used in the experiments were cast iron plates (figure 1) according to en-gjs-450-10 (5.3107) iron grade “standard bs en 1563:2011 spheroidal graphite cast iron” produced by following the same method and technology as employed when manufacturing wheel hubs. cast plates can be used to successfully simulate changes that occur on the original parts, making them easier to handle during experiments. the test plates were manufactured according to the following process. a crucible-type induction furnace with a capacity of 8 tons was used to melt the metals. the charge consisted of crude iron, scrap steel and carbonizing materials. the composition and temperature of the base iron was checked with a spectrometer and pyrometer, respectively. the melt was transferred into a channel-type induction furnace with a capacity of 60 tons, where the base iron was homogenized. the treatment was carried out using the tundish cover method [29]. the treatment vessel was transferred to the molding line, where the slag was removed and then suitable examples of coins were taken from the batch. base quenching was used before casting, while radiation quenching was applied during casting. the charge was discarded after magnesium treatment. the samples were produced by busch-hungária kft. in győr, hungary. herbáth, kovács and jakab hungarian journal of industry and chemistry 46 2.1.2. methods the surface structure of the raw metals was visualized using a keyence vhx-2000 series digital optical light microscope (lm) (figures 2 and 3). the chemical composition of the raw metals was analyzed by a spectro m8 spark and arc-excited optical emission spectrometer (oes) from oxford instruments. the sample plate was remelted/recasted before being tested by converting it from graphite into carbide form. when a spark is produced, the graphite burns, creating a disturbance by sending false signals to the sensors and contaminating the glass window with smoke. when the specimen is remelted, the carbon is in the form of carbide, which is not burned by the spark, thereby yielding the desired excitation, moreover, the carbon is more evenly distributed. since in this case it is important to completely remelt the sample and rapidly cool it, graphite is not reformed. the samples are grinded with 60 grit sandpaper, inductively melted in a remelting furnace and quickly cooled to prevent the formation of graphite. these remelted samples were then ground again with 80 grit sandpaper before being dusted and tested. three measurements were performed on each sample due to the inhomogeneity of the raw material. the chemical composition used during oes (as weight %) of the cast-iron sample plate is presented in table 1. the morphology as well as the shape and size of the crystals were tested by a fei/thermo fisher scientific apreo s lovac scanning electron microscope (sem). observations by a sem were made in the low vacuum mode with an acceleration voltage of 20.0 kv (figure 4). figure 1. photograph of a nodular cast iron test plate figure 2. lm image of the surface of the cast-iron test plate figure 3. 3d lm image of the surface of the test plate figure 4. sem image of the surface morphology of the castiron test plate table 1. chemical composition of samples by oes c si mn p s 3.66 2.276 0.31 0.023 0.005 cr mo ni al co 0.04 0.01 0.02 0.0073 <0.01 cu ti pb sn mg 0.32 0.0149 <0.02 0.005 0.0344 ce sb b n fe 0.009 0.003 0.0006 <0.0010 93.25 the effect of different accelerators on the corrosion protection 51(1) pp. 43-53 (2023) 47 the elemental compositions of the samples were determined by an edax ametek octane elect plus energy dispersive x-ray analyzer (edx). the acceleration voltage was 20 kv and the data collection time period was 180 seconds. the chemical composition (as weight %) of the cast-iron samples is displayed in table 2. metallographic analysis the test plates were cut into pieces with a cutting saw before 4x4x4 cm cubes were cut out using a hand saw in order to carry out the metallographic analysis. special attention was given to ensure the condition of the surfaces was good. the surface was ground in the first step using p120 and in the second with p400 grit sandpaper. it was then polished using neodia diamond abrasive solution; in the first step, a suspension solution formed from 9 μm particles was employed, while in the second step, a polishing machine (struers rotopol-22 with a rotation speed of 150 rpm) was used with grains 3 μm in diameter to smoothen and polish the surface. the sample was also subjected to chemical attack using 2 % nital etchant for 10 seconds to highlight the microstructure of the matrix. the micrographs were processed using a nikon eclipse me600 optical microscope and the "a4idocu" computer program evaluated the images by conducting a metallographic examination, thereby providing the average values of the graphitic, ferritic and pearlitic fractions as well as the number and size of the graphite nodules. microstructure figure 5 shows the surface of the unetched sample in which the graphite are the black spots. it can be seen that the graphite spheres are fine, round and uniform in nature. according to din en iso 945, they are classified as size 6 with a graphite form of class v-vi, i.e. irregular and regular nodular-like graphite particles (reference images of the most common form of graphite according to standard iso 945-1:2017). the surface following the etching process is shown in figure 6 in which the ferrite appears white. its microstructure consists of pearlite/ferrite phases and nodular graphite in the form of microscopic spheres of graphite, while its structure consists of a mixture of pearlite and ferrite, which is the most common matrix for commercial grades of ductile iron. preparation of the zinc phosphate coating the test plates were blasted with s390 (44 hrc) steel grit before zinc phosphating. the surface roughness was rz = 98 µm, that is, the maximum height of the profile. the blasted ductile-iron sample plates were pretreated together with other sample plates as well as pieces made of steel and aluminum alloys in the same technological step simultaneously under industrial conditions according to a previously published process and its parameters [30]. the samples were subjected to surface pretreatment and phosphating using a dipping process with a nitroguanidine or nitrite-based accelerator. after pretreatment, the samples were dried in a laboratory oven. important parameters of phosphate baths are the free acid value (fa) which refers to the free h+ ions present and the total acid value (ta) which represents the total phosphate content of the phosphate bath [8]. in our experiments, these parameters were as follows: fa=1.5 points; ta=22 points [30]. the samples were degreased, rinsed, activated, phosphated and rinsed again in successive steps using different baths. in the degreasing bath, any residual surface contamination was removed from the metal surface; in the rinsing bath(s), the degreasing chemicals were removed with water; in the subsequent bath, the metal surface was activated; in the phosphating bath, insoluble heavy-metal tertiary phosphates formed on the surface; and finally in the rinsing bath, acid residues, soluble salts and non-adhesive particles were removed from the metal surface [30]. table 2. chemical composition of the samples (edx) elements c k al k si k mn k fe k weight % 3.14 0.12 1.93 0.39 58.49 figure 5. micrograph of the spherical morphology of the graphite nodules of the nodular cast iron figure 6. microstructure of the matrix herbáth, kovács and jakab hungarian journal of industry and chemistry 48 gardobond 2600 tricationic (mn2+, zn2+, ni2+) zinc phosphating solution (basf, chemetall ltd.) was used for the experiments, which can be used for phosphating iron and steel by a dipping and spraying process. although this is a nitrite (n)-accelerated system, according to the manufacturer's technical data sheet (tds), it can also work with a nitroguanidine (ng) accelerator. for both series of experiments with the accelerators, a zinc-phosphating solution was used by applying the same settings and the accelerators were dosed at low (l), medium (m) and high (h) levels in accordance with the tds. first, the samples were degreased with the gardoclean s 5197 alkaline cleaner (basf, chemetall ltd.). during the tests, the dipping method was employed with gardobond additive h7400 (basf, chemetall ltd.) as the surfactant at 60 °c for 600 s by intensively mixing the bath. having been rinsed with tap water, the surface was activated with gardolene v6513 solution (basf, chemetall ltd.) at a ph of 8.9. the zinc phosphating step was carried out using gardobond 2600 solution (basf, chemetall ltd.) at a temperature of 53 °c over an exposure time of 180 s. the bath used for both accelerators contained 1.3 g/l zinc and a 2.4 gas-point n accelerator measured by a gas burette or a 500 mg/l ng accelerator measured by photometry. after the phosphating process, the surface was rinsed with water over two steps. in order to remove any residual salt content from the surface, a cascade rinse system using deionized water was employed. finally, the pretreated samples were air-dried [30]. the composition of the bath and labeling of the samples are shown in tables 3 and 4, respectively. cathodic electrocoating the zinc phosphated sample plates were painted using the cathodic dip coating (ced) process with the powercron® p6200he electrocoat (ppg industrial coatings france). the electrocoat consisted of di (deionized water) 50.01 wt.%; cr693a resin 43.51 wt.% and cp471a pigment paste 6.48 wt.%, which was continuously mixed in the painting bath to ensure homogeneity. the temperature of the paint was maintained at the specified temperature by a coolingheating system within the range of ± 1 °c. the solvent in the bath consisted of hexylene glycol (hg) and methoxy propanol (pm). the parameters of the bath and the applications of electrodeposition are shown in tables 5 and 6, respectively. adhesion of the layer of paint was inspected by manual cross-cut testing according to the iso 2409 standard. six parallel cuts were applied using a template and an elcometer 107 cross hatch cutter down to the underlying surface, the distance between which was 1 mm. then six further cuts were made at right angles to each other, resulting in an even rectangular pattern. all loose particles close to where the cross cuts were made were removed with adhesive tape as specified by the standard. the test surface was then assessed by comparing it with images in the table from the standard. depending on their length, cross cuts ranging from 0 to 5 were made. table 4. the symbols of samples accelerator: ng accelerator: n low ngl low n-l medium ng-m medium n-m high ng-h high n-h table 3. chemical composition of the phosphating baths parameters limits bath acidity (points) free acids 1.5 total acids 22.0 tri-cations (g/l) zn2+ 1.3 ni2+ 0.9 mn2+ 0.9 f(ppm) 140-150 accelerator n-l 1.4 gas points n-m 2.4 gas points n-h 3.8 gas points ng-l 0.2 g/l ng-m 0.5 g/l ng-h 1.0 g/l table 5. analysis of the ced bath test specifications results min. max. solids for 1h at 110 °c (%) 17 19 17.77 pigment to binder ratio (p/b) 0.15 0.17 0.161 ph 4.9 5.3 5.31 conductivity (μs/cm) 1200 1800 1621 hg (%) 0.1 0.4 0.3831 pm (%) 0.0 0.2 0.0913 the effect of different accelerators on the corrosion protection 51(1) pp. 43-53 (2023) 49 the level of adhesion on each sample plate was gt0, namely the edges were completely smooth and none of the squares of the lattice detached. corrosion resistance test the test plates were investigated after the coating had been completely cured in accordance with din en iso 9227-nss after 504 hours; evaluation: din en iso 4628-1; surface corrosion: din en iso 4628-3; blistering: din en iso 4628-2 after 168/336/504 hours; delamination: din en iso 4628-8 after just 504 hours. 3. results and discussion 3.1. coating morphology and analysis figure 7 shows that both accelerators create a uniform, thorough zinc phosphate layer on the surface of the spheroidal casting sample. when the nitrite-based accelerator was used (d-f), the crystals formed were larger but their growth was sometimes irregular in some areas. however, when a nitroguanidine accelerator was used (a-c), the structure of the crystalline layer was more uniform. compared with the sem images published by li et al. [8], it can be concluded that by applying the composition of the phosphating bath outlined in table 3, it was possible to create a coating with a suitable structure without having to add sodium molybdate (na2moo4) or other additives. nejrenu et al. [21] showed in their work that the zinc phosphate coating created on the surface of the nodular cast iron substrate deposited by immersion contains acicular dendritic crystallites uniformly distributed over the entire surface with small gaps between them. no needle-like crystals were visible on the surface during our experiments and the coating was free of gaps. the microstructure of the zinc phosphate coating on the ductile cast-iron surface and the structure of the zinc phosphate layer formed on the surface of the s420mcgrade steel during the same process (1-3) using the nitroguanidine accelerator are compared in figure 8: it can be concluded that the uniform zinc phosphate layer on the steel surface was formed only when applying high accelerator dosages (figure 8/3). a uniform, continuous layer of zinc phosphate evenly covering the base metal was formed on the spheroidal cast iron (a-c), even when applying low accelerator dosages. the microstructure of the zinc phosphate coating on the ductile cast iron surface is compared with the structure of the zinc phosphate layer formed on the surface of the s420mc-grade steel during the same figure 7. sem micrographs of samples ng-l(a), ng-m(b) and ng-h(c) as well as n-l(d), n-m(e) and n-h(f) figure 8. sem micrographs of the zinc phosphate coating on s420mc steel (1-low; 2-normal; 3-high level nitroguanidine accelerator) and on the surface of samples ng-l(a), ngm(b) and ng-h(c) table 6. parameters of the applications of electrodeposition voltage temperature baking conditions thickness iso 3882 270 v 34°c 30 mins. (metal) at 165°c ≈ 40 μm ramp time deposition time baking method 15 s 120 s lab oven herbáth, kovács and jakab hungarian journal of industry and chemistry 50 process (4-6) by using the nitrite-based accelerator in figure 9. it can be concluded that a uniform zinc phosphate layer on the steel surface formed only at low accelerator dosages (figure 9/4) since irregular crystals were observed in the surface coating on the samples of spheroidal cast iron (d-f) when all three dosages were applied. the edx measurements of the zinc phosphate layers of the samples are presented in table 7. it can be concluded that due to similarities between the measurements, zinc phosphate layers of similar compositions were formed on each sample, so neither substituting the accelerators nor altering their quantities had any effect on the composition of the layers formed on the surfaces. 3.2. coating morphology and composition after the 504-hour-long natural salt spray test the sample plates were rinsed with deionized water to remove the residues of sodium chloride solution off the surfaces. once the corrosion evaluation had been completed, an sem and edx examination was performed on a 0.5 mm-wide scratch. the sem measurements show that even after the 504-hour-long natural salt spray test, a zinc phosphate layer remained on the base metal as can be seen in figure 10, which is confirmed by the edx results presented in table 8 as both zinc and phosphorus are present in the corrosion scratch on the metal surface. the sodium and chloride seen in the measurement results are the remnants of the sodium chloride used during the corrosion test that remained on the surface of the samples after rinsing. the origin of the copper in the measurements seen in table 8 can be attributed to cross-contamination from the corrosion chamber, since neither the base metal nor the phosphating solution contained copper. 3.3. corrosion resistance test according to iso 9227-nss the sample plates were tested according to iso 9227nss and evaluated according to iso 4628-1,2,3 after 168, 336 and 504 hours. this standard defines a method for determining the quantity and size of defects as well table 7. edx analysis of the zinc phosphate layer of the samples (wt.%) ng-l ng-m ng-h n-l n-m n-h o 24.72 22.74 26.18 25.60 28.40 25.28 al 0.06 0.09 0.12 0.09 0.47 0.00 si 1.29 1.42 1.24 1.57 1.93 1.91 p 7.48 7.69 7.78 7.45 8.38 7.61 mn 1.50 1.51 1.73 1.57 1.56 1.45 fe 53.58 54.66 50.30 51.16 47.42 52.70 ni 0.39 0.30 0.56 0.36 0.24 0.18 zn 10.98 11.59 12.09 12.20 11.61 10.87 figure 10. sem micrographs of the corrosion residue after a 504-hour-long natural salt spray test on samples ng-l(a), ng-m(b), ng-h(c), n-l(d), n-m(e) and n-h(f) figure 9. sem micrographs of the zinc phosphate coating on s420mc-grade steel (4-low; 5-normal; 6-high nitrite-based accelerator dosage) and on the surfaces of the samples nl(d), n-m(e) and n-h(f) the effect of different accelerators on the corrosion protection 51(1) pp. 43-53 (2023) 51 as the degree of change in the appearances of the coatings, moreover, assesses the amount of rusting and blistering of the coatings by comparing them to standard reference images. having been excluded from the evaluation, the cutting edges were not taken into consideration. immediately after the end of the testing period, the painted test panels were evaluated according to iso 4628-8, which outlines a method for assessing delamination and corrosion around a scratch or other artificial defects on a coated panel. before the corrosion test, the thickness of the ced paint layer was measured according to the iso 3882 standard with a “byko-test 8500” portable dry film thickness gauge (byk-gardner). although the thickness of the paint layer was approximately 40 µm on all test plates, due to the high degree of surface roughness, the standard deviation of the measurements varied greatly, so their accuracy could not be guaranteed. an uncoated sample plate was used as a “zero plate” and the gauge calibrated to this plate. the results of the corrosion tests presented in tables 9 and 10 show that neither the accelerator nor change in the dosage amount affected the corrosion resistance of the painted samples. although vehicle manufacturers have different expectations regarding anticorrosion coatings, these results meet their general expectations. according to table 10, no blisters formed on the paint layer of the samples, the degree of delamination was less than 1 mm, moreover, rust on the surface and cut edge corrosion did not occur on the surfaces treated in the phosphating bath containing the nitrite-based accelerator (samples n-l, n-m & n-h). among the samples treated in the phosphating baths containing the nitroguanidine accelerator presented in table 9, slight cut edge corrosion occurred even at low dosages, evidenced in sample ng-l, as early as after 336 hours of testing. the effect of a medium dosage of nitroguanidine was only evident at the end of the test period (ng-m). by applying a dosage exceeding the amount given on the technical data sheet as presented in table 3, the test results were identical to those of the test plates treated in the phosphating bath containing the nitrite-based accelerator (ng-h). 4. conclusions with the multimetal zinc phosphate baths used in these experiments, it was possible to form a uniform and fine table 8. edx analysis of the corrosion residue after a 504hour-long natural salt spray test (wt.%). ng-l ng-m ng-h n-l n-m n-h o 40.27 36.55 35.55 37.68 37.88 33.66 na 0.01 0.00 0.00 0.00 0.00 0.00 si 2.13 4.46 3.36 4.11 3.27 2.22 p 1.42 0.51 0.93 0.40 0.06 0.80 cl 2.60 3.74 4.41 2.87 5.06 3.09 mn 0.27 0.28 0.35 0.22 0.40 0.44 fe 51.62 53.39 52.59 53.49 51.89 57.93 ni 0.09 0.02 0.08 0.18 0.15 0.14 cu 0.27 0.68 0.55 0.76 1.03 0.49 zn 1.33 0.36 0.76 0.28 0.26 1.22 table 9. corrosion evaluation of samples treated with the nitroguanidine accelerator ng-l ng-m ng-h 168 h din en iso 4628-2 blistering on surface 0(s0) 0(s0) 0(s0) din en iso 4628-3 rust on surface ri0 ri0 ri0 iso 4628-1 cut edge corrosion kr0 kr0 kr0 336 h din en iso 4628-2 blistering on surface 0(s0) 0(s0) 0(s0) din en iso 4628-3 rust on surface ri0 ri0 ri0 iso 4628-1 cut edge corrosion kr1 kr0 kr0 504 h din en iso 4628-2 blistering on surface 0(s0) 0(s0) 0(s0) din en iso 4628-3 rust on surface ri0 ri0 ri0 iso 4628-1 cut edge corrosion kr1 kr1 kr0 din en iso 4628-8 delamination <0.5mm <0.5mm <0.5mm table 10. corrosion evaluation of samples treated with the nitrite-based accelerator n-l n-m n-h 168 h din en iso 4628-2 blistering on surface 0(s0) 0(s0) 0(s0) din en iso 4628-3 rust on surface ri0 ri0 ri0 iso 4628-1 cut edge corrosion kr0 kr0 kr0 336 h din en iso 4628-2 blistering on surface 0(s0) 0(s0) 0(s0) din en iso 4628-3 rust on surface ri0 ri0 ri0 iso 4628-1 cut edge corrosion kr0 kr0 kr0 504 h din en iso 4628-2 blistering on surface 0(s0) 0(s0) 0(s0) din en iso 4628-3 rust on surface ri0 ri0 ri0 iso 4628-1 cut edge corrosion kr0 kr0 kr0 din en iso 4628-8 delamination <0.5mm <0.5mm <0.9mm herbáth, kovács and jakab hungarian journal of industry and chemistry 52 crystalline zinc phosphate layer on the surface of the steel plates without modifying the bath and by using nitritebased (n) and nitroguanidine (ng) accelerators. the scanning electron micrographs did not show the different crystal structures of zinc phosphate crystals around the graphite spheres as described in the literature. no significant differences in the morphological properties of the zinc phosphate layers formed on the surfaces of the two base metals were observed by applying the same technological parameters. on the zinc phosphate conversion coating, the layer of electrophoretic paint adhered strongly (gt0) and no defects in the paint were observed. the 504-hour-long natural salt spray test, which is generally defined as the minimum requirement in the automotive industry, yielded satisfactory results when applying both accelerators. since neither 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https://doi.org/10.1515/9783748601074 https://doi.org/10.1515/9783748601074 http://www.irdindia.in/journal_ijacsa/pdf/vol3_iss1/5.pdf https://doi.org/10.33927/hjic-2021-08 https://doi.org/10.3390/cryst13030369 hungarian journal of industry and chemistry vol. 48(1) pp. 1–136 (2020) hjic.mk.uni-pannon.hu contents editorial preface to the special issue dedicated to the workshop “self-driving vehicles" istván szalai 1–1 improving the efficiency of neural networks with virtual training data jános hollósi, rudolf krecht, norbert markó, and áron ballagi 3–10 theoretical background and application of multiple goal pursuit trajectory follower ernő horváth, claudiu pozna, péter kőrös, csaba hajdu, and áron ballagi 11–17 high-power modular inverter development for electric motor testing purposes zoltán szeli and gábor szakállas 19–23 lidar-based collision-free space estimation approach miklós unger, ernő horváth, and csaba hajdu 25–31 identification of the material properties of an 18650 li-ion battery for improving the electrochemical model used in cell testing bence csomós and dénes fodor 33–41 challenges of localization algorithms for autonomous driving hunor medve and dénes fodor 43–49 modeling of autonomous ev vector-controlled power conversion system for battery management system design gábor kohlrusz and dénes fodor 51–59 nonlinear magnetic properties of magnetic fluids for automotive applications barnabás horváth and istván szalai 61–65 vibration generator device based on industrial vibrators péter decsi and istván szalai 67–70 design and construction of a vibration data acquisition system for road vehicles roland nagy and istván szalai 71–75 torque transmission time-constant examination of a disk-type magnetorheological clutch sándor mester and istván szalai 77–80 optimizing the planning and manufacturing processes of electromagnetic energy harvesting equipment lászló móricz and istván szalai 81–85 examination of fuel consumption factors, basics of precision and on-board diagnostic measurements tibor busznyák and istván lakatos 87–93 brownian dynamics simulation of chain formation in eletrorheological fluids dávid fertig, dezső boda, and istván szalai 95–107 localization accuracy improvement of autonomous vehicles using sensor fusion and extended kalman filter istván szalay, krisztián enisz, hunor medve, and dénes fodor 109–115 geospatial data manipulation supporting the implementation of driving simulation environments ferenc speiser, krisztián enisz, and dénes fodor 117–121 new hybrid wavelet and cnn-based indirect tire-pressure monitoring system for autonomous vehicles zoltán márton and dénes fodor 123–130 xbrl utilization as an automated industry analysis alex suta and árpád tóth 131–138 hungarian journal of industry and chemistry vol. 48(1) pp. 1–1 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-01 editorial preface to the special issue dedicated to the workshop “self-driving vehicles" istván szalai1 1institute of mechatronics engineering and research, university of pannonia, gasparich márk utca 18/a, zalaegerszeg h-8900, hungary in the 22nd november 2019 a workshop was held in the automotive proving ground, zalaegerszeg, hungary. the title of workshop was "self-driving vehicles. sensors, algorithms, intelligent materials." the workshop collected experts from the university of pannonia, veszprém, and the széchenyi istván university, győr. the workshop was supported by efop-3.6.2-16-2017-00002. the lectures were mostly presented by talented graduate and postgraduate students, who represent future’s professionals. they will be graduated from the two universities and hopefully will seek career in the automotive industry of hungary, especially, in the industry of slefdriving vehicles. this area of technology is developing fast and strongly supported by governments and various players of the economy due to its potential to drive the development of state-of-the-art technologies. the workshop showed that the research groups working in these two universities can contribute to this development with novel results. this issue of the hungarian journal of industry and chemistry contains the contributions of the lectures. istván szalai professional leader ”research of autonomous vehicle systems related to the autonomous test track in zalaegerszeg“ (efop-3.6.2-16-2017-00002) https://doi.org/10.33927/hjic-2020-01 hungarian journal of industry and chemistry vol. 48(1) pp. 3–10 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-02 improving the efficiency of neural networks with virtual training data jános hollósi*1,2, rudolf krecht2, norbert markó2, and áron ballagi2,3 1department of information technology, széchenyi istván university, egyetem tér 1, győr, 9026, hungary 2research center of vehicle industry, széchenyi istván university, egyetem tér 1, győr, 9026, hungary 3department of automation, széchenyi istván university, egyetem tér 1, győr, 9026, hungary at széchenyi istván university, an autonomous racing car for the shell eco-marathon is being developed. one of the main tasks is to create a neural network which segments the road surface, protective barriers and other components of the racing track. the difficulty with this task is that no suitable dataset for special objects, e.g. protective barriers, exists. only a dataset limited in terms of its size is available, therefore, computer-generated virtual images from a virtual city environment are used to expand this dataset. in this work, the effect of computer-generated virtual images on the efficiency of different neural network architectures is examined. in the training process, real images and computer-generated virtual images are mixed in several ways. subsequently, three different neural network architectures for road surfaces and the detection of protective barriers are trained. past experiences determine how to mix datasets and how they can improve efficiency. keywords: neural network, virtual training data, autonomous vehicle 1. introduction shell eco-marathon is a unique international competition held by royal dutch shell plc. this event challenges university students to design, develop, build and drive the most energy-efficient racing cars. our university’s racing team, the szenergy team, has been a successful participant in the shell eco-marathon for over 10 years. two years ago, shell introduced the autonomous urbanconcept (auc) challenge, which is a separate competition for self-driving vehicles that participate in the shell eco-marathon. participants in the auc challenge have to complete five different tasks, e.g. parking in a dedicated parking rectangle, obstacle avoidance on a straight track, drive one lap of the track autonomously, etc. our long-term goal is to prepare for the auc challenge. one of the main tasks is to create an intelligent system, which perceives the environment of our racing car, e.g. other vehicles, the road surface, other components of the racing track, etc. in this paper, only the segmentation of the road surface and of the protective barriers is taken into consideration. an approach based on neural networks will determine the segmentation, because such networks are one of the best tools to solve problems concerning visual information-based detection and segmentation, e.g. image segmentation. many high-performance neural network architectures are available such as alexnet by krizhevsky et al. [1], vggnet by simonyan and zisser*correspondence: hollosi.janos@sze.hu man [2], googlenet by szegedy et al. [3], fully convolutional networks by shelhamer et al. [4], u-net by ronneberger et al. [5], resnet by he et al. [6] and pyramid scene parsing network by zhao et al. [7]. training neural networks requires a large amount of training data. however, in this case, the number of training samples is insufficient, e.g. no training images of protective barriers are available and the generation and annotation of real world data is labour-intensive and time-consuming. computer simulation environments will be used to generate training data for this task. some attempts that apply virtually generated data to train neural networks have been made. peng et al. [8] demonstrated cad model-based convolutional neural network training for joint object detection. tian et al. [9] presented a pipeline to construct virtual scenes and virtual datasets for neural networks. they proved that mixing virtual and real data to train neural networks for joint object detection helps to improve performance. židek et al. [10] presented a new approach to joint object detection using neural networks trained by virtual model-based datasets. in this paper, an attempt is made to show the effects of computer-generated training data on the learning process of different network architectures. the paper is structured as follows: in section 2, the virtual simulation environment that is used for generating training data is described; in section 3, our neural network architectures are presented; in section 4, the training process of the networks is outlined; in section 5, our https://doi.org/10.33927/hjic-2020-02 mailto:hollosi.janos@sze.hu 4 hollósi, krecht, markó, and ballagi results and experiences are shared; finally, in section 6, our conclusions are stated. 2. our virtual environment our aim is to create highly realistic image sets that depict racing tracks which follow the rulebook of the shell ecomarathon autonomous urbanconcept. in order to ensure repeatability and simple parameter setup, the creation of complete, textured 3d-models of the racing tracks is advised. these simulated environments can be used to create images with desired weather and lighting conditions by scanning the track environment using a camera moving at a predefined constant speed. the images created using this method can be processed further, e.g. segmentation and clustering of different types of objects such as the road surface, protective barriers and vegetation. based on the characteristics of the predefined task, the requirements of the simulation environment can be enumerated: • highly realistic appearance, • easy use of textures, • fast workflow, • characteristics definable by parameters (parametric lights, weather conditions), • modular environment construction, • importability of external cad models. unreal engine 4 [11] is a games engine designed for the fast creation of modular simulated environments by the use of modular relief, vegetation and building elements. in these environments, actors based on external cad models could be used. fields of engineering that apply different visual sensors and cameras require very similar computer simulation technologies to the video game industry. video games need to be highly realistic as well as efficient due to limited computational capacity. the requirements are the same for the simulation of vehicles mounted with cameras. highly realistic computer simulations reduce the cost and duration of real-life tests and camera calibrations. it is also important to mention that by using technology implemented and/or developed by the video game industry, the support of a vast developer community is available. since our goal is to develop image-perceiving solutions for the shell eco-marathon autonomous urbanconcept challenge, it is important to carefully follow the rules of this competition with regard to the racing tracks. the simulated environments and racing tracks created by unreal engine strictly follow the rules defined by the aforementioned rulebook. these rules define that the self-driving vehicles have to compete on racing tracks equipped with protective barriers of a known height painted in alternating red and white segments. it is also defined that every racing track consists of three figure 1: example images from the training set. painted line markings, one that is green to denote the starting position, a yellow one to trigger the self-driving mode, and another that is red to mark the finish line. because the racing tracks and tasks are well defined, it is crucial to create accurate models of the expected environments. differences between real and simulated environments might lead to further developments in the wrong direction. two simulated test environments were created. the first one was based on a readily available city model with streets corresponding to a typical racing track. barrier elements were added to the roads to ensure that the racing track complies with the requirements outlined in the rulebook. this model includes defects in and textures of the road surface to ensure detection of the road surface is robust. in order to create image sets based on this environment model, a vehicle model equipped with a camera travelled around the racetrack on a pre-defined path. the camera was set to take pictures at pre-defined time intervals. the image set was annotated by using a module called airsim. airsim is an open-source, cross-platform simulator simulation platform built on unreal engine, but it also has a unity release. this simulator module consists of a built-in python-based api (application programming interface) which was developed for image segmentation. by using this api, the necessary realistic and segmented image datasets were created. some example pairs of images from our virtual dataset are presented in fig. 1. in order to prepare for all the tasks defined in the rulebook, multiple models of racing tracks were created. all such models are based on the same environment model, which includes vegetation and the sky as shown in fig. 2. the models of sections of racing track were realized according to the challenges defined in the rulebook. the cad models representing elements of the racing track were custom-made to comply with the shapes, sizes and colors outlined in the rulebook. the sections of racing track generated can be used to simulate handling hungarian journal of industry and chemistry improving the efficiency of neural networks with virtual training data 5 figure 2: basic environment of racing tracks. figure 3: parking place and slalom course. (slaloming) and parking tasks. this virtual racing track is shown in fig. 3. the image sets were created by a moving camera in the environment and segmentation was carried out by changing the textures. 3. neural network architectures three different neural network architectures are implemented in this work: fcn, u-net and pspnet. all neural networks are designed for image segmentation, where the size of input images is 256×512×3, and the size of output ones is 256×512×1. every network is trained for the segmentation of the road surface and protective barriers. 3.1 fcn the fully convolutional network (fcn) [4] architecture is based on fully convolutional layers, where the basic idea is to extend effective classification neural networks to conduct segmentation tasks. our fcn architectures are shown in fig. 4. let: γ = (conv, bn, relu) (1) b1 = (γ, γ,mp) (2) b2 = (γ, γ, γ,mp) (3) figure 4: fcn architecture. 48(1) pp. 3–10 (2020) 6 hollósi, krecht, markó, and ballagi figure 5: u-net architecture. where conv denotes a convolutional layer, bn represents a batch normalization layer, relu stands for a rectified linear activation unit and mp is a max pooling layer. let: b1 = (b1, b1, b2) (4) b2 = (b2) (5) b3 = (b2, γ, γ, γ) (6) x = (conv, bn) (7) y = (relu, softmax) (8) z = (relu, softmax) (9) where softmax denotes a softmax layer. in this implementation, the dimensions of all convolutional layers are 3× 3, except for the three fully connected layers in block b3. the dimensions of these convolutional layers are 7×7. in block b1, the first two convolutional layers both contain 64 filters, the third and fourth both contain 128 filters, and the last three convolution blocks each contain 256 filters. the convolutional layers in block b2 contain 512 filters in total. the first three convolutional layers in block b3 contain 512 filters in total, and the fully connected layers are based on 4096 filters in total. 3.2 u-net the u-net [5] neural network architecture was originally created for biomedical image segmentation. it is based on fcn, where the neural network can be divided into two main blocks, namely the downsampling and upsampling figure 6: psp net architecture. blocks. our implementations are shown in fig. 5. let: d1 = d2 = (γ, γ, maxpooling) (10) d3 = d4 = b = (γ, γ, γ,maxpooling) (11) u1 = u2 = u3 = ( convt, bn, relu, γ, γ ) (12) u4 = ( convt, bn, relu, γ, γ, conv, softmax ) (13) where convt is a transposed convolution layer. in the unet neural network, the dimensions of all convolutions and transposed convolutions are 3× 3, and 2× 2, respectively. the number of convolutional filters are as follows: each convolutional layer in d1 consists of 64, in d2 of 128, in d3 of 256 and in d4 as well as b of 512 filters. the upsampling block is very similar. u1 consists of 512, u2 of 256, u3 of 128 and u4 of 64 filters. 3.3 pspnet the pyramid scene parsing network (pspnet) [7] was judged to be the best architecture in the imagenet scene parsing challenge in 2016 [12]. the main building block of the pspnet is a pyramid pooling module, where the network fuses features under four different pyramid scales. our pspnet-based architecture is shown in fig. 6. hungarian journal of industry and chemistry improving the efficiency of neural networks with virtual training data 7 let: b1 = (γ, γ, γ,maxpooling) (14) c = (γ, γ, conv, bn)+ (conv, bn) (15) i = (γ, γ, conv, bn) (16) p = (avg, conv) (17) p1 = (p) (18) p2 = (p, p) (19) p3 = (p, p, p) (20) p4 = (p, p, p, p) (21) b2 = ( γ, dropout, conv, convt, softmax ) (22) where avg denotes an average pooling layer and dropout represents a dropping out unit. in block b1, the dimensions of all convolutions are 3× 3. in blocks c and i , the dimensions of every first & third and every second convolution are 3×3 and 1×1, respectively. in blockb2, the dimensions of the first convolution are 3× 3 and the second 1× 1. the dimensions of the transposed convolution are 16 × 16. each of the first two convolutions in block b1 consist of 64 filters, and the last one of 128. the first block c and first two i blocks contain 64, 64, 256 filters, respectively, while the second block c and the following three i blocks consist of 128, 128 and 512 filters, respectively. the third block c and the following five i blocks contain 256, 256 and 1024, respectively, and the fourth block c along with the last two i blocks consist of 512, 512 and 2048 filters, respectively. 4. training with virtual data an attempt was made to improve the accuracy of neural networks using computer-generated virtual training data that originates from the virtual city environment. some mixed datasets were compiled which contain real-world images and computer-generated virtual images. the realworld images originate from the cityscapes dataset, a large-scale dataset for semantic segmentation [13]. the dataset contains 5000 annotated images with fine annotations created in 50 different cities under various weather conditions. 30 object classes are included, e.g. roads, sidewalks, people, vehicles, traffic lights, terrain, sky, etc. but in this research, only road surface segmentation is examined. the computer-generated images originate from the simulation environment described in section 2. for road surface segmentation, five different datasets are created from the cityscapes dataset and our collection of virtual images. table 1 shows how these two collections were mixed. our goals are to use a minimum amount of data from a real-world dataset, and when the number of virtual images is changed, to observe how the efficiency of the neural networks is affected. dataset a only contains real-world images, therefore, this is regarded as the basic dataset, while the others were compared to it. dataset b already contains the same number of virtual images as real-world images. here, observations of how the introduction of virtual images changes table 1: number of images in our mixed datasets dataset name training set validation set virtual real-world virtual real-world a 0 500 0 125 b 500 500 0 250 c 1500 500 0 500 d 1500 1000 0 625 e 1500 1500 0 750 the initial degree of efficiency are sought. dataset c contains three times more virtual images than dataset b. if the number of virtual images is much higher than the number of real-world images, the efficiency may be reduced. a future paper of ours will investigate this. in datasets d and e the number of real-world images was increased. for the segmentation of protective barriers, only virtual training data were used. how efficiently the neural network recognizes real objects, if only trained by virtual data, will now be shown. the effect of increasing the number of real-world images on efficiency was investigated. adam optimization was used for training with a learning rate of 10−4 and a learning rate decay of 5×10−4. as the objective function, categorical crossentropy is used: l (y, ŷ)= −y×log (ŷ) (23) and the dice coefficient measured: dc (y, ŷ)= 1−2×y×ŷ+1 y+ŷ+1 (24) where y ∈ {0, 1} is the ground truth and 0 ≤ ŷ ≤ 1 is the result of the neural network. 5. results an attempt was made to examine the efficiency of road surface detection, while the composition of the dataset was modified. for examining changes in efficiency, the most useful datasets were a, c and e. dataset a is the basic dataset, which only contains a small set of real-world images. dataset c is based on dataset a, but contains three times as many virtual images as real-world images. dataset c shows how performance changes, when virtual world images are integrated into a small dataset. in dataset e, the size of the collection was expanded. this dataset shows how much greater the efficiency of a larger mixed dataset is. fig. 7 shows the validation accuracy over the training process of road surface detection, while fig. 8 shows the best dice coefficient values for road surface segmentation. fcn is much simpler than both u-net and pspnet neural network architectures. hence the efficiency of the fcn on dataset a is a little less than for the other networks. u-net and pspnet are very robust and complex, therefore, mixed datasets do not significantly increase the efficiency of these architectures. however, for simpler networks like fcn, this method improves the efficiency. fig. 9 shows the perfor48(1) pp. 3–10 (2020) 8 hollósi, krecht, markó, and ballagi figure 7: road surface segmentation performance mances with regard to the segmentation of protective barriers. only virtual images were used to train the neural networks that determine the segmentation of protective barriers. this would not have been possible in the case of road surface segmentation, because the road surface is too complex. the texture of the protective barriers is very simple, therefore, it is possible to recognize it from virtual images alone. it is our intention to use an environment detection system in a low-budget racing car, where the hardware resources available are limited and detection must occur in real time with a high degree of detection accuracy. therefore, the neural network should be designed to be as simple as possible. if the neural network architecture is too simple, it is more difficult to train for complex recognition tasks. moreover, the dataset concerning the racing track, protective barriers, etc. is not large. in this case, it is helpful to be able to train simpler neural networks, e.g. fcn, with virtual datasets to achieve higher degrees of efficiency. experience has shown that the efficiency of road surface detection is improved by using three times as many virtual images, while for protective barrier detection it is sufficient to only use virtual images. 6. conclusion this paper presents how to use computer-generated virtual images to train artificial neural networks when the amount of available real-world images is limited. three different neural network architectures, namely fcn, unet and pspnet, were investigated and these networks trained with mixed datasets. it was shown that virtual imhungarian journal of industry and chemistry improving the efficiency of neural networks with virtual training data 9 figure 8: best accuracy of road segmentation figure 9: barrier segmentation performance ages improve the efficiency of neural networks. our research demonstrates that when the texture of the objects is simple, e.g. that of protective barriers, it is sufficient to only use virtual image-based training datasets. this work may help us to create an efficient environment detector for the shell eco-marathon, where special objects have to be detected in the absence of real-world datasets. acknowledgements the research was carried out as part of the “autonomous vehicle systems research related to the autonomous vehicle proving ground of zalaegerszeg (efop-3.6.216-2017-00002)” project in the framework of the new széchenyi plan. the completion of this project is funded by the european union and co-financed by the european social fund. references [1] krizhevsky, g. a.; sutskever, i.; hinton, g. e.: imagenet classification with deep convolutional neural networks, commun. acm, 2017 60(6), 84–90 doi: 10.1145/3065386 [2] simonyan, k.; zisserman, a.: very deep convolutional networks for large-scale image recognition, 3rd international conference on learning representations, san diego, usa, 2015 [3] szegedy, c.; liu, w.; jia, y.; sermanet, p.; reed, s.: going deeper with convolutions, ieee conference on computer vision and pattern recognition (cvpr), boston, ma, usa, 2015 doi: 10.1109/cvpr.2015.7298594 [4] shelhamer, e.; long, j.; darrell, t.: fully convolutional networks for semantic segmentation, ieee transactions on pattern analysis and machine intelligence, 2017 39(4) 640–651 doi: 10.1109/cvpr.2015.7298965 [5] ronneberger, o.; fischer, p.; brox, t.: u-net: convolutional networks for biomedical image segmentation, in: navab, n.; hornegger, j.; wells, w.; frangi, a. (eds.) medical image computing and computer-assisted intervention – miccai 2015. miccai 2015: lecture notes in computer science, 9351 234–241, springer: cham, switzerland, 2015 doi: 10.1007/978-3-319-24574-4_28 [6] he, k.; zhang, x.; ren, s.; sun, j.: deep residual learning for image recognition, ieee conference on computer vision and pattern recognition, las vegas, nv, usa, 770–778, 2016 doi: 10.1109/cvpr.2016.90 [7] zhao, h.; shi, j.; qi, x.; wang, x.; jia, j.: pyramid scene parsing network, ieee conference on computer vision and pattern recognition (cvpr), honolulu, hi, usa, 6230–6239 2017 doi: 10.1109/cvpr.2017.660 [8] peng, x.; sun, b.; ali, k.; saenko, k.: learning deep object detectors from 3d models, ieee international conference on computer vision (iccv), santiago, chile, 1278–1286, 2015 doi: 10.1109/iccv.2015.151 [9] tian, y.; li, x.; wang, k.; wang, f.: training and testing object detectors with virtual images, ieee/caa j. autom. sin., 2018 5(2) 539–546 doi: 10.1109/jas.2017.7510841 [10] židek, k.; lazorík, p.; pitel, j.; hošovskı, a.: an automated training of deep learning networks by 3d virtual models for object recognition, symmetry, 2019 11 496–511 doi: 10.3390/sym11040496 [11] unrealengine.com 2020. unreal engine | the most powerful real-time 3d creation platform. 48(1) pp. 3–10 (2020) https://doi.org/10.1145/3065386 https://doi.org/10.1145/3065386 https://doi.org/10.1109/cvpr.2015.7298594 https://doi.org/10.1109/cvpr.2015.7298594 https://doi.org/10.1109/cvpr.2015.7298965 https://doi.org/10.1109/cvpr.2015.7298965 https://doi.org/10.1007/978-3-319-24574-4_28 https://doi.org/10.1109/cvpr.2016.90 https://doi.org/10.1109/cvpr.2016.90 https://doi.org/ 10.1109/cvpr.2017.660 https://doi.org/ 10.1109/cvpr.2017.660 https://doi.org/10.1109/iccv.2015.151 https://doi.org/10.1109/iccv.2015.151 https://doi.org/10.1109/jas.2017.7510841 https://doi.org/10.1109/jas.2017.7510841 https://doi.org/10.3390/sym11040496 10 hollósi, krecht, markó, and ballagi https://www.unrealengine.com/en-us/ [accessed 14 september 2019] [12] russakovsky, o.; deng, j.; su, h.; krause, j.; satheesh, s.;ma, s.; huang, z.; karpathy, a.; khosla, a.; bernstein, m.; berg, a. c.; fei-fei, l.: imagenet large scale visual recognition challenge, int. j. computer vision, 2015 115 211–252 doi: 10.1007/s11263-015-0816-y [13] cordts, m.; omran, m.; ramos, s.; rehfeld, t.; enzweiler, m.; benenson, r.; franke, u.; roth, s.; schiele, b.: the cityscapes dataset for semantic urban scene understanding, ieee conference on computer vision and pattern recognition (cvpr), las vegas, nv, usa, 3213–3223 2016 doi: 10.1109/cvpr.2016.350 hungarian journal of industry and chemistry https://www.unrealengine.com/en-us/ https://doi.org/10.1007/s11263-015-0816-y https://doi.org/10.1109/cvpr.2016.350 hungarian journal of industry and chemistry vol. 48(1) pp. 11–17 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-03 theoretical background and application of multiple goal pursuit trajectory follower ernő horváth*1,2, claudiu pozna3, péter kőrös2, csaba hajdu2, and áron ballagi2 1department of computer engineering, széchenyi istván university, egyetem tér 1, h-9026 győr, hungary 2research center of vehicle industry, széchenyi istván university, egyetem tér 1, h-9026 győr, hungary 3faculty of electrical engineering and computer science, transilvania university of brasov, b-dul eroilor nr. 29, 500036 brasov, romania autonomous and self-driving technology is a rapidly emerging field among automotive-related companies and academic research institutes. the main challenges include sensory perception, prediction, trajectory planning and trajectory execution. the current paper introduces a design strategy and the mathematical background of the optimization problem with regard to the multiple goal pure pursuit algorithm. the aim of the algorithm is to provide a low degree of computational complexity and, therefore, a fast trajectory-tracking approach. finally, in terms of our approach, not only the theoretical questions but the application challenges will be described as well. keywords: autonomous, self-driving, algorithm, trajectory-tracking 1. introduction the current paper deals with the design strategies, theoretical background and application of trajectory tracking. the trajectory-follower approach that is discussed is called the multiple goal pure pursuit algorithm, in particular the windowed version. in mobile robots or vehicles, the trajectory design strategy seeks to identify the best possible trajectory which approximates a desired trajectory based on waypoints. this also assumes that the trajectory design phase has already created the desired trajectory. this paper is organized as follows. the first section introduces the general problem and summarizes the stateof-the art and most relevant results. the second section deals with the design strategy of trajectory tracking and defines the problem precisely. the third section defines the optimization problem and possible solutions, while the fourth section summarizes the results. finally, the last section includes a summary and conclusions. the current state-of-the-art results the essence of pure pursuit is to choose a look-ahead point from the desired trajectory in front of the vehicle and steer according to it. this simple idea can be realized in many different ways, e.g., the classical pure pursuit algorithm uses a fixed look-ahead distance. this means that on the given track, a look-ahead point can be determined as a subset *correspondence: herno@ga.sze.hu of waypoints, which are a fixed distance from the vehicle. choosing a look-ahead distance is a tradeoff between control overshoots and precision. if the look-ahead distance is small, the overshoot will appear because the chosen point is so close that the vehicle cannot react instantaneously, thus continuously exceeds its target. in this case, the absolute distance (error) is smaller but the vehicle will oscillate. in contrast, if the chosen point is too far away, the vehicle will follow the point after the following corner so cuts off the bend. this behavior can be eliminated if the look-ahead distance is adjustable or changeable. one of the most obvious ways to modify the look-ahead distance is to scale the speed of the vehicle accordingly [1]. the other method of modifying the look-ahead distance involves a fuzzy controller that automatically adjusts the look-ahead distance based on path characteristics, velocity and tracking errors [2, 3]. similarly to the fuzzy approach [4], it was shown that an autonomous vehicle can drive at a velocity of approximately 80 km/h along explicit paths using differential gps data. to improve the classical pure pursuit algorithm and eliminate steering latency, cf-pursuit [3] replaced the circles employed in pure pursuit with a clothoid curve to reduce fitting errors. although many papers have examined this domain, the available source code is rather rare. a few of the most notable versions are autoware [5], python [6] and raptor unmanned ground vehicle (ugv) [7]. our research group also introduced a pure pursuit method based on multiple look-ahead points [8], in this paper its updated https://doi.org/10.33927/hjic-2020-03 mailto:herno@ga.sze.hu 12 horváth, pozna, kőrös, hajdu, and ballagi version will be presented. 2. the design strategy the motivation of our research was to construct a simple but flexible kinematic trajectory tracking approach. in addition, the implementation of a more human-like thinking was sought, in other words, to track and follow more goal points on a road simultaneously. drivers also take multiple considerations into account, e.g., not only is lanekeeping an important task but a cyclist in the same lane also influences planning. in our previous work the multiple goal pursuit algorithm can be viewed as a supplement to the pure pursuit algorithm. the most significant change was the calculation of curvature. assuming the reference trajectory is given with a set of geometric points t , position p , steering angle γ and orientation θ of the vehicle, g ⊆ t is defined as the set of selected goal points with a preset length n = |g|: g = {g1, g2, . . . , gn |gk, (l+o) ≤ k < (l+o+n)} (1) an angle αf from a domain of possible angles [αmin, αmax] is assumed (presumably the wheel angle limits). a sequence of curvatures can be calculated each with a radius pf = −2/α and a centre point cf . a goal pointgk from setg to anycf determines a line segment: the normalized difference between the length of this segment and radius pf is the distance d ∈ r+ from the curvature. the metric for selecting a good angle is the sum of this difference for each goal point. dsum = n∑ k=0 ∣∣∣ ∥∥∥−−−→cfgk ∥∥∥−ρf ∣∣∣. (2) here dsum denotes the total distance for goal point set g. the aim is to minimize this distance. this paper introduces a new approach to the multiple goal pure pursuit algorithm, which is based on windowing. this algorithm is not regarded as a classical trajectory tracker since it slightly redesigns the original trajectory. with this method, a trajectory similar to the original one is created, but slight modifications render it more suitable for our vehicle to track. the design strategy consists of identifying the optimum trajectory which approximates a desired trajectory defined by a set of chosen points. this means that the aforementioned set is initial data and a minimum problem must be defined. from the multitude of possibilities, the minimum problem will be defined starting with the following hypothesis: 1. during the approximation, the steering angle γ is constant; 2. changing the steering angle γ is an instantaneous process. if the previous hypotheses are correlated, it can be concluded that the initial set of points is approximated by a figure 1: the windowed goal pursuit strategy trajectory composed from arcs of a circle. the transition from one arc to another is instantaneous. for a particular arc of the circle, a subset (referred to here as the working set) is selected from the initial set. the following decisions are subjects of debate: • the number of points included in the working set; • the number of commune points which belong to different working sets; • the position of the car when the next working set is defined. the aforementioned observations are shown in fig. 1, where a possible strategy is illustrated. the figure contains two referential systems. the first, 0, is the global (stationary) referential system; the second, 1, 2, 3, is the mobile referential system attached to the vehicle. the blue triangles denote the abstraction of the vehicle. two windows are labelled as w1,2. each of them contains a working set of three points. the trajectory is a composition of two arcs of a circle, c1 and c2. the first (c1) is defined in referential frame 1 using the window w1, i.e., the points 0x1 , 0x2 and 0x3 . the second (c2) is defined in referential frame 2 using the window w2, i.e. the points 0x4 , 0x5 and 0x6 . each of the mentioned points is defined in referential frame 0. 3. the optimization problem using m windows and n points for each window, the mathematical definition of the problem is rj = arg ( min m∑ i=1 ei ) , (3) where rj denotes the radius of arc cj , ei stands for the distance from point i to arc cj , j represents the current window number j = 1, . . . ,m, and i is the current point number which belongs to window j. the distance from point xi to cj is also debatable. fig. 2 illustrates two possibilities: the first (fig. 2a) only considers one coordinate of the current point. in contrast, in fig. 2b the shortest distance is considered. hungarian journal of industry and chemistry multiple goal pursuit trajectory follower 13 figure 2: possible ways of computing the distances for the first choice: ei = yi − cj (xi) , (4) where jxi jyi 1  = j 0t 0xi =  cθ −sθ 0 sθ cθ 0 0 0 1  xi yi 1  0xi; (5) θ denotes the orientation of the referential system j; and xj , yj represent the coordinates of the origin of referential system j. if this definition is assumed, it is evident that this is a quadratic regression problem with the analytical solution 1 r = κ = ( xtx )−1 ( xty ) , (6) where x =  x2 1 + y2 1 . . . x2 n + y2 n  (7) y =  2y1 . . . 2yn  (8) for the second choice: ei = ∣∣∣∣ r− ∣∣∣∣[ xi yi −r ]∣∣∣∣ ∣∣∣∣ = ∣∣∣∣r−√x2 i + (yi −r) 2 ∣∣∣∣ (9) which has a numerical solution. 3.1 algorithm flowchart in fig. 3, a flowchart is presented in order to understand the approach more comprehensively. the algorithm uses the vehicle parameters, pose, trajectory points and input parameters as inputs. the vehicle parameters are wheelbase b, steering angle γ and its position. also, the points: 0xk are part of the initial data. the algorithm parameters are: working set n, skyline d and curvature limit. this limit decides whether the locomotion is based on a linear or circular trajectory window. for every iteration, a new window is calculated. 4. discussion 4.1 simulation the simulation uses the previous algorithm for a kinematic model which is in accordance with the starting hyfigure 3: algorithm flowchart 48(1) pp. 11–17 (2020) 14 horváth, pozna, kőrös, hajdu, and ballagi xu x(k) x(k + 1) xu+1 x(k + 2) xu+2 xu+3 e(k) figure 4: the definition of lateral deviation pothesis, i.e., the steering is instantaneous. in the first simulation, the following kinematic bicycle model ẋ = v cos (θ) ẏ = v sin (θ) θ̇ = v l tan (γ) γ = ct (10) was used. to analyze the results, the lateral approximation error was defined: • the lateral deviation error of the current position e(k) is the distance between this position and the current segment of the desired trajectory (fig. 4); • the total deviation error et is the sum of the error throughout the simulation from 1 to n ; • the relative deviation error er is the ratio of the total error to the total number of simulated points. e(k) = distance ( x(k), 0xu0xu+1 ) = = ∣∣∣x(k)xu+1 − x̂uxu+1 ( x(k)xu+1 · xuxu+1 )∣∣∣ (11) et = n∑ k=1 e(k) (12) er = et n (13) these errors are dependent on the number of points included in the working set (n) referred to as the skyline and the position of the decision point (d). for the desired trajectory, a study relative to this dependency was conducted and the relative errors for each case were obtained (n, d). the non-instantaneous steering was also simulated (fig. 5). in this case, the kinematic bicycle model can be modified as follows: ẋ = v cos(θ) ẏ = v sin(θ) θ̇ = v l tan(γ) γ = γ0 + γ̇t γ̇ = ct (14) the steering angle is a linear function where the steering velocity is constant during the steering process. the figure 5: simulation result: the blue dots denote the waypoints, the red line represents the trajectory generated by our model trajectory of the robot is no longer an arc of a circle but a combination of two curves. the first of which is a clothoid (also referred to as an euler spiral) when γ = γ0 + γ̇t and an arc of a circle when γ = ct. in this case, the simulation result shows a lower quality of approximation. given this phenomenon, the robot orientation angle error is defined as the difference between the orientation angle in the hypothesis where the steering is instantaneously modified to the final value and the orientation angle in the hypothesis where the steering angle is continuously modified from the initial to the final value. eθ = v l ( tan (γf) ∆t− ∫ ∆t 0 tan(γ0 + γ̇τ)dτ ) = = v γ̇l ( tan (γf) ∆γ − log ( cos(γ0) cos(γf) )) (15) where γ0 denotes the initial steering angle, γf = arctan(lκ represents the final steering angle, γ̇ stands for the steering angle velocity, and ∆t is the steering time. it is observed that eq. 12 is in accordance with our intuitions: if the steering angle velocity increases the orientation error angle will decrease; in contrast, the velocity is proportional to the error. a strategy where a maximum orientation error eθmax is allowed can now be contemplated and since the maximum steering velocity γ̇ is an actuator parameter (which is constant), the following function for the vehicle velocity is proposed: vnew = eθmax eθ vold. (16) in conclusion, the algorithm must be improved in order to yield better results. the following possibilities are suggested (fig. 6): • refine the input set of points: interpolate new points; • change the vehicle velocity during locomotion (eq. 16); hungarian journal of industry and chemistry multiple goal pursuit trajectory follower 15 figure 6: the proposed new strategy • define the new windows by including the points which succeed the decision point in the new working set. with regard to an examined sample trajectory, a 3d graph (fig. 7) is provided which shows the relative dependency obtained in terms of the relative error value in each case (n, d). in fig. 7, the x axis denotes the skyline (n), the figure 7: the relative error depends on the skyline (n) and decision point (d) figure 8: typical behaviors of the examined approaches y axis represents the decision point (d), and the z axis stands for the relative error. 4.2 experiments firstly, the behavior of the algorithm in its own simulation environments was tested; the two presented approaches (the plain multiple goal pursuit and the windowed multiple goal version) were developed in parallel in python and matlab. these simulations also used real-world trajectories and the vehicle model was first a kinematic, and later a dynamic one. subsequently, it became necessary to even test the algorithms in open source robotics foundation’s (osrf) gazebo for two reasons. firstly, implementation of the algorithm as a robot operating system (ros) node was sought and secondly, a more precise dynamic model of the vehicle already existed in gazebo. gazebo also facilitated the integration of the useful software as well as agile migration between development and target. for these purposes, the algorithm had to be recreated in c++ not only because of the ros compatibility but computational resources as well. simulation-based execution yielded no significant deviation from the simulated tests. in fig. 8, some of our results are shown regarding the examined trajectories. the x and y axes are in meters. this simulation is based on real-world measurements taken at the zalazone automotive test track in zalaegerszeg and the gps coordinates are assigned using universal transverse mercator (utm) because of the minimal degree of distortion involved. the follow the carrot and speed ratio-based pure pursuit algorithms had to be implemented in order to experiment with them in the same environment. in another experiment, autonomous functionalities were installed in an electric vehicle (nissan leaf). fig. 9 represents the vehicle in operation. the operational domain of this vehicle was limited to the zalazone auto48(1) pp. 11–17 (2020) 16 horváth, pozna, kőrös, hajdu, and ballagi figure 9: the vehicle used in our experiments motive test track and the university campus, moreover, it was required to reach a relatively slow speed of 25 km/h. the vehicle has front-wheel drive, with a wheelbase of 2.70 meters and a track width of 1.77 meters. to ensure instantaneous localization of the vehicle, two highly accurate real time kinematic (rtk)-capable gpss were used. one was kvh’s fiber optic gyro 3d inertial navigation system (geo-fog 3d ins), the other was swift navigation’s duro inertial rtk. these sensors were also used to capture reference trajectories. our software was based on osrf’s ros [9]. our computing platform first features the nvidia jetson tx2, later the nvidia jetson agx xavier. low-level control is realized by using a national instruments’ compactrio controller, namely crio-9039, as the real-time and fpga modules the ni-9853 can, ni-9403 di, ni9205 voltage input and ni-9264 voltage output modules to be exact. after the algorithm exhibited satisfactory behavior in the simulation environment, it was tested in a realworld scenario. during the experiment, the nvidia jetson tx2 was used in the nissan leaf. the nvidia jetson tx2 is a 7.5-watt embedded controller in which the ubuntu 18.04 lts bionic beaver along with the ros melodic morenia were used. the embedded controller had a memory capacity of 8 gb and memory bandwidth of 59.7 gb/s as well as nvidia’s denver2, quad-core arm cortex-a57 cpu and integrated 256-core pascal gpu installed. during our experiments, only the kvh’s geo-fog 3d ins sensor was used as the source of localization, the wheel angle reference signal in addition to the speed reference via can were provided, and the wheel angle and speed were measured back in the same protocol. nevertheless, during acquisition of the data, all the sensory information was logged by two of velodyne’s 16-channel lidars, sick’s 1-channel laser measurement sensor lms111 and the camera stream into ros bag files. the following chart (fig. 10) shows an example of how the algorithm generated reference trajectories for two bends on the routine track, moreover, the measured wheel angle is shown. the waypoints for the algorithm were provided by driving through a predetermined path then saving as well as filtering the position and speed data via the waypoint_saver node. in this experiment, only the multiple goal pursuit al-4 -2 0 2 4 6 8 10 12 14 0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 an gl e (d eg ) time (s) wheel angle measurements wheel angle reference wheel angle figure 10: changes in the wheel angle around two bends gorithm with one parameter set was used. this set is better compared to autoware’s pure pursuit algorithm in terms of lateral deviation, but the speed ratio-based version worked even better. as a result, the multiple goal pursuit algorithm was able to control the vehicle with the aforementioned embedded controller at slow speeds of approximately 25 km/h. the algorithm is able to perform smooth and continuous movements along a predefined trajectory, even maneuvering around bends and along edges. 5. conclusion the current paper described the development of a trajectory-tracking approach, namely the multiple goal pursuit, and summarized the mathematical and theoretical background needed to understand its working principles. enhancements to and variations in the basic approach are also described with regard to their benefits and weaknesses. furthermore, a brief insight into the development process is given. firstly, an initial version was developed in our own simulation environment, later the code became an ros node and the simulation environment was replaced by gazebo. finally, real-world tests showed the viability of the new algorithm, which was tested by an autonomously guided vehicle in a closed but real-world traffic environment. one of the benefits of this algorithm is that it can be tuned more precisely around bends, moreover, it involves more human-like thinking, that is, tracks and follows more waypoints on the road simultaneously. furthermore, this approach provides quick and reliable reference signals for car-like robot kinematics, thus can follow the trajectory with relatively small errors. the discussed algorithm was implemented in matlab and c++ as a robot operating system node and our measurements were based on debug data generated by this node. this implementation is currently publicly available on github in addition to other measurements, videos, results and source codes: https://github.com/szenergy/ szenergy-public-resources. hungarian journal of industry and chemistry https://github.com/szenergy/szenergy-public-resources https://github.com/szenergy/szenergy-public-resources multiple goal pursuit trajectory follower 17 acknowledgements the research was carried out as part of the “autonomous vehicle systems research related to the autonomous vehicle proving ground of zalaegerszeg (efop-3.6.216-2017-00002)" project in the framework of the new széchenyi plan. the completion of this project is funded by the european union and co-financed by the european social fund. references [1] paden, b.; čáp, m.; yong, s. z.; yershov, d.; frazzoli, e.: a survey of motion planning and control techniques for self-driving urban vehicles, ieee trans. intell. veh., 2016, 1(1), 33–35 doi: 10.1109/tiv.2016.2578706 [2] ollero, a.; garcía-cerezo, a.; martinez, j.: fuzzy supervisory path tracking of mobile reports, control eng. practice, 1994, 2(2), 313–319 doi: 10.1016/09670661(94)90213-5 [3] samuel, m.; hussein, m.; mohamad, m. b.: a review of some pure-pursuit based path tracking techniques for control of autonomous vehicle, int. j. computer applications 2016, 135(1) 35–38 doi: 10.5120/ijca2016908314 [4] rodríguez-castaño, a.; heredia, g.; ollero, a.: analysis of a gps-based fuzzy supervised path tracking system for large unmanned vehicles, ifac proceedings volumes, 2000, 33(25) 125–130 doi: 10.1016/s1474-6670(17)39327-8 [5] kato, s.; tokunaga, s.; maruyama, y.; maeda, s.; hirabayashi, m.; kitsukawa, y.; monrroy, a.; ando, t.; fujii, y.; azumi, t.: autoware on board: enabling autonomous vehicles with embedded systems, in proceedings of the 9th acm/ieee international conference on cyber-physical systems, 2018, 287–296 doi: 10.1109/iccps.2018.00035 [6] sakai, a.; ingram, d.; dinius, j.; chawla, k.; raffin, a.; paques, a.: pythonrobotics: a python code collection of robotics algorithms, 2018, arxiv: 1808.10703 [7] giesbrecht, j.; mackay, d.; collier, j.; verret, s.: path tracking for unmanned ground vehicle navigation: implementation and adaptation of the pure pursuit algorithm, defence research and development canada (drdc), suffield, alberta, canada, 2005. https://apps.dtic.mil/sti/pdfs/ada599492.pdf [8] horváth, e.; hajdu, cs.; kőrös, p.: novel purepursuit trajectory following approaches and their practical, in 10th ieee international conference on infocommunications (coginfocom), naples, italy, 2019. [9] quigley, m.; conley, k.; gerkey, b.; faust, j.; foote, t.; leibs, j.; wheeler, r.; ng, a. y.: ros: an open-source robot operating system, icra workshop on open source software, 2009 3(2) 48(1) pp. 11–17 (2020) https://doi.org/10.1109/tiv.2016.2578706 https://doi.org/10.1109/tiv.2016.2578706 https://doi.org/10.1016/0967-0661(94)90213-5 https://doi.org/10.1016/0967-0661(94)90213-5 https://doi.org/10.5120/ijca2016908314 https://doi.org/10.5120/ijca2016908314 https://doi.org/10.1016/s1474-6670(17)39327-8 https://doi.org/10.1016/s1474-6670(17)39327-8 https://doi.org/10.1109/iccps.2018.00035 https://arxiv.org/abs/1808.10703 https://arxiv.org/abs/1808.10703 https://apps.dtic.mil/sti/pdfs/ada599492.pdf hungarian journal of industry and chemistry vol. 48(1) pp. 19–23 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-04 high-power modular inverter development for electric motor testing purposes zoltán szeli*1 and gábor szakállas1 1research center of vehicle industry, széchenyi istván university, egyetem tér 1, győr, 9026, hungary this paper presents the development process of a high-power modular inverter system. the goal was to develop a universal inverter system (motor controller + power electronics) in which the performance of the power stage is scalable. the design concepts, hardware architecture, system components, built-in features and protections are described regarding the power stage. keywords: modular, universal, desaturation, active clamping, protection 1. introduction power electronics and their control algorithms are very important parts of electric vehicles. the whole system can operate reliably, efficiently and with good dynamics only if all elements of the vehicle are well coordinated. before the different electric drivetrains can finally be applied, they should be tested under different circumstances on electric motor or drivetrain test benches. otherwise it would be difficult to test them in-vehicle as they are already built-in. for such testing processes, a flexible test system is a good solution that can be easily modified at both hardware and software levels, especially for institutions like our research center where various types of electric motors from different manufacturers are dealt with. their inverter systems are usually inaccessible without the help of experts. 2. design concept the purpose of the development was to design a universal and scalable (at the power stage) inverter system. thus, the same system can be used for three-phase electrical machines with different power requirements and applications. the first version is capable of 600 a at a nominal system voltage of 400 v. as the motor controller is equipped with standard interfaces, it is able to adapt power stages to different power levels. for the design of the hardware for the motor controller and power stage, state-of-the-art solutions were used. furthermore, different motor control algorithms are dealt with at the research center, so it was decided to use them with the motor controller to ensure the software en*correspondence: szgabor@ga.sze.hu vironment is capable of further developments and different types of motors can be easily adapted to it. motor control software can be implemented using model-based simulation (matlab/simulink) with automatic code generation. as a result, the behaviour of the motor can be determined in advance by simulation and easily adapted to our specific environment. the system supports different communication protocols, e.g. can, rs232, ethernet and flexray, which can be used for control, data acquisition and status information polling. the system is usually used to test threephase electric machines or can be installed in electric vehicles. 3. results and analysis the inverter system (fig. 1) consists of four separate printed circuit boards (pcbs), namely control board, figure 1: hardware structure https://doi.org/10.33927/hjic-2020-04 mailto:szgabor@ga.sze.hu 20 szeli and szakállas power stage, f-s-800 insulated gate bipolar transistor (igbt) interface board, and a current measurement board for current transducers. only commercially available and automotive qualified components were used for the hardware. with regard to the different circuits on the boards, the spice simulator was used to support the design. the main features: • undervoltage protection • overcurrent protection • isolated sensor supply • isolated voltage measurement • isolated dc/dc power supply for the igbt drivers • temperature measurements • built-in protections: – surge protector – short circuit – desaturation – advanced active clamping 3.1 power stage the power stage was designed to be able to drive a maximum of two igbt modules simultaneously (one igbt module can also be used by us). thus, the output power of the inverter is scalable and can easily be doubled should a different igbt module be used. 3.2 isolated power supply for the gate drivers the power stage includes 6 separate flyback dc/dc converters that produce an isolated +15 v / −8 v asymmetrical power supply for igbt gate drivers as seen in fig. 2. figure 2: power stage design parameters according to the system requirements and the flyback converter datasheet [1]: • 8-18 v dc input voltage • −8 v / +15 v output voltage • 10 w output power (due to igbts in parallel, fsw = 20 khz) • 3, 956 w power consumption per igbt module was calculated from [2] pgdr = qg ( vge(on) − vge(off) ) fsw (1) the output power selected was chosen for 2 igbt modules in parallel. the isolated power supply for the gate drivers works as expected in the real circuit, as can be seen in figs. 3 and 4. 3.3 gate drive circuit the igbt modeules were powered by infineon’s 1ed020i12fa2 galvanically isolated single channel igbt gate driver circuits, which were placed on a separate pcb. the maximum output current of the 1ed020i12fa2 driver was ±2 a. because of this low peak current, significantly increased gate resistors were required, which greatly degraded the switching properties of the igbt driver. therefore, it was necessary to figure 3: simulated flyback dc/dc switching waveform (pout = 5 w) figure 4: flyback dc/dc switching oscilloscope waveform (pout = 5 w) hungarian journal of industry and chemistry high-power modular inverter development 21 figure 5: operation of the surge stopper protection use a so-called bipolar totem-pole amplifier between the output of the driver and the igbt gate terminal. the designed bipolar totem-pole circuit was capable of driving the igbt with the use of a resistor of rgoff = 0.82 ω. 3.4 built-in features surge stopper the voltage supply (+8 v – +16 v) was connected to the load through an overvoltage protection circuit. this circuit protects the other parts of the power stage from high voltage spikes and controls the output voltage in case of input overvoltages (load dumps) as shown in fig. 5. it is also equipped with overcurrent and reverse polarity protection as well as an adjustable low-voltage fault detection limit. desaturation protection the igbt driver is a power semiconductor that is normally used to switch operation in the closed and saturation regions. the closed region can be considered to be a broken wire, and in the saturation region it functions as a short circuit. between the igbt collector and emitter terminals, the saturation voltage, vce, can be measured [3]. this voltage depends on the temperature of the semiconductor, its collector current and the voltage applied to the gate. fig. 6 shows the dependence of the saturation voltage of the fs800r07a2e3 figure 6: output characteristics of the fs800r07a2e3 igbt module figure 7: operation of the desaturation protection igbt module with regard to its collector current on the temperature of the semiconductor. the desaturation voltage can be adjusted using zener or fast diodes, so in our case, the threshold voltage, vce, selected of 1.3 v used in the switching will be subject to a 600 a collector current limitation per module at 25 ◦c. the igbt driver circuit is continuously monitoring the vce, using a comparator, and if that exceeds the reference voltage, that is 9 v, of the integrated circuit, the driver forces its output to vee2 (−8 v) within a maximum tdesatout time of 430 ns as shown in fig. 7. with this kind of protection, short-circuit failures can be avoided and a temperature-dependent current limitation realized. the vce can be monitored only after a period of time equal to tblanking +tdesatout(1.8 µs+430 ns= 2.23 µs) has elapsed following the arrival of the control signal [4]. the fault signal is only active when the igbt driver is switched on. advanced active clamping when working with igbts, parasitic inductances inside them and the converter circuits must be taken into consideration. their effects cannot be completely eliminated for physical reasons and their influence on the system behaviour cannot be neglected. fig. 8 shows the parasitic inductances contained in a commutation circuit. figure 8: parasitic inductances in igbts 48(1) pp. 19–23 (2020) 22 szeli and szakállas figure 9: characteristics of the igbt turn-off process voltage transients are produced at the collector of the igbts during their turn-off process, which are caused by the change in current passing through them as shown in fig. 9. the commutation speed and thus, the turn-off overvoltage at an igbt can, in principle, be affected by the turn-off gate resistance rgoff . this technique is used most often in low-power devices where rgoff must be selected for overload conditions such as turn-off of the double rated current, short circuits and a temporarily increased link circuit voltage. during normal operations, this causes increased turn-off switching losses and turnoff delays, which reduce the efficiency of the modules [5]. the fs800r07a2e3 igbt module has a parasitic inductance of 14 nh. to reduce the voltage spikes, a clamping circuit was used that allows charging of the gate-emitter capacitance and flow charges to the base of the proposed bipolar totem-pole over the specified voltage range through a transient-voltage-suppression diode connected between the collector and the gate, driving the igbt into the normal active mode and reducing the current-change rate, dic/dt as seen in figs. 10 and 11. figure 10: the proposed bipolar totem-pole layout with feedback figure 11: operation of the advanced active clamping circuit @ 340 v/ 800 a (single igbt module) this type of control of the bipolar totem-pole circuit reduces the power dissipation as a result of the resistance rgoff whilst operating. 3.5 cooling system to design the cooling system of the inverter, thermal simulations were carried out. the maximum power dissipation of the igbt module was 1500 w, and its operating temperature range was between −40 and 150 ◦c. the thermal resistance between the liquid coolant (50% water, 50% glycol) and the surface of the heatsink was 0.097 k/w. the igbt manufacturing drawings were used to design the 3d model as seen in fig. 12. 4. conclusion the functional testing of an inverter was carried out at the electric motor test bench laboratory of széchenyi istván university. the developed system and the test environment can be seen in figs. 13 and 14. a permanentmagnet synchronous motor (pmsm) was connected to it and different peripherals and built-in functions tested. on the other side of the test bench, the same type of pmsm connected to a 400 v / 500 a, downscaled (single igbt module) version of the inverter was used. at first, the tests were performed at a speed of 1600 rpm and at low load figure 12: the designed coolant space inside the heatsink hungarian journal of industry and chemistry high-power modular inverter development 23 figure 13: the assembled inverter system figure 14: eletric motor test bench with the mounted inverters torques. the inverters were operated alternately, one in torque-control mode, the other in speed-control mode. in a future paper, these inverters will be tested under heavyload conditions, when the motor control algorithms work reliably. acknowledgements the research was carried out as part of the "autonomous vehicle systems research related to the autonomous vehicle proving ground of zalaegerszeg (efop-3.6.216-2017-00002)" project in the framework of the new széchenyi plan. the completion of this project is funded by the european union and co-financed by the european social fund. references [1] linear technology, ”flyback, forward and isolated controllers“, lt8302 datasheet, sept. 2016 rev. c [2] infineon technologies ag, “automotive igbt module explanation of technical information”, application note an2010-09, 2010 [3] avago technologies, “desaturation fault detection”, application note an5324, 2012 [4] infineon technologies ag, ”galvanic isolated gate driver“, 1ed020i12fa2 datasheet, may 2013 rev. 2.0 [5] rüedi,h.; thalheim, j.; garcia, o.: advantages of advanced active clamping, power electronics europe, 2009 8, 27–29 48(1) pp. 19–23 (2020) hungarian journal of industry and chemistry vol. 48(1) pp. 25–31 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-05 lidar-based collision-free space estimation approach miklós unger∗1, ernő horváth1, and csaba hajdu1 1research center of vehicle industry, széchenyi istván university, egyetem tér 1, győr, 9026, hungary as autonomous technologies flourish within the vehicle industry, an increasing number of academic autonomous competitions are appearing. one of them is the shell eco-marathon autonomous urban concept competition (sem auc) which seeks to provide hands-on experience for the academic community to design, build and test their own driverless vehicles within a realistic infrastructure. the team at our university participates in this competition and our concept is to rely on simple and robust algorithms. this paper presents a simple collision-free space estimation algorithm for the lidar sensor. keywords: autonomous vehicle, voronoi, delaunay 1. introduction nowadays autonomous technology is not only important in the automotive industry but increasingly in the fields of academia and reasearch as well. a sign of this tendency is the increasing number of academic competitions, one of which is the shell eco-marathon autonomous urban concept competition (sem auc). 1.1 shell eco-marathon the shell eco-marathon is a competition for engineering students to design and build the most ultra-efficient car. the participating teams come from all over the world. two main classes of vehicles compete, namely urban concepts and prototypes. both classes can participate in the autonomous category where five different challenges await the teams as follows: • complex track section • maneuverability • obstacle avoidance • the unknown challenge • autonomous distance in this paper, a simple solution for the autonomous distance challenge is presented. 1.2 our team the szenergy team is comprised of students from széchenyi istván university, assisted by tutors and researchers from the fields of the development and construction of electric vehicles. since 2008, the team has ∗correspondence: unger.miklos@ga.sze.hu figure 1: our car szemission. been competing each year in the shell eco-marathon, the biggest fuel-efficiency competition in the world. our team participates in the electric vehicle category of the urban concept class by performing autonomous challenges and regular races using the same car. since 2019, a new car called szemission has been used as shown in fig. 1. 2. the challenge challenges of the auc will be undertaken on the same standard track as the other competitions at the sem or on similar but modified track sections. the track is 970 m long and includes inclines since the track partially consists of closed-off roads (fig. 2). for all five challenges, protective barriers are installed on both sides of the track. the barriers are 0.5 m high separated by small gaps, though the size of these gaps is unspecified. contact with these barriers is forbidden, cars are limited to a top speed of 25 km/h and every car is driven separately on the track. the minimum width of the track is 6 meters unless otherwise specified. https://doi.org/10.33927/hjic-2020-05 mailto:unger.miklos@ga.sze.hu 26 unger, horváth, and hajdu figure 2: simple layout of the challenge. our goal is to create an algorithm that despite the noisy surroundings robustly finds the coordinates of free route between the barriers without touching them based on the output of 3d lidar signals. the route must also be unambiguous. 3. lidars lidar stands for light detection and ranging or laser imaging detection and ranging and is a sensor commonly used in autonomous vehicles to map the environment. the sensor contains a transmitter and receiver. the transmitter fires laser beams towards the ground which interact with the objects of the environment then are deflected back to the receiver. the distance can be computed using a simple formula, where do denotes the distance to the object, cl represents the speed of light, and ∆t stands for the time of flight: do = cl∆t 2 , (1) where the time of flight is measured indirectly by determining the phase shift between the transmitted and received signals, fmod denotes the frequency modulation, ϕr represents the measured difference between the transmitted and received wavelengths [1], and ∆t = ϕr 2πfmod . (2) lidar sensors on autonomous vehicles autonomous vehicles use these rotating beam sensors to scan the environment and detect obstacles. two main types of lidars, the 2d and 3d, are used. 2d lidars, also referred to as lidars with one channel, provide information about the environment in one plane only, hence the objects above and below the lidars are not detected. 3d lidars use more channels (16, 32, 64 or even 128), thus yield all x, y and z coordinates of the surroundings. velodyne’s puck (vlp-16) is a lidar with 16 channels that give a 360◦ three-dimensional view. 4. simulation with ros 4.1 ros in general autonomous vehicles can be regarded as four-wheeled robots. in our project, an ros (robot operating system) is used. it is an open-source, flexible framework for writing robot software. the most important components of it are as follows: topics topics are named buses, in which data is exchanged using ros messages. each topic has a specific name, moreover, one node publishes data to a topic and another node reads the data from the topic by subscribing to it. messages every topic consists of a type of message, moreover, topics send and receive data in the form of ros messages. ros messages form a data structure used by ros nodes to exchange data. different topics send different types of messages, namely 2d lidars use laserscan’s, while 3d lidars use point cloud’s. rosbags bags are a useful utility for the recording and playback of ros topics. while working on autonomous vehicles, some situations may arise where it is necessary to work without actual hardware. using rosbags, sensor data can be recorded and bag files copied to other computers to inspect data by playing it back. gazebo gazebo stands for open source robotic simulators tightly integrated with ros. in this environment, various types of robots, indoor sensors and outdoor elements could be implemented. the values of sensors can be accessed by the ros through topics. rviz rviz is a 3d visualizer in ros to visualize 2d and 3d values from ros topics and parameters which helps to visualize data such as robot models, robot 3d transform data (tf), point clouds, laser and image data, as well as a variety of sensor data [2]. 4.2 simulation simulations are based on models with which we try to copy the physics and geometry of the real world. the more factors that are built into them, the more likely what is expected to happen will actually occur in a real-world test. our car acts as a robot, modelled on a cad program. in this phase of the algorithm, the layout of the car is not important so a nissan leaf was used as our race car. in gazebo, numerous types of sensors are available, the parameters of which can be defined as real-world lidar signals as mentioned in section 3. unfortunately, the exact layout of the racetrack is unknown, so one was created. our track consists of straight sections, curves with hungarian journal of industry and chemistry lidar-based collision-free space estimation approach 27 figure 3: simulation in rviz. different topics can be visualized at the same time. it can be seen that the 3d lidar point cloud originates from two 2d beams, one above the other. different radii as well as white and red protective barriers on both sides. as 3d sensors are used, not only the track but its surroundings are also important. therefore, buildings, trees in addition to cones between and beyond the two barriers were implemented. when the simulation was completed, it was possible to drive a lap of the track in the simulation and collect the ros topics data via rosbags. moreover, with rviz, the following points could be visualized as presented in fig. 3. 5. steps of the algorithm 5.1 filtering our lidar sensor gives information over 360 degrees which is very useful in many cases, however, in this challenge, only information about points in front of the car is needed. if information about displacement of the sensors on the car is available, it can be assumed that the front of the car and all points smaller than the linear equation x = −b+ y m (3) will be deleted, where b denotes the y-intercept and m represents the gradient. 5.2 clustering as from our simulation only raw data (only x, y and z coordinates) are obtained, which points belong to each object has to be defined. clustering is the task of dividing the population or data points into a number of groups such that the data points in a group are more similar to other data points in the same group than to data points in other groups. it is basically a collection of objects arranged according to how similar or dissimilar they are to each other. for us the most effective method is dbscan (density-based spatial clustering of applications with noise), a well-known data clustering algorithm that is commonly used in data mining and machine learning. based on a set of points, dbscan groups together points that are in close proximity to each other based on a distance measurement (usually the euclidean distance) and a minimum number of points. it also marks as outliers the points that are in low-density regions [3]. the dbscan algorithm basically requires two parameters: eps specifies how close points should be to each other to be considered as parts of a cluster. this means that if the distance between two points is smaller or equal to this value (eps), these points are considered to be neighbors. minpoints the minimum number of points to form a dense region. for example, if the minpoints parameter is set as 5, then at least 5 points are needed to form a dense region. after clustering, all of the points belong to a group as shown in fig. 4. 5.3 convex hull even though the point cloud of a 3d lidar stands for more than one thousand points, only a proportion of them is needed, thus points should be filtered. the clustered points have to be packed by each group into a convex hull. the convex hull of a set of points is defined as the 48(1) pp. 25–31 (2020) 28 unger, horváth, and hajdu figure 4: the different clusters denoted by different colors. smallest convex polygon that encloses all of the points in the set [4]. for the purposes of clarification, only the vertices of a convex polygon are used as shown in fig. 5. vertices are side points which form the simplified shape of a polygon. 5.4 delaunay triangulation and voronoi diagram the delaunay triangulation for a given set p of discrete points in a plane is a triangulation dt(p ) such that no point in p is inside the circumcircle of any triangle in dt(p ) [5]. delaunay triangulations maximize the minimum angle of all the angles of the triangles in the triangulation as presented in fig. 6. the circumcenters of delaunay triangles are the vertices of the voronoi diagram. in the 2d case, the voronoi vertices are connected via edges that can be derived from adjacency relations of the delaunay triangles. if two triangles share an edge in the delaunay triangulation, their circumcenters are to be connected with an edge in the voronoi tessellation as shown in fig. 7. for a set of points in 2d space, the voronoi diagram creates cells whose edges are the same distance from two neighboring points. this property grants that all reference points are exactly between two detected items and the edges of voronoi cells are ideal for the representation of a reference line. unfortunately, real environments are never ideal and this method would provide more route options in the presence of noise as presented in fig. 8. figure 5: to clarify the large number of points, only the vertices of the convex hull were used. figure 6: the delaunay triangulation with all the circumcircles and their centers (marked in red). 5.5 ransac at this stage of the algorithm, no information is available about which side of the car the detected points are on. as the reference lines should only be between the two middle barriers, this information is important. for this process, an estimator must be implemented. ransac (random sample consensus) is an iterative method to estimate parameters of a mathematical model from a set of observed data that contains outliers which do not influence the values of the estimated parameters. the input to the ransac algorithm is a set of observed data values, a method of fitting some kind of model to the observations and several confidence parameters. ransac achieves its goal by repeating the following steps [6]: 1. selecting a random subset of the original data, refigure 7: a voronoi diagram is constructed by connecting the centers of the circumstances. hungarian journal of industry and chemistry lidar-based collision-free space estimation approach 29 figure 8: a real scenario from the algorithm. the detected points are denoted in orange, the green points represent the centers of the circumstances, and the black lines stand for the voronoi edges which also represent the reference lines. ferred to as the hypothetical inliers; 2. fitting a model to the set of hypothetical inliers; 3. then testing all other data against the fitted model. those points that fit the estimated model well, according to a model-specific loss function, are considered to be part of the consensus set. 4. the estimated model is reasonably good if a sufficient number of points are classified as part of the consensus set. 5. finally, the model may be improved by reestimating it using all members of the consensus set. if ransac is used for the set of voronoi midpoints, a line is obtained between the protective barriers on either side of the track (fig. 9). now the linear equation for y with its gradient can be written: y = mx+ b, (4) where b denotes the y-intercept and m represents the gradient. points with higher and lower values of y belong to the leftand right-hand sides, respectively. as ransac is an estimator, sometimes it yields wrong results as shown in fig. 10. figure 9: the ransac line (denoted in blue) splits the space into two parts. figure 10: the estimator sometimes yields wrong results. to avoid producing wrong results, some criteria must be declared: • the starting point of the line should be between the protective barriers. • the line must be sufficiently long over the full range of the x-axis. • if the ransac line intersects any of the lines of the convex hull, it must be rotated until it no longer intersects them. 5.6 delete unnecessary reference lines one of our main criteria is that the reference line should exclusively be between the two barriers. to ensure that our car moves in such a way, all unnecessary voronoi midpoints must be eliminated. now all the points that belong to each side can be collected, however, since they are unsorted, an andrew’s monotone chain convex hull algorithm was used [7]. this algorithm sorted the points into a lexicographical order (first by x-coordinates, and should any be equal, by y-coordinates) and then constructed upper and lower hulls of the points as seen in fig. 11. some naive approaches concerning how to use the upper and lower sides of the convex hulls exist. firstly, an attempt was made to copy the shape of the upper hull with a single line using equation (eq. 4), but was not possible when used at corners. figure 11: the leftand right-hand sides were packed into another convex hull. 48(1) pp. 25–31 (2020) 30 unger, horváth, and hajdu figure 12: the reference line along straight sections affected by noise. another idea was that since the borderline was not a single straight line, it could be divided into as many sections as the number of vertices found in the upper hull, however, this resulted in a wavy line which in some cases also deleted inlier voronoi points. then it was realized that the easiest solution would be to delete all the voronoi midpoints which lie inside the left and right convex hulls. 6. results and future works by following the aforementioned steps, the algorithm drew an unambiguous reference line by connecting voronoi midpoints which lie in the middle of the road of the required territory. furthermore, this method also works along straight sections and at corners as shown in figs. 12 and 13. for safety reasons, vehicle speed is limited to 25 km/h. our algorithm is designed to operate at this speed range. the algorithm is based on voronoi cells so its complexity is o(n) [8]. in our test environment the algorithm could estimate the free space with 90 % confidence. with the aid of voronoi diagrams, every detected object has an effect on our reference line. fortunately, the majority of these points are filtered by the steps outlined in section 5.6, however, outliers between the barriers cannot be dealt with. these points have a detrimental effect on the unambiguity of the reference line and lead to the creation of several nodes resulting in some multiplechoice decisions that need to be made by our car. to make our algorithm robust, these points should be eliminated. now a single ransac line divides the sides of the road and works well for the layouts of simple corners, however, one simple line cannot satisfy the criteria for more difficult layouts, e.g. chicanes, because the ransac line is unable to intersect any lines of the convex hull. to avoid this, the line should be divided into smaller sections that need to follow on from each other and determine if any parts of the linked line intersect the line of the convex hull. our path-following algorithm requires that the reference points which follow on from each other are the same distance apart. for this purpose, our reference points must be joined into one line and as many points as the algorithm requires must be generated. figure 13: the reference line at corners. this algorithm has only been examined using test data and has yet to be tested in real environments. 7. conclusion in 2020, our team will participate in the autonomous distance challenge of the shell eco-marathon. the results of this algorithm are promising but a significant amount of research and development has yet to be done until this algorithm can operate and lead our car around a single lap. one of the benefits of the proposed method is that it involves widely used and, over time, highly improved geometric algorithms like delaunay triangulation and voronoi diagrams. acknowledgements the research was carried out as part of the “autonomous vehicle systems research related to the autonomous vehicle proving ground of zalaegerszeg (efop-3.6.216-2017-00002)” project in the framework of the new széchenyi plan. the completion of this project is funded by the european union and co-financed by the european social fund. references [1] verőné wojtaszek, m.: fotointerpretáció és távérzékelés 3., a lézer alapú távérzékelés. 2010 nyugat-magyarországi egyetem [2] lentin, j.: ros robotic projects. (packt publishing ltd., birmingham, uk) 2017, isbn: 978-1-783-55471-3 [3] kriegel, h.-p.; kröger, p.; sander, j.; zimek, a.: density-based clustering, wires data mining knowl. discov., 2011, 1 231–240 doi: 10.1002/widm.30 [4] chazelle, b.: an optimal convex hull algorithm in any fixed dimension, discrete comput. geom., 1993, 10 377–409 doi: 10.1007/bf02573985 [5] de berg, m.; cheong, o.; van kreveld, m.; overmars, m.: computational geometry: algorithms and applications (springer-verlag, berlin, germany) 2008, doi: 10.1007/978-3-540-77974-2 hungarian journal of industry and chemistry https://doi.org/10.1002/widm.30 https://doi.org/10.1002/widm.30 https://doi.org/10.1007/bf02573985 https://doi.org/10.1007/978-3-540-77974-2 lidar-based collision-free space estimation approach 31 [6] fischler, m. a.; bolles, r. c.: random sample consensus: a paradigm for model fitting with applications to image analysis and automated cartography, commun. acm, 1981, 24(6) 381–395 doi: 10.1145/358669.358692 [7] andrew, a. m.: another efficient algorithm for convex hulls in two dimensions, inf. process. lett., 1979, 9(5) 216–219 doi: 10.1016/0020-0190(79)90072-3 [8] seidel, r.; adamy, u.; on the exaxt worst case query complexity of planar point location, j. algorithms, 2000, 37 189–217 doi: 10.1006/jagm.2000.1101 48(1) pp. 25–31 (2020) https://doi.org/10.1145/358669.358692 https://doi.org/10.1145/358669.358692 https://doi.org/10.1016/0020-0190(79)90072-3 https://doi.org/10.1006/jagm.2000.1101 hungarian journal of industry and chemistry vol. 48(1) pp. 33–41 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-06 identification of the material properties of an 18650 li-ion battery for improving the electrochemical model used in cell testing bence csomós∗1 and dénes fodor1 1research institute of automotive mechatronics and automation, university of pannonia, egyetem u. 10, veszprém, 8200, hungary the aim of this paper is to present an application of the generalized warburg element and constant phase element (cpe) for non-fickian diffusion modeling. these distributed elements are intended to provide a better fit of low-frequency impedance data than the standard finite-length warburg element in the case of most batteries. in addition, the current study demonstrates the ambiguity of the finite-length warburg element if impedance data is insufficient within the verylow-frequency impedance spectrum. in order to select the appropriate randles circuit for non-fickian diffusion modeling, several configurations have been investigated. based on the best fit of impedance data, the state-of-charge (soc) dependency of the randles circuit parameters has also been analyzed. this study concerns a samsung icr18650-26f 2600 mah battery cell which was subjected to electrochemical impedance spectroscopy (eis) measurements between 10 mhz and 100 khz as a function of soc. the results were plotted and compared in the form of nyquist plots. the randles circuit parameters such as the resistances rs and rct, double-layer cdl, leaky capacitance cpe and warburg coefficients were estimated using zview software. the present paper shows that cpe – and its qpe form – is a recommended choice to yield the best fit in terms of non-fickian diffusion impedance. in addition, using cpe is a better alternative to avoid problems with initial values and multiple local solutions, which may exist in the case of the warburg element. the resultant randles circuit parameters and their soc characteristics can be effectively used in further electrochemical modeling. keywords: li-ion battery, electrochemistry, material, battery model, parameter estimation 1. introduction the state of health (soh) of a battery plays an important role in electric applications since it has a great influence on the available capacity and power of a battery [1]. soh deteriorates with battery usage and the rate of aging is related to the operating history of the battery. therefore, it is recommended to track the state variables of a cell throughout its life cycle and adapt the soh prediction according to the current condition of the battery cell. a common and reliable electrochemical model used in finite element analysis (fea) is based on the work of newman et al. [2]. it consists of charge and mass balance equations in both solid (electrode) and liquid (electrolyte) materials, which describe the main operating characteristics of the cell. even though these formulae could describe the behavior of the cell in 3d, due to their high degree of nonlinearity and complexity, pseudo-2d (p2d) modeling is favorable in terms of fea [3]. it is also sufficiently representative to model wearout for automotive applications [4]. in fig. 1, a typical pseudo-2d structure of a li-ion cell can be seen. ∗correspondence: csomos.bence@gmail.com since battery manufacturing is still a developing sector, the electrochemical composition of a cell constantly changes. therefore, few battery-chemistry standards and complete databases can describe a given cell structure. insufficiently reliable and valid battery data inhibits battery modeling since a cell must always be inspected to determine its electrochemical parameters before modeling. the standard way to obtain these electrochemical data is usually through an equivalent circuit modeling process with which the electrochemical properties of the cell can be extracted from eis measurements. 2. diffusion modeling techniques it is possible to calculate battery-specific data using several techniques, which can basically be grouped into two types in terms of the measurement approach applied: • direct measurements, which typically require disassembly of the cell, special preparations or an experimental open-cell. these measurements can be, for example, different types of electron microscopy (em), computed tomography (ct), titration, postmortem analysis, etc. https://doi.org/10.33927/hjic-2020-06 mailto:csomos.bence@gmail.com 34 csomós and fodor rp electrodeseparator asep a particle + sei layer vsas εs dl ds εl εsep εb vl vtot figure 1: the relationship between the core material parameters and components of the cell. asep is addressed to the area of the separator. εsep, εb, εs, and εl denote the porosities of the separator, binder, solid matrix and void fraction, respectively.dl represents the salt diffusion coefficient in the electrolyte. ds stands for the diffusion coefficient in the solid electrode. vl, vs and vtot are the volumes of the liquid, solid material and whole electrode, respectively. rp and a denote the average radius of each electrode particle and the specific surface area of the electrode. • indirect measurements that do not require disassembly of the cell, e.g. current impulse excitation, electrochemical impedance spectroscopy (eis), galvanometry, potentiometry, chronoamperometry, etc. [5] eis is a well-established and suitable method in the analysis with regard to battery kinetics and has a solid background in the literature [6]. another advantage of eis is that it does not require special preparation of the cell that would be extortionate and time-consuming. electrochemical parameters are formulated from eis data in the form of resistive, capacitive, inductive or distributed elements such as the constant phase element (cpe) or warburg element. 2.1 standard equivalent circuits in order to obtain battery-specific data, a transmissionline model (tlm) was applied that is introduced and expounded on in [7]. it provides a generalized modeling solution for transport processes in porous electrodes by utilizing a finite number of serially connected resistorcapacitor (rc) pairs in parallel, which resolve the ion and electron transport appropriately. the network obtained in this way is considered to be ambiguous since various arrangements can be reduced to the same circuit resulting in identical resistance and capacitance of the circuit [8]. although the number of rc pairs used can increase the resolution of the transport process and thus improve its accuracy, the increase in the number of elements results in stability as well as local and global optima problems due to equivocality. since this is a major disadvantage of extended tlm networks, they are usually avoided. wr ct r s c dl figure 2: randles equivalent circuit consisting of serial resistance rs, charge-transfer resistance rct, double-layer capacity cdl and distributed impedance element w . a simplified form of tlm is the randles equivalent circuit model (fig. 2) which can be obtained if the theoretical rc line of infinite length is reduced to a single z-distributed element. in other words, the z-distributed element models the limiting case of tlm. its fundamental principles and mathematical background are comprehensively described in barsoukov’s book [9]. the standard randles circuit model couples together the individual characteristics of electrodes and electrolytes into one corresponding circuit element. the randles circuit model consists of relaxation components such as the serial resistance of the electrolyters, charge transfer resistancerct, a double-layer capacitor cdl and distributed impedance for modeling the low-frequency diffusive behavior of the cell. usually, the double-layer effect exhibits non-ideal capacitive behavior so a cpe – the equivalent to a “leaky” capacitor – should be used instead of a cdl. all of these detailed parameters of both electrodes are grouped together, thus they represent the combined behavior of the two electrodes. ion transport that occurs in the low-frequency bandwidth of the impedance spectrum can involve diffusion, migration and convection, however, only diffusion is of interest because distributed elements are responsible for diffusion modeling. diffusion modeling is the bottleneck of model development since it is related to a complex and interleaved electrochemical process that mainly characterizes the long-term operation of the battery. ion transport can be, by and large, divided into two parts, namely lithium diffusion in the solid active electrode material and electrolyte. the “tail” at the beginning of the lowfrequency bandwidth in the nyquist plot shows diffusion in the electrolyte while the transition from the tail through an arc to a straightened end of the impedance curve depicts the solid-phase diffusion inside the electrode matrix (fig. 3). in fact, the cathode is composed of a poor ionconducting material. a general rule of thumb is that its diffusion coefficient is 2− 4 orders of magnitude smaller than the diffusion coefficient of lithium ions in the electrolyte, that is, the salt diffusion coefficient of the electrolyte dl falls within the range of 10−10 − 10−11 m2/s while the diffusion coefficient of lithium ions ds in the solid matrix falls between 10−13 and 10−14 m2/s. in other words, the time constant for diffusion of li-ion transport is smaller in the electrolyte (∼ 10 − 100 s) than in the solid matrix (> 100 s). consequently, the two types of diffusion need to be separated and should be modeled based on their different characteristic impedances. hungarian journal of industry and chemistry identification of the material properties of an 18650 li-ion battery 35 -0.07 -0.06 -0.05 -0.04 -0.03 -0.02 -0.01 0.00 0.07 0.09 0.11 0.13 0.15 0.17 0.19 -i m z [ ω ] re z [ω] i. ii. figure 3: a typical nyquist plot of a li-ion cell; i. denotes a “tail” that mainly represents diffusion in the electrolyte; ii. shows a transition from liquid-phase to solid-phase diffusion. generally, diffusion is modeled by the classical warburg impedance in accordance with the following assumptions: diffusion is fickian (planar diffusion); the electrolyte is supporting, symmetric and binary; the cell remains in a quasi-equilibrium state during excitation; and no reaction occurs in the bulk of the electrolyte. under these premises, the standard warburg impedance has an exponent of 0.5 that implies its 45◦ phase angle. if diffusion occurs in an infinite reservoir where the concentration can decrease to zero, infinite-length warburg impedance can be assumed, otherwise diffusion is restricted and finite-length reflective or transmissive warburg impedance can be assumed depending on whether the equivalent circuit is terminated by an open circuit or a resistor, respectively. the former and latter cases can be mathematically expressed by extending the standard infinite-length warburg impedance with the hyperbolic functions tanh and coth, respectively. all three types of warburg elements exhibit the same 45◦ gradient at the beginning of the low-frequency bandwidth in the nyquist plot. in terms of impedance, using finite-length warburg elements is unsuitable if an insufficient number of data points in the low-frequency bandwidth of the impedance spectrum are available to fit the hyperbolic functions well. this occurs when the eis measurements typically run up until 10 mhz but some cells do not show a clear and distinct effect of diffusion in the solid phase. in this case, only the tail part of the impedance spectra can be reasonably modeled. due to a lack of low-frequency data points, the finite-length warburg elements cannot be effectively applied. on the other hand, the tail part of the diffusion impedance can be modeled by cpe according to [11, 12] which is a similar but more robust alternative to the warburg elements. all the transfer functions of the standard types of distributed elements are summarized in table 1. the transfer function of cpe can be expressed in two different forms according to the position of its time constant for diffusion table 1: transfer functions of standard distributed elements used in fickian diffusion modeling [10]. σ denotes the warburg coefficient, ω represents the excitation frequency, τd stands for the diffusion time constant, q is the qpe time constant, j denotes the imaginary unit and rw represents the warburg resistance. name impedance infinite-length warburg zilw(jω)= rw√ jωτd =σ 1√ ω (1−j) finite-length reflective warburg zflrw(ω)=rw coth ( √ jωτd)√ jωτd finite-length transmissive warburg zfltw(ω)=rw tanh ( √ jωτd)√ jωτd cpe zcpe(ω)= 1√ jωτd qpe zqpe(ω)= 1 q √ jω τd . if τd is emphasized from its square root, it is referred to as qpe, which sometimes provides a more stable regression than cpe. up to this point, only fickian diffusion has been considered that can be clearly identified by its square-rootlike frequency dependency in terms of the transfer function of the distributed elements. however, the impedance fit becomes more interesting when the cell impedance exhibits non-fickian behavior, that is, the phase angle is not 45◦ due to diffusion non-idealities. these phenomena were investigated and are mostly related to multi-phase and multi-scale diffusion in porous electrodes [13, 14], diffusion coupled with migration [15, 16] and/or diffusion in non-conventional space [17–19]. non-fickian diffusion can be treated by fractional order circuits which consist of various types of typical configurations. in the literature [20], warburg impedance is referred to as “generalized” if it reflects the fractional intent. in this case, the warburg exponent is generalized and denoted by γ, the dispersion parameter. 2.2 equivalent circuit development for modeling non-fickian diffusion in order to obtain the most accurate fit of the impedance curves, several configurations of the randles circuit were developed. these setups are presented in fig. 4. the key differences between them can be explored in terms of both the position and type of the distributed elements in the circuit. in some papers from the literature, the distributed element is in series withrct [21], while in others, it is placed in series with the parallelrct-cdl orrct-cpe branch. the distributed element can be either the warburg element or cpe/qpe. birkl et al. [22] shows that it is possible to model diffusion with an rc pair instead of a distributed element in the randles circuit model. all of these configurations have been exhaustively expounded 48(1) pp. 33–41 (2020) 36 csomós and fodor r s qpe wr s cpe qpe qpe wr ct c dl r s i. ii. iii. r ct c dl r s wr ct r s cpe iv. v. vi. r ct r s figure 4: different configurations of randles circuits to study regression performance and fitness. w stands for warburg element. the model of circuits i-iv, relaxation and diffusion are presented together while v-vi only focus on the tail part. on in [23]. based on these results, numerous randles circuits have been evaluated to study the regression performance and fitness. in fig. 4, the arrangements of circuits i-iv model relaxation and diffusion simultaneously while v and vi only account for the tail part. the main reason for separation is that the stability and robustness of the impedance regression could be increased using this technique. the standard warburg element and cpe/qpe had to be adjusted to match with the non-fickian diffusion. at first, since only the tail part of the diffusion impedance was modeled, the hyperbolic part of the finite-length warburg elements was neglected. hence, the warburg impedance was simplified to the infinite-length form. therefore, the warburg impedance zw had to be transformed into a generalized form by replacing the square root in the denominator with γ. as a result, the generalized warburg impedance could be written in the following form: zw(ω) = rw (jωτd) γ (1) where rw denotes the warburg resistance, ω stands for the excitation frequency, τd represents the diffusion time constant, j is the imaginary unit and 0 ≤ γ ≤ 1. now, the jγ term should be practically separated into real and imaginary components to reveal the contribution of γ to each part. using euler’s formula, zw was unbundled and grouped into real and imaginary parts: zw (ω) = rw τγdω γ cos ( π 2 γ ) − rw τγdω γ j sin ( π 2 γ ) (2) τd used in eq. 2 was then expressed as τd = l 1/γ eff deff = ε β/γ l,sepl 1/γ 0 εβl,sepdl,0 (3) where leff denotes the effective diffusion length, deff represents the effective diffusion coefficient, εl,sep stands for the liquid fraction in the separator, and β is the bruggeman coefficient. since τd is emphasized from the denominator of eq. 1, the warburg coefficient σ could be expressed as a fraction of rw and τd according to σ = rw τγd . (4) on the other hand, the transfer functions of cpe and qpe had to be transformed into zcpe (ω) = 1 (jωτd) γ (5) zqpe (ω) = 1 τγd(jω)γ (6) the updated transfer functions of the distributed elements enabled the non-fickian diffusion to be properly fitted. 3. experimental setup this study is devoted to a commercial samsung icr 18650-26f cell with a nominal capacity of 2600 mah. it consists of a double-sided nickel-manganese-cobalt (nmc) cathode and graphite anode according to the manufacturer’s datasheet. the samsung icr 18650-26f cell was evaluated by eis within the 10 mhz – 100 khz bandwidth at different states-of-charge (soc). the test was run at ambient temperature, namely 25 ◦c, which was considered to be constant throughout. a solartron si1287 (electrochemical interface) and a schlumberger si 1255 (hf frequency response analyzer) were used for data acquisition. the nyquist plot of the spectrum and the parametric fitting were produced by zplot and zview software, respectively. an auxiliary measurement had to be performed along with eis to determine the cell’s open circuit potential (ocp) characteristic at a 0.1 c-rated load current. the load current was generated by a tenma 72-13210 programmable dc load in constant current (cc) mode. the data was recorded in ni pxi hardware that ran labview-based data acquisition software. 4. analysis of the measurement results the purpose of the eis analysis of the cell was to evaluate the fitness of the different randles circuit models according to non-fickian cell impedance data. on the other hand, the cell underwent another eis measurement to detect how the parameters of the randles circuit model changed during discharge. the eis measurements presented in fig. 5 and 6 were made between 10 mhz and hungarian journal of industry and chemistry identification of the material properties of an 18650 li-ion battery 37 -0.022 -0.017 -0.012 -0.007 0.08 0.09 0.10 0.11 0.12 0.13 0.14 im z [ ω ] re z [ω] measured cdl-w v1 (i.) cdl-w v2 (i.) cpe-w (ii.) cdl-qpe (iii.) cpe-qpe (iv.) std warburg figure 5: nyquist plot of the measured impedance and different fit functions (seen in fig. 4 i-iv). v1 and v2 indicate that warburg-based models were run on the basis of two different sets of initial parameters. the fit was performed between 13 hz and 10 mhz at ambient temperature with a fully charged cell. the “std warburg” was based on model i in fig. 4 but with a warburg exponent of 0.5. -0.018 -0.016 -0.014 -0.012 -0.010 -0.008 -0.006 0.118 0.120 0.122 0.124 0.126 0.128 0.130 0.132 0.134 im z [ ω ] re z [ω] measured r-w r-qpe figure 6: nyquist plot of the measured impedance and different fit functions (seen in models v-vi of fig. 4. the fit was performed between 80 mhz and 10 mhz (only the tail part) at ambient temperature with a fully charged cell. the left part of the solid line is associated with the end of the relaxation semicircle and helps to locate the position of the tail. 13 hz where relaxation and diffusion occur. in the case of r-w and r-qpe pairs, only the tail part was modeled. in fig. 5, only a slight difference between the fits of the model is observed and the cpe-qpe pair shows the best match. despite the insignificant difference between the non-fickian models, a substantial improvement in accuracy can be observed especially with regard to fitting the tail when the standard warburg element was replaced by any of the generalized warburgor cpe/qpe-based models. the changes in the randles circuit parameters during discharge of the cell was also investigated further where only the best matching cpe-qpe pair was used for fitting. the resultant impedance plot is presented in fig. 7. the eis measurements were performed at 20 % soc level increments. every step of the discharge was followed by a 12-hour-long period of relaxation before the eis measurement was made in order to provide sufficient time for the cell to reach its stationary state. the impedance curves show that the degree of relaxation was high when the rate of the electrode reaction decreased or if the transport of li ions became limited. this occurred, for example, as the rate of li diffusion decreased away from the interface. the evolution of changes in the distinctive impedance curves could be tracked by changes in the parameters of the randles circuits. fig. 7 shows that rs and rct significantly increased as soc decreased due to the decreasing amount of li-ion particles engaged in the charge transfer process. furthermore, the electrolyte resistance rs increased due to the decreasing ionic conductivity of the solution. all of these results agree with a well-known phenomenon, namely that the overall resistance of the cell increases during discharge. the shape and position of the plateau at the beginning of the semicircle was apparently due to a solid electrolyte interphase (sei) layer which formed on the anode particles that was unaffected during discharge. the presence of an sei layer ascertains that the calendar and cycle lives of the cell both reduced. since the gradient of the tails show significant similarities between 100 % and 20 % soc, the diffusion time constant and diffusion coefficient of the electrolyte should change slightly during discharge. at 5 % soc, the 48(1) pp. 33–41 (2020) 38 csomós and fodor -0.045 -0.040 -0.035 -0.030 -0.025 -0.020 -0.015 -0.010 -0.005 0.000 0.0600 0.0800 0.1000 0.1200 0.1400 0.1600 0.1800 0.2000 0.2200 im z [ ω ] re z [ω] 100% 80% 60% 40% 20% 5% fit 100% fit 80% fit 60% fit 40% fit 20% fit 5% figure 7: nyquist plots of the samsung icr 18650-26f 2600 mah li-ion cell at different levels of soc. the temperature was assumed to be constant at 25 ◦c. the regression bandwidth was limited to between 13 hz and 10 mhz. the small plateau at approximately 250 hz is a consequence of a solid electrolyte interphase (sei) layer that formed on the anode particles. this shows that the calendar and cycle lives of the cell were reduced. the fit was made by the model of the cpe-qpe pair. utilizable li-ions in the electrode became exhausted leading to a significant decrease in both the rate of diffusion and reaction. on the other hand, the reaction rates did not vary extensively in the normal operating region since the “valley” between the semicircle and tail possesses a similar imaginary component of the impedance. in order to carry out cell characterization in the time domain, a quasi-equilibrium discharge was run using a 0.1 c-rated load current at a constant temperature of 25 ◦c. the ocv against soc curve is presented in fig. 8 that exhibits typical discharge characteristics with a small plateau around 30 % soc and rapidly decreases below 10 % soc. 4.1 determining randles circuit parameters evaluation of eis data in fig. 5 and the impedance regression were carried out by zview software that applies 2.75 2.95 3.15 3.35 3.55 3.75 3.95 4.15 0 20 40 60 80 100 o c v [ v ] soc [%] figure 8: the open circuit voltage (ocv) against stateof-charge (soc) characteristic of the cell. the non-linear least squares method to fit and calculate the randles circuit parameters. the results summarized in table 2 show that slight changes in rs, rct and cdl were observed with this setup. this was due to fitting on an almost ideal semicircle that exhibits a simple rc characteristic in the impedance spectrum. with regard to the estimation of diffusion time constants, diffusion in a real electrochemical battery cell is usually limited due to the relatively thin electrodes. consequently, from a practical point of view, zview only has finite-length warburg elements at its disposal. since finite-length warburg elements should require data from the very low bandwidth that is unavailable in the present case, it is favorable to check the applicability of this type of element in the current case. for this purpose, the warburg parameters were estimated on the basis of two different sets of initial values as is denoted by v1 and v2 in fig. 5. both cases yielded a similar fit but extremely different warburg parameters. therefore, the estimation of warburg parameters ran into multiple local solutions that erroneously characterize the same system with different diffusion time constants. this problem could be efficiently handled by using either the cpe+qpe pair or just qpe instead. the results are presented in table 3. given the γw values, the warburg exponent is clearly far from 0.5, hence the preliminary assumption of exhibiting non-fickian diffusion was substantiated. the maximum phase error between the standard warburg-elementand cpe+qpe pair-based randles circuit models was 2.3 % at 10 mhz. since randles circuit parameters are very sensitive due to the origin of their exponential functions, even a small improvement in hungarian journal of industry and chemistry identification of the material properties of an 18650 li-ion battery 39 table 2: the estimated randles parameters where diffusion was only modeled by a warburg element and a qpe in two different configurations. the qpe+cpe modeling technique was an effective way to avoid the uncertainties of finite-length warburg elements due to a lack of data points in the very low bandwidth. the cell was fully charged and kept at 25 ◦c. randles parameter qpe+cpe w qpe rs [ω] 0.154 0.1968 0.1967 rct [ω] 0.047 cdl [f] tcpe [s] 2.038 γcpe [-] 0.893 γqpe [-] 0.6868 0.595 rw [ωm2] 0.241 τw [s] 893 235.7 γw [-] 0.595 τd [s0.5/ωm2] 339.5 893 235.7 σ [ωm2/s0.5] 0.0015 0.00424 0.0021 fitting can significantly increase the accuracy in further electrochemical calculations based on these data. the randles circuit parameters were measured when the cell was fully charged but changed as the soc level of the cell was altered as was seen in fig. 7. the estimated parameters at different soc levels are summarized in table 4 and their trends presented in fig. 9. the changes in rs and rct exhibited an exponential-like decreasing tendency against soc while rct slightly increased at approximately 100 % soc. the increase in rs was due to the effect of a reduction in the ionic conductivity, while an increase in rct was due to the decreasing rate of liion transfer through the electrode-electrolyte interface. in fig. 10, the characteristics of changes in the cpe capacity and diffusion time constant can be seen. cpe slightly increased with discharge and its overall variance was about 0.4 f. this behavior along with the increase in rct can be attributed to the relaxation effect. furthermore, less charge was available on the anode surface as the cell became fully discharged. the remarkable increase in diffu0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0% 20% 40% 60% 80% 100% r es is ta n c e [ω ] soc level rs rct figure 9: the trend of rs and rct changes with soc level. the cell shows a well-known increasing overall resistance during discharge. table 3: the estimated randles parameters based on the configurations seen in fig. 4 where diffusion and doublelayer effect have been modeled by warburg-element, qpe and cpe in different coupled configurations. in the table heading, w and c stand for warburg and double-layer capacitor, respectively. the cell has been at fully charged state and kept at 25 ◦c. randles c+w c+w c+qpe cpe+w parameter i ii rs [ω] 0.156 0.156 0.156 0.153 rct [ω] 0.041 0.041 0.041 0.047 cdl [f] 1.731 1.731 1.73 tcpe [s] 2.038 γ [-] 0.579 0.893 rw [ωm2] 0.0855 0.168 0.263 τw [s] 179 569.1 693.2 γw [-] 0.578 0.5792 0.687 τd [s0.5/ωm2] 179 569.1 233.9 693.2 σ [ωm2/s0.5] 0.0043 0.0043 0.0023 0.0029 sion time constants at approximately 100 % soc implies that it was intended that diffusion coefficients should decrease at the end of the discharge. this phenomenon plays a significant role in increasing the overall cell resistance especially when one of the electrodes is exhausted in li. 5. conclusions the current work demonstrated an improved method of diffusion modeling. several configurations of randles circuits were studied in order to obtain the best fit of the impedance characteristics of a battery. the inappropriate fit of standard warburg elements with regard to nonfickian diffusion was corrected by applying generalized warburg elements and cpes. the proposed generalized model compensates well for the phase error between the measured and modeled impedances. 0 50 100 150 200 250 300 350 400 1.9 2.0 2.1 2.2 2.3 2.4 2.5 2.6 0% 20% 40% 60% 80% 100% d if fu si o n t im ec o n st an t [s ] c p e c ap ac it y [ f ] soc level c_cpe tau_d figure 10: charactersitics of changes in cpe capacity constants and diffusion time-constant. diffusion timeconstant remarkably increases during discharge that implies diffusion coefficients to decrease. the cpe does not change significantly. 48(1) pp. 33–41 (2020) 40 csomós and fodor table 4: the estimated randles circuit parameters at given soc levels based on the cpe-qpe randles circuit model. soc levels 100 % 80 % 60 % 40 % 20% 5 % rs 0.0764 0.0763 0.0823 0.0909 0.105 0.1305 rct 0.047 0.0406 0.0413 0.0487 0.056 0.0734 ccpe 2.07 2.255 2.394 2.365 2.383 2.503 τd 358 310 306 336 353 172 the finite-length warburg element is a classical and generally applied tool in diffusion modeling, but it should be used carefully in some cases. the proposed work also shows that the finite-length warburg element yields multiple local solutions depending on its initial values if measured impedance data is insufficient within the very low bandwidth of impedance. this leads to ambiguous results in terms of diffusion-related parameters which should be avoided, however, this problem can definitely be solved by applying cpe or qpe instead in diffusion models. the randles circuit parameters were estimated and can be used in further calculations to determine the electrochemical parameters of batteries [24]. symbols binary diffusion coefficient of electrolyte dl,0 m2/s warburg coefficient σ ω/ √ s diffusion time constant τd s ac excitation frequency ω hz warburg exponent γ – electrolyte resistance rs ω charge transfer resistance rct ω warburg resistance rw ω double-layer capacitance cdl f acknowledgements the research was supported by efop-3.6.2-16-201700002 “research of autonomous vehicle systems related to zalazone autonome proving ground”. we would like to thank zoltán lukács and tamás kristóf to support conducting eis measurements in the laboratory of faculty of physical chemistry and sharing their knowledge in electrochemical modeling. references [1] redondo-iglesias, e.; venet, p.; pelissier, s.: efficiency degradation model of lithium-ion batteries for electric vehicles, ieee transactions on industry applications, 2019, 55(2), 1932–1940 doi: 10.1109/tia.2018.2877166 [2] doyle, m.; fuller, t.f.; newman, j.: 1-modeling of galvanostatic charge and discharge, j. electrochem. soc., 1993, 140(6), 1526–1533 doi: 10.1149/1.2221597 [3] mei, w.; chen, h.; sun, j.; wang, q.: the effect of electrode design parameters on battery performance and optimization of electrode thickness based 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devices, technologies, mathematical models and methods are available in the automotive world, the complexity of the localization problem still cannot be underestimated. the expectation is to determine in real time with a high degree of accuracy the location of a vehicle in order to make correct autonomous decisions and avoid dangerous and potentially damaging situations. various research directions have been undertaken since the birth of autonomous driving from the well-known satellite navigation-based systems that rely on offline maps to the more sophisticated approaches that use odometry and existing sensor data using sensor fusion. the aim of the current work is to review what has been achieved so far in this field and the challenges ahead, e.g. the need for a change in paradigm as today’s global positioning systems are not intended for machines but humans and are based on the abstraction of human thinking and human decision-making processes. keywords: autonomous driving, localization, information fusion, filtering 1. introduction vehicle localization is one of the four functions of autonomous vehicle navigation, namely mapping, localization, motion and interaction, which are the answers to the four basic questions concerning navigation: where am i? where can i move to? how can i do it? how do i interact? if a vehicle is to navigate as expected, these functions need to operate correctly [1]. historically, the purpose of in-car localization was driver assistance in the form of helping the driver to navigate. such systems that are currently in use provide information, with some degree of accuracy, to the driver and then the driver makes decisions based on the information, which can either be accepted and acted upon or rejected in the form of proceeding in another direction. in the case of autonomous driving, it is quite clear that simply rejecting position information since the main control algorithm is not an option as this is the only item of data to be used, therefore, it must be used and a decision made based on it. this raises the question of certainty. the requirement to operate safely anywhere and at anytime makes the performance measures far stricter than ever before. the performance measures are [2]: accuracy the degree of conformity of position information provided by the localization system relative to actual values. *correspondence: medve.hunor@mk.uni-pannon.hu integrity a measure of trust that can be implemented in the information from the localization, which is the likelihood of undetected failures given the specified accuracy of the system. continuity of service the probability of the system continuously providing information without nonscheduled interruptions during the intended working period. availability the percentage of time during which the service is available for use taking into account all the outages irrespective of their origins. the service is available if the requirements concerning accuracy, integrity and continuity are satisfied. over the last 10-15 years, the number of sensors and related advanced driver-assistance systems in passenger vehicles has increased. the primary task of each of these sensors and services is to observe a segment of the surroundings and its status, then assist the driver in that regard. since the data from a single sensor does not contain all the information about the vehicle’s surroundings, further information concerning its absolute location cannot be extracted based on a single sensor. in fact, the sensors provide complementary information and through information fusion the vehicle’s absolute location and status can be obtained. this is shown in fig. 1. the main groups of information sources are the following: https://doi.org/10.33927/hjic-2020-07 mailto:medve.hunor@mk.uni-pannon.hu 44 medve és fodor figure 1: the concept of information fusion • global navigation satellite systems (gnss) • traditional vehicle sensors: – odometer – wheel speed sensor – steering angle sensor • inertial measurement unit (imu): – accelerometer – gyroscope • optical, soundand radio-based sensors: – radar – ultrasonic sensors – vision sensors – lidar (light detection and ranging) • vehicle models with various levels of complexity • databases; offline or cloud-based: – maps – traffic situation • dedicated short-range communication: – vehicle-to-vehicle (v2v) – vehicle-to-infrastructure (v2i). it is important to note that none of these information sources are ideal and error-free. the errors will propagate through the sensor fusion algorithm, moreover, affect the end result and the previously described figures of merit. the following sections address each device family then the fusion methods are analysed. 2. information sources 2.1 global navigation satellite systems the global navigation satellite system (gnss) is a radio positioning-based technology using satellite infrastructure that aims to achieve global coverage. historically, satellite-based sytems have been considered as the core element of localization. currently, a number of systems are in operation, the major ones are gps (usa), beidou (china), glonass (russia) and galileo (eu). every satellite broadcasts a specific signal and its position. the spectral range of the signals is 1.2− 1.6 ghz, utilising frequency bands of between 2 and 40 mhz. any user equipped with a gnss receiver receives the signal and measures the signal propagation delay, then estimates the range of distance from it. by using signals from at least four satellites, the receivers can reduce the estimate to intercept the ranges from each satellite, which basically provides a potential location within the range in terms of geospatial coordinates. it is important to note that the position information is useful only if used together with maps which put the information in context. even though the accuracy of receivers is increased by various augmentation systems, issues resulting from poor satellite constellations, signal blockage and multipath propagation in urban environments cannot be excluded. for this reason, safety-critical applications cannot solely rely on gnss technology. although satellite-based systems are far from perfect, they are and will continue to be the single most important information source of any localization algorithm. 2.2 vehicle model models representing the dynamic model of a vehicle’s range from the simple spring-mass model to a complex multibody multi-level model. a well-known and used model is the single track model [3] with a number simplifications, however, it provides a reasonable solution for modeling lateral dynamics, therefore, it forms the core of the electronic stability program (esp) of many vehicle manufacturers. the inputs of the single track model are lateral acceleration, longitudinal speed and yaw rate, which are provided by the relevant sensors as discussed in section 2.3. another element in a complex model is the tire model which is assumed to be the only part in contact with the road. these models, e.g. pacejka’s magic formula [4], are often semi-empirical. it is important to note that a more detailed model requires more parameters which, in the case of inaccurate identification, may impact the overall accuracy of the model’s output. 2.3 traditional vehicle sensors and inertial measurement unit (imu) a wide range of traditional vehicle sensors have already been installed in most vehicles, moreover, analogue measurements are already being processed digitally. most of them provide basic information to human drivers directly, e.g. the odometer, whilst others are parts of safety features. for autonomous driving, exactly the same information is also required. wheel speed sensors mounted in the wheel drum provide vital inputs to the anti-lock braking system by sensing the movement of the circumference of each tire in a passive or active setting. steering angle sensors are mounted on the steering shaft and measure the steering wheel angle, their outputs are interpreted as the intended direction of the vehicle, which is a key input to the electronic stability program (esp). hungarian journal of industry and chemistry challenges of localization algorithms for autonomous driving 45 accelerometers measure the acceleration of the vehicle on the specified axis, multi-axis accelerometers are also in use. they are primarily used for inertial navigation in combination with yaw-rate sensors. yaw-rate sensors, often referred to as gyroscopes, measure the rotation of the vehicle along the vertical axis. such a sensor provides an input to the single track vehicle model in conjunction with the esp. accelerometers and yaw-rate sensors integrated in one cluster comprise the inertial measurement unit (imu). 2.4 optical as well as soundand radiobased sensors in automotive radar systems, a distinction is made between short range radar (srr) and long range radar (lrr). the detection range of short range radar is from 0.2 to 50 meters with a detection angle of ±35◦, whilst that of the long range radar is from 2 to 150 meters with a detection angle of ±6◦. srr is predominantly used in anti-collision and parking aid systems. radars are able to detect multiple objects as well as measure distance, relative speed and the angle to an object simultaneously. lrr is typically applied in adaptive cruise control and collision avoidance. radar technology is affected by the weather and functionality cannot be guaranteed in extreme conditions. overall information from radars can complement other location-related information sources. vision sensors are primarily used in vehicles to detect and possibly recognise its surroundings, e.g. other vehicles, obstacles, pedestrians and landmarks, which are potentially useful pieces of information for a localization algorithm. charge-coupled (ccd) and complementary metal oxide semiconductor (cmos) devices are the main sensor technologies applied in digital cameras to generate an image of the surroundings, in fact both are semiconductor devices. in cmos devices, every pixel has its own charge-tovoltage conversion and digitalization, so their outputs are digital signals. pixels that perform their own charge-tovoltage conversion decrease their uniformity and image quality as well as remove a useful area from light capture. in ccd sensors, a pixel’s charge signal is sent through a limited number of outputs to be converted into voltage and then transmitted out of the chip as an analogue signal to be processed and digitalized. this requires more time and energy when compared to cmos sensors, however, results in a higher quality but less noisy image. as the cmos manufacturing process is cheaper, recent developments have focused on overcoming the drawbacks of cmos sensors. ultrasonic sensors transmit higher frequency sound waves and evaluate the echo received by the sensors. the sensors also measure the elapsed time between sending and receiving back the signal, then calculate the distance from the object. the types currently used in the automotive industry are able to measure within the range of 0.2 to 1.5 meters, with a horizontal angle of ±60◦ and a vertical angle of ±30◦, and are primarily used in parking aids. nevertheless, the use of such sensors might provide useful inputs for a localization algorithm under given circumstances. lidar (light detection and ranging) measures the distance of an object by emitting laser light and detecting the returning light. the differences in return times and wavelengths then provide the basis for a 3d representation of the surroundings. 2.5 databases and maps maps stored in digital format differ from the classical map representations intended to be read by humans. digital road maps are comprised of nodes and arcs connecting the nodes. arcs are represented in a discrete form and every node and shape point on the arc has geospatial coordinates linked to them. they are often represented as planar models in applications currently on the market. 2.6 dedicated short-range communications for any vehicle to communicate with either the infrastructure (vehicle-to-infrastructure: v2i) or with another vehicle (vehicle-to-vehicle: v2v), it is assumed that a suitable wireless protocol is in place, which allows bidirectional information flow in real time when a vehicle is travelling at high speed and is able to simultaneously handle multiple vehicles. based on these assumptions, only applications related to localization are considered here. the main purpose of v2i communication is to support applications that target safety and mobility. safety applications mainly consist of alerts and warnings, while mobility applications collect data from vehicles in order to capture the actual state of the traffic and provide such information to vehicles. v2v applications determine the state of other nearby vehicles through the transmission of one or several messages. overall, the location-related content of these messages alone might be insufficient for a vehicle to determine its own location, but can still provide useful complementary information to fusion algorithms. 3. fusion algorithms the purpose of information fusion is to obtain more information from the sources than what is accessible from each individual source. this is achieved by combining sources which are complementary, moreover, the use of partially redundant sources reduces the ambiguity of the measured data which, overall, improves the performance of the system. fusion algorithms can be realized in either centralized or decentralized structures, as is shown in fig. 2. 48(1) pp. 43–49 (2020) 46 medve és fodor figure 2: filtering structures: a) centralized, b) decentralized as the name suggests, in centralized structures, one filter performs the filtering of all signals which yields the benefit of minimal information loss as everything is directly available to the filter, while the amount of data to be processed in real time might imply an impractical degree of computational complexity. this is addressed by decentralized filters as every signal is filtered separately before being processed by a master filter. the computational load in general would be significantly less for one filtering unit, however, at the expense of partial information loss and reduced estimation accuracy. in this chapter, selected filtering methods are presented: a conventional and widely used localization method, as well as a linear and a non-linear filtering method. advanced filtering methods require prior knowledge of the system model and dynamics, the type of noise and their probability density functions as these are core elements to design a high-performance filter. the filtering algorithms presented in the following sections are used by the scientific community in various forms but often altered when compared to their originally published format (kalman filter in [5], particle filter in [6]), in order to better suit the actual problem. in this paper, the thought process of [7] is followed. 3.1 simple algorithms: dead reckoning, inertial navigation and map matching the conventional localization algorithm consists of two steps; the first is the gnss which defines the coordinates, the second is to match the given coordinates to a map. this is shown in fig. 3. the process of calculating the position based on its previously known position, elapsed time and speed is referred to as dead reckoning [8]. inertial navigation is a very similar concept where the position is calculated based on data from accelerometers and gyroscopes, also referred to as dead reckoning based on inertial sensors. in the following sections, no specific distinction is made between dead reckoning and inertial navigation. figure 3: conventional localization algorithm traditional vehicle sensors and the inertial measurement unit (imu) provide information about either the first or second order derivatives of the position of the vehicle together with the odometer which measures the distance travelled. all the data provided is relative to the starting position, therefore, none of the sensors provide information about its absolute position. in addition, all data will be incorporated into the coordinate system of the vehicle since all the sensors are mounted on the vehicle, therefore, coordinate transformations to the main coordinate system, which are used for the localization, are required. the measured values are integrated by taking into consideration an initial position and, over time, the errors will be accumulated as part of the integration. it is important to note that the extent to which the error can increase is infinite. despite such a disadvantage, the popularity of the method lies in the fact that it does not rely on external sources of information and the update rate is determined by the system itself, which overall defines the complementary nature of inertial navigation to gnss. map matching is the process of identifying on the map the coordinates given by the gnss on the map. on digital road maps, the road network is represented in a discrete form as nodes and arcs which connect nodes, each of which has geospatial coordinate information linked to it. the purpose of the map matching algorithm is to match the gnss coordinates to the road map. it is highly likely that the map will not contain the exact coordinates defined by the gnss and inertial navigation, therefore, it has to be matched to one of the few possible ones. map matching algorithms assign probabilities to each possible location based on a set of information including previous locations, speed and heading of the vehicle, subsequently the evaluation is concluded based on these probabilities. such algorithms can provide useful inputs to assist a human driver, however, it is easy to realize that rarely rarely can they provide sufficiently reliable inputs for autonomous driving. this creates the need for more reliable algorithms, which are normally more complex and require more computational power. 3.2 linear filtering: the kalman filter the kalman filter is a useful engineering tool in many industries and control applications ranging from robotics, automotive, plant control, aircraft tracking and navigation. in general, they are relatively easy to design and code with an optimal degree of estimation accuracy for linear systems with gaussian noise. let us describe a linear system with the following dishungarian journal of industry and chemistry challenges of localization algorithms for autonomous driving 47 crete state-space model equations: xk = ak−1xk−1 +bk−1uk−1 + wk−1 yk = ckxk + vk (1) where k in subscript refers to states and measurements at each discrete time instant and k − 1 in subscript to those at the previous time instant, xk denotes the vector of the state variable, uk stands for the input or control vector, yk represents the output vector, ak refers to the system matrix, bk and ck denote the input and output matrices, wk and vk stand for the process and measurement noise, respectively, which are white with gaussian distribution and zero mean, and rk and qk are known covariance matrices. wk ∼ (0, rk) vk ∼ (0, qk) e [ wkw t j ] = qkδk−j e [ vkv t j ] = rkδk−j e [ wvtj ] = 0 (2) where δk−j is the kronecker delta function (δk−j = 1, if k = j and δk−j = 0, if k 6= j). the aim is to estimate the system state xk by knowing the system dynamics and the noisy measurements yk. the available information for the state estimation always depends on the actual problem at hand. if all measurements are up to date and accessible, including kth, then a posteriori estimation can be computed, which is denoted by x̂+k . the meaning of the “+” sign in superscript means the estimation is an a posteriori estimation. the best way to estimate the a posteriori estimation is by computing the expected value of xk conditioned to all measurements up to now, including k as well. x̂+k = e [xk|y1, y2, . . . , yk] (3) if all measurements, apart from k, are accessible, then the a priori estimate can be computed, denoted by x̂−k , where the “−” sign in superscript denotes the a priori estimate. the best way to estimate the a priori state estimate is if the expected value of xk conditioned to all measurements up to now, excluding k, is computed: x̂−k = e [xk|y1, y2, . . . , yk−1] (4) it is important to note that x̂−k and x̂+k are estimates of the same quantity, before and after the actual measurement is obtained, respectively. naturally, it is expected that x̂+k is a more accurate estimate as more information is available. at the beginning of the estimation process, the first measurement is obtained at k = 1, therefore, the estimate of x̂+0 (k = 0) is given by computing the expected value of x0: x̂+0 = e [x0] (5) estimation of the error covariance is denoted by pk, therefore, p− k represents the estimation of the error covariance of the a priori estimate x̂−k and p+ k stands for the estimation of the error covariance of the a posteriori estimation x̂+k : p− k = e [( xk − x̂−k ) ( xk − x̂−k )t ] p+ k = e [( xk − x̂+k ) ( xk − x̂+k )t ] (6) the estimation process starts by computing x̂+0 , which is the best available estimate at this time instant for the value of x̂+0 . if x̂+0 is known, x̂−1 can be computed as follows: x̂−1 = a0x̂ + 0 +b0u0 (7) then the general form to compute x̂−k can be established: x̂−k = ak−1x̂ + k−1 +bk−1uk−1 (8) this is referred to as time update from time instants (k − 1) + to k−. no new measurement information is available between the two, therefore, the state estimation propagates from one time instant to the other, and all state estimations are based on knowledge of the system dynamics. the time update is often referred to as the prediction step. the next stage is to compute p , the estimation of the error covariance. the process starts by computing p+ 0 which is the error covariance of x̂+0 . if the initial state is perfectly known, then p+ 0 = 0; if no information is available, then p+ 0 = ∞i . in general, the meaning of p+ 0 is the uncertainty regarding the initial estimation of x0: p+ 0 = e [( x0 − x̂+0 ) ( x0 − x̂+0 )t ] (9) if p+ 0 is known, then p− 1 can be computed as follows: p− 1 = a0p + 0 a t 0 +q0 (10) based on the above, the generic form of the time update of p− k can be stated: p− k = ak−1p + k−1a t k−1 +qk−1 (11) so far, the time update step has been presented, which is based on the system dynamics. the next step is the measurement update, where new information is obtained from the measurements. using the logic from the method of recursive least squares, the availability of the measurement yk changes the value of the constant x in the following way: kk = pk−1c t k ( ckpk−1c t k +rk )−1 = pkc t k r −1 k−1 x̂k = x̂k−1 +kk(yk − ckx̂k−1) pk = (i−kkck)pk−1(i−kkck) t +kkrkk t k = = ( p−1 k−1+c t k r −1 k ck )−1 = = (i−kkck)pk−1 (12) 48(1) pp. 43–49 (2020) 48 medve és fodor where x̂k−1 denotes the estimation and pk−1 stands for the the estimation of the error covariance before processing measurement yk, therefore, x̂k and pk refer to the same informaton but after yk has been processed. if the logic of x̂k−1 → x̂−k and x̂k → x̂+k (a priori and a posteriori, respectively) is applied and the aforementioned equation reformulated, the a posteriori estimation is produced: kk = p− k c t k ( ckp − k c t k +rk )−1 = p+ k c t k r −1 k x̂+k = x̂−k +kk(yk−ckx̂ − k ) p+ k = (i−kkck)p − k (i−kkck) t +kkrkk t k = = [( p− k )−1 +ct k r −1 k ck ]−1 = = (i−kkck)p − k (13) these are the equations for the kalman filter measurement update or a posteriori estimation. the matrix kk is often referred to as the kalman gain. by summarising the kalman filtering algorithm, after initiation, the a priori estimate for every time instant k is given by: x̂−k = ak−1x̂ + k−1 +bk−1uk−1 p− k = ak−1p + k−1a t k−1 +qk−1 (14) and the a posteriori estimation is given by: kk = pkc t k r −1 k−1 x̂+k = x̂−k +kk(yk − ckx̂ − k ) p+ k = (i −kkck)p − k (15) the aforementioned kalman filtering algorithm is the optimal state estimator for linear systems with gaussian unimodal noise processes, however, most real-world systems are nonlinear and, in many cases, with multimodal non-gaussian noise, include a probability density function. a number of variations of kalman filters developed by the scientific community are trying to address the problem of nonlinearity. most of them rely on the basic concept of kalman filters using nonlinear adaptations, e.g. the extended kalman filter which, at its core, is still a linear filter. in general, versions of the nonlinear kalman filter are considered to estimate accuracy well but are often poor compared with the theoretically optimal accuracy, with a real-time computational complexity in the order of d3 where d denotes a dimension of the state vector [9]. 3.3 nonlinear filtering: the particle filter given the concerns about the estimation accuracy of versions of kalman filters, true nonlinear filters or estimators are needed. the particle filter is a statistics-based estimator where at every discrete time instant, a number of state vectors, referred to as particles, are assessed with regard to how likely they are to be the closest to the actual state. the mathematical formulation of the aforementioned idea is summarized in this section. let us describe a nonlinear system using the following equations: xk+1 = fk (xk, wk) yk = hk (xk, vk) (16) where k denotes discrete time instants, xk and yk represent the state and measurement, respectively, and wk and vk stand for the noises of the system and measurement, respectively. the functions fk (·) and hk (·) are a time variant nonlinear system and a measurement function, respectively. the noises of the system and measurement are assumed to be white and independent from each other with known probability density functions. the aim of the generic bayes estimator is to approximate the conditional probability density function xk based on measurements y1, y2, . . . , yk. this conditional probability density function is denoted as follows: p (xk|yk) = xk (17) conditioned on measurements y1, y2, . . . , yk. the particle filter is the numeric implementation of the bayes estimator, in the following section this will be described. at the beginning of the estimation, it is assumed that the probability density function of p(x0) is known, then n number of state vectors based on the probability density function of p(x0) are randomly generated. these state vectors are the particles and are denoted by x+0,i (i = 1, . . . , n). the value of n can be chosen arbitrarily, depending on the expected estimation accuracy and available computational capacity. at every k = 1, 2, 3 . . . discrete time instant, every particle is propagated to the next time instant using process equations fk (·): x−k,i = fk−1 ( x+k−1,i, w i k−1 ) (18) where (i = 1, . . . , n) and every noise vector wi k−1 is randomly generated based on the known probability density function of wk−1. this is the a priori estimate of the particle filter. subsequently, at every time instant k, once the measurement result can be accessed, the relative conditional probability of each x−k,i can be computed and qi = pk ( yk ∣∣∣ x−k,i) evaluated if the nonlinear measurement equation and the probability density function of the measurement noise are known. after the relative conditional probability of each particle has been evaluated, the relative probability of the actual state being equal to each of the particles is correct. the relative probabilities qi are then scaled to the interval [0, 1] as follows: qi = qi∑n j=1 qj (19) hungarian journal of industry and chemistry challenges of localization algorithms for autonomous driving 49 this ensures that the total probability is equal to one. the next stage is the resampling based on the computed and scaled probabilities. this means that a set of new x+k,i particles is generated based on the relative probabilities qi. this is the a posteriori estimation of the particle filter. the resampling is an important step with regard to the implementation due to the required computational capacity which needs to be considered carefully. the distribution of the computed a posteriori x+k,i particles is in accordance with the probability density function pk (xk|yk). based on this, any kind of statistical evaluation can be carried out, for example, of the expected value, which can be considered as the statistical estimation of the actual state vector: e (xk|yk) ≈ 1 n n∑ i=1 x+k,i (20) a number of ways, the resampling algorithm in particular, are available to design and implement the steps of the filter. the number of particles required to achieve a given estimation accuracy increases in direct correlation with the dimension d of the state vector, this is linear for d of a particle filter using a complex resampling algorithm, but exponential for a plain resampling algorithm [10], while the real-time computational complexity is directly proportional to the number of particles. 4. conclusion despite the fact that satellite-based systems are far from perfect, they are and most likely will continue to be the single most important information source of any localization algorithm combined with digital maps. the role of other information sources, on the one hand, is complementary in areas where gnss has its weaknesses, but on the other hand they contribute to an increase in accuracy at the expense of computational complexity. in a practical real-time application, the extra computational capacity and related costs are not necessarily proportional to each other. this seems to be the main drawback of using nonlinear filtering methods, while on the other hand autonomous vehicles are expected, in the long term, to fall into the category of high-volume low-cost products. hybrid approaches can be considered due to the fact that the equations for localization systems are only partially nonlinear or some of the subsystems can provide sufficiently accurate results using a linear approach. the filtering problem can then be divided into a linear and a nonlinear part, where the former, assuming gaussian distributed noise, may be solved by using a simple kalman filter and reducing the computational complexity and, therefore, the cost of the system. the proportion of linear filtering to nonlinear filtering within the full system is determined by the complexity of the system model chosen as the type of filtering is defined by the model, therefore, modeling and filtering cannot be separate elements in the design process. acknowledgements the research was supported by efop-3.6.2-16-201700002 programme of the hungarian national government. references [1] eskandarian, a.: handbook of intelligent vehicles, springer verlag, london, 2012, chapter 50, p. 1278 doi: 10.1007/978-0-85729-085-4 [2] skog, i.; handel, p.: in-car positioning and navigation technologies – a survey. ieee trans. intell. transp. syst. 2009, 10(1), 4–21 doi: 10.1109/tits.2008.2011712 [3] riekert, p.; schunck, t. e.: zur fahrmechanik des gummibereiften kraftfahrzeugs. ing. arch. 1940, 11, 210–224 doi: 10.1007/bf02086921 [4] pacejka, h. b.: tire and vehicle dynamics, butterworth-heinemann, oxford, 2012, 3rd edition doi: 10.1016/c2010-0-68548-8 [5] kalman, r. e.: a new approach to linear filtering and prediction problems. journal of basic engineering, 1960, 82(1), 35–45 doi: 10.1115/1.3662552 [6] gordon, n. j.; salmond, d. j.; smith, a. f. m.: novel approach to nonlinear/non-gaussian bayesian state estimation. ieee proceedings, 140(2): 107–113 doi: 10.1049/ip-f-2.1993.0015 [7] simon, d.: optimal state estimation: kalman, h infinity, and nonlinear approaches, wileyinterscience, 2006 doi: 10.1002/0470045345 [8] karlsson, r.; gustafsson, f.: the future of automotive localization algorithms: available, reliable, and scalable localization: anywhere and anytime. ieee signal processing magazine, 2017, 34(2), 60–69 doi: 10.1109/msp.2016.2637418 [9] daum, f.: nonlinear filters: beyond the kalman filter. ieee aerospace and electronic systems magazine, 2005, 20(8), 57–69 doi: 10.1109/maes.2005.1499276 [10] daum, f. e.; huang, j.: the curse of dimensionality and particle filters. proceedings of ieee conference on aerospace, big sky, mt, usa, 2003, pp. 4-1979– 4-1993. doi: 10.1109/aero.2003.1235126 48(1) pp. 43–49 (2020) https://doi.org/10.1007/978-0-85729-085-4 https://doi.org/10.1109/tits.2008.2011712 https://doi.org/10.1109/tits.2008.2011712 https://doi.org/10.1007/bf02086921 https://doi.org/10.1016/c2010-0-68548-8 https://doi.org/10.1115/1.3662552 https://doi.org/10.1049/ip-f-2.1993.0015 https://doi.org/10.1002/0470045345 https://doi.org/10.1109/msp.2016.2637418 https://doi.org/10.1109/maes.2005.1499276 https://doi.org/10.1109/maes.2005.1499276 https://doi.org/10.1109/aero.2003.1235126 hungarian journal of industry and chemistry vol. 48(1) pp. 51–59 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-08 modeling of autonomous ev vector-controlled power conversion system for battery management system design gábor kohlrusz∗1 and dénes fodor1 1research institute of automotive mechatronics and automation, university of pannonia, egyetem u. 10, veszprém, 8200, hungary abstract since the energy consumption of electric drivetrains can be optimized in an automatically controlled system, the driving ranges and efficiency of driverless electric cars can be enhanced. the analysis of a model of the electric power conversion system provides the opportunity to consider different driving circumstances, moreover, it is possible to evaluate the performance of a power conversion system when the vehicle is driven along different routes. the results provide detailed information on the transient operation of all the power modules as well as their components, and on the overall performance of the power conversion system. in this study, a permanent-magnet synchronous machine (pmsm) acts as the traction motor in the autonomously driven electric car. besides the pmsm, the power electronics and battery are also modeled in an orcad pspice circuit-simulation environment that serves as a model of an electric power conversion system for the simulation and testing of a battery management system algorithm. the battery management system and control algorithm are modeled in simulink and can be tested together with the pspice-modeled circuits utilizing an interconnected simulation environment. the input of the power conversion system model was a driving scenario that included uphill and downhill sections. the performance of the implemented battery management system algorithm was analyzed and evaluated. keywords: electric power conversion system, autonomous vehicle, battery management, interconnected simulation 1. introduction a driverless car is an automated system where the driving task is a self-acting function. as a result, it is possible to optimize the energy efficiency of the car in order to increase its driving range and reduce its energy consumption. the optimal operation can be achieved by applying well-designed control algorithms and battery management functions. the electric power conversion system of an autonomous vehicle is a very complex system, especially when the electronic control unit is also considered to be part of the system. during the test procedure of such a complexly controlled electric power conversion system, several unforeseen or unexpected behaviors can occur which may lead to damage. in order to avoid damage, it is essential to identify unexpected system behaviors as early as possible. in the early phase of development, the testing and design of these systems should be performed simultaneously to take advantage of the interconnected simulation environment. a mixed-signal simulation environment supports the analysis of controlled electric power conversion systems where digital and analogue domains ∗correspondence: kohlrusz.gabor@mk.uni-pannon.hu can be connected and run simultaneously [1]. simulations can be performed by taking into account practical aspects that introduce cycle times and delays into the model. in such a realistic simulation environment, the reliable design of a battery management system can be achieved. 2. electric power conversion system model a system model, including a model of the electronic control unit, is a prerequisite to the simulation. the electric part of the system can be accurately modelled in a circuit design environment, while the digital environment and control algorithm should be implemented in an environment that is capable of running numerical computations. the electronic components were modeled in orcad pspice environment while the control algorithm was realized in matlab-based simulink. the electric parts of the modeled power conversion system can be seen in fig. 1. the system consists of a nickel manganese cobalt oxide (nmc)-type li-ion battery, a three-phase inverter and a permanent-magnet synchronous machine as the traction motor. the modeled system is a low-power counterpart of a vehicle power conversion system assumhttps://doi.org/10.33927/hjic-2020-08 mailto:kohlrusz.gabor@mk.uni-pannon.hu 52 kohlrusz and fodor figure 1: structure of the modeled power conversion system ing that the system behavior is independent of the power rating. 2.1 modeling of energy storage the energy storage element of the modeled power conversion system is a li-ion battery. the modeled battery cell consists of 4 individual nmc-type sony vtc4a 2100 mah battery cells connected in series. as fig.2 shows, the model of the battery contains a state-ofcharge (soc)-dependent voltage source and three passive components. the model of the battery cell was developed and validated by using measurement data. a fully charged sony vtc4a 2100 mah battery cell was discharged slowly by setting the discharge current to a c/10 value until its voltage reached the recommended minimum voltage level. the time, battery voltage and discharge current were recorded and the soc values were determined by timeintegration of the current. using the voltage and soc time series, the u(soc) function of the battery cell could be obtained by curve fitting. the best fit was achieved by u = 0.227 log10 ( 0.1 ( soc + 3.35 · 10−5 )) + 0.535 soc3 + 3.8926 (1) the fitted curve and the measured voltages are shown together in fig. 3 as a function of the soc. in order to complete the battery model, it is also necessary to obtain the electrical parameters of the battery cell. the values of the passive components were provided by measurements which put the transient behavior of the battery cell into focus. in table 1, the values of all three parameters can be seen. figure 2: equivalent circuit model of the battery figure 3: approximation of the voltage response of the battery 2.2 modeling of the three-phase inverter the energy conversion between the electric motor and the battery was provided by a three-phase full-bridge inverter with 2 metal–oxide–semiconductor field-effect transistor (mosfet) semiconductors in each leg. the drive circuit was connected through a gate resistor to avoid an inrush current at the gate of the mosfets. the pulse-width modulated (pwm) gate-source voltages were provided by the digital controller which was implemented in the matlab-based simulink environment. a schematic diagram of the inverter can be seen in fig. 4. as the figure shows, a shunt resistor was added to each phase wire for current sensing. 2.3 modeling of the three-phase pmsm in the modeled system, the traction motor was a permanent-magnet synchronous motor. the implemented model is valid for constructions with surface-mounted magnets on the rotor and distributed winding in the wyewound stator. the electrical model was created by determining the voltages across the stator windings which consisted of table 1: equivalent circuit model parameters of the battery circuit parameter notation value series resistance rs 0.1ω charge transfer resistance rct 0.0052ω double-layer capacitance cdl 0.9 f hungarian journal of industry and chemistry modeling of autonomous ev power system for bms design 53 figure 4: three-phase full-bridge inverter the resistive drop, the voltage across the inductor and the back electromotive force (back emf). in the orcad environment, it was quite easy to create the electric part of the motor model due to the fact that the voltage across the inductor in each phase could be represented by defining time-dependent selfand mutual inductances as passive components of the circuit, while their analytical modeling would have been complicated. the simulation of the motor requires the implementation of the mechanical submodel as well. papers dealing with the model of the three-phase pmsm also included the electromagnetic torque [2, 3], however, it was challenging to determine the expanded form of an expression which could be easily implemented in an orcad environment. in ref. [4], a suitable form is presented for implementation in an orcad environment, hence this model was used in this work to obtain the mechanical model. in the simulation, a maxon ec-4pole 252463 type motor was considered. the parameters of the motor can be seen in table 2. 3. modeling of electronic control unit the electronic control unit was modeled in a matlabbased simulink environment which is suitable for quick algorithm and was equipped with an interface to orcad pspice circuit simulation software. a realistic electronic control unit could be modeled using a trigger-activated simulink function which run the control algorithm when a trigger signal is received. the trigger signals were generated to fit the operating frequency of the digitally controlled discrete-time system. this solution ensured that the control algorithm only ran once during each sampling period, consequently, the pulse width modulation (pwm) signals of each mosfet were generated only once during each sampling period. this solution is able to accurately simulate the operation of a microcontroller or even an electronic control unit. the discrete-time control algorithm was implemented in the trigger-activated block. the structure of the algorithm can vary depending on how the difference equation is determined. table 2: pmsm model parameters motor parameter notation value phase resistance r 0.49 ω leakage inductance lsl 33 µh mean value of the mutual inductances lso 92 µh amplitude of inductance fluctuation lx 10 µh amplitude of permanent magnet-created flux linkage ψpm 22.4 mwb friction coefficient b 5.25×10−5 nms rotor inertia j 220 gcm2 number of pole pairs zp 2 3.1 discrete-time control algorithm the frequently used proportional integral (pi) algorithm was implemented to control the power conversion system. the structure of the control system is shown in fig. 5. as the figure shows, a speed-cascaded torque control loop and a magnetic field control loop were created. this strategy is the widespread field-oriented control scheme of three-phase alternating current (ac) motors. in the case of a pi controller, the only dynamic component of the controller is the integrator since the proportional component simply multiplies the error signal. consequently, the proportional component can be implemented in the same form as in a continuous-time algorithm, however, the discrete-time form of the integrator has to be determined by using a z-transform. the transformation can be conducted using different formulae to approximate the continuous-time system. an easy way to determine the discrete-time form of the integrator is to use the backward euler method. using this method, the value of the integral at time j is yj = yj−1 + ejtti (2) where yj denotes the result of the integral at time j, yj−1 represents the result of the integral at time j−1, ej stands for the error signal at time j, t is the sampling time and ti denotes the integral gain. a drawback of this method is that a continuous-time system could be unstable in its discrete-time form using the backward euler method [5]. the bilinear transform (also known as tustin’s method) could be a more reasonable technique to obtain the discrete-time representation of a system since it preserves stability. the value of an integral at time j is determined by this method as follows: yj = yj−1 + ( ej + ej−1 ) tti 2 (3) where yj denotes the result of the integral at time j, yj−1 stands for the result of the integral at time j − 1, ej represents the error signal at time j, ej−1 is the error signal 48(1) pp. 51–59 (2020) 54 kohlrusz and fodor figure 5: vector-controlled power conversion system of an electric vehicle at time j − 1, t denotes the sampling time and ti stands for the integral gain. the realization of a controller that applies the backward euler method is easier and this form generally provides a stable operation, thus in the implemented model of a controller, the integrator was approximated by eq. 2. 3.2 design of the controller parameters the implemented controllers were pi controllers in parallel form, that is the integral and proportional terms were independent of each other. one of the simplest controller design procedures is the pole-zero cancellation but this method provides a frequency bandwidth for the controller that is identical with that of the controlled system resulting in poor performance occasionally. this problem is particularly severe when a system with a large time constant is controlled by a slow integrator with the same time constant as the system [6]. a better controller performance can be achieved by another analytical tuning method where the closed-loop poles are chosen to obtain an arbitrarily determined closed-loop transfer function. the closed-loop is shaped by utilizing some predefined parameters such as the desired damping factor and bandwidth of frequencies. the parameters of the pi controller can be computed as kc = 2ξω0τ − 1 k (4) where kc denotes the proportional gain of the controller, ω0 stands for the natural frequency of the desired closedloop system, ξ represents the desired damping factor of the second-order closed-loop system, τ is the time constant of the controlled first-order subsystem, and k denotes the gain of the controlled first-order subsystem. the value of the integral gain is determined as ti = ω2 0τ k (5) where ω0 denotes the natural frequency of the desired closed-loop system, τ stands for the time constant of the controlled first-order subsystem, and k represents the gain of the controlled first-order subsystem. the damping ratio was chosen to ensure an overshoot of approximately 1%, therefore, for the computations, ξ = 0.85 was applied. the desired natural frequency of the closed-loop system (ω0) was obtained by determining the desired settling time of the controlled variable by considering a desired error band: ω0 = − ln p ξtb (6) where p denotes the difference between the reference signal and the value of the controlled variable as a percentage of the reference value, ξ stands for the desired damping factor of the second-order closed-loop system, and tb represents the period of time until the controlled variable is expected to reach the desired error band [7–9]. 3.3 implementation of the smith predictor when a discrete-time unit controls a system, a time delay is always present. during each time period, some measurements serve as the basis of control signal generation. hungarian journal of industry and chemistry modeling of autonomous ev power system for bms design 55 however, the calculated control signals are only realized as controller outputs during the following time period, which leads to a delay of one period in duration. compensation for this one-period delay can be solved by implementing a smith predictor. the predictor is an algorithm which modifies the actual measurement signal by extrapolation based on former measurements. the implementation of a smith predictor requires the difference equation of the controlled variable as a function of the controller output to be obtained. based on the difference equation, the measurement signal was compensated by predicting the measurement value of the following time period: 1. at time t1, measurement signal û1 is considered for the computation of controller output y2 which will only take effect at time t2. 2. from y2, it is possible to compute the predicted measurement value û2 that can be used to obtain û1− û0 3. û1 = u1 + (û1 − û0) is the corrected measurement signal, which is used to compute y2 as has already been stated in step 1: where u1 denotes the measured value of the controlled variable at time t1 modified by the correction term, y2 stands for the controller output at time t2, û2 represents the predicted value of the measurement at time t2, and û1 and û1 are the computed values of the controlled variable at times t1 and t0, respectively. in step 2, the difference equation of the controlled subsystem is used for the computation of the predicted û2 at time t2. in the case of the current controllers, the prediction algorithm is ı̂2 = (t2 − t1) r l ( u2 r − ı̂1 ) + ı̂1 (7) where the current ı̂2 is the predicted value of the measurement signal at time t2, which was the basis of the calculation of the correction term ı̂1 − ı̂0. the measured current i1 could be corrected as ı̂1 = i1 + (̂ı1 − ı̂0) . (8) the predictor was the same in both the id and iq current controllers, only the parameters were different as ld was substituted for eq. 7 in case of the id control loop and lq was substituted for eq. 7 in case of the iq control loop. the smith predictor in the cascade control loop requires the difference equation of the angular velocity as a function of the current iq: ω̂2 = (t2 − t1) 1.5zpψpmiq,1 −bω̂1 −mt j +ω̂1 (9) the measured speed ω1 could also be corrected by calculating the values ω̂1 and ω̂0 from ω̂2: ω̂1 = ω1 + (ω̂1 − ω̂0) (10) figure 6: testing of the id and iq current controllers 4. testing of the controlled power conversion system model the testing was performed with an operating frequency of 25 khz in the control loop. the current controllers were designed to provide a settling time of tb = 2 ms with p = 0.02 that equated to an error of 2% which resulted in the desired frequency bandwidth of ω0 = 2301 rad/s. by taking into consideration the frequency bandwidth, the calculated controller parameters were kc,id = 0.12 (11) ti,id = 824 (12) for the d-axis current controller and kc,iq = 0.238 (13) ti,iq = 985 (14) for the q-axis current controller. the testing of the controllers was performed without the implementation of the cascaded speed control loop. a reference current was set up for both current loops, d and q. the results can be seen in figs. 6 and 7. it is shown in fig. 6 that the current id overshot the reference value of 0.5 a and started to oscillate around the setpoint with an amplitude of 50 ma, which is 10% of the reference value. the current iq tracked its setpoint of 0 a with an inappreciable error. the results show that the integral gain of the current id should be decreased, therefore, the controllers were tested with redesigned id figure 7: results of the redesigned current controllers 48(1) pp. 51–59 (2020) 56 kohlrusz and fodor (a) speed of the electric motor (b) performance of the d-axis current controller with and without the smith predictor figure 8: simulation results of the controlled system using the smith predictor in the current controllers controller while the iq controller parameters remain unchanged. kc,id = 0.12 (15) ti,id = 275 (16) for the current controller d. in fig. 7, the results for the d-axis controller testing are presented. the performance of the redesigned daxis current controller id was enhanced. the controlled variable reached the setpoint and stabilized after approximately 2 ms. the angular velocity ω was controlled by a cascaded pi controller in the q-axis current loop. the controller parameters were obtained by determining the desired frequency bandwidth which provided a settling time of tb = 0.05 s and p = 0.05, which equated to an error of 5%: kc,ω = 0.038 (17) ti,ω = 1.627 (18) fig. 8a shows the controlled motor-speed signal which has a reference value of 20 rad/s. it can be seen that the speed signal overshot slightly and stabilized after 0.065 s which was acceptable since the designed settling time was defined as tb = 0.05 s. 4.1 testing of the smith predictor the predictor was only implemented for the current controllers since the speed tracking performance of the system was satisfactory without the application of a predictor. the implemented predictor was tested under the same conditions as the current controllers, that is the current references id and iq were set at 0.5 a and 0 a, respectively. fig. 8b shows the controller performance with and without the smith predictor. in fig. 8b, it can be seen that the controller performed better when the smith predictor modified the error in the input signal of the controller by correcting the measured current signal. the controlled current id stabilized faster and in a steady state it could be observed that the pwmrelated high-frequency oscillation of the current occurred with a reduced amplitude compared to when the smith predictor was not applied. the behavior of the current signal iq did not change significantly since its reference value was set at 0 a and no dynamic changes in the reference signal needed to be handled. 5. battery management system design the controlled power conversion system was validated by tests. the created model of the complex system is suitable for simulations that are intended to analyze the operation of the system. by analyzing the operation of the power conversion system, the design aspects of a battery management system can be summarized. simulation of the power conversion system can be a suitable procedure to validate the operation of the designed battery management system under realistic conditions. 5.1 implementation of a battery management system when a battery management strategy is implemented, it influences both the hardware and software components of the supervised system. battery management solutions actuate in order to ensure efficient system operation as well as keep the system safe. if the management algorithm is used to ensure the system operates safely, all the avoided situations should be summarized during the design phase. moreover, for each undesirable situation, a hardware solution has to be designed, which can be activated when necessary. in this study, a battery overcharge protection system was analyzed as a battery management system. for this purpose, the power electronics had to be extended by additional power switches that were capable of changing operation mode when overcharging occurred (see fig. 9). the implementation of the battery management system also included augmentation of the software. in fig. 9, a power semiconductor (m1) can be seen that ensures an alternative path for the current when the battery cannot be charged. in this case, the recuperated energy is dissipated into a resistor. when switch m1 is hungarian journal of industry and chemistry modeling of autonomous ev power system for bms design 57 figure 9: the analyzed battery management system turned on, another switch (m2) becomes responsible for decoupling the battery, otherwise the battery would be discharged through the resistor. in certain situations, generation of the pwm signal is also affected by the battery management algorithm. in this case, the pwm signals are generated in the same way whether the battery protection circuit operates or not. 5.2 simulation of a driving cycle of a vehicle the simulation of a driving cycle of a vehicle provides the opportunity to observe the efficiency of the battery management strategy of the power conversion system and its interactions with the components of the system. the results serve as a basis for implementing different battery management strategies or modifying the implemented one. a driving cycle can be simulated by defining different load torques of the traction motor. when an uphill or downhill stretch of road should be represented, the motor is loaded with a positive or negative load torque, respectively. if the gradients of the uphill and downhill sections of road are unchanged, the load torque remains constant. a simulation of 5.5 s in duration was performed. the simulated driving cycle consisted of uphill, downhill and flat sections (see fig. 10). in the picture, the load torques of the pmsm can also be seen below the corresponding sections of road. during the driving cycle, the speed of the vehicle was expected to be constant, hence the angular velocity was assumed to also be constant at 20 rad/s. at the beginning of the simulation, it was assumed that the battery was fully charged. the results of the simulation can be seen in figs. 11 and 12. in fig.11, the speed of the traction motor can be seen throughout the driving cycle. it can be observed that the changes in load torque influenced the speed of the motor, however, the controller promptly compensated for the transient overshoots. figure 10: simulated vehicle path and related load torques the currents of the power conversion system are presented in fig. 12. the braking current and the current of the battery are also shown in fig. 9. in fig. 12, it can be noted that the q-axis current controller achieved precise and fast reference tracking when the system was perturbed by changes in load torque. if the reference current iq was negative, the energy was recuperated, that is the traction motor was in generator operation mode. since the battery was fully charged, energy must have been dissipated into the braking resistor. in the simulation, two cases when the battery management system activated the braking circuit can be seen in the figure after t1 = 1.7 s and t2 = 4.4 s. when the current flowed through the resistor the battery current was zero due to decoupling performed by switchm2. in the figure, a current spike can be easily observed when the battery was connected to the circuit after reference current iq became positive. 6. conclusions this paper presents models of the power conversion system of an autonomous electric vehicle as well as the electronic control unit. an interconnected simulation environment enables an integrated model to be simulated. this kind of simulation is useful for the comparative performance analysis of different control algorithms as well 48(1) pp. 51–59 (2020) 58 kohlrusz and fodor figure 11: simulated motor speed during the driving cycle of a vehicle figure 12: the simulated currents of the power conversion system with bms as system level analysis of interactions between different system modules and components. a power conversion system model is very complex and it is hard to predict interactions between components of the system following dynamic changes at system inputs. furthermore, the validation of the controllers is only plausible if the simulation model includes all relevant components of the system and all significant factors such as sampling of the measured data or time delays in the control loop. the simulation is very useful if the operation of the hardware level system is the focus of observations and analyses. however, the simulation of the top-level management system of an autonomous electric vehicle is not feasible due to lengthy simulation times. in order to analyze the performance of different controllers, the simulation must be run with a sampling time of 2 µs or less, while the effectiveness of a higher-level management system can be measured after a few hours of driving. in cases when the analysis of the efficiency of the management system takes into consideration the performance of the digital controller, it is essential to identify a modeling procedure which provides a model of the system that is suitable for long-time simulation. acknowledgements the project has been supported by the european union, co-financed by the european social fund. (efop3.6.216-2017-00002). references [1] kohlrusz, g.; csomós, b.; enisz, k.; fodor, d.: electric energy converter development and diagnostics in mixed-signal simulation environment, acta imeko, 2018, 7(1), 20–26 doi: 10.21014/acta_imeko.v7i1.512 [2] hang, j.; zhang, j.; cheng, m.; huang, j.: online interturn fault diagnosis of permanent magnet hungarian journal of industry and chemistry https://doi.org/10.21014/acta_imeko.v7i1.512 modeling of autonomous ev power system for bms design 59 synchronous machine using zero-sequence components, ieee transactions on power electronics, 2015, 30(12), 6731–6741 doi: 10.1109/tpel.2015.2388493 [3] qi, y.; bostanci, e.; gurusamy, v.; akin, b.: a comprehensive analysis of short-circuit current behavior in pmsm interturn short-circuit faults, ieee transactions on power electronics, 2018, 33(12), 10784–10793 doi: 10.1109/tpel.2018.2809668 [4] kohlrusz, g.; szalay, i.; fodor, d.: orcad pspice implementation of a realistic three-phase pmsm model for diagnostic purposes, san diego, ca, usa, 2019, 372–376 doi: 10.1109/iemdc.2019.8785371 [5] leveque, r. j.: finite difference methods for ordinary and partial differential equations: steadystate and time-dependent problems (society for industrial and applied mathematics, philadelphia, pa, usa), 2007 isbn: 978-0-898716-29-0 [6] åström, k. j.; hägglund, t.: pid controllers : theory, design, and tuning (2nd edition) (international society for measurement and control, research triangle park, n.c., usa), 1995 isbn: 1556175167 9781556175169 [7] kuo, b. c.; golnaraghi, f.: automatic control systems (john wiley and sons inc., new york, ny, usa), 2002 isbn: 0470048964 [8] katsuhiko, o.: modern control engineering, (5th edition) (pearson), 2009 isbn: 0136156738 [9] guzmán, j. l.; moreno, j. c.; berenguel, m.; moscoso, j.: inverse pole placement method for pi control in the tracking problem, in ifac-papersonline, 51(4), 406–411 doi: 10.1016/j.ifacol.2018.06.128 48(1) pp. 51–59 (2020) https://doi.org/10.1109/tpel.2015.2388493 https://doi.org/10.1109/tpel.2018.2809668 https://doi.org/10.1109/iemdc.2019.8785371 https://doi.org/10.1016/j.ifacol.2018.06.128 https://doi.org/10.1016/j.ifacol.2018.06.128 hungarian journal of industry and chemistry vol. 48(1) pp. 61–65 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-09 nonlinear magnetic properties of magnetic fluids for automotive applications barnabás horváth*1 and istván szalai2 1institute of physics and mechatronics, university of pannonia, egyetem utca 10, veszprém h-8200, hungary 2institute of mechatronics engineering and research, university of pannonia, gasparich márk utca 18/a, zalaegerszeg h-8900, hungary the external magnetic field required to activate a magnetic fluid in an industrial application is sufficiently large that magnetization is no longer a linear function of the external field strength, i.e. magnetic fluids exhibit nonlinear characteristics. the aim of our research was to develop a measuring system which is capable of determining the nonlinear ac susceptibility of magnetic fluids at discrete frequencies and in the presence of a high-intensity driving magnetic field. the measurement of susceptibility is based on the determination of the change in frequency of a low-intensity field, which is generated by an lc oscillator. the application of sinusoidal excitation to the material results in a variation in the susceptibility that modulates the frequency of the measured low-intensity field and in the appearance of higher-order harmonics of the driving field. the higher-order components of the nonlinear ac susceptibility are extracted from the measured response by fourier analysis. by applying the measuring system, the nonlinear susceptibility of water-based ferrofluids (ferrotec’s emg 700) and its dependence on the magnetic field strength were investigated. keywords: ac susceptometry, nonlinear susceptibility, ferrofluid 1. introduction regarding automotive applications, one of the most important characteristics of magnetic fluids is their behavior in magnetic fields. the majority of these applications are for seals [1], vibration damping [2] and torque transmission [3]. in most cases, the magnitude of an external magnetic field required to activate a fluid is on the scale where the m magnetization is no longer a linear function of the h field strength. this means that magnetic fluids show nonlinear characteristics, and the χ = ∂m/∂h susceptibility depends on the magnetic field strength. in the case of magnetic fluids, the nonlinearity is the result of two effects: normal saturation (alignment of the magnetic dipole moments) and formation of structures (particle chains). the latter influences the susceptibility as the magnetic field shifts the equilibrium between the structures with different dipole moments (single particles and particle chains of different sizes). in a weak time-varying he(t) = he0 sin(ωt) magnetic field (where t denotes the time and ω = 2πf represents the angular frequency), the magnetization also changes periodically but lags behind the magnetic field because reorientation of the magnetic dipole moments is not instantaneous. in this case, the dynamic magnetic susceptibility can be defined as a complex quantity χ∗(ω) = *correspondence: bhorvath@almos.uni-pannon.hu χ′(ω) − iχ′′(ω). the real part, χ′, is related to the reversible magnetization process and it is in-phase with the alternating field. within the low-frequency limit, (f → 0) χ′ approaches the initial gradient of the steady-state magnetization (initial dc susceptibility). if f → ∞, the reorientation of the magnetic dipole moments cannot follow the alternating field and χ′ approaches zero. the imaginary, out-of-phase component, χ′′, is proportional to power losses due to energy absorption from the field and peaks at a characteristic frequency, fc. however, if the amplitude of the alternating field is sufficiently large, higher-order harmonics appear in the magnetization due to the nonlinear characteristics. in this case, the real part of the alternating current (ac) magnetic susceptibility is: χ′ = χ0 + χ2ω cos(2ωt) + χ4ω cos(4ωt) + . . . , (1) where χ0 denotes the base component, and χ2ω and χ4ω represent the amplitude of the secondand fourth-order harmonics, respectively [4]. a similar equation holds for the imaginary component, χ′′. in this work, only the harmonics of the real part are considered, because the nonlinear susceptibility at frequencies much higher than the characteristic frequency of the magnetic fluid is investigated, where the imaginary part is very close to zero. by taking magnetic fluids into consideration, the amplitudes of sixthand higher-order harmonics are so small https://doi.org/10.33927/hjic-2020-09 mailto:bhorvath@almos.uni-pannon.hu 62 horváth and szalai pc labview md analyzer oscillator c daq gpib power f(t) l amplifier fm = 957 khz hm0 = 0.022 ka/m measuring field helmholtz coil fe = 1 200 hz he0 = 0.2 3.0 ka/m driving field he(t) hm(t) fft χ2 χ4 figure 1: a block diagram of the nonlinear magnetic measuring system. that they can be neglected. in alternating magnetic fields, only the even-order harmonics appear, because the magnetization of magnetic fluids exhibits inversion symmetry with respect to a change in the direction of h. should a symmetry-breaking dc bias field be superimposed on the ac magnetic field, both the oddand even-order harmonics appear. as the nonlinearity is caused partly by structure formation, the components of the nonlinear susceptibility and their ratios are sensitive to changes in the structure of magnetic fluids. numerous studies have discussed the theoretical description of the nonlinear susceptibility of magnetic fluids [4–7], but experimental results are rather scarce. nevertheless, nonlinear magnetic susceptibility measurements are quite useful for the study of magnetic fluids and provide additional information besides linear ac susceptometry. if the linear response to small-amplitude fields is measured, the relaxation processes of the magnetic dipoles can be studied. however, by applying the nonlinear method, it is possible to obtain information about the structural evolution of an activated magnetic fluid. the aim of our work was to develop a measuring system which is capable of determining the nonlinear ac susceptibility of magnetic fluids at discrete frequencies in the presence of external magnetic fields. the dependence of the 2ndand 4th-order nonlinear ac susceptibility of ferrofluids on the magnetic field strength was investigated by the developed susceptometer. 2. experimental 2.1 nonlinear measurement method and setup the measurement method of susceptibility is based on our nonlinear dielectric system [8], which is adapted to magnetic measurements. with this method, the real part of complex ac susceptibility is determined from the change in frequency of a low-intensity measuring field (hm). an air core solenoid (l) was filled with the sample of fluid, and the inductance determined the frequency of the sinusoidal measuring field generated by an lc oscillator (fig. 1). therefore, any change in the susceptibility of the sample caused the resonance frequency fm to shift. the susceptibility of the sample was measured at this base frequency. inside the solenoid, the amplitude of the measuring field is so small (hm0 = 0.022 ka/m) that within this region, the magnetization curve of the fluid can be regarded as linear, thus no significant structural change can be expected. the oscillator which generated the measuring field was a colpitts-type parallel lc circuit. the active feedback element was a double triode vacuum tube (ecc88). the capacitor bank c was composed of high-quality silver mica capacitors with a low temperature coefficient. the measuring coil l was connected in parallel with the capacitor block, and by changing the coil, the base frequency of the oscillator could be varied. with different inductors, the measuring frequency was set to discrete values, namely 153 khz, 590 khz and 957 khz. the dimensions of the measuring coils were identical: 25 mm in length with an inner diameter of 7.1 mm. they were composed of enameled copper wires of different sizes and wound on coil formers made of plexiglass. the resonance frequency of the lc oscillator was measured by a hewlett packard 53310a modulation domain (md) analyzer. the relationship between the resonance frequency and susceptibility of the sample was determined by calibration using different materials of known susceptibility. a high-intensity driving field (he) was generated by a pair of helmholtz coils which were placed around the measuring coil. the axis of the helmholtz coil and, therefore, the direction of the field, were parallel to the axis of the solenoid. the upper limit on the amplitude of the driving magnetic field with the current setup was he0 = 6.4 ka/m, which was two orders of magnitude greater than the amplitude of the measuring magnetic field. the maximum of he0 depended on the frequency of the field: as the frequency increased, the maximum of he0 decreased. the uniformity of the magnetic field strength in the volume of the sample was better than 1 %. the helmholtz coil was driven by a high-current function generator, which consisted of a labworks pa-138 linear hungarian journal of industry and chemistry nonlinear magnetic properties of magnetic fluids 63 power amplifier and a signal source. the input signal of the amplifier was provided by a multifunction data acquisition (daq) card (national instruments pci-6052e). any arbitrary waveform could be generated by the signal generator, and the waveform offset by a dc value. under the influence of the high-intensity driving field, the susceptibility of the sample changes, therefore, the frequency of the measuring field was modulated. if the driving field is sinusoidal, then the time-domain susceptibility response will contain the higher-order harmonics of the field. the 2ndand 4th-order components of the nonlinear ac susceptibility were extracted from the measured response by fourier analysis. the fast fourier transform (fft) algorithm was implemented using custom-developed labview software, which provided control and data acquisition functions of the measuring system. 2.2 supplemental measurements during the nonlinear measurements, the change in susceptibility relative to the zero-field susceptibility was measured, so the real part of the ac susceptibility of the fluid at the base frequency had to be determined by another method. for this purpose, a spectrum was obtained within the frequency range of 200 hz 1 mhz. the initial dc susceptibility of the ferrofluid was determined from the dc magnetization curve. the ac susceptibility in zero field was measured by an inductive method where the inductance of a solenoid filled with the sample was measured by an impedance analyzer (agilent 4284a). by determining the impedances of the empty air core solenoid and when it is filled with the sample, χ′ was calculated. the solenoid used for these measurements was the same as the measuring coil of the nonlinear setup. 2.3 material by applying the nonlinear magnetic measuring system, the nonlinear properties of ferrotec’s emg 700 ferrofluid were investigated. this material is water-based and contains magnetite particles with a nominal diameter of∼ 10 nm. the volume concentration of the particles is 5.8 %(v/v). the fluid is stabilized by an anionic surfactant. for the measurements, glass-tube sample holders with an inner diameter of 3.1 mm were filled with the ferrofluid. the length of the tube extended beyond the length of the measuring coil at both ends. the volume of the sample was 0.49 cm3. 3. results and discussion according to the dc magnetization curve, the initial dc susceptibility of the emg 700 ferrofluid was χdc = 12.57. this is the limiting value of the real part of the complex susceptibility if f approaches zero. the ac susceptibility spectrum of the ferrofluid is shown in fig. 2. relaxation of χ′ was observed within the lower frequency 10-1 1 10 102 103 104 105 106 0 3 6 9 12 15 c = 0.54 cs = 12.55 f (hz) c' he = 0 fc = 39 hz figure 2: relaxation of the real part of ac susceptibility in the absence of a driving magnetic field (hollow symbols) by applying the cole-cole equation (solid line) together with the estimated parameters of the relaxation. region. the experimental frequency-dependent susceptibility data was fitted by the cole-cole equation (solid line in fig. 2). this relaxation model is suitable for describing the response of dipoles to an alternating field should the relaxation not be ideal (e.g. if instead of a single relaxation time, a distribution of relaxation times exists). the fitting process yielded the static (f → 0) χs = 12.55 ± 0.07 and infinite frequency (f → ∞) χ∞ = 0.54±0.02, susceptibilities and the so-called central characteristic time of the relaxation (τ0). the reciprocal of the characteristic time yielded the characteristic frequency fc = 1/(2πτ0), which is 39 ± 5 hz for the ferrofluid emg 700. the spectrum shows that relaxation occurs at much lower frequencies than the base frequency of the nonlinear susceptibility measurements (fc = 39 hz vs. fm = 957 khz). at the high-frequency end (∼1 mhz) of the spectrum, χ′ decreased to ∼ 0.8 and changed slightly as the frequency increased in this region. at such a large distance from fc, the imaginary part of the complex susceptibility was close to zero, thus it is justified to consider only the real part (see eq. 1). to investigate the nonlinear ac susceptibility, sinusoidal excitation was applied. the frequency of the driving magnetic field was changed from 1 hz to 200 hz with an amplitude as high as he0 = 3 ka/m (depending on fe). the nonlinear ac susceptibility was measured at 957 khz in all cases. at he0 = 0, the real part of the ac susceptibility of the ferrofluid at the measurement frequency of fm = 957 khz was χ′ = 0.78. fig. 3 shows a typical susceptibility response of the ferrofluid emg 700 at an excitation frequency of fe = 1 hz and using different magnetic field strengths. it can be seen that the response contained higher-order harmonics. the magnetic field always caused a decrease in the susceptibility (because of the saturation) regardless of its direction. this inversion symmetry was expressed by the fact that the susceptibility response during the first half period 48(1) pp. 61–65 (2020) 64 horváth and szalai 0.0 0.5 1.0 1.5 2.0 0.63 0.66 0.69 0.72 0.75 0.78 0.81 c'(t) he0 = 0.7 ka/m he0 = 1.1 ka/m he0 = 1.4 ka/m t (s) c' he(t) -1 0 1 2 3 4 5 6 7 h e ( ka /m ) figure 3: the susceptibility response of the ferrofluid emg 700 at various driving field amplitudes (fe = 1 hz). of he(t) was the same as during the second half even if the direction of the field was reversed. therefore, the maxima of the susceptibility responses were always 0.78, which corresponded to the point when he(t) intersected the value zero. the dependence of the 2ndand 4th-order harmonics (χ2ω and χ4ω in eq. 1) on the magnetic field strength extracted from the measured response is shown in figs. 4a and 4b. at a given driving field strength, χ2ω was one order of magnitude larger than χ4ω . the amplitude of both components increased as the magnetic field strength rose (at a given driving field frequency). this occurred be0.00 0.02 0.04 0.06 0.08 0.10 0.0 0.5 1.0 1.5 2.0 2.5 3.0 0.000 0.005 0.010 0.015 c 2 w fe = 1 hz fe = 40 hz fe = 100 hz fe = 200 hz a b c 4 w he0 (ka/m) figure 4: the dependence of the components χ2ω (a) and χ4ω (b) of the nonlinear susceptibility of the ferrofluid emg 700 on the amplitude of the driving field at different driving field frequencies. cause at higher magnetic field strengths, the nonlinearity of the magnetization curve increased as the magnetization approached the saturation level. 4. conclusions a nonlinear magnetic measuring system was developed to determine the nonlinear ac susceptibility of magnetic fluids. the system was applied to measure the components of the nonlinear susceptibility of the water-based ferrofluid emg 700 up to the 4th order. it has been shown that by using the aforementioned system, it is possible to determine the dependence of the nonlinear susceptibility on the magnetic field strength. if the excitation frequency is varied, the relaxation of the nonlinear susceptibility can be also studied. our future aim is to investigate this relaxation and other types of ferrofluids (based on organic carrier and polydisperse fluids), moreover, to study the influence of the magnetite concentration on the nonlinear magnetic properties. acknowledgments this project was supported by the european union and co-financed by the european social fund. efop-3.6.216-2017-00002. references [1] ravaud, r.; lemarquand, g.: mechanical properties of a ferrofluid seal: three-dimensional analytical study based on the coulombian model, prog. electromagn. res. b, 2009, 13, 385–407, doi: 10.2528/pierb09020601 [2] sassi, s.; cherif, k.; mezghani, l.; thomas, m.; kotrane, a.: an innovative magnetorheological damper for automotive suspension: from design to experimental characterization, smart mater. struct., 2005, 14(4), 811–822, doi: 10.1088/09641726/14/4/041 [3] rizzo, r.: an innovative multi-gap clutch based on magneto-rheological fluids and electrodynamic effects: magnetic design and experimental characterization, smart mater. struct., 2017, 26(1), 015007, doi: 10.1088/0964-1726/26/1/015007 [4] wang, g.; huang, j.p.: nonlinear magnetic susceptibility of ferrofluids, chem. phys. lett., 2006, 421(4), 544–548, doi: 10.1016/j.cplett.2006.02.010 [5] huke, b.; lücke, m.: magnetic properties of colloidal suspensions of interacting magnetic particles, rep. prog. phys., 2004, 67(10), 1731–1768, doi: 10.1088/0034-4885/67/10/r01 [6] szalai, i.; nagy, s.; dietrich, s.: linear and nonlinear magnetic properties of ferrofluids, phys. rev. e, 2015, 92(4), 042314, doi: 10.1103/physreve.92.042314 hungarian journal of industry and chemistry https://doi.org/10.2528/pierb09020601 https://doi.org/10.1088/0964-1726/14/4/041 https://doi.org/10.1088/0964-1726/14/4/041 https://doi.org/10.1088/0964-1726/26/1/015007 https://doi.org/10.1016/j.cplett.2006.02.010 https://doi.org/10.1088/0034-4885/67/10/r01 https://doi.org/10.1103/physreve.92.042314 https://doi.org/10.1103/physreve.92.042314 nonlinear magnetic properties of magnetic fluids 65 [7] ivanov, a.o.; kuznetsova, o.b.: magnetic properties of dense ferrofluids, j. magn. magn. mater., 2002, 252, 135–137, doi: 10.1016/s03048853(02)00639-x [8] horváth, b.; szalai, i.: structure of electrorheological fluids: a dielectric study of chain formation, phys. rev. e, 2012, 86(6), 061403, doi: 10.1103/physreve.86.061403 48(1) pp. 61–65 (2020) https://doi.org/10.1016/s0304-8853(02)00639-x https://doi.org/10.1016/s0304-8853(02)00639-x https://doi.org/10.1103/physreve.86.061403 https://doi.org/10.1103/physreve.86.061403 hungarian journal of industry and chemistry vol. 48(1) pp. 67–70 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-10 vibration generator device based on industrial vibrators péter decsi *1 and istván szalai1 1institute of mechatronics engineering and research, university of pannonia, gasparich márk utca 18/a, zalaegerszeg, 8900, hungary a low-cost vibration generator device based on industrial vibrators was designed. the control software was implemented in labview environment. the device is able to generate an oscillating force of 8 kn and an amplitude of up to 4 mm at a frequency of 50 hz to model low-amplitude, high-frequency vehicle vibrations. a national instruments myrio device was responsible for data acquisition, with which a signal of a piezoelectric accelerometer was detected. the test results show that the device is able to generate a sinusoidal harmonic acceleration. keywords: industrial vibrator, vibration generator, test equipment 1. introduction the suspension of a car acts as a connector between the chassis and the road. it provides a comfortable ride for passengers while maintaining maneuverability. nowadays, comfort is a prerequisite so car manufacturers have started developing new technologies for isolating vibrations [1, 2]. the vibration can be dampened or converted into electrical energy [3]. electro[4] and magnetorheological dampers [5, 6] are filled with a special fluid. small ferromagnetic particles are dispersed in a carrier fluid, usually silicone oil. the diameters of the particles fall within the microand nanometre ranges. when subjected to an electric or magnetic field, the particles form chains. these chains provide an elevated level of resistance against shear stress, therefore, the apparent viscosity of the fluid rises [7, 8]. using adjustable shock absorbers, the natural frequency of the suspension can be altered. the damping coefficient can be varied depending on the road conditions or the driver’s preference. the reaction time of these fluids is very short (approximately 10ms), so the technology can be used in systems where short reaction times are required [9]. suspension-testing equipment is crucial during the development phase. the acquisition cost of appliances for this task is very high. our goal was to develop a low-cost piece of equipment for testing shock absorbers that is capable of generating high frequencies (within an acceptable range for vehicles) and vibrations of low amplitude. *correspondence: decsi.peter@mk.uni-pannon.hu 𝑥1 𝑥2 𝑚1 𝑚2 𝑘1 𝑏1 𝑘2 𝑏2 𝑥𝑟 (a) structure model 𝑚2 𝑚1 𝑘1 𝑘2 𝑏1 𝑏2 𝑥 1 𝑥 2 𝑥 𝑟 𝑥 𝑟 (b) structure graph figure 1: quarter-car model 2. modeling the vehicle several options of modeling the suspension of vehicles are available; quarter-, halfand full-car models can be used to describe the system, which is chosen depends on the aim of the study. the quarter-car model was chosen for this study due to its simplicity. industrial vibrators are able to generate vibrations of constant amplitude. to change the generated force and amplitude, it is necessary to stop the device and mechanically set the eccentricity, therefore, the roll, pitch and yaw of the vehicle is hard to model with such a device. fig. 1 shows a quarter-car model. the system has two degrees of freedom (dof), m1 denotes the mass of the chassis, m2 represents the mass of the wheel, which is usually referred to as the unsprung mass. the related displacements are labelled as x1 https://doi.org/10.33927/hjic-2020-10 mailto:decsi.peter@mk.uni-pannon.hu 68 decsi and szalai and x2, spring stiffnesses as k and viscous damping coefficients as b. the wheel and chassis are connected through a spring k1 and a damper b1. the wheel and the road are connected through a spring and damper (elastic tire with damping loss) k2, b2. based on the structure graph, the equilibrium equations can be written in the form: m1ẍ1 = −b1(ẋ1 − ẋ2)− k1(x1 − x2) m2ẍ2 = b1(ẋ1 − ẋ2) + k1(x1 − x2)+ +b2(ẋr − ẋ2) + k2(xr − x2). (1) based on fig. 1 and eq. 1, it is clear that the system has a cross-variable source, namely speed. 3. modeling the proposed system this research presents an equivalent model based on industrial vibrators. industrial vibrators are traditional asynchronous motors with a dual shaft on which eccentric masses are mounted. fc = mrω2 (2) where m denotes the eccentric mass, r represents the eccentricity, which is the distance between the axis center point and the center of gravity of the eccentric mass, and ω stands for the rotational speed. due to the eccentricity, a centrifugal force is generated because of the rotation (eq. 2). if two motors of opposite rotational directions are mounted together, lateral forces cancel each other out, therefore, a one-axis oscillation is created. a system with two degrees of freedom was designed using industrial vibrators. the model of the system is depicted in fig. 2: the differential equations of this system are: m1ẍ1 + k1(x1 − x2) + + b1(ẋ1 − ẋ2) + fin = 0 m2ẍ2 − k1(x1 − x2)− − b1(ẋ1 − ẋ2) + k2x2 + ẋ2b2 = 0 (3) x1 xr = s2b1b2 + s(k2b1 + b2k1) + k1k2 s4m1m2 + s3(m1(b1 + b2) +m2b1) + s2(m1(k1 + k2) +m2k1 + b1b2) + s(k1b2 + k2b1) + k1k2 (4) x1 f = s2m2 + s(b1 + b2) + k1 + k2 s4m1m2 + s3(m1(b1 + b2) +m2b1) + s2(m1(k1 + k2) +m2k1 + b1b2) + s(k1b2 + k2b1) + k1k2 (5) according to the impedance network of the quartercar model shown in fig. 3, the transfer function can be written in the form eq. 4. the impedance network of the proposed system is shown in fig. 4 and contains the transfer function of eq. 5: it can be seen that the transfer function x1/xr of the quarter-car model (eq. 4) is similar to that of the transfer 𝑓𝑐 ω 𝑥1 𝑥2 𝑚1 𝑘1 𝑏1 𝑘2 𝑏2 (a) structure model 𝑥 1 𝑥 2 𝑘1 𝑘2 𝑏1 𝑏2 𝑚1 𝑚2 𝑓𝑖𝑛 (b) structure graph figure 2: vibrator model 𝑠 𝑘2 𝑠 𝑘1 1 𝑏1 1 𝑠𝑚1 1 𝑏2 𝑣𝑟 1 𝑠𝑚2 𝑥 1 𝑥 2 figure 3: impedance network of the quarter-car model 𝑠 𝑘2 1 𝑏2 1 𝑠𝑚2 𝑠 𝑘1 1 𝑏1 1 𝑠𝑚1 𝑓𝑖𝑛 𝑥 1 𝑥 2 figure 4: impedance network of the vibrator model hungarian journal of industry and chemistry vibration generator device based on industrial vibrators 69 function x1/f of the proposed system (eq. 5). the characteristic polynomials, i.e. the denominators, are identical as the two systems differ only in terms of the excitation source. the numerators are of the same degree, therefore, the characteristics of the system response are similar, that is to say the dynamics of the two systems are not significantly different. the breakpoints in terms of the frequency response are expected to be shifted. 4. implementation after deriving the differential equations, a simulink model was created to choose the optimal combinations of parameters (mass, spring stiffness and damping coefficients). according to the simulations, the connection between the chassis and the ground should be as stiff as possible in order to focus the force on the shock absorbers. it should not be too rigid, otherwise the force acting on the ground would be excessive and affect the building too significantly. the moving mass, where the motors are mounted, should be small to achieve the maximum possible exciting force, therefore, more force can be used to accelerate the payload. during the design process, models with two or three degrees of freedom were examined. the motion became chaotic with three independent masses, that is 3 dofs, so the spring stiffness available was insufficient to produce a stable and predictable shape of sinusoidal motion. it was concluded that a system with 2 dofs generates a stable sinusoidal oscillation with multiple frequency components in terms of the shape of motion. the device, shown in fig. 5, consists of two threephase asynchronous two-pole industrial vibrators each figure 5: the implemented vibration generator with a nominal performance of 300w. the centrifugal force can be incrementally set up to 4070n at a frequency of 50hz on one motor. the motors are operated with frequency converters, thus the frequency can be set. if the motors operate in opposite rotational directions and a suitable arrangement is applied, the lateral forces cancel each other out, thereby creating a one-axis oscillation. the frequency converters are controlled with analogue signals generated by a national instruments myrio device. a piezoelectric accelerometer was mounted on the sheet holding the vibrating motors. a high-pass filter with a cutoff frequency of 1hz was installed to cancel out the bias voltage of the accelerometer. data was acquired by the field-programmable gate array (fpga) module of the myrio device on analogue channels. the ac signal was coupled to a high-pass filter with a cutoff frequency of 1hz. the sensitivity of the accelerometer was 100mv/g and the analogue input of the myrio device was ±10v. an instrumentation amplifier with an amplification of 7.08 was built to utilize the full range of the a/d converter. the fpga module takes a sample according to the previously set sampling frequency, which can be set up to 100 khz. the data is stored temporarily in the first in first out (fifo) memory on the myrio device. a second virtual instrument (vi), which displays and stores the data in technical data management streaming (.tdms) file format, was run on the controlling pc. the vi read out data from the fifo memory in batches. these batches were stored in the tdms file, creating a reliable data acquisition. meanwhile, following the application of a fast fourier transform algorithm, a frequency spectrum was displayed on the controlling pc. 5. test results a test measurement was taken after the implementation. for test purposes, the frequency converters were set at 16hz. fig. 6 shows a long-term test and fig. 7 shows the measurement of a short-term acceleration. it can be seen that the acceleration is approximately sinusoidal and consists of two main frequency components. fig. 6 shows that the acceleration was stable over an extended period of time with several protrusions. fig. 8 shows that the set 20 30 40 50 60 70 80 90 100 time [s] -6 -4 -2 0 2 4 6 a c c e le ra ti o n [ m /s 2 ] figure 6: test measurement, long duration 48(1) pp. 67–70 (2020) 70 decsi and szalai 30 30.2 30.4 30.6 30.8 31 time [s] -4 -3 -2 -1 0 1 2 3 a c c e le ra ti o n [ m /s 2 ] figure 7: test measurement, short duration 0 10 20 30 40 50 60 70 80 90 100 frequency (hz) -40 -30 -20 -10 0 10 p ow er s pe ct ru m ( db ) figure 8: frequency spectrum of the test measurement frequency was present in the spectrum alongside multiple frequency components. 6. conclusion according to our experience and the aforementioned results, it can be concluded that a cost-effective vibration generator was designed and produced. the device is able to generate an amplitude of vibration equal to 4mm with a frequency of up to 50hz. the total centrifugal force was as high as 8 kn, of which 7500n could be focused on the examined sample. the frequency can be set between 1hz and 50hz, however, as shown in eq. 2, the centrifugal force depends on the rotational speed. the amplitude cannot be set, and when the natural frequency of the system, namely 1.3 hz, is exceeded, the amplitude becomes constant. at this frequency, the centrifugal force is low so resonance can be avoided. the excitation force can be set between 0 and 100% by modifying the eccentricity of the motors. to set the eccentricity, the motors must be powered down and the side covers removed. the vibration generators that are typically used (electrodynamic and hydraulic) are able to create higher amplitudes and higher vibrational frequencies, but these devices belong to a different cost category. acknowledgement the project has been supported by the european union, co-financed by the european social fund. efop-3.6.216-2017-00002 references [1] qin, y.; tang, x.; jia, t.; duan, z.; zhang, j.; li, y.; zheng, l.: noise and vibration suppression in hybrid electric vehicles: state of the art and challenges, renew. sustain. energy rev., 2020, 124, doi: 10.1016/j.rser.2020.109782 [2] ning, d.; sun, s.; du, h.; li, w.; li, w.: control of a multiple-dof vehicle seat suspension with roll and vertical vibration, j. sound vib., 2018, 435, 170–191, doi: 10.1016/j.jsv.2018.08.005 [3] zhang, z.; xiang, h.; shi, z.; zhan, j.: experimental investigation on piezoelectric energy harvesting from vehicle-bridge coupling vibration, energy convers. manag., 2018, 163, 169–179, doi: 10.1016/j.enconman.2018.02.054 [4] holzmann, k.; kemmetmüller, w.; kugi, a.; stork, m.: design, mathematical modeling and control of an assymetrical electrorheological damper, ifac proceedings volumes, 2006, 39(16), 372–377, doi: 10.3182/20060912-3-de-2911.00066 [5] graczykowski, c.; pawłowski, p.: exact physical model of magnetorheological damper, appl. math. model., 2017, 47, 400–424, doi: 10.1016/j.apm.2017.02.035 [6] yao, g.z.; yap, f.f.; chen, g.; li, w.h.; yeo, s.h.: mr damper and its application for semiactive control of vehicle suspension system, mechatronics, 2002, 12(7), 963–973, doi: 10.1016/s09574158(01)00032-0 [7] carlson, j.d.: what makes a good mr fluid?, j. intel. mat. syst. str., 2002, 13(7-8), 431–435, doi: 10.1106/104538902028221 [8] rankin, p.j.; ginder, j.m.; klingenberg, d.j.: electroand magneto-rheology, curr. opin. colloid interface sci., 1998, 3(4), 373–381, doi: 10.1016/s1359-0294(98)80052-6 [9] olabi, a.; grunwald, a.: design and application of magneto-rheological fluid, mater. des., 2007, 28(10), 2658–2664, doi: 10.1016/j.matdes.2006.10.009 hungarian journal of industry and chemistry https://doi.org/10.1016/j.rser.2020.109782 https://doi.org/10.1016/j.rser.2020.109782 https://doi.org/10.1016/j.jsv.2018.08.005 https://doi.org/10.1016/j.enconman.2018.02.054 https://doi.org/10.1016/j.enconman.2018.02.054 https://doi.org/10.3182/20060912-3-de-2911.00066 https://doi.org/10.3182/20060912-3-de-2911.00066 https://doi.org/10.1016/j.apm.2017.02.035 https://doi.org/10.1016/j.apm.2017.02.035 https://doi.org/10.1016/s0957-4158(01)00032-0 https://doi.org/10.1016/s0957-4158(01)00032-0 https://doi.org/10.1106/104538902028221 https://doi.org/10.1106/104538902028221 https://doi.org/10.1016/s1359-0294(98)80052-6 https://doi.org/10.1016/s1359-0294(98)80052-6 https://doi.org/10.1016/j.matdes.2006.10.009 hungarian journal of industry and chemistry vol. 48(1) pp. 71–75 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-11 design and construction of a vibration data acquisition system for road vehicles roland nagy*1 and istván szalai1 1institute of mechatronics engineering and research, university of pannonia, gasparich márk utca 18/a, zalaegerszeg, 8900, hungary this article describes the design of a vibration data acquisition system which can be mounted on the undercarriage of a vehicle to acquire information about the quality of and defects in road surfaces. it is important to be able to deduce the condition of a road section from its data. for practical reasons, a microcontroller-based control unit was used and a separate power supply created. bumps in the road were detected by a piezoelectric accelerometer. once the system was completed, different measurements were made and the results analyzed. according to the results, it can be stated that the whole system worked well since they are identical to reality. the bumps in the road were clearly visible on the diagrams. it was concluded that the completed vibration data acquisition system is more than capable of detecting bumps in roads. the advantage of the system is that it can be easily mounted on any car which does not need to be driven at low speeds. keywords: road vehicle, vibration, data acquisition, microcontroller, accelerometer 1. introduction road vehicles are continuously subjected to vibrations which have very important and serious consequences. these vibrations should be dampened as they have a detrimental effect on both mechanical properties and vehicle occupants. vibrations can significantly reduce the lifetime of mechanical and electrical components. the effects of degradation are greatly increased if the frequency of the vibration is identical to that of a component. these resonances cause health issues for passengers in the car, e.g. back pain is a frequent complaint. vibrational frequencies of between 4 and 8 hz are the most dangerous for the human body [1]. such vibrations can be caused by poor road surfaces and the engine of a car. the former reason is more significant, so this issue will be tackled. due to the important role of vibrations that can occur in road vehicles, it is important to know the condition and characteristics of a road network. in hungary, the measurement of road quality is based almost exclusively on visual observations and manual data recording. inspectors observe the roads and record any defects in a database. even though hardly any automated survey equipment is used, these vehicles have the advantage of faster assessment and more objective evaluation. the purchase of one of these automated measurement systems could cost hundreds of millions of hungar*correspondence: nagy.roland@mk.uni-pannon.hu ian forints [2]. our goal is to design and build a vibration data acquisition system that can be used on road vehicles. the system should easily be mountable on any vehicle and measurements recorded at any speed. the system should be simple, but the measurement results must contain information about the quality of the road section [3]. 2. experimental 2.1 tools of implementation first, a design analysis was carried out and the structure of the system designed accordingly. a compact and light design is important, moreover, the housing should be sufficiently massive. reliability and a constant sampling rate are also crucial. a block diagram of the system is shown in fig. 1. the system is based on an atmega328p microcontroller. the device is optimal for the control task as it supports several communication standards to connect the units to each other as well as possesses an inner a/d converter, pwm channels and several digital pins. the main microcontroller is responsible for managing communication between the individual units and handles the input data. a 16 mhz external oscillator ic is necessary to generate the clock signal and the supply voltage has to be stabilized at 5 v. as the microcontroller possesses a watchdog timer, a reset button is unnecessary. along https://doi.org/10.33927/hjic-2020-11 mailto:nagy.roland@mk.uni-pannon.hu 72 nagy and szalai figure 1: the structure of the system with it, due to stable and robust operation, a pull-up resistor was placed in connection with the microcontroller’s reset pin. in addition, an ftdi connector is placed near the microcontroller which enables it to be programmed in the programming language c++. the wiring diagram of the atmega328p microcontroller is shown in fig. 2. vibrations caused by road defects were detected by a 805m1-0020 piezoelectric accelerometer. the sensitivity of the sensor is 100 mv/g with an offset voltage of 2.5 v. previous studies suggest that accelerations of up to 2 g are expected, and because the analog-to-digital converter has a measuring range of 0 − 5 v, a voltage gain of approximately 16 db was necessary to ensure the analog signal fill the measuring range. for this purpose, an ina128p instrumentation amplifier was used, where the voltage gain was determined by the external resistor rg between pins 1 and 8. the measuring amplifier amplified the potential difference between the two inputs. in this case, due to the 2.5 v offset voltage of the acceleration sensor, a voltage reference ic that provided 2.5 v was used. this voltage reference was connected to the figure 2: a wiring diagram of the atmega328p microcontroller figure 3: a wiring diagram of the amplifier section inverter input of the amplifier, which caused the amplification to change linearly under different accelerations. an ad580 voltage reference ic was used. the output of the instrumentation amplifier is referred to as the output reference terminal. with 2.5 v connected to this pin, the offset voltage of the analog signal was in the middle of the measuring range. a wiring diagram of the amplifying section is shown in fig. 3. following the amplifying section, the analog signal was digitized. due to the increase in resolution, the voltage resolution was 5000/4096, therefore, a change in voltage of 1.22 mv was detected instead of the previous 5 mv. the max186 is a successive-approximation converter with 8-channel single-ended or 4-channel differential inputs. the single-ended input mode was used, so the input signal voltages are referred to as agnd. it should be noted that the device worked in unipolar mode, therefore, an analog input signal of between 0 v and vref could be converted. vref was 5 v in our application [4]. firstly, in terms of programming the max186 process, the parameters were set with the first 8 input bits. these bits were expected to shift synchronously with the clock signal. once set up, the bits of digitized signal could be read out. the read-out process consisted of a 12times repetitive ‘for cycle’, which reads out the digitized value bit by bit. it can be seen that the microcontroller obtains the value of the most significant bit (msb) first. all the input bits have to shift left and must connect to each other with a logical or connection to yield the original measurement of the accelerometer. eventually, the conversion process ends with the a/d converter chip select pin level changing to logic high. a wiring diagram of the max186 is shown in fig. 4. in addition to the accelerations, the gps coordinates were also collected to help identify road humps and potholes that were detected by the accelerometer. for this task, a neo-6m gps module was used that provides momentary velocity and altitude data in addition to longitudinal and latitudinal coordinates. to control this gps module, another atmega microcontroller was installed which was necessary as a debugging process associated with the gps communication was present. its purpose was to verify the adequacy of the data and the connection with the satellites. as a result, the running time and sampling rate of the program cycle became quite slow. hungarian journal of industry and chemistry design and construction of a vibration data acquisition system 73 figure 4: a wiring diagram of the analog-to-digital converter following the installation of a second microcontroller, the program could be run synchronously, which a single atmega328p microcontroller would have been unable to do. as a result, the main microcontroller could be defined as the master and the controller that controls the gps as the slave. the gps unit communicated with the slave controller by using a standard universal asynchronous receiver-transmitter (uart). the two microcontrollers were connected by a bus system, using the i2c protocol which could only handle 8 bits of data in one cycle that corresponded to a number between 0 and 255 in the decimal system. as the gps coordinates had to be transferred, which were 16 bits long in the binary system, these needed to be converted into 3 bit arrays that each contained 8 bits of data. the c++ program of the slave controller handled these numbers in the binary system. first, it executed the right shift by a 16bit command, which was followed by the bitwise and command, masked by 0xff, the hexadecimal number ff. in this way, the first array was obtained, followed by the second array with a right shift using an 8-bit command and finally the last array by masking only. no conversion was needed for data concerning speed and elevation, because these values were only 8 bits long. the master controller decoded the input arrays to the original 16-bitlong data. the data from the first input array had to left shift by 8 bits then perform a bitwise or operation using the 8 bits of the following array to yield the original 16-bit-long data. therefore, the gps data from the slave controller immediately became available, resulting in a much faster sampling frequency. figure 5: a wiring diagram of the power supply unit throughout the measurement process, the acceleration and gps data were collected on an sd card using an arm-mcu sd card module slot socket reader, which communicated with the master controller by applying a standard spi interface. the master controller’s c++ program specified the sampling frequency of the accelerometer, i.e. 60 hz, but is only suitable up to 30 hz according to shannon’s law. the power supply of the system was provided by its own integrated power supply. a maximum of 35 v could be connected to the power input connection of the power supply, thus, the system could be connected to the car’s cigarette lighter. a nee 78h05asc voltage regulator converted 5 v from the input voltage. as ±12 v needed to be supplied to the instrumentation amplifier, an ad941 dc-dc converter was used to convert 5 v into ±12 v. furthermore, 5 v was available from the output of the power supply unit to supply the microcontrollers, other units and sensors. a wiring diagram of the power supply unit is shown in fig. 5. 2.2 construction of the system after designing the system and circuit diagrams, a printed circuit board was planned. given the complexity of the panels, a double-sided pcb was designed. all of the integrated circuits (ics) were used with the housing of the dual inline package (dip). the design rules were set for a cnc machine as the pcbs were handled using an engraving needle. the width of the wiring track was 0.9 mm at 5 v and 1.3 mm at 12 v. the clearance between the wiring tracks and solder pads was 1 mm and 0.4 mm, respectively. by taking into account insulation against electrical noise, larger copper surfaces were left on both sides of the pcb and placed on ground potential. the pcb was designed using eagle cad software. after the design process, the cam programs were generated from cad files. pcb panels were made by an isel icp 4030 3-axes cnc-milling machine. all parts of the system were placed in an ip-protection box. two switches were placed on one side of the box, enabling the 48(1) pp. 71–75 (2020) 74 nagy and szalai figure 6: the completed data acquisition system system to be turned on and the data acquisition process started. the complete system is shown in fig. 6. to check the output signal waveform in the relevant frequency bandwidth, a frequency response function of the amplifier unit was applied. the input signal was in the form of a sine wave within the frequency bandwidth of 10 hz to 3 mhz with an amplitude of 40 mv. the data obtained is shown in fig. 7. the natural frequency was approximately 700 khz, so the frequency response function of the system performed well in the relevant frequency bandwidth. furthermore, amplification of the instrumentation amplifier was checked. the frequency of the input signal was 5 hz with an amplitude of 400 mvpp and an offset voltage of 2.5 v. the amplification factor was set at 6.5 v/v. the data obtained is shown in fig. 8. by plotting the data, the difference between the amplified and original signals can be seen. the waveform of the amplified signal was unchanged and by reading the amplitudes it can be seen that the voltage gain (g) was preset to 6.5 v/v. 3. results and analysis following inspections, the sensor was placed in a car and fixed to the rear control arm to avoid the presence of any damping object between the wheel and sensor [5]. after figure 7: the frequency response function of the amplifier unit, where ω0 = 1 hz figure 8: the amplified and original output signals at 5 hz installing the data acquisition system, several measurements were carried out by vehicle-to-record data on different road surfaces. the results of the measurements are as follows: the first measurement was taken in the vicinity of zalaegerszeg on a 5.5 km stretch of road. the data was saved on an sd card as a txt file and plotted. the gps coordinates helped to analyze the data, through which the exact location of each acceleration value was determined. the voltage gain was set at 16 db (6.5 v/v) [6] and the data from the accelerometer was visible on the diagram without amplification. from the first route, whilst driving in a populated area at the beginning of the measurement period, it can be concluded that the quality of the road surface was generally good with only a few significant potholes and cracks. later, while leaving the town, the poorer quality of the road became immediately obvious given the increase in amplitudes. the road surface consisted of flange grooves and creases. according to the diagram, road defects continued to increase since the highest accelerations occurred towards the end of the measurement period. the acceleration data from the first measurement period is shown in fig. 9. the conditions of the second set of measurements were the same as those of the first. the initial section of this measurement period was identical to that of the first set of measurements (fig. 10). the quality of the road surface was initially quite good as only accelerations of 1 g were recorded, but after leaving the populated area, the quality of the road surface also deteriorated. at the end of the route, several wearing courses, bonding layers and spotting errors were identified on the road surface. the third stretch of road was 3 km long. compared to the other measurements, the quality of the road surface here, which was covered in potholes, patches and surface sinks, was the worst. consequently, in fig. 11, almost all the accelerations reached the limit of 1 g, moreover, for a moment, accelerations of 2 g were also recorded. the right side of the diagram shows that when arriving in a populated area, the amplitudes reduced significantly as the quality of the road substantially improved. only minor cracks were visible on the surface. a small degree of asymmetry can be observed in the graphs, which is caused by the car’s shock absorbers. as hungarian journal of industry and chemistry design and construction of a vibration data acquisition system 75 figure 9: the acceleration of the first set of measurements plotted as a function of time figure 10: the acceleration of the second set of measurements plotted as a function of time figure 11: the acceleration of the third set of measurements plotted as a function of time the damping force of the shock absorbers is less in the negative direction, higher accelerations might occur than in the positive direction. this is also supported by the characteristics of the shock absorbers. 4. conclusion the aim of our research was to design, build and program a vibration data acquisition system suitable for measuring the quality of a motor vehicle. this task involved numerous requirements: the measuring system had to function reliably, withstand the car’s load and be easily installed, moreover, the data had to be produced and recorded as required. in the light of the results, the system worked well; it detected road defects as expected. after measurements were taken, the data was illustrated in charts and the results were identical. the poorest road surface could be detected by the largest amplitudes and was identified according to the gps coordinates when each measurement was made. the advantages of the system are that it can be easily mounted on any model of car and does not require driving at low speeds. acknowledgements this research was supported by the european union and co-financed by the european social fund under the project efop-3.6.2-16-2017-00002. references [1] souissi, h.; hamaoui, a.: effect of human exposure to whole-body vibration in transport, neuroergonomics, 2018, 229 doi: 10.1016/b978-0-12811926-6.00049-x [2] szántó, m.: közúti adatbázisok valós idejű frissítése közösségi megoldás alkalmazásával, útügyi lapok, 2017, 5(1), 13-19 http://utugyilapok.hu/ wp-content/uploads/2017/06/ul_5_c2_szm.pdf [3] brown, j. c.; robertson, a. j.; serpento, s. t.: motor vehicle structures (butterworth-heinemann) 2001, 4–84 isbn: 978-0-7506-5134-9 [4] william, b.: programmable logic controllers, (elsevier books) 2015 isbn 01-28-0-2929-3 [5] bidgoli, m. a.; golroo, a.; nadjar, h. s.; rashidabad, a. g.; ganji, m. r.: road roughness measurement using a cost-effective sensor-based monitoring system, automat. constr., 2019, 104, 140–152 doi: 10.1016/j.autcon.2019.04.007 [6] kennedy, j.; oakley, c.; sumon, s.; parry, i.; wilkinson, e.; brown, j.: impact of road humps on vehicles and their occupants, trl report, 2004, 614, 3–16 https://trl.co.uk/sites/default/files/ trl614%281%29.pdf 48(1) pp. 71–75 (2020) https://doi.org/10.1016/b978-0-12-811926-6.00049-x https://doi.org/10.1016/b978-0-12-811926-6.00049-x http://utugyilapok.hu/wp-content/uploads/2017/06/ul_5_c2_szm.pdf http://utugyilapok.hu/wp-content/uploads/2017/06/ul_5_c2_szm.pdf https://doi.org/10.1016/j.autcon.2019.04.007 https://doi.org/10.1016/j.autcon.2019.04.007 https://trl.co.uk/sites/default/files/trl614%281%29.pdf https://trl.co.uk/sites/default/files/trl614%281%29.pdf hungarian journal of industry and chemistry vol. 48(1) pp. 77–80 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-12 torque transmission time-constant examination of a disktype magnetorheological clutch sándor mester*1 and istván szalai1 1institute of mechatronics engineering and research, university of pannonia, gasparich márk utca 18/a, zalaegerszeg, 8900, hungary in this paper, the torque transmission time-constant of a simple disk-type magnetorheological (mr) clutch is investigated. by using mr fluid, controlled torque transmission can be easily implemented, facilitating the widespread use of similar systems. in order to describe the dynamical properties of the system, time constants were measured at different speeds and magnetic inductions. the time constants were derived by fitting an exponential function to the data. keywords: magnetorheological fluid, clutch, torque transmission 1. introduction the implementation of intelligent materials has significantly increased not only in everyday life, but in the industrial environment as well. magnetorheological fluids are suspensions that consist of at least two phases, whose apparent viscosity changes quickly (within 20 − 30 ms) in the presence of an external magnetic field. the suspension usually consists of small ferromagnetic particles of approximately 10 µm in diameter dispersed in oil. usually surface active agents are also present in the fluid to prevent the particles from being attracted to each other. in the presence of an external magnetic field, the particles gain an induced dipole moment and form pairs, followed by chain-like structures. if the fluid is exposed to shearing, these chain-like structures oppose each other leading to an increase in apparent viscosity which can be used in shock absorbers, torque transmission, superfinishing of optical lenses and civil engineering [1–4]. in addition to the rapid change in apparent viscosity, its low power requirement makes mr fluid ideal for use in semiactive shock absorbers and variable torque-transmission clutches. the most basic forms of magnetorheological clutches are the disk and cylindrical types. the differences between the two types are the transmittable torque and the volume of the idling waste. a stream of particles is present in disk-type clutches due to the centrifugal force. in the cylindrical type, the effect is less significant [5, 6]. this study focuses on a disk-type clutch with a welldefined mathematical model [7]. *correspondence: hollosi.janos@sze.hu 2. experimental the model of our magnetorheological clutch is shown in fig. 1. the clutch consisted of the following main components: 1. dc servomotor with a gearbox; 2. toothed belt drive with 1 : 1 gear ratio; 3. input or drive shaft; 4. input shaft bearings; 5. lower disk; 6. upper disk; 7. upper or driven shaft; 8. upper shaft bearings; 9. torque sensor; and 10. toothed belt drive with 4 : 1 gear ratio. the electromagnetic coil, which consisted of approximately 1000 turns, was located around the disks with the coils encircling them, providing magnetic field lines parallel to the shafts. the mr fluid was loaded into the lower disk. the diameter of the disks was 116 mm and the gap between them was 1 mm. the input and output signals were read and recorded by an national instruments (ni) usb-6281 data acquisition device with a sampling rate of 1 khz. the complete magnetorheological clutch is shown in fig. 2. for future measurements, a 3-phase ac induction motor with a frequency inverter was installed to serve as an artificial load. 2.1 samples and measurements a hall effect sensor, located at the top of the upper disk, measured the magnetic field. an encoder was located at the bottom of the drive shaft of the clutch to measure the input speed. the control and measurement tasks were carried out by a ni usb-6281 data acquisition device controlled by labview software. the input speed and output torque were recorded. the mr fluid used was lord mrf-122eg fluid diluted by 50 m/m% with silicone oil. https://doi.org/10.33927/hjic-2020-12 mailto:hollosi.janos@sze.hu 78 mester and szalai figure 1: model of a disk-type magnetorheological clutch the output side of the clutch was fixed at the torque sensor with the intention of measuring the torque transmission time-constants, so the output speeds at both the sensor and driven shaft were zero. the measurement cycles, using a preset magnetic field, consisted of a 3second-long mixing phase in the absence of a magnetic field, followed by a 6-second-long measurement period with the magnetic field turned on, and finally another 3second-long mixing phase, all at a constant speed. after the cycle, a new speed was set and a new cycle started. the speeds measured were 11.5, 17.5, 23.5, 29.5, 35.5, 40.5, and 46.5 rpm. the magnetic induction was controlled by currents of 1.8, 2.5, 3.3, and 4.4 a applied to the coil, thereafter the corresponding magnetic inductions were 114, 144, 173, and 202 mt. figure 2: complete magnetorheological clutch figure 3: transmission torque from when the magnetic field was turned on at a speed of n = 11.38 rpm and using different magnetic inductions figure 4: transmission torque from when the magnetic field was turned on at a speed of n = 46.5 rpm and using different magnetic inductions 3. results and discussion 3.1 experiments using the aforementioned method, a series of 12 measurements were carried out at each speed and in each magnetic field by taking into consideration the uncertainty of the mechanical parts (toothed belts, bearings, etc.). examples of the measurements can be seen in fig. 3 (n = 11.38 rpm) and fig. 4 (n = 46.50 rpm), as well as a periodicity due to the inaccuracies of the mechanical parts. the maximum output torque was m = 0.85 nm. 3.2 calculation of time constants time constants were determined by fitting an exponential function to the measured data: m(t) = a ( 1− e− t τ ) (1) where m denotes the transmission torque, t represents the time, and τ stands for the time constant. the hungarian journal of industry and chemistry torque transmission time-constant of a disk-type magnetorheological clutch 79 figure 5: cfitted curve of measurements at a speed of n = 46.5 rpm and a magnetic induction of b = 202 mt figure 6: time constants as a function of magnetic induction at different speeds fitting was carried out according to the measurements. an example of the fitting is shown in fig. 5. the fitted curve correlates well with the measurement data. the results of the fitting were averaged to obtain the time constants for the applied magnetic inductions and rotational speeds. the time constants are shown in fig. 6 as a function of magnetic induction. the measured time constants took into account the whole system, including the effects of the mr fluid as well as mechanical parts. by increasing the magnetic field strength, the time constants decreased. in the weakest magnetic field and at the lowest speed, the time constant was extremely high, greater than 1 second to be exact, due to the characteristics of the fluid. the time constants as a function of the speeds are shown in fig. 7. increasing the speed also resulted in a reduction in the time constant that was less significant than in stronger magnetic fields. in strong magnetic fields, the influence of the speed on the time constants was insignificant, therefore, its effect was almost negligible. figure 7: time constants as a function of speed using different magnetic inductions 4. conclusion based on the measurement results, the torque transmission time-constants for our magnetorheological clutch using the mr fluid were obtained. the time constants differed greatly from the response times of a magnetorheological fluid due to the inertia of the mechanical components. in the future, the influence of the mechanical parts on the time constants will be measured. acknowledgements this research was supported by the european union and co-financed by the european social fund under the project efop-3.6.2-16-2017-00002. references [1] rankin, p. j.; ginder, j. m.; klingenberg, d. j.: electroand magneto-rheology. current opinion in colloid & interface science, 1998, 3(4), 373–381 doi: 10.1016/s1359-0294(98)80052-6 [2] olabi, a. g. ; grunwald, a.: design and application of magneto-rheological fluid, mater. des., 2007, 28(10), 2658–2664 doi: 10.1016/j.matdes.2006.10.009 [3] mazlan, s. a. ; ekreem, n. b.; olabi, a. g.: an investigation of the behaviour of magnetorheological fluids in compression mode, j. mater. process. technol., 2008, 201(1–3), 780–785 doi: 10.1016/j.jmatprotec.2007.11.257 [4] lampert, s. g. e. ; van ostayen, r. a. j.: experimental results on a hydrostatic bearing lubricated with a magnetorheological fluid, curr. appl. phys., 2019, 19(12), 1441–1448 doi: 10.1016/j.cap.2019.09.004 [5] törőcsik, d.: some design issues of multi-plate magnetorheological clutches, hungarian j. ind. chem., 2011, 39(1), 41–44 https://mk.uni-pannon. hu/hjic/index.php/hjic/article/view/380 [6] rabinow, j.: the magnetic fluid clutch, trans. am. inst. electr. eng., 1948, 67(2), 1308–1315 doi: 10.1109/t-aiee.1948.5059821 48(1) pp. 77–80 (2020) https://doi.org/10.1016/s1359-0294(98)80052-6 https://doi.org/10.1016/j.matdes.2006.10.009 https://doi.org/10.1016/j.jmatprotec.2007.11.257 https://doi.org/10.1016/j.jmatprotec.2007.11.257 https://doi.org/10.1016/j.cap.2019.09.004 https://mk.uni-pannon.hu/hjic/index.php/hjic/article/view/380 https://mk.uni-pannon.hu/hjic/index.php/hjic/article/view/380 https://doi.org/10.1109/t-aiee.1948.5059821 https://doi.org/10.1109/t-aiee.1948.5059821 80 mester and szalai [7] decsi, p.; mester, s.; szalai, i.: tárcsás magnetoreológiai tengelykapcsoló modellezése, a rendszer időbeli viselkedésének vizsgálata, ogét xxvi. nemzetközi gépészei konferencia 2018, 91–94 hungarian journal of industry and chemistry hungarian journal of industry and chemistry vol. 48(1) pp. 81–85 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-13 optimizing the planning and manufacturing processes of electromagnetic energy harvesting equipment lászló móricz*1 and istván szalai1 1institute of mechatronics engineering and research, faculty of engineering, university of pannonia, gasparich márk u. 18/a, zalaegerszeg, 8900, hungary the main aim of this paper is to create an energy harvesting system, which can convert vibrational energy into electrical energy efficiently. our research was carried out in the field of electromagnetic energy conversion using the principles of linear generator construction for both low and high frequency vibrations. energy can be recovered efficiently. during the measurements, how the induced voltage is dependent on the impulsive frequency and the amplitude of impulses was investigated. keywords: energy harvesting, induced voltage, vibration, linear generator, energy 1. introduction many forms of energy sources exist (vibrational, thermal, wind) in the environment which can be converted into electrical energy with a good degree of efficiency. the harvesting of this energy from the environment has the potential to reduce the rate of depletion of non-renewable energy sources [1] and can be converted by using electromagnetic [2,3], electrostatic [4,5] and piezoelectric [6,7] energy conversion processes. our research was conducted in the field of electromagnetic energy conversion for both low and high frequency vibrations. numerous energy harvesting mechanisms are based on the damped driven harmonic oscillator (ddho) [8]. the essence of the process is to create relative displacement between a permanent magnet and a coil [9]. electric power (energy) is induced in the coil due to changes in magnetic flux. to achieve the relative displacement, the magnet and leading house must come into physical contact which can be achieved mechanically or magnetically [10]. each mechanical system has a mechanical damping factor. if the damping of the system is too low, the device exhibits no resistance to harmonic motion. however, if the value becomes too high, the resistance of the device to motion increases dramatically, thus no relative displacement of the device occurs. both the damping force and relative displacement are essential to convert energy efficiently into the system [11]. one of the most difficult tasks of the design process is to define the appropriate degree of damping that maximizes the extractable efficiency. an important aspect of *correspondence: moricz.laszlo@mk.uni-pannon.hu the design process is the tuning of the natural frequency of the structure. if the impulsive frequency deviates from the resonant frequency, a loss of power can be detected. one possibility is that the bandwidth of operation is enhanced which results in the value of the “quality (q) factor” decreasing and diminishes the amount of extractable energy [5]. to achieve a good degree of efficiency of the system, the harvesting of very low frequency vibrations must be taken into account. regarding energy harvesting systems for low frequency applications, the possibilities of frequency upconversion are introduced and achieved in different ways. ashraf et al. [11] optimized the mechanical design of the system by applying the finite element method to broaden the low frequency range. haroun et al. [9] tried to keep the natural frequency of their system, namely ceh, low. they concluded that if the spring is not fixed to the moving frame (fieh), then the natural frequency of the system is lower than that of the fixed spring system (ceh). 2. design process and evolution of the structure there are two types of generator-based energy harvesting systems: • system 1: based on linear movement • system 2: based on rotational movement the linear generator converts the mechanical movement directly into electrical energy. several basic construction solutions can achieve this, e.g. the linear motors can https://doi.org/10.33927/hjic-2020-13 mailto:moricz.laszlo@mk.uni-pannon.hu 82 móricz and szalai figure 1: mechanical structure of the eh system be straightened versions of permanent magnet motors. the structure chosen is presented in fig. 1. the energy harvesting model was made using solidworks 2016 software. the assembled system is shown in fig. 2. the structure consists of two main parts; the stationary part possesses a coil holder and the moving part was produced from a square section slip. four horseshoe neodymium magnets were mounted on the moving part. the horseshoe magnets consisted of two iron plates and a square neodymium magnet. the thickness of the two iron plates was equal to that of the square neodymium magnet. it is important that the iron plate contains less alloys. the best solution from the options available was to use an iron core of a transformer. to determine the optimum layout of the magnets, the direction of the current vectors (e) must be identical. as the direction of movement of the structure was definite (v), according to the right-hand rule the direction of the magnetic induction vectors (b) must point to the center as shown in fig. 3. figure 2: the assembled system figure 3: optimum layout of the magnets figure 4: schematic structure of the loop test 3. structure of the loop test the equipment for the loop test was provided by the institute of mechatronics engineering and research of the university of pannonia in zalaegerszeg. the schematic structure of the loop test is shown in fig. 4. energy harvesting was executed by a type of labworks et-139 electrodynamic shaker. the induced voltage was displayed by an agilent dso5054a digital oscilloscope. the examined parameters were changed by a function generator, which was connected to a labworks pa-138 amplifier on a vibration table as illustrated in fig. 5. 4. results and analysis 4.1 based on experiments throughout the experiments, the following attributes were examined: figure 5: the set-up of the loop test hungarian journal of industry and chemistry optimizing electromagnetic energy harvesting equipment 83 figure 6: energy-harvesting circuit diagram • maximum induced voltage without load • power without load • load on the power • the impact of the number of coils on the induced voltage and power the examined energy-harvesting circuit diagram is shown in fig. 6. the structure consists of an internal resistance rb and an external resistance rt (load). ptotal = u2 ind rtotal = u2 ind rb + rt (1) um = uind rt rt + rb (2) as a result of the impulsive frequency and amplitude of impulses, electrical energy was induced. the induced voltage was equal to the measured voltage in the absence of external resistance. measured and induced voltages differed when the system was subjected to an external resistance. the relationship between them is described in eq. 2. the maximum power can be determined from eq. 1. 4.2 results initially, the device was tested with 100 turns of the coil. the internal resistance of the coil was 3.1 ω. the impulsive frequency was set between 1 and 20 hz and the amplitude of impulses between 2.5 and 15 mm. during figure 7: induced voltage by applying 100 turns of the coil in the absence of external resistance figure 8: induced voltage by applying 100 turns of the coil in the presence of an external resistance the experiment, a decrease in the induced voltage was observed above 20 hz. thus, the investigated bandwidth was maximized at 20 hz, whereas the trend was still visible in terms of the change in the curves, so 20 measurement points were examined during the experiments. the results are summarized in fig. 7. the maximum induced voltage and power were 986 mv and 322 mw, respectively. during the experiments below, an internal resistance equal to the external resistance was applied to the structure. the applied external resistance was 3.4 ω. the results are summarized in fig. 8. the maximum voltage measured was 520 mv. given the values of the external and internal resistances, the induced voltage was 994 mv based on eq. 2. the maximum power was calculated to be 152 mw from eq. 1. the impact of the external resistance on the power during the experiment, a constant excitation amplitude of 15 mm was applied, while the impact of the resistance on the power was examined. the resistances applied were 1, 3.4, 10, 22, 47 and 74 ω. the relationship between the changes in resistance and power are summarized in fig. 9. as is shown in fig. 9, an exponential decrease in power was observed as the resistance increased. based on previous studies, an external resistance that is smaller figure 9: the relationship between the resistance and power 48(1) pp. 81–85 (2020) 84 móricz and szalai figure 10: induced voltage by applying 240 turns of the coil in the absence of an external resistance than the internal resistance is impractical. ideally, the external resistance would be equal to the internal resistance of the coil. next, the number of turns of the coil was increased from 100 to 240. the other aforementioned variables remained unchanged. the results are summarized in fig. 10. as shown in fig. 11, the maximum induced voltage without a load and the maximum power were 2020 mv and 559 mw, respectively. following the aforementioned procedures, the loaded system was analyzed. the external resistance applied was 8 ω. the maximum voltage measured was 1060 mv. by taking into account the values of the external and internal resistances, the induced voltage was 2020 mv based on eq. 2. based on eq. 1, the maximum power calculated was 268 mw. both the induced voltage and power of the system were doubled by increasing the number of turns of the coil by 60 %, the induced voltage increased from 994 mv to 2020 mv and the maximum power rose from 152 mw to 268 mw to be exact. 5. discussion the aim of the research was based on the principles of linear generator construction and manufacturing. at this stage of the process, it was important that the structure was free of mechanical damping. during the experiment, the structure was examined by means of changing the load resistance and number of turns of the coil in addition to the specified amplitude and frequency. an exponential decrease in the efficiency was observed as the resistance increased. ideally, the external resistance would be equal to the internal resistance of the coil. the induced voltage and the power of the system were doubled by increasing the number of turns of the coil by 60 %. as a result, by increasing the number of turns of the coil by 60 %, the efficiency of the system also increased by approximately 57 %. however, a deeper understanding of the relationship between the efficiency of the structure and variables figure 11: induced voltage by applying 240 turns of the coil in the presence of an external resistance requires further investigation. after doubling the number of turns of the coil, the maximum power generated was 1 w. one advantage of this system in particular is that the neodymium magnets are cheap to produce. applying a series connection to this system results in a sufficient degree of efficiency to operate the electronic devices in cars. 6. conclusion in the aforementioned experiments, the maximum induced voltage and power achieved by applying 240 turns of the coil were 2020 mv and 559 mw, respectively. during the experiments in the presence of a load resistance, the best value of the power was calculated when the external resistance was equal to the internal resistance of the coil. the efficiency of this energy harvesting system can be further enhanced by increasing the number of turns of the coil and the strength of the neodymium magnet. symbols uind induced voltage um measured voltage ptotal power rb internal resistance rt external resistance acknowledgements the project was supported by the european union and co-financed by the european social fund through the project efop-3.6.2-16-2017-00002. references [1] elmes, j.; gaydarzhiev, v.; mensah, a.; rustom, k.; shen, j.; batarseh, i.: maximum energy harvesting control for oscillating energy harvesting systems, 2007 ieee power electronics specialists conference, 2007 doi: 10.1109/pesc.2007.4342461 hungarian journal of industry and chemistry https://doi.org/10.1109/pesc.2007.4342461 optimizing electromagnetic energy harvesting equipment 85 [2] von büren, t.; tröster, g.: design and optimization of a linear vibration-driven electromagnetic micropower generator, sensor actuat. a-phys., 2007, 135(2), 765–775 doi: 10.1016/j.sna.2006.08.009 [3] beeby, s.p.; torah, r.n.; tudor, m.j.; glynnejones, p.; o’donnell, t.; saha, c.r.; roy, s.: micro electromagnetic generator for vibration energy harvesting, j. micromech. microeng., 2007, 117(7), 1257–1265 doi: 10.1088/0960-1317/17/7/007 [4] mitcheson, p.d.; green, t.c.: maximum effectiveness of electrostatic energy harvesters when coupled to interface circuits, ieee t. circuits-i, 2012,59(12), 3098–3111 doi: 10.1109/tcsi.2012.2206432 [5] kiziroglou, m.e.; he, c.; yeatman, e.m.: electrostatic energy harvester with external proof mass, proceedings of powermems, 2007, 117–120 [6] marzencki, m.; basrour, s.; charlot, b.; spirkovich, s.; clin, m.: amems piezoelectric vibration energy harvesting device, proceedings of powermems, 2005, 45–48 [7] isarakorn, d.; briand, d.; janphuang, p.; sambri, a.; gariglio, s.; tricone, j. m.; guy, f.; reiner, j. w.; ahn, c.h.; de rooij, n. f.: energy harvesting mems device based on an epitaxial pzt thin film: fabrication and characterization, technical digest of powermems, 2010, 203–206 [8] niu, p.; chapman, p.: design and performance of linear biomechanical energy conversion devices, (power electronics specialists conference, 2006. pesc ’06. 37th ieee), 2006, 1–6 doi: 10.1109/pesc.2006.1711996 [9] haroun, a.; yamada,i.; warisawa, s.: study of electromagnetic vibration energy harvesting with free/impact motion for low frequency operation, j. sound vib., 2015, 349, 389–402 doi: 10.1016/j.jsv.2015.03.048 [10] móricz, l.; szalai, i.: mágneses lebegtetés elvén működő vibrációs energiaátalakító tervezése és építése, (ogét 2019 xxvii. nemzetközi gépészeti konferencia, nagyvárad, románia), 2019, 352–355 [11] ashraf, k.; md khir, m.h.; dennis, j.o.; baharudin, z.: improved energy harvesting from low frequency vibrations by resonance amplification at multiple frequencies, sensor actuat. a-phys., 2013, 195, 123–132 doi: 10.1016/j.sna.2013.03.026 48(1) pp. 81–85 (2020) https://doi.org/10.1016/j.sna.2006.08.009 https://doi.org/10.1088/0960-1317/17/7/007 https://doi.org/10.1109/tcsi.2012.2206432 https://doi.org/10.1109/pesc.2006.1711996 https://doi.org/10.1109/pesc.2006.1711996 https://doi.org/10.1016/j.jsv.2015.03.048 https://doi.org/10.1016/j.jsv.2015.03.048 https://doi.org/10.1016/j.sna.2013.03.026 hungarian journal of industry and chemistry vol. 48(1) pp. 87–93 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-14 examination of fuel consumption factors, basics of precision and on-board diagnostic measurements tibor busznyák∗1 and istván lakatos1 1department of road and rail vehicles, széchenyi istván university, egyetem tér 1, győr, 9026, hungary in this paper, different factors of fuel consumption are examined. driveload equitation is used as a basis and the parts that handle energy consumption in particular are analyzed. for the purposes of visibility, it was implemented using matlab. in statistical works, fuel consumption data require that the energy consumption of vehicles be analyzed correctly. variables which affect fuel consumption during a given drive are defined. research is analyzed in the second part of the paper where vehicle diagnostics are combined with global positioning. examinations are necessary to create on-board diagnostics-based positioning. keywords: gps, obd, correlation, drive, assistance 1. introduction nowadays, innovation is a key. economical, safetycentred or traffic optimization tasks are increasingly regulated. these criteria require developers to actuate and consequently upgrade their conceptions. new technologies are rapidly emerging so industries have to keep up to date. drive options, including alternative drive solutions, are continuously being updated, the number of driverassistance features is ever-increasing towards a possible fully autonomous level [1]. the role of development focusing on smart city concepts and sustainable traffic is becoming more important. critical aspects of it are efficient energy use (the central question of the present paper), range of online communication systems, autonomous transport systems and conceptions of autonomous vehicles. reliable operation requires cooperation between different participants, e.g. the information technology, urban development and automotive industries. these aspects are interrelated, therefore, a more efficient intelligent transportation system (its) could be realized [2–4]. information technologies between different units of traffic are elementary in terms of automated traffic. the stability of dataflow is unavoidable. communication channels play a key role in everyday life as information is accessed from the internet. as information content defines the quality of data, the demands of traffic quality have recently been increasing. the number of automobiles in hungary has almost doubled over the past twenty years. safety issues and ∗correspondence: busznyaktibor@gmail.com accidents are increasingly commonplace. besides accidents, traffic jams have also become more frequent. as a result, driving has become harder. rush-hour traffic that slowly inches forward, searching for a parking space or simply parking itself put drivers to the test under crowded, metropolitan conditions. the need to avoid similar situations has led to the emergence of driverassistance systems. the quality of data transmissions as well as trouble loggerand indicator systems, which evaluate inputs from sensors or on-board diagnostics, are closely connected to vehicle information. the aforementioned technologies help driver-assistance systems to function. due to information technology and automatization, it is possible to create a vehicle network. one of these networks is the vehicle-to-everything (v2x) communication platform where vehicles communicate with each other along with the infrastructure provider to share information about the locations of traffic jams and avoid congestion. vehicle communication and driver-assistance systems help to improve road traffic safety and make more accurate predictions [5–7]. an important task is to define databases based on the optimization of traffic. several methods, e.g. based on vehicles or infrastructure, are available in order to build a database. if the vehicle investigated predominantly drives in well-maintained, intelligent infrastructure, then the number and complexity of built-in vehicle systems can be reduced. in this case, information is supplied to the vehicle by an uninterrupted connection with external systems. this could also be true of the drive of a vehicle on predefined routes, e.g. buses. it is easier to build infrastructure for https://doi.org/10.33927/hjic-2020-14 mailto:busznyaktibor@gmail.com 88 busznyák és lakatos public transport vehicles because their routes are predefined. on the other hand, a vehicle can be defined as a separate unit. without infrastructure, vehicles rely on built-in sensors and can drive anywhere, external infrastructure is unnecessary. how could the complexity of a given vehicle’s sensor system be reduced? would it be possible to use built-in on-board diagnostics for positioning tasks. basic ideas originate from simple experiences. if people drive uphill in cruise control, the amount of data concerning fuel consumption that appears on the dashboard increases. the core of this research is the possible connection between elevation and fuel consumption: 1. can a connection between elevation data from global positioning and fuel consumption data from on-board diagnostics at a constant or various speeds be identified? 2. is it possible to create a topographic elevation model from fuel consumption data? 3. if it is possible, then the fuel consumption can be predicted from road conditions. 4. by integrating on-board diagnostics into conventional or intelligent transportation systems using the presented relations, a vehicle can be located. connections between data from global positioning systems and fuel consumption are sought. it is necessary to define important variables that affect the fuel consumption of a vehicle. the relevant equations and propulsion power requirements are analyzed. 2. experiment 2.1 propulsion power requirements and fuel consumption – defining variables internal combustion engines function by burning fuel which is blended with air in line with energy requirements. propulsion power is necessary for a vehicle to move but its movement is restricted by various internal and external driving resistances. external driving resistances rolling resistance is fg = µmg (1) the rolling force resists motion when tires are rotating on a given surface. internal and external factors are included in the equation. the external factor is the rolling resistance coefficient which depends on contacting surfaces. the internal factor is the deformation of the tires which is dependent on the load of the vehicle. a loss in power results. power against rolling resistance is pg = fgv (2) aerodynamic drag is fl = cwρav 2/2 (3) drag acts in the opposite direction to which the vehicle is moving. it plays a major role in terms of vehicle dynamics and efficiency. at higher speeds, it is more significant because drag increases with the square of the velocity. power against drag is pl = flv (4) climbing resistance is fe = mg sin(α) (5) climbing resistance depends on the elevation of the route, mass of the vehicle and road gradient. power against climbing resistance is pe = fev (6) internal driving resistances acceleration resistance is fgy = (1 + θ)ma, (7) where θ is a coefficient of rotating components (table 1). energy is required to accelerate. the acceleration resistance can be calculated from the masses of the rotating components and vehicle. power against acceleration resistance is pgy = fgyv (8) other internal resistances, e.g. transmission resistance, are peff = (1− η)ph (9) another internal resistance arises when the transmission system moves and depends on the efficiency of its parts, moreover, it is used to calculate power. this internal resistance is constant and includes the efficiency of the differential (0.93), efficiency of the clutch (0.99), efficiency of the drive shaft (0.99), efficiency of the gearbox (0.97) and efficiency of the bearings (0.98): η = ηtk ηdiff ηkt ηcs ηny (10) finally, energy produced by the combustion of fuel is translated into the energy requirements of given resistances. at constant velocities, the acceleration resistance is zero and transmission resistance constant as well as calculable, as is shown in table 2. thus, the traction force or driveload equitation can be written in the following wellknown form: fv = fe + fg + fl (11) pv = fvv (12) hungarian journal of industry and chemistry examination of fuel consumption factors 89 table 1: values of θ gear [ith] θ 1 0.4 2 0.3 3 0.2 4 0.1 5 0.08 table 2: defined variables known values a, m, g, µ, cw, ρ variables v, α 2.2 matlab implementation the analysis of traction force components was conducted in the matlab development environment to try and define how variations in velocity and road gradient can explain power requirements. an analysis was conducted based on theoretical elements and data were defined by given measurements. vehicle: ford b-max (2014) • empty mass (m) = 1275 kg; • maximum power (pmax, peff ) = 74 kw; • drag coefficient (cw) = 0.32; • frontal area (a) = 2.8 m2; • rolling coefficient (µ) = 0.007 velocity codomain: • v = [0, 140 km/h] road gradient codomain: • α = [0, 30 ◦] figs. 1-3 show the effects of different resistances. the rolling resistance diagram (fig. 1) exhibits a linear trend. the power demand increases as the velocity and road gradient increase. the climbing resistance diagram (fig. 2) also exhibits a linear trend. according to real data, it is necessary to define a power limit, in this case 74 kw, which is the maximum power of the vehicle. analysis above this limit in not required since the engine is incapable of providing more power. on the contrary, the vehicle would decelerate or remain stationary beyond this limit. the air resistance diagram (fig. 3) exhibits a square trend between the velocity and power demand of the vehicle. the power demands of external resistances are presented in fig. 4. important values were compiled in tables 3–5. in the first part of this chapter, constant, discrete velocities were assumed. the next step is the parameterization of acceleration. for this task, values of theta are required (table 1). acceleration codomain figure 1: diagram of the power demand of rolling resistance as a function of velocity and road gradient figure 2: diagram of the power demand of climbing resistance as a function of velocity and road gradient figure 3: diagram of the power demand of air resistance as a function of velocity and road gradient • a = [0, 5 m/s2] gravitational acceleration [g] is a dimensionless, unofficial and descriptive measure. g codomain can be derived from a codomain. the effects of acceleration are shown in fig. 5. it is visible that at predefined shifts, diagram flow refracts and represents real cases. important values are compiled in tables 6–8. 3. results and analyses at high velocities and on steep road gradients, the power demand is also higher. the declaration of variables is necessary as a result of precise planning to follow on-board diagnostics (obd) measurements, especially routes. two independent measurement systems, obd and gps, are 48(1) pp. 87–93 (2020) 90 busznyák és lakatos figure 4: diagram of the power demand of external resistances as a function of velocity and road gradient comparable to connect the concept [8]. precision positioning is widely used and consists of numerous important boundary conditions. this paper examines the obd side of the concept, details of precise gps and gnss measurements are presented in previous papers of ours. a statistical analysis of the fuel consumption database is given from the equation of motion. for this database, work was used, that is the product of the force and displacement in the direction of the force. table 3: notations of v and α variables v(↓) low velocities v(←) medium velocities v(↑) high velocities α(↓) shallow road gradients α(←) medium road gradients α(↑) steep road gradients table 4: values for p [v, α] calculated in the matlab environment v(↓) = 3.6 [km/h] α (↓) = 0◦ p= 0.3064 [kw] α(←) = 5◦ p = 1.178 [kw] α(↑) = 30◦ p = 6.342 [kw] v(←) = 50 [km/h] α (↓) = 0◦ p= 2.824 [kw] α(←)) = 5◦ p = 18.09 [kw] α(↑) = 30◦ p = 74 [kw] v(↑) = 140 [km/h] α (↓) = 0◦ p = 40.78 [kw] αmax (140) = 4◦ p = 74 [kw] α (↑) = α (←) = αmax table 5: p [v, α] matrix p [v, α] v(↓) v(←) v(↑) α(↓) p (↓) p (↓) p (←) α(←) p (↓) p (←) p (↑) α(↑) p (←) p (↑) p (↑) figure 5: diagram of the power demand of acceleration as a function of velocity and g lifting work is wem = fem∆s = mg∆h (13) lifting work is the work that is done by lifting an object over a given period of time. it is proportional to its mass and change in height. friction (or rolling) work is ws = µmg∆s (14) table 6: notation of v and g variables v(↓) low velocities v(←) medium velocities v(↑) high velocities g(↓) low accelerations g(←) medium accelerations g(↑) high accelerations table 7: values for p [v,g] calculated in the matlab environment v(↓)=3.6 [km/h] g(↓)=0.01 p=0.1785 [kw] g(←)=0.1 p=1.185 [kw] g(↑) = 0.3 p = 5.93 [kw] v(←)=50 [km/h] g(↓)=0.01 p=2.142 [kw] g(←)=0.1 p=21.42 [kw] g(↑)=0.3 p=64.26 [kw] v(↑)=140 [km/h] g(↓)=0.01 p=5.508 [kw] gmax(140)=0.1424 p=74 [kw] g(↑)=g(←)=gmax table 8: p [v,g] matrix p [v,g] v(↓) v(←) v(↑) g(↓) p (↓) p (↓) p (←) g(←) p (↓) p (←) p (↑) g(↑) p (←) p (↑) p (↑) hungarian journal of industry and chemistry examination of fuel consumption factors 91 table 9: proportionalities over the period of time wem v, ∆h ws v wgy v2 wk v2 table 10: determination of coefficients constant velocity [km/h] coefficient of determination [r2] 30 0.9549 40 0.9160 50 0.8370 friction work is proportional to its mass and displacement. acceleration work is wgy = 1 2 m∆v2 (15) acceleration work is proportional to its displacement, mass and the square of its velocity. work done by air resistance is wk = 1 2 acwρv 2∆s (16) work done by air resistance is proportional to its displacement, drag coefficient (cw), frontal area (a), density (ρ) and square of its velocity. for the purpose of statistical analysis, proportionalities were compiled in table 9. now the statistical analysis can be conducted. in the first step, a single variable analysis is carried out. previously, a given route was measured, thus gps and obd databases were available. a connection between elevation and fuel consumption data was sought. table 10 shows that the concept is highly usable at low velocities, but when the range of velocities increases, the coefficient of determination becomes less efficient. multivariate analysis provides a solution to this problem. in this case, experienced variables, as summarized in table 9, were used. a route comprised of different road gradients and velocities was examined. a visual check is recommended to summarize the regression model, with which it is possible to forecast correlations according to different predictors (r2). range of velocity = [20, 70 km/h] 1. examination with ∆(v2) • r2 = 57.2% • where ∆(v2) = variation in the square of the velocity. 2. examination with ∆(v2) and ∆h figure 6: results of the multivariate analysis • r2 = 86.4% • where ∆h = change in height. 3. examination with ∆(v2), ∆h and v • r2 = 87.1% • where v = actual velocity. fig. 6 respresents the regression equation with the coefficient of determination. the regression equation can be rewritten in the following form: con = a∆(v2) +b∆h+ cv +d (17) con is an abbreviation of fuel consumption and appears constant. it reflects other possible predictors that have not been examined, for example, losses of the internal combustion engine. 3.1 obd-based positioning a drawback of precision positioning devices on the market are their prices, but the obd connectors are basic, standardized accessories of vehicles. the presented structure, when a connection is made between the positioning and on-board diagnostics, can be used for driver assistance tasks [9]. a matlab implementation of obd-based positioning has been proposed that is connected to the aims of this paper and will be presented shortly. dataflow and the stability of the system with regard to a precision positioning measurement are crucial. its boundary conditions are the following: • connection to 5 gnss satellites simultaneously; • dataflow stability in terms of the satellites and the base; • online connection with the base, from where the correction of data originates. 48(1) pp. 87–93 (2020) 92 busznyák és lakatos figure 7: operation of the matlab algorithm for obdbased positioning while weighing up the risks of two independent measurement methods, it is clear that the precision positioning technique is riskier. a significant safety risk can be reduced if it can be substituted for other alternatives. an alternative to the elevation database of the routes and obd data, which is accessible to every vehicle, may exist. to summarize our matlab implementation, continuously incoming obd data are compared to a reference database which consists of a map with coordinates. by searching for the minima of the squared differences of the two databases, an algorithm was derived that is capable of defining position based on changing trends. fig. 7 presents the operation of the developed algorithm at a constant velocity of 30 km/h. few incorrect obd data points were obtained, for example, at a horizontal displacement of 125 m. as the database of fuel consumption is continuously expanding, the significance of this imprecision is decreasing. 4. conclusion in this article, the driveload equitation was examined and special care taken with regard to its power demands. in the matlab environment, characteristics of different resistances were shown. moreover, the fixing of dependent variables was the main exercise in this research besides understanding the basic connections between onboard diagnostics and precision positioning. obd-based positioning is a possible method to determine the actual position of a vehicle without constantly being connected to gps or gnss. it could be useful as part of v2x or other intelligent transportation systems. in order to extend the concept to electric vehicles, the velocity and road gradient are the main variables, the power demands of both are comparable, and optimal charging points on a given route can be calculated. this could form the basis for a future paper. symbols µ rolling resistance coefficient m mass of moving object g gravitational acceleration v velocity cw drag coefficient ρ density a front surface α road gradient θ coefficient of rotating object a acceleration g gravitational constant η efficiency ηtk efficiency of gearbox ηdiff efficiency of the differential ηkt efficiency of cardan-shaft ηcs efficiency of bearings ηny efficiency of the clutch h altitude s displacement acknowledgements this research was carried out as part of the efop3.6.2-16-2017-00016 project within the framework of the new széchenyi plan. the completion of this project was funded by the european union and co-financed by the european social fund. references [1] takács, á.; rudas, i.; bösl, d.; haidegger, t.: highly automated vehicles and self-driving cars, ieee robotics & automation magazine, 2018, 25(4), 106– 112 doi: 10.1109/mra.2018.2874301 [2] derbel, o.; peter, t.; zebiri, h.; mourllion, b.; basset, m.: modified intelligent driver model for driver safety and traffic stability improvement, ifac proceedings volumes, 2013, 46(21), 744–749 doi: 10.3182/20130904-4-jp-2042.00132 [3] iordanopoulos, p.; mitsakis, e.; chalkiadakis, c.: prerequisites for further deploying its systems: the case of greece, periodica polytechnica transportation engineering, 2018, 46(2), 108–115 doi: 10.3311/pptr.11174 [4] lim, c.; kim, k.; maglio, p. p.: smart cities with big data: reference models, challenges, and considerations, cities, 2018, 82, 86–99 doi: 10.1016/j.cities.2018.04.011 [5] omae, m.; fujioka, t.; hashimoto, n.; shimizu, h.: the application of rtk-gps and steer-by-wire technology to the automatic driving of vehicles and an evaluation of driver behavior, iatss research, 2006, 30(2), 29–38 doi: 10.1016/s0386-1112(14)60167-9 [6] péter, t.; bokor, j.: modeling road traffic networks for control, annual international conference on network technology & communications: ntc 2010, 2010, paper 21, 18–22 isbn: 978-981-08-7654-8 hungarian journal of industry and chemistry https://doi.org/10.1109/mra.2018.2874301 https://doi.org/10.3182/20130904-4-jp-2042.00132 https://doi.org/10.3182/20130904-4-jp-2042.00132 https://doi.org/10.3311/pptr.11174 https://doi.org/10.3311/pptr.11174 https://doi.org/10.1016/j.cities.2018.04.011 https://doi.org/10.1016/j.cities.2018.04.011 https://doi.org/10.1016/s0386-1112(14)60167-9 examination of fuel consumption factors 93 [7] péter, t.; bokor, j.: new road traffic networks models for control, gstf international journal on computing, 2011, 1(2), 227–232 doi: 10.5176/2010-2283_1.2.65 [8] sun, q.; xia, j.; foster, j.; falkmer, t.; lee, h.: pursuing precise vehicle movement trajectory in urban residential area using multi-gnss rtk tracking, transportation research procedia, 2017, 25, 2356– 2372 doi: 10.1016/j.trpro.2017.05.255 [9] busznyák, t.; pálfi, g.; lakatos, i.: on-board diagnostic-based positioning as an additional information source of driver assistant systems, acta polytechnica hungarica, 2019, 16(5), 217–234 issn: 1785-8860 48(1) pp. 87–93 (2020) https://doi.org/10.5176/2010-2283_1.2.65 https://doi.org/10.1016/j.trpro.2017.05.255 hungarian journal of industry and chemistry vol. 48(1) pp. 95–107 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-15 brownian dynamics simulation of chain formation in electrorheological fluids dávid fertig*1, dezső boda1, and istván szalai2,3 1department of physical chemistry, university of pannonia, egyetem u. 10, veszprém, 8200, hungary 2institute of physics and mechatronics, university of pannonia, egyetem u. 10, veszprém, 8200, hungary 3institute of mechatronics engineering and research, university of pannonia, gasparich márk u. 18/a, zalaegerszeg, 8900, hungary brownian dynamics (bd) simulations based on a novel langevin integrator algorithm are used to simulate the dynamics of chain formation in electrorheological (er) fluids that are non-conducting solid particles suspended in a liquid that has a dielectric constant different from that of the er particles. an external electric field induces polarization charge distributions on the spheres’ surfaces that can be modeled as point dipoles in the centers of the spheres. the interaction of these aligned dipoles leads to formation of chains and other aggregates in the er fluid. in this work, we introduce our methodology and report results for various quantities characterizing the structure of the er system as obtained with bd simulations. these quantities include the potential energy, diffusion constant, average chain length, chain length distributions, and pair correlation functions. their behavior as a function of time is presented as the electric field is switched on. the properties of the er fluid change considerably making this system a potential basic material of many applications. keywords: electrorheological fluids, chain formation, brownian dynamics 1. introduction electrorheological (er) fluids are [1] suspensions of fine non-conducting solid particles in an electrically insulating liquid. if the particles, imagined as closely spherical, have a dielectric constant that is different from that of the solvent, the arising dielectric boundaries respond to an applied electric field. this dielectric response is the polarization of the spheres resulting in a polarization charge distribution whose dominant component in the multipole expansion is the dipole moment. the interactions of these dipoles then lead to a structural change in the er fluid known as the er response. this structural change is basically a formation of chains and other forms of clusters as the polarized spheres are linked together into head-to-tail positions. this structural phase transition is reversible and relatively fast. this structural change results in a dramatic change in the physical properties of the er fluid of which the most important is viscosity. this externally controllable, fast and reversible change in viscosity makes er fluids a kind of a smart material, a central component of devices, such as brakes, clutches, dampers, and valves [2,3]. such devices have crucial importance in the industry of various fields. *correspondence: fertig.david92@gmail.com the continuously shrinking size of devices resulted in the development of nanotechnology. understanding the molecular mechanisms behind the workings of nanodevices is especially important because better understanding of microscopic mechanisms can lead to novel designs. er devices are also based on microscopic mechanisms leading to an emergent macroscopic pattern. no wonder that many modeling studies [4–22] aimed at investigating the microscopic processes behind chain formation and corresponding changes in measurable physical properties. the properties of the er fluid in the absence of an applied electric field have been investigated by heyes and melrose [23]. this means the investigation of the core potential that is either the lennard-jones (lj) fluid or its cut-and-shifted version that is a purely repulsive potential. it has been demonstrated that the repulsive version reproduces experimental behavior better [4]. cluster formation has been investigated via cluster size distribution [4, 9, 11, 12, 20, 22], order parameters [12–15,19], mean square displacement and diffusion constant [4, 6, 12], pair distribution functions [6, 12], and relaxation times [5, 11, 12, 21]. in particular, cao et al. [21] identified relaxation times corresponding to various subprocesses such as initial aggregation, chain formation, and column formation. identifying these subprocesses is https://doi.org/10.33927/hjic-2020-15 mailto:fertig.david92@gmail.com 96 fertig, boda, and szalai e 0 p ε in ε out + + + + + σ figure 1: sketch of an er particle in an external electric field, e0. the dielectric constant inside the sphere is εin, while outside the sphere is εout. the surface charge distribution, σ(r), induced on the dielectric boundary (eq. 1) can be approximated by a point dipole, p, in the center of the sphere (eq. 2). also our long-term goal. it is also our intention to simulate the er system in the presence of shear as several authors did [5, 6, 10, 15, 21]. these authors investigated shear stress, various terms of viscosity, oscillatory strain, and dependence on strain rate. in this paper, we do not apply stress, because our main interest is to study the dynamics of the formation of chains with a newly developed simulation package based on a novel langevin integrator [24–26] as opposed to most studies from the 1990s that used the overdamped limit. we intend to test the program on the er fluid in the absence and presence of an applied electric field and to follow the dynamics of chain formation when the field is switched on. we characterize this dynamics by plotting energy, mean square displacement, diffusion constant, average chain length, chain length distributions, and radial distribution functions as functions of time. we use reduced units in this study (see section 4) that are closely related to various parameters used in the literature. these parameters characterize the relations of various effects in the er fluid. these effects are the polarization (dipole-dipole), thermal, and viscous forces. the relation of the polarization and thermal forces is often denoted by λ and it practically corresponds to the square of the reduced dipole moment used in this study. it expresses the relation of the ordering effect of electrostatic forces and the disordering effect of thermal motion. the relation of the viscous force to the electrostatic force is called the mason number (ma). many authors plot the characteristic physical quantities as functions of the mason number [5,10,15]. the relation of the viscous and the electrostatic forces is called the péclet number. . 2. model: the polarizable dielectric sphere we model the er fluid as dielectric spheres of dielectric constant εin inside the sphere immersed in a fluid of dielectric constant εout (fig. 1). the radius of the spheres is r, while their diameter is d = 2r. when a constant electric field, e0 is applied to this system (in the z direction), the dielectric boundary on the sphere’s surface becomes 0 π/8 π/4 3π/8 π/2 θ -0.004 -0.002 0 0.002 in te rm o le c u la r p o te n ti a l permanent dipoles polarizable dipoles surface charge e 0 e 0 e 0 θ figure 2: interaction potential (arbitrary unit) between two dipoles at r = 1.25d distance from each other at different mutual positions characterized by angle θ that is the angle between e0 and rij . the potential is computed from the interaction of the charge distributions in eq. 1 using the icc method (symbols), from the interactions of the permanent point dipoles induced only by e0 (eq. 2) (dashed line), and from the interaction of the polarizable dipoles when the sphere can be polarized by the electric field of other dipoles too (solid line). polarized. the polarization charge density is σ(θ) = 3ε0 ( εin − εout εin + 2εout ) e0 cos θ, (1) where e0 = |e0|, θ is the angle between the point of on the surface and the z-axis, and ε0 is the permittivity of vacuum. as it was discussed in our previous publication [30], the effect of this surface charge distribution can be approximated with an ideal point dipole placed in the center of the sphere computed as [31] p = 4πε0 ( εin − εout εin + 2εout ) r3e0. (2) in that paper, we showed that the point dipole model is a good approximation to the exact solution obtained from the polarization charge using the induced charge computation method [32]. the agreement is better if the spheres are assumed to be polarizable by the electric fields of all the other particles, but even if it is assumed that an er particle is polarized only by e0, the agreement is reasonable (fig 2). the latter assumption means that the er particles carry only the permanent dipoles of eq. 2 that always point into the z-direction. we further assume that the characteristic time of the rearrangement of the surface charge as the particles move is much smaller than the characteristic time of the rotation of the particles. this means that the p dipole always points into the z direction even if the sphere rotates, because the induced charges (that chiefly correspond to polarization of solvent molecules around the sphere) always have enough time to rearrange themselves according to the applied field, e0. the potential produced by a dipole pj (that is at rj) hungarian journal of industry and chemistry brownian dynamics simulation of chain formation 97 at the position ri of another dipole pi is φj(ri) = 1 4πε0 pj · rij r3 ij , (3) where rij = ri − rj and rij = |rij |. the electric field is ej(ri) = 1 4πε0 3nij(nij · pj)− pj r3 ij , (4) where nij = rij/rij . the interaction potential between the two dipoles is udd ij (rij ,pi,pj) = −pi ·ej(ri) = = − 1 4πε0 3(nij · pi)(nij · pj)− pi · pj r3 ij , (5) while the force exerted on dipole pi by dipole pj is fdd ij (rij ,pi,pj) = −(pi · ∇i)ej(ri) = = 1 4πε0 1 r4 ij {3 [pi(nij · pj) + pj(nij · pi)+ + nij(pi · pj)]− 15nij(nij · pi)(nij · pj)} . (6) note that the forms of these equations are simplified when all the dipoles of magnitude p are aligned in the z direction: udd ij (rij , θ) = − p2 4πε0 3 cos2 θ − 1 r3 ij , (7) and fdd(rij , θ) = 3p2 4πε0 (2 cos θ)k + (1− 5 cos2 θ)nij r4 ij , (8) where k is the unit vector in the direction of the z-axis and θ is the angle between k and nij . there is also a torque acting on the dipole, but because the characteristic time of polarization charge formation is much smaller than the characteristic time of the rotation of the sphere, the rearrangement of surface charges is considered instantaneous without inertia. the torque, therefore, has been neglected. the full interaction potential between two er particles consists of this dipole-dipole (dd) term and a shortrange core potential that defines the finite size of the particles: uij = udd ij + uwca ij . (9) for the core potential, we use the cut & shifted lj potential also known as the weeks-chandler-anderson (wca) potential that is uwca ij (rij) = { ulj ij (rij) + ulj ij (rc) if rij < rc 0 if rij > rc , (10) where ulj ij (rij) = 4εlj [( d rij )12 − ( d rij )6 ] (11) is the lj potential. the wca force is fwca ij (rij) = { flj ij (rij) if rij < rc 0 if rij > rc , (12) where flj ij (rij) = 24εlj [ 2 ( d rij )12 − ( d rij )6 ] rij r2 ij (13) is the lj force. in these equations the cutoff distance is rc = 21/6d that is at the minimum of the lj potential, so this potential is a smooth repulsive core potential used widely in dynamical simulations of large spherical particles. 3. method: brownian dynamics simulation when it comes to simulating the trajectories of particles in the phase space interacting with each other via a systematic force, fij (like those given in eqs. 6 and 12), we use newton’s equation of motion in an md simulation. in this case, the particles move in vacuum and the only forces that we take into account are those exerted by the particles themselves (plus, possibly, external forces). when it comes to simulating the trajectories of particles immersed in a solvent, we use langevin’s equations of motion [33] m dvi(t) dt = fi (ri(t))−mγvi(t) + ri(t), (14) where ri, vi, m, and γ are the position, the velocity, the mass, and the friction coefficient of particle i, respectively. the mass and the friction coefficient are assumed to be the same for every particle, but, in general, they can depend on i. the force has three components. in addition to the systematic force, fi (ri(t)) = ∑ j 6=i fij , there are the frictional force,−mγvi(t), and the random force, ri(t). the former describes friction, while the latter describes random collisions with surrounding solvent molecules. the two additional forces represent the interactions with the heat bath and are coupled through the friction coefficient: 〈r(t)〉 = 0 (15) 〈r(t) ·r(t′)〉 = 2ktmγδ(t− t′) (16) this is also known as the fluctuation–dissipation theorem. the langevin equation is a stochastic differential equation that is solved numerically and, therefore, approximately. several algorithms exist in the literature for its integration [34–37]. here, we employ the simple and effective algorithm of grønbech-jensen and farago (gjf). the original version [24] had a verlet-type formalism. recent modifications by farago (gjf-f) [25] and grønbech jensen and 48(1) pp. 95–107 (2020) 98 fertig, boda, and szalai table 1: reduced quantities quantity symbol unit quantity reduced quantity time t t0 = d √ m kt t∗ = t d √ kt m distance r r0 = d r∗ = r d density ρ ρ0 = 1 d3 ρ∗ = ρd3 velocity v v0 = d t0 = √ kt m v∗ = v √ m kt energy u u0 = kt u∗ = u kt force f f0 = kt d f ∗ = fd kt dipole moment p p0 = √ 4πε0ktd3 p∗ = p√ 4πε0ktd3 friction coefficient γ γ0 = 1 t0 = 1 d √ kt m γ∗ = γt0 = γd √ m kt . grønbech-jensen (gjf-2gj) [26] have a leap-frog formalism using velocities in the half time steps. these modifications have the advantage that they accurately sample both kinetic and configurational properties even for large time steps within the stability limit. the authors demonstrated the efficiency of their algorithms for systems under linear and harmonic potentials. we use the gjf-2gj version in this work that reads as vn+ 1 2 = avn− 1 2 + √ b∆t m fn + √ b 2m ( rn −rn+1 ) (17) rn+1 = rn + √ bvn+ 1 2 ∆t, (18) where rn = r(tn) is any position coordinate of any particle, vn = v(tn) is any velocity coordinate of any particle, a = 1− γ∆t/2 1 + γ∆t/2 , (19) b = 1 1 + γ∆t/2 , (20) ∆t is the time step, tn+ 1 2 = tn+ ∆t 2 , and tn− 1 2 = tn−∆t 2 . the discrete time noise rn+1 = ∫ tn+1 tn r(t′)dt′ (21) is a random gaussian number with properties 〈rn〉 = 0 (22) and 〈rmrn〉 = 2ktγm∆tδmn (23) with δmn being the kronecker-delta. 4. scaling and reduced units competing effects exist in an er system. the dd interactions have an ordering effect. the head-to-tail position, in which the dipoles are aligned along nij (θ = 0) at contact (rij = d), has a minimum energy with the value u0 = − 1 4πε0 2p2 d3 . (24) the magnitude of the force in this position is f0 = 3p2 4πε0d4 . (25) the brownian motion has a disordering effect that expresses the coupling to a thermostat of temperature t and friction with the surrounding solvent with viscosity η. it is usual to characterize the disordering effect of the thermal motion energetically by kt . it is also usual to use reduced units in calculations. in reduced units our quantities are expressed as dimensionless numbers obtained by dividing a quantity in a physical unit by a unit quantity in the same unit, t∗ = t/t0, for example. reduced quantities are useful not only because their values are close to 1, so it is easier to work with them, but also because they express relations between quantities in the numerator and the denominator, a kind of scaling [5]. there are different ways of defining reduced units. we use the convention of building the unit quantities from the mass, m, the particle diameter, d, and kt . thus, the reduced units collected in table 1 can be defined. when we perform simulations in reduced units, these quantities can be chosen freely to see how the system behaves at the different combinations of the reduced parameters. how the reduced parameters are related to real-life physical parameters can be computed independently (see section 5). hungarian journal of industry and chemistry brownian dynamics simulation of chain formation 99 table 2: experimental parameters [38, 39]. εin 4 εout 2.7 η (pa s) 0.5 e0 (v/m) 106 t (k) 300 ρout (kg/m3) 2650 the reduced quantities collected in table 1 are determined by the real physical parameters of the system: the temperature, t , the mass density of the material of the er particle, ρin, the diameter of the er particle, d, the dielectric constant of the er particle, εin, the dielectric constant of the solvent, εout, the viscosity of the solvent, η, and the strength of the applied electric field, e0. for a specific er fluid, these variables are tabulated in table 2. this specific example is used because one of the coauthors (i.sz.) published experimental results for this system [38, 39]. a wide variety of er fluids exists, however. the mass of a particle is computed asm = ρinπd 3/6, so it scales with d3. the dipole moment of a particle is given by eq. 2 that shows that p scales with d3. an important parameter is the ratio of the dipolar energy and the thermal energy that is expressed by the square of the reduced dipole moment: (p∗)2 = πε0e 2 0 4kt ( εin − εout εin + 2εout )2 d3 = kd3 (26) that scales with d3. if p∗ is large, the dipolar interactions are strong enough to induce chain formation. if p∗ is too large, the chains freeze, and the er particles solidify (note that the fluid itself does not solidify). if p∗ is small, thermal motion prevents chain formation and/or breaks the chains. the friction coefficient can be computed from stokes’ law as γ = 3πηd m = 18η ρin d−2. (27) so it scales with d−2. the value of γ∗ describes the strength of the coupling with the solvent and it scales with d1/2. if γ∗ is large, friction and the disordering effect of the random force are strong. the diffusivity of the particles in the fluid, therefore, will be smaller. the diffusion constant in the high coupling limit can be expressed by einstein’s relation: d = kt mγ , (28) or, in reduced units,d∗ = 1/γ∗. if γ∗ → 0, the frictional and the random forces vanish, and the langevin equation goes into the newton equation. the particles move in vacuum without a thermostat; this practically corresponds to an md simulation in the microcanonical ensemble. if γ∗ is small, we talk about an md simulation with a langevin thermostat. in the case of the er fluids, we are in the regime of large γ∗. as we will see, γ∗ is in the order of 104 − 106. in this case, our concern is how to make the simulation efficient in order to collect enough information about the dynamics of the system in a reasonable amount of computer time. the parameter with which we can tune the speed of sampling is the time step, ∆t∗. this parameter is also subject of optimization. if ∆t∗ is too small, the simulation will evolve slowly at the price of expensive computation time. if ∆t∗ is too large, the spheres might overlap and the repulsive core force (eq. 12) becomes so large that the particles shoot apart resulting in unphysical movements. this leads to instabilities in solving the langevin equation. various solutions have been proposed in the literature to cope with this problem. if the langevin integration algorithm allows changing the time step during the simulation, it is a reasonable suggestion to reduce the time step if we observe problems (generally, big jumps) in the movements of particles [6,13]. displacements, velocities, or forces can be monitored for unusual events. berti et al. [40] used a uniform time step, while their solution for the jump-problem was that they went back the necessary number of time steps and started again with a different random number seed for the random force. if such a problem is rare, this can be a good solution, because the computational cost of going back a couple of times is balanced by the large time step used in the simulation. they used their simulations for ion channels whose selectivity filter is a high-density region, so overlaps can occur. chain formation in the er fluid also brings particles close to each other, so we need to be careful with large time steps. we can estimate in advance the danger of overlap and judge the optimization between slow simulations (small ∆t) and jumping particles (large ∆t). we can introduce the average distance that a particle moves in a time step with the average thermal velocity, v̄ = √ 3kt/m. let us introduce ∆s∗ = v̄∆t d = √ 3∆t∗, (29) that characterizes the average distance with respect to the particle size. this is proportional to ∆t∗. this reduced distance, and, consequently, the reduced time step should be smaller than 1. this imposes a strict limit to the time step. the product γ∆t = γ∗∆t∗ characterizes how close we are to the overdamped limit. basically, at a fixed γ∗, we can increase ∆t∗ up to the threshold limit to save computer time at the price of losing information about dynamics due to coarser time resolution. the last parameter that we can choose relatively freely is the energy parameter of the lj potential, εlj, see eqs. 10–12. changing this parameter practically changes the effective diameter of the particles. fig. 3 shows the curves of the core potential (eq. 10) for varying values of εlj. smaller values of εlj allows for the particles to 48(1) pp. 95–107 (2020) 100 fertig, boda, and szalai 0.4 0.6 0.8 1 1.2 r/d 0 2 4 6 8 10 u c o re (r )/ k t ε lj =1kt ε lj =10 -1 kt ε lj =10 -2 kt ε lj =10 -3 kt ε lj =10 -4 kt ε lj =10 -5 kt figure 3: the core potential, uwca(r), for varying energy parameters, εlj. approach each other closer: the r/d values at which the core potential reaches large values in kt are smaller for smaller εlj values. the effective diameter, deff , therefore decreases with decreasing εlj. this results in larger dipole-dipole interactions at contact positions that, in turn, increases the weight of the dipolar interactions with respect to the thermal noise. using smaller εlj, and, consequently, smaller deff , however, makes our parameter dwith which we reduced every variable meaningless. we would like the diameter used in the reduced quantities to be the real diameter of the spheres. for this reason, we do not change εlj and fix it at the value of kt . 5. relating reduced units to real er fluids to connect to a real system, we consider the er fluid studied by horváth and szalai [38, 39] experimentally. the experimental parameters are collected in table 2. note that the diameters used in these studies were quite small in order to prevent sedimentation. diameters used in other er fluids are larger reaching 1 µm. we change two parameters in this analysis, the particle diameter, d, and the reduced time step, ∆t∗. according to eq. 2, the dipole moment can be written as p = kd3, where k = 1.922 × 10−6 cm−2 for the parameters in table 2. table 3 contains various quantities computed for different values of d. it is seen that p∗ falls into the regime simulated in this study around d = 1 µm. for diameters below 100 nm, at least, at the present value of k, the reduced dipole moment is too weak to counterbalance the thermal motion and to produce considerable chain formation. the reduced friction coefficient also depends on d; it increases with d1/2. it is in the regime of γ∗ ≈ 105−106. this looks simulatable, though it will require considerable computer time, because ∆t∗ is limited. the parameter ∆s∗ is the same for every diameter; it practically equivalent to ∆t∗. to look at the effect of ∆t∗, we show the same data for varying ∆t∗ at a fixed d (100 nm) in table 4. table 3: change of various variables as the diameter of spheres is changed from 10 to 10,000 nm for time step ∆t∗ = 0.001. d (nm) 10 100 1,000 10,000 ∆t∗ 0.001 m (kg) 1.387e-21 1.387e-18 1.387e-15 1.387e-12 t0 (s) 5.788e-09 1.830e-06 5.788e-04 1.830e-01 v̄ (m/s) 2.993e+00 9.463e-02 2.993e-03 9.463e-05 p (cm) 1.922e-30 1.922e-27 1.922e-24 1.922e-21 p∗ 0.00283 0.0896 2.833 89.60 ∆t (s) 5.788e-12 1.830e-09 5.788e-07 1.830e-04 ∆s∗ 0.00173 0.00173 0.00173 0.00173 γ (1/s) 3.396e+13 3.396e+11 3.396e+09 3.396e+07 γ∗ 1.966e+05 6.216e+05 1.966e+06 6.216e+06 γ∆t 1.966e+02 6.216e+02 1.966e+03 6.216e+04 table 4: change of various variables as the reduced time step ∆t∗ is changed from 0.0001 to 0.1 for diameter d = 100 nm. d (nm) 100 ∆t∗ 0.0001 0.001 0.01 0.1 m (kg) 1.387e-18 1.387e-18 1.387e-18 1.387e-18 t0 (s) 1.830e-06 1.830e-06 1.830e-06 1.830e-06 v̄ (m/s) 9.463e-02 9.463e-02 9.463e-02 9.463e-02 p (cm) 1.922e-27 1.922e-27 1.922e-27 1.922e-27 p∗ 0.0896 0.0896 0.0896 0.0896 ∆t 1.830e-10 1.830e-09 1.830e-08 1.830e-07 ∆s∗ 0.000173 0.00173 0.0173 0.173 γ (1/s) 3.396e+11 3.396e+11 3.396e+11 3.396e+11 γ∗ 6.216e+05 6.216e+05 6.216e+05 6.216e+05 γ∆t 6.216e+01 6.216e+02 6.216e+03 6.216e+04 6. results and discussion in this study, we use a relatively small number of particles (n = 128) in order to save on computer time and be able to explore a wide range of parameters in reduced units. we also fix the packing fraction expressed in term of the reduced density at ρ∗ = 0.05. at these values the width of the simulation cell is l = 13.68 d. the computer code has been written (in fortran) in a way that we perform m0 time steps in the absence of applied electric field (e0 = 0), and me time steps in the presence of it. that way, we can study the dynamics of chain formation after the electric field is switched on. to improve statistics, we can perform several of this mc = m0 +me cycles and average over the cycles. when we start a cycle over, we can choose between two options. we can either continue the simulation from the previous phase state point (configurations and velocities) only without dipoles, or we can restart from a freshly generated initial configuration. in this work, we choose the second option. this choice ensures that we start the simulation with nonzero e0 in a completely disordered state without chains. the first option makes it possible to study the dynamics of the deconstruction of the chains. hungarian journal of industry and chemistry brownian dynamics simulation of chain formation 101 figure 4: typical snapshot of a simulation from the front (perpendicular to the z axis, left panel) and top (parallel to the z axis, right panel) for a state when chains are formed. 6.1 quantities studied as the chains are being formed, certain physical quantities change, so they directly or indirectly characterize chain formation quantitatively. in chains, particles are aligned into head-to-tail position along the z-axis as shown in fig. 4. there are longer and shorter chains and the distribution of chains of various lengths changes continuously as the simulation evolves. since the head-to-tail position is the lowest energy configuration of the er spheres (see fig. 2 and eqs. 24 and 25), the average one-particle dipole-dipole energy, 〈udd〉b/kt , is a good indicator of chain formation. as it turns out, it is the best converging indicator. by average, we mean average over a block in the simulation, denoted by 〈. . . 〉b. the length of a block (mb is the number of time steps in a block), again, is a subject of optimization. if a block is too short, the physical quantities averaged over a block will have bad statistics. if a block is too long, we loose information about the dynamics of the system. diffusion constant when the particles are “frozen” into chains, their mobility decreases. chains are frozen only at very large dipole moments, when even columnar structures are formed. in a moderate range of (p∗)2, chains move around, break apart, and rejoin, see the video clip at https://youtu.be/owxsuz6p0w4. a snapshot of this video clip is shown in fig. 5. the isotropic diffusion constant is computed as the slope of the mean square displacement (msd) as a function of time: db = 〈r2(t)〉b 2tb , (30) where 〈. . . 〉b denotes an average over time steps in a block and particles and tb is the length of the block in time. the exact equilibrium diffusion constant is obtained in the limit of tb →∞. here, we must be satisfied with an approximate value of db obtained over a block of limited length. fig. 6 shows the msd as a function of t∗ for six equidistantly chosen blocks. in this particular case, γ∗ = 5000, so the slope is d∗ = msd/t∗b ≈ 0.0002 for the wca fluid as figure 5: a snapshot of the video clip at https://youtu.be/owxsuz6p0w4. 48(1) pp. 95–107 (2020) https://youtu.be/owxsuz6p0w4 https://youtu.be/owxsuz6p0w4 102 fertig, boda, and szalai 0 200 400 600 800 1000 t* 0 0.05 0.1 0.15 0.2 m s d 1 2 3 4 5 6 figure 6: the mean square displacement for six selected blocks. the blocks are selected in equidistant time periods in way that the first three belong to the e = 0 phase, while the second three belongs to the er phase. parameters: (p∗)2 = 6, γ∗ = 5,000, ∆t∗ = 0.02,mb = 50,000. also expressed by the einstein relation (d∗ = 1/γ∗, eq. 28). here, the time-length of the block is t∗b = ∆t∗mb = 1,000, because ∆t∗ = 0.02 and mb = 50,000. the first three lines are in the e = 0 regime, while the second three lines are in the er regime. the slope apparently is smaller in the er case than in the wca case, but the scattering is large. the sampling can be improved by averaging over cycles, but this does not help on the problem of the diffusion constant being approximate obtained for a too short block. chain length distributions the chain formation can be directly followed by identifying chains in every configuration. if that is done, we can obtain the number of chains, ns, having length s. the average chain length can be computed as l = ∑ s sns∑ s ns . (31) 10000 20000 30000 40000 50000 t* 2 4 6 8 10 a v e ra g e c h a in l e n g th λ e =0.5 λ e =0.7 λ g =1.1 λ g =1.2 figure 7: the trend of the change in the average chain length with various definitions of a chain: energetic with λe = 0.5 and 0.7, geometrical with λg = 1.1 and 1.2. parameters: (p∗)2 = 6, γ∗ = 10,000, ∆t∗ = 0.01, mb = 10,000. 5 10 15 20 chain length 0 1 2 3 4 5 c h a in l e n g th d is tr ib u ti o n 10000 < t* < 250000 25000 < t* < 65000 65000 < t* < 100000 figure 8: chain length distribution averaged over three time intervals at the beginning (10,000 < t∗ < 25,000), in the middle (25,000 < t∗ < 65,000), and at the end (65,000 < t∗ < 100,000) of chain formation. parameters are the same as at fig. 7. this quantity than can be averaged over time steps in a block, so chain formation can be followed by plotting the average chain length, 〈l〉b, as a function of time in steps of t∗b. a chain, however, can be defined in various ways. one simple definition is geometrical. if two particles are closer to each other than a predefined distance: rij < λgd, (32) they are said to be part of the same chain. another definition is energetic. if the dipole-dipole interaction energy is smaller than a predefined threshold: udd ij (rij , θ) < λeu0, (33) then they are said to be part of the same chain, where u0 is the dd interaction energy in the head-to-tail position (eq. 24). fig. 7 shows the increase of the average chain length as a function of time as obtained from different chain definitions and thresholds λe and λg. in general, the trends as shown by the various definitions are the same. the dynamic process of chains breaking up and reforming have the same effect in the cases of the various definitions. this process can be characterized by time constants obtained from fitting exponential functions. these time constants are insensitive to the choice of the chain definition. here, we will use the geometrical definition with the parameter λg = 1.2. the geometrical definition is advantageous, because it can also be used in the absence of an electric field. the average chain length is an informative, but averaged quantity. from the simulations, we have the more detailed ns vs. s chain length distributions that give the average number of chains of different lengths as a function of s. this function varies with time, see the video clip at https://youtu.be/owxsuz6p0w4. to show the dynamics of this function, we average it for three distinct time intervals. the first one refers to the hungarian journal of industry and chemistry https://youtu.be/owxsuz6p0w4 brownian dynamics simulation of chain formation 103 0 200 400 600 800 1000 t* 0 2 4 6 8 10 a v e ra g e c h a in l e n g th 6-12 13-20 210 5 10 15 20 a v e ra g e c h a in l e n g th 2 3 4 5 figure 9: the variation of the number of chains of various lengths in time. top: chains of lengths 2, 3, 4, and 5. bottom: number of chains belonging to the ranges 6−12, 13 − 20, and above 21. parameters are the same as at fig. 7. beginning of the time period in the presence of the field when the chains start forming. in the second, intermediate time interval (25,000 < t∗ < 65,000) longer chains are formed, while in the third time interval (65,000 < t∗ < 100,000), full chains crossing the simulation box are formed. fig. 8 shows these three time-averaged functions. at the beginning, there are many pairs and short chains (black curve). in the intermediate time interval, the number of short chains decreases and longer chains are formed. in the third time interval, a well-defined peak at s = 14 appears that corresponds to the full chains crossing the simulation box of length l = 13.68d. we can get a much better impression of the dynamics of chain formation, if we plot ns as a function of time. because there are too many possible ns numbers to plot, again, we average over certain regions of chain lengths as seen in fig. 9. in the top panel, the behavior of short chains from pairs to s = 5 is shown. the behavior of these chains is qualitatively similar. first, as the electric field is switched on, their numbers increase abruptly, then, as longer chains absorb them, or they fuse into longer chains, their numbers gradually decreases. practically, they behave like reactive intermediates in chemical reactions: their formation is a first necessary step towards the formation of the end products. the number of chains whose lengths are between 6 and 12 (bottom panel) behaves similarly. the curve for the chains whose lengths are between 13 and 20, however, saturates around ns = 4. this means that there are 1 2 3 4 5 6 r* 1 10 r a d ia l d is tr ib u ti o n f u n c ti o n 0 < t* < 10000 10000 < t* < 25000 25000 < t* < 65000 65000 < t* < 100000 figure 10: radial distribution functions averaged over four time intervals in the absence of the electric field (0 < t∗ < 10,000), at the beginning (10,000 < t∗ < 25,000), in the middle (25,000 < t∗ < 65,000), and at the end (65,000 < t∗ < 100,000) of chain formation. parameters are the same as at fig. 7. generally about 4 full chains in the simulation box (this value, of course, depends on system size and packing fraction). they are often accompanied by shorter chains as seen in fig. 4 and the video clip. chains longer than 20 also exist. it can also occur that two chains are stuck together. whether it is a stable, long time-span configuration, depends on the strength of the dipole moment (the electric field, in reality). a particle is attracted to another particle in a chain, if they are aligned in a way that θ = π/4, see fig. 2. this is a relatively weak attraction compared to the head-to-tail position. the chains displace due to thermal motion, so the chains move out of these mutual positions that favors aggregation of chains. if two chains move in a way that the particles get next to each other (θ = π/2), a repulsive force replaces the weak attractive one. so, a strong dipole moment is needed to overcome the thermal motion if we want to see stable columnar aggregations of chains as seen many times in the literature. pair distribution functions as particles aggregate into chains, the structure of the fluid, generally expressed with pair distribution functions, changes. in an anisotropic dipolar fluid, we generally use the series expansion of the pair correlation function of axially symmetric molecules as g(ij) = ∑ nml hmnl(rij)u mnl(ij). (34) this expansion separates distance and angular dependence in such a way that the projections hmnl(rij) depend only on the distance of particles and the projections umnl(ij) are rotational invariants. the projection g(rij) = h000(rij) is the usual radial distribution function (rdf): g(rij) = ∫ g(ij)dωidωj , with u000 = 1, (35) 48(1) pp. 95–107 (2020) 104 fertig, boda, and szalai 0 1 2 3 4 5 6 r* 1 10 100 r d f i n t h e x y p la n e 0 < t* < 10000 10000 < t* < 25000 25000 < t* < 65000 65000 < t* < 100000 figure 11: the xy-plane radial distribution functions averaged over four time intervals as in fig. 10. parameters are the same as at fig. 7. where ωi denotes molecular orientation. in a fluid phase, h000(rij) → 1 when rij → ∞ both in isotropic and anisotropic phases. other projections, called angular correlation functions, can also characterize chain formation, but we will discuss only the rdf in this study. similar to fig. 8, we plot the rdf averaged over the time intervals discussed at the chain length distributions. in addition to those three time intervals, we also consider the time interval 0 < t∗ < 10,000 here, which is the time of the electric field being switched off. fig. 10 shows that the g(r) function behaves like a typical rdf for a dense real gas (ρ∗ = 0.05) in the absence of e0. as the electric field is switched on, however, larger and larger peaks appear as time goes by and longer and longer chains are formed. the peaks appear at every integer multiples of d values that correspond to particles in the chain. a more detailed behavior of g(r) can be followed in the video clip: https://youtu.be/ owxsuz6p0w4. when the chains are formed, they are relatively stable, but they diffuse around in the xy plane. therefore, we also define the rdf in the xy plane to follow how the chains are distributed over the xy plane. we will denote it with gxy(r) and is calculated the same way as the threedimensional rdf. fig. 11 shows these functions averaged over the time periods as in fig. 10. a similar conclusion can be drawn as from that figure except that the first peak now appears at r∗ = 0, where now r = √ ∆x2 + ∆y2. this peak represents particles belonging to the same chain. peaks represent probable distances between chains. the shape of the curve indicates that this er system ((p∗)2 = 6) behaves like a two-dimensional fluid of chains. at a given time (or, in a given block), these series of peaks are absent. snapshots of gxy(r) show where the chains are in a given moment. this can be followed in the video clip: https://youtu.be/owxsuz6p0w4. the gxy(r) function averaged over a longer time period characterizes the behavior of the chains as a twodimensional fluid. -10 -5 0 d ip o le -d ip o le e n e rg y / k t 0.6 0.8 1 1.2 d / d (e = 0 ) 0 5×10 4 1×10 5 2×10 5 2×10 5 5 10 15 a v e ra g e c h a in l e n g th ∆t*=0.005 ∆t*=0.01 ∆t*=0.02 (µ*) 2 =6 γ*=10000 figure 12: the one-particle dipole-dipole energy (top panel), the diffusion constant relative to its value in the absence of e0 (middle panel), and the average chain length (geometrical definition with λg = 1.2, bottom panel) as functions of time using different time steps. parameters: (p∗)2 = 6 and γ∗ = 10,000. themb is changed in a way that ∆t∗ ×mb is constant. 6.2 the effect of time step first, let us consider the effect of the choice of the time step, ∆t∗. fig. 12 shows the variation of the one-particle dipole-dipole energy, the diffusion constant, and the average chain length (geometrical definition with λg = 1.2) for different values of ∆t∗. the length of a block measured in t∗ is kept fixed. it is seen that the measured quantities behave the same way as a function of time, which indicates that the bd simulation algorithm is robust and provides results that are independent of the time step. also, we monitored the temperature computed from the kinetic energy, 〈t 〉 = m〈v2〉/3k, and found that the algorithm reproduces the prescribed temperature very precisely even for this highly anisotropic fluid. this supports the claim of the developers that this algorithm provides a very good langevin thermostat [24–26]. if we change ∆t∗, but we keep mb at the same value, meaning that we change the time length of the block, the dipole-dipole energy and the average chain length are still insensitive to the choice of ∆t∗ (data not shown). the diffusion coefficient, however, changes with the length of the blocks as already discussed above (at fig. 6). this hungarian journal of industry and chemistry https://youtu.be/owxsuz6p0w4 https://youtu.be/owxsuz6p0w4 https://youtu.be/owxsuz6p0w4 brownian dynamics simulation of chain formation 105 -10 -5 0 d ip o le -d ip o le e n e rg y / k t γ*=1000 γ*=2000 γ*=5000 γ*=10000 0.2 0.4 0.6 0.8 1 1.2 d / d (e = 0 ) 0 5×10 4 1×10 5 2×10 5 2×10 5 5 10 15 20 a v e ra g e c h a in l e n g th (µ*) 2 =6 ∆t*=0.01 figure 13: the one-particle dipole-dipole energy (top panel), the diffusion constant relative to its value in the absence of e0 (middle panel), and the average chain length (geometrical definition with λg = 1.2, bottom panel) as functions of time using different friction coefficients. parameters: (p∗)2 = 6 and ∆t∗ = 0.01. means that we have a trade-off between satisfactory sampling over a block and good resolution in time. we do not consider viscosity in this paper; we refer it to future studies. this trade-off will be present in the case of the viscosity (and the stress tensor) as well. it will be even more serious, because the viscosity is even a more poorly converging quantity than the diffusion constant. 6.3 the effect of friction coefficient we fix the dipole moment at (p∗)2 = 6 and the time step at ∆t∗ = 0.01, and change the friction coefficient from γ∗ = 1,000 to 10,000. as discussed in the next section, realistic er fluids have friction coefficients even larger than 10,000, but we refer studying that regime to future publications. as γ∗ is increased, the curves tend to their equilibrium values as e0 is switched on at a lower rate. fitting exponential functions to these curves and identifying processes of different time lengths as parts of the complex process of chain formation will also be the subject of future studies. the change in γ∗ does not influence the value where the energy and the average chain length converge to. -12 -10 -8 -6 -4 -2 0 d ip o le -d ip o le e n e rg y / k t (p*) 2 =2 (p*) 2 =4 (p*) 2 =6 0.5 0.6 0.7 0.8 0.9 1 1.1 d / d (e = 0 ) 0 5×10 4 1×10 5 2×10 5 2×10 5 5 10 15 a v e ra g e c h a in l e n g th ∆t*=0.01γ*=10000 6 6 6 4 4 2 2 2 figure 14: the one-particle dipole-dipole energy (top panel), the diffusion constant relative to its value in the absence of e0 (middle panel), and the average chain length (geometrical definition with λg = 1.2, bottom panel) as functions of time using different dipole moments. parameters: γ∗ = 10,000 and ∆t∗ = 0.01. this figure shows two m0 +me cycles. they converge to the same value but with a different rate. changing friction, however, changes the diffusion constant. fig. 13 shows the diffusion constant relative to its value in the absence of the field computed asd∗ = 1/γ∗. the diffusion constant decreases to a smaller value relative to d∗(e = 0) at smaller values of γ∗. the average chain length shows that smaller γ∗ results in a more wildly fluctuating system than a larger γ∗. the particles diffuse faster and produce larger variations in configurations during a given time period. 6.4 the effect of dipole moment our simulations show (fig. 14) that the quantity that determines the structure of the er fluid is the reduced dipole moment, namely, the relation of the dipole-dipole energy to the thermal energy unit, kt . fig. 14 shows that these quantities converge to their equilibrium values exhibiting a similar trend. the dipole moments studied in this work belong to the regime where the er fluid considered as a collection of chains is still a fluid, namely, it does not solidify. several papers in the literature study solidification of the er 48(1) pp. 95–107 (2020) 106 fertig, boda, and szalai chains [5, 6, 15, 16, 22]. 7. summary in this work, we use a newly developed integrator algorithm to solve the langevin equations and to perform bd simulations for er fluids. our focus was on the methodological development and identifying appropriate system parameters through which we can follow the dynamics of chain formation in the system. the usefulness of computer simulations lies not only in the fact that we can follow the particles’ trajectories, but also in the fact that we can gain a profound amount of information from these trajectories. in the bd simulations, for example, we can follow how the average number of chains of varying lengths changes in time. from that detailed information we can deduce time constants for characteristic processes during chain formation. we intend to dig into those details in subsequent studies. also, we want to examine the behavior of the chains under a 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[8–10]. the continuous avail∗correspondence: szalay.istvan@mk.uni-pannon.hu ability of signals from vehicle sensors required by dead reckoning as well as the absolute positioning accuracy of gps render them combinable to achieve better performance [8, 9]. in this paper, a vehicle localization algorithm is presented that uses an extended kalman filter (ekf) to integrate dead reckoning with gps. dead reckoning is based on a simplified version of the single track model (stm) and uses a steering angle encoder, wheel speed sensors and yaw rate measurements. 2. modeling strategy the aim of the localization algorithm is to estimate the current position (x and y coordinates) and heading (yaw angle ψ) of the vehicle by fusing gps measurements with dead reckoning based on vehicle sensor signals. gps measurements provide the noisy xgps and ygps coordinates. vehicle sensors provide the steering angle δ, the four wheel speed signals ωi and the yaw rate ψ̇. these measurements are available in most commercial vehicles. the lateral acceleration sensors were not used because the acceleration signal is usually less reliable and noisier than the other vehicle signals. the localization algorithm fuses these signals using an extended kalman filter which requires an appropriate system model. the system model connects the available and estimated signals with inputs, states and outputs of the system. the simplest and most practical solution is to https://doi.org/10.33927/hjic-2020-16 mailto:szalay.istvan@mk.uni-pannon.hu 110 szalay, enisz, medve, and fodor xe ye ~r0 ∆~r1 ∆~r2 t0ts x0 u0 noise f ( x0, u0, p0 ) = y1 = h ( x1, u1,m1 ) 1ts x1 u1 noise f ( x1, u1, p1 ) = y2 = h ( x2, u2,m2 ) 2ts x2 u2 noise figure 1: dead reckoning steps and propagation of the system state formulate the system model in a way that produces the true-position and heading state variables, the input variables of vehicle sensor signals and the outputs of gps signals. 3. dead reckoning algorithm dead reckoning or path integration is the process of estimating the current position of a vehicle by using a previously determined position, and projecting that position based upon known or estimated speeds over a time period and course that has elapsed. dead reckoning is subject to cumulative errors. in continuous time, dead reckoning results in the integration of the velocity vector or double integration of the acceleration vector with respect to time. in discrete time of sample time ts, the equivalent of integration can be written as the following in vector-sum form: ~rk = ~rk−1 + ∆~rk = ~r0 + k∑ i=1 ∆~ri (1) the equivalent coordinate form of eq. 1 for a vehicle in planar motion is[ xk yk ] = [ xk−1 yk−1 ] + [ ∆xk ∆yk ] = [ x0 y0 ] + k∑ i=1 [ ∆xi ∆yi ] (2) in the vector form, ~rk denotes the position of the vehicle’s center of gravity (cog) at tk = kts and ∆~rk stands for the displacement between tk−1 = (k − 1)ts and tk = kts. the initial position in vector form is ~r0 and in coordinate form is [x0, y0] t (see fig. 1). dead reckoning is performed in the earth-fixed coordinate system xe − ye. using the vehicle sensors, displacements in the vehicle axis system xv − yv can be calculated. to rotate the displacement into the earthfixed coordinate system, changes in the heading or yaw angle ψ of the vehicle have to be tracked. the yaw angle can be estimated by integrating the yaw-rate signal ψ̇ as ψk = ψk−1 + ψ̇kts = ψ0 + k−1∑ i=1 ψ̇its (3) the displacements ∆xv,k and ∆yv,k have to be calculated in the vehicle axis system xv − yv. the displacements from the vehicle axis system to the earth-fixed coordinate system are transformed using a two-dimensional rotation matrix r(ψk−1) that rotates around the vertical axis ze by ψk−1.[ ∆xk ∆yk ] = [ cosψk−1 − sinψk−1 sinψk−1 cosψk−1 ] ︸ ︷︷ ︸ r(ψk−1) [ ∆xv,k ∆yv,k ] (4) the simplest estimation of the longitudinal displacement ∆xv,k involves the estimation of the longitudinal speed vk as the average of the wheel speed signals divided by the effective radius of the tires r: ∆xv,k = vk−1ts, where vk−1 = r 4 4∑ i=1 ωk−1,i (5) the lateral displacement ∆yv is estimated by the second integral of the lateral acceleration, assuming an initial lateral velocity of zero: ∆yv,k = 1 2 ay,k−1t 2 s . (6) the lateral acceleration ay can be in the form of a sensor signal from an accelerometer or calculated based hungarian journal of industry and chemistry localization accuracy improvement of autonomous vehicles 111 s ~r = [ x y ] xe ye xv + ψ xw xv yv l1 l2 ~v1 ~v ~v2 ~ay o ~fy1 ~fy2 + ψ̇ − α2 − β − α1 + δ ze color coding: velocities: ~v, ~v1, ~v2 forces: ~fy1, ~fy2 lateral acceleration: ~ay yaw rate: ψ̇ figure 2: the physical quantities of the single track vehicle model following [11] on the vehicle dynamics model and other vehicle sensor signals. usually, the accelerometer signals are less reliable and noisier than those of the steering angle, velocity and yaw-rate sensors, therefore, ay was calculated based on a vehicle model and signals from vehicle sensors, in a similar way to ref. [9]. 4. lateral vehicle dynamics as a basis for modeling the lateral vehicle dynamics, the well-known single track vehicle model defined by riekert and schunck [12] was used. fig. 2 shows the physical quantities related to the single track vehicle model. this paper uses the sign conventions defined in ref. [11]. the classical single track vehicle model includes several important simplifications. it only describes lateral motion and rotation around the vertical axis, while neglects vertical dynamics as well as rolling and pitching. furthermore, the equations of motion of the single track vehicle model are linearized. to define the lateral acceleration as a function of the steering angle δ, longitudinal velocity v and yaw rate ψ̇, the lateral force equation of the model can be used: may = fy1(α1) + fy2(α1) (7) the linearized tire forces as the products of the cornering stiffnesses (c1 and c2) and tire slip angles (α1 and α2) are calculated as follows: fy1(α1) = −c1α1 and fy2(α2) = −c2α2. (8) tire slip angles (α1 and α2) are defined by the velocity triangles of the two axles in the following nonlinear forms (see fig. 3): tan (α1 + δ) = v sinβ + ψ̇l1 v cosβ (9) tanα2 = v sinβ − ψ̇l2 v cosβ (10) eq. 9 corresponds to the yellow part of the velocity triangle corresponding to the front axle and eq. 10 to the rear axle. the tire slip angle equations are linearized and the sideslip angle β omitted: α1 ≈ β + ψ̇l1 v − δ ≈ ψ̇l1 v − δ (11) α2 ≈ β − ψ̇l2 v ≈ − ψ̇l2 v (12) the lateral acceleration ay depends on the values of the vehicle sensors according to ay ≈ − c1 m ( ψ̇l1 v − δ ) + c2 m ψ̇l2 v (13) front axle xw xv ~v1 ~v ~̇ψ×~l1 + δ − β − α1 + δ + α1 rear axle xv ~v ~v2 ~̇ψ×~l2 − β − α2 figure 3: velocity triangles in the single track vehicle model 48(1) pp. 109–115 (2020) 112 szalay, enisz, medve, and fodor in this way, the lateral acceleration depends on the usually available cornering stiffnesses (c1 and c2), the mass and length of the vehicle (m, l1 and l2), and the signals of the vehicle sensors. if available, the lateral acceleration signal from an accelerometer can be incorporated into the sensor fusion algorithm. 5. extended kalman filter design the application of an extended kalman filter requires a stochastic mathematical model of the system in a statespace representation including the statistical properties of the process and measurement noises [13, 14]. 5.1 state-space model the state-space representation includes both the state and measurement equations in vector form by introducing the functions f and h, the known input vector u, processnoise vector p and measurement-noise vector m: xk = f ( xk−1, uk−1, pk−1 ) (14) yk = h ( xk,mk ) (15) the system is time invariant, therefore, f and h are not indexed. the discrete-time indexing of the difference equations is illustrated in fig. 1. to estimate the vehicle’s position, the dead reckoning eqs. 2–6 are used augmented to include the lateral acceleration (eq. 13) as a computed value. the resulting state equation of the discrete-time state-space model is eq. 18. by examining eq. 18, it can be concluded that the system is nonlinear and, therefore, a linear kalman filter is unsuitable. in this paper, an extended kalman filter is used. the output vector y of the system includes the gps measurements that consist of the true position and measurement noise m defined by the output function h: yk= [ xgps,k ygps,k ] = [ xk +mx,k yk +my,k ] = h ( xk,mk ) (16) 5.2 jacobians the extended kalman filter requires the jacobians of both the state and measurement functions with respect to the state vector: f k = ∂f ∂x ∣∣∣∣∣ x̂+ k−1 and h = ∂h ∂x ∣∣∣∣∣ x̂+ k−1 = [ 1 0 0 0 1 0 ] (17) the elements of h are constant, while the elements of f k depend on the discrete time k, as defined by eq. 19. the sample time ts was 100 ms, which was sufficiently small to capture the vehicle’s movement but not too small for gps sampling. xk =  xk yk ψk  =  xk−1 + vk−1ts cos (ψk−1)− 1 2 ay,k−1t 2 s sin (ψk−1) + px,k−1 yk−1 + vk−1ts sin (ψk−1) + 1 2 ay,k−1t 2 s cos (ψk−1) + py,k−1 ψk−1 + ψ̇k−1ts + pψ,k−1  = f ( xk−1, uk−1, pk−1 ) (18) f k =  1 0 − sin (ψk−1) vk−1ts − 1 2 cos (ψk−1) ay,k−1t 2 s 0 1 cos (ψk−1) vk−1ts − 1 2 sin (ψk−1) ay,k−1t 2 s 0 0 1  , uk = ay,kvk ψ̇k  (19) 5.3 noise model during the design of the extended kalman filter, a timeinvariant and normally distributed process as well as measurement noise were assumed: p ∼ n ( 0, q ) , m ∼ n ( 0, r ) (20) for the development and testing of our extended kalman filter algorithm, a tesis vedyna vehicle dynamics-based simulation environment was used with configurable noise models (see section 6). although it was possible to match the noise and covariances of the filter perfectly, the filter and noise models were tuned in a slightly different way. the measurementand processnoise covariances for both the filter and noise models have been estimated based on the characteristics of the sensor and gps range error statistics [15]: q = diag ( 0.2 m2, 0.2 m2, 0.01 rad2 ) (21) r = diag ( 1.5 m2, 1.5 m2 ) (22) hungarian journal of industry and chemistry localization accuracy improvement of autonomous vehicles 113 our algorithm performs the dead reckoning in the earthfixed coordinate system and, therefore, no predetermined difference between the direction covariances xe and ye is present, so q11 = q22 and r11 = r22. the displacement variance of 0.2 m2 corresponds to an error of 4.5 m s−1 in the wheel speed-based velocity calculation. in the presence of non-normally distributed noise, the filter is not optimal. 5.4 the extended kalman filter algorithm the extended kalman filter algorithm follows wellknown steps [14]. the prediction equations are x̂−k = f ( x̂+k−1, uk−1, 0 ) (23) p− k = f kp + k−1f t k +q (24) calculation of the kalman gain is kk = p− k h t k ( hkp − k h t k +r )−1 (25) the correction equations are x̂+k = x̂−k +kk ( yk − hk ( x̂−k , uk, 0 )) (26) p+ k = ( i −kkhk ) p− k (27) the initial state is determined based on the first several gps observations whilst in motion. 6. simulation environment the development of the localization algorithm was conducted in a mathworks matlab/simulink-based vehicle dynamics simulation environment. the tesis vedyna model library was used to model the vehicle, road system and maneuvers (fig. 4). the advantage of our simulation platform lies in its integrated structure. algorithms developed in matlab and simulink can be integrated into the tesis vedyna vehicle dynamics simulation which enables softwarein-the-loop testing and real-time hardware-in-the-loop analysis to be implemented by the national instruments pxi hardware system. in our platform, real streets using gps coordinates or map databases can be modeled. this enables the direct comparison of simulations and real-world measurements. 7. simulation results the extended kalman filter was tuned and studied in simulated test maneuvers during which data were collected. the test maneuvers were performed on a virtual test track that included lowand high-speed driving, accelerating, braking and cornering. the size of the test track was around 2 by 2 km and the simulated test maneuvers lasted for 528 s. our extended kalman filter was compared to simple dead reckoning and gps observations. the true path, the result of dead reckoning and the position, estimated by the implementation of our extended kalman filter, are shown in fig. 5. figure 4: tesis dynaanimation user interface 7.1 comparison with dead reckoning dead reckoning without the aid of the extended kalman filter accumulated a large position error during the test maneuvers. the error of the dead reckoning reached 100 m, as can be seen in fig. 5. the position estimated by our extended kalman filter did not include error accumulation and performed better than dead reckoning alone. 7.2 comparison with gps due to the large difference between the size of the path and the position errors, the difference between gps observations and the extended kalman filter estimates were not as clearly visible as the error of dead reckoning (fig. 5). zooming in on certain parts of the path enables visual evaluation of a particular part of the path 0 500 1000 1500 2000 0 500 1000 1500 2000 position, x, [m] po si tio n, y ,[ m ] true path dead reckoning ekf estimation figure 5: the real path, dead reckoning only and ekf estimation 48(1) pp. 109–115 (2020) 114 szalay, enisz, medve, and fodor 0 2 4 6 8 10 12 14 16 18 20 22 24 26 −2 0 2 4 displacement, x, [m] d is pl ac em en t, y ,[ m ] real path gps position ekf estimation figure 6: the initial section of the true, estimated and gps-observed paths (fig. 6). to evaluate the extended kalman filter estimate and make it numerically comparable to the gps observations, the instantaneous and average distance errors were calculated. the distance error dk of the estimation is calculated as the distance between the estimated and true positions: dk = √ (x̂k − xk) 2 + (ŷk − yk) 2 (28) the distance error dgps,k of gps observations is dgps,k = √( xgps − x )2 + ( ygps − y )2 (29) the average distance errors are d̄ = 1 n n∑ k=1 dk and d̄gps = 1 n n∑ k=1 dgps,k (30) the distance errors of the gps observations and the extended kalman filter position estimates are shown in fig. 7. the timespan of the test maneuvers was 528 s, moreover, at a sample time of 100 ms, it produced 5280 points. the average distance error of the gps observations was d̄gps = 751 mm. our extended kalman filter reduced the average distance error significantly, d̄ = 457 mm. besides the average values, the distributions of the distance errors are also of interest. the distance errors are discrete values whose distributions can be approximated by their histograms. such histograms are shown in (fig. 8) with a bin width of 10 cm. 8. conclusions in this paper, a real-time vehicle localization algorithm developed and implemented in a tesis vedyna vehicle dynamics simulation environment was presented. the localization algorithm used an extended kalman filter to fuse gps observations with vehicle sensor measurements of only the steering angle, yaw rate and wheel speeds. the underlying state-space model is based on planar dead reckoning that calculates the longitudinal displacement using wheel speed and lateral displacement in a simplified version of the single track model. the state-space model only includes the x and y coordinates and the yaw angle ψ to minimize the model and filter algorithm. the performance of the position estimator was analyzed during different highand low-speed maneuvers. compared to the dead reckoning and gps observations that were not integrated, the integrated system performed significantly better. the average distance error was reduced by 39 %. further improvement of localization accuracy would be possible by using a more sophisticated vehicle model resulting in a more complex implementation of an extended kalman filter with a much higher computational burden. 0 100 200 300 400 500 0 1 2 3 4 time, t, [s] d is ta nc e er ro rs ,d an d d g p s ,[ m ] gps distance error dgps ekf distance error d gps average d̄gps = 751 mm ekf average d̄ = 457 mm figure 7: distance error comparison hungarian journal of industry and chemistry localization accuracy improvement of autonomous vehicles 115 0 1 2 3 4 0 200 400 600 800 1000 distance error, d, [m] c ou nt histogram of dgps histogram of d d̄gps = 751 mm d̄ = 457 mm figure 8: distance error histograms acknowledgement this research was supported by the project efop-3.6.216-2017-00002 entitled "research of autonomous vehicle systems related to the autonomous vehicle proving ground of zalaegerszeg". references [1] karlsson, r.; gustafsson, f.: the future of automotive localization algorithms: available, reliable, and scalable localization: anywhere and anytime, ieee signal processing magazine, 2017, 34(2), 60–69 doi: 10.1109/msp.2016.2637418 [2] farrell, j.a.; givargis, t.d.; barth, m.j.: realtime differential carrier phase gps-aided ins, ieee transactions on control systems technology, 2000, 8(4), 709–721 doi: 10.1109/87.852915 [3] qi, h.; moore, j.b.: direct kalman filtering approach for gps/ins integration, ieee transactions on aerospace and electronic systems, 2002, 38(2), 687–693 doi: 10.1109/taes.2002.1008998 [4] yu, m.: ins/gps integration system using adaptive filter for estimating measurement noise variance, ieee transactions on aerospace and electronic systems, 2012, 48(2), 1786–1792 doi: 10.1109/taes.2012.6178100 [5] liu, h.; nassar, s.; el-sheimy, n.: two-filter smoothing for accurate ins/gps land-vehicle navigation in urban centers, ieee transactions on vehicular technology, 2010, 59(9), 4256–4267 doi: 10.1109/tvt.2010.2070850 [6] almeida, h.p.; júnior, c.l.n.; d. santos, d.s.; leles, m.c.r.: autonomous navigation of a smallscale ground vehicle using low-cost imu/gps integration for outdoor applications, in 2019 ieee international systems conference (syscon), 1–8 doi: 10.1109/syscon.2019.8836794 [7] yu, m.; guo, h.; gao, w.: realization of lowcost imu/gps integrated navigation system, in 2006 japan-china joint workshop on frontier of computer science and technology, 189–195 doi: 10.1109/fcst.2006.27 [8] kao, w.w.: integration of gps and dead-reckoning navigation systems, in vehicle navigation and information systems conference, 1991, vol. 2, 635– 643 doi: 10.1109/vnis.1991.205808 [9] rezaei, s.; sengupta, r.: kalman filter-based integration of dgps and vehicle sensors for localization, ieee transactions on control systems technology, 2007, 15(6), 1080–1088 doi: 10.1109/tcst.2006.886439 [10] hohman, d.; murdock, t.; westerfield, e.; hattox, t.; kusterer, t.: gps roadside integrated precision positioning system, in ieee 2000. position location and navigation symposium (cat. no.00ch37062), 221–230 doi: 10.1109/plans.2000.838306 [11] iso 8855:2011 road vehicles – vehicle dynamics and road-holding ability – vocabulary, standard, international organization for standardization, geneva, ch, 2011 [12] riekert, p.; schunck, t.e.: zur fahrmechanik des gummibereiften kraftfahrzeugs, ingenieur-archiv, 1940, 11(3), 210–224 doi: 10.1007/bf02086921 [13] bucy, r.s.: linear and nonlinear filtering, proceedings of the ieee, 1970, 58(6), 854–864 doi: 10.1109/proc.1970.7792 [14] simon, d.: optimal state estimation: kalman, h infinity, and nonlinear approaches (wileyinterscience, new york, ny, usa), 2006 isbn: 0471708585 [15] faa william j. hughes technical center: global positioning system (gps) standard positioning service (sps) performance analysis report, 2019 https://www.nstb.tc.faa.gov/reports/ 48(1) pp. 109–115 (2020) https://doi.org/10.1109/msp.2016.2637418 https://doi.org/10.1109/87.852915 https://doi.org/10.1109/taes.2002.1008998 https://doi.org/10.1109/taes.2012.6178100 https://doi.org/10.1109/taes.2012.6178100 https://doi.org/10.1109/tvt.2010.2070850 https://doi.org/10.1109/tvt.2010.2070850 https://doi.org/10.1109/syscon.2019.8836794 https://doi.org/10.1109/fcst.2006.27 https://doi.org/10.1109/fcst.2006.27 https://doi.org/10.1109/vnis.1991.205808 https://doi.org/10.1109/tcst.2006.886439 https://doi.org/10.1109/tcst.2006.886439 https://doi.org/10.1109/plans.2000.838306 https://doi.org/10.1109/plans.2000.838306 https://doi.org/10.1007/bf02086921 https://doi.org/10.1109/proc.1970.7792 https://doi.org/10.1109/proc.1970.7792 https://www.nstb.tc.faa.gov/reports/ hungarian journal of industry and chemistry vol. 48(1) pp. 117–121 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-17 geospatial data manipulation supporting the implementation of driving simulation environments ferenc speiser∗1, krisztián enisz1, and dénes fodor1 1research institute of automotive mechatronics and automation, university of pannonia, egyetem u. 10, veszprém, 8200, hungary a lot of highly detailed geospatial information (obtained by mobile mapping and spatial data processing) is available that can be used to describe the exact road parameters for simulation and modeling. a gap between the freely available geospatial information and the descriptive standards of the road is present that is used in driving/traffic simulation as well as the systems of test vehicles. the toolset of gis (geographic information systems) provides wide-ranging functionality for spatial data processing, but is yet to offer support for standard formats of road description (opendrive data). this paper describes a method for gathering and converting road-network information from openstreetmap to opendrive data format. using a similar conversion tool, the scenario generation and synthesis of realistic road networks for driving simulator applications can be more convenient and faster. keywords: opendrive, openstreetmap, road-network conversion 1. introduction location information plays an important role in our everyday lives. to go somewhere, e.g. shopping, our exact position and destination is required. this location information can be obtained by gps or a cellular network even with a high degree of accuracy, depending on the application area. however, other data (map, road network, terrain model) may be required to reach the destination. detailed route planning can be achieved by these collected data (spatial databases) and has a great degree of significance in driver assistance. the reliability of positioning and location awareness plays a crucial role in the field of autonomous vehicles and communication between them. it is important to validate the entire functionality of vehicles in all possible circumstances that could occur in real life during the development of all systems, subsystems and sensors of the advanced driver-assistance systems (adas) [1]. this kind of testing is expensive and requires a lot of resources to provide real-life conditions, e.g. the establisment of a proving ground like zalazone in hungary. during the first development stages of a function, it is appropriate to test basic functionality in a simulation environment. this environment can simulate all the information that is needed by the sensors of the control unit that runs the test build of the development. of course, the more detailed the simulation environment, the more accurate the validated test result can be. this means that ∗correspondence: kohlrusz.gabor@mk.uni-pannon.hu if a simulation environment were to be established, which can provide data in exactly the same mode as would occur in real life, the number of real-life tests necessary during the development of a functionality could decrease. therefore, the rate of product development would accelerate and development costs decrease [2]. how can a simulation environment emulate real-life signals? software-in-the-loop (sil), hardware-in-theloop (hil) and model-in-the-loop (mil) solutions are able to emulate the signal level of real environments. all the necessary signals are obtained by the software, hardware or model components in the simulation as would be obtained in real life. the location information is a parameter that can also be loaded for the software, hardware or model component that is being tested. what kind of location data can be used for testing, and how can the route, road as well as terrain on which the vehicle drives be described? a huge amount of location data is available, but the accuracy of data is the key question with regard to usability. nowadays, many leading data-mapping and location-data service companies have access to a huge amount of data and services in the traffic-navigation industry partnered with large automotive manufacturers facilitating the development of adas, e.g. here hd live map [3]. the goal of these companies is to provide a high-quality, self-healing map that is a clear representation of the physical world for the navigation services. however, in terms of testing, not only navigation matters. it is important to have the tools necessary to create the data-mapping environment for the https://doi.org/10.33927/hjic-2020-17 mailto:kohlrusz.gabor@mk.uni-pannon.hu 118 speiser, enisz, and fodor simulations. this paper elaborates on the options available to provide the proper format of location data for the tesis dyna4 hil/sil environment toolset of gis (geographic information system). an overview will be given of the available road data formats as well as the available crowdsourced openstreetmap data. a lot of highly detailed geospatial information (obtained from mobile mapping and spatial data processing) is available that can be used to describe the exact road parameters for simulation and modeling. a gap exists between the freely available geospatial information and descriptive standards of roads that is used in driving/traffic simulation and systems of test vehicles. the goal is to provide an accessible, opensource and easy-to-use solution that is able to generate logical data concerning the description and visualization of roads for driving simulation environments based on available map data. 1.1 nds building blocks the navigation data standard (nds) is a standardized format for automotive-grade navigation databases established by automotive original equipment manufacturers (oems), map-data providers and navigationdevice/application providers. this is a standardized binary database format that allows the exchange of navigation data between different systems. the goal is to separate layers of data from the layers of software, mainly for navigation purposes. the following layers of data could be used from the nds in a simulation environment: • digital terrain model • traffic information • basic map display • routing • lane information 1.2 opendrive road format opendrive is an open format specification to describe the road networks developed by vires. it is a standard road description format that should help data exchange between different driving simulation environments. it has direct support without the necessity to convert into dyna4, ipg’s carmaker or carsim formats. opendrive has special features like complex road networks with junctions, crossfall, superelevation, road markings and barriers, traffic signs and lights, gantries, as well as the ability to integrate high-resolution road surface profiles in opencrg format [4]. the toolset of gis (geographic information system) provides a wide range of functions for spatial data processing, but is yet to offer support for the opendrive standard road-description format [5]. this paper describes a way of gathering and converting road network information from openstreetmap into opendrive format. using a conversion tool like this, the generation and synthesis of a scenario with regard to real-life road networks for driving simulator applications can be more convenient and faster. figure 1: the filtered osm dataset of veszprém 1.3 roadxml like opendrive, this is also an open file format for the logical description of road networks. the goal is to simplify the production of road databases as well as improve the consistency and ensure the interoperability of simulation models. this is an xml-based file format that can be easily edited to enhance road descriptions with custom data using a simple text editor. roadxml is used by many driving simulator software programs as an alternative file format for describing road networks [3]. 1.4 freely available map data other commonly used formats for road networks, e.g. openstreetmap and landxml, are available for geographical needs, but are not suitable for adas simulation purposes, however, they can be used as an input source since these have worldwide coverage. openstreetmap is a free, editable map of the whole world that is being built, by and large, from scratch using crowdsourcing methods and has been released under a creative commons share-alike license. the data records are mostly based on gps navigation data that can be used to create configurations of road networks based on the line segments of the database [6]. further descriptive data is necessary to fulfill the needs of simulation environments. a question that might be raised is whether and how vector data can be used in geographic information systems? geofabrik is a free, community-maintained data extraction service from openstreetmap [7]. this can provide the necessary road-segments data in addition to other information to describe the segments, e.g. the number of lanes, traffic signs, etc. (fig. 1). another option to obtain road-vector data is overpassturbo.eu. using this service, interesting map data can be hungarian journal of industry and chemistry geospatial data manipulation for driving simulation environments 119 figure 2: main components of the ni-based system selected by a special query language, downloaded, displayed and used in gis applications. other data sources can be used to obtain other descriptive information. information concerning elevation can be derived from the digital terrain model produced with the aid of satellites (esa’s copernicus sentinel-1 and sentinel-2) and/or aerial images. 1.5 open source gis software if the necessary map data is downloaded, a data management and process system is needed to make further data preparations for this gis software to be used. gis software (geographical information system) is an application that enables geographical data to be managed on different platforms. quantum gis (qgis) is one of the most popular open-source software solutions. qgis is an official project of the open source geospatial foundation (osgeo) that runs on all operating systems and supports numerous vectors, rasters and database formats as well as functionalities, moreover, allows conversion between different reference systems. this has been selected to implement the data management tasks on the downloaded road data. 1.6 simulation software environment the road models are mainly necessary for testing and validating position estimation algorithms as well as advanced driving support systems for autonomous vehicles. a hard real-time environment based on national instruments devices has already been built for testing, and a soft real-time simulation system based on vector’s vt system is currently under construction. ni’s labview as well as veristand are the base software programs, and matlab/simulink-based tesis dyna4 software is used for automotive simulation purposes. veristand provides the connection between the models and hardware components, while labview and dyna4 provide opportunities to develop new models as well as other software components. in addition, ni’s teststand can be used to create tests and automated test sequences as needed (fig. 2). tesis dyna4 is also the development environment for vehicle simulations in the vector-based simulation environment. other software components and add-on models can be developed primarily in visual studio and cafigure 3: main components of the vector-based system noe in this environment, moreover, vteststudio provides a framework for creating tests and test sequences (fig. 3). tesis dyna4 serves as the vehicle simulation development environment in both cases, which is why the initial goal was to be able to use the data exported from the map databases in this environment. 2. results and analysis an important aspect of simulation tests is how to model the different sections of road. this location information can be obtained from real measurements or map databases. the selected sampling area is a short track in veszprém. using the service of geofabrik.de, it is possible to download the latest dataset of the city from the osm database (fig. 4). this dataset provides the network level which consists of more data layers, roads and traffic signs, moreover, the buildings can probably be used as an information base for the description of roads. the necessary information was selected and processed by qgis desktop gis software, moreover, the coordinate information of the points from the selected segment of road was exported in a suitable input format for data conversion. after the data collection task, the next step is to convert the data into the appropriate road-description format figure 4: selected track designated for testing in veszprém (osm) 48(1) pp. 117–121 (2020) 120 speiser, enisz, and fodor figure 5: transformation process that can be imported by the selected simulation environment. dyna4 has a conversion option that can create a track model in its own format from plain gps coordinates, but has limitations. it does not allow the width of the road segments to be changed significantly, as well as data concerning the width of roads, number of lanes to specific coordinates or data concerning imported traffic signs and lights to be assigned, therefore, no descriptive information with regard to traffic levels can be found. furthermore, the dyna4-converted road description cannot be exported into other formats of road data exchange, e.g. opendrive or roadxml. 2.1 data conversion to solve these problems, a self-developed conversion program was created that can create dyna4-compliant path models from csv and xls file formats. the necessary conversion steps are the following: import coordinates (osm); convert input data and normalize (proj); define track segments and calculate; generate descriptive text; and define descriptive parameters, e.g. width, length and number of lanes as well as heights (fig. 5). the program reads the descriptive csv/xls file formats and then converts the coordinate data from the wgs84 geographic coordinate system to the cartesian coordinate system to simplify the calculations. the hd72 – hungarian national datum (epsg:23700 srid) was selected, which is a meter-based coordinate system. a proper coordinate transformation is necessary for transformation between the two coordinate reference systems that is provided by the proj library a special projection string was applied during the transformation, so the standard transformation error remained below 1m. the program creates an approximate path according to the input points based on spatial geometry calculations figure 6: testing track in veszprém compiled from lines, circles and splines corresponding to the dyna4 format. based on the path created in this way, dyna4 files are created that can already be used directly in tesis projects (fig. 6). 3. discussion even though the conversion program worked properly, it has one disadvantage. the dyna4 format does not support the creation of complex intersections and multi-lane roads. further development is needed to solve this problem. the conversion tool has to be able to save data in opendrive format so much more complex track models can be created as well as in other simulation software formats such as ipg’s carmaker. the coordinate transformation also causes a bottleneck because a meter-based coordinate system is needed for the geometric calculations. not all projected and geographic coordinate systems are appropriate for simple meter-based calculations. it is important to apply an accurate transformation method that places the coordinate points accurately. the projection string that was used is only suitable in hungary. 4. conclusion this paper introduced a map-tool that can be applied for the conversion of open-source map data to open road data formats. the converted road-description file can be used in different vehicle test systems as a basis for the functional testing of vehicle dynamics and driver assistance systems. the main advantage of the proposed framework is that if some kind of road network data is available from an area, it is possible to convert it into a road-description format. the created description file can be imported into most vehicle test systems. however, some limitations should be taken into consideration. although a lot of road data can be found from open-source map databases, currently not all of it is available, e.g. traffic signs and lights, and the quality of the data content needs to be enhanced. our goal is to perform data collection tasks on the tracks that have been used in this case study. hungarian journal of industry and chemistry geospatial data manipulation for driving simulation environments 121 acknowledgements the research was supported by efop-3.6.2-16-201700002 “research of autonomous vehicle systems related to zalazone autonome proving ground”. references [1] dupius, m.; strobl, m.; grezlikowski, h.: opendrive 2010 and beyond – status and future of the de facto standard for the description of road networks, proceedings of the driving simulation conference europe 2010, 2010, pp. 231-242 isbn: 978-2-85782-6859 [2] richter, a.; fischer, m.; frankiewicz, t.; schnieder, l.; köster, f.: reducing the gap between simulated and real life environments by introducing highprecision data, driving simulator conference 2015 europe, 16–18 sep. 2015, tübingen, germany isbn 978-3-9813099-3-5 [3] chaplier, j.; nguyen, t.; hewatt, m.; galee, g.: toward a standard: roadxml, the road network database format, proceedings of the driving simulation conference europe 2010, 2010, pp. 211-221 isbn: 978-2-85782-685-9 [4] richter, a.; scholz m.: deploying guidelines and a simplified data model to provide real world geodata in driving simulators and driving automation, transp. res. part f traffic psychol. behav. 2019, 61, 305– 313 doi: 10.1016/j.trf.2017.04.004 [5] despine, g.; baillard, c.: realistic road modelling for driving simulators using gis data, advances in cartography and giscience, 2011, 2, 431–448 doi: 10.1007/978-3-642-19214-2_29 [6] over, m.; schilling, a.; neubauer, s.; zipf, a.: generating web-based 3d city models from openstreetmap: the current situation in germany. comput. environ. urban syst., 2010, 34(6), 496–507 doi: 10.1016/j.compenvurbsys.2010.05.001 [7] kulawiak, m.; dawidowicz, a.; pacholczyk, m. e.: analysis of server-side and client-side webgis data processing methods on the example of jts and jsts using open data from osm and geoportal, comput. geosci., 2019, 129, 26–37 doi: 10.1016/j.cageo.2019.04.011 48(1) pp. 117–121 (2020) https://doi.org/10.1016/j.trf.2017.04.004 https://doi.org/10.1007/978-3-642-19214-2_29 https://doi.org/10.1007/978-3-642-19214-2_29 https://doi.org/10.1016/j.compenvurbsys.2010.05.001 https://doi.org/10.1016/j.compenvurbsys.2010.05.001 https://doi.org/10.1016/j.cageo.2019.04.011 https://doi.org/10.1016/j.cageo.2019.04.011 hungarian journal of industry and chemistry vol. 48(1) pp. 123–130 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-18 new hybrid wavelet and cnn-based indirect tire-pressure monitoring system for autonomous vehicles zoltán márton*1 and dénes fodor1 1research institute of automotive mechatronics and automation, university of pannonia, egyetem u. 10, veszprém, 8200, hungary since the tire pressure has a significant influence on driving safety, even self-driving vehicles need to be aware of their current tire pressures. two major types of methods for estimating tire pressures exist: direct and indirect methods. in spite of recent advancements in direct tire pressure monitoring systems (tpmss), indirect pressure monitoring systems still play a significant role due to their low costs. indirect systems rely on the processing of signals from wheel speed sensors. in most cases, a transformation is applied to generate a frequency spectrum from which the tire pressure-dependent eigenfrequency can be extracted. the most accurate methods apply the fourier transform, but these require the highest computational power. after the spectrum of signals from the wheel speed sensor is created, the eigenfrequency must be extracted. several methods are available to extract significant frequency components. one of the easiest methods is peak searching, however, it is susceptible to noise. on the other hand, more accurate methods that are less sensitive to noise require more computational power. if a transform that consumes less computational power can be applied, then the freed resources can be used by a better eigenfrequency identification method. in this paper, a hybrid wavelet-fourier transform and convolutional neural network-based method is presented, which exhibits a promising level of noise tolerance. keywords: tpms, eigenfrequency, hybrid wavelet-fourier transform, convolutional neural networks, autonomous vehicles 1. introduction the development and spread of autonomous and electric vehicles is about to change everything with regard to the internal structure and operation of cars. however, vehicles will always make contact with the road through tires so tires will continue to play an important role in terms of vehicle safety. the condition of tires is not only dependent on abrasion but on current tire pressures as well. furthermore, tire pressures influence abrasion in addition to fuel or power consumption [1]. as a result, both the eu and usa have legislated that all new vehicles are equipped with tire pressure monitoring systems (tpms) as standard. to achieve safe autonomous driving, the performance parameters of the vehicles must be in accordance with the conditions of the tires, e.g. the driving logic needs to know the current pressure of each tire. nowadays, research is being done with regard to active tires which are capable of adapting to weather and road conditions by changing their own tire pressures according to the requirements [2]. on the other hand, active tires are extortionate compared to their passive counterparts, even those equipped with tpms. an active tire must also include a compressor and be able to transmit the compressed air into the tires, which increases not only their *correspondence: marton.zoltan@mk.uni-pannon.hu cost but also their energy requirements. active tire systems will only be available for high-end vehicles or military applications. mainstream and more cost-effective vehicles will continue to use regular tires and be equipped with tpms. two major types of tpms are available: direct tpms, which includes a pressure sensor in the tires themselves, and indirect tpms, which uses wheel speed sensors (wss) required by the anti-lock braking system (abs), electronic stability program (esp) and other driving safety systems. the indirect tpms (itpms) can be accomplished by following two techniques. the simplest way is to compare the wheel speed signals from three different pairs, the bigger the tire pressure the bigger the radius of the tire will be. these systems are capable of detecting relative pressure changes and require the results to be filtered in such a way that the driving conditions and maneuvers do not affect the system. since tires have different radii, these systems require a learning process to be implemented should any of the tires be changed [3]. nowadays, comparable systems were replaced by signal processing-based systems and research is being done on model-based systems. both approaches are based on the fact that a tire is like a complex system made of springs and masses, where each spring-mass pair has its own eigenfrequencies. one of the springs correhttps://doi.org/10.33927/hjic-2020-18 mailto:marton.zoltan@mk.uni-pannon.hu 124 márton and fodor figure 1: the system architecture of itpms sponds to the air pressure inside the tire, therefore, one eigenfrequency is dependent on the tire pressure [3]. signal processing-based itpmss consist of two major wellseparated steps (fig. 1). the first step is to transform the signal from the time domain into the frequency or a frequency-related domain. these transforms can be fourier [4], cosine [5] or hybrid wavelet-fourier (hwft). the received frequency spectrum of the signal from the wheel speed sensor contains different eigenfrequencies as well as noises originating from the road surface, combustion engine and transmission. the second step is to detect and isolate the pressure-dependent eigenfrequency. different algorithms are available to identify a specific eigenfrequency. each algorithm is only performed on a given bandwidth. the simplest and fastest is the peak search (ps) algorithm. another method is the so-called center of gravity (cog) algorithm which can virtually increase the frequency resolution. although it is more resilient towards noise, noise still may cause the detected eigenfrequency to be shifted. this was subsequently observed in the results presented in table 1. since each eigenfrequency found in the spectrum of the wss exhibits a unique pattern, a pattern-recognition method can also be applied to identify the eigenfrequency in a given bandwidth. one of the most popular and reliable pattern-recognition methods are the deep convolutional neural networks (cnns). deep cnns can learn to recognize and classify patterns through a process called deep learning. in this paper, a novel itpms algorithm is proposed which consists of the hwft and, as an alternative to the cog algorithm, a cnn is used to detect the eigenfrequency. 2. transforms related to itpms the first major step in signal processing-based itpms is always a transform of the wss or other sensor signals from a time into a frequency or frequency-equivalent domain. since one of the major aims of this paper is to compare different transforms and eigenfrequency-detecting methods, a short description will be given of the fourier, cosine and hybrid wavelet-fourier transforms. for the itpms, a “new” hwft will be proposed in this paper. 2.1 fourier transform one of the most mainstream transforms in frequency analysis is the fourier transform, which transforms the time-domain signals directly into the frequency domain [6]. the signals in the frequency domain contain information concerning frequencies, amplitudes and phases. three major varieties of the fourier transform exist depending on the nature of the signal and the number of samples. the continuous fourier transform (cft) is predominantly used in stability and control theory, signal processing theory, symbolic mathematics, electrical engineering, etc. if a continuous signal is sampled, i.e. a discrete signal, by using the integral approximation to the sum, the discrete fourier transform (dft) can be obtained as x [k] = 1√ n n−1∑ n=0 x [n] e−i2πkn/n , (1) where k represents the discrete frequency, x[n] denotes the sampled signal, n stands for the number of samples, x[k] refers to the transformed discrete signal and i is the imaginary unit. unlike the cft, the dft has many practical applications. a special case of dft is when the number of samples can be expressed as a power of two. in this case, dft can be factorized using a divide and conquer approach. hence the factorization of this transform requires less computational power and is referred to as the fast fourier transform (fft), it is the most widespread in signal processing and computer science. 2.2 cosine transform the cosine transform (ct) originates from the fourier transform by removing the imaginary components. unlike the fourier transform, where the phases are encoded in the complex amplitudes, the ct stores the phase information over the entire frequency spectrum if the signal cannot be synthesized entirely from a finite set of cosine functions [7]. ct also consists of three major variants: continuous (cct), discrete (dct) and fast (fct). in practice, fct is predominantly used in the compression of lossy audio, images and motion pictures. dct and fct consist of four different variations, in our case, the so-called dct or fct ii was implemented: x [k] = n−1∑ n=0 x [n] cos [ π ( k + 1 2 ) n n ] . (2) in this paper, fct was examined as an alternative to fft. 2.3 wavelet transform the wavelet transform (wt) can be seen as a transform which transforms a given signal from the time domain into the frequency-time domain. like ft and ct, hungarian journal of industry and chemistry new hybrid wavelet and cnn-based indirect tire-pressure monitoring system 125 table 1: test results of different combinations of transformand eigenfrequency detection methods. test type ref. freq. [hz] transform eigenf. det. average [hz] deviation [hz] correctness [%] sim. 47 fft peak search 46.181 3.808 75.475 fct 46.41 2.515 48.636 hwft-64 46.359 2.493 66.182 fft cog 46.682 0.828 79.986 fct 46.78 0.835 78.616 hwft-64 46.613 0.84 78.029 fft cnn 46.995 0.132 99.853 fct 46.94 0.606 95.724 hwft-64 46.994 0.174 99.347 sim. 43 fft peak search 42.997 4.717 99.539 fct 43.255 0.865 57.852 hwft-64 43.174 0.438 82.529 fft cog 43.73 0.144 99.214 fct 43.806 0.424 89.367 hwft-64 43.886 0.2 79.345 fft cnn 43.011 0.18 99.414 fct 43.446 1.19 82.38 hwft-64 43.092 0.322 91.363 real 45.58 fft peak search 45.21 7.224 the reference frequency was given in the metadata provided by the measurements and it was calculated by a closed source software in off-line processing. hence, there is no guarantee that the reference frequency is always correct. the correctness values are omitted. fct 46.013 5.172 hwft-64 45.775 4.29 fft cog 46.59 1.387 fct 46.671 1.394 hwft-64 47.225 1.407 fft cnn 45.202 3.186 fct 45.254 3.249 hwft-64 45.487 2.831 real 47.03 fft peak search 46.949 3.814 fct 47.374 4.897 hwft-64 46.901 4.53 fft cog 47.339 1.683 fct 47.259 1.584 hwft-64 47.695 1.521 fft cnn 46.711 2.571 fct 46.817 2.406 hwft-64 47.103 2.194 wt also consists of three variants, namely continuous (cwt): x (t, s) = 1√ s ∫ ∞ −∞ x (t)ψ ( τ − t s ) dt, (3) discrete (dwt): x [m, k] = 1√ ck0 n−1∑ n=0 x [n]ψ [( n ck0 −m ) t ] , (4) and fast (fwt), but unlike the aforementioned transforms, wt is not just a transformation, it resembles a whole family of transformations. in the above equations, where ψ(t) is the so-called mother wavelet function, x(t) denotes the continuous input signal or function, and x(t, s) represents the wt. cwt can be discretized. this process requires a scaling base c0 and a time unit of the mother wavelet, t , to be defined: x [m, k] = 1√ ck0 n−1∑ n=0 x [n]ψ [( n ck0 −m ) t ] (5) if the scaling base is two and the total number of samples can be expressed as a power of two, the previously obtained dwt can be factorized. the obtained fwt can be implemented as a cascade of low pass filters (lpf), high pass filters (hpf) and downsampler banks [8]. depending on the mother wavelet function, different wts can be defined. these wts share common properties, e.g. the frequency and time resolutions of the transform are dependent on each other, they can be viewed as bands where both resolutions are in logarithmic steps. their other properties depend on which mother wavelet is selected. the most widespread wts are the mexican hat wavelet, haar (wavelet) transform and cohen48(1) pp. 123–130 (2020) 126 márton and fodor daubechies-feauveau (cdf) wavelets. wts are applied in data compression, e.g. jpeg2000, djvu, cineform, etc., and transient analysis. 2.4 hybrid wavelet-fourier transform while wt was applied in signal processing for transient and fourier transforms in frequency spectrum analysis, demand for both grew simultaneously. one of the solutions to meet this requirement was hwft. the basic idea behind it was that the wt decomposes the signal of the time domain into bandwidths. inside a bandwidth, characteristic information concerning the time domain in the given bandwidth can be found. therefore, it is possible to perform fts on each bandwidth [9]. unlike the continuous hwft: x (f, s) = 1√ s ∫ ∞ −∞ x (t)π ( τ − t s ) dt, (6) which is scarcely applied, the discrete hwft: x [f, k] = n−1∑ m=0 e−i2πfm/n√ nck0 n−1∑ n=0 x [n]ψ [( n ck0 −m ) t ] (7) has some applications in biometry [10]. fast hwft (fhwft) can be synthesised by applying fft to the output of each bandwidth of the fwt. from the perspective of our research, fhwft is suitable to calculate a frequency spectrum of a wss signal for itpms applications. furthermore, fhwft has a special property which can be exploited to reduce the computational complexity by only performing the fft on those bandwidths that are significant with regard to the given application. this property allows it to be used as a lightweight alternative to the traditional fft. however, since the filter banks of the fwt are imperfect, a phenomenon known as spectral leakage can be observed (fig. 2). spectral leakage essentially means that frequency components from one bandwidth also appear in the neighboring bandwidths [9]. this causes additional disturbances in the spectrum necessitating further investigation into how much the detection of eigenfrequencies in an itpms is affected. for this reason, fhwft is compared with fft and fct using different eigenfrequency detection methods in this paper. 3. eigenfrequency detection methods the most important step in an itpms is eigenfrequency detection because this identifies the frequency component inner pressure dependent. several methods are capable of identifying or detecting peaks in a given frequency spectrum. the sensitivity, ability to handle multiple peaks, noise susceptibility, etc. of these methods differ. figure 2: spectral leakage of the hwft demonstrated on a 100 hz signal 3.1 peak search algorithm one of the simplest methods is the peak search (ps) algorithm. in the first step, a bandwidth must be determined in which the interesting and/or important eigenfrequencies can be present. in this bandwidth, a search is performed to identify the frequency which exhibits the maximum amplitude. this simple algorithm is presented in fp = { f ∈ i ∣∣∣max i |s(i)| = |s(f)| } , (8) where fp denotes the set of peaks, i represents the interval of interest, and s(f) stands for the frequency spectrum of a signal. under certain circumstances, multiple frequency components can be found. depending on the application, mostly vibration analysis, error detection as well as searching for local maxima and multiple peaks is required. in such applications, usually a minimum value ε is also defined to restrict the number of possible peaks: fp = {f ∈ i ||s(f)| >ε and ||s(f)| is local max} (9) if noise or disturbances are present, the ps algorithm might identify the wrong peaks. to reduce the impact of the noise, a sliding-window median filter might be applied. if the ps algorithm in eq. 9 is used, then it is more resilient to noise than the global maximum method (eq. 8), but a priori information is required to identify the correct eigenfrequency. neither of the ps methods are as accurate in such systems as the itpms because pressures about 30 % lower than the optimum shift the pressure-dependent eigenfrequency by only approximately 3 − 4 hz. due to disturbances originating from the road surface and transmission, multiple peaks might be present in the interval of interest. 3.2 center of gravity algorithm a more noise-resistant method is the center of gravity (cog) algorithm since it involves weighted averaging. hungarian journal of industry and chemistry new hybrid wavelet and cnn-based indirect tire-pressure monitoring system 127 figure 3: the pressure-dependent eigenfrequency of a tire in the spectrum of the wss signal unlike the ps, cog always yields only one frequency, therefore, this eliminates the problems that originate from multiple peaks present in the interval of interest. furthermore, the eigenfrequency theoretically has a higher resolution than would have resulted from the sampling frequency and sampling time. this theoretically increased frequency resolution can only be achieved in the presence of an error and only in that case when exactly one frequency component is present in the interval of interest. the cog can be calculated by fc = ∫ i f |s(f)|p df∫ i |s(f)|p df , (10) where fc denotes the center frequency and p represents an exponent whose value, depending on the application, is usually between 2 and 3. although this method is more robust than ps, it is still susceptible to noise. 3.3 convolutional neural networks the eigenfrequency of the tire exhibits a very distinct pattern in the frequency spectrum of the wss signal (fig. 3) which facilitates its detection using pattern-matching algorithms. one of the most popular pattern-matching algorithms involves deep (multilayered) cnns. our research focused on developing an algorithm for eigenfrequency detection using cnn. on the downside, cnns demand much more computational power and memory than ps or cog. to compensate for the higher computational power, a fhwft was strictly developed to carry out the transform in the bandwidth where the tire pressuredependent eigenfrequency is located (hwft-64). the artificial neural networks (anns), e.g., cnn, mimic the structure and supposed operation of neurons and neural systems found in living beings. the differences concern the actual operation of neurons and, unlike the central nervous system of a living being, anns often structure artificial neurons (ans) into layers. since in most cases one layer of neurons is insufficient for most figure 4: the structure of a simple image classification cnn [12]. applications, multilayer anns are often constructed. ans often have multiple inputs, each of which has a unique weight assigned to it. unlike living neurons, the inputs and outputs of ans can be vector-valued. anns store the recognizable patterns in the weight values of their ans. the analytical determination of the correct weight values is taxing but like the central nervous system of a living being, anns can learn the desired patterns. the layers of an ann can have different functions. in the case of cnns, at least one of those layers implement spatial discrete convolution, hence the name convolutional neural networks. the structure of a layer depends on its function as well as the connection between the given layers and the previous layer. each an in the layer has a layer-specific activation function (af) which acts as the output function of the an. depending on the function of the layer, the following types of layers can be distinguished: input, convolutional, polling and fully connected layer. since ans can have vector output values, each layer can be regarded as if each component of the output vector has its own parallel layer with its own weights, which are grouped together as matrices. the only thing in common would be the af associated with these virtual parallel layers [11]. pattern recognition that applies cnns usually consists of four different types of an layers: input, convolutional, polling and fully connected (fig. 4) [12]. the simplest layer is the input layer. it has no input weights, moreover, its af is the identity function and serves as a buffer layer. in the case of convolutional layers, each an shares the same input weights matrices which are referred to as convolution kernels. these layers are applied for noise reduction, filtered downsampling, upsampling and feature extraction. the polling layer is used for downsampling or dimension reduction of data. like the input layer, it has no input weights but a kernel radius and step distance. its specific afs are average, minimum and maximum functions. the fully connected (fc) layer is the most important part of an ann-based classifier. the number of ans must be identical to the number of classes the ann has to distinguish. its name originates from the fact that each of its neurons are connected to each of the neurons in the previous layer and each connection has a unique weight assigned to it. the ans in this layer also have a so-called class index attached to them. during the classification, the neurons contain the possibility of their attached classes. this decision can be 48(1) pp. 123–130 (2020) 128 márton and fodor figure 5: the frequency spectrum of a wss signal produced by fft (a) and fhwft (b) after reordering influenced by the chosen af, from which different functions are available. the most commonly used is the socalled softmax function [11]. 4. our new itpms algorithm 4.1 cnn-based determination of eigenfrequencies since similar results can be achieved to fft using fhwft, it can be concluded that fhwft can be safely used as an alternative to fft in itpmss (fig. 5). the eigenfrequency, depending on the tire pressure, is between 42 and 48 hz. using this information, a fhwft can be optimized which only calculates the fft within the bandwidth of 32–63 hz. if the sampling rate is 1024 samples per second, the fft has to be performed on only 64 samples. this fhwft optimized for tpms was labeled by us as hwft-64. the computational power requirements of hwft-64 are about four times less than in the case of a fft with a sampling rate of 1024 (fig. 6). the freed up resources make it possible to use more advanced eigenfrequency detection methods than ps or cog algorithms. since the cnn can learn different patterns, it is possible to construct such learning patterns which include various frequency disturbances. naturally, the cnn must also be constructed in such a way that such patterns could be learnt correctly. furthermore, the cnn should be as simple as possible. as the first step of the design using the a priori information and by taking the available free and open-source cnn software tool into consideration, an interval of 16 hz was selected as the interval of interest with 47 hz (the figure 6: computational complexity of fft and hwft64 eigenfrequency of the non-deflated tire) at the center. one of the goals of this research was to create a better eigenfrequency detection method than ps. this meant that 16 classes had to be and were specified, thus the last layer of the cnn had to be a fully connected layer that consisted of 16 neurons with a softmax function. since the input interval is comprised of 16 elements, the input layer also had to consist of 16 neurons. the structure of the pattern recognition-based eigenfrequency-detecting cnn can be even simpler than the simple image classifier shown in fig. 4 since much less input data is used. the first attempt just applied a two-layer approach, with an input and an fc layer. this design could not be validated during the learning process. to enhance the capabilities of the cnn, an additional layer had to be inserted. the new layer was a convolutional layer consisting of four neurons and a 3x3 convolution kernel. the outputs were 16d vectors (fig. 7). the resulting cnn was capable of passing the validation tests and robust against the simulated disturbances. implementation of the cnn had to be capable of running on an ecu which meant no opencl, compute unified device architecture (cuda), compute shaders or multiprocessor-based implementation could be used. the mojo-cnn was chosen, which is an open-source implementation with different built in solving algorithms such as adam, sgd and adagrad [13]. only the adam solving algorithm was used. the learning samples were created by frequency shifting of the spectrum of a non-deflated tire (fig. 3). additional learning samples were created by injecting a spike at 54 hz because, in most cases, disturbances would occur at this frequency. to prevent overfitting, data augmentation was used. the validation samples were slightly altered versions of learning samples. the amplitude was altered to such a degree of different frequency components that the location of the peaks remained unchanged. hungarian journal of industry and chemistry new hybrid wavelet and cnn-based indirect tire-pressure monitoring system 129 figure 7: structure of eigenfrequency-detecting cnn after the design of the cnn, the new algorithm was tested. for the tests, fft, fct and hwft-64 were selected as the transforms. the eigenfrequency identification algorithms were ps, cog and our new cnn-based pattern recognition. the test data used consisted of both artificial, referred to as “simulated”, and real measurement data. 4.2 simulations and measurements the first sample tests were conducted in such a way to facilitate a known eigenfrequency. this was accomplished by taking real measurement data, which were filtered by a non-ideal band-stop filter (bsf). the bsf being nonideal makes it possible for the original frequency components to be still present but attenuated and, therefore, act as disturbances. following filtration by the bsf, known frequency components were injected (47 hz and 43 hz for the non-deflated and deflated tires, respectively). as previously stated, the other set of test data were unmodified measurement data. the data was provided by continental ag and the expected eigenfrequency was used as a reference frequency. two “simulated” and two unmodified measurement sets of test data were used for the tests. during the tests, the average frequency deviation and accuracy were evaluated. the accuracy was defined as how many times the algorithm would yield the reference frequency compared to the number of times the algorithm was executed. this could only be determined on the “simulated” data set, since on real measurements, the eigenfrequency cannot be guaranteed to be always the same as given in the metadata sheet. the noises and disturbances were uncontrolled and originated from the road surface, transmission and combustion engine. 5. results and discussion the results can be seen in table 1. as can be observed, the cnn yields better results with regard to approaching the reference frequency more appropriately and with less deviation than ps and comparable results to cog in the case of both “simulated” and real measurement data. figure 8: computational complexity of different combinations of transformand eigenfrequency-detecting methods, when the number of samples was 1024 and the interval of interest consisted of 16 frequency spectral amplitudes the most significant improvement of the cnn-based pattern recognition method can be observed in the results from the fct during the “simulated” data tests. however, except for the first test on the 47 hz “simulated” data, the cog yielded the smallest deviations, the differences between the average frequencies of cog and reference frequencies are bigger than in the case of ps or cnn-based pattern recognition methods. in the case of the cnn-based method, the deviation was about 50 % greater than in the case of cog. this is most likely due to the fact that the output of the cnn-based method yielded a lower frequency resolution than cog. on the other hand, the hwft-64 with cnn shows promising and comparable results using just less than half of the computational power required by fft and cog. 6. conclusion in this paper, a new pattern recognition-based eigenfrequency detection algorithm for itpms was presented. by combining this new algorithm with an optimized fhwft, the resulting system is of lower computational complexity, moreover, the reliability and accuracy is almost the same as that of the currently industrial mainstream fft and cog combination (fig. 8). the computational complexity was calculated by how often simple mathematical operations supported natively by the cpu/fpu were used in the implementation and how those embedded in iterations were affected by the input data size. in this case, the input data size was 1024 samples. the cog can also work with the hwft-64 but is slightly less reliable (table 1). since more free resources are still available, when using this new transform optimized for itpms, further improvements or more complex eigenfrequency detection methods can be used without exceeding the computational complexity of the fft. 48(1) pp. 123–130 (2020) 130 márton and fodor acknowledgements the research was supported by efop-3.6.2-16-201700002 programme of the hungarian national government. references [1] national highway traffic safety administration, federal motor vehicle safety standards, tire pressure monitoring systems, controls and displays, march 2009, http://www.nhtsa.dot.gov/cars/rules/ rulings/tirepresfinal/tpmsfinalrule.pdf [2] schoettle, b.; sivak, m.: the importance of active and intelligent tires for autonomous vehicles, the university of michigan sustainable worldwide transportation report, 2017, report no. swt-2017-2 http://umich.edu/~umtriswt/ pdf/swt-2017-2.pdf [3] silva, a.; sánchez, j. r.; granados, g. e.; tudonmartinez, j. c.; lozoya-santos, j. j.: comparative analysis in indirect tire pressure monitoring systems in vehicles, ifac-papersonline, 2019, 52(5), 54–59 doi: 10.1016/j.ifacol.2019.09.009 [4] gustafsson, f.; drevo, m.; forssell, u.; lofgrën, m.; persson, n.; quicklund, h.: virtual sensors of tire pressure and road friction, sae technical paper series, 2001. doi: 10.4271/2001-01-0796 [5] márton, z.; fodor, d.; enisz, k.; nagy, k.: frequency analysis based tire pressure monitoring, 2014 ieee international electric vehicle conference (ievc) doi: 10.1109/ievc.2014.7056187 [6] oberst, u.: the fast fourier transform, siam journal on control and optimization, 2007, 46(2), 496– 540 doi: 10.1137/060658242 [7] strang, g.: the discrete cosine transform, siam review, 1999, 41(1), 135–147 doi: 10.1137/s0036144598336745 [8] goswami, j. c.; chan, a. k.: fundamentals of wavelets, john wiley & sons, inc., 2011 doi: 10.1002/9780470926994 [9] tarasiuk, t.: hybrid wavelet-fourier spectrum analysis, ieee transactions on power delivery, 2004, 19(3), 957–964 doi: 10.1109/tpwrd.2004.824398 [10] ziółko, b.; kozłowski, w.; ziółko, m.; samborski, r.; sierra, d.; gałka, j.: hybrid wavelet-fourierhmm speaker recognition, international journal of hybrid information technology, 2011, 4(4), 25– 41 [11] albawi, s.; mohammed, t. a.; al-zawi, s.: understanding of a convolutional neural network, 2017 international conference on engineering and technology (icet), 2017. doi: 10.1109/icengtechnol.2017.8308186 [12] hijazi, s.; kumar, r.; rowen, c.: using convolutional neural networks for image recognition, ip group, cadence, 2015. https://ip.cadence.com/ uploads/901/cnn/ [13] https://github.com/gnawice/mojo-cnn/wiki hungarian journal of industry and chemistry http://www.nhtsa.dot.gov/cars/rules/rulings/tirepresfinal/tpmsfinalrule.pdf http://www.nhtsa.dot.gov/cars/rules/rulings/tirepresfinal/tpmsfinalrule.pdf http://umich.edu/~umtriswt/pdf/swt-2017-2.pdf http://umich.edu/~umtriswt/pdf/swt-2017-2.pdf https://doi.org/10.1016/j.ifacol.2019.09.009 https://doi.org/10.4271/2001-01-0796 https://doi.org/10.1109/ievc.2014.7056187 https://doi.org/10.1137/060658242 https://doi.org/10.1137/s0036144598336745 https://doi.org/10.1137/s0036144598336745 https://doi.org/10.1002/9780470926994 https://doi.org/10.1002/9780470926994 https://doi.org/10.1109/tpwrd.2004.824398 https://doi.org/10.1109/icengtechnol.2017.8308186 https://doi.org/10.1109/icengtechnol.2017.8308186 https://ip.cadence.com/uploads/901/cnn/ https://ip.cadence.com/uploads/901/cnn/ https://github.com/gnawice/mojo-cnn/wiki hungarian journal of industry and chemistry vol. 48(1) pp. 131–138 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-19 xbrl utilization as an automated industry analysis alex suta*1 and árpád tóth1 1research center of vehicle industry, széchenyi istván university, egyetem tér 1, győr, 9026, hungary in the last two decades, electronic financial reporting went through a significant evolution, where to date, extensible business reporting language (xbrl) has become the leading platform that is already obligatory for listed entities in the united states and was also legislated in the european union from january 1, 2020. the primary objective of this research was to review the us-listed companies’ 2018 quarterly reports. the study generated an automated industry analysis for the automotive industry from the aspect of four main financial item categories as an alternative to statistics-based, manually prepared industry analyses. statistical tests were carried out between two industrial classification methodologies, the securities’ industry identification marks and the reported standard industrial classification (sic) codes. the results showed a significant difference between the industry classification methodologies. automated reporting was more precise with regard to the identification of the listed and reporting entities, however, the data fields of sic codes within the xbrl data set provided an inaccurate classification, which is a potential area of improvement along with additional recommendations outlined in the conclusion. keywords: xbrl, us-listed entities, acl, automated data analytics, industry analysis, sic codes 1. introduction the electronic reporting and automated fundamental reviews in the field of financial reporting is becoming increasingly important considering the difficulties and error-prone procedure of manual analysis from the available source of information. the extensible business reporting language (xbrl) provides a standardized platform for this activity, which supports automated and digitalized reviews compared to the paper-based reports from the previous manual. this electronic reporting platform is already used as the official reporting form in the united states for listed entities, therefore, the application of a proper industry classification is essential. even though xbrl reporting is required by the u.s. securities and exchange commission (sec), research institutions can choose from various generally accepted industry classifications. despite the lack of regulation, it is a primary interest of research institutions to protect their reputations by adequately representing companies from the various industries. the two different approaches might provide different results, which can lead to inaccurate trend projections or unreliable industry comparisons. the validation of the xbrl classification and reports by marketing research firms can only be reconciled and validated to statistical industry reports which identify discrepancies. to date, standard industrial classification (sic) codes are used in the sec’s electronic data gathering, analysis, *correspondence: suta.alex@ga.sze.hu and retrieval (edgar) system to define the type of business of companies. based on its primary activity, each company assigns a four-digit code to itself when registering an initial public offering (ipo) with the sec [1]. the four digits indicate levels of description of the industry classification, e.g. the location hierarchy for car manufacturers is division d manufacturing (codes 2039), code 37: transportation equipment, and code 3711: motor vehicles and passenger car bodies [1]. the objective of this research was to review the us-listed companies, where xbrl reports are already required and implemented. subsequently, through an automated review of the automotive industry, to then identify how these reports can be compared to the european listed entities. this information is crucial for stakeholders and regional policymakers to gain a clear view of the conditions of the target industry. according to the european securities and markets authority (esma), from january 1, 2020 onwards, new requirements on the stock exchange-listed companies in the european union came into effect to provide respective financial statements in a new european single electronic format (esef). this is a significant change to the application of xbrl as companies now have to provide reports in this specific reporting language. the data sets include structured information; for this reason, a new wave of research initiatives is expected in this academic area that could follow on from inconsistent industry classifications, further hindering comparability. https://doi.org/10.33927/hjic-2020-19 mailto:suta.alex@ga.sze.hu 132 suta and tóth 2. literature review 2.1 xbrl utilization in industry-specific data analysis prior literature has documented uses of xbrl in a variety of data analysis environments, generally in the research areas of accounting and financial reporting. systematic financial data provides data analysts and investors with the ability to measure performance and risks, as well as create comparisons, ratings and other value-added products [2]. connected to comparability aspects, several sources have been reviewed that are related to the semantic issue of industrial classification. being a driver of electronic data interchange, xbrl data sets are constructed from multiple identifying tags and numerical data that can be processed by computer software [3]. while the technical background on data-centric analysis is available [4] 2013 [5] 2014, [6], it is uncommon in the industry-specific research literature that xbrl databases are used as the primary source of data. chychyla-leone-meza [7] measured financial reporting complexity by comparing the quantity of text in us generally accepted accounting principles (gaap) and sec regulations of textual data from xbrl filings. in this study, the variation with regard to the data content of different taxonomy versions (denominative tags, labels, documentation) is emphasized. for this reason, the annual changes in published taxonomy updates have to be taken into consideration [8]. despite the existence of the xbrl industry resource group established by the fasb [8], standard industrial classification (sic) codes are not part of taxonomy updates and their current 2007 form seems to be generally accepted for statistical use. felokim-lim [9] observed changes in the information environment of analysts by the overuse of customized tags, creating assumptions based on industrial classification as a factor. zhang-guan-kim [10] proposed an expected investor crash risk model based on financial information gathered from xbrl-based sec databases. in terms of the estimation of the impacts, the industry median of customized tags is generated by 2-digit sic codes as an adjustment tool in the regression model. similarly, industrial classification was taken into account as a dummy variable during the analysis with regard to the xbrl adoption of reductions in audit fees as per shan-troshanirichardson [11]. in other xbrl-based studies, industry-specific assumptions required solutions other than basic sic codes. liu-luo-wang [12] reviewed the effect of xbrl adoption on information asymmetry, where sic was reclassified to identify high-technology industries. 2.2 discrepancies between industrial classification systems since the emergence of the north american industry classification system (naics) in 1997 as a sound replacement of standard industrial classification (sic) codes in u.s. industrial statistics, papers have reviewed the impacts of different frameworks in financial research. effective comparative statistics require the use of a standardized classification system [13]. the u.s. economic census bureau has made regulatory, business and academic purposes of performing economic research on historical data possible. in 1997, the existing framework, the sic, was replaced by the naics [14]. unlike the sic’s mixed production/market system, naics introduced a production-oriented economic concept that supports the examination of industry-specific indicators such as productivity, input-output relationships and capital intensity [15]. the specific rearrangements between industrial classes primarily affected manufacturing industries, where the sic functions as a somewhat outdated alternative. u.s. government departments, namely the bureau of labor statistics (bls), internal revenue service (irs) and social security administration (ssa), alongside the u.s. securities and exchange commission (sec), continue to use the most recent 2007 update of four-digit sic codes. while maintaining a unified classification system is necessary for government departments, the lack of conceptual harmony between industrial classification systems creates a discrepancy with academic research [16]. several papers have been collected that present empirical evidence of disharmonious schemes based on financial statement data sets. kahle-walking [17] observed differences in financial variables gathered from two statistical databases (crsp and compustat) using four-digit sic codes to be substantial, moreover, showed that commonly used methods of industrial classification disagree due to frequent changes in the sic codes of firms. bhojraj-lee-oler reviewed the capital market applications of four broadly available industrial classification schemes and found that a significant degree of variance with regard to the number of companies represented in industry divisions exists. the study argues that the six-digit global industry classification standard (gics), followed by naics, offers better comparability between firms concerning sic in terms of the critical evaluation of financial ratios and that industrial classification is essential in instances of fundamental analysis. while gics reflects the dynamic changes in industry sectors, being a privately available system mainly involved in investment processes, it is unlikely to be suitable in statistical research [18]. kelton-pasquale-rebelein [19] referred to sic codes as outdated in the field of industry cluster analysis and prepared an updated framework using naics. as opposed to classifying establishments according to similar products (sic), the groups are formed from identical production processes (naics). hrazdil-zhang [20] and hrazdil-trottier-zhang [21] published empirical results on the heterogeneity of industry concentration with the use of sic and other classification schemes based on the market shares of sales and financial ratios of companies in the manufacturing sector (sic 2000-3999). according to their findings, the sic system remains inferior to gics and naics in terms of industrial homogeneity. hungarian journal of industry and chemistry xbrl utilization as an automated industry analysis 133 instead of ordinary company databases such as compustat or s&p 1500, papagiannidis et al. proposed an exploratory big data method to gather regional research of industry clusters based in the uk. in this study, keywords connected to business operations were collected from official websites to enhance the level of detail provided by single sic codes, supporting the formation of regional clusters. it is a common conclusion in the reviewed literature that the sole use of sic codes in industry analysis could lead to the loss of information and false estimation of market forces; in this context the potential of xbrl as a primary data source of financial statements has been reviewed. 2.3 the multi-tier supply chain approach one possible outcome of the barriers of traditional statistical classification systems is the addition of extra information to existing schemes. in an industrial analysis, especially in the automotive industry, it is essential to differentiate between operational properties, e.g. their position in the automotive supply chain. the contemporary position of an industry must be judged by the different weights of its market players. assumptions about financial information are heavily affected by the final product, whether it is a part of the interorganizational supply chain, or sold to dealerships or directly to consumers in the form of passenger cars. in terms of a supply chain, manufacturers and suppliers can be classified into multi-tiered groups based on their position in the production chain, as well as the state of raw materials (tier 3 and additional sub-tiers) in addition to finished or semi-finished components (suppliers from tiers 1 and 2) compared to fully finished products (original equipment manufacturers (oems)). concerning the automotive industry, sources from both academia, business and governments [22–24] agree that market players from multi-tier supply chain structures can be ranked as follows: 1. oems: a concentrated group of companies accountable for the main manufacturing, assembly and design processes that possess a large market share and well-known brand names; 2. suppliers from tiers 1 & 2: potentially several hundred large or small companies, accountable for the supply of automotive parts and systems to oems. the range of sold goods is diverse and includes engine components, interior, exterior, transmission as well as cooling and electronic systems. although their role in the supply chain is consistent, suppliers from tiers 1 and 2 vary in their direct/indirect (through other participants) nature of interaction with oems, therefore, from a statistical viewpoint, can be aggregated; 3. tier 3 and sub-tier suppliers: several thousand smaller companies are accountable for the supply of raw materials to suppliers from tiers 1 & 2. in the scientific literature, several utilizations of the multi-tier supply chain approach exist. mena-humphrieschoi [25] reviewed the existing literature at the time on structural arrangements (buyer-supplier-customer) and prepared three cases of theoretical linkage. according to the study, the most typical structure of the automotive industry is the “closed triad”, where the buyer (oem) can insist on certain requirements (either assurance or training function) not only from tier 1 but sub-tier suppliers as well. masoud-mason [26] used the multi-tier system in the automotive industry to simulate cost optimization on a supply-chain level. thomé et al. [27] adopted a similar approach of representing many tiers and their interactions that affect selected flexibility measures (product, responsiveness, sourcing, delivery and postponement). other popular fields of use are sustainability-related questions and green supply chains [28–30]. the available literature clarifies the widespread applicability and general acceptance of tiered levels of suppliers, which supports the methodology examined in the current study. despite its academic use, the application of the well-established oem / tiered system of suppliers in automotive business reports published by major consulting firms [31–33] is common practice. 3. data collection and methods used the sec has published xbrl data sets containing raw aggregate financial statement data quarterly since 2009. at the same time, as a premium service, the sec offers a professional version of its search engine [34] designed specifically to fit the goals of professional financial analytics. however, in line with tendencies identified from the literature review, even a discrepancy on the same platform exists between the standard industrial classification codes current in xbrl data sets and the edgar search tool. to perform an automated industry analysis, a suitable classification is required. in this study, a possible classification using the software program acl (audit command language) robotics professional version 14.1.0.1581 is evaluated. from the listed u.s. entities, those operating in the automotive industry were selected to measure deviance in terms of crucial financial indicators between the two data sources. the specific choice of the automotive industry lies in its accurate definability, while the goal of the study was to provide an industry-independent methodology of data analysis that can be applied to several other fields. the two main platforms of data collection were edgar pro online (2019) operated by the sec, which is equivalent to the quasimanual download process of financial statements, and the obligatory quarterly reports of aggregate data sets in the xbrl format available on the sec website. to avoid existing industrial classification issues, a multi-tier supply chain approach was introduced by grouping companies as oems and suppliers from tiers 1 & 2 (t1&2 s). 48(1) pp. 131–138 (2020) 134 suta and tóth 4. results 4.1 data categorization: number of companies and industries by using the edgar pro online search tool, market segments can be filtered, of which three categories connected to the automotive industry are available. at the same time, in the xbrl data set, companies are provided with much general information, including sic codes that can be used for categorization. according to the list of codes provided by the sec, six four-digit codes cover the automotive industry (and related services with the exception of retail) that were reviewed in the quarterly reports of 2018. a summary of publicly listed entities is presented in table 1. all entities listed on the new york stock exchange (nyse), national association for securities dealers automated quotations (nasdaq) and better alternative trading system (bats) from the entire population are supposedly consistent data sources and regulated by the sec. in addition to the variance in the number of listed entities in the automotive industry, the size of the entire population between the two sources is inconsistent and differs by over 24%. in terms of industrial classification, the taxonomy behind sic codes in xbrl data sets is valid but incomparable to the customary edgar approach in the case of the identification of specific activities. therefore, two additional categories were created to fit the measurement process; oems and suppliers from tiers 1 & 2 (other automotive suppliers). 4.2 errors in terms of the consistency and availability of samples listed entities from both data sources that are unmatched as a result of their supposedly consistent counterparts were found. out of the sample sizes of 103 and 74, 50 companies are common in both which raises concerns over reliability. furthermore, data availability raised concerns in terms of search results from the sec edgar pro online system. out of the strong sample size of 103, 13 annual reports concerning 2018 were unavailable in the electric filing system of the sec, while an additional 10 required data collection from official websites. four financial statement items concerning the wealth and profitability of companies were selected for analysis in order to evaluate the differences between the two industrial classification schemes. the values of total assets, total equity, net sales revenue and profit after-tax are central financial factors of investor decision-making. when necessary, exchange rates of the federal reserve were used according to the asc (accounting standards codification) standards issued by the financial accounting standards board (fasb) [35]. 4.3 comparison of financial information on an industrial level based on the financial statement data, descriptive statistics were calculated on the selected reporting lines. differences were summarized in terms of both absolute values between the two data sources and percent deviations as presented in the tables 2 and 3. a general observation of the data source is that the intervals between the minimum and maximum values are substantial for all four financial statement items. it is likely that – when used as a statistical sample – a normal distribution cannot be assumed. the standard deviation exceeds the mean values in the case of total assets, therefore, the set of values (especially for the financial data of suppliers from tiers 1 & 2) is highly dispersed. a pattern can be observed in the deviation between the two data sources. the total values of oem financial statement items are higher in the xbrl data set, in contrast to data derived from the online sec source, while the opposite is seen in the case of suppliers from tiers 1 & 2, where the total values are dominated by online table 1: industrial specification of data sources sec’s edgar online pro sec’s edgar xbrl data set industrial specification number of companies industry (sic) number of companies o e m s { auto & truck manufacturers 26 3711. motor vehicles & passenger car bodies 20  o e m s su pp lie rs fr om ti er s 1 & 2  automobiles, parts & service retailers 24 3713. truck & bus bodies 2 auto, truck & motorcycle parts 53 3714. motor vehicle parts & accessories 41  su pp lie rs fr om ti er s 1 & 2 3715. truck trailers 1 3716. motor homes 2 3751. motorcycles, bicycles, and parts 8 total 103 total 74 entire population size 5,736 entire population size 7,133 hungarian journal of industry and chemistry xbrl utilization as an automated industry analysis 135 sources. as an attempt to generalize the automotive industry, mean values were calculated where xbrl represents higher values except for the net sales revenues of suppliers. these deviations are partly validated by the amount of incompletely matched samples, but the 103:74 sample-size ratio is not represented by the results. the table 4 summarizes the difference between the results of descriptive statistics in the form of percentages. despite former expectations, oems do not represent the majority of the financial item totals (between 45.1 and 55.9%), total equity (between 31.8 and 48.6%), net sales revenue (44.7 and 57.6%) and profit after-tax (35.452.5%), the differences between data sources can be measured on a scale of 6.7% to 31.9% as seen in table 4. suppliers from tiers 1 & 2 match to an even lesser extent, so percent deviations are typically higher, especially in the case of net sales revenue (56.7%). based on the matrix, the individual averages of companies cannot be used for industry generalization, both in terms of absolute mean values and standard deviations. the deviation “hotspots” are clearly centered around the suppliers from tiers 1 & 2. 4.4 chi-square statistical testing to support our assumptions of statistically significant deviation between data sources, pearson’s chi-squared test was implemented, a full description of the steps is available in appendix a [36, 37]. selected categories of oems and suppliers from tiers 1 & 2 were differentiated along with expected (data derived from online sec-based financial statements) vs. observed (data derived from xbrl data sets) values. based on the performed chi-square test, the results highlighted that the differences between the expected and observed values of financial statement items (total assets, total equity, net sales revenue and profit after-tax) were significant. with a 95% confidence interval (α = 0.05), oems and suppliers from tiers 1 & 2 both exceeded the critical value of 16.92 with 7 degrees of freedom (df = 7). it is important to note the very significant (almost 10 times higher) impact of suppliers from tiers 1 & 2 in terms of the total level of deviance. 5. conclusions xbrl preparation is obligatory, however, the content can include differences from the reported and published financial statements. conclusions can be summarized in the following points: • potential duplication of lines in xbrl sources (e.g. 8 lines of certain financial statement items from china automotive systems, inc.); • lack of standardization in tags: the xbrl platform manages to integrate more financial reporting taxonomy (different annual versions of ifrs and us gaap). due to the different (and potentially customized) tags, the definitions of some financial statement items converge; the structure of financial statements has yet to be fully harmonized between annual reports and xbrl statements; • errors in the reporting period (temporal differences): in some cases, outdated (1 or 2 years prior to table 2: automotive market share of the entire population (%, number) representation % (n) sec’s edgar pro online sec’s edgar xbrl data set entire population 100% (5,736) 100% (7,113) oems 0.45% (26) 0.31% (22) suppliers from tiers 1 & 2 1.34% (77) 0.73% (52) total assets total equity net sales revenue profit after-tax total 1.80% (103) 1.04% (74) oems (matched) 0.28% (16) 0.20% (14) suppliers from tiers 1 & 2 (matched) 0.59% (34) 0.50% (36) total (matched) 0.87% (50) 0.70% (50) table 3: absolute financial data from data sources (left – sec’s edgar pro online / right – sec‘s xbrl data set) (usd in millions) statistics category total assets value total equity attributable to company owners net sales revenues profit after taxes totals oem 783.346 874.139 153.668 221.111 606.225 649.422 23.941 35.125 tier 1&2 s. 953.149 688.812 329.224 234.365 749.694 478.399 43.717 31.834 mean oem 27.012 39.734 5.299 10.050 20.904 29.519 826 1.597 tier 1&2 s. 12.880 13.246 4.449 4.507 10.131 9.200 591 612 st. dev oem 66.884 77.251 11.802 18.956 45.992 52.970 1.875 3.007 tier 1&2 s. 56.749 63.640 21.527 23.684 33.241 34.997 2.971 3.262 48(1) pp. 131–138 (2020) 136 suta and tóth table 4: deviation matrix between data sources (%) statistic category total assets value total equity attributable to company owners net sales revenues profit after taxes totals oem 10.39% 30.50% 6.65% 31.84% t1&2 s. 38.38% 40.48% 56.71% 37.33% mean oem 32.02% 47.28% 29.18% 48.29% t1&2 s. 2.76% 1.29% 10.12% 3.50% st.dev oem 13.42% 37.74% 13.18% 37.65% t1&2 s. 10.83% 9.11% 5.02% 8.93% the current fiscal year) financial information is presented in current filings (e.g. an entity presents information from the 2017 fiscal year in the q4 2018 filing as the most current); • the inability to fully and feasibly automate data analysis in the case of automotive suppliers. mean values are inconsistent between data sources due to the varying sample size of automotive suppliers. to perform a comprehensive industry analysis, error terms need to be defined clearly. otherwise such an analysis would be performed with many predefined assumptions, leading to a decrease in the overall explanatory power and raising concerns about reliability/reproducibility. financial analysts should use xbrl datasets with concern, these points kept in mind. as a currently available best practice, the methodology of the u.s. securities and exchange commission is a precedent for the building of inline xbrl statements into integrated datasets. an emerging challenge of regulatory bodies such as the european securities and markets authorities is the supervision of companies uploading their data to a central system of a similar nature to produce well-structured databases for automated financial analytics. acknowledgements the research presented in this paper was financed by the “research area excellence program – 2019 (tudfo/51757/2019-itm)” and university of győr. references [1] naics association (2019). common sic questions, https://www.naics.com/ frequently-asked-questions/#naicsfaq [2] xbrl international (2019). an introduction to xbrl, https://www.xbrl.org/the-standard/ 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https://www.rolandberger.com/it/publications/global-automotive-supplier-study-2018.html https://pro.edgar-online.com/ https://www.federalreserve.gov/releases/h10/hist/ https://www.federalreserve.gov/releases/h10/hist/ 138 suta and tóth appendix a – chi-square test steps 1) contingency table financial statement items oems suppliers from tiers 1 & 2 total assets expected 783,346 953,149 observed 874,139 688,812 total equity attributable to the owners of companies expected 153,668 329,224 observed 221,111 234,365 net sales revenue expected 606,225 749,694 observed 649,422 478,399 profit after-tax expected 23,941 43,717 observed 35,125 31,834 total 3,346,977 3,509,195 2) h0 the financial values of the xbrl data source (observed values) are not significantly different from the values of the online sec edgar pro online data source (expected values). therefore, industry totals from the two sources are consistent. 3) calculated marginal totals for the observed table 4) expected value calculation based on the specific financial statement item’s proportion in the whole population 5) degree of freedom df = (r − 1)(c− 1) df = (8− 1)(2− 1) = 7 6) calculation of chi-square values financial statement items χ2 = n∑ i=1 (oi − ei) 2 ei oems suppliers from tiers 1 & 2 total assets e-o -90,792 264,337 (e-o)2 8,243,257,799 69,874,243,884 total equity attributable to the owners of companies e-o -67,442 94,860 (e-o)2 4,548,480,637 8,998,332,516 net sales revenue e-o -43,197 271,295 (e-o)2 1,865,960,356 73,600,784,685 profit after-tax e-o -11,184 11,883 (e-o)2 125,073,800 141,206,159 chi-square total chi-square 4,417 43,490 47,907 7) determination of significance level and critical value: significance level (alpha) 0.05 critical value 16.92 8) the chi square test result showed as the h0 hypothesis should be rejected with a 95% confidence interval (degree of freedom = 7). the chi-squared test results showed that the hypothesis h0 should be rejected. hungarian journal of industry and chemistry introduction our virtual environment neural network architectures fcn u-net pspnet training with virtual data results conclusion introduction the design strategy the optimization problem algorithm flowchart discussion simulation experiments conclusion introduction design concept results and analysis power stage isolated power supply for the gate drivers gate drive circuit built-in features cooling system conclusion introduction shell eco-marathon our team the challenge lidars simulation with ros ros in general simulation steps of the algorithm filtering clustering convex hull delaunay triangulation and voronoi diagram ransac delete unnecessary reference lines results and future works conclusion introduction diffusion modeling techniques standard equivalent circuits equivalent circuit development for modeling non-fickian diffusion experimental setup analysis of the measurement results determining randles circuit parameters conclusions introduction information sources global navigation satellite systems vehicle model traditional vehicle sensors and inertial measurement unit (imu) optical as well as soundand radio-based sensors databases and maps dedicated short-range communications fusion algorithms simple algorithms: dead reckoning, inertial navigation and map matching linear filtering: the kalman filter nonlinear filtering: the particle filter conclusion introduction electric power conversion system model modeling of energy storage modeling of the three-phase inverter modeling of the three-phase pmsm modeling of electronic control unit discrete-time control algorithm design of the controller parameters implementation of the smith predictor testing of the controlled power conversion system model testing of the smith predictor battery management system design implementation of a battery management system simulation of a driving cycle of a vehicle conclusions introduction experimental nonlinear measurement method and setup supplemental measurements material results and discussion conclusions introduction modeling the vehicle modeling the proposed system implementation test results conclusion introduction experimental tools of implementation construction of the system results and analysis conclusion introduction experimental samples and measurements results and discussion experiments calculation of time constants conclusion introduction design process and evolution of the structure structure of the loop test results and analysis based on experiments results discussion conclusion introduction experiment propulsion power requirements and fuel consumption – defining variables matlab implementation results and analyses obd-based positioning conclusion introduction model: the polarizable dielectric sphere method: brownian dynamics simulation scaling and reduced units relating reduced units to real er fluids results and discussion quantities studied the effect of time step the effect of friction coefficient the effect of dipole moment summary introduction modeling strategy dead reckoning algorithm lateral vehicle dynamics extended kalman filter design state-space model jacobians noise model the extended kalman filter algorithm simulation environment simulation results comparison with dead reckoning comparison with gps conclusions introduction nds building blocks opendrive road format roadxml freely available map data open source gis software simulation software environment results and analysis data conversion discussion conclusion introduction transforms related to itpms fourier transform cosine transform wavelet transform hybrid wavelet-fourier transform eigenfrequency detection methods peak search algorithm center of gravity algorithm convolutional neural networks our new itpms algorithm cnn-based determination of eigenfrequencies simulations and measurements results and discussion conclusion introduction literature review xbrl utilization in industry-specific data analysis discrepancies between industrial classification systems the multi-tier supply chain approach data collection and methods used results data categorization: number of companies and industries errors in terms of the consistency and availability of samples comparison of financial information on an industrial level chi-square statistical testing conclusions de gruyter open hung. j. ind. chem. 2017 45(2), 1–49 table of contents methyl-tert-butyl-ether synthesis reactor modelling and optimization using aspen custom modeler zeeshan nawaz .............................................................................................................................................. 1–7 modelling the partial demineralization process of cow milk by superpro designer attila csighy, andrás koris, and gyula vatai ......................................................................................... 9–12 investigations of the tlinp2se6–in4(p2se6)3 system and its optical properties valeria tovt, igor barchiy, michal piasecki, iwan kityk, and anatolii fedorchuk ............................. 13–18 examination of innovative high-throughput fermentations áron németh ............................................................................................................................................. 19–21 the effect of advanced oxidation pre-treatment on the membrane filtration parameters of dairy wastewater mihály zakar, ildikó kovács, péter muhi, erika hanczné lakatos, gábor keszthelyi-szabó, and zsuzsanna lászló .............................................................................................................................. 23–27 microencapsulation of vegetable oil: alternative approaches using membrane technology and spray drying krisztina albert, gyula vatai, and andrás koris .................................................................................. 29–33 effect of chain length and order of the alcohol on enzyme activity during enzymatic esterification in organic media zsófia márkus, katalin bélafi-bakó, gábor tóth, nándor nemestóthy, and lászló gubicza ........... 35–39 state-of-the-art recovery of fermentative organic acids by ionic liquids: an overview konstantza tonova .................................................................................................................................. 41–44 application of a hydrophobic polymeric membrane for carbon dioxide desorption from an mea-water solution zenon ziobrowski and adam rotkegel .................................................................................................... 45–49 hungarian journal of industry and chemistry vol. 45(2) pp. 1–7 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0012 methyl-tert-butyl-ether synthesis reactor modelling and optimization using an aspen custom modeler zeeshan nawaz sabic technology & innovation, po box 42503, saudi basic industries corporation (sabic), riyadh, 11551, saudi arabia a pseudo-homogeneous model of methyl-tert-butyl-ether (mtbe) synthesis in a multi-tubular packed-bed reactor has been developed using an aspen custom modeler (acm) for selecting optimum operating strategies, for the maximization and enhancement of mtbe production, and isobutylene consumption, respectively. the model accounts for mass, energy and momentum balances; and the effectiveness factor is evaluated in a onedimensional pseudo-homogeneous model. the kinetic investigation contains kinetic rate expressions as given by the effectiveness factor for accounting the resistance of pellets in terms of mass and heat transfer. an activity coefficient can be used in order to systematically obtain a new steady-state solution. the model used literature-based correlations for the estimation of heat transfer coefficients. the value of the coefficient for gascoolant heat transfer can be adjusted by using a tuning coefficient in order to enrich the process data. reasonable agreement was found between model predictions and data under similar conditions. the studies concerning model sensitivity compute the optimum temperature, pressure, feed flow rate, methanol/isobutylene ratio, heat removal rate, etc. of the reactor and suggest optimum operating conditions of the reactor. keywords: methyl-tert-butyl-ether (mtbe) synthesis, lead reactor, multi-tubular packed-bed, aspen custom modeler (acm), isobutylene 1. introduction methyl-tert-butyl-ether (mtbe) is of importance among petrochemicals due to its physicochemical properties and as an additive in gasoline. it contributes to the gradual elimination of lead-based additives, increasing the octane number (as an octane booster) and serves as a volume extender [1]. it is formed by the etherification reaction of an alcohol with a tertiary olefin. ethers are preferable over alcohols due to their lower sensitivity values, i.e. the difference between the ron (research octane number) and mon (motor octane number) [2]. today, standard (huls ag) and ethermax are the known processes commercialized by snamprogetti, cdtech, universal oil products (uop), axens, fortum, arco, phillips, bp-intevep, sinopec, sumitomo, etc. these are similar processes to each other. in this study a snamprogetti-lead reactor is modelled to maximize its productivity. 2. experimental conditions considered 2.1. reaction chemistry the following five reactions (eqs.(1-5)) are involved in mtbe synthesis when isobutylene reacts with methanol *correspondence: zeeshan@sabic.com (meoh). mtbe synthesis is an exothermic liquidphase reversible reaction catalysed by a cationic ionexchange resin (sulphonated macroporous polystyrene). for each mole of isobutylene converted, ~37.7 kj of heat is released and the thermodynamic equilibrium determines the extent of conversion [1-2]. mtbe: ch3oh + (ch3)2c=ch2  (ch3)3coch3 (1) however, undesirable side reactions may take place such as the dimerization of isobutylene to diisobutenes (dib), 2,4,4-trimethyl-1-pentene (tmp-1) and 2,4,4trimethyl-2-pentene (tmp-2); and the formation of methyl sec-butyl ether (msbe), dimethyl ether (dme) and tert-butyl alcohol (tba). the water produced during the formation of dme may react with isobutylene to form tert-butyl alcohol (tba) and its blending octane number is lower than that of mtbe. on the other hand, the presence of water reduces the acidity of the catalyst (reducing activity) and therefore a higher reaction temperature is required. dib: 2 (ch3)2c=ch2  (ch3)3ch2(ch3)c=ch2 + (ch3)3c(h)c=c(ch3)2 (2) msbe: ch3oh + (c2h5)ch=ch2  ch3ch(och3)(ch2ch3) (3) dme: 2 ch3oh  ch3och3 + h2o (4) tba: (ch3)2c=ch2 + h2o  (ch3)3coh (5) nawaz hungarian journal of industry and chemistry 2 2.2. thermodynamics etherification is an exothermic equilibrium reaction between a primary alcohol and an iso-olefin containing a double bond on a tertiary carbon atom (such as isobutene (ibu) under the operating temperature and pressure. owing to the non-ideality of liquid mixtures due to their disparate polarities and equilibria, the kinetic rate expressions for the synthesis of mtbe are generally given in terms of component activities. equilibrium and rate equations based on activities were first proposed by rehfinger et al. [3] and kinetic (including the effectiveness factor) and equilibrium data from an isothermal packed-bed reactor using the catalyst amberlyst-15 were discussed by zhang et al. [4]. the activity-based equilibrium constant is expressed as: �a = � �mtbe �ibu∙�meoh � eq. = � �mtbe �ibu∙�meoh ∙ �mtbe �ibu∙�meoh � eq. (6) where ameoh, aibu, and amtbe are the activities of methanol, isobutene, and mtbe, respectively, while γ and x are the activity coefficients and mole fractions of these components, respectively. the values of the equilibrium constant (ka) published in the literature vary significantly (fig.1) as a function of temperature [3-10]. deviations may stem from the different bases used for the evaluation of the activity coefficient as well as from the operating temperature of the reactor, for example, employing primary reactors or reactive distillation columns. 2.3. catalysis and kinetics the acidic cation exchange macroporous resin catalysts used commercially for the synthesis of mtbe are provided by bayer, dow chemical (rohm & haas), purolite, kairui, etc. the resins are prepared by the suspension of styrene in the presence of an appropriate cross-linking agent (divinylbenzene (dvb)) for polymerization functionalized by means of sulphonation with sulphuric or chlorosulphonic acid [11]. a reduction in volume of ~20-30% is observed because of the shift of the resin from the hydrated form (as it is generally charged in water) to a more contracted form due to a much less polar-reacting medium (a hydrocarbon/methanol mixture). the usability of the catalyst largely depends upon the process conditions, namely the type of reactor, e.g. a reactor receiving thermal support is better than adiabatic and thermal degradation with breakage of the carbon-sulphur bond (therefore, temperatures below 130 °c are recommended) and feed impurities (cations, e.g. na, ca, fe, al, cr, si, etc., strong n-bases like ammonia and amines, weak n-bases like acetonitrile and propionitrile, and dienes). the rate expressions, essential kinetic parameters and thermodynamic data such as the activation energy, effectiveness of the catalyst, heat of reaction, equilibrium constant and so forth have been selected from the literature [3-14]. the rate of reaction depends substantially on two parameters: acidity (type and number of acidic sites) and accessibility (porosity, content, particle diameter and treating medium). in the homogeneous model (in the absence of the diffusion phenomena), the reaction rate can be described in terms of confined catalyst pores, where the reactant concentration is in a partition equilibrium with the corresponding concentrations in the external solution. the rate-determining step was estimated to be the surface reaction between protonated adsorbed methanol and isobutylene [3-13]. this simplifies the rate of consumption for isobutylene after assuming that polar methanol molecules are preferentially adsorbed onto the ion-exchange resin catalyst (table 1) and the fraction of unoccupied sites over the catalyst surface was small as follows [4]: aibu mtbe ibu 0 2 meoh a meoh 1            e rt a a r a e a k a (7) where ibur is the rate constant of the reaction, r is the universal gas constant, ae is the activation energy of 85.4 kj mol-1 (for amberlyst-15 this value varies between 71 and 93 kj mol-1 and is influenced by not figure 1. values of the equilibrium constant ka as a function of temperature. table 1. properties of the catalyst amberlyst-15. properties specifications porosity of catalyst (ɛp) 0.31-0.39 tortuosity of catalyst (t) 0.7-1.7 density of catalyst (kg m-3) ~2000 physical shape spherical beads ionic form hydrogen moisture content (g/g %) ~50 particle size (mm) 0.3-1.5 functional group rso3h surface area (m2 g-1) ~45 pore diameter (å) ~250 acid sites (eq(h+) kg-1) 4.6-5.2 mtbe synthesis reactor modelling 45(1) pp. 1–7 (2017) 3 only the type of catalyst but also by the composition of the reaction mixture); and a0 = 6.3 x 1012 mol h-1 g-1. the effective diffusion coefficient and activation energy of methanol over amberlyst-15 at 60 oc was estimated to be 2.3·10-9 m2 s-1 and ~35.4 kj mol-1, respectively [4]. the given value of the effective diffusion coefficient is slightly lower than the one rehfinger and hoffmann reported (3.5·10-9 m2 s-1) [3]. the catalysts kastel cs 381 and amberlyst csp used in the synthesis of mtbe possess similar rate constants to amberlyst-15, whereas amberlyst xe 307 and duolite es 276 have significantly higher; and duolite c16p and duolite c26 have substantially lower values for their rate constants [3-15]. every resin undergoes deactivation, if sodium ions are exchanged for their protons. due to the acidic nature of resins, the activity is strongly reduced by the presence of basic substances and/or salts in the reaction mixture. the heat of reaction, ∆hº(mtbe), in the liquid phase at 25 ºc was reviewed by iborra et al. and found to be within the range of -34 to -40 kj mol-1 [5]. the rate for dimerization of isobutene (dib formation) [4, 10] can be calculated as follows: -66.7kj/mol 1 1 2333 ibu dib 0 ad meoh ibu           r t a r k e k a a (8) where the unit of rdib is mmol s-1 eq-1, kad is the ratio of adsorption equilibrium constants, and k0 is the frequency factor of the kinetic constant. 2.4. reactor and process generally, the multi-tubular packed-bed reactor is used exclusively as a front-end for the reactor performing the synthesis of mtbe, where the catalyst is lodged in the tubes (~10,000 tubes of diameter ~30 mm, length ~6 m, ɛ = 0.4). the cooling water flows in the shell side and can either flow coor counter-current. the reactor column is used solely for finishing and exploits the principle of catalytic distillation possessing the normal fractionation trays with reactive trays (where the catalyst is packed) [2, 16]. therefore, the maximum degree of isobutene conversion was achieved and reactants were separated from the product simultaneously, as mtbe has a much higher boiling temperature. reactor parameters used for the modelling are given in table 2. almost all the commercial etherification technologies use similar sections with regard to operation and separation, but are different in terms of type of reactors, numbers and process schemes [16-17]. the mtbe plant consists of a multi-tubular packed-bed reactor, and reactive distillation and methanol recovery sections. there are two separation towers after each reactor that recover the c4/methanol azeotrope from the top and mtbe from the bottom, followed by the washing tower where water removes the methanol from the c4, and then a distillation tower to separate water and methanol. 3. reactor modelling classical models of multi-tubular packed-bed reactors (pseudo-homogeneous one-dimensional) have been extensively discussed in the literature [1, 3-5]. in this study, a custom model of an mtbe water-cooled multitubular packed-bed reactor was built using an aspenbased platform (acm) with the ultimate objective of developing a complete process flow-sheet using the same method as in refs. [18-19]. model equations have been developed based on the following assumptions:  steady-state operation;  plug flow with no axial mixing;  one dimensional as no temperature and composition gradients exist in a radial direction (perfect radial mixing);  pseudo-homogeneous conditions for fluid solid phase interactions: transport limitations in terms of catalyst particles are taken into account by using the concept of an effectiveness factor;  heat transfer coefficient of the liquid phase to coolant (constant value along the reactor axis) is implemented as a sub-model. the heat transfer coefficient was evaluated under various changeable process parameters as defined the coolant inlet temperature, inlet flow rate, inlet pressure and inlet composition;  pressure drops according to the ergun equation in the model. 3.1. mass and energy balance the steady-state material balance in the liquid phase expressed in terms of vectors of the molar flow rates of the components in z direction is d d  a z f r and t b kef   r s r (9) where r is the vector of the rate of production or consumption per unit volume of a component, s is the stoichiometric matrix, rkef is the vector of effective reaction rates, a is the cross-sectional area of the reactor, f is a molar flow rate vector of the component, and b the bulk density of the catalyst. the liquid side of the heat balance equation under steady-state conditions is as follows: table 2. specifications of the reactor system. specification units value reactor length m ~8 reactor diameter m ~3.5 lhsv h-1 ~2-9 porosity ~0.35 feed inlet temperature oc ~40 i-c4/meoh ratio molar ~1.1 pressure bar ~10 recycling ratio % ~15 nawaz hungarian journal of industry and chemistry 4    t r kef f t c t p        ca h d t tdt dz h f c r (10) where δhr is the vector concerning the heat of reaction, cp is the vector concerning the molar specific heat of a component, t and tc are the liquid phase and coolant absolute temperatures, respectively, hfc is the liquid-tocoolant heat transfer coefficient, and dt is the diameter of the reactor tube. the shell side of the heat balance equation under steady-state conditions is as follows:  fc t cc vcool cool s,cool         h d t tdt dz f c (11) where fvcool is the volumetric flow rate of the coolant, cool is the density of the coolant, and cs,cool is the specific heat capacity of the coolant. in terms of modelling, the negative sign stands for the countercurrent and the positive sign for the co-current. the boundary conditions at the inlet of the reactor in terms of the material and energy balance differential equations are z = 0, fi(0) = f0,i , t(0) = t0, tc(0) = tcool,in and tc(rl) = tcool,in. 3.2. effectiveness factor the effectiveness factor for the synthesis of mtbe has been evaluated on the basis of data concerning the generalized thiele modulus (φg) [3]:  = tanh(g) / g . (12) in terms of the pseudo-homogeneous model, the effectiveness factor is expressed as a function of temperature and conversion: 2 3x 1 4 1 conversion % 1.1 100                x rtx e x . (13) the parameters x1 – x4 have been evaluated by minimizing the absolute error between evaluations by zhang et al. [4] and the values predicted by eq. 13. the accuracy of the prediction is shown in fig.2. 3.3. overall heat transfer coefficient the overall heat transfer coefficient, taking into account the small value of the wall thickness, is evaluated as follows: fc te ti fouling fw pipe shell 1 1 1 2           h d d r h h (14) where dti and dte are the internal and external diameters of the reactor tube, respectively, λpipe is the thermal conductivity of the reactor tube, hfw is the fluid-to-wall heat transfer coefficient, hshell is the shell side (wall-tocooling water) heat transfer coefficient, and rfouling is the fouling factor. the evaluation of the fluid-to-wall heat transfer coefficient was conducted on the basis of a newly proposed correlation for the estimation of the total (wall and effective thermal conductivity effects) heat transfer coefficient [16]: 0.643 0.333 f f f ti p 1.37 nu 3.87 3.77 exp re pr                      d d .(15) in this case, both nuf and ref are expressed based on particle diameters. the heat transfer coefficient of the shell side is expressed as a function of nu and re and are both based on the external diameter of the tube, where ɛφ stands for a correction factor accounting for the angle between the coolant stream and reactor tubes: nu s  0.4 e  re s 0.6pr s 0.333 . (16) 3.4. acm property estimations the physical properties of components and mixtures like viscosity, density and specific heat, were estimated by aspen properties (using unifac dortmund property package). the “.appdf” file prepared by aspen properties is the one called in acm for seamless transfer of properties. the kinetic sub-model helps in terms of the calculation of reaction heats using the aspen properties database. figure 2. effectiveness factor for the mtbe synthesis reaction based on data from ref. [4]. mtbe synthesis reactor modelling 45(1) pp. 1–7 (2017) 5 3.5. performance parameters reactor performance is evaluated by the following equations: key_reactant key_reactant 0 z key_reactant 0 conversion( )   f f z f (17) key_product key_product z 0 key_reactant key_reactant 0 z selectivity( )    f f z f f (18) yield( ) conversion( ) selectivity( ) z z z (19) where z stands for the axial coordinate. 4. model predictions and analysis acm is the preferred choice for robust reactor modelling. its equation-oriented modelling platform can be easily exported to aspen plus process flow-sheets. the coding of a multi-tubular packed-bed reactor in terms of the synthesis of mtbe was conducted in a modular form. the main reactor model defines the constitutive equations in the bulk phase and sub-models in terms of the reaction kinetics, the estimation of the heat transfer coefficient, and the development of the pellet design. the normal operating conditions for the primary reactor were selected as the base case in terms of modelling (table 3), where mtbe productivity is ~50 t h-1. the molar concentration profile of the reactants and product along the axis of the reactor is shown in fig.3. the full length of the reactor is used for the synthesis of mtbe. fig.4 shows the temperature profiles of the reactor and coolant. the temperature sensitivity is controlled by keeping the temperature difference between the coolant and feed temperatures constant (fig.5). it was observed that due to the exothermic nature of the reaction, the maximum temperature increased significantly with the table 3. typical base-case operating conditions and results for the primary reactor. specification units value tube length m 6 tube diameter (id) mm 21 number of tubes 10,000 porosity 0.33 feed inlet temperature ºc 50 isobutene/meoh ratio molar 1.1 pressure bar 8 coolant inlet temperature ºc 45 feed flow rate kmol h-1 2,000 isobutene mole fraction 0.35 ∆p bar 0.723 conversion % 84.7 mtbe selectivity % 97.86 figure 3. molar concentration profile along the length of the reactor. figure 4. temperature profiles of the reactor and coolant. figure 5. temperature sensitivity by varying the feed temperature and keeping constant the temperature difference between the coolant and feed temperatures. nawaz hungarian journal of industry and chemistry 6 increase in reaction temperature. at a constant pressure and feed flow rate, the increase in the reaction temperature led to an outer mass transfer limitation that strongly affects the rate of conversion. at the same time the selectivity also decreased due to a significant increase in the maximum temperature of the reactor (product degradation) and the maximum rate of conversion was achieved in almost ~30% of the reactor. the isobutylene/methanol molar ratio is one of the key operating parameters and is always kept higher than its stoichiometric value. table 4 shows that by deviating from the stoichiometric ratio the effect on the rate of conversion and selectivity also decreases with the increase in the isobutylene/methanol molar ratio. the predictions according to reactor modelling were found to be in good agreement with data from the literature. the reaction must reach an equilibrium at the rear end of the lead reactor. the estimated effectiveness factor is 0.75 which was also used in the model. the possible explanation for the occurrence of minor discrepancies could be the use of a different catalyst or errors in terms of experimental measurements. it was observed that the maximum degree of productivity corresponded to an isobutene/meoh molar ratio of close to 1 and a feed inlet temperature of between 50 and 55 ºc. however, it is necessary to synchronize this with the secondary reactor and other unit operations. 5. conclusion an acm-based pseudo-homogeneous model with regard to the synthesis of mtbe using an industrial multi-tubular packed-bed (methyl-tert-butyl-ether) reactor has been developed for enhancing operation strategies. the unifac dortmund property package was used for reactor modelling. the effectiveness factor was implemented as a function of the reaction temperature. the model was validated using data from the literature. various sensitivity evaluations were conducted to determine the operational optimization and maximization of mtbe production under different operating parameters. the model was able to predict reaction behaviour and produce temperature and concentration profiles along the length of the reactor. sensitivity studies were able to calculate the optimum temperature, feed flow rate, methanol/isobutylene ratio as well as heat removal rate of the reactor and thus provide insights into a reasonable operational strategy. symbols a cross-sectional area of the reactor a activity ameoh, aibu, amtbe, ainert activities of methanol, isobutene, mtbe and inert isobutane, respectively a0 6.3 x 1012 mol h-1 g-1 cp molar specific heat vector of a component cs,cool specific heat capacity of the coolant dt diameter of the reactor tube dti, dte internal and external diameters of the reactor tube, respectively ea activation energy in kj mol-1 fvcool volumetric flow rate of the coolant f molar flow rate vector of a component hfc liquid-to-coolant heat transfer coefficient hfw fluid-to-wall heat transfer coefficient hshell shell side (wall-to-cooling water) heat transfer coefficient δhr heat of reaction vector γ activity coefficient ka equilibrium constant (based on activities) kad ratio of adsorption equilibrium constants kmeoh, kibu, kmtbe, kinert adsorption equilibrium constants for methanol, isobutene, mtbe and inert isobutane, respectively k0 frequency factor of the kinetic constant kr reaction rate constant λpipe thermal conductivity of the reactor tube r universal gas constant r vector of the rate of production or consumption per unit volume of a component rkef vector of effective reaction rates rfouling fouling factor b bulk density of the catalyst cool density of the coolant s stoichiometric matrix t , tc absolute temperatures of the liquid phase and coolant, respectively x mole fraction acknowledgement the author gratefully acknowledges the technical support of prof. dr. ing. teodor todinca at the university politechenica timisoara in romania. references [1] nawaz, z.: light alkane dehydrogenation to light olefin technologies: a comprehensive review, rev. chem. engng., 2015 31(5), 413–436 doi 10.1515/revce-2015-0012 table 4. dependence of conversion (%), selectivity (%) and the maximum temperature of the reactor (tmax) on the isobutene/methanol molar ratio (ibu/meoh). ibu/meoh 0.8 0.9 1.0 1.1 1.2 1.3 conversion 84.7 85.4 85.5 84.6 80.7 76.7 selectivity 98.1 98.1 98.1 97.9 97.1 95.4 tmax, ºc 56.1 56.5 56.9 57.7 59.5 62.0 mtbe synthesis reactor modelling 45(1) pp. 1–7 (2017) 7 [2] digirolamo, m.; sanfilippo, d.: etherification: process to improve the quality of distillates, in beccari m.; romano, u.; eds. encyclopaedia of hydrocarbons (eni s.p.a and istituto della enciclopedia italiana fondata da giovanni treccani s.p.a, roma, italy) 2006 vol. ii. pp. 193–209 [3] rehfinger, a.; hoffmann, u.: kinetics of mtbe liquid phase synthesis catalyzed by ion-exchange resin. i. intrinsic rate expression in liquid phase activities, chem. eng. sci., 1990 45(6), 1605–1617 doi 10.1016/0009-2509(90)80014-6 [4] zhang, t.; datta, r.: integral analysis of mtbe synthesis kinetics, ind. eng. chem. res., 1995 34, 730–740 doi 10.1021/ie00042a004 [5] iborra, m.; tejero, j.; ben el-fassi, m.; cunill, f.; izquierdo, j.f.; fite, c.: experimental study of the liquid phase simultaneous synthesis of mtbe and tba, ind. eng. chem. res., 2002 41, 5359–5365 doi 10.1021/ie010640q [6] chen, f.; huss, r.s.; doherty, m.f.; malone, m.f.: multiple steady-states in reactive distillation: kinetic effects, comp. chem. engng., 2002 26, 81– 93 doi 10.1016/s0098-1354(01)00750-5 [7] lisal, m.; smith, w.r.; nezbeda, i.: molecular simulation of multicomponent reaction and phase equilibria in mtbe ternary system, aiche j., 2000 46(4), 867–875 doi 10.1002/aic.690460419 [8] isla, m.; irazoqui, h.: modeling, analysis and simulation of mtbe reactive distillation column, ind. eng. chem. res., 1996 35, 2696–2708 doi 10.1021/ie9505930 [9] venimadhavan, g.; malone, m.f.; doherty, m.f.: bifurcation study of kinetic effects in reactive distillation, aiche j., 1999 45(3), 546–556 doi 10.1002/aic.690450311 [10] oktar, n.; murtezaoglu, k.; dogu, t.; dogu, g.: dynamic analysis of adsorption equilibrium and rate parameters of reactants and products in mtbe, etbe and tame production, can. j. chem. eng., 1999 77, 406–412 doi 10.1002/cjce.5450770229 [11] girolamo, m.; tagliabue, l.: mtbe and alkylate co-production: fundamentals and operating experience, catal. today, 1999 52, 307–319 doi 10.1016/s0920-5861(99)00084-x [12] ancilotti, f.; fattore, v.: oxygenate fuels: market expansion and catalytic aspect of synthesis, fuel proc. technol., 1998 57, 163-194 doi 10.1016/s03783820(98)00081-2 [13] girolamo, m.; lami, m.; marchionna, m.; pescarollo, e.; tagliabue, l.; ancilotti, f.: liquid phase etherification/dimerization of isobutene over sulfonic acid resins, ind. eng. chem. res., 1997 36, 4452–4458 doi 10.1021/ie9700932 [14] miracca, i.; tagliabue, l.; trotta, r.: multitubular reactors for etherifications, chem. engng. science, 1996 51, 2349–2358 doi 10.1016/0009-2509(96)00091-7 [15] panneman, h.j.; beenackers, a.: influence of the isobutene/methanol ratio and of the mtbe content on the reaction rate of the synthesis of mtbe, ind. eng. chem. res., 1995 34, 3817–3825 doi 10.1021/ie00038a019 [16] mariani, n.j.; martinez, o.m.; barreto, g.f.: evaluation of heat transfer parameters in packed beds with cocurrent downflow of liquid and gas, chem. engng. science, 2001 56, 5995–6001 doi 10.1016/s0009-2509(01)00225-1 [17] elkanzi, e.m.: optimization of mtbe synthesis in a packed-bed reactor system, chem. engng. proc., 1996 35, 131–139 doi 10.1016/0255-2701(95)04122-2 [18] nawaz, z.: dynamic modeling of catofin® packed-bed isobutane dehydrogenation reactor for operational optimization, int. j. chem. reactor engng., 2016 14(1), 491–515 doi 10.1515/ijcre-20150087 [19] nawaz, z.: heterogeneous reactor modeling of an industrial multitubular packed-bed ethylene oxide reactor, chem. engng. technol., 2016 39(10), 1845–1857 doi 10.1002/ceat.201500603 hungarian journal of industry and chemistry vol. 45(2) pp. 9–12 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0013 modelling the partial demineralization process of cow milk by superpro designer attila csighy,* andrás koris, and gyula vatai department of food engineering, szent istván university, ménesi út 44, budapest, 1118, hungary milk and dairy products contain a number of biologically active compounds (proteins, lipids, vitamins and minerals) that are essential for human nutrition. the most common procedures for demineralization are based on ion exchange-, nanofiltrationand electrodialysis-based technologies. in this study, the application of membrane filtration-based partial demineralization of cow milk was investigated and the process modelled. using design equations, the partial demineralization process was designed and the economy of the process calculated. the modelling and simulation of the partial demineralization process was carried out by the superpro designer programme. as the first step the unit operations of the demineralization technology were defined using the tools of the programme. the superpro designer possesses industrial tools with reactor models, chemical components, a database of mixtures, and price estimations. by analysing the influence of the operation parameters, the feasibility of the proposed process was investigated. from the results of the modelling it can be concluded that the partial demineralization process can be successfully implemented, achieving the expected demineralization rates with a relatively good payback time of two years. keywords: partial demineralization, superpro designer, modelling, economic analysis 1. introduction dairy products play an important role in the health of humans as milk contains a number of biologically active compounds (proteins, lipids, vitamins and minerals). therefore, the consumption of milk and dairy products is highly recommended [1-2]. milk is the main raw material in the cheese and casein industry. the disposal of whey creates a major environmental problem for the cheese industry due to the high amount of organic compounds it contains. in the cheese industry to manufacture 1 kg of cheese, 9 kg of whey is produced as a by-product. whey possesses a large ‘biochemical oxygen demand’ (bod) value, therefore, treatment is required before it is released into the environment or recycled. suárez [3] observed that the nanofiltration membrane is an effective medium for the demineralization of whey. the demineralization efficiency depends on the transmembrane pressure and the volume concentration ratio (vcr). experimentally, monovalent ions exhibit the highest degree of permeation. [3] whey is a watery, dilute liquid, which generally contains 0.8-1.0% total protein, 4.5-5.0% lactose, 0.50.7% minerals and 93-94% water. whey can be divided into two different compositions, namely sweet and acid whey [4]. another process as part of the treatment of whey is demineralization. upon demineralization, whey *correspondence: csighy.attila@gmail.com can be used for manufacturing drinks, desserts or icecream products. a novel alternative process for demineralization is nanofiltration. nanofiltration is a membrane separation method that lies between ultrafiltration and reverse osmosis. nanofiltration membranes can maintain monovalent ions (nacl) and also organic compounds between 300 and 100 in the dalton range. nanofiltration is an effective technique to remove salts, while preserving valuable components [5]. in order to examine the feasibility of the process, technological and economic experiments were carried out by the superpro designer software [6]. this programme is widely used in the pharmaceutical, biotechnology and food industries. the superpro designer is capable of preparing technological and economic documentations and reports about the modelled process. the programme possesses an industrial tool, where the unit operations (reactions, solid/liquid separation, tanks) can be prepared [7]. the purpose of this study is to model the demineralization process using the superpro designer programme and by analyzing the influence of the operation parameters, the feasibility of the proposed process was investigated. 2. experimental 2.1. materials and methods in this study, one ultrafiltration (uf) and two nanofiltration (nf) membranes were used. the first step was the pre-concentration of milk using the uf csighy, koris, and vatai hungarian journal of industry and chemistry 10 membrane. a schumasiv type 100 nm pore size membrane was used for the pre-concentration phase, a schumasiv type 5 nm pore size membrane for nanofiltration of the ultrafiltration retentate, and a membralox type 5 kda membrane for nanofiltration of the ultrafiltration permeate. the experiments were carried out using ultraand nanofiltration units in a laboratory unit designed by the department of food engineering. the effective area of the membranes was 0.005 m2. the milk sample was circulated at a constant temperature (21±1 ºc) maintained by a thermostat. the optimal working parameters were measured during an experimental design in both the uf and nf processes. during the uf process the transmembrane pressure was 1.5 bars and the recirculation flow rate was 150 dm3 h-1. in both nf processes, the transmembrane pressure was 2 bars and the recirculation flow rate was 200 dm3 h-1. the transmembrane pressure and the recirculation flow rate were controlled by regulating valves. 2.2. process simulation the partial demineralization process was modelled using superpro designer software version 8.5 by intelligen, inc. the main target task was partial demineralization. the superpro designer software possesses an industrial tools section, where models of reactors, chemical components, a database of mixtures, price estimations and economic evaluations can be used. the parameters used were calculated from laboratory experiments as shown in table 1. firstly, the superpro designer tool was used to install the unit operations. the first unit is the ultrafiltration system. the raw milk enters the system and is separated into its permeate and retentate. in the next step, the two fractions are transferred to each diafiltration unit. another major step is the definition of essential material streams for milk, the addition of distilled water to the diafiltration unit and the provision of electricity. the diafiltrated, partially demineralized milk and whey components are then sent to the storage tank. the last part of the process is the packaging system, where the products are completed. the demineralized whey is finally loaded into a truck. the mass of the filled entity is 40 metric tons (mt). the basic process flow diagram of the combined partial demineralization of cow milk is shown in fig. 1. the composition of the milk was defined as illustrated in table 2. in the next step, the transmembrane pressure, flow rate and flux as operating parameters were set and the cost of purchase assigned to each operating unit. the annual operating time is 300 days for this process. the cost of purchase of the ultrafiltration system was set at $100k, the two diafiltration units at $75k, the storage table 1. the characteristics of the membranes used. membrane type process parameters pressure, bar flow rate, dm3 h-1 uf (100 nm) 1.5 150 nf (5 kda) 2.0 200 nf (5 nm) 2.0 200 figure 1. process flow diagram of the demineralization of cow milk. table 2. the composition of the cow milk considered ingredient’s name mass (%) casein 3.4 fats 3.4 lactose 5.2 sodium chloride 1.0 water 87 modelling the partial demineralization process of cow milk 45(2) pp. 9–12 (2017) 11 tanks at $75k, and the packaging unit at $50k. in addition, the cost of raw materials was set at $1/kg, of packaging material at $0.1/piece (100g), and of water at $0.1/kg. the product must be sold at a price that is in line with the market conditions (est. $2.2/kg). each unit operation needs a minimum of one operator, thus the cost of labour was set at a basic rate of $10 per hour. the electricity, cooling and heating energy demands were estimated by the programme (table 3). 3. results and analysis upon the establishment of costs, technological and economic simulations were executed. the summary of the run simulations for the partial demineralization process yielded the relevant costs, revenue and payback time as shown in table 4. according to the simulation results, the annual total revenue is higher than the operating costs. the production costs are given with and without amortization. table 5 summarizes the indices of the project. the ‘payback time’ or ‘return on investment’ (roi) for the partial demineralization process in this case was calculated for four years. the roi is defined by eq. (1): roi (%) = annual net profit capital cost ·100 (1) other important parameters were the ‘internal rate of return’ (irr) before and after tax. the irr is a discount value when the ‘net present value’ (npv) is zero. the npv is determined by calculating the costs and benefits of the technological investment. the npv is defined by eq. (2): npv (usd) = ∑ �t (���)t − �� (2) where ct is the cash flow, t is the lifetime in years, d is the discount rate, and c0 is the initial investment. if the npv remains positive, the process will be economically viable [8]. the costs of materials and supplies are shown in table 6 with the most expensive item being the raw material (cow milk) while the cost of packaging materials is far less. table 7 presents the total cost of the plant for the demineralization process. in addition to purchasing the equipment, other costs were the piping, instrumentation, and electrical, building and construction fees. according to the simulated revenues of the partial demineralization process, the production of milk and lactose solution cost $2.2 and $0.3 per kg, respectively. assuming that the demineralized whey is transferred into a truck, it can be sold to food industries for $40 per metric ton. the composition of the demineralised whey in the form of lactose solution is 4.3% lactose, 0.8% nacl and 95% water, which is suitable for the production of candy, yoghurt and ice cream. it is also important to consider the cost of waste treatment. the superpro designer generated two different costs, namely those of utilities ($25k) and transportation ($874k). 4. conclusion this study examined the feasibility of the partial demineralization process which was successfully table 5. summary of project indices (irr = internal rate of return, npv = net present value). gross margin, % 6.78 return on investment, % 24.90 payback time, years 4.02 irr before tax, % 28.36 irr after tax, % 18.20 npv (at 7.00%) 5,381,025 table 6. summary of the costs of materials (in usd per kg annually). raw materials unit amount cost milk $1.00 21,766,316 21,766,316 water $0.10 10,879,641 1,087,964 packaging material $0.20 10,800,661 2,160,132 total 25,014,412 table 7. total cost of the plant (in thousands of usd). equipment purchase $563k installation $266k process piping $197k instrumentation $225k insulation $17k electrical $56k buildings $253k yard improvements $84k auxiliary facilities $225k engineering $472k construction $66k table 3. cost estimates for energy supplies energy supplies price steam (high p) [242 ℃] $10/mt steam [152 ℃] $6/mt chilled water [5 ℃ 10 ℃] $0.4/mt cooling water [25 ℃ 30 ℃] $0.05/mt std. power $0.1/kwh table 4. summary of economy indices (mp stands for “flow of discrete entity”). total investment $6,279,438 total annual revenue $30,315,042 annual operating cost $28,258,168 annual unit production reference rate (mp entity) $10,800,660 unit product cost (per mp entity) including depreciation $2.62 excluding depreciation $2.59 csighy, koris, and vatai hungarian journal of industry and chemistry 12 modelled by the superpro designer software. according to an economic evaluation, the net present value, return on investment, and internal rate of return were $5.3million for four years, 28% and 18%, respectively. the revenues of the products were $2.2 per unit and $0.3 per kg (or $40 per metric ton) for the milk and lactose solution, respectively. future research will focus on the optimization of costs and exploration of alternative ways of recycling whey. acknowledgement the research was supported by the doctoral school of food sciences at szent istván university. references [1] csapo, j.; csapone, k.zs.: milk and dairy products in food consumption (mezőgazdasági kiadó, budapest) 2002 (in hungarian) isbn 963 9358 68 1 [2] mass, s.; lucot, e.; gimbert, f.; crini, n.; badot, p.m.: trace metals in raw cow’s milk and assessment of transfer to comté cheese, food chem., 2011 129(1), 7–12 doi: 10. 1016/j.foodchem.2010.09.034 [3] suárez, e.; lobo, a.; álvarez, s.; riera, f.a.; álvarez, r.: partial demineralization of whey and milk ultrafiltration permeate by nanofiltration at pilot-plant scale, desalination, 2006 198(1-3), 274–281 doi 10.1016/j.desal.2005.12.028 [4] tsakali, e.; petrotos, k.; alessandro, a.d.; goulas, p.: a review on whey composition and methods used for its utilization for food and pharmaceutical products, proc. 6th int. conf. simul. modelling food bioind., 2010 (cimo research centre, bragança, portugal) pp. 195-201 [5] pan, k.; song, q.; wang, l.; cao, b.: a study of demineralization of whey by nanofiltration membrane, desalination, 2011 267(2-3), 217–221 doi 10.1016/j.desal.2010.09.029 [6] mel, m.; yong, a.s.h.; avicenna; ihsan, s.i.; setyobudi, r.h.: simulation study for economic analysis of biogas production from agricultural biomass, energy procedia, 2015 65, 204-214 doi 10.1016/j.egypro.2015.01.026 [7] flora, j.r.v.; mcanally, s.a.; petrides, d.: treatment plant instructional modules based on superpro designer® v.2.7, environ. model. software, 1998 14(1), 69–80 doi 10.1016/s13648152(98)00059-0 [8] kwan, t.h.; pleissner, d.; lau, k.y.; venus, j.; pommeret, a.; lin, c.s.: techno-economic analysis of a food waste valorization process via microalgae cultivation and co-production of plasticizer, lactic acid and animal feed from algal biomass and food waste, biores. technol., 2015 198, 292–299 doi 10.1016/j.biortech.2015.09.003 hungarian journal of industry and chemistry vol. 45(2) pp. 13–18 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0014 investigations of the tlinp2se6–in4(p2se6)3 system and its optical properties valeria tovt, 1 igor barchiy, 1 * michal piasecki, 2 iwan kityk, 3 and anatolii fedorchuk 4 1 department of chemistry, uzhgorod national university, pidgirna st. 46, 88000 uzhgorod, ukraine 2 institute of physics, jan dlugosz university, armii krajowej 13/15, 42-200 częstochowa, poland 3 faculty of electrical engineering, częstochowa university of technology, dabrowskiego 69, 42201 częstochowa, poland 4 department of inorganic and organic chemistry, lviv national university of veterinary medicine and biotechnologies, pekarska st. 50, 79010 lviv, ukraine the equilibrium phases were investigated and the corresponding phase diagram constructed for the tlinp2se6– in4(p2se6)3 system from physical and chemical analyses, namely differential thermal analysis (dta), x-ray diffraction (xrd), and microstructural analysis (msa). it was established that this system belongs to the eutectic type and is characterized by the formation of boundary solid phases containing complex compounds. single crystals of the compounds tlinp2se6 and in4(p2se6)3 were grown using the bridgman method. both crystals were found to exhibit diffuse reflection spectra and photoinduced dependence of birefringence at various ir wavelengths generated by co2 laser irradiation. birefringence properties were investigated using the senarmont method. keywords: phase diagram, solid solution, crystal structure, optical properties, direct-gap semiconductor, indirect-gap semiconductor, photoinduced birefringence 1. introduction compounds with the formula m2p2se6 possess promising magneto-electric, piezoelectric, electro-optical, and thermoelectric properties that indicate their suitability as functional materials in optoelectronics [1-2]. due to their crystal structure, they exhibit anisotropy in terms of their physical properties. in a multilevel structure of m2p2se6 compounds, metal cations and pairs of phosphorous atoms occupy the octahedral positions between planes of selenium atoms. this structure is characterized by its layered arrangement of atoms, which contributes to the formation of a dipole moment between the layers of cationic and anionic groups. the replacement of the metal cation м2+ by other metal cations (м+, м3+ or м4+) leads to the deformation of the structure [3-4], changes the magnitude of the dipole moment and, consequently, its physical properties. the tl2se–in2se3–“p2se4” ternary system is composed of binary tl2se–in2se3, tl2se–“p2se4” and in2se3–“p2se4” systems. the tl2se–in2se3 system is characterized by the formation of two intermediate ternary compounds: tlinse2 melts congruently at 1023 k and tlin5se8 is formed according to the peritectic reaction l + in2se3  tlin5se8 at 1029 k [5-6]. in the sys *correspondence: i_barchiy@ukr.net tem tl2se–“p2se4” with a ratio of 2 to 1, interoperable components form the compound tl4p2se6 which possesses a congruent nature of melting at 758 k [7]. the in2se3–“p2se4” system is characterized by the formation of the compound in4(p2se6)3 in a syntectic reaction of l1 + l2  in4(p2se6)3 at 880 k [8]. in the tl2se– in2se3–“p2se4” system at the intersection of incisions, the phases tl4p2se6–in4(p2se6)3 and tlinse2–“p2se4” form the complex compound tlinp2se6 [9]. 2. experimental ternary tl4p2se6 and in4(p2se6)3 compounds were prepared by melting stoichiometric quantities of binary tl2se with elementary indium, phosphorous and selenium under a vacuum of 0.13 pa in quartz ampoules using a single temperature method. in all syntheses, components were used that possess a purity greater than 99.999 %. the maximum temperatures of synthesis were 993 and 893 k for in4(p2se6)3 and tlinp2se6, respectively. the rate of heating up to the maximum temperature was 50 k h-1. the melts were maintained at the maximum temperature for 72 hours. cooling was performed at a rate of 50 k h-1 down to an annealing temperature of 573 k. the linearity of the heating and cooling processes was achieved by a rif-101 temperature controller. the homogenization process occurred over 120 hours. identification of the complex compounds and alloys was conducted by differential thermal analy tovt, barchiy, piasecki, kityk, and fedorchuk hungarian journal of industry and chemistry 14 sis (dta) (pra-01, chrome-alumina thermocouple 5 k), x-ray diffraction (xrd) (dron-3 diffractometer, cukα radiation, ni filter) and microstructural analysis (msa) (metallurgical microscope lomo metam r-1). crystal structural calculations were conducted using the software package wincsd [10]. optical properties were investigated using an sf-18 spectrophotometer within the wavelength range of 400 – 750 nm. a co2 laser was used for photoinduced electrons in samples employing 200 ns pulses with a pulse repetition frequency of about 10 hz, a fundamental frequency of 10.6 μm and a frequency doubling of 5.3 μm beams. the birefringence was measured using a er:glass cw laser at 1540 nm by application of the senarmont method. 3. results and analysis 3.1. phase diagram of the tlinp2se6– in4(p2se6)3 system the tlinp2se6–in4(p2se6)3 system is a quasi-binary section of the tl2se–in2se3–“p2se4” ternary system (figs.1 and 2). it belongs to the eutectic type (v-type diagram by rozeboom). the complex compounds tlinp2se6 and in4(p2se6)3 melt congruently at 875 k and 963 k, respectively. tlinp2se6 is characterized by two polymorphic transformations lttlinp2se6  mttlinp2se6 at 680 k and mttlinp2se6  httlinp2se6 at 711 k. the prefixes lt–, mt– and ht– represent low–, medium–, and high–temperature modifications, respectively. in4(p2se6)3 is also characterized by two polymorphic transformations ltin4(p2se6)3  mtin4(p2se6)3 at 665 k and mtin4(p2se6)3  htin4(p2se6)3 at 903 k. when the temperature rises above 791 k, an invariant eutectic process is observed l  httlinp2se6 + mtin4(p2se6)3 (in the presence of 15 mol% in4(p2se6)3). the system is described by the sequence of the efficient peritectic processes httlinp2se6 + mtin4(p2se6)3  mttlinp2se6 (714 k) and mttlinp2se6 + mtin4(p2se6)3  lttlinp2se6 (689 k) based on the polymorphic transformation of tlinp2se6. the polymorphism of in4(p2se6)3 produces metatectic htin4(p2se6)3  l + mtin4(p2se6)3 (884 k) and eutectic mtin4(p2se6)3  lttlinp2se6 + ltin4(p2se6)3 (652 k) processes. regions of homogeneity in solid solutions, based on the batched complex selenides during annealing at a temperature of 573 k, do not exceed 10 mol%. 3.2. crystal structure of the compounds in4(p2se6)3 and tlinp2se6 the crystal structures of the compounds tlinp2se6 and in4(p2se6)3 were solved using the rietveld method. as an initial model for tlinp2se6 [2], the parameters of in4(p2se6)3 were used [8]. analysis of the crystalline structures of the investigated compounds (table 1) showed that it is possible to define the structural group of the anionic group [p2se6] 4–, which is formed by two single tetrahedra (fig.3). cationic atoms occupy positions between the anionic groups and none are located between the layers. figure 1. results of the xrd analysis of the tlinp2se6–in4(p2se6)3 system. (i rel – intensity, 2 theta angle of reflection) figure 2. phase diagram of the tlinp2se6–in4(p2se6)3 system. (1–l, 2–l+htin4(p2se6)3, 3–htin4(p2se6)3, 4–httlinp2se6, 5–l+mtin4(p2se6)3, 6–htin4(p2se6)3+mtin4(p2se6)3, 7–httlinp2se6, 8–httlinp2se6+mtin4(p2se6)3, 9–mtin4(p2se6)3, 10–httlinp2se6+mttlinp2se6, 11–mttlinp2se6, 12–mttlinp2se6+mtin4(p2se6)3, 13–mttlinp2se6+lttlinp2se6, 14–lttlinp2se6+mtin4(p2se6)3, 15–mtin4(p2se6)3+ltin4(p2se6)3, 16–lttlinp2se6, 17–lttlinp2se6+ltin4(p2se6)3, 18–ltin4(p2se6)3). table 1. crystal data of tlinp2se6 and in4(p2se6)3 compounds. compound crystal system space group lattice constant in4(p2se6)3 [8] trigonal r3 h (146) a = 6.362(3), c = 19.929(6) å in4(p2se6)3 trigonal r3 h (146) a = 6.3808(8), c = 20.014(4) å tlinp2se6 [2] triclinic p-1 (2) a = 6.4310, b = 7.5002, c = 12.124 å, tlinp2se6 triclinic p-1 (2) α = 100.553, β = 93.735, γ = 113.451 investigations of the tlinp2se6–in4(p2se6)3 system 45(2) pp. 13–18 (2017) 15 the structure of in4(p2se6)3 can be derived from the structure of sn2p2se6 [11]. it is composed of multiple substitutions of the isovalent cations according to 2m2+  m4+. the crystal structure of the compound in4(p2se6)3 can be presented based on the composition of the anionic group [p2se6] 4– (fig.4), in which the indium atoms occupy the space between the anionic groups. the second coordination environment (sce) [12] is of cuboctahedron form. indium cations are surrounded by a triangular environment of anionic atoms of the group [p2se6] 4–and within the frames of its environment bonding exists with six atoms of selenium while the coordination form is octahedral (fig.5). the structural and chemical properties of the меімеііір2se6 compositions are related to the important role concerning the dimension of the cation on its location between the layers of the anionic [p2se6] 4–groups. crystallographic analysis showed that smaller cations occupy a position in the plane perpendicular to the main axis. atoms located in a second coordination environment of anionic groups in the structure of tlinp2se6 compounds can be presented as a strongly distorted hexagonal-equivalent cuboctahedron (fig.6). the atoms of metallic cations, located in the cavities between the atoms of the anionic groups, are within an asymmetric environment (fig.7). in3+ cations move toward tetrahedral cavities on the boundary between tetrahedral and octahedral cavities, and tl+ cations move in the direction of the octahedral cavities. moreover the in3+ cations are located in the same plane together with the centres of the anionic [p2se6] 4– groups (fig.8) and some tl+ cations are shifted relative to the plane. therefore, this arrangement is a source of the interesting electro-physical and optical properties of materials based on compounds of this type. 3.3. optical response of single crystals of tlinp2se6 and in4(p2se6)3 the most important parameter of the energy spectra of semiconductors is the width of the band gap, eg, which is defined by the difference in energy between the bottom of the conduction band, ec, and the top of the valence band, ev. all semiconductors can be divided into two groups. in the first group, the minimum of the conduction band and the maximum of the valence band occupy the same point in the brillouin zone, i.e. at an identical location in the space of quasi-moments. in this case, the optical transitions of electrons from the valence band to the conduction band (with the absorption of a quantum of light) and from the conduction band to the valence band (with the emission of a quantum of light) occur so that the electrons practically do not change their quasi-moments. such transitions are characteristic of direct-gap semiconductors. for the second group, the absolute minimum of the conduction band and the absolute maximum of the valence band are at different points in the brillouin zone, and optical inter figure 3. structure of the anionic group [p2se6] 4–. figure 4. arrangement of the polyhedra anionic group [p2se6] 4– in in4(p2se6)3. figure 5. coordination environment of the indium atoms in the structure of in4(p2se6)3. figure 6. second (sce) and nearest (nce) coordination environments of atoms in the [p2se6] 4– anionic groups in the structure of tlinp2se6. tovt, barchiy, piasecki, kityk, and fedorchuk hungarian journal of industry and chemistry 16 band transitions must be accompanied by a large change in the electron quasi-moment. these are characteristic of indirect-gap semiconductors. since the photon moment is negligibly small compared with the electron quasi-moment, the latter case is possible only when the electron interacts with the phonon. according to the phase diagram, the single crystals of tlinp2se6 and in4(p2se6)3 were grown using the bridgman method in two vertical zone furnaces. experimental studies of optical spectra in the absorption region yielded information on the energy spectrum of electrons near the edges of the conduction band and band gap. studies concerning the dependence of diffuse reflection on wavelength (r = f(λ)) have shown that the compound tlinp2se6 refers to indirect-gap semiconductors. on the graph there are two rectilinear sections, one of which (for small wavelengths, , and large values of e) characterizes the interband transitions of electrons with phonon emission, and the other (for large  and small e) describes the processes of phonon absorption (fig.9). the intersection of the first section with the wavelength axis, , yields the value of eg + ephonon ( = 560 nm, e = 2.21 ev), and the intersection of the second characterizes eg – ephonon ( = 605 nm and e = 2.05 ev). the length of the segment between the points of intersection of both straight lines with the wavelength axis, , is equal to the doubled energy of the phonons, 2ephonon (0.16 ev), interacting with the electron. the middle of this segment corresponds to the photon energy equal to the width of the band gap of the indirect-gap semiconductor, eg. experimental calculations in terms of the compound tlinp2se6 have shown that eg = 2.13 ev and ephonon = 0.08 ev. the compound in4(p2se6)3 refers to direct-gap semiconductors, which characterizes the interband transitions of electrons in terms of photon absorption (fig.10). the intersection of the line with the wavelength axis,  ( = 651 nm), yields the value of eg = 1.91 ev. the crystals of in4(p2se6)3 and tlinp2se6 were illuminated by 10.6 μm and (its second harmonic) frequency doubling of 5.3 μm beams. each channel of the beam was split by 200-ns co2 laser pulses with a pulse repetition frequency of about 10 hz. the angle between these two laser beams was changed from 18º to 22º. figs.11 and 12 present these dependences. treatment with a 10.6 μm beam achieved a smaller maximum birefringence (about 1.5510-2) in comparison to the 5.2 μm beam. this indicates a different photoinduced anisotropy for the in4(p2se6)3 and tlinp2se6 crystals. because a) b) . figure 7. coordination environments of the thallium (a) and indium (b) atoms in the structure of tlinp2se6. figure 8. arrangement of the polyhedra anionic group [p2se6] 4– in the structure of tlinp2se6. figure 9. dependence of the diffuse reflection r on the wavelength  for the compound tlinp2se6. figure 10. dependence of the diffuse reflection r on the wavelength  for the compound in4(p2se6)3. investigations of the tlinp2se6–in4(p2se6)3 system 45(2) pp. 13–18 (2017) 17 these crystals contain chalcogenide anions that contribute to the anharmonicity of the phonon, they play a crucial role in terms of the second harmonic generation [13-14]. the maximum changes in the birefringence achieved were less than 210-2 and 6.310-2 for co2 laser wavelengths of 10.6 μm and 5.3 μm, respectively. 4. conclusion differential thermal analysis, x-ray diffraction and microstructural analysis were used to construct a phase diagram for the tlinp2se6–in4(p2se6)3 system, which can be characterized by a eutectic-type interaction. the invariant eutectic process l  httlinp2se6 + mtin4(p2se6)3 (15 mol% in4(p2se6)3) occurs at 791 k. two polymorphic transformations were identified for tlinp2se6 at 680 k and 711 k and for in4(p2se6)3 at 665 k and 903 k. new compounds were not detected in the binary system. the regions of solid phases of the complex compounds tlinp2se6 and in4(p2se6)3 do not exceed 10 mol%. single crystals of both test compounds were achieved by the bridgman method. investigations concerning the dependence of the diffuse reflection spectrum showed that the compound tlinp2se6 is characteristic of indirect-gap semiconductors (eg = 2.13 ev, ephonon = 0.08 ev), while the compound in4(p2se6)3 is characteristic of direct-gap semiconductors (eg = 1.91 ev, ephonon = 0.08 ev). the dependence of the birefringence was photoinduced by wavelengths of 5.3 μm and 10.6 μm, which is indicative of different photoinduced anisotropy. acknowledgement we are grateful for the financial support of this work by the ministry of education and science of ukraine under the project db874p_0117u000380. symbols ht high–temperature modification mt middle–temperature modification lt low–temperature modification sce second coordination environment nce nearest coordination environment eg band gap, ev ephonon phonon energy, ev r diffuse reflection  wavelength, nm references galdamez, a., manriquez, v., kasaneva, j., avila, [1] r.e.: synthesis, characterization and electrical properties of quaternary selenodiphosphates: amp2se6 with a – cu, ag and m – bi, sb, mat. res. bull., 2003 38, 1063-1072 doi: 10.1016/s00255408(03)00068-0 mcguire, m.a.; reynolds, t.k.; di salvo, f.j.: [2] exploring thallium compounds as thermoelectric materials: seventeen new thallium chalcogenides, chem. mater., 2005 17, 2875-2884 doi: 10.1021/cm050412c gave, m.a.; bilc, d.; mahanti, s.d.; breshears, [3] j.d.; kanatzidis, m.g.: on the lamellar compounds cubip2se6, agbip2se6 and agbip2s6. antiferroelectric phase transitions due to cooperative cu+ and bi3+ ion motion, inorg. chem., 2005 44, 5293-5303 doi: 10.1021/ic050357 pfeiff, r.; kniep, r.: quaternary selenodiphos-[4] phates(iv): m(i)m(iii)[p2se6], (m(i) = cu, ag; m(iii) = cr, al, ga, in), j. alloys compd., 1992 186, 111-133 doi: 10.1016/0925-8388(92)90626-k figure 11. photoinduced birefringence dependence at wavelengths of 5.3 μm and 10.6 μm the two coherent beams were illuminated under different angles. during the two-beam coherent treatment at optimal power densities (about 400 mw/cm2) and incident angles (18-22 degrees) for crystals of in4(p2se6)3. the birefringence scale should be multiplied by 10-2. figure 12. photoinduced birefringence dependence at wavelengths of 5.3 μm and 10.6 μm the two coherent beams were illuminated under different angles. during the two-beam coherent treatment at optimal power densities (about 400 mw/cm2) and incident angles (18-22 degrees) for crystals of tlinp2se6. the birefringence scale should be multiplied by 10-2. tovt, barchiy, piasecki, kityk, and fedorchuk hungarian journal of industry and chemistry 18 mucha, i.: phase diagram for the quasi-binary thal-[5] lium(i) selenide–indium(iii) selenide system, thermochimica acta, 2012 550, 1-4 doi: 10.1016/j.tca.2012.09.028 guseinov, g.d.; abdullaev, g.b.; godzhaev, [6] e.m.; rzaeva, l.a.; agaev, g.a.: constitutional diagram and physical properties of thallium selenide–indium selenide pseudobinary system, mater. res. bull., 1972 7(12), 1497-1503 doi: 10.1016/00255408(72)90187-0 brockner, w.; ohse, l.; pätzmann, u.; eisenmann, [7] b.; schäfer, h.: kristallstruktur und schwingungsspektrum des tetra-thalliumhexaselenidohypodiphosphates tl4p2se6, z. naturforsch. a, 1985 40, 1248-1252 voroshilov, y.v.; gebesh, v.y.; potorii, m.v.: [8] phase equilibria in the system in–p–se and crystal structure of β-in4(p2se6)3, inorg. mater., 1991 27, 2141-2144 tovt, v.a.; barchiy, i.e.; piasecki, m.; kityk, i.v.; [9] fedorchuk, a.o.; solomon, a.m.; pogodin, a.i.: triangulation of the tl2se–in2se3–“p2se4” quasiternary system, nauch. vestn. uzhgorod. univ. (ser. khim.), 2016 35(2), 14–19 (in russian) akselrud, l.; grin, y.: wincsd: software package [10] for crystallographic calculations (ver.4), j. appl. crystallogr., 2014 47, 803-805 doi: 10.1107/s1600576714001058 israel, r.; de gelder, r.; smits, j.m.m.; [11] beurskens, p.t.; eijt, s.w.h.; rasing, t.h.; van kempen, h.; maior, m.m.; motrya, s.f.: crystal structures of di-tin-hexa(seleno)hypodiphosphate, sn2p2se6, in the ferroelectric and paraelectric phase, z. kristallogr., 1998 213, 34-41 doi: 10.1524/zkri.1998.213.1.34 fedorchuk, a.o.; parasyuk, o.v.; kityk, i.v.: sec-[12] ond anion coordination for wurtzite and sphalerite chalcogenide derivatives as a tool for the description of anion sub-lattice, mat. chem. phys., 2013 139, 92-99 doi: 10.1016/j.matchemphys.2012.12.058 kityk, i.v.: ir-stimulated second harmonic genera-[13] tion in sb2te2se–baf2–pbcl2 glasses, j. modern optics, 2004 51, 1179-1189 doi: 10.1080/09500340408230415 kityk, i.v.: ir-induced second harmonic genera-[14] tion in sb2te3–baf2–pbcl2 glasses, j. phys. chem. b, 2003 107, 10083-10087 doi: 10.1021/jp030058a hungarian journal of industry and chemistry vol. 45(2) pp. 19–21 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0015 examination of innovative high-throughput fermentations áron németh* department of applied biotechnology and food science, budapest university of technology and economics, műegyetem rkp. 3, budapest, 1111, hungary during the investigation of fermentations, issues such as the need for numerous parallel experiments with regard to strain improvement or screening were often met, or in the case of media optimization the need for online measurements to avoid a lack of night-samples was also required. therefore, several new instruments were introduced to solve one or more of these problems: impedimetricand reverse-spin-technologies (rst) were compared via fermentation of a well-known species of yeast, saccharomyces cerevisiae, under both aerobic and anaerobic conditions, resulting in a diauxic growth curve. to identify the most accurate method, a wellknown mathematical description was fitted to the measured data. since the initial parameters were considered reliable as they originated from real experiments, during model fitting, the parameters were further fine-tuned, and the less modifications reported the better the system since it produces a growth curve that is more similar to standard bioreactors. according to our study, the impedimetric equipment was more efficient, and could run 40 parallel experiments, but the rst was more flexible. keywords: fermentation, high-throughput, scale-down, online measurement, mathematical modelling 1. introduction developments in fermentations face numerous challenges which may require expensive analytics, media components or special tools to facilitate aseptic work and sampling. furthermore, these biological processes vary significantly. to overcome these difficulties, the process should be scaled-down in combination with high-throughput methods, resulting in many parallel, small-scale experiments. such experiments are used in terms of strain and technological improvements as well as media optimization. a good solution may be the consideration of micro-bioreactors. however, because of their high investment and operational costs, they have not become widespread in hungary. while each can provide almost every service required for bioreactors, for example, aeration, agitation and sampling in addition to ph and temperature control, they possess considerable limitations, namely non-standard conformations resulting in scaleup difficulties, or special measurement techniques that are incompatible with standard methods. a readily available alternative, to be more precise, microtiter-plates (mtp), for microscale highthroughput fermentations has already been presented and reported [1]. the basic principle is to use sterile ’96-well’ microtiter plates with a special “sandwich cover” that facilitate sufficient aeration but reduce the likelihood of cross-infection. this system requires an *correspondence: naron@f-labor.mkt.bme.hu adapter to be able to mount microtiter plates into a commercial rotary incubator shaker. the next issue is to analyse and follow the processes in the wells since their volumes are so small (ca. 100 l) that sampling is impossible. therefore, either a microplate reader is required or a simple office scanner to produce a greyscale photo taken from the bottom of the plate. the colour of high cell-densities is close to white, but empty broths have a black background. in the case of species that produce high levels of acid, like lactobacillus, even a ph indicator can be applied and besides a greyscale photo a coloured one has to be taken as well; alternatively, caco3 should be added at the start but this can disturb the scanner-based “photometry”. our partner (enzyscreen.com) even offers microtiter plates for fed-batch fermentations. to achieve this, the feed components are adsorbed onto the material of the mtp, and are programmed to slowly release the fresh substrate during cultivation. however, another innovative solution has been developed for small-scale fermentations using online monitoring: biosan ltd. (lithuania) applies reverse-spin technology in the equipment of their personal bioreactor (rts-1). this cost-effective equipment rotates a standard falcon tube, filled with ca. 10 ml of fermentation media, at different rotation speeds in several directions at various controlled temperatures using a variety of aeration holes on the cap. this instrument also involves a photometer to facilitate the programming of measuring frequencies at a given wavelength (= 850 nm). for calibrated and reproducible measurements, a constant film layer is necessary, therefore, the instruments increase the rate of németh hungarian journal of industry and chemistry 20 rotation until 2000 rpm. the changes in parameters effect shear forces as well as levels of aeration. finally, this comparative study used an impedimetric system by sy-lab (austria) which is called bactrac 4100 [2]. this equipment possesses a block thermostat composed of 40 measurement cells, each containing 4 electrodes. one pair of them follows the changes in the impedance of the media, m%, caused by the secreted acids and metabolites. in the case of microorganisms that exhibit high levels of ionic strength in the media, it is hard to detect m%, therefore, with the application of a different frequency the changes in impedance on the other electrode surface (e%) can be followed. in direct measurements, these electrodes are immersed directly into the culture, but in the case of indirect measurements, they are rinsed with koh which can adsorb the formed co2 released by the culture. while this system does not possess mixer/aerator solutions, this result can be transferred carefully to the known systems, namely benchtop fermenters or shaking flasks. however, it is able to follow forty different cultures. in this study, a well-known model organism (s. cerevisiae) was chosen that exhibits special biochemical behaviour. it was used to test the compare the ability of the three systems introduced above. what is special about s. cerevisiae is that it can change from aerobic to anaerobic cultivation according to pasteur and crabtree effects; i.e. under lack of oxygen or excess to sugar, respectively. after changing to anaerobic metabolism, it produces mostly alcohol but later this can be consumed by yeast as well resulting in a stepwise growth curve, also referred to as a diauxic growth profile. thus, the question was whether such a system could show and follow this diauxic growth. 2. experimental commercial s. cerevisiae, i.e. baking yeast produced by lesaffre, was cultured on a media of molasses that were diluted by a factor of 10 resulting in a saccharose concentration of ca. 75 g dm-3 and a 20:1 volume of molasses to nh4oh ratio at 34°c. the 100 l of inoculum possessed a cell-dry-weight (cdw) content of 10 g/dm3. rts-1 collected the data in a microsoft excel database. bactrac only provided the data collected on screen plots, but with the help of digitizelt v.2.3 software the measurement data was transported into microsoft excel. to compare the data in microsoft excel, the structured model of blanch et al. [3] was adopted and programmed in berkeley madonna for windows 8.1. this model can describe both anaerobic cell growth on excess sugar with the formation of alcohol and aerobic cell growth on alcohol as a substrate. it divides cells into two main compartments, i.e. substructures: one is responsible for metabolism (both aerobic and anaerobic), and the other is responsible for cell division. the parameters, for example reciprocal yields and stoichiometric coefficients of the model, were partly determined experimentally, but others were determined by nonlinear model fitting, i.e. model calibration on real samples. 3. results and analysis 3.1. reverse-spin technology vs. personal bioreactor (rts-1) fig.1 presents the results of rts-1. while optical density (od), i.e. turbidity at = 850nm, changed slowly, the specific growth rate calculated online only reflected the uncertainty of the od measurements, but the temperature remained constant as expected. additionally diauxic growth was also detected but over a very long period of time. the model fitting was quite difficult because a satisfactory fit was only achieved after remarkable changes to basic constants, for example maximum specific growth rates on both substrates, etc., had been applied. 3.2. impedimetric system: bactrac in the case of the impedimetric experiments, three different arrangements were tested: an anaerobic cell with (a) (b) figure 1. the measured parameters (temperature, , od850) and calculated data (cdw from od850) along with the data of the predicted (i.e. fitted) model. (a) green line: temperature; blue line: measured turbidity at 850nm; brown line: measured specific growth rate. (b) green line: temperature; red crosses: calculated cell dry weight from the measured turbidity at 850nm; purple line: fitted model-based prediction for cdw. 0 5 10 15 20 25 30 35 40 -2 -1 0 1 2 3 4 0 50 100 150 200 250 300 350 t(°c)od (850nm) fermentation time (h) od(850nm) µ (h ̄ ¹) t °c growth on sugar growth on ethanol d i a u x i c g r o w t h 0 5 10 15 20 25 30 35 40 0 2 4 6 8 10 12 14 16 18 0 50 100 150 200 250 300 350 t(°c)cdw fermentation time (h) cdw predicted cdw t °c examination of innovative high-throughput fermentations 45(2) pp. 19–21 (2017) 21 an incorporated valve for gas release, an aerobic one, and an indirect one (fig.2). only m% values yielded explainable curves. indirect measurements yielded an inverse growth curve (decreasing) as expected, but did not exhibit a two-step decrease, i.e. diauxic growth, therefore, m% values of direct measurements were evaluated. the two curves of aerobic and anaerobic m% values were very similar to each other, but perhaps the anaerobic example is more relevant as in the case of high sugar content, the metabolism of yeast shifted in the anaerobic direction. fig.3 shows the fits of the model in which less constants had to be changed and diauxic growth was detected. 4. conclusion both tested systems – personal bioreactor (rts-1, biosan) and bactrac (sy-lab) – detected diauxic cell growth of baking yeast. rts-1 seemed to be a little bit more flexible, but bactrac gave faster results, was able to make 40 measurements at the same time and offered three options in terms of evaluation. maybe in the near future a solution to regular automatic sampling from larger-scale fermenters will be found and then the results can be compared with the ones presented here. acknowledgement we are sincerely grateful to sy-lab for the support provided with regard to bactrac, and to biocenter kft. for importing rts-1. references [1] németh, á.; kiss, á.; sevella, b.: experiments for d-lactic acid production with fermentation, hung. j. ind. chem., 2011 39(3), 359–362 [2] bankovsky, v.; bankovsky, i.; bankovsky, p.; isakova, j.; djackova, i.; sharipo, a.; eskin, j.; dišlers, a.; rozenstein, r.; saricev, v.; djacenko, s.; makarenko, v.; balodis, u.: reverse–spin® technology innovative principle of microbial cultivation, manufacturer's online leaflet: https://biosan.lv/images/uploads/content/files/reverse_spinner.pdf [3] blanch, h.w.; clark, d.s.: biochemical engineering (marcel dekker, ny, usa), 1996, pp. 231–236 isbn 9780824700997 (a) (b) (c) figure 2. the results of three bactrac measurements: relative changes in impedancy in the m% of media vs. time (h) (a) indirect-; (b) aerobic-direct-; (c) anaerobic-direct measurements. figure 3. model fitting to the anaerobic bactrac curve (m%): red crosses: measured data; purple line: modelpredicted values; green line: temperature (°c). 0 5 10 15 20 25 30 35 40 0 2 4 6 8 10 12 0 20 40 60 80 100 120 t(°c) measured (m%) and predicted impedancy fermentation time (h) m(%) predicted impedancy t °c d i a u x i c g r o w t h growth on ethanol growth on sugar hungarian journal of industry and chemistry vol. 45(2) pp. 23–27 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0016 the effect of advanced oxidation pre-treatment on the membrane filtration parameters of dairy wastewater mihály zakar, 1,2 ildikó kovács, 1 péter muhi, 1 erika hanczné lakatos, 2 gábor keszthelyi-szabó, 1 zsuzsanna lászló 1, * 1 institute of mechanical and process engineering, faculty of engineering, university of szeged, moszkvai krt. 9, szeged, 6724, hungary 2 institute of food sciences, széchenyi istván university, lucsony u. 15-17, mosonmagyaróvár, 9200, hungary the dairy industry generates wastewater characterised by high levels of biological and chemical oxygen demands representative of their high degree of organic content; mainly carbohydrates, proteins and fats that originate from milk. several investigations have been conducted into the reuse of dairy wastewater, e.g. membrane processes are a promising method to treat such wastewater. earlier works have proven that with membrane filtration an appropriate degree of retention can be achieved and the permeate can be reused. however, membrane fouling is a limiting factor in these processes. advanced oxidation processes (aops) are widely used in the fields of water and wastewater treatments and are known for their capability to mineralise a wide range of organic compounds. aops also exhibit some other effects on the filtration process, e.g. the microflocculation effect of ozone may play a significant role in increasing the elimination efficiency and causing a decreased level of irreversible fouling. by comparing ozone and fenton pre-treatment (fpt) processes it can be shown that the fouling propensity of pre-treated pollutants does not depend on the pre-treatment method, while fpt was proven to be more efficient in improving the level of flux. keywords: ultrafiltration, ozone pre-treatment, fenton-reaction, fouling resistances, dairy wastewater 1. introduction the dairy industry is considered to be the largest source of food-processing wastewater in many countries. dairy wastewater exhibits high degrees of biological oxygen demand (bod) and chemical oxygen demand (cod); contains high levels of dissolved or suspended solids including fats, oils and grease; as well as nutrients such as ammonium ions or phosphates. therefore, proper attention must be paid to them before disposal [1]. there are several research projects that aim to identify possibilities of reusing or recycling dairy wastewater [29]. membrane treatment of dairy wastewater with the aim of water reuse could simultaneously lower the total water consumption and effluent production of dairy plants, as the purified water produced could be reused in a dairy plant to heat or cool water. besides additional advantages, e.g. a high degree of separation efficiency in the absence of chemical changes and low levels of energy intensity, membrane filtration also has drawbacks, namely compounds in dairy wastewater that contain protein were found to be significant foulants in terms of existing membrane materials [10-12]. *correspondence: zsizsu@mk.u-szeged.hu the combination of membrane separation and pretreatment with advanced oxidation processes (aops: using ozone, hydrogen peroxide, uv light, or a combination of these) opens up new opportunities, since the ozone and the resulting oxidizing radicals (mainly hydroxyl radicals) efficiently change the characteristics of the colloidal particles or oxidizing compounds, which cause membrane fouling [13]. earlier studies have shown that the microflocculation effect of ozone may play a significant role in increasing the elimination efficiency and may decrease the extent of membrane fouling and increase the degree of gel formation. in addition, aops can be used as a pre-treatment stage before a biological step in order to increase the biodegradability of the recalcitrant compounds and thus lower the toxicity of the wastewaters [13-14]. according to economic evaluation studies, the fenton process is more economical than ozone pretreatment [15]. however, there is little data concerning its effect on membrane filtration parameters. the aim of the present work was to investigate and compare the effect of ozone pre-treatment and the fenton’s reaction on ultrafiltration parameters, fouling mechanisms and the pollutant removal efficiency on a model dairy wastewater. zakar, kovács, muhi, lakatos, keszthelyi-szabó, and lászló hungarian journal of industry and chemistry 24 2. experimental 2.1. samples and measurements model solutions were prepared from milk powder (milk quick, instantpack kft., hungary) composed of 0.3% (g/g) concentrations, 32% (g/g) proteins, 5% (g/g) fat and 50% (g/g) lactose. ozone was produced from oxygen (linde, 3.0) with a flow-type ozone generator (ozomatic modular 4, wedeco ltd., germany). the ozone-containing gas was bubbled continuously through a batch reactor during the treatment. the volume of the treated water was 0.45 dm3. the durations of the treatment were 5, 10 and 20 mins; and the flow rate was 1 dm3 min–1. the ozone concentrations of the bubbling gas before and after it was passed through the batch reactor were measured with a ultraviolet–visible (uvvis) spectrophotometer (nanocolor nuv 0113) at a wavelength of 254 nm (fig.1). the absorbed ozone concentrations were 6.8·10–4 m, 1.43·10–3 m and 2.67·10–3 m, respectively. fenton’s reaction was conducted in a batch stirred ultrafiltration cell with 1.5 mmol dm-3 feso4×7h2o (purity 99%, spektrum-3d, eu) adjusted to ph 3 with h2so4 (purity 96%, farmitalia carlo erba spa, italy), 0.3 wt.% milk powder solution and h2o2 solution (30%, purity 99%, spektrum-3d kft.), the [h2o2]:[fe] ratio was 5:1 (fenton (5:1)) or 50:1 (fenton (50:1)). the ozone or fenton pre-treated samples were used as a feed in ultrafiltration (uf) experiments. the uf experiments were carried out in a batch stirred ultrafiltration cell (millipore, serial n°94, usa) with a capacity of 50 cm3, and the filtrations were performed at transmembrane pressures of 0.1 (only in the case of fenton (50:1)) or 0.3 mpa and the feed solutions were stirred at 350 rpm. for filtration experiments, flat sheet polyethersulfone (pes) membranes (pes-10 series, new logic research inc., usa) and a molecular weight cut-off (mwco) of 10 kda were used with an effective membrane surface area of 1.73 dm2. the initial feed volume was 50 cm3, the ultrafiltration experiments were conducted until 40 cm3 of the total sample had been filtered, when the volume reduction ratio (vrr) was equal to 5. determination of the cod was based on the standard method involving the oxidation of potassium dichromate; for the analysis, standard test tubes (lovibond tintometer ltd.) were used. the digestions were conducted in a cod digester (lovibond et108 thermoreactor); and the cod values were measured with a cod photometer (lovibond pccheckit). for the determination of the residual amount of hydrogen peroxide, cod measurements were performed before and after the addition of the enzyme catalase. 2.2. theoretical methodologies in order to investigate mechanisms of membrane fouling, filtration resistances were calculated according to the resistance-in-series model, eqs.(1-4). the membrane resistance ( mr , m-1) was calculated as 1 m w w [m ] p r j    (1) where p is the difference in pressure either side of the membrane (in mpa), wj is the water flux of the clean membrane, and w is the viscosity of water (in pa·s). the total resistance ( tr , in m–1), can be evaluated from the steady-state flux by using the resistance-inseries model: revt m irrevr r r r   (2) where irrevr is the irreversible resistance (mainly caused by the fouled pores) and revr is the reversible resistance. the irreversible resistance was determined by measuring the water flux through the membrane after filtration, rinsing it with deionized water to remove any particles of the residue layer from the surface, and subtracting the resistance of the clean membrane: mirrev ww a p r r j     (3) where waj is the water flux after concentration tests. the reversible resistance of the layer deposited on the membrane surface was calculated as: r e v mir r e v w wc p r r r j      (4) where cj is the constant flux at the end of the concentration test and ww is the viscosity of the wastewater viscosity [16]. mathematical modelling of the fouling mechanism was studied based on the hermia’s model [17]. the hermia’s model describes the mechanism of membrane fouling based on blocking filtration laws, consisting of complete pore blocking, standard pore blocking and intermediate pore blocking, in addition to cake filtration (table 1) to illustrate the different fouling mechanisms. figure 1. experimental set-up of ozonation. effect of advanced oxidation pre-treatment 45(2) pp. 23–27 (2017) 25 the hermia’s model was then linearized for each model using a fitting equation in terms of the permeate flux versus time as presented in table 1. in terms of the evaluation of the results these models were fitted to experimental data. in table 1, j is the flux, j0 is the initial flux, the various k’s are the fouling coefficients, and a is a constant. to compare the performance of different aops, the oxygen-equivalent chemical-oxidation capacity (occ, kg o2 m-3) was used to quantify the oxidants used in the ozone treatment and fenton’s reaction, and was determined based on stoichiometric calculations [14]: occ =1.000[o3] = 0.471[h2o2] (5) where [o3] is the required ozone concentration (kg o3 m-3), and [h2o2] is the required hydrogen peroxide concentration (kg h2o2 m -3). 3. results and analysis 3.1. experiments the effect of pre-oxidation on filtration parameters was investigated by fitting equations in table 1 to measured data. based on the value of the coefficient of determination, the cake layer filtration yielded the best correlation. in order to compare the different pre-oxidation methods, normalised values of the initial flux (j0, l m-2 h-1 bar-1) and fouling coefficients (k) were calculated and compared (figs.2 and 3). it was found that the effect of ozone treatment and fenton-treatment is different in the case of initial normalised flux. not only the fenton pre-treatment but the addition of reagents in the absence of hydrogen peroxide exhibited coagulationflocculation effects that resulted in an enhanced initial flux. in the case of the fenton’s reaction this effect is independent of the [h2o2]:[fe] ratio. the fouling coefficient also changes by the addition of oxidants, (fig.3) but in this case, the tendency is more likely to depend on the occ than on the applied aop method. at lower oxidation capacities the fouling coefficient decreases resulting in lower degrees of fouling than in non-treated solutions, however, at higher oxidation grades, the fouling coefficient increases. to obtain more information concerning the fouling mechanisms, the filtration resistances of ozone-treated and fenton (5:1) pre-treated solutions were calculated and compared (fig.4). it was found that in accordance with the values of the fouling coefficient filtration resistances decrease as the duration of oxidation pretreatment increases. in particular, mainly pre-treatments of short durations decreased the irreversible fouling resistance and increased the reversible fouling resistance. 4. discussion as an effect of the pre-oxidation of model dairy wastewater two typical pathways were observed that influence membrane filtration parameters: the i) microfigure 2. normalised initial flux values as a function of occ. 0 5 10 15 20 25 0,0000 0,0050 0,0100 0,0150 j 0 (l / m 2 h b a r) occ (kg o2/m3) fenton (50:1) fenton (5:1) ozone untreated figure 3. fouling coefficient as a function of occ. 0 0,001 0,002 0,003 0,004 0,005 0,006 0,00 0,10 0,20 0,30 0,40 0,50 k occ (kg o2/m3) fenton (50:1) fenton (5:1) ozone untreated figure 4. filtration resistances of untreated, fenton (5:1) and ozone pre-treated solutions. 0,00e+00 1,00e+13 2,00e+13 3,00e+13 4,00e+13 5,00e+13 6,00e+13 7,00e+13 f il tr a ti o n r e si st a n ce s (1 / m ) rm r(irrev) r(rev) rt table 1. hermia’s filtration laws. fouling mechanism filtration law constant-pressure filtration j0 a = cont. complete pore blocking j = j0 e -kt ln j = ln j0 kt gradual pore blocking (standard pore blocking) j = j0·(1 + ½ ks (a·j0 ) ½·t)-2 1/j0.5 =1/j0 0.5+ks·t ks = 0.5 ks a 0.5 intermediate filtration j = j0 · (1 + ki·a·j0 ·t) -1 1/j = 1/j0 + ki·t ki = ki a cake filtration j = j0 · (1 + 2kc(a·j0) 2·t)-0.5 1/j2 = 1/j0 2 + kc·t kc = 2kc a 2 zakar, kovács, muhi, lakatos, keszthelyi-szabó, and lászló hungarian journal of industry and chemistry 26 flocculation effect produces associated colloidal particles, and ii) degradation of organic matter (fig.5). the former resulted in decreased fouling of membrane pores as shown by the decreased fouling coefficient and irreversible resistance. this can be observed only during short-term ozone or fenton treatments (occ < 0.05 kg o2 m -3). the latter point may increase the degree of pore fouling [13, 18] due to the formation of small degradation by-products, which can enter membrane pores as the increased values of irreversible resistance also prove. by comparing the ozone and fenton pretreatment processes with similar occs, it can be concluded that the fenton pre-treatment may be more effective in terms of enhancing the flux, probably due to the coagulation-flocculation effect of the ferrous salts themselves. 5. conclusion the comparison of ozone and fenton processes as pretreatments before ultrafiltration of a model sample of dairy wastewater showed that such pre-treatments may improve the filtration parameters in terms of flux or fouling mitigation. by examining the effect of the oxidation capacities of ozone and fenton pre-treatment processes, it was found that the fouling propensity of pollutants does not depend on the pre-treatment method. however, it depends on the occ of the pre-treatment method. although the method of pre-treatment affects the flux, the fenton pre-treatment proved to be more efficient in terms of enhancing the value of the flux. symbols rm membrane resistance (m–1) rrev reversible resistance (m–1) rirrev irreversible resistance (m–1) p pressure difference between the two sides of the membrane (mpa) j flux (1/s) jw water flux (1/s) jc constant flux at the end of the concentration (1/s) j0 initial flux (1/s) ηw water viscosity (pa·s) k fouling coefficient occ oxygen-equivalent chemical-oxidation capacity (kg o2·m –3) acknowledgement this research was supported by the jános bolyai research fellowship of the hungarian academy of sciences. the authors are also grateful for the financial support of the national research, development and innovation office (nkfih k112096). references [1] farizoglu, b.; uzuner, s.: the investigation of dairy industry wastewater treatment in a biological high performance membrane system, biochem. eng. j., 2011 57, 46–54 doi: 10.1016/j.bej.2011.08.007 [2] vourch, m.; balance, b.; chaufer, b.; dorange, g.: treatment of dairy industry wastewater by reverse osmosis for water reuse, desalination, 2008 219(1-3), 190–202 doi 10.1016/j.desal.2007.05.013 [3] perle, m.; kimchie, s.; shelef, g.: some biochemical aspects of the anaerobic degradation of dairy wastewater, water res., 1995 29(6), 1549–1554 doi 10.1016/0043-1354(94)00248-6 [4] bick, a.; plazas, t.j.g.; yang, f.; raveh, a.; hagin, j.; oron, g.: immersed membrane bio reactor (imbr) for treatment of combined domestic and dairy wastewater in an isolated farm: an exploratory case study implementing the facet analysis (fa), desalination, 2009 249(3), 1217– 1222 doi 10.1016/j.desal.2009.06.035 [5] sarkar, b.; chakrabarti, p.p.; vijaykumar, a.; kale, v.: wastewater treatment in dairy industries: possibility of reuse, desalination, 2006 195(1-3), 141–152 doi 10.1016/j.desal.2005.11.015 [6] andrade, l.h.; motta, g.e.; amaral, m.c.s.: treatment of dairy wastewater with a membrane bioreactor, braz. j. chem. engng., 2013 30(4), 759–770 doi 10.1590/s0104-66322013000400008 [7] yip, v.; arntfield, s.d.; hydamaka, a.w.: potential for stainless steel microfiltration processing to reduce effluent from a fluid milk and ice-cream processing plant, j. dairy sci., 1996 79(4), 710–716 doi 10.3168/jds.s0022-0302(96)76417-2 [8] koyuncu, i.; turan, m.; topacik, d.; ates, a.: application of low pressure nanofiltration membranes, for the recovery and reuse of dairy industry effluents, water sci. tech., 2000 41(1) 213–221 web: http://wst.iwaponline.com/content/41/1/213 [9] luo, j.; ding, l.; qi, b.; jaffrin, m.y.; wan, y.: a two-stage ultrafiltration and nanofiltration process for recycling dairy wastewater, bioresour. technol., 2011 102(16), 7437–7442 doi 10.1016/j.biortech.2011.05.012 figure 5. possible effect of 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lászló, zs.; kertész, sz.; beszédes, s.; hovorkahorváth, zs.; szabó, g.; hodúr, c.: effect of preozonation on the filterability of model dairy waste water in nanofiltration, desalination, 2009 240(1-3), 170–177 doi 10.1016/j.desal.2007.12.040 [14] cańizares, p.; paz, r.; sáez, c.; rodrigo, m.a.: costs of the electrochemical oxidation of wastewaters: a comparison with ozonation and fenton oxidation processes, j. environ. mgmt., 2009 90(1), 410–420 doi 10.1016/j.jenvman.2007.10.010 [15] özge, s.; taner, y.: determination of the acute toxicities of physicochemical pretreatment and advanced oxidation processes applied to dairy effluents on activated sludge, american dairy science association, j. dairy sci., 2015 98(4), 2337–2344 doi 10.3168/jds.2014-8278 [16] kertész, sz.; lászló, zs.; forgács, e.; szabó, g.; hodúr, c.: dairy waste-water purification by vibratory shear enhanced processing, desalination water treat., 2012 37(1-3), 1–7 doi 10.5004/dwt.2011.2485 [17] hermia, j.: constant pressure blocking filtration law: application to power law non-newtonian fluids, trans. ind. chem. eng., 1982 60(3), 183– 187 web: http://hdl.handle.net/2078.1/57489 [18] zhu, h.t.; wen, x.h.; huang, x.: pre-ozonation for dead-end microfiltration of the secondary effluent: suspended particles and membrane fouling, desalination, 2008 231(1-3), 166–174 doi 10.1016/j.desal.2007.11.044 hungarian journal of industry and chemistry vol. 45(2) pp. 29–33 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0017 microencapsulation of vegetable oil: alternative approaches using membrane technology and spray drying krisztina albert,* gyula vatai, and andrás koris department of food engineering, szent istván university, ménesi út 44, budapest, 1118, hungary microencapsulation technology is a method that is widely used in the food industry. by comparing the latest encapsulation techniques, a significant number of publications concern membrane technology. the term “membrane-based encapsulation” entails that the first step of the technique is the preparation of emulsion with the help of microporous membranes. generally, in microencapsulation technologies, the wall material is dissolved in a continuous phase and oil is dispersed within it. in the present investigation, a new method of preparing microcapsules composed of vegetable oil and maltodextrin was developed. in the first step, the wall material (maltodextrin) was dissolved in oil and considered as a dispersed phase, subsequently, it was introduced into a continuous phase (water) through a microporous membrane. a comparative study was conducted between conventional microencapsulation techniques and one developed in our laboratory. the average particle size of microcapsules prepared by our method is smaller than the size allowed by other methods. after encapsulation preparation, fine-tuned microcapsules were produced by spray drying. however, the main disadvantage of our proposed technology is rapid membrane fouling, because of high concentrations of solute in the dispersed phase. this problem can be eliminated by judicious and systematic investigations. keywords: vegetable oil, microencapsulation, membrane technology, spray drying 1. introduction the controlled release of food ingredients at the right place and the right time is a key functionality that can be provided by microencapsulation. in food products, fats and oils, aroma compounds, vitamins, minerals, colourants and enzymes are encapsulated. the process of the encapsulation of sensitive compounds consists of two steps: the first is often emulsion production: emulsification of core materials with dense solutions of wall material; the second is drying or cooling of emulsion by some chemical or mechanical process; and at the end of these processes microparticles can be obtained [1]. the two major industrial encapsulation processes are spray drying and extrusion [2]. table 1 summarizes literature reviews that focus on these technologies, where the two steps of microencapsulation are performed by the combination of so-called membrane emulsification and spray drying. membrane emulsification (me) is a relatively new, simple emulsion-production method which can be conducted with the use of a microporous membrane. other emulsification processes within this category, besides me and spray drying, include simple blending as well as homogenization; and secondary reactions that recover the capsules from the emulsion are interfacial *correspondence: albert.krisztina@etk.szie.hu polymerization, vacuum heat treatment, solvent diffusion and freeze drying. different materials are used as the dispersed phase and wall materials of the microcapsules. the continuous phase is typically water. 2. experimental the main objective of this study was to initially prepare emulsions and form microcapsules using three different methods. the first approach was conventional membrane emulsification. the second one was conducted by a modified me process. the third involved the use of a laboratory blender. in all three cases, the second step was the spray-drying technique to recover the microcapsules from the emulsions. 2.1. samples and measurements all chemicals (maltodextrin, tween-80 emulsifier) were procured from shop.builder, hungary and sigmaaldrich, germany. commercial-grade sunflower-seed oil was purchased from a local market in the vicinity of budapest. 2.2. membrane emulsification apparatus a cross-flow membrane emulsification system was used as the emulsification process (fig.1). the apparatus included two manometers positioned at the opposite albert, vatai, and koris hungarian journal of industry and chemistry 30 ends of the membrane to measure the drop in pressure along the membrane. the pressure of the dispersed phase was guaranteed by compressed air from an air pump which was injected from the outer surface of the membrane. the continuous phase was recirculated on the lumen side of the membrane by a pump. a rotameter, placed at the exit of the membrane, allowed the flow rate of the continuous phase to be measured. 2.3. microencapsulation process microcapsules were prepared by a tubular ceramic membrane with a pore size of l.4 μm (pall austria filter gmbh). the membrane was composed of αalumina and the surface area of the active membrane was 50 cm2. cross-flow operation was adopted for emulsion production. the first emulsion was prepared using a conventional membrane emulsification technique. the wall material (maltodextrin) was dissolved in the continuous phase (water) and sunflower-seed oil was dispersed into it. the direction of flow of the dispersed phase was tangential with the surface of the membrane. otherwise, in the second case the wall material was mixed with sunflower-seed oil. this mixture was considered as the dispersed phase and it was pressed through the membrane pores under pressure. in both cases the pressure of the dispersed phase was 2.5 bars and the recirculation flow rate of the continuous phase was 150 dm3 h-1. in the third case the emulsion was prepared at room temperature using a laboratory blender at 2,000 rpm for 40 minutes. 2.4. spray drying the emulsions prepared were spray dried with a laboratory-scale spray dryer (labplant sd-05) equipped with a nozzle of 0.5 mm in diameter. the pressure of the compressed air in terms of the flow of the spray was adjusted to 3.6 bars. the air temperature at the inlet was maintained at 180±5 °c, and the feed rate was adjusted to 475 cm3 h-1, respectively. emulsions were prepared during the spray drying process and were continuously stirred by a magnetic stirrer throughout. the microcapsules were collected from the collecting chamber and stored in darkness until analysed. 2.5. analysis of microcapsules following the emulsion preparation, the average droplet size and span value were measured by a fritsch laser particle sizer analysette 22 nanotec. each sample was analyzed three times and the average data reported. the span value was considered as an indication of the dispersity of the droplet size. the lower the span value, the more monodisperse the emulsion. a vhx-6000 digital microscope manufactured by keyence was used to check the formation of microcapsules and evaluate their morphology. 2.6. surface-oil content and microencapsulation efficiency the procedure modified by calvo et al. [9] to determine the surface-oil content and microencapsulation efficiency was employed to measure the amount of unencapsulated oil present on the surface of the powders. briefly, 5 g of microcapsules were precisely table 1. summary of examples from the literature of microencapsulation technologies. emulsification secondary reaction dispersed phase / wall material membrane emulsification spray-drying oil / polyvinylpyrrolidone (pvp) [3] fish oil / whey protein isolate (wpi), whey protein hydrolysate (wph), sodium caseinate, maltodextrin [4] interfacial polymerization benzene, xylene, liquid paraffin / terephthaloyl dichloride (tdc) [5] vacuum heat treatment oil / polyethersulphone (pes) [6] solvent diffusion oil / polycaprolactone (pcl), dichloromethane (dcm) [7] freeze-drying chloroform + curcumin / poly(lactic-co-glycolic acid) (plga) [8] blending and homogenization spray-drying extra virgin olive oil / gelatin, gum arabic, starch, lactose, maltodextrin [9] olive oil + α-tocopherol / maltodextrin, agave inulin, acacia gum [10] walnut and chia oil / maltodextrin, (hydroxypropyl)methyl cellulose [11] ginger oil / cashew gum, inulin [12] walnut oil / skimmed milk powder (smp), smp+tween 80, smp+maltodextrin [13] nigella sativa oil / sodium caseinate, maltodextrin [14] chili seed oil / sodium octenylsuccinate starch, maltodextrin [15] freeze-drying ziziphora clinopodiodes essential oil / whey protein isolate (wpi), pectin [16] figure 1. experimental set-up for the cross-flow membrane emulsification process: (1) continuous phase tank, (2) graduated disperse phase tank, (3) membrane module, (4) pump, (5) compressor, (6) pressure meter, (7) rotameter, (8) pressure controller, (9) valve on drain, (10) valve, (11) heating / cooling (thermostat). microencapsulation of vegetable oil 45(2) pp. 29–33 (2017) 31 weighed in a beaker and 50 cm3 of hexane was added and shaken by hand for 15 s at ambient temperature to extract the superficial oil. the solvent mixture was then filtered through filter paper, and subsequently the unencapsulated oil was collected after evaporation of the hexane under a vacuum. to measure the total amount of encapsulated oil, the same procedure was conducted, but the powder of microcapsules in hexane as an extraction solvent was stirred for 4 h using a magnetic stirrer. for the production of microcapsules in oil, the encapsulation efficiency (ee) is an important parameter which is strongly related to the amount of oil on the surface, and was calculated using the following equation: �� = ����� ��� – ������� ��� ����� ��� × 100 (1) 3. results and analysis the first part of this section presents the results in terms of the production of sunflower-seed oil/water emulsions by conventional and modified-membrane emulsification techniques using a laboratory blender, then the encapsulation efficiency and the physical characterization of the obtained microcapsules are presented. 3.1. results of emulsification the results of particle-size measurements are summarized in table 2. the average droplet sizes were 9.18 µm, 7.58 µm and 7.12 µm in the three different emulsification cases. the average droplet size of microcapsules prepared in the modified way, when the wall material was mixed with the dispersed phase, was lower than those prepared using the conventional technique. in 2000, joscelyne, along with his co-worker, reported that for membrane emulsification, the size of synthesized emulsion particles might be 2-10 times greater than the pore size of the membrane. the present investigators used a microporous membrane with a pore size of 1.4 μm and it was found that in all three cases the average size of the synthesized microcapsules is in line with the conclusion reached by a previously mentioned research group [17]. as an example, the shape and morphology of synthesized microcapsules prepared by the modified me methods are shown in fig.2. 3.2. spray-drying results sunflower-seed oil microcapsules were obtained by spray drying the oil-in-water (o/w) emulsions. the novelty of the approach adopted in the present study is that it utilizes membrane emulsification, which is a lowenergy technology, to produce sunflower-seed oil/water emulsions stabilized by maltodextrin which has been dried by spray drying. the results, represented in table 3, show that the encapsulation efficiency is enhanced by this modern method, the highest values correspond to microcapsules produced by this membrane technology. by comparing the encapsulation efficiency of microcapsules produced by conventional microencapsulation techniques with our laboratorydeveloped method, it should be mentioned that there is figure 2. microscopic image of emulsion sample at 1000 magnification. table 3. oil encapsulation efficiency of microcapsules. conventional method with me (1) 36.4 % new method with me (2) 34.5 % laboratory blender (3) 28.2 % table 2. results of emulsification. conventional method using me (1) droplet size = 9.18 µm span = 1.5 average flux = 368.36 dm3 m-2 h-1 new method using me (2) droplet size = 7.58 µm span = 1.72 average flux = 159.29 dm3 m-2 h-1 laboratory blender (3) droplet size = 7.12 µm span = 1.88 figure 3. image of microencapsulated sunflower-seed oil powder produced by conventional me at 500 magnification. albert, vatai, and koris hungarian journal of industry and chemistry 32 no significant difference in terms of encapsulation efficiency. the surface and external morphologies of the microcapsules of sunflower-seed oil were studied using optical microscopy (figs.3-5). in terms of particle morphology, the microstructures of the powders containing maltodextrin as a wall material were generally spherical in shape, homogeneous and exhibited a smooth surface as seen in the microscopic images. in 2015, koç et al. [18] reported that the smooth surface of microencapsulated extra virgin olive oil using maltodextrin is related to the low-molecularweight sugar content of maltodextrin. these low molecular weight sugars may act as plasticizers on the surface of the particles during spray drying. in their study, when wpi (whey protein isolate) was selected as the wall material, the particles exhibited a rough surface compared to those containing maltodextrin. 4. conclusion our work focused on basic research in terms of microcapsule production under a laboratory set-up. the main aim of the present investigation was to gain experience with regard to the preparation of microcapsules by membrane emulsification in combination with spray drying using a novel technique and to compare it with the conventional one. the operation of the process and its basic correlations were the primary foci of this paper. based on the results obtained it is possible to draw up experimental plans that refine and optimize the process. the results of this work demonstrate that a modified membrane emulsification technique, in which the wall material is mixed with the dispersed phase and not with the continuous phase, combined with spray drying can be used to produce microcapsules of sunflower-seed oil that possess an appropriate oil-encapsulation efficiency. acknowledgement the authors acknowledge the financial support of the únkp-16-3-iii new national excellence program of the ministry of human capacities. they would like to thank keyence magyarország for providing the microscopic images. references [1] madene, a.; jacquet, m.; scher, j.; desobry, s.: flavour encapsulation and controlled release – a review, ijfst, 2006 41(1), 1–21 doi 10.1111/j.13652621.2005.00980.x [2] gouin, s.: microencapsulation: industrial appraisal of existing technologies and trends, tifs, 2004 15(7-8), 330–347 doi 10.1016/j.tifs.2003.10.005 [3] choi, h.g.; yong, c.s.; yang, k.y.: oral solid preparation composition containing silymarin using membrane emulsification technique, and its production method, 2010, kr20120034264 [4] ramakrishnan, s.; ferrando, m.; güell, c.: food grade microcapsules produced by membrane emulsification, procedia engng., 2012 44, 1530–1533 doi 10.1016/j.proeng.2012.08.855 [5] chu, l.-y.; xie, r.; zhu, j.-h.; chen, w.-m.; jamaguchi, t.; nakao, s.-i.: study of spg membrane emulsification processes for the preparation of monodisperse core-shell microcapsules, j. colloid interface sci., 2003 265(1), 187–196 doi 10.1016/s0021-9797(03)00350-3 [6] figoli, a.; shanthana lakshmi, d.; piacentini, e.; giorno, l.; drioli, e.: preparation of novel ionic liquid loaded polymeric microspheres by membrane emulsification process, procedia engng., 2012 44, 1287–1290 doi 10.1016/j.proeng.2012.08.757 figure 4. image of microencapsulated sunflower-seed oil powder produced by modified me at 500 magnification. figure 5. image of microencapsulated sunflower-seed oil powder produced by a laboratory blender at 500 magnification. microencapsulation of vegetable oil 45(2) pp. 29–33 (2017) 33 [7] imbrogno, a.; piacentini, e.; drioli, e.; giorno, l.: preparation of uniform polycaprolactone microparticles by membrane emulsification/solvent diffusion process, jmsc, 2014 467, 262–268 doi 10.1016/j.memsci.2014.05.037 [8] ho, t.h.; dao, t.p.t.; nguyen, t.a.; le, d.d.; dang, m.c.: cross-flow membrane emulsification technique for fabrication of drug-loaded particles, adv. nat. sci. nanosci. nanotechnol., 2013 4, 045008 1–6 doi 10.1088/2043-6262/4/4/045008 [9] calvo, p.; hernández, t.; lozano, m.; gonzálezgómez, d.: microencapsulation of extra-virgin olive oil by spray-drying: influence of wall material and olive quality, eur. j. lipid sci. technol., 2010 112(8), 852–858 doi 10.1002/ejlt.201000059 [10] turchiuli, c.; jimenez munguia, m.t.; hernandez sanchez, m.; cortesferre, h.; dumoulin, e.: use of different supports for oil encapsulation in powder by spray drying, powder technol., 2014 255, 103– 108 doi 10.1016/j.powtec.2013.08.026 [11] martínez, m.e.; curti, m.i.; roccia, p.; llabot, j.m.; penci, m.c.; bodoira, r.m.; ribotta, p.d.: oxidative stability of walnut (juglans regia l.) and chia (salvia hispanica l.) oils microencapsulated by spray drying, powder technol., 2015 270, 271– 277 doi 10.1016/j.powtec.2014.10.031 [12] fernandes, r.v.; botrel, d.a.; silva, e.k.; borges, s.v.; oliveira, c.r.; yoshida, m.i.; feitosa, j.p.; de paula, r.c.: cashew gum and inulin: new alternative for ginger essential oil microencapsulation, carbohydrate polym., 2016 153, 133–142 doi 10.1016/j.carbpol.2016.07.096 [13] shamaei, s.; seiiedlou, s.s.; aghbashlo, m.; tsotsas, e.; kharaghani, a.: microencapsulation of walnut oil by spray drying: effects of wall material and drying conditions on physicochemical properties of microcapsules, ifset, 2017 39, 101–112 doi 10.1016/j.ifset.2016.11.011 [14] mohammed, n.k.; tana, c.p.; manap, y.a.; alhelli, a.m.; hussin, a.s.m.: process conditions of spray drying microencapsulation of nigella sativa oil, powder technol., 2017 315, 1–14 doi 10.1016/j.powtec.2017.03.04 [15] wang, y.; liu, b.; wen, x.; li, m.; wang, k.; ni, y.: quality analysis and microencapsulation of chili seed oil by spray drying with starch sodium octenylsuccinate and maltodextrin, powder technol., 2017 312, 294–298 doi 10.1016/j.powtec.2017.02.060 [16] hosseinnia, m.; khaledabad, m.a.; almasi, h.: optimization of ziziphora clinopodiodes essential oil microencapsulation by whey protein isolate and pectin: a comparative study, int. j. biol. macromol., 2017 101, 958–966 doi 10.1016/j.ijbiomac.2017.03.190 [17] joscelyne, s.m.; tragardh, g.: membrane emulsification – a literature review, jmsc, 2000 169(1), 107–117 doi 10.1016/s0376-7388(99)00334-8 [18] koç, m.; güngör, ö.; zungur, a.; yalçin, b.; selek, i̇.s.; ertekin, f.k.; ötles, s.: microencapsulation of extra virgin olive oil by spray drying: effect of wall materials composition, process conditions, and emulsification method, food bioprocess technol., 2015 8, 301–318 doi 10.1007/s11947-014-1404-9 hungarian journal of industry and chemistry vol. 45(2) pp. 35–39 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0018 effect of chain length and order of the alcohol on enzyme activity during enzymatic esterification in organic media zsófia márkus, katalin bélafi-bakó, gábor tóth, nándor nemestóthy and lászló gubicza* research institute on bioengineering, membrane technology and energetics, university of pannonia, egyetem u. 10, veszprém, 8200, hungary esters of short chain acids and alcohols are found in nature as compounds of flavors. lately the method for their manufacture has been the enzymatic esterification in non-conventional media. although several reactions have been studied in various media (organic solvents, ionic liquids, supercritical fluids, solvent-free systems), there has been no systematic investigation to clarify the effects of chain length and order of alcohols on the activity of the enzyme. in this work acetic acid was used as an acyl donor and the roles of the linear and branched chains of c2-c8 primary, secondary and tertiary alcohols on the activity of novozym 435, the widely used lipase preparation were studied. both the length of the carbon chain and the order of the alcohol were found to strongly influence the activity of the enzyme using the same operational parameters for the reactions. as a result of this project general conclusions were made with regard to the characters of alcohols affecting the reaction rates, which can be applied to other similar reactions. keywords: enzymatic esterification, non-conventional media, effect of alcohol chain lengths, lipase activity 1. introduction enzyme technology provides a promising solution for the biosynthesis of natural flavor esters, since several enzymes are able to catalyze the synthesis of aroma compounds from precursor molecules [1]. nowadays most flavor compounds are manufactured by conventional methods: chemical synthesis or recovery from natural sources. esters produced chemically are quite common, but their method of production is not considered environmentally safe and cannot be classed as “natural”. recently interest has been growing in the production of these components by biotransformation, that is the manufacture of natural flavor esters by using natural raw materials. lipases belong to the most diverse class of enzymes, they catalyze various reactions due to their wide spectrum of industrial applications. lipase enzymes have been applied in many industrial sectors, e.g. the food and pharmaceutical industries, in the production of biological detergents (esters of carbohydrates), moreover in the manufacture of certain cosmetics and fragrances. recently interest has grown in the production of natural flavor esters by the biosynthesis of short chain acids and alcohols [2,3]. several similar reactions have been studied, most of which focused on the synthesis of acetates, like ethyl *correspondence: gubiczal@almos.uni-pannon.hu [4], butyl [5], hexyl [3], cinnamyl [6], and benzyl [7] acetates. during the investigation of the reactions‘ parameters the roles of temperature, the molar ratio of acid to alcohol and the amount of enzyme were described in almost every paper. from these data the optimal values of these parameters could be estimated. numerous reactions were carried out in organic solvents [8, 9], ionic liquids [10, 11], supercritical fluids (mainly in supercritical carbon dioxide) [12], solvent-free systems [13], in addition to in the gas phase [14]. since these reactions can be conducted in non-aqueous media, the water content, to be more precise the water activity of the reaction mixture plays an extremely important role in terms of the reaction rate. for the operation of the enzyme lipase it is necessary to provide a minimal amount of water. on the other hand it is an equilibrium reaction, thus the greater excess of water shifts the reaction towards hydrolysis, decreasing the conversion rate significantly. the investigation of the effect of water content, or at least an intention to adjust the initial water content by a constant value is missing in several papers. the water content during the reaction continuously changes due to the production of water in the esterification. this effect can be neglected during the investigation of the initial reaction rates, but in terms of the development of continuous production it should be taken into account. a number of methods are known to maintain water content/activity. from a practical point of view membrane separation processes, like pervaporation provide attractive procedures [15]. márkus, bélafi-bakó, tóth, nemestóthy and gubicza hungarian journal of industry and chemistry 36 beyond the parameters mentioned and the water content, only a limited attention was paid to the role of substrates present in the reaction. as pointed out earlier, acetic acid was the acidic component used in most cases. the alcohols applied, however, were much more diverse: linear and branched chains, aromatic and different orders of alcohols were investigated. nevertheless our group has not found a single study in the literature where systematic research was conducted to assess the role of alcohols on enzyme activity. the effect of the chain length of various alcohols was investigated in reactions catalyzed by enzymes in non-conventional media. romero and colleagues conducted experiments in supercritical carbon dioxide using four different alcohols: propanol, butanol, pentanol and octanol. it was found that higher degrees of conversion could be obtained by applying longer chain alcohols. enzymes have a higher affinity towards longer chain alcohols, the difference, however, was small [16]. in another paper romero used butyric acid as an acyl donor and the enzyme novozym 435. an insignificant difference was observed in terms of the reaction rate or conversion during esterification when the four primary alcohols (propanol, butanol, hexanol and octanol) were applied. applying secondary alcohols, e.g. 2-hexanol, however, yielded higher reaction rate and conversion than was the case with 2-butanol [17]. pan et al. studied how the chain length of alcohol compounds can influence the resolution reaction of mandelic acid. using methanol, ethanol, butanol, heptanol and octanol it was found that the highest degree of enantioselectivity could be obtained by ethanol. moreover the reaction was described as following michaelismenten kinetics in all cases and the inhibition constant increased as the carbon chain go longer [18]. varma and madras investigated the esterification of propionic acid and three different alcohols by the enzyme novozym 435 in supercritical carbon dioxide. primary (isobutanol, isoamyl alcohol) and secondary alcohols (isopropyl alcohol) were used, as well. based on the measurements, it was concluded that enzymatic esterification was faster with primary alcohols than with secondary alcohols, moreover a greater degree of conversion was achieved with isobutanol than with isoamyl alcohol [19]. therefore the aim of this paper was to study the role of alcohols by the preparation of a given enzyme whilst maintaining the operation parameters as constants. the esterification primary, secondary and tertiary alcohols of c2-c8 carbon chain lengths were investigated to be able to draw general conclusions concerning the role of alcohol structure on reaction rate. for the measurements a popular immobilized lipase enzyme preparation, novozym 435®, was used. 2. experimental 2.1. chemicals and enzymes all chemicals: acetic acid, ethanol, 1-propanol. 1butanol and n-hexane (merck), 1-pentanol, 2-pentanol tert-butanol (2-methylpropan-2-ol) and 1-hexanol (sigma-aldrich); 1-heptanol (bdh chemicals); 1-octanol and isobutanol (2-methylpropan-1-ol) (spektrum-3d); isoamyl alcohol (3-methylbutan-1-ol) (molar chemicals); and 2-propanol, 2-butanol, tert-amyl alcohol (2methylbutan-2-ol) and toluene (reanal) were of analytical grade. the water content of the chemicals varied greatly, that is why they were dewatered over a 3å molecular sieve in the form of beads (sigma-aldrich). the enzyme used was novozym 435® from candida antarctica lipase b, immobilized on a macroporous acrylic resin with a water content of 1-2% w/w, which was kindly provided as a gift by novo nordisk a/s, denmark. according to their commercial product manual, its catalytic activity was 7000 plu/g (propyl laurate units/gram). 2.2. reaction and analysis reactions were carried out in 50 ml erlenmeyer flasks on a laboratory incubator shaker (ika incubator shaker, ks 4000i) at 150 rpm and 50 oc. the typical reaction mixture contained acetic acid (0.5 mmol), alcohol (3.0 mmol), novozym 435® lipase (60 mg) and n-hexane (20 ml). the reaction was commenced by adding the enzyme. the gas chromatography (gc) analyses for the determination of ester concentrations were conducted by a hp 5890 a gas chromatograph, with an hp-ffap column (macherey-nagel), split: 70 kpa, n2: 19 cm3/min, using a flame ionization detector (fid). toluene was used as an internal standard, the changes in ester yield were followed during the reaction. samples were taken after reaction times of 0.5, 1.0, 2.0 4.0 and 6.0 min. the water contents of the reaction mixtures were determined by a mettler dl35 karl fisher titrator. 3. results and discussion although several publications have presented results on the production of flavor esters, the optimal initial conditions suggested were quite different and a high degree of deviation was found among data in the literature. firstly the average of the literature data was used for our preliminary experiments. based on these figures the following initial parameters were applied: in the reaction mixture the molar ratio of acetic acid to alcohol was 1:6, and 20 ml of n-hexane, 20 mmol of toluene and 60 mg of the enzyme novozym 435 were added to it. enzymatic esterification 45(2) pp. 35–39 (2017) 37 3.1. the effect of water content experiments had to be conducted to determine the correct water content since it could not be found in the literature. the esterification of acetic acid and isoamyl alcohol – a reaction that has been quite frequently studied – was investigated under the conditions mentioned earlier. during the measurements completely dried reaction mixtures (0 % w/w water content) were used and others adjusted the initial water content to the levels of 0.3, 0.5 and 0.7 % w/w by adding water. as can be seen from the data of table 1, the reaction was extremely slow in the case of completely dried solvents and reagents – as was expected. the reaction rate began to rise when the water content grew slowly (and approached the optimal value) due to the water forming in the reaction. based on the experimental results an initial water content of 0.3 % w/w was applied to further measurements since this water concentration provided the highest yield. the yields of esterification after a reaction time of 4 h were presented in fig.1, where the measurements were taken under the conditions given earlier, with an adjusted and the same initial water contents. the yields of esterification were sufficiently high to observe the differences caused by the different structures of alcohols, but saturation levels were not reached and the distinct amounts of water formed during the reaction did not affect such a tendency either. 3.2. primary alcohols our study involved linear and branched alcohols with a chain length of c2-c8. as can be seen from fig.1 for primary alcohols, the yield increased as the length of the carbon chain grew. the effect of chain length was investigated by romero using propanol, butanol, hexanol as well as octanol and a similar conclusion was drawn: acetic acid conversion was greater with alcohols of longer chain lengths, thus the yields of esterification were higher, as well [16]. as far as branched primary alcohols were concerned, the opposite trend was observed: the yield of esterification decreased as the chain length increased. at the beginning of the reactions the differences were only minor: only a difference of 3 % was observed in the yields in the cases of alcohols consisting of a carbon chain of 4 or 5. the behavior of isooctanol was especially interesting, because a significant drop in yield was observed compared to the other linear, 8-carbonchain alcohols – a far smaller amount of ester was formed in the reaction mixture. 3.3. secondary alcohols in this work three secondary alcohols: 2-propanol, 2-butanol and 2-pentanol were used. as presented in table 2, an increase in ester yields was observed as the carbon chain length of secondary alcohols grew, as well. the values, however were not as high as for primary alcohols. neji et al. observed a similar behavior when butanol and 2-butanol were used in the esterification reaction [20]. although both alcohols could perform esterification, yields of esterification were 50 % lower for secondary alcohols. 3.4. tertiary alcohols among tertiary alcohols tert-amyl alcohol and tertbutanol were used, however, the enzyme was not able to convert them into esters using acetic acid. from the literature, stavarache et al. applied tertiary alcohols for transesterification in the production of biodiesel [21]. similarly no activity was observed during their experiments, not even when using ultrasonic radiation. 3.5. discussion of the experimental results although our experimental results did not reveal entirely general conclusions, which are valid in all cases, obvious relationships could be formulated for certain figure 1. ester yields during the reactions of acetic acid and primary alcohols after a reaction time of 4 h 31,4 37,3 46,2 76,1 49,6 73,6 53,9 63,2 76,4 7,2 0 10 20 30 40 50 60 70 80 90 yi e ld [ % ] table 1. the effect of water content on ester yield in the esterification of acetic acid and isoamyl alcohol time (h) 0.0% 0.3% 0.5% 0.7% ester yield (%) 0 0.0 0.0 0.0 0.0 0.5 3.2 16.7 18.5 20.5 1 8.3 28.8 33.4 30.7 2 15.8 50.2 48.3 46.7 4 24.2 73.5 68.2 60.3 6 33.1 85.4 79.7 68.5 table 2. ester yields using secondary alcohols secondary alcohol ester yield after 4 h (%) 2-propanol 2-butanol 35.8 44.8 2-pentanol 50.5 márkus, bélafi-bakó, tóth, nemestóthy and gubicza hungarian journal of industry and chemistry 38 groups of alcohols. it is certain that for alcohols with a linear carbon chain of c2-c8 in length, the conversion rate increases proportionally to the lengthening of the carbon chains. as for branched alcohols, the opposite tendency can be observed: yields were found to decrease as the carbon chain grew. the relationship is more obvious when the order of alcohols is taken into consideration. yields of esterification decreased in the following order: primary alcohol > secondary alcohol > tertiary alcohol (noting that tertiary alcohols did not react at all under the conditions used by novozym 435). by applying other enzymes, e.g. carboxylesterase from bacillus licheniformis, small degrees of conversion were measured, but remained close to the limit of detection [22]. in an attempt to justify such behavior, it can be assumed that access of the hydroxyl group of the alcohol to the active centre of the enzyme is severely sterically hindered in the case of secondary and especially tertiary alcohols, which cause enzyme activity to decline or even cease. 4. conclusion the expected reaction rate produced by a given enzyme can be predicted according to characteristics of the alcohol used, namely carbon chain length, linear or branched, and the order in production of flavor esters by enzymatic esterification of natural acids and alcohols. the expected ester yield of the esterification reaction using acetic acid as an acyl donor depends on certain characteristics of the alcohol according to a welldefined tendency. it can be assumed that a similar tendency (though distinct in terms of rate) could be observed for other enzymes regarding the effect of the alcohol. this should be studied separately to decide whether a similar tendency could be detected if various acids are used with the same alcohol. references [1] bommarius, a.s.; riebel, b.r. biocatalysis (wiley-vch verlag gmbh & co. kgaa, weinheim, germany) 2004 pp. 339-372 doi: 10.1002/aoc.651 [2] yan, h-d.; zhang, q.; wang, z.: biocatalytic synthesis of short-chain flavor esters with high substrate loading by a whole-cell lipase from aspergillus oryzae, catal. commun., 2014 45, 59–62 doi: 10.1016/j.catcom.2013.10.018 [3] almeida, a.g.; de meneses, a.c.; de araújo, p.h.; de oliveira, d.: a review on enzymatic synthesis of aromatic esters used as flavor ingredients for food, cosmetics and pharmaceuticals industries, trends food sci. tech., 2017 69, 95–105 doi: 10.1016/j.tifs.2017.09.004 [4] xu, y.; wang, d.; mu, x.y.; zhao, g.a.; zhang, k.c.: biosynthesis of ethyl esters of short-chain fatty acids using whole-cell lipase from rhizopus chinesis cctcc m201021 in non-aqueous phase, j. mol. cat. b-enzym., 2002 18, 29–37 doi: 10.1016/s1381-1177(02)00056-5 [5] martins, a.b.; schein, m.f.; friedrich, j.l.; fernandez-lafuente, r.; ayub, m.a.; rodrigues, r.c.: ultrasound-assisted butyl acetate synthesis catalyzed by novozym 435: enhanced activity and operational stability, ultrason. sonochem., 2013 20(5), 1155–1160 doi: 10.1016/j.ultsonch. 2013.01.018 [6] tomke, p.d.; rathod, v.k.: ultrasound assisted lipase catalyzed synthesis of cinnamyl acetate via transesterification reaction in a solvent free medium, ultrason. sonochem., 2015 27, 241–246 doi: 10.1016/j.ultsonch.2015.04.022 [7] mcginty, d.; vitale, d.; letizia, c.s.; api, a.m.: fragrance material review on benzyl acetate, food chem. toxycol., 2012 50, s363–s384 doi: 10.1016/j.fct.2012.02.057 [8] gubicza, l.; kabiri-badr, a.; keoves, e.; belafibako, k.: large-scale enzymatic production of natural flavour esters in organic solvent with 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10.1016/j.cofs.2014.09.003 hungarian journal of industry and chemistry vol. 45(2) pp. 41–44 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0019 state-of-the-art recovery of fermentative organic acids by ionic liquids: an overview konstantza tonova* institute of chemical engineering, bulgarian academy of sciences, acad. g. bonchev str., bl. 103, 1113 sofia, bulgaria the main achievements of liquid–liquid extraction (lle) of fermentative organic acids from their aqueous sources using a diverse range of ionic liquids are summarized since the first study appeared in 2004. the literature survey is organized in consideration of the distinct chemical structures of the organic acids. the acids discussed include mono– or dicarboxylic ones (butyric, l-malic and succinic acids), acids bearing both carboxyl and hydroxyl groups (l-lactic, citric and mevalonic acids), and volatile organic acids (mainly acetic acid). information is given about ionic liquids applied in recovery, and the resultant extraction efficiencies and partition coefficients. as the topic is novel and experimental studies scarce, the selection of the ionic liquids that were tested still seems random. this may well change in the future, especially after improving the ecological and toxicological characteristics of the ionic liquids in order to bring about an “in situ” method of extraction without harming the microbial producers of the organic acids. keywords: extraction, ionic liquid, organic acid, recovery, re–extraction 1. introduction room temperature ionic liquids (ils) exist as molten salts at ambient temperature and consist entirely of ions, usually a charge–stabilized organic cation and an inorganic or organic anion. ils can be tailored to a wide variety of applications by combining different ions [1] and for this reason they are often called “designer solvents”. ils exhibit a broad range of unique properties, including negligible vapor pressure, high thermal stability and low chemical reactivity [2]. the union of these particular properties, together with finely tunable density, viscosity, polarity and miscibility with other common solvents favor the application of ils in different kinds of separation and reaction processes [3– 8]. considering the benefits that arise from the properties of ils, matsumoto et al. [9] first proposed an environmentally friendly system for the extraction of fermentative l-lactic acid. they used hydrophobic [cnc1im][pf6] instead of volatile organic solvents as diluents of reactive organic bases. these ils proved to be nontoxic towards the lactic acid producing bacterium lactobacillus rhamnosus, but provided low degrees of solubility of the reactive amines which resulted in insufficient levels of extraction efficiency. nevertheless, these results suggest possible applications of ils in extractive fermentations. *correspondence: konstantzatonova@yahoo.com 2. discussion on the organic acids extracted and the ionic liquids applied 2.1. butyric acid and phosphinate–based ils the most remarkable results regarding the partition coefficient of an organic acid in an il have been documented with regards to the extraction of butyric acid, the four–carbon fatty acid, with phosphinate-based ([phos]) ils. [p6,6,6,14][phos] and a novel ammonium phosphinate, [cncncnc1n][phos], were studied [10-11]. distribution coefficients of about 80 were obtained using the low concentrations of butyric acid, and the extraction efficiency was just as high in the pure (water saturated) il as in the il/water/dodecane reversed micellar solution. the ammonium phosphinate absorbed a relatively high amount of water until saturation was achieved, ca 21 wt%. (about 12 water molecules per ion pair of the il), which implies that an aqueous biphasic system was formed. 2.2. dicarboxylic acids and phosphoniumor imidazolium-based ils among phosphonium-based ils, [p6,6,6,14]cl seems the most suitable extractant for the recovery of low and moderate concentrations of dicarboxylic l-malic acid in aqueous solutions [12]. the other phosphonium-based ils and higher acid concentrations entrain third-phase formation, especially in the case of [p6,6,6,14][phos] when a large amount of the acid content (ca 40%) remains tonova hungarian journal of industry and chemistry 42 uncovered in both phases. the [p6,6,6,14]cl–rich phase is also the best extractant for another dicarboxylic acid, succinic acid [12]. extractions with [dec]and [phos]– based ils resulted in a substantial amount of undetectable acid in both phases, which was attributed to the formation of complexes between the organic acid and the extractants that were not quantified. more recently succinic acid attracted special attention in a comprehensive study where the extraction was carried out by aqueous biphasic systems (abs) of alcohols/salts or imidazolium-based ils/salts [13]. successful recovery was achieved by both systems. succinic acid preferentially migrates to the il–rich phase in all systems formed of [c6c1im]br and a kosmotropic salt (phosphate, sulfate, carbonate or citrate). the il salted out by (nh4)2so4 or k2co3 exhibited the highest levels of extractability. the ph values of these systems were quite different. the ph of the system with (nh4)2so4 was 3.43 which is below the pka values of succinic acid (pka1 = 4.21, pka2 = 5.72), while ph = 10.50 for k2co3 greatly exceeded the pkas. this suggests that unlike the aqueous biphasic systems with alcohols, the extraction capacity of the il/salts systems towards succinic acid is not ph–dependent and is most likely related to the proper nature of the solvent (il/salt) and the solute (acid). for the same il, [c6c1im]br, an excellent solvating capacity to the lactic acid was reported [14] so that the acid could be extracted from a concentrate of white wine. this way the extraction efficiencies of the abs of [c6c1im]br/(nh4)2so4 or k2co3 are comparable to those obtained with the hydrophobic il [p6,6,6,14]cl [12]. moreover, the re–extraction efficiency achieved was superior at ~71%. succinic acid was obtained in a crystalline form by direct precipitation with sodium hydroxide. 2.3. acids with both hydroxyl and carboxyl groups and phosphoniumor imidazolium-based ils different types of phosphonium-based il biphasic systems were applied for l–lactic acid recovery. an extraction efficiency of above 80% was achieved by using either pure [p6,6,6,14][phos] [12] or a mixed biphasic system of [p6,6,6,14]cl and an inorganic kosmotrope, mgso4 [15]. the kosmotropic salt engages more water molecules when hydrated thus rendering the microenvironment of the acid more hydrophobic which favors the undissociated form of acid suitable for extraction. all extraction systems of phosphoniumbased ils with long side chains suffer from the common disadvantage of forming stable emulsions or a third phase between the il–rich phase and aqueous solution. this drawback is avoided by applying ils of an imidazolium cationic moiety, however, in the majority of the cases these ils exhibit low levels of extraction efficiency towards lactic acid [9,16] and other acids bearing both hydroxyl and carboxyl groups (citric and mevalonic acids) [16]. an advantageous abs of imidazolium saccharinate, that possesses a long side chain, [c8/10c1im][sac], has been exploited lately and it was shown that when it is combined with an inorganic kosmotropic salt (that retains water from solubilization into the il–rich phase) an extraction efficiency of 81% and partition coefficient of 5.5 could be achieved [17]. the extraction yield of lactic acid was as high as 90% in a two–step recovery by [c8c1im][sac] with or without the addition of a kosmotropic salt (mgso4). moreover, successful acid re–extraction of 95% from the il–rich phase was attained by means of a solution containing an alkaline kosmotrope, k2hpo4. 2.4. volatile fatty acids and phosphoniumbased ils apart from culture broths, fermented wastewater streams still represent an unexploited source of platform chemicals, including volatile organic acids. volatile fatty acids are versatile carboxylic acids involved in the synthesis of bioplastics and other value–added chemicals [18]. the composition of fermented wastewater typically contains ~1 wt% of volatile fatty acids, but also a significant amount of various dissolved salts. the low concentrations of the volatile fatty acids and the large quantity of inorganic salt–originating ions result in ph–values of between 4 and 6, which are in favor of the deprotonated acid form and thus do not support complexation with the il. the distribution of acetic acid between model solutions with or without salts and different solvents, including phosphoniumbased ils, was recently studied [19]. similarly to the butyric and lactic acids [10,20], the low concentration of acetic acid and the use of [p6,6,6,14][phos] were the best conditions to obtain the highest partition coefficient in the il–rich phase starting from an idealized aqueous solution containing only the acetic acid. in the presence of salts (kcl, na2so4 or na2hpo4), however, the partition coefficients reported for [p6,6,6,14]cl were the highest in the series of ils tested and exceeded even those obtained in the classical extraction by trioctylamine (toa)/n-octanol. [p6,6,6,14]cl as a solvent has an inevitable drawback related to its measurable level of leaching into the aqueous phase due to the hydrophilicity of the [cl]–. contrary to [p6,6,6,14]cl, [p6,6,6,14][phos] and [p6,6,6,14][n(cn)2] were found to be highly stable as significant leaching was not detected in the aqueous phases [19]. extraction by [p6,6,6,14][phos], however, was strongly affected by the ions of the salts present in the feed, while [p6,6,6,14]cl and [p6,6,6,14][n(cn)2] kept extraction capacities constant for acetic acid. when the source contained different acids, mimicking actual fermented wastewater, it was found that the growing hydrophobic domain in the acid leads to higher degrees of extraction. butyric acid was the most extracted acid from the fermented wastewater, while lactic acid was the most challenging acid to extract. by modifying the solvent properties of [p6,6,6,14][phos] by sparging pressurized co2, a further increase in the extractability of acetic acid was observed recovery of fermentative organic acids by ionic liquids: overview 45(2) pp. 41–44 (2017) 43 [21]. the effect was attributed to the altered structure of the fluid which becomes more accessible for the acetic acid. this finding constitutes a general concept for the improvement of extraction processes other than those involving volatile fatty acids. ils can act as solvents and simultaneously mediate reactive extraction to valorize low–titer volatile fatty acids. this has been recently shown through an il– mediated esterification of acetic acid recovered from dilute aqueous streams [22]. the acids produced in anaerobic digestion or fermentation were transferred to a nonvolatile hydrophobic phase where they reacted with an alcohol (ethanol) in order to generate volatile, value–added esters of low solubility. [p6,6,6,14]–ils were selected for their potentially high extracting capacity and hydrophobicity. their hydrophobic character provides a water-excluding site for esterification and a nonvolatile carrier for the evaporation of the ester produced. significant accumulation of acetic acid in the il was achieved by using [p6,6,6,14][n(cn)2], but this was mainly due to the exchange of [n(cn)2] – for the acetate anion as the dicyanamide anion was found to hydrolyze under the extraction conditions used, including at an elevated temperature (75 °c). contrary to the extraction, [p6,6,6,14][n(cn)2] and [p6,6,6,14]cl appeared to be the worst media for performing esterification, while the best was [p6,6,6,14][tf2n], which, however, is poor and costly extractant. thus an il of combined anions, cl– + [tf2n]–, was tested which could be used in a multistage way. starting from an aqueous stream of 0.33 mol dm-3 acetic acid, 0.44 mol dm-3 accumulated in the mixed [p6,6,6,14]cl+[tf2n] which allowed an esterification conversion of 56% to be achieved over 30 min. 3. conclusion ils are commonly considered more sustainable than classical organic solvents. it is well known that the toxicity level of conventional solvents to microbes limits their compatibility with fermentation broths. however, the label of “green solvent”, assigned to the ils, has led to the delusion that they are nontoxic and biodegradable, which is not true about some of the most employed ils. for example, the commonly used [p6,6,6,14]cl may be regarded as toxic in aquatic environments exhibiting much higher levels of ecotoxicity compared to ordinary organic solvents [23]. the biocompetitiveness and biodegradability of ils are not still convincingly argued for [24-25]. the need for novel extractants with improved characteristics from ecological and toxicological standpoints can be put forward. by taking into account that aqueous streams and bioorganics are treated, the environmental impact of ils should be resolved as a result of future studies. symbols il’s cationic moiety: [cnc1im] 1-alkyl-3-methylimidazolium [cncncnc1n] trialkylmethylammonium [p6,6,6,14] tetradecyl(trihexyl)phosphonium il’s anionic moiety: [dec] decanoate [n(cn)2] dicyanamide [phos] bis(2,4,4-trimethylpentyl)phosphinate [sac] saccharinate (which is a benzoic sulfimide) [tf2n] bis(trifluoromethylsulfonyl)imide other: toa trioctylamine acknowledgement this research was supported by the bulgarian science fund (contract grant dfni–b01/23). references [1] blundell, r.k.; licence, p.: quaternary ammonium and phosphonium based ionic liquids: a comparison of common anions, phys. chem. chem. phys., 2014 16(29), 15278–15288 doi: 10.1039/c4cp01901f [2] freemantle, m.: an introduction to ionic liquids (rsc publishing, cambridge, uk) 2009 [3] mutelet, f.; jaubert, j.-n.: interactions between organic compounds and ionic liquids. selectivity and capacity characteristics of ionic liquids, chapter 10 in ionic liquids: theory, properties, new approaches, ed.: kokorin, a. (intech) 2011 doi: 10.5772/14291 [4] tonova, k.: separation of polyand disaccharides by biphasic systems based on ionic liquids, sep. purif. technol., 2012 89, 57–65 doi: 10.1016/j.seppur.2012.01.007 [5] keremedchieva, r.; svinyarov, i.; bogdanov, m.g.: ionic liquid–based aqueous biphasic systems – a facile approach for ionic liquid regeneration from crude plant extracts, processes, 2015 3(4), 769–778 doi: 10.3390/pr3040769 [6] tonova, k.; bogdanov, m.g.: partitioning of αamylase in aqueous biphasic system based on hydrophobic and polar ionic liquid: enzyme extraction, stripping and purification, sep. sci. technol., 2017 52(5), 812–823 doi: 10.1080/01496395.2016.1267211 [7] fehér, e.; illeová, v.; kelemen-horváth, i.; bélafibakó, k.; polakovič, m.; gubicza, l.: enzymatic production of isoamyl acetate in an ionic liquid– alcohol biphasic system, j. mol. catal. b: enz., 2008 50(1), 28–32 doi: 10.1016/j.molcatb.2007.09.019 [8] major, b.; nemestóthy, n.; bélafi-bakó, k.; gubicza, l.: enzymatic esterification of lactic acid under microwave conditions in ionic liquids, hung. j. ind. chem., 2008 36(1-2), 77–81 tonova hungarian journal of industry and chemistry 44 [9] matsumoto, m.; mochiduki, k.; fukunishi, k.; kondo, k.: extraction of organic acids using imidimidazolium–based ionic liquids and their toxicity to lactobacillus rhamnosus, sep. purif. technol., 2004 40(1), 97–101 doi: 10.1016/j.seppur.2004.01.009 [10] marták, j.; schlosser, š.: liquid–liquid equilibria of butyric acid for solvents containing a phosphonium ionic liquid, chem. pap., 2008 62(1), 42–50 doi: 10.2478/s11696-007-0077-5 [11] blahušiak, m.; schlosser, š.; marták, j.: extraction of butyric acid with a solvent containing ammonium ionic liquid, sep. purif. technol., 2013 119, 102–111 doi: 10.1016/j.seppur.2013.09.005 [12] oliveira, f.s.; araújo, j.m.m.; ferreira, r.; rebelo, l.p.n.; marrucho, i.m.: extraction of llactic, l-malic, and succinic acids using phosphonium–based ionic liquids, sep. purif. technol., 2012 85, 137–146 doi: 10.1016/j.seppur.2011.10.002 [13] pratiwi, a.i.; yokouchi, t.; matsumoto, m.; kondo, k.: extraction of succinic acid by aqueous two–phase system using alcohols/salts and ionic liquids/salts, sep. purif. technol., 2015 155, 127– 132 doi: 10.1016/j.seppur.2015.07.039 [14] lateef, h.; gooding, a.; grimes, s.: use of 1hexyl-3-methylimidazolium bromide ionic liquid in the recovery of lactic acid from wine, j. chem. technol. biotechnol., 2012 87(8), 1066–1073 doi: 10.1002/jctb.3843 [15] tonova, k.; svinyarov, i.; bogdanov, m.g.: biocompatible ionic liquids in liquid–liquid extraction of lactic acid: a comparative study, int. j. chem. nuclear mater. metallurgical eng., 2015 9(4), 526–530 https://www.waset.org/publications/10001024 [16] li, q.z.; jiang, x.l.; zou, h.b.; cao, z.f.; zhang, h.b.; xian, m.: extraction of short–chain organic acids using imidazolium–based ionic liquids from aqueous media, j. chem. pharm. res., 2014 6(5), 374–381 http://www.jocpr.com/articles/extraction-ofshortchain-organic-acids-using-imidazoliumbased-ionic-liquidsfrom-aqueous-media.pdf [17] tonova, k.; svinyarov, i.; bogdanov, m.g.: hydrophobic 3-alkyl-1-methylimidazolium saccharinates as extractants for l-lactic acid recovery, sep. purif. technol., 2014 125, 239–246 doi: 10.1016/j.seppur.2014.02.001 [18] straathof, a.j.j.: transformation of biomass into commodity chemicals using enzymes or cells, chem. rev., 2014 114(3), 1871–1908 doi: 10.1021/cr400309c [19] reyhanitash, e.; zaalberg, b.; kersten, s.r.a.; schuur, b.: extraction of volatile fatty acids from fermented wastewater, sep. purif. technol., 2016 161, 61–68 doi: 10.1016/j.seppur.2016.01.037 [20] marták, j.; schlosser, š.: extraction of lactic acid by phosphonium ionic liquids, sep. purif. technol., 2007 57, 483–494 doi: 10.1016/j.seppur.2006.09.013 [21] reyhanitash, e.; zaalberg, b.; ijmker, h.m.; kersten, s.r.a.; schuur, b.: co2–enhanced extraction of acetic acid from fermented wastewater, green chem., 2015 17(8), 4393–4400 doi: 10.1039/c5gc01061f [22] andersen, s.j.; berton, j.k.e.t.; naert, p.; gildemyn, s.; rabaey, k.; stevens, c.v.: extraction and esterification of low–titer short– chain volatile fatty acids from anaerobic fermentation with ionic liquids, chem. sus. chem., 2016 9(16), 2059–2063 doi: 10.1002/cssc.201600473 [23] wells, a.s.; coombe, v.t.: on the freshwater ecotoxicity and biodegradation properties of some common ionic liquids, org. process res. dev., 2006 10(4), 794–798 doi: 10.1021/op060048i [24] siedlecka, e.m.; czerwicka, m.; neumann, j.; stepnowski, p.; fernández, j.f.; thöming, j.: ionic liquids: methods of degradation and recovery, chapter 28 in ionic liquids: theory, properties, new approaches, ed.: kokorin, a. (intech) 2011 doi: 10.5772/15463 [25] egorova, k.s.; ananikov, v.p.: toxicity of ionic liquids: eco(cyto)activity as complicated, but unavoidable parameter for task–specific optimization, chem. sus. chem., 2014 7(2), 336– 360 doi: 10.1002/cssc.201300459 hungarian journal of industry and chemistry vol. 45(2) pp. 45–49 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0020 application of a hydrophobic polymeric membrane for carbon dioxide desorption from an mea-water solution zenon ziobrowski * , adam rotkegel institute of chemical engineering of the polish academy of sciences, ul. balycka 5, 44-100 gliwice, poland carbon dioxide desorption from a monoethanolamine (mea) solution using a hydrophobic polydimethylsiloxane (pdms) tubular membrane on a ceramic support is presented. the effects of operating parameters such as feed temperature, liquid flow rate and mea concentration on mass transfer were examined. the mass transfer of co2 from the liquid to gaseous phase was predicted by a multilayer film model with an accuracy of ±25%. research into new selective materials is needed to develop more efficient and environmentally friendly co2 capture technology keywords: mea, desorption, carbon dioxide, hydrophobic membrane, pdms 1. introduction fossil fuel combustion from power plants is one of the most significant sources of co2 emissions [1]. the separation of carbon dioxide from gases can be realized by processes such as adsorption, absorption, low temperature distillation and membrane separation. the absorption of carbon dioxide in amine based solutions is currently the most widespread method in industry for the post-combustion capture of co2 [2]. the advantage of chemical absorption in amine solutions is the fact that at higher temperatures the chemical reaction can be reversed and the amine recycled. on the other hand, obstacles include a relatively low co2 capture capacity, solvent losses caused by evaporation, thermal stability, highly corrosive characteristics, ecotoxicity and biodegradability in the natural environment [2-4]. it was shown that mea and diethanolamine (dea) might promote potential long-term toxicity effects towards living organisms [5,6]. in addition the regeneration step may increase the total operating costs of the capture plant by up to 70%, especially for primary and tertiary amines where the heat of reaction is quite high [7]. the amine scrubbing processes carried out in packed columns are currently most widely used in industry for the post-combustion capture of co2. limiting factors for the application of this technology are its size and large capital costs. the mass transfer performance of this solution can be reduced by flooding, foaming and entrainment conditions. *correspondence: zenz@iich.gliwice.pl in comparison to the studies on co2 absorption in mea solutions there are only a few concerning co2 desorption, despite the fact that the stripping unit is responsible for most of the separation cost of the process [8]. it is important that materials used in the processes concerning post-combustion capture of co2 exhibit low or no environmental effects. various tubular membranes were operated as catalyst supports [9]. recently a new type of ceramic hollow fiber membrane contactor has been studied [10]. this kind of membrane can be modified to be hydrophobic which enables it to be applied for co2 absorption-desorption in amine solutions. in this study the process of co2 removal from an mea solution using a hydrophobic polydimethylsiloxane (pdms) tubular membrane on a ceramic support was investigated. 2. experimental 2.1. experimental setup the experimental setup shown in fig.1 consisted of a membrane module, reactor vessel, cooling system, as well as circulation and vacuum pumps. the hydrophobic pdms membranes on ceramic support (ceramic tubes with an outer diameter of 0.01 m and length of 0.25 m using a pvm 250 membrane module made by pervatech bv) was studied. the feed was circulated by a pump and the flow rate was controlled by a flowmeter. in all experiments the feed temperature was stabilized by a thermostat (1c). the permeate was condensed and collected in cold traps immersed in liquid nitrogen. the vacuum pump was used to maintain the pressure between 7 and 10 mmhg on the permeate side. the concentration of ziobrowski and rotkegel hungarian journal of industry and chemistry 46 carbon dioxide in the permeate was calculated by measuring the mass of carbon dioxide and water in the analyzed permeate sample. the pressures on the feed and permeate sides were measured by pressure gauges. the temperatures of the feed in the reactor vessel, before and after the membrane module were measured by thermocouples. pure monoethanolamine (mea) and deionised water were used to prepare the liquid-feed solution. afterwards the obtained solution was loaded with co2 by bubbling pure co2 in a magnetically stirred vessel until the required carbonation ratio, , was achieved. in our experiments the carbonation ratio was determined by measuring the mass of absorbed co2 in the amine solution at a given temperature. additionally, independent pervaporation experiments with the same pdms membrane under similar thermal and hydrodynamic conditions for a 2-propanol – water mixture were performed to estimate the membrane resistance (1/km). 2.2. experimental results the performance of the pdms membrane was examined experimentally. the operating temperature was between 323 and 348k (50 and 75°c), liquid flow rate between 20 and 600 l/h and the mea concentrations were 5, 10 and 15 wt%. the effect of liquid flow rate on the co2 mass flux and selectivity is presented in figs.2 and 3 for the temperature of 323k (50°c) and 10% mea concentration. the selectivity of the process is defined as follows: 2 2 2 2 co co co co ( (1 )) ( (1 )) p f w w s w w    (1) the measured fluxes increase with the reynolds number. the highest values were obtained for re>10,000 (turbulent flow). this can be explained by the co2 mass transfer increase in the liquid phase for turbulent regime. the measured selectivities rise with the reynolds number and for turbulent flows reach the value of 10. the operating temperature is an important parameter as far as the efficiency of the membrane is concerned as shown in fig.4. for a given turbulent liquid flow rate the measured co2 mass fluxes rise with the feed temperatures due to the increased driving force in favour of co2 mass transfer. the selectivity does not change significantly with the operating temperature, fig.5. the effect of the mea concentration on mass flux and selectivity is presented in figs.6-7 at an operating temperature of 323k (50°c) and turbulent flow (re of about 40,000). the measured mass fluxes do not change significantly with mea concentration (fig.6), because of the figure 1. the experimental setup: 1 – membrane contactor, 2 – feed tank, 3 – cold traps, 4 – circulation pump, 5 – vacuum pump, 6 – heater figure 3. the effect of re number on selectivity (t = 50°c and wmea = 10 wt%) figure 2. the effect of re number on co2 mass flux (t = 50°c, wmea = 10 wt%) figure 4. the effect of feed temperature on co2 mass flux (wmea = 10 wt%) application of hydrophobic polymeric membrane for co2 desorption ... 45(2) pp. 45–49 (2017) 47 relationship between equilibrium constants of the co2 mea reaction and the co2 solubility in water at a given temperature. the selectivity decreases with mea concentration as a result of the rising amount of co2 absorbed in the mea solution and the constant co2 flux in the permeate, see fig.7. 3. mathematical model and calculation results when co2 is absorbed in aqueous monoethanolamine (mea) solution, the following reactions can be written as [11]: slow 2 2 2co rnh rn h coo  (2) fast 2 2 3rn h coo rnh rnh rnhcoo     (3) the formation of carbamate is well understood and the rate of the forward reaction has been determined as first order with respect to both co2 and rnh2: cf 2 2[co ][rnh ]r k (4) during the desorption process the differences in the concentration of the component and the temperature between the inlet and outlet in the liquid phase are very small. therefore, the desorption rate may be simply calculated using the arithmetic mean value of co2 in the liquid phase. with this assumption we can calculate the mass fluxes of co2 can be calculated as follows: 2 2 2 * lco co co( )n k x x  (5) where nco2 [kmol/s] is the flux of co2 and kl [kmol/m2s] is the overall mass-transfer coefficient of the liquid phase. the overall mass-transfer coefficient for co2 can be evaluated by a resistance-in-series model [12]. the numerical calculations based on model equations were performed and estimated values of membrane resistance (1/km) used. in the calculations the experimental values of the henry’s constant for co2 in water and mea under standard conditions are 1.2456 and 1.5732, respectively [13]. the enhancement factor of the chemical reaction of co2 in the liquid phase, as defined by decoursey [14], was between 20 and 60. the viscosity of the water–mea mixture was calculated according to a grunberg and nissan equation [15]. calculated and experimental values of co2 mass fluxes are figure 5. the effect of feed temperature on selectivity (wmea = 10 wt%) figure 6. the effect of mea concentration on co2 mass flux figure 7. the effect of mea concentration on selectivity figure 8. comparison of calculated values of co2 fluxes with experimental ones ziobrowski and rotkegel hungarian journal of industry and chemistry 48 shown in fig.8. the scattering of calculated and experimental values of co2 mass fluxes was within the range of ±25% . the experimental values of co2 mass fluxes were compared with those obtained from the literature for co2 stripping in a ceramic hollow fiber membrane contactor [10]. in spite of the different types of membrane type and hydrodynamic conditions the measured values of co2 mass fluxes were comparable in both cases. conclusions the application of a membrane in the process of co2 stripping from mea solutions avoids some technical problems that are encountered in industrial practices. the pdms hydrophobic tubular membrane on a ceramic support can be applied for the removal of co2 from mea solutions. in developed turbulent flows the measured co2 mass fluxes and selectivities do not change significantly with re number (figs.2-3). the measured co2 mass fluxes increase as the feed temperature rises (fig.4) and slightly depend on the mea concentration (fig.6). the measured and calculated co2 mass fluxes are in good agreement with each other (fig.8). the ±25% variation in scattering can be explained by the accuracy of the correlations, experimental precision and simplification of the model. 4. symbols c – concentration, kmol m-3 d – diffusion coefficient, m2 s-1 kl – overall mass transfer coefficient, kmol m-2 s-1 km – mass transfer coefficient of the membrane, kmol m-2 s-1 n – mass flux kmol m-2s-1 r – reaction rate, kmol s-1 re – reynolds number s – selectivity t – temperature, k w – mass fraction x – mole fraction of co2 in the liquid phase superscripts * refers to equilibrium subscripts calc – calculation co2 – carbon dioxide exp experimental f – feed g – gaseous phase l – liquid phase p permeate references [1] budzianowski w.m.: single solvents, solvent blends, and advanced solvent systems in co2 capture by absorption: a review, int. j. global warming, 2015 7 (2), 184-225, doi: 10.1504/ijgw.2015.067749 [2] rochelle g.t.: amine scrubbing for co2 capture, science, 2009 325, 1652-1654, doi: 10.1126/science.1176731 [3] zhao b.; sun y.; yuan y.; gao j.; wang s.; zhuo y.; chen c.: study on corrosion in co2 chemical absorption process using amine solution, energy procedia, 2011 4, 93–100, doi: 10.1016/j.egypro.2011.01.028 [4] eide-haugmo i. et al.: environmental impact of amines, energy procedia 2009 1, 1297–1304, doi: 10.1016/j.egypro.2009.01.170 [5] libralato g.; volpi 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2-amino-2-methyl-1-propanol + water, j. chem. eng. data, 1994 39, 444-447, doi: 10.1021/je00015a009 hungarian journal of industry and chemistry vol. 47(2) pp. 17–23 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-16 immobilization of laccase in alginate beads béla varga*1, mónika meiczinger2, and viola somogyi1 1institute of environmental engineering, university of pannonia, egyetem u. 10, veszprém, 8200, hungary 2research institute of biomolecular and chemical engineering, university of pannonia, egyetem u. 10, veszprém, 8200, hungary the elimination or degradation of micropollutants from wastewater is becoming ever more important nowadays. using oxidoreductase enzymes to treat different micropollutants seems a promising solution. however, the viability of the process is highly dependent on the availability and stability of the applied enzymes. in order to improve the stability and provide faster reaction rates, enzymes can be immobilized in various carriers. properties such as simple production, easy retention and biodegradable carrier material are advantageous, e.g. entrapping laccase in alginate beads. this paper shows the results of the preparation and characterization of immobilized laccase entrapped in calcium alginate beads. the technique of adding a mixture of sodium alginate and laccase dropwise into calcium chloride has been applied, improved and standardized to produce laccase-containing beads of uniform size and activity. for the purpose of characterization, a widely used substrate, 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt, was used to evaluate the performance of the laccase-containing alginate beads. in addition to the characterization of the laccase-containing alginate beads, the enzyme kinetic constants (km = 26.43 µm, vmax = 0.23 µm/min) were determined. the reduction in the activity during storage has been described by a decay constant (0.26 d−1) that provides information concerning the design constraints of the process. results will be used to test the method in terms of the removal of organic micropollutants in continuous systems. keywords: laccase, immobilization, alginate, abts, micropollutants 1. introduction awareness concerning the spread of micropollutants in water bodies has been raised in many countries [1] due to their toxic effects on ecological systems [2]. additionally, these pollutants can infiltrate into reservoirs of drinking water in several ways resulting in public health concerns [3]. since conventional treatment systems were designed to easily remove biodegradable compounds [4], the efficiency of micropollutant degradation is insufficient [5]. the partial elimination of these substances is driven by physical adsorption by the sludge [6] and cometabolism during microbial growth [7]. therefore, the development of advanced technologies to improve the efficiency of removal and mitigate ecological effects is needed [8]. organic micropollutants could be converted by oxidoreductase enzymes such as tyrosinase, peroxidase and laccase. laccase has received attention since it does not require additional cofactors. it promotes the production of an organic radical which combines with different transformation products [9]. the toxicity of these compounds is a subject of ongoing research [10], although a reduction in toxicity has been shown in many cases [11]. *correspondence: vargabela@almos.uni-pannon.hu immobilization can be advantageous compared to the free form of the enzyme [12]. it can enhance the stability of the enzymes under more extreme conditions, namely higher ph and temperature [13], and makes the separation of the catalyst from the effluent easier. for example, separation by applying an external magnetic force is possible when laccase is immobilized on magnetic particles [14]. by using macro-sized supports, e.g. alginate beads [15] – unlike nanoparticles – the carriers can be retained by an outlet sieve, thus using them in continuous packedbed reactors is possible [16]. alginates extracted from brown algae [17] are good candidates for water treatment because of their advantageous properties [18], low-cost production and low health risks [19]. calcium alginate microspheres, successfully used to immobilize polygalacturonase for the purpose of cleaning edible products, have shown improved operational stability as the optimum temperature increases and even modifies the ph dependence of the enzyme [20]. calcium alginate beads are formed by reversible crosslinking bonds with bivalent calcium ions between chains of α-l-guluronic acid and β-d-mannuronic acid [19]. their unique properties allow them to be used as an adsorbent for dye removal [21]. transformation of the phehttps://doi.org/10.33927/hjic-2019-16 mailto: vargabela@almos.uni-pannon.hu 18 varga, meiczinger, and somogyi nolic compound with laccase entrapped in alginate was successfully tested for bisphenol a [22] and the decolourization of textile dyes [23]. the aim of this study was to investigate the immobilization of laccase in calcium alginate beads and determine its kinetic behaviour by measuring the conversion of 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (abts). since this substrate is widely used, the results may be easily compared with other laccase immobilization methods. 2. materials and methods 2.1 materials laccase from trametes versicolor (catechol oxidase activity ≥ 0.5 u/mg) and abts were purchased from sigma-aldrich. food grade sodium alginate was purchased from dragonspice naturwaren. citric acid and sodium phosphate used for making mcilvaine buffer solution [24] were supplied by vwr international. calcium chloride was purchased from reanal. reagents were of analytical reagent grade except for sodium alginate. 2.2 measurement of enzyme activity laccase activity was determined by measuring the change in concentration of the abts radical formed in the catalysed oxidation. measurements were performed in a macherey-nagel nanocolor uv/vis spectrophotometer at 420 nm in a citrate-phosphate buffer solution at ph = 5 and within the range of laboratory temperatures (20± 3 °c). the formation of the product was registered by using the extinction coefficient of the abts radical (ε = 36, 000 m−1cm−1 [25]) and calculated using an equation a = evsample lεvtotal (1) based on the beer-lambert law [26], wherea denotes the activity (u/l),e is a measure of the change in absorbance at 420 nm over 1 minute (min−1), vsample represents the amount of enzyme contained in the sample used (ml), l is the pathlength of the beam of light (cm), ε stands for the extinction coefficient of the abts radical (m−1cm−1), and vtotal expresses the total volume used (ml). in the case of immobilized laccase, beads were placed into the tubes instead of the liquid samples. the specific activity was calculated by measuring the weight and number of beads before the activity in a closed tube was measured. between measurements, the beads were stored in distilled water in order to minimize the loss of water. 2.3 immobilization of laccase inside an alginate matrix the immobilization protocol was based on entrapment of the enzyme before the formation of insoluble alginate beads according to daâssi et al. [23]. the sodiumalginate crystals were dissolved in 5 ml of 1 mg/ml laccase stock solution to produce a gel with 2 w/v% alginate content. this was added dropwise from a height of 25 cm into a 2 m/m% solution of calcium chloride where beads formed, then the beads were left for 30 mins to solidify. after this procedure, the beads were extracted from the solution by filtration and washed with distilled water in order to eliminate the unbonded laccase. the beads were stored in distilled water until used for further investigations. the efficiency of the immobilization was determined by measuring the activities of the laccase stock solution (ainitial), the solution of calcium chloride after immobilization (acacl2 ) and the washing liquid (awashing) used. immobilization efficiency (η) was calculated using the following formula η(%) = 100 ainitial −acacl2 −awashing ainitial . (2) 2.4 characterization of the immobilized laccase the weight was measured frequently in a closed vessel by using an analytical balance (kern abj 220-4nm). the size of the drops was determined by measuring the diameter of the freshly prepared beads after filtration on a square membrane filter. in order to determine the water content, twenty pieces of freshly prepared beads were put into an oven at a temperature of 105 °c and dried until their weight became constant. 2.5 effect of temperature on alginate beads in order to gather information regarding the effect of temperature on enzyme activity within the optimal temperature range of wastewater treatment plants [27], the reaction rate of the abts transformation was determined inside a thermostatic cabinet (20− 35 °c). 2.6 storage stability of the beads the storage stability of the immobilized laccase was determined by storing the laccase-containing beads in ultrapure water at 20 °c without mixing. beads were removed every 24 hours from the vessel in order to determine the change in their activity. the exponential decay constant was calculated by fitting the following equation at = ainitiale −kdt (3) to the measured activities, where ainitial and at indicate the specific activities [u/bead] at the initial and given time, respectively, kd denotes the decay constant [d−1] and t stands for the time of sampling [h]. 2.7 reuse of the alginate beads the laccase-containing beads were mixed with a 0.05 mg/ml abts solution in a phosphate-citrate buffer solution (ph = 5) and the change in the abts radical concentration was determined spectrophotometrically. after hungarian journal of industry and chemistry immobilization of laccase in alginate beads 19 figure 1: change of size during drying of the beads (a) beads freshly prepared, (b) beads after drying, grid size: 3 mm measuring the activity of the beads (after 5 mins), they were filtered and washed with 5 ml of distilled water which was considered to be one cycle. during the filtration, a picture was taken to document the change in the size and shape of the beads. after washing, the beads were put into a fresh volume of buffer solution that contained abts and the same cycle repeated six more times. 2.8 determination of kinetic parameters with abts ten beads were put into a ph = 5 citrate-phosphate buffer solution, then different amounts of abts stock solution were pipetted in order to obtain different initial substrate concentrations ([s] = 23, 46, 91, 228, 456, and 911 µm). the change in absorbance was recorded at 420 nm to calculate the concentration of abts radicals (p). the michaelis-menten constant (km) and maximum rate of reaction (vmax) were determined by fitting the michaelis-menten equation. d[p] dt = vmax[s] km + [s] (4) with non-linear regression. 3. results and analysis 3.1 characterization of the alginate beads using the technique described, it was possible to produce a uniform bead weight: 0.0152 g (sd = 0.0016 g) of high immobilization efficiency (98.2 %). the diameters of the beads were between 2 and 3 mm. the weight and density of the beads constantly changed during their handling due to the rapid rate of evaporation of water. therefore, the number of beads was used to calculate the specific activity instead of weight, in a similar way to daâssi et al. [23]. a specific activity of 0.005 u/bead was achieved, which equates to 0.005 µm production of abts radicals in one minute. the water content of the beads was determined to be 98± 1 %. the size of the beads shrank twofold whilst being dried as is shown in fig. 1. 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 0 200 400 600 800 1000 a b t s ra di ca l co nc en tr at io n (µ m ) time (s) figure 2: change of abts radical concentration 3.2 determination of kinetic parameters the change in the concentration of abts radicals as a function of time is presented in fig. 2. a linear curve could be fitted with the results during the initial 2 minutes indicating a first-order reaction. the rate of the reaction can be determined from the gradient of the curves. by plotting the initial rates of reaction against the concentration of the substrate, a lower initial substrate concentration shows a better fit (r2 = 0.96 − 0.99) when compared to the higher range (r2 = 0.95). as a result, common michaelis-menten kinetics were shown (fig. 3). by fitting an equation to the data gathered from three independent experiments with nonlinear least squares regression, the kinetic constants can be determined, namely km = 26.43 µm, vmax = 0.23 µm/min. 3.3 effect of temperature on alginate beads in the range of 20 − 35 °c, the rate of reaction, thus the enzyme activity, increased rapidly as can be seen in fig. 4. as expected, the highest activity was measured at 35 °c since, in the case of the free laccase from trametes versicolor, the optimal temperature for maximum activity was approximately 40 °c [26]. figure 3: fitting of michaelis-menten curve to the measure. initial concentrations used for calculation: 5 µm, 9 µm, 23 µm, 46 µm, 91 µm. 47(2) pp. 17–23 (2019) 20 varga, meiczinger, and somogyi 0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 20 25 30 35 a ct iv ity ( u /b ea d) temperature (�c) figure 4: effect of temperature on the activity of the immobilized enzyme. 3.4 storage stability of the beads during storage, a slow decreasing trend can be observed in the activity of the beads, namely a reduction of 33 % over 5 days. by fitting equation to the measured values, the decay coefficient can be determined as 0.26 d−1. the change in activity and the decay curve produced by the equation are presented in fig. 5. 3.5 reuse of the beads the activity of the beads also decreased when repeatedly used. as an example, the results of an experiment were presented in fig. 6. while the activity of the beads decreased, their weight increased gradually. the change in the size of the beads and accumulation of the green reaction products can be seen in fig. 7. this figure also shows the deformation of the beads in between the experiments. 4. discussion using the method described in this study, uniform beads can be produced with regard to their size and weight by controlling the size of their droplets and the height from which they are dropped. since the alginate powder was dissolved directly in the stock solution of laccase and the thick layer solidified instantly when it came 0.000 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0 1 2 3 4 5 6 7 a ct iv ity ( u /b ea d) storage time (d) measured calculated figure 5: change of the activity during storage of the immobilized laccase. figure 6: change of activity and weight of the beads during reuse into contact with the cacl2 solution, the entrapment was instant and effective. as a result, a high immobilization efficiency was achieved (98.2 %). otherwise, the weight of the beads changed quickly whilst being handled after their formation as the beads dried out easily. however, the change in their water content did not influence their activities. therefore, in order to achieve reliable results for specific activities, the number of beads was calculated rather than their weight. evaluation of the reaction kinetics resulted in a michaelis-menten curve in the case of immobilized laccase, in a similar manner to its free form [28]. this indicates that the mechanism of the reaction was not influenced by the entrapment. nonetheless, the activity of the beads is different from that of free laccase due to steric effects and limitations with regard to the diffusion of reactants. in order to achieve higher degrees of activity, the temperature could be increased. this would have advantageous effects on the rate of reaction and diffusion. additionally, by increasing the number of beads used, the rate of reaction could be fine-tuned to suit the requirements of their application in a similar way to the use of free enzymes. in order to determine the product yield or space-time yield, further investigations are recommended. due to the nature of abts, from visual inspection of radicals in itself, it was evident that the reaction products accumulate inside the beads (see fig. 7). this could result in the deactivation of the enzyme by product inhibition. on the other hand, this phenomenon could be used to remove the transformation products after enzymatic conversion by means of adsorption. as tanaka et al. [29] concluded, the diffusion properties depend on the molecular size of the substrate. since laccase-catalysed reactions tend to result in coupled products of higher molecular weight [9], its release from the beads could be limited by diffusion. in the case of low-molecular-weight compounds, e.g. abts, free diffusion can be assumed in the alginate matrix [30]. as the experiments concerning repeated usage have shown, the beads suffer from major structural changes hungarian journal of industry and chemistry immobilization of laccase in alginate beads 21 cycle 1 cycle 2 cycle 3 cycle 4 cycle 5 cycle 6 cycle 7 figure 7: photos of the laccase containing alginate beads during the repeated use in buffer solutions that contain high concentrations of monovalent cations. this is due to the fact that crosslinking with calcium ions is reversible. these structural changes may result in the enzyme leaking and the specific activity decreasing following repeated usage. the reduction in enzyme activity during storage could also be a result of leakage. however, experiments performed in distilled water fitted well with the decay equation, therefore, this can be taken into consideration during the design of the process. moreover, in the case of a complex solution, e.g. treated wastewater or even tap water, the presence of bivalent cations may limit the deformation of the beads. 5. conclusions uniformly sized alginate beads were produced in the laboratory using a widely available biodegradable polymer. the mechanism of immobilized laccase was similar to that of its free form with regard to the conversion of abts, although the effects of diffusion and adsorption should be taken into consideration. due to the structure of the alginate beads, the use of monovalent ions that contain buffers for measurements results in major structural changes. the beads produced were reused successfully over 7 cycles, while a rapid reduction in activity and structural changes were observed. however, the beads can be stored in distilled water and the reduction in activity estimated by an exponential decay equation which facilitates the design of the process. although further investigations regarding the efficiency of enzymatic transformation are needed, immobilization of laccase in alginate beads is a promising technique for the enzymatic treatment of micropollutants in continuous systems. symbols a activity [u/l] acacl2 activity of calcium chloride solution after immobilization [u/l] ainitial activity of the laccase stock solution used [u/l] at specific activity at a given time [u/bead] awashing activity of the washing liquid [u/l] e change in absorbance at 420 nm over 1 minute [min−1] kd decay constant [d−1] km michaelis-menten constant [µm] l path length of light beam [cm] p reaction product, abts radical concentration [µm] s initial substrate concentration [µm] t time [min.; d] vmax maximum reaction rate [µm/min] vsample amount of enzyme-containing sample used [ml] vtotal total volume used [ml] ε extinction coefficient of abts radicals[m−1cm−1] η immobilization efficiency [%] acknowledgement the financial support of széchenyi 2020 under the projects ginop-2.3.2-15-2016-00016 and tét_15_in1-2016-0094 is greatly appreciated. references [1] ebele, a.j.; abou-elwafa abdallah, m.; harrad, s.: pharmaceuticals and personal care products (ppcps) in the freshwater aquatic environment. emerg. contam., 2017 3(1), 1–16 doi: 10.1016/j.emcon.2016.12.004 [2] shao, y.; chen, z.; hollert, h.; zhou, s.; deutschmann, b.; seiler, t.-b.: toxicity of 10 organic micropollutants and their mixture: implications for aquatic risk assessment. sci. total environ., 2019 666, 1273–1282 doi: 10.1016/j.scitotenv.2019.02.047 [3] ahmad, j.; naeem, s.; ahmad, m.; usman, a.r.a.; al-wabel, m.i.: a critical review on organic micropollutants contamination in wastewater and removal through carbon nanotubes. j. environ. manage., 2019 246, 214–228 doi: 10.1016/j.jenvman.2019.05.152 [4] monteiro, s.c.; boxall, a.b.a.: occurrence and fate of human pharmaceuticals in the environment. in: reviews of environmental contamination 47(2) pp. 17–23 (2019) https://doi.org/10.1016/j.emcon.2016.12.004 https://doi.org/10.1016/j.emcon.2016.12.004 https://doi.org/10.1016/j.scitotenv.2019.02.047 https://doi.org/10.1016/j.scitotenv.2019.02.047 https://doi.org/10.1016/j.jenvman.2019.05.152 https://doi.org/10.1016/j.jenvman.2019.05.152 22 varga, meiczinger, and somogyi and toxicology. 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10.1016/j.colsurfa.2015.01.027 47(2) pp. 17–23 (2019) https://doi.org/10.1002/bit.260260111 https://doi.org/10.1002/bit.260260111 https://doi.org/10.1016/j.colsurfa.2015.01.027 https://doi.org/10.1016/j.colsurfa.2015.01.027 introduction materials and methods materials measurement of enzyme activity immobilization of laccase inside an alginate matrix characterization of the immobilized laccase effect of temperature on alginate beads storage stability of the beads reuse of the alginate beads determination of kinetic parameters with abts results and analysis characterization of the alginate beads determination of kinetic parameters effect of temperature on alginate beads storage stability of the beads reuse of the beads discussion conclusions hungarian journal of industrial chemistry veszprem vol. 30. pp. 95 101 (2002) varying porosity kinetic model for direct and reactive solid-liquid extraction i. seikov a and a. mintchev (department of chemical engineering, university of chemical technology and metallurgy, blvd. kilment ohridski 8, 1756 sofia, bulgaria) received: apri123, 2001 a mathematical model is presented accounting for the effects of porosity increase during extraction from vegetable materials. the relation between the porosity and the total extract release is derived from the solid phase volume balance. the model will be used to interpret the experimental data for alkaloid recovery from leaves and radix of the medicinal plant atropa belladonna. the extractability has been determined by dissolution of alkaloidic salts in polar solvent (direct extraction) and by alkaline transformation of salts to bases in non-polar solvent (reactive extraction). supporting experiments were performed in order to estimate the kinetics of solvent penetration. for inert conditions, the estimated effective diffusivities are nearly equal to those obtained under reaction conditions. the resorted differences in the diffusivity as a result of the porosity changes remain lower in respect to the strong influence of the different initial pore structure of the two raw materials. keywords: solid-liquid extraction, vegetable alkaloid recovery, chemical reaction, porous medium, liquid penetration introduction solid-liquid extraction coupled by chemical or biochemical reaction occurs frequently during valorisation of natural materials [1-2]. generally the kinetics of the process is represented by macroscopic mass balance on the overall solid phase with volume reaction models: ac2 _ z i)t-d~jjv c2 +rv (1) where rv is the rate of chemical reaction per unit volume and c2(t,r) represents the concentration of the diffusing reaction product. this equation allows a constant effective diffusivity dt!jj to be estimated assuming that the initial structure of the porous solid is maintained while the extraction proceeds. in many cases during the treatment of the vegetable material several additional processes, as co-solutes migration, solvent adsorption, hydration or other reactions occur simultaneously with valuable component mass transfer. the structure of the solid can be readily affected and this is accompanied generally by a porosity increase. varying porosity causes an increase in the diffusivity with the course of the extraction. theoretical studies have revealed that the ratio of effective diffusivity to molecular diffusivity varies proportionally by c/3 " 3 depending on the adopted geometric description of the pore structure [3-6]. initial experiments with the considered plant indicated sizeable amounts of dissolved co-solutes. in parallel an increase of the volume of solvent penetrating in the solid was resorted that differed for the various solvents that were used [7]. then, the measurement and evaluation of the porosity effect are important for the accurate prediction of the values of d ~if under reactive or inert conditions. in the present paper a dynamic model is proposed to describe the diffusive-reactive phenomena when the porosity increases with the course of the extraction. to predict the porosity changes a simplified model is adopted that relates the kinetics of solvent penetration to the kinetics of release of the total extract. the presented model will be used to interpret the experimental data of kinetics of alkaloid recovery by direct and reactive extraction from different parts of the medicinal plant atropa belladonna in a batch system. mathematical model the overall process of extraction with simultaneous chemical reaction involves consideration of the following phenomena: 96 (a) chemical conversion of insoluble compound that is initially adsorbed or chemically bounded in a solid to soluble reaction product, prior to its diffusion through the pore space; (b) parallel release of all-soluble compounds initially present accompanied by additional solvent penetration and porosity increase. the approximate model is derived under the following assumptions: the solid represents one monodispersed phase of spherical particles with mean radius rs and initial porosity £p.o; the particles retain their shape and dimension during reaction and extraction, although the porosity increases; the extractable compounds are uniformly distributed in the porous solid particles; the solid-solvent phases ratio f3 is high, so that the solutions are always dilute and density variations and multicomponent effects on the diffusion are negligible; the analysis is restricted to first-order irreversible reaction that takes place all over the solid volume without participation of the pores, according to the rate equation: dcs (t) = -k c (1£ ) dt r s p (2) where kr=fiph, t) is the effective reaction rate constant. under varying porosity condition the transient diffusion of the soluble reaction product within the particle obeys the following reiationship [8]: ij(e.pcp) 1 0 ( 2(ijcp) ) (3) -a-t-=7 or d~g(e.p)r a;-cpvr +k,c,(l-ep) the solvent radial velocity vr in the pores can be related to the porosity increase from the continuity equation: a£p +_!_i_~zv )=0 at r 2 dr r (4) after integration of the continuity equation and substituting this in eq.( 3) the conservation equation takes the form: the associated boundary conditions are: .(acp) =o ur t=o {6} -d • ..-( 0j; l. +<•·,c,>, •••. ~kjc,1, •• , -c,(t>) (7) in the last step of the process~ the solute is transported from the pores opening on the contact surface to the bulk liquid phase at concentration clt): dcl (t) = ]_k f3(c 1-c (t)) (8) d r m p r-r, 1 t s solid phase volume balance may be used as theoretical possibility to correlate the changes in a pore volume with the amount of compounds released [9]. it is known that solvent penetration in the pore space is the initial stage of the extraction. it is assumed that an initial porous volume £p.o vs is immediately filled with solvent. with the disappearance of extractable compounds from the solid the free space volume inside the particles increases and the solvent penetration continues during the whole stage of the extraction. the solid phase apparent volume vs consists of inert solid matter vin• pore volume filled with solvent ~it) and extractable compounds vexlt): (9) the solvent volume impregnated the solid is represented by the varying porosity: (10) the decrease in the volume of the extractable compounds ve.xlt) may be expressed through the amount extracted for the timet. generally, the extract increases in time mexr=f(t), it can be described by sufficient accuracy by equation of the type: (11) where a, b and h are empirical coefficients. then the unextracted fraction in the solid phase '}{ t) is defined from the total balance: y(t) = 1mext(t) xomo (12) where the initial mass fraction x0 is established experimentally after multiple treatment with fresh solvent. the particular volumes can be expressed as follow: x 0m0 me.xr(t) p~xt (13) (14) introducing eqs.(jo), (13) and (14) into eq.(9) gives: vs = ~o (1-=_xo + y_!o) 1 bp pm p~xt (15) when the changes in the dimension of the solid particles are negligible. solvent penetration equals the volume of the disappearance of extractable compounds. the porosity changes in a function of time is given by the fouowing relationships: 1x 0 y(t)x 0 --+--e (t)=l-(1-e ) an pext (16) p p,o 1-x x __ o+_o_ pin pext the porosity changes would affect the solute diffusivity. an exponential increase in the effective diffusivity in respect to the extracted fraction (1-'0 is assumed and it is defined by the following empirical function: d = d expa(l-y) eff eff,o (17) where a is a numerical constant and d eff,o is the effective diffusivity evaluated for the initial conditions. the system of eqs. (2-17) can be rearranged to a dimensionless form: de* (r) 2 * -·-=-th c dr (18) dd;r) =3bif3(c;l~=1 -c;) (20) i.e. c; (o) = 1 , c; co,cp) = o, c; co)= o (21) b.c. ac* a; 11'=0 =o * a c* i cp de l *i *) d __ i' m=l +--p= bi\c "'=1 c olp -r 3 d'f p "1' i with the following dimensionless parameters: * c c =--, cs,o d * _ d eff _ a(l-y) ----exp deff,o f3=i, l d eff,o t r=y, $ (22) (23) (24) where th is called thiele-type modulus for the porous particle that brings out the relative significance of the reaction rate [10,11]. numerical treatment the coupled system of second order,. partial and ordinary differential equations of the presented model is solved numerically. four-order runge-kutta method was utilized for the ordinary differential equations. the 97 a ·~ 0.8 0.2 0.4 0.6 0.8 fig.l reaction rate constant influence on the averaged concentration in the solid phase (computed for bi=400, kr= 0.8 s"\ 0.8 10"2 s"1 and 0.8 10"4s"1) approach for the parabolic partial differential equations is based on crank-nikolson finite difference scheme. for the resolution of the resulting systems of algebraic equations forward-backward thomas' algorithm was used. from the dimensionless mass balance of the solid particle eq. ( 19) it is clear that thiele modulus, the magnitude of variation in porosity ep and effective diffusivity d* will control the process. the integration of this equation around the overall solid particle volume yields the evolution of the averaged concentration <c/> in the particle: . (25) d • a [i . ) { . ac,) (ile,) 1 a r~· . ) .. -< c >=b c = d • --c +th c dt • ar v. r , a~ "'" ih 1'2 a~ 3 , ' the values of this term can be positive or negative depending on the relative magnitude of the rate of diffusion and chemical reaction. fig. i shows the plots <c2 *>=f(t) computed for specific ranges of thiele modulus. the curves are compared with the prediction provided from a pure diffusional model. in the usual situation for large biot numbers there can be distinguished three different kinetic regimes: diffusion-controlling regime (th> > 1 ): in case of instantaneous or very fast chemical reaction the conversion takes place before the solute can diffuse into the interior of the particle; the effect of reaction rate is negligible and the disappearance of the solute is a continuously decreasing function; reaction-diffusion regime (th> 1): the diffusion of solute is not fast enough to compensate for its appearance by reaction and the evolution of the concentration <c2 * > passes through a maximum before the reactant is completely converted; reaction rate-controlling regime (th<l ): the slow consumption of the reactant in respect to the product diffusion leads to slowly increasing accumulation inside the particle volume. the effect of the interaction reaction·diffusion on the kinetic curves c1 * =/( r) in the liquid phase is shown in fig.2. as a result of the resistance induced by the chemical reaction the kinetic curves that are normally convex under diffusion·controlling regime take a sigmoidal form. when the rate of reaction is comparable with the diffusion rate. for large values of thiele 98 0.06 ~ 0.05 .8 1 0.04 8 "' 0.03 j 0.02 ~ :a o.ql 0 0.2 0.4 0.6 0.8 illrrl<'n~innlp~~ tin'lf' fig.2 reaction rate constant influence on the concentration in the liquid phase (computed for bi=400, kr= 0.8 s-1, 0.8 10-2 s-1 and 0.8 w-4s-1 ) 0.06 cr ·~ g o.q45 ~ 8 ~ 0.03 g .! 0.015 :a 0 0.2 0.4 0.6 0.8 rlimensionles.~ time fig.3 the effect of the varying porosity under non-reactive and reactive conditions (th=3.577, kr= 0.8 10-2 s-1 ) modulus (th>40) the prediction approaches an asymptotic curve controlled purely by pore diffusion. physically, for given particle size and reaction rate constant, the parameter th increases as the effective diffusivity d~"ifis decreased: using porous solid of very small pore size; using porous solid having a small porosity or high tortuosity factor. the effect of the varying porosity under reaction or non~reaction conditions is explained by these considerations. in fig.3 are presented the computed values of dimensionless concentration in the liquid phase cl "( 1:) for both diffusion-controlling and reaction­ diffusion regime with porosity as parameter. the kinetic behavior is simulated for three cases: constant porosity (ep=0.4). moderate (£p=0.4+0.55) and very marked porosity change (ep=0.4-f().7). as expected. under diffusion-controjiing regime the higher the porosity the faster the overall extraction process. however. under reaction-diffusion regime a delay in the process is predicted as the porosity is increased. the increasing values of the porosity ep and the effective diffusivity d(ff lead to a decrease in the values of til. when the rate of reaction is decreased in respect to the diffusion rate~ the concentration gradient at the sofid"liquid interface declines rapidly and this effect is not completely compensated by the increasing d~ti fig.4 steps of alkaloid recovery from atropa belladonna plant: a) direct solid-liquid extraction; b) reactive solid-liquid extraction as a result from the contradictory effect of the varying porosity erroneous results can be obtained using a model with constant porosity, namely an apparent decrease in d eff when the reaction is carried out in a reaction-diffusion regime. experimental exemplary vegetable alkaloid recovery by direct or reactive extraction has been studied. small quantities of tropan alkaloids are found in leaves, seeds and radix of the medicinal plant atropa belladonna. these are predominantly in alkaloidic salt form and dissolved in the cellular liquid. the known methods for alkaloid extraction are based on their different solubility according to solvent polarity. the polar organic solvents are appropriate solvents for alkaloid salts. when using non-polar solvent, alkaloid bases dissolve. the co­ solutes are also selectively removed. unvaluable substances, as polysaccharides, mineral salts, tanins, flavanoids dissolve in ethanol. chloroform extracts contain non-polar substances: chlorofils, ac~ds, fatty oils, pigments. the overall process consists of the following stages (fig.4): 1. solid-liquid extraction by direct dissolution of salts in polar solvent (direct extraction) or by prior alkaline transformation of salts to bases in non-polar solvent (reactive extraction). 2. extract purification from associated co-solutes by acidic treatment with aqueous solution. 3. crude-alkaloids recovery from the cleaned-up extract by alkaline transformation in alkaloid bases. in the experimental study the solvent was methanol for direct extraction, and chloroform under reaction conditions. adjustment of ph alkaline of the solution was made by means of 25% nh3• for acidification of the aqueous solutions 8% hci was used. alkaloids were extracted from dried and fractionated samples, provided from two different parts of the plant, namely radix and leaves. the structure of the porous solid was investigated by nitrogen adsorption at 77.4 k by the simplified single-point bet procedure. the results show that the pore spaces of the epigeous and subterraneous tissues strongly differ in their structural parameters: -fit for direct extraction ~experimental -fit for reactive extraction oq,----~----~----~-----r----~----~ 0 600 1200 1800 time, sec 2400 3000 3600 fig.s course of extraction c1=f(t) from radix samples o experimental <> experimental 300 600 900 time{sec) -fit for physical extraction -fit for reactive extraction 1200 1500 1800 fig.6 course of extraction c1=f(t) from leaves samples leaves: specific area 1.7 m2 g-1, free volume 0.6 cm3 g-1 , mean pore radius 11 nm. radix: specific area 0.4 m2 , g-1 , free volume 0.15 cm3 g-1 , mean pore radius 16 nm. the initial content of alkaloids was obtained after continuous extraction in a soxhlet apparatus: 0.3% of the dried mass for leaves and 0.6% for radix. the experimental procedure has been divided in two groups. the first one analyses the recovery of the alkaloids in the cleaned-up extracts to provide the kinetic curves cz=j(t). for this aim the solutions were analysed for alkaloids by spectrophotometric measurement at wavelength a=430 nm [12-13]. the second group investigates the kinetics of total extract removal and solvent penetration. the observations include simply measuring the changes in weight: when the pores are filled with a solvent (msz). and after removing the impregnated solvent by drying at 40 oc for about 12 hours (mss)· from this experimental values the kinetics of total extract release mexi=j( t) and the volume of solvent penetrating into the porous material v~.s=j(t) can be determined by noting that: msl (t)mss (t) pl (26) (27) 0.15 0.125 ;g ~ 0.1 ~ g 0,075 ~ "'" 0.05 2 0.025 99 • reactive extraction with chcr; 0 +-----r-----.------r-----r-----r-----+ 0.6 300 600 900 time(sec) 1200 1500 1800 fig.7 experimental and predicted total extract and solvent penetration increase during direct and reactive extraction of radix samples 0.15,----------------------.. 1.7 0.125 §' g 0.1 ~ i 0,075 'd 0.05 2 0.025 • • -........----o------1:>-------4 1.6 i direct extraction with ch 3 oh 1.5 ~ ;g --l..,_.,o.-o-----c:r-----o-------0 ~ '0 1.4 i i e'""' i! 1.3 8. +----.----r---.---~--..,.----+ 1.2 300 600 900 1200 1500 lsoo time (sec) fig.8 experimental and predicted total extract and solvent penetration increase during direct and reactive extraction of leaves samples results and discussions kinetic experiments were carried out in a stirred batch reactor, at 25 °c, under the following conditions: hyrdomodulus 1]=0.09 m3 kg"1 , particles mean size r;=0.5 10-3 m, extraction time tma.x===:3600 s for radix samples and tmax= 1800 s for leaves. rotation speed of 4 revolutions s"1 assures internal diffusion-controlling process under inert conditions. figs.5 and 6 show the course of direct and reactive extraction of alkaloid ct=:f(t) obtained respectively from radix and from leaves. the symbols are the experimental points, the curves represent the best-fit simulation results. it is evident that the extraction from leaves samples is achieved more easily: the time of equilibration is 2 time smaller and the drawing out alkaloids is more complete: 87% degree of recovery with 72% from the radix. the effect of chemical reaction depicts an identical trend for the two raw materials: shift to sigmoidal extraction~time behaviour characterized by decline of the extraction rate in the early stage of the process, followed by steep increase. the total amount of crude alkaloids gained with chemical reaction is slightly increased. the facts prove that some alkaloids are not originally in salt form, and these bounded in other forms are extracted by chemical reaction. for the different methods of extraction the amounts of the total extract may be varying because of the different dissolving activities. the experimental data for the total extract per unit mass of solid m*exr=fit) thus 100 table i fitted values for model parameters in case of constant or varying porosity plant radix samples plant leaves samples reactive extraction direct extraction reactive extraction direct extraction eu-f(rj en-canst ep-{(y) kn i02 s"1 1.89 1.16 deff,loiomzs-1 1.32 0.78 1.45 a(eq.l7) 2.6 2.3 th 4.6-3.6 4.72 obtained is shown by the points in figs.7 and 8. the following empirical relationships were deduced: m;xt == 0.148 -0.139exp-o.006sst (28) (from radix with methanol) m * = 0.06690.0586exp -o.o07251 (29) .... (from radix with chloroform) * 0 1 06 94 --o.oosjt m.x~ = . -0. exp (from leaves with methanol) m:x~ = 0.0764-0.0631exp-o.oos441 (from leaves with chloroform) (30) (31) a steep increase in the amount of total extract is recorded in the early stage of the process. the same figures represent the comparison between measured (by points) and predicted values (continuous lines) of the volume of the solvent impregnated the solid. the experimental observations confirm that the solvent continuously penetrates in the solid during extraction. the higher the initial porosity, the great~r the initially penetrated solvent volume, but its relative increase during extraction is lower. for direct extraction from radix~ the methanol penetrated in the solid increases from 0.767 to 0.901 mllg solid that represents porosity increases between 0.4-0.56. with the increasing penetrated volume from 1.52 to 1.64 m1/g solid for leaves. the porosity is increased only from 0.6 to 0.65. lower porosity variation was recorded during treatment with chloroform: in the range £p=0.39-0.47 for radix and ep =0.6~0.63 for leaves. the experimental data for the kinetics of solvent penetration is very near to the predicted from the particle volume balance. thust although the experimental data is not sufficiently detailed, it seems that the presented approach is able to determine approximately the range of the porosity increase. the above experimental procedure forms the basis for the estimation of the kinetic parameters (table 1 }. to highlight the possible effects of porosity increase. the values of the adjustable parameters, obtained by the varying porosity model reported here (ep =:f(f))~ are compared with the values obtained in constant porosity model (£p=ep.0). the following conclusions can be made: ?p-const ?p=f(y) ev=const ev=fiy) ?p=const 1.46 1.76 2.89 8.46 7.15 8.62 9.22 0.9 1.1 1.3-1.2 1.43 the values of the reaction rate constant kr are almost identical and remain independent from the solid phase structure. during extraction from radix, or from leaves, the transition from diffusional to mixed diffusion-reaction regime is registered. for the same raw material the values of deff for reacting system were predicted to be smaller than those for inert system using constant porosity model. in order to predict the same rate of extraction at a lower porosity, in diffusion-controlling regime an increased d eff has to be used in the constant porosity model. in contrast, in a mixed diffusion-reaction regime, an apparently lower deff will be calculated. when the varying porosity model is used, identified diffusion coefficients using polar or non-polar solvent are similar. this result seems to be more realistic, since the two solvents have approximately the same viscosity and the solute concentrations are · in the same order of magnitude. in case of direct, or reactive extraction, the diffusivity d 4f in the porous particles from leaves are higher than those from radix the factor between the coefficients is in the range 7-8. the larger deff suggests lower tortuousity factor and more regular pore structure of the leaves samples. the identified values of the adjustable numerical constant a in eq.( 17) show much larger increase in deff in case of lower initial porosity. it is obvious that liquid penetration affects also the interconnectivity of the pores and the tortuosity factor is decreased. appreciable differences in the effective diffusivity were obtained, considering or not porosity increase, for the kinetic behavior of radix samples where porosity increase is greater than 20%. the major deviation of about 200% in the effective diffusivity was obtained for direct extraction from radix when the total extract remove reached 15%. for the examined solid-liquid system dimension increase and swelling of the porous particles is not observed and the penetrated solvent volume remains relatively low. the resorted differences in d~ffas a result of the porosity increase remain lower in respect to the strong influence of the initial pore structure. conclusion a dynamic model with variable transport properties is presented to predict the kint:dc behaviour during direct or reactive extraction from vegetable material. starting point is the experimentally recorded kinetics of solvent penetration and total extract release. the variation of the porosity with the total extract release is taken into account. an exponential increase in the effective diffusivity with the evolution of the fraction extracted is considered. to exploit the model suitability, the extractibility of alkaloids from the medicinal plant atropa belladonna has been reported. different kinetics of extraction of alkaloids was obtained for the different parts of the plant using different method for valuable compound liberation. using chemical reaction the equilibration delays about 2 times in re3pect to the direct dissolution, without sensible increase in the recovery degree. using ethanol, or chloroform as solvent under direct or reactive reaction the estimated values for the effective diffusivities are independent of the method of dissolution, but they depend very strongly on the initial structure of the pore space. the values of effective diffusion calculated at 25 oc varies in the range 1.32 10-10 m2 s-1 for radix to 8.62 10-10 m2 s-1 for leaves. the resorted differences in the kinetic behaviour show that it may be advantageous to characterize porous media changes directly by measuring the kinetics of solvent penetration. while the commonly used techniques of pore space determination, as mercury porosimetry or b .e. t. gas adsorption allows investigation only of dry material, the experimental kinetics of liquid impregnation provides direct information about swelling properties of the solvent and eventual structural changes with advancement of the extraction. the presented approach can be extended to include the particle dimension changes when considerable swelling is observed and the resorted effects are more obvious. c* deff dejj.o d* symbols specific external area, m2 m-3 biot number (=kmr/ dejj,o) solute concentration in bulk liquid phase, kgm-3 solute concentration in pores of particle, kgm-3 volume-averaged concentration in solid phase, kgm-3 transformable compound concentration in solid phase, kg m-3 dimensionless concentrations effective diffusivity. m2 s·1 effective diffusivity at initial porosity, m2 s-1 factor for effective diffusivity increase ( =deff i deff,o) chemical reaction rate constant, s-1 external mass transfer coefficient, m s·1 initial mass of solid phase. kg mass of inert compounds in the solid phase, kg mass of extracted compounds, kg mass of extracted compounds per unit of dried solid, kg kg-1 101 mst common mass of solid phase, impregnated with solvent, kg mss mass of solid phase after removing solvent excess, kg r radial coordinate, m rv volume reaction rate, kg m-3 s-1 rs particle radius, m th thiele-type modulus ( ==rs "vf 1-ep)k/d eff) xo initial mass fraction of extractable compounds, kg kg"1 vexr extractable compounds volume, m3 · vin inert compounds volume, m3 v[ liquid phase volume, m3 v,s solvent volume in the solid phase pores, m3 vs solid phase apparent volume, m3 vr solvent radial velocity in the pores, m s-1 greek letters a empirical constant defined by eq.( 17) f3 phase ratio ( = v /vz) r fraction of unextracted compounds ep porosity of the particle ep,o initial porosity of the particle tp relative coordinate a. wavelenght, nm 1] hydromodulus (=vz/m0 ), m3 kg-1 r dimensionless time(= deff,otir/) references 1. minkov s., mintchev a. and paev k.: j. of food engineering, 1996,29, 107-113 2. goto m., smith j. m. and mccoy b. j.: chern. eng. sci., 1990, 45 (2), 443-448 3. ramachandran p. a. and smith j. m.: chern. eng. j., 1977, 14, 137-146 4. fan l. s., miyanami k. and fan l. t.: chern. eng. j., 1977, 11, 13-20 5. hpollewand m. p. and gladden l. f: chern. eng. sci., 1992,47 (7), 1761-1770 6. marmur a. and cohen r.: j. of colloid and interface science, 1997, 189,299-304 7. seikova i., guiraud p. and mintchev a.: comptes rendues de l' academie bulgare des sciences, 2000, 53(3), 55-58 8. triday j. and smith j.. m.: aich j., 1988, 34 (4), 658--668 9. hinz th. and eggers r.: nabrung, 1996, 40 (3), 116-124 10. satierfied c. n.: heterogeneous catalysis in practice, mcgraw-hall, new york, p.87~119, 1980 11. mcgreavy c., andrade j. s. and rajagopal k.: chern. eng. sci. 1992, 47 (9·11), 2751.-2756 12. sokolov a. v. and popov d. m.: farmatsiya {moscow), 1989, 38 (6); 62-65 13. grjshina m.s., dyukova v. v .• kovalenko l. i. and popov d. m.: khim.·farmatsiya zh. (moscow), 1985, 19 (9) .1102wll05 page 96 page 97 page 98 page 99 page 100 page 101 page 102 hungarian journal of industry and chemistry vol. 46(2) pp. 27–31 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0014 production of a biolubricant by enzymatic esterification: possible synergism between ionic liquid and enzyme zsófia bedő1, katalin bélafi-bakó1, nándor nemestóthy1, and lászló gubicza *1 1research institute of bioengineering, membrane technology and energetics, university of pannonia, egyetem u. 10, veszprém, 8200, hungary the possible replacement of lubricants with fossil-fuel sources and the manufacture of biolubricants with more beneficial features were studied. oleic acid and isoamyl alcohol were reacted with an enzyme in an ionic liquid. during the reaction conventional as well as microwave heating was applied. after the experimental determination of the optimal reaction parameters, it was unexpectedly found that a synergistic effect occurred by applying ionic-liquid and microwave-heat treatment simultaneously. the enzyme exhibited a much higher level of activity than the value expected based on the measurements carried out separately by using an ionic liquid instead of an organic solvent and microwave-heat treatment or a conventional method. in the experiments with recycled enzyme it was found that ionic liquid maintained the enzyme more effectively, as if it was immobilized by it: the enzyme managed to maintain its activity and recycling ability. keywords: synergistic effect, ionic liquid and microwave heating, biolubricant production, enzyme reuse 1. introduction lubricants from mineral oils have a considerable detrimental effect on the environment due to the aromatic organic compounds within their chemical structures. mineral oils that have leached into water or soil are toxic for living organisms, they substantially decrease the level of dissolved oxygen in the water. these lubricants can hardly be degraded biologically. during their manufacture several by-products form and further additives are needed for the lubricants. hence the demand for biolubricants from plant oils has been growing recently, since they are natural, renewable, non-toxic as well as environmentally-friendly compounds, and often cheaper than synthetic oils. therefore, they are suitable for eliminating the disadvantages of mineral oil, moreover, our dependence on mineral oils and other non-renewable sources might be decreased [1, 2]. the production of synthetic and semi-synthetic lubricants is necessary since now it is not possible to conduct all lubrication tasks by using lubricants derived exclusively from mineral oils. in several cases non-coking lubricants with extremely high degrees of viscosity are able to operate at low temperatures (below -50 °c). biolubricants are used in numerous fields of application, but in all of them it is vital to prevent the contamination (only a negligible level is acceptable) of the product and environment. these provide an alternative to the mineral oilbased lubricants in industrial applications that are used in *correspondence: gubiczal@almos.uni-pannon.hu the automotive industry as hydraulic fluids during metal processing and oils for driving gears [3]. they are not considered as biological hazards in water systems when applied in watercrafts. in biotechnological methods for the manufacture of biolubricants, raw materials with a high oleic acid content are generally used for the transesterification processes. biolubricants are mainly produced from plant oils, e.g. sunflower oil, soybean oil and castor oil [4, 5]. the lifetime of these biolubricants that possess esters is usually longer than those obtained from mineral oils. on the other hand, their widespread industrial usage is hindered by the fact that certain equipment must be converted to run on biolubricants [6]. various esters can be enzymatically produced from acids and alcohols of different chain lengths in nonconventional systems (organic solvents, ionic liquids, supercritical fluids, solvent-free media). thus, the esterification of acids and alcohols of short chain lengths by lipase results in flavour esters [7, 8]. the esterification of fatty acids (acids with carbon numbers of between 12 and 18) and alcohols may yield both biolubricants and biofuels depending on alcohols’ chain lengths [9,10]. biodiesel is obtained when alcohols of short chain lengths are used, while biolubricants can be manufactured by alcohols of long chain lengths. the formation of a biolubricant from oleic acid and isoamyl alcohol in organic solvents has been studied previously [11–13]. the term ‘biolubricant’ may be used since both isoamyl alcohol and oleic acid are considered mailto:gubiczal@almos.uni-pannon.hu 28 bedő, bélafi-bakó, nemestóthy, and gubicza to occur naturally and the reaction is carried out by a naturally-occurring catalyst, an enzyme. koszorz et al. studied the same reaction and stated that the water formed as a by-product of the esterification reaction had a negative effect on the rate of reaction and activity of the enzyme. to enhance the effectiveness of the process, water had to be removed by an integrated system where the reaction was combined with a pervaporation unit [14]. turkish researchers applied fusel oil – a by-product of bioethanol production – containing a significant amount of isoamyl alcohol that was used to synthesize a biolubricant with high yield [15]. in addition to organic solvents, good results were achieved recently using ionic liquids as solvents. in the field of heat treatment microwave irradiation has yielded excellent results in both organic synthetic and enzymatic reactions [16, 17]. in transesterification reactions even a synergy effect was observed between the enzyme and ionic liquid [18–20]. the aim of this paper was twofold: (i) to study the possibility of applying ionic liquids instead of organic solvents; (ii) to investigate the role of microwave irradiation to achieve the highest possible degree of conversion in the minimum amount of time. 2. experimental the reactions were conducted in an incubator shaker and microwave equipment using conventional heating and microwave irradiation, respectively. similar compositions and reaction volumes were used in the measurements to be able to compare the experimental results. 2.1 samples and measurements all chemicals were commercially available and used without further purification. novozym 435 (immobilised candida antarctica lipase b, calb), a triacylglycerol acylhydrolase (e.c. 3.1.1.3.) immobilized on an acrylic resin, was a gift from novozymes (bagsvćrd, denmark). its nominal catalytic activity and water content were 7000 propyl laurate units (plu)/g and 1-2 %, respectively. isoamyl alcohol (98 %) and oleic acid (99 %) were used as received from sigmaaldrich. the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]pf6) (≥98.5 %) was purchased from sigma-aldrich while n-hexane and isooctane (99 %) were acquired from reanal. to follow the yield of the ester, a hp-5890a gas chromatograph (gc) was used. the device was equipped with a split/splitless injector, flame ionization detector (fid), and db-ffap column (length: 10 m, inner diameter: 0.53 mm, film thickness: 1.00 µm). the following heating programme was applied: 130 °c, 3 mins.; temperature ramp up: 10 °c min−1; 240 °c, 5 mins. isooctane was used as an internal standard. for the analysis, a 10 µl sample of the reaction mixture was extracted. reaction mixtures that contain ionic liquids cannot be injected into the gc, since they – as a viscous liquid – form a deposit on the inner side of the column that causes fouling. moreover, they may be degraded due to the high temperature, thus, the precision of the measurements will be affected and undesirable peaks may appear in the chromatograms. during the measurements the components are usually separated from the ionic liquid by extraction and injected into the column. in our measurements – to preserve the gc column – fiberglass and adsorbent material were placed inside the injector, which retained the ionic liquid after injection while the component to be analysed was transferred in a gas phase to the column as a result of the high temperature. in this way extraction of the product from the reaction mixture could be avoided, therefore, the errors that originate from the incomplete extraction (effectiveness) could be eliminated. 2.2 experimental setups two different procedures were used for the production of biolubricants. firstly, by using conventional heating the synthesis of biolubricants was conducted in eppendorf tubes (1.5 ml) at 40 °c rotated at 200 rpm (ika incubator shaker ks 4000i). in a typical experiment 5 cm3 of reaction mixture (22.5 mmol of isoamyl alcohol and 3.75 mmol of oleic acid dissolved in n-hexane or [bmim]pf6) was prepared in a volumetric flask, and the eppendorf tubes were each filled with 1 cm3 of the reaction mixture. the reaction started when 10 mg of the enzyme was added. tests under microwave conditions were performed in a commercial microwave synthesizer (discover series, benchmate model, cem corporation, usa). it was equipped with a magnetic stirrer and a fibre-optic sensor to monitor the temperature, which was set by varying the power of the microwave. for the esterification of biolubricant, 10 w of energy was used to maintain the temperature of the reaction between 40 and 60 °c. the volume and composition of the reaction mixture was identical to under conventional conditions. experiments to study the reusability of enzymes were conducted by separating the enzyme from the reaction mixture and starting a novel reaction with a reaction mixture of the same volume. 3. results and analysis 3.1 experiments certain ionic liquids may catalyse esterification reactions. even though in the case of [bmim]pf6 this phenomenon does not occur according to earlier publications, measurements were conducted in reaction mixtures which did not contain enzymes to be able to exclude this effect. our experiments confirmed previous results from the literature: [bmim]pf6 did not catalyse the reactions. hungarian journal of industry and chemistry production of a biolubricant by enzymatic esterification 29 figure 1: biolubricant production in the organic solvent (dashed lines) and ionic liquid (solid lines) using conventional heating. the experimental conditions were selected according to data from the literature in addition to our earlier observations, and they were checked by preliminary measurements. thus, the molar ratio of isoamyl alcohol to oleic acid was adjusted to 6:1, with a shaking rate of 200 rpm. the measurements were conducted at a temperature of between 30 and 50 °c to follow the eventual changes at various temperatures. it would have been possible to carry out measurements at higher temperatures using the enzyme novozym 435 or the ionic liquid [bmim]pf6, furthermore, changes over longer reaction times could be more suitable to follow and evaluate. 3.2 experiments using conventional heating firstly, measurements under the conditions described in section 2.2 were conducted using conventional heating (fig. 1). as can be seen esters were produced in high yields during the reactions in the ionic liquid as well as expected, and the yield was always higher in the ionic liquid at the same temperature. 3.3 experiments using microwave heating the results of the measurements using microwave irradiation are presented in fig. 2. as can be observed, a much shorter time was necessary to reach equilibrium, and the reaction rate was also faster in the ionic liquid. 3.4 investigation of enzyme reuse the reusability of the enzyme novozym 435 was studied under similar conditions in an ionic liquid (i.e. using conventional and microwave heating). the results indicated figure 2: biolubricant production in the organic solvent (dashed lines) and ionic liquid (solid lines) using microwave irradiation. that the activity of the enzyme declined more rapidly using conventional heating. 4. discussion the results of the experiments conducted in the organic solvent, n-hexane, and in the ionic liquid, [bmim]pf6, under similar conditions provided a good basis to compare the effects of conventional and microwave heating during the production of biolubricants using enzymes since in both cases the same reaction volumes were used. as can be seen in fig. 1, the reaction rate was higher in the ionic liquid (il) than in n-hexane (n-h), the organic solvent that was usually applied. the data in table 1 can be further compared. by comparing the values of c, il/c and n-h (the ratio of enzyme activities in the ionic liquid and n-hexane using conventional (c) heating), it can be seen that the activity of the enzyme increased by a factor of 1.2 (on average) at each temperature due to the presence of the ionic liquid. in the organic solvent the activity of the enzyme was found to be 2.8 times greater as a result of the microwave irradiation at each temperature (data of mw, n-h/c, n-h) compared to the conventional heating. in similar experiments in ionic liquids even more significant increases in the activity of enzymes were observed: microwave irradiation (mw) resulted in a 5.8-fold rise (data of mw, il/c, il). a possible explanation for the significant increase is that the ionic liquid and microwave irradiation have a positive synergistic effect on the activity of the enzyme. previously it was observed that ionic liquids seem to protect the enzyme in a similar way to the immobilising suptable 1: comparison of the activity of the enzyme under various conditions. t / °c activity / µmol·min−1·g−1 conventional heating microwave heating c, il/c, n-h mw, n-h/c, n-h mw, il/c, il n-h il n-h il 30 162 194 475 1120 1.19 2.93 5.77 40 342 444 990 2510 1.29 2.89 5.65 50 575 660 1650 3840 1.15 2.86 5.82 46(2) pp. 27–31 (2018) 30 bedő, bélafi-bakó, nemestóthy, and gubicza figure 3: reusability of the enzyme in the ionic liquid using microwave and conventional heating port of the enzymes. in this work an immobilised enzyme was applied, thus, the synergistic effect simply strengthened the enzyme preparation or stabilised the active site of the enzyme. a similar effect has already been described in transesterification reactions in some papers in the literature [18,20], but not with regard to esterification reactions. the stabilisation effect of the ionic liquid was confirmed by the results presented in fig. 3. by re-using the enzyme 5 times under conventional heating, the activity of the enzyme decreased much more rapidly than in the case of microwave heating. while in the first case 50 % of the original activity of the enzyme was maintained after the fifth application, using microwave irradiation this value was 70 %. 5. conclusion the experiments led to a definite answer to the original question, namely whether microwave irradiation may enhance the 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https://doi.org/10.1016/s0011-9164(04)00064-5 https://doi.org/10.1016/j.enzmictec.2006.06.010 https://doi.org/10.1016/j.enzmictec.2006.06.010 https://doi.org/10.1016/j.molliq.2016.11.123 https://doi.org/10.1016/j.molliq.2016.11.123 https://doi.org/10.1016/j.biortech.2012.01.030 https://doi.org/10.1016/j.biortech.2012.01.030 https://doi.org/10.1039/c1gc15114b https://doi.org/10.1039/c1gc15114b https://doi.org/10.1016/j.bej.2016.09.007 introduction experimental samples and measurements experimental setups results and analysis experiments experiments using conventional heating experiments using microwave heating investigation of enzyme reuse discussion conclusion